Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1998-05-07
2002-06-25
Kilkos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S157000, C560S158000, C560S315000
Reexamination Certificate
active
06410778
ABSTRACT:
The present invention relates to a process for preparing organic diurethanes and/or polyurethanes, preferably aliphatic or cycloaliphatic diurethanes, by reacting the corresponding organic diamines and/or polyamines (a) with urea and/or alkyl carbamates (b) and alcohols (c) in the presence of soluble zirconium compounds such as zirconium alkoxides, zirconium acetate or zirconium acetylacetonate, as catalyst (d).
The present invention also relates to the use of diurethanes and/or polyurethanes prepared by the process of the present invention for preparing organic diisocyanates and/or polyisocyanates by thermal dissociation.
Organic polyisocyanates, such as aromatic, aliphatic or cycloaliphatic polyisocyanates, are valuable starting materials for producing polyisocyanate polyaddition products, for example polyurethane (PU) foams, surface coatings, dispersions, adhesives, polyisocyanurate (PIR) foams, thermoplastic PU elastomers (TPU) and compact or cellular PU- or PU-polyurea elastomers.
The industrial processes for preparing organic polyisocyanates are based on reaction of the corresponding organic polyamines with phosgene to give polycarbamic chlorides and thermal dissociation of the latter to give the polyisocyanates and hydrogen chloride and the thermal dissociation of monomeric diurethanes and/or polyurethanes into diisocyanates and/or polyisocyanates and alcohol.
Problems in the process using phosgene are, in particular, the high conversion of chlorine via phosgene and carbamic chloride into hydrogen chloride, the toxicity of the phosgene and the corrosiveness of the reaction mixture, the lability of the solvents generally used and the formation of halogen-containing residues.
There have therefore been many attempts to prepare organic isocyanates, preferably aromatic and (cyclo)aliphatic diisocyanates and/or higher-functional polyisocyanates, by a phosgene-free process.
According to EP-A-28 338 (U.S. Pat. No. 4,290,970) aromatic diisocyanates and/or polyisocyanates are prepared by a two-stage process in which, in the first reaction stage, primary aromatic diamines and/or polyamines are reacted with alkyl carbamates in the absence or presence of catalysts and the absence or presence of urea and alcohol to give aryl diurethanes and/or polyurethanes and the ammonia thus formed is, if desired, separated off, and the aryl diurethanes and/or polyurethanes obtained are converted in the second reaction stage into aromatic diisocyanates and/or polyisocyanates by thermal dissociation
Continuous, multistage processes for the phosgene-free preparation of organic polyisocyanates are likewise known.
EP-A-0 355 443 (U.S. Pat. No. 5,087,739) relates to a circulation process for preparing (cyclo)aliphatic diisocyanates by conversion of the corresponding diamines into diurethanes and thermal dissociation of the latter, which reduces decreases in yield by the reaction mixture from the urethane dissociation stage being recirculated to the urethane formation stage after reaction with alcohol. By-products which cannot be recirculated are removed by distillative fractionation of the reaction mixture from the urethane formation stage; in this fractionation the unusable residue is obtained as bottom product and all lower-boiling components, including the diurethane, are taken off at the top.
EP-A-0 568 782 (U.S. Pat. No. 5,360,931) describes a multistage process for the continuous phosgene-free preparation of (cyclo)aliphatic diisocyanates, comprising the conversion of (cyclo)aliphatic diamines in a distillation reactor into the corresponding (cyclo)alkylenebisureas, their reaction with alcohol in a pressure distillation reactor to give the (cyclo)alkylene biscarbamates and the thermal dissociation of the latter in a combined dissociaton and rectification column to give the (cyclo)alkylene diisocyanates and alcohol in a liquid phase without use of solvents.
According to EP-A-0 566 925 (U.S. Pat. No. 5,386,053), a multistage process for preparing organic polyisocyanates comprises converting the organic polyamines into monomeric polyurethanes using carbonic acid derivatives and alcohols and thermally dissociating the monomeric polyurethanes. In certain reaction stages of this process, the polyisocyanates prepared and unusable residues are separated off and the reusable by-products are recirculated to earlier stages.
