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
1996-10-22
1998-08-25
Short, Patricia A.
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...
524513, 524514, 524517, 524521, 524522, 524523, C08L 3306, C08L 3102, C08L 3700
Patent
active
057984077
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hydrophilic resin composition in which a water-absorptive resin is uniformly and finely dispersed in a specific thermoplastic polymer, so that the water-absorptive resin is not separated from a molded product of the composition even after the resin has absorbed water and the molded product thus can show good retention of shape, and to a process for producing the same. The present invention also relates to a hydrophilic resin composition in which an additive is also uniformly dispersed in the above thermoplastic polymer and mutually acts with the water-absorptive resin, so that the composition is highly retentive of the effect of the additive, and to a process for producing the same.
BACKGROUND ART
Polyolefins, polyamides, polyesters and the like are excellent in moldability, mechanical strength, etc., and have been widely used as raw materials for packaging materials, containers, synthetic paper, fibers, etc. However, they are not so highly reactive that they are poor in printability, adhesive properties, and hydrophilic nature; or even if they are hydrophilic, the hydrophilic nature has not yet reached to a level high enough for such applications as fibers and the like. For this and other reasons, these resins have been hitherto limited in their use.
In order to improve the hydrophilic nature, there has been proposed a resin composition prepared by incorporating a water-absorptive resin into a polyolefin, polyamide, polyester resin or the like. However, it is difficult to uniformly and finely disperse a water-absorptive resin in such a resin. In addition, the diameters of dispersed particles of the water-absorptive resin are as large as 20 to 60 .mu.m, and the particles cannot be uniformly dispersed. Therefore, the water-absorptive resin is separated from a molded product of the composition after it has absorbed water, and the molded product thus shows poor retention of shape and has unsatisfactory mechanical strength.
Some methods have been proposed as methods for uniformly and finely dispersing a water-absorptive resin.
Namely, for instance, a method in which fine powder obtained by polymerization for producing a crosslinked product of vinyl acetate/methyl acrylate copolymer, or fine powder obtained by mechanically grinding this crosslinked product by an apparatus such as a jet mill is incorporated, as a water-absorptive resin, into a polyolefin and the resulting mixture is subjected to molding (Japanese Laid-Open Patent Publication No. 33032/1981). However, although the level of hydrophilic nature can be slightly improved by this method, it is still unsatisfactory because the diameters of the dispersed particles of the water-absorptive resin are still large. Moreover, this method requires a step of grinding the water-absorptive resin, so that it is also disadvantageous from the viewpoint of facilities.
There has also been proposed a method in which a water-absorptive resin containing carboxylate group and a polyolefin containing glycidyl group are melt kneaded with each other (Japanese Laid-Open Patent Publications Nos. 266427/1986 and 31733/1988). However, although the level of hydrophilic nature can be improved by this method, there cannot be obtained a composition uniformly imparted with hydrophilic nature, capable of showing satisfactory retention of shape and mechanical strength even after it has absorbed water. This method has thus been needed to be improved.
Further, there has also been proposed a sheet or film in which a polyamide or polyester is a continuous phase, and a water-absorptive resin existing as dispersed particles with a diameter of 10 to 100 .mu.m is a dispersed phase (Japanese Laid-Open Patent Publication No. 62529/1986). However, although this one has an improved level of hydrophilic nature, it cannot show satisfactory retention of shape after it has absorbed water because the diameters of the dispersed particles of the water-absorptive resin are still large.
In addition, there has been proposed a resin composition which is o
Kaito Hiroyoshi
Wakayama Akeharu
Yada Shuhei
Yano Kazunori
Mitsubishi Chemical Corporation
Short Patricia A.
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