JPS62119285A - Adhesive composition - Google Patents

Abstract

PURPOSE:To provide an adhesive composition for wood, containing a water-soluble polymer solution, a water-based latex or water-based emulsion and a specific isocyanate compound, having excellent water-resistance and stability, long pot- life and excellent workability. CONSTITUTION:The objective composition can be produced by compounding (A) a water-soluble polymer solution (e.g. aqueous solution of PVA) and/or (B) one or more water-based latex or water-based emulsion (e.g. chloroprene latex) and (C) the compound of formula (n is 0-8; isocyanate bonded to ortho- position to methylene accounts for >=5mol% of the whole isocyanate) (e.g. polymethylene polyphenyl polyisocyanate). The amount of the component C is preferably 2-60wt% based on the solid content of the components A and B. The adhesive exhibits high adhesive strength even to a substrate having high water-content by the combined use of a protein composition composed mainly of prolamine (e.g. corn protein).

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a wood adhesive composition with excellent water resistance.

More specifically, the present invention relates to an adhesive composition that has good stability, excellent workability during use, and can exhibit good adhesive strength even on breakable materials containing a large amount of water.

[Conventional technology and its problems]

Traditionally, formaldehyde-based condensation resins have been used as adhesives for wood, but because of problems such as residual free formalin and initial adhesion at low temperatures, in recent years, isocyanate compounds have been used in water-soluble polymers or water-based latex. Adhesive compositions have been used to which the additives have been added.

The isocyanate compound used here is a compound containing two or more isocyanate groups in the molecule,
Examples include tolylene diisocyanate, 4,4°-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, isophorone diisocyanate, polymethylene polyphenyl polyisocyanate, etc.; For this reason, polymethylene polyphenyl polyisocyanates containing 4,4'-diphenylmethane diisocyanate or 4,4'-diphenylmethane diisocyanate are widely used. However, when such an isocyanate compound is mixed with a water-soluble polymer or water-based latex, there are problems such as a rapid reaction between the polymer compound and the isocyanate compound, and a short pot life of the adhesive composition. The problem is that the reaction proceeds while the adhesive is left in a deposited state until a predetermined curing step after coating, making it impossible to obtain sufficient adhesive strength.

In order to solve these problems, for example,
As described in Publication No. 30577, there is a method of diluting and adding an isocyanate compound with a solvent that is insoluble in water and mutually soluble with the isocyanate compound, but even with this method, the bot life extension and curing are not sufficient. The problem of adhesion work, which requires a rapid transition to the compression hardening process after application, cannot be resolved, and when such solvent-diluted isocyanate compounds are used together with water-based latex or emulsion, the cured product becomes plasticized by the solvent. It also has the disadvantage of reducing adhesive properties.

[Means for solving problems]

The present inventor conducted extensive studies to solve these problems, and as a result discovered that the position of the isocyanate group relative to the methylene group in polymethylene polyphenyl polyisocyanate is important, and arrived at the present invention. That is, the present invention provides one or two of a) a water-soluble polymer aqueous solution and/or b) an aqueous latex or an aqueous emulsion.
Isocyanate compound represented by the above-species c, -fa formula (1) (where n is 0 or an integer from 1 to 8, and the isocyanate group bonded to the ortho position to the methylene group bonded to the benzene ring is the total isocyanate compound) 5 mol 26 or more of the group) as an essential component, and an adhesive composition characterized by further containing a protein mainly composed of prolamin. be.

The water-soluble polymer aqueous solution referred to in the present invention is an aqueous solution of a polymer that can form an aqueous solution with a concentration of 5% or more at room temperature, such as a formaldehyde condensation resin aqueous solution, a polyvinyl alcohol aqueous solution, a starch aqueous solution, These include an aqueous solution of a cellulose derivative such as carboxymethylcellulose or methylcellulose, an aqueous solution of sodium polyacrylate, and an aqueous solution of polyacrylamide. An aqueous solution of a polymer that can only form an aqueous solution with a concentration of less than 5% by weight at room temperature will result in excessive moisture in the adhesive composition, which will not only inhibit curing but also reduce the adhesive function, resulting in failure. It is. In the field of wood adhesion where formaldehyde release is not a particular problem, water-soluble polymer water? 8? For &, formaldehyde-based condensation resins are preferable in terms of adhesive performance and economy. Further, when a formaldehyde-based condensation resin containing 1 to 25 fflffi% of phenol is used, the adhesive composition is less likely to exhibit thixotropic properties and exhibits extremely good fluidity, which has the advantage of not causing any trouble in use.

The aqueous latex or aqueous emulsion of the present invention is
Latex made by copolymerizing conjugated dienes such as butadiene and isoprene with various vinyl monomers such as styrene, methyl methacrylate, and acrylonitrile, chloroprene latex, butyl rubber latex, ethylene-vinyl acetate copolymer/emulsion, and polyester. These include vinyl acetate polymer emulsions, acrylic resin emulsions, and phenol formaldehyde cocondensation resin emulsions. These aqueous latexes or aqueous emulsions also contain carboxyl groups, N-methylol L N-alkoxymethyl groups, glycidyl groups, β
- It also includes so-called modified latexes obtained by emulsion polymerization of at least 141 reactive monomers having at least one crosslinkable reactive group such as methylglycidyl group, hydroxyl group, amino group, amide group, and acid anhydride in their side chains. .

