CA1064025A - High speed corrugating adhesives - Google Patents
High speed corrugating adhesivesInfo
- Publication number
- CA1064025A CA1064025A CA256,543A CA256543A CA1064025A CA 1064025 A CA1064025 A CA 1064025A CA 256543 A CA256543 A CA 256543A CA 1064025 A CA1064025 A CA 1064025A
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- Canada
- Prior art keywords
- starch
- saponifiable
- composition
- adhesive
- ester
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
ABSTRACT High speed corrugating adhesives are provided based upon the use of certain specified saponifiable starch ester materials. These may be in the form of no-carrier type formulations, in which a single phase is present whereinthe starch material is in the form of partially swollen granules. Alternatively, the formulation may have a carrier phase and an adhesive phase. The specific formulations described have superior properties that permit higher corrugating machine speeds
Description
BACKGROUN~ OF THE NVENTION
This inventLon relates to starch-based corrugaLing adh~sLves and methods for their prepartion. The invention ls also concerned with ~lethods of uniting articles, particularly laminated articles of fibrous, cellulosic webs, and more particularly, with the production of paperboard Eor use in the production of corrugated containers. The invention is also concerned with articles produced through the use of the new adhesive compositions.
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One usual method of making corrugated board consists of corrugating a strip of paper by means of a corrugated roller,applying an adhesive to the tips of the flutes of the corrugations on one side and adhering another strip of paper called a "liner", to the flute tips by use of heat and under high pressure.
This product, called "single face'l corrugated board may be used as is. However, it is usual to make "double face", also called "double back"
board by sending the single face board into the second stage of the corrugating machine called the l'double backer" stage. The term "singlefacer"generally refers to the first stage of the machine. An adhesive is applied to the opposite flute tips, and a second liner of paper is adhered to said opposite side by the use of heat and under a relatively small amount of pressure. The fact that 2Q the use of a great amaunt of pressure in the adherence of the second strip of paper would tend to crush the corrugations makes the adhesive prohlem in the second step quite difficult.
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Starch-based corrugating adhesive formulations have been -in wide use since the advent of the Stein-Hall technology, as diSclosed in U.S. Patent '1 ~
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~3~ f No. 2~05l,025, granted ~ugust L8, l936, to J. V. Bauer, and U.S. I'~tt~llt No.
This inventLon relates to starch-based corrugaLing adh~sLves and methods for their prepartion. The invention ls also concerned with ~lethods of uniting articles, particularly laminated articles of fibrous, cellulosic webs, and more particularly, with the production of paperboard Eor use in the production of corrugated containers. The invention is also concerned with articles produced through the use of the new adhesive compositions.
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One usual method of making corrugated board consists of corrugating a strip of paper by means of a corrugated roller,applying an adhesive to the tips of the flutes of the corrugations on one side and adhering another strip of paper called a "liner", to the flute tips by use of heat and under high pressure.
This product, called "single face'l corrugated board may be used as is. However, it is usual to make "double face", also called "double back"
board by sending the single face board into the second stage of the corrugating machine called the l'double backer" stage. The term "singlefacer"generally refers to the first stage of the machine. An adhesive is applied to the opposite flute tips, and a second liner of paper is adhered to said opposite side by the use of heat and under a relatively small amount of pressure. The fact that 2Q the use of a great amaunt of pressure in the adherence of the second strip of paper would tend to crush the corrugations makes the adhesive prohlem in the second step quite difficult.
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Starch-based corrugating adhesive formulations have been -in wide use since the advent of the Stein-Hall technology, as diSclosed in U.S. Patent '1 ~
'. , ' ~.
,, , - . . : . .
~3~ f No. 2~05l,025, granted ~ugust L8, l936, to J. V. Bauer, and U.S. I'~tt~llt No.
2~102,937, granted Decemher 2L, l~37, also to J. V. Ba~ler.
A Stein-Hall type adhesive is a two component aqueous system. One component in this system is generally Eormed from a cooked, or gelatlnized starch material, which serves as a carrier phase. Qther materials which can form relatively viscous aqueous slurries, such as carboxymethyl cellulose, may also be used as a carrier phase.
The second component or phase is formed from a raw, ungelatinized starch material. This second phase is a latent or po~ential adhesive phase.
That is, the adhesive characteristics of such a formulation are not fully developed until after the adhesive has been applied to the tips of the flutes ' of the corrugated web, the liner has been pressed against the adhesive~
coated flutes, and heat and pressure have been applied; the heat causing the granular starch material to gelatinize and develop structure.
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The swelling and gelatinization of the latent adhesive phase takes place as the newly assembled corrugated board is passed through a hot plate-dryer system that is associated with a corrugating machine. This system also partially dries the corrugated board and sets the adhesive sufficiently so that .;
` it can be sub~ected to subsequent operations, such as trimming, slitting, and sheeting withouit delamination.
The initial degree of cohesiveness in the bond oE the corrugated board is referred to as the green bond strength. This characteristic detel~ines the ability of the newly formed corrugated board ~o resist the ins-tantaneous f ' .
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high shec~r ~orces tha-t are developed during subsequen-t process-ing operations, such as the -tri~ming. sli-t-ting, and shee-ting operations, and is not necessarily an indica-tion of the ~inal bond strength.
Green bond s-treng-th, or ~or brevi-ty3 green s-trength, is a major limi-ting factor which controls the operating speed at which corrugated board may be manu~actured on a given machine.
An experienced machine operator o~ten will operate a machine a-t the maximum speed of which it is capable without having the board delaminate during the trimming, slitting, and sheeting operations. Since the resistance to delamination is a charact-eristic that is directly dependent on green strength, the characteristics of the corrugating adhesive play a direct role in machine e~ficiency9 which in turn determines the rate of return on -the fixed investment represented by -the machine.
A~ter corrugated board has been trimmed, slit, and sheeted, it is stacked and sent to storage, where the adhesive cures to a full strength. Un-til the bond is dry and ~ull~
cured, the corrugated board may be delaminated by slowly and firmly pulling the liner away from -the corrugated sheet.
Since the middle thirties 9 one of the major advances in corrugating adhesive technology is that disclosed in U.S.
Patent 3,355,307, granted November 28, 1967, to John J.
Schoenberger and Raymond P. Citko. This patent discloses a single phase corrugating adhesive re~erred to as a "no-carrier' system, in which partially swollen starch gr~lules are present as a homogeneous phase, suspended in an aqueous, alkaline vehicle. The elimination of the carrier phase permit-ted sub-stantial operating economies. The no-carrier type corrugating adhesive disclosed and claimed in the Schoenberger-Cit~so patent was applied and cured in the same manner as the Stein-~lall type adhesive formulations.
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()ther advances in the corrugating adhesive EieId reLate(I prim3riIy to building in moistur~ resistance, generally through the addition o~
syn~hetic resins, such as urea-Eormaldehyde, phenol-formaldehyde, and re-sorcino:L-formaldehyde resins.
S The Bauer patents represented a significant advance in the art, for their time. Bauer reported that the use of his adhesive systems permitted corrugated board machines to be operated up to 20~ faster than would have been possible utilizing prior art adhesive compositions. The prior art ~; compositions included preparations based on sodium silicate and adhesive preparations based on the use of gelatinized starches or modified starches such as dextrins.
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In the Stein-Hall type system, according to the teachings of Bauer~ the time required to form an adhesive bond between the corrugated , interliner and a liner or facer sheet is substantially independent of the rate at which the moisture in the adhesive is driven off by heat or absorbed by the paper. According to Bauer, the time required to form the adhesive bond ` depended mainly on the time required to cause gelatinization of the granular starch particles suspended in the gelatinized starch carrier phase. As this granular starch gelatinized, water was taken up, and the viscosity of the adhesive was raised rapidly~ to form an immediate green bond. Bauer considered that tapioca, rye and potato starches were inherently superior to corn, wheat, and rlce starches for making corrugating adhesives in accordcmce with his developments.
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i Bauer described four prlncipal factors that he considered to '1, 25 determine the sultability of the starch for use as the latent adhesi~e component in his system. These four factors were:
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1. the tirne required for complete gelatiniza-tion of the granular starch by m~ans of the heat input on the corrugating machine.
2. The temperature at which the starch gelatinizes.
A Stein-Hall type adhesive is a two component aqueous system. One component in this system is generally Eormed from a cooked, or gelatlnized starch material, which serves as a carrier phase. Qther materials which can form relatively viscous aqueous slurries, such as carboxymethyl cellulose, may also be used as a carrier phase.
The second component or phase is formed from a raw, ungelatinized starch material. This second phase is a latent or po~ential adhesive phase.
That is, the adhesive characteristics of such a formulation are not fully developed until after the adhesive has been applied to the tips of the flutes ' of the corrugated web, the liner has been pressed against the adhesive~
coated flutes, and heat and pressure have been applied; the heat causing the granular starch material to gelatinize and develop structure.
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The swelling and gelatinization of the latent adhesive phase takes place as the newly assembled corrugated board is passed through a hot plate-dryer system that is associated with a corrugating machine. This system also partially dries the corrugated board and sets the adhesive sufficiently so that .;
` it can be sub~ected to subsequent operations, such as trimming, slitting, and sheeting withouit delamination.
The initial degree of cohesiveness in the bond oE the corrugated board is referred to as the green bond strength. This characteristic detel~ines the ability of the newly formed corrugated board ~o resist the ins-tantaneous f ' .
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high shec~r ~orces tha-t are developed during subsequen-t process-ing operations, such as the -tri~ming. sli-t-ting, and shee-ting operations, and is not necessarily an indica-tion of the ~inal bond strength.
Green bond s-treng-th, or ~or brevi-ty3 green s-trength, is a major limi-ting factor which controls the operating speed at which corrugated board may be manu~actured on a given machine.
An experienced machine operator o~ten will operate a machine a-t the maximum speed of which it is capable without having the board delaminate during the trimming, slitting, and sheeting operations. Since the resistance to delamination is a charact-eristic that is directly dependent on green strength, the characteristics of the corrugating adhesive play a direct role in machine e~ficiency9 which in turn determines the rate of return on -the fixed investment represented by -the machine.
A~ter corrugated board has been trimmed, slit, and sheeted, it is stacked and sent to storage, where the adhesive cures to a full strength. Un-til the bond is dry and ~ull~
cured, the corrugated board may be delaminated by slowly and firmly pulling the liner away from -the corrugated sheet.
Since the middle thirties 9 one of the major advances in corrugating adhesive technology is that disclosed in U.S.
Patent 3,355,307, granted November 28, 1967, to John J.
Schoenberger and Raymond P. Citko. This patent discloses a single phase corrugating adhesive re~erred to as a "no-carrier' system, in which partially swollen starch gr~lules are present as a homogeneous phase, suspended in an aqueous, alkaline vehicle. The elimination of the carrier phase permit-ted sub-stantial operating economies. The no-carrier type corrugating adhesive disclosed and claimed in the Schoenberger-Cit~so patent was applied and cured in the same manner as the Stein-~lall type adhesive formulations.
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()ther advances in the corrugating adhesive EieId reLate(I prim3riIy to building in moistur~ resistance, generally through the addition o~
syn~hetic resins, such as urea-Eormaldehyde, phenol-formaldehyde, and re-sorcino:L-formaldehyde resins.
