Lightweight material and its application in shoe material

Abstract

The application provides a light material and application thereof in shoe materials, which comprises a base resin, a dispersed phase resin and an interfacial nucleating agent; the base resin is polyether amide block copolymer PEBA; the dispersed phase resin is thermoplastic polyurethane TPU; the interfacial nucleating agent is a layered silicate, and the layered silicate is dispersed at the phase interface of the PEBA and the TPU; and the solubility parameter difference of the PEBA and the TPU is large. The application constructs a "phase interface-nanoparticle" synergistic constraint system, ingeniously utilizes the specific solubility parameter difference between the PEBA and the TPU, regulates the compatibility of the two phases, and makes the two phases form an island structure with moderate interface bonding force; the layered silicate as the interfacial nucleating agent is enriched and anchored at the phase interface of the PEBA and the TPU under a specific process, the nanosheet layer at the interface acts as a heterogeneous nucleation point, greatly reduces the nucleation energy barrier, and increases the cell density.

Description

Technical Field

[0001] This application relates to the field of polymer foam materials technology, specifically to a lightweight material and its application in footwear materials. Background Technology

[0002] With the rapid development of the athletic footwear industry, higher demands have been placed on the lightweight, high resilience, and fatigue resistance of sole materials. Thermoplastic elastomer foam materials, such as polyether amide block copolymer (PEBA) and thermoplastic polyurethane (TPU) foam materials, are widely used in high-end athletic shoe midsoles due to their excellent elasticity and shock absorption properties. The preparation of microporous or nanoporous structures through supercritical fluid foaming technology can significantly reduce material density and improve mechanical properties, making it a current research hotspot in the field of footwear materials.

[0003] However, existing microporous foam material preparation technologies often face the challenge of balancing process and performance. To obtain nanoporous foams with smaller pore sizes and higher density, traditional technologies typically require the addition of large amounts of nanonucleating agents (such as graphene and carbon nanotubes). This not only significantly increases raw material costs but also leads to the agglomeration of nanoparticles, resulting in decreased material fatigue resistance. Furthermore, existing technologies often rely on harsh process conditions such as ultra-high pressure (>30MPa) and extremely rapid depressurization (>100MPa / s) to suppress bubble growth. This places extremely high demands on the pressure resistance of equipment and control systems, resulting in low production efficiency and low yield, making it difficult to meet the needs of large-scale industrial production.

[0004] In existing technologies, although a dispersed phase can be introduced through simple physical blending, it is difficult to effectively control the growth and coalescence of cells under mild process conditions (medium-low pressure, medium-speed decompression). This can easily lead to excessively large and unevenly distributed cells, thereby affecting the material's resilience and resistance to compression set. Therefore, how to prepare lightweight materials with submicron-scale cell structures and excellent mechanical properties under low-cost and mild process conditions is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] To address the technical problems of demanding preparation processes, high costs, and insufficient mechanical properties in existing microporous foam materials, this application provides a lightweight material and its application in footwear materials.

[0006] The first aspect of this application provides a lightweight material comprising a matrix resin, a dispersed phase resin, and an interfacial nucleating agent; the matrix resin is a polyether amide block copolymer (PEBA); the dispersed phase resin is a thermoplastic polyurethane (TPU); the interfacial nucleating agent is a layered silicate, and the layered silicate is dispersed at the phase interface between the PEBA and the TPU; the solubility parameter difference between the PEBA and the TPU is... Specifically, the solubility parameter can be calculated using the Small group contribution method or by referring to standard values ​​in polymer handbooks. This invention ensures appropriate compatibility between PEBA and TPU by controlling the solubility parameter difference within the aforementioned range. This avoids both excessively large parameter differences (>2.0) leading to weak interfacial bonding and excessively small parameter differences (<0.5) resulting in complete miscibility and the inability to form an interfacial layer.

