Preparation method of thin super-microfiber suede

Abstract

The present application relates to the technical field of super-fiber leather, and provides a preparation method of thin super-fiber suede, which solves the defects of the existing thin super-fiber leather preparation process, such as environmental pollution, thick product, and uneven suede, and comprises the following preparation steps: (1) preparation of elastic microporous framework: thermoplastic polyurethane particles and PVA microspheres are mixed, a composite fiber is prepared through melt spinning, a fiber web is formed through non-woven technology, and the fiber web is subjected to heat pressing and bonding to form an elastic microporous framework with a three-dimensional porous network; (2) electrostatic flocking: suede fibers and atomized water-based photosensitive adhesive slurry are jointly injected into a high-voltage electrostatic field, so that the two are jointly deposited on the surface of the elastic microporous framework in the electrostatic field, the water-based photosensitive adhesive slurry coats the roots of the fibers and penetrates into the surface layer of the framework, and then ultraviolet curing treatment is performed to form a stable suede layer on the framework.

Description

Technical Field

[0001] This invention relates to the field of imitation microfiber leather technology, and in particular to a method for preparing thin imitation microfiber suede leather. Background Technology

[0002] The existing thin imitation microfiber suede is usually made by processes such as base fabric preparation, DMF impregnation treatment, coagulation foaming, washing, weight reduction fiber opening, drying and shaping, and brushing and napping. This preparation process is not only not environmentally friendly, but also results in relatively thick leather products with poor performance.

[0003] Chinese Patent Application No. 201310417270.8 discloses a microfiber thin polyurethane ID card leather and its preparation method. The method uses a 0.45mm imitation microfiber fabric base with a fine, single-sided nap as a carrier. A layer of polyurethane resin of a certain viscosity is directly coated onto the napped fabric surface. After coagulation, a polyurethane film is formed on the base fabric surface. This film-forming process involves sequential steps of water washing to replace DMF solvent, drying, and shaping of the polyurethane film to obtain a semi-finished product. The surface of the semi-finished product is then subjected to directional sanding and width determination, followed by post-treatment and color modification to obtain the finished product. The microfiber thin polyurethane ID card leather manufactured by this method has a fine nap, a soft feel, is lightweight, and has excellent breathability, similar to microfiber velvet. ID card leather linings made from it are eye-catching, elegant, and provide excellent protection against shock, shatter, and scratches for delicate items, making it particularly suitable for linings of mobile phones, computers, and other similar devices. However, its film-forming process relies on the coagulation and displacement of the DMF solvent system. DMF is a toxic and harmful solvent, posing environmental and health risks during its production, washing, and recycling processes, which is inconsistent with the current trend of green manufacturing. In addition, the resulting polyurethane film increases the overall thickness and areal density, making it difficult to meet the application scenarios requiring thinner and lighter materials. Furthermore, its final velvety effect depends on the mechanical abrasion of the formed film surface, which inevitably cuts some surface fibers, resulting in uneven velvet texture and weakening the original strength and durability of the velvet fibers. Summary of the Invention

[0004] Therefore, in view of the above problems, the present invention provides a method for preparing thin imitation microfiber suede, which solves the defects of existing thin imitation microfiber leather preparation process being not environmentally friendly, producing thicker products, and having uneven suede feel.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing thin imitation microfiber suede, comprising the following preparation steps: (1) Preparation of elastic microporous skeleton: thermoplastic polyurethane particles and PVA microspheres are mixed at a weight ratio of 80-85:15-20, and composite fibers are produced by melt spinning. Then, a fiber web is formed by nonwoven technology, and the fiber web is hot-pressed to form an elastic microporous skeleton with a three-dimensional porous network. (2) Electrostatic flocking: The flocked fibers and atomized water-based photosensitive adhesive paste are injected into a high-voltage electrostatic field, so that the two are deposited together on the surface of the elastic microporous skeleton in the electrostatic field. The electrostatic field voltage is controlled at 40-80 kV and the electrode spacing is 10-30 cm. The flocked fibers are implanted into the skeleton at 60-90°, and the water-based photosensitive adhesive paste covers the fiber roots and penetrates into the surface of the skeleton. Then, ultraviolet curing treatment is performed to form a stable flocked layer on the skeleton. During hot pressing, a hot press roller with a micro-protruding structure on the surface is used to press the fiber web at 160-180℃ and 0.2-0.6MPa for 0.5-1s. After the pressing process, a fiber web with localized adhesion on the surface is obtained.

