A method of manufacturing a lightweight face mask

Abstract

The present application relates to the field of processing high molecular substances into porous or honeycomb products or materials, and provides a manufacturing method of a lightweight mask, wherein silicon rubber, white carbon black and silicon oil are transported into a first roller cylinder of a planetary roller extruder for mixing, to obtain a mixture; the mixture and a vulcanizing agent are transported into a second roller cylinder for mixing, to obtain a mixed rubber; a mold is heated and filled with supercritical fluid; the mixed rubber is transported into a cavity of the mold, and the cavity is filled with supercritical fluid again for pressure adjustment, and the mixed rubber and the supercritical fluid are saturated; or the mixed rubber is transported into a third roller cylinder for pre-vulcanization treatment of heating and pressurizing, and then transported into the cavity of the mold for pressure relief, and the mixed rubber after the saturation reaction or the pre-vulcanization treatment is supercritically foamed, the amount of injection is controlled to achieve the purpose of completely filling the cavity, and a mask of high-quality supercritically foamed silicon rubber material is obtained.

Description

Technical Field

[0001] This invention relates to the field of processing polymer materials into porous or honeycomb-shaped products or materials, and specifically to a method for manufacturing a lightweight face mask. Background Technology

[0002] Silicone rubber foam is a porous polymer material with excellent comprehensive properties, and it is widely used in the electronics industry, chemical industry, aerospace and other fields. However, silicone rubber foam produced by traditional foaming methods has uneven cell structure and large pore size, and the commonly used organic foaming agents can cause environmental pollution.

[0003] In the process of realizing this invention, the inventors discovered the following problems in the prior art: the foaming performance of silicone rubber is directly affected by factors such as pre-vulcanization time, additives (e.g., silicone oil), foaming temperature, and foaming pressure, all of which directly influence the foaming quality or effect of silicone rubber. However, when using existing thermoplastic polymers as the matrix for foaming, the chemical foaming method has been found to cause environmental pollution, thus requiring subsequent processing and increasing production costs. Furthermore, existing materials manufactured using autoclaves require post-processing, involving numerous steps. Simultaneously, existing foaming preparation processes have low penetration efficiency into the polymer matrix; existing foaming is affected by mold space, and the shear force experienced by the polymer melt during cavity filling is high, resulting in poor foaming filling effect; furthermore, mold heating-induced foaming leads to long operation time, reduced molding efficiency, and low foaming ratio. Summary of the Invention

[0004] The purpose of this invention is to provide a method for manufacturing a lightweight face mask, which aims to improve the problems of low efficiency and poor foaming quality in existing methods that use molds for foaming.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for manufacturing a lightweight face mask, comprising the following steps:

[0006] Silicone rubber, silica, and silicone oil are fed into the first cylinder of a planetary roller extruder for mixing to obtain a mixture.

[0007] The mixture and vulcanizing agent are fed into the second cylinder of a planetary roller extruder for mixing to obtain a compound rubber;

[0008] The mold is heated to a first temperature and then maintained within a range of ±5°C. Supercritical fluid is then introduced into the mold cavity to complete the pretreatment.

[0009] The compound is fed into the cavity of the mold and supercritical fluid is injected again to regulate the pressure of the cavity, allowing the compound to undergo a saturation reaction with the supercritical fluid; or, the compound is fed into the third cylinder of a planetary roller extruder for heating and pressurization to complete the pre-vulcanization treatment, and then fed into the cavity of the mold.

[0010] The mold cavity is depressurized, and the mixed rubber after saturated reaction or pre-vulcanization is supercritically foamed to completely fill the mold cavity, thus obtaining a mask made of supercritical foamed silicone rubber material.

[0011] As a preferred step of the present invention, the silica is subjected to vacuum drying oven treatment to remove moisture before mixing;

[0012] Then, mix the materials in the first cylinder of the star-shaped roller extruder at 100-110°C for 10-30 minutes.

[0013] As a preferred step of the present invention, the vulcanizing agent is dicumyl peroxide, benzoyl peroxide, or bis(2,5)sulfide; the supercritical fluid is supercritical CO2 or supercritical N2.

