Method for producing compounds with terminal OH groups

Details Method for producing compounds with terminal OH groups Method for producing compounds with terminal OH groups

2001-05-04

2003-05-20

Barts, Samuel (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C560S190000, C560S198000, C560S202000, C568S617000, C568S618000, C568S619000

Reexamination Certificate

active

06566563

ABSTRACT:

This application is a 371 of PCT/EP99/04351, filed Jun. 23, 1999.
BACKGROUND OF THE INVENTION
This invention relates to a process for the production of OH-terminated compounds in which CH
2
OH-terminated diols are reacted with dimethyl carbonate in the presence of a catalyst, the methanol released is continuously distilled off and the catalyst used is then deactivated. Through the choice of special process and material parameters, the products formed are eminently suitable for the production of linear polyurethanes by virtue of their property profile.
Polyurethanes (PURs) are a very broad group of polymers differing widely in their composition and in their property profiles. One feature common to all polyurethanes is the principle on which they are synthesized, i.e. they are produced by the diisocyanate polyaddition process. These compounds are all characterized by urethane groups —NH—CO—O— which are formed by polyaddition of hydroxy compounds, generally diols or polyols, onto the —NCO groups of difunctional or polyfunctional isocyanates. In most cases, the urethane group links polyalkylene ether and/or polyester sequences which have molecular weights of about 200 to 6,000. Polyurethanes are commercially available, for example, as foams, thermoplastic granules, solutions, aqueous dispersions and in the form of prepolymers.
The following products, for example, are produced from polyurethanes: highly elastic foams (mattresses, cushions, auto seats), rigid foams (insulating materials), rigid and flexible moldings with a compact outer skin (window frames, housings, skis, auto fenders, hood and trunk parts, steering wheels, shoe soles), industrial moldings combining high elasticity and rigidity, ski boots, films, blow moldings, auto fenders, printing rolls, paints, adhesives, textile coatings, high-gloss paper coatings, leather finishes, elastomer filaments, wool finishes, etc. The number and scope of applications is constantly increasing. Numerous reference books and articles are available on the production, properties, technology and applications of polyurethanes, cf. for example Gerhard W. Becker (Ed.), “Kunststoff-Handbuch—7. Polyurethane” 3rd Edition 1993, pages 455-467 and 508 and 510-512.
So-called linear polyurethanes have recently assumed particular significance. Compounds belonging to this group can be obtained by reacting CH
2
OH-terminated diols with diisocyanates to form substantially linear polyurethanes. Among the most attractive CH
2
OH-terminated compounds used for the production of linear polyurethanes are polycarbonate copolyether diols and/or polycarbonate copolyester diols. These are compounds which are normally obtained by reacting such compounds as phosgene, diphenyl carbonate, dimethyl carbonate and the like with diols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, hexane-1,6-diol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, polytetrahydrofuran and the like or ethylene oxide or propylene oxide adducts thereof.
U.S. Pat. No. 4,463,141 relates to polyether carbonate diols which can be obtained by linking structural units of poly(tetramethylene-ether)glycol with a dialkyl carbonate, a cyclic carbonate or phosgene. So far as the use of dialkyl carbonates as a structural unit in the synthesis of the required diol is concerned, it is stated that dimethyl and diethyl carbonate are preferred. The reactions are carried out in the presence of typical transesterification catalysts, preferably tetrabutyl titanate. So far as the reaction parameters are concerned, it is stated that the reaction is normally carried out at temperatures of 120 to 240° C. and at atmospheric pressure. More particularly, the carbonate is slowly added to the glycol used as starting material over a period of 5 to 20 hours. According to the teaching of U.S. Pat. No. 4,463,141, the alcohol formed as secondary product during the reaction can be removed either by evaporation or by purging the reaction zone with nitrogen. According to the teaching of U.S. Pat. No. 4,463,141, the diol to be produced is adjusted to the required molecular weight by continuously removing samples from the reaction zone during the reaction and analyzing them and deactivating the catalyst by standard methods, more particularly by addition of phosphoric acid, at the time the required molecular weight is reached. The best embodiment disclosed in U.S. Pat. No. 4,463,141 is in Example 1 which describes the reaction of a polytetrahydrofuran having a molecular weight of 650 with diethyl carbonate in the presence of tetrabutyl titanate. The mixture is heated at a temperature of 210 to 240° C. (the values are based on atmospheric pressure) and the ethanol formed during the reaction is removed by distillation. On completion of the reaction, the catalyst is deactivated by addition of 85% phosphoric acid.
European patent application EP-A-335 416 relates to modified polyoxytetramethylene glycols with a low melting point and high resistance levels and to a process for their production. This application relates in particular to modified polyoxytetramethylene glycols which have a main chain with recurring structural elements, the structural elements in question being on the one hand a polyoxytetramethylene group with the formula —[O(CH
2
)
4
]
n
—, where n is a number of 3 to 28, and a dioxycarbonyl group, the first structural element mentioned making up from 75.5 to 99.3 mole-% and the second structural element making up from 24.5 to 0.7 mole-%.
European patent application EP-A-442 402 relates to polyether polycarbonate diols essentially made up of
(a) 3 to 63.7 mole-% of units derived from polyoxytetramethylene diol,
(b) 63.7 to 3 mole-% of units which are derived from a polyoxyalkylene diol different from a) and which contain C
2-8
alkylene groups, an aliphatic alkanediol containing 2 to 14 carbon atoms, an alicyclic alkanediol containing 3 to 14 carbon atoms or an alkylene oxide containing 2 or 3 carbon atoms or mixtures thereof and
(c) 33.3 to 50 mole-% of units derived from phosgene, a dialkyl carbonate containing C
2-4
alkyl groups, a cyclic carbonate containing C
2-4
alkylene groups or mixtures thereof.
European patent application EP-A-798 327 relates to a two-stage process for the production of polycarbonate copolyether diols. The process is essentially carried out as follows: in a first stage, one or more diols (polyether glycols, PEGs) is/are reacted with dimethyl carbonate at temperatures of 90 to 120° C. in the presence of a basic catalyst selected from the group consisting of oxides, hydroxides, carbonates or alcoholates of an alkali metal or alkaline earth metal (for example sodium methylate). The molar ratio of dimethyl carbonate to PEG selected for the reaction is between 2 and 12:1, i.e. dimethyl carbonate is used in excess. In a second stage, the intermediate product obtained—after the catalyst used in the first stage and the excess dimethyl carbonate used have been removed—is converted into the end product by reaction with the required polyether glycol at 140 to 185° C./atmospheric pressure in the presence of a solvent and an organometallic catalyst which is selected from tin, lead, titanium, zirconium and antimony compounds and which is used in concentrations of 0.0001 to 0.001% by weight. This second reaction step is a typical transesterification reaction in which the terminal methoxy groups of the intermediate product are replaced by terminal PEG groups.
According to page 5, lines 43-44 of EP-A-798 327, the catalyst used in the second stage is neutralized. This is done either by hydrothermal treatment or by using a reagent which is capable of binding the metal ions of the catalyst. In the second case, it is specifically stated in lines 48 to 50 that organic acids or mineral acids, such as phosphoric acid or polyphosphoric acid, are particularly suitable. However, there is no reference in EP-A-798 327 to any particular form of presentation or supply of the acid used to deactivate the catalyst.
EP-A-798 328 describes a process for the productio

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