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

Definitions

• the present invention is related to the use of aluminosilicates in combination with neutralizing agents and tanning materials, to obtain chrome-free leather during tanning and retanning treatments.
• zeolite types aluminosilicates of different nature and composition
• this is due to the fact that the insoluble nature of the zeolites did not allow a vehiculation in fibrillar interstices of the skins in an aqueous environment, in addition to the fact that the extremely basic pH of zeolites limits the range of applications in the classic tanning procedures.
• US-A1-2002/038478 describes the treatment of skins pretanned with aldehydes; carried out in different times and not with joined and concomitant use of the three components of the composition mentioned .
• Object of the present invention is solving the above prior art problem, by providing a use of aluminosilicates in combination with neutralizing agents and tanning materials in one step use (premixed) , to obtain skins free from chrome tanning and retanning, where the alluminosilicic structure of zeolites is disintegrated in the presence of weak acids and tanning agents jointly.
• the specific choice of the tanning component leads to different technical, economic and toxicological results. These preparations can be used both in the canonic tanning process (like "wet white”), and in the subsequent phase of said retanning, for a best characterization of the finished product.
• Chrome tanning leads to a problem of environmental and toxicological importance, having to recover chrome in waste water, and having trivalent chrome in the produced leather that can always oxidize to hexavalent chrome, clearly toxic.
• tannins and synthetic tannins are limited by the technological effectiveness and the prerogative of the finished article, that is not similar to chrome (vegetable leather or vegetable look) , in addition to higher cost and not always to a light color that is not desired for some further dyeing.
• the aldehydes in general are nearly always toxic, and the leather is a bit flatter and tends to yellowish over time.
• Titanium salts have a high cost, even more zirconium salts. Aluminium yields to bright white leather, but its main derivative Al-triformiate is expensive and not fully tanning, being then at the limit of acceptability of the market.
• the main condition to determine the technological achievement of a stable condition of the leather tanning or effective intramolecular bonding is the shrinking temperature, better expressed as Tg temperature .
• chrome salts used in the percentage of 6/8% on the weight of the hides, normally reach 100 °C without bringing narrowing of the piece of skin tested, while almost all the materials listed above, including the composition used in the present invention, always lead to a lower Tg: commercially, temperatures above 75 °C are accepted by the market for the intermediate products (wet white) , alternative to the classic wet- blue (chrome) .
• zeolites natural or synthetic aluminosilicates , known as zeolites, in all their forms, has no practical significance as tanning agent, although it is described in other patents (US-A- 4272242 and others) , but with technological purposes that differ from the present one.
• the zeolite is instead very well known and used in powder detergents, such as calcium ion sequestrant, when it is placed in water, because it determines a reduction of water hardness, thus allowing to synergize the condition in which the detergent is used. This condition has determined then the classification of zeolites, as well as for their steric characteristic, also for the capability of sequestering the calcium ion .
• the nature of the zeolite is not important, but the fact that it must be placed in solution, and then dissolved, to obtain a series of sub-products, such as various aluminum salts, silicates and polisilicic acids in solution, through the use of neutralizing acids, such as mainly oxalic acid / tartaric acid etc.
• Tg results are obtained, which can vary, depending on the percentages of use, on the times and with reference to the tanning agent imployed, between 80 °C and 85 °C normally, as an expression of the result of the tanning effect, with a 10% / 12% of percentage of use on the weight of the skin.
• the present invention relates to the use of a composition containing aluminosilicates in combination with neutralizing agents and tanning materials used simultaneously and correlatively to obtain chrome-free leather during tanning and retanning, in which the zeolites are aluminosilicates, neutralizing agents are weak acids and tanning materials, preferably syntans better described in the claims, however characterized by their ability to bind to a collagen fiber of a skin and determine a tanning effect.
• the zeolites are present in a percentage range varying from 5% to 66.6% of the weight of the composition, weak acids are present in a percentage range varying from 5% to 33.3% of the weight of the composition and the materials tanning agents are present in the composition as completion of the total weight (100%) of the composition, with a lower limit of 5% minimum regarding their presence.
• the materials are tanning syntans, derivation of aromatic sulfonates, such as phenol, cresol, or naphthalene groups, subsequently condensed with formaldehyde and urea (classic syntans) , titanium and its salts, zirconium and its salts, aldehydes and their various similarities, such as glyoxal, natural tannins and tanning extracts, such as tara, mimosa, quebracho, chestnut, mirabolan, tannic acid, gallic acid and pirocatechinic and pirocatecolic structure or the like.
• formaldehyde and urea classic syntans
• titanium and its salts titanium and its salts
• zirconium and its salts zirconium and its salts
• aldehydes and their various similarities such as glyoxal, natural tannins and tanning extracts, such as tara, mimosa, quebracho, chestnut, mirabolan, tannic acid, gallic
