JPS5950271B2 - water resistant adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel adhesive composition that cures under alkaline conditions, and its purpose is to provide an inexpensive adhesive composition with excellent water resistance suitable for bonding wood, inorganic molded products, etc. Our goal is to provide adhesives.

Conventionally, area resin has been the cheapest resin among plastics, and for this reason, it has been used in large quantities in adhesives for plywood and particle board.

Area resins are generally subjected to an addition reaction under alkaline conditions,
A condensation reaction is then carried out under acidic conditions. Therefore, when curing the area resin, use an acidic curing agent and adjust the pH to 3.
-6 acidic and harden. When wood is bonded using urea resin, excellent adhesive strength can be obtained, but water-resistant adhesive performance and durable adhesive performance cannot be said to be sufficient.

Therefore, when high water resistance and durability are required, melamine or the like is co-condensed.

However, since melamine is more expensive than urea, the resin liquid co-condensed with melamine is also expensive.

The reason why area resins have insufficient water resistance and durability is that the acid used when curing the resin remains in the adhesive layer and acts as a decomposition reaction catalyst for methylene bonds. Once the remaining acid is removed, even those bonded with area resin adhesive will exhibit excellent water resistance and durability. Therefore, if the area resin is cured under alkaline conditions, not only can an inexpensive wood adhesive with excellent water-resistant adhesive performance and durable adhesive performance be obtained, but most of them are alkaline and have low strength. It can also be effectively used as an adhesive for relatively brittle inorganic molded products.

From this point of view, the present inventors have been conducting research on amino resins that harden under alkalinity.

By co-condensing 1.5 to 12 moles of formaldehyde and 0.3 to 3 moles of ketone to 1 mole of an amino compound, a modified amino resin liquid that hardens with real alkalinity was produced and a patent application was filed. . (Special application 1987-887
No. 92 (Japanese Unexamined Patent Publication No. 56-11923)) The present invention is
This invention further improves the adhesive performance of the alkali-curable modified amino resin liquid in the prior invention.

That is, the present invention is based on (a) adding a powdery substance whose main component is a protein insoluble in room temperature water to (a) a modified Aria extract that is mainly composed of urea, formaldehyde, and ketone and hardens under alkaline conditions; , and further f→ A water-resistant adhesive comprising one or a mixture of two or more oxides, hydroxides, or basic salts of alkali metals or alkaline earth metals.

The ketone-modified area resin liquid used in the present invention contains, for example, 1.5 to 12 formaldehyde per mole of urea.
One or more ketones such as acetone, methyl ethyl ketone, acetophenone, cyclohexanone, etc. are added to the initial condensate of area resin obtained by mixing in molar ratios and heating and condensing by a known method per 1 mole of urea. 3
It was added at a ratio of ~3 mol, at a temperature of 50 to 90°C, and a pH of 8.
It is produced by a method of co-condensation under alkalinity of 5 to 12.

We also use a ketone-modified area resin solution in which urea and formaldehyde, as well as ketone and formaldehyde, are heated and condensed separately in advance, and these initial condensates are mixed at room temperature or under heat, and then cured under alkaline conditions. be done.

Furthermore, if necessary, the effects of the present invention may be obtained by adding a small amount of one or more of thiourea, ethylene urea, melamine, acetoguanamine, phenol, resorcinol, etc. during the production of the modified area resin liquid. And also,
A small amount of one or more of starch, dextrin, gum arabic, sodium alginate, sodium polyacrylate, polyacrylic acid amide, carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose, etc. may be added.

The most important feature of the present invention is that a powder whose main component is a protein that is insoluble in water at room temperature is added to this ketone-modified area resin liquid.

A powder substance whose main component is protein that is insoluble in room temperature water is a protein-based powder substance that becomes solubilized in a short period of time and does not exhibit significant thickening when added to room temperature water. hand,
For example, high-temperature defatted soybean powder, high-temperature defatted rapeseed powder, corn gluten powder, which is not normally used as a filler,
Examples include water-insoluble proteins such as dried dish flour, milk casein, algae protein, bacterial cell protein, etc., or powders containing such proteins as the main component.

Ordinary adhesives use powdered substances as bulking agents, such as low-temperature defatted soybean meal, egg white, blood albumin, etc., whose main component is protein that easily dissolves in room-temperature water.

