"Method of production of afire-proof leather that does not release smokes and the leather this way obtained"

Technical Field The present invention refers to the leathers' treatment technical field and in particular to the tanning aimed at giving to the leather an ulterior requirement and in particular to make it fireproof.

Background Art Are known since far back different tanning techniques developed during the centuries and that require some standardized phases and some other diversified according to the type of the treated leather and to the desired outcome. The tan allows not only to preserve the leather, but also to make it more or less soft, more or less elastic, and more or less waterproof. One of the oldest tan techniques is the fumigating tan. It is based on the exposure of the leather to the smoke of a fire-room or to another source of heat, in a way that said smoke helps the preservation of the leather by increasing its endurance. Another method, used until the XIX century, is the vegetable tanning that has been probably discovered by soaking the leather in a water pool surrounded by trees. The pieces of wood, the barks and the leaves floating in it, contained natural "chemical agents" that tanned the leathers. More recently we have moved to the chrome tanning, where is used chromium salt to treat the leather, as well as enzymes and many other elements. Particular chemical treatments could increase the fireproof features of the leather by integrating it to its natural heat resistance. This would increase the safety use of the leather when these features are important, as for example in theatres or display rooms, cars, planes or tapestry. The fireproof leather can be also used in common products, as potholders that adhere to any kind of surfaces allowing a better hold. Even if the leather is rather fireproof by nature, and said feature can be increased with specific treatments, until now every leather that comes in contact to the fire changes and releases smokes. It is clear that the fact of realising smokes determinates severe consequences in case of fire, as the smoke is often dangerous as much as the fire and can bring to death from aspiration. Despite different type of leather and tanning methods are known, there are not

leathers or tanning systems that make a leather fire-proof in a way to not release smokes in case in contact with the fire.

The aim of the present invention is to avoid the above and other inconvenient by giving leather and a method to produce it that allow obtaining fireproof leather that does not produce smokes.

It is clear that the ability to make fireproof and smokeless leather presents big advantages especially in the .transportation field, as in case of accident it is extremely important to avoid that the components of a car are flammable. The utility of said product is clear also in different fields and in the furnishings, as there is the possibility that theatres, hotels and houses could burn out and non-flammable furniture would be really useful. To that would add on the advantage to make clothes or other objects with said particular type of leather, well-known advantages. The leather according to the invention comprises any kind of leather that has at least fire-resistant salt and is fireproof and does not release smokes. The method for the realization of the above mentioned leather comprises a set of phases, in which some are needed and others aimed at optimise the desired outcome. Disclosure of invention

A method, reduced to its main structure, according to the present invention for the realization of fireproof leather, requires that during the tanning the following phases are found:

- Soaking in the drum of the tan of a percentage of sodium formate between 0,5% to 2% that shall stay in the drum for a period that goes from 10 to 30 minutes;

- Insertion in the drum of the tan of a percentage of sodium bicarbonate between 1% to 3% that shall stay in the drum for a period that goes from 60 to 120 minutes; - Boost of the PH of 6/6,5, water baths and eventual liquoring of the leather;

- Insertion, in the drum of the tan, of water between 100% and 300% at 45 to 60 degrees with sulphite fish (TM OIL 501);

- Spin the drum for a period that goes from 40 to 90 minutes and reduce the Ph;

- Eventual dying of the leather; - Draining the leather to eliminate the water;

- Soaking in the drum of the tan of a percentage of fire-resistant salt (FIRE- RESISTENT IRL) between 15% and 30% that shall stay in the drum for a period that goes from 30 to 60 minutes;

- Insertion in the drum of the tan of a percentage of formic acid between 0,5% to 1 ,5% that shall stay in the drum for a period that goes from 20 to 40 minutes;

- Insertion in the drum of the tan of a percentage of complex agent or zirconium salt (BLANCOROL ZBE) between 0,5% to 1,5% that shall stay in the drum for a period that goes from 20 to 40 minutes.

After this process the leather is extracted from the drum and a number of mechanical processes, for the extraction of the water and the drying, follow. Afterwards the leather can be softened with the help of appropriate machineries in a way to prepare it for the finishing that can happen in different ways. Advantageously, in a preferred processing solution, the method includes that the two above mentioned phases are processed this way:

- Insertion in the drum of the tan of 1,5% of sodium formate for 20 minutes;

- Insertion in the drum of the tan of 2% of sodium bicarbonate for 90 minutes;

- Increasing the Ph of 6-6,5 with a complete percolation of the section and bath with water, followed by currying the leather;

- Insertion, in the drum of the tan, of 200% of water at 60 degrees with 3% of sulphite fish (TM OIL 501 );

- Spin the drum for about 60 minutes and reduce the Ph with formic acid with a 0.5% percentage. - Eventual dying of the leather;

- Draining the leather to eliminate the water;

- Insertion in the drum of the tan of 20% of fire-resistant salt (FIRE-RESISTENT ERL) for 40 minutes;

- Insertion in the drum of the tan of 1% of formic acid for 30 minutes; - Insertion in the drum of the tan of 1% of complex agent or zirconium salt

(BLANCOROL ZBE) for 30 minutes.

