CN117120678A

CN117120678A - Differential vat dyed yarn and method of making the same

Info

Publication number: CN117120678A
Application number: CN202280027865.XA
Authority: CN
Inventors: R·R·萨金特; D·J·琼斯
Original assignee: Verana Chemical Co ltd
Current assignee: Verana Chemical Co ltd
Priority date: 2021-02-22
Filing date: 2022-02-22
Publication date: 2023-11-24

Abstract

The yarns described herein, in some embodiments, include a layer or a single strand dyed with at least one vat dye to create a tweed or variegated appearance. In one aspect, a yarn comprises a first layer and a second layer, each layer being dyed with at least one vat dye, wherein the absolute value of the color depth Difference (DL) between the dyed first single strand and the dyed second single strand is at least 2 when the vat dye is in an oxidized state. As further described herein, the first layer and the second layer are dyed in the same dyeing bath. In another aspect, the yarn comprises a first layer and a second layer, each layer being dyed with at least one vat dye, wherein the reflectance between the second layer and the first layer is in the range of 0.05 to 0.95.

Description

Differential vat dyed yarn and method of making the same

Data of related applications

According to patent Cooperation treaty, clause 8, the present application claims priority from U.S. provisional patent application Ser. No. 63/152,118 filed on 22 nd month 2021 and U.S. provisional patent application Ser. No. 63/283,716 filed on 29 th 11 th 2021, both of which are incorporated herein by reference in their entireties.

Technical Field

The present application relates to vat dyed yarns (vat dyed yarns), in particular to vat dyed yarns comprising layers (piles) that produce a tweed (tweed) or variegated (cured) appearance.

Background

Current processes for producing colored nylon floor coverings, such as carpets, have several drawbacks. For example, acid dyes are commonly used for the coloration of nylon fibers in carpet yarns because cationic nylon polymers readily absorb the dye. However, if the nylon fibers are exposed to contaminants having dye characteristics during use, this ease of staining can also result in a susceptibility to staining. In addition, acid dyes are commonly applied to nylon fibers in batch or continuous processes. Under this method, if the material is placed in a hot and humid environment, there is a risk that ozone acts to cause discoloration. To increase the resistance of acid dyed nylon to ozone fade, several treatments have been developed. These treatments include the use of phenolic resins, acrylic polymers, tannins, or various combinations thereof. However, such treatment may alter the hue of the dyed fiber and/or result in a decrease in the lightfastness of the dyed fiber.

In addition, these drawbacks complicate the production of nylon floor coverings having a tweed or variegated appearance. In many cases, acid-dyed nylon layers of different colors are produced separately and then twisted (twisted) or entangled (entangled). The lack of tight color control in acid dyeing batches can create color anomalies, thereby reducing the effect of tweed or mottle.

Disclosure of Invention

In view of the foregoing, the yarns described herein comprise a layer dyed with at least one vat dye, thereby creating a tweed or variegated appearance. In one aspect, a yarn includes a first layer and a second layer, each layer being dyed with at least one vat dye, wherein a denier ratio (denier) between the first layer and the second layer is greater than 1. In another aspect, the yarn comprises a first single strand and a second single strand, each strand being dyed with at least one vat dye, wherein the absolute value of the color depth Difference (DL) between the dyed first single strand and the dyed second single strand is at least 2 when the vat dye is in an oxidized state. In some embodiments, the absolute value of DL is in the range of 2-50 or 3-30. In some embodiments, the absolute value of DL may also be in the range of 5-20 or 10-30. As described herein, the terms "first layer and second layer" may be used interchangeably with "first single strand and second single strand". As described herein, the first layer and the second layer may be dyed in a single dyeing process and in the same dyeing bath (dye bath). In another aspect, the yarn comprises a first layer and a second layer, each layer being dyed with at least one vat dye, wherein the reflectance between the second layer and the first layer is in the range of 0.05 to 0.95. In some embodiments, the reflectivity is in the range of 0.4 to 0.6. The first and second layers of yarns described herein may be formed of any desired composition. In some embodiments, the first layer and the second layer are synthetic fibers. For example, the first and second layers may be formed from polyamide. In addition, the yarns described herein may be used to make a variety of textiles, including floor coverings such as carpets.

