JPH0892540A - Urethane-based aqueous adhesive composition - Google Patents

Abstract

PURPOSE: To obtain the subject composition capable of suppressing corrosion of a metal adherend and retaining excellent water-resistant adhesion by dispersing an urethane polymer obtained by polymerizing a polyisocyanate compound with a polyol compound and a specific functional compound into water and adding a polytannic acid compound thereto. CONSTITUTION: This composition is obtained by dispersing an urethane polymer obtained by polymerizing (A) a polyisocyanate compound (e.g. 1,4-tetramethylene diisocyanate or 2,4-tolylene diisocyanate) with (B) a polyol compound having >=2 hydroxyl groups (e.g. ethylene glycol or 1,4-butanediol) and (C) a functional compound having >=2 active hydrogen atoms capable of reacting with isocyanate group and having a hydrophilic group of a carboxyl group and/or sulfonyl group into water and adding a polytannic acid compound in an amount of 0.5-20 pts.wt. based on 100 pts.wt. of the urethane polymer to the dispersion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a urethane-based water-based adhesive composition which suppresses corrosion of a metal adherend due to an adhesive and maintains excellent water-resistant adhesion for a long period of time.

[0002]

2. Description of the Related Art Urethane-based adhesives have been used for many purposes because they have excellent adhesion to a wide range of adherends and excellent properties such as flexibility. Particularly, in recent urethane adhesives, the conventional solvent-based adhesives have been actively changed to water-based adhesives because they have no toxicity and no risk of fire and are economical.

However, when an aqueous adhesive is produced, a large amount of an emulsifier must be used in the step of dispersing the urethane polymer in water, and as a result, when the adhesive is used for adhering a metal adherend There is a problem that the emulsifier therein takes in water into the adhesive layer or the adhesive interface, corrodes the surface of the metal adherend, and further significantly reduces the adhesiveness.

To solve the above problems, a method for producing a urethane-based water-based adhesive composition which does not require an emulsifier by introducing an ionic functional group such as a carboxyl group into the molecule of a urethane polymer has been disclosed ( For example, JP-A-3-
21626).

However, as compared with an aqueous adhesive using an emulsifier, the effect of taking in water is reduced, but the ionic functional group such as a carboxyl group in the molecule of the urethane polymer also causes an adhesive layer or an adhesive interface. Since water is taken in, it was not sufficient to suppress the corrosion of the surface of the metal adherend.

Further, as a method of suppressing surface corrosion due to water taken in at the interface of a metal adherend, a chromate-based, lead-based, phosphate-based rust-preventive pigment in a urethane-based water-based adhesive composition is used. However, since these are hydrophobic inorganic pigments, there is a problem that storage stability is lowered due to sedimentation. Further, there is a problem that the usable applications are limited due to the toxicity of the water-based adhesive itself due to the chromium compound or the lead compound added as the rust preventive pigment.

On the other hand, there is a method of adding a water-soluble organic substance such as tannic acid, an organic phosphoric acid ester and various amines. For example, the corrosion resistance is improved by adding tannic acid to a urethane polymer or its aqueous dispersion. Also disclosed are urethane-based water-based paints (JP-A-53-1).
16240).

[0008]

However, since the water-soluble organic compound is generally a hydrophilic low molecular weight compound, there is a problem that sufficient water resistance cannot be obtained when it remains in the pressure-sensitive adhesive. .

An object of the present invention is to provide a urethane-based water-based adhesive composition which is excellent in water-resistant adhesion to a metal adherend such as a steel plate and storage stability as a water-based adhesive and has no problem in toxicity. To do.

[0010]

The urethane polymer used in the present invention is obtained by polymerizing a polyisocyanate compound (A), a polyol compound (B) and a functional compound (C).

