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 invention relates to special chrome tanning agents, their production and their use for tanning hides and skins and the leather and furs obtainable thereby.
• leather folding shavings which mainly consist of material containing collagen. If the leather was previously tanned using a chrome tanning agent, the still moist tanned leather, also referred to as wet blue, usually contains around 2 to 6% by weight of chromium in the oxidation state (III) in addition to collagen.
• chromium (III) compounds present in professionally tanned leather are considered harmless to health, toxic or carcinogenic chromium (VI) compounds can form if the leather or shavings are not tanned or treated properly.
• chrome tanning is the most widespread tanning method, large quantities of chrome-containing leather shavings are produced (approx. 17,000 t per year in Germany alone). Separation into the components protein and chromium and, above all, the reuse of the chromium content, which is only possible with great effort, often makes the complete recycling of the large amounts of waste uneconomical, so that leather shavings are landfilled and disposed of as hazardous waste, pressed into leather pulp or burned under controlled conditions , but this is at the expense of the environment. In addition, a large amount of collagen is lost, which could otherwise be used, i.e. without contamination by chromium, for cosmetics, medicine and food for humans and animals.
• the basic, possibly in combination with enzymatic hydrolysis of leather shavings has the advantage that the protein content, as an economically more interesting part, can be obtained in the first step without chromium, such as in DE4238979 A1 disclosed where the protein portion obtained as gelatin has a chromium content of ⁇ 0.1 ppm.
• the chromium is separated first, with the aim of keeping the protein content as free of chromium as possible.
• the problem here is that after a After a single treatment of the chrome shavings with acid, a relatively large proportion of chrome remains in the collagen. So describes Ferreira (Waste Management, 2010, 30, pp. 1091-1100 ) that only 55 - 60% of the chromium can be recovered with a single, very long treatment time of 3-5 days with sulfuric acid. The remaining protein residue still has such a high proportion of chromium (40 - 45%) and the toxic Cr(VI) compounds resulting from the treatment that disposal in a landfill is not possible.
• the currently most practiced method for separating protein and chromium is the decomposition of the leather shavings with bases, if necessary combined with microbial or enzymatic degradation under heat (as described, for example, in Cabeza, LF, JALCA, 1998, 93, pp. 83-97 ).
• the leather shavings are first decomposed with magnesium oxide and, in addition to gelatine, a chromium-containing residue, the so-called chromium cake, is obtained.
• This is further decomposed by enzymes to form collagen hydrolyzate and a chromium-containing solid.
• the problem with this is that the chrome cake cannot be reused directly as a tanning agent because it still contains significant amounts of proteins that prevent the tanning effect.
• the chromium cake was first dissolved in sulfuric acid and then the pH value was raised with sodium hydroxide in two further stages in order to free the chromium-containing residue from the protein content.
• Each of these steps requires a filtration step, whereby, in addition to a lot of protein-containing waste products that cannot be reused, the purified chromium(III) sulfate is also ultimately produced, which can then be used again as chrome tanning agent.
• the large number of processing steps and the not inconsiderable proportion of protein-containing waste products that cannot be reused stand in the way of the economics of the process.
• Another method for processing the chromium cake is in CN103014191A disclosed.
• the chromium cake is dissolved in a strong acid and then toxic and mutagenic Cr(VI) compounds are added in order to remove the protein-containing components still present by oxidation.
• a reducing agent is then added to remove excess Cr(VI).
• This step has to be carefully controlled because if chromium(VI) residues are not completely removed, the chromium tanning agent recovered in this way cannot be reused.
• the virtually protein-free chrome tanning agent obtained in this way can then be used as chrome tanning agent.
• the use of the Cr(VI) compounds places high safety requirements on the production plants and the personnel with regard to the implementation of the process and is therefore actually undesirable.
• Chrome tanning agents can be used directly in the form of, for example, chromium salts or solutions thereof, but for many applications it is advantageous to mask the tanning agents with organic acids, for example aliphatic or aromatic carboxylic acids such as acetic acid or salts thereof.
• organic acids for example aliphatic or aromatic carboxylic acids such as acetic acid or salts thereof.
• chrome tanning agents are in DE1230170B described.
• Masked chrome tanning agents are known for being suitable for the gentle and risk-free tanning and retanning of leather and for having a higher alkali stability. This reduces the risk of chrome stains appearing during neutralization in the tanning process.
• the leathers obtained have better fullness and a softer hand.
• the grain pattern is particularly fine and smooth and the surface smoothness is increased.
