Production process of fluorine-free dynamic waterproof suede leather

Abstract

The present application relates to the field of shoe leather production, and particularly relates to a production process of fluorine-free dynamic waterproof suede shoe leather. First, the suede microfiber base leather is soaked in a composite biological enzyme preparation to remove surface impurities and open the fiber gap, and then is treated by helium-oxygen mixed gas normal pressure plasma to build micro-pits and active groups on the fiber surface. Subsequently, the base leather is sequentially soaked in waterproof agents containing various modified substances, and a two-stage gradient temperature and pressure padding process is adopted to realize the gradient distribution and crosslinking of the waterproof agent from inside to outside. Finally, a three-stage temperature oscillation drying is adopted, the crosslinking reaction is triggered in the medium temperature section, the siloxane chain is induced to directional arrangement to form a stress buffer layer in the high temperature section combined with mechanical oscillation, and the finished product is obtained through low temperature polishing and setting. The process completely avoids fluorine-containing compounds, solves the problem of easy cracking of traditional waterproof leather in dynamic bending, and maintains the softness of suede. The process is suitable for high-end shoe materials, outdoor equipment and other fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of shoe leather production, and particularly relates to a production process of fluorine-free dynamic waterproof suede shoe leather. BACKGROUND

[0002] Suede leather occupies an important position in the high-end shoe material market due to its unique suede appearance and comfortable wearing experience. However, its porous fiber structure is prone to adsorbing moisture. Although traditional fluorocarbon waterproof agents can impart static waterproofness, they have two major defects: first, fluorine-containing compounds are difficult to degrade in the environment, and there is an ecological accumulation risk; second, the solidified film layer is too rigid, and repeated bending can easily cause micro-cracks, leading to dynamic waterproof failure. With the tightening of global environmental regulations and the increasing demand of consumers for functional shoe materials, developing suede leather with both fluorine-free environmental protection and dynamic waterproof durability has become an urgent need in the industry.

[0003] Current fluorine-free waterproof technology mainly relies on silicone resins or wax emulsions, which achieve basic waterproofing by reducing surface energy. However, it faces some technical challenges. First, the capillary effect formed by the dense pile on the surface of suede leather hinders the penetration of waterproof agents, and conventional treatment can only form a surface coating that is prone to peeling when bent. Second, the cross-linked network of silicone lacks deformation buffering capacity under dynamic stress, and repeated bending can cause brittle fracture of the film layer. Third, adding additional substances to the waterproof agent to improve static waterproofness can easily damage the softness of the leather material. SUMMARY

[0004] To solve the aforementioned technical problems, the present application provides a production process for fluorine-free dynamic waterproof suede shoe leather, which completely avoids fluorine-containing compounds, solves the problem of easy cracking of traditional waterproof leather when dynamically bent, and maintains the softness of suede. This is achieved through the following technical solutions.

[0005] The production process for fluorine-free dynamic waterproof suede shoe leather of the present application comprises the following steps:

[0006] Step 1: immerse the suede microfiber base leather in a complex biological enzyme preparation with a mass ratio of 3:1 of cellulase and protease for 2-5 minutes, and then treat it with plasma generated from a mixture of helium and oxygen gases with a volume ratio of 10-19:1 at a power of 8 kW;

[0007] Step 2: mix hydrophobic silicone resin, reactive block copolymer, modified nano-ZnO, water-based polycarbodiimide crosslinking agent, penetrant, and deionized water to obtain a waterproof agent;

[0008] Step 3: sequentially treat the base leather treated in Step 1 as follows:

[0009] First immersion: soak in the waterproof agent at 32-35°C for 3-5 minutes, and press to a liquid retention rate of 60%-70%;

[0010] Second dip: soak in waterproofing agent at 42-45℃ for 3-5min, and roll to 45%-55% liquid rate;

[0011] Step 4: three-stage gradient drying for the base leather treated in step 3:

[0012] First stage: static drying at 85-95℃ for 2min;

[0013] Second stage: static drying at 125-135℃ for 3min;

[0014] Third stage: oscillation drying along the length of the base leather at 145-155℃ for 4min;

[0015] Step 5: calendering the dried base leather at 67-73℃ and 2MPa for 9-11s to obtain the fluorine-free dynamic waterproof suede leather.

[0016] Preferably, the total enzyme concentration of the composite biological enzyme preparation in step 1 is 1.5g / L, and the treatment temperature is 35-45℃.

