CA2146670A1 - Method of preparing stabilized aromatic diamines, and their use in the production of heat-resistant polyurethane/urea elastomers - Google Patents

Abstract

A method of preparing polyurethane urea elastomers by reacting polyisocyanates and polyester and/or polycarbonate polyol reaction products containing terminal NCO groups and having a molecular weight of 400 to 10,000 with finely divided diamino diphenyl ureas having the general formula

Description

21 ~6670 Le A 29 324 - PCT

A method of preparing stabilised aromatic diamines and use thereof for producing heat-resistant polyurethane-urea elastomers The invention relates to a simple industrial method of producing polyurethane-urea elastomers, in which aromatic diamines stabilised by reaction with organic and/or inorganic acid chlorides and in the solid phase are reacted with isocyanate prepolymers.
It is known to prepare polyurethane-urea elastomers from polyisocyanates, higher-molecular polyhydroxyl compounds and aromatic diamines. In order to process reactive systems of the aforementioned starting components within a reasonable time, the reactive aromatic isocyanates normally used in industry are advantageously reacted with diamines, which are slow to react. In practice in this connection, the best results have been obtained with aromatic diamines in which the basicity and consequently the reactivity with isocyanates have been reduced by introducing halogen or carboxy substituents. One example is the substance most frequently used hitherto, i.e. 3,3'-dichloro-4,4'-diamino diphenyl methane (MOCA).

US-A 3 891 606 describes cross-linking of NCO prepolymers of polyhydroxyl compounds and an excess of polyisocyanates with aromatic diamines whose reactivity with isocyanate groups has been reduced by complexing with certain alkali-metal salts. The disadvantage of this method is that it is limited to two particular aromatic diamines. In addition, the complex between the aromatic diamine and the alkali-metal salt must be produced in a separate step.

Another possible method of controlling the rate~-of reaction between polyisocyanates and aromatic diamines is to carry out the reaction in an organic solvent. Methods of this kind are described e.g. in US-A 3 926 922 and in Japanese Laid-Open Specification 9195/70. The disadvantage of using organic solvents is obvious. On the one hand the risk of fire and explosion is increased and on the other hand the solvent has to be recovered in a complicated industrial process, for economic and ecological reasons.

At present little is known about production of polyurethane ureas by reaction of polyisocyanates with aromatic diamines in the heterogeneous phase. In the prior art, higher-melting aromatic diamines, which are generally of particular importance in industry, are used either in dissolved form, with the aforementioned disadvantages, or are reacted with polyisocyanates in the melt. Processing of aromatic diamines in the melt is described e.g. in the previously-mentioned US-A 3 926 922 or in DE-A 1 122 699.
DE-A 1 122 699 relates to a method of producing poly-urethane elastomers by cross-linking of liquid isocyanate prepolymers by reaction with mixtures of primary diamines and compounds containing a number of hydroxyl groups and shaping, in which a dispersion of a pulverulent crystalline diamine in a liquid polyester containing a number of hydroxyl groups or in a polyether or in castor oil is introduced into the prepolymer at a temperature below the melting-point of the diamine, and the material is hardened in known manner at temperatures above the melting-point of the diamine in the mixture. In this method also, therefore, the actual "amine cross-linking" occurs in the liquid homogeneous phase. The main disadvantage of the method in DE-AS 1 122 699 is the high temperatures , 21q6~7D

required, particularly when processing high-melting diamines such as 1,5-naphthylene diamine (m.p. = 189C) or 4,4'-diamino diphenyl ether (m.p. = 186C), since experience shows that decomposition reactions a}ready occur to a considerable extent in polyurethane and uncontrollably affect the mechanical properties of the products.

US-A 3 105 062 describes a method of producing polyurethane ureas in which higher-molecular pre-adducts containing isocyanate groups are reacted in the heterogeneous phase with diamines, preferably aromatic. The reaction mixtures are solidified at a temperature at which the "two-phase"
system changes into a "single-phase" system. The temperature is usually about 100 to 170C.
However the aromatic diamines cited in US-A 3 105 062 are still soluble, even though slightly, in the reaction medium (NC0 pre-adduct), so that when the two components are mixed, uncontrollable preliminary reactions occur even at room temperature. The result is that the reacting batches thicken in a very short time and in some cases the formulations become pasty. They are difficult to process by normal casting and therefore have to be introduced into the required mould under pressure before the actual solidification by heating. According to US-A 3 105 062 the stability in storage (pot life) of the thickened reaction mixtures is sufficient for subsequent processing (shaping under pressure and coating) and amounts to several hours.
The examples, however, show that the reaction mixtures are preferably those having a maximum pot life of about 1 hour.
They therefore cannot be regarded as long-time systems.

In US-A 3 105 062 it is expressly pointed out that the use of the cited diamines, in solid form only, in a single-stage process results in unsatisfactory polyurethanemoulded members. In that case the undesired preliminary reaction between the diamine and the diisocyanate is intensified, and the difficultly-soluble polyurea precipitates from the reaction mixture and ceases to react.

