Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-09-29
2003-07-15
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S125000, C524S127000, C524S141000, C524S143000, C524S147000, C524S148000, C524S149000, C525S067000, C525S071000, C525S080000, C525S085000
Reexamination Certificate
active
06593404
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to flame-retardant thermoplastic resin compositions. More particularly, the present invention relates to the thermoplastic resin compositions which comprise a polycarbonate, a styrene containing graft copolymer, a styrene containing copolymer, a mixture of alkyl substituted, preferably t-butyl substituted, monophosphate esters, a phosphate ester compound, and a fluorinated polyolefin, whose stress cracking resistance and flame retardancy are improved.
2. Discussion of Related Art
Polycarbonate resin compositions are widely used for parts of electrical products and automotive-components because they have a good combination of transparency, high impact strength, and heat resistance. But, polycarbonate resin compositions have poor ocessability during molding process, so polycarbonate resin compositions are usually blended with other resins for improving these properties. For example, a molding composition comprising a polycarbonate resin and a styrenic resin has good processability as well as high notched impact strength.
Furthermore, the polycarbonate molding composition used for parts of home and office appliances should be flame resistant to prevent fires.
To confer flame retardancy to thermoplastic molding compositions, halogen and/or antimony containing-compounds have been incorporated. In U.S. Pat. Nos. 4,983,658 and 4,883,835, a halogen-containing compound is used as a flame retardant. The halogen-containing compound, however, results in corrosion of the mold itself by the hydrogen halide gases released during a molding process and is fatally harmful due to the toxic gases liberated in the case of fire.
As a method for conferring flame-retardancy without using a halogen-based flame retardant, a method using a phosphate ester-based flame retardant is commonly used. The use of halogen-free phosphate ester compound as flame retardants avoids the problems caused by the corrosive and harmful by-products of halogen-based flame retardants. However, the phosphate ester-based flame retardants have tendency to cause deterioration of heat resistance, occurring of stress crack by volatilization of a flame retardant, and juicing during a molding process.
As a method for overcoming these problems, Japanese Patent Publication No. (Sho)62-25706 describes the use of a mixture of an arylphosphate ester prepared by reacting a phosphorus oxychloride with a divalent phenol and a monovalent phenol, and an oligomeric phosphate ester as a flame retardant. However, in this method, the flame retardant prepared by such method results in the corrosion of the mold itself by a phosphorus oxychloride and a residual metal ion derived from a metal salt used as a catalyst such as aluminum chlorides, magnesium chlorides, and so on.
U.S. Pat. Nos. 5,061,745 and 5,030,675 describe polymer blends prepared from an aromatic polycarbonate, an ABS graft copolymer, a styrene containing copolymer, a monophosphate ester such as triphenylphosphate(TPP) as flame retardants, and a fluorinated polyolefin. However, the low stress cracking resistance of these molding compositions often restricts the application of non-halogen-PC/ABS in the field of making parts of electronic and electric products, especially thin-walled parts. And heat resistance of these blends also deteriorates substantially.
In order to reduce the occurrence of stress cracking and deterioration of heat resistance by the use of a monophosphate ester, U.S. Pat. No. 5,204,394 describes a polymer mixture comprising an aromatic polycarbonate, a styrene containing copolymer and/or a styrene containing graft copolymer and an oligomeric phosphate as a flame retardant. In this polymer mixture, it is possible to obtain a V-O rating according to UL-94 using by the oligomeric phosphate whose condensation degree is about 1.4. However, if the condensation degree of the oligomeric phosphates exceed 2.8, the flame retardancy of this polymer mixture decreases rapidly to HE rating and stress cracking resistance of the mixture also decreases.
U.S. Pat. No. 5,672,645 describes flame retardant polycarbonate/ABS molding compounds whose stress cracking resistance is improved by a combination of additives comprising a monomeric phosphorus compound and an oligomeric phosphorus compound as compared with the molding compounds comprising only a monophosphorus compound or an oligomeric phosphorus compound, respectively. However, the heat resistance and stress cracking resistance of these compounds are not sufficient, so an improvement is required.
