US3887429A

US3887429A - Device for untangling and dispersing fibrous materials

Info

Publication number: US3887429A
Application number: US338848A
Authority: US
Inventors: Eduard Schmid; Reinold Nascher; Rene Egli; Noel James Parratt; Ronald William Gooding
Original assignee: Lonza AG
Current assignee: Lonza AG
Priority date: 1972-03-08
Filing date: 1973-03-07
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03
Also published as: CH535291A; FR2175177A1; FR2175177B3; DE2307885A1; NL7303285A; BE796391A; JPS48103803A; GB1422463A

Abstract

A device for untangling and dispersing fibrous materials present in fluid suspension in matted and interlocking form. The device includes a hollow stator and at least one rotor arranged for rotation about its longitudinal axis within the stator, the stator having an inner cross-section so shaped and the cylindrical rotor having a cross-section so shaped that, in use, on rotational movement of the rotor, suspending fluid located between the stator and the rotor is subjected to shear-forces which are continuously and uniformly built up and subsequently reduced again. A method for untangling and dispersing fibrous materials present in fluid suspension in matted and interlocking form, wherein the suspension is subjected to shear-forces which are continuously and uniformly build up and subsequently reduced again.

Description

United States Patent n 1 Schmid et al.

1 1 DEVICE FOR UNTANGLING AND DISPERSING FIBROUS MATERIALS [75] Inventors: Eduard Schmid, Bonduz Gr; Reinold Nascher, Visp Vs; Ren Egli, Sins Ag, all of Switzerland; Noel James Parratt, Loughton; Ronald William Gooding, Waltham Addey, both of England [73] Assignee: Lonza, Ltd., Basle, Switzerland [22] Filed: Mar. 7, 1973 21 Appl. No: 338,848

[30] Foreign Application Priority Data Mar. 8, 1972 Switzerland 3358/72 [52] U.S. Cl 162/261; 19/66 R; 162/380 [51] Int. Cl. D2 lj 3/00 [58] Field of Search 162/11, 100, 102, 336,

[56] References Cited UNITED STATES PATENTS 1,745,727 2/1930 Sterzl 241/244 3,164,513 1/1965 Calehulf 162/336 1 1 June 3, 1975 3,476,641 11/1969 Milewski 162/152 3,589,977 6/1971 Foumet 162/100 3,694,312 9/1972 Skoldkuist 162/343 5 7 ABSTRACT A device for untangling and dispersing fibrous materials present in fluid suspension in matted and interlocking form. The device includes a hollow stator and at least one rotor arranged for rotation about its longitudinal axis within the stator, the stator having an inner cross-section so shaped and the cylindrical rotor having a cross-section so shaped that, in use, on rotational movement of the rotor, suspending fluid located between the stator and the rotor is subjected to shearforces which are continuously and uniformly built up and subsequently reduced again. A method for untangling and dispersing fibrous materials present in fluid suspension in matted and interlocking form, wherein the suspension is subjected to shear-forces which are continuously and uniformly build up and subsequently reduced again.

8 Claims, 6 Drawing Figures ED Q |975 3.887.429

SHEET 2 4 I M I PATENTEDJIJH3 m5 13.887. 129 SHEET 3 Fig.3

DEVICE FOR UNTANGLING AND DISPERSING FIBROUS MATERIALS The invention relates to a process and a device for untangling and dispersing predominantly fibrous materials present in fluid suspension in a tangled or inter locking form.

For untangling and dispersing predominantly fibrous materials, the use of known devices, such as agitators, mixers or endless screws, has proved to be unsatisfactory and unsuitable. Such devices have turned out to be insufficiently effective or led to excessively severe destruction and contraction of the fibrous materials. In particular with these devices, no definite time is given for the fibres staying in the shear zone of the devices.

It is an object of the present invention to eliminate or at least reduce the above disadvantages.

