A low shrinkage thermoplastic polyamide elastomer foam and a method for producing the same

Abstract

The present application provides a low-shrinkage thermoplastic polyamide elastomer foamed material and a preparation method thereof. The foamed material is prepared from a thermoplastic polyamide elastomer composition, which comprises the following raw materials by weight: 90-99 parts of thermoplastic polyamide elastomer, 0-10 parts of polyamide, 0.5-5 parts of inorganic filler, 1-2 parts of lubricant, 0.1-0.5 parts of antioxidant, and 0-1.5 parts of chain extender. The interfacial tension between the inorganic filler and the thermoplastic polyamide elastomer is greater than or equal to 2, and the apparent density of the thermoplastic polyamide elastomer composition is 0.05-0.2 g / cm 3 The present application solves the technical problems of the existing process, such as serious volume shrinkage, bubble collapse and combination, and significant performance decline of the thermoplastic polyamide elastomer foamed material due to the closed-cell structure, and endows the thermoplastic polyamide elastomer with excellent adsorption performance.

Description

Technical Field

[0001] This invention belongs to the field of foamed materials, specifically relating to a low-shrinkage thermoplastic polyamide elastomer foamed material and its preparation method. Background Technology

[0002] Polyamide elastomers are a type of thermoplastic elastomer (TPE) material composed of alternating soft and hard segments. The hard segments are highly crystalline polyamides, while the soft segments are amorphous polyethers or polyesters. Because polyamide elastomers possess both the elasticity of rubber and the strength, toughness, and abrasion resistance of polyamide resins, their foamed materials exhibit superior resilience, thermal insulation, and compression resistance, making them widely used in footwear, medical, permeable, and sporting goods industries. This patent uses nylon 6 elastomer, which is lower in cost and has greater development potential compared to the widely used nylon 12 elastomer. Furthermore, research on polyamide elastomer foamed materials is relatively limited both domestically and internationally, indicating ample room for future development.

[0003] Like other elastomer foams, polyamide elastomer foams based on supercritical fluid foaming technology are primarily closed-cell structures, exhibiting significant shrinkage issues. The closed-cell structure often results in a time lag between the foaming agent and air displacement. Therefore, when CO2 is used as a physical foaming agent, its diffusion rate is much higher than that of air. As CO2 rapidly escapes from the cells, air cannot diffuse into them in time, causing the pressure inside the cells to fall below atmospheric pressure. This makes the polyamide elastomer foam unable to withstand the negative pressure, leading to severe volume shrinkage, cell collapse and rupture, and a significant decline in performance, ultimately rendering it unusable in practical applications.

[0004] To address the problem of severe shrinkage after foaming of thermoplastic elastomer materials, previous researchers have conducted extensive studies. Chinese patent documents CN103709726 and CN104385479 disclose an extruded thermoplastic polyurethane elastomer foamed beads and its preparation method. This method uses supercritical fluid and adds 1-3 wt% of inorganic fillers such as silica, montmorillonite, and talc as foaming nucleating agents to prepare TPU foamed particles through continuous extrusion foaming. However, due to the low melt strength of TPU in the molten state, the cell structure of the material is difficult to control, resulting in severe sample shrinkage.

[0005] Subsequently, Chinese patent documents CN108239386A and CN109867946A disclosed a thermoplastic polyurethane foam particle and its preparation method. This invention involves extruding and granulating thermoplastic polyurethane elastomer, thermoplastic resin polymer, compatibilizer, and inorganic filler as a foaming nucleating agent to obtain blended alloy particles. These particles are then obtained through a supercritical CO2 foaming molding process. The invention primarily utilizes the high modulus of thermoplastic resin to suppress foam shrinkage, resulting in particles with good dimensional stability and a minimum density as low as 0.06 g / cm³. 3 It has minimal shrinkage and a full appearance of TPU foam particles, but the addition of a large amount of thermoplastic resin reduces the elasticity of the thermoplastic polyurethane elastomer.

[0006] While methods exist for preparing TPU foam particles with minimal shrinkage, the shrinkage problem of thermoplastic polyamide elastomer foam materials, which offer lower costs and higher potential, requires further research. Chinese patent document CN109943079A discloses a polyamide elastomer foam material and its preparation method. This invention first uses polyamide elastomer as the matrix, citric acid as a melt viscosity modifier, 0.5-5 wt% of inorganic fillers such as nano-silica, talc, and nano-calcium carbonate as nucleating agents, and suitable foaming aids for extrusion molding. Subsequently, the pre-foamed material is prepared using an intermittent foaming method with supercritical fluid as the physical foaming agent. Although the resulting polyamide elastomer foam material is lightweight, flexible, has uniform cell size, and low density, this invention does not provide an effective solution to the shrinkage problem of polyamide elastomer foam materials.

