Thermal modified rubber wood with uniform color and control method thereof

Abstract

The invention provides heat modified rubber wood uniform in color and a control method thereof. The control method comprises the specific steps that (1) the rubber wood is cut into square timber or plates; (2) adding into an oxidation solution, performing ultrasonic extraction, and performing microwave hydrothermal treatment; (3) carrying out high-pressure water washing treatment; (4) stacking and air-drying, and standing for 3-10 days until the water content is less than 70%; (5) performing staged drying treatment, specifically, raising the temperature to 50 DEG C and maintaining for 0.5-2 hours, then raising the temperature to 60 DEG C and maintaining for 0.5-5 hours, continuously raising the temperature to 70 DEG C and maintaining for 0.5-2 hours, raising the temperature to 80 DEG C and maintaining for 0.5-2 hours, continuously raising the temperature to 85 DEG C and maintaining for 0.5-2 hours, then raising the temperature to 90 DEG C and maintaining for 1-4 hours, continuously raising the temperature to 95 DEG C and maintaining for 1-4 hours, and finally raising the temperature to 120-140 DEG C and maintaining for 12-48 hours. The rubber wood which is rapidly dried and uniform in color is obtained; and (6) performing color regulation and control by using the prediction model to obtain uniform rubber wood with a preset color, performing cooling and humidity regulation, and discharging the rubber wood out of the cellar. By means of the method, the rubber wood uniform in color is obtained, meanwhile, the expected color can be achieved according to the prediction model, and the value of the thermal modification rubber wood is improved.

Description

Technical Field

[0001] The invention relates to the technical field of wood modification, and in particular to heat-modified rubber wood with uniform color and a control method thereof. Background Art

[0002] At present, high temperature heat treatment technology (thermal modification treatment) is a means of physical modification of wood. Generally, the temperature is raised to between 160-260°C in hot oil or oxygen-deficient environment (water vapor, inert gas protection, etc.), and the heat causes the wood to undergo physical and chemical reactions to achieve the purpose of improving its surface color decorativeness, dimensional stability, biological durability, and environmental safety. However, it is difficult to obtain the expected specific color and uniform color of wood with existing technology.

[0003] For example, patent CN1449900A provides a physical control method for wood color, which is to put wood (mainly light-colored fast-growing wood) into a sealed container and pass saturated steam below 200°C for treatment. By regulating the initial moisture content of the wood, the temperature of the saturated steam and the treatment time, the original color of the fast-growing wood is darkened to brown without substantially affecting the mechanical properties of the fast-growing wood. Although this method greatly improves the decorative properties and decorative effects of various fast-growing wood products, it does not solve the problem of color uniformity or the problem of controlling the expected color.

[0004] Patent CN105415470A provides a method for accurately controlling the color of bamboo, including the following process steps: (1) establishing a three-dimensional sample library of bamboo heat treatment; (2) converting the sample library into a color library; (3) preliminary selection of heat treatment schemes; (4) multi-dimensional optimization of heat treatment schemes; (5) database refinement. A three-dimensional database of sample colors of bamboo after heat treatment is established using the three factors of temperature, medium, and time, providing a benchmark for the heat treatment scheme of the target bamboo color. Due to the different characteristics of different heat treatment media, a reasonable heat treatment scheme can be selected from multiple technical dimensions. Although the heat treatment scheme can be selected by the size of the total color difference value, it can achieve the effect of controlling different colors, but lacks an accurate prediction model to achieve the desired color regulation.

[0005] Patent CN112589939A provides a method for quantitatively controlling the surface color of teak solid wood floor heating floor, which is based on the surface color requirements of the teak floor heating floor to be regulated, obtains the corresponding set heat treatment temperature and set heat treatment time from the surface color physical comparison database, selects the corresponding colorimetric parameters in the colorimetric parameter database; substitutes the overall color difference parameter in the colorimetric parameter into the regression equation of the corresponding heat treatment time condition, and calculates the corresponding calculated heat treatment temperature; compares all the calculated heat treatment temperatures obtained, and selects the lowest calculated heat treatment temperature as the actual heat treatment temperature; heat treats the blank; the present invention has the characteristics of being able to quantitatively control the surface color of the teak solid wood floor heating floor blank and improve the surface color difference. Although this method uses a regression model, it has limitations and cannot be applied to the wood heat treatment modification (heat treatment time and temperature) of the present invention.

