Preparation method of flame-retardant superfine fiber synthetic leather based on water decrement technology

Abstract

The invention relates to the technical field of synthetic leather, in particular to a preparation method of flame-retardant superfine fiber synthetic leather based on a water decrement technology. The method comprises the following steps: dipping pretreatment of PET / PVA sea-island fiber non-woven fabric in a polyvinyl alcohol aqueous solution, synthesis of a modified polyurethane emulsion with fluorine-containing chain modified melamine coated ammonium polyphosphate as a flame-retardant component, multiple padding and water decrement treatment of a composite base material, and sizing finishing by adding a softening agent and an antistatic agent. Through application of fluorine chain modified melamine, dissolution of flame-retardant components in the water decrement process is effectively prevented, meanwhile, the quality of a carbonized layer is improved, and the flame-retardant efficiency is improved. The obtained superfine fiber synthetic leather has excellent flame retardance, good washing resistance and mechanical properties, comfort and high moisture permeability, and is suitable for clothing and special fields with high safety and durability requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic leather, and particularly to a preparation method of a flame-retardant ultra-fine fiber synthetic leather based on water reduction technology. Background Art

[0002] As a substitute for natural leather, synthetic leather has been widely used in furniture, automotive interiors, clothing, luggage and other fields. With the improvement of people's safety awareness, flame retardancy has become a key performance requirement for synthetic leather in many application scenarios. However, traditional synthetic leather still faces major challenges in the balance of flame retardancy, comfort and mechanical properties.

[0003] Traditional flame-retardant synthetic leather mainly achieves flame retardant effects by adding halogen-based flame retardants, inorganic hydroxides or phosphorus-based flame retardants. Although halogen-based flame retardants have high flame retardant efficiency, they will release toxic gases during combustion, posing potential threats to the environment and human health. Inorganic hydroxides such as aluminum hydroxide and magnesium hydroxide need to be added in large amounts to achieve ideal flame retardant effects, often resulting in a significant decline in the mechanical properties of synthetic leather. Phosphorus-based flame retardants such as ammonium polyphosphate have good environmental protection, but are easily dissolved and lost during the water treatment process, and the flame retardant effect is difficult to last.

[0004] Ultra-fine fiber synthetic leather has gradually become the mainstream of high-end synthetic leather due to its excellent hand feeling and physical properties. In its preparation process, the water reduction technology is usually adopted, that is, water-soluble substances (such as polyvinyl alcohol) are dissolved through an aqueous medium to form a microporous structure. However, the water reduction process has also become the main way for the loss of flame retardant components, resulting in insufficient or unstable flame retardant performance of the final product. How to maintain the stability of flame retardant components in the water reduction process is a technical problem faced by the industry.

[0005] In summary, developing an ultra-fine fiber synthetic leather with excellent flame retardant performance and comfort, especially being able to overcome the problem of loss of flame retardant components caused by the water reduction process, has important practical value and market prospects. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a preparation method of a flame-retardant ultra-fine fiber synthetic leather based on water reduction technology, so as to provide an ultra-fine fiber synthetic leather with both excellent flame retardant performance and comfort, especially to overcome the problem of loss of flame retardant components caused by the water reduction process.

[0007] Based on the above purpose, the present invention provides a preparation method of a flame-retardant ultra-fine fiber synthetic leather based on water reduction technology, including the following steps: S1: Immerse the PET / PVA sea-island fiber non-woven fabric in an aqueous solution of polyvinyl alcohol, and dry it to obtain a pretreated substrate; S2: Under a nitrogen atmosphere, mix isophorone diisocyanate, polytetrahydrofuran glycol, core-shell ammonium polyphosphate, and acetone, heat up to 75 - 85 °C, stir and react for 0.5 - 1.5 h, then add 2,2-dimethylolpropionic acid and stannous octoate, continue to stir and react for 2 - 4 h, cool down to 45 - 55 °C, add triethylamine, stir and react for 0.5 - 1.5 h, cool to room temperature, add ethylenediamine and deionized water, stir and react for 25 - 35 min, rotary evaporate to remove acetone to obtain a modified polyurethane emulsion; S3: Continuously pad the pretreated substrate three times in the modified polyurethane emulsion and dry it to obtain a polyurethane composite substrate; S4: Immerse the polyurethane composite substrate in deionized water at 85 - 95 °C for weight reduction for 40 - 50 min, take it out and wash it with water to obtain a water-weight-reduced polyurethane composite substrate; S5: Dip the water-weight-reduced polyurethane composite substrate twice and pad it twice in a treatment solution containing a softener and an antistatic agent, set and dry it, and wind it up after finishing with a calender to obtain a flame-retardant superfine fiber synthetic leather based on the water-weight reduction technology.

