Preparation process of full-water-based environment-friendly microfiber synthetic leather

Abstract

The invention provides a preparation process of full-water-based environment-friendly microfiber synthetic leather, which comprises the following steps of: blending and melting polycaprolactam serving as an island phase and water-soluble polycarbonate serving as a marine phase to prepare sea-island fibers, and performing wet impregnation, solidification, water-washing decrement splitting and post-treatment to obtain the full-water-based environment-friendly microfiber synthetic leather. The full-water-based environment-friendly microfiber synthetic leather which is excellent in performance and environment-friendly is prepared through three innovations of creatively using heat-resistant water-soluble polycarbonate as a marine facies, using functional resin and using a double-hole mechanism. A solvent system is replaced by a full-water-based process, and REACH and OEKO-TEX standards are met; through material compounding and structural design, the industrial problems of water-soluble microfiber width shrinkage, difficult stripping and the like are solved, and meanwhile zero emission of VOC is achieved; the prepared full-water-based environment-friendly microfiber synthetic leather is suitable for the high-end fields of automobiles, clothes and the like.

Description

Technical Field

[0001] The present invention relates to the field of making ultra-fine leather, and particularly relates to a preparation process for a fully water-based environmentally friendly ultra-fine synthetic leather.

Background Art

[0002] Currently, the synthetic leather industry is facing the dual pressures of increasingly strict environmental regulations and consumers' demand for healthy materials. Synthetic leather usually uses solvent-based polyurethane resin or water-based polyurethane resin. The solvent-based polyurethane resin process has problems of VOC emissions and solvent residues due to the use of toxic solvents such as DMF (the EU requires DMF residue ≤ 10 ppm). Although water-based polyurethane resin is environmentally friendly, the following technical problems usually exist in the process of making water-based ultra-fine synthetic leather:

[0003] 1. The sea-island fiber is made of a PA / PVA system. Since the heat-resistant temperature of the sea component PVA is less than 95 °C and cannot adapt to the high-temperature setting process (the high-temperature setting requirement is ≥ 120 °C), when the ultra-fine base fabric is opened by hot water, the fiber structure is easily damaged due to the swelling of hydrophilic groups, resulting in a width shrinkage rate of the ultra-fine base fabric higher than 30%, and poor dimensional stability; at the same time, the PA fiber of the island component has poor hygroscopicity, resulting in uneven fiber opening.

[0004] 2. During the impregnation process, there is a lack of an effective pore formation control mechanism. The formation of micropores depends on mechanical foaming, with a low porosity (< 40%, and the solvent method can reach 65%), and at the same time, the connectivity of the pore structure is poor (the closed pore rate > 70%), affecting the air permeability and softness of the finished product.

[0005] 3. After filling with water-based polyurethane resin, it is easy to form lumps, and the adhesion between the fiber layer and the resin layer is too strong, with an interlayer peel strength > 8 N / cm (the standard requirement is 3 - 5 N / cm), resulting in difficulty in separation during the peel test of the finished leather; in addition, after the water-based polyurethane resin solidifies, the crosslinking density is low, resulting in insufficient tensile resistance (< 12 MPa, such as the requirement for automotive interiors is ≥ 15 MPa).

[0006] In view of this, the inventor of this case conducted in-depth research on the above problems, and thus this case was born.

Summary of the Invention

[0007] The present invention aims to solve the above technical problems existing in the preparation process of water-based ultra-fine synthetic leather in the prior art, and provides a preparation process for a fully water-based environmentally friendly ultra-fine synthetic leather. The entire production process does not use organic solvents, and through the innovative use of heat-resistant water-soluble polycarbonate as the sea phase, functional resin, and double-pore mechanism, a fully water-based environmentally friendly ultra-fine synthetic leather with excellent performance and environmental protection is obtained.

[0008] The present invention is implemented as follows: A preparation process for a fully water-based environmentally friendly ultra-fine synthetic leather includes the following steps:

[0009] (1) Melt spinning: Prepare sea-island fibers by melt blending 40 - 70% polycaprolactam as the island phase and 30 - 60% water-soluble polycarbonate as the sea phase; Needle-punch and shape the sea-island fibers to obtain the base fabric;

[0010] (2) Wet impregnation: Perform wet impregnation treatment on the base fabric to obtain the impregnated base fabric; The aqueous impregnating material includes pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent; The mass ratio of pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent is 100:(15 - 25):(1 - 3):(2 - 4); The water-soluble filler is a mixture of 40 - 60% water-soluble foaming agent and 40 - 60% PVA microspheres;

[0011] (3) Coagulation: Coagulate the impregnated base fabric with an aqueous citric acid solution at a temperature of 20 - 30°C;

[0012] (4) Washing and weight reduction for fiber opening: Perform staged temperature-rising washing and fiber opening on the coagulated base fabric, and cooperate with a low-pressure roller. During the repeated washing and rolling process, wash out the water-soluble filler and water-soluble polycarbonate in the base fabric;

[0013] (5) Post-treatment: After the fiber-opened base fabric is shaped, dried, oiled, and buffed, obtain a fully aqueous environmentally friendly superfine synthetic leather.

[0014] Further, the melt spinning includes the following stages:

[0015] (1.1) Put polycaprolactam chips into a vacuum drying oven and dry for 2 - 3 h at a drying temperature of 80 - 100°C. The moisture content of the dried polycaprolactam is below 500 ppm; Place the water-soluble polycarbonate in a vacuum drying oven and dry for 8 - 10 hours at a drying temperature of 45 - 55°C. The moisture content of the dried water-soluble polyester is below 20 ppm;

[0016] (1.2) Mix the dried polycaprolactam chips and water-soluble polycarbonate, and send them into a single-screw extruder for melt blending. The heating temperature of the four zones of the single-screw extruder is 210 - 245°C, and then spin through a spinneret. The spinning temperature is 230 - 270°C. During the spinning process, perform horizontal uniform air supply cooling to obtain primary polycaprolactam / water-soluble polycarbonate blended fibers;

[0017] (1.3) After the primary polycaprolactam / water-soluble polycarbonate blended fibers are oiled in an oil bath, pass through a multi-stage hot drawing godet roller, perform water bath drawing at 40 - 50°C with a drawing ratio of 4.0 - 5.0 times, and then curl through a coiler with 15 - 21 curls per 25 mm; Then perform relaxation heat setting in five zones at 65°C, 60°C, 55°C, 50°C, and 50°C, and finally cut to obtain sea-island fibers with a fineness of 6 - 8 dtex.

[0018] Further, in step (1), in the shaping stage, the density of the base fabric is 0.28 - 0.35 g / cm 3 .

