Polymer foam product with multi-level pore structure and preparation method thereof

Abstract

The present invention provides a polymer foam product with a multi-level pore structure and a preparation method thereof. The outer surface of the polymer foam product has a dense unfoamed skin structure, and the skin structure constitutes the first-level pore structure of the polymer foam product; the second-level pore structure exists inside the skin structure; and the third-level pore structure exists inside the second-level pore structure. Compared with polymer foam products prepared by conventional processes, the polymer foam product prepared by the present invention has higher tear strength and resilience, and also has better appearance quality, is more resistant to external impact and wear, and the dense, smooth and flat skin layer can also give the polymer foam product better anti-fouling ability.

Description

Technical Field

[0001] The invention belongs to the technical field of molding technology, and in particular relates to a polymer foam product with a multi-level pore structure and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Thermoplastic elastomer foam is an important type of polymer foam material. It has become an ideal material for making sports shoe midsoles due to its excellent rebound properties. At present, sports shoe midsoles made of thermoplastic elastomer foam are mainly processed and manufactured using two process routes. One process route is to foam the blanks first and then press them into shape, and the other is to foam the foam beads first and then sinter them into shape. The thermoplastic elastomer foam sports shoe midsoles prepared by the first route have excellent appearance quality, but due to the single pore structure, their rebound and tear strength are poor; although the sports shoe midsoles prepared by the second route have higher rebound and tear strength, the appearance of the product is not fine enough, there is a strong sense of graininess, and it is not resistant to external impact and wear, and the surface is easily damaged. Summary of the invention

[0004] In order to solve the problems of poor tear strength, low resilience and poor appearance quality of thermoplastic elastomer foam products prepared by conventional foaming molding processes, the present invention provides a polymer foam product with a multi-level pore structure and a preparation method thereof. The thermoplastic elastomer foam product prepared by the present invention has a dense skin structure and a three-level pore structure, which can give the foam product better tear strength and resilience, and can also significantly improve the appearance quality of the foam product. The dense flat layer can also improve the impact resistance of the foam product and reduce the surface damage during use.

[0005] In order to achieve the above object, the present invention provides the following technical solutions.

[0006] The first aspect of the present invention provides a polymer foam product with a multi-level pore structure. The outer surface of the polymer foam product has a dense unfoamed skin structure, and the skin structure constitutes the first-level pore structure of the polymer foam product; the second-level pore structure exists inside the skin structure, and the inside of the skin structure is composed of the second-level pore structure; the third-level pore structure exists inside the second-level pore structure, and the inside of the second-level pore structure is composed of the third-level pore structure, wherein the thickness of the skin structure ranges from 2μm to 500μm; the equivalent sphere diameter of the second-level pore structure ranges from 0.5mm to 10mm, and the wall thickness ranges from 0.5μm to 50μm; the equivalent sphere diameter of the third-level pore structure ranges from 5μm to 500μm.

[0007] Preferably, the thickness of the cortical structure ranges from 10 μm to 100 μm.

[0008] Preferably, the equivalent sphere diameter of the second-level cell structure ranges from 2 mm to 8 mm, and the wall thickness ranges from 5 μm to 30 μm.

[0009] Preferably, the equivalent spherical diameter of the third-level cells is in the range of 20 μm to 200 μm.

[0010] The dense cortical structure has a smooth and delicate appearance and high strength. It can protect the internal cell structure well, significantly improve the external impact resistance and abrasion resistance of the foam products, and improve the overall appearance quality of the foam products and enhance the surface anti-fouling ability. The second-level cells can effectively enhance the tear resistance of polymer foam products and improve the resilience of polymer foam products. The third-level cells cooperate with the second-level cells to give the polymer foam products light and high resilience. At the same time, the third-level cells are the smallest in size, which can enhance the scattering ability of polymer foam products to natural light, thereby giving the polymer foam products more beautiful colors.

[0011] The second aspect of the present invention provides a method for preparing the polymer foam having a dense skin layer and a multi-level pore structure, comprising the following steps:

[0012] (1) sintering the thermoplastic elastomer bead foam once to obtain a preform with a certain shape and structure;

[0013] (2) placing the preform in a mold for secondary sintering, rapidly heating the mold, and then closing the mold to press the preform. After pressing and forming, rapidly cooling the mold to allow the polymer foam product in the mold to cool and set.

