EP0017618A1 - Process for optically brightening polyester fibres by the exhaust process - Google Patents

Abstract

Process for the optical brightening of polyester fibers with a polyester brightener and a shading dye after the pull-out process, the fibers being treated in a brightener dispersion which has a pH of more than 9, preferably between 11 and 13.5.

Description

The present invention relates to a new, improved process for the optical brightening of polyester fibers in the exhaust process with the aid of conventional polyester brighteners with the use of shading dyes.

In bleaching and optical brightening, it is an often practiced method to use violet or blue dyes to improve the bleaching or lightening effect. If such a dye is applied together with an optical brightener, this can serve two different purposes: on the one hand, an increase in the degree of whiteness can be sought by compensating for the yellow portion of the fiber, the color tone produced by the brightener on the fiber being largely retained. On the other hand, a change in the shade of the color tone produced by the brightener on the fiber can be aimed for with said dye, and here too an attempt is made to additionally increase the degree of whiteness. You can use it to set the desired shade of white.

Particularly interesting white effects can be achieved in this way on fiber materials with a high basic whiteness, in which the achievement of a low increase in brightness (whiteness) means a considerable additional effort in the bleaching or lightening process. , 1.25% based on the amount of fluorescent whitening agent to - for shading are employed, small amounts of dye, typically about 0.0025 - 2.5 l _o, preferably 0.025. In terms of process technology, the nuance of continuously producible optical brightenings (for example in the padding thermal process) generally presents no difficulties. The shading, for example with disperse dyes, of optical brightening after the pull-out process, on the other hand, is frequently associated with considerable problems of uniformity. Up to now, the shading of optical brightenings using the pull-out process on polyester fibers has proven to be almost impossible if disperse dyes adapted to the authenticity standard of the brightener were used as shading dyes. The usual lightening, but also the dyeing of polyester fibers after the exhaust process is usually carried out from weakly acidic to neutral baths. In this way, if a shading dye is used in addition to the brightener, very uneven lightenings are obtained, since the dye quickly deposits on the fiber and so the fabric stains too strongly at certain points. Attempts have already been made to counter this disadvantage by adding leveling agents. On the one hand, however, this did not completely solve the problem, and on the other hand the process becomes more uneconomical due to the need to use expensive leveling agents.

A new, improved method has now been found which completely eliminates the disadvantages of the known methods just described.

The process according to the invention for the optical brightening of polyester fibers in the exhaust process by treating the fibers in an aqueous polyester brightener which contains one or more polyester bristles which are stable under the application conditions and which absorbs onto the substrate, and a small amount of a blue to violet disperse dye or mixtures of such dyes as shading dye Dispersion is characterized in that the treatment in said dispersion is carried out at a pH of more than 9.

In principle, there is no need to limit the pH upwards. Also . Amounts of alkali that lead to a pH of over 14 in the dispersion do not affect the levelness of the brightening. An upper limit is at most given for economic reasons. An upper limit of the alkalinity would be given, for example, by the process conditions of the "peeling process" of the polyester material (for example at a concentration of 10-20 g / 1 NaOH).

Preferably the dispersion has a pH between 11 and 14, e.g. between 11 and 13.5, in particular between 11 and 12.5.

The pH is adjusted using a suitable alkaline substance, preferably using alkali metal hydroxides, in particular using KOH, but especially NaOH.

The treatment is carried out in the usual manner at a temperature between room temperature and 140 ° C., in particular between 50 ° and 130 ° C. It is advantageous to deal with the fiber material at a lower temperature (e.g. 50 ° C), whereupon the temperature is increased (e.g. to 120 ° C).

In order to ensure that the brightener is optimally drawn onto the fiber, practice is preferably carried out under high temperature (HTI conditions, that is to say the fibers are treated in a conventional HT dyeing machine above 100 ° C., for example between 100 and 130 ° C, e.g. at 120 ° C.

