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CN-122011488-A - Method for efficiently preparing high-magnification PVDF microporous foam board

CN122011488ACN 122011488 ACN122011488 ACN 122011488ACN-122011488-A

Abstract

The invention discloses a method for efficiently preparing a high-magnification PVDF microporous foam board, and belongs to the technical field of high polymer material foaming. The method comprises the steps of reacting inorganic particles with a porous structure with a silane coupling agent in absolute ethyl alcohol, immersing the obtained functionalized particles with double bonds on the surface in a foaming agent solution, filtering and drying to obtain functionalized particles loaded with the foaming agent, melting and extruding PVDF resin, the functionalized particles loaded with the foaming agent and a free radical initiator to form a pre-foaming sheet, placing the pre-foaming sheet in a high-pressure foaming kettle, introducing supercritical CO 2 , and releasing pressure after saturation to obtain the PVDF microporous foaming sheet. The invention integrates crosslinking and pre-foaming into an extrusion process, omits the traditional irradiation crosslinking and one-time foaming process, shortens the gas saturation time, improves the production efficiency, realizes the efficient preparation of PVDF foaming materials with high multiplying power and fine cell structures, and is suitable for continuous production.

Inventors

  • YANG JINTAO
  • CHEN RUI
  • WANG GAOPENG

Assignees

  • 浙江工业大学

Dates

Publication Date
20260512
Application Date
20260409

Claims (9)

  1. 1. The method for efficiently preparing the high-magnification PVDF microporous foam board is characterized by comprising the following steps of: (1) The surface functionalization of porous particles, namely, reacting inorganic particles with porous structures with a silane coupling agent in absolute ethyl alcohol to obtain functionalized particles with double bonds on the surfaces; (2) The foaming agent loading, namely immersing the functional particles with double bonds on the surface into a foaming agent solution, filtering and drying to obtain the functional particles loaded with the foaming agent; (3) Extruding pre-crosslinking and pre-foaming, namely melting and extruding PVDF resin, functionalized particles loaded with foaming agent and free radical initiator to form a pre-foaming sheet; (4) And (3) supercritical carbon dioxide foaming, namely placing the pre-foamed sheet into a high-pressure foaming kettle, introducing supercritical CO 2 , and releasing pressure after saturation to obtain the PVDF microporous foaming sheet.
  2. 2. The method for efficiently preparing the high-magnification PVDF microporous foamed sheet according to claim 1, wherein the inorganic particles are porous silica, porous boron nitride, zeolite or aerogel particles, the average pore diameter of the inorganic particles is 5-50nm, and the specific surface area is more than or equal to 200m < 2 >/g.
  3. 3. The method for efficiently preparing the high-magnification PVDF microporous foam board according to claim 1, wherein the silane coupling agent is used in an amount of 1-5% of the mass of the inorganic particles.
  4. 4. The method for efficiently preparing the high-magnification PVDF microporous foam sheet material according to claim 1, wherein the silane coupling agent is KH570.
  5. 5. The method for efficiently preparing the high-magnification PVDF microporous foam board according to claim 1, wherein the foaming agent is one or more of p-toluenesulfonyl hydrazide, azodicarbonamide and 4,4' -oxo-bis-benzenesulfonyl hydrazide, and the loading amount of the foaming agent is 10-30% of the mass of functionalized particles loaded with the foaming agent.
  6. 6. The method for efficiently preparing the high-magnification PVDF microporous foam sheet material according to claim 1, wherein the free radical initiator is dicumyl peroxide or di-tert-butyl peroxide, and the dosage of the free radical initiator is 0.1-2.5% of the mass of the PVDF resin.
  7. 7. The method for efficiently preparing the high-magnification PVDF microporous foam sheet material according to claim 1, wherein the mass ratio of PVDF resin to functionalized particles loaded with foaming agent is 90-99:1-10.
  8. 8. The method for efficiently preparing the high-magnification PVDF microporous foam sheet material according to claim 1, wherein the melt extrusion temperature is 170-190 ℃.
  9. 9. The method for efficiently preparing the high-magnification PVDF microporous foamed sheet according to claim 1, wherein the supercritical carbon dioxide foaming conditions are that the pressure is 8-20MPa, the temperature is 165-180 ℃, the saturation time is 0.5-2 hours, and the pressure relief rate is more than or equal to 20MPa/s.

