CN1860269A - Method for the preliminary treatment of cellulose-containing textile - Google Patents

Abstract

Disclosed is a method for the preliminary treatment of cellulose-containing textile, comprising the following steps: a) cellulose-containing textile is treated with a polymer or copolymer solution obtained by (a1) polymerizing or copolymerizing N-vinylamide of general formula (I), wherein R is selected among hydrogen and C1-C10 alkyl, and (a2) optional partial hydrolysis, b) the treated textile is optionally dried, and c) at least some of the amide groups are saponified. At least one of steps (a2) and (c) is carried out.

Description

Method for pretreatment of cellulose-containing fabrics

The present invention relates to a kind of method of pretreatment cellulosic fabric, it comprises the following steps:

(a) Treatment of cellulosic fabrics with solutions of polymers or copolymers obtainable by:

(a1) polymerizing or copolymerizing N-vinylamides of general formula I:

in

R is selected from hydrogen and _C1 to _C10 alkyl, and

(a2) if appropriate, partial hydrolysis,

(b) optionally drying the treated fabric, and

(c) optionally saponifying all or some of the amide groups,

wherein at least one of steps (a2) and (c) is carried out.

Cellulose fabrics can be dyed in a variety of ways. At present, reactive dyes, vat dyes or direct dyes are usually used for dyeing. However, unsatisfactory dye uptake (ie the fraction of the dyestuff transferred from the dyeing liquor to the fabric) and dyeing fastness are often observed.

Reactive dyes in particular often yield dye uptakes well below 80%. One reason is that in many cases the reaction system of the dye has not achieved sufficient reaction with the OH groups of the cellulose. The remaining dye usually goes to wastewater treatment plants.

A particular reason why the color fastnesses are often unsatisfactory is that not all dyes are sufficiently fixed. In use with fabrics, it has been observed that unfixed dye washes out when the consumer launders. If the chemical bond between reactive dyes and fibers is broken during routine laundering operations, even apparently well-fixed dyes can be washed away, discoloring washed fabrics and staining adjacent fabrics.

Currently, dyed fabrics are usually treated with cationic after-treatment agents to especially increase the fastness of dyeing with reactive dyes, but this leads to additional steps during dyeing or in the finishing stage and thus increases costs.

It has also been suggested to apply cationic after-treatments as well as polyvinylamine to cellulosic fabrics prior to the actual dyeing operation. This application can significantly enhance the dyeing (Bunt-Denim, TI/T 240d, July 1993, BASF Aktiengesellschaft), but in many cases this leads to undesired ring dyeing, in which all or some fibers are only on the surface and not Not evenly stained across the entire section. When coarsely dyed fibers are subjected to mechanical stress, the dye tends to be removed mechanically and the fibers quickly take on an undesirable appearance.

It is therefore an object of the present invention to provide a method for the pretreatment of fabrics which avoids the disadvantages of the prior art and which, more particularly, provides uniformly through-dyed fabrics. Another object of the present invention is to provide a method whereby fabrics can be dyed without leaving an excessive salt load on the dyeing liquor to be treated.

We have found that these objects can be achieved by the methods defined at the beginning of this paper.

Cellulosic fabrics within the scope of the present invention refer to cellulose fabric fibers, cellulose fabric intermediates and final products and final parts made thereof, which include, for example, carpets and other household fabrics and Fabric structure for industrial purposes. They also include unformed structures (e.g. staple fibers), linear structures (e.g. twine, filament, yarn, long hemp, doubling, lace, rolls, ropes, threads) and three-dimensional structures (e.g. felt, woven, non-woven and stuffing). The cellulosic fabric can be a natural fabric (eg cotton, wool or linen) or a blend (eg cotton-polyester, cotton-polyamide), the size of the cellulose fraction is not critical.

