Manufacturing method of upper-pulling breathable protective shoes

Abstract

The invention relates to the technical field of shoe manufacturing, in particular to a manufacturing method of upper-pulling breathable protective shoes. The method comprises the following steps: preparing a carboxyl-terminated polyether polyurethane dispersion, taking one part of the dispersion as a vamp side prime coat, and mixing the other part of the dispersion with nano zinc oxide and water-based polycarbodiimide to obtain sole side main glue; the process comprises the following steps: firstly, coating a prime coat on the edge of a pull upper of a vamp, drying, and then spraying a zinc salt treating fluid; meanwhile, coating main glue on the attached edge of the sole, and then aligning, hot-pressing and post-curing the main glue and the sole. The method aims at synchronously improving the bonding strength, flex fatigue resistance and damp-heat aging resistance of the uppers and the soles through partitioned sizing and gradient interface construction, and meanwhile, the high moisture permeability of the vamps is kept.

Description

Technical Field

[0001] This invention relates to the field of footwear manufacturing technology, and in particular to a method for manufacturing a breathable and protective shoe with uppers. Background Technology

[0002] In the field of protective footwear, especially in the area of ​​upper-strap protective shoes that emphasize breathability, a long-standing and seemingly irreconcilable contradiction exists. Traditional shoemaking processes and adhesive systems often struggle to maintain the high moisture permeability of the upper while providing durable and reliable bonding strength between the upper and sole. While conventional solvent-based adhesives or high-solids-content hot melt adhesives can provide high initial adhesion, their dense adhesive layers or their blocking effect on the shoe's air channels can significantly impair the upper's water vapor permeability, affecting the dryness and comfort of the wearer. Therefore, the industry has developed various more environmentally friendly adhesive systems, such as waterborne polyurethanes, aiming to reduce the impact on the breathable structure.

[0003] However, simply switching to a water-based system does not fundamentally solve the problem of durable bonding. Due to the significant difference in material properties between the sole and the upper (especially composite uppers), stress concentration easily occurs at the interface during long-term wear and bending, leading to adhesive layer fatigue, which manifests as the upper and sole separating after bending. Even more problematic is that protective shoes inevitably come into contact with sweat and moisture during actual use. The hot and humid environment exacerbates the hydrolysis, plasticization, or interface damage of the adhesive layer, causing a sharp decline in adhesive strength, while moisture permeability often decreases simultaneously. Existing technical solutions often improve adhesion by increasing the thickness of the adhesive layer, using stronger cross-linking agents, or heavily treating the upper. However, these methods often sacrifice the softness and breathability of the upper, or cause interface embrittlement, making it more prone to microcracks and their propagation during bending.

[0004] Some improvements attempt to enhance interfacial interactions by introducing metal ions (such as zinc ions) or nanomaterials. However, simply mixing these components into the adhesive matrix makes it difficult to control their effective concentration and distribution at the interface, resulting in limited enhancement and potential impact on application performance due to premature reaction. Other solutions employ multiple crosslinking or complex primers, but the functions of each component interfere with each other, leading to a narrow process window, large performance fluctuations, and difficulty in achieving a stable balance of breathability, adhesion, and durability in large-scale production. Therefore, how to achieve synergistic innovation in molecular design, interface construction, and process pathways to build a gradient and stable bonding interface that can synergistically resist mechanical stress and hygrothermal aging without blocking breathable micropores has become a critical technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a method for manufacturing breathable protective shoes with uppers, so as to solve the problem that in the prior art, it is difficult to simultaneously achieve the bonding strength of the upper and sole, the interface stability after long-term folding resistance, and the performance retention rate after damp heat aging, and that existing reinforcement methods are prone to damaging the breathability of the shoe upper or causing interface embrittlement.

[0006] To achieve the above objectives, the present invention provides a method for manufacturing breathable protective shoes with uppers, comprising the following steps: (1) Polytetrahydrofuran ether diol was reacted with isophorone diisocyanate to obtain a polyether-type polyurethane prepolymer with isocyanate groups at both ends; (2) The polyether-type polyurethane prepolymer was extended with 1,4-butanediol chain, and β-alanine was prepared into anhydrous N,N-dimethylacetamide suspension and then reacted with the chain-extended system to obtain carboxyl-terminated polyether-type polyurethane resin. (3) After diluting the carboxyl-terminated polyether polyurethane resin with acetone, it is partially neutralized with triethylamine to convert some of the chain-terminal carboxyl groups into triethylamine salts. Then, deionized water is added for emulsification and dispersion, and acetone and anhydrous N,N-dimethylacetamide are removed to obtain a carboxyl-terminated polyether polyurethane dispersion. (4) Take a portion of the carboxyl-terminated polyether polyurethane dispersion as the side coating of the shoe upper, and take another portion of the carboxyl-terminated polyether polyurethane dispersion and add nano zinc oxide and waterborne polycarbodiimide crosslinking agent to obtain the main adhesive of the shoe sole side; (5) Dissolve zinc acetate dihydrate in deionized water and anhydrous ethanol to obtain zinc salt treatment solution; (6) After applying the shoe upper side sole coating to the edge of the prefabricated breathable shoe upper and drying it, spray the zinc salt treatment solution onto the edge of the shoe upper; (7) After applying the main adhesive to the bonding edge of the sole and drying it, align the edge of the prefabricated breathable upper with the bonding edge of the sole and heat press it together, and then perform post-curing to obtain a breathable protective shoe with a gusset.