[0007] Therefore, the preparation of a polyamide elastomer foam material with good stability, low shrinkage, full appearance, good resilience and excellent adsorption performance has broad market prospects. Summary of the Invention

[0008] This invention provides a low-shrinkage thermoplastic polyamide elastomer foam material and its preparation method, which solves the technical problems of severe volume shrinkage, cell collapse and merging, and significant performance degradation caused by the closed-cell structure of thermoplastic polyamide elastomer foam materials.

[0009] According to a first aspect of the present invention, a low-shrinkage thermoplastic polyamide elastomer foam material is provided, characterized in that it is made by foaming a thermoplastic polyamide elastomer composition, wherein the thermoplastic polyamide elastomer composition comprises, by weight, the following raw materials: 90-99 parts of thermoplastic polyamide elastomer, 0-10 parts of polyamide, 0.5-5 parts of inorganic filler, 1-2 parts of lubricant, 0.1-0.5 parts of antioxidant, and 0-1.5 parts of chain extender, wherein the interfacial tension between the inorganic filler and the thermoplastic polyamide elastomer is greater than or equal to 2 mN / m, and the thermoplastic polyamide elastomer composition has a shrinkage density of 0.05-0.2 g / cm³.3 Apparent density within the range.

[0010] Optionally, in the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material, the thermoplastic polyamide elastomer is a polyamide-type thermoplastic elastomer material with alternating soft and hard segments, wherein the hard segments are selected from at least one of polyamide 6, polyamide 12, polyamide 66, polyamide 610, polyamide 11, and polyamide 1010, and the soft segments include at least one of polyether and polyester.

[0011] Optionally, in the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material, the interfacial tension between the inorganic filler and the thermoplastic polyamide elastomer is greater than or equal to 5 mN / m.

[0012] Optionally, in the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material, the inorganic filler is calcium silicate, and the inorganic filler is 1-3 parts.

[0013] Optionally, in the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material, the inorganic filler is wollastonite, preferably surface-treated wollastonite, and the inorganic filler content is 0.5-3 parts.

[0014] Optionally, in the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material, the chain extender is at least one of a random copolymer of styrene and maleic anhydride (SMA) or a multifunctional epoxy compound.

[0015] According to a second aspect of the present invention, a method for preparing the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material is provided, comprising the following steps: S1. Adding thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender to an extruder in proportion, performing melt blending at 220-240°C, and then extruding and granulating to prepare a thermoplastic polyamide elastomer composition, and extruding the thermoplastic polyamide elastomer composition into an extruder to form sheets or plates; S2. Placing the thermoplastic polyamide elastomer composition sheet into a high-pressure furnace, high-pressure autoclave or molding press, setting the temperature of the high-pressure furnace, high-pressure autoclave or molding press between 200-220°C, introducing a physical foaming agent into the molten thermoplastic polyamide elastomer composition, making the saturation pressure between 10-20 MPa, saturating for 0.5-2 hours, and then depressurizing and foaming to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0016] According to a third aspect of the present invention, a method for preparing the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material is provided, comprising the following steps: S1. Adding thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender to an extruder in proportion, melting and blending at 220-240°C, and then extruding and granulating to prepare a thermoplastic polyamide elastomer composition; S2. Adding the thermoplastic polyamide elastomer composition to a two-stage extrusion foaming system, wherein the temperature of the first stage extruder is between 210-230°C, and 0.1-3 parts by weight of a foaming agent are introduced into the molten thermoplastic polyamide elastomer composition. The gas-containing thermoplastic polyamide elastomer composition melt is obtained by mixing the gas-containing thermoplastic polyamide elastomer composition melt with the melt through a second-stage single-screw extruder or melt cooler to 190-210℃, so that the die head pressure is greater than 10MPa. After extrusion through the die head, a low-shrinkage thermoplastic polyamide elastomer foam material is obtained. Alternatively, at least one plunger cylinder is connected after the second-stage single-screw extruder, and the gas-containing thermoplastic polyamide elastomer composition melt is extruded into the plunger cylinder, and then injected into the mold through the plunger cylinder for foaming and molding to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0017] According to a fourth aspect of the present invention, a method for preparing the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material is provided, comprising the following steps: S1. Adding thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender to an extruder in proportion, melting and blending at 220-240°C, and then extruding and granulating to prepare a thermoplastic polyamide elastomer composition; S2. Adding the thermoplastic polyamide elastomer composition to an injection molding machine at a temperature between 210-230°C, introducing 0.1-5 parts by weight of a foaming agent into the molten thermoplastic polyamide elastomer composition and mixing it evenly to obtain a gas-containing thermoplastic polyamide elastomer composition melt, and then injecting the gas-containing thermoplastic polyamide elastomer composition melt into a mold at an injection pressure greater than or equal to 50 MPa to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0018] According to a fifth aspect of the present invention, a method for preparing the above-mentioned low-shrinkage thermoplastic polyamide elastomer foam material is provided, comprising the following steps: S1. Adding thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender to an extruder in proportion, melting and blending at 220-240°C, and then extruding and granulating to prepare a thermoplastic polyamide elastomer composition; S2. Adding the thermoplastic polyamide elastomer composition to an extruder, the temperature of the extruder being between 200-230°C, introducing 0.1-10 parts by weight of a foaming agent into the melt of the thermoplastic polyamide elastomer composition and mixing it evenly to obtain a gas-containing thermoplastic polyamide elastomer composition melt, extruding it through a sheet die, releasing the pressure, the foaming agent forming microbubbles, which are encapsulated in the thermoplastic polyamide elastomer, and cooling and shaping to form a low-shrinkage thermoplastic polyamide elastomer foam sheet with a uniform cross-section and honeycomb structure.

