Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N1/00—Pretreatment of moulding material
  • B27N1/02—Mixing the material with binding agent
  • B27N1/0209—Methods, e.g. characterised by the composition of the agent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N1/00—Pretreatment of moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
  • B27K9/00—Chemical or physical treatment of reed, straw, or similar material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/007—Manufacture of substantially flat articles, e.g. boards, from particles or fibres and at least partly composed of recycled material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
  • B27K2240/00—Purpose of the treatment
  • B27K2240/10—Extraction of components naturally occurring in wood, cork, straw, cane or reed

Definitions

• the present invention relates to a method of manufacturing composite boards including improving the bondability of annual plant fibrous material such as straw.
• Defibration means disruption of the morphological structure of annual plant fibres, straw leading to the creation of individual fibres.
• the waxy and the silica layer encircling the straw inhibit sufficient direct contact between the binder and the straw fibres.
• thermal treatment combined with high shear forces disrupts the original morphological structure of straw leading to higher accessibility of individual fibres to the binder and consequently, an increase in the affinity of straw towards bonding.
• the process of opening up the morphological structure of straw is similar to that of pulping wood for paper making.
• the properties of the boards made from straw could be further improved if the straw was treated or pre-treated with a dilute solution of sodium hydroxide containing 0.01 - 2% NaOH based on the straw material.
• alkaline materials other than sodium hydroxide could be also used to achieve the same effect. It was disclosed that such chemicals could be formaldehyde catchers such as urea and other catchers well known in the art.
• the present invention provides a process for the manufacture of composite boards in which annual plant and/or agri-waste material is treated to improve bondability to synthetic or natural binders by subjecting the material to treatment with an aqueous medium containing an agent capable of removing waxy or silica layers from the material, which agent is a strong acid, a strong alkali or a surfactant or a combination of acid or alkali and surfactant and the treatment is continued until the waxy or silica layers are sufficiently removed so as not to interfere with the bond to the binder.
• the preferred agent is a combination of strong acid or alkali and surfactant.
• the process of the invention can be applied either to undefibrated plant material that is plant material in which the stalks are merely chopped or to defibrated plant material in which the original material has been broken down to individual fibres .
• Modification of the process of the present invention is the addition of such an agent to a material while it is being subjected to high shear treatment providing such agent is a combination of a surfactant with an acid or alkali to reduce the energy consumption or improve properties of the boards.
• a process for the treatment of annual plant material to improve bondability to synthetic or natural binders comprising subjecting the material to treatment with a surfactant in a liquid acidic or alkaline dispersion or solution before or during at least part of an attrition treatment of the material to reduce the energy consumption or improve properties of the boards.
• a process in which the plant material is treated with an aqueous system containing acid or non-alkaline surfactant is treated with an aqueous system containing acid or non-alkaline surfactant.
• the treatment can precede or be simultaneous with a high shear treatment of the material to effect defibration to reduce the energy consumption or improve properties of the boards.
• a combination of strong alkali e.g. NaOH
• a surfactant to treat the plant material.
• a strong acid in high strength for example 36% by weight solution in water of hydrochloric acid
• high strength is meant a solution in water of the highest strength possible with risk of damage to the straw (for example at too great a concentration sulphuric and nitric acids for example could damage the basic straw structure) .
• a surfactant which is sufficiently strong to remove waxy layers in straw material.
• the effectiveness of the de-waxing or de- silification agent can be verified by achieving a water absorption (% weight gain on soaking in water) of at least 200% or by forming a board and verifying that the board has a certain IB (Internal Bond) strength.
• the IB strength is the tensile strength perpendicular to the plane of the board, e.g. according to EN312-2 for 19mm- thick particleboard at least an IB strength of 0.24N/mm 2 is considered to be necessary.
• Acids which can be employed include strong inorganic acids such as sulphuric acid or hydrochloric acid and strong organic acids such as formic, acetic or sulfonic acid.
• Surfactants which can be employed in the invention are those surface active agents which are sufficiently powerful to effect the removal of wax or silica layers from the surface of straw. In particular some surfactants are not easily dispersible or soluble in water or other solvents and should be added to water or solvent along with an alkaline or acidic agent to enable adequate dispersion or solution.
• a typical surfactant is o,p-dodecyl sulfonic acid but this is only exemplary of the well known agents. This surfactant when used with sodium hydroxide, as alkali was very effective.
• surfactants are alkyl benzene sulphonic acid for example with sodium hydroxide; cetyl trimethyl ammonium chloride for example with hydrochloric acid.
