Rubber wood surface strengthening and superheated steam preservative treatment method

Abstract

The invention relates to the technical field of physical modification treatment of wood, in particular to a rubber wood surface strengthening and superheated steam preservative treatment method, which comprises the following steps of: preheating at the preheating temperature of 160-180 DEG C for 30 seconds, hot pressing at the hot pressing temperature of 160-180 DEG C, pressurizing to the hot pressing temperature, and cooling to the room temperature, thereby obtaining the rubber wood surface strengthening and superheated steam preservative treatment. The hot pressing pressure is 10 MPa, the hot pressing pressure maintaining time is 10-60 s, the pressure maintaining temperature is 160-180 DEG C, the pressure is reduced to the pressure maintaining pressure, the pressure maintaining pressure is 1.5-2 MPa, the pressure maintaining time is 10 min, and the pressure is relieved; the working procedure of superheated steam treatment comprises the following stages: heating: heating a medium to 170-190 DEG C at a heating speed of 40-45 DEG C per hour, carrying out superheated steam treatment, taking superheated steam as the medium in the stage, and carrying out treatment for 1.5 hours, and cooling. The rubber wood plate prepared by the method provided by the invention can meet the requirements of indoor stressed wood members and furniture such as wood floors, stressed panels and wallboards, and is suitable for batch production.

Description

Technical Field

[0001] The present invention relates to the technical field of physical modification treatment of wood, and specifically to a method for surface strengthening and superheated steam anti-corrosion treatment of rubber wood. Background Art

[0002] Rubber wood has beautiful patterns, large output and consumption. In China, rubber wood is mainly used for furniture and interior decoration. However, the density and strength of rubber wood are medium, and its surface hardness and bending strength are insufficient to meet the requirements of stressed wooden components and furniture such as wooden floors, stressed panels, and wall panels. At the same time, this wood is not resistant to decay, and there is a possibility of decay even for indoor use.

[0003] Existing compression wood technologies can improve the density and strength of wood, especially the surface hardness and bending strength. For example, the technical solution described in the invention patent application with the publication number CN118081929A and the name "A method for in-situ softening-compression-thermal treatment of wood": Lay the wood in a single layer on a hot press, heat the upper heating plate of the hot press to 80-100°C to heat the wood for humidity adjustment treatment to obtain humidity-adjusted wood; after turning over the humidity-adjusted wood, raise the temperature of the upper heating plate to 130-160°C for softening treatment to obtain softened wood; compress the softened wood under a pressure of 2-15 MPa to obtain compressed wood; perform heat treatment on the compressed wood at 190-280°C, and cool it after heat treatment to obtain single-sided surface compressed wood. The above technical solution uses methods of humidity adjustment, softening, compression, and heat treatment to prepare single-sided surface compressed wood with a large density and excellent dimensional stability and mechanical properties.

[0004] The technical solution described in the invention patent application with the publication number CN103753664A and the name "A compressed wood and its preparation method": includes (1) performing first high-frequency heating on wood with a moisture content of 12-30% by weight to make the core temperature of the wood reach 80-120°C; (2) hot pressing the wood obtained in step (1); (3) performing second high-frequency heating on the wood obtained in step (2) to make the core temperature of the wood reach 180-220°C. The compressed wood prepared by the preparation method of the compressed wood provided by the present invention is not prone to rebound, has simple steps and short required time; the density, surface hardness and wear resistance of the compressed wood obtained according to the method of the present invention are greatly increased, and the water absorption recovery rate and moisture absorption recovery rate of the compressed wood are small.