[0019] The beneficial effects of this invention are as follows:

[0020] Using polyamide elastomer as raw material, this invention modifies it by adding inorganic fillers with high interfacial tension to the thermoplastic polyamide elastomer. This results in a lower nucleation energy barrier between the polyamide elastomer matrix phase and the inorganic filler dispersion phase, facilitating heterogeneous gas nucleation at the interface. Furthermore, since polyamide elastomer and inorganic fillers are incompatible systems, the interaction between the two phases is very weak. Subsequent bubble growth leads to the detachment of the polymer interfacial adhesion, promoting the formation of open-cell structures. By preparing the polyamide elastomer foam material into an open-cell structure, the foaming agent and air can be replaced at the same order of magnitude, thus avoiding severe foam shrinkage caused by large negative pressures. Therefore, the low-shrinkage thermoplastic polyamide elastomer foam material obtained by this invention through supercritical foaming process exhibits high foaming ratio, high open-cell ratio, and extremely low shrinkage. This method is simple and easy to operate, effectively solving the problems of severe volume shrinkage and cell collapse in thermoplastic elastomer foam materials, and endowing thermoplastic polyamide elastomers with excellent adsorption properties. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0022] Figure 1 This is a flowchart of the preparation method of the low-shrinkage thermoplastic polyamide elastomer foam material of the present invention.

[0023] Figure 2 This is a comparison chart of the open area ratio and shrinkage rate of the products of Examples 1, 2, 3, 4, 5, 6 and Comparative Example 1 of the present invention.

[0024] Figure 3This is a scanning electron microscope image of the foamed product of Embodiment 1 of the present invention.

[0025] Figure 4 The image shown is a scanning electron microscope (SEM) image of the foamed product in Comparative Example 1. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples, but these should not be construed as limiting the present patent.

[0027] Unless otherwise specified, the experimental or testing methods in the following examples are conventional methods; the reagents and materials, unless otherwise specified, are obtained from conventional commercial sources or prepared by conventional methods.

[0028] The low-shrinkage thermoplastic polyamide elastomer foam material of the present invention is made by foaming a thermoplastic polyamide elastomer composition. The thermoplastic polyamide elastomer composition comprises, by weight, the following raw materials: 90-99 parts thermoplastic polyamide elastomer, 0-10 parts polyamide, 0.5-5 parts inorganic filler, 1-2 parts lubricant, 0.1-0.5 parts antioxidant, and 0-1.5 parts chain extender. The interfacial tension between the inorganic filler and the thermoplastic polyamide elastomer is greater than or equal to 2 mN / m, preferably greater than or equal to 5 mN / m, and more preferably greater than or equal to 8 mN / m, so that the growth of bubbles during foaming can lead to the detachment of the polymer two-phase interfacial adhesion, thereby promoting the formation of an open-cell structure. The thermoplastic polyamide elastomer composition has a shrinkage rate of 0.05-0.2 g / cm³. 3 The apparent density is within a certain range to achieve good resilience. Polyamide can improve the melt viscoelasticity and modulus of TPAE, enabling the preparation of lower-density foamed materials and improving the resilience of the products. The low-shrinkage thermoplastic polyamide elastomer foamed material of the present invention has good foaming performance, high open cell ratio and extremely low shrinkage rate, with a foaming ratio greater than or equal to 12 times and an open cell ratio of more than 65%, preferably greater than or equal to 90%.

