GB2126258A - Cationic dyestuff preparation for non-woven fabrics - Google Patents

Abstract

Non-woven fabrics, including tissue paper, are coloured using a filler which has been dyed with a water- soluble cationic dyestuff. The dyed filler may be applied to a finished non- woven fabric in a printing ink or paste, or may be applied with an aqueous binder dispersion during the manufacture of the non-woven fabric.

Description

SPECIFICATION Improvements in or relating to organic compounds Nonwoven fabrics are flexible, porous, two dimensional structures which generally consist of textile fibres laid down in random directions. The random mat of fibres may be prefixed by mechanical means such as needling and then fixed, usually with a binder or alternatively by partial solution or melting of the fibres, or by a combination of these techniques.

Tissue paper is similar to a nonwoven fabric, in that it is prepared as a fine random web of fibres (cellulose pulp fibres instead of textile fibres) which is often then fixed by mechanical means such as embossing or creping, possibly followed by the use of a binder. In this specification, the terms "nonwoven fabrics" or "non-wovens" will be taken to include tissue paper.

In the preparation of non-wovens in which the mat is fixed with an aqueous dispersion of a binding agent, colouring is usually achieved by mixing organic or inorganic pigments with the binder dispersion. Similarly, finished non-wovens are generally coloured by printing or impregnating with printing inks or pastes containing organic or inorganic pigments.

If the binding agent dispersion contains fillers such as kaolin and chalk as well as the coloured pigments, which is often the case in the manufacture of artificial leather on the basis of a non-woven fabric, then the white filler and the coloured pigment tend to separate from each other in the impregnation process, giving rise to poor levelness, shade variations and poor colour yield.

Similarly, when in printing inks or pastes, mixtures of differently coloured pigments are used to obtain particular shades, the individual pigments tend to migrate to different extents when the printed or impregnated substrate is dried, leading to variations in shade and poor levelness.

A further disadvantage of the use of organic or inorganic pigments as colouring agents is that the resulting non-wovens are not bleachable, or bleachable only with difficulty, which causes problems in the recycling of such materials.

If water-soluble dyestuffs are used for the dyeing or printing of non-woven fabrics, the resulting dyeings and printings do not meet the fastness requirement for many applications. In particular the bleeding fastness in water, alcohol, milk and soap solution as well as the light fastness are frequently inadequate. Furthermore the same problems of differential migration during drying occur as when coloured pigments are used.

It has now been found that these disadvantages may largely be overcome when white pigments (fillers) dyed with cationic dyestuffs are used as colouring agents.

Accordingly, the present invention provides a process for the preparation of coloured non-woven fabrics, including tissue paper, characterised in that the colouring agent is a filler which has been dyed with a water-soluble cationic dyestuff.

Suitable fillers may be organic, for example urea/formaldehyde condensation products such as the commercially available products PergopakR (Ciba-Geigy) or LytronR (Monsanto), but are preferably inorganic. Preferably the filler is a white inorganic pigment. Examples are finely divided silicates, e.g.

kaolin (china clay), talc (soapstone), diatomite (kieselguhr or filter earth), french chalk, asbestine, calcium silicate (obtainable in particularly suitable form by mixing cold concentrated CaCI2 solution with cold concentrated sodium silicate solution), quartz sand and asbestos; sulphates e.g. gypsum, annaline, lenzine, satin white (calcium sulphoaluminate), heavy spar and permanent white (both BaSO4); carbonates e.g. calcium carbonate (e.g. chalk), magnesite, whiterite, white lead, dolomite and calamine; oxides or hydroxides e.g. alumina, bayrites, titanium dioxide, slaked lime, burned magnesia and zinc white; sulphides e.g. lithopone and zinc sulphide; and sulphites e.g. calcium sulphite. Preferred fillers for dyeing with cationic dyes are kaolin, calcium carbonate, talc, permanent white and titanium dioxide, especially kaolin, calcium carbonate and talc.It is surprising that even cheap fillers such as chalk give excellent results, particularly with the selected groups of cationic dyes.

Preferred cationic dyestuffs are polycationic dyestuffs having at least 1.3 cationic groups (quaternary or protonated nitrogen atoms) per dye molecule, whereby a non-integral number of cationic groups is to be understood as an average value for the molecules of the dyestuff in question.

