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
1999-10-01
2002-10-15
Cain, Edward J. (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...
C524S111000, C524S115000, C524S457000
Reexamination Certificate
active
06465555
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flame-retardant thermoplastic resin composition, more precisely, to a flame-retardant thermoplastic resin composition and its injection moldings, which contain red phosphorus serving as a flame retardant, which can be readily colored even in pale color or light color, and which has good moldability, high impact strength and high rigidity.
2. Description of the Related Art
As having the advantages of impact resistance, heat resistance, good electric properties and dimension stability, polycarbonate resins have many applications in various fields of, for example, office automation appliances, information and communication appliances, electric and electronic appliances for industrial use and household use, car parts and building materials. As a rule, polycarbonate resins are self-extinguishable. However, some fields of typically office automation appliances, information and communication appliances, and electric and electronic appliances for industrial use and household use require high flame retardancy, for which are used various flame retardants to ensure their flame retardancy.
On the other hand, moldings for housings and parts for office automation appliances such as duplicators and facsimiles, information and communication appliances such as telephones and other communication devices, and for other various electric and electronic appliances are being required to have a complicated shape with local projections or depressions, for example, having ribs or bosses therewith, and to be lightweight and thin-walled from the viewpoint of resources saving. Therefore, desired are polycarbonate resins having increased melt fluidity, or that is, having enhanced injection moldability. Various polycarbonate resin compositions having enhanced moldability have heretofore been proposed, to which are added rubber-modified styrenic resins in consideration of the physical properties such as impact resistance of the moldings of the compositions.
Compositions of polycarbonate resins, to which are added styrenic resins such as acrylonitrile-butadiene-styrene resins (ABS resins), rubber-modified polystyrene resins (HIPS resins) or acrylonitrile-styrene resins (AS resins) for increasing the melt fluidity of the compositions, are known as polymer alloys, and have many applications in the field of various moldings as having good heat resistance and impact resistance. Of such polycarbonate resin moldings, those for office automation appliances, information appliances and other electric and electronic appliances are required to have higher flame retardancy of not lower than a predetermined level so as to ensure and increase the safety of their moldings for those applications.
For improving the flame retardancy of polycarbonate resins, halogen-containing flame retardants such as bisphenol A halides and halogenated polycarbonate oligomers have been used along with a flame retardation promoter such as antimony oxide, as their flame-retarding ability is good. However, with the recent tendency toward safety living and environmental protection, the market requires flame retardation with non-halogen flame retardants. As non-halogen flame retardants, phosphorus-containing organic flame retardants, especially organic phosphate compounds may be added to polycarbonate resin compositions, for which various methods have been proposed. Concretely, for example, Japanese Patent Laid-Open No. 55145/1986 discloses a thermoplastic resin composition comprising (A) an aromatic polycarbonate resin, (B) an ABS resin, (C) an AS resin, (D) a halogen compound, (E) a phosphate, and (F) a polytetrafluoroethylene component. Japanese Patent Laid-Open No. 32154/1990 discloses a molding polycarbonate composition with high flame retardancy and high impact resistance, comprising (A) an aromatic polycarbonate resin, (B) an ABS resin, (C) an AS resin, (D) a phosphate, and (E) a polytetrafluoroethylene component. Japanese Patent Laid-Open No. 239565/1996 discloses a polycarbonate resin composition comprising (A) an aromatic polycarbonate, (B) a rubber-like elastomer-containing, impact-resistant polystyrene resin, (C) a non-halogen phosphate, (D) a core/shell-type, grafted rubber-like elastomer, and (E) talc.
These are all to improve the melt fluidity of polycarbonates thereby improving the moldability thereof, and to improve the impact resistance and the flame retardancy of polycarbonate moldings. With such their good properties, the moldings have many applications. However, in order to make the compositions comprising a polycarbonate resin and a (rubber-modified) styrenic resin and having good melt fluidity have good flame retardancy by adding thereto a phosphorus-containing, organic flame retardant, a relatively large amount of the flame retardant such as a phosphate compound must be added to the compositions. Though their flame-retarding ability is good, phosphate compounds often cause some problems when added to resin compositions. For example, they will bloom resin moldings, or corrode molds used for molding resin compositions, and, in addition, they will lower the impact strength of resin moldings or will yellow them in high-temperature conditions or in high-humidity conditions.
On the other hand, it is well known to use a non-halogen flame retardant, red phosphorus for making polycarbonate resins have flame retardancy. For example, Japanese Patent Publication No. 18356/1993 discloses a flame-retardant thermoplastic resin composition containing spherical red phosphorus with no milled surface, in which the red phosphorus is directly obtained through conversion from yellow phosphorus, and discloses a method for coating treatment of red phosphorus. Japanese Patent Laid-Open No. 53779/1995 discloses the same composition containing spherical or fine-powdery red phosphorus, in which, however, the red phosphorus is obtained through conversion in the presence of a dispersing agent followed by surface treatment. As is obvious from those disclosures, red phosphorus serving as a flame retardant is stabilized by coating its surface with a thermosetting resin or an inorganic compound to thereby ensure its safety and to prevent phosphine gas formation from it during storage, safe-keeping, transportation, handling, and mixing with thermoplastic resins.
Though red phosphorus exhibits its good flame-retarding ability even when its amount is relatively small, polycarbonate resins containing it color in red, and are difficult to color in light color or pale color. Japanese Patent Laid-Open No. 295164/1993 discloses a technique of improving the outward appearance of pale color moldings, for which is used red phosphorus as so controlled that the amount of red phosphorus grains having a grain diameter of 25 &mgr;m or larger therein is not larger than 10% by weight of the total. According to the disclosed technique, red phosphorus added is prevented from forming spots on the surfaces of the moldings to worsen the outward appearance of the moldings. However, as in Examples in the laid-open specification, red phosphorus is substantially combined with an organic phosphorus compound, of which the amount is 20 parts by weight relative to 100 parts by weight of the resin. Therefore, the disclosed technique still involves the problem with organic phosphorus compounds, and, in addition, could not still solve the problem with red phosphorus to color in red. Anyhow, so far as red phosphorus is used as a flame retardant in resin moldings, red coloration with it must be canceled in order that the moldings could have a desired color tone. For that purpose, in general, an excessive amount of titanium oxide over necessity shall be added to resins for color control. However, adding too much titanium oxide to polycarbonate resin compositions in an amount of 3% by weight or more is often problematic in that the heat resistance of the compositions is lowered to cause resin decomposition, that the strength including impact strength of the resin moldings is greatly lowered, and that silver
Mitsuta Naoki
Nodera Akio
Cain Edward J.
Idemitsu Petrochemical Co. Ltd.
LandOfFree
Flame-retardant thermoplastic resin compositions and their... 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 thermoplastic resin compositions and their..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flame-retardant thermoplastic resin compositions and their... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2957866