GB2036091A - Transfer Printing - Google Patents

Abstract

In an improved method of transfer printing by the dry-film method, a temporary support is used in which a substrate coated with a release layer carries a removable layer comprising a dyestuff and a binder. The binder is based on a film forming polymer and is soluble in organic solvent to facilitate printing onto the temporary support as an ink containing a dyestuff and the polymer, but is also soluble in water to facilitate its being washed out of a fabric to which it has been transferred. The substrate of the temporary support can be paper, and transfer of the removable layer to a fabric is achieved by application of heat and pressure. The release layer is a continuous coating whilst the removable layer will generally be a printed design which need not be continuous.

Description

SPECIFICATION Improvements In or Relating to Transfer Printing This invention relates to transfer printing, and in particular to a dry transfer printing process i.e. a process in which a dyestuff or pigment is transferred from a carrier to a dry fabric under the influence of heat and pressure.

The usual dry transfer process relies upon disperse dyestuffs, which volatilize under the transfer conditions, and thus can transfer onto the fabric. The snag with this process is that disperse dyestuffs are not substantive to cellulosic and other natural fibres such as cotton and wool and the dry transfer printing process using these dyestuffs does not give good results on cotton or wool fabrics or polyester/cotton blends.

There have been several different approaches tried as ways to achieve satisfactory results on such fabrics, proposing various treatments of the cotton fibres to render them substantive to the dyestuffs concerned.

An alternative approach has been proposed in UK Patents Nos. 1,496,891 and 1,496,892 in which a decoration material is described which comprises a flexible substrate having thereon a removable layer containing a dyestuff and/or pigment and a film-forming polymer which on heating becomes sufficiently adhesive to adhere under the effect of pressure to a textile more strongly than the layer adheres to the flexible substrate. The removable layer is transferred to a textile fabric under the influence of heat and pressure and the dyestuff or pigment fixed on the fabric by a heat treatment. In the heat treatment used for fixing, the film forming polymer may fuse into the fabric or may wholly or substantially decompose leaving no residue which would adversely affect the handle or other property of the fabric.

In this process it is difficult to avoid affecting the handle of the fabric being printed and it is also difficult to avoid the print being strictly limited to the surface of the fabric, with little penetration into the fabric.

According to the present invention a temporary support for use in transfer printing in a dry process comprises a flexible substrate having at least one surface coated with a release layer, and on said release layer a removable layer comprising a dyestuff and a binder which under heat and pressure will adhere to a textile fabric preferentially over said release layer, said binder being a film-forming polymer which is soluble in both organic solvents and water, such that it may be coated on said release layer with said dyestuff as a solution in organic solvent and removed by water from a textile fabric.

The invention also provides a method of decorating a textile fabric which comprises contacting said textile fabric under heat and pressure, with the removable layer on a temporary support as defined above, to transfer said removable layer to the fabric, fixing the dyestuff on the fabric, and washing said fabric in water.

The flexible substrate preferably comprises a paper which is coated on at least one surface with the release layer. The latter includes a binder, which is generally a polymeric material chosen primarily for its low adhesion to the ink, i.e. the materials in the removable layer, plus a release agent.

Suitable binders are cellulose derivatives, such as the esters and ethers, rubber derivatives such as chlorinated and cyclised rubber, polystyrene and other hydrocarbon resins, and some rosin derivatives. The cellulose derivatives give the best results, especially cellulose acetate-butyrate and ethyl hydroxy-ethyl cellulose, sold by Hercules Chemicals as "EHEC".

The release agents are added at about 10% to 40% by weight based on weight of binder, and are preferably natural or synthetic rubbers and/orwaxes. Good results are given by some waxy esters, by some montan wax derivatives, by some oxidised polyethylene waxes, and by natural rubber.

The binder and release agent may be applied to the paper as a solution in a suitable solvent blend, to give a continuous coating with a dry coating weight of from 2.5 to 10 g/m2.

The flexible substrate carrying the release layer is printed to form the removable layer, with an ink which comprises a mixture of a dye suited to the fabric to be transfer printed and the film-forming polymer mentioned above.

The film-forming polymer must be soluble in both water and organic solvents. Suitable resins are shellac, rosin, some rosin derivatives, some maleic resins, and a cellulose derivative, hydroxypropyl cellulose, sold by Hercules Chemicals under the name "KLUCEL".

