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
  • C14C3/04—Mineral tanning
  • C14C3/06—Mineral tanning using chromium compounds

Definitions

• the present invention relates to a process for the mineral tanning of unpickled pelts with chromium salts without increasing the basicity of the liquor using low molecular weight polyols as penetration auxiliaries; formulations of said polyols with fungicides, and a kit comprising, in separate containers, a chromium salt, a low molecular weight polyol and optionally a fungicide, or a mixture of said polyol and a fungicide.
• the one-bath process which comprises steps for pickling, tanning with chromium salt and increasing the basicity, has become established in tanning with mineral salts.
• pickling the animal hide digested and degreased in the beamhouse is treated with strong acids, for example sulphuric acid or formic acid, and salts, for example sodium chloride. With this treatment, the degree of association of the carboxyl groups in the collagen is reduced so that the animal hide has a high pH below 2. In this pH range, the fixing of the chromium salt is greatly reduced and the permeation of the salts is increased.
• the chromium salts can be masked with organic carboxylic acids. The tanning effect is then developed by increasing the pH to about 3.5 to 6.
• alkaline compositions are added (for example, magnesium oxide or sodium carbonate) when increasing the basicity of the liquor, in amounts such that the optimum value for tanning is established.
• chromium salts have a Schorlemmer basicity of at least 30%.
• Fungicides which likewise penetrate into the pelts and have to disperse in order to provide sufficient protection against fungal attack, particularly if the hide is split, are often added to the liquors.
• the tanning is carried out in the pickling bath.
• US-A-4,715,861 recommends treating pickled pelts or pelts during the pickling first with aldehyde acids or keto acids, for example glyoxalic acid, in order to increase the exhaustion of the liquor and to decrease the consumption of chromium salt.
• aldehyde acids or keto acids for example glyoxalic acid
• the steps of pickling and of increasing the basicity are, however, still required.
• Aldehyde acids and keto acids are physiologically unsafe and require special safety measures.
• the action of the aldehyde acids and keto acids consists in reaction with amino groups of the collagen, leading to an increase in the acidity of the pelt and hence better chromium absorption.
• EP-A-0 822 263 describes a process for tanning with chromium salts, in which pelts are treated with 3-hydroxybutyraldehyde and pickling and increasing the basicity are dispensed with.
• the isoelectric point is reduced so that chromium salts penetrate sufficiently and an increase the basicity is superfluous.
• WO 00/66793 discloses the same process with ⁇ - or ⁇ -hydroxyaldehydes.
• the compositions used for the pretreatment are volatile compounds which can be handled in tanneries only with difficulty.
• aldehydes are physiologically unsafe.
• the use of these processes requires particular safety apparatuses, which, from economic points of view, eliminates the advantages of dispensing with pickling and increasing the basicity.
• the published Brazilian Patent Application PI 0004258-7 A discloses chromium complexes of chromium salts and oligomeric masking compositions having a low Schorlemmer basicity of from 10 to 20%. They are suitable for the tanning of pelts without pickling and increasing the basicity. The required penetration is achieved by the low basicity, these compositions for tanning being capable of penetrating only slowly because their molecular weights are too high and therefore being unconvincing.
• WO 95/13400 describes a composition for the tanning of pelts which contains water as a carrier, a chromium salt, brine and a long-chain alkylpolyglucoside and has a pH of from 1 to 3.
• the alkylpolyglucoside is intended to improve the permeation. Owing to the molecular size and the surfactant structure, however, the effect is not very pronounced.
• the basicity of the liquor must be increased after the penetration of the chromium salts.
• CZ-A-8188-88 describes solid or aqueous, stabilized formulations of basic chromium salts which contain a polyol, such as, for example, sugar or glycerol, as a stabilizer.
• Bases such as, for example, MgO or NaHC0 3 , must be added to the formulations for increasing the basicity (self-basification).
• Processes for the direct tanning of pelts from the beamhouse have not become established, owing to the existing disadvantages, although said tanning is truly desirable because of the ecological and economic advantages.
• the invention firstly relates to a process for tanning of unpickled pelts and without increasing the basicity of the liquor by the action of basic chromium(lll) salts in an aqueous liquor, which is characterized in that
• Pelts are understood as meaning degreased and digested hides (if the skin was unhaired) and skins prepared in the beamhouse for tanning.
• the process variant (a) is preferred according to the invention.
• polyol and chromium salt can be added all at once or in portions.
