Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
  • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
  • D21B1/30—Defibrating by other means
  • D21B1/32—Defibrating by other means of waste paper
• • 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
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
  • D21C5/02—Working-up waste paper
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/64—Paper recycling

Definitions

• the present invention relates to the recycling of lignocellulose based board (or panel) material comprised of a matrix of adhesively bonded lignocellulosic elements so as to permit recovery of constituents of the board material, particularly but not exclusively of the lignocellulose.
• various board materials comprise a matrix of lignocellulosic elements (e.g. in the form of chips, particles or fibres) bonded together by means of an adhesive such as, for example, a polyurethane, urea/formaldehyde, melamine-urea or phenolic resin.
• an adhesive such as, for example, a polyurethane, urea/formaldehyde, melamine-urea or phenolic resin.
• board materials produced in this way include MDF (Medium Density Fibreboard) , particle board and chip board.
• Board materials of the type described above are used extensively for producing finished articles such as, for example, furniture. For this purpose, the board materials are entirely satisfactory. However there is a substantial amount of waste material for which disposal poses a problem. To illustrate the point, the UK furniture manufacturing industry generates over 170,000 tonnes of MDF waste every year. This does not include rejected and damaged furniture items. Ideally the waste material would be recycled to recover constituents thereof, particularly the lignocellulose for reuse. However, no satisfactory recycling process is currently available. The problem is made worse by the fact that the waste board material may be laminated to a surface layer such as, for example, paper foil or plastics (e.g. for decorative purposes) or may have, for example, plastic or metal inserts. As such, any recycling process will need to remove the laminates and/or inserts. In the absence of any suitable recycling process, most of the waste board material will be dumped in landfill site, which is becoming more difficult and very expensive.
• a method of recovering a constituent of a board material comprised of a matrix of adhesively bonded lignocellulosic elements comprising subjecting the material to a combination of (i) electromagnetic radiation and (ii) soaking or immersion in a liquid medium, and recovering the constituent.
• the constituent to be recovered will generally comprise lignocellulose, which may, however, incorporate residual resin, for example urea-formaldehyde resin.
• the electromagnetic radiation will typically have a frequency in the range of from 100 kHz to 300 GHz, more typically from 10 MHz to 300 GHz.
• the liquid medium will typically comprises water or an aqueous solution.
• the liquid medium could, however, comprise any suitable organic or inorganic solvent capable of swelling the material so that the constituent can be recovered.
• Possible other examples include ethyl alcohol, ethyl alcohol/water mixtures, and dilute sodium hydroxide (for example 0.1-9% by volume). This latter example has been found to improve fibre texture.
• the invention has been based in part on our discovery that treatment of board materials comprised of an adhesively bonded matrix of lignocellulosic elements, for example particles or fibres, by exposure to electromagnetic energy in the frequency range of from 10 MHz to 2500 MHz and soaking with a liquid medium such as water produces substantial swelling of the board material, which, we believe, mechanically disrupts and possibly at least partially hydrolyses the adhesive bonding the lignocellulosic elements together so that these elements can now be readily separated from each other.
• the degree of swelling achieved is considerably more that that which is obtained simply by soaking the board material in the liquid medium.
• Steps (i) and (ii) may be effected simultaneously or sequentially.
• the degree of swelling achieved in the thickness dimension of the board should generally be in the range of from 3 to 6 times the original thickness.
• the lignocellulosic elements may be achieved using a relatively low degree of mechanical agitation while the treated material is in the liquid medium, for example water. Once the elements have been separated, it is possible to recover a desired constituent of the board, which will usually comprise the lignocellulose.
• the resultant dispersion of fibres may be dried, for example by press-drying (if the fibres are to be transported) or by a fan-assisted blowing system (if the fibres are to be re-used on site) .
• surface laminates for example paper, foil, melamine, veneer or other finishes commonly used on board materials to which the invention relates, can readily be separated from the treated board prior to recovery of the fibres, for example by agitation, as may inserts or other bodies included in the panels .
• the board material will typically have a density of from 200 Kg irf 3 to 1200 Kg rrf 3 .
• the invention is applicable to a wide variety of wood based boards, including particle boards and fibre boards. Specific examples of board materials to which the present invention is applicable include MDF, chip board, hard board, soft board, orientated strand board, flax board and wood chip board, and combination of any two or more thereof.
• microwaves in the frequency range from 896 + 20 MHz to 2450 + 25 MHz are employed (such as generated by a magnetron).
• the electromagnetic radiation used may be 896 + 20 MHz or 2450 + 25 MHz, both of which are frequencies reserved for domestic/industrial microwave use. These frequencies have been found to result in substantial swelling of the board material in the liquid medium.