[0006] Further: In step (1), after hot pressing and bonding, the fiber web is immersed in warm water at 60-80℃ for 20-30 minutes and then dried.

[0007] Furthermore, the water-based photosensitive adhesive paste is composed of the following raw materials in parts by weight: 50-70 parts of water-based polyurethane dispersion, 3-6 parts of photoinitiator, 0.5-3 parts of wetting and leveling agent, 1-2 parts of thickener, 0.3-0.8 parts of defoamer, and 20-45 parts of deionized water. The viscosity of the water-based photosensitive adhesive paste is 1000-2000 mPa·s, and the solid content is 30-50wt%.

[0008] Furthermore, the velvet fiber is a polyamide or polyester microfiber with a cross-shaped or Y-shaped cross section and a fineness of 0.05-0.2D.

[0009] Furthermore: after the ultraviolet curing treatment in step (2), a heat treatment is also performed: the material is placed in an environment of 100-130℃ for 2-5 minutes to promote the formation of a stable cross-linked structure between the velvet fibers and the fiber-skeleton interface of the water-based photosensitive adhesive paste.

[0010] Furthermore, the average particle size of the PVA microspheres is 5-20 μm.

[0011] Furthermore, the melt spinning temperature is 190-210℃.

[0012] Furthermore, the porosity of the elastic microporous framework is greater than 80%.

[0013] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows: 1. This application achieves cleaner production by using a process that combines an elastic microporous skeleton with suede fibers and adhesive paste, replacing the traditional high-pollution DMF solvent impregnation process and the destructive mechanical abrasion process. The suede obtained has a complete and strong structure because its fibers are directly embedded in the skeleton. In addition, the high porosity of the skeleton gives the product better air permeability.

[0014] 2. Through specific warm water immersion treatment, PVA microspheres, which act as pore-forming agents, can be dissolved and removed, thereby forming uniform and interconnected micron-sized pores in situ within the TPU fiber network.

[0015] 3. The water-based photosensitive adhesive paste does not contain organic solvents, making it relatively environmentally friendly and safe. The appropriate solid content and viscosity ensure its good atomization performance and penetration. The photoinitiator ensures rapid curing and shaping, while the wetting and leveling agent and defoamer ensure the uniformity of the coating. The thickener can control the penetration depth of the paste in the skeleton, thereby achieving strong bonding while maintaining the softness and elasticity of the skeleton to a large extent.

[0016] 4. Using ultra-fine fibers with irregular cross-sections such as cross-shaped or Y-shaped, compared with round cross-section fibers, it can provide a fuller and softer suede feel at the same fineness. The extremely fineness (0.05-0.2D) ensures the delicacy and high-end texture of the suede, making its feel close to that of natural high-grade suede.

[0017] 5. Heat treatment after UV curing can further drive the thermal movement and interaction of polymer chain segments in the adhesive slurry, promote the further cross-linking of unreacted functional groups, thereby significantly enhancing the internal strength of the adhesive layer and its interfacial bonding force with the skeleton and fibers, and ultimately improving the durability, anti-pilling and anti-friction properties of the velvet layer. Detailed Implementation

