Zero-hardness sponge and preparation method thereof

Abstract

The invention relates to the technical field of sponge processing, in particular to zero-hardness sponge and a preparation method thereof.The zero-hardness sponge is prepared from, by weight, polyester polyol A, polyester polyol B, polyether polyol, diisocyanate, methoxypolyethylene glycol, glycerin, a nonionic surfactant, a catalyst and N, N-dimethylformamide. According to the formula, polyester polyol A, polyester polyol B, polyether polyol, polyethylene glycol monomethyl ether and other components are added into a reaction kettle, the reaction kettle is made of polyether polyol A, polyether polyol B, N, N-dimethyl cyclohexylamine, polyoxyethylene fatty amide, an antioxidant, an anti-ultraviolet agent, a chain extender, a modifier and water, the modifier is composed of polyether modified polydimethylsiloxane, ethylhexyl palmitate, chitosan and a glacial acetic acid solution, and in the formula, polyester polyol A, polyester polyol B, polyether polyol, polyethylene glycol monomethyl ether and other components are added into the reaction kettle. On the premise that the rebound resilience is not reduced, the hardness of the sponge is reduced to a new level, the requirements of underwear and other application scenarios for extreme softness are met, meanwhile, the sponge can still quickly restore to the original shape after being pressed for a long time, and the attractiveness and wearing comfort of the clothes are kept.

Description

Technical Field

[0001] This application relates to the field of sponge processing technology, and more specifically, to a zero-hardness sponge and its preparation method. Background Technology

[0002] Currently, most foam products on the market use polyurethane foam materials. By adjusting the formula and process, different levels of hardness and elasticity are achieved, and they are widely used in clothing, furniture, automotive interiors, and many other fields. However, despite the significant achievements in the research and application of polyurethane foam, some problems still need to be solved under current technological conditions. In particular, when pursuing ultimate softness, traditional polyurethane foam often faces a dilemma of difficulty in achieving a balance. When efforts are made to improve its softness to meet the extremely high requirements for material softness in applications such as intimate apparel, especially bras, the foam's resilience and durability are difficult to maintain at an ideal level simultaneously.

[0003] Specifically, while existing polyurethane foams achieve a low hardness to provide a soft touch, they are prone to poor resilience. This directly results in the foam's inability to return to its original shape during actual use, especially under prolonged pressure. For example, in intimate apparel such as bras, the cumulative deformation of the foam significantly affects wearing comfort and the aesthetics of the garment, failing to provide consumers with a consistently good user experience.

[0004] To address this issue, some manufacturers have attempted various improvements. For example, they have reduced the sponge's hardness by adding softeners or altering the physical conditions during the foaming process to meet softness requirements. However, these existing solutions also have significant limitations. Adding softeners and similar methods has led to a decline in the sponge's mechanical properties, with increased compression set being particularly prominent. This undoubtedly shortens the product's lifespan considerably, requiring replacement more frequently and increasing costs for consumers.

[0005] Meanwhile, over-reliance on fabric softeners may also bring new safety hazards. During long-term use, fabric softeners may migrate, gradually transferring to the skin surface and triggering allergic reactions and other skin problems. This poses a significant potential risk, especially for applications such as intimate apparel that come into direct contact with the skin. Therefore, there is an urgent need for a polyurethane foam that combines extremely low stiffness with excellent resilience. Summary of the Invention

[0006] To address the issue that existing polyurethane foam cannot simultaneously maintain high resilience, durability, and extreme softness, this application provides a zero-hardness sponge and its preparation method.

