US3777550A

US3777550A - Continuous measurement of viscosity

Info

Publication number: US3777550A
Application number: US00187698A
Authority: US
Inventors: E Kleinschmidt
Original assignee: HERBIG HAARHAUS HERBOL WERKE
Current assignee: HERBIG HAARHAUS HERBOL WERKE; HERBOL WERKE HERBIG HAARHAUS AG DT
Priority date: 1970-10-08
Filing date: 1971-10-08
Publication date: 1973-12-11
Anticipated expiration: 1990-12-11
Also published as: DE2049381B2; DE2049381A1

Abstract

A viscometer is provided which operates on the principle of an oscillating or vibrating tongue or reed and includes means for bringing the surrounding liquid to be measured into laminar flow in the vicinity of the tongue.

Description

United States Patent [1 1 Kleinschmidt 1 Dec. 11, 1973 CONTINUOUS MEASUREMENT OF VISCOSITY Inventor: Ernst Kleinschmidt, Schildgen,

Germany Herbol-Werke Herbig-Haarhaus e sti n sss l s t kayd. v Nordrhein-Westfalen, Germany Filed: Oct. 8, 1971 Appl. No.: 187,698

[73] Assignee:

Foreign Application Priority Data [52] U.S. Cl. 73/59 1m. c Go g/1n I [58] Field oisirhg 73/54, 59, 32 A,

[56] References Cited UNITED STATES PATENTS 3,393,553 7/1968 Kleinschmidt 73/54 Primary Examiner-Richard C. Queisser Assistant Examiner-Joseph W. Roskos Attorney-Johnston, Root, OKeeffe, Keil, Thompson & Shurtleff [57] ABSTRACT A viscometer is provided which operates on the principle of an oscillating or vibrating tongue or reed and includes means for bringing the surrounding liquid to be measured into laminar flow in the vicinity of the tongue.

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. body provided with openings on both sides and surrounding the end portion of the measuring probe.

In chemical processes rapid and continuous measurement of the viscosity of liquid and semiliquid media is often a great importance since it enables conclusions to be drawn as to the progress of the reaction.

A viscometer for reaction mixtures in stirred vessels operating on the principle of the vibrating tongue is already known from U.S. Pat. 3,393,553 according to which the measuring probe is surrounded by a tube which is circular in cross-section, which extends beyond the measuring probe on both sides and which is open on both sides, the said tube being constricted in the direction of flow of the reaction mixture entering the tube up to the tongue and thenceproceeding cylindrically to the outlet, and its internal diameter at the location of the tongue being such that laminar flow prevails at this point. Other features of the prior art apparatus are that the tube is turned up like a funnel at the point of entry of the reaction mixture and the probe is surrounded by a conical jacket having a convex front end which provides with the tube enclosing it an annular space of practically constant size for the passage of the reaction mixutre. The accurancy of measurements achievable with the prior art measuring meansdepends largely on the flow within the stirred vessel which is determined by the design of the stirred vessel, the stirring speed, the presence of cooling or heating coils in the stirred vessel and on obstacles to flow in the vicinity of the measuring point such as dip tubes for thermometers, gas inlet pipes for inert gas and the like.

The objects of the present invention is to provide means that do not have the disadvantages of the prior art means and which achieve a laminar flow in the vicinity of the vibrating tongue irrespective of the flow of the liquid, so that high accuracy ofmeasurement is ensured and influences disturbing the measurement are substantially avoided.

This object is achieved in accordance with the invention by means for producing a laminar flow of liquid along the vibrating tongue, said means being arranged beyond the free end of the tongue.

The invention prevents the vibrations of the tongue being disturbed, e.g. by undesirable particles present in the liquid such as insoluble material, gel or skin particles, overcondensed or underpolymerized substances, and also vapors and the like.

In a special embodiment of the invention the measuring probe is located in a cylindrical tube open at both ends, a funnel-shaped widened tube portion attached to a cylindrical portion of the tube containing the coil being arranged around the tongue. In this way a suction force is exerted which acts on the immediate environment of the tongue and which (a) maintains the continuous flow of reaction mixutre past the tongue and (b) removes extraneous particles from the vicinity of the tongue.

According to another embodiment of the invention the end portion of the measuring probe incorporating the tongue is located in a cylindrical container which Y 2 narrows from the free end of the tongue and which is attached by the constricted portion to a hollow body open at both ends.

In a further embodiment of the invention the hollow body open at both ends has at least one constriction of its cross-section so that a suction effect is created in the interior of the container. It is thus possible to arrange a straight measuring probe with the tongue in axial direction in the stirred vessel although the flow in the stirred vessel is predominatly transverse to the axis of the stirred vessel.

According to yet another embodiment of the invention, the measuring probe is located in a bypass of the stirred vessel which incorporates means for producing the flow of the reaction mixture. Better accessibility and therefore a better control of the measuring probe is thus achieved.

Other features of the invention may be seen from the accompanying drawings and the following description of some embodiments.

The diagrammatic drawings show:

In FIG. 1 a stirred vessel, partly broken away, with a greatly enlarged measuring probe is a container;

In FIGS. 2 to 4 a straight measuring probe in a cylindrical container;

cooling coil 4 is shown. A thermometer 5 is provided in a dip tube on a side wall 6 of the vessel. A measuring probe 7 may be seen greatly enlarged in stirred vessel 1. The lower end of the measuring probe 7 projects into a cylindrical container 8 which beyond the end of a tonge 9 of the measuring probe 7 has a funnel-shaped constrictuion and at this constriction 10 there is provided a tube 11, open at both ends, arranged transversely to the axis of the measuring probe and also constructed at the point of attachment. The measuring probe passes thorugh the wall of the stirred vessel 1 at 12. An electrical lead extends outsides to a measuring instrument 13 having a scale 14. One half of the tongue 9 consists of a magnetostrictive metal alloy and is arranged in a coil 15, and the second half, consisting of stainless and acid-resistant steel, dips into the reaction mixture to be measured. The tongue 9 is vibrated from the measuring instrument 13 by means of ultrasonic waves, the vibration causing shear stresses in the boundary surfaces of the reaction mixture. The damping of the vibrations of the tongue thus effected produces a change in the electrical data in the excitation circuit which is visible on the scale 14 as a deflection of the pointer. Naturally the measured values may be recorded by means of recording means (not shown).