In another aspect, a yarn includes a first layer and a second layer, each layer being dyed with at least one vat dye, wherein the first layer and the second layer are formed from different polyamides. In some embodiments, the polyamide of the first layer has a lower crystallinity than the polyamide of the second layer. For example, the first layer may be formed of nylon 6 and the second layer formed of nylon 6,6. Furthermore, in some embodiments, the polyamide of the second layer may exhibit anionic properties. The polyamide of the second layer may have a sulfur content. The polyamide yarns may exhibit any of the deniers and/or reflectivities described herein.

In another aspect, a method of dyeing a yarn is described herein. In some embodiments, the method includes providing a yarn comprising a first layer and a second layer, and contacting the yarn with a dye composition comprising at least one vat dye in reduced form. Upon application of the vat dye to the first and second layers, the vat dye is oxidized, wherein the dyed first layer exhibits a darker or darker color than the dyed second layer. The first layer is darker or darker in color relative to the second layer, possibly due to the first layer receiving or absorbing more vat dye. In some embodiments, the absolute value of the color depth difference (DL x) between the dyed first layer or first individual strand and the dyed second layer or second individual strand is at least 2 when the vat dye is in an oxidized state. In some embodiments, DL is in the range of 2-50 or 3-30. Further, in some embodiments, the difference in denier between the first layer and the second layer may create a difference in reflectance where a lower denier layer reflects less light, resulting in lighter coloration.

These and other embodiments are further described in the detailed description that follows.

Detailed Description

Embodiments described herein may be understood more readily by reference to the following detailed description, examples and figures. However, the elements, devices, and methods described herein are not limited to the specific embodiments shown in the detailed description, examples, and diagrams. It should be understood that these embodiments are merely illustrative of the principles of the present application. Many modifications and variations of this application can be made by those skilled in the art without departing from its spirit and scope.

In one aspect, a yarn includes a first layer and a second layer, each layer being dyed with at least one vat dye, wherein a denier ratio (denier) between the first layer and the second layer is greater than 1. In some embodiments, the denier ratio is greater than 1.5 or greater than 2. In some embodiments, the denier ratio between the first layer and the second layer may be in the range of 1.2 to 10, for example. The denier ratio may be selected based on a number of considerations including, but not limited to, the composition of the first and second layers, the chemical nature of the vat dye, and the degree of dyeing of the vat dye on the first and second layers. In some embodiments, the first ply has a denier of 12 or greater and the second ply has a denier of less than 12. The denier ratio or denier differential between the first layer and the second layer may be used to adjust the respective reflectance values of the first layer and the second layer. For example, a first layer of higher denier may exhibit higher reflectivity, while a second layer of lower denier exhibits lower reflectivity. This gradient of reflectivity may make the second layer appear lighter to the viewer, producing the desired tweed or variegated effect.

In another aspect, the yarn comprises a first layer and a second layer, each layer being dyed with at least one vat dye, wherein the reflectance between the second layer and the first layer is in the range of 0.05 to 0.95. In some embodiments, the reflectivity is in the range of 0.3 to 0.7 or 0.4 to 0.6.

The first and second layers of yarns described herein may be formed of any desired composition. The first layer and the second layer may be formed of the same composition or different compositions. The first and second layers may comprise synthetic compositions, natural compositions, or various combinations of synthetic and natural compositions. The specific compositions of the first and second layers are selected in accordance with the technical purpose of providing yarns having a tweed or variegated appearance as described herein. In some embodiments, for example, the first layer and the second layer may be selected or chemically designed to receive different amounts of vat dye. For example, the first layer and the second layer may exhibit different levels of crystallinity. The first layer may exhibit lower crystallinity than the second layer, thereby providing an interlocking chain structure, and thus the first layer may receive more vat dye relative to the second layer having higher crystallinity. Further, in some embodiments, the first layer may exhibit a chemical structure that is more receptive to vat dyes relative to the second layer. The first layer may contain more cationic molecules or molecules with a positive dipole moment relative to the second layer for interaction with the anionic character of the vat dye. Furthermore, during dyeing, the second layer may contain more anionic molecules or molecules with negative dipole moments to repel or otherwise interfere with the anionic character of the vat dye. Such chemical modulation may cause the first layer to absorb more vat dye than the second layer, thereby creating a desired color difference between the layers to provide a tweed or variegated appearance.