[0014] Furthermore, the thermoplastic elastomer is a mixture of one or more of thermoplastic polyurethane (TPU), thermoplastic polyester elastomer (TPEE), thermoplastic nylon elastomer (PEBA), olefin elastomer (TPO, TPV or POE), and polybutylene adipate terephthalate (PBAT).

[0015] Furthermore, the equivalent spherical diameter of the thermoplastic elastomer bead foam is in the range of 0.5 mm to 10 mm, and the preferred equivalent spherical diameter is in the range of 2 mm to 8 mm. The density of the bead foam is 0.05 g / cm 3 ~0.18g / cm 3 , and the further preferred density range is 0.08 g / cm 3 ~0.15g / cm 3 .

[0016] Furthermore, the primary sintering molding may be steam heating molding or microwave heating molding, and the temperature range of the primary sintering molding is 100°C to 160°C, and the further preferred sintering temperature range is 110°C to 140°C.

[0017] Furthermore, the secondary sintering molding rapidly heats the mold temperature to 110°C to 180°C, and a further preferred mold temperature range is 120°C to 160°C.

[0018] The function of the secondary sintering molding is to give the polymer foam preform prepared in the first step a dense skin structure and a precise shape appearance structure.

[0019] Compared with the prior art, the present invention has the following obvious advantages:

[0020] Compared with polymer foam products prepared by conventional processes, the polymer foam products prepared by the present invention have higher tear strength and resilience, as well as better appearance quality and are more resistant to external impact and wear. At the same time, the dense, smooth and flat skin layer can also give the polymer foam products better anti-fouling ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 Schematic diagram of a polymer foam product with a multi-level pore structure.

[0023] Figure 2 The invention discloses a processing process for polymer foam products having a dense skin layer and a multi-level pore structure.

[0024] Figure 3 This is the processing process of the midsole of sports shoes.

[0025] Figure 4 It is a schematic diagram of the cross-sectional structure of the midsole of a sports shoe. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0027] The present invention relates to a polymer foam product having a dense skin layer and a multi-level pore structure. Figure 1 As shown, the outer surface of the polymer foam product has a dense unfoamed skin structure, which also constitutes the first-level pore structure of the polymer foam product. There is a second-level pore structure inside the dense skin, and there is a third-level pore structure inside the second-level pores.

[0028] Among them, the thickness of the cortical structure ranges from 2μm to 500μm, and the further preferred range is 10μm to 100μm. The dense cortical structure has a smooth and delicate appearance and high strength, which can protect the internal pore structure well, significantly improve the external impact resistance and wear strength of the foam product, and at the same time improve the overall appearance quality of the foam product and enhance the surface anti-fouling ability. The equivalent spherical diameter of the second-level pores ranges from 0.5mm to 10mm, and the further preferred equivalent spherical diameter ranges from 2mm to 8mm. The pore wall thickness of the second-level pores ranges from 0.5μm to 50μm, and the further preferred range is 5μm to 30μm. This level of pores can effectively enhance the tear strength of polymer foam products and improve the resilience of polymer foam products. The equivalent spherical diameter of the third-level cells is in the range of 5μm to 500μm, and the further preferred equivalent spherical diameter is in the range of 20μm to 200μm. The third-level cells cooperate with the second-level cells to give the polymer foam products the characteristics of light weight and high resilience. At the same time, the third-level cells have the smallest size, which can enhance the scattering ability of the polymer foam products to natural light, thereby giving the polymer foam products more beautiful colors.

[0029] The method for preparing a polymer foam having a dense skin layer and a multi-level pore structure comprises two process steps: Figure 2The first process step is a one-time sintering molding, which is to sinter the thermoplastic elastomer bead foam into a preform with a certain shape and structure. The thermoplastic elastomer is a mixture of one or more of thermoplastic polyurethane (TPU), thermoplastic polyester elastomer (TPEE), thermoplastic nylon elastomer (PEBA), olefin elastomer (TPO, TPV or POE), polybutylene adipate terephthalate (PBAT), and the equivalent ball diameter of the bead foam is in the range of 0.5 mm to 10 mm, and the preferred equivalent ball diameter is in the range of 2 mm to 8 mm. The density of the bead foam is 0.05 g / cm 3 ~0.18g / cm 3 , and the further preferred density range is 0.08 g / cm 3 ~0.15g / cm 3 The primary sintering molding can be steam heating molding or microwave heating molding. The temperature range of the primary sintering molding is 100°C to 160°C, and the further preferred sintering temperature range is 110°C to 140°C. The second process step is secondary sintering molding, which is used to give the polymer foam preform prepared in the first step a dense skin structure and a precise shape appearance structure. During the secondary sintering molding, the polymer preform prepared in the first step is placed in a mold, and the mold temperature is quickly heated to 110°C to 180°C, and the further preferred mold temperature range is 120°C to 160°C. Then, the polymer foam preform is pressed by closing the mold. After the pressing molding, the mold is quickly cooled to cool and shape the polymer foam product in the mold. Finally, the mold is opened to take out the final formed polymer foam product.