[0006] Patent CN112589939A provides a prediction method and prediction model for the color of the tangentially cut surface of heat-treated wood. The present invention provides a prediction method and prediction model for the color of the tangentially cut surface of heat-treated wood. According to the established color prediction model, the color change of the tangentially cut surface of the heat-treated wood at different positions along the thickness direction can be accurately predicted without destroying the heat-treated wood; and by controlling the heat treatment temperature, the color of the tangentially cut surface of the heat-treated wood at a specified position along the thickness direction can be regulated. Although this method can use the model to predict color, it does not fundamentally solve the problem of color uniformity of heat-treated wood, and the complexity of the model is limited in actual production applications.

[0007] Therefore, a method is needed to achieve uniform rubber wood with the expected specific color, which is an effective means to improve the value of thermally modified rubber wood and has practical significance. Summary of the invention

[0008] In view of this, the present invention provides a heat-modified rubber wood with uniform color and a control method thereof.

[0009] The technical solution of the present invention is achieved in this way:

[0010] A heat-modified rubber wood with uniform color, comprising the following preparation steps:

[0011] (1) cutting the rubber wood into square timber or plates to obtain pretreated rubber wood;

[0012] (2) adding the pretreated rubber wood to an oxidizing solution, ultrasonically extracting, and then subjecting the pretreated rubber wood to a microwave hydrothermal treatment to obtain softened rubber wood;

[0013] (3) subjecting the softened rubber wood to high pressure water washing to obtain washed rubber wood;

[0014] (4) piling the washed rubber wood for air drying for 3-10 days until the moisture content is less than 70%, thereby obtaining air-dried rubber wood;

[0015] (5) Drying the air-dried rubber wood in stages, specifically: first raise the temperature to 50±2°C and maintain for 0.5-2h, then raise the temperature to 60±2°C and maintain for 0.5-5h, continue to raise the temperature to 70±2°C and maintain for 0.5-2h, raise the temperature to 80±2°C and maintain for 0.5-2h, continue to raise the temperature to 85±2°C and maintain for 0.5-2h, then raise the temperature to 90±2°C and maintain for 1-4h, continue to raise the temperature to 95±2°C and maintain for 1-4h, and finally raise the temperature to 120-140°C and maintain for 12-48h, to obtain rubber wood with uniform color after rapid drying;

[0016] (6) Using the prediction model to control the color, uniform rubber wood with a preset color is obtained, and the temperature and humidity are reduced before the wood is taken out of the cellar.

[0017] Furthermore, in step (1), the thickness of the pretreated rubber wood is 1-10 cm.

[0018] Furthermore, in step (2), the oxidizing solution is hydrogen peroxide or peracetic acid solution with a concentration of 0.1%-3% v / v.

[0019] Furthermore, in step (2), the ultrasonic extraction is performed at 200-300 rpm and 30-50° C. for 30-60 min.

[0020] Furthermore, in step (2), the microwave hydrothermal treatment is heated at 500-800W and 50-90°C for 2-4h.

[0021] The present invention uses ultrasonic extraction supplemented by microwave hydrothermal treatment to maximize the dissolution of substances without changing the molecular structure of the effective components, thereby achieving efficient separation of rubber wood extracts and starch, protein and sugars. The color of the rubber wood after the hydrothermal treatment is changed to a certain extent, which has a mild bleaching effect and achieves color uniformity.

[0022] Furthermore, in step (3), the pressure of the high-pressure water washing treatment is 1.8-2.2 MPa, the temperature is 20-25° C., the flow rate is 10-20 L / min, and the time is 20-30 min.

[0023] The invention uses high-pressure water washing to clean the surface of the rubber wood and the residual oxidation solution inside.

[0024] Furthermore, in step (6), the color control is specifically as follows: setting the temperature range to 150-220°C, the time to 60-360min, continuing to spray steam during the heating process, and stopping the spray steam after reaching the preset temperature, and continuing to dry for a preset time.

