WO2009053720A2

WO2009053720A2 - Method of manufacturing an article

Info

Publication number: WO2009053720A2
Application number: PCT/GB2008/003630
Authority: WO
Inventors: Alistair Banks; Thomas Anthony Mcnulty; John Evans
Original assignee: Ecobond (Rugeley) Limited
Priority date: 2007-10-25
Filing date: 2008-10-24
Publication date: 2009-04-30
Also published as: EP2225053A2; WO2009053720A3; GB0720958D0; GB2454169A

Abstract

A method of producing a composite article comprising the steps of obtaining material in fibre or particulate form, coating fibres or particles of the material with a binder, and pressing at least a portion of the material in a mould to form an article.

Description

METHOD OF MANUFACTURING AN ARTICLE

The present invention relates to methods of manufacturing articles.

Increasing demand on natural resources and a growing desire to make the best use of all available materials contribute to a need to devise methods of forming durable, useful and aesthetically attractive products from recycled materials.

The construction industry has come under pressure to play a significant part in the recycling of building materials, the reduction in waste, conservation of natural resources and the overall conservation of energy. There is a clear need for construction products that are produced in an energy efficient manner and have a minimal or even negative impact on natural resources and/or the environment.

Current methods of producing building materials, such as roof and flooring tiles, require energy intensive activities such as quarrying and firing at temperatures of up to HOO⁰C. Moreover, it is common that these methods create waste disposal problems, thus leaving legacies of land spoil tips.

Meanwhile, current methods of producing materials from recycled aggregates require the use of substances such as phenolics, isocyanates and urea formaldehyde. Use of such substances is clearly undesirable from both public health and environmental perspective, particularly as these substances are understood to produce leachate. Furthermore, recycled materials are typically used as fillers, so the methods still use significant quantities of natural resources.

The present invention seeks to address these problems by providing an energy efficient method for manufacturing building materials from reclaimed aggregates and waste products.

In a first aspect, the invention relates to a method of producing a composite article comprising the steps of obtaining material in fibre or particulate form, coating fibres or particles of the material with a binder, and pressing at least a portion of the material in a mould to form an article.

Preferably, the material comprises waste product such as any material selected from organic or inorganic wastes or by-products of other processes. Indeed, the material may comprise any material that is generally considered to be waste.

Preferably, the material comprises material selected from the group comprising : mineral, cement block, bagasse, paper, sterilised municipal waste, glass. More preferably, the waste product comprises a mineral material such as slate, mica, granite, sands, marble, dolomite, flint, basalt, slag, bauxite, calcite or andulucite.

Advantageously, the method may produce, for example, a tile or brick which is tough and strong and takes on the aesthetic characteristics of the waste material from which it is made. Alternatively, if waste material which would not be considered to be aesthetically pleasing were used to manufacture a brick or tile, a dye might be used to provide a tough and strong article having a substantially uniform colour.

Preferably the particles of material have a size distribution between 20μm and 2000μm. More preferably, the material has a size distribution of between 520 μm and 2000 μm. Of course, should the material be obtained having a materially different size distribution, it may be milled and/or sized to control the size distribution accordingly. In certain embodiments, it is desirable to separate the material into a number of size ranges which may then be homogeneously mixed together.

In some embodiments, the material comprises, at least in part, material reclaimed from the waste product of the method of the present invention. In other embodiments, the material comprises, at least in part, material milled from articles formed according to the method of the present invention.

Preferably, the material has a moisture content of 2% or lower. If the material has a moisture content of above 2%, it may be subjected to an auxiliary drying step, therein reducing the moisture content to 2% or lower.

Preferably, the binder comprises a water based polymer. More preferably, the binder comprises an acrylic polymer. Most preferably, the binder comprises a blend of acrylic polymers in aqueous solution or held in a water suspension.

Preferably the coating step comprises mixing the material with the binder in a mixer. The mixer may comprise a continuous mixer or a batch mixer. The material and binder are preferably mixed for less than 20 minutes. More preferably, the material and binder are mixed for less than 10 minutes. If the material and binder are mixed continuously, they are mixed so as to have a Froude number less than 1.

