GB2330583A

GB2330583A - Flame-retardant thermoplastic resin compositions

Info

Publication number: GB2330583A
Application number: GB9817271A
Authority: GB
Inventors: Jun Hyuk Shin; Sam-Joo Yang; Young Kil Chang
Original assignee: Cheil Industries Inc
Current assignee: Cheil Industries Inc
Priority date: 1997-10-23
Filing date: 1998-08-07
Publication date: 1999-04-28
Anticipated expiration: 2018-08-07
Also published as: GB2330583B; JPH11172094A; GB9817271D0; DE19842713B4; JP3936806B2; KR19990033149A; KR100360714B1; DE19842713B8; DE19842713A1

Abstract

Flame-retardant thermoplastic resin compositions comprise a polycarbonate, a styrene-containing graft copolymer and a mixture of alkyl-substituted monophosphate esters of 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. The composition may also contain a phosphate ester of formula (II): in which: R 1 . R 2 , R 4 , and R 5 are independently cresyl, phenyl, xylenyl, propylphenyl, butylphenyl, or brominated or chlorinated derivatives thereof, R 3 is an arylene group, and M is 0 to 5, a styrene-containing copolymer and a fluorinated polyolefin.

Description

2330583 1 THERMOPLASTIC RESrN COMPOSITION The present invention relates to

flame-retardant thermoplastic resin compositions. More particularly, the present invention relates to the thermoplasfic resin compositions which comprise a polycarbonate, a styrenecontaining 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.

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. However, polycarbonate resin compositions have poor processability 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.

2 To confer flanie retardancy to thernioplastle iiioldifill colilpositioils, lialo-en C) and/or aminiony cojitaiiiiii(y-cotiipoLinds have been incorporated. In U. S. Patent Nos.

4,983,658 and 4,883,835, a halogen-contalnirig compound is uscd as a flarne 1 C> retardant. The halo-en-containing compound, however, results in corrosion of the 0 i-nold itself by the hydrogen halide gases released duning a rnolding process and is 0 c Z1 fatally lianiiftil 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 corrimonly used. The use of halogen-free phosphate ester compoiind as flame retardants avoids the problems caused by the corrosive and harmflil by-products of halogen-based flame retardants. However, the phosphate ester-based flame retardants have tendency to cause deterioration of heat resistance, occtming 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)62-2570.6 describes the use of a mixt-ure of an arylphosphate ester prepared by reacting a pliosphonis oxychlonide 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 rnethod results in the corrosion of the mold itself by a phosphonis oxychloride and a residual rnetal ion derived frorn a metal salt used as a catalyst such as altiminum chlonides, i-na,,,,,nesitim chlorides, and so on.

U.S. Patent Nos. 5,061,745 and 5,030,675 desenibe polymer blends prepared from an aromatic polycarbonate, an ABS graft copolymer, a styrene containing copolymer, a rnonophosphate ester such as triplienylpliospliate(TPP) as flarrie retardants, and a fluorinated polyolefin.

However, the low stress crackinly resistance of these inoldiii,, compositions often restricts the application of 11011- 0 1 1 1 1 1 i 3 lialogcii-PC/ABS in the field of making parts of electronic and electric products, especially thin-walled parts. And licat resistance of these blends also deteriorates substantially.

In order to reduce the occuri-ence of stress cracking and deterioration of heat resistaiwe by the use of a monophospliate ester, U.S. Patent No. 5,204,394 describes a polymer mixture comprising an aromatic polycarbonate, a styrenecontainim, copolymer and/or a styrene-containing graft copolymer and an ollgomeric phosphate as a flame retardant. In this polymer mixture, it is possible to obtain a V-0 ratinc, according to UL94 using by the ollgomeric phosphate whose condensation degree is about 1. 4. However, if die 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. Patent No. 5,672,645 describes flame retardant polycarbonate/ABS rnolduip compounds whose stress crackino, resistance is improved by a combination of additives comprising a monomeric phosphorus compound and an oligomedc phosphorus compound as compared with the molding compounds comprising only a monophosphonis compound or an oligomenic phosphorus compound, respectively. Ho\..evcr, the heat resistance and stress crackim, resistance of these compounds are not stifficient, so an improvement is required.