[0025] Furthermore, in step (6), the cooling and humidity adjustment is to cool the temperature to 70-80°C, adjust the humidity, and when the moisture content is 8%-12%, reduce the temperature to below 40°C.

[0026] A control method for heat-modified rubber wood with uniform color is provided, and uniform rubber wood with target color is obtained through a color prediction model.

[0027] Furthermore, the regression equation of the color prediction model is:

[0028] ΔE * =406.88-3.84T-0.27t+0.0010Tt+0.0094T 2 +0.0002t 2

[0029] L * =-3.05+1.28T+0.01t-0.0007Tt-0.0047T 2 +0.00020t 2

[0030] a * =-69.46+0.79T+0.05t-0.00020Tt-0.0020T 2 -0.00002t 2

[0031] b * =-122.43+1.65T+0.10t-0.0006Tt-0.0046T 2 -0.00001t 2

[0032] Where, ΔE * is the color difference, L * is the brightness value, a * and b * is the chromaticity index, T is the temperature, and t is the time.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention treats rubber wood by ultrasonic extraction assisted by microwave hydrothermal treatment in an oxidizing solution, and then performs high-pressure water washing and air drying, and then performs staged drying treatment. After high-temperature heat treatment, rubber wood with uniform color is obtained, and the expected color is achieved according to the prediction model, thereby improving the value of heat-modified rubber wood.

[0035] 2. The present invention establishes a color prediction model for thermally modified rubber wood, and measures the lightness value L * 、Chromaticity index a * 、b * and color difference ΔE * It is related to the function of heat treatment temperature and heat treatment time. According to this prediction model, the desired expected color can be achieved by adjusting the heat treatment temperature and heat treatment time, which can reduce production costs and improve production efficiency, and have rich decorative effects.

[0036] 3. The ultrasonic extraction of the oxidation solution of the present invention is assisted by microwave hydrothermal treatment to reduce the extract content in rubber wood to the greatest extent, and the treatment solution cost is low; air drying can not only reduce moisture content, reduce energy consumption, but also release the stress of rubber wood, which is conducive to reducing the cracking problem in high temperature treatment; the specific staged drying treatment provided not only avoids the early anticorrosion operation, but also greatly reduces the early drying time cost, and the late drying can significantly reduce the starch and sugar content in rubber wood, preventing pests and diseases from invading. The time cycle of the whole staged drying treatment is 2-3 days, and the time of conventional drying needs 5-15 days, which reduces production costs and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The rubber wood obtained in Example 1-6 (150-220° C., 210 min).

[0038] Figure 2 The rubber wood obtained in Example 1 (150° C., 210 min) and Comparative Example 1 (150° C., 210 min).

[0039] Figure 3 The rubber wood obtained from Example 3 (185° C., 210 min) and Comparative Example 2 (185° C., 210 min).

[0040] Figure 4 The rubber wood obtained from Example 3 (185° C., 210 min) and Comparative Example 3 (185° C., 210 min).

[0041] Figure 5 The rubber wood obtained in Example 3 (185° C., 210 min) and Comparative Example 4 (185° C., 210 min). DETAILED DESCRIPTION

[0042] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0043] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0044] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0045] Example 1

[0046] A heat-modified rubber wood with uniform color, comprising the following preparation steps:

[0047] (1) cutting the rubber wood into square timber or plates with a thickness of 5 cm to obtain pretreated rubber wood;

[0048] (2) adding the pretreated rubber wood to 1% v / v hydrogen peroxide, ultrasonically extracting at 250 rpm and 40° C. for 45 min, and then subjecting the pretreated rubber wood to microwave hydrothermal treatment at 600 W and 70° C. for 3 h to obtain softened rubber wood;

[0049] (3) subjecting the softened rubber wood to high-pressure water washing for 25 min (pressure of 2.0 MPa, temperature of 23° C., flow rate of 15 L / min) to obtain washed rubber wood;

[0050] (4) piling the washed rubber wood for air drying for 5 days until the moisture content is less than 70%, thereby obtaining air-dried rubber wood;

