Patent RU-2235731-C1 (RU)
Inventor: BITJUKOV V K
IPC: C08F136/06
Filed: 2003-07-18
Granted: 2004-09-10
Abstract: FIELD: polymerization processes. 
     SUBSTANCE: task of invention consists in increasing accuracy in controlling function of molecular weight distribution of linear polybutadiene in the course of synthesis on polymerization reactor set. Task is achieved by providing a method of automatically controlling molecular weight distribution of linear polybutadiene including feeding and measuring catalysts' uptake, principal and additional streams of the charge into polymerization set reactors, stabilizing viscosity of polymerizate in polymerization set reactors by influencing uptake of aluminum catalyst, and measuring and stabilizing temperature of polymerizate in polymerization set reactors, which is characterized by that automatic control of molecular weight distribution of linear polybutadiene involves feeding catalyst and additional streams of charge into all reactors, measuring consumption of principal and additional streams of charge and catalyst on the inlet and outlet of each of reactor, stabilizing temperature in all reactors, using thus measured values to calculate distribution of residence time of linear polybutadiene molecules for each reactor and value of function of molecular weight distribution of linear polybutadiene M( l ) for each reactor in terms of the following equation: M( l ) = K f (1/Θ·Sh) N ·(l·C) N-1 /((N-1)!)·e -(1/Θ·Sh)+kRP)lC , where k = K 0 e -E/RT , Θ = V eff /G pol , G pol  = G ch +G cat ; M is molecular weight of polymer molecules with certain length; N is number of reactors in polymerization set;  l  length of a molecule measured by number of monomer units; Θ average polymerizate residence time in current rector of polymerization set, h; V eff  volume of polymerizate in reactor, m 3 ; G pol  consumption of charge in total reactor set, m 3 /h; G ch  intake of charge in total reactor set, m 3 /h; G cat  intake of catalyst in total reactor set, m 3 /h; k polymerization growth rate constant, 1/h; E activation energy of polymerization process, J/mole; R absolute gas constant, L/(mole·K); Sh correction coefficient taking into account effect of set loading on the width of molecular weight distribution; Rp correction coefficient taking into account effect of polymerization growth rate constant k on the width of molecular weight distribution; C correction coefficient transforming time scale into macromolecule length scale; K f  polymerization set reactor-averaged coefficient relating molecular weight of polymer molecules with distribution of their concentration on the scale of their residence time in polymerization set reactors, %·h; and T temperature of polymerization mixture in current polymerization set reactor, K. Thus obtained data are used to plot, experimental curve of the molecular weight distribution function for each reactor, whereupon criterion S J  of discrepancy with etalon curve of molecular weight distribution function is found from formula:  , where S J  is criterion of discrepancy of experimental and etalon curves of the molecular weight distribution function; j reactor number in polymerization set, j =1…N; N number of reactors in polymerization set; i sequential number of points of division of the molecular weight distribution function; and M( l ) i  value of experimental function of the molecular weight distribution in ith point. From S j  value new values of intakes of additional stream of charge G       ch   j        and catalyst G       cat   j        for each reactor are calculated according to formulas: G       ch   j        = a j S j  and G       cat   j        = b j S j  wherein j is reactor number in polymerization set, j =1…N, N is number of reactor in polymerization set; and   are empirically determined vectors of coefficients. 
     EFFECT: increased accuracy of controlling function of molecular weight distribution of linear polybutadiene. 
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