GB2027437A - Polymeric dyes soluble in spinning solvents - Google Patents

Abstract

A dye soluble in polymer fibre spinning solvents is obtained by salifying a basic or acid dye, or a basic or acid optical bleaching agent, with a functional fibre grade polymer containing at least 200 micro- equivalents/g of acid or basic groups respectively. The functional polymer may be a copolymer of acrylonitrile with a functional monomer, e.g. methyl vinyl pyridine, dimethylaminoethyl methacrylate or sodium methallyl sulphonate. The polymeric dyes may be used to dye acrylic and modacrylic fibres.

Description

SPECIFICATION Process for the preparation of dyes soluble in spinning solvents for polymers used in.the production of fibres, and the dyes therefrom obtained The present invention concerns a process for preparing dyes that are soluble in spinning solvents for polymers used in the production of synthetic fibres.

More particularly, this invention relates to a process for preparing dyes particularly suited for solution dyeing of acrylic fibres during the spinning operation.

It is already known to dye in solution acrylic fibres with organic or inorganic coloured pigments.

However, the addition of coloured pigments to the spinning solution has certain drawbacks due mainly to the fact that the coloured pigments are not soluble in the spinning solvent.

The main drawbacks are the obstruction of the spinneret holes, the modification of the coagulation of the protofibre with the formation of discontinuities of matter which lead to frequent breakages of the filaments, and the impossibility of obtaining bright colours and shiny fibres. Moreover, the use of pigments involves serious problems of environmental hygene. In fact, due to their very fine granulometry (particle size), the pigments disperse themselves easily in the air during weighing and dosing operations.

In order to overcome the above drawbacks, in principle there may be used, for the solution dyeing of acrylic fibres, the same basic or acid dyes as used in dyeing plants for the dyeing of staples, yarns or of manufactured articles in general.

Unfortunately, this alternative is not practically feasible owing to the very poor solubility of the dyes in the organic spinning solvents used in the production of fibres and for the great quantity of salts that usually are present in the dyes and which form by reaction with the reactive groups of the polymer.

In order to overcome the solubility problem, it has been suggested to modify the structure of the dyes in order to improve their solubility in the spinning solvent. However, this alternative was also not altogether free of drawbacks due mainly to the very limited number of dyes that proved suitable for structural modification, without leading to alterations in the tinctorial characteristics. Moreover, their still remains the problem of the formation of insoluble salts originating from the reaction of the dyes with the polymer.

Thus, an object of some embodiments of the invention is to provide a process which will render soluble in spinning solvent of polymers used in the production of fibres, and in particular of acrylic polymers, those dyes commonly used in the dyeing of said fibres, and so as to mitigate the above drawbacks.

It has now been found by this applicant that said object may be obtained by salifying a basic or acid dye, or a basic or acid optical bleaching agent, with a functional fiber grade polymer of the type used for the production of the fibre, containing at least 200 micro equivalents/g of acid or respectively basic groups.

Thus, the invention provides dye soluble in spinning solvents for polymer used in the production of fibres, which comprises the salification reaction product of a basic or acid dye, or of a basic or acid optical bleacher, with a functional fiber grade polymer containing at least 200 micro-equivalents/g of acid or basic groups respectively. The salification product thus obtained is subsequently filtered and repeatedly washed with water.

As functional polymer is preferred in practice an acrylonitrile polymer, although other polymers and copolymers may be used too.

The invention further provides process for the production of a dye soluble in polymer fibre spinning solvents, which comprises salifying a basic or acid dye, or a basic or acid optical bleacher, with a functional polymer of the type used for the production of fiber and containing at least 200 microequivalents/g of acid of basic groups.

The upper limit of the quantity of micro-equivalents acid or basic groups contained in 1 g. of the functional polymer, is limited by the solubility of said polymer in the reaction medium.

Thus, if the polymer is based on acrylonitrile and contains acid groups and the reaction medium is water it is preferred that the acid groups be present in not greater than 1,500 micro-equivalents/g of polymer, depending on the type of co-monomer.

