Fatliquoring, filling and hydrophobicizing leathers and furs

A process for fatliquoring, filling and hydrophobicizing leathers and furs, comprises using ene adducts of maleic anhydride with unsaturated fatty acids of from 12 to 24 carbon atoms or their C.sub.1 - to C.sub.20 -alkyl or C.sub.2 - to C.sub.20 -alkenylesters, triglycerides, amides, mono- or di(C.sub.2 - to C.sub.4 -alkanol)amides, mono- or dipolyetheramides or polyetheresters, or ene adducts partially or completely derivatized by reaction with amines or alcohols to form amides or esters, respectively.

The present invention relates to an improved process for fatliquoring, 
filling and hydrophobicizing leathers and furs and to an improved 
fatliquoring agent for leathers and furs. 
To control the mechanical properties of leather such as softness, 
flexibility or suppleness it is common to use fat liquors, aqueous 
emulsions of in general petrochemically produced or natural oils and fats 
rendered water-emulsifiable by partial sulfonation or by means of 
emulsifiers or solubilizers. 
This class of fat liquor ingredients has the disadvantages of incomplete 
liquor exhaustion, lack of resistance to extraction by solvents or water, 
migratory phenomena and unsatisfactory fastness profiles. 
For instance, DE-A-39 09 614 (1) concerns a process for fatliquoring and 
hydrophobicizing leathers and furs by using sulfonated compounds of 
succinic acid with unsaturated fatty acids or esters, amides or 
alkanolamides, for example, the product of reacting oleic acid or an oleic 
acid derivative with maleic anhydride in the presence of a free radical 
initiator and subsequently sulfonating with sulfuric acid. 
U.S. Pat. No. 3,656,881 (2) discloses that alkenyl-substituted saturated 
dibasic acids such as isooctadecenylsuccinic acid are suitable for 
softening leather. Here adequate solubility or emulsifiability is achieved 
using organic solvents as solubilizers. Since organic solvents are in 
general not bound by leather, this gives rise to ecological problems, in 
particular contamination of the waste water by residual liquors and of the 
air through evaporation during the drying process. 
It is an object of the present invention to provide an improved product for 
fatliquoring, filling and hydrophobicizing leathers and furs that is free 
of the prior art disadvantages. 
We have found that this object is achieved by a process for fatliquoring, 
filling and hydrophobicizing leathers and furs, which comprises using ene 
adducts of maleic anhydride with unsaturated fatty acids of from 12 to 24 
carbon atoms or their C.sub.1 - to C.sub.20 -alkyl or C.sub.2 - to 
C.sub.20 -alkenyl esters, triglycerides, amides, mono- or di(C.sub.2 - to 
C.sub.4 -alkanol)amides, mono- or dipolyetheramides or polyetheresters, or 
ene adducts partially or completely derivatized by reaction with amines or 
alcohols to form amides or esters, respectively. 
The ene adducts mentioned are known in principle from (1) and from DE-C-27 
54 831 (3). In (1) they are mentioned as intermediates in the synthesis of 
the sulfonated fatliquoring agents claimed therein, but are not 
recommended for use as leather treatment assistants in their own right. In 
(3) they are claimed as solubilizers for nonionic surfactants in alkaline 
aqueous solution. 
The ene adducts are prepared in a conventional manner by a thermal addition 
of maleic anhydride to unsaturated fatty acids or derivatives thereof in 
which the unsaturated fatty acid, irrespective of its number of double 
bonds, adds per mole about 0.4-2 mol, preferably from 0.7 to 1 mol, of 
maleic anhydride. The addition can be carried out for example in boiling 
toluene or without a solvent at from 100.degree. to 200.degree. C., 
preferably in the presence of catalytic amounts of iodine. The unsaturated 
fatty acids have from 12 to 24, preferably from 14 to 18, carbon atoms and 
one or more olefinic double bonds. The amount of maleic anhydride added 
per double bond is preferably not more than one mole, although more could 
be added, since only the double bond from maleic anhydride is used up in 
the addition and not that of the fatty acid. Examples of suitable 
unsaturated fatty acids [are] in particular oleic acid 
(cis-9,10-octadecenoic acid), but also the corresponding transisomer 
elaidic acid, lauroleic acid (9,10-eicosenoic acid), erucic acid 
(13,14-docosenoic acid) and selacholeic acid (15,16-hexadecenoic acid). 
Examples of suitable fatty acids having two or more olefinic double bonds 
are in particular linoleic acid (9,10-12,13-octadecadienoic acid) and 
linolenic acid (9,10-12,13-15,16-octadecatrienoic acid). 