The present invention involves treating cellulosic fabrics in step (a) with a polymer or copolymer solution obtainable by:

(a1) polymerizing or copolymerizing N-vinylamides of general formula I:

wherein R is selected from branched or preferably unbranched _C1 to _C10 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl , n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isopentyl, n-hexyl, isohexyl, sec-hexyl, n-heptyl, n-octyl, 2- Ethylhexyl, n-nonyl, n-decyl; more preferably unbranched _C1 to _C4 alkyl, such as methyl, ethyl, n-propyl, n-butyl; especially hydrogen.

and (a2) if appropriate, partial hydrolysis.

A particular embodiment of the invention utilizes copolymers obtainable by copolymerization of N-vinylamides of general formula I with at least one suitable comonomer, wherein the copolymers may be random copolymers, block Copolymers and especially graft copolymers. Suitable comonomers include, for example, methacrylates/salts such as methyl acrylate, methyl methacrylate, ethyl acrylate, N-vinylpyrrolidone, N-vinylimidazole, ethyl methacrylate, ethylene, Propylene, 1-butene or 1,3-butadiene.

In a particular embodiment, the copolymer obtainable by copolymerization of N-vinylamides of general formula I with at least one suitable comonomer comprises at least 20% by weight of the copolymer, preferably at least 30% by weight of N-vinyl amides of general formula I.

A particular embodiment of the invention utilizes copolymer solutions obtainable by copolymerization and optional subsequent partial hydrolysis of:

20 to 90% by weight of N-vinylamides of general formula I, and

10 to 80% by weight of comonomers selected from N-vinylpyrrolidone and N-vinylimidazole,

In each case, they are measured in percent by weight, based on the copolymer used.

A particular embodiment of the invention utilizes copolymer solutions obtainable by copolymerization and optional subsequent partial hydrolysis of:

20 to 80% by weight of N-vinylamides of the general formula I,

10 to 70% by weight of N-vinylpyrrolidone, and

10 to 70% by weight of N-vinylimidazole,

In each case, they are measured in percent by weight, based on the copolymer used.

Another embodiment of the invention utilizes a copolymer solution formed from at least two different monomers of general formula I, wherein the copolymer may be a random copolymer, a block copolymer and especially a graft copolymer.

A preferred embodiment of the invention utilizes a homopolymer solution of N-vinylformamide.

A particular embodiment of the invention utilizes in step (a) polymers or copolymers whose molecular weight M _W is between 10,000 and 1,000,000 g/mol, and preferably between Between 30,000 and 400,000 g/mol.

A particular embodiment of the present invention utilizes in step (a) polymers or copolymers obtainable by polymerizing or copolymerizing N-vinylamides of general formula I followed by e.g. dilute alkali metal hydroxide Aqueous or dilute alkali metal carbonate solution or dilute aqueous acid (eg phosphoric or sulfuric acid) partially hydrolyzes the amide groups, wherein, for example, 60 mol % or 30 mol % or 10 mol % of all amide groups are hydrolyzable.

A particular embodiment of the invention utilizes polymers or Aqueous solutions of copolymers.

A particular embodiment of the invention utilizes 0.1% to 10% by weight, preferably 2% to 8% by weight, based on the cellulosic fabric, of a partially hydrolyzed polymer or copolymer, which can be obtained by Obtained by the polymerization or copolymerization of N-vinylamides of general formula I.

Step (a) may be carried out one or more times within the scope of the present invention. In this connection, different polymers or copolymers can be used, at least one of which is obtainable by polymerization or copolymerization of N-vinylamide. However, it is also possible to use the same polymers or copolymers as are obtainable by polymerization or copolymerization of N-vinylamides and, if appropriate, partial hydrolysis.

The treatment in step (a) can be carried out, for example, by exhaust or pad dyeing.

In order to carry out step (a) by exhaust dyeing, the cellulosic fabric to be pretreated can be drawn through a preferably aqueous dyeing liquor comprising a polymerized or co-polymerized N-vinylamide of the general formula I. A solution of a polymer or copolymer obtained by polymerization. The cellulosic fabric to be pretreated is then pulled through rollers to squeeze out excess solution.