On the other hand, in the case of a functional polymer based on acrylonitrile which contains basic groups, still using water as reaction medium, the basic groups may be present in a very much greater quantity, for instance 5,000 micro-equivalentsJg of polymer.

The salification reaction is conducted in an aqueous medium, at a temperature and a pH similar to those used under normal dyeing conditions of the particular dye used.

The reaction product obtained appears in the form of a coloured powder containing from 15% to 200% or more, with respect to the starting functional polymer, of bound pure dye that is highly soluble even at room temperature in those solvents used in the spinning of acrylic polymers.

The coloured powder may be dispersed and then dissolved in a spinning solution containing the polymer to be spun for producing coloured fibre.

The salification reaction between the acid or basic dye and the functional polymer may be achieved by dispersing the polymer in water, then adding under stirring the stoichiometric quantity of dye, bringing the pH to a value corresponding to that used for dyeing by the dye used (generally between ph 3 and 7), heating up to boiling temperature the suspension for between 15 and 90 minutes, and finally filtering the coloured product thus obtained.

If the functional polymer is prepared by polymerization in an aqueous medium, the salification reaction may be carried out by mixing the polymerization product coming from the polymerization reactor directly with the dye in the state in which this is marketed, or more conveniently, with dye coming directly from the synthesis phase, before its separation and purification.

While in the conventional process of the production of the dyes particular conditions are required for obtaining insolubilization of the product, with the process of this invention the reaction product between the dye and the functional polymer separates directly in easily filtered aggregates.

The coloured powder, after centrifuging and filtering, may be pressed through a perforated plate and then transformed into small cylinders, in general having a diameter of 2-10 mm and a length of 3-1 5 mm, which after drying can be handled without any dusting of the product occurring. Because of its high solubility, the coloured powder, even in this form, disperses and dissolves rapidly in the spinning solvent without leaving insoluble residues.

The functional polymer containing acid or basic groups, and in particular an acrylic functional polymer, may be prepared by polymerizing in bulk, in solution, in suspension or in emulsion a mixture of the monomer, in particular acrylonitrile, and a co-monomer containing acid or basic groups according to standard polymerization techniques; or by grafting such co-monomers to the polymers.

As acid co-monomer may be used any ethylenically unsaturated compound polymerizable with acrylonitrile and containing acid groups, such as carboxyl, sulphonic or phosphoric groups.

Examples of acid comonomers copolymerizable with acrylonitrile are; sodium-p.sulphophenylmethallyl ether, sodium-p,sulpho-phenyl-allyl ether, sodium-sulphophenyl-methacrylamide, sodium or potassium-isopropenyl-benzene-su Ip honate,styrene-phosphoric acid, sodium or potassium vinyl- benzene-sulphonate, cinnamic acid, itaconic acid, p-meta-acrylamido-benzoic acid, sodium-methylallyl-su Iphonate, and 2-acrylamido-2-methylpropan-sulphonic acid.

As a co-monomer containing basic groups there may be used: methyl-vinyl-pyridine, dimethylethyl-amino-acrylate, or 2-vinylpyridine.

Any basic or acid dye may be modified according to this process in order to make it soluble in the spinning solvents for the polymers used for producing fibres.

By way of example we shall list some acid dyes which are suitable: - Blue Supramine GW Bayer C.l. Acid Blue 82 - Blue Alizarine A2G ACNA " " " 40 - Red Supramine GW Bayer ,, ,, Red 118 - Ruby-red Alizarine R ACNA ,, ,, Red 80 -Yellow Supramine GW Bayer C.l. Acid Yellow 61 -Yellow Novamine 2GP ACNA ,, ,, Yellow 39 and from the group of basic dyes: - Blue Stenacril BL ACNA C.I.Basic Blue 65 -BlueMaxilonTL CIBA ,, ,, Blue 123 - Red Astrazon BBL BAYER ,, ,, Red 23 - Bordeaux Maxilon 2BL CIBA ,, " Red 59 -YellowAstrazon 7GLL BAYER ,, ,, Yellow 21 - Yellow Stenacril 3GL ACNA ,, ,, Yellow 11 The determination of the acid or basic groups in the acrylonitrile-based polymers is carried out by potentiometric titration of a polymer solution desalified with ion exchanging resins.