Most of the resins listed above have the disadvantage of requiring a mildly alkaline bath to dissolve them, but "KLUCEL" will dissolve in plain cold water. It has, however, the disadvantage that it is insoluble in hot water, so that the process using this material has to include at least one cold rinse.

Two other polymers found promising as filmforming polymers for this process are "GANTREX AN" a poly(methyl vinyl ether/maleic anhydride) with the repeating unit

which is commercially available from G.A.F.

Corporation, and "CARBOSET" an acrylic copolymer commercially available from B. F.

Goodrich.

The ink may also include a plasticiser for the fiim-forming polymer to lower its softening point.

One of the most useful plasticisers for "KLUCEL" is Polyethylene Glycol 600, which is soluble in both water and solvents, and also acts as a dyeing assistant.

The dyestuff loading in the ink may be up to 350% of binder.

The ink is a solution of the film-forming polymer in an organic solvent such as a mixture of toluene and methylated spirits in which the dyestuff may be dissolved or dispersed. When a blended fabric containing different fibre types is to be decorated, the ink may contain different fibre types in order to dye the different types of fibre in the fabric.

Transfer of the removable layer from the flexible substrate to a fabric is preferably carried out at a temperature in the range 850C to 1 800C and a pressure of from 50 to 1000 Ibs/in2 either between heated rollers or in a flat press.

After transfer of the removable layer to the fabric a fixation treatment suitable to fix the dyestuff to the fabric is undertaken. The fixation process depends upon the particular type of dyestuff used in the removable layer and the type of fabric being dyed, any of the types of dyestuff normally used for dyeing and printing fabrics being usable, for example acetate disperse dyestuffs, reactive dyestuffs, any of the dyestuffs used for wet transfer printing, vat dyes. It is thus possible to select the type of dyestuff appropriate to the fabric to be decorated. The fixation treatment may be that normally used for the dye/fabric combination and may involve washing the fabric in which case the film forming polymer may be removed by the fixation treatment. If no washing is involved in fixation, a separate washing step is used to remove the film-forming polymer.

The invention will now be illustrated by means of several Examples.

Examples Release coatings Four formulations A to D for the release layer are as follows.

parts by A weight Hercules "EHEC" Resin, Extra low viscosity 140 BASF WAX "OP" 40 Toluene 900 Methylated Spirits 100 The toluene is mixed with the methylated sprits and OP wax and heated to about 600C to dissolve the wax. The resin is then stirred in and dissolved and the solution allowed to cool.

B As formulation A except that the BASF Wax OP is replaced by BASF Wax E.

parts by C weight EASTMAN CAP 482-20 140 BASF Wax OP 40 Methyl Ethyl Ketone 400 300 Methylated Spirits 200 This is made up in the same way as formulation A except that the toluene and methyl ethyl ketone mixture is used instead of toluene alone.

parts by D weight EASTMAN CAB 171-2 140 BASF Wax E 40 Methyl Ethyl Ketone 400 Toluene 300 Methylated Spirits 200 This formulation is made up in the same way as formulation C.

Papers are coated with one of these four different formulations by a roller coating method to give a uniform coating of dry weight in the range 4 to 8 g/m2.

The removable layer is printed by any normal method of printing onto the release layer on the paper using inks containing film-forming polymers. Three basic ink formulations 1, 2 and 3, suitable for gravure printing, are detailed below.

These may need modification if some other printing method is used.

Ink formulations parts by 1 weight Hercules "KLUCEL" type E 150 DYE (Reactive type) 50-450 Polyethylene glycol 10 Methylated Spirits 2000 The ink is made by mixing together the methylated spirits, polyethylene glycol and dye and 20% of the resin, and ball milling the mixture until the dye is dispersed. The remainder of the resin is then added and stirred until dissolved.

parts by 2 ' weight "GANTREZ" AN 119 150 DYE (Reactive type) 50-450 Methyl Ethyl Ketone 500 Methylated Spirits 1 500 This ink is made in the same way as No. 1 above.

3 As No. 2 except that the 1 50 parts of "GANTREZ" AN 119 are replaced by "CARBOSET 525".

These three formulations may all be improved, if desired, by replacing 25% of the binder polymer by the polymer "CARBOSET 515" which will act as a tackifier and plasticizer for the other polymers.

Notes (a) "EHEC" is ethyl hydroxyethyl cellulose, made by Hercules Chemicals.