S The Bauer patents represented a significant advance in the art, for their time. Bauer reported that the use of his adhesive systems permitted corrugated board machines to be operated up to 20~ faster than would have been possible utilizing prior art adhesive compositions. The prior art ~; compositions included preparations based on sodium silicate and adhesive preparations based on the use of gelatinized starches or modified starches such as dextrins.
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In the Stein-Hall type system, according to the teachings of Bauer~ the time required to form an adhesive bond between the corrugated , interliner and a liner or facer sheet is substantially independent of the rate at which the moisture in the adhesive is driven off by heat or absorbed by the paper. According to Bauer, the time required to form the adhesive bond ` depended mainly on the time required to cause gelatinization of the granular starch particles suspended in the gelatinized starch carrier phase. As this granular starch gelatinized, water was taken up, and the viscosity of the adhesive was raised rapidly~ to form an immediate green bond. Bauer considered that tapioca, rye and potato starches were inherently superior to corn, wheat, and rlce starches for making corrugating adhesives in accordcmce with his developments.
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i Bauer described four prlncipal factors that he considered to '1, 25 determine the sultability of the starch for use as the latent adhesi~e component in his system. These four factors were:
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1. the tirne required for complete gelatiniza-tion of the granular starch by m~ans of the heat input on the corrugating machine.
2. The temperature at which the starch gelatinizes.
3~ The viscosity developed a-fter gelatinization.
. The degree oE tackiness developed after gelatinization.
However, subsequent developments indicate that the green bond strength depends significantly on the evaporation oE moisture from the bond site: Thayer & Thomas Analysis of the Glue Lines in Corru~ated Board, TAPPI; 22nd Corrugated Containers Con-ference, May 1971.
- It has now been discovered that a select class of starch materials, when used as the adhesive component in a corrugating adhesive composition, demonstrate superior properties. One way to take advantage of these properties is by the use of machine speeds that are ordinarily from 5~/O to 100% higher than had been considered possible with conventional Stein-Hall type corrugating adhesive compositions, or with the more recently introduced no-carrier corrugating adhesive compositions, at generally the same levels of adhesive usage.
According to the invention in one aspect there is provided a composition suitable for use as a corrugating adhesive including at least two phases, comprising a carrier phase and a la~ent adhesive phase that is dispersed in tha carrier phase; the latent adhesive phase comprising an ungelatinized, granular saponifiable starch ester and a quantity of alkali sufficient to substantially completely ~ saponify the saponifiable starch ester, the composition < being tractable on a corrugating machine.
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In another aspect of the invention there is provided a process for uniting at least two items of materia:L comprising applying between the items a composition of the invention, and activating the composition to form an adhesive bond.
Still further the invention provides in another aspect an article of manufacture comprising a plurality of items of material joined with an adhesive boncl comprised of a composition of the invention.
` In yet another asp2ct of the invention there is provided an improvement in a process for the preparation of a corrugating adhesive of the no-carrier type, which consists in replacing at least a portion of the starch material with a saponifiable starch ester.
- Stated in another way, superior results have been obtained when the primary active adhesive component in a corrugating adhesive formulation is a saponifiable starch ester material which exhibits at Least about a 3~/O greater area under anInstron force-time heating curve and at least about a 30/0 greater area under an Instron force-time cooling curve, compared with unmodified corn starch under the same test conditionsO
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Preferred adhesive compositions of the present invention are based on the use of primary adhesive components which are saponifiable starch esters having a saponifiable degree of substi-tution (D.S.) o~ at least about 0.015.
As used herein, "saponifiable degree of subs-titution" means the total D,S, of all saponifiable ester groups on the starch moleculeO Particularly preferred starch lester materials are starch acetate, starch succinate and starch acetate succinate.
One or more of these active adhesive components can be used 10 to advantage either in a Stein-Hall type formulation or in a no-carrier type formulation, with equally superior improvements over the prior art.
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- - -The most ~reEerred aclhesive component is a stclrcil acetate su(clnate having a saponifiable degree of substitution (D.S ) in the range ~rom abouL
0.025 to about 0.045. Thase D.S. levels represent ranges that are appLicable to starch acetate succinate. Other derivatives that are usef~ll in accordance with the invention will have their own preferred D.S. ranges. Gener~lly, if the D.S. level is too low, the derivatized material will not exhibit significant improvement over unmodified corn starch when used in a corrugating adhesive formulation. If the D.S. level is too high, the gelatinization temperature may be unworkable.
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The specific materials that have been identified, for use in accordance with the invention~ are starch derivatives identified above. These starch derivatives may be prepared immediately prior to use, i.e., in situ at the corrugating machin~, or they may be prepared in advance, and may be formulated into corrugating adhesive compositions as with other starch ., materials that are to be used for such purposes in accordance with prior art practices.
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It is also possible to utilize modified starch materials which ~ may be produced from the aforementioned starch esters. These modified ;~ starch materials are produced by substantially completely saponifying the 2Q starch esters and removing the salts formed thereby. The resulting modi~ied , starch material may then be drled. Although the derivative has been sub-', stantially completely removed from the starch material, the modified starch ` ~ retains the beneficial properties of the ester materialO
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- Wh:ile we do not fully understand the reason l~hy the speclclL
materials identi~ied hy our invention are superior Eor use in corrugating adhesives in partlcular, it can be theorized that they not on]y develop unusually high viscosity upon gelatinization, but in addition, provide a hlgh green strength without the necessity oE solvent evaporation.
I~hile the flnal form of the useful starch materials of this invention is not known, it is known that the esters materials saponiEy substantially completely in a short period of time in the environment present in the mixing apparatus on the corrugating machine.
The invention will be better understood by a more detailed explanation of several specific embodiments thereof. All parts and percentages are by weight, on a commercial basis, unless express'y stated to be otherwise~ The commercial basis for the starch materials includes about 12r moisture.
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I)l`'l`AILI~I) DESCRIP'I`10~ OF TtlE PREFERRED EMBODIMEN'rS
The proper selection of the primary active aclhes-Lve component is of great importance Eor the proper practice of the present invention.
In preparing saponifiable starch esters for use as the primary active adhesive components, the starting starch material may be derived from any vegetable source. Starches derived from non waxy grain sources, such as, for example, corn, wheat, rice, and grain sorghum are preferred.
The ~erm "starch" is used broadly herein and encompasses flour, un-modified starch and tailings. Corn starch is a preferred starting starch ~ 10 material.
- The initial starcll is esterified, as will be described presently, to produce the primary active adhesive component that has the desired characteristics in accordance with the invention.
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In a typical corrugating adhesive formulation, it is usual to add bora~ and caustic to increase the adhesive strength and tack, and to ad-~ust the gelatiniæation temperature. When using either a carrier-type or a no-carrier type adhesive formulation, the Stein-Hall viscosity of the formulation must be within the conve.ntional range to permit an adequate amount of adhesive to be applied to the flute tips at all machine , 20 speedsO Generally, to be tractable on a corrugating machine, an adhesive :,j ~orDlation should have a Stein~Hall viscosity in the range of about ' 20 sec. to about 100 sec. The optimum Stein-Hall viscosity of the formu-"
lation will depend on the particular corrugating machine.
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Unless otherwise speciEied, the materiaLs ~escribed an~l claimed herein are those ~hich are to be added to ~orm the adhesive formulation. In the particular environment of the adhestve formula-tion, the form of certain materials may be altered. For example, the starch ester will saponify in a typical corrugating adhesive formulation.
This will reduce the actual amount of alkali present. The borax may be present in any of several species, or as an equilibrium mixture of these species, depending prilDarily on the pH of the formulation.
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As previously described, it is standard practice in the corrugating industry to add alkali and borax to the adhesive formulations.
While formulations ~hich do not include these materials may be used as corrugating adhesives, it is preferred to include both of these materials to the formulations of this invention.
The borax is generally utilized to increase the gel structure of the adhesive paste. However, an excess of borax may have an adverse effect on the cured bond strength. In addition, borax has the tendency to increase the gel tempe~ature of the formulation. Generally, up to about 5% borax (10 mol) may be incorporated into the formulations.
A more usual quantity would be about 2% to about 3%. The percentages are based on the total starch material present in the formulation, including both the primary active adhesive material and the carrier material. If 5 mol borax is to be used instead of 10 mol, it is necessary to compensate for the reduced water of hydration. In no-carrier systems, ` boric acid may be utilized as a reaction stopper. The boric acid will : .
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~uicklv be conver~ed to a horate and is tllen able to serve as a substL-tute for added borax. As used herein, the term "borax" will include those borates which are present due to the addition of boric acid.
Any standard alkali may be used. However, for economic reasons, S sodium hydroxide is most commonly utili~ed. The aLkali serves to reduce the gel temperature of the adhesive formulation to a readily tractable point. Generally this will be in the range of frorn about 145~F to about 150F, but may in some applications range from about 140F to about 160F.
It is important that large amounts of alkali not be used in any corru-. ~
gating adhesive formulation, whether conventional or in accordance with - this invention, as alkali tends to reduce gel structure format:Lon.
Generally up to about 5% alkali (calculated as sodlum hydroxide) may be used, based on total starch material in the system. More usual amounts would be from about 3% to about 3.5%.
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~--` 15 It is of critical importance to the practice of this invention that at least enough alkali to substantially completely saponify the . , ~ starch ester be used. Tha amounts of alkali referred to above are . .
~ the quantity of alkali in excess of this minimum amount.
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The particular starch ester to be used in the practice of this invention is not critical, as long as it will saponify in the environ-ment of a corrugating adhesive formulation. Consequently, inexpensive and " .
" ~ simple starch esters, such as starch acetate are preferred. Particularly ;l~ preferred is the mixed ester, starch acetate succinate.
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The starch esters may be obtained commercially, or may be made by any conven-tional method, such as by reacting unmodified starch with acid anhydrides 3 acid halides, vinyl esters and -the like. The same reagents may be used when util-izing the 1n situ method of this invention. I-t is necessary however that the esterification be carried out at a temperature which is below -the ac-tual gelatiniza-tion -temperature of both the unmodified starch and the starch es-ter.
In addition, the water conten-t of an adhesive form-ulation should be adjus-ted so -that an extremely -tacky adhesive characteristic is obtained immediately after gelatinization.
This implies that sufficient water is present for complete ~-gelatinization. It is most desirable that rapid developmen-t ;~ of tack is obtained upon the application of heat in the corrugating equipment.
The amounts of starch materials utilized in the ad-hesive formulations of this invention are similar to those utilized in conventional formulations. Generally, -the granular starch component of a Stein-Hall type formulation will contain from about 10% to about 25% starch. The final adhesive mixture generally has from about 12% to about 25% of its total s-tarch ~,~
in the form of the gelatinized carrier.
; The starch esters of this invention may also be u~ed as the carrier portion of a Stein-Hall type adhesive. In such instances, it may be possible to reduce -the quantity of carrier `!` somewhat due to -the greater thickness of these starch es-ters.
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The desirable clegree of substitution depencls upon the ~lrt i( ular initiaL starch material selected However, in general, it hcls been ~o~lncl desirable to utilize a saponifiable D.S. of at least about 0.015. Starch esters having a saponifiable D.S. of at least about 0.015 have been found to satisfy the Instron test criteria, discussed infra, and therby permlt machine speeds at least about 20% greater than those attainable utilizing unmodified corn starch as the primary active adhesive component.
