POLYPHENYLENE SULFIDE FIBERS

TECHNICAL FIELD OF THE INVENTION

[0001] This application relates to textile materials containing aramid fibers and dyed polyphenylene sulfide fibers and methods for producing the same.

BACKGROUND

[0002] Polyphenylene sulfide is a thermoplastic polymer that exhibits many desirable properties. For example, polyphenylene sulfide exhibits resistance to heat, various chemicals (e.g., acids, alkalis, and bleaches), mildew, aging, UV exposure (e.g., sunlight), and abrasion. Due to its thermoplastic nature and the desirable properties, polyphenylene sulfide polymer has been extruded into fibers suitable for use in making textile materials. These polyphenylene sulfide fibers have been used in industrial textile materials, such as high temperature filtration media and automotive hose reinforcement, for many years. However, despite the many advantages offered by the polyphenylene sulfide polymer, the textile fibers made from the polymer have not found practical use in apparel or decorative textile applications. The main reason for this lack of use is that no practical means for dyeing polyphenylene sulfide polymers has been developed.

[0003] A need therefore remains for a method of dyeing polyphenylene sulfide fibers that produces fibers with the full range of colors and shades desired for apparel and decorative textile applications and exhibiting the colorfastness needed for such applications and combining them with aramid fibers for a blended yarn. The invention described in this application seeks to provide such a method and the dyed polyphenylene sulfide fibers produced by such a method.

BRIEF SUMMARY OF THE INVENTION

[0004] In a first embodiment, the invention provides a textile material comprising a plurality of yarns containing an intimate blend of dyed polyphenylene sulfide fibers and aramid fibers, wherein the polyphenylene sulfide fibers have a cross-sectional area, the polyphenylene sulfide fibers comprise a disperse dye that is distributed substantially evenly across the cross-sectional area of the fibers, and the disperse dye is selected from the group consisting of disperse dyes having a molar mass of about 350 g/mol or more, disperse dyes comprising a nitro group, and mixtures thereof.

[0005] In a second embodiment, the invention provides a method for dyeing polyphenylene sulfide fibers, the method comprising the steps of:

(a) providing a plurality of polyphenylene sulfide fibers and aramid fibers;

(b) spinning the blend of fibers into a plurality of yarns;

(c) forming the yarns into a textile material;

(d) subjecting the textile material to a polyphenylene sulfide dyeing process comprising:

(i) providing a dye liquor comprising a liquid medium and a disperse dye selected from the group consisting of disperse dyes having a molar mass of about 350 g/mol or more, disperse dyes comprising a nitro group, and mixtures thereof;

(ii) applying the dye liquor to the textile material;

(iii) heating the textile material under ambient atmosphere to a temperature sufficient to evaporate substantially all of the liquid medium from the textile material; and

(iv) heating the textile material under ambient atmosphere to a temperature of about 180 °C or more to fix the disperse dye to the

polyphenylene sulfide fibers;

DETAILED DESCRIPTION OF THE INVENTION

[0006] In a first embodiment, the invention provides a textile material comprising yarns, the yarns comprising a plurality of aramid fibers and dyed polyphenylene sulfide fibers (the aramid fibers may be dyed or undyed).

By "yarn" is meant an assemblage of fibers spun or twisted together to form a continuous strand, which can be used in weaving, knitting, braiding, or plaiting, or otherwise made into a textile material or fabric. The textile material of this first embodiment can take any suitable form. For example, the plurality of dyed polyphenylene sulfide fibers and aramid fibers can be consolidated to provide a yarn. In such an embodiment, the yarn can contain other fibers in addition to the dyed polyphenylene sulfide fibers and aramid fibers, as is described in further detail below. In another embodiment, the plurality of aramid fibers and dyed

polyphenylene sulfide fibers can be consolidated into a nonwoven textile material. The textile material can also be a woven textile material comprising a plurality of interlaced yarns, at least one of which contains the aramid fibers and dyed polyphenylene sulfide fibers. The textile material can also be a knit textile material comprising one or more interlooped yarns, at least one of which contains the aramid fibers and dyed polyphenylene sulfide fibers. Preferably, the weight range of the fabric is between about 2.5 and 20 oz/yd ² , more preferably between about 4 and 12 oz/yd ² .

[0007] The dyed polyphenylene sulfide fibers can comprise any suitable polyphenylene sulfide polymer. The polyphenylene sulfide polymer can have any suitable molar mass. Preferably, the polyphenylene sulfide polymer has a mass average molar mass of about 20,000 g/mol or more. More preferably, the

polyphenylene sulfide polymer has a mass average molar mass of about 30,000 g/mol or more, about 40,000 g/mol or more, or about 50,000 g/mol or more.