[0007] This application constructs a "phase interface-nanoparticle" synergistic constraint system, cleverly utilizing the specific solubility parameter difference between PEBA and TPU to regulate the compatibility of the two phases, forming an island structure with moderate interfacial bonding. Layered silicates, acting as interfacial nucleating agents, are enriched and anchored at the PEBA-TPU phase interface under specific processes. This unique interfacial structure has dual technical effects: firstly, the nanosheets at the interface act as heterogeneous nucleation sites, significantly reducing the nucleation energy barrier and substantially increasing the pore density; secondly, the robust phase interface forms a physical barrier similar to a "Pickering emulsion," playing a "pinning" and "cage" role during bubble growth, effectively inhibiting bubble coalescence and excessive growth. Based on this mechanism, this application can prepare submicron porous foam materials with fine and uniform pores at relatively low depressurization rates (8-15 MPa / s), breaking the dependence on traditional high-speed depressurization equipment and achieving a balance between low cost and high performance. The PEBA can be commercially available Pebax series resin, the TPU can be thermoplastic polyurethane elastomer from BASF or Lubrizol, and the layered silicate is preferably organomontmorillonite.

[0008] Furthermore, by weight, the PEBA comprises 60-90 parts, the TPU comprises 10-40 parts, and the interfacial nucleating agent comprises 0.2-1.0 parts. This ratio range ensures that the PEBA forms a continuous phase to provide overall support, and the TPU forms a dispersed phase to construct an interfacial constraint network, while avoiding a decrease in material modulus or processing difficulties due to excessive TPU content. Specifically, the PEBA content can be 60, 70, 80, or 90 parts; the TPU content can be 10, 20, 30, or 40 parts.

[0009] Furthermore, the PEBA has a hardness of 55D-70D, and the TPU has a hardness of 80A-95A; the layered silicate is organomontmorillonite, and the polarity of its surface organic modifier is between that of PEBA and TPU. Using high-hardness PEBA provides a higher melt modulus and prevents foam collapse; using TPU with a specific hardness facilitates viscosity matching with PEBA, promoting the exfoliation and dispersion of the layered silicate at the interface. The polarity matching of the organic modifier further enhances the residence stability of nanoparticles at the interface.

[0010] Furthermore, the lightweight material is a submicron porous foam material with a cell diameter of 100-400 nm. Cells within this size range can effectively scatter light and suppress stress concentration, giving the material excellent resilience and fatigue resistance. Specifically, the cell diameter can be 100 nm, 180 nm, 250 nm, 350 nm, or 400 nm.

[0011] The second aspect of this application provides a method for preparing the lightweight material, comprising the following steps: Step S1: preparing an interfacial nucleation masterbatch, wherein the interfacial nucleation masterbatch comprises an interfacial nucleating agent and thermoplastic polyurethane (TPU); Step S2: uniformly mixing polyether amide block copolymer (PEBA), thermoplastic polyurethane (TPU), the interfacial nucleation masterbatch, and additives, and injection molding the mixture into a preform, wherein the injection mold temperature is controlled at 50-60°C; Step S3: placing the preform in an autoclave and impregnating it with fluid; Step S4: depressurizing and foaming the preform at a rate of 8-15 MPa / s.

[0012] The preparation method provided in this application has a wide process window, making it suitable for industrial production. In step S1, the masterbatch pre-dispersion process utilizes the high viscosity shearing effect of TPU to achieve effective exfoliation and pre-dispersion of layered silicates, laying the foundation for subsequent interface positioning. In step S2, the injection mold temperature is controlled at 50-60℃. This specific temperature range acts as "online annealing," promoting the perfection of PEBA hard segment microcrystals, improving the melt strength and physical crosslinking point density of the preform, thereby effectively resisting cell collapse during subsequent foaming and significantly improving the material's resistance to compression set.

[0013] Furthermore, in step S3, the fluid is CO2 or N2; the impregnation temperature is 5-20°C below the melting point of PEBA, the impregnation pressure is 12-20 MPa, and the impregnation time is 2-6 hours. These process conditions fall within the medium-low pressure range, reducing the pressure resistance requirements of the autoclave equipment and decreasing equipment investment and operating costs. Specifically, the impregnation pressure can be selected from 12 MPa, 15 MPa, 18 MPa, or 20 MPa.

[0014] Furthermore, the additives include antioxidants, lubricants, and chain extenders. Antioxidants prevent thermal oxidative degradation during processing, lubricants improve processing fluidity, and chain extenders enhance melt strength, particularly showing significant modifying effects for recycled or reclaimed materials.

