Highly functional wood with a surface modified by high-speed friction treatment

Abstract

Aim to improve the functionality of wood surfaces. [Solution] The present invention provides wood whose surface has been modified by high-speed friction treatment, the wood surface modification being to improve water repellency, smoothness, or gloss, and the high-speed friction treatment is a process in which the wood is friction-treated while a high-speed rotating metallic cylindrical tool applies a predetermined pressure to the wood surface, and the wood is friction-treated by feeding the wood at a predetermined speed while pressing the high-speed rotating metallic cylindrical tool against the wood with a predetermined reduction. The high-speed wood surface friction treatment device of the present invention that achieves this includes a base on which the wood is placed, a metallic cylindrical tool with a smooth surface that can be rotated at high speed, a mechanism for feeding the base with the wood placed on it at a predetermined speed, and a mechanism for pressing the metallic cylindrical tool against the surface of the wood placed on the base with a predetermined reduction.

Description

[Technical Field]

[0001] The present invention relates to wood whose surface has been modified by high-speed friction treatment, a method for modifying the wood, and an apparatus for realizing the same. [Background technology]

[0002] In recent years, the acceleration of global warming due to the increase in atmospheric carbon dioxide has become a problem, and numerous attempts have been made to reduce atmospheric carbon dioxide. Because trees grow by absorbing carbon dioxide from the atmosphere and wood is a material that accumulates carbon from the atmosphere within its structure, there is a need to expand the use of wood in order to realize a decarbonized society. One of the attempts is to improve the functionality of wood, and in particular, improving the functionality of wood surfaces has attracted attention. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-186338 Summary of the Invention [Problem to be solved by the invention]

[0004] Examples of wood surface treatments include chemical treatments and coatings of wood surfaces. The chemicals and coatings used for chemical treatments and coatings of wood surfaces are prepared by methods separate from the wood itself, resulting in complex processes when applied to wood. Furthermore, many of these chemicals and coatings are chemically synthesized rather than naturally occurring, and therefore often contain substances that impact the global environment and contribute to global warming. This offsets the inherent benefits of wood (e.g., its role in preventing global warming). Therefore, there is a demand for improving the properties of wood itself and enhancing the functionality of wood and its surfaces. Friction-induced chemical reactions (tribochemical reactions) have been proposed as a technique for producing fluorine-containing polymer composite particles using cellulose (Patent Document 1). While this technique is considered useful as a means of enhancing the functionality of wood, it has rarely been applied to wood itself. [Means for solving the problem]

[0005] The present invention improves the functionality of wood surfaces by modifying the wood itself using a method that fully utilizes the properties of the wood itself, and achieves high functionality of wood and wood surfaces through tribochemical reactions, and specifically has the following features. (1) The present invention relates to wood whose surface has been modified by high-speed friction treatment of the wood surface, and the modification of the wood surface is to improve water repellency, smoothness, or gloss. The high-speed friction treatment is a process of friction-processing the wood while applying a predetermined pressure to the wood surface with a metal cylindrical tool (referred to as a metal cylinder) rotated at high speed, characterized in that the wood is friction-processed by feeding the wood at a predetermined speed while pressing the metal cylindrical tool (referred to as a metal cylinder) rotated at high speed against the wood with a predetermined pressure reduction. (2) In addition to (1), the present invention is characterized in that the surface of the wood subjected to the high-speed friction treatment is coated with a lubricant, the lubricant being linseed oil, and a silane coupling agent is applied to the surface of the wood. The metal cylinder is made of SK material (carbon tool steel) or SUS (304), and the surface of the metal cylinder is coated with a coating containing PTFE or graphite.

