# US 4,393,016 A · Process for producing plate-like polystyrene resin foam

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- Number: US 4,393,016 A
- Document ID: US4393016A
- Status: Granted
- Kind: A
- Application number: 06/297,172
- Filed: 1981-08-28
- Granted: 1983-07-12
- Earliest claimed: 1980-09-01
- Assignees: Japan Styrene Paper Corporation
- Inventors: Hiroyuki Akiyama; Hideo Hatakeyama; Nobuyoshi Shimoyashiki; Yoshiaki Momose; Fusao Imai
- Web page: https://patentgrep.com/patent/US4393016A

## CPC

- C08J 9/143: {Halogen containing compounds}
- C08J 2325/04: Homopolymers or copolymers of styrene
- Y10S 264/05: Use of one or more blowing agents together
- Y10S 264/13: Cell size and distribution control while molding a foam
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

In a process for producing a plate-like polystyrene resin foam which comprises extruding a molten mixture consisting of a polystyrene resin and a volatile blowing agent by an extruder into a zone having a lower pressure than the inside of the extruder; the improvement wherein said volatile blowing agent is a mixture consisting of dichlorodifluoromethane, ethyl chloride and methyl chloride in which dichlorodifluoromethane accounts for 50 to 70% by weight of the mixture and the remainder consists of ethyl chloride and methyl chloride and the amount of ethyl chloride is at least 30% by weight based on the total amount of ethyl chloride and methyl chloride; and wherein said volatile blowing agent is present in said molten mixture in a proportion of 8 to 17 parts by weight per 100 parts by weight of the polystyrene resin component.

## Claims

### Claim 1

In a process for producing a plate-like polystyrene resin foam which comprises extruding a molten mixture consisting of a polystyrene resin and a volatile blowing agent by an extruder into a zone having a lower pressure than the inside of the extruder; the improvement wherein said volatile blowing agent is a mixture consisting of dichlorodifluoromethane, ethyl chloride and methyl chloride in which dichlorodifluoromethane accounts for 50 to 70% by weight of the mixture and the remainder consists of ethyl chloride and methyl chloride and the amount of ethyl chloride is at least 30% by weight based on the total amount of ethyl chloride and methyl chloride; and wherein said volatile blowing agent is present in said molten mixture in a proportion of 8 to 17 parts by weight per 100 parts by weight of the polystyrene resin component.

### Claim 2 (depends on 1)

The process set forth in claim 1 wherein the amount of dichlorodifluoromethane in the mixed blowing agent is 52.5 to 62.5% by weight.

### Claim 3 (depends on 1)

The process set forth in claim 1 wherein the remainder of the mixed blowing agent consists of 30 to 95% by weight of ethyl chloride and 5 to 70% by weight of methyl chloride.

### Claim 4 (depends on 1)

The process set forth in claim 1 wherein the polystyrene resin has a weight-average molecular weight, measured by gel permeation chromatography (GPC), of 20.times.10.sup.4 to 35.times.10.sup.4.