[0007] Preferably, the mass ratio of polytetrahydrofuran ether diol, isophorone diisocyanate, 1,4-butanediol, β-alanine and triethylamine in the raw materials for preparing the carboxyl-terminated polyether polyurethane dispersion is 950-1050:315-355:21-25:42-48:18-22.

[0008] Preferably, the solid content of the carboxyl-terminated polyether polyurethane dispersion is 34%-36%.

[0009] Preferably, the mass ratio of the carboxyl-terminated polyether polyurethane dispersion used in the side coating of the shoe upper to the carboxyl-terminated polyether polyurethane dispersion used in the main rubber base material of the shoe sole is 1150-1250:1450-1550.

[0010] Preferably, the average particle size of the nano zinc oxide is 20-40 nm.

[0011] Preferably, the mass ratio of carboxyl-terminated polyether polyurethane dispersion, nano zinc oxide, and waterborne polycarbodiimide crosslinking agent in the raw materials for preparing the main adhesive of the shoe sole side is 1450-1550:2.5-3.5:70-85.

[0012] Preferably, the zinc salt treatment solution is prepared by mixing zinc acetate dihydrate, deionized water and anhydrous ethanol in a mass ratio of 18-22:75-85:190-210.

[0013] Preferably, in step (6), after dusting the 20mm wide area of ​​the lasting edge of the prefabricated breathable shoe upper, it is preheated at 50-58℃ for 2 minutes; then, the shoe upper side coating is evenly applied to the lasting edge, the wet film width is controlled to be 17-18mm, and it is baked at 50-58℃ for 3 minutes and then baked at 70-78℃ for 2 minutes. Immediately afterwards, zinc salt treatment solution is evenly sprayed onto the area and left to stand at 45-52℃ for 1 minute.

[0014] Preferably, in step (7), the main adhesive of the sole side is evenly applied to the bonding edge of the sole, the width of the wet film is controlled to be 17-18mm, and it is baked at 55-62℃ for 4min; then immediately the upper edge of the prefabricated breathable upper is aligned with the bonding edge of the sole, and hot-pressed at 95-100℃ and 380-420kPa for 13-15s, placed at room temperature for 25-30min, and then post-cured at 55-65℃ for 6-10h.

[0015] Preferably, the prefabricated breathable upper is a breathable composite upper, which includes, from the outside to the inside, a high-strength polyester warp-knitted mesh layer, a microporous thermoplastic polyurethane film layer, and a polyester fiber spacer mesh lining layer, and a layer of microfiber polyurethane synthetic leather reinforcing strip is laminated at the edge area of ​​the upper.

[0016] Preferably, the sole is a double-layer protective sole, comprising an upper polyurethane foam midsole and a lower wear-resistant and slip-resistant nitrile rubber outsole, and the fitting edge of the sole is configured as an upturned polyurethane edge-wrapping structure.

[0017] Preferably, the polytetrahydrofuran ether diol is of the type PolyTHF 1000; and the aqueous polycarbodiimide crosslinking agent is of the type CARBODILITE V-02-L2.

[0018] The beneficial effects of this invention are: This invention employs a chain-terminal carboxylated polyurethane resin, combined with a partially neutralized dispersion process, to achieve excellent wetting and shallow anchoring capabilities of the adhesive system on the shoe upper side. During the upper pretreatment stage, the zinc salt treatment solution can directionally interact with the chain-terminal carboxyl groups, achieving rapid fixation of the shallow structure of the upper material. This provides a stable substrate for subsequent main bonding, effectively preventing excessive infiltration of the adhesive layer during hot pressing and ensuring sufficient and continuous adhesive at the interface.

[0019] By independently introducing nano-zinc oxide and water-based polycarbodiimide crosslinking agents into the main adhesive layer on the sole side, the reinforcement effect can be controlled in a zonal and delayed manner. The coordination effect of nano-zinc oxide and the post-crosslinking reaction of water-based polycarbodiimide mainly occur during the hot pressing and post-curing stages after bonding. This significantly strengthens the adhesive layer near the sole side and its interface with the sole, forming a dense structure with a gradient transition from the upper to the sole. This structure can more effectively dissipate bending stress and inhibit the initiation and propagation of microcracks.

[0020] The synergistic strategy of shallow fixation on the upper side and cross-linking reinforcement on the sole side works together on the active site of the carboxyl group at the chain end to construct a transition interface of gradient polarity and modulus. This interface structure has better stability in humid and hot environments and can resist plasticization and adhesion degradation caused by moisture erosion, thus maintaining high upper and sole bonding strength and moisture permeability even after long-term use.

