GB2174424A - Treatment of keratinous materials - Google Patents

Abstract

Untreated scaly fibrous keratinous materials namely wool, when wetted, on average slide towards the fibre roots, manifesting itself as shrinkage of fabric made from wool. In order to ameliorate or overcome shrinking and particularly felting shrinkage, the wool is treated with an effective amount of an oxidant, namely peroxyphthalic acid or its salt, in an aqueous liquor followed by a sulphite reduction. It is especially preferable to use as oxidant magnesium monoperoxyphthalate at a pH of 3 to 5 and in an amount providing 0.3 to 0.5% peracid active oxygen on weight of wool. The subsequent sulphite reduction preferably employs at least 2% by weight reductant, e.g. sodium metabisulphite, and preferably at pH 5 to 9.

Description

SPECIFICATION Treatment of keratinous materials The present invention relates to the treatment of keratinous materials and more particularly to the treatment of materials consisting wholly or partly of scaly fibres, namely wool.

Individual fibres of wool move during laundering or other wet treatments causing felting.

Although wool scientists disagree about the detailed mechanism of felting, there is a general consensus that felting occurs because wool and other hair fibres are scaly, producing a ratchetlike profile, as a consequence of which the frictional coefficient of the fibre is higher in the tipto-root direction than in the root-to-tip direction. This is known as the directional frictional effect or DFE. Accordingly it requires less force for the tip to slide towards the root than for the fibre to straighten out again. This manifests itself as shrinkage of fabric made from these fibres during wet treatments. This change is normally referred to as felting shrinkage so as not to be confused with any shrinkage caused by the release of tension from the wool which is termed relaxation shrinkage.Any significant shrinkage of woollen items is usually extremely inconvenient and may render that item unfit for its purpose, and the requirement to keep woollen items under tension during cleansing or other operations is exceedingly inconvenient. Accordingly, for many uses, it is necessary to ameliorate the propensity of wool to shrink.

In view of the foregoing, it has been common practice to seek to reduce felting shrinkage by reducing the differential effect of the scales of the wool. One common method employs an oxidising agent to degrade the proteinacious scales. Hitherto, the most widely used oxidising agent has been chlorine, but in view of the toxic nature of chlorine fumes, and the increased awareness of the need to protect workers from the effects of noxious chemicals, it is becoming increasingly necessary to employ ever more complicated and hence expensive precautions and apparatus to prevent the emission of chlorination fumes. In addition, there is a pronounced tendency for chlorine to impart a deep yellowing to the wool during chlorine treatment.For similar reasons of safety, similar increased precautions and modified apparatus would be needed for proofing carried out in non-aqueous solvents such as chlorinated hydrocarbons. It would therefore be advantageous if an alternative oxidative system could be employed in order to ameliorate either or both of the foregoing disadvantages.

One alternative class of oxidants comprises organic peroxyacids, and their use in connection with shrink-proofing wool was described in British Patent Specification 656938 (Wolsey Limited).

The specification asserted that excellent shrink resistance could be obtained using a treatment with any alkyl, aryl, or substituted alkyl or aryl peroxyacid. When the examples of the specification are reviewed, the best result using the process employed a single-stage contact of the wool with about its own weight of the peroxycarboxylic acid. The most effective peroxyacid shown was peroxyacetic acid, the higher molecular weight peroxycarboxylic acids showing less capability of imparting shrink-proofing to wool.Particularly on a continuous treatment of wool, it would be difficult to maintain sufficiently concentrated solutions of, for example, peroxyacetic acid, to enable the wool to take up its own weight of oxidant and in any event, such a consumption is commercially impractical so that it is necessary to investigate whether similar shrink-proofing can be obtained with markedly reduced oxidant consumption.

In the course of the investigations leading to the instant invention, it was found that if a certain class of peroxycarboxylic acids is employed as oxidant in aqueous conditions, wool shrink-proofing can be achieved with a markedly reduced consumption of oxidant, provided that a subsequent reduction stage is employed. When such a technique was employed using the corresponding reduced amount of peroxyacetic acid though, the wool samples were not rendered shrink resistant irrespective of whether the oxidation step was followed by a reduction stage, or not.Accordingly, it is apparent that there is disparity between the various sub-classes of peroxycarboxylic acids in the context of shrink-proofing wool in aqueous conditions and the assertion in USP 3634020 that peracetic acid is ideal applies solely to its use in halogenated hydrocarbon organic solvents and not to water based processes.

