A method of making a rubber rain shoe having a latex upper

Abstract

The application discloses a preparation method of a rubber rain shoe with a latex shoe upper, and belongs to the technical field of rubber product manufacturing. The method comprises the following steps: performing cleaning treatment on the surface of a metal shoe tree, applying a release agent and fixing; immersing the shoe tree into impregnated latex, wherein the impregnated latex comprises, in terms of weight parts, 85-120 parts of natural latex, 3-4 parts of water-based 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 and the like; performing pre-drying treatment on the shoe tree after the impregnation is completed; performing vulcanization treatment; and performing debarking and bonding assembly with a rubber sole to complete the preparation. The application adopts a latex impregnation process to replace a traditional dry rubber mixing process, improves the upper latex content under the premise of ensuring the strength and durability of the product, improves the softness and lightness of the product, prolongs the flex life, simultaneously reduces environmental pollution in the production process, and meets the market demand for high-quality and environment-friendly rain shoes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rubber product manufacturing, in particular to a preparation method of rubber rain shoes with latex shoe uppers. BACKGROUND

[0002] Rain shoes, as an important waterproof shoe product, are widely used in rainy days, agricultural production, industrial operation and other occasions. With the continuous improvement of consumers' requirements for the comfort, lightness and durability of rain shoes, the traditional rain shoe manufacturing process is facing many challenges.

[0003] The mainstream rubber rain shoes on the market are mainly produced by using dry rubber mixing process. In this process, natural rubber dry rubber or synthetic rubber is first mixed with various additives in an open mill or internal mixer to form a mixing rubber with certain properties; then the rubber sheet is made by calendering or extruding process; then the rubber sheet is attached to the shoe last, and the final product rain shoes are formed after vulcanization. In this process, in order to improve the processing performance and reduce the production cost, a large amount of filler (such as carbon black, calcium carbonate, etc.) is usually added, resulting in that the content of rubber component in the final product is usually only 45%-55%. The rain shoes produced by dry rubber mixing process are heavy, lack of softness, and have poor wearing comfort. At the same time, the mixing process itself will produce a large amount of dust and volatile organic compounds (VOCs), pollute the environment, and has high energy consumption. In addition, the rubber rain shoes prepared by dry rubber mixing process have insufficient bending fatigue performance, and the flex life is usually between 100,000-150,000 times, which affects the service life. SUMMARY

[0004] Based on the problems in the background art, the present application provides a preparation method of rubber rain shoes with latex shoe uppers, which improves the rubber content of the shoe upper, improves the softness and lightness of the product, prolongs the flex life, reduces environmental pollution in the production process, and meets the market demand for high-quality and environmentally friendly rain shoes.

[0005] The present application is implemented by the following technical solutions:

[0006] A preparation method of rubber rain shoes with latex shoe uppers, comprising the following steps:

[0007] S1. Clean the surface of the metal shoe last, apply release agent, and fix the shoe last on the dipping equipment;

[0008] S2. Dip the shoe last into the dipping latex;

[0009] S3. Pre-dry the shoe last after dipping;

[0010] S4. After pre-drying, the latex shoe upper with the last enters the vulcanization cylinder for vulcanization treatment;

[0011] S5. The vulcanized latex upper is separated from the shoe tree and bonded with the rubber sole to complete the preparation of the rubber rain shoe.

[0012] Further, the dipping latex in step S2 includes, 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.

[0013] Further, the water-based polyurethane emulsion is a water-based polyether type polyurethane emulsion with a solid content of 35±1%.

[0014] Further, the specific preparation method of the surface modified nanocellulose is: mixing γ-aminopropyl triethoxysilane with 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℃, the reaction time is 4-6 hours; centrifugal washing, redispersion to obtain surface modified nanocellulose.

[0015] Further, the dipping latex also includes ammonia water, and the pH of the dipping latex is adjusted to 9.2±0.2.

[0016] Further, the solid content of the natural latex is 60-65%, and the ammonia content is 0.6-0.8%.

[0017] 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℃ 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 to obtain the dipping latex.

[0018] 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℃, draining time after dipping is 2-3 minutes, and repeating dipping 2 times.

