GB2041388A - Sulphited polyoxyethylene esters - Google Patents

Abstract

Compounds of general formula <IMAGE> wherein: A is the residue of a compound containing 2-6 reactive hydrogen atoms; one of R1 and R2 represents a hydrogen atom and the other represents a C1-22 alkyl group; x represents an integer greater than 1 but no more than 6; m and n each have average values such that the molecular weight, determined by hydroxyl number, of the @@CHR,CHR2O@@ fraction is from 900 to 7,500 and the molecular weight of the polyoxyethylene portion comprises 20-90% of the combined polyester units; y is at least one but not exceeding x; and B represents a group of formula:- <IMAGE> or of formula:- <IMAGE> wherein R3 and R4 each independently represents hydrogen, methyl, but both may not represent methyl, and each M, which may be the same or different, represents a hydrogen atom, ammonium, an alkali metal atom or the equivalent of an alkaline earth metal atom, Use: in disperse dye compositions.

Description

SPECIFICATION Improvements relating to disperse dye compositions The present invention provides novel compounds, their methods of preparation and their use as dispersion stabilising agents in both powder and liquid disperse dye compositions and to the use of such compounds as dispersing and levelling agents during application of disperse dyes to textile substrates.

According to the present invention, there are provided novel compounds of general formula I,

wherein: A is the residue of a compound containing two to six reactive hydrogen atoms: one of R, and R2 represents a hydrogen atom and the other represents an alkyl group having one to twenty-two carbon atoms: x represents an integer greater than 1 but no more than 6: m and n, each represent on a molecular scale, an integer with the proviso that they have average values such that the molecular weight, determined by hydroxyl number of the 4(CHRiCHR2n]x fraction is from 900 to 7,500 and the molecular weight of the CH2CH20Gm]X fraction constitutes from 20 to 90% by weight of a compound of general formula:

wherein A, Rr, R2, m, n and x are as previously defined y represents an integer of at least one but not exceeding x; and B represents a group of the formula:

or of the formula:

wherein R3 and R4 each independently represents a hydrogen atom or a methyl group, with the proviso that both may not represent methyl groups, and each M, which may be the same or different, represents a hydrogen atom, ammonium, an alkali metal atom or the equivalent of an alkaline earth metal atom, or a mixture of such compounds of formula I.

The term "reactive hydrogen" used in the definition of A means a hydrogen capable of reacting with an alkylene oxide.

On a macromolecular scale, since the values of n and m vary from molecule to molecule, they will assume average values and therefore may not be whole numbers except on a molecular scale.

The present invention also includes a process for the preparation of compounds of formula I, or a mixture of such compounds, which comprises reacting one mole of a compound of general formula:

wherein A, R1, Rz, m and x have the meanings previously defined, with y moles of an unsaturated acid anhydride of general formula:

wherein R3 and R4 have the meanings previously defined, at a temperature in the range 20 to 2200C.

preferably 50 to 1 500 C, to yield the corresponding semi-ester which is then neutralised with an aqueous alkali and subsequently converted to the corresponding sulphited semi-ester of general formula I by reaction with y to 1.5y moles, preferably 1.05y to 1.1 y moles, of a sulphite, bisulphite or pyrosulphite at 10 to 1000C, preferably 40 -- 800C, in aqueous solution.

Reaction of the compounds of general formula II with unsaturated acid anhydrides is carried out by mixing the components followed by heating and stirring. It is preferable to remove any moisture from the compounds of general formula II before the addition of the unsaturated acid anhydride. A temperature within the range 20 to 2200C is employed, preferably 50 to 1 500C, optionally in the presence of an alkali metal hydroxide, which is employed at a concentration of from 0.05 to 1.5% by weight, calculated on the total mixture. Since unsaturated acid anhydrides, particularly maleic anhydride have a tendency to sublime, it is advantageous although not mandatory to work in a sealed vessel, typically under a pressure of 0.2 to 1.0 bar.

The reaction is allowed to proceed at elevated temperature to the extent required as indicated by acid number determination on a sample of diluted reaction mixture. The remaining bulk is then cooled to room temperature and neutralised with an aqueous alkali, preferably sodium hydroxide solution.

The conversion of the unsaturated acid semi-ester into the corresponding sulphited derivative of general formula I is carried out by the addition of an aqueous solution of a sulphite, bisulphite or metabisulphite salt.

