PROCESS FOR PRINTING PREDETERMINED PATTERNS OM POLY (M-PHENYLENE- ISOPTHALAMIDE)TEXTILE FABRIC AND STABLE, HOMOGENEOUS PRINT PASTE THEREFOR

Abstract: A process of printing a predetermined pattern on a poly(m-phenyleneisophthalamide)-containing textile fabric comprises the successive steps of: (a) applying a print paste, composed of a highly polar solvent selected from the group consisting of dimethylsulphoxide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and mixtures thereof, the polar solvent adapted to swell the aramid fibre and introduce a dyestuff therein, at least one organic dyestuff that is soluble in the polar solvent, a print paste thickening agent compatible with both the polar solvent and the dyestuff, water and optionally at least one flame retardant, in a predetermined pattern onto the surface of the aramid textile; and (b) drying and curing the thus printed fabric at an elevated temperature sufficient to permeate and fix the dyestuff molecules inside the aramid fibres.

Description: This invention relates to processes for printing predetermined patterns on poly(m-phenyleneisophthalamide) - aramid - textile fabric and stable, homogeneous print paste therefor. In particular, the present invention relates to the surprising discovery that particular print paste formulations are functional so as to enable printing of textile fabrics derived from aramid fibres with a variety of conventional organic dyestuffs to produce printed patterns of full tinctorial values having good overall fastness properties especially to washing, crocking, sublimation, and light without adversely affecting the excellent flame resistant and tensile properties of these fibres. Disclosed is a printing process in which conventional organic dyestuffs, i.e. cationic, anionic, fibre reactive, disperse, vat, solvent, azoic, and mixtures thereof, can now be utilized in accordance with this invention for the printing of aramid fabrics. The inclusion of a flame-retardant chemical in the print paste allows the simultaneous printing and flame retardant treating of aramid fibres. Print paste compositions for conducting the process are also described. High molecular weight wholly aromatic polyamides or aramids made by the condensation or reaction of aromatic or essentially aromatic monomeric starting material or materials described in US-A-4,198,494 and sold under the trademarks Nomex by E. I. duPont de Nemours and Co., Conex by Teijin Corp., and Apyeil and Apyeil-A ( Apyeil containing finely divided carbon) by Unitika Ltd. are extremely strong and durable and have excellent flame resistant properties. Shaped articles made of these aramid fibres such as yarn and textile fabrics are commercially important and gaining in popularity especially in the protective fabric field and other markets where the combined flame resistance and high tensile properties are essential. A serious problem limiting the full commercial exploitation of aramid fibres has been the fact that fabrics made from these highly crystalline fibres of extremely high glass transition temperature are very difficult to print into colored patterns and designs with good overall fastness properties, especially to light and washing, without adversely affecting their handle, tensile, and flame resistant properties. Recently, it has been proposed in US-A-4,525,168 to print aramid fabrics with anionic dyes, i.e. acid dyes, premetalized acid dyes, and direct dyes. This is accomplished by introducing into the aramid fibre dye site receptor substances such as aromatic and aliphatic amines capable of forming ionic bonds with anionic dyes. The dye site substances are introduced and fixed inside the fibre by a special process prior to the printing operation. After printing the fabric with an anionic dyestuff and drying, the printed fabric is turbo steamed under pressure to penetrate and fix the anionic dyestuff inside the fibre. This process suffers a number of technical and economic drawbacks. It requires a special pretreatment process involving the use of speciality chemicals to provide the fibre with dye sites. Only anionic dyestuffs, i.e. dyestuffs containing one or more sulphonic acid groups or their sodium salts, can be used in the printing operation. Furthermore, it requires turbo steaming, a non-continuous operation to penetrate and fix the anionic dyes inside the fibre in order to develop the true shade and fastness properties of the prints. Further, experienced operators report that turbo steaming of printed fabrics tends to give rise to track-off problems in production. In another development it has also been proposed