The isocyanate compound referred to in the present invention has the general formula (however,
n is 0 or an integer of 1 to 8, and the isocyanate i bonded at the ortho position to the methylene group bonded to the benzene ring accounts for 5 mol% or more of the total isocyanate groups.

When n exceeds 8, the isocyanate compound becomes highly viscous and becomes difficult to handle. In addition, if the isocyanate group bonded to the ortho position is less than 5 mol% of the total isocyanate groups, the reaction with the water-soluble polymer aqueous solution, water, latex, etc., and the reaction with the adherend material will be accelerated, and as mentioned in the present invention, Isocyanate compounds that do not show pot life extension effects or deposition time extension effects after application may be used in combination with other isocyanate compounds, or may be mixed with various polyols etc. in advance and used as a so-called prepolymer. good.

The protein of the present invention whose main component is prolamin is, for example, corn protein, wheat protein, or the like. Corn protein is a protein contained in corn, which is easy to use industrially from an economic standpoint.Gluten meal, which is obtained as a by-product when starch n is extracted from corn, is a typical example. 60 prolamins
Contains JRffi% or more. The manufacturing method includes, for example, soaking corn in an aqueous sulfite solution, crushing it in a crusher, separating and removing the germ, and then grinding it in a grinding mill to separate a milky substance. Next, starch is separated from the emulsion, and the remaining liquid is concentrated, filtered, dried, and crushed to obtain gluten meal, which usually contains 60 to 80% by weight of prolamins and the remainder is starch.
Naturally, it is full of water.

When using a large amount of protein with low prolamin content in order to obtain adhesion to high moisture content wood, the fluidity of the blended glue deteriorates and the viscosity increases over time, causing problems for practical use. The prolamin content should be greater than 60% by weight. It is desirable that the corn protein has a particle size of 80 mesh or less in order to improve miscibility with the blended flour and uniform application of the blended paste.

In the present invention, C for a water-soluble polymer aqueous solution and/or b aqueous latex or aqueous emulsion
The total amount of the isocyanate compound is not particularly limited, but it is preferable to add 2% or more and 60% or less based on the total nonvolatile content of a and b, 2! If it is less than if%, the water resistance improving effect of the isocyanate compound,
It is difficult to improve adhesion on wood substrates with high moisture content. If the content exceeds 60% by weight, the resulting adhesive composition will increase in viscosity.Also, there are no particular limitations on the 4'' protein particles mainly composed of prolamin (d), but the non-volatile components of a and b may be combined. It is better to add 4 to 100% heavy weight to 0
When a protein containing prolamin as a main component is used in the adhesive composition of the present invention, the adhesion performance is improved, especially on wood substrates with high moisture content, but when the amount added is less than 4% by weight, such It is difficult to see the effect, and if it exceeds 100% by weight, the fluidity of the adhesive composition tends to deteriorate.

In addition to the above-mentioned components, the adhesive composition of the present invention may contain fillers such as wheat flour, calcium carbonate, kuruk, clay, coconut flour, and wood flour, and additives such as insect repellents, preservatives, and dyes. It's okay. Furthermore, especially when a formaldehyde condensation resin is used, a curing agent for the formaldehyde resin such as an ammonium salt or an acidic substance, or an additive such as urea or melamine may be used in combination.

〔Example〕

Next, the present invention will be explained with reference to Examples, but the present invention is not limited in any way by these Examples. All parts and % are ffIMt parts and weight % unless otherwise specified.

Example 1 Adhesive mainly composed of polyvinyl alcohol and SBR-based aqueous latex (Mitsui Toatsu Chemical Co., Ltd. x L-To
ll, non-volatile content 23.2%) to 100 parts of polymethylene polyphenyl polyisocyanate compound (tJR-4005 manufactured by Mitsui Toatsu Chemical Co., Ltd., NGOL @ content 32.2
%, ortho position NGO content 16.8) was added to obtain an adhesive composition.

The resulting adhesive composition had a moisture content of 8% and a thickness of 1.6 mm.
Apply 35g to both sides of a 00 square lauan veneer, stack the same veneers without adhesive on the top and bottom so that the fiber direction is perpendicular to the adhesive-coated veneer, leave it at room temperature for 30 minutes, and then apply 10kg.
Cold pressure was applied for 15 minutes at a pressure of "g/cm".

After that, after leaving it at room temperature for 60 minutes, the temperature was 115℃ and the pressure was 10kg/c+w! Heat pressing was carried out for 1 minute and 40 seconds to obtain plywood.

