JP2023050430A - Method for suppressing occurrence of eye mucus in extrusion molding of polystyrene-based resin composition - Google Patents

Abstract

To provide a method for suppressing occurrence of eye mucus in extrusion molding of a polystyrene-based resin composition.SOLUTION: A method for suppressing occurrence of eye mucus in extrusion molding of a polystyrene-based resin composition is obtained by blending a polystyrene-based resin with a polypropylene wax having a weight average molecular weight of 27,000-45,000.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for suppressing die build-up during extrusion molding of a polystyrene-based resin composition.

Among thermoplastic resins, polystyrene resins are inexpensive and have high processability, and are used in a wide range of fields such as food packaging materials, CD cases, and housings for home electric appliances.

Polystyrene resins are generally extruded after being blended with various additives such as impact modifiers, lubricants, and fillers. Deposits called "tar" may accumulate in the die port of the extruder. When the generated amount is large, there is a problem that defective products are generated by adhering to the molded product as foreign matter.

As a conventional technology for suppressing the occurrence of die buildup during extrusion molding of a polystyrene resin composition, pellets made of a rubber-modified polystyrene resin and having a pellet moisture content of 150 ppm or less, and a rubber-modified polystyrene resin using the same The melt extrusion method (Patent Document 1), the surface of the portion facing the resin flow path is coated with either titanium nitride or tungsten carbide, or the surface of the portion facing the resin flow path is nitrided out A die for a resin foam sheet manufacturing apparatus (Patent Document 2) is disclosed, which is characterized by having the resin flow path formed by a ring.

However, it is difficult to control the moisture content of the raw material depending on the type of raw material and the time of manufacture, and the design of dies with special coatings is complicated because it is necessary to design dies for each type of molding. Therefore, there has been a demand for a more excellent technique for suppressing die buildup during extrusion molding of a polystyrene resin composition.

JP-A-11-236422 JP-A-2000-246782

An object of the present invention is to provide a method capable of suppressing die build-up during extrusion molding of a polystyrene resin composition.

The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have found that the above problems can be solved by blending a polypropylene wax with a specific molecular weight into a polystyrene resin. Based on these findings, the present inventors have further studied and completed the present invention.
That is, the present invention comprises a method for suppressing die build-up during extrusion molding of a polystyrene-based resin composition, characterized by blending a polypropylene wax having a weight average molecular weight of 27,000 to 45,000 into a polystyrene-based resin. there is

By using the present invention, it is possible to suppress the occurrence of die build-up during extrusion molding of a polystyrene resin composition.

The polystyrene-based resin used in the present invention is not particularly limited as long as it is a polystyrene-based resin generally used in polystyrene-based resin molded articles. styrene, etc.), one type of homopolymer (e.g., polystyrene, polymethylstyrene, polychlorostyrene, etc.), two or more types of copolymers of styrenic monomers, styrenic monomers and other monomers and a copolymer of a styrene-based monomer and an elastomer. Mixtures of two or more of these polystyrene resins, and mixtures of these polystyrene resins and other thermoplastic resins may also be used.

Other monomers constituting the above-mentioned "copolymer of a styrene-based monomer and another monomer" include, for example, acrylonitrile, acrylonitrile such as methacrylonitrile, acrylic acid, unsaturated monomer such as methacrylic acid, Carboxylic acids, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene, butadiene and isoprene, olefins such as 1-butene and 1-pentene, α,β-unsaturated carboxylic acids ( for example, maleic anhydride, etc.) or its anhydride.

Examples of the elastomer constituting the above-mentioned "copolymer of a styrene-based monomer and an elastomer" include polydiene rubbers such as butadiene rubber, chloroprene rubber and isoprene rubber, styrene-diene elastomers such as styrene-butadiene rubber, and styrene-butadiene. -Block copolymer elastomers having polydiene blocks in the molecular structure such as styrene rubber.

