GB2174731A

GB2174731A - Extinguishing or preventing optical brightening

Info

Publication number: GB2174731A
Application number: GB08610951A
Authority: GB
Inventors: Karl-Heinz Weible
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1985-05-08
Filing date: 1986-05-06
Publication date: 1986-11-12
Also published as: FR2581672B1; DE3614377A1; JPS61255965A; IT1203785B; IT8647991A0; GB8610951D0; CH677167GA3; CH677167B5; FR2581672A1; NL8601155A; GB2174731B; HK106591A; DE3614377C2

Abstract

In a process for extinguishing the optical brightening effect produced on a substrate by an optical brightening agent or preventing optical brightening effects from being produced on a substrate by an optical brightening agent, the substrate is brought into contact with an UV-absorber which is subsequently fixed on the substrate, both steps being effected either before or after the treatment of the substrate with the optical brightening agent. The UV-absorber may be applied to the substrate before, during or after dying or printing the substrate.

Description

1 GB 2 174 731 A 1

SPECIFICATION Improvements in or Relating to Organic Compounds

The present invention relates to a process for extinguishing or preventing the fluorescence of optically brightened substrates.

As is known, an optical brightener absorbs invisible ultraviolet light and re-emits it in the blue or green region of the visible spectrum. The re-emitted light masks the undesirable yellow tint of textiles or other substrates. Therefore optically brightened materials appear whiter to the eye than untreated substrates and optical brighteners are largely used to improve the white effect of substrates suQh as-textiles, paper, leather, coatings, pigments etc.

Nevertheless the presence of an optical brightener is sometimes undesirable. For example, when an 10 optically brightened textile is overdyed or overprinted with a dyestuff, the total effect produced on the textile in daylight illumination results from the adsorption of the dyestuff used and additionally f rom the fluorescence of the optical brightener. On exposure of such dyeings or printings to artificial light which is substantially free from UV light, the fluorescence is not apparent and the observer notices a strong alteration of the shade.

Accordingly, the invention provides a process for extinguishing at least partially the optical brightening effect produced on a substrate by an optical brightening agent or preventing optical brightening effects from being produced on a substrate by an optical brightening agent, which process comprises the steps of bringing the substrate into contact with an UV-absorber and subsequently fixing the UV-absorber on the substrate, both steps being effected either before or after the treatment of the substrate with the optical 20 brightening agent.

By "UV-absorber" is to be understood a product which strongly absorbs light in the near UV range, (<400 nm, particularly within 250-350 nm) without significant re-emission at longer wavelengths. The expression "optical brightening effect" used in the present disclosure mainly refers to the fluorescence effect of the optical brightener.

Suitable UV-absorbers include benzotriazole derivatives, for example 2 (2' -hydroxy -phenyl) - benzotriazole derivatives such as 2 - (2' hydroxy - 3' - tert. - butyl - 5' - methylphenyl) - 5 chlorobenzotriazole, benzophenone derivatives, for example 2-hydroxybenzophenone derivatives optionally further substituted in the 2',4',4 and/or 5-positions, such as 4-chloro-2,2',4'- trihydroxybenzophenone, 2,2',4-trihydroxybenzophenone, 2,4-dihydroxy-4'- methoxy-benzophenone, 30 2,2',4,4'-tetrahydroxy-benzophenone, 2,4-dihydroxy-benzophenone or 2hydroxy-4-methoxy benzophenone, benzoic acid derivatives, for example resorcinol monobenzoate, salicylic acid esters, for example 4-Cl-12a[kyl phenyl salicylate, dibenzoyl benzene derivatives, for example p-di(4 hydroxysalicyloyl)-benzene or 2,4-dibenzoylresorcinol, a-cyanoacrylic acid ester derivatives and benzylidene malodinitriles. Such UV-absorbers are known and disclosed for example in USP 3 214 463 and 35 3 383 241, DAS 1 101437 and 1 213 407 and British Patent 796 003.

According to the invention, a mixture of UV-absorbers may also be used.

