JP4387480B2 - Adhesive composition and method for producing the same - Google Patents

Description

【００４０】
【表２】

【００４１】
表１および表２から判るように、実施例１〜６の接着剤組成物は常態、耐熱および耐水のいずれの試験においても高い圧縮剪断接着強さを示した。このうち、ポリ酢酸ビニル系エマルジョンをする際の保護コロイドとして無変性のポリビニルアルコールを用いた実施例１、２に比べて、アセトアセチル化ポリビニルアルコールを保護コロイドとした実施例３〜６はさらに接着強さが高く、特に実施例３および４の接着剤組成物は、高温時にもしばしば材料破壊を起こすほどの十分な接着強さを示した。
一方、ポリイソシアネート化合物を反応させなかった比較例１、３およびポリイソシアネート化合物の使用量が少ない比較例２、４では、対応する実施例１、３に比べて圧縮剪断接着強さが低かった。また、ポリイソシアネート化合物の使用量が多すぎる比較例５では、上述のように組成物を被着材に均一に塗布することができなかった。
【００４２】
（２）加熱接着適性試験
上記実施例１〜６および比較例１〜４、６の接着剤組成物を用いて以下の接着条件でホットプレスを行い、下記項目につき評価した。その結果を表３におよび表４に示す。
［接着条件］
被着材：厚さ１ｍｍのスプルース化粧単板×厚さ３０ｍｍのツガ集成材
塗布量（有姿）：１２０ｇ／ｍ²（ツガ集成材側に塗布）
熱盤表面温度：１１０℃
圧締圧力：０．７ＭＰａ
圧締時間：９０秒間
養生時間：４８時間（２３±２℃）
［試験方法］
解圧直後の接着状態：スプルース化粧単板の剥離の有無、および接着材の熱盤への付着の有無を目視評価する。
浸せき剥離試験：養生後の試験片を日本農林規格（ＪＡＳ）の浸せき剥離試験により評価する。
【００４３】
【表３】

【００４４】
【表４】

【００４５】
表３および表４に示すように、実施例１〜６の接着剤組成物は耐熱性が高いため、この組成物により接着された木材はホットプレスの解圧直後にも剥離を起こすことはなかった。また、これらの接着剤組成物により接着された木材はＪＡＳの浸せき剥離試験に合格するものであった。
一方、無変性のポリビニルアルコールを保護コロイドとし、ポリイソシアネート化合物を使用しないかあるいは使用量の少ない比較例１、２の接着剤組成物により接着された木材は耐熱性、耐水性ともに不良であり、アセトアセチル化ポリビニルアルコールを保護コロイドとした比較例３、４の接着剤組成物では耐水性は改善されたものの、耐熱性の点ではまだ性能が不十分であった。そして、ポリイソシアネート化合物を接着直前に配合した比較例６の接着剤組成物によると、プレス時に木材からはみ出した接着剤が熱盤に付着し、この接着剤のため、加熱接着後の木材が熱盤から剥がれなくなるという問題が生じた。
【００４６】
なお、本発明においては、前記具体的実施例に示すものに限られず、目的、用途に応じて本発明の範囲内で種々変更した実施例とすることができる。
【００４７】
【発明の効果】
本発明の接着剤組成物は、高度な耐熱性能および耐水性能を発揮するので、特に木材などを高周波プレスやホットプレスなどを用いて加熱接着する用途に好適である。この接着剤組成物は、残存イソシアネート基が所定量以下に抑えられているので、木材に対しては十分な接着性を示すとともに、高周波プレスの極盤やホットプレスの熱盤などに対して不必要に接着することがないので作業性が良い。そして、本発明の組成物は、非ホルムアルデヒド系の接着剤組成物であるため、建材製造用の接着剤などとして有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an adhesive composition using a polyvinyl acetate emulsion and a method for producing the same. Since the adhesive composition of the present invention is non-formaldehyde and has good heat adhesion suitability, it is suitably used as an adhesive for heat bonding wood or the like by high frequency press, hot press or the like.