DE-A 26 35 400 describes another method of producing polyurethane urea elastomers, in which aromatic diamines for lengthening the chain are reacted in a single or multi-stage process. This process is characterised in that the aromatic diamines are present in solid form in the reaction mixtures and melt at above 130C. The batches are solidified by heating at a temperature of 80 to 120C, i.e.
below the melting-point of the aromatic diamine. As a result of a choice of suitable diamines for lengthening the chain, no premature reaction and no thickening of the batches occurs with the NC0-containing pre-adduct (NC0 prepolymer). These systems therefore can also be efficiently processed by casting. Since the pot life of these reactive systems is very long, the process is suitable for many aromatic diamines which were very difficult to work by the previously-known method.

The examples in DE-A 26 35 400 show that the pot life of the liquid reaction mixtures, depending on the reactivity or solubility of the aromatic diamine in a temperature range, varies from a few minutes to several hours. Under normal processing conditions, e.g. manual casting, these reaction batches, particularly those with long pot lives, can usually be processed without great difficulty.
Problems occur if, as a result of failures of machinery or other involuntary shut-downs, there is a prolonged pause between production and reaction batches and the solidification phase. The requirement for a long processing time at low temperature and a short processing time at elevated temperature is therefore becoming progressively more urgent in practice.

The finished PUR plastics are stated to have good mechanical properties in general and often also have thermal stability suitable for their intended use. In the prior art, the thermal stability of PUR elastome~rs is closely dependent on the nature of the chain-lengthening substances. If for example glycolic chain-lengtheners are used in the production of elastomers, the resulting PUR
members have lower thermal stability than when compounds containing amino groups are used. Of course, there are also considerable differences in thermal stability within each kind of chain-lengtheners (compounds containing H0 or NH2 groups).

DE-A 26 35 400 states that numerous diamines varying in constitution are suitable chain-lengtheners for producing polyurethane-urea elastomers. The only representative of a diamino diphenyl urea mentioned is 2,2'-diamino diphenyl urea.

No experimental example is given.

A check of the application showed that an NC0 pre-adduct reacted with the aforementioned diamino diphenyl urea yields a resilient PUR moulded member having perfectly acceptable mechanical properties. However, the thermal stability of these elastomers is unexpectedly low. If the moulded member is subsequently heat-treated at only 120 -130C, a considerable decrease in mechanical strength occurs after a short time. At 140 - 150C there is only a viscous melt, irrespective of whether the test-piece is hot or cold (example).

DE-A 3 732 728 describes a method of preparing polyurethane-urea elastomers in which finely-divided diamino diphenyl ureas having the general formula 21~6670 H2N ~ NH-Co-N~ ~ NH2 Rl-R4 Rl-R4 in which the NH2 groups are in the m and/or p position relative to the urea group and R1, R2, R3, R4 (which may be the same or different) denote H or Cl - C6-alkyl radicals, in combination with NCO pre-adducts yield reaction mixtures which, at the respective processing temperature, have processing times of at least several hours, preferably at least 8 hours (long-time system). The heterogeneous reaction batches can be solidified at a relatively low temperature within an economically advantageous time. If on the other hand the chain-lengtheners according to the invention are added in dissolved form to the NCO pre-adducts, they behave like conventional aromatic diamines.After a few seconds the reaction becomes batch cross-linked and the resulting swollen product can no longer be worked.

It is stated that the pre-adducts comprising NCO groups are prepared by using polyhydroxyl compounds having a molecular weight of 400 to 10,000. These include polyester and polycarbonate polyols particularly suitable for cast elastomers having excellent mechanical properties, as described in DE-A 3 732 728 on page 5, lines 51 ff. The reaction components are reacted by the known single-stage method or the prepolymer method or the semi-prepolymer method, often using mechanised equipment, e.g. as described in US-A 2 764 S65, where performance of the method according to DE-A 3 732 728 is described on page 8, lines 17 ff.

21~6670 It is specially pointed out that the processing temperature on the one hand is closely dependent on the nature of the NC0 pre-adduct and on the other hand should not be too high, when premature reactions cannot be prevented. This is particularly critical when highly reactive NC0 pre-products, which are solid or highly viscous at room temperature, have to be processed by casting. In that case the processing temperature has to be raised until the reaction batch can be properly degassed and cast. The temperatures are usually up to 130C. In the case of the polyester polyol-based prepolymers used in examples 1 and 7 in DE-A 3 732 728, the temperature is usually at least 80C. Under these conditions, it is of course more difficult to meet the requirement for long-time systems with a processing time of at least several hours, particularly in view of the already high reactivity of NCO
prepolymers based on polyester or polycarbonate polyols, compared e.g. with polyether polyols. The stability in storage of diamino diphenyl ureas in polyester polyol-based NC0 prepolymers at a temperature of 40 - 50C is therefore not in reality as described in examples 1 and 7 of DE-A 3 732 728. In the case of 4,4'-diamino diphenyl urea, it appears possible to increase the storage temperature to the 80C required in practice. In the case of meta-diamino phenyl urea in example 7, on the other hand, the stability in storage is relatively low (2 hours) even at 40 to 50C, showing that processing at 80C is impossible. This is confirmed by a comparative test (example 1 in this application). At the normal processing temperature of about 80C for this system, the reaction batch is found to thicken so strongly within a very short time (less than 1 minute) that it cannot be degassed and cast to form a high-quality industrial moulded part.