[0007] In the first aspect, this application provides a zero-hardness sponge, which adopts the following technical solution: A zero-hardness sponge is prepared from the following raw materials in parts by weight: Polyester polyol A 5-10 parts Polyester polyol B8-15 parts 10-20 parts of polyether polyol 15-25 parts of diisocyanate 2-5 parts of polyethylene glycol monomethyl ether 1-2 parts glycerin 0.5-1.5 parts of nonionic surfactant Catalyst 0.05-0.2 parts 0.1-0.5 parts of N,N-dimethylcyclohexylamine Polyoxyethylene fatty amide 0.5-2 parts Antioxidant 0.2-0.8 parts UV protectant 0.2-0.8 parts Chain extender 0.5-2 parts 5-8 parts of modifier 2-5 parts water The modifier is composed of polyether-modified polydimethylsiloxane, ethylhexyl palmitate, chitosan and glacial acetic acid solution in a weight ratio of (3-5):(2-3):(2-4):10.

[0008] By adopting the above technical solution, the formula rationally combines different types of polyols, including polyester polyols A and B, polyether polyols, and polyethylene glycol monomethyl ether, etc., to reduce the hardness of the sponge to a new low without reducing its resilience. This meets the requirements for ultimate softness in applications such as intimate apparel, allowing users to feel a cloud-like softness when wearing the garment. At the same time, the sponge can quickly return to its original shape after being subjected to pressure for a long time, maintaining the appearance and comfort of the clothing.

[0009] This application, by rationally adjusting the proportions and types of raw materials, reduces the hardness of the sponge while avoiding the significant decrease in mechanical properties caused by the addition of softeners. The sponge not only possesses excellent softness but also maintains high tensile strength, tear strength, and other mechanical properties, capable of withstanding certain external forces without easily deforming or breaking, ensuring the durability and reliability of clothing and other items used under normal conditions. The introduction of polyethylene glycol monomethyl ether and glycerin can, to a certain extent, increase the flexibility of the polymer chain segments, making the sponge even softer. They can react with polyols and isocyanates to form relatively flexible connecting parts, thereby reducing the rigidity of the entire network structure and contributing to the improvement of the sponge's softness.

[0010] The modifier consists of polyether-modified polydimethylsiloxane, ethylhexyl palmitate, chitosan, and glacial acetic acid solution. These components work synergistically to create a unique effect. Polyether-modified polydimethylsiloxane provides excellent flexibility and lubricity, reducing the sponge's coefficient of friction and minimizing skin irritation. Ethylhexyl palmitate further enhances the sponge's softness and skin-friendliness. Chitosan possesses certain bioactivity and antibacterial properties, improving the sponge's safety. Glacial acetic acid solution may regulate pH during the reaction, promoting the reaction and synergistic effect between the components, collectively improving the sponge's overall performance, including softness, resilience, durability, and safety.

[0011] Furthermore, the raw materials used, such as polyether polyols, have good hydrophilicity and biocompatibility, which makes the sponge non-irritating when in contact with human skin, reducing skin allergies and other problems caused by material incompatibility. It is especially suitable for applications that come into direct contact with human skin, such as clothing.

[0012] During the foaming process, nonionic surfactants can reduce the surface tension of the liquid, allowing bubbles to be more evenly dispersed in the reaction system. They also stabilize the bubbles, preventing them from merging and bursting, thus forming a uniform and fine sponge pore structure. This uniform pore structure improves the sponge's resilience and comfort.

[0013] Preferably, the polyester polyol A is composed of polycaprolactone diol and polyhexyl adipate in a weight ratio of (4-6):3; The molecular weight of the polycaprolactone diol is 2000-6000; The molecular weight of the polyhexyl adipate is 5000-15000.

[0014] By adopting the above technical solution, the high flexibility of the polycaprolactone diol molecular chain gives polyester polyol A excellent hydrolysis resistance and flexibility. It also allows for the formation of hydrogen bonds between molecular chains, enhancing interactions and network structure stability, thereby improving the sponge's resilience. The crystalline regions of polyhexyl adipate serve as physical crosslinking points, improving durability and resilience, and enhancing the ability to recover after repeated compression. The combination of the flexibility and hydrolysis resistance of polycaprolactone diol with the crystallinity of polyhexyl adipate creates a synergistic effect, enabling the sponge to maintain softness while possessing good resilience, durability, and heat resistance. This synergistic effect not only optimizes the performance of individual components but also overcomes the shortcomings of traditional polyurethane sponges, which struggle to balance other properties while pursuing softness, providing a superior material choice for demanding applications such as intimate apparel.