Preferably the coating step comprises mixing the waste material and the binder in a material : binder ratio of 65-95:35-5. More preferably, the coating step comprises mixing the material and the binder in a material: binder ratio of 90: 10.

Preferably the method comprises a drying step following the coating step to dry coated material before pressing. Advantageously, the drying of the coated particles or fibres allows them to be stored in a condition ready for moulding. Moreover, when dry, the coated particles have improved fluidic properties over wet particles or fibres. This quality provides far easier and more efficient processing.

The drying step preferably comprises drying the coated material in a continuous dryer to produce dried coated material. Alternatively, the drying step comprises drying the coated material in a batch dryer.

Preferably, the drying step comprises exposing the coated material to a current of air at elevated temperature. In some embodiments the current of air is at a temperature of between about 100⁰C and about 200⁰C.

Preferably the drying step has a duration of less than 20 minutes. More preferably, the drying step has a duration of less than 10 minutes. Preferably an aliquot of dried coated material is introduced to the coated material prior to the drying step.

Preferably, the drying step reduces the moisture content of the coated materialto 5% or lower. More preferably, the drying step reduces the moisture content of the coated material to 3% or lower. Most preferably, the drying step reduces the moisture content of the coated material to 2% or lower.

Preferably, the step of pressing the material comprises introducing a first aliquot of the coated material to a mould. Preferably, the first aliquot of coated material is smoothed within the mould to create a first layer of coated material.

The mould may be of plain or textured pattern. A textured pattern mould may be used when it is desirable to provide an article with a patterned surface, such as for decorative or non-slip applications.

Preferably, reinforcing agents are introduced to the mould. Preferably, the reinforcing agents comprise materials selected from the group: metal, plastic, glass, natural or synthetic materials in the form of rods, fibres, meshes and/or lattices. Preferably, the reinforcing agents are introduced to the mould atop the first layer of coated waste material.

Preferably, a second aliquot of the coated material is introduced to the mould. Preferably, the second aliquot is introduced to the mould atop the first layer of coated material or atop the reinforcing agents. The second aliquot of coated material is preferably smoothed within the mould to create a second layer of coated material.

Preferably the step of pressing the material comprises applying a pressure of between lOOkgcm^"2 and 200kgcm^"2 to the material. It is desirable for the pressing to be performed by a pressing machine. In preferred embodiments, the pressing machine is arranged to lock the mould shut at elevated pressure, such that pressing may continue after the mould is removed from the pressing machine.

Preferably the step of pressing the material is performed at elevated temperature. More preferably the pressing step is performed at between 90⁰C and 250⁰C. Most preferably, the pressing step is performed at between 180⁰C and 220⁰C. This may be achieved by, for example, providing internal heaters in the mould.

Preferably, the material is at elevated temperature during the pressing step. More preferably, the material is at between 9O⁰C and 250⁰C during the pressing step. Most preferably, the material is at between 180⁰C and 22O⁰C during the pressing step.

Preferably the material is pressed for less than 10 minutes. More preferably the material is pressed for between 30 seconds and 5 minutes.

Preferably, the article so-formed has a density between 200 kg/m³ and 4000 kg/m³. In a second aspect of the invention, there is provided a method of producing a composite article comprising obtaining first and second materials in fibre or particulate form, separately coating fibres or particles of the first material and the second material, layering particles of the first material and the second material within a mould, and pressing the layered first and second materials to form an article.

In a further aspect, the invention relates to a composite article manufactured according to a method as described above.

In order that the invention may be more fully understood, reference is made to the accompanying drawings, in which :

Figure 1 displays a schematic process diagram of a process including the method of the invention.

Figure 2 displays a first aliquot of waste material in a mould.

Figure 3 displays a first layer of waste material in a mould.

Figure 4 displays a reinforcing agent resting atop a first layer of waste material in a mould.

Figure 5 displays a second aliquot of waste material in a mould.

