Finishing step

Polymer is separated from the polymerisation slurry and slurried with acetic anhydride and sodium acetate catalyst. Acetylation of polymer end groups is carried out in a series of stirred tank reactors at temperatures up to 140°C. End-capped polymer is separated by filtration and washed at least twice, once with acetone and then with water. Polymer is made ready for extmsion compounding and other finishing steps by drying in a steam-tube drier. 

In contrast to dyes, fluorescent whiteners are not appHed exclusively in special processes, but often in combination with bleaching and finishing steps. Fluorescent whiteners used in such processes must be stable and should not interfere with the operation. 

Saponification can proceed direcdy as a one-step reaction as shown above, or it can be achieved indirectly by a two-step reaction where the intermediate step generates fatty acids through simple hydrolysis of the fats and oils and the finishing step forms soap through the neutralization of the fatty acid with caustic soda. There are practical considerations which must be addressed when performing this reaction on a commercial scale. 

Chemistry of SBR. There are three steps in the manufacturing of SBR polymerization, monomer recovery and finishing. The polymerization step determines the basic characteristics of SBR, whereas the product form (latex or dry rubber, oil extended or not) depends on the finishing step. 

As suggested by Barrett (2), it is assumed that following the particle nucleation stage, the polymerization proceeds in the particle (monomer/polymer) phase with no mass transfer limitation. Therefore, the dispersion polymerization is similar to a mass or suspension polymerization, and kj can not be assumed to be constant even at isothermal conditions, since kp and even kp are dependent on the degree of polymerization because of a gel effect. (2., ,D However, since the application of the model is for a finishing step, with polymer molecular weight and viscosity fairly well established, further changes in kp and kp should be minimal. 

MODEL TO PREDICT RESIDUAL MONOMER FOR AN ISOTHERMAL SEMI-BATCH POLYMERIZATION AND AN ISOTHERMAL BATCH FINISHING STEP. 

Thus, the initial value of the initiator concentrations, [Il]° and [I2]°, are calculated with Equation 15, for given values of the initial loading, feed rates, temperature, and time for the main semi-batch step, and [M]° is fixed according to experimental data from the base case semi-batch step. The nonlinear differential equation for [M] in terms of [II] and [I2] is given by Equation 16. Equation 10, with a redefinition of terms, is the differential equation mass balance for [II] and [12]. In the finishing step, only one of the initiators would be added for residual monomer reduction. Thus, Qm = 0,... 

Q = Qi (i=l or 2), and W° becomes the total amount of material in the reactor at the start of finishing step. Since the amount of initiator added is insignificant compared to the total reactor charge, it is assumed that the total amount is constant during the finishing process. With this assumption, the analytical integration of Equation 10 is straight forward. 

The SimuSolv optimize function can be used for minimization of a user defined cost expression. However, at this early stage of process development, no attempt was made to determine parameters for an economic optimum. Instead, many simulations were run to determine parameter sensitivities and malce comparisons of various possibilities which satisfied a necessary objective of reaching the desired low level of residual monomer. Attention was given to minimizing total finishing time, the amount of initiator required and residual initiator level at the end of the finishing step. Based on simulation results for... 

In-mould labelling (IML) used for injection-moulded products and blow-moulded bottles is an alternative to self-adhesive or heat-transfer decoration, eliminating a finishing step. 

An increase or decrease in production scale during finishing steps that involves new or different equipment. 

The second approach, high severity followed by a finishing step, is more common, and several examples of this have been reported (14,109,114-116, 138-140). The major concern in this approach is that high severity with present commercial catalysts produces color fluorescence in the low-sulfur product, and hydrofinishing is necessary to restore quality. An example of exploratory studies to identify the optimal conditions in a two-stage process using conventional catalysts is shown in Table XX (114). The table shows... 

Analytical methods for monitoring the compounds were developed or modified to permit the quantification of all 23 compounds of interest. As noted earlier, the compounds were initially studied in small-scale extractions by groups. This approach assured minimal interferences in the analyses conducted during the initial supercritical fluid carbon dioxide extractions. Table II summarizes the data on the recovery of organics from aqueous samples containing the compounds of interest at concentration levels listed in Table I when the sample preparation techniques and analytical methods described were used. For each experimental run, blank and spiked aqueous samples were carried through the sample prepration and analytical finish steps to ensure accurate and reproducible results. Analyses of sodium, calcium, and lead content were also conducted on selected samples by using standard atomic ab-... 

The development of low profile polyester resin adds an additional dimension to SMC and BMC. The post-molding finishing steps with FRP have been a strong deterrent in high appearance requirement applications. The low profile resins utilize thermoplastic additives to obtain... 

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