[0018] Example 1

[0019] A method for preparing thin imitation microfiber suede includes the following preparation steps: (1) Preparation of elastic microporous skeleton: thermoplastic polyurethane particles and PVA microspheres with an average particle size of 5 μm are mixed at a weight ratio of 80:20 and melt-spun into composite fibers at a temperature of 190℃. Then, a fiber web is formed by nonwoven technology and the fiber web is hot-pressed and bonded. The fiber web is then immersed in warm water at 60-80℃ for 20-30 minutes and then dried to form an elastic microporous skeleton with a three-dimensional porous network. The porosity of the elastic microporous skeleton is greater than 80%. (2) Electrostatic flocking: Polyamide microfibers with a fineness of 0.05D and cross-section are injected together with atomized water-based photosensitive adhesive paste into a high-voltage electrostatic field, so that the two are deposited together on the surface of the elastic microporous skeleton in the electrostatic field. The electrostatic field voltage is controlled at 40 kV and the electrode spacing is 10 cm. The flocked fibers are implanted into the skeleton at 60°, and the water-based photosensitive adhesive paste covers the fiber roots and penetrates into the surface of the skeleton. Then, ultraviolet curing treatment is performed to form a stable flocked layer on the skeleton. During hot pressing, a hot press roller with a micro-protrusion structure on the surface is used to press the fiber web at 160°C and 0.2MPa for 0.5s. After the pressing process, a fiber web with localized adhesion on the surface is obtained. The water-based photosensitive adhesive paste is composed of the following raw materials in parts by weight: 50 parts water-based polyurethane dispersion, 3 parts photoinitiator, 0.5 parts wetting and leveling agent, 1 part thickener, 0.3 parts defoamer, and 20 parts deionized water. The viscosity of the water-based photosensitive adhesive paste is 1000 mPa·s, and the solid content is 30 wt%. The specific process of UV curing is as follows: The flocked skeleton material is immediately transferred to a UV curing device equipped with a medium-pressure mercury lamp (main wavelength 365nm) for curing. Curing is carried out under a nitrogen atmosphere to eliminate the oxygen inhibition effect. The UV light intensity is set to 100 mW / cm². 2 The material spends 2 seconds in the light-exposed area (i.e., curing time). After curing, a non-sticky preliminary solidified layer forms on the material surface. (3) Heat treatment: The material is placed in an environment of 100°C for 2 minutes to promote the formation of a stable cross-linked structure between the velvet fibers and the fiber-skeleton interface of the water-based photosensitive adhesive paste.

[0020] Example 2 A method for preparing thin imitation microfiber suede includes the following preparation steps: (1) Preparation of elastic microporous skeleton: thermoplastic polyurethane particles and PVA microspheres with an average particle size of 10 μm were mixed at a weight ratio of 83:17 and melt-spun into composite fibers at a melt spinning temperature of 200℃. Then, a fiber web was formed by non-woven technology and the fiber web was hot-pressed and bonded. The fiber web was then immersed in warm water at 70℃ for 25 min and then dried to form an elastic microporous skeleton with a three-dimensional porous network. The porosity of the elastic microporous skeleton is greater than 80%. (2) Electrostatic flocking: Polyester microfibers with a fineness of 0.1D and atomized water-based photosensitive adhesive paste are injected into a high-voltage electrostatic field, so that the two are deposited together on the surface of the elastic microporous skeleton in the electrostatic field. The electrostatic field voltage is controlled at 60 kV and the electrode spacing is 20 cm. The flocked fibers are implanted into the skeleton at 85°, and the water-based photosensitive adhesive paste covers the fiber roots and penetrates into the surface of the skeleton. Then, ultraviolet curing treatment is performed to form a stable flocked layer on the skeleton. During hot pressing, a hot press roller with a micro-protruding structure on the surface is used to press the fiber web at 170°C and 0.4MPa for 0.8s. After the pressing process, a fiber web with localized adhesion on the surface is obtained.

[0021] The water-based photosensitive adhesive paste is composed of the following raw materials in parts by weight: 60 parts of water-based polyurethane dispersion, 4.5 parts of photoinitiator, 1.7 parts of wetting and leveling agent, 1.5 parts of thickener, 0.5 parts of defoamer, and 30 parts of deionized water. The viscosity of the water-based photosensitive adhesive paste is 1500 mPa·s, and the solid content is 40wt%.

[0022] (3) Heat treatment: The material is placed in an environment of 120°C for 3.5 min to promote the formation of a stable cross-linking structure between the velvet fibers and the fiber-skeleton interface of the water-based photosensitive adhesive paste.

