CA1059681A - Flame retardant polycarbonate composition - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A thermoplastic composition comprises in admixture 100 parts of a halogen containing aromatic carbonate polymer and from 0.5 to 1.5 parts of a diorganopolysiloxane gum.
Compositions are illustrated which conform to the SE-0 standard of the UL-94 flame test.

Description

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: ~ i- This inven~ion is directed to a f1ame-retardant composi- ~-tion comprising in admixture an aromatic polycarbonate and a minor~
amount of an organopolysiloxane po:Lymer.
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With ~he increabing concern for safety, there is a ~..
positive move towards provid.ing sa:Eè materla1s for pub~ic and : - .' : household use. One particular area o~ need is that of providing ~:
., flame re'sistant or flame retardant products for use by,the u1t~mac . .-' consumer. As:a result of this demsnd, many products are,~:1ng .~ ~
, required'to meet certain flame retardant criteria both by~ cal ~ .
¦~ . . :and federal government and the manufacturers of such products.. ..~. ..: ., One particular cet of conditlons employed as a measuring standard'~
.,:, for flame:retardancy is set for~h in Underwritérs Laboratoriec9,,,,~, .. ~:
~, "-~ Inc. Bul1etin 94. Th~s Bulletin sets for~h certain conditionc by;~
}5~ ¦ wbi-h materials re~r-ted for self-extinguisbing baraqterLst~cc. :~

~ ~ ~ ~ ~ It ic well known in the art to prepare flame retsrdant ~, ~/
: - polycarbonate compositions by'employing halogen ~subs itu~ed bis-~ ; ~: , . ¦phenol-A in the preparation thereof. Specifical1y~, U.S. patent~ .~ ~,,' ' . -. ¦3,334,l54 disc1Oses such a eomposition wherein tetrabromobis ~enol~ i~
:; 20 is employed to prepar~ a polycarbonate composition having f:lame'~"~
.~ retardant properties.
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~ Also, it L~ known to use or~anopolysiluxane in admlxture¦
with polycarbonates to provide a composi~ion havin~ good mold .
release properties from U.S. patent 2,999,~35. Also. U.S. patent - 3,087,908 discloses resinous material comprising organosiloxane in admixture with polycarbonates, which composition facilitates the formation of clear films which are free from blemishes, un :
desirable color effects, bubbles~ and craters. .
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However, none of the above references disclose that when a minor amount of a particular organopolysiloxane polymer is mixed with an aromatic polycarbonate, the aromatic polycarbonate Ls rendered flame retard nt. ~ .
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The organopolysiloxane polymer additive is able to stop the dripping of molten, flame particles from burning thermoplastic parts. In the case of self-extinguishing polymers,~these ma eriaL~
- can be ignited and do burn as long as the ignition source is~
present but extinguish themselves within a few seconds~ after its removal. However, during the burning period, before f lame-out, the self-extinguishing polymer tends to drip molten flaming frag-ments which will ignite other material situated below the ~ir,st fire. However, the instant additive in admixture wi~h the aro-- matic polycarbonate prevents this dripping of molten~ flaming ~ ~-~par~icle .

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This invention relates to a flame-retardant ' composition comprising in admixture (~) an aromatic carbonate polymer selected from the group consisting of (1) a poly-carbonate of a halogen substituted dihydric phenol, (2) a ... .
copolycarbonate of a non-halogen substituted dihydric phenol and a halogen substituted dihydric phenol; (3) a mixture of ~ ' (1) and (2); and (4) a mixture of a member selected from '-the group consisting of (1), and (2) with a polycarbonate of a non-halogen substituted dihydric phenol; and (B) a minor amount of a diorganopolysiloxane polymer wherein the organo substituents therein are selected from the group consisting of alkyl, aryl and vinyl radi~als and mixtures thereof. The '~.
amount of organopolysiloxane polymer can vary but preferably -i5 present in from 0.5 to about 1~5 weight percent based on ~ .
the'weight of the aromatic carbonate'polymer.
The diorganopolysiloxane polymers employed in the practice of this invention are gums which have a '.'' viscosity of from about 8Q,.OOO,'.OOO'to 100,000,000 centistokes.
These hïgh molecular weight' diorganopolysiloxane polymers are'prepared by methods known in the'art, as for example, by the methods set forth'in.U.S.'patents 2,445,794; 2,448,756;

