Manufacturing method of light mask

Abstract

The invention relates to the field of porous or honeycomb products or materials processed from macromolecular substances, and provides a manufacturing method of a lightweight mask, which comprises the following steps: conveying silicone rubber, white carbon black and silicone oil into a first roller cylinder of a planetary roller extruder for mixing to obtain a mixture; conveying the mixture and the vulcanizing agent into a second roller cylinder for mixing to obtain a rubber compound; the mold is heated and filled with supercritical fluid; conveying the rubber compound into a cavity of a mold, filling the supercritical fluid again to adjust the pressure of the cavity, and carrying out saturation reaction on the rubber compound and the supercritical fluid; or the rubber compound is conveyed into a third roller cylinder to be subjected to pre-vulcanization treatment of heating and pressurizing and then conveyed into a cavity of a mold to be subjected to pressure relief, supercritical foaming is carried out on the rubber compound subjected to saturation reaction or pre-vulcanization treatment, and the purpose of completely filling the cavity is achieved by controlling the injection amount. And the high-quality mask made of the supercritical foaming silicone rubber material is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of processing high molecular substances into porous or honeycomb products or materials, and in particular to a manufacturing method of a lightweight mask. BACKGROUND

[0002] Silicone rubber foam is a kind of porous polymer material, which has excellent comprehensive performance and is widely used in electronic industry, chemical industry, aerospace and other fields. However, the traditional foaming method has the problems of uneven cell size and environmental pollution caused by the commonly used organic foaming agent.

[0003] In the process of implementing the present application, the inventors found that the foaming performance of silicone rubber is directly affected by the pre-vulcanization time, additives (such as silicone oil), foaming temperature and foaming pressure, etc., which directly affect the foaming quality or effect of silicone rubber. However, the existing thermoplastic polymer as a matrix in the foaming process, it is found that the chemical foaming method has the problem of environmental pollution, so subsequent treatment is needed, which increases the survival cost. Moreover, the existing material made by autoclave needs to be treated in the later stage, and the process is more. At the same time, the existing foaming preparation process has the problems of low permeation efficiency of the polymer matrix, the existing foaming is affected by the mold space, the polymer melt filling cavity process suffers from large shear force, resulting in poor foaming filling effect; and the operation time is long by mold heating induction foaming, the forming efficiency is reduced, and the foaming ratio is low. SUMMARY

[0004] The present application aims to provide a manufacturing method of a lightweight mask, which aims to improve the problems of low foaming efficiency and poor foaming quality of the existing mold.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: a manufacturing method of a lightweight mask, comprising the following steps: The silicone rubber, white carbon black and silicone oil are transported to the first roller cylinder of the planetary roller extruder for mixing to obtain a mixture; The mixture and the vulcanizing agent are transported to the second roller cylinder of the planetary roller extruder for mixing to obtain a mixed rubber; The mold is heated to a first temperature and kept within a range of ±5℃, and a supercritical fluid is filled into the cavity of the mold to complete the pretreatment; The mixed rubber is transported to the cavity of the mold, and the supercritical fluid is filled again for pressure adjustment of the cavity, and the mixed rubber and the supercritical fluid are saturated; or the mixed rubber is transported to the third roller cylinder of the planetary roller extruder for heating and pressurizing to complete the pre-vulcanization treatment, and then transported to the cavity of the mold; The mold cavity is depressurized, and the mixed rubber after saturation reaction or pre-vulcanization treatment is supercritically foamed to completely fill the mold cavity, so that a mask of supercritically foamed silicone rubber material is obtained.

[0006] As a preferred step of the present application, the white carbon black is subjected to vacuum oven treatment to remove moisture before mixing; And in the first roller cylinder of the star roller extruder, mixing is carried out at 100-110℃ for 10-30 minutes.

[0007] As a preferred step of the present application, the vulcanizing agent is dicumyl peroxide, benzoyl peroxide or bis-dipentasulfide agent; and the supercritical fluid is supercritical CO2 or supercritical N2. In the second roller cylinder of the star roller extruder, mixing is carried out at 20-40℃ for 8-20 minutes. The thread inclination angle of the roller in the second roller cylinder is smaller than that of the first roller cylinder, so that the moving speed of the mixed rubber 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 temperature regulation of the planetary roller cavity, and the wall thickness of the first temperature regulating cavity is 1-5mm, and the center of the center screw is provided with a second temperature regulating cavity.

