JPS5831112B2 - Method for bonding solid lignocellulose materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method for bonding solid lignocellulosic materials, particularly wood.

BACKGROUND OF THE INVENTION Bonding of lignocellulosic materials such as wood is widely used commercially, such as in the production of plywood and planks from particulate wood.

Current commercial bonding operations use adhesives such as urea or phenol formaldehyde;
These adhesives are spread or otherwise applied to the surface of the material and penetrate the wood structure, thereby creating an adhesive bond.

Procedures for effecting the above-mentioned bonds by chemical reactions between the reagents and the wood itself have been proposed, but have not gained commercial acceptance.

That is, U.S. Patent No. 2495 in the name of Willey et al.
No. 043 and US Pat. No. 2,639,994 to Wilson propose acid treating the wood and then pressing.

Neither method has yielded satisfactory results, ie, a bond of adequate strength.

This is probably because at any moderate pressure, i.e. at a pressure that does not collapse the cellular structure of the wood, only a portion of the bonded surfaces will be in contact due to the non-uniform cellular nature of the wood surface.

Acids have a hydrolytic effect on the cellulose of wood, thus permanently reducing its strength.

For example, wood was heated in an autoclave with 0.5% hydrochloric acid at 9 atm (132 p), which corresponds to a temperature of 348 below.
si) for 15 minutes produces 22% of the weight of the wood in simple sugars.

Hydrolysis of wood carbohydrates to sugars results in a significant loss of strength because, in addition to the partial conversion of the carbohydrates to sugars, the unhydrolyzed carbohydrates are highly depolymerized and fragmented into shorter molecular chain fragments.

This hydrolytic degradation cannot be limited to superficial layers with the intention of creating a "tie layer" without affecting adjacent layers.

These adjacent layers are always at least partially degraded and have significantly lower wood strength.

Similarly, U.S. Pat. No. 220 of S. al.
No. 4,384 does not produce a bond that is resistant to cold or hot water.

Furthermore, the bonding adhesive is applied in cold conditions.

Starch and sucrose are stabilized with a fixed acid, mixed at moderate temperatures, and then cooled to produce a water-soluble adhesive in powder form, which is then diluted with water before use.

DISCLOSURE OF THE INVENTION According to one aspect of the present invention, one or more sugars or starches or mixtures thereof and a catalyst capable of carrying out the conversion of said sugars and starches are provided on the surface of a lignocellulosic material, preferably as a layer. A method for bonding solid lignocellulosic materials is provided, characterized in that the surfaces of the materials are pressed together at a high temperature and pH that avoids hydrolytic deterioration of the wood to produce a waterproof bond. be done.

The method of the invention can be used to produce laminates, plywood and composite products from particulate wood without the use of conventional adhesives.

Any lignocellulosic material, regardless of size and shape, can be bonded by the method of the present invention.

It is believed that the bonds are produced by chemical transformation of sugars and starches applied to the wood surface and possibly by coupling of those transformation products with wood lignin.

The chemical reactions involved in the bonding systems of the present invention are not fully understood and applicants do not wish to be bound by any theory.

However, theoretically the depolymerization of sugars and starches,
Several reaction systems are involved simultaneously, such as dehydration of monosaccharides to furan-type compounds, condensation of furan monomers with lignin or other phenolic compounds present in the wood, and with each other.

distinguished from methods based on the hydrolysis of wood carbohydrates,
A basic feature of the invention is that sugars and starches can be converted into water-insoluble solids or condensates with wood phenols without the use of strong acids that cause hydrolysis of the wood, which has a detrimental effect on the strength of the wood.

Monosaccharides do not require any hydrolysis, trisaccharides-sucroses are easily hydrolyzed to simple sugars at low concentrations of hydrogen ions, ammonia ions and other compounds such as dimethylformamide, and starches are hydrolyzed in hot water. It is hydrolyzed inside.

Additionally, the chemical conversion of simple sugars to water-insoluble solids can be produced without acids and occurs at higher pH without hydrolytic effects on the wood.

As a result, wood deterioration does not occur and the full strength of the wood can be utilized.