[0014] The compound is mixed in the second roller cylinder of a planetary roller extruder at a temperature of 20-40°C for 8-20 minutes.

[0015] The thread inclination angle on the roll in the second roller cylinder is smaller than that on the first roller cylinder, so that the speed at which the compound is pushed in the second roller cylinder is smaller than that of the first roller cylinder.

[0016] The first roller cylinder and the second roller cylinder have a first temperature regulating cavity for regulating the temperature of the planetary roller cavity, and the wall thickness of the first temperature regulating cavity is 1 to 5 mm. A second temperature regulating cavity is provided at the center of the central screw.

[0017] As a preferred step of the present invention, the first temperature is 100-125°C, and the environmental pressure during the saturation reaction or pre-vulcanization treatment of the compound is 5-8 MPa.

[0018] As a preferred step of the present invention, the mold includes an upper mold and a lower mold having a mask cavity formed after mold closing, and a plurality of elastic ejection components for easy demolding;

[0019] The upper mold has an air inlet for supplying supercritical fluid into the cavity and an exhaust outlet for discharging gas on the non-forming critical area of ​​the neck.

[0020] The vent is formed in the micro vent groove at the edge of the mold parting surface. The micro vent grooves on the upper and lower molds form a conical vent after the mold is closed. The conical vent extends along the edge of the cavity to form a channel for accelerating venting.

[0021] The upper mold cavity is provided with a cylindrical limiting groove for pushing the cavity insert to move downward. The bottom surface of the cavity insert is provided with a protruding cylindrical block. The lower mold and the bottom surface of the cavity insert are fitted with a circular groove that matches the protruding cylindrical block.

[0022] As a preferred step of the present invention, after the compound is injected into the mold under supercritical fluid conditions, the supercritical fluid is filled into the cavity of the mold to 9-12 MPa within 10-20 seconds, and the compound undergoes a saturation reaction for 15-22 seconds.

[0023] The time for depressurizing the mold cavity to atmospheric pressure or zero gauge pressure is within 3 seconds, and the time for supercritical foaming of the compound is 40 to 45 seconds.

[0024] As a preferred step of the present invention, after obtaining the compound rubber, the compound rubber is conveyed to the third roller cylinder of the planetary roller extruder for heating and pressurization to complete the pre-vulcanization treatment, and then conveyed to the cavity of the mold.

[0025] As a preferred step of the present invention, supercritical fluid is continuously supplied into the mold during the pretreatment of the mold.

[0026] When the compound is delivered into the cavity of the mold, the mold outlet is closed, and supercritical fluid is continuously delivered for 10 to 20 seconds to saturate the compound with the supercritical fluid.

[0027] As a preferred step of the present invention, when obtaining the mixture, the first cylinder of the planetary roller extruder is heated to melt and mixed evenly;

[0028] When the mixture and vulcanizing agent are fed into the second cylinder of the planetary roller extruder for compounding, supercritical CO2 is introduced into the second cylinder for blending to obtain a polymer-supercritical CO2 homogeneous system.

[0029] The air pressure inside the second roller cylinder is 8-15 MPa.

[0030] As a preferred step of the present invention, after obtaining the face mask made of supercritical foamed silicone rubber material, the cavity of the mold is heated for 30 to 50 minutes at a temperature of 160 to 230°C.

[0031] Alternatively, the mask made of supercritical foamed silicone rubber material can be removed and placed in a heating mold with the same cavity, and heated for 10 to 15 minutes at a temperature of 160 to 230°C.

[0032] As a preferred step of the present invention, when the face mask is heated in the mold or heating mold, it is first subjected to complete vulcanization for 10 to 20 minutes, and the temperature of complete vulcanization is 160 to 180°C.

[0033] Then perform heat treatment for another 20 to 30 minutes at a temperature of 180 to 230°C;

[0034] The obtained products are tested using a dynamic thermomechanical analyzer to obtain the value of the number of bubbles and the average value of the bubble diameter. The average value is then calculated with a 90% to 96% distortion ratio to obtain the actual average value.

[0035] The cell density and porosity are calculated by using the number of cells and the average cell diameter.

