TREATMENT OF FIBRES

Abstract: A method of treating inorganic fibrous material such as glass fibre, ceramic fibre, mineral wool, basalt wool, rock wool, comprises feeding the fibrous material to apparatus comprising a rotating shaft carrying external protruberances, with an associated screen, resulting in size reduction of the fibrous material without significant production of fines. The invention has particular, but not exclusive, application to the processing of waste fibre residue, e.g. downchute residue, which can be processed directly in the method of the invention, while still wet (with water and usually also size), resulting in the production of smaller fibres which constitute a valuable product that can be used in a number of ways. The invention thus enables reclamation of material previously rejected as waste, which could only be disposed of by landfill due to its unmanageable nature.

Description: Title: Treatment of Fibres Field of Invention - This invention relates to treatment of fibres, particularly inorganic fibrous material such as glass fibre, ceramic fibre, mineral wool, basalt wool, rock wool, which may be in the form of continuous strands, mats, wools etc. The invention has particular, but not exclusive, application in the recovery of waste fibres, particularly glass fibre process residues. Background to the Invention Inorganic fibres are now widely used in many industries, including, for example, the construction industry, boat building, vehicle components, telecommunications, domestic products, insulation products etc. Inorganic fibres are made from a melt of various mineral materials. Fibres can be generated from the melt by, for example, passing it through a bushing containing an array of small nozzles from which molten material exudes and is drawn into a plurality of individual fine fibres, called filaments, or by allowing a fine stream of melt to impinge upon the edge of a spinning disc. The filaments can then be subjected to a sizing stage in which the filaments are coated with material of various sorts, depending on desired properties and intended uses of the material. Inorganic fibres eg glass fibres can be processed in a number of ways, eg to produce cohesive bundles known as strands, each comprising a plurality (eg about 200) of parallel filaments, from which yarns can be fabricated, into blankets comprising a mass of fine fibres, boards in which the fibres are bound together, wool for loose infill applications etc. In the production of and fabrication of products from mineral fibres large volumes of waste material is produced; eg in the production of glass fibre, once the melt has been established, glass flow from the bushings is continuous so any downstream process interruption results in fibre residues. In the production of glass fibre, strand as produced is typically collected on a rotating cylinder, called a collet, carrying a removable tube onto which the strand is wound. When sufficient strand has been wound onto a collet, the collet is stopped and the package of strand, called a cake, is removed. The winding and strand-collection operation is then restarted. Strand production nevertheless continues in the meantime. Pull-down rollers are commonly provided in glass manufacturing equipment, downstream of sizing and strand formation steps, which function to pull coarse fibre strand produced from an idling bushing between completion of one cake on another. The material passing from the rollers is collected for disposal. This material and other waste material arising during manufacture is known as downchute waste or downchute residue. In practice, downchute residues are substantial and can amount to up to 20% by weight of the total output of glass fibre production. At present this material is treated as waste which is difficult and costly to dispose of. For further discussion of the production of glass fibre see K. Lowenstein, The Manufacturing Technology of Glass Fibre (3 rd edition, 1993). Many attempts have been made to reclaim inorganic fibre waste residues. These include cutting and milling of the residue material. These attempts have largely been unsuccessful due to a number of reasons, including excessive wear of equipment due to the abrasive nature of the material rendering processing uneconomic, and the production of unacceptable levels of microfme material. It is also known to treat natural organic fibrous material (the cellular structure of which means that it can be squashed or flattened) by cutting or impacting, eg using a hammer mill, for instance as disclosed in GB 2062497, GB 2057402, GB 2016302, GB 1005081 and GB 659111, in a way that inevitably produces dust and fines. GB 533942 concerns the release of asbestos in the form of short fibres from granules of asbestos-bearing rock, using apparatus having a series