DD160783A3 - METHOD AND DEVICE FOR THE CONTINUOUS DETERMINATION OF RHEOLOGICAL SUBSTANCES - Google Patents

Abstract

The invention relates to methods and apparatus for the continuous determination of rheological properties under different loading conditions. The object of the invention is to continuously determine rheological material values at low cost, the device being able to be adjusted within a wide range of stresses and having a high level of interference immunity, and rheological values being determined by the process. The object of the invention is to provide methods and apparatus for the continuous determination of rheological material values with laminar Druckstroemung, different stresses and high Stroemungsunanfaelligkeit. According to the invention, this object is achieved in that material flows through nozzle systems (in series and / or parallel), at least one of which has several nozzles, thereby reducing the pressure over the nozzle systems (nozzle number k below 1, k below 2.. 1 and k below 1 = k below 2 = ... = 1), and from geometric and flow-technical conditions rheological material values are calculated by means of substance equations. The practice of the invention allows for processes involving fluid flows, e.g. Quality assurance and process optimization in manufacturing and processing processes through continuous material value determination.

Description

230110 2

LP 8139

Method and device for the continuous determination of rheological St off values . '

Field of application of the invention

The invention "relates to a method and an apparatus for the continuous determination of rheological properties, in particular non-Newtonian fluids such as polymer melts and solutions, under different, defined stress conditions.

Characteristic of the known technical solutions ·,

The determination of rheological material values is carried out, as is known, in such a way that samples are taken from the material stream at predetermined time intervals and their rheological material values are determined in rheometers; such rheometers are, for example, capillary rheometer, Rotationsrheometer. with cylindrical shear gap, cone-plate or plate-plate viscometer (author collective} Examination of hochpolymerer materials, Leipzig 1977) · Furthermore, Ilfeßsysteme are known, with which it is possible, immediately, continuously rheological properties to eat. Thus, an apparatus for the continuous determination of rheological properties of non-ionic liquids is known (US Pat. No. 3,468,158), which is based on _K passing through the material stream through a plurality of identical or different capillaries connected in parallel or in series. The volume dosing with one or more conveyor

2QMAI1981. * 93 9slH.

-a-

It is also known to determine rheological St off values by the fact that the substance in a closed or for continuous material passage system simultaneously several shear fields, but at least one Schleppströmungs- and a pressure flow field under predetermined stress conditions is exposed (DE OS 1798201).

Similarly, one or more shear fields are realized in a flow system consisting of a unit which generates a volume flow of specific temperatures and pressures and is connected to a capillary system, a control system ensuring that a predetermined pressure and pressure are achieved corresponding shear stresses can be set in conjunction with the capillary. Switching to a capillary of other geometry, the stress condition is varied (Technical Information Seiscor-melt rheometer, Schwing Process Engineering KG / Duisburg-Buchholzj Rheology - IHPO Hr .. 3/80, Göttfert Werkstoff-Prüfmaschinen GmbH).

In the repeated removal of samples from the stream and their rheological characterization in classical rheometers, z. B. iui capillary rheometer are the equipment and time costs are very high. For the control or regulation of the rheological or thus correlating properties of the material flow, the time delay between sampling and the decision made by the rheological characterization is often unreasonably large. If the rheological properties are determined directly, continuously according to US Pat. No. 5,468,158, Hachteil states that disturbances in the substance stream, eg. B. in the form of inhomogeneities, beita passage through the capillary lead to a significant deviation from the average measurement signal and thus are the starting point of 'wrong intervention decisions; In addition, there is only one single measured value per measuring point. The adaptation of the capillaries to the specified stress range is also

L JU i I

see and / or therian-rheological reasons often problematic.

On the other hand, if a drag flow field and a pressure flow field are used, as proposed in DE OS 1798 201, the stress dependence of the rheological data, eg. B. by the influence of the hydrostatic pressure and the dissipated energy, the transferability are significantly limited; the effort in this solution is very high. ,

The switching to capillaries of different geometry, which are arranged in the side stream, as in Seiscor-melt. Rheometer realized requires a lot of effort, especially for the control, and there are fluidic problems, eg. As in the acceleration of the material and by-run-in effects.