[0036] The pore density value is less than 10. 8 cells / cm 3 If the heat treatment time is increased by 20-30 minutes, or the pre-vulcanization time is increased by 1-2 minutes; if the cell density value is greater than or equal to 10 8 cells / cm 3 If the product is qualified, then a qualified face mask will be obtained.

[0037] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0038] 1. The lightweight face mask manufacturing method disclosed herein employs a planetary roller extruder for mixing and compounding, with pre-vulcanization or saturation reaction using supercritical fluid for preliminary preparation. Subsequently, the prepared compound is injected into a mold. Injection can be performed by filling the mold with supercritical fluid, followed by a second filling with supercritical fluid to ensure a sufficient saturation reaction, thereby improving the subsequent foaming effect and achieving good filling. During depressurization foaming, the injection volume is controlled to achieve complete filling of the cavity, improving the quality and effect of foaming.

[0039] 2. The silicone rubber foam material prepared by the supercritical fluid foaming method disclosed herein has a smaller pore size than that of foam materials prepared by conventional methods. Furthermore, the preparation process of this method is not only environmentally friendly but also exhibits high safety and stability. Attached Figure Description

[0040] Figure 1 This is a flowchart of the manufacturing method of the lightweight face mask according to the present invention;

[0041] Figure 2 This is a block diagram of the manufacturing method of the lightweight face mask according to the present invention.

[0042] Figure 3 This is a schematic diagram of the structure of the present invention;

[0043] Figure 4 This is a schematic diagram of the upper mold structure of the present invention;

[0044] Figure 5 This is a schematic diagram of the upper mold structure of the present invention;

[0045] Figure 6 This is an enlarged cross-sectional view of the exhaust port structure of the present invention;

[0046] Figure 7 This is a schematic diagram of the lower mold structure of the present invention;

[0047] Figure 8 This is a schematic diagram of the lower mold structure of the present invention;

[0048] Figure 9 This is a schematic diagram of the cavity insert structure of the present invention;

[0049] In the picture:

[0050] 1. Upper mold, 2. Lower mold, 3. Spring ejector pin, 4. Conical vent hole, 5. Air inlet hole, 6. Cylindrical limiting groove, 7. Cavity insert, 8. Protruding cylindrical block, 9. Circular groove. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. Those skilled in the art will be able to understand the specific meaning of the above terms in the invention according to the specific circumstances.

[0053] Please refer to Figure 1 and Figure 2 As shown, this embodiment provides a method for manufacturing a lightweight face mask, including the following steps:

[0054] S101. Silicone rubber, silica, and silicone oil are fed into the first cylinder of a planetary roller extruder for mixing to obtain a mixture.

[0055] The planetary roller extruder disclosed herein can be an L-WE30 type planetary screw extruder. The planetary mixing system of the L-WE30 type planetary screw extruder consists of a central large screw, several planetary screws, and a barrel with internal helical teeth. The planetary screws mesh not only with the central screw but also with the barrel. For precise material temperature control, heating / cooling media are present on both the outer wall and the inner center of the barrel assembly. The temperature-controlling liquid efficiently and precisely controls the material temperature through a wall thickness of less than 2-4 mm. It can not only heat but also cool, achieving a relatively precise temperature control effect. This avoids excessively high or low temperatures, which can cause degradation and increased viscosity, or even solidification of the conveyed material.

[0056] Silicone oil helps improve the dispersibility of silica in the matrix, increases heterogeneous nucleation sites, and thus increases cell density. When the silicone oil content is 40 phr, the cell structure of the silicone rubber foam material is better. Compared with methyl vinyl silicone rubber (VMQ), methyl vinyl phenyl silicone rubber (PVMQ) has a larger free volume and a higher gas saturation concentration, so the cell morphology is not very dependent on the pre-curing time. Compared with fumed silica A200, the addition of precipitated silica T36-5 helps the gas to form heterogeneous nucleation sites in the matrix, thereby increasing the cell density of the silicone rubber foam material and reducing the cell size.

