JP2010126555A - Adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition that is an aqueous polymer-isocyanate-based adhesive composition and has excellent initial adhesiveness, normal state strength, boiling water resistance and pot life at the same time. <P>SOLUTION: The adhesive composition contains (C) a compound having an isocyanate group as a crosslinking agent based on a base resin obtained by blending (A) an ethylene-vinyl acetate copolymer resin emulsion with (B) polyvinyl alcohol. (A) The ethylene-vinyl acetate copolymer resin emulsion is obtained by conducting an emulsion polymerization in the presence of 20-200 pts.mass of (E) an inorganic filler based on 100 pts.mass of a vinyl acetate monomer using (D) a protective colloid component comprising polyvinyl alcohol and starch as protective colloid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adhesive composition that can be suitably used for woodworking applications, and more specifically, an aqueous polymer-isocyanate having both initial adhesiveness, normal strength, boiling water resistance, and pot life and excellent storage stability. The present invention relates to a system adhesive composition.

  Conventionally, in the plywood market, as a water-resistant adhesive not containing formaldehyde, an aqueous emulsion, an aqueous polymer, an adhesive containing an isocyanate compound, a so-called aqueous polymer-isocyanate adhesive has been widely used. . As the aqueous emulsion, styrene / butadiene copolymer resin latex or ethylene / vinyl acetate copolymer resin emulsion is used, but when styrene / butadiene copolymer resin latex is used, it has excellent boiling water resistance but initial adhesiveness. When using an ethylene / vinyl acetate copolymer resin emulsion, the initial adhesiveness is superior to that of styrene / butadiene copolymer resin latex, but the boiling water resistance is insufficient. There was a problem. When a styrene / butadiene copolymer resin latex introduced with a carboxyl group was used, the initial adhesiveness was slightly improved, but was insufficient in practice.

  Patent Document 1 discloses a method for improving water resistance by a vinyl acetate emulsion obtained by copolymerizing a primary hydroxyl group-containing monomer, and Patent Document 2 improves initial adhesiveness by copolymerizing a carboxyl group. However, the adhesive obtained by such a method has a drawback that the increase in viscosity after addition of isocyanate is increased and the pot life is shortened.

Japanese Patent Laid-Open No. 5-1270 JP 2000-226562 A

  Accordingly, the present invention is an aqueous polymer-isocyanate-based adhesive composition comprising a compound having an isocyanate group as a crosslinking agent with respect to a main agent obtained by blending an ethylene vinyl acetate copolymer resin emulsion and polyvinyl alcohol. An object of the present invention is to provide an adhesive composition having excellent initial adhesiveness, normal strength, boiling water resistance, and pot life.

  As a result of intensive studies, the present inventors have found that the above problem can be solved only when an ethylene vinyl acetate copolymer resin emulsion obtained by polymerizing polyvinyl alcohol and starch as protective colloids in the presence of an inorganic filler is used. The present invention has been completed.

  That is, the present invention relates to an adhesive composition comprising (C) a compound having an isocyanate group as a crosslinking agent with respect to a main agent comprising (A) an ethylene vinyl acetate copolymer resin emulsion and (B) polyvinyl alcohol. The (A) ethylene vinyl acetate copolymer resin emulsion comprises (D) a protective colloid component comprising polyvinyl alcohol and starch as a protective colloid. E) It is related with the adhesive composition obtained by performing emulsion polymerization in presence of an inorganic filler.

  Furthermore, it is preferable to mix | blend (F) inorganic filler with a main ingredient.

  (A) The amount of polyvinyl alcohol used as the protective colloid component (D) is 0.5 to 10 parts by mass and the amount of starch used is 0.1 to 5 per 100 parts by mass of the ethylene vinyl acetate copolymer resin emulsion. It is preferable that it is a mass part.

The present invention relates to an adhesive composition comprising (C) a compound having an isocyanate group as a crosslinking agent with respect to a main agent obtained by blending (A) an ethylene vinyl acetate copolymer resin emulsion and (B) polyvinyl alcohol. The compressive shear strength measured by the method shown in condition (1) described later is 98 to 560 N / cm ² , and the compressive shear strength measured by the method shown in condition (2) is 1800 to 3000 N. / cm ^2, compressive shear strength measured by the method shown in the condition (3) is directed to adhesive compositions that are 588～1500N / cm ^2.

