JPH04264182A - Adhesive composition - Google Patents

Abstract

PURPOSE:To provide an adhesive composition improved in durability and waterproofness, in particular, adhesiveness after repeated boiling. CONSTITUTION:An adhesive composition consisting of polyvinyl alcohol having in its molecule at least one functional group selected from a primary amino group, a primary ammonium salt group, a secondary amino group and a secondary ammonium salt group; a filler; and a waterproofness improver. The amounts of the filler and the waterproofness improver are 5-500 and 1-50 parts by weight, respectively, per 100 parts by weight of the polyvinyl alcohol. This adhesive composition is improved in waterproofness and durability and hence can be used advantageously as an adhesive for wooden materials. The adhesive of the invention has a long service life since the viscosity of its solution hardly changes after the addition of a waterproofness improver. In addition, it can exhibit excellent waterproofness and adhesiveness after repeated boiling without the necessity for severe hot pressing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive composition having excellent coating properties and water resistance.

0002

BACKGROUND OF THE INVENTION Hitherto, urea resins, urea-melamine resins, phenolic resins, etc. have been mainly used as adhesives for wood such as plywood or for secondary processing of plywood. Many of these adhesives were inexpensive and had excellent initial adhesive strength and water resistance. Other woodworking adhesives include water-based emulsion adhesives such as polyvinyl acetate emulsions, ethylene-vinyl acetate copolymer emulsions, and acrylic emulsions, latex adhesives such as styrene-butadiene copolymer latex, and PVA-based adhesives. Adhesives, isobutylene-maleic anhydride copolymer adhesives, etc. have been used. These adhesives also had good initial adhesion and water resistance.

0003

[Problems to be Solved by the Invention] Formalin adhesives such as urea resin and urea-melamine resin, which are commonly used as adhesives for wood, contain residual formaldehyde (hereinafter abbreviated as formalin). Formalin has become a major problem in recent years, as it worsens the working environment when manufacturing plywood, and furniture and houses made with plywood using these adhesives emit formalin. Recently, attempts have been made to reduce the release of formalin from these resins. For example, attempts have been made to reduce the molar ratio of formalin to urea and melamine, or to add absorbents for free formalin, but it is essentially impossible to eliminate formalin and it is not completely safe. The current situation is that it cannot be said. Furthermore, it is said that these formalin-based adhesives do not exhibit sufficient water resistance unless they are heated and compressed, and there are also problems in weather resistance and durability. In addition, although emulsion adhesives and latex adhesives have a certain degree of water resistance, they have weak distortion resistance when immersed in hot water or hot water, have problems with heat creep resistance, and are bonded after repeated boiling. They have problems such as lack of power. PVA adhesives and isobutylene-maleic anhydride copolymer adhesives have excellent initial adhesion and good water resistance, but because they use polyvalent isocyanate compounds as waterproofing agents, they may be harmful to the body. If it comes into contact with it, it may cause a rash, resulting in problems with workability. Further, there are other problems such as the viscosity increasing quickly after mixing the water-resistant agent and the base agent, and the water-resistant agent reacting with water and becoming deactivated when left standing, resulting in insufficient water resistance.

0004

[Means for Solving the Problems] As a result of repeated studies on the problems that conventional adhesives had, the present inventors have developed a method that includes a primary amino group, a primary ammonium base, a secondary amino group, and a secondary amino group in the molecule. Polyvinyl alcohol (hereinafter referred to as polyvinyl alcohol) having at least one functional group selected from class ammonium bases
(abbreviated as PVA) (A), a filler (B) and a waterproofing agent (C), and the blending ratio of each component is component (A) 10
They discovered an adhesive composition containing 5 to 500 parts of component (B) and 1 to 50 parts of component (C) to 0 parts by weight (hereinafter, parts by weight are abbreviated as parts), and completed the present invention. .

