Preparation method of high-resilience lightweight synthetic volleyball leather and volleyball leather

Abstract

The application discloses a kind of high resilience lightweight volleyball synthetic leather preparation methods, including preparation surface layer: first low modulus aliphatic waterborne polyurethane dispersion, leveling agent, thickener, water-based color paste and deionized water are mixed, scraping and drying;Preparation foaming middle layer: second low modulus aliphatic solvent-free waterborne polyurethane dispersion, light calcium, thickener, curing agent, water-based color paste and deionized water are mixed, and mechanically foamed to 1.5±0.1 times volume, scraping and drying;Preparation unfoamed bottom layer: unfoamed bottom layer slurry is scraped after adhering and curing with superfiber base material, and stripping release paper;The elastic modulus of surface layer and foaming middle layer resin is 2.0-2.5MPa.The volleyball synthetic leather prepared by the synergy of full water-based system, low modulus resin and foaming middle layer has the advantages of environmental protection, softness 50-60 degrees, resilience ≥55%, gram weight 540-600g / m², wear resistance more than 12000 times, etc., realizes the balance of lightweight and durability, and has excellent competitive feel.

Description

Technical Field

[0001] This invention relates to the field of volleyball synthetic leather technology, specifically to a method for preparing high-resilience lightweight volleyball synthetic leather and the volleyball leather itself. Background Technology

[0002] In competitive volleyball, the requirements for the ball's outer material are quite high. Athletes want the ball to be relatively light, generally between 260-280g, so that spikes can be fast and passes accurate. However, the outer material also needs to be thick enough, usually 1.4-1.6mm, otherwise it simply cannot withstand the powerful spikes at speeds of over 100 km / h, because if it's too thin, it will wear through after just a few hits. This creates a contradiction: making it too thick makes it heavy and clunky to handle; making it too thin makes it less durable, and the leather surface will break down after a short period of use. Therefore, achieving a balance between thickness, weight, and durability has always been a challenge in the design of synthetic leather for volleyballs.

[0003] To improve the wear resistance of the ball skin, the current mainstream approach is to chemically cross-link the surface layer. For example, patent CN114645470B adds a specially modified inorganic powder to the surface resin, utilizing isocyanate groups to undergo a cross-linking reaction with the epoxy resin, forming a relatively dense network structure, thereby improving wear resistance. While this approach does solve the wear resistance problem, it also introduces two new issues: The first point is environmental friendliness: the wear-resistant surface layer of this solution uses oil-based resin with added organic solvents such as xylene and acetone. Solvents will evaporate during the production process, and trace amounts of residue are inevitable in the finished product.

[0004] The second aspect is the feel: Volleyball's feedback relies heavily on touch. If the surface layer is too hard, the ball will feel stiff and difficult to control. Furthermore, the cross-linked structure designed for wear resistance naturally makes the material harder, leading to a decrease in feel.

[0005] Therefore, current technology rarely focuses on the optimal range of softness and hardness for volleyball leather. Thus, achieving lightweight design and high abrasion resistance while maintaining environmental friendliness and a comfortable feel remains a major technical challenge for synthetic volleyball leather. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing high-resilience lightweight volleyball synthetic leather, successfully producing a volleyball synthetic leather that is environmentally friendly, lightweight, wear-resistant, has a good feel when played, and exhibits clear rebound.

