GB1592572A - Process for preparing curable amphoteric polymers - Google Patents

Description

(54) PROCESS FOR PREPARING CURABLE AMPHOTERIC POLYMERS (71) We, I.W.S. NOMINEE COMPANY LIMITED, a British Company, of Wool House, Carlton Gardens, London, S.W.1., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to curable polymers having both anionic and cationic groups in their molecule, and to an improved process for their preparation.

In our copending Application No. 9467/75 (Serial No. 1547958) we have described amphoteric polymeric compounds comprising at least one polymeric chain and having both anionic and cationic groups, the compounds containing per molecule at least two groups capable of undergoing a cross-linking reaction, either directly or by means of a cross-linking agent.

One group of polymeric compounds described in the said Application contains cationic groups in the form of protonated amino groups and anionic groups which either, like the protonated amino groups, are cross-linkable under alkaline curing conditions, for example bisulphite-blocked isocyanate (carbamoylsulphonate) groups or thiol groups (which are weakly ionised in alkaline solution) or are not cross-linkable, for example carboxyl groups, but accompanied by cross-linkable groups such as thiol groups.

Preferred polymers contain protonated amino groups and bisulphite-blocked isocyanate groups and can be prepared from isocyanate-terminated polymers by the reaction sequence shown schematically as follows:

where R is the remainder of the polymeric molecule.

Other cross-linkable amphoteric polymers can be prepared from polymers with functional terminal groups by reaction with an organic di-isocyanate of which a proportion of the isocyanate groups have been converted to protonated amino groups by the reaction (1) above, where R is a divalent organic radical.

For reaction (1) a mineral acid is employed in the aforementioned Application, with which must be present the amount of water necessary to form the H30+ ion which is the effective agent. It is undesirable, however, for excess water to be present since this could lead to unwanted side reactions and reduce the cross-linking activity of the product of reaction (2).

According to the present invention, a process of preparing a curable polymeric compound, comprising at least one polymeric chain, cationic protonated amino groups and anionic groups in the molecule and containing at least two cross-linkable groups per molecule, comprises: partially hydrolysing an organic di- or poly-isocyanate compound to form cationic protonated amino groups by means of a strong organic acid (as herein defined) in an organic medium containing the amount of water necessary for the partial hydrolysis; and reacting the residual isocyanate groups with a further compound to introduce the remaining groups of the curable compound including anionic groups, either the isocyanate or the further compound including the said polymeric chain.

The preferred embodiment of the invention is the preparation of a polymeric compound containing cationic protonated amino and anionic carbamoyl sulphonate groups from a polymeric compound containing isocyanate groups in which the isocyanate compound is first partially hydrolysed by the acid and the resulting intermediate compound is reacted with a bisulphite to convert the remaining isocyanate groups into the bisulphite adduct.

By a "strong acid" is here meant an acid capable of bringing about hydrolysis of the isocyanate groups to protonated amino groups, and the suitability of an acid can readily be determined by simple trial.

The organic acids are preferably other than carboxylic acids. Carboxyl groups are undesirable in an acid employed for this purpose since they can react directly with isocyanate groups.

It has further been found that particularly good and reproducible results are obtained if the acid hydrolysis of reaction (1) is carried out by means of a stoichiometric hydrate of the acid, i.e. a hydrate in which the water bears a fixed stoichiometric relationship to the acid.

Such hydrates are available in crystalline solid form, whereby exact quantities can easily be weighed and already contain the stoichiometrically exact requirement of water.

Monohydrates of monobasic organic acids forming readily characterized crystalline solids are preferred, more especially the monohydrate of 4-toluenesulphonic acid, but other crystalline monohydrates of strong organic acids behave similarly.

Where the organic acid does not form a crystalline hydrate it is necessary to include the appropriate amount of water to achieve the hydrolysis reaction.

An example of such an acid is methanesulphonic acid (MSA). When used with one mole of added water per mole of MSA (equivalent to 84% acid by weight) one mole of hydroxonium ion is formed and one mole of isocyanate is converted to one mole protonated primary amine. Other organic sulphonic acids found to give satisfactory results are 2- and 3-toluenesulphonic acids.

Suitable solvents for the acid hydrolysis reaction are those which are relatively inert towards both isocyanate groups and the acids employed, for example ethyl acetate, acetone or dioxan. Where the stoichiometric quantity of water is supplied by the acid hydrate it is preferred that the solvent be substantially anhydrous.

The preferred polymeric compounds are amphoteric because they contain both protonated amino groups, which are cationic under neutral to acid conditions, and bisulphite blocked isocyanate groups, which are anionic. Experiments have shown that compounds of this type, which can be prepared from commercially available polyisocyanate shrink-resist resins, exhaust readily on to keratin fibres over a wide range of pH values.