[0021] The entire approach, through the organic combination of molecular structure design, dispersion state control, and zoned adhesive application, avoids interference between various additives and achieves a broad and stable process operation window. This results in simultaneous improvements in initial bond strength, flexural fatigue resistance, and resistance to damp heat aging in the prepared breathable protective shoes, with strong interlayer bonding in the upper, excellent overall performance, and good repeatability. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0023] In the examples and comparative examples, polytetrahydrofuran ether diol was BASF's PolyTHF 1000; isophorone diisocyanate was Covestro's Desmodur I; and the waterborne polycarbodiimide crosslinking agent was Nisshinbo's CARBODILITE V-02-L2. The prefabricated upper was a breathable composite upper, consisting of, from the outside in, a high-strength polyester warp-knitted mesh layer, a microporous thermoplastic polyurethane film layer, and a polyester fiber spacer mesh lining layer. The areal density of the high-strength polyester warp-knitted mesh layer was 260 g / m². 2The microporous thermoplastic polyurethane membrane layer is 0.03 mm thick, the polyester fiber spacer mesh lining layer is 1.5 mm thick, and a 0.8 mm thick microfiber polyurethane synthetic leather reinforcing strip is laminated to the edge area of ​​the upper. The sole is a double-layer protective sole, including an upper polyurethane foam midsole and a lower wear-resistant and slip-resistant nitrile rubber outsole; the density of the polyurethane foam midsole is 0.45 g / cm³. 3 The nitrile rubber outsole has a Shore A hardness of 68. The sole's bonding edge is designed with an upturned polyurethane edging structure, which is 18mm wide and serves as the main bonding area between the upper edge and the main rubber of the sole side.

[0024] Example 1: Step 1: Add 1000g of polytetrahydrofuran ether diol to a reactor equipped with stirring, temperature control and nitrogen protection, dehydrate at 110℃ and -0.08MPa for 1h, then add 1g of dibutyltin dilaurate after cooling to 75℃, and then add 335g of isophorone diisocyanate. Maintain the reaction at 75℃ for 2h under nitrogen protection, and then raise the temperature to 80℃ for 1h to obtain a polyether-type polyurethane prepolymer with isocyanate groups at both ends. Step 2: Keep the system obtained in Step 1 at 80℃, add 23g of 1,4-butanediol dropwise over 30min, and continue to keep warm for 90min to obtain the chain growth intermediate; separately take 180g of anhydrous N,N-dimethylacetamide, add 45g of β-alanine at 25℃ and stir for 30min to form a uniform suspension; lower the chain growth intermediate to 35℃, add the β-alanine suspension over 40min, controlling the system temperature not to exceed 45℃, after the addition is complete, raise the temperature to 55℃ and keep warm for 2h, then raise the temperature to 60℃ and keep warm for 1h to obtain carboxyl-terminated polyether polyurethane resin; Step 3: Cool the carboxyl-terminated polyether polyurethane resin to 45°C, add 900g of acetone to dilute and stir for 20min, then add 20g of triethylamine and stir for 20min to convert some of the chain-terminated carboxyl groups into triethylamine salts; then emulsify the resin phase in 2400g of deionized water at 1000rpm for 20min, and then remove acetone and anhydrous N,N-dimethylacetamide at 50°C and -0.08MPa to obtain a carboxyl-terminated polyether polyurethane dispersion with a solid content of 35%. Step 4: Take 1200g of carboxyl-terminated polyether polyurethane dispersion as the sole coating for the upper side and set aside separately; take another 1500g of carboxyl-terminated polyether polyurethane dispersion as the main adhesive base for the sole side, add 3g of nano zinc oxide with an average particle size of 30nm and disperse for 10min, then add 80g of water-based polycarbodiimide crosslinking agent and stir for 8min, let stand for 15min to degas, and obtain the main adhesive for the sole side; Step 5: Take 80g of deionized water, dissolve 20g of zinc acetate dihydrate at room temperature, then add 200g of anhydrous ethanol and stir until clear to obtain zinc salt treatment solution; Step 6: Take one pair of 430g prefabricated uppers and one pair of 760g soles. Roughen the edges of the soles with 240-grit sandpaper and remove dust. Remove dust from a 20mm wide area along the edge of the upper and preheat at 55℃ for 2 minutes. Then, evenly apply 8g of upper side coating to the edge of the upper, controlling the wet film width to 18mm. Bake at 55℃ for 3 minutes and then at 75℃ for 2 minutes. Immediately afterward, evenly spray 2g of zinc salt treatment solution onto the area and let it stand at 50℃ for 1 minute. Step 7: Apply 10g of the main adhesive to the sole edge evenly, control the wet film width to 18mm, and bake at 60℃ for 4min; then immediately align the upper edge with the sole edge, hot press at 98℃ and 400kPa for 14s, place at room temperature for 30min, and then post-cur at 60℃ for 8h to obtain the upper-stitched breathable protective shoe.