It is also possible to use the circumscribed esters of the unsaturated 
fatty acids mentioned, eg. methyl, ethyl, propyl, butyl, 2-ethylhexyl, 
decyl, dodecyl, tetradecyl, hexadecyl, stearyl, hexadecenyl, oleyl, 
linoleyl and linolenyl esters. 
In addition to the circumscribed monoesters it is also possible to use the 
triglycerides of the unsaturated fatty acids, ie. especially natural fats 
and in particular oils, which contain predominant proportions, ie. more 
than 50 mol %, preferably more than 75 mol %, based on the fatty acid 
total present in the mixture, of the aforementioned unsaturated fatty 
acids as esters. Suitable examples are linseed oil, olive oil, castor oil, 
ground-nut oil, sesame seed oil, corn seed oil, sunflower oil, soybean 
oil, poppy seed oil, cotton seed oil, hemp seed oil and palm kernel oil 
and also the various animal fats and in particular oils such as fish oil, 
whale oil and sperm oil. The last one contains not only glycerides but 
also appreciable amounts of esters with wax alcohols, including 
unsaturated alcohols. 
Suitable fatty acid amides are in particular the compounds which are 
unsubstituted at the amide nitrogen. 
Suitable mono- or di(C.sub.2 - to C.sub.4 -alkanol)amides are in particular 
N-monoethanolamide, N,N-diethanolamide, N-monoisopropanolamide and 
N,N-diisopropanolamide. 
Examples of suitable mono- or dipolyetheramides are compounds that are 
substituted at the amide nitrogen by polyoxyethylene groups having a 
respective degree of ethoxylation of from 1 to 30, in particular from 2 to 
20. 
Examples of suitable polyetheresters are the reaction products of 
unsaturated fatty acids with from 1 to 30 mol, in particular from 2 to 20 
mol, of ethylene oxide. 
The preparation of the amide or ester derivatives is effected in a known 
manner by addition of the amine or alcohol to the anhydride 
group-containing ene adduct at temperatures between customarily 20.degree. 
and 200.degree. C., preferably between 50.degree. and 150.degree. C. The 
addition can be catalyzed, for example with p-toluenesulfonic acid. Per 
mole of anhydride group it is preferable to use not more than one mole of 
amine or alcohol. The addition can be carried out for example in toluene 
or in the absence of a solvent, preferably in the same reaction medium as 
used in the preparation of the ene adduct. For instance, the alcohols used 
can be for example methyl, ethyl, propyl, butyl, 2-ethylhexyl, decyl, 
dodecyl, tetradecyl, hexadecyl, stearyl, oleyl alcohol or alkoxylated 
fatty or oxo alcohols or carbohydrates such as, for example, glucose. 
Preference is given to using straight-chain or branched C.sub.1 -C.sub.20 
-alkanols, in particular C.sub.4 -C.sub.18 -alkanols, and also to C.sub.8 
-C.sub.18 -alkanols reacted with from 2 to 20 mol of ethylene oxide and/or 
propylene oxide per mole of alkanol. The amines used can be for example 
mono- or di-N-alkylamines such as n-butylamine, 2-ethylhexylamine, 
morpholine, piperidine or tallowamine or amino acids such as sarcosine, 
taurine or iminodiacetic acid or amino alcohols such as iminodiethanol or 
hydroxyethylamine. Preference is given to using saturated or unsaturated 
secondary or in particular primary aliphatic amines having a total of from 
1 to 30, in particular from 4 to 18, carbon atoms. 
In a preferred embodiment the ene adducts used of maleic anhydride are with 
unsaturated fatty acids of from 14 to 18 carbon atoms or their C.sub.14 - 
to C.sub.18 -alkenyl esters or triglycerides, but in particular with oleic 
acid, oleyl oleate or a triglyceride containing more than 50 mol % of 
unsaturated fatty acids of from 14 to 18 carbon atoms, based on total 
fatty acid present in the mixture, as esters, or ene adducts derivatized 
partially or completely by reaction with aliphatic amines having in total 
from 1 to 30 carbon atoms or with C.sub.1 -C.sub.20 -alkanols or with 
alkoxylated alcohols to form amides or esters, respectively. 
On being dissolved in an aqueous alkaline medium, the anhydride groups 
still present on the added maleic anhydride hydrolyze to form carboxylate 
groups, which, together with original carboxyl groups of unsaturated fatty 
acids that are likewise still in the salt form, ensure the solubility of 
the products to be used according to the invention. 
The ene adducts described make it possible to produce very soft leathers 
without conventional fat liquors. This advantage is reflected in simple 
and short application recipes. 
