Optimization treatment method of wood for musical instruments

Abstract

The invention discloses an optimization treatment method for wood for musical instruments. The optimization treatment method comprises the steps of low-temperature forced circulation drying treatment, low-temperature vacuum drying treatment, content regulation and control treatment, accelerated aging treatment and humidity regulation and balance treatment. The accelerated aging treatment comprises high-temperature treatment and low-temperature moisture absorption treatment, the oxygen content of the treatment environment is controlled in the high-temperature treatment process, and the two types of treatment are cyclically alternated for 2-8 times. The method has the advantages of being efficient, environmentally friendly, low in cost, free of additives, capable of keeping the original characteristics of wood and the like, the optimization treatment period of the wood is shortened, and the acoustic performance and the dimensional stability of the wood are further improved while the natural characteristics of the wood are kept to the maximum extent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wood property improvement treatment, and particularly relates to an optimized treatment method for wood used for musical instruments. BACKGROUND

[0002] At present, musical instruments represented by pianos, guitars and violins are deeply loved by Chinese families. Chinese traditional stringed instruments such as qin, se, pipa, ruan and yueqin also have great consumer demand. These musical instruments are mainly made of wood, especially spruce, which is used in large quantities as raw material for important components such as piano soundboard, keyboard board, guitar and violin soundbox panel.

[0003] There are several reasons for using wood as raw material in the process of musical instrument manufacturing. First, wood is widely available and easy to process. Musical instrument manufacturing has been around for thousands of years. In ancient times, when the level of production and processing technology was relatively low, wood was more easily obtained and processed than other materials, making it a popular choice for musical instrument manufacturing. Second, the wood species selected for musical instrument manufacturing has excellent acoustic properties. Commonly used musical instrument wood such as spruce, paulownia and fir has a longitudinal sound propagation speed of over 4500 m / s, which is comparable to that of metal. Wood also has ideal elastic modulus, strength-to-weight ratio and other characteristic parameters. Third, natural wood is non-toxic and harmless, making it more suitable for use in musical instruments, which require long-term direct contact with the human body. Fourth, wood undergoes a process known as "natural aging" in the musical instrument field, which is caused by a combination of environmental factors such as temperature, humidity, light and oxygen. This process improves the sound quality, expressiveness and dimensional stability of musical instruments. After long-term storage and natural aging, the longitudinal sound propagation speed of wood may increase to over 5000 m / s, resulting in better sound quality for musical instruments made from it. Finally, wood is a renewable biomass material derived from trees. With proper planning and scientific management, wood resources can be sustainably utilized, allowing the musical instrument manufacturing industry to develop in the long term.

[0004] Despite this, the wood used for high-end musical instruments has always been in short supply due to the high requirements for tree species, texture and material in the process of musical instrument manufacturing. Some high-end products even require specific production locations and slope orientations. With the full implementation of China's natural forest protection project, high-quality natural forests are no longer available for harvesting. Although China ranks first in the world in terms of artificial forest area, the main tree species planted are fast-growing trees such as poplar, eucalyptus and fir due to the short planting time. Therefore, the wood used for musical instrument manufacturing, especially Western musical instrument manufacturing, still relies on imports at the current stage. As the world's largest musical instrument manufacturing and exporting country, the shortage of high-quality wood for musical instruments not only affects the quality of musical instruments but also restricts the development of the industry.