[0005] The technical solution recorded in the invention patent application with publication number CN102423889A and titled "Steam-spraying cooling hot press and single-sided compressed wood board and its production method" is as follows: the steam-spraying cooling hot press comprises upper and lower hot pressing plates, and a steam channel, a steam outlet hole connected to the steam channel, a heating device and a cooling channel are arranged in the lower hot pressing plate. The present technology also provides a single-sided compressed wood board and its production method which can be more practical and improve the utilization rate of wood. The production method is to put the slab between two hot pressing plates, heat the lower hot pressing plate to a certain temperature, move the lower hot pressing plate relative to the upper hot pressing plate to pressurize the slab, spray steam with a pressure of 5 to 8 atmospheres into the steam channel for 5 to 10 seconds, and when the compression rate of the slab reaches the requirement, stop heating the hot pressing plate, pass the cooling medium into the cooling channel to cool the lower hot pressing plate, and then release the pressure. The production method can shorten the cooling time, improve productivity and effectively prevent the board from cracking.

[0006] Existing heat treatment technology can improve the anti-corrosion performance of wood. For example, the publication number is CN101224593A, and the name is "A method for heat treatment of wood" The technical solution recorded in the invention patent application is as follows: (1) stacking the wood in a heat treatment chamber; (2) setting the temperature and oxygen content values ​​of the first stage at 80-150°C, the oxygen content at 12-21%, and the treatment time at 0.5-1.5 hours per 1 cm thickness of the wood; (3) setting the temperature and oxygen content values ​​of the second stage at 150-200°C, the oxygen content at 6-12%, and the treatment time at 0.5-2 hours per 1 cm thickness of the wood; (4) setting the temperature and oxygen content values ​​of the third stage at 180-260°C, the oxygen content at 2-6%, and the treatment time at 0.5-2 hours per 1 cm thickness of the wood; (5) the fourth stage is the cooling and balancing treatment stage. When the temperature in the treatment chamber is reduced to below 100°C, the moisture content of the wood is balanced by steam spraying. After the moisture content of the wood reaches the value required by the product, the temperature is further reduced to 40-50°C, and the treated wood is taken out. Summary of the invention

[0007] Different from the wood generally processed by the prior art, the felled rubber trees are generally younger, the diameter of the rubber wood logs is smaller, and the proportion of core wood is relatively high, so the obtained rubber wood sawn timber is mostly tangentially cut boards with a relatively high proportion of core wood. At the same time, there is 8% starch and sugar in the wood of rubber wood. These special structures and material properties make rubber wood sawn timber not easy to be compressed. Even if compression is barely achieved through high humidity, high temperature, high pressure or long compression time, compression rebound is prone to occur.

[0008] On the other hand, as is known to those skilled in the art, high-temperature heat treatment is an effective way to fix compression and avoid compression rebound. At the same time, it can also improve the stability of wood and enhance the decay resistance of wood. However, high-temperature heat treatment will weaken the strength of wood. For the compressed wood, although the compressed part is fixed and not prone to rebound, the density and strength of the compressed part will also be weakened.

[0009] The purpose of the present application is to provide a method for surface strengthening and superheated steam anti-corrosion treatment of rubber wood. The surface strengthening treatment method of the present application is applicable to improving the strength of rubber wood sawn timber (including surface hardness and bending strength). This method does not require the use of too high a temperature, too long a holding time in the pressurized hot pressing stage, and too long a holding time in the pressure relief and pressure holding stage, which means lower production energy consumption, shorter production cycle, and safer production environment, so it is suitable for mass production. At the same time, the synergy of the specific preheating time, short-time pressurized hot pressing, and a pressure holding of 1.5 - 2 MPa in this method can achieve surface compression of rubber wood sawn timber at low temperature, low moisture content, and short time, so that the compressed thickness layer has relatively low compression rebound even without any form of compression fixation treatment.

[0010] The superheated steam anti-corrosion treatment method of the present application is applicable to improving the decay resistance of rubber wood sawn timber, upgrading it from the level of non-decay resistance to the level of slightly decay resistance. This method has a fast heating rate, the medium in the treatment stage does not contain oxygen, and the treatment temperature and treatment time are relatively moderate, which means lower production energy consumption, shorter production cycle, and safer production environment, so it is suitable for mass production. More importantly, under the process conditions defined in the present application, it is possible to take into account the improvement of the decay resistance and stability of rubber wood sawn timber, and at the same time can effectively improve the wood strength.