In addition to improving the mechanical properties, for example the 
breaking strength, these ene adducts bring about a distinct enhancement in 
the softness profile of the leather. 
As well as improving the mechanical properties, for example the tensile 
strength, these ene adducts bring about a distinct enhancement in the 
fastness profile of the leather. 
For instance, they have a very positive effect on the light fastness and 
the thermal yellowing resistance of such leathers. In addition to 
producing a virtually quantitative exhaustion of the liquor, the high 
yield of fixation in the leather results in resistance to extraction by 
solvent or water. This results in washable leathers, ie. leathers which on 
washing do not lose their properties such as softness, firmness and 
suppleness, unlike leathers fatliquored with conventional fat liquors. 
As well as a softening effect, the products described also have a 
hydrophobicizing effect, ie. leathers and furs which have been treated 
therewith are water-repellent and absorb only minimal amounts of water. 
A further advantage of the aqueous ene adduct emulsions to be used 
according to the invention is that they do not contain additional 
emulsifiers. As will be known, leathers and furs treated with 
emulsifier-containing products must afterwards be subjected to expensive 
processes, for example aftertreatment with polyvalent metal salts, in 
order to render the emulsifiers in the leather or fur skin, where they 
have a negative effect on the water repellency, ineffective. 
The present invention also provides leather and fur fatliquoring, filling 
and hydrophobicizing compositions comprising the above-described ene 
adducts of maleic anhydride with unsaturated fatty acids or derivatives 
thereof. 
The leather treatments of the invention are suitable for any conventional 
tanned hide. Tanned hides are customarily neutralized prior to the 
treatment. They may have already been dyed prior to the treatment. 
However, dyeing may also be delayed until after the treatment according to 
the invention. 
The tanned hides are advantageously treated with the aqueous emulsions of 
the ene adducts in an aqueous liquor obtainable by diluting the emulsions 
with water at pH 4-10, preferably pH 5-8, and 20.degree.-60.degree. C., 
preferably 30.degree.-50.degree. C., for 0.1-5 hours, in particular 0.5-2 
hours. This treatment may take the form for example of drumming. The 
amount of emulsion required is, based on the shaved weight of the leather 
or the wet weight of the fur skin, from 0.1 to 30% by weight, preferably 
from 1 to 20% by weight. 
The liquor length, ie. the percentage weight ratio of treatment liquor to 
goods, based on the shaved weight of the leather or the wet weight of the 
fur skin, is customarily from 10 to 1000%, preferably from 30 to 150% in 
the case of leathers and from 50 to 500% in the case of fur skins. 
After the treatment with the above-described aqueous liquor, the pH of the 
treatment liquor is adjusted with acids, preferably organic acids, eg. 
formic acid, to pH 3-5, preferably pH 3.5-4. 
If customary retanning agents are additionally employed in the finishing of 
the leather or fur skin, the treatment with the aqueous emulsion of the 
ene adducts can be carried out before or after the retanning operation.

EXAMPLES 
The percentages in the Examples are by weight, unless otherwise stated. 
Preparation of aqueous ene adduct emulsions 
EXAMPLE 1 
240 g of oleic acid (hydrogenation iodine number 90.1) and 108 g of maleic 
anhydride were heated together in a nitrogen atmosphere at 200.degree. C. 
for 4.5 hours. Unconverted maleic anhydride was then distilled off (26 g) 
under a water jet vacuum, leaving 320 g of product. 
To 57 g of the oleic acid-ene adduct were added 12 g of 50% strength NaOH 
in 172 g of water to obtain a 25% strength brown emulsion. 
EXAMPLE 2 
Example 1 was followed to react 348 g of ester oil (hydrogenation iodine 
number 112.6) with 166 g of maleic anhydride. This resulted in 535 g of 
product, leaving 13 g of unconverted maleic anhydride. 
To prepare an emulsion 24 g of 50% strength NaOH in 295 g of water were 
added to 97 g of ene adduct. 
EXAMPLE 3 
Example 1 was followed to react 375 g of capellan oil (hydrogenation iodine 
number 122) with 176 g of maleic anhydride. This resulted in 540 g of 
product leaving 10 g of unconverted maleic anhydride. 
To prepare an emulsion 92 g of the ene adduct were dissolved in 24 g of 50% 
strength NaOH in 279 g of water. 
EXAMPLE 4 
Example 1 was followed to react 266 g of oleyl oleate (hydrogenation iodine 
number 95.5) with 127 g of maleic anhydride. This resulted in 365 g of 
product, leaving 20 g of unconverted maleic anhydride. 
