Double-sided jean fabric with front and back different colors and preparation method thereof

Abstract

The invention discloses a front and back different-color double-sided jean fabric and a preparation method thereof, and belongs to the technical field of textile materials and processing. The double-sided jean fabric with the front side and the back side different in color comprises a back side weave composed of line axis warp yarn and a front side weave composed of earth axis warp yarn, and the front side weave is of a full-covering type twill structure and can completely cover back side patterns; the back texture is formed by alternately arranging blue warp yarns and white warp yarns to form blue-white stripes; the double-faced jean fabric further comprises edge weaves located on the two sides, each side is composed of 24 pieces of edge yarn, and a 2 / 2 variable warp rip weave is adopted. Wherein the earth axis warp yarns are dyed by using a compound dyeing agent containing a sulfur black main dye, and the blue warp yarns in the line axis warp yarns are dyed by using a compound dyeing agent containing a carboxymethylated reductive indigo main dye; the compound coloring agent comprises a main dye, a reactive color fixing microcapsule and a nanometer coordination auxiliary agent. The double-sided jean fabric has the characteristics of high coloring rate, high color fastness and excellent mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of textile materials and processing technology, specifically relating to a double-sided denim fabric with opposite colors on the front and back and its preparation method. Background Technology

[0002] Denim is a relatively thick, yarn-dyed twill cotton fabric. The warp yarns are dark, usually indigo, while the weft yarns are light, usually light gray or bleached off-white.

[0003] Currently, most traditional denim fabrics on the market use single-axis weaving and single-sided dyeing processes, which have obvious limitations: First, they are functionally limited, usually only the front is denim color and the back is light color, making it impossible to achieve reversible or double-sided designs, thus restricting the product's flexibility and fashionability; Second, their colorfastness is generally insufficient, because cotton yarn is prone to "ring dyeing" and sulfur black and indigo dyes have weak bonding with fibers, causing the fabric to fade and show white after washing and rubbing, affecting its appearance and durability.

[0004] To expand the applications of denim fabric, reversible denim fabric with contrasting colors on the front and back has emerged, widely used in denim garments with cuffs / legs that can be rolled up, reversible shirts, and reversible denim-style bed sheets. However, this fabric faces serious challenges in practical use: long-term washing and friction can easily cause the colors on the front and back to bleed into each other, especially causing color bleeding along the white edges of the striped side, making the product look old quickly and reducing its aesthetic appeal, which seriously restricts its market promotion.

[0005] The root of this problem lies in the fundamental contradiction between the style and craftsmanship of denim fabrics and the requirements for colorfastness. To maintain the classic "ring-dye" style of denim, the warp yarns must maintain a cross-sectional structure of "colored on the outside and white on the inside" during dyeing, and through-dyeing is not allowed. Traditional methods of improving colorfastness by deepening the dye are completely ineffective here. Therefore, how to simultaneously achieve high colorfastness, resistance to color bleeding, and the mechanical properties required for high-intensity use while maintaining the "ring-dye" structure of the yarn has become a key technical challenge that urgently needs to be overcome in the denim fabric industry.

[0006] Patent application CN214088822U discloses a double-sided denim fabric, woven from warp and weft yarns; both warp and weft yarns are made of pure cotton fibers; both warp and weft yarns include plain yarn and slub yarn; the front of the fabric has a 3-up-1-down twill weave, and the reverse side has a 1-up-3-down twill weave. The fabric has a clear, smooth, and structured texture, a crisp surface, is wrinkle-resistant, and has good shape retention. This fabric can be used to design reversible denim tops, particularly catering to the fashion-conscious and individualistic needs of many young people. However, this technology cannot simultaneously achieve a synergistic improvement in colorfastness and mechanical properties. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a double-sided denim fabric with contrasting front and back colors and its preparation method. The double-sided denim fabric features high colorfastness, high color strength, and excellent mechanical properties.

[0008] To achieve the above objectives, according to one aspect of the present invention, a double-sided denim fabric with opposite front and back colors is provided, comprising a back weave composed of top-axis warp yarns and a front weave composed of bottom-axis warp yarns. The front weave is a full-coverage twill structure capable of completely covering the back pattern. The back weave consists of alternating blue and white warp yarns forming blue and white stripes. The double-sided denim fabric also includes selvage weaves on both sides, each side consisting of 24 selvage yarns, using a 2 / 2 variable warp-weight plain weave. The bottom-axis warp yarns... The blue warp yarns in the main warp yarns are dyed using a compound dyeing agent containing carboxymethylated reduced indigo as the main dye. The compound dyeing agent comprises the main dye, reactive color-fixing microcapsules, and nano-coordination auxiliaries, with a mass ratio of (25-30):2:1. The reactive color-fixing microcapsules have glycidyltrimethylammonium chloride as the core material and polyurea as the wall material, with an average particle size of 1-5 μm. The nano-coordination auxiliaries are nano-silica particles with surface-modified phosphate groups and loaded with Zn²⁺.

[0009] In this invention, the front fabric adopts a 3 / 1 right twill structure; the back fabric adopts a 3 / 1 left twill, 2 / 2 double flat, 3 / 1 right twill, or 1 / 3 right twill structure.

[0010] In this invention, the sulfur black has a particle size of 8-12 nm; the degree of substitution of the carboxymethylated reduced indigo is 0.6-0.9. By controlling the sulfur black particle size within the range of 8-12 nm, smaller particle sizes allow it to penetrate the fiber more easily, improving color strength and uniformity, and ensuring good dispersibility and penetration. The degree of substitution of the carboxymethylated reduced indigo is specified as 0.6-0.9, ensuring a moderate degree of carboxymethylation that facilitates dyeing while retaining sufficient hydrophobic structure to maintain color fastness. Too low a substitution level results in poor dye solubility, while too high a degree leads to easy hydrolysis and shedding.

[0011] In this invention, the reactive color-fixing microcapsules begin to rupture above 65°C, and the release rate exceeds 85% at 70-80°C. Microcapsule rupture is triggered simultaneously during the conventional dyeing heating stage, enabling in-situ color fixation without additional steps; this avoids premature release of the core material, preventing ineffective losses or equipment contamination; and simultaneously improves reaction efficiency, shortens color-fixing time, and reduces energy consumption.

[0012] In this invention, the compound dyeing agent further includes a penetrant and caustic soda. The penetrant is selected from fatty alcohol polyoxyethylene ether or sodium secondary alkyl sulfonate, and the amount added is 0.5-1.5% of the total mass of the compound dyeing agent. The caustic soda is used to adjust the pH to 11.0-11.5. In this invention, the penetrant significantly improves the wetting ability of the dye liquor on cotton yarn, shortens the soaking time, and prevents color unevenness; the caustic soda precisely controls the pH to 11.0-11.5, ensuring that the carboxymethyl indigo is in a soluble and reduced state; the overall dye liquor system is stable, without precipitation or stratification, and is suitable for continuous production.

[0013] In this invention, a compound dyeing agent system is introduced, comprising a main dye, reactive color-fixing microcapsules, and a nano-coordination auxiliary agent in a ternary synergistic composition, with a mass ratio optimized to (25-30):2:1, balancing dyeing uniformity and fastness. Nano-silica with surface-modified phosphate groups and loaded with Zn²⁺ is used as a coordinating auxiliary agent. The phosphate groups can form hydrogen bonds with the hydroxyl groups of cotton fibers, achieving self-anchoring of the auxiliary agent. Zn²⁺ coordinates with the -COO⁻ group of carboxymethyl indigo, promoting dye deposition. Through the dual effects of hydrogen bonding and metal coordination, the dye is stabilized, enhancing its anchoring ability on the fiber and improving evenness and color fastness. The reactive color-fixing microcapsules use glycidyltrimethylammonium chloride as the core material, releasing quaternizing agents in situ during the dyeing heating process, thus improving covalent bonding efficiency. The technical solution described in this invention is particularly applicable to denim products with special wearing or usage functions, such as denim garments with cuffs or hems that can be rolled up, reversible denim jackets, and reversible denim-style bed sheets. For these textiles that require frequent rubbing, folding, or double-sided contact, this system, through the dual anchoring effect of hydrogen bonds and metal coordination, can effectively resist dye loss caused by repeated folding and rubbing, ensuring excellent colorfastness on both the inner and outer sides of the rolled-up edges and on both sides of the garment, significantly improving the durability and aesthetic consistency of such high-intensity denim products.

[0014] In this invention, the compound dyeing agent containing sulfur black as the main dye is prepared as follows: sulfur black as the main dye, the reactive color-fixing microcapsules and nano-coordination aids are added and dispersed in water to obtain the compound dyeing agent containing sulfur black as the main dye.

