(a) Technical Field
The invention provides a non-painting and high-gloss polycarbonate resin composition. In certain embodiments, the invention provides a polycarbonate resin composition having superior impact strength, heat-resistance, electric characteristics, weather resistance, and light resistance. The resin composition is obtained by mixing a butadiene-based impact modifier (such as, acrylonitrile-butadiene-styrene (ABS), and methacrylate-butadiene-styrene) and an acryl-based impact modifier in polycarbonate resin to obtain a mixture, followed by adding an ultraviolet (UV) absorbent to the mixture.
(b) Background Art
As an engineering plastic material for interior and exterior uses in vehicles and housings of office equipment is continuously exposed to a light source, such as, ultraviolet (UV) rays, light resistance or weather resistance of the engineering plastic material is desired to prevent aging of the plastic materials caused by the UV rays. The materials need high temperature heat-resistance so that they would not be deformed at a temperature as high as 110° C. Consequently, the material can stand hot weather in outdoor environments under sunlight during the summertime. It is also desired that the material has low-temperature brittleness, so that its strength is not minimized at an extremely low temperature during the wintertime. The materials also need a high flow index to make it possible for a complex injection molding by using a mold, as well as a high tensile strength to a stand flow stress that is applied during use.
However, physical properties, such as, low-temperature brittleness, tensile strength, fluidity, heat resistance, and light resistance, generally tend to be inversely proportional to one another. Thus, it is difficult to manufacture a product which satisfies all the needs of consumers needs, as it is almost impossible to make a resin having various characteristics at the same time. Accordingly, when different resins having different characteristics are properly mixed for molding, schemes capable of providing new characteristics, that is, a characteristic which has not been provided by the resins, and in the meantime capable of maintaining the characteristics and advantages of the resins, have been contemplated. However, the adhesive strength between the resins is deteriorated through a simple mixing of the resins, failing to show new synergistic effects. Further, only the characteristics through a simple mixing are provided; or, the characteristics could even degrade.
To develop a resin composition having various physical properties, first, it is important to develop products which contain polycarbonate resin having a high heat resistance, dimensional stability, and tensile strength as the main resin. Polycarbonate is an engineering plastic resin that has transparency, a high-gloss feature, and high strength. When it is blended with an impact modifier, it minimizes certain disadvantages, such as, moldability, the relationship between impact and thickness, the anti-chemical property, and so forth.
Next, it is desirable to develop a resin having a superior thermal stability, impact resistance, self-extinguishing property (such as, that of polycarbonate), processibility, and an economical efficiency. Acrylonitrile-butadiene-styrene, a polycarbonate/styrene-based resin, particularly, acrylonitrile-butadiene-styrene alloy, has been developed as an engineering plastic material, which has been increasingly used as interior and exterior materials of vehicles and housings of office equipment. However, a combination of polycarbonate and acrylonitrile-butadiene-styrene alloy resin can be easily discolored by lights due to the poor light resistance that acrylonitrile-butadiene-styrene has. Therefore, the use of the combination of polycarbonate and acrylonitrile-butadiene-styrene as a structure is limited, unless the structure is painted or coated with a pad to prevent discoloring.
For the above concerns, various methods for improving the light resistance of a polycarbonate resin composition have been developed, for example, those provided in Korean Patent No. 802752, Japanese Patent Application Publication No. Hei 8-0199055, Japanese Patent Application Publication No. 2002-0114903, and Japanese Patent Application Publication No. 2002-0114902. However, the techniques described in these references fail to provide a method of manufacturing a molding product having low-temperature brittleness, tensile strength, fluidity, heat resistance, and light resistance, and etc. Generally, when the weather resistance is improved by adding a weather-resistance resin, such as acrylonitrile-styrene-acrylate resin, the low-temperature brittleness of the acrylonitrile-styrene-acrylate resin is reduced, compared to that of the acrylonitrile-butadiene-styrene resin, thus degrading the low-temperature impact strength of the resin. On the other hand, despite that low-temperature brittleness may be reinforced by adding a silicon-based impact modifier, there is a limitation in reinforcing the low-temperature brittleness while maintaining the light resistance.
Therefore, there is an urgent need for development of a material having superior light resistance while maintaining all of the main characteristics of a polycarbonate/acrylonitrile-butadiene-styrene alloy, such as, impact resistance, moldability, dimensional stability, and stiffness.