  According to the adhesive composition of the present invention, an adhesive composition having excellent initial adhesiveness, boiling water resistance, and pot life can be provided.

  Hereinafter, the present invention will be described in more detail. The ethylene-vinyl acetate copolymer resin emulsion (A) used in the adhesive composition of the present invention is 20 to 200 parts by weight of inorganic with respect to 100 parts by weight of vinyl acetate monomer using polyvinyl alcohol and starch as protective colloid components (D). What is necessary is just to manufacture by performing emulsion polymerization in presence of a filler (E).

  The polyvinyl alcohol used as the protective colloid component (D) of the ethylene vinyl acetate copolymer resin emulsion (A) used in the adhesive composition of the present invention has a saponification degree of 80 mol% or more used in ordinary emulsion polymerization. In addition to those modified with anions such as sulfonic acid groups and carboxylic acid groups, those modified with cation such as quaternary amine groups, amide modification, acetoacetyl modification, ethylene modification, etc. Modified polyvinyl alcohol can also be used. The average degree of polymerization of the polyvinyl alcohol is preferably 500 to 2400, and by setting it to 500 or more, the polymerization stability becomes better and good initial adhesiveness is obtained, which is preferable. By setting it as 2400 or less, the viscosity of the obtained ethylene vinyl acetate copolymer resin emulsion does not become too high, which is preferable.

  The amount of polyvinyl alcohol used is preferably 0.5 to 10 parts by weight, more preferably 2 to 8 parts by weight with respect to 100 parts by weight of the nonvolatile content of the ethylene vinyl acetate copolymer resin emulsion (A). More preferably, it is used so as to be a part. When the content is 0.5 parts by mass or more, necessary polymerization stability can be obtained, and good initial adhesiveness can be obtained. By setting it to 10 parts by mass or less, the boiling water resistance when used as an aqueous polymer-isocyanate adhesive can be further improved.

  Starch used as protective colloid component (D) is not particularly limited, such as potato starch, corn starch, tapioca starch, wheat starch, etc., etherified with hydroxyalkyl group, carboxyalkyl group, etc., carboxylic acid, phosphoric acid, etc. Modified modified starches such as those esterified by, oxidized starches oxidized with sodium hypochlorite or the like can also be used. Of these, oxidized starch and phosphate esterified starch are preferred because the dispersibility of the inorganic filler (E) and inorganic filler (F) is good.

  The amount of starch used is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the nonvolatile content of the ethylene vinyl acetate copolymer resin emulsion (A), and further 0.5 to 3 parts by mass. More preferably, it is used so as to be a part. By setting the content to 0.1 parts by mass or more, the sedimentation of the inorganic filler can be suppressed and the storage stability can be improved, and by setting the content to 5 parts by mass or less, resistance to water when used as an aqueous polymer-isocyanate adhesive is obtained. The boiling water can be further improved.

  As the protective colloid, water-soluble polymers such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used in addition to polyvinyl alcohol and starch.

  The method for adding the protective colloid is not particularly limited, and the whole amount may be added to the reaction vessel before or simultaneously with the start of the polymerization, or a part thereof may be added to the reaction vessel and the rest may be added as the polymerization proceeds. May be.

  In addition to protective colloids, various surfactants can be used. By using the surfactant, the dispersion of the compound (C) having an isocyanate group becomes good, and the boiling water resistance strength becomes good.

  The inorganic filler (E) that can be used for emulsion polymerization of the ethylene vinyl acetate copolymer resin emulsion (A) of the present invention is not particularly limited, and clay, aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate, talc, etc. Is mentioned. In particular, calcium carbonate is preferred because it is inexpensive and easy to disperse.

  An inorganic filler (E) may be used independently and 2 or more types may be used together. The addition method of the inorganic filler (E) is not particularly limited, and the whole amount may be added to the reaction vessel before or simultaneously with the start of the polymerization, or a part thereof may be added to the reaction vessel, and the rest may be appropriately progressed in the polymerization. You may add together.