[0029] The thermoplastic polyamide elastomer is a polyamide-type thermoplastic elastomer material with alternating soft and hard segments. The hard segments are highly crystalline polyamides selected from at least one of polyamide 6, polyamide 12, polyamide 66, polyamide 610, polyamide 11, and polyamide 1010. The soft segments include at least one of polyether and polyester, wherein the polyether is at least one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran ether glycol, and the polyester is polycaprolactone glycol and / or polycarbonate-type glycol.

[0030] The polyamide is polyamide 6.

[0031] The inorganic filler is selected from at least one of calcium silicate, talc, calcium carbonate, wollastonite, diatomaceous earth, silica, kaolin, and montmorillonite; preferably, it is selected from at least one of calcium silicate, talc, calcium carbonate, and wollastonite. More preferably, the inorganic filler is calcium silicate, and the amount of inorganic filler is 1-3 parts; more preferably, the amount of inorganic filler is 1-2 parts.

[0032] More preferably, the inorganic filler is wollastonite, and the inorganic filler content is 0.5-3 parts; more preferably, the inorganic filler content is 0.5-2 parts.

[0033] The antioxidant is at least one of antioxidant 168, antioxidant 3114, and antioxidant 1098. Preferably, the antioxidant is present in 0.1-0.3 parts.

[0034] The lubricant is one or both of stearamide and monoglyceride stearate.

[0035] The chain extender is at least one of a random copolymer of styrene and maleic anhydride (SMA) or a multifunctional epoxy compound.

[0036] Performance testing:

[0037] Interfacial tension testing: First, the contact angle θ between the thermoplastic polyamide elastomer and inorganic filler and various liquids such as water, diiodomethane, ethylene glycol, and glycerol was measured using an optical contact angle tensiometer. Then, the contact angle θ was determined according to the Owens-Wendt formula:

[0038]

[0039] The surface tension γ of thermoplastic polyamide elastomer and inorganic filler can be calculated, where s and l represent solid and liquid, respectively, and γ d γ p These represent the dispersive and polar components that indicate tension, respectively. right By drawing a graph, the intercept of the line can be determined. and slope The surface tension of the sample was thus determined. The surface tension, dispersive component, and polar component of the different liquids used in the tests are shown in Table 1.

[0040] Then according to the formula The interfacial tension γ between the inorganic filler and the thermoplastic polyamide elastomer can be calculated. 12 .

[0041] Table 1

[0042]

[0043] Foaming ratio test: After the foamed sample is removed from the reactor, the apparent density of the foamed product is tested using an analytical balance according to standard GB1033-86. The ratio of the density of the blended sample before foaming to the density after foaming is the foaming ratio.

[0044] Shrinkage test: Shrinkage rate Q of the foamed sample i Based on the initial foaming ratio of the sample Foaming ratio of the sample over time The calculation formula is as follows:

[0045] Opening ratio test: The foamed sample can be directly tested using the Ultrafoam 1000 opening ratio tester to obtain the open ratio of the foamed sample.

[0046] The foamed sample was cut into strips with an ultra-thin blade, the strips were quenched in liquid nitrogen, and then gold sputtering was performed to enhance conductivity. The cross-sectional morphology was observed using a scanning electron microscope, and the obtained SEM images were obtained.

[0047] like Figure 1 As shown, the preparation method of the low-shrinkage thermoplastic polyamide elastomer foam material of the present invention includes the following steps:

[0048] S1. The thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender are melt-blended at 220-240℃ in proportion, and then extruded and granulated to prepare a thermoplastic polyamide elastomer composition.

[0049] In this step, in a preferred embodiment, thermoplastic polyamide elastomer, polyamide, inorganic filler, chain extender, antioxidant, and lubricant are added together to a twin-screw extruder and melt-blended at 220-240°C. After extrusion granulation, a thermoplastic polyamide elastomer composition is obtained. The thermoplastic polyamide elastomer composition is then added to an extruder and extruded into sheets or plates; or the thermoplastic polyamide elastomer composition is added to an injection molding machine and injected into an unfoamed preform.

[0050] In this step, thermoplastic polyamide elastomer is used as raw material. A certain amount of inorganic filler with high interfacial tension with thermoplastic polyamide elastomer is added for modification. The inorganic filler can reduce the nucleation energy barrier at the interface with polyamide elastomer and promote heterogeneous nucleation at the interface between the two phases. A large number of bubbles are opened during the growth of the bubble cells due to tensile stress, thus obtaining an open-cell material.

[0051] S2. The thermoplastic polyamide elastomer composition is prepared into a low-shrinkage thermoplastic polyamide elastomer foam material by a foaming process.

