JPH08169998A - Styrenic resin composition - Google Patents

Abstract

PURPOSE: To provide a styrenic resin compsn. capable of mass production of molded products excellent in releasability from a mold with no deformation of the molded products. CONSTITUTION: The compsn. comprises (a) 100 pts.wt. styrene resin; (b) 0.1-2.0 pts.wt. mixed ester of pentaerythritol and/or dipentaerythritol with a dibasic org. acid and a higher fatty acid, and/or higher fatty acid ester of pentaerythritol and/or dipentaerythritol; (c)0.1-2.0 pts.wt. ethylenebisstearylamide; and (d) 0.1-2.0 pts.wt. low-mol.-wt. polyethylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene resin composition having excellent mold releasability of a molded product from a mold.

[0002]

2. Description of the Related Art When a resin is molded by a molding method such as injection molding, the molded product adheres to a mold or the like and is difficult to separate from the mold or the like, which causes a defective appearance such as breakage or deformation of the molded product. However, there is a problem that it is impossible to mass-produce molded products. Therefore, as a means for solving such a problem of mold release failure, generally, a mold release agent is applied to a mold or the like, or a resin is preliminarily mixed with a mold release agent to improve the mold release property of the resin. It is known to improve. As a releasing agent used for this purpose, higher fatty acids, metal salts of higher fatty acids, silicone oil, low molecular weight polyethylene and the like are known.

[0003]

However, when such a release agent is added to the resin to improve the releasability, a large amount must be added, which is economically disadvantageous.
Problems such as a decrease in the heat distortion temperature of the molded product occur. The object of the present invention is to obtain a styrene resin composition having low adhesion to a metal part of a molding machine or a mold, excellent mold releasability from a mold, no deformation of a molded product and no problem in mass production. As a result of repeated studies, it was found that a combination of specific lubricants and a compounding amount unexpectedly exhibit a combined effect, and the present invention has been completed.

[0004]

The present invention comprises (a) 100 parts by weight of a styrenic resin (b) pentaerythritol and / or dipentaerythritol, a mixed ester of dibasic organic acid and higher fatty acid; and / or penta Higher fatty acid of erythritol and / or dipentaerythritol 0.1 to 2.0 parts by weight (c)
Provided is a styrene-based resin composition containing 0.1 to 2.0 parts by weight of ethylenebisstearylamide (d) 0.1 to 2.0 parts by weight of low molecular weight polyethylene.

The styrene resin which is the component (a) of the present invention is a homopolymer or copolymer of styrene or a styrene derivative such as α-methylstyrene and vinyltoluene, and these monomers and acrylonitrile and methylmethacrylate. It is obtained by graft-polymerizing styrene or a styrene derivative and another vinyl monomer onto a copolymer with a vinyl monomer such as, a diene rubber such as polybutadiene, an ethylene / propylene rubber, an acrylic rubber, and the like. , High impact polystyrene, AS resin, ABS resin, AAS resin, AES resin and the like.

Pentaerythritol and / or dipentaerythritol which is the component (b) in the present invention,
A mixed ester of a dihydrochloric acid and a higher fatty acid or / and a higher fatty acid ester of pentaerythritol and / or dipentaerythritol can be produced from the raw material by a known alkyd synthesis or esterification reaction.

Strictly speaking, the reaction product is a polymolecular polycondensate having different esterification rates.
A typical example of the case of 00% is as follows.
~ (V) is displayed. However, R is a hydrocarbon group of a saturated or unsaturated fatty acid, and has 8 to 24 carbon atoms, preferably 1
0-22, Indicates a dibasic organic acid residue.

The esterification rate of the product suitable for the present invention is about 70 to 100%, and the esterified product in this range has excellent moldability and excellent heat resistance of molded products. Brings flammability and mechanical properties.

As the dibasic organic acid shown here, malonic acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, dithiopropionic acid, dimer acid, phthalic acid and the like, and suitable higher fatty acids are Examples thereof include C _{10 to} C ₂₂ saturated or unsaturated fatty acids such as stearic acid, behenic acid, and oleic acid.

The ethylenebisstearylamide which is the component (c) of the present invention is a higher fatty acid amide type which is generally used as a lubricant. Further, here, a special product having a high softening point having an ethylenebisstearylamide-based structure is also included. The low molecular weight polyethylene which is the component (d) of the present invention is a linear or branched polyethylene having a molecular weight in the range of about 900 to 10,000, and in particular, its branching is small and its density is 0. Particularly preferably, the molecular weight is 0.88 to 0.98 and the molecular weight is 2000 to 8000. This is because when the molecular weight is less than 900, the heat resistance tends to decrease and the bleed-out tends to occur.
This is because if it exceeds 0, the strength tends to decrease.