According to a first aspect of the invention, there is provided a device for untangling and dispersing fibrous materials present in fluid suspension in matted and interlocking form, comprising a hollow stator and at least one rotor arranged for rotation about its longitudinal axis within the stator, the stator having an inner crosssection so shaped and the cylindrical rotor having a cross-section so shaped that, in use, on rotational movement of the rotor, suspending fluid located between the stator and the rotor is subjected to shearforces which are continuously and uniformly built up and subsequently reduced again.

According to a second aspect of the invention, there is provided a method for untangling and dispersing fibrous materials present in fluid suspension in matted and interlocking form, wherein the suspension is subjected to shearforces which are continuously and uniformly built up and subsequently reduced again which, in relation to 1 metre of relative circumference, as hereinafter defined is from to 30, preferably from 18 to 22.

The relative circumference U means that circumference of the circle which the outermost points of the rotor describe in a rotational movement of the rotor about its longitudinal axis.

The peripheral circumferential speed of the rotor preferably is from 8 to m/sec suitably, more preferably from 14 to l7 m/sec. The side faces of the rotor are advantageously provided with trough-shaped recesses in the direction of the longitudinal axis. Advantageously, the stator has a generally circular inner crosssection, but advantageously has the same number of trough-shaped bulges in the direction of the longitudinal axis as the number of side faces of the rotor.

The minimum clearance arising between stator and rotor preferably is from I to 3 mm, more preferably from l to 2 mm; the resulting maximum clearance is preferably from 8 to mm, more preferably 10 to 15 The fibre concentration is preferably from to 500 mg/l, more preferably from 50 to 200 mg/l. Advantageously, relatively low concentrations, below I00 mg/I, are used with long fibres. With relatively short fibres the concentration can be increased to over 100 mg/l without disadvantages. Water having a glycol content of O to 10 per cent by weight may be used as a suspension fluid. The present method may be used with advantage where whiskers constitute the fibrous material.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example an embodiment thereof, and in which:

FIG. 1 is a perspective view ofa device for the untangling and dispersion of predominantly fibrous materials present in matted and interlocking form, some internal parts of the device being shown in unbroken lines for the sake of clarity;

FIG. 2 is a sectional side elevation of the device shown in FIG. 1',

FIG. 3 is a sectional end elevation of the device shown in FIG. 1; and

FIGS. 4 to 6 are sectional end elevations of modifications of the device shown in FIG. 1.

Referring now to the drawings, the device comprises a stator l which also acts as a casing wall. The inner cross-section of the stator is fundamental. In the device shown in FIG. 1 the cross-section bounds a circle but is extended by three regularly disposed bulges 2. A rotor 3 is disposed within the stator l and in crosssection has a triangular shape with sharply rounded corners. The stator 3 is positioned towards the rear of the stator 1 (the righbhand end as viewed in FIG. I) and a space 5 is defined between the rotor and the front end of the casing. The rotor is arranged to rotate about its longitudinal axis, e.g. by means of an electric motor. It will be appreciated that on rotational movement of the rotor, the gaps between the stator and the rotor are of continually changing dimensions getting narrower and broader in sequence. The described cross-sections of the rotor and stator of FIG. 1 are merely an example of suitable shapes; further possible shapes for the stator and rotor are depicted in FIGS. 4, 5 and 6.

It will be appreciated that the illustrated shapes do not represent any limitation in the number of possible shapes.

First and second feed-

lines

4 and 7 respectively are provided at one end of the stator casing, and an outlet 6 is provided at its other end. A vent 8 is provided at the top of the stator casing. In an alternative arrange ment, the feed-

lines

4 and 7 are provided at the front of a side of the stator casing. The outlet 6 may alternatively be located at the side of the stator casing or even at its front.

More than one rotor may be provided.