[0017] The airflow speed of the plasma treatment is 10L / min, and the treatment speed is 6m / min.

[0018] Preferably, the components in step 2 are as follows in terms of mass fraction:

[0019] Hydrophobic silicone resin 18-22 parts, which is hydroxyl-terminated polydimethylsiloxane with a viscosity of 800mPa·s;

[0020] Reactive block copolymer 14-18 parts, which is a bifunctional copolymer containing glycidyl ether groups and polydimethylsiloxane segments, with a siloxane mass fraction of 60%-70%;

[0021] Modified nano-ZnO 5-7 parts, with a particle size of 30nm and modified by γ-(methacryloyloxy)propyl trimethoxysilane;

[0022] Water-based polycarbodiimide crosslinking agent 3-5 parts;

[0023] Penetrating agent 0.8-1.2 parts.

[0024] Preferably, the water-based polycarbodiimide crosslinking agent is an aliphatic polycarbodiimide with terminal grafted polyethylene glycol monomethyl ether or sulfonate groups.

[0025] Preferably, the penetrating agent is a fatty alcohol polyoxyethylene ether.

[0026] Preferably, the first rolling pressure in step 3 is 0.2MPa, and the second rolling pressure is 0.6MPa.

[0027] Preferably, the oscillation frequency of the oscillation drying in step 4 is 10 Hz, and the amplitude is 2 mm.

[0028] Preferably, the thickness of the suede microfiber base leather in step 1 is 1.8-2.0 mm.

[0029] After the above technical solutions are adopted, the application has the following beneficial effects:

[0030] 1. The biological enzyme-plasma synergistic pretreatment is adopted to open deep penetration channels while removing fiber impurities, so that the fluorine-free waterproof agent can effectively penetrate into the fiber interior, and the ecological toxicity risk is eliminated from the source.

[0031] 2. The first dip-jet low-temperature light pressure ensures that the waterproof agent penetrates into the fiber capillary, and the second dip-jet high-temperature heavy pressure promotes the formation of a flexible film on the surface; during the drying stage, the mechanical oscillation induces the directional arrangement of the siloxane chain to form a molecular stress buffer layer, so that the waterproof film remains intact after 100,000 times of bending.

[0032] 3. The modified nano zinc oxide is added to construct a micro-nano secondary rough structure on the fiber surface, impart super-hydrophobicity, and maintain the soft and fluffy touch of the suede.

[0033] 4. The reaction-type block copolymer is covalently bonded to the active groups of the base leather to achieve deep anchoring, and the water-based polycarbodiimide crosslinking agent constructs a three-dimensional network to solve the easy peeling problem of the traditional coating and significantly improve the waterproof durability in a humid and hot environment.

[0034] 5. The biological enzyme treatment replaces the strong acid and strong alkali process, the plasma parameters are precisely controlled to regulate the surface pit structure, the gradient temperature and pressure design realizes the accurate balance of penetration and film formation, and the energy consumption and waste liquid treatment cost are greatly reduced. DETAILED DESCRIPTION

[0035] The features and exemplary embodiments of various aspects of the application will be described in detail below, in order to make the purposes, technical solutions and advantages of the application more clear and apparent, the application will be further described in detail below in combination with specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the application, and are not configured to limit the application. The application can be implemented without some of these specific details for those skilled in the art. The following description of the embodiments is only to provide a better understanding of the application by showing examples of the application.

[0036] The embodiment of the application provides a production process of a fluorine-free dynamic waterproof suede leather, which specifically comprises the following steps.

[0037] Step 1:

[0038] The suede microfiber base leather is soaked in a composite biological enzyme preparation at 35-45℃ for 2-5min, then taken out and water controlled until the surface is dry, and then treated by a normal pressure plasma machine.

[0039] The thickness of the suede microfiber base leather is 1.8-2.0mm.

[0040] The total enzyme concentration of the biological enzyme in the composite biological enzyme preparation is 1.5g / L, and the cellulase and protease are mixed in a mass ratio of 3:1.

[0041] The plasma power in the normal pressure plasma machine is 8kW, the mixed gas is prepared by mixing helium and oxygen in a volume ratio of 10-19:1, the gas flow rate is 10L / min, and the processing speed is 6m / min.

[0042] In the above process, the composite biological enzyme preparation is used for the surface of the suede microfiber base leather. The cellulase in the composite biological enzyme preparation can selectively hydrolyze the microfibers on the surface of the microfiber base leather, eliminate roughness, open the gap between fibers, and increase the specific surface area. The protease in the composite biological enzyme preparation can degrade collagen residues and expose more active groups such as hydroxyl and amino groups. The soaking process controls the temperature at 35-45℃ to maintain the activity of the biological enzyme and ensure the surface treatment effect.

