GB2325675A

GB2325675A - Fabric finishing process

Info

Publication number: GB2325675A
Application number: GB9808602A
Authority: GB
Inventors: Ruth Helene Mussawir-Key
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-05-30
Filing date: 1998-04-22
Publication date: 1998-12-02
Anticipated expiration: 2018-04-22
Also published as: GB9808602D0; GB2325675B

Abstract

A process of finishing a fabric comprising a substrate which is resistant to chemical attack and a fibre which is susceptible to erosion by the chemical is described. The process is particularly suitable for use with bi-stretch denim. A chemical, eg. aluminium sulphate, paste which selectively attacks the fibre but not the substrate is printed onto the fabric. The fabric is then dried and heat treated. After washing, the fabric can be rubbed to remove the residue of susceptible fibre from the areas treated with the chemical paste. If the synthetic substrate is elastic, the opaque areas with fibre still attached can become puckered up to produce a high relief knobbly effect.

Description

FABRIC FINISHING PROCESS The present invention relates to a fabric finishing process. The process is particularly suitable for use with bi-stretch denim, which can be transformed into a partially see-through fabric.

Technical Background It is known to treat certain fine fabrics such as velvet or satin with chemicals to remove portions of the fabric pile in order to create a pattern of flattened or translucent textured areas. This process is known as the Devore process.

The Devore process typically uses a solution of aluminium sulphate in a thickening medium such as INDALCA" solution. The resulting chemical paste is applied to the fabric to be finished by means of, for example, a silk screen printing process. Silk screening is a known technique used extensively in the textile finishing arts.

A silk screen consists of a fine net, cloth or gauze of suitable composition, strength and weave density and fibre thickness. The material of the screen must be resistant to attack by the chemical paste. The screen is held and stretched in a frame. The frame may be flat or cylindrical. The cylindrical frame is used in the case of the rotary process.

The screen is coated with a photo-sensitive resin which is exposed by photographic techniques to produce a pattern or design of areas of resin which have been hardened by the light exposure. Where the resin has been hardened the screen becomes impermeable to penetration by the chemical paste. These hardened areas correspond to the light parts of the design where the fabric will retain its original fibre composition.

The chemical paste, which may be mixed with a dye, is applied to the fabric by pressing it through the screen in a process similar to printing.

After this printing step, the fabric is baked in an oven or stove in order to accelerate the chemical attack on the surface of the fabric in order to develop the pattern desired. This heating step also dries the fabric.

Typically, in the Devore process, the fabric would be baked at a 1500C. for four minutes. The exact combination of temperature and time depend on the finish to be achieved and the fabric used.

In most cases the fabric finished with the Devore process will be expected to lie flat.

Technical Problem and Solution The present invention is concerned with a finishing process which can be used to make a novel fashion fabric.

In accordance with the present invention the starting fabric comprises a fabric such as bi-stretch denim which comprises a preferably synthetic substrate resistant to attack by a chemical and a fibre which is susceptible to said chemical. The selection of a fabric like denim instead of a luxury fabric such as velvet or satin for this type of treatment is original. Denim is normally regarded as industrial or tough and is not seen as appropriate for use in the creation of delicate fashion fabrics.

In accordance with the invention the fabric is treated with a chemical or chemicals of sufficient concentration to erode entirely the susceptible fibre. In a preferred embodiment of the process bi-stretch denim is pre-washed and then treated in selected areas with a chemical paste, baked and then washed in order to remove at least part of the exposed portions of the susceptible fibre. Treatment with the chemical is preferably by means of a process such as silk-screen printing.

Description of a preferred embodiment In the following description, the finishing process of the invention will be described in more detail. The reader skilled in the art will appreciate that many and various results can be obtained by adjusting the parameters of the process.

Selecting the starting fabric The fabric to be finished must have a chemical-resistant substrate, usually of a synthetic as opposed to a natural fibre. The substrate has sufficient strength to retain its integrity as a fabric after processing. In bistretch denim the stretch fibre, usually LYCRAO, is woven through both the warp and the weft of the fabric.