FIG. 2 shows measuring probe 7 on an enlarged scale. Container 8 is shown in section so that the end portion of measuring probe 7 and tongue 9 are visible. Above tongue 9, coil 15 is indicated which normally is enclosed by the measuring probe. Container 8 has beneath its cover 16, around is casing, openings 17 for the reaction mixture to enter as indicated by arrows l8 and 19. At the constricted portion 10 of the container there is attached a narrow cylindrical tube 20 which opens into a narrowed portion 21 of tube 11. The reaction mixture flows through the constriction in tube 11 at a greater speed than through the normal tube crosssection. According to Bernoullis principle a decreased pressure is produced in container 8 so that the reaction mixture enters through openings 17 into the container whose cross-section is chosen having regard to the Reynolds number so that a laminar flow is produced in the interior, passes tongue 9 in laminar flow and then flows away through portion 21 and tube 11. Flow through tube 11 is produced by the stirring movement of blade 3. This flow, however, only has importance as a means for producing the decreased pressure, whereas the flow in container 8 is kept laminar and constant, substantially independently of the flow in the stirred vessel. Undesirable particles and vapors are sucked out as quickly as possible from the environment of the tongue so that the vibration of the tongue 9 is not hindered and accurate results are obtained. In FIGS. 3 and 4 the measuring probe is again located in containers 8 as in FIG. 2 and corresponding parts therefore have the same reference numbers. It is merely the decrease in pressure which is produced by other means in the embodiments of FIGS. 3 and 4. In FIG. 3, the cylindrical tube 20 opens into a tube 22 of constant diameter. Upstream of the point where tube 20 passes into tube 22 a constriction is provided by securing in tube 22 a tubular portion 23 having a smaller diameter which is widened at one end. In FIG. 4 the cylindrical tube 20 passes into a tube 24 widened in the direction of flow and having at one end a nozzle 25 through which an inert gas, for example nitrogen, is forced, so that reduced pressure is produced in container 8. In FIG. the angled measuring probe 26 enters a tube 27 which narrows in the direction of flow. Around the angled portion of the measuring probe 26 a guttiform flow guiding member 28 is provided and the coil (not shown) is enclosed by a cylindrical tube portion 29 to which is attached a funnel portion 30 around tongue 9. The constricted tube cross-section is formed between the tube 27 and the funnel portion 30. FIG. 6 shows a stirred vessel 1 according to FIG. 1. A measuring tube 33 is attached at the bottom 32; the tube 33 has an S- shaped bend and leads to a device 34 known as a pulsometer. The pulsometer is connected with the upper portion of the stirred vessel 1 through a lifting pipe 35 and has a third tube attachment 36 for the supply of compressed gas. The measuring probe is introduced between the vertical portion of the S-shaped bend and the pulsometer where it is easily accessible. The curvature of the tube and the diameter, especially in the vicinity of the measuring probe 7, are similarly determined by the Reynolds number whose value of less than 2,400 is a prerequisite for a laminar flow. In the path of the measuring tube 33 there are arranged a shutoff valve 37, a sieve 38, a relief valve 39, a resistance thermometer 40 and a nonreturn valve 41. Nonreturn valve 41 prevents backflow of the liquid in the measuring tube 33 and prevents damage to measuring probe 7. A pump of known type may be used instead of the pulsometer 34. In this embodiment also the production of a laminar flow of the reaction mixture along the tongue 9 is ensured by means of a pulsometer 34 located beyond the free end of tongue 9. The flow produced by stirring blade 3 is illustrated in the drawing by arrows l. The

tubes

11, 22, 23, 24 and 27 are formed with their surfaces closed.

The embodiments of the invention described above relate to the measurement of viscosity in the production of synthetic resins and polymers. The measuring apparatus may also be used successfully in the production of synthetic resins when an entrainer, for example xylene, is used for esterification and the elimination of water associated therewith.

Accurate results are achieved with less susceptibility to trouble in the measuring apparatus when measuring means as shown in the drawings are used. It has been found that for example vapors are sucked off from the tubes or containers in which tongue 9 is located and there is continuous flow of liquid past tongue 9, which can be concluded from the fact that the viscosity rises continuously with the reaction time at constant temperature.

I claim:

1. A device for the continuous measurement of the viscosity of a liquid reaction mixture, in particular a reaction mixture in a stirred vessel, which comprises a viscosimeter having a vibrating tongue and including a tubular measuring probe supporting the tongue on one end, the tongue being positioned within a container between openings in the container for the entry and exit of one stream of the liquid reaction mixture, the container having a portion extending beyond the free end of the tongue, and said portion being provided with a substantially constricted flow cross-section and communicating with a tubular section for a second stream of the said reaction mixture to induce a laminar flow along the tongue at a Reynolds number of less than 2,400.

2. A device as claimed in claim 1, wherein said container is of substantially cylindrical shape and has said constricted portion downstream of the free end of the tongue, and said constricted portion being attached to a narrowed portion of said tubular section, the latter being provided with inlet and outlet openings for said second stream of the liquid reaction mixture.

3. A device as claimed in claim 1, said tubular section comprising an outer tube having its flow cross-section reduced by an inner tube within said outer tube.