Goal of. invention

The object of the invention is to provide a method and a device for the continuous determination of rheological material values, wherein it is to be achieved that the device is adjustable over a wide range of stresses, has a high degree of safety against disturbances in the flow of the substance and by the method primarily acquired data can be converted into material values. In addition, the expenses for the construction and operation of the device and for the method for determining the physical properties should be low.

Explanation of the essence of the invention

The invention has for its object to provide a method and apparatus for the continuous determination of rheological properties, which allow laminar, in a certain time constant pressure flow to measure at different predetermined stress conditions and thereby a great security against interference

I 1 U I

at the flow of the substance, like ζ. Inhomogeneity. · ·. '. ,

According to the invention, this object is achieved in that in the au niessenden and if necessary to regulate the stream or -teilstrom nozzle systems, of which at least one has multiple nozzles are introduced and from the fluidic and geometric conditions under specification of material equations rheological properties, as Also, relations between the stress conditions in the nozzle systems and between the physical properties can be calculated. Depending on the material flow and the rheological values to be obtained, the nozzle systems are used either in series and / or parallel connection and nozzles of the same or different dimensions are used.

The device for carrying out the method has at least two nozzle systems which are arranged in series or in parallel or in series and parallel to one another and whose number of nozzles k ^, k ₂ ..., where k ^, k ₂ »··· * 1 and k ^ j = ko = φ 1. The nozzles are preferably of circular cross-section (capillary); to generate or avoid certain geo me trieabhängiger effects in the flow, eg. | 5th the reduction of the current stored in the material dissipated shearing work other, non-circular nozzle cross-sections, such. For example, breadwinners are used. When the nozzle systems are connected in series, they are connected to one another by a gap, which ensures a uniform pressure build-up in front of the subsequent nozzle system.

\ "". ''. ' *.

Flows through a temporally constant volume flow through the nozzle systems arranged one behind the other, 'fall over them pressure losses. From the number and geometry of the nozzles in the nozzle system, the given and measured values volume throughput and pressure loss, the rheological stress conditions and material values are calculated. Due to the forced condition of the same material flow through the nozzle systems connected in series, the rheological behavior in a given stress range is the measured pressure drop values and the geometric conditions

-5- 2301 IO I

to calculate the nozzle system. Since the nozzle systems in. generally consist of several nozzles, is a high .Fließstabilität the material flow against disturbances z. B. inhomogeneities. A further advantage is that the measured values are averages of the integral quantities arising over the individual nozzles and thus a high quality of the measured values is achieved. Compared to the known measuring devices is also advantageous that the great variability of the stress range while maintaining the simplicity makes it possible to arrange the device in the main stream of a manufacturing or processing plant, which accounts for significant technical expenses.

In the parallel connection, the nozzle systems with nozzles of the same or different cross sections and the same or different nozzle numbers are arranged side by side. The total flow of material is divided according to the rheological resistance of the nozzle systems or supplied to the nozzle systems by means of conveyors. The respective pressure losses are measured.

Compared to the series connection of the nozzle systems, the parallel connection has the advantage of a wide range continuous Regulier'barkeiif the shear stress when using conveyors. When the nozzle systems are connected in parallel, the throughput of the same shear load is lower in comparison to the series connection of the same nozzle systems. -

embodiment

The invention will be explained in more detail below with reference to two embodiments. The accompanying drawings show: '. Fig. 1 is a schematic representation of a series circuit

of jet systems}.

Pig. 2 the schematic representation of a parallel connection of nozzle systems ·

In the following examples is on nozzle systems with

23Ό I ϊ U

 cylindrical nozzles, d. H. Capillaries reference. '

example 1

According to FIG. 1, the device consists of nozzle systems 1 and 2 connected in series with k ₁ capillaries in the nozzle system T and capillaries in the nozzle system 2. The lengths and radii of the capillaries are L ₁ , R ₁ for the nozzle system 1 and Lp >> R ₂ for the nozzle system 2. In the volume flow rate Q through the nozzle systems arranged one behind the other, the pressure losses ^ p ₁ fall above the nozzle system 1 and, <4ρ ₂ above the nozzle system 2. To determine the rheclogischen substance data of a non-Newtonian substance, the C ^ (1) is described by a power law in the form f ^IQ =, in a shear rate range to differ by a factor of 40, the following conditions ^::% ÜR the Nozzle systems chosen:

Dissection system 1: k, - = 1

Nozzle system 2: k ₂ = 5 Ί "" P * - '' I -.-- * - 'ρ

The volume flow rates through the nozzle system amount to

• \ 'Ί'. ,

and 3

The ratio of the volume flow rates in the capillaries of the two nozzle systems is calculated as

R ₂ = u. R ₁ ; , I ₂ = ν . I ₁ too

Q ₁ ι.