[0015] In this invention, the compound dyeing agent containing carboxymethylated reduced indigo as the main dye is prepared as follows: using carboxymethylated reduced indigo with a degree of substitution of 0.6-0.9 as the main dye, the reactive color-fixing microcapsules and nano-coordination auxiliaries are added, and the pH is adjusted to 11.0-11.5 to obtain the compound dyeing agent containing carboxymethylated reduced indigo as the main dye.

[0016] Specifically, the preparation method of the carboxymethylated reduced indigo main dye includes: dispersing natural reduced indigo in a water-ethanol mixed solvent, adding sodium hydroxide to adjust the pH to above 12.0 to form an alkaline dissolution system; heating to 60-65℃ under nitrogen protection, adding sodium chloroacetate in batches, wherein the molar ratio of indigo to sodium chloroacetate is 1:2.8-3.2, and then adding sodium hydroxide solution dropwise to maintain the pH of the reaction system at 11.5-12.5, and continuously stirring the reaction for 5-7 hours; after the reaction is completed, adjusting the pH to 7.0 with acid to terminate the reaction, and obtaining carboxymethylated reduced indigo after centrifugation, washing with deionized water and ethanol, and vacuum drying.

[0017] The preparation method of the nano-coordination aid in this invention includes: dispersing nano-silica particles in anhydrous ethanol, adding γ-aminopropyltriethoxysilane, and refluxing at 60-70°C for 6-8 hours; obtaining aminated silica after centrifugation, washing, and drying; reacting polyethylene glycol with phosphorus oxychloride in an ice bath under nitrogen protection for 2.5-3 hours to generate biphosphorylated polyethylene glycol; dissolving the biphosphorylated polyethylene glycol in anhydrous tetrahydrofuran and adding it dropwise to the aminated silica suspension; stirring and reacting at room temperature for 12-14 hours to achieve phosphate group grafting; subsequently dispersing it in deionized water, adjusting the pH to 5.5-6.5, adding 0.1-0.2 mol / L zinc nitrate solution, and stirring and complexing at 25°C for 6-8 hours; obtaining the nano-coordination aid after centrifugation, washing, and freeze-drying.

[0018] The preparation method of the reactive color-fixing microcapsules in this invention includes: using an aqueous solution containing glycidyltrimethylammonium chloride and ethylenediamine as the inner aqueous phase; dissolving sorbitan monooleate and octadecyl alcohol together in liquid paraffin to form an oil phase containing a thermosensitive phase change material; slowly adding the inner aqueous phase to the oil phase, and forming a water-in-oil microemulsion through high-speed shearing; adding a toluene solution of hexamethylene diisocyanate dropwise, and prepolymerizing at 40-50°C to generate a prepolymer with -NCO end groups on the surface; subsequently introducing an outer aqueous phase containing ethylenediamine to form a W / O / W dual emulsion, and causing the ethylenediamine in the outer aqueous phase to undergo an interfacial condensation reaction with the prepolymer at 55-60°C to generate a polyurea wall material in situ; and then drying after post-treatment to obtain reactive color-fixing microcapsules with an average particle size of 1-5 μm. Preferably, the mass percentage of octadecyl alcohol in the oil phase is 6-10 wt%. This invention successfully creates microcapsules that respond to specific temperature windows and release according to predetermined kinetics by precisely combining octadecyl alcohol and polyurea and by strictly controlling emulsification and polymerization temperatures and times.

[0019] The reactive color-fixing microcapsule wall material of this invention is dense, exhibits good storage stability, and does not leak at room temperature. The oil phase of the microcapsule contains dissolved octadecyl alcohol, a typical organic phase change material with a melting point between 55-60°C. When the ambient temperature rises above its melting point, octadecyl alcohol changes from a solid to a liquid state. This phase change process is accompanied by significant volume expansion, generating mechanical pressure inside the microcapsule. This causes the reactive color-fixing microcapsule to begin rupturing above 65°C. As the temperature further rises to 70-80°C, the octadecyl alcohol completely liquefies and continues to expand, reaching its peak internal pressure. Simultaneously, the heat intensifies the molecular chain movement of the polyurea wall material, altering the material's toughness. Under the combined effect of internal high pressure and thermal softening of the wall material, cracks propagate rapidly or the wall material undergoes large-scale rupture, and the core material is quickly extruded, achieving a release rate exceeding 85%.

[0020] According to another aspect of the present invention, a method for preparing the double-sided denim fabric described in any one of the above claims is also provided, comprising the following steps: (1) Warping process: A double warp beam weaving system is adopted. The top beam and the bottom beam are configured according to the yarn count and the head share. The two beams are independently wound and formed under constant machine speed and single yarn tension. (2) Dyeing process: The ground warp yarns are dyed by rope continuous dyeing process, and the top warp yarns are dyed by sheet dyeing process. During the dyeing process, the temperature is gradually raised to 70-80℃ and kept warm for 5-8 minutes to break the reactive color-fixing microcapsules and release the core material, thereby completing the in-situ color fixation. The moisture regain of the dyed yarn is controlled within the range of 6-8%. (3) Warp separation and sizing process: The top and bottom warps after dyeing are separated and sizing is applied by double immersion and double pressure. The temperature of the sizing tank is controlled at 90-94℃, the viscosity is 5-6.5s, the temperature of the drying room is 105-125℃, the winding tension is 1700-2300N, and the flat yarn tension is 0.2-0.3kN. (4) Warp threading process: Using a 10-page heddle frame, the ground warp yarns are threaded into the 3rd, 4th, 5th and 6th heddles, and the top warp yarns are threaded into the 7th, 8th, 9th and 10th heddles, so as to achieve independent opening control of the top and bottom layers; in the top warp area, 4 yarns are threaded into each reed, and the dyed warp yarns and the original white warp yarns are arranged alternately in a 16 blue 4 white pattern to form a 3 / 1 left twill, 2 / 2 plain, 3 / 1 right twill or 1 / 3 right twill; 24 edge yarns are set on each side, 4 yarns are threaded into each reed, and a 2 / 2 variation warp plain weave is adopted; (5) Weaving process: The upper and lower warp yarns are introduced simultaneously on the rapier double warp beam loom to weave the greige fabric; the reed is 95 / 10cm with a width of 170.1cm, the weft density is set to 54 threads / inch, the loom speed is controlled at 500-600r / min; the heald frame height is set to 120mm, 120mm, 116mm, 115mm and 114mm respectively, the shedding time is 310°, the shedding stroke is 26°, the loom tension is 3000N, the workshop ambient temperature is maintained at 26-32℃ and the relative humidity is 70-75%; (6) Finishing process: The fabric is processed in sequence through a multi-tank pre-shrinking equipment containing enzyme desizing, water washing and softening finishing to obtain the double-sided denim fabric with different colors on the front and back.

[0021] In this invention, the inventors have constructed a process for preparing double-sided denim fabric with different colors, encompassing warping, dyeing, sizing, warping, weaving, and finishing. A dual warp beam system is used to independently control the tension and shedding action of the top and bottom layers, ensuring structural stability. The dyeing process is combined with a heating program to activate microcapsules, achieving in-situ color fixation. By precisely setting weaving parameters (high on-machine tension 3000N, early shedding 310°), the bottom warp yarns are prevented from jumping to the front, causing the bottom to show through.

[0022] The top-axis warp yarns come in two colors, and the threading method is more complex than that of the bottom-axis warp yarns, which are passively fed. Placing the blue and white warp yarns on the top-axis makes it easier for workers to pass the warp yarns and for the weaving process to be convenient. If the blue and white warp yarns were placed on the bottom-axis warp yarns, workers would have to avoid the top-axis warp yarns overhead and lie prone on the loom to thread the bottom-axis warp yarns, causing inconvenience and increasing the risk of warp breakage.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention creatively designs a double-sided denim fabric with opposite colors on the front and back. By employing a double warp beam system to construct the front and back fabrics separately, independent design of the colors, textures, and functions of the front and back sides is achieved. This invention applies a compound dyeing agent containing sulfur black and carboxymethylated reduced indigo to the ground and top warp yarns, respectively. The dyeing agent comprises a main dye, reactive color-fixing microcapsules, and a nano-coordination auxiliary agent, with a mass ratio of (25-30):2:1, forming a synergistic system. The nano-coordination auxiliary agent binds to cotton fibers via hydrogen bonds through phosphate groups and enhances dye adsorption by coordinating Zn²⁺ with dye functional groups. The reactive color-fixing microcapsules rupture upon heating during dyeing, releasing glycidyltrimethylammonium chloride, which undergoes a quaternization reaction with the fiber hydroxyl groups, achieving in-situ chemical color fixation. This significantly improves dye utilization and color fastness, resulting in rich, uniform color and solving the problems of poor dye fastness, easy fading, and low strength in traditional double-sided denim fabrics. The denim fabric of this invention maintains a colorfastness of 4-4.5 after 10 washes, solving the problems of poor colorfastness on both the front and back sides, and easy fading and staining on the blue and white sides of the double-sided denim fabric. This makes the double-sided denim fabric of this invention more suitable as a garment fabric for cuffs and trouser hems, where the blue and white stripes on the back side are exposed, and it can still maintain high colorfastness after 10 washes.