[0008] Preferably, in step S1, the concentration of the polyvinyl alcohol aqueous solution is 10 wt% - 15 wt%, the weight-average molecular weight of polyvinyl alcohol is 18000 - 22000, and the impregnation time is 2.5 - 3.5 min.

[0009] Preferably, in step S2, the weight ratio of isophorone diisocyanate, polytetrahydrofuran glycol, core-shell ammonium polyphosphate, acetone, 2,2-dimethylolpropionic acid, stannous octoate, triethylamine, ethylenediamine, and deionized water is 22.2:64.2:10 - 15:100 - 150:4.6:1.2:3.5:2:400 - 500.

[0010] Preferably, in step S2, the weight-average molecular weight of polytetrahydrofuran glycol is 1500 - 2500.

[0011] Preferably, in step S2, the core-shell ammonium polyphosphate is ammonium polyphosphate wrapped with a polymer formed by fluorine-chain modified melamine, lauryl diamine, and a 37 wt% formaldehyde aqueous solution.

[0012] Preferably, the weight ratio of the fluorine-chain modified melamine, lauryl diamine, 37 wt% formaldehyde aqueous solution, and deionized water is 15 - 25:5 - 15:40 - 80:80 - 120.

[0013] Preferably, the fluorine-chain modified melamine is melamine modified with tridecafluoroheptanoyl.

[0014] Preferably, the weight ratio of tridecafluoroheptanoyl and melamine is 35 - 45:12.6.

[0015] Preferably, in step S3, the padding pressure is 0.18 - 0.22 MPa, and the liquor pickup is 120% - 140%.

[0016] Preferably, in step S5, the softener is Magnasoft 68 with a concentration of 2.5 wt% - 3.5 wt%, and the antistatic agent is Permalose TM with a concentration of 0.5 wt% - 1.5 wt%.

[0017] Preferably, in step S5, the temperature for setting and drying is 125 - 135 °C, and the time is 1.5 - 2.5 min.

[0018] Preferably, in step S5, the linear pressure for calendering finishing is 75 - 85 N / mm, and the temperature is 95 - 105 °C.

[0019] Advantages of the present invention: The flame - retardant ultrafine fiber synthetic leather based on the water reduction technology provided by the present invention exhibits excellent flame - retardant performance, with extremely short after - flame time and after - glow time. The innovative application of fluorine - chain modified melamine forms a more effective flame - retardant system, which can effectively prevent the dissolution of ammonium polyphosphate during the water reduction process, and moreover, creates a more stable char layer during the combustion process, effectively blocking heat transfer and oxygen diffusion.

[0020] The flame - retardant ultrafine fiber synthetic leather based on the water reduction technology provided by the present invention has excellent wash - fastness. After multiple washing cycles, the flame - retardant performance remains stable, indicating that the flame - retardant components are firmly integrated into the material structure. This durability ensures that the product can maintain long - term flame - retardant protection throughout its life cycle, even under harsh usage conditions.

[0021] The flame - retardant ultrafine fiber synthetic leather based on the water reduction technology provided by the present invention has excellent mechanical properties, especially in terms of tear strength. Using lauryl diamine as a comonomer, its long - chain alkyl structure provides better chain segment flexibility and intermolecular entanglement ability. The long alkyl chain of lauryl diamine promotes a more uniform stress distribution in the polymer network, reducing stress concentration points, thereby improving the material's ability to resist tearing force.

[0022] The flame - retardant ultrafine fiber synthetic leather of the present invention successfully achieves the harmonious unity of functionality and comfort. Its excellent flame - retardant performance combined with good mechanical properties makes it suitable for application scenarios requiring safety and durability. At the same time, its high moisture permeability and appropriate air permeability ensure wearing comfort, solving the common problem that functional improvement often sacrifices comfort. Detailed implementation manners

[0023] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in detail with reference to specific embodiments.

