[0001] The present invention relates to a composition comprising (a) a mononuclear chromium
salt having anions of low molecular weight carboxylic acids and sulphate anions, the
mononuclear chromium salts having a Schorlemmer basicity of not more than 25%, (b)
alkali metal sulphates and (c) optionally water; and a process for tanning unpickled
pelts with a strongly addic solution of the composition in water.
[0002] In tanning with mineral salts, the one-bath process, which comprises the steps of
pickling, tanning with chromium salt and basifying, has become established. During
pickling, the animal hide which has been digested and degreased in the beamhouse is
treated with strong acids, for example sulphuric acid or hydrochloric acid, and salts,
for example sodium chloride. By means of this treatment, the degree of dissociation
of the carboxyl groups in the collagen is reduced so that the animal hide has a low
pH of less than 2. In this pH range, the fixing of the chromium salts is greatly reduced
and the permeation of the salts is increased. The tanning effect is then displayed
by an increase in the pH to about 3.5 to 6. For this purpose, when basifying the liquor,
alkaline compositions are added in amounts (for example magnesium oxide or sodium
carbonate) such that the optimum value for the tanning is established. For this method
of tanning, chromium salts have a Schorlemmer basicity of at least 30%.
[0003] Large amounts of chemicals are required for this form of tanning, which leads to
a high level of pollution of the wastewater. The residual content of, for example,
chromium salts in the liquor necessitates an aftertreatment for reducing the chromium
content in the wastewater. Improvements have therefore been proposed in order to increase
the liquor exhaustion and reduce the consumption of chemicals in order to meet ecological
requirements and to increase the cost-efficiency.
[0004] It is also known that organic acids, such as, for example, formic acid, are added
to the pickle without being able to eliminate the disadvantages described above.
[0005] The use of smaller amounts of low molecular weight organic acids, for example formic
acid, acetic acid or oxalic acid, or salts thereof, e.g. sodium formate, sodium acetate
or sodium oxalate, for masking the chromium salts is also known. Such products are
commercially available. Alternatively, small amounts of these complex-active compounds
can be added to the liquors for tanning. The Schorlemmer basicity is also at least
30% in the case of chromium sulphates modified in this manner. By means of this method,
the reliability of the tanning process is increased. However, the fact that the tanning
capacity of the chromium compound is reduced since polynuclear chromium complexes
are present is disadvantageous.
[0006] US-A-4,715,861 recommends treating pickled pelts or pelts during the pickling initially with aldehyde-
or ketocarboxylic acids, for example glyoxalic acid, in order to increase the exhaustion
of the liquor and to reduce the consumption of chromium salts. The steps of pickling
and of basifying are, however, still necessary. Aldehyde and keto acids are physiologically
unsafe and require special protective measures. The effect of the aldehyde and keto
acids consists in the reaction with amino groups of collagen, which leads to an increase
in the acidity of the pelt and hence better chromium uptake.
[0007] EP-A-0 822 263 describes a process for tanning with chromium salts, in which pelts are treated with
3-hydroxybutyraldehyde, and pickling and basifying are dispensed with. As a result
of reaction of the aldehyde group with amino groups of the collagen, the isoelectric
point is reduced so that chromium salts penetrate sufficiently and basifying is superfluous.
WO 00/66793 discloses the same process using α- or ß-hydroxyaldehydes. The agents used for the
pretreatment are volatile compounds which can be handled only with difficulty in tanneries.
Furthermore, aldehydes are physiologically unsafe. The use of these processes requires
special protective means, which cancels out the advantages of dispensing with pickling
and basifying from economic points of view.
[0008] Brazilian Published Patent Application
PI 0004258-7 A discloses chromium complexes of chromium salts and oligomeric masking agents having
a low Schorlemmer basicity of from 10 to 20%. They are suitable for tanning pelts
without pickling and basifying. The required penetration is achieved by the low basicity,
these agents penetrating only slowly owing to their excessively high molecular weights
and therefore being unconvincing.
[0009] GB 547 129 A1 refers to chromium tanning of unpickled animal hide with an aqueous solution comprising
caustic soda. Thus, the pH is much greater than 2.8.
[0010] Processes for the direct tanning of pelts from the beamhouse have not become established
owing to the existing disadvantages, although said direct tanning is extremely desirable
owing to the ecological and economic advantages.
