Vegetable extract for tanning

Abstract

The invention relates to the use of a tannin-containing product which can be produced or is produced by means of (i) an aqueous solution or dispersion, containing one or more polar organic solvents, in the form of an extract, or (ii) a supercritical solvent in the form of a residue of the extraction, or (iii) pure water in the form of a residue of the extraction, or (iv) a mixture of a supercritical and a polar solvent in the form of a residue of the extraction, for tanning and / or retanning hides or skins or intermediate products thereof resulting from leather production; and further related subject matter of the invention.

Description

[0001] Vegetable extracts for tanning

[0002] The invention relates to the use of a tanning agent-containing product which can be produced or is produced by extracting a vegetable tanning agent-containing material by means of (i) an aqueous solution or dispersion containing one or more polar organic solvents or (ii) by means of a supercritical solvent or (iii) pure water or (iv) a mixture of a supercritical and a polar solvent, as described below and in the claims, for tanning and / or retanning hides or skins or their intermediate products obtained in leather production, and / or also to related inventive subjects as set out below and in particular in the examples.

[0003] During tanning, collagen fibers from animal hide are cross-linked to protect against bacterial or fungal degradation. Common tanning agents are chromium sulfate, glutaraldehyde, vegetable tanning agents, or synthetic tanning agents. Synthetic tanning agents, often referred to as synthans or synonymously as syntans, are usually aldehyde condensation products of aromatic parent compounds, particularly phenol, cresol, naphthalene, and naphthol, made solubilized by sulfonation or sulfomethylation. Condensates of naphthalenesulfonic acids, phenolsulfonic acid, diphenylsulfones, or sulfonated diaryl ethers with formaldehyde and / or urea are particularly preferred. Such condensates are known, for example, from Herfeld's (editor) "Bibliothek des Leders," Vol. 3, pages 53 to 59, Umschau-Verlag 1984, or Reich, G.Theory and Practice of Organic Tanning Agents, Part 2: Synthetic Organic Tanning Agents, Das Leder, 1996, pp. 157-171, and can be produced using the processes described in the references cited therein. With the widespread acceptance of chromium sulfate or glutaraldehyde tanning, the use of both vegetable tanning agents and syntans has shifted, and these are primarily used in the retanning process. In this process step, the collagen fibers are already cross-linked, and thus the focus is less on the tanning effect and more on fine-tuning the desired leather properties. Here, too, syntans can be used to more precisely control the properties of the leather due to their more uniform chemical basis. However, the effect of non-tanning agents in vegetable tanning agents, namely filling looser parts of the hide, which ensures a more uniform thickness across the entire leather surface, cannot be achieved to the same extent.This requires the use of larger quantities of syntans or, more often, other products based on a different chemical basis, such as resin tanning agents or other polymers (e.g., acrylates), in the retanning process. A further disadvantage is the fact that all of these synthetic products are petroleum-based, thus running counter to the desire for a more sustainable leather value chain.

[0004] There has been no lack of attempts to overcome or limit the disadvantages of both technical and ecological nature of today's syntans and to replace some of the ingredients with renewable materials.

[0005] Vegetable tanning (i.e., tanning with plant-based tanning agents, also known as vegetable tanning (VG)) is known for tanning animal hides and skins. See, for example, G. Moog, The Tanner, Professional Leather Production, Eugen Ulmer KG, 2016. Plant-based tanning agents are very diverse and usually complex compounds, also known as tannins or polyphenols. They are found in almost all plants. They serve as protection against rot, browsing by game, and fungal or mold infestation. They can be found in bark (e.g., oak, spruce, mimosa, or willow bark), wood (e.g., oak, quebracho, or chestnut), roots (e.g., badan, canaigre), leaves (e.g., sumac or gambir), fruits (e.g., valonea, trillo, myobalana, or tara), and outgrowths (e.g., galls or galls). These substances are normally extracted with water to form a tanning broth and have an astringent effect.

[0006] For example, a distinction is made between so-called (hydrolyzable) pyrogallol tanning agents and condensed pyrocatechin tanning agents. The former contain sugars, which can lead to acid formation in the broths due to fermentation; the latter contain large, poorly soluble tannin particles (so-called phlobaphenes), which settle as sludge and then no longer have any tanning effect. The tanner must have a very precise understanding of the properties of the tannins he is using – each tannin behaves differently in terms of solubility, particle size, diffusion, binding, color, body, firmness, odor, etc.