The dyestuffs may also contain anionic groups, particularly sulphonic acid groups, but if any such are present, then the number of cationic groups per molecule must be at least one greater than the number of anionic groups per molecule. Expressed numerically, if there are x cationic and y anionic groups per molecule, then x)1.3 and 0y(x-1). More preferably the dyestuffs are biscationic.

The dyes may be metallized or metal free, but metal complex dyes are preferred, more preferred being 1:1 and 1:2 metal complex azo dyes. For 1:2 complexes, containing two dyestuff units per metal atom, the requirement of at least 1.3 cationic groups per molecule applies to each dyestuff unit and not to each molecule of complex. As well as azo dyes, other cationic dyes, for example phthalocyanine (preferably copper phthalocyanine) dyes and anthraquinone dyes may be used. Dyes containing a fibre-reactive group may also be employed.

Preferably the dyes have, as the metal-free cation, a molecular weight of at least 400, preferably 500-1 500, more preferably 500-1000. They must be substantive to the filler to be used, and preferably they exhaust from an aqueous solution containing 1% dyestuff, based on the weight of filler, on to the filler, at 20-900C and without the use of dyeing assistants, to an extent of at least 90%.

More preferred dyes are those which give a high degree of exhaust on cotton, as measured by the following test: the dye should give an exhaust ratio (ratio of dye exhausted on to substrate to total dye in bath) of 90100% as defined by DIN 54000 or ISO RlOS/I 1 959, part 1, when dyed on to mercerised cotton at 1/1 standard depth from a boiling aqueous electrolyte-free bath at 20:1 liquor to goods ratio, dyeing time 90 minutes.

Dyestuffs meeting these conditions are predominantly those having peripheral or terminal cationic groups in the molecule. One preferred groups of dyestuffs are phthalocyanine dyestuffs containing two or more cationic groups which are attached to the periphery of the planar phthalocyanine ring system. A further preferred group of dyestuffs have a substantially linear structure comprising three or more homo- or hetero-aromatic rings or fused ring systems joined directly or by bridging groups in such a way that there are two terminal rings or ring systems and one or more medial rings or ring systems, there being on average at least 1 .3 cationic groups per molecule attached to terminal rings or ring systems, and none elsewhere.In a more preferred group there are two or more, preferably two cationic groups per molecule, one or more, preferably one on each terminal ring or ring system and none elsewhere.

Dyestuffs having the above properties and structural features are known in the art, and are disclosed for example in the following published patents and patent applications: German published applications 1 061 010,1 064 661,1 621 702,2250676,2251 041,2 604 699,2 627 680 and 2 810 246; US Patents 3 709 903, 3 784 599,3 839 426, 3 933 787, 3 935 182,3 996 282, 4-046 502,4 103 092,4 146 558,4 153 598 and 4213 897; and European published applications 13 751,14 677,14 678,15 232,15 233,15 511,16 726,24321,24322,24 725,38 299, 54 616, 56 574, 62 824, 62 825, 63 261 and 65 595.Particularly preferred cationic dyestuffs are those disclosed in published British Patent Applications 2 076 421A, 2 081 734A, 2 082 615A and 2 104 538A, British Patent 2 019 873 and published European Application 41 040, the contents of which are incorporated herein by reference.

The dyed filler may be prepared by making the white pigment into a paste with water, or by dispersing it in water with the aid of a non-ionic and/or cationic dispersing agent, the solids content of the resulting paste or dispersion being from 0.1% to 90% by weight, preferably 1 0-70%. To the stirred paste or dispersion is then added a 0.190% wt. aqueous solution, preferably a 540% solution, of the cationic dyestuff, at a temperature of 1-1 000C, preferably 20--700C. The required dyeing time is from 10 seconds to 60 minutes, a time of 1-20 minutes generally being sufficient.

Optionally a conventional fixing agent may be used.

Alternatively, the dry white pigment may be mixed thoroughly with dry dyestuff in powder or granulate form, and the resulting mixture made into a paste with water of dispersed in water with the aid of a dispersing agent. The dyeing conditions are then the same as given above.

The resulting dyed pigment may be isolated e.g. by filtration, centrifuging or spray drying, and the product further washed and dried if required. Alternatively the dyed slurry may be used directly in the next step.

