Preparation method of high-strength and high-wear-resistance superfine fiber synthetic leather for massage chair

Abstract

The invention discloses a preparation method of high-strength and high-wear-resistance superfine fiber synthetic leather for a massage armchair, which is characterized in that the synthetic leather is based on an electrostatic spinning superfine fiber technology, polyamide acid (PAA) is used as a spinning precursor, DMF (Dimethyl Formamide) is used as a solvent, and a uniform and continuous superfine fiber membrane is prepared under a 25 kV high-voltage electric field; then through high-temperature curing and cross-linking, PAA is converted into high-strength polyamide (PA), meanwhile, a superfine fiber network structure is kept, and the mechanical property and the fatigue resistance are improved. The surface layer adopts the wear-resistant waterborne polyurethane elastomer, and nano silicon dioxide and a fluorosilicone modification additive are added, so that the surface wear resistance, the pollution resistance and the flexibility are improved. The obtained synthetic leather has high modulus, high tensile strength and excellent wear resistance, and is suitable for the high-end fields of massage chairs, automobile seats, sporting goods and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional synthetic leather materials technology, and specifically relates to a method for preparing high-strength, high-wear-resistant microfiber synthetic leather for massage chairs. Background Technology

[0002] Under repeated squeezing, friction, and load, the leather used for the surface of a massage chair must simultaneously possess the following properties:

[0003] (1) High tensile strength and tear strength;

[0004] (2) Excellent wear resistance and resistance to repeated fatigue;

[0005] (3) Good feel and flexibility;

[0006] (4) Stain-resistant, sweat-resistant, and aging-resistant properties.

[0007] While traditional PU synthetic leather possesses a certain degree of softness, its mechanical properties, particularly abrasion resistance and fatigue life, are limited, making it difficult to meet the requirements of high-load applications like massage chairs. Microfiber synthetic leather has attracted attention due to its superior mechanical properties resulting from its three-dimensional network fiber structure. Polyamide (PA) exhibits high strength, high toughness, and abrasion resistance, but direct electrospinning of PA is challenging. Polyamic acid (PAA), on the other hand, has good spinnability but lacks sufficient mechanical properties and is not solvent-resistant. Therefore, there is an urgent need to develop a high-performance microfiber synthetic leather system that combines the spinnability of PAA with the high strength of PA, further enhanced by a wear-resistant polyurethane surface layer to synergistically improve performance. Summary of the Invention

[0008] This invention provides a method for preparing high-strength, high-wear-resistant microfiber synthetic leather for massage chairs, solving the problems of insufficient strength, inadequate wear resistance, and limited lifespan of existing synthetic leather.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing high-strength, high-wear-resistant microfiber synthetic leather for massage chairs includes the following steps:

[0011] Step 1: Preparation of the ultrafine fiber skeleton:

[0012] Step 11, PAA solution preparation:

[0013] PAA solution was prepared by polymerization of diacid anhydrides and diamines in DMF;

[0014] Step 12: Preparation of electrospun ultrafine fiber membrane:

[0015] The PAA solution was placed in an electrospinning device to form an electrospun ultrafine fiber network membrane with a diameter of 200–800 nm.

[0016] Step 13: High-temperature curing and conversion of microfibers:

[0017] The electrospun ultrafine fiber network membrane was subjected to a dehydration imidization reaction at 250–350°C to obtain a PA ultrafine fiber membrane.

[0018] Step 2, Functional layer preparation:

[0019] Step 21, Intermediate layer coating:

[0020] Solvent-free polyurethane resin is selected as the intermediate layer. The hydroxyl value of the intermediate layer resin is 90-97 and the NCO equivalent is 270-290. It is applied to the surface of the PA microfiber membrane by a doctor blade and then heated and cured to form a high-solids polyurethane intermediate layer.

[0021] Step 22, Preparation of surface layer PU slurry:

[0022] Take a high wear-resistant waterborne polyurethane emulsion, add nano-SiO2 and fluorosilicone modifiers and mix well to obtain the surface layer PU slurry.