[0051] (5) The air-dried rubber wood is dried in stages, specifically: first, the temperature is raised to 50°C and maintained for 0.5-2h, then the temperature is raised to 60°C and maintained for 2h, then the temperature is raised to 70°C and maintained for 1h, the temperature is raised to 80°C and maintained for 1h, then the temperature is raised to 85°C and maintained for 1h, then the temperature is raised to 90°C and maintained for 2h, then the temperature is raised to 95°C and maintained for 2h, and finally the temperature is raised to 130°C and maintained for 24h, to obtain rubber wood with uniform color after rapid drying;

[0052] (6) Raise the temperature to 150°C, and continue to spray steam during the heating process. When the temperature reaches 150°C, stop spraying steam and continue drying for 60 min, 100 min, 210 min, 240 min, 320 min, and 360 min, then cool down to 75°C and adjust the humidity. When the moisture content reaches 10%, continue to reduce the temperature to below 40°C and then take the product out of the cellar.

[0053] Example 2

[0054] The difference from Example 1 is that the temperature of step (6) is set to 160° C., and the rest is the same as Example 1.

[0055] The step (6) is as follows: heating to 160°C, continuously spraying steam during the heating process, stopping the spraying steam after reaching 150°C, and continuing drying for 60 min, 100 min, 210 min, 240 min, 320 min, and 360 min, respectively, then cooling to 75°C, adjusting the humidity, and when the moisture content is 10%, continuing to reduce the temperature to below 40°C before taking out of the cellar.

[0056] Example 3

[0057] The difference from Example 1 is that the temperature of step (6) is set to 185°C, and the rest is the same as Example 1.

[0058] The step (6) is as follows: the temperature is raised to 185°C, and steam is continuously sprayed during the heating process. When the temperature reaches 150°C, the steam is stopped, and the drying is continued for 60 min, 100 min, 210 min, 240 min, 320 min, and 360 min, respectively. The temperature is then lowered to 75°C for humidity adjustment. When the moisture content reaches 10%, the temperature is further lowered to below 40°C before being taken out of the cellar.

[0059] Example 4

[0060] The difference from Example 1 is that the temperature of step (6) is set to 200° C., and the rest is the same as Example 1.

[0061] The step (6) is as follows: the temperature is raised to 200°C, and steam is continuously sprayed during the heating process. When the temperature reaches 150°C, the steam is stopped, and the drying is continued for 60 min, 100 min, 210 min, 240 min, 320 min, and 360 min, respectively. The temperature is then lowered to 75°C for humidity adjustment. When the moisture content reaches 10%, the temperature is further lowered to below 40°C before being taken out of the cellar.

[0062] Example 5

[0063] The difference from Example 1 is that the temperature of step (6) is set to 210° C., and the rest is the same as Example 1.

[0064] The step (6) is as follows: heating to 210°C, continuously spraying steam during the heating process, stopping the spraying steam after reaching 150°C, and continuing drying for 60min, 100min, 210min, 240min, 320min, and 360min, respectively, then cooling to 75°C, adjusting the humidity, and when the moisture content is 10%, continuing to reduce the temperature to below 40°C before taking out of the cellar.

[0065] Example 6

[0066] The difference from Example 1 is that the temperature of step (6) is set to 220° C., and the rest is the same as Example 1.

[0067] The step (6) is as follows: heating to 220°C, continuously spraying steam during the heating process, stopping the spraying steam after reaching 150°C, and continuing drying for 60 min, 100 min, 210 min, 240 min, 320 min, and 360 min, respectively, then cooling to 75°C, adjusting the humidity, and when the moisture content is 10%, continuing to reduce the temperature to below 40°C before taking out of the cellar.

[0068] Test example

[0069] Measurement method: According to the CIE standard colorimetric system, the three basic indicators of rubber wood are measured: * 、a * and b * The color of heat-treated rubber wood is accurately and quantitatively characterized, and the overall color difference ΔE is calculated based on the experimental results. * The rubber wood prepared in Examples 1-6 was measured by using the visual physical parameter analysis.

[0070] Where: L * is the brightness, a completely white object is considered 100, and a completely black object is considered 0; a * b is the chromaticity index of the red-green axis. The larger the positive value, the more the color tends to red, and the larger the negative value, the more the color tends to green. * It is the chromaticity index of the yellow-blue axis. The larger the positive value, the more yellow the color is, and the larger the negative value, the more blue the color is.

