Foaming elastomer shoe insole injection molding mold device and molding method

Abstract

The invention relates to a foaming elastomer shoe insole injection molding mold device and a forming method, which adopt a supercritical fluid foaming technology and realize accurate control on different forming areas by arranging a sliding block mechanism, a temporary feeding space, a porous gas diffusion insert and an independent gas control system. The mold comprises a first half mold body and a second half mold body, a shoe insole cavity is formed after mold closing, and the sliding block mechanism divides the cavity into a temporary feeding space and a relatively independent forming area. The forming method comprises the steps of plasticizing and mixing, injecting, sliding block retreating, compressed gas unloading, vacuum negative pressure communicating, cooling and shaping and the like. According to the technical scheme, the product density can be remarkably reduced, the skin layer thickness is reduced, the cushioning performance is improved, and the forming efficiency is greatly improved. The method is suitable for manufacturing shoe insoles made of various thermoplastic elastomer materials and has the advantages of being light in weight, high in resilience and low in cost, and application of the supercritical fluid injection molding foaming technology in the field of shoe materials is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of injection molding, and in particular to a mold device and a molding method for injection molding a foamed thermoplastic elastomer shoe midsole, which is particularly suitable for manufacturing lightweight, high-resilience thermoplastic elastomer shoe midsole using a supercritical fluid foaming agent. Background Art

[0002] Due to the environmental advantages and shock-absorbing and rebound properties of supercritical fluid foaming agents (N2, CO2, etc.) in thermoplastic resin foaming applications, they have been widely used in the manufacture of elastomer midsoles for shoes. Currently, mature applications include E-TPU compression molding, such as the thermoplastic elastomer midsole foaming method disclosed in Nike's patent application CN109940916B or US10005209B2. The method involves impregnating granular materials or preformed products with supercritical fluid, inducing heat / microwave or infrared radiation, and then compression molding. The density of the molded products produced by this method is as low as 0.1g / cm 3 The cortex is easier to control below 200μm, but the process and time are extremely long and the cost is high.

[0003] Microcellular foaming technology using supercritical foaming agents (N2 or CO2) is well-known for manufacturing thin-walled thermoplastic products. Its advantages lie in the ability to easily incorporate supercritical fluids into molten thermoplastics to create a homogeneous mixture or single-phase solution, reducing melt viscosity and improving fluidity, allowing for rapid molding at low mold temperatures. However, its lightweighting effect is limited, with the density of foamed parts ranging from approximately 85% to 95% of the apparent density of solid parts, and the thickness of the skin in contact with the mold cavity exceeding approximately 500μm. Direct injection foaming of thermoplastic elastomer midsoles presents a challenge. While a short manufacturing process and high molding efficiency are obvious advantages, challenges remain in terms of weight reduction, cell morphology, and skin thickness.

[0004] Authorized patent CN103608158B discloses an injection molding system and method, in which the molding method is direct molding by injection mold, first injecting and then expanding the mold cavity to foam. According to the disclosed method, due to the use of a pressure holding process before cavity expansion and foaming, the thickness of the product skin is difficult to control below 500μm, affecting the performance and lightweight effect of the product. At the same time, the expansion is relatively large in the thick-walled area, which easily forms large bubbles of 3mm to 5mm and delamination defects.

[0005] Patent application document US20150038605A1 discloses low-density foam for footwear and its manufacturing method, which involves a direct injection molding method using a supercritical fluid foaming agent (N2 or CO2); according to the embodiment, when the foaming agent content is 5%wt (including CO2 4%wt), the density of the molded TPU foam product is 0.28g / cm 3 This result is quite different from the apparent density of the shoe material made by E-TPU process. One of the reasons is that the thickness of the cortex is large, which limits the weight reduction ratio.

[0006] Authorized patent CN113492493B discloses a polymer foam molding device and method. According to the disclosed method, the material injected into the cavity contacts most of the cavity surface at a high pressure before the mold is slightly opened, resulting in the surface thickness of the final molded product being difficult to control below 500μm, affecting the performance and lightweight effect of the product, and the molding efficiency is low, affecting the scope of application.

[0007] Based on the existing problems of direct injection foaming of shoe midsoles using supercritical fluid foaming agents, as well as the large thickness difference between the front and back of the shoe midsole, the inventors have proposed a solution, including a mold device and a corresponding molding method, with the goal of reducing the density of the molded product to 0.2g / cm 3 The skin thickness is controlled below 200μm, with good rebound performance, short molding cycle and high production efficiency, which can replace the long process, high cost and high energy consumption process such as E-TPU or molding. Technical Solution