The total amount of water employed, which includes that used at the neutralisation stage and for dissolving the sulphiting agent varies according to the solubiiity of the acid semi-ester and the viscosity of its solution but is preferably within the range of 5085% by weight calculated on the total solution or mixture weight.

As the reaction proceeds an increase in viscosity occurs, followed by a decrease in viscosity towards completion of the reaction. Heating and stirring is then prolonged for a further period to ensure complete reaction. The final product is in the form of a solution at a concentration typically between 1 5 and 50% by weight, the water however, may be eliminated by drying, for example by spray drying, to produce a dry preparation.

Compounds of general formula II are polyoxyalkylene non-ionic surfactants which employ a suitably substituted polyoxyalkylene chain i.e. (CHR1CHR2O)x as the hydrophobic element. They may be prepared by condensing the required amount of suitably substituted alkylene oxide, e.g. propylene oxide, butylene oxide or cr-olefin oxide, with a reactive hydrogen compound from which the residue A is derived, and then providing the hydrophilic element by reacting this compound with ethylene oxide.

Specific examples of compounds containing active hydrogen atoms include amines, (e.g. ammonia, primary amines and/or secondary amines, alkylene polyamines, heterocyclic nitrogen compounds), alcohols, (e.g. polyhydric aliphatic alcohols of at least two carbon atoms), carboxylic acids (e.g. multifunctional organic carboxylic acids) and compounds containing reactive hydrogen atoms of different types (e.g. hydroxylamine, aminophenol).

A preferred compound is derived from ethylene diamine as the reactive hydrogen species and propylene oxide as the hydrophobic element,QCHR,CHR20X, whereby the molecular weight of the latter is in the range of 1000 to 5000. The weight per cent of oxyethylene groups,QCH2CH20G, is from 25-55. Thus typical values of n, m and x for a compound falling within the middle of this range would be 12, 11 and 4, respectively. A further preferred compound is derived from propylene glycol as reactive hydrogen species and propylene oxide as the hydrophobic element such that the molecular weight of the latter is at least 1 500 and the oxyethylene groups present constitute 4070% by weight of the mixture. Thus typical values of n, m and x for a compound falling within the middle of this range would be 13, 22 and 2, respectively.

The unsaturated organic acid anhydride is selected from maleic anhydride and citraconic anhydride, the preferred compound being maleic anhydride.

The addition of a sulphite group to the double bond of the unsaturated acid semi-ester is achieved using ammonium, alkali metal or alkaline earth metal sulphites, bisulphites or metabisulphites. Preferred compounds for conversion of the semi-ester compound into the sulphited derivative are sodium sulphite, sodium bisulphite or sodium metabisulphite.

M is preferably the sodium atom.

Incorporation of the products of the current invention into disperse dye compositions affords a number of advantages compared with prior art compositions.

In the production of disperse dyes, the water insoluble or slightly water soluble dyes are pulverised and dispersed with a dispersing agent or mixture of dispersing agents by conventional means in continuous or batch kneaders and/or in grinding units until a mean particle size of typically 0.1 to 1.0 ym has been attained. Examples of grinding units are, ball mills, sand mills, stirred mills and high speed mills which contain ceramic, steel, glass or sand grinding media. Typical anionic dispersing agents which are used are ligno-sulphonates, condensation products or naphthalene sulphonic acid and formaldehyde, and of cresol/phenol formaldehyde and sodium sulphite.After milling, the aqueous dispersions are either dried to produce a powder, for example by spray drying, or are produced in liquid form often with further additives to prevent the sedimentation of dispersed particles on storage.

Typically disperse dye powders contain 30 to 80% by weight of dispersing agent and liquids contain 5 to 40% by weight of dispersing agent.

During drying of the milled aqueous dispersion some agglomeration of the dye particles is a frequent occurrence. These agglomerates are very stable and do not readily break down when the powder is redispersed in water. When agglomerates are present during the dyeing of textile substrates, by both batch or continuous techniques, problems of unlevelness and poor rubbing fastness of the dyed textile are encountered. When applying dyestuffs to textile substrates by printing techniques, the presence of agglomerates results in printed textiles on which dye specks are visible.

