Halogen-free flame resistant polystyrol moulding materials

Details Halogen-free flame resistant polystyrol moulding materials Halogen-free flame resistant polystyrol moulding materials

1999-05-19

2000-09-26

Dawson, Robert

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

524139, 524141, 524442, 524174, 525387, 525 68, C08K 332

Patent

active

06124385&

DESCRIPTION:

BRIEF SUMMARY
The invention relates to flame-retardant thermoplastic molding compositions based on polyphenylene ethers (PPE) and styrene polymers (PS). Such mixtures are known per se and are suitable for producing moldings which have better heat resistance than impact-modified styrene polymers which are not blended with polyphenylene ether. The material properties of such moldings are generally satisfactory but these polymer mixtures have the disadvantage of encouraging the spread of fire. However, many attempts to make these materials flame retardant have resulted in reduced heat resistance.
DE-A-41 01 805 discloses the preparation of halogen-free, impact-modified and flame-retardant molding compositions with improved flowability, based on mixtures of impact-resistant polystyrene and polyphenylene ethers, which contain aromatic sulfonamides and phosphorus-containing compounds, such as triphenyl phosphate or triphenylphosphine oxide, as flame-retardant additives.
Typical molding compositions of the type proposed in DE-A-41 01 805 consist of, for example
Impact-modified polystyrene achieves improved flowability when aromatic sulfonamides are added, but at the cost of a significant reduction in heat resistance.
There are commercially available flame-retardant molding compositions which consist of about 30% by weight of polyphenylene ether, 60% by weight of impact-modified polystyrene, 10% by weight of phosphorus compounds, and a certain amount of melamine as well as conventional auxiliaries and stabilizers, but these mixtures are expensive, since they contain a relatively large amount of polyphenylene ether, which is complicated to prepare.
It is an object of the present invention to provide mixtures which are based on impact-modified styrene polymers and polyphenylene ethers and which give improved flame retardancy at lower raw material costs and production costs, especially for the consumer electronics sector (eg. TV cabinets).
We have found that this object is achieved by means of thermoplastic molding compositions based on a flame-retardant-containing mixture of an impact-modified styrene polymer and a polyphenylene ether, having a particularly good combination of properties and an especially good price-value ratio, comprising, in each case based on the total of A to E, ether A, impact-modified styrene polymer B,
The polyphenylene ethers A are known and are preferably prepared by oxidative coupling of ortho-disubstituted phenols.
Examples of substituents are halogen, such as chlorine and bromine, and alkyl having from 1 to 4 carbon atoms, preferably without tertiary hydrogen in the .alpha.-position, eg. methyl, ethyl, propyl and butyl. The alkyl radicals may themselves be substituted with halogen, such as chlorine or bromine, or hydroxy-substituted. Further examples of possible substituents are alkoxy, preferably having up to 4 carbon atoms, and phenyl, which may be substituted with halogen and/or alkyl. Copolymers of various phenols, such as copolymers of 2,6-dimethylphenol and 2,3,6-trimethylphenol, are likewise suitable. Mixtures of various polyphenylene ethers may, of course, also be employed.
Preference is given to polyphenylene ethers which are compatible with vinylaromatic polymers, ie. are completely or very largely soluble in these polymers (cf. A. Noshay, Block Copolymers, p. 8-10, Academic Press, 1977 and O. Olabisi, Polymer-Polymer Miscibility, 1979, p. 117-189).
Examples of polyphenylene ethers are
Preference is given to polyphenylene ethers in which the substituents are alkyl radicals with from 1 to 4 carbon atoms, such as
Graft copolymers of polyphenylene ethers and vinylaromatic polymers, such as styrene, .alpha.-methylstyrene, vinyltoluene and chlorostyrene, are also suitable.
Suitable polyphenylene ethers generally have an intrinsic viscosity .eta..sub.sp /c of from 0.2 to 0.7 dl/g, measured in chloroform at 25.degree. C. This corresponds to a molecular weight range of from about 10000 to 60000.
Poly(2,6-dimethyl-1,4-phenylene) ether is preferred for the novel molding compositions.
Component B is an

REFERENCES:
patent: 3737479 (1973-06-01), Haaf
patent: 5194476 (1993-03-01), Casarini et al.
patent: 5268425 (1993-12-01), Furuta

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