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
  • C14C9/00—Impregnating leather for preserving, waterproofing, making resistant to heat or similar purposes
  • C14C9/02—Impregnating leather for preserving, waterproofing, making resistant to heat or similar purposes using fatty or oily materials, e.g. fat liquoring
• • 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
  • C14C13/00—Manufacture of special kinds or leather, e.g. vellum

Definitions

• the present invention relates to the treatment of raw hides for manufacturing leather destined to be used in clothing items, footwear, leather goods, etc.
• the present invention relates to a method for manufacturing a leather having an improved combination of characteristics that make it particularly suitable for the above uses.
• the raw hides undergo a series of treatments having the aim of smoothing and cleaning them so as to make them suitable for being tanned.
• the treatments of this first manufacturing step generally include:
• the cleaned hides are tanned according to any of a variety of conventional methods.
• the hides are tanned by using a tanning agent of the mineral or vegetal type.
• the hides are first treated with a saline and acid solution (so called pickling) and then with a solution of the tanning agent (e.g. cromium sulphate) containing additives facilitating the fixing of the tanning agent to the hide.
• a saline and acid solution so called pickling
• a solution of the tanning agent e.g. cromium sulphate
• the hides are generally first treated with a solution containing tannin and suitable additives and then with an acid solution facilitating the fixing of the tannin to the hide and the removal of the residual tannin.
• a vegetal agent typically tannin
• the third manufacturing step begins, wherein the tanned hide may undergo a variety of treatments according to the final destination of use and to the desired characteristics to be conferred to the hide itself.
• the hide can be lubricated with a suitable mixture of fats and oils to improve for instance its characteristics of softness, and it can be dyed by using any of the conventional methods known to the skilled in the art.
• washing characteristics can be conferred to the hides, these characteristics giving the possibility of subjecting the hide to a washing treatment with common household means without incurring in dye release for example on possible fibres coupled with the hide itself.
• the hides also undergo a retanning treatment for introducing further additives able to confer to the hide additional characteristics, e.g. waterproofing, fulness to the touch, etc. and/or to enhance the previously conferred characteristics.
• a retanning treatment for introducing further additives able to confer to the hide additional characteristics, e.g. waterproofing, fulness to the touch, etc. and/or to enhance the previously conferred characteristics.
• the problem underlying the present invention is that of providing a method for manufacturing leather satisfying all the above needs.
• washable leather comprising the preparation, in a conventional way, of tanned hides starting from raw hides and characterised in that it comprises the following additional steps of:
• the method further comprises, before step b), at least one of the following steps:
• the preparation of tanned hides starting from raw hides includes the normal operations of cleaning the raw hides so as to get them ready for the tanning and the tanning treatment itself.
• the operations of cleaning the raw hides can be carried out in a conventional way by following the above described procedures, which render the hides smooth, clean and hides ready for being tanned.
• the tanning is carried out by means of a cromium tanning agent so as to obtain hides of the type known as Wet Blue.
• a cromium tanning agent so as to obtain hides of the type known as Wet Blue.
• hides can be subjected, before retanning, to a bleaching treatment with sodium hydrosulphite and oxalic acid, the latter as a reducing agent.
• bleaching treatment results being efficient to get rid of superficial dirt and thus it is preferable especially if, in the following manufacturing steps, a light dye is to be given to the hides.
• the bleaching treatment is preferably carried out by placing the hides in a conventional apparatus known as tumbler and thus by adding in sequence, the percentages by weight on the weights of the hides to be treated, 100-300% of water, preferably around 200%, 1-3%, preferably 2% by weight of anhydrous sodium hydrosulphate and 0,3-1%, preferably 0,5% of a conventional dislubricating agent chosen among fatty acids and soaps.
• the tumbler is then placed in rotation for a period of around 30-90 minutes, preferably 60 minutes and, at the end of the rotation 0,7-1,5% by weight of oxalic acid are added, preferably 1%. After having placed the tumbler again in rotation for around 30-60 minutes, preferably 40 minutes, an abundant washing with running water is then carried out.