[0023] Step 23, Coating and Curing:

[0024] The surface layer PU slurry is uniformly coated onto the surface of the high-solids polyurethane intermediate layer and dried at 80–120°C to form a dense and highly wear-resistant surface layer, thus obtaining the microfiber synthetic leather.

[0025] In the above technical solution, in step 11, the solid content of the PAA solution is 12–18%.

[0026] In the above technical solution, in step 12, the positive voltage is 25 kV and the distance between the collecting plates is 15–20 cm.

[0027] In the above technical solution, in step 22, the hard segment content of the high wear-resistant waterborne polyurethane emulsion is 35–45%.

[0028] In the above technical solution, in step 22, the mass percentage of the high wear-resistant waterborne polyurethane emulsion is 95%, the mass percentage of nano-SiO2 is 2–5%, and the mass percentage of the fluorosilicone modifier is 0.3–1%.

[0029] The beneficial effects of this invention are as follows: By combining a PA microfiber reinforcing film with a breathable cushioning base and then performing embossing and shaping processes, a high-strength, wear-resistant synthetic leather suitable for massage chairs is obtained. The microfiber synthetic leather of this invention has the following advantages: Significantly enhanced strength: The three-dimensional network of PA microfibers formed by electrospinning significantly improves tensile and tear strength. Extremely high wear resistance: The nano-SiO2+ high-wear-resistant PU structure enhances the wear resistance of the synthetic leather by 2–5 times. Excellent flexibility and feel: The microfiber structure and elastic PU surface layer together ensure a soft feel, suitable for the skin contact experience of massage chairs. High durability: It has fatigue resistance, sweat resistance, oil resistance, and anti-aging functions, making it suitable for long-term mechanical friction environments. Environmentally friendly manufacturing process: It uses a water-based PU surface layer, reducing volatile organic compound emissions. Detailed Implementation

[0030] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below in conjunction with specific embodiments. This invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art. This invention will be defined only by the claims.

[0031] This invention provides a method for preparing high-strength, high-wear-resistant microfiber synthetic leather for massage chairs, comprising the following steps:

[0032] I. Preparation of the ultrafine fiber skeleton

[0033] 1. Preparation of polyamic acid (PAA) solution

[0034] Polyamic acid (PAA) solution was prepared by polymerizing diacid anhydrides and diamines in DMF; the solid content was controlled at 12–18%, and the viscosity was suitable for high-voltage electrospinning.

[0035] 2. Preparation of electrospun ultrafine fiber membranes

[0036] A polyamic acid (PAA) solution is placed in an electrospinning apparatus with a positive voltage of 25 kV and a collection plate distance of 15–20 cm to form an electrospun ultrafine fiber network membrane with an average diameter of 200–800 nm.

[0037] 3. High-temperature curing and conversion of microfibers

[0038] Electrospun microfiber network membranes were subjected to dehydration imidization at 250–350°C to complete the chemical transformation from PAA to polyamide (PA), thus preparing PA microfiber membranes. The fiber strength was significantly improved, forming a three-dimensional structure similar to the bundled fibers of natural leather. Impregnation with PVC significantly enhanced the feel and abrasion resistance.

[0039] II. Functional Layer Preparation

[0040] 1. Intermediate layer coating:

[0041] Solvent-free polyurethane resin is selected as the adhesive layer. The intermediate layer resin has a hydroxyl value of 90-97 and an NCO equivalent of 270-290. It is applied to the surface of the PA microfiber membrane by a doctor blade with a blade depth of 0.2-0.4 mm. It is then heated and cured to form a high-solids polyurethane intermediate layer.