To carry out step (a) by padding, conventional machines can be used. Preference is given to a pad dyeing machine, the basic components of which are two rollers in pressing contact with each other, through which the cellulosic fabric to be pretreated is drawn. A dye liquor containing a polymer or copolymer solution obtainable by polymerization or copolymerization of N-vinylamides of general formula I is injected over the rollers and wets the fabric. The pressure squeezes out the fabric and ensures a constant liquid delivery. Another form of pad dyeing employs one or more dipping tanks through which the cellulosic fabric to be treated is drawn. The fabric then passes through a pad dyeing machine where excess solution is squeezed out.

In a specific embodiment of the present invention, the pretreatment in step (a) is carried out in the presence of at least one color fixing agent. Examples of suitable fixatives include the following:

Urea-formaldehyde adducts and melamine-formaldehyde adducts, if appropriate in combination with inorganic salts (e.g. MgCl ₂ 6H ₂ O or NH ₄ Cl), especially whose hydroxyl groups can be partially or quantitatively etherified with e.g. methanol Urea-formaldehyde-glyoxal condensate,

Condensates of N,N'-dimethylurea and glyoxal,

Isocyanates and/or their dimers or trimers, for example, 4,4'-methylene(diphenylisocyanate) (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate, Free in each case or blocked by 3,5-dimethylpyrazole, acetone oxime or sec-butylketone oxime, for example, especially trimerhexamethylene diisocyanate and trimeric isophorone diisocyanate Isocyanates, in each case free or blocked. Examples can be seen in EP-B 0206059,

Di-, tri- and polyepoxides selected from polyamines, diamines, polyols, diols which react with e.g. epichlorohydrin,

oligomeric carbodiimide (oligomeric carbodiimine),

Dialdehydes and trialdehydes, such as glutaraldehyde, glyoxal, dextran polyaldehyde, and starch aldehyde, prepared according to, for example, US 2001-0025102 A1;

Epoxy silanes, prepared according to for example DE 3528006 and DE 4128894,

polyalkoxycarbonylamino derivatives,

and aziridine compounds such as trimethylolpropane tris(β-aziridinyl)propionate.

Particularly preferred di-, tri- and polyepoxides are:

However, z is an integer of 0 to 10 in each case.

Step (a) may be followed by a step (b) in which the fabric treated according to step (a) is dried. This optional drying (b) can be carried out in customary apparatus (for example drying cabinets) or in the open air. The temperature is more suitable in the range of 30°C to 120°C, preferably 70°C to 110°C. Drying times typically depend on the drying temperature and the desired residual moisture content and can range from 30 seconds to 3 hours, although longer or shorter times are also possible.

If step (a) is carried out more than once, drying can be carried out after each treatment step (a), or preferably only after the last treatment step (a).

Optional step (c) of the process of the invention comprises saponifying some or all of the amide groups. Said amide groups are the amide groups of polymers or copolymers obtainable by polymerization or copolymerization of N-vinylamides of general formula (I), applied to the fabric according to step (a).

Within the scope of the present invention, at least one of steps (a2) and (c) is carried out. In other words, cellulosic fabrics may be treated with partially hydrolyzed polymers or copolymers of N-vinylamides of general formula I without carrying out step (c), or step (c) may be carried out omitting the partial hydrolysis according to (a2) .

A particular embodiment of the invention consists in: treating cellulosic fabrics with a solution of polymers or copolymers obtainable by polymerization or copolymerization of N-vinylamides of general formula I and partial hydrolysis according to step (a2); any Optionally, drying according to step (b); and then saponifying some or all of the amide groups according to step (c).

A specific embodiment of the present invention comprises step (c) carried out as follows: use dilute alkali metal hydroxide aqueous solution or alkali metal carbonate aqueous solution (preferably use sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate or potassium carbonate solution ) to the treated and if appropriate dried fabric. A suitable concentration is, for example, between 0.5% and 10% by weight, and preferably between 2% and 5% by weight.

In a specific embodiment, step (c) is carried out at a temperature between room temperature and 90°C, and preferably between 70 and 90°C.