In recent years, the development of new dyeing techniques, for example the high temperature package and beam dyeing of synthetic fibres, has demanded improved dispersion properties in the disperse dyes used. In particular, the use of lower liquor ratios has resulted in the use of higher dye concentrations, which in modern machines are subjected to severe shear forces at temperatures above 100 C. If, under these more demanding conditions, the dye dispersion breaks down or some agglomeration takes place, then again problems of unlevelness and poor rubbing fastness of the dyed substrate are encountered.

It is known that dye dispersions in the presence of carriers such as chlorobenzene, phenyl phenols, methyl naphthalenes etc. or levelling agents such as polyoxylated alkyl phenols or polyoxyalkylated fatty acids and alcohols, are often unstable. This is believed to be due to the interaction between the protective layers of dispersing agent surrounding the dye particles and the carrier or levelling agent, which destablises the dispersion and causes agglomeration.

A further probiem during the dyeing of textiles may arise from the presence of residual oils or sizing agents derived from earlier processing of the textile materials. Although attempts are made to eliminate these agents by scouring the textile before dyeing, a residue often remains which may interact with the stabilised dye particles resulting in agglomeration.

Thus there was a need for a compound which would increase the stability of aqueous dye dispersions to the spray drying process and subsequently to withstand the more stringent conditions of modern dyeing processes and techniques, in order to prevent the agglomeration of the fine dye particles and overcome the attendant problems arising from such agglomeration. It is also desirable that dye dispersions be more tolerant to the presence of carriers, levelling agents, residual spinning oils and sizes during application to textile substrates.

We have now found that dyestuffs preparations in which 2 to 30% by weight of the conventional dye dispersing agent has been replaced by products of the current invention do not have the stated disadvantages. The new aqueous dye dispersions can be dried to produce powders free of agglomerates and both liquid and powder preparations are more stable under the more stringent conditions of application to textile substrates. In addition, the dilute aqueous dispersions produced from such preparations are more tolerant to the presence of carriers, levelling agents, spinning oils and sizes.

Thus, according to the present invention, there are provided powder and liquid disperse dye compositions which are characterised in that they contain the conventional amounts of coloured component, but that the normal dispersing agent content, typically 30 to 80% by weight for powders and 5 to 40% for liquids, is replaced by 2 to 30% of compounds of general formula I. The dyes which may be used may be any of the conventional insoluble or sparinyly soluble disperse dyes which fall into the various chemical classes such as azo, anthraquinone, nitrodiphenylamine, methine or quinophthalone.

The invention further provides a process for the production of these compositions which comprises the reduction in particle size of the dye in the presence of compounds of general formula I, or in the presence of conventional dispersing agents with the subsequent addition of compounds of general formula I or in the presence of a mixture of such compounds, optionally with an addition of antifoaming agent until a mean particle size of 0.1 to 1ym has been attained. This particle size reduction process is readily effected in conventional equipment. The resulting aqueous dye dispersion is then standardised with respect to strength, optionally with further additions of conventional dispersing agents, products of the current invention, stabilising agents, humectants or anti-foaming agents to produce a liquid dye preparation.Alternatively, the milled dye dispersion is dried, preferably spray dried, optionally with further additions of conventional dye dispersing agents or compounds af the current invention to produce a powder preparation. Thus the compounds of the current invention are incorporated into the disperse dye composition before or after ilie process of size reduction or at both stages of the manufacturing process. Strength adjustment is carried out before or after drying and optionally other additives such as inert diluents e.g. sugar, dextrin or dedusting agents may be employed.

The new preparations are used for the dyeing and printing of textile materials by continuous or batch processes and depending on the dyes used are suitable for application to a wide variety of textile materials including polyester, cellulose acetate and nylon.

A further advantage of the current invention is that the new disperse dye compositions were found to have improved levelling properties compared to conventional disperse dye compositions. Thus the compounds of the current invention are acting as both dye stabilising agents and levelling agents. This observation is not wholly unexpected since compounds of formula II are known to act as levelling agents. However, it is only after conversion to compounds of formula I that the additional dye stabilising properties are obtained.

Since compounds of formula I have the ability to improve the level dyeing characteristics of disperse dyes, they may be used as an additive to the dyebath in order to effect such improvements. A further advantage of using the said compounds as levelling agents is their compatibility with conventional dye dispersing agents, reducing the possibility of dye agglomeration taking place, when compared to conventional wholly non-ionic levelling agents.

