IT202100009920A1 - METHOD OF TREATMENT FUNCTIONALIZING THE LEATHER FOR THE IMPROVEMENT OF THE ELASTIC PROPERTIES. - Google Patents

Description

?Method of functionalising treatment of the leather for the improvement of the properties? elastic?.

DESCRIPTION

The present invention relates to a method for functionalizing treatment of leather for improving its properties. Pi? particularly, the invention relates to a method for improving the elastic characteristics of hides of animal origin.

By leather we mean the well-known material of animal origin consisting at least in part of dermis of animal origin and also commonly called ?leather?. Therefore the method pu? be applied, in a very general way, on any skin or hide of animal origin.

The method object of the present invention finds its main application in the tanning industry, in the leather processing steps upstream of the known tanning processes.

As ? known, the animal skin, to which the present invention refers, is formed by epidermis (also called flower side) and dermis (also called flesh side) whose structure is? made up of spatially ordered and organized collagen fibers and fibrils to form a highly interconnected structure.

The method object of the present invention therefore consists in a functionalizing treatment for the leather, i.e. a treatment which gives the leather functions and/or properties additional.

Pi? in detail, the functionalizing treatment object of the present invention ? aimed at improving the properties elastic properties of the leather, i.e. control, modulate and improve the properties? of extension and elastic recovery of the animal dermis thus giving the leather products greater elasticity? without compromising the native organoleptic characteristics such as softness to the touch and breathability.

Different methods are currently used to make the leather elastic.

In a first known typology of methods for conferring elasticity? to leathers, we proceed to create a leather/lycra hybrid or other synthetic materials that possess elasticity. The combination of a very thin layer of leather with lycra gives the leather itself characteristics of elasticity.

In a second known typology of methods for conferring elasticity? mixes of polyurethanes, elastomers or other exogenous molecules that are able to confer elasticity are added to the hides during the phases of the well-known tanning and retanning process. and softness to the leathers.

Some significant limitations and disadvantages are known for both types of methods listed above.

In particular, in the first case the fabrics made are not in natural leather since there ? the addition of a layer of synthetic material to a very thin layer of natural leather, in many cases it even starts from materials in polyurethane or PVC similar to leather. Fifteen? what is obtained downstream of these processes? a fabric actually? synthetic, imitation leather with characteristics of elasticity?.

As for the second known typology of methods for conferring elasticity? to leathers, the degree of elasticity? what can you impart? in relation to the quantity?/percentage of polymer or elastomer or polyurethane that is used during the tanning and retanning phases: greater ? the quantity?/percentage greater sar? the degree of elasticity; however, excessively increasing the amount? of these molecules some of the main characteristics of natural leathers are reduced, such as softness to the touch, fullness and breathability.

The main task of the present invention ? that of realizing a method of functionalizing treatment of the leather capable of solving the problems and overcoming the limits of the prior art set out above, improving the properties? elasticity of the leather without the addition of exogenous and/or synthetic molecules or in any case without altering the main characteristics of natural leathers such as softness to the touch, fullness and breathability.

Within the scope of this aim, an object of the present invention is to provide a functionalizing treatment method for leather which is capable of improving the extensional characteristics of the animal dermis by conferring high elasticity to the leather. to leather products, modulating and improving the properties? of stretching and elastic recovery, without the addition of exogenous and/or synthetic molecules.

Another object of the present invention ? that of realizing a method of functionalizing treatment of the leather which allows to confer elasticity? to leathers while maintaining the natural breathability unchanged? and softness and also making the hides adaptive to different shapes, with improved performance and characteristics compared to the prior art.

Another aim of the present invention ? that of creating a method of functionalizing treatment of the leather that can be inserted within the chain processes and standard manufacturing currently used in the tanning sector.

A further object of the present invention consists in conceiving a functionalizing treatment method which is highly reliable, relatively simple to produce and at competitive costs compared to the prior art.

The task set out above, as well as? the objects mentioned and others which will become clearer hereinafter are achieved by a method according to claim 1.

Further characteristics and advantages will become clearer from the description of a preferred, but not exclusive, embodiment of a functionalizing treatment method of leather for improving the properties of the leather. elastic bands of said leather, illustrated for indicative and non-limiting purposes with the aid of the attached drawings in which:

figure 1 ? a flow chart illustrating the essential steps of the method according to the invention;

figure 2 ? a flow chart illustrating the steps of a preferred embodiment of the method according to the invention.

With reference to the figures cited, the method ? generally indicated with the reference numbers 1 and 10 according to the embodiment.

The method 1, 10, as already? mentioned, ? a functionalizing treatment method of hide of the type comprising a dermis of animal origin which in turn comprises collagen fibers and/or fibrils and an aqueous component. The method ? aimed at improving the properties leather elastic.