Preferably, the polyphenylene sulfide polymer has a mass average molar mass of about 100,000 g/mol or less. More preferably, the polyphenylene sulfide polymer has a mass average molar mass of about 80,000 g/mol or less, about 70,000 g/mol or less, or about 60,000 g/mol or less. In a particularly preferred embodiment, the polyphenylene sulfide polymer has a mass average molar mass of about 40,000 g/mol to about 60,000 g/mol. The polyphenylene sulfide polymer can have any suitable melt viscosity. Preferably, the polyphenylene sulfide polymer has a melt viscosity of about 1 ,000 poise or more when measured at 300 °C and an apparent shear rate of 400 s ^_1 in accordance with ASTM Test Method 3835. More preferably, the polyphenylene sulfide polymer has a melt viscosity of about 1 ,000 poise to about 3,000 poise or about 1 ,000 poise to about 2,200 poise when measured as described above. [0008] The polyphenylene sulfide polymer can exhibit any suitable degree of crystallinity. Preferably, the percent crystallinity of the polyphenylene sulfide polymer is 10% or more. More preferably, the percent crystallinity of the polyphenylene sulfide polymer is about 20% or more, about 25% or more, or about 30% or more. The percent crystallinity of the polyphenylene sulfide polymer preferably is about 80% or less. More preferably, the percent crystallinity of the polyphenylene sulfide polymer is about 75% or less. Thus, in a series of preferred embodiments, the percent crystallinity of the polyphenylene sulfide polymer is from 10% to about 80%, about 20% to about 80%, or about 30% to about 75%.

[0009] The dyed polyphenylene sulfide fibers of the textile material comprise at least one dye. The dye can be any suitable dye, but disperse dyes are particularly preferred. Preferably, the dye is a disperse dye selected from the group consisting of disperse dyes having a molar mass of about 350 g/mol or more, disperse dyes comprising a nitro group, and mixtures thereof. In another preferred embodiment, the dye is a disperse dye selected from the group consisting of disperse dyes having a molar mass of about 400 g/mol or more, disperse dyes comprising a nitro group, and mixtures thereof. While not wishing to be bound to any particular mechanism or theory, it has been observed that disperse dyes having a higher molar mass (e.g., about 350 g/mol or more or about 400 g/mol or more) and/or a polar nature (such as disperse dyes containing a nitro group) are capable of satisfactorily dyeing the polyphenylene sulfide fibers, whereas disperse dyes that do not possess either of these characteristics are not. For example, it has been observed that dyes that do not possess either of these characteristics do not become sufficiently fixed in the polyphenylene sulfide fiber. With the exception of nitrodiphenylamine disperse dyes, the disperse dye preferably has a boiling point of 590 °C or more, more preferably about 600 °C or more. With the exception of nitrodiphenylamine disperse dyes, the disperse dye preferably has a flash point of 300 °C or more, more preferably about 310 °C or more. In a particular embodiment, the disperse dye has a boiling point of 590 °C or more (e.g., about 600 °C or more) and a flash point of 300 °C or more (e.g., about 310 °C or more).

[0010] The disperse dye can be any suitable disperse dye that possesses one or more of the characteristics described above. In a more specific preferred embodiment, the disperse dye is selected from the group consisting of azo dyes (e.g., azothiophene dyes, azobenzothiazole dyes), diazo dyes, anthraquinone dyes, nitro dyes (e.g., nitrodiphenylamine dyes), quinoline dyes, dibenzofuran dyes, naphthalimide dyes (e.g., aminoketone dyes), and mixtures thereof. Specific disperse dyes that have been found useful in dyeing the polyphenylene sulfide fibers include, but are not limited to, C.l. Disperse Red 356, C.l. Disperse Red 167, C.l. Disperse Blue 77, C.l. Disperse Orange 30, C.l. Disperse Orange 44, C.l. Disperse Red 91 , C.l. Disperse Blue 77, C.l. Disperse Blue 27, C.l. Disperse Blue 60, C.l. Disperse Yellow 86, C.l. Disperse Yellow 42, C.l. Disperse Yellow 58, C.l. Disperse Yellow 163, C.l. Disperse Red 86, C.l. Disperse Violet 57, C.l. Disperse Red 159,

C.l. Disperse Red 279, C.l. Disperse Yellow 1 14, C.l. Disperse Blue 56, C.l.

