Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1990-12-06
1992-02-25
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521131, 521167, 521107, 25218226, 427244, 427245, 4272556, C08G 1814
Patent
active
050914340
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a polyol composition for rigid polyurethane foams which has good adhesion to low temperature substrates and which is able to considerably reduce the amount of a specific type of from and also to a method for producing rigid polyurethane foams, and more particularly, to a polyol composition which is adapted for making a rigid polyurethane foam capable of spray foaming in place and a method for producing a rigid polyurethane foam using the same.
2. Technical Background
In polyol compositions which are employed for producing heat-insulating polyurethane foams applied by in-place foaming, it is usual to use, as a blowing agent, R-11 (trichloromonofluoromethane) and water. However, R-11 has the possibility of depleting the ozone layer in the stratosphere to adversely influence the living system. In a near future, limitation will be placed on its amounts in use and production.
Accordingly, in the field of urethane foaming, it will become necessary to appreciably reduce the amount of R-11. Under these circumstances, it is considered that the amount of water which is a component of the blowing agent is increased with a reduction in amount of R-11. In the production of rigid polyurethane foams according to a known spraying method, R-11 has been used in 55-70 parts by weight per 100 parts by weight of polyol. This amount has to be reduced in the future.
However, attention should be paid to the fact that in spray foaming, a mixing ratio of the polyol-based composition (stock solution) and a polyisocyanate compound is required to be within a range suitable for spraying machines in view of the structure of the machine. In known spraying compositions, if R-11 is merely reduced in amount with an increase in amount of water, the mixing ratio is so shifted or the average hydroxyl value in the polyol based composition is so increased that the amount of the polyisocyanate compound to be used becomes too excessive, making it difficult to perform spray foaming with use of the machine.
Moreover, more increase in amount of water involves problems that the resultant foam becomes brittle with a considerable lowering of adhesion to low temperature substrates, so that the foam may separate or fall off from the substrate or may be lifted owing to a phenomenon called transverse spreading immediately after the spraying, coupled with another problem that with spraying in a large thickness, scorching is apt to occur, thus making the practical application impossible.
It will be noted that the low temperature substrate means a substrate of low temperatures at the time of inplace foaming in cold districts (e.g. walls of buildings). For the in-place foaming, the substrate at an ambient temperature is usually sprayed and a foam with good quality has to be formed not only at normal temperatures, but also at lower temperatures (e.g. -5.degree. C. to 5.degree. C.).
In spray blowing polyol composition wherein water used as a foaming agent is formulated in amounts larger than in conventional ones, the average hydroxyl value of the total polyols has to be lowered.
In order to totally lower the hydroxyl value of the polyol mixture, it may occur that high molecular weight polyols ordinarily used to produce a flexible polyurethane foam or polyols with a reduced number of functional groups and a low hydroxyl value are formulated. This presents the problem that a cured foam is liable to suffer shrinkage under low temperature conditions.
DISCLOSURE OF THE INVENTION
An object of the present invention is to overcome the problems involved in the case where the amount of water as a blowing agent is increased while low boiling halogenated hydrocarbon foaming agents, such as R-11 (trichloromonofluoromethane), used as a blowing agent of starting materials for in-place spray foaming urethane foams are considerably reduced in amount, e.g. problems such as extreme brittleness of the resulting foam, a failure in adhesion to low temperature substrates, and shrinkage of the foam at a low temperature.
REFERENCES:
patent: 3112281 (1963-11-01), Gromacki et al.
patent: 4585807 (1986-04-01), Christman
Kamemura Ichiro
Kodaka Hiromitsu
Suzuki Masahiro
Asahi Glass Company Ltd.
Welsh Maurice J.
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