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Polymerization continuous solution

Solution Polymerization. Solution polymerization of vinyl acetate is carried out mainly as an intermediate step to the manufacture of poly(vinyl alcohol). A small amount of solution-polymerized vinyl acetate is prepared for the merchant market. When solution polymerization is carried out, the solvent acts as a chain-transfer agent, and depending on its transfer constant, has an effect on the molecular weight of the product. The rate of polymerization is also affected by the solvent but not in the same way as the degree of polymerization. The reactivity of the solvent-derived radical plays an important part. Chain-transfer constants for solvents in vinyl acetate polymerizations have been tabulated (13). Continuous solution polymers of poly(vinyl acetate) in tubular reactors have been prepared at high yield and throughput (73,74). [Pg.465]

Application of Wiener type predictive controller to the continuous solution polymerization reactor... [Pg.861]

Experiments were conducted with a dual catalyst chain shuttling system in a continuous solution polymerization reactor. A series of ethylene-octene copolymers of similar melt index were produced with a composition of ca. 30% (by weight) hard and 70% soft blocks. The level of DEZ was systematically varied to study the effects of CSA ratio on polymer microstructure. [Pg.89]

Continuous SO3 single-pass sulfonation processes, 23 543-552, 550 Continuous solution polymerization, reactors used for, 23 394-395 Continuous steel casting, 23 266-270 difficulties of, 23 266-267 universality of, 23 269-270 Continuous sterilization, in fermentation, 11 35-36... [Pg.214]

F. Teymour and W.H. Ray. The dynamic behavior of continuous solution polymerization reactors-IV. Dynamic stabihty and bifurcation analysis of an experimental reactor. Chem. Eng. Sci., 44(9) 1967-1982, 1989. [Pg.32]

When a monomer such as acrylonitrile is polymerized in a poor solvent, macroradicals precipitate as they are formed. Since these are living polymers, polymerization continues as more acrylonitrile diffuses into the precipitated particles. This heterogeneous solution polymerization has been called precipitation polymerization. [Pg.187]

Continuous solution polymerization is the most important method for the commercial production of polystyrene although suspension polymerization is also used [Moore, 1989]. [Pg.302]

Fig. 3-19 Continuous solution polymerization of styrene. After Moore [1989] (by permission of Wiley-Interscience, New York). Fig. 3-19 Continuous solution polymerization of styrene. After Moore [1989] (by permission of Wiley-Interscience, New York).
The particle number remains the same in interval III as in interval II, but the monomer concentration decreases with time, since monomer droplets are no longer present. The decrease in 4>m is slower with the more water-soluble monomers as the monomer in solution acts as a reservoir. The presence of a gel effect continues in interval IE. The quantitative interplay of a decreasing monomer concentration with the gel effect determines the exact behavior observed in this interval (GF or H). Polymerization continues at a steadily decreasing rate as the monomer concentration in the polymer particles decreases. Final conversions of essentially 100% are usually achieved. The final polymer particles, spherical in shape, usually have diameters of 50-300 nm, which places them intermediate in size between the initial micelles and monomer droplets. [Pg.356]

Deionized water (720 g), sodium lauryl sulfate (4.3 g), dioctanoyl peroxide (40 g), and acetone (133 g) were emulsified using an ultrasonic probe for 10 minutes. The step 1 polystyrene seed (48.0 g seed, 578 g latex) was added to the emulsion together with lauryl sulfate (0.8 g) and acetone (29.6 g). The mixture was transferred to a flask and left to agitate at approximately 25°C for 48 hours. Acetone was then removed and the solution added to a 5-liter double-walled glass reactor. The temperature was increased to 40°C while styrene (336 g) and divinyl benzene (0.88 g) were added drop-wise over approximately 60 minutes. After 4 hours the mixture was treated with deionized water (1200 g), potassium iodide (1.28 g), and polyvinyl pyrrolidone (18.48 g) with the temperature increased to 70°C. The polymerization continued for 6 hours at 70°C and 1 hour at 90°C. Styrene-based oligomer particles with a diameter of 1.7 pm and with a narrow size distribution were obtained. [Pg.469]

At present all commercial polystyrene (with average molecular weights between 100,000 and 400,000) is manufactured by radical polymerization, which yields atactic polymers.476 Peroxides and azo compounds are commonly used initiators. The suspension process (usually as a batch process in water at 80-140°C) produces a product with relatively high residual monomer content.223 More important is the continuous solution process (usually in ethylbenzene solvent at 90-180°C), which yields high-purity product. Styrene can be copolymerized with numerous other monomers.477 One of these copolymers, the styrene-divinylbenzene copolymer produced by free-radical polymerization, has a crosslinked stucture and is used in... [Pg.774]