Disperse Blue 165, C.l. Disperse Red 153, C.l. Disperse Brown 1 , C.l. Disperse Violet 33, C.l. Disperse Red 92, and C.l. Disperse Blue 87. Any of the above- mentioned dyes can be used in combination to produce polyphenylene sulfide fibers and textile materials exhibiting the desired color and shade.

[0011] The disperse dye preferably is distributed substantially evenly throughout the thickness of the polyphenylene sulfide fibers. In other words, the disperse dye preferably is distributed substantially evenly across the cross-sectional area of the polyphenylene sulfide fibers. This distribution of the disperse dye within the polyphenylene sulfide fibers is believed to be unique. For example, prior attempts to dye polyphenylene sulfide fibers have relied upon surrounding the polyphenylene sulfide polymer with a sheath of an easily-dyed polymer (e.g., a polyamide). In such products, the dye only penetrates and fixes in the sheath, and the polyphenylene sulfide polymer remains undyed (or contains very little dye at the interface between the polyphenylene polymer and the sheath). The distribution of the disperse dye through the thickness or across the cross-sectional area can be determined by any suitable technique. For example, individual polyphenylene sulfide fibers can be sectioned and the coloration of the fibers can be examined, for instance, using an optical microscope. When the coloration of the fibers is observed to be substantially even through the thickness or across the cross-sectional area of the fibers, one has confirmed that the dye is substantially evenly distributed through the thickness or across the cross-sectional area of the fiber. [0012] In another embodiment, the invention provides a textile material comprising yarns, at least a portion of the yarns comprising a plurality of aramid fibers and dyed polyphenylene sulfide fibers (the aramid fibers may be dyed or undyed). In one embodiment, the textile material comprises at least about 50% by weight yarns that contain a plurality aramid fibers and dyed polyphenylene sulfide fibers, more preferably at least about 60%, at least about 70%, at least about 90%, and at least about 95% by weight. The polyphenylene sulfide and aramid fibers may have any suitable denier, preferably between 1 and 8 denier, more preferably between about 1 and 3 denier.

[0013] As used herein, "aramid" is meant a polyamide wherein at least 85% of the amide (-CONH-) linkages are attached directly to two aromatic rings. Additives can be used with the aramid and, in fact, it has been found that up to as much as 10 percent, by weight, of other polymeric material can be blended with the aramid or that copolymers can be used having as much as 10 percent of other diamine substituted for the diamine of the aramid or as much as 10 percent of other diacid chloride substituted for the diacid chloride of the aramid. Suitable aramid fibers are described in Man-Made Fibers-Science and Technology, Volume 2, Section titled Fiber-Forming Aromatic Polyamides, page 297, W. Black et al., Interscience

Publishers, 1968. Aramid fibers are, also, disclosed in U.S. Pat. Nos. 4,172,938; 3,869,429; 3,819,587; 3,673,143; 3, 354,127; and 3,094,51 1 . M-aramid are those aramids where the amide linkages are in the meta-position relative to each other, and p-aramids are those aramids where the amide linkages are in the para-position relative to each other. In the practice of this invention the aramids most often used are poly(paraphenylene terephthalamide) and poly(metaphenylene isophthalamide).

[0014] The yarns contain aramid fibers, preferably meta-aramid fibers. The most well-known meta-aramid fibers are available as NOMEX ^® available from DuPont. NOMEX ^® and related aramid polymers are related to nylon, but

have aromatic backbones, and hence are more rigid and more durable. NOMEX ^® is produced by condensation reaction from the monomers m- phenylenediamine and isophthaloyl chloride. Meta-aramids are preferred as they are inherent flame resistant fibers and are compatible with the polyphenylene sulfide fibers and their dyeing processes. The aramid fibers may also preferably be para- aramid fibers. The most well-known para-aramid fibers are available as KEVLAR ^® available from DuPont. In another embodiment, the aramid fibers may be a blend of meta-aramid and para-aramid fibers. In one embodiment, the aramid fibers are NOMEX ^® IIIA which is a blend of 93% NOMEX® (meta-aramid), 5% KEVLAR® (para-aramid) +2% P140 carbon fiber (antistatic fiber).

[0015] In another embodiment, the invention provides a textile material comprising yarns, at least a portion of the yarns comprising a plurality of polyamide- imide fibers and dyed polyphenylene sulfide fibers (the polyamide-imide fibers may be dyed or undyed). In one embodiment, the textile material comprises at least about 50% by weight yarns that contain a plurality of polyamide-imide fibers and dyed polyphenylene sulfide fibers.

