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
2000-07-24
2002-08-13
Seidleck, James J. (Department: 1711)
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...
C524S165000, C524S506000, C524S588000, C524S268000
Reexamination Certificate
active
06433050
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to flame-retardant polycarbonate resin compositions. More particularly, it relates to flame-retardant polycarbonate resin compositions improved in flame retardance without sacrificing the inherent outstanding properties of the polycarbonate resin, such as impact resistance and other mechanical properties, flow properties, and outward appearance of molded parts, and which contain neither a halogen type flame retardant containing chlorine or bromine compound or a phosphorus type flame retardant.
BACKGROUND OF THE PRIOR ART
Polycarbonate resins, a class of engineering plastics with excellent transparency, impact strength, heat resistance, and electrical properties, are used extensively in electrical, electronic, office automation, and many other applications.
In the electrical-electronic and OA fields there are many components, such as personal computer housings, that are required to possess high flame retardance (conforming to Underwriters' Laboratories (UL) 94V ratings) and great impact resistance. Polycarbonate resins are self-extinguishing, highly flame-retardant plastics themselves. Still, in electrical-electronic and OA applications where safety is the primary consideration, they are required to have even greater flame retardance, high enough to meet the requirements of UL94V-0 and 94V-1.
A commonly used method to improve the flame retardance of the polycarbonate resin has been to mix it with a large proportion of an oligomer or polymer of a carbonate derivative of brominated bisphenol A.
Problems Encountered
The large addition of an oligomer or polymer of a carbonate derivative of brominated bisphenol A improves the flame retardance of the polycarbonate resin. However, it reduces the impact resistance of the resin and thereby poses a problem of frequent cracking of articles molded from the resin.
On the other hand, mixing the resin with a large amount of a halogen type compound that contains bromine can evolve a gaseous product containing the particular halogen upon combustion. Thus from environmental considerations there is a demand for the use of a flame retardant free from chlorine, bromine or the like.
Meanwhile, many attempts have thus far been made to utilize silicone compounds as flame retardants. The compounds have high heat resistance, produce negligible noxious gas upon combustion, and are remarkably safe in use.
The silicone compound as a flame retardant s a polymer that results from the polymerization of at least any of the following four siloxane units (unit M, unit D, unit T, and unit Q).
where R represents an organic group.
where R represents an organic group.
where R represents an organic group.
Of these units, unit T and/or unit Q, when contained in the compound, forms a branched structure.
In order to utilize silicone compounds as flame retardants, various silicone compounds having organic groups have hitherto been tried, as taught in Japanese Patent Application Public Disclosure (Kokai) No. 1-318069, Japanese Patent Application Publication (Kokoku) No. 62-60421, etc.
However, very few of those compounds can achieve an appreciable flame-retarding effect when added singly. Even one found relatively effective must be added in a large quantity if it is to meet the strict standards for electrical-electronic appliances. The large addition is not practicable because it unfavorably affects the molding, kneading, and other needed properties of the resulting plastics, and also because it adds to the cost.
Methods of combining a silicone compound with a metal salt have been reported as attempts to enhance the flame-retarding effect of a silicone compound while reducing the amount to be added. They include the combined use of polydimethyl silicone, a metal hydroxide, and a zinc compound (Japanese Patent Application Public Disclosure (Kokai) No. 2-150436) polydimethyl silicone and a Group IIa metal salt of an organic acid (Japanese Patent Application Public Disclosure (Kokai) No. 56-100853); and silicone resin, especially one represented by units M and Q, silicone oil, and a Groups IIa metal salt of an organic acid (Japanese Patent Application Publication (Kokoku) No. 3-48947). Fundamental problems common to those methods are inadequate flame-retarding effect and difficulty in substantially reducing the amount to be added.
A further combination of an organopolysiloxane having an epoxy group (&ggr;-glycidoxypropyl group) and phenyl group and/or vinyl group and an alkali metal salt and alkaline earth metal salt of an organic sulfonic acid (Japanese Patent Application Public Disclosure (Kokai) No. 8-176425) has been reported. Since this silicone compound contains highly reactive epoxy and vinyl groups, the silicone compound can react with itself to form high molecular weight gels when mixed with the polycarbonate resin, because of high temperature, hampering thorough mixing and increasing the viscosity of the mixture. This presents problems of undesirable polycarbonate resin moldability, especially delamination, sinking, and/or unevenness of molded part surface. Moreover, the gelation does not allow the silicone compound to be thoroughly dispersed in the polycarbonate resin. This, in turn, causes problems of difficulty in attaining a noticeable flame-retarding effect and of declined strength properties such as impact strength of the molded articles.
SUMMARY OF THE INVENTION
The present inventors have intensively searched for a solution of the afore-described problems of the prior art. They have now found, as a result, that the combined use of a specific silicone compound and a metal salt of an aromatic sulfur compound or a metal salt of a perfluoroalkanesulfonic acid as a flame retardant to be mixed with a polycarbonate resin and the additional use of a fiber-forming fluoropolymer provide flame-retardant polycarbonate resin compositions possessing high flame retardance without a sacrifice of their impact resistance and molding properties. The finding has led to the perfection of the present invention.
The flame-retardant polycarbonate resin compositions according to the invention, free from a bromine type or other halogen type flame retardant, have no danger at the time of combustion of evolving gases containing the halogen that results from the halogen type flame retardant, and thereby exhibit outstanding performance from the viewpoint of environmental protection.
In brief, the invention concerns a flame-retardant polycarbonate resin composition characterized by mixing a polycarbonate resin (A) with a silicone compound (B) whose backbone structure is branched and which has aromatic groups in the organic groups it contains, and a metal salt of an aromatic sulfur compound (C) or a metal salt of a perfluoroalkanesulfonic acid (D). It also concerns a flame-retardant polycarbonate resin composition characterized by the addition of a fiber-forming fluoropolymer (E). The flame-retardant polycarbonate resin compositions according to the invention will now be described in detail.
DETAILED DESCRIPTION OF THE INVENTION
The polycarbonate resin (A) to be used in this invention is any of the polymers obtained either by the phosgene process in which one of varied dihydroxydiaryl compound is reacted with phosgene or by the ester exchange process in which a dihydroxydiaryl compound is reacted with a carbonic ester such as diphenyl carbonate. Typical of them is a polycarbonate resin produced from 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).
Examples of the dihydroxydiaryl compounds, besides bisphenol A, are: bis(hydroxyaryl)alkanes, such as bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxyphenyl-3-methylphenyl)propane, 1,1-bis(4-hydroxy-3-tert.butylphenyl)propene, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, and 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane; bis(hydroxyaryl)cycloalkanes, such as 1,1-bis(4-hydroxyphenyl)cyclopentane and 1,1-bis(4-hydroxyph
Iji Masatoshi
Sato Ichiro
Serizawa Shin
Shinomiya Tadashi
Gary C. Cohn PLLC
Rajguru U. K.
Seidleck James J.
Sumitomo Dow Limited
LandOfFree
Flame-retardant polycarbonate resin composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flame-retardant polycarbonate resin composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flame-retardant polycarbonate resin composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2957743