WO2013114414A1

WO2013114414A1 - Use of aluminosilicates in combination with neutralizing agents and tanning materials to obtain chrome-free leathers in tanning and retanning treatments

Info

Publication number: WO2013114414A1
Application number: PCT/IT2013/000017
Authority: WO
Inventors: Marco Antonio ROBBIATI
Original assignee: Robbiati Marco Antonio
Priority date: 2012-01-31
Filing date: 2013-01-18
Publication date: 2013-08-08
Also published as: WO2013114414A9; ITMI20120110A1

Abstract

The invention relates to the use of a composition containing aluminosilicates in combination with neutralizing agents and materials to obtain tanning hides in chrome-free tanning and retanning, in which the zeolites are aluminosilicates, neutralizing agents are weak acids and tanning materials, preferably syntans, are determined by their ability to bind to a collagen fiber of a skin and determine a tanning effect, the zeolite being present in a percentage range varying from 5% to 66% of the weight of the composition, weak acids being present in a percentage range varying from 5% to 33.3% of the weight of the composition and the tanning materials being present in the composition in completion of the total weight of the composition, with a minimum proportion of 5%, wherein the composition is used with the components already mixed prior to use, so that, during use, they act on the hides concomitantly.

Description

USE OF ALUMINOSILICATES IN COMBINATION WITH NEUTRALIZING AGENTS

AND TANNING MATERIALS TO OBTAIN CHROME-FREE LEATHERS IN TANNING AND RETANNING TREATMENTS

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.

The use of aluminosilicates of different nature and composition (zeolite types) , in the process of tanning and retanning of skins, up to now has not found practical use: 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. The same, in this situation, have never exercised a direct bond with the aminoacids constituting the collagen structure of the skins, as maximum effect, have led to a reduction of the amount of auxiliary tannic material detected, with a reduction of the polluting load through potting of the same in their cage structure, and therefore in fact a non-detection of a pollution load present.

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.

In this way a synergy is expressed between the active components that develop a tanning capacity of the alluminosilicate as an expression product of a level not obtainable from single components used individually.

The above and other objects and advantages of the invention, as will appear from the following description, are achieved with the use of aluminosilicates in combination with neutralizing agents and tanning materials, to obtain chrome free leather during tanning and retanning, as claimed in claim 1 .

Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It is intended that the appended claims are an integral part of the present description.

The present invention will be better described below by some preferred embodiments thereof, provided as a non-limiting example.

In these recent years, the elimination of chrome from the tanning process has been sought, and in general obtaining an economically sustainable process of leather with low environmental and toxicologic impact for the nature and for the man who benefit through direct contact of final goods. Such triple composition of the invention leads to the obtainment of leather chrome-free, white in color, and with very low load of substances that are potentially harmful to human health, depending on the tannic agent employed, syntans, aluminum (triformiate type) , titanium salts, zirconium salts, aldehydes and derivatives, and all natural tannins (tara, mimosa, chestnut quebracho, myrobalan, etc.) .

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.

The use of tannins and synthetic tannins is 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.

The phosphines or phosphonium derivatives, of relatively recent employ, often do not fix in an irreversible way, are expensive and with some aspects of toxicity. 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 .

The 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) .

The use of 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 .

For the use that is intended to describe with this document, 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.

The concomitant use in a mixture of zeolite, neutralizing and tanning agent, leads to a synergy not comparable with the use of the individual component, or in any case of only one substance like the tanning material, or the couple of zeolite / neutralizing material (the zeolite alone would not lead to any result because insolubile in water, as well as the use of acid by itself or coupled with tannic material), with results of Tg (shrinking temperature) less than 60 °C (not satisfactory) . Instead, when coupled all three together, good 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.

In summary, 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.

In particular, 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.

Furthermore, 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.

Still in particular, 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 present invention will be described below by means of

Examples which are explanatory and absolutely not limitative of its scope.

Example 1

Best sinergic effect (ratio 40 / 26 / 33 )

As a first general example of 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.

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.

The use technique (single step addition) , the timing (180 minutes) and the following pauses, and standard dosages (10/12%) are related to the common processing, and are not dissimilar from the procedures commonly used for working with the use of chrome salts; it is advisable to acidify in the final stage in a more incisive way, as all aluminum-based tanning, well described in the literature instead of basifying as common with 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 .

Example 2

Practical example with maximum costs / benefits optimisation (ratio 55/ 25/ 20)

The following is a practical example that allows a maximum optimization of costs and benefits, using 55 parts of zeolite powder, mixed with 25 parts of oxalic acid and other 20 parts of synthetic tannin.