Furthermore, when applied to the wood surface to be bonded, the sugars and starches desirably form a continuous film on that surface, filling cellular interstices and other interstices, and are more effective than in methods based on wood hydrolysis. also provides a higher level of bonding.

The strength of the bond produced between pieces of wood using the present invention is at least comparable to the strength of the bond obtained with conventionally used adhesives.

Furthermore, the bond is water resistant.

BEST MODE FOR CARRYING OUT THE INVENTION In the production of plywood, the surface of the wood veneer veneer is coated with a carrier, such as a liquid containing sugar and/or starch and a catalyst, and this surface is bonded between the surfaces to be bonded. contact with the surface of the other veneer with or without a coating of the bonding composition such that an interfacial layer of the composition is present, and then in a conventional press for a sufficient time to effect bonding by a conversion bonding reaction. It is only necessary to press them at high temperature at .

Similarly, wood particles of various shapes coated with a bonding composition can be pressed to produce various planks.

Alternatively, a liquid composition containing sugar and/or starch and catalyst may be added to
Sugars and starches may be converted to furan-type intermediates by heating at temperatures of 30 to 120 minutes.

The thermal composition can be applied to the wood surface in the same manner as the unheated composition and then pressed under heat and pressure for a sufficient period of time to form a bond.

Use of this thermal composition may be advantageous where shorter pressing times are required.

In some cases it may be advantageous to subject the wood veneers or particles coated with this liquid binding composition to elevated temperatures for a short period of time before pressing.

Such preheating results in a partial chemical conversion of the sugars and starches, which reduces the required pressing time or lowers the pressing temperature.

Preheating temperatures of up to about 300° C. for times up to about 60 minutes may be used.

If the sugar-starch-catalyst mixture described above is pre-steamed before application to the wood surface or the wood surface coated with this mixture is dried before pressing to evaporate the liquid carrier from the binding composition; It has been found that the amount of catalyst, pressing temperature and pressing time can be minimized and the bonding properties can also be increased.

In this way, the rate of chemical conversion of carbohydrates into water-insoluble solids is increased.

The binding composition may contain liquid carriers that are non-reactive with the lignocellulosic material, such as water, ethyl alcohol, and other solvents.

The amount of this liquid carrier in the bonding composition need only be sufficient to provide a composition that can be easily handled and applied to wood in the desired manner and at the desired rate.

Generally, vapors from this carrier can easily escape from an unsealed press during press operations.

In addition to mixtures of different catalysts in carriers, mixtures of different sugars and starches can also be used.

The composition may also contain other chemical reagents that can affect the binding reaction depending on the reaction conditions, which can vary widely, i.e., agents that accelerate or reduce the extent of reactions involving sugars and starches, or crosslinking agents. You may.

Such reagents may be incorporated into the liquid carrier in desired amounts along with the sugar and/or starch and the catalyst.

Examples of reagents that can accelerate the reaction rate include ethylene glycol, furfuryl alcohol, common amines such as ethylamine, n-propylamine, cetylamine, diethylamine, methylethylamine, diphenylamine, triethylamine, aniline, etc., such as methylammonium chloride. , dimethylammonium bromide, trimethylammonium nitrate, monoethanolamine, n
- Amine salts such as phenyldiamine, polyvinyl chloride, and others are briefly mentioned.

The amount of promoter effective in the combined composition is variable over a wide range and depends on a variety of factors, including the activity of the individual promoter, this latter factor resulting in an economically viable product. This is an extremely important matter from this point of view.

Generally, however, the amount of accelerator can range from as little as about 2% of the amount of sugar and starch to as much as 30% of the amount of sugar and starch, but usually from about 4 to 10% of the amount of sugar and starch.
%.

Excess amounts of sugar and starch applied to the wood surface do not affect the efficiency of bonding, but are uneconomical.

It is only necessary to provide sufficient carbohydrate and catalyst to carry out the binding reaction under heat and pressure in a press.

The minimum amounts of carbohydrate and catalyst required are variables that depend on the pH of the wood, sugar and starch, the type and reactivity of the sugar and starch, the temperature and moisture content of the wood, the desired reaction rate and other factors.