[0005] Due to the shortage of wood resources in China at present, in order to alleviate the dependence on foreign wood for musical instruments, on the one hand, more investment is needed in the breeding of forest resources to cultivate high-quality timber tree species, on the other hand, the existing available wood is modified and optimized to improve its basic properties to meet the requirements of higher products. Overall, the method of wood modification and optimization is an important means to solve the current practical problems. The main methods include heat treatment, carbon fiber composite treatment, ultrasonic treatment, chemical modifier treatment, extraction treatment, densification treatment, microbial treatment, etc. Patent US6667429B2 discloses a wood heat treatment method, which uses high-pressure steam to treat wood at 120-200℃, but high-pressure steam can cause excessive discharge of inclusions, reduce the overtone of wood, and reduce the performance of sound integrity and richness. When the treatment temperature is too high, especially when the temperature is ≥160℃, the chemical composition of wood begins to change significantly, and hemicellulose begins to decompose significantly, which has a significant impact on the original chemical structure of wood. In addition, the high-pressure treatment process has special requirements for equipment, which belongs to special pressure equipment, and has high requirements for production equipment and operating personnel, increasing the production cost and safety hazard. Patent CN201810535457.0 discloses a carbon fiber composite wood, which can significantly improve the dimensional stability, compressive strength and reduce the deformation rate of wood by composite treatment of carbon fiber and wood. However, the chemical additives used in the production process may cause chemical residues, which is not suitable for applications such as musical instruments that directly contact the human body, and the cost of carbon fiber is high, increasing the production cost. CN105082285A discloses a method for improving the acoustic performance of wood, which uses ultrasonic treatment on wood, but the moisture content of wood needs to be higher than 80% and the natural inclusions of wood are discharged during ultrasonic treatment, affecting the performance and richness of wood sound. Yano et al. (J. acoust. Soc. Am, 1992, 92(3): 1222-1227, DOI: 10.1121 / 1.403972) showed that formaldehyde was used as the main component, SO2 was used as the catalyst, and wood was treated to make formaldehyde and wood cell wall material cross-linking reaction, which improved the acoustic properties and dimensional stability of wood. Chang et al. (Holzforschung, 2000, 54(6): 669-675, DOI: 10.1515 / HF.2000.113) showed that treating spruce wood with chemical substances such as glycol, succinic anhydride, modified cellulose, and alkali solution could improve its acoustic vibration properties. Patent CN202010310593.7 discloses a treatment method of impregnating wood with extractives of logwood, which can be used to make musical instruments, but the uniformity of the impregnated wood may be difficult to guarantee. Although chemical modification can improve the acoustic, vibration and dimensional stability of wood, it inevitably introduces a certain amount of chemicals into the wood.Since the musical instruments are directly in contact with human body for a long time during daily use, the modification of wood by chemicals is not accepted by the market, especially for many learners of musical instruments are young children or even preschool children, whether long-term contact with musical instruments made of chemically modified wood will affect their growth and health needs further testing. Patents CN202211050597.1, CN202310172447.6, etc. disclose wood densification treatment methods, which can significantly improve the density and strength of wood by softening the wood under heat and moisture and then compressing it. However, the compressed wood has the risk of deformation and rebound during long-term use, and the dimensional stability of wood used for musical instruments is extremely high, so the application of wood densification treatment to musical instruments needs long-term and systematic verification. Patent CN108604441A discloses a method for improving the acoustic properties of spruce resonance wood, which uses microorganisms (transparent discolored sublateral fungus) to treat spruce wood. The microorganisms erode and decompose the cell wall of the wood, increasing the porosity and permeability of the wood, and thus improving the acoustic properties of the wood. However, this method has high requirements for operators, sites and equipment, and the wood is prone to infection with miscellaneous bacteria during microbial treatment. Moreover, the uniformity of the treatment on the surface and inside of the wood cannot be guaranteed.

[0006] From the previous invention patents and research papers, it can be seen that although there are many methods for treating wood for musical instruments at the present stage, there are still few treatment methods suitable for large-scale production of modern musical instrument manufacturing enterprises, and the previous treatment methods have high requirements for equipment investment, technical personnel level, site, etc. of the enterprise. The most widely used wood treatment method for musical instrument manufacturers is still a combination of natural drying and artificial conventional steam drying. Generally, after sawing the logs into lumber, natural drying for 6 to 12 months is performed to reduce the moisture content of the wood. Some wood that is difficult to dry may even need more than 2 to 5 years of drying time. After natural drying, the moisture content of the wood is generally reduced to below 15%, and then artificial conventional steam drying is performed to reduce the moisture content to 6 to 8%. Finally, warehouse storage aging is performed, and the enterprise generally refers to the long-term storage process as long-term "natural aging". Obataya Eiichi (Journal of Cultural Heritage, 2017, 27:63-69, DOI: 10.1016 / j.culher.2016.02.011) and Sonderegger et al. (Journal of Cultural Heritage, 2015, 16:883-889, DOI: 10.1016 / j.culher.2015.02.002) showed that as the time of "natural aging" increases, the speed of sound propagation in wood increases, the density remains essentially unchanged in a well-preserved state, the elastic modulus gradually increases, so the ratio of elastic modulus to density increases, thereby improving the acoustic and vibration characteristics. Generally, higher-grade musical instruments have requirements for the natural aging time of raw materials. For example, some piano manufacturing companies use wood that has been naturally aged for 5 to 10 years to manufacture pianos. The natural drying and "natural aging" time of wood used for violins is even longer, generally 10 to 20 years, and sometimes more than 50 years.