[0007] To achieve the above objectives, the present invention provides a method for preparing high-resilience lightweight volleyball synthetic leather, comprising the following steps: S1: Preparation of the surface layer: Mix 100 parts of a first low-modulus aliphatic waterborne polyurethane dispersion, 1-2 parts of leveling agent, 0.5-1 parts of thickener, 5-12 parts of waterborne color paste with deionized water to obtain a surface layer slurry; the solid content of the first low-modulus aliphatic waterborne polyurethane dispersion is 27-29%, and the elastic modulus is 2.0-2.5 MPa; coat the surface layer slurry onto release paper and dry to obtain the surface layer; S2: Preparation of the foamed intermediate layer: Mix 100 parts of a second low-modulus aliphatic solvent-free waterborne polyurethane dispersion, 8-12 parts of light calcium carbonate, 0.5-1 parts of thickener, 0.2-0.5 parts of curing agent, 3-10 parts of waterborne colorant, and deionized water, and mechanically foam to 1.5 ± 0.1 times the volume to obtain the intermediate layer foaming slurry; the solid content of the second low-modulus aliphatic solvent-free waterborne polyurethane dispersion is 46-50%, and the elastic modulus is 2.0-2.5 MPa; coat the intermediate layer foaming slurry onto the top layer and dry to obtain the foamed intermediate layer; S3: Preparation of unfoamed base layer: Mix 100 parts of second low modulus aliphatic solvent-free waterborne polyurethane dispersion, 8-12 parts of light calcium carbonate, 0.5-1 parts of thickener, 0.2-0.5 parts of curing agent, 3-10 parts of waterborne color paste with deionized water, stir and disperse evenly to obtain unfoamed base layer slurry; scrape the unfoamed base layer slurry onto the foamed middle layer, bake until semi-dry, then bond it to the microfiber substrate, dry and cure, peel off the release paper to obtain the volleyball synthetic leather.

[0008] Furthermore, the coating amount of the surface layer slurry is 120-150 g / m², and the dry film thickness of the surface layer is 0.01-0.03 mm.

[0009] Furthermore, the coating amount of the intermediate foaming slurry is 200-250 g / m², and the dry film thickness of the foamed intermediate layer is 0.05-0.07 mm.

[0010] Furthermore, the coating amount of the unfoamed underlayer slurry is 250-300 g / m², and the dry film thickness of the unfoamed underlayer is 0.06-0.08 mm.

[0011] Furthermore, the thickness of the microfiber substrate is 1.3-1.4 mm, and the basis weight is 380-440 g / m².

[0012] Furthermore, the leveling agent in the top layer slurry is a modified polyether siloxane copolymer, and the thickener is a nonionic polyether polyurethane thickener; the curing agent in the middle layer foamed slurry and the unfoamed bottom layer slurry is an active blocked hydrophilic aliphatic isocyanate.

[0013] Furthermore, in S1, the surface slurry is dried using a wind-avoided gradient drying process. The wind-avoided gradient drying process is as follows: first, it is dried at 80±2℃ until the surface is dry, and then the temperature is raised to 100-110℃ to dry thoroughly. The process does not involve high-temperature rapid drying above 130℃.

[0014] Furthermore, in S2, the foamed middle layer is dried slowly with low air volume at 80-100℃; in S3, the unfoamed bottom layer is dried to semi-dry at 80±2℃, then bonded to the microfiber substrate, and then dried and cured by a gradient temperature increase of 100-130℃.

[0015] On the other hand, a volleyball leather is prepared using the aforementioned method for preparing high-resilience lightweight synthetic volleyball leather.

[0016] Furthermore, the volleyball leather has a thickness of 1.4-1.6 mm, a weight of 540-600 g / m², a softness of 50-60 degrees, and a compression resilience of ≥55%.

[0017] The present invention provides a method for preparing high-resilience, lightweight synthetic leather for volleyballs. By using all-water-based materials and low-modulus materials, the following beneficial effects are achieved: 1. Compared with existing technologies, this invention is the first to explicitly propose and achieve the technical goal of controllable feel in the field of volleyball synthetic leather. Through the synergistic effect of low-modulus resin selection, gentle drying process, and water-based foaming middle layer, the softness is stably controlled at 50-60 degrees, and the rebound rate is increased to over 55%. Feedback from blind tests conducted by professional athletes indicates that this feel range is considered the ideal range for clear feel, soft rebound, and precise ball control. This solves the long-standing technical contradiction in existing technologies where the pursuit of abrasion resistance sacrifices feel.

[0018] 2. Excellent environmental performance. The top layer, foamed middle layer, and unfoamed bottom layer are all made of water-based resin, and no organic solvents are used in the production process, completely avoiding the VOC emission problems of traditional oil-based systems. Testing shows that the content of harmful substances such as benzene compounds and aldehydes in the finished leather is below the detection limit, fully meeting the stringent health and environmental protection requirements of high-end events and athletes.