[0008] As a preferred step of the present application, the first temperature is 100-125℃, and the environmental pressure during saturation reaction or pre-vulcanization treatment of the mixed rubber is 5-8MPa.

[0009] As a preferred step of the present application, the mold comprises an upper mold and a lower mold which form a mask cavity after closing, and a plurality of elastic ejection assemblies for facilitating demolding; The neck of the upper mold has an air inlet hole for providing supercritical fluid into the cavity and an air outlet hole for discharging gas on a non-shaped key area; The air outlet hole is provided in a micro air outlet groove at the edge of the mold parting surface, and the micro air outlet grooves on the upper mold and the lower mold form a conical air outlet hole after closing, which extends along the edge of the cavity to form a channel for accelerating air exhaust; The cavity of the upper mold is provided with a cylindrical limiting groove for pushing the cavity insert to move downward, and the lower bottom surface of the cavity insert is provided with a protruding cylindrical block, and the plane of the lower mold which is in close contact with the lower bottom surface of the cavity insert is provided with a circular groove which is matched with the protruding cylindrical block.

[0010] As a preferred step of the present application, after the mixed rubber is injected into the mold filled with supercritical fluid, the supercritical fluid in the cavity of the mold is filled to 9-12MPa within 10-20 seconds, and the saturation reaction of the mixed rubber is carried out for 15-22 seconds. The time length for pressure relief of the mold cavity to normal pressure or zero gauge pressure is less than 3 seconds, and the time length for supercritical foaming of the rubber compound is 40-45 seconds.

[0011] As a preferred step of the present application, after obtaining the rubber compound, the rubber compound is transported into the third roller cylinder of the planetary roller extruder for heating and pressurization, to complete the pre-vulcanization treatment, and is transported into the cavity of the mold.

[0012] As a preferred step of the present application, when the mold is pre-treated, the supercritical fluid is continuously transported into the mold; When the rubber compound is transported into the cavity of the mold, the output port of the mold is closed, and the supercritical fluid is continuously transported for 10-20 seconds to saturate the rubber compound with the supercritical fluid.

[0013] As a preferred step of the present application, when the mixture is obtained, the first roller cylinder of the planetary roller extruder is heated to melt and mix uniformly; When the mixture and the vulcanizing agent are transported into the second roller cylinder of the planetary roller extruder for mixing, the supercritical CO2 is filled into the second roller cylinder for blending, to obtain a polymer-supercritical CO2 homogeneous system; The air pressure in the second roller cylinder is 8-15 MPa.

[0014] As a preferred step of the present application, after the face mask of the supercritical foaming silicone rubber material is obtained, the cavity of the mold is heated for 30-50 minutes, and the heating temperature is 160-230°C; Alternatively, the face mask of the supercritical foaming silicone rubber material is taken out and placed in a heated mold with the same cavity, and is heated for 10-15 minutes, and the heating temperature is 160-230°C.

[0015] As a preferred step of the present application, when the face mask is heated in the mold or the heated mold, the face mask is first fully vulcanized for 10-20 minutes, and the temperature for full vulcanization is 160-180°C; Then, the face mask is heat treated for 20-30 minutes, and the temperature for heat treatment is 180-230°C; The obtained product is detected by a dynamic mechanical analyzer to obtain the value of the cell number and the mean value of the cell diameter, and the mean value is calculated by a 90%-96% distortion ratio to obtain an actual mean value; The cell density value and the void ratio are calculated by the value of the cell number and the mean value of the cell diameter; The cell density value is less than 10 8 cells / cm 3If the cell density value is less than 8 cells / cm2, then 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 cells / cm2, then a qualified product mask is obtained. 8 cells / cm 3 If the cell density value is less than 8 cells / cm2, then 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 cells / cm2, then a qualified product mask is obtained.

