EP2257650A1

EP2257650A1 - Method for manufacturing leather

Info

Publication number: EP2257650A1
Application number: EP09722872A
Authority: EP
Inventors: Stephan Hüffer; Sebastien Garnier; Michael Kluge; Markus Brym; Franz Glocknitzer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2008-03-20
Filing date: 2009-03-16
Publication date: 2010-12-08
Also published as: WO2009115487A1; BRPI0909178A2; CN101978077A

Abstract

The present invention relates to a method for manufacturing leather, characterized in that the pre-tanning, main-tanning or post-tanning is carried out in the presence of (a) at least one compound of the general formula (I) (b) and oxalic acid or the corresponding ammonium or alkali metal salts thereof, respectively, where R¹is selected from methyl, ethyl, phenyl, benzyl, hydroxymethyl, isopropyl, isobutyl and sec.-butyl.

Description

Process for the production of leather

The present invention relates to a process for the production of leather, characterized in that the pretanning, main tanning or retanning in the presence of (a) at least one compound of general formula I.

(b) and oxalic acid or in each case the corresponding ammonium or alkali metal salts, wherein R ^{1 is} selected from methyl, ethyl, phenyl, benzyl, hydroxymethyl, isopropyl, isobutyl and sec-butyl.

Furthermore, the present invention relates to mixtures of

(a) at least one compound of general formula I and

(b) oxalic acid,

(c) optionally alkali metal formate and

(D) optionally at least one di- or polycarboxylic acid or in each case the corresponding ammonium or alkali metal salts.

Bright leather is in demand in many applications. In particular, if you want a brilliant color of the leather, black, brown or dark gray spots are undesirable. In conventional tanning processes, however, such unwanted stains are often observed.

The formation of black, brown or dark gray patches is in many cases due to iron compounds, especially iron oxides and iron hydroxide, Fβ2θ3-aq, as well as the iron stains typical of Fe when using vegetable tannins. Such stains are formed, for example, by separating chips from knives or other metal parts from folding machines having rotating blades made of steel, and dissolving them in the aqueous tanning liquor to form iron compounds. During neutralization, iron oxide and / or iron hydroxide can then be deposited on the leather.

Particularly serious are the problems with the dark spots when using vegetable tannins. Vegetable tannins usually contain gallic acid or gallate. Gallic acid forms complexes with iron, these have a deep black Color and have been known as an ingredient of inks since the Middle Ages. To produce light leathers, avoid the presence of gallic acid inks during tanning and retanning.

There has been no lack of attempts to prevent the formation of iron compounds in the tanning process. Steel seems indispensable in the production of folding machines. Therefore, one tries to prevent the dissolved iron by masking (sequestration, complexing) from being deposited on the leather. However, the common ligands are associated with disadvantages.

Attempts to complex iron with ethylenediaminetetraacetate (EDTA) have been successful in masking the iron. However, EDTA can mobilize heavy metals from sludge in waters and is therefore undesirable in wastewater. In addition, EDTA is difficult to decompose and the COD (chemical oxygen demand) is high.

It was therefore the object to provide a process for the production of leather, which remedies the known disadvantages and provides stain-free leather available. There was also the task of providing substances or mixtures of substances with which it is possible to produce stain-free leather.

Accordingly, the method defined at the outset was found, which is also referred to below as the method according to the invention.

The process according to the invention is a process for pretanning, main tanning-which also includes tanning-or retanning, preferably the process according to the invention is a retanning process.

The inventive method is based on pretreated hides of dead animals such as cattle, pigs, goats or deer. It is not essential for the method according to the invention, whether the animals were killed, for example, by slaughtering or huntsman or died of natural causes. Conventional methods of pre-treatment include, for example, liming, descaling, pickling and pimpling, as well as mechanical operations, for example, for fleshing out the hides, and in particular folding.

In one embodiment of the present invention, the process according to the invention is carried out as a retanning process. For this purpose, one starts from tanned hides, so-called semi-finished products, whereby the tanning can be carried out with any known tanning substances, for example with Cr (III) compounds, with polymer tanning agents, with aldehyde tanning agents, with vegetable tanning agents or with syntans. It Thus, the semi-finished products used may be wet blue or wet white.

The process according to the invention is carried out in an aqueous liquor. Suitable flotation lengths can be, for example, 50 to 250%.

