Preparation method of rubber rain shoes with latex vamps

Abstract

The invention discloses a preparation method of rubber rain shoes with latex vamps, and belongs to the technical field of rubber product manufacturing. The method comprises the steps that the surface of a metal shoe tree is cleaned, coated with a release agent and fixed; the dipping latex is prepared from the following components in parts by weight: 85 to 120 parts of natural latex, 3 to 4 parts of waterborne polyurethane emulsion, 1.4 to 1.6 parts of sulfur, 0.5 to 0.8 part of accelerant TBBS, 0.2 to 0.3 part of accelerant TMTD, 2.0 to 2.8 parts of zinc oxide, 0.6 to 1.0 part of stearic acid, 0.28 to 0.32 part of surface modified nano cellulose and the like; carrying out pre-drying treatment on the shoe tree subjected to gum dipping; performing vulcanization treatment; and delasting and bonding and assembling with a rubber sole to finish preparation. According to the invention, a latex impregnation process is adopted to replace a traditional dry glue mixing process, so that on the premise of ensuring the strength and durability of the product, the rubber content of the vamp is increased, the softness and portability of the product are improved, the flexural life is prolonged, meanwhile, the environmental pollution in the production process is reduced, and the requirements of the market on high-quality environment-friendly rain shoes are met.

Description

Technical Field

[0001] The invention relates to the technical field of rubber product manufacturing, in particular to a method for preparing rubber rain boots with latex uppers. Background Art

[0002] As an important waterproof footwear product, rain boots are widely used in rainy travel, agricultural production, industrial operations, and other occasions. As consumers' demands for rain boots' comfort, lightness, and durability continue to increase, traditional rain boot manufacturing processes face many challenges.

[0003] Currently, mainstream rubber rain boots on the market are primarily produced using a dry rubber mixing process. This process first mixes natural or synthetic rubber with various compounding ingredients in an open or internal mixer to form a rubber mix with specific properties. This mix is ​​then formed into a rubber sheet through calendering or extrusion. The sheet is then laminated to a shoe last and vulcanized to form the finished rain boot. To improve processing performance and reduce production costs, this process typically requires the addition of large amounts of fillers (such as carbon black and calcium carbonate), resulting in a rubber content of only 45%-55% in the final product. Rain boots produced using the dry rubber mixing process are heavy, lack flexibility, and offer poor comfort. Furthermore, the mixing process itself generates significant amounts of dust and volatile organic compounds (VOCs), which pollute the environment and consume a high amount of energy. Furthermore, rubber rain boots produced using the dry rubber mixing process exhibit limited flex fatigue resistance. Testing has shown that their flex life is typically between 100,000 and 150,000 cycles, limiting their service life. Summary of the Invention

[0004] Based on the problems existing in the background technology, the present invention provides a method for preparing rubber rain boots with latex uppers. On the premise of ensuring product strength and durability, the rubber content of the upper is increased, the softness and lightness of the product are improved, the flex life is extended, and the environmental pollution in the production process is reduced, thereby meeting the market demand for high-quality environmentally friendly rain boots.

[0005] The present invention is implemented through the following technical solutions: A method for preparing rubber rain boots with latex uppers comprises the following steps: S1. Clean the surface of the metal shoe last, apply a release agent, and secure the shoe last to the dipping equipment; S2. Dipping the shoe last into the dipping latex; S3. Pre-drying the finished shoe last; S4. After pre-drying, the latex upper with the last enters the vulcanization tank for vulcanization; S5. Separate the vulcanized latex upper from the shoe last and bond it to the rubber sole for assembly. Curing the adhesive layer completes the preparation of the rubber rain boots.

[0006] Further, the dipping latex in step S2 comprises, by weight parts: natural latex 85-120 parts, water-based polyurethane emulsion 3-4 parts, sulfur 1.4-1.6 parts, accelerator TBBS 0.5-0.8 parts, accelerator TMTD 0.2-0.3 parts, zinc oxide 2.0-2.8 parts, stearic acid 0.6-1.0 parts, surface modified nanocellulose 0.28-0.32 parts, polyethylene glycol 400 0.5-0.8 parts, antioxidant 6PPD 0.9-1.5 parts, epoxy soybean oil 0.5-0.8 parts, silane coupling agent KH-570 0.10-0.15 parts.