[0008] A mold device 1 for injection molding a foamed thermoplastic elastomer shoe midsole is provided, comprising: - a first half-mold 100 and a second half-mold 110 which, when closed, form a cavity 120 in the shape of a shoe midsole; - at least two slider mechanisms 1101 and 1102 are provided on the second mold half 110 adjacent to the feed channel 101 and, when extended, divide the mold cavity 120 into a temporary feed space 300 and at least two relatively independent molding areas, including a thin-wall molding area 1201 and a thick-wall molding area 1202; - porous gas diffusion inserts 1103, 1104, 1105 and gas connection holes 1106, 1107, 1108 connected thereto, arranged on the surfaces of the cavities of the temporary feeding space 300 and the relatively independent molding areas 1201, 1202; - Sealing device 130 at the cavity parting surface and the joint between the slider mechanism and the cavity; - Independent piping systems 410, 510, and 610 connected to the gas connection holes 1106, 1107, and 1108, which connect the compressed gas source 400 and the vacuum negative pressure sources 500 and 600, wherein the valves in the piping are controlled by the PLC gas control system 1000 in communication with the injection molding machine control system to achieve opening and closing, connecting, or emptying operations.

[0009] Among them, according to the mold device, it is characterized in that the slider mechanisms 1101 and 1102 are arranged in the second half mold 110 opposite to the first half mold 100 containing the feed channel 101, and are arranged on both sides of the connection port between the feed channel 101 and the cavity along the length direction of the cavity 120, and a porous gas diffusion insert 1103 and a corresponding gas connection hole 1106 combination are configured in the area defined by the slider mechanism.

[0010] Among them, according to the mold device, it is characterized in that the slider mechanisms 1101 and 1102 are controlled by the injection molding machine control system and the PLC gas control system 1000 in conjunction with each other, and automatically retreat during injection foaming molding. The retreat method includes graded retreat or retreat at a set speed, wherein the PLC gas control system 1000 controls the coordination and timing between the retreat of the slider mechanism and the removal of compressed gas in different molding areas in the mold cavity, and the connection and removal of the vacuum negative pressure in relatively independent molding areas.

[0011] Wherein, according to the mold device, it is characterized in that the volume Vt of the temporary feeding space 300 does not exceed 25% of the volume Vc of the cavity 120, preferably does not exceed 20%, and more preferably does not exceed 15%.

[0012] Among them, according to the mold device, it is characterized in that the porous gas diffusion inserts 1103, 1104, and 1105 are made of sintered metal material, with a pore size between 5μm and 30μm, and a thickness between 2mm and 5mm, and the temporary feed space 300 and the porous gas diffusion inserts 1103, 1104, and 1105 of different relatively independent molding areas 1201 and 1202 are not connected to each other; further, temperature and pressure sensors 1109, 1110, and 1111 are arranged in the porous gas diffusion inserts 1103, 1104, and 1105, and the sensors are connected to the PLC gas control system 1000 to feedback the temperature and pressure conditions in the cavity.

[0013] The mold device is characterized in that the compressed gas source 400 can provide compressed gas with a maximum pressure of 30 MPa, and preheat the compressed gas to 200°C to heat the cavity surface to a temperature lower than the melting point of the thermoplastic elastomer (T m) a temperature of 50°C to 80°C; the vacuum negative pressure source provides a negative pressure of 20kPa to 100kPa, and the vacuum negative pressure in different molding areas may be different.

[0014] According to any of the above mold devices, a method for injection molding a foamed thermoplastic elastomer shoe midsole is also provided, comprising the following steps: - S1: Plasticize and mix the foamable supercritical fluid thermoplastic elastomer homogeneous mixture melt and store it in an injection cylinder, wherein the mixture melt temperature is between the melting point of the thermoplastic elastomer (T m ) 10°C to 20°C above, pressure 20MPa to 30MPa; - S2: The mold is closed, and the slider mechanisms 1101 and 1102 are pushed forward, dividing the mold cavity into a temporary feeding space 300 and relatively independent thin-wall molding areas 1201 and thick-wall molding areas 1202; - S3: Inject preheated compressed gas into the temporary feeding space 300 to establish a pressure of 5.0 MPa to 15.0 MPa, and at the same time preheat the cavity surface to a temperature lower than the melting point of the thermoplastic elastomer (T m ) Temperatures between 50°C and 80°C; - S4: injecting a predetermined volume of a homogeneous mixture melt of a foamable supercritical fluid thermoplastic elastomer into the temporary feeding space 300, wherein the predetermined volume of the homogeneous mixture melt is between 90% and 100% of the volume of the temporary feeding space 300; - S5: The slider mechanisms 1101 and 1102 retract, and the compressed gas in the relatively independent molding areas 1201 and 1202 is quickly discharged, thereby forming a communication channel between the temporary feeding space 300 and the relatively independent molding areas 1201 and 1202, as well as a foaming and expansion molding space; - S6: connecting the relatively independent molding areas 1201 and 1202 to their respective vacuum negative pressure sources 500 and 600, respectively, to remove the compressed gas in the temporary feeding space 300; - S7: Remove the vacuum negative pressure of each relatively independent molding area 1201, 1202, and cool and shape.