[0015] Preferably, the polyester polyol B is composed of polycarbonate triol and polycaprolactone triol in a weight ratio of (5-7):3; The molecular weight of the polycarbonate triol is 500-5000; The molecular weight of the polycaprolactone triol is 3000-10000.

[0016] By employing the above technical solutions, polycarbonate triol, due to its molecular structure characteristics, possesses excellent chemical resistance and mechanical strength, enabling the sponge to maintain its performance over a wide temperature range and in complex environments, providing a foundation for high tensile strength. Polycaprolactone triol's flexible molecular chains reduce the sponge's hardness, making it softer. The combination of these two components—polycarbonate triol providing stiffness and support, and polycaprolactone triol adding flexibility and elasticity—works synergistically to achieve a balance between softness and firmness, resulting in excellent resilience. Simultaneously, the combination of polycaprolactone triol's durability and polycarbonate triol's stability significantly enhances the sponge's resistance to deformation and compression set, extending its service life.

[0017] Preferably, the polyether polyol has a hydroxyl value of 200-400 mgKOH / g, a functionality of 1-4, and a molecular weight of 1000-20000.

[0018] Preferably, the polyether polyol includes at least one of polypropylene triol, polytetrahydrofuran diol, polypropylene diol, trihydroxy polyether, or tetrahydrofuran-propylene oxide copolydiol.

[0019] By adopting the above technical solutions and optimizing the hydroxyl value, functionality, molecular weight and type of polyether polyols, their role in zero-hardness sponge formulations can be fully utilized, achieving an excellent balance in terms of softness, resilience, durability and mechanical properties, and meeting the demand for high-quality sponges in applications such as intimate apparel.

[0020] Preferably, the chain extender is composed of dimethylolpropionic acid and 1,5-pentanediol in a weight ratio of (2-3):1.

[0021] By adopting the above technical solutions, the performance of polyurethane foam can be significantly improved. Dimethylolpropionic acid contains three reactive functional groups, which can increase crosslinking points, build a denser network, and improve the strength, toughness, and durability of the foam. The linear structure of 1,5-pentanediol facilitates bridging between polymer chains, enhances interchain forces, improves tensile strength and modulus, and optimizes network regularity, thus improving elasticity. The synergistic effect of these two factors allows the foam's network structure to effectively resist deformation during stretching and quickly return to its original shape upon rebound, enhancing resilience.

[0022] Preferably, the nonionic surfactant includes at least one of lauryl alcohol polyoxyethylene ether, isotridecyl alcohol ether, secondary alcohol polyoxyethylene ether, octyl alcohol polyoxyethylene ether, fatty acid methyl ester polyoxyethylene ether, linear decadecyl alcohol polyoxyethylene ether, linear octadecyl isooctyl alcohol polyoxyethylene ether, and polyoxyethylene dehydrated sorbitan tristearate.

[0023] By adopting the above technical solutions and optimizing the types of nonionic surfactants, it is possible to promote the uniform distribution of bubbles in the reaction system, forming a stable and dense bubble structure, thereby improving the porosity and uniformity of the sponge and laying the foundation for the sponge's flexibility and comfort.

[0024] Secondly, this application provides a method for preparing a zero-hardness sponge, which adopts the following technical solution: A method for preparing a zero-hardness sponge includes the following preparation steps: S1. Mix polyether polyol A, polyether polyol B and polyethylene glycol monomethyl ether evenly to obtain the first component; S2. Mix the polyether polyol, glycerol, nonionic surfactant, and modifier evenly to obtain the second component. S3. Mix the catalyst with N,N-dimethylcyclohexylamine and polyoxyethylene fatty amide evenly, and then add water, antioxidant and anti-ultraviolet agent to obtain the third component; S4. Mix the first component and the second component evenly to obtain a mixture. Add the third component, chain extender and diisocyanate to the mixture and stir until foaming. Send the stirred mixture into a foaming box for curing and demolding. S5. Cool the sponge obtained after curing and demolding, and then process and cut it into finished products.