The aim of the invention therefore is to discover a method of preparing polyurethane ureas in which the processing " " ~

time of the reaction batches, consisting of a combination of highly-reactive NC0 prepolymers which are highly viscous or solid at room temperature, based on polyester and/or polycarbonate polyols and therefore needing to be processed at elevated temperature, and solid diamino diphenyl ureas in finely divided form and having the general formula H2N~t~H-CO-NH~NH2 Rl-R4 Rl-R4 in which the NH2 groups are in the meta position relative to the urea group and Rl, R2, R3, R4 (which may be the the same or different) denote H or Cl - C6- alkyl radicals, at the respective reaction temperature is within a range enabling the reaction mixture to be efficiently degassed and cast. It is also desirable that the liquid reaction batches should solidify at the lowest possible reaction temperatures within an economically advantageous time.
It has now surprisingly been found that finely-divided diamino diphenyl ureas having the general formula H2N ~ NH-C0-NH ~ NH2 Rl-R4 Rl-R4 in which the NH2 groups are in the meta position relative to the urea group and Rl, R2, R3, R4 (which may be the same or different) denote H or Cl-C6-alkyl radicals, which can be stabilised by reaction with organic and/or inorganic acid chlorides in a proportion of more than 200 ppm relative to the amount of NC0 pre-product, so that the processing time of the reaction batches, consisting of the combination of NC0 pre-polymers, which are highly reactive and/or highly viscous or solid at room temperature and based on polyester 2t~46670 and/or polycarbonate polyols and the aforementioned stabilised ureas at the respective reaction temperature is prolonged so that the mixture can be efficiently degassed and cast. Solidification is then brought about in conventional manner by action of heat (120 to 180C) yielding polyurethane elastomers having very good mechanical properties and good resistance to heating.

The diamino diphenyl ureas suitable according to the invention are produced by known methods. For example nitro-anilines with phosgene or diphenyl carbonate can be converted into the corresponding dinitro diphenyl ureas and then converted into the desired diamino diphenyl ureas by reduction. Another universally applicable method is a reaction of amino acetanilides with phosgene or diphenyl carbonate and subsequent alkaline saponification of the acetamide group to the desired product.

A particularly simple method, which is consequently preferred for manufacturing the ureas according to the invention, is to react aromatic m-diamines with urea as described in US-A 16 17 847 (in an inert solvent or in the melt) or in US-A 25 03 797 (in sulphuric-acid or neutral aqueous solution).
As a result of the method of manufacture, however, higher-molecular, multi-nuclear products having the general formula II

NH2 11 ~ NH2 [~ ~NH~--NH ~ n > 2 R R R R
~ n 21~6670 are usually formed together with the monomeric diamino diphenyl ureas I, but within certain limits do not have any negative influence on the properties of the elastomers.
However the proportion of ureas with n = 1 - 3 must be at least 60~ by weight relative to the total amount. Ureas with a maximum proportion of "monomers" (n = 1) are preferred.

One simple method of producing diamino diphenyl ureas with a high yield and very low proportions of higher-nuclear ureas is to react aromatic m-diamines with urea in chlorobenzene under specific concentration conditions, as described in EP-A 374 653.

The diamino diphenyl ureas, which are solids, are usually first finely ground, e.g. in a ball mill, until they have an average particle size of 1 to 50 ~m, preferably 3 to 10 ~m.

The following are examples of preferred diamines for preparing the ureas according to the invention: m-phenyl diamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 1-methyl-3,5-diethyl-2,6-diaminobenzene and 1,3,5- triethyl-2,4-diaminobenzene. The following are examples of preferred diamines for producing the ureas according to the invention: p-phenylene diamine, m-phenylene diamine, 2,5-diaminotoluene, 2,4-diaminotoluene, 2,6-diaminotoluene, l-methyl-3,5-diethyl-2,6-diaminobenzene and 1,3,5-triethyl-2,4-diaminobenzene. The resulting diamino powders can be mixed directly with the NCO pre-product or are preferably applied in suspension form with a small amount of the high-molecular polyol on which the NCO pre-adduct is based.

Of course, use can also be made of mixtures of the aforementioned diamino diphenyl ureas with other chain-lengtheners known in PUR chemistry and comprising at least two hydrogen atoms which react with isocyanates and have a molecular weight of 60 to 400.

The polyhydroxyl compound suitable for the method according to the invention of producing the pre-adducts comprising NC0 groups have a molecular weight of about 400 to 10,000, preferably 600 to 6,000. The polyesters and polycarbonates in question contain at least 2 and preferably 2 to 4 hydroxyl groups, as known per se for producing homogeneous and cellular polyurethanes.

The polyesters in question comprising hydroxyl groups are e.g. reaction products of polyhydric, preferably dihydric or optionally additionally trihydric alcohols with polyvalent, preferably divalent carboxylic acids. Instead of the free polycarboxylic acids, the corresponding poly-carboxylic acid anhydrides or corresponding polycarboxylic acid esters of low alcohols or mixtures thereof can be used to obtain the polyesters. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and optionally substituted e.g. by halogen atoms and/or can be unsaturated. The following are examples: succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic acid anhydride, tetrahydrophthalic acid anhydride, hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride, endomethylene tetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimeric and trimeric fatty acids such as oleic acid, optionally mixed with monomeric fatty acids, terephthalic acid dimethyl ester or terephthalic acid-bis-glycolic ester. The polyhydric alcohols can e.g.
be ethylene glycol, propylene glycol-(1,2) and -(1,3), butylene glycol-(1,4) and -(2,3), hexanediol-(1,6), octanediol-(1,8), neopentyl glycol, cyclohexane dimethanol (1,4-bis-hydroxymethyl cyclohexane), 2-methyl-1,3-. .

propanediol, glycerol, trimethylol propane, hexanetriol-(1,2,6), butanetriol-(1,2,4), trimethylol ethane, pentaerythritol, quinitol, mannitol or sorbitol, methyl glycoside, or diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycols, dibutylene glycol or polybutylene glycols. The polyesters can contain proportions of terminal carboxyl groups. Polyesters from lactones, e.g. ~-caprolactone or hydroxycarboxylic acids such as ~-hydroxycaproic acid can also be used.