[0002]
[Prior art]
Conventionally, when heat-bonding wood or the like with a high-frequency press or hot press, amino resin adhesives obtained by reacting urea or melamine with formaldehyde have been frequently used. However, formaldehyde released from these adhesives has recently been regarded as a problem, and therefore, replacement with non-formaldehyde adhesive compositions is being considered.
[0003]
[Problems to be solved by the invention]
As a non-formaldehyde wood adhesive, an adhesive composition comprising a polyvinyl acetate emulsion using polyvinyl alcohol as a protective colloid is widely used. This adhesive composition has good workability because it has good adhesion to wood and can be used in a single solution. However, since this adhesive composition generally has low water resistance, it is not suitable for applications that require high water resistance. In addition, because heat resistance is low, when heat-bonding wood, etc., by high-frequency press, hot press, etc., it cannot withstand the shrinkage stress caused by the moisture content change of wood heated by the press, and it is easy to peel off immediately after decompression There is.
[0004]
Further, as a polyvinyl acetate emulsion type adhesive having improved water resistance and heat resistance, acetoacetylated polyvinyl alcohol is protected as in the vinyl compound polymerization method disclosed in JP-A-60-54961. Adhesive compositions obtained by a colloid polymerization method are known. However, higher heat resistance may be required depending on the type of wood and the size of the lamina.
[0005]
On the other hand, a two-pack type aqueous adhesive composition in which an aqueous emulsion of a vinyl acetate polymer containing polyvinyl alcohol and an isocyanate compound (curing agent) are blended at the time of use is also known, for example, Japanese Patent Publication No. 55-9437. It is disclosed in the publication. This two-component adhesive composition exhibits higher heat resistance and water resistance than the polyvinyl acetate emulsion adhesive composition described above. However, since this composition is a two-component type, it takes time and effort to mix the curing agent, and foaming at the time of mixing and adhesion, and thickening of the adhesive with time, etc. occur, resulting in poor workability. In addition, in applications where wood is heat-bonded using a high-frequency press or hot press, if the adhesive that protrudes from the adhesive layer adheres to the pole plate of a high-frequency press or the hot plate of a hot press, Since it contains a large amount of unreacted isocyanate compound, it has strong adhesion to the above-mentioned electrode board and hot plate (usually made of iron plate), so that the wood after heat bonding will not peel off from the surface of the press machine. There's a problem.
[0006]
An object of the present invention is an adhesive composition that exhibits high heat resistance and water resistance, and is particularly suitable for non-formaldehyde-based water-based bonding suitable for heat-bonding wood or the like using a high-frequency press or hot press. It is to provide an agent composition.
[0007]
[Means for Solving the Problems]
The present inventors are a composition obtained by reacting a specific polyvinyl acetate emulsion and a polyisocyanate compound in advance, wherein the amount of residual isocyanate groups in the composition is a predetermined value or less. According to the composition, the present invention has been completed by finding that the above-mentioned problems can be solved.
[0008]
That is, the adhesive composition according to claim 1 of the present invention is a polyisocyanate compound having two or more isocyanate groups in one molecule with respect to 100 parts by weight of the nonvolatile content of the polyvinyl acetate emulsion containing polyvinyl alcohol. It is obtained by reacting 3 to 50 parts by weight until the amount of residual isocyanate groups is 5 mol% or less with respect to the amount of isocyanate groups contained in the polyisocyanate compound.
[0009]
The “polyvinyl acetate emulsion containing polyvinyl alcohol” includes (1) a polyvinyl acetate emulsion obtained by emulsion polymerization using polyvinyl alcohol as a protective colloid, and (2) a vinyl acetate emulsion obtained by solution polymerization. After adding polyvinyl alcohol and water to the polymer, the polyvinyl acetate emulsion obtained by stirring and emulsification, and (3) the polyvinyl alcohol emulsion obtained using another protective colloid or emulsifier Added ones and the like. Among these, in the present invention, it is preferable to use the polyvinyl acetate emulsion (1). Further, polyvinyl alcohol may be added after the polyvinyl acetate emulsion (1).