[0025] By adopting the above technical solution, various polyols, auxiliaries, and reactive substances are mixed in groups to form the first component, the second component, and the third component. This allows each raw material to be fully dispersed and uniformly mixed before addition, avoiding problems such as excessively high local concentrations or uneven dispersion caused by one-time mixing. It ensures the uniform participation of polyols in the reaction, which is conducive to the formation of a uniform sponge structure. The orderly mixing and reaction of each component allows chain extenders, modifiers, etc. to play a full role. The final sponge has extremely low hardness, meeting the extremely high requirements for softness in close-fitting clothing, and also has good resilience, which can quickly return to its original shape after being compressed, and has a long service life.

[0026] Preferably, the foaming time is 30-50 seconds, the foaming temperature is 40-50°C, and the foaming pressure is 135-140 kPa.

[0027] By adopting the above technical solutions and strictly controlling the foaming time, temperature, and pressure, the foaming process of the sponge can be precisely adjusted, which helps to stabilize the formation and uniform distribution of bubbles, prevents bubbles from bursting due to excessive pressure or bubbles from becoming too large and uneven due to excessive pressure, thereby obtaining a fine and uniform sponge pore structure, improving the softness and resilience of the sponge, and ensuring its good mechanical properties.

[0028] In summary, this application has the following beneficial effects: 1. This application achieves an excellent balance of softness, resilience, durability, and mechanical properties through the combination of various raw materials. The synergistic effect of polyester polyols A and B with polyether polyols and polyethylene glycol monomethyl ether reduces the sponge's hardness to an extremely low level without sacrificing resilience, meeting the stringent softness requirements of intimate apparel. Simultaneously, it can quickly recover its shape after prolonged compression, maintaining the garment's appearance and comfort. By optimizing the proportions and types of raw materials, the mechanical property degradation problem caused by traditional softeners is avoided, ensuring the sponge possesses high tensile and tear strength, improving durability and reliability. The addition of polyethylene glycol monomethyl ether and glycerin further reduces the rigidity of the polymer chain segments, making the sponge even softer. The polyether-modified polydimethylsiloxane, ethylhexyl palmitate, chitosan, and glacial acetic acid solution in the modifier work synergistically, not only enhancing the sponge's flexibility, resilience, durability, lubricity, and skin-friendliness, but also improving safety through the antibacterial properties of chitosan. During the foaming process, nonionic surfactants reduce the surface tension of the liquid, allowing the bubbles to disperse evenly and stably, forming a fine and uniform sponge pore structure, further optimizing resilience and comfort. The hydrophilicity and biocompatibility of the selected raw materials ensure that the sponge is non-irritating to the skin, reducing the risk of allergies, making it particularly suitable for applications such as underwear that come into direct contact with the skin. Detailed Implementation Example