Generally D.S. levels greater than 0.015 will produce even faster machine speeds. It has been found preferable to utilize saponifiable starch esters havlng a saponifiable D~S. in the range of from about 0.025 to about 0.045. The utilization of such materials will generally permit operation of a corrugating machine at speeds of up to about 100% higher than those attaînable using conventional adhesives.
The green strength, and the viscosity of ~he gelatinized corrugating adhesive that produces the green stren~th, cannot conveniently be sub~ected to direct quantitative measurement at the exact site of the bond. However, it appears tnat the inherent ability of a corrugating adhesive to form ~igher green strength, which permits lmproved corru-gating speeds, may be predicted by a measurement of the area under an Instron force-time curve of a paste made in a particular manner from the prlmary active adhesive component that is selected for use in accordance with the present invention.
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` The Instron force-time curve of a paste of a prlmary active adhesive component may be determined in accordance with the following procedure.
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ST~NDARD INSTRON Ml~r[HOD
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An Instron Tensile Tester Model TT is fitted with com~resslon load cell "CM". A culture tube approximately 22 mm in diameter and 175 mm high ls fitted into a constant temperature cha~lber This chamber is a ~ 5 metal sleeve approximately 23 mm in diameter and 116 mm hLgh, wrapped ; with about 4 feet of 3/16 inch copper tubing and covered with asbestos wrap. The copper tubing is connected to constant temperature baths through appropriate inlets.
The starch slurry to be tested is placed into the culture tube to a depth of 2.75 inches.
The culture tube is lowered into the sleeve, which has been preheated by circulating water at a temperature of 210F through the copper tubing. A thermocouple probe having a diameter of 0.184 inch is inserted about 1 inch deep into the top surface of the slurry. Simul-` 15 taneously the machine and recorder are turned on, with the probe being driven into the slurry at a speed of 0.02 in/min. This heating cycle is :~ .
continued for 14 min. and then the hot water circulation is stopped.
After another minute, lce water is circulated through the tubing and continued for 15 minutes.
The curve generated on tbe recorder is called a force-tlme curve. The first 15 minute segment wlll be referred to as the heating , :
~ cycle and the second 15 ~inute segment as the cooling cycle.
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'' The test slurries for use OA the Instron are made as follows.
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~ predetermined quantity of unmodified corn starcl~ is slurried ln 110 ml ~ater. A ~redetermined amount oE a 4~ w/v borax (10 mol) soLution and a ~redetermined amount of a 20~ w/v NaO~I solution are added. Sufficient water is added to produce a total additional volume of 60 ml. The re-sulting slurry is heated at a temperature of 212F, with agitation for 5mimltes, and then allowed to stand for 5 minutes. It is then immediately added to the ~econd slurry which has been previously prepared.
The second slurry is prepared by slurrying 50 gm of the test starch in 165 ml of water. The first slurry is then mixed with this slurry and the admixture stirred for 15 min. It is then immediately tested on the Instron tester.
A sample of unmodified corn starch is run as the test starch under these standard test conditions. The force-time heating and cooling curves are generated as described above and the area under each of these ; 15 segments is independently determined.
The identical procedure is then followed for the starch material to be tested. The areas under the heating curve for the test starch is compared with the area for unmodified corn starch. The same is done for the areas under the cooling curve. It must be stressed that the areas -20 under each of the segments of the curves are treated independently of each other.
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- The absolute areas determined in this manner are arbitrary ~ .
; values largely determined by the test procedure. The crucial feature of the test ~s not these absolute values~ but the ratio of the areas ., .
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for the test starch to the areas Eor the unmodified corn starch, ~hcn performe~ under the same test conditions. This means that the pre-determined amounts of carrier starch, borax and sodium hydroxicle are identical.
While the Instron test does not duplicate exactly the viscosity and gel structure on the glue line, it does give a relative measurement of the ability of a particular primary adhesive component to develop high green strength in a corrugating honding environment.
~' It has been found that to produce the desired 20% improvement in machine speed, the ester material must exhibit at least about a 30%
greater area under both the Instron heating and cooling curves compared to unmodified corn starch. In other words, a saponifiable starch ester which will exhibit a 30% Instron improvement (greater area) Imder both `~ heating and cooling curves will produce machine speeds at least about 20%
faster than machine speeds obtainable using unmodified corn starch, on the same machine.
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The useful starch ester materials may also be defined as having a total saponifiable degree of substitution (D.S.) of at least about 0.015. The upper limit on saponifiable D.S. is economic and functional.
It is necessary that the material have a gel temperature high ellough so that it will not gelatini~e prior to use; such as dur:lng manufacture of the derivative or during formulation of the adhesive composition.
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~ -17-While the exact upper limit on saponLELable D.S. w-Lll depeQ(I on the ~)lrtl-cular substituent belng used, in general, for esters oE monocarboxyL-Lc acids it will be about 0.1 and for mono-esters oE dlc:arboxylic ~I`id9 about n.o6.
It ls known that in the environment of the adhesive formulation, the ester will saponify in a relatively short time. This means that the ester will have substantially completely saponified prior to its appli-cation to the flute tips. The exact form of the saponified starch material is not known. It is possibly a complex with either the caustic or borax which are generally present in the system.
It is believed that a portion of the imp~svement in machine speed may be ascribed to a reduced alkali ]evel in the formulation. As the ester material saponifies, some of the alkali is used up.
. ' Certain of the beneficial properties of the starch esters are retained in the saponified product. Prior to actually being applied to the~flute tips, the ester has substantially completely saponified. It has been found that a modified starch material may be produced by -~ saponifying the starch ester. The saponification is carried out in the presence of alkali and may fur~her include borax in the sapon~lfication medium~ The ~odified material may then be dried. This process, i.e., esterification followed by saponification yields a material whi~h is different from the original unmodified s~arch material. This modified ` material may be used in a corru~ating adhesive formulation in a manner `-' ,, .
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similar to the use of the starch esters. Improvecl green bond strengtl compared with unmodified corn starch is found. The exact mechanism of the modification is not known, but may be a pllysical disruption of the granules, or may be a small amount of a complex formed between the alkali and the starch.
The use of a reduced quantity of alkali in the corrugating adhesive formulation does not account for all of the machine speed improvement. When unmodified corn starch and a starch ester in accord-ance with this invention are run at identical actual alkali levels9 machine speeds are still greatly faster using the starch ester materials.
The starch esters may be formed in sitù at the corrugating machine when preparing the adhesive formulation. It is merely necessary to add an ester forming reagent to the formulation. The conditions are those which wil~ permit very rapid esterificationp followed by irrever:lble eapDDitication to take :
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place. The esterifyillg reagents are the aforementioned conventional materials.
The quantity of reagent to be added is that amount which would, in the absellcc of saponi~ication, produce a product having a saporlifiable D.S. suitable Eor use in accordance with this inventionO Generally, a reagent such as acetic anhydride will have a reaction efficiency of about 50~ to about 70% under the conditions found in a corrugating adhesive formulation.
The order of addition of the materials to the adhesive formulation is not critical to the success of the in situ method. It is, of course, necessary that the esterification reagent not be allowed to remaln in an environment for any lengthy period of time where it might, at least in part, decompose.
In order to more fully understand the invention the following demon-strations of specific embodiments of the invention are described. They are illustrative and informative in nature and in no way are intencled to limit the scope of the invention.
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E~AMPLE I
Comparative Corrugated Board Production Runs In order to demonstrate that the corxugating adhesives of the present $nvention provide improvements over conventional unmodified starch Stein-Hall adhesive formulations, it was necessary to establish a limit, above which speed, conventional s~arch adhesives no longer bind the corrugating board sufficiently to prevent dela~ination during the subsequent operations, and then determine at what machine speed corrugated board using adhesives prepared ln accordance with the presen~ invention could be produced before they reached the failure point.
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The corrugatecl board man~lfact~lred in all tests oE th-Ls example wa~ a double backer board consisting of a 26 pound corrugated sheet positioned between two 42 pound Kraft liners. A commercial double-backer corrugated paper machine was used. All hot plate temperatures were set at 300 F. for this trial.
Initially the glue clearance of the adhesive applicator was set at 0.014 in. A
Stein-Hall type conventional corrugating adhesive, for use as a control, and corrugating adhesive formulations prepared in accordance with the present inventlon, were made as tabulated below.
Conventional Doub_e Backer Formula Primary Mixer Add 10.0 gal. water Add 20.0 lb. unmodified corn starch Heat to 150 F.
Add 3.3 lb. NaOH dissolved in 2.0 gal. water Agitate for 15 min.
Then add 10.0 gal. cooling water Mix for 10 min. and hold at 110 F.
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Seconda~x MixPr .' .
Add 30 gal. water ancl heat to 90 F.
Add 3.4 lb. 10 mol borax Add 100 lb. unmodified corn starch Add primary to secondary over a period of 30 min.
and hold at llO F.
Adjust viscosity to 60 sec~ with 4.5 gal. water -.
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Double Backer Formula ~ccorclLn~_to the Present [llventio Primary _ixer Add 10.0 gal. water Add 19.0 lb. unmodified corn starch Heat to 150 F
Add 3.9 lb. NaOH dissolved in 2.0 ~al. water `~ Agitate for 15 min.
Add 10.0 gal. cooling water and hold at 110 F.
Secondary Mixer Add 30.0 gal. water and heat to 90 F.
Add 1.5 lb. 10 mol borax Add 100 lb. starch acetate succinate (0.027 D.S.
acetate, 0.01 D.S. succinate)~
Add primary to secondary over a period of 30 min.
and hold at 110 F.
` Mix 5 min. and add 1.5 lb. 10 mol borax Add 4.5 gal. water to adjust viscosîty in 60 sec.
The adhesive properties of these formulations were determined to be as indicated beIo~.
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Stein-Hall Temp.
Solids Viscosity Sec. F.
Conventional 19.1 65 110 s~ Acetate/Succinate 20.0 45 110 :!
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- Bo~h of ~hese adheslve formulations were evaluated, successively, ~ on the same corrugati~g machine.
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Using the control adl~esive above, ttle maximum speecl obtal~lab:le On the corrugating machine, before the corrugated board began to deLamlnate at the cutting knife, was 450 fpm.
Using the starch acetate succinate as the raw starch portion oE the Stein Hall double backer adhesive formulation, speeds of 600 feet per minute were achieved. At this point, the glue clearance on the double backer applicator was increased from 0.014 inches to 0.016 inches and the corrugating machine was run at 700 feet per minute, or 55% better than the control, with excellent double backer green strength. Above this speed the single facer corrugating machine, which was supplying the single face corrugated paper to the double backer, would not keep up due to the fact that the adhesive formulation being used in the single facer stage was a typical conventional unmodified starch adhesive and not enough heat could be applied by the machine to cause sufficiently rapld gelatinization of that adhesive.
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~ owever, wlth the single facer bridge full of board made at lower machine speeds,the double backer section could be run in brief spurts at speeds well over 800 feet per minute. The limitation on these spurts occurred when unbonded single facer sheets would reach the double backer glue machine. It is apparent, therefore, that the starch acetate succinate adhesive will produce good double backer corrugated board at corrugator speeds considerably in excess of 700 feet per minute.
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EXAMPI~ II
Corrugated_Board Production Runs A further test of corrugat~ng was conducted using the same corrugating - machine, and :ubstantially the same operating conditions, as for the runs in .
E~ample I. The machine was used for making board usi~g 42 pound llners and a 26 pound corr~ated medium, with glue clearances of 0.013 :Lnches and 0.014 inches.
