• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method for removing, reducing and/or lightening the dis-coloration of wo od caused by blue-stain fungi in a workpiece using a kiln having a humidificati on system wherein the method includes placing a workpiece for drying in a kiln, integrating a bleaching agent into the humidification system in the kiln so that moisture from the humidificati on system entering the kiln contains the bleaching agent, commencing drying of the workpiece in the kiln, and injecting moisture from the humidification system into the kiln so that the moisture contacts the workpiece.
    公开号:CA2534479A1
    申请号:C2534479
    申请日:2006-01-30
    公开日:2006-07-28
    发明作者:Fred Spinola；Carla Waters；John R. Stevens
    申请人:Fred Spinola；Carla Waters；John R. Stevens；Coe Newnes/Mcgehee Ulc；Coe Newnes/Mcgehee Inc.；Usnr/Kockums Cancar Company；Usnr Kockums Cancar Holdings Ulc；
    IPC主号:B27K5-04
    专利说明:
    METHOD OF BLEACHING WOOD Field of the Invention S The invention relates to the field of treating wood, and more particularly, i.t relates to a method of treating so-called blue-stained wood to reduce the discolouration of the wOOd. Background of the Invention The mountain pine beetle has infected many hectares of pine trees and the infestation still continues to grow and expand. When pine beetles attack a pine tree, they introduce fungi that kill the pine tree by cutting off paths for nutrients and water. The fungi also change the color of the wood to blue or grey, hence the reference to such wood as "blue-1 S stained" or "denim-pine". Most trees attacked by the mountain pine beetle inevitably di.e and it is estimated that the pine beetles will create approximately S00 million cubic meters of blue-stain.ed wood over the next one to three years. Although it is applicani's opinion that the wood remains structurally sound and may be safely used in many situations where pine would usually be suitable, the blue-stained wood is for the most part today cosmetically undesirable to the lumber industry.The deterioration of pine trees is due to the introduction of blue-stain fungi by the mountain pine beetle into the pine tree. Blue-stain fungi are spread by spores, which are "sticky" and may be carried into the wood by insects. Onee the blue-stain fungi spores land on the surface of a nutrient-rich environment, such as the sapwood of a pine tree, the spores grow rapidly. The fungi grow within the tree and disrupt the nat~~ral defenses within the tree. In conjunction with the feeding of the mountain pine beetle, the tree weakens and is rapidly destroyed. The fungi typically give a blue-gray appearance to the wood of the pine tree, although various shades of yellow, orange, purple, and red sometimes appear. The exact color of the stain depends on the infecting organism and the species and moisture content of the wood. The discoloration may completely cover the sapwood or may appear as specks, spots, streaks, or patches of various color intensities. The fungi only infect the sapwood of the tree because it uses parts of the sapwood, including simple sugars and starches, for food. The fungi do not grow in heartwood or most wetwood as they do not provide the necessary food substances to the fungi. Although the blue-stain fungi are prone to cause bluish or grayish discoloration of the wood, they do not cause decay or affect the strength of the wood. In the decorative wood market, some people like the look produced in wood by blue stain, similar to the appreciation of spalted wood. However, blue-stained wood is still generally considered undesirable in the lumber industry as some standard lumber grading roles limit the amount of blue stain permitted on exposed structural lumber. It is therefore desirable to devise a method of removing discoloration from wood, and more particularly, a method of decolorizing (herein alternatively referred to as "bleaching") wood to remove the blue stain from pine beetle infected wood. United States Patent No. 5,242,464 to Armstrong et al. describes a method of bleaching wood wherein a single layer of bleaching solution comprising sodium hydroxide and hydrogen peroxide is applied to the wood surface. The bleaching solution remains on the wood surface for a ten minute time period before it is agitated with an abrasive pad. United States Patent No.3,645,666 to Bailey et al. also describes a method for uniformly bleaching the color of wood by preheating the wood and applying a bleaching solution of hydrogen peroxide. The wood may then be exposed to vapors of anhydrous ammonia to activate the peroxide. Altl~.ough the Armstrong patent and the Bailey patent provide a means to remove the coloration of wood, the use of peroxide, caustic