of similar casings, each with a horizontally rotating shaft carrying fixed beater arms or rods. WO 97/43043 concerns a grinder of fibrous material of vegetable or mineral origin, treated wet or dry, comprising a rotor carrying rigid radial blades for rotation about a horizontal axis within a cylindrical casing including screen. JP 8117625 discloses a pulveriser using rotary blades. These techniques and equipment again inevitably produce dust or fines. WO 98/19973 concerns treatment of glass fibre that involves crushing between pairs of rotatable rollers having intermeshing elongate protruberances extending across the width of the rollers. US 3584796 concerns the production of glass fibre blowing wool (up to about 50mm in length) from bonded glass fibre material containing binder using various cutting devices in place of known milling techniques with the aim of reducing, but not eliminating, dust formation. The techniques employed nevertheless inevitably result in the production of some dust and fines. US 4043779 concerns chopping of binder and/or size coated glass fibre strands, each formed from a number of filaments, into chopped strands or bundles eg about 3.18mm long by the use of cutting blades. The cutting technique employed again inevitably results in the production of some .dust and fines. In addition both these methods employs cutting knives with the associated problems of wear and blunting of the knife edges requiring constant replacement and maintenance. Summary of the Invention In one aspect the present invention provides a method of treating inorganic fibrous material, comprising feeding the fibrous material to apparatus comprising a rotating shaft rigidly carrying external protruberances lacking sharp edges, with an associated screen, resulting in size reduction of the fibrous material without significant production of fines. Unlike prior art processes, no cutting, crushing or grinding action is involved. The term "fines" is used to mean small particles each having a diameter greater than or equal to its length. Fines are thus to be distinguished from a fibre, which has a length greater than its nominal diameter, with the length of a fibre generally being several times the diameter, eg at least 2 times the diameter (ie having an aspect ratio (length: nominal diameter) of at least 2). The form of the fibrous material being treated is not critical and the invention is well suited to treatment of entangled masses of fibre as well as more ordered or regular fibres. The nature of the products obtained by processing fibrous material in accordance with this invention is governed by the physical characteristics and physical form of the fibrous material and the geometry of the apparatus used. In general, treatment of fibrous material of a more rigid/brittle nature (this rigidity being imparted to the fibrous material either by its physical nature or by the coating of the fibre with a rigid binder or size) results in shorter fibres, typically in the form of rigid monofilament fibres. The term monofilament fibre means an individual, separate filament or fibre rather than a fibre bundle or strand. The monofilament fibres are intact across their diameter or width, ie they are not split along their length, so that fibre integrity is maintained. The monofilament fibres are rigid, ie stiff and non-flexible. The monofilament fibres have a free-flowing characteristic, with no tendency to agglomerate. Treatment of more flexible fibrous material, eg in the form of wool or needled mat etc, produces chunks of entangled masses of fibres. Depending on the nature of the fibrous material, the method is carried out either wet or dry. Fibres in the form of wools, mats etc, such as glass fibre needlemat or ceramic material, are generally processed in the dry state, resulting in the production of smaller sized fibrous chunks or balls. Other fibrous material processed in the dry or wet state result in the production of individual separate shorter fibres (typically rigid monofilament fibres), eg certain E-glass fibre residues, A-glass fibre residues bound with resin for filter manufacture, mineral wool slabs (bound with resin). The shorter fibres typically have a length less than 25mm. The fibres may be of mixed length, the range being dependent upon the fibre type being processed, or may be classified or sorted so that the fibres are of substantially similar length or have lengths within any desired ranges. The rigid monofilament fibres typically have widths or diameters in the range lOμm to 500μm, eg 20μm to 150μm. In certain embodiments at least 30% of the monofilament fibres may have a diameter greater than about 30μm and/or at least 50% of the monofilament fibres may have an aspect ratio of less than 30. Such rigid monofilament fibres are the subject of a copending application