Patent Description:
The term "hides" refers the known material of animal origin constituted at least partly by dermis of animal origin and commonly also called "leather". Therefore, the method can be applied, in a fully general way, to any leather or hides of animal origin.

The method according to the present invention mainly finds application in the tanning industry, in the hide processing steps upstream of known tanning processes.

As is known, animal leather, to which the present invention relates, is formed by the epidermis (also called grain side) and the dermis (also called flesh side), the structure of which consists of fibers and fibrils of collagen spatially ordered and organized to form a highly interconnected structure.

The method according to the present invention consists therefore of a functionalizing treatment for hides, i.e., a treatment that gives the hides additional functions and/or properties.

In greater detail, the functionalizing treatment according to the present invention is aimed at improving the elastic properties of hides, i.e., at controlling, modulating and improving the properties of elastic extension and recovery of the animal dermis, therefore giving leather articles greater elasticity without compromising native organoleptic characteristics such as softness to the touch and breathability.

Currently, various methods for making hides elastic are used.

In a first known type of methods for giving elasticity to hides, one proceeds to create a hybrid of hides/Lycra or other synthetic materials that have elasticity. The coupling of a very thin layer of leather with Lycra makes said leather acquire elastic characteristics.

In a second known type of methods for giving elasticity to hides, during the steps of the known tanning and retanning process, mixes of polyurethanes, elastomers or other exogenous molecules that can give elasticity and softness to the hides are added.

For both types of methods listed above, some considerable limitations and drawbacks are known.

In particular, in the first case the provided fabrics are not made of natural leather, since a layer of synthetic material is added to a very thin layer of natural leather, in many cases one even starts polyurethane or PVC materials similar to leather. Therefore, what is obtained downstream of these processes is actually a synthetic, leather-like fabric with elastic characteristics.

Instead, as regards the second known type of methods for giving elasticity to hides, the degree of elasticity that can be given is related to the quantity/percentage of polymer or elastomer or polyurethane that is used during the tanning and retanning steps: the greater the quantity/percentage, the greater the degree of elasticity; however, increasing excessively the quantities of these molecules reduces some of the main characteristics of natural hides, such as softness to the touch, fullness and breathability.

<CIT> discloses preliminary treatment steps for animal hides.

The aim of the present invention is to provide a method for functionalizing treatment of hides capable of solving the problems and overcoming the limitations of the background art mentioned above, improving the elastic properties of the hides without adding exogenous and/or synthetic molecules or in any case without altering the main characteristics of natural hides such as softness to the touch, fullness and breathability.

Within this aim, an object of the present invention is to provide a method for functionalizing treatment of hides that is capable of improving the extensional characteristics of animal dermis, giving high elasticity to leather articles, modulating and increasing the stretching and elastic recovery properties, without adding exogenous and/or synthetic molecules.

Another object of the present invention is to provide a method for functionalizing treatment of hides which allows to give elasticity to the hides by keeping unchanged the natural breathability and softness and also making the hides adaptable to different shapes, with improved performance and characteristics with respect to the background art.

Another object of the present invention is to provide a method for functionalizing treatment of hides that can be inserted within the processes of the supply chain and the standard processes used currently in the tanning field.

Another object of the present invention is to conceive a functionalizing treatment method that is highly reliable, relatively simple to provide and at competitive costs if compared with the background art.

This aim and these and other objects that will become better apparent hereinafter are achieved by a method according to claim <NUM>.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of a method for functionalizing treatment of hides to improve the elastic properties of said hides, illustrated by way of non-limiting example with the aid of the accompanying drawings, wherein:.

With reference to the figures, the method is generally designated by the reference numerals <NUM> and <NUM> depending on the embodiment.

The method <NUM>, <NUM> as already mentioned, is a method for functionalizing treatment of hides of the type comprising a dermis of animal origin which in turn comprises fibers and/or fibrils of collagen and an aqueous component. The method is aimed at improving the elastic properties of the hides.

In its essential traits, with reference to <FIG>, the method comprises the following two main steps (performed in this order):.

The first step of selective removal of the aqueous component of the animal dermis, more specifically, provides for the complete removal of the aqueous component of the animal dermis without significant alteration of the macromolecular structure of the dermis, i.e., with a total volumetric change of the tissue of less than <NUM>% with respect to the hydrated product, i.e., this step is performed so as to cause a total volumetric reduction of the dermis of less than <NUM>%.

