年产1.2万吨PTFE(聚四氟乙烯)悬浮聚合工段设计 聚合反应工程设计

This Review aims to be a comprehensive, authoritative, and critical review of general interest to the chemistry community (both academia and industry) as it contains an extensive overview of all published data on the homopolymerization of tetrafluoroethylene (TFE), detailing the TFE homopolymerization process and the resulting chemical and physical properties. Several reviews and encyclopedia chapters on the properties and applications of fluoropolymers in general have been published, including various reviews that extensively report copolymers of TFE (listed below). Despite this, a thorough review of the specific methods of synthesis of the homopolymer, and the relationships between synthesis conditions and the physicochemical properties of the material prepared, has not been available. This Review intends to fill that gap. As known, PTFE and its marginally modified derivatives comprise some 60-65% of the total international fluoropolymer market with a global increase of ca. 7% per annum of its production. Numerous companies, such as Asahi Glass, Solvay Specialty Polymers, Daikin, DuPont/Chemours, Juhua, 3F, 3M/Dyneon, etc., produce TFE homopolymers. Such polymers, both high-molecular-mass materials and waxes, are chemically inert and hydrophobic and exhibit an excellent thermal stability as well as an exceptionally low coefficient of friction. These polymers find use in applications ranging from coatings and lubrication to pyrotechnics, and an extensive industry (electronic, aerospace, wires and cables, and textiles) has been built around them. South Africa, being the third largest producer of fluorspar (CaF2), the precursor to hydrogen fluoride and fluorine, has embarked on an industrial initiative to locally beneficiate its fluorspar reserves, with the local production of fluoropolymers being one projected outcome. As our manuscript focuses specifically on the homopolymerization of TFE (the starting point for all fluoropolymer industries), it will be of considerable use to start-up companies and other commercial entities looking to enter the fluoropolymer market, as well as to end-user companies. The manuscript commences with a short discussion on the synthesis and production of TFE (both at industrial and laboratory scales), including the safety aspects surrounding handling (because that monomer is regarded as explosive if brought into contact with oxygen due to the formation of peroxides), transport, and storage, and then expands into detailed discussions dealing with aspects such as the various additives used (buffers, chain transfer agents, surfactants, etc.), the solvent environment, and the reaction conditions. A further section reports the properties of PTFE with respect to the polymerization conditions as well as an overview on the specialized techniques used to characterize PTFE. Finally, the applications of PTFE in various fields, ranging from electrical insulation to tribological to medical applications, as well as chemically resistant coatings and pyrotechnics, are discussed.

… standard PTFE, modified PTFE, and PFA materials. The influence of the polymerization type … of the melt-processable PTFE (emulsion and suspension polymerization) on the MWD and …

… Because of its high molecular weight, PTFE does not … suspension polymerized PTFE is usually fabricated by modified metallurgy techniques. Emulsion polymerized, coagulated PTFE is …

… referred to as suspension and dispersion polymerization, are … Suspension polymerization of TFE involvesthe use of little or … stable colloidal dispersion of PTFE particles. Carbon dioxide …

… Fine-cut granular resins produced by size reduction of the suspension polymer have a typical average particle size from 20 to 40 μm. The small particle size of fine-cut PTFE imparts the …

… (PTFE) obtained by aqueous suspension polymerization have … for native PTFE from aqueous emulsion polymerization. One … evidenced for PTFE from aqueous emulsion polymerization. …

… particles of PTFE prepared by radiationinduced emulsion and suspension polymerization. The … behavior of PTFE as-polymerized in emulsion and suspension were investigated by …

… to the mechanisms of polymerization. There are two principal varieties of PTFE 9. The granular resin is prepared by aqueous 'suspension' free-radical polymerization and consists of …

… polymer products obtained by suspension polymerization … management of a suspension polymerization process is as … of polymer particles produced by suspension polymerization, using …

Abstract PTFE homopolymer synthesised using ammonium persulfate initiator discolours at sintering temperatures of approximately 380 °C. No report on this phenomenon is available in the open literature. To shed light on the problem, PTFE samples were synthesised using various initiators and different pH buffers. The initiators used included ammonium persulfate, sodium persulfate, potassium permanganate, di-tertiary butyl peroxide and hydrogen peroxide. Borax and potassium carbonate were used as the buffering agents. The samples were pressed into discs and sintered at 380 °C. The samples were analysed using FTIR and Raman spectroscopy to determine the influence of decomposition of the end-groups during sintering. Each initiator resulted in unique end-groups, with a suggestion of multiple termination reactions in several of the samples. The discolouration of the samples occurs because of amorphous carbon deposition into the polymer matrix after elimination from the end-groups during sintering. The level of discolouration is dependent on the type and concentration of initiator used.