• This surfactant can be employed by itself for example a fatty alcohol surfactant can be selected from cationic, anionic or neutral surfactants which one skilled in the art would appreciate, given the teaching of the invention would be likely to affect the waxy/silicious agents.
• Alkalis which can be employed include sodium hydroxide or other strong inorganic alkalis, ammonia or organic strongly alkaline materials.
• the active agents can be contacted with the straw in either a pre-treatment step or as a part of a defibration treatment step. If the fibrous material is to be brought into contact with active agent as a pre-treatment step then it is convenient to use a tank.
• a tank can be filled with the appropriate chemical and then the residence time of the fibrous material in the tank can be adjusted accordingly depending on the actual chemical used, the concentration of the chemical and the temperature of the acidic or alkaline solution or the temperature of the aqueous wetting agent solution. It will be recalled that the purpose of the treatment is to dissolve or otherwise remove the waxy layer and/or the silica layer from the surface of the plant fibres.
• An important aspect of the invention is that in case of acid curing binders the plant material after treatment is adjusted (if necessary) to a pH of 3-8. This can be achieved by addition of either alkali or acid as appropriate or by extensive washing.
• the plant material particularly straw is chopped or cut to a length of less than 10cm preferably between 0.5cm and 5cm. It is also possible to split the straw stalks in the middle (lengthwise) to make the interior of the fibre accessible to subsequent treatment.
• Material that is used in the process of the invention is annual plant material and/or agri-waste such as rice, straw, rice husks, wheat straw, rice straw, barley straw, corn residues, miscanthus, sorghum, sunflower etc. However, most preferably, straws are utilized in the processes of the invention.
• High shear devices which can be used when required include high shear attrition systems discussed in the earlier application UK 9607566.8. However, it is also possible to use attrition mills which employ less energy than high shear systems. Such attrition mills are well known in the art.
• the fibres pre-treated by acid or alkali and/or wetting agent can be subjected to processing through the attrition mill or alternatively the acid/alkali/wetting agent treatment chemicals can be contacted with the fibres as they enter the attrition mill .
• the fibres can be dried using conventional dryers used in particleboard factories, e.g. drum dryer, or a tube dryer like that used in medium density fibreboard mills. From then onwards, the dried fibres follow the conventional procedure as for the production of particleboard, medium or high density fibreboard.
• conventional dryers used in particleboard factories e.g. drum dryer, or a tube dryer like that used in medium density fibreboard mills. From then onwards, the dried fibres follow the conventional procedure as for the production of particleboard, medium or high density fibreboard.
• Materials particularly straw treated in accordance with this invention have improved bondability to synthetic and natural bonding agents and isocyanate binders.
• Binders which can be used to bond treated straw are formaldehyde-based resins such as urea-formaldehyde resins (UF-resins) , melamine-urea-formaldehyde resins (MUF-resins) , melamine-formaldehyde resins (MF-resins) , phenol-formaldehyde resins (PF-resins) , melamine-urea- phenol-formaldehyde resins (MUPF-resins) , tannin- formaldehyde resins (TF-resins) and isocyanate binders.
• the binders can be added in the amount of 5 - 25% based on dry straw material.
• the invention is particularly applicable to amino resins.
• the straw can be mixed with the binder when the straw is in the high shear machine when that is employed or in a separate blender.
• Addition of a sizing agent is not obligatory but can be added if necessary either in the defibration treatment or separately.
• a method of assessing the effectiveness of a treating agent is to measure the water absorption of the treated material.
• Samples of treated straw are dried at 65°C for 48hours. This will usually achieve a moisture content of 5% (dry basis) .
• Treatments 1, 2 and 3 were for comparison with the teaching of GB 709569A and GB 2084212A
• the straw After the straw has been dried to a moisture content of approximately 4% it was placed in a Loedige blender and a urea formaldehyde resin was applied with a spraying system. The resin was catalyzed with an ammonium salt to accelerate the curing. The glued material was then formed to boards and the boards were pressed in a hot press. The initial temperature of the press was 200°C.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Manufacturing & Machinery (AREA)
• Paper (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Laminated Bodies (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Adhesives Or Adhesive Processes (AREA)

Applications Claiming Priority (5)

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• 1998
  • 1998-07-10 EP EP98930962A patent/EP1011939B1/de not_active Expired - Lifetime
  • 1998-07-10 IL IL13333898A patent/IL133338A0/xx unknown
  • 1998-07-10 AU AU81233/98A patent/AU8123398A/en not_active Abandoned
  • 1998-07-10 PL PL98337927A patent/PL337927A1/xx unknown
  • 1998-07-10 CN CN98807138A patent/CN1263490A/zh active Pending
  • 1998-07-10 BR BR9810704-6A patent/BR9810704A/pt not_active Application Discontinuation
  • 1998-07-10 KR KR1020007000254A patent/KR20010021695A/ko not_active Application Discontinuation
  • 1998-07-10 WO PCT/GR1998/000021 patent/WO1999002318A1/en not_active Application Discontinuation
  • 1998-07-10 CA CA002292661A patent/CA2292661A1/en not_active Abandoned
  • 1998-07-10 DE DE69801585T patent/DE69801585D1/de not_active Expired - Lifetime
  • 1998-07-10 JP JP2000501882A patent/JP2001512058A/ja active Pending
• 1999
  • 1999-12-14 BG BG104004A patent/BG104004A/xx unknown

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