Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1999-04-22
2001-02-06
O'Sullivan, Peter (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C521S170000, C521S172000, C524S195000, C528S080000, C528S083000, C528S084000, C528S272000, C560S025000, C560S027000, C560S084000, C564S056000, C564S252000
Reexamination Certificate
active
06184410
ABSTRACT:
The present invention relates to carbodiimides based on 1,3-bis(1-methyl-1-isocyanatoethyl)benzene containing from 12 to 40% by weight of ethylene oxide units [—CH
2
—CH
2
—O—], based on the weight of the carbodiimides.
The invention further relates to processes for preparing these carbodiimides and mixtures comprising these carbodiimides and compounds which contain ester structures, preferably polyurethanes containing ester structures.
Organic carbodiimides are known and are used, for example, as stabilizers against hydrolytic degradation of compounds containing ester groups, for example polyaddition and polycondensation products such as polyurethanes. Carbodiimides can be prepared by generally known methods, for example by action of catalysts on monoisocyanates or polyisocyanates with elimination of carbon dioxide. Suitable catalysts are, for example, heterocyclic compounds containing bound phosphorus, e.g. phospholines, phospholenes and phospholidines and also their oxides and sulfides and/or metal carbonyls.
Such carbodiimides, their preparation and use as stabilizers against hydrolytic dissociation of plastics based on polyesters are described, for example, in DE-A 4 318 979, DE-A 4 442 724 and EP-A 460 481.
Particularly for preparing elastomers based on polyurethanes, for example cellular or microcellular polyurethane elastomers, it has been found to be advantageous to mix the carbodiimides as stabilizers into the component comprising water as crosslinker and blowing agent in order to avoid a reaction of acid groups with the carbodiimides.
It is precisely the miscibility of known carbodiimides and thus their incorporation into such an aqueous system which is generally difficult owing to the low solubility.
DE-A 4 318 979 describes the use of 1,3-bis(1-methyl-1-isocyanatoethyl)benzene for preparing carbodiimides and/or oligomeric polycarbodiimides containing terminal isocyanate, urea and/or urethane groups. The terminal isocyanate groups of the carbodiimides described in this document are reacted with customary isocyanate-reactive compounds. Although the carbodiimides described in the examples have, owing to the reaction with polyoxyethylene glycols, a sufficient hydrophilic character due to the very high proportions of ethylene oxide units and are readily miscible with aqueous components, polyurethane elastomers which have been prepared using these carbodiimides display poorer mechanical properties than elastomers which have been prepared without stabilizer. Possible ways of improving these carbodiimides result from the influence of the stabilizers on the dynamic and mechanical properties of, in particular, foamed polyurethane elastomers.
It is an object of the present invention to develop carbodiimides as stabilizers against hydrolytic dissociation of plastics based on polyesters, which carbodiimides can be optimally incorporated into the starting components of the plastics or into the plastics themselves and, in addition, do not have an adverse effect on the dynamic and static properties of the plastics, in particular polyurethane elastomers.
We have found that this object is achieved by carbodiimides based on 1,3-bis(1-methyl-1-isocyanatoethyl)benzene and containing from 12 to 40% by weight, preferably from 15 to 35% by weight, of ethylene oxide units [—CH
2
—CH
2
—O—], based on the weight of the carbodiimides.
The preparation of the carbodiimides of the present invention is essentially carried out by means of two reaction steps. On the one hand, (1) carbodiimide structures are generated by the generally known reaction of isocyanate groups with one another to eliminate carbon dioxide in the presence of customary catalysts which are known for this reaction and have been described at the outset, on the other hand, (2) isocyanate groups are reacted with compounds which are reactive toward isocyanates to form urethane and/or urea structures. The order of these two essential process steps (1) and (2) can be as desired, as long as free isocyanate groups are available for the respective reaction.
For example, the carbodiimides of the invention can be obtained by reacting 1,3-bis(1-methyl-1-isocyanatoethyl)benzene in the presence of catalysts with elimination of carbon dioxide to form carbodiimides and subsequently reacting the carbodiimide containing isocyanate groups with at least one compound (i) which is reactive toward isocyanates and comprises ethylene oxide units [—CH
2
—CH
2
—O—]. The molar ratio of the NCO groups of the carbodiimide containing isocyanate groups to the groups which are reactive toward isocyanates is usually from 10:1 to 0.2:1, preferably from 5:1 to 0.5:1, particularly preferably from 1:1 to 0.5:1, in particular 1:1.
As an alternative, the carbodiimides of the present invention can be obtained by reacting 1,3-bis(1-methyl-1-isocyanatoethyl)-benzene with at least one compound (i) comprising ethylene oxide units [—CH
2
—CH
2
—O—], where the ratio of isocyanate groups used to groups which are reactive toward isocyanates is at least 2:1, and subsequently reacting the reaction product containing isocyanate groups in the presence of catalysts with elimination of carbon dioxide to form carbodiimides.
In this process variant, up to 50% by weight, preferably up to 23% by weight, of the isocyanate groups of the diisocyanate are first reacted with the compounds which are reactive toward isocyanates and the free isocyanate groups are then completely or partially condensed in the presence of catalysts with elimination of carbon dioxide to form carbodiimides and/or oligomeric polycarbodiimides.
Preferably, the reaction to form the carbodiimides is carried out first and the carbodiimide containing isocyanate groups is subsequently reacted with the compounds which are reactive toward isocyanates.
The ethylene oxide units in the carbodiimides are introduced into the carbodiimides via the compounds (i) which are reactive toward isocyanates. For this reason, the isocyanate-reactive compounds (i) which are used according to the present invention in the preparation of the carbodiimides of the present invention are those which contain ethylene oxide units, preferably at least 5 and particularly preferably from 6 to 200 ethylene oxide units, and usually have a number average molecular weight of from 200 to 10,000 g/mol. The ethylene oxide units, which can be represented by the following structure [—CH
2
—CH
2
—O—], can be arranged blockwise or distributed in the compound (i). These isocyanate-reactive compounds (i) according to the invention can be prepared, for example, by the generally customary alkoxylation of hydrogen-active initiator substances, for example water, monools, diols, triols, monoamines, diamines and/or triamines usually having molecular weights of from 18 to 500 g/mol, usually in the presence of generally known catalysts, for example alkali metal hydroxides or alkoxides, using alkylene oxides, for example ethylene oxide, propylene oxide and/or butylene oxide, preference being given, according to the present invention, to using ethylene oxide, if desired in admixture with at least one further alkylene oxide. As a result of this method of preparation, for example, these compounds (i) which are reactive toward isocyanates have hydroxyl groups as reactive groups which react with the isocyanates.
These isocyanate-reactive compounds (i) according to the present invention can, if desired, be used in admixture with further compounds (ii) which are reactive toward isocyanates and have less than 5 or no ethylene oxide units in the preparation of the carbodiimides of the present invention. Possible additional compounds which are reactive toward isocyanates are, for example, compounds which bear at least one, usually from 1 to 3, reactive group(s); suitable reactive groups are, for example, hydroxyl, thiol, primary amino and/or secondary amino groups. These substances which may be used in addition to the isocyanate-reactive compounds (i) according to the present invention usually have molecular weights of from 32 to 5
Bollmann Heinz
Haberle Karl
Kokel Nicolas
Thärigen Raina
B orrego Fernando A.
BASF - Aktiengesellschaft
O'Sullivan Peter
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