CA1139038A - Polycarbonate compositions having improved flame retardance and improved water vapor transmission - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Improved flame retardance and improved water vapor transmission are imparted to high molecular weight aromatic polycarbonate resins by selecting appropriate diphenols and controlling the degree to which these particular diphenols are halogenated.

Description

~ ~33~ 8CH-2526 This invention re]ates to aromatic polycarbonate resinshaving improved flame retardance and improved water vapor transmission.
BACKGROUND O~ THE I~VENTION
Polycarbonate polymers are known as being excellent molding materials since products made therefrom exhibit such properties as high impact strength, toughness, high transparency, wide temperature limits (high impact resistance below -60C and a U~
thermal endurance rating of 115C with impact), good dimensional stability, good creep resistance, and the like. It would be desirable to add to this list of properties that of improved flame retardance so that products made from such polycarbonate polymers could be safely used by the consumer and also meet the increasing requirements of certain flame retardant criteria being established by local and federal government agencies as well as the manufacturers of such products. It would also be desirable to improve the moisture barrier property of such poly-carbonates thereby enabling them to be used in a wider range of product applications.
It is known to obtain polycarbonates which contain halogen-ated monomers as -their main, polymeric building blocks. For example, U.S. Patent 3,028,365 discloses a host of polycarbonate compositions including tetrabromobisphenol-A and a dichloro-methylenediphenol monomer, as well as processes for obtaining these polycarbonates.
U.S. Patent 3,062,781 discloses that halogenated polycar-bonates can be obtained by first halogenating a diphenol contain-ing at least two halogen substituents. However, the only dihalogenated diphenol disclosed is dichlorobisphenol-A.
German Patent P25 20 317.2 discloses that halogenated poly-carbonates can be obtained by halogenating bisphenol-A

~3~03~ 8C~1-2526 (~,4~-isopropylidenediphenol) to produce a mix-ture of unreacted bisphenol-A and statistical mixtures of halogena-ted bisphenol-A
(BPA). The halogenated bisphenols disclosed comprise, primarily, tri- and tetrahalogenated BPA.
In general, these prior art re~erences recogniæe that flame retardance can be imparted to polycarbonates by halogenating the monomeric building blocks from which they are obtained. In addition, these references suggest that the greater the degree of halogenation of the monomer, the better will be the fire retar-dance imparted to the polymer. U.S. Patent 3,062,781 also indicates that halogenated diphenols have reduced permeability to steam. However, none of these references discloses or sugges-ts that a high molecular weight aromatic polycarbonate resin having improved flame retardance as well as improved water vapor trans-mission can be obtained from particular halogenated diphenols.
SUMMARY OF THE INVENTION
It has now been found that improved flame retardance and water vapor transmission can be imparted to high molecular weight, aromatic polycarbonate resins by selecting appropria-te diphenols to be halogenated. In general, -this is accomplished by control ling the degree to which the particular diphenols are halogenated.
Accordingly, the diphenols are halogenated so that there are obtained either highly pure dihalogenated diphenols or predeter-mined statistical mixtures comprising predominantly mono- and dihalogenated diphenols together with some unreacted diphenol.
Preferably, these predetermined, statistical, halogenated diphenol mixtures can be continuously obtained by either:
(l) dissolving or suspending the diphenol in a solvent system comprising methylene chloride and water and thereafter introducing ~,~; ;, .
.~

~ CH-2526 a halogen into the solven~ system; or, (2) dissolving or suspending the diphenol in methylene chloride and then reacking the diphenol with sulfuryl chloride and, optionally, introducing another halogen therein; or (3) dissolving or suspending the diphenol in methylene chloride and then introducing a halogen therein while concurrently purging the reaction with an inert gas. These processes are described inter alia in United States Patent 'L~O. 4,210,765 aated July 1, 1980, which is assigned to the same assignee of this case.
While any of the halogens can be employed, chlorine and bromine are preferred~ Thus, the diphenols that can be used to obtain the high molecular weight aromatic polycarbonates of the invention can be represented by the general form~lla Xn (I) C\ { ~ OH