[0015] Wherein, according to the described method, it is characterized in that the foamable supercritical fluid thermoplastic elastomer homogeneous mixture melt is made by fully mixing a thermoplastic elastomer and 1% to 5%wt of a supercritical fluid foaming agent, the thermoplastic elastomer is selected from EVA, TPU, TPEE, PEBA, POE or a combination thereof, and the supercritical fluid foaming agent is selected from N2, CO2 or a combination thereof, preferably 1% to 2.5%wt of N2.

[0016] Among them, according to the described method, it is characterized in that, in the step S5, the relatively independent molding areas 1201, 1202 are filled with sheet materials with a thickness of 1.0mm to 5.0mm extruded from the temporary feed space 300, and the width of the sheet material is roughly equal to the width of the cavity, and its thickness is controlled by adjusting the slider retraction mode and speed.

[0017] Among them, according to the method described, it is characterized in that, in the step S6, the vacuum negative pressure is between 20kPa and 100kPa, and is maintained for 3 seconds to 5 seconds, and the vacuum negative pressure in different relatively independent molding areas may be different; further, after the relatively independent molding areas 1201 and 1202 are connected to the vacuum negative pressure, the compressed gas pressure in the temporary feed space 300 is maintained within 0.5 seconds to 3 seconds to improve the filling and foaming efficiency.

[0018] The density of the foamed thermoplastic elastomer shoe midsole prepared according to the method described above is below 0.3 g / cm³, preferably below 0.2 g / cm³, the thickness of the skin layer does not exceed 300 μm, preferably does not exceed 200 μm, and the maximum cell diameter does not exceed 100 μm.

[0019] According to the method described above, the molding time is between 60 seconds and 65 seconds. Attached photos

[0020] Figure 1 Schematic diagram of the slider mechanism pushing forward and then backward when the mold is closed Figure 2 Schematic diagram of the second half mold structure layout Figure 3 Schematic diagram of the state of injecting the mixture melt into the temporary feed space Figure 4 Schematic diagram of foam filling when the sliding mechanism retracts and vacuum negative pressure is applied; Figure 5 Schematic diagram of the lamellar body filling mode when the sliding mechanism retracts; Figure 6 Cooling and shaping status diagram The label number; 1 - Mold assembly, 2 - Molded product, 100 - First mold half, 101 - Feed channel, 110 - Second mold half, 120 - Product cavity; 1101, 1102 - Slide mechanism, 300 - Temporary feed space, 1201 - Thin-walled cavity area, 1202 - Thick-walled cavity area; 1103, 1104, 1105 - Porous gas diffusion inserts; 1106, 1107, 1108 - Gas connection holes; 111 - First independent negative pressure air channel, 112 - Second independent negative pressure air channel; 1109, 1110, 1111 - Temperature and pressure sensors; 130 - Cavity seal, 200 - Injection cylinder nozzle, 400 - Compressed gas source, 410, 510, 610 - Gas pipeline; 401, 501, 601 - Reversing valve; 402, 502, 602 - switch valve; 403, 503, 603 - exhaust port; 500 - first negative pressure source, 600 - second negative pressure source, 1000 - PLC gas control system. DETAILED DESCRIPTION

[0021] The following is combined with Figures 1 to 6 The specific implementation methods and advantageous manifestations of this technical solution are further explained.

[0022] like Figure 1 、 2 6 shows a mold device for producing a foamed thermoplastic elastomer shoe midsole according to the present technical solution. The molded shoe midsole is designed in accordance with ergonomic principles and has a thickness difference along the length direction, with a thin front portion and a thick heel portion.

[0023] Not explicitly shown in the drawings, cooling water channels can be arranged in the first and second half molds according to known techniques and methods. For example, a cooling water channel is opened 15 mm from the cavity surface to provide the mold with a cooling water channel of less than 30 o C~50 o C basic mold temperature to improve cooling and shaping efficiency.

[0024] As shown in the accompanying drawings, the mold device 1 includes: - a first half-mold 100 and a second half-mold 110 which, when closed, form a cavity 120 in the shape of a shoe midsole; - at least two slider mechanisms 1101 and 1102 are provided on the second mold half 110 adjacent to the feed channel 101 and, when extended, divide the mold cavity 120 into a temporary feed space 300 and at least two relatively independent molding areas, including a thin-wall molding area 1201 and a thick-wall molding area 1202; - porous gas diffusion inserts 1103, 1104, 1105 and gas connection holes 1106, 1107, 1108 connected thereto, arranged on the surfaces of the cavities of the temporary feeding space 300 and the relatively independent molding areas 1201, 1202; - Sealing device 130 at the cavity parting surface and the joint between the slider mechanism and the cavity; - Independent piping systems 410, 510, and 610 connected to the gas connection holes 1106, 1107, and 1108, which connect the compressed gas source 400 and the vacuum negative pressure sources 500 and 600, wherein the valves in the piping are controlled by the PLC gas control system 1000 in communication with the injection molding machine control system to achieve opening and closing, connecting, or emptying operations.

