The present invention relates to a polycarbonate resin composition, more precisely, to a polycarbonate resin composition not containing halogen and phosphorus but containing a minor additive to exhibit good flame retardancy and have good impact resistance, high stiffness, good melt flowability and good chemical resistance.
As having the advantages of impact resistance, heat resistance and good electric properties, polycarbonate resins have many applications in various fields of, for example, OA (office automation) appliances, information and communication appliances, other electric and electronic appliances for industrial use and household use, automobile parts and building materials. As a rule, polycarbonate resins are self-extinguishable. However, some fields of typically OA appliances, information and communication appliances, and other electric and electronic appliances for industrial use and household use require high flame retardancy, for which are used various flame retardants to improve their flame retardancy.
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 with polycarbonate resin products and toward environmental protection from discarded and incinerated wastes of the products, the market requires flame retardation of polycarbonate resins with non-halogen flame retardants. Given that situation, polycarbonate resin compositions with phosphorus-containing organic flame retardants, especially organic phosphate compounds that are non-halogen flame retardants have been proposed, and their flame retardancy is good. Such phosphorus-containing organic flame retardants serve also as a plasticizer, and various methods of using them for making polycarbonate resins resistant to flames have been proposed.
However, in order to make polycarbonate resins have good flame retardancy by adding thereto an organic phosphate compound, a relatively large amount of the compound must be added to the resins. In general, polycarbonate resins require relatively high molding temperatures, and their melt viscosity is high. Therefore, for molding them into thin-walled and large-sized moldings, the molding temperature will have to be more higher. For these reasons, organic phosphate compounds often cause some problems when added to such polycarbonate resins, though their flame-retarding ability is good. For example, organic phosphate compounds often corrode molds used for molding resins containing them, and generate gas to have some unfavorable influences on the working environments and even on the appearance of the moldings. Another problem with organic phosphate compounds is that, when the moldings containing them are left under heat or in high-temperature and high-humidity conditions, the compounds lower the impact strength of the moldings and yellow the moldings. In addition, polycarbonate resin compositions containing organic phosphate compounds are not stable under heat, and therefore do not meet the recent requirement for recycling resin products. This is still another problem with organic phosphate compounds.
On the other hand, for machine parts which will be often stained with oil or copying ink having scattered therearound and for products that will be coated with grease or the like, resin materials are further required to have good chemical resistance in addition to flame retardancy.
To meet the market requirements, proposed is another technique of adding silicone compounds to polycarbonate resins to make the resins have flame retardancy. In this, silicone compounds added to the resins do not give toxic gas when fired. For example, (1) Japanese Patent Laid-Open No. 139964/1998 discloses a flame retardant that comprises a silicone resin having a specific structure and a specific molecular weight.
(2) Japanese Patent Laid-Open Nos. 45160/1976, 318069/1989, 306265/1994, 12868/1996, 295796/1996, and Japanese Patent Publication No. 48947/1991 disclose silicone-containing, flame-retardant polycarbonate resin compositions. The flame retardancy level of the products in (1) is high in some degree, but the impact resistance thereof is often low. The technology of (2) differs from that of (1) in that the silicones used in (2) do not act as a flame retardant by themselves, but are for improving the dripping resistance of resins, and some examples of silicones for that purpose are mentioned. Anyhow, in (2), the resins indispensably require an additional flame retardant of, for example, organic phosphate compounds or metal salts of Group 2 of the Periodic Table. Another problem with the flame-retardant polycarbonate resin compositions in (2) is that the flame retardant added thereto worsens the moldability and even the physical properties of the resin compositions and their moldings.
Also known is a flame-retardant polycarbonate resin composition that comprises a polycarbonate resin, a polycarbonate-polyorganosiloxane copolymer-containing resin and a fibril-forming polytetrafluoroethylene (Japanese Patent Laid-Open No. 81620/1996). Even though its polyorganosiloxane content is low, falling within a defined range, the composition exhibits good flame retardancy. Though its flame retardancy is good, however, the composition is problematic in that its impact resistance intrinsic to polycarbonate resins is often low.
For improving the chemical resistance of polycarbonate resins, it is generally known to add a thermoplastic polyester to the resins. For example, Japanese Patent Laid-Open No. 181265/1999 discloses a polycarbonate resin composition prepared by adding a polyester resin, an alkali metal or alkaline earth metal perfluoroalkanesulfonate, a fluororesin and a silicone, to a polycarbonate resin. However, since its high-temperature thermal stability in dwell time in an extruder or the like is often poor, the resin composition is difficult to recycle.
The present invention has been made in the current situation as above, and its object is to provide a non-halogen and non-phosphorus, flame-retardant polycarbonate resin composition of which the flame retardancy is good and which has good impact resistance, high stiffness, good melt flowability and good chemical resistance.
I, the present inventor have assiduously studied, and, as a result, have found that, when a thermoplastic polyester, a polyfluoro-olefin resin, and a polycarbonate-polyorganosiloxane copolymer and/or a specific silicone compound are added to a polycarbonate resin, then the above-mentioned object of the invention can be effectively attained. On the basis of this finding, we have completed the present invention.
Specifically, the invention is summarized as follows:
1. A polycarbonate resin composition which comprises a resin mixture of (A) from 1 to 99% by weight of a polycarbonate and (B) from 1 to 99% by weight of a thermoplastic polyester, and contains, relative to 100 parts by weight of the resin mixture, (C) from 0.01 to 3 parts by weight of a polyfluoro-olefin resin, and (D) from 1 to 400 parts by weight of a polycarbonate-polyorganosiloxane copolymer and/or (E) from 0.1 to 10 parts by weight of a functional silicone compound, and of which the silicone content derived from the component (D) and/or the component (E) falls between 0.5 and 10% by weight of the composition.
2. The polycarbonate resin composition of above 1, which further contains (F) from 1 to 50 parts by weight of an inorganic filler.
3. The polycarbonate resin composition of above 1 or 2, wherein the functional silicone compound for the component (E) has a basic structure of a general formula (1):
R1a R2bSiO(4xe2x88x92axe2x88x92b)/2xe2x80x83xe2x80x83(1)
wherein R1 indicates a functional group, R2 indicates a hydrocarbon residue having from 1 to 12 carbon atoms, and a and b are numbers satisfying the relations of 0 less than axe2x89xa63, 0xe2x89xa6b less than 3, and 0 less than a+bxe2x89xa63.
4. The polycarbonate resin composition of any of above 1 to 3, wherein the functional group in the functional silicone compound for the component (E) is selected from an alkoxy group, a vinyl group, a hydrogen residue and an epoxy group.
5. The polycarbonate resin composition of any of above 1 to 4, wherein the functional group in the functional silicone compound for the component (E) is a methoxy group or a vinyl group.
6. The polycarbonate resin composition of any of above 1 to 5, wherein the polyfluoro-olefin resin for the component (C) is a fibril-forming polytetrafluoroethylene having a mean molecular weight of at least 500,000.
7. The polycarbonate resin composition of any of above 1 to 6, wherein the polycarbonate for the component (A) has a viscosity-average molecular weight of from 15,000 to 20,000.
8. The polycarbonate resin composition of any of above 2 to 7, wherein the inorganic filler for the component (F) is talc having a mean particle size of from 0.2 to 20 xcexcm.
9. Housings or parts of electric and electronic appliances, which comprise the polycarbonate resin composition of any of above 1 to 8.