[0007] In recent decades, attempts have been made to replace vegetable tanning agents with the aforementioned synthetic tanning agents, the syntans, which have largely reproducible, uniform particle size and consistently defined properties.

[0008] On the other hand, however, there is still a need, and recently a renewed interest, for new vegetable tanning agents, as these are natural substances and generally exhibit good ecological and / or biological compatibility. When disposing of leather and its production, it is desirable to avoid synthetic materials and prefer naturally degradable materials. There has been no shortage of attempts to overcome the disadvantages, both technical and ecological, of today's syntans or other tanning agents and to replace at least some of the ingredients with renewable materials.

[0009] It has now been found that when a residue obtained by means of an aqueous organic solvent, a supercritical solvent, such as supercritical carbon dioxide, or a mixture of a supercritical and a polar solvent, or in particular an extract of a tannin-containing vegetable product, for example green tea, is added to the liquor as a tanning agent, a very good tanning and / or retanning effect is surprisingly achieved, which enables the production of leather / tanned skins with very good properties, described in more detail below, and in some cases shows advantageous results in tanning and retanning compared to known vegetable tanning agents and / or requires or has lower concentrations of residue or extract and / or other positive properties.

[0010] In the case of green tea extracts, the properties may not be due solely to the content of polyphenols and / or proanthocyanidins.

[0011] Surprisingly, extracts of green tea, in particular, as tanning products containing tannins (using aqueous polar solvents, particularly ethanol / water), exhibit a better tanning effect and improved retanning properties compared to water extracts, and at least comparable and in some cases better results in leather production compared to previously known vegetable tanning agents. Conversely, extraction with pure water (without added solvents) or with supercritical solvents can yield products relatively enriched in tannins in the residues (quasi "pomace") of the extracted material, which exhibit a stronger tanning effect than the vegetable starting material.

[0012] Thus, with the residues or in particular extracts to be used according to the invention, good shrinkage temperature ("TS") or an improved shrinkage temperature ("TS") compared to known vegetable tanning agents, better or good penetration (and thus more even tanning), better or good levelness (evenness of coloration) and / or better or good dyeability, better or good fullness, better or good softness, better or good tightness, better or good grain breakage, better or good color intensity or two or more of these properties of the resulting leather or tanned hide can be obtained, in comparison to leather or hide produced with known vegetable tanning agents such as from Tara or Mimosa. As a rule, a comparable or better classification can be found overall with comparable amounts or concentrations of tanning agents.

[0013] The hydrothermal stability of the leather, the so-called shrinkage temperature (TS), is considered an important measure of tanning. This can be measured according to the DIN 53336:1977-01 method. The shrinkage temperature of an untanned hide is ideally below 60 °C. An increase above this (e.g., to 65 °C or higher) indicates tanning. For example, when tanned with vegetable tanning agents, the shrinkage temperature is above 60 °C, depending on the type, for example, 65-85 °C. The other properties mentioned are determined by expert assessment and qualitatively classified according to the following values, where "+" indicates a positive characteristic and "negative" indicates a negative characteristic of the respective property:

[0014] +3 / -3 extreme severity, +2 / -2 significant severity, -1 / +1 severity, -0.5 / +0.5 mild severity, 0 reference value

[0015] Other positively influenced properties include improved color intensity combined with good color uniformity and penetration; a pleasantly round and supple feel; and excellent grain break of the leather before and after milling. A special feature is the excellent internal softness of the tanned or retanned material with good body and grain elasticity.

[0016] In particular, by extraction using a mixture of water and one or more polar solvents (always meaning an organic polar solvent), with the same amount of extract and in particular polyphenol concentration compared to a known vegetable tanning agent (e.g. from Mimosa or in particular Tara), even with lower absolute amounts of extract and in particular polyphenols during the tanning process or retanning process, approximately equally good to better and, with comparable absolute amounts, even better properties of the resulting tanned leather or skins can be found, in particular with an extract from green tea ("Green Tea") obtained by means of water in a mixture with one or more polar solvents.

[0017] The reverse applies to residues enriched with polyphenols in the residue relative to the total mass. In general, the tannin-containing products to be used according to the invention advantageously have an enriched proportion of tannins, such as polyphenols, compared to the original plant-based tannin-containing product.

