Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-29
2002-08-20
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S096000, C524S127000, C524S141000, C525S067000, C525S133000, C525S148000
Reexamination Certificate
active
06437029
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a flame retardant thermoplastic resin composition. More particularly, the present invention relates to a flame retardant thermoplastic resin composition that comprises a polycarbonate resin, a rubber modified styrene-grafted copolymer, a styrene-containing copolymer, a (meth)acrylic acid ester copolymer, a phosphoric acid ester as a flame retardant and a fluorinated polyolefin resin.
BACKGROUND OF THE INVENTION
Polycarbonate resin is excellent in transparency, mechanical strength and heat resistance, therefore, the resin is widely applied to electric or electronic goods, automobile parts, office supplies, etc. However, the polycaronate resin has poor processability and notched impact strength. In order to overcome the shortcomings, the polycarbonate resin is blended with other polymer resin(s). For example, a blend of a polycarbonate resin and a rubber modified styrene grafted polymer is a resin composition which has improved processability maintaining the good notched impact strength.
The polycarbonate resin compositions should further have good flame retardancy as well as high mechanical strength because the resin compositions are applied to electric or electronic goods, automobile parts, office supplies, etc. When such blends of polycarbonate resin and styrene-containing copolymer are retained at a high temperature during extrusion or injection, the domain size is getting larger. If the viscosity of the blend becomes lower, the domain size is easily getting larger. If the domain size is getting larger, the mechanical properties of a molded article are rapidly deteriorated.
To provide the polycarbonate resin with good flame retardancy, a halogen-containing flame retardant and/or an antimony-containing compound were used. U.S. Pat. Nos. 4,983,658 and 4,883,835 disclose resin compositions employing a halogen-containing compound as flame retardant. However, the disadvantages could be observed that the halogen-containing compound results in the corrosion of the mold itself by the hydrogen halide gases released during the molding process and is fatally harmful due to the toxic gases liberated in case of fire. Especially, since a polybromodiphenyl ether, mainly used for a halogen-containing flame retardant, can produce toxic gases such as dioxin or furan during combustion, flame retardants which are prepared without a halogen-containing compound have become a major concern in this field.
A general method is employ a phosphoric acid ester compound as flame retardant to provide the polycarbonate resin with flame retardancy without using a halogen-containing compound. However, the more phosphoric acid ester compound is used, the lower the heat resistance of the resin composition is getting and the more easily the coalescence of the domain resin occurs. The is large sized domain resin functions as a fuel source when combusting, resulting that the combustion time is lengthened not to give good flame retardancy. Further the resin composition containing a low molecular phosphoric acid ester has a poor weld-line strength.
U.S. Pat. No. 5,292,786 discloses a resin composition composed of a polycarbonate resin, an ABS resin, a phosphorous flame retardant and a polyalkylmethacrylate resin. However, if the polyalkylmethacrylate resin is used in excess of a certain amount, the polyalkylmethacrylate resin is depolymerized and results in poor heat resistance, appearance and flame retardancy.
The present inventors have developed a flame retardant thermoplastic resin composition that comprises a polycarbonate resin, a rubber modified styrene-grafted copolymer, a styrene-containing copolymer, a (meth)acrylic acid ester copolymer, a phosphoric acid ester as a flame retardant and a fluorinated polyolefin resin, which does not show coalescence of the domain resin that might be caused by the low viscosity at a high temperature, lowering of flame retardancy, weld-line strength and mechanical properties such as impact strength, and which has a good balance of physical properties such as impact strength, heat resistance, heat stability, processability and appearance.
OBJECTS OF THE INVENTION
A feature of the present invention is the provision of a flame retardant thermoplastic resin composition that does not show coalescence of the domain resin that might be caused by the low viscosity at a high temperature during extrusion or injection.
Another feature of the present invention is the provision of a flame retardant thermoplastic resin composition with good flame retardancy.
A further feature of the present invention is the provision of a flame retardant thermoplastic resin composition with good mechanical properties such as impact strength at a high temperature during extrusion or injection.
A further feature of the present invention is the provision of a flame retardant thermoplastic resin composition with good weld-line strength.
A further feature of the present invention is the provision of a flame retardant thermoplastic resin composition with a good balance of physical properties such as impact strength, heat resistance, heat stability, processability and appearance.
Other objects and advantages of this invention will be apparent from the ensuing disclosure and appended claims.
SUMMARY OF THE INVENTION
A flame retardant thermoplastic resin composition according to the present invention comprises (A) about 45 to 95 parts by weight of a polycarbonate resin, (B) about 1 to 50 parts by weight of a rubber modified styrene-grafted copolymer prepared by graft-polymerizing (b
1
) about 5 to 95 parts by weight of a monomer mixture consisting of about 50 to 95% by weight of styrene, &agr;-methylstyrene, halogen- or alkyl-substituted styrene or a mixture thereof and about 5 to 50% by weight of acrylonitrile, methacrylonitrile, maleic acid anhydride, C
1-4
alkyl- or phenyl N-substituted maleimide or a mixture thereof onto (b
2
) about 5 to 95 parts by weight of a rubber polymer selected from the group consisting of butadiene rubber, acryl rubber, ethylene-propylene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, isoprene rubber, copolymer of ethylene-propylene-diene (EPDM), polyorganosiloxane-polyalkyl(meth)acrylate rubber or a mixture thereof, (C) about 0.5 to 50 parts by weight of a styrene-containing copolymer polymerized with (c
1
) about 50 to 95% by weight of styrene, &agr;-methylstyrene, halogen- or alkyl-substituted styrene or a mixture thereof and (c
2
) about 5 to 50% by weight of acrylonitrile, methacrylonitrile, maleic acid anhydride, C
1-4
alkyl- or phenyl N-substituted maleimide or a mixture thereof, (D) about 0.5 to 50 parts by weight of a (meth)acrylic acid ester copolymer polymerized with (d
1
) about 44 to 90% by weight of a C
1-8
methacrylic acid alkyl ester, a C
1-8
acrylic acid alkyl ester, or a mixture thereof, (d
2
) about 5 to 55% by weight of styrene, &agr;-methylstyrene, halogen- or alkyl-substituted styrene or a mixture thereof and (d
3
) about 1 to 20% by weight of acrylonitrile, methacrylonitrile, or a mixture thereof, (E) about 1 to 30 parts by weight of a phosphoric acid ester as a flame retardant, and (F) about 0.05 to 5.0 parts by weight of a fluorinated polyolefin resin with average particle size of about 0.05 to 1000 &mgr;m and density of about 1.2 to 2.3 g/cm
3
as per 100 parts by weight of (A)+(B)+(C)+(D).
DETAILED DESCRIPTION OF THE INVENTION
A flame retardant thermoplastic resin composition according to the present invention comprises (A) about 45 to 95 parts by weight of a polycarbonate resin, (B) about 1 to 50 parts by weight of a rubber modified styrene-grafted copolymer, (C) about 0.5 to 50 parts by weight of a styrene-containing copolymer, (D) about 0.5 to 50 parts by weight of a (meth)acrylic acid ester copolymer, (E) about 1 to 30 parts by weight of a phosphoric acid ester as a flame retardant, and (F) about 0.05 to 5.0 parts by eight of a fluorinated polyolefin resin. Each component will be described in detail as follow:
(A) Polycarbonate Resin
The polycarbonate resin is p
Lim Jong-Cheol
Seo Kyung-Hoon
Yang Sam-Joo
Buttner David J.
Cheil Industries Inc.
Tungol Maria Parrish
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