The pressure conditions of step (c) are not critical, since it can be carried out, for example, at atmospheric pressure, but also at a pressure of, for example, 1.1 bar to 10 bar.

Step (c) can be carried out in a continuous manner or in a batch manner.

Step (c) generally involves saponifying at least part of the amide groups.

A particular embodiment of the invention comprises saponifying one third or more, preferably 90 mole % or more, more preferably 95 mole % or more, of the amide groups of the polymer or copolymer from step (a).

A particular embodiment of the present invention consists in saponifying the amide groups of the polymer or copolymer from step (a) in a quantitative manner.

It should be understood that the scope of the present invention also encompasses the implementation of a neutralization step after step (c), preferably with an organic acid such as citric acid, tartaric acid, adipic acid or succinic acid. Similarly, it is within the scope of the present invention that step (c) may be followed by a washing and drying step.

If the pretreatment according to the invention is carried out in the presence of one or more fixing agents, a fixing step (d), for example a thermal fixing step, is preferably carried out after the pretreatment. For example, color fixing may be performed at a temperature of 150° C. to 190° C. for 30 seconds to 5 minutes. The color-fixing step (d) is suitable on all color-fixing and drying devices customary in the textile industry, such as tenter frames and, for example, drying ovens using, for example, circulating air.

Another aspect of the invention provides a cellulosic fabric pretreated by the method of the invention. It is especially suitable for the production of dyed fabrics. A further aspect of the invention therefore provides the use of cellulosic fabrics which have been pretreated according to the invention for the production of dyed fabrics.

Another aspect of the present invention provides a method for producing dyed fabrics, hereinafter referred to as the inventive dyeing method. The dyeing process according to the invention, starting from cellulose fabrics which have been pretreated according to the invention, comprises at least one dyeing step using at least one of reactive, vat or direct dyes, the choice of which is not critical .

The dyeing process according to the invention can be carried out, for example, at atmospheric pressure or at a pressure of 1.1 to 20 bar. The dyeing process according to the invention is preferably carried out at atmospheric pressure.

The dyeing method of the present invention can be carried out under pressure from, for example, room temperature to 100°C, and a temperature of 50 to 90°C is preferred. When carrying out the dyeing process according to the invention at a pressure of 1.1 to 20 bar, the temperature can be between 100 and 130°C.

The dyeing method of the present invention can be carried out in aqueous dyeing liquor, in this case, the liquor ratio and concentration of reactive dyes, vat dyes or direct dyes can be of the order of magnitude of conventional dyeing factories.

In a specific embodiment of the dyeing process according to the invention, the dyeing liquor can be admixed with customary amounts of inorganic salts, such as alkali metal salts or alkaline earth metal salts, such as halides, carbonates or sulfates, preferably NaCl or _{Na2SO 4} . Usual amounts of inorganic salts may be, for example, 60 to 80 g/l of dyeing liquor.

In a preferred embodiment of the invention, the dyeing liquor contains 0 to 20 g/l of inorganic salts (eg NaCl or Na ₂ SO ₄ ), in particular up to 15 g/l.

It can be observed that the dye uptake rate of the staining solution is increased. Cuts made on fabrics dyed according to the invention showed even through dyeing with little ring dyeing. The colors of fabrics dyed according to the invention remain bright after prolonged mechanical wear and repeated washings. In addition, even without using high-salt dyeing solution, good dyeing effect can still be obtained.

It is to be understood that the scope of the present invention encompasses the post-treatment steps customary in dyeing technology carried out after the actual dyeing step; examples of which are post-dipping steps, washing steps, drying steps and finishing steps.

Practice of the dyeing process of the present invention provides novel dyed cellulosic fabrics, which is also an aspect of the present invention.

The dyed cellulosic fabrics according to the invention are particularly useful for producing brightly colored and strong base fabrics such as trousers, which retain their bright colors after mechanical stress and repeated washing.

The present invention is illustrated by practical examples below.

