WO2005023499A1

WO2005023499A1 - Particle board

Info

Publication number: WO2005023499A1
Application number: PCT/AU2004/001225
Authority: WO
Inventors: John Gorman
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-09-09
Filing date: 2004-09-09
Publication date: 2005-03-17
Anticipated expiration: 2006-03-09

Abstract

According to one aspect of the present invention there is provided a method of manufacturing particle or fibre board, the method including the steps of: preparation of agricultural fibre into fractions of a generally selected size; blending the fractions with an adhesive having selected properties to form a mixture; the blended mixture being pressed into a part panel having selected properties. According to another aspect of the present invention there is provided a board or panel which is produced from fractionated agricultural fibre and an adhesive; the adhesive and agricultural fibre being blended and pressed to form the panel or board.

Description

PARTICLE BOARD

This invention relates generally to fibreboard and particleboard and methods of manufacture of fibreboard and particleboard.

Fibreboard and particleboard for use as panelling and other structural applications are known and generally comprise wood chips or fibres produced from trees of various types. This material is usually mixed with a binder to form the board or panel. However, the types of binders currently in use generally include adhesives such as isocyanates, urea formaldehydes and contribute to "sick building syndrome" and, even after curing and use, emit VOCs and other carcinogenic substances. This clearly presents safety hazards.

Also, many other complicated processes are generally required in order to ensure proper curing and adhesion of binder to the fibres or chips.

The present invention seeks to ameliorate one or more of the abovementioned disadvantages.

According to one aspect of the present invention there is provided a method of manufacturing particle or fibre board, the method including the steps of: preparation of agricultural fibre into fractions of a generally selected size; blending the fractions with an adhesive having selected properties to form a mixture; the blended mixture being pressed into a panel having selected properties. According to another aspect of the present invention there is provided a board or panel which is produced from fractionated agricultural fibre and an adhesive; the adhesive and agricultural fibre being blended together and pressed to form the panel or board.

Preferably the agricultural fibre is in the form of what is generally considered waste materials, which in one form is crop stubble, the stubble in one form being rice stubble.

This has the advantage of increasing product and therefore dollar yield per megalitre of water and unit area, as well as producing a new product from what is generally considered a waste product.

It is common practice to destroy the remaining crop stubble by a process such as for example burning after the seed, head, fruit or flowering portion of the crop has been harvested. It is believed that Government regulations will soon prevent the burning of crop stubble after a harvest is complete.

In one preferred form the agricultural fibre is timber, although it will be appreciated that the requirement for timber plantations and the subsequent harvesting thereof adds to the cost of production of chipboard.

Preferably the panel includes crop stubble fractions which have been filtered for weeds, and subsequently milled or chopped. Preferably the panel includes crop stubble fractions of differing sizes: a first size of crop stubble, having fibres of a size suitable for use with a core of the panel, and a second size of crop stubble having fibres of a size suitable for use with a surface of the panel. Preferably, the first crop stubble size is larger than the second size of crop stubble; the larger fibres being better suited to maintaining rigidity and structural strength, the smaller fibres providing an acceptable finish for consumers.

In a preferred embodiment both sizes of fractionated crop stubble are able to pass through screens having apertures in a range of 1 to 65mm. Preferably the first size of fractionated crop stubble pass through screens having apertures of approximately 6.35mm. The second size of stubble is sized so that it will pass through the first screen, but also a further screen having apertures as small as 3.16mm.

The proportions of fractions in the panels may vary between 10%/90% first and second sizes respectively, to 90% and 10% of the first and second sizes respectively. In one embodiment the panel includes the first and second fractions sizes in equal proportions. Preferably the sizes of fractionated stubble are utilised in laminates comprising only like sizes of fractionated stubble. Any suitable number of laminates are contemplated as required, the laminates having fractionated stubble oriented in any suitable orientation. In one preferred embodiment there are three laminates: two exterior laminates consisting of the second size of fractionated crop stubble surrounding an interior laminate consisting of the first size of crop stubble. In this manner the exterior of the board presents a superior finish to a customer's eye while the structure of the board provides superior bending strength, torsional strength and rigidity.

The preparation step of the crop stubble may further include drying to remove moisture so that the fibres' strength may be properly utilized. This drying in preferred forms is a matter of simply leaving harvested or unharvested stubble until the sun and general atmospheric conditions dry out the stubble, or it may in other preferred forms be commercial processes such as blow line drying or batch processes such as oven drying overnight. Any suitable temperature and humidity may be employed such as for example between 40 and 200 degrees Celsius, however, preferably the temperature is approximately 105°C. The dried crop stubble may be stored in sealed containers until the stubble is blended with the adhesive. Preferably the moisture content of the agricultural fibre after drying is in a range of between 0.5% and 10%. In one form contemplated by preferred embodiments of the invention, the moisture content of rice stubble is 1% - 2%.

