IE47293B1 - Fat-liquoring process - Google Patents

Abstract

of the Invention Hydroxylated phosphatides are used as component in or as the sole fattening agent in fat-liquoring. The hydroxylated phosphatide penetrates throughout the whole thickness of the leather, as opposed to non-modified phosphatides, giving the leather suppleness and softness. Rest fat content in the liquoring bath is low.

Description

The invention relates to a process for fat-liquoring tanned leather. In the technical process for converting hides and skin to leather, one of the steps is the fat-liquoring step. In this step the tanned leather is contacted with an aqueous emulsion of a fatty substance. After tanning, which serves to remove all undesirable substances from the leather, the leather is hard and stiff. The fat-liquoring serves to introduce a fatty substance into the fibre structure of the leather. The fatty substance has lubricating properties which impart to the leather suppleness, elasticity, strength and feel.

To fulfil the above functions, the fatty substance must be able to penetrate throughout the whole thickness of the leather and moreover he chemically or physically bound in the leather to prevent sweating out. To obtain this fixation, the fatty substance should contain polar groups.

The most used method for introducing the fatty substance is fat-liquoring. In this method the leather is contacted with an aqueous emulsion of the fatty substance. From an economical point of view it is also important that the leather should take up most of the fatty substance from the liquoring bath, i.e. the residual fat content of the liquor should be as low as possible to avoid undesirable losses.

As fatty substances sulphonated mineral, vegetable and animal oils are mostly used, often in admixture with nonsulphonated oils. Examples of such oils are Turkey red oil, sulphonated train oil, sulphonated sperm oil, neatsfoot oil, sulphonated fatty alcohols and also partially chlorinated, sulphonated or oxidised fats and fatty oils'.

In carrying out the fat-liquoring the leather is contacted at about 30 to 60°C with 100 to 200.% by weight of water containing 5 to 10% by weight of the fat,' both percentages being calculated cn the weight of the leather. The liquoring is continued until the maximum amount of fat has been taken up by the leather, which usually takes about 40 to 60 minutes.

It has been proposed (French Patent Specification 647/156) to use phosphatides in fat-liquoring because of its emulsifying properties and it was claimed that said phosphatides would assist in the penetration of the fat into the leather and would increase its fat uptake, However, in practice the use of phosph'atides in fat-liqupring has been very restricted, due to the fact that they are insufficiently taken up.-by the leather, leading to insufficient fattening of the interior of the leather. Such insufficient fatteniig leaves the leather too hard and too stiff. Moreover the poor fat uptake leads to high rest contents of fat in tne liquor and hence to high fat losses.

It has now beer found that' hydroxylated phosphatides are eminently suitable ior use as the fatty substance in fat liquors for fattening leather. In contrast to non-modified phosphatides, the hydroxylated phosphatides penetrate throughout the thickness of'the leather and they are almost completely taken up by the leather from the fat-liquor, making the rest content in the liquoring bath very low.

Therefore,the present invention provides a process for fat-liquoring tanned leather with an aqueous emulsion of a fatty substance comprising a phosphatide, which process is characterized iir that ai the phosphatide a hydroxylated phosphatide is used and the - fatty substance comprises 30 to 100% by weight,, more preferably 70 to luO% by weight of the hydroxylated phosphatide.

Preferably as the fatty substance a mixture of hydroxylated phosphatides is used, as obtained by hydroxylating a vegetable phosphatide mixture, separated from a vegetable oil, such as soyabean oil, peanut oil, rapeseed oil, cottonseed oil, etc. by a suitable degumming process; for instance by ‘0 treatment of the oil with water or steam. Especially soyabean phosphatides are being, preferred because of their general availability.

Further, phosphatides which before or after the hydroxylation have been modified in other ways can be used. Especi15 ally useful in this respect are phosphatides which before or after the hydroxylation have been subjected to a partial hydrolysis by treatment with an acid, a base or an enzyme, such as phospholipase A. Preferably, hydroxylated phosphatides are used which have been hydroxylated until the iO iodine value has decreased by 5 to 25%.

Also phosphatide fractions obtained by fractionation of crude or modified phosphatide mixtures with a solvent or a mixture of solvents may be used as the starting material for the hydroxylation; also the hydroxylated phosphatide mixture can be fractionated, and one or both of the fractions be used as the fattening agent- of the invention.

The fatty substance additionally may comprise oils which are customarily used in the art of fat-liquoring, such as neatsfoot oil, spenn oil, and/or sulphonated oil. Alternatively the fatty substance may contain soyabean oil.

For use with chromium-tanned leather it is desirable that the fattening mixture of the invention should contain a substance which increases its chromium resistance. As such substances ethoxylated alkyi phenols may be used, such as an ethoxylated nonyl phenol, available under the trade name Arkopal - N 150 (Arkopal is a Registered Trade Mark) frcm Farbwerke Ifoechst, Germany. When used, the amount of the chromium resistance increasing agent added is usually about 3 to 15% by weight, preferably 3 to 10%, and more preferably about 4 to 6(, calculated on the total fattening mixture. Also the salt stability of the fattening mixture is increased by such agents. Optionally an emulsifier may be added.