The above technical principle is illustrated by forming the first layer and the second layer from different polyamides. For example, the first layer may be nylon 6 and the second layer nylon 6,6. Nylon 6 exhibits a lower crystallinity relative to nylon 6,6. Lower crystallinity may provide a more open structure to receive more vat dye. In addition, nylon 6 may contain more cationic amine groups for interaction with vat dyes. Conversely, nylon 6,6 fibers may contain sulfur content for generating anionic groups or functional groups to repel or otherwise interfere with the anionic character of the vat dye during the dyeing process. In some embodiments, nylon 6,6 has a sulfur content of at least 2,000ppm. For example, nylon 6,6 has a sulfur content of 2,000 to 3,300ppm.

Yarns having the structures and characteristics described herein may be used to provide a variety of textile products. In some embodiments, the yarn is used in a floor covering, such as a carpet. For example, yarns may be tufted and coated to produce a tweed or variegated carpet finish. Alternatively, the yarns comprising the first and second layers may be tufted into a greige carpet construction and then dyed in either batch mode or continuous mode using a vat dyeing system. The vat dye grey cloth is then coated to provide a tweed or variegated carpet finish.

In addition to exhibiting the color differences between the first and second layers described herein, the dyed yarns may also exhibit enhanced light fastness, wet fastness, ozone fastness, and/or home bleach resistance. For example, dyed yarns can withstand undiluted household bleach or diluted bleach with 0.3% sodium hypochlorite solution. In some embodiments, nylon fibers dyed with one or more vat dyes may meet one or more of the criteria set forth in table I.

TABLE I Properties of dyed Nylon fibers

Characteristics of	Testing	Gray Scale (GS) level
			Light resistance	AATCC test method 16, options	3-5
Ozone fastness to colour	AATCC 129	4-5
			Wet fastness	Conversion to undyed control group	4-5
Resistance to household bleaching agents	Application of household bleaching agent (24 hours)	4-5

Any vat dye that does not depart from the object of the present application can be used for nylon fibers having the described structure and/or characteristics. Suitable vat dyes may contain two or more ketone groups separated by a conjugated bond system. In some embodiments, the vat dye includes indigo and derivatives thereof. Vat dyes may also include various derivatives of anthraquinones (anthraquinones). Table II provides a non-limiting list of vat dyes for nylon fibers according to some embodiments described herein.

Table II vat dyes for dyeing nylon fibers

Vat yellow 33
	Reduction green 13
Reduction of Brown 1
	Reduction of Brown 3
Reduction of Brown 57
	Vat blue 6
Reduced black 22
	Reduced black 25
Reduced black 27
	Vat yellow 4
Reduction green 1

In another aspect, a method of dyeing a yarn is described herein. In some embodiments, the method includes providing a yarn comprising a first layer and a second layer, and contacting the yarn with a dye composition comprising at least one vat dye in reduced form. Upon application of the vat dye to the first and second layers, the vat dye is oxidized, wherein the dyed first layer exhibits a darker or darker color than the dyed second layer. As described herein, the first layer is darker or darker in color relative to the second layer, possibly due to the first layer receiving or absorbing more vat dye. Further, in some embodiments, the difference in denier between the first layer and the second layer may create a difference in reflectance where a lower denier layer reflects less light, resulting in lighter coloration. Notably, the first and second layers are combined to form the yarn prior to dyeing in the same or a common vat dye bath. Thus, the different color effects between the dyed first layer and the second layer are achieved in a single dyeing bath or a single dyeing process. The ability to achieve different color effects in a single or common process increases process efficiency compared to the process of first dyeing the first and second layers separately and then incorporating the separately dyed layers into the yarn structure.

The dye composition may comprise one or more vat dyes in amounts which are not inconsistent with the objectives of the present application. In some embodiments, the vat dye is added to the dye composition in an amount of at least 0.1% by weight of the fiber. Vat dyes may also be added to the dye compositions in the amounts indicated in Table III.