The process according to the invention is continued

(a) in the presence of at least one compound of general formula I.

and

(b) oxalic acid by or in each case the corresponding ammonium or alkali metal salts, wherein alkali metal is selected from lithium, rubidium, cesium, preferably potassium and more preferably sodium, and

wherein R ^{1 is} selected from methyl, ethyl, phenyl, benzyl, hydroxymethyl, isopropyl, isobutyl and sec-butyl. Preferably, R ^{1 is} selected from methyl and hydroxymethyl, in particular methyl.

In this case, the nitrogen atom in compound of the general formula I may be unprotonated or protonated.

Among the corresponding ammonium or alkali metal salts of compound of the general formula I are mono-, di and triammonium salts or mono-, di- and Trialkalimetallsalze of compound of general formula I to understand where in the case of di- and Trialkalimetallsalze also mixed salts for example, the monosodium monopotassium salt, the disodium monopotassium salt and the monosodium monoammonium salt.

Compound of the general formula I can be present as a racemate or in the form of one or the other enantiomer.

The preparation of compounds of the general formula I is known per se and is achieved, for example, by carboxymethylation of amino acids. In the process according to the invention, furthermore, oxalic acid (b) or a corresponding ammonium or alkali metal salt is used. Corresponding ammonium or alkali metal salts of oxalic acid are understood as meaning mono- and diammonium salts or mono- and dialkali metal salts of oxalic acid, and in the case of dialkali metal salts also mixed salts are included, for example monosodium monokoxaloxalate and monosodium monoammonium oxalate.

In one embodiment of the present invention leads to the inventive

Process additionally in the presence of (c) at least one alkali metal formate, wherein alkali metal is selected from lithium, rubidium, cesium, preferred

Potassium and more preferably sodium, or in the presence of formic acid as the corresponding free acid. In this case, the implementation in the presence of a formic acid / formate buffer is also included.

In one embodiment of the present invention, the process according to the invention is additionally carried out in the presence of (d) at least one di- or polycarboxylic acid or in each case the corresponding ammonium or alkali metal salts, alkali metal being selected from lithium, rubidium, cesium, preferably potassium and particularly preferably Sodium.

In analogy to compound of the general formula I, mixed di- or polyalkali metal salts are also included, and also those ammonium and alkali metal salts are included, which are attributable to a partial neutralization of di- or polycarboxylic acid (d).

Dicarboxylic acid (d) is different from oxalic acid. For example, dicarboxylic acid (d) may be a C3-C12 dicarboxylic acid.

Dicarboxylic acid (d) may have a straight or branched C chain, and it may be cyclic or preferably non-cyclic. Dicarboxylic acid (d) may have an aromatic or alicyclic ring, and dicarboxylic acid (d) may have a bicyclic or polycyclic carbon skeleton. Dicarboxylic acid (d) may have one or more ethylenically unsaturated double bonds. Examples of suitable dicarboxylic acids (d) are phthalic acid, terephthalic acid, isophthalic acid, maleic acid, fumaric acid, itaconic acid, cyclohexanedicarboxylic acid, in particular the isomeric 1,4-cyclohexanedicarboxylic acids, norbornanedicarboxylic acid and norbornenedicarboxylic acid.

However, dicarboxylic acid (d) is preferably one or more aliphatic dicarboxylic acids, unsubstituted or mono- or polysubstituted by hydroxycarboxylic acids. xylgruppe (s). In a variant of the present invention, dicarboxylic acid (d) is a mono- or dihydroxydicarboxylic acid. Examples of particularly suitable aliphatic dicarboxylic acids are tartaric acid, malic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, pimellic acid; preferred are tartaric acid, succinic acid, glutaric acid and adipic acid and binary and ternary mixtures of succinic acid, glutaric acid and adipic acid.

Polycarboxylic acid (d) may have a straight or branched C chain. Preferably, polycarboxylic acid (d) is a compound having three to five carboxylic acid groups per molecule, particularly preferably aliphatic polycarboxylic acids, unsubstituted or mono- or polysubstituted with hydroxyl group (s). Butane-1, 2,3,4-tetracarboxylic acid is preferred, citric acid is particularly preferred.

In one embodiment of the present invention, the process according to the invention is additionally carried out in the presence of ascorbic acid (s). In this case, the implementation is also included in the presence of ammonium ascorbate or one or more alkali metal ascorbates. Ascorbic acid can be present as a racemate or in the form of one of its enantiomers, in particular as (L) -ascorbic acid.