Another way to make it easier to attach the brightener to the fiber is to add one in the dyeing practice usual carriers to the treatment bath. With carrier addition it is also possible to achieve very good results _/ at lower temperatures, for example below 100 ° C. However, carrier additives can also be used under HT conditions. Suitable carriers are those customary in dyeing practice, for example aromatic hydrocarbons, aromatic halogenated hydrocarbons and esters and ethers of aromatic carboxylic acids. Preferred carriers are dichlorobenzenes and trichlorobenzenes, optionally also diphenyl and mixtures of the substances mentioned.

The duration of the treatment of the textiles in the brightener dispersion can vary within wide limits, but an application duration of at least 20 to 30 ° minutes is advantageous.

The amount of brightener (pure substance) in the dispersion can, depending on the brightener used, vary between 0.002 and 0.5%, based on the material to be lightened.

. The amount of shading dye (pure dye) is, depending on the dye and the desired shade, about 0.0025-2.5%, preferably 0.025-1.25%, based on the amount of brightener (pure substance) used.

The usual polyester brighteners are used as brighteners, which in practice are applied together with shading dyes. These are mostly benzoxazole, stilbene and naphthalimide brighteners.

bzw.

wobei die Ringe A, B und C noch einfache Reste, wie niedere Alkyl-oder Alkoxygruppen oder Chloratome enthalten können, vor allem das 2,5-bis-Benzoxazol-2-yl-thiophen, das 2,5-bis-(5-Methylbenzoxazol-2-yl)-äthylen und das 1,4-bis-Benzoxazol-2-yl-naphthalin; oder der Formel

worin n 0 oder 1 bedeutet und die Ringe A und B weitersubstituiert sein können, z.B. mit Alkyl, Alkoxy, Phenyl, Chlor, Cyano, Carboxy und dessen Derivaten, z.B. die Verbindungen: 4-Phenyl-4'-(5-t-butylbenzoxazol-2-yl) stilben, 4-Phenyl-4'-(5,8-dimethylbenzoxazol-2-yl)stilben, 5,6-Dimethyl-2-(4-methoxycarbonyl-styryl)benzoxazolund 5,6-Dimethyl-2-(4-cyanostyryl) benzoxazol.Of the benzoxazole brighteners, for example bis-benzoxazole, styryl or stilbenyl benzoxazole types are to be mentioned, especially compounds of the formulas

respectively.

rings A, B and C may also contain simple radicals, such as lower alkyl or alkoxy groups or chlorine atoms, especially 2,5-bis-benzoxazol-2-yl-thiophene, 2,5-bis- (5- Methylbenzoxazol-2-yl) ethylene and 1,4-bis-benzoxazol-2-yl-naphthalene; or the formula

in which n denotes 0 or 1 and the rings A and B can be further substituted, for example with alkyl, alkoxy, phenyl, chlorine, cyano, carboxy and their derivatives, for example the compounds: 4-phenyl-4 '- (5-t-butylbenzoxazole -2-yl) stilbene, 4-phenyl-4 '- (5,8-dimethylbenzoxazol-2-yl) stilbene, 5,6-dimethyl-2- (4-methoxycarbonyl-styryl) benzoxazole and 5,6-dimethyl-2 - (4-cyanostyryl) benzoxazole.

bzw.

worin die Ringe A, B und C verschiedene Substituenten tragen können, wie z.B. Alkyl, Alkoxy, Chlor, Cyano, Carboxy und dessen Derivate usw., zu erwähnen, insbesondere die Verbindungen 2-Cyano-4-(naphtho[1,2-d]v-triazol-2-yl-)-4'chlorstilben, 4-(Naphtho[1,2-d]v-triazol-2-yl)-4'-methoxycarbonylstilben, sowie 1,4-bis-(2-Cyanostyryl)benzol.Of the stilbene brighteners are those of the formulas

respectively.

in which the rings A, B and C can carry different substituents, such as alkyl, alkoxy, chlorine, cyano, carboxy and its derivatives etc., to mention, in particular the compounds 2-cyano-4- (naphtho [1,2-d ] v-triazol-2-yl -) - 4'chlorstilbene, 4- (naphtho [1,2-d] v-triazol-2-yl) -4'-methoxycarbonylstilbene, and 1,4-bis- (2- Cyanostyryl) benzene.