  The amount of the inorganic filler (E) is 20 to 200 parts by mass with respect to 100 parts by mass of the vinyl acetate monomer, and preferably 20 to 150 parts by mass. When the amount is less than 20 parts by mass, the effects of the present invention of improving initial adhesiveness and boiling water resistance strength are not obtained by copolymerizing ethylene and vinyl acetate in the presence of the inorganic filler (E), which is not preferable. When it exceeds 200 parts by mass, the adhesive strength and the initial adhesive strength are lowered, which is not preferable.

  As the unsaturated monomer that can be used in the present invention, in addition to ethylene and vinyl acetate, monomers copolymerizable with ethylene and vinyl acetate can be used as long as the object of the present invention is not impaired. Specifically, vinyl butyrate, vinyl propionate, vinyl pivalate, vinyl laurate, vinyl isononanoate, vinyl acid vinyl ester such as vinyl versatate, vinyl halides such as vinyl chloride, vinyl bromide, etc. , Vinylidene halides such as vinylidene chloride, vinyl compounds such as vinylphosphonic acid, vinylsulfonic acid and their salts, aromatic vinyl such as styrene, α-methylstyrene and chlorostyrene, methyl (meth) acrylate, (meta ) (Meth) acrylates such as butyl acrylate, 2-ethylhexyl (meth) acrylate, nitriles such as (meth) acrylonitrile, conjugated dienes such as butadiene and isoprene, allyl sulfonate, diallyl phthalate, triallylsia Nurate, triallyl isocyanurate Allyl compounds, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol hexaacrylate, polyfunctional acrylates such as trimethylolpropane triacrylate and the like.

  As the polymerization catalyst used in the present invention, a catalyst that forms a radical usually used in emulsion polymerization can be used. Examples of the polymerization catalyst include hydrogen peroxide, potassium persulfate, ammonium persulfate, tertiary butyl hydroperoxide, azobis- (2-amidinopropane) hydride, lauroyl peroxide, a, a′-azobisisobutyrate. Examples include rhonitrile, ketone hydroperoxide, and the like. These polymerization catalysts can be used as so-called redox catalysts either alone or in an appropriate combination with a reducing agent.

  Examples of the reducing agent include amines, ferrous salts, sodium thiosulfate, sodium sulfite, sodium hyposulfite, formaldehyde sodium sulfoxylate, tartaric acid and its salts, ascorbic acid and its salts, erythorbic acid and its salts, and the like.

  The used amount of the polymerization catalyst and the reducing agent added as necessary is 0.001 to 10% by mass relative to the mass of the unsaturated monomer, and the addition method is performed before or simultaneously with the start of the polymerization. It may be added to the reaction vessel, or a part thereof may be added to the reaction vessel and the rest may be added as the polymerization proceeds.

  During polymerization, acids such as acetic acid, hydrochloric acid and sulfuric acid, bases such as ammonia, amine caustic soda, caustic potash and calcium hydroxide, or buffers such as alkali carbonates, phosphates and acetates are used as necessary. The

  If necessary, mercaptans, alcohols and the like may be added as a polymerization degree modifier.

  The polymerization is carried out under ethylene pressure. The pressure of ethylene varies depending on the required amount of ethylene polymer in the copolymer, but is usually up to 20 MPa, preferably 10 MPa or less. The polymerization is usually carried out at 20 to 100 ° C, preferably 40 to 90 ° C. It is preferable that the component derived from ethylene monomer is 5 to 30 parts by mass with respect to 100 parts by mass of the component derived from vinyl acetate monomer in the ethylene vinyl acetate copolymer resin emulsion (A). When the amount is less than 5 parts by mass, the film formability at a low temperature is lowered, and when the amount is more than 30 parts by mass, the cohesive force tends to be reduced.

  As the polyvinyl alcohol (B) used in the adhesive composition of the present invention, any of ordinary saponified products or partially saponified products can be used, and those that are anion-modified with a sulfonic acid group, a carboxylic acid group, etc. In addition to those modified with a cation with a quaternary amine group or the like, modified polyvinyl alcohol modified with amide, acetoacetyl, or ethylene can also be used. From the viewpoint of boiling water resistance, it is preferable to use a completely saponified product.

