A METHOD OF FOAMING PLASTIC MATERIALS AND A BLOWING AGENT FOR USE THEREWITH

Abstract: By the intensive endeavours for finding harmless substitutes for freon as a blowing agent in the production of foamed materials there has so far been indicated only very few substances usable under ambient pressure and temperature conditions. Of particular importance has been a mixture of trichloroethane and R-22, but even these substances exhibit a certain ozone decomposing effect. However, according to the present invention it is possible to replace these two substances entirely or partly by trichloroethylene and tetrafluoroethane, respectively, these substances being both well usable and negligibly ozone decomposing.

Description: A method of foaming plastic materials and a blowing agent for use therewith. The present invention relates to a method of foam¬ ing plastic, preferably polyurethane, for producing a plastic foam, whereby a liquid plastic substance is brought to expand into foam by admixing and boiling of a blowing agent. In the production of polyurethane foam it has been traditional to use the blowing agent -ll, but as well known this substance has come under well-founded suspicion of being ozone decomposing, such that for safeguarding the ozone layer of the earth this substance should not be used any longer. On this background, in the chemical industry very large efforts and costs have been spent for finding a suitable substitute for R-ll, but generally without any usable result. However, in a single instance, confer WO89/00594, an advantageous alternative has been pro¬ vided, viz. by the use of 1.1.1.trichloroetane in combi¬ nation with the component R-22, whereby a fully usable foaming effect is achievable by means of components that are substantially less ozone decomposing compared with the R-ll as used hitherto. It has been found, however, that even 1.1.1. tri- chloroethane as well as R-22 exhibit a certain ozone decomposing effect, although weak, and it is the purpose of the present invention to provide a substance which is usable as an alternative with good results as to both the foaming effect and a lacking ozone decomposing ef¬ fect. The intensive research that has gone on has not left much hope that such a substance could exist at all, but neverthe less it has been found that there are a couple of substances which are perfectly usable, when they are used according to the mixture principle dis¬ closed in said W089/00594, i.e. where two or more compo- nents having widely different boiling points are used in a mixture, which will then have a resulting, practically usable boiling point range. One of these two substances is FC-134A, 1.1.1.2. tetrafluoroethane, and the other is 1.1.2. trichloroethylene. The boiling point of FC-134A is -26.5°C, and it has been found that this substance is usable not only to¬ gether with the said other substance, but even as a substitute for the R-22 in the mixture according to O89/00594, that is where the substance is effective in admixture with 1.1.1. trichloroethane having the boiling point of 75-76°C. Already thereby an alternative of significant importance will be provided, because it is then possible to lower the ozone decomposing effect of the blowing agent to far below the more rigorous limit which is now supposed to be in force through the many years to come, and apparently this has been obtained for the first time just by the present invention in con¬ nection with the considered preferred type of technique. The other of the said two substances, the 1.1.2. trichloroethylene, has a boiling point of 87°C, and the substance is usable with very good results in admixture with FC-134A, but also in admixture with R-22, i.e. as a substitute for 1.1.1. trichloroethane. However, the more attractive mixture will be the one with FC-134A, because of its extremely low ozone decomposing effect. In fact, already in WO89/00594 the trichloro¬ ethylene has been suggested as a possible alternative to 1.1.1. trichloroethane, but it has now been demonstrated that this substance is not only a hypothetical alterna¬ tive, as it has been verified that 1.1.2. trichloro¬ ethylene is practically usable with good results. It should be mentioned, however, that 1.1.2. tri¬ chloroethylene is a substance which in the working phase may re protection, but no more than already known by the handling of many other substances. Soon after the foam- ing the products will be entirely non-dangerous. By experiments it has been found that the said two 'new' substances can be used in practically exactly the same way as R-22 and 1.1.1. trichloroethane, respective¬ ly, according to WO89/00594, without marked modifica¬ tions of the formulation examples given therein, this per se being a positive surprise. It should only be mentiioned that with the use of the two new substances it has been found preferable to make use of the additive pentane entirely or partly in stead of butane, to the extent it is desirable to add components from that group of substances. On this background it is here considered unneces¬ sary to specify more detailed examples relating to the realization of the invention, because all the examples and the more detailed explanation given in WO89/00594 are fully applicable also to the present invention, including for the combined use of the respective com¬ ponents in arbitrary mutual mixing proportions. It should be mentioned that there are already known other blowing agent mixtures consisting of components of mutually different boiling points, but it is an impor¬ tant characteristic for the present invention as well as for the invention according to W089/00594 that the mix¬ tures here concerned are effective and are handable and operative by atmospheric pressure and ambient working temperature.

Claims: C L I M S : 1. A method of foaming a plastic compound for pro¬ ducing plastic foam, in particular polyurethane foam, whereby a liquid base mixture is brought to expand by boiling of an admixed blowing agent, which, itself, is a mixture of substances having boiling points substantial¬ ly above and substantially below normal working tempera¬ ture, respectively, characterized in that as the blowing agent a mixture of 1.1.1.2. tetrafluoroethane and 1.1.2. trichloroethylene is used, the former optionally in combination with R-22 and the latter optionally in com¬ bination with or substituted by 1.1.1. trichloroethane. 2. A compound including a blowing agent for con¬ verting the compound into a foam product by a boiling of the blowing agent, characterized by the blowing agent at least to a substantial degree being constituted by the agent specified in claim 1. 3. A blowing agent for use with the method accord¬ ing to claim 1, characterized in that it is at least mainly constituted by the mixture specified in the char¬ acterizing clause of claim 1, preferably at a ratio such that the mixture is stable by atmospheric pressure and normal working temperature.

Inventors: OESTERGAARD HANS JOERGEN, OESTERGAARD, HANS, JOERGEN
Applicants: OESTERGAARD HANS JOERGEN, OESTERGAARD, HANS, JOERGEN
Application year: 1990
Main classification: C08J9
IPC codes: C08J9