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
1996-12-12
2000-09-19
Cain, Edward J.
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...
C08K 510
Patent
active
061213551
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a water-dispersion type pressure-sensitive adhesive composition which is excellent in terms of balance between water resistance and adhesive strength, balance between moisture resistance and adhesive strength, balance between cohesive strength and adhesive strength, and adhesiveness to a substrate. It also relates to a method of producing the same, and to a pressure-sensitive adhesive product employing the same.
BACKGROUND OF THE INVENTION
In consideration of various factors such as environmental protection, safety in the working environment, resource saving, cost etc. there has been a large trend in recent years away from supplying adhesives of solution type (using an organic solvent as solvent medium) and more to supplying adhesives in non-solvent type (which do not use organic solvents). Amongst these non-solvent type, the use of water-dispersion type, i.e. so-called emulsion type pressure-sensitive adhesives has been favoured in consideration of their general purposeness and workability.
However, with these water-dispersion type pressure-sensitive adhesives, it is necessary to have a dispersant such as an emulsifying agent in order to disperse the pressure-sensitive adhesive polymer into the aqueous medium, and since such dispersants are hydrophilic materials, there has been the major problem that the water resistance of such adhesives is poor compared to solvent-type adhesives. In addition to the reduction in water resistance, the presence of the dispersant also has a bad affect on the adhesive strength itself, balance between cohesion and adhesion, adhesiveness to a substrate, transparency etc. and at present there has not been developed a water-dispersion type pressure-sensitive adhesive which displays levels of water resistance and adhesive properties on a par with solvent types.
In an attempt to resolve the above-mentioned problems with water-dispersion type pressure-sensitive adhesives, there have been reported methods of improving the dispersion itself or adopting cross-linking means etc. As one such cross-linking means, there is known a method involving forming the dispersion by the copolymerization of monomers having functional groups when producing the pressure-sensitive adhesive polymer, and then adding a cross-linking agent which reacts with these functional groups. However, if the cross-linking is carried out to such an extent that a sufficient degree of water resistance can be realized, there then arises the problem that the flowability, which is necessary for wetting the adherend, is reduced with a consequent lowering in adhesive strength.
On the other hand, in Japanese Patent Application Publication No. H-1-221402, the applicant of this invention discloses that a water-dispersion type pressure-sensitive adhesive employing as an emulsifying agent a polymer having a specific structure is excellent in terms of several physical properties such as adhesive strength, water resistance, moisture resistance etc., and that by using a monomer having functional groups which can react with the carboxyl groups of the emulsifying agent as the monomer for the pressure-sensitive adhesive polymer, the emulsifying agent and the pressure-sensitive adhesive polymer react with each other after the formation of a layer of the pressure-sensitive adhesive i.e. after the adhesive is applied and dried to create a film, with a resulting further increase in the water resistance. However, when compared with the superior water resistance displayed by solvent-type pressure-sensitive adhesives, the pressure-sensitive adhesives disclosed in Japanese Patent Application Publication No. H-1-221402 cannot be described as satisfactory. The inventors of the present invention made continued studies with a view to increasing the water resistance, and found that it is not desirable to just simply increase the amount of functional groups in the pressure-sensitive adhesive polymer, since the result is that the adhesive strength is reduced thereby causing problems with res
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Banba Akikazu
Tanaka Yasumasa
Tsunemine Naoki
Cain Edward J.
Nippon Shokubai Co. , Ltd.
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