[0006] (3) The present invention is a method for high-speed friction processing of wood, which includes the steps of pressing a high-speed rotating metal cylindrical tool (referred to as a metal cylinder) against the surface of wood with a predetermined amount of pressure, and feeding the wood at a predetermined speed to friction-process the surface of the wood, and further includes the step of applying a lubricant to the surface of the wood before the high-speed friction processing method.Furthermore, the material of the metal cylinder is SK material (carbon tool steel) or SUS (304), and the surface of the metal cylinder is coated with a coating containing PTFE or graphite. (4) The present invention is a high-speed wood surface friction treatment device that includes a base on which wood is placed, a metal cylindrical tool (called a metal cylinder) with a smooth mirror surface that can rotate at high speed, a mechanism for feeding the base on which the wood is placed at a predetermined speed, and a mechanism for pressing the metal cylindrical tool (metal cylinder) against the surface of the wood placed on the base with a predetermined amount of pressure reduction. It also includes a mechanism for applying a lubricant to the wood surface, and the metal cylinder is made of SK material (carbon tool steel) or SUS (304), and the surface of the metal cylinder is coated with a coating containing PTFE or graphite. [Effects of the Invention]

[0007] According to the present invention, a method is used in which a rotating metal cylindrical tool (metal cylinder) is pressed against a wood surface with a predetermined pressure or reduction amount to deliver the wood, and high-speed friction treatment is performed on the wood surface. This method modifies the wood surface through a tribochemical reaction on the wood surface, thereby improving its functionality. For example, the water repellency of the wood surface can be increased, thereby improving the water resistance of the wood. Furthermore, the smoothness and gloss of the wood surface can be increased, thereby improving the appearance and texture of the wood. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the mechanism of a wood surface high-speed friction treatment device that performs high-speed friction treatment on a wood surface. [Figure 2] FIG. 2 is a diagram showing the change in cylindrical tool temperature depending on the feed rate. [Figure 3] FIG. 3 is a graph showing the feed rate dependency of the water droplet contact angle on the wood surface. [Figure 4] FIG. 4 is a diagram showing the feed rate dependency of the average roughness of the wood surface. [Figure 5] FIG. 5 is a diagram showing the feed rate dependency of the specular gloss of the wood surface. [Figure 6] FIG. 6 is a diagram (table) showing types of cylindrical tool components. [Figure 7] FIG. 7 shows the water droplet contact angle on various cylindrical tools after high-speed friction treatment. [Figure 8] FIG. 8 is a diagram showing the specular gloss of various cylindrical tools after friction treatment. [Figure 9] FIG. 9 is a diagram showing the surface roughness due to friction treatment for various cylindrical tools. [Figure 10] FIG. 10 is a diagram showing the surface roughness due to friction treatment for various cylindrical tools. [Figure 11] FIG. 11 shows the results of chemical analysis by SEM-EDX (scanning electron microscope energy dispersive X-ray spectroscopy) of the surface of wood (spruce) that was subjected to high-speed friction treatment under the condition of a Mo-PTFE cylindrical tool. [Figure 12] FIG. 12 shows the results of chemical analysis of the wood surface before high-speed friction treatment using SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy). [Figure 13] FIG. 13 shows SEM (scanning electron microscope) images of the surface of wood (spruce) before and after high-speed friction treatment. [Figure 14] FIG. 14 shows SEM (scanning electron microscope) images of the surface of wood (spruce) before and after high-speed friction treatment. [Figure 15] FIG. 15 shows the change in the water droplet contact angle on a wood surface that has been subjected to high-speed friction treatment after a silane coupling agent has been applied to the wood surface. [Figure 16] FIG. 16 is a schematic diagram showing the reaction mechanism of the silane coupling agent attached to the surface of wood. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention relates to improving the functionality of wood by modifying the wood surface (tribochemical reaction) through high-speed friction treatment to improve the wood surface's smoothness, water repellency, gloss, etc. Figure 1 is a schematic diagram showing the mechanism of a high-speed wood surface friction treatment device that performs high-speed friction treatment on wood surfaces. The high-speed wood surface friction treatment device 11 comprises a smooth-surfaced metal cylindrical tool 12, a base 13 on which the wood is placed, an electric cylinder 14 that advances the base 13 with the wood at a predetermined speed (feed rate), and a slide rail 15 that smoothly slides the base 13 with the wood. A load cell 16 is also located between the base 13 and the cylinder 14. The high-speed friction treatment of wood surfaces (high-speed wood surface friction treatment) involves rotating the metal cylindrical tool 12 at high speed, and feeding a piece of wood 21 placed on the base 13 at a predetermined feed rate in a predetermined direction, thereby frictionally processing the surface of the piece of wood 21 at high speed. This is a means of achieving a tribochemical reaction on the wood surface. The reduction amount is the distance between the bottom end of the tool 12 (the bottom end of the cylinder of the cylindrical tool) and the wood surface, and is the depth to which the tool presses against the wood surface. Pressing the wood surface with a specified reduction amount applies a specified pressure to the wood surface. Linseed oil is applied as a lubricant to the surface of the wood piece before rubbing, and high-speed rubbing is performed under lubrication. Without lubricant during rubbing, the wood surface becomes rough and uneven due to mechanical action, but under lubrication, the wood surface becomes smooth.