[0011] It has now surprisingly been found that existing disadvantages can be avoided and
more rapid and uniform penetration and a higher uptake of basic chromium salts in
the pelt and hence also greater exhaustion of the liquor are achieved, excellent complete
tanning of the pelts and hence very good physical properties (for example, tensile
strength, ultimate tensile strength, stitch tear resistance) are obtained, the salt
consumption (for example, sodium chloride) is reduced, pickling and basifying are
avoided and the time required for complete tanning is reduced if the pelts for tanning
are treated with an effective amount of a reaction product of (a) chromium sulphates
having a Schorlemmer basicity of from 30 to 50% and (b) amounts of low molecular weight
carboxylic acids sufficient for the formation of mononuclear chromium salts, in aqueous
and weakly acidic liquor.
[0012] The invention firstly relates to a composition comprising
(a) a mononuclear chromium salt having anions of mono- and polycarboxylic acids having
a molecular weight of not more than 200 and sulphate anions, the mononuclear chromium
salts having a Schorlemmer basicity of not more than 25%,
(b) an alkali metal sulphate, and
(c) optionally water,
(d) the pH of a 10 percent strength by weight solution of the composition in water
being not more than 2.8.
[0013] Mono- and polycarboxylic acids are known. The mono- and polycarboxylic acids have
a molecular weight of not more than 200, preferably not more than 150 and particularly
preferably not more than 120. Some examples of mono- and dicarboxylic acids are formic
acid, acetic acid, propionic acid, lactic acid, methoxyacetic acid, monochloro- or
monofluoroacetic acid, oxalic acid and malonic acid. The carboxylic acids may be used
individually or as a mixture of at least two carboxylic acids.
[0014] The Schorlemmer basicity of the mononuclear chromium salt is preferably not more
than 23% and particularly preferably not more than 21%. The lower limit may be, for
example, at least 14% and preferably at least 16%.
[0015] The pH of the composition according to definition (d) is preferably not more than
2.5. The lower limit of the pH may be, for example, 0.2 and preferably 0.5.
[0016] The amount of the mononuclear chromium salt in the composition may be, for example,
from 5 to 30% by weight and preferably from 10 to 20% by weight, calculated as the
content of Cr
2O
3.
[0017] The alkali metal sulphate is preferably potassium sulphate or particularly preferably
sodium sulphate. The amount of the alkali metal sulphate may be, for example, the
remaining amount up to 100% by weight. The complete drying of the composition is difficult
and technically complicated owing to the water of hydration bound to the chromium
salt. It is therefore more advantageous if small amounts of water are present in the
composition, for example up to 15% by weight and more preferably up to 10% by weight.
[0018] The composition according to the invention may be present as an aqueous solution,
as an aqueous concentrate or as a solid, water-soluble formulation. The amount of
the composition according to the invention in aqueous solution and aqueous concentrates
may be, for example, from 35 to 85% by weight, preferably from 40 to 70% by weight.
The solid composition can, as mentioned above, contain up to 15% by weight and more
preferably up to 10% by weight of water, owing to the difficult drying. The solid
composition may be powder or granules. Concentrates having a water content of less
than about 35% are highly viscous and difficult to handle, particularly when filling
and removing from containers. These water contents are therefore less preferred.
[0019] The composition according to the invention may additionally contain agents customary
in the tannery, for example solvents, standardizing agents and fungicides.
[0020] The composition according to the invention is obtainable by reacting an aqueous solution
of chromium sulphates having a Schorlemmer basicity of, for example, from 30 to 50%,
which contains alkali metal sulphates, with low molecular weight mono- or polycarboxylic
acids.
[0021] Chromium salts for tanning have long been known and are commercially available as
solid or liquid formulations. They are sulphates of trivalent chromium. The products
available are generally mixtures of basic chromium sulphates and alkali metal sulphates,
such as, for example, sodium sulphate, since the basicity is established by adding
alkali metal hydroxides. The basicity is established by means of the amount of alkali
metal hydroxides, which is stated in percent Schorlemmer. In this context, a basicity
of 0% is assigned to pure chromium sulphate and a basicity of 100% to pure chromium
hydroxide. Forms in between, such as, for example, Cr(OH)SO
4, have a basicity of 33.3%.
[0022] The chromium sulphates used for the preparation of the composition preferably have
a Schorlemmer basicity of from 30 to 50%, more preferably from 30 to 45%, and particularly
preferably from 30 to 42%. Such chromium sulphates are standard products for the tanneries
and are commercially available or can be prepared in a simple manner.