Xm ~ Y

wherein Xm and Xn can each independently be a halogen and mixtures thereof; m and n are each 0.0 to about 2.5 with the proviso that m + n equal at least 0.1 and no more than about 2.5;
and, Y and Y' can independently be hydrogen and a halogen, preferably chlorine or bromine. In formula I above, the values for m and n represent the number of halogen substituen-ts per mole of monomer.
It is possible to employ two or more different diphenols or a copolymer with a glycol or with hydroxy or acid terminated polyester, or with a dibasic acid in the event a carbonate copolymer or interpolymer rather than a homopolymer is desired for use in preparing khe aromakic polycarbonate. Blends of any of these materials can also be used -to obtain the aromatic poLycarbonates.

~CLI-2526 , These halogenated diphenols can then be employed to obtain th~
high molecular weight aromatic polycarbonates of the invention which can be linear or branched homopolymers or copolymers as well as mixtures thereof or polymeric blends and which generally have an intrinsic viscosity (IV) or about 0.40-].. 0 dl/g as measured in methylene chloride at 25C. These high molecular weight aromatic polycarbonates can be typically prepared by reacting the halogenated diphenol with a carbonate precursor.
~he carbonate precursor used can be either a carbonyl halide, a carbonate ester or a haloformate. The carbonyl halides can be carbonyl bromide, carbonyl chloride and mixtures thereof. The carbonate esters can be diphenyl carbonate, di-(halophenyl) carbonates such as di-(chlorophenyl) carbonate, di-(bromophenyl) carbonate, di-(trichlorophenyl) carbonate, di-(tribromophenyl) carbonate, etc., di-(alkylphenyl) carbonate such as di(tolyl) carbonate, etc., di-(naphthyl) carbonate, di-(chloronaphthyl) carbonate, phenyl tolyl carbonate, chlorophenyl chloronaphthyl carbonate, etc., or mixtures thereof. Th~ haloformates that can be used include bis-haloformates o~ dihydric phenols (bischloro-formates of hydroquinone, etc.) or ylycols (bishaloformates of ethylene glycol, neopentyl glycol, polyethylene glycol, etc.).
While other carbonate precursors will occur to those skilled in the art, carbonyl chloride, also known as phosgene, is preferred.
Also included are the polymeric derivatives of a dihydric phenol, a dicarboxylic acid and carbonic acid such as are disclosed in U.S. Patent 3rl69,121 dated February 9, 1965 -Goldberg.
Molecular weight regulators, acid acceptors and catalysts can also be used in obtaining the aromatic polycarbonates o~ tllis ;~.