[0043] This step improves the cleanliness and hydrophilicity of the base leather surface by soaking treatment with the composite biological enzyme preparation, creating a channel for the subsequent penetration of the waterproof agent, and replacing the traditional strong chemical treatment and other traditional methods to avoid damage to the fiber strength.

[0044] In the above process, during the operation of the normal pressure plasma machine, the proportion of helium in the mixed gas is high, so that a high-density uniform plasma can be generated to form an active atmosphere protection layer, facilitating the action of oxygen on the surface of the base leather. The oxygen in the mixed gas is ionized to form oxygen free radicals or ozone molecules, which then react with the surface of the base leather to introduce active groups such as carboxyl and carbonyl groups on the surface of the base leather.

[0045] In addition, adjusting the power of the normal pressure plasma machine to 8kW can ensure that the electron energy is greater than 10eV, so that the electrons can break the carbon-carbon bond or carbon-hydrogen bond on the surface of the fiber, playing a certain etching role and forming micron-level pits on the surface of the base leather.

[0046] Therefore, the treatment process of the normal pressure plasma machine combines the dual effects of physical etching and chemical modification, which can significantly improve the surface energy of the base leather and make the hydrophobic waterproof agent more easily spread and penetrate.

[0047] Step 2:

[0048] The waterproofing agent is prepared by mixing 18-22 parts of hydrophobic silicone resin, 14-18 parts of reactive block copolymer, 5-7 parts of modified nano-ZnO, 3-5 parts of water-based polycarbodiimide crosslinking agent, 0.8-1.2 parts of penetrant and 130-170 parts of deionized water.

[0049] The hydrophobic silicone resin is a hydroxyl-terminated polydimethylsiloxane with a viscosity of 800 mPa·s.

[0050] The reactive block copolymer is a dual-functional copolymer containing epoxy and siloxane groups, the epoxy group is a glycidyl ether group, and the siloxane is polydimethylsiloxane. The mass fraction of siloxane in the copolymer is 60-70%.

[0051] The modified nano-ZnO has a particle size of 30 nm. The modified nano-ZnO is obtained by modifying zinc oxide nanoparticles with γ-(methacryloyloxy)propyl trimethoxysilane. In this process, the silane hydrolysis forms a covalent bond with the surface of zinc oxide, and the hydrophobic group in the silane coupling agent is exposed outward, thereby significantly enhancing the hydrophobicity of nano-ZnO.

[0052] The water-based polycarbodiimide crosslinking agent is an aliphatic polycarbodiimide with terminal grafted polyethylene glycol monomethyl ether or sulfonate groups, which can effectively improve the water dispersibility of each component.

[0053] The penetrant is a fatty alcohol polyoxyethylene ether.

[0054] In the above process, the hydrophobic silicone resin undergoes a condensation reaction during drying, in which the Si-OH group dehydrates to form a Si-O-Si three-dimensional network, and the methyl groups in the molecular chain are oriented outward, thereby forming a low surface energy barrier on the surface of the leather and enhancing its waterproof performance. The hydroxyl and carboxyl groups in the resin react with the unsaturated groups in the water-based polycarbodiimide crosslinking agent to form acylurea bonds or ester bonds, further increasing the crosslinking density and further enhancing its water resistance.

[0055] The glycidyl ether groups in the reactive block copolymer in the waterproofing agent can undergo ring-opening reaction with the carboxyl or amino groups on the surface of the leather fibers to form covalent bonds, thereby achieving the anchoring effect of the waterproofing agent on the leather. At the same time, the polydimethylsiloxane segment in the copolymer has excellent molecular chain flexibility, which can impart the waterproofing film with deformation recovery ability under dynamic bending, thereby imparting the waterproofing agent with dynamic waterproofing effect.

[0056] The modified nano-zinc oxide avoids nano-agglomeration and enhances compatibility with organic silicon. In addition, the nano-particles of zinc oxide can construct micro-nano secondary structures on the surface of the fibers, making the contact angle of water greater than 150 degrees and further enhancing its hydrophobicity.

[0057] The penetrating agent can improve the non-ionic surface activity, thereby reducing the surface tension of the waterproof agent, so that the effective components of the waterproof agent can quickly penetrate into the micro-pores of the fibers, thereby realizing the combination of the waterproof layer and the base leather.