[0019] Further, the specific parameters of the pre-drying treatment in step S3 are: pre-drying temperature 50-70℃, pre-drying time 10-25 minutes, relative humidity controlled at 40-60%, and hot air circulation speed 1-3m / s.

[0020] Further, the specific parameters of the vulcanization treatment in step S4 are: vulcanization in a saturated steam environment at 115-120℃ for 7-10 minutes, and vulcanization cylinder pressure maintained at 0.6-0.8 MPa.

[0021] Advantages of the present application:

[0022] 1. The present application adopts a latex impregnation process, avoiding the use of a large amount of fillers in the traditional dry rubber mixing process, and the rubber component content in the final product can reach 70-80%, which is significantly higher than the 45-55% in the traditional process, making the rain shoes 25-35% lighter in weight, greatly improving the portability of wearing. The inherent high elasticity and softness of natural latex, combined with the toughening effect of water-based polyurethane emulsion, make the prepared rain shoes have excellent softness and resilience. Through the reinforcing effect of surface modified nanocellulose and the optimized vulcanization crosslinking network structure, the bending fatigue performance of the product is significantly improved. The flex-to-break life can reach 250-350 thousand times through the Demattia bending test, which is 150-250% higher than the 10-15 thousand times of the traditional process, greatly prolonging the service life.

[0023] 2. The present application adopts a water-based system, and the VOCs emission is reduced by more than 80%, completely avoiding the dust pollution generated by the traditional mixing process, and the overall energy consumption is reduced by 35-45%, meeting the requirements of green manufacturing and energy saving and emission reduction. Compared with the traditional mixing-calendering-laminating process, the process steps of the present application are more simplified, the degree of automation is higher, the product thickness uniformity and performance stability are better than the traditional process, and the defective product rate is significantly reduced. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be further described below in combination with specific embodiments, but the protection scope of the present application is not limited to the following embodiments.

[0025] In the embodiments and comparative examples of this invention, the preparation method of surface-modified nanocellulose is as follows: 50g of γ-aminopropyltriethoxysilane is mixed with 500ml of an ethanol / water mixture (volume ratio 9:1), stirred at room temperature, and hydrolyzed for 72 hours to obtain a hydrolyzed silane solution. The above hydrolyzed silane solution is mixed with nanocellulose slurry (solid content 2%) at a silane / cellulose mass ratio of 1:10, and reacted at 55°C for 5 hours while maintaining stirring. After the reaction is complete, the nanocellulose is washed three times by centrifugation with deionized water (8000rpm, 10min) to remove unreacted silane coupling agent. Finally, the modified nanocellulose is redispersed in deionized water, and the slurry concentration is adjusted to 10% for later use.

[0026] Example 1

[0027] A method for preparing a rubber rain boot with a latex upper includes the following steps:

[0028] Step S1. Shoe last pretreatment: Select aluminum alloy shoe lasts, clean the surface oil stains with alcohol, let them dry, and then evenly apply silicone oil release agent. Fix the shoe lasts on the automatic glue dipping equipment.

[0029] Step S2. Preparation of Impregnated Latex: By weight, take 100 parts of natural latex (62% solid content, 0.7% ammonia content) and dilute with deionized water to a solid content of 48%. Under conditions of 28℃ and stirring speed of 350 rpm, add in sequence: 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, and stir for 18 minutes; then add 3.5 parts of waterborne polyether polyurethane emulsion (35% solid content) and 0.30 parts of surface-modified nanocellulose (0.30 parts on a dry basis, i.e., 3.0 parts of 10% concentration slurry), and stir for 12 minutes; finally, add 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, and stir for 6 minutes. The pH was adjusted to 9.2 with ammonia, filtered through a 200-mesh sieve, and allowed to stand for 2 hours to remove bubbles, thus obtaining the impregnated latex.

[0030] Step S3. Impregnation process: The latex temperature is controlled at 25℃, the impregnation speed is 20mm / s for descent and 15mm / s for ascent, the dwell time is 12 seconds, the draining time is 2.5 minutes, and the impregnation is repeated twice.

[0031] Step S4. Pre-drying: Pre-dry for 18 minutes at 60℃, 50% relative humidity, and hot air circulation speed of 2m / s.