invention. The use~ul molecular weight regulators inclu~e mono-hydric phenols such as phenol, chroman-I, paratertiarybutylphenol, parabromophenol, primary and secondary amines, etc. Preferably, phenol is employed as the molecular weight regulator.
A suitable acid acceptor can be either an organic or an inor~anic acid acceptor. A suitable organic acid acceptor is a tertiary amine such as pyridine, triethylamine, dimethylaniline, tributylamin~, etc. The inorganic acid acceptor can be either a hydroxide, a carbonate, a bicarbonate, or a phosphate of an alkali or alkaline earth metal.
The catalysts which can be employed are those that typically aid the polymerization of the diphenol with phosgene. Suitable catalysts include tertiary amines such as triethylamine, tripro-pylamine, N,N-dimethylaniline, quaternary ammonium compounds such as, for example, tetraethylammonium bromide, cetyl triethyl ammonium bromide, tetra-n-heptylammonium lodide, tetra-n-propyl ammonium bromide, tetramethylammonium chloride, tetramethyl ammonium hydroxide, tetra-n-butyl ammonium iodide, benzyltrimethyl ammonium chloride and quaternary phosphonium compounds such as, for example, n-butyltriphenyl phosphonium bromid~ and methyl triphenyl phosphonium bromide.
Also included herein are branched polycarbonates wherein a polyfunctional aromatic compound is reacted with the diphenol and carbonate precursor to provide a thermoplastic randomly branched polycarbonate. These polyfunctional aromatic compounds contain at least three functional ~roups which are carboxyl, carboxylic anhydride, haloformyl, or mixtures thereof. Illus-tra-tive of polyfunctional aromatic compounds which can be employed include trimellitic anhydride, trimellitic acid, trimellityl trichloride, 4-chloroformyl phthalic anhydride, pyromellitic acid, pyromelli-tic dianhydride, mellitic acid, mellitic anhydride, t:rimesic acid, ~ 8C~1-2526 benzophenonetetracarboxylic acid, benzophenonetetracarboxylic anhydride, and the like. The preferred polyEunctional aromatic compounds are trimellitic anhydride and trimellitic acid or their acid halide derivatives.
Blends of linear and branched aromatic polycarbonates are also included within the scope of this invention.
Other well known materials can also be employed for their intended function and inc]ude such materials as anti-sta-tic agents, mold release agents, thermal stabili~ers, ultraviolet light stabilizers, reinforcing fillers such as glass and other inert fillers, foaming agents, and the li~e.
Accordingly, the high molecular weight aromatic polycarbon-ates of the invention can be represented by the general formula (II) ~ {~ I ~ O -- C

wherein Xm, Xn, m, n, Y and Y' are the same as identified in formula I above.
PREFERRED EMBODIMENT OF THE INVENTIQN
The following examples are set forth to more fully and clearly illustrate the present invention and are intended to be, and should be construed as being, exemplary and not limitative of the invention. Unless otherwise stated, all parts and percentages are by weight.
In the following examples, the ilame retardancy of the poly-carbonates obtained was determined by feeding the polycarbonates into an extruder which was operated at about 26SC and the extrudates were each cornminuted into pellets. The pellets were then injection molded at about 3l5C in-to test bars of about 5 in.

.~. . .
~.

~CH-2526 by 1/2 in. hy about 1/16-1/8 in. thick. The test bars (5 for each polycarbonate) were then subject to the test procedure set forth in Underwriters' Laboratories, Inc. Bulletin UL-94, Burning Test for Classifying Materials. In accordance with this test procedure, materials so investigated are rated either V 0, V-I or V-II based on the results of 5 specimens. The criteria for each V tfor vertical) rating per UL-94 is briefly as follows:
"V-0": Average flaming and/or glowing after removal of the igniting flame shall not exceed 5 seconds and none of the specimen5 shall drip flaming particles which ignite absorbent cotton.
"V-I": Average flaming and/or glowing after removal of the igniting flame shall not exceed 25 seconds and the glowing does not travel vertically for more than 1/~" of -the specimen after flaming ceases and glowing is incapable of igniting absorbent cotton.
"V II": Average flame and/or glowing after removal of the igniting flame shall not exceed 25 seconds and the specimens drop flaming particles which ignite absorbent cotton.
In addition, a test bar which continues to burn for more than 25 seconds after removal of the igniting flame is classified, not by UL-94, but by the standards of the instant invention, as "burns".
~5 Further, UL-94 re~uires that all test bars in each test group must meet the V type rating to achieve the particular classifica-tion Otherwise, the 5 bars receive the rating of the worst single bar. For example, if one bar is classified as V-II and the other four (4) are classified as V-0, then the rating for all would be V-II.

-~;r ,~ - 7 ~CH-2S26 0~

The moisture barrier properties for the polycarbonates and copolycarbonates in the ensuing examples were determined using Modern Controls, Inc. instruments, i.e., water vapor transmission rate (WVTR) measurements were obtained on an I~D-2C instrument pursuant to ASTM F-372-73. This method is based on infrared analysis and the results obtained are expressed in grams/24 hrs./
100 in.2/mil at 100F and 90~ relative humidity (RH).