[0025] In which, according to the mold device, the slider mechanisms 1101 and 1102 are arranged in the second half mold 110 opposite to the first half mold 100 containing the feed channel 101, and are arranged on both sides of the connection port between the feed channel 101 and the cavity along the length direction of the cavity 120, and a porous gas diffusion insert 1103 and a corresponding gas connection hole 1106 combination are configured in the area defined by the slider mechanism.

[0026] Among them, according to the mold device, the slider mechanisms 1101 and 1102 are controlled by the injection molding machine control system and the PLC gas control system 1000, and automatically retreat during injection foaming molding. The retreat method includes graded retreat or retreat at a set speed, wherein the PLC gas control system 1000 controls the coordination and timing between the retreat of the slider mechanism and the removal of compressed gas in different molding areas in the mold cavity, and the connection and removal of the vacuum negative pressure in relatively independent molding areas.

[0027] According to the mold device, the volume Vt of the temporary feeding space 300 does not exceed 25% of the volume Vc of the cavity 120, preferably does not exceed 20%, and more preferably does not exceed 15%.

[0028] According to the mold device, the porous gas diffusion inserts 1103, 1104, and 1105 are made of sintered metal material with a pore size between 5 μm and 30 μm and a thickness between 2 mm and 5 mm, and the temporary feed space 300 and the porous gas diffusion inserts 1103, 1104, and 1105 of different relatively independent molding areas 1201 and 1202 are not connected to each other; further, temperature and pressure sensors 1109, 1110, and 1111 are arranged in the porous gas diffusion inserts 1103, 1104, and 1105, and the sensors are connected to the PLC gas control system 1000 to feedback the temperature and pressure conditions in the cavity.

[0029] According to the mold device, the compressed gas source 400 can provide compressed gas with a maximum pressure of 30 MPa and preheat the compressed gas to 200 o C, to heat the cavity surface to a temperature below the melting point of the thermoplastic elastomer (T m ) 50 o C to 80 o C temperature; the vacuum negative pressure source provides a negative pressure of 20kPa to 100kPa, and the vacuum negative pressure in different molding areas may be different.

[0030] Among them, not explicitly shown in the drawings, cooling water channels can be arranged in the first half mold and the second half mold according to known technologies and methods, for example, a cooling water channel is opened 15 mm from the cavity surface to provide the mold with a cooling water channel of less than 30 o C~50 o Before injecting material into the cavity, the preheated compressed gas is injected to quickly heat the cavity surface, thereby achieving a rapid cycle of mold temperature, low energy consumption and long mold life.

[0031] The feed channel 101 and the connection port with the mold cavity can be configured as a structure that is easy to demould and remove from the molded product, including a cylindrical or elliptical cylindrical shape.

[0032] like Figure 1 and 2 A more advantageous embodiment is shown, in which two slider mechanisms 1101 and 1102 are disposed in the second half of the mold 110, arranged along the length of the cavity on either side of the feed channel 101 and its connection with the cavity. The two sliders and the cavity walls within the area they define form a temporary feed space 300, including the connection between the feed channel 101 and the cavity. Thus, the cavity 120 is divided into the temporary feed space 300 and a thin-walled molding area 1201 and a thick-walled molding area 1202, which are connected to the temporary feed space 300 but relatively independent of each other. When the slider mechanism is in the upper limit position, the slider is sufficiently close to the cavity wall, and the temporary feed space 300 and the relatively independent molding areas 1201 and 1202 can be connected through the gap between the slider and the cavity wall, at least allowing compressed gas to flow.

[0033] The slider mechanism can be driven by the injection molding machine's drive system, including a programmable ejection mechanism. The slider mechanism is controlled by the injection molding machine control system and the PLC gas control system 1000 to automatically retract during injection foam molding, which can include a graded retraction method and a retraction method according to a set speed. In an advantageous embodiment, each slider mechanism is independently controlled, which facilitates adjustment of the gap between the slider and the cavity wall. Furthermore, the PLC gas control system 1000 controls the coordination and timing between the retraction of the slider mechanism and the removal of compressed gas from different molding zones in the cavity, as well as the connection and removal of vacuum negative pressure from relatively independent molding zones, to achieve a favorable foaming method.