[0015] Furthermore, by weight, the antioxidant comprises 0.1-0.5 parts, the lubricant comprises 0.2-0.8 parts, and the chain extender comprises 0.1-0.5 parts. Specifically, the antioxidant may be a hindered phenol or a phosphite, and the lubricant may be zinc stearate or calcium stearate.

[0016] A third aspect of this application provides the application of the aforementioned lightweight material in footwear materials.

[0017] Furthermore, the shoe material is a midsole for athletic shoes, and the lightweight material provides lightweight, high elasticity, and fatigue resistance in the midsole.

[0018] The present invention has the following beneficial effects:

[0019] This application constructs a "phase interface-nanoparticle" synergistic constraint system and uses the difference in solubility parameters to control the phase structure, so that layered silicates are precisely anchored at the PEBA / TPU interface, forming a robust physical barrier. Under medium-speed decompression conditions of 8-15 MPa / s, stable formation of submicron-level pores (100-400nm) can be achieved, breaking through the dependence of existing nanofoaming technology on ultra-fast decompression equipment, and significantly reducing equipment costs and process difficulty.

[0020] By controlling the injection mold temperature at 50-60℃, the crystallization of PEBA hard segments is improved, the melt strength of the matrix and the stability of physical cross-linking points are enhanced, the problem of cell collapse during the foaming process is effectively solved, and the material is endowed with excellent resistance to permanent compression deformation and fatigue resistance.

[0021] The formulation of this application is inexpensive, requiring only a small amount of layered silicate to replace expensive graphene or carbon nanotube nucleating agents. It also has a wide process window and a high yield rate, making it very suitable for large-scale industrial production of sports shoe midsoles. Detailed Implementation

[0022] To facilitate understanding of this application, a more complete description will be provided below. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0026] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0028] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0029] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0030] The term "particle" as used in this application, or a substance with a defined particle size distribution, is not necessarily spherical in shape; it may be irregular and can be either primary or secondary particles. The particle size of irregular particles is calculated as the average of their maximum and minimum diameters.

[0031] In some preferred embodiments, the polyether amide block copolymer PEBA can be selected from polyether block amide resins, such as Pebax RNew, Pebax 60D, Pebax 70D, etc., or any one of the Pebax series from Arkema with a hardness in the range of 55D-70D.

[0032] In some preferred embodiments, the thermoplastic polyurethane (TPU) can be selected from polyester-type TPU or polyether-type TPU, such as BASF's 1185A, 1190A, and 1195A, or any of Lubrizol's TPUs with a hardness in the range of 80A-95A.

[0033] In some preferred embodiments, the layered silicate is organomontmorillonite, specifically selected from sodium-based montmorillonite modified with organic amine salts, and its interlayer spacing is typically greater than 2 nm, which is beneficial for peeling in polymer melt.

[0034] In some preferred embodiments, the injection mold temperature can be selected from any one of 50°C, 52°C, 55°C, 58°C, and 60°C; the pressure relief rate can be selected from any one of 8 MPa / s, 10 MPa / s, 12 MPa / s, and 15 MPa / s.

[0035] Example 1: This example provides a lightweight material and its preparation method.

[0036] The raw materials for preparing lightweight materials include: PEBA (brand name Pebax 60D, Arkema, 80 parts), TPU (brand name 1190A, BASF, 20 parts), organomontmorillonite (brand name Cloisite 15A, 0.5 parts), antioxidant 1010 (0.2 parts), zinc stearate (0.5 parts), and chain extender (epoxy chain extender, 0.3 parts).

[0037] Based on polymer handbooks and group contribution methods, the solubility parameters of the selected PEBA (Pebax 60D) are calculated. The solubility parameters of the selected TPU (1190A) The absolute value of the difference in solubility parameters between the two. The difference is located at Within the specified range, it meets the thermodynamic conditions for constructing an interface-constrained structure.

[0038] Preparation methods include:

[0039] Step S1: Premix organomontmorillonite with a portion of TPU (5 parts) in a high-speed mixer, and then melt extrude and granulate in a twin-screw extruder to obtain interfacial nucleation masterbatch.

[0040] Step S2: Mix the remaining TPU (15 parts), PEBA, interface nucleating masterbatch and additives evenly, and injection mold them into preforms. The injection mold temperature is controlled at 55℃.

[0041] Step S3: Place the preform in an autoclave, introduce CO2, impregnate at 150℃ (PEBA melting point Tm-5℃), impregnate at 18 MPa, and impregnate for 4 hours.

