CN-122011259-A - Modified fusible polytetrafluoroethylene and preparation method and application thereof

CN122011259ACN 122011259 ACN122011259 ACN 122011259ACN-122011259-A

Abstract

The invention relates to a modified fusible polytetrafluoroethylene, a preparation method and application thereof, wherein the preparation method comprises the steps of preparing small-particle-size PTFE microemulsion serving as seeds through aqueous phase polymerization of tetrafluoroethylene monomers in a first polymerization reactor. And adding the seed emulsion, the tetrafluoroethylene monomer and the perfluoroalkyl vinyl ether comonomer into a second polymerization reactor, and initiating copolymerization reaction on the surface of seed particles to realize uniform compounding of molecular chain level. In the reaction process, the growth process of the copolymer molecular chain is controlled by continuously supplementing the monomer and accurately regulating and controlling the stirring rate. And (3) condensing, washing and drying the obtained composite emulsion, performing melt granulation through a strong shearing extrusion device, and performing fluorination treatment to obtain a finished product. Compared with the prior art, the material prepared by the invention has obviously enhanced cracking resistance and flexibility.

Inventors

KONG XIANDA
CHENG JINGDONG
WU TONG

Assignees

上海华谊三爱富新材料有限公司
常熟三爱富振氟新材料有限公司
福建华谊三爱富氟佑新材料有限公司

Dates

Publication Date: 20260512
Application Date: 20260205

Claims (10)

1. The preparation method of the modified fusible polytetrafluoroethylene is characterized by comprising the following steps of: S1, preparing polytetrafluoroethylene seed emulsion in a first polymerization reactor, and obtaining PTFE microemulsion with small particle size through aqueous phase polymerization of tetrafluoroethylene monomer; S2, adding the small-particle-size PTFE microemulsion into a second polymerization reactor to serve as a core of a polymerization reaction, adding tetrafluoroethylene monomer and perfluoroalkyl vinyl ether comonomer, and carrying out a copolymerization reaction on the surfaces of seed particles to realize uniform compounding of molecular chain grades; S3, continuously supplementing tetrafluoroethylene monomer and perfluoroalkyl vinyl ether comonomer under the condition of maintaining the stability of a reaction system, and controlling the growth process of a copolymer molecular chain on the surface of seed particles by regulating and controlling the stirring rate to obtain composite emulsion; S4, carrying out condensation, washing and drying treatment on the obtained composite emulsion, carrying out melt granulation through a strong shearing extrusion device, enabling polytetrafluoroethylene molecular chains to realize fiber transformation, forming a mutually entangled net structure with copolymer molecular chains, and carrying out fluorination treatment to obtain the modified fusible polytetrafluoroethylene material with enhanced cracking resistance and flexibility.
2. The method for preparing modified fusible polytetrafluoroethylene as claimed in claim 1, wherein in S1, the method specifically comprises the following steps: Adding 400-500 parts by weight of deionized water, 1-3 parts by weight of surfactant and 30-50 parts by weight of paraffin into a first polymerization reactor, evacuating and replacing until the oxygen content is lower than 30ppm, adding 20-45 parts by weight of tetrafluoroethylene monomer, initiating the polymerization reaction of the tetrafluoroethylene monomer by adding 0.001-0.5 part by weight of initiator solution at the temperature of 60-90 ℃ and the pressure of 1.2-3.5 MPa, and maintaining the stable reaction condition by continuously adding the tetrafluoroethylene monomer, thereby finally obtaining the small-particle-size PTFE microemulsion with the particle size of 50-150 nm and the molecular weight of 100-600 ten thousand.
3. The method for preparing modified fusible polytetrafluoroethylene according to claim 2, wherein in S1, the temperature of the polymerization reaction is controlled to be 60-90 ℃, and the pressure of the polymerization reaction is controlled to be 1.2-3.5 mpa; The initiator is ammonium persulfate aqueous solution with the concentration of 1-5wt% an aqueous solution of potassium persulfate or a blend thereof; The surfactant is one or more of tridecafluorooctyl triethoxysilane, perfluoro trioxaheptacarbonic acid, perfluoro polyether and perfluoro dioxaoctacarbonic acid with the concentration of 10-50wt%.
4. The method for preparing modified fusible polytetrafluoroethylene as claimed in claim 1, wherein in S2, the method specifically comprises the following steps: Adding 400-500 parts by weight of deionized water, 1-40 parts by weight of small-particle-size PTFE microemulsion obtained in the step S1 and 2-6 parts by weight of surfactant into a second polymerization reactor, evacuating and replacing until the oxygen content is lower than 30ppm, adding 20-50 parts by weight of tetrafluoroethylene monomer and 5-15 parts by weight of perfluoroalkyl vinyl ether comonomer, and then initiating copolymerization reaction by adding 1-4 parts by weight of initiator solution at the temperature of 60-120 ℃ and the pressure of 1.0-4.5 MPa.
5. The preparation method of the modified fusible polytetrafluoroethylene as claimed in claim 1, wherein in S2, the added small-particle-size PTFE micro emulsion accounts for 0.01% -5% of the final target product in terms of the dry quantity; in S2, the temperature of the copolymerization reaction is controlled to be 60-120 ℃, and the pressure is controlled to be 1.0-4.5 MPa.
6. The method for preparing modified fusible polytetrafluoroethylene as claimed in claim 1, wherein in S3, the method specifically comprises the following steps: Continuously supplementing tetrafluoroethylene monomer into the second polymerization reactor after initiation of the copolymerization reaction, continuously supplementing 3-10 parts by weight of perfluoroalkyl vinyl ether comonomer, simultaneously gradually increasing the stirring rotation speed from 30-50 rpm to 50-120 rpm, maintaining the reaction pressure at 1.0-4.5 MPa, simultaneously continuously adding an initiator solution at the speed of 2-10 parts/h, controlling the reaction temperature at 60-120 ℃, and stopping the reaction until the total amount of tetrafluoroethylene monomer added reaches 150-250 parts by weight; And S3, gradually increasing the stirring rotation speed from 30-50 rpm to 50-120 rpm to control the coating growth and mass transfer process of the copolymer molecular chains on the surfaces of the PTFE seed particles, so as to obtain the composite emulsion with uniform structure.
7. The method of claim 1, wherein in S4, the strong shear extrusion device is a twin screw extruder with an aspect ratio of 32:1-64:1, and the screw combination comprises a plurality of shearing elements to ensure that sufficient shearing force is applied to the PTFE molecular chain in the melt extrusion granulation process to realize the fibrous transformation and the sufficient entanglement with the PFA molecular chain; And S4, in the fluorination treatment, the end capping of an unstable group at the tail end of a molecular chain of the material is realized by carrying out the fluorination treatment for 6-16 hours at the temperature of 200-220 ℃ in a fluorine/nitrogen mixed gas atmosphere with the fluorine concentration of 10-25wt%.
8. The method of preparing a modified fusible polytetrafluoroethylene according to claim 1 wherein said perfluoroalkyl vinyl ether comonomer is one or more of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, or perfluoro-n-propyl vinyl ether.
9. A modified meltable polytetrafluoroethylene obtainable by the process of any one of claims 1 to 8.
10. Use of a modified meltable polytetrafluoroethylene as defined in claim 9 for the preparation of seals, pipes, valve liners, cable jackets or specialty films requiring high resistance to cracking and high flexibility.