[0034] The temporary feeding space 300 formed in the above manner has a temporary filling volume V t , the volume V t The volume V can be set at the product volume or the complete cavity volume 120 c The volume of the temporary feed space 300 is less than 25%, preferably less than 20%, and further preferably less than 15%; that is, the foaming ratio is at least 4 times, or more than 7 times. The volume size of the temporary feed space 300 is set according to the basic physical properties of the thermoplastic elastomer to be molded; for resins with low foaming ratios, such as some EVA material formulas, it is appropriate to select 25% of the cavity volume for the temporary feed space; for high-performance thermoplastic elastomers such as TPU, TPEE, and PEBA, it is appropriate to select no more than 15% of the cavity volume. An advantageous way to select the volume of the temporary feed space is that the pre-filled homogeneous mixture melt should basically or completely fill the temporary feed space 300, which, on the one hand, realizes the physical isolation of the thin-wall molding area 1201 and the thick-wall molding area 1202 when the slider mechanism retreats, and on the other hand, is conducive to the sheet flow filling of the thin-wall molding area 1201 and the thick-wall molding area 1202.

[0035] After the mold is configured in this manner, it is secured to the injection molding machine. The injection cylinder nozzle is in close contact with the inlet of the feed channel 101 of the first mold half 100, creating a sealed cavity and preventing material overflow and gas leakage. Simultaneously, the injection molding machine's control system is connected to the PLC gas control system 1000 via signal lines, forming a complete injection molding system.

[0036] like Figure 2 As shown, a porous gas diffusion insert 1103 and a gas connection hole 1106 are arranged on the cavity wall and surface defined by the slider mechanisms 1101 and 1102 in the temporary feed space 300, so as to inject preheated compressed gas into the cavity 120. Figure 3As shown, before injecting the foamable supercritical fluid thermoplastic elastomer mixture melt into the cavity, the cavity surface is heated to a desired temperature, and a cavity pressure is established to suppress the escape of the supercritical fluid foaming agent in the melt and pre-foaming, and the injected mixture melt is confined in the temporary feed space 300. On the other hand, as shown in FIG. Figure 5 As shown in the figure, in the process of the mixture melt filling the relatively independent molding area from the temporary feeding space, the compressed gas is uniformly squeezed on the melt through the porous gas diffusion insert 1103, and a sheet flow is obtained in the filling direction, forming a higher pressure drop rate, which is conducive to improving the filling speed and foaming nucleation efficiency; further, combined with the slider retraction mode and speed direction, a sheet material with a thickness between 1mm and 5mm can be obtained to fill the relatively independent molding area.

[0037] like Figure 2 As shown, at the ends of the filling direction of the cavity walls and surfaces of relatively independent molding areas, such as the thin-wall molding area 1201 and the thick-wall molding area 1202, a combination of porous gas diffusion inserts 1104 and gas connecting holes 1107 and a combination of porous gas diffusion inserts 1105 and gas connecting holes 1108 are arranged to form mutually independent first independent air channels 111 and second independent air channels 112, which are used to quickly unload the compressed gas in the mutually independent molding areas and introduce the same or different vacuum negative pressures, thereby further improving the filling efficiency, pressure drop rate and expansion efficiency.

[0038] The porous gas diffusion inserts and gas connection hole combinations between different molding zones are not interconnected. Combined with the seals arranged on the mold surface outside the mold cavity and the seal 130 between the slider mechanism and the mold, the atmosphere within the cavity can be effectively controlled, including pressure and temperature. To further sense and control the atmosphere within the cavity during the molding process, temperature and pressure sensors can be arranged in each porous gas diffusion insert, as marked 1109, 1110, and 1111 in the accompanying drawings. The temperature and pressure sensors are connected to the PLC gas control system 1000 to feedback the temperature, pressure, and time status, providing a basis for adjusting process parameters and timing.

[0039] Around the periphery of the mold, independently controlled pipelines are connected to the gas connection holes in the mold cavity, as well as to a compressed gas source and a vacuum negative pressure source connected through these pipelines. Specifically, gas connection hole 1106 in the temporary feed space 300 is connected to gas pipeline 410 and compressed gas source 400; gas connection hole 1107 in the thin-wall molding area 1201 is connected to gas pipeline 510 and a first negative pressure source 500; and gas connection hole 1108 in the thick-wall molding area 1202 is connected to gas pipeline 610 and a first negative pressure source 600.

[0040] The independently controlled gas pipelines 410, 510, and 610 are all provided with switch valves 402, 502, and 602, and reversing valves 401, 501, and 601, and the reversing valves are provided with connection states and exhaust ports 403, 503, and 603. The valves in the pipelines are controlled by the PLC gas control system (1000) in communication with the injection molding machine control system to switch, connect, or exhaust, thereby realizing cavity atmosphere control that is beneficial to foam molding.

[0041] The first negative pressure source 500 and the second negative pressure source 600 connected to the relatively independent molding area can provide a vacuum negative pressure between 20kPa and 100kPa. The vacuum negative pressures between them can be different to facilitate fine-tuning of the foaming state.