(B) Mixed ester of (b) pentaerythritol and / or dipentaerythritol, a dibasic organic acid and a higher fatty acid to be blended with a styrene resin; or / and a higher fatty acid ester of pentaerythritol and / or dipentaerythritol. The amounts of (c) ethylenebisstearylamide and (d) low molecular weight polyethylene used are each 0.1 to 2 parts by weight. Mixed ratio of pentaerythritol and / or dipentaerythritol, dibasic organic acid and higher fatty acid; or / and higher fatty acid ester of pentaerythritol and / or dipentaerythritol with ethylenebisstearylamide and low molecular weight polyethylene , 1 to 5: 1: 1 to 10, and preferably 1 to 3: 1: 1.5 to 5. When the amount of each used is less than 0.1 part by weight, the releasability of the styrene resin composition is insufficiently improved, and when it is more than 2 parts by weight, the physical properties of the resin, particularly impact resistance and heat resistance are improved. Is unfavorable because of the decrease in

Preparation of Final Composition Mixed ester of pentaerythritol and / or dipentaerythritol, dibasic organic acid and higher fatty acid; or / and higher fatty acid ester of pentaerythritol and / or dipentaerythritol and ethylenebisstearyl. The amide and the low molecular weight polyethylene may be individually blended with the styrene resin. As a method of blending these with a styrene-based resin, they may be mixed using an ordinary extruder or roll,
Further, they may be mixed by adhering to the surface of powdery or pelletized styrene resin. Further, as a compounding method, the styrene resin may be mixed in the monomer solution at the time of polymerization, or may be mixed during the polymerization or at the final stage of the polymerization. In addition, a flame retardant in this styrene resin composition,
A flame retardant auxiliary agent, a stabilizer accompanying it, etc. may be added.

[0013]

The present invention will be described in more detail below by showing Examples and Comparative Examples, but the scope of the present invention is not limited to these Examples. Examples 1 and 2 and Comparative Examples 1 to 4 Daicel Styrol R81 (high impact polystyrene manufactured by Daicel Chemical Industries, Ltd.) as a styrene resin.
A release agent was mixed with 100 parts by weight in the composition (parts by weight) shown in Table 1, kneaded with an extruder, and then pelletized. A tensile impact test piece was molded using the pellet by an injection molding machine. The cylinder temperature and the metal temperature of the injection molding machine were constant at 200 ° C. and 50 ° C., respectively. Releasability evaluation method

Although an absolute method has not been established as a method for evaluating the releasability, the releasability of the molded product depends on the pressure at the time of injection. It can be evaluated by the molding pressure width up to the maximum injection pressure at which the molded product can be released from the mold without any inconvenience. That is, the higher the injection pressure when injecting the resin into the mold, the better the molded product can be obtained, but
Since the adhesiveness of the resin to the mold is improved and the mold releasability of the molded product decreases rapidly, the better the mold releasability of the resin, the better the injection pressure that can be achieved without causing mold release defects. Can be determined. The mold release failure in this case was visually judged whether or not a crack was generated in the central portion when the mold was released during the molding of the tensile impact test piece.

[0015]

[Table 1]

[0016]

Effect of the Invention Pentaerythritol and / or dipentaerythritol, a mixed ester of a dibasic organic acid and a higher fatty acid; or / and a higher fatty acid ester of pentaerythritol and / or dipentaerythritol with ethylenebisstearylamide and a low molecular weight By adding polyethylene to the styrene-based resin in a prescribed blending amount and blending ratio, the adhesion to the metal part of the molding machine and the mold is low, the mold releasability is excellent, and there is no deformation of the molded product for mass production. It is possible to obtain a styrene resin composition having no problem.

Claims (1)

[Claims] 1. (a) Styrene resin
100 parts by weight (b) Mixed ester of pentaerythritol and / or dipentaerythritol, dibasic organic acid and higher fatty acid; or / and higher fatty acid ester of pentaerythritol and / or dipentaerythritol 0.1-2.0 Parts by weight (c) ethylenebisstearylamide
0.1 to 2.0 parts by weight (d) Low molecular weight polyethylene
Styrenic resin composition consisting of 0.1 to 2.0 parts by weight