[0019] 3. Combining lightweight and durability. Lightweighting is achieved through a water-based foamed middle layer. The foaming resin forms a microporous structure after mechanical foaming, maintaining a thickness of 1.4-1.6mm and providing support while controlling the basis weight at 540-600g / m². 2 Meanwhile, the volleyball did not show any skin damage, deformation, or glue detachment after 12,000 cycles of dynamic fatigue testing, and its wear resistance fully meets the requirements of competitive matches. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a method for preparing high-resilience, lightweight synthetic leather for volleyballs, comprising the following steps: S1: Preparation of the surface layer: Mix 100 parts of a first low-modulus aliphatic waterborne polyurethane dispersion, 1-2 parts of leveling agent, 0.5-1 parts of thickener, 5-12 parts of waterborne color paste with deionized water to obtain a surface layer slurry; the solid content of the first low-modulus aliphatic waterborne polyurethane dispersion is 27-29%, and the elastic modulus is 2.0-2.5 MPa; coat the surface layer slurry onto release paper and dry to obtain the surface layer; S2: Preparation of the foamed intermediate layer: Mix 100 parts of a second low-modulus aliphatic solvent-free waterborne polyurethane dispersion, 8-12 parts of light calcium carbonate, 0.5-1 parts of thickener, 0.2-0.5 parts of curing agent, 3-10 parts of waterborne colorant, and deionized water, and mechanically foam to 1.5 ± 0.1 times the volume to obtain the intermediate layer foaming slurry; the solid content of the second low-modulus aliphatic solvent-free waterborne polyurethane dispersion is 46-50%, and the elastic modulus is 2.0-2.5 MPa; coat the intermediate layer foaming slurry onto the top layer and dry to obtain the foamed intermediate layer; S3: Preparation of unfoamed base layer: Mix 100 parts of second low modulus aliphatic solvent-free waterborne polyurethane dispersion, 8-12 parts of light calcium carbonate, 0.5-1 parts of thickener, 0.2-0.5 parts of curing agent, 3-10 parts of waterborne color paste with deionized water, stir and disperse evenly to obtain unfoamed base layer slurry; scrape the unfoamed base layer slurry onto the foamed middle layer, bake until semi-dry, then bond it to the microfiber substrate, dry and cure, peel off the release paper to obtain the volleyball synthetic leather.

[0022] In the preparation method of this invention: First, S1 uses low-modulus aliphatic waterborne polyurethane to prepare the top layer, providing basic wear resistance and a soft feel for the finished product; S2 introduces a waterborne foamed middle layer, which forms a microporous structure through mechanical foaming 1.5 times, providing resilience support while achieving lightweighting; S3 uses an unfoamed bottom layer of the same system as the middle layer foaming slurry to bond with the microfiber substrate, ensuring interlayer bonding force; secondly, water is used as the sole dispersion medium in all three steps of the slurry to avoid the defects of residual organic solvents; finally, the top layer and the foamed middle layer use low-modulus resin with matching modulus to ensure overall consistency of feel and avoid the defect of hardening due to cross-linking hardening.

[0023] In this invention, the surface layer possesses the advantages of being non-slip, wear-resistant, and having a delicate feel, enabling the volleyball to remain wear-resistant during high-intensity competition while providing excellent ball feel and grip. The foamed middle layer achieves lightweighting while maintaining a stable thickness level, combining excellent softness and elastic support. The unfoamed bottom layer uses soft microfiber to ensure both strength and lightweight softness.

[0024] Preferably, the first low-modulus aliphatic waterborne polyurethane dispersion of the surface layer slurry is selected from HU2570-1 aliphatic waterborne polyurethane dispersion of Lishui Haiweite New Materials Co., Ltd., with a solid content of 27-29% and an elastic modulus of 2.0-2.5 MPa.

[0025] Preferably, the second low-modulus aliphatic solvent-free waterborne polyurethane dispersion of the intermediate foaming slurry is selected from HU2590-7A aliphatic solvent-free waterborne polyurethane dispersion of Lishui Haiweite New Materials Co., Ltd., with a solid content of 46-50% and an elastic modulus of 2-2.5 MPa.