[0042] The mold device provided according to the above technical solution can realize a variety of methods that are conducive to the foaming injection molding of supercritical fluid thermoplastic elastic shoe midsoles, which include the following steps: - S1: Plasticize and mix the foamable supercritical fluid thermoplastic elastomer homogeneous mixture melt and store it in an injection cylinder, wherein the mixture melt temperature is between the melting point of the thermoplastic elastomer (T m ) 10°C to 20°C above, pressure 20MPa to 30MPa; - S2: The mold is closed, and the slider mechanisms 1101 and 1102 are pushed forward, dividing the mold cavity into a temporary feeding space 300 and relatively independent thin-wall molding areas 1201 and thick-wall molding areas 1202; - S3: Inject preheated compressed gas into the temporary feeding space 300 to establish a pressure of 5.0 MPa to 15.0 MPa, and at the same time preheat the cavity surface to a temperature lower than the melting point of the thermoplastic elastomer (T m ) Temperatures between 50°C and 80°C; - S4: injecting a predetermined volume of a homogeneous mixture melt of a foamable supercritical fluid thermoplastic elastomer into the temporary feeding space 300, wherein the predetermined volume of the homogeneous mixture melt is between 90% and 100% of the volume of the temporary feeding space 300; - S5: The slider mechanisms 1101 and 1102 retract, and the compressed gas in the relatively independent molding areas 1201 and 1202 is quickly discharged, thereby forming a communication channel between the temporary feeding space 300 and the relatively independent molding areas 1201 and 1202, as well as a foaming and expansion molding space; - S6: connecting the relatively independent molding areas 1201 and 1202 to their respective vacuum negative pressure sources 500 and 600, respectively, to remove the compressed gas in the temporary feeding space 300; - S7: Remove the vacuum negative pressure of each relatively independent molding area 1201, 1202, and cool and shape.

[0043] According to the method described, the foamable supercritical fluid thermoplastic elastomer homogeneous mixture melt is made by fully mixing a thermoplastic elastomer and 1% to 5% wt of a supercritical fluid foaming agent, the thermoplastic elastomer is selected from EVA, TPU, TPEE, PEBA, POE or a combination thereof, and the supercritical fluid foaming agent is selected from N2, CO2 or a combination thereof, preferably 1% to 2.5% wt of N2.

[0044] Among them, according to the described method, in the step S5, the relatively independent molding areas 1201 and 1202 are filled with sheet materials with a thickness of 1.0 mm to 5.0 mm extruded from the temporary feed space 300, and the width of the sheet material is roughly equal to the width of the cavity, and its thickness is controlled by adjusting the slider retraction mode and speed.

[0045] According to the described method, in step S6, the vacuum negative pressure is between 20 kPa and 100 kPa, and is maintained for 3 seconds to 5 seconds; further, after the relatively independent molding areas 1201 and 1202 are connected to the vacuum negative pressure, the compressed gas pressure in the temporary feed space 300 is maintained for 0.5 seconds to 3 seconds to improve the filling and foaming efficiency.

[0046] According to any of the methods described above, the density of the foamed thermoplastic elastomer shoe midsole prepared is below 0.3 g / cm³, preferably below 0.2 g / cm³, the thickness of the leather layer does not exceed 300 μm, preferably does not exceed 200 μm, and the maximum pore diameter does not exceed 100 μm.

[0047] According to any of the above methods, the molding time is between 60 seconds and 65 seconds.

[0048] The following is further described by way of examples.

[0049] Example 1 TPEE foamed shoe midsole In the embodiment, the mold cavity is set according to the shape of the midsole of a casual shoe, with a length of 250mm, a width of about 100mm, a thickness of 10mm at the front, and a thickness of 25mm at the heel. The volume of the foamed product or the cavity volume is 400cm 3 .

[0050] According to the technical solution of the present invention, a mold device is set, wherein the volume of the temporary feeding space is set to 60cm 3 The first negative pressure source is connected to the front thin-wall molding area of ​​the cavity, the second negative pressure source is connected to the thick-wall molding area at the back of the cavity, and the compressed gas source is connected to the temporary feeding space; the slider mechanism is connected to the neutron of the injection molding machine and is controlled by the injection molding machine control system and the PLC gas control system.

[0051] The PLC gas control system was made by the inventor according to the control requirements. It has a PLC control module and a communication module, which communicates with the control system of the injection molding machine and controls the output pressure and / or temperature of the compressed gas source and vacuum source, as well as the opening and switching of the valves on the connecting pipelines.

[0052] The injection molding machine used is a Haitian Changfei 360T full-electric machine, the supercritical fluid foaming agent metering injection system used is the SCFoam system homemade by the inventor, and the resin and supercritical fluid foaming agent plasticizing and mixing device is specially designed and manufactured by the inventor, with a screw diameter of 40 mm and an aspect ratio of 27D.