Advantageously after the above phases, the skin is extracted from the drum and then dried.

Advantageously the above phases are preceded from the following processing phases that allow preparing better the skit to the treatment.

The method according to the invention, expects, before proceeding with the above phases, given a tanned skin, called wet blue, to process the following phases:

Insertion of the tanned skin in the drum with 300% of water at 35° and 0,5%

of acetic acid added.

Spin the machine for 40 minutes and wash with water at 35°. Addition of basic and synthetic tannic chromium salts in combination to resins. - Introduce in the drum 150% of water at 35° with 6% of synthetic chromium, and spin for 30 minutes.

Addition of 6% of aliphatic aldehyde (TM GE) in combination with 7% of sulphite fish (TM OLIO 501) and 3% of synthetic tannin (TAMATAN H74) Spin for 90 minutes. Advantageously, after the above phases, a night shall be elapsed, or anyway about 10/12 hours, before proceeding with the main phases of the method. Advantageously, the main phases of the method are followed by the following processing phases that allow maintaining better the fireproof effect on the leather. Advantageously, after the skin has been dried according to what has been said before, the process of at least one of the following phases follows:

- Spraying on the skin polyurethane and acrylic resins and dyes particularly resistant to light and heat.

Advantageously, after the skin has been dried according to what has been said before, the process of at least one of the following phases follows: - Coating of the skin with soft and elastic fireproof products.

Advantageously the said coating is made by applying on the product, preferably through double cross spay, at least the following products:

- 150 gr. RP 6020 (dispersion of aliphatic polyurethane) which has great adhesion properties for the last coatings; - 150 gr. RAI 5401 (attaching acrylic resin) soft and very elastic;

- 50 gr. BP 605 (emulsion of reactive aromatic polyurethane);

- 50 gr. BP 705 (self-reticulate polymeric bicomponent)

- 50 gr. F 16 (generic wax free filler)

- 100 gr. Extremely concentrated dispersed pigment - 600 gr. Water.

Advantageously, after the above phases, the skin is stretched with the rotopress for then go back through another double cross spray until uniformity is obtained. Advantageously, after the skin has been dried according to what has been said

before, the process of at least one of the following phases follows: -application, though double cross spay, of the following products:

- 100 gr. BP 605

- 100 gr. BP 705 - 20/30 gr analine (liquid dye)

- 400 gr water.

Advantageously, after the skin has been dried according to what has been said before, the process of at least one of the following phases follows:

- finishing with an aqueous solution of catalyst and silicone polyurethane to obtain the best required endurance during the requested tests.

Advantageously the above phases require two or three passages from the spray machine.

Advantageously, after the skin has been dried according to what has been said before, the process of at least one of the following phases follows: - application, though double cross spay, of the following products:

- 100 gr. BP 605

- 100 gr. BP 705

- 200 gr. CP 815 (urethane fixative in water) appropriate for the final applications. - 100 gr. MAT 606 (matt fixative)

- 50 gr. VU 445 ( very glossy fixative with paint effect)

- 30 gr. TS 3434 (tact modifier)

Advantageously the method includes that the skin is then stretched or pressed. Advantageously, after the skin has been dried according to what has been said before, the process of at least one of the following phases follows:

- cross spay application on the meat side of the fireproof composed by:

- 100 gr. FL 105

- 50 gr. Water.

Advantageously at the end the skins are then replaced in the drum and span, for at least 10 hours to moisturize them, and then stretched.

The complete realization process of the undertaken leather, in a preferred implemented phase, comprises a first phase, called beamhouse or re-tanned, that consists in giving to the treated skin the principal features of softness, colour fullness

and shade, as the required chemical-physics qualities. Further on it is applied also a finishing stage that defines the article both for the colour tone and the requested characteristics.

