Tear-resistant degradable foam pad and preparation method thereof

Abstract

The invention discloses a tear-resistant degradable foam pad and a preparation method thereof, and belongs to the technical field of high polymer materials, the tear-resistant degradable foam pad is prepared from the following raw materials in parts by weight: 50-60 parts of PVC resin, 30-40 parts of plant fiber, 10-15 parts of liquid nitrile rubber, 65-78 parts of filler, 72-90 parts of plasticizer, 5-7 parts of foaming agent and 2-4 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate. A mixture of montmorillonite and light calcium carbonate is adopted as a filler, and the characteristic that montmorillonite can block crack extension in a foaming pad matrix is utilized, so that the crack extension in the foaming pad matrix needs to consume more energy, the tearing strength of the foaming pad can be improved, and the service life of the foaming pad is prolonged. The foaming mat can meet the tearing strength requirements of high-end yoga mats and sports mats.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a tear-resistant biodegradable foam pad and its preparation method. Background Technology

[0002] PVC foam mats are widely used in yoga mats, sports cushioning mats, and bathroom anti-slip mats due to their low cost and excellent elasticity. However, PVC resin itself is not biodegradable, making it difficult to efficiently recycle and reuse PVC foam mats through conventional methods after waste disposal. Large accumulations of waste products can easily cause sustained negative impacts on the soil, water bodies, and other ecological environments. To address this issue, existing technologies generally employ the introduction of biodegradable components such as plant fibers into the raw material system of PVC foam mats to reduce their adverse environmental impact.

[0003] However, PVC resin has always had compatibility issues with plant fibers. Therefore, when plant fibers replace part of the PVC resin, the mechanical strength of biodegradable foam mats is still difficult to match that of PVC foam mats without added plant fibers. Although existing technologies can improve the mechanical strength of the mat, especially the tear strength (which can reach 36 N / cm), by introducing liquid nitrile rubber into the raw material system of PVC foam mats, this tear strength is still insufficient to meet the tear strength requirements of high-end yoga mats and sports mats. Summary of the Invention

[0004] The purpose of this invention is to provide a tear-resistant biodegradable foam pad and its preparation method, aiming to solve the problem that the tear strength improvement of existing biodegradable PVC foam pads is limited.

[0005] The first aspect of the present invention provides a tear-resistant biodegradable foam pad, the raw materials for which, by weight, are: 50-60 parts of PVC resin, 30-40 parts of plant fiber, 10-15 parts of liquid nitrile rubber, 65-78 parts of filler, 72-90 parts of plasticizer, 5-7 parts of foaming agent, and 2-4 parts of stabilizer; wherein the filler is a mixture of montmorillonite and light calcium carbonate.

[0006] Optionally, the particle size of the montmorillonite is 1-5 μm, and the thickness of the montmorillonite sheets is 1-5 nm.

[0007] Optionally, the ratio of the light calcium carbonate and montmorillonite by weight is (12-14):1.

[0008] Optionally, the plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate.

[0009] Optionally, the epoxidized soybean oil, dioctyl terephthalate, and citrate are mixed in a weight ratio of (1-1.5):2:(3-4).

[0010] Optionally, the citrate is a mixture of tributyl citrate and acetylated tributyl citrate; the ratio of tributyl citrate and acetylated tributyl citrate by weight is 1:(1-1.5).

[0011] Optionally, the stabilizer is a zinc-potassium stabilizer.

[0012] Optionally, the foaming agent is an AC foaming agent.

[0013] A second aspect of the present invention provides a method for preparing a tear-resistant biodegradable foam pad, which includes the following steps: S001. Weigh the raw materials for preparing the tear-resistant biodegradable foam pad according to the specified ratio; S002. Mix liquid nitrile rubber and plant fiber evenly, then add PVC resin, plasticizer, filler, foaming agent and stabilizer, and mix evenly to obtain foamed slurry; S003. Apply the foaming slurry onto the mesh fabric and foam to obtain the tear-resistant and biodegradable foam pad.

[0014] Optionally, the foaming temperature is 185–195℃.

