JPH0241541B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a styrenic polymer composition with improved mold release properties, and more particularly to a styrenic polymer composition containing a styrenic grafted polyethylene wax. Styrenic polymers with high molecular weight are thermoplastic resins called polystyrene, high-impact polystyrene, styrene-acrylonitrile copolymer, or ABS, and molded products by injection molding, blow molding, extrusion molding, etc. are used in various fields. There is. When taking injection molded thermoplastic resin products, including styrene polymers, out of the mold, a draft angle is usually provided in the mold or a release agent is applied to the mold to make it easier to release the mold. There is. However, when molded products are used in precision machinery or electrical appliance parts, draft angles are often not allowed. Furthermore, if the molded product has a complicated shape, the position and thickness of the ejecting pin are restricted, which may cause strain when removing the molded product, which increases the frequency of damage to the molded product. Its use has become unavoidable. Methods for improving mold release properties include adding lubricants such as higher fatty acids, higher fatty acid amides, metal salts of higher fatty acids, higher fatty acid esters, liquid paraffin, and waxes to the resin, and adding mold release agents such as silicone oil to the mold. They also apply it. However, adding the lubricant to the resin to improve mold release requires a large amount of lubricant, which may result in a decrease in the mechanical strength of the resin, and the application of the mold release agent is complicated during molding. Invite the
Since this may impair the appearance of the molded product, the weld strength, etc., a method for improving the mold releasability without impairing the mechanical strength of the resin is desired. On the other hand, styrene-based polymers with low molecular weights are used as toners for electrophotography, base materials for hot-melt coating materials, and pigment dispersants. There is a phenomenon in which a part of the resin adheres to the roll during heat fusing, and it is desired to improve the mold releasability. Therefore, the present inventor conducted studies to improve the mold releasability, which is the drawback of styrene-based polymers, and found that by adding styrene-based grafted polyethylene wax to styrene-based polymers, the mechanical strength of styrene-based polymers was improved. Alternatively, it has been found that mold releasability can be improved without impairing melt fluidity. That is, the present invention provides a styrenic polymer (A):
Intrinsic viscosity 0.06 dl/g or more per 100 parts by weight
A styrene-based product containing 0.1 to 20 parts by weight of a styrene-based grafted polyethylene wax (B) obtained by grafting 1 to 90 parts by weight of a styrene monomer to 99 to 10 parts by weight of 2.0 dl/g polyethylene wax. A polymer composition is provided. The styrenic polymer used in the present invention is a homopolymer of styrene or a copolymer with acrylonitrile, butadiene, etc., and is called polystyrene, high impact polystyrene, styrene-acrylonitrile copolymer, or ABS with a molecular weight of 2 to It is a thermoplastic resin with a molecular weight of 30,000 or more or a low molecular weight polystyrene with a molecular weight of several hundred to tens of thousands. Polyethylene wax grafted with styrene monomer has an intrinsic viscosity of 0.06 dl/g to 2.0
dl/g, preferably 0.06 dl/g to 0.5 dl/g
(decalin solvent 135°C), products obtained by thermal decomposition of high-pressure polyethylene, high-pressure polymerized polyethylene wax obtained by radical polymerization of ethylene at high pressure, and also ethylene or ethylene and propylene, 1-butene, 1 -hexene, 4-methyl-1
- It is obtained by low-pressure polymerization of α-olefins such as pentene and 1-decene using a Ziegler type catalyst. The styrene monomers include styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, m-methylstyrene, and the like. The amount of styrene monomer grafted onto the polyethylene wax is 99%.
1 to 10 parts by weight to 1 to 90 parts by weight. If the amount of styrene monomer grafted is less than 1 part by weight, it will have poor dispersibility when blended with styrenic polymer and will impair mechanical strength, so it is not preferable, whereas if the amount of styrenic monomer grafted exceeds 90 parts by weight. Even if it is blended with a styrene polymer, the mold releasability is not improved. Any known method can be used to graft the styrene monomer onto the polyethylene wax. For example, a method can be exemplified in which polyethylene wax is directly melted or dissolved in a solvent, and a styrene monomer is added with or without a radical initiator for grafting. As radical initiators, organic peroxides, organic peresters such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-
tert-butyl peroxide, 2,5-dimethyl-
2,5-di(peroxybenzoate)hexyne-3,1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-di(tert- butylperoxy)hexane-3,2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl penbenzoate, tert-butyl perphenylacetate, tert-butyl perisobutyrate,
These include tert-butyl per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate and tert-butyl perdiethyl acetate, as well as other azo compounds such as azobis-isobutylnitrile, dimethylazoisobutyrate. Among these, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-
di(tert-butylperoxy)hexine-3,
Dialkyl peroxides such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 1,4-bis(tert-butylperoxyisopropyl)benzene are preferred. The blending amount of the styrene-based graft polyethylene wax with respect to the styrene-based polymer is 0.1 to 20 parts by weight per 100 parts by weight of the styrene-based polymer.
