Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-11-23
2001-03-06
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S496000
Reexamination Certificate
active
06197869
ABSTRACT:
The present invention relates to flame-retardant thermoplastic molding materials having improved resistance to dripping, their use for the production of fibers, films and moldings, and the fibers, films and moldings produced therefrom.
Polymer blends comprising polyethylene ether (PPE) and 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 are distinguished by a better heat distortion resistance compared with high impact polystyrene (HIPS) which is not 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 a polyphenylene ether 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 mentioned in particular. With regard to the use in the area of electrical engineering, in particular the testing of the flame-retardancy according to UL 94 (in J. Troitzsch, International Plastics Flammability Handbook, page 346 et seq., Hanser Verlag, Munich, 1990) is critical. In this test, a flame is repeatedly applied to vertically fastened test specimens. The test specimen heats up to a very great extent, resulting in many cases in the dripping of burning polymer material which ignites the cotton wool pad mounted under the rod. This undesired behavior is observed particularly when large amounts of flameproofing agents have to be used to achieve short combustion times.
The problem of the dripping of burning particles in the UL 94 test has long been known and is solved in the industry generally by adding small amounts of Teflon as an antidrip agent (U.S. Pat. No. 4,107,232). However, attempts have recently been made completely to avoid the use of halogen-containing compounds in thermoplastic molding materials. However, suitable alternative antidrip agents have not been found to date.
EP 0 297 868 discloses the use of expandable graphite in combination with carbon black of a certain specification for establishing the conductivity of thermoplastic or heat-curable resins. The resins obtained according to EP 0 297 888 are suitable in particular for the production of electrically conductive materials, such as electrodes, and for shielding electromagnetic waves. However the problem of improving the resistance to dripping is not tackled therein.
JO 3181 532 likewise disclosed the use of expandable graphite for thermoplastic molding materials. However, no flame-retardant molding materials are described therein. The purpose of adding graphite according to JO 3181 532 was to improve the electrical conductivity as well as the thermal conduction and frictional properties.
It is an object of the present invention to provide flameproofed thermoplastic molding materials, in particular molding materials based on polyphenylene ethers and styrene polymers, with resistance to dripping has been improved by the addition of a halogen-free antidrip agent.
We have found that this object is achieved and that, surprisingly, the addition of an amount of expandable graphite which increases the resistance to dripping, in particular of from about 0.5 to about 10% by weight of expandable graphite, can reduce the dripping of flame-retardant molding materials. According to the invention, it is possible in particular to obtain molding materials based on PPE and HIPS whose resistance to dripping has been substantially increased. In the fire test according to UL 94, these novel molding materials can achieve the classification V 0.
This result is all the more surprising since neither EP 0 297 888 nor JO 31 81 532 gives any indication that the fire behavior and in particular the dripping behavior of thermoplastic molding materials, for example molding materials comprising polyphenylene ethers and high impact polystyrene, can be improved simply by means of expanded graphite.
The present invention therefore relates to flame-retardant, thermoplastic molding materials containing a thermoplastic resin based on one or more polyphenylene ethers and at least one vinylaromatic polymer, a flameproofing agent and an amount of expandable graphite which increases the resistance to dripping of the molding material. Preferably, the expandable graphite is present in an amount of from about 0.5 to about 10, preferably from about 0.5 to about 9, in particular from about 0.5 to about 7.5, % by weight, based on the total weight of the molding material.
An advantageous embodiment of the invention provides a thermoplastic, flame-retardant molding material which contains, based in each case on the total weight of the molding material
A) from about 5 to about 97.5% by weight of polyphenylene ether,
B) from about 1 to about 93.5% by weight of styrene polymer,
C) from about 1 to about 20% by weight of flame-proofing agent,
D) from about 0.5 to about 10% by weight of expandable graphite,
E) from about 0 to about 50% by weight of impact modifier and
F) from about 0 to about 60% by weight of conventional additives.
The preferably provided molding material is one which contains, based in each case on the total weight of the molding material,
A) from about 15 to about 87.5% by weight of polyphenylene ether,
B) from about 10 to about 82.5% by weight of styrene polymer,
C) from about 2 to about 19% by weight of flame-proofing agent,
D) from about 0.5 to about 9% by weight of expandable graphite,
E) from about 0 to about 25% by weight of impact modifier and
F) from about 0 to about 50% by weight of conventional additives.
A particularly preferred molding material is one which contains, based on the total weight of the molding material,
A) from about 20 to about 82% by weight of polyphenylene ether,
B) from about 15 to about 77% by weight of styrene polymer,
C) from about 2.5 to about 18% by weight of flame-proofing agent,
D) from about 0.5 to 7.5% by weight of expandable graphite,
E) from about 0 to about 20% by weight of impact modifier and
F) from about 0 to about 30% by weight of conventional additives.
According to the invention, at least one polyphenylene ether known per se is used as component A). These are 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, and alkyl of 1 to 4 carbon atoms which preferably has no a tertiary hydrogen atom, e.g. 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. Also suitable are copolymers of various phenols, for example copolymers of 2,6-dimethylphenol and 2,3,6-trimethylphenol. Mixtures of different polyphenylene ethers can of course also be used.
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-dibromo-1,4-phenylene ether). Preferably used polyphenylene ethers are those in which the substituents are alkyl of 1 to 4 carbon atoms, such as poly
Heckmann Walter
Hingmann Roland
Horn Peter
Weber Martin
Weiss Robert
BASF - Aktiengesellschaft
Keil & Weinkauf
Niland Patrick D.
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