[0042] 2. Preparation of surface layer PU slurry:

[0043] Using 95% high abrasion-resistant waterborne polyurethane emulsion (hard segment content 35–45%), 2–5 wt% nano-SiO2 is added to improve abrasion resistance, strength and scratch resistance, and 0.3–1 wt% fluorosilicone modifier (e.g., polytrifluoropropylmethylsiloxane) is added to improve stain resistance, water resistance and oil resistance. Finally, the mixture is mixed to obtain the surface PU slurry.

[0044] 3. Coating and curing:

[0045] The surface layer of PU paste is evenly coated onto the surface of the intermediate layer and dried at 80–120°C to form a dense and highly wear-resistant surface layer, thus producing microfiber synthetic leather.

[0046] This invention utilizes high-voltage electrospinning to form a uniform and continuous ultrafine fiber membrane, which is then subjected to high-temperature dehydration and imidization to transform it into PA ultrafine fibers, possessing both a fine structure and high strength. The constructed three-dimensional reinforced network structure of the PA ultrafine fiber membrane provides a strong and tough three-dimensional network skeleton, giving the material high tensile strength, high tear resistance, and fatigue resistance. The wear-resistant waterborne polyurethane surface treatment uses a high-strength, wear-resistant waterborne polyurethane elastomer as the surface layer; nano-silica is introduced to improve wear resistance and mechanical strength; fluorosilicone additives enhance stain resistance, aging resistance, and friction coefficient control. This results in a high-strength, high-wear-resistant, and flexible synthetic leather material combining a PA ultrafine fiber network and a PU surface layer, giving the material strength, wear resistance, flexibility, and a comfortable feel.

[0047] Example 1

[0048] (1) Preparation of ultrafine fiber skeleton

[0049] 1) Preparation of PAA solution

[0050] Pyromellitic dianhydride and p-phenylenediamine were added to N,N-dimethylformamide (DMF) in a molar ratio of 1:1 and stirred at room temperature under nitrogen protection to obtain a polyamic acid (PAA) solution; the solid content of the solution was controlled to be 15%.

[0051] 2) Preparation of electrospun ultrafine fiber membranes

[0052] The above PAA solution was placed in an electrospinning apparatus, a positive voltage of 25 kV was applied, the distance from the nozzle to the collecting plate was 18 cm, and continuous spinning was performed to obtain an ultrafine fiber network membrane with an average diameter of about 400 nm.

[0053] 3) High-temperature curing and conversion of microfibers

[0054] The electrospun PAA microfiber membrane was heated sequentially at 250 °C, 300 °C and 330 °C in air to complete the dehydration imidization reaction, thus obtaining a high-strength polyamide (PA) microfiber membrane.

[0055] (2) Functional layer preparation

[0056] 1) Intermediate layer coating

[0057] Solvent-free polyurethane resin was selected as the adhesive layer, and the intermediate layer resin had a hydroxyl value of 93 and an NCO equivalent of 280. It was coated onto the surface of the PA microfiber membrane using a doctor blade with a blade depth of 0.3 mm, and then heated and cured to form a high-solids polyurethane intermediate layer.

[0058] 2) Preparation and coating of surface PU slurry

[0059] Take 95% high-wear-resistant waterborne polyurethane emulsion (hard segment content 40%), add 4.5 wt% nano-SiO2 and 0.5 wt% fluorosilicone modifier, and fully disperse and mix. The resulting surface PU slurry is evenly coated onto the surface of the intermediate layer and dried at 100 ℃ to form a film. Finally, high-strength, high-wear-resistant microfiber synthetic leather for massage chairs is obtained.

[0060] Example 2

[0061] Synthetic leather with different nanofiller contents

[0062] Compared with Example 1, the difference is that the amount of nano-SiO2 added in the surface PU slurry is 4.2 wt%;

[0063] The amount of fluorosilicone modifier added was 0.8 wt%. The resulting synthetic leather surface abrasion resistance was further improved, while maintaining good flexibility and stain resistance.