[0016] The textile material of this first embodiment can take any suitable form. For example, the plurality of dyed polyphenylene sulfide fibers and polyamide-imide fibers can be consolidated to provide a yarn. These polyamide-imide fibers may be used with the dyed polyphenylene sulfide fibers or in combination with other fibers such as aramid fibers or cellulosic fibers. One such polyamide-imide fiber is available and marketed under the tradename KERMAL ^® . Polyamide-imide fibers are typically colored as the fibers are formed as it is very difficult to color them once formed into a fiber, yarn, or textile.

[0017] Staple fibers for use in spinning yarns are generally of a particular length and of a particular linear density. For use in this invention, the fibers can have any length which is adequate for manufacture of spun yarns. Staple lengths of 2.5 to 15.2 centimeters (1 to 6 inches) can be used and lengths of 3.8 to 1 1 .4 centimeters (1.5 to 4.5 inches) are preferred. In another embodiment, the fibers making up the yarns have a staple cut length of between about 30 and 60 mm, more preferably between about 38 and 52 mm. The yarn formed from the fibers may be any type of yarn formed by any suitable process. For example, the yarn can be made be a jet spun, open end spun, ring spun, vortex spun yarn, it can be Z type twist or S type twist; can be single ply, 2 ply, 3 ply, etc. Yarn size preferably ranges from 40 count to 5 count (cotton yarn count system). [0018] As utilized herein, the term“inherent flame resistant fibers” refers to synthetic fibers which, due to the chemical composition of the material from which they are made, exhibit flame resistance without the need for an additional flame retardant treatment. In one embodiment, the yarns can contain additional inherent flame resistant fibers. In such embodiments, the inherent flame resistant fibers can be any suitable inherent flame resistant fibers, such as polyoxadiazole fibers, polysulfonamide fibers, poly(benzimidazole) fibers, aramid fibers (e.g., para- aramid fibers), polypyridobisimidazole fibers, polybenzylthiazole fibers, polybenzyloxazole fibers, melamine-formaldehyde polymer fibers, phenol-formaldehyde polymer fibers, oxidized polyacrylonitrile fibers, polyamide-imide fibers and combinations, mixtures, or blends thereof. In a preferred embodiment, the textile material comprises aramid fibers in addition to the polyphenylene sulfide fibers. Other fibers can additionally be included into the textile material concluding polyamidimid fibers, phenol- formaldehyde fibers, melamine fibers, glass fibers, metal fibers, elastomeric fibers/yarns, and carbon fibers. In some embodiments, the elastomeric yarn is a spandex yarn. While in some embodiments the preferred elastomeric fiber yarn is a spandex fiber yarn, any fiber generally having stretch and recovery can be used. As used herein, "spandex" has its usual definition, that is, a manufactured fiber in which the fiber-forming substance is a long chain synthetic polymer composed of at least 85% by weight of a segmented polyurethane. The textile material may also, in some embodiments, comprise a core spun yarn which is a mono or multifilament core covered with a fiber covering.

[0019] The yarns making up the textile material and the textile material can contain any suitable amounts of polyphenylene sulfide fibers and aramid / polyamide-imide fibers. Preferably, the plurality of yarns comprises at least about 40% by weight polyphenylene sulfide fibers. In another embodiment, the plurality of yarns comprises at least about 50%, at least about 60% or at least about 70% by weight polyphenylene sulfide fibers. In another embodiment, the plurality of yarns comprises between about 20 and 80% by weight polyphenylene sulfide fibers, more preferably between about 40 and 70% weight. In another embodiment, the plurality of yarns comprises between about 20 and 80% by weight aramid fibers, more preferably between about 40 and 70% weight. In another embodiment, the yarns contain less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of polyphenylene sulfide fibers.

In another embodiment, the yarns contain less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of aramid fibers.

[0020] Preferably, the textile material comprises at least about 40% by weight polyphenylene sulfide fibers. In another embodiment, the textile material comprises at least about 50%, at least about 60% or at least about 70% by weight

polyphenylene sulfide fibers. In another embodiment, the textile material comprises between about 20 and 80% by weight polyphenylene sulfide fibers, more preferably between about 40 and 70% weight. In another embodiment, the textile material comprises between about 20 and 80% by weight aramid fibers, more preferably between about 40 and 70% weight. In another embodiment, the textile material contains less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of polyphenylene sulfide fibers.

In another embodiment, the textile material contains less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of aramid fibers.