[0018] For example, polyphenols can be determined using a Folin / Ciocalteu assay, sugar content using a phenol-sulfuric assay, and proanthocyanidin content using an acid-butanol assay according to SOPs of the Bern University of Applied Sciences (Biel, Switzerland) with the aid of UV / VIS spectroscopy.

[0019] In a first embodiment, the invention relates to a use of a tannin-containing product obtained by extraction of a vegetable tannin-containing product by means of

[0020] (i) an aqueous solution or dispersion containing one or more polar organic solvents in the form of an extract, or

[0021] (ii) a supercritical solvent in the form of an extraction residue, or

[0022] (iii) pure water in the form of an extraction residue, or

[0023] (iv) a mixture of a supercritical solvent and a polar solvent in the form of an extraction residue, for the tanning and / or retanning of hides or skins or their intermediate products obtained in the manufacture of leather.

[0024] Advantageously or in a second embodiment of the invention, the tannin-containing product to be used is an extract obtainable or obtained according to variant (i) in liquid or dried form of the aqueous dispersion or, in particular, solution containing one or more polar organic solvents.

[0025] Alternatively, or in a third embodiment of the invention, the tannin-containing product to be used is a solid or dispersed residue, in particular "pomace", obtainable or obtained according to one of the variants (ii) or (iii), an extraction with pure water or, in particular, with a supercritical solvent.

[0026] In an advantageous embodiment, in particular of the previously mentioned embodiments of the invention, phenolic compounds, in particular polyphenols and / or proanthocyanidins, are present as tannins in the tannin-containing product to be used.

[0027] Preferably, in a further particular embodiment of the invention, the tanning agent-containing product to be used is a green tea extract in liquid or dried form, which contains or is in particular the product of an extraction by means of an aqueous dispersion or, in particular, a solution containing one or more polar organic solvents. The green tea extract is preferably used for retanning intermediate products obtained from hides or skins during leather production, characterized in that the intermediate product or products is or are a material resulting from pickling, in particular pelt, and this intermediate product is subjected to a tanning or a tanning with subsequent retanning, in each case using the green tea extract.The intermediate product(s) is / are, for example, a material obtainable after a first tanning step, in particular wet white, wet brown or wet blue, with this material being retanned using the green tea extract.

[0028] In a further embodiment of the invention, in particular a green tea extract or the extract of the respective liquor can be added in solid, e.g. granular or in particular powdered form, to a liquor for tanning or retanning.

[0029] A further embodiment of the invention provides that a green tea extract is added to a respective liquor in liquid form, in particular as an aqueous-ethanolic solution.

[0030] A further particular embodiment of the invention relates in each case to one of the embodiments mentioned in the last three paragraphs, wherein an extract of green tea is obtained (= obtainable or obtained) by means of a polar solvent or polar solvent mixture in water at a weight ratio, based on the total weight of dry green tea, water and polar solvent (mixture), of polar solvent (mixture) to water of 5:95 to 90:10, preferably of 10:90 to 80:20, in particular of 30:70 to 70:30, preferably by extraction in the range up to the boiling temperature of the respective mixture, for example at 80 to 105 °C, wherein the extract is used as a liquid or after drying in solid form, in this case in particular as granules or preferably as a powder.

[0031] In all embodiments of the invention, preference is given to one in which a polar solvent is understood to be one which is miscible with water and which is selected from alcohol, in particular methanol, ethanol, propanol or isopropanol, a diol, in particular ethylene glycol, diethylene glycol or triethylene glycol, a ketone, in particular acetone or methyl ethyl ketone, a di-lower alkyl sulfoxide, in particular dimethyl sulfoxide or diethyl sulfoxide, a nitrile, such as acetonitrile, a water-soluble ether, such as dioxane or tetrahydrofuran, an amide, such as formamide, N-methylformamide, dimethylformamide or diethylformamide, and a heterocyclic solvent, such as piperidine or N-methyl-2-pyrrolidone, or a mixture of two or more thereof.

[0032] Where a supercritical solvent is used, the invention relates, in a further embodiment, to one selected from dinitrogen monoxide, sulfur dioxide, a fluorocarbon, or, in particular, carbon dioxide; a mixture of polar organic solvent and supercritical solvent is also possible.