2',:484,595 and 3,514,424. The:diorganopolysiloxane ~.'' polymers of the present:invention consist essentially ~ .
of silicon a~oms, oxygen atoms:and organic groups ~ ;
seIected.from the group consisting of alkyl such as lower alkyl, aryl such as phenyl, and~substituted p~enyl such :--- 4 -- .

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~as te~rachloro phenyl radicals, etc. and vinyl radicals and mix-tures thereof. Preferably, the or~anic ~roups are selected from the group consisting of methyl, phenyl and vinyl radicals. ~rom 1 to 35 mole percent of the organic groups being silicon-bonded S ¦aryl radicals, preferably phenyl radicals and from 0 to 2 mole Ipercent of the organic groups being silicon-bonded vinyl radicals.
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~ 'rhe aromatic carbonate polymers of the instant invention ' are polymers o dihydric phenols. The dihydric phenols that can be employed are bisphenols such as bis(4-hydroxyphenyl)-methane, 2,2-bis(4-hydroxyphenyl) propane (hereinafter referred to as bis-~
phenol-A), 2,2-bis(4-hydroxy-3-methylphenyl) propane, 4,4-bls(4-hydroxyphenyl) heptane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl) ~' ¦ propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl) propane, etc., dihydric phenol ethers such as bis(4-hydroxyphenyl) ether, bi~
lS (3,5-dichloro-4-hydroxyphenyl) ether, etc.; dihydroxydiphenyls such as p,p' dihydroxydiphenyl, 3,3'-dichloro-4,4'-dihydroxydi-1- ~phenyl, etc.; dihydroxyaryl sulfones such as bis(4-hydroxyphenyl) sulfone, bis(3,5-dimethyl-4-hydroxyphenyl) sulfone, etc., di-hydroxy benzenes, resorcinol, hydroquinone, halo- and alkyi~ '~1 '20 substituted dihydroxy benzenes such as 1,4-dihydroxy-2,$-dic~lor~-' ¦~
bcnzene, 1,4-dihydroxy-3-methylbenzene, etc., and dl~ydroxy di- ' phenyl sulfoxides such as bis(4-hydroxyphenyl) sulfoxide, bis-~ ¦(3,5-dibromo-4-hydroxyphenyl) sulfoxlde, etc.~ a variety of - ¦additional dihydric phenols are also available to provide 'carbon~t¦ polymers and are disclosed in U.S. patents 2,999?~35; 3,028,365 : ~ -5-. : ., :
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¦I $CH-li13 ! lCJ~5968i and 3,153,008. Also suitable for preparing the aromatic carbonate polymers are copolymers prepared ~rom any of the above copoly-merized with halogen-containing dihydric phenols such as 2,2-bis ¦(3,5-dichloro-4-hydroxyphenyl) propane, 2,2-bis(3,5-dibromo-4-Ihydroxyphenyl) propane, etc. Also employed in the practice of this invention may be blends o~ any o~ the abo~e materials to Iprovide the aromatic carbonate polymer. -I !
The aromatic carbonate polymers employed in the practice;
of this invention are those tha~ are prepared by reacting the di-¦hydric phenol with a carbonate precursor. The carbonate precursor may be either a carbonyl halide, a carbonate ester or a halofor~
mate. The carbonyl halides which can be employed herein are carbonyl bromide, carbonyl chloride and mixtures thereof. Typical of ~he carbonate esters which may be employed herein are diphenyl carbonate, di-~halophenyl) carbonates such asldi-~hlorophenyl) carbonate, di-(bromophenyl3 carbonate, di-(trichlorophenyl) carbonate, di-(tribromophenyl) carbonate, etc., di-(alkylphenyl)~
carbonate such as di-~tolyl) carbonate, etc., di-(naphthyl) oar-bonate, di-(chloronaphthyl) carbonate, phenyl tolyl carbonate, chlorophenyl chloronaphthyl carbonate, etc., or mixtures thereof.
The halofor=ates suitable for use herein include bi8-haloformates of dihydric phenols (bischloroformates of hydroqumone, etc.) or ¦ glycols (bishaloformates of ethylene glycol, neopentyl glycol, l polyethylene glycol, etc.). While other carbonate precursors ¦ will occur to those skilled in the art, carbonyl chloride also ¦ known as phosgene is preferre~.