[0021] The yarns making up the textile material and the textile material can contain any suitable amounts of polyphenylene sulfide fibers and polyamide-imide fibers. Preferably, the plurality of yarns comprises at least about 40% by weight polyphenylene sulfide fibers. In another embodiment, the plurality of yarns comprises at least about 50%, at least about 60% or at least about 70% by weight polyphenylene sulfide fibers. In another embodiment, the plurality of yarns comprises between about 20 and 80% by weight polyphenylene sulfide fibers, more preferably between about 40 and 70% weight. In another embodiment, the plurality of yarns comprises between about 20 and 80% by weight polyamide-imide fibers, more preferably between about 40 and 70% weight. In another embodiment, the yarns contain less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of polyphenylene sulfide fibers. In another embodiment, the yarns contain less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of polyamide-imide fibers.

[0022] Preferably, the textile material comprises at least about 40% by weight polyphenylene sulfide fibers. In another embodiment, the textile material comprises at least about 50%, at least about 60% or at least about 70% by weight

polyphenylene sulfide fibers. In another embodiment, the textile material comprises between about 20 and 80% by weight polyphenylene sulfide fibers, more preferably between about 40 and 70% weight. In another embodiment, the textile material comprises between about 20 and 80% by weight polyamide-imide fibers, more preferably between about 40 and 70% weight. In another embodiment, the textile material contains less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of polyphenylene sulfide fibers. In another embodiment, the textile material contains less than about 80% by weight, more preferably less than about 70%, less than about 60%, or less than about 50% by weight of polyamide-imide fibers.

[0023] The textile materials described above are believed to be well-suited for use in applications where the textile material must meet certain requirements for flame resistance. For example, the textile material can be a fabric used in the manufacture of curtains or window treatments, which fabric should meet the most stringent requirements of NFPA 701 . The textile material can also be used in the manufacture of upholstery and furniture fabrics, automotive fabrics (e.g., woven, knit, or nonwoven textiles used in automotive applications), aircraft interiors, etc. In one embodiment, the textile materials are formed into garments. According to one embodiment, the garment comprises a structure comprising an internal layer, optionally an intermediate layer made of a breathing waterproof material, and an outer layer made of the above-described fabric of the invention. In another embodiment, a water and/or vapor resistant layer may be adhered to the textile material.

[0024] The textile material described above can contain other fibers in addition to the polyphenylene sulfide, aramid fibers, and optional additional inherent flame resistant fibers discussed above. In such embodiments, the textile material can further comprise any suitable natural fiber or synthetic fiber or combination of natural fibers and/or synthetic fibers. These additional fibers can be intimately blended with the polyphenylene sulfide and aramid fibers within the textile material. For example, the textile material can be a yarn in which the polyphenylene sulfide and aramid fibers are intimately blended with, for example, cellulosic fibers. Alternatively, the additional fibers and the polyphenylene sulfide and aramid fibers can be present in separate elements within the textile material. For example, the textile material can comprise a first yarn containing the polyphenylene sulfide and aramid fibers and a second yarn containing, for example, cellulosic fibers.

[0025] As noted above, the textile material can comprise any suitable natural or synthetic fiber(s) in addition to the polyphenylene sulfide, aramid fibers, and optional additional inherent flame resistant fibers discussed above. In a preferred embodiment, the textile material further comprises cellulose fibers. The cellulose fibers used in such an embodiment can be natural cellulose fibers (e.g., cotton fibers), regenerated cellulose fibers, or any combination thereof. Suitable

regenerated cellulose fibers include, but are not limited to, rayon fibers (e.g., viscose rayon fibers, high wet modulus rayon fibers, modal fibers, and polynosic fibers), lyocell fibers, and mixtures thereof.

[0026] When the textile material comprises cellulose fibers, the textile material can further comprise a flame retardant that is added to improve the flame resistance of the cellulose fibers and the textile material containing the same. In such embodiments, any suitable flame retardant can be used. Preferably, the flame retardant is a phosphorus-based flame retardant, such as the flame retardants based on tetrahydroxymethlphosphonium salts and condensates thereof. Suitable examples of such flame retardants include, but are not limited to, those flame retardants described in U.S. Patent No. 7,713,891 ; U.S. Patent No. 8,012,890; U.S. Patent No. 8,012,891 ; U.S. Patent No. 8,722,551 ; U.S. Patent No. 9,091 ,020; U.S. Patent No. 9,453,1 12; and U.S. Patent Application Publication No. US 2015/01 18931 A1 , each of which is hereby incorporated by reference.

