IL30364A - Process for brightening organic materials and temporary support therefore - Google Patents

Description

30364/2 Process for brightening organic 'materials and temporary support therefore SOCIETE D'EXPLOITATION DES PROCEDES SUBLISTATIC C. 28633 Attempts have already been made to whiten organic materials , for example, textile fibres by the sublimation of optical brightening agents. Thus, French Patent Specification 1»440,550 discloses the whitening of textile filaments in the absence of water by applying optical brightening agents in a pulverulent and dry form or in the vapour phase to the goods to be treated and thereafter thermo-fixing the optical brightening agents.

The above process is particularly suitable for the optical brightening of synthetic textile filaments and fibres made for example of cellulose acetate,, including cellulose triacetate, and above all fibres of linear polyesters. It is thus addressed to the manufacturers of fibres and filaments and relates to the preparation of fibres which are brightened before weaving.

According to the process of the present invention organic materials in the form of sheets, strips or ribbons, for example woven fabrics, veils, lawns, knitted fabrics, felts or carpets and other surfaces of organic materials preferabl which may be natural or artificial or even fully synthetic can be whitened,s -even locally if desired,,! and all sorts of contrasts or brightening effects may be achieved which it is not possible to obtain by the known process. The present process also includes the concomitant application of dyestuffs and the production of designs and prints which are coloured and whitened or brightened locally or completely which cannot be carried out by the known process.

The present invention comprises a process wherein a a tem orar su ort in^the form of a sheet stri or ribbon is optionally glue-backed onto a strip of paper, a film of a plastic material or a sheet of paper of low r or zero porosity,, is printed by means of solution, an emulsion or a dispersion, which is pre erably totally or almost totally free from water that contains an optical brightening agent heat-stable up to 250°C which vapourises at atmospheric pressure at between 150 and 220°G, advantageously at 180° to 205°C, and a binder or thickener which is heat-stable up to 250°C at least and non-sublimable at the sublimation temperature of the brighteners; . b) after drying the print, the surface thus printed is brought into contact with the surface of the organic material to be whitened or brightened, preferably in the form of a sheet, strip or ribbon, and heated to above 150°C for the time required to permit vaporisation or sublimation and penetration of the optical brightening agent into the material to be whitened or brightened, The sheet of the temporary support may be heated in contact with a woven fabric by various known means of heating, inter alia an iron or pressing machine, a heating plate large enoug for continuous working,, or one or more heated cylinders. Paper is particularly suitable, as a temporary support in view ofjits low cost price but other similar materials, for example a film of a plastic material which resists heating in contact with the woven fabric may be used, for example films of regenerated cellulose or other substances in, the form of a sheet having a high melting point, for example thin aluminium sheets which furthermore have the advantage of a lower retention. of the brightening agent.

The invention thus also comprises a temporary- support in the form of a sheet, strip, or ribbon which on one surface carries an optical brightening agent heat -stable up to 250°C which vaporizes at between 150 and 220°C at atmospheric pressure, and a binder or thickener which is heat-stable - up to 250°C at least and non-sublimable at the sublimation temperature of the brigh eners, preferably a binder which is infusible at the vaporization temperature and is preferably also insoluble in water, and if desired, one or more dyestuffs /which vaporize between 150 and 220°C at atmospheric pressure.

The thickeners or tinders which must bo inert at the temperature at vhich the material vapourises are commercially available and are extensively sed for direct printing of textile materials but . they must be chosen from amongst those which have a low content of solid substances. They must be capable of being dried to give a non-sticky film which retains tho brightening agent and tho dyes uff or dye&tuffs vhich may optionally be used at the sane time as tho brightening, agent.

Inert binders are preferably used, w ich must retain the vaporisable substances used without modifying then. By way of example there may be mentioned those which are capablo of being dried, for example in. a stream of hot air, so as to form a non-sticky film on the printed support sheet, for example the alginates of alkali me uls, for example sodium alginate, natural g ns for example carob or gum tragacanth, carboxy- mothylcellulose and preferably slightly soluble or insoluble in water binders which are soluble in organic solvents for example nitrocellulose and cellulose ethers of low molecular The optical brightening agents to be used in accordance with the process of the invention, must be. resistant to high temperatures rangin for example up to 250°C; furthermore, they are preferably free from acid groups which render the product soluble in water, for example from sulphonic acid groups,. Compounds which contain at least one benzoxazolethiophene residue are particularly valuable. They correspond for example to the formula in which represents a benzene residue which is condensed: with the oxazole ring in the manner indicated and represents a benzene residue, another benzoxazole residue bound in 2-position to the thiophene nucleus, or a functionally modified carboxyl group Depending on the materials to be whitened the following brightening agents may also be usedi dibenzothiophene-S-dioxides which may contain amino groups, which may be aeetylated, derivatives of coumarin, pyrazolines, mono-oxazoles or bis-oxazoles as well as products corresponding to the formulae : • - .- · . pressure Within the same temperature range. It is thus possible to obtain designs showing contrast or brightening effects on a single support, these designs thereafter being transferred to the material to be treated. As materials of this type the majority of textile materials may be mentioned for example, a textile made of or containing oellulose material but more especially woven fabrics, veils, lawns, knitted fabrics felts and non-woven articles , carpets , sheets and more or less Impermeable foils made of synthetic or semi-synthetic fibres 6f hydrolysed or unhydrolysed cellulose acetate and more particularly of vinyl polymers for example polyacrylonitrile or linear polyesters of the polyethylene terephthalate type, polyamides, especially "nylon" and other synthetic fibres capable of -bein dyed with so-called dispersion dyestuffs, and fibres which consist of mixtures of the said synthetic fibres with one another or with cotton and/or wool or other natural fibres.