[0033] In a specific embodiment, the invention relates to a use wherein the green tea extract is one in which 100 to 300 parts of green tea with 300 to 900 parts of water and 200 to 600 parts (each based on the weight) of the polar solvent, in particular ethanol, were used to produce the extract.

[0034] Advantageously, in the case of use according to the invention during extraction, the ratio of the weights of green tea to water to polar solvent, in particular ethanol, is (10-30) : (40-60) : (25-40), preferably such that the sum of the ratios is one hundred.

[0035] A particular embodiment of the invention also relates to a tanning agent and / or retanning substance, comprising a tanning agent-containing product that can be produced or is produced as defined in the above embodiments, in particular for tanning and / or retanning hides or skins or their intermediate products obtained during leather production. In a particular variant of this embodiment, the tanning agent and / or retanning substance (i.e., the corresponding material) contains a green tea extract as defined in one of the above embodiments. Combinations with syntans and / or lignins are also conceivable embodiments of the invention.

[0036] A further embodiment of the invention relates to a process for vegetable tanning and / or retanning, characterized in that a tanning agent-containing product produced according to one of the preceding embodiments, or a tanning agent and / or substance for retanning according to the last paragraph, is added to a hide, a pelt or, in the case of retanning, to an already tanned material resulting from the materials mentioned, in aqueous solution or dispersion with or without further additives, and the mixture is incubated for a longer time, for example 0.1 to 5 days, for example 0.5 to 3 days, in each case preferably with agitation.

[0037] The invention also relates to the embodiments defined in the claims, which are incorporated herein by reference.

[0038] The most important preferred embodiments for various methods and processes are described below.

[0039] The extraction with water and one or more polar (organic) solvents preferably takes place by extracting a tannin-containing plant material, for example bark (e.g. oak, spruce, mimosa or willow bark), wood (e.g. oak, quebracho or chestnut wood), roots (e.g. badan, canaigre), stems, leaves or petals (e.g. sumac or gambier or in particular green tea from Camellia sinensis or also assamica), fruits (e.g. valonea, trillo, myobalans or tara) or outgrowths (e.g. galls or knobbers) or kernels, which are extracted in unchanged or in dried, in each case uncrushed or crushed (e.g. chopped or ground) form.

[0040] The extraction is preferably carried out by heating with the extraction agent (mixture of water and one or more polar solvents), for example to temperatures between 50 °C and the boiling point of the respective batch (=extraction agent plus plant material to be extracted), for a sufficient time, for example over a period of 0.5 to 10 hours, in particular from 2 to 5 hours, for example (based on the mass or, under normal conditions of gravity, the weight of the plant material to be extracted) in a ratio of mass of plant material: mass of extraction agent of 10:1 up to 1:100, preferably from 5:1 to 1:25, in particular from 3:1 to 1:10.

[0041] The extracts obtainable or obtained in this way can, if appropriate after filtering off solid components, after further dilution or as such or in liquid form concentrated by partial removal of extraction agent (e.g. by distillation or evaporation, in each case with or without vacuum), or after complete drying (e.g. by evaporation of the extraction agent, spray drying, fluidized bed process, freeze drying or the like), be obtained in dried form, for example as solid masses, granules or (particularly after grinding) as powder and stored (e.g. with cooling) and later added to the respective liquor during tanning or retanning. The residues after extraction with water or with a supercritical solvent as extraction agent are obtained analogously by using the extraction agent to remove the components of the tanning agent soluble therein (e.g.tannin)-containing plant material is dissolved and discarded, and the remaining residue is then used as a basis for a tanning agent.

[0042] Tanning with an extract (or a residue) to be used according to the invention is carried out by conventional processes, for example in a process for tanning and / or retanning hides and / or skins, in particular pelts or, in the case of retanning pre-tanned hides and / or skins, in a liquor, comprising the steps:

[0043] - placing a hide and / or skin or pelt or, in the case of retanning, a pre-tanned hide or skin in a float,

[0044] - adding the extract (or residue) to the hide, skin, pelt or pre-tanned hide or leather or two or more of the above materials in the liquor,

[0045] - the extract added to the liquor acting on the said materials in a penetration step, with or without coloring, wherein advantageously a refatting step (fat liquoring) is subsequently carried out with a refatting agent (fat liquor) and, if necessary, the pH is adjusted with an organic acid, in particular formic acid, to a value between 2.5 and 5, in particular between 3 and 4, and after washing with water a resulting vegetable-tanned or vegetable-retanned skin and / or hide product is obtained.