[0015] The beneficial effects of this invention are: The first aspect of this invention provides a tear-resistant biodegradable foam pad and its preparation method. By using a mixture of montmorillonite and light calcium carbonate as filler, and taking advantage of the property of montmorillonite to block crack propagation in the foam pad matrix, the cracks in the foam pad matrix need to consume more energy to propagate, thereby improving the tear strength of the foam pad and enabling the foam pad to meet the tear strength requirements of high-end yoga mats and sports mats.

[0016] The second aspect of this invention provides a method for preparing a tear-resistant biodegradable foam pad. The preparation method is simple and efficient. By optimizing the type and ratio of plasticizers, the foaming temperature can be completely reduced to below 200°C, further improving the carbonization of plant fibers and thus solving the problem of yellowing of foam pads caused by production temperature fluctuations. Attached Figure Description

[0017] Figure 1 This is a flowchart of the preparation method of the tear-resistant biodegradable foam pad provided by the present invention.

[0018] Figure 2 This is a photograph of a finished yoga mat containing the foam pad provided by this invention. Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] The first aspect of the present invention provides a tear-resistant biodegradable foam pad, the raw materials for which, by weight, are: 50-60 parts of PVC resin, 30-40 parts of plant fiber, 10-15 parts of liquid nitrile rubber, 65-78 parts of filler, 72-90 parts of plasticizer, 5-7 parts of foaming agent, and 2-4 parts of stabilizer; wherein the filler is a mixture of montmorillonite and light calcium carbonate.

[0020] In the raw materials for preparing the aforementioned tear-resistant biodegradable foam pad, PVC resin serves as the matrix skeleton, providing basic elasticity, formability, and durability, and is the core carrier supporting the cell structure. Plant fibers reduce the amount of PVC resin used while imparting biodegradable properties to the foam pad, thus reducing the non-degradable portion. Liquid nitrile rubber, as a surface modifier for plant fibers, can form hydrogen bonds with the hydroxyl groups of plant fibers through its nitrile groups, thereby solving the problem of poor compatibility between plant fibers and PVC resin, improving the phenomenon of plant fiber particle peeling, and preventing fiber peeling from causing a decrease in the tear resistance of the foam pad. The filler reduces the total cost of raw materials while filling the gaps between PVC resin and plant fibers, improving the matrix density and the mechanical strength of the foam pad. The foaming agent, during the foaming process, enables the formation of fine cells in the matrix, thereby imparting elasticity and cushioning to the foam pad. The stabilizer can prevent PVC pyrolysis and has a certain activating effect on the foaming agent, thereby reducing the foaming temperature and making the foaming temperature close to the plasticizing temperature of PVC resin. Foaming and plasticizing can be carried out simultaneously, thus obtaining a foamed pad with fine pores.

[0021] To further improve the tear strength of the foam mat and enable it to meet the tear strength requirements of high-end yoga mats and sports mats, this invention uses a mixture of montmorillonite and lightweight calcium carbonate as filler. Montmorillonite is a layered material composed of multiple layers of silicon-oxygen tetrahedra and aluminum-oxygen octahedra. When the montmorillonite layers are uniformly dispersed in the PVC-based composite system of the foam mat, they form a three-dimensional interwoven framework. When the foam mat is subjected to external forces, the montmorillonite layers can prevent crack propagation; cracks must bypass or pass through the montmorillonite layers rather than propagating directly within the PVC matrix, thus consuming more energy and improving the tear strength of the foam mat.

[0022] In an optional embodiment, the particle size of the plant fiber can be 10-15 nm. The particle size of the montmorillonite is 1-5 μm, and the thickness of the montmorillonite sheets is 1-5 nm. When the particle size and sheet thickness of the montmorillonite are within the above ranges, the fibers can be synergistically dispersed by the sheets encapsulating them, thus preventing the aggregation of montmorillonite and plant fibers. However, montmorillonite is a layered mineral. If montmorillonite with a particle size greater than 5 μm is selected, the strength of the sheet aggregates is high, and the compatibility between the sheet aggregates and the PVC matrix is ​​poor, making it easy for voids to form at the interface. When external force is applied to the foam pad, the stress will be concentrated at the interface between the aggregates and the matrix, leading to interface peeling or aggregate detachment. This means that the tear strength of the foam pad not only fails to improve but is actually prone to decrease.