[0026] Preferably, the coating amount of the topcoat slurry is 120-150 g / m², and the dry film thickness of the topcoat is 0.01-0.03 mm. This ensures sufficient wear resistance while avoiding increased weight and a hardened feel due to an excessively thick topcoat. This thickness range, combined with the low-modulus resin, results in a thin yet soft topcoat, achieving a balance between lightweight design and a soft feel.

[0027] Preferably, the coating amount of the intermediate foaming slurry is 200-250 g / m², and the dry film thickness of the foamed intermediate layer is 0.05-0.07 mm. Combined with mechanical foaming to 1.5 times its volume, a microporous buffer layer of appropriate thickness is formed. This structure accounts for a large proportion of the total thickness of the finished product and is the key to achieving lightweight. At the same time, the microporous structure gives the material excellent compressive resilience, ensuring rapid and stable energy feedback during impact.

[0028] The unfoamed underlayer provides a stable support base for the top layer and the foamed middle layer. Preferably, the coating amount of the unfoamed underlayer slurry is 250-300 g / m², and the dry film thickness of the unfoamed underlayer is 0.06-0.08 mm. This thickness, in conjunction with the microfiber substrate, ensures the uniformity of the overall thickness of the volleyball synthetic leather and the interlayer bonding strength, avoiding peeling problems caused by an unfoamed underlayer that is too thin or weight increase caused by an unfoamed underlayer that is too thick.

[0029] Preferably, the microfiber substrate has a thickness of 1.3-1.4 mm and a basis weight of 380-440 g / m². The microfiber substrate possesses excellent flexibility and stable thickness dimensions. When combined with the water-based unfoamed underlayer, it ensures both the overall flexibility of the finished product and provides sufficient tear resistance, forming a crucial foundation for achieving a balance between lightweight and durability in volleyball synthetic leather.

[0030] Preferably, the leveling agent in the surface layer slurry is a modified polyether siloxane copolymer. Leveling agent R3, sourced from Lishui Haiweite New Materials Co., Ltd., is selected; its viscosity (25℃) is 25-50 cst, and its active ingredient content is 100%.

[0031] Preferably, the thickener is a nonionic polyether polyurethane thickener. Thickener T50B from Lishui Haivit New Materials Co., Ltd. was selected.

[0032] Preferably, the curing agent in the middle layer foaming slurry and the unfoamed bottom layer slurry is an active closed-type hydrophilic aliphatic isocyanate, specifically F8 from Lishui Haiweite New Materials Co., Ltd. This curing agent releases isocyanate groups under heating conditions, which undergo a cross-linking reaction with the resin, improving the cohesive strength and interlayer bonding of the foamed middle layer and the unfoamed bottom layer, while maintaining the environmentally friendly characteristics of the system.

[0033] Preferably, the light calcium carbonate is Y-1168 from Quanzhou Yiluoke New Material Co., Ltd., with a mesh size of 600, a whiteness of ≥94%, and a pH of 8-10.

[0034] Preferably, in S1, the surface slurry is dried using a windproof gradient drying process. The windproof gradient drying process is as follows: first, it is dried at 80±2℃ until the surface is dry, about 2-3 minutes, and then the temperature is raised to 100-110℃ until it is completely dry. The process does not use high-temperature rapid drying above 130℃ to prevent the surface resin from hardening and cracking due to high-temperature rapid overheating and cross-linking, thereby preserving the soft feel brought by its low modulus characteristics.

[0035] Preferably, in S2, the foamed middle layer provides support, lightweight, softness, and resilience. The foamed middle layer is dried slowly with low airflow at 80-100°C to avoid the collapse of the foam pore structure or hardening of the resin caused by high-temperature rapid drying, and also to prevent the resin from hardening and cracking due to high-temperature rapid overheating and cross-linking.

[0036] Preferably, in step S3, the unfoamed substrate is dried to semi-dry at 80±2℃, then bonded to the microfiber substrate, and subsequently dried and cured by a gradient temperature increase of 100-130℃. The process of drying the unfoamed substrate to semi-dry at 80℃ before bonding ensures that the unfoamed substrate maintains appropriate tackiness to guarantee good adhesion to the substrate. The subsequent drying and curing by a gradient temperature increase of 100-130℃ ensures sufficient cross-linking reaction. This process system guarantees the integrity of each layer structure and the interlayer bonding strength.