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The aromatic carbonate polymers of this invention are prepared by employing a molecular weigh~ regulator al~d an acid ¦acceptor. The molecular weight regulators which may be employed ~lin carrying out the process of thi6 invention are phenol, cyclo-~jhexanol, methanol, para-tertiarybutylphenol~ parabromophenol, etc.
Preferably, para-tertiarybutylphenol is employed as the molecular weight regula~or.
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A suitable acid acceptor may be either an organic or an linorganic acid acceptor. A ~uitable organic acid acceptor is a 10 l tertiary amine and includes such materials as pyridi~e, triethyl-amine, dimethylaniline, ~ributylamine, etc. The inorganic acid acceptor may be one which can be either a hydroxide, a car~onate,~
a bicarbonate, or a phosphate of an alkali or alkali eareh ~¦
metal. ~
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¦ The aromatic carbonate polymer of this invention is selected from the group consisting of (1~ a polycarbonate oi a halogen subs~ituted dihydric phenol, (2) a copolyca~bona~e o~ an t unsubstitu~ed dihydric phenol and a halogen substi~uted dihydric :
phenol, (3) a mixture o~ (1) and (2), and (4) a mixture of a, ~0 member selected from the group consisting of (1), (2) and (3) with a polycarbonate of an unsubsti~uted dihydric phenol~
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Preferably, the aromatic carbonate polymer is a mixture ¦of (a) 30-99 weight percent of a polycarbonate of a dihydric ~ , ' .:

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phenol and correspondingly, (b) 70-1 weight percent of a copoly- -carbonate of 75-25 weight percent of the residue of a halogen -substituted dihydric phenol and correspondingly, 25 to 75 weight percent of the residue of a dihydric phenol; the halogen being selected from the group consisting of chlorine and bromine. More ; . -preferably, the aromatic carbonate polymer is a mixture of (a) , . . .
30-99 weight percent of a polycarbonate of a dihydric ph~nol and correspondingly, (b) 70-1 weight percent of a copolycarbonate of 75-25 weight percent of tetrabromobisphenol-A or tetrachlorbis-phenol-A and correspondingly, 25 to 75 weight percent of bis~ ;~
phenol-A.
Obviously other materials can also be employed with the aromatic carbonate polymer of this invention and include such materials as anti-static agents, pigments, mold release agents, `
stabilizers, etc.
The composition of this invention can be prepared by a number of procedures familiar to those skilled in the art, for example, a master batch of 50 parts of a homopolymer of bisphenol-A and 50 parts of the diorganopolysiloxane polymer. This master batch is then blended with the aromatic carbonate polymer. ~he master batch may be prepared by several known procedures. For example, one procedure involves placing the homopolymer of bis-phenol-A in a high intensity mixer and adding the diorganopoly-siloxane polymer to this. After the master batch is added to the ;'`' ' . : .

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aromatic carbonate polymer, it is fed into an extruder and then comminuted into pellets or other suitable shapes. This mixture is then fed into a conventional molding machine which produces a molded product.
Description of the Preferred Embodiment The following examples are set forth to illustrate more clearly the principle and practice of this invention to those skilled in the art. Unless otherwise specified, where parts or percents are mentioned, they are parts or percents by weight. ~, Example I
100 pounds of a mixture of (1) a carbonate homopolymer of ~isphenol-A having an intrinsic viscosity of 0.57 (measured in dioxane at 30C.) and (2) a carbonate copolymer of bisphenol-A
and tetrabromo-bisphenol-A (bromine content of approximately 27%) to give a powder blend containing 6% bromine by weight. The mixture is then fed into an extruder, and the extrudate is comminuted into pellets. The pellets are then injection molded into test bars whi~h are 1/16" x 1/2" x 5". These bars are then subjected to the Underwriters Laboratories Subject 94 flame test.
The results are given in the TABLE.