The woven structure is strong enough to produce a substrate which also resists tearing and laddering. In the case of bi-stretch denim this strength is introduced because the fabric was originally intended for hardwearing applications. It will be appreciated that fabrics may be deliberately woven for use in this finishing process which have a suitably strong synthetic substrate.

It is desirable that the synthetic substrate should be a stretch fibre as this results in the areas of the fabric which have not been chemically eroded being pulled and crumpled to give a knobbly effect. This gives the resulting fabric a much higher relief than is obtainable with a non-stretch substrate.

As well as the synthetic substrate, the fabric must comprise a fibre susceptible to chemical attack.

Cotton or other cellulose fibres and other natural fibres are suitable for this purpose and are eroded satisfactorily by the use of a chemical such as aluminium sulphate.

Selecting the chemical paste Devore processes which work on cotton typically use a paste in which 20g of aluminium sulphate is mixed with 80g of INDALCA. By contrast, in the present process, a stronger chemical solution is required. In one example of the process applied to bi-stretch denim the chemical paste was prepared from 40g aluminium sulphate with 60g of INDALCA. The skilled reader will appreciate that the appropriate concentration for a particular starting fabric and desired finish can readily be ascertained by a series of simple experiments.

Instead of aluminium sulphate, an acid or combination of acids may be used. Other chemicals capable of dissolving or degrading natural fibres may also be used. The selected chemical material and its concentration depends on the susceptible fibre to be attacked.

INDALCA is a suitable medium for producing an appropriate consistency of chemical paste for application to the fabric. It will be appreciated that other proprietary media may also be used.

Other thickeners, stabilisers, buffers, preservatives or dies may be added to the paste.

Preferably a 40% aluminium sulphate in INDALCA solution is used in the finishing process. This contrasts with a 20% aluminium sulphate in INDALCA solution used in traditional Devore process.

Selecting the application method The chemical must be selectively applied to areas of the fabric. This step is generically described as printing in this specification whatever the application method may be. For small batches the chemical paste may be applied by hand, such as with a cloth, brush, sponge, coating knife, coating cylinder(s) or by other coating/printing method. The chemical paste could also be sprayed onto the fabric.

Preferably flat or cylindrical silk-screen printing is used as the printing method. The mesh size on the screen may need to be more open than normally used for silkscreen printing in the Devore process in order to achieve sufficient chemical penetration in the desired areas.

The process is also suitable for use with computer controlled printing equipment.

It will be appreciated that the consistency of chemical paste used will be dependent upon the application method chosen.

The printing step will apply the chemical paste to selected areas only of the fabric. It will be appreciated that many patterns may be employed at the discretion of the designer and that these will produce different results with more or less translucent areas.

The finishing process The fabric to be processed is pre-treated by washing to remove any excess dye, oils and sizes used in the textile process. The fabric is then dried. This step is necessary where the denim fabric contains a finishing which makes it stiff and therefore resistant to the attack of the chemical paste. The washing step softens the fabric and makes it more susceptible to attack by the chemical paste. If the fabric has been specially manufactured for use in this process, then this step may be omitted.

The chemical paste is then printed on to the fabric.

The printed fabric is then dried. This is preferably carried out by means an electrically powered fan assisted heater propelling hot air over the fabric. This step is optional.

The fabric is then heat-treated or baked in an oven. An oven such as that used to fix dies on fabric is suitable.

In this type of oven, the fabric is suspended inside the oven. In one embodiment, the fabric passed into the oven is heated at 1500C. for fifteen minutes. In another embodiment using a continuous production line the ovening step was at 2000C for four minutes. The duration of the baking step and the temperature depend upon the starting fabric and the chemical paste used. The baking step reacts the chemical better and stiffens the fabric. The temperature of the heat treatment is preferably in the range of 120"C to 2200C.

In some embodiments of the process it is possible to combine the drying and baking steps described. This is particularly appropriate where the finishing is carried out as a continuous production line process. Tunnel or cylindrical ovens may be used.

The fabric is then subjected to washing. The fabric is preferably soaked in a wash of water. Such a water wash is not used in the normal Devore process at all.

