JPH089711B2 - Adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition. More specifically,
The present invention relates to an adhesive composition suitable for producing wood such as plywood, wood-metal plywood, overlay plywood, laminated wood, particle board, wood wool cement board, wood materials, and composite wood materials.

[Object of the Invention] An object of the present invention is to produce an adhesive having excellent viscosity stability and workability in the above-mentioned wood adhesive.

[Prior Art] Conventional adhesives for wood materials include urea-formaldehyde, melamine-formaldehyde, phenol-
Precondensation resins such as formaldehyde are widely used alone or in the form of co-condensates. Since such a thermosetting synthetic resin adhesive has a large adhesive force and excellent water resistance, it is mainly used in large quantities in fields requiring strength and water resistance. However, these thermosetting resin adhesives inherently have the following drawbacks.

First, all of these adhesives are thermosetting, and exert their effect only when a large amount of heat is applied and they are heat-cured. This heating process requires equipment, time and labor, and is a major obstacle when using this kind of adhesive.

For example, in the production of plywood, a huge hot press machine is required, and when thick boards are used, it takes a very long time because the heat conduction of wood is poor. .

Secondly, unreacted formaldehyde remains for a long time even after it becomes a final product, and this odor is a serious social and environmental problem.

In addition, there are drawbacks such as insufficient initial adhesive strength and difficulty in bonding when the water content of the adherend wood is large. For this reason, there is a drawback that large equipment is required for drying the single plate.

On the other hand, when a plywood is produced by using an adhesive mainly composed of a synthetic latex represented by a styrene-butadiene copolymer latex, it has an adhesive force only by cold pressure (compression bonding at room temperature), but conversely has a water resistance. It has inferior drawbacks. Therefore, various studies have been conducted to improve the water resistance of a carboxylated synthetic latex by using a metal compound such as an oxide or an epoxy compound. It has not reached the point of solving defects such as bad.

[Problems to be Solved by the Invention] As a modification of the conventional formalin condensation type thermosetting resin, a copolymer of an α-olefin monomer and a compound having a carboxyl group, particularly α-olefin and maleic anhydride. An adhesive composition comprising an acid copolymer (copolymer containing a carboxyl group) and a natural or synthetic rubber latex has been proposed.

This composition does not contain formalin at all, and has characteristics such as good normal-state adhesive strength and good water-resistant adhesive strength as compared with conventional adhesives, but poor compatibility between the copolymer containing a carboxyl group and latex. Therefore, the viscosity of the adhesive composition increases,
As a result, a variation occurs in the amount of the adhesive composition applied, the adhesive force becomes unstable, the adhesive force decreases, and the viscosity becomes high, it becomes difficult to handle and the coating operability with a spreader is poor. It has defects due to defects.

[Means and Actions for Solving Problems] The present invention includes I. maleic anhydride / α-olefin copolymer II.a) fumaric acid 0.5 to 5% by weight b) conjugated diene monomer 25 to 50% by weight c) A synthetic rubber having a composition of 45 to 74.5% by weight of a monomer copolymerizable with a) and b), having an average particle size of 1600 to 3000Å and a gel content of 65 to 95%. An adhesive composition comprising a latex and having a II / I weight ratio (solid content) of 90/10 to 10/90 is provided.

The synthetic rubber latex used in the present invention is fumaric acid.
Emulsion polymerization of 0.5 to 5% by weight, conjugated diene monomer 25 to 50% by weight, and copolymerizable monomer 45 to 74.5% by an appropriate method, average particle size 1600 to 3000Å, gel content 65
~ 95%.

The ratio of fumaric acid is 0.5 to 5% by weight, preferably 0.7 to 4
% By weight. If it is less than 0.5% by weight, the viscosity of the adhesive composition increases, the coating amount varies, and uniform adhesive strength cannot be obtained. Moreover, since the viscosity is high, the coating workability is poor. If it exceeds 5% by weight, the stability of the synthetic rubber latex decreases.

