GB2102824A - Polymer-modified polyols - Google Patents

Abstract

Dispersions of a poly-addition product in a polyester polyol are obtained by reacting a polyisocyanate with an olamine, especially a trialkanolamine, in the presence of a polyester polyol. The dispersions are useful for preparing harder polyurethane flexible foams and elastomers.

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 polyester polyol ad the reaction product of a polyisocyanate and an olamine, the olamine reacting predominantly polyfunctionally with the polyisocyanate.

Other aspects of the invention include a method of forming the polymer-modified polyol, its use in the manufacture of polyurethane products, especially polyurethane flexible foams and elastomers, 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 polyp rears and polyhydrazo-dicarbonamides in polyethers obtained by reacting polyisocyanates with primary and secondary amines, hydrazines or hydrazidesiin 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 an olamine in a polyester polyol.

The polyester polyol used in the invention may be any of the polester polyols used in the manufacture of polyurethanes or mixtures thereof. These are well known to polyurethane technologists and are documented in the relevant literature. Generally, the polyester polyol wll be the reaction product of a polyhydric alcohol, preferably a dihydric alcohol with the optional addition of a trihydric alcohol, with polybasic, preferably dibasic, carboxylic acids, their anhydrides or alkyl esters or mixtures thereof. The polycarboxylic acid or derivative thereof may be aliphatic, cycloaliphatic, aromatic or heterocyciic and may be substituted for example, by halogen atoms or may be unsaturated.Examples of polycarboxylic acids or derivatives thereof are succinic acid, adipic acid, suberic acid, azelic acid, sebacic acid, phthalic acid, isophthalic acid,trimellitic acid, phthalic anhydride, tetrachlorophthalic anhydride, glutaric acid, maleic acid, maleic anhydride, fumaric acid, basic fatty acids, terephthalic acid dimethyl ester and terephthalic acid-bis-glycol ester.Examples of polyhydric alcohols are ethylene glycol, 1,2- and 1,3-propylene glycol, 1,4- and 2,3-butylene glycol, 1,6-hexane diol, 1,8-octane diol, neopentyl glycol, cyclohexane dimethanol (1,4-bishydroxymethylcyclohexane), 2-methyl-1 3-propane diol, glycerol, trimethylol propane, 1,2,6-hexane triol, 1,2,4-butane triol, trimethylol ethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, also diethylene glycol, triethylene glycol, tetraethylene glycol, higher polyethylene glycols, dipropylene glycol, higher polypropylene glycols, dibutylene glycol and higher polybutylene glycols.

The polyesters may also contain terminal carboxyl groups. Polyesters of lactones, for example, Ecaprolactone, or hydroxy carboxylic acids, for example E-hydroxy caproic acid, may be used.

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 and 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 polyisocycanates 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 of 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 low molecular weight polyols such as trimethylolpropane, dipropylene glycol ortripropylene glycol.

By the term "olamine" is meant an organic compound having one or more hydroxyl groups and also one or more primary, secondary or tertiary amine groups. Having two or more active hydrogen atoms, the olamine can react polyfunctionally with the polyisocyanate to form a poly-addition product.

Where the olamine in a primary or secondary amine it has hydroxyl and amine groups with active hydrogen atoms which may be reactive towards the isocyanate groups of the polyisocyanate. Where it is a tertiary amine it has two or more hydroxyl groups with active hydrogen atoms all of which may be reactive towards the isocyanate groups of the polyisocyanate. In each case all or some of the reactive hydrogen atoms may, in fact, react with isocyanate groups.

Suitably the olamine is an alkanolamine which may carry substituents such as halogen atoms. The alkanolamine may be a primary, secondary or tertiary alkanolamine, such as a mono-alkanolamine or a dialkanolamine either of which optionally carries an N-alkyl substituent in which the alkyl group conveniently contains 1 to 4 carbon atoms.

Preferably it is a trialkanolamine, such as tri isopropanolamine and especially triethanolamine.

Thus in a preferred aspect of the invention there is provided a polymer-modified polyol comprising a polyester polyol and the reaction product of a polyisocyanate and a trialkanolamine.