[0016] Compared with the background art, the present application has the following advantages: 1. The manufacturing method of the lightweight mask of the present disclosure adopts a process of mixing and mixing by a planetary roller extruder, and realizes the preparation treatment in the early stage by pre-vulcanization or saturation reaction of a supercritical fluid. Then, the mixing rubber after the treatment is injected into a mold, which can be injected after the mold is filled with a supercritical fluid, and then the saturation reaction can be fully performed when the supercritical fluid is filled again, so as to improve the subsequent foaming effect and form a good filling purpose. Then, by controlling the amount of injection, the purpose of completely filling the cavity is achieved, and the quality and effect of foaming are improved.

[0017] 2. The silicone rubber foam material prepared by the supercritical fluid foaming method of the present disclosure has a smaller cell diameter than the foam material prepared by a traditional method. Moreover, the preparation process of the method has no pollution to the environment, and the safety and stability are relatively high. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The flow chart of the manufacturing method of the lightweight mask of the present disclosure; Figure 2 The module block diagram of the manufacturing method of the lightweight mask of the present disclosure.

[0019] Figure 3 The structure diagram of the present disclosure; Figure 4 The upper die structure diagram of the present disclosure; Figure 5 The upper die structure diagram of the present disclosure; Figure 6 The enlarged structure diagram of the exhaust hole of the present disclosure; Figure 7 The lower die structure diagram of the present disclosure; Figure 8 The lower die structure diagram of the present disclosure; Figure 9 The cavity insert structure diagram of the present disclosure; In the figure: 1, upper die, 2, lower die, 3, spring needle, 4, conical exhaust hole, 5, air inlet hole, 6, cylindrical limiting groove, 7, cavity insert, 8, protruding cylindrical block, 9, circular groove. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0021] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise, and it should also be understood that, when the terms "comprise" and / or "include" are used in the specification, there is a presence of a feature, step, operation, device, component and / or combination thereof. The specific meaning of the above terms in the present application can be understood by those skilled in the art according to the specific circumstances.

[0022] Please refer to Figure 1 and Figure 2 The present embodiment provides a manufacturing method of a lightweight mask, comprising the following steps: S101, silicon rubber, white carbon black and silicone oil are transported into the first roller cylinder of the planetary roller extruder for mixing to obtain a mixture.

[0023] The planetary roller extruder of the present disclosure can be an L-WE30 type planetary screw extruder. The planetary mixing system of the L-WE30 type planetary screw extruder is composed of one center large screw, several planetary screws and a barrel with internal helical teeth. The planetary screws are not only meshed with the center screw, but also meshed with the barrel. For precise temperature control of the material passing through the outer wall and the internal center of the barrel assembly, the temperature control liquid passes through the wall with a thickness of less than 2-4 mm to precisely control the material temperature. Not only heating, but also cooling can be performed to achieve a relatively precise temperature control effect. Avoiding too high or too low temperature can respectively cause degradation and increase in viscosity, or even cause solidification of the transported material.

[0024] Silicone oil helps to improve the dispersibility of white carbon black in the matrix, increase the heterogeneous nucleation point, and thus increase the cell density. When the content of silicone oil is 40 phr, the cell structure of the silicone rubber foam material is better. Compared with methyl vinyl silicone rubber (VMQ), the free volume in methyl vinyl phenyl silicone rubber (PVMQ) is larger, and the saturation concentration of gas is high, so the dependence of cell morphology on pre-vulcanization time is not large. Compared with fumed silica A200, the addition of precipitated silica T36-5 helps to heterogeneous nucleation of gas in the matrix, thereby increasing the cell density and reducing the cell diameter of the silicone rubber foam material.

[0025] Specifically, the white carbon black in the present disclosure is subjected to vacuum oven treatment to remove moisture before mixing (for example, treated at 120°C for 3 hours in a vacuum oven), so as to eliminate the influence of the adsorbed moisture in the white carbon black on the reinforcing effect thereof in the matrix, and then mixed in the first roller cylinder of the planetary roller extruder at 100-110°C (preferably 105°C) for 10-30 minutes (preferably 15 minutes). The material (silicone rubber, white carbon black and silicone oil) is sheared into a very thin layer of 2-3 mm by mixing in a central large screw, a plurality of planetary screws and a barrel with internal helical teeth, that is, subjected to repeated stretching and kneading between the tooth flanks and in the radial gap, the material surface is constantly mixed and updated, the material engaged by the helical teeth flows back, forming a vortex, which is conducive to transverse mixing. The helical angle of the helical teeth is 45°, which can ensure the forward flow of the material and avoid accumulation of the material in the planetary section, so that the planetary section has good self-cleaning performance and achieves the purpose of high-efficiency mixing.