[0019] Further, the water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 10 - 15 wt% acrylic oligomer, and the proportion of sodium dodecyl sulfate as a surfactant in the water-soluble foaming agent is 1 - 3%.

[0020] Further, the pore diameter of the PVA microspheres is 10 - 50 μm.

[0021] Further, the solid content of the aqueous impregnating material is 45 - 55% and the viscosity is 2000 - 3000 cps; the prepared aqueous impregnating material is injected into the impregnating tank, and the base fabric is impregnated and rolled in the impregnating tank with an impregnating pressure of 1.8 - 2.3 kg, a gap of 1.3 - 1.4 mm, and a material temperature of 20 - 30°C, and the impregnating rolling rate is controlled at 50 - 70%.

[0022] Further, in the solidification step, the impregnated base fabric is solidified at a temperature of 20 - 30°C for a use path length of 80 - 120 m in a 15% by mass aqueous citric acid solution, and the pH of the aqueous citric acid solution is < 5.

[0023] Further, the water washing and fiber opening in stages is carried out through eight water washing tanks, and the water temperatures are sequentially controlled as follows: two tanks at 30 - 40°C, two tanks at 40 - 50°C, two tanks at 60 - 75°C, and two tanks at 85 - 95°C.

[0024] Further, the low-pressure roll is 2 - 4 kg / cm 2 .

[0025] The advantages of the present invention are as follows: By pioneering the use of heat-resistant water-soluble polycarbonate (WSPC) as the sea phase, using a functional resin (PH-responsive waterborne polyurethane), and a dual-pore mechanism (the water-soluble foaming agent dissolves to form pores and the PVA microspheres decompose to form closed pores), an environmentally friendly all-aqueous ultra-fine synthetic leather with excellent performance is prepared. The all-aqueous process replaces the solvent system and meets the REACH and OEKO-TEX standards; through material compounding and structural design, industry problems such as the shrinkage of the water-soluble ultra-fine width and the difficulty in peeling are solved; the prepared all-aqueous environmentally friendly ultra-fine synthetic leather is suitable for high-end fields such as automobiles and clothing.

Specific Embodiments

[0026] In order to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0027] The present invention provides a preparation process for an all-aqueous environmentally friendly ultra-fine synthetic leather, including the following steps:

[0028] (1) Melt spinning: Island-phase sea-island fibers are prepared by melt blending 40 - 70% polycaprolactam (PA6) and 30 - 60% water-soluble polycarbonate (WSPC) as the sea-phase; the sea-island fibers are needled and shaped to obtain a base fabric. The heat resistance of the water-soluble polycarbonate is > 120 °C.

[0029] (2) Wet impregnation: The base fabric is subjected to wet impregnation treatment to obtain an impregnated base fabric; the aqueous impregnating material includes pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent; the mass ratio of the pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent is 100:(15 - 25):(1 - 3):(2 - 4); the water-soluble filler is a mixture of 40 - 60% water-soluble foaming agent and 40 - 60% PVA microspheres.

[0030] (3) Coagulation: The impregnated base fabric is coagulated using an aqueous citric acid solution at a temperature of 20 - 30 °C. The coagulation step triggers the self-crosslinking of the pH-responsive aqueous polyurethane, and the tensile strength of the microfiber synthetic leather is increased by about 30%.

[0031] (4) Water washing and fiber opening by weight reduction: The coagulated base fabric is subjected to stepwise temperature-rising water washing and fiber opening, in cooperation with a low-pressure roller (2 - 4 kg / cm 2 ). During the repeated water washing and rolling processes, the water-soluble filler and water-soluble polycarbonate in the base fabric are washed out. Through stepwise temperature-rising water washing and fiber opening in cooperation with a low-pressure roller, the fibers are thoroughly superfine while reducing fiber breakage during the fiber opening process and maintaining pore integrity.

[0032] (5) Post-treatment: After the fiber-opened base fabric is shaped, dried, oiled, and skived, a fully aqueous environmentally friendly microfiber synthetic leather is obtained. The tensile strength of the fully aqueous environmentally friendly microfiber synthetic leather is ≥ 15 MPa, the air permeability is ≥ 10000 mL / cm 2 ·h, the VOC emission is ≤ 50 μg / m 3 , and the DMF residue is not detected.

[0033] The preparation process of the fully aqueous environmentally friendly microfiber synthetic leather of the present invention innovatively uses heat-resistant water-soluble polycarbonate (WSPC) as the sea-phase, uses a functional resin (pH-responsive aqueous polyurethane), and a dual-pore mechanism (the water-soluble foaming agent dissolves to form pores and the PVA microspheres decompose to form closed pores) to prepare a fully aqueous environmentally friendly microfiber synthetic leather with excellent performance and environmental friendliness. The fully aqueous process replaces the solvent system and complies with REACH and OEKO-TEX standards; through material compounding and structural design, industry problems such as the width shrinkage and peeling difficulty of water-soluble microfibers are solved; the prepared fully aqueous environmentally friendly microfiber synthetic leather is suitable for high-end fields such as automobiles and clothing.

[0034] Preferably, in step (1), in the needling stage, a high-needling and high-needle-density needling process is adopted, which further improves the problem of width contraction; in the setting stage, the density of the base fabric is 0.28 - 0.35 g / cm 3 .

[0035] Preferably, the breaking strength of the sea-island fiber prepared by melt spinning reaches ≥3.1 cN / dtex. The melt spinning includes the following stages:

[0036] (1.1) The polycaprolactam chips are placed in a vacuum drying oven and dried for 2 - 3 h at a drying temperature of 80 - 100°C. The moisture content of the dried polycaprolactam is below 500 ppm. The water-soluble polycarbonate is placed in a vacuum drying oven and dried for 8 - 10 h at a drying temperature of 45 - 55°C. The moisture content of the dried water-soluble polyester is below 20 ppm.

[0037] (1.2) The dried polycaprolactam chips and the water-soluble polycarbonate are mixed and fed into a single-screw extruder for melt blending. The heating temperature of the four zones of the single-screw extruder is 210 - 245°C, and then spinning is carried out through a spinneret. The spinning temperature is 230 - 270°C. During the spinning process, lateral uniform air supply cooling is carried out to obtain the as-spun polycaprolactam / water-soluble polycarbonate blend fiber.

[0038] (1.3) After the as-spun polycaprolactam / water-soluble polycarbonate blend fiber is oiled in an oil bath, it passes through multi-stage hot drawing godet rolls, and is drawn in a 40 - 50°C water bath with a draw ratio of 4.0 - 5.0 times, and then crimped by a winder with 15 - 21 crimps per 25 mm; then it is subjected to relaxation heat setting in five zones at 65°C, 60°C, 55°C, 50°C, and 50°C, and finally the obtained sea-island fiber with a fineness of 6 - 8 dtex is cut.

