Classifications

• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/08—Chemical tanning by organic agents
  • C14C3/18—Chemical tanning by organic agents using polycondensation products or precursors thereof

Definitions

• the invention relates to the use of bisulfite-blocked polyisocyanates containing ether groups as tanning agents.
• the tanning transforms animal skins into leather by cross-linking the collagen.
• One of the most important characteristics of leather is the increased shrinking temperature compared to untanned hides, i.e. the improved hot water resistance, and the white appearance (non-transparent, non-pigment-like) after drying.
• the still dominant type of tanning is chrome tanning, in which covalent bonds with the carboxyl groups of the collagen are formed using chromium (III) compounds under the influence of OH ions.
• the hydrogen bonds to the amide groups of collagen that can be obtained with polyfunctional vegetable tannins are much weaker, which also results in a moderately increased shrinking temperature.
• Aliphatic aldehydes e.g. Glutaraldehyde, which leads to crosslinking via the primary amino groups of collagen, has been recommended as a tanning agent (US Pat. No. 2,941,859).
• the resulting aldimines can reversibly react back to aldehyde and amine in the presence of water.
• aliphatic diisocyanates such as hexamethylene diisocyanate (DE-PS 72 981) has not been able to gain acceptance for toxicological reasons.
• reaction products to be used according to the invention can be obtained from the intermediates obtainable from A, B and optionally C with NCO contents of 3 to 50, preferably 5 to 45, in particular 20 to 45% by weight (based on the intermediate) by subsequently blocking the free ones Obtained isocyanate groups.
• the products according to the invention then - calculated as sodium salt and based on solids - contain 9.7 to 78, preferably 14 to 74, in particular 46.5 to 74% by weight of carbamoyl sulfonate groups.
• Suitable organic polyisocyanates A) are aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic polyisocyanates as described, for example, by W. Siefken in Liebigs Annalen der Chemie 562 , pages 75 to 136.
• Preferred polyisocyanates A) are compounds of the formula Q (NCO) n with an average molecular weight below 800, where n is a number of at least 2, preferably from 2 to 4, Q is an aliphatic C4-C12 hydrocarbon radical, a cycloaliphatic C6-C15 hydrocarbon radical , an araliphatic C7-C15-coblenhydrogen radical or a heterocyclic C2-C12 radical with 1 to 3 heteroatoms from the series oxygen, sulfur, nitrogen mean, for example (i) diisocyanates such as ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate , 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate and any mixtures of these isomers, 1-isocyanato-2-isocyanatomethyl
• polyisocyanates produced by trimerization are the trimerizate of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane obtainable by isocyanurate formation and the isocyanurate groups obtainable by trimerization of hexamethylene diisocyanate, optionally in a mixture with 2,4'-diisocyanatotoluene containing polyisocyanates.
• trimerizate of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane obtainable by isocyanurate formation and the isocyanurate groups obtainable by trimerization of hexamethylene diisocyanate, optionally in a mixture with 2,4'-diisocyanatotoluene containing polyisocyanates.
• biuretization Polyisocyanates are tris (isocyanatohexyl) biuret and its mixtures with its higher homologues, as are accessible, for example,
• Particularly preferred polyisocyanates A are those with a molecular weight of 140 to 400 with NCO groups bound to aliphatics or cycloaliphatics, such as 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,5-diisocyanato-2,2-dimethylpentane, 2 , 2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,3- and 1,4-diisocyanatohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 1-isocyanato-1-methyl-4-isocyanatomethyl-cyclohexane and 4,4'-diisocyanatodicyclohexyl-methane, and any mixtures of such diisocyanates.
• araliphatic polyisocyanates such as the xylylene diisocyanates of
• diisocyanates are preferably used.
• monofunctional aliphatic isocyanates such as butyl isocyanate, hexyl isocyanate, cyclohexyl isocyanate, stearyl isocyanate or dodecyl isocyanate and / or polyisocyanates with an average functionality of 2.2 to 4.2 can also be used.
• the higher-functionality polyisocyanates are preferably essentially composed of trimeric 1,6-diisocyanatohexane or 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane and optionally dimeric 1,6-diisocyanatohexane or 1-isocyanato-3 , 3,5-trimethyl-5-isocyanatomethyl-cyclohexane and the correspondingly higher homologues of isocyanurate groups and optionally uretdione groups containing polyisocyanate mixtures with an NCO content of 19 to 24 wt .-%, as obtained by known catalytic trimerization and under isocyanurate Formation of 1,6-diisocyanatohexane or 1-Isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane can be obtained and which preferably have an (average) NCO functionality of 3.2 to 4.2.