[0052] In this step, in a preferred embodiment, a sheet of thermoplastic polyamide elastomer composition is placed in a high-pressure furnace, autoclave, or molding press. The temperature of the high-pressure furnace, autoclave, or molding press is set between 200-220°C. A physical foaming agent is introduced into the molten thermoplastic polyamide elastomer composition to maintain a saturation pressure between 10-20 MPa for 0.5-2 hours. Then, the pressure is released and foaming occurs to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0053] In another preferred embodiment, a thermoplastic polyamide elastomer composition is added to a two-stage extrusion foaming system. The temperature of the first-stage extruder is between 210-230°C. 0.1-3 parts (by weight) of foaming agent are introduced into the molten thermoplastic polyamide elastomer composition and mixed uniformly to obtain a gas-containing thermoplastic polyamide elastomer composition melt. The gas-containing thermoplastic polyamide elastomer composition melt is cooled to 190-210°C by a second-stage single-screw extruder or melt cooler. The feed rate and extrusion process parameters are adjusted to ensure that the die head pressure is greater than 10 MPa. After extrusion through the die head, a low-shrinkage thermoplastic polyamide elastomer foam material is obtained. Alternatively, at least one plunger cylinder is connected after the second-stage single-screw extruder, and the gas-containing thermoplastic polyamide elastomer composition melt is extruded into the plunger cylinder and then injected into a mold through the plunger cylinder to foam and form a thermoplastic polyamide elastomer foam material.

[0054] In another preferred embodiment, a thermoplastic polyamide elastomer composition is added to an injection molding machine at a temperature between 210-230°C. 0.1-5 parts (by weight) of a foaming agent are introduced into the molten thermoplastic polyamide elastomer composition. The screw plasticizing length is between 50-70% of the full injection length, and the mixture is homogeneously mixed to obtain a gas-containing thermoplastic polyamide elastomer composition melt. The gas-containing thermoplastic polyamide elastomer composition melt is then injected into a mold at an injection pressure of ≥50 MPa, preferably ≥100 MPa, to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0055] In another preferred embodiment, the thermoplastic polyamide elastomer composition is added to an extruder at a temperature between 200-230°C. 0.1-10 parts by weight of a foaming agent are introduced into the melt of the thermoplastic polyamide elastomer composition and mixed evenly to obtain a gas-containing thermoplastic polyamide elastomer composition melt. This melt is then extruded through a sheet die, and the pressure is released. The foaming agent forms microbubbles that are encapsulated within the thermoplastic polyamide elastomer. After cooling and shaping, a low-shrinkage thermoplastic polyamide elastomer foam sheet with a uniform cross-section and a honeycomb structure is formed.

[0056] The method of this invention is simple and easy to operate, effectively solving the shortcomings of severe volume shrinkage and cell collapse in thermoplastic elastomer foam materials, and endowing thermoplastic polyamide elastomers with excellent adsorption properties.

[0057] Example 1:

[0058] Raw materials: by weight, 97.7 parts of thermoplastic polyamide elastomer (TPAE), 2 parts of inorganic filler calcium silicate, and 0.1 parts and 0.2 parts of antioxidants 168 and 1098, respectively.

[0059] Preparation method:

[0060] S1. First, thermoplastic polyamide elastomer, antioxidant, and calcium silicate are put into a twin-screw extruder in proportion and melt-blended at 225°C. Then, the mixture is extruded and granulated to form a thermoplastic polyamide elastomer composition. The thermoplastic polyamide elastomer composition is then added to the extruder and extruded into a 1mm thick sheet.

[0061] S2. Using an intermittent foaming process, the extruded thermoplastic polyamide elastomer composition sheet is placed into a high-pressure autoclave at a temperature of 215°C, and CO2 at 15MPa is introduced into the molten thermoplastic polyamide elastomer composition. After holding the pressure for 30 minutes, the pressure is quickly released to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0062] After testing and calculation, the test results of various properties of the low-shrinkage thermoplastic polyamide elastomer foam material in Example 1 are shown in Table 1.

[0063] Example 2:

[0064] Raw materials: by weight, 98.2 parts of thermoplastic polyamide elastomer (TPAE), 1.5 parts of inorganic filler calcium silicate, and 0.1 parts and 0.2 parts of antioxidants 168 and 1098, respectively.

[0065] The remaining steps are the same as in Example 1.

[0066] After testing and calculation, the various performance test results of the low-shrinkage thermoplastic polyamide elastomer foam material in Example 2 are shown in Table 1.

