FLAME RETARDANT POLYGLUTARIMIDE COMPOSITIONS AND METHOD OF MAKING THEM

Abstract: In the compositions and methods of the invention, flame resistance is imparted to polyglutarimide by the blen­ ding therewith of decabromodiphenyl oxide having an aver­ age particle size of less than 12 microns. The physical properties such as impact strength and heat distortion pro­ perties are not unacceptably reduced. Preferred composi­ tions also include antimony trioxide and/or zinc borate and impact modifiers, preferably acrylic- or butadiene- based are preferably included, as is polycarbonate. The preferred average particle size of the decabromodiphenyl oxide is 8 to 10 microns.

Description: FLAME RETARDANT POLYGLUTARIMIDE COMPOSITIONS AND METHOD OF MAKING THEM This invention is concerned with flame retardant polyglutarimide compositions and method of making them. The field to which the invention relates is the imparting of flame retardant properties to thermoplastic polyglutarimide-containing compositions. Many hundreds of compounds are known which impart flame resistance to thermoplastic systems, see Kirk Othmer, Encyclopaedia of Chemical Technology, Second Edition, Volume 9, page 301. However, it has generally proved extremely difficult to achieve a high degree of flame resistance without harming other physical properties such as impact strength and heat distortion temperature, especially in aliphatic polymers. The particular flame retardants used in this invention are well known per se, but they have not previously been shown in combination with polyglutarimides as flame retardants in which respect they have surprisingly little adverse effect on other physical properties, particularly impact strength and heat distortion temperature. The compositions of the invention comprise a mixture of polyglutarimide and decabromodiphenyl oxide having an average particle size of less than 12 microns. Advantageously the compositions of the invention also contain one or more of antimony trioxide and zinc borate, which we have found to act synergistically with the decabromodiphenyl oxide in these compositions. We have discovered the unexpected importance of the particle size of the decabromodiphenyl oxide on the physical properties of the compositions. The polyglutarimides used in the present invention are preferably those disclosed in Belgian patent 848,496. Other polyglutarimides are also suitable in this invention, but those disclosed by the Belgian patent are very much preferred because of their superior properties. Generally, these glutarimide polymers are prepared from acrylic polymers such as poly(methyl methacrylate) and copolymers thereof by reaction as described with ammonia or methylamine so that 1 to 100% by mole of the acrylic ester groups are imidized. The optimum results are obtained with degrees of imidization of 20 to 100% by mole. The weight average molecular weights of the preferred glutarimide polymers are typically about 100,000 to 200,000. It is also very highly preferred to further include in the compositions of the invention butadiene- or acrylicbased multiple stage polymer to impart additional impact strength to the polyglutarimide component. The butadienebased multiple stage polymer can be of MBS (methacrylatebutadiene-styrene) type or ABS (acrylonitrile-butadienestyrene) type. For example, multiple stage polymers having a butadiene-styrene first stage, a styrene second stage, and a methylmethacrylate-styrene final stage or an acrylonitrile-styrene final stage can be used. The acrylic-based multiple stage polymer can have a crosslinked butylacrylate first stage and a methylmethacrylate final stage. Ratios of rubber stage to hard stage can be varied from about 1:1 to about 9:1 by weight. Suitable amounts of butadiene or acrylic-based multiple stage polymer are typically about 5 to 40% by weight, and preferably about 15 to 35% by weight of the blend of the polyglutarimides, butadiene-based or acrylic-based impact modifier, flame retardant, and optional polycarbonate. European Patent Application No. 79302791.3 teaches the inclusion of polycarbonate in polyglutarimide compositions to achieve unexpectedly high Izod impact strength and Gardner VHIT impact values, especially when the polycarbonate comprises at least 12% by weight of the ternary blend of polyglutarimide, multiple stage polymer and polycarbonate. The concept of using a combination of butadienebased and acrylic-based multiple stage polymers is more fully discussed in a European Patent Application filed on the same day as this Application and claiming priority from United States Serial No. 036,951, filed 7th May 1979. Suitable polycarbonates include any having a molecular weight (weight average) of at least 20,000 up to 1 million. Preferred molecular weights of the polycarbonate are 20,000 to 40,000. Polycarbonates are well known commercially available materials. About O to 30, more preferably over 13% by weight, of the blend of plastics and flame retardants is polycarbonate. The decabromodiphenyl oxide is a commercially available material. It must have an average particle size of less than 12 microns, and more preferably an average particle size of about 8 to 10 microns. Surprisingly, when the decabromodiphenyl oxide has average particle size within the essential, even more so in the preferred, range, the flame resistance, impact strength and heat distortion properties are excellent of the total composition as compared to compositions containing material of larger particle size. For example, decabromodiphenyl oxide from Great Lakes Chemical Corporation sold in 1978 under the trademark DE-83R having an average particle size of about 9.2 microns gave significantly better properties in this system than did a material having an average particle size of 16.6 microns identified in 1978 as Dow Chemical Corporation's FR-300BA. For DE-83R the range of particle sizes was 1 to 15 microns, whereas for FR-300BA the range of particle sizes was 1 to 140 microns. This discovery of the advantages of smaller particle size material is especially surprising in view of the fact that a larger particle size modifier would be expected to give a better impact strength. It is preferred to use metal oxide in combination with the decabromodiphenyl oxide, since it synergizes the activity of the decabromodiphenyl oxide. The metal oxide can be either antimony trioxide or zinc borate or a mixture thereof. Antimony oxide is preferred for its synergistic properties, but since zinc borate may be more economically advantageous, it may be partially or totally substituted for the antimony trioxide. The commercially available zinc borates are hydrated, containing about 3.5 moles of water, and are useful as the metal oxide synergist. The preferred ratio of decabromodiphenyl oxide to metal compounds is 3:1 to 2:1 by weight. Poly(tetrafluoroethylene) and/or fumed silica are also preferably included in the compositions of the inventions as co-synergist(s). Broadly, the preferred amounts of decabromodiphenyl oxide and metal compound(s) are each 0.1 to 30%, based on weight of polyglutarimide. Based on polyglutarimide, impact modifier polymer, and optional polycarbonate, the weight ratios of decabromodiphenyl oxide to metal compound to blend of polyglutarimide and impact modifier (if any) is preferably 20:20:100 to 6:2:100, and more preferably 14:7:100 to 12:5:100. The compositions of this invention are useful as molding or other forming compositions. The following Example illustrates a few preferred embodiments of the invention. Unless otherwise specified, all parts and percentages are by weight. Example and Comparative Tests This Example illustrates the importance of the particle size of the decabromodiphenyl oxide. To a formulation of 31.68 parts of a polyglutarimide which was prepared according to the Belgian Patent 848,496 from methylamine and polymethyl methacrylate to an 83 to 85 by weight degree of imidization, were blended on a Killion extruder the following ingredients: 15 parts of an MBS impact modifier prepared in accordance with Example 1 of U.S. Patent 3,985,704, 15 parts of an acrylic impact modifier, 20 parts of polycarbonate, 5 parts of antimony oxide, 0.1 part phenolic antioxidant (American Cyanamid Cyanox 1790"), 0.02 parts dilaurylthiodipropionate (American Cyanamid), 0.1 parts poly(tetrafluoroethylene) (Teflon 6 by duPont) and 0.1 parts stearamide. Six formulations were made, varying the decabromodiphenyl oxide ratio and type. The formulations were molded into specimens and tested for Gardner impact and UL-94 flammability rating (using 1/16 inch specimens). The results are reported in the following table. The DE-83R had an average particle size of 9.2 microns. The FR-300 BA had an average particle size of 16.6 microns. TABLE Gardner Flammability Decabromodiphenyl Impact Time to Self Oxide (VHIT) Extinguish Parts Type J (in-lb) UL-94 (sec) Example (a) 13.0 DE-83R 12.43 (110) V-0 3.8 " (b) 12.0 DE-83R 12.43 (110) V-0 2.1 " (c) 11.0 DE-83R 11.30 (100) V-0 4.3 Test (a) 13.0 FR-300BA 7.91 (70) F above 15.5 " (b) 12.0 FR-300BA 4.52 (40) F above 15.5 " (c) 11.0 FR-300BA 6.33 (56) F above 15.8