The adhesive may take any suitable form, however it is preferred that phenol formaldehyde (PF) resins are utilised to reduce safety hazards from use of adhesives such as VOCs, isocyanates and other hazardous and carcinogenic compounds such as MDIs.

In preferred embodiments, PF resins which "wet" surfaces of fractionated crop stubble are utilised to aid the adhesive process. When crop stubble such as rice stubble is used as agricultural fibre, this type of resin is advantageous because the rice stubble has a high-gloss, waxy, silicacious surface which repels water and has a low surface energy.

Preferably, a PF resin such as that described in Australian patent 763697 is utilised. In other preferred embodiments, Commonwealth Scientific and Industrial Research Organisation (CSIRO) PF resin #779 is utilised. Advantageously, cured PF resins have substantially no free formaldehyde emissions, and MDIs are associated with carcinogenic issues when aero-soled and inhaled by workers.

Blending of adhesive and agricultural fibre may be performed by any suitable process. First and second sizes of fractionated agricultural fibres are preferably blended with adhesive separately. Blending is preferably performed in a paddle style blender or high velocity blow line blender, or a tumbling drum, or dry air mix in an airless spray blender, so that each fibre is substantially coated with resin about its outside surface. The adhesive is generally applied in a much drier state than typically is performed with other resins or processes, and appears as a powdery coating on the surface of each fractionated agricultural fibre. The adhesive and agricultural fibre may be blended in any suitable proportions, such as for example within a range of between approximately 8% and 15%. In a preferred embodiment the mixture has an approximately 10% adhesive loading, meaning the adhesive is applied at a rate of 10% solids on oven dry straw (weight of water on total weight).

The mixture is laid down into a mat. Subsequent to that laying down, pressing takes place. The pressing of the mixture may include heating, and in a preferred form, simultaneous heating and pressing by utilising heated rollers or platens. In preferred embodiments, hot pressing is carried in multiple daylight presses out using platen temperatures in a range of approximately 150 - 250°C, for a time period of between approximately 3 and 10 minutes. One preferred embodiment utilises a temperature of 200°C for 7.5 minutes using position control. Further processing may be performed, after pressing, in the form of cooling. The cooling may, in a preferred form occur slowly by placing the panel between insulated surfaces in a process called "hot stacking". Industrially, several panels may be laid on one another to form a hot stack, so as to provide this slow cooling under flat surfaces. The heating and pressure activates the PF resin and the resin seeks out any available moisture. The resin diffuses throughout the panel, then sets. No added steam is required to activate the resin.

The panel may be any suitable size or density, however in preferred embodiments the thickness of the panels lie in the range of approximately 3 - 50mm. In one preferred form the panel thickness is approximately 15mm and the density is within a range of approximately 500 - 900kg/m³.

Vibration of the mat may take place to enhance compaction of the mixture before pressing. The mixture is preferably relatively dry, therefore vibrating or patting the mat allows the mixture to settle, reducing the thickness of the mat, increasing its density. In this manner, it is believed that the fractionated fibres are moved into a position normal to the plane of the panel and improve its density.

Advantageously, as each fibre is coated with adhesive, and the mat is pressed into a high-density but light panel structure, the panel is provided with an ability to tolerate aggressive environments such as elevated temperatures and high humidity and wet environments. The panel emits substantially no VOCs once pressed, and is lighter than chipboard, even though fractions may be packed more tightly than in other boards. It is believed that preferred embodiments of the panel will not allow oxygen to enter the laminate, and the panel will smolder only when placed under fire tests, because the fibre of preferred embodiments comprises starch and cellulose, rather than sugars.

In order to enable a clearer understanding of the invention, a drawing illustrating an example embodiment is attached, and in that drawing:

Figure 1 is a section view of a panel in accordance with the present invention.

Descriptions of other variations and examples also follow. Referring to the drawing there is shown a section view of a panel 10 which includes agricultural fibre 11 in the form of fractionated rice stubble 12. The fibre 11 has been blended with binder in the form of phenol formaldehyde (PF) resin (not shown) and pressed utilising a heated mandrel (not shown). The rice stubble 12 has been fractionated into two sizes, a first size 14 suitable to fit through a screen of 6.35mm (not shown). The first size of fractionated rice stubble 14 is disposed in the core 16 of the panel 10, so that increased strength may be obtained. The second size 18 of the fractionated rice stubble 12 in the panel 10 is smaller than the first size 14, being suitable to fit through a screen of 3.16mm (not shown). The second size 18 of rice stubble 12 is smaller and is grouped and utilized on the outside 20 of the panel 10, so as to present an aesthetically pleasing finish to users.