[0025] Example 2 Step 1: Add 950g of polytetrahydrofuran ether diol to a reactor equipped with stirring, temperature control and nitrogen protection. Dehydrate at 108℃ and -0.08MPa for 0.8h. After cooling to 74℃, add 0.9g of dibutyltin dilaurate, then add 315g of isophorone diisocyanate. Maintain the reaction at 74℃ for 1.8h under nitrogen protection, then raise the temperature to 79℃ and react for 0.8h to obtain a polyether-type polyurethane prepolymer with isocyanate groups at both ends. Step 2: Keep the system obtained in Step 1 at 79℃, add 21g of 1,4-butanediol dropwise over 25min, and continue to keep warm for 80min to obtain the chain growth intermediate; separately take 170g of anhydrous N,N-dimethylacetamide, add 42g of β-alanine at 25℃ and stir for 25min to form a uniform suspension; lower the chain growth intermediate to 34℃, add the β-alanine suspension over 35min, controlling the system temperature not to exceed 44℃, after the addition is complete, raise the temperature to 54℃ and keep warm for 1.8h, then raise the temperature to 59℃ and keep warm for 0.8h to obtain carboxyl-terminated polyether polyurethane resin; Step 3: Cool the carboxyl-terminated polyether polyurethane resin to 44°C, add 850g of acetone to dilute and stir for 15 min, then add 18g of triethylamine and stir for 15 min to convert some of the chain-terminated carboxyl groups into triethylamine salts; then, at 900 rpm, add the resin phase to 2280g of deionized water to emulsify for 15 min, and then remove acetone and anhydrous N,N-dimethylacetamide at 48°C and -0.08MPa to obtain a carboxyl-terminated polyether polyurethane dispersion with a solid content of 34%. Step 4: Take 1150g of carboxyl-terminated polyether polyurethane dispersion as the sole coating for the upper side and set aside separately; take another 1450g of carboxyl-terminated polyether polyurethane dispersion as the main adhesive base for the sole side, add 2.5g of nano zinc oxide with an average particle size of 20nm and disperse for 8min, then add 70g of water-based polycarbodiimide crosslinking agent and stir for 6min, let stand for 10min to degas, and obtain the main adhesive for the sole side; Step 5: Take 75g of deionized water, dissolve 18g of zinc acetate dihydrate at room temperature, then add 190g of anhydrous ethanol and stir until clear to obtain zinc salt treatment solution; Step Six: Take one pair of 420g prefabricated uppers and one pair of 750g soles. Roughen the edges of the soles with 240-grit sandpaper and remove dust. Remove dust from a 20mm wide area along the edge of the upper and preheat at 50℃ for 2 minutes. Then, evenly apply 7.5g of upper side coating to the edge of the upper, controlling the wet film width to 17mm. Bake at 50℃ for 3 minutes and then at 70℃ for 2 minutes. Immediately afterward, evenly spray 1.8g of zinc salt treatment solution onto the area and let it stand at 45℃ for 1 minute. Step 7: Apply 9.5g of the main adhesive to the sole edge evenly, control the wet film width to 17mm, and bake at 55℃ for 4 minutes; then immediately align the upper edge with the sole edge, hot press at 95℃ and 380kPa for 13 seconds, place at room temperature for 25 minutes, and then cure at 55℃ for 6 hours to obtain the upper-stitched breathable protective shoe.

[0026] Example 3 Step 1: Add 980g of polytetrahydrofuran ether diol to a reactor equipped with stirring, temperature control and nitrogen protection. Dehydrate at 109℃ and -0.08MPa for 0.9h. After cooling to 75℃, add 1.0g of dibutyltin dilaurate, then add 325g of isophorone diisocyanate. Maintain the reaction at 75℃ for 1.9h under nitrogen protection, then raise the temperature to 80℃ and react for another 0.9h to obtain a polyether-type polyurethane prepolymer with isocyanate groups at both ends. Step 2: Keep the system obtained in Step 1 at 80℃, add 22g of 1,4-butanediol dropwise over 28 min, and continue to keep warm for 85 min to obtain the chain growth intermediate; separately take 175g of anhydrous N,N-dimethylacetamide, add 43g of β-alanine at 26℃ and stir for 28 min to form a uniform suspension; lower the chain growth intermediate to 35℃, add the β-alanine suspension over 38 min, control the system temperature not to exceed 45℃, after the addition is complete, raise the temperature to 55℃ and keep warm for 1.9 h, then raise the temperature to 60℃ and keep warm for 0.9 h to obtain carboxyl-terminated polyether polyurethane resin; Step 3: Cool the carboxyl-terminated polyether polyurethane resin to 45°C, add 880g of acetone to dilute and stir for 18 min, then add 19g of triethylamine and stir for 18 min to convert some of the chain-terminated carboxyl groups into triethylamine salts; then, at 950 rpm, add the resin phase to 2350g of deionized water to emulsify for 18 min, and then remove acetone and anhydrous N,N-dimethylacetamide at 49°C and -0.08MPa to obtain a carboxyl-terminated polyether polyurethane dispersion with a solid content of 34.5%. Step 4: Take 1180g of carboxyl-terminated polyether polyurethane dispersion as the sole coating for the upper side and set aside separately; take another 1480g of carboxyl-terminated polyether polyurethane dispersion as the main adhesive base for the sole side, add 2.8g of nano zinc oxide with an average particle size of 25nm and disperse for 9min, then add 75g of water-based polycarbodiimide crosslinking agent and stir for 7min, let stand for 12min to degas, and obtain the main adhesive for the sole side; Step 5: Take 78g of deionized water, dissolve 19g of zinc acetate dihydrate at room temperature, then add 195g of anhydrous ethanol and stir until clear to obtain zinc salt treatment solution; Step Six: Take one pair of prefabricated uppers (425g) and one pair of soles (755g). Roughen the edges of the soles with 240-grit sandpaper and remove dust. Remove dust from a 20mm wide area along the edge of the upper and preheat at 52℃ for 2 minutes. Then, evenly apply 7.8g of side coating to the upper edge, controlling the wet film width to 17.5mm. Bake at 52℃ for 3 minutes, then at 72℃ for 2 minutes. Immediately afterward, evenly spray 1.9g of zinc salt treatment solution onto this area and let it stand at 48℃ for 1 minute. Step 7: Apply 9.8g of the main adhesive to the sole edge evenly, control the wet film width to 17.5mm, and bake at 58℃ for 4min; then immediately align the upper edge with the sole edge, hot press at 97℃ and 390kPa for 13.5s, place at room temperature for 28min, and then post-cur at 58℃ for 7h to obtain the upper-stitched breathable protective shoe.

