EP1241270A1

EP1241270A1 - Dying, greasing and fixation/finishing procedure of leather

Info

Publication number: EP1241270A1
Application number: EP02003637A
Authority: EP
Inventors: Gianni Maitan
Original assignee: GE MA TA SpA
Current assignee: GE MA TA SpA
Priority date: 2001-03-13
Filing date: 2002-02-18
Publication date: 2002-09-18
Also published as: ITVI20010060A1

Abstract

Concerns a dying, greasing and fixation procedure for leather, which is characterised in that the leather, leaving the usual dying treatments, such as the one by immersion or the one by spreading, is subsequently introduced into a vaporisation chamber, in which the thermodynamic equilibrium is maintained between the liquid, arranged at the base of the chamber and the vapour thereof which, expanding, comes into contact with the dyed and still wet leather, ensuring, in such a way, the fixation of the dye to the inside of the fibres.

Description

The patent regards a dying, greasing and fixation procedure for leather, as described in claim 1.
As is well known, leather, from whatever type of animal, after having undergone all of the tanning process are subjected to the dying and greasing operation with which the leather itself gains determined aesthetic characteristics, required by the market.
At the current state of the art, a first method for dying leather is realised through the use of drums containing the leather and a mixture of water and dye.
With the leather staying for a few hours in the drum, the dye transfers from the water to the leather, thus realising the homogenous dying of the leather itself.
To carry out the dying operation in a drum substantial quantities of water are necessary which, in general, come to around 1000% with respect to the starting weight of the leather being treated and an average treatment time for each drum load of 4/5 hours is required, such a value being independent from the amount of leather to be dyed for each load.
From this, therefore, it can be seen that to dye one or one thousand leather items, disregarding the time required for loading and the unloading of the leather into and from the drum and the time to feed and discharge the water in the different treatment steps, the dying time always remains the same.
Therefore, it is absolutely clear that the dying of medium/small stocks of leather is very expensive, for the substantial execution time and for the enormous consumption of water; for example, to dye 1000 kg of leather about 10,000 litres of water are necessary.
Still in the state of the art, as an alternative to dying in a drum, a so-called immersion dying procedure is used, based on the concept of impregnation and subsequent squeezing of the leather which, transported sandwiched between two conveyors, are firstly immersed in a dying solution, contained in a horizontal tank and then are squeezed through the passage between two rollers arranged at the exit of said tank.
Still in the state of the art and still as an alternative to dying in a drum a so-called spreading dying procedure is used, in which the leather is transported from a roller or from a rubber conveyor and pressed against an opposite engraved roller which deposits a uniform layer of dye onto the surface of the leather.
These two procedures are valid since they allow the continuous transportation of the leather during the entire dying operation but, at the same time, they also have some limitations and drawbacks.
Indeed, with such ways of operating, basically the application of the dye onto the leather is achieved, but it does not guarantee the fixation thereof onto the leather itself, even if said leather is subjected, after the dying operation, to a drying action either naturally or in a drying tunnel.
A purpose of the present finding is that of realising a treatment procedure of the continuous dying type in which there is, after the per se known application steps of the dye, a final innovative step which takes care of the optimal and definitive fixation of the dye to the inside of the fibres of the leather itself.
A further purpose of the finding is that of optimising the continuous dying procedure of tanned leather to produce fixed dyes, with an equal or greater degree of quality with respect to the qualities which leather dyed in a drum possess, making it more environmentally-friendly, thanks to the substantial reduction both in the consumption and in the purifying operation of the water used in the work cycle.
As an example, to dye 1000 kg of leather with the procedure according to the finding, only 1000 litres of water are needed which, very advantageously, arrives at the discharge without impurities to be purified and this allows, therefore, a saving of 9000 litres of water for every 1000 kg of dyed leather with respect to known dying procedures.
Moreover, the procedure according to the finding can be used, as well as for the dying step, also for application operations of retanning agents, of greasing agents and softening agents, which up to now are only possible with the use of drums.
Operatively, the leather which has just been dyed, which comes out of the dying tank or the coating machine, according to the treatment undergone, that is by immersion or by spreading, is arranged in a vaporisation chamber in which the temperature, pressure and humidity values are appropriately regulated to match that which is most suitable for the different types of dye used in dying, said leather remaining inside said fixation chamber for the time necessary until the dye attaches definitively to the inside of the leather fibres.
In greater detail, with the procedure according to the finding it is foreseen that, through the suction of the incondensable fluids, the vaporisation chamber is in a state of slight depression, for which reason the thermodynamic equilibrium between the liquid, arranged at the base of the chamber itself, and the vapour thereof which, expanding, comes into contact with the dyed and still wet leather, attaching the dye to it, is realised at a temperature of less than 100°C.
Finally, to increase the fixation action of the dye on the leather it is foreseen that the vapour, which fills the fixation chamber and which comes into contact with the leather, has an acidic pH value.

Claims

DYING, GREASING AND FIXATION PROCEDURE FOR LEATHER,
characterised in that
the leather, leaving the usual dying treatments, such as the one by immersion or the one by spreading, is subsequently introduced into a vaporisation chamber, in which the thermodynamic equilibrium is maintained between the liquid, arranged at the base of the chamber and the vapour thereof which, expanding, comes into contact with the dyed and still wet leather, ensuring, in such a way, the fixation of the dye to the inside of the fibres.
DYING, GREASING AND FIXATION PROCEDURE FOR LEATHER, according to claim 1, characterised in that in the vaporisation chamber, through the sucking out of the incondensable vapours, a slight depression is maintained which allows the fluid/vapour thermodynamic equilibrium to be maintained at temperatures of less than 100°C.
DYING, GREASING AND ATTACHMENT PROCEDURE FOR LEATHER, according to claim 1 as well as claim 2, characterised in that the vaporisation vapour has an acidic pH value.
DYING, GREASING AND ATTACHMENT PROCEDURE FOR LEATHER, according to claim 1, characterised in that it is regulated according to three parameters: the temperature and pressure of the vaporisation chamber and the time that the leather stays in the aforementioned chamber.