In one embodiment of the present invention, the process according to the invention is carried out in the presence of

0.01 to 1 wt .-%, preferably 0.03 to 0.25 wt .-% compound of general formula I, 0.005 to 0.75 wt .-%, preferably 0.02 to 0.125 wt .-% oxalic acid ( b), optionally 0.001 to 4 wt .-%, preferably 0.02 to 2 wt .-% alkali metal formate

(C), optionally a total of 0.001 to 0.75 wt .-%, preferably 0.03 to 0.175 wt .-% of di- or polycarboxylic acid (s) (d), optionally 0.001 to 0.3 wt .-%, preferably 0 , 05 wt .-% ascorbic acid (s), wherein in wt .-% are based on the shaved weight.

The process according to the invention is carried out, for example, by reacting at least one compound of the general formula I and oxalic acid (b) optionally in admixture with alkali metal formate (c), di- or polycarboxylic acid (d) or ascorbic acid (e) in one or more portions Add portions immediately before or during a tanning step. The process according to the invention is then preferably carried out at a pH of 2.5 to 4, it being frequently observed that the pH during the performance of the process according to the invention increases by about 0.3 to three units. It is also possible to increase the pH by about 0.3 to three units by adding blunting agents. The inventive method is generally carried out at temperatures ranging from 10 to 45 ° C, preferably in the range 20-30 ⁰ C from. A duration of 10 minutes to 12 hours has proven useful, a duration of up to 3 hours is preferred. The process of the invention can be carried out in any conventional tanning vessels, for example, by walking in barrels or in rotatable drums with internals.

In one variant of the process according to the invention, at least one compound of the general formula I and oxalic acid (b), optionally in admixture with alkali metal formate (c), di- or polycarboxylic acid (d) or ascorbic acid (e) together with one or more conventional tanning agents, For example, with chrome tanning agents, mineral tannins, Syntanen, polymer tanning or especially vegetable tanning agents, as described for example in Ullmann's Encyclopedia of Industrial Chemistry, Volume A15, pages 259 to 282 and in particular page 268 ff., 5th edition, (1990), Verlag Chemistry Weinheim. Particularly preferred vegetable tannins are quebracho extracts and mimosa.

In one variant of the process according to the invention, at least one compound of the general formula I and oxalic acid (b) is present as a mixture with alkali metal formate (c), di- or polycarboxylic acid (d) or ascorbic acid (e) in one portion or in several portions during the Vorgerbens, in a special variant already in the pimple.

In a further variant of the process according to the invention, at least one compound of the general formula I and oxalic acid (b) is optionally present as a mixture with alkali metal formate (c), di- or polycarboxylic acid (d) or ascorbic acid (e) in one or more portions or during a retanning step. This variant will also be referred to below as a post-treatment process according to the invention. The Nachgerbverfahren invention is based on pre-tanned hides.

The retanning process according to the invention can be carried out under otherwise customary conditions. It is expedient to choose one or more, for example 2 to 6, action steps and to be able to rinse with water between the interaction steps. The temperature during the individual treatment steps is in each case from 5 to 60 ⁰ C, preferably 20 to 45 ° C. It is possible to use one or more further agents customarily used during the retanning, for example fatliquors, one or more conventional retanning agents, for example chromium tanning agents, mineral tanning agents, syntans, polymer tanning agents or, in particular, vegetable tanning agents, furthermore leather dyes, pH-dulling agents or emulsifiers. In one variant of the present invention, at least one compound of the general formula I and oxalic acid (b), if appropriate alkali metal formate (c), di- or polycarboxylic acid (d) or ascorbic acid (e), are used separately in the tanning, prebirth or retanning to.

The inventive method gives - optionally after a workup by conventional methods - stain-free leather with excellent mechanical properties. Furthermore, effluents are obtained which are generally readily workable and whose chemical and biological oxygen demand can be obtained by combining the general formula I and oxalic acid (b) optionally together with alkali metal formate (c), di- or polycarboxylic acid (d) or ascorbic acid (e). , is not unduly increased.

Another object of the present invention are mixtures comprising (a) at least one compound of general formula I.

(b) and oxalic acid or in each case the corresponding ammonium or alkali metal salts, wherein R ^{1 is} selected from methyl, ethyl, phenyl, benzyl, hydroxymethyl, isopropyl, isobutyl and sec-butyl. Preferably, R ^{1 is} selected from methyl and hydroxymethyl, especially methyl.