In the wood industry, there are operations in which low molecular weight sugars are involuntarily produced from lignocellulosic materials.

For example, in the process of disintegrating wood fibers, high-pressure steam is often used to plasticize the wood before grinding in a refiner.

High water vapor pressure causes partial hydrolysis of hemicellulose to sugars.

In current operations, these sugars are washed out of the fibers as they are known to be detrimental to conventional bonding using common bonding resins.

Since the low molecular weight sugars present in the fibers can be used for binding according to the present invention, there is no need to add sugars;
Only the catalyst and, if necessary, a buffering alkaline substance need be added.

Sugarcane bagasse is also used in the production of particleboard, and this bagasse contains about 8% residual sugar, which allows the wood to be bound according to the invention.

The optimum amounts of sugar and starch used are such that the amount of bonding composition applied fills the open cell cavities present on the wood surface, increases the contact area between adjacent wood surfaces, and substantially increases the bonding force. This will vary depending on the nature of the wood, the reactivity or other properties of the sugars and starches used, the surface roughness of the wood and the desired pressing conditions.

In the case of bonding veneers, it is only necessary to apply a film of the composition, which can suitably be carried out by brushing, spraying or rolling.

Typically 2 to 321 based on an area of 1000 cm
An amount of the binding composition that provides the sugar and starch can be used.

From the above description it can be seen that monosaccharides and trisaccharides such as mannose, glucose, maltose, lactose, sucrose, amylose and amylopectin, dextrin,
It will be appreciated that a wide variety of sugars and starches may be used, including starches such as wheat or corn flour, molasses from seed sources and mixtures of sugars and starches.

Cheap molasses shows interesting potential.

Catalysts used include dimethylformamide and iodine, dimethyl sulfoxide, propylene oxide and ethylene glycol, and zinc chloride, aluminum chloride, ammonium chloride, ammonium nitrate, sodium nitrate,
Potassium nitrate, ammonium sulfate, potassium tartrate, sodium phosphate, calcium phosphate, sodium sulfate,
There are organic and inorganic salts such as zinc chloride, ammonium linoate, superphosphate, and others.

Ammonium salts or ammonium salts are preferably used.

Nitrates and phosphates are the most effective and economical.

In addition to catalyzing the conversion of sugars and starches, phosphates also provide some fire protection to the wood.

The amount of catalyst present is generally 1 based on sugar and starch.
50% by weight, and up to about 100% or more, especially if higher degrees of fire protection are desired.

The most preferred ratio depends on the identity of the sugar and starch and the identity of the starch and the type of catalyst.

The amount of catalyst used is preferably kept at the minimum level necessary to catalyze the conversion of sugars and starches to furan-type compounds and polymerize those compounds.

Without buffering, large excesses of catalyst can be detrimental to wood strength over long periods of time.

The conversion of polymeric starches, such as potato starch, to furan-type compounds at a given reaction rate requires a slightly higher proportion of catalyst than the conversion of simpler sugars, such as glucose or sucrose.

Chemical conversion of sugars and starches, e.g. 35 to 5.5
It has now been found that this occurs at pHs not lower than <3.0, close to the neutral pH of wood.

Alkaline substances or "buffers" may be used to maintain the pH within the desired range.

For example, an aqueous solution of 20% ammonium nitrate has a pH of about 6.5.

At higher temperatures, ammonium nitrate dissociates and the pH
decreases to about 2.

If the pH of the solution is lowered to about 10 by adding an alkali, for example sodium hydroxide or ammonium hydroxide,
．． 5, the pH of the product decreases to the wood pH because the pH at higher temperatures drops to the level of the wood pH.
It is between 3.5 and 5.5.

Using a carbonate such as an alkali carbonate or an alkali metal carbonate in place of the base, or an amine such as those mentioned above,
It is possible to prevent H from dropping below 3.0.

By keeping the pH of the liquid carrier and final product at appropriate levels, any hydrolytic effects that reduce the strength of the wood are removed, and this is critical to the bonding properties.

In a preferred embodiment of the invention, a mixture of sugars and starches, such as sucrose and wheat flour, may be used.