The polycarbonates comprising hydroxyl groups can be those of known kind, prepared e.g. by reacting diols such as propanediol-(1,3), butanediol-(1,4) and/or hexanediol-(1,6), dimethylene glycol, triethylene glycol ortetraethylene glycol with diaryl carbonates, e.g. diphenyl carbonate, or with phosgene.

Representatives of these compounds for use according to the invention are described e.g. in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology", compiled by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32 - 42 and pages 44 - 54 and Volume II, 1964, pages 5 - 6 and 198 - 199, and in Kunststoff-Handbuch, Volume VII, Vieweg- Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 45 to 71.

Of course, use can be made of mixtures of the afore-mentioned compounds containing at least two hydrogen atoms capable of reacting with isocyanates and having a molecular weight of 400 to 10,000, e.g. mixtures of polyesters and polycarbonates.

The starting compounds for use according to the invention can also be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic polyisocyanates, described e.g. by 21~6670 W. Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136, e.g. ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3 and 1,4-diisocyanate or any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane (DAS 1 202 785), 2,4- and 2,6-hexahydrotoluylene diisocyanate or any mixtures of these isomers, hexahydro-1,3- and/or -1,4-phenylene diisocyanate, perhydro-2,4'-and/or 4,4'-diphenylmethane diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-toluylene diisocyanate or any mixtures of these isomers, diphenyl methane-2,4'-and/or -4,4'-diisocyanate, naphthylene-1,5- diisocyanate, triphenylmethane-4,4'4''-triisocyanate, polyphenyl polymethylene polyisocyanates obtained by aniline-formaldehyde condensation and subsequent phosgenation and described e.g. in British PSS 874 430 and 848 671, perchlorinated aryl polyisocyanates as described e.g. in German laid-open specification 1 157 601, polyisocyanates containing carbodiimide groups as described in German PS 1 092 007, diisocyanates as described in US-PS 3 492 330, polyisocyanates containing allophanate groups as described e.g. in GB-A 994 890, BE-A 761 626 and NL-A 7 102 524, polyisocyanates containing isocyanate groups as described e.g. in DE-A 1 022 789, 1 222 067 and 1 027 394 or 1 929 034 and 2 004 048, polyisocyanates containing urethane groups as described e.g. in BE-A 752 261 or in US-A 3 394 164, polyisocyanates containing acylated urea groups according to DE-A 1 230 778, polyisocyanates containing biuret groups as described e.g. in DE-A 1 101 394, GB-A 889 050 and FR-A 7 017 514, polyisocyanates produced by telomerisation reactions as described e.g. in BE-A 723 640, polyisocyanates containing ester groups as mentioned e.g. in GB-A 965 474 and 1 072 956, US-A 3 567 763 and DE-A 1 231 688, or reaction products of the aforementioned isocyanates with acetals according to DE--A 1 072 385.

5 Use can also be made of distillation residues, optionally dissolved in one or more of the aforementioned poly-isocyanates, and comprising isocyanate groups obtained during industrial isocyanate production. Any mixtures of these polyisocyanates can also be used.
Usually special preference is given to polyisocyanates which are easily obtainable industrially, e.g. 2,4- and 2,6-toluylene diisocyanate or any mixtures of these isomers ("TDI"), polyphenyl polymethylene polyisocyanates obtained 15 by aniline-formaldehyde condensation and subsequent phosgenisation ("crude MDI") and polyisocyanates comprising carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisocyanates").
The polyisocyanates or the isocyanate prepolymers prepared from the aforementioned polyisocyanates and the afore-mentioned higher and/or lower-molecular polyols should be present in liquid form in the reaction with the powdered or 25 suspended aromatic diamine.

If the method according to the invention is used to produce polyurethane foam, water and/or easily volatile organic substances are used as the foaming agent. The organic 30 foaming agent can e.g. be acetone, ethyl acetate, methanol, ethanol, halogen-substituted alkanes such as methylene chloride, chloroform, ethylidene chloride, vinylidene chloride, monofluorotrichloromethane, chloro-difluoromethane, dichlorodifluoromethane, or butane, 35 hexane, heptane or diethyl ether. The foaming effect can also be obtained by adding compounds, e.g. azo compounds such as azo-isobutyric acid nitrile, which decompose at elevated temperatures with evolution of gases, e.g.
nitrogen. Other examples of foaming agents and details about the use of foaming agents are described in Kunststoff-Handbuch, Volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 108 and 109, 453 and 455 and 507 - 510.