[0026] S102, conveying the mixture and the vulcanizing agent to the second roller cylinder of the planetary roller extruder for mixing to obtain a mixed rubber.

[0027] The vulcanizing agent of the present disclosure can be dicumyl peroxide, benzoyl peroxide or bis-dipentasulfur, etc., and preferably dicumyl peroxide. Specifically, the mixture is mixed at 100-110°C (preferably 105°C) in the first roller cylinder before entering the second roller cylinder, the first roller cylinder of the planetary roller extruder is heated to melt and mix uniformly, and the mixing time is 8-20 minutes (preferably 10 minutes).

[0028] In the step of the present disclosure, the mixed rubber can be conveyed to the third roller cylinder of the planetary roller extruder for heating and pressurizing to complete the pre-vulcanization treatment, and then conveyed to the cavity of the mold Specifically, the mixed rubber is mixed in the third roller cylinder of the planetary roller extruder at a temperature of 20-40°C (preferably 25°C) and a gas pressure of 8-15 MPa (preferably 10 MPa) for 8-20 minutes (preferably 10 minutes) by filling supercritical CO2 in the third roller cylinder, so that the polymer and the vulcanizing agent are fully reacted to obtain a polymer-super critical CO2 homogeneous system, so as to facilitate subsequent filling of the corresponding supercritical CO2 for foaming. Then, the temperature and pressure are adjusted, and the mixed rubber is subjected to pre-vulcanization treatment at 125°C and 10 MPa in the third roller cylinder, and the pre-vulcanization time can be preferably 6 minutes.

[0029] Further, the first roller cylinder and the second roller cylinder have a first temperature regulating cavity for temperature regulation of the planetary roller cavity, and the wall thickness of the first temperature regulating cavity is 1-5 mm, and the center of the central screw is provided with a second temperature regulating cavity, the first temperature regulating cavity can be designed as a threaded pipe structure, which can not only meet the flow of temperature regulating liquid (such as water), but also can form a stable support inside the temperature regulating cavity, guarantee the structural strength, prevent deformation, and also achieve good temperature regulation effect. The second temperature regulating cavity is a pipeline structure designed in the central screw to regulate the temperature of the central screw, so as to ensure that the central screw maintains a constant temperature state during the mixing process, and avoids the local overheating of the material caused by friction to cause premature vulcanization. The second temperature regulating cavity is in communication with an external temperature control system, and precise temperature control is realized through circulating medium, further improving the mixing uniformity and process stability. The design effectively enhances the adaptability of the equipment to high-viscosity materials and guarantees the temperature consistency in continuous production.

[0030] The thread inclination angle of the roller in the second roller cylinder of the present disclosure is smaller than that of the first roller cylinder, so that the speed of pushing the rubber compound to move in the second roller cylinder is smaller than that of the first roller cylinder, for example, the thread inclination angle of the roller in the second roller cylinder can be between 30°-55°, preferably 45°, so as to reduce the conveying rate of the material in the second roller cylinder, prolong the residence time of the material between the rollers, and be beneficial to further shear dispersion and heat conduction balance. At the same time, cooperating with the precise gap design of the inner wall of the second roller cylinder and the screw (the gap range can be 2-3 mm), the homogeneity and density of the rubber compound can be effectively improved, and the gas bubble retention is avoided, so as to provide stable rheological property guarantee for the subsequent pre-vulcanization and foaming process.

[0031] S103, heat the mold to a first temperature and keep it within a range of plus or minus 5°C, and fill the mold cavity with supercritical fluid to complete the pretreatment. The supercritical fluid is supercritical CO2 or supercritical N2, and the present disclosure selects supercritical CO2 for use.

