BG111207A - Method for determination the sedimentation stability and performing a sedimentation analysis of liquid dispersion systems - Google Patents

Abstract

The invention relates to a method for determination the sedimentation stability and performing a sedimentation analysis of liquid dispersion systems, which finds application in food, cosmetic, pharmaceutical, chemical, oil crushing and other industries for researches in biomedicine and physical chemistry. The homogenized dispersion system is placed in a container (1) to sediment and during pre-selected time intervals is measured a determining parameter and it establishes at particular time point ti of the measurement, the shift qt of the masses centre ?ti, compared to the initial position O. The current sedimentation stability Sti is determined for this particular time point ti as a ratio of the mass tf of the dispersed phase to the mass t of the entire dispersion system, which fills the container (1), multiplied to the ratio of time ti to the shift of the masses centre qti =?Oti of the dispersion system. The end of the sedimentation process is determined by the maximum value qof qti and the marginal sedimentation stability S of the dispersion system is calculated from the maximum value q and the time t, for which it is reached. From the determined values of qti versus time ti, is drawn a sedimentation curve, by which is carried out the sedimentation analysis. By this method is achieved complete and accurate characterization of the sedimentation process of a dispersion system and can be applied regardless of the color or optical transmittance of the tested dispersion system.

Description

METHOD FOR DETERMINING SEDIMENTAL STABILITY AND

PERFORMANCE OF A SEDIMENTAL ANALYSIS

OF LIQUID DISPERSION SYSTEMS

TECHNICAL FIELD

The invention relates to a method for determining sedimentation stability and performing sedimentation analysis of liquid dispersion systems, which is applicable: in the food, cosmetic, pharmaceutical, chemical, oil and other industries; for research in biomedicine and physicochemistry.

BACKGROUND OF THE INVENTION

A technical solution disclosed in the application for the invention is numbered [BG51838A], which describes a method for determining the sedimentation stability of liquid dispersion systems by determining the displacement of the center of mass during sedimentation. Three vessels are used for this purpose: the first two vessels are of the same geometric shape, the bottom of the second vessel being a filter barrier through which it is connected to the third vessel. The second vessel is filled with the liquid dispersion system, after which the liquid is pumped into the third vessel and the dispersed phase remains in the second vessel.

The processes in this method are: filling the first and second vessels with a homogenized liquid dispersion system; pumping the liquid medium from the second vessel through a filtration barrier through a device mounted in the third vessel until a dispersive phase is obtained in the second vessel of constant height; measuring the height of the dispersed phase with a ruler; separating the second vessel from the third and weighing it with the mass of the dispersed phase. Finally, the displacement of the center of mass and hence the sedimentation stability are calculated using certain formulas.

This method is complex and has a long sequence of operations, and it is necessary for each dispersion system to perform the operations described above in advance.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a simpler and more easily applicable method for determining sedimentation stability, as well as for carrying out sedimentation analysis of liquid dispersion systems, which achieves a complete and precise characterization of the sedimentation process of a dispersed system and can be applied regardless of the color or optical transmittance of the dispersion system under study.

The problem is solved by the proposed method for determining sedimentation stability and performing sedimentation analysis of liquid dispersion systems. In this case, sedimentation stability is determined by determining the displacement of the center of mass of a homogenized dispersion system, which is placed in an elongated vessel.

According to the invention, the container is completely filled with the homogenized dispersion system and then closed and placed to sediment. At predetermined time intervals a determining parameter is measured and it is used to determine at the specific moment of measurement, after a time (/ '= 1, 2, ..., n) from the beginning of the sedimentation process, the displacement of q _tj at the center of mass O _tj , relative to its initial position O. Current sedimentation stability S _t is defined at this particular time as the ratio of the mass m _d of the dispersed phase to the mass m of the whole dispersive system, filling the vessel multiplied by the ratio of time /, to the displacement of the center of the m-I masses q _t - O , Of the disperse system, according to the formula S, = - ¹ -. The end of '''t q, the sedimentation process is determined by reaching the maximum value q of q _t , and the marginal sedimentation stability S of the dispersed system is calculated from the maximum value q and the time t for which it is reached. From the determined values of q _t ., Versus time /, ·, a sedimentation curve is constructed, through which the sedimentation analysis is performed.

In one particular embodiment, the vessel is placed to settle in a gravity field, and in another case, the vessel with the dispersion system is placed in a centrifugal field to accelerate the sedimentation process.

