Washable sunscreen jean fabric and preparation method thereof

Abstract

The invention discloses a washable sunscreen jean fabric and a preparation method thereof, and belongs to the technical field of textiles. The washable sun-proof jean fabric is provided with a 2 / 1 right twill weave, warp yarns of the fabric are tencel fibers, and weft yarns of the fabric are polyamide fibers; wherein a first ultraviolet light absorber is bonded on the polyamide fiber; a three-dimensional net-shaped protective film formed by curing a cross-linking agent is also attached to the surface of the fabric and among the fibers, and sustained-release microcapsules are embedded in the protective film; a capsule core of the sustained-release microcapsule comprises a hindered amine light stabilizer and a second ultraviolet light absorber. According to the jean fabric, a synergistic protection system of fiber bonding, three-dimensional network coating and sustained-release microcapsule supplementing is constructed, the extremely high initial ultraviolet protection performance is ensured, meanwhile, the lasting stability of the sun protection function after multiple times of washing is achieved, and meanwhile the inherent soft draping feeling of the fabric is kept.

Description

Technical Field

[0001] This invention belongs to the field of textile technology, specifically relating to a washable and sun-resistant denim fabric and its preparation method. Background Technology

[0002] With the intensification of global warming, the intensity of ultraviolet radiation in sunlight is increasing, posing a potential threat to human skin. The market demand for clothing with sun protection functions is strong. Traditional denim fabric is widely popular due to its unique style and durability, but it is usually thick, not breathable, and unsuitable for hot environments. Existing technologies have attempted to develop sun-protective denim fabrics, but most suffer from the following problems: traditional processes rely on finishing methods to apply UV absorbers to the fiber surface, resulting in weak bonding between the absorbers and fibers. This not only poses a potential risk of the absorbers migrating to the skin due to friction or sweat, but also makes them prone to loss after repeated washing, exhibiting poor wash resistance. Wash resistance is particularly crucial for summer sun-protective clothing. Frequent sweating in hot weather necessitates frequent washing to maintain cleanliness; if the sun protection function significantly diminishes after just a few washes, it will directly lead to the loss of its sun protection function.

[0003] Therefore, there is an urgent need in this field to develop a new type of functional denim fabric that can achieve excellent and long-lasting UV protection while maintaining a lightweight structure, thereby truly meeting the market demand in high-temperature and high-UV environments.

[0004] CN119332507A discloses a sun-protective fabric and its preparation method, which involves immersing a base fabric in different agents to obtain the sun-protective fabric. This sun-protective fabric uses modified nylon as the base material. The modified nylon molecules have a branched structure, and the molecular chain contains a hydroxybenzophenone structure. The ketone group and hydroxyl group form an intrinsic hydrogen bond, constituting a chelate ring. When ultraviolet light is absorbed, the hydrogen bond breaks, the chelate ring opens, and the energy of the ultraviolet light is converted into heat energy and released. The sun-protective fabric contains an imidazole zinc framework structure, whose high specific surface area and porous structure can capture and scatter ultraviolet light, reducing the penetration depth and achieving the effect of shielding ultraviolet light. However, the fabric is stiff and heavy, and the bonding force between its functional layer and the fiber base is weak, failing to fundamentally solve the core defects of unstable sun protection performance and poor washability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a washable and sun-protective denim fabric and its preparation method. The denim fabric, through the construction of a synergistic protection system of fiber bonding, three-dimensional network coating and slow-release microcapsule supplementation, ensures extremely high initial UV protection performance while achieving long-lasting stability of sun protection function after multiple washes, and at the same time maintains the inherent softness and drape of the fabric.

[0006] To achieve the above objectives, according to one aspect of the present invention, a washable and sun-protective denim fabric is provided, having a 2 / 1 right-hand twill weave structure, wherein the warp yarns of the fabric are Tencel fibers and the weft yarns are nylon fibers; wherein a first ultraviolet absorber is bonded to the nylon fibers; a three-dimensional network protective film formed by curing a crosslinking agent is also attached to the surface of the fabric and between the fibers, and the protective film contains sustained-release microcapsules; the core of the sustained-release microcapsules contains a hindered amine light stabilizer and a second ultraviolet absorber.

[0007] In this invention, the first ultraviolet absorber is a sulfonated ultraviolet absorber. Preferably, the sulfonated ultraviolet absorber is 2-phenyl-5-benzimidazole sulfonic acid.

[0008] In this invention, the second ultraviolet absorber is a hydrophobic benzotriazole ultraviolet absorber, and the molecular weight of the second ultraviolet absorber is greater than 500 g / mol.

[0009] The inventors discovered that the first UV absorber is a sulfonated UV absorber. Utilizing the negative charge generated by the ionization of its sulfonic acid groups under weakly acidic conditions, it forms a strong ionic bond with the positive charge of the amino groups at the ends of the nylon fiber macromolecular chains, achieving a specific binding with the weft yarn and ensuring the durability of the sun protection function in the weft direction. Furthermore, the second UV absorber is a hydrophobic benzotriazole compound with a molecular weight greater than 500 g / mol, encapsulated in microcapsules. Its high hydrophobicity and large molecular weight allow it to remain stably within the oily core of the microcapsules, slowing the outward permeation rate and thus achieving long-lasting sustained release. The synergistic effect of the two absorbers ensures that the denim fabric maintains extremely high initial UV protection performance while achieving long-lasting stability of the sun protection function after multiple washes.