The first stage is the mentioned beamhouse phase. The beamhouse operation is made through a process carried out in drums made in wood or metal. For this operation is required a tanned hide called wet blue. This means that the material is already treated with chromium salts that give to the hide the strength required to avoid the natural degradation. The first passage consists in giving to the hide the amount of water that has been lost in the preceding treatments that have given to the material the right thickness expressed in millimetres. The processing percentage depends on the shaved weight. The first phase of the beamhouse operations includes the soaking of the tanned skin in the drum with 300% of water kept at 35° and 0,5% of acetic acid added. Inserted what mentioned above, the machine is span for 40 minutes, afterwards is washed with water kept at 35°.

After the combination of water with acids has been provided, the real processing phase starts by adding the basic and tannic synthetic chromium salts in combination to divers resins. Afterwards it is introduced in the drum 150% of water at 35° with 6% of synthetic chromium, and span for 30 minutes. At this point, is added 6% of aliphatic aldehyde (TM GE) in combination with 7% of sulphite fish (TM OLIO 501) and 3% of synthetic tannin (TAMATAN H74), and span for 90 minutes.

The above mentioned operations are exclusively needed to give to the hide the roundness feature, but a particular attention shall be given to the type of formulation that must take under consideration the specific strength requested by the article.

After the above phases, a night shall be elapsed, or anyway about 10/12 hours, before proceeding with the main phases of the method that make fireproof the leather. It is then inserted in the drum of the tan 1,5% of sodium formate for 20 minutes, and then of 2% of sodium bicarbonate for 90 minutes, until a 6-6,5 Ph is reached with a complete percolation of the section.

Is then washed with water. After the bathing Ph has been raised, follows the fatliquoring process, which gives to the hide the soften features required, as also the strength to avoid tears and breakage.

At this stage it is inserted, in the drum of the tan, 200% of water at 60 degrees with

3% of sulphite fish (TM OIL 501 )\ and span the drum for about 60 minutes. Then the Ph is reduced with 0.5% percentage formic acid.

The next operation is the dyeing process, which is the application, through acid dyes, of the right mixture of aniline to obtain the requested shade.

The last operation regards the main feature, which is the endurance to chemical- physics test, acquired through the use of complex inorganic salt products.

After draining the water from the drum., it is inserted in the drum of the tan 20% of fire-resistant salt (FIRE-RESISTENT IRL) for 40 minutes, then is acidified with 1% of formic acid for 30 minutes and after entered 1% of complex agent or zirconium salt (BLANCOROL ZBE) for 30 minutes

Once the hide is taken out from the drum, a number of mechanical operations are processed to drain the water and dry the hide.

Afterwards, still with the help of machineries, the hide is moisturized again to be ready for the finishing phase.

The second phase is the finishing one.

Said phase can be made in different manners, but the following one is the best way to strengthen and maintain the fireproof features of the leather.

For the final dyeing and finishing of the article, the hide is sprayed with a polyurethane and acrylic resin and with dyes with particular endurance to light and heat.

The first refine operation starts with the coating of the leather through soft, elastic and with specific requested physics feature fireproof products.

The coating is made by applying on the product, preferably through double cross spay, at least the following products:

- 150 gr. RP 6020 (dispersion of aliphatic polyurethane) which has great adhesion properties for the last coatings;

- 150 gr. RAI 5401 (attaching acrylic resin) soft and very elastic;

- 50 gr. BP 605 (emulsion of reactive aromatic polyurethane); - 50 gr. BP 705 (self-reticulate polymeric bicomponent)

- 50 gr. F 16 (generic wax free filler)

- 100 gr. Extremely concentrated dispersed pigment

- 600 gr. Water.

After the above spraying operation, the skin is pressed with the rotopress and then goes back through another double cross spray until uniformity is obtained The following phase is the aniline result that comprises the application by double cross spray of the following products: - 100 gr. BP 605

- 100 gr. BP 705

- 20/30 gr analine (liquid dye)

- 400 gr water.

The next operation comprises the finishing with an aqueous solution of catalyst and silicone polyurethane to obtain the best-required endurance during the requested tests. Also this operation requires two or three passages through the spraying machine. It comprises the application, though double cross spay, of the following products:

- 100 gr. BP 605 - 100 gr. BP 705

- 200 gr. CP 815 (urethane fixative in water) appropriate for the final applications.

- 100 gr. MAT 606 (matt fixative)

- 50 gr. VU 445 (very glossy fixative with paint effect) - 30 gr. TS 3434 (tact modifier)

After that, the hide is stretched or pressed according to the desired result.

Then it is applied by cross spay application on the meat side, the flame retardant composed by:

- 100 gr. FL 105 - 50 gr. Water.

At the end the skins are then replaced in the drum and span, for at least 10 hours to moisturize them, and then stretched.

The invention comprises the leather obtained by the above method or by one or more of its phases.