Timber is contemplated for use as the agricultural fibre instead of the rice stubble.

EXAMPLE

The example panel described herein was produced under laboratory conditions and as such, some equipment used was laboratory-scale. Clearly, similar panels would easily be produced using commercial-scale equipment.

A particle board panel 10 was manufactured from agricultural fibre in the form of milled rice stubble 12 and binder in the form of phenol formaldehyde (PF) resin. Desired panel density was 675 kg/m³. Mean panel density was lower than the desired density, being approximately 630 kg/m . This was likely to have been caused by thickness spring-back on exiting the hot press.

The stubble was reduced in size to smaller fractions using a chopping action (without creating a hollow drinking-straw effect), in the form of being passed through a

Wiley mill (a hammer mill) fitted with screen having apertures of 6.35 mm (1/4 inch). During subsequent milling, the straw was screened through a 3.16 mm (1/8 inch) sieve. This produced two fractions: firstly, a coarse fraction for 'core' material which provides strength and secondly a fine fraction for use in panel faces to provide an acceptable finish to a consumer. The proportion of core material to face material was 1:1.

The separated straw fractions were oven dried overnight at 105°C and sealed in plastic bags until used for panel fabrication.

A binder was used, which has the ability to "wet" the surface of the stubble to improve the binding process. The binder was in the form of a phenol formaldehyde resin, in the form described by AU patent 763697 and /or CSIRO phenol formaldehyde (PF) resin #779. This was applied to rice straw fractions, each size being mixed with the binder in separate operations using an airless spray in a tumbling drum. The fine fraction was set aside to be used in a lamina at the panel surface layers and the coarse fraction set aside for use in a lamina disposed at the panel core. The blended rice straw furnish was hand-laid into mattresses in a 55x55 cm forming box and transferred to the heated platen press, sandwiched between non-stick mylar sheets (0.1 mm thick) and aluminium caul plates (2.5 mm thick). Hot pressing was carried out using platen temperatures of 200°C for 7.5 minutes using position control. Target panel thickness was 15 mm, with a target density of approximately 675 kg/m³. On exiting the press, panels were placed between plywood sheets to facilitate controlled slow cooling. After trimming, the surfaces of panels were lightly sanded with 180 grit paper.

The panel is neither standard particle board nor MDF but a highly moisture resistant particle board with fine particle structure and hence suitable for wet area construction and for those items of furniture manufacture normally the domain of MDF.

It is to be understood that the example above is merely one example of a process and panel which produced a panel of the group of superior qualities which until now have been elusive. Many panels were produced utilising varying amounts of each variable in the process, which produced good results for varying applications. For example: 1. Panels were created using a range of thicknesses and varying proportions of lamina thickness. That is, panels were created where the internal lamina was between approximately 20 and 60mm thick before pressing and the external laminae were between approximately 5 and 25 mm thick before pressing. Other proportions and thicknesses are clearly useful and provide good properties depending on the application.

2. Panels were created using differing amounts of water. It was found that sufficient water is required to be present in the agricultural fibre to initiate a chemical curing reaction, but not so much as to create unstable bonds. Thus, a range of 5% to 15% of residual water in the agricultural fibre was utilised in other examples.

3. The size of the fractions depends on the rate of feed through the mill. Average thicknesses of the first size of fractions were approximately 6.35mm, however, they varied between 4 and 30 mm in other panels which were made. The second size of fractions varied in size between 1 and 7 mm in length, in panels which were made.

4. In preferred embodiments, the mandrels were heated up to temperature so that full curing was initiated, and then pressure was applied. The load required was approximately 200 tonnes. Heating up the mandrels to temperature before pressing ameliorated the problem of hot patches and cold patches within the panel, and provided a more even heating.

5. Other densities of panel were obtained depending on the load applied by the press and the time spent in the press. The range of densities produced which provided good results was within a range of approximately 500 - 900 kg/m³. The panel can be produced to tolerate aggressive environments. The panel, in preferred embodiments is made from a renewable source and is environmentally beneficial. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or

"comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. Finally, it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.

Claims

CLAflvIS:

1. A method of manufacturing particle or fibre board, the method including the steps of: preparation of agricultural fibre into fractions of a generally selected size; blending the fractions with an adhesive having selected properties to form a mixture; the blended mixture being pressed into a part panel having selected properties.

2. A method of manufacturing particle or fibre board in accordance with claim 1 wherein the agricultural fibre is in the form of what is generally considered waste materials.

