GB2102822A - Polymer-modified polyols - Google Patents

Abstract

A polymer-modified polyol comprises a polyol and the reaction product of a polyisocyanate and a trialkanolamine, the trialkanolamine being obtained by treating a mixture of alkanolamines containing a trialkanolamine and a minor proportion of a dialkanolamine or monoalkanolamine or both with an alkylene oxide and the treatment being continued until the mono-, di- or combined mono- and dialkanolamine content, expressed as dialkanolamine, is less than 5% by weight of the treated mixture. The polyol is preferably a polyoxyalkylene polyol. The resulting dispersions of polymer- modified polyol can be used for preparing highly resilient flexible polyurethane foams for cushioning applications.

Description

SPECIFICATION Polymer-modified polyols This specification describes an invention which relates to polymer-modified polyols useful in polyurethane manufacture.

According to one aspect of the invention there is provided a polymer-modified polyol comprising a polyol and the reaction product of a polyisocyanate and a trialkanolamine, the trialkanolamine being obtained by treating a mixture of alkanolamines containing a trialkanolamine and a minor proportion of a dialkanolamine or monoalkanolamine or both with an alkylene oxide and the treatment being continued until the mono-, di- or combined monoand dialkanolamine content, expressed as dialkanolamine is less than 5%, preferably 2% or less, by weight of the treated mixture.

Other aspects of the invention include a method of forming the polymer-modified polyol, its use in the manufacture of polyurethane products, especially polyurethane foam, and the polyurethane products so obtained.

By the term "polymer-modified polyol" is meant a polyol containing additional polymeric material.

Such polymer-modified polyols are described in, for example, British Patent 1453258. These are dispersions of polyureas and polyhydrazo-dicarbonamides with primary and secondary amines hydrazines or hydrazides in polyethers. The polymer-modified polyol of the present invention is generally a dispersion but may be a solution of a poly-addition product of a polyisocyanate and a trialkanolamine, as hereinbefore defined, in a polyol.

The polyol used in the invention may be any of the polyols used in the manufacture of polyurethanes or mixtures thereof. These polyols contain two or more hydroxyl groups. They are well known to polyurethane technologists and are documented in the relevant literature. Normally the polyol will be a polymeric polyol such as a polyether, polythioether, polyester, polyesteramide, polyacetal or polycarbonate or a mixture thereof. Of particular interest, however, are polyether polyols having a molecular weight of from 200 to 10,000 such as are described in British Patent No. 1482213. Suitably they are polyoxyalkylene polyols obtained by reacting an alkylene oxide or mixture of alkylene oxides with an active hydrogen-containing initiator.Ethylene oxide-tipped polyoxypropylene polyols are especially useful for the manufacture of high resilience flexible polyurethane foams. Other poly(oxypropyleneoxyethylene)polyols in the form of random or block copolymers are also useful.

Any suitable organic polyisocyanate, i.e. an organic isocyanate having two or more isocyanate groups, may be used in the invention including aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates. Such isocyanates are well known to polyurethane technologists are documented in the relevant literature (see, for example, British Patent No. 1453258). Of particular interest are the aromatic polyisocyanates, for example tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) which are commercially available in substantially pure and crude forms.More particularly these include 2,4 and 2,6-tolylene diisocyanates and mixtures thereof; diphenylmethane-2,4'- and -4,4'-diisocyanates and mixtures thereof (generally referred to as pure MDI), for example, a mixture containing from 70 to 100%, especially 80% by weight, of the 4,4'-isomer and from 0 to 30%, especially 20% by weight, of the 2,4'-isomer; mixtures of MDI with polyphenyl polymethane polyisocyanates made by phosgenating a mixture of polyamines which is obtained by condensing aniline with formaldehyde (generally referred to as crude or polymeric MDI); and mixtures of TDI and MDI, pure or crude, for example, a mixture containing 60% by weight of TDI and 40% by weight MDI. There may also be used diisocyanates which have been modified in known manner to introduce a significant isocyanurate, carbodiimide, uretonimine, buiret or allophanate content.Other polyisocyanates which may be used include isocyanate-ended prepolymers, for example, reaction products of a diisocyanate with a deficiency of one or more lower moelcular weight polyols such as trimethylolpropane, dipropylene glycol ortripropyleneglycol.