[0057] Specifically, in this disclosure, the silica is treated in a vacuum oven to remove moisture before mixing (e.g., at 120°C for 3 hours in a vacuum oven) to eliminate the influence of adsorbed moisture on its reinforcing effect in the matrix. Then, it is mixed in the first cylinder of a star-shaped roller extruder at 100–110°C (preferably 105°C) for 10–30 minutes (preferably 15 minutes). Mixing is achieved through a central large screw, several planetary screws, and a barrel with internal helical teeth. This involves repeated stretching and kneading between the tooth sides and in the radial gaps, cutting the materials (silicone rubber, silica, and silicone oil) into very thin layers of 2–3 mm. The material surface is constantly mixed and renewed, and the material engaged by the helical teeth flows back, forming a vortex, which is beneficial for lateral mixing. The 45° helix angle of the helical teeth ensures forward flow of the material, preventing accumulation in the planetary sections and giving them good self-cleaning properties, while simultaneously achieving efficient mixing.

[0058] S102. The mixture and vulcanizing agent are fed into the second cylinder of a planetary roller extruder for mixing to obtain a compound rubber.

[0059] The vulcanizing agent disclosed herein can be dicumyl peroxide, benzoyl peroxide, or bis(2,5-dimethyl)sulfide, etc., with dicumyl peroxide being preferred. Specifically, before entering the second roller cylinder, the mixture is kneaded in the first roller cylinder at 100-110°C (preferably 105°C), by heating the first roller cylinder of the planetary roller extruder until it melts and mixes evenly, and the kneading time is 8-20 minutes (preferably 10 minutes).

[0060] In the steps of this disclosure, the compounded rubber can be fed into the third roller cylinder of a planetary roller extruder for heating and pressurization to complete the pre-vulcanization treatment, and then conveyed into the mold cavity.

[0061] Specifically, supercritical CO2 is introduced into the third roller cylinder for blending. The compound is then placed in the third roller cylinder of a planetary roller extruder at a temperature of 20–40°C (preferably 25°C) and a pressure of 8–15 MPa (preferably 10 MPa) for 8–20 minutes (preferably 10 minutes) to allow the polymer and vulcanizing agent to react fully, obtaining a polymer-supercritical CO2 homogeneous system for subsequent foaming with appropriate supercritical CO2. Subsequently, the temperature and pressure are adjusted, and the compound is pre-vulcanized in the third roller cylinder at 125°C and 10 MPa for a duration preferably 6 minutes to complete the pre-vulcanization.

[0062] Furthermore, the first and second roller cylinders each contain a first temperature-regulating chamber for temperature control of the planetary roller cavity, with a wall thickness of 1-5 mm. A second temperature-regulating chamber is located at the center of the central screw. The first temperature-regulating chamber features a threaded tube structure, accommodating the flow of the temperature-regulating liquid (e.g., water) while providing stable support to the interior, ensuring structural strength, preventing deformation, and achieving good temperature regulation. The second temperature-regulating chamber is a pipe structure designed within the central screw to regulate its temperature, ensuring it remains at a constant temperature during mixing and preventing premature vulcanization due to localized overheating caused by frictional heat. The second temperature-regulating chamber is connected to an external temperature control system, achieving precise temperature control through a circulating medium, further improving mixing uniformity and process stability. This design effectively enhances the equipment's adaptability to high-viscosity materials and ensures temperature consistency in continuous production.

[0063] The thread inclination angle of the rollers in the second roller cylinder disclosed herein is smaller than that of the first roller cylinder. This results in the compound being moved at a slower speed in the second roller cylinder compared to the first roller cylinder. For example, the thread inclination angle of the rollers in the second roller cylinder can be between 30° and 55°, preferably 45°. This reduces the material's conveying rate in the second roller cylinder, prolonging its residence time between the rollers, which is beneficial for further shear dispersion and balanced heat conduction. Simultaneously, the precise clearance design between the inner wall of the second roller cylinder and the screw (this clearance range can be 2-3 mm) effectively improves the homogeneity and density of the compound, preventing air bubble retention and providing stable rheological properties for subsequent pre-vulcanization and foaming processes.

[0064] S103. After heating the mold to a first temperature and maintaining it within a range of ±5°C, supercritical fluid is filled into the mold cavity to complete the pretreatment. The supercritical fluid is either supercritical CO2 or supercritical N2; this disclosure selects supercritical CO2 for use.