  The added amount of the polyvinyl alcohol (B) is 2 to 100 parts by mass, more preferably 5 to 100 parts by mass of the solid content of the polyvinyl alcohol (B) with respect to 100 parts by mass of the solid content of the ethylene vinyl acetate copolymer resin emulsion (A). It is good to mix | blend so that it may become the range of 50 mass parts. When the polyvinyl alcohol (B) is 2 parts by mass or more, good initial adhesiveness is obtained, which is preferable. Moreover, when polyvinyl alcohol (B) is 100 mass parts or less, the water resistance of the adhesive composition finally obtained can be further improved.

  The compound (C) having an isocyanate group used in the adhesive composition of the present invention is not particularly limited as long as it has two or more isocyanate groups in one molecule. Aliphatic isocyanates such as diisocyanates, m- and p-phenylene diisocyanates, tolylene-2,4- and -2,6-diisocyanates, diphenylmethane-4,4'-diisocyanates, diphenylene-4,4'-diisocyanates, 4, Aromatic isocyanates such as 4'-diisocyanate-3,3'-dimethyldiphenyl, 3-methyl-diphenylmethane-4,4'-diisocyanate, diphenyl ether diisocyanate, and cyclohexane-2,4- and -2,3-diisocyanate, Isophorone diisocyanate Alicyclic isocyanates such as bets and the like. These can be used alone or in admixture of two or more. Also, isocyanate-terminated prepolymers formed by reaction of excess diisocyanate or polyfunctional polyisocyanate with hydroxyl-terminated polyester or hydroxyl-terminated polyether, and excess diisocyanate or polyfunctional polyisocyanate with ethylene glycol, trimethylolpropane or 1,3 Products obtained by reaction with monomeric polyols such as butanediol or mixtures thereof can also be used. Of these, polymethylene polyphenyl isocyanate is preferable in that it has moderate curability and a good balance with the pot life.

  The compounding amount of the compound (C) having an isocyanate group may be arbitrarily determined depending on the purpose of use, but preferably the non-volatile content of the main component containing the ethylene vinyl acetate copolymer resin emulsion (A) and the polyvinyl alcohol (B). It is good to mix | blend so that it may become the range of 2-100 mass parts by solid content with respect to 100 mass parts. More preferably, it is good to mix | blend so that it may become the range of 10-50 mass parts. When the compounding amount of the compound (C) having an isocyanate group is 2 parts by mass or more, a sufficient adhesive force can be provided in any of the initial adhesive strength, normal strength, and boiling water resistance strength, which is preferable. Moreover, when the compounding quantity of the compound (C) which has an isocyanate group is 100 mass parts or less, while being able to make the pot life after a compounding further longer, a raise in a viscosity can also be suppressed.

  Various additives such as preservatives and rust preventives can be appropriately added to the adhesive composition of the present invention. Moreover, you may add general SBR latex, NBR latex, an acrylic emulsion, a styrene-acryl emulsion, EVA emulsion, and EVA acrylic emulsion as needed as long as a physical property does not fall.

  Moreover, not only the inorganic filler (E) used at the time of emulsion polymerization, but also an inorganic filler (F) may be added to the adhesive composition of the present invention. Examples of the inorganic filler (F) include clay, aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate, and talc. In particular, calcium carbonate is preferred because it is inexpensive and easy to disperse.

  An inorganic filler (F) may be used independently and 2 or more types may be used together. The amount of the inorganic filler (F) is preferably added in an amount of 50 to 200 parts by mass with respect to 100 parts of the solid content of the ethylene vinyl acetate copolymer resin emulsion. By setting it to 50 parts by mass or more, the cohesive force of the adhesive can be increased and sufficient adhesive strength can be obtained. By setting it as 200 mass parts or less, the adhesive film property, adhesive strength, and water resistance of an adhesive agent can be improved further. Moreover, you may use together organic fillers, such as wheat flour, starch, and wood flour, besides an inorganic filler (F).

  The adhesive composition of the present invention preferably has a nonvolatile content of 45% or more. When the nonvolatile content of the adhesive composition is lower than 45%, the initial adhesiveness tends to be lowered.

