Patent Grant
7838081
The invention refers to the use of a liquid that, in contact with humid or dry wood, avoids the formation of the blue stain and stains of other colors (red, yellow, green and others) produced by fungi. This way it avoids the strong devaluation of the stained wood and has advantages on compounds used for that aim at the present time.
The fresh cutted wood and the one with a humidity superior to 30%, stains with blue color, color that predominates generally, but also can acquire stains of other colors, like yellow, red, green and white. This phenomenon is more pronounced in a humid climate and not in a very cold one. The stains appear specially due to the growth of the fungi: 1) Ceratocystis species, like pilifera C., C. piceae (blue stain), 2) Ophiostoma species (blue stain), 3) Antirhynium sp. (blue stain), 4) Aureobasidium species (yellow stain) and 5) Fusarium sp. species (red stain).
The formation of stains in the sawed wood is a serious problem for the distant sawmills, where the tables and planks have to be piled up until being transported to the commercial centers where they will be used, because these stains can already appear in few days. Also, during the transport of humid wood in the store-rooms of ships, a fast appearance of the stains is caused by the fungi. This means a serious economic problem for Chile, which is a great exporter of wood to distant countries like United States, Europe, Arabia and Far East.
The exposed facts and the International Norms have motivated the search of solutions for the elimination of the phenomenon of the stains in the wood, which appearance means an obviously diminution of the price of the affected lignocellulosic products. There have been intents to fight the formation of stains by submerging the wood in liquids or by sprinkling liquids with different inhibitors of the growth of the fungi.
One of first compound which obtained good results was chloroorganic Pentachlorophenol. Nevertheless, already in the early 90s, its use was prohibited for its great toxicity (mutagenic, cancerogenic, liver damages). In general the chloroorganic compounds had great importance for their properties like fungicides, insecticides, plaguicides in general and chemical arms, but actually many of them had to be withdrawn of the market. Further the mentioned chloroorganics release the chlorodioxines to the environment, which enormous toxicity restricts even more the use of these chloroderivatives.
After that Pentachlorophenol was replaced by Tribromophenol, which obtained good results in the combat against the stains of the wood, but subsequently it was possible to verify that the bromocompounds also have a high toxicity. For that reason Tribromophenol has been replaced recently by compounds like Copper oxiquinolinate, PQ-8, also toxic, although also nonvolatile, actually very used. Oxiquinolinate is used together with Carbendiazime to reinforce its action. Metiolenbis-tiocianate/2-(T-Benzothiazol) is also used. All these substancies produce health problems (see table 1).
Among the disadvantages of Copper oxiquinolinate, PQ-8, can be mentioned in addition, that it has a relatively high price and that it dyes the wood yellow.
During the development of a process of accelerated petrifaction of wood and in general of lignocellulosic materials, patent request number 1332-2001, patent request number 2746-2002 and US publication number 2004/0105938 A1, (Jun. 3, 2004), could be observed that the liquid used for the treatment not only prevented the combustion of the wood, its putrefying and the attack of the termites, but also prevented the formation of stains by fungi. Afterwards studies were made to avoid the formation of stains by the treatment of the wood and in general of lignocellulosic material with liquids of a similar composition, including substances which nature allowed to suppose an utility. The realized tests allowed to choose a mixture of large shredss and alkaline benzoates in an middle alkaline medium as the most powerful inhibitors of the staining fungi. These ions also can be used besides the ions which are ingredients of the petrifaction of the wood, borates and silicates.
The proposed ingredients have not been used yet to avoid the formation of the blue stain nor stains of another color produced by fungi.
The presented invention refers to a aqueous liquid that contains oxalate and benzoate ions in an alkaline medium. To this liquid can be added borate or borate and silicate. Even a solution that contains only oxalate and borate can be used. The best results were obtained with oxalate and alkaline benzoate in an alkaline medium. When the recently cutted wood and in general lignocellulosic material, humid or dry, is bathed or sprinkled or moistened its surface in another form by all these liquids, they avoid the coloration by formation of stains produced by fungi, like:
Ceratocystis pilifera (blue stain), 2) Antirhynium sp. (blue stain), 3) Aureobasidium sp. (yellow stain) and 4) Fusarium sp. (red stain).
The treated wood remains clean. This indicate the studies made in the laboratory, where the mentioned fungi are artificially inoculated to plates of agar agar in for their growth ideal conditions of temperature and humidity, which contain little pieces of pine wood. Furthermore this results were corroborated by tests in industrial scale. For this tables of two meters forty of length by one by four inches and large shreds of three meters twenty of length by two by two inches, partly treated with the protective liquid and partly without treatment. A part of the humid wood was left outdoors during the month of June with abundant rain and humidity, another part of the humid wood was covered with a polyethylene awning (see pictures).
Formation of stains was not observed in a period of more than 3 weeks from the applied bath. However, the treated wood presented abundant formation of stains, with 70 to 90% of the surface stained.
The inhibiting effect of the stains produced by fungi was studied in pine wood. This wood is very sensitive to the attack of the staining fungi, but it is also the most produced and exported wood in great scale in Chile (almost 90%).
Studies of the inhibiting effect of the stains produced by fungi were made on laboratory and industrial scale. In the studies on laboratory scale two pieces of wood of 25 mm×3 mm×3 mm were placed in a Petri plate of 100 mm diameter with agar agar. One of the pieces had been treated during 10 seconds with the protective liquid and the other during 2 minutes. There were no difference between the time of treatment and the effect of the fungi. In the center of the Petri plate there were placed a drop with the culture of the staining fungus. It is incubated during 30 days at 25° C. in darkness. The results of some typical tests with the staining fungi Ceratocystis pilifera (blue stain1), Antirhynium sp. (blue stain), Aureobasidium sp. (yellow stain) and two types of Fusarium sp. (red stain) can be observed in the attached
The results derived from a great amount of tests that contained single salts, combination of two salts, combination of three salts or combination of four salts, all in alkaline medium, with the 5 types of fungi that most frequently produce stains, demonstrated that the most effective solutions were the chosen ones, all with oxalate as ingredient.
The time of incubation was 30 days at 25° C. in darkness.
The same way the growth kinetic of the different staining fungi was studied. Examples of the growth kinetic of the same fungi shown in the first two graphics can be seen at
The last industrial tests with tables and planks were made only during a little more than two weeks, but in a very humid month and they did not show evidence of stains, which can be observed in the attached pictures of
It is assumed that the wood treated with the indicated salts will continue with an antistain effect on a long term. No stains appeared in the material impregnated with a liquid of borate silicate, which was elaborated in a previous project, material that maintaines outdoors since 2001 until today as sticks, tables and bridges in several places in the Bío Bío Region. The liquid that contains oxalate and benzoate has demonstrated to have an inhibiting effect very superior to the one of BS system (borate silicate) in the laboratory tests. Therefore, solutions of oxalate and benzoate, that also can be used mixed with borate and silicate or only with borate must maintain the lignocellulosic material clean and specially the wood in the time required by the wood industry.
While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1636-2005 | Jun 2005 | CL | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4737154 | Gaines et al. | Apr 1988 | A |
| 20040105938 | Seeger Stein | Jun 2004 | A1 |
| 20040166246 | Holcomb | Aug 2004 | A1 |
| Number | Date | Country |
|---|---|---|
| WO 2006072672 | Jul 2006 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20070033826 A1 | Feb 2007 | US |