[0030] Implementation Case 1

[0031] Figure 3 The processing process of Example 1 is given. The polymer foam beads used in this example are aliphatic TPU bead foams, and their true density is 0.08 g / cm 3 The equivalent ball diameter of the bead foam is 4mm, and the molding process is as follows:

[0032] In the first step, the TPU bead foam is sintered into a TPU foam preform by steam molding process. The sintering temperature is 130°C and the density of the TPU foam preform is 0.09g / cm 3 .

[0033] In the second step, the TPU foam preform obtained in the first step is placed in a hot molding mold, the mold is quickly heated to 150°C, and then the mold is closed to press the TPU foam preform. After the pressing is completed, the mold and the TPU foam product therein are quickly cooled, and finally the mold is opened to take out the pressed TPU foam product.

[0034] The density of the final pressed TPU foam product was measured to be 0.13 g / cm 3 The compact skin thickness of the foam product is 30μm, the equivalent ball diameter of the second-level pores is 3.7mm, the wall thickness of the second-level pores is 10μm, and the equivalent ball diameter of the third-level pores is 120μm; the ball rebound coefficient of the foam product is 72%, the tensile strength is 3.5MPa, the elongation at break is 350%, and the tear strength is 2.2kg / cm 2 , permanent compression deformation 25%. Figure 4 A schematic diagram of the cross-sectional structure of the final prepared sports shoe midsole is given.

[0035] Implementation Case 2

[0036] The polymer foam beads used in this example are TPEE bead foams, and their true density is 0.08 g / cm 3 The equivalent ball diameter of the bead foam is 2.4 mm, and the molding process is as follows:

[0037] In the first step, the TPEE bead foam is sintered into a TPEE foam preform by microwave sintering molding process. The sintering temperature is 140°C and the density of the TPEE foam preform is 0.08g / cm 3 .

[0038] In the second step, the TPEE foam preform obtained in the first step is placed in a hot molding mold, the mold is quickly heated to 160°C, and then the mold is closed to press the TPEE foam preform. After the pressing is completed, the mold and the TPEE foam product therein are quickly cooled, and finally the mold is opened to take out the pressed TPEE foam product.

[0039] The density of the final pressed TPEE foam product was measured to be 0.12 g / cm 3 The compact skin thickness of the foam product is 10μm, the equivalent ball diameter of the second-level pores is 2mm, the wall thickness of the second-level pores is 10μm, and the equivalent ball diameter of the third-level pores is 20μm; the ball rebound coefficient of the foam product is 70%, the tensile strength is 3.8MPa, the elongation at break is 300%, and the tear strength is 2.6kg / cm 2 , permanent compression set 27%.

[0040] Implementation Case 3

[0041] The polymer foam beads used in this example are PEBA bead foams, and their true density is 0.13 g / cm 3 The equivalent ball diameter of the bead foam is 8mm, and the molding process is as follows:

[0042] In the first step, the PEBA bead foam is sintered into a PEBA foam preform by microwave sintering molding process. The sintering temperature is 140°C and the density of the PEBA foam preform is 0.14g / cm 3 .

[0043] In the second step, the PEBA foam preform obtained in the first step is placed in a hot molding mold, the mold is quickly heated to 140°C, and then the mold is closed to press the PEBA foam preform. After the pressing is completed, the mold and the PEBA foam product therein are quickly cooled, and finally the mold is opened to take out the pressed PEBA foam product.

[0044] The density of the final pressed PEBA foam product was measured to be 0.16 g / cm 3 The compact skin thickness of the foam product is 40μm, the equivalent ball diameter of the second-level pores is 7mm, the wall thickness of the second-level pores is 25μm, and the equivalent ball diameter of the third-level pores is 75μm; the ball rebound coefficient of the foam product is 75%, the tensile strength is 2.6MPa, the elongation at break is 280%, and the tear strength is 1.8kg / cm 2 , permanent compression set 22%.