However, when these commonly used protein-based powders that are soluble in room temperature water are added to the ketone-modified area resin solution, oxides, hydroxides, or basic salts of alkali metals or alkaline earth metals are added. When added, the viscosity increases instantaneously and the mixture turns into a gel.

However, as in the present invention, when a powder mainly composed of proteins insoluble in water at room temperature, which is not normally used as a filler, is added, oxides, hydroxides, or bases of alkali metals or alkaline earth metals are added. Even when a salt is added, no rapid thickening is observed, and the adhesive thickens slowly to give a highly viscous adhesive.

In addition, many powdered materials whose main component is protein that is insoluble in room-temperature water are relatively inexpensive, so they not only have the economical effect of lowering the cost of adhesives, but also allow the ketone-modified area resin liquid to adhere to the adherend. Since it prevents excessive penetration, it has a remarkable effect on improving temporary adhesion and normal and water-resistant adhesion performance.

The oxides, hydroxides or basic salts of alkali metals or alkaline earth metals used in the present invention refer to alkali metals such as lithium, potassium, sodium, etc. or alkaline earth metals such as magnesium, calcium, strontium, barium, etc. metal oxides, hydroxides, carbonates, bicarbonates, silicates, borates, aluminates,
One type or a mixture of two or more types of zincates, etc.,
These alkaline metal compounds have the effect of accelerating the curing of the ketone-modified area resin.

Among these metal compounds exhibiting alkalinity, oxides and hydroxides of alkaline earth metals such as magnesium and calcium have the effect of increasing the water resistance of the adhesive by binding with added proteins, and therefore are suitable for use in the present invention. This is preferable in order to bring out the effect more markedly. Furthermore, these metal compounds may contain oxides, hydroxides, hydrochlorides, sulfates, nitrates, phosphates, silicates of polyvalent metals such as copper, aluminum, zinc, iron, chromium, molybdenum, etc. Even if salts such as salts are used or added, the effect of the present invention remains unchanged (Cl).

The adhesive of the present invention comprises (a) a ketone-modified area resin liquid, (
b) Powder material whose main component is protein that is insoluble in room temperature water, ←→
It has three essential components: one or a mixture of two or more of oxides, hydroxides, or basic salts of alkali metals or alkaline earth metals, and the blending ratio is equal to that of the ketone-modified area resin liquid. Based on 100 parts by weight, the main component is protein that is insoluble in room temperature water. 5 to 200 parts by weight of powder, an alkali metal or alkaline earth metal oxide,
The amount of hydroxide or basic salt is preferably 0.5 to 50 parts by weight.

At this time, if the blending amount of the powder whose main component is protein that is insoluble in water at room temperature exceeds 200 parts by weight, the water-resistant adhesion performance will decrease, and the oxides of alkali metals or alkaline earth metals will deteriorate. , the amount of hydroxide or basic salt is 5
If the amount exceeds 0 parts by weight, the usable life of the adhesive will be significantly shortened, causing a practical problem. When used, the adhesive of the present invention can be used with fillers mainly consisting of starch such as wheat flour, barley flour, rice flour, corn starch, tapioca starch, etc., gypsum,
The effects of the present invention are not affected by the addition of inorganic fillers such as diatomaceous earth, clay, zeolite, talc, asbestos, etc., or organic fillers such as walnut flour, corn flour, wood flour, etc.

Furthermore, thermoplastic resin emulsion such as vinyl acetate resin, ethylene vinyl acetate copolymer resin, acrylic acid ester resin, etc., or synthetic rubber latex such as SBR, NBR, IR, CR, etc. may be added.

The water-resistant adhesive of the present invention can be applied to plywood, laminated veneer wood, laminated wood,
Suitable for bonding wood materials such as particle boards, hardboards, wood panels, etc., as well as asbestos slate boards, calcium silicate boards, magnesium carbonate boards, rock wool boards, valve cement boards, gypsum boards, and wood wool cement. board,
It can also be used to bond inorganic molded materials such as foamed concrete plates and glass fibers, and exhibits excellent water-resistant adhesive performance that can withstand strong immersion in boiling water.

Next, examples of the present invention will be given.

Example 1 116 g of acetone, 148 g of paraform (formaldehyde content 81%), and 162 g of 37% formalin were placed in a four-sided flask with a capacity of 11, and while stirring, a 2% aqueous sodium hydroxide solution was added dropwise little by little to bring the pH of the reaction solution to 8.4. ~
Adjusted to within the range of 9.6 (T, B test paper).