[0024] 2. The preparation method provided by the present invention integrates the entire process of warping, dyeing, warp sizing, heddle threading, double-layer independent weaving and environmentally friendly finishing, and has high feasibility and industrialization value. Attached Figure Description

[0025] The double-layer four-way stretch denim fabric of the present invention will be described below with reference to the accompanying drawings.

[0026] Figure 1 Example 2: Denim fabric shown before washing.

[0027] Figure 2 Example 2: Denim fabric washed 10 times with soap. Detailed Implementation

[0028] This invention provides a double-sided denim fabric with opposite front and back colors, comprising a back weave composed of top-axis warp yarns and a front weave composed of bottom-axis warp yarns. The front weave is a full-coverage twill structure that can completely cover the back pattern. The back weave consists of alternating blue and white warp yarns forming blue and white stripes. The double-sided denim fabric also includes selvage weaves on both sides, each side consisting of 24 selvage yarns, using a 2 / 2 variable warp plain weave. The bottom-axis warp yarns use a sulfur-containing black primary dye. The blue warp yarn in the axial warp is dyed using a compound dyeing agent containing carboxymethylated reduced indigo as the main dye. The compound dyeing agent comprises the main dye, reactive color-fixing microcapsules, and nano-coordination auxiliaries, with a mass ratio of (25-30):2:1. The reactive color-fixing microcapsules have glycidyltrimethylammonium chloride as the core material and polyurea as the wall material, with an average particle size of 1-5 μm. The nano-coordination auxiliaries are nano-silica particles with surface-modified phosphate groups and loaded with Zn²⁺.

[0029] In some embodiments, the front fabric adopts a 3 / 1 right twill pattern; the back fabric adopts a 3 / 1 left twill, 2 / 2 double flat, 3 / 1 right twill, or 1 / 3 right twill pattern.

[0030] In some embodiments, the sulfur black has a particle size of 8-12 nm; and the carboxymethylated reduced indigo has a degree of substitution of 0.6-0.9.

[0031] In some embodiments, the reactive color-fixing microcapsules begin to rupture above 65°C, and the release rate exceeds 85% at 70-80°C.

[0032] In some embodiments, the compound dyeing agent further includes a penetrant and caustic soda. The penetrant is selected from fatty alcohol polyoxyethylene ether or sodium secondary alkyl sulfonate, and the amount added is 0.5-1.5% of the total mass of the compound dyeing agent. The caustic soda is used to adjust the pH to 11.0-11.5.

[0033] In some embodiments, the compound dyeing agent containing sulfur black as the main dye is prepared as follows: sulfur black as the main dye, the reactive color-fixing microcapsules and nano-coordination aids are added and dispersed in water to obtain the compound dyeing agent containing sulfur black as the main dye.

[0034] In some embodiments, the compound dyeing agent containing carboxymethylated reduced indigo as the main dye is prepared as follows: using carboxymethylated reduced indigo with a degree of substitution of 0.6-0.9 as the main dye, the reactive color-fixing microcapsules and nano-coordination auxiliaries are added, and the pH is adjusted to 11.0-11.5 to obtain the compound dyeing agent containing carboxymethylated reduced indigo as the main dye.

[0035] In some embodiments, the preparation method of the nano-coordination aid includes: dispersing nano-silica particles in anhydrous ethanol, adding γ-aminopropyltriethoxysilane, refluxing at 60-70°C for 6-8 h, and obtaining aminated silica after centrifugation, washing, and drying; reacting polyethylene glycol with phosphorus oxychloride in an ice bath under nitrogen protection for 2.5-3 h to generate biphosphorylated polyethylene glycol; dissolving the biphosphorylated polyethylene glycol in anhydrous tetrahydrofuran, adding it dropwise to the aminated silica suspension, and stirring at room temperature for 12-14 h to achieve phosphate group grafting; subsequently dispersing it in deionized water, adjusting the pH to 5.5-6.5, adding 0.1-0.2 mol / L zinc nitrate solution, and stirring at 25°C for complexation for 6-8 h; and obtaining the nano-coordination aid after centrifugation, washing, and freeze-drying.

[0036] In some embodiments, the preparation method of the reactive color-fixing microcapsules includes: using an aqueous solution containing glycidyltrimethylammonium chloride and ethylenediamine as the inner aqueous phase; dissolving sorbitan monooleate and octadecyl alcohol together in liquid paraffin to form an oil phase containing a thermosensitive phase change material; slowly adding the inner aqueous phase to the oil phase and forming a water-in-oil microemulsion by high-speed shearing; adding a toluene solution of hexamethylene diisocyanate dropwise and prepolymerizing at 40-50°C to generate a prepolymer with -NCO end groups on the surface; subsequently introducing an outer aqueous phase containing ethylenediamine to form a W / O / W dual emulsion, and causing the ethylenediamine in the outer aqueous phase to undergo an interfacial condensation reaction with the prepolymer at 55-60°C to generate a polyurea wall material in situ; and obtaining reactive color-fixing microcapsules with an average particle size of 1-5 μm by post-treatment and drying.

[0037] The present invention also provides a method for preparing the double-sided denim fabric described in any one of the above claims, comprising the following steps: (1) Warping process: A double warp beam weaving system is adopted. The top beam and the bottom beam are configured according to the yarn count and the head share. The two beams are independently wound and formed under constant machine speed and single yarn tension. (2) Dyeing process: The ground warp yarns are dyed by rope continuous dyeing process, and the top warp yarns are dyed by sheet dyeing process. During the dyeing process, the temperature is gradually raised to 70-80℃ and kept warm for 5-8 minutes to break the reactive color-fixing microcapsules and release the core material, thereby completing the in-situ color fixation. The moisture regain of the dyed yarn is controlled within the range of 6-8%. (3) Warp separation and sizing process: The top and bottom warps after dyeing are separated and sizing is applied by double immersion and double pressure. The temperature of the sizing tank is controlled at 90-94℃, the viscosity is 5-6.5s, the temperature of the drying room is 105-125℃, the winding tension is 1700-2300N, and the flat yarn tension is 0.2-0.3kN. (4) Warp threading process: Using a 10-page heddle frame, the ground warp yarns are threaded into the 3rd, 4th, 5th and 6th heddles, and the top warp yarns are threaded into the 7th, 8th, 9th and 10th heddles, so as to achieve independent opening control of the top and bottom layers; in the top warp area, 4 yarns are threaded into each reed, and the dyed warp yarns and the original white warp yarns are arranged alternately in a 16 blue 4 white pattern to form a 3 / 1 left twill, 2 / 2 plain, 3 / 1 right twill or 1 / 3 right twill; 24 edge yarns are set on each side, 4 yarns are threaded into each reed, and a 2 / 2 variation warp plain weave is adopted; (5) Weaving process: The upper and lower warp yarns are introduced simultaneously on the rapier double warp beam loom to weave the greige fabric; the reed is 95 / 10cm with a width of 170.1cm, the weft density is set to 54 threads / inch, the loom speed is controlled at 500-600r / min; the heald frame height is set to 120mm, 120mm, 116mm, 115mm and 114mm respectively, the shedding time is 310°, the shedding stroke is 26°, the loom tension is 3000N, the workshop ambient temperature is maintained at 26-32℃ and the relative humidity is 70-75%; (6) Finishing process: The fabric is processed in sequence through a multi-tank pre-shrinking equipment containing enzyme desizing, water washing and softening finishing to obtain the double-sided denim fabric with different colors on the front and back.

[0038] The present invention will be described in detail below through embodiments. It should be understood that the following embodiments are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0039] Example 2 is the best embodiment.

[0040] The chemical additives used in the embodiments and comparative examples of this invention are all commercially available, and the specific information is as follows: Warp yarns: OEC12S plain yarn, C12 slub yarn; Weft yarns: TP / R / C65 / 20 / 1514S (70D); Silica nanoparticles: purchased from Suzhou Meibang Nanomaterials Co., Ltd.; Sulfur black: purchased from Jiangsu Jiluke Chemical Plant; γ-aminopropyltriethoxysilane: purchased from Aladdin Reagent Co., Ltd.; Glyceryl oxytrimethylammonium chloride: purchased from Shanghai Jizhi Biochemical Technology Co., Ltd.; Indigo: purchased from Shandong Pingju Biotechnology Co., Ltd.; Other auxiliaries and solvents: purchased from Aladdin Reagent Co., Ltd.