The UV-absorber is advantageously applied from an aqueous medium. Depending on its solubility in water, it may be used as an aqueous solution or in the form of an emulsion or dispersion in the aqueous medium. The emulsions are advantageously prepared by dissolving the UVabsorber in an organic solvent, 40 for example white spirit, and adding the resulting solution to water, preferably in the presence of an emulsifier. Preferred emulsifiers are non-ionic emulsifiers, e.g. oxyalkylation products, preferably ethoxylation products, Of C8-20 alcohols, C4-12 alkyl-substituted phenols, C9'_C20 fatty acids or castor oil.

Preferably the non-ionic emulsifiers contain from 5 to 50, more preferably from 5 to 30 ethyleneoxy units.

As already mentioned, the UV-absorber may also be used in the form of an aqueous dispersion of fine 45 particles, optionally in the presence of a dispersing agent. Suitable dispersing agents are those used for dispersing disperse dyestuffs, e.g. lignine sulphonates orformaldehyde naphthalene sulphonic acid condensation products.

The UV-absorber may be applied to the substrate according to known methods compatible with the type of UV-absorber used, as generally used for dyeing or printing, for example by-exhaustion from a long 50 bqth at a temperature from 20 to 140'C, impregnation and dwelling at a temperature from 20 to 90'C for 30 minutes to 48 hours depending on the dwelling temperature, impregnation and fixation with saturated steam, superheated steam at 160-190'C or warm dry air at 160-220'C or treatment at a high frequency or heat contact. The UV-absorber may also be applied by known printing methods, for example thermoprinting, in combination with organic polymers, for example surface coatings whether oil or water 55:

based, or by pigment printing.

The method used for the application and fixation of the UV-absorber and the amount of UV-absorber to be used depend on the substrate-to be treated, the optical brightening agents used or to be used, the properties of the UV-absorber and the type of dyestuffs if used. In general good extinguishing properties are obtained when the UV-absorber is used in an amount of from 0.1 to 5% by weight based on the weight 60 of the substrate.

According to the invention the UV-absorber may be applied to an optically brightened substrate. In a preferred embodiment, the UV-absorber is applied either before, during or after the dyeing or printing of the optically brightened material, particularly after dyeing or printing. The UV-absorber may also be applied 2 GB 2 174 731 A to the substrate before the optical brightening of the substrate is carried out. In a preferred embodiment, the UV-absorber is applied on a non-brightened material, either before, during or after the dyeing or printing with a dyestuff or a mixture of dyestuffs.

The nature of the dyeing or printing process used on the material in connection with the UV-absorber treatment is not critical as long as the dyestuffs used and the dyeing or printing conditions are compatible 5 with the UV-absorber employed.

Nowadays optical brighteners are frequently incorporated in domestic detergents. When dyed or printed clothes are washed with such a detergent, the shade after drying is altered, particularly in the case of light dyeings and printings such as yellow and beige shades. Such a drawback is avoided when the dyed or printed articles are treated with a UV-absorber according to the invention and are washed at a later stage 10 with a domestic detergent containing an optical brightener.

According to the invention, the brightening effect of an optical brightening agent may be extinguished or significantly reduced either on the whole surface of the substrate or only locally. Thus the UV-absorber may be applied locally by printing according to a desired pattern on an optically brightened material or a material to be optically brightened. On exposure to UV light, the material treated according to the invention 15 shows a fluorescent pattern, e.g. as used in theatres or dancing clubs or for safety signs.

The process of the invention is used for preventing or extinguishing the brightening effects produced by optical brighteners of various classes, e.g. anionic, cationic or disperse-type optical brightening agents such as used in domestic detergents, in washing or bleaching agents for the pre-treatment of cellulosic fibres or other natural or synthetic fibres, or for the optical brightening of paper or synthetic fibres in the 20 mass. Examples of optical brighteners whose brightening or fluorescent effects are extinguished or reduced according to the invention are bis-(triazinylamino)stilbene disulphonic acids, triazolyl derivatives of stilbene sulphonic acids, bis-stilbene compounds, pyrazoline derivatives, naphthalimides, amino cournarins, oxacyanines, oxazoles, benzoxazoles or bis-(benzimidazolyl) derivatives.

The process of the invention can be used on any types of material which can be optically brightened, 25 e.g. textile fibres, paper or leather. Textile fibres may be in any conventional form, e.g. yarns, woven or knitted goods or non-wovens. Examples of textile substrates are those comprising wool, cotton, linen, silk, synthetic polyamides, polyester, cellulose acetate or triacetaLe, polyacrylonitrile, polyvinyl chloride or polyolefin fibres or blends thereof.