[0024] In the specific embodiment of the present invention, the PET / PVA sea-island fiber nonwoven fabric is purchased from Ningbo Hengqide Chemical Fiber Company, and the base fabric is 500 g / m 2 , and the fiber is a water-soluble sea-island fixed-island fiber with an index of 70% PA6 / 30% PVA. The fiber has 36 islands, a fineness of 5 D, and a length of 51 mm. Example 1:

[0025] (1) Immerse the PET / PVA sea-island fiber nonwoven fabric in an aqueous solution of polyvinyl alcohol (weight-average molecular weight of 20,000) with a concentration of 10 wt% for 2.5 min, take it out and dry it at 80 °C for 10 min to obtain a pretreated substrate; (2) Add 35 g of tridecafluoroheptanoyl and 12.6 g of melamine to 200 g of N,N-dimethylformamide, heat up to 75 °C, stir and react for 5 h, perform rotary evaporation, and vacuum dry to obtain fluorine-chain modified melamine; (3) Add 15 g of fluorine-chain modified melamine, 5 g of lauryl diamine, and 40 g of an aqueous formaldehyde solution with a concentration of 37 wt% to 80 g of deionized water, then adjust the pH of the solution to 8.5 with an aqueous sodium carbonate solution with a concentration of 8 wt%, heat up to 75 °C, stir and react for 30 min to obtain a fluorine-chain modified prepolymer; (4) Disperse 8 g of ammonium polyphosphate in 15 g of ethanol, then add 20 g of fluorine-chain modified prepolymer, and then adjust the pH value of the solution to 3.3 with acetic acid, heat up to 75 °C, stir and react for 2 h, perform suction filtration, washing, and vacuum drying to obtain core-shell ammonium polyphosphate; (5) Under a nitrogen atmosphere, mix 22.2 g of isophorone diisocyanate, 64.2 g of polytetrahydrofuran ether glycol (weight-average molecular weight of 2,000), 10 g of core-shell ammonium polyphosphate, and 100 g of acetone, heat up to 75 °C, stir and react for 0.5 h, then add 4.6 g of 2,2-dimethylolpropionic acid and 1.2 g of stannous octoate, continue to stir and react for 2 h, cool down to 45 °C, add 3.5 g of triethylamine, stir and react for 0.5 h, cool down to room temperature, add 2 g of ethylenediamine and 400 g of deionized water, stir and react for 25 min, perform rotary evaporation to remove acetone to obtain a modified polyurethane emulsion.

[0026] (6) Continuously pad the pretreated substrate three times in the modified polyurethane emulsion, keep the impregnation pressure at 0.15 MPa each time, control the pick-up rate at 125%, take it out and dry it at 90 °C for 20 min to obtain a polyurethane composite substrate; (7) Immerse the polyurethane composite substrate in deionized water at 85 °C for weight reduction for 40 min, take it out and wash it 3 times with water to obtain a water-weight-reduced polyurethane composite substrate; (8) The water-reduced polyurethane composite substrate is dip-rolled twice in a treatment solution containing 2.5 wt% softener Magnasoft 68 and 0.5 wt% antistatic agent Permalose TM, dried and set at 125 °C for 1.5 min, and then wound up after finishing by a calender (linear pressure 75 N / mm, temperature 95 °C) to obtain a flame-retardant superfine fiber synthetic leather based on the water reduction technology. Example 2:

[0027] (1) The PET / PVA sea-island fiber nonwoven fabric is immersed in an aqueous solution of polyvinyl alcohol (weight-average molecular weight 20,000) with a concentration of 12 wt% for 3 min, taken out and dried at 85 °C for 15 min to obtain a pretreated substrate; (2) 38.2 g of tridecafluoroheptanoyl and 12.6 g of melamine are added to 250 g of N,N-dimethylformamide, heated to 80 °C, stirred and reacted for 6 h, rotary evaporated and dried under vacuum to obtain fluorine-chain modified melamine; (3) 20 g of fluorine-chain modified melamine, 10 g of lauryl diamine, 60 g of an aqueous formaldehyde solution with a concentration of 37 wt% are added to 100 g of deionized water, and the pH of the solution is adjusted to 8.6 with an aqueous sodium carbonate solution with a concentration of 10 wt%, heated to 80 °C, stirred and reacted for 35 min to obtain a fluorine-chain modified prepolymer; (4) 10 g of ammonium polyphosphate is dispersed in 20 g of ethanol, then 25 g of fluorine-chain modified prepolymer is added, and the pH value of the solution is adjusted to 3.5 with acetic acid, heated to 80 °C, stirred and reacted for 3 h, filtered, washed and dried under vacuum to obtain core-shell ammonium polyphosphate; (5) Under a nitrogen atmosphere, 22.2 g of isophorone diisocyanate, 64.2 g of polytetrahydrofuran ether glycol (weight-average molecular weight 2000), 12 g of core-shell ammonium polyphosphate and 120 g of acetone are mixed, heated to 80 °C, stirred and reacted for 1 h, then 4.6 g of 2,2-dimethylolpropionic acid and 1.2 g of stannous octoate are added, and stirring and reaction continue for 3 h. The temperature is lowered to 50 °C, 3.5 g of triethylamine is added, stirring and reaction continue for 1 h. The temperature is lowered to room temperature, 2 g of ethylenediamine and 450 g of deionized water are added, stirring and reaction continue for 30 min, and acetone is removed by rotary evaporation to obtain a modified polyurethane emulsion.

[0028] (6) The pretreated substrate is continuously dip-rolled three times in the modified polyurethane emulsion, with the impregnation pressure maintained at 0.2 MPa each time and the pick-up rate controlled at 130%. After taking out, it is dried at 95 °C for 25 min to obtain a polyurethane composite substrate; (7) The polyurethane composite substrate is immersed in deionized water at 90 °C for water reduction for 45 min, taken out and washed 3 times with water to obtain a water-reduced polyurethane composite substrate; (8) Dip the water-reduced polyurethane composite substrate into a treatment solution containing 3 wt% softener Magnasoft 68 and 1 wt% antistatic agent Permalose TM for two dips and two nips, set and dry at 130 °C for 2 min, and wind up after finishing with a calender (linear pressure 80 N / mm, temperature 100 °C) to obtain a flame-retardant ultrafine fiber synthetic leather based on the water reduction technology. Example 3:

[0029] (1) Immerse the PET / PVA sea-island fiber nonwoven fabric in an aqueous solution of polyvinyl alcohol (weight average molecular weight of 20,000) with a concentration of 15 wt% for 3.5 min, take it out and dry at 90 °C for 20 min to obtain a pretreated substrate; (2) Add 45 g of tridecafluoroheptanoyl and 12.6 g of melamine to 300 g of N,N-dimethylformamide, heat up to 85 °C, stir and react for 7 h, rotary evaporate, and vacuum dry to obtain fluorine-chain modified melamine; (3) Add 25 g of fluorine-chain modified melamine, 15 g of lauryl diamine, and 80 g of an aqueous formaldehyde solution with a concentration of 37 wt% to 120 g of deionized water, then adjust the pH of the solution to 8.8 with an aqueous sodium carbonate solution with a concentration of 12 wt%, heat up to 85 °C, stir and react for 40 min to obtain a fluorine-chain modified prepolymer; (4) Disperse 12 g of ammonium polyphosphate in 25 g of ethanol, then add 30 g of fluorine-chain modified prepolymer, and then adjust the pH value of the solution to 3.8 with acetic acid, heat up to 85 °C, stir and react for 4 h, filter, wash, and vacuum dry to obtain core-shell ammonium polyphosphate; (5) Under a nitrogen atmosphere, mix 22.2 g of isophorone diisocyanate, 64.2 g of polytetrahydrofuran ether glycol (weight average molecular weight of 2000), 15 g of core-shell ammonium polyphosphate, and 150 g of acetone, heat up to 85 °C, stir and react for 1.5 h, then add 4.6 g of 2,2-dimethylolpropionic acid and 1.2 g of stannous octoate, continue to stir and react for 4 h, cool down to 55 °C, add 3.5 g of triethylamine, stir and react for 1.5 h, cool down to room temperature, add 2 g of ethylenediamine and 500 g of deionized water, stir and react for 35 min, and rotary evaporate to remove acetone to obtain a modified polyurethane emulsion.