[0023] When montmorillonite with a particle size of less than 1 μm is selected, its specific surface area increases significantly, resulting in high surface energy. This makes it prone to spontaneous aggregation through van der Waals forces, forming secondary agglomerates. These secondary agglomerates can puncture the cell walls during foaming, causing the cells to merge and rupture. This alters the appearance and elasticity of the foam pad. Furthermore, the high-particle-size secondary agglomerates have poor compatibility with the PVC matrix, making it easy for voids to form at the interface, thus creating system defects and reducing the tear strength of the foam pad.

[0024] In an optional embodiment, the ratio of the light calcium carbonate and montmorillonite by weight is (12-14):1.

[0025] Light calcium carbonate, a traditional filler, has a higher density than PVC matrix and montmorillonite. Adding an appropriate amount can adjust the specific gravity of the foamed mat. If the proportion of light calcium carbonate in the total filler is significantly reduced, while the proportion of montmorillonite is significantly increased, the density of the foamed mat will decrease, making the mat soft after foaming and unable to meet the support requirements of yoga mats and sports mats. Furthermore, excessive montmorillonite tends to agglomerate, creating defects within the foam system and reducing the tear strength of the foamed mat. Conversely, when the proportion of light calcium carbonate in the total filler is significantly increased, insufficient montmorillonite will not significantly improve the tear strength of the foamed mat.

[0026] In an optional embodiment, the plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate.

[0027] Specifically, in the aforementioned plasticizer system, epoxidized soybean oil combines environmental friendliness, migration resistance, and thermal stability. It can mitigate the problem of easy exudation of citrate ester plasticizers, making the foamed mat less prone to hardening and decreased toughness after long-term use. Moreover, epoxidized soybean oil can further lower the plasticizing temperature of PVC resin, further reducing the carbonization of plant fibers and preventing yellowing of the mat.

[0028] In an optional embodiment, the epoxidized soybean oil, dioctyl terephthalate, and citrate are mixed in a weight ratio of (1-1.5):2:(3-4).

[0029] Specifically, in the plasticizer system mentioned above, citrate has a higher plasticizing efficiency than epoxidized soybean oil and dioctyl terephthalate. Therefore, citrate has the highest proportion in the plasticizer system, which enables the foaming process and the plasticizing of PVC resin to be synchronized.

[0030] Specifically, in the aforementioned plasticizer system, terephthalate has good compatibility with PVC resin and low migration rate, avoiding the problem of insufficient migration resistance of citrate and preventing the foam pad from hardening and becoming brittle due to plasticizer precipitation during long-term use. Since the plasticizing efficiency of terephthalate is lower than that of citrate, an excessive proportion of terephthalate will lead to an increase in plasticizing temperature, while simultaneously reducing the flexibility of the foam pad and insufficient improvement in tear strength.

[0031] Specifically, in addition to further reducing the plasticizing temperature of PVC resin, the epoxy groups in epoxidized soybean oil can react with the active chlorine atoms of the PVC molecular chain, enhancing the thermal stability of PVC resin. Simultaneously, the polarity of epoxidized soybean oil lies between the organic phase (PVC, liquid nitrile rubber) and the inorganic phase (plant fiber, montmorillonite), which can improve the compatibility of each component and prevent montmorillonite agglomeration. However, the high viscosity of epoxidized soybean oil will reduce the fluidity of the foaming slurry, easily causing knife marks and uneven thickness when applied to the mesh (affecting the flatness of the foamed pad). Therefore, the amount of epoxidized soybean oil used should not be excessive.

[0032] In an optional embodiment, the citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. Specifically, both tributyl citrate and acetylated tributyl citrate belong to the citrate ester plasticizer class. However, the plasticizing efficiency of tributyl citrate is lower than that of acetylated tributyl citrate, while the low-temperature toughness of tributyl citrate is better than that of acetylated tributyl citrate. Therefore, by using both tributyl citrate and acetylated tributyl citrate as plasticizers simultaneously, the present invention can synergistically improve the plasticizing efficiency of PVC resin. At the same time, it can improve the low-temperature embrittlement resistance of the foam pad without making the plasticizer cost too high.

