WO1999054536A1

WO1999054536A1 - Treatment of fibrous material

Info

Publication number: WO1999054536A1
Application number: PCT/GB1999/001227
Authority: WO
Inventors: William Robertson Cunningham Erskine; Rodney Taylor
Original assignee: Asset Associates Limited
Priority date: 1998-04-22
Filing date: 1999-04-22
Publication date: 1999-10-28
Also published as: GB0025704D0; AR015276A1; GB9808381D0; AU3617399A; GB2351982A; TW440621B

Abstract

Fibrous material, such as mineral fibre, glass fibre, basalt fibre etc. is treated by a method involving treating a plurality of discrete fibrous chunks, each chunk comprising a mass of entangled fibres, by a mechanical tumbling action such that each chunk forms a respective denser, rounded fibrous cell with entrapped air. The cells have properties that make them useful in a wide range of applications. In particular, the entrapped air of the cells means that the cells have insulation properties, thermal and acoustic, useful in many contexts.

Description

Title: Treatment of Fibrous Material

Field of the Invention

This invention relates to treatment of fibrous material and concerns a method of treating fibrous material, fibrous cells and uses thereof.

Discussion of Prior Art

US 4618531, US 4783364, US 5112684, US 5238612 and US 5338500 describe the formation of fibrous spheres of spirally- or helically- crimped polyester fibres and other mechanically crimped synthetic organic fibres by a process that involves recirculating tufts of material entrained in air through a modified Lorch loosener/blender machine so that the tufts are repeatedly tumbled against the wall of the vessel. The process produces fibrous bodies having generally smooth surfaces, with few protruding fibres, so there is low cohesion between bodies, resulting in a free-flowing product. The product consists mainly of ball-like or spherical bodies but invariably includes a significant proportion of elongate cylindrical or rod-like bodies. The technique is only effective with fibre of crimped form: see Example 1 comparison of US 4618531. The product is used as a refluffable filling for pillows etc.

Summary of the Invention

In one aspect the invention provides a method of treating fibrous material, comprising treating a plurality of discrete fibrous chunks, each chunk comprising a mass of entangled fibres, by a mechanical tumbling action such that each chunk forms a respective denser, rounded fibrous cell with entrapped air.

The invention is applicable to a wide range of inorganic fibrous materials, particularly mineral fibre, including glass fibre, ceramic fibre, basalt fibre, carbon fibre, fibrous horticultural waste, etc, the fibre possibly being coated with organic resins etc, and possibly 2 being in the form of wool, eg mineral wool, glass wool, rock wool, basalt wool, glass fibre wool, non-woven mat, woven mat etc. The form of the fibre is not critical and need not be crimped, for example. The invention is applicable to fibre, with or without opening treatment, ie mechanical pulling apart or teasing action. The fibrous material can be waste material, or good quality unused material, not of waste grade. Mixtures of fibrous materials may be used.

The fibrous chunks generally have a maximum dimension in the range 10mm to 50mm and can be of variable geometry, including generally cubic, rectangular, spherical, pillow- shaped, egg-shaped etc. Different sizes and forms are better suited to different fibrous materials, in a way that can be determined experimentally.

Each individual chunk typically comprises a plurality of fibres of various different lengths and/or diameters in the form of an entangled mass.

It will generally be necessary to process fibrous material to produce a plurality of similar fibrous chunks of similar size and shape, resulting in production of a plurality of similar cells of similar size and shape. A number of different techniques, particularly cutting or shredding techniques, may be used for this purpose, with different techniques generally being better suited to different fibrous materials.

For example, a fibrous mass, eg of basalt wool, mineral wool, glass wool, ceramic fibre etc, may be cut into chunks using a rotary cutter or other knife means. Chunk size may be regulated by varying factors including speed of rotation of the cutter and the size and geometry of the cutting edges.

Good results have been obtained with a wide range of materials using a novel size reduction technique as disclosed in British Patent Application No. 9819800.5 that involves feeding fibrous material to apparatus comprising a rotating shaft rigidly carrying external protruberances lacking sharp edges, with an associated screen, that processes the material into short fibrous lengths in the form of chunks. This technique may be performed using a modified biomass shredder, having modified protruberances with a form closely resembling -> j that of the upper shank and head of a countersunk screw (without slot). Each protruberance thus comprises a generally cylindrical shaft or shank, with a frusto-conical head, lacking sharp edges. Chunk size may be regulated by varying factors including shaft speed, screen geometry and aperture size, and the arrangement and form of the protruberances.