[0041] Preparation Example 1 The compound dyeing agent A described in this preparation example comprises sulfur black as the main dye, reactive color-fixing microcapsules A, and nano-coordination aid A, with a mass ratio of 25:2:1; the sulfur black has a particle size of 8-12 nm; the reactive color-fixing microcapsules A begin to rupture above 65°C, and the release rate exceeds 85% at 70-80°C.

[0042] The preparation method of the nano-coordination aid A includes: ultrasonically dispersing 50.0 g of nano-silica particles in 1000 mL of anhydrous ethanol, adding 9.0 g of γ-aminopropyltriethoxysilane, and refluxing at 60 °C for 8 h under nitrogen protection. After the reaction, centrifuging at 8000 rpm for 10 min, washing the precipitate three times with ethanol, and vacuum drying at 60 °C for 12 h to obtain white powdered aminated silica; dissolving 10.0 g of PEG-200 in 50 mL of THF, placing it in an ice bath, and slowly adding 3.2 g of phosphorus oxychloride dropwise under nitrogen protection, while continuously stirring for 2.5 h. After the reaction, removing the solvent and byproducts by vacuum distillation to obtain biphosphorylated polyethylene glycol. Redispersing the above aminated silica in 50 mL of anhydrous ethanol, dissolving the biphosphorylated polyethylene glycol in 50 mL of anhydrous tetrahydrofuran, and slowly adding it dropwise to the anhydrous ethanol suspension of aminated silica, and stirring at room temperature for 12 h. After the reaction was complete, the solid was collected by centrifugation, washed three times with ethanol, and dried at 60°C to achieve phosphate group grafting. It was then dispersed in 500 mL of deionized water, and the pH was adjusted to 6.5 with acetate-sodium acetate buffer solution. 500 mL of 0.1 mol / L zinc nitrate solution was added, and the mixture was stirred and complexed at 25°C for 6 h. After centrifugation at 8000 rpm for 10 min, the supernatant was discarded, and the precipitate was washed three times alternately with water and ethanol, and then freeze-dried to obtain the nano-coordination aid A.

[0043] The preparation method of the reactive color-fixing microcapsule A includes: dissolving 150.0 g of glycidyltrimethylammonium chloride and 10.0 g of ethylenediamine in 100 mL of deionized water to form an inner aqueous phase; dissolving 12.0 g of dehydrated sorbitan monooleate and 60.0 g of octadecyl alcohol in 800 mL of liquid paraffin; ultrasonically dispersing the mixture to form an oil phase containing a thermosensitive phase change material; and slowly adding the inner aqueous phase to the oil phase under high-speed homogeneous shearing conditions at 8000 rpm, continuously emulsifying for 10 min to form a stable water-in-oil microemulsion. Subsequently, 320 mL of toluene solution containing 80.0 g hexamethylene diisocyanate was added dropwise, and prepolymerization was carried out at 40 °C under nitrogen protection for 60 min. After prepolymerization, the system was slowly poured into 200 mL of deionized water containing 5.0 g ethylenediamine, and a W / O / W dual emulsion was formed under stirring at 1000 rpm. The temperature was raised to 58 °C and reacted for 60 min, so that ethylenediamine and -NCO groups on the surface of microspheres underwent interfacial condensation to form polyurea wall material. After washing and drying, reactive color-fixing microcapsules A with an average particle size of 1-5 μm were obtained.

[0044] The compound dyeing agent A containing sulfur black as the main dye is prepared as follows: 250g of sulfur black with a particle size of 8-12nm is taken as the main dye, 20g of reactive color-fixing microcapsules A and 10g of nano-coordination agent A are added, and then 42.0g of fatty alcohol polyoxyethylene ether AEO-9 is added as a penetrant. The mixture is dispersed in 8.0L of deionized water and sheared at 1500rpm for 30min using a high-speed stirrer to form a uniform and stable suspension. Then, 24g of caustic soda is added to adjust the pH of the system to 11.0 to obtain compound dyeing agent A.

[0045] Preparation Example 2 The compound dyeing agent B described in this preparation example comprises sulfur black as the main dye, reactive color-fixing microcapsules B, and nano-coordination aid B, with a mass ratio of 30:2:1; the sulfur black has a particle size of 8-12 nm; the reactive color-fixing microcapsules B begin to rupture above 65°C, and the release rate exceeds 85% at 70-80°C.

[0046] The preparation method of the nano-coordination aid B includes: ultrasonically dispersing 50.0 g of nano-silica particles in 1000 mL of anhydrous ethanol, adding 9.0 g of γ-aminopropyltriethoxysilane, and refluxing at 70 °C for 6 h under nitrogen protection. After the reaction, centrifuging at 8000 rpm for 10 min, washing the precipitate three times with ethanol, and vacuum drying at 60 °C for 12 h to obtain white powdered aminated silica; dissolving 10.0 g of PEG-200 in 50 mL of THF, placing it in an ice bath, and slowly adding 3.2 g of phosphorus oxychloride dropwise under nitrogen protection, while continuously stirring for 3 h. After the reaction, removing the solvent and byproducts by vacuum distillation to obtain biphosphorylated polyethylene glycol. Redispersing the above aminated silica in 50 mL of anhydrous ethanol, dissolving the biphosphorylated polyethylene glycol in 50 mL of anhydrous tetrahydrofuran, and slowly adding it dropwise to the anhydrous ethanol suspension of aminated silica, and stirring at room temperature for 14 h. After the reaction, the solid was collected by centrifugation, washed three times with ethanol, and dried at 60°C to achieve phosphate group grafting. It was then dispersed in 500 mL of deionized water, and the pH was adjusted to 5.5 with acetate-sodium acetate buffer solution. 500 mL of 0.2 mol / L zinc nitrate solution was added, and the mixture was stirred and complexed at 25°C for 8 h. After centrifugation at 8000 rpm for 10 min, the supernatant was discarded, and the precipitate was washed three times alternately with water and ethanol, and then freeze-dried to obtain the nano-coordination aid B.

[0047] The preparation method of the reactive color-fixing microcapsule B includes: dissolving 150.0 g of glycidyltrimethylammonium chloride and 10.0 g of ethylenediamine in 100 mL of deionized water to form an inner aqueous phase; dissolving 12.0 g of dehydrated sorbitan monooleate and 80.0 g of octadecyl alcohol in 800 mL of liquid paraffin; ultrasonically dispersing the mixture to form an oil phase containing a thermosensitive phase change material; and slowly adding the inner aqueous phase to the oil phase under high-speed homogeneous shearing conditions at 8000 rpm, continuously emulsifying for 10 min to form a stable water-in-oil microemulsion. Subsequently, 320 mL of toluene solution containing 80.0 g hexamethylene diisocyanate was added dropwise, and prepolymerization was carried out at 50 °C under nitrogen protection for 30 min. After prepolymerization, the system was slowly poured into 200 mL of deionized water containing 5.0 g ethylenediamine, and a W / O / W dual emulsion was formed under stirring at 1000 rpm. The temperature was raised to 58 °C and reacted for 60 min, so that ethylenediamine and -NCO groups on the surface of microspheres underwent interfacial condensation to form polyurea wall material. After washing and drying, reactive color-fixing microcapsules B with an average particle size of 1-5 μm were obtained.

[0048] The compound dyeing agent B containing sulfur black as the main dye is prepared as follows: 300g of sulfur black with a particle size of 8-12nm is taken as the main dye, 20g of reactive color-fixing microcapsules B and 10g of nano-coordination agent B are added, and then 130.5g of sodium secondary alkyl sulfonate SAS-60 is added as a penetrant. The mixture is dispersed in 8.0L of deionized water and sheared at 1500rpm for 30min using a high-speed stirrer to form a uniform and stable suspension. Then, 240g of caustic soda is added to adjust the pH of the system to 11.5 to obtain compound dyeing agent B.

[0049] Preparation Example 3 The compound dyeing agent C described in this preparation example comprises carboxymethylated reduced indigo as the main dye, reactive color-fixing microcapsules C, and nano-coordination aid C, with a mass ratio of 25:2:1; the degree of substitution of the carboxymethylated reduced indigo is 0.6; the reactive color-fixing microcapsules C begin to rupture above 65°C, and the release rate exceeds 85% at 70-80°C.

[0050] The preparation method of the carboxymethylated reduced indigo main dye includes: dispersing 250.0g of natural reduced indigo in 3.0L of water-ethanol mixed solvent (H2O:EtOH=1:1), adding 30.0g of sodium hydroxide to adjust the pH to above 12.0 to form an alkaline dissolution system; heating to 60-65℃ under nitrogen protection, adding 216.4g of sodium chloroacetate in batches (the molar ratio of indigo to sodium chloroacetate is 1:1.8), and then adding 30% sodium hydroxide solution dropwise while stirring to maintain the pH of the reaction system at 11.5-12.5. The reaction is continuously stirred for 5h. After the reaction is completed, the pH is adjusted to 7.0 with dilute hydrochloric acid to terminate the reaction. After centrifugation at 8000rpm for 10min, the precipitate is washed three times with deionized water and ethanol, and dried under vacuum at 60℃ for 12h to obtain carboxymethylated reduced indigo with a degree of substitution of 0.6.