• the treatment composition of use has a weight variable from 3% to 40% in total on the weight of the leather to be treated, also obtained through a plurality of additions during the treating time.
• This composition is used on the hide undergoing riviera / liming / tanning, instead of basic salts of chrome, or is used on the leather during retanning / dye / fatliquoring, instead of basic salts of chrome as well.
• aluminosilicates type zeolites are natural or synthetic, of the type having the ability to bind calcium according to the generic formula from 20 to 200 mg CaO / gm of anhydrous substance measured according to the standardized analytical method of calcium binding, typically used in the detergent field.
• Weak acids are weak organic or inorganic salts, adapted to determine in water the occurrence of a pH buffering situation in conjunction with the use of basic crystalline zeolites, dissolving the crystal structure insoluble in water of the zeolites; these acids are, for example: formic acid, acetic acid, oxalic acid, citric acid, tartaric acid, ascorbic acid or organic diacids and multiples thereof, where the carbon atom chain can vary between 2 and 16, linear or branched, fatty acids, inorganic acids, such as phosphoric acid, sulfamic acid, or their above mentioned mixtures, suitable to dissolve the crystalline structure of the zeolite in an aqueous medium with a final result of a solution that has a pH between 2.5 and 8.
• the formulation of the composition which allows achieving the best synergy between the components, 40 parts are taken of the zeolite powder commonly used in detergent formulations as a hardness inhibitor, mixed with 26 parts of oxalic acid and 33 parts of a common syntan for white (like 4 , 4dioxiidifenil-sulphone) . All parts mentioned above are considered in percentage in weight, 100 being the total weight of the composition.
• This mixture placed in an aqueous environment, dissolves, forming a solution / dispersion, with a pH of about 5 - 5.5. This is, between the infinite combinations, the one that best expresses the synergic potential in practical applications.
• the inventive composition When the inventive composition is used in the tanning phase, before or just after the commonly known PIKEL step, depending on whether more or less marked situations of osmotic gradient related to the pH of use are desired, and in concentrations which can vary from 5% to 20% (for economic and practical reasons) of the leather weight, whether sheep, goat, bovine or others, when in drum, it exerts a penetration of the product, growing gradually the dissolution of the zeolite in solution, and acting as buffering action also useful for a better penetration and fixing of the tanning material (in this case, the classic syntan for white) ; a semifinished leather clear, free of chrome, is thereby obtained, with fully acceptable prerogatives for the subsequent processing, of both types: mechanical and chemical, as well the retanning, dyeing and its fatliquoring, all that yield to strongly competitive economic conditions compared to any other tanning agent in a univocal application, excluding chrome salts.
• Tanning and retanning baths after a proper timing and related to the percentage of use of the product, are well exausted, hides do not have product release under torsion (so- called bleeding) , and the baths are clear with a very small material load in solution, that yields to a very low enviromental impact .
• Tanning test take an adult goatskins in the common phase called internationally "Pikel" (skin from a particularly acidic bath, with a pH approximately of 2.5 to 2.8).
• a homogeneous mixture should be added simultaneously in a drum, which has the acid bath from the stage of Pikel without downloading or replace it, such homogenous mixture, premixed previously, containing 55 parts of Zeolite, 25 parts of oxalic acid and 20 parts of pure syntan type 4-4 ' -diossidifenilsulfone (commonly called syntan for white) .
• the addition is dosed with the ratio of 12% by weight with respect to the weight of the loaded hides.
• the skins at this point, will have a uniform passes section, a pH of the cross section equal to about 4 to 4.2 (control with methyl orange indicator) , a relaxed appearance, white, with a flower fine. If the pH of the bath and the section is in the specified field and looks exhausted (transparent bath) , it is necessary to unload the bathroom and put the skins on a horse to rest for the night, to give time to fix, to continue next day with the usual mechanical operations that normally take place after the traditional tanning (chrome way) .
• zeolite is decreased to its minimum specifications, using the same criteria (ratio 5/47,5/47,5), thereby increasing the scids and tannic materials equally, one arrives at a situation of mild pre-tanning, actually determined only from the tannic substance present, not commercially acceptable, with a Tg below 50 °C and article prerogatives leading to vegetable look (when syntan as from Example 1 is used as tannic substance) , not forgetting that the aim is replacing the chrome from tanning and retanning, and then getting a similar technological / economic result. As indicated in Example 3, the positive results are considered to rise as percent concentration of the highlighted component with respect to the lower limit (in this case the zeolite) .
• the zeolite is partially dissolved, lacking a part of acid, and does not have a sufficient tanning result, lacking the contribution of the tanning substance, that moves away from the optimum ratios; this is considered to be the maximum limit of the expression of zeolite percentage that can be used.
• Example 7 Compared to Example 3, and not substantially dissimilar from Example 7, lacking a triple synergy, with TG around 55/60 °C.

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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)

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Citations (2)

• 2012
  • 2012-01-31 IT IT000110A patent/ITMI20120110A1/it unknown
• 2013
  • 2013-01-18 WO PCT/IT2013/000017 patent/WO2013114414A1/en active Application Filing

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