Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2000-01-11
2002-06-04
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S060000, C528S061000, C528S064000, C528S068000, C528S076000, C528S085000
Reexamination Certificate
active
06399736
ABSTRACT:
BACKGROUND OF INVENTION
This invention concerns polyurea or polyurethane elastomers prepared from aspartic esters, and processes for the preparation thereof.
Polyurea and polyurethane elastomers have previously been made using primary amines as reactants. One common problem with such systems is the high reactivity of the polymerization reaction. As a result, it is difficult to obtain smooth finishes in coatings made from the polyurea and polyurethane elastomers. To decrease the reactivity of the system, it has been previously proposed to employ secondary amines as the amine component of the system. One such secondary amine that has been proposed is polyaspartic ester, which is derived from a primary polyamine and diethyl maleate, for example. The polyaspartic ester derived polyureas have a number of advantageous properties, such as smooth, glossy film surface, excellent elongation (high) at a high elastomer strength, excellent ultraviolet color stability, good low temperature property retention and flexibility, slow reactivity for ease of processing and substrate wet-out (improved adhesion). Use of the polyaspartic esters, however, results in slow polymerization reaction. A polyaspartic ester system has proven to be too slow for rapid coating applications. Hence, these systems heretofore required catalysts such as organo tin compounds to increase the reactivity to acceptable levels. However, the catalysts increase cost of such polyureas and polyurethanes, increase the complexity of the manufacturing processes. In addition, use of catalysts lead to poor component stability over extended periods, increased moisture sensitivity in the system, overall system reactivity being affected by changes in environmental and substrate temperature, and polymer breakdown under stressful conditions that do not normally affect polyurea and polyurethane systems (i.e., high heat/humidity, UV light).
SUMMARY OF INVENTION
This invention solves one or more of the problems and disadvantages described above.
In one broad respect, this invention is a method for the preparation of polyurea elastomers, comprising: (a) reacting an amine chain extender with dialkyl maleate or dialkyl fumarate to form an aspartic ester, wherein the chain extender has a molar amount of amine groups that is greater than the moles of dialkyl maleate; (b) blending the aspartic ester with one or more polyoxyalkyleneamines to prepare a resin blend; (c) contacting the resin blend with an isocyanate under conditions effective to form a polyurea elastomer.
In another broad respect, this invention is a polyurea elastomer, comprising the reaction product of (a) a resin blend containing one or more polyoxyalkyleneamine and an aspartic ester and (b) an isocyanate, wherein the aspartic ester in the resin blend comprises a reaction product of an amine chain extender and a dialkyl maleate or dialkyl fumarate, wherein the mole ratio of amine functionality in the amine chain extender to dialkyl maleate or fumarate is greater than 1:1.
In one broad respect, this invention is a method for the preparation of polyurethane elastomers, comprising: (a) reacting an diamine chain extender with dialkyl maleate or fumarate, wherein the mole ratio of primary amine functionality in the diamine chain extender to dialkyl maleate or fumarate is more than 1:1; (b) coating a substrate with effective film forming amounts of the product of step (a), an isocyanate, and a polyhydroxyl compound under conditions effective to form a the polyurethane elastomer.
In another broad respect, this invention is a polyurethane elastomer, comprising the reaction product of (a) a resin blend containing one or more polyoxyalkyleneamine and a reaction product of a diamine chain extender and a dialkyl maleate or fumarate, wherein mole ratio of primary amine functionality in the diamine chain extender to the dialkyl maleate or fumarate is greater than 1:1, (b) an isocyanate, and (c) a polyhydroxyl compound.
The polyurea and polyurethane of this invention advantageously possesses acceptable gel and tack free times. As a result, the polyureas and polyurethanes provide smooth coatings when applied. In addition, by varying the dialkyl maleate content of the polyaspartic ester there is some primary amine available for reaction control such that a variety of system reactivities can be achieved. As a result, the present invention advantageously provides a rapid, predictable cure. The process of this invention provides a slower cure aliphatic polyurea spray elastomer, resulting in smooth, level surfaces without the presence of spray lines or overspray. Furthermore, the present aspartic ester systems of this invention flow together well and become tack free in a reasonable time at wide ranges of ambient temperature. Moreover, the aspartic ester systems of this invention achieve excellent adhesion to smooth steel panels and other substrates as described herein, probably due to improved elastomer wet out of the surface.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates generally to sprayable polyurea and polyurethane elastomers and methods for preparation of such elastomer systems. The present polyurea elastomer systems include the reaction product of (a) a pre-blend of an amine terminated polyether and an aspartic ester and (b) an isocyanate compound to produce a polyurea elastomer. Because of the reactivity of the preferred aliphatic system, the elastomers of the present invention are more useful in spray systems relative to other elastomer systems, such as reactive injection molding systems.
Aspartic Esters
The aspartic esters that can be employed in the practice of this invention comprise the reaction product of a polyamine and a dialkyl maleic or fumaric acid ester. The aspartic esters can be formed by known methods, which generally entail reacting the polyamine with the dialkyl maleic or fumaric acid ester such that a reaction product is formed. Such procedures are set forth in the examples herein and are described in U.S. Pat. No. 5,243,012. In the practice of the present invention, the mole ratio of amine functionality in the amine chain extender to dialkyl maleate or fumarate is greater than 1:1. Typically, the mole ratio of amine functionality to dialkyl maleate or fumarate is greater than about 4:1. In one embodiment of this invention, the mole ratio is about 2:1 (about one-half of the amine groups have been reacted with the double bond of the dialkyl maleate or fumarate).
The primary polyamines generally correspond to the formula: X(NH
2
)
n
wherein X represents an organic group which as a valence of n and is inert towards isocyanate groups at a temperature of 100 centigrade or less. In certain embodiments, X represents a divalent hydrocarbon group obtained by removal of the amino groups from an aliphatic, araliphatic or cycloaliphatic polyamine, particularly a diamine. The “n” represents an integer with a value of at least about 2, in certain embodiments from about 2 to about 4, and in one embodiment 2. Representative examples of such polyamines include, but are not limited to, ethylene diamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,3-diaminopentane, 1,6-diaminohexane, 2,5-diamino-2,5-dimethlhexane, 2,2,4- and/or 2,4,4-trimethyl-1,6-diaminohexane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,3- and/or 1,4-cyclohexane diamine, 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, 2,4- and/or 2,6-hexahydrotoluylene diamine, 2,4′ and/or 4,4′-diaminodicyclohexyl methane and 3,3′-dialkyl-4,4′-diamino-dicyclohexyl methanes such as 3,3′-dimethyl-4,4-diamino-dicyclohexyl methane and 3,3′-diethyl-4,4′-diaminodicyclohexyl methane; aromatic polyamines such as 2,4- and/or 2,6-diaminotoluene and 2,6-diaminotoluene and 2,4′ and/or 4,4′-diaminodiphenyl methane; and polyoxyalkylene polyamines (also referred to herein as amine terminated polyethers), especially diamines, as are described hereinbelow. Mixtures of polyamines can be employed in preparing the aspartic esters used in the practice of this invention.
The maleic
Hillman Kenneth M.
Primeaux, II Dudley J.
Zimmerman Robert L.
Huntsman Petrochemical Corporation
O'Keefe, Egan & Peterman
Sergent Rabon
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