Sanyo Electric Co., Ltd.

Minoru Takezawa

Akihiro Morita

Yuji Kishi

Shigeo Yatsu

Fumihisa Endo

A method for the mixing of a polyol with a low-boiling foaming agent for the manufacture of a rigid foamed polyurethane. The polyol is blended in advance with a specific amount of the low-boiling foaming agent such as chlorodifluoromethane (designated by HCFC-22) or the like in a liquid state. In this case, it is possible to uniformly supply the polyol and the specific amount of HCFC-22 to a polyurethane foaming system, resulting in a homogeneous foaming reaction whereby a rigid foamed polyurethane having excellent cell uniformity without any voids may be obtained.

Method for the mixing of low-boiling foaming agent

According to the present invention, there is provided a rigid foamed polyurethane and a process for the manufacture of the polyurethane wherein the polyurethane is made up substantially of closed cells which contain at least a foaming agent designated by HCFC-22 and CO.sub.2 gas therein. The foamed polyurethane can be obtained by using HCFC-22 or a blend of the HCFC-22 with HCFC-142b as foaming agent which has a short life in the atmosphere because of having hydrogen atoms in their molecules. Thus, according to the present invention, it is possible to avoid the use of conventional foaming agents which are suspected of being substances eating a hole in the atmospher's layer of ozone and consequently linking to global warming. The rigid foamed polyurethanes of the present invention, which contain a foaming agent designated by HCFC-22 having a boiling point of -40.8.degree. C. in their closed cells, can retain their good thermal insulating properties over a temperature of from about -30.degree. to -40.degree. C., and can be used for most applications in the extremely cold conditions. Further, when employing a HCFC-22 blend containing a specific amount of HCFC-142b as foaming agent, there is provided a rigid foamed polyurethane having a less change in thermal insulating properties on standing while retaining good flame resistance of the rigid foam.

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Ohta, Japan

Minoru Takezawa