In many dyeing processes, particularly when substrates are being dyed to pale shades an addition is made to the dyebath of conventional anionic dispersing agents in order to augment the dispersant already present, which has been derived from the disperse dye addition. This practice reduces the susceptibility of the dye dispersion to the aforementioned application problems. It has now been found that compounds of formula 1, when added to the dyebath, serve as additional dye dispersing agent is addition to promoting level dyeing.

Thus according to the present invention, there are provided compounds and compositions based on compounds of formula I, which when used as dyebath additives promote level dyeing of disperse dyes, do not interact with the dispersed dye particles and obviate the need to add additional dye dispersing agent to the dyebath. The said compounds may be in the form of a liquid, preferably 10 to 60% by weight concentration, optionally combined with other accepted levelling agents such as higher molecular weight aromatic esters and/or alcohols or combined with conventional dye dispersing agents.

Alternatively, the above liquid compositions may be dried, preferably spray dried to produce a solid preparation, provided the process is feasible with the combination of additives selected. The preparations are particularly useful for the promotion of migration and levelling of disperse dyes on synthetic hydrophobic fibres such as polyester and triacetate. Typically, they are employed at dyebath concentrations between 0.5 and 5.0g/litre.

The invention also includes a method of dyeing using the compounds and compositions of the invention and textile materials so produced.

The following examples illustrate the invention without in any way limiting its scope. 'Parts' and percentages are given as parts by weight.

EXAMPLE 1 The starting material is a block copolymer of ethylene oxide/propylene oxide derived from propylene glycoi as the reactive hydrogen compound. The molecular weight of the propylene oxide fraction is 1680, thus n is approximately 1 5 (x = 2) and the ethylene oxide fraction constitutes 40% of the total weight. 280.9g (0.1 mole) of this block copolymer and 10.0 g (0.102 mole) of maleic anhydride are weighed out into a glass reaction vessel equipped with stirrer, thermometer and a nitrogen inlet and outlet. The mixture is then heated to 140-1 450C and the temperature maintained for 3 hours, after which time, the reaction mixture is allowed to cool. In a separate vessel 1.24 g of sodium hydroxide is dissolved in 200 g of water and 100.0 g of the maleic acid half ester prepared as above is added with stirring. A homogeneous solution is formed. 3.3 g of sodium metabisulphite is then added and the mixture heated to 90"C and maintained for 45 minutes. After cooling, an almost water white, low viscosity solution is obtained of approximately 34% solids content. The amount of sodium metabisulphite used in this example is such that addition to the maleic acid residue occurs at only half of the available sites i.e. y = 1.

In the table below two more compositions are given. The method of preparation is similar to that given in Example 1, making suitable adjustments to the weights of reactants so that substantially stoichiometric amounts are employed, and the amount of water so that the viscosity at the second stage (reaction with sodium metabisulphite) is not too high.

Block Copolymer Final Hydrophobic element Ethylene solids Reactive hydrogen oxide Acid content Ex. No. compound Type M. Wt. (%) Anhydride y (8/o) 2 Propylene glycol Butylene 2,900(n=20) 30% Maleic 2 ~ 28 (x=2) oxide . anhydride 3 Adipic acid Propylene 1,000(n=8) 45% Maleic 1 35 (x =2) oxide anhydride

EXAMPLE 4 125 parts of C.l. Disperse Blue 321 wet press cake of 39% solids content,40 40 parts of a lignin sulphonate and 30 parts of the product of Example 1 are mixed into a paste with 450 parts of water.

The paste is then milled in a sand mill until a mean particle size of about 1,um has been achieved. The resulting milled paste is then dried in a spray drier with a gas inlet temperature of 1600 C. The resulting dye powder disperses readily in water and is free of agglomerates. In the absence of the product of Example 1, the dye powder shows definite signs, as evident by microscopic examination, that some agglomeration of the dispersed dye particles occurs during drying.

EXAMPLE 5 100 parts of C.l. Disperse Red 82 press-cake of 33% solids content are slurried with 1 6 parts water and 20 parts of a condensation product of cresol, formaldehyde and sodium sulphite. This slurry is then added to a ball mill containing ceramic milling media, and the mill run until the dye is reduced to a mean particle size of approximately 0.6 Mm. To the resulting milled paste are added 1 5 parts of the product of Example 2 and 5 parts of diethylene glycol. A well dispersed storage stable liquid is produced.