[0045] Implementation Case 4

[0046] The polymer foam beads used in this embodiment are polyester TPU bead foams, and their true density is 0.15 g / cm 3 The equivalent ball diameter of the bead foam is 10 mm, and the molding process is as follows:

[0047] In the first step, the TPU bead foam is sintered into a TPU foam preform by microwave sintering molding process. The sintering temperature is 150°C and the density of the TPU foam preform is 0.16g / cm 3 .

[0048] In the second step, the TPU foam preform obtained in the first step is placed in a hot molding mold, the mold is quickly heated to 160°C, and then the mold is closed to press the TPU foam preform. After the pressing is completed, the mold and the TPU foam product therein are quickly cooled, and finally the mold is opened to take out the pressed TPU foam product.

[0049] The density of the final pressed TPU foam product was measured to be 0.18 g / cm 3 The compact skin thickness of the foam product is 100μm, the equivalent ball diameter of the second-level pores is 8mm, the wall thickness of the second-level pores is 30μm, and the equivalent ball diameter of the third-level pores is 200μm; the ball rebound coefficient of the foam product is 65%, the tensile strength is 3.8MPa, the elongation at break is 360%, and the tear strength is 2.8kg / cm 2, permanent compression set 28%.

[0050] Implementation Case 5

[0051] The polymer foam beads used in this embodiment are olefin thermoplastic elastomer (TPO) bead foams, and their true density is 0.09 g / cm 3 The equivalent ball diameter of the bead foam is 2mm, and the molding process is as follows:

[0052] In the first step, the TPO bead foam is sintered into a TPO foam preform by microwave sintering molding process. The sintering temperature is 125°C and the density of the TPO foam preform is 0.11g / cm 3 .

[0053] In the second step, the TPO foam preform obtained in the first step is placed in a hot molding mold, the mold is quickly heated to 135°C, and then the mold is closed to press the TPO foam preform. After the pressing is completed, the mold and the TPO foam product therein are quickly cooled, and finally the mold is opened to take out the pressed TPO foam product.

[0054] The density of the final pressed TPO foam product was measured to be 0.12 g / cm 3 The compact skin thickness of the foam product is 5μm, the equivalent ball diameter of the second-level pores is 1.8mm, the wall thickness of the second-level pores is 8μm, and the equivalent ball diameter of the third-level pores is 100μm; the ball rebound coefficient of the foam product is 65%, the tensile strength is 2.4MPa, the elongation at break is 200%, and the tear strength is 1.6kg / cm 2 , permanent compression set 32%.