The present invention will be explained in detail below. PVA (A
) is a copolymer with a monomer having the functional group, or a monomer that produces the above amino group or ammonium base through a saponification reaction or hydrolysis reaction after copolymerization. Examples include PVA obtained by saponification reaction or hydrolysis reaction, and graft polymers or block polymers containing PVA as one component and having the functional group. The average degree of polymerization of PVA (A) is
Usually 100-5000, preferably 200-25
It is 00. If the average degree of polymerization is less than 100, the performance as a binder, especially the adhesive strength, will be insufficient, and the average degree of polymerization will be less than 500.
If it exceeds 0, the viscosity of the solution becomes too high, which is unfavorable in terms of workability. The average saponification degree of PVA (A) is 60-100
Mol% is preferred. If the average saponification degree is less than 60 mol%, it is not preferable because it becomes difficult to dissolve in water. The content of primary amino groups, primary ammonium bases, secondary amino groups, and secondary ammonium bases in PVA (A) is not particularly limited as long as it is 0.05 mol% or more, but is usually 0.1 to 30 mol. Selected from a range of %. If the content of the amino group or ammonium base is less than 0.05 mol%, the effects of the present invention cannot be obtained, and even if the content exceeds 30 mol%, the expected effect may not be obtained. can't get it.

[0006] Any method can be used to produce PVA (A) having at least one functional group selected from a primary amino group, a primary ammonium base, a secondary amino group, and a secondary ammonium base in its molecule. Examples are shown below. ■Primary amino group, primary ammonium base,
An olefinically unsaturated monomer having a secondary amino group or a secondary ammonium base, or an olefinically unsaturated monomer having a substituent that can produce the amino group or the ammonium base by saponification or hydrolysis reaction, and vinyl It is copolymerized with ester and then subjected to saponification or hydrolysis reaction. (2) Introducing an aldehyde or the like having the amino group or the ammonium base into PVA by an acetalization reaction. ■ Utilizes the Hofmann rearrangement reaction of amino groups. Among the above methods, method (2) is preferred. In the method represented by (2), specific examples of the olefinically unsaturated monomer having the above-mentioned functional group and the olefinically unsaturated monomer having a substituent capable of producing the functional group by hydrolysis reaction, etc. Examples include vinylamines represented by the following chemical formula 1 or salts of organic or inorganic acids thereof, N-vinylamides represented by the following chemical formulas 2, N-vinylimides represented by the following chemical formulas 3, etc. .

[0007]

[Chemical formula 1]

[Case 2]

[Formula 3] (wherein, R1 is a hydrogen atom or a methyl group, R2 is a hydrogen atom or a lower alkyl group, R3 is a hydrogen atom, a lower alkyl group, a methylol group, or an ethylol group, and n is 0 to 4
m represents an integer of 2 to 4, respectively. )

000
8] An acid or an alkali can be used as a catalyst for hydrolyzing the above copolymer. When using an acid catalyst, the amino group generated by hydrolysis of the amide group in the unit consisting of the monomer represented by Chemical Formula 2 or Chemical Formula 3 above is converted into an ammonium base by subsequently reacting with the acid catalyst. Can be done. Also, when using an alkaline catalyst,
An amino group can be generated by hydrolysis of the above-mentioned amide group, which can be further reacted with an acid to form an ammonium base. Examples of the aldehyde having the amino group or the ammonium base in the molecule used in the method represented by (1) above include aminoacetaldehyde, aminobutyraldehyde,
N-alkylacetaldehyde, N-alkylbutyraldehyde (here, alkyl refers to an alkyl group having 1 to 6 carbon atoms), N-methylolacetaldehyde, N-alkylbutyraldehyde
Examples include, but are not limited to, -ethylolacetaldehyde, dialkyl acetals or ammonium salts thereof, and the like.

[0009] Among the PVAs (A) containing the amino group or the ammonium base, PVA having a primary amino group or a primary ammonium base in the molecule is preferred from the viewpoint of water-resistant adhesive strength and water resistance. In addition, as the filler (B) of the present invention, organic fillers such as wood flour, walnut shell powder, urea resin, melamine resin, clay, talc, calcium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, oxidized Inorganic fillers such as titanium and silicon oxide are used. The average particle size of the filler (B) is preferably 10 μm or less, more preferably fine particles of 5 μm or less. The effect of these fillers (B) is to improve the initial adhesive strength,
It works to increase creep resistance and shear adhesive strength, and also improves the fluidity of the adhesive during application. The water resistant agent (C) of the present invention reacts with a primary amino group, a primary ammonium base, a secondary amino group or a secondary ammonium base,
Any compound that can crosslink with these may be used, such as formaldehyde, monoaldehyde compounds such as acetaldehyde, glyoxal, glutaraldehyde,
Polyvalent aldehyde compounds such as dialdehyde starch, methylol compounds such as methylolmelamine and dimethylolurea, aldehyde compounds such as the reaction product of ammonia and formaldehyde such as hexamethylenetetramine, aluminum, iron, copper, zinc, titanium, magnesium, chromium. ,
Water-soluble salts of metals such as zirconium, or ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di(or tri)
Examples include polyvalent epoxy compounds such as glycidyl ether, trimethylolpropane triglycidyl ether, and hexanediol diglycidyl ether, among which aldehyde compounds are preferred, and polyvalent aldehyde compounds are particularly preferred. Dialdehyde compounds are particularly preferred because the viscosity of the adhesive changes little after the water-resistant agent is added and the pot life is long.