[0007] Further, the water-based polyurethane emulsion is a water-based polyether type polyurethane emulsion, and the solid content is 35±1%.

[0008] Further, the specific preparation method of the surface modified nanocellulose is: mixing γ-aminopropyl triethoxysilane with an ethanol / water mixed solution at a volume ratio of 9:1, hydrolyzing for 72 hours; mixing the hydrolyzed silane solution with nanocellulose slurry, the reaction temperature is 50-60°C, and the reaction time is 4-6 hours; centrifugal washing, redispersion, and then the surface modified nanocellulose is obtained.

[0009] Further, the dipping latex further comprises ammonia water, and the pH of the dipping latex is adjusted to 9.2±0.2.

[0010] Further, the solid content of the natural latex is 60-65%, and the ammonia content is 0.6-0.8%.

[0011] Further, the preparation method of the dipping latex is: diluting the natural latex with deionized water to a solid content of 45-50%, adding stearic acid, zinc oxide, antioxidant 6PPD, polyethylene glycol 400, and epoxy soybean oil in sequence under the conditions of 25-30°C and stirring speed of 300-400 rpm, stirring for 15-20 minutes; then adding water-based polyether type polyurethane emulsion and surface modified nanocellulose, stirring for 10-15 minutes; finally adding sulfur, accelerator TBBS, accelerator TMTD, and silane coupling agent KH-570, stirring for 5-8 minutes, adjusting the pH to 9.2±0.2 with ammonia water, filtering through a 200 mesh screen, and obtaining the dipping latex.

[0012] Further, the dipping process parameters in step S2 are specifically: dipping speed is 15-25 mm / s downward and 10-20 mm / s upward, residence time is 8-15 seconds, latex temperature is 22-28°C, draining time after dipping is 2-3 minutes, and repeating dipping 2 times.

[0013] Furthermore, the specific parameters of the pre-drying treatment in step S3 are: pre-drying temperature 50-70° C., pre-drying time 10-25 minutes, relative humidity controlled at 40-60%, and hot air circulation speed 1-3 m / s.

[0014] Furthermore, the specific parameters of the vulcanization treatment in step S4 are: vulcanization in a saturated steam environment at 115-120° C. for 7-10 minutes, and the pressure of the vulcanization cylinder is maintained at 0.6-0.8 MPa.

[0015] Beneficial effects of the present invention: 1. The present invention adopts a latex impregnation process, which avoids the use of a large amount of fillers in the traditional dry rubber mixing process. The rubber component content in the final product can reach 70-80%, which is a significant increase compared to the 45-55% of the traditional process, making the rain boots weight reduced by 25-35%, greatly improving the lightness of wearing. The high elasticity and softness inherent in natural latex, combined with the toughening effect of aqueous polyurethane emulsion, make the prepared rain boots have excellent softness and resilience. Through the reinforcing effect of surface modified nanocellulose and the optimized vulcanized cross-linked network structure, the bending fatigue performance of the product is significantly improved. After Dematia bending test testing, the flexural life can reach 250,000 to 350,000 times, which is 150-250% higher than the 100,000 to 150,000 times of the traditional process, greatly extending the service life.

[0016] 2. This invention utilizes a water-based system, reducing VOC emissions by over 80%, completely avoiding dust pollution generated by traditional mixing processes, and reducing overall energy consumption by 35-45%, meeting the requirements of green manufacturing and energy conservation and emission reduction. Compared to the traditional mixing-calendering-laminating process, this invention simplifies the process steps, achieves a higher degree of automation, and achieves superior product thickness uniformity and performance stability compared to traditional processes, significantly reducing the defective product rate. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0018] In the Examples and Comparative Examples of the present invention, the surface-modified nanocellulose was prepared as follows: 50g of γ-aminopropyltriethoxysilane was mixed with 500ml of an ethanol / water mixture (9:1 by volume), stirred at room temperature, and hydrolyzed for 72 hours to obtain a hydrolyzed silane solution. The hydrolyzed silane solution was then mixed with nanocellulose slurry (2% solids content) at a silane / cellulose mass ratio of 1:10, and reacted at 55°C for 5 hours with stirring. After the reaction was complete, the slurry was centrifuged and washed three times with deionized water (8000 rpm for 10 minutes) to remove any unreacted silane coupling agent. Finally, the modified nanocellulose was redispersed in deionized water, and the slurry concentration was adjusted to 10% for later use.

