WO1994019531A1

WO1994019531A1 - Treatment of fibrous materials

Info

Publication number: WO1994019531A1
Application number: PCT/AU1994/000086
Authority: WO
Inventors: Daryl Robb
Original assignee: Fibresaver Pty. Ltd.
Priority date: 1993-02-25
Filing date: 1994-02-24
Publication date: 1994-09-01

Abstract

A process for the treatment of fibrous materials to provide a fibrous mass suitable for making useful products, the process consisting of the following steps: (a) forming a slurry containing the fibres; (b) treating the slurry so that the fibres preferentially align in a common direction; and (c) reducing the slurry to a fibrous mass whilst maintaining a proportion of the fibres in alignment and an apparatus for the production of a fibrous mass suitable for making useful products, the apparatus comprising a slurry bed for acting on a slurry containing fibres to preferentially align the fibres in a common direction, a drawing off device for removing fibres from the slurry and reduction apparatus for reducing the removed fibres to a mass form whilst maintaining fibres in alignment.

Description

TREATMENT OF FIBROUS MATERIALS This invention relates to the treatment of fibrous materials and in particular but not limited to the treatment of used paper products or the like. In this specification, the term fibrous materials refers to any material that can be broken down in its structure into basic fibres which can be interlinked or woven to form a fibrous structure. In this specification, paper and the like refers to any animal, plant or mineral based composite material which has a fibrous structure and has undergone some form of processing where the fibrous character has been retained to some degree.

The present invention arises out of the recognised need to recycle waste paper products such as newsprint, glossprint, cardboard and like.

The present techniques for recycling paper products involves breaking down of waste paper and then compressing the waste paper to form the finished product. Under this process, the resulting product includes defects and flaws which limit its acceptability when compared to products made from new fibres.

In one known process, used paper products are saturated to form a slurry which is then treated to break up the paper into its fibres usually under the action of high speed rotation. In the case of newsprint, ink is extracted using a suitable solvent. The fibres are usually damaged and solvent further weakens the fibres. The slurry is then laid out on a clay bed which is used to remove a substantial portion of the moisture from the slurry resulting in a mass of damp fibres. The damp fibres are then rolled to form a cardboard which itself is then further rolled in heated rollers or steam jets are applied to remove residual moisture from the fibres. Further rolling may be used at this stage to provide a compressed cardboard. The compressed cardboard can then be further treated to be given a suitable surface finish. As this product is made from waste materials, it is inferior to new products and in some cases, is more expensive. In order to provide an acceptable and relatively strong product using this process, it is usually necessary to combine new fibres with recycled fibres in a ratio of about 1:1. The process involves around 20% waste.

Clearly, this process does not involve a product made completely from recycled waste paper as it requires the addition of 50% new fibres from cut timber and with 20% waste makes the process on the whole environmentally unsound.

It is an object of the present invention to alleviate at least to some degree the aforementioned problems associated with prior art processes for treatment of fibrous materials.

With the foregoing and other objects in view, the present invention resides in one aspect, in a process for the treatment of fibrous materials to provide a fibrous mass suitable for making useful products, the process consisting of the following steps:-

(a) forming a slurry containing the fibres;

(b) treating the slurry so that the fibres preferentially align in a common direction; and

(c) reducing the slurry to a fibrous mass whilst maintaining a proportion of the fibres in alignment. In a further aspect, the invention resides in an apparatus for the production of a fibrous mass suitable for making useful products, the apparatus comprising a slurry bed for acting on a slurry containing fibres to preferentially align the fibres in a common direction, drawing off means for removing fibres from the slurry and reduction means for reducing the removed fibres to a mass form whilst maintaining fibres in alignment. The slurry can be formed using any known technique but preferably involves the use of water to saturate the fibres. Additives may be employed including bonding agents, such as glues and starches and/or pigments. The slurry can be relatively thick but should be flowable so that settling of fibres can occur but the fibres should be free to align under the influence of vibration, controlled agitation or flow techniques.