It may be advantageous to carry out preliminary testing to select the UVabsorber which is particularly 30 effective on the substrate to be treated, so as to arrive at the optimum working conditions. An UV-absorber which is particularly effective on a substrate comprising polyester fibres is for example an UV-absorber of the benzotriazole type, preferably 2-(2'-hydroxy-3'-te rt.-butyl-5'-m ethyl p henyl)-5-ch loro-benzotriazo le.

In a preferred embodiment of the invention, the UV-absorber is applied on an optically brightened substrate, particularly a textile substrate, in which the optical brightening agent has been either incorporated in the spin mass when the textile substrate comprises synthetic fibres, or applied in a pre- treatment step, e.g. a bleaching step. It may also be advantageous to apply the UV-absorber on such a material after a dyeing or printing step including fixation of the dyestuffs. The process of the invention is particularly suitable fortreating textile materials comprising synthetic fibres, especially polyester fibres.

The UV-absorber is selected to extinguish, preferably completely, or to preventthe optical brightening effects of optical brighteners used for such synthetic fibres. In the case of polyester, the UV-absorber used for extinguishing or preventing the optical brightening effects of a disperse optical brightening agent is preferably a benzotriazole derivative.

The invention is further illustrated by the following Examples in which the temperatures are in degrees Centigrade. All parts and percentages are by weight.

EXAMPLE 1

A polyester yarn, optically brightened in the mass, is treated in a cheese and cone dyeing machine with an aqueous bath containing, per 1000 parts, 0.17parts of 2-(2'-hydroxy-3'-tert.-buty]-5'-methylphenyi)-5-chlorobenzotriazole dispersed in water 0.5 parts ammonium sulphate, and 0.3 parts glacial acetic acid.

The liquor to goods ratio is 30: 1. The temperature of the treatment bath is raised from 40 to 125' in the course of 40 minutes and then the yarn is treated for 30 minutes at 125'. After cooling the yarn is rinsed and prepared for the dyeing.

On exposure to UV-irradiation, the treated yarn exhibits no fluorescence.

EXAMPLE 2

A 100% polyester fabric, previously optically brightened with C.I. Fluorescent Brightening Agent 330 by a thermosol process, is printed in a stripped pattern with a printing paste containing, per 1000 parts, 4 parts of 2-(2'-hydroxy-3-tert.-butyi-5'-methylphenyi)-5- chlorobenzotriazole in the form of an aqueous dispersion 3 GB 2 174 731 A 3 400 parts of a 13% thickening composition based on guar (Indalca H 735, Ce.salpinia-Hercules S.A. Bergamo, Italy) and water in an amount sufficient to balance up to 1000 parts.

After drying, the printed fabric is treated with superheated steam for 7 minutes at 175'. Afterwards, the fabric is rinsed warm and then cold and finally dried. On exposure to UV light, the printed fabric exhibits a 5 dark stripped pattern on a bright white bluish ground.

EXAMPLE 3

Polyamide knitted goods, previously optically brightened with C.I. Fluofescent Brightening Agent 328 by a thermosol process, is treated for 30 minutes at 98' and pH 5 with a bath containing 0.5% by weight, based on the weight of the polyamide goods, of 2-hydroxy-4-n- octoxybenzophenone dissolved in white spirit and emulsified in water with oleic acid polyglycol ester. After completion of the treatment the knitted goods are rinsed with cold water.

On exposure to UV light, the treated knitted goods exhibit no fluorescence.

EXAMPLE 4

By repeating the procedure of Example 3 but replacing the 2-hyd roxy-4-noctoxybenzophen one 15 emulsion by a 0.5% aqueous solution of 2-hydroxy-4-methoxy-benzophenone-5- sulphonic acid, the fluorescence of the 66 polyamide knitted goods is substantially extinguished.

EXAMPLE 5

A polyacrylonitrile fabric, previously optically brightened by exhaustion with C.I. Fluorescent Brightening Agent 340, is treated for 60 minutes at 980 and at pH 6 with a bath containing 1 %by weight, 20 based on the weight of the fabric, of 2,2'-dihydroxy-4,4'- dimethoxybenzophenone in the form of an aqueous dispersion. After the treatment, the fabric is rinsed warm and then cold.