[0019] Example 1 A method for preparing rubber rain boots with latex uppers comprises the following steps: Step S1. Shoe last pretreatment: Select an aluminum alloy shoe last, clean the surface oil with alcohol, evenly apply silicone oil release agent after drying, and fix the shoe last on the automatic dipping equipment.

[0020] Step S2. Preparation of the impregnated latex: 100 parts by weight of natural rubber latex (62% solids, 0.7% ammonia) was diluted with deionized water to a solids content of 48%. At 28°C and stirring at 350 rpm, the following ingredients were added, in order: 0.8 parts of stearic acid, 2.4 parts of zinc oxide, 1.2 parts of antioxidant 6PPD, 0.65 parts of polyethylene glycol 400, and 0.65 parts of epoxidized soybean oil. The mixture was stirred for 18 minutes. Furthermore, 3.5 parts of a water-based polyether polyurethane emulsion (35% solids) and 0.30 parts of surface-modified nanocellulose (0.30 parts on a dry basis, i.e., 3.0 parts of a 10% concentration slurry) were added. The mixture was stirred for 12 minutes. Finally, 1.5 parts of sulfur, 0.65 parts of accelerator TBBS, 0.25 parts of accelerator TMTD, and 0.12 parts of silane coupling agent KH-570 were added. The mixture was stirred for 6 minutes. The pH was adjusted to 9.2 with aqueous ammonia, filtered through a 200-mesh sieve, and allowed to stand for degassing for 2 hours to obtain an impregnated latex.

[0021] Step S3. Dipping process: latex temperature is controlled at 25°C, dipping speed is: descending 20 mm / s, ascending 15 mm / s, residence time is 12 seconds, draining time is 2.5 minutes, and dipping is repeated twice.

[0022] Step S4. Pre-drying: pre-drying for 18 minutes at 60°C, relative humidity 50%, and hot air circulation speed 2m / s.

[0023] Step S5. Vulcanization treatment: vulcanization in a saturated steam environment at 118° C. for 8 minutes with a vulcanization tank pressure of 0.7 MPa.

[0024] Step S6. De-lasting and assembling: After vulcanization is completed and the rubber upper is naturally cooled, the latex upper is separated from the shoe last and bonded to the prefabricated rubber sole with neoprene glue, and cured at 80°C for 15 minutes to complete the preparation of the rain boots.

[0025] Example 2 According to the technical process of Example 1, the dipping latex formula is adjusted as follows: Natural latex 120 parts, water-based polyurethane emulsion 4.0 parts, sulfur 1.6 parts, accelerator TBBS 0.8 parts, accelerator TMTD 0.3 parts, zinc oxide 2.8 parts, stearic acid 1.0 part, surface-modified nanocellulose 0.32 parts, polyethylene glycol 400 0.8 parts, antioxidant 6PPD 1.5 parts, epoxy soybean oil 0.8 parts, silane coupling agent KH-570 0.15 parts.

[0026] Dipping process parameters: descending speed 25 mm / s, ascending speed 20 mm / s, residence time 15 seconds.

[0027] Pre-drying conditions: 70°C, 20 minutes.

[0028] Vulcanization conditions: 120°C, 10 minutes.

[0029] Example 3 According to the process flow of Example 1, adjust the dipping latex formula as follows: Natural latex 85 parts, water-based polyurethane emulsion 3.0 parts, sulfur 1.4 parts, accelerator TBBS 0.5 parts, accelerator TMTD 0.2 parts, zinc oxide 2.0 parts, stearic acid 0.6 parts, surface-modified nanocellulose 0.28 parts, polyethylene glycol 400 0.5 parts, antioxidant 6PPD 0.9 parts, epoxy soybean oil 0.5 parts, silane coupling agent KH-570 0.10 parts.