The fibrous cells generally have a maximum dimension in the range 1mm to 15mm, preferably 2mm to 12mm. The cells as produced are all of rounded form, each cell having a generally curved surface and having a variation in size in different directions of less than 100%, ie with the maximum dimension being not more than twice the minimum dimension. The terms "rounded cell" or "rounded fibrous cell" are to be construed accordingly. The cells are thus not flattened disc-like form nor of elongate cylindrical or rod-shaped form: instead the cells are all generally spherical, generally oval or egg-shaped etc, with certain different materials tending to produce cells of different form. For example, glass fibres tend to produce generally spherical cells, while basalt fibres produce more oval or egg-shaped cells.

The cells have a whiskery surface finish, with protruding fibres, so that the cells have a tendency to stick together and have high cohesion there between, with the cells thus not being free-flowing.

The cells as produced may be sorted or classified by size if required or desired.

The bulk density of the chunks (ie the density of a bulk quantity of material) is typically in the range 50 to 150 kg/m³. References to bulk density relate to material in uncompressed condition unless otherwise specified.

The bulk density of the cells is typically in the range 100 to 200 kg/m⁵, depending on fibre type, fibre diameter and cell size.

The bulk density of cells relative to that of chunks from which they are formed is generally increased by a factor of at least 1.5. For example, basalt wool chunks having a bulk density of about 100 kg m^" were converted into cells having a bulk density of about 150 kg/m³ by treatment in accordance with the invention. The cells nevertheless contain entrapped^' air. having air-filled interstices between the fibres.

The mechanical rumbling action that converts chunks into cells can be achieved in a number of different ways, with different techniques being better suited to different fibrous materials.

For example, tumbling to convert chunks to cells can be obtained with a vibratory motion along a linear path, eg by transporting the chunks along a suitably configured vibrating screen such as a wire mesh deck. The chunks, as they pass along the deck, are retarded by the wire mesh, tending to roll and tumble as they move along. This technique is well suited to chunks of weaker fibres such as basalt fibres, but can be used for all fibre types given correct processing variables. The processing variables are: screen length, screen aperture size and geometry (eg round or square) and vibration frequency. Suitable values for the variables for any given material can be readily determined by experiment.

In other instances, where the fibres are stronger, e.g. glass fibre, a rotary tumbling motion is preferred to convert chunks to cells, with chunks conveniently being tumbled along a circular path in a horizontal plane, eg around the circumference of a container, with a superimposed vertical or sinusoidal component of motion and/or a superimposed inwards and outwards motion relative to the axis of rotation. Such rotary rumbling motion is conveniently achieved using a generally cylindrical or bowl-shaped container having a generally central rotating agitator or rotor.

The agitator preferably comprises one or more arms mounted for rotation in a generally horizontal plane. The arms are preferably apertured.

The container may be sloped or curved slightly inwardly towards the top to promote the circular spiral motion of the chunks, and/or may optionally include one or more suitably shaped and located baffles. The container may include suitable inlet and outlet means for the chunks and cells, respectively. The action of the rotating agitator is desirably such that the fibrous chunks are both swept round and thrown outwardly and upwardly, thereafter to tumble inwardly and downwardly to re-enter the path of the rotating agitator. Thus, the chunks are continually swept round along a circular sinusoidal path with a spiral motion.

The speed of rotation of the agitator may be adjusted, typically within the range 15 to 30 rpm, to assist in producing cells having desired properties.

A number of similar containers may be used in series to enable continuous rather than batch production of cells.

The linear or rotating tumbling motion flexes the fibres until they are interwoven and tucked into a rounded fibrous cell with small, air-filled interstices between the fibres. Conversion of a chunk into a cell occurs after tumbling for sufficient time, which may be a few seconds or a few minutes depending upon the nature of the chunks and tumbling technique used: continued tumbling has no effect on the cells.