If exhaustion is carried out below pH 6 then cross-linking in the bath does not occur since the bisulphite blocked isocyanate groups are stable under acid conditions. Cross-linking of the absorbed resin can be brought about by increasing the pH of the bath. Desorption of the resin does not occur under the alkaline conditions required for crossing-linking. A further advantage is that if a dyestuff is exhausted on to the wool at the same time as the resin, then the latter acts in a similar manner to conventional amphoteric dyeing auxiliaries and promotes level, non-skittery dyeings.

The ratio of cationic to anionic groups can be varied at will simply by altering the amount of acid used to promote the reaction shown in equation (1). It is assumed that all the free isocyanate groups remaining after this stage react in the second stage, for example according to equation (2). There is in fact an optimum ratio of cationic to anionic groups which produces both good exhaustion and excellent shrink-resistance and this is found to be about 60:40. However, if the ratio of protonated amino groups is increased, optimum cross-linking may be restored by adding formaldehyde, or a formaldehyde source, to the bath.

It has been found that the effectiveness of amphoteric compounds according to this invention in preventing shrinkage of wool textiles in washing varies with the ratio of cationic:anionic groups in the polymer. It is preferred that this ratio should lie in the range from 45:55 to 65:35, the most preferred ratio being about 60:40. Below 40% of cationic groups exhaustion is substantially reduced while above 70% cationic groups the polymer does not spread as readily on unchlorinated wool to form the film necessary for effective shrink-resistance.

The preferred polymeric chains in the compounds of this invention are polyether, polyester, polyamide or polyurethane chains, but polyether chains are especially preferred.

They may readily be produced by condensation of alkylene oxides and a variety of prepolymers containing such chains, and terminated by hydroxyl groups or by reactive groups such as thiol or isocyanate, are commercially available and may be used as starting materials in the preparation of the curable compounds of this invention.

Examples of polyether chains which may appear in compounds of the invention include: polyoxyethylene, polyoxypropylene and, because of their excellent light stability, especially polytetramethylene oxide chains. The term 'polyether' is also intended to include polythioethers, such as condensation products of thiodiglycol. Examples of polyester chains include polyester chains produced by reacting dicarboxylic acids, such as adipic acid, malic acid, terephthalic acid, sebacic acid, malonic acid and itaconic acid, with diols such as hexanediol, ethylene glycol or diols of the type OH-(CmH2mO)n-H where m is 2 to 12 and n is 2 to 50.

Polyamide chains which may be present include, for example, polyhexamethylene adipamide and polycaprolactam chains, and also chains of the type: HOOC(CH,)CO[NH( CH,),NH(CH,),NHCO( CH,),CO].NH(CH2),NH (CH2)2NH2 Polyurethane chains which may be employed include, for example, those formed by the reaction of diisocyanates such as hexamethylene diisocyanate (HMDI) or toluene diisocyanate (TDI) with a diol such as those listed above.

The preferred compounds of the invention form particularly effective shrink-resist resins for keratinous fibres. Keratinous fibres which may be treated include cashmere, vicuna, mohair, hair, llama and especially wool. The fibres may be treated as loose stock, tops, slubbings, yarns or fabrics, woven, non-woven or knitted.

A further advantage of these resins lies in their ability to impart a smooth drying finish to fabrics. Thus, it is possible to produce permanent press fabrics by an exhaust rather than a padding technique.

The treatment may be carried out in conventional textile machine and it is an advantage of the compounds of the invention that they will exhaust on to wool from long liquor baths without the necessity for oxidative pretreatment of the wool, such as chlorination.

Furthermore, the preferred compounds which are applied under acid conditions can be applied in the dye bath either before, after or simultaneously with dyeing, when they have the advantage that they promote level dyeing. In the latter case it may not be necessary to use a conventional dye levelling agent.

Once exhausted on to the wool, the prepolymer may be cross-linked to complete the formation of the resin product. Curing can be brought about by dry heat or by raising the pH of the bath to a value above pH 7.5. Curing in an alkaline bath occurs at any temperature. Particularly useful conditions are 10 minutes at 70"C and pH 8.5, since this is often used for the after-treatment of some classes of reactive dye. Curing by dry heat, which may be used for example with thiol groups, can be combined with drying of the treated fibres after removal from the exhaustion bath.

Further details of the structure, application and curing of these compounds and suggested mechanisms therefor can be obtained from the specification of our aforementioned Application No. 9467/75 Serial No. 1547958.

The following are typical examples of the preparation and use of polymeric compounds in accordance with the present invention.