[0029] Example 1 A zero-hardness sponge is prepared by the following method: S1. Mix 50g of polyether polyol A, 80g of polyether polyol B and 20g of polyethylene glycol monomethyl ether evenly to obtain the first component; Polyester polyol A is composed of polycaprolactone diol and polyhexamethylene adipate in a weight ratio of 4:3; The molecular weight of polycaprolactone diol is 2000-6000; The molecular weight of polyhexyl adipate is 5000-15000; Polyester polyol B is composed of polycarbonate triol and polycaprolactone triol in a weight ratio of 5:3; The molecular weight of polycarbonate triol is 500; The molecular weight of polycaprolactone triol is 3000; S2. Mix 100g of polyether polyol, 10g of glycerol, 5g of nonionic surfactant (lauryl alcohol polyoxyethylene ether) and 50g of modifier evenly to obtain the second component; The polyether polyol is a polycarbonate triol with a hydroxyl value of 200 mg KOH / g, a functionality of 1, and a molecular weight of 1000. The modifier is composed of polyether-modified polydimethylsiloxane, ethylhexyl palmitate, chitosan and glacial acetic acid solution in a weight ratio of 3:2:2:10; S3. Mix 0.5g of catalyst (stannous octoate) with 1g of N,N-dimethylcyclohexylamine and 5g of polyoxyethylene fatty amide evenly, and then add 20g of water, 2g of antioxidant (2,6-di-tert-butyl-4-methylphenol) and 2g of UV stabilizer (benzotriazole) to obtain the third component; S4. Mix the first component and the second component evenly to obtain a mixture. Add the third component, 5g of chain extender and 150g of diisocyanate (toluene diisocyanate) to the mixture and stir until foaming. Then, send the stirred mixture into a foaming box for curing and demolding. The chain agent is composed of dimethylolpropionic acid and 1,5-pentanediol in a weight ratio of 2:1. The foaming time is 30 seconds, the foaming temperature is 40℃, and the foaming pressure is 135 kPa. S5. Cool the sponge obtained after curing and demolding, and then process and cut it into finished products.

[0030] The polyether-modified polydimethylsiloxane was purchased from Guangdong Haohui New Materials Co., Ltd., model number HC5833.

[0031] The difference between Examples 2-3 and Example 1 lies in the types, amounts, and parameters of raw materials used to prepare the zero-hardness sponge. Specific differences are shown in Table 1. Table 1. Raw material types, dosages, and parameters for preparing zero-hardness sponges. In Example 2, polyester polyol A is composed of polycaprolactone diol and polyhexyl adipate in a weight ratio of 5:3; the molecular weight of polycaprolactone diol is 4000. The molecular weight of polyhexyl adipate is 10,000; Polyester polyol B is composed of polycarbonate triol and polycaprolactone triol in a weight ratio of 6:3; The molecular weight of polycarbonate triol is 2000; The molecular weight of polycaprolactone triol is 6000.

[0032] In Example 3, polyester polyol A is composed of polycaprolactone diol and polyhexyl adipate in a weight ratio of 6:3; The molecular weight of polycaprolactone diol is 6000; The molecular weight of polyhexyl adipate is 15,000; Polyester polyol B is composed of polycarbonate triol and polycaprolactone triol in a weight ratio of 7:3; The molecular weight of polycarbonate triol is 5000; The molecular weight of polycaprolactone triol is 10,000.

[0033] Example 4 A zero-hardness sponge, the difference between this embodiment and embodiment 1 is that: polyester polyol A is polycaprolactone diol with a molecular weight of 2000.

[0034] Example 5 A zero-hardness sponge, the difference between this embodiment and embodiment 1 is that: polyester polyol A is polyhexanediol ester with a molecular weight of 5000.

[0035] Example 6 A zero-hardness sponge, the difference between this embodiment and embodiment 1 is that: polyester polyol B is a polycarbonate triol with a molecular weight of 500.

[0036] Example 7 A zero-hardness sponge, the difference between this embodiment and Embodiment 1 is that the molecular weight of the polycarbonate triol is 6000.

[0037] Example 8 A zero-hardness sponge, the difference between this embodiment and Embodiment 1 is that the chain extender is dimethylolpropionic acid.

[0038] Comparative Example Comparative Example 1 A sponge, which differs from Example 1 in that no modifier is added.

[0039] Comparative Example 2 A sponge, the difference between this comparative example and Example 1 is that the modifier is composed of polyether-modified polydimethylsiloxane, chitosan and glacial acetic acid solution in a weight ratio of 3:2:10.