worin R und R₂ Wasserstoff oder Alkoxy bedeuten, zu erwähnen, insbe- so_ndere solche, worin R₁ Wasserstoff und R₂ Methoxy bedeuten oder worin R und R₂ jeweils für Aethoxy stehen.Of the naphthalimide brighteners are those of the formula

wherein R and R ₂ is hydrogen or alkoxy, to mention, in particular as _n particular those wherein R ₁ is hydrogen and R ₂ is methoxy or wherein R and R ₂ are each ethoxy.

worin die Benzolringe A gegebenenfalls substituiert sein können, z.B. durch Alkyl, Alkoxy, Halogen usw. Besonders gut eignen sich dabei solche Farbstoffe,deren Benzolringe A unsubstituiert sind oder in para-Stellung mit Chlor oder Methoxy substituiert sind.Blue to violet disperse dyes are used as shading dyes, which of course must be suitable for treatment in an alkaline liquor. Acylaminoanthraquinone dyes are preferably used, in particular those of the formula

in which the benzene rings A can be optionally substituted, for example by alkyl, alkoxy, halogen etc. Dyes whose benzene rings A are unsubstituted or substituted in the para position with chlorine or methoxy are particularly suitable.

In addition to the optical brightener (s) and the shading dye (s), the aqueous dispersion advantageously also contains one or more dispersants and, if appropriate, wetting agents, stabilizers and / or other customary dyeing auxiliaries.

Suitable dispersants include: alkali metal salts, especially sodium salts of alkyl or alkylarylsulfonic acids and carboxylic acids, alkali metal salts, especially sodium salts of condensation products from arylsulfonic acids with formaldehyde, macromolecular substances which are suitable for liquefying and dispersing, carboxy latex of the polymerized maleic acid or polymerized acrylic acid type and copolymers of maleic acid with allyl acetate. The following may be mentioned as examples of such dispersants: lauryl sulfate Na salt, oleyl sulfate Na salt, oleyl sulfate diethanolamine salt, benzylnaphthalenesulfonic acid Na, di- (2-sulfo-l-naphthyl) methane di-Na salt, m-xylenesulfonic acid Na, dodecylbenzenesulfonic acid Na Na salt, dodecylbenzenesulfonic acid, diethanolamine, diisopropylnaphthalenesulfonic acid Na, di-n-butylnaphthalenesulfonic acid Na, n-propyl-n-hexylnaphthalenesulfonic acid Na, N-oleylmethyl taurine Na salt, Na salt of the condensation product of naphthalenesulfonic acid and formaldehyde acid formaldehyde , Banzolsulfonic acid Na salt, cumene sulfonic acid Na salt, toluenesulfonic acid Na salt, oxyethylated resin bodies, N-polyvinylpyrrolidone, sulfite cellulose waste liquor (CaO-free), starch ether and polysaccharides. However, particularly preferred dispersants are nonionogenic, water-soluble ethoxylated or propoxylated fatty alcohols and alkylphenols and fatty alcohol polyglycol ethers, for example alkanals, alkenols (C ₈ -C ₂₂ ) with different amounts of ethyleneoxy or propyleneoxy groups, alkyl or arylpolyglycol ethers with up to 50 ethyleneoxy or propylene ygruppen _ox, such as octyl, nonyl or Dodecylphenolpolyglykoläther.

The individual components can be introduced separately into the treatment bath, which is already alkaline or is only then adjusted to the desired pH.

However, there is preferably a concentrated, storage-stable stock dispersion of the optical brightener (s) and the shading dye (s). Such dispersions contain brightener and dye in the desired ratio. They are prepared by introducing the brightener and dye, preferably together with a dispersant, into a small amount of water. It is advantageous if this dispersion is subjected to grinding (for example in a ball mill) in order to achieve particle sizes of less than 10 μm, preferably less than 2 μm to obtain.