[0051] The preparation method of the nano-coordination aid C includes: ultrasonically dispersing 50.0 g of nano-silica particles in 1000 mL of anhydrous ethanol, adding 9.0 g of γ-aminopropyltriethoxysilane, and refluxing at 60 °C for 8 h under nitrogen protection. After the reaction, centrifuging at 8000 rpm for 10 min, washing the precipitate three times with ethanol, and vacuum drying at 60 °C for 12 h to obtain white powdered aminated silica; dissolving 10.0 g of PEG-200 in 50 mL of THF, placing it in an ice bath, and slowly adding 3.2 g of phosphorus oxychloride dropwise under nitrogen protection, while continuously stirring for 2.5 h. After the reaction, removing the solvent and byproducts by vacuum distillation to obtain biphosphorylated polyethylene glycol. Redispersing the above aminated silica in 50 mL of anhydrous ethanol, dissolving the biphosphorylated polyethylene glycol in 50 mL of anhydrous tetrahydrofuran, and slowly adding it dropwise to the anhydrous ethanol suspension of aminated silica, and stirring at room temperature for 12 h. After the reaction was complete, the solid was collected by centrifugation, washed three times with ethanol, and dried at 60°C to achieve phosphate group grafting. It was then dispersed in 500 mL of deionized water, and the pH was adjusted to 6.5 with an acetate-sodium acetate buffer solution. Then, 500 mL of 0.1 mol / L zinc nitrate solution was added, and the mixture was stirred and complexed at 25°C for 6 h. After centrifugation at 8000 rpm for 10 min, the supernatant was discarded, and the precipitate was washed three times alternately with water and ethanol, and then freeze-dried to obtain the nano-coordination aid C.

[0052] The preparation method of the reactive color-fixing microcapsule C includes: dissolving 150.0 g of glycidyltrimethylammonium chloride and 10.0 g of ethylenediamine in 100 mL of deionized water to form an inner aqueous phase; dissolving 12.0 g of dehydrated sorbitan monooleate and 52.0 g of octadecyl alcohol in 800 mL of liquid paraffin; ultrasonically dispersing the mixture to form an oil phase containing a thermosensitive phase change material; and slowly adding the inner aqueous phase to the oil phase under high-speed homogeneous shearing conditions at 8000 rpm, continuously emulsifying for 10 min to form a stable water-in-oil microemulsion. Subsequently, 320 mL of a toluene solution containing 80.0 g of hexamethylene diisocyanate was added dropwise, and prepolymerization was carried out at 40 °C under nitrogen protection for 60 min. After prepolymerization, the system was slowly poured into 200 mL of deionized water containing 5.0 g of ethylenediamine, and a W / O / W dual emulsion was formed under stirring at 1000 rpm. The temperature was raised to 60 °C and reacted for 60 min, so that ethylenediamine and -NCO groups on the surface of the microspheres underwent interfacial condensation to form a polyurea wall material. After washing and drying, reactive color-fixing microcapsules C with an average particle size of 1-5 μm were obtained.

[0053] The compound dyeing agent C containing carboxymethylated reduced indigo as the main dye was prepared as follows: 250g of carboxymethylated reduced indigo was taken as the main dye, 20g of reactive color-fixing microcapsules C and 10g of nano-coordination aid C were added, and 42.0g of fatty alcohol polyoxyethylene ether AEO-9 was added as a penetrant. The mixture was dispersed in 8.0L of deionized water and sheared at 1500rpm for 30min using a high-speed stirrer to form a uniform and stable suspension. Then, 80g of caustic soda was added to adjust the pH of the system to 11.2 to obtain compound dyeing agent C.

[0054] Preparation Example 4 The compound dyeing agent D described in this preparation example contains carboxymethylated reduced indigo as the main dye, reactive color-fixing microcapsules D, and nano-coordination aid D, with a mass ratio of 30:2:1; the degree of substitution of the carboxymethylated reduced indigo is 0.9; the reactive color-fixing microcapsules D begin to rupture above 65°C, and the release rate exceeds 85% at 70-80°C.

[0055] The preparation method of the carboxymethylated reduced indigo main dye includes: dispersing 250.0g of natural reduced indigo in 3.0L of water-ethanol mixed solvent (H2O:EtOH=1:1), adding 30.0g of sodium hydroxide to adjust the pH to above 12.0 to form an alkaline dissolution system; heating to 60-65℃ under nitrogen protection, adding 360.6g of sodium chloroacetate in batches (the molar ratio of indigo to sodium chloroacetate is 1:3), and then adding 30% sodium hydroxide solution dropwise while stirring to maintain the pH of the reaction system at 11.5-12.5, and continuing to stir the reaction for 5h. After the reaction is completed, adjusting the pH to 7.0 with dilute hydrochloric acid to terminate the reaction, centrifuging at 8000rpm for 10min, washing the precipitate three times with deionized water and ethanol, and drying under vacuum at 60℃ for 12h to obtain carboxymethylated reduced indigo with a degree of substitution of 0.9.

[0056] The preparation method of the nano-coordination aid D includes: ultrasonically dispersing 50.0 g of nano-silica particles in 1000 mL of anhydrous ethanol, adding 9.0 g of γ-aminopropyltriethoxysilane, and refluxing at 70 °C for 6 h under nitrogen protection. After the reaction, centrifuging at 8000 rpm for 10 min, washing the precipitate three times with ethanol, and vacuum drying at 60 °C for 12 h to obtain white powdered aminated silica; dissolving 10.0 g of PEG-200 in 50 mL of THF, placing it in an ice bath, and slowly adding 3.2 g of phosphorus oxychloride dropwise under nitrogen protection, while continuously stirring for 3 h. After the reaction, removing the solvent and byproducts by vacuum distillation to obtain biphosphorylated polyethylene glycol. Redispersing the above aminated silica in 50 mL of anhydrous ethanol, dissolving the biphosphorylated polyethylene glycol in 50 mL of anhydrous tetrahydrofuran, and slowly adding it dropwise to the anhydrous ethanol suspension of aminated silica, and stirring at room temperature for 14 h. After the reaction, the solid was collected by centrifugation, washed three times with ethanol, and dried at 60°C to achieve phosphate group grafting. It was then dispersed in 500 mL of deionized water, and the pH was adjusted to 5.5 with acetate-sodium acetate buffer solution. 500 mL of 0.2 mol / L zinc nitrate solution was added, and the mixture was stirred and complexed at 25°C for 8 h. After centrifugation at 8000 rpm for 10 min, the supernatant was discarded, and the precipitate was washed three times alternately with water and ethanol, and then freeze-dried to obtain the nano-coordination aid D.

[0057] The preparation method of the reactive color-fixing microcapsules D includes: dissolving 150.0 g of glycidyltrimethylammonium chloride and 10.0 g of ethylenediamine in 100 mL of deionized water to form an inner aqueous phase; dissolving 12.0 g of dehydrated sorbitan monooleate and 90.0 g of octadecyl alcohol in 800 mL of liquid paraffin; ultrasonically dispersing the mixture to form an oil phase containing a thermosensitive phase change material; and slowly adding the inner aqueous phase to the oil phase under high-speed homogeneous shearing conditions at 8000 rpm, continuously emulsifying for 10 min to form a stable water-in-oil microemulsion. Subsequently, 320 mL of toluene solution containing 80.0 g hexamethylene diisocyanate was added dropwise, and prepolymerization was carried out at 40 °C under nitrogen protection for 60 min. After prepolymerization, the system was slowly poured into 200 mL of deionized water containing 5.0 g ethylenediamine, and a W / O / W double emulsion was formed under stirring at 1000 rpm. The temperature was raised to 55 °C and reacted for 60 min, so that ethylenediamine and -NCO groups on the surface of microspheres underwent interfacial condensation to form polyurea wall material. After washing and drying, reactive color-fixing microcapsules D with an average particle size of 1-5 μm were obtained.

[0058] The compound dyeing agent D containing carboxymethylated reduced indigo as the main dye was prepared as follows: 300g of carboxymethylated reduced indigo was taken as the main dye, 20g of reactive color-fixing microcapsules D and 10g of nano-coordination aid D were added, and 130.5g of sodium secondary alkyl sulfonate SAS-60 was added as a penetrant. The mixture was dispersed in 8.0L of deionized water and sheared at 1500rpm for 30min using a high-speed stirrer to form a uniform and stable suspension. Then, 240g of caustic soda was added to adjust the pH of the system to 11.5 to obtain compound dyeing agent D.