As the solvent may be used a mixture of ethylene carbonate and propylene carbonate in a volumetric ratio of 3/1.

The desalification is brought about by percolating the polymer solution through a glass column of 2 cm diameter provided with a porous diaphragm G2 and filled in the following order with: -cationic resin "Dovex 50W-X8" produced by Baker, to a height of 10 cm; -regenerated anionic resin "IRA 410" produced by BDH, to a height of 8 cm; -cationic resin "Dovex 50W-X8" produced by Baker, to a height of 10 cm.

Titration is carried out by means of a "Metrohme. E 436" recording potentiometer provided with an automatic burette synchronized with the advance of the paper.

The acid groups are titrated with tetramethylammonium hydroxide 0.02N using as a measuring apparatus a platinum foil electrode indicator coupled to a standard platinum foil electrode introduced into the titration substance flow.

For the titration of the basic groups, to the desalified solution obtained by operating according to the above reported conditions is added 10% by volume of glacial acetic acid and the mixture titrated with 0.02N perchloric acid by means of a "Metrohm.E 436" recording potentiometer; using as a measuring apparatus a glass electrode indicator coupled with a standard Ag/AgCI electrode introduced into glacial acetic acid saturated with KCI.

When the equivalence point of the potentiometric curve obtained has been determined, it is possible to trace back to the ml of titrant used, and thus to estimate the acid or basic groups present in the polymer by means of the equation: 20xml of 0,02 Ntitrant Acid or basic groups (in eq/g) P wherein P is the weight of the polymer expressed in grams.

The dye obtained according to the process of this invention may be used in solution dyeing of either acrylic or modacrylic fibres, in the colouring of plastic materials, and in the production of inks and paints.

In the case of solution dyeing also called bulk dyeing of acrylic or modacrylic fibres, the dye obtained according to the process of this invention may be dissolved directly in the spinning solution. In practice, however, it is preferred to prepare separately, owing to its high solubility, a concentrated solution containing from 5% to 30% of dye salified with the functional polymer in the spinning solvent, and then to inject said concentrated solution into the spinning solution just upstream of the spinneret.

This allows easy changes from one colour to another to be made and even allows the production of a plurality of coloured fibres contemporaneously on the different spinnerets of the same spinning unit.

For the produciton of acrylic or modacrylic fibres any known polymer or mixture of known polymers containing at least 50 mol % of acrylonitrile may be used.

The spinning process used is altogether similar to that known for the production of acrylic and modacrylic fibres, both by wet and dry spinning.

The complete dissolution of the dye according to the process of this invention, in those solvents usually used for the spinning of acrylic polymers, allows the preparation of completely transparent spinning dopes without any granules capable of obstructing the holes of the spinnerets or causing the rupture of the filaments.

The dyes fibres and filaments thus obtained, do not show any striations and are characterized by a high fastness to light, to thermofixing, to vaporizing and to washing.

Moreover, the fact that the dyes prepared according to this invention are insoluble, or at any rate hardly soluble in water, makes them particularly suitable for being used in wet spinning, in as much as they are not substantially extracted by the coagulation bath.

In order to better understand the inventive idea of the present invention and in order to facilitate its practical working, there will now be given some Examples for purely illustrative and not limiting purposes.

EXAMPLE 1 Into a 2 1 polymerization reactor containing: 400 g of water and 5 g of S 2 and maintained at 500C, were introduced over 30 minutes, 1 g of potassium persulphate, 80 g of acrylonitrile and20 g of sodium methyl-allyl-sulphonate.