[0027] The textile material can also comprise synthetic fibers in addition to the polyphenylene sulfide, aramid fibers, and optional additional inherent flame resistant fibers, such as thermoplastic synthetic fibers. Suitable thermoplastic synthetic fibers include, but are not necessarily limited to, polyester fibers (e.g., poly (ethylene terephthalate) fibers, poly (propylene terephthalate) fibers, poly (trimethylene terephthalate) fibers), poly (butylene terephthalate) fibers, and blends thereof), polyamide fibers (e.g., nylon 6 fibers, nylon 6,6 fibers, nylon 4,6 fibers, and nylon 12 fibers), polyvinyl alcohol fibers, and combinations, mixtures, or blends thereof.

Preferably, the thermoplastic synthetic fibers are selected from the group consisting of polyester fibers, polypropylene fibers, and mixtures thereof.

[0028] When the textile material comprises thermoplastic synthetic fibers, the textile material can further comprise a flame retardant that is added to improve the flame resistance of the thermoplastic synthetic fibers and the textile material containing the same. Any flame retardant suitable for use with thermoplastic synthetic fibers can be used in such embodiments.

[0029] In a preferred embodiment, the polyphenylene sulfide fibers and the aramid fibers are intimately blended together and formed into yarns. Intimately blended means that the two types of fibers are not formed into separate yarns and then twisted together, but that the yarn contains both polyphenylene sulfide fibers and the aramid fibers entangled with each other. Preferably, the yarns are formed by the process of spinning, wherein the process of spinning is selected from the group consisting of open-end, ring, jet, vortex, rotor-spun, and Siro-spun spinning. Most preferred are the open-end spinning and ring spinning processes. In ring spinning, the ring yarn has consistent fiber orientation. Most of the fibers look to be oriented to the same angle, so most of the fibers help contribute to the yarn strength. Open end spinning is an alternative to ring spinning. Unlike the fiber orientation seen in ring spun yarns, the fiber orientation in an open end yarn tends to be more random and inconsistent.

[0030] In a second embodiment, the invention provides a method for dyeing textiles that contain polyphenylene sulfide fibers. The method generally comprises the steps of: (a) providing a textile material comprising polyphenylene sulfide fibers and aramid fibers; (b) providing a dye liquor comprising a liquid medium and a disperse dye; (c) applying the dye liquor to the textile material; (d) heating the textile material under ambient atmosphere to a temperature sufficient to evaporate substantially all of the liquid medium from the textile material; and (e) heating the textile material under ambient atmosphere to a temperature sufficient to fix the disperse dye to the polyphenylene sulfide fibers.

[0031] The textile material utilized in the method can be any suitable textile material comprising polyphenylene sulfide and aramid fibers, such as any of the textile materials described above.

[0032] As noted above, the dye liquor comprises a liquid medium and a disperse dye. The liquid medium can be any liquid medium suitable for use with disperse dyes. Typically, the liquid medium is an aqueous medium, such as water. The liquid medium can comprise a surfactant or wetting agent in order to improve wetting of the polyphenylene sulfide fibers with the dye liquor. In a preferred embodiment, the dye liquor has a pH of about 4 to about 7.5, more preferably about 5 to about 7.

[0033] The disperse dye present in the dye liquor can be any of the disperse dyes discussed above in connection with the textile material of the invention. In a preferred embodiment, the dye liquor further comprises a volatile organic acid having a boiling point of about 100 °C to about 170 °C. Suitable examples of such volatile organic acids include, but are not limited to, acetic acid, formic acid, propionic acid, butyric acid, and mixtures thereof. While not wishing to be bound to any particular theory, it is believed that such volatile organic acids improve the color yield of the dyeing process, especially when the dye is fixed at temperatures of 180 °C or more. Further, with a boiling point of 100 °C to 170 °C, it is believed that the organic acid vaporizes during the dye fixation step and does not leave any harmful residue on the fibers.

[0034] In a preferred embodiment, the dye liquor further comprises a dye carrier. Suitable dye carriers include, but are not limited to, propylene glycol, ethylene glycol, dipropylene glycol, tripropylene glycol, diethylene glycol, triethylene glycol, benzoic acid, triethanolamine, polyethylene oxide, polyethylene glycol, copolymers of ethylene oxide and propylene oxide, and mixtures thereof. While not wishing to be bound to any particular theory, it is believed that such dye carriers can assist in dye solubilization and/or dye penetration and diffusion into the

polyphenylene sulfide fibers.

[0035] The dye liquor can be applied to the textile material in any suitable fashion and using any suitable apparatus. Typically, the textile material is passed through a bath of the dye liquor so that it is saturated with the dye liquor. Upon exiting the bath, the textile material can be passed through one or more nip rollers, which apply pressure to the textile material and remove excess dye liquor before the drying step. Alternatively, the dye liquor can be sprayed directly onto the surface of the textile material.

