Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-05-01
2002-07-09
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000, C428S412000
Reexamination Certificate
active
06417319
ABSTRACT:
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/JP99/07045 which has an international filing date of Dec. 15, 1999, which designated the United States of America and was not published in English.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flame retardant polycarbonate resin composition having an improved melt fluidity. More particularly, the present invention is concerned with a flame retardant polycarbonate resin composition having an improved melt fluidity, which comprises (A) an aromatic polycarbonate having a weight average molecular weight of from 12,000 to 25,000, (B) a styrene-acrylonitrile-butyl acrylate copolymer having a butyl acrylate unit content of from 1 to 30% by weight, (C) a complex rubber graft copolymer obtained by a process comprising graft-polymerizing at least one graft-polymerizable monomer onto a complex rubber comprising a polyorganosiloxane and a polyalkyl (meth)acrylate, (D) a phosphoric ester, and (E) a tetrafluoroethylene polymer. The resin composition of the present invention not only has excellent melt fluidity, but is also excellent in flame retardancy, impact resistance and modulus of elasticity. The resin composition of the present invention can be advantageously used for producing various types of shaped articles (including those for use in office automation machines and in electric and electronic equipment), and is especially advantageous for producing small-thickness shaped articles.
2. Prior Art
Polycarbonates have been widely used in various fields such as engineering plastics having excellent heat resistance, impact resistance and transparency. A resin composition comprising a polycarbonate, an ABS resin/and a phosphoric ester flame retardant (such a resin composition is hereinafter, frequently referred to as a “PC/ABS/phosphoric ester flame retardant composition”) is known as a flame retardant resin composition which has an improved melt fluidity, as compared to the polycarbonate per se which disadvantageously has poor melt fluidity. Hence, such a flame retardant resin composition has been widely used in application fields in which flame retardancy is important, such as in the fields of office automation machines, and electric and electronic equipment.
Recently, with office automation machines and household electric appliances, in order to meet the recent demand for reducing the size of the products (i.e., office automation machines and household electric appliances), there has been a tendency to increase the density of the arrangement of the parts in the products and this tendency requires that the resin housings for these products have a complicated inside configuration. Further, there has also been a tendency to reduce the amount of the resins used for producing the housings by reducing the wall thickness of the housings so as to meet the recent demand for reducing the production cost and the weight of the products. Therefore, as a material for the housings for office automation machines and household electric appliances, it has become necessary to use a PC/ABS/phosphoric ester flame retardant composition which not only has a high melt fluidity, but is also excellent in impact resistance and modulus of elasticity. The objective of increasing the melt fluidity of a PC/ABS/phosphoric ester flame retardant composition has been achieved by using a low molecular weight polycarbonate and a low molecular weight ABS resin. However, such a resin composition (containing a low-molecular weight polycarbonate and a low molecular weight ABS) necessarily has problems in that the impact resistance of a shaped article obtained from the resin composition becomes low, and that the flame retardancy of the resin composition becomes unsatisfactory so that a dripping of flaming particles is likely to occur when the resin composition is on fire. Therefore, it has been strongly desired to develop a flame retardant polycarbonate resin composition which not only has high melt fluidity, but is also excellent in impact resistance, flame retardancy, and modulus of elasticity.
In an attempt to obtain such a flame retardant polycarbonate resin composition, a method has been proposed in which a component which improves the impact resistance and the flame retardancy of the resin composition is used. For example, in Unexamined Japanese Patent Application Laid-Open Specification No. 6-240127, it is attempted to improve the flame retardancy of the PC/ABS/phosphoric ester flame retardant composition by adding a complex rubber graft copolymer, which is obtained by a process comprising graft-polymerizing a vinyl monomer onto a complex rubber comprising a polyorganosiloxane and a polyalkyl (meth)acrylate, to the resin composition. However, in this patent document, the flame retardancy of the resin composition is improved by the use of both the ABS resin (which is a graft copolymer obtained by graft-polymerizing an aromatic vinyl monomer and acrylonitrile monomer onto a rubbery polymer) and the above-mentioned complex rubber graft copolymer, so that the rubber content of the resin composition is high. Therefore, the resin composition of this patent document is disadvantageous not only in that the melt fluidity of the resin composition is unsatisfactory, but also in that the modulus of elasticity of the resin composition is low. In addition, since the resin composition of this patent document contains an ABS resin, the thermal stability of the resin composition is poor.
Unexamined Japanese Patent Application Laid-Open Specification No. 7-179673 discloses a PC/ABS/phosphoric ester flame retardant resin composition which contains an ABS resin having added thereto a styrene-acrylonitrile-butyl acrylate copolymer and a small amount of a complex rubber graft copolymer, which is obtained by a process comprising graft-polymerizing a vinyl monomer onto a complex rubber comprising a polyorganosiloxane and a polyalkyl (meth)acrylate, as an anti-dripping agent (i.e., an agent for preventing the occurrence of the dripping of flaming particles when the resin composition is on fire). However, the resin composition of this patent document has a disadvantageously low flame retardancy.
Unexamined Japanese Patent Application Laid-Open Specification No. 11-189713 discloses a flame retardant polycarbonate resin composition comprising a polycarbonate and a styrene-acrylonitrile-butyl acrylate copolymer having a high butyl acrylate unit content (butyl acrylate unit content: 50 to 90% by weight) (which is a so-called “butyl rubber”). However, this resin composition has a disadvantageously low melt fluidity and flame retardancy.
Further, it has also been attempted to produce a flame retardant polycarbonate resin composition having the above-mentioned desired properties simultaneously (excellent melt fluidity, flame retardancy, impact resistance and modulus of elasticity) without using a graft copolymer (such as an ABS resin) obtained by graft-polymerizing an aromatic vinyl monomer and an acrylonitrile monomer onto a rubbery polymer. For example, Unexamined Japanese Patent Application Laid-Open Specification No. 10-120893 proposes a flame retardant polycarbonate resin composition comprising a polycarbonate; an acrylonitrile-styrene copolymer (AS resin); a complex rubber graft copolymer obtained by graft-polymerizing a vinyl monomer onto a complex rubber comprising a polyorganosiloxane and a polyalkyl (meth)acrylate; and a phosphoric ester, wherein the complex rubber graft copolymer has a specific composition and a specific average particle diameter. The resin composition of this patent document is improved in its flame retardancy and impact resistance. However, as can be seen from the working examples of this patent document, a graft copolymer (such as an ABS resin) obtained by graft-polymerizing an aromatic vinyl monomer and an acrylonitrile monomer onto a rubbery polymer is not used, and hence the complex rubber graft copolymer (rubber component) needs to be used in a large amount so as to achieve a
Hachiya Hiroshi
Nanba Nobutsugu
Shibuya Kazuhiro
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Boykin Terressa M.
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