Alternatively, the measured determining parameter is angle a. of tilting the vessel with the dispersed system relative to a plane perpendicular to the vector $ of the intensity of the gravitational field. For this purpose, the vessel is suspended only for the moment of the relevant measurement, at a point from its outer wall, located at the top of the vessel, about the level of its original center of mass O. The vessel is left free to balance and then measured. the angle a _t of its tilting.

In another embodiment of the proposed method, the measured determining parameter is the mass reduced relative to the total mass M of the vessel with the dispersion system. For this purpose, the vessel is fixed in an inclined position at a given angle a = const with respect to a plane perpendicular to the vector of gravity field intensity, so that the lower end of the vessel presses on a horizontal plate of an electronic balance and then the reduced mass m _t is measured.

In one particular case, to measure the reduced mass m _t . the vessel shall be fixed in an inclined position only for the specific moment during the relevant measurement.

In another particular case for measuring the reduced mass m _{t, the} vessel is fixed in an inclined position, remaining so throughout the sedimentation and measurement process, with the dispersed system sedimented in a gravitational field.

The advantages of the proposed method for determining sedimentation stability and for performing sedimentation analysis of liquid dispersion systems are that the dynamics of the dispersion phase transfer is monitored by detecting the displacement of the center of mass at specified intervals by measuring parameters which are independent of the color and optical transmittance of the dispersed system and whose measurement does not require sophisticated apparatus. This method makes a more complete and accurate characterization of the sedimentation of a dispersed system because it takes into account the total behavior of all particles. The resulting sedimentation curve gives more accurate information about the sedimentation process, which also allows for more accurate sedimentation analysis. Another advantage of the method is that it provides an additional opportunity to characterize sedimentation, such as to trace the influence of a factor on sedimentation stability under uniform other conditions. In addition, the sedimentation stability of different liquid dispersions can be compared under the same conditions.

The proposed method, in the variations in which the vessel is anchored in an inclined position, is only suitable for the moment of measurement to determine the sedimentation stability and to carry out sedimentation analysis of any suspensions and emulsions of sufficient viscosity so as not to change the shape of the vessel. flush when tilting the vessel during the measurement process.

The proposed method in the variant where a determining mass is measured and the vessel is tilted throughout the sedimentation and measurement process is suitable for determining sedimentation stability and carrying out sedimentation

analysis of sedimentary fine suspensions and any emulsions. The measurement of the reduced mass parameter is continuous and non-invasive throughout the sedimentation process. Another advantage of this particular application is that the method allows automatic transmission of data from the instrument to an electronic device for recording and processing.

EXPLANATION OF THE FIGURES Attached

The invention is illustrated by the exemplary embodiment shown in the accompanying drawings, of which:

FIG. 1 is a schematic diagram for sedimentation of a dispersed system that fills a straight cylindrical vessel.

FIG. 2 is a schematic diagram for measuring the determining parameter, the tilt angle a _t , of a vessel suspended at a point from its outer wall, located at the top of the vessel, about the level of the original center of mass O.

FIG. 3 is a schematic diagram for measuring the determining parameter - the tilt angle a _t of a vessel suspended at a point from its outer wall at the level of the original center of mass O.

FIG. 4 shows a table of measurement and calculation data for a particular embodiment of the method shown in FIG. 1 and FIG. 3.

FIG. 5 is a graph of current sedimentation stability S _{t with} respect to time ί _ζ , for a specific implementation of the method shown in FIG. 1 and FIG. 3.

FIG. 6 is a graph of a sedimentation curve obtained from the displacement of q _{t with} respect to time in a particular embodiment of the method shown in FIG. 1 and FIG. 3.

FIG. 7 is a table showing data from the sedimentation analysis of a particular embodiment of the method shown in FIG. 1 and FIG. 3.

FIG. 8 is a table of measurement and calculation data for a particular embodiment of the method shown in FIG. 1 and FIG. 4.

FIG. 9 - a table of measurement and calculation data for another specific implementation of the method.

EXAMPLE IMPLEMENTATION OF THE INVENTION

FIGS. 1 to 3 show various exemplary embodiments of the present invention which do not limit it:

EXAMPLE 1. The method for determining sedimentation stability and for conducting sedimentation analysis of liquid dispersion systems according to FIG. 1, FIG. 2 and FIG. 3, is performed as in an elongated straight cylindrical vessel 1 made of homogeneous material, pouring the homogeneous dispersed system under test with the same thickness of the walls until it is completely filled, after which the vessel is closed.

In one particular embodiment of the method, the vessel 1 with the dispersed system is placed upright (Fig. 1) and left under the action of a gravity field with intensity / at constant temperature and external pressure.