[0010] Figure 2 shows the change in tool temperature as a function of feed rate, measured using the apparatus shown in Figure 1. The (cylindrical) tool 12 was made of SK105 (carbon tool steel), and the tool temperature was measured using a thermocouple within 10 seconds after machining. The cylindrical tool had a diameter of 54 mm, a width of 120 mm, an arithmetic mean roughness of the cylindrical tool surface of 0.1 μm, a tool rotation speed of 8000 rpm, and a reduction of 300 μm. The wood samples used were cedar, cypress, and spruce, and the specimen sizes were 30 mm wide, 100 mm long, and 20 mm thick. The tool temperature increased during high-speed friction treatment, but decreased as the feed rate increased. This is likely due to the reduced contact time between the tool and the wood as the feed rate increased.

[0011] Figure 3 shows the feed rate dependency of the water droplet contact angle. The water droplet contact angle was measured using the drop method. A feed rate F of 0 mm / sec indicates that no (high-speed) friction treatment was performed, i.e., the untreated sample. The friction treatment increases the water droplet contact angle, improving water repellency. However, the feed rate dependency of the water droplet contact angle is small. From the above, it can be seen that high-speed friction treatment improves water repellency. Figure 4 shows the feed rate dependency of the average roughness. Surface roughness was measured using a tactile surface roughness meter (Tokyo Seimitsu, Surfcom130a). Here, the fiber direction is the direction of the wood grain, and the tangential direction is the direction perpendicular to the wood grain direction. In both cases, the average roughness is reduced by friction treatment, resulting in smoothing. However, this smoothing is only slightly dependent on the feed rate. From the above, it can be seen that high-speed friction treatment improves smoothness.

[0012] Figure 5 shows the dependence of specular gloss on feed rate. Specular gloss was measured using a glossmeter (PG-1M, manufactured by Nippon Denshoku Industries Co., Ltd.). Here, the fiber direction refers to the direction of the wood grain, and the tangential direction refers to the direction perpendicular to the grain direction. In both cases, high-speed rubbing treatment improved gloss. Furthermore, smoothness and gloss were slightly improved at a feed rate of F = 0.5 mm / sec compared to other feed rates. Regarding various functionalities (water droplet contact angle (water repellency), average roughness, and gloss) due to differences in wood species, the changes in these functionalities with increasing feed rate were nearly identical across all wood species. Furthermore, while cypress and spruce, which have similar specific gravities, showed similar values ​​for these functionalities, cedar showed values ​​that differed from the other two wood species. These findings suggest that high-speed rubbing treatment improves various functionalities (smoothness, gloss, and water repellency). In addition, functionality (smoothness, glossiness) excluding water repellency is best when the feed speed is 0.5 mm / sec, but the difference with other feed speeds (1 mm / sec or higher) is small, so from the perspective of productivity, it is thought that it would be better to increase the feed speed to 3 mm / sec.

[0013] Next, we will explain how tool components are transferred to improve functionality. Figure 6 is a diagram (table) showing the types of tool components. The symbols are associated with the tool components (tool material, processing conditions). For example, the symbol SK indicates that the tool is made of SK105 (carbon tool steel) and has no coating on its surface. The symbol Cr indicates that the tool is made of SUS (stainless steel) 304 and has been coated with chromium (Cr). The symbol SCA-SK indicates that a silane coupling agent was applied to the test specimen (wood) and then a high-speed friction treatment was performed using a tool (SK105). Furthermore, a lubricant (linseed oil) was applied to the surface of the wood to be processed as a lubricant before processing.