In a preferred aspect of the invention there is thus provided a method of treatment of fibrous material which comprises: a) cutting a fibrous mass into chunks; b) tumbling the chunks in a container having a generally central rotating agitator so that the chunks are tumbled along a circular spiral path, both round the container and upwards towards the outside of the container, inwards and downwards into the agitator; and c) continuing the tumbling action until the chunks are formed into rounded, woven fibrous cells containing air-filled interstices.

According to another aspect of the invention, there is provided apparatus for the treatment of fibrous material comprising: a) a knife means for cutting a fibrous mass into chunks of the same order of size; and b) a container having a central rotating agitator for tumbling the chunks along a circular spiral path, both round the container and upwards towards the outside of the container. inwards, and downwards into the agitator, until the chunks are formed into rounded fibrous cells containing air-filled interstices.

The fibrous chunks may be tumbled wet or dry, but are preferably in damp or moist condition. Water or other liquids may be added in suitable amount prior to or during tumbling. Examples of liquid additives are: silicates (as a binder or to modify the surface characteristics of the cells), surface active agents (to impart water repellency), size solutions (to improve wetting characteristics), silanes (to improve compatibility with polymers), binders (to form agglomerates, panels etc).

A wide range of additives (liquid or solid) may optionally be added to the chunks prior to or during tumbling. The additives may be selected to have one or more of the following effects on the cells:

1. impart flame and/or smoke retardancy or resistance (eg zinc stannate)

2. remove impurities (eg slag dust to absorb and remove oil)

3. add colour (eg iron oxide)

4. impart water repellency properties (eg stearates)

5. modify chemical characteristics (eg silanes)

6. modify other surface characteristics (eg sodium silicate).

Suitable additive materials for performing the various functions are well known in the art.

Short lengths of fibrous material, preferably rigid or semi-rigid fibrous material, may optionally be added prior to or during tumbling.

Treatment of the cells after formation may additionally or alternatively optionally be carried out, eg by surface coating with materials to modify cell properties. In particular, additives may be applied to the cells after formation to modify the surface properties of the cells themselves, and not the properties of the majority of the fibres within the cell. For example, the addition of a sodium silicate solution to basalt cells, for example by vacuum coating or 7

spraying, followed by drying produces a cell with a significantly stronger and less friable surface.

The invention also includes within its scope cells produced by the method of the invention.

In a further aspect, the invention also provides a product consisting of rounded fibrous cells with entrapped air, ie comprising only generally spherical, oval or similar cells without discshaped or elongate cylindrical or rod-shaped cells.

The cells have properties that make them useful in a wide range of applications. In particular, the entrapped air of the cells means that the cells have insulation properties (thermal and acoustic) useful in many contexts. The cells can also be capable of absorbing large amounts of liquid: for example it has been found that some cells can absorb up to 6 times their weight of water. Other characteristics, eg water repellency, may optionally be imparted to the cells by suitable treatment. The cells themselves are also generally inert, chemically and physically, and are non-combustible, lacking organic binder.

Uses of the cells include the following:

1. As a loose-fill material, either alone or mixed with other materials, in a wide range of applications that can exploit the insulation properties of the cells, including in structural elements and components such as building panels, fire doors, automotive silencers, vehicle doors; in buildings and industrial plant, eg in partitions, between the inner and outer liners of chimney flues, between floors of buildings; in garments, pillows, lagging and blankets; as growing medium. For fire-stopping or fire-retarding purposes it may be advantageous to use a mixture of cells in accordance with the invention and intumescent material, eg in paniculate or powder form.

The cells are easily handled, and can be readily blown or sucked into regions to be filled, conforming themselves to fill irregular shapes without difficulty, and being capable of removal eg by suction. In the manufacture of automotive silencers, industrial chimneys and industrial silencers etc., cells in accordance with the invention eg made from basalt wool can 8

be used to advantage in place of traditional rolled-up basalt etc. This means that the silencer or other component can be pre-built and then the acoustic/fireproof cells can be easily and efficiently sucked or blown into the component cavity, so that the cells completely fill the cavity and conform to the cavity shape regardless of geometry. Moreover, by varying the suction or vacuum applied during filling, the density of packing of the cells be regulated, allowing production of components, eg silencers, with differing properties and performance. When the component is to be disposed of, the cells can be removed for disposal or recycling, with other metal parts of the component being available for separate disposal or recycling.