in our name filed on the same day as the present application. The monofilament fibres may be of mixed diameter or substantially similar diameter. The fibres may have the form of regular circular cross-section cylinders, or may be of more irregular form. For example, glass fibre residue originating from the fibre forming process (downchute residue) which may be in the form of an entangled mass of fibres, while still wet (with water and usually also binder) can be directly processed in the method of the invention, resulting in production of shorter rigid monofilament fibres which constitute a product that can be used in a number of ways as will be discussed below. Dry fibres of a variety of types, eg wet downchute residue that has been dried, can .e processed in a similar way, possibly with the addition eg by spraying of a suitable wetting agent, if appropriate. The wetting agent is preferably a dilute aqueous solution of a surface active agent. Good results have been obtained with V_-l % by volume of the surfactant Alcopol (Alcopol is a Trade Mark) from Allied Colloids. Alcopol is sodium dioctyl sulpho succinate. Other surfactants may be used. When processing wet but unsized glass fibre residue, it may also be appropriate to add a wetting agent, eg Alcopol. The wetting agent solution acts as a lubricant, facilitating slip between fibres, and also functions as a coolant. The process (both wet and dry) primarily involves shear forces in breaking down material. Minimal grinding or impact is involved, unlike in prior art processes. This results in the production of smaller pieces of material, eg shorter monofilament fibres, substantially lacking dust or fines. Processing may be followed by washing and drying steps. After wet processing, the resulting mulch material may be conveyed to a washing screen, eg a Thule Rigtech VSM 100™ shaker screen, for washing and dewatering of the fibres. After washing, if required, the product material may be conveyed to a dryer for drying in conventional mariner. Suitable dryers include band dryers, ring dryers, rotary driers and batch dryers. Dried material may then be classified in conventional manner, eg by use of mechanical screens or air classification techniques, giving a range of fibre or chunk/ball sizes that may be used in a variety of ways. ~ The protruberances carried by the shaft are conveniently of knob-like form, possibly generally mushroom-like in shape. In a further aspect the invention provides inorganic fibrous material size reduction apparatus, comprising a rotatable shaft rigidly carrying a plurality of external protruberances of knob-like form lacking sharp edges, with an associated screen. Good results have been obtained using a modified biomass shredder, having protruberances with a form closely resembling 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. Another aspect of the invention provides inorganic fibrous material size reduction apparatus, comprising a rotatable shaft carrying external protruberances, with an associated screen, each protruberance comprising a rigid shank with a frusto-conical head lacking sharp edges tapering outwardly therefrom. The rotatable shaft is suitably located in a part cylindrical housing, part of which is constituted by the screen, with a gap between the protruberances and the housing screen. The apparatus may include a hopper above the shaft, for receiving material to be supplied to the shaft. In a typical embodiment the rotatable shaft is 182mm in diameter and 456mm in length, and is made of steel. The shaft is arranged for rotation about a generally horizontal axis. The shaft carries a plurality protruberances of the preferred form discussed above (having a generally cylindrical shaft or shaft with a frusto-conical head, lacking sharp edges), extending 10mm from the shaft surface. The spatial arrangement of the protruberances is designed to create the specific effect required. In particular, the protruberances "are positioned to ensure an even feed of fibrous material to the screen and to prevent any grinding by lateral movement across the screen. The associated screen subtends an angle of about 90°, and is constructed from perforated mild steel plate. The perforations are suitably circular, although the shape is not critical, and conveniently have a diameter in the range 10 to 30mm. The spacing between the protruberances and the screen is about 13mm. ' This comparatively large clearance minimises attrition of the fibrous material. In use, material to be processed is fed into the modified shredder and is presented to the rotating shaft by a horizontally reciprocating hydraulic ram to apply the necessary pressure to ensure consistent feed to the shaft. As a further modification it is preferred to fit a containment plate vertically above the rotating shaft, the height