[0036] Following application of the dye liquor, the textile material is heated under ambient atmosphere to a temperature sufficient to evaporate substantially all of the liquid medium (and any volatile organic acid and/or dye carrier in the dye liquor) from the textile material. The textile material can be heated to any suitable temperature in this step. Preferably, the textile material is heated to a temperature greater than 40 °C, more preferably 100 °C, 130 °C, or 140 °C.

[0037] Following the drying step, the textile material is heated to a

temperature sufficient to fix the dye in the polyphenylene sulfide fibers. This dye fixation step preferably is performed under ambient atmosphere, meaning that the step is not performed in a closed system under elevated pressure. The textile material can be heated to any suitable temperature in order to fix the dye.

Preferably, the textile material is heated to a temperature of 160 °C or more. More preferably, the textile material is heated to a temperature of about 180 °C or more or about 190 °C or more. The textile material preferably is not heated to a temperature greater than 260 °C because such temperatures have been observed to cause adverse dye degradation. In a preferred embodiment, the textile material is heated to a temperature of about 180 °C to about 260 °C, more preferably about 190 °C to about 240 °C.

[0038] Following the dye fixation step, the textile material can be further treated in order to remove and/or neutralize any unfixed disperse dye that remains on the textile material. Thus, in a preferred embodiment, the method described above further comprises the step of treating the textile material from step (e) with a caustic solution to remove or neutralize unfixed disperse dye on the textile material. The textile material can be treated with the caustic solution in any suitable manner. For example, the textile material can be immersed in a bath of the caustic solution (maintained at a temperature of 40 °C to about 80 °C) for a sufficient amount of time to remove and/or neutralize the unfixed dye. Alternatively, the textile material can be impregnated with the caustic solution and then steamed. The caustic solution preferably comprises a reducing agent that is capable of reducing any unfixed disperse dye to an uncolored form. Suitable reducing agents include, but are not limited to, sodium bisulfite. Following treatment with the caustic solution as described above, the textile material is then washed in water to remove the dye residues and dried.

[0039] When the textile material comprises other fibers in addition to the polyphenylene sulfide fibers, the method described above can be modified in order to dye the additional fibers. For example, when the textile material comprises cellulose fibers in addition to the polyphenylene sulfide fibers, the dye liquor can further comprise one or more vat dyes, which will dye the cellulose fibers. The method can also be preceded or succeeded by a series of steps that dye the additional fibers. For example, when the textile material comprises polyester fibers, the textile material can be jet dyed using disperse dyes in order to impart the desired color and shade to the polyester fibers. In such an embodiment, the textile material can be jet dyed before or after dyeing in accordance with the method described above. Alternatively, the polyester fibers and the polyphenylene sulfide fibers can be dyed simultaneously using the method described above using one or more suitable disperse dyes. In such an embodiment, one can select a single disperse dye having the appropriate properties to dye both the polyphenylene sulfide fibers and the polyester fibers, or one can use a mixture of disperse dyes, at least one of which possesses the appropriate properties (as described above) to dye the polyphenylene sulfide fibers.

[0040] The aramid fibers may have been dyed during manufacture of the fibers and would not need any additional steps of dyeing once the fibers were formed into yarns or textile materials (unless it was desirable to dye the fibers again).

Aramid fiber may also be used in their natural state and would need to be dyed in a yarn or textile if it was desired to have the aramid fibers have color. This dyeing process can be performed before or after the PPS fiber dyeing process.

[0041] Fabric containing meta-aramid fibers can be dyed in a piece dyeing process where certain amount of fabric is placed into a dyeing equipment capable of getting the fabric in contact with a hot dyeing liquid under agitation at elevated temperatures (typically 70°C - 150°C) in a closed system and potentially under pressure. Typical piece dye equipment includes jet dyeing machine, beck dyeing machine and jig dyeing machine. The dye liquid includes at least one dye, a carrier organic solvent, an inorganic salt, pH control agent, and water.

[0042] The dye in the dye liquid can be a disperse dye or a cationic dye.

Typically, a cationic dye is used. Various mixtures and amounts of cationic dyes or disperse dyes can be used to achieve desirable colors on the fabric.

[0043] A carrier organic solvent is used to help swell the meta-aramid fiber to facility dye diffusion into the fiber interior. Typical carrier organic solvents include 1 - phenoxy-2-propanol, benzyl alcohol, n-methyl pyrrolidone, n-cyclohexyl 2- pyrrolidone, N,N-diethyl-m-toluamide, N-methylformanilide, and a commercial product called Cindye DNK marketed by Bozzetto Group. The carrier organic solvent can be used at an amount of 0.2 - 10 g/liter of dye liquid, typically, 1 -4g/liter.