After heating for further 30 minutes at 500C, the polymerization slurry was discharged. To 500 g of this slurry (containing 64.6 g of polymer) 115 g of yellow Stenacril 3 GL (marketed by ACNA) were added and the suspension was brought to a pH value of 4 and heated to boiling temperature for 20 minutes.

The reaction mixture was then filtered. The filtration water was colourless, due to the fact that the whole dye had been fixed by the polymer. The obtained product was washed and dried in an oven at 500C, at a pressure of 200 mm Hg.

90 g of a powder deep yellow coloured and containing 28.3% of the pure starting dye were obtained. The powder, dissolved in dimethyl-acetamide at a concentration of 26% yielded a completely clear, fluid clog-free solution.

EXAMPLE 2 Into a 3,700 cc reactor, precharged with 1850 cc of water, 3.65 cc of H2SO4 1 N and 10 cc of a FeSO4 solution containing 10 g/cc of Fe++, was continuously introduced 9.11 g/min. of acrylonitrile; 28.6 g/min. of an aqueous solution containing 5.79% of sodium p-sulphophenyl-methallyl-ether, 0.1155% of potassium persulphate, 2.045% sodium sulphate and 36 cc/litre of a solution of iron sulphate containing 10-4 g/cc of Fe++; 0.271 g/min. of gaseous SO2; and 3.63 cc/min of a 0.903% solution of NaOH.

The reaction temperature was 500C and the residence time 85 minutes.

Under stationary conditions, the polymerization conversion was 75% while the copolymer separated by filtering contained 700 micro-equivalents/g of acid groups.

To 100 g of dry polymer dispersed in 300 g of water 100 g of Blue Joracryl 3 RL (marketed by Yorkshire) were added. The suspension was brought to pH 4.5 by acetic acid and, after 30 min. of boiling, was filtered. The product was washed with water and dried in an oven at 500C and at a pressure of 200 mm Hg.

The powder thus obtained had a deep blue shade and contained 20% of the pure starting dye.

EXAMPLE 3 Into a 5 430 cc reactor containing 2 715 cc of water, 2.7 cc of 1 N H2SO4 and 4 cc of a solution of ferrous sulphate containing 10-4 g/cc of Fe++, was continuously introduced under steady stirring 13 cc/min. of acrylonitrile;* 25 cc/min. of a solution, at 6 pH, containing: 7.8% by weight of dimethyl-ethyl-amino-methacrylate and 1.25% by weight of H2SO4 at a 96% concentration; 25 cc/min. of a solution containing 0.264% of potassium persulphate, 2.4% of sodium sulphate, 0.1745% of NaOH and 1 ppm of Fe++ in the form of FeSO4; and 0.081 g/min. of gaseous SO2. The polymerization temperature was 5O0C. Under stationary conditions, the conversion amounted to 65% and the obtained polymer, separated by filtering, contained 600 micro-equivalent/g of basic groups.

To 100 g of the copolymer thus obtained, suspended in 500 g of water, were added under stirring 100 g of Supramine GW Red. The suspension was then brought to a pH 4 by addition of acetic acid and after 30 minutes of boiling, the suspension was filtered. The coloured powder thus obtained was repeatedly washed with water and then dried in an oven at 500C at a pressure of 200 mm/Hg.

The coloured powder thus obtained contained 20% of the pure starting dye and was soluble in solvents of polyacrylonitrile, such as dimethyl-acetamide, dimethyl-formamide and dimethyl-sulphoxide.

EXAMPLE 4 Into a 5 litre reactor, fitted with a stirrer and immersed in a thermostatically regulated bath, 1 500 ml of distilled water and 42.25 ml of H2SO4 at 10% concentration were pro-loaded. At a temperature of 500C and for 150 minutes there were then continuously fed in: - 485.7 ml of H2SO4 at 10% concentration; - 328.3 g of acrylonitrile; - 328.3 g of methyl-vinyl-pyridine.