[0010]
As the protective colloid, polyvinyl alcohol having a saponification degree of 75 to 99% and an average polymerization degree of 100 to 10,000 is preferably used. Further, when producing the polyvinyl acetate emulsion of the above (1), in addition to polyvinyl alcohol, cellulose derivatives such as hydroxymethylcellulose, methylcellulose, carboxymethylcellulose, various processed starches, or anionic, cationic, or Various nonionic surfactants may be used in combination.
[0011]
As the polyvinyl alcohol, in addition to unmodified polyvinyl alcohol, various modified polyvinyl alcohols such as carboxy modification, sulfonic acid modification, thiol modification, silanol modification, cationic group modification, diacetone acrylamide modification, and acetoacetylation modification are used. can do. In particular, the use of acetoacetylated polyvinyl alcohol as described in claim 2 is preferable because an adhesive composition having high water resistance can be obtained.
[0012]
When the polyvinyl acetate emulsion used in the present invention is produced by emulsion polymerization using acetoacetylated polyvinyl alcohol as a protective colloid, the degree of acetoacetylation of this acetoacetylated polyvinyl alcohol is more preferably 0.05 to 20 mol%. The range of 0.05 to 15 mol% is appropriate. The specific polymerization operation is performed according to a general emulsion polymerization method except that acetoacetylated polyvinyl alcohol is added to the reactor at any time before the start of emulsion polymerization, during polymerization, or after completion of polymerization. Just do it. The addition of acetoacetylated polyvinyl alcohol is preferably performed before the start of emulsion polymerization or during the polymerization. The addition amount of acetoacetylated polyvinyl alcohol is 0.1 to 30% by weight, preferably 0.2 to 20% by weight, based on the solid content of the polyvinyl acetate emulsion obtained after polymerization.
[0013]
As the monomer used in the production of the polyvinyl acetate emulsion, one or more selected from vinyl acetate monomers such as vinyl acetate and vinyl propionate are used. Further, these vinyl acetate monomers and One or more kinds of other copolymerizable monomers can be used as long as the effects of the present invention are not impaired.
[0014]
Examples of the “other monomers” include acrylic acid esters, methacrylic acid esters, maleic acid esters, crotonic acid esters, itaconic acid esters, vinyl halides such as vinyl chloride and vinylidene chloride, ethylene, propylene, etc. Glycidyl group-containing compounds such as ethylenes, acrylonitrile, methacrylonitrile, styrene, glycidyl acrylate, glycidyl methacrylate, glycidyl divinyl ether, glycidyl vinyl ether, methylol group-containing compounds such as N-methylol acrylamide, N-methylol methacrylamide and the like Derivatives, carboxylic acid amides such as acrylamide and methacrylamide, carboxyl group-containing monomers such as acrylic acid and methacrylic acid, and anhydrides thereof, divinyl adipate, divinyl Cuccinate, triallyl cyanurate, diallyl fumarate, triallyl citrate, diallyl malate, vinyl versatate, hydroxyl group-containing monomer, amino group-containing monomer, amide group-containing monomer, sulfone group-containing monomer, polyvinyl compound, etc. It is done.
[0015]
As the polymerization initiator used for the production of the polyvinyl acetate emulsion, generally used radical polymerization initiators, for example, persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide, t-butyl Peroxide polymerization initiators such as hydroperoxide, benzoyl peroxide, lauroyl peroxide; 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, Examples include azo polymerization initiators such as 2,2′-azobis (2,4-dimethylvaleronitrile).
[0016]
The polyisocyanate compound used in the present invention has two or more isocyanate groups in one molecule, and specifically includes tolylene diisocyanate (hereinafter referred to as “TDI”), TDI adduct, diphenylmethane- Examples include 4,4′-diisocyanate (hereinafter referred to as “MDI”), polymeric MDI, hexamethylene diisocyanate (hereinafter referred to as “HDI”), and the like. Among these, it is preferable to use polymeric MDI or MDI liquefied by carbodiimidization because it is liquid and easy to handle and has high safety due to low volatility. Further, a so-called self-emulsifying polyisocyanate compound with improved water dispersibility may be used, and self-emulsifying polymeric MDI is particularly preferably used.