[0027] Example 4 Step 1: Add 1020g of polytetrahydrofuran ether diol to a reactor equipped with stirring, temperature control and nitrogen protection, dehydrate at 111℃ and -0.08MPa for 1.0h, then add 1.0g of dibutyltin dilaurate after cooling to 76℃, and then add 345g of isophorone diisocyanate. Maintain the reaction at 76℃ for 2.0h under nitrogen protection, and then raise the temperature to 81℃ for 1.0h to obtain a polyether-type polyurethane prepolymer with isocyanate groups at both ends; Step 2: Keep the system obtained in Step 1 at 81℃, add 24g of 1,4-butanediol dropwise over 30min, and continue to keep warm for 90min to obtain the chain growth intermediate; separately take 185g of anhydrous N,N-dimethylacetamide, add 46g of β-alanine at 25℃ and stir for 30min to form a uniform suspension; lower the chain growth intermediate to 35℃, add the β-alanine suspension over 40min, controlling the system temperature not to exceed 45℃, after the addition is complete, raise the temperature to 56℃ and keep warm for 2.0h, then raise the temperature to 61℃ and keep warm for 1.0h to obtain carboxyl-terminated polyether polyurethane resin; Step 3: Cool the carboxyl-terminated polyether polyurethane resin to 45°C, add 920g of acetone to dilute and stir for 20min, then add 21g of triethylamine and stir for 20min to convert some of the chain-terminated carboxyl groups into triethylamine salts; then emulsify the resin phase in 2450g of deionized water at 1000rpm for 20min, and then remove acetone and anhydrous N,N-dimethylacetamide at 50°C and -0.08MPa to obtain a carboxyl-terminated polyether polyurethane dispersion with a solid content of 35.5%. Step 4: Take 1220g of carboxyl-terminated polyether polyurethane dispersion as the sole coating for the upper side and set aside separately; take another 1520g of carboxyl-terminated polyether polyurethane dispersion as the main adhesive base for the sole side, add 3.2g of nano zinc oxide with an average particle size of 35nm and disperse for 10min, then add 82g of water-based polycarbodiimide crosslinking agent and stir for 8min, let stand for 15min to degas, and obtain the main adhesive for the sole side; Step 5: Take 82g of deionized water, dissolve 21g of zinc acetate dihydrate at room temperature, then add 205g of anhydrous ethanol and stir until clear to obtain zinc salt treatment solution; Step Six: Take one pair of prefabricated uppers (435g) and one pair of soles (765g). Roughen the edges of the soles with 240-grit sandpaper and remove dust. Remove dust from a 20mm wide area along the edge of the upper and preheat at 56℃ for 2 minutes. Then, evenly apply 8.2g of upper side coating to the edge of the upper, controlling the wet film width to 18mm. Bake at 56℃ for 3 minutes, then at 76℃ for 2 minutes. Immediately afterward, evenly spray 2.1g of zinc salt treatment solution onto this area and let it stand at 50℃ for 1 minute. Step 7: Apply 10.2g of the main adhesive to the sole edge evenly, control the wet film width to 18mm, and bake at 60℃ for 4min; then immediately align the upper edge with the sole edge, hot press at 99℃ and 410kPa for 14.5s, place at room temperature for 30min, and then cure at 62℃ for 8.5h to obtain the upper-stitched breathable protective shoe.

[0028] Example 5 Step 1: Add 1050g of polytetrahydrofuran ether diol to a reactor equipped with stirring, temperature control and nitrogen protection. Dehydrate at 112℃ and -0.08MPa for 1.1h. After cooling to 76℃, add 1.1g of dibutyltin dilaurate, then add 355g of isophorone diisocyanate. Maintain the reaction at 76℃ for 2.1h under nitrogen protection, then raise the temperature to 82℃ and react for 1.1h to obtain a polyether-type polyurethane prepolymer with isocyanate groups at both ends. Step 2: Keep the system obtained in Step 1 at 82℃, add 25g of 1,4-butanediol dropwise over 32min, and continue to keep warm for 95min to obtain the chain growth intermediate; separately take 190g of anhydrous N,N-dimethylacetamide, add 48g of β-alanine at 25℃ and stir for 32min to form a uniform suspension; lower the chain growth intermediate to 36℃, add the β-alanine suspension over 42min, controlling the system temperature not to exceed 46℃, after the addition is complete, raise the temperature to 56℃ and keep warm for 2.1h, then raise the temperature to 62℃ and keep warm for 1.1h to obtain carboxyl-terminated polyether polyurethane resin; Step 3: Cool the carboxyl-terminated polyether polyurethane resin to 46°C, add 950g of acetone to dilute and stir for 20min, then add 22g of triethylamine and stir for 20min to convert some of the chain-terminated carboxyl groups into triethylamine salts; then emulsify the resin phase in 2500g of deionized water at 1050rpm for 20min, and then remove acetone and anhydrous N,N-dimethylacetamide at 51°C and -0.08MPa to obtain a carboxyl-terminated polyether polyurethane dispersion with a solid content of 36%. Step 4: Take 1250g of carboxyl-terminated polyether polyurethane dispersion as the sole coating for the upper side and set aside separately; take another 1550g of carboxyl-terminated polyether polyurethane dispersion as the main adhesive base for the sole side, add 3.5g of nano zinc oxide with an average particle size of 40nm and disperse for 10min, then add 85g of water-based polycarbodiimide crosslinking agent and stir for 8min, let stand for 15min to degas, and obtain the main adhesive for the sole side; Step 5: Take 85g of deionized water, dissolve 22g of zinc acetate dihydrate at room temperature, then add 210g of anhydrous ethanol and stir until clear to obtain zinc salt treatment solution; Step Six: Take one pair of prefabricated uppers (440g) and one pair of soles (770g). Roughen the edges of the soles with 240-grit sandpaper and remove dust. Remove dust from a 20mm wide area along the edge of the upper and preheat at 58℃ for 2 minutes. Then, evenly apply 8.5g of upper side coating to the edge of the upper, controlling the wet film width to 18mm. Bake at 58℃ for 3 minutes, then at 78℃ for 2 minutes. Immediately afterward, evenly spray 2.2g of zinc salt treatment solution onto this area and let it stand at 52℃ for 1 minute. Step 7: Apply 10.5g of the main adhesive to the sole edge evenly, control the wet film width to 18mm, and bake at 62℃ for 4min; then immediately align the upper edge with the sole edge, hot press at 100℃ and 420kPa for 15s, place at room temperature for 30min, and then cure at 65℃ for 10h to obtain the upper-stitched breathable protective shoe.

