Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-02-10
2002-08-13
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S137000, C521S155000, C521S163000, C521S168000, C521S174000
Reexamination Certificate
active
06433033
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to high-durability flexible polyurethane cold cure molded foams and a process for producing the foams. More particularly, the invention relates to flexible polyurethane cold cure molded foams which are lightweight, have improved durability such as wet heat compression set and are favorably used for interior trims of vehicles, cushioning materials for furniture, bedding and miscellaneous goods, and to a process for producing the foams.
BACKGROUND OF THE INVENTION
Because of their cushioning properties, flexible polyurethane cold cure molded foams (sometimes referred to as “flexible foams” hereinafter) are widely used for vehicles, furniture, bedding and miscellaneous goods. Such flexible foams are produced by reacting an aromatic polyisocyanate with a polyol and/or a polymer polyol containing dispersed polymer particles obtained by radical polymerizing acrylonitrile and/or styrene in the polyol, in the presence of water as a blowing agent, a silicone base surfactant, a catalyst such as amine or a tin compound, and if necessary, a crosslinking agent, and additives such as a flame retardant and a pigment.
Water functions as a blowing agent, that is, water reacts with an aromatic polyisocyanate to generate a carbonic acid gas which acts as a blowing gas, and at the same time, an aromatic polyurea is produced. Recently, use of CFC-
11
(CCl
3
F) has been prohibited by the Montreal Protocol for the purpose of global environmental protection. As a result, the amount of water used in the formulation has been increased so as to counterbalance the blowing effect of the conventional blowing additive (physical blowing agent).
In recent years, further, reduction in cost of flexible foams has been strongly demanded, and low density of flexible foams is desired for the purpose of weight reduction. In application of flexible foams for vehicles, lowering of foam density is also required for weight reduction to cope with regulation of fuel consumption. In order to satisfy the requirement of low density, the amount of water used as the blowing agent tends to be further increased.
Increase of the amount of water used leads to greater amount of the carbonic acid gas generated and is thus effective for lowering of density of the flexible foam. However, if the amount of the aromatic polyurea produced at the same time is increased, it becomes difficult to maintain durability of the flexible foam such as compression set property. Moreover, lowering of the density of the flexible foam per se causes deterioration of durability such as compression set property of the flexible foam.
Deterioration of the compression set property means that the shape stability of the flexible foam is bad, and this leads various inconveniences. For example, the thickness of bedding cushions is reduced in the course of use, or the thickness or hardness of cushions for vehicles varies in the course of use. Particularly in cushions for vehicles, long time driving reduces thickness or hardness of the cushions initially designed. As a result, the prescribed position of the driver is lowered, or sitting or riding comfort is impaired. These problems are those on the durability of the flexible foam, and the durability can be evaluated by a change of hardness in a repeated compression test or a wet heat compression set.
Accordingly, there has been desired development of flexible polyurethane cold cure molded foams which are lightweight and have a small wet heat compression set and a low hardness change ratio in a repeated compression test, namely, excellent durability.
Under such circumstances, the present inventors have made various studies, and as a result, they have-found a flexible polyurethane cold cure molded foam which has excellent durability in spite of a low density. Based on the finding, the present invention has been accomplished. The present inventors have also found that a flexible foam having excellent durability can be produced efficiently by using a polymer and/or a polymer polyol containing dispersed polymer microparticles (vinyl polymer particles) obtained by radical polymerizing a compound having an unsaturated bond such as acrylonitrile or styrene in the polyol and by using, as the polyol, a polyol synthesized by the use of a catalyst containing at least one compound selected from the group consisting of a compound having a nitrogen-phosphorus double bond, cesium hydroxide and rubidium hydroxide. Based on the finding, the process of the present invention has been accomplished.
OBJECT OF THE INVENTION
The present invention is intended to solve such problems associated with the prior art as described above, and it is an object of the invention to provide a flexible polyurethane cold cure molded foam which has a lower density and is excellent in durability, particularly in hardness change ratio in a repeated compression test and thickness change properties such as wet heat compression set. It is another object of the invention to provide a process for producing the foam.
In the production process provided by the invention, it is the other object to provide a process capable of economically producing a high-durability flexible polyurethane cold cure molded foam using a resin premix which exhibits excellent moldability in the production of flexible foam.
SUMMARY OF THE INVENTION
The flexible polyurethane cold cure molded foam according to the invention has an overall density of not less than 35 kg/m
3
and not more than 45 kg/m
3
and a wet heat compression set of not more than 15%.
The flexible polyurethane cold cure molded foam according to the invention preferably has a hardness change ratio, as determined in a repeated compression test, of not more than 15%.
The flexible polyurethane cold cure molded foam according to the invention is preferably a flexible polyurethane cold cure molded foam obtained from a polyol and/or a polymer polyol containing dispersed polymer microparticles obtained by radical polymerizing a compound having an unsaturated bond in the polyol, water, a catalyst, a polyisocyanate, and if necessary, a crosslinking agent and/or a foam stabilizer, wherein:
the polyol is a polyoxyalkylene polyol selected from the group consisting of
(1) a polyoxyalkylene polyol having a hydroxyl value of not less than 15 mgKOH/g and not more than 25 mgKOH/g and overall degree of unsaturation of not more than 0.060 meq/g,
(2) a polyoxyalkylene polyol having a hydroxyl value exceeding 25 mgKOH/g and not more than 35 mgKOH/g and overall degree of unsaturation of not more than 0.050 meq/g, and
(3) a polyoxyalkylene polyol having a hydroxyl value exceeding 35 mgKOH/g and not more than 45 mgKOH/g and overall degree of unsaturation of not more than 0.040 meq/g.
The polyol is preferably one synthesized by the use of a catalyst containing at least one compound selected from the group consisting of a compound having a nitrogen-phosphorus double bond, cesium hydroxide and rubidium hydroxide.
The viscosity of a resin premix containing the polyol and/or the polymer polyol, water, the catalyst, and if necessary, the crosslinking agent and/or the foam stabilizer is preferably not more than 2500 mPa.s.
The polyisocyanate is preferably tolylene diisocyanate or a mixture of tolylene diisocyanate and polymethylenepolyphenyl polyisocyanate in a weight ratio of 98:2 to 50:50, said polymethylenepolyphenyl polyisocyanate being represented by the following formula (1):
wherein n is 0 or an integer of 1 or more.
The compound having a nitrogen-phosphorus double bond is preferably a phosphazenium compound or a phosphine oxide compound.
The process for producing a flexible polyurethane cold cure molded foam according to the invention is a process for producing a flexible polyurethane cold cure molded foam obtained from a polyol and/or a polymer polyol containing dispersed polymer microparticles obtained by radical polymerizing a compound having an unsaturated bond in the polyol, water, a catalyst, a polyisocyanate, and if necessary, a crosslinking agent and/or a foam stabilizer, wherein:
Isobe Masahiro
Ohkubo Kazuhiko
Sakai Seijiro
Birch & Stewart Kolasch & Birch, LLP
Cooney Jr. John M.
Mitsui Chemicals Inc.
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