by Cook and co-workers, Effect of Auxiliary Solvents in STX Coloration of Aramids and PBI with Cationic Dyes in "Book of Papers, AATCC National Technical Conference," New Orleans, Louisiana, October 5 - 7, 1983, pp. 314 - 326, to improve the screen printing of Nomex aramid fabrics. In the procedure described the Nomex aramid fabric is pretreated in certain highly polar solvents such as DMSO under suitable conditions, i.e. pad-squeeze, heated at 66°C (150°F) for 10 minutes, washed at 38°C (100°F) and dried prior to the printing operation. In this case too, the fabric has to be pretreated in a special process prior to the printing operation as outlined above. Furthermore, such pretreatment if not properly controlled, may cause drastic reductions in the tensile and mechanical properties of the fabric. In FR-A-2,016,980, there is disclosed a process for dyeing a poly-(m-phenyleneisophthalamide-) fibre by contacting the fibre with a dyeing solution of a highly polar solvent selected from the group consisting of dimethylsulphoxide, N,N-dimethylactamide, N-methyl-2-pyrrolidone and mixtures thereof, and an organic dyestuff that is soluble in the polar solvent. The treated fibre is then heated to fix the dye in the fibre. FR-A-2,016,980 uses a dyeing solution and not a print paste, and it also does not disclose the use of a flame retardant. The present invention seeks to provide an improved process for the printing of aramid fabrics, whereby fabrics made of aramid fibres can be printed with a variety of conventional organic dyestuffs such as cationic, anionic, disperse, fibre reactive, solvent, vat, azoic, dyes as well as mixtures thereof to obtain printed patterns with superior overall fastness properties. The present invention also seeks to provide a process for the concurrent printing and flame retardant treating of aramid fabrics when a flame retardant is included in the print paste. The process allows the use of two or more dyestuffs of different classes in the same print paste formulation, and this is believed to be unique. The present invention further seeks to provide an improved process for the printing of aramid fabrics in which penetration and fixation of dyestuffs inside the aramid fibre are achieved. The present invention relates to the discovery that aramid fibre or products made from said fibre, such as textile fabrics, previously thought of as being very difficult to print into coloured patterns and designs of good overall fastness properties without having, for example, to introduce into the fibre dye site substances in order to make them printable with anionic dyes as disclosed in US-A-4,525,168, are nonetheless capable of being printed in a single step with a variety of organic dyestuffs using a specially formulated print paste. This print paste according to the present invention is capable of swelling the aramid fibre and permeating the dyestuff, which is also soluble in the print paste, inside the fibre. A flame retardant, present in the print paste, may also be introduced inside the fibre together with the dyestuff. The swollen fibre is then collapsed and allowed to shrink back to its original dimensions by subsequent drying and curing operations thereby trapping and fixing the dyestuff inside the fibre. According to one aspect of the present invention there is provided a process of printing a pre-determined pattern on a poly(m-phenyleneisophthalamide)-containing textile fabric characterised by comprising the steps of: (a) applying a print paste, composed of a highly polar solvent selected from the group consisting of dimethylsulphoxide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and mixtures thereof, the polar solvent being adapted to swell the aramid fibre and introduce a dyestuff therein, at least one organic dyestuff that is soluble in the polar solvent, a print paste thickening agent compatible with both the polar solvent and the dyestuff, water and at least one flame retardant, in a pre-determined pattern onto the surface of the aramid textile; and (b) drying and curing the printed fabric at an elevated temperature sufficient to permeate and fix the dyestuff molecules inside the aramid fibres. According to another aspect of the present invention there is provided a stable, homogeneous print paste for printing and dyeing a poly(m-phenyleneisophthal-amide)-containing textile fabric in a pre-determined pattern, the print paste being characterised by consisting essentially, in percent by weight, of: about 70 to about 85% of a highly polar solvent adapted to swell poly(m-phenylene-isophthalamide) fibres and introduce a dyestuff