[0046] Usual post-treatment steps may follow, such as turning to loosen, jacking up, aligning, drying (e.g. in a vacuum), studding or walking.

[0047] Embodiments for procedures, methods of measuring parameters and other steps can be found in the examples.

[0048] The following examples serve to illustrate the invention without limiting its scope. Definition of branded products mentioned:

[0049] BORRON® SAF - Anionic stabilizer for fatliquoring agents with softening effect

[0050] CORIPOL® SLG - Anionic fatliquoring agent for all soft and hard-grain leather articles, based on a combination of natural and synthetic fats

[0051] CORIPOL® BZE-N - Anionic fatliquoring agent for shoe upper leather based on a combination of sulfated natural fats

[0052] TANIGAN BN pwd . - Anionic exchange tanning agent for the tanning and retanning of soft and full leathers, based on methylene condensation products of arylsulfonic acid and hydroxyaryl acid

[0053] SELLATAN MBS gran.- Tanning agent with good lightfastness, based on anionic condensation products of phenolic sulfonic acid

[0054] SELLASOL® CV conditioning agent MAGNOPAL ® Pure A biofiller

[0055] SELLA® FAST Brown HF-R metal complex dye

[0056] SELLA® FIX E Formaldehyde-free fixative for anionic dyes

[0057] These are always trademarks of TFL Ledertechnik GmbH, Rheinfelden, Germany.

[0058] Example 1: Green tea extract extraction with water or water / ethanol mixtures a) Extract with water:

[0059] In a 3-liter reactor equipped with a three-blade stirrer (2 stages), 400 g of green tea and 2000 g of demineralized water were placed. The stirrer was switched on and heated to boiling point (temperature set at 99 °C). After 3 hours and 30 minutes, the reactor was cooled with stirring (temperature adjusted to 20 °C). After a further 2 hours and 30 minutes, the reactor was placed in a water bath at 47 °C, stirring was stopped, the reactor was emptied, and the mixture was filtered through a stocking filter. After drying at 105 °C, the filtrate had a dry matter content of 6.75 wt.%, based on the original filtrate. b) Extract with water and ethanol:

[0060] In a 3-liter reactor with three-blade stirrer (2 stages), 400 g of green tea, 1200 g of demineralized water (50%, based on both solvents 60%) and 800 g of ethanol (33.33%, based on both solvents 40%) were placed. The stirrer was set at 150 rpm and the mixture was stirred for 20 min in a water bath set at 50 °C, then for 25 min in a water bath set at 60 °C.

[0061] C water bath, then for 15 min in a water bath set at 70 °C, then 15 min in a water bath set at 80 °C, then 15 min in a water bath set at 90 °C, until after a further 15 min the water / ethanol mixture boiled. The mixture was left to boil for three hours and thirty minutes with stirring. It was then cooled with stirring (temperature adjusted to 20 °C). After a further 2 hours, the batch was placed in a water bath at 53.6 °C, stirring was stopped, the reactor was emptied and the mixture was filtered through a stocking filter. After drying at 105 °C, the filtrate had a dry matter content of 6.5 wt.%, based on the original filtrate.

[0062] Both extracts were stored as liquids in a refrigerator at 10 °C until use.

[0063] Example 2: Importance of ethanol in the extraction of green tea for its effectiveness as a tanning agent using the example of a liquid

[0064] Green tea extract

[0065] Article Shoe leather

[0066] nakedness, pieces

[0067] MATERIAL De-pimpled nakedness

[0068] COLOR Natural

[0069] Process % Product Time Comments

[0070] tanning

[0071] 1- 440g 170 Green Tea Water Extract 120 pH : 4.5

[0072] Shake well min . cutting sample

[0073] +240 after 3.5h min . TS after 48h 2- 440g 170 Green Tea Water Extract + 120 pH 4.9 -

[0074] Ethanol addition to the min. cutting sample

[0075] Water extract - well +240 after 3.5 h shaking min. TS after 48h

[0076] 3 - 440g 170 Liquid Green Tea - 120 pH

[0077] Extract - Water + min 5.4: Cutting

[0078] Ethanol for extraction +240 sample after

[0079] - shake well min 3.5 h

[0080] TS after 48h

[0081] Everything for a day in the 120 TS 2

[0082] Incubate tanning barrel min .