[0067] Example 3:

[0068] S1. By weight, 95.2 parts of thermoplastic polyamide elastomer, 2 parts of surface-treated wollastonite, 0.1 parts of antioxidant 168, 0.2 parts of antioxidant 1098, 1 part of lubricant monoglyceride stearate, and 1.5 parts of chain extender SMA are weighed and added to an extruder. The extruder temperature is set to 230℃, and the thermoplastic polyamide elastomer composition is prepared by extrusion granulation.

[0069] S2. The thermoplastic polyamide elastomer composition prepared in step S1 is added to an extruder. The temperature of the extruder is set to 210°C. 4 wt% CO2 is introduced into the molten thermoplastic polyamide elastomer composition polymer melt and mixed evenly to obtain a gas-containing thermoplastic polyamide elastomer composition polymer melt. The melt is then extruded through a sheet die, the pressure is released, and the material is cooled and shaped to form a low-shrinkage thermoplastic polyamide elastomer foam sheet with a uniform cross-section and a honeycomb structure.

[0070] After testing and calculation, the various performance test results of the low-shrinkage thermoplastic polyamide elastomer foam material in Example 3 are shown in Table 1.

[0071] Example 4:

[0072] S1. By weight, 91.7 parts of thermoplastic polyamide elastomer, 5 parts of polyamide 6, 2 parts of inorganic filler wollastonite, 0.1 parts of antioxidant 168, 0.2 parts of antioxidant 1098, and 1 part of lubricant monoglyceride were weighed and added to an extruder. The extruder temperature was set to 230℃, and the thermoplastic polyamide elastomer composition was prepared by extrusion granulation.

[0073] S2. The thermoplastic polyamide elastomer composition prepared in step S1 is added to a two-stage extrusion foaming system. The temperature of the first-stage extruder is 210°C. 3 wt% CO2 is introduced into the molten thermoplastic polyamide elastomer composition and mixed evenly to obtain a gas-containing thermoplastic polyamide elastomer composition melt. The gas-containing thermoplastic polyamide elastomer composition melt is cooled to 195°C using a second-stage single-screw extruder or melt cooler. The feed rate and extrusion process parameters are adjusted to ensure that the die head pressure is greater than 10 MPa. Subsequently, the gas-containing thermoplastic polyamide elastomer composition melt is extruded into a plunger cylinder connected to the second extruder, and then injected into a mold through the plunger cylinder to foam and mold, obtaining a low-shrinkage thermoplastic polyamide elastomer foam material.

[0074] After testing and calculation, the various performance test results of the low-shrinkage thermoplastic polyamide elastomer foam material in Example 4 are shown in Table 1.

[0075] Example 5:

[0076] S1. By weight, 96.8 parts of thermoplastic polyamide elastomer, 1 part of inorganic filler calcium carbonate, 0.1 parts of antioxidant 168, 0.1 parts of antioxidant 1098, 1 part of lubricant monoglyceride stearate, and 1 part of chain extender SMA are weighed and added to an extruder. The extruder temperature is set at 230℃, and the thermoplastic polyamide elastomer composition is prepared by extrusion granulation.

[0077] S2. Add the thermoplastic polyamide elastomer composition prepared in step S1 into an injection molding machine. Set the injection molding machine temperature to 220°C. Introduce 1 wt% N2 into the molten thermoplastic polyamide elastomer composition and mix it evenly. Then inject the gas-containing melt into the mold to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0078] After testing and calculation, the various performance test results of the low-shrinkage thermoplastic polyamide elastomer foam material in Example 5 are shown in Table 1.

[0079] Example 6:

[0080] By weight, the thermoplastic polyamide elastomer (TPAE) is 98.7 parts, the inorganic filler talc is 1 part, and the antioxidants 168 and 1098 are 0.1 parts and 0.2 parts, respectively.

[0081] Preparation method:

[0082] S1. By weight, 98.7 parts of thermoplastic elastomer, 1 part of inorganic filler talc, 0.1 parts of antioxidant 168 and 0.2 parts of antioxidant 1098 are added to a twin-screw extruder and blended at 225°C. After extrusion granulation, a thermoplastic polyamide elastomer composition is obtained. The thermoplastic polyamide elastomer composition is added to an injection molding machine to be injected into an unfoamed preform.

[0083] S2. Using an intermittent foaming process, the injection-molded unfoamed preform is placed into a high-pressure autoclave at a temperature of 215°C, and CO2 at 15 MPa is introduced into the molten thermoplastic polyamide elastomer composition. After holding the pressure for 30 minutes, the pressure is quickly released to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

[0084] The performance test results of the low-shrinkage thermoplastic polyamide elastomer foam material in Example 6 after testing and calculation are shown in Table 1.