[0044] Inorganic salts, such as NaCI, NaNCh, Na ₂ S0 ₄ , and others can be added to the dye liquid to help improve the dyeing of meta-aramid fiber. NaNCh is typically used at an amount of 1 g/l to 50g/l, or typically 1 g/l - 10g/I. Acetic acid or other organic acid is typically added to the dye liquid to adjust the pH of the liquid to a range of pH 2-5, or 2.5 - 4.5. The ratio by weight of dyeing liquid to the fabric is typically 50:1 to 1 :1 . Most typically, 10:1 to 2:1 .

[0045] Once the fabric is loaded into the dye equipment, and brought into contact with the dye liquid under agitation, the dye liquid is heated up controllably to an elevated temperature, and held at an elevated temperature for a set amount of time to allow the dye(s) to diffuse into the meta-aramid fiber sufficiently. In a typical dyeing cycle the dye liquid may be heated at a controlled rate to 130°C, and held at 130°C for 1 hour, then cooled down to about 50-70°C. The fabric is then rinsed with a hot aqueous liquid containing cleaning agents (such as surfactants and/or redox chemicals) to remove unfixed surface dyes on the meta-aramid fiber surface. [0046] Additional description of dyeing meta-aramid fiber in a fabric can be found in US Patents 4898596, 5207803, 6867154, 3884626, 3986827, 4525168, 5306312, and 6840967, which are hereby incorporated by reference.

[0047] The following examples further illustrate the subject matter described above but, of course, should not be construed as in any way limiting the scope thereof.

Example 1

[0048] A woven or knit fabric can be made by using yarn made from blending solution-dyed aramid fiber (20% - 80%) and polyphenylene sulfide (PPS) fiber (80% - 20% by wt.). Other fibers in small amounts (preferably 2-10% wt.) including antistatic fibers, para-aramid fibers, and polyoxadiazole (POD) fibers may optionally be added. The fabric is then dyed with a disperse in a continuous dyeing process according to the method described in the specification to dye the PPS fiber portion of the fabric. The dyed fabrics are expected to exhibit good flame resistance in a vertical flame test. The color fastness to light and washing are expected to be superior to piece dyed NOMEX ^® IMA type fabrics.

Example 2

[0049] A NOMEX ^® 111 A blended fabric (which contained 93% NOMEX ^® meta- aramid material with 5% KEVLAR ^® para-aramid and 2% antistatic fiber) was padded with several disperse solutions and run through a thermosol continuous dyeing process. There was virtually no staining of the NOMECQIIIA fabric by the disperse dyes. Accordingly, the polyphenylene sulfide fiber in the fabric can be independently dyed without causing problematic cross-staining issues, as evidenced by the fact that the aramid fiber does not dye using the PPS dyeing process.

Example 3 [0050] Similar to Example 1 except the aramid fiber is replaced by polyamide- imide fiber (available from KERMAL ^® ). A wide range of solution dyed KERMAL ^® fiber are commercially available and can be blended with PPS fiber.

Example 4

[0051] FR rayon fiber can be added to the fabric of Example 1 or Example 3 at 5% - 50% by weight to embody improved moisture absorption and other comfort benefit. The dyeing process will include dye solution comprising a mixture of disperse dyes/vat dyes, or disperse dyes/reactive dyes and the dyeing process is similar to continuous dyeing used for polycotton fabrics.

Example 5

[0052] The fabrics similar to what are described in Example 1 can be made by using natural aramid fiber (aramid fiber that has not been dyed). The PPS fiber portion of the fabric is first dyed with disperse dye in a process as described in Example 1 . The fabric is subsequently dyed with cationic dyes in a batch jet dyeing process to dye the aramid fibers within the fabric. The disperse dyed PPS fiber portion is not expected to lose disperse dye in the jet or be stained by the cationic dyes. The dyed fabric would be expected to have a smooth and uniform color appearance.

[0053] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0054] The use of the terms“a” and“an” and“the” and similar referents in the context of describing the subject matter of this application (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,”“having,”“including,” and“containing” are to be construed as open- ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g.,“such as”) provided herein, is intended merely to better illuminate the subject matter of the application and does not pose a limitation on the scope of the subject matter unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the subject matter described herein.

[0055] Preferred embodiments of the subject matter of this application are described herein, including the best mode known to the inventors for carrying out the claimed subject matter. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the subject matter described herein to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above- described elements in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.