• Chromium salts for tanning have long been known and are commercially available as solid or liquid formulations. They are salts of trivalent chromium with mineral acids, the sulphates having become established in practice. The products available are generally mixtures of chromium trioxide and alkali metal sulphates, such as, for example, sodium sulphate. The basicity, which is stated as a percentage according to Schorlemmer, is adjusted by means of the mixing ratio. Here, a basicity of 0% is assigned to pure chromium trisulphate and a basicity of 100% to pure chromium trihydroxide. Intermediate forms, such as, for example, Cr(OH)S0 4 , have a basicity of 33.3%.
• the chromium salts can be masked in a manner known per se with aliphatic mono- or dicarboxylic acids and are preferably unmasked.
• the chromium salts used in the process according to the invention preferably have a Schorlemmer basicity of from 15 to 50%, more preferably from 25 to 50%, particularly preferably from 30 to 45% and very particularly preferably from 30 to 42%.
• nonsaccharide means that the aliphatic polyols are not sugars.
• sugars do not have the effect of the aliphatic polyols and can therefore be used only additionally as fillers or extenders.
• the aliphatic polyols are preferably of low molecular weight and preferably have molecular weights of not more than 1 000, more preferably not more than 500, particularly preferably not more than 300 and very particularly preferably not more than 150.
• the aliphatic polyols to be used according to the invention may contain from 2 to 20, preferably from 2 to 10 and particularly preferably from 2 to 8 carbon atoms and optionally oxygen atoms, and from 2 to 12, preferably from 2 to 6, particularly preferably from 2 to 4 hydroxyl groups. They may be soluble or emulsifiable in water. Particularly preferably, the aliphatic polyols contain altogether from 2 to 8 carbon atoms and optionally oxygen atoms and from 2 to 4 hydroxyl groups.
• the aliphatic groups to which hydroxyl groups are bonded may be derived from linear or branched alkanes, cycloalkanes, mono- or dialkylcycloalkanes having hydroxyl groups bonded to the alkyl groups, dialkylbenzene having hydroxyl groups bonded to the alkyl groups, O-heterocycles (for example tetrahydrofuran, oxacyclohexane or dioxane), mono- or dialkyl-O-heterocycles having hydroxyl groups bonded to the alkyl groups, and polyoxaalkylenediols.
• the rings of cyclic polyols may be unsubstituted or substituted by C ⁇ -C 4 -alkyl or C ⁇ -C 4 -alkoxy.
• the alkanes may be, for example, ethane and the isomers of propane, butane, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane and eicosane.
• the aliphatic polyols based on alkanes are preferably diols, triols and tetrols.
• diols examples are those of the formula HO-C n H 2 n-OH, in which n is a number from 2 to 20, preferably from 2 to 12 and particularly preferably from 2 to 6.
• n is a number from 2 to 20, preferably from 2 to 12 and particularly preferably from 2 to 6.
• Some specific examples are ethylene glycol, 1,2- or 1 ,3-propylene glycol, 1,2-, 1,3- and 1,4-butylene glycol, 1,2-, 1,3-, 1,4- and 1 ,5-pentylene glycol, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexylene glycol, 1,2-, 1 ,3-, 1,4-, 1,5-, 1,6- and 1 ,7-heptylene glycol, 1,2-, 1,3-, 1 ,4-, 1,5-, 1,6-, 1,7- and 1,8-octylene glycol, nonylene glycol, decylene glycol, undecylene glycol, tetrade
• the triols may correspond to the formula (HO ⁇ -CnH ⁇ -.OH, in which n is a number from 3 to 12 and preferably from 3 to 8.
• Specific examples are 1,2,3-propanetriol, 1,2,3- or 1,2,4- butanetriol, 1 ,2,3-, 1,2,4-, 1,2,5- or 2,3,5-pentanetriol, 1,2,3-, 1,2,4-, 1,2,5-, 2,3,5-, 1,3,6- or 1,2,6-hexanetriol, 1 ,4,7-heptanetriol, 1 ,4,8-octanetriol, trihydroxymethylmethane, 1,1,1- trihydroxymethylethane and 1 ,1,1-trihydroxymethylpropane.
• the tetrols may correspond to the formula (HO) 2 -CnH 2 n- 2 (OH) 2 , in which n is a number from 4 to 12 and preferably from 4 to 8.
• n is a number from 4 to 12 and preferably from 4 to 8.
• Specific examples are 1,2,3,4-tetrahydroxybutane, 1,2,3,5- tetrahydroxypentane, 1 ,2,3,6-tetrahydroxyhexane, 1,2,6,8-tetrahydroxyoctane and tetrahydroxymethylmethane (pentaerythritol).