The polyisocyanate compound (A) is
An organic polyisocyanate that has two or more isocyanate groups in the molecule and is used in the production of ordinary urethane resins is used. For example, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 3-isocyanate methyl-3,5
5-trimethylcyclohexyl isocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexyl-2,4-diisocyanate, methylcyclohexyl-2,6-diisocyanate, xylylene diisocyanate, 1,3-bis (isocyanate)
Aliphatic diisocyanates such as methylcyclohexane, tetramethylxylylene diisocyanate, transcyclohexane-1,4-diisocyanate, lysine diisocyanate, 2,4-toluylene diisocyanate,
2,6-toluylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 1,5'-naphthene diisocyanate, tolidine diisocyanate, diphenylmethylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3 -Aromatic diisocyanates such as phenylene diisocyanate, lysine ester triisocyanate, triphenylmethane triisocyanate, 1,6,11-undecane triisocyanate,
Triisocyanates such as 1,8-diisocyanate-4,4-isocyanatomethyloctane, 1,3,6-hexamethylenetriisocyanate and bicycloheptane triisocyanate may be mentioned. These may be used alone or in combination of two or more.

The above-mentioned polyol compound (B) has two or more hydroxyl groups in the molecule, and the physical properties such as hardness and adhesiveness of the urethane polymer obtained by selecting it according to the purpose and application are arbitrarily selected. It can be designed, for example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol,
1,6-hexanediol, trimethylolpropane,
Polyhydric alcohols such as glycerin, polyethylene glycol, polyether polyols such as polypropylene glycol, adipic acid, sebacic acid, itaconic acid, maleic anhydride, terephthalic acid, dicarboxylic acids such as isophthalic acid and ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, 1,6-
Polyester polyols obtained from glycols such as hexanediol, tripropylene glycol, neopentyl glycol, polycaprolactone polyol, polytetramethylene ether glycol, polybutadiene polyol, hydrogenated polybutadiene polyol, polycarbonate polyol, polythioether polyol, polyacrylic ester polyol Etc. These may be used alone or in combination of two or more.

The above-mentioned functional compound (C) has two or more active hydrogens capable of reacting with an isocyanate group and one or more hydrophilic groups selected from a carboxyl group and a sulfonyl group. Examples of the compound having a group include 2,2-dimethylol lactic acid and 2,2
-Dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid and the like can be mentioned. Examples of the compound having a sulfonyl group include 3,4-diaminobutanesulfonic acid and 3,6-diamino- 2-toluenesulfonic acid etc. are mentioned. These may be used alone or in combination of two or more.

When the proportion of the hydrophilic group in the functional compound (C) is small, it becomes difficult to obtain dispersion stability of the urethane-based water-based adhesive composition of the present invention in water. Since the water resistance of the adhesive composition after drying is reduced, it is preferably 0.1 to 2.0 mmol, more preferably 0.1 to 1.0 mmol, per 1 g of the urethane polymer solid content obtained.

The urethane polymer is obtained by polymerizing the polyisocyanate compound (A), the polyol compound (B) and the functional compound (C), and has a residual isocyanate group.

The molecular weight of the above polymer is the equivalent ratio of isocyanate groups to active hydrogen, that is, [isocyanate equivalent in (A)] / [active hydrogen equivalent in (B) and (C)].
When the above equivalence ratio is close to 1.0, the molecular weight of the obtained polymer becomes high, and the dispersibility in water to be performed later is remarkably reduced, and when it becomes large, the polymer has a low molecular weight and after chain extension. Since it becomes difficult to obtain sufficient physical properties, the above equivalence ratio is preferably 1.1 to 2.0, more preferably 1.3 to 2.0.

The residual isocyanate group content in the urethane polymer solids is determined according to JIS K1603-1985.
5.3, the urethane polymer becomes a polymer and cannot maintain good dispersibility in water when it becomes low, and when it becomes high, a large amount of residual isocyanate groups cause a strong chain extension reaction to cause aggregation and solidification. 2.0 to 20% by weight in the solid content of urethane polymer
Is preferable, and more preferably 2.5 to 10% by weight.

Examples of the method of polymerizing the above compounds (A), (B) and (C) include bulk polymerization and solution polymerization. However, solution polymerization is preferable from the viewpoint of easy reaction control.

The solvent used in the solution polymerization is one having a boiling point of 100 ° C. or less because it is inert to isocyanate groups and can effectively remove only the solvent out of the system when the solvent is removed. Are preferred, and examples thereof include acetone, methyl ethyl ketone, tetrahydrofuran, and methyl acetate.