The range is preferably from 0.5 to 10 parts by weight, particularly preferably from 0.5 to 5 parts by weight. If the blending amount is less than 0.1 part by weight, there is no improvement in mold release properties,
If the blending amount exceeds 20 parts by weight, strength may decrease and heat fixability may deteriorate. The styrenic graft polyethylene and the styrenic polymer can be mixed using known methods such as Henschel mixer, V
- Use directly after mixing with a blender or ribbon blender, or kneading and granulating with an extruder, etc., or melt-kneading with a Banbury mixer, single-screw or multi-screw extruder, kneader, etc., then granulate or crush. methods etc. can be adopted. In addition, the styrenic polymer may contain other additives within the range that does not impair the purpose of the present invention.
Inorganic substances such as dyes and pigments, glass fibers, carbon black, antistatic agents, weathering stabilizers, calcium carbonate, etc.
Polymers such as SBR, NBR, and styrene-maleic acid copolymer may also be added. If the styrenic polymer has a high molecular weight, the styrenic polymer composition of the present invention can be used not only in injection molding but also in molds, dies, etc. in blow molding, injection blow molding, compression molding, extrusion molding, rotation molding, etc.
It reduces adhesion to rolls, etc., improves work efficiency, and improves fluidity, so molded products with excellent appearance and dimensional accuracy can be obtained, and are useful for industrial parts and electrical appliance parts. On the other hand, if the resin has a low molecular weight, it has good heat fixability and improves adhesion to the fixing roll, so it is useful as a resin for electrophotographic toners. Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples. Example 1 350 g of high-density polyethylene wax (trade name: Mitsui Hiwax 100P, manufactured by Mitsui Petrochemical Industries, Ltd.) having an intrinsic viscosity of 0.07 dl/g was charged into a glass reactor 1 and melted at 140°C. Next, 13 g of styrene monomer and 2.8 g of di-tert-butyl peroxide (hereinafter abbreviated as DTBPO) were added and reacted by heating for 6 hours, followed by degassing in a 5 mmHg vacuum for 1 hour to remove volatile components. , then cooled. The amount of styrene grafted in the obtained styrene-grafted polyethylene wax (hereinafter referred to as GR-) was 3.2 g per 100 g of styrene-grafted polyethylene wax. Next, the obtained GR-I and polystyrene (trade name: Toporex 500-51 manufactured by Mitsui Toatsu Chemical Co., Ltd.) were mixed into a first
After dry blending at the ratio shown in the table, the mixture was granulated using a 15 mmφ extruder (temperature set at 200°C). The granulated sample was molded into a square plate of 200 x 200 x 1 mm using a compression molding machine. Performance was evaluated using the method described below. Melt properties: Measured according to ASTM D 1238E. Tensile properties: Measured by ASTM D 638 method. Mold releasability: Depending on the condition when taking out the formed square plate from the metal frame, 5 indicates a state in which the square plate can be removed from the metal frame without resistance, and a state in which it cannot be removed without forcibly peeling between the square plate and the metal frame with a razor etc. 1, and the middle was divided into 3 stages, and the evaluation was performed on a 5-stage scale. Dispersibility: By visual inspection of the condition of the formed square plate, 1 indicates a state in which polyethylene wax agglomerates are visible in the formed square plate, 2 indicates a state in which no agglomerates are visible but is heterogeneous, and 2 indicates a state in which the formed square plate is homogeneous. As 3,
This was done using a three-level evaluation. Example 2 350 g of high-density polyethylene wax (trade name: Mitsui Hiwax 200P, manufactured by Mitsui Petrochemical Industries, Ltd.) having an intrinsic viscosity of 0.12 dl/g was charged into a glass reactor No. 1 and melted at 140°C. Next, 37.1 g of styrene monomer and 8.6 g of DTBPO were added and reacted by heating for 6 hours.