Catalysts can also often be used according to the invention. The catalysts can be those of known kind, e.g.
tertiary amines such as triethyl amine, tributyl amine, N-methyl morpholine, N-ethyl morpholine, N,N,N',N'-tetramethyl ethylene diamine, 1,4-diaza-bicyclo-(2,2,2)-octane, N-methyl-N'-dimethyl aminoethyl piperazine, N,N-dimethyl benzylamine, bis-(N,N-diethyl aminoethyl)-adipate, N,N-diethyl benzylamine, pentamethyl diethylene triamine, N,N-dimethyl cyclohexyl amine, N,N,N',N'-tetramethyl-1,3-butanediamine, N,N-dimethyl-~-phenyl ethylamine, 1,2-dimethyl imidazole or 2-methyl imidazole.
The following are examples of tertiary amines containing hydrogen atoms which react with isocyanate groups:
triethanolamine, triisopropanolamine, N-methyl-diethanolamine, N-ethyl-diethanolamine, N,N-dimethyl-ethanolamine or reaction products thereof with alkyleneoxides such as propylene oxide and/or ethylene oxide.

The catalysts may also be silaamines with carbon-silicon bonds, as described e.g. in DE-A 1 229 290, e.g. 2,2,4-trimethyl-2-silamorpholine and 1,3-diethyl aminomethyl tetramethyl disiloxane.

The catalysts can be nitrogen-containing bases such as tetraalkyl ammonium hydroxides or alkali-metal hydroxides such as sodium hydroxide, alkali-metal phenolates such as sodium phenolate or alkali-metal alcoholates such as sodium 21~6670 "

methylate. Hexahydrotriazines can also be used as catalysts.

According to the invention other organic metal Gompounds, more particularly organic tin compounds, can be used as catalysts.

The organic tin compounds are preferably tin(II) salts of carboxylic acids such as tin(II) acetate, tin(II) octoate, tin(II) ethyl hexoate or tin(II) laurate and dialkyl tin salts of carboxylic acids such as dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin maleate or dioctyl tin diacetate.

Other examples of catalysts used according to the invention and details about the operation of the catalysts are described in Kunststoff-Handbuch, Volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g.
on pages 96 to 102.
The catalysts are normally used in a proportion between about 0.001 and 10% by weight relative to the quantity of polyhydroxyl compounds having a molecular weight of 400 to 10, 000.

Surface-active additives (emulsifiers and foam stabilisers) can also be used according to the invention. The emulsifiers can e.g. be sodium salts of castor oil sulphonates or of fatty acids or salts of fatty acids with amines, such as diethylamine oleate or diethanolamine stearate. Alkali-metal or ammonium salts of sulphonic acids, e.g. dodecylbenzene sulphonic acid or dinaphthyl-methane disulphonic acid or of fatty acids such as ricinoleic acid or polymeric fatty acids can also be used as surface-active additives.

The main foam stabilisers are water-soluble polyether siloxanes. These compounds are usually constructed by bonding an ethylene oxide and propylene oxide copolymer with a polydimethyl siloxane radical. Foam sta~ilisers of this kind are described e.g. in US-A 2 764 565.

According to the invention, use can also be made of cell regulators of known kind, such as paraffins or fatty alcohols or dimethyl polysiloxanes or pigments or dyes and flame retardants of known kind, e.g. tris-chloroethyl phosphate or ammonium phosphate or polyphosphate, or stabilisers against ageing and weathering, or softeners, fungistatic and bacteriostatic substances, fillers such as barium sulphate, diatomite, carbon black or whiting.
Other examples of surface-active additives optionally of use according to the invention, and of foam stabilisers such as cell regulators, reaction-delaying substances, stabilisers, flame retardants, plasticisers, dyes, fillers, fungicidal and bacteriostatic substances and details about the use and operation of these additives are described in Kunststoff-Handbuch, Volume VI, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 103 to 113.
The organic acid chlorides can be compounds having the general formula (ClCO)n-R or (ClCOX)-R
where n = 1 - 4, preferably n = 2 - 4, R denotes an aliphatic, cycloaliphatic or aromatic radical and X = 0 and/or N. The following are examples of compounds according to the invention: acetic acid chloride, oleic acid chloride, stearic acid chloride, phthalic acid chloride, terephthalic acid chloride, or toluylene-2,4-bis carbomoyl chloride. Use can also be made of inorganic acid chloride derived from oxo-acids such as sulphuric acid or phosphoric acid. Thionyl chloride or phosphorus pentachloride are examples. Hydrochloric acid ~dded to the NCO prepolymer reacts immediately in situ with free isocyanate and gives carbamic acid chlorides which can be classified among the aforementioned organic acid chlorides.