A part of this stock dispersion can then be introduced (calculated on the desired amount of brightener in the bath) into the treatment bath, which may also contain a dispersant and / or other auxiliaries. After the desired pH has been set, polyester fibers in the form of yarn, woven fabric, etc. can be treated with the dispersion thus obtained in the corresponding dyeing apparatus.

If a chlorite-resistant shading dye was used, the bleaching bath can then be bleached directly. Sodium chlorite is preferably added to the liquor, the alkaline bath is acidified and then heated to about boiling temperature.

In the present application, "polyester fibers" naturally also include polyester fibers in blended fabrics, e.g. to be understood in mixed fabrics polyester / cotton. The nuanced lightening of such blended fabrics by the process according to the invention can also be advantageous with the lightening of the cotton portion, with the bleaching (e.g. with peroxide) and / or the various customary finishing and finishing processes (e.g. crease-resistant, wash and wear, soft handle and other equipment) can be combined.

The following examples serve to explain the process according to the invention in more detail, but without restricting it to them.

Example 1: a) Preparation of a brightener stock dispersion

werden mit 20 mg des violetten Pigmentfarbstoffes der Formel

versetzt, zusammen mit 20 g eines Anlagerungsproduktes von 35 Aethylenoxidgruppen an 4-Nonylphenol in 40 ml Wasser gegeben, gemischt und mit 50 g Quarzkugeln von 1 mm Durchmesser in einer Kugelmühle während ca. 24 Stunden gemahlen. In der resultierenden Dispersion haben die Teilchen einen Durchmesser von ≦ 2um . Die Dispersion wird von den Quarzkugeln durch Filtration durch ein engmaschiges Sieb abgetrennt und mit einer Lösung von 1 g Carboxymethylcellulose in 19 ml Wasser versetzt. Man erhält eine lagerstabile Dispersion.20 g of the optical brightener of the formula

with 20 mg of the purple pigment of formula

added, added together with 20 g of an adduct of 35 ethylene oxide groups to 4-nonylphenol in 40 ml of water, mixed and ground with 50 g of quartz balls of 1 mm in diameter in a ball mill for about 24 hours. In the resulting dispersion, the particles have a diameter of ≦ 2 µm. The dispersion is separated from the quartz spheres by filtration through a close-meshed sieve and a solution of 1 g of carboxymethyl cellulose in 19 ml of water is added. A storage-stable dispersion is obtained.

b) brightening

0.4 g of the stock dispersion described under a) and 0.2 g of a dispersant (adduct of 35 ethylene oxide groups on stearyl alcohol) are processed into a dispersion with 400 ml of water and the latter is made alkaline with 0.8 ml of NaOH 30%.

40 g of polyester staple fabric (washed and heat-set at 180 ° C for 20 seconds) are evenly formed as a fabric tape of approx. 250 x 12 cm sig wound on bobbin tubes and treated in an HT dyeing machine with the dispersion just described. The fleet had an initial pH of 11.5. At the start of the treatment, the temperature is 50 ° C, then the mixture is heated to 130 ° C within 30 minutes and then left at this temperature for 30 minutes. The mixture is then cooled to 70 ° C., the liquor is drained off, the fabric is rinsed twice warm and dried in a drying cabinet at 80 ° C. for 5 minutes.

The lightened fabric has a high degree of whiteness with perfect levelness.

Comparison:

For comparison purposes, the experiment is repeated, but not 0.8 ml of NaOH 30%, but 0.2 ml of acetic acid 80% are added to the dispersion (pH of the liquor: 5.5). In this way, the brightening is carried out according to the conventional method. After drying, a fabric is obtained which is very uneven and therefore unusable. The shading dye is largely deposited in the inner part of the ribbon.

Example 2: Analogously to Example 1 a), 20 g of the brightener of the formula

und 20 mg des Pigmentfarbstoffes der Formel

eine stabile Dispersion bereitet.

and 20 mg of the pigment dye of the formula

prepares a stable dispersion.

As described in Example 1b), 0.4 g of this stock dispersion is processed into a liquor (pH approx. 11.5) and thus 40 g of polyester staple fabric is lightened in the manner given there.