It is advantageous to use sugars and starches that have almost the same rate of decomposition.

Simple sugars and starches are preferred over polymeric sugars and starches because of their greater rate of decomposition.

However, price and availability are probably the most important factors in deciding which raw materials to use.

The pressing conditions in the press depend on the type of sugar and starch,
Variables such as wood type, catalyst type and amount, and product requirements will vary widely.

For any given system, typically the lower the temperature, the longer the pressing time, and vice versa.

The pressing temperature should not exceed the temperature at which carbonization of the lignocellulosic material occurs and the pressure should not exceed the amount of product desired.

The preferred temperature range is 140-300°C and the preferred pressure range is 5-50 kg/crrt.

The press time required under these conditions is the time required to raise the core temperature to the temperature at which chemical conversion of the sugar and starch to a water-insoluble solid occurs, and this temperature depends on the type and amount of catalyst. The temperature is 160 to 212°C.

The invention is applicable to any type of wood bonding, such as plywood or composite plank production.

In the manufacture of composite products such as particleboard or fibreboard, the particles are coated with a carrier containing sugar, starch and catalyst by spraying and mixing, followed by planking and pressing in a press. Follow the same operations as in manufacturing.

Embodiments of the invention are described by way of the detailed description of the following examples.

Percentages are by weight.

Example 1 On both sides of a yellow pine veneer, 30 cIrL square, 3.5 mm thick, and with a moisture content of about 4%, 3
An aqueous solution containing 5% wheat flour, 15% sucrose, 2.5% ammonium chloride, and 2.5% ammonium sulfate was coated in an amount of 181 solutions based on 900c4.

After application of the solution, the veneer was exposed to a temperature of 150° C. for 4 minutes, so that the surface of the veneer became completely dry and blackened.

One side of the two veneers not coated with the bonding solution was moistened with water in an amount of approximately 51 g based on an area of 900 c4.

A veneer with a wet surface has a dry bonding solution on both sides such that the wet surface is in contact with the dry bonding solution on the veneer which is interposed in the fiber direction perpendicular to the direction of the fibers on the veneer surface. Overlaid on adjacent veneer.

The stacked veneers were placed in a cold press at 14 kg/crA for 5
Pressed for a minute.

After removal from the press, the veneers were stuck together so that they could be handled without risk of separation.

This pre-pressed plywood sample was then pressed at a temperature of 170° C. and a pressure of 14 kg/crA for 10 minutes.

The plywood was boiled in water for 10 minutes and after cooling to ambient temperature a knife test was carried out according to British Standards.

This result shows that a high-quality bond of the external type was obtained, comparable to conventional phenol-formaldehyde bonding.

Example 2 Example 1 except that the veneer was coated with an aqueous solution containing 25% flour, 20% molasses, 2.5% ammonium chloride, and 2.5% ammonium sulfate.
Samples of Douglasfir plywood were prepared under zero conditions.

Strength tests showed it to have a shear strength of about 16 kg/c4, which is comparable to similar products using phenol-formaldehyde adhesives.

After boiling in boiling water for 4 hours, drying at 53°C for 20 hours, and boiling again for 4 hours, the shear strength under wet conditions is approximately 8.
kg/crA.

Example 3 Instead of a dry veneer, 35% wheat flour, 15% sucrose, 1.5% in an amount of about 181 based on an area of 900 c4 on a wet veneer with a moisture content greater than 35% A pine plywood sample was prepared under the conditions of Example 1 except that it was coated with an aqueous solution containing 1.5% ammonium chloride and 1.5% ammonium sulfate.

After application of this solution, the veneer was dried in a conventional veneer dryer for 5 minutes at a temperature of 145-175°C, so that the veneer surface became completely dry and blackened.

Test results showed that a good quality bond was obtained on the outer surface after pressing.

Example 4 Japanese pine shavings with a moisture content of approximately 4% were sprayed with an aqueous solution containing 35% sucrose and 10% ammonium nitrate.

The amount used was a solution of 25% of the weight of the wood.

The sprayed particles were then dried for 5 minutes at a temperature of 155°C.

