CA1149984A - Flame retardant abs polymers - Google Patents

Abstract

FLAME RETARDANT ABS POLYMERS

Abstract:

Flame retardant ABS polymer compositions containing a halogenated styrene and a metal synergist such as antimony trioxide.

Description

078050~

FLAM~ RETARDANT ABS POLYMERS
Description Acrylonitrile-butadiene-styrene (ABS) polymers are engineering thermoplastics having excellent physical characteristics and are used in pipes and fittings, principally for drain, waste and vent, business machine housings, telephone housings, refrigerator doors and tank liners, luggage, sporting goods, building components and automobiles.
In many of these applications, such as telephones, business machines, building materials and appliances, it is necessary that the ABS polymer be flame retardant.
The use of heavily halogenated organic chemical com-pounds and a heavy metal oxide (antimony oxide) as additives to produce flame retarded ABS or styrenic compositions is well known. The commonly used, highly brominated aromatic organic compounds result in a number of adverse effects to the thermoplastic flame retarded products.
These adverse effects are (1) mold build-up of the brominated compound during processing with resultant surface degradation o~ molded parts, (2) severe degradation of overall balance of physical properties of the ABS polymer, parti-cularly heat distortion and impact strength, (3) poor e~iciency, i.e., high levels of halogen and antimony oxide are requi~ed to obtain adequate flame retardancy in thin sections, and (4) bloom or extrudate of flame retardants onto surface of molded specimens.
These adverse e~fects, in general, are du~ to the low molecular weight, volatility and incompatibility of the halogenated organiccompounds with the thermoplastic polymers.

~' 078050~ 9~84 Various attempts have been made to avoid the use of halogenated additives in the preparation of flame retardant ABS polymers. One such attempt is found in U. S. Patent

2,842,518 wherein the butadiene of the ABS polymer is re-placed with chloroprene, and a third halogen monomer,vinylidene chloride, is added to the styrene and acrylo-nitrile in the preparation of the polymer. No additives are thus necessary to obtain a flame retardant polymer.
Another like attempt is found in U. S. Patent 4,017,559 which discloses a polyblend of (1) a styrene-acrylonitrile copolymer, (2) a graft polymer prepared by polymerizing styrene and acrylonitrile in the presence of polychloroprene,

(3) a graft polymer prepared by polymerizing styrene and acrylonitrile in the presence of polybutadiene and (4) antimony trioxide. The grafted chloroprene provides the polyblend with good physical characteristics and flame retardancy without sacrificing the heat distortion temperature. The patent mentions, incidentally, at coll~n 2, lines 66-68, that the monovinylidene aromatic monomer may be halogen substituted to provide an additional halogen source for ilame retarding. No specific teaching of such substitution, however, is disclosed.
The present invention relates to a flame retardant polymer based on interpolymers of styrene, mono or dihalo styrene, acrylonitrile and butadiene formulated with a metal oxide synergist. The flame retardant polymers of this invention are inherently flame retardant requiring no additional halogen additives.
Incorporation of the halogenated moiety into the thermoplastic polymer eliminates the aforementioned adverse effects of adding halogenated organic compounds to ABS
polymers.

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078050~ 4 The present invention relates to the use of ring-ha-logenated styrenes to prepare interpolymers of ABS, SAN
or other styrenic compositions, which when formulated with metal oxides such as antimony oxide, normal process aids and stabilizers, produce optimum flame retardant thermo-plastic products.
The flame retardant ABS polymers of the present in-vention are prepared in substantially the same manner as is used in preparing conventional ABS polymers, i.e., styrene and acrylonitrile are polymerized in the presence of a butadiene rubber or a graft ABS containing a greater amount o~ butadiene rubber is blended with a rigid styrene-acrylonitrile (SAN) copolymer. The difference is that a halogenated styrene is substituted for a part of the styrene in the high rubber gra~t ABS or in the rigid SAN copolymer, or in both, and a metal synergist is added to the ABS con-taining the halogenated styrene. The rubber of the high rubber graft is preferably polybutadiene but may be a copolymer o~ butadiene and a monomer such as styrene or acrylonitrile. While styrene is the preferred monomer in the high rubber graft ABS and the SAN, other monovinylidene aromatic monomers may be used, especially alphamethylstyrene.
Likewise, while acrylonitrile is the pre~erred monomer of the composition, other vinyl cyanides such as ethacrylo-nitrile and methacrylonitrile may be employed.
The halogenated styrene o~ the high rubber graft ABS, the SAN, or both, is preferably monobromostyrene but may be other halogenated styrenes such as monochlorostyrene or ortho, para and di chlorostyrene and bromostyrene.
In preparing the flame retardant ABS polymers of the present invention, the diene rubber content o~ the polymers ~``~ 078050~ 3~ ~

may range ~rom 15 to 60 parts by weight, based on 100 parts by weight of the flame retardant ABS polymer; the styrene content may range from 20 to 60 parts by weight; the halogenated styrene from lO to 50 parts by weight; and the acrylonitrile ~rom 15 to 35 parts by weight. When brominated styrene is employed as the halogenated styrene, sufficient brominated styrene monomer should be used to provide from 4% to 20% bromine in the ABS polymer. The preferable range of bromine in the polymer is 8% to 17%.
While antimony trioxide is the preferred metal synergist, other synergists may be substituted therefor. U. S. Patent