[0023] The preparation of the composition according to the invention can be effected in
a simple manner by dissolving chromium sulphates in water and adding the desired amount
of alkali metal hydroxides. Commercially available products are advantageously used.
Specifically, it is possible to add the desired amount of carboxylic acid, optionally
as an aqueous solution, to the aqueous solution of chromium sulphate and alkali metal
sulphate, and then to stir, optionally with heating, until the carboxylic acids have
dissolved. Heating may mean up to 100°C and preferably up to 50°C. The reaction is
expediently carried out at room temperature.
[0024] On the one hand, the basicity of the chromium sulphate and, on the other hand, the
pH are adjusted with the amount of the mono- and polycarboxylic acids. It is possible
to add less than stoichiometric amount or an excess, based on the Cr
2O
3 present in the solution. The molar ratio of chromium sulphate, based on Cr
2O
3, to carboxylic acid may be, for example, from 1:0.1 to 1:1.5, preferably from 1:0.2
to 1:1.
[0025] A typical composition according to the invention can be prepared from an amount of
water of, for example, 45-55% by weight, an amount of chromium sulphate, calculated
as Cr
2O
3, of, for example, 10-20% by weight, and an amount of carboxylic acid of, for example,
4-10% by weight, the remaining amount to 100% by weight being an alkali metal sulphate.
[0026] The reaction product obtained can, if necessary and desired, be worked up by removing
water to give aqueous solutions, aqueous concentrates or solid formulations. The removal
of water can be effected by heating, optionally in vacuo. Solid formulations can be
obtained by means of freeze-drying, spray-drying, fluidized-bed drying, granulation
or removal of water with heating, optionally in vacuo, and milling of the dried product
to give powders. Liquid and solid compositions according to the invention have no
substantial differences with regard to their outstanding tanning effect.
[0027] Aqueous concentrates can be prepared in a simple manner directly in the tannery.
Such concentrates can, however, also be supplied as the prepared solution. Pulverulent
or granulated solid compositions are preferred delivery forms, owing to the smaller
volume. However, it is also possible to supply dilute aqueous solutions which can
be used directly as tanning liquor, particularly if the amount of hides to be tanned
is not too large.
[0028] Furthermore, it is possible to fill chromium sulphates and carboxylic acids according
to the amounts used into containers and thus to supply the tanneries, so that it is
possible to prepare the liquor for tanning with formation of mononuclear chromium
salts directly in the tannery.
[0029] Also useful is a kit, consisting of two containers, which each contain:
- (a) a chromium sulphate having a Schorlemmer basicity of from 30 to 50% and an alkali
metal sulphate, in the form of an aqueous solution, of an aqueous concentrate or of
a solid formulation, and
- (b) at least one low molecular weight mono- or polycarboxylic acid, either as such,
in aqueous solution or as an aqueous concentrate.
[0030] Amounts and molar ratios are as stated above.
[0031] Also useful is a process for the preparation of a liquor for tanning pelts, comprising
an aqueous solution of chromium salts, wherein
a) a chromium salt having a Schorlemmer basicity of from 30 to 50% as a mixture with
an alkali metal sulphate, in the form of an aqueous solution, of an aqueous concentrate
or of a solid formulation, and
b) at least one low molecular weight mono- or polycarboxylic acid, either as such,
in aqueous solution or as an aqueous concentrate,
c) are mixed in molar ratios and amounts in water, and allowed to react with formation
of mononuclear chromium salts having anions of low molecular weight carboxylic acids
and sulphate anions, such that the mononuclear chromium salts have a Schorlemmer basicity
of not more than 25%, the pH of the aqueous solution is not more than 2.8, and the
amount of chromium salt in the liquor is from 1 to 8% by weight of chromium trioxide
(Cr2O3), based on the weight of the pelt.
[0032] The molar ratios and amounts are preferably chosen so that the pH of the aqueous
solution is not more than 2.5 and, for example, from 2.5 to 0.2 and in particular
from 2.5 to 0.5.
