CA2025377A1 - Low gloss flame retardant thermoplastic blends - Google Patents

Abstract

LOW GLOSS FLAME RETARDANT THERMOPLASTIC BLENDS
Abstract of the Disclosure Low gloss flame retardant thermoplastic blends are provided by blending an aromatic carbonate polymer, polybutylene terephthalate and a gloss reducing amount of an interpolymer of acrylonitrile, butadiene and styrene, at least part of which is ring-brominated styrene, especially ring-dibrominated styrene.

Description

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LOW GLOSS FLAME RETARDANT THERMOPLASTXC BLENDS
~ACK~R~OUND OF_THE INVENTION
Field of the Invention The invention is directed to physical blends of aromatic carbona~e polymers, polybutylene terephthalate and an acrylonitrile-butadiene-(brominated styrene) interpolymer.
Brief Descri~io~n of the Prior Art It has been known to physically blend polycarbonates with polyesters such as polybutylene terephthalate. PolycarbQnate/polyes~er blends generally require the presence of an impact modifier to attain a high ductility. Frequently, rubbery ABS
polymers are used to achieve high impact strength blends. Such blends are taught, ~or example, in General Electric~s European Pat. 105,388 (Sept. 28, 1982).
However, articles molded ~rom such blends have been characteristically high in surface gloss and to achieve flame retardant properties, flame retardant additives have been necessary. For many important applications, such as machine housings and interior automotive parts, ~lame retardancy and a dull (matte or nonglossy) surface is desirable.
The u~e of additive ~elustrants (gloss-reducing additives) is co~mercially practiced but entails some significant disadvantages. The additives are commonly particulate solids, and cause loss of physical strength properties, most commonly loss of tensile and impac~ strength, and impairmen~ of heat resistanceO They also cause pigmentation which is :; . : :, . . ~ , , 03cLO679~ r r~ 7 often undesired. Some additive~ are ~ound to decrease heat stability, in the sense of lowering heat distortion temperature and also in the sense of favoring degradation and lo~s of molecular weight in the molding operation as well as in s~bsequent aging.
Flame retardancy is also desirable and often required for many pla~tic3 products, notably in molded eleatrical parts, business machine housings, and automotive interior parts. The requirement in electrical applications is usually a rating of VO in the more stringent applications and rating of V~2 or HB in the less stringent applications, as determined by the Underwriters' Laboratory UL~94 flammability test. Additives used to obtain flame retardancy, such as polybrominat~d phenyl ethers, are prone to plate out (deposit~ on molds during processing, and also are prone to bloom to the sur~ace in the finished articles~ Certain flame retardant additives such as polybrominated polystyrene avoid the plating out and blooming proble~s b~t tend to cause a deficiency in impac~ strength and some~imes cause mold coxrosion problems because of insufficient thermal stability. The volatility of some flame retardant a~ditives, in processing or in flaming conditions, can cause undesirable emissions o~ vapor in the wGrk space.
Antimony oxide additive gives good 1ammability resistance. However, antimony oxide degrades polycarbonate resin. The presence of antimony oxides also leads to difficulty in producing colored articles, since antimony oxides react with polycarbonate to produce a gray color.