Further, the polymerization temperature is preferably in the range of 50 to 150 ° C., because the lower the polymerization reaction rate, the lower the polymerization reaction rate, and the higher the polymerization temperature, the more easily gelation occurs during the polymerization reaction.

When the viscosity of the urethane polymer obtained by the above-mentioned polymerization method becomes high, it becomes difficult to obtain sufficient dispersibility in water, and therefore the viscosity is preferably 10,000 cps or less,
More preferably, it is 5,000 cps or less.

Before the urethane polymer is dispersed in water, it may be diluted to adjust the viscosity to the above. Examples of the diluting solvent include the same solvents as those used in the solution polymerization. If the amount of solvent is large, a large amount of energy is required in the solvent removal process, and the emulsion viscosity increases due to the large amount of solvent.
It is preferably 0% by weight or more, more preferably 40% by weight or more, and particularly preferably 60% by weight or more.

The urethane polymer obtained by the above method is added with a neutralizing agent for the purpose of neutralizing its hydrophilic group to facilitate ionization in water and stabilize the dispersed state in water. Examples thereof include ammonia, trimethylamine, triethylamine and the like.

A chain extender is used to extend the chain of the urethane polymer. The chain extender has two or more active hydrogens capable of reacting with the residual isocyanate groups in the urethane polymer. Ethylenediamine, 1,2-propanediamine, 1,4-tetramethylenediamine, 1,6-hexamethylenediamine, 1,4
-Cyclohexanediamine, 3-aminomethyl-3,
5,5-trimethylcyclohexylamine, piperazine, 2,5-dimethylpiperazine, 4,4′-dicyclohexylmethanediamine, 3,3′-dimethyl-4,
4'-dicyclohexylmethanediamine, hydrazine,
Examples thereof include amine compounds such as diethylenetriamine and triethylenetetramine, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, polyalkylene glycol represented by polyethylene glycol, and water. These may be used alone or in combination of two or more.

The urethane polymer used in the present invention is as described above, but when the urethane polymer is dispersed in water, the particles are sufficiently dispersed by stirring the side to be charged, so that the final particles are dispersed. Storage stability is improved.

Examples of the mixing and stirrer for realizing the above stirring state include a dissolver, a homogenizer, a disperser, a static mixer, a line mill, an ultrasonic emulsifier and the like.

As a method for adding the chain extender, the urethane polymer may be previously dissolved in water before being dispersed, or the urethane polymer may be added and dissolved in water while being dispersed, Alternatively, the urethane polymer may be dispersed in water and then added and dissolved.

The above polytannic acid compound is, for example,
It is obtained by condensing a hydrolyzable tannic acid represented by the formula (1), a monovalent or divalent or higher valent phenol other than tannic acid, and one kind of aldehyde or ketone in the presence of an acid catalyst (for example, Japanese Patent Laid-Open No. 61-4775
Issue).

[0029]

[Chemical 1]

In the equation, G is represented by the equation (2).

[0031]

[Chemical 2]

When the amount of the polytannic acid compound added is small, it is difficult to obtain sufficient rust-preventing property, and when it is large, the cohesive force of the adhesive layer is low, and it is difficult to obtain sufficient adhesiveness. It is limited to 0.5 to 20 parts by weight, preferably 1 to 100 parts by weight of the urethane polymer.
10 parts by weight.

The polytannic acid compound (D) may be added, for example, by dissolving the polytannic acid compound in a hydrophilic solvent such as methanol, isopropanol or n-butanol in advance and then directly adding it to the aqueous adhesive. Examples thereof include a method of dissolving a hydrophilically modified polytannic acid compound in water and then adding it to an aqueous adhesive, and a method of dissolving the polytannic acid compound in a urethane polymer before water dispersion and then dispersing it in water.

The polytannic acid compound (D) can be modified to be hydrophilic by, for example, neutralizing the residual carboxyl groups in the polytannic acid compound with a base, or a water-soluble polymer such as a water-soluble acrylic resin. And the like, but the neutralization ratio of the carboxyl group of the former and the amount of the water-soluble polymer to be complexed of the latter can be adjusted while paying attention not to impair the water resistance which is one of the objects of the present invention. I have to decide.

