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...
Patent
1998-06-16
2000-04-04
Wu, David W.
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...
524406, 524430, 524539, C08K 310
Patent
active
060462647
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to thermoplastic molding materials and injection molded articles produced therefrom.
Plastics blends comprising predominantly polyalkylene terephthalate are known. PET and PBT blends with about 30% of added glass fibers for increasing the strength, the stability and the modulus of elasticity are known. PBT blends are preferred for injection moldings since they can be more readily processed than PET blends, but they have lower strength.
Ultradur.RTM. B4300G2 is a glass fiber-reinforced PBT molding material from BASF Aktiengesellschaft. This molding material is free-flowing, suitable for injection molding and contains 10% by weight of glass fibers. The industrial shaped articles produced therefrom are rigid, tough and dimensionally stable, for example for program switches, toggles, buttons, thermostat parts and handles of heating apparatuses (cf. BASF Kunststoffe, Ultradur.RTM. Polybuthylenterephthalat (PBT) Sortimentsubersicht, Produktmerkmale Verwendung Richtwerte, April 1994).
It is an object of the present invention to provide a PET blend which is more economical to produce and which in some cases has more advantageous parameters than known PBT blends.
We have found that this object is achieved by a thermoplastic molding material which essentially contains from 37 to 96% by weight of a thermoplastic polyethylene terephthalate as component A), from 1 to 20% by weight of a polymer material as component B) and from 4 to 30% by weight of a pigment-like reinforcing agent as component C).
This gives a very advantageous and readily injection moldable molding material which differs substantially from known molding materials. Thermoplastic molding materials which are likewise advantageous and are intended for injection molding of shaped articles contain predominantly a thermoplastic polyethylene terephthalate (PET), pigments and a polymer material in a weight ratio of produced therefrom being injection moldable at from above 245 to 300.degree. C.
Other advantageous thermoplastic molding materials for injection molding of shaped articles, containing predominantly a thermoplastic polyethylene terephthalate and a polymeric material, comprise a weight ratio of articles being injection moldable at a melt temperature of from about 245 to 300.degree. C.
It is advantageous if the molding materials contain predominantly polyurethane as the polymer material so that they are readily injection moldable and easily processable. It is also advantageous if the moisture content of the molding materials is not more than 0.1, in particular 0.05, % by weight.
The pigment reinforcing material advantageously consists of metal pigments and/or metal oxide pigments.
In an advantageous embodiment, the pigments may have a mean average particle size of less than or equal to 400 .mu.m. This makes it possible to achieve a uniform pigment distribution.
It is also advantageous if the pigments have a length/width ratio of from about 5:1 to about 15:1.
The properties of the injection molded articles can be improved if from about 0.2 to about 0.8, in particular about 0.5, % by weight of talc is present in the molding material. This improves the flowability, the demoldability and the surface smoothness of the shaped articles while reducing the required hydraulic pressure in the system.
The novel molding materials are also advantageous owing to their very low isotropic shrinkage of about 0.2% each in the longitudinal and transverse directions.
The molding materials can be particularly advantageously processed in injection molding apparatuses having a shut-off nozzle and a hot runner system, in order to produce optimum shaped articles in relatively good cycle times.
The molding materials have a density of greater than or equal to 1.4 g/cm.sup.3, in particular of 1.48 g/cm.sup.3.
The molding materials may advantageously contain, as pigments, chromium dioxide pigments which are finely divided and can be readily distributed in the molding material.
The molding materials moreover possess a volume flow index (MVI) of at least
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Eicher Jochen
Muller Norbert
Sartor Karl-Heinz
Choi Ling Sui
EMTEC Magnetics GmbH
Wu David W.
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