soda, andlor ammonia is known to destroy the wood fibers and cause a yellowing effect. In an article entitled "Bleaching the Blues" published by the Centre far Advanced Wood Processing in the CC: CAWP Communications Newsletter Vol. 4, Issue 4, ('~ctober 20(i4, the Centre for Advanced Wood Processing conducted a research project c. ~, . comparing the ability of various bleaching agents to remove the blue color from blue~stained pine sapwood without adversely affecting the color of unstained heartwood. Although the research suggested that sodium hypochiorite may be an effective treatment to remove the blue colour from blue-stained pine wood, the article indicated that further research was required to develop an industrially effective treatment process to remove the blue coloration from the pine.United States Patent No. 5,532,164 to Blanchette et aI. describes a biological means to suppress the color staining of wood by inoculating the cut ends of timber with a fungus that grows white and/or colorless and which acts to reduce the pitch content of the wood, thereby reducing the food source of the blue staining fungi. Although the Bianchette patent provides a means to confrol or prevent further discoloration of wood, it does not teach a means to bleach or remove existing discoloration in the wood. Therefore, it is necessary to provide a method of bleaching blue-stained wood that minimizes the adverse effects typically associated with wood bleaching methods known in the art. Summary of the Invention The present invention provides a method for removing, reducing, and/or lightening the discolouration of wood caused by the blue-stain fungi. Advantageously, the method also controls and/or eliminates the blue-stain fungi in the discoloured wood. The method also minimizes the undesirable effects typically associated with the use of conventional wood bleaches. The method of bleaching wood according to the present invention includes the steps of transporting the blue-stained wood to a kiln for drying, integrating a bleaching agent into the humidification system of the kiln, and injecting moisture from the humidification system into the kiln during the drying process wherein the moisture contains the bleaching agent. In an embodiment of the invention, the bleaching agent may be applied to the blue-stained wood during the equalization process. The bleaching agent may be injected into the kiln air along with the steam spray during the equalization process to simultaneously increase the humidity in the kiln to equalize the moisture content between pieces of wood and within individual pieces of wood and remove, reduce, and/or lighten the discolouration of the blue-stained wood. In another embodiment of the invention, the bleaching agent may be applied to the blue-stained wood during the conditioning process. The bleaching agent may be introduced in the kiln along with the steam vapour during the conditioning process to simultaneously remove the offset tension set of the wood and reduce, and/or lighten the discolouration of the blue-stained wood. The kiln schedule may be set such that the temperature and hmnidity used during kiln operation advantageously cooperates with the bleaching agent to uniformly bleach the blue-stained wood and inactivate the blue-stain fungi.In the further alternative, the bleaching agent may be applied to the blue~stained wood prior to being dried in the kiln. In another embodiment of the invention, the bleaching agent may be applied to the blue-stained wood after the wood has been kiln dried, the method including the steps of transporting the kiln dried blue-stained wood to a bleaching facility, placing the blue-stained wood into a bleaching container, sealing the bleaching container, and introducing the bleaching agent into the sealed bleaching container. The pressure in the bleaching container may be increased to force the bleaching agent into the wood to remove, reduce, andlor lighten the discolouration of the blue-stained wood. Preferably, the bleached blue-stained wood is re-dried after being removed from the sealed bleaching container. In an alternative embodiment, the blue-stained wood may be treated at the bleaching facility without being kiln dried first and then transported to the k~Ill for drying after being bleached in the bleaching container. The bleaching agent may also be applied independent of the kiln drying process. The blue-stained wood may be treated through a spray box or spray system wherein the bleaching agent is sprayed and applied to all sides of the blue-stained wood. Alternatively, the bleaching agent may be brushed an the surface of the blue-stained wood and allowed to rest for a predetermined amount of time. In the further