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
2000-07-17
2002-06-11
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...
C264S328100, C264S328600, C528S060000, C528S061000, C528S068000, C528S076000, C528S080000, C528S085000
Reexamination Certificate
active
06403752
ABSTRACT:
BACKGROUND OF THE INVENTION
As a subclass of commercially available polymers, polyurethane elastomers have several properties that give them unique benefits. Typically, polyurethanes and the related polyureas show high abrasion resistance with high load bearing, excellent cut and tear-resistance, broad hardness range, and resistance to ozone degradation, yet are portable and castable. Compared to metals, polyurethanes are lighter in weight, less noisy in use, show better wear and excellent corrosion resistance while being capable of less expensive fabrication. Compared to other plastics, polyurethanes are non-brittle, much more resistant to abrasion, and exhibit good elastomeric memory. Polyurethanes find use in such diverse products as aircraft hitches, bushings, cans, gaskets, star wheels, washers, scraper blades, impellers, gears, and also serve as coatings in a wide variety of uses.
Part of the utility of polyurethanes (and polyureas) derives from their enormous diversity of properties resulting from a relatively limited number of reactants. Typically, polyurethanes are prepared by reacting (curing) the terminal isocyanate groups of a monomeric polyisocyanate or of a low molecular weight prepolymer with the isocyanate-reactive hydrogens of a polyfunctional compound or compounds so as to form high polymers through chain extension and, in some cases, crosslinking. Urethane prepolymers are adducts of polyisocyanates and polyhydric alcohols as exemplified by the 2:1 adducts of a diisocyanate and a diol, and urea prepolymers are adducts of monomeric polyisocyanates and polyamines. Prepolymers are described later in more detail.
Diols, and especially alkylene diols, are often used as curing agents and lead to linear polymers by chain extension. Where a triol or a higher polyhydric alcohol is used crosslinking occurs to afford a non-linear polymer. Although other polyfunctional materials, especially diamines, are theoretically suitable, only a few have achieved commercial importance as curing agents. Some of these exceptions are 4,4-methylene-di-ortho-chloroaniline, usually referred to as MOCA, the 2,4- and 2,6-diamino-3,5-diethyl-1-methylbenzene, often referred to as diethyltoluene diamine or DETDA, and the 2,4- and 2,6-diamino-3,5-dimethylthio-1-methylbenzene, and the aliphatic diamine isophorone diamine. These diamines can function as curing agents which are both chain extenders and crosslinkers. More recently selected secondary aromatic diamines and polyamines have found favor as curing agents. The secondary aromatic diamines act solely as chain extenders. Even more recently we have described some bis(N-alkylaminocyclohexyl)methanes as chain extenders for polyurethanes and polyureas; see U.S. Pat. No. 5,312,886.
Among the unsatisfied needs in the polyurethane and polyurea high-pressure impingement mixing field is a need for a product which shows excellent light stability while having the toughness of polymers made using amine-based curing agents. A disadvantage of many current products is their tendency to yellow in sunlight, whereas it would be highly advantageous to have products which show no darkening with time for particular applications such as coatings generally, elastomers such as topcoats for automobiles and outdoor implements, for roofs, coatings for bridges and decks, for certain adhesives, and in molded parts where optical clarity is desired. High-pressure impingement mixing as used herein is meant to include the broad field of reaction injection molding technology including reaction injection molding as well as reaction injection spraying. Reaction injection spraying is understood in the art and more fully described in U.S. Pat. No. 5,504,181; Primeaux II, D. J.
Modern Paints and Coatings
, June 1991, p. 46-54; Primeaux II, D. J.; Anglin, K. C.a Texaco Chemical Company publication; and Schrantz, J.,
Industrial Finishing
, October 1992.
Some chain-extending agents are described in Reiff et al., U.S. Pat. No. 3,868,350, in the context of thermoplastic polyurethane and polyureas made by melting pre-made polymer powders. Unlike the powder coatings of Reiff et al., high-pressure impingement mixing techniques such as spraying or molding require shorter pot lives, shorter tack free times and different physical properties of the reaction components. Another important difference between the present invention and the invention of Reiff et al. is that the polymers disclosed by Reiff et al. are fully cured before they are applied to the substrate. After the powder is applied to the substrate, it is then heated whereupon it melts and flows together to form the homogeneous coating. In the high-pressure impingement mixing technique used in the present invention, the formulation is applied to the substrate as it is reacting and a homogeneous coating is directly produced. Subsequent heating to fully cure the coating is not a requirement. Chain extenders suitable for powder coatings are not necessarily successful in high-pressure impingement mixing techniques. Applicants have discovered specific chain extenders which are successful when used to form high-pressure, impingement mixed, molded, or sprayed products.
SUMMARY OF THE INVENTION
A purpose of the present invention is to prepare light-stable polymers of the polyurethane and polyurea types using high-pressure impingement mixing and several specific aliphatic diamines as chain extenders. An embodiment comprises using as chain extenders diamines of the classes di(alkylamino)cyclohexanes, the saturated analogs of DETDA, N,N′-dialkylisophorone diamine, and di(alkylamino)-hexanes where the alkyl groups are lower alkyls of not more than 20 carbons when bonded to nitrogen and not more than 10 carbons when bonded to the cyclohexyl ring. In a specific embodiment the diamine is 1,4-di(sec-butylamino)cyclohexane. In another specific embodiment the diamine is 1-methyl-2,4-di(sec-butylamino)-3,5-diethylcyclohexane. Other embodiments and aspects will be clear from the following description.
DETAILED DESCRIPTION OF THE INVENTION
One technique used in forming polyurethane and polyurea polymers is high-pressure impingement mixing wherein, for example, metered amounts of a polyisocyanate (e.g., a monomer, a quasi prepolymer, or a blend of polyisocyanates), a polyol or a polyamine, a diol or diamine chain extender, and optional component(s), if any, are sprayed or impinged into each other in the mix head of the high-pressure, impingement mixing machine using pressures typically between 500 and 3,000 psig. The mixed formulation immediately exits the mix head into a mold (for cast elastomers) or as a spray to form a coating. The formulations are applied as a reacting polymer, and full curing takes place after the polymer has been applied to the substrate or injected into the mold. The overall reaction is very fast and the pot lives of successful formulations are typically on the order of a few seconds and tack free times range from a few seconds to minutes as compared to coating formulations that are applied as powders and then heated to melt the powders into coatings which have pot lives and tack free times that are dependent upon the melting temperatures of the powders and the duration of the heating.
The subject polymers of this application are the high-pressure impingement mixed, molded, or sprayed products of one or more polyisocyanate reactants with isocyanate-reactive amines which are di(alkyl-amino)cyclohexanes (I), 1-methyl-2,4-di(alkylamino)-3,5-dialkylcyclohexanes (II), N,N′-dialkylisophoronediamine (III), di(alkylamino)hexanes (IV), 1,3-di(1′-methyl-1′-alkylamino-ethyl)benzene (V), and blends of these amines with other isocyanate-reactive materials, principally polyols and/or other polyamines. The structures of the amines of the present invention are given below. (The term “polymer” as used in this application is intended to encompass elastomers and coatings.) Many variants arise because of the distinct combination of reactants which are possible.
High-pressure impingement mixing is particularly useful in pre
House David W.
Scott, Jr. Ray V.
Maas Maryann
Molinaro Frank S.
Sergent Rabon
Tolomei John G.
UOP LLC
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