U.S. Pat. No. 5,206,404 describes compositions of alkylated triphenyl phosphate esters comprising 1 to 20% by weight trialkylphenyl phosphate, 10 to 50% by, weight dialkylphenyl monophenyl phosphate, 15 to 60% by weight monoalkylphenyl diphenyl phosphate and less than 2% by weight triphenyl phosphate. However, this publication contains no indication of any improvement in stress cracking resistance and flame retardancy of thermoplastic resin compositions by adding these mixtures of triaryl phosphate esters.
The present invention is based on the discovery that flame retardant thermoplastic resin compositions with excellent stress cracking resistance and heat-resistance may be produced by adding flame retardants comprising a phosphate ester and a mixture of alkyl substituted, preferably t-butyl substituted, monophosphate esters of U.S. Pat. No. 5,206,404. The flame retardant thermoplastic resin compositions of this invention have good stress cracking resistance and elevated heat resistancy as compared with the molding compound of U.S. Pat. No. 5,672,645 comprising a monophosphorus compound and an oligomeric phosphorus compound as a flame retardant.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a flame-retardant thermoplastic resin composition with excellent stress cracking resistance and improved heat resistance which comprises a polycarbonate, a styrene containing graft copolymer, a styrene containing copolymer, a mixture of alkyl substituted, preferably t-butyl substituted, monophosphate esters, a phosphate ester, and a fluorinated polyolefin.
SUMMARY OF THE INVENTION
The present invention relates to thermoplastic resin compositions comprising:
(A) 40 to 95 parts by weight of a halogen-free, thermoplastic polycarbonate;
(B) 5 to 50 parts by weight of a styrene containing graft copolymer prepared by grafting (B-1) onto (B-2)
(B-1) 5 to 95% by weight, based on (B), of a mixture of
(B-1.1) 50 to 100% by weight of styrene, &agr;-methyl styrene, nucleus-substituted styrene, methyl methacrylate or a mixture thereof, and
(B-1.2) 50 to 0% by weight of acrylonitrile, methacrylonitrile, C
1
-C
8
alkyl methacrylate, C
1
-C
8
alkyl acrylate, maleic anhydride, N-substituted maleimide, or a mixture thereof
(B.2) 95 to 5% by weight, based on (B), of a rubber with a glass transition temperature(Tg) of below −10° C. and selected from the group consisting of butadiene rubbers, acryl rubbers, ethylene/propylene rubbers, styrene/butadiene rubbers, acrylonitrile/butadiene rubbers, butadiene/styrene rubbers, polyisoprene, EPDM (ethylene-propylene-diene terpolyrner) rubbers, polyorganosyloxane, and mixtures thereof;
(C) 0 to 30 parts by weight of a styrene containing copolymer prepared from
(C-1) 50 to 95% by weight of styrene, &agr;-methyl styrene, nucleus-substituted styrene, methyl methacrylate or a mixture thereof, and
(C-2) 50 to 5% by weight of acrylonitrile, C
1
-C
8
alkyl methacrylate, C
1
-C
8
alkyl acrylate, or a mixture thereof,
(D) 5 to 20 parts by weight, based on 100 parts by weight of (A)+(B)+(C), of a mixture comprising
(D-1) 100 to 5% by weight of admixture of alkyl substituted, monophosphate esters of the formula(I)
in which,
R is an alkyl group selected from t-butyl, isopropyl, isobutyl, isoamyl, t-amyl and N is 0 or an integer from 1 to 3, and
(D-2) 0 to 95% by weight of phosphate esters of the formula (II)
in which,
R
1
, R
2
, R
4
, and R
5
are independently cresyl, phenyl, xylenyl, propylphenyl
Chang Young Kil
Shin Jun Hyuk
Yang Sam Joo
Cheil Industries Inc.
Niland Patrick D.
Tungol Maria Parrish
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