In its essential features, with reference to figure 1, the method includes the following two main steps (performed in this order):

a1) selective removal of the aqueous component of the animal dermis (ie of the interstitial water), which is advantageously performed so as not to alter the microstructure of the collagenous network constituting the dermis itself;

a2) execution of an anhydrous thermal treatment for the activation of the reactive groups present in the collagen and more? precisely of reactive groups of chemical end groups on the macromolecular chain of the protein and promotion of trans-esterification reactions in anhydrous environment.

The first step of selective removal of the aqueous component of the animal dermis, more? specifically, it provides for the complete removal of the aqueous component of the animal dermis without significant alteration of the macromolecular structure of the dermis, or with an overall volumetric variation of the tissue lower than 5% compared to the hydrated product, i.e. this step ? performed in such a way as to cause an overall volumetric reduction of the dermis of less than 5%.

The 5% limit in the total volumetric contraction of the dermal tissue guarantees the preservation of the correct structure, i.e. the native one (therefore the average distance between the collagen fibrils) and consequently limiting the possible reduction of mobility? molecular structure of collagen following the stage of removal of interstitial water.

According to the invention , the practical execution of this step of selective removal of the aqueous component provides for the use of one or more organic solvents with which to treat the leather and appropriately includes the simultaneous and concomitant use of organic solvents characterized by: suitable properties? which give them the ability to replace the aqueous phase and at the same time adequate surface tensions which allow their subsequent removal from the organic matrix without involving changes in the macromolecular structure of the dermis, or rather of the collagenous network constituting the hides.

Are preferably used one or more? blends of organic solvents.

The solvents, or solvent mixtures, which have proved to be effective in carrying out the step of selective removal of the aqueous phase, preferably but not exclusively include:

- Acetone,

- Ethanol,

- Propanol,

- Isopropyl alcohol.

The controlled removal of the aqueous phase can take place also through the use of solvents ?in critical conditions?.

The modalities? with which can? occur the controlled removal of? interstitial water provide for the execution of one or more? solvent treatment cycles and preferably 1 to 10 different solvent treatment cycles.

The different cycles can include alternating the use of different solvents, for example ? possible to alternate: Acetone, Isopropyl Alcohol, Ethanol.

The duration of the treatment cycles in solvent can? vary from 10 minutes to 10 hours.

The temperature of the water extraction process can vary from 2-4 ?C up to 37-40 ?C.

The quantity? of solvent used pu? vary from 1 to 500% with respect to the weight of the leather to be treated.

Referring now to the subsequent execution step of an anhydrous thermal treatment for the activation of the reactive groups present on the collagen macromolecule, more? specifically, this step ? designed to promote intramolecular reactions. There? ? obtainable through a specific control and modulation of the environmental conditions by operating a stabilization process of the collagenous network known as anhydrous thermal treatment or with the acronym DHT (?Dehydrothermal Treatment?).

DHT treatment? a cross-linking process of a physical nature commonly used to stabilize networks of collagen or collagen-based materials, by forming zero-length chemical bridges; more specifically the anhydrothermal treatment step leads to the formation of intermolecular crosslinks through condensation reactions by esterification or amide formation.

Also, DHT treatment ? mainly used to induce the formation of chemical condensation reactions between reactive groups present on the protein chain, such as, for example, the formation of amide bonds between carboxyl and amino groups, as well as? ester bonds between carboxyl and hydroxyl groups.

The formation of zero-length chemical bridges is achieved when crosslinks reactions form directly between collagen chains without any exogenous molecules/bridges being incorporated into the collagen fiber network.

To make sure that the aforementioned reactions can take place, ? It is necessary to have a fine control over the environmental conditions that are established, more? specifically ? Is it appropriate to establish a temperature high enough to ensure the necessary mobility? molecular structure, and to establish a completely anhydrous reaction environment. The above conditions are obtained in environments with a high degree of vacuum (<100 mTorr) and at temperatures above 90 ?C. About that ? important to underline that the? use of vacuum ? fundamental to promote the reactions of crosslinks, chemical bridges at zero length, as well as? to reduce the risks of denaturation and proteolysis favored by the increase in humidity levels? residual.

In essence, therefore, the activation of reactive groups present in the collagen, ? made through an anhydrous thermal treatment which is achieved in practice by placing the leather in an environment in which the pressure? equal to or less than 100 mTorr (ie less than 13.33 Pa) and the temperature ? equal to or greater than 90?C.

The anhydrous thermal treatment (DHT) can? take place at temperatures ranging from 90 to 150 ?C.

The duration of the treatment can vary from 2 to 48 hours.

Optionally, the anhydrous thermal treatment (DHT) ? preceded by a drying phase of the leather which can take place for a time ranging from 2 to 10 hours at a temperature ranging from 25 to 55°C.