The operation of the device will now be described. Raw material in the form of suspension consisting of matted and interlocking fibre materials suspended in a fluid is fed through the first feed-line 4 into the device. Excessively compact fibreformations are to be loosened or split up beforehand so that their free passage through the feed-line is ensured. By means of the second supply-line 7 more fluid can be introduced into the device and thus in a simple manner the desired fibre concentration can be set. Water or water with a glycol content up to 10 percent by weight may for example be used as the suspension fluid. Known fluids or possible mixtures thereof can be used, depending upon the nature of the fibres to be treated, for example acetone, alcohols, or hydrocarbons. As a consequence of differences in viscosity, the aperture width, the peripheral speed of the rotor, the number of shear-cycles and the time to be spent in the shear-zones have to be chosen to suit the particular suspension fluid being used. For a fluid of high viscosity for example. the aperture width would have to be increased, and the peripheral speed of the rotor and the number of shear-cycles reduced. For fluids of low viscosity the procedure must be the reverse. The fluid used should be free of gas such that no foaming occurs. Gases carried over or emanating from the fluid, for example air, are removed through the vent 8. Since the

feedlines

4 and 7 are disposed at one end of the stator casing or at a front side of the stator casing, the space before the rotor is termed the thinning space. The fibre suspension is compressed through surging of the suspension into the gaps between the rotor and the stator. As previously stated. the rotor rotates about its longitudinal axis. The peripheral speed of the rotor, calculated as the product of the rela tive circumference and speed of rotation of the rotor, is preferably between 8 and m/sec for water or for water with a low glycol content. Through the rotational movement. fluid and fibres are carried along, continuously subjected to the increasing and decreasing shear forces, produced by rotation of the rotor in the stator, and the matted fibres loosen and become uniformly distributed in the fluid. As a result of the special shape of the stator and the rotor and the shear forces resulting therefrom, the fibres to be treated are extremely well preserved and are protected to a considerable degree from destruction. The shear forces necessary to untangle and disperse a particular product completely can be obtained by suitably varying the minimum and maximum aperture width between rotor and stator, of the peripheral speed of the rotor, the number of shearcycles and the time the suspension spends in the shearzone.

After treatment has been carried out, the suspension emerges from the device, conveniently at the opposite end of the stator to the inlet. The present device enables an extremely homogenous fibre suspension to be obtained. A uniform and adjustable throughput can be ensured through controlled introduction of the fibre suspension and the thinning fluid. Conveniently a hose compression pump is used. for conveying the fibre suspension, which makes possible precise adjustment of the throughput without risk of blockage.

The present device is particularly suitable for fibrous materials in the form of whiskers, that is to fibrous monocrystals, for example of SiC or A1 0 it is preferred when dispersing whiskers to select the dimensions of the stator and the rotor such that a minimum aperture width of l to 2 mm can be obtained between stator and rotor. Apart from a good dispersive effect this also causes a release and a certain degree of de struction of the impurities accompanying the whiskers and which are present in the form of spherical agglomerations containing the whisker components. If the whiskers are only to be re-dispersed, a minimum aperture width between stator and rotor of 2 to 3 mm is advantageous as this ensures gentler treatment of the whiskers.

The invention will now be illustrated by the following Example:

EXAMPLE A device having a stator and a rotor in accordance with the invention, with a cross-section as illustrated in FIG. 6 and having a maximum rotor diameter of lOO mm. with a resulting narrowest aperture width of 2 mm and a resulting largest aperture width of 15 mm, and having an edge-length of the rotor of I00 mm was used. A suspension of whiskers in a fluid was supplied through an inlet. The concentration was 5 gm of fibres to l litre of fluid. Through a second inlet, further fluid was introduced into the device as a thinning fluid. Water with a glycol content of 4 percent by weight was used as the fluid.

The ratio of supply of fibre suspension and thinning fluid was chosen such that about to mg of whiskers were present per litre of fluid.

The thinned suspension was forced into the zone of the rotor by the continuous supply. The rotor revolved at 3000 revolutions per minute and the feed-flow was adjusted such that about 400 litres of fluid were intro duced per minute, which resulted in individual particles being in the shear zone for an average time of 4 seconds. An extremely homogenous and durably stable dispersion was obtained.