[0029] Comparative Example 1: The difference from Example 1 is that β-alanine is not added in step two, and the amount of 1,4-butanediol is increased from 23g to 35g to maintain the chain growth of the resin; steps three to seven remain unchanged. The remaining conditions are the same as in Example 1.

[0030] Comparative Example 2: The difference from Example 1 is that triethylamine is not added in step three. All other conditions are the same as in Example 1.

[0031] Comparative Example 3: The difference from Example 1 is that the amount of triethylamine added in step three is increased from 20g to 50g, so that almost all of the carboxyl groups at the chain end are converted into triethylamine salt. The other conditions are the same as in Example 1.

[0032] Comparative Example 4: The difference from Example 1 is that: in step five, the zinc salt treatment solution is not prepared; in step six, after applying the shoe upper side sole coating to the edge of the shoe upper and completing pre-drying, the zinc acetate dihydrate treatment solution is not sprayed. The remaining conditions are the same as in Example 1.

[0033] Comparative Example 5: The difference from Example 1 is that in step four, 3g of nano zinc oxide is not added to the main rubber base material on the sole side, and 3g of deionized water is used to make up the total amount of the main rubber on the sole side. The other conditions are the same as in Example 1.

[0034] Comparative Example 6: The difference from Example 1 is that in step four, 80g of water-based polycarbodiimide crosslinking agent is not added to the main rubber base material on the sole side, and 80g of deionized water is used to make up the total amount of the main rubber on the sole side. The other conditions are the same as in Example 1.

[0035] Comparative Example 7: The difference from Example 1 is that in step four, 3g of nano zinc oxide is added to the side coating of the shoe upper and dispersed for 10 minutes, while nano zinc oxide is no longer added to the main rubber base material of the shoe sole. The remaining conditions are the same as in Example 1.

[0036] Comparative Example 8: The difference from Example 1 is that in step four, 80g of water-based polycarbodiimide crosslinking agent is added to the side coating of the shoe upper and stirred for 8 minutes, while water-based polycarbodiimide crosslinking agent is no longer added to the main rubber base material of the shoe sole. The remaining conditions are the same as in Example 1.

[0037] Performance testing: Sample preparation: Shoe samples were prepared according to the methods of Examples 1-5 and Comparative Examples 1-8, respectively. The shoe size was uniformly 250. Five pairs of samples were prepared for each group. Two pairs were used for testing the initial upper-sole bonding strength and the upper-sole bonding strength after wet heat aging. One pair was used for testing the upper-sole bonding strength after folding resistance of the whole shoe. Two pairs were used to cut samples from the ventilation area of ​​the upper and 20mm above the edge of the upper for testing water vapor permeability, water vapor coefficient, upper interlayer peel strength, and upper folding resistance. After preparation, all shoes were placed in a standard environment of 23°C and 50% relative humidity for 24 hours. Considering the influence of post-curing of the upper and sole adhesive on the results, the tests related to upper-sole bonding strength were all carried out 72 hours after shoe production.

[0038] Upper-sole bonding strength: Tested according to GB / T 21396-2022. Two pairs of finished shoes were taken for each group. One sample was cut from the inner and outer waistbands of each pair of shoes. The sample width was uniformly 25mm. After pre-peeling the starting end of the upper-sole bonding interface, the sample was installed on an electronic tensile testing machine and peeled at a speed of 100mm / min. The force value during the continuous peeling process was recorded, and the upper-sole bonding strength was calculated by averaging the values ​​of 5 equidistant measuring points.

[0039] The retention rate of the adhesive strength of the upper and sole after flexing is as follows: First, the flexing resistance test of each component shoe is carried out according to GB / T 3903.1-2017. The flexing angle is set to 50°, the flexing frequency is set to 230 times / min, and the number of flexing cycles is set to 40,000. After the flexing resistance test, samples are cut from the same part according to the method of upper and sole adhesive strength test and the adhesive strength of upper and sole is measured. The retention rate is calculated by the ratio of the adhesive strength of upper and sole after flexing resistance to the initial adhesive strength of upper and sole.

[0040] Water vapor permeability of shoe upper: Tested according to GB / T 20991-2024. Three pieces of shoe upper composite material were cut from the ventilation area of ​​the front of the finished shoe, avoiding seams, toe caps and obvious indentations. Each sample included an outer layer, a breathable layer and an inner lining structure consistent with actual use, but did not include the glued edge of the upper and sole. The samples were placed in a standard water vapor permeability testing device and tested continuously for 8 hours at 23°C. The mass change of the moisture permeability cup was weighed every hour, and the water vapor permeability was calculated according to the standard method.