[0053] Material: Arnitel® FM8226 (T m = 158 o C, density 1.09g / cm 3 ) Process parameters: Foaming agent: N2, 2%wt Mold cooling water temperature: 30 o C; Melt mixture temperature: 175 o C; Injection speed: 140mm / s; Injection pressure: 100MPa; Injection melt volume: 58cm 3 ; Cavity gas pressure before injection: 10.0MPa; Cavity surface temperature before injection: 100 o C; Injection time: 0.33s; Slider retraction time: 0.33s after injection; Vacuum negative pressure: 50kPa in thin-walled area, 70kPa in thick-walled area: Compressed gas unloading time in thin-walled and thick-walled areas: 0.33s after injection; Molding cycle: 60~65s.

[0054] result: - Density: 0.14g / cm 3 - Rebound rate: 70%~75% - Cortical thickness: 150~180μm - Cell size: 30~50μm The density is in accordance with ASTM D792, and the rebound rate is in accordance with ASTM D2632. The skin thickness and cell size are measured by vertically cutting the product in the middle along the length and width directions and measuring under a 100X electron microscope.

[0055] Example 2 TPU shoe midsole Material: ELASTOLLAN® SP 9552 TW (Tm=160°C, density 1.15 g / cm³) The process parameters are similar to those in Example 1, and the injection melt volume is 60 cm 3 .

[0056] result: - Density: 0.168g / cm³ - Rebound rate: 65-68% - Cortical thickness: 160-190 μm - Cell size: 30-50μm Comparative Example TPU shoe midsole - Reference technology: CN113492493B method - Material: ELASTOLLAN® SP 9552 TW (Tm=160°C, density 1.15 g / cm³) - Parameters: Foaming agent N2 + CO2 5%wt, molding time 85-95 seconds - result: - Density: 0.218g / cm³ - Rebound rate: 59-63% - Cortical thickness: 400-500μm - Cell size: 40-60μm, maximum 800μm The data comparison table is as follows: Example 1 Example 2 Comparative Example Recent technologies Thermoplastic elastomer resin TPEE TPU TPU Cirql rTPU30 Foaming agent & wt% <![CDATA[N2, 2%]]> <![CDATA[N2, 2%]]> <![CDATA[N2+CO2, 5%]]> - <![CDATA[Apparent density (g / cm 3 )]]> 0.14 0.168 0.218 0.20 Ball rebound (%) 70~75 65~68 59~63 60~65 Cortical thickness (μm) 150~180 160~190 400~500 250~300 Cell size (μm) 30~50 30~50 40~60 (max. 800) 50~100 Molding time (s) 60~65 60~65 85~90 70~80 (Among them, recent technical information comes from the website https: / / ortholitecirql.com / and other public information.) As can be seen from the table, the present invention is superior to the comparative examples and recent technologies in terms of density, skin thickness, bubble uniformity and production efficiency, verifying the effectiveness of the technical solution.

[0057] The technical effects achieved by the present invention reach or exceed the levels of E-TPU or compression foaming technology in terms of low density, high rebound rate, cell uniformity, and skin thickness; and in terms of molding efficiency, efficient molding can be achieved between 60s and 65s, which not only significantly reduces energy consumption but is also suitable for large-scale production, meeting the footwear industry's demand for sustainable development. It can greatly expand the application of green and environmentally friendly supercritical fluid injection molding and foaming technology in footwear materials, including midsoles, insoles, etc.

[0058] It is easy for technicians in the same industry to understand that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments and descriptions are only for explaining the concept of the present invention. Without departing from the spirit and scope of the present invention, the present invention will naturally have various changes and improvements, and these changes and improvements will fall within the scope of the present invention to be protected.

Claims

1. A mold device and molding method for injection molding a foamed elastomer shoe midsole, comprising: - a first half mold (100) and a second half mold (110), which, when closed, form a cavity (120) having the shape of a shoe midsole; - at least two slider mechanisms (1101, 1102), arranged on the second half mold (110), adjacent to the feed channel (101), and when extended, dividing the mold cavity (120) into a temporary feed space (300) and at least two relatively independent molding areas, the molding areas including a thin-wall molding area (1201) and a thick-wall molding area (1202); - porous gas diffusion inserts (1103, 1104, 1105) and gas connection holes (1106, 1107, 1108) communicating therewith, arranged on the surfaces of the cavities of the temporary feeding space (300) and the relatively independent molding areas (1201, 1202); - a sealing device (130) at the parting surface of the cavity and at the junction of the slider mechanism and the cavity; - an independent piping system (410, 510, 610) connected to the gas connection holes (1106, 1107, 1108), the piping system being connected to a compressed gas source (400) and a vacuum negative pressure source (500, 600), wherein the valves in the piping are controlled by a PLC gas control system (1000) communicating with an injection molding machine control system to achieve switching, connection, or emptying operations.

2. The mold device according to claim 1, characterized in that The slider mechanisms (1101, 1102) are arranged in a second half mold (110) opposite to a first half mold (100) containing a feed channel (101), and are arranged on both sides of a connection port between the feed channel (101) and the mold cavity along the length direction of the mold cavity (120). A combination of a porous gas diffusion insert (1103) and a corresponding gas connection hole (1106) is configured within an area defined by the slider mechanisms.

