JP2002356664A - Two-component adhesive - Google Patents

Abstract

(57) [Problem] To provide a two-part adhesive excellent in initial adhesiveness, exhibiting permanent adhesiveness, and also excellent in water-resistant adhesiveness. An aqueous liquid containing a polyvinyl alcohol resin (A) modified with a reactive group having active hydrogen and an aqueous emulsion (B), and a curing agent containing a polyvalent isocyanate compound (B). And the condition of the following equation (1) is satisfied. [Mole number of isocyanate group in (C)] / [mol number of hydroxyl group in (A) + mol number of reactive group in (A)] = 0.1 to 2.0 (1)

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-part adhesive comprising a polyvinyl alcohol-based resin (hereinafter may be abbreviated as PVA) and an isocyanate-based compound. The present invention relates to a two-part adhesive excellent in the above.

[0002]

2. Description of the Related Art Conventionally, as a formalin-free adhesive, a two-part reactive adhesive comprising an aqueous polymer such as an aqueous emulsion or PVA and an isocyanate compound has been known. It has been proposed to use various modified PVAs for the purpose of improving the adhesiveness.

For example, JP-A-57-190061 discloses a modified PVA having both a hydrophobic group and a hydrophilic group.
JP-A-8-259921 discloses an ethylene-modified P.
VA is disclosed in JP-A-10-219218, amine-modified PVA, and JP-A-11-181395 is disclosed in JP-A-11-1813.
No. 96 discloses a cation-modified PVA disclosed in
JP-A-256130 and JP-A-11-27950 each disclose carboxylic acid-modified PVA.

[0004]

However, there is a demand for higher adhesiveness from the recent market, and higher durability is required for structural adhesives and the like, and further improvement in adhesiveness is desired. . And aqueous polymer (PV
A)-In the isocyanate-based wood adhesive, PVA
It has been reported that the cross-linking reaction between water and isocyanate compound is the main reaction rather than the cross-linking reaction between hydroxyl group and isocyanate compound (Japanese Journal of Adhesion Society, Vol.23, No.10, p394-399). It is also anticipated that increasing the blending ratio of the PVA does not contribute to the improvement of the adhesive strength.
It is considered that there is sufficient room for studying the mixing ratio of the isocyanate compound and the isocyanate compound.

[0005]

In view of the above situation, the present inventors have conducted intensive studies on the relationship between the modified species of PVA and the mixing ratio of the isocyanate compound, and as a result, have found that the modified group is modified with a reactive group having active hydrogen. An aqueous liquid containing PVA (A) and an aqueous emulsion (B), and a curing agent containing a polyvalent isocyanate compound (C),
The inventors have found that a two-part adhesive satisfying the following condition (1) meets the object of the present invention, and has completed the present invention. [Mole number of isocyanate group in (C)] / [mol number of hydroxyl group in (A) + mol number of reactive group in (A)] = 0.1 to 2.0 (1) In the present invention, it is also preferable to set the block character [η] of the PVA (A) to 0.58 or less in that the effects of the present invention can be efficiently obtained.

[0006] The block character [η] referred to here is measured by ¹³ C-NMR (as an internal standard substance).
3- (Trimethylsilyl) propionic-2,2,3,3, -d ₄ acid, sodium
salt, the absorption based on the methylene carbon moiety found in the range of 40 to 49 ppm [(OH, OH) dy
ad = absorption of 46 to 49 ppm, (OH, OR) dyad = 4
3.5-45.5 ppm absorption, (OR, OR) dyad =
Absorption of 40 to 43 ppm, where OR represents an O-acetate group or an O-acetoacetate group], and more specifically, a value calculated from the following formula (2). .