• polyisocyanates A are polyisocyanates prepared by modifying aliphatic or cycloaliphatic diisocyanates with uretdione and / or isocyanurate, urethane and / or allophanate, biuret or oxadiazine structure, as described, for example, in DE-OS 1 670 666, 3 700 209 and 3 900 053 and are described by way of example in EP 336 205 and 339 396.
• Suitable polyisocyanates are e.g. also the ester group-containing polyisocyanates, e.g.
• triisocyanates accessible by reacting pentaerythritol or trimethylolpropane silyl ethers with isocyanatocaproic acid chloride (cf. DE-OS 3 743 782). It is also possible to use triisocyanates such as e.g. Tris-isocyanatodicyclohexylmethane to use.
• the use of monofunctional and more than difunctional isocyanates is preferably limited to amounts of at most 10 mol%, based on all polyisocyanates A.
• the polyether alcohols B are accessible in a manner known per se by alkoxylation of suitable starter molecules. Any mono- or polyhydric alcohols with a molecular weight of 32 to 250 can be used as starter molecules to produce the polyether alcohols. Monofunctional aliphatic C1-C18, preferably C1-C4 alcohols are preferably used as starter molecules. The use of methanol, butanol, ethylene glycol monomethyl ether or ethylene glycol monobutyl ether as starter is particularly preferred.
• Alkylene oxides suitable for the alkoxylation reaction are, in particular, ethylene oxide and propylene oxide, which can be used in the alkoxylation reaction in any order. Any other epoxides such as butylene oxide, dodecene oxide or styrene oxide can also be used. Pure polyethylene oxide alcohols are particularly preferred.
• Ester group-containing polyalkylene oxide alcohols are OH-terminated polyester ethers which are reacted by reacting aliphatic C2-C8 dicarboxylic acids or their esters or acid chlorides with polyethers from the group consisting of polyethylene oxides, polypropylene oxides, their mixtures or mixed polyethers, with 0.8 to 0 per OH equivalent of the polyether 0.99 equivalents of carboxyl groups or their derivatives are used, are available and have an average molecular weight below 10,000, preferably below 3,000.
• the optionally used NCO-redactive components C comprise conventional mono- to tetrafunctional building blocks used in polyurethane chemistry, such as alcohols, amines, amino alcohols and mercaptans with molecular weights below 6,000, preferably below 2,000, such as e.g. Polyesters, polyether esters and polycarbonates, unless they fall under definition B.
• Preferred components C are long-chain, optionally branched, so-called fatty alcohols or fatty amines with 12 to 30 carbon atoms which have a "fatty" or “re-fatty” effect, and esters of natural fatty acids, such as stearic acid, oleic acid, palmitic acid, linoleic acid, linolenic acid, etc., which contain OH groups.
• Very particularly preferred components C are natural fats and oils carrying OH groups, such as castor oil.
• reaction products from components A to D to be used according to the invention can contain up to 20% by weight of incorporated residues of component C.
• Preferred blocking agents D are preferably the sodium salts of sulphurous or disulphurous acid, i.e. Sodium hydrogen sulfite (NaHSO3) or sodium disulfite (Na2S2O5).
• alkali and ammonium salts of these acids namely potassium bisulfite, potassium disulfite, lithium bisulfite, lithium disulfite, ammonium bisulfite, ammonium disulfite and simple tetraalkylammonium salts of these acids, such as, for example, tetramethylammonium bisulfite, can also be used advantageously. Tetraethylammonium bisulfite etc.
• the salts are preferably used as aqueous solutions with solids contents of 5 to 40% by weight.
• reaction products to be used according to the invention can be prepared, for example, as follows: In a first step, the polyisocyanate is reacted with the polyether alcohol B until all OH groups have been urethanized. The NCO-terminated prepolymer thus obtained is then blocked in a second step with alkali metal or ammonium bisulfite or disulfite until all NCO groups have been reacted.
• the entire process is particularly preferably carried out solvent-free as a one-pot process.
• the reaction (1st step) is carried out in the temperature range up to 130 ° C., preferably in the range between 50 ° C. and 120 ° C., particularly preferably between 80 ° C. and 110 ° C.
• the reaction can be followed by titration of the NCO content or by measurement of the IR spectra and evaluation of the carbonyl band at approx. 2 100 cm ⁇ 1 and is complete when the isocyanate content is not more than 0.1% by weight above the value which is to be achieved with complete sales. As a rule, response times of less than 4 hours are sufficient.
• NCO prepolymers thus obtained with NCO contents of 5 to 45% by weight are then in a second step at 0 to 60 ° C, preferably at 10 to 40 ° C, with aqueous solutions of alkali or ammonium sulfites and Water reacted until all NCO groups have reacted. This generally requires reaction times of 1 to 12, preferably 3 to 8 hours.
• the end products are optically clear aqueous solutions, in a few individual cases stable, fine-particle emulsions with average particle diameters below 8000 nanometers. It may be advantageous to first react the NCO prepolymers with 20 to 50% by weight aqueous solutions of the alkali metal or ammonium bisulfites or disulfites and to add the remaining water after 5 to 45 minutes, so that then a solids content of the aqueous preparations of 10 to 50 wt .-%, preferably 25 to 40 wt .-% results.