[0010] In this invention, the wall material of the sustained-release microcapsules is a gelatin-gum arabic composite aggregate.

[0011] In this invention, the crosslinking agent is a modified acrylic crosslinking agent, and the three-dimensional mesh protective film is bonded to the Tencel fiber and nylon fiber through covalent bonds.

[0012] The warp and weft density of the washable and sun-protective denim fabric is: 150-160 warp threads / inch and 80-90 weft threads / inch; in the preferred embodiment, the warp density is 153 warp threads / inch and the weft density is 83 weft threads / inch.

[0013] The preferred warp yarn count is 38-42 English count, with 40 English count being the most preferred embodiment. The warp yarn is preferably made of domestically produced Tencel fiber, and more preferably, Tencel fiber produced by Tianhong Changzhou Weiye Co., Ltd.

[0014] The weft yarn specification is 130-145D nylon filament, and each weft yarn contains 130-150 monofilaments.

[0015] The yarn twist range is: 99-102 twists / 10 cm for warp yarns and 39-41 twists / 10 cm for weft yarns; in specific implementation, the preferred warp yarn twist is 100 twists / 10 cm and the preferred weft yarn twist is 40 twists / 10 cm.

[0016] In this invention, the mass ratio of the hindered amine light stabilizer and the second ultraviolet absorber in the core of the sustained-release microcapsule is 1:2 to 1:4. Limiting the mass ratio within this range ensures that the two active ingredients are continuously released at an optimal efficiency ratio during the microcapsule's sustained-release process, thereby forming a dynamic and durable protective layer on the fiber surface. This avoids the potential for depletion and failure due to the second ultraviolet absorber acting alone, and also compensates for the inability of the hindered amine light stabilizer to directly absorb ultraviolet light. Ultimately, this allows the fabric to maintain excellent photostability and ultraviolet protection throughout its entire lifespan.

[0017] In this invention, the potential risk of instability in the ionic bonding between nylon fibers and the first UV absorber under washing conditions is addressed by a synergistic mechanism combining physical fixation of a three-dimensional cross-linked network with dynamic replenishment via slow-release microcapsules. First, a modified acrylic cross-linking agent solidifies to form a dense three-dimensional network protective film at the fiber surface and interlacing points. This film acts like a robust armor, encapsulating and locking the absorber, which has been initially bonded by ionic and hydrogen bonds, onto the fiber surface. This effectively blocks the penetration of water molecules and the direct impact of mechanical friction during washing, thus greatly improving the durability of the ionic bonding. Even after long-term use and multiple washes, resulting in trace amounts of absorber loss, the slow-release microcapsules embedded in the protective film slowly release hindered amine light stabilizers and hydrophobic second UV absorbers under external stimuli such as friction and humidity, promptly repairing and replenishing the protective effect in situ. This dual guarantee of static anchoring and dynamic replenishment synergistically ensures the long-lasting stability of the fabric's sun protection performance, ultimately achieving a washability far exceeding that of single finishing techniques.

[0018] According to another aspect of the present invention, a method for preparing a washable and sun-resistant denim fabric as described in any of the preceding claims is also provided, comprising the following steps: S1. Warp preparation: Tencel fibers are used as warp yarns and dyed. S2. Weft yarn preparation: Nylon fiber is used as weft yarn and immersed in a finishing solution containing the first ultraviolet absorber. It is then heat-treated at 120-140℃ for 3-10 minutes to combine the first ultraviolet absorber with the nylon fiber. S3. Microcapsule preparation: The core material containing a hindered amine light stabilizer and a second ultraviolet absorber is microencapsulated, and the wall material of the microcapsule is a gelatin-gum arabic composite aggregate to obtain a sustained-release microcapsule dispersion. S4. Weaving: The warp yarns treated in step S1 are sized, threaded, and reed, and then interwoven with the weft yarns treated in step S2 on the loom to form a 2 / 1 right twill fabric. S5. Functional finishing: After desizing and cleaning the fabric obtained in step S4, it is immersed in a composite finishing solution containing a crosslinking agent and the sustained-release microcapsule dispersion obtained in step S3. S6. Film Formation and Fixation: The fabric treated in step S5 is baked at high temperature to cure the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and the slow-release microcapsules are embedded therein to obtain the washable and sun-protective denim fabric.

[0019] In this invention, step S1 involves using Tencel fibers as warp yarns and performing a dyeing process. The specific steps of the dyeing process in step S1 include: passing the Tencel fiber warp yarns through an indigo dyeing machine at a speed of 20 m / min for multiple stages of padding and oxidation. The dyeing solution mainly consists of: 1.7 g / L indigo powder, 3.7-3.9 g / L sodium hydroxide, and 1.6-1.7 g / L sodium hydrosulfite. The dyeing rate is controlled to be approximately 5.13%. After dyeing, the yarns undergo sequential alkaline boiling, washing, acid washing, and softening treatments, with the moisture regain controlled at 6-8% to ensure the warp yarns are in a neutral and clean state.

