Since 1997, a flooring factory in Liuzhou has achieved good economic benefits from the production of wood flooring with olive wood. However, the nature of the tree species that is easily discolored when the moisture content is high has not received enough attention. The phenomenon that the warehouse is discolored and cannot be sold. I have bleached it and initially achieved success. The initial results are reported below.
1 Materials and methods
1 1 material
1 1 1 Wood color-changing floor strips are provided by the factory and the entire surface is black.
1 1 2 Wood treatment The original floorboard has a high moisture content of more than 20%. The author dries it before bleaching to reduce the water content to about 14%.
1 1 3 bleaching agent bleaching agent has hydrogen peroxide (concentration of 30%), ammonia water (concentration of 8%), oxalic acid solution (concentration of 7%), acetic acid, sodium chlorite, sodium hypochlorite, sodium hydroxide solution (concentration 50%).
1 2 Test method
A line is drawn in the middle of each floor strip, and it is treated with a medicine while being blank, so as to check the bleaching effect.
1 2 1 Hydrogen peroxide (H2O2) Take 50ml of hydrogen peroxide, pour into a container, heat to 50 °C in a water bath, then pour the same amount of ammonia to adjust the pH to 10~1. The bleach was applied to the floor strips with a white nylon brush, and the other side was treated with the reticle line, and the oxalic acid solution was applied to the bleached wood for about 45 minutes. After standing for a few minutes, wipe it off with clean water and let it dry in a ventilated place.
1 2 2 Glacial acetic acid (CH3 COOH) Take 50ml of hydrogen peroxide, pour it into the container (plug the plug), heat it to 50 °C, add the same amount of glacial acetic acid, adjust the mixture with oxalic acid to acidity, and apply the bleach solution. On the floor strip, after about 45 minutes, wipe it with clean water and let it dry in a ventilated place.
1 2 3 sodium chlorite (NaClO2) Take crystalline sodium chlorite 100g, urea 50g, hydrogen peroxide 10g, mix evenly, adjust the pH value to acid with glacial acetic acid, and then apply the bleach to the surface of the wood, about 45min Afterwards, wipe it with clean water and let it dry in a ventilated place.
1 2 4 sodium hypochlorite (NaClO) Take 5g sodium hypochlorite and 95g water [1], heat it to 50 °C in a water bath, apply this mixture to the surface of the floor strip with a brush, and then wash the wood surface with a trace of oxalic acid after treatment. Leave it to dry in a ventilated place.
1 2 5 Sodium hydroxide solution (NaOH) The NaOH solution was applied to the surface of the wood and treated with hydrogen peroxide after 30 min. After the treatment, wipe it with clean water and let it dry in a ventilated place.
2 Results and analysis
The bleaching agents used in the above experiments are oxidized or reduced agents, which can oxidize and reduce with chromophoric groups or color-promoting groups and color-related constituents in wood to achieve decolorization. However, from the experimental results, the bleaching effect of the different components of the bleaching liquid is significantly different. The bleaching effect of the bleached wood after two days of natural drying is shown in Table 1.
3 Summary
(1) Preliminary experiments have shown that it is feasible to bleach the wood with hydrogen peroxide and sodium hypochlorite, and the bleaching effect with hydrogen peroxide is the best. Suitable bleaching conditions are: the concentration of hydrogen peroxide is 30%, the ratio of ammonia to hydrogen peroxide is from 0:5 to 1:1, and the treatment time is from 25 to 40 minutes. When the temperature is low, the heating method can be used to increase the bleaching speed. When the treatment is finished, a small amount of weak acid is used for treatment to avoid yellow discoloration.
(2) The wood of the tree species is susceptible to fungal attack
Color, it is recommended to dry it after sawing the board, dry it to a wooden floor when the water content is about 14%, and it should be treated with anti-corrosion treatment when it can not be dried immediately.
(3) Hydrogen peroxide and some paints are prone to yellow discoloration, so wood bleached with hydrogen peroxide should be fully washed.
(4) Hydrogen peroxide and sodium hypochlorite have good bleaching effect on light wood, and the bleaching effect on dark wood is not ideal, and the bleaching depth is very limited. This remains to be further explored
1 Materials and methods
1 1 material
1 1 1 Wood color-changing floor strips are provided by the factory and the entire surface is black.
1 1 2 Wood treatment The original floorboard has a high moisture content of more than 20%. The author dries it before bleaching to reduce the water content to about 14%.
1 1 3 bleaching agent bleaching agent has hydrogen peroxide (concentration of 30%), ammonia water (concentration of 8%), oxalic acid solution (concentration of 7%), acetic acid, sodium chlorite, sodium hypochlorite, sodium hydroxide solution (concentration 50%).
1 2 Test method
A line is drawn in the middle of each floor strip, and it is treated with a medicine while being blank, so as to check the bleaching effect.