[0064] Example 3

[0065] Synthetic leather with different microfiber structural parameters

[0066] Compared with Example 1, the differences are: the solid content of the PAA solution is 12%; the average diameter of the fibers obtained by electrospinning is about 700 nm; and the maximum temperature of dehydration imidization is 350 °C.

[0067] The resulting synthetic leather has improved overall modulus and tensile strength, making it suitable for high-load massage chair parts.

[0068] Comparative Example 1

[0069] Synthetic leather that has not undergone high-temperature imidization treatment

[0070] Except for omitting the high-temperature dehydration and imidization treatment of PAA microfiber in step (1), the remaining steps are the same as in Example 1.

[0071] The resulting synthetic leather still contains microfibers with a PAA structure, which are significantly lacking in heat resistance and mechanical strength. It is prone to breakage under repeated friction and bending conditions, and its durability is significantly lower than that of Example 1.

[0072] Comparative Example 2

[0073] Synthetic leather without the introduction of microfiber skeleton

[0074] Without performing the electrospinning step, a solvent-free intermediate layer and a wear-resistant PU surface layer are directly coated onto a regular nonwoven fabric substrate in sequence, and the remaining steps are the same as in Example 1.

[0075] The resulting synthetic leather exhibited significantly reduced tensile and tear strength, and its wear life was significantly shorter than that of Example 1, making it difficult to meet the requirements of long-term high-load use of massage chairs.

[0076] Comparative Example 3

[0077] Synthetic leather without added nano-SiO2

[0078] Except for the absence of nano-SiO2 in the surface PU slurry, the other steps are the same as in Example 1.

[0079] The resulting synthetic leather has acceptable flexibility, but its wear resistance is significantly reduced. The surface is prone to wear under high-frequency friction conditions, indicating that nano-SiO2 has a significant effect on improving wear resistance.

[0080] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing high-strength, high-wear-resistant microfiber synthetic leather for massage chairs, characterized in that: Includes the following steps: Step 1: Preparation of the ultrafine fiber skeleton: Step 11, PAA solution preparation: PAA solution was prepared by polymerization of diacid anhydrides and diamines in DMF; Step 12: Preparation of electrospun ultrafine fiber membrane: The PAA solution was placed in an electrospinning device to form an electrospun ultrafine fiber network membrane with a diameter of 200–800 nm. Step 13: High-temperature curing and conversion of microfibers: The electrospun ultrafine fiber network membrane was subjected to a dehydration imidization reaction at 250–350°C to obtain a PA ultrafine fiber membrane. Step 2, Functional layer preparation: Step 21, Intermediate layer coating: Solvent-free polyurethane resin is selected as the intermediate layer. The hydroxyl value of the intermediate layer resin is 90-97 and the NCO equivalent is 270-290. It is applied to the surface of the PA microfiber membrane by a doctor blade and then heated and cured to form a high-solids polyurethane intermediate layer. Step 22, Preparation of surface layer PU slurry: Take a high wear-resistant waterborne polyurethane emulsion, add nano-SiO2 and fluorosilicone modifiers and mix well to obtain the surface layer PU slurry. Step 23, Coating and Curing: The surface layer PU slurry is uniformly coated onto the surface of the high-solids polyurethane intermediate layer and dried at 80–120°C to form a dense and highly wear-resistant surface layer, thus obtaining the microfiber synthetic leather.

2. The preparation method according to claim 1, characterized in that: In step 11, the solid content of the PAA solution is 12–18%.

3. The preparation method according to claim 1, characterized in that: In step 12, the positive voltage is 25 kV and the distance between the collecting plates is 15–20 cm.

4. The preparation method according to claim 1, characterized in that: In step 22, the hard segment content of the high abrasion-resistant waterborne polyurethane emulsion is 35–45%.

5. The preparation method according to claim 1, characterized in that: In step 22, the mass percentage of the high wear-resistant waterborne polyurethane emulsion is 95%, the mass percentage of nano-SiO2 is 2–5%, and the mass percentage of the fluorosilicone modifier is 0.3–1%.