[0037] This invention also provides a volleyball leather, which is prepared using the aforementioned method for producing high-resilience lightweight synthetic volleyball leather. The volleyball leather has the advantages of being environmentally friendly, having a soft feel, being lightweight, and having high resilience.

[0038] The volleyball leather has a thickness of 1.4-1.6mm and a weight of 540-600g / m², ensuring a balance between lightweight and durability; its softness of 50-60 degrees (ASKER-C type) is an ideal feel range confirmed by athlete testing; and its compression rebound rate is ≥55%, ensuring energy feedback performance when the ball is impacted.

[0039] The following examples and comparative examples illustrate the beneficial technical effects of the high-resilience lightweight volleyball synthetic leather obtained by the preparation method of the present invention and the volleyballs made from the synthetic leather. Example 1

[0040] This example provides a method for preparing high-resilience, lightweight synthetic leather for volleyballs, as follows: Topcoat: 100 parts HU2570-1 resin, 1.5 parts leveling agent, 0.8 parts thickener, 8 parts color paste, coating amount 135g / m²; surface dry at 80℃ for 2.5min, bake at 105℃ until completely dry.

[0041] Foamed middle layer: 100 parts HU2590-7A resin, 10 parts light calcium carbonate, 0.8 parts thickener, 0.35 parts curing agent, 6 parts color paste, mechanically foamed to 1.5 times the volume, coating amount 225g / m², dried slowly at 90℃ with low air volume. Unfoamed base layer: 100 parts HU2590-7A resin, 10 parts light calcium carbonate, 0.8 parts thickener, 0.35 parts curing agent, 6 parts color paste, coating amount 275g / m², bake at 80℃ until semi-dry; Microfiber substrate: 1.35mm thick, 410g / m², bonded to an unfoamed base layer, then cured by gradient temperature increase from 100-130℃; resulting in high-resilience, lightweight volleyball synthetic leather. Example 2

[0042] This example provides a method for preparing high-resilience, lightweight synthetic leather for volleyballs, as follows: Topcoat: 100 parts HU2570-1 resin, 1 part leveling agent, 0.5 parts thickener, 5 parts color paste, coating amount 120g / m²; surface dry at 80℃ for 2.5min, bake at 105℃ until completely dry.

[0043] Foamed middle layer: 100 parts HU2590-7A resin, 8 parts light calcium carbonate, 0.5 parts thickener, 0.2 parts curing agent, 3 parts color paste, mechanically foamed to 1.5 times the volume, coating amount 200g / m², dried slowly at 90℃ with low air volume. Unfoamed base layer: 100 parts HU2590-7A resin, 8 parts light calcium carbonate, 0.5 parts thickener, 0.2 parts curing agent, 3 parts color paste, coating amount 250g / m², bake at 80℃ until semi-dry; Microfiber substrate: 1.35mm thick, 410g / m², bonded to an unfoamed base layer, then cured by gradient temperature increase from 100-130℃; resulting in high-resilience, lightweight volleyball synthetic leather. Example 3

[0044] This example provides a method for preparing high-resilience, lightweight synthetic leather for volleyballs, as follows: Topcoat: 100 parts HU2570-1 resin, 2 parts leveling agent, 1 part thickener, 12 parts color paste, coating amount 150g / m²; surface dry at 80℃ for 2.5min, bake at 105℃ until completely dry.

[0045] Foamed middle layer: 100 parts HU2590-7A resin, 12 parts light calcium carbonate, 1 part thickener, 0.5 parts curing agent, 10 parts color paste, mechanically foamed to 1.5 times the volume, coating amount 250g / m², dried slowly at 90℃ with low air volume. Unfoamed base layer: 100 parts HU2590-7A resin, 12 parts light calcium carbonate, 1 part thickener, 0.5 parts curing agent, 10 parts color paste, 300g / m² coating amount, bake at 80℃ until semi-dry; Microfiber substrate: 1.35mm thick, 410g / m², bonded to an unfoamed base layer, then cured by gradient temperature increase from 100-130℃; resulting in high-resilience, lightweight volleyball synthetic leather.