[0040] Comparative Example 3 A sponge, which differs from Example 1 in that the modifier is composed of polyether-modified polydimethylsiloxane and ethylhexyl palmitate in a weight ratio of 3:2.

[0041] Comparative Example 4 A sponge, which differs from Example 1 in that it does not contain polyester polyol B.

[0042] Comparative Example 5 A sponge, which differs from Example 1 in that it does not contain polyethylene glycol monomethyl ether.

[0043] Comparative Example 6 A sponge, which differs from Example 1 in that it does not contain polyoxyethylene fatty amide.

[0044] Detection methods / test methods Shore hardness tester test: The hardness of a sponge is measured using a Shore hardness tester.

[0045] Ball rebound test: The test shall be conducted in accordance with the standard method GB / T 6670-2008.

[0046] Dynamic fatigue test: Simulate repeated compression and deformation during actual use, and conduct dynamic fatigue test according to GB / T 18941-2003.

[0047] Tear strength test: Dumbbell-shaped specimens were cut from the zero-hardness sponge sample using a cutter conforming to DIN 53527. The gauge length was 25 mm wide and 100 mm long. The tear strength was then measured using an Instron universal testing machine. The experimental data are shown in Table 2. Table 2. Experimental data of Examples 1-8 and Comparative Examples 1-6 Comparative analysis of the examples and comparative examples reveals that the formulation of this zero-hardness sponge is reasonably designed, and the various raw material components work together synergistically, enabling the sponge to maintain extremely low hardness while also possessing good resilience, durability, and high tear strength and other mechanical properties.

[0048] The experimental data from Example 1 and Comparative Examples 1-6 demonstrate that by rationally combining different types of polyols, adding modifiers and other auxiliary components, and optimizing the proportions of each raw material, it is possible to effectively balance resilience, durability, and mechanical properties while reducing the hardness of the sponge. This allows the sponge to possess excellent tensile strength, tear strength, and other mechanical properties on top of its extreme softness, enabling it to withstand certain external forces without easily deforming or breaking, thus ensuring the durability and reliability of intimate apparel during normal use.

[0049] The experimental data from Examples 1 and 4-8 demonstrate that by using polyols, modifiers, and chain extenders of different types and molecular weights, a synergistic effect was achieved among the components, resulting in an optimal balance of hardness, resilience, durability, and mechanical properties in the sponge. Example 4 used only polycaprolactone diol with a molecular weight of 2000, which increased the hardness by 3 units compared to Example 1, decreased the resilience by 8.2 percentage points, and also reduced the tear strength. This indicates that while polycaprolactone diol still possesses a certain degree of softness when used alone, its ability to provide high resilience and high strength is limited.

[0050] Example 5, using only polyhexyl adipate with a molecular weight of 5000, showed a significant increase in hardness, but a marked decrease in resilience and tear strength. This indicates that when polyhexyl adipate is used alone, it is difficult to maintain high resilience and tear strength while reducing hardness.

[0051] Example 6 used only polycarbonate triol with a molecular weight of 500 as polyester polyol B, resulting in a slight increase in hardness, but little change in resilience and tear strength. The dynamic fatigue test results were even slightly better than in Example 1. This indicates that the compositional change of polyester polyol B has some impact on hardness, but it still maintains good performance in other properties.

[0052] In Example 7, the molecular weight of the polycarbonate triol was increased to 6000. Its hardness remained the same as in Example 5, but the resilience was slightly improved. Dynamic fatigue testing showed a reduction in compression set and an increase in tear strength. Overall, increasing the molecular weight of the polycarbonate triol helps improve the resilience, durability, and tear strength of the sponge, but it has a certain impact on hardness, requiring a comprehensive balance.

[0053] Example 8 used only dimethylolpropionic acid as a chain extender, and its hardness was the same as in Example 5. The resilience was lower than in Example 1, and dynamic fatigue testing showed an increase in compression set. The tear strength was similar to that of Example 1. In summary, changing the type of chain extender has a certain impact on resilience and durability. Different chain extenders have different focuses in improving sponge performance. The combined use of chain extenders in Example 1 better balances these properties.