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. This is put under rotation in a drum, cold temperature, the object of the invention is added to the drum bath and leathers, and after 15' after addition, a first control is made of the pH that must be between 3.5 and 3.8; if the result is positive, the drum is rotated for 180' min. At the end of that, a test is made on the final pH of the bath, which must be less than pH 4; if required, this is corrected with a small addition (0.5%) of formic acid 85%, prolonging the rotations for 30' min to maintain the pH in the above parameters, expression of the best achievable result. 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) . The next morning the expression of the results can be verified, performing a test on the shrinking temperature (TG) expressed in °C, which will be between 78 °C and 82 °C, as function of the treated leathers (origin, state of preservation, etc.).

EXAMPLE 3

ratio 47.5 / 47.5 / 5% minimum Deputy tannins)

If the same test mentioned above is carried out with the same parameters but a decreasing percentage of sequentially one of the components, for matters of reasonableness testing, moves as the first example to the minimum concentration proportional to the tannic substance of the mixture, although it increases proportionally and the joint use of the other two (in fact more zeolite and more oxalic acid are used in proportion) and then with a component ratio of 47.5 / 47.5 / 5, the final result, although academically acceptable, would be with an expression ot Tg in c lower than the one in Example 2, and technically comparable to what is commonly defined as "light pretanning", with the result of a Tg around 55/60 °C and then with limited expression of synergy between the components fulcrum of this invention. This example is in fact the lower acceptability limit for the percentage of tannic substance; this delimits a limit for the component to highlight the efficacy of the triple combination.

EXAMPLE 4

(ratios 5/47,5/47,5 zeolite minimum)

If 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) .

EXAMPLE 5

(ratios 05/05/90 zeolite & acid minimum tannins max)

The latter is even more so for the drop of zeolite and acid concentrations to the minimum ratio (5/5/90) , and increase the ceiling of tannic substance used. It is generally recognized that, to acnxeve signiiicant expressions or eiiecLiveaesb WILII ±y

75°C/80 °C similar to Example 1, the percentage of use of the single syntan that has to be employed (weight percentage of use on skin weight) for synthetic tannin used individually are very high (in the order of 20% minimum) : therefore a relationship between the components employed with extreme ratio 5/5/90 to 12% by weight as in Example 2, does not provide acceptable technical results, resulting in an ineffective synergism (Tg 50 °C / 55 °C will be achieved) ; and the article appears with features aimed at the so- called classic article, vegetable / sole leather, far away in the article chrome; the antipodes appear in their fullness with an article internationally called "NAPPA", which is soft, full, flexible and lightweight and which can be obtained with the right above mentioned relationships in Examples 1 and 2.

EXAMPLE 6

(ratio 47,5/5/47,5 acid minimum)

As a logical consequence, if it leads to the minimum concentration acid with respect to the other two components expressed in equal ratio (47.5 /5/47, 5), the zeolite does not come into play except in the very small and not significant part; rather, it is out of the pH range with a partial overtanning surface which damages the skins themselves, shrinking the flower. Zeolite having a high pH, and the tannic substance which was not in sufficient quantity to deliver a result (see Example above) , since the pH which develops (around 6.5 / 7). This is therefore the difficulty of penetrating into the skin itself, which is also deposited on the surface layers and prevents a homogeneous penetration of the tanning materials. Therefore, a absolutely not desired result, even in articles deliberately called "wrinkled", in which a differential pH is aimed for the purpose. Moreover, a large part of the zeolite is not dissolved, together with the tannic substance not linked, creating de facto a waste situation when dumped at the end of the treatment. The first results are obtained by increasing the acid from the above-mentioned report to this relationship, positively expressed from general Example 1 and specific Example 2.

EXAMPLE 7

(ratio 66/16,5/16,5 zeolite max)

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 8

(ratio 62/33/5 Max acid )

Not different, compared to Example 3, and not substantially dissimilar from Example 7, lacking a triple synergy, with TG around 55/60 °C.