~ Compound: 2,2'-Dichloro-4,4'-(dichlorovinylidene)diphenol (DCDVD) Into a slurry of 281.14 parts by weight (l.0 partmole) of 4,4l-(dichlorovinylidene)diphenol (DVD) in 2000 parts by volume methylene chloride that was purged continuously with a slow stream of nitrogen, there was introduced, at ambient temperature, in the course of ca. 5 hours, 142 parts by weight (2.0 partmole) of chlorine gas. At the end of the slightly exothermic reaction, only a small amount of DVD remained undissolved. This was filtered off and the essentially colorless solution was analyzed by gas chroma-tography, which indica-ted -the following compos:ition:
Retent~on Composition Compound _ Time (Min.) (Mole %) 4,4'-(dichlorovinylidene)diphenol (DVD)18.97 0.2

2-chloro-4,4'-(dichlorovinylidene) 20.11 8.6 diphenol (CDVD) 2,2 7 -dichloro~4,4'-(dichlorovinylidene)20~91 91.0 diphenol (DCDVD) 2,2',~'-trichloro-4,4'-(dichlorovinyli- 21.91 0.2 dene)diphenol (TCDVD) p-cumylphenol (reference) 12.36 Incremental addition of 2.8 parts by weight of more chlorine raised the assay of dichloro-DVD (DCD~D) as follows:

~ 3~8CH-2526 Compound Composition (Mole %) CDVD 2.2 TCDVD 4.1 Washings of the nearly colorless methylene chloride solution with water produced a yellow methylene chloride solution tha-t was separated from the aqueous phase. Circa one-fourth of its volume of methanol was added to it and decolorized by stirring the yellow solution with 5 parts by wei~ht zinc powder for about 1 hour. Filtration an~ evaporation of the solvent mixture on a rotary evaporator left behind a white crystalline mass that was recrystallized from a mixture of hexane and cyclohexane (1.0:1.5 volume ratio). The colorless crystals of 2,2'-dichloro-4,4'-(dichlorovinylidene)diphenol thus ob-tained had an assay of 99.1%
and a melting point of 110.0-110.5C. Elemental analysis confirmed its composition. Chlorine: found, 40.6; theoretical, 40.5~. Carbon: found, 4~.0; theoretical, ~8.0~ ~Iydrogen: found, 2,2; theoretical, 2.3%.

Preparation of the polycarbonate of 2,2'-Dichloro-4,4' ~ )diphenol Into a mixture of 87.5 parts by weight (0.25 partmole) 2,2'-dichloro-4,4'-(dichlorovinylidene)diphenol (DCDVD), 300 parts by volume water, 300 parts by volume methylene chloride, 0.47 parts by weight phenol and 0.5 parts by weight triethylamine, there was introduced, at ambient temperature, 30 parts by weight phosgene in 30 minutes while maintaining the p~ value of the two-phase system at approxima'cely 11 (between 10 and 12~5) by simultaneously '~' .,~.

8CH~252~
t~3~38 adding a 25 percent sodium hydroxide solution. ~t the end of the addition period, the pH of the aqueous phase was 11.4 and the DCDVD content o~ this phase was less than l part per million, as determined by ultraviolet analysis. The methylene chloride phase was separated from the aqueous phase, washed with an excess of dilute lO.01 normal) a~ueous hydrochloric acid, and three times with deionized water. The polymer was precipitated by adding the neutral and salt-free methylene chloride solution to an excess of methanol and filtering off the white polymer, which was dried at 95C. The resultant pure DCDVD polycarbonate had the properties shown in the Table.

The procedure of Example 2 was repeated except that DCDVD
was replaced with a mixture of 43.75 parts by weight DCDVD (0.125 partmole) and 28.5 parts by weight 4,4'-isopropylidenediphenol, (BPA) (0.125 partmole). Work-up of the reaction product yielded a copolycarbonate with the properties shown in the Table.