[0083] Add 6 Mimosa

[0084] 2 days

[0085] FATLIQUOR 50 Water, 45°C

[0086] 16 Mixture of commercially available

[0087] Fat leagues

[0088] 120

[0089] Overnight, without min.

[0090] Heat

[0091] 50 water, 45°C 20 min .

[0092] 4 _ X Formic acid, 75% 3x 30 pH : 3 , 5-3 , 6

[0093] 1 min . +

[0094] 6£ min .

[0095] WASH 300 water, 40°C 10 min .

[0096] WASH 300 water, 30°C 15 min .

[0097] Stand overnight, hang to dry, and stollen. TS = shrinkage temperature (a measure of the strength of the cross-linking bonds in the hide's fine structure) is determined as described in the general section of the description. Evaluation of the resulting dried leather:

[0098] Note on table usage: +3 / -3 extreme severity, +2 / -2 significant severity, -1 / +1 severity, -0.5 / +0.5 mild severity, 0 reference value.

[0099] The extract prepared according to the invention with ethanol / water showed surprisingly significant advantages in the tanning effect (high dry matter content) and high levelness. Extraction with ethanol / water improved the tanning performance. Adding ethanol to aqueous green tea extract did not show any improvement; therefore, the higher tanning effect depends on the extraction with ethanolic water, not solely on the ethanol content in the liquor. Example 3: Tanning compared with Mimosa extract as powder.

[0100] ARTICLE Upper Pickled skin, pieces + 20% to the pickled

[0101] MATERIAL Weight -

[0102] COLOR natural

[0103] Process % Product Time Comments

[0104] DE-PICKLING / Water, 20 °C TANNING 50 Water, pH3.0

[0105] Beaume Pickelflotte 0 :

[0106] 6.5 4 Sodium formiate

[0107] 1 BORRON® SAF

[0108] 2 CORIPOL® SLG

[0109] 2.3 Sodium bicarbonate 120 pH : 7.1 min. Cut Indicator Bromocresol green (BCG) : Cut Blue

[0110] Overnight, slowly

[0111] 8 SELLASOL CV 90 pH 7.6

[0112] (conditioning min medium)

[0113] 100 water, 20°C 20 min

[0114] Separate pieces

[0115] 100 dye fleet

[0116] 1 40 Mimosa 120 min .

[0117] 2 20 Green tea extract 120 min .

[0118] Slowly overnight, 2 days

[0119] FATLIQUOR 100 Water, 45°C

[0120] 1 BORRON® SAF

[0121] 8 CORIPOL® BZE-N

[0122] 10 CORIPOL® SLG 120 mm . 6 Formic acid, 75% 3x 20 pH: 3.4 min .

[0123] WASH 300 water, 40°C 10 min .

[0124] WASH 300 water, 30°C 15 min .

[0125] Note on table usage: +3 / -3 extreme severity, +2 / -2 significant severity, -1 / +1 severity, -0.5 / +0.5 mild severity, 0 reference value

[0126] Results of the evaluation:

[0127] What's special and truly exceptional about the experiment described above is that the 40% powdered mimosa extract could be more or less replaced with 20% green tea extract. This allows for a significant reduction in tannin.

[0128] Example 4: Retanning of a glutaraldehyde-tanned leather with green tea extract powder (extracted with ethanol / water)

[0129] ARTICLE Shoe

[0130] Glutaraldehyde

[0131] MATERIAL tanned leather, 1.1 mm COLOR beige

[0132] Process % Product Time Comments

[0133] WASH 30 water, 30 °C

[0134] 0

[0135] 0,

[0136] 3 BORRON® SAF

[0137] 0, Formic acid 85%

[0138] 5 (1:5) 20 min. pH 3.7

[0139] NEUTRAL 15 Water, 30 °C

[0140] IZATION 0

[0141] SELLASOL® CV (condition pH 4.8 -

[0142] 8 tioning agents) 40 min. 5.2

[0143] A 20 Tara 60 min.

[0144] Green tea extract 50%

[0145] B 10 Polyphenol 60 min. 4 COMMERCIALLY FATTENING AGENT

[0146] 6 MAGNOPAL ® Pure A biofiller 120 min.