, m

For the flow exponent m results

³ QA

log ( \ ) + log (

0 2

k ₂ is Q ₁ =

and

log (^) + log

Q _{1 2}

if k ,, Φ k. _o is, ie -r- = - becomes for

Q ₂ ^

+ -log ( ^k 2 / ^k 1)

log (-) + log

receive.

The apparent shear rates and actual shear rates at the capillary wall in the nozzle systems are related to each other

w ₂

The ratio of apparent and effective viscosities in the nozzle snares becomes

% Λ ? Ef f 1 22 ν

*? s2 Veff 2 is1 u

obtained or with equation (9)

^ 32? Eff 2 k ₂ *

The proportionality constant in the power law, the shear rates and the viscosities are calculated in a known manner. According to the example, the splitting exponent m is calculated according to equation (8)

8th -

- ⁸ - ZJU 5

log (U ^) + go C " ⁷ ^), 1.6021

^k 2 / _k .

log -i'V ⁺ log .. <** "^ p ₂ J" log C * ^p V

and for the constant of proportionality C follows

The ratio of the viscosities in the nozzle systems is according to equation (11),

^ s2 % ff 2 k ₂ "JP ^ p _2. 160

Through the arrangement and design of the nozzle systems as well as through the evaluation of the measured values, characteristic substances are determined in a wide range of shear properties via the substance system to be investigated, in the aforementioned case a liquid which can be described by the law of potency They are suitable both for process monitoring and control in the production of the substance and as characteristics for the application, in particular where there are differences in the shear rates or deforlation conditions, the specification of the number, the .capillaries in the individual capillary systems and the design The advantage of capillary systems with several capillaries is also that very low shear rates can be chosen, thus keeping the material close to or in Newtonian condition ch the initial viscosity can be detected. The formation of a nozzle system, consisting of several capillaries, also has an advantageous effect on the stability of the flow against disturbances, eg. B. Inhomogeneities of the flowing material from »At the same time it is advantageous that the pressure loss measured over the nozzle system is a -'Mittelwert the falling over the individual capillaries pressure losses at the respective streams, whereby. Wfeßv / erte arise with high quality. The devices

-9- · ZdUI IU L

Due to the forced condition for the volume throughput through the nozzle systems, only a constant volume flow is required which is predetermined by the system in which the device is located.

Example 2 _/ ' . '.'; .. "

As shown in Figure 2, the device consists of parallel nozzle systems 1 and 2 with k, capillaries in the nozzle system 1 and k ₂ capillaries in the nozzle system 2. The lengths and radii of the capillaries are 1, and R * for the nozzle star. 1 and I ₂ , R ₂ for the nozzle system 2. The volume flow rate Q consists of the proportions Q- through the nozzle system 1 and Q ₂ through the nozzle system 2; over the Düsensy stones the pressure losses 4p, j and ^ p ₂ occur. If the nozzle systems successively of at least two different volume flow rates Q. Qv ,, ... flows through Q _o / Qu =. et and ad. , au

\₂ - k₂)-s_ _(15>

the flow exponent becomes

ν1

k ₂ ) '(16)

m = log -j ~ log oc (17)

receive; while the forming Schergeschwindigkeitsfeider in the nozzle systems are not the same. , The value 0 is calculated from

m '·'. '

G (W, k. + W, _o . Ko) (18)

Flows the constant volume flow Qu first through both nozzle systems, then only through a nozzle system, d. H.

^Ck 1 · ^W k1 ^{+ k}

•and . m

that's how it is

· ^K i · ^w ki

- 1C -

'JU

, w _{k1 +} k ₂ . w _k2 y

or ta from it

 . = log - ^. log --_ -

and 0 from equations (19) "and (20), respectively.