[0033] In an optional embodiment, the ratio of tributyl citrate to acetylated tributyl citrate is 1:(1-1.5) by weight. Within the above ratio range, if the proportion of tributyl citrate in the citrate ester is further increased, not only will more plasticizer migration occur, causing the foam pad to become brittle and crack after long-term use, but a higher foaming temperature will also be required. Furthermore, if the proportion of acetylated tributyl citrate in the citrate ester is further increased, not only will the cost of using plasticizers increase, but the low-temperature toughness of the foam pad will also decrease, making it prone to cracking when bent in cold regions.

[0034] In an optional embodiment, the stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0035] Specifically, zinc-potassium stabilizers can inhibit the pyrolysis of PVC resin, preventing molecular chain breakage that leads to matrix loosening. At the same time, they can activate AC foaming agents, allowing foaming and plasticizing to occur simultaneously, forming a fine and uniform cell structure and reducing stress concentration within the foam pad under external force.

[0036] The uniform micropores produced by the decomposition of AC foaming agent can disperse the stress within the foam pad, and when combined with zinc-potassium stabilizers, they can strengthen the cell walls, making it difficult for cracks to propagate quickly, thus significantly improving the tear resistance of the foam pad.

[0037] like Figure 1 As shown, a second aspect of the present invention provides a method for preparing a tear-resistant biodegradable foam pad, which is used to prepare the tear-resistant biodegradable foam pad described above, comprising the following steps: S001. Weigh the raw materials for preparing the tear-resistant biodegradable foam pad according to the specified ratio; S002. Mix liquid nitrile rubber and plant fiber at a speed of 4000 rpm until homogeneous. Then add PVC resin, plasticizer, filler, foaming agent and stabilizer, and mix until homogeneous to obtain foamed slurry. S003. Apply the foaming slurry onto the mesh fabric and foam to obtain the tear-resistant and biodegradable foam pad.

[0038] In an optional embodiment, the foaming temperature is 185–195°C. Compared to the foaming temperature of existing biodegradable foam pads, this invention, by optimizing the type and ratio of plasticizers, can completely reduce the foaming temperature to below 200°C, further improving the situation of carbonization of plant fibers and solving the problem of yellowing of foam pads caused by production temperature fluctuations.

[0039] To further illustrate the tear-resistant biodegradable foam pad provided by the present invention, the following embodiments and comparative examples are provided.

[0040] Example 1 This embodiment provides a tear-resistant biodegradable foam pad, which is prepared by weight of the following raw materials: 50 parts of PVC resin (degree of polymerization 1500), 30 parts of plant fiber (particle size 10nm), 10 parts of liquid nitrile rubber, 65 parts of filler, 72 parts of plasticizer, 5 parts of foaming agent, and 2 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0041] The ratio of light calcium carbonate to montmorillonite by weight is 12:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0042] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The epoxidized soybean oil, dioctyl terephthalate, and citrate are mixed in a weight ratio of 1:2:3.

[0043] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate is 1:1 by weight.

[0044] This embodiment also provides a method for preparing a tear-resistant biodegradable foam pad, including the following steps: S001. Weigh the raw materials for preparing the tear-resistant biodegradable foam pad according to the specified ratio; S002. Mix liquid nitrile rubber and plant fiber at a speed of 4000 rpm until homogeneous. Then add PVC resin, plasticizer, filler, foaming agent and stabilizer, and mix until homogeneous to obtain foamed slurry. S003. Apply the foaming slurry onto the mesh fabric and foam to obtain the tear-resistant biodegradable foam. The foaming temperature is 195℃.