The adhesive composition of the present invention has a compressive shear strength measured by the method shown in condition (1) of 98 to 560 N / cm ² , and the compressive shear strength measured by the method shown in condition (2) is a 1800~3000N / cm ^2, compressive shear strength measured by the method shown in the condition (3) is a 588~1500N / cm ^2. Here, the compressive shear strength measured by the method shown in the condition (1) represents the initial adhesive strength, and the compressive shear strength measured by the method shown in the conditional condition (2) represents the normal strength. The compressive shear strength measured by the method shown in the condition (3) represents the boiling water resistance strength. If the compressive shear strength measured by the method shown in condition (1) is less than 98 N / cm ² , the pressing time must be lengthened, leading to a decrease in productivity. When the compressive shear strength measured by the method shown in the condition (2) is smaller than 1800 N / cm ^2, it is not practically sufficient as a laminated material for structural use and production. If the compressive shear strength measured by the method shown in condition (3) is less than 588 N / cm ² , the adhesive cannot be used as a structural laminate.

  Condition (1), condition (2), and condition (3) are as follows.

Condition (1):
The adhesive composition is applied at a coating amount of 125 g / m ² on a 2.5 cm square cover panel (water content: 6 to 15%). At 5 ° C., two cover grids coated with the adhesive composition are bonded together and pressed at 10 kg / cm ² for 10 minutes to prepare a test piece. After the pressing, the prepared test piece is immediately measured for compression shear strength by a compression shear test shown in condition (4) at 23 ° C. and 65% RH.

Condition (2):
The adhesive composition is applied at a coating amount of 125 g / m ² on a 2.5 cm square cover panel (water content: 6 to 15%). At 23 ° C., two cover plates coated with the adhesive composition are bonded together and pressed at 10 kg / cm ² for 24 hours. After pressing, a test piece is obtained by curing at 23 ° C. and 65% RH for 72 hours. The prepared test piece is immediately measured for compression shear strength by a compression shear test shown in condition (4) at 23 ° C. and 65% RH.

Condition (3):
The adhesive composition is applied at a coating amount of 125 g / m ² on a 2.5 cm square cover panel (water content: 6 to 15%). At 23 ° C., two cover plates coated with the adhesive composition are bonded together and pressed at 10 kg / cm ² for 24 hours. After pressing, a test piece is obtained by curing at 23 ° C. and 65% RH for 72 hours. The prepared test piece was immersed in boiling water for 4 hours, dried at 60 ° C. for 20 hours, subsequently immersed in boiling water for 4 hours, and further immersed in water at 23 ° C. to be cooled to 23 ° C., 65 The compression shear strength is measured by the compression shear test shown in condition (4) at% RH.

  Condition (4) is as follows.

Condition (4):
Attach the test piece so that the load direction by the compression shear test machine is parallel to the bonding direction of the cover plate, perform the compression shear test at a load speed of 9.81 kN / min, and set the maximum load until the test piece breaks. taking measurement. From the measured maximum load, formula (a):

により、圧縮剪断強度を求める。

To obtain the compression shear strength.

  These compression shear tests are performed in accordance with JIS K-6852 issued in 1994.

  The adhesive composition of the present invention can provide excellent adhesive strength, initial adhesive strength and boiling water-resistant adhesive force, and is improved in workability with very little precipitation of inorganic filler. That is, the adhesive composition of the present invention has extremely great advantages and features as already described, and is useful as a wood adhesive for a wide range of uses.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these examples. In Examples and Comparative Examples, “parts” and “%” indicate mass standards unless otherwise specified.

Example 1
(I) Synthesis of ethylene-vinyl acetate copolymer resin emulsion 5 parts of polyvinyl alcohol “JP-18” (manufactured by Nippon Acetate / Poval Co., saponification degree 88 mol%, average polymerization degree 1800) with respect to 800 parts of distilled water, An aqueous solution in which 50 parts of “JP-05” (manufactured by Nippon Vinegar Poval Co., Ltd., saponification degree 88 mol%, average polymerization degree 500) and Oji Ace A (oxidized starch, Oji Cornstarch Co., Ltd.) 15 parts are dissolved. 350 parts of Softon 1200 (manufactured by Bihoku Powder Chemical Co., Ltd., calcium carbonate) was dispersed. This dispersion and 70 parts of vinyl acetate were charged into a 3 liter stainless steel autoclave equipped with an irrigation type stirrer. Subsequently, the air in the autoclave was sufficiently replaced with ethylene. Under stirring, the temperature in the autoclave was increased to 75 ° C., and the ethylene pressure was increased to 5.0 MPa. Subsequently, 200 parts by mass of a 1% by mass aqueous solution of ammonium persulfate was uniformly added dropwise over 8 hours. At the same time, 630 parts of vinyl acetate was uniformly dropped over 6 hours. The ethylene pressure was maintained at 5.0 MPa until the end of vinyl acetate addition. After completion of the catalyst addition, the mixture was cooled and an antifoaming agent was added to obtain an ethylene vinyl acetate copolymer resin emulsion. The obtained ethylene-vinyl acetate copolymer resin emulsion had a nonvolatile content of 56.5% and a viscosity of 3400 mPa · s.