The catalytic system was continuously fed for 165 minutes in the following quantities: - 437.5 ml of an aqueous solution of K2S201, at 0.30%, with a flow rate of 2.5 ml/minute.

- 437.5 ml of an aqueous solution of NaHSO3 at 0.25%, with a flow rate of 2.5 ml/minute.

At the end of the reaction the mixture was treated with ammonia up to pH6 in order to coagulate the obtained polymer which was then separated, washed and dried in an oven at 500C at 200 mm Hg.

The polymer contained 49% of methyl-vinyl-pyridine and the specific viscosity determined in dimethylformamide was 0. 155.

The conversion amounted to 94%.

To 10 g of dry polymer, 1 7 g of Blue Supramine GW (marketed by Bayer) and 250 ml of water were added and the suspension was brought to pH 4.5 by the addition of acetic acid.

After heating to boiling point for 60 min., the reaction mixture was filtered and then washed with water and dried. A deep blue coloured powder was obtained having an extinction coefficient of 12 lq1 cm-' equal to that of the commercial starting product whose extinction coefficient amounted to 11.9 lg1cm1.

The extinction coefflicient is the absorbance of a solution having a concentration of 1 g/l and a thickness of 1 cm, measured on a spectrophotometer in correspondence to the wavelength of maximum absorption.

The coloured powder thus obtained, dissolved in dimethylacetamide, gave place to a 10% solution fluid and free of clogs.

EXAMPLE 5 The process described in Example 1 was repeated, using the commercial dyes indicated in following Table 1. Also in this case there were obtained powders deeply coloured, easily soluble in all the solvents of polyacrylonitrile, such as dimethylformamide, dimethylacetamide, dimethylsulphoxide, ethylene carbonate, and y-butyrolactone.

In order to show that the process of this invention does not alter but in some cases improves the tinctorial capacity of the starting dye, in table 1 the extinction coefficients (E) of the obtained coloured powders in comparison with that of the corresponding starting dyes, were recorded.

TABLE 1 @ (1g-1cm@) dye (1g1cm1) salified commercial with the functional starting polymer of example dye No. 1 (1) Yellow Stenacril 3GL 20.1 25.8 (2) Bordeaux maxilon GR 36.8 40.0 (3) Blue Maxilon TL 47.2 33.0 (4) Yellow Astrazon 7GLL 24.4 45.3 EXAMPLE 6 With some of the salified dyes of Example 5, a solution in dimethylacetamide at 1 5% concentration was prepared. The solution thus obtained was injected with an injection ratio of 13 into a 25% solution of an acrylic polymer in dimethylacetamide, having a molecular weight of 42,000 and containing 92.8% of acrylonitrile and 7.2% of vinylacetate.

The dope thus obtained was extruded through a 500 holes spinneret having holes of 76 ju diameter. The spinning and the increase of pressure on the filter were altogether analogous to those that are met with in the spinning of the polymer without the salified dye.

The fibres thus obtained, when operating at the spinning conditions reported in Table 2, proved to be shiny, deeply dyed, with a hield of about 100% and showed excellent fastnesses to the fadepmeter, to washing in water at 400C and at 600 C, to dry-cleaning, to perspiration, to vaporization, to a hot iron and to rubbing.

On Table 2 the fastnesses have been determined according to the following UNI Italian Standards Institute: - Fastness to the Fadeometer : UNI SOL 5 -Fastness to rubbing : UNI 5153 - Fastness to perspiration : UNI SOL 13 - Fastness to washing in water at 400C -: UNI 5156 - Fastness to dry cleaning : UNI 5150 - Fastness to a hot iron : UNI 5152 -Fastness to water : UNI 5157 - Fastness to vaporization : UNI 5164 TABLE 2

