Propylene monomer pressure

Under the following conditions temperature, 30° C propylene partial pressure, 2.5 bar metallocene concentration, 6.25 x 10 6 mol/liter MAO/metallocene molar ratio, 250 (24). monomer is monomer concentration (mol/liter). 

Synthesis. The early PP plants used a slurry process adopted from polyethylene technology. An inert liquid hydrocarbon diluent, such as hexane, was stirred in an autoclave at temperatures and pressures sufficient to keep 10-20 percent of the propylene monomer concentrated in the liquid phase. The traditional catalyst system was the crystalline, violet form ofTiCl3 and A1C1(C2H5)2. Isotactic polymer particles that were formed remained in suspension and were removed as a 20-40 percent solid slurry while the atactic portion remained as a solution in the liquid hydrocarbon. The catalyst was deactivated and solubilized by adding HC1 and alcohol. The iPP was removed by centrifuging, filtration, or aqueous extraction, and the atactic portion was recovered by evaporation of the solvent. The first plants were inefficient because of low catalyst productivity and low crystalline yields. With some modifications to the catalyst system, basically the same process is in use today. 

Novolen Process (Figure 7) With this technology, which comprises two vertical stirred gas-phase reactors in series, homopolymers as well as impact and random copolymers are produced. The first reactor operates at 80°C and 20-35 bar monomer pressure and is used exclusively for the homopolymerization of propylene. Propylene is injected as a liquid and cools the exothermic polymerization by its... 

Atactic polypropene has been synthesized with homogeneous catalytic systems based on mono-Cp trialkoxo titanium complexes activated by MAO.951 Syndiotactic polystyrene has been synthesized with different mono-Gp trialkoxo titanium derivatives activated by MAO and AlMe3, and the catalytic efficiency has been compared with bis-Cp titanium catalysts.952 The titanium ligands affect both catalytic activity and stereoregularity of the polypropylene obtained. For the CpTi(OPrn)3/MAO system, factors influencing the propylene polymerization, such as temperature, Al/Ti molar ratio, and monomer pressure, have been studied. 

Others, which used propylene under pressure as the solvent, required washing after the unreacted monomer was removed and recycled. The particular process was unique to each of the polymer manufacturers. 

Some late-transition metal catalysts, such as the Ni-diimine catalyst shown in Figure 2.14(d), have an intriguing property called chain walking when polymerizing ethylene, the active center can move away from the chain end and walk on the polymer backbone, leading to the formation of SCBs in the absence of a-olefin comonomers. By varying the polymerization temperature and monomer pressure, it is possible to make polymers with densities varying from those of FfDPE to LLDPE, VLDPE, ULDPE, and, in fact, to that of a complete amorphous, ethylene-propylene like elastomer [26,27],... 

In 1973, Stallings reportedly ] the polymerization of vinylidene fluoride into a polymer suitable for coatings applications. The polymerization took place in the presence of beta-hydroxyethyl tertiary butyl peroxide (initiator), a lower alkylene oxide and a water-soluble fluorinated surfactant at 10.4 MPa or higher monomer pressure. Alkylene oxide (0.02-0.5% of the monomer weight) played a beneficial role in minimizing polymer build-up on the reactor walls during the run times of 0.5-6 hours. An effective lower alkylene oxide contained 8 carbons or less in its molecule, e.g., ethylene or propylene oxide. 

We have followed the rate of polymerization of propylene initiated by a typical MgCl2 matrix impregnated TiCl3 catalyst. Figure 1 shows the results obtained at 60° and 3.5 atm. of monomer pressure. From the total polymer yield after 4 hrs. one calculated Rav (m mole Ti)=661. Therefore, the initial rate of polymerization is actually about ten-fold faster. After one hr. of polymerization the catalytic activity is only about one-fourth of the initial yielded, about 66% of the total polymer. 

Perhaps the most positive evidence for diffusion control in propylene polymerization with high activity catalysts is the comparison of reactions performed at different monomer pressure. 

Synthesis The early polypropylene plants used a slurry process adopted from polyethylene technology. An inert liquid hydrocarbon diluent, such as hexane, was stirred in an autoclave at temperatures and pressures sufficient to keep 10 to 20 percent of the propylene monomer concentrated in the liquid phase. The traditional catalyst system was the crystalline, violet form of TiCla and AlCl (C2Hs)2- Isotactic polymer particles... 

