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
  • C14C1/00—Chemical treatment prior to tanning
• • 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
  • C14C1/00—Chemical treatment prior to tanning
  • C14C1/08—Deliming; Bating; Pickling; Degreasing

Definitions

• the present invention relates to the application of silica soils for obtaining a so-called stabilized pickled white or stabilized white skin.
• the tanner hires after manual selection, a raw hide in the tanning process, in order to obtain the requested article.
• This procedure requires a large stock of raw hide and leads to long delivery times because the transformation of raw hide into leather generally requires more than a month. Consequently, the tanner wishes to have at his disposal hides in the state of technological intermediaries, in particular in the state of stabilized pickled white or stabilized white, capable of being quickly and weakly transformed into the desired article.
• an aqueous silica sol makes it possible to obtain a pickled white having excellent stability, physico-mechanical and thermal properties capable of subjecting it without damage conventional mechanical operations allowing a choice in quality and thickness at this stage of the preparation and that said use did not give the skin any coloring by tanning, nor any significant modification.
• the present invention makes it possible to obtain, from a pickled or unpicked skin, depilated or not, skinned or not, a technological intermediate having not only excellent stability but also better reactivity towards tanning agents and a temperature gelatinization, hereinafter referred to as TG, sufficient to protect the skin against possible overheating.
• a silica sol in particular an aqueous silica sol, particularly an aqueous silica sol containing by weight from 10 to 50% of silica in the state of discrete particles, not linked to each other by siloxane bonds and having an average diameter of between 3 and 100 nm, for obtaining a stabilized pickled white or stabilized white from a skin.
• the starting skin can be pickled or not, shaved or not, skinned or not.
• skin can denote, for example, the skin of sheep, goats, pigs, sheep, horses, fish, reptiles such as boa, and more generally of a terrestrial or marine mammal such as sheep, kid, pork, goat, foal, heifer, cow, beef, horse, reindeer, antelope, seal.
• pickled skin or not, depilated or not, flaked or not may denote, for example, a skin of hairs, a skin of pickled hairs, a skin of hairs that is sparse and not picked, a skin of hairs that is sparse and pickled, a skin of tripes not picked, a skin of pickles , a pickled and split guts skin, a non-pickled and split guts skin.
• silica soils according to the present invention causes on the treated skins a significant reduction in the activity of the water, hereinafter referred to as Aw (cf. Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd edition, volume 11, page 173 - John WILEY and SONS, New-York 1980), and, as a result, the development of microorganisms decreased on treated skin, thus allowing their storage without alteration for several months .
• aqueous silica soils containing from 10 to 50% by weight of silica in the form of discrete particles not linked to one another by siloxane bonds, having an average diameter of 3 to 100 nm are today commercial products sold in particular by the Applicant under the generic designation of "KLEBOSOL" R.
• a skin is treated, before or after pickling, before or after depilation, before or after fleshing, before or after slitting, at a temperature below 35 ° C., preferably at room temperature, at a pH between 1 and 10, preferably at a pH between 1 and 9 and more particularly at a pH between 1 and 8, in an aqueous bath or in a brine of density between 1.01 and 1.10, in particular between 1.014 and 1.09, with an aqueous silica sol.
• brine is preferably meant an aqueous solution of sodium chloride or other salts such than sodium sulfate or calcium chloride.
• the above-described treatment is carried out with an aqueous silica sol containing 10 to 50% by weight of silica in the form of discrete particles, of an average diameter included between 3 and 100 nm, in particular between 5 and 50 nm, preferably between 7 and 50 nm and more preferably between 9 and 50 nm, not linked to each other by siloxane bonds.
• the stabilized pickled whites or stabilized whites obtained according to the invention have, in the working environment, a gelatinization temperature of 65 ⁇ 1 ° C. This considerable elevation of TG is particularly advantageous during mechanical sawing, skinning, or declutching operations, it also makes it possible to work serenely and quickly without fear of burns, all the more so since the coefficient of friction of the skin is very noticeably increased, thus improving machine handling.
• the use according to the invention also gives treated skins a better reactivity towards tanning agents.
• tanning agents mention may be made of vegetable tannins, mineral tannins, organic tannins such as those extracted from oak wood, chestnut wood, sumac leaves, mirobolan pods, pine bark, quebracho wood, cane roots , chromium derivatives such as chromium III sulfate, zirconium salts, aluminum salts such as aluminum sulfate, formaldehyde, polyphenols.
• vegetable tannins mineral tannins
• organic tannins such as those extracted from oak wood, chestnut wood, sumac leaves, mirobolan pods, pine bark, quebracho wood
• chromium derivatives such as chromium III sulfate, zirconium salts
• aluminum salts such as aluminum sulfate, formaldehyde, polyphenols.
• the amounts of residual chromium in the bath at the end of the tanning are always less than 100 mg of chromium expressed as Cr2O3 per liter of bath.
• aqueous silica sol can vary widely, but usually 0.3 to 3% by weight expressed as SiO2 is used, relative to the weight of the skins used. Depending on the doses used, the Aw of the treated skins can vary from 0.92 to 0.8.
• the skins are generally dropped, then placed in a pile and stored. They can also be wrung out and dried. In this case, they are treated with an agent allowing their rewetting and avoiding the crystallization of mineral salts.
• the stabilized whites obtained according to the present invention can also be immediately engaged in the tanning process: the unpeeled stabilized whites can be depilated, the unpeeled stabilized whites can be skinned, the guts stabilized whites can be split and / or loose or they can be tanned using a conventional tanning process.
• the present invention thus offers the tanner a large choice of possibilities and a great flexibility of execution in order to obtain the quality of the leather which he desires.
• Another advantage of the use according to the present invention is the recovery of waste.
• the various wastes from mechanical operations are not not soiled with metals and / or tanning agents, they contain, in addition to the natural products present in the original skin, only silica. Therefore, this waste can be easily used in other fields, such as the preparation of animal and human foodstuffs.
• this pretanning can be carried out either before or after the treatment of the pickled skin or not, depilated or not, skinned or not, with the silica sol, but preferably this pretanning is carried out after the treatment with the silica sol.
• this pre-tanning is carried out afterwards, it is then carried out in a conventional manner in an aqueous bath containing the necessary quantities of sodium chloride and glyoxylic acid, at an acid pH in the presence of mineral and organic acids. It can in particular be carried out according to the method described in United States patent No. 4,978,361.