Preferably the fibres are aligned using a vibration or pulsation bed which causes the fibres to align with the direction of vibration. Other alignment techniques can be employed but preferably a vibrating bed is applied to the slurry in such a way that the fibres can settle and align giving densification and alignment. The bed can include a drawn off means in the form of a.conveyor mounted on a vibratory surface so that during intermittent or continuous operation of the conveyor, a layer of settled and aligned fibres can be drawn off for further processing into the fibrous mass. The layer is preferably reduced by drying or by application of reduction means in the form of heated rollers which compress the aligned fibres together and squeeze out residual liquid. The rollers preferably heat the layer to about 240 C but temperatures anywhere in the range of 160°C to 320°C are suitable. The waste liquid from the vibratory bed and from the reduction means is preferably recycled and mixed with incoming fibres. At this stage, the compressed aligned fibres are usually in the form of a flexible sheet with the sheet having a proportion of fibres aligned in one predominate direction. It is preferable to further dry the sheet prior to further processing. Any form of drying can be employed including using fans or simply laying the sheets out to dry. Prior to drying, sheets can be laid as a composite or laminate. For example, a useful product can be formed whereby sheets are laminated with the fibres running in mutually orthogonal directions either by simply rolling sheets together or by applying adhesive between the sheets with subsequent rolling. The sheets can be dried prior to lamination.

Subsequent to step (c), the fibrous mass can be broken to form a fibrous chip material.

The fibrous mass can be chipped in any fashion and in this regard, the apparatus preferably includes a chipper. It is preferable that the chipper be a cylindrical mill including randomly located projections so that the fibrous mass can be chipped fairly randomly so that the mass preferentially fractures at flaws rather than at its strongest points. Advantageously, chips are produced which are of uniform shape and size. The chip size selected preferably relates to the average fibre length and the chip dimensions can be multiples of the average fibre length in the slurry bearing in mind that the periphery of each chip should, where possible, represent a flaw or boundary between the strongest parts of the mass. The breaking up step is therefore effectively removing flaws in the connection or interweaving between the fibres that were not properly aligned during the alignment stages.

The chips can be used by softening in the presence of a bonding agent or with the addition of water. If a bonding agent was included in the slurry, then heating the chips will be sufficient to soften the bonding agent and the heated chips can be rolled to form sheets or injection moulded to form other articles.

It will be appreciated that as a result of the present invention being applied principally to used paper products, the strength and character of the fibres in the used paper has been changed by virtue of their first use. The characteristics of the fibres is fairly amorphous as some fibres will be broken resulting in a slurry which is generally inhomogenous. The result of this is that all fibres will not align according to the ideal situation and depending on the nature of the fibres, a large or only a small proportion of the fibres may, in fact, align. Nevertheless, even if the alignment of a small proportion of fibres is the result, the final product resulting from application of the present invention will be stronger than would be the case without using the teachings of the present invention.

Where the fibres are not in a free state prior to the slurry being formed as in say, newsprint, the process preferably involves disentangling the fibres using a fibre extraction technique. The fibre extraction technique can include high speed rotation of saturation paper or a slurry, drying and/or fluffing of fibres, in order to extract and free the fibres.

In order that the invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawings and examples dealing with preferred embodiments of the present invention.

Figure 1 illustrates an apparatus by which a fibrous mass according to the present invention can be made;

Figure 2 is a schematic view illustrating a chipper which can be used to chip a fibrous mass made in accordance with the apparatus of Figure 1.

Referring to the drawings and initially to Figure 1, there is illustrated an apparatus 10 for the production of a fibrous mass which in this case is in the form of a sheet 11, the apparatus comprises a slurry bed 12 for acting on a slurry 13 containing fibres to preferentially align the fibres in a common direction, the bed 12- includes a vibrating plate 14 over which an endless conveyor 15 travels as a drawing off means for removing settled and aligned fibres from the slurry 13. The fibres drawn off at 16 travel along the endless conveyor 15 to a bank of rollers 17 where they are progressively rolled and compressed to form the finished sheet 11.

It may desirable to include an adhesive such as a polyvinyl acetate in the slurry 13 so that fibres contained in the slurry are individually coated with the adhesive solution. The rollers 17 can be heated and in one preferred embodiment, the last set of rollers 18 heat the material to a temperature of around 420 C so that the resultng sheet 11 is flexible. Sumps 19 and 20 are employed to collect excess liquid removed during the processing of the fibres and the excess liquid can be returned to the slurry.