The <NUM>% limit in total volumetric contraction of the dermal tissue ensures that the correct structure i.e., the native structure (therefore, the mean space between collagen fibrils), is preserved, and therefore ensures that any reduction of the molecular mobility of collagen as a consequence of the step of removing the interstitial water is limited.

According to the invention, the practical execution of this step of selective removal of the aqueous component entails the use of one or more organic solvents with which the hides are treated and conveniently includes the simultaneous and concurrent use of organic solvents characterized by: suitable properties, which give them the capacity to replace the aqueous phase, and at the same time suitable surface tensions, which allow their subsequent removal from the organic matrix without entailing a variation of the macromolecular structure of the dermis, i.e., of the collagen network that constitutes the hides.

Preferably, one or more mixtures of organic solvents are used.

The solvents, or the mixtures of solvents, that have proven themselves effective in performing the step of selective removal of the aqueous phase comprise preferably but not exclusively:.

The controlled removal of the aqueous phase can occur also by means of the use of solvents "in critical conditions".

The methods by which the controlled removal of the interstitial water can occur provide for the execution of one or more treatment cycles with solvents and preferably <NUM> to <NUM> different solvent treatment cycles.

The different cycles can provide for alternating the use of different solvents; for example, it is possible to alternate acetone, isopropyl alcohol, ethanol.

The duration of the solvent treatment cycles can vary from <NUM> minutes to <NUM> hours.

The temperature of the water extraction process can vary from <NUM>-<NUM> up to <NUM>-<NUM>.

The quantity of solvent used can vary from <NUM> to <NUM>% with respect to the weight of the hides to be treated.

With reference now to the subsequent step of execution of a dehydrothermal treatment for the activation of the reactive groups present on the collagen macromolecule, more specifically, this step is performed in order to promote intramolecular reactions. This can be obtained by means of a specific control and modulation of the environmental conditions, by performing a process for the stabilization of the collagen network known as dehydrothermal treatment or by its acronym DHT.

DHT is a physical cross-linking process commonly used to stabilize collagen networks or collagen-based materials by forming zero-length chemical bridges; more specifically, the dehydrothermal treatment step leads to the formation of intermolecular cross-link bonds by virtue of reactions of condensation by esterification or formation of amides.

Furthermore, DHT is mainly used to induce the forming of chemical condensation reaction between reactive groups present on the protein chain, such as for example the forming of amide bonds between carboxyl and amine groups, as well as ester bonds between carboxyl and hydroxyl groups.

The forming of zero-length chemical bridges is obtained when the cross-link reactions are formed directly between the collagen chains without any exogenous/bridge molecule being incorporated in the network of collagen fibers.

In order to allow the above reactions to take place, it is necessary to have fine control over the environmental conditions that are established; more specifically, it is appropriate to establish both a temperature that is high enough to ensure the necessary molecular mobility and a completely anhydrous reaction environment. The above conditions are obtained in environments with a high degree of vacuum (<NUM> mbar (<NUM> mTorr) and at a temperature above <NUM>. In this respect, it is important to emphasize that the use of vacuum is essential to promote cross-link reactions, zero-length chemical bridges, as well as to reduce the risks of denaturation and proteolysis facilitated by the increase in the levels of residual moisture.

Basically, therefore, the activation of reactive groups present in collagen is achieved by means of a dehydrothermal treatment that is provided in practice by placing the hides in an environment in which the pressure is equal to or lower than <NUM> mbar (<NUM> mTorr) and the temperature is equal to or greater than <NUM>.

The dehydrothermal treatment (DHT) can occur at temperatures varying from <NUM> to <NUM>.

The duration of the treatment can vary from <NUM> to <NUM> hours.

Optionally, the dehydrothermal treatment (DHT) is preceded by a hide drying step which can occur for a time that varies from <NUM> to <NUM> hours at a temperature that varies from <NUM> to <NUM>.

By increasing the temperature and duration of the dehydrothermal treatment (DHT) it is possible to stabilize the collagen network and also to increase the mechanical properties of the collagen fibers. The high temperatures used during said process entails a denaturation of the collagen, i.e., the rearrangement of the collagen triple helix in a random configuration of said chain. This phenomenon leads to the destruction of the native conformation of the collagen and thus to the collapse of the macromolecular structure and the loss of the characteristic properties of the collagen network.