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' 03CL06791 ~ç~ r) This invention allows for flame retardancy without th~ need or flame retarding additives such as antimony oxide. All of the adverse phenomena commonly found with prior art additives represent problems overcome by the present invention. The use of a flame retardant impact modifier allows one to achieve both impact modification and flame retardance at the same time wi~hout adverse effect.
We have found advantageous blends of aromatic carbonate polymers, polybutylene tereph~halate (PBT) and a certain specific class of ac~ylonitrile- :
butadiene-styrene (ABS1 which une~pectedly provide the desired low glo~s and flame retardance while retaining good thermomechanical and processing properties.
SUMMARy_OF T~E_I~VENTION
The low gloss thermoplastic molding compositions of the invention comprise:
an aromatic carbonate polymer;
polybutylene terephthalate; and a gloss-reducing and flame retarding amount of an interpolymer of acxylonitrile, butadiene and styrene, o~ which at least part is ring-brominated styrene. The preferred ring-bromina~ed styrene is dibromostyrene.
DETAILED DESCRIPTI~N OF THE PREFE~RED
EMBO~IME~TS OF THE INy~NTION _ _ All percentages referred to hereinafter are by weight unless otherwise specified.
The aroma~ic carbo~ate polymers useful as com~onent (a) include polycarbonates as well as polyester-carbonate~. Polycarbonate and polyester-.
. -- . , . . , . -` ' ;
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': . ' ' ' '' ' '. . ' ' . ' carbona~es are well known resins, commercially available. Methods of preparing polycarbonates by interfacial pol~meriza~ion are well known; see for example the details provided in th~ U.S. P~tents 3,028,365; 3,334,154; 3,275,601 3,915,926;
3,030,331; 3,169,121 3,027,814; and 4,188~314, all of which are incorporated herein by reference thereto.
In ganeral, the method of interfacial polymerization comprises the reaction of a dihydric phenol with a carbonyl halide (the carbonate precursor).
Although the reaction conditions of the preparative processes may vary, ~everal o~ the preferred processes typically involve dissolving or dispersing the diphenol reactants in aqu~ous caustic, adding the resulting mixture to a suitable water immiscible solvent medium and contacting the reactants with the carbonate precursor, such as phosgene, in the presence of a suitable catalyst and under controlled pH conditionsO The most commonly used water immiscible solvent~ include methylene chloride, 1,2-dichloroethane, chlorobenzene, toluene, and the like.
The catalyst employed accelerates the rate o~
polymerization of the dihydric phenol reactant wi~.h the carbonate precursor. Representative catalysts include but are not limited to tertiary amines such as triethylamine, quaternary phosphonium compounds, quaternary ammonium compounds, and the like. The preferred process for preparing polycarbonate resins .. . .

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comprises a phosgenation reaction. The temperature a~ which ~he phosg~na~iQn reaction proceeds may vary from below 0 C, to above 100~C. The phosgenation reaction preferably proceeds at temperatures of from room temperatures (25C~ to 50C. Since the reaction is exothermic, the rat~ of phosgene addition may be used to control ~he reaction temper ature. The amount of phosgene required will generally depend upon the amount of the dihydric phenols.
The dihydric phenols employed are known, and the reactive groups are the two phenolic hydroxyl groups. Some o~ the dihydric phenols are represented by the general formula:
(X)0_~ (X)0_4 HO ~ A ~ - ~ OH

(I) wher2in A is a divalent hydrocarbon radical containing from 1 to abou~ 15 carbon atoms; a substituted divalent hydrocarbon radical containing from 1 to about 15 carbon atoms and substituent groups such as halogen; -S- ; -SS-; -S(O~ S(O)2- ;
-O- : or -C- ~ach X is independently selected from the group consisting of hydrogen, halogen, and a monovalent hydrocarbon radical such as an alkyl group of from 1 to about 8 carbon atoms, an aryl group of from 6-1~ carbon atoms, an aralkyl group of from 7 to about 14 carbon atoms, an alkaryl group of ~rom 7 to abou~ 14 carbon atoms, an alkoxy group of from 1 to about 8 carbon atoms, or an aryloxy group ,~ . . :. .
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of from 6 to 18 carbon atoms; and m is zero or 1 and n is an integer of from 0 to 5.
Typical o~ some of the dihydric phenols employed are bis-phenols such as (~hydroxy-phenyl)me~hane, 2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol-A), 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane; dihydric phenol ethers such as bis(4-hydroxyphenyl~ ether~ bis(3,5-dichloro-4-hydroxyphenyl) ether; dihydroxydiphenyls such as p,p'- dihydroxydiphenyl, 3,3l-dichloro-4,4'-dihydroxydiphenyl dihydroxya~yl sulfones such as bis(4-hydroxyphenyl) sulfone, bis (3,5-dimethyl-4-hydroxyphenyl) sul~one, dihydroxybenzene~ such as resorcinol, hydroquinone, halo- and alkyl substituted dihydro~ybenzene~ such a 1,4-dihydroxy-2,5-dichlorobenzen~, 1,4-dihydroxy-3-methylben~ene;
and dihydroxydiphenyl sulfides and sulfoxides such as bis(4-hydroxyphenyl) sulfide, bis(4-hydroxyphenyl) sul~oxide and bis(3,5-dibromo-4-hydroxyphenyl) sulfoxide. A variety of additionaldihydric phenols are available and are disclosed in U.S. Pat. No~. 2,999,835: 3,028,365 and 3,153,008;
all of which are incorporated herein by reference.
It is, of course, pos~ible to employ two or more di~erent dihydric phenols or a combination of a dihydric phenol with glycol.
The carbonate precursor can be either a carbonyl halide, a diarylcarbonate or a bishaloformate. The carbonyl halide~ include carbonyl bromide, carbonyl chloride, and mixtures thereof. The bishaloformates include the bishaloformate~ of dihydric phenol~ ~uGh as ~ ~ . `' .

