RU2122197C1 - Method determining degree of inhomogeneity of polymer in apparatus with agitator - Google Patents

Abstract

FIELD: chemical technologies of polymers, production of chemical fibers and plastic materials. SUBSTANCE: method consists in measurement of momentary values of molecular mass by pumping of polymer mass contained in apparatus through blades of agitator. Parameters of cycles of vibrations of molecular mass, its average values in cycles and rate of its change are found. Functional dependencies of average molecular mass in cycles and rate of its change in time are brought out. Values of average molecular mass at any time moment are computed and periodic component of change of molecular mass in time is isolated. Integrated content of molecular mass in cycle is determined and used to evaluate degree of inhomogeneity of polymer in apparatus with agitator. EFFECT: enhanced measurement precision. 5 dwg

Description

 The invention relates to the field of chemical technology of polymers and can be used in the production of chemical fibers and plastics.

 Known methods for determining particle sizes based on the conversion of these sizes into electrical pulses and analysis of the amplitude and frequency spectra using electronic equipment.

 A known method for determining the ratio of the mass of particles of the required size to the total mass of the system of the studied particles [1].

 The disadvantage of this method is the impossibility of its application in a process where the polymer mass is in motion under pressure or under vacuum at high temperature.

 The closest analogue is a method for controlling the homogeneity of a concrete mixture, which consists in measuring sound vibrations near the mixer body, highlighting the intensity and spectrum of the measured vibrations, and the homogeneity of a concrete mixture is judged by the coincidence of intensity and spectrum [2].

 The disadvantage of this method is the inaccuracy of controlling the homogeneity of the polymer mass in the apparatus with a stirrer, the inability to determine the average molecular weight and its rate of change.

 An object of the invention is to increase the control accuracy, expand the functionality by pumping the polymer mass through the mixer blades, isolating the unipolar component characterizing the average molecular weight from a function that reflects the time dependence of the power of the mixer motor and calculating the rate of change of the average molecular weight in current time.

 The problem is solved by the proposed method.

 Mixing is a mandatory and integral stage of technological processes in the production of most polymers, plastics in the process of polycondensation or other processes.

 The mass G located in the apparatus with the mixer, coming into translational and rotational motion, is pumped through the blades of the mixer L, as shown in FIG. one.

 In this case, the friction, collision of particles and molecules of the polymer mass with each other, with the blades of the mixer, with the casing of the apparatus expends the power of the electric motor D of the mixer.

A certain volume of the stirred mass in contact with the blades of the mixer at a certain point in time τ ₁ having a molecular mass M1 corresponds to the expended power P1 of the mixer motor.

At the next instant of time τ _{2, a} polymer volume with a molecular mass M2, for example, greater than M1, enters the mixer blades, therefore, the power of the mixer motor increases to P2.

 The direction of motion of the polymer mass G in FIG. 1 is shown by an arrow. The process of pumping the polymer mass G through the agitator blades occurs continuously cyclically, as shown in FIG. 2, and the average molecular weight in this case usually increases.

Из фактической зависимости молекулярной массы от времени M = M = Ф(τ) (кривая 1) вычитают зависимость средней молекулярной массы во времени M_ц = f(τ) (кривая 2), получая таким образом периодическую составляющую M_пер = π(τ) изменения молекулярной массы во времени (фиг. 3).Vibrations of the agitator motor power that arise during mixing, depending on the molecular weight of the polymer, are analyzed by intensity and spectrum, the amplitudes and frequencies of harmonics, the duration (periods) of the cycles T ₁ , T ₂ , T _n-1 ..., T _n , T _{n + 1} , their half-periods t ₁ , t ₂ , ... t _n-1 , t _n , t _{n + 1} , average molecular weight cycles Мс ₁ , Мц ₂ , ..., Мц _n-1 , for cycles Mc _n , Mc _{n + 1} , corresponding to time instants τ _ts1 , τ _ts2 , .., τ _tsn-1 , τ _tsn , τ _{tsn + 1} , average values of the rate of change V, for example, an increase in molecular weight equal to
V _1,2 = 2 (Mc ₂ - Mc ₁ ) / (T ₁ + T ₂ );
V _{n-1, n} = 2 (Mc _n - Mc _n-1 ) / (T _n-1 + T _n );
V _{n, n + 1} = 2 (Mc _{n + 1} - Mc _n ) / (T _n + T _{n + 1} );
according to average molecular weight values Мц ₁ , Мц ₂ , Мц _n-1 , Мц _n , Мц _{n + 1} , cycle periods T ₁ , T ₂ ... T _n-1 , T _n , T _{n + 1} and average values of speed changes in the molecular weight V _{1,2, ...} , V _{n-1, n} , V _{n, n + 1} reveal the functional dependences of the average molecular weight Mts in time M _c = f (τ) and the average rate of its change in time
V = φ (τ),
calculate the average molecular weight at any time, for example, at the end of the process τ _to

From the actual time dependence of the molecular mass M = M = Ф (τ) (curve 1), the dependence of the average molecular weight in time M _c = f (τ) (curve 2) is subtracted, thereby obtaining the periodic component M _per = π (τ) changes in molecular weight over time (Fig. 3).

получая зависимость относительной величины молекулярной массы во времени (фиг. 4).For each point in time in each cycle, for example, in cycle n, the ratio

obtaining the dependence of the relative value of the molecular weight in time (Fig. 4).

Assuming that during the cycle, in this case T _n , the entire mass of polymer G, occupying the volume Q of the apparatus, is pumped through the blades of the mixer, the integral relative content of the relative molecular weight in the volume Q of the apparatus is determined, and the relative volume of the entire mass of γ polymer is taken to be unity (Fig. 5). By the integral relative content of the relative value of the molecular weight, the heterogeneity of the polymer in the apparatus with the mixer is judged.

 Thus, the proposed method allows you to determine the moment of completion of the process, to intensify and optimize it, to determine the causes of heterogeneity and to suggest ways to influence it.

Bibliographic list
1. Patent 510165 (USSR). The method of determining the ratio of the mass of particles of the required size to the total mass of the system of the studied particles / Wallace Henry Coulter and Walter Robert Hogg (USA). Publ. in BI, 1976, No. 13.

 2. Copyright certificate 1629205 (USSR) A method for monitoring the uniformity of concrete mix / Blyvas and other publ. in BI, 1991, N 7.

Claims (1)

 A method for determining the degree of polymer heterogeneity in an apparatus with a stirrer, comprising isolating the intensity and spectrum of the measured molecular weight vibrations, characterized in that the instantaneous molecular weight is measured by pumping through the blades of the stirrer the mass of the polymer in the apparatus, the parameters of the molecular vibration cycles, its average values in cycles, the rate of change, reveal the functional dependence of the average molecular weight in cycles and the rate of change over time, calculating yayut values of average molecular weight at any one time, allocate periodic component changing over time the molecular weight is determined relative to the integral content relative molecular weight in the cycle on which judge the degree of the inhomogeneity of the polymer in a stirred vessel.

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