Isocyanate compositions for blown polyurethane foams

Details Isocyanate compositions for blown polyurethane foams Isocyanate compositions for blown polyurethane foams

2001-05-24

2002-09-24

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...

C521S130000, C521S155000, C521S160000, C521S170000, C521S174000, C560S026000, C560S359000

Reexamination Certificate

active

06455601

ABSTRACT:

The present invention is directed to processes for the production of rigid polyurethane foams and reaction systems for use therein. More specifically, the present invention is directed to processes for the production of rigid polyurethane foam utilizing a specific polyisocyanate composition, an isocyanate-reactive composition and hydrofluorocarbon or hydrocarbon blowing agents.
Rigid polyurethane foams have many known uses, such as in building materials and thermal insulation. Such foams are known to have superior structural properties, outstanding initial and long term thermal insulation and good fire retardation properties.
Rigid polyurethane foams have conventionally been prepared by reacting appropriate polyisocyanate and isocyanate-reactive compositions in the presence of a suitable blowing agent. With regard to blowing agents, chlorofluorocarbons (CFC's) such as CFC-11 (CCl
3
F) and CFC-12 (CCl
2
F
2
) have been used most extensively as they have been shown to produce foams having good thermal insulation properties, low flammability and excellent dimensional stability. However, in spite of these advantages, CFC's have fallen into disfavor, as they have been associated with the depletion of ozone in the earth's atmosphere, as well as possible global warming potential. Accordingly, the use of CFC's has been severely restricted.
Hydrochlorofluorocarbons (HCFC's) such as HCFC 141b (CCl
2
FCH
3
) and HCFC22(CHClF
2
) have become a widely used interim solution. However, HCFC's have also been shown to cause a similar depletion of ozone in the earth's atmosphere and accordingly, their use has also come under scrutiny. In fact, the widespread production and use of HCFCs is scheduled to end shortly.
Therefore, there has existed a need to develop processes for the formation of rigid polyurethane foams which utilize blowing agents having a zero ozone depletion potential and which still provide foams having excellent thermal insulation properties and dimensional stability.
A class of materials which have been investigated as such blowing agents include various hydrocarbons such as n-pentane, n-butane and cyclopentane. The use of such materials is well-known and disclosed, e.g., in U.S. Pat. Nos. 5,096,933, 5,444,101, 5,182,309, 5,367,000 and 5,387,618. However, known methods for producing foams with such blowing agents and reaction systems used in such methods have not been found to produce rigid polyurethane foams having commercially attractive physical properties at densities which are sufficiently low to make their use feasible. In short, the properties associated with such hydrocarbon blown foams have generally been inferior to CFC and HCFC blown foams.
Attention has also turned to the use of hydrofluorocarbons (HFC's) including 1,1,1,3,3-pentafluoropropane (HFC 245fa); 1,1,1,3,3-pentafluorobutane (HFC 365mfc); 1,1,1,2-tetrafluoroethane (HFC 134a); and 1,1-difluoroethane (HFC 152a). The use of such materials as blowing agents for rigid polyurethane foams is disclosed, e.g., in U.S. Pat. Nos. 5,496,866; 5,461,084; 4,997,706; 5,430,071; and 5,444,101. However, as with hydrocarbons, attempts to produce rigid foams with such materials have generally not resulted in foams having structural, thermal and thermal properties comparable to those attained using CFC-11 as the blowing agent.
The majority of attempts to solve this problem have centered around the blending of different hydrofluorocarbons, hydrocarbons or the blending of hydrocarbons with hydrofluorocarbons and/or other blowing agents. Such attempts have met with limited success.
Accordingly, there remains a need for a process for the production of rigid polyurethane foam which utilizes hydrofluorocarbon or hydrocarbon blowing agents and which provides foams having excellent physical properties.