On exposure to LIV irradiation, the treated fabric exhibits a. significantly reduced fluorescence.

EXAMPLE 6

Knitted articles made from PA66texturized yarn are introduced at a goods to liquor ratio of 1:15 into a 25 liquor containing 0.1 % of the dyestuff C.I. Acid Orange 145 and 1.0% of sodium 2,2'dihydroxy-4,4'-dimethoxybenzophenone-5-sulphonic acid salt and adjusted to pH 4.5 with acetic acid.

The % are based on the dry weight of the knitted goods. The temperature of the bath is raised from 60' 30 to 98' at a heating rate of 10C/min while under a constant mechanical agitation and dyeing is continued at 98'for a further 30 minute period. Afterwards the goods are rinsed at 50', then cold rinsed and then dried at 800.

When the dyed articles are washed at a liquor to goods ratio of 30:1 for 30 minutes at 40'with 3 g/1 of a commercially available domestic detergent for fine clothes (Wollana(B), registered Trade Mark, Eswa AG, 35 Switzerland) and then rinsed and dried, no significant alteration of the shade is observed compared with an unwashed article.

Knitted articles are dyed according to the procedure indicated above but in the absence of the benzophenone derivative (LIV-absorber) and then washed with the same domestic detergent under the same conditions as indicated above. When compared with an unwashed article, the washed article exhibits 40 a significant alteration of the shade.

Claims

1. A process for extinguishing at least partially the optical brightening effect produced on a substrate by an optical brightening agent or preventing optical brightening effects from being produced on a substrate by an optical brightening agent, which process comprises the steps of bringing the substrate into contact 45 with an UV-absorber and subsequently fixing the UV-absorber on the substrate, both steps being effected either before or after the treatment of the substrate with the optichl brightening agent.

2. A process according to Claim 1, in which the UV-absorber is selected from benzotriazole derivatives, benzophenone derivatives, benzoic acid derivatives, salicylic acid esters, dibenzoyl benzene derivatives, a-cyanoacrylic acid ester derivatives and benzylidene malodinitriles.

3. A process according to Claim 2, in which the UV-absorber is selected from 2-(2'-hydroxy-phenyl) benzotriazole derivatives, 2-hydroxy-benzophenone derivatives, optionally further substituted in the 2',4',4 and/or 5 positions, resorcinol monobenzoate, 4-Cl-12 alkyl phenyl salicylate, p-di(4-hydroxy-salicyloyl) benzene and 2,4-dibenzoylresorcinol.

4. A process according to Claim 3, in which the UV-absorber is selected from 2-(2'-hydroxy-3'-tert.butyl-5'-methylphenyl)-5-chlorobenzotriazole, 4-chloro-2,2',4'trihydroxybenzophenone, 2,2'-4 trihydroxybenzophenone, 2,4-dihydroxy-4'-methoxybenzophenone, 2,2',4,4'tetrahydroxy-benzophenone, 2,4-dihydroxy-benzophenone and 2-hydroxy-4-methoxy-benzophenone.

4 GB 2 174 731 A 4

5. A process according to any one of the preceding claims in which the UV- absorber is used as an aqueous solution or in the form of an emulsion or dispersion.

6. A process according to any one of the preceding claims in which the UVabsorber is applied to the substrate by exhaustion, impregnation or printing techniques.

7. A process according to any one of the preceding claims, in which the UV-absorber is applied to an 5 optically brightened substrate.

8. A process according to any one of Claims 1 to 6, in which the UVabsorber is applied to the substrate before the optical brightening of the substrate is carried out.

9. A process according to any one of the preceding claims, in which the UV-absorber is applied either before, during or after dyeing or printing the substrate.

10. A process according to any one of the preceding claims, in which the substrate is textile fibres, paper or leather.

11. A process according to Claim 10, in which the substrate is a textile substrate comprising polyester, polyamides or polyacrylonitrile.

12. A process substantially as hereinbefore described, with reference to any one of the foregoing 15 Examples 1 to 6.

13. A substrate having been subjected to the process of any one of the preceding claims.

Printed for Her Majesty's Stationery Office by Courier Press, Leamington Spa. 1111986. Demand No. 8817356. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.