[0020] In this invention, in step S2, nylon fibers are used as weft yarns and immersed in a finishing solution containing a first ultraviolet absorber. The solution is then heat-treated at 120-140°C for 3-10 minutes to allow the first ultraviolet absorber to bond with the nylon fibers. In step S2, the finishing solution contains 10-30 g / L of the first ultraviolet absorber, 1-3 g / L of citric acid, 1-3 g / L of fatty alcohol polyoxyethylene ether, and deionized water, with a pH of 4-5. This acidic condition causes the amino groups of the nylon fibers to protonate, forming ionic bonds with the sulfonate groups of the first ultraviolet absorber.

[0021] In this invention, step S3 involves microcapsule preparation: a core material containing a hindered amine light stabilizer and a second ultraviolet absorber is microencapsulated, wherein the wall material of the microcapsules is a gelatin-gum arabic composite aggregate, resulting in a sustained-release microcapsule dispersion. The microencapsulation employs a composite aggregation method, comprising the following steps: S3.1 The hindered amine light stabilizer and the second ultraviolet absorber are dissolved in ethyl acetate to form an oil phase core; S3.2 Prepare aqueous solutions of gelatin and gum arabic separately, and maintain the temperature at 50-55℃; S3.3 The oil phase is added to the gelatin solution under high-speed shearing to form a primary emulsion; S3.4 Add gum arabic solution to the primary emulsion and adjust the pH to 4.0-4.5 to carry out a complex coagulation reaction; S3.5 is cooled to below 10℃, and glutaraldehyde (10%-20% of the gelatin mass) is added for wall material curing. After washing and dispersion, a sustained-release microcapsule dispersion is obtained.

[0022] In this invention, in step S4, weaving: the warp yarns treated in step S1 are sized, threaded, and reed, and then interwoven with the weft yarns treated in step S2 on a loom to form a 2 / 1 right twill fabric.

[0023] In this invention, step S5 involves functional finishing: after desizing and cleaning the fabric obtained in step S4, it is impregnated in a composite finishing solution containing a crosslinking agent and the sustained-release microcapsule dispersion obtained in step S3. In the composite finishing solution, the mass concentration of the crosslinking agent is 50-100 g / L, and the solid content of the sustained-release microcapsules is 20-50 g / L.

[0024] In this invention, in step S6, the fabric treated in step S5 is subjected to high-temperature baking to solidify the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and embedding the slow-release microcapsules therein. The three-dimensional network formed by the solidification of the crosslinking agent constitutes a continuous protective film on the fiber surface and between the interlacing points. This film itself can scatter and reflect ultraviolet rays, forming a physical barrier. In addition, the network mechanically embeds and locks the slow-release microcapsules, effectively preventing their physical loss during subsequent washing and use, and achieving the long-term effectiveness of the microcapsule slow-release function. The network structure interweaves and fixes the ultraviolet absorbers already bonded to the fibers in S1 and S2 together, significantly improving the overall functional layer's abrasion resistance and wash fastness, thereby achieving high wash resistance and long-lasting sun protection.

[0025] Furthermore, the high-temperature baking conditions are as follows: pre-baking at 100-110℃ for 1-3 minutes, followed by baking at 160-180℃ for 1-3 minutes. Pre-baking at 100-110℃ for 1-3 minutes gently removes most of the moisture from the composite finishing solution, allowing the protective film to initially set, while simultaneously enabling the microcapsule wall material to smoothly transition to a relatively dry and robust state. If the temperature is directly increased from room temperature to above 160℃, the pressure generated by the rapid vaporization of moisture can easily cause the microcapsules to rupture.

[0026] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention's denim fabric utilizes a synergistic protective system comprised of fiber bonding, a three-dimensional network coating, and sustained-release microcapsules. This ensures extremely high initial UV protection while maintaining stable sun protection after multiple washes, and preserves the fabric's inherent softness and drape. Specifically, this invention employs a first UV absorber containing sulfonic acid groups, ionicly bonded to the amino groups of nylon fibers, forming a robust first layer of wash-resistant protection. On top of this, a three-dimensional network protective film is formed on the fabric surface and between fibers using a crosslinking agent curing film-forming technology. This film not only enhances durability but also acts as a carrier to physically embed and fix sustained-release microcapsules containing hindered amine light stabilizers and highly hydrophobic second UV absorbers, forming a second layer of dynamic supplementary protection. This structure ensures that the fiber bonding remains stable after multiple washes, while the microcapsules slowly release active ingredients, continuously repairing and enhancing sun protection, thus achieving an extremely high initial UV protection factor (UPF) and a very low attenuation rate after 40 washes.

[0027] 2. The preparation method of this invention innovatively integrates and optimizes the three key functionalization steps of UV absorber bonding, microcapsule preparation and film formation. This not only achieves the orderly construction of the above-mentioned triple protection structure, but also effectively avoids functional conflicts or deterioration of hand feel that may be caused by multiple processes. Ultimately, it ensures that the resulting fabric has high washability and sun protection while maintaining the style and wearing comfort that denim fabric should have.

[0028] 3. This invention, through the selection of optimal warp and weft yarn materials (Tencel and nylon), the rational setting of warp and weft density and yarn twist, and the combination of a low-stress finishing process that does not affect the feel, gives the fabric a natural soft and draping characteristic. The nylon fiber used has good moisture absorption and wicking properties and is not prone to static electricity; the Tencel fiber is smooth and has excellent moisture absorption and wicking effect. The combination of the two makes the resulting summer clothing drape without clinging to the skin, preventing sweat or static electricity from adhering to the skin surface, thereby promoting heat dissipation and providing a cool wearing experience.