Stirring was continued while maintaining the temperature at around 70°C, and a 2% aqueous sodium hydroxide solution was added to continue the reaction for 3 hours while maintaining the pH within the range of 8.4 to 9.6.

After that, the acetone resin initial condensate obtained by cooling and a commercially available area resin liquid (manufactured by Hounen Oil Co., Ltd., UL-1002) were mixed 1:1.
(weight ratio) were uniformly mixed at room temperature.

For 100 parts of the acetone-denatured area resin solution obtained in this way, K) Powder whose main component is protein such as blood albumin soluble in room temperature water, low temperature defatted soybean flour, or high temperature defatted soybean insoluble in room temperature water. A paste was prepared by adding 10 parts of a protein-based powder such as powder, high-temperature defatted rapeseed powder, etc., 10 parts of slaked lime powder, and 5 parts of water.
Changes in the state of these glue solutions were observed when they were left at room temperature. In addition, these paste liquids were mixed to a thickness of 2.0 nm) with a moisture content of 7 to
150. on each of the front and back sides of 8% lauan veneer. ! 9/m
”, lauan veneers of the same thickness were stacked so that the fiber directions were perpendicular to each other, and pre-compressed for 15 minutes at a pressure of 10k9/CwL, then the temperature was 120°C and the pressure was 10°C.
Plywood was manufactured by heating and pressurizing at k9/c-d for 25 minutes.

The adhesive tensile strength of the obtained plywood was measured according to the JAS standard plywood test method.

The results of the above tests are summarized in the table below.

From the above results, the water-resistant adhesive of the present invention requires the use of a powder material whose main component is protein that is insoluble in water at room temperature. It can be seen that when a water-soluble protein-based powder is used, the mixed liquid turns into a gel, making it unsuitable as an adhesive.

Example 2 Acetone, methyl ethyl ketone, and cyclohexanone were used as ketone components, and the reaction molar ratio of ketone and formaldehyde was fixed at a ratio of 1:3, and acetone/formaldehyde, methyl ethyl ketone/formaldehyde, and cyclohexanone were prepared according to the method shown in Example 1. - A solution of formaldehyde resin initial condensate was obtained.

Each of these initial condensate solutions was mixed with a commercially available area resin solution (manufactured by Hounen Oil Co., Ltd., UL-002) at a ratio of 1:1 (weight ratio), stirred at 80°C for 30 minutes, and mixed. A condensation reaction was carried out. To 100 parts of each ketone-modified area resin solution obtained in this way, 10 parts of corn gluten powder insoluble in room temperature water, 5 parts of wheat flour, 10 parts of water, 5 parts of 25% caustic soda aqueous solution, and 10 parts of magnesium carbonate were added. In addition, a glue solution was prepared.

These glue solutions were applied to the front and back surfaces of lauan veneers with a thickness of 2.07 nm and a moisture content of 7 to 8% at a ratio of 1509/Trl, respectively, and the lauan veneers of the same thickness were placed so that the fiber directions were perpendicular to each other. After being temporarily pressed for 15 minutes at a pressure of 101<9/d, the
．． Plywood was manufactured by heating and pressurizing for 5 minutes.

The adhesive tensile strength of the obtained plywood was measured according to the JAS standard plywood test method, and the results are shown in the following table.

As a control, 15 parts of wheat flour, 10 parts of water, 5 parts of 25% caustic soda aqueous solution, and 10 parts of magnesium carbonate were added to 100 parts of the acetone-modified area resin solution obtained by the above method without adding corn gluten powder. At the same time, the results of measuring the adhesive tensile strength when using a paste prepared by adding 100% of the above amount are also shown. From the above results, the water-resistant adhesive of the present invention has much better adhesive strength than the ketone-modified area resin adhesive, which does not contain powdery substances mainly composed of water-soluble proteins in room-temperature water. It can be seen that the performance was significantly improved.

Claims (1)

[Claims] 1 (a) Ketone-modified area resin liquid, (b) Powder mainly composed of proteins insoluble in water at room temperature, and (c) oxides, hydroxides, or basic salts of alkali metals or alkaline earth metals. A water-resistant adhesive mainly consisting of .