DE-A 3 732 728, page 7, lines 56 ff mentions use of acid-reacting substances such as hydrochloric acid or organic acid halides for delaying the reaction. This relates to the possibility, generally known in the prior art, of using Brondsted or Lewis acids in ppm proportions for inhibiting the NCO reaction (Becker/Braun, Kunststoff-Handbuch, Part 7, Munich, Carl Hanser Verlag, 1983, page 98). This - method is used mainly for stabilising NCO prepolymers and/or for forming prepolymers from highly active polyols or amines. The effect is explained by neutralisation of traces of bases or inactivation of metals by the acids.
The delaying effect of organic acids in combination with amines is attributed to salt formation. During the starting phase, isocyanate is trapped by the acid, thus delaying the start. The influence of acids and bases on the production of urethane prepolymers is described in detail by H. L. Heiss et al in Ind. Eng. Chem., S1 (1959), pages 929 - 934. One important finding is that addition of a few ppm of HCl (10 to 20 ppm) is observed to result in a considerable decrease in exothermy or the speed of the reaction between toluylene-2,4-diisocyanate with a polyethylene glycol (MW 400) (see Fig. 1, page 931 in H. L.
Heiss et al in Ind. Eng. Chem., 51 (1959)). If however the quantity of HCl is considerably increased (> 200 ppm) there is actually an increase in the rate of reaction. This shows that inhibitors do not influence the NCO-OH or NH
reaction so much as suppress the side-reaction of isocyanate to form allophanate, biuret or trimers 21~6670 (see Fig. 19, page 214 in H. J. Saunders and K. C. Frisch:
Polyurethanes, Chemistry and Technology, Volume 1, New York, Interscience, 1962 (High Polymers, Volume 16). From this prior art, the skilled man would mainly be;inclined to use organic acids in ppm proportions for delaying the NCO-NH2 reaction.

In the present case, however, where solid diamino ureas combine with liquid NCO polymers, no stabilising effect of organic acids is observed, even if a considerably larger proportion is used than normally. Consequently there was no reason to foresee the effect of organic and/or inorganic acid chlorides which, in a proportion of > 250 ppm relative to the NCO pre-adduct, i.e. considerably above the normal proportion, are found to be excellent stabilisers of solid diamino ureas, without appreciably interfering with the process of hardening into high-quality end products.

According to the invention, the components are reacted by the known prepolymer method or the semi-prepolymer method, often using mechanised equipment, e.g. as described in US-A
2 764 565. Details about processing equipment also used according to the invention are described in Kunststoff-Handbuch, Volume VI, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 121 to 205.

In the method according to the invention, the proportions of components in the reaction are usually chosen so that the molar ratio of polyisocyanates to chain-lengtheners plus the compound with reactive OH groups - depending on the particular method of processing - is usually between 0.7 and 1.5, preferably between 0.90 and 1.15. The percentage of NCO in the prepolymer, if the prepolymer stage is included, can be 1.8 to 6% by weight. The molar ratio of reactive hydrogen in the chain-lengtheners to reactive OH groups can vary within wide limits, preferably between 0.4 and 1.5, resulting in soft to hard types of polyurethane. In addition to the diamines used according to the invention, the chain-lengtheners can comprise other diamines or diols, e.g. those mentioned hereinbefore in the production of polyhydroxyl compounds. However, the molar fraction of the amine according to the invention in the chain-lengthener should be between 1 and 0.5, preferably between 1 and 0.8.

The invention is worked by a simple method. The polyol component, which has at least two hydroxyl groups and has a molecular weight of 400 to 10,000, is reacted in known manner with an excess of diisocyanate to obtain the pre-adduct containing the NCO groups. The reaction can be monitored by NCO titration. At the end of the poly-addition, the stabiliser is added. The temperature during addition of the stabiliser depends on the solubility thereof in the NCO pre-adduct. It is simplest to add the stabiliser at the respective processing temperature of the batches for casting. In most cases the temperature is about 80C. Of course, the processing temperature should not be too high, since in that case it is impossible to prevent a premature reaction after adding the chain-lengthener. The diamino diphenyl urea is introduced in the form of a solid powder (particle size about 5 to 50 ~m) using a suitable agitator, and the resulting suspension is intimately mixed. The processing time (Pot Life) of the system depends on the nature of the diamino diphenyl urea, the NCO pre-adduct and the proportion of stabiliser.
The proportion of stabiliser is chosen to obtain efficient degassing and casting under the respective processing conditions. There should never be a premature reaction between the NCO pre-adduct and the aromatic diamine, since any uncontrollable increase in the viscosity of the batch will increase the difficulty of subsequent processing during casting. On the other hand, not too much stabiliser 214667~

should be added, since otherwise the solidification process will suffer, and it will be necessary to accept uneconomically high solidification temperatures and poorer mechanical properties. The upper limit of the concentration of stabiliser is about 5,000 to 10,000 ppm relative to the prepolymer used. It is simplest to estimate the optimum proportion of stabiliser for the respective system and the respective working conditions in a preliminary test, using a series of concentrations.
In a variant of the process, the solid diamine powder can first be mixed with the high-molecular liquid polyols on which the NC0 pre-adduct is based. The batch can then be degassed, optionally at elevated temperature. In this case the stabiliser can be added either on the side of the NC0 pre-adduct as already described, or in the polyol-diamine suspension. The resulting pourable suspension or paste can then be added to the NC0 pre-adduct. This process has the advantage of simplicity.
The solidification temperature of the reactive systems according to the invention varies from 100 to 180C.

When the solidification temperature increases, the solidification time decreases. The duration of baking, depending on the temperature, can vary from less than 1 minute to several hours. It is often advantageous to heat-treat the plastics at lOO~C for a short time after removal from the mould, to ensure complete and thorough hardening.

Elastomers produced according to the invention have numerous uses, e.g. for highly mechanically stressed moulded members such as tyres, rollers, V-belts or seals exposed to severe thermal or chemical stress, or for hot-21~6670 water pipes or motors or for producing sheets, textilecoatings or polyurethane powder.