To prepare an emulsion 66 g of the ene adduct were dissolved in 75 g of 50% 
strength NaOH in 197 g of water. 
EXAMPLE 5 
To 114 g of the capellan oil-ene adduct of Example 3 were added 6.2 g of 
n-butylamine at from 70.degree. to 80.degree. C. 120 g of product were 
obtained after three hours at 80.degree. C. 
To prepare an emulsion 100 g of product were added to 300 g of water and 16 
g of 50% strength sodium hydroxide solution. 
EXAMPLE 6 
To 88 g of the capellan oil-ene adduct of Example 3 were added 33.2 g of 
n-tallowamine at from 70.degree. to 80.degree. C. 121 g of product were 
obtained after three hours at 80.degree. C. 
To prepare an emulsion 100 g of product were added to 300 g of water and 
10.5 g of 50% strength sodium hydroxide solution. 
EXAMPLE 7 
To 107 g of the capellan oil-ene adduct of Example 3 were added 0.6 g of 
p-toluenesulfonic acid at from 70.degree. to 80.degree. C. 14.1 g of 
isobutanol were added at from 120.degree. to 130.degree. C. 119 g of 
product were obtained after three hours at 130.degree. C. 
To prepare an emulsion 100 g of product were added to 300 g of water and 10 
g of 50% strength sodium hydroxide solution. 
EXAMPLE 8 
To 40.5 g of the capellan oil-ene adduct of Example 3 were added 0.6 g of 
p-toluenesulfonic acid at from 70.degree. to 80.degree. C. 81.6 g of a 
commercial mixture of C.sub.12 -C.sub.15 -salkanols which had been reacted 
with ethylene oxide and propylene oxide (together about 9 mol per mole of 
alkanol) were added at from 120.degree. to 130.degree. C. 122 g of product 
were obtained after three hours at 130.degree. C. 
To prepare an emulsion 100 g of product were added to 300 g of water and 
3.5 g of 50% strength sodium hydroxide solution. 
Use in leathermaking 
EXAMPLE 9 
Chrome tanned cattlehide leather which had a shaved thickness of 1.8 mm and 
had been adjusted to a pH of 5.0 was drummed at 40.degree. C. for 2 hours 
with an amount of the emulsion of Example 1 to correspond to 15% of active 
ingredient, based on the shaved weight. The total liquor length was 150%. 
The leather was then dyed with 1% by weight of a conventional anionic 
aniline dye. It was then adjusted to pH 3.8 with formic acid and finally 
washed, mechanically set out and dried. 
The leather obtained was very soft, supple, highly filled and uniform in 
color. 
EXAMPLE 10 
Chrome tannned cattlehide leather which had a shaved thickness of 1.8 mm 
and had been adjusted to a pH of 5.0 and dyed with 0.7% by weight of a 
conventional anionic aniline dye was drummed at 40.degree. C. for 1.5 
hours with an amount of the emulsion of Example 2 to correspond to 20% of 
active ingredient, based on shaved weight. Thereafter the leather was 
adjusted with formic acid to pH 3.6 and finished in a conventional manner. 
The leather thus obtained was very soft and pliable. 
EXAMPLE 11 
Chrome tanned cattlehide leather which had a shaved thickness of 1.8 mm and 
had been adjusted to pH 5.0 and dyed with 0.7% of a conventional anionic 
aniline dye was drummed at 40.degree. C. for 30 minutes with an amount of 
the emulsion of Example 3 corresponding to 15% of active ingredient, based 
on shaved weight, and then further treated with 3% of a conventional 
synthetic tanning agent for one hour. The leather was then adjusted with 
formic acid to pH 3.6 and finished in a conventional manner. 
The leather thus obtained had a pleasantly soft and pliable feel. 
EXAMPLE 12 
The emulsion of Example 4 was used in the manner of Example 9. 
The leather thus obtained had soft and round hand properties. 
EXAMPLE 13 
The emulsion of Example 5 was used in the manner of Example 9. 
The leather thus obtained had soft and pleasant hand properties. 
EXAMPLE 14 
The emulsion of Example 6 was used in the manner of Example 9. 
The leather obtained was soft with a slightly creamy hand. No water 
penetration occurred in the course of 12 hours in the penetrometer under 
10% compression. 
EXAMPLE 15 
The emulsion of Example 7 was used in the manner of Example 9. 
The leather thus obtained was pleasantly soft and pliable. 
EXAMPLE 16 
The emulsion of Example 8 was used in the manner of Example 9. 
The leather obtained had a pleasantly soft hand and a uniform coloring.