A PROCESS FOR NON-UNIFORM DYEING OF TEXTILE PRODUCTS

Technical Field

The invention relates to a process for non-uniform dyeing of textile products.

Background Art

It is well-known that for some types of textiles or articles of clothing, such as for example trousers, jerkins, pullovers, an artificial ageing treatment is required, which is obtained by localised discolouring or de-colouring of the original and already-dyed material.

A process for obtaining this effect is the one known as "stone-washing". This process consists in immersing the textile products in water or in a bath containing a chemical agent which decolours and/or bleaches, such as for example a hypochlorite solution, and agitating the articles together with granules or stones made of an abrasive material and having sizes of between 1 and 10 cm. This process produces textile products that are discoloured or lightened in colour, with dark-light tones at the stitching areas and with uniformity of colour contrast in the remaining part of the textile product, typical of the natural wear to which the textiles are subjected during use.

The prior art also describes a dry decolouring process for textiles, i.e. without immersion in a water-based bath as happens in the stone-washing process. This process is described in EP-A-0238779. The process consists in bringing the already-dyed textile products into random contact with a granular material which is permeable, porous and highly-absorbent, such as for example pumice granules, which has been first impregnated with a de-colouring chemical agent. The textile products can be in the dry or damp state when they come into contact with the porous granular material and the contact is prolonged for a time sufficient for obtaining the desired effect.

With this process a particular type of discolouring of the textile product is obtained, consisting in an irregular de-colouring characterised by a nonuniform staining effect that is irregularly distributed over all the textile product.

OnIy the zones that come into contact with the porous granular material containing the bleaching agent are decoloured by combined chemical effect of the bleach and mechanical effect of the porous material, while the remaining zones are left unchanged. The processes of the known art exhibit some drawbacks which limit the use thereof.

They are, in fact, difficult to apply to delicate textiles, such as wool, which cannot survive the bleaching treatment with aggressive chemical agents and/or the mechanical abrading action exerted by the granules. Disclosure of Invention

There is, therefore, a strong need to have available a process which enables the ageing effect to be obtained with delicate textiles such as wool, without any need to use bleaching treatments and/or to employ mechanical actions based on abrasion. The aim of the present invention is to provide a process having structural and functional characteristics such as to satisfy the above-mentioned requirements and also such as to obviate the drawbacks mentioned with reference to the prior art. The aim is attained by the process for non-uniform dyeing of textile products as set out in claim 1.

The dependent claims delineate preferred embodiments which are particularly advantageous of the process for non-uniform dyeing of textile products of the invention. Best Mode for Carrying Out the Invention Further characteristics and advantages of the invention will emerge from a reading of the following description, which is provided by way of non-limiting example.

For the purposes of the following description the term "textile products", refers to textiles in the form of cloth as well as already-made articles of clothing, such as trousers, jeans, jackets, jerkins, shirts, skirts, overcoats, pullovers and so on.

In its broadest aspect, the process of the present invention enables nonuniform dyeing of textile products in the following stages:

- arranging the textile products to be dyed in a chamber, for example a rotating drum, together with a plurality of permeable and absorbent granules impregnated with an inertizing liquid substance for rendering the textile to be dyed at least partially inert to dyeing;

- bringing the textile products to be dyed into contact with the granules, the granules and the textile products being moved together in a relatively random way, for a sufficient amount of time to wet parts of the textile of the textile products with the inertizing substance; then

- separating the textile products from the granules;

- bringing the textile products to a temperature and for a sufficient amount of a time to cause the inertizing substance to react with the parts of the textile which were dampened with the substance; and finally - dyeing the textile products.

By the term "inert" in relation to dyeing, a resistance to dyeing by the usual dyes commonly used for colouring textiles is meant.

Substantially, a part of dye-inert textile will not absorb the dye colour and therefore will not be coloured. It is specified that in the present invention the parts of textile wet with the inertizer can be made totally inert to the dye, and will not colour, or can be made partially inert to the dye, and will colour more blandly than the parts of the same textile which have not come into contact with the inertizer. This enables a "modulating" of the process of the present invention according to a desired final effect, enabling zones of different intensities to be obtained in the dyed textile.

In order to eliminate any traces of dirt, especially water-repellent dirt, such as, for example, oily residues, the textile products are subjected to a preliminary wash using water and detergent or a dry-cleaning process.

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Thereafter the washed products are dried before being placed in the drum with the granules. However, it is possible to subject still-damp products to the treatment.

The permeable granules usable in the process of the present invention can be selected according to the absorption capacity and the resistance to strong acidity, and a subsequent release of the inertizing substance they are drenched with.