According to the present invention, there is provided a process for shrink-proofing wool in which woollen fibre is brought into contact with an aqueous liquor containing an effective amount of peroxyphthalic acid or salt thereof, and thereafter brought into contact with a sulphite reducing agent.

With respect to the oxidation step, it is especially desirable to employ magnesium monoperoxyphthalate as the source of the monoperoxyphthalic acid in solution because it is a safe, readily storable and rapidly soluble crystalline hexahydrate solid salt. Advantageously, magnesium monoperoxyphthalate (MMPP) can be stored readily at ambient temperatures without enduring an excessive rate of loss of active oxygen, thereby avoiding the need for refridgerated storage that would be necessary for various other peroxyacid species and furthermore, by virtue of its inherent insensitivity towards impact or thermal shock, it is a solid material ideally adapted to bulk or containerised handling and transportation. Its use also avoids the acrid smell associated with concentrated solutions of peroxyacetic acid as would be required to operate the Wolsey process.

The amount of monoperoxyphthalic acid (MPPA) salts thereof to employ corresponds preferably to use of at least 0.2% by weight of peracid-active oxygen on weight of wool. The peracid active oxygen of any solid can be determined readily by the standard titration technique employing iodide and titration against thiosulphate. MMPP, as supplied by Interox Chemicals Limited or its associated companies typically has a peracid active oxygen content of about 5 to 6% w/w so that the active oxygen amount of 0.2% w/w corresponds to an MMPP usage of about 3% w/w on the wool.Whilst it is possible to employ higher concentrations of oxidant, if desired, it has been found unnecessary to exceed an addition of MPPA or salts thereof corresponding to more than 1% active oxygen on weight of wool in view of the fact that amounts of selected oxidant providing below 1% active oxygen on weight of wool have markedly reduced the felting shrinkage of the wool and in many instances brought it to zero or near zero. It is preferable to employ addition of at least 0.25% w/w active oxygen on weight of wool and in many instances the addition is selected within the range of 0.3% w/w oxygen to 0.5% w/w active oxygen.

However, and advantageously, it is a feature of the instant invention that a similar resistance to felting shrinkage can be attained over a relatively wide range in additions of the selected oxidant to the wool. Accordingly, such tolerance by the system to changes in oxidant concentration means that the solution does not require constant monitoring and the inevitable slow decomposition of the oxidant in the shrink-proofing bath causes little change in the shrink-proofing effectiveness during the working day.

The oxidation step can be carried out in acidic or mildly alkaline conditions, such as from pH 2 to pH 8. It is most convenient, however, to select a pH in the range of pH 3 to pH 5 in that such a pH can often be attained by the simple dissolution of the oxidant in water, thereby avoiding the need for any pH adjustment chemicals in this step The oxidising step of the shrink-proofing process according to this present invention can be carried out at any temperature at which the oxidant can be applied to the wool in the form of a solution. Thus, under normal ambient pressure conditions, the temperature range is normally from 5 to about 100 C. However, excellent results can be obtained using an ambient temperature bath, or a bath whose temperature is regulated by the temperature of the wool feed from a preceeding treatment.Accordingly the treatment temperature is often within the range of 15 to 50"C. Whilst it is possible to carry out the invention process batch-wise, if desired, by immersing the wool in a relatively dilute solution of the oxidant for a sufficient length of time for the wool to come into contact with the greater part of the active ingredient, followed by separation of the wool from the solution and the discarding of it or its restoration to its initial oxidant concentration, the invention process is well suited to continuous operation employing a somewhat more concentrated solution of the oxidant through which the wool is passed at a predetermined rate so that it takes up the solution and is permitted to retain a desired proportion of liquor. Such liquor retention is often selected in the range of from 70 to 200% w/w of the wool and preferably 80 to 120% w/w.In practice, this means that the concentration of oxidant in the bath in a continuous process is often selected in the range of from 30 to 100 grams per litre of oxidant which in conjunction with a suitably selected liquor retention can result in the retention of oxidant by the wool within the active oxygen ranges given earlier herein.