[0058] Step 3:

[0059] The suede microfiber base leather treated in step 1 is soaked in the waterproof agent obtained in step 2, the temperature of the waterproof agent is 32-35℃, the soaking time is 3-5min, after soaking, it is taken out and rolled in the rolling mill, the rolling pressure is 0.2MPa, and the rolling is carried out until the liquid retention rate of the suede microfiber base leather is 60%-70%;

[0060] The rolled suede microfiber base leather is soaked in the waterproof agent at 42-45℃ for 3-5min, after soaking, it is taken out and rolled in the rolling mill, the rolling pressure is 0.6MPa, and the rolling is carried out until the liquid retention rate of the suede microfiber base leather is 45%-55%.

[0061] In the above steps, in the first immersion, the temperature is 32-35℃, which delays the cross-linking reaction and allows the waterproof agent molecules to fully diffuse into the capillary tubes inside the fibers; 0.2MPa light pressure is used to retain high liquid retention rate, which prevents the surface from forming film too early and blocking the penetration channel.

[0062] In the second immersion, the temperature is 42-45℃, which promotes the pre-crosslinking of polycarbodiimide and forms a nascent network inside the fibers; 0.6MPa is used to extrude excess additives, which avoids the migration of additives to the surface during drying, and finally maintains a liquid retention rate of 45%-55%, which can balance the drying energy consumption and ensure the continuity of film formation.

[0063] The above steps realize the gradient distribution of the waterproof layer on the surface of the base leather by combining deep penetration and shallow film formation, so that the inner waterproof agent and the internal fibers of the base leather realize the highest degree of cross-linking, and the outer waterproof agent maintains the optimal waterproof performance and softness.

[0064] Step 4:

[0065] The suede microfiber base leather treated in step 3 is dried by using a three-stage gradient temperature oscillation process.

[0066] Specific operation process of the three-stage gradient temperature oscillation process is as follows:

[0067] First stage: temperature is 85-95℃, time is 2min, and no vibration;

[0068] Second stage: temperature is 125-135℃, time is 3min, and no vibration;

[0069] The third segment: the temperature is 145-155℃, the time is 4min, oscillate along the length direction of suede microfiber base leather, the frequency is 10Hz, and the amplitude is 2mm.

[0070] In the above step process, the first stage uses a lower temperature to remove water mildly, that is, to evaporate part of free water to maintain a certain humidity to prevent the surface layer from peeling off, thereby preserving the internal diffusion channel.

[0071] The second stage temperature rises to 125-135℃, which exceeds the activation threshold of the water-based polycarbodiimide crosslinking agent, triggering rapid crosslinking with the silicone resin to form the main waterproof network.

[0072] The third stage uses a temperature range of 145-155℃, which can further improve the density of the silicone crosslinking network to enhance the heat resistance, combined with mechanical oscillation along the length direction of the base leather, which can induce the directional arrangement of siloxane chains to form a molecular stress buffer layer to support the subsequent dynamic waterproof performance. In addition, the addition of mechanical oscillation during the drying process can offset the hydrogen bond rearrangement between fibers to a certain extent, maintain the fluffiness of the suede, and the unidirectional oscillation can enable the flexible siloxane chain segments to be arranged in a certain direction to form a stress buffer layer, thereby enabling the film layer to withstand bending stress during dynamic bending without cracking, achieving its dynamic waterproof effect.

[0073] Step 5:

[0074] The suede microfiber base leather treated in step 4 is processed using a calender to prepare the final fluorine-free dynamic waterproof suede shoe leather.

[0075] The working parameters of the calender are as follows: the surface temperature is 67-73℃, the pressure is 2MPa, and the pressure holding time is 9-11s.

[0076] In the above step process, the calender surface temperature of 67-73℃ is lower than the glass transition temperature of the silicone resin, which can avoid thermal damage and soften the resin chain for easy shaping.

[0077] The compaction is performed at a pressure of 2MPa, which can flatten the loose pile on the surface layer, thereby improving the flatness of the surface. In addition, this step should avoid excessive pressure that causes the structure of nano-zinc oxide to collapse, resulting in a decrease in hydrophobicity.

[0078] In order to facilitate further understanding of the present application, several embodiments and comparative examples of the present application are given below.

