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
1998-08-24
2002-09-03
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...
C252S182210, C252S182220, C521S159000, C521S160000, C528S059000, C528S065000, C528S066000, C528S067000, C528S076000, C528S077000, C528S080000, C528S081000, C528S084000, C560S025000, C560S026000, C560S330000, C560S359000
Reexamination Certificate
active
06444777
ABSTRACT:
The present invention relates to a process for producing compact and preferably cellular polyurethane elastomers based on polyisocyanate mixtures containing 3,3′-dimethylbiphenyl 4,4′-diisocyanate, hereinafter also referred to in abbreviated form as PU elastomers, by reacting
a) relatively high molecular weight polyhydroxyl compounds and, if desired,
b) low molecular weight hydroxyl-containing chain extenders and/or crosslinkers with
c) 3,3′-dimethylbiphenyl 4,4′-diisocyanate and at least one additional aromatic diisocyanate selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate, 1,2-diphenylethane diisocyanate and phenylene diisocyanate, and/or at least one aliphatic diisocyanate having from 4 to 12 carbon atoms and/or at least one cycloaliphatic diisocyanate having from 6 to 18 carbon atoms, where the formative components (a), (c) and, if used, (b) are preferably reacted by the prepolymer method,
in the absence or preferably in the presence of
d) catalysts,
e) blowing agents and
f) additives,
and isocyanate prepolymers suitable for this purpose, preferably those based on diphenylmethane 4,4′-diisocyanate (MDI) and 3,3′-dimethylbiphenyl 4,4′-diisocyanate (TODI).
The microcellular PU elastomers have excellent static and dynamic properties. Owing to their specific damping characteristics and long-term use properties, they are used particularly in vibration- and shock-damping systems.
The production of compact or cellular, eg. microcellular, PU elastomers has been known for a long time from numerous patent and literature publications.
Their industrial importance is based on the combination of good mechanical properties with the advantages of low-cost processing methods. The use of various types of chemical formative components in different mixing ratios enables the production of thermoplastically processible or crosslinked, compact or cellular PU elastomers which have a wide variety of processing behaviors and mechanical properties. An overview of PU elastomers, their properties and uses is given, for example, in the Kunststoff-Handbuch, Volume 7, Polyurethane. 1st Edition, 1966, edited by Dr. R. Vieweg and Dr. A. Höchtlen, 2nd Edition, 1983, edited by Dr. G. Oertel, and 3rd edition, 1993, edited by Prof. G. W. Becker and Prof. D. Braun, Carl-Hanser-Verlag, Munich, Vienna.
In comparison with the types of rubber which can be used in a similar manner, microcellular PU elastomers have significantly better damping properties with an excellent volume compressibility, so that they are used as constituents of vibration- and shock-damping systems, particularly in the automobile industry. To produce microcellular PU elastomers, useful starting materials have been found to be the reaction products of naphthylene 1,5-diisocyanate (1,5-NDI) and poly(ethylene glycol adipate) having a molecular weight of 2,000, which are reacted in the form of an isocyanate prepolymer with an activator-containing aqueous solution of a fatty acid sulfonate. (Kunststoff-Handbuch, Volume 7, Polyurethane, 1st Edition, page 270 ff.)
Since such base formulations give microcellular PU elastomers having very good damping characteristics and static and dynamic performance parameters, the prior art has disclosed only isolated efforts to replace the 1,5-NDI, which is responsible for the good elastomer properties but is more difficult to handle because of its high melting point, by more easily handled and less costly diisocyanates, since this results in significant losses in mechanical properties. Characteristic property differences between compact PU elastomers in general and microcellular PU elastomers in particular based on 1,5-NDI, tolylene diisocyanate (TDI) and 4,4′-MDI are shown in Journal of Elastomers and Plastics, Vol. 21 (1989), pages 100 to 121. Important disadvantages of a microcellular PU elastomer based on 4,4′-MDI are given as a distinctly higher degree of damping with increased heating of the material and significantly increased consolidation on dynamic loading, which finally lead to quicker material wear in comparison with PU elastomers based on 1,5-NDI.
Despite these obvious disadvantages, attempts have been made in the production of microcellular PU elastomers to replace the 1,5-NDI by the lower-melting and lower-cost 4,4′-MDI. However, these experiments have been restricted to the use of new starting components, in particular relatively high molecular weight polyhydroxyl compounds, the use of which has improved certain mechanical properties of the microcellular PU elastomers.
EP-A-0 496 204 (U.S. Pat. No. 5,173,518) describes a process for producing cellular PU elastomers using polyether polycarbonate diols, which comprise condensed polyoxytetramethylene glycol units having a mean molecular weight of from 150 to 500, as relatively high molecular weight polyhydroxyl compounds. This improves the mechanical properties, in particular the elongation at break, even at relatively low temperatures. However, it is not possible to recognize any improvement in the static compressive set values in accordance with DIN 53 572 at 70° C. which are known to correlate with the dynamic consolidation values. Even when using 1,5-NDI as polyisocyanate, only average static compressive set values are obtained.
EP-B-0 243 832 (U.S. Pat. No. 4,798,851), which describes the use of pseudoprepolymers based on 4,4′-MDI, for example in combination with water as blowing agent, for producing elastic, compact or cellular PU or PU-polyurea moldings, teaches the use of a hydroxyl-containing polycondensate from a short-chain polyoxytetramethylene glycol and an aliphatic dicarboxylic acid as relatively high molecular weight polyhydroxyl compound, with the object of obtaining a polyhydroxyl compound containing ester groups and readily able to be metered by means of pumping for producing cellular or compact PU elastomers having improved mechanical and hydrolytic properties. Details of the permanent deformation on static or dynamic loading, by means of which vibration-resistant materials are usually characterized, are not disclosed.
DE-A-36 13 961 (U.S. Pat. No. 4,647,596) describes a microcellular PU elastomer based on 4,4′-MDI which, owing to a defined composition of the relatively high molecular weight polyhydroxyl compounds, comprising a copolymer of polytetrahydrofuran and &egr;-caprolactone, has mechanical properties which represent a useful compromise between static strength and dynamic stressability. Despite the use of expensive raw materials for producing the polyhydroxyl compounds, the gain in performance achieved thereby appears to be relatively small in terms of the test parameters “product durability, flexural strength by the De Mattia method and permanent deformation at 50% compression”. For example, the measured values for the compressive set, which are directly related to the practically important value of the dynamic consolidation, show only slight improvements when the teachings of the invention are applied.
In addition, the test criteria used, viz. “product durability and flexural strength by the De Mattia method” appear insufficiently suitable for an evaluation of the dynamic properties which is close to practice, since, especially in the case of partial property improvements, they are not able to give a satisfactory picture of the real performance differences between 4,4′-MDI-based and 1,5-NDI-based polyurethane elastomers. Thus, the example based on 1,5-NDI shows no better level of properties than the examples based on 4,4′-MDI.
Also known is the stepwise production of PU elastomers. According to DE-A-25 47 864 (U.S. Pat. No. 4,191,818), a heat-resistant PU elastomer can be produced by reacting an essentially linear relatively high molecular weight dihydroxyl compound with an excess of diisocyanate to give an adduct containing terminal hydroxyl groups and subsequently reacting this adduct with a symmetric aromatic diisocyanate in excess and alkanediols or di(alkylene glycol) terephthalates as chain ex
Bollmann Heinz
Genz Manfred
Haselhorst Walter
Hellmann Gerhard
Jeschke Torsten
BASF - Aktiengesellschaft
Borrego Fernando A.
Sergent Rabon
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