Application examples have been included here in the classic field of tanning; to complement the explanation for the practical use in tanning / dye / fatliquoring phases, as for chrome in this second application phase, using the preparation to an extent lower in percentage terms than the use of phase tanning already described, the practical use is normally to the extent of 3-9% by weignt on tne "snavea weignt" oi suns, ror economic reasons mainly. The practical use is in place of the canonical chrome in all respects, normally before the usual neutralization step, and the infinite combinations that lead to various commercially available items, almost never provide for the use of chrome to achieve the unique characteristics peculiar of the finished product; on the contrary, the use of the unique triple mixture, although in this specific case more unbalanced at the expense of the relationships between them with respect to the previously described limits as in Example 5, which leads to a finished article, vegetable type, or in Example 8, which leads to an extreme softness / fullness, yield, during retanning, more acceptable results that are able to better characterize the final desired item. Much depends, however, by the addition of other substantial components, such as filling acrilic resins, fillers, fatliquors, except that the colorimetric rendering of the leather expressed with the use of the mixture in question is estremely increased, compared to the use of chrome, allowing also a savings on the percentage of colorant to be used, up to 20% less, all with the ecologic advantage, in general the colorants being almost always anilines or toxic aromatic derivatives.

Claims

Use of a composition containing aluminosilicates in combination with neutralizing agents and materials to obtain chrome-free hides in tanning and retanning, in which the zeolites are aluminosilicates, neutralizing agents are weak acids and tanning materials, preferably synthetic tannins, and are determined by their ability to bind to the collagen fiber of a skin and determine a tanning effect, the zeolites being present in a range varying from 5% to 66% by weight of the composition, weak acids being present in a range varying from 5% to 33.3% by weight of the composition, and the tanning materials being present in the composition as completion of the total weight of the composition, with a minimum proportion of 5%, wherein the composition is used with the components already mixed prior to its direct application, so that, during use, the components concomitantly act on the hides.

Use according to claim 1, wherein the tanning materials are synthetic tannins, derived from aromatic sulfonates like phenol, cresol, naphthalene, subsequently condensed with formaldeide / urea

Use according to claim 1, wherein the tanning materials are titanium and its salts, zirconium and its salts, aldehydes and derivatives thereof, such as glyoxal.

Use according to claim 1, wherein the tanning materials are natural tannins and tannic extracts.

Use according to claim 1, wherein the natural tannins and tannic extracts are tara, mimosa, quebracho, chestnut, myroDaian, tannic aci , game acid, ana pirocatecninic ana pirocatecolic structures or their equivalents.

6. Use according to claim 1, wherein the composition has a weight ranging from 3% to 40% as total of the weight of the leather to be treated, also obtained through a plurality of additions over time .

7. Use according to claim 6, wherein the composition is employed on the hide after deliming and in substitution of the common pikel process, obtaining a leather tanned without chrome and without the use of salt and strong inorganic acids.

8. Use according to claim 6, wherein the composition is employed on the hides undergoing tipical tanning after PIKEL instead of basic salts of chrome.

9. Use according to claim 6, wherein the composition is employed on the leather during retanning / dye / fatliquoring instead of basic salts of chrome, or in place of and in the reduction of synthetic tannins and their derivatives, or in place of and in the reduction of aldehydes and their derivatives, or in place of and in the reduction of titanium salts and its derivatives, or in place of and in the reduction of zirconium and its derivatives .

10. Use according to claim 6, wherein the composition is used on the leather during retanning / dye / fatoiquoring in place and in reduction of natural tannins, such as mimosa, tare, chestnut, quebracho and tannic gallic, pirocatecinic and pirocatecolic structures and the like.

11. Use according to claim 1, wherein aluminosilicates type ieuiiLBb die iidi-Ui-dx ui ayiiLiicLiu, υι ι_ιit: uyjjfc: n viiiy i_ne ability to bind calcium according to the generic formula from 20 to 200 mg CaO / gm of anhydrous substance measured according to the standard analytical method of power binding of calcium, typically used in the detergent sector.

2. Use according to claim 1, wherein the weak acids are organic or inorganic salts, adapted to determine the occurrence of buffer situations in conjunction with the use of basic crystalline zeolites, and to disgregate the crystal structure insoluble in water.

3. Use according to claim 12, wherein the weak acids are formic acid, acetic acid, oxalic acid, citric acid, tartaric acid, adscorbic acid or organic diacids, and their multiples of the carbon atom chain between 2 and 16, linear or branched acids, inorganic acids, such as phosphoric acid, sulfamic acid or at least mixtures thereof, suitable to dissolve the crystalline structure of the zeolites in an aqueous medium with a final result of a solution that has a pH between 2.5 and 9.

4. Use according to any one of the preceding claims, wherein the composition comprises 60% of zeolite, 20% of weak acid and 20% of tannin.