U.S. Patent No. 5,206,404 describes compositions of alkylated triplienyl pliospliatc esters compfising 1 to 20% by weight trialkylphenyl phosphate, 10 to 50% by weight dialkylphenyl rnonoplienyl phosphate, 15 to 60% by weight monoalkylphenyl diphenyl phosphate and less than 2% by weight tniplienyl pliospliale. However, this publication contains no indication of any improvement in stress. cracking resistance and flame retardancy of thermoplastic resin 4 compositions by adding these rnixtures of triat-yl phosphate esters.

The present invention is based on the discovery that flame retardant theriTioplastic resin compositions with excellent stress cracking resistance and licatresistance may be produced by adding flame retardants compnsing a phosphate ester and a inixture of alkyl substituted, preferably t-butyl substituted, monophospliate esters of U.S. Patent 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. Patent No. 5,672, 645 comprising a monophosphorus compound and an oligomeric phosphonis compotmd as a flame retardant.

An object of the present invention is to provide a flame-retardant thermoplastic resin composition with excellent stress cracking resistance and unproved heat resistance which comprises a polycarbonate, a styrenecontaining graft copolymer, a styrene containing copolymer, a mixture of alkyl substituted, preferably t-butyl substituted, monophosphate esters, a phosphate ester, and a fluorinated polyolefin.

The present invention relates to thermoplastic resin compositions comprising:

(A) 40 to 95 parts by weight of a lialogen-ftee, thermoplastic polycarbonate; (B) 5 to 50 parts by weight of a styrene-containing graft copolymer prepared by graffing (BA) onto (B-2) (B-]) 5 to 95% by weIght, based oil (B), of a mixture of,' 0 (13-1.1) 50 to 100% by weight of styreiie, a -i-netliyl styrene, ringstibstlitited styrene, iiictliyl rnetliacrylate or a rnixture thereof, aiid (13-1.2) 50 to 0% by weight of acrylonitrile, nietliacrylonitrile, Ci-C8 alkyl iiietli,nct,,late, C,-Cm alkyl aerylate, maleic anhydride, N- substituted rnaleimide, or a mixture thereof; (B.2) 95 to 5% by weight, based on (B), of a rubber with a glass transition tempei,ittire(Tg) of below -ITC and selected from the group consisting of butadiene nibbers, acryl nibbers, ethyl enelpropylen e rubbers, styrenebutadiene rubbers, acryloiiltrile/butadiene rubbers, butadienelstyrene rubbers, polyisoprene, EPDM (ethylene-propylene-diene terpolymer) rubbers, polyorganosiloxane, and mixtures thereof, (C) 0 to 30 parts by weight of a styrene-containing copolymer prepared from,., (CA) 50 to 95% by weight of styTene, a -methyl styTene, ring- substituted sty,Tciie, methyl methacrylate or a mixture thereof, and (C-2) 50 to 5% by weight of acrylonitrile, C,-C& alkyl methaerylate, Ci- CS 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 compnsing (D- 1) 100 to 5% by weight of a mixt-tire of alkyl substituted, monophosphate esters of the formula (I):

6 0 11 0 P 0- on )N)3-N in which:

R is an alkyl group selected from t-butyl, isopropyl, isobuty], isoamyl and 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):

0 0 11 11 R,-O-P-O-R3-0-P-01 1 OR2 UR4 J in which:

-Rs m (11) Ri, R2, R4, and R5 are independently cresyl, phenyl, xylenyl, propylphenyl, btitylplienyl, or brominated or chlorinated derivatives thereof, R3 is an arylene group, and Mis Oto5; and (E) 0 to 2 parts by weight, based on 100 parts by weight of (A)+(B)+(C), of a fluorinated polyolefin polymer.

In addition to the components mentioned liereinbefore, the thermoplastic resill compositions according to the present invention inay ffirther contain one or rnore conventional additives. For example, inorganic fillers stich as rnica, talc, zeolite, and inonti-norillonite, pigments, dyes, glass fibers, carbon fibers, tlierinal stabilizers, 7 light stabilizers, antioxidants, plasticizers, and rnold release agents rnay be added in flabricalions as needed.