EXAMPLE I 1. Preparation The first step involves hydrolysis with toluene 4-sulphonic acid monohydrate (TSA) of a proportion of the isocyanate groups of the trifunctional isocyanate Synthappret LKF prepared from a 3000 M.W. polyether triol and HMDI to form protonated amino groups.

The second step involves blocking of the remaining isocyanate groups with sodium metabisulphite.

i) Preparation of polymer containing cationic groupings.

Synthappret LKF (100 g. of 100%) was dissolved in ethyl acetate (25 g). To this was added a solution of TSA (8.3 g.). The mixture was stirred for 45 min. and then iso-propanol (IPA, 125 g.) was added. To this solution was added sodium metabisulphite (9 g.) and sodium bicarbonate (3 g.) dissolved in water (60 g.). Stirring was continued until the isocyanate peak had disappeared from the infrared spectrum (20 - 30 min.). The mixture was brought to pH 2-3 by the addition of hydrochloric acid (ca 10 g.) and diluted to 25% resin solids by the addition of 50:50 IPA/water.

Analysis of the product prepared above showed that 44% of the NCO groups had been blocked by sodium bisulphite, thus giving 56% cationic groups by difference. This product is designated APS 56.

ii) Preparation of polymer containing about 60% cationic groups.

The method as used to prepare a 55% cationic polymer was employed except that 9.0 g.

of TSA was used instead of 8.3g.

Analysis of the product showed that it contained 37% anionic groups and thus 63% cationic groups by difference. This product is designated APS 63.

Other products can be obtained by suitably varying the amount of TSA used.

2. Methods of Application The polymer can be applied with either a wetting agent, such as sodium dioctyl sulphosuccinate (Aerosol OT - Trade Mark) or sodium lauryl sulphate (SLS), and with or without an assistant such as methyl cellulose. Inclusion of methyl cellulose in the exhaust bath enables a larger pH range to be employed without drastically affecting the time to complete exhaustion of the polymer.

Use of SLS instead of Aerosol OT, leaves the treated wool with a more acceptable hand.

i) Without Methyl Cellulose Wet out the goods and set the bath with acetic acid to pH 4 - 4.3 at 60 - 65 "C. Mix the polymer resin (3% owf i.e. on the weight of fibre) with 33% of its own weight of SLS solids.

(The SLS is best kept as a 10% solids solution. Slowly add to this warm water (40"C) to dilute until a clear solution is obtained. This dispersion is then added to the bath. The temperature of the bath is held at 600C until the bath is clear (20 - 30 min.). After a further 10 min. at this temperature sodium carbonate is added and the pH is slowly raised to pH 9.

The bath is then held for 10 min. at these conditions. The goods are then moved, hydro-extracted and dried.

ii) With Methyl Cellulose Wet out the goods and set the bath with either formic or acetic acid to H 3.0 - 5.0 at 60 65"C. Mix the polymer with 33% of its own weight of SLS solids and 1% of its own weight methyl cellulose mol. wt 10000 (Celacol - Trade Mark) solids. This mixture is then diluted with warm water and the procedure set out in (i) is then followed.

3. Wash Test Results The felting shrinkage of treated samples was determined by the IWS TM 185 test method in an International Cubex Felting machine containing 15 litres of wash liquor.

Table I sets out the results obtained with single jersey wool fabric.

TABLE I Treatment Details Area Shrinkage (%) 1 hr 3 hr Wash Wash 3% APS 56 + SLS (33% owp*) pH 4.1 1.0 0 3% APS 56 + SLS 33% owp) + Celacol 1% owp) pH 3.0 2.5 2.5 3% APS 56 + SLS 33% owp + Celacol 1% owp pH 4.0 1.5 1.8 3% APS 56 + SLS 33% owp + Celacol 1% owp pH 5.0 2.0 5.0 * owp = on weight of polymer The results in Table II have been obtained on a wool serge fabric.

TABLE II Treatment Details Area Shrinkage (%) 1 hr 3 hr Wash Wash 2.5% APS 63 + SLS (33%) + Celacol (1%) pH 3.5 1.0 2.0 Example 11 A curable polymer comprising polyether chains, protonated amino groups and thiol groups (which are somewhat ionized in alkaline solution, as explained in No. 1547958) can be prepared by reaction of thiol-terminated derivative of a polyether triol with a partially hydrolysed di-isocyanate according to Example XXII of Application No. 9467/75, (Serial No. 1547958) the stoichiometrically equivalent quantity of TSA being substituted for the sulphuric acid in the earlier Application.

