Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1994-09-22
1998-04-28
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524512, 524593, C08K 535
Patent
active
057445273
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a polyacetal resin having an excellent weather (light) resistance. More specifically, a UV absorber and two kinds of the specific hindered amine series light stabilizers are used in combination for a polyacetal resin to provide a polyacetal resin composition having excellent weather resistance and environment resistance, which suppresses resin deterioration and discoloration and gloss reduction caused by bleeding of additives in extended exposure to light to the utmost and maintains an initial molded product surface condition.
As known well, in recent years, a polyacetal resin is utilized in a very wide field as an engineering resin which excels in the physical characteristics such as a mechanical property and an electrical property and the chemical characteristics such as a chemical resistance and a heat resistance. However, expansion of the field in which the polyacetal resin is utilized is accompanied with further requirement of a specific property to the character thereof as a material in some cases. Further improvement in a weather (light) resistance is desired as one of such specific properties. That is, an environment in which the interior and exterior parts for automobiles and the parts for electric appliances are used under sun light, humidity (rain and bedewing) and other aerial contacting causes discoloration on a molded product surface and gloss reduction attributable to loss of a surface flatness and in addition, generates cracks on the parts surfaces to cause inconveniences such as damaging the appearances in some cases. In order to prevent these defects, it has so far been proposed to add various weather (light) stabilizers to the polyacetal resin to improve the weather (light) resistance of the polyacetal resin. In particular, it is known that combined use of various UV absorbers and hindered amine series light stabilizers give an effect to the weather (light) resistance.
However, in order to maintain the weather (light) resistance over a long period of time, a lot of the additives described above have to be added. However, addition in a lot of amounts brings about reduction of a mechanical property and provides a problem that in molding, adhesion and deposition (so-called mold deposit) on a die generate inferior dimension and poor appearance of a molded product. Further, in case of the polyacetal resin, since it is a high crystalline polymer, the additives are bleeded due to recrystallization caused by heat and a temperature difference (bedewing) under an exposing environment to cause discoloration and gloss reduction on a molded product surface and resultingly show the same action as resin deterioration. In particular, with respect to, for example, the automobile interior parts which are used under very high temperature or high humidity environment, the influences thereof are exerted to so large extent that addition of a lot of the additives causes damage of appearance on a molded product surface.
Accordingly, there has has been desired the development of a polyacetal resin material which does not have bleeding of the additives and maintains a molded product appearance over a long period of time while maintaining a weather (light) resistance.
The intensive researches made by the present inventors in order to develop a polyacetal resin composition which suppresses surface discoloration caused by bleeding of the additives to the utmost and maintains an initial molded product surface status over a long period of time while maintaining an excellent weather (light) resistance without sacrificing the inherent characteristics of the polyacetal resin have resulted in coming to complete the present invention.
That is, the present invention is a polyacetal resin composition (I) characterized by blending:
(A) 100 parts by weight of a polyacetal resin, with
(C) 0.01 to 2.0 parts by weight of a UV absorber and,
(D) 0.01 to 1 part by weight of a low-molecular hindered amine series substance (D-1) having a molecular weight of less than 700 and 0.01 to 4 parts by weight o
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patent: 4730015 (1988-03-01), Ikenaga et al.
patent: 5086095 (1992-02-01), Katsumata
patent: 5149723 (1992-09-01), Hayes
patent: 5171770 (1992-12-01), Kanagawa
patent: 5502093 (1996-03-01), Katsumata et al.
patent: 5523341 (1996-06-01), Kobayashi et al.
Katsumata Toru
Matsunaga Nobuyuki
Polyplastics Co. Ltd.
Sarofin N.
Schofer Joseph L.
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