Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-03-03
1998-12-08
Teskin, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 80, 525 86, 525235, 525239, 525310, 525316, 528502R, C08L 5104
Patent
active
058470506
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for particles agglomeration and enlargement of a diene type polymer rubber latex; a graft copolymer obtained from the thus obtained particles-enlarged diene type polymer rubber latex; and a thermoplastic resin composition comprising such a graft copolymer.
BACKGROUND ART
Thermoplastic resins are in wide use in various fields for their excellent mechanical and chemical properties but generally have a drawback of low impact resistance. In order to alleviate the drawback, there were proposed methods for imparting impact resistance to a thermoplastic resin by adding thereto an impact resistance-improving resin such as an ABS resin which is a hard resin reinforced with an elastic body, an MBS resin and a graft polymer of a monomer (e.g. methyl methacrylate, styrene, acrylonitrile, etc.) on a poly(alkyl acrylate) rubber polymer (JP-A-57-102940, JP-A-60-235854 and JP-A-58-152039).
Graft copolymers of particles-enlarged rubber have been used for the impact resistance improvement of thermoplastic resin. With respect to the technique for obtaining this particles-enlarged rubber, there have been reported enlargement techniques using an electrolyte, a high-molecular organic acid latex, an acid or the like. A number of researches have been made particularly on an enlargement technique using an acid, and a method is well known which comprises adding an acid to a rubbery polymer latex to reduce the pH of the latex and agglomerate and enlarge the latex particles and then adding a basic substance to make the pH of the system alkaline and stabilize the latex.
In the above method, it is an important task to, at the time of particles agglomeration and enlargement, keep the stability of the latex and obtain a particles-enlarged latex without generating rubber coagulum.
As methods improved in the above important task, there were proposed a method which comprises adding an acid to a rubbery polymer latex, effecting particles enlargement at a pH of below 7.0, and then adding thereto a basic substance, these steps being conducted at a temperature of 40.degree. C. or higher at an agitation intensity of not more than half that used during graft polymerization) (JP-B-55-19246); and a method which comprises adding an acid to a rubbery polymer latex containing a fatty acid soap and effecting particles enlargement at a pH of 4.0 or less, wherein the acid is added in a shower or fog state (JP-B-2-9601).
In JP-B-55-19246, while there is a description of the agitation intensity not more than half that used during graft polymerization, there is no description of specifying the level of the agitation intensity used during the graft polymerization; therefore, the agitation intensity to be employed during the particles enlargement is unknown. Further, while the agitation intensity is largely dependent upon the shape of the agitating element used, no description is made on the shape of agitating element even in Examples. Furthermore, in Examples, the solid content of the latex after particles enlargement is 25% by weight or less in all cases; such a method shown in Examples is applicable only to a latex of low solid content in which rubber coagulum are unlikely to appear. Therefore, the method described in the literature is unable to show high productivity.
The method described in JP-B-2-9601 is as well applicable only to a latex of low solid content (the solid contents of particles-enlarged latexes shown in Examples being 21-23% by weight). Therefore, this method is unable, either, to show high productivity. Further in this method, since the mixing of acid and latex is conducted by molecular diffusion without agitation, uniform agglomeration is unlikely to take place; even if any uniform agglomeration occurs at all, a considerably long time is required until it is over, making productivity low.
For obtaining a particles-enlarged latex of high solid content, there were proposed, for example, a method wherein, in the step of adding an acid to a polymer latex to give rise to agglomerat
Nakata Akira
Osuka Masahiro
Shishido Koichi
Toritani Akihiro
Mitsubishi Rayon Co. Ltd.
Teskin Fred
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