In another embodiment of the method, to accelerate the sedimentation process, the vessel 1 with the dispersion system is placed to sediment in a centrifugal field.

At predetermined time intervals (i = 1, 2, ..., η) a determining parameter is measured - the angle a _t of the tilting of the vessel 1 with the dispersed system, relative to a plane perpendicular to the vector / intensity of the gravitational field. The vessel 1 with the dispersion system hangs only for a specific moment a measurement time at point A] from its outer wall (Fig. 2), which is located at the top of the vessel, fixed at a point from its outer wall, located at the upper part at the level of the original center of mass O, after which the vessel 1 is left free to balance and the angle a _tj is measured. By a _tj , the displacement q _t of the center of mass O _t is determined from its initial position O at the instant of measurement time by the formula q _t _ = r - tga ₀ ), where r is the distance from the axis of the vessel 1 to the point of Suspension and a ₀ is the angle at the start of the measurement when the dispersed system is homogenized.

A particular embodiment of the method is possible in which the vessel 1 with the dispersed system is suspended only for the moment of corresponding measurement at the point A ₂ from its outer wall, which lies at the level of the original center of mass O (Fig. 3). In this case the angle «0 = 0.

In one particular case, as indicated in Example 1, the dispersed system of distilled water and starch, with a total mass of m = 30.12 g and a mass of the dispersed phase (starch) mj- 0.63 g (~ 2%) fills a straight cylindrical vessel 1 with dimensions h = 200 mm and r = 8 mm. The vessel 1 with the dispersion system is allowed to sediment in a static homogeneous gravity field with intensity at constant temperature and external pressure. At intervals of time t - 5 min, only for the moment of measurement, the vessel 1 is suspended in item A ₂ . After the vessel is equilibrated, the angle a _t is measured for the appropriate time and the displacement of the center of mass q _t = rtga _t and the sedimentation stability ts _t ¹ t q _ti are calculated.

From the results obtained, shown in the table in FIG. 4 and the graph of FIG. 5, the limiting sedimentation stability is considered to be h

S = 0,024 --- with a maximum value of the displacement of the center of mass q = 0,63 tm tt corresponding to the tilting angle a _t = 4,5 ° of the vessel 1 with the dispersion system, which is reached over time t - 45 min.

A sedimentation curve of q _t is constructed on the basis of the obtained values. according to FIG. 6. From it, at equal intervals of time t-10 min, 4 points are determined, for which the Stokes radii r _t (/ = 1,2,3,4) of the particles of the dispersed phase and the percentage of the corresponding fraction 7½ are found (Fig. 7).

2. The method for determining sedimentation stability and performing sedimentation analysis of liquid dispersion systems is carried out as in Example 1, except that the measured determining parameter is the mass m _t reduced to the total mass M of the vessel 1 with the dispersed system. Vessel 1, only at the moment of the particular measurement ((z = 1, 2, ..., η), is fixed in an inclined position, at a given angle a = const, about a plane perpendicular to the vector $ of the intensity of the gravitational field as its lower base, rests on a horizontal plate of an electronic scale and measures the mass, by which it determines the offset q ₍ at the center of mass O, relative to its initial position O at the instant (time (zzz -zn ₀ ) j measurement by the formula q, = - ^! ------, where a is the distance from the point of contact 't cos a on the basis of the cuvette and on the platter up to the line parallel to the vector $ of ··>

the intensity of the gravitational field passing through the point of attachment of vessel 1, and m is the mass of the liquid dispersion.

The determination of sedimentation stability S _z and the sedimentation analysis are performed as in Example 1.

In the following specific case, as indicated in Example 2, the dispersed system of distilled water and starch having a total mass of m = 50.1 g and a mass of the dispersed phase (starch) m ^ -1 g (= 2%) cylindrical vessel 1 with dimensions h = 244 mm and r = 9 mm. The vessel 1 with the dispersion system was allowed to sediment in a static homogeneous gravity field with intensity at constant temperature and external pressure. At intervals of time t = 5 min, only for the moment of measurement t _t , the vessel 1 is fixed at an angle a = 45 °, with the lower base of the vessel 1 resting on the plate of the electronic balance and measuring the mass m _t . At the initial moment t ₀ = 26.55g and from the values found for m _t , [m _t -m ^ d calculates the displacement of the center of mass q _t = —'------- and the sedimentation 't cos a stability S _t = ———.

't q _t .