The trialkanolamine used in the invention and its method of manufacture are described in British Patent No. 1140867. It is obtained by treating a mixture of alkanolamines, particularly a commercial grade of triethanolamine which contains 83 to 85% by weight of triethanolamine, about 15% by weight of diethanolamine and 1 to 2% of monoethanolamine, with an alkylene oxide, for example, ethylene oxide, propylene oxide, a butylene oxide and epichlorohydrin, in an amount approximately stoichiometrically equivalent to the amount of mono- and dialkanolamines present or by a suitable excess. The treatment is continued until the mono-, di- or combined mono- and dialkanolamines content, expressed as dialkanolamine for analytical convenience, is less than 5%, preferably 2% or less by weight of the treated mixture.

The conditions of treatment may be those generally employed for the reaction of alkylene oxide with primary or secondary amines. Thus, for example, temperatures of from 50 to 150 C, preferably from 90 to 120"C, and pressures of up to 5.5 bar gauge may conveniently be employed. In the case where a commerial grade of triethanolamine is treated with an alkylene oxide, such as ethylene or porpylene oxide, it is suitale to continue treatment until the product has an equivalent weight of from 150 to 180, preferably from 150 to 165.

According to another aspect of the invention there is provided a method of forming a polymer-modified polyol in which a polyisocyanate is reacted with a trialkanolamine in the presence of a polyol, the trialkanolamine being obtained by treating a mixture of alkanolaines containing a trialkanolamine and a minor proportion of a dialkanolamine or monoalkanolamine or both with an alkylene oxide and the treatment being continued until the mono-. di- or combined mono- and dialkanolamine content, expressed as dialkanolamine, is less than 5%, preferably 2% or less, by weight of the treated mixture.

In carrying out the method of the invention, the polyisocyanate and trialkanolamine are mixed together in a molar ratio of about 0.5:1.0 to 1.5:1, preferably 0.8:1.0 to 1.1 :1.0 and especially 1.0:1.0, in the presence of the polyol. The molecular weight and viscosity of the poly-addition product so formed may be varied by adjusting the ratio of polyisocyanate and trialkanolamine. Generally, the higher the proportion of polyisocyanate used, the higher is the molecular weight and viscosity of the product.

The molecular weight of the poly-addition product may be varied by introducing monofunctionally reactive compounds to act as chain terminators.

Such compounds are described in British Patent No.

1453258 and include monofunctional isocyanates, amines and N-dialkylalkanolamines. They may usefully be used in amounts of up to 25 mol % of the trialkanolamine.

The reaction may be catalysed by a catalyst of the type and in an amount conventionally used for the formation of polyurethanes, for example, an organemetallic compound such as stannous octoate and dibutyl tin dilaurate or an amine such as triethylene diamine.

The concentration of the poly-addition product in the polyol may vary within wide limits but for most purposes it will be between 1 and 35% by weight, usually from 3 to 30% by weight, of the polyol. The reaction is exothermic. Generally, the higher the concentration of the poly-addition product to be formed, the greater is the exotherm.

The polymer-modified polyol of the invention may be formed by a batch process in which one of the trialkanolamine and polyisocyanate reactants is dissolved or dispersed in the polyol followed by the addition, with agitation, of the other reactant. Where a dispersion is formed, it will normally have a finer particle size if the reactants are mixed more efficiently. The viscosity of the product will also tend to be lower. Alternatively, the polymer-modified polyol may be formed by a continuous in-line blending process. In this process the trialkanolamine, polyisocyanate and polyol are pumped at controlled rates and may be mixed simultaneously or one reactant may be mixed firstly with the polyol followed by addition and mixing of the other reactant.

Normally it will be sufficient to add the components at room temperature allowing the temperature to rise up to 1 50"C through the exothermic reaction ad heat generated by high shear mixing, if used.

The polymer-modified polyols of the invention are useful in the manufacture of polyurethane products, especially polyurethane foams.