[0007] In summary, although there are many methods to improve the performance of wood at the present stage, these technologies are rarely applied to the actual production of musical instrument enterprises. The main reason is that the processing period is long, the cost is high, and chemicals are added during the processing process, which is not suitable for the application scenario of musical instruments that need to be in contact with the human body for a long time. SUMMARY

[0008] To solve the above technical problems, the present application provides an optimized treatment method for wood used in musical instruments, which has the advantages of high efficiency, environmental protection, low cost, no addition, and the ability to retain the original characteristics of the wood, etc. The "long-term natural aging" time of wood used in musical instruments is greatly reduced, and the storage cost of raw materials is reduced.

[0009] In order to achieve the above purpose, the present application provides an optimized treatment method for wood used in musical instruments, comprising the following steps: (1) Forced air circulation drying: the wood is processed into sawn timber, and is stacked at 20-40℃ for forced air circulation drying until the moisture content of the sawn timber is 15-20%; (2) Low-temperature vacuum drying: hot plate heat drying under vacuum conditions until the moisture content of the sawn timber is 4-6%; (3) Inclusion regulation: the sawn timber is heated to 60-80℃, and is kept warm and intermittently vacuumed to remove volatile inclusions; (4) Accelerated aging: the sawn timber obtained in step (3) is subjected to high-temperature treatment and low-temperature moisture absorption treatment, and is cycled 2-8 times to obtain aged sawn timber; (5) Moisture balance: the aged sawn timber is balanced to a moisture content of 6-8% to obtain the optimally treated wood for musical instruments.

[0010] Preferably, the height of the air circulation channel for forced air circulation drying in step (1) is 15-25 mm, and the width is 400-600 mm; the circulation speed of the forced air is 0.5-2.0 m / s.

[0011] Further preferably, the height of the air circulation channel is 20-25 mm; and the circulation speed of the forced air is 1.0-1.5 m / s.

[0012] Preferably, the vacuum condition in step (2) is a vacuum degree of -93.7 KPa to -81.2 KPa and a temperature of 40-60℃.

[0013] Further preferably, the vacuum degree is -93.7 KPa to -88.8 KPa, and the temperature is 40-50℃.

[0014] Preferably, the pressure of the hot plate on the sawn timber in step (2) is 0.4-0.5 MPa.

[0015] Preferably, a strong water absorbent is used to absorb the removed water in the low-temperature vacuum drying in step (2).

[0016] Further preferably, the strong water absorbent is phosphorus pentoxide or concentrated sulfuric acid with a mass concentration of 95%.

[0017] Preferably, the heat preservation time in step (3) is 1 h / mm to 2 h / mm; the frequency of the intermittent vacuuming is 30-60 min / time, and the vacuum degree is -60 KPa to -50 KPa.

[0018] Preferably, the high-temperature treatment condition in step (4) is an oxygen content of 2-10%, a temperature of 130-150℃, and a treatment time of 2 h / cm; and the moisture content of the sawn timber after the high-temperature treatment is 2-3%.

[0019] Further preferably, the oxygen content is adjusted according to the temperature, when the temperature is 110-120℃, the oxygen content is 10%; when the temperature is 120-150℃, the oxygen content is 5%; when the temperature is < 110℃, the oxygen content is not required.

[0020] Preferably, the low-temperature moisture absorption treatment condition in step (4) is that the humidity is 50-75%, the temperature is 70-80℃, and the treatment time is 2h / cm; the moisture content of the sawn timber after the high-temperature treatment is 6-12%.

[0021] Further preferably, the temperature adjustment rate during the high-temperature treatment and the low-temperature moisture absorption treatment is 5-10℃ / h.

[0022] Further preferably, when the thickness of the sawn timber is < 30mm, the temperature adjustment rate is 10℃ / h; when the thickness of the wood is between 30mm and 50mm, the temperature adjustment rate is 5℃ / h.

