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US 5,670,102 AGranted
Method of making thermoplastic foamed articles using supercritical fluid
AssigneeMinnesota Mining and Manufacturing Company
InventorsCraig A. Perman, William A. Hendrickson, Manfred E. Riechert
Life of this patent
Estimating the term…
Abstract
Foamed thermoplastic articles, both filled and unfilled foamed articles have a foamed density of greater than 0.03 grams per cubic centimeters (g/cm.sup.3), cell sizes in the range of 10 to 300 micrometers (.mu.m) with cell wall thicknesses of greater than 0.1 .mu.m but less than 2 .mu.m and a process for making the same.
Claims14
A process for producing low density cellular foamed thermoplastic articles comprising the steps:
- (1) charging a pressure vessel with a solid thermoplastic polymer;
- (2) heating the pressure vessel containing the solid thermoplastic polymer to a predetermined saturation temperature using an external heat source, heated to a temperature at or near the Vicat softening point of the solid thermoplastic polymer;
- (3) simultaneously charging a gas, while heating the pressure vessel;
- (4) equilibrating the pressure vessel, the solid thermoplastic polymer, and the gas at or near the Vicat softening point the external heat source;
- (5) adjusting the pressure in the pressure vessel by adding additional gas to achieve a final pressure wherein the gas is a supercritical fluid and soluble in the solid thermoplastic polymer;
- (6) saturating the solid thermoplastic polymer with the supercritical fluid for a predetermined period of time;
- and
- (7) venting the pressure vessel to rapidly depressurize the pressure vessel to foam the solid thermoplastic polymer.
5 more elements
A process for producing low density cellular foamed thermoplastic articles comprising the steps:
- (1) charging a pressure vessel with a solid thermoplastic polymer;
- (2) charging the pressure vessel with an additive;
- (3) heating the pressure vessel containing the solid thermoplastic polymer to a predetermined saturation temperature using an external heat source, heated to a temperature at or near the Vicat softening point of the solid thermoplastic polymer;
- (4) simultaneously charging a gas, while heating the pressure vessel;
- (5) equilibrating the pressure vessel, the solid thermoplastic polymer, and the additive, and the gas at or near the Vicat softening point by the external heat source;
- (6) adjusting the pressure in the pressure vessel by adding additional gas to achieve a final pressure wherein the gas is a supercritical fluid and soluble in the solid thermoplastic polymer;
- (7) saturating the solid thermoplastic polymer with the supercritical fluid for a predetermined period of time;
- and
- (8) venting the pressure vessel to rapidly depressurize the pressure vessel.
6 more elements
Dependencies are inferred from the claim text.