• the retanning treatment of the hides is carried out in a conventional way, preferably by using a cromium tanning agent, e.g. powder oxide cromium.
• a cromium tanning agent e.g. powder oxide cromium.
• the retanning treatment is carried out by adding to the tumbler containing the hides to be treated, in percentages by weight on the weight of the hides, 50-200% of water, preferably around 100%, 5-6% of cromium oxide and 0,5-0,6% of sodium bicarbonate. Then the tumbler is placed in rotation for a period of 2-4 hours, preferably 3 hours and at the end of the rotation an abundant washing with running water is carried out.
• the enhancement of the pH of the retanned hides is preferably carried out by adding to the tumbler containing hides, in percentages by weight on the weight of the hides to be treated, 50-200% of water, preferably around 100% and 1,5-3%, preferably 2% of ammonium bicarbonate (pH regulator) so as to enhance the pH to a value of 6-7. Then the tumbler is placed in rotation for a period of 60-120 minutes, preferably 90 minutes and, at the end of the rotation an abundant washing with running water is carried out.
• pH regulator ammonium bicarbonate
• the enhancement of the acid pH typical of the retanned hides to a value around the neutrality advantageously allows to prepare the hides in the best way for the subsequent treating steps and it results to be particularly suitable for obtaining a good softness of the hides in said subsequent steps.
• the optional treatment of the retanned hides with the mixture of acrylic resins is preferably carried out in the tumbler containing the hides to be treated by adding therein, in percentages by weight on weight of the hides, 100-300% of water, preferably around 200% and 3-5% of a watery solution of acrylic resins.
• the tumbler is placed in rotation for a peroiod of 30-90 minutes, preferably 60 minutes and, at the end of the rotation, an abundant washing with running water is carried out.
• the acrylic resins useful in the method according to the invention are composed of polymers and co-polymers of the methacrylic acid, the percentage by weight of the resins in the solution is of around 40% and the pH of the solution is comprised between 4,2 and 5,5.
• the treatment of the retanned hides with the mixture of acrylic resins advantageously confers to the hide the proper degree of fulness to touch.
• step b A very important aspect of the present invention is given by the lubrication step (step b).
• such lubrication step is carried out by treating the hides in a tumbler with an emulsion obtained by mixing under agitation 70-90 parts by weight on the total weight of the emulsion of an organic phase constituted of hydrophobic synthetic oils and 10-30 parts by weight of a watery phase constituted of an emulsion of silicone compounds.
• the hydrophobic synthetic oils constituting the organic phase preferably have anionic character, i.e. they comprise anionic organic units.
• a preferred product for the organic phase is sold by Dermacolor s.r.1. with the name of DERMADOL W 300 and it comprises a mixture of syntetical oils able to confer waterproofing to the hide.
• the silicone compounds constituting the emulsion of the watery phase are chosen from the group comprising silane and siloxane compounds and respective polymeric products of condensation.
• a preferred product for the watery phase is constituted of a watery emulsion of dimethylpolysiloxane.
• the emulsion used in the lubricating process is prepared in situ and it is used in percentages by weight on the weight of the hides to be treated comprised between 8% and 15%.
• the tumbler is placed in rotation for a period of 60-120 minutes, preferably 90 minutes and, at the end of the rotation, an abundant washing with running water is carried out.
• the above specified lubricating treatment confers to the hides characteristics of softness, waterproofing, transpiration and elasticity desired for the final application.
• the lubricated hides as specified above are dryed in a conventional way, e.g. by means of vaccum applications and windy conditioning for then being selected for the following manufacturing steps.
• step c before subjecting the selected hides to dyeing (step c), it is preferred to carry out on the same a second lubricating treatment with the same emulsion used for the first lubrication.
• the emulsion is used in proportions from 2% to 8% by weight on the weight of the dryed hides.
• This second lubricating treatment allows to improve, i.e. enhancing, the characteristics of softness, waterproofing/transpiration and elasticity already conferred to the hides in the previous lubrication.
• the lubricated hides (in one or two steps as specified above) are then subjected to the dyeing treatment.