[0023] Preferably, the humidity balancing treatment condition in step (5) is that the temperature is reduced to 30℃ at a rate of 5℃ / h, then the temperature is kept constant at 30℃, the relative humidity is maintained at 30-45%, and the moisture content of the wood is adjusted to 6-8%.

[0024] The present application has the following beneficial effects: 1. The air flow circulation speed is controlled in the forced air flow circulation drying process, so that the air flow circulation speed is 1.0 m / s~1.5 m / s. Compared with the natural drying without forced air flow circulation in the past, the forced air flow circulation can greatly accelerate the natural drying speed of the wood, and the drying time of 6-12 months is reduced to 1-2 months.

[0025] 2. In the low-temperature vacuum drying process, the wood is heated by a hot plate. Not only the heat transfer efficiency of the vacuum drying process is improved by the direct contact between the wood and the hot plate, but also the pressure is applied to the wood by the hot plate during the drying process, and the pressure range is 0.3MPa~0.4MPa, which can avoid the warping deformation of the wood during the drying process. The selected pressure range is less than the common wood transverse compressive strength (about 2MPa), so that the warping deformation of the wood is prevented, and the wood structure is not compressed or damaged.

[0026] 3、Low temperature vacuum drying of wood, for spruce, fir and other musical instrument wood, mainly to remove the resin, the main components of the resin and turpentine, in the case of low moisture content of wood, low temperature drying at 60~80℃ can remove the resin turpentine oil while reducing the loss of wood in the pine pitch, because the softening point of the pine pitch is generally more than 80℃, and the pine oil can accelerate the volatilization at this temperature. Therefore, the treatment time is significantly less than the long-term "natural aging" of wood (5~20 years, even longer), the reduction of turpentine oil makes the sound propagation speed in the wood faster, and improves the acoustic performance of the wood.

[0027] 4、The wood is subjected to accelerated aging treatment, including high temperature treatment of controlling the oxygen content of the environment and low temperature hygroscopic treatment of controlling the humidity of the environment, the two treatments are alternately performed, and in this process, the moisture content of the wood is repeatedly changed alternately, simulating the moisture content fluctuation of the wood caused by seasonal changes in the process of "natural aging" of the wood, that is, high air humidity in spring and summer (wood absorbs moisture), low air humidity in autumn and winter (wood desorption drying). The size of the wood also expands and shrinks. After repeated drying and wetting, the wood properties become more stable, similar to the "fatigue" of the material, reducing the influence of external humidity changes on the wood. Such treatment also accelerates the "aging" of the wood. The wood aging time is shortened from 10 years to 24 hours or less, significantly saving the wood aging time.

[0028] 5、The temperature used in the high temperature and low humidity process during the accelerated aging treatment of the wood does not exceed 150℃, which is lower than the treatment temperature of 160℃ used in the production of "carbonized wood" (or high temperature heat treated wood) in the wood processing field, has little effect on the original chemical composition of the wood, and the color of the wood changes little, especially the color of the light-colored wood changes little. The treatment process controls the oxygen content of the environment, further reducing the wood property loss caused by oxygen in the high temperature and low humidity environment.

[0029] 6、In the optimization treatment of the wood of the present application, no chemical agent is introduced into the wood, which ensures the original safety and non-toxicity of the wood, and meets the green environmental protection requirements. The treatment equipment of the present application is simple, the action of the treatment process is clear and definite, and the process is easy to control and adjust, which is suitable for enterprise scale production and application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The wood pile diagram of the present application, figure 1 is sawn timber, 2 is a spacer, 3 is a forced circulation air flow channel. DETAILED DESCRIPTION

[0031] The technical solutions of the present application are further explained in combination with the drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present application, and should not be understood as limiting the present application. The protection scope of the present application should be based on the content recorded in the claims. The modifications and replacements of the technical solutions of the present application made by those skilled in the art without creative labor fall within the protection scope of the present application.

[0032] The wood treated in the following embodiments is spruce Picea sitchensis , produced in Alaska, USA, with the initial moisture content of the log ranging from about 70% to 120%; standard radial cut plate samples of wood with a size of 500-2000 mm (lengthwise) x 50-200 mm (radial) x 5-20 mm (tangential) are sawn from spruce log sections, and the standard radial cut plate is required to be free of knots, cracks, resin pockets, decay, insect damage and other undesirable defects.