[0071] The L was measured by portable integrating sphere spectrophotometer. * 、a * and b * The measurement results are shown in Table 1.

[0072] Color difference ΔE * The calculation formula is: ΔE * =(ΔL *2 +Δa *2 +Δb *2 ) 1 / 2

[0073] ΔL * is the brightness change before and after heat treatment, Δa * is the change in the red-green axis chromaticity index before and after heat treatment, Δb * It is the change value of the yellow-blue axis chromaticity index before and after heat treatment.

[0074] Table 1

[0075]

[0076]

[0077]

[0078] As can be seen from Table 1, the rubber wood obtained by different heat treatment temperatures and heat treatment times has different colors and rich surface decoration. The heat-treated rubber wood of the present invention can improve the color of the rubber wood, and the color is uniform, the aesthetics is enhanced, the decoration is rich, and the use value of the rubber wood is improved.

[0079] In addition, based on the test results of Examples 1-6, a surface color prediction model for rubber wood was established.

[0080] ΔE * =406.88-3.84T-0.27t+0.0010Tt+0.0094T 2 +0.0002t 2

[0081] L * =-3.05+1.28T+0.01t-0.0007Tt-0.0047T 2 +0.00020t 2

[0082] a * =-69.46+0.79T+0.05t-0.00020Tt-0.0020T 2 -0.00002t 2

[0083] b * =-122.43+1.65T+0.10t-0.0006Tt-0.0046T 2 -0.00001t 2

[0084] According to the regression equation of the color prediction model, the present invention selects rubber wood treated with a drying time of 180 min and temperatures of 170° C., 190° C. and 210° C., and calculates the predicted value ΔE by the regression equation of the color prediction model. * , L * 、a * and b * The actual measured values ​​obtained by the portable integrating sphere spectrocolorimeter are shown in Table 2.

[0085] Table 3

[0086]

[0087]

[0088] As can be seen from Table 2, the L *The relative errors between the measured values ​​and the predicted values ​​calculated by the regression equation of the color prediction model are both less than 5%, indicating that the model has good predictive performance.

[0089] Comparative Example 1

[0090] The difference from Example 1 is that no oxidation treatment is performed in step (2), and the rest is the same as Example 1.

[0091] The step (2) of this comparative example is specifically as follows: adding the pretreated rubber wood into the aqueous solution, ultrasonically extracting at 250 rpm and 40° C. for 45 min, and then subjecting the pretreated rubber wood to a microwave hydrothermal treatment at 600 W and 70° C. for 3 h to obtain softened rubber wood.

[0092] from Figure 2 It can be seen that the rubber wood prepared in Comparative Example 1 has uneven color and is darker than that in Example 1.

[0093] Comparative Example 2

[0094] The difference from Example 3 is that step (2) lacks microwave heating, that is, only ultrasonic hydrothermal extraction treatment is performed, and the rest is consistent with Example 3.

[0095] The step (2) of this comparative example is specifically as follows: adding the pretreated rubber wood into 1% v / v hydrogen peroxide, and ultrasonically extracting at 250 rpm and 40° C. for 45 min to obtain softened rubber wood.

[0096] from Figure 3 It can be seen that the rubber wood prepared in Comparative Example 2 has uneven color compared to that in Example 3, with some colors being darker and some lighter.

[0097] Comparative Example 3

[0098] The difference from Example 3 is that the washing procedure in step (3) is missing, and the rest is the same as Example 3.

[0099] from Figure 4 It can be seen that the rubber wood prepared in Comparative Example 3 is uneven in color and has stripe marks compared to Example 3.

[0100] Comparative Example 4

[0101] The difference from Example 3 is that step (5) lacks a staged drying process, and the rest is consistent with Example 3.

[0102] The step (5) of this comparative example is specifically as follows: the air-dried rubber wood is subjected to rapid high-temperature drying, firstly the temperature is raised to 60°C and maintained for 2 hours, then the temperature is raised to 80°C and maintained for 0.5 hours, then the temperature is further raised to 95°C and maintained for 2 hours, and finally the temperature is raised to 130°C and maintained for 24 hours, to obtain the rapidly dried rubber wood.