• the present invention also relates to a process for obtaining a stabilized pickled white or stabilized white from a pickled skin or not, depilated or not, skinned or not, characterized in that the skin is treated at a temperature below 35 ° C, preferably at room temperature, at a pH between 1 and 10, preferably at a pH between 1 and 9 and more particularly at a pH between 1 and 8, in an aqueous or brine bath with a density between 1.01 and 1.1, preferably between 1.014 and 1.09, with a aqueous silica sol containing 10 to 50% by weight of silica in the form of discrete particles, not linked to one another by siloxane bonds and having an average diameter of between 3 and 100 nm, preferably between 7 and 50 nm.
• the process described above can be carried out on the skins defined above, in particular a pile skin, a pickled pile skin, a skin with plucked and non-pickled hairs, a skin with plump and pickled hairs, a skin in non-pickled tripe, a pickled tripe skin, a pickled and split tripe skin, a non-pickled and split tripe skin.
• the above process is particularly characterized in that the silica particles in the aqueous silica sol have an average diameter of between 9 and 50 nm.
• 0.3 to 3% of silica is used by weight relative to the weight of the tripe skins used.
• the present invention also relates to the use of stabilized pickled white prepared by the process of the invention, for obtaining commercial hides or skins.
• the stabilized white pickle or stabilized white, resulting from the process of the present invention allows in particular the obtaining of a finished leather of good presentation, of excellent hold of flower, presenting neither stain, no defect, nor burn and uniform coloring even when the finished item is colored in pastel or light shades.
• reaction medium is then stirred, then 13.3 kg of an aqueous silica sol containing 30% by weight of silica are introduced in the form of discrete particles with an average diameter of 50 nm, and finally 200 kg of crocodile skins partially skinned, and salted, wound on themselves, in the form of cylinders of suitable diameter and size.
• the reaction medium is left under stirring at room temperature until penetration into the heart of the bath.
• the skins are then removed from the bath, resalated, and sent to the user for their final transformation into tanned skin.
• colloidal silica on the surface of the flesh allows the reception factories to carry out a good fleshing, conducive to degreasing and to a tanning of excellent quality avoiding the surface stains noted on badly skinned skins.
• the weight of the skins after draining and spinning is 69 kg.
• the hides are then sawn to a thickness of 1.5 mm, then stripped to 1.3 mm in order to obtain, after tanning, a thickness of 1.5 to 1.6 mm.
• the weight of the skins is 2.5 kg and the weight of the crusts is 21 kg.
• the skins are then treated in a bath consisting of 70 kg of water and 3.5 kg of sodium chloride. After 30 minutes of stirring, 140 g of concentrated sulfuric acid and 700 g of an aqueous solution of glyoxylic acid at 40% by weight are introduced into the bath, so as to obtain a pH of the bath of 2.6. Stirring is continued for 1 hour and then the chromium salts necessary for carrying out a conventional chromium tanning are introduced. At the end of the tanning, the chromium salt content of the bath is 0.035 g / l expressed as Cr+++.
• the silica content of the bath decreases very quickly, from 30 g / l it decreases to 8.6 g / l after 45 minutes of stirring, then to 3 g / l after 90 minutes to reach 1.5 g / l after 150 minutes of agitation.
• the skins are then taken out of the bath, placed on pallets and drained for 24 hours.
• the Aw value of the pickled skin is 0.943. They are then spun and drawn in two batches. The first batch of 30 skins is derailed at 1.8 mm; 200 kg of skins and 40 kg of spines are thus obtained.
• the second batch of 30 skins is offset at 2 mm; thus obtaining 220 kg of skins and 20 kg of spines. These 60 kg of skins are suitable for use in the food industry.
• the first batch is chrome tanned with a pre-tanning process using glyoxylic acid. To do this, the 30 skins (200 kg) are placed in a bath containing 40 kg of water, 10 kg of sodium chloride, 400 g of concentrated sulfuric acid and 1.6 kg of an aqueous acid solution. glyoxylic 40% by weight.
• chromium III salts at 33 ° from Schorlemmer chromium sulfate with a basicity index of 33%) are introduced into the bath, followed by stirring for 90 minutes. at room temperature and finally 3 kg of basifying salts (magnesium oxide) are introduced. Agitation is carried out for 6 hours and then the skins are left for 16 hours with agitation for 10 minutes every two hours. Then introduced 100 kg of water at 70 ° C, stirred for one hour while maintaining the temperature at 45 ° C. The tanned hides are then taken out and the residual chromium is measured in the bath of tanning. There is 0.0125 g / l of chromium expressed as Cr+++.
• the second batch is tanned with a vegetable tannin.
• the 30 skins (220 kg) are placed in a bath containing 110 kg of water and 14 kg of sodium chloride. After dissolution of the salt, about 1.1 kg of sodium hyposulfite is introduced into the bath so as to obtain a pH of 3 and then 11 kg of a replacement tannin dissolved in 110 kg of water. The mixture is stirred for one hour and then 5.5 kg of a neutralizing agent are introduced before adding the powdered vegetable tannin.
• the Au value of the pickled skin is 0.925.
• the split skins are then pre-tanned with glyoxylic acid and then tanned with chromium as in Example 5.
• a bath is obtained containing 0.07 g / l of chromium expressed as Cr+++.
• the Aw value of the pickled skin is 0.836.
• the skins have a water content of 4% lower than that found in skins of the same origin and having undergone the same treatment without silica sol.
• the skins are then skinned and derailed. The skinning and cutting operations are carried out very well and the flesh is smooth and shiny.
• the skinned and husked skins are then tanned in a fuller in a conventional manner with 5% by weight relative to the weight of the skins of a chromium III salt at 33 ° from Schorlemmer (chromium sulfate with a basicity index of 33%) and at 25% by weight of Cr2O3 followed after two hours of stirring with the addition of 0.5% by weight relative to the weight of the dolomite skins (dolomite).
• the skins are then left for 4 hours with stirring and then 16 hours with intermittent stirring for 5 minutes every hour.
• the pH of the final bath is 3.6 and its chromium salt content, expressed as Cr+++ is 0.13 g / l. Skins contain 4.1% of Cr2O3 expressed on the dry weight.
• reaction medium After 6 hours of stirring, the reaction medium is left overnight with stirring for 5 minutes per hour. The following day, into the reaction medium, which is at the temperature of 38 ° C., 500 kg of water are introduced at 75 ° C., the mixture is stirred for 1 hour and the temperature of the medium is 45 ° C. The skins are removed from the bath, they have a very fine flower, they are relaxed, the wrinkle is not marked, the vein is not visible.
• the bath contains 0.02 g / l of chromium in the Cr+++ state and after filtration, it is recycled for a new operation.
• the finished leather has excellent grain grip and a 3% increase in surface area, a full hand, exceptional grain fineness, a load-bearing side significantly reducing the need for cutting.