[0046] Comparative Example 1 This example provides a synthetic leather for volleyballs, as follows: Topcoat: Oil-based system, 100 parts matrix resin, 90 parts solvent (acetone), 0.5 parts leveling agent, 8 parts epoxy resin color paste, and 30 parts anti-wear agent; Solvent-free foam layer: 100 parts of aqueous polyether polyol, 65 parts of MDI, and 45 parts of filler; Base fabric layer: non-woven fabric.

[0047] Comparative Example 2 This example provides a method for preparing synthetic leather for volleyballs, as follows: Topcoat: 100 parts of ordinary aliphatic waterborne polyurethane resin (elastic modulus 8-10MPa), 1.5 parts of leveling agent, 0.8 parts of thickener, 8 parts of color paste, and a coating amount of 135g / m²; surface dry at 80℃ for 2.5min, then bake at 105℃ until completely dry.

[0048] Foamed middle layer: 100 parts of ordinary aliphatic waterborne polyurethane resin (elastic modulus 8-10MPa), 10 parts of light calcium carbonate, 0.8 parts of thickener, 0.35 parts of curing agent, 6 parts of color paste, mechanically foamed to 1.5 times the volume, coating amount 225g / m², dried slowly at 90℃ with low air volume. Unfoamed base layer: 100 parts of ordinary aliphatic waterborne polyurethane resin (elastic modulus 8-10MPa), 10 parts of light calcium carbonate, 0.8 parts of thickener, 0.35 parts of curing agent, 6 parts of color paste, 275g / m² coating amount, baked at 80℃ until semi-dry. Microfiber substrate: 1.35mm thick, 410g / m², bonded to an unfoamed base layer, then cured by gradient temperature increase from 100-130℃; thus obtaining volleyball synthetic leather.

[0049] Comparative Example 3 This example provides a method for preparing synthetic leather for volleyballs, as follows: Topcoat: 100 parts HU2570-1 resin, 1.5 parts leveling agent, 0.8 parts thickener, 8 parts color paste, coating amount 135g / m²; bake at 130℃ until dry.

[0050] Foamed middle layer: 100 parts HU2590-7A resin, 10 parts light calcium carbonate, 0.8 parts thickener, 0.35 parts curing agent, 6 parts color paste, mechanically foamed to 1.5 times the volume, coating amount 225g / m², dried slowly at 90℃ with low air volume. Unfoamed base layer: 100 parts HU2590-7A resin, 10 parts light calcium carbonate, 0.8 parts thickener, 0.35 parts curing agent, 6 parts color paste, coating amount 275g / m², bake at 80℃ until semi-dry; Microfiber substrate: 1.35mm thick, 410g / m², bonded to an unfoamed base layer, then cured by gradient temperature increase from 100-130℃; thus obtaining volleyball synthetic leather.

[0051] Comparative Example 4 This example provides a method for preparing synthetic leather for volleyballs, as follows: Topcoat: 100 parts HU2570-1 resin, 1.5 parts leveling agent, 0.8 parts thickener, 8 parts color paste, coating amount 135g / m²; surface dry at 80℃ for 2.5min, bake at 105℃ until completely dry.

[0052] Unfoamed base layer: 100 parts HU2590-7A resin, 10 parts light calcium carbonate, 0.8 parts thickener, 0.35 parts curing agent, 6 parts color paste, 500g / m² coating amount, bake at 80℃ until semi-dry; Microfiber substrate: 1.35mm thick, 410g / m², bonded to an unfoamed base layer, then cured by gradient temperature increase from 100-130℃; thus obtaining volleyball synthetic leather.

[0053] Comparative Example 5 This example provides a method for preparing synthetic leather for volleyballs, as follows: Topcoat: 100 parts HU2570-1 resin, 1.5 parts leveling agent, 0.8 parts thickener, 8 parts color paste, coating amount 135g / m²; surface dry at 80℃ for 2.5min, bake at 105℃ until completely dry.