Increasing the temperature and duration of the anhydrous thermal treatment (DHT) ? Is it possible not only to stabilize the collagen network, but also to increase the properties? mechanics of collagen fibers. The high temperatures used during this process lead to a denaturation of the collagen, i.e. the rearrangement of the collagen triple helix in a random configuration of the chain itself. This phenomenon results in the destruction of the native conformation of the collagen and therefore in the collapse of the macromolecular structure and the loss of the properties? characteristics of the collagen network.

The method according to the invention allows this limit to be overcome since the aforementioned anhydro-thermal treatment step ? preceded by the step of selective removal of the aqueous component from the animal dermis. This water removal phase that precedes the DHT treatment allows to preserve the micro and macroscopic components of the collagen fibers, their spatial organization and their mobility. intrinsic.

AND? known that the micro and macroscopic components of collagen fibers, their spatial organization and their mobility? intrinsic, determine the properties? final physicomechanics of the leather product as well as? of its properties? organoleptic characteristics and its performance.

Carrying out the anhydrous thermal treatment (DHT) on a native animal skin subjected to a dehydration process, with the step described above (i.e. through the selective removal of the interstitial water), avoiding making significant variations in the interfibrillar distance, allows on the one hand to increase the constraints of interfibrillar movement and on the other hand avoids altering the mobility? inherent in the fibrils. All of that? it translates into a significant increase in the elastic recovery of the collagen network following any imposed deformation.

The increase in elastic recovery? due to the presence of nodal points generated thanks to the anhydrous thermal treatment which does not involve appreciable variation of the elastic modulus of the product.

So, the combination of the two main steps a1) and a2) just described allows to modulate the properties? extensional of the dermis but above all it gives a significant increase in the elastic recovery to the collagen network, following an imposed deformation, since? nodal points are generated between the fibers, therefore there is an increase in the constraints of interfibrillar movement leaving the mobility unchanged? inherent in the fibers themselves.

Preferably, before the step of removing the aqueous component ? a step b1) of neutralization and maceration is provided, i.e. the execution in sequence of a neutralization process followed by a maceration process.

The neutralization process serves to reduce the acidity? of the semi-finished leather (pickled), from a pH of about 3 to a pH of about 6.5. This pH value? operational for a better activity? enzyme and to be able to change with a pi? easy manipulation the pH of the dermis in order to successfully carry out some chemical and physical treatments. The neutralization can be carried out with a two-phase treatment, initially by treating the leather (more precisely the dermis) with sodium formate and subsequently with sodium bicarbonate.

The maceration process follows that of neutralization and provides for an enzymatic degradation which consists in treating the hide (and more precisely the dermis) with synthetic/industrial enzymes capable of modifying the protein composition of the animal dermis.

Lipogenic enzymes can be used to eliminate any lipid component or enzymes with active elastinolytic to remove any fraction of elastin (or both types). The ultimate goal? to obtain meshes of the collagen network pi? lasse / open to make s? that the fibers are better exposed and facilitate the subsequent phases of the treatment in question.

The enzymes used for maceration are chosen preferably, but not exclusively, from:

- Novocor AX, this name? referred to an enzymatic mix of subtilisin and ?-amylase which both in the case of wet blue and in the case of picklate preferentially degrade elastin showing a very low degrading action against collagen, this enzyme carries out its action at a pH between 5.5 and 9.5;

- Basozym C10, which consists of a mix of macerating pancreatic extracts for all skin types with different tanning states, exerts its action at a pH between 5.5 and 9.5;

- Prozyme OR-R, which consists of a mix that includes a combination of enzymes based on the active principles of trypsin, amylase and lipase, exerts its action at acid pH between 3 and 5.5;

- Prozyme PK, which consists of an enzymatic mix, macerating in an acid environment (optimum pH for its action between 3 and 5.5);

- Prozyme WB (optimal pH for its action between 3 and 5.5);

- Prozyme VE (optimal pH for its action between 3 and 5.5);

- Globalbatin WB, what ? an agent suitable for acid maceration (optimum pH for its action between 3 and 5.5);

- Globalbatin VP, which consists of a microbiological-based macerating agent which exerts its action in a weakly acidic field (optimal pH between 6 and 6.5);

- NS45 for maceration for 6 and 18 hours, it performs its action at a pH between 10 and 11.

Preferably, after step a1) of selective removal of the aqueous component and before step a2) of anhydrous thermal treatment, a step b2) of mechanical traction is performed on the hide.

This step of mechanical traction provides that the hide (and more precisely the animal dermis) is subjected to mechanical effort through traction carried out in the direction of the vertebral axis (which corresponds to the head-tail axis of the animal from which the hide comes) in order to transfer the? elasticity? only in one direction (side-to-side).