Concentr. Maximum Maximum Fastness % by weight speed(1) stretch to the other Die Solified with of fibre in mt/min. (2) Fadeometer fastnesses - - - - 16.1 8.1 - Yellow Stenacril 3 GL 0.64 16.2 8.1 # 7 from 4 to 5 " " 3 GL 1.28 16.0 8.1 # 7 " 4 " 5 Yellow Astrazon 7 GLL 0.64 16.0 8.2 # 7 5 " " 7 GLL 1,28 16.0 8.0 # 7 5 Blue Maxilon TL 0.64 16.5 8.2 # 6 " 4 to 5 " " TL 1,28 16.0 8.1 # 6 " 4 to 5 (1) Maximum gathering speed for the fibre from the coagulation bath having solvent/water composition of 45/55.

(2) Maximum stretch in water at 100 C.

Claims (21)

1. Dye soluble in spinning solvents for polymer used in the production of fibres, which comprises the salification reaction product of a basic or acid dye, or of a basic or acid optical bleacher, with a functional fiber grade polymer containing at least 200 micro-equivalents/g of acid or basic groups respectively.

2. Dye according to claim 1 , wherein the functional fiber grade polymer comprises acrylonitrile.

3. Dye according to claim 2, wherein the functional copolymer is a copolyrner of acrylonitrile and an ethylenically unsaturated comonomer copolymerisable therewith and containing acid groups.

4. Dye according to claim 2, wherein the functional copolymer is a copolymer of acrylonitrile and an ethylenically unsaturated comonomercopolymerisable therewith and containing basic groups.

5. Dye soluble in polymer fibre spinning solvents substantially as described in any Example.

6. Process for the production of a dye soluble in polymer fibre spinning solvents, which comprises salifying a basic or acid dye, or a basic or acid optical bleacher, with a functional polymer of the type used for the production of fiber and containing at least 200 micro-equivalents/g of acid or basic groups.

7. Process according to claim 6, wherein the functional polymer is based on acrylonitrile.

8. Process according to either claim 6 or 7, wherein the upper limit of micro-equivalents/g of acid or basic group is determined by the solubility of the functional polymer in the reaction medium.

9. Process according to claim 8, wherein the acid groups are not greater than 1500 microequivalents/g when the functional polymer is based on acrylonitrile and the reaction medium is water.

10. Process according to claim 8, wherein the basic groups are up to 5000 micro-equivalents/g, when the functional polymer is based on acrylonitrile and the reaction medium is water.

11. Process according to any of claims 7 to 10, wherein the functional polymer based on acrylonitrile is obtained by copolymerizing acrylonitrile with an ethylenically unsaturated co-monomer, copolymerizable with acrylonitrile and containing acid groups.

12. Process according to claim 1 wherein the acid group is a carboxylic, sulphonic or phosphonic acid moiety.

1 3. Process according to any of claims 7 to 10, wherein the functional polymer based on acrylonitrile is obtained by copolymerizing acrylonitrile with an ethylenically unsaturated comonomer co-polymerizable with acrylonitrile and containing basic groups.

14. Process according to claim 13, wherein the basic group-containing comonomer is methylvinyl-pyridine, dimethyl-ethyl-amino-acrylate or 2-vinyl-pyridine.

1 5. Process for the production of a dye soluble in polymer fibre spinning solvents substantially as disclosed in any Example.

1 6. Method of producing dyed fibres, which comprises preparing a dye according to any preceding claim from the same polymer as that used to form the fibres, dissolving the dye in the spinning solution, and spinning the solution into fibres,

1 7. Method according to claim 1 6, wherein the spinning solution is wet spun.

1 8. Method according to claim 1 6 or 17, wherein the fibres are acrylic or modacrylic fibres.

19. Method according to any of claims 16 to 18, wherein the dye ispredissolved in the spinning solvent to form a concentrate, which is subsequently injected into the spinning solution just upstream of the spinneret.

20. Use of the dye of claim 1 in the colouring of plastic materials, or in thz production of inks and paints.

21. Polymer fibres dyed with the dye of any preceding dye claim.