Treatment of wool

Abstract: A process at present widely used for the treatment of wool to improve its resistance to shrinkage entails subjecting the wool first to an oxidation treatment (eg with chlorine) and then to treatment with an epichlorhydrin resin to supplement the shrink resistance imparted by the oxidation treatment. Resin treatment is accompanied or followed by treatment with a softening agent to soften the harsh handle associated with use of the epichlorhydrin resin. This process generates an aqueous effluent which, through its content of chlorine covalently bound to carbon, is harmful. By the present invention generation of such effluent is avoided, without loss of desirable properties in the finished wool, by using as the "supplementary treatment resin" a colloidal melamine resin, with a silicone polymer as softening agent.

Description: This invention relates to the treatment of wool, and is particularly concerned with a process for improving its resistance to shrinkage. A process very widely used for this purpose entails subjecting the wool to an oxidation treatment, usually a chlorination, as with free chlorine or a hypochlorite or dichloroisocyanurate salt; removing unreacted (and potentially very damaging) oxidising agent from the wool fibres, as by passage through a reducing medium such as sodium sulphite solution, followed by a water rinse; and then treating the wool with a synthetic resin to impart a resistance to shrinkage which supplements that given by the oxidation treatment. Usually thereafter, but sometimes simultaneously with the resin treatment, the wool is treated with a softening agent to soften the harsh handle which it would otherwise have as a result of the resin treatment; and in due course the treated wool is dried evenly at a moderate raised temperature to ensure that adequate curing of the resin has taken place. The process just outlined can be applied to the treatment of wool tops (ie wool fibre before it is spun) as well as to the treatment of yarn and of woollen piece goods and garments. Probably the resins most used in the process are those obtained by reaction of epichlorhydrin (a compound having a reactive epoxy group attached to the radical -CH₂C1) with a polyamide whose repeating unit contains basic -NH- or -NH₂ groups, as distinct from the non-basic -NH- groups of the amide linkage -CO.NH-. Such a resin is for example that obtained by the reaction of epichlorhydrin with the condensation product of a polyalkylene amine, eg diethylene triamine (H₂NCH₂CH₂NHCH₂CH₂NH₂) and adipic acid (HO₂C.CH₂CH₂CH₂CH₂CO₂H). Not all such resin is exhausted onto the wool from whatever medium the epichlorhydrin resin is applied, and there is now strong evidence that the resin-containing aqueous effluent from the proceed is harmful because of the presence in it of chlorine covalently bound to carbon, as in the -CH₂Cl group. We have found that a treated wool product can be obtained with properties just as good as those that result when an epichlorhydrin resin is employed, by using a colloidal melamine resin as the resin to impart resistance to shrinkage. Colloidal melamine resins are used in the treatment of paper to improve its wet strength, and are obtained by dissolving a partially condensed melamine formaldehyde resin in an acid such as hydrochloric, formic, acetic or lactic acid under controlled conditions, and further diluting with water. The solution becomes infinitely miscible with water, and on ageing develops a bluish haze. The solution contains positively charged colloidal particles of the melamine resin. Such resins have also been used, in conjunction with a non-ionic silicone elastomer, in the treatment of silk, to improve crease resistance and stability to washing, as disclosed in GB-A-2217741-A. According to the invention, there is provided a process for the treatment of wool to improve its resistance to shrinkage, by subjecting it first to an oxidation treatment and then to a colloidal melamine resin treatment to supplement the shrink resistance imparted by the oxidation treatment, the resin treatment being accompanied or followed by treatment with a softening agent to soften the harsh handle associated with use of the resin, in which process the softening agent employed is a silicone polymer. Preferably, the silicone polymer is dispersed in the colloidal melamine resin,ie in the aqueous phase which constitutes the dispersion medium of that system. There is described in EP-A-80272 a process for the shrink-resist treatment of wool, by a chlorinating the wool with an acidified hypochlorite b removing excess chlorinating agent from the wool c applying to the acidified wool an acid colloid solution of a methylol melamine resin, which solution may contain a suitable softening agent, such as for example those of the polyethylene type. EP-A-80272 is not, however, concerned to avoid effluent problems arising from the presence of -CH₂Cl or like groups in the resin conventionally used for wool treatment; nor does it mention the use of a silicone polymer as softening agent, a use which we have found has the advantage over polyethylene softeners of producing in the wool better stabilisation against shrinkage and better non-felting properties during washing. The silicone polymer employed as softening agent may be cationic, but is preferably non-ionic. In general the silicone polymer used shows no chemical reactivity towards the colloidal melamine resin. The melamine resin employed is preferably one which has at least two -CH₂OR groups per melamine nucleus, where R = H or is an alkyl group containing from one to four carbon atoms. The invention is further illustrated by the following Examples. Example 1 An acidic melamine resin solution was produced by mixing the following ingredients in the following proportions by weight. Aqueous solution (80% reactive solids; pH at 1:1 H₂O dilution=8.5) of partially condensed melamine formaldehyde resin available as BEETLE® 336 10kg Concentrated hydrochloric acid (specific gravity=1.16) 1kg Water at 40° C 36kg The mixture was allowed to stand for 2 hours to develop colloidal properties, and was then diluted with an equal volume of water to give a colloidal melamine resin having a shelf life of more than 6 months. The diluted composition (1 part by weight) was further diluted with water (4 parts) and to this mixture was added an aqueous emulsion of a non-ionic polydimethylsiloxane (0.5 parts by weight; silicone content 35% by weight). (The silicone release agent sold by Basildon Chemicals under the designation BC330 is very suitable.) The mixed melamine resin/silicone polymer composition was then applied, from a bath adjusted with acetic acid to pH 5-6, to knitted wool garments which had been conventionally chlorinated with a dichloroisocyanurate salt, treated with antichlor, and rinsed.The bath temperature was slowly raised from ambient to 40° C during 10 minutes, and held at that temperature for a further 10 minutes to exhaust the melamine resin and silicone polymer onto the wool. Weight gain was about 1.5% by dry weight of the wool.The material was then removed from the bath, hydroextracted and tumble-dried at 60-80° C. Example 2 For the treatment of wool tops the procedure of Example 1 was modified as follows. The mixed melamine resin/silicone polymer was applied in the 4th bowl of a conventional 5-bowl unit to deposit about 1.5% of solid mixture onto the tops. The treated tops were then passed to the 5th bowl, in which a cationic substituted stearamide had been included as additional softener. The tops were finally dried at 70-80° C.