An unscoured polyethylene glycol terephthalate woven fabric is wound onto a beam and charged to a beam dyeing machine together with a dyebath liquor made up as follows: 3.0% on weight of fabric of the product of Example 5.

1.0% on weight of fabric of Acetic Acid (48%) Water to give a liquor ratio of 1:10 The temperature is raised to 1 300C and maintained for 70 minutes before cooling to room temperature and rinsing the fabric. Examination of the dyed fabric showed it to be free of patches or spots and to exhibit good rubbing fastness. There are no deposits of dye on the internal surfaces of the dyeing machine.

For comparison purposes, a liquid of the same colour strength is prepared using only the condensation product of cresol, formaldehyde and sodium sulphite as dispersing agent and a dyeing of the same fabric carried out under identical conditions. The resulting fabric showed some degree of unlevelness and.an inferior rubbing fastness. In addition, some deposition of dye occurs on internal surfaces of the dyeing machine.

A further dyeing was carried out utilizing the same dyeing liquid which did not contain any product of the current invention. However an addition of 2 g/l of the product of Example 2 was made to the dyebath. After completion of the dyeing cycle, the resulting fabric was again found to be level and exhibited good rubbing fastness.

EXAMPLE 6 A 5.0g piece of knitted polyester fabric is dyed for 30 minutes.at 1 300C in a high temperature dyeing machine containing 100 ml of water, 0.5 ml of 10% acetic acid (80%) and 10 ml of a 1% dispersion of C.l. Disperse Red 82 commercial powder. The sample used was a commercial powder in which a formaldehyde condensate of sulphonated cresol had been employed as dispersing agent. After cooling, the fabric is washed in warm water and 2.5 g of this fabric placed together with 2.5 g of the same undyed material and 100 ml of water in the same dyeing machine. 0.2 g of the product of Example 3 is added to the dyebath liquor and the temperature raised to 1 250C and held for 30 minutes.

After removing the fabric pieces from the dyeing machine it is seen that at least half of the dye from the original dyed pattern has transferred to the undyed pattern.

When the test is repeated in the absence of the product of Example 3, it is observed that much less dye is transferred from the original dyed pattern to the undyed pattern. The degree of transfer of dye is a measure of ease of levelling, which in this instance has been improved considerably by the addition of a compound of the current invention.

Claims (29)

1. A compound of general formula I:

wherein A is the residue of a compound containing two to six reactive hydrogen atoms; One of R1 and R2 represents a hydrogen atom and the other represents an alkyl group having one to twenty-two carbon atoms; x represents an integer greater than 1 but no more than 6; m and n represent, on a molecular scale an integer, with the proviso that they have average values such that the molecular weight, determined by hydroxyl number, of the [(CHR1 CHR2njx fraction is from 900 to 7,500 and the molecular weight of the Ak CH2 CH2OHm]X fraction constitutes from 20 to 90% by weight of a compound of the general formula

wherein A, R1, R2, m, n and x are as previously defined; y represents an integer of at least one but not exceeding x; and B represents a group of formula;

or of the formula

wherein R3 and R4 each independently represents a hydrogen atom or a methyl group, with the proviso that both may not represent methyl groups, and each M, which may be the same or different, represents a hydrogen atom, ammonium, an alkali metal atom or the equivalent of an alkaline earth metal atom, or a mixture of such compounds of formula

2. A compound as claimed in claim 1, which is derived from ethylene diamine as the compound containing two to six reactive hydrogen atoms and polyoxypropylene as the CHR,CHR204n]x fraction and wherein the molecular weight of the latter is in the range of 1000 to 5000 and the weight percent of the [(CH2CH2O-m]x fraction is 25 to 55.

3. A compound as claimed in claim 2, in which n, m and x have values of 12, 11 and 4, respectively.

4. A compound as claimed in claim 1, which is derived from propylene glycol as the compound containing two to six reactive hydrogen atoms and polyoxypropylene as the ACHR1CHR204n]x fraction and wherein the molecular weight of the latter is at least 1 500 and the weight percent of the [(CH2CH2O-)m]x fraction is 40 to 70.