[0042] Step S4: Depressurize and foam at a rate of 12 MPa / s.

[0043] Example 2: This example provides a lightweight material and its preparation method.

[0044] The difference from Example 1 is that: the amount of TPU is 30 parts, the amount of PEBA is 70 parts, the amount of organomontmorillonite is 0.8 parts, the injection mold temperature is 60°C, the impregnation pressure is 20 MPa, and the depressurization rate is 15 MPa / s.

[0045] Example 3: This example provides a lightweight material and its preparation method.

[0046] The difference from Example 1 is that: the amount of TPU is 10 parts, the amount of PEBA is 90 parts, the amount of organomontmorillonite is 0.3 parts, the injection mold temperature is 50°C, the impregnation pressure is 12 MPa, and the depressurization rate is 8 MPa / s.

[0047] Example 4: This example provides a lightweight material and its preparation method.

[0048] The difference from Example 1 is that the amount of organomontmorillonite used is 0.2 parts.

[0049] Example 5: This example provides a lightweight material and its preparation method.

[0050] The difference from Example 1 is that the amount of organomontmorillonite used is 1.0 part.

[0051] Example 6: This example provides a lightweight material and its preparation method.

[0052] The difference from Example 1 is that the impregnation fluid is N2 and the impregnation time is 6 hours.

[0053] Comparative Example 1: This comparative example does not include the TPU dispersion phase and the interfacial nucleation masterbatch.

[0054] The raw materials for preparation include: PEBA (brand name Pebax 60D, Arkema, 100 parts), nano TiO2 (3 parts, as a conventional nucleating agent), antioxidant 1010 (0.2 parts), and zinc stearate (0.5 parts).

[0055] The preparation method includes: directly mixing all raw materials and injection molding at a mold temperature of 55°C. Impregnation conditions are the same as in Example 1 (18 MPa, CO2), with a depressurization rate of 12 MPa / s. This comparative example simulates a conventional formulation of the prior art, which lacks an interface constraint mechanism under a mild depressurization rate.

[0056] Comparative Example 2: The injection mold temperature in this comparative example is relatively low.

[0057] The only difference from Example 1 is that the injection mold temperature is controlled at 25°C (conventional cold mold process). This comparative example is used to verify the effect of a specific mold temperature on crystallization perfection and compressibility.

[0058] Comparative Example 3: No interfacial nucleation masterbatch was prepared in this comparative example.

[0059] The only difference from Example 1 is that step S1 is omitted, and the organomontmorillonite is directly mixed with PEBA, TPU, and other additives in a single injection molding process. This comparative example is used to verify the importance of the masterbatch pre-dispersion process for the interfacial positioning of nanoparticles.

[0060] Cell structure observation: The cross-sectional morphology of the foamed material was observed using a scanning electron microscope (SEM), and the average cell diameter and cell density were statistically analyzed.

[0061] Apparent density: tested according to GB / T 6343 standard.

[0062] Hardness: Tested according to GB / T 531.1 standard using an Asker C hardness tester.

[0063] Ball rebound rate: Tested according to GB / T 6670 standard.

[0064] Compression permanent deformation: Tested according to GB / T 6669 standard, under the conditions of 50% compression rate, 70℃ × 22 hours.

[0065] Table 1 Test results of the examples and comparative examples

[0066] Testing items unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Average cell diameter nm 180 120 350 280 150 190 4500 850 1200 Pore ​​density ( ) <![CDATA[per cm 3 > 3.2 8.5 0.08 1.5 5.6 2.8 0.0004 0.065 0.021 Apparent density <![CDATA[g / cm 3 ]]> 0.18 0.2 0.17 0.19 0.21 0.18 0.22 0.19 0.21 hardness Asker C 52 55 48 50 56 53 58 48 50 Ball rebound rate % 68 70 63 65 69 67 52 56 58 Compression permanent deformation % 18 16 22 20 17 19 35 42 30

[0067] As shown in Table 1, under the same mild decompression rate (12 MPa / s), Example 1 achieved a submicron pore structure of 180 nm, while Comparative Example 1 (conventional TiO2 nucleation formulation) had a pore size as high as 4.5 μm and an extremely low pore density. This indicates that relying solely on heterogeneous nucleation of inorganic particles cannot suppress bubble coalescence and growth at low decompression rates. Example 1, by constructing a PEBA / TPU / layered silicate interface structure, utilized the nanosheets at the interface to form a robust physical barrier, effectively limiting excessive bubble growth and verifying the validity of the "interface pinning" effect.