In the making of double wall chimneys, for example, cells can readily provide the necessary thermal insulation between the stainless or enamel etc. walls as the cells can be blown or sucked in and will conform to the shape of the cavity.

For use as a hydroponic growing medium it is appropriate to use high water absorbency cells without additives. The cells can be packed in containers of desired form at desired densities, suitable to anchor growing plants.

2. As an insulating panel, when mixed with binding materials, which can be formed, eg by pressing or moulding techniques into components such as boards, tiles, slabs etc. which may be of simple or complex form, eg constituting car body panels etc. For such uses, it may be appropriate to mix the cells with other ingredients, such as other fibrous materials, binders, cements, plasters etc. As a specific example, a solid phenolic resin eg novolak may be added to fibrous chunks prior to or during tumbling. The resulting cells may be placed in a mould and heated, causing the resin to cure and bind the cells together, forming a bound solid insulating material.

3. As a surface coating, eg on building or vehicle surfaces. The cells, mixed with suitable adhesive eg polymeric resin may conveniently be applied by spraying, painting or other techniques, forming a directly applied insulating coating conforming exactly to the surface on which it is applied. 4. In fire fighting, by spraying a mixture of cells and water. The cells absorb water and produce material than can deprive fire of air, effectively functioning as a sprayable fire blanket. For such use, the cells may advantageously be pre-treated with flame-retardant or smoke-depressant materials.

The invention also includes within its scope a product incorporating fibrous cells in accordance with the invention.

The invention will be further described, by way of illustration, in the following Examples and with reference to the accompanying drawings, in which:

Figure 1 is a schematic side view, partly in section, of fibre size reduction apparatus suitable for forming fibrous chunks;

Figure 2 is a schematic view of the rotating shaft of the apparatus of Figure 1 to an enlarged scale;

Figure 3 is schematic view of one of the protruberances of the shaft of Figure 2 to a further enlarged scale;

Figure 4 is a sectional view of part of the shaft of Figure 2 to an enlarged scale;

Figure 5 shows the screen of the apparatus of Figure 1 to an enlarged scale;

Figure 6 is a schematic perspective view, showing some hidden detail, of one embodiment of apparatus for tumbling fibrous material in accordance with the invention;

Figure 7 is a graph of acoustic absorption coefficients versus frequency (1/3 octave bands- mid range frequencies (Hz)) showing results of impedance tube test on basalt fibre cells produced as described in Example 1 ; 10

Figure 8 is a graph similar to Figure 7 for glass fibre cells produced as described in Example

2;

Figure 9 is a graph of 'k' value (W/mK) versus temperature (°C) illustrating the thermal conductivity of the glass fibre cells of Example 2;

Figure 10 is a graph of volume reduction (%) under 50kg/m² loading versus temperature (°C) illustrating the thermal volumetric stability profile of the glass fibre cells of Example 2; and

Figure 11 is a graph of 'k' value (W/mK) versus temperature (°C) comparing the thermal conductivity of basalt fibre blanket at various densities and fibrous cells in accordance with the invention.

Detailed description of the drawings

Figures 1 to 5 illustrate one embodiment of shredder apparatus 10 suitable for forming various types of fibrous materials into chunks suitable for processing by the method of the invention.

Apparatus 10 is based on a modified biomass shredder known as the Castoro model from P.O.R. SpA of Italy. The apparatus comprises a cylindrical steel shaft or drum 12 182mm in diameter and 456mm in length arranged for rotation about a generally horizontal axis. Nineteen similar steel protruberances 14 are secured to the external surface of the shaft 12. The spatial arrangement of the protruberances is designed to create the specific effect required. Each protruberance is of the form shown in Figure 3, and comprises a generally cylindrical rigid shaft or shank 16 with a frusto-conical head 18 tapering outwardly therefrom. The top circular edge 20 is not sharpened. A central bore 22 extends through the shaft and head, for securing of the protruberance to the shaft 12 by means of a screw (not shown). The protruberances are inclined at an angle of about 5° with respect to the shaft radius, as shown in Figure 4, and extend about 10mm from the shaft surface. 1 1

The shaft 12 is mounted for rotation under the control of a reversible drive (not shown) in a housing 24 via externally mounted waterproof roller bearings (not shown).