The time it takes for the adhesive composition to reach a viscosity of 100 voids (hereinafter abbreviated as pot life) is 2.3 hours,
The adhesive strength of the obtained plywood based on the repeated boiling test according to the Japanese Agricultural Standards was lo, 3 kg/cm'', and the xylem fracture W rate was 47%.

Example 2 Melamine/phenol/formaldehyde combination resin (
Niloid 881 non-volatile content 52 manufactured by Mitsui Toatsu Chemical Co., Ltd.
．． 5%) 100 parts of protein whose main component is prolamin (FM-200 manufactured by Mitsui Toatsu Chemical Co., Ltd., prolamin content 72.4%) 10 parts, SBR-based aqueous latex (S B manufactured by Mitsui Toatsu Chemical Co., Ltd.) -1051, non-volatile content 49.2%) 10 parts, wheat flour Jto part, U I? -
400,510 parts, 20 parts of water, and 0.5 part of ammonium chloride were mixed to obtain an adhesive composition. Using the obtained composition with a moisture content of 8% and 25% veneer, the ambient temperature was set to 4.
Plywood was manufactured in the same manner as in Example 1 except that the temperature was 0°C.

The pot life of the obtained composition was 3.5 hours, and the adhesive strength in the repeated boiling test was 10.8 kg/c+w'' when using a veneer with a moisture content of 8%, and the wood breakage rate was 40.
%, adhesive force 9.3 kg when using a single machine with a moisture content of 25%
/cm”, cotton with xylem breakage rate of 15%.

Example 3 An adhesive composition was obtained by mixing 100 parts of Niroid 881, 10 parts of FM-200, 10 parts of wheat flour, 515 parts of UR-400, 25 parts of water, and 0.5 part of ammonium chloride.

The pot life of the resulting composition was 3.3 hours.

Plywood was produced and evaluated in the same manner as in Example 2. Moisture content 8%
When using a veneer with a veneer of there were.

Comparative Example 1 Polymethylene polyphenyl polyisocyanate compound CR was used instead of U R1005 as an incyanate compound.
-200 (Mitsui Toatsu Ihigaku Co., Ltd. NGO total content 3
1.0%, ortho NGO content! An adhesive composition and plywood were produced in the same manner as in Example 1, except that 3%) was used. The pot life of the obtained adhesive composition was 1.5 hours, the plywood adhesive strength was 7.2 kg/Cm'', and the wood breakage rate was O.
%, which was an inferior result compared to Example I.

Comparative Example 2 An adhesive composition and plywood were produced in the same manner as in Example 2, except that CR-200 was used instead of UR-4005 as the isocyanate compound. The pot life of the obtained composition was 2.0 hours, and the results of repeated boiling tests on plywood showed that when using a veneer with a moisture content of 8%, the adhesive strength was 8.4 kg.
/cab", xylem breakage rate 4%, when using veneer with moisture content 25% Adhesive cuff, 2kg/am", xylem breakage rate 0%
Therefore, it was significantly inferior to Example 2.

Comparative Example 3 An adhesive composition and plywood were produced in the same manner as in Example 3, except that CR-200 was used instead of UR-4005 as the isocyanate compound. Bo/ of the resulting composition
) The life is 1.8 hours, and the results of repeated boiling tests on plywood show that when using veneer with a moisture content of 8%, the adhesive cuff is 9.
When using a veneer with kg/cm', wood breakage rate of 7%, and moisture content of 25%, the adhesive force was 6.7 kg/c+w'', and the wood breakage rate was 0%, which was significantly inferior to Example 3.

〔Effect of the invention〕

The adhesive composition obtained by mixing the isocyanurate compound of the present invention with a water-soluble polymer aqueous solution and/or an aqueous latex or an aqueous emulsion is superior to a composition using a conventional polymethylene polyphenyl polyisocyanate. It has a long pot life, has the effect of extending the deposition time after application of the adhesive until it hardens, and has no particular adhesion performance. In addition, when used in combination with a protein whose main component is prolamin, it is possible to exhibit good adhesive strength even when the base has a high moisture content.

Claims (2)

[Claims] (1) a. Water-soluble polymer aqueous solution and/or b. One or more of aqueous latex or aqueous emulsion; c. Isocyanate compound represented by general formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼(I) (However, n is 0 or an integer from 1 to 8, and the isocyanate group bonded to the ortho position to the methylene group bonded to the benzene ring accounts for 5 mol% or more of the total isocyanate groups), An adhesive composition characterized by containing it as an essential component. (2) a. Water-soluble polymer aqueous solution and/or b. One or more of aqueous latex or aqueous emulsion; c. Isocyanate compound represented by general formula (I) ▲ Numerical formula, chemical formula, table, etc. Yes▼(I) (However, n is 0 or an integer from 1 to 8, and the isocyanate group bonded to the ortho position to the methylene group bonded to the benzene ring accounts for 5 mol% or more of the total isocyanate groups), d , a protein whose main component is prolamin, and an adhesive composition characterized by containing as essential components.