In the preferred embodiment, with reference to Figure 2, the method consists of all the steps previously described, performed in this order:

b1) neutralization and maceration;

a1) selective removal of the aqueous component;

b2) mechanical traction;

a2) anhydrous thermal treatment (DHT).

At the end of the aforementioned steps, the properties? organoleptic characteristics of the leather, such as silky touch, round hand and breathability, remain unchanged but in addition enhanced characteristics of stretching and elastic recovery of deformations are obtained.

At the end of the different steps of which the method according to the invention is composed, the hides can be tanned following the chain processes and the standard workings currently used in the tanning field.

Yes ? in practice it has been observed that the functionalizing treatment method according to the present invention achieves the aim as well as? the intended purposes, as it allows you to improve the properties? elasticity of the leather without the addition of exogenous and/or synthetic molecules.

Another advantage of the method according to the invention consists in the fact that it improves the extensional characteristics of the animal dermis, giving it high elasticity. to leather products, modulating and improving the properties? of stretching and elastic recovery, without the addition of exogenous and/or synthetic molecules.

Another advantage of the method according to the invention consists in the fact that it confers elasticity to the leathers while also maintaining the natural breathability unchanged? and softness and also making the hides adaptive to different shapes, with improved performance and characteristics compared to the prior art.

Another advantage of the method according to the invention consists in the fact that it can be inserted within the chain processes and standard workings currently used in the tanning field.

Not least advantage of the method according to the invention consists in the fact that it is highly reliable, relatively simple to manufacture and at competitive costs compared to the prior art.

The method of functionalizing treatment of the leather so? conceived ? susceptible to numerous modifications and variations, all of which are within the scope of the appended claims.

Furthermore, all the details may be replaced by other technically equivalent elements.

In practice, the materials used, as well as? the contingent shapes and dimensions may be any according to the requirements and to the state of the art.

Claims (11)

R E V E N D I C A T I O N S 1. Method (1, 10) for the functionalizing treatment of leather of the type comprising a dermis of animal origin comprising collagen fibers and/or fibrils and an aqueous component, for improving the properties of the leather. elastic bands of said leather, characterized by the fact that it includes the steps which consist in: a1) selectively remove the aqueous component of the dermis of said leather, through the use of one or more? organic solvents; a2) carry out an anhydrous thermal treatment for the activation of reactive groups present in the collagen, carried out by placing the leather in an environment where the pressure is ? equal to or less than 100 mTorr and the temperature? equal to or greater than 90?C. 2. Method (1, 10) according to claim 1, wherein said step a1) which consists in removing the aqueous component of the dermis is carried out in such a way as to cause an overall volumetric reduction of the dermis lower than 5%. 3. Method according to claim 1 or 2, wherein said organic solvents are selected from: - acetone, - ethanol, - propanol, - Isopropyl alcohol. 4. Method according to one or more? of the preceding claims, wherein in said step a1) which consists in selectively removing the aqueous component, one or more? leather treatment cycles in said one or more? solvents, each cycle having a duration of between 10 minutes and 10 hours and being carried out at a temperature of between 2°C and 40°C; the quantity? of solvent used in each cycle being between 1% and 500% of the weight of the leather to be treated. 5. Method according to one or more? of the preceding claims, wherein said anhydrous thermal treatment? carried out at a temperature between 90 ?C and 150 ?C for a duration between 2 and 48 hours. 6. Method according to one or more? of the preceding claims, wherein before step a1) which consists in removing the aqueous component ? carried out a step which consists in: b1) neutralizing and macerating, in which the following are performed in sequence: - a neutralization process designed to reduce acidity? of the hide, followed by - a maceration process which consists in treating the leather with one or more? enzymes able to modify the protein composition of the dermis. 7. A method according to claim 6, wherein said neutralization process is made by treating the leather first with sodium formate and then with sodium bicarbonate. 8. A method according to claim 6 or 7, wherein one or more substances are used in the maceration process. lipogenic enzymes to eliminate a possible lipid component and/or one more? enzymes with activity elastinolytic to remove any fraction of elastin. 9. Method according to one or more? of the claims from 6 to 8, which said one or more? enzymes are chosen from: - Novocor AX; - Basozym C10; - Prozyme; - Prozyme PK; - Prozyme WB; - Prozyme VE; - Global batin WB; - Globalbatin VP; - NS45. 10. Method according to one or more? of the preceding claims, characterized in that after step a1) which consists in selectively removing the aqueous component and before step a2) of anhydrous thermal treatment, a step is performed of: b2) mechanical traction, in which the leather ? subjected to a mechanical traction carried out in the direction of a vertebral axis corresponding to the head-tail axis of the animal from which the hide comes. 11. Method according to one or more? of the preceding claims, wherein said step a2) of carrying out an anhydrous thermal treatment? preceded by a drying phase of the leather for a time between 2 and 10 hours and at a temperature between 25 and 55°C.