A part cylindrical section of the housing 24 is constituted by a screen 26, as shown in Figure 5, which subtends an angle of about 90°, formed of punched perforated mild steel plate with circular apertures 27. Screen 26 is removable and replaceable. Screens with apertures 10mm, 15mm, 20mm and 30mm diameter are supplied.

The spacing between the screen 26 and the upper surface of the protruberances 14 is about 13mm.

The housing 24 includes a funnel-like upper portion or hopper 28 for receiving fibrous material to be processed. The housing includes an optional, horizontally extending containment plate 30 located above the rotatable shaft. The horizontal position of plate 30 may be adjusted in a manner not illustrated.

Apparatus 10 further includes a reciprocable hydraulic ram 40 mounted to run along the base of portion 28. An output chute 42 is located below the screen 26, for receiving product after processing.

In use, material 50 to be processed is fed into the top of the apparatus via housing portion 28. Shaft 12 is caused to rotate at a speed of about 150 rpm. Ram 40 is caused to reciprocate at an appropriate rate, typically about 6 times per minute, with appropriate limits of travel being determined and set.

The feed material 50 falls down to the bottom of the housing where it is presented to the rotating shaft 12 by the action of the horizontal reciprocating hydraulic ram 40, which acts to apply the necessary pressure to ensure consistent feed to the shaft. The material is picked up by and caused to rotate with the shaft, with the arrangement acting to maintain positive feed of material to the rotating shaft and preventing cavitation. 12

Initial calibration of variables such as speed of rotation of shaft 12, speed of reciprocation and extent of travel of hydraulic ram 40 and vertical height of containment plate 30 (if present) may be required to produce chunks of desired size and form.

Figure 6 illustrates one embodiment of apparatus for tumbling fibrous material to convert chunks into cells. The apparatus is based on a modified commercially available food processor equipment in the form of a Nilma Speedy Cutter, model DS3.

The apparatus illustrated in Figures 6 comprises a generally cylindrical stainless steel container 100 with a smooth internal side wall 102 and base 104. The container has a hinged polycarbonate lid 106 with handle (not shown) and a small closeable opening (not shown) for material supply. A stainless steel rotor or agitator 108 comprising two similar, curved. apertured, tapered, blunt-edged arms or blades 110, mounted on a shaft 112, with the two arms vertically separated along the length of the shaft by about 25mm, is rotatably mounted within the container on base wall 104 for rotation with the arms in a generally horizontal plane. The apparatus includes a variable speed electric motor (not shown) mounted in a housing 114 below the container, arranged to cause rotation of the agitator via a rotatable boss connected to the motor and extending upwardly through a centrally located aperture in the base wall, for engagement by a corresponding recess in the agitator shaft. Controls 116 are mounted on a panel 118. A curved inclined, stainless steel baffle 120 is adjustably secured to the inner side wall of the container, located approximately 75mm above the higher agitator blade 110. An outlet opening 122 in cylinder side wall 102, with a removable plug (not shown), leads to a tube 124 for removal of material from the cylinder, eg by use of a suction pump (not shown). The container 100 and housing 114 are pivotally mounted on a framework 126. The container and housing can be pivoted about a horizontal axis between the upright position of use, as shown, in which position the container and housing may be secured, and an inclined, partly inverted condition which may be adopted eg to facilitate cleaning of the container interior.

In use, a batch of chunks of fibrous material is introduced to the container 100, and the lid 106 shut. Liquid additives may be added via the opening in the lid, if desired. The motor is operated to cause rotation of the agitator 108 at a suitable speed, eg in the range 15 to 30 φm. This causes rotary tumbling motion of the chunks, with the chunks being swept around in a circular path and also being swept upwardly and downwardly, in a sinusoidal path around the periphery of the container, with a degree of inwards and outwards motion, assisted by the baffle 120. The apertures in the agitator blades 1 10 promote air flow and assist in constraining the cells to move in the desired path. After a suitable time, the chunks are formed into cells, as described above. The agitator is stopped, and the cells removed via the outlet tube 124. The cells may be passed for suitable downstream processing as desired, eg on screen shakers for removing any parti culate debris, for sorting etc.

