Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-22
2002-02-19
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...
C524S140000, C524S311000, C524S487000
Reexamination Certificate
active
06348527
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoplastic resin composition and its injection moldings, more precisely, to a thermoplastic resin composition having good melt fluidity and its injection moldings having good mold releasability and physical properties.
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, electric and electronic appliances, car parts and building materials. However, there are some problems with polycarbonate resins in that they require high molding and working temperatures and their melt fluidity is low. Like ordinary thermoplastic resins, polycarbonate resins are molded into various moldings through injection molding. Where they are molded into parts or housings of office automation appliances such as duplicators or facsimiles or those of electric and electronic appliances, the moldings shall have a complicated shape with local projections or depressions, for example, having ribs or bosses therewith. Those moldings of polycarbonate resins are often difficult to release from molds, and their smooth release from molds is often impossible. As the case may be, the moldings will be gapped in holes. Even though released from molds, the moldings will be often deformed, whitened or distorted with residual strain. For these reasons, polycarbonate resin moldings are often problematic in that they could not ensure good dimension accuracy, strength and appearance.
As a rule, polycarbonate resins are self-extinguishable. However, some of their applications to office automation appliances, electric and electronic appliances and others require high-level flame retardancy. To meet the requirement, various flame retardants are added to polycarbonate resins. On the other hand, compositions of polycarbonate resins to which are added styrene resins such as acrylonitrile-butadiene-styrene resins (ABS resins), acrylonitrile-styrene resins (AS resins) and the like are known as polymer alloys, and have many applications in the field of moldings as having good heat resistance and impact resistance. Of their applications, where such polycarbonate resin compositions are used for electric and electronic appliances and car parts, they are required to have high flame retardancy of not lower than a predetermined level so as to ensure and increase the safety of their moldings, especially electric and electronic appliances for household use and office automation appliances.
To meet the requirements as above, various methods have heretofore been proposed. Concretely, JP-A 61-55145 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. JP-A 2-32154 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. JP-A 8-239565 discloses a polycarbonate resin composition comprising (A) an aromatic polycarbonate, (B) an impact-resistant polystyrene resin with rubber-like elasticity, (C) a halogen-free phosphate, (D) a core/shell-type grafted rubber-like elastomer, and (E) talc.
These are all to improve the melt fluidity and therefore the moldability of polycarbonates, and to improve the impact resistance and the flame retardancy of the moldings of polycarbonates. As having such improved properties, the polycarbonate compositions proposed are formed into various practicable moldings. However, in special fields of office automation appliances, electric and electronic appliances especially those for household use, etc., parts and housings of those appliances are required to be more lightweight and thin. In particular, their shape is being more complicated to have fine projections and depressions such as ribs and bosses therewith or have a lattice structure, so that they are applicable to any complicated and large-sized appliances. To the moldings of the parts and housings for the appliances, especially to those to be formed in injection moldings, good releasability from molds is important. However, in order to ensure good releasability from molds of the moldings, thinning their walls and designing them is naturally limited. Therefore, some solutions to the limitation are desired.
In order to improve the mold releasability of polycarbonate resins, mold lubricants are often added to them. For example, JP-B 61-41939 discloses a molding composition containing a specific ester of an alcohol and an acid. They say therein that the moldings of the composition are degraded and yellowed little. To support the mold releasability of the composition, they did a test, in which the moldings not containing the mold release agent of a specific ester were broken by the ejector pin, and the pressure to the ejector pin was shown in terms of psi for the moldings containing the mold release agent. However, the difference in the data shown therein between Examples containing the specific ester and Comparative Examples not containing it is small. In addition, in this patent publication, any concrete disclosure is not shown relating to a technical idea of adding styrene resins to polycarbonate resins and to the flame retardancy of polycarbonate resin compositions.
JP-A 8-48844 discloses a flame-retardant resin composition with good mold releasability, which comprises (A) a polycarbonate, (B) a styrenic resin, (C) a resorcinol polyphosphate compound and (D) polytetrafluoroethylene, and contains (E) from 0.1 to 2 parts by weight, relative to 100 parts by weight of the resin composition, of a saturated fatty acid ester wax having a mean molecular weight of from 1000 to 50000, and (F) from 0.01 to 2 parts by weight, relative to the same, of a polyethylene wax having a mean molecular weight of from 1000 to 3000. Obviously, they say therein that the two waxes are effective only a little or are not effective at all when separately added to the resin composition, but could exhibit a significant mold-releasability improving effect only when added both together.
SUMMARY OF THE INVENTION
In that situation, the object of the present invention is to provide an improved thermoplastic resin composition comprising a polycarbonate resin and also its injection moldings well applicable even to thin-walled and complicated office automation appliances, electric and electronic appliances and car parts. The composition has good moldability, and its moldings have good impact resistance and high mechanical strength, especially having good flame retardancy. In particular, the moldings of the composition are easy to release from molds, even though being thin-walled and complicated in shape, and the freeness in designing products of the moldings is significant.
To attain the object as above, I, the present inventor have assiduously studied various thermoplastic resin compositions comprising a polycarbonate resin, with varying the ratio of the polycarbonate resin to various thermoplastic resins therein, not only for their moldability and physical properties but also for their mold releasability relative to different types of mold release agent to be combined with them. As a result, I have found that, when a specific additive is added to a thermoplastic resin composition comprising a polycarbonate resin and a styrene resin, then the resulting resin composition can be well produced and molded into good moldings. In particular, I have found that the resin composition has good melt fluidity and can be surely and stably molded into thin-walled, complicated and even relatively large-sized moldings, that the moldings can be surely released from molds, and that the moldings have high impact strength. On the basis of these findings, I have completed the present invention.
Specifically, the in
Buttner David J.
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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