[0065] Before using the mold, the mold should be preheated to a temperature of 100–125°C (i.e., a first temperature), plus a margin of 95–130°C, preferably 120°C, and maintained at this temperature. Simultaneously, air should be expelled from the mold cavity to ensure it is filled with supercritical fluid, thus eliminating the influence of air on the foaming of the compound.

[0066] Specifically, during the pretreatment of the mold, supercritical fluid is continuously supplied into the mold; when the compound is delivered into the mold cavity, the mold outlet is closed, and supercritical fluid is continuously supplied for 10 to 20 seconds, so that the compound reacts with the supercritical fluid at 120°C to achieve saturation.

[0067] S104. The compound is delivered to the cavity of the mold, and supercritical fluid is injected again to regulate the pressure of the cavity, so as to saturate the compound and the supercritical fluid.

[0068] In this disclosure, the mold pretreatment process involves injecting supercritical fluid. After the rubber compound is delivered to the mold cavity, supercritical fluid is injected again to adjust the air pressure in the cavity. That is, the ambient pressure of the mold during the saturation reaction of the rubber compound is 5-8 MPa, preferably 8 MPa. The pre-vulcanization time can be 5-8 minutes, preferably 6 minutes, to fully inject the supercritical fluid into the rubber compound and prepare it for the subsequent foaming process.

[0069] S105. Depressurize the mold cavity and perform supercritical foaming on the saturated reaction or pre-vulcanized rubber compound to completely fill the mold cavity and obtain a mask made of supercritical foamed silicone rubber material.

[0070] After the first saturation reaction is completed, this disclosure will fill the mold cavity with supercritical fluid within 10 to 20 seconds, and cause the pressure inside the cavity to rise to 9 to 12 MPa (preferably 10 MPa), thus completing the air pressure regulation.

[0071] Then, the mold cavity is depressurized to one atmosphere (i.e., the ambient pressure) or the gauge pressure is zero (in actual operation, the gauge pressure is within the range of 0 to 0.1 MPa, which meets the depressurization requirements). The depressurization time is within 3 seconds. Foaming is carried out by rapid depressurization, and the supercritical foaming of the compound is completed within 40 to 45 seconds to achieve the purpose of rapid foaming.

[0072] S106. After obtaining the face mask made of supercritical foamed silicone rubber material, heat the cavity of the mold for 30 to 50 minutes at a temperature of 160 to 230°C; or, take out the face mask made of supercritical foamed silicone rubber material and place it in a heated mold with the same cavity for 10 to 15 minutes at a temperature of 160 to 230°C.

[0073] This disclosure, through secondary heating, can further round out the foam cells, optimize the foam cell structure, and to a certain extent eliminate the internal stress of the material, improve the mechanical properties of the material, and further improve the quality of the product.

[0074] Specifically, when heating the mask in a mold or heated mold, it can first undergo complete vulcanization for 10 to 20 minutes at a temperature of 160 to 180°C (preferably 175°C); then undergo heat treatment for 20 to 30 minutes at a temperature of 180 to 230°C (preferably 220°C).

[0075] like Figure 3 , Figure 7 , Figure 8 and Figure 9 As shown; the mold provided in this embodiment has the following specific structure: both the upper mold 1 and the lower mold 2 are made of mold steel and the surface is nitrided to improve the mold hardness and corrosion resistance; after the upper mold 1 and the lower mold 2 are closed, a cavity is formed that perfectly matches the contour of the medical mask, ensuring the product size is accurate.