Trialkanolamines which may be used include substantialy pure trialkanolamine, for example, 98% by weight of pure triethanolamine which contains about 2% by weight of diethanolamine and trace amounts of monoethanolamine; commercial grades of trialkanolamines, for example, a commerical grade of triethanolamine which contains 83 to 85% by weight of triethanolamine, about 15% by weight of diethanolamine and 1 to 2% of monoethanolamine; and commercial grades which have been oxyalkylated ro reduce the di- and monoalkanolamine content, for example a commercial grade of triethanolamine which has been treated with an alkylene oxide such as ethylene oxide, a butylene oxide or epichlorohydrin and especially propylene oxide, until the combined mono- and di-alkanolamine content, expressed as dialkanolamine, has been reduced to less than 5%, preferably 2% or less, by weight of the treated material.

Oxyalkylated trialkanolamines of this type are described in British Patent No. 1140867.

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 an olamine in the presence of a polyester polyol, the olamine reacting at least predominately polyfunc tionallywith the isocyanate. In another preferred 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 the polyester polyol.

In carrying out the method of the invention, the polyisocyanate and olamine 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 polyester polyol. The molecular weight and viscosity of the poly-addition product so formed may be varied by adjusting the ratio of polyisocyanate and olamine. 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 olamine.

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 organometallic 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 polyester 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 polyester polyol. The reaction is exothermic. Generally, the higher the concentration of the polyaddition product to be formed, the greater is the exotherm. For example, in producing a 20% by weight dispersion an exotherm of 70"C may occur whereas in producing a 10% by weight dispersion using the same reactants an exotherm of 40"C may occur.

The polymer-modified polyol of the invention may be formed by a batch process in which one of the olamine and polyisocyanate reactants is dissolved or dispersed in the polyester 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 olamine, polyisocyanate and polyester polyol are pumped at controlled rates and may be mixed simultaneously or one reactant may be mixed firstly with the polyester polyol followed by addition and mixing of the other reac tans.

Normally it will be sufficient to add the components at room temperature allowing the temperature to rise to up to 1 500C through the exothermic reaction and 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 flexible foams and elastomers.

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 product polyurethanes in the form of, for example, elastomers, microcellular elastomers, foams, coatings and rigid plastics. The nature of the polyurethane foam will depend on the particular polyester polyol chosen in preparing the polymer-modified polyol and also on the polyisocyanate and other ingredients conventionally used in the manufacture of polyurethanes. They may be selected in known mannerto produce the type of product desired.

Polyisocyanates which may be used in making polyurethane products are comprehensively described in relevant literature and include the organic polyisocyanates described hereinbefore for the 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 water blown flexible foams and microcellular elastomers which are suitable as shoe soles. These types of products and their method of manufacture are well-known in the polyurethane foam industry. Such products made from the polymer-modified polyols of the invention have advantages in respect of increased hardness and shrinkage properties.

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 polyiso cyanate and olamine to be completed where this is slow. Polymer-modified polyol dispersions have good storage stability and can be stored before use.

Other conventional ingredients may be used in making the polyurethanes. These include catalysts, for example, tertiary amines and organic tin compounds, surfactants, cross linking 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 folr forming polyurethane foams and low density elastomers include water, which reacts with the polyisocyanate to form carbon dioxide, and inert low boiling liquids such as halogenated hydrocarbons, examples of which are trichlorofluoromethane 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 technologist. In the case of 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 the foam density.

In general, the composition of the polyurethaneforming 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 artforthe 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 (4)

1. A polymer-modified polyol comprising a polyester polyol and the reaction product of a polyisocyanate and an olamine, the olamine reacting predominantly polyfunctionally with the polyisocyanate.

2. A polymer-modified polyol comprising a polyester polyol and the reaction product of the polyisocyanate and a trialkanolamine.

3. A method of forming a polymer-modified polyol in which a polyisocyanate is reacted with an olamine in the presence of a polyester polyol, the olamine reacting at least predominantly polyfunc tionaily with the isocyanate.

4. A method of forming a polymer-modified polyol in which a polyisocyanate is reacted with a trialkanolamine in the presence of a polyester polyol