therein, the highly polar solvent being selected from the group consisting of dimethylsulphoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and mixtures thereof; a tinctorial amount of an organic dyestuff soluble in the highly polar solvent and capable of dyeing and fixing in said fibres; a print paste thickening agent soluble in the highly polar solvent and compatible with the organic dyestuff, the thickening agent together with the other ingredients being present in an amount sufficient to provide the print paste with a viscosity in the range of about 5 kPa (5,000 cps) to about 36 kPa (36,000 cps); a flame retardant that is compatible with the other components of the print paste; and balance water. Polyaramid fabrics can now be printed with the process of the invention, thereby providing the printer with a wide range of dyestuffs, such as cationic dyes, anionic dyes, disperse dyes, fibre reactive dyes, vat dyes, azoic dyes, solvent dyes, and mixtures thereof from which to choose to print any colour pattern required having outstanding overall fastness properties, especially to washing, dry cleaning, crocking, sublimation and light, without adversely affecting the handle and excellent mechanical and flame resistant properties of the aramid fabrics. Curing of the printed goods may be carried out continuously under atmospheric pressure. The use of a combination of two or more dyes from different dyestuff classes in the same print paste formulation in the printing process, particularly on aramid fibres, is believed to be unique. The print paste of the present invention will preferably include about 3.0 to 4.0 parts thickening agent, 70 to 85 parts highly polar solvent, 5 to 20 parts water and from 1 to 10 parts of a flame retardant; all parts being by weight. Other compatible print paste adjuvants such as UV absorbers, anti-static agents, water repellants and other finishing and processing aids may also be present in the print paste. A tinctorial amount of at least one compatible dyestuff is, of course, included in the print paste. The thickening agent used in the process can be any of the conventional thickeners for print pastes usable for printing textile materials such as natural starch, British gum, crystal gum, natural and etherified locust bean gums, carboxymethyl cellulose, gum tragacanth, polyacrylic acid sodium salt and sodium alginate, provided that it is soluble in the polar solvent or mixture of solvents used in the print paste and capable of forming a stable, homogeneous printing paste of appropriate viscosity to be able to be used in practice. Preferably the thickening agent will be of a polyacrylic acid type molecular weight range 450,000 to 4,000,000 and will be present in an amount sufficient so that the resulting print past will have viscosity ranging between 5 kPa (5,000 cps) to about 36 kPa (36,000 cps). The solvent used in the process can be any solvent capable of solvating the aramid fibre. By solvating is meant the formation of a complex between one or more molecules of the solvent and the aramid fibre molecules resulting in swelling of fibres and fibrids without dissolving or destroying them. Solvents such as N,N-dimethylformamide (DMF), dimethylsulphoxide (DMSO), N,N-dimethylacetamide (DMAC), and N-methyl-2-pyrrolidone (NMP), and combinations of two or more of these solvents have been found suitable as solvating agents in accordance with the present invention. In addition, none of these highly polar solvents cause an excessive reduction in mechanical properties. Any organic dyestuff may be used. Such dyestuffs may be selected from cationic dyes, anionic dyes i.e. acid dyes, metalised acid dyes, direct dyes; solvent dyes, disperse dyes, fibre reactive dyes, vat dyes, and azoic dyes, provided that the dye selected is soluble in the print paste and does not affect the homogenity and stability of the print paste. Combinations of these days can also be used in the same print paste provided that they are soluble in the print paste and do not affect the homogenity and stability of the print paste. Flame-retardant chemicals suitable for incorporation into the print paste must be compatible with the other components of the formulation. Below is a listing of suitable flame retardant agents, reference sometimes being made for convenience to the trade names of these flame retardant agents: Antiblaze 19 (Mobil Chemicals) - cyclic phosphonate compound containing 21% phosphorus (93% active), a mixture of 55% mono-ester and 45% di-ester. Antiblaze 19T - Antiblaze 19 containing 7% water. Pyrovatex 3887 (made by Ciba-Geigy distributed by