# US 5,700,407 A · Molded polymeric foam preparation method

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- Number: US 5,700,407 A
- Document ID: US5700407A
- Status: Granted
- Kind: A
- Application number: 08/639,717
- Filed: 1996-04-29
- Granted: 1997-12-23
- Earliest claimed: 1995-02-14
- Inventors: Robert Michael Branger
- Web page: https://patentgrep.com/patent/US5700407A

## CPC

- B29C 44/105: {the counterpressure being exerted by a fluid}
- B29C 35/00: Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor (moulds with incorporated heating or cooling means B29C33/02 {; thermal after-treatment of shaped articles B29C71/02}; curing devices for plastics dental prostheses A61C13/14; before moulding B29B13/00)
- 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

Foamed articles having excellent properties are prepared by partially filling a mold with foamable composition, pressurizing the mold while heating to activate blowing agent and crosslinking agent, and releasing the pressure while the polymer is at least partially crosslinked to permit the foam to fill the mold.

## Claims

### Claim 1

A process for the preparation of foamed polymeric articles consisting essentially of:
(a) formulating a foamable polymer composition comprising polymer, crosslinking agent and blowing agent, the blowing agent having a decomposition temperature;
(b) heating a mold to a temperature higher than the decomposition temperature of the blowing agent;
(c) filling less than about 25% of the volume of the mold with the foamable composition, sealing the mold and pressurizing the sealed mold with inert gas to a pressure of at least about 500 psi;
(d) heating the foamable polymer composition to above the decomposition temperature of the blowing agent and above the activation temperature of the crosslinking agent;
(e) maintaining the pressure within the mold to maintain the resulting decomposed blowing agent substantially in solution within the foamable polymer composition until the polymer in the foamable polymer composition is at least partially crosslinked; and
(f) releasing the pressure within the mold.

### Claim 2 (depends on 1)

A process of claim 1 wherein the foamable polymer composition further polymer comprises at least one nucleating agent.

### Claim 3 (depends on 1)

A process of claim 1 wherein the blowing agent comprises at least one carbonamide.

### Claim 4 (depends on 3)

A process of claim 3 wherein the blowing agent consists essentially of azodicarbonamide and the foamable composition is heated to a temperature of at least about 160 degrees C.

### Claim 5 (depends on 1)

A process of claim 1 wherein the mold is pressurized to about from 500 to 3000 psi.

### Claim 6 (depends on 5)

A process of claim 5 wherein the mold is pressurized to about from 800 to 2000 psi.

### Claim 7 (depends on 1)

A process of claim 1 wherein the polymer is selected from the group consisting of polyolefins and ethylene polymers comprising at least about 50% ethylene.

### Claim 8 (depends on 1)

A process of claim 1 wherein up to about 20% of the volume of the mold is filled with the foamable polymer composition.

### Claim 9

A process for the preparation of foamed polymeric articles consisting essentially of:
(a) formulating a foamable polymer composition comprising polymer, crosslinking agent and blowing agent, the blowing agent having a decomposition temperature, wherein the polymer consists essentially of ethylene/vinyl acetate copolymer;
(b) heating a mold to a temperature higher than the decomposition temperature of the blowing agent;
(c) filling up to about 50% of the volume of the mold with the foamable composition, sealing the mold and pressurizing the mold with inert gas to a pressure of at least about 500 psi;
(d) heating the foamable polymer composition to above the decomposition temperature of the blowing agent and above the activation temperature of the crosslinking agent;
(e) maintaining the pressure within the mold to maintain the resulting decomposed blowing agent substantially in solution within the foamable polymer composition until the polymer in the foamable polymer composition is at least partially crosslinked; and
(f) releasing the pressure within the mold.