The starch derivative used as the primary adhesive component was characterized as follows. It was a starch acetate succinate having a D.S.
acetate = 0.011; D.S. succinate = 0.015. It was found that an adhesive formu-lation made up as descrlbed below could be run successfully at quite high machine speeds. The formulation was as follows:
Primary Water 50 gal.
Unmodified corn starch 90 lbs.
Caustic Soda (dissolved -in 5 gals. water)20 lbs.
Eleat to 160 F. and hold 15 minutes Water 33 gals.
Secondar~
Wa~er 200 gals.
Borax (10 mol) 9 lbs.
Starch Acetate Z0 Succinate 500 lbs.
Add the primary over a period of 30 min.
Add additional Borax (10 mol) 5 lbs.
With the glue settings set a 0.013 inches, the corrugat~r could be run efficiently at 700 feek per minute. Decreasing the glue clearances to 0.009 inches allowed the attainmen~ of sustained corrugator speedæ of o~er 800 fpm. At this point the corrugating machine had reached its practical limit and 62 pound liners were then substituted for the 42 pound l:Lners.
. - 2~ -With the heavier liner, the corrugatlng ~lachlne eEfLcientLy produced corrugated board at speeds of 650 fpm. at a setting of :350 F. on the corrug~tor hot plates. Conventional starch adhesives have a limLt of 300-500 fpm. at 300 F. and 350-400 Epm at 350 F. hot plate temperatures when uslng these liners on this machine. Corrugating efficiency was dramatically superior, using the Eormulations of the invention.
EXAMPLE III
dditional Production Runs, Stein-Hall Formulations Additional runs were made on the same machine in accordance with the last-mentioned procedure of Example II using 62 pound liners with primary ad-hesive components characterized as follows:
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- Starch Derivative -~ Starch acetate succinate (D.S. acetate = 0.013;
D.S. succinate = 0.016).
S~arch acetate succinate (D.S. acetate = 0.013;
D.S. succinate = 0.014) The starch derivative identified as (a) was prepared in an adhesive formulation as described in Example II, and used on a corrugating machine with glue clearances of 0.007 inches with the hot plate set at 300 F. Initially machine speeds of 600 fpm were attained. As the glue clearance was opened up to 0.010 inches, machine speeds of up to 750 fpm were achieved. When the hot plate temperatures were raised to 350 F., machine speeds of 775 fpm were attained, with satisfactory board production.
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When an adhesive formulation as described in Example II, incorporating , ~, the starch derivative identiEied above as ~b), was run on the corrugating machine .
wi~h ~he glue clearance~ at 0.007 inches, and the hot plates set at 350 F., corrugated board was made successfully at 800 fpm.
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t~' EX~MPLE LV
_-Carrier Type FormuLation A small-scale demonstration was conducted with an adhesive Eormu:Lation (IV-l) containing 18-20% of starch acetate succinate (D S. acetate 0.0266;
~.S. succinate 0.018) as the primary adhesive component~ in an aqueous slurry.
This is equivalent, in composition, to a conventional ]l-bag mix in a mill (i.e., equivalent to a formulation containing 11 bags oE the adhesive compon&nt in approximately 650 gallons of total adhesive).
A second demonstration was conducted with an adhesive formulation (IV-2) made of a mixture of unmodified corn starch and the primary adhesive component, in such proportions that on a mill scale~ 2 of the 11 bags (i.e., about 18%) would be unmodified corn starch, the ramainder being the primary adhesive component.
Stein-Hall viscosity measurements were made on each of these formu-lations after they were made up ready for use. The make-up procedure was that described in U. S. 3?355~307~ and was as follows. 250 g of starch material was slurried in 890 ml of water at 105 F. 275 ml of 4.0% sodium hydroxide (caustic~ was added to the starch slurry at room temperature over a perlod of
. The degree oE tackiness developed after gelatinization.
However, subsequent developments indicate that the green bond strength depends significantly on the evaporation oE moisture from the bond site: Thayer & Thomas Analysis of the Glue Lines in Corru~ated Board, TAPPI; 22nd Corrugated Containers Con-ference, May 1971.
- It has now been discovered that a select class of starch materials, when used as the adhesive component in a corrugating adhesive composition, demonstrate superior properties. One way to take advantage of these properties is by the use of machine speeds that are ordinarily from 5~/O to 100% higher than had been considered possible with conventional Stein-Hall type corrugating adhesive compositions, or with the more recently introduced no-carrier corrugating adhesive compositions, at generally the same levels of adhesive usage.
According to the invention in one aspect there is provided a composition suitable for use as a corrugating adhesive including at least two phases, comprising a carrier phase and a la~ent adhesive phase that is dispersed in tha carrier phase; the latent adhesive phase comprising an ungelatinized, granular saponifiable starch ester and a quantity of alkali sufficient to substantially completely ~ saponify the saponifiable starch ester, the composition < being tractable on a corrugating machine.
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In another aspect of the invention there is provided a process for uniting at least two items of materia:L comprising applying between the items a composition of the invention, and activating the composition to form an adhesive bond.
Still further the invention provides in another aspect an article of manufacture comprising a plurality of items of material joined with an adhesive boncl comprised of a composition of the invention.
` In yet another asp2ct of the invention there is provided an improvement in a process for the preparation of a corrugating adhesive of the no-carrier type, which consists in replacing at least a portion of the starch material with a saponifiable starch ester.
- Stated in another way, superior results have been obtained when the primary active adhesive component in a corrugating adhesive formulation is a saponifiable starch ester material which exhibits at Least about a 3~/O greater area under anInstron force-time heating curve and at least about a 30/0 greater area under an Instron force-time cooling curve, compared with unmodified corn starch under the same test conditionsO
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Preferred adhesive compositions of the present invention are based on the use of primary adhesive components which are saponifiable starch esters having a saponifiable degree of substi-tution (D.S.) o~ at least about 0.015.
As used herein, "saponifiable degree of subs-titution" means the total D,S, of all saponifiable ester groups on the starch moleculeO Particularly preferred starch lester materials are starch acetate, starch succinate and starch acetate succinate.
One or more of these active adhesive components can be used 10 to advantage either in a Stein-Hall type formulation or in a no-carrier type formulation, with equally superior improvements over the prior art.
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- - -The most ~reEerred aclhesive component is a stclrcil acetate su(clnate having a saponifiable degree of substitution (D.S ) in the range ~rom abouL
0.025 to about 0.045. Thase D.S. levels represent ranges that are appLicable to starch acetate succinate. Other derivatives that are usef~ll in accordance with the invention will have their own preferred D.S. ranges. Gener~lly, if the D.S. level is too low, the derivatized material will not exhibit significant improvement over unmodified corn starch when used in a corrugating adhesive formulation. If the D.S. level is too high, the gelatinization temperature may be unworkable.
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The specific materials that have been identified, for use in accordance with the invention~ are starch derivatives identified above. These starch derivatives may be prepared immediately prior to use, i.e., in situ at the corrugating machin~, or they may be prepared in advance, and may be formulated into corrugating adhesive compositions as with other starch ., materials that are to be used for such purposes in accordance with prior art practices.
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It is also possible to utilize modified starch materials which ~ may be produced from the aforementioned starch esters. These modified ;~ starch materials are produced by substantially completely saponifying the 2Q starch esters and removing the salts formed thereby. The resulting modi~ied , starch material may then be drled. Although the derivative has been sub-', stantially completely removed from the starch material, the modified starch ` ~ retains the beneficial properties of the ester materialO
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- Wh:ile we do not fully understand the reason l~hy the speclclL
materials identi~ied hy our invention are superior Eor use in corrugating adhesives in partlcular, it can be theorized that they not on]y develop unusually high viscosity upon gelatinization, but in addition, provide a hlgh green strength without the necessity oE solvent evaporation.
I~hile the flnal form of the useful starch materials of this invention is not known, it is known that the esters materials saponiEy substantially completely in a short period of time in the environment present in the mixing apparatus on the corrugating machine.
The invention will be better understood by a more detailed explanation of several specific embodiments thereof. All parts and percentages are by weight, on a commercial basis, unless express'y stated to be otherwise~ The commercial basis for the starch materials includes about 12r moisture.
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I)l`'l`AILI~I) DESCRIP'I`10~ OF TtlE PREFERRED EMBODIMEN'rS
The proper selection of the primary active aclhes-Lve component is of great importance Eor the proper practice of the present invention.
In preparing saponifiable starch esters for use as the primary active adhesive components, the starting starch material may be derived from any vegetable source. Starches derived from non waxy grain sources, such as, for example, corn, wheat, rice, and grain sorghum are preferred.
The ~erm "starch" is used broadly herein and encompasses flour, un-modified starch and tailings. Corn starch is a preferred starting starch ~ 10 material.
- The initial starcll is esterified, as will be described presently, to produce the primary active adhesive component that has the desired characteristics in accordance with the invention.
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In a typical corrugating adhesive formulation, it is usual to add bora~ and caustic to increase the adhesive strength and tack, and to ad-~ust the gelatiniæation temperature. When using either a carrier-type or a no-carrier type adhesive formulation, the Stein-Hall viscosity of the formulation must be within the conve.ntional range to permit an adequate amount of adhesive to be applied to the flute tips at all machine , 20 speedsO Generally, to be tractable on a corrugating machine, an adhesive :,j ~orDlation should have a Stein~Hall viscosity in the range of about ' 20 sec. to about 100 sec. The optimum Stein-Hall viscosity of the formu-"
lation will depend on the particular corrugating machine.
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Unless otherwise speciEied, the materiaLs ~escribed an~l claimed herein are those ~hich are to be added to ~orm the adhesive formulation. In the particular environment of the adhestve formula-tion, the form of certain materials may be altered. For example, the starch ester will saponify in a typical corrugating adhesive formulation.
This will reduce the actual amount of alkali present. The borax may be present in any of several species, or as an equilibrium mixture of these species, depending prilDarily on the pH of the formulation.
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As previously described, it is standard practice in the corrugating industry to add alkali and borax to the adhesive formulations.
While formulations ~hich do not include these materials may be used as corrugating adhesives, it is preferred to include both of these materials to the formulations of this invention.
The borax is generally utilized to increase the gel structure of the adhesive paste. However, an excess of borax may have an adverse effect on the cured bond strength. In addition, borax has the tendency to increase the gel tempe~ature of the formulation. Generally, up to about 5% borax (10 mol) may be incorporated into the formulations.
A more usual quantity would be about 2% to about 3%. The percentages are based on the total starch material present in the formulation, including both the primary active adhesive material and the carrier material. If 5 mol borax is to be used instead of 10 mol, it is necessary to compensate for the reduced water of hydration. In no-carrier systems, ` boric acid may be utilized as a reaction stopper. The boric acid will : .
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~uicklv be conver~ed to a horate and is tllen able to serve as a substL-tute for added borax. As used herein, the term "borax" will include those borates which are present due to the addition of boric acid.
Any standard alkali may be used. However, for economic reasons, S sodium hydroxide is most commonly utili~ed. The aLkali serves to reduce the gel temperature of the adhesive formulation to a readily tractable point. Generally this will be in the range of frorn about 145~F to about 150F, but may in some applications range from about 140F to about 160F.
It is important that large amounts of alkali not be used in any corru-. ~
gating adhesive formulation, whether conventional or in accordance with - this invention, as alkali tends to reduce gel structure format:Lon.