(Ii) Blending of Adhesive Composition A 15% aqueous solution of polyvinyl alcohol “PVA117” (manufactured by Kuraray Co., Ltd., fully saponified) was added to the ethylene-vinyl acetate copolymer resin emulsion obtained above to obtain a main agent. Polyvinyl alcohol “PVA117” was added in an amount such that the solid content was 15 parts with respect to 100 parts of the solid content of the ethylene vinyl acetate copolymer resin emulsion. 36 parts of a compound having an isocyanate group, Millionate MR-100 (manufactured by Nippon Polyurethane Industry Co., Ltd., polymethylene polyphenyl isocyanate) is added to 100 parts of the solid content of the main agent, and the mixture is thoroughly mixed to produce the adhesive composition of Example 1. As a performance evaluation.

Example 2
In the synthesis of Example 1 (i) ethylene vinyl acetate copolymer resin emulsion, 640 parts by mass of Softon 1200 and 350 parts by mass of dripped vinyl acetate were used in the same manner as in Example 1, except that ethylene vinyl acetate copolymer resin was used. An emulsion was obtained. The obtained ethylene-vinyl acetate copolymer resin emulsion had a non-volatile content of 56.3% and a viscosity of 3500 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, all were carried out in accordance with the formulation of (ii) adhesive composition of Example 1, and as the adhesive composition of Example 2. Performance evaluation was performed.

Example 3
In the synthesis of Example 1 (i) ethylene vinyl acetate copolymer resin emulsion, an ethylene vinyl acetate copolymer resin emulsion was obtained in the same manner as Example 1 except that the amount of Oji Ace A used was 80 parts by mass. It was. The obtained ethylene-vinyl acetate copolymer resin emulsion had a nonvolatile content of 56.9% and a viscosity of 4200 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, it was carried out in accordance with the formulation of (ii) adhesive composition of Example 1 as the adhesive composition of Example 3. Performance evaluation was performed.

Example 4
An ethylene vinyl acetate copolymer resin emulsion was obtained in the same manner as in Example 1, except that (i) synthesis of the ethylene vinyl acetate copolymer resin emulsion of Example 1 was changed to 175 parts by mass of Softon 1200. The obtained ethylene-vinyl acetate copolymer resin emulsion had a non-volatile content of 52.5% and a viscosity of 2600 mPa · s. Subsequently, all except that the obtained ethylene vinyl acetate copolymer resin emulsion was used and 175 parts by mass of Softon 1200 was blended, all in accordance with the blending of the adhesive composition of Example 1 (ii). The performance of the adhesive composition of Example 4 was evaluated.

Example 5
An ethylene-vinyl acetate copolymer resin emulsion was obtained in the same manner as in Example 1 except that Softon 1200 of Example 1 was changed to LMS-400 (manufactured by Fuji Talc Industrial Co., Ltd., talc). The obtained ethylene-vinyl acetate copolymer resin emulsion had a nonvolatile content of 56.0% and a viscosity of 6800 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, all were carried out according to the formulation of (ii) adhesive composition of Example 1, and as the adhesive composition of Example 5. Performance evaluation was performed.

Example 6
An ethylene-vinyl acetate copolymer resin emulsion was obtained in the same manner as in Example 1 except that Softon 1200 of Example 1 was changed to Kaoblite (made by Shiraishi Calcium Co., Ltd., clay). The obtained ethylene-vinyl acetate copolymer resin emulsion had a non-volatile content of 56.0% and a viscosity of 6200 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, all were carried out in accordance with the formulation of (ii) adhesive composition of Example 1, and as the adhesive composition of Example 6. Performance evaluation was performed.