• the coloring of the leather is more intense and more even, such as in Library of Leather, Volume 3, Tanning Agents, Tanning, Retanning, Kurt Faber, 2nd Edition, 1990, pages 79-80 disclosed. Due to the masking, the utilization of such tanning agents with the same final pH value in the tanning is somewhat below that of the unmasked chrome tanning agents, but since the higher alkali stability of the masked tanning agents means that higher final pH values can also be used during tanning. a comparable exhaustion as with unmasked chrome tanning agents is achieved, with a higher leather quality at the same time.
• the higher stability to alkali can be measured by determining the flocculation point, which is expressed as a percentage of basicity.
• the basicity of chrome tanning agents is a measure of the number of hydroxyl groups per chromium ion and is known as such to those skilled in the art.
• An explanation of the term and a method for determining the basicity are e.g. in Library of Leather, Volume 3, Tanning Agents, Tanning, Retanning, Kurt Faber, 2nd edition, 1990, pages 73-75 and pages 283-285 specified.
• the amount of base is measured up to flocculation, the molar amount of hydroxide ions generated by the base is divided by three times the molar amount of chromium ions and added to the basicity value of the chrome tanning agent used.
• the amount of base required to change the basicity by 1% is known to the person skilled in the art and is, for example, 20.9 mg Na 2 CO 3 per 1000 mg chromium oxide, calculated as Cr 2 O 3 (cf. Library of Leather, Volume 3, Tanning Agents, Tanning, Retanning, Kurt Faber, 2nd edition, 1990, page 75 ).
• an aqueous solution of the chrome tanning agent is prepared (100 ml) containing 2.6% by weight of chromium oxide calculated as Cr 2 O 3 , stirred continuously at room temperature for 8 hours and mixed with a 1.5 molar aqueous sodium carbonate solution (drop rate of 10ml/min) until a permanent flocculation can be seen.
• the flocculation point in the present invention is measured exactly 8 hours after the chromium oxide content of the solution is adjusted to 2.6%, the solution being was continuously stirred at room temperature.
• a further object of the invention was therefore to provide a masked chrome tanning agent which can be obtained, at least in part, in an efficient and economical manner from recycled chrome- and collagen-containing material
• the flocculation point can be adjusted by adding chrome tanning agents, in particular chromium(III) compounds, preferably one or more compounds selected from the group consisting of chromium(III) oxides, chromium(III) hydroxides, chromium(III) halides and chromium(III) sulfates and particularly preferably basic chromium (III) sulfate.
• chrome tanning agents in particular chromium(III) compounds, preferably one or more compounds selected from the group consisting of chromium(III) oxides, chromium(III) hydroxides, chromium(III) halides and chromium(III) sulfates and particularly preferably basic chromium (III) sulfate.
• the last two process steps are combined by lowering the pH by adding acidic chromium(III) compounds.
• Suitable acidic chromium(III) compounds as a mixture (10% by weight) in water at RT have a pH of less than 6.0, preferably less than 3.0 and particularly preferably less than 2.0.
• Chromium compounds from the group consisting of chromium(III) oxides, chromium(III) hydroxides, chromium(III) halides and chromium(III) sulfates are preferably used, and basic chromium(III) sulfate is particularly preferred.
• Protein-masked chrome tanning agents are understood to be mixtures of chrome tanning agents, in particular chromium(III) compounds such as chromium(III) oxides, chromium(III) hydroxides, chromium(III) halides and chromium(III) sulfates, and the protein content obtainable by basic hydrolysis of collagen .
• chromium(III) compounds such as chromium(III) oxides, chromium(III) hydroxides, chromium(III) halides and chromium(III) sulfates, and the protein content obtainable by basic hydrolysis of collagen .
• the chromium(III) compounds added are preferably chromium(III) oxides, chromium(III) hydroxides, chromium(III) halides and/or chromium(III) sulfates or mixtures of these substances, particularly preferably basic chromium(III) sulfate.
• material containing chromium and collagen includes, in its broadest meaning, all materials containing chromium and collagen, preference is given to leather containing chromium, and particularly preferably shavings of leather containing chromium.
• the pH is lowered by adding an acid, preferably a mineral acid, particularly preferably sulfuric acid and/or hydrochloric acid, very particularly preferably sulfuric acid.
• an acid preferably a mineral acid, particularly preferably sulfuric acid and/or hydrochloric acid, very particularly preferably sulfuric acid.
• Chrome-containing leather is to be understood as meaning hides and skins tanned using a chrome tanning agent, in which the shrinkage temperature of the tanned skin material is typically so high that at least hydrothermal stabilization of the skin material has been achieved, which allows subsequent processing by mechanical operations and damage by which avoids mechanical and thermal stress, such as frictional heat during folding.
• the chromium oxide content in the chromium and collagen-containing material used is typically less than 10% by weight, particularly preferably less than 7% by weight, very particularly preferably less than 5% by weight, based on the total mass of the dried chromium and collagen-containing material at a residual moisture content of 10% by weight.