The treated fabric also has a high degree of whiteness with perfect levelness.

Example 3: The procedure is completely analogous to Example 2, but a mixture of the two compounds of the formulas is used as brightener

und

so kommt man ebenfalls zu einem stark aufgehellten Polyestergewebe von einwandfreier Egalität.

and

so you also get a highly lightened polyester fabric of perfect levelness.

Example 4: If example 2 is repeated, but the polyester brightener used is that of the formula

ein, so erhält man ebenfalls ein stark aufgehelltes Polyestergewebe von ausgezeichneter Egalität.

a, you also get a highly lightened polyester fabric of excellent levelness.

Example 5: 0.4 g of the stock dispersion described in Example 1a) and 0.2 g of a dispersant (adduct of 35 ethylene oxide groups with stearyl alcohol) are processed into a dispersion with 400 ml of water and the latter is alkaline with 0.8 ml of NaOH 30% made.

40 g of polyester staple fabric (washed and heat-set at 180 ° C. for 30 seconds) are wound evenly onto bobbin tubes as a fabric tape of approx. 250 x 12 cm and treated with the dispersion just described in an HT dyeing machine. The fleet had an initial pH of 11.5. The fabric is introduced at 50 ° C. and the liquor is heated to 120 ° C. in 30 minutes, treated at this temperature for 15 minutes, cooled to 70 ° C., 0.8 g of sodium chlorite 80% is added and the liquor is made up with 1 , 4 ml of formic acid 85% to a pH of 3-4. The mixture is heated to about 100 ° C. in 20 minutes, treated at this temperature for 30 minutes, then the liquor is drained off, rinsed and dried. The piece of fabric is immaculate and shows _. a high degree of whiteness.

Example 6: In Examples 1 to 5, the respective dye is replaced by the same amount of the dye of the formula

und verfährt ansonsten genau nach den dort angegebenen Vorschriften, so erhält man ebenfalls jeweils Polyestergewebe von hohem Weissgrad und einwandfreier Egalität.

and otherwise proceeds exactly according to the regulations given there, you also get polyester fabrics with a high degree of whiteness and perfect levelness.

Claims (10)

1. Process for the optical brightening of polyester fibers in the exhaust process by treatment of the fibers in an aqueous polyester brightener which is stable under the application conditions and is drawn onto the substrate and a small amount of a blue to violet disperse dye or mixtures of such dyes as a shading dye, characterized in that the treatment is carried out in said dispersion at a pH of more than 9. 2. The method according to claim 1, characterized in that the dispersion has a pH between 11 and 14, in particular between 11 and 12.5. 3. The method according to claim 1, characterized in that the shading dye is used in an amount of 0.025 to 1.259, based on the polyester brightener used. 4. The method according to claim 1, characterized in that a conventional benzoxazole, e.g. a bis-benzoxazole, styryl or stilbenyl benzoxazole, a triazolyl or styryl. stilbene or a naphthalimide - polyester brightener or mixtures of these brighteners are used. 5. The method according to claim 1, characterized in that a blue to violet dye from the class of acylaminoanthraquinones is used as the shading dye. 6. The method according to any one of claims 1 to 5, characterized in that the dispersion contains, in addition to the brightener and the shading dye, one or more conventional dispersants and, if appropriate, wetting, stabilizing and other conventional dyeing auxiliaries. 7. The method according to any one of claims 1 to 5, characterized in that from a concentrated stock dispersion which contains the optical brightener, the shading dye and a dispersant, the particle size being less than 2 µm, a proportion is introduced into a bath which contains a dispersant and was adjusted to the desired pH with NaOH, and treated with the bath obtained polyester fabric in the usual manner. 8. The method according to claim 1, characterized in that the fabric is then bleached in the same bath, preferably with sodium chlorite. 9. The method according to claim 1, characterized in that the treatment of the polyester fibers with the alkaline brightener dispersion is carried out under high temperature (HT) conditions. 10. The method according to claim 1, characterized in that the alkaline brightener dispersion contains a carrier customary in dyeing practice.