[0017]
The amount of the polyisocyanate compound used should be 3 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the nonvolatile content of the polyvinyl acetate resin emulsion. When the amount of the polyisocyanate compound used is less than 3 parts by weight, the resulting adhesive composition does not sufficiently exhibit the effect of improving water resistance and heat resistance. On the other hand, when the addition amount of the polyisocyanate compound exceeds 50 parts by weight, the fluidity of the obtained adhesive composition is lowered and the coating property is deteriorated.
[0018]
In the adhesive composition of the present invention, the polyisocyanate compound is 5 mol% or less (more preferably 2 mol%) based on the number of isocyanate groups contained in the polyisocyanate compound in which the number of remaining isocyanate groups is used. Hereinafter, it is obtained by further reacting until it becomes 1 mol% or less. When an isocyanate group exceeding 5 mol% remains in the composition, the storage stability such as foaming occurs when the isocyanate group reacts with moisture in the composition during storage of the adhesive composition of the present invention. Deteriorate. In addition, when heat-bonding wood, etc., using a high-frequency press or hot press, the adhesive adheres firmly to the hot platen of the press machine due to the action of residual isocyanate groups in the adhesive protruding from the adherend. For this reason, there arises a problem that the wood after heat bonding does not peel off from the surface of the press machine.
[0019]
As a method of reacting the polyvinyl acetate emulsion and the polyisocyanate compound, the polyisocyanate compound is added to the polyvinyl acetate emulsion and stirred at a temperature of 20 to 55 as described in claim 3. A method of reacting at a temperature of more preferably 30 to 50 ° C., more preferably 35 to 45 ° C. is preferable. When the reaction temperature exceeds 55 ° C., the reaction solution foams violently, making it difficult to control the reaction. On the other hand, when the reaction temperature is less than 20 ° C., the reaction rate of the isocyanate group is slow, and for example, it takes 24 hours or more until the amount of the remaining isocyanate group is less than 5 mol%, so the productivity of the adhesive composition is lowered. In addition, by performing reaction under stirring, the carbon dioxide gas which generate | occur | produces with reaction is escaped out of a liquid, the effect which suppresses foaming of a reaction liquid and prevents gelatinization is acquired.
[0020]
The method for measuring the amount of residual isocyanate groups contained in the adhesive composition is to add excess di-n-butylamine to the sample and react at room temperature, and then reverse the unreacted amine with hydrochloric acid. The method of titrating is mentioned.
[0021]
In the adhesive composition of the present invention, various plasticizers, organic solvents and the like can be blended for the purpose of improving flexibility and adhesiveness. Examples of plasticizers include aromatic dibasic acid dialkyl esters such as dibutyl phthalate and dioctyl phthalate; aliphatic dibasic acid dialkyl esters such as dimethyl succinate and diisobutyl adipate. Organic solvents include aromatic solvents such as toluene and xylene; glycol ether solvents such as ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and propylene glycol monomethyl ether; ketones such as cyclohexanone and methyl isobutyl ketone Solvents such as acetate solvents such as butyl acetate and isobutyl acetate can be used.
[0022]
Moreover, various fillers can be mix | blended with the adhesive composition of this invention. Examples of the filler include wheat flour, corn starch, calcium carbonate, silica, kaolin clay, talc, aluminum hydroxide, titanium oxide, zinc oxide, and shirasu balloon. In addition, antifoaming agents, preservatives, fragrances, thickeners, stabilizers and the like may be added to the adhesive composition of the present invention as necessary.
[0023]
The adhesive composition of the present invention exhibits high heat resistance and water resistance even when used as a one-pack type, but various cross-linking agents (curing agents) may be blended at the time of use as necessary. Examples of the crosslinking agent include various metal salts, amino resins, aldehyde compounds such as glyoxal, isocyanate compounds such as 4,4′-diphenylmethane diisocyanate, and epoxy compounds.
[0024]
Moreover, it is preferable that the adhesive composition of this invention is 30-70 weight% of non volatile matters, and it is preferable that the viscosity at the time of use is 1-100 Pa.s / 30 degreeC.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, “parts” means parts by weight, and “%” not specifically mentioned means% by weight.