Example III A curable polymer comprising a polyester/polyether backbone, protonated amino and carboxyl groups and cross-linkable thiol groups can be made by reaction of the esterification product of a polyoxy-alkylene diol and 2-mercaptosuccinic acid with a partially hydrolysed di-isocyanate according to the last example, (Example XXIII of Application No. 9467/75) (Serial No. 1547958) using TSA instead of sulphuric acid for hydrolysis of the isocyanate.

Example IV Synthappret LKF (Baker) (220 g of 80% solution in perchloroethylene) was diluted with ethyl acetate (60 g). To this was added a solution of toluene-4-sulphonic acid monohydrate (14.6 g) in dried dioxan (14.6 g). The mixture was stirred rapidly for 60 min. after which iso-propanol (225 g) was added. Stirring was continued during the addition of a solution of sodium metabisulphite (16 g) and sodium sulphite (1.6 g) in water (100 g). It is essential at this stage to maintain a homogeneous solution by the addition of small amounts of iso-propanol and/or water. The pH of the solution should be between 5 and 6 (obtained by the addition, if necessary, of an aqueous solution of sodium bicarbonate). Stirring was continued until the infra-red spectrum showed the disappearance of the characteristic isocyanate peak. The product was stabilised by the addition of a mineral acid, such as hydrochloric, to give a pH of between 2 and 3.

The final product was a clear solution with a polymer solids content of approximately 25-27%. Titration by the previously published procedure (J.A. Rippon and M.A.

Rushforth, Textilveredlung, 11, (1976), 224) showed the percentage of the original isocyanate content converted to anionic carbamoyl sulphonate groups to be 40%.

(Theoretical- 45%).

Example V The procedure of Example IV is repeated except that the toluene-4-sulphonic acid monohydrate was dispersed in hot ethyl acetate (50 gl instead of dioxan. This mixture was cooled at 200C before being added to the polyisocyanate solution.

Example VI Synthappret LKF (220 g of 80% solution in perchloroethylene) was diluted with ethyl acetate (60 g). To this was added with stirring a solution of methane sulphonic (7.43 g) in water (1.39 g) (i.e. 84% w/w acid). Stirring was continued for 60 min. after which iso-propanol (225 g) was added followed by a solution of sodium metabisulphite (16 g) and sodium sulphite (1.6 g) in water (100 g). A homogeneous solution was maintained by the addition, where necessary, of either water or iso-propanol. The pH of the solution was adjusted to 5-6 by the addition of an aqueous solution of sodium bicarbonate. After the free isocyanate groups had reacted the product was stabilised as in Example IV.

Example VII A sample of all-wool single jersey fabric (10 g) was wet-out at a temperature of 65"C in 400 g of softened water contaning 1 g/l acetic acid. The product from Example IV (1.2 g) was mixed with a 10% solution of Aerosol OT75 (Cyanamid) in isopropanol (1.32 g) and the mixture diluted to 25 ml with water at 600C. This dispersion was added to the bath containing the wool which was stirred while the temperature was held at 60-650C. The cloudiness of the bath increased initially and then decreased until, after 30 min., it was water-clear, indicating complete exhaustion of the polymer. To cure the polymer on the fabric a solution of sodium carbonate was added to the exhausted liquor until the pH was between 8.5 and 9.0. The temperature was then raised to 700C where it was held for 10-15 min. The sample was removed, hydro-extracted and dried for 30 min. at 1000C in a forced draught oven. After steaming for 1 min. at 100"C the sample was tested for felting shrinkage according to IWS Test Method 185. After washing for 3 hours the area felting shrinkage was less than 4%.