3. A method of manufacturing particle or fibre board in accordance with claim 1 or 2 wherein the agricultural fibre is crop stubble.

4. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the agricultural fibre is rice stubble or timber.

5. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the agricultural fibre is filtered for weeds before being fractionated by a chopping process.

6. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the board includes fibre fractions of differing sizes: a first size of fibre having fibres of a size suitable for use with a core of the board, and a second size of fibre having fibres of a size suitable for use with a surface of the board.

7. A method of manufacturing particle or fibre board in accordance with claim 6 wherein the first fibre size is larger than the second size of fibre.

8. A method of manufacturing particle or fibre board in accordance with any previous claim wherein both sizes of fractionated fibre are able to pass through screens having apertures in a range of 1 to 65mm.

9. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the first size of fractionated fibre pass through screens having apertures of approximately 6.35mm and the second size of fibre is sized so that it will pass through a further screen having apertures as small as 3.16mm.

10. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the proportions of fractions in the panels varies between 10% / 90% first and second sizes respectively, to 90% and 10% of the first and second sizes respectively.

11. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the board includes the first and second fractions sizes in equal proportions.

12. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the sizes of fractionated fibre are utilised in laminates comprising only like sizes of fractionated stubble.

13. A method of manufacturing particle or fibre board in accordance with any previous claim wherein three laminates are provided: two exterior laminates consisting of the second size of fractionated crop stubble surrounding an interior laminate consisting of the first size of crop stubble.

14. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the preparation step of the fractionated fibre includes drying to remove moisture, by either leaving harvested or unharvested stubble until the sun and general atmospheric conditions dry out the stubble, or a cornmercial processes such as blow line drying or batch processes such as oven drying overnight.

15. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the temperature of drying is between 40 and 200 degrees Celsius.

16. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the dried agricultural fibre is stored in sealed containers until the stubble is blended with the adhesive.

17. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the moisture content of the agricultural fibre after drying is in a range of between 0.5% and 10%.

18. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the moisture content of rice stubble is 1% - 2%.

19. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the adhesive is phenol formaldehyde (PF) resins.

20. A method of manufacturing particle or fibre board in accordance with any previous claim wherein PF resins which "wet" surfaces of fractionated rice stubble are utilised to aid the adhesive process.

21. A method of manufacturing particle or fibre board in accordance with any previous claim wherein a PF resin such as that described in Australian patent 763697 is utilised.

22. A method of manufacturing particle or fibre board in accordance with any previous claim wherein Commonwealth Scientific and Industrial Research Organisation (CSIRO) PF resin #779 is utilised.

23. A method of manufacturing particle or fibre board in accordance with any previous claim wherein first and second sizes of fractionated agricultural fibres are blended with adhesive separately.

24. A method of manufacturing particle or fibre board in accordance with any previous claim wherein blending is performed in a paddle style blender or high velocity blow line blender, or a tumbling drum, or dry air mix in an airless spray blender, so that each fibre is substantially coated with resin about its outside surface.

25. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the adhesive and agricultural fibre are blended together in a range of between approximately 8% and 15%.

26. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the blend has an approximately 10% adhesive loading, meaning the adhesive is applied at a rate of 10% solids on oven dry straw (weight of water on total weight).

27. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the mixture is laid down into a mat and pressing of the mixture includes heating, by heated platens or mandrels in multiple daylight presses using a temperature range of approximately 150 - 250°C, for a time period of between approximately 3 and 10 minutes.

28. A method of manufacturing particle or fibre board in accordance with any previous claim wherein a temperature of 200°C for 7.5 minutes using position control is utilised.

29. A method of manufacturing particle or fibre board in accordance with any previous claim wherein a slow cooling step is provided by placing the panel or panels between insulated surfaces or several panels may be laid on one another to form a hot stack, so as to provide this slow cooling under flat surfaces.

30. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the panel has a thickness of between 3 and 50mm.

31. A method of manufacturing particle or fibre board in accordance with any previous claim wherein the panel thickness is approximately 15mm and the density is within a range of approximately 500 - 900kg/m³.

32. A method of manufacturing particle or fibre board in accordance with any previous claim wherein vibration of the mat takes place to enhance compaction of the mixture before pressing.

33. A board or panel which is produced from fractionated agricultural fibre and an adhesive; the adhesive and agricultural fibre being blended and pressed to form the panel or board.

34. A board or panel produced in accordance with any one of the previous claims.

35. A method of manufacturing particle or fibre board substantially as hereinbefore described with reference to the attached drawing.

36. A board or panel substantially as hereinbefore described with reference to the attached drawing.