[Η] = (OH, OR) / 2 (OH) (OR) (2) [However, (OH, OR), (OH), and (OR) are all expressed in mole fractions. Calculate)

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The two-part adhesive of the present invention comprises an aqueous liquid containing PVA (A) modified with a reactive group having active hydrogen and an aqueous emulsion (B), and a polyvalent isocyanate compound (C). PVA (A) used for such a base material is modified with a reactive group having active hydrogen, and the reactive group having active hydrogen includes an acetoacetate group, Reactive groups such as α-methylene and the like adjacent to a primary hydroxyl group and a carbonyl group can be exemplified. Among them, any reactive group of an acetoacetate group and an α-methylene adjacent to a carbonyl group is preferable. The PVA modified with a group will be specifically described, but the present invention is not limited thereto.

[Acetoacetate Group-Modified PVA] An acetoacetate group-modified PVA (hereinafter sometimes referred to as an AA-PVA) is used to react PVA with diketene or react PVA with acetoacetate as described below. Or a transesterification reaction to introduce an acetoacetic ester group into PVA. Such PVA is generally prepared by saponifying a lower alcohol solution of polyvinyl acetate with a saponification catalyst such as an alkali or an acid. A saponified product or a derivative thereof is used, and a saponified product of a copolymer of vinyl acetate and a monomer having a copolymerizability with vinyl acetate can also be used.

Examples of the monomer include ethylene, propylene, isobutylene, α-octene, α-dodecene,
Olefins such as α-octadecene, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride,
Unsaturated acids such as itaconic acid or salts thereof or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefins such as ethylenesulfonic acid, allylsulfonic acid and methallylsulfonic acid Sulfonic acids or salts thereof, alkyl vinyl ethers,
N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylallylvinylketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl Polyoxyalkylene (meth) allyl ether such as ether, polyoxyethylene (meth) acrylate, polyoxyalkylene (meth) acrylate such as polyoxypropylene (meth) acrylate, polyoxyethylene (meth)
Polyoxyalkylene (meth) acrylamide such as acrylamide, polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, poly Oxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine and the like can be mentioned.

Next, an acetoacetate group is introduced into the obtained PVA. The shape of the PVA is, for example, uniform adsorption of diketene described later, uniformization of the reaction by absorption, and improvement of the reaction rate with diketene. In consideration of the above, it is preferable that the powdery material, particularly, the one having a narrow particle size distribution and being porous, has a particle size of 50 to 450 mesh, more preferably 80 to 320 mesh.

Further, the PVA may contain several weight% of alcohols and water during the production process, and these components react with diketene to consume diketene and reduce the reaction rate of diketene. So, when submitting to the reaction,
It is desirable to reduce the temperature as much as possible by performing heating and decompression operations before use.

Further, as described above, powdered PVA is
VA, but considering the simplification of the production process, a solvent (methanol, ethanol, (iso) propanol, etc.) after the saponification process in the production of the raw material PVA
It is preferable to replace the slurry-containing PVA containing a with fatty acid ester and use it as a raw material PVA.

In introducing an acetoacetate group into the PVA obtained as described above, a method of reacting PVA with diketene, a method of transesterifying PVA with acetoacetate, or a method of reacting vinyl acetate with vinyl acetoacetate can be used. Although a method of copolymerization and the like can be mentioned, it is preferable to produce by a method of reacting PVA (powder) with diketene from the viewpoint that the production process is simple and a high quality AA-PVA is obtained.

Hereinafter, such a method will be described, but the method is not limited thereto. As a method of reacting PVA powder and diketene, PVA may be directly reacted with gaseous or liquid diketene, or an organic acid may be reacted with PVA.
A method of spraying and reacting liquid or gaseous diketene under an inert gas atmosphere after pre-adsorbing and absorbing the powder, or spraying and reacting a mixture of an organic acid and liquid diketene on PVA powder is used. .