[0032] The present disclosure requires heating the mold before using the mold, so that the temperature of the mold is 100-125°C (i.e. the first temperature), plus or minus 95-130°C, preferably 120°C, and is kept at this temperature. At the same time, the air in the mold cavity needs to be discharged, and the mold cavity needs to be filled with supercritical fluid to eliminate the influence of air on the foaming of the rubber compound.

[0033] Specifically, when the mold is pretreated, the supercritical fluid is continuously fed into the mold; when the rubber compound is fed into the mold cavity, the output port of the mold is closed, and the supercritical fluid is continuously fed for 10-20 seconds, so that the rubber compound is saturated with the supercritical fluid at 120°C.

[0034] S104, the rubber compound is transported into the cavity of the mold, and the supercritical fluid is filled again to adjust the pressure of the cavity, and the rubber compound and the supercritical fluid are saturated.

[0035] In the present disclosure, when the mold is pretreated by filling the supercritical fluid, the supercritical fluid will be filled again to adjust the pressure of the cavity after the rubber compound is transported into the cavity, that is, the environmental pressure of the mold during the saturation reaction of the rubber compound is 5-8 MPa, preferably 8 MPa, and the pre-vulcanization time can be 5-8 min, preferably 6 min, so as to fully fill the supercritical fluid into the rubber compound and prepare for the subsequent foaming process.

[0036] S105, the mold cavity is depressurized, and the rubber compound after the saturation reaction or pre-vulcanization treatment is supercritically foamed to completely fill the mold cavity, so as to obtain a mask of supercritically foamed silicone rubber material.

[0037] In the present disclosure, after the first saturation reaction is completed, the supercritical fluid is filled into the cavity of the mold within 10-20 seconds, and the pressure in the cavity is increased to 9-12 MPa (preferably 10 MPa), so as to complete the adjustment of the gas pressure.

[0038] Then, the mold cavity is depressurized to an atmospheric pressure (i.e. the normal pressure of the environment) or a gauge pressure of zero (in actual operation, the gauge pressure is in the range of 0-0.1 MPa, which meets the requirement of depressurization), and the depressurization time is within 3 seconds. The foaming is carried out by rapid depressurization, and the supercritical foaming of the rubber compound is completed within 40-45 seconds, so as to achieve the purpose of rapid foaming.

[0039] S106, after obtaining the mask of supercritically foamed silicone rubber material, the cavity of the mold is heated for 30-50 minutes, and the heating temperature is 160-230℃; or the mask of supercritically foamed silicone rubber material is taken out and placed in a heated mold with the same cavity, and heated for 10-15 minutes, and the heating temperature is 160-230℃.

[0040] After the second heating in the present disclosure, the cell can be further rounded, the cell structure can be optimized, the internal stress of the material can be eliminated to a certain extent, the mechanical properties of the material can be improved, and the quality of the product can be further improved.

[0041] Specifically, when the mask is heated in the mold or the heated mold, the mask is first fully vulcanized for 10-20 minutes, and the fully vulcanized temperature is 160-180℃ (preferably 175℃); and then the mask is heat treated for 20-30 minutes, and the heat treatment temperature is 180-230℃ (preferably 220℃).

[0042] As Figure 3 ,Figure 7 、 Figure 8 and Figure 9 ; the mold provided by the embodiment has the following specific structure: the upper mold 1 and the lower mold 2 are both made of mold steel, and the surfaces thereof are subjected to nitriding treatment to improve the hardness and corrosion resistance of the molds; the upper mold 1 and the lower mold 2 form a cavity that completely matches the contour of the medical mask after being combined, thereby ensuring the accuracy of the product size.