• the pH should be at least 7.5 to preferably a maximum of 9.5.
• the blocked isocyanate groups react with cross-linking of the collagen (with simultaneous elimination of the bisulfite group).
• All known blunting agents customary in tannery are suitable for basifying the reaction products according to the invention: Sodium carbonate and bicarbonate, magnesium oxide, dolomite, tertiary amines, etc.
• the controlled addition of sodium or potassium hydroxide is generally possible (but not common).
• Magnesium oxide is particularly preferred.
• a low pH is not required, as is customary, for example, in mineral tanning. This can save you the addition of salt (pimples). Nakedness is e.g. decalcified to a pH of 5 to 8 (preferably by 7), the reaction product to be used according to the invention is added and the basification is started after an hour's running time. (In the case of annealed magnesium oxide, the addition can be started immediately).
• the tanning and preferably the simultaneous basification can be completed in 4 to 6 hours.
• the mixture is left to run overnight in a further 2 steps (each after 1 hour running time), rinsing the next morning and continuing as usual.
• the reaction products to be used according to the invention can be used as a replacement for mineral tanning agents. Amounts of 1 to 20% by weight, preferably 3 to 15% by weight, of the reaction product, based on the pelt weight, are generally used.
• the leather tanned with the reaction product with shrinkage temperatures of above 70 ° C., preferably above 75 ° C., serves as a preliminary stage (analogue wet blue) for retanning with synthetic organic polymers (incl. resin tanning agents) or vegetable tanning agents.
• the leathers can of course still be dyed and greased.
• the tanning with the reaction products to be used according to the invention proceeds particularly well at pH values of 4 to 10, preferably 5 to 8. There is no need to pick or pickle. Pickling can also be an advantage to achieve a softer leather; even pimples don't bother.
• reaction products to be used according to the invention can also be used in such a way that they are only tanned up to a shrinkage temperature of 65 to 70 ° C. This gives colorless leather (wet white) which can then be mineral-tanned and retanned with synthetic organic polymers or vegetable tanning agents.
• the percentages in the following examples relate to the weight and to the bare / leather.
• the following examples contain an additional component C or 10 mol% trimerized HDI (22.1% NCO). Production analogous to example 1.
• E.g. Polyisocyanate Moles of polyisocyanate Polyether Mole polyether Mole bisulfite Component C % blocked NCO 26 HDI 0.262 12th 0.047 0.433 A, 17 g 17.0 27 HDI 0.212 12th 0.047 0.191 B, 11 g 7.9 28 HDI plus trim.
• HDI 0.095 0.009 5 0.063 0.152 - 5.8 30th HDI 0.328 12th 0.028 0.626 C, 5.2 g 23.9 31 HDI 0.221 5 0.039 0.210 D, 16 g 9.3 32 HDI 0.179 12th 0.047 0.232 E, 13.4 g 9.0 33 HDI 0.211 1 0.025 0.390 C, 14.1 g 14.9 34 HDI 0.217 8th 0.036 0.390 C 13.9 g 14.9 35 HDI 0.218 5 0.040 0.373 C, 13.8 g 14.4 36 HDI plus trim.
• Example A-1 The procedure was analogous to Example A-1, the reaction product from Example 7 (10% in each case) being used as the active ingredient and the truncating agents used varying.
• E.g. Anesthetic% Final pH Shrink temp. ° C Appearance A-38 3.4% soda 9.1 81 white / transparent A-39 6.6% NaHCO3 9 80 transparent A-40 12.4% triethanolamine 9 76 transparent A-41 2% MgO 9 83 white / transparent
• a ashed bare beef was decalcified as follows: 100% water (35 ° C) and 2% ammonium sulfate; after 30 minutes, 1% Polyzym 202 was added, the mixture was run for 60 minutes (pH 8); then the fleet was drained.
• Pretanning was carried out as follows: 50% water (30 ° C.) and 10% reaction product from example 7, after 90 minutes addition of 0.5% magnesium oxide, after 7 hours addition of further 0.5% magnesium oxide. When left to run overnight, the pH was 7.2.
• the leathers were unloaded, rolled over, beaten on the box overnight, vacuumed the next day, rolled up and dried out hanging.
• the chrome-free leather was full and soft - similar to the chrome-tanned one.
• Both leathers can be dyed very well.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Polyurethanes Or Polyureas (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (10)

• 1994
  • 1994-06-28 DE DE4422569A patent/DE4422569A1/de not_active Withdrawn
• 1995
  • 1995-06-01 US US08/456,972 patent/US5618317A/en not_active Expired - Fee Related
  • 1995-06-14 DE DE59507234T patent/DE59507234D1/de not_active Expired - Fee Related
  • 1995-06-14 ES ES95109198T patent/ES2140581T3/es not_active Expired - Lifetime
  • 1995-06-14 EP EP95109198A patent/EP0690135B1/fr not_active Expired - Lifetime
  • 1995-06-23 CA CA002152539A patent/CA2152539A1/fr not_active Abandoned
  • 1995-06-23 JP JP7179594A patent/JPH08199200A/ja active Pending
  • 1995-06-27 BR BR9502950A patent/BR9502950A/pt not_active IP Right Cessation

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