[0045] Example 2 This embodiment provides a tear-resistant biodegradable foam pad, which is prepared by weight of the following raw materials: 55 parts of PVC resin (degree of polymerization 1500), 35 parts of plant fiber (particle size 10nm), 12 parts of liquid nitrile rubber, 70 parts of filler, 78 parts of plasticizer, 6 parts of foaming agent, and 3 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0046] The ratio of light calcium carbonate to montmorillonite by weight is 13:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0047] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The weight ratio of epoxidized soybean oil, dioctyl terephthalate, and citrate is 1.2:2:3.3.

[0048] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate by weight is 1:1.2.

[0049] This embodiment also provides a method for preparing a tear-resistant biodegradable foam pad, including the following steps: S001. Weigh the raw materials for preparing the tear-resistant biodegradable foam pad according to the specified ratio; S002. Mix liquid nitrile rubber and plant fiber at a speed of 4000 rpm until homogeneous. Then add PVC resin, plasticizer, filler, foaming agent and stabilizer, and mix until homogeneous to obtain foamed slurry. S003. Apply the foaming slurry onto the mesh fabric and foam to obtain the tear-resistant biodegradable foam. The foaming temperature is 185℃.

[0050] Example 3 This embodiment also provides a tear-resistant biodegradable foam pad, which, by weight, is prepared from the following raw materials: 60 parts of PVC resin (degree of polymerization 1500), 40 parts of plant fiber (particle size 10nm), 15 parts of liquid nitrile rubber, 78 parts of filler, 90 parts of plasticizer, 7 parts of foaming agent, and 4 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0051] The ratio of light calcium carbonate to montmorillonite by weight is 14:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0052] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The ratio of epoxidized soybean oil, dioctyl terephthalate, and citrate by weight is 1.5:2:4.

[0053] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate by weight is 1:1.5.

[0054] This embodiment also provides a method for preparing a tear-resistant biodegradable foam pad, including the following steps: S001. Weigh the raw materials for preparing the tear-resistant biodegradable foam pad according to the specified ratio; S002. Mix liquid nitrile rubber and plant fiber at a speed of 4000 rpm until homogeneous. Then add PVC resin, plasticizer, filler, foaming agent and stabilizer, and mix until homogeneous to obtain foamed slurry. S003. Apply the foaming slurry onto the mesh fabric and foam to obtain the tear-resistant biodegradable foam. The foaming temperature is 190℃.

[0055] Comparative Example 1 This comparative example provides a biodegradable foam pad, which, by weight, is prepared from the following raw materials: 50 parts of PVC resin (degree of polymerization 1500), 30 parts of plant fiber (particle size 10nm), 10 parts of liquid nitrile rubber, 65 parts of filler, 72 parts of plasticizer, 5 parts of foaming agent, and 2 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0056] The ratio of light calcium carbonate to montmorillonite by weight is 9:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0057] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The epoxidized soybean oil, dioctyl terephthalate, and citrate are mixed in a weight ratio of 1:2:3.

[0058] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate is 1:1 by weight.

[0059] This comparative example also provides a method for preparing a tear-resistant biodegradable foam pad, which is the same as the preparation method provided in Example 1.

[0060] Comparative Example 2 This comparative example provides a biodegradable foam pad, which, by weight, is prepared from the following raw materials: 50 parts of PVC resin (degree of polymerization 1500), 30 parts of plant fiber (particle size 10nm), 10 parts of liquid nitrile rubber, 65 parts of filler, 72 parts of plasticizer, 5 parts of foaming agent, and 2 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0061] The ratio of light calcium carbonate to montmorillonite by weight is 19:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0062] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The epoxidized soybean oil, dioctyl terephthalate, and citrate are mixed in a weight ratio of 1:2:3.

[0063] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate is 1:1 by weight.

[0064] This comparative example also provides a method for preparing a tear-resistant biodegradable foam pad, which is the same as the preparation method provided in Example 1.

[0065] Comparative Example 3 This embodiment provides a biodegradable foam pad, which, by weight, is prepared from the following raw materials: 50 parts of PVC resin (degree of polymerization 1500), 30 parts of plant fiber (particle size 10nm), 10 parts of liquid nitrile rubber, 65 parts of filler, 72 parts of plasticizer, 5 parts of foaming agent, and 2 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0066] The ratio of light calcium carbonate to montmorillonite by weight is 12:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0067] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The ratio of epoxidized soybean oil, dioctyl terephthalate, and citrate by weight is 1:2:2.5.