What is claimed is:

1. Apparatus for treatment ofa suspension of matted, tangled and interlocked fibrous materials suspended in a liquid to obtain a suspension in untangled form in said fluid which comprises:

a. a hollow stator casing closed at both ends and haw ing b. inlet means for feeding the suspension of said matted fibrous materials suspended in said fluid into one end of said hollow stator casing,

c. outlet means for withdrawing a suspension of said fibrous materials in untangled form suspended in the fluid from the other end of said hollow stator casing, and

d. a rotor body arranged for rotation about its longitudinal axis within said hollow stator casing, said hollow stator casing having an inner cross-section substantially in the form of a first regular polygon, said rotor body having an outer cross-section substantially in the form of a second regular polygon with rounded corners. the inscribed circle of said inner cross-section of said hollow stator casing and the circumscribed circle of said outer cross-section of said rotor body being concentric to each other, said longitudinal axis of said rotor body being ar ranged in the common center of said inscribed and said circumscribed circles. and the number of corner of said first polygon being equal to the number of corners of said second polygon.

2. Apparatus as claimed in claim 1 wherein the number of sides of said second polygon in relation to one meter of said circumscribed circle is from [0 to 30.

3. Apparatus as claimed in claim 2 wherein the number of sides of said second polygon in relation to one meter of said circumscribed circle is from 18 to 22.

4. Apparatus as claimed in claim 1 wherein the minimum clearance between the stator and the rotor is from I to 3 mm and the maximum clearance between the stator and the rotor is from 8 to 25 mm.

5. Apparatus as claimed in claim 4 wherein said minimum clearance is from 1 to 2 mm and said maximum clearance is from it) to l5 mm.

6. Apparatus as claimed in claim 1 wherein the end face at the said one end of said stator casing is spaced from the adjacent end face of said rotor body, said inlet means comprising a first inlet for said suspension and at least one second inlet for additional fluid, and said first and second inlets communicate with the space between the face at the said one end of said stator casing and the adjacent end face of said rotor body.

7. Apparatus as claimed in claim 1 wherein the end face at the said other end of said stator casing is spaced from the adjacent end face of said rotor body, said staof curvature of said rounded corners of said second polygon is the radius of said circumscribed circle thereofi

Claims

1. Apparatus for treatment of a suspension of matted, tangled and interlocked fibrous materials suspended in a liquid to obtain a suspension in untangled form in said fluid which comprises: a. a hollow stator casing closed at both ends and having b. inlet means for feeding the suspension of said matted fibrous materials suspended in said fluid into one end of said hollow stator casing, c. outlet means for withdrawing a suspension of said fibrous materials in untangled form suspended in the fluid from the other end of said hollow stator casing, and d. a rotor body arranged for rotation about its longitudinal axis within said hollow stator casing, said hollow stator casing having an inner cross-section substantially in the form of a first regular polygon, said rotor body having an outer cross-section substantially in the form of a second regular polygon with rounded corners, the inscribed circle of said inner cross-section of said hollow stator casing and the circumscribed circle of said outer cross-section of said rotor body being concentric to each other, said longitudinal axis of said rotor body being arranged in the common center of said inscribed and said circumscribed circles, and the number of corner of said first polygon being equal to the number of corners of said second polygon.

2. Apparatus as claimed in claim 1 wherein the number of sides of said second polygon in relation to one meter of said circumscribed circle is from 10 to 30.

4. Apparatus as claimed in claim 1 wherein the minimum clearance between the stator and the rotor is from 1 to 3 mm and the maximum clearance between the stator and the rotor is from 8 to 25 mm.

5. Apparatus as claimed in claim 4 wherein said minimum clearance is from 1 to 2 mm and said maximum clearance is from 10 to 15 mm.

7. Apparatus as claimed in claim 1 wherein the end face at the said other end of said stator casing is spaced from the adjacent end face of said rotor body, said stator casing is provided with vent means, and said vent means and said outlet means communicate with the space between the face at the said other end of said stator casing and the adjacent end face of said rotor body.