[0029] 4. Addressing the issue of frequent washing of summer sun-protective clothing and the rapid decline in the sun protection performance of traditional products, the fabric of this invention significantly improves the durability of sun protection. When applied to sun-protective clothing, sun-protective pants, and other products, it can still effectively and sustainably maintain both UV protection and comfortable drape even after frequent washing. Attached Figure Description

[0030] Figure 1 This is a pattern diagram of the denim fabric texture obtained in the example. Detailed Implementation

[0031] This invention provides a washable and sun-protective denim fabric with a 2 / 1 right-hand twill weave. The warp yarns of the fabric are Tencel fibers, and the weft yarns are nylon fibers. A first ultraviolet absorber is bonded to the nylon fibers. A three-dimensional network protective film formed by curing a crosslinking agent is also attached to the surface of the fabric and between the fibers, and the protective film contains slow-release microcapsules. The core of the slow-release microcapsules contains a hindered amine light stabilizer and a second ultraviolet absorber.

[0032] In some embodiments, the second ultraviolet absorber is a hydrophobic benzotriazole ultraviolet absorber, and the molecular weight of the second ultraviolet absorber is greater than 500 g / mol.

[0033] In some embodiments, the wall material of the sustained-release microcapsules is a gelatin-gum arabic composite aggregate.

[0034] In some embodiments, the crosslinking agent is a modified acrylic crosslinking agent, and the three-dimensional mesh protective film is covalently bonded to the Tencel fiber and nylon fiber.

[0035] In some embodiments, the mass ratio of the hindered amine light stabilizer and the second ultraviolet absorber in the core of the sustained-release microcapsule is 1:2 to 1:4.

[0036] The present invention also provides a method for preparing the washable and sun-protective denim fabric described in any one of the above claims, comprising the following steps: S1. Warp preparation: Tencel fibers are used as warp yarns and dyed. S2. Weft yarn preparation: Nylon fiber is used as weft yarn and immersed in a finishing solution containing the first ultraviolet absorber. It is then heat-treated at 120-140℃ for 3-10 minutes to combine the first ultraviolet absorber with the nylon fiber. S3. Microcapsule preparation: The core material containing a hindered amine light stabilizer and a second ultraviolet absorber is microencapsulated, and the wall material of the microcapsule is a gelatin-gum arabic composite aggregate to obtain a sustained-release microcapsule dispersion. S4. Weaving: The warp yarns treated in step S1 are sized, threaded, and reed, and then interwoven with the weft yarns treated in step S2 on the loom to form a 2 / 1 right twill fabric. S5. Functional finishing: After desizing and cleaning the fabric obtained in step S4, it is immersed in a composite finishing solution containing a crosslinking agent and the sustained-release microcapsule dispersion obtained in step S3. S6. Film Formation and Fixation: The fabric treated in step S5 is baked at high temperature to cure the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and the slow-release microcapsules are embedded therein to obtain the washable and sun-protective denim fabric.

[0037] In some embodiments, in step S2, the finishing solution contains 10-30 g / L of a first ultraviolet absorber, 1-3 g / L of citric acid, 1-3 g / L of fatty alcohol polyoxyethylene ether, and deionized water, with a pH value of 4-5.

[0038] In some embodiments, step S3, the microencapsulation employs a composite agglomeration method, including the following steps: S3.1 The hindered amine light stabilizer and the second ultraviolet absorber are dissolved in ethyl acetate to form an oil phase core; S3.2 Prepare aqueous solutions of gelatin and gum arabic separately, and maintain the temperature at 50-55℃; S3.3 The oil phase is added to the gelatin solution under high-speed shearing to form a primary emulsion; S3.4 Add gum arabic solution to the primary emulsion and adjust the pH to 4.0-4.5 to carry out a complex coagulation reaction; S3.5 is cooled to below 10℃, and glutaraldehyde (10%-20% of the gelatin mass) is added for wall material curing. After washing and dispersion, a sustained-release microcapsule dispersion is obtained.

[0039] In some embodiments, in step S5, the mass concentration of the crosslinking agent in the composite finishing liquid is 50-100 g / L, and the solid content of the sustained-release microcapsules is 20-50 g / L; in step S6, the conditions for high-temperature baking are: first pre-baking at 100-110℃ for 1-3 min, and then baking at 160-180℃ for 1-3 min.

[0040] 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.

[0041] Example 1 is the best embodiment.

[0042] 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 yarn: Made of Tencel fiber, with a yarn count of 40 English count, supplied by Tianhong Changzhou Weiye Co., Ltd.

[0043] Weft yarn: Made of nylon filament, specification FDY 140D / 136F (FDY means fully drawn yarn; 140D is denier, i.e. yarn thickness; 136F means that a single weft yarn is composed of 136 filaments), purchased from Qingdao Fiber Research New Material Technology Co., Ltd.

[0044] Yarn twist: Warp twist is 100 twists / 10 cm, and weft twist is 40 twists / 10 cm.