[0059] Example 1 A double-sided denim fabric with contrasting front and back colors includes a back weave composed of top-axis warp yarns and a front weave composed of bottom-axis warp yarns. The front weave is a full-coverage twill structure that completely covers the back pattern. The back weave consists of alternating blue and white warp yarns forming blue and white stripes. The double-sided denim fabric also includes side weaves on both sides, each side consisting of 24 side weave yarns, using a 2 / 2 variation warp plain weave. The bottom-axis warp yarns are dyed with a compound dyeing agent A containing sulfur black as the primary dye (compound dyeing agent A was prepared in Preparation Example 1), and the blue warp yarns in the top-axis warp yarns are dyed with a compound dyeing agent C containing carboxymethylated reduced indigo as the primary dye (compound dyeing agent C was prepared in Preparation Example 3). The front weave uses a 3 / 1 right-hand twill structure, and the back weave uses a 3 / 1 left-hand twill structure.

[0060] The method for preparing the double-sided denim fabric includes the following steps: (1) Warping process: A double warp beam weaving system is adopted. The top beam and the bottom beam are configured according to the yarn count and the number of yarns. The two beams are independently wound and formed under constant machine speed and single yarn tension. The machine speed is controlled at 260m / min; the single yarn tension is controlled at 35cN. Among them, the bottom beam: 310 OEC12S plain yarns × 6 beams + 310 C12 slub yarns × 6 beams; the top beam: 298 OEC12S yarns × 10 beams of warp yarns (used for dyeing indigo) + 372 OEC12S yarns × 2 beams (retaining the original white). (2) Dyeing process: The 298 warp yarns / axis × 10 axes in the top axis are dyed by rope continuous dyeing process; the warp yarns in the bottom axis are dyed by sheet dyeing process. During the dyeing process, the temperature is gradually raised to 70℃ and kept at that temperature for 8 minutes to break the reactive color-fixing microcapsules and release the core material, thereby completing the in-situ color fixation. The moisture regain of the dyed yarn is controlled within the range of 6-8%. (3) Warp separation and sizing process: The top and bottom warps after dyeing are separated and the sizing material is applied by double immersion and double pressure. The temperature of the sizing tank is controlled at 90℃, the viscosity is 6.5s, the temperature of the drying room is 105℃, the winding tension is 1700N and the flat yarn tension is 0.2kN. (4) Warp threading process: Using a 10-page heddle frame, the ground warp yarns are threaded into heddles 3, 4, 5, and 6, and the top warp yarns are threaded into heddles 7, 8, 9, and 10, so as to achieve independent opening control of the top and bottom layers; in the top warp area, 4 yarns are threaded into each reed, and the indigo-dyed warp yarns and the original white warp yarns are alternately arranged in a 16-blue-4-white pattern to form a 3 / 1 left twill weave; 24 edge yarns are set on each side, 4 yarns are threaded into each reed, and a 2 / 2 variation warp-flat weave is used; (5) Weaving process: The upper and lower warp yarns are introduced simultaneously on the rapier double warp beam loom to weave the greige fabric; the reed is 95 / 10cm with a width of 170.1cm, the weft density is set to 54 threads / inch, the loom speed is controlled at 500-600r / min; the heald frame height is set to 120mm, 120mm, 116mm, 115mm and 114mm respectively, the shedding time is 310°, the shedding stroke is 26°, the loom tension is 3000N, the workshop ambient temperature is maintained at 26℃ and the relative humidity is 70%; (6) Finishing process: The fabric is processed in sequence through a multi-tank pre-shrinking equipment containing enzyme desizing, water washing and softening finishing to obtain the double-sided denim fabric with different colors on the front and back.

[0061] Example 2 This embodiment describes a double-sided denim fabric with contrasting front and back colors, comprising a back weave composed of top-axis warp yarns and a front weave composed of bottom-axis warp yarns. The front weave is a full-coverage twill structure that completely covers the back pattern. The back weave consists of alternating blue and white warp yarns forming blue and white stripes. The double-sided denim fabric also includes side weaves on both sides, each side consisting of 24 side weave yarns, using a 2 / 2 variation warp plain weave. The bottom-axis warp yarns are dyed with a compound dyeing agent B containing sulfur black as the primary dye (compound dyeing agent B was prepared in Preparation Example 2), and the top-axis warp yarns are dyed with a compound dyeing agent D containing carboxymethylated reduced indigo as the primary dye (compound dyeing agent D was prepared in Preparation Example 4). The front weave uses a 3 / 1 right twill structure, and the back weave uses a 3 / 1 left twill structure.

[0062] The method for preparing the double-sided denim fabric includes the following steps: (1) Warping process: A double warp beam weaving system is adopted. The top beam and the bottom beam are configured according to the yarn count and the number of yarns. The two beams are independently wound and formed under constant machine speed and single yarn tension. The machine speed is controlled at 260m / min; the single yarn tension is controlled at 35cN. Among them, the bottom beam: 310 OEC12S plain yarns × 6 beams + 310 C12 slub yarns × 6 beams; the top beam: 298 OEC12S yarns × 10 beams of warp yarns (used for dyeing indigo) + 372 OEC12S yarns × 2 beams (retaining the original white). (2) Dyeing process: The 298 warp yarns / axis × 10 axes in the top axis are dyed by rope continuous dyeing process; the warp yarns in the bottom axis are dyed by sheet dyeing process. During the dyeing process, the temperature is gradually raised to 80℃ and kept at that temperature for 5 minutes to cause the reactive color-fixing microcapsules to break and release the core material, thereby completing the in-situ color fixation. The moisture regain of the yarn after dyeing is controlled within the range of 6-8%. (3) Warp separation and sizing process: The top and bottom warps after dyeing are separated and the sizing is applied by double immersion and double pressure. The temperature of the sizing tank is controlled at 94℃, the viscosity is 5s, the temperature of the drying room is 125℃, the winding tension is 2300N and the flat yarn tension is 0.3kN. (4) Warp threading process: Using a 10-page heddle frame, the ground warp yarns are threaded into the 3rd, 4th, 5th and 6th heddles, and the top warp yarns are threaded into the 7th, 8th, 9th and 10th heddles, so as to achieve independent opening control of the top and bottom layers; in the top warp area, 4 yarns are threaded into each reed, and the indigo-dyed warp yarns and the original white warp yarns are alternately arranged in a 16-blue-4-white pattern to form a 3 / 1 left twill weave; 24 edge yarns are set on each side, 4 yarns are threaded into each reed, and a 2 / 2 variation warp-over plain weave is adopted; (5) Weaving process: The upper and lower warp yarns are introduced simultaneously on the rapier double warp beam loom to weave the greige fabric; the reed is 95 / 10cm with a width of 170.1cm, the weft density is set to 54 threads / inch, the loom speed is controlled at 500-600r / min; the heald frame height is set to 120mm, 120mm, 116mm, 115mm and 114mm respectively, the shedding time is 310°, the shedding stroke is 26°, the loom tension is 3000N, the workshop ambient temperature is maintained at 26℃ and the relative humidity is 70%; (6) Finishing process: The fabric is processed in sequence through a multi-tank pre-shrinking equipment containing enzyme desizing, water washing and softening finishing to obtain the double-sided denim fabric with different colors on the front and back.

[0063] Example 3 This embodiment describes a double-sided denim fabric with contrasting front and back colors, comprising a back weave composed of top-axis warp yarns and a front weave composed of bottom-axis warp yarns. The front weave is a full-coverage twill structure that completely covers the back pattern. The back weave consists of alternating blue and white warp yarns forming blue and white stripes. The double-sided denim fabric also includes side weaves on both sides, each side consisting of 24 side weave yarns, using a 2 / 2 variation warp plain weave. The bottom-axis warp yarns are dyed with a compound dyeing agent A containing sulfur black as the primary dye (compound dyeing agent A was prepared in Preparation Example 1), and the top-axis warp yarns are dyed with a compound dyeing agent D containing carboxymethylated reduced indigo as the primary dye (compound dyeing agent D was prepared in Preparation Example 4). The front weave uses a 3 / 1 right-hand twill structure, and the back weave uses a 3 / 1 left-hand twill structure.