When an organic solvent is contained in the water-based adhesive used in the present invention or in the urethane-based water-based adhesive composition of the present invention, the solvent resistance and heat resistance of the film after drying are lowered, Alternatively, since the deterioration of the working environment becomes a problem, a water-based adhesive or a urethane-based water-based adhesive composition containing no organic solvent can be obtained by heating or depressurizing.

The urethane-based water-based adhesive composition of the present invention further comprises, depending on the purpose, other physical properties within a range not impaired.
Tackifying resins, plasticizers, fillers, thickeners, defoamers, fungicides and the like may be added.

The urethane-based water-based adhesive composition obtained as described above can be used for adhesion of various adherends by adjusting the viscosity and concentration so that it can be applied, sprayed or impregnated.

[0038]

[Function] Since the urethane-based aqueous adhesive composition of the present invention contains a polytannic acid compound, tannic acid in the polytannic acid compound forms a chelate with ferric iron on the surface of the steel sheet to prevent the tannic acid. In addition, it exhibits rust resistance, and the polytannic acid compound is a polymer of tannic acid, and has a high molecular weight compared to tannic acid, so it has hydrophobicity and does not reduce water resistance even if it remains in the adhesive. it is conceivable that.

[0039]

EXAMPLES Next, examples of the present invention will be described. still,
Hereinafter, "part" means "part by weight".

(Examples 1 and 2, Comparative Examples 1 to 3 and 5)
According to the formulation of Table 1, in a reactor equipped with a reflux condenser,
Polycaprolactone polyol (OH group value 57, number average molecular weight 2,000, manufactured by Daicel Chemical Industries, Ltd., trade name "P
LACCEL L220AL ") or polypropylene glycol polyol (OH group value 58, number average molecular weight 2,000, manufactured by NOF CORPORATION, trade name" Nissan Uniol D-2000 ", hereinafter referred to as" NU D-2000 "), dimethylol. Add propionic acid (made by Trimet Technical Products) and methyl ethyl ketone to give 8
Stir at 0 ° C. until uniform. After confirming that the solvent was refluxed, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (manufactured by Huls, trade name "VESTANT IPDI", hereinafter "IP
DI ”) was added and the polymerization was carried out until the isocyanate group content in the polymer was 2.3% by weight or less.
Further, a urethane polymer was obtained by adding triethylamine and methyl ethyl ketone for adjusting the viscosity. Next, 300 parts of water was added to 200 parts of the urethane polymer under vigorous stirring under room temperature conditions, subsequently 10% by weight-ethylenediamine aqueous solution was added, and the mixture was further stirred for 1 hour and then depressurized to remove the solvent. An aqueous adhesive having a solid content of 35% by weight was obtained. Then, based on 100 parts of the solid content of the aqueous adhesive, a polytannic acid resin solution (solid content 42%, manufactured by Teika, trade name "K polymer L8", solvent: water, isopropanol, n-butanol), tripolyphosphoric acid Aluminum dihydrogen powder (manufactured by Teika, trade name "K White 105") or tannic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added to obtain a urethane-based aqueous adhesive composition.

Example 3 According to the blending composition shown in Table 1, "NU D-2000", dimethylolpropionic acid and methyl ethyl ketone were placed in a reactor equipped with a reflux condenser and stirred at 80 ° C. until uniform. did. After confirming that the solvent was refluxed, "IPDI" was added and polymerization was carried out until the isocyanate group content in the polymer was 4.2% by weight or less. Further, a urethane polymer was obtained by adding triethylamine and methyl ethyl ketone for adjusting the viscosity. Then, the urethane polymer 200
Part under room temperature with vigorous stirring to 300 parts of water
Part by weight, subsequently 10% by weight-ethylenediamine aqueous solution was added, and the mixture was further stirred for 1 hour and then depressurized to remove the solvent to obtain an aqueous adhesive having a solid content of 35% by weight. Next, with respect to 100 parts of the solid content of the aqueous adhesive, a polytannic acid resin solution (solid content 42%, manufactured by Teika, trade name "K polymer L8", solvent: water, isopropanol, n
-Butanol) was added to obtain a urethane-based water-based adhesive composition.