The method according to the invention allows to overcome this limitation, since said dehydrothermal treatment step is preceded by the step of selective removal of the aqueous component from the animal dermis. This water removal step which precedes DHT allows to preserve the micro- and macroscopic components of the collagen fibers, their spatial organization and their intrinsic mobility.

It is well-known that the micro- and macroscopic components of collagen fibers, their spatial organization and their intrinsic mobility, determine the final physical-mechanical properties of the leather item as well as its organoleptic properties and performance.

Performing the dehydrothermal treatment (DHT) on a native animal hide subjected to a dehydration process, with the step described above (i.e., by selective removal of the interstitial water), avoiding to cause significant changes in the interfibrillar space, allows to increase the interfibrillar movement constraints and avoids altering the intrinsic mobility of the fibrils. All this results in a significant increase in the elastic recovery of the collagen network consequent to any deformation imposed.

The increase in elastic recovery is due to the presence of nodal points generated by virtue of the dehydrothermal treatment, which does not entail an appreciable variation of the elastic modulus of the manufactured article.

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

Preferably, prior to the step of removing the aqueous component there is a step b1) of neutralization and bating, i.e., the execution in sequence of a neutralization process followed by a bating process.

The neutralization process is used to reduce the acidity of the semifinished (pickled) hides from a pH of about <NUM> to a pH of about <NUM>. This pH value is operative for better enzymatic activity and to be able to modify with an easier manipulation the pH of the dermis in order to be able to perform successfully some chemical and physical treatments. Neutralization can be performed with a two-step treatment, treating the hides (more precisely the dermis) initially with sodium formate and subsequently with sodium bicarbonate.

The bating process follows the neutralization process and provides an enzymatic degradation that consists in treating the hides (and more precisely the dermis) with synthetic/industrial enzymes adapted to modify the protein composition of the animal dermis.

It is possible to use lipogenic enzymes to eliminate any lipidic component or enzymes with elastinolytic activity to remove any elastin fraction (or both types). The final goal is to obtain looser/more open meshes of the collagen network so that the fibers are better exposed and to facilitate the subsequent steps of the treatment according to the invention.

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

This step of mechanical traction entails that the hides (and more precisely the animal dermis) is subjected to mechanical stress by traction performed in the direction of the vertebral axis (which corresponds to the head-tail axis of the animal from which the hides originate) so as to transfer the elasticity only in one direction (side-to-side).

In the preferred embodiment, with reference to <FIG>, the method is composed of all the previously described steps, performed in the following order:.

At the end of said steps, the organoleptic properties of the hides, such as silky feel, round handfeel and breathability, remain unaltered 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 by following the standard supply chain processes and treatments currently used in the tanning industry.

In practice it has been found that the method for functionalizing treatment according to the present invention achieves the intended aim and objects, since it allows to improve the elastic properties of the hides without adding exogenous and/or synthetic molecules.

Another advantage of the method according to the invention is that it improves the extensional characteristics of the animal dermis by giving high elasticity to the leather articles, modulating and improving the properties of stretching and elastic recovery, without adding exogenous and/or synthetic molecules.

Another advantage of the method according to the invention resides in that it gives elasticity to the hides while maintaining furthermore unchanged the natural breathability and softness and also making the hides adaptable to different shapes, with improved performance and characteristics with respect to the background art.

Yet another advantage of the method according to the invention resides in that it can be inserted within the standard supply chain processes and treatments used currently in the tanning field.

Not last advantage of the method according to the invention resides in that it is highly reliable, relatively easy to provide and at competitive costs if compared with the background art.

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

Claim 1:
A method (<NUM>, <NUM>) for the functionalizing treatment of hides of the type comprising a dermis of animal origin comprising fibers and/or fibrils of collagen and an aqueous component, in order to improve the elastic properties of said hides, characterized in that it comprises the steps of:
a1) removing selectively the aqueous component of the dermis of said hides, by using one or more organic solvents;
a2) performing a dehydrothermal treatment for the activation of reactive groups present in the collagen, provided by arranging the hides in an environment in which the pressure is equal to or lower than <NUM> mbar (<NUM> mTorr) and the temperature is equal to or higher than <NUM>.