In the method using an organic acid, acetic acid is most advantageous as the organic acid, but is not limited thereto, and propionic acid, butyric acid, isobutyric acid and the like can be optionally used. The amount of the organic acid is preferably an amount within a range in which the PVA powder in the reaction system can be adsorbed and occluded, in other words, an amount such that no organic acid separated from the resin in the reaction system exists. Specifically, 0.1 to 80 parts by weight, preferably 0.5 to 50 parts by weight, particularly preferably 5 to 30 parts by weight of an organic acid is suitably co-present with 100 parts by weight of PVA.
Outside this range, the degree of acetoacetic esterification (hereinafter referred to as A
(It may be abbreviated as degree A.) A product having an uneven distribution is likely to be obtained, unreacted diketene tends to increase, and a gel or the like may be generated, which is not preferable.

In order to uniformly adsorb and occlude the organic acid on PVA, any means such as a method of spraying the organic acid alone onto the PVA, a method of dissolving the organic acid in an appropriate solvent and spraying the same can be used. is there. As for the reaction conditions of PVA and diketene, when liquid diketene is uniformly adsorbed and absorbed by means such as spraying on PVA powder, it is heated to a temperature of 20 to 120 ° C. in an inert gas atmosphere and stirred for a predetermined time. Alternatively, it is preferable to continue fluidization.

When the diketene gas is reacted, the contact temperature is 0 to 250 ° C., preferably 25 to 100 ° C., and the gaseous diketene is contacted at a temperature at which it does not liquefy when it comes into contact with PVA and a diketene partial pressure condition. Although it is preferable that some of the gas is turned into droplets, there is no problem. The contact time depends on the contact temperature, that is, when the temperature is low, the time is long, and when the temperature is high, the time may be short, and is appropriately selected from the range of 1 minute to 6 hours.

When the diketene gas is supplied, the diketene gas may be used as it is, or a mixed gas of the diketene gas and the inert gas. The gas may be heated after the gas is absorbed by the powder PVA. However, it is preferable to bring the gas into contact after heating.

As a catalyst for the reaction of acetoacetic acid esterification (hereinafter sometimes abbreviated as AA), basic compounds such as sodium acetate, potassium acetate, primary amine, secondary amine and tertiary amine are effective. The amount of the catalyst may be smaller than that of a known reaction method, and may be less than 0.1% based on the PVA powder.
1 to 1.0% by weight. Since PVA powder usually contains sodium acetate, it is often unnecessary to add a catalyst. If the amount of the catalyst is too large, a side reaction of diketene easily occurs, which is not preferable.

The reaction apparatus for carrying out AA conversion includes:
A device that can be heated and has a stirrer is sufficient. Examples thereof include a kneader, a Henschel mixer, a ribbon blender and other various blenders, and a stirring and drying device.

[Α-methylene modified PVA adjacent to carbonyl group]
Examples of the comonomer to be introduced into A include diacetone acrylamide and the like, and such PVA will be specifically described, but is not limited thereto.

The diacetone acrylamide-modified PVA is
It is obtained by saponifying a copolymer of diacetone acrylamide and vinyl ester (particularly vinyl acetate).
As a method for copolymerizing diacetone acrylamide and vinyl ester, various methods such as conventionally known bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be adopted, and among them, solution polymerization using methanol as a solvent is preferable. Industrially preferred. Monomer reactivity ratio (ra) in copolymerization of diacetone acrylamide (a) and vinyl acetate (b)
= 4.8, rb = 0.075) by the Hanna method.

In saponifying the obtained copolymer, conventionally known alkali saponification and acid saponification can be applied. Among them, a methanol solution of the polymer or methanol and water, methyl acetate, benzene, etc. Industrially preferred is a method of adding an alkali (such as sodium hydroxide or potassium hydroxide) to a mixed solution of the above to carry out alcoholysis.

Also, diacetone acrylamide-modified PV
In A, various monomers having copolymerizability in the same manner as described above can be further copolymerized as long as the effects of the present invention are not impaired.