The procedure of Example ?. was repeated, except that DCDVD
was replaced with a mixture consisting oE 21.9 parts by weight DCDVD (0.0625 partmole) and 42.75 parts by weight 4,4'-isopropyli-denediphenol (BPA) (0.1875 partmole). The resultant polycarbonate had the properties shown in the Table.

Preparation of a New Ternary Composition The procedure of Example 1 was repeated except that 71.0 parts by weight (1.0 partmole) chlorine was employed. At the end of the reaction, gas chromatographic analysis indicated the following composition:

Reten~ion Composition Diphenol Compound Time (Min.) (Mole %) 4,4'-(dichlorovin~lidene)diphenol 20.80 28.7 2-chloro-4,4'-(dichlorovinylidene) 22.34 45.2 diphenol 2,2'-dichloro-4,4'-(dichlorovinylidene) 23.52 26.1 diphenol p-cumylphenol (reference) 15.32 ~AMPLE 6 The procedure of Example 2 was repeated except for substitu-ting an equivalent amount of the ternary mixture (78.9 parts by weight) Gbtained in Example 5, for the 87.5 parts by weight of DCDVD. A colorless, tough polycarbonate was obtained having the properties set forth in the Table.

Preparation of a New Compound: 2,2'-Dibromo-4,4'-(dichlorovinylidene)diphenol The procedure of Example l was repeated, except that the chlorine gas was replaced with an equivalent amount of liquid bromine (320.0 parts by weight, 2 partmole), diluted with five fold its volume of methylene chloride. After decolorization with zinc powder and purification by charcoaling a white crystalline mass, comprising 2,2'-dibromo-4,4'-(dichlorovinylidene)diphenol was obtained that, after recrystallization from a hexane-cyclo-hexane mixture (1:1) yielded white crystals of 97.8% purity and 107.5-108.5C melting point. Elemental analysis confirmed the composition. Chlorine: found 16.1; theoretical, 16.2%. Bromine:
found 36.6; theoretical, 36.4%. Carbon: found 38.1; theoretical, 38.3%. Hydrogen: found, 1.8; theoretical, 1.8%.
EX~MPLE 8 The procedure of Example 2 was repeated except that 109.7 parts by weight (0.25 partmole) of 2,2'-dibromo-4,4'-(dichloro-~ 8CH-2526 vinylidene)diphenol was usea in place of DCDVD. A polycarbonate was obtained havin~ the properties set forth in the Table.
TABLE
Properties of Polycarbonates and Copolycarbonates UL Ratin~
ExampleSpecimen Thickness No. _ I.V. 1.56 mm 3.13 mm WVTR
2 0.55 V-0 V-0 1.4

3 0.588 V-0 V-0 3.3

4 0.592 V-0 V-0 6.1 6 0.576 V-0 V-0 1.8 8 0.482 V-0 V-0 3.0 As the results in the foregoing table reveal, excellent flame retardance is imparted to the polycarbonates and copolycar-bonates of the invention while concurrently improving their water vapor transmission properties.

Claims (6)

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

1. A high molecular weight aromatic polycarbonate having improved flame retardance and improved water vapor transmission, said polycarbonate having an I.V. of about 0.40-1.0 dl/g and being represented by the general formula wherein Xm and Xn can each independently be a halogen and mixtures thereof; m and n are each 0.0 to about 2.5 with the proviso that m + n equal at least 0.1, but no more than about 2.5 and, Y and Y' can independently be hydrogen and a halogen.

2. The polycarbonate of claim 1 wherein Xm and Xn are each chlorine.

3. The polycarbonate of claim 1 wherein Xm and Xn are each bromine.

4. The polycarbonate of claim 1 wherein m + n equal 1.5.

5. The polycarbonate of claim 1 wherein Y and Y' are each hydrogen.

6. The polycarbonate of claim 1 wherein Y and Y' are each chlorine or bromine.