TABLE III-amount of dye by weight of fibers (owf)

≥0.25
	≥0.5
≥1
	0.1-1
0.25-1

The dye composition, which includes one or more vat dyes, can be prepared according to a variety of techniques. In some embodiments, an aqueous dispersion of one or more vat dyes (aqueous dispersion) is first provided. Purified water free or substantially free of hardening species (e.g., calcium and magnesium) may be used as the dispersed continuous phase. Optionally, one or more water softeners may be added to the dispersion to isolate the hardening species. Such purified or treated water is generally referred to herein as soft water. Vat dye was added to the continuous aqueous phase in an amount consistent with the amount provided in table III. The continuous aqueous phase may be heated to a temperature of 30-35 ℃ and then stirred to aid in the dispersion of the vat dye.

The vat system is prepared to combine with the aqueous dispersion of vat dye. In some embodiments, the reducing system includes one or more chemicals for reducing the vat dye, thereby placing the dye in a water-soluble form. In some embodiments, the reduction of the vat dye may convert the dye into a colorless form. Any suitable type of reducing agent may be used without departing from the purpose of the present application. For example, sodium dithionite and/or sodium bisulfite may act as a reducing agent for one or more vat dyes. In some embodiments, ferrous sulfate may be used with sodium dithionite for dye reduction. The reducing agent may be added to soft water to provide a reducing system. In some embodiments, the water is heated to a temperature of 30-35 ℃ and then one or more reducing agents are added with stirring or other mechanical agitation. The amount of reducing agent added to the soft water is sufficient to reduce all or substantially all of the vat dyes used in the dyeing process. Once the vat system has achieved dispersion and wetting, it can be added to a dip dyeing apparatus containing vat dye in dispersed form and an initial water addition (initial water charge). In some embodiments, a reducing system is not necessary as the manufacturer may provide the vat dye in reduced form. For example, solutions for vat dyes are commercially available and are used according to the methods described herein.

One or more alkaline substances for adjusting the pH of the dye composition are dispersed in soft water. For example, caustic soda (NaOH) or aqueous ammonia may be used as the alkaline pH adjuster. Other pH adjusting agents are well known in the art and may also be used. After the production is completed, the pH adjusting composition is added to the dip dyeing equipment. In a further step of the dye composition, dispersants and/or levelling agents are added. For example, polyvinylpyrrolidone can be used as a dispersant for vat dyes and provide some level and slow-down effect. Furthermore, benzyl alcohol may also be used if the carrier is found to be useful for a given formulation. In addition, there are a number of dispersants, leveling agents, carriers and/or bulking agents that can be used in the nylon fiber dye composition. Table IV provides the amounts of reducing agent and pH adjuster for dye compositions having various dye concentrations (owf) for use in dip dyeing systems.

Table IV-reducing agent and pH regulator

Dye concentration (owf)	Sodium hydrosulfite (g/L)	50% caustic soda (g/L)
			0.1％	2-3	2.5-3.5
0.11-1.0％	2-3	4-5
			>1.0％	3-4	5-7

Table V provides the amounts of reducing agent and pH adjuster for dye compositions having different dye concentrations (owf) for use in a continuous dyeing system at 450% pick-up.

Table V-reducing agent and pH regulator

Dye concentration (owf)	Sodium hydrosulfite (g/L)	50% caustic soda (g/L)
			0.1％	4-5	9-10
0.11-1.0％	5-7	14-16
			>1.0％	6-8	17-20

Table VI provides the amounts of reducing agent and pH adjuster for dye compositions having various dye concentrations (owf) for use in continuous interval dyeing at 100% pick-up.

Table IV-reducing agent and pH regulator

In addition, table VII provides various Liquor Ratios (LR) for dip dyeing processes, continuous dyeing processes, and continuous space dyeing processes according to some embodiments.

Table VII-liquid ratio

Dyeing process	Liquid ratio
		Dip dyeing	25：1
Continuous dyeing	4.5：1
		Continuous interval dyeing	1：1

For the use of the dip dyeing apparatus, the dye composition may be initially mixed and moistened with nylon fibers, yarns or greige goods for a period of at least 15 minutes at a temperature of 30-35 ℃. Then, the temperature raising treatment is performed. In some embodiments, the temperature is raised to 80 ℃ at a rate of 1.5 ℃/min and held for 45 minutes. Once the dyeing cycle is complete, the bath may be overflowed for preliminary cooling, and the used dyeing bath is then removed from the dip dyeing apparatus. A sink of ambient water is then provided and the dyed nylon fibers are circulated in the sink for at least 15 minutes to remove the non-fixed material from the fiber surface. Depending on the dye composition, the addition of an organic acid component (e.g., acetic acid) may help remove the unfixed material and lower the pH of the nylon fiber. In some embodiments, a dye uptake of 30% to 80% is achieved.

