Wood dyeing method

Abstract

The invention provides a wood dyeing method, and belongs to the technical field of wood dyeing. The method comprises the following steps: bleaching wood, pretreating the bleached wood by using an inorganic alkaline solution, placing the pretreated wood in a cation modification solution for cation modification, and placing the cation modified wood in an acid dye dyeing solution for dyeing to obtain the cation modified dyed wood. The inorganic alkaline solution is used for pretreating the bleached wood, under the alkaline condition, hydroxyl groups on the surface of wood fibers are more easily activated, the reaction activity of the wood fibers is improved, cationic groups in the cationic modifier and hydroxyl groups in wood cellulose are more easily subjected to chemical reaction, and therefore more stable covalent bond combination is formed; more cationic modifiers are grafted to wood fibers through a chemical grafting method, more groups with positive charges are introduced to the surface of wood, then the dye uptake is increased, and the cationic modifier is suitable for dyeing processing of wood materials such as recombined decorative veneers and veneer veneers.

Description

Technical Field

[0001] This invention relates to the field of wood staining technology, and more particularly to a method for staining wood. Background Technology

[0002] Engineered wood, as a new type of wood material, has been widely used in interior decoration due to its ability to accurately reproduce the texture and rich colors of rare woods. However, increasingly stringent environmental regulations and the need for resource conservation have led to a double bottleneck in traditional dyeing processes due to insufficient color fastness and high pollution load of dye wastewater.

[0003] Acid dyes are widely used for dyeing reconstituted decorative veneers due to their vibrant colors, simple dyeing process, and good penetration. However, acid dyes have poor stability and are prone to desorption from the fiber surface, resulting in lower color fastness of the final product. Furthermore, both acid dye molecules and the surface of wood fibers carry a negative charge, which, due to Coulomb repulsion, hinders the binding of the dye to the wood fibers during the dyeing process.

[0004] Currently, mainstream dye fixation technologies mainly involve the use of color stabilizers, which not only increases the complexity of the dyeing process but also leads to serious environmental pollution. Furthermore, existing chemical modification methods may be difficult to industrialize due to their complex procedures, high costs, or negative impacts on wood properties. A related technology discloses a wood dyeing method that uses specific amine compounds to pretreat wood, enabling it to have a strong adsorption and fixation effect on acid dyes, thereby significantly improving dyeing efficiency; however, the problem of low dye uptake still exists. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for dyeing wood. The dyeing method of the present invention has a high dyeing rate.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for staining wood, comprising the following steps: The wood is bleached to obtain bleached wood; The bleached wood was pretreated with an inorganic alkaline solution to obtain pretreated wood. The pretreated wood is subjected to cationic modification in a cationic modification solution to obtain cationic modified wood (CBW); the cationic modification solution includes a cationic modifier, an inorganic alkaline compound, and water; The cationic modified wood was placed in an acidic dyeing solution for dyeing to obtain cationic modified dyed wood (DCBW).

[0007] Preferably, the concentration of the inorganic alkaline solution is 0~50g / L and not 0.

[0008] Preferably, the inorganic alkaline compound includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0009] Preferably, the concentration of the inorganic alkaline compound in the cationic modified solution is 0~50g / L and not 0.

[0010] Preferably, the cationic modifier includes epoxy quaternary ammonium salt cationic modifiers and / or chlorotriazine type quaternary ammonium salts.

[0011] Preferably, the epoxy quaternary ammonium salt cationic modifier includes one or more of glycidyl dimethyl butyl ammonium chloride, glycidyl trimethyl ammonium chloride, and glycidyl triethyl ammonium chloride.

[0012] Preferably, the concentration of the cationic modifier in the cationic modified solution is 0.1~30 g / L.

[0013] Preferably, the temperature for cationic modification is 35~95℃ and the time is 0.25~3h.

[0014] Preferably, the concentration of the acid dye dyeing solution is 0.36~0.6g / L.

[0015] Preferably, the dyeing process further includes sequential lamination, molding, and slicing.