[0043] The elastic ejection assembly is arranged in the lower mold 2 and includes separable spring ejectors 3 and a cavity insert 7; in this embodiment, the spring ejectors 3 are arranged in an annular array on the bottom of the cavity insert 7, and the interval between the spring ejectors 3 is equal, thereby ensuring force balance; the spring ejector 3 includes a separable ejector portion and an ejection spring; a plurality of limiting grooves for placing the ejection spring are arranged on the plane of the lower mold 2 that is in contact with the lower plane of the cavity insert 7, the diameter of the limiting groove is slightly larger than the outer diameter of the spring, and the difference is between 0.5 cm and 1 cm, so that the ejection spring can be easily compressed and rebounded in the limiting groove, and the stable transmission direction of the force is ensured; the top end of the ejector portion is in contact with the bottom of the cavity insert 7 when the mold is combined, and the bottom end is in contact with the ejection spring; when the mold is first installed, the ejection spring is installed in the limiting groove, and then the ejector portion is placed in the limiting groove; at this time, the ejector portion is partially located in the limiting groove to play a positioning and guiding role, and is partially exposed outside the limiting groove to be pressed by the bottom of the cavity insert 7 when the mold is combined, thereby compressing the ejection spring, achieving mold combination, and when the mold is opened, the rebounding force of the ejection spring is transmitted to the ejector portion to eject the cavity insert 7 by a small distance, thereby achieving the demolding of the mask. Through the structure design, on the one hand, the installation is convenient, and the spring ejector 3 is also easy to replace; on the other hand, the function is easy to implement, and the ejection of the mask product can be achieved through a very low-cost structure, thereby avoiding the problem of mask damage caused by the traditional demolding mode.

[0044] The lower bottom surface of the cavity insert 7 is provided with a protruding cylindrical block 8, and the plane of the lower mold 2 that is in contact with the lower bottom surface of the cavity insert 7 is provided with a circular groove 9 that is matched with the protruding cylindrical block 8, thereby achieving the preliminary positioning of the cavity insert 7 during installation and improving the stability during overall mold combination.

[0045] As shown in Figure 5 , the neck portion of the upper mold 1 is provided with air inlet holes 5 in a non-molding key area, the number of the air inlet holes 5 is two, the air inlet holes 5 are symmetrically distributed, the hole diameter is 1.8 mm, the air inlet holes 5 are sealingly connected with the gas injection pipeline of the supercritical foaming device, and the supercritical fluid is uniformly injected into the cavity.

[0046] As shown in Figure 4 and Figure 6As shown, the parting surface edge of the mold is provided with a micro exhaust groove, and the micro exhaust grooves on the upper mold 1 and the lower mold 2 form a conical exhaust hole 4 after the mold is closed. The conical exhaust hole 4 has four numbers, respectively extending to the southeast, southwest and northwest, and the conical exhaust hole 4 continuously extends along the cavity edge until it communicates with the outside of the mold. The inner diameter of the conical exhaust hole 4 is 0.2mm, and the outer diameter is 1.2mm. The inner side communicates with the cavity, and the outer side communicates with the atmosphere, realizing efficient exhaust and preventing material overflow.

[0047] As shown in Figure 5 , Figure 8 and Figure 9 , the inner top of the upper mold 1 is integrally formed with a cylindrical limiting groove 6, and the axis of the cylindrical limiting groove 6 coincides with the center axis of the cavity insert 7. When the mold is closed, the cylindrical limiting groove 6 can precisely act on the center of the cylindrical part at the top of the cavity insert 7, and push the cavity insert 7 to move downward stably. Figure 5 and Figure 6 , the lower bottom surface of the cavity insert 7 can be further provided with a protruding cylindrical block 8. The lower mold 2 is further provided with a circular groove 9 on the plane which is in close contact with the lower bottom surface of the cavity insert 7, so as to realize the preliminary positioning of the cavity insert 7 during installation and improve the stability during overall mold closing. The cavity insert 7 is made of hard alloy material, and the forming surface is mirror polished to reduce the adhesion between the forming surface cover and the cavity insert 7, and to improve the smoothness of demolding and the surface finish of the product.

[0048] The working process of the embodiment is as follows: Green body placement: the foaming material green body is placed in the cavity inside the upper mold 1, and the size of the green body is slightly smaller than the cavity to ensure that there is expansion space after the mold is closed.

[0049] Mold closing: the upper mold 1 is controlled to move downward, and after the cylindrical limiting groove 6 contacts the top of the cavity insert 7, the cavity insert 7 is pushed to move downward along the vertical direction, and the spring needle 3 is compressed until the bottom of the cavity insert 7 is in close contact with the positioning surface in the lower mold 2, and the parting surface of the upper mold 1 and the lower mold 2 is in close contact, and the cavity is closed.