Example 1 (Basalt Wool)

Basalt wool is shredded into chunks about 20 to 30mm in length, either using a Hallde RG 400 sheer rotary cutter comprising a cylindrical bowl in which rotates a horizontal cutting blade at high speed, or by shredding in the shredder apparatus of Figures 1 to 5 above using a 20mm diameter round hole screen.

The resulting chunks are processed over a vibrating deck in the form of a Triton single deck open trough linear vibratory screen, model number TRS 2500/1100. This deck comprises a relatively fine mesh screen to remove unwanted contaminants eg overshot! The vibrating deck is configured so that it induces a rolling and tumbling action in the chunks which, as they move along the deck, form into cells.

The size of the resulting cells can be varied by varying the size of the chunk, altering the configuration of the screen of the vibrating deck, and/or altering the frequency of the vibration and the length of time spent on the screen.

A liquid additive, eg to impart water repellency or to otherwise modify the surface characteristics of the cell, is optionally applied by spray towards the end of the vibrating deck.

This results in cells all of generally oval or egg-shaped form, having a maximum dimension of about 6mm and a bulk density of about 130 kg/m³. The maximum dimension of each cell 14

is much less than the twice the minimum dimension of each cell, with the ratio of the dimensions generally being less than 3:2. The cells have a whiskery surface finish, with protruding fibres.

The acoustic absoφtion characteristics of the resulting basalt cells are shown in Figure 7.

The cells can find application in the fields of acoustic, thermal and fire insulation and as a growing medium in the hydroponics industry. The superior thermal insulation characteristics of the 6mm diameter basalt cells over those of conventional basalt blanket is shown in Figure 11.

Basalt wool cells prepared in the same way but from slightly larger chunks so that the cells have a maximum dimension of about 12mm (after sorting and classification if necessary) were sprayed with sodium silicate solution and dried, to provide a surface coating of silicate. The cells were used as loose fill insulation in automotive silencers, as described above.

Example 2 (Glass fibre wool)

Damp textile grade borosilicate glass fibre wool (E glass) (at approximately 4% moisture content) is shredded, using the apparatus of Figures 1 to 5 fitted with a 20mm diameter round hole screen, to form fibrous chunks about 20mm in length.

These chunks are tumbled in the apparatus of Figure 6, with the agitator being rotated at a speed in the range 16-24φm.

After 6 mins rotation each individual chunk has formed a largely spherical fibrous cell of approximately 3mm diameter. The cells have a whiskery surface finish, with protruding fibres.

The cells have a bulk density of about 150 kg/m². 15

The acoustic absoφtion properties of the resulting glass fibre cells are shown in Figure 8. with Figure 9 illustrating thermal conductivity. Figure 10 shows the thermal/volumetric stability of the cells when compressed to have a bulk density of about 200 kg/m².

A typical chemical composition (by weight) of the cells is as follows:-

Silicon Oxide SiO₂ 52-56%

Aluminium Oxide Al₂O₃ 13-16%

Calcium + Magnesium Oxides CaO + MgO 21-25%

Sodium + Potassium Oxides Na₂O + K₂O 0.01-1%

Boron Oxide B₂O₃ 5-9%

Iron Oxide Fe₂O₃ 0.01-0.5%

Loss on ignition 1% (typical)

Fibre diameters are as follows :-

Mean filament diameter lOμm Minimum filament diameter 7μm Maximum filament diameter 14μm

Thermal/volumetric stability of the cells under static test loading of 50 kg/m^" was as follows:-

Packing Density Range 150kg/m³ 175kg/m³ 200kg/m^J Upper Stability Temperature (volume loss=10%) 650°C 750°C 850°C

The cells have unique packing characteristics and exceptionally low thermal conductivity properties. Further, the cells are stable in arduous environments and, being non-hydroscopic, do not accelerate corrosion of metallic components, making them suitable for use in twin- walled hot flue applications.

The fibrous spheres are sufficiently mobile to enable automated mechanical filling procedures. When brought into contact with curved surfaces or in occupation of cavities of irregular shape, the material exhibits excellent contouring properties. A moderate degree of 16

sphere-to-sphere cohesion is specifically incoφorated into the product, reinforcing the unique conformal qualities whilst avoiding "clumping".