[0033] Example 1 (1) Forced air circulation drying: spruce wood is made into sawn timber with a size of 2000 mm x 200 mm x 20 mm, which is stacked in a low-temperature drying house according to the method shown in Figure 1 , at 30°C, with an air circulation speed of 1.0 m / s, the moisture content of the sawn timber is reduced to 15%; wherein the size of the spacer is 25 mm x 25 mm x 1500 mm, and the placement interval is 500 mm, wherein the thickness of the spacer is 25 mm and the placement interval is 500 mm, which forms an air circulation channel; wherein the length of the whole stack is 2000 mm, the width is 1200 mm, and the height is 1200 mm; (2) Low-temperature vacuum drying: the sawn timber treated in step (1) is transferred to a vacuum drying tank (produced by Yasujima Company, Japan, model HED-0603), and phosphorus pentoxide is placed as a water absorbent, heated by hot plate contact, the temperature is set to 50°C, the vacuum degree in the vacuum drying tank is adjusted to -88.8 KPa, the pressure applied by the hot plate to the wood is 0.3 MPa, and the drying is carried out until the moisture content of the wood is 5%; (3) Inclusion regulation: the sawn timber obtained in step (2) is transferred to a wood heat treatment equipment (HD74 / TA II type), the temperature is raised to 80°C for inclusion removal, the vacuum degree is maintained at -50 KPa, and the removal time is 1 h / mm, i.e. 20 mm thick wood is treated at 80°C, vacuum degree -50 KPa for 20 h for inclusion removal; wherein the volatile inclusions are discharged every 30 min; wherein the discharge mode is to open the vacuum pump of the equipment and run for 2 min to exhaust the volatile gas in the heat treatment equipment from the equipment; (4) Accelerated aging: the sawn timber obtained in step (3) is subjected to accelerated aging treatment, specifically, low-temperature moisture absorption treatment and high-temperature treatment are carried out in turn, and the cycle alternation is 2 times; wherein the low-temperature moisture absorption treatment conditions are 4h at 70℃ and humidity of 60%; the high-temperature treatment conditions are 4h at 130℃ and oxygen content of 5%; wherein the temperature change rate in the cycle alternation process is 10℃ / h; wherein the oxygen content is controlled by introducing nitrogen into the treatment equipment (5) Humidity balance: the sawn timber obtained in step (4) is cooled from 130℃ to 30℃ at a speed of 5℃ / h, and then transferred to a constant temperature and humidity box (produced by Japan ESPEC Company, model LHU-113), and subjected to humidity balance under the conditions of 30℃ and relative humidity of 45%, and the optimized wood for musical instruments is obtained when the moisture content of the sawn timber is 6%; wherein the oxygen content is 10% when the temperature is 110-130℃.

[0034] Example 2 The method and steps are the same as in Example 1, and the temperature in step (3) is adjusted to 60℃, and the vacuum degree is adjusted to -60KPa; The cycle alternation times in step (4) are adjusted to 4 times; The optimized wood for musical instruments is prepared.

[0035] Example 3 The method and steps are the same as in Example 1, and the sawn timber in step (1) is dried to a moisture content of 20%; The temperature in step (2) is changed to 40℃, and the vacuum degree is changed to -93.7KPa; The high-temperature treatment temperature in step (4) is changed to 140℃, and the cycle alternation times are 4 times; The optimized wood for musical instruments is prepared.

[0036] Example 4 The method and steps are the same as in Example 1, and the temperature in step (3) is changed to 70℃, and the vacuum degree is changed to -50KPa; The high-temperature treatment temperature in step (4) is changed to 150℃, and the cycle alternation times are changed to 8 times; The optimized wood for musical instruments is prepared.

[0037] Example 5 The method and steps are the same as in Example 1, and only the gas for controlling oxygen content in step (4) is replaced with water vapor, and the optimized wood for musical instruments is prepared.