Figure 6 displays a second layer of waste material in a mould ready for pressing.

Figure 7 displays waste material being pressed within a mould.

Figure 8 displays a bi-layered article made according a process including a method of the invention. In a preferred embodiment, the invention relates to a method of making tiles, in particular roof tiles, from waste materials. It is envisaged, for example that the method be used to manufacture high quality tiles from waste aggregate materials such as dust, slag or granules of such materials as slate, mica, granite, marble, andulucite, sands, cement block waste, sterilised municipal waste, bagasse, waste paper and sludge.

In a first step, waste material is provided and transferred via a material transfer unit 14 to a pre-sieve hopper 16. From the pre-sieve hopper 16, the waste material is introduced to sieve 18 to be sized, such that a particle size distribution of between 20μm and 2000μm is collected in a collection hopper 20. Particles of waste material found to be too large for the preferred particle size distribution may be transferred to a mill (not shown) to be milled and reintroduced to pre-sieve hopper 16, thereby maximising the use of available material.

It is preferred that the particles of waste material do not comprise more than about 2% moisture at this stage of the process. If the moisture content is found to be too high, then the waste material is dried by an auxiliary belt drier 21.

The sized waste material is transferred from the collection hopper 20 to a storage hopper 22, which gravimetrically feeds the sized waste material into a continuous mixer 24. An accurate pumping system 26 provides a water based, acrylic polymer binder to the mixer 24, such that the ratio of waste material to binder is 90: 10 by weight. The mixer 24 is operated to effect a thorough coating of the waste product particles. This is achieved by ensuring that the mixing has a Froude number less than 1. The mixer 24 effects mixing for a period of between 4 minutes and 10 minutes, during which time the particles of waste material are evenly coated with the binder.

Once coated, the particles of waste material are introduced to a belt dryer 28, where they are exposed to a current of air, preferably at a temperature between 150⁰C and 200⁰C for between 1 and 10 minutes. The drying step may be optimised by the introduction of a quantity of fully dried coated waste material to the wet coated waste material before the step commences. After the drying step, the coated waste material is has a moisture content of around 2% to 3%.

Once dry, the dryer transfers the dried coated waste product to a mould filling hopper 30, from where aliquots of the product are introduced to moulds 32 by a mould filling device 34. This is preferably achieved by adding a first aliquot 38 of dried coated waste material to a mould 32, as shown in Figure 2, then smoothing the first aliquot 38 of waste material to create a first layer 40, as shown in Figure

3. Optional reinforcing materials 42, such as metal or plastic rods, or glass, natural or synthetic fibres, or meshes or lattices, may be introduced to the mould

32 atop the first layer, as is shown in Figure 4. Such reinforcing materials significantly increase the strength of the finished article. A second aliquot 44 of the dried coated waste product is then introduced to the mould 32, as shown in

Figure 5 and smoothed over the first layer 40 to create a second layer 46, as is shown in Figure 6. Press 36 is then actuated to exert a pressure of around lOOkgcm^"2 to 200kgcm^'2 onto the waste product within the moulds 32, as shown in Figure 7, for around 2 minutes at a temperature of around 200⁰C. The pressing step effects a sintering of the coated waste product particles, such that a solid article is formed.

The finished tile is removed from the mould and allowed to cool.

Those skilled in the art will recognise that some of the steps and apparatus described above may be changed without departing from the scope of the invention. For example, the dryer is preferably a belt dryer, or some other such dryer that allows for continuous drying, but in other embodiments the dryer may be a drum dryer, or some other dryer suitable for batch drying. In some preferred embodiments, the mixing step and drying step are performed within the same apparatus, in a substantially simultaneous manner. Furthermore, in some alternative embodiments, the quantity of sized waste material and binder introduced to the mixer is measured volumetrically.

In some embodiments, a bi-layered composite article 48, as shown in Figure 8, is formed. A second waste product is coated and dried in a separate process line, by a method substantially as described above, eventually being collected in a second mould filling hopper 30.