(Comparative Example 4) In accordance with the composition of Table 1, "NU D-2000", 1, was added to a reactor equipped with a reflux condenser.
4-Butanediol (manufactured by Wako Pure Chemical Industries, Ltd.) and methyl ethyl ketone were added and stirred at 80 ° C. until uniform. After confirming that the solvent was refluxed, "IPDI" was added and polymerization was carried out until the isocyanate group content in the polymer became 2.3% by weight or less. Further, a urethane polymer was obtained by adding triethylamine and methyl ethyl ketone for adjusting the viscosity. Then, 380 parts of 1.3 wt% -nonionic emulsifier aqueous solution (manufactured by Nippon Emulsifier Co., Ltd., trade name "Newcol 210") was added to 200 parts of the urethane polymer under vigorous stirring under room temperature conditions, followed by 10 wt%. -Aqueous ethylenediamine solution was added, and the mixture was further stirred for 1 hour and then depressurized to remove the solvent to obtain an aqueous adhesive having a solid content of 35% by weight. Then
Polytannic acid resin solution (solid content 42%, manufactured by Teika Co., trade name "K polymer L8", solvent: water, isopropanol, n-butanol) was added to 100 parts of the water-based adhesive solid content, and urethane was added. A water-based adhesive composition was obtained.

The evaluation items and evaluation methods are shown below. (Adhesive Strength Test) The urethane-based water-based adhesive compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were JIS L-31.
02 standard canvas (normal cotton 9, width 25 mm, length 250 m)
m) and then dried for 4 minutes in a 80 ° C. blast drying oven to obtain an adhesive-impregnated canvas with a coating amount of 100 g / m ^{2 in} terms of solid content. Similarly, cold-rolled steel sheet (width 25
mm, length 125 mm, thickness 2 mm), then 80 ℃
An adhesive-coated cold-rolled steel sheet having a coating amount of 40 g / m ^{2 in} terms of solid content was obtained by drying in a blast drying oven for 4 minutes. Then, the coated surface of the adhesive-impregnated canvas and the coated surface of the adhesive-coated cold-rolled steel sheet were aligned, and the linear pressure of the roll: 60 kg /
A test piece was obtained by laminating it at 25 mm. Table 1 shows the results of 90 ° peel test at a pulling speed of 50 mm / min after curing the obtained test piece for 1 week at 23 ° C. (Water resistance adhesive strength test) A test piece similar to the above adhesive strength test was prepared, dipped in 3% -salt water at 40 ° C for 48 hours and then wiped off moisture, and under a condition of 23 ° C, a pulling speed of 50 mm /
The results of the 90 ° peel test at min are shown in Table 1. (Storage stability test) Examples 1 to 3 and Comparative Examples 1 to 5 above
Table 1 shows the results of visually confirming the presence or absence of precipitates in the urethane-based water-based adhesive composition obtained in 1. by leaving it in a closed glass container at 23 ° C. for 2 months.

[0044]

[Table 1]

[0045]

EFFECT OF THE INVENTION Since the urethane-based water-based adhesive composition of the present invention contains a polytannic acid compound of a water-soluble organic substance, even when it is used for a metal adherend, it absorbs water at the bonding interface and rusts. Since it is not such a case, the water-resistant adhesiveness is good, and since it is an organic substance, there is almost no problem of toxicity, and since it is water-soluble, the dispersion stability in water is good. Therefore, it is a urethane-based water-based adhesive that is particularly suitable for use with metal adherends.

Claims (1)

[Claims] 1. A polyisocyanate compound (A), (B)
A polyol compound having two or more hydroxyl groups, and (C)
1 or more having at least two active hydrogens capable of reacting with an isocyanate group and selected from a carboxyl group and a sulfonyl group
A urethane polymer obtained by polymerizing a functional compound having at least one kind of hydrophilic group is dispersed in water, and 100 parts by weight of the urethane polymer is mixed with a polytannic acid compound of 0.
A urethane-based water-based adhesive composition, characterized in that 5 to 20 parts by weight is added.