Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-12-14
2004-05-18
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C521S128000, C521S129000, C521S130000, C521S159000, C521S172000, C521S173000, C521S174000, C524S284000, C524S300000, C524S306000, C524S314000, C524S315000, C528S048000, C528S049000, C528S052000, C528S053000, C528S059000, C528S060000, C528S065000, C528S066000, C528S076000, C528S080000
Reexamination Certificate
active
06737471
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to solid and/or cellular polyurethane elastomers (PUR elastomers) which are produced using polyester polyols and which exhibit improved stability to hydrolysis, and to methods for the production thereof.
SUMMARY OF THE INVENTION
A solid and/or cellular polyurethane elastomers which are produced using polyester polyols are disclosed. The elastomers which exhibit improved stability to hydrolysis are characterized in that their preparation is carried out in the presence of at least one esters of monobasic carboxylic acid or polybasic carboxylic acids, the (first) dissociation constant (pK) of which is 0.5 to 4.
BACKGROUND OF THE INVENTION
Semi-rigid, elastic polyurethane moldings in solid or cellular form, i.e. in slightly foamed form, are often synthesized based on polyester-polyurethane materials. In order to improve the durability of these material in humid environments, i.e. under conditions which give rise to hydrolysis, EP-A 982 336 teaches that acids or acid derivatives should be admixed with the isocyanate component in order to effect blocking, by protonation, of the amines and of the amine catalysts which are possibly contained therein, which are released due to the hydrolysis of the polyisocyanate polyaddition product, and thus to prevent any further cleavage of the urethane bond. For this purpose, the acids or acid derivatives are used in a molar excess in relation to the amines contained in the mixture. DE-OS 198 38 167 proposes the use of acid anhydrides for the same purpose.
It has now been found that polyester-polyurethanes which are particularly stable to hydrolysis are obtained if esters of mono- or polybasic carboxylic acids, the (first) dissociation constant of which has a pK value of 0.5 to 4, are added in substoichiometric amounts to the polyurethane formulation.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to polyurethane elastomers prepared by reacting
a) di- and/or polyiisocyanates with
b) at least one polyester polyol with an OH number of 20 to 280, preferably 28 to 150, and a functionality of 1 to 3, preferably 1.8 to 2.4, and optionally with
c) other polyether polyols or polyether ester polyols with OH numbers of 10 to 149 and functionalities of 2 to 8, and optionally with
d) low molecular weight chain extenders and/or crosslinking agents with OH numbers of 150 to 1870,
in the presence of
e) amine catalysts,
f) esters of mono- or polybasic carboxylic acids, the (first) dissociation constant (pK) of which is 0.5 to 4, preferably of 1 to 3, and optionally of
g) foaming agents, and optionally of
h) additives, wherein the maximum ratio of the number of ester groups in component f) to the number of amino groups in component e) is 1.0, preferably 0.5 to 0.8.
The PUR elastomers are preferably produced by the prepolymer method, wherein in the first step a polyaddition product which contains isocyanate groups is advantageously produced from at least part of the polyester polyol b) or from a mixture thereof with polyol component c) and at least one di- or polyisocyanate a). In the second step, solid PUR elastomers are produced by reacting the product obtained in the first step with low molecular weight chain extenders and/or crosslinking agents d) and/or with the remaining part of polyol components b) or c) or a mixture thereof. If water or other foaming agents, or mixtures thereof, are used in conjunction in the second step, microcellular PUR elastomers may be produced.