4,016,139 discloses a wide variety of synergists for use with halogenated compounds. The amount of synergist which is necessary to impart good flame retardancy to the polymers oi this invention varies between 4 and 10 parts per lO0 parts o~ ABS polymer. The preferred amount is from about 6.5 to 7.5 parts per lO0 parts of polymer.
The present invention will be more clearly understood ~rom the following examples which set forth a number of the exemplary halostyrene con~taining interpolymers prepared in accordance with the present invention. In each o~ the examples all parts are by weight, unless otherwise indicated.
Example 1 To a stirred reactor was added:
Polybutadiene (latex) 40 DM Water 216 Sodium Tallowate 3.75 Sodium Hydroxide 0.120 The temperature of the stirred polybutadiene emulsion was raised to 60C and to the stirred emulsion was charged.

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078050-M ~ 4 Styrene 12.2 Acrylonitrile 21.45 ~ono Bromostyrene 45.77 Tert Dodecyl Mercaptan 0.1125 Cumene Hydroperoxide 0.516 Sodium Pormaldehyde Hydrosul~ite 0.500 Ferrous Sulfate 0.009 The monomer and catalysis was charged over a period of 90 minutes and the reaction mixture was stirred for one hour at 60C after completion of monomer addition.
The latex was coagulated using Ca Cl2 and dried in a hot air oven at 65C.
Example l was repeated while varying the composition of the iour primary monomers and in some cases eliminating the halostyrene to prepare controls. These examples are listed in Table 1 below.
Table 1 Example 1 2 3 4 Polybutadiene 40 30 20 40 Styrene 12.2 12.2 38.78 38.55 ~ono Bromostyrene 45.77 55.77 22.20 None ' Acrylonitrile 21.45 21.45 28.6 21.45 T-DDM 0.112 0.112 0.200 0.112 % Conversion g9 99 99 97-98 % Insolubles 64.7 71.2 44.3 64.9 Graft Ratio .61 .78 1.21 .62 % Br (total polymer) 16.86 24.68 9.24 None % Br (rigid) 18.65 27.55 10.72 None % Br (gra~t) 13.26 21.70 5.46 None Mn (rigid) 35,000 34,000 30,000 37,000 DSC 15/Min.Air 186 205 202 192 ~ : :
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078050~

Stabilizers and process aids were added to the graft ABS polymers of Examples 1-4 inclusive and in the case of the graft polymers of Examples 1, 2 and 4 sufficient poly-SAN of 6700 Mn was added to reduce the rubber level of the 6 composition to 20 phr and the halogen content to 8.5 - 11.8%.
The components are blended with antimony oxide synergist at a 2 to l or 3 to l halogen to antimony oxide ratio to prepare a ~lame retardant ABS without addition of a halogen containing additive. These flame retardant ABS polymers are identified as polymers A-D inclusive in Table II below:
Table II
Flame Retardant ABS ~ ymer A B C D
From Example 1 50 15 From Example 2 --- 66.6 --- ---From Example 3 --- --- 100 ---From Example 4 --- --- --- 50 polySAN (6700 Mn) 50 33.4 --- 50 Antimony Trioxide 7.5 7.5 7.5 7.5 1,2-bis (2,4,6-trlbromo- --- --- --- 24 phenoxy) ethane (Prior Art) Magnesium Stearate 0.75 0.75 0.75 0.75 Flamma~ility and Physical Properties Oxygen Index 30.0 31.0 27.5 29.0 UL 94 (60 Mils) V-O V-O V-l V-O
Tensile Strength 5200 5200 5375 5152 Falling Dart Impact 15-16 16-18 18-20 10-12 Notched Izod Impact 3.9 4.2 6.2 3.2 ,.' . ~
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Example 1 was repeated to prepare interpolymers of halogenated styrenes without the rubber phase present.
Co and terpolymers were prepared containing varying com positions of the four primary monomers and in some cases eliminating the styrene. These examples are listed in Table III.

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To establish the performance of the halostyrene rigid phase polymers of Table III for uses in preparing flame retardant ABS polymers, the rigid polymers of Table III are used in accordance with the recipes of Table IV to produce a final composition that contains 18 to 20 phr graft rubber. Halogen concentration of the final Flame Retardant ABS compositions was adjusted by adding small amounts of polySAN from Example 5.
For all examples specimens were prepared by mixing the components in a Banbury mixer 3 minutes at 320F.
The composition was sheeted off on a two-roll mill, cooled, ground and compression or injection molded to form 60 mil or 125 mil test specimens.