[0026]
Example 1
In a glass polymerization container, 606 parts by weight of water and 58 parts of PVA217 (manufactured by Kuraray Co., Ltd., trade name of polyvinyl alcohol having an average polymerization degree of about 1700 and a saponification degree of about 88%) were charged and dissolved by heating and stirring. Thereafter, 0.65 part of tartaric acid and 30 parts of vinyl acetate were added, 5 parts of 3% hydrogen peroxide aqueous solution was added, and initial polymerization was carried out at 80 ° C. Subsequently, 320 parts of vinyl acetate and 15 parts of a 3% aqueous hydrogen peroxide solution were polymerized while continuously dropping uniformly over 3 hours and 30 minutes, followed by aging for 1 hour from the end of dropping.
Next, the system was cooled to 40 ° C., and at this temperature, 52 parts of Millionate MR-200 (trade name of Polymeric MDI, manufactured by Nippon Polyurethane Industry Co., Ltd.) (12.7 with respect to 100 parts of the solid content of the polyvinyl acetate emulsion). Part) was added and allowed to react with stirring for 16 hours. Thereafter, 42 parts of dibutyl phthalate (hereinafter referred to as “DBP”) was added, and an aqueous adhesive having a nonvolatile content of 43.1%, a viscosity of 6.6 Pa · s / 30 ° C., and a residual isocyanate group of 0.3 mol%. A composition was obtained.
[0027]
(Example 2)
The non-volatile content was 44.8% and the viscosity was the same as in Example 1 except that the amount of Millionate MR-200 was 104 parts (25.5 parts relative to 100 parts of the solid content of the polyvinyl acetate emulsion). A water-based adhesive composition having 15.2 Pa · s / 30 ° C. and a residual isocyanate group of 0.5 mol% was obtained.
[0028]
(Example 3)
In a glass polymerization vessel, 550 parts by weight of water and Goseifamer Z-210 (product name of acetoacetylated polyvinyl alcohol having an average polymerization degree of about 1300 and a saponification degree of about 96%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) After charging 53 parts and dissolving by heating and stirring, 30 parts of vinyl acetate was added, 12 parts of a 2% aqueous ammonium persulfate solution was added, and initial polymerization was carried out at 80 ° C. Subsequently, 377 parts and 2 of vinyl acetate were added. 28 parts of an aqueous ammonium persulfate solution was polymerized while continuously dropping uniformly over 3 hours and 30 minutes, and aging was performed for 1 hour from the end of dropping.
Next, the system was cooled to 40 ° C., and 54 parts of Millionate MR-200 (11.7 parts with respect to 100 parts of the solid content of the polyvinyl acetate emulsion) was added at this temperature, and the reaction was allowed to proceed with stirring for 16 hours. . Thereafter, 32 parts of DBP was added to obtain an aqueous adhesive composition having a nonvolatile content of 46.3%, a viscosity of 5.3 Pa · s / 30 ° C., and a residual isocyanate group of 0.3 mol%.
[0029]
(Example 4)
As the isocyanate compound, the same amount of Coronate 3053 (trade name of self-emulsifying MDI manufactured by Nippon Polyurethane Industry Co., Ltd.) was used instead of Millionate MR-200, and the non-volatile content was 46. An aqueous adhesive composition having 5%, a viscosity of 5.5 Pa · s / 30 ° C., and a residual isocyanate group of 0.2 mol% was obtained.
[0030]
(Example 5)
The non-volatile content of 45.5 was the same as in Example 3 except that the same amount of Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name of TDI adduct) was used as the isocyanate compound instead of Millionate MR-200. %, A viscosity of 5.4 Pa · s / 30 ° C., and an aqueous adhesive composition having a residual isocyanate group of 0.4 mol% was obtained.
[0031]
(Example 6)
As the isocyanate compound, the same amount of Aquanate 110 (Nippon Polyurethane Industry Co., Ltd., trade name of self-emulsifying HDI) was used instead of Millionate MR-200, in the same manner as in Example 3, except that the nonvolatile content was 46 An aqueous adhesive composition having a viscosity of 6.3 Pa · s / 30 ° C. and a residual isocyanate group of 0.3 mol% was obtained.