of the plate being adjustable, to maintain positive feed of the material to the rotating shaft. In trials of such apparatus with the shaft rotating at about 150 rpm, feed directly with wet glass fibre downchute residue, rigid monofilament fibres substantially in the range 50μm to 5mm were produced. .It was observed that after about 6 to 8 revolutions of the shaft, masses of fibres began to extrude as a mulch through the screen. Residence time and hence throughput is affected by screen size, within limiting values, with larger apertures giving faster throughput. Within these limiting values, no significant difference in fibre size was observed. In a further example dry fibre glass waste, originating from needlemat production, was processed through the size reduction apparatus. The resulting product consisted of individual clumps comprising of intertwined fibres. These clumps possess excellent thermal and acoustic insulation characteristics. The size reduction apparatus thus produces in this instance a valuable, added value, secondary insulation product. Similar processing of waste basalt fibre mat can result in the formation of discrete chunks of fibre which has potential for use as a dry fill material or which is in a form which can readily be recycled to the mat laying line or remelted in a furnace. By routine experimentation, suitable apparatus variables and processing conditions can be determined to suit any particular material being processed. Investigations have shown that the apparatus operates under different modes with different fibrous material. 1. With glass fibre downchute residue, which is presented as generally continuous lengths of fibre, the apparatus functions via a threshing action. 2. With glass fibre fabrication waste, which is presented as short lengths, the apparatus acts to entangle the fibres and thus increase the bulk density of the fibre mass. Any cutting action occurs incidentally to the main action which is a rolling action over the rotor. 3. With fibre blankets etc, rolling action mentioned above is preceded by a ripping/tearing mode which liberates the fibres. The final nature of the product in 2 and 3 is dependent upon the material being treated, the number and size of the apertures in the screen, the protruberance arrangement and the shaft rotational speed. The present invention also includes within its scope fibrous material treated by the method of the invention or using the apparatus of the invention. The resulting fibrous material may be used, eg in the following applications:- laminates cementatious materials bituminous materials insulating material (thermal, fire, acoustic) structural composites protective coatings recycled raw material ~~ There are numerous sources of potential feed material for treatment by the method of the invention, as well as glass fibre residue, eg downchute residue, as discussed above. These include other production waste, for example so called front end waste, trimmings and offcuts from conversion processes and discarded end products. It is not necessary to use waste material as the feed, and good quality, unused material not of waste grade can instead be used for this purpose. The present invention can thus enable reclamation of material previously rejected as waste which could only be disposed of by landfill due to its unmanageable nature. Moreover, the invention produces material useful in its own right. The low power requirement of this process and the associated low levels of wear make the process highly attractive economically with processing costs being less than those of traditional landfill, with the process also producing useful, valuable fibre materials. A preferred embodiment of the invention, in the form of apparatus for directly treating wet glass fibre downchute residue, will now be described, by way of illustration, with reference to the accompanying drawings in which: - Figure 1 is a schematic side view, partly in section, of the inorganic fibrous material size reduction apparatus in accordance with the invention; 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 flow chart of the process steps involved in treatment of wet glass fibre downchute residue, using the apparatus of Figures 1 to 5; and Figures ' 7 and 8 are graphs of filament diameter (micron) versus frequency for batches of glass fibre downchute residue treated by the method of the invention, after screening through a 500μm and a 210μm screen, respectively. Detailed description of the drawings Referring to the drawings, Figures 1 to 5 illustrate one embodiment of size reduction apparatus 10 in accordance with the invention, and Figure 6 illustrates use of this apparatus for processing a wet waste stream of glass fibre downchute residue, carrying water and binder, collected from various formers and/or bushings of a nearby glass fibre production line (not shown), and fed to apparatus 10 via a shaker conveyor (not shown). Referring to Figures 1 to 5, the illustrated 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. In particular, the protruberances are positioned to ensure an even feed of fibres to the screen and to prevent any grinding by lateral movement across the screen. 