After rinsing, the dyed nylon fibers are removed from the dip dyeing apparatus and extracted to mechanically remove as much water as possible without damaging the fibers. The extracted fibers were then air dried. Air drying may be performed at ambient or elevated temperatures. In some embodiments, for example, air drying occurs at a temperature of 200 to 300°f (e.g., 240 to 260°f). Drying is continued until the moisture content reaches 5% or less. The drying process also serves as an oxidation step of the vat dye on the nylon fiber. This drying and oxidation process can fix the vat dye to the nylon fiber, thereby greatly improving the fastness properties of the nylon fiber as set forth in Table I. Dye oxidation and dye fixation during heating are essentially different from prior art methods that use one or more oxidizing agents to oxidize the vat dye. For example, existing processes may use peroxides and/or other oxidizing agents for dye oxidation. Surprisingly, the process of the present application enables oxidation and fixation of vat dyes without such oxidizing substances, thereby simplifying the dyeing process.

For a continuous dyeing process, the main difference from a dip dyeing process is that the vat dye dispersion is separated from the vat system before the dye composition is applied to the nylon fiber. For example, tank A may be filled with a bath containing pre-dispersed vat dye, while tank B is filled with a reducing system, pH adjustor and other auxiliary materials (e.g., wetting agents, leveling agents, carriers, etc.). The contents of tank a and tank B are metered and mixed together in the appropriate proportions to provide the dye composition. The dye composition is then applied to the nylon yarn or carpet tile, and the continuous treatment is performed by space dyeing threads (in the case of yarn application) or a continuous wide loom dyeing range (in the case of nylon carpet tile). After the two baths are mixed and used, the fibers may be heated to promote dye uptake of the vat dye on the fibers. In general, saturated steam may be used as a heat source. After the heating cycle, the dyed fibers may be rinsed, extracted and dried as described above. The vat dye is oxidized during the drying process.

In some embodiments, the pretreatment process is applied to one or more layers (including cationic and/or anionic layers). A pretreatment process may be incorporated into the exemplary method to increase the hydrophobic character of the cationic and/or anionic layers. For example, the pretreatment may include contacting the layer with wax (e.g., in the form of a wax emulsion) to produce a wax-treated ply.

Some embodiments of the present disclosure may include yarns made of at least two layers (e.g., a first layer and a second layer), wherein one of the at least two layers is a wax treated layer. In these embodiments, the yarn may have a structure that defines a spatial relationship between the wax treated layer and one or more other layers of the at least two layers along the length of the yarn. For example, one of the structures may include a "spiral pattern" (barberpole) structure in which one of the wax treated layer and the other layer are twisted or otherwise intertwined with one another to create a diagonal stripe effect. Under this striped effect, a point moving from one location on the yarn to a second location along the length of the yarn will pass from the wax treated layer through the yarn to another layer surrounding the yarn and then through the wax treated layer again to repeat the pattern.

Various aspects of the spiral stripe structure may include regular or irregular stripe effects. In a regular striped effect, the positions of the wax treated layer and the positions of the other layer wrapped around the wax treated layer are regularly spaced such that the positions of the wax treated layer repeat at least every 2mm along the length of the yarn (e.g., between 0.2cm and 2cm, between 0.5cm and 1.5cm, between 0.5cm and 1cm, or between 0.6cm and 0.8 cm). This effect can be adjusted in a number of ways. For example, the thickness of the wax treated layer and/or other layers surrounding the wax treated layer may be adjusted. Alternatively or additionally, the twist and/or density in the yarn may be adjusted. For a structure with an irregular streak effect, the positional intervals of the wax-treated layer are irregular, and thus there is no specific repetition value.

More specifically, some structures may be produced by arranging a first layer and a second layer. Arranging aspects of the first and second layers may include introducing a twist into the yarn at a density of 1 twist per inch to 10 twists per inch, such as 2 to 8 twists per inch, 1 to 5 twists, or 8 to 10 twists per inch. In these arrangements, the turns may be regularly spaced to produce a regular striped effect or irregularly spaced to produce an irregular striped effect. In some constructions, the twist may or may not vary along the length of the yarn.