In one embodiment of the present invention, mixtures according to the invention additionally contain (c) an alkali metal formate.

In one embodiment of the present invention, mixtures according to the invention additionally comprise

(D) at least one di- or polycarboxylic acid or corresponding ammonium or alkali metal salts. In one embodiment of the present invention polycarboxylic acid (d) is a tri- or tetracarboxylic acid or a corresponding ammonium or alkali metal salt.

In one embodiment of the present invention, di- or polycarboxylic acid is a mono- or dihydroxydi- or polycarboxylic acid.

Corresponding ammonium salts or alkali metal salts of compound of the general formula I, of di- or polycarboxylic acid (d) and of oxalic acid (b) are as described above.

(e) ascorbic acid.

In one embodiment of the present invention, mixtures according to the invention may further comprise water.

In another embodiment of the present invention, mixtures according to the invention may also contain a salt which improves the flowability, for example sodium sulfate. For example, mixtures according to the invention may contain from 5 to 30% by weight of salt, in particular sodium sulfate.

In one embodiment of the present invention, mixtures according to the invention contain

From 10 to 60% by weight, preferably from 15 to 50% by weight, of the compound of the general formula I,

5 to 50 wt .-%, preferably 10 to 25 wt .-% oxalic acid (b), optionally 1 to 50 wt .-%, preferably 10 to 30 wt .-% alkali metal formate (c), optionally a total of 1 to 50 wt. -%, preferably 15 to 35 wt .-% di- or polycarboxylic acid (s) (d), optionally 1 to 20 wt .-%, preferably 2.5 to 10 wt .-% ascorbic acid (s), wherein in wt .-% based on total mixture according to the invention.

Mixtures according to the invention are particularly suitable for carrying out the process according to the invention. Another object of the present invention is the use of the mixtures according to the invention for carrying out the method according to the invention. Another object of the present invention is a process for the production of leather using at least one mixture according to the invention. In one embodiment, from 0.1 to 1, 5 wt .-% mixture according to the invention, preferably 0.2 to 0.5 wt .-%, based on the shaved weight, for carrying out the method according to the invention.

Mixtures according to the invention can be prepared by processes known per se, in particular by mixing compound of general formula I with oxalic acid (b), optionally an alkali metal formate (c), optionally at least one di- or polycarboxylic acid (d) and optionally ascorbic acid (e), in particular by stirring.

The invention will be explained by working examples.

I. Preparation of mixtures according to the invention

The components according to Table 1 were mixed in a stirred vessel and the novel mixtures M.2 to M.5 and comparison mixture V-M.1 were obtained.

Table 2 Composition of the mixtures according to the invention M.2 to M.5 and the comparison mixture V-M.1

Explanatory notes: (a.1):

N / A )

N-CH ₂ COONa

H ₃ C

COO Na ⁺

(c.1): sodium formate

(d.1): C4-C6 dicarboxylic acid mixture, mixture of succinic acid: glutaric acid: adipic acid, weight ratio: 1: 1: 3.

(d.2): citric acid

(b): oxalic acid; (e): (L) -ascorbic acid Data in% by weight

II. Use of mixtures according to the invention and comparative mixtures in the

Retanning / inventive process for the production of leather

Data in% by weight in each case relate to the shaved weight and denote the amount of active ingredient, unless expressly stated otherwise.

In the examples, no dye was used to more easily measure staining. In addition, iron granules powder was added. However, the examples can also be carried out using one or more leather dyes and omitting the defined treatment with iron granules powder.