• Basic hydrolysis means a reduction in the molecular weight of collagen under basic conditions.
• the basic hydrolysis is typically carried out using oxides or hydroxides of the alkali and/or alkaline earth metals, preferably oxides or hydroxides of sodium, potassium and/or magnesium, particularly preferably magnesium oxide.
• the material obtained in this way contains proteins which typically have a weight-average molecular weight Mw of less than 310, preferably less than 280 and particularly preferably less than 250 daltons.
• proteins obtained in the acidic hydrolysis of chromium- and collagen-containing material have a weight-average molecular weight Mw of 320 daltons or more.
• the protein-masked chrome tanning agent obtainable by the present process is obtained in the form of an aqueous solution.
• this solution is converted into a powder or granules by drying, preferably spray drying.
• a further object of the invention is therefore protein-masked chrome tanning agents containing chromium in oxidation state 3 and proteins obtained by basic hydrolysis of collagen, the chrome tanning agents having a flocculation point in the range from 66 to 150% basicity.
• both the proteins and part of the chromium in the +3 oxidation state originate from the insoluble or sparingly soluble residue resulting from the basic hydrolysis of a chromium- and collagen-containing material.
• the other part of the chromium in the +3 oxidation state then comes from chromium tanning agents added to this residue in the form of chromium(III) compounds, preferably chromium(III) oxides, chromium(III) hydroxides, chromium(III) halides and chromium(III). ) sulfates or mixtures of these substances, particularly preferably basic chromium (III) sulfate.
• the chromium oxide content of the protein-masked chrome tanning agents is typically more than 5% by weight, preferably more than 8% by weight and particularly preferably from 10 to 26% by weight. This chromium oxide content relates to the total weight of the dried protein-masked chrome tanning agents with a residual water content of ⁇ 10% by weight, preferably 5% by weight.
• the content of proteins obtained by basic hydrolysis of collagen in the protein-masked chrome tanning agents is typically from 2 to 50% by weight, preferably from 4 to 25% by weight and particularly preferably from 5 to 12% by weight.
• This protein content relates to the total weight of the dried protein masked Chrome tanning agents with a residual water content of ⁇ 10% by weight, preferably 5% by weight.
• the protein-masked chrome tanning agents obtainable by the present process typically have a basicity of 0 to 65%, preferably 4 to 55%, particularly preferably 9 to 40%.
• the protein-masked chrome tanning agents can be in the form of a powder, granules or an aqueous solution.
• Another object of the invention is the use of the protein-masked chrome tanning agents for the tanning and/or retanning of leather or furs.
• Another subject is a process for tanning and/or retanning leather or skins by treating skins or skins with the protein-masked chrome tanning agents according to the invention.
• the invention also includes leather or skins obtainable by the process according to the invention for tanning and/or retanning leather or skins.
• the present invention is therefore ideal for recycling chromium and collagen-containing material, in particular leather manufacturing waste such as leather shavings, which can be converted into advantageous protein-masked chromium tanning agents and returned to the tanning process, thereby reducing the amount of chromium-containing waste in leather production can be significantly reduced, leading to significant economic, ecological and logistical advantages.
• the chromium-containing solution A used in the following examples comes from a commercially operated plant for the alkaline processing of the shavings from chrome-tanned cowhide, in which a residue containing chromium and collagen (chromium cake) occurs. This residue is dissolved with sulfuric acid and then the pH is adjusted to 2.3.
• the solution has a basicity of 9.1% and the chromium oxide content of the solution, calculated as Cr 2 O 3 , is 3.6%. The solids content is 35%.
• the measured flocculation point (of the solution diluted to 2.6% chromium oxide) is 520% basicity.
• the chrome tanning agent added in the examples is a basic chromium sulfate powder ( Chromosal® B from Lanxess GmbH) which has a basicity of 33% and a chromium oxide content of about 26%, calculated as Cr 2 O 3 .
• the measured flocculation point of the solution diluted to 2.6% chromium oxide is 62% basicity.
• the mixture has a basicity of 24% and contains 8.8% chromium oxide calculated as Cr 2 O 3 .
• the solution diluted to 2.6% chromium oxide has a flocculation point of 89% basicity.
• the mixture has a basicity of 30% and contains 8.4% chromium oxide calculated as Cr 2 O 3 .
• the solution diluted to 2.6% chromium oxide has a flocculation point of 72% basicity.
• the mixture has a basicity of 30% and contains 11.8% chromium oxide calculated as Cr 2 O 3 .
• the solution diluted to 2.6% chromium oxide has a flocculation point of 76% basicity
• chromium-containing solution A 155 g of water and 545 g of basic chromium sulfate are added to 300 g of chromium-containing solution A in a stirred flask. The solution is then heated to 80° C. and stirred at this temperature for 1 hour.