C.S. Tanner) - hexabromocyclododecane -dispersion system F/R P 58 (White Chemical) XC - 5311 (Great Lakes Chemical) based on pentabromodiphenyl oxide Apex 401 (Apex Chemical) Polygard 123 (Hamilton Auslander) Pyrosan 546 (Laurel Band Product) Pyron 650 (Chemiconics Industries) Fyrol FR-2 (Stauffer Chemical) Apex 197 or 212 (Apex Chemical) Pentabromodiphenyl oxide (Great Lakes Chemical) Pyron 5115 (Chemonics Industries) RC 9431 (Pennwalt Chemical) FR 1030/190 (Sandoz) Antiblaze 78 (Mobil Chemical) Antiblaze 77 (Mobil Chemical) Apex 331 (Apex Chemical) Firemaster PHT4 (Michigan Chemical) Phosgard C-22-R (Monsanto) Phosgard 2XC-20 (Monsanto) Phosgard 1227 (Monsanto) Firemaster PHT4 Diol (Michigan Chemical) Kromine 9050 (Kiel Chemical) Kromine 9050-XS (Kiel Chemical) 2,3-dibromopropyl methacrylate (Great Lakes Chemical) Tribromophenoxyethylacrylate (Great Lakes Chemical) 2,3-dibromo-2-butene-1,4-diol (GAF) K 23 (Mobil Chemical) Any of these flame-retardant chemicals can be used in the process provided that the flame-retardant chemical selected is soluble in the print paste, does not affect the homogenity and stability of the print paste, and does not affect the colour and fastness properties of the printed patterns. Combinations of two or more flame-retardant chemicals in the same print paste can also be used in the process. The aramid fibre for which the present invention is particularly well suited can be in any suitable structural form, i.e., light, medium and heavy weight woven and knitted fabrics of different weaves constructed from continuous filament and spun yarns of different types and counts, non-woven, felt and carpet materials. The term high molecular weight aromatic polyamide or aramid are used herein is to be understood as those described in US-A-4,198,494. Fibres amenable to the process of this invention are the meta isomers, specifically they are composed of poly(m-phenyleneisophthalamide). These fibres are sold under the trademarks Nomex by E. I. duPont de Nemours and Co., Conex by Teijin Corp., and Apyeil and Apyeil-A ( Apyeil containing finely divided carbon) by Unitika. Fabrics made of these fibres are extremely strong and have excellent inherent flame resistant properties. These flame resistance properties may be improved by the inclusion of at least one flame retardant in the print paste formulation. The suitability of a particular fibre or type of fibre to the process of this invention can readily be determined by a single test. Dyeing of the fibre is acceptable; staining of a candidate fibre is not. The process of the present invention can also be conveniently carried out using conventional printing techniques. For example, the fabric can be printed in those portions where colored patterns are required with the print paste of this invention. The thus printed fabric is dried at about 135 to 150°C then cured for 2 to 5 minutes or so at 160 to 180°C under atmospheric pressure. Residual unfixed dyestuffs, thickener and impurities from the printed goods are then removed from the textile fabric by subsequent washing treatments. Novel printed aramid fabrics, printed in any design or pattern, are also disclosed. The invention will be further described with reference to the following nonlimiting examples in which the parts and percentages noted are by weight unless otherwise indicated. EXAMPLE 1 A plain weave aramid fabric made of intimate fibre blend of 95% Nomex /5% Kevlar (trade mark) (duPont T-455 Nomex ) weighing 135 g/m² (4ozs./sq. yd.) of staple warp and fill yarns 38/2, 26z//18s (32240 m/kg - 15960 yd./lb.), for use in garments offering protection against brief exposure to extreme thermal fluxes was printed in accordance with a predetermined pattern with a print paste having the following composition: Carbopol 934 - molecular weight approximately 3,000,000 (Acrylic acid polymer sold by B. F. Goodrich) 3 parts Dimethylsulphoxide (DMSO) 82 parts Sevron Yellow 6DL (Basic Yellow 29) 5 parts Water 10 parts The fabric was then dried at 148°C for 2 minutes, and subsequently cured for 3 minutes at 165°C under atmospheric pressure. The cured fabric was then rinsed in cold and hot water, treated for 5 minutes in an aqueous solution of 0.5 % sodium carbonate and 0.2% of a non-ionic detergent at 80°C, rinsed in hot water followed by cold water, and finally dried. A bright reddish yellow print pattern of good overall fastness properties was obtained without any adverse affect on the excellent tensile and flame resistance properties of the fabric. A cross-section photomicrograph of the printed fibres revealed that the dyestuff molecules completely penetrated