Description

Method for efficiently preparing high-magnification PVDF microporous foam board Technical Field The invention relates to the technical field of high polymer material foaming, in particular to a method for efficiently preparing a high-magnification PVDF microporous foaming sheet material. Background Polyvinylidene fluoride (PVDF) has inherent defects of semicrystalline property, low melt strength, narrow foaming window and the like, and is difficult to realize a microporous foaming material with high multiplying power and uniform structure through a conventional foaming process. The supercritical fluid foaming process commonly used in the industry at present adopts a 'two-step method', namely, the melt strength is firstly improved through irradiation or chemical crosslinking, and then gas saturation and foaming are carried out. The process has the problems of complex equipment, high energy consumption, long flow, difficult continuous production and the like. For example, the fluoropolymer foam preparation method disclosed by the Sott foam Co., ltd, comprises preparing PVDF sheet by extrusion process, pre-crosslinking PVDF by electron beam irradiation, saturating resin with gas at high temperature (185 ℃ C.) and high pressure (670 bar), cooling and depressurizing to achieve partial foaming (nucleation and preliminary expansion), transferring the partially foamed sample to a second container, and heating for the second time under lower pressure to complete final foaming. Similar irradiation crosslinking segmented foaming technology is adopted by Shenzhen Wall nuclear materials limited company, and the problems of complicated flow, difficult serialization, limited foaming multiplying power and the like still exist. The method improves the nucleation density, but still needs to extrude sheet materials, irradiate crosslinking, primary pre-foaming nucleation, secondary foaming and other multi-step operations, the process flow is divided into 4 sections, meanwhile, the sheet materials are solid plates in the primary foaming, the supercritical gas infiltration saturation time is longer, and the overall production efficiency is limited. Therefore, the method which has the advantages of simple and convenient process, high efficiency, no irradiation, continuous production and remarkable improvement of PVDF foaming multiplying power is developed, and the method has important industrial application value. Disclosure of Invention The invention aims to overcome the defects of the prior art and provides a method for efficiently preparing a high-magnification PVDF microporous foaming sheet material. The porous particles which are loaded with the foaming agent and have double bond groups on the surface are added in the process of extruding the PVDF sheet to realize one-step realization of micro-crosslinking, pre-foaming and sheet molding in the process of extruding, and the foaming sheet is prepared by combining a supercritical carbon dioxide one-step foaming process, so that the problems of complex two-step foaming process, long time consumption and low foaming multiplying power in the prior art are solved. In order to achieve the above purpose, the present invention adopts the following technical scheme: A method for efficiently preparing a high-magnification PVDF microporous foam board comprises the following steps: (1) The surface functionalization of porous particles, namely, reacting inorganic particles with porous structures with a silane coupling agent in absolute ethyl alcohol to obtain functionalized particles with double bonds on the surfaces; (2) The foaming agent loading, namely immersing the functional particles with double bonds on the surface into a foaming agent solution, filtering and drying to obtain the functional particles loaded with the foaming agent; (3) Extruding pre-crosslinking and pre-foaming, namely melting and extruding PVDF resin, functionalized particles loaded with foaming agent and free radical initiator to form a pre-foaming sheet; (4) And (3) supercritical carbon dioxide foaming, namely placing the pre-foamed sheet into a high-pressure foaming kettle, introducing supercritical CO 2, and releasing pressure after saturation to obtain the PVDF microporous foaming sheet. Further, the inorganic particles are porous silica, porous boron nitride, zeolite or aerogel particles, the average pore diameter of the inorganic particles is 5-50nm, and the specific surface area is more than or equal to 200m2/g. Further, the amount of the silane coupling agent is 1-5% of the mass of the inorganic particles. Further, the silane coupling agent is KH570. Further, the foaming agent is one or more of p-toluenesulfonyl hydrazide, azodicarbonamide and 4,4' -oxo-bis-benzenesulfonyl hydrazide, and the load capacity of the foaming agent is 10-30% of the mass of the functionalized particles loaded with the foaming agent. Further, the free radical initiator is dicumyl peroxide or di-tert-butyl peroxide, and the dosage o