[0016] This invention provides a method for dyeing wood, comprising the following steps: bleaching wood to obtain bleached wood; pretreating the bleached wood with an inorganic alkaline solution to obtain pretreated wood; cationically modifying the pretreated wood in a cationic modifying solution to obtain cationic modified wood; wherein the cationic modifying solution comprises a cationic modifier, an inorganic alkaline compound, and water; and dyeing the cationic modified wood in an acidic dyeing solution to obtain cationic modified dyed wood.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes an inorganic alkaline solution to pretreat the bleached wood. Under alkaline conditions, the hydroxyl groups on the surface of the wood fibers are more easily activated, increasing their reactivity. The cationic groups in the cationic modifier react more readily with the hydroxyl groups in the wood cellulose, forming more stable covalent bonds. By chemically grafting more cationic modifiers onto the wood fibers, more positively charged groups are introduced onto the wood surface. In the dyeing solution, this makes the surface of the wood veneer fibers electropositive. These cationic groups can generate strong electrostatic attraction with the anions (such as sulfonate groups) in acid dyes, increasing the binding force between them and the acid dye molecules. This overcomes the technical bottleneck of low dye uptake due to low cationic modification in existing dyeing processes, thereby improving the dye adsorption rate during wood dyeing. Furthermore, it exhibits higher dye absorption and lower dye residue during the dyeing process, further demonstrating its advantages in dyeing efficiency and environmental friendliness. This invention utilizes the increased cationic groups introduced on the surface of wood fibers to achieve high dye uptake rates for acid dye molecules through chemical and electrostatic adsorption. By employing a synergistic mechanism of chemical and electrostatic adsorption, the fixation efficiency of acid dyes on the fiber surface is significantly enhanced, and the concentration of dyeing solution during the dyeing process is reduced, thereby mitigating the environmental impact of dyeing wastewater.

[0018] Furthermore, this invention limits the concentration of the inorganic alkaline solution. The concentration of the inorganic alkaline solution has a significant impact on the degree of reaction of the surface groups of wood fibers. As the concentration of the inorganic alkaline solution increases, the dyeing rate of wood shows a trend of first increasing and then decreasing. The dyeing rate is lower at lower (0 g / L) and higher (greater than 50 g / L) concentrations. This indicates that not adding or adding less inorganic alkaline solution will lead to insufficient catalytic activation reaction, while excessively high inorganic alkaline solution concentration may cause hydrolysis of the cationic modifier, reduce the active epoxy groups, and reduce its modification effect.

[0019] Furthermore, the present invention specifies that the cationic modifier includes an epoxy quaternary ammonium salt cationic modifier, whose epoxy group is more likely to open in an alkaline environment, making it easier to react with the hydroxyl groups in wood and further improving the dyeing rate.

[0020] Furthermore, this invention limits the concentration of the acid dye dyeing solution, significantly reducing dye residue and treatment costs in dyeing wastewater. It is applicable to the dyeing and processing of wood materials such as reconstituted decorative veneers and thin wood veneers, and has broad industrial application prospects.

[0021] Data from the embodiments show that the dyeing method of the present invention increases the dye uptake rate to 96.27%, and can still achieve the dyeing effect of unmodified veneer even when the dyeing solution concentration is reduced by 40%. Attached Figure Description

[0022] Figure 1The staining rate curves for different sodium hydroxide solution concentrations and the actual sample images of the remaining staining solution (staining residue) after staining are shown. Detailed Implementation

[0023] This invention provides a method for staining wood, comprising the following steps: The wood is bleached to obtain bleached wood; The bleached wood was pretreated with an inorganic alkaline solution to obtain pretreated wood. The pretreated wood is subjected to cationic modification in a cationic modification solution to obtain cationic modified wood; the cationic modification solution includes a cationic modifier, an inorganic alkaline compound, and water; The cationic modified wood was placed in an acidic dye solution for dyeing to obtain cationic modified dyed wood.

[0024] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

[0025] This invention involves bleaching wood to obtain bleached wood.

[0026] In this invention, the wood is preferably wood veneer.

[0027] In this invention, the bleaching solution used for bleaching preferably contains the following components by mass percentage: 5% hydrogen peroxide, 0.4% sodium hydroxide, 10% sodium silicate, and 74.6% water.

[0028] In this invention, the preferred bleaching bath ratio is 20:1, the preferred temperature is 60°C, and the preferred time is 5 hours.

[0029] After bleaching is completed, the present invention preferably performs water washing and drying in sequence to obtain the bleached wood.

[0030] After obtaining bleached wood, the present invention pretreats the bleached wood with an inorganic alkaline solution to obtain pretreated wood.