[0030] Dipping process parameters: descending speed 15 mm / s, ascending speed 10 mm / s, residence time 8 seconds.

[0031] Pre-drying conditions: 50°C, 25 minutes.

[0032] Vulcanization conditions: 115°C, 7 minutes.

[0033] Comparative Example 1 Prepare rubber rain shoes using traditional dry rubber mixing process: Formula (parts by weight): natural rubber 100 parts, carbon black N330 50 parts, zinc oxide 5 parts, stearic acid 2 parts, sulfur 2.5 parts, accelerator CZ 0.8 parts, accelerator DM 0.5 parts, antioxidant 4020 2 parts, paraffin wax 1 part.

[0034] Process flow: plasticizing on an open mill → mixing → calendering to make pieces → piece cutting and lamination → vulcanization molding. Vulcanization conditions: 145°C x 25 minutes.

[0035] Comparative Example 2 According to the formula and process of Example 1, but without adding surface-modified nanocellulose.

[0036] Comparative Example 3 The formulation and process of Example 1 were followed, but without adding the aqueous polyurethane emulsion.

[0037] Comparative Example 4 The formulation and process of Example 1 were followed, but the surface-modified nanocellulose was replaced with the same amount of unmodified nanocellulose.

[0038] Test Example 1 The performance of the rain boots prepared in each embodiment and comparative example was tested using standard testing methods, and the results are shown in Table 1.

[0039] Table 1 As can be seen from the data in Table 1, the weight of Examples 1-3 (420-435g) is about 33% lighter than that of Comparative Example 1 (630g). This is mainly due to the fact that the present invention adopts a latex impregnation process to replace the traditional dry rubber mixing process, which avoids the use of a large amount of fillers and increases the rubber component content in the product from 45-55% of the traditional process to 70-80%, fundamentally improving the lightness of the product. The tensile strength of the embodiment reaches 18.2-18.8 MPa, which significantly surpasses the 15.2 MPa of the traditional process. This is mainly due to the strengthening effect of the surface-modified nanocellulose and the toughening effect of the aqueous polyurethane emulsion. The contribution of each component can be verified from the data of Comparative Examples 2-4: the tensile strength of Comparative Example 2, which lacks surface-modified nanocellulose, drops to 16.8 MPa, and the tensile strength of Comparative Example 3, which lacks polyurethane emulsion, drops to 15.5 MPa, indicating that these two key components have played a synergistic role in improving material strength. At the same time, the changing trend of the elongation at break shows a reasonable inverse relationship with the hardness. Example 3 shows the best flexibility (620%) due to the relatively small amount of formula used, while the traditional process with a high filler content shows obvious brittle characteristics (420%). The flexural life of the embodiment reaches 250,000-350,000 times, which is an increase of 150-250% compared to the 120,000 times of the traditional process. This improvement is directly related to the service life of the product. This performance improvement is due to the optimized cross-linked network structure and the introduction of nano-reinforced materials, which enable the material to better disperse stress during repeated bending and delay the generation and expansion of fatigue cracks. This is also confirmed by the compression permanent deformation data. The rebound performance of the embodiment (12-18%) is better than that of the traditional process (35%), indicating that the cross-linked network constructed by the new process has better elastic recovery ability.

[0040] Test Example 2 The rubber rain boots prepared in the examples and comparative examples were tested for comfort and usability.

[0041] Thirty volunteers (half male and half female) aged between 25 and 45 years old, with foot lengths of 235-270 mm, who were in good health and had no foot diseases were selected.

[0042] The test items and standards are shown in Table 2.

[0043] The test results are shown in Table 3.

[0044] Table 2 Table 3 The subjective evaluation data in Table 3 show a high degree of consistency with the objective test results in Table 1: the weight perception score corresponds to the actual weight data: the weight perception score of the embodiment reaches 8.8-9.4 points, while the actual weight is only 405-425g; the weight perception score of comparative example 1 is only 4.5 points, corresponding to its actual weight of 630g. The softness experience score also shows a reasonable inverse relationship with the Shore A hardness data. The softness score of the embodiment is between 8.6-9.3 points, corresponding to its hardness value of 42-48; while the softness score of the traditional process is only 5.2 points, but the hardness is as high as 58. This correlation shows that hardness control achieved by optimizing material formulation and process parameters can effectively enhance the user's tactile experience.