Comparative Example 1
An ethylene vinyl acetate copolymer resin emulsion was obtained in the same manner as in Example 1 except that Oi Ace A was not used in the synthesis of Example 1 (i) ethylene vinyl acetate copolymer resin emulsion. The obtained ethylene-vinyl acetate copolymer resin emulsion had a non-volatile content of 56.1% and a viscosity of 2800 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, it was carried out in accordance with the formulation of (ii) the adhesive composition of Example 1, and as the adhesive composition of Comparative Example 1. Performance evaluation was performed.

Comparative Example 2
In the synthesis of Example 1 (i) ethylene vinyl acetate copolymer resin emulsion, the same procedure was used as in Example 1 except that the amount of Oji Ace A used was 80 parts by mass and no polyvinyl alcohol was used during the polymerization. Thus, an ethylene vinyl acetate copolymer resin emulsion was obtained. The obtained ethylene-vinyl acetate copolymer resin emulsion had a non-volatile content of 56.2% and a viscosity of 2000 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, all were carried out in accordance with the formulation of (ii) adhesive composition of Example 1, and as an adhesive composition of Comparative Example 2. Performance evaluation was performed.

Comparative Example 3
In the synthesis of Example 1 (i) ethylene vinyl acetate copolymer resin emulsion, ethylene vinyl acetate was used in the same manner as in Example 1 except that Softon 1200 was not used during polymerization and the amount of vinyl acetate dropped was 980 parts by mass. A copolymer resin emulsion was obtained. The resulting ethylene-vinyl acetate copolymer resin emulsion had a non-volatile content of 56.4% and a viscosity of 4200 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, it was carried out in accordance with the formulation of (ii) adhesive composition of Example 1 as an adhesive composition of Comparative Example 3. Performance evaluation was performed.

Comparative Example 4
Example 1 (i) Example 1 is the same as Example 1 except that 787.5 parts by mass of Softon 1200 used for polymerization and 192.5 parts by mass of vinyl acetate to be dropped are used in the synthesis of an ethylene vinyl acetate copolymer resin emulsion. Similarly, an ethylene vinyl acetate copolymer resin emulsion was obtained. The obtained ethylene-vinyl acetate copolymer resin emulsion had a nonvolatile content of 56.5% and a viscosity of 2800 mPa · s. Subsequently, except that the obtained ethylene-vinyl acetate copolymer resin emulsion was used, all were carried out in accordance with the formulation of (ii) adhesive composition of Example 1, and as an adhesive composition of Comparative Example 4. Performance evaluation was performed.

Block Compression Shear Test Test pieces were prepared using the adhesives obtained in Examples and Comparative Examples, and the adhesive performance was measured. The measurement method and measurement conditions are described below. The measurement results are shown in Table 1.

(1) Adhesion conditions (1-1) Normal strength, boiling water resistant base material: birch panel, moisture content 11%
Application amount: 250 g / m ² (Double-sided application, 125 g / m ² each applied to ^two cover plates, and the two are bonded together)
Clamping: normal temperature 10 kg / cm ² -24 hours

(1-2) Initial adhesive strength base material: birch panel, moisture content 11%
Application amount: 250 g / m ² (Double-sided application, 125 g / m ² each applied to ^two cover plates, and the two are bonded together)
Crushing: 5 ° C. 10 kg / cm ² -10 minutes Bonding of the base material and adhesive at 5 ° C.

(2) Test method Compressive shear test according to JIS K-6852

(3) Measuring method Normal adhesive strength: Measured in a standard state at 23 ° C. and 65% RH.
Repeated boiling adhesive strength: Measured after being immersed in boiling water for 4 hours, then dried at 60 ° C. for 20 hours, then immersed in boiling water for 4 hours, further immersed in water left at room temperature, and cooled.
Initial adhesive strength: Measured immediately at 23 ° C. and 65% RH after pressing at 5 ° C. for a predetermined time.

(4) Pot life Time Based on the viscosity immediately after compounding the compound having an isocyanate group, the viscosity increase after standing at 23 ° C. for 60 minutes is 1.5 times or less, better than 1.5 times The case was considered bad.