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O~CL06791 ~ J~ 7, bischloroformates o~ 2,2-bis(4-hydroxyphenyl)-propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)-propane, hydroquinone, and the like, or bishaloformates of glycols such as bishalo~ormates of ethylene glycol, and the like. While all of the abov~ carbonate precursors are useful, carbonyl chloride, also known as phosgene, is preferred.
A1SQ included within the scope of the present invention are ~he high molecular weight thermoplastic randomly branched polycarbonates.
These randomly branched polycarbonates are prPpared by coreacting a polyfunctional organic compound with the aforedescribed dihydric phenols and carbonate precursor. The poly~unctional organic compounds use~ul in making the branched polycarbonates are set forth in U.S. Pat. No~. 3,635,895 and 4,001,184 which are incorporated herein by reference. These polyfunctional compounds are generally aromatic and contain at least three functional groups which are carboxyl, carboxylic anhydrides, phenols, haloformyls or mixtures thereof. Some nonlimiting examples of thes~ polyfunctional aromatic compounds include 1,~ ri(4-hydroxyphPnyl) e~hane, trimellitic anhydride, trimellitic acid, trim~llitoyl trichloride, 4-chloro~ormyl phthalic anhydride, pyromellitic acid, pyromellitic dianhydride, mellitic acid, mellitic anhydride, trimesic acid, benzophenonetetxacarboxylic acid, benzophenonetetracarboxylic anhydride, and the like.
ThQ preferred polyfunctional aromatic co~pounds are 1,l,l~tri(4-hydroxyphenyl)ethane, trimellitic anhydride or trimellitic acid or their halo~ormyl ' :

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derivatives. Also included herein arP blends of a linear polycarbonate and a branched polycarbonate.
The aromatic carbonate polymers suitable for use as component (a) of tha compositions of the invention include polyester-carbonates, al~o known as copolyester-polycarbonates, i.e., resins which contain, in addition to recurring polycarbonate chain units of the formula:
r 0-~ O - D - O - c - _ tIIa) wherein D is a divalen~ aroma~ic ra~ical of the dihydric phenol employed in the polymerization reaction, repeating or recurring carboxylate units, for example of the formula:
`~-O-C(O)-Rl-C(O)-O-D-]- (IIb) wherein D is as defined above and Rl is as defined balow.
The copolyester-polycarbonate resins are also prepared by interfacial polymeriza~ion technique, w~ll known to those skilled in the art; see for example the U.S. patents 3,169,121 and 4,4~7,896.
In general the copolyester-polycarbonate resins are prepared as described above for ~he preparation of polycarbona~e homopolymers, but by the added pre enc~ of a dicarboxylic acid (e~ter precursor) in the water immiscible solvent.
~ n general, any dicarboxylic acid conventionally used in the preparation o~ linear polyesters may be utilized in the pr~paration of the copolyester-carbonate resins. Generally, the dicarboxylic acid~ which may be u~ilized include the aliphatic dicarboxylic acids, the aromatic .. ,.,, ~,...................... . .