[0045] First UV absorber: 2-phenyl-5-benzimidazole sulfonic acid, purchased from Aladdin Reagent Co., Ltd.; Second UV absorber: UV-360, molecular weight 658.9, purchased from Nanjing Milan Chemical Co., Ltd.; Modified acrylic crosslinking agent: ACRODUR® DS3558; Hindered amine light stabilizer: HS-944, purchased from Aladdin Reagent Co., Ltd.; Fatty alcohol polyoxyethylene ether, gelatin, gum arabic, other additives and solvents: all purchased from Aladdin Reagent Co., Ltd.

[0046] Example 1 This embodiment describes a washable and sun-protective denim fabric with a 2 / 1 right-hand twill weave. The warp yarns of the fabric are Tencel fibers, and the weft yarns are nylon fibers. A first ultraviolet absorber is bonded to the nylon fibers. A three-dimensional mesh protective film formed by curing a cross-linking agent is also attached to the surface of the fabric and between the fibers, and the protective film contains slow-release microcapsules. The core of the slow-release microcapsules contains a hindered amine light stabilizer and a second ultraviolet absorber in a mass ratio of 1:3.

[0047] The method for preparing the washable and sun-protective denim fabric includes the following steps: S1. Warp preparation: Tencel fiber is used as the warp yarn. The Tencel fiber warp yarn is passed through an indigo dyeing unit at a speed of 20m / min for multiple padding and oxidation processes. The main components of the dyeing solution are: 1.7g / L indigo powder, 3.8g / L sodium hydroxide, and 1.6g / L sodium hydrosulfite. The dyeing rate is controlled at approximately 5.13%. After dyeing, the yarn is subjected to alkali boiling, water washing, acid washing, and softening treatment in sequence. The moisture regain is controlled at 6% to ensure that the warp yarn is in a neutral and clean state. S2. Weft yarn preparation: Nylon fiber is used as the weft yarn and immersed in a finishing solution containing a first ultraviolet absorber. It is then heat-treated at 130°C for 5 minutes to combine the first ultraviolet absorber with the nylon fiber. The finishing solution contains 20 g / L of the first ultraviolet absorber, 2 g / L of citric acid, 2 g / L of fatty alcohol polyoxyethylene ether, and deionized water, with a pH value of 4.5. S3. Microcapsule preparation: The hindered amine light stabilizer and the second ultraviolet absorber are dissolved in ethyl acetate to form an oil phase capsule core; gelatin and gum arabic are separately prepared into aqueous solutions and kept at 53°C; the oil phase is added to the gelatin solution under high-speed shearing to form a primary emulsion; the gum arabic solution is added to the primary emulsion, and the pH is adjusted to 4.3 to carry out a composite coagulation reaction; the temperature is lowered to below 10°C, and glutaraldehyde (15% by weight of gelatin) is added to solidify the wall material. After washing and dispersion, a sustained-release microcapsule dispersion is obtained. S4. Weaving: The warp yarns treated in step S1 are sized, threaded, and reed, and then interwoven with the weft yarns treated in step S2 on the loom. The warp density is controlled to be 153 threads / inch and the weft density to be 83 threads / inch, forming a 2 / 1 right twill fabric. S5. Functional finishing: After desizing and cleaning the fabric obtained in step S4, it is immersed in a composite finishing solution containing a crosslinking agent and the sustained-release microcapsule dispersion obtained in step S3; in the composite finishing solution, the mass concentration of the crosslinking agent is 80 g / L and the solid content of the sustained-release microcapsules is 30 g / L. S6. Film Formation and Fixation: The fabric treated in step S5 is first pre-baked at 105℃ for 2 minutes, and then baked at 170℃ for 2 minutes to cure the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and the slow-release microcapsules are embedded therein to obtain the washable and sun-protective denim fabric.

[0048] Example 2 This embodiment describes a washable and sun-protective denim fabric with a 2 / 1 right-hand twill weave. The warp yarns of the fabric are Tencel fibers, and the weft yarns are nylon fibers. A first ultraviolet absorber is bonded to the nylon fibers. A three-dimensional mesh protective film formed by curing a cross-linking agent is also attached to the surface of the fabric and between the fibers, and the protective film contains slow-release microcapsules. The core of the slow-release microcapsules contains a hindered amine light stabilizer and a second ultraviolet absorber in a mass ratio of 1:2.