• the cycloalkanes may be those having 3 to 12 and preferably 5 to 8 carbon atoms in the ring. Some specific examples are cyclopentane-1 ,3-diol, cyclohexane-1 ,3- or -1,4-diol and cyclooctane-1 ,2-, -1 ,3- or -1 ,4-diol.
• the cycloalkane ring preferably contains from 3 to 12 and particularly preferably from 5 to 8 carbon atoms in the ring.
• the alkyl groups contain preferably from 1 to 4 and particularly preferably 1 or 2 carbon atoms.
• Some specific examples are 1-hydroxymethylcyclopentan-3- ol, 1-hydroxymethylcyclohexan-4-ol, 1-hydroxyethylcyclopentan-3-ol, 1 -hydroxyethyl- cyclohexan-4-ol, 1,3-dihydroxymethylcyclopentane, 1,4-dihydroxymethylcyclohexane, 1,3- dihydroxyethylcyclopentane, 1 ,4-dihydroxyethylcyclohexane and 1 -hydroxymethyl-4- hydroxyethylcyclohexane.
• the alkyl groups contain preferably from 1 to 4 and particularly preferably 1 or 2 carbon atoms.
• Some specific examples are 1 ,3- or 1 ,4-dihydroxymethylbenzene, 1 ,3- or 1 ,4-dihydroxyethylbenzene and 1 , 1 -hydroxymethyl-4-hydroxyethylbenzene.
• polyols of O-heterocycles are 2,3-dihydroxytetrahydrofuran and 3,4- dihydroxy-1 -oxacyclohexane.
• Examples of mono- or dialkyl-O-heterocycles having hydroxyl groups bonded to the alkyl groups are 2-hydroxy-3-hydroxymethyltetrahydrofuran, 3-hydroxy-4-hydroxymethyl-1- oxacyclohexane, 2,3-dihydroxymethylterahydrofuran and 3,4-dihydroxymethyl-1 -oxacyclohexane.
• the polyoxaalkylenediols may correspond, for example, to the formula HO-(R-0) x H, in which R is 1 ,2-propylene and preferably ethylene and x is a number from 2 to 12 and preferably from 2 to 4.
• R is 1 ,2-propylene and preferably ethylene and x is a number from 2 to 12 and preferably from 2 to 4.
• Some examples are diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol and mixed polyoxaalkylenediols, such as, for example, ethylene 1,2- propylene ether glycol.
• the polyols also include those cyclic polyols in which some or all of the hydroxyl groups bonded to the ring have been etherified with hydroxyalkyl, preferably hydroxyethyl.
• the polyols may be used as an individual component or as a mixture of at least two polyols.
• the polyols can be used alone or in combination with monoethers of glycol.
• mixtures of such monoethers with polyols or the individual components may be added to the liquor.
• the amount of the components in the mixture may be, for example, from 10 to 70% by weight, preferably from 20 to 60% by weight and particularly preferably from 30 to 50% by weight of monoether and from 90 to 30% by weight, preferably from 80 to 40% by weight and particularly preferably from 70 to 50% by weight of polyol.
• the monoethers of glycols may be, for example, those of the formula C 1 -C12-, preferably C-r C 8 - and particularly preferably C ⁇ -C 4 -alkyl-0-(C m H 2m )-OH, in which m is a number from 2 to 12, preferably from 2 to 8 and particularly preferably from 2 to 4.
• the monoethers of glycols may also be, for example, those of the formula C 1 -C 12 -, preferably CrC 8 - and particularly preferably C 1 -C 4 -alkyl-(0-C y H 2y ) z -OH, in which y is a number from 2 to 6 and preferably 2 or 3 and z is a number from 2 to 6 and preferably 2 or 3.
• Examples of the group -Cmr are ethylene, 1,2- or 1 ,3-propylene, 1,2-, 1,3- and 1 ,4-butylene, 1,2-, 1,3-, 1 ,4- and 1,5- pentylene, 1 ,2-, 1,3-, 1 ,4-, 1,5- and 1,6-hexylene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6- and 1,7- heptylene, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7- and 1,8-octylene, nonylene, decylene, undecylene and dodecylene.
• the alkyl group may be linear or branched alkyl, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl and hexyl.