[0030] (6) Continuously dip and nip the pretreated substrate three times in the modified polyurethane emulsion, keep the impregnation pressure at 0.25 MPa each time, control the pick-up rate at 135%, take it out and dry at 100 °C for 30 min to obtain a polyurethane composite substrate; (7) Immerse the polyurethane composite substrate in deionized water at 95 °C for 50 min to reduce the weight, take it out and wash it three times with water to obtain a water-reduced polyurethane composite substrate; (8) Dip the water-reduced polyurethane composite substrate into a treatment solution containing 3.5 wt% softener Magnasoft 68 and 1.5 wt% antistatic agent Permalose TM twice, then pad-roll it, set and dry it at 135 °C for 2.5 min, and wind it up after finishing with a calender (linear pressure 85 N / mm, temperature 105 °C) to obtain a flame-retardant superfine fiber synthetic leather based on the water reduction technology.

[0031] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the fluorine-chain modified melamine in step (3) is replaced by melamine; The specific steps are as follows: (1) Immerse the PET / PVA sea-island fiber nonwoven fabric in an aqueous solution of polyvinyl alcohol (weight-average molecular weight of 20,000) with a concentration of 12 wt% for 3 min, take it out and dry it at 85 °C for 15 min to obtain a pretreated substrate; (2) Add 20 g of melamine, 10 g of lauryl diamine, and 60 g of an aqueous formaldehyde solution with a concentration of 37 wt% to 100 g of deionized water, then adjust the pH of the solution to 8.6 with an aqueous sodium carbonate solution with a concentration of 10 wt%, raise the temperature to 80 °C, and stir and react for 35 min to obtain a prepolymer; (3) Disperse 10 g of ammonium polyphosphate in 20 g of ethanol, then add 25 g of the prepolymer, and then adjust the pH value of the solution to 3.5 with acetic acid, raise the temperature to 80 °C, stir and react for 3 h, filter by suction, wash, and dry in vacuum to obtain core-shell ammonium polyphosphate; (4) Under a nitrogen atmosphere, mix 22.2 g of isophorone diisocyanate, 64.2 g of polytetrahydrofuran ether glycol (weight-average molecular weight of 2,000), 12 g of core-shell ammonium polyphosphate, and 120 g of acetone, raise the temperature to 80 °C, stir and react for 1 h, then add 4.6 g of 2,2-dimethylolpropionic acid and 1.2 g of stannous octoate, continue to stir and react for 3 h, cool down to 50 °C, add 3.5 g of triethylamine, stir and react for 1 h, cool down to room temperature, add 2 g of ethylenediamine and 450 g of deionized water, stir and react for 30 min, and remove acetone by rotary evaporation to obtain a modified polyurethane emulsion.

[0032] (5) Continuously dip and roll the pretreated substrate in the modified polyurethane emulsion three times, keep the impregnation pressure at 0.2 MPa each time, control the liquor pickup rate at 130%, take it out and dry it at 95 °C for 25 min to obtain a polyurethane composite substrate; (6) Immerse the polyurethane composite substrate in deionized water at 90 °C for 45 min to reduce the weight, take it out and wash it three times with water to obtain a water-reduced polyurethane composite substrate; (7) Dip the water-reduced polyurethane composite substrate into a treatment solution containing 3 wt% softener Magnasoft 68 and 1 wt% antistatic agent Permalose TM twice, then pad it through a calendar (linear pressure 80 N / mm, temperature 100 °C), set and dry it at 130 °C for 2 min, and wind it up after finishing to obtain synthetic leather.