Generally up to about 5% alkali (calculated as sodlum hydroxide) may be used, based on total starch material in the system. More usual amounts would be from about 3% to about 3.5%.
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~--` 15 It is of critical importance to the practice of this invention that at least enough alkali to substantially completely saponify the . , ~ starch ester be used. Tha amounts of alkali referred to above are . .
~ the quantity of alkali in excess of this minimum amount.
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The particular starch ester to be used in the practice of this invention is not critical, as long as it will saponify in the environ-ment of a corrugating adhesive formulation. Consequently, inexpensive and " .
" ~ simple starch esters, such as starch acetate are preferred. Particularly ;l~ preferred is the mixed ester, starch acetate succinate.
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The starch esters may be obtained commercially, or may be made by any conven-tional method, such as by reacting unmodified starch with acid anhydrides 3 acid halides, vinyl esters and -the like. The same reagents may be used when util-izing the 1n situ method of this invention. I-t is necessary however that the esterification be carried out at a temperature which is below -the ac-tual gelatiniza-tion -temperature of both the unmodified starch and the starch es-ter.
In addition, the water conten-t of an adhesive form-ulation should be adjus-ted so -that an extremely -tacky adhesive characteristic is obtained immediately after gelatinization.
This implies that sufficient water is present for complete ~-gelatinization. It is most desirable that rapid developmen-t ;~ of tack is obtained upon the application of heat in the corrugating equipment.
The amounts of starch materials utilized in the ad-hesive formulations of this invention are similar to those utilized in conventional formulations. Generally, -the granular starch component of a Stein-Hall type formulation will contain from about 10% to about 25% starch. The final adhesive mixture generally has from about 12% to about 25% of its total s-tarch ~,~
in the form of the gelatinized carrier.
; The starch esters of this invention may also be u~ed as the carrier portion of a Stein-Hall type adhesive. In such instances, it may be possible to reduce -the quantity of carrier `!` somewhat due to -the greater thickness of these starch es-ters.
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The desirable clegree of substitution depencls upon the ~lrt i( ular initiaL starch material selected However, in general, it hcls been ~o~lncl desirable to utilize a saponifiable D.S. of at least about 0.015. Starch esters having a saponifiable D.S. of at least about 0.015 have been found to satisfy the Instron test criteria, discussed infra, and therby permlt machine speeds at least about 20% greater than those attainable utilizing unmodified corn starch as the primary active adhesive component.
Generally D.S. levels greater than 0.015 will produce even faster machine speeds. It has been found preferable to utilize saponifiable starch esters havlng a saponifiable D~S. in the range of from about 0.025 to about 0.045. The utilization of such materials will generally permit operation of a corrugating machine at speeds of up to about 100% higher than those attaînable using conventional adhesives.
The green strength, and the viscosity of ~he gelatinized corrugating adhesive that produces the green stren~th, cannot conveniently be sub~ected to direct quantitative measurement at the exact site of the bond. However, it appears tnat the inherent ability of a corrugating adhesive to form ~igher green strength, which permits lmproved corru-gating speeds, may be predicted by a measurement of the area under an Instron force-time curve of a paste made in a particular manner from the prlmary active adhesive component that is selected for use in accordance with the present invention.
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` The Instron force-time curve of a paste of a prlmary active adhesive component may be determined in accordance with the following procedure.
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ST~NDARD INSTRON Ml~r[HOD
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An Instron Tensile Tester Model TT is fitted with com~resslon load cell "CM". A culture tube approximately 22 mm in diameter and 175 mm high ls fitted into a constant temperature cha~lber This chamber is a ~ 5 metal sleeve approximately 23 mm in diameter and 116 mm hLgh, wrapped ; with about 4 feet of 3/16 inch copper tubing and covered with asbestos wrap. The copper tubing is connected to constant temperature baths through appropriate inlets.
The starch slurry to be tested is placed into the culture tube to a depth of 2.75 inches.
The culture tube is lowered into the sleeve, which has been preheated by circulating water at a temperature of 210F through the copper tubing. A thermocouple probe having a diameter of 0.184 inch is inserted about 1 inch deep into the top surface of the slurry. Simul-` 15 taneously the machine and recorder are turned on, with the probe being driven into the slurry at a speed of 0.02 in/min. This heating cycle is :~ .
continued for 14 min. and then the hot water circulation is stopped.
After another minute, lce water is circulated through the tubing and continued for 15 minutes.
The curve generated on tbe recorder is called a force-tlme curve. The first 15 minute segment wlll be referred to as the heating , :
~ cycle and the second 15 ~inute segment as the cooling cycle.
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'' The test slurries for use OA the Instron are made as follows.
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~ predetermined quantity of unmodified corn starcl~ is slurried ln 110 ml ~ater. A ~redetermined amount oE a 4~ w/v borax (10 mol) soLution and a ~redetermined amount of a 20~ w/v NaO~I solution are added. Sufficient water is added to produce a total additional volume of 60 ml. The re-sulting slurry is heated at a temperature of 212F, with agitation for 5mimltes, and then allowed to stand for 5 minutes. It is then immediately added to the ~econd slurry which has been previously prepared.
The second slurry is prepared by slurrying 50 gm of the test starch in 165 ml of water. The first slurry is then mixed with this slurry and the admixture stirred for 15 min. It is then immediately tested on the Instron tester.
A sample of unmodified corn starch is run as the test starch under these standard test conditions. The force-time heating and cooling curves are generated as described above and the area under each of these ; 15 segments is independently determined.
The identical procedure is then followed for the starch material to be tested. The areas under the heating curve for the test starch is compared with the area for unmodified corn starch. The same is done for the areas under the cooling curve. It must be stressed that the areas -20 under each of the segments of the curves are treated independently of each other.
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- The absolute areas determined in this manner are arbitrary ~ .
; values largely determined by the test procedure. The crucial feature of the test ~s not these absolute values~ but the ratio of the areas ., .
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for the test starch to the areas Eor the unmodified corn starch, ~hcn performe~ under the same test conditions. This means that the pre-determined amounts of carrier starch, borax and sodium hydroxicle are identical.
While the Instron test does not duplicate exactly the viscosity and gel structure on the glue line, it does give a relative measurement of the ability of a particular primary adhesive component to develop high green strength in a corrugating honding environment.
~' It has been found that to produce the desired 20% improvement in machine speed, the ester material must exhibit at least about a 30%
greater area under both the Instron heating and cooling curves compared to unmodified corn starch. In other words, a saponifiable starch ester which will exhibit a 30% Instron improvement (greater area) Imder both `~ heating and cooling curves will produce machine speeds at least about 20%
faster than machine speeds obtainable using unmodified corn starch, on the same machine.
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The useful starch ester materials may also be defined as having a total saponifiable degree of substitution (D.S.) of at least about 0.015. The upper limit on saponifiable D.S. is economic and functional.
It is necessary that the material have a gel temperature high ellough so that it will not gelatini~e prior to use; such as dur:lng manufacture of the derivative or during formulation of the adhesive composition.
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~ -17-While the exact upper limit on saponLELable D.S. w-Lll depeQ(I on the ~)lrtl-cular substituent belng used, in general, for esters oE monocarboxyL-Lc acids it will be about 0.1 and for mono-esters oE dlc:arboxylic ~I`id9 about n.o6.
It ls known that in the environment of the adhesive formulation, the ester will saponify in a relatively short time. This means that the ester will have substantially completely saponified prior to its appli-cation to the flute tips. The exact form of the saponified starch material is not known. It is possibly a complex with either the caustic or borax which are generally present in the system.
It is believed that a portion of the imp~svement in machine speed may be ascribed to a reduced alkali ]evel in the formulation. As the ester material saponifies, some of the alkali is used up.
. ' Certain of the beneficial properties of the starch esters are retained in the saponified product. Prior to actually being applied to the~flute tips, the ester has substantially completely saponified. It has been found that a modified starch material may be produced by -~ saponifying the starch ester. The saponification is carried out in the presence of alkali and may fur~her include borax in the sapon~lfication medium~ The ~odified material may then be dried. This process, i.e., esterification followed by saponification yields a material whi~h is different from the original unmodified s~arch material. This modified ` material may be used in a corru~ating adhesive formulation in a manner `-' ,, .
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similar to the use of the starch esters. Improvecl green bond strengtl compared with unmodified corn starch is found. The exact mechanism of the modification is not known, but may be a pllysical disruption of the granules, or may be a small amount of a complex formed between the alkali and the starch.
The use of a reduced quantity of alkali in the corrugating adhesive formulation does not account for all of the machine speed improvement. When unmodified corn starch and a starch ester in accord-ance with this invention are run at identical actual alkali levels9 machine speeds are still greatly faster using the starch ester materials.
The starch esters may be formed in sitù at the corrugating machine when preparing the adhesive formulation. It is merely necessary to add an ester forming reagent to the formulation. The conditions are those which wil~ permit very rapid esterificationp followed by irrever:lble eapDDitication to take :
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place. The esterifyillg reagents are the aforementioned conventional materials.
The quantity of reagent to be added is that amount which would, in the absellcc of saponi~ication, produce a product having a saporlifiable D.S. suitable Eor use in accordance with this inventionO Generally, a reagent such as acetic anhydride will have a reaction efficiency of about 50~ to about 70% under the conditions found in a corrugating adhesive formulation.
The order of addition of the materials to the adhesive formulation is not critical to the success of the in situ method. It is, of course, necessary that the esterification reagent not be allowed to remaln in an environment for any lengthy period of time where it might, at least in part, decompose.
In order to more fully understand the invention the following demon-strations of specific embodiments of the invention are described. They are illustrative and informative in nature and in no way are intencled to limit the scope of the invention.
"`'~
E~AMPLE I
Comparative Corrugated Board Production Runs In order to demonstrate that the corxugating adhesives of the present $nvention provide improvements over conventional unmodified starch Stein-Hall adhesive formulations, it was necessary to establish a limit, above which speed, conventional s~arch adhesives no longer bind the corrugating board sufficiently to prevent dela~ination during the subsequent operations, and then determine at what machine speed corrugated board using adhesives prepared ln accordance with the presen~ invention could be produced before they reached the failure point.
~:~
~:' . .
:.
The corrugatecl board man~lfact~lred in all tests oE th-Ls example wa~ a double backer board consisting of a 26 pound corrugated sheet positioned between two 42 pound Kraft liners. A commercial double-backer corrugated paper machine was used. All hot plate temperatures were set at 300 F. for this trial.
Initially the glue clearance of the adhesive applicator was set at 0.014 in. A
Stein-Hall type conventional corrugating adhesive, for use as a control, and corrugating adhesive formulations prepared in accordance with the present inventlon, were made as tabulated below.
Conventional Doub_e Backer Formula Primary Mixer Add 10.0 gal. water Add 20.0 lb. unmodified corn starch Heat to 150 F.
Add 3.3 lb. NaOH dissolved in 2.0 gal. water Agitate for 15 min.
Then add 10.0 gal. cooling water Mix for 10 min. and hold at 110 F.
. .
Seconda~x MixPr .' .
Add 30 gal. water ancl heat to 90 F.
Add 3.4 lb. 10 mol borax Add 100 lb. unmodified corn starch Add primary to secondary over a period of 30 min.
and hold at llO F.
Adjust viscosity to 60 sec~ with 4.5 gal. water -.
' ' : .