In the preparation of binding agent dispersions, printing inks and pastes, it is desirable to add 0.110% by weight of the filler of a dispersing agent e.g. a polyphosphate or polyacrytate to the dyed filler. Other suitable dispersing agents include condensation products of sulphonated aromatic compounds with aldehydes, e.g. condensation products of sulphonated naphthalene, diphenyl, diphenyl oxide and related products with formaldehyde. The preferred dispersing agents are condensation products of P-naphthalene sulphonic acid with formaldehyde, containing units-of structure.

These dispersing agents, which are known, may also be used in combination with other dispersing agents such as polyacrylate, particularly when large amounts of dyestuff are used, or low viscosities must be attained.

If light shades of colour are required, the dyed filler may be mixed in suitable proportions with undyed white pigment. In this case it is preferred that the white pigment used is identical to the filler before dyeing.

The process of the invention is preferably either colouration during the fixing of the non-woven by addition of an aqueous binder dispersion containing the dyed filler or dyeing or printing of the finished non-woven using a printing ink or paste containing the dyed filler.

Preferably the substrate is a non-woven comprised of textile fibres (not tissue paper), and the preferred process is printing of the finished non-woven using a printing ink or paste containing the dyed filler. Such printing inks and pastes preferably contain a binding agent in addition to the dyed filler.

The preparation of printing inks, printing pastes and aqueous binder dispersions for non-wovens is well known. They are normally based upon dispersions of homo- or co-polymers of monomers such as butadiene, styrene, acrylonitrile, isobutylene, vinyl esters, vinyl alcohol, vinyl halides, vinylidene chloride, acrylic esters, acrylamide, methylacrylamide and methylene-bis-acrylamide; or of ureaaldehyde, melamine or carbamate resins; or of starches, carboxyalkylcellulose and their derivatives; or of saponifiable maleinate resins.

Preferred binding agents for binder emulsions, printing inks and pastes include those based on acrylates, butadiene/acrylonitrile, styrene/butadiene, polyvinyl chloride, polyvinylidine chloride, polyvinyl alcohol, polyvinyl acetate and copolymers and mixtures of these, as described for example in German published application 2 938 896. They preferably constitute from 220% by weight of the composition.

The coloured non-woven fabrics prepared according to the process of the present invention are readily bleachable and have level dyeings with good bleeding- and light-fastness and a high colour yield. They are prepared with minimum pollution of equipment and of waste water. Problems of differential migration as between white and coloured filler do not arise if the same filler is used both dyed and undyed; similarly different coloured dyeings on the same filler will have the same migration properties.

Aqueous binder dispersions, printing inks and pastes containing the dyed fillers also show good stability.

The following Examples in which all parts and percentages are by weight illustrate the invention: Example 1 100 parts of a 35% aqueous dispersion of kaolin (English China Clay Ltd.) are stirred at room temperature (200 C) and 1 5 parts of a 25% aqueous solution of the dye

are added. After 2 minutes dyeing time 1.5 parts of a dispersing agent based on sodium polyacrylate (Polysalz F, BASF) are added.

To 40 parts of this pigment slurry are added 40 parts water, 1 5 parts ethylene glycol and 5 parts of a binder dispersion containing 50% butadiene/styrene polymer (Dow Latex 620). The resulting printing composition is used to print tissue paper by the conventional flexoprint process or deep print process. A printing with good bleeding fastness to water, alcohol and milk is obtained without further heat treatment.

Example 2 100 parts of a 35% aqueous suspension of kaolin (English China Clay) are dyed with 1 5 parts of the dyestuff solution of Example 1. To 40 parts of this dyed pigment slurry are added 30 parts of an aqueous dispersion containing 46% polyacrylate binder (Primal E-32, Rohm a Haas) and 20 parts of a 10% solids starch solution.

The resulting printing paste is applied by the conventional deep print process to a non-woven fabric comprising 50% viscose, 25% polyamide and 25% cellulose fibres. The printed non-woven is dried for 60 seconds in a convection drier at 1 500C, giving a green print with good fastness to milk, water and alcohol.