• the mixture has a basicity of 31% and contains 15.2% chromium oxide calculated as Cr 2 O 3 .
• the flocculation point of the solution diluted to 2.6% chromium oxide is 69% basicity
• pelt weight After liming, split and weighed pelts (cattle) are used as the starting material, the thickness of which is approx. 1.8-2.0 mm. All of the following quantities of chemicals are based on this reference weight (pelt weight).
• Table 1 process wt% chemicals running time [min] Remarks 200 Water 32°C 10' drain fleet 50 Water 32°C 1.5 ammonium chloride 0.2 nabisulfite 45' Section with phenolphthalein: colorless, pH 8.6 drain fleet 50.0 Water 35°C 5' 0.20 PELTEC ADN 1:5 0.15 LEVAZYME AF 60' drain fleet 100 Water 20°C 6.0 table salt 5' 0.4 formic acid 1:10 10' 0.8 sulfuric acid 1:10 90' pH 3.4 18 mixture M1 60' + 0.4 BLANCOROL BA-I 480' pH 3.8 Automatic 40°C drain fleet
• the semi-finished leather products are stored on a trestle, sammed and seamed.
• the wet blue have a shrinkage temperature of >100°C and a Cr 2 O 3 content of 4.1%.
• the Cr 2 O 3 content of the residual liquor is 4.2 g/l.
• the wet blues produced in this way are characterized in particular by good fullness and a soft handle.
• the grain pattern is particularly fine and smooth and the surface smoothness is increased.
• the wet blue have a shrinkage temperature of >100°C and a Cr 2 O 3 content of 4.4%.
• the Cr 2 O 3 content of the residual liquor is 2.1 g/l.
• the wet blue produced in this way does not show any chromium precipitation and has a beautiful blue color.
• the fullness, the handle, the grain pattern and the surface smoothness are comparable to application example 1.
• the wet blue have a shrinkage temperature of >100°C and a Cr 2 O 3 content of 4.3%.
• the Cr 2 O 3 content of the residual liquor is 2.7 g/l.
• the wet blues produced in this way are characterized in particular by good fullness and a soft handle.
• the grain pattern is particularly fine and smooth and the surface smoothness is increased.
• the wet blue have a shrinkage temperature of >100°C and a Cr 2 O 3 content of 4.6%.
• the Cr 2 O 3 content of the residual liquor is 1.9 g/l.
• the wet blue produced in this way does not show any chromium precipitation and has a beautiful blue color. They also have a good fullness and a soft handle.
• the grain pattern is particularly fine and smooth and the surface smoothness is increased.
• the wet blue have a shrinkage temperature of >100°C and a Cr 2 O 3 content of 4.5%.
• the Cr 2 O 3 content of the residual liquor is 2.0 g/l.
• the wet blues produced in this way have a greener color than the wet blues produced with the chrome tanning agents according to the invention. They also have less fullness and a harder grip. The grain pattern is coarser and the surface smoothness is less.
• Table 2 shows the process steps of the process according to the invention for producing crust leather (the percentages by weight relate to the shaved weight).
• Table 2 shows the process steps of the process according to the invention for producing crust leather (the percentages by weight relate to the shaved weight).
• Table 2 shows the process steps of the process according to the invention for producing crust leather (the percentages by weight relate to the shaved weight).
• Table 2 shows the process steps of the process according to the invention for producing crust leather (the percentages by weight relate to the shaved weight).
• Table 2 shows the process steps of the process according to the invention for producing crust leather (the percentages by weight relate to the shaved weight).
• the crust leathers produced in this way are characterized in particular by good fullness and a soft feel.
• the grain pattern is particularly fine and smooth and the surface smoothness is increased.
• the coloring of the crust leather is remarkably intense and even.

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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)
• Compositions Of Macromolecular Compounds (AREA)

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• 2019
  • 2019-01-11 PT PT197001936T patent/PT3740595T/pt unknown
  • 2019-01-11 ES ES19700193T patent/ES2914983T3/es active Active
  • 2019-01-11 WO PCT/EP2019/050672 patent/WO2019141603A1/de not_active Ceased
  • 2019-01-11 CN CN201980008495.3A patent/CN111601902B/zh active Active
  • 2019-01-11 KR KR1020207020145A patent/KR102643029B1/ko active Active
  • 2019-01-11 EP EP19700193.6A patent/EP3740595B1/de active Active
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  • 2019-01-11 US US16/962,484 patent/US11851722B2/en active Active
  • 2019-01-14 TW TW108101295A patent/TWI804562B/zh active
  • 2019-01-15 AR ARP190100080A patent/AR114210A1/es active IP Right Grant

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