[0033] The composition according to the invention is outstandingly suitable for tanning
pelts in aqueous liquor, it being possible completely to dispense with pickling and
basifying, and optionally only smaller amounts of electrolyte salts are added to the
water, for example up to 5% by weight, based on the dry weight of the pelt. The electrolyte
salt used is mainly sodium chloride. The pH of the liquor at the beginning of the
process is strongly acidic. The optimum pH required for effective tanning in the aqueous
liquor is automatically established after addition of the composition, since basic
components present in the pelt as a result of the pretreatment increase the pH. After
the end of the tanning, the pH has increased to about 3 to 3.5.
[0034] The invention furthermore relates to a process for tanning unpickled pelts by the
action of chromium(III) sulphates in aqueous liquor, which is characterized in that
an effective amount of a composition comprising
(a) a mononuclear chromium salt having anions of mono- and polycarboxylic acids having
a molecular weight of not more than 200 and sulphate anions, the mononuclear chromium
salts having a Schorlemmer basicity of not more than 25%,
(b) an alkali metal sulphate, and
(c) optionally water,
(d) the pH of a 10 percent strength by weight solution of the composition in water
being not more than 2.8,
is added to the pelt in aqueous liquor and allowed to act on the pelt, whereby
[0035] an effective amount from 1 to 8% by weight and preferably from 1.5 to 5% by weight
of chromium trioxide (Cr
2O3) is present in the liquor, based on the weight of the pelt. The amount is calculated
in the tannery, usually on the basis of the theoretical content of chromium trioxide.
[0036] The process according to the invention can be carried out by introducing washed pelts
into water, adding a salt, for example sodium chloride, to the liquor, and allowing
to act for a short time on the pelts. The composition according to the invention for
tanning is then added, which composition can be allowed to act, for example, for about
2 to 10 hours at room temperature. Heating is then effected and the reaction time
is allowed to continue, for example for up to 10 hours. The temperature may be up
to 50°C and preferably up to 45°C. After the tanning, the leather obtained is washed
and is then ready for further processing. The pH of the liquor after the tanning may
be from 3 to 5.5.
[0037] The invention also relates to the use of a composition containing
a) a mononuclear chromium salt having anions of mono- and polycarboxylic acids having
a molecular weight of not more than 200 and sulphate anions, the mononuclear chromium
salts having a Schorlemmer basicity of not more than 25%,
b) an alkali metal sulphate, and
c) optionally water,
d) the pH of a 10 percent strength by weight solution of the composition in water
being not more than 2.8,
for tanning pelts in aqueous liquor.
[0038] The examples which follow explain the invention in more detail.
A) Preparation of compositions
Example A1: Solution of chromium sulphate, lactic acid and formic acid
[0039] In a stirred vessel, 109.3 g of a solution of 18 g of formic acid (85% strength)
and 42.7 g of lactic acid in water are added to a solution of 830 g of chromium(III)
sulphate and sodium sulphate [Schorlemmer basicity 33% (theoretically Cr(OH)SO
4; 15% by weight content of Cr
2O
3)]. Stirring is then effected for 30 minutes at room temperature. The composition
contains 12.49% by weight of Cr
2O
3 and has a Schorlemmer basicity of 20.6% and a density of 1.47 g/cm
3 at 20°C. The pH of the composition is 1.40 and the pH of a 10 percent strength by
weight solution in water is 2.42.
Example A2: Solution of chromium sulphate, lactic acid and formic acid
[0040] In a stirred vessel, 109.3 g of a solution of 23 g of formic acid (85% strength)
and 37.7 g of lactic acid in water are added to a solution of 830 g of chromium(III)
sulphate and sodium sulphate [Schorlemmer basicity 33% (theoretically Cr(OH)SO
4; 15% by weight content of Cr
2O
3)]. Stirring is then effected for 15 minutes at room temperature. The composition
contains 12.40% by weight of Cr
2O
3 and has a Schorlemmer basicity of 20.0% and a density of 1.47 g/cm
3 at 20°C. The pH of the composition is 1.40 and the pH of a 10 percent strength by
weight solution in water is 2.39.
Example A3: Solution of chromium sulphate and oxalic acid and formic acid
[0041] In a stirred vessel, 109.3 g of a solution of 28.5 g of oxalic acid in water are
added to a solution of 830 g of chromium(III) sulphate and sodium sulphate (Schorlemmer
basicity 33% (theoretically Cr(OH)SO
4; 15% by weight content of Cr
2O
3)]. Stirring is then effected for 30 minutes at from 40 to 50°C. Thereafter, after
cooling to 30°C, 32.8 g of formic acid (85% strength) are added and stirring is effected
for a further 15 minutes. The composition contains 14.49% by weight of Cr
2O
3 and has a Schorlemmer basicity of 19.2% and a density of 1.63 g/cm
3. The pH of the composition is 0.98 and the pH of a 10 percent strength by weight
solution in water is 2.27.
