Hydrofluoropropene blowing agents for thermoplastics

Abstract

The present invention relates to blowing agent compositions comprising the unsaturated halogenated hydroolefin 3,3,3-trifluoropropene (HFO 1243zf) and combinations including primarily 3,3,3-trifluoropropene (HFO 1243zf). The blowing agent compositions are useful in that they provide sufficient plasticization to permit the production of low density insulating thermoplastic foams with improved k-factor.

Description

SUMMARY OF INVENTION[0001]The present invention relates to blowing agent compositions comprising the unsaturated halogenated hydroolefin, 3,3,3-trifluoropropene (HFO 1243zf or TFP), alone and in combination with compatible materials used in the preparation of thermoplastic foam compositions. HFO 1243zf blowing agent compositions are useful in that they provide sufficient plasticization to permit the production of low density insulating foams with improved k-factor.BACKGROUND OF INVENTION[0002]HFC's, being non-ozone depleting compounds, have been identified as alternative blowing agents to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) in the production of thermoplastic foams. However, it has been found that it can be more difficult to process thermoplastic foams being blown with HFC's than with CFC's or HCFC's. For instance in the production of extruded polystyrene (XPS) foam, HFC-134a (tetrafluoroethane) and HFC-125 (pentafluoroethane) have limited solubility and h...

AI Technical Summary

Benefits of technology

The present invention is about using a specific chemical called 3,3,3-trifluoropropene (HFO 1243zf or TFP) to create low-density insulating foams with improved insulation. This chemical helps to plasticize the foam and reduce its k-factor, which measures its insulation ability. The invention also includes using other materials that are compatible with HFO 1243zf to further improve the foam's performance.

Problems solved by technology

However, it has been found that it can be more difficult to process thermoplastic foams being blown with HFC's than with CFC's or HCFC's.

The higher degassing pressure makes the foaming more difficult to control and the higher operating pressure may be too high for some extrusion systems.

However, the specific advantages and benefits of using TFP as a blowing agent in thermoplastic resins have not been disclosed.

However, those skilled in the art recognize that the difficulty is in finding blowing agents that are capable of producing foamed products with useful characteristics.

These references also disclose that TFP may not be suitable for many applications due to its flammability.

However, the examples demonstrating the use of these formulations as blowing agents in thermoplastic resin and polystyrene foams only give typical operating conditions for a foam extrusion process familiar to one skilled in the art.

Those skilled in the art recognize that an effective blowing agent for polyurethane foaming systems will not necessarily be effective in thermoplastic foaming systems.

Furthermore, no formulations for producing expandable resin compositions are disclosed, and no blowing agent compositions useful for foaming are disclosed.

Many compositions covered by the broad disclosure are not suitable for producing low density closed-cell foams.

However, these references do not teach preferred compositions for the foaming of thermoplastics, and many of the compositions disclosed will not be as useful as blowing agents particularly for polystyrene due to the high content of HFO-1225, which the present inventors found not to be a particularly good blowing agent for polystyrene.

The examples in the patent are limited to polyurethane foam manufacture.

HFC-134a also has a very high nucleation density such that foams produced with it tend to have a very fine cell structure, which is not desired in all applications.

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