The washing step removes the chemical paste. The washing step softens the denim. The washing step may include additional abrasion, rubbing or friction in order to rub away from the synthetic substrate those parts of the susceptible fibre which have been attacked by the chemical paste.

The fabric is then dried.

If the printing step uses a silk screen of sufficient permeability and the chemical is sufficiently strong this additional abrasion step can be eliminated. However, hand finishing results in a particularly distinctive fabric.

Finally the fabric can be scrubbed. The scrubbing action is applied to those areas which were printed with the chemical paste or concentrates on those areas. The scrubbing step is carried out with a brush or an abrasive device such as a wire wool pad. The brush or abrasive device may be hand operated or power driven. This final finishing step is to rub away and pull away at the susceptible fibre from the areas which were treated with the chemical paste. This results in areas of the synthetic substrate becoming exposed. In the case of a LYCRAX mesh substrate these areas are then translucent to the eye. Because a LYCRAS mesh is elastic, the exposed areas will cause the remaining areas or edges of the fabric, to which the susceptible fibre is still attached, to pucker up producing a desirable knobbly effect.

The scrubbing step can be replaced by a simple washing step if the chemical attack is efficient at completely degrading the susceptible fibre.

Advantages of the finished fabric Denim fabric finished in this way is transformed into a delicate partially transparent and variegated fashion cloth. The fabric has variations of the texture and transparency which transform it into a totally different looking and feeling fabric, far removed from its traditional usage. This new fabric lends itself to the making of garments which are more striking and are more revealing of the body of the wearer. The degree of transparency can be controlled by the aggresiveness of the applied chemical paste and the temperature and time of ovening.

Bi-stretch denim is thus given a pattern of transparent or semi transparent and opaque areas. The opaque areas in stretch fabrics may acquire a knobbly or embossed effect on certain designs. The fabric thus obtained lends itself to being used for clothing which has a more exciting or sexy appeal. The fabric is preferably made up into garments which reveal through the transparent or translucent areas in the cloth, the body of the eventual wearer.

The use of this finishing process will completely change the perception of denim. It is presently woven as a fabric for hard wearing social and work garments.

Previously it has been regarded as unsuitable for finishes like the Devore process. Many designers have made an attempt to smarten up denim. A feature in the British newspaper, The Daily Telegraph of 27 May 1997 describes the use of denim by various designers. Denimlinen mixes are described, and various garments using denim by well-known designers are featured. None of these previous uses of denim in anyway anticipates the novelty created by this original finishing process.

Claims

1. A process for finishing a fabric which comprises a substrate resistant to attack by a chemical or chemicals and a fibre which is susceptible to erosion by said chemical or chemicals, said process comprising the steps of applying said chemical or chemicals to selected areas of the fabric, heat treating the fabric to erode the fibre to which the chemical or chemicals has been applied, and washing the fabric in water in order that at least in parts of the selected areas the susceptible fibre is removed leaving the substrate exposed.

2. A process as claimed in claim 1, wherein the fabric is washed prior to applying the chemical or chemicals.

3. A process as claimed in claim 1 or 2, wherein the chemical or chemicals is applied in the form of a paste applied by silk screen printing.

4. A process as claimed in any one of the preceding claims, wherein the chemical is aluminium sulphate.

5. A process as claimed in any one of the preceding claims, wherein the heat treating step comprises ovening the fabric in a tunnel or cylinder oven.

6. A process is claimed in any one of the preceding claims, wherein heat treatment comprises suspending the fabric in an oven at a temperature in the range 1200C to 2200C.

7. A process as claimed in any one of the preceding claims, wherein the process further comprises the steps of drying the fabric after it has been washed and abrading it at least in the selected areas.

8. A process is claimed in any one of the preceding claims, wherein the fabric is dried before the heat treatment step.

9. A process for finishing fabrics substantially as herein described.

10 A fabric finished in accordance with a process as claimed in any one of the preceding claims, which is a bi-stretch denim having an elastic substrate which is substantially transparent or translucent to the eye when the denim cotton fibres have been eroded therefrom.