(12) Patent Application Publication (10) Pub. No.: US 2013/0253084 A1 Duggal Et Al
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US 20130253O84A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2013/0253084 A1 Duggal et al. (43) Pub. Date: Sep. 26, 2013 (54) POLYURETHANEELASTOMERS MADE Publication Classification USING MIXTURES OF ALPHATIC DOL CHAIN EXTENDER AND SECONDARY (51) Int. Cl. AMINE C08G 18/08 (2006.01) C08G 18/22 (2006.01) (76) Inventors: Rajat Duggal, Pearland, TX (US); (52) U.S. Cl. Nathan Wilmot, Missouri City, TX CPC ................ C08G 18/08 (2013.01); C08G 18/14 (US); Richard Keaton, Pearland, TX (2013.01); C08G 18/222 (2013.01) (US); Alan K. Schrock, Pensacola USPC .............................. 521/124; 528/73:521/156 Beach, FL (US) (21) Appl. No.: 13/990,488 (57) ABSTRACT (22) PCT Filed: Nov. 16, 2011 Polyurethane elastomers are formed by curing a reaction mixture containing at least one polyisocyanate at least one (86). PCT No.: PCT/US11 f60901 polyol, an aliphatic diol chain extender and a small amount of a secondary amino compound that may have none or one or S371 (c)(1), more hydroxyl groups. The reaction is catalyzed with a metal (2), (4) Date: May 30, 2013 catalyst. In certain embodiments, the catalyst is an organozir conium, organotitanium or tertiary amine-based catalyst. The Related U.S. Application Data presence of the secondary amine compound in those cases (60) Provisional application No. 61/420,385, filed on Dec. provides for a good Surface appearance and good physical 7, 2010. properties. US 2013/0253084 A1 Sep. 26, 2013 POLYURETHANEELASTOMERS MADE 0010 Unfortunately, few catalysts successfully mimic the USING MIXTURES OF ALPHATIC DOL performance of the organomercury catalysts. Few other cata CHAIN EXTENDER AND SECONDARY lysts provide the reaction profile that is wanted. Among the AMINE few catalysts that provide a reaction profile similar to that of the organomercury catalysts are certain organozirconium, 0001. This application claims priority from U.S. Provi organotitanate and certaintertiary amine catalysts. However, sional Patent Application No. 61/420,385, filed 7 Dec. 2010. when the cast polyurethane system contains a large amount of 0002 This invention relates to a process for making cast chain extender, the cast elastomers made using these catalysts polyurethane elastomers. often exhibit a surface appearance characterized by the pres 0003 Polyurethane elastomers are made by reacting a ence of discrete transparent or translucent regions together high equivalent weight polyol and a chain extender material with discrete opaque regions. Such an appearance is often with a polyisocyanate compound. The starting materials are cosmetically unacceptable to the consumer, again resulting in mixed, usually degassed, and transferred into a mold where a high reject rate. In certain cases the mechanical properties the elastomer is cured, usually with application of heat. Some may also suffer. or all of the high equivalent weight polyol may be pre-reacted 0011. It would be desirable to provide a cast elastomer with the polyisocyanate in a preliminary step to form an process which provides for an acceptable open time followed isocyanate-terminated prepolymer or quasi-prepolymer. by a rapid cure, and which produces an elastomer that has Such a prepolymer is then caused to react with the chain acceptable physical properties and an acceptable Surface extender and optionally a remaining portion of the high appearance. It is also desirable to achieve these results while equivalent weight polyol during the molding step. avoiding the use of mercury-containing catalysts. 0004 Open time is very important in cast elastomer pro 0012. This invention is in one aspect a process for prepar cesses. Once the starting materials are mixed, they must ing a noncellular or microcellular polyurethane elastomer, remain in an uncured, flowable state for up to several minutes comprising 1) forming a reaction mixture containinga) one or to allow the mixture to be degassed (in most cases) and more aliphatic diols having a hydroxyl equivalent weight of transferred into the mold. If the reaction proceeds too quickly, from about 30 to about 100, b) one or more secondary amine the mold may not fill completely and/or flow lines or other compounds having a molecular weight of 200 or less and at defects may appear in the parts. This can lead to high reject least one of c-1) and c-2), wherein c-1) includes one or more rates. organic polyisocyanates having an isocyanate content of at 0005. Once the mold is filled, however, a rapid cure is least 15% by weight and one or more polyols having a wanted to reduce cycle times and maximize mold usage. hydroxyl equivalent weight of at least 250 and c-2) includes 0006 Polyurethane cast elastomers can be generally char one or more isocyanate-terminated prepolymers or quasi acterized into polyurethane types and polyurethane-urea prepolymers having an isocyanate content of less than 15% types. The difference