The proportion of the conjugated diene-based monomer is 25 to 50% by weight, preferably 30 to 45% by weight. If it is less than 25% by weight, it will be too hard and the adhesion will be poor, and if it exceeds 50% by weight, it will be too soft and the adhesion will be poor.

The ratio of the fumaric acid and the monomer copolymerizable with the conjugated diene monomer is 45 to 74.5% by weight, preferably 50 to 65% by weight. If it is less than 45% by weight, the amount of the conjugated diene-based monomer will be too large and the adhesive strength will be too low, and if it exceeds 74.5% by weight, the amount of the conjugated diene-based monomer will be relatively small. Adhesion is reduced because it becomes too much.

The conjugated diene-based monomer is preferably an aliphatic conjugated diene-based monomer, 1,3-butadiene, 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2-cyano-1,3-butadiene, substituted linear conjugated pentadienes , Straight chain and side chain conjugated hexadiene and the like. Of these, the use of 1,3-butadiene is particularly preferred.

Further, the fumaric acid, the monomer copolymerizable with the conjugated diene-based monomer, vinyl acetate, methyl acrylate,
Butyl acrylate, 2-ethylhexyl acrylate,
(Meth) acrylic acid alkyl ester such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate, styrene, divinylbenzene, chlorostyrene, acrylonitrile,
Examples thereof include vinyl cyanide such as methacrylonitrile, vinyl pyridine, and the like. Of these, styrene, (meth) acrylic acid esters, and acronitrile are particularly preferable. Moreover, it is not limited to these, and they may be used alone or as a mixture of two or more kinds.

In the production of synthetic rubber latex, an ethylenically unsaturated acid other than fumaric acid can be used if necessary so long as it does not affect the present invention.

The synthetic rubber latex of the present invention is produced by an ordinary method using a radical initiator, a surfactant, and a regulator in an aqueous system.

Surfactants used for emulsion-polymerizing these monomers include anionic surfactants, nonionic surfactants and amphoteric surfactants.

Examples of the anionic surfactant include sulfuric acid ester of higher alcohol, alkylbenzene sulfonate, and aliphatic sulfonate.

As the nonionic surfactant, an ordinary polyethylene glycol alkyl ester type, alkyl ether type,
An alkyl phenyl ether type or the like is used.

Examples of the amphoteric surfactant include those having a carboxylate salt, a sulfuric acid ester salt, a sulfonate salt, and a phosphoric acid ester salt as the anion portion, and those having an amine salt or a quaternary ammonium salt as the cation portion. As the salt of alkyl betaine, each salt of lauryl betaine, stearyl betaine, cocoamidopropyl betaine, 2-undecyl-hydroxyethyl imidazolinium betaine, as the amino acid type, lauryl-
Examples thereof include β-alanine, stearyl-β-alanine, lauryldi (aminoethyl) glycine, octyldi (aminoethyl) glycine, and dioctyldi (aminoethyl) glycine.

Fumaric acid is used as the carboxyl group-containing monomer used in the present invention. The use of fumaric acid improves the viscosity stability, workability and adhesive strength.

In addition, in the case of other unsaturated carboxylic acids, the increase in viscosity is large, the workability is poor, and the adhesive strength is largely reduced.

The gel content of the synthetic rubber latex used in the present invention is 65-
95%, preferably 70-90% is suitable. 65 gel content
If it is less than%, the viscosity stability and workability are poor, and the adhesive strength (wood break) decreases. If it exceeds 95%, viscosity stability,
Workability is poor and adhesive strength (wooden break) is also reduced.

The particle size of the synthetic rubber latex used in the present invention is 1600 to
3000Å, preferably 1800 to 2600Å are suitable. Particle size 16
If it is less than 00Å, the viscosity is high and the viscosity stability and workability are poor. If the particle size exceeds 3000Å, the viscosity will be low, and there will be problems in viscosity stability and workability, and the adhesive strength (wood break) will also decrease.

