Note: Descriptions are shown in the official language in which they were submitted.
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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 be 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 substahces sulphonated mineral, vegetable and
animal oils are mostly used, often in admixture with non~
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sulphonated oils. Examples of such oils are Turkey red oil,
sulphonated train oil, sulphonated sperm oil, neatsfoot oil,
sulphonated fatty alcohols and also partially chlorinated,
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sulphonated or oxidised fats and fatty oils.
In carrying out the fat-liquoring the leather is contacted
at about 30 to 60C with 100 to 200% by weight of water
containing 5 to 10% by weight of the fat, both percentages
being calculated on the weight of the leather. The liquoring
is continued until the maximum amount of fat has be-en taken
up by the leather, which usually takes about 40 to 60 minutes.
It has been proposed (~rench Patent Specification
647,Ll56) to use phosphatides in fat-liquoring because of its
10 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 phosphatides in
fat-liquoring has been very restricted~ due to the fact that
15 they are insufficiently taken up by the leather, leading to
insufficient fattening of the interîor of the leather. Such
insufficient fattening leaves the leather too hard and too
stiff. Moreover the poor fat uptake leads to high rest
contents of fat in the liquor and hence to high fat losses.
It has now been found that hydroxylated phosphatides are
eminently suitable ~or use as the fatty substance in fat
liquors ~for fattening leather. In contrast to non-modified
phosphatides, the hydroxylated phosphatides penetratethrough-
out the thlckness of the leather and they are almost
25 completely taken up by the leather from the fat-liquor, making
the rest content in the iiquorine bath very low.
Therefore~the present invention provides a process for
fat-liquoring tanned leather with an aqueous emulsion of a
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fatty substance comprising a phosphatide, which process is
characterized in that as the phosphatide a hydroxylated phosphatide is
used. Preferably, the fatty substance comprises 30 to 100% by weight,
more preferably 70 to 100% by weight of the hydroxylated phosphatide.
- Preferably as the fatty substance a mixture of hydroxy-
lated 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
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 hydroxy-
lation have been modified in other ways can be used. Especi-
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
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 custo-
marily used in the art of fat-liquoring, such as neatsfoot oil, sperm
oil, and/or sulphonated sperm oil. Alternatively the fatty
substance may contain soyabean oil.
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~or use with chromium-tanned leather it is desirable
that the fattening mixture of the invention should contain a
substance which increases its chromium resistance. ~s such
substances ethoxylated alkyl phenols may be used, such as an
ethoxylated nonyl phenol, availab]e under the trade name
Arkopal -N 150 ~ from ~arbwer~e ~loechst, ~ermany. When used,
the amount of the chromium resistance lncreasing agent
added is usually about 3 to 15% by weight, pre~erably 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. Opt;ionally an emulsifier
may be added.
Process for hydroxylating phosphatides are described in
USP 2,445,948 and in USP 2,629,662. In said process the
phosphatides are reacted with an oxidising agent, preferably
hydrogen peroxide, optionally in the presence of an acid,
such as acetic acid, however preferably lactic acid, serving
as a catalyst. By the reaction double bonds contained in the
fatty acid chains of the phosphatides are converted to
glycolic hydroxyl groups,some of which may be esterified
with acylgroups. By this pxocess the iodine value of the
phosphatides, which for scyabean phosphatides ls originally
about 95 to 100, is decreased by 5 to 25%.
The phosphatide 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 40 to 69C
with 100 to 200~ by weight of water containing 5 to 10% by
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weight of the phosphatide fattening agent ufftil the desired
degree of fattening is reached.
The fattening agent of the invention can be used for
fat-liquoring ali kinds of leather, such as buckskin, split
upper leather, vegetable tanned leather~ grain leather,
suède 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%
Cr203g 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 55C was added. Then 2% by weight,
calculated on the hides, of Tanigan PC ~ (a tanning agent
Bayer, Germany) was added. Af`ter 10 minutes o.8% by
weight of Luganilbraun NT ~ (a dyestuff of BASF, Germany)
dissol~ed 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
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of the liquoring bath was 38C and its pH 4.72. After 20
minutes a mixture of 2% by weight of wattle3 2% by weight
of Tanigan PR ~ (a tanning agent of Bayer, Germany) and 2%
by weight of P.etingan R7 ~ (a kanning agent of Bayer,
Germany) was added to the bathO 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
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washed with 400% by weight of water at 25C for 10 minutes,
whereafter the hides were allowed to drip dry overnight.
Then the hides were pressed, vacuum-dried at 85C for
2.5 minutes and post~dried at 25-30C for 1.5 hours.
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, ca]culated on the dry
leather (determined by extraction with methylenechloride).
The physical properties of the fattened hides ful-
filled all the requirements of a good quality sides
leather.
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