[0147] Move slowly overnight

[0148] 50 water, 45°C

[0149] 2 Formic acid, 85% 2x 30 min. pH: 3.7

[0150] - 4.0

[0151] WASH 30 water, 45 °C 10 min

[0152] 0

[0153] FATLIQUO 15 Water, 45 °C

[0154] RING 0

[0155] 14 Mixture of commercially available

[0156] Fat liquors

[0157] 90 min.

[0158] 50 water, 45°C

[0159] 2 Formic acid, 85% 2x 20 min pH 3.7

[0160] WASH 30 water, 45 °C 10 min

[0161] 0

[0162] WASH 30

[0163] 0 water, 20°C 10 min.

[0164] Jack up overnight, align, vacuum dry, 45 °C / 3 min, stud, and tumble. Evaluation results:

[0165] Note on using the table: +3 / -3 extreme severity, +2 / -2 significant severity, -1 / +1 severity, -0.5 / +0.5 slight severity, 0 reference value. Surprisingly, it can be observed that for a similar tanning effect with green tea extract, only half the amount of powder is needed as for tara, a vegetable tanning agent. Nevertheless, comparable leather properties are achieved.

[0166] Example 5: Retanning of chrome-tanned leather (better result with the same amount used)

[0167] MATE-US Wet Blue

[0168] RIAL 1.1 mm 1 skin in 4 pieces

[0169] % based on color brown shaved weight :

[0170] Process Time Coming-

[0171] % tare

[0172] WASH 300 water, 30 °C

[0173] 0.3 Formic acid, 85% 10 pH min 3.4

[0174] NEUTRAL- 150 water, 30 °C

[0175] IZATION

[0176] 2 sodium formate 20 min. 1.5 sodium bicarbonate 90 pH min. 5.9

[0177] WASH 300 water, 30°C 10 min .

[0178] Dyeing 150 water, 30°C

[0179] 1 10 TANIGAN BN powder. 120 pH min. 5.0

[0180] 2 10 SELLATAN MBS gran . 120 pH min. 5.1

[0181] 3 10 Tare 120 pH min . 4.6

[0182] 4 10 Green Tea Extract 120 pH

[0183] (powder) min. 5.0

[0184] 100 water 50°C

[0185] 1.0 formic acid, 85% 30 min .

[0186] 1.0 Formic acid, 85% 30 pH min . 3.8

[0187] WASH 300 water, 50°C 10 min .

[0188] WASH 300 water, 50 °C

[0189] 0.5 sodium bicarbonate 10 pH min 5.4

[0190] 3 SELLA FAST Brown 30

[0191] HF-R min .

[0192] 14 CORIPOL® MK 60 min .

[0193] 1.0 formic acid, 85% 30 min .

[0194] 1.5 Formic acid, 85% 30 pH min . 3.5

[0195] WASH 300 water, 50°C 10 min .

[0196] WASH 300 water, 30 °C 0.5 SELLA® FIX E 30 min .

[0197] Note on using the table: +3 / -3 extreme expression, +2 / -2 significant expression, -1 / +1 expression, -0.5 / +0.5 slight expression, 0 reference value Surprisingly, comparable to better properties of the leather were found with the same amount of extract.

[0198] Example 6 : Tanning to produce a vegetable leather

[0199] Tara is a plant tannin that comes from the small Tara tree

[0200] (Cesalpina spinosa). Leather evaluation:

[0201] 1 / +1 severity, -0.5 / +0.5 mild severity, 0 reference value

[0202] It turns out that green tea extract produced results that were about as good as mimosa extract and better than tara extract.

Claims

Claims 1. Use of a tannin-containing product obtained by extraction of a vegetable tannin-containing product by means of (i) an aqueous solution or dispersion containing one or more polar organic solvents in the form of an extract, or (ii) a supercritical solvent in the form of an extraction residue, or (iii) pure water in the form of an extraction residue, or (iv) a mixture of a supercritical and a polar solvent in the form of an extraction residue, for the tanning and / or retanning of hides or skins or their intermediate products obtained in the manufacture of leather.

2. Use according to claim 1, wherein the tannin-containing product is an extract obtainable or obtained according to variant (i) in liquid or dried form of the aqueous dispersion or, in particular, solution containing one or more polar organic solvents.

