Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-09-02
2002-04-09
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S109000, C524S114000, C524S127000, C525S065000, C525S067000, C525S09200D
Reexamination Certificate
active
06369142
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoplastic resin composition, precisely, to that having good moldability and capable of being molded into moldings, especially injection moldings applicable to, for example, office automation appliances, and other electric and electronic appliances for household. More precisely, the invention relates to a thermoplastic resin composition having good moldability and good resin compatibility and to its injection moldings having good impact resistance.
The invention also relates to a flame-retardant polycarbonate resin composition, precisely to that capable of being molded into good moldings having good flame retardancy, good thermal stability and good outward appearance, and to its injection moldings having good durability and good recyclability.
2. Description of the Related Art
As having the advantages of impact resistance, heat resistance and good electric properties, polycarbonate resins have many applications in various fields of, for example, office automation appliances, information appliances, electric and electronic appliances for industrial use and household use, car parts and building materials. However, there are some problems with polycarbonate resins in that they require high molding and processing temperatures and their melt fluidity is low.
On the other hand, moldings for housings and parts for of ice automation appliances and information appliances such as duplicators and facsimiles, and for other electric and electronic appliances are required to have a complicated shape with local projections or depressions, for example, having ribs or bosses therewith, and to be and thin-walled for reasons of weight and resources saving. Therefore, desired are polycarbonate resin compositions having increased melt fluidity, or that is, having increased injection moldability. Various polycarbonate resin compositions having increased melt fluidity and increased moldability have heretofore been proposed, to which are added rubber-modified styrenic resins in consideration of physical properties such as impact resistance of the moldings.
As mentioned hereinabove, polycarbonate resins are problematic in that they require high molding and processing temperatures and their melt fluidity is low. Because of such problems with them, the molding and working temperatures for polycarbonate resins are generally high. In particular, when some additives are added to them, the thermal stability of polycarbonate resins is often lowered when they are molded, and their moldings could not often exhibit the excellent properties intrinsic to polycarbonate resins. As a rule, polycarbonate resins are self-extinguishing. However, some of their applications to office automation appliances, information appliances, electric and electronic appliances for industrial use and for household use require high-level flame retardancy. To meet the requirement, various flame retardants are added to polycarbonate resins.
Compositions of polycarbonate resins, to which are added styrenic resins such as acrylonitrile-butadiene-styrene resins (ABS resins) or acrylonitrile-styrene resins (AS resins) for improving the melt fluidity of the compositions, and have many applications in the field of moldings, being polymer alloys with their typical good heat resistance and impact resistance. Though polycarbonate resins are self-extinguishing, their polymer alloys 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.
To meet the requirements as above, various methods have heretofore been proposed. Concretely, 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.
In those compositions, however, the compatibility of the polycarbonate resin with the styrenic resin is not satisfactory. Therefore, the compositions are still problematic in that, when they are molded into large-sized moldings or thin-walled moldings in a rapid injection molding process, the resulting moldings are often troubled by surface layer peeling, and the impact resistance, especially the surface impact resistance of the moldings is poor. In addition, the flame-retardant compositions comprising a phosphate compound that serves as a flame retardant therein are further problematic in that they are readily degraded in high-temperature and high-humidity atmospheres and their recyclability is poor. Concretely, when the moldings of the compositions are re-melted and recycled, after having been once used in practice, then the impact resistance and other physical properties of the recycled moldings are often poor, and, in addition, the recycled moldings are often yellowed.
For improving the compatibility of a polycarbonate resin with a styrenic resin in a composition comprising the two resins, a method has been proposed of adding from 0.5 to 5 parts by weight of an epoxy-modified block copolymer to 100 parts by weight of the resin mixture, in which the epoxy-modified block copolymer added comprises polymer blocks of essentially a vinyl aromatic compound and polymer blocks of essentially a conjugated diene compound, the latter epoxidized at the unsaturated carbon-carbon double bond (see Japanese Patent Laid-Open No. 48894/1997). Another method has also been proposed of adding an organic phosphorus compound which serves as a flame retardant to that composition to prepare a flame-retardant resin composition (see Japanese Patent Laid-Open Nos. 324086/1997 and 168273/1998). These proposed compositions are characterized in that they have greatly improved impact resistance.
On the other hand, it is well known that adding a rubber-like polymer to a resin composition comprising a polycarbonate resin and a styrenic resin improves the impact strength of the resin composition. For example, Japanese Patent Laid-Open 3397/1996 discloses a flame-retardant, thermoplastic resin composition comprising (A) a polycarbonate resin, (B) an AS resin, (C) an ABS resin, (D) a composite rubber-type graft copolymer, and (E) a flame retardant; and Japanese Patent Laid-Open No. 239565/1996 discloses a polycarbonate resin composition comprising (A) an aromatic polycarbonate, (B) a rubber-based elastomer incorporated in an impact-resistant polystyrene resin, (C) a non-halogen phosphate, (D) a core/shell-type, grafted rubber-like elastomer, and (E) a polycarbonate resin substance containing talc.
The method of adding an epoxy-modified block copolymer to a polycarbonate-styrene composition in which the epoxy-modified block copolymer comprises polymer blocks with a vinyl aromatic compound as a main component and polymer blocks with a conjugated diene compound as a main component the latter epoxidized at the unsaturated carbon-carbon double bond, and also the method of adding a composite rubber-based graft copolymer thereto are both excellent in that the impact resistance of the resulting polymer compositions is greatly improved. However, in our experiments, we, the present inventors, have demonstrated that the impact resistance of the moldings of those resin compositions, especially the surface impact resistance thereof is not always satisfactory in practical use. In addition, we have further found that the moldings are often troubled by surface layer peeling and, in particular, the resistance to aging due to moisture of the moldings of the resin compositions that contains a phosphorus-containing flame retardant is not good.
F
Mitsuta Naoki
Nodera Akio
Buttner David J.
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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