Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-04-14
2001-01-09
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S101000, C524S446000, C524S447000
Reexamination Certificate
active
06172148
ABSTRACT:
The present invention relates to flame-retardant thermoplastic molding materials containing
A) from 5 to 97.7% by weight of a polyphenylene ether,
B) from 1 to 93.7% by weight of vinylaromatic polymers,
C) from 0 to 50% by weight of impact modifiers,
D) from 0.3 to 20% by weight of sheet silicates which contain one or more nitrogen-containing compounds in amounts of from 0.1 to 50% by weight, based on the sheet silicates,
E) from 1 to 20% by weight of a flameproofing agent and
F) from 0 to 60% by weight of further additives.
The present invention furthermore relates to the use of flame-retardant thermoplastic molding materials for the production of fibers, films and moldings and to the fibers, films and moldings obtainable therefrom.
Thermoplastic polymer blends comprising polyphenylene ether (PPE) and vinylaromatic polymers, such as styrene polymers, are disclosed, for example, in U.S. Pat. Nos. 3,383,435; 4,128,602 and 4,128,603. Such molding materials are suitable for the production of shaped articles which, in comparison with high impact polystyrene (HIPS) which are not blended with polyphenylene ethers, are distinguished by better heat distortion resistance. A detailed description of the properties of these polymer blends also appears in L. Bottenbruch, “Technische Polymer-Blends”, Kunststoff Handbuch 3/2, page 63 et seq., Hanser Verlag, Munich, 1993.
An important advantage of the polymer blends comprising polyphenylene ethers and styrene polymers is that, by admixing halogen-free additives, in particular phosphorus-containing compounds, it is possible to obtain molding materials which are flame-retardant and can therefore be used for many applications in the electrical industry. In particular, the test for flame retardancy according to UL 94 (for example, described in J. Troitzsch, “International Plastics Flammability Handbook”, page 346 et seq., Hanser Verlag, Munich, 1990) is critical for use in the electrical industry. In this test, a flame is applied repeatedly to vertically fastened test specimens. The test specimen heats up to a very great extent, leading in many cases to the dripping of flaming polymer material and ignition of the cotton wool mounted below the rod. This undesirable behavior is observed in particular when large amounts of flameproofing agents must be used in order to achieve short combustion times.
The problem of the dripping of flaming particles in UL 94 test has long been known and is solved in industry in general by adding small amounts of Teflon as an antidrip agent (U.S. Pat. No. 4,107,232). However, owing to the evident toxicity of harmful substances liberated in the combustion of halogen-containing substances, attempts have very recently been made completely to avoid the use of such compounds in thermoplastic molding materials.
It is known that the dripping of flaming particles by molding material can be limited or completely suppressed by adding high molecular weight or ultra high molecular weight polymers to thermoplastic molding materials comprising polyphenylene ethers and polystyrene.
European Application EP-A 550 204 described ultra high molecular weight polyethylene as a halogen-free antidrip agent. According to this publication, the addition of ultra high molecular weight polyethylene completely prevents dripping by thermoplastic molding materials comprising polyphenylene ethers and styrene polymers. However, owing to the incompatibility of polyethylene with polyphenylene ether or polystyrene, even small amounts of polyethylene lead to a deterioration of the mechanical properties of the molding materials, in particular the damaging energy W
s
declining dramatically.
High molecular weight polystyrenes, too, lead to an improvement in the dripping behavior (European Patent 305,764). U.S. Pat. No. 5,008,314 however discloses that high molecular weight polystyrene substantially improves the stress cracking resistance of the polymer blends comprising polyphenylene ether and high impact polystyrene. High molecular weight polystyrene is also used for the preparation of polyphenylene oxide/polystyrene molding materials which are suitable for processing by blow molding (EP-A 476 366). However, the high molecular weight polystyrene generally prepared by free radical polymerization increases the amount of viscosity in a disadvantageous manner at the shear rates relevant for injection molding. Moreover, the toughness of the molding material decreases with increasing proportion of high molecular weight polystyrene. Additionally disadvantageous is the fact that long combustion times are to be expected in the UL 94 test, both with the use of high molecular weight polystyrene and with the use of high molecular weight polyethylene as antidrip agents.