[0038] Example 6 (1) Forced air circulation drying: spruce wood is made into sawn timber with a size of 2000mm×200mm×40mm, and the sawn timber is subjected to forced air circulation drying according to the following conditions: Figure 1The method utilizes the batten to be placed in a stack in a low-temperature drying room, and the moisture content of the sawn timber is reduced to 15% at 40°C and with an air circulation speed of 1.5 m / s; wherein the size of the batten is 20 mm x 20 mm x 1500 mm, and the placement interval is 500 mm, wherein the thickness of the batten is 20 mm and the placement interval is 500 mm to form an air circulation channel; wherein the length of the whole timber stack is 2000 mm, the width is 1200 mm, and the height is 1200 mm; (2) Low-temperature vacuum drying: the sawn timber treated in step (1) is transferred to a vacuum drying tank (produced by Yasujima Company, Japan, model HED-0603), and concentrated sulfuric acid (mass fraction 95%) is placed as a water absorbing agent, and a hot plate is used for contact heating, the temperature is set to 60°C, the vacuum degree in the vacuum drying tank is adjusted to -93.7 KPa, the pressure applied by the hot plate to the wood is 0.5 MPa, and the wood is dried to a moisture content of 5%; (4) Accelerated aging: the sawn timber treated in step (3) is subjected to accelerated aging treatment, specifically low-temperature moisture absorption treatment and high-temperature treatment in turn, and the cycle is alternated 2 times; wherein the low-temperature moisture absorption treatment conditions are 8 h at 75% humidity and 80°C; the high-temperature treatment conditions are 8 h at 130°C and 10% oxygen content; wherein the temperature change rate during the cycle alternation process is 5°C / h; wherein the oxygen content is controlled by introducing nitrogen into the inside of the treatment equipment; (5) Humidity balance: the sawn timber treated in step (4) is cooled from 130°C to 30°C at a rate of 5°C / h, and then transferred to a constant temperature and humidity box (produced by ESPEC Company, Japan, model LHU-113), and subjected to humidity balance at 30°C and 30% relative humidity, and when the moisture content of the sawn timber is 6%, the optimized wood for musical instruments is obtained; wherein when the temperature is 110-130°C, the oxygen content is 10%, and when the temperature is lower than 110°C, the oxygen content is not controlled.

[0039] Comparative Example 1 (1) Natural drying: spruce wood is sawn into timber with a size of 2000 mm x 200 mm x 20 mm, and the timber is naturally dried in a room with a temperature of 20°C and a humidity of 50% for 6 months. Figure 1The illustrated mode is to code into a timber pile in a dedicated air-drying shed, avoid direct sunlight or rain wet wood, place a batten between each layer of wood to form a uniform distribution of air circulation channel, facilitate the heat and moisture exchange between the standard sample and the surrounding environment, and conduct natural drying to reduce the moisture content of the wood to 15%; wherein the length of the timber pile is 2000mm, the width is 1200mm, the height is 1200mm, the size of the batten is 25mm*25mm*1500mm, and the placement interval of the batten is 500mm; (2) Steam drying: the sawn timber treated in step (1) is subjected to conventional steam drying, the drying temperature is maintained <80℃, the relative humidity range during the drying process gradually decreases from 95% to 30%, and the wood moisture content is dried to 6%; (3) Equilibrium conditioning treatment: the sawn timber treated in step (2) is placed in a constant temperature and humidity box (produced by Japan ESPEC Company, model LHU-113), the temperature is set to 30℃, the relative humidity is set to 45%, and the equilibrium conditioning treatment is performed, and the optimized treated musical instrument wood is obtained after 240h of treatment.

[0040] Comparative Example 2 The method and steps are the same as those in Comparative Example 1, except that step (3) is omitted, and the sawn timber treated in step (2) is directly stored in a raw material warehouse, and the optimized treated musical instrument wood is obtained after 8 years of storage.

[0041] Comparative Example 3 The method and steps are the same as those in Comparative Example 2, except that the storage time is changed to 14 years.

[0042] Comparative Example 4 The method and steps are the same as those in Example 1, except that step (4) is changed to only high-temperature treatment, wherein the high-temperature treatment conditions are 130℃ for 4h, without low-temperature moisture absorption and cycle alternation, and the optimized treated musical instrument wood is prepared.

[0043] Comparative Example 5 The method and steps are the same as those in Example 1, except that step (4) is changed to only low-temperature moisture absorption treatment, and the optimized treated musical instrument wood is prepared.

[0044] Comparative Example 6 The method and steps are the same as those in Example 1, except that the forced air circulation speed in step (1) is changed to 2.5m / s, and the optimized treated musical instrument wood is prepared.