and fixed inside the fibre. EXAMPLE 2 The procedures given in Example 1 were repeated using the following dye in the print paste: Basacryl Red GL (C. I. Basic Red 29) 2 parts A red print pattern of good overall fastness properties was obtained without any adverse effect on the excellent tensile and flame resistance properties of the fabric. The dyestuff molecules were completely penetrated and fixed inside the fibre as shown in a cross-section photomicrograph. EXAMPLE 3 The procedures of Example 1 were repeated using the following dye in the print paste. Basacryl Blue GL (C. I. Basic Blue 54) 5 parts A dark blue pattern with the same type of results was obtained as in Examples 1 & 2 above. Complete dye penetration inside the fibre was achieved. EXAMPLE 4 The above procedures of Example 1 were repeated using the following cationic dyestuffs in the print paste; Sevron Yellow 6DL (C. I. Basic Yellow 29) 29 parts Basacryl Red GL1 (C. I. Basic Red 29) 2.5 parts Basacryl Blue GL (C. I. Basic Blue 54 ) 2.5 parts A solid black pattern of good overall fastness properties was obtained without any adverse effect on the tensile and flame resistance properties of the fabric. The dyestuffs molecules were completely penetrated and fixed inside the fibre as shown in a cross-section photomicrograph. EXAMPLE 5 The above procedures of Example 1 were repeated using a metalized acid dyestuff in a print paste having the following composition: Carbopol 934 4 parts DMSO 81 parts Irgalan Yellow 2GL (C. I. Yellow 129) 3 parts Water 12 parts A yellow print pattern of good overall fastness properties was obtained with complete dye penetration and fixation inside the fibre while the original excellent tensile and flame resistant properties of the fabric were not adversely affected. EXAMPLE 6 The procedures of Example 1 were repeated using 3 parts of the metalized acid dyestuff Nylanthrene Red B2B in the print paste of Example 5. A bright red print pattern of good overall fastness properties was obtained with complete dye penetration and fixation inside the fibre. The original excellent tensile and flame resistant properties of the fabric were not affected by the printing process. EXAMPLE 7 The procedures of Example 1 were repeated this time using three parts of the metalized acid dyestuff Nylanthrene Blue LFWG in the print paste of Example 5. A dark blue print pattern of good overall fastness properties was obtained. Complete dye penetration and fixation inside the fibre were achieved and the fabric's properties were not adversely affected in any way. EXAMPLE 8 The procedures of Example 1 were repeated using 3 parts of the direct dye Pyrazol Red 7BSW (C.I. Direct Red 80) in the print paste of Example 5. A bright red print pattern with complete dye penetration and fixation inside the fibre was obtained with the same type of results obtained in the previous examples. EXAMPLE 9 The procedures of Example 1 were repeated using 3 parts of direct dye Diphenyl Orange EGLL (C. I. Direct Orange 39) in the print paste. A bright orange print pattern with good overall fastness properties and complete dye penetration and fixation inside the fibre was obtained. EXAMPLE 10 The procedures of Example 1 were repeated using 3 parts of the solubilized vat dye Indigosol Blue 1BS (C. I. Solubilized Vat Blue 6) in the print paste of Example 5. A dark blue print pattern with good wash fastness properties and complete dye penetration and fixation inside the fibre was obtained. EXAMPLE 11 A plain weave aramid fabric made of an intimate fibre blend of 95% Nomex /5% Kevlar (duPont T-455 Nomex ) weighing 135 g/m² (4 ozs./sq. yd.) of staple warp and fill yarns 38/2, 26z/18s (32240 m/kg - 15960 yd./lb), for use in garments offering protection against brief exposure to extreme thermal fluxes, was printed into a 100% coverage pattern composed of four colors with four different print pastes having the following compositions, expressed in percent by weight: The fabric was then dried at 148°C for 2 minutes, and subsequently cured for 3 minutes at 165°C under atmospheric pressure. The cured fabric was then rinsed in cold and hot water, treated for 5 minutes in an aqueous solution of 0.5% sodium carbonate and 0.2% of non-ionic detergent at 80°C, rinsed in hot water followed by cold water, and finally dried. Flammability test results of the printed fabric are given in Table III. Example 12 (Comparative) The procedures of Example 11 were repeated except that no fire retardant (Antiblaze 19) was used in the print formulation. Flammability test results of the printed fabrics of both examples are outlined in Table III.