The second step in the invention process is the subsequent reduction of the oxidised wool with a sulphite reductant. Most coveniently, it has been found that the sulphite addition can be made either in the same bath as the oxidant or in a separate bath. The sulphite reduction step is carried out in mildly acid or alkaline conditions, preferably at a pH of at least pH 4. A convenient range for this step is from pH 5 to pH 9, which can be obtained by introduction of alkali metal, coveniently sodium, salts such as sodium carbonate or bicarbonate or sodium hydroxide. If desired, such pH control can be effected automatically by feeding an alkali solution through a control valve governed by a pH stat. The pH of this step is in many instances and indeed normally higher than in the oxidation step.

The amount of sulphite reducing agent to employ preferably corresponds to an addition of at least 2% reducing agent on weight of oxidised wool. Conveniently, the amount of reducing agent is often selected in the region of 2.5% to 15% by weight added on weight of wool. By the use of such an amount of sulphite reducing agent, the shrink-proofing capabilities of the reduced amount of the MPPA or salt oxidising agent can be revealed. Whilst the use of a higher amount of reducing agent is possible, such high uses being not necessary or rarely employed. The sulphite reduction step can be carried out in the same range of temperatures as the oxidation step, that is to say are typically carried out in the range of 15 to 50"C.

It has hitherto been suggested that an alternative way of improving the shrink-proofing of wool is to coat its outer surface with a polymer. Suitable shrink-resistance polymers comprise poly(ethylene-vinyl actate) carrying carboxylic acid chloride reactive groups, polyaminoamides bearing azetidinium reactive groups, polyacrylates bearing N-methylolamide reactive groups, dimethypolysiloxane bearing sianol reactive groups and polypropylene oxides bearing either thiol, isocyanate or carbamoyl sulphate reactive groups.It is possible to employ any one or more of the aforementioned polymeric surface treatments subsequent to the two-stage oxidation and sulphite reduction process of the present invention However, it has been found that provided the oxidation/sulphite reduction process has been carried out effectively, there is little significant gain achievable by the use of the addition polymeric reagents. It is accordingly of considerable benefit in the implementation of the instant invention that no subsequent polymeric treatment is required in order to achieve substantially zero felting shrinkage.

The instant invention can be employed in respect of wool sliver, yarn or woven or knitted material. It is normally employed in respect of sliver. The wool fibres are most often obtained from sheep but other animai hair can also be treated likewise such as mohair, alpaca, cashmere and camel.

Having described the invention in general terms, specific embodiments thereof will be hereinafter described in greater detail by way of example only.

In the following Examples and Comparisons, and except where indicated to the contrary, the wool was treated batch-wise in the form of samples of scoured knitted shetland wool. The wool was soaked for one hour in an aqueous solution containing approximately 0.5 gl 1 of a nonionic surfactant available under the Registered Trademark SYNPERONIC, grade NX at a liquor ratio of approximately 30:1. Oxidant was then introduced into the bath at a specified concentration, and if necessary the pH of the solution was adjusted. In Ex 1 to C16, the liquour to wool ratio in the oxidant bath was 45:1 w/w and 100 g wool samples were used, and in C17 to Ex31, the liquor to wool ratio was 37.5:1 and 4 g wool samples were used. The oxidant bath was maintained at the stated temperature and pH for 45 minutes.At the end of the oxidation step, the oxidised wool was subjected to a sodium metabisulphite reduction stage in procedures A and B or simply washed in procedure C.

In procedure A, for 100 g wool samples, sodium metabisulphite solution (260 cm3, 20 gl ') and sodium bicarbonate (260 cm3, 20 gl ' as the anhydrous salt) were introduced directly into the oxidation bath, producing the solution adjusted to pH 8 with further alkali which was maintained for 20 minutes at laboratory ambient temperature, about 20"C. Thereafter the wool was squeezed dry, and rinsed twice, each time using 4000 cm3 of demineralised water with a pH of 7.5 for 3 minutes at ambient temperature. Finally, the wool was squeezed, spin dried and then dried in an oven at 40"C. For 4 g wool samples, the volumes used were 1/25th the foregoing. The shrinkage of the wool was then measured by the technique outlined below.

In procedure B, procedure A was followed with the exception that the wool was removed from the oxidation bath, squeezed dry and then transferred to a fresh bath of 4000 cm3 demineralised water (150 cm3 for 4 g samples) into which the metabisulphite and bicarbonate solutions were introduced.

