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
2000-02-24
2003-05-13
Buttner, David J. (Department: 1712)
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...
C524S267000, C524S268000, C525S063000, C525S067000, C525S101000
Reexamination Certificate
active
06562887
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polycarbonate resin composition, particularly the one having excellent sliding properties.
Recently, for the purpose of expediting size and weight reduction or decrease of the number of parts of OA equipment and electronic devices in general, use of synthetic resins for the sliding members is prevailing. Among such synthetic resins, polycarbonate resins are favorably used for the parts of the sliding members such as gears because of their excellent dimensional precision and mechanical strength.
Usually, for improving the sliding properties, a sliding material is added to the polycarbonate resins. For instance, Japanese Patent Application Laid-Open (KOKAI) No. 63-213555 discloses a resin composition comprising a polycarbonate resin and ethylene tetrafluoride resin. Such a resin composition, however, has a problem that it tends to cause delamination or mold deposit during the molding operations because a large amount of a fluorine resin having no miscibility must be used. Japanese Patent Application Laid-Open (KOKAI) No. 4-136065 discloses a resin composition comprising polybutylene terephthalate and a polycarbonate. This resin composition involves a problem that not only the excellent properties (mechanical strength, heat resistance and flame retardancy) inherent to the polycarbonate resins are impaired but there also is a risk of phase separation taking place during molding.
Further, a resin composition produced by blending a silicone oil in a polycarbonate resin has been proposed. In the case of this composition, there is a problem that the article surface becomes tacky to spoil the sliding properties because the silicone oil in the surface of the molded article oozes out in a short time. As a solution to this problem, use of a high-molecular weight silicone oil has been proposed. In this case, however, as it is necessary to add a large quantity of silicone oil for obtaining satisfactory sliding properties, there tends to arise problems such as non-uniform glossiness of the molding surface due to phase separation of the silicone oil in the surface of the molded article, so that this resin composition is unsuited for practical use.
Further, Japanese Patent Application Laid-Open (KOKAI) No. 9-255864 provides a polycarbonate resin composition in which a high-viscosity dimethyl silicone oil and a polyolefin, polystyrene, acrylonitrile-styrene resin or acrylonitrile-butadiene-styrene resin are added to a basic polycarbonate resin for improving miscibility between the polycarbonate resin and the silicone oil. This polycarbonate resin composition, however, is not always satisfactory in balance of mechanical properties, molded article appearance and sliding properties.
As a result of the present inventors' earnest studies to solve the above problem, it has been found that by blending a silicone oil having specific dynamic viscosity and a rubber component having a specific structure with a polycarbonate resin, the obtained resin composition has excellent sliding properties without imparting the inherent properties of polycarbonate resin.
The present invention has been attained on the basis of the above finding.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a polycarbonate resin composition having excellent sliding properties and capable of providing good appearance to its molded articles without impairing the inherent properties such as mechanical strength and heat resistance of the polycarbonate resins.
To attain the above aim, in the first aspect of the present invention, there is provided a polycarbonate resin composition comprising 100 parts by weight of a polycarbonate resin, 0.05 to 5 parts by weight of a silicone oil (BH) having a dynamic viscosity of not less than 10,000 m
2
/s at 25° C., and 0.5 to 25 parts by weight of a composite rubber (C) having such a structure that the polyorganosiloxane rubber component and the polyalkyl (meth)acrylate rubber component are interlocked to form a unitary composite (intertwined with each other).
In the second aspect, there is provided a polycarbonate resin composition comprising:
100 parts by weight of a polycarbonate resin;
0.05 to 5 parts by weight of a mixture of silicone oil (BH) having a dynamic viscosity of not less than 100,000 mm
2
/s at 25° C. and a silicone oil (BL) having a dynamic viscosity of less than 100,000 mm
2
/s at 25° C., with the BH/BL ratio by weight being defined to be 2/1 to 200/1; and
0.5 to 25 parts by weight of a composite rubber (C) having such a structure that the polyorganosiloxane rubber component and the polyalkyl (meth)acrylate rubber component are interpenetrated with each other.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
As the polycarbonate resin (A) (which may hereinafter be referred to as a “PC resin”) usable in the present invention, there exemplified aromatic PC resins, aliphatic PC resins, and aromatic/aliphatic PC resins. Of these resins, aromatic PC resins are preferred. Examples of such aromatic PC resins include thermoplastic aromatic polycarbonate polymers or copolymers which may be branched, which can be obtained by reacting an aromatic hydroxyl compound or this compound and a small quantity of a polyhydroxyl compound with phosgene or a carbonic acid diester. The preparation method of these PC resins is not specified in the present invention; the conventional methods such as phosgene method (interfacial polymerization method) and melting method (ester exchange method) can be used. It is also possible to use aromatic PC resins produced by the melting method, with the number of the terminal OH groups being properly adjusted.
Examples of the aromatic dihydroxyl compounds usable for the above reaction include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), tetramethylbisphenol A, bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, 4,4-dihydroxydiphenyl and the like. Of these compounds, bisphenol A is preferred. It is possible to use compounds having at least one tetraalkylphosphonium sulfonate combined with the said aromatic dihydroxyl compounds and/or polymers or oligomers having a siloxane structure and containing phenolic OH groups at the terminal for the purpose of further enhancing flame retardancy.
For obtaining a branched aromatic PC resin, a polyhydroxyl compound such as phloroglucin, 4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptene-2,4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptane, 2,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptene-3,1,3,5-tri(4-hydroxyphenyl)benzene and 1,1,1-tri(4-hydroxyphenyl)ethane; 3,3-bis(4-hydroxyaryl)oxyindole (isatinbiphenol), 5-chloroisatin, 5,7-dichloroisatin, 5-bromoisatin or the like is used as part of the aromatic dihydroxyl compound mentioned above. Such an additive compound is used in an amount of usually 0.01 to 10 mol %, preferably 0.1 to 2 mol %.
The monovalent aromatic hydroxyl compounds can be used for modifying the molecular weight. Examples of such monovalent aromatic hydroxyl compounds include m- and p-methylphenol, m- and p-propylphenol, p-tert-butylphenol and p-long-chain alkyl substituted phenol.
As the aromatic PC resin, it is preferable to use the PC resins derived from 2,2-bis(4-hydroxyphenyl)propane or the PC copolymers derived from 2,2-bis(4-hydroxyphenyl)propane and other aromatic dihydroxyl compounds. They may be copolymerized with a polymer or oligomer having a siloxane structure for further enhancing flame retardancy. Two or more different types of aromatic PC resin may be used as a mixture.
The viscosity-average molecular weight of the PC resin used in the present invention, as calculated by conversion from the solution viscosity measured at 25° C. using methylene chloride as solvent, is usually in the range of 16,000 to 30,000. If the viscosity-average molecular weight is less than 16,000, the produced composition may be poor in mechanical strength, and if the viscosity-average molecular weight exceeds 30,000, the articles molded from the composition tend to become defective in app
Kurasawa Yoshihiro
Miyajima Takashi
Obayashi Naoto
Buttner David J.
Edwards & Angell LLP
Mitsubishi Engineering-Plastics Corporation
Neuner George W.
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