Bulk slurry process

For the production of standard high-impact block copolymers, similar differences were found in overall economics between processes as found with homopolymers gas-phase and bulk slurry processes with three or more continuous reaction stages in series. Such processes are significantly more costly than our standard two-reactor, gas-phase and bulk slurry processes, but the products they produce are very high performance and cannot yet be matched in a two-stage reaction system. The products command significantly higher prices, and these complex slurry processes are, therefore, expected to remain in use (at least in Japan and Western Europe) beyond the 1993 timeframe. 

The share of competing technologies in production of polypropylenes in the three industrialized regions is undergoing dramatic change at the present time. Many of the existing heavy diluent slurry process plants are being revamped to bulk slurry processes, and many more new bulk slurry plants are presently under construction. 

There are three major commercial polymerization processes for isotactic PP production solvent slurry, bulk slurry, and gas phase (Fiasse, 1994). The solvent slurry process was designed for the first generation of catalysts. Although the process is relatively complex, its flexibility can produce some of the finest and cleanest grades of PP. The bulk slurry process is similar to solvent slurry but is much simpler thus, it displaced the solvent slurry process for PP production. The gas phase process has simplicity similar to that of the bulk slurry process, and thus these two processes are competitive with each other. However, the gas phase process is more suitable for copolymerization with a high level of comonomers. 

Gas phase olefin polymerizations are becoming important as manufacturing processes for high density polyethylene (HOPE) and polypropylene (PP). An understanding of the kinetics of these gas-powder polymerization reactions using a highly active TiCi s catalyst is vital to the careful operation of these processes. Well-proven models for both the hexane slurry process and the bulk process have been published. This article describes an extension of these models to gas phase polymerization in semibatch and continuous backmix reactors. 

Another method of manufacturing polypropylene employs the liquid monomer as the polymerization solvent. This process, known as the liquid propylene or bulk-phase process, has a major advantage over the slurry method in that the concentration of the monomer is extremely high. The high concentration increases the rate of the reaction relative to that seen... 

The processes for making PP are very similar to those for polyethylene—bulk, slurry phase, and gas phase. In fact, the same plants shown in Figures 23-2, 23-4, and 24—5 can be used. 

In the bulk process, liquid propylene (polymer grade propylene here too) replaces the hydrocarbon diluent used in the slurry phase process. The PP is continuously withdrawn from the solution and any unreacted monomer is flashed off and recycled. The back end of the process, atactic PP removal and catalyst deactivation and removal, is the same as the slurry process. 

Commercial suppliers of bulk slurry delivery equipment have taken several different approaches to measuring slurry constituents. In addition, there are different approaches to replenishing a daytank as its slurry is consumed by the polishing process. To further complicate things, measure-... 

No study has been made to discover which of the several resistances is important, but a simple rate equation can be written which states that the rate of the over-all process is some function of the extent of departure from equilibrium. The function is likely to be approximately linear in the departure, unless the intrinsic crystal growth rate or the nucleation rate is controlling, because the mass and heat transfer rates are usually linear over small ranges of temperature or pressure. The departure from equilibrium is the driving force and can be measured by either a temperature or a pressure difference. The temperature difference between that of the bulk slurry and the equilibrium vapor temperature is measured experimentally to 0.2° F. and lies in the range of 0.5° to 2° F. under normal operating conditions. 

Conventional HP HP Bulk Process Solution Process Slurry Process Gas-Phase Process... 

The technologies that have been developed for the production of polyolefins, olefin homopolymers and copolymers are slurry, solution and gas-phase polymerisation bulk polymerisation of propylene in the liquid monomer as a special case of the slurry process has also emerged. The fundamental differences in the various olefin polymerisation processes reflect the different approaches that have been devised to remove the substantial heat of polymerisation. In addition, processes can be operated in a batch or a continuous mode. In the batch process the reagents are loaded into a polymerisation vessel, the polymer forms and the vessel is emptied before a new charge of reagents is introduced. In the continuous process, the catalyst precursor, activator and other necessary... 

More than 40 years after its introduction, polypropylene is the largest chemical consumer of propylene in the United States. It is produced primarily by a bulk or gas phase process, with the older slurry process still... 

This section discusses boundary layers that exist between the wafer surface and the bulk slurry. CMP involves chemical reactions between the wafer surface and the slurry. In order for the reactions to continue, new reactants must be transported to the wafer surface and old products must be transported away from the wafer surface. Boundary layers are an important consideration in CMP processes, because boundary layers act as diffusion barriers to the reactants and products of these chemical reactions. As a... 

In PP manufacture, modern bulk (liquid monomer) and gas-phase processes have largely replaced the earlier slurry processes in which polymerization was carried out in hydrocarbon diluent. The most widely adopted process for PP is Basell s Spheripol process.317 Homopolymer production involves a pre-polymerization step at relatively low temperature, followed by polymerization in a loop reactor using liquid propylene random co-polymers are produced by introducing small quantities of ethylene into the feed. The pre-polymerization step gives a pre-polymer particle with the capacity to withstand the reaction peak, which occurs on entering the main loop reactor. The addition of one or two gas-phase reactors for EP co-polymerization makes it possible to produce heterophasic co-polymers containing up to 40% of E/P rubber within the homopolymer matrix. 

Bulk polymerization using conventional initiators (AIBN, peroxides) at < 100°C Continuous slurry process Emulsion polymerization... 

Diluent slurry processes for polypropylene are expensive to build and to run because of the number of pieces of equipment involved. They have largely been replaced by the more efficient bulk and gas-phase processes. Most of the remaining diluent slurry plants in the world now focus on producing speciality polymers, as diluent slurry processes do offer some advantages over other bulk and gas-phase processes. An example is the production of high-crystallinity polypropylene (HCPP), where most of the atactic polymer is dissolved in... 

It is tempting to suggest that polymer processes will gradually evolve toward bulk. Recently, the suspension process for impact polystyrene has been supplanted by the bulk process, and the emulsion process for ABS may similarly be replaced. However, the modern gas-phase process for polyethylene appears to represent an opposite trend. It seems that polymerization technology tends to eliminate solvents and suspending fluids other than the monomers themselves. When the monomer is a solvent for the polymer, bulk processes are preferred. When the monomer is not a solvent, suspension and slurry processes like those for polyethylene and polypropylene are employed. 

The medium for polymerization can be liquid or gaseous propylene or an inert hydrocarbon diluent such as hexane. Today about 25% of PP is produced in inert hydrocarbon slurry processes. Their relative proportion will steadily decrease because practically all new plants and investments are based on gas phase, bulk or combined bulk/gas phase technologies. 

Continuous Slurry Process. This process is similar to bulk polymerization, but the monomer is isolated into small suspended droplets in an aqueous medium. 

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