[0054] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A zero-hardness sponge, characterized in that, It is prepared from the following raw materials in parts by weight: Polyester polyol A 5-10 parts Polyester polyol B8-15 parts 10-20 parts of polyether polyol 15-25 parts of diisocyanate 2-5 parts of polyethylene glycol monomethyl ether 1-2 parts glycerin 0.5-1.5 parts of nonionic surfactant Catalyst 0.05-0.2 parts 0.1-0.5 parts of N,N-dimethylcyclohexylamine Polyoxyethylene fatty amide 0.5-2 parts Antioxidant 0.2-0.8 parts UV protectant 0.2-0.8 parts Chain extender 0.5-2 parts 5-8 parts of modifier 2-5 parts water The modifier is composed of polyether-modified polydimethylsiloxane, ethylhexyl palmitate, chitosan and glacial acetic acid solution in a weight ratio of (3-5):(2-3):(2-4):

10.

2. The zero-hardness sponge according to claim 1, characterized in that: The polyester polyol A is composed of polycaprolactone diol and polyhexamethylene adipate in a weight ratio of (4-6):3; The molecular weight of the polycaprolactone diol is 2000-6000; The molecular weight of the polyhexyl adipate is 5000-15000.

3. The zero-hardness sponge according to claim 1, characterized in that: The polyester polyol B is composed of polycarbonate triol and polycaprolactone triol in a weight ratio of (5-7):

3. The molecular weight of the polycarbonate triol is 500-5000; The molecular weight of the polycaprolactone triol is 3000-10000.

4. The zero-hardness sponge according to claim 1, characterized in that: The polyether polyol has a hydroxyl value of 200-400 mgKOH / g, a functionality of 1-4, and a molecular weight of 1000-20000.

5. The zero-hardness sponge according to claim 1, characterized in that: The polyether polyol includes at least one of polypropylene triol, polytetrahydrofuran diol, polypropylene diol, trihydroxy polyether, or tetrahydrofuran-propylene oxide copolydiol.

6. The zero-hardness sponge according to claim 1, characterized in that: The chain extender is composed of dimethylolpropionic acid and 1,5-pentanediol in a weight ratio of (2-3):

1.

7. The method for preparing a zero-hardness sponge according to claim 1, characterized in that: The nonionic surfactant includes at least one of lauryl alcohol polyoxyethylene ether, isotridecyl alcohol ether, secondary alcohol polyoxyethylene ether, octyl alcohol polyoxyethylene ether, fatty acid methyl ester polyoxyethylene ether, linear decadecyl alcohol polyoxyethylene ether, linear octadecyl isooctyl alcohol polyoxyethylene ether, and polyoxyethylene dehydrated sorbitan tristearate.

8. A method for preparing a zero-hardness sponge as described in any one of claims 1-7, characterized in that, The preparation steps include the following: S1. Mix polyether polyol A, polyether polyol B and polyethylene glycol monomethyl ether evenly to obtain the first component; S2. Mix the polyether polyol, glycerol, nonionic surfactant and modifier evenly to obtain the second component; S3. Mix the catalyst with N,N-dimethylcyclohexylamine and polyoxyethylene fatty amide evenly, and then add water, antioxidant and anti-ultraviolet agent to obtain the third component; S4. Mix the first component and the second component evenly to obtain a mixture. Add the third component, chain extender and diisocyanate to the mixture and stir until foaming. Send the stirred mixture into a foaming box for curing and demolding. S5. Cool the sponge obtained after maturation and demolding for 24 hours, and then process and cut it into finished products.

9. The method for preparing a zero-hardness sponge according to claim 8, characterized in that: The foaming time is 30-50 seconds, the foaming temperature is 40-50°C, and the foaming pressure is 135-140 kPa.

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