• the electromagnetic energy may have a frequency in the range of from 10 MHz to 50 MHz.
• the microwaves may be generated by means of a magnetron in a conventional way.
• the power output to the cavity which may, for example, be in the form of a metallic vessel or pipe, is preferably in the range 500 W to 30 kW.
• the microwaves propagate through the cavity, which contains the wood-based panels immersed in the liquid medium such as water.
• Electromagnetic radiation having a frequency in the range of from 100 kHz to 100 MHz may also be used, which is typical of radio frequency (RF) waves.
• RF radio frequency
• the process according to the present invention is not restricted to the use of microwaves.
• RF may also be utilised due to the lower frequencies of operation resulting in greater penetration through the board, which is often advantageous.
• RF may be defined as all frequencies used for communication, corresponding to 100 kHz to 300 GHz. Further details may be found in Kitchen, R. (2001) RF and Microwave Radiation Safety. Newnes ppl-2.
• the invention may be practised in a number of ways.
• the board material is initially subjected to the electromagnetic radiation and is then immersed substantially immediately into the liquid medium, for example within 5 to 15 seconds.
• the liquid medium for example water, is preferably at an elevated temperature, for example 60°-90°C, preferably about 80°C.
• the board material does have internal moisture content, preferably a minimum of 8%, which may, if necessary, be enhanced prior to the treatment with electromagnetic radiation.
• Immersion of the board material that has been subjected to electromagnetic radiation into the liquid medium causes substantial swelling to occur.
• the exposure time to the electromagnetic radiation will be in the range of from 30 to 90 seconds. Subsequently the material is soaked in the liquid medium to swell the material.
• the degree of swelling may be to 3 to 6 times the original degree of thickness, for which an immersion time of typically 10-25 minutes in, for example, water may be required, although the exact time will depend on factors such as the nature of the board, the. arameters employed (for example frequency and power) employed during the treatment with electromagnetic energy, and the temperature of the water.
• Any surface laminate applied to the board may easily be removed from the swollen board (and in fact the laminate may start to peel-off during the treatment with electromagnetic radiation) .
• any inserts may also be removed easily.
• the swollen material may then readily be converted to a fibrous suspension using, for example, a moderate degree of agitation such as provided a low power mechanical blender, for example.
• the fibrous suspension may then be dried, for example by press-drying or by means of a fan-assisted blowing system as described previously.
• the board materials is immersed in the liquid medium (for example water) and subjected to electromagnetic radiation as discussed previously followed by soaking in the liquid medium without irradiation.
• the liquid medium for example water
• this embodiment of the invention tends to produce a lower degree of swelling of the board than the above described preferred embodiment and does not lend itself as readily to continuous or semi-continuous operation as the above described preferred embodiment. It may however be possible to recover heat from the liquid medium using, for example, a heat exchanger to assist in drying of the board.
• this embodiment involves not only heating of the board material by the electromagnetic radiation but also the liquid medium in which it is immersed, thus reducing energy efficiency.
• this embodiment may provide more problems with effluent disposal than the above described more preferred embodiment.
• the board material may initially be subjected to a vacuum impregnation so as to increase its moisture content, for example up to 50% by weight.
• the liquid medium in which the board is immersed may incorporate an additive such as, for example a surface active agent or surfactant, to assist penetration of the water into the board.
• the board material may be "turned” during treatment with the electromagnetic radiation to ensure uniform exposure.
• the invention is able to provide clean recycled fibre for a number of possible uses, for example production of other board products, wood plastic components, fillers and insulating materials.
• a (approx. 150 x 150 x 18) mm sample of MDF was subjected to microwave radiation at a frequency of approximately 2450 + 25 MHz at a power level of approximately 12 kW for a period of about 45 seconds and then added immediately to water at a temperature of above about 60 °C and allowed to stand for approximately 10 to 15 minutes .
• the MDF was found to have swollen in thickness to approximately 90.42 mm.
• the swollen material could easily be converted to a fibrous suspension in either approximately 2 minutes using a pulp disintegrator rated at 1.5 kW or in approximately 4 minutes using a 700 W laboratory stirrer.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Forests & Forestry (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Processing Of Solid Wastes (AREA)
• Paper (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2004
  • 2004-07-16 AU AU2004257920A patent/AU2004257920A1/en not_active Abandoned
  • 2004-07-16 WO PCT/GB2004/003134 patent/WO2005007968A1/en not_active Ceased
  • 2004-07-16 EP EP20040743469 patent/EP1649103A1/de not_active Withdrawn
  • 2004-07-16 US US10/564,881 patent/US20060254731A1/en not_active Abandoned
  • 2004-07-16 CA CA 2532346 patent/CA2532346A1/en not_active Abandoned
  • 2004-07-16 NZ NZ544667A patent/NZ544667A/en not_active IP Right Cessation
  • 2004-07-16 BR BRPI0412564 patent/BRPI0412564A/pt not_active IP Right Cessation

Non-Patent Citations (1)

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