The thermoplastic resin compositions according to the invention comprise a polycarbonate, a styrene containing graft copolymer, a styi-ene containing copolymer, a mixture of alkyl substituted monophosphate esters, a phosphate ester COMPOLMd. and a fluorinated polyolefin polymer.

Hereinafter the detailed description regarding the respective components is provided.

(A) Thermoplastic, Halogen-free Polycarbonates Suitable component (A) thermoplastic halogen-free polycarbonates according to the invention are those generally prepared by reacting with a phosgene or a carbonic diester, bisphenols of the following formula (III):

HO A--- OH (111) in which:

A is a sin-le bond, Ci-C5 alkylene, C2-Cs alkylidene, CS-C6 cycloalkylidene, -S- or -SO2-.

Suitable diplienols of the fon-nula (111) are, for example, 4,4'-dihydroxybiphenyl, 2,2-bis-(4-hydroxyphenyl) propane, 13-bis-(4liydroxyplieiiyl) cyclohexane, and the like. The jilost pi-cfet-red and widely, used thermoplastic, lialogen-fi-ce polycarbonates are aromatic polycai.boii-,ites synthesized frorn 2,2-bis(4-Iiydroxy-plieilyl)propaiie, called "Bispliellol A". - - The production of the polycarbonates of component (A) suitable for use in accordance with the invention is known ftom literature, for example U.S. Patent No. 3,169,12 1, and may be carried out in a known manner from bisphenols with phosgene using the phase interface process or with phosgene using the homogeneous phase process.

Preferred polycarbonates according to the present invention have average molecular weights (M,,, as measured for example by ultracentrifugation or by scattered light measurement) of from 10,000 to 500,000 and preferably from 18,000 to 300,000. Polycarbonates with a certain molecular weight may be obtained by using a monophenol such as phenol, paracresol, or paraisooctylphenol as chain terminator. The polycarbonates suitable for use in accordance with the invention include both homopolycarbonates and copolycarbonates.

In the present invention, the polycarbonate resins(A) comprise a base resin along with styrene containing graft copolymers and styrene containing copolymers.

(B) Styrene containing graft Copolymer 0 Styrene containing graft copolymer which may be used accord] rig to the 1 (B-1) onto (B-2):

invention are those prepared by grafting constituent (BA) 5 to 95% by weight, based on (B), of a mixture of:

(B-1.1) 50 to 100% by weight of styrene, a-i-netliyl styrene, ringsubstituted styrene, i-netliyl inethacrylate or a inixture thereof, and (13-1.2) 50 to 0% by weight ofacrylonitrile, inetliaci-yloiiitrile, C,-Cm alkyl 9 i-nctll,lci.ylate, G-C8 alkyl acrylate, rnaleic anhydride, N'substitlited maleimide a rnixtu - re thereof, (B.2) 95 to 5% by weight, based on (B), of a rubber having a glass transition tei-npei.ittire(Tg) of below - 10 C and selected from the group consisting of butadien nibbers, acryl rubbers, ethylene/propylene rubbers, styrenelbutadiene rubbers, aeryloiiltrile,Ititadiene rubbers, butadiene/styrene rubbers, polyisoprene, EPDM rubbers, polyorganosiloxane and imixt-ures thereof. Particularly preferred styrene containing graft copolymer(B) is the so-called ABS resin.

The preferred average particle size of the rubber is from 0.05 to 41M in order to improve the impact strength and the appearance of the moldings.

The styrene containing graft copolymers of component (B) may be prepared according to conventional methods of preparing copolymer, in particular, emulsion, suspension, solution or bulk polymerization. Preferred method for preparing the graft copolymer (B) is emulsion or bulk process.

or e (C) Styrene containing copolymers The styi-ene containing copolymers of component (C) to be used in accordance with the invention are those prepared from: (1) 50 to 95% by weight of styrene, a methyl styrene, ringsubstituted styrene, methyl methacrylate or a mixt-ure thereof(C-1), and (2) 50 to 5% by weight of acrylonitrile, Ci-C8 alkyl methacrylate, Ci-C8 alkyl acrylate, or a mixture thereof(C-2).