3. Use according to claim 1, wherein the tannin-containing product is a solid or dispersed residue, in particular "pomace", obtainable or obtained according to one of the variants (ii) or (iii), an extraction with pure water or in particular with a supercritical solvent. Use according to one of claims 1 to 3, wherein phenolic compounds, in particular polyphenols and / or proanthocyanidins, are present as tannins in the respective product. Use according to claim 1, wherein the tannin-containing product is a green tea extract in liquid or dried form, which contains or is in particular the product of an extraction by means of an aqueous dispersion or, in particular, solution containing one or more polar organic solvents.Use of a green tea extract according to claim 5 for retanning intermediate products obtained from hides or skins in leather production, characterized in that the intermediate product or products is a material resulting from pickling, in particular pelt, and this intermediate product is subjected to tanning or to tanning with subsequent retanning, in each case using the green tea extract. Use according to claim 6, characterized in that the intermediate product or products is or are a material obtainable after a first tanning step, in particular wet white, wet brown or wet blue, and this material is retanned, in each case using the green tea extract. Use according to one of claims 5 to 7, wherein the green tea extract is added to the respective liquor in solid,. e.g. granular or especially powdery form, a Liquor is added for tanning or retanning. Use according to one of claims 5 to 8, wherein the green tea extract is added to one or the respective liquor in liquid form, in particular as an aqueous-ethanolic solution. Use according to one of claims 5 to 9, wherein the green tea extract is obtained by means of a polar solvent or polar solvent mixture in water at a weight ratio, based on the total weight of dry green tea, water and polar solvent (mixture), of polar solvent (mixture) to water of 5:95 to 90:10, preferably 10:90 to 80:20, in particular 30:70 to 70:30, preferably by extraction in the range up to the boiling point of the respective mixture, for example at 80 to 105 °C, wherein the extract is used as a liquid or after drying in solid form, in this case in particular as granules or preferably as a powder.Use according to one of claims 1 to 10, characterized in that a polar solvent is understood to be one which is miscible with water and which consists of alcohol, in particular methanol, ethanol, propanol or isopropanol, a diol, in particular ethylene glycol, diethylene glycol or triethylene glycol, a ketone, in particular acetone or methyl ethyl ketone, a di-lower alkyl sulfoxide, in particular dimethyl sulfoxide or diethyl sulfoxide, a nitrile, such as acetonitrile, a water-soluble ether, such as dioxane or tetrahydrofuran, an amide, such as formamide, N-methylformamide, dimethylformamide or diethylformamide, and a hetero-. cyclic solvent such as piperidine or N-methyl-2-pyrrolidone, or a mixture of two or more thereof.

12. Use according to any one of claims 1, 3 or 4, wherein the supercritical solvent is selected from nitrous oxide, sulfur dioxide, a fluorocarbon, or, in particular, carbon dioxide; a mixture of polar organic solvent and supercritical solvent is also possible.

13. Use according to any one of claims 5 to 12, wherein the green tea extract is one in which 100 to 300 parts of green tea with 300 to 900 parts of water and 200 to 600 parts (each based on the weight) of the polar solvent, in particular ethanol, were used to prepare the extract.

14. Use according to one of claims 5 to 12, characterized in that during extraction the ratio of the weights of green tea to water to polar solvent, in particular ethanol, is (10-30) : (40-60) : (25-40).

15. Tanning agent and / or substance for retanning, comprising as tanning component a tanning agent-containing product which can be produced or is produced according to one of claims 1 to 14, in particular for tanning and / or retanning hides or skins or their intermediate products obtained in leather production.

16. Tanning agent and / or retanning agent according to claim 15, comprising a green tea extract as defined in any one of claims 1 to 14. Process for vegetable tanning and / or retanning, characterized in that a process according to one of the claims 1 to 14, or a tanning agent and / or substance for retanning according to claim 15 or 16, is added to a hide, a skin, a pelt or, in the case of retanning, to an already tanned material made from the materials mentioned, in an aqueous solution or dispersion with or without further additives, and the mixture is incubated for a prolonged time, for example 0.1 to 5 days, preferably with agitation. A process for retanning a semi-finished leather product, in particular after tanning with glutaraldehyde or chromium, comprising treating the semi-finished leather product with an extract of green tea as defined in any one of claims 5 to 15 as a tanning agent in an aqueous solution, if desired in combination with one or more other customary products or auxiliaries for leather production.

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