[0039] In the present invention, the pH-responsive waterborne polyurethane is used as the main resin and has good compatibility with fillers and additives. The pH-responsive waterborne polyurethane uses water as the dispersion medium and is an environmentally friendly polyurethane resin that contains no or only trace amounts of organic solvents. It combines the high mechanical properties (such as wear resistance and weather resistance) of traditional polyurethanes and environmental protection advantages. The pH-responsive waterborne polyurethane is composed of a hydrophobic chain segment (hard segment), a hydrophilic chain segment (soft segment), and a carboxylic acid group. By adjusting the ionization state of the carboxylic acid group, pH responsiveness is achieved, endowing the resin with pH sensitivity and having the functional characteristic of triggering changes in material properties with changes in the environmental pH value. Preferably, the simplified structural formula of the pH-responsive waterborne polyurethane is as follows:

[0040] -[O-C-NH-R-NH-C-O-(soft segment)]m-[O-C-NH-R’-NH-C-O-(hard segment)]n-side chain containing carboxylic acid group: -CH2-C(CH2OH)(COOH)-CH2-.

[0041] Preferably, the glass transition temperature Tg of the pH-responsive aqueous polyurethane is ≥130 °C to avoid insufficient heat resistance and shrinkage during high-temperature shaping.

[0042] When the water-soluble foaming agent is opened, it dissolves in water to form micron-sized pores (pore diameter 10 - 50 μm), and the porosity is increased to more than 60%. Preferably, the water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 10 - 15 wt% acrylic oligomer. Sodium dodecyl sulfate accounts for 1 - 3% in the water-soluble foaming agent as a surfactant, which can effectively reduce the surface tension of the resin. The 10 - 15 wt% acrylic oligomer acts as a foam stabilizer to delay the bubble rupture. If the acrylic oligomer is excessive (>15 wt%), it will cause too high viscosity of the system.

[0043] Preferably, the pore diameter of the PVA microspheres is 10 - 50 μm. Utilizing the characteristics that the aqueous resin is insoluble in water and PVA after solidification, at a washing temperature of 85 - 95 °C, the PVA microspheres are decomposed by washing to form a closed-cell structure, increasing the resilience of the base fabric. After drying, the PVA microspheres are thermally decomposed to form a closed-cell structure, enhancing the resilience of the microfiber synthetic leather.

[0044] Preferably, the aqueous thickener is cellulose ether, which can adjust the viscosity of the system and improve the wall-hanging property and bubble stability of the aqueous impregnating material.

[0045] Preferably, the aqueous reinforcing agent is a pre-dispersed nano-SiO2 slurry to enhance the hardness, wear resistance, and mechanical strength of the PU.

[0046] Preferably, the solid content of the aqueous impregnating material is 45 - 55% and the viscosity is 2000 - 3000 cps. The prepared aqueous impregnating material is injected into the impregnating tank, and the base fabric is impregnated and rolled in the impregnating tank at an impregnating pressure of 1.8 - 2.3 kg, a gap of 1.3 - 1.4 mm, and a material temperature of 20 - 30 °C. The impregnation rolling rate is controlled at 50 - 70%.

[0047] Preferably, in the solidification step, the impregnated base fabric is solidified at a temperature of 20 - 30 °C for a use path length of 80 - 120 m in a 15% mass percentage aqueous citric acid solution with a pH < 5. The solidification step triggers the self-crosslinking of the pH-responsive aqueous polyurethane, and the tensile strength of the microfiber synthetic leather is increased by about 30%.

[0048] Preferably, the water washing and fiber opening in stages is carried out through eight water washing tanks, and the water temperature is controlled in turn as follows: two tanks at 30 - 40 °C, two tanks at 40 - 50 °C, two tanks at 60 - 75 °C, and two tanks at 85 - 95 °C. By combining the water washing and fiber opening in stages with a low-pressure roller (2 - 4 kg / cm 2 ), the fibers are thoroughly superfine while reducing fiber breakage during the fiber opening process and maintaining the integrity of the pores.

[0049] The beneficial technical effects of the preparation process of the fully water-based environmentally friendly ultra-fine synthetic leather of the present invention are described below through several examples and comparative examples.

[0050] Example 1

[0051] A preparation process of fully water-based environmentally friendly ultra-fine synthetic leather includes the following steps:

[0052] (1) Melt spinning: Using 50% polycaprolactam as the island phase and 50% water-soluble polycarbonate as the sea phase to blend and melt to prepare sea-island fibers; Needling and shaping the sea-island fibers to obtain a base fabric; The melt spinning includes the following stages: (1.1) Put the polycaprolactam chips into a vacuum drying oven and dry for 3 hours, the drying temperature is 100 °C, and the moisture content of the dried polycaprolactam is below 500 ppm; The water-soluble polycarbonate is placed in a vacuum drying oven and dried for 10 hours, the drying temperature is 50 °C, and the moisture content of the dried water-based polyester is below 20 ppm. (1.2) Mix the dried polycaprolactam chips and water-soluble polycarbonate, send them into a single-screw extruder for melt blending, the heating temperature of the four zones of the single-screw extruder is 210-245 °C, and then spin through a spinneret, the spinning temperature is 250 °C, and horizontal uniform air supply cooling is carried out during the spinning process to obtain primary polycaprolactam / water-soluble polycarbonate blend fibers. (1.3) After the primary polycaprolactam / water-soluble polycarbonate blend fibers are oiled in an oil bath, they are then passed through a multi-stage hot drawing guide roller, stretched in a 40-50 °C water bath, the draw ratio is 4.0 times, and then curled by a winder, the number of curls is 15-21 per 25 mm; Then relax and heat set in five zones of 65 °C, 60 °C, 55 °C, 50 °C, and 50 °C, and finally cut to obtain sea-island fibers with a fineness of 6-8 dtex.