[0032] Step S5. Vulcanization treatment: Vulcanize for 8 minutes in a saturated steam environment at 118℃, with a vulcanization cylinder pressure of 0.7MPa.

[0033] Step S6. Last removal and assembly: After vulcanization, allow the shoe to cool naturally, then detach the latex upper from the last and bond it to the pre-made rubber sole with neoprene rubber adhesive. Cure at 80°C for 15 minutes to complete the preparation of the rain boots.

[0034] Example 2

[0035] Following the process flow of Example 1, the impregnation latex formula was adjusted as follows:

[0036] 120 parts natural rubber latex, 4.0 parts waterborne polyurethane emulsion, 1.6 parts sulfur, 0.8 parts accelerator TBBS, 0.3 parts accelerator TMTD, 2.8 parts zinc oxide, 1.0 part stearic acid, 0.32 parts surface-modified nanocellulose, 0.8 parts polyethylene glycol 400, 1.5 parts antioxidant 6PPD, 0.8 parts epoxidized soybean oil, and 0.15 parts silane coupling agent KH-570.

[0037] Dipping process parameters: descent speed 25mm / s, ascent speed 20mm / s, residence time 15 seconds.

[0038] Pre-drying conditions: 70℃, 20 minutes.

[0039] Vulcanization conditions: 120℃, 10 minutes.

[0040] Example 3

[0041] Following the process flow of Example 1, the impregnation latex formula was adjusted as follows:

[0042] 85 parts natural rubber latex, 3.0 parts waterborne polyurethane emulsion, 1.4 parts sulfur, 0.5 parts accelerator TBBS, 0.2 parts accelerator TMTD, 2.0 parts zinc oxide, 0.6 parts stearic acid, 0.28 parts surface-modified nanocellulose, 0.5 parts polyethylene glycol 400, 0.9 parts antioxidant 6PPD, 0.5 parts epoxidized soybean oil, and 0.10 parts silane coupling agent KH-570.

[0043] Dipping process parameters: descent speed 15mm / s, ascent speed 10mm / s, residence time 8 seconds.

[0044] Pre-drying conditions: 50℃, 25 minutes.

[0045] Vulcanization conditions: 115℃, 7 minutes.

[0046] Comparative Example 1

[0047] Rubber rain boots are manufactured using traditional dry rubber mixing processes.

[0048] Formula (parts by weight): 100 parts natural rubber, 50 parts carbon black N330, 5 parts zinc oxide, 2 parts stearic acid, 2.5 parts sulfur, 0.8 parts accelerator CZ, 0.5 parts accelerator DM, 2 parts antioxidant 4020, and 1 part paraffin wax.

[0049] Process flow: Plasticizing on an open mill → Mixing → Calendering and sheet forming → Sheet cutting and lamination → Vulcanization molding. Vulcanization conditions: 145℃ × 25 minutes.

[0050] Comparative Example 2

[0051] The formulation and process of Example 1 are followed, but without the addition of surface-modified nanocellulose.

[0052] Comparative Example 3

[0053] The formulation and process of Example 1 are followed, but without the addition of aqueous polyurethane emulsion.

[0054] Comparative Example 4

[0055] The formulation and process of Example 1 were followed, but the surface-modified nanocellulose was replaced with the same amount of unmodified nanocellulose.

[0056] Experimental Example 1

[0057] 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.

[0058] Table 1

[0059]

[0060] As shown in Table 1, the weight of Examples 1-3 (420-435g) is approximately 33% lighter than that of Comparative Example 1 (630g). This is mainly due to the use of a latex impregnation process instead of 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% in the traditional process to 70-80%, fundamentally improving the product's lightweight properties. The tensile strength of the examples reaches 18.2-18.8 MPa, significantly exceeding the 15.2 MPa of the traditional process. This is mainly attributed to the reinforcing effect of surface-modified nanocellulose and the toughening effect of the waterborne polyurethane emulsion. The data from Comparative Examples 2-4 verify the contribution of each component: the tensile strength of Comparative Example 2, lacking surface-modified nanocellulose, decreases to 16.8 MPa, and that of Comparative Example 3, lacking polyurethane emulsion, decreases even further to 15.5 MPa, indicating that these two key components play a synergistic role in improving the material strength. Meanwhile, the trend of elongation at break and hardness showed a reasonable inverse relationship. Example 3 exhibited the best flexibility (620%) due to its relatively small formulation dosage, while the traditional process with high filler content showed obvious brittleness (420%). The flexural life of the examples reached 250,000-350,000 cycles, which is 150-250% higher than the 120,000 cycles of the traditional process. This improvement is directly related to the service life of the product. This performance improvement stems from the optimized cross-linked network structure and the introduction of nano-reinforcing materials, which enable the material to better disperse stress during repeated bending, delaying the initiation and propagation of fatigue cracks. Compression set data also confirms this. The resilience of the examples (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.