[0064] The method for preparing the double-sided denim fabric includes the following steps: (1) Warping process: A double warp beam weaving system is adopted. The top beam and the bottom beam are configured according to the yarn count and the number of yarns. The two beams are independently wound and formed under constant machine speed and single yarn tension. The machine speed is controlled at 260m / min; the single yarn tension is controlled at 35cN. Among them, the bottom beam: 310 OEC12S plain yarns × 6 beams + 310 C12 slub yarns × 6 beams; the top beam: 298 OEC12S yarns × 10 beams of warp yarns (used for dyeing indigo) + 372 OEC12S yarns × 2 beams (retaining the original white). (2) Dyeing process: The 298 warp yarns / axis × 10 axes in the top axis are dyed by rope continuous dyeing process; the warp yarns in the bottom axis are dyed by sheet dyeing process. During the dyeing process, the temperature is gradually raised to 70℃ and kept at that temperature for 8 minutes to break the reactive color-fixing microcapsules and release the core material, thereby completing the in-situ color fixation. The moisture regain of the dyed yarn is controlled within the range of 6-8%. (3) Warp separation and sizing process: The top and bottom warps after dyeing are separated and the sizing material is applied by double immersion and double pressure. The temperature of the sizing tank is controlled at 90℃, the viscosity is 6.5s, the temperature of the drying room is 105℃, the winding tension is 1700N and the flat yarn tension is 0.2kN. (4) Warp threading process: Using a 10-page heddle frame, the ground warp yarns are threaded into the 3rd, 4th, 5th and 6th heddles, and the top warp yarns are threaded into the 7th, 8th, 9th and 10th heddles, so as to achieve independent opening control of the top and bottom layers; in the top warp area, 4 yarns are threaded into each reed, and the indigo-dyed warp yarns and the original white warp yarns are alternately arranged in a 16-blue-4-white pattern to form a 3 / 1 left twill weave; 24 edge yarns are set on each side, 4 yarns are threaded into each reed, and a 2 / 2 variation warp-over plain weave is adopted; (5) Weaving process: The upper and lower warp yarns are introduced simultaneously on the rapier double warp beam loom to weave the greige fabric; the reed is 95 / 10cm with a width of 170.1cm, the weft density is set to 54 threads / inch, the loom speed is controlled at 500-600r / min; the heald frame height is set to 120mm, 120mm, 116mm, 115mm and 114mm respectively, the shedding time is 310°, the shedding stroke is 26°, the loom tension is 3000N, the workshop ambient temperature is maintained at 26℃ and the relative humidity is 70%; (6) Finishing process: The fabric is processed in sequence through a multi-tank pre-shrinking equipment containing enzyme desizing, water washing and softening finishing to obtain the double-sided denim fabric with different colors on the front and back.

[0065] Comparative Example 1 The double-sided denim fabric with different colors on the front and back described in this comparative example is exactly the same as that in Example 2, except that the compound dyeing agent contains a main dye, reactive color-fixing microcapsules and nano-coordination auxiliaries, with a mass ratio of 20:2:1.

[0066] Comparative Example 2 The double-sided denim fabric with different colors on the front and back described in this comparative example is exactly the same as that in Example 2, except that the compound dyeing agent contains a main dye, reactive color-fixing microcapsules and nano-coordination auxiliaries, with a mass ratio of 35:2:1.

[0067] Comparative Example 3 The double-sided denim fabric with contrasting front and back colors described in this comparative example is exactly the same as that in Example 2, except that the degree of substitution of the carboxymethylated reduced indigo is 0.4.

[0068] Comparative Example 4 The double-sided denim fabric with contrasting front and back colors described in this comparative example is exactly the same as that in Example 2, except that the nano-coordination agent is not loaded with Zn. 2+ This refers to nano-silica particles with phosphate groups modified on their surface.

[0069] Performance testing The double-sided denim fabrics with different colors on the front and back obtained in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests according to the following methods, and the specific results are shown in Table 1.

[0070] (1) Staining rate: Using a UV-Vis spectrophotometer, collect the original solution V0 (mL) before staining and the residual solution V1 (mL) after staining, dilute them to the same multiple (e.g., 100 times), and measure the absorbance A0 and A1 at the maximum absorption wavelength. Calculate the staining rate: Staining rate (%) = (1−A1×V1 / A0×V0)×100%.

[0071] (2) Dry rubbing fastness: The rubbing fastness tester is used. The sample is fixed on the platform with the front facing up. A clean dry rubbing cloth (white cotton cloth, 5×5cm) is used to rub back and forth 10 times with a stroke of 10cm and a load of 9N. Rating method: The staining grade on the rubbing cloth is evaluated using the staining gray card (grades 1-5). Grade 5: no staining; Grades 4-5: slight staining; Grades below 3 are unqualified.

[0072] (3) Washing fastness: Tested using a wash fastness meter. Test conditions: Washing solution: 0.15% soap + 0.04% Na2CO3, L:R=50:1, temperature: 49±1℃, time: 45min, steel balls: 10 stainless steel balls; Post-treatment: Rinse with clean water and air dry. Rating method: Compare the color change of the sample before and after washing using a gray scale. Grade 4.5-4 is excellent.

[0073] (4) Fracture strength: Tested according to ASTM D5034.

[0074] (5) Tear strength: Tested according to ASTM D1424.

[0075] (6) Elastic recovery rate: Tested according to ASTM D3107.

[0076] (7) Elastic growth rate: Tested according to ASTM D3107.

[0077] Table 1 Performance data of Examples 1-3 and Comparative Examples 1-4 .

[0078] As shown in Table 1, Examples 1-3 all employed the compound dyeing agent and double warp beam weaving process of the present invention, exhibiting excellent overall performance. Among them, Example 2 showed the best overall performance, with the best dry rubbing fastness (grade 4.5) and washing fastness (grade 4.5), while also having the highest breaking strength (radial 1031N), tearing strength (radial 64.5N), and elastic recovery rate (92.7%). This was mainly due to the use of compound dyeing agent B with a high dye ratio (30:2:1) on the ground warp beam and compound dyeing agent D with a high degree of substitution (0.9) on the top warp beam, achieving efficient in-situ color fixation at 80°C. This combination ensured efficient dye uptake and firm fixation, while the synergistic effect of reactive microcapsules and nano-coordination auxiliaries effectively protected the yarn during the color fixation process, thereby significantly improving the physical and mechanical properties and durability of the fabric. Examples 1-3 also show that the denim fabric of the present invention can still achieve a soap wash color fastness of 4-4.5 after 10 soap washes, which solves the problem of poor fastness of the front and back sides of the double-sided denim fabric of the present invention, and the easy fading and staining of the blue and white sides.

[0079] Figure 1 This is a display image of the denim fabric from Example 2 before washing. Figure 1 As can be seen from Embodiment 2 of this application, a double-sided denim fabric with different colors on the front and back is black, and the back has blue and white stripes.

[0080] Figure 2 This is a demonstration image of denim fabric from Example 2, which shows the fabric after 10 soap washes. Figure 2 It can be seen that the denim fabric in Example 2 showed no significant change in surface color after 10 soap washes. Figure 2 The blue and white stripes are bright and contrasting, and there is no problem with fading or staining. When denim fabric is used for cuffs and pant legs, the blue and white stripes are well-preserved when rolled up, and the color remains bright even after 10 washes without fading or staining.

[0081] A comparison of Example 2 and Comparative Examples 1 and 2 reveals that in Comparative Example 1, the proportion of the main dye was too low (20:2:1), resulting in a reduction in the total amount of dye and auxiliary agents. This reduced the absolute amount of dye fixed on the fiber, leading to a thinner dye layer. A thinner dye layer, under swelling and chemical action, is more easily extracted or peeled from the fiber interior, resulting in decreased color fastness to washing. In contrast, in Comparative Example 2, the proportion of the main dye was too high (35:2:1). Due to insufficient microcapsule content and limited cationic crosslinking sites, dye molecules easily aggregated and precipitated, causing uneven distribution. This not only affected color uniformity but also weakened the fiber-dye interface bonding, resulting in a significant decrease in dry rubbing and washing fastness. The breaking strength and tearing strength were also significantly lower than in Example 2.

[0082] A comparison of Example 2 and Comparative Example 3 reveals that the indigo in Comparative Example 3 has a low degree of substitution (0.4), resulting in insufficient carboxymethyl groups on the molecular chain. This leads to poor water solubility, slow diffusion rate, and difficulty in effectively penetrating into the fiber interior, resulting in ineffective dye uptake and a low dyeing rate. Simultaneously, due to insufficient anionic charge density, it cannot form a stable multi-layer cross-linked network with the cationic groups released from the microcapsules and Zn²⁺, causing weak dye bonding. This manifests as a dry rubbing fastness of only grade 3 and a soaping color change fastness of grade 3, with severe color floating. Furthermore, the low degree of substitution also affects the uniform distribution of the dye on the fiber surface and the interfacial bonding force, leading to a decrease in inter-fiber adhesion and a significant deterioration in mechanical properties. Simultaneously, the lack of structural stability also reduces the elastic recovery rate to 86.0%, while the elastic growth rate is as high as 3.2%, indicating that the material is prone to permanent deformation after repeated deformation.