A specific example of the styrene containing copolymer is SAN(styrene/acrylonitrile) resin, which is prepared by copolyrnerizing styrene and acryloiiitrile. In the copolyrnerization, 60 to 90% by weight of styrene and 40 to 10% by weight of acrylonitrile are used.

The styrene containing copolymer of component (C) may be prepared by conventional copolymerizatioii processes, in particular, by stispension or btilk polymerization.

Q-Q A i-nixttire of alkyl siibtittited l-nQnQpliQsplinte esters The thermoplastic resin compositions according to the present invention contain as a flame retardant a mixture of alkyl substituted monophosphate esters(D-1), and a phosphate ester compound(D-2). Component (D-1) is a mixture of alkyl substituted monophosphate esters of the followm'g formula ( 1):

0 Q11 NU p c)-C)3-N ( 1) R in which:

R is an alkyl group selected from t-butyl, isopropyI, isobutyl, isoamyl, t-amyl, and N is 0 or an integer from 1 to 3.

Preferably, the component (D-1) is a mixture of alkyl substituted monophosphate esters comprising by weight,' 1 to 20% trialk-ylphenyl phosphate(N=3), 10 to 50% dialkylphenyl monophenyl phosphate(N=2), 15 to 60% monoalkylphenyl diphenyl phosphate(N=1) and less than 2% triphenyl phosphate(N=O). The preferred substituent R is t-butyl and isopropyl. The most preferred substituent R is t-btityl. A mixture of the mixed tbtitylplienyl phosphate esters and the mixed isopropylphenyl phosphate esters are also preferrable.

(D-2) Phosphate Esters The phosphate esters according to the invention have the followin b g 1 ' 01111111a (1l):

11 0 11 0 11 R,-O-P-O-R3- -P-O--RS 1 1 UR2 L_ OR4 J m (11) in which, Ri, R2, R4, and Rs are independently halogen-free phenyl group or Ci C4 alkylated aryl group, R3 is an arylene group, and M is 0 or an integer from 1 to 5.

In the formula, the compound of which M is 0, is a usual monomeric phosphate ester (herinafter referred to as compound group D-2. 1) and the compound of which M exceeds 0, is an oligomeric phosphate compound (hereinafter referred to as compound group D-2.2). That is, the phosphatebased flame retardant useful in the thermoplastic resin compositions according to the present invention comprises compounds of the formula (II) having M values from 0 to 5.

Preferred substituents R,, R2, R4, and Rs are independently one of cresyl, phenyl, xylenyl, propylphenyl, butylphenyl, and brominated or chlorinated derivatives thereof R3 is derived from diphenols such as, for example, bisphenol A, resorcinol or hydroquinone. Examples of preferred phosphate esters are a phosphate ester such as triphenyl phosphate, tri(2, 6-dimethylplienyl) phosphate, tri(4-iTictliylphenyl) phosphate, tricresyl phosphate, diphenylcresyl phosphate, tri(isopropylplienyl) phosphate, tfixylenyl phosphate, xylenyldiphenylphosphate, an oligonieric phosphonis compound tlirereof, or mixtures of these compounds.

The thermoplastic resin compositions according to the invention contain a niixttii.e of (D-1) and (D-2) as a flai-ne retardant. The weight ratios of (DA) and (D2) inay be varied within a wide range. The weight ratio of (DA) to (1)-2) is 12 preferably between 100:0 and 5:95, more preferably between 80:20 and 5.. 95 and most preferably between 55:45 and 15:85.

(E) Fluorinated Polyolefin Preferred fluorinated polyolefins (E) are polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene/vinylldene fluoride copolymer, and tetrafluoroethylene/llexafiuoropropylene copolymer. These fluorinated polvolefins may be used alone or in admixture with two or more other fluorinated polyolefins. These polymers may be produced by knomm processes, such as for example, by polymerization of tetrafluoroethylene in an aqueous medium with a fTee radical forming catalyst.

The use of fluorinated polyolefins decreases flow viscosity of the thermoplastic resin composition and increases coefficient of shrinkage of the composition by forminc, a fibrillar network during extruding, threreby reducing or preventing the JC dripping of the melting resin.