[0045] Comparative Example 7 The method and steps are the same as those in Example 1, except that the temperature change rate of the cycle alternation process in step (4) is changed to 5℃ / h, and the optimized treated musical instrument wood is prepared.

[0046] Comparative Example 8 The method, steps are the same as example 1, wherein the number of cycles of step (4) is changed to 10 times.

[0047] Result detection: the wood for musical instruments prepared in the above examples and comparative examples was detected for longitudinal sound propagation speed, specific dynamic elastic modulus, dimensional stability and extract content, respectively, and the specific detection methods were as follows: (1) Longitudinal sound propagation speed test: The longitudinal sound propagation speed of wood was tested by using a Hungarian ultrasonic microsecond timer (Fa-kopp Ultrasonic Timer). The microsecond timer device comprises a signal processor and two piezoelectric sensors. During the test, the transmitting sensor emits an ultrasonic pulse, which propagates along the longitudinal direction of the wood sample. When the pulse signal reaches the receiving sensor, it is received. After signal processing, the propagation time of the pulse between the two sensors is displayed on the screen of the processing box, and the signal propagation time is recorded. Then, the vertical distance between the two piezoelectric sensors is measured, and then the sound propagation speed is calculated according to the following formula: V = L / t, wherein V is the longitudinal sound propagation speed of wood, L is the length of the wood sample to be tested, and t is the sound propagation time. The results are shown in Table 1. (2) Specific dynamic elastic modulus test: The dynamic elastic modulus of wood was tested by modal analysis. The test equipment comprises a collector, a sensor and analysis software. The collector is model INV3062T, the sensor comprises an excitation hammer of INV9310 and a sound pressure sensor of model INV9206. The two ends of the wood sample are suspended horizontally by a flexible string. The excitation hammer is used to knock the sample at one end to excite vibration. The signal is received by the sound pressure sensor, and the dynamic elastic modulus E of the wood sample is calculated and analyzed by the analysis software. Then, the density of the wood is measured according to the national standard "Wood Density Test Method" (GB / T 1933-2009), and the calculation is carried out according to the following formula: E' = E / ρ, wherein E' is the specific dynamic elastic modulus, E is the dynamic elastic modulus, and p is the density. The results are shown in Table 1. (3) Hygroscopic dimensional stability test: The wood hygroscopic dimensional stability test was carried out according to the forestry industry standard "Wood and Wood-based Material Hygroscopic Dimensional Stability Test Specification" (LY / T 3222-2020). The results are shown in Table 1. (4) Moisture content test: The wood sample was placed in an environment with a temperature of 20°C and a relative humidity of 65% to obtain the equilibrium moisture content of the wood according to the operating method specified in the forestry industry standard "Wood and Wood-based Material Hygroscopic Dimensional Stability Test Specification" (LY / T 3222-2020). The results are shown in Table 1. (5) Extract content test: According to the national standard "Determination of Organic Solvent Extractives Content of Papermaking Raw Materials" (GB / T 2677.6-1994), the spruce wood samples were extracted by Soxhlet extractor to determine the extractives content of wood in different examples, and the results are shown in Table 1. (6) The fiber saturation point test method adopted in the academic paper (Telkki, V.V., Yliniemi, M., Jokisaari, J. (2013) Moisture in softwoods: fiber saturation point, hydroxyl site content, and the amount of micropores as determined from NMR relaxation time distributions. Holzforschung 67: 291-300.) was used for testing, and the results are shown in Table 1. Table 1 Performance parameters of wood for musical instruments

[0048] The results show that: compared with Comparative Example 1, the wood treated by the method of the examples has a significantly higher longitudinal sound propagation speed and specific dynamic elastic modulus, and the longitudinal sound propagation speed and specific dynamic elastic modulus of the wood treated by the method of the examples are similar to those of the spruce wood treated by "natural aging" for 8 years and 14 years in Comparative Examples 2 and 3, respectively. This indicates that the alternation of high-temperature treatment and low-temperature moisture absorption treatment can simulate the "natural aging" process and does not affect the physical and chemical properties of the wood, significantly shortening the aging treatment time of the wood.