[0041] Adhesion strength and moisture retention rate of the upper and sole after damp heat aging: Damp heat aging treatment was carried out according to GB / T 3903.7-2019. Two pairs of finished shoes for upper and sole adhesion strength test and three upper samples for moisture retention test were taken from each group and placed in a damp heat aging chamber at 70℃ and 100% relative humidity for 168h. After being removed, the shoes were restored to the standard environment specified in GB / T 22049-2019 for 24h. Subsequently, the adhesion strength and water vapor permeability of the upper and sole after damp heat aging were measured, and the adhesion strength retention rate and moisture retention rate of the upper and sole were calculated respectively.

[0042] Interlayer peel strength of the upper: Tested according to GB / T 3903.39-2019. Three samples were cut from the ventilation area of ​​the upper and 20mm above the edge of the upper for each group. The sample size was uniformly 70mm×25mm. After manually pre-peeling 30mm along the interlayer of the composite, the samples were clamped in an electronic tensile testing machine and peeled at a speed of 100mm / min. The average force value of the stable peeled section was recorded and converted into interlayer peel strength.

[0043] The test results are shown in Table 1.

[0044] Table 1 Performance Test Results Data Analysis: As can be seen from the data in Table 1, the breathable protective shoe prepared by the present invention maintains a relatively stable water vapor transmission capacity in the breathable area of ​​the upper, while the bonding strength of the upper and sole, the strength after folding, and the performance after wet heat aging are all at a relatively good level. Moreover, the peel strength between the upper layers is improved simultaneously. This indicates that the solution does not simply rely on increasing the hardness of the adhesive layer or increasing the amount of adhesive to achieve interface enhancement, but achieves a coordinated unity between interface continuity, stress transmission, and aging stability. The possible reason is that the carboxyl groups introduced by β-alanine enable the carboxyl-terminated polyether polyurethane dispersion to be oriented and enriched along the interface before and after hot pressing. After the upper side is treated with zinc acetate dihydrate, a shallow fixation effect is formed. The nano zinc oxide and water-based polycarbodiimide crosslinking agent on the sole side continue to enhance the density and moisture and heat resistance of the adhesive layer during the bonding and post-curing stages. This forms an interface structure that gradually transitions from the upper to the sole, which reduces local stress concentration during repeated flexing and inhibits interface relaxation and microcrack propagation under moisture and sweat conditions. Therefore, it can balance initial adhesion, durable adhesion and breathability.

[0045] As can be seen from the data in Table 1 for Example 1 and Comparative Example 1, when the chain growth is maintained solely by increasing 1,4-butanediol without introducing β-alanine, the initial upper-sole adhesive strength, folding resistance retention rate, and upper-sole retention rate after damp heat aging all decrease significantly, and the interlayer peel strength of the upper is poor. The main reason for this is that after the system loses the carboxyl sites at the chain ends, the shallow fixation effect of zinc acetate dihydrate on the upper side and the post-crosslinking effect of the waterborne polycarbodiimide crosslinking agent on the sole side are difficult to establish effectively, and the coordination reinforcement effect of nano-zinc oxide is also difficult to fully exert.

[0046] As can be seen from the data in Example 1 and Comparative Example 2 in Table 1, without the addition of triethylamine, the initial adhesive strength and flexural retention rate of the upper and sole decreased simultaneously, but the initial moisture permeability did not change significantly. This indicates that the problem is not with the common upper material itself, but rather with the fact that the carboxyl-terminated polyether polyurethane resin, lacking adequate ionization, makes it difficult for the dispersion particles to balance construction stability and interfacial rearrangement capabilities. The undercoat's wetting and spreading at the edges of the upper is insufficient, making it difficult to form a continuous and uniform stress layer during hot pressing. Although the carboxyl groups at the chain ends are still present, they are unable to form effective interfacial enrichment before bonding, thus weakening the synergistic basis for subsequent zinc acetate dihydrate treatment and crosslinking of the sole's sides and back.

[0047] As can be seen from the data in Example 1 and Comparative Example 3 in Table 1, when the amount of triethylamine added is too high, causing almost all of the carboxyl groups at the chain ends to be converted into triethylamine salts, although the initial adhesive strength of the upper and sole does not drop to the minimum, the retention rate and moisture permeability of the upper and sole decrease more significantly after wet heat aging. The main reason is that excessive neutralization makes the interface too hydrophilic, and the residual ionized structure after drying is more likely to absorb moisture and induce interface relaxation. In addition, the reorientation ability of the chain segments before and after hot pressing decreases, which is not conducive to the formation of a dense structure that gradually transitions from the upper to the sole.

[0048] As can be seen from the data in Example 1 and Comparative Example 4 in Table 1, without the application of zinc acetate dihydrate treatment solution, the initial adhesive strength of the upper and sole and the retention rate after folding both decreased, and the improvement in the interlayer peel strength of the upper was also relatively limited. This indicates that the zinc salt treatment after pre-drying the upper side is not an optional additional step, but an important step used to fix the shallow structure of the upper and suppress excessive inward flow of the adhesive layer during hot pressing.