[0053] (2) Wet impregnation: Inject the prepared water-based impregnating material into the impregnating tank, and impregnate and roll the base fabric through an impregnating tank with an impregnating pressure of 1.8-2.3 kg, a gap of 1.3-1.4 mm, and a material temperature of 20-30 °C, and control the rolling liquid rate of impregnation at 60%; The water-based impregnating material includes a pH-responsive water-based polyurethane, a water-soluble filler, a water-based thickener, and a water-based strengthening agent; The mass ratio of the pH-responsive water-based polyurethane, the water-soluble filler, the water-based thickener, and the water-based strengthening agent is 100:20:2:3; The water-soluble filler is a mixture of 40% water-soluble foaming agent and 60% PVA microspheres; The water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 10 wt% acrylic oligomer, and the proportion of sodium dodecyl sulfate as a surfactant in the water-soluble foaming agent is 2%. The pore size of the PVA microspheres is 30 μm. The water-based thickener is cellulose ether, and the water-based strengthening agent is a pre-dispersed nano-SiO2 slurry. The solid content of the water-based impregnating material is 50% and the viscosity is 2500 cps.

[0054] (3) Coagulation: The impregnated base fabric is coagulated at a temperature of 25°C for a length of 100 m in a citric acid aqueous solution with a mass percentage of 15%, and the pH of the citric acid aqueous solution is 4.2.

[0055] (4) Water washing and fiber opening with weight loss: The coagulated base fabric is subjected to stepwise temperature-rising water washing and fiber opening. The stepwise temperature-rising water washing and fiber opening is carried out through eight water washing tanks, and the water temperature is controlled in sequence as follows: two tanks at 30 - 40°C, two tanks at 40 - 50°C, two tanks at 60 - 75°C, and two tanks at 85 - 95°C; in cooperation with a low-pressure roller (3 kg / cm 2 ), during the process of repeated water washing and rolling, the water-soluble fillers and water-soluble polycarbonate in the base fabric are washed out.

[0056] (5) Post-treatment: After the fiber-opened base fabric is shaped, dried, oiled, and skived, a fully water-based environmentally friendly ultra-fine synthetic leather is obtained.

[0057] Example 2

[0058] A preparation process for a fully water-based environmentally friendly ultra-fine synthetic leather includes the following steps:

[0059] (1) Melt spinning: Using 55% polycaprolactam as the island phase and 45% water-soluble polycarbonate as the sea phase to blend and melt to prepare sea-island fibers; the sea-island fibers are needled and shaped to obtain a base fabric; the melt spinning includes the following stages: (1.1) The polycaprolactam chips are placed in a vacuum drying oven and dried for 3 h at a drying temperature of 100°C, and the moisture content of the dried polycaprolactam is below 500 ppm; the water-soluble polycarbonate is placed in a vacuum drying oven and dried for 10 hours at a drying temperature of 50°C, and the moisture content of the dried water-based polyester is below 20 ppm. (1.2) The dried polycaprolactam chips and water-soluble polycarbonate are mixed and fed into a single-screw extruder for melt blending. The heating temperature of the four zones of the single-screw extruder is 210 - 245°C, and then spun through a spinneret, and the spinning temperature is 245°C. During the spinning process, horizontal uniform air supply cooling is carried out to obtain primary polycaprolactam / water-soluble polycarbonate blend fibers. (1.3) After the primary polycaprolactam / water-soluble polycarbonate blend fibers are oiled in an oil bath, they pass through a multi-stage hot drawing guide roller, and are drawn in a water bath at 40 - 50°C with a draw ratio of 5.0 times, and then curled by a winder with 15 - 21 curls per 25 mm; then relaxation heat setting is carried out in five zones at 65°C, 60°C, 55°C, 50°C, and 50°C, and finally the obtained sea-island fibers with a fineness of 6 - 8 dtex are cut.

[0060] (2) Wet impregnation: Inject the prepared aqueous impregnating material into the impregnation tank. Pass the base fabric through the impregnation tank with an impregnation pressure of 1.8 - 2.3 kg, a gap of 1.3 - 1.4 mm, and a material temperature of 20 - 30 °C for impregnation and rolling. Control the rolling liquid rate of impregnation at 60%; the aqueous impregnating material includes pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent; the mass ratio of pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent is 100:15:1:2; the water-soluble filler is a mixture of 50% water-soluble foaming agent and 50% PVA microspheres; the water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 12 wt% acrylic oligomer, and sodium dodecyl sulfate accounts for 2% in the water-soluble foaming agent as a surfactant. The pore size of the PVA microspheres is 30 μm. The aqueous thickener is cellulose ether, and the aqueous reinforcing agent is pre-dispersed nano-SiO2 slurry. The solid content of the aqueous impregnating material is 50% and the viscosity is 2500 cps.

[0061] (3) Coagulation: The impregnated base fabric is coagulated by passing through a path length of 100 m and filled with a 15% mass percentage aqueous citric acid solution at a temperature of 25 °C, and the pH of the aqueous citric acid solution is 4.2.

[0062] (4) Water washing and fiber opening with weight reduction: The coagulated base fabric is subjected to staged temperature-rising water washing and fiber opening. The staged temperature-rising water washing and fiber opening is carried out through eight water washing tanks, and the water temperatures are sequentially controlled as follows: two tanks at 30 - 40 °C, two tanks at 40 - 50 °C, two tanks at 60 - 75 °C, and two tanks at 85 - 95 °C; in cooperation with a low-pressure roller (3 kg / cm 2 ), during the process of repeated water washing and rolling, wash out the water-soluble filler and water-soluble polycarbonate in the base fabric.

[0063] (5) Post-treatment: After the fiber-opened base fabric is shaped, dried, oiled, and leather-rubbed, a fully aqueous environmentally friendly superfine fiber synthetic leather is obtained.

[0064] Example 3

[0065] A preparation process of a fully aqueous environmentally friendly superfine fiber synthetic leather, comprising the following steps:

[0066] (1) Melt spinning: Prepare sea-island fibers by melt blending 70% polycaprolactam as the island phase and 30% water-soluble polycarbonate as the sea phase; subject the sea-island fibers to needling and shaping to obtain a base fabric; the melt spinning includes the following stages: (1.1) Put polycaprolactam chips into a vacuum drying oven and dry for 3 h at a drying temperature of 100 °C, and the moisture content of polycaprolactam after drying is below 500 ppm; place the water-soluble polycarbonate in a vacuum drying oven and dry for 10 hours at a drying temperature of 50 °C, and the moisture content of the water-based polyester after drying is below 20 ppm. (1.2) Mix the dried polycaprolactam chips and water-soluble polycarbonate, send them into a single-screw extruder for melt blending, the heating temperature of the four zones of the single-screw extruder is 210 - 245 °C, and then spin through a spinneret, the spinning temperature is 250 °C, and horizontal uniform air supply cooling is carried out during the spinning process to obtain primary polycaprolactam / water-soluble polycarbonate blend fibers. (1.3) After the primary polycaprolactam / water-soluble polycarbonate blend fibers are oiled in an oil bath, they pass through multi-stage hot drawing guide rollers, are drawn in a water bath at 40 - 50 °C with a draw ratio of 4.0 times, and then are crimped by a winder with 15 - 21 crimps per 25 mm; then they are subjected to relaxation heat setting in five zones at 65 °C, 60 °C, 55 °C, 50 °C, and 50 °C, and finally cut to obtain sea-island fibers with a fineness of 6 - 8 dtex.