1 2 1 Hydrogen peroxide (H2O2) Take 50ml of hydrogen peroxide, pour into a container, heat to 50 °C in a water bath, then pour the same amount of ammonia to adjust the pH to 10~1. The bleach was applied to the floor strips with a white nylon brush, and the other side was treated with the reticle line, and the oxalic acid solution was applied to the bleached wood for about 45 minutes. After standing for a few minutes, wipe it off with clean water and let it dry in a ventilated place.
1 2 2 Glacial acetic acid (CH3 COOH) Take 50ml of hydrogen peroxide, pour it into the container (plug the plug), heat it to 50 °C, add the same amount of glacial acetic acid, adjust the mixture with oxalic acid to acidity, and apply the bleach solution. On the floor strip, after about 45 minutes, wipe it with clean water and let it dry in a ventilated place.
1 2 3 sodium chlorite (NaClO2) Take crystalline sodium chlorite 100g, urea 50g, hydrogen peroxide 10g, mix evenly, adjust the pH value to acid with glacial acetic acid, and then apply the bleach to the surface of the wood, about 45min Afterwards, wipe it with clean water and let it dry in a ventilated place.
1 2 4 sodium hypochlorite (NaClO) Take 5g sodium hypochlorite and 95g water [1], heat it to 50 °C in a water bath, apply this mixture to the surface of the floor strip with a brush, and then wash the wood surface with a trace of oxalic acid after treatment. Leave it to dry in a ventilated place.
1 2 5 Sodium hydroxide solution (NaOH) The NaOH solution was applied to the surface of the wood and treated with hydrogen peroxide after 30 min. After the treatment, wipe it with clean water and let it dry in a ventilated place.
2 Results and analysis
The bleaching agents used in the above experiments are oxidized or reduced agents, which can oxidize and reduce with chromophoric groups or color-promoting groups and color-related constituents in wood to achieve decolorization. However, from the experimental results, the bleaching effect of the different components of the bleaching liquid is significantly different. The bleaching effect of the bleached wood after two days of natural drying is shown in Table 1.
Table 1 Experimental results Item first group second group third group fourth group fifth group coating times 2 2 2 2 2 Processing time (min) 45 45 45 45 45 Excellent bleaching effect, slightly poor, poorlyIt can be seen from Table 1 that among the above five formulations, the best bleaching effect with hydrogen peroxide is that it completely removes the black color of the wood surface and achieves the desired whiteness. The bleaching effect of sodium hypochlorite is second, it can achieve the desired whiteness of the wood, but at the same time it will cause a slight yellow discoloration on the surface of the wood. The reason for the discoloration is estimated to be that the sodium hypochlorite remaining on the surface of the wood is not completely decomposed. The bleaching effects of the other three bleaches were less than ideal. The second group of bleaches did not discolor the wood; the fifth group of bleaches removed the blackness of the wood surface, but caused a more severe yellow discoloration of the wood. The main cause of discoloration is that the tree species have the property of discoloration of alkali. Therefore, at the end of the treatment, a small amount of weak acid should be used to treat the surface to make the surface of the wood weakly acidic and prevent yellow discoloration. During the wood bleaching process, more factors were found to affect the bleaching effect. For example, in the case of hydrogen peroxide, the concentration of hydrogen peroxide, the ratio of hydrogen peroxide to ammonia, reaction time and temperature are directly related to the bleaching effect. The concentration of hydrogen peroxide is too high, which easily damages the wood fiber and increases the inefficient decomposition; the concentration is too low, and the bleaching effect is not achieved. The concentration is preferably 30%. Ammonia water is a co-agent for hydrogen peroxide. Adding an appropriate amount of ammonia water can increase the concentration of hydroxyl ions (HO-2) in the solution and accelerate the reaction rate. However, too much addition will make the reaction too intense and increase the decomposition and damage of wood fiber. Experiments have shown that the ratio of ammonia to hydrogen peroxide is preferably controlled from 0:5 to 1:1. Reasonable bleaching conditions for several other bleaching agents have yet to be further explored.
3 Summary
(1) Preliminary experiments have shown that it is feasible to bleach the wood with hydrogen peroxide and sodium hypochlorite, and the bleaching effect with hydrogen peroxide is the best. Suitable bleaching conditions are: the concentration of hydrogen peroxide is 30%, the ratio of ammonia to hydrogen peroxide is from 0:5 to 1:1, and the treatment time is from 25 to 40 minutes. When the temperature is low, the heating method can be used to increase the bleaching speed. When the treatment is finished, a small amount of weak acid is used for treatment to avoid yellow discoloration.
(2) The wood of the tree species is susceptible to fungal attack
Color, it is recommended to dry it after sawing the board, dry it to a wooden floor when the water content is about 14%, and it should be treated with anti-corrosion treatment when it can not be dried immediately.
(3) Hydrogen peroxide and some paints are prone to yellow discoloration, so wood bleached with hydrogen peroxide should be fully washed.
(4) Hydrogen peroxide and sodium hypochlorite have good bleaching effect on light wood, and the bleaching effect on dark wood is not ideal, and the bleaching depth is very limited. This remains to be further explored
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