Example A4: Powder comprising chromium sulphate, lactic acid and formic acid
[0042] 109.3 g of a solution of 18 g of formic acid (85% strength) and 42.7 g of lactic
acid in water are added to a solution of 830 g of chromium(III) sulphate and sodium
sulphate [Schorlemmer basicity 33% (theoretically Cr(OH)SO
4; 15% by weight content of Cr
2O
3)]. Stirring is then effected for 30 minutes at room temperature. The composition
is dried in a water jet vacuum at 60°C. The green residue is then milled to give a
powder. The pH of a 10 percent strength by weight solution in water is 2.48.
Example A5: Powder comprising chromium sulphate, lactic acid and formic acid
[0043] 109.3 g of a solution of 23 g of formic acid (85% strength) and 37.7 g of lactic
acid in water are added to a solution of 830 g of chromium(III) sulphate and sodium
sulphate [Schorlemmer basicity 33% (theoretically Cr(OH)SO
4; 15% by weight content of Cr
2O
3)]. Stirring is then effected for 15 minutes at room temperature. The composition
is dried in a water jet vacuum at 60°C. The green residue is then milled to give a
powder. The pH of a 10 percent strength by weight solution in water is 2.46.
[0044] Example A6: Powder product comprising chromium sulphate and oxalic acid and formic acid 109.3
g of a solution of 28.5 g of oxalic acid in water are added to a solution of 830 g
of chromium(III) sulphate and sodium sulphate [Schorlemmer basicity 33% (theoretically
Cr(OH)SO
4; 15% by weight content of Cr
2O
3)]. Stirring is then effected for 30 minutes at from 40 to 50°C. Thereafter, after
cooling to 30°C, 32.8 g of formic acid (85% strength) are added and stirring is effected
for a further 15 minutes. The composition is dried in a water jet vacuum at 60°C.
The green residue is then milled to give a powder. The pH of a 10 percent strength
by weight solution in water is 2.45.
B) Use examples
Example B1: Tanning of hides (Swiss bull)
[0045] 20% by weight of water are added to 50 kg (dry weight) of delimed, bated, unsplit
and washed hides (Swiss bull) in a tanning drum and then 3% by weight of NaCl are
added. The liquor is allowed to act for 15 minutes. Thereafter, 10% by weight of the
undiluted composition according to example A1 and 0.1% by weight of fungicide (Acticide
4A
®) are added and allowed to act for 6 hours at room temperature. The temperature is
then increased to 44°C and the liquor is allowed to act for a further 9 hours. The
tanned hide is then removed and washed. The pH of the liquor is 3.25, and the liquor
contains only 0.15% by weight of chromium. The hides have been completely tanned.
Example B2: Tanning of hides (Russian cows)
[0046] 20% by weight of water are added to 300 kg (dry weight) of delimed, bated, unsplit
and washed hides (Russian cows) in a tanning drum and then 3% by weight of NaCl are
added. The liquor is allowed to act for 15 minutes. Thereafter, 10% by weight of the
undiluted composition according to example A1 and 0.1% by weight of fungicide (Acticide
4A
®) are added and allowed to act for 6 hours at room temperature. The temperature is
then increased to 44°C and the liquor is allowed to act for a further 9 hours. The
tanned hide is then removed and washed. The pH of the liquor is 3.0. The hides have
been completely tanned.
Example B3: Tanning of hides (Brazilian zebu)
[0047] 20% by weight of water are added to 35 kg (dry weight) of delimed, bated, unsplit
and washed hides (Brazilian zebu) in a tanning drum and then 3% by weight of NaCl
are added. The liquor is allowed to act for 15 minutes. Thereafter, 10% by weight
of the undiluted composition according to example A2 and 0.1% by weight of fungicide
(Acticide 4A
®) are added and allowed to act for 6 hours at room temperature. The temperature is
then increased to 42°C and the liquor is allowed to act for a further 9 hours. The
tanned hide is then removed and washed. The pH of the liquor is 3.4. The hides have
been completely tanned.