[0049] Compared with Comparative Example 1, the extractives content in the wood treated by the method of the examples is significantly reduced, and the extractives content in the wood treated by the method of the examples is similar to that of the spruce wood treated by "natural aging" for 8 years and 14 years in Comparative Examples 2 and 3, respectively. This further indicates that the alternation of high-temperature treatment and low-temperature moisture absorption treatment can simulate the "natural aging" process, accelerate the aging process of the wood, and reduce the storage cost of raw materials.

[0050] In Comparative Example 4, only high-temperature treatment was used, and the longitudinal sound propagation speed and specific dynamic elastic modulus of the wood prepared by high-temperature treatment were not significantly improved compared with those of untreated Comparative Example 1. This indicates that only high-temperature treatment without low-temperature moisture absorption treatment and cyclic aging treatment does not significantly improve the performance of the wood, and the optimization effect on the wood is limited.

[0051] In Comparative Examples 6-8, the forced air circulation speed, temperature rising rate, and cycle alternation times were changed, and the wood performance changed insignificantly, but the power consumption increased significantly, which does not comply with the cost-saving principle.

Claims

1. A method for optimizing the treatment of wood used in musical instruments, characterized in that: Includes the following steps: (1) Forced airflow circulation drying: The wood is processed into sawn timber and piled up at 20-40℃ for forced airflow circulation drying until the moisture content of the sawn timber is 15-20%; (2) Low-temperature vacuum drying: Under vacuum conditions, the sawn timber is dried by heat transfer through a hot plate until the moisture content is 4-6%; (3) Inclusion control: Heat the sawn timber to 60-80℃, keep it warm and intermittently vacuum to remove volatile inclusions; (4) Accelerated aging: The sawn timber obtained in step (3) is subjected to high temperature treatment and low temperature moisture absorption treatment, and the cycle is repeated 2-8 times to obtain aged sawn timber; (5) Moisture balance: The aged sawn timber is conditioned to a moisture content of 6-8% to obtain optimized musical instrument wood.

2. The method for optimizing the wood used in musical instruments according to claim 1, characterized in that: The height of the airflow circulation channel for the forced airflow circulation drying in step (1) is 15-25mm and the width is 400-600mm; the circulation speed of the forced airflow is 0.5-2.0m / s.

3. The method for optimizing the wood used in musical instruments according to claim 1, characterized in that: The vacuum conditions described in step (2) are a vacuum degree of -93.7KPa to -81.2KPa and a temperature of 40-60℃.

4. The method for optimizing the wood used in musical instruments according to claim 1, characterized in that: The pressure exerted by the hot plate on the sawn timber in step (2) is 0.4-0.5 MPa.

5. The method for optimizing the wood used in musical instruments according to claim 1, characterized in that: The heat preservation time in step (3) is 1h / mm to 2h / mm; the frequency of the intermittent vacuuming is 30-60min / time, and the vacuum degree is -60KPa to -50KPa.

6. The method for optimizing the wood used in musical instruments according to claim 1, characterized in that: The high-temperature treatment conditions in step (4) are an oxygen content of 2-10%, a temperature of 130-150℃, and a treatment time of 2h / cm; the moisture content of the sawn timber after the high-temperature treatment is 2-3%.

7. The method for optimizing the wood used in musical instruments according to claim 1, characterized in that: The low-temperature moisture absorption treatment conditions in step (4) are a humidity of 50-75%, a temperature of 70-80℃, and a treatment time of 2h / cm; the moisture content of the sawn timber after the high-temperature treatment is 6-12%.

8. A method for optimizing the treatment of musical instrument wood according to claim 6 or 7, characterized in that: The temperature adjustment rate during the high-temperature treatment and low-temperature moisture absorption treatment is 5-10℃ / h.

9. The method for optimizing the wood used in musical instruments according to claim 8, characterized in that: When the thickness of the sawn timber is less than 30 mm, the temperature adjustment rate is 10℃ / h; when the thickness of the timber is between 30 mm and 50 mm, the temperature adjustment rate is 5℃ / h.

10. The method for optimizing the wood used in musical instruments according to claim 1, characterized in that: The humidity balance treatment conditions described in step (5) are to cool down to 30°C at a rate of 5°C / h, then keep the temperature constant at 30°C and maintain the relative humidity at 30-45%, thereby adjusting the moisture content of the wood to 6-8%.

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