[0031] In this invention, the concentration of the inorganic alkaline solution is preferably 0~50 g / L and not 0, specifically 0.1, 0.5, 1, 2, 5, 8, 10, 20, 30, 40 or 50 g / L. Pretreatment with the inorganic alkaline solution significantly improves the dyeing rate. This is because under alkaline conditions, the hydroxyl groups on the surface of wood fibers are more easily activated, thereby increasing their reactivity. The concentration of the inorganic alkaline solution has a significant impact on the degree of reaction of the fiber surface groups. As the concentration of the inorganic alkaline solution increases, the dyeing rate shows a trend of first increasing and then decreasing. The dyeing rate is low at both lower and higher concentrations. This indicates that not adding or adding a small amount of inorganic alkaline solution will lead to insufficient catalytic activation reaction, while excessively high concentrations of inorganic alkaline solution may cause hydrolysis of the cationic modifier, reducing the active epoxy groups and decreasing its modification effect.

[0032] In this invention, the inorganic alkaline solution preferably includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and potassium carbonate solution.

[0033] In this invention, the pretreatment is preferably performed by immersing the bleached wood in an inorganic alkaline solution.

[0034] In this invention, the pretreatment is preferably carried out at room temperature and pressure or at room temperature and pressure, and the time is preferably 0.5 to 1 hour. The pressure of the room temperature and pressure is preferably -0.075 to 0 MPa.

[0035] After obtaining the pretreated wood, the present invention further cationically modifies the pretreated wood in a cationic modification solution to obtain cationically modified wood; the cationic modification solution includes a cationic modifier, an inorganic alkaline compound, and water.

[0036] In this invention, the inorganic alkaline compound preferably includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0037] In this invention, the concentration of the inorganic alkaline compound in the cationic modified liquid is preferably 0~50 g / L and not 0, specifically 0.1, 0.5, 1, 2, 5, 8, 10, 20, 30, 40 or 50 g / L.

[0038] In this invention, the cationic modifier preferably includes epoxy quaternary ammonium salt cationic modifiers and / or chlorotriazine type quaternary ammonium salts.

[0039] In this invention, the epoxy quaternary ammonium salt cationic modifier preferably includes one or more of glycidyl dimethyl butyl ammonium chloride, glycidyl trimethyl ammonium chloride, and glycidyl triethyl ammonium chloride. The epoxy groups of the cationic modifier are more likely to open in an alkaline environment and react more readily with the hydroxyl groups in wood, thereby further improving the dyeing rate.

[0040] In this invention, the concentration of the cationic modifier in the cationic modified solution is preferably 0.1~30 g / L, specifically 0.1, 0.5, 1, 5, 10, 15, 20, 25 or 30 g / L.

[0041] In this invention, the preferred bath ratio of the cationic modified liquid to the bleached wood is 20:1.

[0042] In this invention, the preferred temperature for cationic modification is 35~95℃, specifically 35, 45, 55, 65, 75, 85 or 95℃, and the preferred time is 0.25~3h, specifically 0.25, 0.5, 1, 2 or 3h.

[0043] In this invention, the cation modification is preferably carried out under normal pressure conditions, without the need for a special pressure vessel.

[0044] After the pretreatment is completed, the present invention preferably adds a cationic modifier to the pretreated system to perform the cationic modification.

[0045] After the cationic modification is completed, the present invention preferably performs water washing and drying in sequence to obtain the cationic modified wood, without the need to add other auxiliary agents during the dyeing process.

[0046] After obtaining cationic modified wood, the present invention places the cationic modified wood in an acidic dyeing solution for dyeing to obtain cationic modified dyed wood.

[0047] In this invention, the dye in the acid dye dyeing solution preferably includes one or more of Acid Red 266, Acid Yellow 199 and Acid Blue 62.

[0048] In this invention, the concentration of the acid dye dyeing solution is preferably 0.36~0.6 g / L, specifically 0.36, 0.4, 0.45, 0.5, 0.55 or 0.6 g / L.

[0049] In this invention, the preferred dyeing temperature is 96~98℃, specifically 96, 97 or 98℃, and the preferred time is 5h.

[0050] In this invention, the dyeing bath solution ratio is preferably 1:20.

[0051] After the dyeing is completed, the present invention preferably washes away the residual dye on the surface with water and then dries it to obtain the cationic modified dyed wood.

[0052] In this invention, the dyeing process preferably further includes sequential lamination, molding, and slicing to obtain a cationic modified reconstituted decorative veneer. This invention does not impose specific limitations on the parameters of the lamination, molding, and slicing processes; methods well-known to those skilled in the art can be used.