Bovine wet blue (short: wb, US-Packer) and bovine wet white (short: ww) were folded to 1, 8 mm and cut to the core area. Then they were distributed to two separate barrels. The mixture was then neutralized by allowing to work at 20 ^° C. and a liquor length of 100% by weight of water, 0.7% by weight of sodium formate and 0.2% by weight of NaHCO 3 over a period of 60 minutes. At the end of the treatment, a pH of 4.8 to 5.0 was measured. Subsequently, the semi-finished products were washed twice with 100 wt .-% water and cut into 10 strips (wb and ww), each about 400 g. Now, the semifinished strips were sprinkled evenly with 0.5 g of iron granulated powder per dm ² (50 μm average diameter). Then you put the semi-finished strips for 8 hours with a plastic film covered over Bock. The semifinished strips were then distributed to 20 separate rotatable drums and treated with 60 wt .-% water and treated with 6 wt .-%% of the sulfone Fongerbstoffs from EP-B 0 459 168, Example K1. After a walk time of 20 minutes at 30 ⁰ C was metered 0.9 wt .-% sodium formate and further 30 minutes (30 ⁰ C). Subsequently, 0.3% by weight of the mixtures according to the invention or comparative mixtures or complexing agents listed in Table 1 were added, followed by 1% by weight of a fatliquor according to WO 03/023069, Example A (base sulfited fish oil). After 15 minutes of bathing, 6% by weight of the vegetable tanning substances Mimosa and Quebracho were each dosed. After a flexing time of a further 40 minutes, 3% by weight of a fatliquor according to WO 03/023069, Example A were metered. The reaction was carried out for a further 20 minutes and then 2% by weight of a naphthalenesulfonic acid-formaldehyde condensation product prepared according to US 5,186,846, example "Dispersant 1." The reaction was continued for a further 120 minutes, after which the liquor was drained off.

After draining the liquor, the pieces of leather obtained were washed twice with 100% by weight of water each time. The leather pieces were covered with a foil, stored for at least 6 hours over Bock. After stretching, the pieces of leather were then dried at 60 to 70 ⁰ C over a period of 4 minutes in vacuo. The conditioning prior to visual inspection was carried out at 40 ⁰ C in a conditioned room for 12 hours, or alternatively by insertion into moistened sawdust. The comparative leathers VL.1 to VL.10 and the leathers L.1 1 to L.20 produced according to the invention were obtained.

The results of the visual inspection are summarized in Table 1.

The leathers according to the invention and the comparative leathers were evaluated according to a grading system of 1 to 5. Note 1 in this case means based on the color number no discoloration beyond the intrinsic color of Crust leather (wet blue or wet white) and correspondingly neither iron stains nor inhomogeneities in the appearance of the leather. Grade 5 corresponds to a gray-black leather.

Table 2: Test results of comparative leather V-L.1 to V-L.10 and leathers L.11 to L.20 produced according to the invention

The effluents produced in the production of V-L.3 and V-L.4 had extremely unfavorable COD (chemical oxygen demand) and contained unused EDTA.

Claims

claims

1. A process for the production of leather, characterized in that the

Pre-tanning, main tanning or retanning in aqueous liquor in the presence of

(a) at least one compound of general formula I

(b) and oxalic acid or in each case the corresponding ammonium or alkali metal salts, wherein R ^{1 is} selected from methyl, ethyl, phenyl, benzyl, hydroxymethyl,

Isopropyl, isobutyl and sec-butyl.

2. The method according to claim 1, characterized in that it additionally in the presence of

(C) performs an alkali metal formate.

3. The method according to any one of claims 1 or 2, characterized in that it additionally in the presence of

(d) at least one di- or polycarboxylic acid or in each case carries out the corresponding ammonium or alkali metal salts.

4. The method according to any one of claims 1 to 3, characterized in that polycarboxylic acid (d) is a tri- or tetracarboxylic acid or a corresponding ammonium or alkali metal salt.

5. The method according to any one of claims 1 to 4, characterized in that it is a mono- or dihydroxydi- or polycarboxylic acid in the case of di- or polycarboxylic acid.

6. The method according to any one of claims 1 to 5, characterized in that it is in the presence of

(e) performs ascorbic acid.

7. The method according to any one of claims 1 to 6, characterized in that it is carried out in the presence of at least one vegetable tanning agent.

8. Mixture containing

(a) at least one compound of general formula I.

9. Mixture according to claim 8, containing in addition

(c) an alkali metal formate.

10. Mixture according to claim 8 or 9, additionally containing

(D) at least one di- or polycarboxylic acid or corresponding ammonium or alkali metal salts.

11. A mixture according to any one of claims 8 to 10, characterized in that polycarboxylic acid (d) is a tri- or tetracarboxylic acid or a corresponding ammonium or alkali metal salt.

12. Mixture according to one of claims 8 to 1 1, characterized in that it is di- or polycarboxylic acid is a mono- or dihydroxydi- or -polycarbonsäure.

13. A mixture according to any one of claims 8 to 12, additionally containing

(e) ascorbic acid.

14. Use of mixtures according to one of claims 8 to 13 in a method according to one of claims 1 to 7.