From the results obtained shown in FIG. 8, it is reported that for this dispersion system h

the marginal sedimentation stability is S = 0,024 --- with a maximum value of tm displacement of the center of mass q = 1,25 tm corresponding to the measured reduced mass m _t = 26,89g of vessel 1 with a dispersive system that is reached over time t = 90 min.

3. The method for determining sedimentation stability and performing sedimentation analysis of liquid dispersion systems is carried out as in example embodiment 2, except that for measuring the reduced mass m _{t the} vessel 1 with the dispersion system is fixed in an inclined manner position and remains in this position throughout the sedimentation and measurement process, taking into account the mass m _tj at pre-selected time intervals tj (/ = 1, 2, ..., η). Through it, as in example embodiment 2, the displacement q _t is established. of the center of mass O _t , relative to its initial position O at the instantaneous time T of the measurement.

V. ·

A particular embodiment of the method is possible, in which the vessel 1 with the dispersion system is fixed in an inclined position such that at the initial moment, the vessel 1 is in stable equilibrium and the starting mass read on the electronic balance is m ₀ = 0.

The determination of sedimentation stability S _tj and the sedimentation analysis are performed as in Example 1.

In another specific case, as indicated in example embodiment 3, an emulsion of distilled water and olive oil with a total mass of m = 484.65 g and mass of the dispersed phase (olive oil) = 48.46 g (= 40%) cylindrical vessel 1 with parallel upper and lower bases at an angle α = 45 ° to its walls and dimensions h = 300 mm and d = 23 mm. The vessel 1 with the dispersion system is fixed so that the vessel 1 is inclined at an angle α = 45 ° with respect to the electronic balance plate, with the lower base of the vessel resting on the electronic balance plate. Moreover, at the initial moment, vessel 1 is in stable equilibrium and m $ = 0. Vessel 1 remains to sediment in this position. At intervals t = 1 min, the mass m _t is recorded on the instrument.

From the results obtained in FIG. 9 it is taken into account that for this dispersion system h the sedimentation marginal stability is S = 0.0017 --- with a maximum value of tm displacement of the center of mass q = 1.95 tm corresponding to the measured reduced mass m _t = 6.07 g of the vessel 1 with the dispersion system and is reached for a time t = 10 min.

Patent Claims

Claims (7)

1. A method for determining sedimentation stability and performing sedimentation analysis of liquid dispersion systems, comprising detecting the displacement of the center of mass of a homogenized dispersion system, which is placed in an elongated vessel, characterized in that the vessel (1) is completely filled with it, after which it is closed and placed to sediment, by determining at a pre-selected intervals a determining parameter and by means of which it is established at the specific moment of measurement, after time t, from the beginning of the sedimentation process, the displacement q _t of the center of mass O _t , relative to its initial position O, where i = 1, 2, ..., η, whereby the current sedimentation stability S is determined at that particular time point Ζ _; · As the ratio of the mass m _f of the dispersed phase to the mass m of the whole dispersive system filling the vessel (1), multiplied by the ratio of time /, to the displacement of the center of m _f t by the masses q _t of the dispersed system, by the formula S, = ——, and the sedimentation analysis '' ^t Qt is performed by a sedimentation curve constructed from the specified values of q _t ., Relative to time /, ·. Method according to claim 1, characterized in that the vessel (1) with the dispersed system is placed to settle in a gravity field. Method according to claim 1, characterized in that in order to accelerate the sedimentation process, the vessel (1) with the dispersion system is placed to sediment in a centrifugal field, A method according to claims 1 to 3, characterized in that the measured determining parameter is an angle a _t . of tilting the vessel (1) with the dispersion system with respect to a plane perpendicular to the vector of gravity field intensity, the vessel (1) being suspended only for the moment t _t of the corresponding measurement at a point from its outer wall, which is located at the top at the level of its original center of mass O leaving the vessel (1) free to balance and then measuring the angle a,. Method according to claim 1, characterized in that the measured determining parameter is a mass reduced to the total mass M of the vessel (1) by the dispersed system, the vessel (1) being fixed in an inclined position at a given angle a = const relative to a plane perpendicular to the vector $ of the intensity of the gravitational field such that the lower end of the vessel (1) exerts a pressure on a horizontal plate of an electronic balance, after which the mass m _t is measured. Method according to claims 1 to 3 and 5, characterized in that for measuring the reduced mass m _t , the vessel (1) is fixed in an inclined position, only for the instant Z at the respective measurement. Method according to Claims 1, 2 and 5, characterized in that for measuring the reduced mass m _{tj the} vessel (1) is fixed in an inclined position while remaining in this position throughout the sedimentation process.