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078050-M 1~ 4 Bloom or Extrudate Test Flame Retardant ABS Polymers A-G inclusive of Tables II and IV were tested for bloom by injection molding test specimens. The test specimens (tensile bars) were placed in a hot air oven at 160F and were rated for bloom by comparing the flame retarded specimens with an ABS
control containing no ~lame retardant. Samples ~were removed and inspected at the end of 24, 48, 72, 120 and 168 hours and were rated on the following scale:
0 - no bloom 1 - very slight bloom 2 - slight bloom - 3 - medium bloom 4 - severe bloom 5 - very severe bloom The test results are tabulated in Table V below.
TABLE V
Bloom Rating (Hours) 24 48 - 72 120 168 * Control (ABS) 0 0 0 0 Polymer A (Table II) 0 0 0 0 0 Polymer B (Table II) 0 0 0 0 0 Polymer C (Table II) 0 0 0 0 0 Polymer D (Table II) 1 4 5 -- --Polymer E (Table IV) 2 4 5 -- __ Polymer F (Table IV) 0 0 0 0 0 Polymer G (Table IV) 0 0 0 0 0 -* Control ABS contains 20 parts polybutadiene, 54 parts styrene and 26 parts acrylonitrile.

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Referring to Table V above, the flame retardant ABS polymers prepared from halogenated styrene inter-polymers, Polymers A-D, F and G, did not bloom or show surface extrudate during the test. The flame retardant ABS polymers containing an additive halogen flame retardant, Polymers D and E, showed se~ere bloom after 48 hours of exposure to the test conditions.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flame retardant ABS composition comprising by weight of from about 15 to about 60 parts of a diene rubber selected from the group consisting of polybutadiene, butadiene-styrene copolymer and butadiene-acrylonitrile copolymer, from about 20 to about 60 parts of a monovinylidene aromatic hydrocarbon, from about 15 to about 35 parts of a vinyl cyanide, from about 10 to about 50 parts of a halogenated monovinylidene aromatic hydrocarbon; and from about 4 to about 10 parts of a metal synergist.

2. A flame retardant ABS composition in accordance with claim 1 wherein the diene rubber, at least a portion of said monovinylidene aromatic hydrocarbon and at least a portion of said vinyl cyanide form an ABS graft copolymer.

3. A flame retardant ABS composition in accordance with claim 1 wherein said diene rubber and, at least a portion of each of said monovinylidene aromatic hydrocarbon, said vinyl cyanide and said hologenated monovinylidene aromatic hydrocarbon form an ABS graft polymer.

4. A flame retardant ABS composition in accordance with claim 1, 2 or 3 wherein the diene rubber is polybutadiene, the monovinylidene aromatic hydrocarbon is styrene, the vinyl cyanide is acrylonitrile and the halogenated monovinylidene aromatic hydrocarbon is monobromostyrene.

5. A flame retardant ABS composition in accordance with claim 1, 2 or 3 wherein the diene rubber is polybutadiene, the monovinylidene aromatic hydrocarbon is styrene, the vinyl cyanide is acrylonitrile and the halogenated monovinylidene aromatic hydrocarbon is monobromostyrene, and wherein the metal synergist is antimony trioxide.

6. A flame retardant ABS composition in accordance with claim 1 wherein the ABS composition comprises (L) a graft ABS polymer comprising by weight of about 15 to about 35 parts polybutadiene, from about 30 to about 45 parts styrene, from about 15 to about 30 parts monobromostyrene and from about 20 to about 32 parts acrylonitrile and (2) about 7.5 parts antimony trioxide.

7. A flame retardant graft ABS polymer comprising by weight of about 20 parts polybutadiene, about 39 parts styrene, about 22 parts monobromostyrene, about 29 parts acrylonitrile and about 7.5 parts antimony trioxide.

8. A flame retardant composition in accordance with claim 3 comprising about 20 parts polybutadiene, about 41 parts styrene, about 26 parts acrylonitrile, about 23 parts monobromo-styrene and about 7.5 parts antimony trioxide, wherein 20 parts polybutadiene, 6 parts styrene, 11 parts acrylonitrile and 23 parts monobromostyrene from an ABS graft copolymer.

9. A flame retardant ABS composition in accordance with claim 2 comprising about 18 parts polybutadiene, 11.5 parts styrene, 22.5 parts acrylonitrile, 25 parts monochlorostyrene, 21 parts monobromostyrene and 7.5 parts antimony oxide, wherein 18 parts polybutadiene, 11.5 parts styrene and 6.5 parts acrylonitrile form an ABS graft copolymer.

10. A flame retardant ABS composition in accordance with claim 2 comprising about 20 parts polybutadiene, about 26 parts styrene, about 22.5 parts acrylonitrile, about 32.5 parts monobromostyrene and about 6.5 parts antimony trioxide, wherein 20 parts polybutadiene, 13 parts styrene and 7 parts acrylonitrile form an ABS graft copolymer.