[0049] The method for preparing the washable and sun-protective denim fabric includes the following steps: S1. Warp preparation: Tencel fiber is used as the warp yarn. The Tencel fiber warp yarn is passed through an indigo dyeing unit at a speed of 20m / min for multiple padding and oxidation processes. The main components of the dyeing solution are: 1.7g / L indigo powder, 3.7g / L sodium hydroxide, and 1.6g / L sodium hydrosulfite. The dyeing rate is controlled at approximately 5.13%. After dyeing, the yarn is subjected to alkali boiling, water washing, acid washing, and softening treatment in sequence. The moisture regain is controlled at 6% to ensure that the warp yarn is in a neutral and clean state. S2. Weft yarn preparation: Nylon fiber is used as the weft yarn and immersed in a finishing solution containing a first ultraviolet absorber. It is then heat-treated at 120°C for 10 minutes to combine the first ultraviolet absorber with the nylon fiber. The finishing solution contains 10 g / L of the first ultraviolet absorber, 1 g / L of citric acid, 1 g / L of fatty alcohol polyoxyethylene ether, and deionized water, with a pH value of 4. S3. Microcapsule preparation: The hindered amine light stabilizer and the second ultraviolet absorber are dissolved in ethyl acetate to form an oil phase core; gelatin and gum arabic are prepared into aqueous solutions and kept at 50°C; the oil phase is added to the gelatin solution under high-speed shearing to form a primary emulsion; the gum arabic solution is added to the primary emulsion, and the pH is adjusted to 4.0 to carry out a composite coagulation reaction; the temperature is lowered to below 10°C, and glutaraldehyde (10% by weight of gelatin) is added to solidify the wall material. After washing and dispersion, a sustained-release microcapsule dispersion is obtained. S4. Weaving: The warp yarns treated in step S1 are sized, threaded, and reed, and then interwoven with the weft yarns treated in step S2 on the loom. The warp density is controlled to be 153 threads / inch and the weft density to be 83 threads / inch, forming a 2 / 1 right twill fabric. S5. Functional finishing: After desizing and cleaning the fabric obtained in step S4, it is immersed in a composite finishing solution containing a crosslinking agent and the sustained-release microcapsule dispersion obtained in step S3; in the composite finishing solution, the mass concentration of the crosslinking agent is 50 g / L and the solid content of the sustained-release microcapsules is 20 g / L. S6. Film Formation and Fixation: The fabric treated in step S5 is first pre-baked at 100℃ for 3 minutes, and then baked at 160℃ for 3 minutes to cure the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and the slow-release microcapsules are embedded therein to obtain the washable and sun-protective denim fabric.

[0050] Example 3 This embodiment describes a washable and sun-protective denim fabric with a 2 / 1 right-hand twill weave. The warp yarns of the fabric are Tencel fibers, and the weft yarns are nylon fibers. A first ultraviolet absorber is bonded to the nylon fibers. A three-dimensional mesh protective film formed by curing a cross-linking agent is also attached to the surface of the fabric and between the fibers, and the protective film contains slow-release microcapsules. The core of the slow-release microcapsules contains a hindered amine light stabilizer and a second ultraviolet absorber in a mass ratio of 1:4.

[0051] The method for preparing the washable and sun-protective denim fabric includes the following steps: S1. Warp preparation: Tencel fiber is used as the warp yarn. The Tencel fiber warp yarn is passed through an indigo dyeing unit at a speed of 20m / min for multiple padding and oxidation processes. The main components of the dyeing solution are: 1.7g / L indigo powder, 3.9g / L sodium hydroxide, and 1.7g / L sodium hydrosulfite. The dyeing rate is controlled at approximately 5.13%. After dyeing, the yarn is subjected to alkali boiling, water washing, acid washing, and softening treatment in sequence. The moisture regain is controlled at 8% to ensure that the warp yarn is in a neutral and clean state. S2. Weft yarn preparation: Nylon fiber is used as the weft yarn and immersed in a finishing solution containing a first ultraviolet absorber. It is then heat-treated at 140°C for 3 minutes to combine the first ultraviolet absorber with the nylon fiber. The finishing solution contains 30 g / L of the first ultraviolet absorber, 3 g / L of citric acid, 3 g / L of fatty alcohol polyoxyethylene ether, and deionized water, with a pH value of 5. S3. Microcapsule preparation: The hindered amine light stabilizer and the second ultraviolet absorber are dissolved in ethyl acetate to form an oil phase core; gelatin and gum arabic are separately prepared into aqueous solutions and kept at 55°C; the oil phase is added to the gelatin solution under high-speed shearing to form a primary emulsion; the gum arabic solution is added to the primary emulsion, and the pH is adjusted to 4.5 to carry out a composite coagulation reaction; the temperature is lowered to below 10°C, and glutaraldehyde (20% by weight of gelatin) is added to solidify the wall material. After washing and dispersion, a sustained-release microcapsule dispersion is obtained. S4. Weaving: The warp yarns treated in step S1 are sized, threaded, and reed, and then interwoven with the weft yarns treated in step S2 on the loom. The warp density is controlled to be 153 threads / inch and the weft density to be 83 threads / inch, forming a 2 / 1 right twill fabric. S5. Functional finishing: After desizing and cleaning the fabric obtained in step S4, it is immersed in a composite finishing solution containing a crosslinking agent and the sustained-release microcapsule dispersion obtained in step S3; in the composite finishing solution, the mass concentration of the crosslinking agent is 100g / L and the solid content of the sustained-release microcapsules is 50g / L. S6. Film Formation and Fixation: The fabric treated in step S5 is first pre-baked at 110°C for 1 minute, and then baked at 180°C for 1 minute to cure the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and the slow-release microcapsules are embedded therein to obtain the washable and sun-protective denim fabric.

[0052] Comparative Example 1 The washable and sun-protective denim fabric described in this comparative example is exactly the same as that in Example 1, except that the crosslinking agent in the composite finishing liquid in step S5 is replaced with an ordinary non-crosslinked acrylic emulsion of the same mass concentration (80g / L).

[0053] Comparative Example 2 The washable and sun-protective denim fabric described in this comparative example is exactly the same as that in Example 1, except that in step S3, when preparing the microcapsules, only hydrophobic benzotriazole UV absorbers (second UV absorbers) are used as the core material, and no hindered amine light stabilizers are added. The total mass is the same as that of the core material in Example 1.