[0050] Supercritical foaming: the supercritical foaming equipment injects supercritical CO2 fluid into the cavity through the gas inlet hole 5, and the supercritical fluid uniformly penetrates the green body and makes it expand to fill the cavity. The air and excess fluid in the cavity are discharged through the conical exhaust hole 4, and at the same time, the foaming process is carried out according to the conventional foaming parameters.

[0051] Demolding: after the foaming is completed, the upper mold 1 is controlled to move upward, and after the cylindrical limiting groove 6 is separated from the cavity insert 7, the top of the cavity insert 7 loses the downward pressure, and at this time, multiple spring needles 3 simultaneously rebound, pushing the cavity insert 7 to move upward by a small distance, and the cavity insert 7 drives the forming surface cover to separate from the lower mold 2 cavity. The operator directly takes down the cover, completing a molding cycle.

[0052] The embodiment realizes convenient demolding, efficient exhaust and uniform air intake of the medical mask supercritical foaming forming, and effectively improves production efficiency.

[0053] The product obtained in the present disclosure is detected by a dynamic mechanical analyzer to obtain the numerical value of the cell number and the mean value of the cell diameter of the product, the mean value is calculated at a distortion ratio of 90% to 96% to obtain the actual mean value; the cell density value and the void ratio are calculated by the numerical value of the cell number and the mean value of the cell diameter; when the cell density value is less than 10 8 cells / cm 3 , the heat treatment time is increased by 20-30 minutes, so that if unqualified conditions occur during each production process, timely adjustment can be made; or it can be known whether the equipment has structural defects for maintenance. If the cell density value is greater than or equal to 10 8 cells / cm 3 , a qualified product mask is obtained. It should be noted that the longer the heat treatment or pre-vulcanization time, the higher the cell density. Because a high cell density means that the bubble nucleation rate is fast and uniformly distributed during foaming, thereby improving the structural density and mechanical properties of the product, so that the mask produced in this way fits the facial contour better when worn, effectively improving the sealing performance and comfort.

[0054] Specifically, the temperature and time curve of the vulcanized silicone rubber compound is determined by a dynamic mechanical analyzer (DMA) RSA-III; the cell morphology of the microcellular foamed silicone rubber sample is characterized and analyzed by a scanning electron microscope (SEM); the cell diameter and cell number of the foamed sample are determined by Image J software, and the cell density is calculated by a formula.

[0055] The cell density N of the microcellular foamed silicone rubber sample is calculated by the following formula: N=(n / A) 3 / 2 ×(1 / 1-V f ); Wherein n is the number of cells (cells) in the SEM photo, A is the actual area (cm 2 ) of the SEM photo, V f is the porosity of the foamed sample, which is defined as: V f =1-P f / P; Wherein P f is the density (g / cm3) of the fully vulcanized sample after foaming, and P is the density (g / cm3) of the fully vulcanized rubber strip before foaming.

[0056] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical scope disclosed by the present application, which can be easily thought by those skilled in the art, should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of manufacturing a lightweight face mask, characterized by, The method comprises the following steps: The silicone rubber, white carbon black and silicone oil are fed into the first roller cylinder of the planetary roller extruder for mixing to obtain a mixture; The mixture and vulcanizing agent are fed into the second roller cylinder of the planetary roller extruder for mixing to obtain a mixed rubber; The mold is heated to a first temperature and kept within a range of ±5℃, and a supercritical fluid is filled into the cavity of the mold to complete the pretreatment; the first temperature is 100-125℃; The mixed rubber is fed into the cavity of the mold, and the supercritical fluid is filled again for pressure adjustment of the cavity, and the mixed rubber and the supercritical fluid are saturated; The mold cavity is depressurized, and the mixed rubber after the saturation is supercritically foamed to completely fill the cavity of the mold to obtain a face mask of supercritically foamed silicone rubber material; After the mixed rubber is injected into the mold filled with the supercritical fluid, the supercritical fluid is filled into the cavity of the mold to 9-12 MPa within 10-20 seconds, and the mixed rubber is saturated for 15-22 seconds; The mold cavity is depressurized to normal pressure or zero gauge pressure within 3 seconds, and the mixed rubber is supercritically foamed for 40-45 seconds.