• monoethers of glycols are ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, 1 ,2- or 1 ,3-propylene glycol monomethyl ether, 1 ,2- or 1 ,3-propylene glycol monoethyl ether, 1,2- or 1,3-propylene glycol monopropyl ether, 1,2- or 1,3-propylene glycol monobutyl ether, butylene glycol monomethyl ether, butylene glycol monoethyl ether, butylene glycol monopropyl ether, butylene glycol monobutyl ether, diethylene glycol monomethyl or monoethyl ether, triethylene glycol monomethyl or monoethyl ether and di- 1,2-propylene glycol monomethyl or monoethyl ether.
• the pH of the liquor at the time of addition of products to be used according to the invention may be, for example, from 3 to 8, preferably from 3.5 to 6 and particularly preferably from 3.5 to 4.5.
• the pH is adjusted by adding acids, for example formic acid, and amounts of sodium chloride which are reduced compared with the pickling.
• acids for example formic acid
• sodium chloride which are reduced compared with the pickling.
• the pH of the liquor is preferably in the neutral to slightly basic range since these chromium salts impart to the liquor an acidic pH sufficient for the tanning.
• the pH is advantageously in the slightly acidic range.
• the amount of chromium salts in the liquor may be, for example, from 1 to 8% by weight and preferably from 1.5 to 5% by weight of chromium trioxide (Cr 2 ⁇ 3 ), based on the weight of the pelt. In the tannery, the amount is usually calculated on the basis of the theoretical content of chromium trioxide.
• the polyol acts in the desired manner.
• the minimum amount of polyols is, for example, 0.1% by weight, based on the weight of the pelts. The addition of larger amounts can be avoided since no further substantial improvement can be achieved.
• the upper limit may be 20 and preferably 10% by weight. More preferably, the amount is from 0.5 to 5% by weight and particularly preferably from 0.5 to 2% by weight.
• Combinations of glycols with monoethers can be used in amounts such that the glycol component is present in the abovementioned amounts in the liquor.
• fungicides which are required for protection against fungal attack penetrate considerably better into the pelt with the use of the polyols, and effective protection can therefore be achieved with smaller amounts. It is therefore advantageous concomitantly to use a fungicide in the process stage (a) or (b).
• the amount may be from 0.01 to 5% by weight and preferably from 0.1 to 3% by weight, based on the weight of the pelts. Fungicides for this purpose are known and commercially available.
• Some examples are 2-(thiocyanomethylthio)benzothiazole, 2-octyl-2H-isothiazol-3-one, 4,5- dichloro-2-octyl-2H-isothiazol-3-one, zinc bis-(2-pyridinethiol-1 -oxide), zinc pyrothione and 3- iodo-2-propynylbutyl carbamate.
• the polyols may be added directly to the liquor, or mixtures of the polyols with fungicides may be added.
• the polyols may also be added as a mixture with a chromium salt and optionally additionally a fungicide if the mixtures are prepared immediately before use without heating.
• the invention furthermore relates to mixtures of
• the amount of chromium(lll) salts may be, for example, from 30 to 95% by weight, preferably from 40 to 90% by weight and particularly preferably from 40 to 80% by weight
• the amount of the polyol may be from 70 to 5% by weight, preferably from 60 to 10% by weight and particularly preferably from 60 to 20% by weight
• the amount of the fungicide may be from 0.1 to 5% by weight and preferably from 1 to 3.5% by weight, the percentages by weight summing to 100.
• the invention also relates to mixtures of
• the amount of aliphatic polyol may be from 90 to 99% by weight and preferably from 97 to 99% by weight and the amount of the fungicide may be from 10 to 1% by weight and preferably from 3 to 1% by weight.
• the mixtures according to the invention may additionally contain water, for example up to 50% by weight and preferably up to 35% by weight, based on the total mixture.
• the preparation of the mixtures can be carried out in a simple manner by mixing the components by means of known methods. However, it is also possible to provide ready- made mixtures. Known methods are likewise used for this purpose. Depending on the consistency and amounts of the components, it is possible to prepare powders or granules by dissolving or dispersing the components, optionally in an inert solvent, precipitating the components and then drying them, or spray-drying the solutions or dispersions.
• the invention also relates to a kit consisting of two or three containers which each contain
• the invention furthermore relates to the use of at least one nonsaccharide, aliphatic polyol for improving the penetration of basic chromium salts and optionally additionally of fungicides in the tanning of pelts in acidic, aqueous solution.
• the process according to the invention can be carried out in such a way that washed pelts are introduced into water, a salt is added to the liquor, for example sodium chloride, and an acid is then added, for example formic acid. The pH in the liquor is adjusted thereby. Thereafter, either the aliphatic polyol can be added and allowed to act on the pelt or the polyol and the chromium salt can be added simultaneously.
