Vapor-phase polymerization process

Most commercial processes produce polypropylene by a Hquid-phase slurry process. Hexane or heptane are the most commonly used diluents. However, there are a few examples in which Hquid propylene is used as the diluent. The leading companies involved in propylene processes are Amoco Chemicals (Standard OH, Indiana), El Paso (formerly Dart Industries), Exxon Chemical, Hercules, Hoechst, ICl, Mitsubishi Chemical Industries, Mitsubishi Petrochemical, Mitsui Petrochemical, Mitsui Toatsu, Montedison, Phillips Petroleum, SheU, Solvay, and Sumimoto Chemical. Eastman Kodak has developed and commercialized a Hquid-phase solution process. BASE has developed and commercialized a gas-phase process, and Amoco has developed a vapor-phase polymerization process that has been in commercial operation since early 1980. 

FIGURE 10.7 A continuous vapor-phase polymerization process for coating wool yarn (a) yam bobbin, (b) methanol-FeClj solution container, (c) pyrrole container, (d) glass tubular reactor, (e) scrubber, and (f) collector. 

Gray clay treating a fixed-bed (q.v.), usually fuller s earth (q.v.), vapor-phase treating process to selectively polymerize unsaturated gum-forming constituents (diolefins) in thermally cracked gasoline. 

The impurities in phthalic anhydride obtained in the vapor phase oxidation process may he caused to condense or polymerize by heating either with or without the addition of special agents. The vapor pressure of these materials is so lowered by this treatment that subsequent sublimation of tlu- mass results in pure product, the condensed materials remaining in the retort. 

Rexene Co. and Philips Petroleum Co. first developed the bulk polymerization process with the first-generation TiCU catalyst [8,11,70]. It was then commercialized by Dart Industries in 1964. The reactor feed contains 10-30% propylene in the liquid phase. A mixture of hexane and isopropanol was employed for the removal of catalyst residue as well as the amorphous polypropylene. The process step of removing residual catalyst was later eliminated after the high-efficiency catalyst was adopted, constituting the so-called liquid pool process. Subsequently, Philips and Sumitomo companies further developed the liquid-phase polymerization process. This process enhances the reaction rate, catalyst efficiency, monomer conversion, and therefore results in high productivity. It also eliminates the need for solvent recovery and reduces environmental pollution. However, the process is somewhat complicated by the unreacted monomer, which has to be first vaporized and then liquefied before it is reused. The reaction vessel must be designed to operate under high pressures. In most cases, this process employs autoclaves for batch operation and tubular reactors for continuous operation. 

The preferred polymerization medium was a saturated fluorocarbon or chlorofluorocarbon solvent, although an aqueous medium could also be used. The solvent system was used to control the reaction conditions and increase the polymerization reaction rate. The reaction medium could also improve melt processability and increase the thermal stability and chemical resistance of the polymer. The reaction could be carried out by bulk, solution, suspension, emulsion, or vapor phase polymerization regimes. Azo compounds, peroxy compounds, ultraviolet radiation, or high-energy ionizing... 

Polymerization of the quarterpolymers took place in a stirred reactor in an aqueous or a nonaqueous reaction medium. Preferred organic solvents were fluoroalkanes or chlorofluoroalkanes and their mixtures with water. Polymerization reaction could be carried out by bulk, solution, suspension, emulsion, or vapor phase polymerization methods. The reaction conditions depended on the selected polymerization process. The reaction temperature was in the range of 20°C to 100°C. An organic solvent medium required the use of organic peroxy or azo compounds as the reaction initiator. In aqueous media, water-soluble initiators such as ammonium persulfate could be employed. The best initiators for aqueous media were acids of manganese and their salts, such as potassium permanganate. The total pressure was in the range of 0.2-10 MPa. 

Vapor phase polymerization is a solvent-free process and polymers are synthesized by delivering monomers to a surface through the vapor phase... 

Vapor phase polymerization from SI-NMP of various vinylic monomers resulted in polymer bmshes with greater thicknesses than those formed by the solution phase process [21]. To explain this result, the authors supposed a more efficient reaction on the surface as a result of prolongation of the mean path of vaporized monomers in a vacuum, higher thermal energy of the monomer, and the possibility of adjusting the reaction parameters independently. Thin films of PS grafted polymer, poly (acrylic acid) (PAA), poly(2-hydroxypropyl methacrylamide) (PHPMA), and poly(lV-isopropylacrylamide) (PNIPAM) were prepared with thicknesses of a few nanometers to submicrometers. This process was also used for the preparation of block copolymers (e.g., PS-b-PAA and PAA-b-PS-PHPMA). It is important to mention that solution phase polymerization of AA, HPMA, and NIPAM is impossible with TEMPO-based alkoxyamines. 

The feedstocks used ia the production of petroleum resias are obtaiaed mainly from the low pressure vapor-phase cracking (steam cracking) and subsequent fractionation of petroleum distillates ranging from light naphthas to gas oil fractions, which typically boil ia the 20—450°C range (16). Obtaiaed from this process are feedstreams composed of atiphatic, aromatic, and cycloatiphatic olefins and diolefins, which are subsequently polymerized to yield resias of various compositioas and physical properties. Typically, feedstocks are divided iato atiphatic, cycloatiphatic, and aromatic streams. Table 2 illustrates the predominant olefinic hydrocarbons obtained from steam cracking processes for petroleum resia synthesis (18). 

Thermal polymerization is not as effective as catalytic polymerization but has the advantage that it can be used to polymerize saturated materials that caimot be induced to react by catalysts. The process consists of the vapor-phase cracking of, for example, propane and butane, followed by prolonged periods at high temperature (510—595°C) for the reactions to proceed to near completion. Olefins can also be conveniendy polymerized by means of an acid catalyst. Thus, the treated olefin-rich feed stream is contacted with a catalyst, such as sulfuric acid, copper pyrophosphate, or phosphoric acid, at 150—220°C and 1035—8275 kPa (150—1200 psi), depending on feedstock and product requirement. 

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

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