The fluormiated polyolef[ns may be used in powder form or in emulsion form. Fluorinated polyolefins of emulsion form have good dispersibility, but make the preparation process complicated. Threrefore, it is desired to use powder form fluorinated polyolefins capable of being dispersed evenly in the total resins and forming fibri'llar network.

The fitioninated polyolefin suitable for use in accordance with the Invention is poly-tetrafluoroethylene. Polytetrafluoroethylene with an average particle size of 0.05 to 1,0001m is suitable for blending.

0 to 2. 0 parts by weight of a fluorinated polyolefin polymer, based on 100 parts by weight of the base resin (A)+(B)+(C) is blended.

1 1 Conventional Additives Iii addition to the above-mentioned constituents, the thermoplastic resin compositions according to the invention may flirtlier contain one or more other conventional additives. For example, inorganic fillers, thermal stabilizers, antioxidants, lig it stabilizers, plasticizers, pigments, dyes, and mold releasing agents may be added. The content of these conventional additives may be 0 to 50 parts by wel glit based on 100 parts by weight of the base resin (A)+(B)+(C).

The thermoplastic resin compositions are prepared according to the conventional techniques of preparing resin compositions, for example, by mixing together the constituents including the various additives and meltextruding wth extruders in pellet form, Following are examples which illustrate procedures including the best mode b for practising the invention. They are not to be construed to limit the scope of invention defined by the appended claims in any manner whatsoever. All percentages are by weight unless otherwise noted.

The following constituents were used Mi the examples hereinafter:

(A) Polycarbonate Polycarbonate of Bisplienol A having a weight average molecular weight of 20,000 was used.

(B) Styrene-containing graft copolymer (ABS) parts by weiglit of butadiene latex in powder, 36 paris by weight of styrene, 14 pails by weiglit of acrylonitrile, and 150 parts by weight of deionized water were 14 mixed, and 1.0 parts by weiglit of potassium oleate, 0.4 parts by weiglit of clillictic liydi-o peroxide, and 0.3 parts by weight of mercaptan-based cliain transfer agelit 0 were added to the mixed solution. The resulting sohition was kept at 75t foi- 5 l hours to prepare a graft ABS(g-ABS) latex. To the resulting graft copolymer, 1 % sulfuric acid solution was added to prepare ABS resin in powder.

(C) Styrene-containing copolymer(SAN) To a mixed solution of 70 parts by weight of styrene, 30 parts by weight of acrylonitrile and 120 parts by weight of deionized water, 0.2 pails by weight of azobis(isobutyronitrile) and 0.5 parts by weight of tricalcium phosphate were added. SAN copolymer was prepared by suspension polymerization by washing, dehydratmig and drying the resultant product. SAN copolymer Mi powder form was obtaffied.

(D- 1) A mixture of t-butyl substituted monopho sphate. esters A mixture of t-butyl substituted monophosphate esters contaiiiing 0.5% by weight of triphenyl phosphate, 33.2% by weight of diphenyl (t- butylphenyl) phosphate, 49.5% by weight of phenyl di(t-butylphenyl) phosphate and 12.5% by weight of tri(t-butylphenyl) phosphate was used.

(D-2. 1) Monomenic phosphate ester Triphenyl phosphate (TPP) of Dailiachi Co. of Japan was used.

(D-2.2) Oligomeric phosphate ester Resoreinoldipliospliatc(RDP) with an average M vakie of 1.3 in Forimila (II) was used.

1 (E) Fluorinated polyolefin Polytetrafluoroethylene with an average particle size of 10-501m was used.

EXA2LES 1-4-AND COMPARATIVE EXAMPLES 1-4 Eight different thermoplastic resin compositions were prepared from the above -mentioned constituents 'm the amount as indicated in the followinú? Table 1 and the propeilles of the compositions were also shown in Table 1. The indicated constituents were mixed with an antioxidant and a thermal stabilizer, and then compounded in a twin-screw extruder(L/D 29, 0=45). The resulting extnidates were pelletized and the test pieces were injection-molded from the pellets at the temperature of 220-280'C and maintained at 23t, 50% RH before rheasuring the properties.

