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
  • C14C3/16—Chemical tanning by organic agents using aliphatic aldehydes
• • 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

• Chrome tanning which has achieved a dominant position in leather production over the past 60 to 80 years, has come under increasing ecological pressure over the past decade due to the high wastewater pollution with chromium (III) salts.
• chromium (III) salts As a return to the tanning methods with vegetable or animal tanning agents that had been in use for thousands of years before chrome tanning with drastic loss of properties, e.g. If the lightfastness or temperature resistance of the leather had to be paid for, there has been no shortage of attempts to replace chromium (III) salts in tanning with other purely mineral tanning agents such as titanium, zirconium or aluminum salts or by combining them with vegetable tanning agents .
• Methyl or butyl etherified melamine-formaldehyde resins are also suggested as tannins (Miekeley (see above); Hachihama, Kyogoku, Technol. Repts. Osaka Univ. 6, 397 (1956); CA 52, 10622a (1958)).
• the leather tanned with butyl etherified melamine-formaldehyde resins was too thin, the leather tanned with methyl etherified melamine-formaldehyde resins were pure white, had excellent lightfastness and fullness, and high alkali resistance, and due to their cationic character showed a good absorption capacity for acid and substantive dyes.
• these leathers had a very serious deficiency with regard to their tear resistance behavior over time.
• these leathers tanned with melamine-formaldehyde resins had very good tear resistance.
• the tear strength decreased sharply and fell to 50% or less of the original value within about four weeks.
• a resin mixture which consists of 20 to 80% of a melamine-formaldehyde resin and 80 to 20% by weight of an anionically modified melamine-formaldehyde resin is preferred.
• the melamine resins free from anionic groups are prepared in a known manner by alkaline condensation of melamine with 1.5-6 mol of formaldehyde.
• the condensation can also be carried out in the presence of plasticizers known for melamine resin condensation, such as mono- and polyhydric alcohols and non-reducing sugars, with partial etherification.
• plasticizers known for melamine resin condensation, such as mono- and polyhydric alcohols and non-reducing sugars, with partial etherification.
• additional alcohols e.g. Suitable: methanol, ethanol, glycol, glycerin, sorbitol, other mono- or polyhydric alcohols individually or in mixtures with each other.
• the amount of these alcohols or sugars is about 0 to 20% by weight of the total solid resin.
• the melamine resins described here should not contain any anionic groups. Up to 50% by weight of this melamine resin can also be replaced by other aminoplast formers such as guanamine, dicyandiamide or urea.
• the anionically modified melamine resin used as the second component is produced in the same manner as the unmodified resin described. In the production of this resin, however, at least 0.3 mol, preferably up to 1.5 mol, of an alkali sulfite, alkali hydrogen sulfite or alkali sulfamate are added per mole of melamine, so that the resulting resin bears the corresponding number of sulfo groups and thus anionic Has properties.
• alkali sulfites or alkali sulfamates are, for example, potassium or sodium sulfites or sulfamates in the form of individual compounds or in Form of mixtures of several alkali sulfites and / or alkali sulfamates used.
• the hydrogen sulfites can also be taken in the same way.
• a second aspect of the present invention consists in producing a mixed resin and using it in the method according to the invention.
• a conventional melamine-formaldehyde resin is produced in one batch with the addition of a correspondingly reduced amount of sulfite or sulfamate.
• the same melamine resins as described above can be used for such mixed resins.
• alkali sulfite 0.25 to 0.8 mol of an alkali sulfite, alkali hydrogen sulfite or alkali sulfamate are added per mole of melamine during their preparation, so that the resulting resin carries the corresponding number of sulfo groups and thus has anionic properties.
• alkali sulfites or alkali sulfamates e.g. Potassium or sodium sulfites
• hydrogen sulfites or sulfamates are used in the form of individual compounds or in the form of mixtures of several alkali sulfites and / or alkali sulfamates.
• This partially anionically modified resin is obtained as a liquid solution and can be used directly for tanning in this form.
• This liquid setting is characterized by improved durability over a similar resin obtained by mixing an unmodified melamine resin with an anionically modified melamine resin.
• the resin mixtures or mixed resins thus produced are used in the customary manner in the tanning process.
• soaked, ashed and pickled hides regardless of the animal species, are used in an aqueous liquor at pH values from 7 to 8.5 with 4 to 20%, based on pelt weight, of the resin solutions used according to the invention at temperatures from 30 to 45 ° C in one of the tanneries common in tanneries treated for about 6 to 8 hours.
• the temperature of the liquor is then raised to up to 50 ° C. and, after a further run time of 1 h, 0.5 to 3%, based on the block weight, of an acid catalyst is added to the bath.
