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
1999-11-15
2003-06-17
Szekely, Peter (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...
C524S447000, C524S449000, C524S127000
Reexamination Certificate
active
06579926
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates to a flame-retarded polyphenylene ether (PPE) compositions and to a method of making same.
PPE is a thermoplastic material with high glass transition temperature, high dimensional stability, low specific gravity, hydrolytic stability and good mechanical performance. This combination of properties allows PPE based formulations to be injected molded into products which are used for high heat applications, for example in the automotive, electrical, and construction industries. For some applications, where increased modulus and strength are required, PPE may be reinforced with glass fibers. However, these reinforced PPE formulations have undesirable flammability characteristics. At high temperature or when exposed to flame, glass-filled PPE tends to burn continuously without extinguishing. Because of this, fire-retarded grades of glass-filled PPE (especially those rated UL94 V0) tend to be formulated using a large amount (for example >15% by weight for a rating of UL94 V0 at {fraction (1/16)}th inch thickness) of fire-retardant additives such as phosphorus-containing organic compounds. This increases the cost of the product, and also makes it more difficult to formulate glass fiber-reinforced PPE to meet UL94 V0 fire-retardant standards, because the addition of large amounts of phosphorus-containing organic compounds like resorcinol diphosphate plasticizes the composition and significantly reduces the heat deflection temperature of the formulation.
SUMMARY OF THE INVENTION
The present invention provides PPE compositions with good fire and flame-retardant characteristics, which utilize lower levels of organophosphate fire-retardant and which therefore do not suffer from the drawbacks of previously known fire- and flame-retardant PPE compositions. The compositions comprise
(a) a polymer component comprising at least 50% by weight of a polyphenylene ether;
(b) glass reinforcing fibers in an amount sufficient to increase the modulus and strength of the polymer component;
(c) a fire retardant component, preferably comprising an organophosphate fire retardant;
(d) an organoclay component in an amount effective to enhance the flame-retardant characteristics of the composition; and
(e) a mineral component. Other conventional additives utilized in formulation of PPE may be included. This composition can be used in the manufacture of injection molded articles such as electronic components, including television internals such as deflection yokes; printer chassis and plastic pallets.
The present invention further provides a method for preparation of a glass-reinforced PPE composition. In accordance with this method, the composition is prepared by compounding a mixture of
(a) a polymer component comprising at least 50% by weight of a polyphenylene ether;
(b) glass reinforcing fibers in an amount sufficient to increase the modulus and strength of the polyphenylene ether matrix;
(c) a fire retardant component, preferably comprising an organophosphate fire retardant;
(d) an organoclay component in an amount effective to enhance the flame-retardant characteristics of the composition; and
(e) a mineral component., as well as optional other components at elevated temperature to provide a homogenous blend of the materials. This compounding is suitably carried out in a screw type extruder at a temperature of 520 to 620° F., preferably from 540 to 560° F.
DETAILED DESCRIPTION OF THE INVENTION
The PPE compositions of the present invention comprise a polymer component comprising at least 50% by weight of a polyphenylene ether; glass reinforcing fibers in an amount sufficient to increase the modulus and strength of the polyphenylene ether matrix; an organophosphate fire retardant component; an organoclay component in an amount effective to enhance the flame-retardant characteristics of the composition; and a mineral component. These components act synergistically to provide glass-fiber reinforced PPE with good fire and flame-retardant characteristics, which utilize lower levels of organophosphate fire-retardant and which therefore do not suffer from the drawbacks of previously known fire- and flame-retardant PPE compositions.
This synergism is demonstrated in the results of the tests described below in the Examples which are summarized in Tables 1, 3 and 4. In these tests, samples of glass-fiber reinforced PPE without organoclay and with various loadings of organoclay were prepared by compounding in a twin screw extruder. Some of the compositions were prepared with a mineral component (mica) and others without a mineral component. The samples were then injection molded and tested for flame-out time in accordance with the UL protocol for V0 rating.
The experiments indicated that addition of small amounts of organoclay along with a mineral component to fire-retardant glass-fiber reinforced PPE allowed achievement of enhanced fire-retardant performance and compliance with the UL94 V0 standard. Addition of larger amounts of organoclay, or the addition of small amounts of organoclay in the absence of the mineral component resulted in a deterioration of the fire-retardant performance. Thus, it is clear that there is a critical and synergistic combination of ingredients which leads to the improved characteristics of the compositions of the present invention.
The composition of the invention is made from a polymer component in which various fillers and additives are incorporated. As used herein, the term “polymer component” refers to the combined mass of all organic polymers present in the composition. While the polymer component may be 100% of a polyphenylene ether, it may also include other polymers selected to achieve desired properties in the final composition. Thus, the polymer component of the composition comprises at least 50% by weight of one or more species of polyphenylene ether. As used herein, the term “polyphenylene ether” refers to individual polymeric PPE species or to mixtures of polymeric PPE species unless the context indicates otherwise.
PPE useful in the present invention is a polymer having repeat units of the general formula
wherein in the formula, R
1
, R
2
, R
3
, and R
4
which may be the same or different each represent a member selected from the group consisting of hydrogen atoms, halogen atoms, substituted and unsubstituted alkyl groups and substituted and unsubstituted alkoxy groups. The PPE may be a homopolymer, i.e. the repeat units have the same structural formula, or a copolymer consisting of a combination of two or more types of repeat units where at least one of the R
1
, R
2
, R
3
, and R
4
are different for each different repeat unit comprising the copolymer. The polymer is terminated at each end by a monovalent chemical group or atom such as hydrogen, a halogen, a monovalent hydrocarbon radical (saturated, unsaturated or aromatic) or the like. There are no particular restrictions on the method of manufacturing PPE. For example, this may be produced by reacting phenols according to the procedures presented in the specifications of U.S. Pat. Nos. 3,306,874, 3,257,357, or 3,257,358. Examples of these phenols include 2,6-dimethylphenol, 2,6-diethylphenol, 2,6-dibutylphenol, 2,6-dilaurylphenol, 2,6-dipropylphenol, 2,6-diphenylphenol, 2-methyl-6-ethylphenol, 2-methyl-6-cyclohexylphenol, 2-methyl-6-tolyl)phenol, 2-methyl-6-methoxyphenol, 2-methyl-6-butylphenol, 2,6-dimethoxyphenol, 2,3,6-trimethylphenol, 2,3,5,6-tetramethylphenol, 2,6-diethoxyphenol, etc., but the invention is not limited to these. One may either use a corresponding homopolymer obtained by reacting one of the above substances or a corresponding copolymer obtained by reacting two or more of the above substances and having the different units contained in the above formula. Specific examples of PPE polymers useful in the invention include but are not limited to 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) e
General Electric Company
Szekely Peter
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