[0083] A comparison between Example 2 and Comparative Example 4 shows that the nano-coordination aid described in Comparative Example 4 was not loaded with Zn. 2+ The colorfastness was significantly reduced, the breaking and tearing strength was noticeably weakened, and the elastic recovery rate was below 87%, with an elastic increase of only 3.3%, indicating weak inter-fiber bonding and a loose structure. This comparison fully demonstrates that the technical solution of this invention can effectively ensure the high strength, durability, and performance of the fabric while achieving the function of different colors on the front and back.

[0084] Therefore, this invention creatively designs a double-sided denim fabric with opposite colors on the front and back. By employing a dual warp beam system to construct the front and back fabrics separately, it achieves independent design of the colors, textures, and functions of the front and back sides. This invention applies a compound dyeing agent containing sulfur black and carboxymethylated reduced indigo to the top and bottom warp yarns, respectively. The dyeing agent comprises a main dye, reactive color-fixing microcapsules, and a nano-coordination auxiliary agent, with a mass ratio of (25-30):2:1, forming a synergistic system. The nano-coordination auxiliary agent binds to cotton fibers via hydrogen bonds through phosphate groups and enhances dye adsorption by coordinating Zn²⁺ with the dye functional groups. The reactive color-fixing microcapsules rupture upon heating during the dyeing process, releasing glycidyltrimethylammonium chloride, which undergoes a quaternization reaction with the fiber hydroxyl groups, achieving in-situ chemical color fixation. This significantly improves dye utilization and color fastness, resulting in rich, uniform color and solving the problems of poor dye fastness, easy fading, and low strength in traditional double-sided denim fabrics.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A double-sided denim fabric with opposite colors on the front and back, characterized in that, The fabric comprises a back weave consisting of top-axis warp yarns and a front weave consisting of bottom-axis warp yarns. The front weave is a full-coverage twill structure that completely covers the back pattern. The back weave consists of alternating blue and white warp yarns forming blue and white stripes. The double-sided denim fabric also includes side weaves on both sides, each consisting of 24 side weave yarns, using a 2 / 2 variation warp plain weave. The bottom-axis warp yarns are dyed with a compound dyeing agent containing sulfur black as the main dye, and the blue warp yarns in the top-axis warp yarns are dyed with a compound dyeing agent containing carboxymethylated reduced indigo as the main dye. The compound dyeing agent comprises the main dye, reactive color-fixing microcapsules, and nano-coordination auxiliaries in a mass ratio of (25-30):2:

1. The reactive color-fixing microcapsules have glycidyltrimethylammonium chloride as the core material and polyurea as the wall material, with an average particle size of 1-5 μm. The nano-coordination auxiliaries are nano-silica particles with surface-modified phosphate groups and loaded with Zn²⁺.

2. The double-sided denim fabric with contrasting colors on the front and back as described in claim 1, characterized in that, The front side has a 3 / 1 right twill weave; the back side has a 3 / 1 left twill, 2 / 2 double flat, 3 / 1 right twill, or 1 / 3 right twill weave.

3. The double-sided denim fabric with contrasting colors on the front and back as described in claim 1, characterized in that, The sulfur black has a particle size of 8-12 nm; the carboxymethylated reduced indigo has a degree of substitution of 0.6-0.

9.

4. The double-sided denim fabric with contrasting colors on the front and back as described in claim 1, characterized in that, The reactive color-fixing microcapsules begin to rupture above 65°C, and the release rate exceeds 85% at 70-80°C.

5. The double-sided denim fabric with contrasting colors on the front and back as described in claim 1, characterized in that, The compound dyeing agent containing sulfur black as the main dye is prepared as follows: sulfur black as the main dye, the reactive color-fixing microcapsules and nano-coordination aids are added and dispersed in water to obtain the compound dyeing agent containing sulfur black as the main dye.

6. The double-sided denim fabric with contrasting colors on the front and back as described in claim 1, characterized in that, The compound dyeing agent containing carboxymethylated reduced indigo as the main dye is prepared as follows: using carboxymethylated reduced indigo with a degree of substitution of 0.6-0.9 as the main dye, the reactive color-fixing microcapsules and nano-coordination auxiliaries are added, and the pH is adjusted to 11.0-11.5 to obtain the compound dyeing agent containing carboxymethylated reduced indigo as the main dye.

7. The double-sided denim fabric with contrasting colors on the front and back as described in claim 1, characterized in that, The compound dyeing agent also includes a penetrant and caustic soda. The penetrant is selected from fatty alcohol polyoxyethylene ether or sodium secondary alkyl sulfonate, and the amount added is 0.5-1.5% of the total mass of the compound dyeing agent. The caustic soda is used to adjust the pH to 11.0-11.

5.

8. The double-sided denim fabric with contrasting colors on the front and back as described in claim 1, characterized in that, The preparation method of the nano-coordination aid includes: dispersing nano-silica particles in anhydrous ethanol, adding γ-aminopropyltriethoxysilane, and refluxing at 60-70℃ for 6-8 h, followed by centrifugation, washing, and drying to obtain aminated silica; reacting polyethylene glycol with phosphorus oxychloride in an ice bath under nitrogen protection for 2.5-3 h to generate biphosphorylated polyethylene glycol; dissolving the biphosphorylated polyethylene glycol in anhydrous tetrahydrofuran, adding it dropwise to the aminated silica suspension, and stirring at room temperature for 12-14 h to achieve phosphate group grafting; subsequently dispersing it in deionized water, adjusting the pH to 5.5-6.5, adding 0.1-0.2 mol / L zinc nitrate solution, and stirring at 25℃ for complexation for 6-8 h; and obtaining the nano-coordination aid after centrifugation, washing, and freeze-drying.

9. The double-sided denim fabric with contrasting front and back colors as described in claim 1, characterized in that, The preparation method of the reactive color-fixing microcapsules includes: using an aqueous solution containing glycidyltrimethylammonium chloride and ethylenediamine as the inner aqueous phase; dissolving sorbitan monooleate and octadecyl alcohol together in liquid paraffin to form an oil phase containing a thermosensitive phase change material; slowly adding the inner aqueous phase to the oil phase and forming a water-in-oil microemulsion by high-speed shearing; adding a toluene solution of hexamethylene diisocyanate dropwise and prepolymerizing at 40-50°C to generate a prepolymer with -NCO end groups on the surface; subsequently introducing an outer aqueous phase containing ethylenediamine to form a W / O / W dual emulsion, and causing the ethylenediamine in the outer aqueous phase to undergo an interfacial condensation reaction with the prepolymer at 55-60°C to generate a polyurea wall material in situ; and obtaining reactive color-fixing microcapsules with an average particle size of 1-5 μm after post-treatment and drying.

10. The method for preparing double-sided denim fabric according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Warping process: A double warp beam weaving system is adopted. The top beam and the bottom beam are configured according to the yarn count and the head share. The two beams are independently wound and formed under constant machine speed and single yarn tension. (2) Dyeing process: The ground axis warp yarn is dyed by rope continuous dyeing process, and the top axis warp yarn is dyed by sheet dyeing process. During the dyeing process, the temperature is gradually raised to 70-80℃ and kept warm for 5-8 minutes to break the reactive color-fixing microcapsules and release the core material, thereby completing the in-situ color fixation. The moisture regain of the dyed yarn is controlled within the range of 6-8%. (3) Warp separation and sizing process: The top and bottom warps after dyeing are separated and sizing is applied by double immersion and double pressure. The temperature of the sizing tank is controlled at 90-94℃, the viscosity is 5-6.5s, the temperature of the drying room is 105-125℃, the winding tension is 1700-2300N, and the flat yarn tension is 0.2-0.3kN. (4) Warp threading process: Using a 10-page heddle frame, the ground warp yarns are threaded into the 3rd, 4th, 5th and 6th heddles, and the top warp yarns are threaded into the 7th, 8th, 9th and 10th heddles, so as to achieve independent opening control of the top and bottom layers; in the top warp area, 4 yarns are threaded into each reed, and the dyed warp yarns and the original white warp yarns are arranged alternately in a 16 blue 4 white pattern to form a 3 / 1 left twill, 2 / 2 plain, 3 / 1 right twill or 1 / 3 right twill; 24 edge yarns are set on each side, 4 yarns are threaded into each reed, and a 2 / 2 variation warp plain weave is adopted; (5) Weaving process: The upper and lower warp yarns are introduced simultaneously on the rapier double warp beam loom to weave the greige fabric; the reed is 95 / 10cm with a width of 170.1cm, the weft density is set to 54 threads / inch, the loom speed is controlled at 500-600r / min; the heald frame height is set to 120mm, 120mm, 116mm, 115mm and 114mm respectively, the shedding time is 310°, the shedding stroke is 26°, the loom tension is 3000N, the workshop ambient temperature is maintained at 26-32℃ and the relative humidity is 70-75%; (6) Finishing process: The fabric is processed in sequence through a multi-tank pre-shrinking equipment containing enzyme desizing, water washing and softening finishing to obtain the double-sided denim fabric with different colors on the front and back.

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