This equation can be put in a more usable form for semi-continuous solution or emulsion polymerization by algebraic manipulation, equation 2. [Pg.346]

Four polymerization examples are presented here to illustrate both available sensitivity, experimental difficulties, and hopefully some interesting aspects of the polymerization processes. The first two examples are the semi-continuous emulsion polymerization of methyl methacrylate (MMA) and styrene, respectively. The third example is a batch charged copolymerization of butyl acrylate (BA) with MMA. The fourth example is a semi-continuous solution polymerization of an acrylic system. In this last example aliquots were taken manually and analyzed at 29.7°C under static conditions. No further polymerization occurred after the samples were cooled to this temperature. [Pg.347]

Since mixing and good heat transfer are of vital importance in viscous polymerization reactions, a mechanically agitated continuous stirred-tank reactor is widely used in polymerization processes. Solution polymerization, emulsion polymerization, and solid-catalyzed olefin polymerization are all carried out in a mechanically agitated slurry reactor. [Pg.143]

Continuous solution Anionic Pure styrene monomer Much recycled solvent Anionic initiators Polymerize to completion Low residual monomer High polymerization rate Good for spec, copolymer Sensitivity to impurities Initiator cost Color of product Cannot produce HIPS Not proven for high-volume GP... [Pg.67]

The system utilized in Figure 3.13 for HIPS can also be used to produce a solution polymerization ABS. This type of ABS is used in non-glossy applications. The glossy ABS is usually produced in an emulsion process in which emulsified polybutadiene latex is grafted and agglomerated and blended with a continuous phase of SAN. This blended material is then dried and pelletized. This process is not cost competitive with the continuous solution polymerization, but it produces a product with a superior balance of properties that commands a premium price. [Pg.69]

Just as the products of polycondensation are greatly varied, so are the reaction conditions used in their production. Some are produced in the melt (many polyamides and polyesters), some initially in the melt but with extensive polymerization continuing in the solid state (polyurethane foams and elastomers), in solution (some polyurethane fibres) or in non-homogeneous liquid systems (some polycarbonates, very high melting polyamides). [Pg.474]

Various molecular weights of random ethylene vinyl acetate copolymers can be obtained by high-pressure radical polymerization, bulk continuous polymerization, or solution polymerization. [Pg.285]

A mathematical model for styrene polymerization, based on free-radical kinetics, accounts for changes in termination coefficient with increasing conversion by an empirical function of viscosity at the polymerization temperature. Solution of the differential equations results in an expression that calculates the weight fraction of polymer of selected chain lengths. Conversions, and number, weight, and Z molecular-weight averages are also predicted as a function of time. The model was tested on peroxide-initiated suspension polymerizations and also on batch and continuous thermally initiated bulk polymerizations. [Pg.13]

Wang, W.-J. Yan, D. Zhu, S. Hamielec, A.E. Kinetics of long chain branching in continuous solution polymerization of ethylene using constrained geometry metallocene. Macromolecules 1998, 31 (25), 8677-8683. [Pg.266]

Styrene is one of the oldest and most studied monomers. It spontaneously generates free radials upon heating above 100 °C and polymerizes yielding amorphous polystyrene (PS). Styrene can also be polymerized by other mechanisms (anionic, cationic, or Zeigler-Natta) with the aid of chemical initiators. Commercially, over twenty billion pounds of PS are produced annually worldwide. All of this polystyrene is produced via free radical (FR) chemistry, and mostly via continuous solution polymerization processes. The commercial preference for the continuous solution process is due mainly to economic factors. Non-solution polymerization processes (suspension and emulsion) have lower reactor efficiency (product/reactor volume) due to reactor volume occupied by the water which adds to the manufacturing cost. [Pg.69]

Polystyrene was first manufactured commercially (1938) by The Dow Chemical Company. Styrene was non-continuously bulk polymerized, without the aid of a chemical initiator, to high conversion by heating it in metals cans. The cans were opened and the solid PS ground into small pieces. Over the next 35 years, most of the research focused on understanding the mechanism of self-initiated (spontaneous) polymerization of styrene and developing continuous solution polymerization processes. In recent years, solution polymerization research emphasis has focused upon understanding the chemistry of chemical initiators. Today, most PS is produced via continuous solution polymerization with the aid of peroxide initiation. [Pg.69]


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See also in sourсe #XX -- [ Pg.36 ]




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