[0061] Experimental Example 2

[0062] The rubber rain boots prepared in the examples and comparative examples were subjected to comfort and usability tests.

[0063] Thirty volunteers aged 25-45 (half male and half female) were selected, with foot lengths of 235-270mm, good health, and no foot diseases.

[0064] The test items and standards are shown in Table 2.

[0065] The test results are shown in Table 3.

[0066] Table 2

[0067]

[0068] Table 3

[0069]

[0070] The subjective evaluation data in Table 3 shows a high degree of consistency with the objective test results in Table 1: the perceived weight score corresponds to the actual weight data; the weight perceived score of the example is 8.8-9.4, while the actual weight is only 405-425g; the weight perceived score of Comparative Example 1 is only 4.5, 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 example is between 8.6-9.3, corresponding to its hardness value of 42-48; while the softness score of the traditional process is only 5.2, but the hardness is as high as 58. This correlation indicates that hardness control achieved through optimizing material formulation and process parameters can effectively improve the user's tactile experience.

[0071] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a rubber rain boot with a latex upper, characterized in that, Includes the following steps: S1. Clean the surface of the metal shoe last, apply a release agent, and fix the shoe last on the dipping equipment; S2. Immerse the shoe last in the impregnated latex; S3. Pre-dry the shoe lasts that have been impregnated with glue; S4. After pre-drying, the latex upper with the last is put into the vulcanization tank for vulcanization treatment; S5. Separate the vulcanized latex upper from the shoe last and bond it to the rubber sole. Then, cure the adhesive layer to complete the preparation of the rubber rain boot. The impregnated latex in step S2, by weight, comprises: 85-120 parts of natural latex, 3-4 parts of waterborne 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; The specific preparation method of surface-modified nanocellulose is as follows: γ-aminopropyltriethoxysilane is mixed with an ethanol / water mixture at a volume ratio of 9:1 and hydrolyzed for 72 hours; the hydrolyzed silane solution is mixed with nanocellulose slurry at a reaction temperature of 50-60℃ for 4-6 hours; after centrifugation, washing and redispersing, surface-modified nanocellulose is obtained.

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

3. The preparation method according to claim 2, characterized in that, The impregnating latex also includes ammonia water to adjust the pH of the impregnating latex to 9.2±0.

2.

4. The preparation method according to claim 1, characterized in that, Natural latex has a solid content of 60-65% and an ammonia content of 0.6-0.8%.

5. The preparation method according to claim 3, characterized in that, The preparation method of impregnated latex is as follows: dilute natural latex with deionized water to a solid content of 45-50%, and add stearic acid, zinc oxide, antioxidant 6PPD, polyethylene glycol 400 and epoxidized soybean oil in sequence at 25-30℃ and stirring speed of 300-400rpm, and stir for 15-20 minutes. Add water-based polyether polyurethane emulsion and surface-modified nanocellulose, and 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, and filter through a 200-mesh sieve to obtain impregnated latex.

6. The preparation method according to claim 1, characterized in that, The specific parameters for the impregnation process in step S2 are as follows: impregnation speed is 15-25 mm / s for descent and 10-20 mm / s for ascent, residence time is 8-15 seconds, latex temperature is 22-28℃, and the draining time after impregnation is 2-3 minutes. The impregnation is repeated twice.

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

8. The preparation method according to claim 1, characterized in that, The specific parameters for the vulcanization process in step S4 are as follows: vulcanize for 7-10 minutes in a saturated steam environment at 115-120℃, and maintain the pressure in the vulcanization cylinder at 0.6-0.8MPa.

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