[0067] (2) Wet impregnation: Inject the prepared water-based impregnating material into an impregnation tank, and impregnate and roll the base fabric through an impregnation tank with an impregnation pressure of 1.8 - 2.3 kg, a gap of 1.3 - 1.4 mm, and a material temperature of 20 - 30 °C, and control the rolling liquid rate of impregnation at 60%; the water-based impregnating material includes a pH-responsive water-based polyurethane, a water-soluble filler, a water-based thickener, and a water-based reinforcing agent; the mass ratio of the pH-responsive water-based polyurethane, the water-soluble filler, the water-based thickener, and the water-based reinforcing agent is 100:25:3:4; the water-soluble filler is a mixture of 60% water-soluble foaming agent and 40% PVA microspheres; the water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 15 wt% acrylic oligomer, and the proportion of sodium dodecyl sulfate as a surfactant in the water-soluble foaming agent is 2%. The pore size of the PVA microspheres is 50 μm. The water-based thickener is a cellulose ether, and the water-based reinforcing agent is a pre-dispersed nano-SiO2 slurry. The solid content of the water-based impregnating material is 50% and the viscosity is 2500 cps.

[0068] (3) Coagulation: The impregnated base fabric is coagulated at 25 °C using a 100 m long channel filled with a 15% mass percentage aqueous citric acid solution, and the pH of the aqueous citric acid solution is 3.8.

[0069] (4) Water washing and fiber opening for weight reduction: The solidified base fabric is subjected to stepwise temperature-rising water washing and fiber opening. The stepwise temperature-rising water washing and fiber opening is carried out through eight water washing tanks, and the water temperatures are controlled in sequence as follows: two tanks at 30 - 40°C, two tanks at 40 - 50°C, two tanks at 60 - 75°C, and two tanks at 85 - 95°C; in cooperation with a low-pressure roller (3 kg / cm 2 ), during the process of repeated water washing and rolling, the water-soluble fillers and water-soluble polycarbonate in the base fabric are washed out.

[0070] (5) Post-treatment: After the fiber-opened base fabric is subjected to shaping and drying, oiling, and leather rubbing, a fully water-based environmentally friendly ultra-fine synthetic leather is obtained.

[0071] Comparative Example 1

[0072] A preparation process for a fully water-based environmentally friendly ultra-fine synthetic leather includes the following steps:

[0073] (1) Melt spinning: Using 50% PA as the island phase and 50% PVA as the sea phase to blend and melt to prepare sea-island fibers; subjecting the sea-island fibers to needling and shaping to obtain a base fabric; the melt spinning includes the following stages: (1.1) The PA chips are placed in a vacuum drying oven and dried for 3 h at a drying temperature of 100°C, and the moisture content of the dried PA is below 500 ppm; the PVA is placed in a vacuum drying oven and dried for 10 hours at a drying temperature of 50°C, and the moisture content of the dried PVA is below 20 ppm. (1.2) The dried PA chips and PVA are mixed and fed into a single-screw extruder for melt blending. The four-zone heating temperature of the single-screw extruder is 210 - 245°C, and then spinning is carried out through a spinneret, and the spinning temperature is 250°C. During the spinning process, horizontal uniform air supply cooling is carried out to obtain primary blended fibers. (1.3) After the primary blended fibers are oiled in an oil bath, they pass through multi-stage hot drawing godets, are drawn in a 40 - 50°C water bath with a draw ratio of 4.0 times, and then are curled by a winder with 15 - 21 curls per 25 mm; then relaxation heat setting is carried out in five zones at 65°C, 60°C, 55°C, 50°C, and 50°C, and finally cut to obtain sea-island fibers.

[0074] (2) Wet impregnation: The prepared water-based impregnating material is injected into an impregnation tank, and the base fabric is impregnated and rolled in an impregnation tank with an impregnation pressure of 1.8 - 2.3 kg, a gap of 1.3 - 1.4 mm, and a material temperature of 20 - 30°C. The impregnation rolling liquid rate is controlled at 50 - 70%; the water-based impregnating material includes water-based polyurethane, water-soluble filler, water-based thickener, and water-based reinforcing agent; the mass ratio of water-based polyurethane, water-soluble filler, water-based thickener, and water-based reinforcing agent is 100:20:2:3; the water-soluble filler is calcium carbonate; the water-based thickener is cellulose ether; the water-based reinforcing agent is a pre-dispersed nano-SiO2 slurry. The solid content of the water-based impregnating material is 50% and the viscosity is 2500 cps.

[0075] (3) Coagulation: The impregnated base fabric is coagulated with an aqueous solution of length 100 at a temperature of 25°C. Pure water is used for coagulation without acid-triggered crosslinking.

[0076] (4) Washing and weight reduction for fibrillation: The coagulated base fabric is subjected to stepwise temperature-rising washing and fibrillation. The stepwise temperature-rising washing and fibrillation is carried out through eight washing tanks, and the water temperature is controlled in sequence as follows: two tanks at 30 - 40°C, two tanks at 40 - 50°C, two tanks at 60 - 75°C, and two tanks at 85 - 95°C; in cooperation with a low-pressure roller (3 kg / cm 2 ), during the process of repeated washing and rolling, the water-soluble fillers and water-soluble polycarbonate in the base fabric are washed out.

[0077] (5) Post-treatment: After the fibrillation of the base fabric, through shaping and drying, oiling, and leather rubbing, a fully water-based environmentally friendly ultra-fine synthetic leather is obtained.