After drying, the particles changed color and had a moisture content of about 4%.

A particle mat is produced from the dried particles, and the mat is transferred into a hot press heating plate at a temperature of 170°C.
Particle boards with a thickness of 12 mvt were pressed for 10 minutes, cooled to room temperature, and then subjected to internal bonding tests under dry conditions and after boiling in water for 2 hours.

These tests showed that in dry conditions 8 kg/cr
A, An internal binding value of 2 kg/crA was obtained after boiling.

Example 5 Particles contain 30% wheat flour, 15% sucrose, and 15%
A particle board of pine wood particles was produced under the same conditions as in Example 4, except that a solution containing ammonium nitrate was sprayed.

The strength properties were almost the same as in Example 4.

Example 6 A particle board of okume wood particles was produced under the same conditions as in Example 4, except that the particles were sprayed with a solution containing 60% molasses and 8% ammonium nitrate.

The strength properties obtained were almost the same as in Example 4.

Example 7 40% sucrose in pinewood particles having a moisture content of about 6%, 25
% superphosphate, and 7% zinc chloride.

The amount used was a solution of 15% of the weight of the wood.

The sprayed particles were placed in a dryer at a temperature below 250°C.
It was dried for a minute to give a moisture content of about 4%.

A particle mat was produced from the dried particles and the mat was transferred to a hot press with a press hot plate at a temperature below 410°C to press a particle board with a thickness of 1271 nm for 10 minutes.

After cooling to room temperature, internal bonding and thickness swelling were tested after soaking in cold water for 24 hours and boiling in water for 2 hours.

As a result of the test, the internal bond value was 75! Values of 9/crA, 6% swelling in cold water, and 8% swelling in flooding were obtained.

Example 8 Sucrose and dimethylformamide in a weight part ratio of 6:4 were boiled with traces of iodine for 30 minutes.

A pale and colored liquid was obtained.

Dissolve 1 part of zinc chloride in water and make this steamed sucrose.
In addition to the dimethylformamide mixture, the final component ratio was a 6:4:1 parts by weight ratio.

A solution of 10% based on the weight of the wood is sprayed onto the pine wood particles, and the particles are then placed in a dryer at 250'F for 30 minutes.
It was dried for 0 minutes to give a moisture content of about 4%.

Particle board is made by transferring the dried particles into a press with a press hot plate at a temperature below 410°C to a thickness of 12.7°C.
mm particle board was produced from dry particles by pressing for about 10 minutes.

Example 9 Particle board was prepared according to the procedure of Example 8 using 10% of a solution consisting of sucrose, dimethylformamide, and zinc chloride in a weight ratio of 6:6:1.

Example 10 Particle board was prepared according to the procedure of Example 8 using a solution consisting of 10% sucrose, ethylene glycol, propylene oxide and zinc chloride in the ratio of 6:3:1.7:1 based on the weight of the wood. Created.

Propylene oxide was added to the cooked mixture of sucrose, ethylene glycol and zinc chloride after cooling to room temperature.

Particle boards made using the procedure of Examples 8-10 had good properties and were resistant to hot water.

Example 11 Pressing times and pressing pressures in the production of particle board according to the invention were determined using powdered or molten sucrose instead of a solution of sucrose, anhydrous aluminum chloride alone or with others as a catalyst, and without a liquid carrier. can be further reduced to

Aluminum chloride AlCl3 or A12C16 is commercially available as a powder.

A-Powder Application Procedure 87-97% sucrose, 2-8% aluminum chloride, and 1-5% ethylene glycol are thoroughly mixed.

A small amount of ethylene glycol, 0HCH2CH20H, is used to obtain a more homogeneous distribution of aluminum chloride in sucrose and accelerate the conversion reaction.

The percentage of aluminum chloride for a particular type of wood will vary due to differences in the chemical composition of the wood.

The sucrose-aluminum chloride mixture is mixed with wood particles to obtain a uniform distribution of sucrose on the particle surface.

The moisture content of the wood should be lower than 5%, since the lower the moisture content of the wood, the greater the reaction rate obtained.