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dicarboxylic acids, and the aliphatic-aromatic dicarboxylic acids. These acids are well known and are disclosed for example in U.S. Pat. No. 3,169,121 which is hereby incorporated herein by re~erence.
Representative of such aromatic dicarboxylic acids are those represented by the general formula:

(III) wherein Rl represents an aromatic radical such as phenylene, naphthylene, biphenylene, substituted phenylene and the like; a divalent aliphatic-aromatic hydrocarbon radical such as an aralkyl or alka~yl radical; or two or more aromatic groups connected through non-aromatic linkages o~ the -15 formula:
- E -wherein E is a divalent alkylene or alkylidene group. E may also consist of two or more alkylene or alkylidene groups, connected by a non-alkylene or alkylidene group, such as an aro~atic linkage, a tertiary amino linkage, an e~her linkage, a carbonyl linkage, a silicon-containing linkage, or by a sulfur-containing linkage such as sulfide, sulfoxida, sulfon~ and the like. In addition, E may be a cycloaliphatic group of five to seven carbon atoms, inclusive, (e.g. cyclopentyl, cyclohexyl), or a cycloalkylidene of five to seven carbon atoms, inclusive, such a~ cyclohexylidene. E may al~o be a carbon-free sulfur-containing linkage, such as sulfide, sulfoxide or sulfone; an ether linkage: a carbonyl group a dixect bond; a ~ertiary nitrogen group; or a silicon-containing linkage such as .

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silane or siloxy. Other groups which E may represent will occur to ~hose skilled in the art.
For purposes of the present inven~ion, the aromatic dicarboxylic acids are pre~erred. Thus, in the preferr~d aromatic difunctional carboxylic acids of the ~ormula (III), Rl is an aromatic radical such as phenylene, biphenylene, naph~hylene, or substituted phenylene. Some non-limiting examples of aromatic dicarboxylic acids which may be used in prepariny the poly(ester-carbonate) or polyarylate resins of the instant invention includ~ phthalic acid, isophthalic acid, terephthalic acid, homophthalic acid, o-, m-, and p-phenylenediacetic acid, and the polynuclear aromatic acids such as diphenyl dicarboxylic acid, and isomeric naphthalene dicarboxylic acids. The aromaties may be substituted with Y groups. Y may be an inorganic ato~ such as chlorine, bro~ine, fluorine and the like; an organic group such as the nitro group, an organic group such as alkyl; or an oxy group such as alkoxy, it baing only necessary that Y be inert to and unaffected by the reactants and ths reaction conditions. Particularly use~ul aro~atic dicarboxylic acids are those represented by the general formula:-(R3)j HOOC ~ (IV) ~ O ~ COOH