[0079] Example 1

[0080] Step 1:

[0081] The suede microfiber base leather with a thickness of 2.0 mm is soaked in a complex biological enzyme preparation with a total enzyme concentration of 1.5 g / L, in which cellulase and protease are mixed in a mass ratio of 3:1, for 3 min. After soaking, the water is controlled to dry, and then the surface treatment is performed using an atmospheric pressure plasma machine under the following conditions: power 8 kW, mixed gas (helium and oxygen in a volume ratio of 19:1), gas flow rate 10 L / min, and processing speed 6 m / min.

[0082] Step 2:

[0083] According to the mass fraction, 20 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 800 mPa·s, 16 parts of a bifunctional copolymer containing epoxy and siloxane groups, 6 parts of modified nano-ZnO with a particle size of 30 nm modified by γ-(methacryloyloxy)propyltrimethoxysilane, 4 parts of an aliphatic polycarbodiimide with terminal polyethylene glycol monomethyl ether or sulfonate groups, 1 part of a fatty alcohol polyoxyethylene ether, and 150 parts of deionized water are mixed uniformly to prepare a waterproofing agent.

[0084] Step 3:

[0085] The suede microfiber base leather treated in step 1 is soaked in the waterproofing agent obtained in step 2, with a temperature of 35℃ and a soaking time of 4 min. After soaking, the leather is taken out and rolled in a rolling mill with a pressure of 0.2 MPa to remove excess water, and the resulting suede microfiber base leather has a liquid retention rate of 65%.

[0086] The suede microfiber base leather after rolling is soaked in a waterproofing agent at 45℃ for 4 min, and then taken out and rolled in a rolling mill with a pressure of 0.6 MPa to remove excess water, and the resulting suede microfiber base leather has a liquid retention rate of 50%.

[0087] Step 4:

[0088] The suede microfiber base leather treated in step 3 is sequentially treated using the following three-stage process:

[0089] First stage: temperature 90℃, time 2 min, no vibration;

[0090] Second stage: temperature 130℃, time 3 min, no vibration;

[0091] Third stage: temperature 150℃, time 4 min, oscillation along the length direction of the suede microfiber base leather with a frequency of 10 Hz and an amplitude of 2 mm.

[0092] Step 5:

[0093] The suede microfiber base leather treated by step 4 is processed by a calender with a surface temperature of 70 DEG C and a pressure of 2 MPa, and the pressure holding time is 10 s, to prepare the final fluorine-free dynamic waterproof suede shoe leather.

[0094] Example 2

[0095] This example is based on example 1, and the volume ratio of helium and oxygen in step 1 is adjusted, specifically:

[0096] Step 1:

[0097] The suede microfiber base leather with a thickness of 2.0 mm is soaked in a composite biological enzyme preparation with a total enzyme concentration of 1.5 g / L at 40 DEG C, and the cellulase and protease are mixed in a mass ratio of 3:1, and the soaking time is 3 min. After soaking, the water is controlled to dry, and then the surface treatment is carried out by using an atmospheric pressure plasma machine under the following conditions: power 8 kW, mixed gas prepared by mixing helium and oxygen in a volume ratio of 10:1, gas flow rate 10 L / min, and processing speed 6 m / min.

[0098] The remaining steps are the same as example 1.

[0099] Example 3

[0100] This example is based on example 1, and the proportion of each additive in step 2 is adjusted, specifically:

[0101] Step 2:

[0102] According to the mass fraction, 20 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 800 mPa·s, 18 parts of a bifunctional copolymer containing epoxy and siloxane groups, 5 parts of modified nano-ZnO with a particle size of 30 nm and modified by γ-(methacryloyloxy) propyl trimethoxysilane, 5 parts of aliphatic polycarbodiimide with terminal grafted polyethylene glycol monomethyl ether or sulfonate groups, 1 part of fatty alcohol polyoxyethylene ether, and 130 parts of deionized water are mixed uniformly to prepare a waterproof agent for standby.

[0103] The remaining steps are the same as example 1.

[0104] Example 4

[0105] This example is based on example 1, and the temperature of the waterproof agent in step 3 and the final liquid rate are adjusted, specifically:

[0106] Step 3:

[0107] The suede microfiber base leather treated in step 1 is soaked in the waterproofing agent obtained in step 2, the waterproofing agent temperature is 32℃, the soaking time is 4min, after soaking, it is taken out and water-rolled in a rolling mill, the rolling mill pressure is 0.2MPa, and the water-rolling is performed until the suede microfiber base leather has a liquid rate of 60%;

[0108] The water-rolled suede microfiber base leather is soaked in the waterproofing agent at 42℃ for 4min, after soaking, it is taken out and water-rolled in a rolling mill, the rolling mill pressure is 0.6MPa, and the water-rolling is performed until the suede microfiber base leather has a liquid rate of 45%.