Polyurethane products are made by reacting a polyisocyanate with a polyol. A blowing agent is added to produce a foamed product. The polymermodified polyol of the invention may be used as the polyol component to produce flexible, elastomeric, semi-rigid and rigid foams. The nature of the foam will depend on the particular polyol chosen in preparing the polymer-modified polyol and also on the polyisocyanate and other ingredients conventionally used in the manufacture of polyurethane foams. They may be selected in known manner to produce the type of foam desired.

Polyisocyanates which may be used in making polyurethane products are comprehensively described in relevant literature and include the organic polyisocyanates described hereinbeforeforthe preparation of the polymer-modified polyol. The particular polyisocyanate used may be the same or different from that used to prepare the polymermodified polyol.

The polymer-modified polyols of the invention are of particular value in making high resilient flexible foams for cushioning and similiar applications.

These types of foam and their method of manufacture are well-known in the polyurethane foam industry. Such foams made from the polymer-modified polyols of the invention have advantages in respect of increased hardness and shrinkage properties. For foams of thins type the polymer-modified polyol is usefully prepared from polyoxyalkylene polyols, especially ethylene oxide-tipped polyoxypropylene polyols, and reacted with TDI, pure or crude MDI, or mixtures of TDI or a TDI prepolymer and pure or crude MDI.

The polymer-modified polyols of the invention may be used directly they are made, or stored. If they are made by a continuous in-line blending process an intermediate storage vessel between the blending unit and polyurethane mixing head may be used, if necessary, to allow reaction between the polyisocyanate and trialkanolamine to be completed where this is slow. Polymer-modified polyol dispersions have good storage stability and can be stored before use.

Other conventional ingredient may be used in making the polyurethanes. These include catalysts, for example, tertiary amines or chain lengthening agents, for example, low molecular weight diols, triols and diamines, flame proofing agents, for example, halogenated alkyl phosphates, fillers and pigments. Blowing agents used for forming polyurethane foams include water, which reacts with the polyisocyanate to form carbon dioxide, and inert low boiling liquids such as halogenated hydrocarbons, examples of which are trichiorofluoromethane and dichlorodifluoromethane. Foam stabilisers, for example polysiloxane-polyalkylene oxide block copolymers, may be used to stabilise or regulate the cells of the foam.

The amount of these minor ingredients and blowing agents used will depend on the nature of the product required and may be varied within limits well known to a polyurethane foam technologist. In the case of high resilient water blown flexible foams, it is appropriate to use from 1.0 to 5.5%, preferably from 1.5 to 4.0%, by weight of water based on the weight of the total polyol component. An inert low boiling liquid may be used as an additional blowing agent, if it is desired to reduce to the foam density.

In general, the composition of the foam-forming reaction mixture should be such that the ratio of isocyanate groups to active hydrogen atoms is within the range of 0.7:1 to 1.2:1, preferably 0.8:1 to 1.1:1.

One shot, prepolymer or quasi-prepolymer methods may be employed as may be appropriate for the particular type of polyurethane being made. The components of the polyurethane forming reaction mixture may be mixed together in any convenient manner, for example by using any of the mixing equipment described in the prior art for the purpose. If desired, some of the individual components may be pre-blended so as to reduce the number of component streams requiring to be brought together in the final mixing step. It is often convenient to have a two-stream system whereby one stream comprises a polyisocyanate or prepolymer and the second stream comprises all the other components of the reaction mixture.

Claims (2)

1. A polymer-modified polyol comprising a polyol and the reaction product of a polyisocyanate and a trialkanolamine, the trialkanolamine being obtained by treating a mixture of alkanolamines containing a trialkanolamine and a minor proportion of a dialkanolamine or monoalkanolamine or bother with an alkylene oxide and the treatment being continued until the mono-, di- or combined monoand dialkanolamine content, expressed as dialkanolamine, is less than 5% by weight of the treated mixture.

2. A method of forming a polymer-modified polyol in which a polyisocyanate is reacted with a trialkanolamine in the presence of a polyol, the trialkanolamine being obtained by treating a mixture of alkanolamines containing a trialkanolamine and a minor proportion of a dialkanolamine or monoalkanolamine or both with an alkylene oxide and the treatment being continued until the mono-, di- or combined mono- and dialkanolamine content, expressed as dialkanolamine, is less than 5% by weight of the treated mixture.