wherein j is a positive whole integer having a value of from O to 4 inclusive; and each R3 i5independently selected fro~ the group consisting of . ~ .
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alkyl radicals, pre~erably lower alkyl (1 to about 6 C atoms).
Mixtures of ~hese dicarboxylic acids may be employed. There~ore, where ~he term dicarboxylic acid is used herein i~ is to be understood that this term incl~des mixtures of ~wo or more dicarboxylic acids.
Most preferred as aromatic dicarboxylic acids are isophthalic acid~ terephthalic acid, and mixtures thexeof. A particularly u-~eful difunctional carboxylic acid comprises a mixture of isophthalic acid and terephthalic acid wherein the weight r~tio of terephthalic acid to isophthalic acid is in the range of from about 10:1 to about 0.2:9.8.
Rather than utilizing the dicarboxylic acid per se, it is possible, and sometimes even preferred, to employ the reactive derivatives of said acid.
Illustrative of these reactive derivatives are the acid halides. The preferred acid halides are the acid dichlorides and the acid dibromideq. Thus, for example instead of using isophthalic acid, terephthalic acid or mixtures thereof, it is possible to employ isoph~haloyl dichloride, terephthaloyl dichloride, and mixtures thereof.
The ~roportions of reactants employed to pr~pare the copolyester carbona~e resins will vary in accordance with the proposed use of the blends of the invention containing this product resin. Those skilled in the art are aware o~ usaful proportions, as described in the U.S. patents referred to above.
In general, the amount of the ester bonds may be .
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from about S to about 90 mole percent, relative to the carbonate bonds. For example, 5 moles of bisphenol A reacting completely wi~h ~ moles of isophthaloyl dichloride and l mole of phosgene would S give a copolyester-carbonat~ of 80 mole percent ester bonds.
The preferred polycarbonates for use in the prasent invention are those derived from bisphenol A
and phosgPne and having an intrinsic viscosity of about 0.3 to about 1.5 deciliters per gram measured in methylene chloride at a temperature of 25C.
The polybutylene terephthalate polymer for use in the compositions of the invention are also well known in the art: see for example, U. S. Pat.
4,684,686 (Aug. 1987). Preferably it is a polyester obtained by polymerizing a glycol component, at least 70 mole % (preferably at least 80 mole %) of which consists of 1,4-butanediol and an acid component at least 70 mole % (preferably at least 80 mole %) of which consists of terephthalic acid, or polyester-forming derivatives thereof.
The glycol component may contain not more than 30 mole ~ (preferably not more than 20 mole %) o~
another glycol, such as ethylene glycol, trimethyl-eno glycol, 2-methyl-1,3-propanediol, hexamethylene glycol, decamathylene glycol,cyclohexanedimethanol, neopentylene glycol or the like.
The acid component may contain not more than 30 mole ~ (preferably not more than 20 mole %) of another acid such as isophthalic acid, 2,6-naphtha-lenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, l,5-naphthalenedicarboxylic acid, 4,4'-..
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o~cLo679l 2 ~ ~ ~ 3 7 7 diphenoxy- ethanedicarboxylic acid, 4l4l diphenyldicarboxylic acid, p hydroxybenzoic acid, sebacic acid, adipic acid, or polyester-forming derivatives thereof.
The polybutylene terephthala~e u~ed in this invention preferably has an intrin~ic viscosity [n]
measured in a 60/40 mixture by weight of phenol/tetrachloroethane at 30 C, of 0.3 to 1~5 dl/g.
The relative proportions of the polycarbonate and the PBT resins may vary over a broad range. In ganeral the blends of the invention will contain 5 to 90S ~y wei~h~ o~ the carbonate poly~er of the polybutylene terephthalate component, preferably 5%
to 20~.
The ~BS polymer for use as a component in ~he compositions o~ the invention is, most broadly, any ABS made using a ring-brominated styrene. ABS
itself is w~ll known in the plastics art and is defined, for example, in the Modern Plas~ics Encyclopedia, 1~8~ edition, page 92, as the family o~ ther~oplastics made from the thrae mon ers acrylonitrile f butadiene and styrene, and includes a mixture ~alloy) of styrene~acrylonitrile copolymer with SAN-grafted polybutadiene rubber. The use of a ring-bro~inated styrene in preparing ABS is well known and is described for example by Arthur et al.
in Canadian Patent 1 149 984 (i~sued July 12, 1983), as well a~ by Ikeda et al. in Japanese Patent 1987-10689 published Jan. 31, 1978.
The preferred AB8 polymer made from a ring brominated styrene is that made using dibromostyrene .

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as a monomer, this polymer having a particularly good balance of physical properties, s~ability and cost.
The ring-brominated styrenes used to make the ABS interpolymers for lse in the invention are themselves well known in the art, and include the various ring position isomers o~ mono-, di-, tri-, tetra- and pentabromastyrene. Any isomer or mixture of isomers is usable. For reasons of cost, stability, polymerizability, and availability, the di- and tribrominated styrenes are pref~rred and the dibrominated styrenes most preferred.
The ABS made utilizing ring-brominated styrene may be made using all ring-brominated styrene and no unbrominated styrene, but it is pre~erred that some unbrominated styrene be usedO The A~S should have a~
least 10% conkent of brominated styrene and preferably at least 20%, relative to total ABS (by weight).
A gloss reducing and flame retarding proportion of the A~S employed he~ein is genarally in the range of from about 10% to about 80~ by weight of the total blend of carbsnate polymer and PBT. A
preferred range is 10% to 30%. It will be appreciated that if another ~loss reducing component is added, such as ~ilica or other d~lustrant, or another flame retardant, somewhat lesser amounts o~
the ABS can su~fice, whereas if very low surface gloss is required, somewhat greater amounts of the ABS component can he used.
The compositions of the in~ention may be modified by the addition o~ other additives conven-, . . .
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O~CL0679 tionally used in the art of plastics compounding.
Such additives can include filler~ (such as clay or talc), supplementary delustrants, reinforcing agents (such as glass fibers), impact modifiers, antistats, plasticizers, flow promo~ rs and other processing aids, stabilizers, rolorants, mold release agents, supplementary or synergistic ~lame re~ardants, ultraviolet screening agents, drip inhibitors such as polytetrafluoroethylene (PTFE) and the like; see for example U.S. Patents 3,005,795; 3,671,487 and 4,463,130. It is advantageous to use a drip-retarding amount of ~ibrilar polytQtrafluoro-ethylene. This is added as a concen~rate at the rate o~ about 0.02 to 2% by weight and has a favorable effect in retarding the occurre~ce of flaming drips in cnmbustion of ar~icle molded from the compositions of the invention.
The production of ths compositions of th~
invention is done by any of the blending operations known for the blending of th~rmoplastics, such as blending in a kneading machine such as a Banbury mixer or a~ extruder, or solvent blending. The sequence of addition is not critical but all components should be thoroughly blended together.
Blending can ba done continuously or batchwise. A
preferred blending method is melt blending with the USQ of an extruder, such a~ a twin screw extxuder.
The invention will be better understood with reference to the following examples, which are pre~ented for purposes of illustratiun ra~her than for limitation, and which sa~ forth the best mode contemplatad for carrying out the invention.