[0078] Comparative Example 2

[0079] A preparation process for a fully water-based environmentally friendly ultra-fine synthetic leather includes the following steps:

[0080] (1) Melt spinning: Using 35% polycaprolactam as the island phase and 65% water-soluble polycarbonate as the sea phase, a sea-island fiber is prepared by melt blending; the sea-island fiber is needled and shaped to obtain a base fabric; the high content of water-soluble polycarbonate results in a fiber breaking strength < 2.8 cN / dtex. The melt spinning includes the following stages: (1.1) The polycaprolactam chips are placed in a vacuum drying oven and dried for 3 h at a drying temperature of 100°C, and the moisture content of the dried polycaprolactam is below 500 ppm; the water-soluble polycarbonate is placed in a vacuum drying oven and dried for 10 hours at a drying temperature of 50°C, and the moisture content of the dried water-based polyester is below 20 ppm. (1.2) The dried polycaprolactam chips and water-soluble polycarbonate are mixed and fed into a single-screw extruder for melt blending. The four-zone heating temperature of the single-screw extruder is 210 - 245°C, and then spinning is carried out through a spinneret, and the spinning temperature is 250°C. During the spinning process, horizontal uniform air supply cooling is carried out to obtain a primary polycaprolactam / water-soluble polycarbonate blend fiber. (1.3) After the primary polycaprolactam / water-soluble polycarbonate blend fiber is oiled in an oil bath, it passes through a multi-stage hot drawing guide roller, and is drawn in a 40 - 50°C water bath with a draw ratio of 4.0 times, and then is curled by a coiler with 15 - 21 curls per 25 mm; then it is subjected to relaxation heat setting in five zones at 65°C, 60°C, 55°C, 50°C, and 50°C, and finally cut to obtain the sea-island fiber.

[0081] (2) Wet impregnation: Inject the prepared aqueous impregnating material into the impregnation tank. Pass the base fabric through the impregnation tank with an impregnation pressure of 1.8 - 2.3 kg, a gap of 1.3 - 1.4 mm, and a material temperature of 20 - 30 °C for impregnation and rolling. Control the rolling liquid rate of impregnation at 50 - 70%; the aqueous impregnating material includes pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent; the mass ratio of pH-responsive aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent is 100:20:2:3; the water-soluble filler is a mixture of 50% water-soluble foaming agent and 50% PVA microspheres; the water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 20 wt% acrylic oligomer, and sodium dodecyl sulfate accounts for 2% in the water-soluble foaming agent as a surfactant. The pore size of the PVA microspheres is 30 μm. The aqueous thickener is cellulose ether, and the aqueous reinforcing agent is pre-dispersed nano-SiO2 slurry. The solid content of the aqueous impregnating material is 50% and the viscosity is 4000 cps. If the content of acrylic oligomer is too high, the viscosity of the system is too high, resulting in uneven penetration of the aqueous impregnating material.

[0082] (3) Coagulation: The impregnated base fabric is coagulated at a temperature of 25 °C using a path length of 100 m and filled with a 25% mass percentage aqueous citric acid solution, and the pH of the aqueous citric acid solution is <5. If the citric acid concentration is 25% too high, it will cause excessive cross-linking and embrittlement of the resin.

[0083] (4) Water washing and fiber opening by weight reduction: The coagulated base fabric is subjected to staged temperature-rising water washing and fiber opening. The staged temperature-rising water washing and fiber opening is carried out through eight water washing tanks, and the water temperature is sequentially controlled as follows: two tanks at 30 - 40 °C, two tanks at 40 - 50 °C, two tanks at 60 - 75 °C, and two tanks at 85 - 95 °C; in cooperation with a low-pressure roller (3 kg / cm 2 ), during the process of repeated water washing and rolling, wash out the water-soluble filler and water-soluble polycarbonate in the base fabric.

[0084] (5) Post-treatment: After the fiber-opened base fabric is shaped, dried, oiled, and leather-rubbed, a fully aqueous environmentally friendly ultra-fine synthetic leather is obtained.

[0085] Comparative Example 3

[0086] A preparation process for a fully aqueous environmentally friendly ultra-fine synthetic leather includes the following steps:

[0087] (1) Melt spinning: Prepare sea-island fibers by melt blending 50% PA as the island phase and 50% PE as the sea phase; Needle-punch and shape the sea-island fibers to obtain the base fabric; Melt spinning includes the following stages: (1.1) Put PA chips into a vacuum drying oven and dry for 3 h at a drying temperature of 100 °C. The moisture content of PA after drying is below 500 ppm; Place PE in a vacuum drying oven and dry for 10 hours at a drying temperature of 50 °C. The moisture content of PE after drying is below 20 ppm. (1.2) Mix the dried PA chips and PE and send them into a single-screw extruder for melt blending. The heating temperature of the four zones of the single-screw extruder is 210 - 245 °C, and then spin through a spinneret. The spinning temperature is 250 °C. During the spinning process, blow air horizontally and evenly for cooling to obtain the as-spun blend fibers. (1.3) After oiling the as-spun blend fibers through an oil bath, pass them through multi-stage hot drawing godets, perform water bath drawing at 40 - 50 °C with a drawing ratio of 4.0 times, and then crimp through a winder with 15 - 21 crimps per 25 mm; Then perform relaxation heat setting in five zones at 65 °C, 60 °C, 55 °C, 50 °C, and 50 °C, and finally cut to obtain sea-island fibers.

[0088] (2) Wet impregnation: Inject the prepared aqueous impregnating material into the impregnation tank, and impregnate and roll the base fabric through the impregnation tank with an impregnation pressure of 1.8 - 2.3 kg, a gap of 1.3 - 1.4 mm, and a material temperature of 20 - 30 °C. Control the impregnation rolling rate at 50 - 70%; The aqueous impregnating material includes aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent; The mass ratio of aqueous polyurethane, water-soluble filler, aqueous thickener, and aqueous reinforcing agent is 100:20:2:3; The water-soluble filler is calcium carbonate; The aqueous thickener is cellulose ether; The aqueous reinforcing agent is a pre-dispersed nano-SiO2 slurry. The solid content of the aqueous impregnating material is 50% and the viscosity is 2500 cps.

[0089] (3) Coagulation: Immerse the impregnated base fabric in an aqueous solution with a path length of 100 and coagulate at a temperature of 25 °C. Use pure water for coagulation without acid-triggered crosslinking.

[0090] (4) Washing and weight reduction for fiber opening: The coagulated base fabric is subjected to stepwise temperature-rising washing and fiber opening. The stepwise temperature-rising washing and fiber opening is carried out through eight washing tanks, and the water temperature is controlled in turn as follows: two tanks at 30 - 40 °C, two tanks at 40 - 50 °C, two tanks at 60 - 75 °C, and two tanks at 85 - 95 °C; Cooperate with a low-pressure roller (3 kg / cm 2 ), and during the repeated washing and rolling process, wash out the water-soluble filler and water-soluble polycarbonate in the base fabric.

[0091] (5) Post-treatment: After the fiber-opened base fabric is shaped, dried, oiled, and rubbed, a fully aqueous environmentally friendly ultra-fine synthetic leather is obtained.