• Acidic catalysts in particular organic acids which do not damage the skin, such as, for example, formic acid, or acidic salts, such as, for example, ammonium chloride, can be used alone or in a mixture with one another.
• the leather is then deposited and processed like any other tanned skin material.
• the process can be carried out successfully on all types of leather, fur and fur.
• the leather obtained in the process according to the invention have, depending on the process control, shrinking temperatures of 70 to 90 ° C, have a good fullness, are soft to permanent, have very good dyeing properties for dyeing with commercially available anionic dyes due to their predominantly cationic character and because of their also in cross-section white color an excellent basis for the production of pure white leather. They are solid-grain, have a very good light fastness and a similar abrasion behavior, tensile strength and tear behavior like chrome-tanned leather, as well as good self-extinguishing properties after contact with a pilot flame and give freedom any type of aftertreatment customary in leather production, such as retanning, greasing or dressing.
• the particular advantages of the method according to the invention lie in the environmental friendliness and simplicity of the process.
• the process saves both the wastewater-polluting pimple before tanning and the neutralization step necessary in the mineral tanning process.
• the tannery wastewater is not polluted by any environmentally harmful mineral salts.
• the main advantage of the process according to the invention is that there is no appreciable loss of tear strength when the leather is stored.
• the pH is 10.6-11.
• the mixture is heated to 85 ° in about 40 minutes and condensed at this temperature for about 2 hours until it can be diluted with saturated saline at 1: 4 (measured after cooling to 23 ° C.). After cooling to room temperature, 2100 g of a clear, thin resin are obtained; Burn-in content: 47%, viscosity: 14 DIN seconds, pH: 9.6-9.8, density: 1.215, turbidity hardening time: 110-140 minutes, shelf life up to 6 months, no flash point until boiling.
• Cowhide as is common in the practice of leather production, is soaked, ashed, fleshed, decalcified and pickled.
• the pH of the nakedness is 7.8 after pickling.
• the percentages of the further process steps relate to the weight of the beef skin.
• the nakedness is taken up in a conventional tanning vessel in 50% water at 38 ° C. and mixed with 6% of a 1: 1 mixture of resins A and B, prepared according to Examples 1 and 2, and left to run for 6 hours. Then another 50% water of 55 ° C is added and it is left to run at this temperature for another hour. Then 1% formic acid 85% is added. After a further 30 minutes, the leather is removed from the tanning vessel, deposited overnight and completed after the further process steps, such as folding, greasing, retanning, dyeing, etc., which are customary in leather production.
• the leather thus obtained has a fine, uniform and firm grain, is well filled, has a smooth, pleasant grip, very good color uniformity and lightfastness and good tear resistance, which, even after 12 weeks of storage, maintains the unchanged high level of immediately after completion of the Leather has a measured initial value, as the table shows.
• the leathers have good self-extinguishing properties after contact with an ignition flame.
• the leathers obtained in this way have a very fine, uniform and firm grain, are not very heavily filled, and have a very smooth, pleasant grip.
• the leather thus obtained is very well filled and stable. They have a uniform, emphatically structured scars and a full, pleasant grip and have very good lightfastness and color uniformity.
• the tear strength does not quite reach the level of the leather processed according to Examples 4 and 5.
• the leathers have good self-extinguishing properties after contact with an ignition flame.
• Cowhide is soaked, ashed, fleshed, descaled and stained, as is common in the practice of leather production.
• the pH of the nakedness is 8.2 after pickling.
• the percentages of the further process steps relate to the weight of the beef skin.
• the pickled nakedness is taken up in a conventional tanning vessel in 50% water at 38 ° C. and mixed with 10% of the mixed condensate (50%) prepared in accordance with Example 3 and left to run for 6 hours.
• the leather thus obtained has a uniformly fine, firm grain. They are well filled, soft to firm and have a round, full grip. They have high tear resistance values and have very good color levelness and lightfastness. The leathers have good self-extinguishing properties after contact with an ignition flame.

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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)
• Chemical Or Physical Treatment Of Fibers (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

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• 1987
  • 1987-09-18 DE DE8787113669T patent/DE3765616D1/de not_active Expired - Fee Related
  • 1987-09-18 ES ES87113669T patent/ES2018807B3/es not_active Expired - Lifetime
  • 1987-09-18 EP EP87113669A patent/EP0265657B1/de not_active Expired - Lifetime
  • 1987-09-23 PT PT85776A patent/PT85776B/pt not_active IP Right Cessation
  • 1987-09-24 BR BR8704915A patent/BR8704915A/pt unknown
  • 1987-09-25 KR KR870010644A patent/KR880004101A/ko not_active Application Discontinuation
  • 1987-10-05 US US07/104,252 patent/US4810252A/en not_active Expired - Fee Related

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