[0076] The elastic ejection assembly is disposed within the lower mold 2, including separable spring ejector pins 3 and cavity inserts 7. In this embodiment, six spring ejector pins 3 are evenly distributed in a circular array along the bottom of the cavity insert 7, with equal spacing to ensure force balance. Each spring ejector pin 3 includes a separable ejector pin portion and an ejection spring. Several limiting grooves for placing the ejection springs are provided on the plane where the lower mold 2 and the lower surface of the cavity insert 7 meet. The diameter of the limiting grooves is slightly larger than the outer diameter of the spring, with a difference between 0.5cm and 1cm, to facilitate easy compression and rebound of the ejection springs within the limiting grooves. The design ensures stable force transmission. The top of the ejector pin contacts the bottom of the cavity insert 7 during mold closing, while the bottom contacts the ejector spring. Initially, the ejector spring is installed in the limiting groove before the ejector pin is placed in. At this point, part of the ejector pin is positioned within the limiting groove for positioning and guidance, while the remaining portion protrudes outside the groove. During mold closing, the ejector pin is pressed down by the bottom of the cavity insert 7, compressing the ejector spring and achieving mold closing. Upon mold opening, the rebound force of the ejector spring, transmitted through the ejector pin, ejects the cavity insert 7 a short distance, thus demolding the mask. This structural design facilitates installation and subsequent replacement of the spring-loaded ejector pin 3. Furthermore, it is functionally simple, enabling the ejection of the mask product at extremely low cost, avoiding the damage to the mask that can occur with traditional demolding methods.

[0077] The bottom surface of the cavity insert 7 is provided with a protruding cylindrical block 8. The plane of the lower mold 2 that is in contact with the bottom surface of the cavity insert 7 is provided with a circular groove 9 that is adapted to the protruding cylindrical block 8, so as to realize the initial positioning of the cavity insert 7 during installation and improve the stability of the overall mold closing.

[0078] like Figure 5 As shown, the neck of the upper mold 1, which is not a critical forming area, has two air inlets 5, which are symmetrically distributed and have a diameter of 1.8 mm. They are sealed to the air injection pipe of the supercritical foaming equipment to ensure that the supercritical fluid is injected into the cavity evenly.

[0079] like Figure 4 and Figure 6 As shown, the parting surface edge of the mold has micro-venting grooves. The micro-venting grooves on the upper mold 1 and the lower mold 2 form a conical venting hole 4 after the mold is closed. There are four conical venting holes 4, which extend in the four directions of east, south, west and north respectively. The conical venting holes 4 extend continuously along the edge of the cavity until they are connected to the outside of the mold. The inner diameter of the conical venting hole 4 is 0.2 mm and the outer diameter is 1.2 mm. The inner side is connected to the cavity and the outer side is connected to the atmosphere, so as to achieve efficient venting and prevent overflow.

[0080] like Figure 5 , Figure 8 and Figure 9As shown, the inner top of the upper mold 1 is integrally formed with a cylindrical limiting groove 6. The axis of the cylindrical limiting groove 6 coincides with the central axis of the cavity insert 7. When the mold is closed, the cylindrical limiting groove 6 can accurately act on the center of the cylindrical part at the top of the cavity insert 7, pushing the cavity insert 7 to move smoothly downward; as Figure 5 and Figure 6 A protruding cylindrical block 8 can be further provided on the bottom surface of the cavity insert 7. A circular groove 9 can be further formed on the plane where the lower mold 2 and the bottom surface of the cavity insert 7 meet, so as to achieve the initial positioning of the cavity insert 7 during installation and improve the stability of the overall mold closing. The cavity insert 7 is made of hard alloy material, and its forming surface is mirror polished to reduce the adhesion between the forming mask and the cavity insert 7, improve the smoothness of demolding and the surface finish of the product.

[0081] The working process of this embodiment is as follows:

[0082] Placement of the blank: Place the foam material blank into the cavity of the upper mold 1. The size of the blank should be slightly smaller than that of the cavity to ensure that there is room for expansion after the mold is closed.

[0083] Mold closing: Control the upper mold 1 to move downward. After the cylindrical limiting groove 6 contacts the top of the cavity insert 7, push the cavity insert 7 to move downward in the vertical direction. The spring ejector pin 3 is compressed until the bottom of the cavity insert 7 fits with the inner positioning surface of the lower mold 2. The parting surfaces of the upper mold 1 and the lower mold 2 fit tightly together, and the cavity is closed.

[0084] Supercritical foaming: The supercritical foaming equipment injects supercritical CO2 fluid into the mold cavity through the air inlet 5. The supercritical fluid penetrates the green body evenly and causes it to expand and fill the mold cavity. The air and excess fluid inside the mold cavity are discharged through the conical exhaust hole 4. At the same time, the foaming process is carried out according to the conventional foaming parameters.