• the pretreatment may last from about 30 minutes to 2 hours.
• the chromium salt is added and can be allowed to act, for example, for from about 2 to 10 hours. With simultaneous addition, the treatment time may be from about 2.5 to 10 hours.
• the process is carried out at from room temperature to 50°C and preferably up to 45°C. After the tanning, the leather obtained is washed and is ready for further processing.
• Example A1 Mixture of polyol and fungicide
• 150 g of -D-glucose are stirred in 150 g of water at 50°C for 20 minutes in order to dissolve the glucose completely.
• the temperature is reduced to 30°C and 700 g of 1 ,2-propanediol (water content 0.2%) are added and stirring is effected for 10 minutes.
• 3% of 2- (thiocyanomethylthio)benzothiazole (TCMTB) are added and stirring is effected for a further 5 minutes. A brownish liquid is obtained.
• Example A2 Mixture of polyol and chromium salt
• Example A3 Mixture of polyol, chromium salt and fungicide
• Example B1 a) 100 g of ⁇ -D-glucopyranosyl- ⁇ -D-fructofuranoside were added at 30°C to 400 g of water and stirred until completely dissolved (about 20 minutes). 500 g of ethylene glycol (water content about 0.2%) were then added and stirring is effected for a further 10 minutes. A colourless and slightly viscous product is obtained.
• Example B2 a) 150 g of ⁇ -D-Glucose is added at 50°C to 150 g of water and then stirred until completely dissolved. The temperature is reduced to 30°C and 700 g of 1 ,2-propanediol (water content about 0.2%) are added and stirring is effected for a further 10 minutes. A colourless and slightly viscous product is obtained.
• Example B3 a) 500 g of 1 ,2-ethanediol are added at 25°C to 300 g of water and stirred for 10 minutes until completely dissolved. Thereafter, 200 g of butane-1,4-diol are added and stirring is effected for a further 10 minutes. The product is a colourless liquid. b) 40% of water are added to 35 kg of pelt (from 6 to 7 mm, Brazilian zebus) in a drum, 4.2% of sodium chloride are added and a waiting period of 10 minutes is allowed. Thereafter, 0.5% of formic acid is added and the pelt is treated for one hour. 1% of the mixture according to a) is then added and allowed to act on the pelt for 1.5 hours.
• the pH of the liquor is 4.2. 5% of chromium sulphate having a basicity of 33% is then added and tanning is effected for 3 hours. A further 0.8% of sodium chloride is then added and treatment is effected overnight. Heating to 44°C is then effected and the liquor is kept at this temperature for 12 hours. The pH is then 4.0-4.1. The liquor is discharged and the tanned hide is washed with water. The hide has been completely tanned. The liquor contains only 0.12% of chromium.
• Example B4 a) 100 g of hexane-1,6-diol (water content about 0.1%) are melted at 50°C in a closed glass flask. In a second glass flask, 100 g of glucose (water content about 1.0%) and 100 g of water are stirred at 50°C until the glucose has completely dissolved. Cooling to 30°C is then effected. The molten hexanediol is then added to the solution and stirring is effected for a further 10 minutes. 700 g of propane-1 ,2-diol are then added and stirring is effected for a further 10 minutes at 25 - 30°C. A colourless and slightly viscous product is obtained.
• Example B6 a) 150 g of ⁇ -D-Glucose is added at 50°C to 100 g of water and then stirred until the glucose is completely dissolved. The temperature is reduced to 30°C, 100g of 1,2-propylene glycol methyl ether are added and stirring is effected for 10 minutes. Thereafter, 700 g of 1,2- propanediol (water content about 0.2%) are added and stirring is effected for a further 10 minutes. A colourless and liquid product is obtained. b) 40% of water are added to 50 kg of pelt (Swiss bulls) in a drum, 4% of sodium chloride are added and a waiting period of 10 minutes is allowed.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)
• Detergent Compositions (AREA)

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• 2003
  • 2003-12-01 WO PCT/EP2003/050917 patent/WO2004053170A1/en not_active Application Discontinuation
  • 2003-12-01 BR BR0316299-0A patent/BR0316299A/pt not_active IP Right Cessation
  • 2003-12-01 AU AU2003298336A patent/AU2003298336A1/en not_active Abandoned
  • 2003-12-01 AT AT03796071T patent/ATE550445T1/de active
  • 2003-12-01 EP EP03796071A patent/EP1567678B1/de not_active Expired - Lifetime

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