[0033] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that: lauryl diamine in step (3) is replaced by melamine; The specific steps are as follows: (1) Immerse the PET / PVA sea-island fiber nonwoven fabric in an aqueous solution of polyvinyl alcohol (weight-average molecular weight of 20,000) with a concentration of 12 wt% for 3 min, take it out and dry it at 85 °C for 15 min to obtain a pretreated substrate; (2) Add 38.2 g of tridecafluoroheptanoyl and 12.6 g of melamine to 250 g of N,N-dimethylformamide, heat up to 80 °C, stir and react for 6 h, perform rotary evaporation, and vacuum dry to obtain fluorine-chain modified melamine; (3) Add 20 g of fluorine-chain modified melamine, 10 g of melamine, and 60 g of formaldehyde aqueous solution with a concentration of 37 wt% to 100 g of deionized water, then adjust the pH of the solution to 8.6 with a 10 wt% sodium carbonate aqueous solution, heat up to 80 °C, stir and react for 35 min to obtain a fluorine-chain modified prepolymer; (4) Disperse 10 g of ammonium polyphosphate in 20 g of ethanol, then add 25 g of fluorine-chain modified prepolymer, and adjust the pH value of the solution to 3.5 with acetic acid, heat up to 80 °C, stir and react for 3 h, perform suction filtration, washing, and vacuum drying to obtain core-shell ammonium polyphosphate; (5) Under a nitrogen atmosphere, mix 22.2 g of isophorone diisocyanate, 64.2 g of polytetrahydrofuran ether glycol (weight-average molecular weight of 2000), 12 g of core-shell ammonium polyphosphate, and 120 g of acetone, heat up to 80 °C, stir and react for 1 h, then add 4.6 g of 2,2-dimethylolpropionic acid and 1.2 g of stannous octoate, continue to stir and react for 3 h, cool down to 50 °C, add 3.5 g of triethylamine, stir and react for 1 h, cool down to room temperature, add 2 g of ethylenediamine and 450 g of deionized water, stir and react for 30 min, and perform rotary evaporation to remove acetone to obtain a modified polyurethane emulsion.

[0034] (6) Continuously dip and pad the pretreated substrate in the modified polyurethane emulsion three times, keep the impregnation pressure at 0.2 MPa each time, control the wet pick-up rate at 130%, take it out and dry it at 95 °C for 25 min to obtain a polyurethane composite substrate; (7) Immerse the polyurethane composite substrate in deionized water at 90 °C for water reduction for 45 min, take it out and wash it three times with water to obtain a water-reduced polyurethane composite substrate; (8) Dip the water-reduced polyurethane composite substrate into the treatment liquid containing 3 wt% softener Magnasoft 68 and 1 wt% antistatic agent Permalose TM for two dips and two rolls, set and dry at 130 °C for 2 min, and wind up after finishing with a calender (linear pressure 80 N / mm, temperature 100 °C) to obtain synthetic leather.

[0035] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the core-shell ammonium polyphosphate in step (5) is replaced by ammonium polyphosphate; The specific steps are as follows: (1) Immerse the PET / PVA sea-island fiber nonwoven fabric in an aqueous solution of polyvinyl alcohol (weight average molecular weight of 20,000) with a concentration of 12 wt% for 3 min, take it out and dry at 85 °C for 15 min to obtain a pretreated substrate; (2) Under a nitrogen atmosphere, mix 22.2 g of isophorone diisocyanate, 64.2 g of polytetrahydrofuran ether glycol (weight average molecular weight of 2000), 12 g of ammonium polyphosphate and 120 g of acetone, heat up to 80 °C, stir and react for 1 h, then add 4.6 g of 2,2-dimethylolpropionic acid and 1.2 g of stannous octoate, continue to stir and react for 3 h, cool down to 50 °C, add 3.5 g of triethylamine, stir and react for 1 h, cool down to room temperature, add 2 g of ethylenediamine and 450 g of deionized water, stir and react for 30 min, and remove acetone by rotary evaporation to obtain a modified polyurethane emulsion.

[0036] (3) Continuously dip and roll the pretreated substrate in the modified polyurethane emulsion three times, keep the dipping pressure at 0.2 MPa each time, control the pick-up rate at 130%, take it out and dry at 95 °C for 25 min to obtain a polyurethane composite substrate; (4) Immerse the polyurethane composite substrate in deionized water at 90 °C for water reduction for 45 min, take it out and wash it three times to obtain a water-reduced polyurethane composite substrate; (5) Dip the water-reduced polyurethane composite substrate into the treatment liquid containing 3 wt% softener Magnasoft 68 and 1 wt% antistatic agent Permalose TM for two dips and two rolls, set and dry at 130 °C for 2 min, and wind up after finishing with a calender (linear pressure 80 N / mm, temperature 100 °C) to obtain synthetic leather.

[0037] Performance test: Flame retardancy test: According to the vertical method of GB / T 5455-2014, three specimens of 300 mm × 80 mm were cut from the synthetic leather prepared in the examples and comparative examples, conditioned in an environment with a temperature of (23 ± 2) °C and a relative humidity of (50 ± 5)% for 24 h. Using an LFY-601B vertical burning tester, the specimens were vertically fixed in the middle of the combustion chamber. After contacting the lower end of the specimen with a 38 mm standard methane flame for 12 s and then removing it, record the afterflame time and smoldering time of the specimen. The results are shown in Table 1.

