Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-11-30
2001-03-20
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...
C524S139000, C524S141000
Reexamination Certificate
active
06204315
ABSTRACT:
The present invention relates to flame-retardant thermoplastic molding materials based on polyphenylene ethers and vinylaromatic polymers having improved fire resistance and the use of the novel thermoplastic molding materials for the production of fibers, films and moldings.
Polymer blends comprising polyphenylene ethers (PPE) and vinylaromatic 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 have better heat distortion resistance than high impact polystyrenes (HIPS) which have not been blended with polyphenylene ethers. A detailed description of the properties of these polymer blends is also to be found in L. Bottenbruch, “Technische Polymer-Blends”, Kunststoff Handbuch 3/2, Hanser Verlag, Munich, 1993.
An important advantage of the polymer blends comprising polyphenylene ethers and styrene polymers is that molding materials which are flame-retardant and are therefore used for many applications in the area of electrical engineering can be prepared by adding halogen-free flameproofing agents, phosphorus-containing compounds being particularly noteworthy. For electrical applications, in particular the testing of the flame retardants according to UL 94 (in J. Troitzsch, “International Plastic Flammability Handbook”, page 346 et seq., Hanser Verlag, Munich, 1990) is critical. In this test, a flame is applied several times to vertically fastened test specimens, the test specimen heating up to a very great extent, which in many cases leads to the dripping of flaming polymer material and the ignition of the cotton wool pad mounted below the rod. This undesirable behavior is observed in particular when large amounts of flameproofing agents have to be used to achieve short burning times.
The problem of the dripping of flaming particles in the UL 94 test has long been known and is solved in industry generally by adding small amounts of Teflon as an antidrip agent (U.S. Pat. No. 4,107,232). As part of the efforts completely to avoid the use of halogen-containing compounds in thermoplastic molding materials, there is a need for effective halogen-free antidrip agents for flameproofed molding materials based on polyphenylene ethers and vinylaromatic polymers.
It is known from the prior art, for example, that the drip resistance of thermoplastic PPE/HIPS molding materials can be improved by adding high molecular weight polyethylene. Thus, EP 0550204 proposes, as an antidrip agent, ultrahigh molecular weight polyethylene having a weight average molecular weight of more than 100,000, in particular from 2 to 6 million.
Moreover, the prior art states that the dripping behavior of PPE/HIPS molding materials can be improved by adding high molecular weight polystyrene. For example, EP 0305764 describes the use of polystyrene having a weight average molecular weight of more than 400,000, and EP 0476366 describes the use of polystyrene having a molecular weight of more than one million.
However, the addition of high molecular weight polyethylene or high molecular weight polystyrene has disadvantages. As shown by a UL 94 test for the PPE/HIPS molding materials modified in this manner, these antidrip agents cause a substantial increase in the burning time.
It is an object of the present invention to provide a halogen-free antidrip agent which can be used in thermoplastic molding materials based on polyphenylene ethers and vinylaromatic polymers without their burning time being substantially impaired.
We have found, surprisingly, that this object is achieved by providing flame-retardant thermoplastic molding materials containing
A) at least one polyphenylene ether,
B) at least one vinylaromatic polymer and
C) at least one flameproofing agent,
which furthermore comprise
D) as an antidrip agent, a high molecular weight polymer based on acrylamide and having a viscosity of more than about 1.5 mPas, measured in 0.1% strength aqueous solution at 25° C.
Preferably, the viscosity of the antidrip agent is from about 2 to 6, in particular from about 3 to 4.5, mPas.
Furthermore, the antidrip agent may contain up to 95, for example from about 10 to about 70 or from about 20 to about 50, % by weight of comonomer units other than acrylamide.
At least one compound selected from among acrylic acid, methacrylic acid, styrenesulfonic acid, ethylenesulfonic acid and the salts thereof, dimethylaminoethyl methacrylate, dimethylaminioethyl acrylate and hydrochlorides thereof and diallyldimethylammonium chloride may be used as a comonomer.
A preferred embodiment of the invention relates to a molding material containing
A) from about 5 to about 97.5% by weight of polyphenylene ether,
B) from about 1 to about 93.5% of styrenepolymer,
C) from about 1 to about 20% by weight of a flameproofing agent,
D) from about 0.5 to about 25% by weight of antidrip agent,
E) from 0 to about 50% by weight of impact modifier, and
F) from 0 to about 60% by eight of conventional additives.
Owing to the high efficiency of the polyacrylamide polymers used according to the invention, the mechanical properties of flame-retardant PPE/HIPS blends are moreover not impaired.
The present invention furthermore relates to the use of a molding material according to the above definition for the production of fibers, films and moldings, and fibers, films and moldings which were produced using these molding materials.
The polyphenylene ethers (Component A) contained in the novel molding materials are known per se. Polyphenylene ethers are contained in the novel molding materials in an amount of from about 5 to about 97.5, preferably from about 15 to about 87.5, in particular from about 20 to about 82, % by weight, based on the total weight of the molding material.
Component A comprises in particular 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, long-chain alkyl of up to 20 carbon atoms, such as lauryl and stearyl, and short-chain alkyl of 1 to 4 carbon atoms which preferably have no &agr; tertiary hydrogen atom, e.g. methyl, ethyl, propyl or butyl. The alkyl radicals may in turn be monosubstituted or polysubstituted by halogen, such as chlorine or bromine, or by hydroxyl. Further examples of possible substituents are alkoxy, preferably of 1 to 4 carbon atoms, of phenyl which is unsubstituted or monosubstituted or poly-substituted by halogen and/or by C
1
-C
4
-alkyl according to the above definition. Copolymers of different phenols, e.g. copolymers of 2,6-dimethylphenol and 2,3,6-trimethylphenol, are also suitable. Mixtures of different polyphenylene ethers can of course also be used.
Examples of polyphenylene ethers which may be used according to the invention 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-dichlor-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-chlor-1,4-phenylene ether),
poly(2,5-dibromo-1,4-phenylene ether).
Polyphenylene ethers substituted by alkyl of 1 to 4 carbon atoms are preferably used, 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).
For the purposes of the present invention, polyphenylene ethers are also to be understood as meaning those which have been modified with monomers, such as fumaric acid, maleic acid, maleic anhydride or citric acid.
Such polyphenylene ethers are described, in
Hahnle Hans-Joachim
Heckmann Walter
Hingmann Roland
Weber Martin
Weiss Robert
BASF - Aktiengesellschaft
Hoke Veronica P.
Keil & Weinkauf
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