Claims: A process of printing a pre-determined pattern on a poly(m-phenyleneisophthalamide)-containing textile fabric characterised by comprising the steps of: (a) applying a print paste, composed of a highly polar solvent selected from the group consisting of dimethylsulphoxide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and mixtures thereof, the polar solvent being adapted to swell the aramid fibre and introduce a dyestuff therein, at least one organic dyestuff that is soluble in the polar solvent, a print paste thickening agent compatible with both the polar solvent and the dyestuff, water and at least one flame retardant, in a pre-determined pattern onto the surface of the aramid textile; and (b) drying and curing the printed fabric at an elevated temperature sufficient to permeate and fix the dyestuff molecules inside the aramid fibres. A process as claimed in claim 1 characterised by including the additional step of: (c) rinsing and washing the printed and cured fabric to remove any residual print paste and unfixed dyestuff from the fabric. A process as claimed in claim 1 or 2 characterised in that the fabric is cured in step (b) at a temperature in the range of about 115°C to about 190°C. A process as claimed in any preceding claim characterised in that the print paste includes thickening agent composed of an acrylic acid polymer. A process as claimed in any preceding claim characterised in that the highly polar solvent is present in an amount of between about 70 and 85% by weight. A stable, homogeneous print paste for printing and dyeing a poly(m-phenyleneisophthalamide)-containing textile fabric in a pre-determined pattern, the print paste being characterised by consisting essentially, in percent by weight, of: about 70 to about 85% of a highly polar solvent adapted to swell poly(m-phenyleneisophthalamide) fibres and introduce a dyestuff therein, the highly polar solvent being selected from the group consisting of dimethylsulphoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and mixtures thereof; a tinctorial amount of an organic dyestuff soluble in the highly polar solvent and capable of dyeing and fixing in said fibres; a print paste thickening agent soluble in the highly polar solvent and compatible with the organic dyestuff, the thickening agent together with the other ingredients being present in an amount sufficient to provide the print paste with a viscosity in the range of about 5 kPa (5,000 cps) to about 36 kPa (36,000 cps); a flame retardant that is compatible with the other components of the print paste; and balance water. A print paste as claimed in claim 6 characterised in that the thickening agent is a polyacrylic acid having a molecular weight in the range of from about 450,000 to about 4,000,000. A print paste as claimed in claims 6 or 7 characterised in that the highly polar solvent is dimethylsulphoxide. A print paste as claimed in any of claims 6 to 8 characterised in that the organic dyestuff is selected from the group consisting of cationic dyes, anionic dyes, disperse dyes, fibre reactive dyes, vat dyes, azoic dyes, solvent dyes, and mixtures thereof.

Inventors: HUSSAMY, SAMIR
Applicants: BURLINGTON INDUSTRIES, INC.
Application year: 1987
Main classification: D06P3
IPC codes: D06P3, D06P5, D06M13, D06P1