[0038] Wash resistance test: According to GB / T 8629-2017, using an SW-12A wash fastness tester, the specimen size was 100 mm × 100 mm, and 5 standard washing cycles were carried out at a water temperature of 40 °C, and then the afterflame time was tested. The results are shown in Table 1.

[0039] Tear strength: According to the trapezoidal method of GB / T 3917.2-2009, the test was carried out on a YG033A tear tester. The pre-cut length was 75 mm, and the tensile speed was 100 mm / min. The tear strength was tested. The results are shown in Table 1.

[0040] Water vapor permeability and air permeability test: The water vapor transmission rate was tested according to GB / T 12704.1-2009, and the air permeability was tested according to GB / T 5453-1997. The set test pressure difference was 100 Pa. The results are shown in Table 1.

[0041] Table 1 Performance test results

[0042] Data analysis: From the data of Examples 1-3 in Table 1, it can be seen that the flame-retardant ultra-fine fiber synthetic leather based on the water reduction technology provided by the present invention exhibits excellent comprehensive performance. In terms of flame retardancy, the material shows extremely short afterflame time and smoldering time. Notably, after washing, the afterflame time of the material hardly increases, indicating that the flame-retardant ultra-fine fiber synthetic leather based on the water reduction technology has excellent wash resistance. In terms of mechanical properties, the relatively high tear strength indicates that the material has good mechanical strength. In addition, the material shows a high water vapor transmission rate and a moderate air permeability, achieving the coordinated unity of functionality and comfort.

[0043] From the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that after using fluorine-chain modified melamine to replace pure melamine, the flame retardant performance of the material has been significantly improved. This may be because fluorine-chain modified melamine can effectively prevent the dissolution of ammonium polyphosphate during the water loss process. Especially after water washing, the flame retardant performance of Example 2 remains stable, with a continuous combustion time of only 3.3 seconds, while that of Comparative Example 1 is extended to 10.2 seconds, indicating that fluorine-chain modification improves the water-washing resistance of the flame retardant system. At the same time, fluorine-chain modified melamine may improve the mechanical properties of the material through the interaction with the polyurethane molecular chain, increasing the tear strength. It is worth noting that this modification does not significantly affect the moisture permeability and air permeability of the material, indicating that fluorine-chain modification mainly acts on the flame retardant mechanism and interface structure of the material, and has little impact on the microscopic pore structure.

[0044] From the data of Example 2 and Comparative Example 2 in Table 1, it can be seen that after using lauryl diamine to replace melamine as a comonomer, although it has little effect on the flame retardant performance, it has a significant impact on the mechanical properties of the material. In terms of flame retardant indicators, the continuous combustion time, smoldering time, and continuous combustion time after water washing are basically the same, indicating that both formulations can form an effective flame retardant system. However, the tear strength of Example 2 reaches 68 N, which is about 33% higher than 51 N of Comparative Example 2. This may be because the long-chain alkyl structure of lauryl diamine provides better chain segment flexibility and intermolecular entanglement ability. As a chain extender, lauryl diamine may promote a more uniform stress distribution in the polymer network, reducing stress concentration points, thereby increasing the tear strength of the material.

[0045] From the data of Example 2 and Comparative Example 3 in Table 1, it can be seen that after using core-shell ammonium polyphosphate to replace ordinary ammonium polyphosphate, both the flame retardant performance and mechanical properties of the material have been significantly improved. The continuous combustion time and smoldering time of Example 2 are reduced by about 64% and 78% respectively compared with Comparative Example 3, and the continuous combustion time after water washing is even greatly reduced by about 79%. This significant performance difference may be attributed to the fact that the core-shell structure provides a protective layer for ammonium polyphosphate, reducing its migration during processing and use. The outer shell layer in the core-shell structure may form better interfacial compatibility with the polyurethane matrix, enabling the flame retardant to be more evenly dispersed in the material. At the same time, this structure may promote the synergistic effect of the carbonization process, forming a denser and more stable carbon layer, improving the heat insulation and oxygen barrier effects. In addition, the crosslinking network that may exist on the surface of core-shell ammonium polyphosphate forms a mechanical interlocking effect with the polyurethane molecular chain, which not only enhances the overall structural stability of the material but also increases the tear strength.