The thermoplastic resin compositions of Examples 1 to 4 were those comprising a mixture of Autyl substituted monophosphate esters(D-1), and a m on orneric phosphate ester (D2. 1) or an oligomeric phosphate ester (D2.2). The thennoplastic resin compositions of Comparative Examples 1 to 4 are-those having the sarne compositions with the composition of example 1 but as a flarne retardant containing only a monophosphate ester compound, an oligomeric phosphate ester compound or both, respectively.

TABLE 1

EXAlvTLE NO. EXAMPLES COMPARATIVE EXAMPLES

1 2 3 4 1 2 3 4 COMPOSITIONS (parts by weight) (A) Polycarbonate 80 80 80 80 80 80 80 0 (B) Gnift copolymer (g-ABS) 10 10 10 10 10 10 10::10 0 16 (C) SAN 10 10 10 10 10 10 10 10 (D- 1) A mixture of t-buyl 7 3 7 substituted monopliostpliates (1)-2 1) TPP 3 7 - - 10 - 7 3 (D-22) RDP - 3 7 - 10 3 7 (E) Fluorinated polyolefin(7AJ) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 PROPERTIES Heat Resistance (VST, C)(') 100 97 103 102 9 99 96 97 Number of cracks(2) 3 7. 2 6 31 24 19 1 3) Total length of the cracks (MM) (3) 13.5 35.4 11.3 33.7 235,5 194. 150. 8 9. 3 J TEST 1VIETHOD, Heat resistance was determined according to ASTM D306.

Determined by measuring the number of the cracks generated following the storage for 24 hours in the oven at the temperature of 80t after injection molding the test pieces by a box-shaped mold. (1) Determined by measuring the total length of the cracks generated following the storage for 24 hours in the oven at the temperature of 80t after injection molding die test pieces by a box-shaped mold.

EXANTLES 5-11 AN-D COMPARATWE EXAMPLES 5-8 Thermoplastic resin compositions having a composition as shown in Table 2 and Table 3 were prepared by tile sarne method with Example 1-4 and the measured properties were also shown in Table 2 and Table 3.

1 17 TABLE2

1:XAlvTLE NO. EXAlvTLES.

16 17 18 19 110 1 COMPOSITIONS (parts by weight) (A) Polyearbonates 80 80 80 80 80 80 80 (B) Graft polymer (g-ABS) 10 10 10 10 10 10 10 (C) SAN 10 10 10 10 10 10 10 (D- 1) A mixture of t-butyl substituted 10 8 8 6 6 4 4 monophosphates (D-2. 1) TPP - 2 - 4 - 6 - (D-2.2-) RDP - - 2 - 4 - 6 (E) Fluorinated polyolefin(7AJ) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 PROPERTIES Heat Resistance (VST, C) 105 103 104 101 103 98 102 Number of cracks 1 3 2 6 5 11 7 Total length of the cracks 5.3 13.5 11.3 33.7 29,6 53.1 36.7 TABLE3

EXMvfPLE NO. CONTARATIVE EXAlvTLES 57 6 1 7 1 8 COMPOSITIONS (parts by weight) (A) Polycarbonates 80 80 80 80 (B) Graft copolymer (g-ABS) 10 10 10 10 (C) SAN 10 10 10 10 (D- 1) A mixture of t-butyl substituted monophosphates (D-2. 1) Tpp 8 2 6 4 18 (1)-2.2) RDP 2 8 4 6 (E) Fluorinated polyolefin (7AJ) 0.4 0.4 0.4 0.4 PROPERTIES Heat Resistance (VST, 'C) 95 99 97 96 Number of cracks 28 18 25 23 Total length of the cracks 124.3 103.2 117.6 110.8 As shown in Tables 1 and 2, examples 1-4 and 5-11 showed 'unproved heat resistance and drastic reduction in number and- length of the cracks. By contrast, comparative examples 1-4 and 5-8 showed poor heat resistance and increased number and length of the cracks. As can be seen from the results of Tables 1, 2 and 3, the thermoplastic resin compositions according to the 'invention, which contain as a flame retardant, a mixture of alkyl substituted monophosphate esters, and a monomeric phosphate ester or an oligomenic phosphate ester showed distinctly higher stress cracking resistance and 'unproved heat resistance than those of the comparative examples with only monomeric phosphate ester(Comparative Example 1), only ollgomeric phosphate ester(Comparative Example 2) or a mixture of monomenic phosphate ester and oligomeric phosphate ester (Comparative Examples 3-8).