[0054] Comparative Example 3 The washable and sun-protective denim fabric described in this comparative example is exactly the same as that in Example 1, except that the weft yarn is not impregnated with the first UV absorber in step S2. That is, the weft yarn uses nylon fibers that have not undergone any sun protection treatment.

[0055] Comparative Example 4 The washable and sun-protective denim fabric described in this comparative example is exactly the same as that in Example 1, except that UV-P, an ultraviolet absorber, is used as the second ultraviolet absorber.

[0056] Comparative Example 5 The washable and sun-protective denim fabric described in this comparative example is exactly the same as that in Example 1, except that step S6 is: the fabric treated in step S5 is baked at 170°C for 4 minutes to cure the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and the slow-release microcapsules are embedded therein to obtain the washable and sun-protective denim fabric.

[0057] Performance testing The washable and sun-resistant denim fabrics obtained in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests according to the following methods, and the specific results are shown in Table 1.

[0058] Fracture strength: tested according to ASTM D5035; Tear strength: Tested according to ASTM D1424; Joint slippage: Tested according to ASTM D434; Drape: Tested according to GB / T23329; Abrasion resistance test: conducted according to GB / T21196.2; Fabric sun protection: tested according to GB / T18830; Sun protection performance after 40 washes: tested according to GB / T18830.

[0059] Table 1 Performance data of Examples 1-3 and Comparative Examples 1-5 .

[0060] As shown in Table 1, within the specified ratios and process parameters of this invention, Examples 1-3 all exhibit excellent overall performance. Example 1, after 40 washes, still maintains a UV protection factor (UPF) as high as 165, demonstrating that the protective system formed through bonding and cross-linking microcapsule technology possesses good wash fastness, solving the problem of insufficient sun protection durability in traditional sunscreen fabrics. Simultaneously, all examples demonstrate excellent mechanical properties; for instance, Example 1 exhibits a weft breaking strength exceeding 1000N, and all seams show no slippage, indicating that the functional finishing process not only did not damage the fabric matrix but also enhanced the cohesion between yarns through a dense cross-linked network, improving the material's durability.

[0061] A comparison between Example 1 and Comparative Example 1 shows that Comparative Example 1, which uses a non-crosslinked acrylic emulsion, had its sun protection factor (UPF) reduced to 95 after 40 washes, and its mechanical properties and abrasion resistance were reduced to varying degrees. This indicates that ordinary coatings have a weak effect on fixing and protecting yarns, and may even affect the original structural integrity of the fabric.

[0062] A comparison of Example 1 and Comparative Example 2 shows that, although Comparative Example 2 did not contain hindered amine light stabilizers, there was no significant difference in initial physical and mechanical properties (such as breaking strength, tear strength, abrasion resistance, and seam slippage). However, after 40 washes, the UPF value of Example 1 remained as high as 165, while that of Comparative Example 2 decreased to 124. This indicates that in the absence of hindered amine light stabilizers, sunscreen active ingredients are more prone to decomposition and inactivation due to environmental factors such as light, heat, and humidity during long-term use and washing.

[0063] A comparison between Example 1 and Comparative Example 3 shows that Comparative Example 3, due to the lack of sun protection treatment on the weft yarn, exhibited poor initial sun protection performance and sun protection performance after 40 washes. This is because the protective film alone cannot completely cover the three-dimensional microscopic gaps formed by the interlacing of warp and weft yarns, resulting in a large amount of ultraviolet rays passing through the untreated weft yarn fibers. After washing, as the protective film gradually breaks and falls off due to friction and water flow impact, the sun protection performance drops significantly.

[0064] A comparison of Example 1 and Comparative Example 4 reveals that the second ultraviolet absorber in Comparative Example 4, UV-P, is a hydrophilic ultraviolet absorber with a molecular weight less than 500 g / mol. Its initial and post-wash sun protection performance (UPF 160 / 123) are significantly lower than that of Example 1. This is because its hydrophilic properties and small molecular weight make it easily dissolve and rapidly lose during washing, preventing effective fixation within fibers or microcapsules. Furthermore, its poor compatibility with the hydrophobic microcapsule wall material and fiber substrate makes it difficult to form a stable synergistic protective network, ultimately leading to a significant reduction in sun protection function.

[0065] A comparison of Example 1 and Comparative Example 5 shows that Comparative Example 5, by directly subjecting the fabric to high-temperature baking without a pre-drying step, caused the moisture in the composite finishing liquid on the fabric surface to rapidly vaporize at high temperatures, generating enormous pressure. This resulted in the premature rupture of a large number of slow-release microcapsules during the processing stage, directly reducing the initial sun protection value. Furthermore, the microcapsule structure was damaged, losing its slow-release protective function, thus leading to a significant drop in sun protection performance during washing. Simultaneously, the intense vaporization process also hindered the formation of a uniform and strong protective network by the cross-linking agent, causing a decrease in the fabric's tear strength and abrasion resistance.