Polymerization in Hquid monomer was pioneered by RexaH Dmg and Chemical and Phillips Petroleum (United States). In the RexaH process, Hquid propylene is polymerized in a stirred reactor to form a polymer slurry. This suspension is transferred to a cyclone to separate the polymer from gaseous monomer under atmospheric pressure. The gaseous monomer is then compressed, condensed, and recycled to the polymerizer (123). In the Phillips process, polymerization occurs in loop reactors, increasing the ratio of available heat-transfer surface to reactor volume (124). In both of these processes, high catalyst residues necessitate post-reactor treatment of the polymer. 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

At this point in the process, thermoplastic and chlorosulfonated polyethylene (CSPE) membranes are complete and are ready for packaging. In the case of ethylene—propylene—diene monomer (EPDM), the curing step occurs before the membrane is ready for packaging. The curing process is accomphshed by placing the membrane in a large vulcanizer where the material is heated under pressure to complete the cure. 

The reactivity of ethylene is high, whereas that of propylene is low and the various dienes have different polymerisation reactivities. The viscous mbber solution contains some unpolymerised ethylene, propylene, unpolymerised diene, and about 10% EPDM, all in homogeneous solution. This solution is passed continuously into a flash tank, where reduced pressure causes most of the unpolymerised monomers to escape as gases, which are collected and recycled. 

FIGURE 23.16 Thickness (volume) changes from exposing ethylene propylene diene monomer (EPDM) to 8300 psi inert gas pressures. 

Coordination polymerization Can engineer polymers with specific tacticities based on the catalyst system Can limit branching reactions Polymerization can occur at low pressures and modest temperatures Otherwise non-polymerizable monomers (e.g., propylene) can be polymerized Mainly applicable to olefinic monomers... 

UNIPOL [Union Carbide Polymerization] A process for polymerizing ethylene to polyethylene, and propylene to polypropylene. It is a low-pressure, gas-phase, fluidized-bed process, in contrast to the Ziegler-Natta process, which is conducted in the liquid phase. The catalyst powder is continuously added to the bed and the granular product is continuously withdrawn. A co-monomer such as 1-butene is normally used. The polyethylene process was developed by F. J. Karol and his colleagues at Union Carbide Corporation the polypropylene process was developed jointly with the Shell Chemical Company. The development of the ethylene process started in the mid 1960s, the propylene process was first commercialized in 1983. It is currently used under license by 75 producers in 26 countries, in a total of 96 reactors with a combined capacity of over 12 million tonnes/y. It is now available through Univation, the joint licensing subsidiary of Union Carbide and Exxon Chemical. A supported metallocene catalyst is used today. 

At the pressure P, knowing the interaction parameter, and the vapour pressure of the monomer, Po, the volume-fraction, tj), of the monomer sorbed can be estimated from Equation 5.4-9. Figure 5.4-6 shows the pressure- and temperature dependence of the volume fraction of absorbed propylene in a given amorphous polypropylene [12],... 

All products were characterized by DTA, DTG analysis, infrared and x-ray spectra. The pressure was varied between 50 and 1,000 atm. Copolymerization with other monomers, vinyl methyl ether, propylene, and hexavinylbenzene gave products with chlorine contents of 2-15 Vinyl chloride and vinylidene chloride gave only homopolymers. 

The first free radical initiated copolymerization was described by Brubakerl) in a patent. A variety of peroxides and hydroperoxides, as well as, 02, were used as initiators. Olefins that were copolymerized with CO included ethylene, propylene, butadiene, CH2=CHX (X—Cl, OAc, CN) and tetrafluoroethylene. A similar procedure was also used to form terpolymers which incorporated CO, C2H4 and a second olefin such as propylene, isobutylene, butadiene, vinyl acetate, tetrafluoroethylene and diethyl maleate. In a subsequent paper, Brubaker 2), Coffman and Hoehn described in detail their procedure for the free radical initiated copolymerization of CO and C2H4. Di(tert-butyl)peroxide was the typical initiator. Combined gas pressures of up to 103 MPa (= 15,000 psi) and reaction temperatures of 120—165 °C were employed. Copolymers of molecular weight up to 8000 were obtained. The percentage of CO present in the C2H4—CO copolymer was dependent on several factors which included reaction temperature, pressure and composition of reaction mixture. Close to 50 mol % incorporation of CO in the copolymer may be achieved by using a monomer mixture that is >70 mol% CO. Other related procedures for the free radical... 

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