[0045] Finally, it should be noted that the above-described embodiments merely represent several implementation methods of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made by a person skilled in the art without departing from the spirit of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention should be based on the appended claims.

Claims

1. A method for preparing rubber rain boots with latex uppers, characterized in that: The following steps are involved: S1. Clean the surface of the metal shoe last, apply a release agent, and secure the shoe last to the dipping equipment; S2. Dipping the shoe last into the dipping latex; S3. Pre-drying the finished shoe last; S4. After pre-drying, the latex upper with the last enters the vulcanization tank for vulcanization; S5. Separate the vulcanized latex upper from the shoe last and bond it to the rubber sole for assembly. Curing the adhesive layer completes the preparation of the rubber rain boots.

2. The preparation method according to claim 1, characterized in that The impregnated latex in step S2 includes, by weight, 85-120 parts of natural rubber latex, 3-4 parts of aqueous polyurethane emulsion, 1.4-1.6 parts of sulfur, 0.5-0.8 parts of accelerator TBBS, 0.2-0.3 parts of accelerator TMTD, 2.0-2.8 parts of zinc oxide, 0.6-1.0 parts of stearic acid, 0.28-0.32 parts of surface-modified nanocellulose, 0.5-0.8 parts of polyethylene glycol 400, 0.9-1.5 parts of antioxidant 6PPD, 0.5-0.8 parts of epoxidized soybean oil, and 0.10-0.15 parts of silane coupling agent KH-570.

3. The preparation method according to claim 2, characterized in that The water-based polyurethane emulsion is a water-based polyether polyurethane emulsion with a solid content of 35±1%.

4. The preparation method according to claim 2, characterized in that The specific preparation method of surface-modified nanocellulose is as follows: γ-aminopropyltriethoxysilane is mixed with an ethanol / water mixed solution in a volume ratio of 9:1, and hydrolyzed for 72 hours; the hydrolyzed silane solution is mixed with nanocellulose slurry, the reaction temperature is 50-60°C, and the reaction time is 4-6 hours; and the surface-modified nanocellulose is obtained after centrifugal washing and redispersion.

5. The preparation method according to claim 2, characterized in that The dipping latex further includes ammonia water, and the pH of the dipping latex is adjusted to 9.2±0.

2.

6. The preparation method according to claim 2, characterized in that The solid content of natural rubber latex is 60-65% and the ammonia content is 0.6-0.8%.

7. The preparation method according to claim 2, characterized in that The preparation method of the impregnated latex is as follows: natural rubber latex is diluted with deionized water to a solid content of 45-50%, stearic acid, zinc oxide, antioxidant 6PPD, polyethylene glycol 400, and epoxidized soybean oil are added in sequence at 25-30°C and a stirring speed of 300-400 rpm, and stirred for 15-20 minutes; Then add water-based polyether polyurethane emulsion and surface-modified nanocellulose, stir for 10-15 minutes; finally add sulfur, accelerator TBBS, accelerator TMTD, and silane coupling agent KH-570, stir for 5-8 minutes, adjust the pH to 9.2±0.2 with ammonia water, filter through a 200-mesh sieve to obtain an impregnated latex.

8. The preparation method according to claim 1, characterized in that The specific dipping process parameters in step S2 are: dipping speed is 15-25 mm / s for descending and 10-20 mm / s for ascending, residence time is 8-15 seconds, latex temperature is 22-28° C., draining time after dipping is 2-3 minutes, and dipping is repeated twice.

9. The preparation method according to claim 1, characterized in that The specific parameters of the pre-drying treatment in step S3 are: pre-drying temperature 50-70° C., pre-drying time 10-25 minutes, relative humidity controlled at 40-60%, and hot air circulation speed 1-3 m / s.

10. The preparation method according to claim 1, characterized in that The specific parameters of the vulcanization treatment in step S4 are: vulcanization in a saturated steam environment at 115-120° C. for 7-10 minutes, and the pressure of the vulcanization cylinder is maintained at 0.6-0.8 MPa.

Images