It is an object of the present invention to provide flame-retardant thermoplastic molding materials, in particular molding materials based on polyphenylene ethers and vinylaromatic polymers, which contain an antidrip agent which does not adversely affect the mechanical and Theological properties and the combustion times according to UL 94.
We have found that this object is achieved by the thermoplastic molding materials defined at the outset.
We have also found the use thereof for the production of fibers, films and moldings, and the fibers, films and moldings obtainable hereby.
The flame-retardant thermoplastic molding materials preferably contain
A) from 15 to 87% by weight of a polyphenylene ether,
B) from 10 to 82% by weight of vinylaromatic polymers,
C) from 0.5 to 30% by weight of impact modifiers,
D) from 0.5 to 10% by weight of sheet silicates which contain one or more nitrogen-containing compounds in amounts of from 0.1 to 50% by weight, based on the sheet silicates,
E) from 2 to 15% by weight of a flameproofing agent and
F) from 0 to 50% by weight of further additives.
The sum of the % by weight of the individual components is 100.
According to the invention, at least one polyphenylene ether known per se is used as component A) In particular, these compounds based on substituted, in particular disubstituted polyphenylene ethers, the ether oxygen of one unit being bonded to the benzene nucleus of the neighboring unit. Polyphenylene ethers substituted in the 2- and/or 6-position relative to the oxygen atom are preferably used. Examples of substituents are halogen, such as chlorine or bromine, and alkyl of 1 to 4 carbon atoms which preferably has no &agr; tertiary hydrogen atom, eg. methyl, ethyl, propyl or butyl. The alkyl radicals may in turn be substituted by halogen such as chlorine or bromine, or by hydroxyl. Further examples of possible substituents are alkoxy, preferably of up to 4 carbon atoms, such as methoxy, ethoxy, n-propoxy and n-butoxy, or phenyl which is unsubstituted or substituted by halogen and/or by alkyl. Copolymers of different phenols, for example copolymers of 2,6-dimethylphenol and 2,3,6-trimethylphenol, are also suitable. It is of course also possible to use mixtures of different polyphenylene ethers. The polyphenylene ethers A) are present in the novel molding materials in an amount of from 5.0 to 97.7, preferably from 15.0 to 87, % by weight.
Examples of polyphenylene ethers are
poly(2,6-dilauryl-1,4-phenylene ether),
poly(2,6-diphenyl-1,4-phenylene ether),
poly(2,6-dimethoxy-1,4-phenylene ether),
poly(2,6-diethoxy-1,4-phenylene ether),
poly(2-methoxy-6-ethoxy-1,4-phenylene ether),
poly(2-ethyl-6-stearyloxy-1,4-phenylene ether),
poly-(2,6-dichloro-1,4-phenylene ether),
poly(2-methyl-6-phenyl-1,4-phenylene ether),
poly(2,6-dibenzyl-1,4-phenylene ether),
poly(2-ethoxy-1,4-phenylene ether), poly(2-chloro-1,4-phenylene ether) and poly(2,5-dibrom-1,4-phenylene ether). Preferably used polyphenylene ethers are those which are substituted by alkyl of 1 to 4 carbon atoms; poly(2,6-dialkyl-1,4-phenylene ether) such as poly(2,6-dimethyl-1,4-phenylene ether),
poly(2,6-diethyl-1,4-phenylene ether),
poly(2-methyl-6-ethyl-1,4-phenylene ether),
poly(2-methyl-6-propyl-1,4-phenylene ether),
poly(2,6-dipropyl-1,4-phenylene ether) and
poly(2-ethyl-6-propyl-1,4-phenylene ether), has proven
Gottschalk Axel
Heckmann Walter
Horn Peter
M{umlaut over (u)}ller Ulrich
Weber Martin
BASF - Aktiengesellschaft
Hoke Veronica P.
Keil & Weinkauf
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