[0109] The remaining steps are the same as those in example 1.

[0110] Example 5

[0111] This example is based on example 1, and the temperature parameters of the three-stage gradient temperature oscillation process in step 4 are adjusted, specifically:

[0112] Step 4:

[0113] The suede microfiber base leather treated in step 3 is treated by using the following three-stage process in sequence:

[0114] First stage: temperature is 85℃, time is 2min, and no vibration;

[0115] Second stage: temperature is 125℃, time is 3min, and no vibration;

[0116] Third stage: temperature is 145℃, time is 4min, oscillation along the length direction of the suede microfiber base leather, frequency is 10Hz, and amplitude is 2mm.

[0117] The remaining steps are the same as those in example 1.

[0118] Example 6

[0119] This example is based on example 1, and the working parameters of the calender in step 5 are adjusted, specifically:

[0120] Step 5:

[0121] The suede microfiber base leather treated in step 4 is processed by using a calender with a surface temperature of 67℃ and a pressure of 2MPa, and the pressure maintaining time is 9s, to prepare a final fluorine-free dynamic waterproof suede shoe leather.

[0122] Comparative example 1

[0123] This comparative example is based on example 1, and step 1 is modified, specifically:

[0124] Step 1:

[0125] The suede microfiber base leather with a thickness of 2.0 mm is treated by the atmospheric pressure plasma machine under the following conditions: a power of 8 kW, a mixed gas prepared by mixing helium and oxygen at a volume ratio of 19:1, a gas flow rate of 10 L / min, and a treatment speed of 6 m / min, and is then reserved.

[0126] The remaining steps are exactly the same as those in Example 1.

[0127] Comparative Example 2

[0128] This comparative example is based on Example 1, and the proportion of bio-enzymes in the composite bio-enzyme preparation is adjusted, specifically as follows:

[0129] Step 1:

[0130] The suede microfiber base leather with a thickness of 2.0 mm is soaked in a composite bio-enzyme preparation in which the total enzyme concentration of bio-enzymes is 1.5 g / L, and the cellulase and protease are mixed at a mass ratio of 1:1, for 3 min at 40°C. After soaking, the leather is taken out, water is controlled until the surface is dry, and then the surface is treated by the atmospheric pressure plasma machine under the following conditions: a power of 8 kW, a mixed gas prepared by mixing helium and oxygen at a volume ratio of 19:1, a gas flow rate of 10 L / min, and a treatment speed of 6 m / min, and is then reserved.

[0131] The remaining steps are exactly the same as those in Example 1.

[0132] Comparative Example 3

[0133] This comparative example is based on Example 1, and Step 2 is modified, specifically as follows:

[0134] Step 2:

[0135] According to mass parts, 20 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 800 mPa·s, 16 parts of a bifunctional copolymer containing epoxy and siloxane groups, 4 parts of an aliphatic polycarbodiimide with a terminal grafting of polyethylene glycol monomethyl ether or sulfonate groups, 1 part of a fatty alcohol polyoxyethylene ether, and 150 parts of deionized water are uniformly mixed to prepare a waterproof agent for standby.

[0136] The remaining steps are exactly the same as those in Example 1.

[0137] Comparative Example 4

[0138] This comparative example is based on Example 1, and Step 3 is modified, specifically as follows:

[0139] Step 3:

[0140] The suede microfiber base leather treated in step 1 is soaked in the waterproofing agent obtained in step 2, the waterproofing agent temperature is 40℃, the soaking time is 4 min, after soaking, it is taken out and put into the calender for water rolling, the calender pressure is 0.6 MPa, and the water rolling is performed until the liquid rate of the suede microfiber base leather is 50%;

[0141] The remaining steps are exactly the same as those in Example 1.

[0142] Comparative Example 5

[0143] This comparative example is based on Example 1, and step 4 is modified, specifically:

[0144] The suede microfiber base leather treated in step 3 is treated by using the following three-stage process in sequence:

[0145] The first stage: the temperature is 90℃, and the time is 2 min;

[0146] The second stage: the temperature is 130℃, and the time is 3 min;

[0147] The third stage: the temperature is 150℃, and the time is 4 min.

[0148] The remaining steps are exactly the same as those in Example 1.