Once the first layer of dried coated waste product and the optional reinforcing agents have been introduced to the mould 32, as described above, an aliquot of the second dried coated waste product is introduced atop the first layer and smoothed to make a second layer. The first ,and second waste products are then pressed together, as described above, to make a bi-layered article.

The bi-layered article created has two major surfaces, each having a characteristic appearance, dependent largely on the visual and textural qualities of the two waste materials used. Such a bi-layered article affords an additional level of choice to the end-user. For example, if the product is a tile, then the user may lay an array of tiles in a chequered pattern, without exhausting his or her supply of tiles of one of the colours.

A bi-layered article, as described above, could also be manufactured by using two aliquots of a single waste product, coated and dried substantially as described above, with one or both of the two layers having a pigment or dye introduced in the coating or drying step. Additionally, or alternatively, each of the major surfaces of the bi-layered product may have a different finish applied to it in a final step of manufacture.

In further embodiments, certain inclusions may be made in the mixture such that the finished article exhibits secondary functionality. For example, metallic elements may be included to enable a tile to discharge static electricity, so enabling it to be used in electrically sensitive locations. Such metallic elements could also be heated to provide a source of heating for the area of use.

The composite material made by the method described above exhibits exceptional qualities of, for example, dimensional stability throughout exposure to the water and extremes of temperature. The composite material is thus suitable for many applications beyond tiles, including bricks, lintels and decorative or bespoke construction mouldings. Furthermore, the composite material exhibits excellent wear characteristics when tested for deep abrasion properties.

Example 1

A tile was manufactured according to the method described above. The tile was then tested according to the appropriate ISO standards, unexpectedly yielding excellent results. The results of these tests are shown below.

Water absorption % by mass: 0.1% to 0.6% ISO 10545-3

Dimensional stability: Length & Width +/- 1% ISO 10545-2 Thickness +/- 2% ISO 10545-2

Straightness of sides +/- 0.1% ISO 10545-2 Recta ngularity +/- 0.1% ISO 10545-2) Surface Flatness +/- 1% (ISO 10545-2)

Frost resistance: Minimum of 100 cycles (ISO 10545-12) Water impregnation by full immersion method.

Strength Modulus of rupture: lON/mm² - 70 N/mm² ISO (10545 - 4)

Breaking strength : Not less than 750N (ISO 10545 - 4) Deep abrasion resistance: Not more than 124mm³ (ISO 10545-6)

Example 2

End of life tiles made according to the present invention were milled to a suitable particle size and used as at least part of a starting material for use in the method. No deleterious properties of the so-formed article were identified.

Tiles at the end of their useful life can also be used as a filler for other uses.

Claims

1. A method of producing a composite article, comprising obtaining material in fibre or particulate form, coating particles or fibres with a binder, drying the coated material and pressing at least a portion of the dried coated material in a mould to form an article.

2. A method according to Claim 1, wherein the material comprises a material selected from organic or inorganic wastes or by-products of other processes.

3. A method according to Claim 1 or 2, wherein the material comprises material selected from the group comprising: mineral, cement block, paper, sterilised municipal waste, glass.

4. A method according to Claim 3, wherein the material comprises a mineral material selected from the group slate, mica, granite, sands, marble, dolomite, flint, basalt, copper slag, bauxite, calcite or andulucite.

5. A method according to any preceding Claim comprising the step of milling and/or sizing the product before coating, to provide a controlled size distribution.

6. A method according to any preceding Claim, wherein the particles of material have a size distribution between 20μm and 2000μm, preferably between 520 μm and 2000 μm.

7. A method according to any preceding Claim, wherein the material comprises, at least in part, material reclaimed from the waste material of the method according to any preceding Claim.

8. A method according to any preceding Claim, wherein the material has a moisture content of 2% or lower.

9. A method according to any preceding Claim, wherein the binder comprises a water based polymer, such as an acrylic polymer.

10. A method according to Claim 9, wherein the binder comprises a blend of acrylic polymers held in a water suspension or in aqueous solution.

11. A method according to any preceding Claim, wherein the coating step comprises mixing the material with the binder in a mixer.