[0053] This invention first bleaches the wood, then pretreats it in an inorganic alkaline solution, then grafts it in an alkaline cationic modified solution, and finally dyes it with acidic dyes under salt-free conditions. This reduces the concentration of the dye solution and optimizes the process, thereby significantly reducing the environmental impact of dyeing wastewater while increasing the dyeing rate.

[0054] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0055] Example 1 The wood veneer was immersed in a bleaching solution (containing the following components by mass percentage: 5% hydrogen peroxide, 0.4% sodium hydroxide, 10% sodium silicate, and 74.6% water) at a liquor ratio of 1:20. After bleaching at 60°C for 5 hours, it was removed, washed with distilled water until neutral, and then dried in an oven at 85°C for 4 minutes to obtain bleached veneer. Bleached veneer was pretreated in a sodium hydroxide solution (1 g / L) for 30 minutes under reduced pressure (-0.075 MPa) to obtain pretreated wood. Then, the cationic modifier glycidyltrimethylammonium chloride was added and stirred to dissolve it, forming a cationic modification solution. The pretreated wood was then cationic modified. The sodium hydroxide concentration in the cationic modification solution was 1 g / L, the cationic modifier concentration was 25 g / L, the temperature was raised to 65℃, the cationic modification time was 1 hour, and the ratio of cationic modification solution to pretreated wood was 20:1. After modification, the veneer was removed, washed with water until neutral, and dried to obtain cationic modified veneer. The cationic modified veneer was dyed in a dyeing solution at 95℃ for 5 hours. After that, the veneer was removed, the residual dye on the surface was washed off, and the veneer was dried until the moisture content was 12% to obtain the cationic modified dyed veneer. The dyeing bath-to-solution ratio was 1:20. The dyeing solution included Acid Red 266 and water, and the concentration of Acid Red 266 in the dyeing solution was 0.6 g / L.

[0056] Example 2 Same as Example 1, except that the concentration of the cationic modifier is 5 g / L.

[0057] Example 3 Same as Example 1, except that the concentration of the cationic modifier is 10 g / L.

[0058] Example 4 Same as in Example 1, except that the concentration of Acid Red 266 in the staining solution is 0.36 g / L.

[0059] Example 5 Same as Example 1, except that the dye used in the dyeing solution is Acid Yellow 199.

[0060] Example 6 Same as Example 1, except that the dye used in the dyeing solution is Acid Blue 62.

[0061] Example 7 Same as in Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 0.1 g / L.

[0062] Example 8 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 50 g / L.

[0063] Example 9 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 0.5 g / L.

[0064] Example 10 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 2 g / L.

[0065] Example 11 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 5 g / L.

[0066] Example 12 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 8 g / L.

[0067] Example 13 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 10 g / L.

[0068] Example 14 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 20 g / L.

[0069] Example 15 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 30 g / L.

[0070] Example 16 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 40 g / L.

[0071] Example 17 Same as Example 1, except that glycidyltrimethylammonium chloride is replaced with a chlorotriazine-type quaternary ammonium salt.

[0072] Comparative Example 1 (Ctrl) Same as Example 1, except that the pretreated single plate is not pretreated and is cationic modified.

[0073] Comparative Example 2 Same as Example 1, except that the concentration of sodium hydroxide solution in both the pretreatment and cationic modification solutions is 0 g / L.

[0074] Comparative Example 3 Same as Example 5, except that the pretreated single plate is not pretreated and is cationic modified.

[0075] Comparative Example 4 Same as Example 6, except that the pretreated single plate is not pretreated and is cationic modified.