In the present invention, the content of the reactive group in the PVA (A) modified with the reactive group having active hydrogen is not particularly limited, but may be 2 to 15 mol% (further 4 to 13 mol%). In particular, when the content is less than 2 mol%, P modified with active hydrogen is preferably used.
Because the surface activity of VA is reduced and the efficiency of generation of derivatives such as biuret and urea generated by the reaction between water and the isocyanate-based compound is deteriorated, the contribution of the adhesive strength expression by the Filer effect can be sufficiently expected. 15
If it exceeds mol%, no improvement in adhesive strength can be expected, which is not preferable.

The hydrolysis rate (content of hydroxyl group) of the vinyl ester moiety in PVA (A) is not particularly limited either, but is 70 mol% or more (further 80 to 99.9 mol%,
In particular, it is preferably 85 to 95 mol%, particularly 85 to 93 mol%), and if the hydrolysis rate is less than 70 mol%, the cohesive force of the adhesive layer is undesirably reduced.

Further, the average degree of polymerization of PVA (A) is not particularly limited, either, but may be 300 to 4000 (more preferably 500 to 2).
When the degree of polymerization is less than 300, it is difficult to obtain sufficient adhesive strength. On the other hand, when the degree of polymerization exceeds 4,000, the viscosity of the adhesive becomes too high, resulting in a problem in workability. In addition to this, it is not preferable because the permeability to the adherend is reduced and the adhesive strength is reduced.

In the present invention, the block character
PVA having [η] of 0.58 or less (further, 0.56 or less)
It is also preferable to use (A). If the block character [η] exceeds 0.58, the storage stability of the base material is lowered, which is not preferable. In addition, a large amount of an isocyanate compound is required to develop the adhesive force. It is not preferable because it may be caused.

The block character [η] can be controlled by arbitrarily selecting the solvent, reaction temperature, stirring conditions, and the like during saponification. When such a block character is larger than 0.58, the storage stability of the main ingredient is lowered, which is not preferable. In addition, the amount of polyvalent isocyanate used to develop a predetermined amount of adhesive strength increases, which is not preferable.

The aqueous emulsion (B) used as the main component of the two-part adhesive of the present invention includes vinyl acetate homopolymer, vinyl acetate and acrylic acid, maleic acid, fumaric acid,
Copolymer emulsions with unsaturated acids such as crotonic acid and esters thereof, styrene-butadiene copolymer latex, ethylene-vinyl acetate copolymer emulsion,
Specific examples include α, β-unsaturated carboxylic acid-containing ethylene-vinyl acetate copolymer emulsion, butadiene-acrylonitrile copolymer latex, chloroprene latex, butyl rubber latex, polybutadiene latex, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, etc. Among them, styrene-butadiene copolymer latex and ethylene-vinyl acetate copolymer emulsion are preferably used. Further, the aqueous emulsion (B) may be one in which the above-mentioned modified PVA (A) is used as a protective colloid agent.

The main component of the two-part adhesive of the present invention contains the modified PVA (A) and the aqueous emulsion (B) as described above. The content of the PVA (A) in the main component is determined by the isocyanate described later. Although it cannot be said unconditionally due to the relationship of the compounding ratio with the compound, the modified PVA (A) and the aqueous emulsion (B)
Of PVA (A) / solid content (weight ratio)
Aqueous emulsion (B) is preferably 99/1 to 5/95 (more preferably 95/5 to 10/90), and when the weight ratio is larger than 99/1 or smaller than 5/95. Are not preferred because the cohesive force of the adhesive layer is reduced.