alternative, the blue-stained wood may be dipped in a dip tank containing the bleaching agent and allowed to soak for a predetern~ined amount of time before being removed. The blue-stained wood may be bleached according to any of the methods described above as individual pieces or as a group. After the blue-stained wood is bleached, a neutralizing agent may be applied to the treated blue-stained wood to neutralize the bleaching agent present in the treated wood. Detailed Description of Embodiments of the Invention In an embodiment of the method of bleaching wood according to the present invention includes the steps of transporting the blue-stained wood to a kiln for kiln drying, integrating a bleaching agent into the humi.difzeation system of the kiln, and injecting the bleaching agent from the humidification system into the kiln during the drying process to remove, reduce, andlor lighten the discolouratian on the blue-stained wood caused by the bIue-stain fungi. Bleaching agent is herein defined as any agent capable of removing, reducing, and/or lightening any discoloration in wood, especially the blue stain found iz~ wood infected by the blue-stain fungi.Wood, such as boards, lumber, and timber, are typically kiln dried to lower the moisture content of the wood.. During the drying process; some pieces of wood znay dry more quickly than others due to, for example, differences in moisture content between sapwood and heartwood. Equalizing is a procedure to equalize the moisture content from piece to piece, as well as equalize the moisture content within individual pieces, by incxeasing the humidity in the kiln such that the driest pieces dry no further wlxile the wetter pieces continue to dry.During the equalization process, moisture, such as a steam spray, may be injected into the kiln air to ilicrease the humidity in the kiln to equalize and minimize the variability of moisture content between pieces of wood arid within individual pieces of wood. In an embodiment of the invention, a bleaching agent nay be integrated in the humidification system of the kiln such that, during the equalization process, the bleaching agent may be applied on to the blue-stained wood by injecting the bleaching agent along with the steam spray into the kiln from the S humidification system. The steam spray and bleaching agent may simultaneously equalize the moisture content of the wood and remove the discolouration of the blue-stained wood.Alternatively, the bleaching agent may be applied to the blue-stained wood during the conditioning process. The conditioning process relieves the tension set or drying stresses caused by the differential rate of drying between the outer cells and the inner cells of the wood.During the conditioning process, humidity in the kiln may be rapidly increased at a high temperature to offset the tension set_ Preferably, the bleaching agent is integrated in the steam humidification system of the kiln such that, during the conditioning process, the bleaching agent may be introduced in the kiln along with the steam vapour and applied on to the blue-stained wood to simultaneously offset the tension set and remove the discolouration from the blue-stained wood. In the further alternative, the bleaching agent may be applied to the blue-stained wood prior to being dried in the kiln. The l~iln schedule may be set such that the temperature and humidity used during kiln operation advantageously cooperates with the bleaching agent to uniformly bleach the blue-stained wood and inactivate the blue-stain fungi. Kiln drying the blue-stained wood may also reduce the moisture content of the blue-stained wood such that the growth of the blue-stain fungi is impeded, Preferably, the moisture content of the blue-stained wood is reduced below 22%, which is the approximate moisture level at which the blue-stain fungi cease to grow. The high temperatures during kiln operation may also be lethal to the blue-stain fungi. Preferably, the kiln schedule is sat such that the temperature at some point during the drying operation is at least above 130°F, which is the approximate temperature at which the blue-stain fungi are destroyed.2S In another embodiment of the invention, the bleaching agent may be applied to the blue-stained wood after the wood has been kiln dried, the method including the steps of transporting the kiln dried blue-stained wood to a bleaching facility, placing the blue-stained wood into a bleaching container, sealing the bleaching container, and introducing the bleaching agent into the sealed bleaching container. Typically, air is removed from the bleaching container by conventional means such as a vacuum prior to introducing the bleaching agent into the bleaching