The volatiles were removed by degassing in a Hg vacuum for 1 hour and then cooled. The amount of styrene grafted in the obtained styrene-grafted polyethylene wax (hereinafter referred to as GR-) was 9.1 g per 100 g of styrene-grafted polyethylene wax.
Thereafter, it was mixed with polystyrene in the same manner as in Example 1 to obtain a composition, and its performance was evaluated. The results are shown in Table 1. Example 3 350 g of high-density polyethylene wax (trade name: Mitsui Hiwax 400P, manufactured by Mitsui Petrochemical Industries, Ltd.) having an intrinsic viscosity of 0.22 dl/g was charged into a glass reactor (No. 2) and melted at 140°C. Next, 742 g of styrene monomer and 180 g of DTBPO were added and reacted by heating for 6 hours.
The mixture was degassed in vacuum for 1 hour to remove volatile components, and then cooled. The amount of styrene grafted in the obtained styrene grafted polyethylene wax (hereinafter referred to as GR-) was 64 g in 100 g of styrene grafted polyethylene wax. Thereafter, it was mixed with polyethylene in the same manner as in Example 1 to obtain a composition, and its performance was evaluated. The results are shown in Table 1. Example 4 A graft reaction was carried out in the same manner as in Example 2, using p-methylstyrene instead of the styrene monomer. The amount of p-methylstyrene grafted in the obtained grafted polyethylene wax (hereinafter referred to as GR-) was 8.9 g per 100 g of grafted polyethylene wax. Example 1 below
A composition was obtained by mixing it with polystyrene in the same manner as above, and its performance was evaluated. The results are shown in Table 1. Comparative Examples 1 and 2 GR- and GR of Example 1 and Example 2
- Mitsui Hiwatukus in place of each
The same procedure as in Example 1 and Example 2 was carried out except that 100P and Mitsui Hiwax 200P were used. The results are shown in Table 1. Comparative Example 3 1 part by weight of commercially available low molecular weight polystyrene (trade name Hymer ST-95 manufactured by Sanyo Kasei Co., Ltd., molecular weight 1400) was added to 100 parts by weight of polystyrene (trade name Toporex 500-51 manufactured by Mitsui Toatsu Chemical Co., Ltd.). The mixture was dry blended in the same proportion as in Example 1, and then granulated in the same manner as in Example 1. Thereafter, a square plate was formed using a compression molding machine, and the performance was evaluated. The results are shown in Table 1.

【table】

[Table] *: Molded square plate breaks inside the mold Example 5, Comparative Examples 4 and 5 93 parts by weight of low molecular weight polystyrene used in Comparative Example 3, GR-5 parts by weight obtained in Example 2 and carbon Black (MA-100 manufactured by Mitsubishi Chemical Industries, Ltd.)
2 parts were kneaded for 4 minutes using three rolls heated to 130°C. As a result, the mixture hardly adhered to the rolls and could be easily peeled off from the rolls even after kneading. On the other hand, when 2 parts by weight of the carbon black was added to 98 parts by weight of the low molecular weight polystyrene used in Comparative Example 3 and similarly kneaded using three rolls, the mixture showed significant adhesion to the rolls and was extremely difficult to work with. Unfortunately, it was very difficult to peel off from the roll even after kneading. On the other hand, high-density polyethylene wax (product name Mitsui Hiwax 200P:
A mixture of low molecular weight polystyrene and carbon black (manufactured by Mitsui Petrochemical Industries, Ltd.) had significantly improved adhesion to rolls, but wax bleed out from the mixture was so severe that it could not be put to practical use.

Claims (1)

[Claims] 1 Styrenic polymer (A): For 100 parts by weight,
Styrenic grafted polyethylene wax (B) obtained by grafting 1 to 90 parts by weight of a styrene monomer to 99 to 10 parts by weight of polyethylene wax with an intrinsic viscosity of 0.06 dl/g to 2.0 dl/g.
A styrenic polymer composition characterized by containing 0.1 to 20 parts by weight.