[0014] Figure 7 shows the water droplet contact angle after high-speed friction treatment on various tools. The upper graph in Figure 7 shows cedar, the middle graph shows cypress, and the lower graph shows spruce. For all tree species and all tool conditions, friction treatment increases the water droplet contact angle, improving water repellency. In particular, a higher water droplet contact angle was obtained under the Mo-PTFE, Gr, and PTFE conditions compared to the SK condition (no coating), demonstrating improved water repellency.

[0015] Figure 8 shows the specular gloss after friction treatment for various tools. Regarding the tree species, the upper graph in Figure 8 is for cedar, the middle graph is for cypress, and the lower graph is for spruce. Figure 8 shows the specular gloss at three points in the tangential direction (perpendicular to the fiber direction). For all tree species and all tool conditions, friction treatment increases the specular gloss. In particular, gloss increases significantly under the conditions of Mo-PTFE, Gr-PTFE, and PTFE compared to other tool conditions.

[0016] Figures 9 and 10 show the surface roughness of various tools after friction treatment. Regarding the tree species, the upper panels of Figure 9 and the upper panels of Figure 10 show cedar, the middle panels of Figure 9 and the middle panels of Figure 10 show cypress, and the lower panels of Figure 9 and the lower panels of Figure 10 show spruce. Figure 9 shows the average roughness in the grain direction, while Figure 10 shows the average roughness in the tangential direction (perpendicular to the grain direction). For all tree species and all tool conditions, friction treatment reduces the average roughness and improves smoothness. In particular, the Mo-PTFE and Gr conditions consistently smoothed the wood surface. The results of varying the tool conditions above indicate that the use of tools coated with PTFE significantly improved functionality compared to other conditions, suggesting that the wood surface changes due to the transfer of tool components (PTFE).

[0017] Figure 11 shows the results of SEM-EDX (scanning electron microscope energy dispersive X-ray spectroscopy) chemical analysis of the wood (spruce) surface subjected to high-speed friction treatment using a Mo-PTFE tool. Figure 12 shows the results of SEM-EDX (scanning electron microscope energy dispersive X-ray spectroscopy) chemical analysis of the wood surface before high-speed friction treatment. Comparing these results, peaks for fluorine (F) and molybdenum (Mo) were observed after high-speed friction treatment in addition to carbon and oxygen, which are the main components of wood. This suggests that high-speed friction treatment using a PTFE-containing tool results in the transfer of fluorine components, which in turn changes (improves) the functionality of the wood (water repellency, gloss, smoothness). In other words, using a tool containing fluorine components can achieve high functionality through the transfer of fluorine components. Figures 13 and 14 show SEM (scanning electron microscope) images of the wood (spruce) surface before and after high-speed friction treatment. It can be seen that the surface after treatment (FIG. 14) is smoother than the surface before treatment (FIG. 13).

[0018] Figure 15 shows the change in water droplet contact angle on wood surfaces after high-speed rubbing treatment following application of a silane coupling agent. The top panel in Figure 15 shows cedar, the middle panel shows cypress, and the bottom panel shows spruce. Compared to wood without a silane coupling agent (sk), wood with a silane coupling agent applied and dried at high temperature (SCA-sk high-temperature drying) exhibited a significant increase in water droplet contact angle after high-speed rubbing treatment, demonstrating high water repellency. Furthermore, wood with a silane coupling agent applied and dried at room temperature (SCA-sk room-temperature drying) exhibited a decrease in water droplet contact angle after high-speed rubbing treatment for cedar, but the other wood species (cypress and spruce) exhibited similar behavior to wood without a silane coupling agent (sk). When a silane coupling agent was applied and then dried at room temperature, its volatility caused it to evaporate from the surface without sufficient adhesion, resulting in results similar to those observed under the sk condition. Figure 16 is a schematic diagram showing the reaction mechanism of a silane coupling agent applied to a wood surface. When the silane coupling agent is applied and then dried at high temperature, the silane coupling agent reacts with the hydrophilic wood surface, causing the hydrophilic groups of the silane coupling agent to bond with the wood surface, exposing the lipophilic portion (lipophilic functional groups, etc.), which is thought to result in high water repellency. The temperature for high-temperature drying is not particularly limited, but is preferably 105°C or higher.