In procedure C, procedure A was followed with the exception that the addition of the metabisulphite and bicarbonate step was omitted completely.

In order to demonstrate the effect of employing the subsequent treatment stage with å resin, the following procedure was adopted. Interposed after the second wash and before the spin drying oven drying in treatments A, B or C, the wool was squeezed dry, and then transferred to a bath containing demineralised water, 4000 cm3 maintained 30"C, into which was introduced an aqueous solution of a polyamide epichlorhydrin resin available under the Trademark HERCOSETT 125, 100 gl 1 to give 2% w/w resin on wool, approximately 150 cm3 for 100 g wool sample.

The bath was maintained at pH 7.5 for 30 minutes.

The shrinkage trials were carried out using a modification of IWS test procedure TM185.

The trials to determine % Area Relaxation Shrinkage (%ARS) were carried out in a Philips front loader automatic washing machine with a volume of approximately 20 litres liquor, employing a load of 1 kilogram comprising the wollen test pieces together with items of cotton to make up the total load. The washing solution was free from added peroxygen compounds and the washing composition was added at 1 gl 1, and the machine was set at programme G with a washing temperature of 40"C and an-intermediate spin speed.

The trials to determine % Area Felting Shrinkage (%AFS) were then carried out similarly in the same machine, but employing the washing composition at only 0.3 gl ' and employing programme C which also used a washing temperature of 40"C but maximum spin speed. The results given are those after an %ARS wash and two %AFS washes.

The length and width of the wool samples were each measured at 3 points to give average values, before the relaxation trials, after the relaxation trials and after the shrinkage trials. All measurements were made in shallow water for consistency and accuracy.

The process conditions and the results are summarised in the subsequent Tables.

In the results tabulated in Table 1, the oxidation step was carried out at 25"C using a liquor ratio of liquor:wool of 45:1, and the oxidant comprised magnesium monoperoxyphthalate (available from Interox Chemicals Limited under their trade designation H48) at a concentration of 1.75 gl 1 All of the %ARS and %AFS results have been rounded to the nearest %, a minus indicating expansion of the woollen test material.

Table 1 Example/ Oxid Sulphite Resin %ARS %AFS Comparison pH Redn used Ex1 3 A yes -2 0 Ex2 3 A no -3 -4 Ex3 3 B yes -2 0 Ex4 3 B no O 0 C5 3 C yes 5 32 C6 3 C no 10 45 Ex7 4 A yes -2 1 Ex8 4 A no 3 0 Ex9 4 B yes -2 1 Ex10 4 B no -2 -2 C11 4 C yes 6 38 C12 4 C no 6 41 Ex13 5 A yes 3 -2 Ex14 5 A no 0 2 Ex15 5 B yes 2 0 Ex16 5 B no 3 11 C17 5 C yes 6 45 C18 5 C no 9 51 From Table 1, it can be seen that when the sulphite reduction is omitted, i.e. a Type C treatment is followed, the % Area Felting Shrinkage (%AFS) is much worse.Secondly, there is very great similarity between the results of type A and type B sulphite reduction, and thirdly at pH 3 and 4 there appears to be substantially little advantage in employing a resin treatment in addition to the oxidation and sulphite reduction treatments. However, at pH 5 one pair of results would suggest there may be some benefit whereas the other pair does not.

Comparison C19 to Examples 25 In the results summarised in Table 2, the procedure followed was that of example 8, i.e.

oxidation at pH 4, 250C but at a liquor ratio of 37.5:1 and using a varying amount of magnesium monoperoxyphthalate (MMPP) followed by sulphite reduction type A without a resin treatment.

Table 2 Example/ MMPP % oxidant % active % AFS Comparison conc added w/w oxygen added gl 1 on wool w/w on wool C19 0 0 0 48 Ex20 0.67 2.5 0.14 25 Ex21 1.0 3.8 0.21 8 Ex22 1.33 5 0.27 5 Ex23 1.73 6.5 0.35 -1 Ex24 1.87 7 0.38 1 Ex25 2.67 10 0.54 -4 From Table 2, it can be seen that the % area felting shrinkage decreased rapidly as the weight of oxidant employed increased up to about 4% (active oxygen 0.24%) and thereafter change in oxidant amount had little effect on % Area Felting Shrinkage.