[0068] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate is 1:1 by weight.

[0069] This comparative example also provides a method for preparing a tear-resistant biodegradable foam pad, which is the same as the preparation method provided in Example 1.

[0070] Comparative Example 4 This embodiment provides a biodegradable foam pad, which, by weight, is prepared from the following raw materials: 50 parts of PVC resin (degree of polymerization 1500), 30 parts of plant fiber (particle size 10nm), 10 parts of liquid nitrile rubber, 65 parts of filler, 72 parts of plasticizer, 5 parts of foaming agent, and 2 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0071] The ratio of light calcium carbonate to montmorillonite by weight is 12:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0072] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The ratio of epoxidized soybean oil, dioctyl terephthalate, and citrate by weight is 1:2.3:3.

[0073] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate is 1:1 by weight.

[0074] This comparative example also provides a method for preparing a tear-resistant biodegradable foam pad, which is the same as the preparation method provided in Example 1.

[0075] Comparative Example 5 This embodiment provides a biodegradable foam pad, which, by weight, is prepared from the following raw materials: 50 parts of PVC resin (degree of polymerization 1500), 30 parts of plant fiber (particle size 10nm), 10 parts of liquid nitrile rubber, 65 parts of filler, 72 parts of plasticizer, 5 parts of foaming agent, and 2 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0076] The ratio of light calcium carbonate to montmorillonite by weight is 12:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0077] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The ratio of epoxidized soybean oil, dioctyl terephthalate, and citrate by weight is 0.5:2:3.

[0078] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate is 1:1 by weight.

[0079] This comparative example also provides a method for preparing a tear-resistant biodegradable foam pad, which is the same as the preparation method provided in Example 1.

[0080] Comparative Example 6 This embodiment provides a biodegradable foam pad, which, by weight, is prepared from the following raw materials: 50 parts of PVC resin (degree of polymerization 1500), 30 parts of plant fiber (particle size 10nm), 10 parts of liquid nitrile rubber, 65 parts of filler, 72 parts of plasticizer, 5 parts of foaming agent, and 2 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

[0081] The ratio of light calcium carbonate to montmorillonite by weight is 12:1. The stabilizer is a zinc-potassium stabilizer. The foaming agent is an AC foaming agent.

[0082] The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate. The epoxidized soybean oil, dioctyl terephthalate, and citrate are mixed in a weight ratio of 1:2:3.

[0083] The citrate ester is a mixture of tributyl citrate and acetylated tributyl citrate. The ratio of tributyl citrate to acetylated tributyl citrate by weight is 1:0.8.

[0084] This comparative example also provides a method for preparing a tear-resistant biodegradable foam pad, which is the same as the preparation method provided in Example 1.

[0085] The biodegradable foam pads provided in the above embodiments and comparative examples were subjected to performance tests. The tests included tear strength and whiteness of the foam pads. Tear strength was tested according to standard GB10808-1989 "Test Method for Tear Properties of Flexible Foamed Plastics", and the whiteness of the foam pads was tested using a whiteness meter. The test results are shown in the table below.

[0086]

[0087] As can be seen from the table above, the biodegradable foam pads provided in Examples 1 to 3 have higher whiteness and significantly improved tear strength compared to the biodegradable foam pads provided in the comparative examples. The tear strength of the foam pads can reach more than 40 N / cm, which enables the foam pads to meet the tear strength requirements of high-end yoga mats and sports mats.

[0088] Further comparing Comparative Example 1 with Example 1, in Comparative Example 1, the amount of montmorillonite used was further increased compared to Example 1. When the amount of montmorillonite is too high, agglomeration is prone to occur, which will make the foaming system more susceptible to defects, resulting in a decrease in the tear strength of the foam pad.