• the dyeing is carried out by adding to the hides to be dyed placed in a tumbler, 100-300% by weight on the weight of the hides of water and 1-6% by weight of a dyeing agent of a conventional type chosen according to the colour which is to be conferred to the final hide.
• the tumbler is then placed in rotation according to the normal dyeing times.
• the hides are further treated with a solution containing 1-3% by weight of cationic acrylic resins.
• These resins act as auxiliaries for dyeing, facilitating the fixing of the chosen dyeing agent to the hide and thus allow the improvement of the characteristics of fastness of the colour.
• the dyeing is generally completed by a fixing step which allows to bind permanently in the pores of the hides all the chemical products used in the previous treatments (es. lubrication and dyeing).
• the silicone compounds are preferably chosen from the group comprising silane and siloxane compounds and their respective polymeric products of condensation whereas the nature of the metallic salts varies according to the chosen dyeing agent.
• Suitable metallic salts are chosen among cromium, alluminium and zirconium salts.
• the fixing treatment is carried out by adding in the tumbler containing the dyed hides, in percentages by weight on the weight of the hides, 100-300% of water, preferably 200%, 0,5-3% of silicone emulsion and 3-6% of metallic salts.
• the leather obtained with the method according to the invention has high qualities and characteristics of softness, waterproofing, transpiration, elesticity, fulness to touch, colour fastnessand stability, washability, fastness to light and to fading, which fully satisfy the standards required by the international rules in this field.
• the leather obtained according to the invention has mean values on the scale of the grey in the range of 4-5 as determined according to the international rule IUF 423.
• samples of dyed leather are coupled with particular non-dyed fabrics, agitated in a neutral solution of synthetic detergent and then rinsed and dryed.
• variations of colour on the samples as well as the degree of migration of the colour on the accompanying fabrics are evaluated by comparing them with the scale of the grey.
• the results are then expressed in values of the scale of the grey variable from 1 to 5 wherein a significant bleaching of the hide and/or a significant migration of the colour from the hide to the coupling fabric correspond to the minimum value of 1 whereas the maximum value of 5 is given to a leather that, at the end of the test, has no variation of the colour of the leather and/or colouring of the accompanying fabric.
• the leather according to the invention also has improved characteristics of transpiration and waterproofing.
• measures on samples of leather carried out on according to the international rule IUP 15 have shown transpiration values (i.e. permeability to water vapour) higher or equal to 10 mg/cm 2 h and generally comprised between 10 and 15 mg/cm 2 h.
• measures on samples of leather carried out according to the international rule IUP 10 have shown values of resistance to the penetration of water comprised between 90 and 120 minutes with absorption of water varying from 10% to 15% by weight on the weight of the examined sample of leather.
• the leather obtained according to the method of the invention also has excellent elasticity characteristics.
• a breaking load higher or equal to 12 N/mm 2 and a stretch higher or equal to 40% have been detected.
• the main advantage of the leather obtained through the method according to the invention lies in the fact that it can be efficiently subjected to washing with neutral detergent at a temperature of around 40°C without any substantial structural alteration of the hide (e.g. loss of elasticity and/or shrinking) and of the softness, and without any release and variation of colour.
• the leather obtained according to the invention is advantageously suitable for being used as it is alone or coupled to other natural or synthetic fibres for manufacturing washable items, e.g in the field of clothing, footwear, leather goods and furnishing.
• the leather does not need further specific finishing treatments.
• the method according to the invention is efficiently appliable to all the raw hides of natural origin with particular reference to bovine and ovogoaty hides.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Diaphragms For Electromechanical Transducers (AREA)

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Cited By (6)

Citations (3)

• 2003
  • 2003-10-03 EP EP03425647A patent/EP1520911B1/fr not_active Expired - Lifetime
  • 2003-10-03 AT AT03425647T patent/ATE451479T1/de not_active IP Right Cessation
  • 2003-10-03 DE DE60330458T patent/DE60330458D1/de not_active Expired - Lifetime

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