(5) Storage stability Main ingredient blended by the method described in Example 1 into a wide-mouthed plastic bottle (diameter 125 mm, height 245 mm) using the ethylene vinyl acetate copolymer resin emulsion obtained in each Example and Comparative Example. 2 kg, and allowed to stand for 60 days in a 23 ° C. atmosphere and stored. After 60 days, an emulsion sample is collected from a portion about 1 cm high from the bottom of the plastic bottle. Similarly, the non-volatile content of the emulsion sample collected from a portion about 1 cm below the liquid surface is measured, and the non-volatile content difference is less than 1%. The storage stability was good, and those with 1% or more were regarded as poor.

  According to the present invention, there is provided an adhesive composition that does not dissipate formaldehyde, has good initial adhesive strength, normal strength, boiling water strength, pot life, and good storage stability, and has a wide range of uses. It is useful as an adhesive for wood.

Claims (4)

(A) An ethylene / vinyl acetate copolymer resin emulsion, (B) an adhesive composition containing a compound having an isocyanate group (C) as a crosslinking agent with respect to the main agent formed by blending polyvinyl alcohol, (A) The ethylene vinyl acetate copolymer resin emulsion comprises (D) 20 to 200 parts by mass of (E) inorganic filler with respect to 100 parts by mass of vinyl acetate monomer, using a protective colloid component comprising polyvinyl alcohol and starch as a protective colloid. An adhesive composition obtained by performing emulsion polymerization in the presence. Furthermore, the adhesive composition of Claim 1 formed by mix | blending (F) inorganic filler with a main ingredient. (A) The amount of polyvinyl alcohol used as the protective colloid component (D) is 0.5 to 10 parts by mass and the amount of starch used is 0.1 to 5 per 100 parts by mass of the ethylene vinyl acetate copolymer resin emulsion. It is a mass part, The adhesive composition of Claim 1 or 2 characterized by the above-mentioned. (A) An ethylene / vinyl acetate copolymer resin emulsion, (B) an adhesive composition containing a compound having an isocyanate group (C) as a crosslinking agent with respect to the main agent formed by blending polyvinyl alcohol,
The compression shear strength measured by the method shown in condition (1) is 98 to 560 N / cm ² , the compression shear strength measured by the method shown in condition (2) is 1800 to 3000 N / cm ² , The adhesive composition whose compression shear strength measured by the method shown by conditions (3) is 588-1500 N / cm < ² >.
Condition (1):
The adhesive composition is applied at a coating amount of 125 g / m ² on a 2.5 cm square cover panel (water content: 6 to 15%). At 5 ° C., two cover grids coated with the adhesive composition are bonded together and pressed at 10 kg / cm ² for 10 minutes to prepare a test piece. After the pressing, the prepared test piece is immediately measured for compression shear strength by a compression shear test shown in condition (4) at 23 ° C. and 65% RH.
Condition (2):
The adhesive composition is applied at a coating amount of 125 g / m ² on a 2.5 cm square cover panel (water content: 6 to 15%). At 23 ° C., two cover plates coated with the adhesive composition are bonded together and pressed at 10 kg / cm ² for 24 hours. After pressing, a test piece is obtained by curing at 23 ° C. and 65% RH for 72 hours. The prepared test piece is immediately measured for compression shear strength by a compression shear test shown in condition (4) at 23 ° C. and 65% RH.
Condition (3):
The adhesive composition is applied at a coating amount of 125 g / m ² on a 2.5 cm square cover panel (water content: 6 to 15%). At 23 ° C., two cover plates coated with the adhesive composition are bonded together and pressed at 10 kg / cm ² for 24 hours. After pressing, a test piece is obtained by curing at 23 ° C. and 65% RH for 72 hours. The prepared test piece was immersed in boiling water for 4 hours, dried at 60 ° C. for 20 hours, subsequently immersed in boiling water for 4 hours, and further immersed in water at 23 ° C. to be cooled to 23 ° C., 65 The compression shear strength is measured by the compression shear test shown in condition (4) at% RH.
Condition (4):
Attach the test piece so that the load direction by the compression shear test machine is parallel to the bonding direction of the cover plate, perform the compression shear test at a load speed of 9.81 kN / min, and set the maximum load until the test piece breaks. taking measurement. From the measured maximum load, formula (a):

To obtain the compression shear strength.