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Example II
100 pounds of a mixture of (1) a carbonate homopolymer of bisphenol-A having an intrinsic viscosity of 0.57 (measured in dioxane at 30C.) and (2) a carbonate copolymer of bisphenol-A
and tetrabromo-bisphenol-A (bromine content of approximately 27%) to give a powder blend containing 6% bromine is prepared~ To this is added a composition, by dry blending, of a 50-50 mixture ;
of a homopolymer of bisphenol-A and high molecular weight methyl phenyl vinyl siloxane to give a 1.0% level of the additive in the copolymer. The mixture is extruded into tes-t bars as in Example I
and subjected to the UL-94 flame test. The results are given in , tha TABLE.
Example III , Example II is repeated except that the final bromine content is adjusted to 5% by weight instead of 6%. The mixture is extruded into test bars as in Example I and subjected to the UL-94 flame test. The results are given in the TABLE.
~ Example IV
Example II is repeated except that the additive is ad-justed to a 0.5% level instead of 1.0%. The mixture is extruded `
into test bars as in Example I and subjected to the UL-94 flame test. The results are given in the TABLE.

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1~59681 Example V
Example IV is repeated except that the additive is a diphenyl dimethyl siloxane fluid (viscosity 190 centistokes) instead of the methyl phenyl vinyl siloxane. The mixture is ex-truded into test bars as in Example IV and subjected to the UL-94 flame test. The results are given in the TAsLE. ~-Example VI
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Example II is repeated ex~ept that the additive is a `
diphenyl dimethyl siloxane fluid (viscosity 190 centistokes) instead of the methyl phenyl vinyl siloxane. The mixture is ex-truded into test bars as in Example I and subjected to the UL-94 flame test. The results are given in the TABLE.
Example VII~
Example II is repeated except that the additive is adjusted to a 1.5% level instead of 1.0%. Also, the additive is a diphenyl dimethyl siloxane fluid (viscosity 190 centistokes) ,~-instead of the methyl phenyl vinyl siloxane. The mixture is extruded into test bars as in Example I and subjected to the UL-94 flame teet. The results are given in the TA~

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Example IV is repeated except that the additive is a dimethyl silicone fluid containing 3 mole percent tetrachloro-phenyl siloxy units, the remainder being methyl substituents and containing trimethyl siloxy chain stopping units (viscosity 70 centistokes) instead of the methyl phenyl vinyl siloxane additive. ~' The mixture i5 extruded into test bars as in Example IV and subjected to the UL-94 flame test. The results are given in the TABLE.
Example IX
Example II is repeated except that the additive is ad-justed to a 1.5~ level instead of 1.0%. Also, the additive is a dimethyl silicone fluid containing 3 mole percent tetrachloro- ' phenyl siloxy units, the remainder being methyl substituents and containing trimethyl siloxy chain stopping units (viscosity 70 centistokes`i instead of the methyl phenyl vinyl siloxane additive.
The mixture is extruded into test bars as in Example II and subjected to the UL-94 flame test. The results are given in the TABLE.
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The test bars of the Examples are evaluated in accordance with the ~est procedure of Underwriters Laboratories, Inc. Standard UL-94, September, 1~72, Vertical Burning Test for ;~
Classifying Materials. In accordance with the test procedure, materials are classified as either S~-0, SE-I or SE-II. The results are based on 5 specimens, each supported vertically.
The criteria for SE rating per UL-94 is briefly as follows:
"SE-0": Average flaming and/or glowing after removal of the igniting flame shall not exceed 5 ~-seconds and none of the specimens burn for -, longer than 10 seconds nor shall drip flaming '~
particles which ignite absorbent cotton that is placed 12 inches below the specimen.
"SE~ Average flaming and/or glowing after removal -of the igniting flame shall not exceed 25 seconds and no one sample shall exceed 30 seconds nor shall the specimen drip flaming particles that ignite absorbent cotton that is placed 12 inches below the specimen.
"SE-II'': Average flaming and/or glowing after removal of the igniting flame shall not exceed 25 seconds and no one sample shall exceed 30 seconds but the specimens may drip flaming -particles which ignite absorbent cotton.