[0092] Comparative Example 4

[0093] A fully water-based environmentally friendly ultra-fine synthetic leather preparation process, comprising the following steps:

[0094] (1) Melt spinning: Using 60% polycaprolactam as the island phase and 40% water-soluble polycarbonate as the sea phase, blend and melt them to prepare sea-island fibers; subject the sea-island fibers to needling and shaping to obtain a base fabric. The melt spinning includes the following stages: (1.1) Put the polycaprolactam chips into a vacuum drying oven and dry for 3 h at a drying temperature of 100 °C. After drying, the moisture content of the polycaprolactam is below 500 ppm; place the water-soluble polycarbonate in a vacuum drying oven and dry for 10 hours at a drying temperature of 50 °C. After drying, the moisture content of the water-based polyester is below 20 ppm. (1.2) Mix the dried polycaprolactam chips and water-soluble polycarbonate, and feed them into a single-screw extruder for melt blending. The heating temperature of the four zones of the single-screw extruder is 210-245 °C, and then spin through a spinneret. The spinning temperature is 250 °C. During the spinning process, perform horizontal uniform air supply cooling to obtain primary polycaprolactam / water-soluble polycarbonate blend fibers. (1.3) After the primary polycaprolactam / water-soluble polycarbonate blend fibers are oiled in an oil bath, pass through a multi-stage hot drawing guide roller, perform water bath drawing at 40-50 °C with a drawing ratio of 4.0 times, and then curl through a winder with 15-21 curls per 25 mm; then perform relaxation heat setting in five zones of 65 °C, 60 °C, 55 °C, 50 °C, and 50 °C, and finally cut to obtain sea-island fibers.

[0095] (2) Wet impregnation: Inject the prepared water-based impregnating material into an impregnation tank, and impregnate and roll the base fabric through an impregnation tank with an impregnation pressure of 1.8-2.3 kg, a gap of 1.3-1.4 mm, and a material temperature of 20-30 °C. The impregnation rolling rate is controlled at 50-70%; the water-based impregnating material includes water-based polyurethane, water-soluble filler, water-based thickener, and water-based reinforcing agent; the mass ratio of water-based polyurethane, water-soluble filler, water-based thickener, and water-based reinforcing agent is 100:20:2:3; the water-soluble filler is a mixture of 50% water-soluble foaming agent and 50% PVA microspheres; the water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 18 wt% acrylic oligomer, and sodium dodecyl sulfate accounts for 2% in the water-soluble foaming agent as a surfactant. The pore size of the PVA microspheres is 30 μm. The water-based thickener is cellulose ether, and cellulose ether accounts for 4% in the water-based impregnating material; the water-based reinforcing agent is a pre-dispersed nano-SiO2 slurry. The solid content of the water-based impregnating material is 50% and the viscosity is 2500 cps.

[0096] (3) Coagulation: The impregnated base fabric is coagulated in an aqueous solution with a use path length of 100 at a temperature of 25 °C. Use pure water for coagulation without acid-triggered crosslinking.

[0097] (4) Water washing and fiber opening with weight reduction: The solidified base fabric is subjected to stepwise temperature-rising water washing and fiber opening. The stepwise temperature-rising water washing and fiber opening is carried out through eight water washing tanks, and the water temperature is controlled successively as follows: two tanks at 30 - 40 °C, two tanks at 40 - 50 °C, two tanks at 60 - 75 °C, and two tanks at 85 - 95 °C; in combination with a pressure roller (if the pressure is too high, the pressure is 5 kg / cm 2 ), during the process of repeated water washing and rolling, the water-soluble fillers and water-soluble polycarbonate in the base fabric are washed out.

[0098] (5) Post-treatment: After the fiber opening, the base fabric is subjected to shaping and drying, oiling, and leather rubbing to obtain a fully water-based environmentally friendly ultra-fine synthetic leather.

[0099] Table 1 Comparison of performance test results of several groups of examples and comparative examples

[0100]

[0101] Conclusion:

[0102] 1. The breaking strength of the sea-island fiber is the core prerequisite for ensuring the dimensional stability of the base fabric and the physical properties of the synthetic leather. Examples 1 - 3 adopt the co-spinning process of polycaprolactam / water-soluble polycarbonate (PA6 / WSPC) system (draft ratio 4.0 - 5.0 times, five-zone relaxation heat setting), and the breaking strength of the obtained sea-island fibers is all ≥ 3.5 cN / dtex, meeting the high strength and toughness requirements of the base fabric. The high breaking strength directly ensures the integrity of the fibers (reducing breakage) during the subsequent fiber opening process, thereby improving the tensile properties of the synthetic leather (tensile strength of Examples 1 - 3 ≥ 15 MPa). In Comparative Example 1 (PA / PVA), poor heat resistance leads to molecular chain breakage during fiber setting, and the breaking strength is only 2.8 cN / dtex, and the base fabric is prone to shrinkage (35%); in Comparative Example 2 (excessive sea phase), the proportion of water-soluble polycarbonate is 65%, resulting in uneven sea-island fiber structure, and the breaking strength drops to 2.7 cN / dtex; in Comparative Example 3 (PA / PE), the melting point of PE is low (105 °C), and the sea-island fibers are melted and deformed after high-temperature setting, and the breaking strength is only 2.5 cN / dtex, and the base fabric shrinks severely (42%); in Comparative Example 4 (without PH-responsive resin), although the strength of the sea-island fiber is close to the standard (3.0 cN / dtex), due to the lack of self-crosslinking of the resin, the tensile strength of the final synthetic leather is still insufficient (11.2 MPa). Therefore, in Examples 1 - 3, water-soluble polycarbonate (WSPC) is used as the sea phase to replace traditional PVA or PE, and the width shrinkage rate after high-temperature setting is controlled within 11 - 14% (the shrinkage rate of Comparative Examples 1 / 3 is > 35% due to insufficient heat resistance of PVA / PE). The water-based impregnating material selects a PH-responsive resin and uses citric acid for coagulation, triggering self-crosslinking to increase the tensile strength to more than 15 MPa (Comparative Examples 1 / 3 / 4 do not have this mechanism, and the tensile strength < 12 MPa).

[0103] 2. The water-soluble foaming agent and PVA microspheres cooperate to form connected pores (fiber opening and dissolution) and closed pores (drying and decomposition), with air permeability ≥ 10,000 mL / cm 2 ·h (in Comparative Example 1, 1 / 3 of the filler is calcium carbonate, and the air permeability < 5,000).

[0104] 3. The staged water washing and low-pressure roller (2 - 4 kg / cm 2 ) process reduces fiber breakage and maintains the integrity of the pores (in Comparative Example 4, the pores are damaged by the high-pressure roller and the air permeability decreases).