[0010] The adhesive composition of the present invention comprises the above component (A).
, component (B) and component (C), it still has excellent performance as an adhesive composition, but the adhesive performance is significantly improved by further adding the aqueous emulsion (D). Examples of the aqueous emulsion (D) of the present invention include styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, chloroprene latex, poly(meth)acrylate emulsion, butyl rubber latex, polyvinylidene chloride emulsion, and polyvinyl chloride. Examples include emulsion, polybutadiene latex, methyl methacrylate-butadiene copolymer latex, ethylene-vinyl acetate copolymer emulsion, polyvinyl acetate emulsion, and the like. The aqueous emulsions of the present invention include those modified with carboxyl groups or those modified with primary alcohol groups. The effect of adding these aqueous emulsions (D) is to improve the fluidity of the coating solution, enable high-speed coating, and improve the initial adhesive strength and peel resistance strength. The blending ratio of each component of the adhesive composition of the present invention is component (A) 100%
component (B) 5 to 500 parts, component (C) 1 to 5 parts
It is 0 copies. In addition, when adding the aqueous emulsion (D), the blending ratio is 100 parts of component (A) to 100 parts of component (D).
) 5 to 400 parts. If component (B) is less than 5 parts, the total solid content of the adhesive cannot be increased sufficiently;
The initial adhesive strength is not sufficiently developed, and not only does it not function as an adhesive, but it also leads to a decrease in shear adhesive strength, which is undesirable. Moreover, if the amount of component (B) exceeds 500 parts, it is not preferable because there is a problem of a decrease in adhesive strength and fluidity of the coating liquid. The preferred blending ratio of component (B) is 20 to 300 parts, more preferably 50 to 200 parts. Component (C) is 1
If the amount is less than
If C) exceeds 50 parts, the stability of the adhesive becomes poor, which is not preferable. The preferred blending ratio of component (C) is 5 to 2.
It is 0 copies. If the amount of component (D) is less than 5 parts, the effects of adding the aqueous emulsion, such as improvement in the flow characteristics of the size liquid, improvement in peel adhesion, and improvement in water resistance, will not be exhibited. Moreover, if the content of component (D) exceeds 400 parts, water resistance, especially repeated boiling adhesive strength, will not be developed, which is not preferable. The preferred blending ratio of component (D) is 30 to 300 parts, more preferably 50 to 200 parts.

As mentioned above, the present invention uses PVA (A) having a primary amino group, a primary ammonium base, a secondary amino group or a secondary ammonium base in its molecule, and a water resistant agent (B).
) and a filler (C), and functions as an excellent adhesive only in the case of the above-mentioned compounding ratio, and even if one of the constituent requirements is missing, a problem will occur. When used as an actual adhesive, in addition to the above ingredients, preservatives, antifungal agents, antifoaming agents, thickeners, wettability improvers, fragrances, coloring agents, etc. may be added. Can be done. As other additives, starches, gums, CMC, MC, sodium alginate, etc. can be added for the purpose of improving coatability and adhesiveness. In addition to the PVA (A) of the present invention, unmodified PVA and the PV of the present invention may be used within a range that does not impair the effects of the present invention.
Modified PVA other than A (A) can be added.