3. The mold device according to claim 1 or 2, characterized in that: The slider mechanism (1101, 1102) is controlled by the injection molding machine control system and the PLC gas control system (1000) in a linkage manner, and automatically retracts during injection foam molding. The retraction method includes step-by-step retraction or retraction at a set speed, wherein the PLC gas control system (1000) controls the coordination and timing between the retraction of the slider mechanism and the discharge of compressed gas from different molding areas in the mold cavity, and the connection and discharge of vacuum negative pressure in relatively independent molding areas.

4. The mold device according to claim 1, characterized in that The volume Vt of the temporary feeding space (300) does not exceed 25% of the volume Vc of the cavity (120), preferably does not exceed 20%, and further preferably does not exceed 15%.

5. The mold device according to claim 1, characterized in that The porous gas diffusion inserts (1103, 1104, 1105) are made of sintered metal material, have a pore size between 5μm and 30μm, and a thickness between 2mm and 5mm, and the temporary feed space (300) and the porous gas diffusion inserts (1103, 1104, 1105) of different relatively independent molding areas (1201, 1202) are not connected to each other; furthermore, temperature and pressure sensors (1109, 1110, 1111) are arranged in the porous gas diffusion inserts (1103, 1104, 1105), and the sensors are connected to the PLC gas control system (1000) to feedback the temperature and pressure conditions in the cavity.

6. The mold device according to claim 1, characterized in that The compressed gas source (400) is capable of providing compressed gas with a maximum pressure of 30 MPa, and preheating the compressed gas to 200°C to heat the cavity surface to a temperature lower than the melting point of the thermoplastic elastomer (T m ) a temperature of 50°C to 80°C; the vacuum negative pressure source provides a negative pressure of 20kPa to 100kPa, and the vacuum negative pressure in different molding areas may be different.

7. A method for injection molding a foamed elastomeric shoe midsole using the mold apparatus according to any one of claims 1 to 6, comprising the following steps: - S1: Plasticize and mix the foamable supercritical fluid thermoplastic elastomer homogeneous mixture melt and store it in an injection cylinder, wherein the mixture melt temperature is between the melting point of the thermoplastic elastomer (T m ) 10°C to 20°C above, pressure 20MPa to 30MPa; - S2: The mold is closed, and the slider mechanism (1101, 1102) is pushed forward, dividing the mold cavity into a temporary feeding space (300) and relatively independent thin-wall molding areas (1201) and thick-wall molding areas (1202); - S3: Inject preheated compressed gas into the temporary feeding space (300) to establish a pressure of 5.0 MPa to 15.0 MPa, and at the same time preheat the cavity surface to a temperature lower than the melting point of the thermoplastic elastomer (T m ) Temperatures between 50°C and 80°C; - S4: injecting a predetermined volume of a foamable supercritical fluid thermoplastic elastomer homogeneous mixture melt into the temporary feeding space (300), wherein the predetermined volume of the homogeneous mixture melt is between 90% and 100% of the volume of the temporary feeding space (300); - S5: the slider mechanism (1101, 1102) retracts, and simultaneously the compressed gas in the relatively independent molding areas (1201, 1202) is quickly discharged, thereby forming a communication channel between the temporary feeding space (300) and the relatively independent molding areas (1201, 1202), as well as a foaming and expansion molding space; - S6: connecting the relatively independent molding areas (1201, 1202) to their respective vacuum negative pressure sources (500, 600), and removing the compressed gas in the temporary feeding space (300); - S7: Remove the vacuum negative pressure of each relatively independent molding area (1201, 1202) and cool and shape.

8. The method according to claim 7, characterized in that The foamable supercritical fluid thermoplastic elastomer homogeneous mixture melt is made by fully mixing a thermoplastic elastomer and 1% to 5% wt of a supercritical fluid foaming agent, wherein the thermoplastic elastomer is selected from EVA, TPU, TPEE, PEBA, POE or a combination thereof, and the supercritical fluid foaming agent is selected from N2, CO2 or a combination thereof, preferably 1% to 2.5% wt of N2.

9. The method according to claim 7, characterized in that In step S5, the relatively independent molding areas (1201, 1202) are filled with sheet materials with a thickness of 1.0 mm to 5.0 mm extruded from the temporary feeding space (300), the width of the sheet material being roughly equal to the width of the cavity, and the thickness thereof being controlled by adjusting the slider retraction mode and speed.

10. The method according to claim 7, characterized in that In step S6, the vacuum negative pressure is between 20 kPa and 100 kPa and is maintained for 3 to 5 seconds; further, after the relatively independent molding areas (1201, 1202) are connected to the vacuum negative pressure, the compressed gas pressure in the temporary feeding space (300) is maintained for 0.5 to 3 seconds to improve the filling and foaming efficiency.

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