[0085] Comparative Example 1:

[0086] Raw materials: by weight, 99.7 parts of thermoplastic polyamide elastomer (TPAE), 0.1 parts of antioxidant 168 and 0.2 parts of antioxidant 1098.

[0087] S1. By weight, 99.7 parts of polyamide elastomer, 0.1 parts of antioxidant 168 and 0.2 parts of antioxidant 1098 are placed together in a twin-screw extruder and melt-blended at 225°C. Then, the mixture is extruded and granulated to form a thermoplastic polyamide elastomer composition. The thermoplastic polyamide elastomer composition is then added to an extruder and extruded into a sheet with a thickness of 1 mm.

[0088] S2. Using an intermittent foaming process, the extruded thermoplastic polyamide elastomer composition sheet is placed into a high-pressure autoclave at a temperature of 212°C, and CO2 at 15MPa is introduced into the molten thermoplastic polyamide elastomer composition. After holding the pressure for 30 minutes, the pressure is quickly released to obtain a shrinkable thermoplastic polyamide elastomer foam material.

[0089] The performance test results of the shrinkage thermoplastic polyamide elastomer foam material in Comparative Example 1 after testing and calculation are shown in Table 1.

[0090] Table 2. Performance test results of the foamed materials prepared in the examples and comparative examples.

[0091]

[0092] As can be seen from Table 2, when the same foaming process is used, such as in Examples 1, 2, 6 and Comparative Example 1, the density of the fully stabilized blended foam material is much smaller than that of the pure TPAE material, and the shrinkage rate of the blended elastomer foam material is much smaller than that of the pure TPAE foam material. In particular, when the inorganic filler is calcium silicate, the blended modified elastomer material not only has a lower apparent density, but also has a very high porosity and a very low shrinkage rate.

[0093] During the foaming process of pure TPAE, rapid depressurization induces cell nucleation and growth. At this time, the soft and hard segments of the TPAE molecular chain are subjected to bidirectional tensile forces. Since pure TPAE foam is primarily a closed-cell structure, it cannot avoid the negative pressure caused by the rapid displacement of the foaming agent with air, resulting in severe foam shrinkage. Furthermore, it can be seen that the interfacial tension between calcium silicate and TPAE is much higher than that between talc and TPAE, indicating lower adhesion and poorer compatibility between calcium silicate and TPAE. Therefore, the poorer compatibility between calcium silicate and the TPAE matrix leads to immiscibility at the interface, resulting in localized CO2 accumulation at the interface. The increased CO2 concentration at the interface lowers the nucleation energy barrier. According to the heterogeneous nucleation theory, the high interfacial tension between calcium silicate and TPAE further lowers the heterogeneous nucleation energy barrier, accelerating the heterogeneous nucleation rate of CO2 bubbles at the interface. A large number of bubbles are subjected to tensile stress during cell growth, leading to the detachment of the poorly compatible interfacial bonding, thereby promoting the formation of open-cell structures. Figure 2 It can be seen that pure TPAE foam material with low open cell ratio has an extremely high shrinkage rate, while blended TPAE foam material with extremely high open cell ratio has a significantly reduced shrinkage rate. This fully demonstrates that the formation of open cell structure allows the foaming agent and air to be replaced at the same rate in the cells, thereby avoiding severe foam shrinkage caused by large negative pressure.

[0094] Furthermore, in Examples 3 and 4, although the interfacial tension between the inorganic filler wollastonite and TPAE was greater than that of calcium silicate, the open porosity of the foamed samples was not as high as that of the blended foamed samples in Examples 1 and 2. This is because the surface of calcium silicate has a porous structure, which further facilitates the formation of open pores. On the other hand, the apparent density of the blended samples in Examples 3 and 4 was higher than that of the blended foamed samples in Examples 1 and 2, which is due to the different foaming processes used.

[0095] Figure 3 and Figure 4 The comparison of the cell morphology of the products in Example 1 and Comparative Example 1 shows that the cell size of Example 1 is smaller, the number of cells is greater, and most of the cells are open-cell structures, which further confirms the effect and function of the method of the present invention.

[0096] The above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low-shrinkage thermoplastic polyamide elastomer foam material, characterized in that, The product is made by foaming a thermoplastic polyamide elastomer composition, which comprises, by weight, the following raw materials: 90-99 parts thermoplastic polyamide elastomer, 0-10 parts polyamide, 0.5-5 parts inorganic filler, 1-2 parts lubricant, 0.1-0.5 parts antioxidant, and 0-1.5 parts chain extender, wherein the interfacial tension between the inorganic filler and the thermoplastic polyamide elastomer is greater than or equal to 5 mN / m, and the thermoplastic polyamide elastomer composition has a molecular weight distribution of 0.05-0.2 g / cm³. 3 Apparent density within the range.