[0049] As can be seen from the data in Table 1 for Examples 1, 5, and 7, neither adding nano-zinc oxide to the main outsole rubber nor adding it to the side coating of the upper reduces the initial bonding strength, flexural strength retention, and hygrothermal aging retention. The misaligned addition scheme did not show a reinforcement effect comparable to the original scheme. This is because nano-zinc oxide is more conducive to interfacial coordination and adhesive densification during the hot pressing and post-curing stages when it is in the main outsole rubber. However, when dispersed prematurely in the side coating of the upper, its reinforcing effect is easily dissipated during the pre-drying stage, making it difficult to reach the outsole side interface, which is most susceptible to stress and hygrothermal aging.

[0050] As can be seen from the data in Table 1 for Examples 1, 6, and 8, the absence of a water-based polycarbodiimide crosslinking agent in the sole side base rubber, or its addition to the upper side coating, significantly reduces the retention rate of the upper and sole after humid heat aging and the retention rate after folding. The main reason is that the water-based polycarbodiimide crosslinking agent can only continuously react with the chain-terminal carboxyl groups during the bonding and post-curing stages when placed in the sole side base rubber, gradually increasing the crosslinking density of the adhesive layer and inhibiting interfacial relaxation under humid heat conditions. If added to the upper side coating prematurely, it is more likely to cause localized premature curing during the pre-drying stage, weakening the interfacial rearrangement during hot pressing and losing the post-crosslinking reinforcement of the sole side.

[0051] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for manufacturing a breathable protective shoe with uppers, characterized in that, Includes the following steps: (1) Polytetrahydrofuran ether diol was reacted with isophorone diisocyanate to obtain a polyether-type polyurethane prepolymer with isocyanate groups at both ends; (2) The polyether-type polyurethane prepolymer was extended with 1,4-butanediol chain, and β-alanine was prepared into anhydrous N,N-dimethylacetamide suspension and then reacted with the chain-extended system to obtain carboxyl-terminated polyether-type polyurethane resin. (3) After diluting the carboxyl-terminated polyether polyurethane resin with acetone, it is partially neutralized with triethylamine to convert some of the chain-terminal carboxyl groups into triethylamine salts. Then, deionized water is added for emulsification and dispersion, and acetone and anhydrous N,N-dimethylacetamide are removed to obtain a carboxyl-terminated polyether polyurethane dispersion. (4) Take a portion of the carboxyl-terminated polyether polyurethane dispersion as the side coating of the shoe upper, and take another portion of the carboxyl-terminated polyether polyurethane dispersion and add nano zinc oxide and waterborne polycarbodiimide crosslinking agent to obtain the main adhesive of the shoe sole side; (5) Dissolve zinc acetate dihydrate in deionized water and anhydrous ethanol to obtain zinc salt treatment solution; (6) After applying the shoe upper side sole coating to the edge of the prefabricated breathable shoe upper and drying it, spray the zinc salt treatment solution onto the edge of the shoe upper; (7) After applying the main adhesive to the bonding edge of the sole and drying it, align the edge of the prefabricated breathable upper with the bonding edge of the sole and heat press it together, and then perform post-curing to obtain a breathable protective shoe with a gusset.

2. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, The mass ratio of polytetrahydrofuran ether diol, isophorone diisocyanate, 1,4-butanediol, β-alanine and triethylamine in the raw materials for preparing the carboxyl-terminated polyether polyurethane dispersion is 950-1050:315-355:21-25:42-48:18-22.

3. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, The solid content of the carboxyl-terminated polyether polyurethane dispersion is 34%-36%.

4. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, The mass ratio of the carboxyl-terminated polyether polyurethane dispersion used in the side coating of the shoe upper to the carboxyl-terminated polyether polyurethane dispersion used in the main rubber base material of the shoe sole is 1150-1250:1450-1550.

5. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, The average particle size of the nano zinc oxide is 20-40 nm.

6. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, The mass ratio of carboxyl-terminated polyether polyurethane dispersion, nano zinc oxide, and waterborne polycarbodiimide crosslinking agent in the raw materials for preparing the main adhesive of the shoe sole is 1450-1550:2.5-3.5:70-85.

7. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, The zinc salt treatment solution was prepared by mixing zinc acetate dihydrate, deionized water and anhydrous ethanol in a mass ratio of 18-22:75-85:190-210.

8. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, In step (6), after removing dust from the 20mm wide area of ​​the lasting edge of the prefabricated breathable shoe upper, it is preheated at 50-58℃ for 2 minutes; then, the shoe upper side coating is evenly applied to the lasting edge, the wet film width is controlled to be 17-18mm, and it is baked at 50-58℃ for 3 minutes and then baked at 70-78℃ for 2 minutes. Immediately afterwards, zinc salt treatment solution is evenly sprayed onto the area and left to stand at 45-52℃ for 1 minute.

9. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, In step (7), the main adhesive of the sole side is evenly applied to the bonding edge of the sole, and the width of the wet film is controlled to be 17-18mm. It is then baked at 55-62℃ for 4min. Immediately afterwards, the upper edge of the prefabricated breathable upper is aligned with the bonding edge of the sole, and hot-pressed at 95-100℃ and 380-420kPa for 13-15s. After being placed at room temperature for 25-30min, it is then post-cured at 55-65℃ for 6-10h.

10. The method for manufacturing breathable protective shoes according to claim 1, characterized in that, The polytetrahydrofuran ether diol is designated as PolyTHF 1000; the waterborne polycarbodiimide crosslinking agent is designated as CARBODILITE V-02-L2.

Images