.9 L.~ d ~ ~
Double Backer Formula ~ccorclLn~_to the Present [llventio Primary _ixer Add 10.0 gal. water Add 19.0 lb. unmodified corn starch Heat to 150 F
Add 3.9 lb. NaOH dissolved in 2.0 ~al. water `~ Agitate for 15 min.
Add 10.0 gal. cooling water and hold at 110 F.
Secondary Mixer Add 30.0 gal. water and heat to 90 F.
Add 1.5 lb. 10 mol borax Add 100 lb. starch acetate succinate (0.027 D.S.
acetate, 0.01 D.S. succinate)~
Add primary to secondary over a period of 30 min.
and hold at 110 F.
` Mix 5 min. and add 1.5 lb. 10 mol borax Add 4.5 gal. water to adjust viscosîty in 60 sec.
The adhesive properties of these formulations were determined to be as indicated beIo~.
, ~
:, .
, Double Backer .' ' ' :
' ~GOe . ::
Stein-Hall Temp.
Solids Viscosity Sec. F.
Conventional 19.1 65 110 s~ Acetate/Succinate 20.0 45 110 :!
~J
- Bo~h of ~hese adheslve formulations were evaluated, successively, ~ on the same corrugati~g machine.
~`' ., .
~ ~ - 22 --,. . : . :
Using the control adl~esive above, ttle maximum speecl obtal~lab:le On the corrugating machine, before the corrugated board began to deLamlnate at the cutting knife, was 450 fpm.
Using the starch acetate succinate as the raw starch portion oE the Stein Hall double backer adhesive formulation, speeds of 600 feet per minute were achieved. At this point, the glue clearance on the double backer applicator was increased from 0.014 inches to 0.016 inches and the corrugating machine was run at 700 feet per minute, or 55% better than the control, with excellent double backer green strength. Above this speed the single facer corrugating machine, which was supplying the single face corrugated paper to the double backer, would not keep up due to the fact that the adhesive formulation being used in the single facer stage was a typical conventional unmodified starch adhesive and not enough heat could be applied by the machine to cause sufficiently rapld gelatinization of that adhesive.
' ' .
~ owever, wlth the single facer bridge full of board made at lower machine speeds,the double backer section could be run in brief spurts at speeds well over 800 feet per minute. The limitation on these spurts occurred when unbonded single facer sheets would reach the double backer glue machine. It is apparent, therefore, that the starch acetate succinate adhesive will produce good double backer corrugated board at corrugator speeds considerably in excess of 700 feet per minute.
,:
EXAMPI~ II
Corrugated_Board Production Runs A further test of corrugat~ng was conducted using the same corrugating - machine, and :ubstantially the same operating conditions, as for the runs in .
E~ample I. The machine was used for making board usi~g 42 pound llners and a 26 pound corr~ated medium, with glue clearances of 0.013 :Lnches and 0.014 inches.
The starch derivative used as the primary adhesive component was characterized as follows. It was a starch acetate succinate having a D.S.
acetate = 0.011; D.S. succinate = 0.015. It was found that an adhesive formu-lation made up as descrlbed below could be run successfully at quite high machine speeds. The formulation was as follows:
Primary Water 50 gal.
Unmodified corn starch 90 lbs.
Caustic Soda (dissolved -in 5 gals. water)20 lbs.
Eleat to 160 F. and hold 15 minutes Water 33 gals.
Secondar~
Wa~er 200 gals.
Borax (10 mol) 9 lbs.
Starch Acetate Z0 Succinate 500 lbs.
Add the primary over a period of 30 min.
Add additional Borax (10 mol) 5 lbs.
With the glue settings set a 0.013 inches, the corrugat~r could be run efficiently at 700 feek per minute. Decreasing the glue clearances to 0.009 inches allowed the attainmen~ of sustained corrugator speedæ of o~er 800 fpm. At this point the corrugating machine had reached its practical limit and 62 pound liners were then substituted for the 42 pound l:Lners.
. - 2~ -With the heavier liner, the corrugatlng ~lachlne eEfLcientLy produced corrugated board at speeds of 650 fpm. at a setting of :350 F. on the corrug~tor hot plates. Conventional starch adhesives have a limLt of 300-500 fpm. at 300 F. and 350-400 Epm at 350 F. hot plate temperatures when uslng these liners on this machine. Corrugating efficiency was dramatically superior, using the Eormulations of the invention.
EXAMPLE III
dditional Production Runs, Stein-Hall Formulations Additional runs were made on the same machine in accordance with the last-mentioned procedure of Example II using 62 pound liners with primary ad-hesive components characterized as follows:
.
- Starch Derivative -~ Starch acetate succinate (D.S. acetate = 0.013;
D.S. succinate = 0.016).
S~arch acetate succinate (D.S. acetate = 0.013;
D.S. succinate = 0.014) The starch derivative identified as (a) was prepared in an adhesive formulation as described in Example II, and used on a corrugating machine with glue clearances of 0.007 inches with the hot plate set at 300 F. Initially machine speeds of 600 fpm were attained. As the glue clearance was opened up to 0.010 inches, machine speeds of up to 750 fpm were achieved. When the hot plate temperatures were raised to 350 F., machine speeds of 775 fpm were attained, with satisfactory board production.
, .
When an adhesive formulation as described in Example II, incorporating , ~, the starch derivative identiEied above as ~b), was run on the corrugating machine .
wi~h ~he glue clearance~ at 0.007 inches, and the hot plates set at 350 F., corrugated board was made successfully at 800 fpm.
.
'' . ~
:.
. .
. .
t~' EX~MPLE LV
_-Carrier Type FormuLation A small-scale demonstration was conducted with an adhesive Eormu:Lation (IV-l) containing 18-20% of starch acetate succinate (D S. acetate 0.0266;
~.S. succinate 0.018) as the primary adhesive component~ in an aqueous slurry.
This is equivalent, in composition, to a conventional ]l-bag mix in a mill (i.e., equivalent to a formulation containing 11 bags oE the adhesive compon&nt in approximately 650 gallons of total adhesive).
A second demonstration was conducted with an adhesive formulation (IV-2) made of a mixture of unmodified corn starch and the primary adhesive component, in such proportions that on a mill scale~ 2 of the 11 bags (i.e., about 18%) would be unmodified corn starch, the ramainder being the primary adhesive component.
Stein-Hall viscosity measurements were made on each of these formu-lations after they were made up ready for use. The make-up procedure was that described in U. S. 3?355~307~ and was as follows. 250 g of starch material was slurried in 890 ml of water at 105 F. 275 ml of 4.0% sodium hydroxide (caustic~ was added to the starch slurry at room temperature over a perlod of
4.5 min. The reaction was then stopped at 60~ cps. with 4.7g boric acid. The resulting paste consisted in each case of a substantially homogeneous suspension ~ of partially swollen ~ranules.
`~ The Stein-~all viscosity observations were made at once, and then af~er each formulation had been stored for 24 hours, at 100 F. with mild agitation. Viscositie~ were similar to those for typical conven~ional formu-lations.
.
' d.~ ~
VLscoslt-ies of No-Carr-ier Adhe~iv~ Form~lLatio~s IV-l LV-2Typlcal conven~Lonal _ _ Eormulation Stein-Hall Viscos:ity seconds ` after makeup 21 20 ~1 after overnight storage 20 20 20 EXAMPLE V
An adhesive composition having the following formulation was prepared.
::
Primary Mixer Water lOO gal.
Unmodified corn ~tarch 220 lb.
NaOH (dissolved in lO gal.) 40 lb.
Heat to 160 F and hold 15 min.
Water 66 gal.
Secondary Mixer ~, Water 380 gal.
; Borax ~lO mol) 18 lb, Starch acetate succinate 1000 lb.
Drop primary over 30 minutes Water 20 gal.
Borax (10 mol~ lO lb.
Thi8 composition was run on a commercial machine using a 90 lb. liner on the single face side and two 90 lb. liners laminated on the machine on the double backer side. Good bonding was observed at speeds oE 320 fpm. Conventional adhesives can normally be run at about 200-250 fpm under the same test conditions.
.
The same composition was used as a laminating adhesive with satisfactory results. However, no numerical data was obtained as this particular machlne was-~ abl~ to operate at its top speed when using either a conventional fo~mulation or . ~ , ~ a eor:ul-tlon in accordance with this lnvention.
:, :, , . - : .-.
EXAMPL~ VI
Another batch oE adhe~sive was prepare~ using the same starcl~ acetn~e succinate as in Example V. The amount of carrier starch was 210 lbs; ~he remainder of the formulation identical to that of Example V. Using the ldentical 90, 90/90 laminate, liners as in Example V, speeds of 420 fpm were achleved. A
further run was made where the double backer liner consisted of a 90 lb. liner laminated on the machine using this adhesive formulation to a 69 lb. liner.
Speeds of 410 fpm. were obtained. The average speeds for both of these grades of board was 200 fpm. using conventional adhesives. The machine speed was not lir.21ted in these two cases by glue line failure, but by the possibility of drive overload at higher speeds.
`; EXAMPLE VII
~ .
To a slurry of 24.6g of unmodified corn starch in 330 ml water, 25 ml of a 2.75% (wt/vol~ borax xolution, 45 ml of 3.09% (wt/vol) NaOH and a mixture of 0.018 mole of succinic anhydride and 0.048 mole of acetic anhydride were added.
A laboratory evaluation of the resulting slurry indicated it to have superior adhesive properties.
EXAMPLE YIII
Example VII was repeated except that the succinic anhydride was re-. . .
placed by adipic anhydride. The product was again evaluated as being a superior , corrugating adhesive.
,~ ~
E~MPLE IX
, ~
Commercial runs were made on a series of products using the following formula~ions.
l . :
., , ;' ~ ' :
'' : ' -~
:~, ~ - 28 . .
.~ ~ . ,.
,3 ~ L~ q ?
. ' Pri~ary Mixer Water 50 gal.
Unmodified corn starch:LOO lb~s.
NaOH 17 lbs.
Heat to 160 F. and hold 15 min.
Water 33 gal.
Secondary Mixer Water 200 gal.
Borax (10 mol) 17 lbs.
Test starch 500 lbs.
Drop primary over 30 min.
When using the ester materials, the NaOH was increased to 20 lbs. and the bora~ to 18 lbs.
~ .
The formulations were run using 60 lb. liners with glue settings of 0.020" on the single facer and 0.018" on the double backer.
Run Machine sReed 7 fpm 1. Unmodified corn starch 425 2. Starch acetate succinate (DS 0.016~ 525 3. Starch acetate succinate (DS 0.024) 575 4. Starch acetate ~DS 0.020) 625 ` EXAMPLE X
Instron force-time curves were produced following the standard method for the following starch materials.
., .
.
~7 .j .i1~ .
.i ::
!
: :
. - 29 -.
. . . - . . - -:
~:
lleat CycleCool Cycle MaterLal ~ Imp. ~ p. _ I).S.
acetate/succinate40 78 .016 (a) acetate/succinate53 98 .024 acetate/succinate62 95 .024 (b) acetate/succinate74 134 .021 acetate 55 113 .020 (c) acetate/succinate71 163 .039 (d) acetate/succinate88 170 .02G (e) acetate/succinate22 75 .024 (f) ~ acetate/succinate44 88 .028 (g) :~ acetate/succinate68 118 .026 (h) ~ acetate/succinate79 122 .023 (i) ~,~
(a) This is material from Example IX, Run 2.