[0046] Those of ordinary skill in the art should understand that any discussion of the above embodiments is exemplary only and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A preparation method of a flame-retardant superfine fiber synthetic leather based on water reduction technology, characterized in that, It includes the following steps: S1: Immerse the PET / PVA sea-island fiber nonwoven fabric in an aqueous solution of polyvinyl alcohol, and dry it to obtain a pretreated substrate. S2: Under a nitrogen atmosphere, mix isophorone diisocyanate, polytetrahydrofuran ether diol, core-shell ammonium polyphosphate, and acetone, heat up to 75 - 85 °C, stir and react for 0.5 - 1.5 h, then add 2,2-dimethylolpropionic acid and stannous octoate, continue to stir and react for 2 - 4 h, cool down to 45 - 55 °C, add triethylamine, stir and react for 0.5 - 1.5 h, cool down to room temperature, add ethylenediamine and deionized water, stir and react for 25 - 35 min, and rotary evaporate to remove acetone to obtain a modified polyurethane emulsion. S3: Continuously pad the pretreated substrate three times in the modified polyurethane emulsion, and dry it to obtain a polyurethane composite substrate. S4: Immerse the polyurethane composite substrate in deionized water at 85 - 95 °C for weight reduction for 40 - 50 min, take it out and wash it with water to obtain a water-weight-reduced polyurethane composite substrate. S5: Dip and pad the water-weight-reduced polyurethane composite substrate twice in a treatment liquid containing a softener and an antistatic agent, set and dry it, and wind it up after finishing with a calender to obtain a flame-retardant superfine fiber synthetic leather based on the water-weight reduction technology. In step S2, the core-shell ammonium polyphosphate is ammonium polyphosphate wrapped by a polymer formed by fluorine-chain modified melamine, lauryl diamine, and a 37 wt% aqueous formaldehyde solution; the weight ratio of the fluorine-chain modified melamine, lauryl diamine, 37 wt% aqueous formaldehyde solution, and deionized water is 15 - 25:5 - 15:40 - 80:80 - 120; the fluorine-chain modified melamine is melamine modified by tridecafluoroheptanoyl; the weight ratio of the tridecafluoroheptanoyl and melamine is 35 - 45:12.

6.

2. The preparation method of the flame-retardant superfine fiber synthetic leather based on the water reduction technology according to claim 1, wherein, In step S1, the concentration of the aqueous polyvinyl alcohol solution is 10 wt% - 15 wt%, the weight-average molecular weight of polyvinyl alcohol is 18000 - 22000, and the impregnation time is 2.5 - 3.5 min.

3. The preparation method of the flame-retardant ultrafine fiber synthetic leather based on the water reduction technology according to claim 1, wherein, In step S2, the weight ratio of isophorone diisocyanate, polytetrahydrofuran ether diol, core-shell ammonium polyphosphate, acetone, 2,2-dimethylolpropionic acid, stannous octoate, triethylamine, ethylenediamine, and deionized water is 22.2:64.2:10 - 15:100 - 150:4.6:1.2:3.5:2:400 - 500.

4. The preparation method of the flame-retardant superfine fiber synthetic leather based on the water reduction technology according to claim 1, characterized in that, In step S2, the weight-average molecular weight of polytetrahydrofuran ether diol is 1500 - 2500.

5. The preparation method of the flame-retardant superfine fiber synthetic leather based on the water reduction technology according to claim 1, characterized in that, In step S3, the padding pressure is 0.18 - 0.22 MPa, and the liquor pickup is 120% - 140%.

6. The preparation method of the flame-retardant ultrafine fiber synthetic leather based on the water reduction technology according to claim 1, characterized in that, In step S5, the softener is Magnasoft 68, with a concentration of 2.5 wt% - 3.5 wt%, and the antistatic agent is Permalose TM, with a concentration of 0.5 wt% - 1.5 wt%.

7. The preparation method of the flame-retardant superfine fiber synthetic leather based on the water reduction technology according to claim 1, characterized in that, In step S5, the temperature for setting and drying is 125 - 135 °C, and the time is 1.5 - 2.5 min.

8. The preparation method of the flame-retardant superfine fiber synthetic leather based on the water reduction technology according to claim 1, characterized in that, In step S5, the linear pressure for calender finishing is 75 - 85 N / mm, and the temperature is 95 - 105 °C.

Images