Examples 1 to 16 and Comparative Example V1

1. Substances used

1.1 Preparation of poly-N-vinyl formamide (homopolymer)

Preparation of poly-N-vinylformamide by free radical polymerization, see "Kinetics and modeling of free radical polymerization of N-vinylformamide", L.Gu, S.Zhu, A.N.Hrymak, R.H.Pelton, Polymer 2001, 42, 3077.

Subsequently, hydrolysis, more precisely partial hydrolysis, was carried out at 80° C. using a 25% by weight aqueous solution of sodium hydroxide.

Molecular weights were determined by gel permeation chromatography (GPC) using polystyrene standards. The degree of hydrolysis is measured by titration.

Table 1: An exemplary overview of poly-N-vinylformamides used in step (a) of the pretreatment process according to the invention polyvinyl formamide Hydrolyzed amide groups after step (a2) [mol%] M _W [g/mol] P1 0 30 000 P2 10 400 000 P3 30 400 000 P4 60 400 000 P5 0 400 000

1.2. Preparation of N-vinylformamide copolymers

Prepare P7

To a 2-liter three-necked flask were added 550 grams of distilled water and 34 grams of N-vinylimidazole, and the initial charge was heated to 75°C. During 2 hours of stirring, a mixture of 138.8 g of N-vinylformamide and 170 g of N-vinylpyrrolidone was added dropwise. At the same time, a solution of 1.7 g of azobisisobutyronitrile dissolved in 100 g of distilled water was added dropwise. After 3 hours, the addition of the azobisisobutyronitrile solution and the mixture of N-vinylformamide and N-vinylpyrrolidone was stopped. Stirring was continued at 75°C for 2 hours, resulting in a clear colorless viscous solution. M _W (GPC): 620000 g/mol, solids content: 20.1% by weight.

The above procedure was followed for the preparation of P6, P8 and P9, the total amount of comonomer in each case was 342.8 g, N-vinylimidazole was included in the initial charge in each case, and N-vinyl imidazole was added in all cases Nylformamide and/or N-vinylpyrrolidone comonomers. Molecular weights are given in Table 1a.

The copolymers discussed are all random copolymers.

Table 1a: An overview of examples of poly-N-vinylformamide copolymers used in step (a) of the pretreatment process of the present invention polyvinyl formamide copolymer Comonomer [wt%] M _W [g/mol] VFA NVP NVI P6 80 - 20 580000 P7 40 50 10 620000 P8 90 - 10 590000 P9 20 40 40 610000

Abbreviations: NVFA: N-vinylformamide, NVP: N-vinylpyrrolidone, NVI: N-vinylimidazole

In each case, weight percents are based on the total mass of the poly-N-vinylformamide copolymer.

P8 was used as an aqueous solution with a solids content of 19.7% by weight, and P9 was used as an aqueous solution with a solids content of 25.1% by weight.

1.3. Dyes used

Dye 1: Hexasodium salt of the following dyes:

Dye Mixture 2: 33.3% by weight each of the following dyes:

Dye Index Reactive Yellow 208,

Dye Index Reactive Red 268,

Dye index reactive blue 263.

Dye Mixture 3: 33.3% by weight each of the following dyes:

Dye Index Reactive Orange 84,

Dye Index Reactive Red 141,

Dye Index Reactive Blue 160.

Dye 4:

Dye index reactive blue 71.

Dye 5:

octasodium salt of

Dye 6: Pentasodium salt of

1.4 Fixing agent used

Fixing agent F1: Trimeric hexamethylene diisocyanate modified by methyl polyethylene glycol, prepared according to Examples 1 and 2 of EP-B0206059, is dissolved in propylene carbonate at a concentration of 70% by weight solution. In each case, the amounts used are based on the entire solution.