Example 3 100 parts of a 50% suspension containing 25 parts kaolin (English China Clay), 25 parts chalk (Omyalite 90) and 50 parts water are stirred into 100 parts of a 5% solution of the dyestuff of formula

After stirring for 5 minutes, 1 part of the dispersing agent Polysalz F (as in Example 1) is added.

50 parts of the resulting blue-dyed chalk/kaolin slurry are then stirred into 50 parts of an aqueous dispersion containing 47.5% butadiene/acrylonitrile binder (Perbunan N Latex 341 5 M), 3 parts of an ethoxylated alkyl-polyalkylamine (heat sensitizer) are added, and the pH value is adjusted to approx. 7.

The resulting dispersion is used to impregnate a mechanically pre-fixed fibre mat consisting of cellulose and polyester fibres, at a pick-up of 200% of the dry weight of the mat. The impregnated mat is dried and the binder cured using a combination of infra-red lamps and a convection drier, giving a finished non-woven fabric, evenly coloured both on the surface and in section, easily bleached, and having good light fastness, rubbing fastness and excellent bleeding fastness to water and alcohol.

Claims (20)

Claims

1. A process for the preparation of coloured non-woven fabrics, including tissue paper, characterised in that the colouring agent is a filler which has been dyed with a water-soluble cationic dyestuff.

2. A process according to Claim 1 in which the filler is kaolin, calcium carbonate or talc.

3. A process according to Claim 1 or Claim 2 in which the dyestuff is a polycationic dyestuff having at least 1.3 cationic groups per dye molecule.

4. A process according to Claim 3 in which the dyestuff is biscationic.

5. A process according to any one of the preceding claims in which the dyestuff is a metal complex dyestuff.

6. A process according to Claim 5 in which the dyestuff is a 1:1 or 1:2 metal complex azo dye

7. A process according to any one of the preceding claims in which the dyestuff, as the metal-free cation, has a molecular weight of at least 400.

8. A process according to any one of the preceding claims in which the dyestuff exhausts from an aqueous solution containing 1 % dyestuff, based on the weight of filler, on to the filler, at 20-900C and without the use of dyeing assistants, to an extent of at least 90%.

9. A process according to any one of the preceding claims in which the dyestuff gives an exhaust ratio (ratio of dye exhausted on to the substrate to total dye in bath) of 90100% as defined by DIN 54000 or ISO RlOS/l 1959, part 1, when dyed on the mercerised cotton at 1/1 standard depth from a boiling aqueous electrolyte-free bath at 20:1 liquor to goods ratio, dyeing time 90 minutes.

10. A process according to any one of the preceding claims in which the dyestuff is a phthalocyanine dyestuff containing 2 or more cationic groups which are attached to the periphery of the phthalocyanine ring system.

11. A process according to any one of Claims 1-9 in which the dyestuff has a substantially linear structure comprising three or more homo- or hetero-aromatic rings or fused ring systems joined directly or by bridging groups in such a way that there are two terminal rings or ring systems and one or more medial rings or ring systems, there being on average at least 1.3 cationic groups per molecule attached to terminal rings or ring systems, and none elsewhere.

1 2. A process according to Claim 11 in which the dyestuff has one cationic group on each terminal ring or ring system and none elsewhere.

1 3. A process according to any one of the preceding claims in which the dyestuff is one of those disclosed in published British Patent Applications 2 076 421A, 2 081 734A, 082 615A, British Patent 2 019 873 or published European Application 41 040.

14. A process according to any one of the preceding claims in which the colouring agent is applied in a printing ink, printing paste or aqueous binder dispersion.

1 5. A process according to Claim 14 in which a non-woven fabric is coloured during fixation by addition of an aqueous binder dispersion containing the dyed filler.

16. A process according to Claim 1 5 in which a finished non-woven fabric is dyed or printed using a printing ink or paste containing the dyed filler.

1 7. A process according to any one of Claims 14-1 6 in which the printing ink, printing paste or aqueous binder dispersion contain 0.1-1 0% of a dispersing agent based on the dry weight of the filler.

1 8. A process according to Claim 1 7 in which the dispersing agent is a condensation product of p-naphthalene sulphonic acid with formaldehyde, containing units of structure

19. A process for the colouration of non-woven fabrics as described in any one of the Examples.

20. A coloured non-woven fabric containing a filler which has been dyed with a water-soluble cationic dyestuff.