Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From heterocyclic reactant containing as ring atoms oxygen,...
Reexamination Certificate
2002-05-21
2003-11-25
Trinh, Ba K. (Department: 1625)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From heterocyclic reactant containing as ring atoms oxygen,...
C525S208000, C528S045000, C528S048000, C528S066000, C528S085000, C568S624000
Reexamination Certificate
active
06653441
ABSTRACT:
The present invention relates to polyetherols, their preparation and their use for producing polyurethanes.
Polyether alcohols are used in large quantities for producing polyurethanes. They are usually prepared by catalytic addition of lower alkylene oxides, in particular ethylene oxide and propylene oxide, onto H-functional initiator substances. As catalysts, use is usually made of basic metal hydroxides or salts, with potassium hydroxide having the greatest industrial importance.
Many industrial application areas use polyether alcohols whose polyether chains are built up of more than one alkylene oxide. In the industry, use is usually made of lower alkylene oxides such as ethylene oxide, propylene oxide and butylene oxide, with ethylene oxide and propylene oxide having the greatest industrial importance. The molecular addition can be carried out by the block method, i.e. only one alkylene oxide is added on at a time. The polyether alcohols prepared in this way have polyether chains in which segments of one alkylene oxide are arranged in sequence. A further possible way of preparing polyether alcohols from at least two alkylene oxides is the random, also known as heteric, molecular addition of the alkylene oxides. Here, the alkylene oxides are metered into the reaction mixture in the form of a mixture. These mixtures usually contain the alkylene oxides in a constant ratio to one another. This method of introduction of the alkylene oxides will hereinafter be referred to as “classical random”. The ratio referred to here is the quotient of the amounts of the alkylene oxides, with it being immaterial whether the “amount” is the weight or the molar amount, for example expressed in the unit “mol”, of the alkylene oxides.
The known processes for preparing polyether alcohols have disadvantages which become particularly apparent when using catalysts having a high catalytic activity and result in the molecular addition of the alkylene oxides proceeding at a high rate. Thus, when multimetal cyanide catalysts, also known as DMC catalysts, are used to prepare polyether alcohols by molecular addition of a plurality of alkylene oxides, quality problems in respect of the polyether alcohols frequently occur. The blockwise molecular addition of the alkylene oxides frequently results in a very high molecular weight distribution and to turbidity in the polyether alcohol, while the random procedure frequently results in a content of ethylene oxide segments at the end of the chain which is too high for many applications. The addition of terminal ethylene oxide blocks onto propoxylates or blocks of random mixtures of alkylene oxides results in the formation of very high molecular weight ethoxylates which tie up a large proportion of the ethylene oxide fed in. These polyols have viscosities which are undesirably high for processing. This has the additional consequence that the content of ethylene oxide in the polyether alcohol has to be very high in order to achieve the high contents of terminal ethylene oxide desired for reactive polyols, as a result of which the hydrophilicity of the polyethers increases greatly. Even in the cases where processing of these polyethers to give polyurethane foam is possible, this results in formation of foams which are very susceptible to hydrolysis. A further problem often results from the fact that various organic or inorganic substances such as water, glycerol and catalysts, which are customary formulation constituents in the production of polyurethanes, have to be dissolved in the polyol during processing to give the polyol component which is then used in the urethane reaction. The type of blocks, block lengths and block distributions are therefore frequently subject to tight restrictions.
WO 97/27,236 (EP 876,416) describes a polyether alcohol for use in highly elastic flexible foams, which polyether alcohol comprises a propylene oxide inner block comprising not more than 35% by weight of the total amount of alkylene oxide and one or more external blocks of ethylene oxide and propylene oxide having an ethylene oxide content of at least 2% by weight, where the inner block is catalyzed at least partly and the external blocks are catalyzed completely by means of multimetal cyanide catalysts. However, such polyether alcohols are usually substantially more reactive than commercial, base-catalyzed polyether alcohols and can thus not be readily incorporated into known polyurethane systems. In addition, the polyether alcohols prepared in this way are usually turbid.
The problems indicated are particularly apparent in the case of polyurethane foams, in particular flexible foams, and are most distinct in the case of flexible slabstock foams. In particular, crack formation in the foam and a deterioration in the mechanical properties of the foams occur.
When using multimetal cyanide catalysts, high contents of terminal primary hydroxyl groups can be achieved by means of ethylene oxide end blocks only at the price of high hydrophilicity and extremely high viscosities.
DD-A-275 695 describes a process for preparing polyether alcohols in which ethylene oxide and propylene oxide are added on as a random mixture in which the ratio of the alkylene oxides rises or falls uniformly. However, owing to the low catalytic activity of the potassium hydroxide used as catalyst, the incorporation of the alkylene oxides into the polyether chain is not in the ratio in which they are fed in, but instead is changed by backmixing with previously introduced alkylene oxide which has not yet been added on. As a result, the desired block structures can be realized to only a limited extent and the properties of the polyether alcohols prepared in this way sometimes differ little from those of the polyether alcohols prepared by means of the classical random method. Although this deficiency could be alleviated by slower metering-in, this would lead to uneconomically long batch times. The use of catalysts which are not highly active, e.g. potassium hydroxide, leads to undesirable secondary reactions during the synthesis and these cause losses of alkylene oxide and also impair the product quality. Thus, iodine numbers of less than 0.4 cannot be achieved, which indicates a still considerable level of secondary reactions. The formation of unsaturated constituents in particular leads to a loss of hydroxyl functionality, as a result of which the amount of polyetherol required in the polyurethane reaction increases. In addition, formation of colored or odor-imparting by-products adversely affects the quality of the polyetherols prepared in this way.
In addition, the starting point and the end point of the metered introduction of alkylene oxides described in DD-A-275 695 has to be a pure alkylene oxide in each case. As a result, the random blocks described in DD-A-275 695 cannot always be advantageously combined with classical random blocks. Thus, polyols having intermediate contents of primary hydroxyl groups cannot be obtained. Furthermore, polyether alcohols which have been prepared by this procedure and commence with ethylene oxide always contain chain sections consisting of pure ethylene oxide. These lead to an undesirably high susceptibility to hydrolysis, to high viscosities and to susceptibility to turbidity of the polyether. If these random polyethers end with ethylene oxide, the backmixing effects become undesirably noticeable, so that some propylene oxide is always to be found at the end of the chain.
It is an object of the present invention to provide polyether alcohols which can be prepared by catalytic addition of at least two alkylene oxides onto H-functional initiator substances, which have no turbidity, which have viscosities favorable for processing and which can be processed without problems to give polyurethanes, in particular flexible polyurethane foams. In addition, the content of alkylene oxides at the end of the polyether chain should be able to be adjusted in a targeted way. High molecular weight tails, as occur in the molecular addition of alkylene oxides by a customary block procedur
Bauer Stephan
Grosch Georg Heinrich
Harre Kathrin
Höppner Gerd
Lorenz Reinhard
BASF - Aktiengesellschaft
Borrego Fernando A.
Trinh Ba K.
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