Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1991-05-30
1993-04-06
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524503, 524507, C08K 334
Patent
active
052004589
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an adhesive composition, and more particularly to an adhesive of a vinyl acetate polymer emulsion suitable as an adhesive for wood.
BACKGROUND ART
Previously, various adhesives mainly composed of polymer emulsions have been proposed.
In Japanese Patent Publication No. 51-30576, there has been proposed "a water-resistant adhesive comprising an aqueous emulsion which contains polyvinyl alcohol and in which an isocyanate compound or an isocyanate polymer (hereinafter sometimes referred to as an isocyanate), and an extender and/or a filler reactive to said isocyanate are compounded".
However, when the isocyanate is thus directly compounded in the aqueous polymer emulsion containing water, the reaction proceeds with violence by the reaction of the isocyanate with water, which causes severe foaming and a significant increase in viscosity of the adhesive, a shorter available time, deteriorated coating workability and a remarkable reduction in adhesive strength. These cause serious obstacles on practical use.
Then, in order to remove such disadvantages, it has come to be carried out that the isocyanate once dissolved in a solvent is compounded in the aqueous polymer emulsion.
Namely, in Japanese Patent Publication No. 51-30577, there is proposed "a water-resistant adhesive comprising an aqueous emulsion which contains polyvinyl alcohol and in which an isocyanate compound or an isocyanate polymer dissolved in a solvent having little mutual solubility with water, but having mutual solubility with said isocyanate is dispersed". Further, in Japanese Patent Publication No. 58-29826, there is proposed "a water-resistant adhesive comprising an aqueous emulsion in which (1) polyvinyl alcohol, (2) a compound having an isocyanate group dissolved in a hydrophobic solvent and (3) a surface active agent and/or a formalin condensation resin are compounded".
As described above, these adhesives intend to prolong the available time by the use of the solvent.
However, there occurs the phenomenon that also these adhesives foam, increase in viscosity and thereby rapidly decrease in water resistance after an elapse of about 1 to 2 hours, when used at a temperature of 30.degree. to 40.degree. C. in summer. This brings about the situation that the temperature of a working room must be reduced to 25.degree. C. or lower, or that the adhesives must be used up within a short period of time such as 1 to 2 hours.
On the other hand, there is advanced an emulsion adhesive using acetoacetylated polyvinyl alcohol as a protective colloid.
The adhesive of a vinyl acetate polymer emulsion using the acetoacetylated polyvinyl alcohol as the protective colloid is superior in water resistance, when compared to the adhesive of the vinyl acetate polymer emulsion using the polyvinyl alcohol not acetoacetylated as the protective colloid as described above. This adhesive is therefore used as an adhesive for paper, furniture and thin veneer. However, in the water resistance of the adhesive concerned, the adhesive property is apt to be insufficient for fields in which the high water resistance is required, including the above-mentioned applications, for example, for applications such as laminated lumber, high-grade furniture, thick veneer and flash boards, and therefore a problem is practically encountered.
Under present conditions, it is intended to improve the water resistance of the emulsions concerned by compounding formalin resins such as urea-formalin resins and melamine-formalin resins in vinyl acetate polymer emulsions as means to solve this problem. However, these methods have the disadvantages that the available time is short and that formalin is released from furniture to produce a pollution problem.
On the other hand, in Japanese Patent Publication No. 59-1581, there is proposed an adhesive composition for wood comprising a vinyl acetate polymer emulsion in which the acetoacetylated polyvinyl alcohol concerned is used as the protective colloid and to which an isocyanate compound, an epoxy compoun
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Iwasaki Masaharu
Koda Katsuhiro
Morinaga Hiroyasu
Okajima Satoshi
Yonehara Takashi
Guarriello John J.
Michl Paul R.
Oshika Shinko Co. Ltd.
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