[0149] According to the above examples and comparative examples, no-fluorine dynamic waterproof suede shoes are prepared, and the finished products are cut into multiple 75mm×60mm rectangular specifications with neat edges and no burrs. The multiple samples of each example and comparative example are tested by a leather dynamic waterproof testing machine, and the number of flexes of each sample is recorded.

[0150] Among them, the working principle of the dynamic waterproof testing machine is to detect the water penetration resistance index of the material through periodic flexing action, and then simulate the waterproof performance of leather, artificial leather, cloth and the like in a bending state. Through automatic detection of penetration, when water penetration causes the circuit to be conductive, the device automatically stops counting and records the time or the number of flexes.

[0151] In addition, the static water pressure resistance of each sample is tested according to ISO 811:2018 “Determination of Resistance to Water Penetration of Textiles Hydrostatic Pressure Test”, and the static water pressure resistance data is recorded.

[0152] The test data of the samples prepared in each example and comparative example are as follows:

[0153]

[0154] According to the analysis of the above data:

[0155] Example 1 adopts the complete optimization process chain to achieve excellent static and dynamic waterproofing. The high hydrostatic pressure resistance is derived from the synergistic pretreatment of biological enzymes and plasma: cellulase precisely opens the fiber micro-gap, protease removes impurities to expose active groups, and helium-oxygen plasma constructs micro-pits on the fiber surface and introduces chemical anchoring sites, laying the foundation for deep penetration of waterproofing agent. The dynamic bending durability relies on the dual action of gradient padding and oscillation drying: the first low-temperature light padding ensures that the waterproofing agent penetrates into the internal capillary of the fiber, and the second high-temperature heavy padding promotes the formation of a shallow film; mechanical oscillation during the drying stage effectively induces the directional arrangement of siloxane chains, forming a molecular-level stress buffer layer that maintains the structural integrity of the film during repeated bending.

[0156] In Example 2, excessive oxygen causes excessive oxidation etching on the fiber surface, and the micro-pit structure becomes unstable with a reduced number of active groups. The binding force of the waterproofing agent on the substrate surface is weakened, resulting in a simultaneous decrease in static waterproofing and dynamic durability.

[0157] In Example 3, the proportion of the waterproofing agent formula is adjusted, with an increase in the amount of block copolymer and crosslinking agent, and a simultaneous decrease in the amount of nano-zinc oxide and solvent. More block copolymer strengthens the covalent anchoring of active groups on the substrate, and additional crosslinking agent enhances network density, supporting dynamic bending durability. However, the reduction in the amount of nano-zinc oxide weakens the micro-nano rough structure, resulting in a slight decrease in static waterproofing performance.

[0158] In Example 4, reducing the padding temperature does not significantly affect the formation of the static waterproofing layer, but delays the crosslinking reaction process, resulting in insufficient internal crosslinking network density, making the molecular chains prone to slipping and causing micro-cracks when the material is bent.

[0159] In Example 5, the third segment temperature does not reach the activation threshold of the crosslinking agent, resulting in insufficient crosslinking of the waterproofing network. The fragile network structure cannot withstand bending stress, accelerating the cracking of the film.

[0160] In Comparative Example 1, enzyme treatment is not used, resulting in the failure to open the micro-gaps on the fiber surface, and the waterproofing agent can only cover the surface layer of the substrate. There is a lack of deep anchoring between the film and the substrate, and interfacial peeling occurs easily when bending.

[0161] In Comparative Example 2, the proportion of biological enzymes is imbalanced, with an excessively high proportion of protease leading to excessive degradation of collagen, expanding the gap between fibers and making the structure loose. This not only weakens the mechanical strength of the substrate, but also reduces the anchoring effect of the waterproofing agent, significantly reducing the bending life.

[0162] In Comparative Example 3, nano-zinc oxide is not added, and the absence of the micro-nano secondary rough structure leads to an increase in surface energy, making water molecules more easily penetrate the surface. At the same time, the material loses the stress dispersion carrier, and the bending stress is concentrated in local areas, accelerating the cracking of the waterproofing layer.

[0163] Comparative Example 4 uses single padding, which makes waterproofing agent accumulate in the shallow layer and cannot penetrate into the fiber interior. When bending, the surface film is broken first, and water penetrates along the unprotected fiber capillary, and the dynamic waterproof function is completely invalid.