When producing the adhesive composition of the present invention, PVA (A), filler (B), etc. are poured into water with stirring, and the temperature is raised to dissolve PVA (A). . When further blending an aqueous emulsion (D), the aqueous emulsion (D) is mixed under stirring after cooling the solution. Although the waterproofing agent (C) varies depending on its type, it is usually added to the above-mentioned solution immediately before use as an adhesive. The adhesive composition of the present invention is suitable as an adhesive for wood. It is particularly excellent as an adhesive for plywood or its secondary processing, and is also excellent as an adhesive for woodworking. The adhesive composition of the present invention can be used not only for wood but also for paper,
It can be used as an adhesive for particle boards, cardboard, etc. Furthermore, it can be suitably used as an adhesive for metal/wood, cloth, fiber processing, ceramics, inorganic boards, mineral and inorganic boards, plastic sheets, glass, etc. When adhesion is performed using the aqueous adhesive composition of the present invention, adhesion is sufficient only by room-temperature adhesion (cold press), providing excellent water-resistant adhesive strength and durability. Furthermore, by performing hot pressing, the adhesion speed can be increased.

[0013]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way. In addition, in the following, "part" and "%"
Unless otherwise specified, "parts by weight" and "parts by weight" respectively.
% by weight”

Example 1 A copolymer of N-vinylacetamide and vinyl acetate was saponified with an alkali to contain 5 mol% of primary amino groups, a degree of saponification of vinyl acetate units of 92.5 mol%, and a degree of polymerization of 1150.
A modified PVA having a primary amino group in the molecule was obtained. 10.7 parts of the above modified PVA, 20.3 parts of kaolin clay and 0.05 part of an antifoaming agent were added to 36.5 parts of water with stirring, and heated from the outside to dissolve the modified PVA. This slurry solution was cooled to 30° C. and the pH was adjusted to 6 by adding a small amount of lactic acid. Next, 29.2 parts of ethylene-vinyl acetate copolymer emulsion (ethylene content 12.8%, solid content 52%) and glyoxal (40% solution) were added.
3.3 parts were added and mixed under stirring to obtain an adhesive composition of the present invention. This adhesive composition has a solid content of 47.2% and a pH of 6.
．． 3. Type B viscosity at 30°C was 9600 centipoise. Using this adhesive composition, an adhesion test for woodworking was conducted. The results are shown in Table 1. Table 1 also shows the viscosity immediately after adding glyoxal, a water resistance agent, and the viscosity after standing at 30° C. for 24 hours.

Example 2 Instead of N-vinylacetamide used in Example 1,
N-vinylsuccinimide was copolymerized with vinyl acetate and saponified with an alkali to produce primary amino group-modified PVA. This modified PVA contains 6 mol% of primary amino groups, a saponification degree of vinyl acetate units of 96.4 mol%, and a polymerization degree of 1.
It was 260. An adhesive composition was prepared in the same manner as in Example 1, except that the above modified PVA was used in place of the modified PVA used in Example 1, and glutaraldehyde was used in place of glyoxal, and an adhesive composition for woodworking was conducted. I did it. The results are also shown in Table 1.

Example 3 A modified polyvinyl acetate containing 14 mol % of acrylamide was synthesized by copolymerizing acrylamide and vinyl acetate. Next, the modified PVA obtained by saponification was subjected to a Hoffman rearrangement reaction to obtain PVA having a primary amino group. Saponification degree of vinyl acetate unit: 98.6 mol%, polymerization degree: 1750
, the degree of primary amino group modification was 8 mol%. This modified PV
An adhesive composition was prepared and performance evaluated in the same manner as in Example 1, except that A was used in place of the modified PVA used in Example 1 and glycolic acid was used in place of lactic acid. The results are also shown in Table 1.

Example 4 Modified PVA containing 8 mol % of secondary ammonium base was obtained by acetalizing PVA with a saponification degree of 98.3 mol % and a polymerization degree of 1200 with N-methylaminoacetaldehyde in an acidic aqueous solution of hydrochloric acid. , used in place of the modified PVA used in Example 1, and styrene-butadiene copolymer latex (manufactured by Japan Synthetic Rubber Co., Ltd., JSR069) in place of the ethylene-vinyl acetate copolymer emulsion.
An adhesive composition was prepared and its performance was evaluated in the same manner as in Example 1, except that 2) was used and 15 parts of ethylene glycol diglycidyl ether was used in place of glyoxal. The results are also shown in Table 1.