The polypropylene wax (hereinafter also simply referred to as "polypropylene wax") used in the present invention is polypropylene obtained by polymerizing propylene or depolymerizing high molecular weight polypropylene, and has a weight average molecular weight of 27,000 to 45,000, It is preferably between 35,000 and 45,000. The method for measuring the weight-average molecular weight is not particularly limited, but for example, the polystyrene-equivalent weight-average molecular weight measured by GPC (gel permeation chromatography) under the following measurement conditions can be employed.
[Measurement condition]
Column: TSKgel column (manufactured by Tosoh Corporation) x 4
Temperature: 140°C
Eluent: o-dichlorobenzene Flow rate: 1.0 mL/min
Sample concentration: 0.15 mg/mL
Conversion standard: polystyrene

Examples of polypropylene waxes include Viscol 330P (trade name; weight average molecular weight: 40,000; manufactured by Sanyo Chemical Industries, Ltd.), Hiwax NP805 (trade name; weight average molecular weight: 32,600; manufactured by Mitsui Chemicals, Inc.), Viscol 440P ( Trade name: weight average molecular weight 30,000; manufactured by Sanyo Chemical Industries, Ltd.), LICOCENE PP2602 (trade name; weight average molecular weight 29,700; metallocene polypropylene wax; manufactured by Clariant Chemicals), etc. are commercially manufactured and sold. and these can be used in the present invention.

In the present invention, the method of blending the polypropylene wax with the polystyrene resin is not particularly limited as long as the polypropylene wax can be uniformly dispersed in the polystyrene resin. preferably. When an extruder is used, blending of the polypropylene wax into the polystyrene resin by heat kneading and extrusion molding of the blended polystyrene resin composition can be performed simultaneously. As a specific method of compounding and extrusion molding using an extruder, a polystyrene resin and polypropylene wax are charged into an extruder, and heat-kneaded to obtain a polystyrene resin composition blended with polypropylene wax, and further the polystyrene A system resin composition is extruded. The extruder to be used includes, for example, a single-screw extruder, a twin-screw extruder, etc. From the viewpoint of kneading power and productivity, it is preferable to use a twin-screw extruder. Types of twin screw extruders include, for example, twin screw non-intermeshing direction extruder, twin screw non-intermeshing direction extruder, twin screw co-direction non-intermeshing type extruder, twin screw co-direction intermeshing type An extruder and the like can be mentioned.

In the present invention, the blending temperature of the polypropylene wax with the polystyrene resin is the temperature at which the polystyrene resin and the polypropylene wax are melted or higher as the temperature for heating and kneading when using an extruder (barrel temperature of the extruder), Although there is no particular limitation as long as the temperature is within a range where these components are not excessively deteriorated, 120 to 230°C is preferable.

In the present invention, when blending the polypropylene wax with the polystyrene-based resin, it is preferable to prepare a masterbatch in advance by blending the polypropylene wax with the polystyrene-based resin, and blend the masterbatch with the polystyrene-based resin. This method is effective for effectively dispersing the polypropylene wax in the polystyrene resin. The content of polypropylene wax in 100% by mass of the masterbatch is usually 5 to 40% by mass, preferably 10 to 30% by mass.

In the present invention, the amount of polypropylene wax blended with respect to the polystyrene resin is usually 0.1 to 20% by mass, preferably 1 to 5% by mass, in 100% by mass of the polystyrene resin composition after blending polypropylene wax or the like. be.

In the present invention, components other than polypropylene wax may be added to the polystyrene resin. The component is not particularly limited as long as it is a component normally blended in a polystyrene resin. agents, neutralizers, plasticizers, pigments, dyes, conductive agents, and the like.

The present invention is illustrated by the following examples, which are merely illustrative of the invention and are not intended to limit the invention.