The polyvalent isocyanate compound (C) used in the curing agent of the two-part adhesive of the present invention may be an aromatic, aliphatic, cycloaliphatic, or alicyclic polyisocyanate or a mixture thereof. And specifically, tolylene diisocyanate (T) such as 2,4-tolylene diisocyanate or 2,6-tolylene diisocyanate.
DI), and mixtures thereof, diphenylmethane diisocyanate (MDI), hydrogenated diphenylmethane diisocyanate (H-MDI), polyphenylmethane polyisocyanate (crude MDI), modified diphenylmethane diisocyanate (modified MDI), hydrogenated xylylene diisocyanate ( H-XDI), trimethylolpropane-TDI adduct, xylylene diisocyanate (XDI), 4,4-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate (HMD)
I), trimethylhexamethylene diisocyanate (T
Aromatic polyisocyanates such as MXDI) or trimer compounds of these polyisocyanates; aliphatic polyisocyanates such as isophorone diisocyanate (IPDI); norbornene diisocyanate (NBDI); and reaction products of these polyisocyanates and polyols. Diphenylmethane diisocyanate (MD
I), 2,4-tolylene diisocyanate (TDI) is preferably used.

The two-part adhesive of the present invention comprises the above-mentioned main agent and a curing agent.
PVA modified with a reactive group having an active hydrogen in the main component, characterized by the compounding ratio of the main component and the curing agent.
(A) and the polyvalent isocyanate compound (C) in the curing agent
Is characterized by satisfying the condition of the following equation (1). [Mole number of isocyanate group in (C)] / [mol number of hydroxyl group in (A) + mol number of reactive group in (A)] = 0.1 to 2.0 (1)

In the above formula (1), if the ratio is less than 0.1, the adhesive strength and the water resistance are reduced. On the other hand, if the ratio is more than 2.0, the usable time is reduced and the adhesive strength is also reduced. The object of the invention cannot be achieved. A more preferred range of such a ratio is 0.2 to 1.8, especially 0.2 to 1.8.
1.5.

In order to adjust the ratio, the content of PVA (A) or polyvalent isocyanate (C) contained in the base material and the curing agent, the content of the reactive group of PVA (A),
It is possible by controlling the mixing ratio of the main agent and the curing agent.

As described above, in the present invention, PVA (A) having a reactive group introduced therein by blending a base agent and a curing agent according to the above formula (1) functions as a reactive surfactant, and as a result, It has been found that a reaction product (isocyanate derivative) of a polyvalent isocyanate and water is efficiently generated, and the adhesive strength is greatly improved by the filler effect as compared with the case where conventional PVA is used. It is.

In the two-part adhesive of the present invention, wheat flour, starches, defatted soy flour, clay, kaolin, talc, calcium carbonate, titanium oxide and the like can be further used as extenders. The amount of these extenders varies depending on the purpose of use, but generally, the amount of the aqueous emulsion (B) 100
It is preferably at most 200 parts by weight, more preferably at most 150 parts by weight, based on parts by weight (in terms of solid content).

The two-component adhesive of the present invention may further contain an antifreezing agent such as ethylene glycol and propylene glycol, a nonionic surfactant-based dispersing aid, and an antifoaming agent as long as the properties are not impaired. Preservatives, fungicides, coloring agents, solvents, thickeners and the like may be added as appropriate. When the two-component adhesive of the present invention is used, the adhesive can be sufficiently bonded only by a cold press (normal temperature and pressing treatment), but for the purpose of further improving the productivity, a hot press (pressing treatment by a heating plate) is used. Can also be processed.

The two-component adhesive of the present invention is excellent in initial adhesiveness, exhibits permanent adhesiveness, and is also excellent in water-resistant adhesive strength. Suitable for plywood adhesives, woodworking adhesives, particleboard adhesives, etc., and wood / plastic material adhesives (PVC plywood adhesives, foamed resin / wood adhesives, etc.). Further, packaging adhesives (paper / paper adhesive, paper / plastic adhesive, paper / aluminum foil adhesive, etc.), cloth adhesives (cloth / plastic adhesive, cloth / paper adhesive, cloth / wood) Adhesives) and adhesives for building materials (concrete / wood adhesives, wood / adhesives for various boards, etc.).

[0042]

The present invention will be described below in more detail with reference to examples. Unless otherwise noted in the examples, “%” indicates a weight basis.