[0011] The present application specifically adopts the following technical solutions: A method for surface strengthening and superheated steam anti-corrosion treatment of rubber wood, including the process of compressing the sawn timber and the process of superheated steam treatment. Among them, The process of the compression treatment includes the following stages: Preheating, the preheating temperature is 160 - 180 °C, and the preheating duration is 30 s. Hot pressing, the hot pressing temperature is 160 - 180 °C, pressurized to the hot pressing pressure, the hot pressing pressure is 10 MPa, and the holding time of the hot pressing pressure is 10 - 60 s. Pressure holding, the pressure holding temperature is 160 - 180 °C, depressurized to the pressure holding pressure, the pressure holding pressure is 1.5 - 2 MPa, and the holding time of the pressure holding pressure is 10 min, and Pressure relief; The process of the superheated steam treatment includes the following stages: Heat up, raise the medium temperature to 170 - 190°C at a heating rate of 40 - 45°C per hour, Superheated steam treatment, in this stage, the medium is superheated steam, and the treatment duration is 1.5 h, and Cool down.

[0012] As a preferred embodiment, in the pressure relief stage, the pressure relief temperature is 160 - 180°C; the pressure of a pair of the pressing plates decreases step by step in multiple times from the holding pressure, and stays at each platform pressure point for 15 - 25 s. After the platform pressure drops to 0.2 MPa, open a pair of the pressing plates to make them in contact with the surface of the sawn timber to form a contact gap, and completely lift the upper pressing plate after staying for 15 - 25 s.

[0013] As a further preference, the pressure of a pair of the pressing plates is decreased from the holding pressure to 0.2 MPa in three or four times.

[0014] As a further preference, the contact gap is 0.2 - 0.5 mm.

[0015] As a further preference, in the pressure relief stage, the decreasing gradient of the holding pressure is 0.3 - 0.5 MPa.

[0016] In the treatment method of the prior art, the temperature of the pressing plates and the sawn timber is forced to decrease by passing circulating cold water into a pair of the pressing plates. There are three technical problems in the prior method: (1) The cooling process and the process of reheating take a long time, extending the production cycle and making the process of the prior art not suitable for mass production; (2) A large amount of heat energy is wasted in the cooling process, and a large amount of electric energy is wasted in the process of reheating, which also makes the process of the prior art not suitable for mass production; (3) During the cooling process, the pressing plates are always attached (with pressure or without pressure) to the surface of the sawn timber, resulting in the moisture migrating to the board surface due to hot pressing in the sawn timber being unable to volatilize and leaving, and forming condensed water on the board surface during the cooling process, affecting the board surface quality.

[0017] In this application, through the process design of the above-mentioned pressure relief stage, thus, in the first aspect, the temperature of a pair of the pressing plates is always 160 - 180°C, so the energy consumption loss is relatively small. Only during the process of discharging under pressure, it is necessary to supplement the energy consumption loss of heat dissipation, so the energy consumption of the treatment method of this application is relatively low; in the second aspect, a pair of the pressing plates do not need to go through the processes of repeated cooling and heating, so the production rhythm is fast and the production cycle is short; in the third aspect, step-by-step pressure reduction, the pressing plates always maintain the same temperature, and the upper pressing plate forms a gap with the surface of the sawn timber at a constant temperature, which can quickly dissipate the moisture migrating to the board surface due to hot pressing in the sawn timber, keep the board surface of the sawn timber flat, avoid explosion of the sawn timber, and avoid defects such as bulging.

[0018] As a preferred embodiment, during the hot pressing stage, the pressure of a pair of the pressing plates is increased to the hot pressing pressure within 15 s to achieve the purpose of rapid pressurization.