The hot particles produced from the particle dryer can be advantageously mixed with the sucrose-aluminum chloride powder.

Particles coated with sucrose-aluminum chloride powder can be pressed into slabs without pre-drying.

Since the powder is slightly moist, it adheres well to the wood particles, so that no powder buildup on the lower caul plate is observed.

At the pressing temperature, the sucrose turns into a liquid that plasticizes the wood, so lower pressures are required to obtain the final composition of the particle mat.

The results obtained using a powder application operation at a pressure of 25 kg/ca are shown in Table 1 below.

B-Heat Application Operation Thoroughly mix the composition of 95-99% sucrose and 1-5% anhydrous aluminum chloride.

Heat the sucrose-aluminum chloride mix with constant mixing until the sucrose turns into a black viscous liquid.

A composition of 10(1) containing 98.5% sucrose and 1.5% aluminum chloride is transformed into a black liquid in about 3 minutes in a beaker heated on a hot plate.

Spray or rub hot black molten sucrose as an adhesive (L
odige system) on wood particles.

Ethylene glycol can be used to adjust the viscosity if necessary.

Because molten sucrose is liquid only while hot, application equipment must be kept at higher temperatures.

It was found that the addition of ammonium nitrate to heat-molten sucrose before application to wood increases the binding reaction rate.

The particles spread with molten sucrose can be pressed into slabs without any pre-drying.

As long as the spread particles are warm and molten, the sucrose provides good adhesion and the pre-pressing operation produces a well-prepressed particle mat.

When cooled, molten sucrose becomes extremely viscous, almost solid, and cannot be spread.

Once cooling occurs, the resulting solid is heated to become a liquid again.

Advantageously, the hot melt is applied to the hot particles originating from a particle dryer.

The results obtained by the steam application operation are shown in Table 2 below.

C - Discussion of Results for Example 11 Anhydrous aluminum chloride was found to be an effective catalyst with powdered or molten sucrose.

There was no need to pre-dry the wood particles before pressing, and pressing time and pressing pressure were substantially reduced.

The pressing time depends on the amount of catalyst and the water present in the particles.

The lower the amount of catalyst, the faster the binding reaction will proceed.

By using sucrose in powder or melt, the amount of water in the reaction system is substantially reduced.

It has been found to be beneficial to incorporate ethylene glycol into the system instead of water in order to obtain a better distribution of chlorides in the powdered bran or to adjust the viscosity in the molten bran. .

Ethylene glycol probably improves heat transfer into the center of the panel.

The amount of aluminum chloride must be kept at the lowest level and desired pressing time for the particular wood type.

It was found that a 19 mvt thick panel was cured in 6 minutes at 190°C to the extent that it could be removed from the press.

Although internal binding under dry conditions is fully developed, the binding reaction in the center of the panel is not completed as seen from the boiling test.

If further exposure to heat occurs, for example by thermal cooking of the panel removed from the press, the central portion of the thermal panel will also become sufficiently hot water resistant.

Samples A, B 7, and 13-9 in Table 2 were used for 6 minutes (
sample B-7) and 8 minutes (sample B-9), followed by an additional 10 minutes and 7 minutes in the press, respectively.
kept under pressure.

The center portion of each sample was fully cured.

The amount of sucrose that must be used to obtain good bonding of the particles depends on the geometry of the particles.

Redwood sawdust was very fine and had a large surface area, so an amount of 10% based on the weight of the wood was used.

Amounts between 4 and 10% are suitable for commercially available particles.

The amount of aluminum chloride used varies depending on the type of wood.

A percentage of about 0.2 to 1.0% based on the weight of the wood appears to be practical.

For any individual wood type, the percentage of aluminum chloride must be found by routine experimentation.

Amounts of ammonium nitrate between about 0.5 and 4% are believed to be practical, although there will be some variation depending on the individual wood type.

Strap molasses reacts with aluminum chloride similarly to molten sucrose, assuming its moisture content is reduced before mixing with aluminum chloride.

Further tests on plywood showed that the rate of the bonding reaction was increased by applying aluminum chloride as a catalyst in the plywood instead of aluminum sulfate.