[Production of masterbatch containing wax component]
(1) Raw materials 1) Polystyrene resin (trade name: Toyo Styrol HRM-12; general-purpose polystyrene; manufactured by Toyo Styrene Co., Ltd.)
2) Polypropylene wax 1 (trade name: Viscol 330P; weight average molecular weight 40,000; manufactured by Sanyo Chemical Industries, Ltd.)
3) Polypropylene wax 2 (trade name: Hi-Wax NP805; weight average molecular weight 32,600; manufactured by Mitsui Chemicals, Inc.)
4) Polypropylene wax 3 (trade name: Viscol 440P; weight average molecular weight 30,000; manufactured by Sanyo Chemical Industries, Ltd.)
5) Polypropylene wax 4 (trade name: LICOCENE PP 2602; metallocene polypropylene wax; weight average molecular weight 29,700; manufactured by Clariant Chemicals)
6) Polypropylene wax 5 (trade name: Hi-Wax NP505; weight average molecular weight 25,700; manufactured by Mitsui Chemicals, Inc.)
7) Polypropylene wax 6 (trade name: Hi-Wax NP105; weight average molecular weight 11,200; manufactured by Mitsui Chemicals, Inc.)

(2) Composition Table 1 shows the composition of the masterbatch prepared using the above raw materials.

(3) Manufacturing method The raw materials shown in Table 1 are weighed so that the total amount is 1000 g, and a twin-screw co-rotating intermeshing extruder (model: KZW15TW-45MG-NH; screw diameter = 15 mm; L / D = 45; manufactured by Technobel Co., Ltd.), the barrel (C1-C6, H/D) temperature is 140-220 ° C. (C1 = 140 ° C., C2-C6 = 220 ° C.), and the screw rotation speed is 300 rpm. A polystyrene resin composition containing a wax component was extruded. The polystyrene-based resin composition extruded into strands was cut with a pelletizer to produce cylindrical masterbatches 1 to 6 (3 mm in diameter and 3 mm in length).

[Evaluation test for suppressing the occurrence of die build-up]
Polystyrene resin (trade name: Toyo Styrol HRM-12; general-purpose polystyrene; manufactured by Toyo Styrene Co., Ltd.), elastomer (trade name: JSR-RB810; 1,2-polybutadiene; manufactured by JSR), masterbatch 1 to 6 were weighed to a total of 2000 g according to the formulation shown in Table 2, and these raw materials were placed in a plastic bag, held by hand, and mixed uniformly for 30 seconds. The resulting mixture was extruded into barrels (C1 to C6, H /D) Heat kneading for 20 minutes at a temperature of 140 to 220 ° C. (C1 = 140 ° C., C2 to C6 = 220 ° C.), a screw rotation speed of 300 rpm, and an extrusion rate of 3 kg / h, and extrusion molding of a polystyrene resin composition. did After 20 minutes had passed, all the die build-up near the die opening was removed with a spatula, and the mixture was heated and kneaded for another 20 minutes to extrude the polystyrene-based resin composition into test groups 1 to 11. For each test section, the die build-up generated near the die opening was collected with tweezers, the mass was measured, and evaluation was performed according to the evaluation criteria shown in Table 3 below. Table 4 shows the results.

In each test section, the amounts of the polystyrene resin (including the polystyrene resin contained in the masterbatch) and the elastomer in the polystyrene resin composition were adjusted so that they were always the same amount. In each test section, the elastomer was blended with the polystyrene resin as an impact modifier. Test groups 1 to 8 are examples of the present invention, test groups 9 and 10 are comparative examples of the present invention, and test group 11 is a reference example of the present invention.

As is clear from the results, Test Groups 1 to 8 had the results of "O" or better, and an excellent effect of suppressing die buildup was obtained. On the other hand, test plots 9 and 10 gave the results of "Δ" or "x", indicating that there was no eye dandruff suppressing effect.

Claims (1)

A method for suppressing die build-up during extrusion molding of a polystyrene-based resin composition, comprising blending a polypropylene wax having a weight average molecular weight of 27,000 to 45,000 with a polystyrene-based resin.