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 10mm from the shaft surface. The shaft 12 is mounted for rotation under the control of a reversible hydraulic motor (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 circular 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. This comparatively large clearance minimises attrition of the fibres. The housing 24 includes of funnel-like upper portion or hopper 28 for receiving fibrous material to be processed. The housing includes a horizontally extending containment plate 30 located above the rotatable shaft 12. The horizontal position of plate 30 may be adjustable 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 in an anticlockwise direction as seen in Figure 1 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 collected by the rotating protruberances 14 of the shaft, with the containment plate 30 acting to retain material in place, maintaining positive feed ~ of material to the rotating shaft and preventing cavitation. The gap between the protruberances and screen enables feed material collected by the protruberances to be dragged down towards the screen on rotation of the shaft. The trailing ends of the fibrous feed material are threshed across the screen causing fracturing of the ends of the material into pieces which are ejected through the screen apertures. No crushing or grinding action is involved. 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 may be required. During use for processing of wet glass fibre downchute residue, after about 6 to 8 revolutions of the shaft 12, masses of rigid monofilament fibre begin to extrude as a mulch trough the screen 26, to be passed on chute 42 for further processing. Figure 6 illustrates use of the apparatus 10 for processing a wet waste stream 50 of glass fibre downchute residue, carrying water and binder. The wet waste stream may comprise downchute residue, as discussed above, or glass fibre deliberately diverted from glass fibre production equipment, downstream of size-coating and strand formation stages. The wet waste stream is fed to apparatus 10, where it is converted from an unmanageable assortment of strands, clumps, hanks, webs and fibres into short lengths of rigid monofilament fibre, with fibre lengths being substantially in the range 50μm to 5mm, substantially lacking fines. The fibrous product is fed via chute 42 (Figure 1), represented by line 52 in Figure 6, to a washing and de watering apparatus 54 such as by a Thule Rigtech VSM 100™ shaker screen. After washing and dewatering, the fibres are conveyed via line 56 to a dryer 58, such as a band dryer. After drying, the material is conveyed via line 60 to classifying apparatus 62 such as a Gough Vibrecon™ Separator, resulting in a number of separate product streams 64 eacfrof different fibre size range, that may be used in a variety of ways as discussed above. The washing/dewatering stage 54, the drying stage 58 and the classifying stage 62 are all optional. For treatment of some fibres, such as wet fibre glass downchute residue, it has been found that benefits can be obtained using a screen with holes in the form of elongate generally parallel-sided slots or slits, eg with each slot being 5mm wide and 20mm long, rather than circular holes as shown in Figure 5, with a tapering gap between housing 24 (including screen 26) and the protruberances 14 of the shaft 12. The gap is widest adjacent the base of portion 28 (eg gap width about 13mm) and reduces gradually in width in an anticlockwise direction as shown in Figure 1, ie in the direction of rotation of the shaft, to a smallest gap width eg of about 3mm. By varying the slot length, the length of the resulting fibres can be controlled. Experiments indicate slot density in screen 26 affects throughput but not product length. Suitable slot dimensions and density can be readily determined by experiment for particular feed material and desired product characteristics . Example 1 Experiments were carried out using the apparatus of Figures 1 to 5 for processing of wet E-glass fibre downchute residue, carrying water and PVA binder, with downstream processing including all optional steps of Figure 6. Grading analysis was performed on the final product, obtained using three different screens 26, with apertures 10mm, 15mm and 20mm in diameter, respectively. The grading analyses are given below. Grading Analysis (10mm) Grading Analysis (15mm) Grading Analysis (20mm) It will be seen that