Embodiments of the present disclosure may also include a method for producing dyed yarns. An exemplary method of producing dyed yarns may include obtaining a first layer and a second layer, optionally applying a pretreatment process to at least one of the first layer, the second layer, or both, arranging the first layer and the second layer to form a yarn having a structure (e.g., a spiral stripe structure), exposing the yarn to a dyeing bath containing at least one vat dye in reduced form (i.e., a vat dye), and oxidizing the vat dye applied to the yarn.

Some advantages of preparing dyed yarns according to the methods of the present disclosure may include improving the color difference between the first layer and the second layer. For example, it has been found that pre-treating one or more layers prior to dyeing the yarn may result in a greater difference in color value between the first layer and the second layer than the untreated layer or layers. In addition, properties such as ionic properties (e.g., anions or cations) can also affect dye absorption. Furthermore, by exposing the yarns comprising the layers together to a dye bath, rather than dyeing each layer separately, these differences in dye absorption can be achieved in a more economical manner. Thus, yarns according to the present disclosure may exhibit improved color values to provide a variegated or tweed appearance while also exhibiting economic advantages in manufacture.

In some exemplary embodiments, various fiber properties may be achieved by differentiation between the first and second layers, for example, a spiral stripe effect and/or a tweed effect by application of vat dyes. In some cases, the first layer or filament may be darker after dyeing, while the second layer or filament may be lighter after dyeing. The differences between the layers after dyeing can adjust various properties of the fiber. In some embodiments, the total ply denier may be different, wherein the total ply denier of the first ply is greater than the second ply, the second plyThe total ply denier is less than the first ply. In some embodiments, the denier per filament may be different, with the first layer having a higher denier per filament (i.e., fewer filaments of larger cross-section) relative to the second layer and the second layer having a lower denier per filament (i.e., more total number of filaments of smaller cross-section) relative to the first layer. In some embodiments, the gloss level (e.g., tiO ₂ Content) may be different, wherein the first layer has a higher gloss value (i.e., lower TiO than the second layer ₂ Content), while the second layer has a lower gloss value (i.e., higher TiO ₂ Content). In some embodiments, filament cross-sections (e.g., fiber profile (modification ratio)) may be different, with the first layer having a higher fiber profile (MR) cross-section (i.e., a more angular cross-section) relative to the second layer and the second layer having a lower MR cross-section (i.e., a more circular cross-section) relative to the first layer. In some embodiments, the chemical properties of the nylon may be different, with the first layer being cationic or highly cationic and/or having a high amine group content (e.g., relative to the second layer), and the second layer being anionic or highly anionic, having a high sulfur content (e.g., relative to the first layer). In some embodiments, the physical properties of the nylon may be different, with the first layer having a low crystallinity (e.g., nylon 6 type) and the second layer having a higher crystallinity (e.g., nylon 6.6 type). In some embodiments, the extrusion surface treatment characteristics may be different, with the first layer having a surface treatment with a high wetting speed (i.e., to promote high dye uptake) and the second layer having a surface treatment or repellent finish with a low wetting speed, such as a wax treatment (e.g., to promote low dye uptake).

Various embodiments of the present application have been described in order to achieve various objects of the present application. It should be understood that these embodiments are merely illustrative of the principles of the present application. Numerous modifications and adaptations of the present application will occur to those skilled in the art without departing from the spirit and scope of the present application.

Example

Examples herein provide various aspects of embodiments of the present disclosure. These examples are not intended to limit the embodiments to only these examples, but rather to illustrate some of the possible embodiments.

The preparation method of table 1 is: first, 11 different twisted, heat-set packages (yarn packages) were produced using dyeable commercial yarns for carpet use. The self-twisting bobbin can be produced from each yarn type using a 5.25 twist per inch setting and a Superba heat setting.

A series of dyed yarn skeins were made using 1200 assnd yarn and 2200 parts sulfur, with dye intensities ranging from 0% (no dye) to 1.5% owf dye, with 0.25% owf incremental dye. This information was used to establish a relationship between L x value (color depth) and% owf of dye, and to estimate how much dye was present on the dyed yarn combination produced in this study.