[0068] Comparative Example 2 reduced the injection mold temperature to a conventional 25°C. Although the cell size (850nm) was still acceptable, the compression set deteriorated sharply to 42%, far exceeding the 18% in Example 1. This is because the low-temperature mold resulted in incomplete crystallization of the PEBA hard segments and insufficient strength of the physical cross-linking points. During the foaming process and subsequent use, the imperfect crystals are prone to slippage or melting, causing the material to be unable to return to its original state. The 55°C mold temperature in Example 1 served as "online annealing," significantly improving the structural stability and fatigue resistance of the material.

[0069] Comparative Example 3, using a direct mixing process, showed an increased pore size of 1.2 μm with uneven distribution. This is because the undispersed nano-montmorillonite could not be precisely positioned at the phase interface, but instead randomly aggregated in the matrix, losing the "interface pinning" effect, resulting in uneven bubble wall strength and the rupture and merging of some bubbles. This demonstrates that the preparation of masterbatch is a key step in achieving interfacial positioning of nanoparticles.

[0070] Comparing Examples 1-6, it can be seen that as the nucleating agent content increases (Examples 2 and 5), the cell size decreases and the density increases; appropriately increasing the depressurization rate (Example 2) helps to obtain finer cells. Example 3, even at a lower pressure (12 MPa) and a lower depressurization rate (8 MPa / s), still achieves cells of 350 nm, demonstrating that the present invention has an extremely wide process window, can adapt to different levels of production equipment, and truly achieves high cost-effectiveness.

[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

[0073] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A lightweight material, characterized in that, It comprises a matrix resin, a dispersed phase resin, and an interfacial nucleating agent; the matrix resin is a polyether amide block copolymer (PEBA); the dispersed phase resin is a thermoplastic polyurethane (TPU); and the interfacial nucleating agent is a layered silicate, wherein the layered silicate is dispersed at the phase interface between the PEBA and the TPU. The difference in solubility parameters between PEBA and TPU .

2. The lightweight material according to claim 1, characterized in that, By weight, the PEBA is 60-90 parts, the TPU is 10-40 parts, and the interfacial nucleating agent is 0.2-1.0 parts.

3. The lightweight material according to claim 1, characterized in that, The hardness of the PEBA is 55D-70D, and the hardness of the TPU is 80A-95A; the layered silicate is organomontmorillonite, and the polarity of its surface organic modifier is between that of PEBA and TPU.

4. The lightweight material according to claim 1, characterized in that, The lightweight material is a submicron porous foam material with a pore diameter of 100-400 nm.

5. A method for preparing the lightweight material according to any one of claims 1-4, characterized in that, The process includes the following steps: Step S1: Prepare an interfacial nucleation masterbatch, which includes an interfacial nucleating agent and thermoplastic polyurethane (TPU); Step S2: Mix polyether amide block copolymer (PEBA), thermoplastic polyurethane (TPU), the interfacial nucleation masterbatch, and additives evenly, and injection mold the mixture into a preform, with the injection mold temperature controlled at 50-60℃; Step S3: Place the preform in an autoclave and introduce fluid for impregnation; Step S4: Depressurize and foam at a rate of 8-15 MPa / s.

6. The preparation method according to claim 5, characterized in that, In step S3, the fluid is CO2 or N2; the impregnation temperature is 5-20°C below the melting point of PEBA, the impregnation pressure is 12-20 MPa, and the impregnation time is 2-6 hours.

7. The preparation method according to claim 5, characterized in that, The additives include antioxidants, lubricants, and chain extenders.

8. The preparation method according to claim 7, characterized in that, The antioxidant is 0.1-0.5 parts by weight, the lubricant is 0.2-0.8 parts by weight, and the chain extender is 0.1-0.5 parts by weight.

9. The application of the lightweight material as described in any one of claims 1-4 in footwear materials.

10. The application according to claim 9, characterized in that, The shoe material is a midsole for athletic shoes.

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