. 08CL06791~ 7 Molding compositions were prepared by melt blending the ingredients indicated in the table below in a twin screw extruder at 240 315 and 200~500 rpm.
The blended and extxuded material was then pelletized, dried and injection molded at about 260~C
to prepare test specimens. The gloss was measured by AST~ method D-1003 at 60 using a Gardner gloss meter. Flammability was tested by the UL-94 method of Underwriters' Laboratory. The ~orm~lations and test results are as follows:
Exa~ple No.: 1 2 3 Composition ~t.%L;

P~ 67.2 49.74 32.31 PB~3 11.81 8.77 5.7 4 0.3 0.3 0.3 PTFE
~e~
Gloss 60 65~1 82.5 78.2 UL94 rating ~ 0.06" V2 HB HB
Average flameout time " " 10 75 81 UL94 rating Q 0.125i' HB5 HB HB
Average flameou~ time " " 7.3 55 107 ~otes to ta~
1. A bromine containing A~S made by General Electric Company, using 27% dibromostyrPne, 16.7% acrylonitrile, 21% butadiene, and 35.5%
styxen~.
2. High Flow Lexan ~ polycarbonate made by General Electric Co.

3. Valox ~ 315 PBT made by General Electric Co.
20% Fibrillar polyte~rafluoroethylene in an ~0 polycarbonate concentrate. Small amounts O~CL067sl 2~ c~ 7 ~

( less than O . 6% ~ of customary PBT and ABS
stabilizers also present, well known to those skilled in the art.
5 . Two samples out of 10 burned over 3 o seconds;
i. e. close to V2 .
The data shows the substantial lowering of gloss by inclusion of the specified ABS in the blend, and surprising flame retardancy effect re ulting from the lowest level of DABS.

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Claims (8)

1. A low gloss flame retardant thermoplastic blend which comprises:
(a) an aromatic carbonate polymer;
(b) polybutylene terephthalate; and (c) a gloss-reducing flame-retarding amount of an interpolymer of acrylonitrile, butadiene, and styrene of which at least part of the styrene is ring-brominated styrene.

2. A low gloss flame retardant thermoplastic blend which comprises:
(a) an aromatic polycarbonate;
(b) from about 5% to about 90% by weight of the polycarbonate of polybutylene terephthalate: and (c) from about 10% to about 80% by weight of (a) and (b) of an interpolymer of acrylonitrile, butadiene, and styrene, at least part of which is ring-brominated styrene, said interpolymer having a ring-brominated styrene content of at least 10%.

3. A low gloss flame retardant thermoplastic blend which comprises:
(a) an aromatic polycarbonate;
(b) from about 5% to about 20% by weight of the polycarbonate of polybutylene terephthalate; and (c) from about 10% to about 30% by weight of (a) and (b) of an interpolymer of acrylonitrile, butadiene, and styrene, at least part of which is ring-brominated styrene, said interpolymer having a ring-brominated styrene content of at least 10%.

4. The thermoplastic blend of in claim 2 wherein said interpolymer has a ring-brominated styrene content of at least 20%.

5. The thermoplastic blend of claim 4 wherein said ring-brominated styrene is dibromostyrene.

6. The thermoplastic blend of claim 5 wherein said polycarbonate is made principally from bisphenol A and phosgene.

7. An article molded from the blend of claim 1.

8. The invention as defined in any of the preceding claims including any further features of novelty disclosed.