Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-02-20
2003-03-18
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...
C252S182240, C252S182270, C521S131000
Reexamination Certificate
active
06534556
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to dimensionally stable closed cell spray rigid polyisocyanate based foams, and more particularly to foaming reaction mixtures which froth at a spray dispensing head, employing as a blowing agent a hydrofluorocarbon. With more particularity, the invention pertains to dimensionally stable closed cell spray rigid polyisocyanate based foams which froth at a spray dispensing head and the polyol resin blends used to make such foams.
BACKGROUND OF THE INVENTION
Various hydrofluorocarbons (HFCS) have been investigated in the industry as blowing agents for polyisocyanate based foams due to their low or nonexistent ozone depletion potentials. It would be desirable to utilize a hydrofluorocarbon (HFC) blowing agent in a sprayable froth polyurethane system. Such a system would allow for production of an environmentally friendly closed cell polyurethane foam that exhibits improved cell structure and expands at a lower temperature range. It is also desirable to produce a polyurethane foam that avoids excessive creep and allows for improved dimensional stability.
SUMMARY OF THE INVENTION
The present invention provides a formulated resin composition for producing a closed cell rigid polyisocyanate based foam. In one embodiment the formulated resin composition for use in a polyurethane froth spraying system comprises: a hydrofluorocarbon blowing agent; a Mannich polyol; at least one additional polyol; a catalyst system; and a surfactant. The formulated resin composition has a hydroxyl content of at least 400 mg KOH/g and a polyurethane foam produced utilizing the formulated resin composition has a closed cell content of at least 90 percent.
The formulated resin composition exhibits a zero ozone depleting potential and produces a polyurethane foam that cures faster than conventional sprayed polyurethane foams.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A “froth foaming mixture” is produced by a combination of a formulated isocyanate-reactive polyol stream containing a hydrofluorocarbon blowing agent with an organic polyisocyanate stream where the hydrofluorocarbon blowing agent sufficiently and spontaneously vaporizes when the two combined streams are exposed to atmospheric pressure upon discharge from a dispensing head to produce a froth. Thus, the hydrofluorocarbon acts as a frothing agent. It is to be understood that not all of the hydrofluorocarbon blowing agent needs to vaporize instantaneously from the two stream mixture when discharged, but at least an amount sufficient to produce a froth upon discharge from the dispensing head onto a substrate.
These mixtures are used to form both rigid and closed cell foams. The term a rigid foam is meant to describe a foam having a high ratio of compressive strength to tensile strength of 0.5:1 or greater and an elongation of 10 percent or less. The term a closed cell foam is meant to describe a foam having at least 85 percent closed cells and preferably 90 percent or more closed cells. The foams are polyisocyanate based meaning that they are made by reacting the isocyanate-reactive ingredients in a resin composition with an organic isocyanate or polyisocyanate. In preferred embodiments, all of the hydrofluorocarbon used as a frothing agent is added to the resin composition to form a formulated resin composition.
The formulated resin composition comprises a Mannich polyol, at least one additional polyol, a hydrofluorocarbon blowing agent, a polyurethane linkage promoting catalyst system, a surfactant, and, optionally, flame retardants, fillers, stabilizers, fungicides, pigments or dyes and bacteriostats.
A Mannich polyol is made by alkoxylating a Mannich compound, which is the condensation product of phenol or a substituted phenol, formaldehyde, and an alkanoamine, such as diethanol amine.
For example, the Mannich reaction is conducted by premixing the phenolic compound with a desired amount of the ethanolamine and then slowly adding formaldehyde to the mixture at a temperature below the temperature of Novolak formation. At the end of the reaction, water is stripped from the reaction mixture to provide a crude Mannich reaction product.
The Mannich reaction product is then alkoxylated with an alkylene oxide such as, for example, propylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide. The alkylene oxide may suitably comprise from 100% to about 80% propylene oxide and from 0 to about 20 wt. % ethylene oxide. Alkoxylation of Mannich reaction products is described in U.S. Pat. Nos. 3,297,597 and 4,137,265, the disclosures of which are herein incorporated by reference.
The alkoxylation with propylene oxide is carried out by introducing the propylene oxide, preferably under pressure, into a vessel containing the Mannich reaction product. No added catalyst is needed since the basic nitrogen in this product provides sufficient catalytic activity to promote the reaction. Reaction temperatures between about 30° C. and about 200° C. may be employed, but the preferred reaction temperatures are in the range of from about 90° to 120° C. Under these conditions the phenolic hydroxyl group and the alkanolamino hydroxyls are reactive to form hydroxypropyl groups. Unreacted and partially reacted materials are removed from the final condensation product in any suitable manner (e.g., by vacuum stripping) to provide clear amber to brown liquids having hydroxyl numbers in the range of 400 to 550 and viscosities between about 4,000 and 45,000 centipoises at 25° C.
In a preferred embodiment of the present invention the Mannich polyol is present in the formulated resin composition at an amount of from 20 to 40 weight percent, based on the total weight of the formulated resin composition.
The formulated resin composition also includes at least one additional polyol compound having at least two isocyanate-reactive hydrogens. The compounds having at least two isocyanate-reactive hydrogens preferably have an average hydroxyl number ranging from 150 to 800 mg KOH/g of compound.
Examples of these polyols include polythioether polyols, polyester amides and polyacetals containing hydroxyl groups, aliphatic polycarbonates containing hydroxyl groups, amine-terminated polyoxyalkylene polyethers, polyester polyols, and polyoxyalkylene polyether polyols. In addition, mixtures of at least two of the aforesaid polyols can be used.
The term “polyester polyol” as used in this specification and claims includes any minor amounts of unreacted polyol remaining after the preparation of the polyester polyol and/or unesterified polyol (e.g., glycol) added after the preparation of the polyester polyol. The polyester polyol can include up to about 40 weight percent free glycol.
Suitable polyester polyols can be produced, for example, from organic dicarboxylic acids with 2 to 12 carbons, preferably aliphatic dicarboxylic acids with 4 to 6 carbons, and multivalent alcohols, preferably diols, with 2 to 12 carbons, preferably 2 to 6 carbons. Examples of dicarboxylic acids include succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. The dicarboxylic acids can be used individually or in mixtures. Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives may also be used such as dicarboxylic acid mono- or di-esters of alcohols with 1 to 4 carbons, or dicarboxylic acid anhydrides. Dicarboxylic acid mixtures of succinic acid, glutaric acid and adipic acid in quantity ratios of 20-35:35-50:20-32 parts by weight are preferred, especially adipic acid. Examples of divalent and multivalent alcohols, especially diols, include ethanediol, diethylene glycol, 1,2- and 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, glycerine and trimethylolpropanes, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol, tetramethylene glycol, 1,4-cyclohexane-dimethanol, ethanediol, diethylene glycol, 1,4-butanediol, 1
Gardin Greg
Harris Thomas
Lacarte Chris
BASF Corporation
Borrego Fernando A.
Cooney Jr. John M.
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