[0019] As a preferred embodiment, during the pressure holding stage, the pressure of a pair of the pressing plates is decreased to the pressure holding pressure within 20 s to achieve the purpose of rapid depressurization.

[0020] As a further preference, during the pressure holding stage, when the pressure of a pair of the pressing plates is decreased to 5 MPa, it is held at this pressure point for 10 - 15 s.

[0021] As a preferred embodiment, the moisture content of the sawn timber is 6 - 10%.

[0022] As a preferred embodiment, a first balancing treatment process is arranged after the compression treatment process, and a second balancing treatment process is arranged after the superheated steam treatment process.

[0023] In summary, compared with the prior art, the rubberwood board prepared by the rubberwood surface strengthening and superheated steam anti - corrosion treatment method provided in this application has higher surface hardness, flexural strength and slightly better corrosion resistance, and can meet the requirements of indoor stressed wooden components and furniture such as wooden floors, stressed panels, wall panels, etc.; at the same time, it has lower production energy consumption, shorter production cycle and safer production environment, so it is suitable for mass production. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is the process curve diagram of the surface strengthening treatment provided in Embodiment 1 of the present application.

[0026] Figure 2 It is the density distribution curve diagram in the thickness direction of Specimens 1 - 4 and Control Specimen C1 in the embodiments of the present application.

[0027] Figure 3 It is the process flow schematic diagram of a rubberwood surface strengthening and superheated steam anti - corrosion treatment method provided in Embodiments 5 and 6 of the present application.

[0028] Figure 4 It is the photo of the board colors of Specimens 1, 5, 6 and Control Specimen C1 in the embodiments of the present application. Detailed implementation mode

[0029] In order to enable those skilled in the art to better understand the technical solutions in this application, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application. Embodiment

[0030] Refer to Figure 1 As shown, this embodiment provides a method for surface strengthening treatment of rubber wood, including the process (A) of compressing sawn timber and the process (B) of the first balancing treatment.

[0031] The material to be processed is 26 mm thick tangentially sawn rubber wood with a moisture content of 6 - 10%; the equipment used includes a flat press and a superheated steam treatment box. The thickness gauge used in conjunction with the flat press is 20 mm thick, so the compression ratio is 23.1%.

[0032] The process (A) of compression treatment includes the following stages: (A1) Preheating: Heat the temperature of a pair of press plates (upper press plate and lower press plate) of the flat press to 160°C, place the sawn timber on the lower press plate and quickly lift and close the lower press plate, and start timing for 30 s from the moment the upper press plate contacts the surface of the sawn timber; (A2) Hot pressing: After the 30 s timing ends, while maintaining the constant temperature of 160°C of a pair of press plates, quickly apply pressure to the hot pressing pressure (the pressure application process takes no more than 15 s). The hot pressing pressure is 10 MPa, and start timing for 10 s from the moment the pressure reaches the hot pressing pressure; (A3) Pressure holding: After the 10 s timing ends, while maintaining the constant temperature of 160°C of a pair of press plates, quickly reduce the pressure of the press plates to the pressure holding pressure (the pressure reduction process takes no more than 20 s). The pressure holding pressure is 1.5 MPa, and start timing for 10 min from the moment the pressure reduction reaches the pressure holding pressure. And when the pressure of a pair of press plates drops to 5 MPa, maintain at this pressure point for 10 s.

[0033] (A4) Pressure relief: After the 10-minute timing ends, while maintaining a constant temperature of 160 °C for a pair of pressing plates, the pressing plates are stepped down in pressure, and the pressure drop gradient of the holding pressure is 0.3 - 0.5 MPa. Specifically, first step down the pressure to the first platform pressure (1 MPa) and hold at the pressure point of the first platform pressure for 20 s, then continue to step down the pressure to the second platform pressure (0.5 MPa) and hold at the pressure point of the second platform pressure for 20 s, then continue to step down the pressure to the third platform pressure (0.2 MPa) and hold at the pressure point of the third platform pressure for 20 s, and finally open the lower pressing plate of a pair of pressing plates to form a contact gap of 0.2 - 0.5 mm with the upper surface of the sawn timber. After holding for 20 s, fully open a pair of pressing plates and take out the two plates with compressed surfaces.