[0032]
(Comparative Example 1)
A water-based adhesive composition having a non-volatile content of 40.4% and a viscosity of 4.8 Pa · s / 30 ° C. was obtained in the same manner as in Example 1 except that Millionate MR-200 was not added.
[0033]
(Comparative Example 2)
The non-volatile content was 40.9% and the viscosity was the same as in Example 1 except that the amount of Millionate MR-200 was 10 parts (2.5 parts relative to 100 parts of the solid content of the polyvinyl acetate emulsion). An aqueous adhesive composition having 5.2 Pa · s / 30 ° C. and a residual isocyanate group of 0.1 mol% was obtained.
[0034]
(Comparative Example 3)
A water-based adhesive composition having a nonvolatile content of 43.7% and a viscosity of 4.0 Pa · s / 30 ° C. was obtained in the same manner as in Example 3 except that Millionate MR-200 was not added.
[0035]
(Comparative Example 4)
The non-volatile content was 44.2% and the viscosity was the same as in Example 1 except that the amount of Millionate MR-200 was 10 parts (2.2 parts relative to 100 parts of the solid content of the polyvinyl acetate emulsion). An aqueous adhesive composition having 4.5 Pa · s / 30 ° C. and a residual isocyanate group of 0.1 mol% was obtained.
[0036]
(Comparative Example 5)
Except that the amount of Millionate MR-200 added was 250 parts (54 parts based on 100 parts of the solid content of the polyvinyl acetate emulsion), the non-volatile content was 52.3% and the viscosity was 9. An aqueous adhesive composition having 5 Pa · s / 30 ° C. and a residual isocyanate group of 0.5 mol% was obtained. However, since this composition had low fluidity and the adhesive could not be uniformly applied to the test piece, the adhesion performance test described later was not performed.
[0037]
(Comparative Example 6)
Immediately before the heat adhesion suitability test described later, 11.7 parts of Millionate MR-200 were added to and mixed with 100 parts of the nonvolatile content of the aqueous adhesive composition of Comparative Example 3 to obtain a nonvolatile content of 43.9% and a viscosity of 4 A water-based adhesive composition having 2 Pa · s / 30 ° C. and a residual isocyanate group of 92 mol% was prepared.
[0038]
The following adhesive performance test was done about the obtained adhesive composition.
(1) Compression shear bond strength test (conforms to JIS K 6852)
Using the adhesive compositions of Examples 1 to 6 and Comparative Examples 1 to 4, test pieces were prepared under the following bonding conditions, and the compression shear bond strength (N / mm ² ) was measured by the following test method. did. The results are shown in Tables 1 and 2.
In Tables 1 and 2, “PVA” represents polyvinyl alcohol, and “AA-modified PVA” represents acetoacetylated polyvinyl alcohol.
[Adhesion conditions]
Substrate: glazing material x glazing material application amount (solid): 200 g / m ²
Clamping pressure: 1 MPa
Clamping time: 24 hours (23 ± 2 ° C)
Curing time: 48 hours (23 ± 2 ° C)
[Test method]
Normal test: Measured under the same conditions after preparing the test piece.
Heat resistance test: The test piece is measured after being left in a thermostat at 60 ± 3 ° C. for 2 hours.
Water resistance test: A test piece is left in water at 30 ± 1 ° C. for 3 hours, then immersed in water at room temperature until it cools, and measurement is performed in a wet state.
[0039]
[Table 1]

[0040]
[Table 2]

[0041]
As can be seen from Tables 1 and 2, the adhesive compositions of Examples 1 to 6 exhibited high compression shear adhesive strength in any of the tests of normal state, heat resistance and water resistance. Among these, Examples 3 to 6 using acetoacetylated polyvinyl alcohol as a protective colloid were further bonded as compared with Examples 1 and 2 using unmodified polyvinyl alcohol as a protective colloid when making a polyvinyl acetate emulsion. The strength was high, and in particular, the adhesive compositions of Examples 3 and 4 showed sufficient adhesive strength to cause material breakage even at high temperatures.