generally similar fibre size distribution was obtained for all three sizes of screen 26. Example 2 Experiments similar to Example 1 were carried out, but with the material being processed dry, using a screen 26 with 20mm apertures. Following mechanical screening (through a 500μm and a 210μm screen) the products were analysed by microscopy. For the 500μm sample (ie material passing through a 500μm screen but retained on a 210μm screen, which is referred to as -500μm +210μm fraction), data for filament length (in mm) was as follows: Maximum 130 Minimum 0.03-0.12 Average 2.0 - 6.5 Data for filament diameter (in μm) was as follows: Maximum 714 Minimum 11 Average 50-150 Standard deviation 114 For the 210μm sample (ie material passing through a 210μm screen, which is referred to as a -210μm fraction), data for filament length (in mm) was as follows: Maximum 55-95 Minimum 0.15 Average 0.8-3.0 Data for filament diameter (in μm) was as follows: Maximum 164 Minimum 8 Average 60-90 Standard deviation 27 Figures 7 and 8 are graphs of filament diameter distribution for the 500μm and 210μm samples, respectively. Example 3 Plastics composite materials were prepared by a standard compounding technique involving batch mixing in a Z-blade type mixer from dough moulding compound (DMC) including chopped strand glass fibre (control samples). In some samples (samples- in accordance with the invention), 20% by weight of the chopped strand glass fibre content was replaced by the same weight of rigid monofilament glass fibres in accordance with the invention, prepared as described in Example 2. A -500μm +210μm fraction was used, the monofilament fibres of which have an average aspect ratio of 10.4. This fibrous material is referred to as grade A material. The strength of the resulting composite materials were tested, and no significant difference was observed. Results were as follows: Control Invention Flexural strength (MPa) 64.0 61.7 Flexural modulus (GPa) 10.7 11.0 Impact Strength (KJ/mm 2 ) 28.1 23.7 Example 4 Similar dough moulding compound (DMC) to that of Example 3 was prepared but with unwashed fibres, produced in accordance with Example 2, replacing all the chopped strand glass fibre. Two types of monofilament fibres in accordance with the invention were used: grade A material as described above, and similar material but in the form of a -210μm fraction, which has an average aspect ratio of 11.2 and which is referred to as grade B material. It was found that good dispersion of the fibres was achieved during mixing and that two to three times the standard amount of glass could be incorporated whilst achieving the correct compound consistency without the need for thickening agents. Such compounds processed similarly to typical DMC and produced well-consolidated mouldings with good surface finish. The Flexural Modulus (GPa) of a range of compounds produced with loadings of grade A and grade B monofilament fibres in accordance with the invention 2x and 3x (by weight) standard glass loadings were: 2 x A 13.39 3 x A 13.35 2 x B 12.95 3 x B 15.05 These values are generally higher than those observed with conventional DMC. Example 5 Monofilament fibres produced in accordance with Example 2 (grade A material and grade B material as discussed above) were compounded with polypropylene by standard compounding techniques. The glass loading was limited to 40% by weight. The fibres blended with the polymer easily and visual inspection indicated satisfactory dispersion. Tensile, impact and flexural strength measurements were similar to that of commercial grades of talc filled polypropylene. Example 6 Epoxy resin coating compositions based on proprietary products were prepared, with some of the samples including 10% by weight, based on the total weight of the resin composition, of fine grade glass fibres in accordance with the invention, prepared as described in Example 2 (grade B material) . The coatings were painted onto test panels to provide coatings of a thickness as used in conventional floor coating treatments. The panels coated with resin alone (control samples) and resin with glass fibres (samples in accordance with the invention) were tested for slip resistance properties on addition of water, oil and oil and water together. The test method involves the preparation of a small skid block to which is attached a rubber pad. The skid block is then pulled over the test surface attached to a spring weight which measures the force required to move the skid block. Each test was repeated three times and on each occasion the same result was achieved. The results normalised to unity for the control with oil are set out below: Dry Water Oil Water & Oil Invention 2.67 2.33 1.33 1.20 Control 1.20 1.00 1.00 1.00 Example 7 A proprietary polyester resin had added thereto 60% by weight, based on the