[0103] from Figure 5 It can be seen that the rubber wood prepared in Comparative Example 4 has uneven color, drying defects, cracks, etc. compared with Example 3.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A heat-modified rubber wood with uniform color, characterized in that: The method comprises the following preparation steps: (1) cutting the rubber wood into square timber or plates to obtain pretreated rubber wood; (2) adding the pretreated rubber wood to an oxidizing solution, ultrasonically extracting, and then subjecting the pretreated rubber wood to a microwave hydrothermal treatment to obtain softened rubber wood; (3) subjecting the softened rubber wood to high pressure water washing to obtain washed rubber wood; (4) piling the washed rubber wood for air drying for 3-10 days until the moisture content is less than 70%, thereby obtaining air-dried rubber wood; (5) Drying the air-dried rubber wood in stages, specifically: first raise the temperature to 50±2°C and maintain for 0.5-2h, then raise the temperature to 60±2°C and maintain for 0.5-5h, continue to raise the temperature to 70±2°C and maintain for 0.5-2h, raise the temperature to 80±2°C and maintain for 0.5-2h, continue to raise the temperature to 85±2°C and maintain for 0.5-2h, then raise the temperature to 90±2°C and maintain for 1-4h, continue to raise the temperature to 95±2°C and maintain for 1-4h, and finally raise the temperature to 120-140°C and maintain for 12-48h, to obtain rubber wood with uniform color after rapid drying; (6) Using the prediction model to control the color, uniform rubber wood with a preset color is obtained, and the temperature and humidity are reduced before the wood is taken out of the cellar.

2. The heat-modified rubber wood with uniform color as claimed in claim 1, characterized in that: In step (1), the thickness of the pretreated rubber wood is 1-10 cm.

3. The heat-modified rubber wood with uniform color as claimed in claim 1, characterized in that: In step (2), the oxidizing solution is hydrogen peroxide or peracetic acid solution with a concentration of 0.1%-3% v / v.

4. The heat-modified rubber wood with uniform color as claimed in claim 1, characterized in that: In step (2), the ultrasonic extraction is carried out at 200-300 rpm and 30-50° C. for 30-60 min.

5. The heat-modified rubber wood with uniform color as claimed in claim 1, characterized in that: In step (2), the microwave hydrothermal treatment is performed at 500-800W and 50-90°C for 2-4h.

6. The heat-modified rubber wood with uniform color as claimed in claim 1, characterized in that: In step (3), the pressure of the high-pressure water washing treatment is 1.8-2.2 MPa, the temperature is 20-25° C., the flow rate is 10-20 L / min, and the time is 20-30 min.

7. The heat-modified rubber wood with uniform color as claimed in claim 1, characterized in that: In step (6), the color control is specifically as follows: setting the temperature range to 150-220°C, the time to 60-360 minutes, continuing to spray steam during the heating process, and stopping the spray steam after reaching the preset temperature, and continuing to dry according to the preset time.

8. The heat-modified rubber wood with uniform color as claimed in claim 1, characterized in that: In step (6), the temperature is lowered to 70-80°C for humidity control, and when the moisture content is 8%-12%, the temperature is lowered to below 40°C.

9. The method for controlling heat-modified rubber wood with uniform color according to any one of claims 1 to 8, characterized in that: The color prediction model is used to obtain uniform rubber wood of target color.

10. The method for controlling heat-modified rubber wood with uniform color according to claim 9, characterized in that: The regression equation of the color prediction model is: ΔE*=406.88-3.84T-0.27t+0.0010Tt+0.0094T 2 +0.0002t 2 L*=-3.05+1.28T+0.01t-0.0007Tt-0.0047T 2 +0.00020t 2 a*=-69.46+0.79T+0.05t-0.00020Tt-0.0020T 2 -0.00002t 2 b*=-122.43+1.65T+0.10t-0.0006Tt-0.0046T 2 -0.00001t 2 Among them, ΔE* is the color difference, L* is the lightness value, a* and b* are the chromaticity indexes, T is the temperature, and t is the time.

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