Example 1 (Production of PVA) Polyvinyl acetate obtained by a conventional method (average degree of polymerization: 2,000; completely saponified to JIS K6)
Methyl acetate was added to a methanol solution of polyvinyl acetate / methanol /
After adjusting so that methyl acetate = 48/39/13 (weight ratio) to obtain a polyvinyl acetate solution, 100 parts of the solution was charged into a kneader, and the solution temperature was adjusted to 40 ° C. When the liquid temperature reached 40 ° C., 3 parts of a 2% aqueous sodium hydroxide solution was charged as a catalyst and saponification was carried out for 1.5 hours. Then, after neutralizing with acetic acid to stop the saponification reaction, the resultant is repeatedly washed with methanol, and then dried to obtain PVA having a saponification degree of 91.1 mol% (residual acetic acid group: 8.9 mol%). I got

(Production of AA-PVA)
200 parts of VA powder was charged into a kneader, and acetic acid 2 was added thereto.
After adding 0 parts and swelling, the temperature was raised to 60 ° C. while stirring at a rotation speed of 20 rpm, 24.8 parts of diketene was added dropwise over 4 hours, and the mixture was further reacted for 30 minutes to obtain AA-PVA. The degree of acetoacetylation of the obtained AA-PVA was 3.
1 mol%, and the block character [η] was 0.51.

The block character [η] was calculated from the result of ¹³ C-NMR measurement under the following conditions. Measurement instrument: Burker Co. "AVANCE DPX400" solvent: D ₂ O integration number: 8192 pulse interval: 2 seconds Internal standard substance: 3- (Trimethylsilyl) propionic-2,2,3,3 , -d 4 acid, sodium Salt measurement temperature: 50 ° C Concentration: 7.5%

[Preparation of Two-Part Adhesive] The following main agent (solid content: 43.5%) and a curing agent were prepared. Main agent: 15% aqueous solution of the above-mentioned AA-PVA (A) 40 g Styrene-phthalic acid copolymer emulsion (B) having a solid content of 50% 35 g ("DL612" manufactured by Asahi Kasei Corporation) Calcium carbonate 20 g Water 5 g Hardening agent: MDI (NCO group content 6.71 × 10 ⁻³ mol / g) 9.72 g

The AA-PV in 100 g of the above main agent
The hydroxyl group contained in A is 0.105 mol, the reactive group (AA group) is 0.00369 mol, and the NCO group contained in 9.72 g of the curing agent is 0.0652 mol. Substituting it into the left side of equation (1) yields 0.6.

The following evaluation was performed by mixing and stirring the two-part adhesive prepared above.

Normal adhesive strength The above-mentioned adhesive was applied to one of the two birch pieces having a size of 25 mm × 30 mm × 10 mm on one of the surfaces to be adhered so as to be 100 g / m ² ± 10 g. / Cm ² for 12 hours, and the adhesive strength at that time was measured according to JIS K6.
It was measured according to 852.

Initial bonding strength: Bond both sides of the birch material in the same manner as above to obtain 8 kg / cm ²
Pressure for 5 or 10 minutes, and the adhesive strength at that time is JI
It was measured according to SK 6852.

Water-Resistant Adhesive Strength An adhesive sample was prepared in the same manner as above, and
After immersing in boiling water for 4 hours after drying, drying in air at 60 ° C for 20 hours, immersing again in boiling water for 4 hours, immersing in water at room temperature, allowing it to cool down, and immediately taking it out of the water JIS K (wet) adhesive strength
It was measured according to 6852.

Example 2 According to Example 1, the degree of acetoacetylation was 7.2 mol%,
Block character [η] is 0.58, hydroxyl group is 85.
An AA-PVA of 1 mol% (residual acetic acid group: 7.7 mol%) was obtained, a two-part adhesive was obtained in the same manner as in Example 1, and the evaluation was performed in the same manner. The amount of the curing agent was 9.29 g. The hydroxyl group contained in the AA-PVA in 100 g of the main agent is 0.0%
958 mol, and the reactive group (AA group) is also 0.008
10 moles of NCO contained in 9.29 g of curing agent
The group is 0.0623 mol, and when substituted into the left side of the expression (1) in the text, it becomes 0.6.