Consequently, these results show that stress cracking resistance and heat resistance of the thermoplastic resin compositions according to the present invention are subtantially improved by a combination of flame retardants comprising a mixture of alkyl substituted monophosphate esters and a phosphate ester compound.

19

Claims

CLAIMS:

1. A thermoplastic resin composition 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 (BA) onto (B-2):

(BA) 5 to 95% by weight, based on (B),-of a mixture of (B-1. 1) 50 to 100% by weight of styrene, a -methyl styrene, ringsubstituted styrene, methyl methacrylate or a mixture thereof, and (B-1.2) 50 to 0% by weight of acrylonitrile, methaerylonitrile, Ci-G alkyl methaerylate, C,-G alkyl acrylate, alkyl acrylate, maleic anhydride, N-substituted malelmide or a mixture thereof; (B.2) 95 to 5% by weight, based on (B), of a rubber with a glass transition temperaturejg) of below - 1 Ot and selected from the group consisting of butadiene rubbers, acryl rubbers, ethylene/propylene rubbers, styrene/butadiene nibbers, acrylonitrilelbutadiene rubbers, butadienelstyrene rubbers, polyisoprene, EPDM rubbers, polyorganosiloxane:, and mixtures thereof, (C) 0 to 30 parts by weight of a styrene containing copolymer prepared from..

(CA) 50 to 95% by weight of styrene, a -methyl styrene, ringsubstituted styrene, methyl methacrylate or a mixture thereof, and (C-2) 50 to 5% by weight of acrylonitrile, C-C8 alkyl methacrylate, CC8 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 a mixture of alkyl substituted monophosphate esters of'tlie formula (I):

0 Q11 w N p O-C) R (1) 3-N 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):

0 0 11 11 Rro-P-0--R3-0-P-0--Rs 1 1 UK2 UK4 --J M in wl-cli; (11) Ri, R2, R4, and Ri are independently cresyl, phenyl, xylenyl, propylphenvI, butylphenyl, or brominated or chlorinated derivatives thereof, R3 is an arylene group, and MisOto 5; and (E) 0 to 2 parts by weight, based on 100 parts by weight of (A)+(B)+(C), of a fluoninated polyolefin polymer.

2. A thermoplastic resin composition according to claim 1, wherein said component (D- 1) is a mixture comprising by weight: 1 to 20% of the alkyl -substituted monophosphate ester wherein N is 3, 10 to 50% of the alkylsubstituted monophosphate ester.wherein N is 2, 15 to 60% of the alkyl substituted monophosphate ester wherein N is 1, and less than 2% tniphenyl phosphate.

21

3. A thermoplastic resin composition according to claim 1, wherein the weight ratio of (1)- 1) to (D-2) is between 80:20 and 5:95.

4. A thermoplastic resin composition according to claim 1, wherein the weight ratio of (13-1) to (D-2) is between 55:45 and 15:85.

5. A thermoplastic resin composition according to claim 1, wherein said alkyl grotip(R) is t-butyl.

6. A thermoplastic resin composition according to claim 1, wherein said alkyl group(R) is isopropyl.

7. A thermoplastic resin composition according to claim 1, whereffi said component (DA) is a mixture of the mixed t-butyl substituted monophosphate esters and the mixed isopropyl substituted monophosphate esters.

8. A thermoplastic resin composition according to claim 1 or claim 2, wherein saQ resin composition further includes at least one additive selected from the group consisting of inorganic fillers, glass fibers, carbon fibers, thermal stabilizers, antioxidants, light stabilizers, plasticizers, mold release agents, pigments, and dyes.

9. A thermoplastic resin composition according to claim 2, wherein said component (D- 1) is a mixed t-butyl substituted monophosphate ester composition comprising by weight:

1 to 20% tri(t-butylphenyl) phosphate, to 50% di(t-butylphenyl) phosphate, to 60% diphenyl (t-butylphenyl) phosphate and less than 2% triphenyl phosphate.

10. A thermoplastic resin composition according to claim 1, substantially as described herein with reference to the Examples.

1 1