Color Fixing Agent F2: Trimethylolpropane Tris(β-Aziridinyl) Propionate

II. The present invention uses poly-N-vinyl formamide to pretreat cellulosic fabric and the general scheme of drying

II.1 General scheme of the present invention for pretreatment of cellulosic fabrics using poly-N-vinylformamide

According to Tables 1 and 2 X grams of poly-N-vinylformamide were dissolved in 100 ml of water. The resulting polymer solution was then used on a pad dyeing machine (available from Mathis, model HVF12085) to saturate cellulosic fabric (100% cotton fabric, fabric basis weight 160 g/cm2, bleached, ready for dyeing). The fiber dosing amount is between 50% and 85% by weight based on the fiber weight. Subsequently, the fabric was dried at 80° C. for 5 minutes.

The fabric treated according to the invention was then treated with a 3 g/l aqueous solution of sodium hydroxide at 70°C at a liquor ratio of 20:1, followed by two washes with 25°C water, followed by washing with 1.5 g/l lemon An aqueous acid solution was used for neutralization (20:1 liquid ratio each time and treatment at 30° C. for 10 minutes). The fabrics treated according to the invention were dried in a circulating air drying cabinet at 95°C.

A comparative example was carried out according to the above scheme, but no poly-N-vinylformamide was used.

II.2 General protocol for dyeing pretreated cellulosic fabrics from II.1

Prepare an aqueous stain using 1 g/L reactive dye, 1 g/L 1-hydroxymethylenebisphosphonic acid, 1 g/L sodium p-nitrobenzenesulfonate, and 60 g/L sodium chloride and water liquid. 10 grams of fabric pretreated according to the invention were placed in 100 ml of dyeing liquor and transferred to a dyeing tank. The staining jar was sealed and placed in a staining apparatus (Ahiba Labomat) preheated to 50°C. It was then heated to 82°C over 15 minutes and dyed for an additional 30 minutes at 82°C. The dyeing tank was then removed _from the dyeing bath, opened and the dyeing liquor was mixed with 1.5 g of _Na2CO3 , dissolved in 10 ml of water and homogenized. The dyeing jar was then sealed, placed in the dyeing apparatus and kept at 82°C for an additional 60 minutes to fix the dye. It is then cooled to about 30°C for 5 minutes, at which point the dyeing tank is opened and the fabric dyed according to the invention is taken out and washed under running water at 60 to 70°C for 5 minutes.

After washing, the fabric dyed according to the invention was soaped with a solution of 2 g/l sodium polyacrylate (M _W 70000 g/mol) pH 8.5 at a liquor ratio of 10:1 at 98° C. for 15 minutes. It was then washed under running water at 60 to 70°C for 5 minutes, then at 20 to 35°C for a further 5 minutes, and thereafter dried at 80°C for 20 minutes in a circulating air drying cabinet.

Inventive dyed fabrics according to Examples 1 to 16 (Table 2) and a control fabric according to Comparative Example V1 were thus produced. The inventive fabrics of Examples 1 to 16 exhibit vivid dyeing. Shearing revealed that these fabrics, unlike those of the control fabrics of Comparative Example VI, were evenly through dyed and no ring dyeing occurred.

Table 2: Results of the inventive pretreatment method, the inventive dyeing method using dye 1 and the comparative experiment (V1) Example number V1 1 2 3 4 Poly-N-vinyl formamide - P1 P1 P1 P1 Dosage X [g] - 0.625 1.25 2.5 5.0 Fiber liquid absorption (weight%) - 80 80 80 80 Washing fastness (ISO 105 C03) 4 to 5 5 5 5 5 Chromaticity (V1=100%) 100 nd nd nd 135.1

Table 2 (continued) Example number 5 6 7 8 Poly-N-vinyl formamide P2 P2 P2 P2 Dosage X [g] 0.625 1.25 2.5 5.0 Fiber liquid absorption (weight%) 80 80 80 80 Washing fastness (ISO 105 C03) 4 to 5 4 to 5 5 5 Chromaticity (V1=100%) nd nd nd 137.2

Table 2 (continued) Example number 9 10 11 12 Poly-N-vinyl formamide P3 P3 P3 P3 Dosage X [g] 0.625 1.25 2.5 5.0 Fiber liquid absorption (weight%) 80 80 80 80 Washing fastness (ISO 105 C03) 5 4 to 5 5 5 Chromaticity (V1=100%) nd nd nd 139.0