The chains can also be lengthened in the presen,ce of the aforementioned foaming agents and additives, preferably in closed moulds, thus forming foams with a cellular core and a compact surface.

The resilient, semi-elastic foamed materials obtainable by the process according to the invention are used e.g. as cladding materials, mattresses, packing material or, owing to their resistance to flame, in all sectors where these properties are particularly important, e.g. in car and aircraft construction and in the transport sector in general. The foamed materials can be produced either by foaming in a mould or by fabrication from slab stock.

The following examples illustrate the method according to the invention. Unless otherwise stated, numerical values are proportions or percentages by weight.

Examples Prepolymer A: A straight-chain polyester (OH number = 56, molecular weight = 2,000) prepared from adipic acid and ethylene glycol was reacted with 2,4-diisocyanato-toluene in the molar ratio 1:2 at 60 - 80C by the normal process, yielding a pre-adduct containing NCO groups and having an NCO content of 3.6 to 3.85% by weight.
Prepolymer B: A straight-chain polyester prepared from adipic acid with ethylene glycol and butanediol-1,4 was reacted with 2,4-diisocyanatotoluene in the molar ratio 1:2 at 60 to 80C by the normal process, yielding a pre-adduct lS containing NCO groups and with an NCO content of 3.3 to 3.5% by weight.

ExamPle 1 Comparative example, not according to the invention.

This example describes an attempt to cast an NCO polyester pre-adduct with TDAH without addition of stabiliser.

100 g of prepolymer A were intimately mixed at 70 to 80C
with 26.32 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared from 2,4-diaminotoluylene and urea as per EP 0 374 653, NH number 390 mg KOH/g). At the aforementioned temperature, the viscosity increased considerably in a very short time (< 60 seconds) so that the batch could neither be degassed nor cast.

Example 2 according to the invention Use of 1,000 ppm terephthalic acid dichloride 400 g of prepolymer B were heated to 70 to 80C. After addition of 0.4 g (1,000 ppm) terephthalic acid dichloride, the mixture was stirred for a further 30 minutes. Next, 45.1 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) was intensively mixed with the prepolymer. The suspension was thoroughly degassed in a water-jet vacuum.

The time for processing the resulting reactive system was at least 6.5 hours at 80C. During this time there was no premature reaction resulting in a considerable increase in the viscosity of the batch.

The liquid reactive system was poured into a preheated mould coated with a separating agent, and heated to 140 to 150C.

After 1 to 2 hours the batch solidified and the moulding could be removed from the mould. It was advantageously heat-treated at 150C for a further 4 hours.

The product was a highly elastic PUR elastomer having the following mechanical properties:

Modulus (100%) (MPa) 10.0 Tensile strength (MPa) 31.0 Elongation at break (%) 580 Resistance to tear propagation (KN/m) 87.9 Elasticity (%) 39 Hardness Shore A 94 ExamPle 3 according to the invention Use of terephthalic acid dichloride 400 g of prepolymer B were heated to 70 to 80C. After addition of 0.2 g (500 ppm) terephthalic acid dichloride, the mixture was stirred for a further 30 minutes. Next, 45.1 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) wasintensively mixed with the prepolymer. The suspension was thoroughly degassed in a water-jet vacuum.

The time for processing the resulting reactive system was at least 6.5 hours at 80C. During this time there was no premature reaction resulting in a considerable increase in the viscosity of the batch.

The liquid reactive system was poured into a preheated mould coated with a separating agent, and heated to 140 to 150C.

After 1 to 2 hours the batch solidified and the moulding could be removed from the mould. It was advantageously heat-treated at 150C for a further 4 hours.

The product was a highly elastic PUR elastomer having the following mechanical properties:

Modulus (100%) (MPa) 11.5 Tensile strength (MPa) 38.9 Elongation at break (~) 570 Resistance to tear propagation (KN/m) 101 35 Elasticity (~) 39 Hardness Shore A 93 ExamPle 3 not according to the invention Use of 200 ppm terephthalic acid dichloride 400 g of prepolymer B were heated to 70 to 80C. After addition of 0.08 g (200 ppm) terephthalic acid dichloride, the mixture was stirred for a further 30 minutes. Next, 45.1 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) wasintensively mixed with the prepolymer. After 10 minutes the batch had thickened so much as a result of a premature reaction that degassing and casting to obtain a high-quality moulded part were impossible.

ExamPle 5 according to the invention Use of 1,250 ppm oleic acid chloride 200 g of prepolymer A were heated to 70 to 80C. After addition of 0.25 g (1250 ppm) oleic acid chloride, the mixture was stirred for a further 30 minutes. Next, 26.3 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) was intensively mixed with the prepolymer. The suspension was thoroughly degassed in a water-jet vacuum.

The time for processing the resulting reactive system was at least 5 hours at 80C. During this time there was no premature reaction resulting in a considerable increase in the viscosity of the batch.

The liquid reactive system was poured into a preheated mould coated with a separating agent, and heated to 140 to 150C.

After 1 to 2 hours the batch solidified and the moulding could be removed from the mould. It was advantageously heat-treated at 150C for a further 4 hours.