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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)
• Silicon Compounds (AREA)
• Cosmetics (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Detergent Compositions (AREA)
• Paper (AREA)
• Medicinal Preparation (AREA)

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• 1992
  • 1992-01-14 FR FR9200304A patent/FR2686099B1/fr not_active Expired - Fee Related
  • 1992-12-30 ES ES92403588T patent/ES2070613T3/es not_active Expired - Lifetime
  • 1992-12-30 EP EP92403588A patent/EP0551785B1/de not_active Expired - Lifetime
  • 1992-12-30 DE DE69201945T patent/DE69201945T2/de not_active Expired - Fee Related
  • 1992-12-30 AT AT92403588T patent/ATE120804T1/de not_active IP Right Cessation
  • 1992-12-30 DK DK92403588.4T patent/DK0551785T3/da active
• 1993
  • 1993-01-11 ZA ZA93171A patent/ZA93171B/xx unknown
  • 1993-01-12 NZ NZ245659A patent/NZ245659A/en unknown
  • 1993-01-12 TR TR00033/93A patent/TR28996A/xx unknown
  • 1993-01-13 AU AU31185/93A patent/AU656448B2/en not_active Ceased
  • 1993-01-13 KR KR1019930000353A patent/KR100237982B1/ko not_active Expired - Fee Related
  • 1993-01-13 CA CA002087228A patent/CA2087228A1/fr not_active Abandoned
  • 1993-01-14 TW TW082100199A patent/TW215930B/zh active
  • 1993-01-14 BR BR9300140A patent/BR9300140A/pt not_active IP Right Cessation
• 1994
  • 1994-06-03 US US08/253,578 patent/US5480456A/en not_active Expired - Fee Related

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