Suitable starting components a) for the method according to the invention are aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates. These are described, for example, by of W. Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136; for example those of formula
Q(NCO)
n
wherein n=24, preferably 2, and Q denotes a aliphatic hydrocarbon radical containing 2-18, preferably 6-10 C atoms, a cycloaliphatic hydrocarbon radical containing 4-15, preferably 5-10 C atoms, an aromatic hydrocarbon radical containing 6-15, preferably 6-13 C atoms, or an araliphatic hydrocarbon radical containing 8-15, preferably 8-13 C atoms, e.g. ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane 1,3- and -1,4-diisocyanates and any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 2,4- and 2,6-hexahydrotoluene diisocyanates and any mixtures of these isomers, hexahydro-1,3-and 1,4-phenylene diisocyanate, perhydro-2,4- and 4,4′-diphenylmethane diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 1,4-durol diisocyanate (DDI), 4,4′-stilbene diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI), toluene 2,4- and 2,6-diisocyanates (TDI), and any mixtures of these isomers, diphenylmethane-2,4′- and/or -4,4′-diisocyanate (MDI), or naphthylene-1,5-iisocyanate (NDI).
Examples of other suitable isocyanates include triphenylmethane 4,4′,4″-triisocyanate, polyphenyl-polymethylene polyisocyanates such as those which are obtained by aniline-formaldehyde condensation and subsequent phosgenation and which are described in GB-PS 874 430 and GB-PS 848 671 for example, m- and p-isocyanatophenylsulphonyl isocyanates according to U.S. Pat. No. 3,454,606, perchlorinated aryl polyisocyanates such as those described in U.S. Pat. No. 3,277,138, polyisocyanates which contain carbodiimide groups such as those described in U.S. Pat. No. 3,152,162 and in DE-OS 25 04 400, 25 37 685 and 25 52 350, norbornane diisocyanates according to U.S. Pat. No. 3,492,301, polyisocyanates comprising allophanate groups such as those described in GB-PS 994 890, BE-PS 761 626 and NL-A 7 102 524, polyisocyanates comprising isocyanurate groups such as those described in U.S. Pat. No. 3,001,9731, in DE-PS 10 22 789, 12 22 067 and 1 027 394 and in DE-OS 1 929 034 and 2 004 048, polyisocyanates comprising urethane groups such as those described in BE-PS 752 261 or in U.S. Pat. Nos. 3,394,164 and 3,644,457, polyisocyanates comprising acylated urea groups according to DE-PS 1 230 778, polyisocyanates comprising biuret groups such as those described in U.S. Pat. Nos. 3,124,605, 3,201,372 and 3,124,605 and in GB-PS 889 050, polyisocyanates produced by telomerisation reactions such as those described in U.S. Pat. No. 3,654,106, polyisocyanates comprising ester groups such as those cited in GB-PS 965 474 and 1 072 956, in U.S. Pat. No. 3,567,763 and in DE-PS 12 31 688, reaction products of the aforementioned isocyanates with acetals according to DE-PS 1 072 385, and polymeric polyisocyanates containing fatty acid esters according to U.S. Pat. No. 3,455,883, all of which are incorporated herein by reference.
It is also possible to use distillation residues which result from the industrial production of isocyanates and which are optionally dissolved in one or more of the aforementioned polyisocyanates. Moreover, it is possible to use any mixtures of the aforementioned polyisocyanates.
The polyisocyanates which are preferably used are those which are readily obtainable industrially, e.g. 2,4- and 2,6-toluene diisocyanate and any mixtures of these isomers (“TDI”), 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate and polyphenyl-polymethylene polyisocyanates, such as those which are produced by aniline-formaldehyde condensation and subsequent phosgenation (“crude MDI”) and polyisocyanates which comprise carbodiimide groups, uretonimine groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups (“modified polyisocyanates”), particularly those modified polyisocyanates which are derived from toluene 2,4- and/or 2,6-diisocyanate or from 4,4′- and/or 2,4′-diphenylmethane diisocyanate. Naphthylene 1,5-diisocyanate and mixtures of the aforementioned polyisocyanates are also quite suitable.
The prepolymers which are most preferably used in the method acco
Eckhardt Alexander
Lorenz Klaus
Michels Erhard
Schütze Marc
Bayer Aktiengesellschaft
Franks James R.
Gil Joseph C.
Preis Aron
Sergent Rabon
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