(b) BASF Waxes E and OP are modified Montan waxes, made by BASF.

(c) C.A.P. is a cellulose acetate-proportionate made by Eastman Chemicals.

(d) C.A.B. is a cellulose acetate-butyrate made by Eastman Chemicals.

(e) "KLUCEL" is a hydroxypropyl ether of cellulose, made by Hercules Chemicals.

(f) "GANTREZ AN" is a copolymer of methyl vinylether and maleic anhydride, made by the GAF Corporation.

(g)"CARBOSET 525" is an acrylic copolymer made by B. F. Goodrich Chemicals.

(h) "CARBOSET 515" is a lower molecular weight acrylic copolymer also made by B. F.

Goodrich Chemicals.

The removable layer so produced is transferred to a cotton textile fabric by pressing the printed side of the paper sheet in contact with the fabric under a pressure of about 500 psi. at 95 to 1 300C in a heated press for 60 seconds. To fix the reactive dyestuff the design is overprinted with a thickened 1.5% solution of Sodium Carbonate solution in water, the fabric is then steamed for 5 minutes and finally washed.

In this case the fixation treatment serves also to remove the film-forming polymer.

It should be appreciated that whilst the invention has been described above with reference to printing on textile fabrics it may be used for printing other materials such as anodised Aluminium.

Claims (21)

Claims

1. A temporary support for use in transfer printing in a dry process comprises a flexible substrate having at least one surface coated with a release layer, and on said release layer a removable layer comprising a dyestuff and a binder which under heat and pressure will adhere to a textile fabric preferentially over said release layer, said binder being a film-forming polymer which is soluble in both organic solvents and water, such that it may be located on said release layer with said dyestuff as a solution in organic solvent and removed by water from a textile fabric.

2. A temporary support according to claim 1 in which the flexible substrate comprises a paper crated on at least one surface with the release layer.

3. A temporary support according to claim 2 in which the release layer comprises a polymeric binder and a release agent.

4. A temporary support according to claim 3 in which the amount of release agent in the release layer is 10% to 40% by weight based on weight of binder.

5. A temporary support according to claim 1, 2, 3 or 5 in which the release layer is a continuous coating with a dry coating weight of from 2.5 to 10 g/m2.

6. A temporary support according to any preceding claim in which the release layer includes as a binder a cellulose derivative, a chlorinated or cyclised rubber, or polystyrene.

7. A temporary support according to claim 6 in which the release layer includes as a binder a cellulose ester or ether.

8. A temporary support according to claim 7 in which the release layer includes as a binder cellulose acetate-butyrate, cellulose acetatepropionate or hydroxy-ethyl cellulose.

9. A temporary support according to any preceding claim in which the release layer includes as a release agent a natural or synthetic rubber or a wax.

10. A temporary support according to claim 9 in which the release agent is a waxy ester, a montan wax, an oxidised polyethylene wax or a natural rubber or montan wax derivative.

11. A temporary support according to any preceding claim in which the removable layer comprises as binder shellac, rosin, a maleic resin, a cellulose derivative, a poly (methyl vinyl ether/maleic anhydride) or an acrylic copolymer.

12. A temporary support according to claim 11 in which said binder is hydroxy-propyl cellulose.

13. A temporary support according to claim 11 in which said binder is a poly (methyl vinyl ether/maleic anhydride) with the repeating unit.

where n is an integer.

14. A temporary support according to claim 11, 12 or 13 in which the removable layer contains a plasticizer or the film-forming polymer to lower its softening point.

1 5. A temporary support according to claim 14 in which the plasticizer is polyethylene glycol.

1 6. A temporary support according to claim 11 in which the binder is a mixture of polymers.

1 7. A method of decorating a printable substrate which comprises contacting said printable substrate under heat and pressure with the removable layer on a temporary support as claimed in any one of the preceding claims to transfer said removable layer to the substrate, fixing the dyestuff on the substrate and washing the substrate in water.

18. A method according to claim 1 7 in which the removable layer is produced by printing on the temporary support an ink in an organic solvent containing dyestuffs, said binder polymer and plasticizer and driving off said solvent.

19. A method according to claim 18 in which the organic solvent is a mixture of toluene and methylated spirits.

20. A temporary support as claimed in claim 1 substantially as described herein with reference to the foregoing Examples.

21. A method of decorating a textile fabric substantially as described herein with reference to the foregoing Examples.