[0089] Further comparing Comparative Example 2 with Example 1, in Comparative Example 2, the amount of montmorillonite used was less than that in Example 1, making it difficult to form a three-dimensional skeleton that prevents crack propagation. Therefore, the tear strength of the foam pad would decrease.

[0090] Further comparing Comparative Example 3 with Example 1, in Comparative Example 3, the proportion of styrene ester in the plasticizer system is reduced compared to Example 1. At this time, under the existing foaming temperature, the PVC resin will not be fully plasticized, and the structure of the foam pad matrix material will be loose, which will reduce the tear strength of the foam pad.

[0091] Further comparing Comparative Example 4 with Example 1, the amount of dioctyl terephthalate used in Comparative Example 4 was increased compared to Example 1. When the proportion of terephthalate is too high, it will lead to an increase in plasticizing temperature, and at the same time, it will reduce the flexibility of the foam pad and the tear strength will not be improved enough.

[0092] Further comparing Comparative Example 5 with Example 1, in Comparative Example 5, the amount of epoxidized soybean oil was further reduced compared to Example 1, which would cause the epoxidized soybean oil to be unable to effectively improve the compatibility of the organic and inorganic phases, resulting in uneven dispersion of montmorillonite, which would reduce the tear strength of the foam pad. Moreover, the thermal stabilizing effect of epoxidized soybean oil was weakened, which would cause slight pyrolysis of PVC resin during the foaming process, resulting in a decrease in the whiteness of the foam pad.

[0093] Further comparing Comparative Example 6 with Example 1, in Comparative Example 6, the amount of tributyl citrate was further increased compared to Example 1, requiring a higher foaming and plasticizing temperature. However, the existing foaming temperature would lead to incomplete plasticization of PVC resin, resulting in a decrease in the tear strength of the foamed pad.

[0094] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A tear-resistant, biodegradable foam pad, characterized in that, The raw materials for its preparation, by weight, include: 50-60 parts of PVC resin, 30-40 parts of plant fiber, 10-15 parts of liquid nitrile rubber, 65-78 parts of filler, 72-90 parts of plasticizer, 5-7 parts of foaming agent, and 2-4 parts of stabilizer; the filler is a mixture of montmorillonite and light calcium carbonate.

2. The tear-resistant biodegradable foam pad according to claim 1, characterized in that, The montmorillonite has a particle size of 1–5 μm and a lamellar thickness of 1–5 nm.

3. The tear-resistant biodegradable foam pad according to claim 1, characterized in that, The ratio of the light calcium carbonate and montmorillonite by weight is (12-14):

1.

4. The tear-resistant biodegradable foam pad according to claim 1, characterized in that, The plasticizer is a mixture of epoxidized soybean oil, dioctyl terephthalate, and citrate.

5. The tear-resistant biodegradable foam pad according to claim 4, characterized in that, The epoxidized soybean oil, dioctyl terephthalate, and citrate are mixed in the following weight ratios: (1-1.5):2:(3-4).

6. The tear-resistant biodegradable foam pad according to claim 4, characterized in that, The citrate is a mixture of tributyl citrate and acetylated tributyl citrate; the ratio of tributyl citrate and acetylated tributyl citrate by weight is 1:(1-1.5).

7. The tear-resistant biodegradable foam pad according to claim 1, characterized in that, The stabilizer is a zinc-potassium stabilizer.

8. The tear-resistant biodegradable foam pad according to claim 1, characterized in that, The foaming agent is AC foaming agent.

9. A method for preparing a tear-resistant biodegradable foam pad, used to prepare the tear-resistant biodegradable foam pad according to any one of claims 1-8, characterized in that, Includes the following steps: S001. Weigh the raw materials for preparing the tear-resistant biodegradable foam pad according to the specified ratio; S002. Mix liquid nitrile rubber and plant fiber evenly, then add PVC resin, plasticizer, filler, foaming agent and stabilizer, and mix evenly to obtain foamed slurry; S003. Apply the foaming slurry onto the mesh fabric and foam to obtain the tear-resistant and biodegradable foam pad.

10. The method for preparing the tear-resistant biodegradable foam pad according to claim 9, characterized in that, In step S003, the foaming temperature is 185–195°C.

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