This chapter covers the processing of polytetrafluoroethylene (PTFE) resins, which include granular and fine powder resins. These materials are very different, therefore each requires different processing techniques. Granular resins are processed by a technique similar to that in powder metallurgy. They are commonly processed by compression molding and ram extrusion. In compression molding the resins are preformed into a billet, which is then sintered and cooled. Cooling and its rate are important because they have important effects on the final products. Billets are frequently converted to films and sheets by skiving. Other molding methods are automatic molding used for small parts, coining used for parts with complex shapes, and isostatic molding using uniform pressure from all directions. Ram extrusion is a process to produce PTFE extrudates of continuous lengths. The resin is fed into one end of a straight die tube of uniform diameter, where it is compacted by a ram and forced through the tube, which incorporates a heated sintering zone. Granular PTFE resins are most frequently extruded as rods or tubes, but it is possible to produce extrudates of noncircular cross-sections. The processing of fine powders is more complex. Because PTFE fine powders do not melt and flow, they are commonly fabricated by a technology adopted from ceramic processing called paste extrusion. In paste extrusion, the paste is prepared by mixing the powder with a 15 to 25% hydrocarbon lubricant. The basic steps are preparation of the extrusion mix, preforming, extrusion, and drying. Additional steps are used for specific products. Some extrudates are calendered or sintered, and stretched. Typical products are unsintered tape, wire and cable insulation, tubing, rods, and articles from expanded PTFE, such as membranes, sheets, and tubing.

… to kinetic studies of emulsion and suspension copolymerization of tetrafluoroethylene (TFE) … In water-suspension polymerization of other monomer^,^ the role of the stirring speed has …

Abstract In a typical suspension polymerization system, one or more water-insoluble monomers containing oil-solube initiator(s) are dispersed in the continuous aqueous phase by a combination of strong stirring and the use of small amounts of suspending agents (stabilizers). Suitable conditions of mechanical agitation are maintained while the monomer droplets are slowly converted from a highly mobile liquid state, through a sticky syrup-like dispersion (conversion 20–60%), to hard solid polymer particles (conversion > 70%) [1–3]. The stabilizers hinder the coalescence of the monomer droplets first, and later stabilize tHe polymer beads whose tendency to agglomerate may become critical when the polymerization has advanced to the point where the polymer beads become sticky.

… Suspension Polymerization In suspension polymerization, monomer droplets with dissolved … However, the most powerful approach for modeling polymerization kinetics is the detailed …

… An interesting example is tetrafluoroethylene polymerization … that kt in isothermal suspension polymerization becomes diffusion-… hindrances in styrene suspension polymerization in an …

… Many (but not all) important commercial suspension polymers yield bead sizes above 10 μm, and … The polymerization kinetics and the mechanism of primary particle aggregation in the …

… In present review, suspension polymerization technique is … the basics of suspension polymerization for the synthesis of … initiator on the kinetics of heterogeneous polymerization, on …

Abstract The tetrafluoroethylene (TFE) polymerization process is an essential industrial process to produce polytetrafluoroethylene (PTFE), which is extensively utilized in aerospace and medical domains. A precise mechanism model is a prerequisite for comprehensively understanding this process. However, significant uncertainties in the kinetic model parameters may hinder attaining an optimal reaction rate. This study proposes a hybrid polymerization reaction model that integrates process mechanism modeling and data-driven modeling to address this challenge. In the hybrid modeling approach, the mechanism model for the polymerization reaction is developed based on reaction kinetic and thermodynamic assumptions. Additionally, a long short-term memory (LSTM) neural network is employed to predict the reaction rate for chain initiation by leveraging temporal relationships derived from archived measurements. The proposed methodology is implemented using a PTFE polymer reactor system, and experimental comparisons affirm its superior performance and effectiveness.

… After PTFE recovery, the reactor was cleaned with liquid water to remove residual surfactant and polymer … where high purity PTFE is necessary as in the case of electronic industry. Quite …

Fluoropolymers have had a profound effect on all aspects of industry since their discovery during the 1930s. This review briefly describes the historical development of the fluoropolymer industry, with a focus on traditional fluoroplastics, and lists the major industrial and commercial materials currently in use. These include polytetrafluoroethylene (PTFE, Teflon), polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), the ethylene copolymer of tetrafluoroethylene (ETFE), the ethylene copolymer of chlorotrifluoroethylene (ECTFE), perfluoroalkoxy (PFA), polyvinylfluoride (PVF), polyvinyldifluoride (PVDF), Nafion, fluoroethylenevinylether (FEVE), a semicrystalline three component terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), Teflon-AF, Cytop, and Hyflon. The production, processing, and properties of these fluoropolymers are discussed, together with examples of the specific uses in chemical industry, manufacturing, electronics, architecture, energy, health and domestic sectors. Other related fluoropolymers such as fluoroelastomers, perfluoropolyethers, and fluorosurfactants are briefly mentioned. Environmental aspects of fluoropolymers are considered as is the current state of the fluoropolymer industry.