5. A compound as claimed in claim 4, in which n, m and x have values of 13, 22 and 2, respectively.

6. A compound as claimed in any of claims 1 to 5, in which M is sodium.

7. A process for the preparation of a compound of formula I, as defined in claim 1 , or a mixture of such compounds, which comprises reacting one mole of a compound of general formula:--

wherein A, R1, R2, n, m and x have the meanings given in claim 1, withy moles of an unsaturated acid anhydride of general formula:

wherein R3 and R4 have the meanings given in claim 1, at a temperature in the range of 20 to 2200C, to yield the corresponding semi-ester, neutralising the semi-ester with an aqueous alkali, and subsequently converting to the corresponding sulphited semi-ester of formula I by reaction with y to 1.5y moles of a sulphite, bisulphite or metabisulphite at 10 to 1000C in aqueous solution.

8. A process as claimed in claim 7, in which the compound of formula II and the unsaturated acid anhydride are reacted at a temperature of 50 to 1 500C.

9. A process as claimed in claim 7 or claim 8, in which the neutralised semi-ester is reacted with 1.05y to 1.1 y moles of the sulphite, bisulphite or metabisulphite.

10. A process as claimed in any of claims 7 to 9, in which the neutralised semi-ester and the sulphite, bisulphite or metabisulphite are reacted at a temperature of 40 to 800 C,

11. A process as claimed in any of claims 7 to 10, in which the compound of formula Il and the unsaturated acid anhydride are reacted in the presence of 0.05 to 1.5% by weight, based on the weight of the total mixture, of an alkali metal hydroxide.

12. A process as claimed in any of claims 7 to 11, in which the reaction of the compound of formula II with the unsaturated acid anhydride is effected in a sealed vessel.

13. A process as claimed in claim 12, in which the pressure in the sealed vessel is 0.2 to 1.0 bar.

14. A process as claimed in any of claims 7 to 13, in which the aqueous alkali used to neutralise the semi-ester is sodium hydroxide solution.

1 5. A process as claimed in any of claims 7 to 14, in which the unsaturated acid anhydride is maleic anhydride.

16. A process as claimed in any of claims 7 to 1 5, in which the sulphite, bisulphite or pyrosulphite is sodium sulphite, sodium bisulphite or sodium metabisulphite.

1 7. A disperse dye composition, which is in the form of a powder or aqueous dispersion and comprises a dye, a dispersing agent and at least one compound of formula I, as claimed in any of claims 1 to 6, said dispersing agent being present in an amount of 70 to 90% by weight and said compound(s) of formula I being present in an amount of 30 to 2% by weight, both percentages being based on the combined weight of dispersing agent and compound(s) of formula I.

1 8. A process for the preparation of a composition as claimed in claim 17, which comprises reducing the particle size of the dye in the presence of the compound(s) of formula I, or in the presence of a dispersing agent with the subsequent addition of the compound(s) of formula I, or in the presence of a mixture of such compounds, until an aqueous dispersion is attained in which the mean particle size is 0.1 to,um.

19. A process as claimed in claim 18, in which an anti-foaming agent is present during the particle size reduction step.

20. A process as claimed in claim 1 8 or claim 19, in which the resulting aqueous dye dispersion is standardised with respect to strength and, if desired, a further addition of at least one material selected from dispersing agents, compounds of formula I, stabilising agents, humectants and anti-foaming agents is made.

21. A process as claimed in claim 1 8 or claim 19, in which the resulting aqueous dispersion is dried to obtain the composition in powder form and, if desired a further addition of dispersing agent and/or compound(s) of formula I is made.

22. A process as claimed in claim 21, in which the aqueous dispersion is spray dried.

23. A process for dyeing textile materials, which comprises contacting a textile material with a disperse dye composition containing at least one compound of formula I, as claimed in any of claims 1 to 6,

24. A compound as claimed in claim 1 and substantially as hereinbefore described with reference to any of Examples 1 to 3.

25. A process as claimed in claim 7 and substantially as hereinbefore described with reference to any of Examples 1 to 3.

26. A disperse dye composition as claimed in claim 1 7 and substantially as hereinbefore described with reference to either Example 4 or Example 5.

27. A process as claimed in claim 1 8 and substantially as hereinbefore described with reference to Example 4 or Example 5.

28. A process as claimed in claim 23 and substantially as hereinbefore described with reference to Example 6.

29. Textile material whenever dyed by a process as claimed in claim 23 or 28.