# US 5,703,135 A · Production of expanded polyolefin beads

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- Number: US 5,703,135 A
- Document ID: US5703135A
- Status: Granted
- Kind: A
- Application number: 08/793,101
- Filed: 1997-02-24
- Granted: 1997-12-30
- Earliest claimed: 1994-08-23
- Assignees: BASF SE
- Inventors: Jurgen Schweinzer; Joachim Fischer; Isidoor De Grave; Wolfram Kogel
- Web page: https://patentgrep.com/patent/US5703135A

## CPC

- C08J 9/18: by impregnating polymer particles with the blowing agent
- B29C 44/3461: {Making or treating expandable particles}
- C08J 2203/06: CO2, N2 or noble gases
- C08J 2203/14: Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
- C08J 2323/02: not modified by chemical after treatment
- 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)
- 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)

## Abstract

The invention relates to a process for the production of expanded polyolefin beads by impregnating polyolefin particles with volatile blowing agents in a fluidized bed.

## Claims

### Claim 1

A process for the production of expanded polyolefin beads by impregnating polyolefin particles with volatile blowing agents at a temperature at most 50.degree. C. below and at most 30.degree. C. above the crystallite melting point of the polyolefin, the crystallite melting point being the maximum of the DSC curve obtained by heating from 3 to 6 mg of the polyolefin granules to 220.degree. C. at a heating rate of 20.degree. C./min, by means of a differential calorimeter, which comprises fluidizing particulate propylene or ethylene polymers under pressure in a fluidized bed and at the same time impregnating them with a blowing agent which is gaseous at the selected temperature, and expanding the impregnated polyolefin particles by decompression.

### Claim 2 (depends on 1)

A process as claimed in claim 1, wherein polyolefin particles having a particle size of from 0.1 to 6 mm are employed.

### Claim 3 (depends on 1)

A process as claimed in claim 1, wherein the impregnation is carried out at a pressure which is at least 25% of the saturation vapor pressure of the blowing agent at the operating temperature.

### Claim 4 (depends on 1)

A process as claimed in claim 1, wherein the polyolefin is a copolymer of propylene with from 0.5 to 15% by weight of ethylene and/or C.sub.4 - to C.sub.8 -.alpha.-olefin or a copolymer of ethylene with from 3 to 18% by weight of a C.sub.3 - to C.sub.10 -.alpha.-olefin.

### Claim 5 (depends on 1)

A process as claimed in claim 1, wherein the blowing agent is propane, a butane, a pentane, a hexane or carbon dioxide, or a mixture thereof.

### Claim 6 (depends on 1)

A process as claimed in claim 1, wherein the blowing agent is ammonia or a mixture of ammonia with nitrogen.

### Claim 7 (depends on 1)

A process as claimed in claim 1, wherein the gas velocity U at which the blowing agent is circulated satisfies the condition
U-UMF=0.02 to 1.5 m.multidot.sec.sup.-1,
where UMF is the minimum fluidization velocity of the polymer particles under the particular operating conditions.