… kg −1 for commodity polymers, 10–12€ kg −1 for PTFE or PSU, … that are produced on a very large scale, there exists a variety … industrial polymerization processes and the related reactor …

… The scale-up/-down of polymerization reactors has to deal with large viscosity changes during the process, addressing mass- and heat-transfer issues. A practical example on …

Current industrial production of polymer resins is generally undertaken in large multi-tonne stirred tank reactors. These are characterised by relatively slow heating and cooling cycles, resulting in long vessel cycle times and extended production campaigns. In this work we present a design for a hybrid microwave/oil jacket proof of concept system capable of producing up to 4.1 kg of polymer resin per batch. By exploiting rapid volumetric heating effects of microwave energy at 2.45GHz, we have optimised the synthetic regime, such that a 3.7 kg batch of polyester resin pre-polymer can be made in only 8 hours 20 minutes, with higher molecular weight (Mn 2,100) compared to the conventional process taking 22 hours 15 minutes (Mn 1,200), yielding an increase in synthesis rate of at least 265. The increase in polymer molecular weight also suggests a higher conversion was achieved over a shorter time scale.

… Moreover, in the single initiator systems, the applicability of … suspension polymerization with different reaction rates and different temperatures. Optimal dosing rate profiles of the initiator …

… Molecular weight distribution (MWD) is an important polymer … the polymers. Particle size distribution (PSD) is another crucial property of suspension polymerization process that controls …

The free radical polymerization controlled by 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) was carried out in a water/oil suspension at 120–135°C. Suspension polymerization is a polymerization reaction with high conversion and allows high-molecular-weight polymers to be synthesized. The polymerization was started by a styrene macroinitiator. The block length is determined by the level of conversion and the initial macroinitiator concentration. A kinetic model is introduced which predicts a drastic reduction of polymerization time (at ca. 90% conversion a reduction from ca. 20 h to 5–3 h) and improved polydispersity through selective addition of initiator. The agreements between the simulated results and the experimental findings are surprisingly good. From model calculation, the percentage and molar mass distributions of the dead polymers can also be derived.

Molecular and morphological properties of poly(vinyl chloride) (PVC) grains produced by suspension polymerization of VCM in the presence of a mixture of fast, mild and slow initiators (named as Cok process) was experimentally investigated in a pilot-scale reactor. In contrast to nonisothermal and fast initiator dosage process, using initiators mixture has the smallest influence on molecular weight and polydispersity index compared to the control process. It is found that Cok-PVC grains have the lowest cold plasticizer absorption and porosity among productivity-enhancing processes. Scanning electron microscopy showed that the particles produced by Cok process are more regularly shaped, with a smoother surface compared with the control resin. All three productivity-enhancing techniques lead to an apparent quality enhancement, higher flowability and greater bulk density of final grains when compared with control resin grains. While both nonisothermal and fast initiator dosage polymerization process broaden the particle size distribution (PID) of final PVC grains, applying Cok process produces particles with the same PID as a control process. In comparison with nonisothermal trajectory and continuous fast initiator dosage system, the Cok polymerization process leads to the most delay of motionless conversions, fusion time and the formation of a three-dimensional skeleton of primary particles as well.

… determine the need for special control systems. In this … controlling the operation of a batch polymerization reactor, utilizing an adaptive controller of the type STC (Self Tuning Controller). …

Process for the preparation of polymers which comprises a suspension free radical polymerization of monomers in the presence of the initiator O,O-t-amyl-O-(2-ethylhexyl)monoperoxycarbonate.

… Seeded suspension polymerization is a promising way to … in emulsion polymerization systems in order to control particle … seeded emulsion polymerization is how to control secondary …

A comparative study of the suspension polymerization of … /particles from the suspension polymerization and dispersion … transition stage in a suspension polymerization is sufficient to …

… The main advantages of suspension polymerization compared to the bulk process are the easier control of the reaction temperature due to the presence of the dispersion medium (eg, …

… A batch polymerization reactor in which suspension polymerization of MMA takes place is used for this investigation. The article is organized as follows. Flrst, the experimental system is …

… The process control challenges involve the design and control of the particle size … suspension polymer particles. The collection of emulsion particles modifies the suspension polymer …

… The PSD in suspension polymerization is controlled by a dynamic equilibrium of mechanisms of droplet breakdown and coalescence. Therefore mechanical mixing is the major factor in …

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolytetrafluoroethyleneW. E. Hanford and R. M. JoyceCite this: J. Am. Chem. Soc. 1946, 68, 10, 2082–2085Publication Date (Print):October 1, 1946Publication History Published online1 May 2002Published inissue 1 October 1946https://pubs.acs.org/doi/10.1021/ja01214a062https://doi.org/10.1021/ja01214a062research-articleACS PublicationsRequest reuse permissionsArticle Views2074Altmetric-Citations104LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

… polymer (3) supports the belief that polytetrafluoroethylene is … polytetrafluoroethylene, the most highly fluorinated polymer … In order to oxidize polytetrafluoroethylene, it is necessary to …

… virtual industrial production process optimization with reduced … of a sophisticated industrial suspension polymerization reactor … weight and PDI for the fluoropolymers. However, it is well …

… of the aqueous suspension in the kettle are … optimize the incineration/combustion of fluoropolymer-containing materials to recover HF and/or CaF2 from the off-gases. Such processes …

… The current chapter examines the underlying chemistry of fluoropolymers and their derivatives, as … fluorine content, as well as a technical summary of fluoropolymer processing behavior. …