Description

Modified fusible polytetrafluoroethylene and preparation method and application thereof Technical Field The invention relates to the technical field of fluorine-containing polymers, in particular to a modified fusible polytetrafluoroethylene, a preparation method and application thereof. Background The fusible Polytetrafluoroethylene (PFA) is a modified Polytetrafluoroethylene (PTFE) material in which tetrafluoroethylene and a perfluoroalkyl vinyl ether (PAVE) are copolymerized, and the perfluoroalkyl vinyl ether content is about 5%. The PFA is a perfluorinated polymer, so that the excellent physical and chemical properties of PTFE, such as heat resistance, chemical reagent resistance, electrical property, self-lubricating property, non-tackiness and the like, are maintained, meanwhile, due to the introduction of a perfluoroalkoxy side group in PAVE, molecular chains are more easily intertwined, the defect of poor rebound resilience and easy creep caused by poor adhesion of straight and flexible molecular chain segments and easy sliding of PTFE is overcome, and due to the introduction of the perfluoroalkoxy side group, the compact spiral conformation of a PTFE fluorocarbon main chain is broken, the crystallinity of the PTFE is reduced, and the PTFE can be subjected to melt processing through equipment such as an extruder, an injection molding machine and the like, so that the PTFE is called as fusible polytetrafluoroethylene. Along with the diversification and severity of PFA in the application scenes of the high-end fields of the military industry, the information industry and the like, higher requirements are put on the performances of cracking resistance, flexibility and the like of pipes, cables or complex structural members of the PFA. Therefore, how to improve the performances of cracking resistance, flexibility and the like of PFA, meet the requirements of high-end diversified application of PFA and stable application in the prior manufacturing field of PFA, and are the problems to be solved urgently. In the prior art, the performance of PFA is improved primarily by physical blending. For example, in the prior art CN110229449a, after blending a PTFE emulsion having a number average molecular weight of not less than 100 ten thousand with a PFA emulsion and a surfactant, high-strength PFA particles are obtained after coagulation, washing, drying, fluorination, and granulation, but the problem of the interface between PTFE and PFA is not solved, and the problem of insufficient phase-separation interface bonding force still exists. In the prior art CN103068910A, 1550wt% of low molecular weight PTFE micro powder and PFA are blended and subjected to high-temperature aging, so that the PFA and the PTFE are induced to perform epitaxial co-crystallization, the continuous use temperature and the physical properties of the PTFE are improved, but the processability of the PTFE is reduced, and the interface problem still exists. In the prior art CN120554684A, modified and ball-milled PTFE and PFA granules are blended by a torque rheometer and then subjected to high-temperature hot pressing to prepare a PFA/PTFE composite film, in addition, the prior art CN103122114A, CN101437892A, US20120034406A1 and the like are compound PTFE and PFA, wherein PTFE is used as a physically doped disperse phase, after being subjected to hot melt processing by various post-processing processes, the macroscopic miscibility of the PTFE and the PFA can be improved, but the interface problem of the PTFE and the PFA, especially the problem that the fusion entanglement among molecular chains exists an obvious phase interface, so that defects such as crystal points, pimples, white spots and the like are easy to generate in downstream processing, and the product has the problems of easy cracking, poor toughness, low breaking elongation and the like. In summary, the prior technologies achieve the aim of improving the performances of PFA strength, continuous use temperature and the like through the mixing optimization of components such as emulsion, powder and the like and the adjustment optimization of a rear end processing technology, but have macroscopic and microscopic phase interface flaws, so that short plates with poor cracking resistance, poor toughness, difficult processing and the like exist in the comprehensive performances. Disclosure of Invention The invention aims to overcome the defects of the prior art and provide a modified fusible polytetrafluoroethylene, a preparation method and application thereof, so as to solve the problems of easy cracking, poor toughness, low elongation at break and the like caused by more crystal points, pimples, white spots and the like of products due to the phase interface problem of mixed PFA/PTFE due to the insufficient performances of PFA cracking resistance, flexibility and the like in the high-end diversified application field in the background. Aiming at the problems in the prior art, the inv