Figure 2 illustrates a further possible step in the process where the sheet 11 is transferred to a mill 21 wherein the sheet is chipped into chips of uniform size so that the sheet 11 fractures preferentially at flaws in the sheet. In use, the chips can be laid out randomly and under the action of heat and pressure, the adhesive can be softened so that the chips can be glued together to form a sheet of greater strength. Likewise, the chips can be used in an injection mould under the influence of heat and pressure to provide moulded articles of greater strength than would otherwise be the case.

In another embodiment, sheets 11 can be laid crosswise and glued together to form a laminate of improved strength. The following examples illustrate application of the process of the present invention. Example No. 1

Fibres were extracted from newsprint to form one tonne of dry fibre, 80 litres of water was added and the resulting slurry was subjected to vibration to align the fibres. For the particular newsprint employed in this example, about 25% of the fibres aligned after ten minutes vibration. The liquid was drained from the slurry and an 18mm layer was removed and rolled through staged rollers which resulted in a flexible sheet which was later dried. This sheet was then cut into lengths and adhesive was applied to the surfaces, the lengths were located with the fibres running in mutually orthogonal directions to form a laminate. The laminate could be cut and had improved strength when compared to the unlaminated sheet. Example No. 2

Fibres were extracted from newsprint to form one tonne of dry fibre having fibre lengths varying from one millimetre to five millimetres with the greater proportion of fibres being less 2mm in length. Forty litres of water was added along with forty litres of P.V.A. (polyvinyl acetate) as bonding agent. The resulting slurry was then subjected to vibration to align the fibres. For the particular newsprint employed in this example, about 50% of the fibres aligned after ten minutes vibration. The liquid was drained from the slurry and an 18mm layer was removed and rolled through staged rollers with the last stage heating the layer to 240 C resulting in a flexible sheet of 4mm thickness. The sheet was dried and a portion retaind for comparison. The remainder of the sheet was chipped to form fairly uniform chips of around 5mm in length. The chips were then heated to 140 C and laid randomly over a pulsating bed to a thickness of 25cm and compressed applying a pressure of about .25 tonne per square centimetre to form a solid sheet of board 1cm thick. A comparison was made between the post-chipping board and the pre-chipping board and it was found that the pre-chipping board was layered and included a larger proportion of flaws than the post-chipping board. The post-chipping board was drilled and sawn without fracture and the section appeared amorphous. Example No. 3

Chips were formed as in example No. 2 but the chip size was reduced to 3mm. The chips were heated to 150 C and fired into an injection mould to form a small container.

The mould was allowed to dry and the container retrieved.

The container exhibited smooth surface characteristics and on sawing, the section appeared amorphous.

Whilst the above has been given by way of illustrative example of the present invention, many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as herein set forth.

Claims

CLAIMS : -

1. A process for the treatment of fibrous materials to provide a fibrous mass suitable for making useful products, the process consisting of the following steps:- (a) forming a slurry containing the fibres;

(c) reducing the slurry to a fibrous mass whilst maintaining a proportion of the fibres in alignment.

2. A process as claimed in claim 1 wherein alignment of the fibres is effected by means of a vibration or pulsation bed acting to influence the fibres to align with the direction of vibration.

3. A process as claimed in claim 1 wherein the fibrous mass is in the form of a layer of aligned fibres, the layer being compressed to squeeze out residual liquid.

4. A process as claimed in claim 3 wherein compressed layers are formed into a composite laminate with the fibres of adjacent layers arranged in mutually orthogonal directions.

5. A process as claimed in claim 1 wherein the fibrous mass is broken to form a fibrous chip material.

6. An apparatus for the production of a fibrous mass suitable for making useful products, the apparatus comprising a slurry bed for acting on a slurry containing fibres to preferentially align the fibres in a common direction, drawing off means for removing fibres from the slurry and reduction means for reducing the removed fibres to a mass form whilst maintaining fibres in alignment.

7. An apparatus as claimed in claim 6 including a vibration or pulsation bed acting to influence the fibres to align with the direction of vibration.

8. An apparatus as claimed in claim 6 wherein the drawing off means is in the form of a conveyor mounted on a vibratory surface and includes means for drawing off a layer of settled and aligned fibres.

9. An apparatus as claimed in claim 8 including rollers arranged and constructed to receive the layers of settled and aligned fibres drawn off and to roll and compress the layer to form a finished sheet.

10. An apparatus as claimed in claim 9 including means to chip the finished sheet into chips of uniform size.