[0076] The dyeing rate and surface color depth of the obtained samples were tested according to GB / T 23976.1-2009 "Determination of Dyeing Rate Curve and Method for Determination of Color Uptake Rate", as shown in Table 1. It can be seen that compared with the untreated veneer (Comparative Example 1), cationic modification of the veneer changes the surface electrical properties of the wood veneer fibers in the dyeing solution, reduces the binding resistance between the veneer and acid dye molecules, and promotes dye uptake. Example 1 increased the dyeing rate of the obtained cationic modified dyed veneer by 2.38 times, and the surface color depth was significantly better than that of the veneer obtained in Comparative Example 1. Compared with the untreated single-layer plates dyed with yellow and blue acid dyes in Comparative Examples 3-4, the cationic modified single-layer plates can achieve a 2.92-fold and 2.38-fold increase in dye uptake for Acid Yellow 199 and Acid Blue 62, respectively. Compared with Comparative Example 2, the staining effects of the cationic modified staining veneers obtained in Examples 1 and 7-16 show that the presence or absence of sodium hydroxide causes a significant difference in the cationic modification effect. -The concentration of NaOH has a significant impact on the degree of reaction of the fiber surface groups. Too high a concentration of NaOH can lead to a decrease in the modification effect. As the concentration of NaOH increases, the dyeing rate of the cationic modified dyeing veneer shows a trend of first increasing and then decreasing. The dyeing rate of the cationic modified dyeing veneer prepared at lower and higher NaOH concentrations is lower. This indicates that no or less NaOH will lead to insufficient catalytic activation reaction, while too high a concentration of NaOH may cause the cationic modifier to hydrolyze, reduce the active epoxy groups, and reduce its modification effect. Figure 1 The staining rate curves for different sodium hydroxide solution concentrations and the actual sample images of the remaining staining solution (staining residue) after staining are shown.

[0077] Excessively high concentrations of cationic modifiers have limited effect on improving dyeing rates. As shown in Table 1 for Examples 1-3, reducing the cationic modifier concentration to 5-10 g / L only decreases the dyeing rate of the cationic modified dyeing veneers by 8.3-12.2%, which is still far superior to untreated veneers. Furthermore, the surface color depth of the obtained cationic modified dyeing veneers actually increases. Lowering the modifier concentration reduces the cost of cationic modification treatment, making industrial use possible. Comparing Example 1 and Example 17, it can be seen that Example 1 has a higher dyeing rate. The reason is that the epoxy group of the cationic modifier is more likely to open in an alkaline environment, making it easier to react with the hydroxyl groups in the wood.

[0078] Table 1. Test results of dyeing rate and surface color depth of samples obtained from the examples and comparative examples.

[0079] Table 2 shows the test results of the surface color parameters of the samples obtained in the examples and comparative examples. It can be seen that, compared with the untreated veneer (Comparative Example 1), after the veneer is cationic modified, the dyeing effect of the untreated veneer under the dyeing solution with a concentration of 0.36 g / L can be obtained under the dyeing solution with a concentration of 0.6 g / L. In comparison, the color difference is only 2.5.

[0080] Table 2. Test results of surface color parameters of samples obtained from the examples and comparative examples.

[0081] As can be seen from the above, the dyeing method provided by the present invention can enable wood to have a high dyeing rate and surface color depth, and can reduce the amount of dye used in the dyeing solution and the cost of dyeing wastewater treatment.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for staining wood, characterized in that, Includes the following steps: The wood is bleached to obtain bleached wood; The bleached wood was pretreated with an inorganic alkaline solution to obtain pretreated wood. The pretreated wood is subjected to cation modification in a cation modification solution to obtain cation-modified wood; The cationic modified liquid comprises a cationic modifier, an inorganic alkaline compound, and water; The cationic modified wood was placed in an acidic dye solution for dyeing to obtain cationic modified dyed wood.

2. The staining method according to claim 1, characterized in that, The concentration of the inorganic alkaline solution is 0~50g / L and is not 0.

3. The staining method according to claim 1, characterized in that, The inorganic alkaline compound includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

4. The staining method according to claim 1 or 3, characterized in that, The concentration of the inorganic alkaline compound in the cationic modified solution is 0~50g / L and is not 0.

5. The staining method according to claim 1, characterized in that, The cationic modifiers include epoxy quaternary ammonium salt cationic modifiers and / or chlorotriazine quaternary ammonium salts.

6. The staining method according to claim 5, characterized in that, The epoxy quaternary ammonium salt cationic modifier includes one or more of glycidyl dimethyl butyl ammonium chloride, glycidyl trimethyl ammonium chloride, and glycidyl triethyl ammonium chloride.

7. The staining method according to claim 1 or 5, characterized in that, The concentration of the cationic modifier in the cationic modified solution is 0.1~30 g / L.

8. The staining method according to claim 1, characterized in that, The cationic modification is performed at a temperature of 35~95℃ for a time of 0.25~3h.

9. The staining method according to claim 1, characterized in that, The concentration of the acid dye dyeing solution is 0.36~0.6 g / L.

10. The staining method according to claim 1, characterized in that, The dyeing process also includes sequential lamination, molding, and slicing.

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