The dye used was color index reduced Black 27 (Vat Black 27), sold as indanthrene olive (Indanthrene Olive) R liquid by desida (Dystar). Color measurements were performed using an Ahiba laboratory dyeing apparatus and Gretag Macbeth Color-eye 7000A to determine the tristimulus values of the cut ends of dyed skeins. The L information was used to determine the DL (al) difference between the two competitively dyed yarns in each test case, and to determine the estimated Vat Black 27 content on each yarn hank.

Table 1 exemplary properties of dyed yarn skein.

Table 2 shows the dyeing properties of two twisted bobbins. In one of the bobbins, a wax pretreatment (NF 8185%) is carried out before dyeing. The resulting dyed yarn has a greater DL value than the yarn without pretreatment.

Table 2 comparison of dyeing characteristics of wax pretreated yarn and control yarn

Claims

1. A yarn, comprising:

the first and second strands, each strand being dyed with at least one vat dye, wherein the absolute value of the colour depth Difference (DL) between the dyed first and second strands is at least 2 when the vat dye is in an oxidized state.

2. The yarn of claim 1, wherein the first single ply and the second single ply are dyed using the same vat dye.

3. The yarn of claim 1 wherein the first and second individual strands are formed from polyamide.

4. The yarn of claim 3 wherein the polyamide of the first single ply and the polyamide of the second single ply are different.

5. The yarn of claim 4 wherein the crystallinity of the polyamide of the first individual strand is lower than the crystallinity of the polyamide of the second individual strand.

6. The yarn of claim 4 wherein the first individual strand is formed from nylon 6 and the second individual strand is formed from nylon 6,6.

7. The yarn of claim 4 wherein the polyamide of the first single strand has a different number of amine end groups relative to the polyamide of the second single strand.

8. The yarn of claim 1, wherein the sulfur content of the first and second individual strands are different.

9. The yarn of claim 1, wherein the first single strand and the second single strand exhibit different wetting rates for vat dyes.

10. The yarn of claim 9, wherein the first single strand or the second single strand comprises a wax treated face.

11. The yarn of claim 1 wherein the first and second individual strands have different TiO ₂ The content is as follows.

12. A textile composition comprising the yarn of any one of claims 1 to 11.

13. The textile composition of claim 12, wherein the textile composition is a floor covering.

14. The textile composition of claim 13, wherein the floor covering is a carpet.

15. A method of dyeing yarn comprising:

providing a yarn comprising a first single strand and a second single strand;

contacting the yarn with a dye composition comprising at least one vat dye in reduced form; and

the vat dye applied to the yarn is oxidized, wherein the dyed first strand exhibits a darker color than the dyed second strand.

16. The method according to claim 15, wherein the absolute value of the color depth Difference (DL) between the dyed first single strand and the dyed second single strand is at least 2 when the vat dye is in an oxidized state.

17. The method of claim 15, wherein the first single strand and the second single strand are dyed using the same vat dye.

18. The method of claim 15, wherein the first and second single strands are formed from polyamide.

19. The method of claim 18, wherein the polyamide of the first single strand and the polyamide of the second single strand are different.

20. The method of claim 19, wherein the crystallinity of the polyamide of the first individual strand is lower than the crystallinity of the polyamide of the second individual strand.

21. The method of claim 19, wherein the first single strand is formed of nylon 6 and the second single strand is formed of nylon 6,6.

22. The method of claim 19, wherein the polyamide of the first single strand has a different number of amine end groups relative to the polyamide of the second single strand.

23. The method of claim 15, wherein the sulfur content of the first single strand and the second single strand are different.

24. The method of claim 15, wherein the first single strand and the second single strand exhibit different wetting rates for vat dyes.

25. The method of claim 24, wherein the first single strand or the second single strand comprises a wax treated surface.

26. The method of claim 15, wherein the first and second single strands have different TiO ₂ The content is as follows.

27. A yarn, comprising:

a first layer and a second layer, each layer being dyed with at least one vat dye, wherein at least one of the first layer and the second layer is wax treated.

28. The yarn of claim 27, wherein the first and second layers are twisted with each other to create a spiral bar stripe structure.

29. The yarn of claim 27, wherein the first layer and the second layer are dyed with the same vat dye.