Table 2 (continued) Example number 13 14 15 16 polymer P4 P4 P4 P4 Dosage X [g] 0.625 1.25 2.5 5.0 Fiber liquid absorption (weight%) 80 80 80 80 Washing fastness (ISO 105 C03) 4 to 5 5 5 5 Chromaticity (V1=100%) nd nd nd 135.6

n.d.: not determined

Table 2 (continued) Example number 17 18 19 20 twenty one Poly-N-vinyl formamide P5 P5 P5 P5 P5 Dosage X [g] 5.0 5.0 5.0 5.0 5.0 Dye/Dye Mix No. 2 3 4 5 6 Amount of dye/dye mixture [wt%] 6 6 2 2 2 Washing fastness (ISO 105 C03) 4 to 5 5 5 4 to 5 5 Fiber absorbency [wt%] 80 80 80 80 80 Washing fastness (ISO 105 C03) 4 to 5 5 5 4 to 5 4 to 5 Chroma[%] 108 112 108 106 107

In each case, the shade of the dyed fabric sample without polymer pretreatment was set at 100%.

III. General scheme of the present invention for pretreatment of cellulosic fabrics using poly-N-vinylformamide copolymerization

III.1 Pretreatment according to the invention without color fixing agent

50 g of poly-N-vinyl formamide copolymer and 50 g of the aqueous solution of poly-N-vinyl formamide copolymer in Table 1a were supplemented with water to prepare 1000 ml of dyeing solution. Subsequently, cellulosic fabric (100% cotton fabric, fabric basis weight 160 g/m2, bleached and ready for dyeing) was impregnated with the dye liquor thus obtained using a pad dyeing machine (manufacturer Mathis, type HVF12085). The amount of the dyeing solution is between 50% and 85% by weight based on the weight of the product. The pretreated fabric was then dried at 80° C. for 5 minutes.

III.2 Inventive pretreatment with color fixing agent

50 grams of poly-N-vinyl formamide copolymer, 50 grams of poly-N-vinyl formamide copolymer aqueous solution of Table 1a and 1.5 grams of color fixing agent of Table 3 were supplemented with water to prepare 1000 ml of dyeing solution. Cellulosic fabric (100% cotton fabric, fabric basis weight 160 g/cm2, bleached and ready for drying) was then impregnated with the dye liquor thus obtained using a pad dyeing machine (manufacturer Mathis, type HVF12085). The amount of dyeing liquid supplied was 80% by weight based on the weight of the product. The pretreated fabric was then dried at 160° C. for 3 minutes and thus heat-fixed.

III.3 Dyeing of pretreated fabrics from II.1 and II.2

Prepare an aqueous staining solution with 2 g/L dye 4, 1 g/L 1-hydroxymethylene bisphosphonic acid, 1 g/L p-nitrobenzenesulfonic acid sodium salt, sodium chloride in Table 3, and water. 10 grams of fabric treated according to the invention were placed in 100 ml of dyeing liquor and the mixture was transferred to a dyeing tank. The staining jar was sealed and placed in a preheated staining apparatus (Ahiba Labomat) at 50°C. It was then heated to 82°C over 15 minutes and dyed for an additional 30 minutes at 82°C. The dyeing jar was then removed from the dyeing bath, opened and a solution of 1.5 g _{of Na2CO3} dissolved in 10 ml of water was added to the dyeing liquor and the mixture was homogenized. The dyeing jar was then sealed, placed in the dyeing apparatus and kept at 82°C for an additional 60 minutes to fix the dye. Following cooling to about 30° C. over 5 minutes, the dyeing tank was opened, and the fabric dyed according to the invention was taken out, which was then washed under running water at 60 to 70° C. for 5 minutes.