Figure 11 shows the thermal conductivities of conventional basalt fibre blanket with basalt cells produced as described in Example 1 (line 6) and glass fibre spheres produced as described in Example 2 (line 7).

Example 3 (Glass fibre needlemat)

Off-cuts of glass fibre needlemat are shredded using the apparatus of Figures 1 to 5, using a 20mm diameter round hole screen, to produce fibrous chunks about 20mm in length. These chunks are tumbled in the apparatus of Figure 6, with the agitator being rotated at a speed in the range 16 to 24 φm.

After 3 minutes rotation each individual chunk has formed a into a respective generally spherical fibrous cell of approximately 5mm diameter. The cells have a whiskery surface finish, with protruding fibres.

Claims

17Claims

1 A method of treating fibrous mate╧Çal, comp╧Çsmg treating a plurality of discrete fibrous chunks, each chunk comp╧Çsmg a mass of entangled fibres, by a mechanical tumbling action such that each chunk forms a respective denser, rounded fibrous cell with entrapped air

2 A method according to claim 1, wherein the fibrous chunks have a maximum dimension in the range 10mm to 50mm.

3 A method according to claim 1 or 2, wherein the fibrous mate╧Çal is initially processed to produce fibrous chunks.

4 A method according to claim 3, wherein the fibrous mate╧Çal is processed to produce fibrous chunks by cutting or shredding.

5 A method according to any one of the preceding claims, wherein the fibrous cells have a maximum dimension in the range 1mm to 15mm, preferably 2mm to 12mm

6 A method according to any one of the preceding claims, wherein the bulk density of cells relative to that of chunks from which they were formed is increased by a factor of at least

1 5

7 A method according to any one of the preceding claims, wherein the mechanical tumbling action is obtained with a vibratory motion along a linear path.

8 A method according to any one of the preceding claims, wherein the mechanical tumbling action is obtained with a rotary tumbling motion, with chunks being tumbled along a circular path m a ho╧Çzontal plane, with a supe╧Çmposed vertical or sinusoidal component of motion and/or a supe╧Çmposed inwards and outwards motion relative to the axis of rotation 18

9. A method according to claim 8, wherein the rotary tumbling motion is achieved using a generally cylindrical or bowl-shaped container having a generally central rotating agitator or rotor.

10. A method according to claim 9, wherein the agitator comprises one or more arms mounted for rotation in a generally horizontal plane.

11. A method according to claim 9 or 10, wherein the speed of rotation of the agitator is within the range 15 to 30 ╧åm.

12. A method according to any one of the preceding claims, wherein one or more additives are added to the chunks prior to or during tumbling.

13. A method according to any one of the preceding claims, wherein the fibrous material is inorganic fibrous material.

14. A method according to claim 13, wherein the fibrous material comprises mineral fibres.

15. A method according to any one of the preceding claims, wherein all of the cells are of generally spherical or oval form.

16. A method according to any one of the preceding claims, wherein all of the cells have a whiskery surface finish, with protruding fibres.

17. Cells produced by the method of any one of the preceding claims.

18. A product consisting of rounded fibrous cells with entrapped air.

19. Cells according to claim 17 or 18, having a maximum dimension in the range 1mm to 15mm, preferably 2mm to 12mm. 19

20. Cells according to claim 17, 18 or 19, having a bulk density in the range 100 to 200 kg/m³.

21. Cells according to any one of claims 17 to 20, having a whiskery surface finish, with protruding fibres.

22. Cells according to any one of claims 17 to 21, wherein all of the cells are of generally spherical or oval form.

23. Cells according to any one of claims 17 to 22, comprising inorganic fibre.

24. Cells according to claim 23, comprising glass fibre.

25. Cells according to claim 23, comprising basalt fibre.

26. A product inco╧åorating fibrous cells in accordance with any one of claims 17 to 25.

27. A product according to claim 26, wherein the cells are in loose-fill form.

28. A product according to claim 27, comprising an automotive silencer.

29. A product according to claim 28, comprising hydroponic growing medium.

30. A product according to claim 26, wherein the cells are moulded or pressed to form a solid insulating panel.

31. A product according to claim 26, wherein the cells are applied to form a surface coating.