초록 ▼

The invention disclosed provides a method for producing ultramicrocellular polymer foams at low pressures. A polymer is saturated with a blowing agent at low temperatures and pressures within a short time period, due to retrograde vitrification. The blowing agent may be in the form of a gas or a vol

The invention disclosed provides a method for producing ultramicrocellular polymer foams at low pressures. A polymer is saturated with a blowing agent at low temperatures and pressures within a short time period, due to retrograde vitrification. The blowing agent may be in the form of a gas or a volatile liquid. Polymer-blowing agent combinations are selected to provide a processing temperature/pressure in the area below the positive slope portion of the retrograde vitrification profile of the glass transition temperature of the polymer versus pressure. The polymer thus saturated has an exceptionally high blowing agent content, and is then foamed to produce materials with small cells and high cell density.

대표청구항 ▼

[ We claim:] [1.] A method for producing closed cell polymer foams in the microcellular to ultramicrocellular range, comprising(a) selecting a suitable solid polymer and inert blowing agent combination, wherein the blowing agent is in the form of a gas or a volatile liquid which induces retrograde v

[ We claim:] [1.] A method for producing closed cell polymer foams in the microcellular to ultramicrocellular range, comprising(a) selecting a suitable solid polymer and inert blowing agent combination, wherein the blowing agent is in the form of a gas or a volatile liquid which induces retrograde vitrification in the polymer,(b) determining the retrograde vitrification profile of the glass transition temperature(T.sub.g) of the polymer versus gas pressure, and the saturation vapor temperature versus pressure curve of the blowing agent, wherein the Tg versus gas pressure profile of the polymer and the saturation vapor temperature versus pressure curve of the blowing agent both have a positive slope portion,(c) exposing the polymer to the blowing agent in the gas or liquid state for a time sufficient to establish a saturated polymer-blowing agent solution, while maintaining a processing pressure and temperature below the positive slope portion of the retrograde vitrification profile, and wherein the polymer is in a rubbery state,(d) quickly transferring the saturated polymer to an environment at ambient pressure and a temperature from the processing temperature up to the Tg of the neat polymer in the presence of a heat transfer medium, to form the foam, and(e) quenching the foamed polymer by rapidly cooling to a lower temperature.