Classifications

• • 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
  • B27K7/00—Chemical or physical treatment of cork
• • 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
  • B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
  • B27K5/003—Treating of wood not provided for in groups B27K1/00, B27K3/00 by using electromagnetic radiation or mechanical waves
  • B27K5/0055—Radio-waves, e.g. microwaves
• • 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

• This invention relates to a process, and to the resulting material, that allows the volumetric expansion of cork without using substances foreign to the cork system. More precisely, it relates to a process that consists in submitting cork to microwave radiation, obtaining a more bulky material and consequently increasing its yield and reducing its specific weight.
• the European patent no. EP1677386 claims that wood, a material different from cork but also lignocellulosic, can be submitted to microwave radiations in order to destroy insects, parasites or their larvae.
• the international patent no. WO03002923 describes the use of microwave radiation for fast wood drying, increasing additionally its permeability. In that case, the use of microwaves radiation is applied for wood cleaning, so its scope is not within the present application.
• Microwave radiations are also used to cure polymers such as latex, as described in the Spanish patent no. ES2019514, or to cure resins for the production of wood derivatives, as described in the international patent no. WO9823132. Again, the scope of these inventions is different from the present application.
• cork can be described as a homogeneous tissue of thin cells, without space between them, and an alveolar structure similar to a honeycomb.
• the cork cells show diverse shapes depending if observed on the radial direction ( Figure 1) or in a perpendicular direction to radial, i.e., axial or tangential ( Figure 2) .
• the closed structure of cork cells and the presence of air inside determine the low specific weight of cork, as well as some of its mechanical properties.
• the specific weight of cork might however show a significant variability, between 120kg.rtf 3 and 240kg.irf 3 , as described by M.
• volumetric increase in the three spatial directions
• the volumetric increase in the three spatial directions
• the present application describes a process capable of promoting cork expansion without using external substances to the cork system. Subsequently, the produced cork might be submitted to standard cork industrial processes.
• This process can be used in continuous or non-continuous mode and has three stages, the first stage being the dosing of the material, followed by the expansion stage, and finally the discharge stage or preferably cooling and discharge.
• the dosing stage intends to feed continuously and over time the expansion zone and can be done using a feeding endless screw or a conveyor.
• the expansion stage should ensure the contact of the product to the action of the microwave radiation by a conveyor or dielectric containers such as for example, fibber glass, wood, plywood, among others.
• the radiation power should range between 200 watt and 1000 watt, preferably between 400 watt and 800 watt.
• the exposure time to the microwave radiation should be between 10 seconds and 5 minutes, preferably between 15 seconds and 2 minutes or even more preferably between 15 seconds and 50 seconds.
• the collecting stage could be performed using an endless screw that might have a sealant "lock", a manual or electropneumatic plate valve or a conveyor.
• the samples should have a humidity higher than 5%, which can be achieved by immersion in water at temperature ranging between 25 0 C and 100 °C or by autoclave at temperatures between 100 °C and 150 °C.
• the dosing stage aims to feed the microwave chamber and can be performed using a feeding endless screw that may have a dosing sealant "lock" or a manual or electropneumatic plate valve or a conveyor.
• the cork expansion stage will occur inside a closed chamber made of a dielectric material such as, for example, glass fibber, wood, plywood, among others.
• the radiation power should range between 200 watt and 1000 watt, preferably between 400 watt and 800 watt.
• the exposure time to the microwave radiation should be between 10 seconds and 5 minutes, preferably between 15 seconds and 2 minutes or even more preferably between 15 seconds and 50 seconds.
• the expansion stage by submission to microwave radiation can be performed in one or more cycles.
• the product collecting stage in the non-continuous process for cork expansion by submission to microwave radiation can be performed using an endless screw that may have a sealant "lock” or a manual or electropneumatic plate valve or a conveyor. During the expansion, process by submission to microwave radiation the presence of moisture is crucial for the expansion to occur. Product resulting from the pre-expansion. process
• the present application seeks to demonstrate the increase of the cork dimensions and consequently the decrease of its specific weight after submission to microwave radiation.
• the cork can be submitted to this pre-expansion process independently of its shape, origin, quality or pre-treatments already performed, namely, falca cork, virgin or reproduction cork, cork planks, cork residues (resulting from stopper production or cork plank transformation) , grinded cork, granulated cork or cork powder, any of them boiled or not boiled.
• the increase on cork dimensions after being submitted to microwave radiations with controlled moisture, has two effects: promotes a yield increase of the material, i.e., less material used for the same application; and promotes an increase of the material quality, due to the reduction in specific weight. These two aspects represent commercial benefit.
• cork material such as falca cork, virgin or reproduction cork, cork planks, cork residues (resulting from stopper production or cork plank transformation) , grinded cork, granulated cork or cork powder, any of them boiled or not boiled, shows an increase on its dimensions between 40% and 85%, when submitted to a pre-expansion process by submission to microwave radiation such as above described. This fact implies the reduction of its specific weight. It should be emphasized that in addition to the increase on the material yield (higher volume of cork after the treatment) , the cork with lower specific weight presents higher economical value.
• Example 1 Cork expansion by submission to microwave radiation.
• Cubic shaped cork samples were submitted to microwave radiation with 550 watt power. One group of samples was exposed for 25 seconds whereas another group was exposed to five cycles of 5 seconds each. The observed expansions were, respectively, 48% and 46%, emphasizing the importance of the exposure time and not the operation mode (continuous or several cycles) .
• Example 2 Cork expansion with different humidity by submission to microwave radiation.
• Cubic shaped cork samples were submitted to microwave radiation with 550 watt power. A group of samples with 1.4% of humidity presented, after treatment, a volumetric expansion of
• Cubic shaped cork samples were submitted to microwave radiation, after immersion in water at different temperatures and for different time periods.
• the results of the expansion and the detailed conditions are presented in Figure 3. Besides showing the microwave radiation effect on the volumetric increase of cork samples, expansion between 40% and 65%, these results allow to conclude that humidification by immersion in water is a possible method to be used, the immersion water temperature having a positive effect on the cork volumetric expansion.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Mechanical Engineering (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Processing Of Solid Wastes (AREA)

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Publications (1)

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Cited By (3)

Citations (2)

• 2007
  • 2007-03-21 PT PT103697A patent/PT103697A/pt not_active Application Discontinuation
• 2008
  • 2008-03-20 WO PCT/PT2008/000012 patent/WO2008115086A1/en active Application Filing
  • 2008-03-20 PT PT08724036T patent/PT2125310E/pt unknown
  • 2008-03-20 AT AT08724036T patent/ATE530310T1/de not_active IP Right Cessation
  • 2008-03-20 EP EP08724036A patent/EP2125310B1/de active Active
  • 2008-03-20 ES ES08724036T patent/ES2376152T3/es active Active

Patent Citations (2)

Non-Patent Citations (1)

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