[0034] Here, the contact gap should not be too large, otherwise it is not conducive to maintaining the surface flatness of the plate and is likely to cause accidents such as explosion and bulging of the plate.

[0035] The equilibrium environment for the first equilibrium treatment process (B) is 20 °C / 65% RH, and the equilibrium treatment is carried out until the moisture content of the pressed material is constant.

[0036] Mark the plate prepared in this example as Specimen 1. Example

[0037] The difference between this example and Example 1 is that in the hot pressing stage (A2), timing starts 60 s after the pressure is applied to reach the hot pressing pressure. Mark the plate prepared in this example as Specimen 2. Example

[0038] The difference between this example and Example 1 is that in the compression treatment process (A), the temperature of a pair of pressing plates is always 180 °C. Mark the plate prepared in this example as Specimen 3. Example

[0039] The difference between this example and Example 1 is that in the compression treatment process (A), the temperature of a pair of pressing plates is always 180 °C; at the same time, in the hot pressing stage (A2), timing starts 60 s after the pressure is applied to reach the hot pressing pressure. Mark the plate prepared in this example as Specimen 4. Example

[0040] The difference between this example and Example 1 is as follows: Refer to Figure 3 As shown, a method for surface strengthening and superheated steam anti-corrosion treatment of rubber wood is provided. After the compression treatment process (A) and the first equilibrium treatment process (B) of the sawn timber, the superheated steam treatment process (C) and the second equilibrium treatment process (D) are continued.

[0041] Among them, the superheated steam treatment process (C) includes the following stages: (C1)Temperature rise: The boards are placed in the superheated steam treatment chamber at intervals to make the superheated steam treatment chamber relatively enclosed. The medium temperature is raised to 170°C at a heating rate of 42°C per hour, and steam is introduced simultaneously. (C2)Superheated steam treatment: When the dry-bulb temperature of the medium in the superheated steam treatment chamber reaches 170°C and the wet-bulb temperature reaches 100°C, it enters the superheated steam treatment stage. In this stage, the medium is only superheated steam and does not contain oxygen, and the treatment duration is 1.5 h. (C3)Temperature drop: After 1.5 h of timing, heating is stopped to cool the medium in the superheated steam treatment chamber to 50°C under the forced air circulation of the fan. The superheated steam treatment chamber is opened and the boards treated with superheated steam anti-corrosion are taken out.

[0042] The equilibrium environment for the second equilibrium treatment process (D) is 20°C / 65%RH, and the equilibrium treatment is carried out until the moisture content of the boards is constant.

[0043] The boards prepared in this example are marked as Specimen 5. Example

[0044] The difference between this example and Example 5 is that in the process (C) of superheated steam treatment, the treatment temperature is 190°C. The boards prepared in this example are marked as Specimen 6.

[0045] Control Example 1 The rubber wood sawn timber that has not been treated by any means of the prior art or the means of the technology of this application, with a thickness of 26 mm, is marked as Control Specimen C1.

[0046] Specimens 1 - 4 and Control Specimen C1: Analyze the density distribution curve in the thickness direction, and the results are as Figure 2 shown.

[0047] Specimens 1, 5, 6 and Control Specimen C1: Observe the appearance, and the results are as Figure 4 shown.

[0048] Specimens 1 - 6 and Control Example C1: (1) Determine the impact resistance performance in accordance with the provisions of GB / T 17657 - 2022 "Test Methods for Physical and Chemical Properties of Wood-Based Panels and Decorated Wood-Based Panels"; (2) Determine the bending strength in accordance with the provisions of Part 9 of GB / T 1927 - 2021 "Test Methods for Physical and Mechanical Properties of Clear Wood Specimens", determine the moisture expansion rate in the thickness and width directions in accordance with the provisions of Part 8, and determine the surface hardness in accordance with the provisions of Part 19; (3) Determine the mass loss rate of decay resistance in accordance with the provisions of GB / T 13942.1 - 2009 "Wood Durability - Part 1: Laboratory Test Methods for Natural Durability". The results of the above tests are shown in Table 1.