In parallel connected Düsensy different stones, which are acted upon by associated Iordereinrichtungen with constant, equal or different volume throughputs, arises

- (1) (23)

and for the flow exponent

+ log ^ 2 ^ 1) + log (u ³ )

(24) 1 ° S (TT) + log ("^ 1 // Ip ₂ )

The ratio of shear rates in the nozzle systems is

^m ta · '-.,

, (1) (25)

Tdzw. _ ^:. _ -. '

J - -Al - A Ϊ2 "5

- · - / 3 · ν · ^u

The viscosity ratio in the nozzle systems is thus too

m-1 /, m-1

? s2? eff Z " \ ^ Λ y * ^ ⁿ

 *? eff 1 ν

? s2 ~? eff 2. ß. u ⁴ "

- 11 -

- ¹¹ - 2'Sl) ii υ- L

That is _;

R ₂ su. R ₁ and I ₂ = ν. I ₁ (29)

Fourth of the viscosities and extender speeds are calculated in a known manner.

In the case of parallel-connected nozzle systems 1 and 2, which are characterized by two constant Forderstrom, ζ. B. generated by gear pumps, are fed, the ratio of the flow rates Q J \ - & = 3; the geometric conditions of the nozzle systems are:

-Ie ₁ = 5, k ₂ = 10; R ₁ = 0.5 R ₂ i I ₁ = I ₂ .

The factor of the shear rates in the nozzle systems is calculated for this example as ^ ^s "1 / >> ₂ = 48 and the flow exponent m is determined according to equation (24)

_ log IS + log ( ^k 2 ^{/ k} 1) H log (U ^) _ _1t6812 :

log (v / ") + log (^ 1 / App) log (4W.) -0,? 010

The ratio of the viscosities in the nozzle systems is increased according to equation (28)

*? Eff

? s2? eif 2 TT ^ V received. - '

Compared to the series connection of the nozzle systems, the parallel connection has the advantage of a controllable speed of the sensor speed which is constant over a wide range and due to the specification of the material flow. As a result, the same measuring conditions can be realized in a system, especially if the flow rate is not stationary over time, and, if necessary, the shear rate range can be continuously adjusted. The parallel-connected measuring system results in a larger volume throughput and a lower total vision load for the material flow, so that e.g. shear-sensitive substances can be rheologically characterized.

, · · · 12 -

Claims (2)

23U i 1 υ invention claim. 1.6. Procedure next point 1.1. b is 1.5. characterized in that, using the power law, the flow exponent, the proportionality constant in the po- r-13.- / JU i I υ * - law, the apparent and effective viscosities, the apparent and effective shear forces, and the relationships between them. 2.1. Apparatus for carrying out the method according to item 1, characterized in that at least two nozzle systems whose number of nozzles k, -, ko ^; , ..., where kxj, k ₂ ... - 1 and k ^ = k ₂ = ... * 1, 'are arranged in series and / or parallel to each other. 2.2. Device according to point 2.1. characterized in that the nozzle systems are in the main flow and / or secondary flow of a system. .2.5 '. Device according to point 2.1. characterized in that two parallel nozzle systems, of which a nozzle system is fed by a predetermined flow generating device, are located in the main stream of a plant. 2.4. Device according to point 2.1. characterized in öa & nozzles have a circular cross-section. 1.5. Procedure according to point 1.1. characterized in that flows through nozzle systems arranged in parallel with nozzles of the same or different dimensions from associated conveyors with the same or different volume flow rates and thereby the pressure losses are measured. 1.4. Method according to point 1.1 · characterized in that the streams initially by two nozzle systems arranged in parallel, the nozzles have the same or unter ^% different dimensions, then passed through one of them or vice versa, and thereby the pressure losses are measured. 1.5 · Method according to point 1.1 · characterized by the fact that at least two different volume flow rates of the substance in succession passed through parallel nozzle systems with nozzles of the same or different dimensions and the pressure losses are measured. 1.2. Procedure according to point * 1.1. characterized in that the Stoffström passed through series-connected nozzle systems with nozzles of the same or different dimensions and the pressure losses are measured. 1.1. Method for the continuous determination of rheological material values of a constant stream of material in a specific time range, which is produced or conveyed in a plant, characterized in that the stream flows laminarly through nozzle systems, at least one of which has a plurality of nozzles, thereby measuring the pressure losses across the nozzle systems and from the geometric and fluidic conditions using material equations rheological values or relations between them are calculated. 2.5. Device according to point 2.1. characterized in that the nozzles have non-circular cross-section, such. B. slot dies. , , Dazu.//"..Seiten drawings