[0085] Demolding: After foaming is completed, control the upper mold 1 to move upward. After the cylindrical limiting groove 6 is disengaged from the cavity insert 7, the top of the cavity insert 7 loses the downward pressure. At this time, multiple spring ejector pins 3 rebound simultaneously, pushing the cavity insert 7 to move upward a small distance. The cavity insert 7 drives the molding mask to disengage from the cavity of the lower mold 2. The operator can directly remove the mask to complete one molding cycle.

[0086] Through the above structural design, this embodiment achieves convenient demolding, efficient exhaust, and uniform air intake in the supercritical foaming molding of medical masks, thereby effectively improving production efficiency.

[0087] In this disclosure, the obtained product is tested using a dynamic thermomechanical analyzer to obtain the average number of bubbles and the average bubble diameter. The average value is then adjusted for a 90%–96% distortion rate to obtain the actual average value. The bubble density and porosity are calculated using the average number of bubbles and the average bubble diameter. A bubble density value less than 10... 8cells / cm 3 If necessary, increase the heat treatment time by 20-30 minutes. This ensures that if any defects occur during each production process, adjustments can be made promptly; alternatively, it allows for the identification of structural defects in the equipment for maintenance. If the cell density value is greater than or equal to 10... 8 cells / cm 3 If the heat treatment or pre-vulcanization time is longer, a qualified product mask is obtained. It should also be noted that a longer heat treatment or pre-vulcanization time does not necessarily mean a higher cell density. This is because a higher cell density means that the bubble nucleation rate is faster and the distribution is more uniform during the foaming process, which in turn improves the structural density and mechanical properties of the product. Masks made in this way fit the facial contours better when worn, effectively improving sealing and comfort.

[0088] Specifically, the temperature and time curves of the vulcanization of silicone rubber compound were determined using a Dynamic Thermomechanical Analyzer (DMA) RSA-Ⅲ; the cell morphology of the microporous foamed silicone rubber samples was characterized and analyzed using a scanning electron microscope (SEM); the cell diameter and number of cells in the foamed samples were determined using ImageJ software, and the cell density was calculated using a formula.

[0089] The cell density N of the microporous foamed silicone rubber sample was calculated using the following formula:

[0090] N=(n / A) 3 / 2 ×(1 / 1-V f );

[0091] Where n is the number of cells in the SEM image, and A is the actual area of ​​the SEM image (cm²). 2 ), V f The porosity of the foamed sample is defined as:

[0092] V f =1-P f / P;

[0093] Where P f P represents the density of the fully vulcanized sample after foaming (g / cm3), and P represents the density of the unfoamed fully vulcanized rubber strip (g / cm3).

[0094] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included 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 method for manufacturing a lightweight face mask, characterized in that, Includes the following steps: Silicone rubber, silica, and silicone oil are fed into the first cylinder of a planetary roller extruder for mixing to obtain a mixture. The mixture and vulcanizing agent are fed into the second cylinder of a planetary roller extruder for mixing to obtain a compound rubber; The mold is heated to a first temperature and maintained within ±5°C. Supercritical fluid is then introduced into the mold cavity to complete the pretreatment. The first temperature is 100–125°C. The compound is fed into the cavity of the mold, and supercritical fluid is injected again to regulate the pressure of the cavity, so that the compound and supercritical fluid can undergo a saturation reaction. The mold cavity is depressurized, and the saturated reaction compound is subjected to supercritical foaming to completely fill the mold cavity, thereby obtaining a mask made of supercritical foamed silicone rubber material. After the compound is injected into the mold under supercritical fluid conditions, the supercritical fluid is filled into the cavity of the mold to 9-12 MPa within 10-20 seconds, and the compound undergoes a saturation reaction for 15-22 seconds. The time for depressurizing the mold cavity to atmospheric pressure or zero gauge pressure is within 3 seconds, and the time for supercritical foaming of the compound is 40 to 45 seconds.

2. The method for manufacturing a lightweight face mask according to claim 1, characterized in that: Before mixing, the silica is subjected to vacuum drying oven treatment to remove moisture; And mix them in the first cylinder of the planetary roller extruder at a temperature of 100-110°C for 10-30 minutes; The planetary roller extruder has flow channels on the rolls for the compound to flow through; The ambient pressure during the saturation reaction of the compound is 5-8 MPa.