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Further, UL-94 states that if only one specimen from a set of five specimens fails to comply wit:h the requirements, another set of five specimens shall be tested. All specimens from this second set shall comply with the appropriate requirements in order for the material in that thickness to be classified "SE-0",, "SE-I" -or "SE-II".
TABLE
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U.L. 94 Sample Classification -:
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Example I SE-II ~:.
Example II SE-0 Example III SE-0 Example IV SE-0 Example V SE-II
Example VI SE-II
Example VII SE-II ~~
Example VIII SE-II .
Example IX SE~
As seen by the Examples, the composition of the instant .
invention is classified as SE-0 while the compositions with no additive (Example I) and the compositions with a low molecular ~ :
weight polysiloxane (Examples V to IX) are classified as SE-II
when tested by the procedure of the UL-94 test.
It will thus be seen that the objects set forth above among those made apparent ~rom the preceding descrip-tion are - 14 - `~
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efficiently attained, and since certain changes may be made in carrying out the above process and in -the composition set forth without departing from the scope of this invention, i-t is intended that all matters contained in the above description shall be ~, interpreted as illustrative and not in a limiting sense.

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Claims (8)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A flame-retardant composition comprising in admixture (A) an aromatic carbonate polymer selected from the group consisting of (1) a polycarbonate of a halogen substituted dihydric phenol, (2) a copolycarbonate of a non-halogen substituted dihydric phenol and a halogen substituted dihydric phenol, (3) a mixture of (1) and (2); and (4) a mixture of a member selected from the group consisting of (1), and (2) with a polycarbonate of a non-halogen substituted dihydric phenol; and (B) from about 0.5 to about 1.5 parts by weight per 100 parts of said aromatic carbonate polymer of a diorgano-polysiloxane polymer gum wherein the organo substituents therein are selected from the group consisting of lower alkyl, aryl and vinyl radicals and mixtures thereof.

2. The composition of claim 1 wherein the aromatic carbonate polymer is a mixture of (a) 30-99 weight percent of a polycarbonate of a dihydric phenol and correspondingly, (b) 70-1 weight percent of a copolycarbonate of 75-25 weight percent of the residue of a halogen substituted dihydric phenol and, correspondingly 25 to 75 weight percent of the residue of a non-halogen substituted dihydric phenol.

3. The composition of claim 2 wherein the aromatic carbonate polymer is a mixture of (a) 30-99 weight percent of a polycarbonate of a non-halogen dihydric phenol and correspondingly, (b) 70-1 weight percent of a copolycarbonate of 75-25 weight percent of tetrabromobisphenol-A or tetrachloro-bisphenol-A and correspondingly 25 to 75 weight percent of bisphenol-A.

4. The composition of claim 1 wherein the aromatic carbonate polymer is a copolycarbonate of a halogenated bisphenol-A and a non-halogen substituted dihydric phenol.

5. The composition of claim 4 wherein the aromatic polycarbonate is a copolycarbonate of bisphenol-A and tetrachloro-bisphenol-A.

6. The composition of claim 4 wherein the aromatic polycarbonate is a copolycarbonate of bisphenol-A and tetra-bromo-bisphenol-A.

7. The composition of claim 4, 5 or 6 wherein the organopolysiloxane polymer gum has a viscosity of about 80,000,000 to 100,000,000 centistokes at 20°C.

8. The composition of claim 4, 5 or 6 wherein the diorganopolysiloxane polymer contains methyl, phenyl and vinyl groups.