Example 3 According to Example 1, AA conversion of acetoacetylation degree 4 mol%, block character [η] 0.54, hydroxyl group 88.4 mol% (residual acetic acid group 7.6 mol%) Get PVA,
A two-part adhesive was obtained in the same manner as in Example 1, and was evaluated in the same manner. The amount of the curing agent was 13.08 g. Main agent 1
The hydroxyl groups contained in the AA-PVA in 00 g are 0.10
5 mol, the reactive group (AA group) is 0.0047 mol, and the NCO group contained in 13.08 g of the curing agent is 0.088 mol, which is substituted into the left side of the formula (1) in the text. 0.8.

Example 4 The procedure of Example 1 was repeated, except that the styrene-butadiene copolymer emulsion having a solid content of 50% was replaced with Sumikafl.
ex 450 "(manufactured by Sumitomo Chemical Co., Ltd., solid content 55% ethylene-vinyl acetate emulsion) was used in the same manner to obtain a two-part adhesive, which was similarly evaluated.

Example 5 A two-part adhesive was obtained in the same manner as in Example 3 except that the amount of the curing agent was changed so that the left side of the equation (1) became 1.4. Was done.

Example 6 A two-part adhesive was obtained in the same manner as in Example 3 except that the amount of the curing agent was changed so that the left side of the equation (1) became 0.4. Was done.

Example 7 An evaluation was performed in the same manner as in Example 2 except that the preparation of the two-part adhesive was changed as follows. [Preparation of two-pack adhesive] The following main ingredients (solid content: 59.7)
%) And a curing agent. -Main agent: 15% aqueous solution of the above-mentioned AA-PVA (A) 18g 50% solid content of styrene-phthalic acid copolymer emulsion (B) 50g ("DL612" manufactured by Asahi Kasei Corporation) Calcium carbonate 32g-Hardening agent: MDI (NCO group content 6.71 × 10 ^-3 mol / g) 6.04 g the hydroxyl contained in the AA-PVA in the main agent 100g is 0.0431 mol, similarly reactive group (AA group) in 0.00365 mol The NCO group contained in 6.04 g of the curing agent is 0.0405 mol, which is 0.87 when assigned to the left side of the expression (1) in the text.

Example 8 Evaluation was performed in the same manner as in Example 3 except that the preparation of the two-part adhesive was changed as follows. [Preparation of two-pack adhesive] The following main ingredients (solid content: 59.7)
%) And a curing agent. -Main agent: 15% aqueous solution of the above-mentioned AA-PVA (A) 18g 50% solid content of styrene-phthalic acid copolymer emulsion (B) 50g ("DL612" manufactured by Asahi Kasei Corporation) Calcium carbonate 32g-Hardening agent: MDI (NCO Group content 6.71 × 10 ⁻³ mol / g) 7.0 g The hydroxyl group contained in the AA-PVA in 100 g of the main agent is 0.0472 mol, and the reactive group (AA group) is 0.00214 mol. The NCO group contained in 7.0 g of the curing agent is 0.04697 mol, which is 0.95 when substituted into the left side of the expression (1) in the text.

Example 9 (Production of diacetone acrylamide-modified PVA) A solution (methanol solvent) was polymerized at the boiling point by the hanna method using the reactivity ratio described in the text, and the degree of polymerization was 1200 and the amount of modification of diacetone acrylamide was changed. 4 mol% of polyvinyl acetate was obtained. Then, the polyvinyl acetate was saponified according to Example 1 so that the block character [η] was 0.1.
At 56, a diacetone acrylamide-modified PVA having a saponification degree of 90 mol% was obtained. [Preparation and evaluation of two-part adhesive]
A two-part adhesive was obtained in the same manner except that the diacetone acrylamide-modified PVA was used in place of the A-PVA (A), and the amount of the curing agent was changed to 16.3 g. Was. The hydroxyl group contained in the modified PVA in 100 g of the main agent was 0.105 mol, and the reactive group diacetone acrylamide was 0.0046 mol,
The NCO group contained in 16.3 g of the curing agent is 0.1096.
When the value is substituted into the left side of the expression (1) in the text, it becomes 1.0.