the sealed container. The pressure in the bleaching container may be increased to force the bleaching agent into the wood to remove, reduce, and/or lighten the discolouration of the blue-stained wood. After the bleaching treatment is complete, the excess bleaching agent is drained or pumped out of the bleaching container and the bleached blue-stained wood is removed. Preferably, the bleached blue-stained wood is re dried after being removed from the sealed bleaching container. In an. alternative embodiment, the blue-stained wood may be transported to aid treated at the bleaching facility first without being dried in the kiln and then transported to the kiln for drying after being bleached in the bleaching container. In another embodiment of the invention, the bleaching agent may be brushed on or otherwise applied to the surface of the blue-stained wood such that the bleaching agent may penetrate into the blue-stained wood a predetermiized amount of time. For example, the bleaching agent may be integrated in a day tank unit of a spray box or a spray system such that the bleaching agent may be pumped into a plurality of spray tips or spray heads and applied to all sides of the blue-stained wood within a spray chamber. Offset chainways may be provided in the spray box or spray system to ensure complete coverage of the blue-stained wood and end guns may also be provided to ensure treatment of the ends of the blue-stained wood.Preferably, the bleaching agent is allowed to penetrate the blue-stained wood for one week. In the further alternative, the blue-stained wood may be dipped in a dip tank containing the bleaching agent and allowed to soak for a predetermined amount of time before being removed. The blue-stained wood may be immersed in the bleaching agent between fifteen to thirty minutes before it is removed from the dipping tank. The blue-stained waod may be bleached according to any of the methods described above a<s individual pieces or as a group. After the blue-stained wood is bleached, a neutralizing agent may be applied to the treated blue-stained wood to deactivate or otherwise counteract the active component of the bleaching agent present in the treated wood. The neutralizing agent rnay be brushed on or otherwise applied to the surface of the treated wood such that the neutralizing agent may penetrate into the treated wood. In an embodiment of the invention, the neutralizing agent rnay be treated through a spray box or a spray system such that the neutralizing agent may applied to all sides of the treated wood, As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alteratio~~s and modifications are possible in the practice of this invention without departing from the spirit or scope thereof Accordingly, the scope of the invention is to be eanstrued in accordance with the substance defined by the following claims.
    权利要求:
    Claims (8)
    [1] 1. A method for removing, reducing and/or lightening the dis-coloration of wood caused by blue-stain fungi in a workpiece using a kiln having a humidification system: a) placing workpiece for drying in a kiln, b) integrating a bleaching agent into the humidification system in the kiln so that moisture from the humidification system entering the kiln contains the bleaching agent, c) commencing drying of the workpiece in the kiln, d) injecting moisture from the humidification system into the kiln so that the moisture contacts the workpiece.
    [2] 2. The method of claim 1 wherein said step of injecting moisture is during an equalization process in said kiln.
    [3] 3. The method of claim 2 wherein said moisture is steam spray during said equalization process.
    [4] 4. The method of claim 2 wherein said moisture is steam spray during the conditioning process in said kiln.
    [5] 5. The method of claim 2 wherein said moisture is steam spray during steam vaporization.
    [6] 6. The method of claim 1 further comprising the step of setting the temperature and humidity in the kiln to cooperate with the bleaching agent to uniformly bleach the workpiece.
    [7] 7. The method of claim 6 further comprising the steps of reducing moisture below twenty-two percent humidity and increasing temperature above one hundred thirty degrees Fahrenheit in the kiln.
    [8] 8. The method of claim 1 further comprising the step of applying a neutralizing agent to said workpiece.
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    同族专利:
    公开号 | 公开日
    CA2534479C|2015-02-17|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2011-01-11| EEER| Examination request|
    优先权:
    申请号 | 申请日 | 专利标题
    US64743705P| true| 2005-01-28|2005-01-28||
    US60/647,437||2005-01-28||
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