[0055] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to perform equivalent replacements on parts thereof. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Although the above describes the specific implementation methods of the present invention, it is not intended to limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A method for preparing a polymer foam product having a multi-level pore structure, characterized in that: The outer surface of the polymer foam product has a dense unfoamed skin structure, and the skin structure constitutes the first-level pore structure of the polymer foam product; the second-level pore structure exists inside the skin structure, and the inside of the skin structure is composed of the second-level pore structure; the third-level pore structure exists inside the second-level pore structure, and the inside of the second-level pore structure is composed of the third-level pore structure; The method for preparing the polymer foam product having a multi-level pore structure comprises: (1) The polymer foam beads used are aliphatic TPU bead foams with a true density of 0.08 g / cm 3 The equivalent ball diameter of the bead foam is 4mm, and the molding process is as follows: In the first step, the TPU bead foam is sintered into a TPU foam preform by steam molding process. The sintering temperature is 130°C and the density of the TPU foam preform is 0.09g / cm 3 ; The second step is to place the TPU foam preform obtained in the first step into a hot molding mold, quickly heat the mold to 150° C., and then close the mold to press the TPU foam preform. After the pressing is completed, quickly cool the mold and the TPU foam product therein, and finally open the mold to take out the pressed TPU foam product. The density of the pressed TPU foam product is 0.13g / cm 3 The compact skin thickness of the foam product is 30μm, the equivalent ball diameter of the second-level pores is 3.7mm, the wall thickness of the second-level pores is 10μm, and the equivalent ball diameter of the third-level pores is 120μm; the ball rebound coefficient of the foam product is 72%, the tensile strength is 3.5MPa, the elongation at break is 350%, and the tear strength is 2.2kg / cm 2 , permanent compression deformation 25%; (2) The polymer foam beads used are TPEE bead foams, and their true density is 0.08 g / cm 3 The equivalent ball diameter of the bead foam is 2.4 mm, and the molding process is as follows: In the first step, the TPEE bead foam is sintered into a TPEE foam preform by microwave sintering molding process. The sintering temperature is 140°C and the density of the TPEE foam preform is 0.08g / cm 3 ; The second step is to place the TPEE foam preform obtained in the first step into a hot molding mold, quickly heat the mold to 160°C, and then close the mold to press the TPEE foam preform. After the pressing is completed, quickly cool the mold and the TPEE foam product therein, and finally open the mold to take out the pressed TPEE foam product. The density of the pressed TPEE foam product is 0.12g / cm 3 The compact skin thickness of the foam product is 10μm, the equivalent ball diameter of the second-level pores is 2mm, the wall thickness of the second-level pores is 10μm, and the equivalent ball diameter of the third-level pores is 20μm; the ball rebound coefficient of the foam product is 70%, the tensile strength is 3.8MPa, the elongation at break is 300%, and the tear strength is 2.6kg / cm 2 , permanent compression deformation 27%; (3) The polymer foam beads used are PEBA bead foams, and their true density is 0.13 g / cm 3 The equivalent ball diameter of the bead foam is 8mm, and the molding process is as follows: In the first step, the PEBA bead foam is sintered into a PEBA foam preform by microwave sintering molding process. The sintering temperature is 140°C and the density of the PEBA foam preform is 0.14g / cm 3 ; In the second step, the PEBA foam preform obtained in the first step is placed in a hot molding mold, the mold is quickly heated to 140° C., and then the mold is closed to press the PEBA foam preform. After the pressing is completed, the mold and the PEBA foam product therein are quickly cooled, and finally the mold is opened to take out the pressed PEBA foam product; The density of the pressed PEBA foam product is 0.16 g / cm 3 The compact skin thickness of the foam product is 40μm, the equivalent ball diameter of the second-level pores is 7mm, the wall thickness of the second-level pores is 25μm, and the equivalent ball diameter of the third-level pores is 75μm; the ball rebound coefficient of the foam product is 75%, the tensile strength is 2.6MPa, the elongation at break is 280%, and the tear strength is 1.8kg / cm 2 , permanent compression deformation 22%; (4) The polymer foam beads used are polyester TPU bead foams with a true density of 0.15 g / cm 3 The equivalent ball diameter of the bead foam is 10 mm, and the molding process is as follows: In the first step, the TPU bead foam is sintered into a TPU foam preform by microwave sintering molding process. The sintering temperature is 150°C and the density of the TPU foam preform is 0.16g / cm 3 ; The second step is to place the TPU foam preform obtained in the first step into a hot molding mold, quickly heat the mold to 160° C., and then close the mold to press the TPU foam preform. After the pressing is completed, quickly cool the mold and the TPU foam product therein, and finally open the mold to take out the pressed TPU foam product. The density of the pressed TPU foam product is 0.18g / cm 3 The compact skin thickness of the foam product is 100μm, the equivalent ball diameter of the second-level pores is 8mm, the wall thickness of the second-level pores is 30μm, and the equivalent ball diameter of the third-level pores is 200μm; the ball rebound coefficient of the foam product is 65%, the tensile strength is 3.8MPa, the elongation at break is 360%, and the tear strength is 2.8kg / cm 2 , permanent compression deformation 28%; (5) The polymer foam beads used are olefin thermoplastic elastomer (TPO) bead foams, and their true density is 0.09 g / cm 3 The equivalent ball diameter of the bead foam is 2mm, and the molding process is as follows: In the first step, the TPO bead foam is sintered into a TPO foam preform by microwave sintering molding process. The sintering temperature is 125°C and the density of the TPO foam preform is 0.11g / cm 3 ; The second step is to place the TPO foam preform obtained in the first step into a hot molding mold, quickly heat the mold to 135° C., and then close the mold to press the TPO foam preform. After the pressing is completed, quickly cool the mold and the TPO foam product therein, and finally open the mold to take out the pressed TPO foam product. The density of the pressed TPO foam product is 0.12g / cm 3 The compact skin thickness of the foam product is 5μm, the equivalent ball diameter of the second-level pores is 1.8mm, the wall thickness of the second-level pores is 8μm, and the equivalent ball diameter of the third-level pores is 100μm; the ball rebound coefficient of the foam product is 65%, the tensile strength is 2.4MPa, the elongation at break is 200%, and the tear strength is 1.6kg / cm 2 , permanent compression deformation 32%.

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