Claims: A process for the treatment of wool to improve its resistance to shrinkage, by subjecting it first to an oxidation treatment and then to a colloidal melamine resin treatment to supplement the shrink resistance imparted by the oxidation treatment, the resin treatment being accompanied or followed by treatment with a softening agent to soften the harsh handle associated with use of the resin, characterised in that the softening agent is a silicone polymer. A process according to claim 1, in which the silicone polymer is dispersed in the colloidal melamine resin. A process according to claim 1 or 2, in which the silicone polymer is non-ionic. A process according to claim 3, in which the silicone polymer is a polydimethylsiloxane. A process according to any of claims 1 to 4, in which the melamine resin has at least two -CH₂OR groups per melamine nucleus, where R = H or C₁₋₄ alkyl. A process according to any of claims 1 to 5, in which the oxidation treatment is a chlorination. A process according to claim 6, in which the chlorination utilises a dichloroisocyanurate salt. A process according to any of claims 1 to 7, applied to the treatment of wool tops. A process according to any of claims 1 to 7, applied to the treatment of knitted wool garments.

Inventors: HEYWOOD DEREK WALLWORK, HEYWOOD, DEREK WALLWORK
Applicants: BIP CHEMICALS LTD, BIP CHEMICALS LIMITED
Application year: 1991
Main classification: D06M15
IPC codes: D06M15