Integral skin foams employing pentafluorobutane blowing agents

Details Integral skin foams employing pentafluorobutane blowing agents Integral skin foams employing pentafluorobutane blowing agents

2002-09-23

2004-07-06

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...

C521S131000, C521S170000

Reexamination Certificate

active

06759444

ABSTRACT:

The present invention relates to integral skin foams and a process for preparing such foams utilizing non-chlorinated fluorocarbons as the sole blowing agent or with water as a co-blowing agent.
BACKGROUND OF THE INVENTION
Integral skin foams are well known to those skilled in the art of polyurethane foams. Such foams have a cellular interior and a higher density microcellular or non-cellular skin. In general, to prepare such foams an organic isocyanate is reacted with a substance having at least one isocyanate reactive group in the presence of a catalyst, blowing agent, and a variety of optional additives. The reaction is carried out in a mold where a higher density skin forms at the interface of the reaction mixture and the relatively cool inner surface of the foam.
Generally the blowing agent used in integral skin polyurethane foams have been chlorofluorocarbons (CFCs) or combinations of CFCs and other blowing agents. However, in view of regulations for a reduction and eventual elimination of the use of CFCs, alternatives are considered necessary.
U.S. Pat. No. 5,506,275 describes the use of 1,1,1,2-tetrafluoroethane (HFC 134a) as an alternative to conventional chlorinated fluorocarbon blowing agents in integral skin foam formulations. While this blowing agent offers an alternative to halogenated hydrocarbon blowing agents, it boils at about −27° C. and may require special gas delivery systems to introduce and maintaining the blowing agent in solution. In addition, HFC 134a has a limited solubility in the polyol component.
U.S. Pat. Nos. 5,906,999 and 6,010,649 disclose the use of pentafluoropropane blowing agents, particularly 1,1,1,3,3-pentafluoropropane for producing integral skin foams. The pentafluoropropane blowing agents are reported to give acceptable appearance and exhibit enhanced resistance to abrasion and cracking.
While tetrafluoroethane and pentafluoropropane blowing agent present alternatives to the conventional CFCs, there remains a need for non-chlorinated hydrocarbon blowing agents. It has been found that integral skin foams utilizing pentafluorobutane blowing agents can meet the stringent requirements inherent to integral skin foam applications to give an acceptable appearance and exhibit acceptable resistance to abrasion and cracking upon flex. Furthermore, the pentafluorobutane blowing agents utilized in the present invention are generally soluble in the polyol component thus eliminating or greatly reducing the need for specialized gas delivery systems.
SUMMARY OF THE INVENTION
The present invention is to provide an integral skin polyurethane foam comprising the reaction product of
a) a polyisocyanate component; and
b) a polyol composition; in the presence of
c) a blowing agent including non-chlorinated pentafluorobutane and optionally water;
d) a catalyst; and
optionally one or more compounds selected from the group consisting essentially of chain extenders, surfactants, alcohols, fillers, pigments, antioxidants, stabilizers and mixtures thereof.
In another embodiment the present invention is a process of making a molded integral skin polyurethane foam article comprising the steps of:
a) providing an organic polyisocyanate;
b) providing a resin comprising;
i) a polyol composition;
ii) a blowing agent including non-chlorinated pentafluorobutane and optionally water;
iii) a catalyst; and
iv) optionally one or more compounds selected from the group consisting essentially of chain extenders, surfactants, alcohols, fillers, pigments, antioxidants, stabilizers and mixtures thereof.
c) introducing components a) and b) into a mold and reacting the components for a period of time sufficient to produce a molded integral skin polyurethane article.
In another embodiment, the present invention is a cellular polyurethane foam characterized in that the foam has an integral skin and the gas content of the cells comprises non-chlorinated pentafluorobutane. In yet another embodiment of the present invention, the blowing used in the above process, and formation of an integral skin foam is a combination of tetrafluoroethane and pentafluorobutane and optionally water.
In a further embodiment, the blowing agent used in the present invention is a combination of a heptafluoropropane and pentafluorobutane and optionally water.
In yet another embodiment, the blowing agent is a combination of pentafluorobutane, tetrafluoroethane and heptafluoropropane, optionally in the presence of water.
DETAILED DESCRIPTION
The isocyanates which may be used in the present invention are aromatic polyisocyanates.
Examples of suitable aromatic isocyantes include the 4,4′-, 2,4′ and 2,2′-isomers of diphenylmethane diisocyante (MDI), blends thereof and polymeric and monomeric MDI blends toluene-2,4- and 2,6-diisocyanates (TDI), m- and p-phenylenediisocyanate, chlorophenylene-2,4-diisocyanate, diphenylene-4,4′-diisocyanate, 4,4′-diisocyanate-3,3′-dimehtyldiphenyl, 3-methyldiphenylmethane-4,4′-diisocyanate and diphenyletherdiisocyanate and 2,4,6-triisocyanatotoluene and 2,4,4′-triisocyanatodiphenylether.
Mixtures of isocyanates may be used, such as the commercially available mixtures of 2,4- and 2,6-isomers of toluene diisocyantes. A crude polyisocyanate may also be used in the practice of this invention, such as crude toluene diisocyanate obtained by the phosgenation of a mixture of toluene diamine or the crude diphenylmethane diisocyanate obtained by the phosgenation of crude methylene diphenylamine. TDI/MDI blends may also be used. Prepolymers based on the polyisocyanates can also be used. Isocyanate-terminated prepolymers are prepared by reacting an excess of polyisocyanate with polyols, including aminated polyols or imines/enamines thereof, or polyamines.
The polyisocyanates are prepared by conventional methods known in the art such as the phosgenation of the corresponding organic amine.
Especially useful, due to their availability and properties, are 2,4′-diphenyl diisocyanate, 4,4′-diphenylmethane diisocyanate, polymethylene polyisocyanate and mixtures thereof. Mixtures of polymeric diphenylmethane diisocyanate (polymeric MDI) and carbodiimide or urethane modified MDI are preferred. The polyisocyanate is generally added in an amount to provide an isocyanate index between 80 and 125, preferably between 100 to 110.
The polyol component includes those materials having two or more groups containing an active hydrogen atom capable of undergoing reaction with an isocyanate. Preferred among such compounds are materials having at least two hydroxyl, primary or secondary amine, carboxylic acid, or thiol groups per molecule Compounds having at least two hydroxyl groups per molecule are especially preferred due to their desirable reactivity with polyisocyanates.
The hydroxyl number and molecular weight of the polyol can vary according to the desired property of the cellular foam. In general the hydroxyl number will range from about 20 to 800. In applications for producing flexible articles, typically polyols include those having an average hydroxyl number ranging from 20 to 100 mg KOH/g, preferably from 20 to 70 mg KOH/g. Such polyols also advantageously have a functionality between 1.5 and 4, preferably between 2 and 3. Generally the number average molecular weight is 2,000 to 10,000, preferably from 3000 to 6000 and more preferred from 3500 to 5100. For applications for producing rigid articles, typically polyols include those having an average molecular weight of 60 to 10,000, preferably 600 to 7,000 and more preferred from 600 to 3,000. Such polyols also advantageously have a functionality between 2 and 6, preferably between 2 and 4.
Representative polyols include polyether polyols, polyester polyols, polyhydroxy-terminated acetal resins, hydroxyl-terminated amines and polyamines. Examples of these and other suitable isocyanate-reactive materials are described more fully in U.S. Pat. No. 4,394,491.
Preferred are polyether polyols prepared by adding an alkylene oxide, such as ethylene oxide, propylene oxide, butylene oxide or a combina

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