Example B4: Tanning of hides (Russian cows)
[0048] 20% by weight of water are added to 30 kg (dry weight) of delimed, bated, unsplit
and washed hides (Russian cows) in a tanning drum and then 3% by weight of NaCl are
added. The liquor is allowed to act for 15 minutes. Thereafter, 10% by weight of the
undiluted composition according to example A3 and 0.1% by weight of fungicide (Acticide
4A
®) are added and allowed to act for 6 hours at room temperature. The temperature is
then increased to 44°C and the liquor is allowed to act for a further 8 hours. The
tanned hide is then removed and washed. The pH of the liquor is from 3.2 to 3.3 and
the liquor contains only 0.16% by weight of chromium. The hides have been completely
tanned.
Example B5: Tanning of hides (Swiss bull)
[0049] 20% by weight of water are added to 50 kg (dry weight) of delimed, bated, unsplit
and washed hides (Swiss bull) in a tanning drum and then 3% by weight of NaCl are
added. The liquor is then allowed to act for 15 minutes. Thereafter, 6% by weight
of the pulverulent composition according to example A4 and 0.1% by weight of fungicide
(Acticide 4A
®) are added and the liquor is allowed to act for 6 hours at room temperature. The
temperature is then increased to 40°C and the liquor is allowed to act for a further
9 hours. The tanned hide is then removed and washed. The pH of the liquor is 3.23,
and the liquor contains only 0.08% by weight of chromium. The hides have been completely
tanned.
Example B6: Tanning of hides (Swiss bull)
[0050] 20% by weight of water are added to 50 kg (dry weight) of delimed, bated, unsplit
and washed hides (Swiss bull) in a tanning drum and then 3% by weight of NaCl are
added. The liquor is then allowed to act for 15 minutes. Thereafter, 6% by weight
of the pulverulent composition according to example A5 and 0.1% by weight of fungicide
(Acticide 4A
®) are added and the liquor is allowed to act for 6 hours at room temperature. The
temperature is then increased to 40°C and the liquor is allowed to act for a further
9 hours. The tanned hide is then removed and washed. The pH of the liquor is 3.20,
and the liquor contains only 0.20% by weight of chromium. The hides have been completely
tanned.
Example B7: Tanning of hides (Swiss bull)
[0051] 20% by weight of water are added to 50 kg (dry weight) of delimed, bated, unsplit
and washed hides (Swiss bull) in a tanning drum and then 3% by weight of NaCl are
added. The liquor is then allowed to act for 15 minutes. Thereafter, 6% by weight
of the pulverulent composition according to example A6 and 0.1% by weight of fungicide
(Acticide 4A
®) are added and the liquor is allowed to act for 6 hours at room temperature. The
temperature is then increased to 40°C and the liquor is allowed to act for a further
9 hours. The tanned hide is then removed and washed. The pH of the liquor is 3.04,
and the liquor contains only 0.13% by weight of chromium. The hides have been completely
tanned.
1. Composition comprising
a) a mononuclear chromium salt having anions of mono- and polycarboxylic acids having
a molecular weight of not more than 200 and sulphate anions, the mononuclear chromium
salts having a Schorlemmer basicity of not more than 25%,
b) an alkali metal sulphate, and
c) optionally water,
d) the pH of a 10 percent strength by weight solution of the composition in water
being not more than 2.8.
2. Composition according to Claim 1, characterized in that the mono- and polycarboxylic acids are formic acid, acetic acid, propionic acid,
lactic acid, methoxyacetic acid, monochloro- or monofluoroacetic acid, oxalic acid
and malonic acid.
3. Composition according to Claim 1, characterized in that the Schorlemmer basicity of the mononuclear chromium salt is from 16% to not more
than 23%.
4. Composition according to Claim 1, characterized in that the amount of the chromium salt is from 5 to 30% by weight, calculated as the content
of Cr2O3, and the remaining amount is the alkali metal sulphate and optionally water.
5. Composition according to Claim 1, characterized in that it is present as an aqueous solution, as an aqueous concentrate or as a solid, water-soluble
formulation.
6. Composition according to Claim 5, characterized in that the amount of the composition in aqueous solution and aqueous concentrates is from
35 to 85% by weight.
7. Composition according to Claim 6, characterized in that the aqueous concentrate contains more than 40 and up to 70% by weight of water.