[0066] Therefore, this invention utilizes a first UV absorber containing sulfonic acid groups to ionicly bond with the amino groups of nylon fibers, forming a robust first layer of wash-resistant protection. On top of this, a three-dimensional mesh protective film is formed on the fabric surface and between fibers using a crosslinking agent curing film-forming technology. This not only enhances the fabric's durability but also acts as a carrier to physically embed and fix slow-release microcapsules containing hindered amine light stabilizers and highly hydrophobic second UV absorbers, forming a second layer of dynamic supplementary protection. This structure ensures that the fiber bonds remain stable after multiple washes, while the microcapsules slowly release active ingredients to continuously repair and enhance sun protection, achieving an extremely high initial UV protection factor (UPF) and a very low attenuation rate after 40 washes.

[0067] Figure 1 The image shown is a weave pattern diagram of the denim fabric obtained in the embodiment, which is actually a weave pattern diagram of the ground weave of the fabric of the present invention. It can be seen that it is a 2 / 1 right-hand twill fabric. Black squares represent warp yarns on top, and white squares represent warp yarns on the bottom. This structure not only improves the coverage and density of the yarns on the fabric surface, effectively enhancing the fabric's ability to block ultraviolet rays, but also gives the fabric good softness and moderate freedom of movement, resulting in good drape under its own weight.

[0068] 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 washable and sun-resistant denim fabric, characterized in that, The fabric has a 2 / 1 right-hand twill weave structure, with Tencel fibers as warp and nylon fibers as weft; wherein a first ultraviolet absorber is bonded to the nylon fibers; a three-dimensional network protective film formed by curing a cross-linking agent is also attached to the surface of the fabric and between the fibers, and a sustained-release microcapsule is embedded in the protective film; the core of the sustained-release microcapsule contains a hindered amine light stabilizer and a second ultraviolet absorber.

2. The washable and sun-protective denim fabric as described in claim 1, characterized in that, The first ultraviolet absorber is a sulfonated ultraviolet absorber.

3. The washable and sun-protective denim fabric as described in claim 1, characterized in that, The second ultraviolet absorber is a hydrophobic benzotriazole ultraviolet absorber, and the molecular weight of the second ultraviolet absorber is greater than 500 g / mol.

4. The washable and sun-protective denim fabric as described in claim 1, characterized in that, The wall material of the sustained-release microcapsules is a gelatin-gum arabic composite aggregate.

5. The washable and sun-protective denim fabric as described in claim 1, characterized in that, The crosslinking agent is a modified acrylic crosslinking agent, and the three-dimensional mesh protective film is bonded to the Tencel fiber and nylon fiber through covalent bonds.

6. The washable and sun-resistant denim fabric as described in claim 1, characterized in that, The mass ratio of the hindered amine light stabilizer and the second ultraviolet absorber in the core of the sustained-release microcapsule is 1:2 to 1:

4.

7. A method for preparing a washable and sun-resistant denim fabric as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Warp preparation: Tencel fibers are used as warp yarns and dyed. S2. Weft yarn preparation: Nylon fiber is used as weft yarn and immersed in a finishing solution containing the first ultraviolet absorber. It is then heat-treated at 120-140℃ for 3-10 minutes to combine the first ultraviolet absorber with the nylon fiber. S3. Microcapsule preparation: The core material containing a hindered amine light stabilizer and a second ultraviolet absorber is microencapsulated, and the wall material of the microcapsule is a gelatin-gum arabic composite aggregate to obtain a sustained-release microcapsule dispersion. S4. Weaving: The warp yarns treated in step S1 are sized, threaded, and reed, and then interwoven with the weft yarns treated in step S2 on the loom to form a 2 / 1 right twill fabric. S5. Functional finishing: After desizing and cleaning the fabric obtained in step S4, it is immersed in a composite finishing solution containing a crosslinking agent and the sustained-release microcapsule dispersion obtained in step S3. S6. Film Formation and Fixation: The fabric treated in step S5 is baked at high temperature to cure the crosslinking agent, forming a three-dimensional mesh protective film on the fabric surface and between fibers, and the slow-release microcapsules are embedded therein to obtain the washable and sun-protective denim fabric.

8. The preparation method according to claim 7, characterized in that, In step S2, the finishing solution contains 10-30 g / L of a first ultraviolet absorber, 1-3 g / L of citric acid, 1-3 g / L of fatty alcohol polyoxyethylene ether, and deionized water, with a pH value of 4-5.

9. The preparation method according to claim 7, characterized in that, In step S3, the microencapsulation is performed using a composite agglomeration method, which includes the following steps: S3.1 The hindered amine light stabilizer and the second ultraviolet absorber are dissolved in ethyl acetate to form an oil phase core; S3.2 Prepare aqueous solutions of gelatin and gum arabic separately, and maintain the temperature at 50-55℃; S3.3 The oil phase is added to the gelatin solution under high-speed shearing to form a primary emulsion; S3.4 Add gum arabic solution to the primary emulsion and adjust the pH to 4.0-4.5 to carry out a complex coagulation reaction; S3.5 is cooled to below 10℃, and glutaraldehyde (10%-20% of the gelatin mass) is added for wall material curing. After washing and dispersion, a sustained-release microcapsule dispersion is obtained.

10. The preparation method according to claim 7, characterized in that, In step S5, the mass concentration of the crosslinking agent in the composite finishing liquid is 50-100 g / L, and the solid content of the sustained-release microcapsules is 20-50 g / L; in step S6, the high-temperature baking conditions are: first pre-baking at 100-110℃ for 1-3 min, and then baking at 160-180℃ for 1-3 min.

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