12. A method according to Claim 11, wherein the mixer comprises a batch mixer.

13. A method according to Claim 11 or 12, wherein the material and binder are mixed for less than 20 minutes.

14. A method according to Claim 13, wherein the material and binder are mixed for less than 10 minutes.

15. A method according to Claim 11, wherein the mixer comprises a continuous mixer.

16. A method according to Claim 15, wherein, the material and binder are mixed so as to have a Froude number less than 1.

17. A method according to any of Claims 11 to 16, wherein the coating step comprises mixing the material and the binder in a material: binder ratio of 65-95:35-5.

18. A method according to Claim 17, wherein the coating step comprises mixing the material and the binder in a materiakbinder ratio of 90: 10.

19. A method according to Claim 18, wherein the drying step comprises drying the coated material in a continuous or batch, dryer to produce dried coated material.

20. A method according to Claim 18 or 19, wherein the drying step comprises exposing the coated material to a current of air at elevated temperature.

21. A method according to Claim 20, wherein the current of air is at a temperature of between about 100⁰C and about 200⁰C.

22.A method according to any of Claims 18 to 21, wherein the drying step has a duration of less than 20 minutes.

23.A method according to Claim 22, wherein the drying step has a duration of less than 10 minutes.

24.A method according to any of Claims 18 to 23, wherein an aliquot of dried coated material is introduced to the coated material prior to the drying step.

25.A method according to any of Claims 18 to 24, wherein the drying step reduces the moisture content of the coated material to 5% or lower.

26.A method according to any preceding Claim, wherein the step of pressing the material comprises introducing a first aliquot of the coated material to a mould.

27.A method according to Claim 26, further comprising the step of smoothing the first aliquot of coated material within the mould to create a first layer of coated material.

28.A method according to Claim 26 or 27, further comprising the step of introducing reinforcing agents to the mould.

29.A method according to Claim 28, wherein the reinforcing agents comprise materials selected from the group: metal, plastic, glass, natural or synthetic materials in the form of rods, fibres, meshes and/or lattices.

30. A method according to Claim 28 or 29, wherein the reinforcing agents are introduced to the mould atop the first layer of coated material.

31. A method according to any of Claims 26 to 30, wherein a second aliquot of the coated material is introduced to the mould.

32.A method according to Claim 31, wherein the second aliquot is introduced to the mould atop the first layer of coated material

33. A method according to Claim 31, wherein the second aliquot is introduced to the mould atop the reinforcing agents.

34.A method according to any of Claims 31 to 33, further comprising the step of smoothing the second aliquot of coated material within the mould to create a second layer of coated material.

35.A method according to any preceding Claim, wherein the step of pressing the material comprises applying a pressure of between lOOkgcm^"2 and 200kgcm^~2 to the dried coated material.

36.A method according to any preceding Claim, wherein the step of pressing the dried coated material is performed at elevated temperature.

37.A method according to Claim 36, wherein the step of pressing the dried coated material is performed at between 90⁰C and 250⁰C, say, between

180⁰C and 220⁰C.

38.A method according to any preceding Claim, wherein the dried coated material is at elevated temperature during the pressing step.

39.A method according to Claim 38, wherein the dried coated material is at between 90⁰C and 250⁰C during the pressing step, say, between 18O⁰C and 22O⁰C.

40. A method according to any preceding Claim, wherein the dried coated material is pressed for less than 10 minutes, say, between 30 seconds and

5 minutes.

41. A method according to any preceding Claim, wherein the article so-formed has a density between 200 kg/m³ and 4000 kg/m³.

42.A method of producing a composite article comprising obtaining first and second materials in fibre or particulate form, separately coating particles or fibres of the first material and the second material, separately drying the coated particles or fibres of first and second materials, layering particles of the first material and the second material within a mould, and pressing the layered first and second materials to form an article.

43.A method according to any preceding Claim, wherein the material comprises, at least in part, material milled from articles formed according to a method according to any preceding Claim.

44.A composite article formed by a method according to any preceding Claim.