[0164] In Comparative Example 5, the oscillation drying process is not used, so that the static waterproof layer can be formed, but the drying process causes the hydrogen bond rearrangement to make the suede structure hard, and the siloxane chain is arranged in disorder. The material lacks the molecular level deformation buffer capacity when bending, and the film layer is easy to crack.

[0165] From the above data and analysis, it can be seen that the use of biological enzyme pretreatment is the basis for penetration, and the technology that can selectively open the fiber channel is irreplaceable, and the absence will directly lead to insufficient anchoring depth of waterproofing agent; the use of two dip two roll process can realize gradient crosslinking structure, which can determine the dynamic performance, because the deep layer of strong anchoring and the surface flexibility are designed in coordination, which is the key to resist repeated bending stress, and the single padding process destroys this structure and is devastating; the nano zinc oxide in the waterproofing agent component not only improves the surface hydrophobicity through micro-nano structure, but also disperses the bending stress as a rigid particle, and the performance drops sharply after the absence; the use of three-stage gradient temperature oscillation process, mechanical oscillation not only maintains the suede fluffiness, but also realizes stress buffering through induced molecular chain directional arrangement, and this implicit process makes a significant contribution to dynamic waterproofing.

[0166] In addition, the component ratio fluctuates within a reasonable range, and the moderate adjustment of the calendering temperature has limited effect on the performance.

[0167] According to the above embodiments of the present application, these embodiments do not describe all the details and are not limited to the specific embodiments. Obviously, according to the above description, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A production process for fluorine-free dynamic waterproof suede shoe leather, characterized in that, Includes the following steps: Step 1: Immerse the suede microfiber base leather in a compound biological enzyme preparation of cellulase and protease at a mass ratio of 3:1 for 2-5 minutes, then remove it and treat it with plasma. The plasma is generated by a mixture of helium and oxygen at a volume ratio of 10-19:1 at a power of 8kW. Step 2: Prepare a waterproofing agent by mixing hydrophobic silicone resin, reactive block copolymer, modified nano-ZnO, waterborne polycarbodiimide crosslinking agent, penetrant and deionized water; Step 3: Process the base leather treated in Step 1 sequentially as follows: First impregnation and rolling: Immerse in waterproofing agent at 32-35℃ for 3-5 minutes, then roll until the liquid content is 60%-70%; Second impregnation: Immerse in waterproofing agent at 42-45℃ for 3-5 minutes, then roll until the liquid content is 45%-55%; Step 4: Perform a three-stage gradient drying process on the base leather treated in Step 3: First step: Dry at 85-95℃ for 2 minutes; Second step: Dry at 125-135℃ for 3 minutes; Third stage: Dry along the length of the base leather at 145-155℃ with vibration for 4 minutes; Step 5: Calender the dried base leather at 67-73℃ and 2MPa for 9-11 seconds to obtain fluorine-free dynamic waterproof suede shoe leather; In step 2, the components are expressed in parts by mass as follows: 18-22 parts of hydrophobic organosilicon resin, which is a hydroxyl-terminated polydimethylsiloxane with a viscosity of 800 mPa·s; 14-18 parts of reactive block copolymer, which is a bifunctional copolymer containing glycidyl ether groups and polydimethylsiloxane segments, with siloxane accounting for 60%-70% by mass; 5-7 parts of modified nano-ZnO with a particle size of 30 nm and modified with γ-(methacryloyloxy)propyltrimethoxysilane; 3-5 parts of water-based polycarbodiimide crosslinking agent; Penetrant 0.8 to 1.2 parts.

2. The process according to claim 1, characterized in that: The total enzyme concentration of the compound biological enzyme preparation mentioned in step 1 is 1.5 g / L, and the treatment temperature is 35–45 °C; The plasma treatment has a gas flow rate of 10 L / min and a processing speed of 6 m / min.

3. The process according to claim 1, characterized in that, The aqueous polycarbodiimide crosslinking agent is an aliphatic polycarbodiimide terminally grafted with polyethylene glycol monomethyl ether or sulfonate groups.

4. The process according to claim 1, characterized in that: The penetrant is fatty alcohol polyoxyethylene ether.

5. The process according to claim 1, characterized in that, In step 3, the first rolling pressure is 0.2 MPa, and the second rolling pressure is 0.6 MPa.

6. The process according to claim 1, characterized in that, In step 4, the oscillation frequency of the oscillation drying process is 10 Hz and the amplitude is 2 mm.

7. The process according to claim 1, characterized in that, The thickness of the suede microfiber base leather mentioned in step 1 is 1.8 to 2.0 mm.

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