8. Composition according to Claim 6, characterized in that, as a solid composition, it is a powder or granules which may contain up to 15% by
weight of water.
9. Process for tanning unpickled pelts by the action of chromium(III) sulphates in aqueous
liquor,
characterized in that an effective amount of a composition containing
a) a mononuclear chromium salt having anions of mono- and polycarboxylic acids having
a molecular weight of not more than 200 and sulphate anions, the mononuclear chromium
salts having a Schorlemmer basicity of not more than 25%,
b) an alkali metal sulphate, and
c) optionally water,
d) the pH of a 10 percent strength by weight solution of the composition in water
being not more than 2.8,
is added to the pelt in aqueous liquor and allowed to act on the pelt, whereby an
effective amount from 1 to 8% by weight of chromium trioxide (Cr
2O
3), based on the weight of the pelt, is present in the liquor.
10. Use of a composition containing
a) a mononuclear chromium salt having anions of mono- and polycarboxylic acids having
a molecular weight of not more than 200 and sulphate anions, the mononuclear chromium
salts having a Schorlemmer basicity of not more than 25%,
b) an alkali metal sulphate, and
c) optionally water,
d) the pH of a 10 percent strength by weight solution of the composition in water
being not more than 2.8,
for tanning pelts in aqueous liquor.
1. Zusammensetzung enthaltend:
a) ein mononukleares Chromsalz aufweisend Anionen von Mono- und Polycarbonsäuren mit
einem Molekulargewicht von nicht mehr als 200 und Sulfatanionen, das mononukleare
Chromsalz hat eine Schorlemmer Basizität von nicht mehr als 25%.
b) ein Alkalimetallsufat, und
c) optional Wasser,
d) der pH-Wert einer 10 gewichtsprozentigen Lösung der Zusammensetzung in Wasser ist
nicht mehr als 2.8.
2. Zusammensetzung gemäß Anspruch 1, dadurch gekennzeichnet, daß die Mono- und Polycarbonsäuren Ameisensäure, Essigsäure, Propionsäure, Milchsäure,
Methoxyessigsäure, Monochlor- oder Monofluoressigsäure, Oxalsäure und Malonsäure sind.
3. Zusammensetzung gemäß Anspruch 1, dadurch gekennzeichnet, daß die Schorlemmer Basizität des mononuklearen Chromsalzes von 16 % bis nicht mehr als
23% ist.
4. Zusammensetzung gemäß Anspruch 1, dadurch gekennzeichnet, daß der Anteil des Chromsalzes 5 bis 30 Gewichtsprozent ist, bezogen auf den Anteil an
Cr2O3, und der verbleibende Anteil ist das Alkalimetallsulfat in optional Wasser.
5. Zusammensetzung gemäß Anspruch 1, dadurch gekennzeichnet, daß sie eine wässrige Lösung, ein wässriges Konzentrat oder eine feste, wasserlösliche
Formulierung ist.
6. Zusammensetzung gemäß Anspruch 5, dadurch gekennzeichnet, daß der Anteil der Zusammensetzung in der wässrigen Lösung und wässrigem Konzentrat 25
bis 85 Gewichtsprozent ist.
7. Zusammensetzung gemäß Anspruch 6, dadurch gekennzeichnet, daß das wässrige Konzentrat mehr als 40 und bis zu 70 Gewichtsprozent Wasser enthält.
8. Zusammensetzung gemäß Anspruch 6, dadurch gekennzeichnet, daß sie als feste Zusammensetzung, ein Pulver oder ein Granulat enthaltend bis zu 15
Gewichtsprozent Wasser ist.
9. Verfahren zum Gerben von nicht-gepickelten Fellen durch Einwirkung von Chrom(III)sulfaten
in wässriger Flotte,
dadurch gekennzeichnet, dass ein wirksamer Anteil einer Zusammensetzung enthaltend
a) ein mononukleares Chromsalz aufweisend Anionen von Mono- und Polycarbonsäuren mit
einem Molekulargewicht von nicht mehr als 200 und Sulfatanionen, das mononukleare
Chromsalz hat eine Schorlemmer Basizität von nicht mehr als 25%.
b) ein Alkalimetallsufat, und
c) optional Wasser,
d) der pH-Wert einer 10 gewichtsprozentigen Lösung der Zusammensetzung in Wasser ist
nicht mehr als 2.8,
zu den Fellen in wässriger Flotte zugegeben wird und auf die Felle einwirkt, wobei
ein wirksamer Anteil von 1 bis 8 Gewichtsprozent an Chromtrioxid (Cr
2O
3), basierend auf dem Gewicht der Felle, in der Flotte vorhanden ist.
