Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-05-02
2002-06-04
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S127000, C524S156000, C524S157000, C524S284000
Reexamination Certificate
active
06399681
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a colored thermoplastic resin composition containing a black dye exhibiting excellent dispersibility and/or compatibility for a crystalline thermoplastic resin, a method for molding said colored thermoplastic resin composition, a method for lowering the crystallizing temperature of a thermoplastic resin, and a fiber-reinforced colored thermoplastic resin molded product.
BACKGROUND OF THE INVENTION
Being excellent in mechanical and chemical properties, thermoplastic resins are widely used for molded plastic products in the field of parts of automobiles, electric and electronic products, etc., and their demand is increasing in the field of engineering plastics as well.
As such, thermoplastic resins are colored for decoration, color identification, improvement of light fastness of molded products, content protection and shading and for other purposes; in particular, black coloring is the most important for industrial applications. Traditionally, various inorganic pigments and organic dyes/pigments, such as carbon black, black metal complex dyes, azine dyes and perinone black, have been used for black coloring of thermoplastic resins.
More specifically, examples of colored thermoplastic resins include a molding formula comprising a polyamide resin colored with carbon black and nigrosine (Japanese Patent Examined Publication no.43379/1985); a molding composition comprising a polyamide resin colored with carbon black and a copper phthalocyanine pigment (Japanese Patent Unexamined Publication No. 226551/1985); a molding composition comprising an unsaturated polyester resin colored with aniline black and solvent blue (Japanese Patent Examined Publication No. 46524/1989); a plastic molding composition comprising a thermoplastic resin supplemented with carbon black and titanium oxide (Japanese Patent Unexamined Publication No. 186633/1993); a colored resin composition comprising a thermoplastic resin colored with a red organic pigment, a blue organic pigment and a yellow organic pigment (Japanese Patent Unexamined Publication No.230278/1993); and a mixed resin of polyethylene terephthalate resin and polybutylene terephthalate resin with carbon black dispersed therein (Japanese Patent Unexamined Publication No. 194825/1993).
However, these conventional colored thermoplastic resin compositions do not always have good appearance and surface gloss, many of which undergo physical property deterioration in comparison with the original thermoplastic resins; further investigation remains to be conducted.
In addition, there have been attempts to improve the heat resistance and chemical resistance of thermoplastic resins and confer mechanical characteristics suited for various uses, by formulating a fibrous reinforcing material therein, to meet the requirements of a wide variety of industrial applications. Furthermore, in recent years, there has been a marked trend toward replacement of conventional metal parts of electronic products, electrical equipment for automobiles, etc. with fiber-reinforced thermoplastic resins, for the purpose of weight reduction, manufacturing process simplification and corrosion prevention, taking note of the good physical properties of fiber-reinforced crystalline thermoplastic resins as molding materials.
Examples of conventional fiber-reinforced colored thermoplastic resins include a polyester resin composition for molding comprising a polybutylene terephthalate having a specific viscosity of not less than 0.35, a reinforcing material and carbon black (Japanese Patent Unexamined Publication No. 117951/1990); a thermoplastic resin composition comprising a thermoplastic resin, a modified polyolefin, a fibrous reinforcing material and carbon black (Japanese Patent Unexamined Publication No. 50263/1991); a glass fiber-reinforced black polyamide resin composition comprising a polyamide resin, surface-treated glass fiber and an azine dye (Japanese Patent Unexamined Publication No. 128479/1994); and an antistatic-fiber-reinforced polybutylene terephthalate resin composition comprising a glass fiber-reinforced polybutylene terephthalate resin having a volume resistivity of not more than 1×10
10
&OHgr;cm, and carbon black formulated therein (Japanese Patent Unexamined Publication No. 53610/1996).
In conventional fiber-reinforced colored thermoplastic resins, however, the problem is likely to arise in which it is difficult to thoroughly and uniformly disperse a coloring agent (e.g., black pigment) in the resin even by kneading them together for a long time, because of the presence of a fibrous reinforcing material in the resin. In addition, adding a coloring agent can deteriorate the physical properties, can intensify the warpage deformation of the molded product due to a temperature change during molding, or can considerably reduce the fluidity, in comparison with the original thermoplastic resin which does not contain the coloring agent. In particular, the flotation of the fibrous reinforcing material on the surface of the molded product during molding is somewhat problematic in that the gloss, appearance, etc. of the colored molded product are affected.
For these reasons, there is a strong commercial demand for a fiber-reinforced colored thermoplastic resin which is moldable at high precision for details, which has good light fastness, and which exhibits better gloss and appearance in the markets of various molded products etc.
In addition, injection molding, a method for molding a thermoplastic resin, is a method wherein a plastic material, previously fluidized by heating, is injected into the hollow (cavity) of a mold and cooled and solidified in the mold to yield a molded product fitting to the inside shape of the cavity, making it possible to obtain products of high precision and high quality with highest efficiency and productivity.
In this case, the temperature of the mold governs the cooling solidification conditions for the molten resin filled in the mold. Specifically, as the difference from the resin temperature increases (mold temperature decreases), the cooling rate increases. In the case of a crystalline material, in particular, there is a remarkably high correlation between cooling rate and degree of crystallinity, and the degree of crystallinity significantly affects the physical property values of the molded product.
Regarding the general tendency, as the mold temperature decreases, the degree of crystallinity decreases and the molded product becomes more ductile. As the mold temperature increases, the degree of crystallinity increases and the strength of the molded product becomes higher but the molded product becomes more brittle.
Injection time in injection molding refers to the period of time during which a thermoplastic resin is inject-filled in the cavity. In the case of a thin molded product, injection time shortens. As the molded product becomes larger, more complex, and thicker, more injection time is taken. It is therefore possible to mold a more complex molded product by broadening the range of optimum injection time for a thermoplastic resin.
In molding treatment of a thermoplastic resin, the temperature at which the material is thermally plasticized varies over a wide range from about 180 to 430° C., including the temperature of the heating cylinder. In addition, molding temperature, i.e., the temperature required to cool and harden the material, refers to the temperature of the mold, and normally ranges from about 120 to 200° C. Causes of molding failures in the injection molding process include uneven coloring, sinks, short shots, and burned marks. These are caused by high mold temperatures and uneven cooling circuits. The flow mark is known to be a molding failure and to be prevented by increasing the mold temperature. If the mold temperature is increased, however, additional heat energy is required; in addition, a great amount of heat energy must be transferred to cool the once-heated mold; these factors raise production cost. Furthermore, if the mold temperature is increased,
Hayashi Akihiko
Takeuchi Hiroshi
Tsuruhara Tohru
McGlew and Tuttle , P.C.
Orient Chemical Industries Ltd.
Sanders Kriellion A.
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