2. The low-shrinkage thermoplastic polyamide elastomer foam material according to claim 1, characterized in that, The thermoplastic polyamide elastomer is a polyamide-type thermoplastic elastomer material with alternating soft and hard segments, wherein the hard segments are selected from at least one of polyamide 6, polyamide 12, polyamide 66, polyamide 610, polyamide 11, and polyamide 1010, and the soft segments include at least one of polyether and polyester.

3. The low-shrinkage thermoplastic polyamide elastomer foam material according to claim 1, characterized in that, The inorganic filler is calcium silicate, and the inorganic filler is 1-3 parts.

4. The low-shrinkage thermoplastic polyamide elastomer foam material according to claim 1, characterized in that, The inorganic filler is wollastonite, and the inorganic filler content is 0.5-3 parts.

5. The low-shrinkage thermoplastic polyamide elastomer foam material according to claim 1, characterized in that, The chain extender is at least one of a random copolymer of styrene and maleic anhydride (SMA) or a multifunctional epoxy compound.

6. The method for preparing the low-shrinkage thermoplastic polyamide elastomer foam material according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender are added to an extruder in proportion, melt-blended at 220-240℃, and then extruded and granulated to prepare a thermoplastic polyamide elastomer composition. The thermoplastic polyamide elastomer composition is added to an extruder and extruded into sheets or plates. S2. Place the thermoplastic polyamide elastomer composition sheet into a high-pressure furnace, high-pressure autoclave, or molding machine. Set the temperature of the high-pressure furnace, high-pressure autoclave, or molding machine between 200-220°C. Introduce a physical foaming agent to make the saturation pressure between 10-20 MPa. Saturate for 0.5-2 hours, then depressurize and foam to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

7. The method for preparing the low-shrinkage thermoplastic polyamide elastomer foam material according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender are added to an extruder in proportion, melt-blended at 220-240℃, and then extruded and granulated to prepare a thermoplastic polyamide elastomer composition; S2. The thermoplastic polyamide elastomer composition is added to a two-stage extrusion foaming system. The temperature of the first-stage extruder is between 210-230°C. 0.1-3 parts by weight of foaming agent are introduced into the molten thermoplastic polyamide elastomer composition and mixed evenly to obtain a gas-containing thermoplastic polyamide elastomer composition melt. The gas-containing thermoplastic polyamide elastomer composition melt is cooled to 190-210°C through a second-stage single-screw extruder or melt cooler, so that the die head pressure is greater than 10MPa. After extrusion through the die head, a low-shrinkage thermoplastic polyamide elastomer foam material is obtained. Alternatively, at least one plunger cylinder is connected after the second-stage single-screw extruder, and the gas-containing thermoplastic polyamide elastomer composition melt is extruded into the plunger cylinder and then injected into a mold through the plunger cylinder for foaming and molding to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

8. The method for preparing the low-shrinkage thermoplastic polyamide elastomer foam material according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender to an extruder in proportion, melt blend at 220-240℃, and then extrude and granulate to prepare a thermoplastic polyamide elastomer composition; S2. The thermoplastic polyamide elastomer composition is added to an injection molding machine at a temperature between 210-230°C. 0.1-5 parts by weight of foaming agent are introduced into the molten thermoplastic polyamide elastomer composition and mixed evenly to obtain a gas-containing thermoplastic polyamide elastomer composition melt. The gas-containing thermoplastic polyamide elastomer composition melt is then injected into a mold at an injection pressure of ≥50 MPa to obtain a low-shrinkage thermoplastic polyamide elastomer foam material.

9. The method for preparing the low-shrinkage thermoplastic polyamide elastomer foam material according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Thermoplastic polyamide elastomer, polyamide, inorganic filler, lubricant, antioxidant and chain extender are added to an extruder in proportion, melt-blended at 220-240℃, and then extruded and granulated to prepare a thermoplastic polyamide elastomer composition. S2. The thermoplastic polyamide elastomer composition is added to an extruder at a temperature between 200-230°C. 0.1-10 parts by weight of a foaming agent are introduced into the melt of the thermoplastic polyamide elastomer composition and mixed evenly to obtain a gas-containing thermoplastic polyamide elastomer composition melt. The melt is extruded through a sheet die, and the pressure is released. The foaming agent forms microbubbles that are encapsulated within the thermoplastic polyamide elastomer. After cooling and shaping, a low-shrinkage thermoplastic polyamide elastomer foamed sheet with a uniform cross-section and honeycomb structure is formed.

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