[0019] As described in detail above, the present invention provides a method for modifying a wood surface by subjecting it to a high-speed friction treatment, thereby inducing a tribochemical reaction on the wood surface and improving its functionality (e.g., improved water repellency, smoothness, gloss, etc.). The high-speed friction treatment refers to a treatment that utilizes a tribochemical reaction caused by friction between the wood surface and a high-speed rotating cylindrical tool to modify the wood surface. The rotation speed, reduction amount, and feed rate of the cylindrical tool are exemplified as 8000 rpm, 300 μm reduction amount, and 0.5-3 mm / s, but are not limited to these as long as they are within the ranges that allow the tribochemical reaction to occur. As described above, the tribochemical reaction results in the formation of a modified layer on the wood surface, improving at least one of the water repellency, smoothness, and gloss of the wood surface compared to before treatment. It goes without saying that, in this specification, if the content described in a certain part of the specification can be consistently applied to other parts not described, the content can also be applied to those other parts. Furthermore, the above-described embodiment is merely an example, and various modifications can be made without departing from the spirit of the present invention. It goes without saying that the scope of the present invention is not limited to the above-described embodiment and examples. [Explanation of symbols]

[0020] 11. Wood surface high-speed friction treatment device, 12. Metal cylindrical tool, 13. Base, 14 Electric cylinder, 15 Slide rail, 16 Load cell, 21 Wood

Claims

1. Wood whose surface has been modified by high-speed friction treatment.

2. The wood according to claim 1, characterized in that the modification of the wood surface is an improvement in water repellency, smoothness, or gloss.

3. The wood according to claim 1, characterized in that the high-speed friction treatment is a process in which the wood is friction-processed while applying a predetermined pressure to the surface of the wood with a metal cylindrical tool (referred to as a metal cylinder) rotated at high speed.

4. The wood according to claim 1, characterized in that the high-speed friction treatment is a process in which the wood is frictionally processed by pressing a metal cylindrical tool (referred to as a metal cylinder) rotated at high speed against the wood with a predetermined amount of pressure while feeding the wood at a predetermined speed.

5. The wood according to claim 1, characterized in that the surface of the wood subjected to the high-speed friction treatment is coated with a lubricant.

6. The wood according to claim 5, characterized in that the lubricant is linseed oil.

7. The wood according to claim 5 or 6, characterized in that a silane coupling agent is applied to the surface of the wood before applying a lubricant.

8. The wood according to claim 3 or 4, characterized in that the material of the metal cylinder is SK material (carbon tool steel) or SUS (304).

9. 5. The wood according to claim 3 or 4, wherein the metal cylinder has a surface coated with a coating containing PTFE or graphite.

10. The process involves pressing a metal cylindrical tool (referred to as a metal cylinder) rotated at high speed against the surface of wood with a predetermined amount of pressure, and A process of feeding the wood at a predetermined speed and friction-processing the surface of the wood. A high-speed friction treatment method for wood, including wood.

11. 10. The method for high-speed friction treatment of wood according to claim 9, further comprising a step of applying a lubricant to the surface of the wood prior to the high-speed friction treatment.

12. 12. The method for high-speed friction processing of wood according to claim 10 or 11, wherein the material of the metal cylinder is SK material (carbon tool steel) or SUS (304).

13. 12. The method for high-speed friction treatment of wood according to claim 10 or 11, wherein the metal cylinder is a metal cylinder whose surface is coated with a coating containing PTFE or graphite.

14. A high-speed wood surface friction treatment device comprising: a base on which wood is placed, a metal cylindrical tool (called a metal cylinder) with a smooth surface that can rotate at high speed, a mechanism for feeding the base with the wood placed on it at a predetermined speed, and a mechanism for pressing the metal cylindrical tool (metal cylinder) against the surface of the wood placed on the base with a predetermined amount of pressure reduction.

15. 15. The wood surface high-speed friction treatment device according to claim 14, further comprising a mechanism for applying a lubricant to the wood surface.

16. 16. The wood surface high-speed friction treatment device according to claim 14 or 15, wherein the material of the metal cylinder is SK material (carbon tool steel) or SUS (304).

17. 16. The wood surface high-speed friction treatment device according to claim 14 or 15, wherein the metal cylinder has a surface coated with a coating containing PTFE or graphite.

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