JPH0319260B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to thermoplastic resin pellets, and more specifically to a thermoplastic resin with excellent moldability that is used to mold a molded article with a very small amount of a specific compound uniformly adhered to the surface of the styrenic thermoplastic resin pellet. It concerns pellets. More specifically, during injection molding or extrusion molding, silver streaks, gas marks, and burns on molded products occur due to pellet fluidity, non-uniform resin melting rate, shear heat generation during plasticization, etc. An object of the present invention is to provide a styrenic thermoplastic resin pellet that can prevent such phenomena from occurring. Conventionally, a method for improving the molding processability of styrenic thermoplastic resins involves kneading compounds with internal and external lubricity into resin pellets to make the molten resin lubricious between the molding machine cylinder wall and screw surface. By creating internal lubricity between the resins, frictional heat generation during heating and kneading has been prevented, and defective phenomena such as silver streaks, gas, and discoloration have been improved and the product has been put into practical use. However, in recent years, advances in molding machines have led to the emergence of so-called high-kneading, high-plasticization molding, which reduces the clearance between the barrel and the screw, makes the cylinder longer, and increases the screw rotation speed. With molded resin pellets, there is a high incidence of silver streaks, gas smudges, and discoloration due to thermal decomposition of the resin due to frictional heat generation, air entrainment during screw rotation, uneven plasticization speed, etc. Measures to deal with molding machines from the resin perspective are beginning to be considered. As a countermeasure for lubricant-mixed resin pellets, increasing the amount of lubricant added is often used, but increasing the amount will lower the heat resistance of the resin and increase the volatile components of the additive itself, resulting in silver streaks, discoloration, This not only causes defects in the appearance of the molded product such as coloring, but also leads to deterioration in physical properties. Furthermore, in kneaded resin pellets, the resin and lubricant are melted at the same time, so the lubricity until the pellets melt is low. However, it is necessary to add a large amount of lubricant, which leads to a further deterioration in overall quality.Therefore, it has been desired to develop an additive and an additive method that can be more effective even when added in small amounts. The present inventors have studied various additives and methods of addition that achieve the above objectives by adding small amounts,
The invention has been completed. That is, in the present invention, based on 100 parts by weight of styrene thermoplastic resin pellets, (1) organopolysiloxane, (2) aliphatic hydrocarbon wax, (3) ester wax of higher fatty acid and higher alcohol, (4) At least one compound selected from higher fatty acid bisamides and (5) higher fatty acid metal salts 0.01 to 0.1
The present invention relates to thermoplastic resin pellets which have excellent moldability and can be used directly to form molded products with the weight part uniformly adhered to the surface of the resin pellets. What is the styrenic thermoplastic resin referred to in the present invention?
These include ABS resin, AES resin, AAS resin, AS resin, polystyrene resin, impact-resistant polystyrene resin, etc., and usually have a hardness that allows them to be handled as pellet particles. The size of the pellets is preferably one that does not pass through 20 meshes, and preferably 2 to 10 meshes. Additives used in the present invention include organopolysiloxanes represented by polydimethylsiloxane, polydiethylsiloxane, polymethyl phenylsiloxane, or modified products thereof, liquid paraffin, synthetic paraffin, polyethylene wax, polypropylene wax, etc. Aliphatic hydrocarbon waxes represented by carnauba wax,
Montan waxes, ester waxes of higher fatty acids and higher alcohols such as beeswax, methylene bis stearamide, ethylene bis stearamide, ethylene bis valmitic acid amide, ethylene bis oleic acid amide, etc. Examples include metal salts of higher fatty acids such as bisamides of higher fatty acids, barium laurate, cadmium myristate, calcium stearate, magnesium stearate, and aluminum stearate. On the other hand, fatty acid esters of alcohols with a relatively small number of carbon atoms such as butyl stearate, dibutyl sebacate, and glycerin fatty acid esters, fatty alcohols such as palmityl alcohol and stearyl alcohol, lauric acid, and palmitin Acids, fatty acids such as stearic acid, etc. have little effect on the purpose of the present invention. The amount of additive added so that it is evenly attached to the pellet surface is the styrene thermoplastic resin pellet.
The amount ranges from 0.01 to 0.1 parts by weight per 100 parts by weight. If the amount added is less than 0.01 part by weight, the effect of improving molding processability is insufficient, while if it is added in excess of 0.1 part by weight, the pellets may slip in the feed zone of the screw, or the kneading may be insufficient. , a delay in the molding cycle, non-uniformity in quality, and an increase in air entrainment during screw rotation, conversely resulting in poor molding appearance, decreased productivity, and decreased quality, making it impossible to obtain a desirable molded product. A method for uniformly adhering the additive to the pellet surface is to mix the resin pellet and the additive using a normal Henschel type mixer, tumbler, ribbon mixer, wax blender, etc. without requiring any special equipment. It can be easily implemented by Also commonly used dioctyl phthalate,
The above additives may be applied after a wetting agent such as dibutyl phthalate or butyl stearate is applied to the pellet surface. The thus obtained styrenic thermoplastic resin pellets having good moldability are directly fed to a molding machine to form a molded article. By using the resin pellets of the present invention, not only conventional molding machines but also high-kneading, high-plasticization molding machines can achieve stable supply from the hopper to the screw feed zone and a stable feed zone. This improves the fluidity of the pellets, reduces entrained air through uniform plasticization in the compression zone and metering zone, and reduces frictional heat generation during heating and kneading, thereby preventing quality deterioration and appearance defects. It has become possible to improve productivity by shortening the molding cycle and increasing the amount of discharge. Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 ABS resin pellets (particle size 2-10 mesh product)
To 100 parts by weight, a predetermined amount of each of the following powder compounds or liquid compounds was added, and after stirring and mixing in a tumbler for 10 minutes, the pellets were dried at 80 ° C. for 2 hours.
A 200 mm x 250 mm x 3 mm plate was molded using a 13 _pz injection molding machine, and the appearance of the molded product was visually evaluated and the screw metering time was measured. The molding conditions were such that defects are likely to occur, ie, low cylinder temperature, low mold temperature, high injection pressure, low screw back pressure, and high screw rotation. The results are shown in Table-1. Molding conditions cylinder temperature 200℃, mold temperature 30℃,
Injection pressure 1200Kg/cm ² , screw back pressure 2
Kg/cm ² (gauge pressure), screw rotation speed
100rpm

[Table] Comparative Example 1 The following compounds were evaluated in exactly the same manner as in Example 1. The results are shown in Table-2.

[Table] Comparative Example 2 Each pellet to which the additive of Example 1 was attached was passed through an extruder with a cylinder temperature of 200°C to obtain pellets in which the additive was kneaded into the pellet. Using this pellet, a plate was molded in the same manner as in Example 1 and evaluated. The evaluation results are shown in Table-3. In Comparative Example 2, which used pellets mixed with additives, silver streaks and discoloration could not be improved.

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Claims (1)

[Scope of Claims] 1 Based on 100 parts by weight of styrene thermoplastic resin pellets, (1) organopolysiloxane, (2) aliphatic hydrocarbon wax, (3) ester wax of higher fatty acid and higher alcohol, ( 4) at least one compound selected from higher fatty acid bisamides and (5) higher fatty acid metal salts 0.01 to 0.1
A thermoplastic resin pellet that is directly used for molding a molded product with the weight part uniformly attached to the surface of the resin pellet.