weight of the resin, of glass fibres in accordance with the invention, prepared as described in Example 2 (grade A material). The resin and fibres were thoroughly mixed and formed into a solid shape by cold casting in a simple mould. After curing, the moulding was dropped 5 times from a height of 10m onto a hard surface, without breaking. Example 8 A 1 : 1 by weight mix of polyester resin and fibres produced in accordance with Example 2 (grade A material. A standard catalyst was added, the mixtures poured into a open mould and allowed to cure at room temperature. The glass mixed readily, producing a free- flowing compound. The glass in this premix was found to stay in suspension for several days with very little tendency to settle out. The incorporation of the glass produced a significant improvement in stiffness of the cured casting, with an almost twofold increase in flexural modulus. Additional benefits accrued from reduced shrinkage increased dimensional stability at elevated temperature and surface hardness. Example 9 Basalt wool waste in dry condition was treated using the apparatus of Figures 1 to 5, fitted with a screen 26 having apertures 20mm in diameter, resulting in production of fibrous chunks or balls having a major dimension of approximately 15mm. The chunks or balls were fed into the pulper of a vacuum forming machine together with a suitable poly vinyl acetate (PVA) binding agent. The resulting pulp was vacuum formed into panels having good properties of thermal and acoustic insulation. - Example 10 Waste E-glass needlemat in dry condition was treated using the apparatus of Figures 1 to 5, fitted with a screen 26 having apertures 20mm in diameter, resulting in production of small clumps of fibrous material about 25mm in length. The clumps were used as a cavity fill material, eg in automotive exhausts for acoustic attenuation and in the cavity of twin wall flues for thermal insulation, and were found to have excellent thermal and acoustic insulating properties. Example 11 Offcuts of basalt wool were treated as described in Example 9 but using a screen 26 having apertures 15mm in diameter. The resulting material was intimately mixed with conventional basalt furnace feed and was successfully recycled for product of basalt fibres.

Claims: Claims 1. A method of treating inorganic fibrous material, comprising feeding the fibrous material to apparatus comprising a rotating shaft rigidly carrying external protruberances lacking sharp edges, with an associated screen, resulting in size reduction of the fibrous material without significant production of fines. 2. A method according to claim 1, wherein the fibrous material is processed in the wet or dry state, resulting in the production of individual separate shorter fibres. 3. A method according to claim 2, wherein wetting agent is added to the fibrous material to be treated. 4. A method according to any one of the preceding claims, wherein the inorganic fibrous material comprises fibre glass residue. 5. A method according to claim 4, wherein the fibre glass residue is treated directly after production, while still wet. 6. A method according to claim 4 or 5, wherein the inorganic fibrous material comprises fibre glass downchute residue. 7. A method according to any one of claims 2 to 6, wherein the product material is washed and dewatered. 8. A method according to any one of claims 2 to 7, wherein the product material is dried. 9. A method according to claim 8, wherein the dried product material is classified. 10. A method according to claim 1, wherein fibrous material in the forms of wools, mats etc are processed in the dry state, resulting in the production of fibrous chunks or balls. 11. Inorganic fibrous material size reduction apparatus, comprising a rotatable shaft rigidly carrying a plurality of external protruberances of knob-like form lacking sharp edges, with an associated screen. 12. Apparatus according to claim 10, wherein each protruberance comprises a rigid shank with a frusto-conical head tapering outwardly therefrom. 13. Apparatus according to claim 11 or 12, wherein the rotatable shaft is located in a part-cylindrical housing, part of which is constituted by the screen, with a gap between the protruberances and housing. 14. Apparatus according to claim 11, 12 or 13, further comprising a hopper above the shaft for receiving material to be treated. 15. Fibrous material produced by the method of any one of claims 1 to 10 or by use of the apparatus of any one of claims 11 to 14.

Inventors: ERSKINE WILLIAM ROBERTSON CUNN, ERSKINE, WILLIAM, ROBERTSON, CUNNINGHAM
Applicants: ASSET ASSOC LTD, ERSKINE WILLIAM ROBERTSON CUNN, ASSET ASSOCIATES LIMITED, ERSKINE, WILLIAM, ROBERTSON, CUNNINGHAM
Application year: 1999
Main classification: C03B37
IPC codes: B02C13, C03B37, C03C1, C04B14, C08K3, D21B1