(b) This is material rom Example IX, Run 3.
(c) This is material from Example I~9 Run 4.
(d) This is material rom Example I.
:
' (e) This is material from Exa~ple V.
(f) This product showed only 13% machine speed lmprovement.
; 20 ~g) This is material from Example III, Run a.
h) This is material from Example III, Run b.
~i (i) This product showed 38% machine speed improvement.
, ~ .
"'~
. '~ .
~ ' ~`'i ' :'`1( i ', ~ ~ 30 -,' :
,. .
p~ 3~
EXAMPLE XI
Standard Instron force-time areas were determlned for the follow-ing starch materials.
Heat CycleCool Cycle Material 7O Imp. % Imp._ D.S.
Maleate 143 196 .037 Phthalate 138 64 .031 Proprionate 72 147 .035 Butyrate 74 133 .041 Iso-butyrate 75 110 .036 : Acetate 110 337 .102 Acetate 67 101 .033 Succinate 57 46 .014 Succinate 76 174 .044 ~; 15 Acet-ate 80 336 .080 ,~ .
. ~
Succinate 76 108 .024 ac~t.ate/succinate 86 228 .058 acetate/succinate 63 113 .029 . j :
acetate/succinate 27 25 .014 acetate/succinate 31 20 .009 Proprionate 40 42 .018 ~:~ Proprionate 26 35 .009 :
.~;
:i~
. ~~
. i . .
', d d `': 7 ' ' .
EXA~LE XII
The material from Example I was saponified in the presence of NaOH and borax. It was then washed with water to remove the caustic, borax and salts. A standard Instron force-time determination was made.
The material showed 58% heating cycle improvement and 82~ cooling cycle improvement.
EXAMPLE XIII
Example XII was repeated using the material of Example V. This showed 58% heating cycle improvement and 102% cooling cycle improvement.
'~
When an acid neutrali~ation step was introduced, no significant improvement compared with unmodified corn starch was shown.
' , :
While the starch acetate succinate, and the other specific primary adhesive components identifie~ herein, produce superior results as compared to formulations based on unmodified corn starch and other conveDtional materials, generally they may be used in making up corrugating adhesive formulations in the same general manner and i~ -~
substantially the same proportions as conventional materials~ such ... . .
~l as unmo~ified corn starch, would be used. Generally, the primary ., .
`adhesive components of this in~entlon may be used to replace a portion, ~, 20~ or preferably all, of the conventional primary adhesive components 1 , :
j in both Stein-Hall type and no-carrier type adhesi~e formulations. Specific variations ln amounts of componen~s and the addition of other components may be made in the formulations uslng these primary adhesive components '1 :
.~ , ~32 .' . ` ' in the same manner as are made for conventional adhesive -formu-lations. These variations are well known to those skilled in the art.
The details of the Stein-Hall type adhesive system may be found in the aforementioned U.S. Patent Nos. ~,051,025 and 2,102,937. The details of no-carrier type adhesive systems may be found in the disclosure of U.S. Patent No. 3,3S5,307.
When utilizing the novel compositions in a no-carrier environment, reaction stoppers such as acid anhydride~ and acid chlorides may be used. These may be broadly defined as acid or acid producing materials. Careful selection of the reaction stopper may thus allow the same material to serve as reaction stopper and ester-ifying reagent.
It is, of course, necessary that the final bond strength, ascontrasted with the green bond strength be suffi-ciently high to permit all conventional use of the product~
,, Pin adhesion tests have shown that the final bond strengths using the adhesiv~ formulations of thi~ invention are sub~
~ stantially equal to bond strengths of conventional adhesives, `~ 20 The adhesive formulations of this invention are also useful in applications other than producing corrugated paper-board~ For example, these formulations can find application in tube winding and manufacturing laminated board and multiwall paper sacks~
In addition, the conventional additives which will .~
impart water-resistance to the cured bonds may also be incorpor-ated into the formulation~
, ~ , ~
'J
~ 33 _ . . . .
. - - . .
l~hile the inventlon has been described in co[mect:ion with speciEic embodiments thereof, it will be understood that it :is capable of further modification, and thls application is intendecl to cover other variations, uses, or adaptions of the invention :Eollow:Lng, in general, the principles of the invention and including such departures from the present disclosure as are within Icnown or customary practice in the art to ~hich the inventipn pertains and as may be applied to the essential features hereinbefore set forth, and as are within the scope of the invention.
~' .
~:' : 34 ' ~ ' , . .
.
`~ The Stein-~all viscosity observations were made at once, and then af~er each formulation had been stored for 24 hours, at 100 F. with mild agitation. Viscositie~ were similar to those for typical conven~ional formu-lations.
.
' d.~ ~
VLscoslt-ies of No-Carr-ier Adhe~iv~ Form~lLatio~s IV-l LV-2Typlcal conven~Lonal _ _ Eormulation Stein-Hall Viscos:ity seconds ` after makeup 21 20 ~1 after overnight storage 20 20 20 EXAMPLE V
An adhesive composition having the following formulation was prepared.
::
Primary Mixer Water lOO gal.
Unmodified corn ~tarch 220 lb.
NaOH (dissolved in lO gal.) 40 lb.
Heat to 160 F and hold 15 min.
Water 66 gal.
Secondary Mixer ~, Water 380 gal.
; Borax ~lO mol) 18 lb, Starch acetate succinate 1000 lb.
Drop primary over 30 minutes Water 20 gal.
Borax (10 mol~ lO lb.
Thi8 composition was run on a commercial machine using a 90 lb. liner on the single face side and two 90 lb. liners laminated on the machine on the double backer side. Good bonding was observed at speeds oE 320 fpm. Conventional adhesives can normally be run at about 200-250 fpm under the same test conditions.
.
The same composition was used as a laminating adhesive with satisfactory results. However, no numerical data was obtained as this particular machlne was-~ abl~ to operate at its top speed when using either a conventional fo~mulation or . ~ , ~ a eor:ul-tlon in accordance with this lnvention.
:, :, , . - : .-.
EXAMPL~ VI
Another batch oE adhe~sive was prepare~ using the same starcl~ acetn~e succinate as in Example V. The amount of carrier starch was 210 lbs; ~he remainder of the formulation identical to that of Example V. Using the ldentical 90, 90/90 laminate, liners as in Example V, speeds of 420 fpm were achleved. A
further run was made where the double backer liner consisted of a 90 lb. liner laminated on the machine using this adhesive formulation to a 69 lb. liner.
Speeds of 410 fpm. were obtained. The average speeds for both of these grades of board was 200 fpm. using conventional adhesives. The machine speed was not lir.21ted in these two cases by glue line failure, but by the possibility of drive overload at higher speeds.
`; EXAMPLE VII
~ .
To a slurry of 24.6g of unmodified corn starch in 330 ml water, 25 ml of a 2.75% (wt/vol~ borax xolution, 45 ml of 3.09% (wt/vol) NaOH and a mixture of 0.018 mole of succinic anhydride and 0.048 mole of acetic anhydride were added.
A laboratory evaluation of the resulting slurry indicated it to have superior adhesive properties.
EXAMPLE YIII
Example VII was repeated except that the succinic anhydride was re-. . .
placed by adipic anhydride. The product was again evaluated as being a superior , corrugating adhesive.
,~ ~
E~MPLE IX
, ~
Commercial runs were made on a series of products using the following formula~ions.
l . :
., , ;' ~ ' :
'' : ' -~
:~, ~ - 28 . .
.~ ~ . ,.
,3 ~ L~ q ?
. ' Pri~ary Mixer Water 50 gal.
Unmodified corn starch:LOO lb~s.
NaOH 17 lbs.
Heat to 160 F. and hold 15 min.
Water 33 gal.
Secondary Mixer Water 200 gal.
Borax (10 mol) 17 lbs.
Test starch 500 lbs.
Drop primary over 30 min.
When using the ester materials, the NaOH was increased to 20 lbs. and the bora~ to 18 lbs.
~ .
The formulations were run using 60 lb. liners with glue settings of 0.020" on the single facer and 0.018" on the double backer.
Run Machine sReed 7 fpm 1. Unmodified corn starch 425 2. Starch acetate succinate (DS 0.016~ 525 3. Starch acetate succinate (DS 0.024) 575 4. Starch acetate ~DS 0.020) 625 ` EXAMPLE X
Instron force-time curves were produced following the standard method for the following starch materials.
., .
.
~7 .j .i1~ .
.i ::
!
: :
. - 29 -.
. . . - . . - -:
~:
lleat CycleCool Cycle MaterLal ~ Imp. ~ p. _ I).S.
acetate/succinate40 78 .016 (a) acetate/succinate53 98 .024 acetate/succinate62 95 .024 (b) acetate/succinate74 134 .021 acetate 55 113 .020 (c) acetate/succinate71 163 .039 (d) acetate/succinate88 170 .02G (e) acetate/succinate22 75 .024 (f) ~ acetate/succinate44 88 .028 (g) :~ acetate/succinate68 118 .026 (h) ~ acetate/succinate79 122 .023 (i) ~,~
(a) This is material from Example IX, Run 2.
(b) This is material rom Example IX, Run 3.
(c) This is material from Example I~9 Run 4.
(d) This is material rom Example I.
:
' (e) This is material from Exa~ple V.
(f) This product showed only 13% machine speed lmprovement.
; 20 ~g) This is material from Example III, Run a.
h) This is material from Example III, Run b.
~i (i) This product showed 38% machine speed improvement.
, ~ .
"'~
. '~ .
~ ' ~`'i ' :'`1( i ', ~ ~ 30 -,' :
,. .
p~ 3~
EXAMPLE XI
Standard Instron force-time areas were determlned for the follow-ing starch materials.
Heat CycleCool Cycle Material 7O Imp. % Imp._ D.S.
Maleate 143 196 .037 Phthalate 138 64 .031 Proprionate 72 147 .035 Butyrate 74 133 .041 Iso-butyrate 75 110 .036 : Acetate 110 337 .102 Acetate 67 101 .033 Succinate 57 46 .014 Succinate 76 174 .044 ~; 15 Acet-ate 80 336 .080 ,~ .
. ~
Succinate 76 108 .024 ac~t.ate/succinate 86 228 .058 acetate/succinate 63 113 .029 . j :
acetate/succinate 27 25 .014 acetate/succinate 31 20 .009 Proprionate 40 42 .018 ~:~ Proprionate 26 35 .009 :
.~;
:i~
. ~~
. i . .
', d d `': 7 ' ' .
EXA~LE XII
The material from Example I was saponified in the presence of NaOH and borax. It was then washed with water to remove the caustic, borax and salts. A standard Instron force-time determination was made.
The material showed 58% heating cycle improvement and 82~ cooling cycle improvement.
EXAMPLE XIII
Example XII was repeated using the material of Example V. This showed 58% heating cycle improvement and 102% cooling cycle improvement.
'~
When an acid neutrali~ation step was introduced, no significant improvement compared with unmodified corn starch was shown.
' , :
While the starch acetate succinate, and the other specific primary adhesive components identifie~ herein, produce superior results as compared to formulations based on unmodified corn starch and other conveDtional materials, generally they may be used in making up corrugating adhesive formulations in the same general manner and i~ -~
substantially the same proportions as conventional materials~ such ... . .
~l as unmo~ified corn starch, would be used. Generally, the primary ., .