The economics of the continuous phosgene-free processes for preparing organic polyisocyanates is decisively influenced by the purity of the organic monomeric diurethanes and/or higher polyurethanes used for the thermal dissociation and the undesired secondary reactions, partly resulting from impurities and by-products, and the tendency of the reaction mixture to form deposits, of resinous material and blockages in reactors and work-up apparatus.
Organic monomeric diurethanes and/or higher polyurethanes can be prepared by reacting organic polyamines with carbonic acid derivatives, preferably urea and/or alkyl carbamates, and alcohols in the absence or presence of catalysts.
According to EP-B-0 018 586 (U.S. Pat. No. 4,713,476 and U.S. Pat. No. 4,851,565) aliphatic and/or cycloaliphatic diurethanes and/or polyurethanes can be prepared by reacting the corresponding polyamines with urea and alcohols in the presence of catalysts. In a similar manner, according to EP-B-0 019 109 (U.S. Pat. No. 4,611,079), aromatic diurethanes and/or polyurethanes can be obtained using aromatic polyamines. Suitable catalysts mentioned are inorganic or organic compounds containing one or more cations of metals of groups IA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIB, VIIB and VIIIB of the Periodic Table, eg. halides, sulfates, phosphates, nitrates, borates, alkoxides, phenoxides, sulfonates, oxides, hydrated oxides, hydroxides, carboxylates, chelates, carbonates and thio- or dithiocarbamates. Aryl mono-, di- and/or polyurethanes can, according to EP-B-0 018 538 (U.S. Pat. No. 4,278,805 and U.S. Pat. No. 4,375,000), be prepared by reacting corresponding primary aromatic monoamines or polyamines with alkyl carbamates in the presence of the abovementioned catalysts.
N,O-disubstituted urethanes can, according to EP-A-0 028 331 (U.S. Pat. No. 4,480,110), be prepared by reacting mixtures of substituted ureas and N-unsubstituted urethanes and/or urea and/or polyurets with alcohols in the presence of esterification catalysts for carboxylic acids. According to EP-B-0 027 940 (CA-A-1 144 562), urethanes can be prepared by reacting urea or polyurets with primary amines and alcohols in the presence of compounds which exercise a catalytic influence on the esterification reaction of carboxylic acids with alcohols and which also have an accelerating action on the urethane reaction. Suitable catalysts mentioned are: inorganic and organic bases which are inert under the reaction conditions, Lewis acids and salts or complexes, in particular chelates of transition metals. Among numerous catalysts which can be used, mention is also made, by way of example, of coordination compounds of iron, nickel, cobalt, zinc, manganese, molybdenum, titanium, zirconium, thorium, hafnium and vanadium with &bgr;-diketones, eg. acetylacetone and &bgr;-ketoesters. The best catalytic activity was shown by zinc octoate with a conversion of 97 mol %, while iron acetylacetonate with 90 mol % gave a comparatively low catalytic effect, particularly for industrial-scale processes.
To ensure sufficient quality of the organic diurethanes and/or higher polyurethanes for a thermal dissociation to give organic polyisocyanates, it is desirable to have preparative processes for polyurethanes which ensure both a high space-time yield and a high selectivity, eg. of ≧98 mol % of polyurethane, based on the organic polyamine used.
Partially reacted intermediates containing urea groups cause considerable interference in the urethane dissociation to give the polyisocyanate and can be separated from the polyurethane formed only with difficulty.
It is an object of the present invention to prepare diurethanes and/or higher polyurethanes in very high space-time yiel
Laqua Gerhard
Otterbach Andreas
Schoner Ulrich
Schwarz Hans Volkmar
BASF - Aktiengesellschaft
Borrego Fernando
Kilkos Paul J.
Oh Taylor V.
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