Comparative Example 1 A two-part adhesive was obtained in the same manner as in Example 3 except that the mixing amount of the curing agent was changed to 1.54 g, and a similar evaluation was performed. The hydroxyl group contained in the AA-PVA in 100 g of the main agent was 0.095 mol, the reactive group (AA group) was 0.0081 mol, and the curing agent was 1.54 mol.
The NCO group contained in g is 0.0103 mol, and is 0.1 when substituted into the left side of the expression (1) in the text.

Comparative Example 2 A two-part adhesive was obtained in the same manner as in Example 3 except that the mixing amount of the curing agent was changed to 35.3 g, and a similar evaluation was performed. The hydroxyl group contained in the AA-PVA in 100 g of the main agent was 0.095 mol, the reactive group (AA group) was 0.0081 mol, and the curing agent was 35.3.
The NCO group contained in g is 0.237 mol, which is 2.3 when substituted into the left side of the expression (1) in the text. Table 1 shows the evaluation results of the examples and the comparative examples.

[Table 1] Normal adhesive strength Initial adhesive strength Waterproof adhesive strength After 5 minutes and after 10 minutes Example 1 190 40 52 100 〃 2 201 48 60 105 ３ 3 220 58 65 125 〃 4 188 40 50 98 ５ 5 228 60 66 128 〃 6 210 56 62 118 ７ 7 198 46 58 101 〃 8 210 54 61 119 ９ 9 200 47 58 98 Comparative Example 1 60 25 305 〃 2 120 28 38 38 75 Note) All units are kgf / cm ^2.

[0063]

According to the two-part adhesive of the present invention, the ratio of the functional groups of the main agent and the curing agent is adjusted to a specific range.
Excellent initial adhesion, permanent adhesion, and excellent water resistance, wood / wood adhesive (wood, plywood, particle board, hard board, etc.), wood / plastic Adhesives, adhesives for building materials (concrete / wood adhesives, wood / various board adhesives, etc.), packaging adhesives (paper / paper adhesives, paper / plastic adhesives, paper / aluminum adhesives, etc.) ), Useful for bonding cloth adhesives and the like.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Yamada 836 Otani, Shizuoka-shi, Shizuoka Pref. DA141 DA142 DB051 DB052 DC031 DC032 DC071 DC072 DE021 DE022 DE031 DE032 DF011 DF012 DF021 DF022 EF181 EF182 EF191 EF192 EF291 EF292 EF301 EF302 GA05 GA06 GA07 GA08 GA14 GA20 GA22 JA13 LA06 LA07 MA10 MA08 MA09

Claims (4)

[Claims] An aqueous liquid containing a polyvinyl alcohol-based resin (A) modified with a reactive group having active hydrogen and an aqueous emulsion (B) and a curing agent containing a polyvalent isocyanate compound (C). And a two-component adhesive satisfying the following condition (1). [Mole number of isocyanate group in (C)] / [mol number of hydroxyl group in (A) + mol number of reactive group in (A)] = 0.1 to 2.0 (1) 2. The content of a reactive group having an active hydrogen in the polyvinyl alcohol resin (A) is 2 to 15 mol%.
And the hydrolysis ratio of the vinyl ester portion is 70 mol%
2. The two-part adhesive according to claim 1, wherein: 3. The two-part adhesive according to claim 1, wherein the reactive group having active hydrogen is any one of an acetoacetate group and an α-methylene adjacent to a carbonyl group. . 4. The two-part adhesive according to claim 1, wherein the block character [η] of the polyvinyl alcohol resin is 0.58 or less.