# US 9,517,579 B2 · Polystyrene melt extrusion process

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- Number: US 9,517,579 B2
- Document ID: US9517579B2
- Status: Granted
- Kind: B2
- Application number: 13/990,533
- Filed: 2011-11-22
- Published: 2013-09-26
- Granted: 2016-12-13
- Earliest claimed: 2010-12-17
- Assignees: Dow Global Technologies LLC
- Applicants: Shari L. Kram; Simon Lee; William G. Stobby; Ted A. Morgan
- Inventors: Shari L. Kram; Simon Lee; William G. Stobby; Ted A. Morgan
- Web page: https://patentgrep.com/patent/US9517579B2

## CPC

- B29C 44/3403: {Foaming under special conditions, e.g. in sub-atmospheric pressure, in or on a liquid}
- C08J 9/0061: {characterized by the use of several polymeric components}
- C08J 9/127: {Mixtures of organic and inorganic blowing agents}
- C08J 2203/06: CO2, N2 or noble gases
- C08J 2203/10: Water or water-releasing compounds
- C08J 2203/12: Organic compounds only containing carbon, hydrogen and oxygen atoms, e.g. ketone or alcohol
- C08J 2203/202: of physical blowing agents
- C08J 2325/04: Homopolymers or copolymers of styrene
- C08J 2425/18: Homopolymers or copolymers of aromatic monomers containing elements other than carbon and hydrogen
- C08J 2453/02: of vinyl aromatic monomers and conjugated dienes
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- 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)

## Abstract

Extruded polystyrene foams are made with an added brominated styrene-butadiene polymer as a flame retardant. The blowing agent is a mixture of carbon dioxide, ethanol and water, which may also contain a C4-C5 hydrocarbon. The blowing agent mixture overcomes a tendency of the brominated styrene-butadiene to form very small cells. This allows the foam to expand fully to form good quality, low density extruded foam.

## Claims

### Claim 1

A process for making a polymer foam, comprising forming a pressurized melt that contains a molten styrenic polymer, a flame retarding amount of a brominated styrene-butadiene polymer and 1.1 to 1.70 moles of a blowing agent mixture per kilogram of the styrenic polymer, and forcing the melt through an opening into a zone the blowing agent expands and the polymer cools and solidifies to form a foam, wherein the blowing agent mixture includes 0.65 to about 0.9 moles of carbon dioxide per kilogram of the styrenic polymer, 0.25 to 0.45 moles of ethanol per kilogram of the styrenic polymer, 0.1 to 0.3 moles of a C4-C5 hydrocarbon per kilogram of the styrenic polymer and 0.1 to 0.3 moles of water per kilogram of the styrenic polymer, wherein the average cell size of the foam is from 0.25 mm to 1 mm.

### Claim 2 (depends on 1)

The process of claim 1, wherein the C4-C5 hydrocarbon is isobutene.

### Claim 3 (depends on 1)

The process of claim 1 wherein the amount of blowing agent mixture is from 1.15 to 1.65 moles per kilogram of the styrenic polymer.

### Claim 4 (depends on 1)

The process of claim 1 wherein the blowing agent mixture contains, per kilogram of the styrenic polymer, 0.65 to 0.9 moles of carbon dioxide, 0.25 to 0.45 moles of ethanol, 0.1 to 0.3 moles of isobutane and from 0.1 to 0.3 moles of water, with the total amount of blowing agent mixture being from 1.15 to 1.65 moles per kilogram of the styrenic polymer.

### Claim 5 (depends on 1)

The process of claim 1 wherein the foam density is no greater than 36 kg/m3.

### Claim 6 (depends on 1)

The process of claim 1 wherein the foam has an open cell content of no greater than 30%.

### Claim 7 (depends on 1)

The process of claim 1 wherein the foam has a thickness of at least 12 mm.

### Claim 8 (depends on 1)

The process of claim 1 wherein the foam has a thickness of at least 20 mm.

### Claim 9 (depends on 1)

The process of claim 1 wherein the brominated styrene-butadiene polymer is a brominated block copolymer of styrene and butadiene which contains at least 50% by weight bromine.