The transfer of the optical brightening agents and the optional dyestuffs on the temporary support to the material to v,b§ brightened may be effected by heating to 150°-250°G. , advantageously 180 to 2O5°0., preferably by heating the temporary support to 210°-230°C. whilst gently pressing the material to be' brightened which may, if necessary, be at least slightly cooled at the surface which is not in contact with the temporary support.

According to a particular embodiment of the invention optical brightening agents of the type indicated and sublimable or vaporisable dyestuffs may be applied simultaneously, that is to say to the same temporary support, at the same temperature ironing machine is placed at a temperature of 185° for 1 minute on the unprinted side of the paper placed on top of the woven fabric which is in turn placed oh top of a flat support. After removing the treated paper the polyester woven fabric is considerably whiter than the original untreated woven fabric.*: The process may also be carried out continuously by heating to a higher temperature and controlling the speeds of the printed paper and the woven fabric to be whitened so that they for example remain in contact for 15 seconds at 210° or 25 seconds at 200°.

Instead of the product of the formula indicated compounds of the following formulae, which give similar optical whitening effects, may also be used: is then heated continuously in an industrial press, the temperature inside the press.being maintained at 200° - 205°» the time of passage being so regulated that the woven fabric and the temporary support are kept in the press for 30 seconds. An exact reproduction of the original design is thus obtained*

Claims (1)

1. n e n -pos on o e op ene r ng or a unctional y 30364/2 . : : ' - 16 - ? modified carboxyl group. 8., A support as claimed In any one of claims 1 to 7 that carries a binder which is slightly soluble or insoluble in water. " ■ ·j ■ · " ' , ■ 9. ! A. support as claimed in any one of claims 1 to 8 that carries a cellulose ether as the binder. 10» ' A support as claimed in claim 9 that carries ethylcellulose , hydroxyethylcellulose and/or hydroxypropyi-cellulose as the binder. 11. A support as claimed in any one of claims 1 to 10 that carries in addition to the binder and the optical brightening agent a design obtained by means of a dyestuff which also yapourises at the indicated temperature» 12. A support as claimed in any one of claims 1 to 11 that carries an Optionally multi-coloured print and a brightening agent over its entire surface or only locally.. 13. A support as claimed in claim 12 that carries a multicolour design produced by means of dyestuffs which are ver similar as regards their behaviour under the influence of heat. 14. A support as claimed in claim 13 that carries a multicolour design produced by means of dyestuffs whose vaporisation or sublimation curves are similar to one another. 15· A support as claimed in any one of claims 12 to 14 that in addition to an optical brightening agent carries at least one of the following dyestuffs : 1-hydfoxy-3-phenoxy-4-aminoanthraquinone fVhydroxyquinophthalone , 1,4-dimethylamino anthraquinone, 4*(4' -methyl*2'-nitrophenylazo)-3-methyl-5-pyrazolone and the butyl or propyl ester of 1,4-diamino÷anthra quinone-2-carboxylie acid. - 30364/2 - 17 - 16* A support as claimed in any one of claims 1 to 15 obtainable substantially as described herein, 17. > Any one of the supports obtainable as described in Examples 1 and 2 herein* 18, A process for whitening or brightening an organic material wherein a) a print is produced on a temporary support in the form of a sheet, strip or ribbon by means of a solution, an emulsion or a dispersion which contains an optical brightening agent which is heat-stable up to 250°C and which vapourises at between 150°; and 220°C a atmospheric pressure, and a binder or thickener which is heat-stable „ up to 250°C and whioh is non-sublimable at the sublimation temperature of the brightener, and b) .after drying the print, the surface thus printed is brought into, contact with the material to be whitened , or brightened, and heated to above !50°C for the time required to allow vaporisation and penetration of the optical brightening agent into the material to be whitened , or brightened. 19. . A process as claimed in claim 18 wherein the temporary support consists of a sheet of paper or metal. 20. A. process as claimed in claim 19 wherein the ' temporary support consists of an aluminium foil glue-backed with a sheet of paper. 21. A process as claimed in claim 19 wherein the temporary support is a sheet, of paper hich is slightly porous or non-porous. '