10. Verwendung einer Zusammensetzung enthaltend
a) ein mononukleares Chromsalz aufweisend Anionen von Mono- und Polycarbonsäuren mit
einem Molekulargewicht von nicht mehr als 200 und Sulfatanionen, das mononukleare
Chromsalz hat eine Schorlemmer Basizität von nicht mehr als 25%.
b) ein Alkalimetallsufat, und
c) optional Wasser,
d) der pH-Wert einer 10 gewichtsprozentigen Lösung der Zusammensetzung in Wasser ist
nicht mehr als 2.8,
zum Gerben von Fellen in wässriger Flotte.
1. Composition comprenant
a) un sel de chrome mononucléaire comportant des anions d'acides mono- et polycarboxyliques
ayant un poids moléculaire inférieur ou égal à 200 et des anions sulfate, le sel de
chrome mononucléaire ayant une basicité de Schorlemmer inférieure ou égale à 25 %,
b) un sulfate de métal alcalin, et
c) éventuellement de l'eau,
d) le pH d'une solution d'une force de 10 pour cent en poids de la composition dans
l'eau ne dépassant pas 2,8.
2. Composition selon la revendication 1, caractérisée en ce que les acides mono- et polycarboxyliques sont l'acide formique, l'acide acétique, l'acide
propionique, l'acide lactique, l'acide méthoxyacétique, l'acide monochloro- ou monofluoroacétique,
l'acide oxalique et l'acide malonique.
3. Composition selon la revendication 1, caractérisée en ce que la basicité de Schorlemmer du sel de chrome mononucléaire est de 16 % à pas plus
de 23 %.
4. Composition selon la revendication 1, caractérisée en ce que la quantité du sel de chrome est de 5 à 30 % en poids, calculée comme la teneur en
Cr2O3, et la quantité restante correspond au sulfate de métal alcalin et éventuellement
à l'eau.
5. Composition selon la revendication 1, caractérisée en ce qu'elle est présente sous la forme d'une solution aqueuse, d'un concentré aqueux ou d'une
formulation solide hydrosoluble.
6. Composition selon la revendication 5, caractérisée en ce que la quantité de la composition en solution aqueuse et en concentré aqueux est de 35
à 85 % en poids.
7. Composition selon la revendication 6, caractérisée en ce que le concentré aqueux contient plus de 40 et jusqu'à 70 % en poids d'eau.
8. Composition selon la revendication 6, caractérisée en ce que, sous la forme d'une composition solide, il s'agit d'une poudre ou de granulés qui
peuvent contenir jusqu'à 15 % en poids d'eau.
9. Procédé de tannage de peaux non picklées par l'action de sulfates de chrome (III)
dans une liqueur aqueuse,
caractérisé en ce qu'une quantité efficace d'une composition contenant
a) un sel de chrome mononucléaire comportant des anions d'acides mono- et polycarboxyliques
ayant un poids moléculaire inférieur ou égal à 200 et des anions sulfate, le sel de
chrome mononucléaire ayant une basicité de Schorlemmer inférieure ou égale à 25 %,
b) un sulfate de métal alcalin, et
c) éventuellement de l'eau,
d) le pH d'une solution d'une force de 10 pour cent en poids de la composition dans
l'eau ne dépassant pas 2,8, est ajoutée à la peau dans la liqueur aqueuse et mise
à agir sur la peau une quantité efficace de 1 à 8 % en poids de trioxyde de chrome
(Cr2O3), rapportée au poids de la peau, étant présente dans la liqueur.
10. Utilisation d'une composition contenant
a) un sel de chrome mononucléaire comportant des anions d'acides mono- et polycarboxyliques
ayant un poids moléculaire inférieur ou égal à 200 et des anions sulfate, le sel de
chrome mononucléaire ayant une basicité de Schorlemmer inférieure ou égale à 25 %,
b) un sulfate de métal alcalin, et
c) éventuellement de l'eau,
d) le pH d'une solution d'une force de 10 pour cent en poids de la composition dans
l'eau ne dépassant pas 2,8, pour le tannage de peaux dans une liqueur aqueuse.