The product was a highly elastic PUR elastomer having the following mechanical properties:

Modulus (100%) (MPa) 11.2 Tensile strength (MPa) 37.1 Elongation at break (%) 645 15 Resistance to tear propagation (KN/m) 111 Elasticity (%) 35 Hardness Shore A 95 Example 6 according to the invention Use of 833 ppm sebacic acid dichloride 300 g of prepolymer A were heated to 70 to 80C. After addition of 0.25 g (833 ppm) sebacic acid dichloride, the mixture was stirred for a further 30 minutes. Next, 39.5 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) was intensively mixed with the prepolymer. The suspension was thoroughly degassed in a water-jet vacuum.

The time for processing the resulting reactive system was at least 4 hours at 80C. During this time there was no 21~6fi70 premature reaction resulting in a considerable increase in the viscosity of the batch.

The liquid reactive system was poured into a pr~2heated 5 mould coated with a separating agent, and heated to 140 to 150C.

After 1 to 2 hours the batch solidified and the moulding could be removed from the mould. It was advantageously 10 heat-treated at 150C for a further 4 hours.

The product was a highly elastic PUR elastomer having the following mechanical properties:

Modulus (100%) (MPa) 10.6 Tensile strength (MPa) 33.5 Elongation at break (%) 640 Resistance to tear propagation (KN/m) 99.5 Elasticity (%) 30 Hardness Shore A 94 Example 7 according to the invention Use of 1250 ppm stearic acid dichloride 200 g of prepolymer A were heated to 70 to 80C. After addition of 0.25 g (1250 ppm) stearic acid dichloride, the 30 mixture was stirred for a further 30 minutes. Next, 26.3 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) was intensively mixed with the prepolymer. The suspension was thoroughly degassed in 35 a water-jet vacuum.

21~6670 The time for processing the resulting reactive system was at least 5 hours at 80C. During this time there was no premature reaction resulting in a considerable increase in the viscosity of the batch.

The liquid reactive system was poured into a preheated mould coated with a separating agent, and heated to 140 to 150C.

After 1 to 2 hours the batch solidified and the moulding could be removed from the mould. It was advantageously heat-treated at 150C for a further 4 hours.

The product was a highly elastic PUR elastomer having the following mechanical properties:

Modulus (100%) (MPa) 12.3 Tensile strength (MPa) 45.6 Elongation at break (%) 650 20 Resistance to tear propagation (KN/m) 116 Elasticity (%) 31 Hardness Shore A 94 ExamPle 8 according to the invention Use of 250 ppm phosphorus pentachloride (PCl5) 200 g of prepolymer B were heated to 70 to 80C. After addition of 0.05 g (250 ppm) PCl5, the mixture was stirred for a further 30 minutes. Next, 26.3 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) was intensively mixed with the prepolymer. The suspension was thoroughly degassed in a water-jet vacuum.

21~6670 The time for processing the resulting reactive system was at least 4 hours at 80C. During this time there was no premature reaction resulting in a considerable increase in the viscosity of the batch.

The liquid reactive system was poured into a preheated mould coated with a separating agent, and heated to 140 to 150C.

After 1 to 2 hours the batch solidified and the moulding could be removed from the mould. It was advantageously heat-treated at 150C for a further 4 hours.

The product was a highly elastic PUR elastomer having the following mechanical properties:

Modulus (100%) (MPa) 10.7 Tensile strength (MPa) 25.7 Elongation at break (%) 580 20 Resistance to tear propagation (KN/m) 97.8 Elasticity (%) 34 Hardness Shore A 94 Example 9 according to the invention Use of 2,500 ppm thionyl chloride (SOCl2 200 g of prepolymer A were heated to 70 to 80C. After addition of 0.5 g (2,500 ppm) SOCl2, the mixture was stirred for a further 30 minutes. Next, 26.3 g of 3,3'-diamino-4,4'-dimethyl-diphenyl urea (prepared according to EP 0 374 653 from 2,4-diaminotoluylene and urea, NH number 390 mg KOH/g) was intensively mixed with the prepolymer.

The suspension was thoroughly degassed in a water-jet vacuum.

The time for processing the resulting reactive system was at least 6 hours at 80C. During this time there was no premature reaction resulting in a considerable increase in the viscosity of the batch.

The liquid reactive system was poured into a preheated mould coated with a separating agent, and heated to 140 to 150C.

After 1 to 2 hours the batch solidified and the moulding could be removed from the mould. It was advantageously heat-treated at 150C for a further 4 hours.

The product was a highly elastic PUR elastomer having the following mechanical properties:

Modulus (100%) (MPa) 10.0 Tensile strength (MPa) 28.1 Elongation at break (%) 600 Resistance to tear propagation (KN/m) 98.1 25 Elasticity (%) 30 Hardness Shore A 92

Claims

C L A I M

A method of preparing polyurethane urea elastomers by reacting polyisocyanates and polyester and/or polycarbonate polyol reaction products containing terminal NCO groups and having a molecular weight of 400 to 10,000 with finely divided diamino diphenyl ureas having the general formula in which the NH2 groups are in the meta position relative to the urea group and R1, R2, R3, R4 (which may be the same or different) denote H or C1 - C6-alkyl radicals, characterised in that organic and/or inorganic acid chlorides in a proportion greater than 200 ppm relative to the NCO pre-adduct are added in order to stabilise the reactive mixture of one or both components before premixing.