[0105] 4. From Comparative Example 1 (PA / PVA), it can be seen that the poor heat resistance of PVA leads to a shrinkage rate of the base fabric reaching 35%, and uneven fiber opening. The ordinary water-based resin has no self-crosslinking, and the tensile strength is only 9.3 MPa. From Comparative Example 2 (marine phase overlimit), it can be seen that the excessive amount of acrylic oligomer (20 wt%) leads to too high viscosity of the system, uneven impregnation, and the air permeability is only 4,200 mL / cm 2 ·h. From Comparative Example 3 (PA / PE), it can be seen that the poor heat resistance of PE (melting point 105 °C), melts after high-temperature setting, the fiber structure collapses, the width shrinkage rate is 42%, and the air permeability is 2,800 mL / cm 2 ·h. From Comparative Example 4 (no PH-responsive resin), it can be seen that the ordinary resin has no self-crosslinking, and the tensile strength is only 11.2 MPa; the excessive amount of acrylic oligomer (18 wt%) leads to high viscosity, and the interlayer peeling force is 6.7 N / cm (not up to the standard).

[0106] 5. The all-aqueous process of the present invention systematically solves the problems of high shrinkage rate, poor air permeability, and excessive peeling force of traditional water-based synthetic leather through three core technologies: using water-soluble polycarbonate (WSPC) as the marine phase, self-crosslinking of PH-responsive resin, and double-porous structure design. The comparative examples prove that any deviation in a single link (such as material substitution, parameter overlimit, process simplification) will lead to unqualified key performance.

[0107] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments we described are illustrative rather than used to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered by the scope protected by the claims of the present invention.

Claims

1. A preparation process for a fully water-based environmentally friendly ultra-fine synthetic leather, characterized in that: The steps include: (1) Melt spinning: 40-70% polycaprolactam as the island phase and 30-60% water-soluble polycarbonate as the sea phase are melt-blended to prepare sea-island fibers; the sea-island fibers are needle-punched and shaped to obtain a base fabric; (2) Wet impregnation: The base fabric is subjected to wet impregnation treatment to obtain an impregnated base fabric; the water-based impregnation material includes a pH-responsive water-based polyurethane, a water-soluble filler, a water-based thickener, and a water-based enhancer; The mass ratio of pH-responsive waterborne polyurethane, water-soluble filler, water-borne thickener and water-borne enhancer is 100:(15-25):(1-3):(2-4); the water-soluble filler is a mixture of 40-60% water-soluble foaming agent and 40-60% PVA microspheres; (3) Solidification: The impregnated base fabric is solidified with citric acid aqueous solution at a temperature of 20-30°C; (4) Washing, reducing and opening the fibers: The solidified base fabric is washed and opened in stages by heating the base fabric, and a low-pressure roller is used to wash and press the base fabric repeatedly to clean the water-soluble filler and water-soluble polycarbonate. (5) Post-treatment: After the fiber is opened, the base fabric is shaped, dried, oiled, and kneaded to obtain a fully water-based environmentally friendly microfiber synthetic leather.

2. The preparation process of the all-aqueous environmentally friendly superfine fiber synthetic leather according to claim 1, characterized in that: Melt spinning includes the following stages: (1.1) The polycaprolactam slices are placed in a vacuum drying oven and dried for 2-3 hours at a drying temperature of 80-100°C. After drying, the moisture content of the polycaprolactam is less than 500ppm; the water-soluble polycarbonate is placed in a vacuum drying oven and dried for 8-10 hours at a drying temperature of 45-55°C. After drying, the moisture content of the water-based polyester is less than 20ppm; (1.2) The dried polycaprolactam slices and water-soluble polycarbonate are mixed and sent to a single screw extruder for melt blending. The heating temperature of the four zones of the single screw extruder is 210-245° C., and then the fibers are spun through a spinneret at a spinning temperature of 230-270° C. During the spinning process, uniform transverse air supply cooling is performed to obtain primary polycaprolactam / water-soluble polycarbonate blended fibers; (1.3) The nascent polycaprolactam / water-soluble polycarbonate blended fibers are oiled in an oil tank, and then passed through a multi-stage heat-stretching guide roller, drawn in a 40-50°C water bath with a draw ratio of 4.0-5.0 times, and then curled by a winder with the number of curls being 15-21 / 25mm; then, they are relaxed and heat-set in five zones at 65°C, 60°C, 55°C, 50°C, and 50°C, and finally cut to obtain the sea island fibers with a fineness of 6-8dtex.

3. The preparation process of the fully water-based environmentally friendly ultra-fine synthetic leather according to claim 1, characterized in that: In step (1), in the shaping stage, the density of the base fabric is 0.28 - 0.35 g / cm 3 .

4. The preparation process of the fully water-based environmentally friendly ultra-fine synthetic leather according to claim 1, characterized in that: The water-soluble foaming agent is a mixture of sodium dodecyl sulfate and 10-15 wt % of acrylic acid oligomers. Sodium dodecyl sulfate as a surfactant accounts for 1-3% of the water-soluble foaming agent.

5. The preparation process of the fully water-based environmentally friendly ultra-fine synthetic leather according to claim 4, characterized in that: The pore size of the PVA microspheres is 10-50 μm.

6. The preparation process of the fully water-based environmentally friendly ultra-fine synthetic leather according to claim 5, characterized in that: The solid content of the aqueous impregnation material is 45-55% and the viscosity is 2000-3000cps; the prepared aqueous impregnation material is injected into the impregnation tank, and the base cloth is impregnated and squeezed through the impregnation tank with an impregnation pressure of 1.8-2.3kg, a gap of 1.3-1.4mm, and a material temperature of 20-30℃, and the impregnation squeeze rate is controlled at 50-70%.

7. The preparation process of the fully water-based environmentally friendly ultra-fine synthetic leather according to claim 1, characterized in that: In the solidification step, the impregnated base fabric is solidified by passing through a path length of 80 - 120 m and being filled with an aqueous solution of citric acid with a mass percentage of 15% at a temperature of 20 - 30°C, and the pH of the aqueous solution of citric acid is <5.

8. The preparation process of the fully water-based environmentally friendly ultra-fine synthetic leather as described in claim 1, characterized in that: The fiber opening by washing with water in stages is carried out through eight water washing tanks, and the water temperature is sequentially controlled as follows: two tanks at 30 - 40°C, two tanks at 40 - 50°C, two tanks at 60 - 75°C, and two tanks at 85 - 95°C.

9. The preparation process of the fully water-based environmentally friendly superfine fiber synthetic leather according to claim 8, characterized in that: The low-pressure roll is 2 - 4 kg / cm 2 .

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