Claims: CLAINS: 1. A composition comprising polyglutarimide and decabromodiphenyl oxide having an average particle size of less than 12 microns. 2. A composition as claimed in claim 1, further including one or both of the metal compounds: antimony trioxide and zine borate. 3. A composition as claimed in claim 2, further including acrylic-based or butadiene-based impact modifier. 4. A composition as claimed in claim 2 or 3, wherein the weight ratio of decabromodiphenyl oxide to metal compound to total weight of polyglutarimide and impact modifier (if any) is 20:20:100 to 6:2:100. 5. A composition as claimed in claim 4, wherein the ratio is 14:7:100 to 12:5:100. 6. A composition as claimed in any preceding claim, further including poly(tetrafluoroethylene) and/or fumed silica. 7. A composition as claimed in any preceding claim, wherein the decabromodiphenyl oxide has an average particle size of 8 to 10 microns. 8. A composition as claimed in any preceding claim, further including up to 30% by weight polycarbonate. 9. A composition as claimed in any preceding claim containing decabromodiphenyl oxide in an amount of 0.1 to 30% by weight, and the metal compounds (if any) in an amount of 0.1 to 30% by weight, based on polyglutarimide. 10. A composition as claimed in any of claims 2 to 9, wherein the ratio of decabromodiphenyl oxide to metal compound(s) is 3:1 to about 2:1. 11. A method of improving the flame retardant properties of polyglutarimide comprising blending therewith decabromodiphenyl oxide having an average particle size of less than 12 microns. 12. A method as claimed in claim 11 as applied to the preparation of a composition as claimed in any of claims 2 to 10.

Inventors: CROOK, EVAN HANEY, WEESE, RICHARD HENRY
Applicants: ROHM AND HAAS COMPANY
Application year: 1980
Main classification: C08L79
IPC codes: C08L33, C08L1, C08K5, C08L27, C08L7, C08L51, C08L21