This objective is obtained by the present invention which utilizes polymeric polyisocyanates of a specific composition in the process for the production of rigid polyurethane foam with hydrofluorocarbon or hydrocarbon blowing agents. The present invention provides foams having improved physical and thermal insulation properties.
The present invention is directed to a process for making rigid polyurethane foams comprising reacting:
(1) a polyphenylene polymethylene polyisocyanate composition;
(2) an isocyanate-reactive composition containing a plurality of isocyanate-reactive groups which are useful in the preparation of rigid polyurethane or urethane-modified polyisocyanurate foams;
(3) a hydrofluorocarbon or hydrocarbon blowing agent;
(4) optionally, water or other carbon dioxide evolving compounds, and
wherein said polyphenylene polymethylene polyisocyanate comprises
(a) a 15 to 42 percent by weight, based on 100% of the polyisocyanate component (1), of diphenylmethane diisocyanate;
(b) 3-ring oligomers of polyphenylene polymethylene polyisocyanate (henceforth referred as triisocyanate) in an amount such that the ratio of diisocyanate to triisocyanate is between about 0.2 to about 1.8; and
(c) the remainder being higher homologues of polyphenylene polymethylene polyisocyanate.
The present invention is further directed to reaction system useful for the preparation of rigid polyurethane foams comprising
(1) a polyphenylene polymethylene polyisocyanate composition;
(2) an isocyanate-reactive composition containing a plurality of isocyanate-reactive groups which are useful in the preparation of rigid polyurethane or urethane-modified polyisocyanurate foams;
(3) a hydrofluorocarbon or hydrocarbon blowing agent;
(4) optionally, water or other carbon dioxide evolving compounds, and
wherein said polyphenylene polymethylene polyisocyanate comprises:
(a) a 15 to 42 percent by weight, based on 100% of the polyisocyanate component (1), of diphenylmethane diisocyanate;
(b) 3-ring oligomers of polyphenylene polymethylene polyisocyanate (henceforth referred as triisocyanate) in an amount such that the ratio of diisocyanate to triisocyanate is between about 0.2 to about 1.8; and
(c) the remainder being higher homologues of polyphenylene polymethylene polyisocyanate.
The polyphenylene polymethylene polyisocyanates used in the present invention are those of Formula I
3-ring oligomers of component 1(b) are those represented by Formula I where n=1. The higher homologues of component 1(c) are those represented by Formula I where n>1.
The polyphenylene polymethylene polyisocyanate composition (1) used in the present invention comprises about 15 to about 42 percent, preferably about 20 to about 40 percent and more preferably 24 to about 38 percent by weight, based upon 100 percent of the polyisocyanate component, of diphenylmethane diisocyanates. Diphenylmethane diisocyanate in the form of its 2,2′, 2,4′ and 4,4′ isomers and mixtures thereof may be used as in the present invention. Any variation of the 2,2′, 2,4′ and 4,4′ isomers may be utilized.
The polyphenylene polymethylene polyisocyanate composition (1) further comprises the triisocyanate component in an amount such that the ratio of diisocyanate to triisocyanate is between 0.2 to 1.8 and preferably between about 0.33 to about 1.8. Thus, the actual triisocyanate content is determined based upon the amount of diphenylmethane diisocyanate in the polyphenylene polymethylene composition (1) utilizing the above-stated ratio. The amount is on a percent by weight basis based on 100 percent by weight of the total polyisocyanate composition.
For purposes of clarification, if the amount of diphenylmethane diisocyanate in a given polyphenylene polymethylene polyisocyanate composition is 30 percent and the ratio of diisocyanate to triisocyanate is 1.5, the amount of triisocyanate which must be incorporated into the polyphenylene polymethylene polyisocyanate composition would then be 20 percent by weight based upon 100 percent by weight of the total composition. As used herein, the term “triisocyanate” means all isomers of 3-ring oligomers of polyphenylene polymethylene polyisocyanate (i.e., n=1 in Formula I) containing th

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