`adhesive components of this in~entlon may be used to replace a portion, ~, 20~ or preferably all, of the conventional primary adhesive components 1 , :
j in both Stein-Hall type and no-carrier type adhesi~e formulations. Specific variations ln amounts of componen~s and the addition of other components may be made in the formulations uslng these primary adhesive components '1 :
.~ , ~32 .' . ` ' in the same manner as are made for conventional adhesive -formu-lations. These variations are well known to those skilled in the art.
The details of the Stein-Hall type adhesive system may be found in the aforementioned U.S. Patent Nos. ~,051,025 and 2,102,937. The details of no-carrier type adhesive systems may be found in the disclosure of U.S. Patent No. 3,3S5,307.
When utilizing the novel compositions in a no-carrier environment, reaction stoppers such as acid anhydride~ and acid chlorides may be used. These may be broadly defined as acid or acid producing materials. Careful selection of the reaction stopper may thus allow the same material to serve as reaction stopper and ester-ifying reagent.
It is, of course, necessary that the final bond strength, ascontrasted with the green bond strength be suffi-ciently high to permit all conventional use of the product~
,, Pin adhesion tests have shown that the final bond strengths using the adhesiv~ formulations of thi~ invention are sub~
~ stantially equal to bond strengths of conventional adhesives, `~ 20 The adhesive formulations of this invention are also useful in applications other than producing corrugated paper-board~ For example, these formulations can find application in tube winding and manufacturing laminated board and multiwall paper sacks~
In addition, the conventional additives which will .~
impart water-resistance to the cured bonds may also be incorpor-ated into the formulation~
, ~ , ~
'J
~ 33 _ . . . .
. - - . .
l~hile the inventlon has been described in co[mect:ion with speciEic embodiments thereof, it will be understood that it :is capable of further modification, and thls application is intendecl to cover other variations, uses, or adaptions of the invention :Eollow:Lng, in general, the principles of the invention and including such departures from the present disclosure as are within Icnown or customary practice in the art to ~hich the inventipn pertains and as may be applied to the essential features hereinbefore set forth, and as are within the scope of the invention.
~' .
~:' : 34 ' ~ ' , . .
.
Claims (23)
1. A composition suitable for use as a corrugating adhesive including at least two phases, comprising:
a carrier phase and a latent adhesive phase that is dispersed in said carrier phase;
said latent adhesive phase comprising:
a) an ungelatinized, granular saponifiable starch ester, having a saponifiable D.S. of at least about 0.015; and b) a quantity of alkali sufficient to substantially completely saponify the saponifiable starch ester, said composition being tractable on a corrugating machine.
a carrier phase and a latent adhesive phase that is dispersed in said carrier phase;
said latent adhesive phase comprising:
a) an ungelatinized, granular saponifiable starch ester, having a saponifiable D.S. of at least about 0.015; and b) a quantity of alkali sufficient to substantially completely saponify the saponifiable starch ester, said composition being tractable on a corrugating machine.
2. A composition in accordance with claim 1, wherein said carrier phase comprises a gelatinized, unmodified corn starch.
3. A composition in accordance with claim 1, wherein said carrier phase comprises carboxymethylcellulose.
4. A composition in accordance with claim 1, wherein said composition further includes up to about 5% additional alkali and up to about 5% borax (10 mol), based on total starch material, commercial basis.
5. A composition in accordance with claim 4, wherein said saponifiable starch ester is a saponifiable corn starch ester.
6. A composition in accordance with claim 4, wherein said saponifiable starch ester is selected from the group consisting of starch acetate, starch succinate, starch acetate succinate, and mixtures thereof.
7. A composition suitable for use as a corrugating adhesive including at least two phases, comprising:
a carrier phase and a latent adhesive phase that is dispersed in said carrier phase;
said latent adhesive phase comprising:
a) an ungelatinized, granular saponifiable starch ester that is characterized as having at least about 30% greater area under an Instron force-time heating curve and at least about 30%
greater area under an Instron force-time cooling curve, compared with unmodified corn starch under the same test conditions; and b) a quantity of alkali sufficient to substantially completely saponify said saponifiable starch ester, said composition being tractable on a corrugating machine.
a carrier phase and a latent adhesive phase that is dispersed in said carrier phase;
said latent adhesive phase comprising:
a) an ungelatinized, granular saponifiable starch ester that is characterized as having at least about 30% greater area under an Instron force-time heating curve and at least about 30%
greater area under an Instron force-time cooling curve, compared with unmodified corn starch under the same test conditions; and b) a quantity of alkali sufficient to substantially completely saponify said saponifiable starch ester, said composition being tractable on a corrugating machine.
8. A composition in accordance with claim 7, and further including up to about 5% additional alkali and up to about 5%
borax (10 mol), based on total starch material, commercial basis.
borax (10 mol), based on total starch material, commercial basis.
9. A composition in accordance with claim 7, wherein said carrier phase comprises gelatinized, unmodified corn starch.
10. A composition in accordance with claim 7, wherein said carrier phase comprises carboxymethyl cellulose.
11. A composition in accordance with claim 7, wherein said saponifiable starch ester is a saponifiable corn starch ester.
12. A composition in accordance with claim 7, wherein said saponifiable starch ester is selected from the group consisting of starch acetate, starch succinate, starch acetate succinate and mixtures thereof.
13. A composition in accordance with claim 7, wherein said saponifiable starch ester has a saponifiable D.S. of at least about 0.015.
14. A composition in accordance with claim 7, wherein said saponifiable starch ester is a corn starch acetate succinate, having a saponifiable D.S. in the range of from about 0.025 to about 0.045.
15. A process for uniting together at least two webs of fibrous material comprising:
applying therebetween a layer of a starch base potential adhesive composition that includes at least two phases; com-prising a carrier phase and a latent adhesive phase that is dispersed in the carrier phase;
said latent adhesive phase comprising an ungelatinized, granular saponifiable starch ester having a saponifiable D.S.
of at least about 0.015 and a quantity of alkali sufficient to substantially completely saponify said saponifiable starch ester; and, activating the potential adhesive composition to form an adhesive bond.
applying therebetween a layer of a starch base potential adhesive composition that includes at least two phases; com-prising a carrier phase and a latent adhesive phase that is dispersed in the carrier phase;
said latent adhesive phase comprising an ungelatinized, granular saponifiable starch ester having a saponifiable D.S.
of at least about 0.015 and a quantity of alkali sufficient to substantially completely saponify said saponifiable starch ester; and, activating the potential adhesive composition to form an adhesive bond.
16. A process according to claim 15, the improvement wherein said saponifiable starch ester is a corn starch acetate succinate.
17. A process for uniting together at least two webs of fibrous material comprising:
applying therebetween a layer of a starch based potential adhesive composition that includes at least two phases; comprising a carrier phase and a latent adhesive phase that is dispersed in the carrier phase;
said latent adhesive phase comprising an ungelatinized, granular, saponifiable starch ester characterized as having at least about 30% greater area under an Instron force-time heating curve and at least about 30% greater area under an Instron force-time cooling curve compared with unmodified corn starch under the same test conditions and a quantity of alkali sufficient to substantially completely saponify said saponifiable starch ester; and activating the potential adhesive composition to form an adhesive bond.
applying therebetween a layer of a starch based potential adhesive composition that includes at least two phases; comprising a carrier phase and a latent adhesive phase that is dispersed in the carrier phase;
said latent adhesive phase comprising an ungelatinized, granular, saponifiable starch ester characterized as having at least about 30% greater area under an Instron force-time heating curve and at least about 30% greater area under an Instron force-time cooling curve compared with unmodified corn starch under the same test conditions and a quantity of alkali sufficient to substantially completely saponify said saponifiable starch ester; and activating the potential adhesive composition to form an adhesive bond.
18. A process in accordance with claim 17, wherein said saponifiable starch ester is a corn starch acetate succinate having a saponifiable D.S. in the range of from about 0.025 to about 0.045.
19. In a process for the preparation of a corrugating adhesive composition of the no-carrier type, comprising the steps of preparing a heated reaction mixture of ungelatinized starch material, water and alkali, allowing the reaction to proceed until a Stein-Hall viscosity of from about 20 to about 90 seconds is reached, and adding a reaction stopper to the mixture, the improvement which consists of replacing at least a portion of the starch material with a saponifiable starch ester having a saponifiable D.S. of at least about 0.015.
20. A process according to claim 19, the improvement wherein said saponifiable starch ester is a corn starch acetate succinate.
21. In a process for the preparation of a corrugating adhesive composition of the no-carrier type, comprising the steps of preparing a heated reaction mixture of ungelatinized starch material, water and alkali, allowing the reaction to proceed until a Stein-Hall viscosity of about 20 to about 90 seconds is reached, and adding a reaction stopper to the mixture, the improvement which consists of replacing at least a portion of the starch material with a saponifiable starch ester chara-cterized as having at least about 30% greater area under an Instron force-time heating curve, and at least about a 30%
greater area under an Instron force-time cooling curve compared with unmodified corn starch under the same test conditions.
greater area under an Instron force-time cooling curve compared with unmodified corn starch under the same test conditions.
22. A process in accordance with claim 21, the improve-ment wherein said saponifiable starch ester is a corn starch acetate succinate having a saponifiable D.S. in the range of from about 0.025 to about 0.045.
23. A laminated panel suitable for use in the manufacture of a corrugated container, said panel consisting of at least two backers and at least one intercalary corrugated sheet joined together with an adhesive bond comprised of the composition of claim 1.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US59809575A | 1975-07-22 | 1975-07-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064025A true CA1064025A (en) | 1979-10-09 |
Family
ID=24394207
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA256,543A Expired CA1064025A (en) | 1975-07-22 | 1976-07-07 | High speed corrugating adhesives |
Country Status (3)
| Country | Link |
|---|---|
| JP (3) | JPS5928594B2 (en) |
| CA (1) | CA1064025A (en) |
| TR (1) | TR19215A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5984802A (en) * | 1982-11-08 | 1984-05-16 | Sumitomo Chem Co Ltd | Aerosol for expelling injurious insect in space |
| JPS5984801A (en) * | 1982-11-08 | 1984-05-16 | Sumitomo Chem Co Ltd | Aerosol for expelling injurious insect in space |
| DE3703547A1 (en) * | 1987-02-06 | 1988-08-18 | Spanset Inter Ag | METHOD FOR PRODUCING A ROUND Sling |
| JP2889618B2 (en) * | 1988-12-28 | 1999-05-10 | 株式会社リコー | Array type semiconductor light emitting device |
| JP4753000B2 (en) * | 2005-01-25 | 2011-08-17 | 日立工機株式会社 | Electric tool |
-
1976
- 1976-07-07 CA CA256,543A patent/CA1064025A/en not_active Expired
- 1976-07-22 TR TR1921576A patent/TR19215A/en unknown
-
1981
- 1981-04-16 JP JP5635381A patent/JPS5928594B2/en not_active Expired
- 1981-04-16 JP JP5635581A patent/JPS5928596B2/en not_active Expired
- 1981-04-16 JP JP5635481A patent/JPS5928595B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5928595B2 (en) | 1984-07-13 |
| TR19215A (en) | 1978-06-07 |
| JPS5928594B2 (en) | 1984-07-13 |
| JPS5928596B2 (en) | 1984-07-13 |
| JPS5716079A (en) | 1982-01-27 |
| JPS5716080A (en) | 1982-01-27 |
| JPS5716081A (en) | 1982-01-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |
Effective date: 19961009 |