In substance, the permeable granules can be made using any material able to be drenched with a liquid which will have to be released when the granules are made to rotate together with the textile products in the drum.

Among the materials that can be used for making the granules are porous polymer gels, in particular polyoxometallates (POMs). The size of the granules can be selected according to the desired final result; generally they are between 1 and 30 mm in size. According to the present invention, the inertizing substance used for drenching the porous granules is a sulphamic acid in water solution. The quantity of sulphamic acid used is comprised between 1 % and 30% of the overall weight of the water solution with which the granules are drenched. The quantity of solution used to drench the granules to be placed in the drum for treating the textile products depends on the desired final effect and on the contact time between the drenched granules and the products present in the drum, as well as the rotation velocity of the drum. An example will be reported herein below. Usually a sufficient time for obtaining different dyeing intensities is considered to be between 10 minutes and one hour with a drum rotation velocity comprised between 5 and 50 rpm, the drum having a mean diameter of between 50 and 200 cm.

Once the contact between the granules wet with the sulphamic acid and the textile products has been concluded, the textile products exhibit zones, arranged randomly, which are wet with the sulphamic acid released by the

granules. These zones are at least partially inert to dyeing, i.e. it is not possible to die them, or they can be dyed only less intensely.

In substance, the sulphamic acid behaves as an inhibitor, i.e. it prevents the zones of textile wet by the acid from absorbing the colouring material. Naturally, as the textile is wet by random zone and amount with the sulphamic acid, the final effect after dyeing will be a varied localized intensity of colour which is more or less random.

This is obtained without occasioning abrasive wear to the textile and without using bleaching and/or de-colouring products, To make the zones of sulphamic acid-dampened textile impervious to the dye, the already-treated textile products in the drum are dried at a temperature comprised between 100°C and 150°C for a sufficient time to enable the sulphamic acid to bond with the fibres of the textile, preventing the subsequent dyeing thereof. By way of example, it is sufficient to dry the textile at a temperature of 135°C for about 25 minutes.

At the end of the drying period the textile products can be dyed using the typical dyeing techniques and dyes of the sector, and thus not described in detail herein, obtaining textile products that are not uniformly dyed, as the dye will not take (or will take only partially) in the zones of the textile previously dampened with sulphamic acid.

In order to optimise the reaction between the sulphamic acid and the fibres of the textile, urea can be used as a catalyst to the reaction.

Further, to prevent the strong acidity of the sulphamic acid from attacking textile fibres of vegetable origin (cellulosic), the acidity is reduced by adding a base, for example isobutanolamine (2-amine-2methyl -1 -propanol).

In addition, to control the release velocity of the sulphamic acid from the granules to the textile, a compound for increasing the viscosity thereof, such as for example glycerol, is added to the sulphamic acid. Further, the water-repellent quality of the textile can be increased, with respect to the sulphamic acid-based solution with which the granules are

drenched, by adding chemical compounds which improve the water-repellent properties, such as, for example, caprolactam.

Herein below two examples are reported, for purposes of non-limiting illustration, of watery solutions used for wetting the granules for the treatment of, respectively, cotton and wool textiles.

1. Solution used for textile products made of cotton: sulphamic acid 6 urea 9 glycerol 3 caprolactam 3 isobutanolamine 9 softened water 70

2. Solution used for textile products made of wool: sulphamic acid 15 urea 10 glycerol 1.5 softened water 73.5

All the values in the two above- reported examples are expressed in percentages of weight with respect to the solution for drenching the granules.

Each of the two above solutions is used for a quantity comprised between 50 and 200 grams per dm ³ of polyoxometallate (POM-GEL).

The process of the present invention can be used for any type of textile material either made of natural fibres (wool, silk, cotton etc) or of synthetic fibres (nylon, polyester etc).

As can be appreciated from the above description, the process for non- uniformly dyeing textile products of the present invention satisfies the requirements and obviates the drawbacks mentioned in the introduction to the present description with reference to the prior art. Indeed, the process of the invention allows an ageing effect to be obtained in textile products without the use of any bleaches and/or de-colouring agents,

such as sodium hypochlorite or potassium permanganate, which inevitably attack the most delicate textile fibres, apart from having a high environmental impact as waste.

Further, the process of the invention requires no further mechanical abrading action on the textile, such as the effect produced using pumice, and therefore ensures longer life in comparison with textiles treated using traditional processes.

Obviously an expert in the sector, with the aim of satisfying contingent and specific requirements, might make numerous modifications and changes to the process for non-uniform dyeing of textile products, all relating to the ambit of protection sought for the invention as defined in the following claims.