[0054] Middle layer (unfoamed): 100 parts HU2590-7A resin, 10 parts light calcium carbonate, 0.8 parts thickener, 0.35 parts curing agent, 6 parts color paste. No mechanical foaming is performed. The coating amount is 225g / m². Dry at 90℃ with low air volume. Unfoamed base layer: 100 parts HU2590-7A resin, 10 parts light calcium carbonate, 0.8 parts thickener, 0.35 parts curing agent, 6 parts color paste, coating amount 275g / m², bake at 80℃ until semi-dry; Microfiber substrate: 1.35mm thick, 410g / m², bonded to an unfoamed base layer, then cured by gradient temperature increase from 100-130℃; thus obtaining volleyball synthetic leather.

[0055] The following tests were conducted on the volleyball synthetic leather of Examples 1-3 and Comparative Examples 1-5: 1. VOC content: Refer to GB / T 27630-2011 standard.

[0056] 2. Softness: Refer to ASTM D2240 standard and use an ASKER-C type hardness tester.

[0057] 3. Rebound rate: Refer to GB / T 24142.

[0058] 4. Weight and thickness: Refer to GB / T 8949 standard.

[0059] 5. Interlayer peel strength: Refer to GB / T 8949 standard.

[0060] 6. Abrasion resistance: The volleyball is made of synthetic leather, inflated to the standard air pressure, fixed on a ball abrasion tester, and repeatedly impacted on the ball surface at a hitting speed of 100km / h. The number of hitting cycles when the first skin damage, delamination, or obvious wear occurs is recorded.

[0061] Table 1 Performance parameters of volleyball synthetic leather in Examples 1-3 and Comparative Examples 1-5

[0062] Based on Table 1, the following conclusions can be drawn: 1. No VOCs were detected in Examples 1-3, while VOCs were detected in Comparative Example 1; this indicates that the all-water system is significantly more environmentally friendly than the oil-based system.

[0063] 2. Examples 1-3 all exhibited a softness between 52-58 degrees, which aligns with the ideal hand feel range. Comparative Example 2, using a high-modulus resin, achieved a softness of 78 degrees, which was significantly harder, with a rebound rate dropping to 50%, indicating a deterioration in softness, and athletes reported a noticeably worse feel. Comparative Example 3, employing high-temperature rapid drying, achieved a softness of 72 degrees; this demonstrates that even using the same low-modulus resin, improper drying processes can significantly harden the hand feel. Comparative Examples 2 and 3 together illustrate that low-modulus resin and a gentle drying process are crucial for achieving a soft hand feel; only through their combined use can the final hand feel target be achieved.

[0064] 3. Examples 1-3 showed a rebound rate ≥56%; Comparative Example 4, without a foamed middle layer, had a rebound rate of only 42%, and Comparative Example 5, with no foamed middle layer, had a rebound rate of 48%, both significantly lower than the examples; this demonstrates the crucial role of the water-based foamed middle layer in rebound performance. Examples 1-3 had a basis weight of 540-590 g / m²; Comparative Example 4, without a foamed middle layer, had a basis weight of 680 g / m². 2 The weight increase of about 20% indicates that the foamed middle layer is the key to lightweight design.

[0065] 4. Comparative Example 4 lacks a foamed interlayer. To maintain thickness, the only solution is to increase the coating amount, resulting in a basis weight of 680 g / m². Due to the lack of a foamed layer's cushioning structure, both abrasion resistance and resilience decrease. Example 1, using a water-based foamed interlayer, achieves a lower basis weight (570 g / m²) with the same or even slightly higher thickness (1.52 mm), while exhibiting significantly higher abrasion resistance and resilience. This demonstrates that thickness, weight, and durability are not inherently contradictory. Through the water-based foamed interlayer technology, all three can be achieved simultaneously: thick yet not heavy, heavy yet not bulky, and light yet not brittle.