The maleic anhydride / α-olefin-based copolymer resin used in the present invention is obtained by copolymerizing maleic anhydride with an α-olefin-based monomer copolymerizable with the maleic anhydride. As the monomer, an α-olefin having 3 to 10 carbon atoms is preferable. As the α-olefin having 3 to 10 carbon atoms, propylene, 1-butene, 1
Examples thereof include-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, styrene, and mixtures thereof. These α-
Of the olefin-based monomers, styrene and isobutylene are particularly preferable.

Synthetic rubber latex II in the adhesive composition of the present invention
And the maleic anhydride / α-olefin copolymer I weight ratio (solid content) II / I is 90/10 to 10/90, especially 65/35 to 35/65.
Is preferred. When the II / I is out of the range of 90/10 to 10/90, the viscosity stability and workability are poor, and the adhesive strength (wood break) is greatly reduced.

The adhesive composition of the present invention comprises (I) maleic anhydride / α
-Olefin-based copolymer and (II) synthetic rubber latex are the main components, but if necessary, pH regulator, filler, viscosity regulator, curing agent, antioxidant, etc. can be added. . These include, for example, slaked lime, wood flour, wheat flour, casein, ammonium chloride, and phenolic antioxidants. Slaked lime (pH adjuster and filler) is (I), (I
Usually, 20 to 60 parts by weight are used per 100 parts by weight of the main component of I), and ammonium chloride (hardening agent) is usually used in an amount of 0.05 to 0.7 parts by weight per 100 parts by weight of the main components.

[Examples] The present invention will be described in more detail below with reference to Examples. The measuring method and the like are as follows.

1) Method of measuring average particle size The average particle size was measured with a Nisizer made by Nikkaki.

2) Method for measuring gel content The latex was adjusted to pH 8, the copolymer in the latex was coagulated with isopropanol, washed and dried, and 0.3 g of the solid content obtained was immersed in 100 ml of toluene at room temperature for 20 hours, Then, the weight ratio to the residual solid content obtained by filtering with a 120 mesh wire mesh.

3) Method of controlling particle size The larger the amount of emulsifier that can be controlled by the amount of emulsifier during polymerization, the larger the particle size.

4) Method of controlling gel content It can be controlled by the amount of the molecular weight modifier used during polymerization. The higher the content, the lower the gel content.

5) Method for measuring change with time of viscosity The adhesive composition is put in a plastic bottle and stored in a gear oven at 40 ° C, and the change with time of viscosity is measured for 15 days. Viscosity was measured at 25 ° C. at 7 × 20 rpm BH type rotor. The evaluation criteria are as follows.

Good: The change in viscosity with time is small, and the smaller the viscosity increase ratio below, the better.

Poor: The change with time of viscosity is large, and the larger the following thickening ratio, the worse.

6) Workability test method According to the method of measuring the change with time of viscosity, 500 g of the adhesive composition is charged in a spray and rotated at a constant speed to measure the change with time of viscosity and workability. The evaluation criteria are as follows.

Good: Spray coating is applied uniformly.

Bad: Spray coating is unevenly applied.

7) Adhesive Evaluation Method The obtained adhesive composition was applied to an adherend by the method described below to prepare a test piece for measuring the adhesive strength.

Using a 1.6 m / m thick lauan veneer with a water content of 11 to 13% on the adherend, apply the adhesive with a hand roll on the lauan veneer at a rate of 20 g / m ² and then Attach the same lauan veneer to. Further, the same amount of the adhesive was applied on the same and the same lauan veneer was stuck together to form a plywood of a total of three sheets.

The resulting plywood 10kg / cm ² × 5 minutes room temperature after pressing (with respect to plywood), (against the plywood) 10 kg / cm ² at further 120 ° C.
× 3 minutes hot pressing was performed.

After curing at room temperature for 20 hours, a test piece was prepared by cutting the test piece of ordinary plywood into the dimensions specified in the Japanese Agricultural Standards. The test is specified in the Japanese Agricultural Standards for ordinary plywood.