Example 12 Study of curing temperature - A study of the time relationship was conducted along with an exploration of the possibility of accelerating the bonding reaction.

To determine the minimum pressing time at various temperatures, a sample of particle board 2.5 mm thick was
80.300.320 and 350″F (126,14
8,158°C, and 176°C).

Thickness swelling after 24 hours of cold sonication in water and after 2 hours of boiling in water was used as a criterion to determine whether the binding reaction was complete.

The specific gravity of the sample was approximately 0.730.

Particles of Japanese pine, sugar pine, and Incensedar were used in this study.

From the results shown in Table 3, the bonding reaction is completed in 1 minute at a temperature of 175°C, depending on the type of wood, 2.5 to 5 minutes at 160°C, 5 to 10 minutes at 150°C, and 5 to 10 minutes at 140°C. for 10 to 30 minutes and 130℃
It can be concluded that the process can be completed in 15 to 60 minutes.

The pH of the wood probably affects the reaction time.

Wood particles with a moisture content of 6% in the form of wood fibers produced by a chemical method were sprayed with an aqueous solution containing 36% sucrose and 10% ammonium nitrate.

The total amount sprayed (of solution) was 15% with respect to the weight of the fibers dried in the dryer.

After air-drying to a moisture content of about 8%, the fiber mat is hand-formed and 1/41-thick node boards are made from the mat at temperatures below 450°C and pressures between about 550 and 150 PSI.
/ Pressed for 2 minutes.

This hardboard had the following properties.

Specific gravity 1.05, modulus of rupture 4200psi, modulus of elasticity 530
000 PSI, 170 PSI internal bond, 12% thickness swelling after 24 hours noking in water and 24.5% thickness swelling after 2 hours boiling in water.

Example 14 Using the procedure and composition of Example 13 except as noted below, solution (a) in the first sample was prepared by adding sodium hydroxide and buffering 10% of ammonium nitrate to pH 1.
It was set as 0.5.

(b) In the second sample, ammonium nitrate was replaced with the same amount of sodium nitrate.

(C) In the third sample, ammonium nitrate was replaced with an equal amount of potassium nitrate.

(d) In the fourth sample, ammonium nitrate was replaced with the same amount of superphosphate.

(e) In the fifth sample, ammonium nitrate was replaced with the same amount of ammonium phosphate.

Composite planks were made from wood fibers using

This plank had properties comparable to those of the Example 13 plank.

A buffer was used to adjust the pH of the final product to the level of the neutral pH of wood, which is between 3.5 and 5.5.

Buffering was found to be advantageous with ammonium nitrate, but unnecessary with potassium and sodium nitrates.

At the amounts shown in Example 13, superphosphate and ammonium phosphate do not require any buffering.

Buffering may be advantageous at higher amounts of superphosphate and ammonium phosphate, which are desired to provide a higher degree of flame retardation.

A review of these examples shows that the bond is removed under heat and pressure by the addition of small amounts of sugar and/or starch and a catalyst, preferably the indicated salt, to the surface to be bonded.

The strength of the bond is comparable to that obtained with conventional adhesives, and the bond is water resistant.

The cost of the sugars and starches applied to this bonding system is approximately 1/2 to 1/9 the price of most widely used adhesives such as urea or phenol formaldehyde adhesives.
This system has great economic advantages.

It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention, and that the invention is not to be considered limited to what is described herein. It is.

Claims (1)