Comparisons C26 and C27 In these Comparisons, the procedures of respectively Example 8 (C26) and Comparison 10 (C27) were repeated but using an equivalent molar amount of peroxyacetic acid instead of MMPP on samples of wool that shrank 70% without treatment. In C26, the wool still shrank 59% whilst in C27 the wool shrank 60%. From these results, it can be seen that there is no benefit to be gained by incorporating a sulphite reduction stage after a peroxyacetic acid oxidation stage. Secondly, and of practical importance both C26 and C27 showed that at the active oxygen levels at which MMPP was capable of fully shrinkproofing the wool (when followed by a sulphite reduction), a peroxyacetic acid treatment hardly improved the shrink resistance of the wool at all.

Examples 28 and 29 In these Examples, Example 8 was repeated but using respectively half (Ex28) and double (Ex29) the concentration of sodium metabisulphite. At half concentration the % Area Felting Shrinkage was 8% and at double concentration it was only -2%. These results demonstrate that the sodium metabisulphite concentration can be varied over a wide range whilst retaining excellent shrinkproofing.

Examples 30 and 31 In these Examples, Example 8 was repeated but using respectively half (Ex30) and double (Ex31) the concentration of sodium bicarbonate. In Ex30 the 96 Area Felting Shrinkage was 5% whereas in Ex31 it was -5%. These results demonstrate that the sodium bicarbonate concentration can be varied over a wide range whilst retaining excellent shrinkproofing.

Examples 32 and 33 In these Examples, the general procedure of Example 1 was followed but at a liquor ratio of 37.5:1, and at a temperature of 40"C and at an MMPP % wt on wool of 7.5% and in Ex33 at pH 7. At pH 4 (Ex32) the % Area Felting Shrinkage was -3% and at pH 7 (Ex33) it was -5%.

Example 34 In a simulation of a continuous system, a further 10 g sample of knitted wool was immersed for 10 seconds in a bath containing MMPP (50 gl I, pH 4) squeezed to 80% liquor retention and after 10 seconds subjected to a sulphite reduction for 10 seconds in a bath containing 20 gl ' sodium bicarbonate (calculated as the anhydrous salt) and 20 gl | sodium metabisulphite at a 100:1 liquor ratio, rinsed twice at a 100:1 liquor ratio with demineralised water, spin dried and then oven dried at 40"C. It was found that the resultant wool enjoyed a % Area Felting Shrinkage of less than 2%, measured in a non-standard technique, demonstrating that MMPP is applicable in a continuous system.

Claims (15)

1. A process for shrink-proofing wool in which woollen fibre is brought into contact with an aqueous liquor containing an effective amount of peroxyphthalic acid or salt thereof, and thereafter brought into contact with a sulphite reducing agent.

2. A process according to claim 1 in which the peroxyphthalic acid salt used is magnesium monoperoxyphthalate.

3. A process according to claim 1 or 2 in which the peroxyphthalic acid or salt provides at least 0.2% w/w peracid active oxygen added on the wool.

4. A process according to claim 3 in which the peroxyphthalic acid or salt provides 0.3 to 0.5% w/w peracid active oxygen added on the wool.

5. A process according to claim 3 in which the wool is passed through a bath containing a solution of 30 to 100 grams peroxyphthalic acid or salt per litre and thereafter permitted to retain 50 to 200% of its weight of solution.

6. A process according to any preceding claim in which the oxidation is carried out at pH 2 to pH 8.

7. A process according to claim 6 in which the oxidation is carried out at pH 3 to pH 5.

8. A process according to any preceding claim in which the oxidataion is carried out at a temperature of 15 to 50"C.

9. A process according to any preceding claim in which the reduction step is carried out at a pH of at least pH 4.

10. A process according to claim 9 in which the reduction step is carried out at a pH of pH 5 to pH 9.

11. A process according to any preceding claim in which the amount of sulphite reducing agent is from 2.5 to 15% by weight on weight of wool.

12. A process according to any preceding claim in which the reduction step is carried out at 15 to 50"C.

13. A process according to any preceding claim in which the wool is subsequently coated with an organic polymer.

14. A process for treating wool employing a method substantially as described herein with respect to any one Example of Examples 1 to 4, 7, 8, 11 to 14, 19 to 23 and 26 to 32.

15. Wool having a reduced tendency to shrink whenever obtained by a process according to any preceding claim.