A normal state adhesive strength test, a type 1 immersion peel test (boiling water) and a type 2 immersion peel test (70 ° C. hot water) were performed.

The tester uses a tensile tester for plywood manufactured by Toyo Tester Co.,
Both tests were performed at a peeling speed of 50 mm / min.

Example 1 After mixing 55 parts by weight of an isobutylene-maleic anhydride copolymer (hereinafter abbreviated as "parts"), 1.0 part of caustic soda, and 65 parts of water, 6 parts were mixed.
Dissolve by heating at 5 ℃. To this solution, 30 parts of slaked lime and 45 parts of water were sequentially added, and after stirring, 45 parts of plywood rubber latex [A] shown in Table 1 was added to the solution in solid content, and 0.3 part of ammonium chloride was further mixed. To obtain an adhesive composition. The evaluation results are shown in Table-1.

Examples 2-7, Comparative Examples 1-10 The isobutylene-maleic anhydride copolymer of Example 1 was changed to the compounding amount shown in Table-1, and synthetic rubber latex was further changed to the kind of latex shown in Table-1. An adhesive composition was obtained in the same manner as in Example 1 except that the amount was changed. The evaluation results are shown in Table-1.

In Examples 1 to 7, the adhesive composition intended by the present invention can be obtained.

 A comparative example will be described below.

Comparative Example 1: This is an example in which the amount of conjugated diene in the synthetic rubber latex is below the range of the present invention, and the adhesive strength is poor.

Comparative Example 2: This is an example in which the amount of conjugated diene in the synthetic rubber latex exceeds the range of the present invention, and the adhesive strength is poor.

Comparative Examples 3 and 4: Examples in which acrylic acid and itaconic acid other than fumaric acid, which are outside the scope of the present invention, were used as the acid monomer of the synthetic rubber latex, and the adhesive strength and workability were poor.

Comparative Examples 5 and 6: The gel content of the synthetic rubber latex is less than the range of the present invention in Comparative Example 5 and exceeds the range of the present invention in Comparative Example 6, and the adhesive strength is also poor in Comparative Examples 5 and 6.

Comparative Examples 7 and 8: The average particle size of the synthetic rubber latex is Comparative Example 7
Then, the examples below the range of the present invention and Comparative Example 8 are examples exceeding the range, and the adhesive strength and workability of both Comparative Examples 7 and 8 are poor.

Comparative Examples 9 and 10: Regarding the compounding ratio of the synthetic rubber latex [II] and the copolymer [I], Comparative Example 9 is an example in which the synthetic rubber latex [II] is less than the range of the present invention.
Is an example beyond the range. Both Comparative Examples 9 and 10 have poor adhesive strength and workability.

[Advantages of the Invention] An adhesive composition containing a maleic anhydride-α-olefin copolymer and a synthetic rubber latex of the present invention is a synthetic rubber latex in which a diene rubber latex copolymerized with a specific amount of fumaric acid is used. By using a special synthetic rubber latex having an average particle size of 1600 to 3000Å and a gel content of 65 to 95%, it is possible to obtain a much better adhesive force and coating than the conventional adhesive composition for wood materials. It is an adhesive composition which has an excellent workability and is of extremely high industrial value.

Front Page Continuation (72) Inventor Hiroshi Tatenuma 2-11-14 Tsukiji, Chuo-ku, Tokyo Within Nippon Synthetic Rubber Co., Ltd. (56) References Japanese Patent Publication No. 49-93448 (JP, A) 17967 (JP, B1) JP-B 61-60875 (JP, B2)

Claims (1)

[Claims] 1. A maleic anhydride / α-olefin copolymer II.a) fumaric acid 0.5 to 5% by weight b) conjugated diene monomer 25 to 50% by weight c) these a) and b) It contains a synthetic rubber latex having a composition of 45 to 74.5% by weight of a monomer copolymerizable with, an average particle size of 1600 to 3000Å and a gel content of 65 to 95%, and II / I is a weight ratio ( Solid content) 90/10 to 10/90, The adhesive composition characterized by the above-mentioned.