Claims: 1. On the surface of a solid lignocellulosic material, at least one sugar, starch, or a mixture thereof and an amount of said sugar or starch sufficient to act as a conversion catalyst for the sugar or starch. After heating, the solid lignocellulose becomes more essentially a sugar or starch conversion catalyst that is converted to create a water-resistant bond between the adjacent lignocellulosic material and an interlayer of adhesive-free bonding composition. applying a layer of adhesive-free bonding composition having a pH approximately the same as that of the lignocellulosic material; an acidic catalyst buffered with a sufficient amount of a basic catalyst to have approximately the same pH as the sugar or starch; 1. A method for joining solid lignocellulosic materials comprising pressing the surfaces of said lignocellulosic materials together for a period of time sufficient to cause a permanent bond. 2. The method according to claim 1, wherein the sugar is selected from trisaccharides, monosaccharides, molasses and the starch is selected from starch obtained from wheat flour or corn flour. 3. A method according to claim 1, wherein the binding composition is characterized by at least one sugar and at least one starch. 4. The method of claim 3, wherein the binding composition features substantially equal amounts of sugar and starch. 5. The method of claim 1, wherein the amount of catalyst present is 1 to 50% by weight of the amount of sugar and starch in the combined composition. 6. The method of claim 1, wherein the binding composition is characterized by a liquid carrier that does not react with sugars or starches. 7. A method according to claim 6, wherein the liquid carrier is selected from water and ethanol. 8 Bonding composition 2 to 3 based on surface 1000c4
applied to the surface in an amount giving 21 sugars and starches;
A method according to claim 1. 9 The surface was heated to a temperature of 140 to 300°C and 5 to 50°C.
2. The method according to claim 1, wherein the pressing is carried out at a pressure of kg/crA. 10. The method of claim 1, wherein the bonding composition is heated before being applied to the surface. 11. The method of claim 10, wherein the bonding composition is heated at a temperature of 100 to 130°C for 30 to 120 minutes. 12. The method of claim 1, wherein the lignocellulosic material is heated after application of the binding composition and before pressing. 13. The method of claim 12, wherein the lignocellulosic material is heated at a temperature not exceeding 300° C. for a period of up to 60 minutes. 14. The method of claim 1, wherein the lignocellulosic material is a wood veneer veneer that is laminated together during a press. 15. The method of claim 14, wherein the bonding composition is applied to only one side of each veneer surface to be pressed together. 16. The method of claim 1, wherein the lignocellulosic material consists of wood particles. 17 The catalyst is a combination of dimethylformamide and iodine, dimethyl sulfoxide, propylene oxide and ethylene glycol, and zinc chloride, aluminum chloride, ammonium chloride, ammonium nitrate, sodium nitrate, potassium nitrate, ammonium sulfate, potassium tartrate, sodium phosphate, calcium phosphate, and mixtures thereof. 2. The method of claim 1, wherein the catalyst is in admixture with an alkali selected from the group consisting of: 1, 2 and 3, which provides a pH in the alkaline range before heating. 18. pressing the non-reactive liquid carrier in the binding composition in an unsealed press to dissipate the vapor of said liquid carrier;
A method according to claim 1. 19. The method according to claim 1, wherein the sugar consists of waste molasses. Claim 1, wherein the original binding composition further comprises an accelerator.
The method described in section. 21. The method of claim 20, wherein the accelerator is selected from the group consisting of ethylene glycol and amines. 22. The method of claim 21, wherein the binding composition is substantially dry and comprises a mixture of the sugar or starch, aluminum chloride and ethylene glycol. The binding composition is dried after application and before pressing, and the pressing operation is carried out in two stages, the first stage being a cold press and the second stage being a hot press.
The method described in Section 8. 24 An amount sufficient to effect bonding to a solid lignocellulosic material in the range of 2 to 321 per 1000 crA of area of the lignocellulosic material, and after heating 3.5
A combined composition having a pH of from 5.5 to 5.5 and comprising a sugar, starch or a mixture thereof, an alkaline buffer and a sugar and starch conversion catalyst in an amount of 1 to 100% by weight of said sugar, starch or mixture thereof. and the solid lignocellulosic material together have a concentration of about 140 to 3
0.0° C. per mm thickness of the solid lignocellulosic material at a pressure in the range of about 5 to 50 kg/sub.
A method according to claim 1, comprising pressing for 2 to 2 minutes. 25. Process according to claim 1, characterized in that said layer of binder is applied as a composition of sugar, starch or mixtures thereof, catalyst and basic substances, and said composition is characterized. 26 The bonding material layer is 32 per 1000c77f of the surface.
? 2. Process according to claim 1, characterized in that added sugar, starch or mixtures thereof. 27. The method of claim 1, wherein the composition is applied in an amount sufficient to fill the surface voids of the lignocellulosic material.