After washing, the fabric dyed according to the invention was soaped at 98° C. for 15 minutes with a 2 g/l solution of polyacrylic acid sodium salt (M _W 70000 g/mol) pH 8.5 at a liquor-to-commercial ratio of 10:1. This is followed by washing under running water at 60 to 70° C. for 5 minutes, then at 20 to 35° C. for another 5 minutes, and thereafter drying at 80° C. for 20 minutes in a circulating air drying cabinet.

In each case, comparative examples were carried out on unpretreated fabrics.

Inventive dyed fabrics of Examples 17 to 24 (Table 3) and comparative fabrics of Comparative Examples V2 to V6 (Table 4) were thus produced. The inventive fabrics of Examples 17 to 24 exhibit vivid dyeing. The cross-section showed that the fabric was uniformly through dyed and no ring dyeing occurred, unlike the comparative fabrics of Comparative Examples V2 to V6.

The values of L, A, B and ΔE were determined according to CIELAB.

Table 3: Dyeing of pretreated fabrics Example number 17 18 19 20 Poly-N-vinyl formamide copolymer P6 P7 P8 P9 Sodium chloride [g/L] 20 20 20 20 Fixative - - - - L 56.48 56.85 57 55.51 A -28.08 -28.26 -27.53 -27.23 B -34.26 -34.42 -32.87 -33 ΔE 0.93/5 1.27/5 0.8/3 1.34/3

Table 3 (continued) Example number 17 18 19 20 Poly-N-vinyl formamide copolymer P8 P9 P8 P9 Sodium chloride [g/L] 20 20 0 20 Fixative F1 F1 F2 F2 L 55.56 54.3 56 52.99 A -27.33 -26.11 -27.22 -26.22 B -34.16 -33.5 -34.29 -35.79 ΔE 1.36/3 1.32/4 1.21/3 1.97/4

Table 4: Comparative example: Dyeing of non-pretreated fabrics Example number V2 V3 V4 V5 V6 Poly-N-vinyl formamide copolymer - - - - - Sodium chloride [g/L] - 20 40 80 70 Fixative - - - - - L 64.07 60.54 56.59 53.94 55.75 A -27.79 -28.54 -27.88 -27.09 -28.43 B -29.23 -31.39 -33.46 -34.3 -33.8 ΔE - - - - -

Claims (11)

1. A method for pretreating cellulose fabrics, comprising the steps of: (a) Treatment of cellulosic fabrics with solutions of polymers or copolymers obtainable by: (a1) polymerizing or copolymerizing N-vinylamides of general formula I: in R is selected from hydrogen and _C1 to _C10 alkyl, and (a2) if appropriate, partial hydrolysis, (b) optionally drying the treated fabric, and (c) optionally saponifying all or some of the amide groups, wherein at least one of steps (a2) and (c) is carried out. 2. The method of claim 1 utilizing an aqueous solution of a polymer or copolymer. 3. The method according to claim 1 or 2, wherein R in general formula I represents hydrogen. 4. The process according to any one of claims 1 to 3, wherein the polymer or copolymer obtainable by polymerizing or copolymerizing N-vinylamides of general formula I has a Mw of 10,000 to 1,000,000 g/mol . 5. The method according to any one of claims 1 to 4, wherein the copolymer is obtainable by (a1) combining an N-vinylamide of general formula I with at least one other compound selected from N-vinylpyrrolidone Copolymerized with comonomers of N-vinylimidazole. 6. A method as claimed in any one of claims 1 to 5 utilizing a polymer or copolymer obtainable by: (a1) polymerizing or copolymerizing N-vinylamides of general formula I, and (a2) Subsequent partial hydrolysis. 7. Cellulosic fabric pretreated by a method as claimed in any one of claims 1 to 6. 8. Use of a cellulosic fabric pretreated by a method as claimed in any one of claims 1 to 6 for the production of dyed fabrics. 9. A method of producing a dyed cellulosic fabric comprising dyeing the pretreated cellulosic fabric of claim 7 with a reactive, vat or direct dye. 10. The method of claim 9, wherein the staining liquor contains 0 to 20 g/liter of one or more inorganic salts. 11. Dyed cellulosic fabric obtainable by a method as claimed in claim 9 or 10.