Process for hy< roxylating phosphatides are described in USP 2,445,948 and ii USP 2,629,662. In said process the phosphatides are re icted with an oxidising agent, preferably hydrogen peroxide, ipfcionally in the presence of an acid, such as acetic acid, however preferably lactic acid, serving as a catalyst. By + ie reaction double bonds contained in the fatty acid chains if the phosphatides are converted to glycolic hydroxyl r-’oups,some of which may be esterified with acyl groups. By this process the iodine value of the phosphatides is originally about 95 to 100, is decreased by 5 to 25%.

The phosphatid is fattening agents of the invention are used in substantially the same way as the fattening agents customarily used in fat-liquoring of leather, viz. in a rotating container the leather is contacted at 4o to 60°C with 100 to 200% by weight of water containing 5 to 10% by - 5 “ weight of the phosphatide fattening agent until the desired degree of fattening is reached.

The fattening agent of the invention can be used for fat-liquoring all kinds of leather, such as buckskin, split upper leather, vegetable tanned leather, grain leather, suede etc.

Example A number of chromium-tanned wet-blue cow hides were shaved to a thickness of 1.6 mm. The hides contained 5.9% CrgO-j, calculated on the dry matter, and their pH was 3.3.

The hides were brought into a rotating container and 200% by weight of water of 55°C was added. Then 2% by weight, calculated on the hides, of Tanigan PC (Tanigan is Registered Trade Hark) , (a tanning agent of Bayer, Germany) was added. After 10 minutes O.8S by weight of Luganilbraun NT (a dyestuff of BASF, Germany) dissolved in 15 times its weight of water was added, followed, after a further 10 minutes, by 6.3% by weight of a hydroxylated soyabean phosphatide mixture (iodine value 87-6 and containing 5% by weight of Arkopal-N 150, an ethoxylated nonyl phenol of Farbwerke Hoechst, Germany), dispersed in 7 times its weight of water. The temperature of the liquoring bath was 38°C and its pH %.72. After 20 minutes a mixture of 2% by weight of wattle, 2% by weight of Tanigan PR (a tanning agent of Bayer, Germany) and 2% by weight of Eetingan R7 (Retingan is a Trade Mark) (a tanning agent of Bayer, Germany) vzas added to the- bath. After 15 minutes 0.15% by weight of formic acid was added, and after a further 15 minutes the liquor was drained off. Next the hides were - 6 47293 washed with 400% by weight of water at 25°C‘for 10 minutes, whereafter the hides were allowed to drip dry overnight. Then the hides were pressed, vacuum-dried at 85°C for 2.5 minutes and post-dried at 25-30°C for 1.5 hours.

J After a few days the hides were staked.

After the fattening step the liquor contained only 0.95 g/l of the phosphatides. In view of the fact that 50% of the 200% of water added had been taken up by the hides, this means that 98% of the phosphatides had been taken up by the leather. The fattened hides contained 8.5% by weight of the phosphatides, calculated on the dryleather (determined by extraction with methylenechloride).

The physical properties of the fattened hides fulfilled all the requirements of a good quality sides leather.

Claims (12)

1. CLAIMS :1. A process for fat-liquoring tanned leather vzith an aqueous emulsion of a fatty substance comprising a phosphatide, which process is characterized in that as the phos5 phatide a hydroxyiated phosphatide is used and the fatty substance comprises 30 to 100% by weight of the hydroxyiated phosphatide.

2. Process according to claim 1, characterized in that a hydroxyiated vegetable phosphatide mixture is used. 10

3. A process according to claims 1 to 2, characterized in that hydroxyiated soyabean phosphatides are used.

4. Process according to claims 1 to 3, characterized in that a phosphatide is used which has been hydroxyiated until the iodine value has decreased by

5. To 25%. 15 5. Process according to any one of claims 1 to 4, characterized in that a partially hydrolysed, hydroxyiated phosphatide is used.

6. Process according to any one of claims 1 to 5, - 8 47293 characterized in that additionally a fatty oil and/or sulphonated oil, such as neatsfoot oil, sperm oil and sulphonated sperm oil, is used in the liquoring bath.

7. Process according to claim 6, characterized in that as the fatty oil soyabean oil is used.

8. Process according to any one of claims 1 to 7, characterized in that a chromium resistance improving agent is added.

9. Process according to claim 8, characterised in that as the chromium resistance improving agent an ethoxylated alkylphenol is used.

10. Process according to claim 9, characterized in that as the chromium resistance improving agent 3 to 15% by weight of an ethoxylated nonylphenol is used, calculated on the fatty substance.

11. Process according to any one of claims 1 to 10, characterized in that the liquoring bath contains an emulsifier.

12. Leather whenever treated according to a process as claimed in any one of claims 1 to 11.