2. The method of manufacturing a lightweight face mask according to claim 1, wherein: The white carbon black is treated in a vacuum oven before mixing to remove moisture; The first roller cylinder of the planetary roller extruder is mixed at 100-110℃ for 10-30 minutes; The roller of the planetary roller extruder has a flow channel for the flow of the mixed rubber; The saturation or presulfurization of the mixed rubber is carried out at an ambient pressure of 5-8 MPa.

3. The method of manufacturing a lightweight face mask according to claim 2, wherein: The vulcanizing agent is dicumyl peroxide, benzoyl peroxide or bis-dipentasulfur. The second roller cylinder of the planetary roller extruder is mixed at 20-40℃ for 8-20 minutes; The thread inclination angle of the roller in the second roller cylinder is smaller than that of the first roller cylinder, so that the moving speed of the mixed rubber in the second roller cylinder is smaller than that in the first roller cylinder; The first roller cylinder and the second roller cylinder have a first temperature regulating cavity for temperature regulation of the planetary roller cavity, and the wall thickness of the first temperature regulating cavity is 1-5 mm, and the center of the central screw is provided with a second temperature regulating cavity.

4. The method of manufacturing a lightweight face mask of claim 1, wherein: The mold comprises an upper mold and a lower mold forming a mask cavity after closing, and a plurality of elastic ejection assemblies for facilitating demolding; The neck of the upper mold has an air inlet hole for providing the supercritical fluid in the cavity and an air outlet hole for discharging the gas in the non-shaped key area; The air outlet hole is provided in a micro air outlet groove at the edge of the mold parting surface, and the micro air outlet grooves on the upper mold and the lower mold form a conical air outlet hole after the mold is closed, which extends along the edge of the cavity to form a channel for accelerating the air outlet; The cavity of the upper mold is provided with a cylindrical limiting groove for pushing the cavity insert block downward, and the lower bottom surface of the cavity insert block is provided with a protruding cylindrical block, and the lower mold is provided with a circular groove on the plane fitted with the lower bottom surface of the cavity insert block, which is matched with the protruding cylindrical block.

5. The method of manufacturing a lightweight face mask of claim 1, wherein: After the rubber compound is obtained, the rubber compound is transported to the third roller cylinder of the planetary roller extruder for heating and pressurization to complete the pre-vulcanization treatment and is transported to the cavity of the mold.

6. The method of manufacturing a lightweight face mask according to claim 1, wherein, When the mold is pretreated, the mold is continuously supplied with supercritical fluid; When the rubber compound is transported into the cavity of the mold, the output port of the mold is closed, and the supercritical fluid is continuously supplied for 10-20 seconds to saturate the rubber compound with the supercritical fluid.

7. The method of manufacturing a lightweight face mask according to claim 1, wherein, When the mixture is obtained, the first roller cylinder of the planetary roller extruder is heated to melt and mix uniformly; When the mixture and the vulcanizing agent are transported to the second roller cylinder of the planetary roller extruder for mixing, the second roller cylinder is filled with supercritical CO2 for blending to obtain a polymer-supercritical CO2 homogeneous system; The air pressure in the second roller cylinder is 8-15 MPa.

8. The method of manufacturing a lightweight face mask according to claim 1, wherein, After the mask of the supercritically foamed silicone rubber material is obtained, the cavity of the mold is heated for 30-50 minutes at a temperature of 160-230℃; Alternatively, the mask of the supercritically foamed silicone rubber material is taken out and placed in a heated mold with the same cavity for heating for 10-15 minutes at a temperature of 160-230℃.

9. The method of manufacturing a lightweight face mask according to claim 8, wherein, When the mask is heated in the mold or the heated mold, the mask is first fully vulcanized for 10-20 minutes at a temperature of 160-180℃; Then, the mask is heat treated for 20-30 minutes at a temperature of 180-230℃. The obtained product is subjected to dynamic mechanical analysis to obtain the number of cell numbers and the average cell diameter of the product, and the average value is calculated at a distortion ratio of 90%-96% to obtain the actual average value. The number of cell numbers and the average cell diameter are used to calculate the cell density value and the void fraction. The cell density value is less than 10 8 cells / cm 3 If the cell density value is greater than or equal to 10 8 cells / cm 3 , then the product face mask is qualified.

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