3. The method for manufacturing a lightweight face mask according to claim 2, characterized in that: The vulcanizing agent is dicumyl peroxide, benzoyl peroxide, or bis(2,5)sulfide, and the supercritical fluid is supercritical CO2 or supercritical N2. The compound is mixed in the second cylinder of a planetary roller extruder at a temperature of 20-40°C for 8-20 minutes. The thread inclination angle on the roll in the second roller cylinder is smaller than that on the first roller cylinder, so that the speed at which the compound is pushed in the second roller cylinder is smaller than that of the first roller cylinder. The first roller cylinder and the second roller cylinder have a first temperature regulating cavity for regulating the temperature of the planetary roller cavity, and the wall thickness of the first temperature regulating cavity is 1 to 5 mm. A second temperature regulating cavity is provided at the center of the central screw.

4. The method for manufacturing a lightweight face mask according to claim 1, characterized in that: The mold includes an upper mold and a lower mold that form a mask cavity after mold closing, as well as multiple elastic ejection components for easy demolding; The upper mold has an air inlet for supplying supercritical fluid into the cavity and an exhaust outlet for discharging gas on the non-forming critical area of ​​the neck. The vent is formed in the micro vent groove at the edge of the mold parting surface. The micro vent grooves on the upper and lower molds form a conical vent after the mold is closed. The conical vent extends along the edge of the cavity to form a channel for accelerating venting. The upper mold cavity is provided with a cylindrical limiting groove for pushing the cavity insert to move downward. The bottom surface of the cavity insert is provided with a protruding cylindrical block. The lower mold and the bottom surface of the cavity insert are fitted with a circular groove that matches the protruding cylindrical block.

5. The method for manufacturing a lightweight face mask according to claim 1, characterized in that: After obtaining the compound rubber, the compound rubber is conveyed to the third roller cylinder of the planetary roller extruder for heating and pressurization to complete the pre-vulcanization treatment, and then conveyed to the cavity of the mold.

6. The method for manufacturing a lightweight face mask according to claim 1, characterized in that, During the pretreatment of the mold, supercritical fluid is continuously supplied into the mold; When the compound is delivered into the cavity of the mold, the mold outlet is closed, and supercritical fluid is continuously delivered for 10 to 20 seconds to saturate the compound with the supercritical fluid.

7. The method for manufacturing a lightweight face mask according to claim 1, characterized in that, In obtaining the mixture, the first cylinder of the planetary roller extruder is heated to melt and mixed evenly; When the mixture and vulcanizing agent are fed into the second cylinder of the planetary roller extruder for compounding, supercritical CO2 is introduced into the second cylinder for blending to obtain a polymer-supercritical CO2 homogeneous system. The air pressure inside the second roller cylinder is 8-15 MPa.

8. The method for manufacturing a lightweight face mask according to claim 1, characterized in that, After obtaining the face mask made of supercritical foamed silicone rubber material, the mold cavity is heated for 30 to 50 minutes at a temperature of 160 to 230°C. Alternatively, the mask made of supercritical foamed silicone rubber material can be removed and placed in a heating mold with the same cavity, and heated for 10 to 15 minutes at a temperature of 160 to 230°C.

9. The method for manufacturing a lightweight face mask according to claim 8, characterized in that, When the face mask is heated in the mold or heating mold, it first undergoes complete vulcanization for 10 to 20 minutes at a temperature of 160 to 180°C. Then perform heat treatment for another 20 to 30 minutes at a temperature of 180 to 230°C; The obtained products are tested using a dynamic thermomechanical analyzer to obtain the value of the number of bubbles and the average value of the bubble diameter. The average value is then calculated with a 90% to 96% distortion ratio to obtain the actual average value. The cell density and porosity are calculated by using the number of cells and the average cell diameter. The pore density value is less than 10. 8 cells / cm 3 If the heat treatment time is increased by 20-30 minutes, or the pre-vulcanization time is increased by 1-2 minutes; if the cell density value is greater than or equal to 10 8 cells / cm 3 If the product is qualified, then a qualified face mask will be obtained.

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