between the two types relates to the type formed in a reaction of an organic polyisocyanate with one or of chain extender that is used to produce the elastomer. The more polyols having a hydroxyl equivalent weight of at least polyurethane types are made using a diol chain extender, 250 and 2) curing the reaction mixture in the presence of a whereas the polyurethane-urea types are made using a catalyst to form the polyurethane elastomer, wherein: diamine chain extender. Most diamine chain extenders are 0013 A) the reaction mixture contains no more than much more reactive towards isocyanates than are diol chain 0.25% by weight of a chemical blowing agent; extenders. Most diamine-extended systems tend to have open 0014 B) the secondary amine compound contains from times which are too short for the cast elastomer process. Some one to four secondary amino groups, is devoid of primary diamines like methylene bis(2-chloroaniline) provide for amino groups, and contains from Zero to three hydroxyl long open times, but worker exposure issues relating to meth groups, provided that the combined number of secondary ylene bis(2-chloroaniline) make it an undesirable choice. In amino groups and hydroxyl groups is from one to four, addition, the properties of polyurethane-urea elastomers 0015. 3) the weight ratio of componenta) to component b) often cannot match those of polyurethane elastomers. is from 60:40 to 95:5; 0007 Organomercury compounds are often the catalysts 0016 4) the hard segment content of the polyurethane of choice for cast elastomer processes. Organomercury cata elastomer is from 30 to 60% by weight; and lysts offer an important combination of attributes, which are (0017. 5) the isocyanate index is from 70 to 125. extremely difficult to duplicate with other catalyst systems. 0018. A “noncellular elastomer is essentially devoid of These organomercury catalysts provide a very desirable cur cells or other voids produced by gasses present during the ing profile in which a long open time is followed by a rapid curing step. A noncellular elastomer typically has a bulk cure. A second attribute of organomercury catalysts is that density of at least 0.9 g/cc and/or a void volume of 5% or less. they produce polyurethane elastomers that have very desir A“microcellular elastomer, for purposes of this invention, is able physical and mechanical properties. produced by conducting the curing step in the presence of a 0008. A third attribute of organomercury catalysts relates Small amount of blowing agent. A "microcellular elastomer to the appearance of the finished polyurethane product. Orga has a bulk density of at least 0.4 g/cc, and more typically has nomercury catalysts tend to produce elastomers that have a a bulk density of from 0.5 to 0.9 g/cc, and/or avoid volume of highly uniform surface appearance, even when the polyure from 5 to 60%. thane system contains large amounts of chain extender. 0019. The physical properties of elastomers produced in 0009. It is desirable to find a replacement for organomer accordance with this invention tend to approximate those that cury catalysts. Such a replacement catalyst system ideally are exhibited by otherwise like polyurethane elastomers hav would provide the attributes of organomercury catalysts, ing the same hard segment content, but which are made with including a desirable cure profile, good property development out the secondary amine compound (component b). Surpris in the product, and good surface appearance. ingly, these elastomers also exhibit a highly uniform Surface US 2013/0253084 A1 Sep. 26, 2013 appearance, with few if any transparent or translucent regions up to 4, carbon atoms. The aryland/or alkyl groups of these interspersed among opaque regions. This desirable Surface compounds may be substituted as described with respect to appearance is even seen when no organomercury catalysts are the dialkyl amines. present in the reaction system. Elastomers having good Sur 0025 Alicyclic compounds that contain one or more sec face appearance can be produced even when organozirco ondary nitrogen atoms in the ring structure are also useful. nium, organotitanate or tertiary amine catalysts are used These include, for example, piperidine, morpholine, pipera instead of organomercury catalysts. Zine and the like. The carbonatoms on the ring structure may 0020 Component a) is one or more aliphatic diols that be substituted as described before. have a hydroxyl equivalent weight of from 30 to about 100, 0026 Dialkanolamines such as diethanolamine and diiso preferably from 31 to 60. Materials of this type are commonly propanolamine are also useful component b) materials. Simi known as “chain extenders’. By “aliphatic diol, it is meant a larly, the reaction product of a diamine Such as ethylene compound having exactly two hydroxyl groups, each of diamine with about three moles of an alkylene oxide such as which is bound to an aliphatic (or cycloaliphatic) carbon ethylene oxide and/or propylene oxide per mole of diamine atom.