JPS6021706B2 - Styrenic resin composition - Google Patents

Description

[Detailed description of the invention] The present invention relates to improved styrenic resin compositions.

More specifically, the object is to provide a styrene-based resin composition that prevents defective phenomena such as cracking and whitening by improving the template for injection molding of styrene-based resin, and improves the deterioration of the hue of molded products. . Conventionally, additives that improve mold release properties during injection molding of styrenic resins include
Metal salts of higher fatty acids are used.

By adding a relatively small amount of this compound, mold releasability can be improved, but this compound has extremely poor compatibility with styrene resins, and when added in an amount that produces a high degree of mold release effect, transparency The appearance of the molded product will be significantly impaired, and its commercial value will suffer as a result. On the other hand, when using a higher fatty acid as a template agent, a high mold release effect can only be obtained by adding it in a considerably larger amount than the higher fatty acid metal salt.

On the other hand, adding large amounts of higher fatty acids to styrenic resins may corrode extruders, injection molding machines, molds, etc., and may also prevent the melting of iron and the mixing of oxidation products of higher fatty acids into the molten resin. This is not preferred from a practical point of view, since it causes the color of the molded product to deteriorate. Furthermore, aliphatic higher alcohols have an even worse template effect than the above-mentioned higher fatty acids, and require a larger amount to be added.

In this case, the deterioration of the hue is relatively small, but as the amount added increases, the softening temperature of the composition decreases, the heat resistance of the composition decreases, the cooling solidification rate in the mold during injection molding slows down, and the molding cycle becomes shorter. It is not a preferred molding agent because it becomes long and reduces productivity. As described above, higher fatty acids, higher fatty acid metal salts, aliphatic higher alcohols, etc. that have been put to practical use so far lack a balance between mold release properties, hue deterioration, and moldability, and are not practically satisfactory.

The purpose of the present invention is to have a high degree of patternability during injection molding,
It is an object of the present invention to provide a styrenic resin composition which has high molded product productivity and does not cause deterioration in the hue of molded products.

In the present invention, the total amount of at least one type of higher fatty acid (a) and at least one type of aliphatic higher alcohol (b') is 0.06 to 0.06 to 100 parts by weight of the styrene resin.
Contains 0.4 parts by weight and the weight ratio of {a}:'b} is 1:0
．． The object of the present invention is to provide a styrenic resin composition characterized in that it has a molecular weight of 3 to 10.

The styrenic resin used in the present invention refers to at least one of a styrene homopolymer, a monomer copolymerizable with styrene, such as Q-methylstyrene, nuclear-substituted halogenated styrene, acrylonitrile, maleic anhydride, chloroprene, and methyl methacrylate. and a graft copolymer of the above-mentioned styrene or a mixture of a monomer copolymerizable with styrene and synthetic rubber.

Substantially transparent styrenic polymers include the above-mentioned styrene homopolymers, styrene-Q-methylstyrene copolymers, styrene-acrylonitrile copolymers, and styrene-Q-methylstyrene copolymers.
Examples include methyl styrene-acrylonitrile terpolymer, styreso-butadiene block copolymer, mixture of styrene homopolymer (general-purpose polystyrene) and a small amount of styrene-butageso graft copolymer (impact-resistant polystyrene), etc. It will be done.

The higher fatty acids in the present invention are C, o to C3o linear or branched saturated fatty acids, such as lauric acid, myristic acid,
Particularly preferred are saturated higher fatty acids such as palmitic acid, stearic acid, aragic acid, and behenic acid.

These can be used alone or in a mixture of two or more. Further, the aliphatic higher alcohol is a C, o to C3o linear or branched saturated aliphatic alcohol, and saturated aliphatic higher alcohols such as lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol are particularly preferred.

These can be used alone or in a mixture of more than one kind. In the present invention, the total amount of higher fatty acids and fatty acid higher alcohol at a ratio of 0.3 to 1M volume is 0.0 parts by weight to 0 parts by weight for 100 parts by weight of styrene resin.
．． Add 4 parts by weight.

The preferred amount is 0.08 parts by weight to 0.08 parts by weight. This is a phantom weight department. If the blended amount is less than 0.0 part by weight, the template properties will be insufficient and the molded product will suffer from cracks, whitening, etc. during injection molding.

Moreover, if it exceeds 0.4 parts by weight, the softening temperature decreases and the cooling rate during injection molding becomes slow, resulting in a decrease in productivity.
If the ratio of aliphatic higher alcohol is less than 0.3 times that of higher fatty acid, it will not be possible to reduce the corrosion to the extruder injection molding machine mold or the deterioration of the hue of the molded product that occurs when higher fatty acid is used alone. Generally, among styrene resins, those containing rubber components such as styrene-polybutadiene graft copolymers have better mold release properties during injection molding than styrene homopolymers and styrene-acrylonitrile copolymers. There is.

This is presumed to be because styrene-based resins containing rubber components have a larger molding shrinkage, or because they have a smaller coefficient of friction against the mold surface and are easier to release from the mold. Therefore, the composition according to the present invention exhibits particularly remarkable effects when using a styrenic resin that does not contain a rubber component or contains only a small amount of rubber component, that is, a styrenic resin that is substantially transparent. However, even when a styrene resin is blended with a rubber component, the composition according to the present invention is extremely effective in improving mold releasability when injection molding is performed using a mold having a portion with an extremely small draft angle. In addition, in the case of the above-mentioned substantially transparent styrene resin, it is extremely sensitive to deterioration of hue and devitrification, and these have a large effect on the commercial value of molded products, so the composition of the present invention is extremely useful. You can say that. The composition according to the invention may contain other commonly used additives, such as flow improvers such as liquid paraffin, BH
An antioxidant such as T or BHA, an external thickening agent such as ethylene bisstearylamide, etc. can be mixed and used.

The present invention will be explained below by way of examples.

Note that % in the examples represents weight %. Examples Various styrene resins and various mold release agents were uniformly kneaded using an extruder according to the formulations shown in the experiment numbers in Tables 2 and 3 to obtain pellets of styrene resin compositions.

The styrene resin used was general purpose polystyrene (GPPS).
) Toporex #550 (manufactured by Mitsui Tosho Co., Ltd.),
Lightack #100 (abbreviated as AS) of AS copolymer resin (abbreviated as AS)
(manufactured by Mitsui Toshosha). Using these pellets, the mold pressure during injection molding was measured, and the appearance of the molded products, such as transparency and hue, was observed. The mold release pressure was determined by measuring the hydraulic pressure corresponding to the resistance when ejecting the molded product (cup) from the mold using a strain gauge.

The injection molding machine is Nissei Jushi Kogyo TS-100 (plasticization capacity 3
The molding conditions were changed depending on the resin as shown in Table 1.

(Note to Table 1) *Minimum injection pressure refers to the lowest injection pressure at which a completely finished cedar product can be obtained.

The results using GPPS as the styrene resin are shown in Table 2, and the results using AS are shown in Table 3. Table 2 Table 3

Claims (1)

[Claims] 1. A total of 0.06 to 0.4 parts by weight of at least one type of higher fatty acid (a) and at least one type of aliphatic higher alcohol (b) based on 100 parts by weight of styrenic resin. 1. A styrenic resin composition characterized in that the weight ratio of (a):(b) is 1:0.3 to 10. 2. The styrenic resin composition according to claim 1, wherein a styrenic polymer having substantially transparency is used as the styrenic resin.