WHAT WE CLAIM IS: 1. A process of preparing a curable polymeric compound comprising at least one polymeric chain, cationic protonated amino groups and anionic groups in the molecule and containing at least two cross-linkable groups per molecule, which process comprises: partially hydrolysing an organic di- or poly-isocyanate compound to form cationic protonated amino groups by means of a strong organic acid (as herein defined) in an organic medium containing the amount of water necessary for the partial hydrolysis; and reacting the residual isocyanate groups with a further compound to introduce the remaining groups of the curable compound including anionic groups, either the isocyanate or the further compound including the said polymeric chain.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. Example III A curable polymer comprising a polyester/polyether backbone, protonated amino and carboxyl groups and cross-linkable thiol groups can be made by reaction of the esterification product of a polyoxy-alkylene diol and 2-mercaptosuccinic acid with a partially hydrolysed di-isocyanate according to the last example, (Example XXIII of Application No. 9467/75) (Serial No. 1547958) using TSA instead of sulphuric acid for hydrolysis of the isocyanate. Example IV Synthappret LKF (Baker) (220 g of 80% solution in perchloroethylene) was diluted with ethyl acetate (60 g). To this was added a solution of toluene-4-sulphonic acid monohydrate (14.6 g) in dried dioxan (14.6 g). The mixture was stirred rapidly for 60 min. after which iso-propanol (225 g) was added. Stirring was continued during the addition of a solution of sodium metabisulphite (16 g) and sodium sulphite (1.6 g) in water (100 g). It is essential at this stage to maintain a homogeneous solution by the addition of small amounts of iso-propanol and/or water. The pH of the solution should be between 5 and 6 (obtained by the addition, if necessary, of an aqueous solution of sodium bicarbonate). Stirring was continued until the infra-red spectrum showed the disappearance of the characteristic isocyanate peak. The product was stabilised by the addition of a mineral acid, such as hydrochloric, to give a pH of between 2 and 3. The final product was a clear solution with a polymer solids content of approximately 25-27%. Titration by the previously published procedure (J.A. Rippon and M.A. Rushforth, Textilveredlung, 11, (1976), 224) showed the percentage of the original isocyanate content converted to anionic carbamoyl sulphonate groups to be 40%. (Theoretical- 45%). Example V The procedure of Example IV is repeated except that the toluene-4-sulphonic acid monohydrate was dispersed in hot ethyl acetate (50 gl instead of dioxan. This mixture was cooled at 200C before being added to the polyisocyanate solution. Example VI Synthappret LKF (220 g of 80% solution in perchloroethylene) was diluted with ethyl acetate (60 g). To this was added with stirring a solution of methane sulphonic (7.43 g) in water (1.39 g) (i.e. 84% w/w acid). Stirring was continued for 60 min. after which iso-propanol (225 g) was added followed by a solution of sodium metabisulphite (16 g) and sodium sulphite (1.6 g) in water (100 g). A homogeneous solution was maintained by the addition, where necessary, of either water or iso-propanol. The pH of the solution was adjusted to 5-6 by the addition of an aqueous solution of sodium bicarbonate. After the free isocyanate groups had reacted the product was stabilised as in Example IV. Example VII A sample of all-wool single jersey fabric (10 g) was wet-out at a temperature of 65"C in 400 g of softened water contaning 1 g/l acetic acid. The product from Example IV (1.2 g) was mixed with a 10% solution of Aerosol OT75 (Cyanamid) in isopropanol (1.32 g) and the mixture diluted to 25 ml with water at 600C. This dispersion was added to the bath containing the wool which was stirred while the temperature was held at 60-650C. The cloudiness of the bath increased initially and then decreased until, after 30 min., it was water-clear, indicating complete exhaustion of the polymer. To cure the polymer on the fabric a solution of sodium carbonate was added to the exhausted liquor until the pH was between 8.5 and 9.0. The temperature was then raised to 700C where it was held for 10-15 min. The sample was removed, hydro-extracted and dried for 30 min. at 1000C in a forced draught oven. After steaming for 1 min. at 100"C the sample was tested for felting shrinkage according to IWS Test Method 185. After washing for 3 hours the area felting shrinkage was less than 4%. WHAT WE CLAIM IS:

1. A process of preparing a curable polymeric compound comprising at least one polymeric chain, cationic protonated amino groups and anionic groups in the molecule and containing at least two cross-linkable groups per molecule, which process comprises: partially hydrolysing an organic di- or poly-isocyanate compound to form cationic protonated amino groups by means of a strong organic acid (as herein defined) in an organic medium containing the amount of water necessary for the partial hydrolysis; and reacting the residual isocyanate groups with a further compound to introduce the remaining groups of the curable compound including anionic groups, either the isocyanate or the further compound including the said polymeric chain.

2. A process according to claim 1 in which a polymeric compound containing isocyanate

groups is first partially hydrolysed by the organic acid and water in the organic medium and the resulting intermediate compound is reacted with a bisulphite to convert the remaining isocyanate groups into the bisulphite adduct.

3. A process according to claim 1 or 2 wherein the organic acid is free from carboxyl groups.

4. A process according to claim 3 wherein the organic acid is an organic sulphonic acid.

5. A process according to any preceding claim wherein the organic acid employed is a stoichiometric hydrate of a strong organic acid in which the acid is combined with the exact quantity of water for the hydrolysis reaction.

6. A process according to claim 5 wherein the acid hydrate is an organic monosulphonic acid monohydrate.

7. A process according to claim 5 wherein the acid hydrate is toluene 4-sulphonic acid monohydrate.

8. A polymeric compound prepared by a process according to any preceding claim.

9. A keratinous textile fabric containing the cured product of a polymeric compound according to claim 8.