[0066] 5. The abrasion resistance of Examples 1-3 is ≥12000 cycles, which meets the requirements of competition; the abrasion resistance of Comparative Example 3 (high temperature rapid drying) drops to 10500 cycles, indicating that excessive cross-linking is actually detrimental to abrasion resistance.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-resilience lightweight volleyball synthetic leather, characterized in that: Includes the following steps: S1: Preparation of the surface layer: Mix 100 parts of a first low-modulus aliphatic waterborne polyurethane dispersion, 1-2 parts of leveling agent, 0.5-1 parts of thickener, 5-12 parts of waterborne color paste with deionized water to obtain a surface layer slurry; the solid content of the first low-modulus aliphatic waterborne polyurethane dispersion is 27-29%, and the elastic modulus is 2.0-2.5 MPa; coat the surface layer slurry onto release paper and dry to obtain the surface layer; S2: Preparation of the foamed intermediate layer: Mix 100 parts of a second low-modulus aliphatic solvent-free waterborne polyurethane dispersion, 8-12 parts of light calcium carbonate, 0.5-1 parts of thickener, 0.2-0.5 parts of curing agent, 3-10 parts of waterborne colorant, and deionized water, and mechanically foam to 1.5 ± 0.1 times the volume to obtain the intermediate layer foaming slurry; the solid content of the second low-modulus aliphatic solvent-free waterborne polyurethane dispersion is 46-50%, and the elastic modulus is 2.0-2.5 MPa; coat the intermediate layer foaming slurry onto the top layer and dry to obtain the foamed intermediate layer; S3: Preparation of unfoamed base layer: Mix 100 parts of second low modulus aliphatic solvent-free waterborne polyurethane dispersion, 8-12 parts of light calcium carbonate, 0.5-1 parts of thickener, 0.2-0.5 parts of curing agent, 3-10 parts of waterborne color paste with deionized water, stir and disperse evenly to obtain unfoamed base layer slurry; scrape the unfoamed base layer slurry onto the foamed middle layer, bake until semi-dry, then bond it to the microfiber substrate, dry and cure, peel off the release paper to obtain the volleyball synthetic leather.

2. The method for preparing high-resilience lightweight volleyball synthetic leather according to claim 1, characterized in that: The coating amount of the surface layer slurry is 120-150 g / m², and the dry film thickness of the surface layer is 0.01-0.03 mm.

3. The method for preparing high-resilience lightweight volleyball synthetic leather according to claim 1, characterized in that: The coating amount of the intermediate foaming slurry is 200-250 g / m², and the dry film thickness of the foamed intermediate layer is 0.05-0.07 mm.

4. The method for preparing high-resilience lightweight volleyball synthetic leather according to claim 1, characterized in that: The coating amount of the unfoamed underlayer slurry is 250-300 g / m², and the dry film thickness of the unfoamed underlayer is 0.06-0.08 mm.

5. The method for preparing high-resilience lightweight volleyball synthetic leather according to claim 1, characterized in that: The thickness of the microfiber substrate is 1.3-1.4 mm, and the basis weight is 380-440 g / m².

6. The method for preparing high-resilience lightweight volleyball synthetic leather according to claim 1, characterized in that: The leveling agent in the top layer slurry is a modified polyether siloxane copolymer, and the thickener is a nonionic polyether polyurethane thickener; the curing agent in the middle layer foamed slurry and the unfoamed bottom layer slurry is an active blocked hydrophilic aliphatic isocyanate.

7. The method for preparing high-resilience lightweight volleyball synthetic leather according to claim 1, characterized in that: In S1, the surface slurry is dried using a wind-avoided gradient drying process. The wind-avoided gradient drying process is as follows: first, it is dried at 80±2℃ until the surface is dry, and then the temperature is raised to 100-110℃ to dry thoroughly. The process does not use high-temperature rapid drying above 130℃.

8. The method for preparing high-resilience lightweight volleyball synthetic leather according to claim 7, characterized in that: In S2, the foamed middle layer is dried slowly with low air volume at 80-100℃; in S3, the unfoamed bottom layer is dried to semi-dry at 80±2℃, then bonded to the microfiber substrate, and then dried and cured by a gradient temperature increase of 100-130℃.

9. A type of volleyball leather, characterized in that: It is prepared by the method for preparing high-resilience lightweight volleyball synthetic leather according to any one of claims 1-8.

10. The volleyball leather according to claim 9, characterized in that: The volleyball leather has a thickness of 1.4-1.6mm, a weight of 540-600g / m², a softness of 50-60 degrees, and a compression resilience of ≥55%.

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