Example 5 40 parts of the primary amino group-modified PVA used in Example 1 and 65 parts of calcium carbonate were added to 121 parts of water with stirring and dissolved by heating. After cooling, 25 parts of a 20% aqueous solution of dialdehyde starch was added to obtain an adhesive composition. Solid content concentration 43.
6%, the viscosity of the as-prepared adhesive composition was 7730 centipoise. The results are also shown in Table 1.

Example 6 Instead of N-vinylacetamide used in Example 1,
A secondary amino group-modified PVA was obtained by copolymerizing N-methyl vinylacetamide with vinyl acetate, saponifying it with an alkali, and then hydrolyzing it in the presence of water. This modified PVA contains 4 mol% of secondary amino groups, a saponification degree of vinyl acetate units of 98.2 mol%, and a polymerization degree of 1.
It was 750. Except that the above modified PVA was used instead of the modified PVA used in Example 1, and 10 parts of methylolmelamine resin was used instead of glyoxal.
An adhesive composition was prepared in the same manner as in Example 1. The results are also shown in Table 1.

Comparative Example 1 Instead of the primary amino group-modified PVA used in Example 1,
Unmodified PV with saponification degree of 98.5 mol% and polymerization degree of 1750
An adhesive composition was prepared and its performance was evaluated in the same manner as in Example 1, except that A was used. The results are also shown in Table 1.

Comparative Example 2 An adhesive composition was prepared in the same manner as in Example 1, except that the filler kaolin clay used in Example 1 was omitted. The results are also shown in Table 1. This adhesive has a solid content concentration of 2
Since it was as low as 6.4%, the initial adhesive strength was low and the normal adhesive strength was not sufficiently developed.

[Table 1]

Example 7, Comparative Example 3 30 parts of the primary amino group-modified PVA used in Example 1 and 100 parts of talc were added to 128.5 parts of water with stirring and dissolved by heating. This slurry solution was cooled to 30°C and mixed with styrene-butadiene copolymer latex (Japan Synthetic Rubber Co., Ltd.).
manufactured by JSR0692), 140 copies, glyoxal (40
% solution) was added and thoroughly stirred to prepare an adhesive composition of the present invention. Apply adhesive composition to 3mm plywood of 0.8/1.4/0.8mm veneer structure in an amount of 30g/900.
cm2, and then compressed with cold pressure (10Kg/cm2, 10 minutes), then hot pressure (120℃, 10Kg/cm2,
The adhesive force was measured according to JAS. The results are shown in Table 2. In addition, plywood was prepared by cold pressing (pressing conditions: 10 kg/cm2, 5 minutes) instead of hot pressing, and the adhesive strength was measured in the same manner. The results are also shown in Table 2. To test durability, the plywood was cut into 30cm squares and left on a rooftop facing south at a 45 degree angle for one year. Further, as Comparative Example 3, a commercially available Type 1 plywood (adhesive: phenol resin) was also subjected to a standing test. After standing, a test piece was cut out from this plywood and the adhesive strength was measured after repeated boiling. The results are also shown in Table 2.

[Table 2]

[0023]

Effects of the Invention The adhesive composition of the present invention has excellent water resistance and durability, especially when used as a wood adhesive. In addition, the adhesive composition of the present invention has a small viscosity change after adding a water-resistant agent, a long pot life, and sufficient water resistance without particularly severe heat compression. It has characteristics such as adhesive strength and adhesive strength after repeated boiling.

Claims (3)

[Claims] Claim 1: Polyvinyl alcohol (A) having at least one functional group selected from a primary amino group, a primary ammonium base, a secondary amino group, and a secondary ammonium base in its molecule, a filler (B), and water resistance. Curing agent (C)
The mixing ratio of each component is 100 parts by weight of component (A), 5 to 500 parts by weight of component (B), and component (C).
1 to 50 parts by weight of an adhesive composition. 2. The adhesive composition according to claim 1 contains an aqueous emulsion (D), and the blending ratio of each component is (
Component (B) 5 to 500 parts by weight, component (C) 1 to 50 parts by weight, and component (D) 5 to 40 parts by weight per 100 parts by weight of A).
0 parts by weight of an adhesive composition. 3. The adhesive composition according to claim 1, wherein the water resistant agent (C) is a dialdehyde compound.