On the other hand, in Comparative Examples 1 and 3 in which the polyisocyanate compound was not reacted and in Comparative Examples 2 and 4 in which the amount of the polyisocyanate compound used was small, the compression shear adhesive strength was lower than in the corresponding Examples 1 and 3. Further, in Comparative Example 5 in which the amount of the polyisocyanate compound used was too large, the composition could not be uniformly applied to the adherend as described above.
[0042]
(2) Heat adhesion suitability test Using the adhesive compositions of Examples 1 to 6 and Comparative Examples 1 to 4 and 6, hot pressing was performed under the following adhesion conditions, and the following items were evaluated. The results are shown in Table 3 and Table 4.
[Adhesion conditions]
Substrate: 1 mm thick spruce decorative veneer x 30 mm thick tsuga laminated wood application amount (solid): 120 g / m ² (applied to the tsuga laminated wood side)
Hot plate surface temperature: 110 ° C
Clamping pressure: 0.7 MPa
Clamping time: 90 seconds Curing time: 48 hours (23 ± 2 ° C)
[Test method]
Adhesion state immediately after decompression: The presence or absence of peeling of the spruce decorative veneer and the presence or absence of adhesion of the adhesive to the hot platen are visually evaluated.
Immersion peeling test: The test piece after curing is evaluated by a Japanese Agricultural Standard (JAS) immersion peeling test.
[0043]
[Table 3]

[0044]
[Table 4]

[0045]
As shown in Tables 3 and 4, since the adhesive compositions of Examples 1 to 6 have high heat resistance, the wood bonded by this composition does not cause peeling immediately after the hot press is decompressed. It was. Moreover, the wood bonded with these adhesive compositions passed the JAS immersion peel test.
On the other hand, unmodified polyvinyl alcohol is used as a protective colloid, and the wood bonded with the adhesive composition of Comparative Examples 1 and 2 in which the polyisocyanate compound is not used or the amount used is small is poor in both heat resistance and water resistance. Although the water resistance of the adhesive compositions of Comparative Examples 3 and 4 using acetoacetylated polyvinyl alcohol as a protective colloid was improved, the performance was still insufficient in terms of heat resistance. Then, according to the adhesive composition of Comparative Example 6 in which the polyisocyanate compound was blended immediately before bonding, the adhesive protruding from the wood at the time of pressing adheres to the hot platen, and because of this adhesive, the wood after heat bonding is heated. There was a problem that it could not be removed from the board.
[0046]
In addition, in this invention, it can restrict to what is shown to the said specific Example, It can be set as the Example variously changed within the range of this invention according to the objective and the use.
[0047]
【The invention's effect】
Since the adhesive composition of the present invention exhibits high heat resistance and water resistance, it is particularly suitable for applications in which wood or the like is heated and bonded using a high frequency press or a hot press. Since this adhesive composition has a residual isocyanate group suppressed to a predetermined amount or less, the adhesive composition exhibits sufficient adhesiveness to wood and is not suitable for a high-frequency press pole plate or a hot press hot platen. Workability is good because there is no need to bond. And since the composition of this invention is a non-formaldehyde type adhesive composition, it is useful as an adhesive etc. for building materials manufacture.

Claims (3)

3 to 50 parts by weight of the polyisocyanate compound having two or more isocyanate groups in one molecule with respect to 100 parts by weight of the nonvolatile content of the polyvinyl acetate emulsion containing polyvinyl alcohol, and the amount of the remaining isocyanate groups is the above polyisocyanate. An adhesive composition obtained by reacting until the amount of isocyanate groups contained in the compound is 5 mol% or less. The adhesive composition according to claim 1, wherein the polyvinyl alcohol is acetoacetylated polyvinyl alcohol. 3 to 50 parts by weight of a polyisocyanate compound having two or more isocyanate groups in one molecule is added to 100 parts by weight of the nonvolatile content of the polyvinyl acetate emulsion containing polyvinyl alcohol, and the mixture is stirred at a temperature of 20 to 50 ° C. By making it, it is made to react until the quantity of a residual isocyanate group will be 5 mol% or less with respect to the quantity of the isocyanate group in the said polyisocyanate compound, The manufacturing method of the adhesive composition characterized by the above-mentioned.