[0023] Example 3 A method for preparing thin imitation microfiber suede includes the following preparation steps: (1) Preparation of elastic microporous skeleton: thermoplastic polyurethane particles and PVA microspheres with an average particle size of 20 μm are mixed at a weight ratio of 85:15 and melt-spun into composite fibers at a temperature of 210°C. The fibers are then formed into a web by nonwoven technology and hot-pressed together. The web is then immersed in warm water at 80°C for 30 min and dried to form an elastic microporous skeleton with a three-dimensional porous network. The porosity of the elastic microporous skeleton is greater than 80%. (2) Electrostatic flocking: Polyester microfibers with a fineness of 0.2D and Y-shaped cross-section are injected together with atomized water-based photosensitive adhesive paste into a high-voltage electrostatic field, so that the two are deposited together on the surface of the elastic microporous skeleton in the electrostatic field. The electrostatic field voltage is controlled at 80 kV and the electrode spacing is 30 cm. The flocked fibers are implanted into the skeleton at 90°, and the water-based photosensitive adhesive paste covers the fiber roots and penetrates into the surface of the skeleton. Then, ultraviolet curing treatment is performed to form a stable flocked layer on the skeleton. During hot pressing, a hot press roller with a micro-protrusion structure on the surface is used to press the fiber web at 180°C and 0.6MPa for 1 second. After the pressing process, a fiber web with localized adhesion on the surface is obtained. The water-based photosensitive adhesive paste is composed of the following raw materials in parts by weight: 70 parts water-based polyurethane dispersion, 6 parts photoinitiator, 3 parts wetting and leveling agent, 2 parts thickener, 0.8 parts defoamer, and 45 parts deionized water. The viscosity of the water-based photosensitive adhesive paste is 2000 mPa·s, and the solid content is 50 wt%. (3) Heat treatment: The material is placed in an environment of 130°C for 5 minutes to promote the formation of a stable cross-linked structure between the velvet fibers and the fiber-skeleton interface of the water-based photosensitive adhesive paste.

[0024] The properties of the thin imitation microfiber suede leather obtained by the preparation methods of Examples 1 to 3 of this application were tested, and the results are shown in the table below:

[0025] All three examples of the product demonstrate the advantages of being ultra-thin, lightweight, and highly environmentally friendly, thus replacing the traditional solvent-based impregnation and sanding processes.

[0026] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for preparing thin imitation microfiber suede, characterized in that, The preparation steps include the following: (1) Preparation of elastic microporous skeleton: thermoplastic polyurethane particles and PVA microspheres are mixed at a weight ratio of 80-85:15-20, and composite fibers are produced by melt spinning. Then, a fiber web is formed by nonwoven technology, and the fiber web is hot-pressed to form an elastic microporous skeleton with a three-dimensional porous network. (2) Electrostatic flocking: The flocked fibers and atomized water-based photosensitive adhesive paste are injected into a high-voltage electrostatic field, so that the two are deposited together on the surface of the elastic microporous skeleton in the electrostatic field. The electrostatic field voltage is controlled at 40-80 kV and the electrode spacing is 10-30 cm. The flocked fibers are implanted into the skeleton at 60-90°, and the water-based photosensitive adhesive paste covers the fiber roots and penetrates into the surface of the skeleton. Then, ultraviolet curing treatment is performed to form a stable flocked layer on the skeleton. During hot pressing, a hot press roller with a micro-protruding structure on the surface is used to press the fiber web at 160-180℃ and 0.2-0.6MPa for 0.5-1s. After the pressing process, a fiber web with localized adhesion on the surface is obtained.

2. The method for preparing a thin imitation microfiber suede according to claim 1, characterized in that: In step (1), after hot pressing and bonding, the fiber web is immersed in warm water at 60-80℃ for 20-30 minutes and then dried.

3. The method for preparing a thin imitation microfiber suede according to claim 1, characterized in that: The water-based photosensitive adhesive paste is composed of the following raw materials in parts by weight: 50-70 parts of water-based polyurethane dispersion, 3-6 parts of photoinitiator, 0.5-3 parts of wetting and leveling agent, 1-2 parts of thickener, 0.3-0.8 parts of defoamer, and 20-45 parts of deionized water. The viscosity of the water-based photosensitive adhesive paste is 1000-2000 mPa·s, and the solid content is 30-50wt%.

4. The method for preparing a thin imitation microfiber suede according to claim 1, characterized in that: The velvet fibers are polyamide or polyester microfibers with a cross-shaped or Y-shaped cross section and a fineness of 0.05-0.2D.

5. The method for preparing a thin imitation microfiber suede according to claim 1, characterized in that: After the UV curing treatment in step (2), a heat treatment is also performed: the material is placed in an environment of 100-130℃ for 2-5 minutes to promote the formation of a stable cross-linked structure between the velvet fibers and the fiber-skeleton interface of the water-based photosensitive adhesive paste.

6. A method for preparing a thin imitation microfiber suede according to claim 1, characterized in that: The average particle size of the PVA microspheres is 5-20 μm.

7. The method for preparing a thin imitation microfiber suede according to claim 1, characterized in that: The melt spinning temperature is 190-210℃.

8. The method for preparing a thin imitation microfiber suede according to claim 1, characterized in that: The porosity of the elastic microporous framework is greater than 80%.

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