[0049] Table 1

[0050] As can be seen from Table 1, after the specimens were surface strengthened and heat treated with superheated steam, the surface impact resistance was increased by 28% compared with the control material; the bending strength was increased by 42%; the surface hardness was increased by 82%; the set recovery decreased by 76%; the thickness swelling rate decreased by 27%; the width swelling rate decreased by 60%; the mass loss rate of decay decreased from 57.42% (not decay-resistant) of the control material to 38.15% (slightly decay-resistant). It shows that the strength of the wood is greatly improved and the decay resistance is significantly improved after surface strengthening and superheated steam treatment, which can meet the technical requirements of stressed wood components for indoor use, such as solid wood floors, wall panels, and furniture.

[0051] The above description is for illustrative purposes and not for limitation. Many embodiments and many applications other than the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but should be determined by reference to the appended claims and the full scope of equivalents to which those claims are entitled. For the sake of completeness, all articles and references including patent applications and published announcements are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not a waiver of that subject matter, nor should it be considered that the applicant has not considered that subject matter as part of the disclosed subject matter of the application.

Claims

1. A method for surface strengthening and superheated steam antiseptic treatment of rubber wood, comprising a step of compressing sawn timber and a step of superheated steam treatment, characterized in that: The compression process includes the following stages: Preheating: the preheating temperature is 160~180℃ and the preheating time is 30s. Hot pressing, the hot pressing temperature is 160~180℃, pressurizing to the hot pressing pressure, the hot pressing pressure is 10MPa, and the hot pressing pressure is maintained for 10~60s, Holding pressure, the holding temperature is 160-180°C, the pressure is reduced to the holding pressure, the holding pressure is 1.5-2MPa, the holding time of the holding pressure is 10min, and Pressure relief; The process of superheated steam treatment includes the following stages: Heating: Raise the medium temperature to 170~190℃ at a rate of 40~45℃ per hour. Superheated steam treatment, in which the medium is superheated steam, and the treatment time is 1.5 hours, and Cool down.

2. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 1, characterized in that: During the pressure relief stage, the pressure relief temperature is 160-180°C; the pressure of the pair of pressing plates is reduced in steps from the holding pressure in multiple steps, and maintained at each pressure point of the platform pressure for 15-25 seconds. After the platform pressure drops to 0.2MPa, the pair of pressing plates are opened to form a contact gap with the surface of the sawn timber, and the pair of pressing plates are opened after maintaining for 15-25 seconds.

3. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 2, characterized in that: The pressure of the pair of pressing plates is reduced from the holding pressure to 0.2 MPa three or four times.

4. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 2, characterized in that: The contact gap is 0.2-0.5 mm.

5. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 2, characterized in that: In the pressure relief stage, the decreasing gradient of the holding pressure is 0.3-0.5 MPa.

6. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 1, characterized in that: During the hot pressing stage, the pressure of the pair of pressing plates was increased to the hot pressing pressure within 15 seconds.

7. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 1, characterized in that: During the holding stage, the pressure of the pair of pressing plates is reduced to the holding pressure within 20 seconds.

8. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 7, characterized in that: In the pressure-maintaining stage, when the pressure of the pair of pressing plates drops to 5 MPa, the pressure point is maintained for 10 to 15 seconds.

9. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 1, characterized in that: The moisture content of the sawn timber is 6-10%.

10. The method for surface strengthening and superheated steam antiseptic treatment of rubber wood according to claim 1, characterized in that: A first balancing process step is provided after the compression process step, and a second balancing process step is provided after the superheated steam process step.

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