Manufacturing method of wood shaving sheet capable of replacing veneer

Abstract

The invention belongs to the technical field of artificial board production and manufacturing, and particularly discloses a manufacturing method of a wood shaving sheet capable of replacing a veneer. According to the manufacturing method of the wood shaving sheet, by controlling the size of wood shavings and the initial moisture content, on the premise that a magnesium gel system serves as an inorganic adhesive and combining special improvement of a hot pressing and curing process, it is guaranteed that the obtained wood shaving sheet with the thickness of 3-5 mm is free of the problem of buckling deformation easily occurring, the flatness of the sheet surface is high, and the wood shaving sheet can be used for manufacturing the wood shaving sheet with the thickness of 3-5 mm. And the mechanical property of the plywood reaches the level close to that of a veneer, the plywood can be used as a substitute of the veneer, the production cost of the plywood is greatly reduced, wood branches, processing residues and the like can be effectively utilized as wood raw materials, and the production cost is further reduced.

Description

Technical Field

[0001] This invention belongs to the field of engineered wood products production and manufacturing technology, specifically, it relates to a method for producing particleboard that can replace veneer. Background Technology

[0002] Due to the prominent contradiction between forest supply and demand in my country, the scarcity of forest resources has led to a continuous rise in timber prices, resulting in increasing production costs for engineered wood products (AWD) manufacturers. Therefore, avoiding the use of whole veneers and utilizing smaller pieces of wood, such as wood processing residues, for board production is an effective way to reduce AW production costs.

[0003] Currently, the main type of engineered wood that can be produced using small-sized wood processing residues is particleboard. The general process involves processing wood processing residues into shavings of different sizes, and then using glue, laying, hot pressing, and curing processes to create particleboard with a thickness greater than 6mm. However, compared to plywood (made by gluing together veneers from large-diameter timber), this type of particleboard has lower strength and poorer workability.

[0004] At the same time, the structure of my country's wood-based panel market is not matched with the supply of timber resources. my country's plywood production accounts for nearly 60%, but the large-diameter timber resources it needs are relatively scarce, and it is highly dependent on imports.

[0005] Therefore, if small-sized wood such as wood processing residues can be used to make particleboard (generally requiring a thickness of 3mm to 5mm) to replace veneer, thereby reducing the production cost of plywood, it is of great significance to the healthy development of enterprises and the conservation of forest resources. Summary of the Invention

[0006] To address the issues of low strength and poor processability of conventional particleboard (thickness greater than 6mm) in existing technologies, as well as the high raw material requirements and production costs of plywood, a particleboard that can replace veneer is developed.

[0007] However, during the research and development process, the inventors discovered that when using conventional particleboard manufacturing processes to produce thin particleboard, warping and deformation are highly likely to occur. Analysis revealed that this is because after the particleboard is hot-pressed, it transitions from a high-temperature environment to a room-temperature environment. The surface temperature of the board is higher than that of the core layer, resulting in a lower moisture content in the surface layer compared to the core layer. Furthermore, the surface adhesive is more thoroughly cured than the core adhesive. These differences create unevenly distributed stress within the board, making it more prone to warping and deformation. This effect is negligible in thicker conventional particleboard. Simultaneously, the use of inorganic adhesives like magnesium-based cementitious materials in particleboard production involves a hydration reaction, leading to a higher moisture content compared to particleboard made with urea-based or formaldehyde-free adhesives. Therefore, thin particleboard made with magnesium-based cementitious materials is more susceptible to warping. To address this, by limiting and controlling the raw materials for thin particleboard and improving the manufacturing process, a new manufacturing process for thin particleboard was developed, overcoming the problem of warping and deformation.

[0008] Therefore, the present invention adopts the following technical solution:

[0009] A method for manufacturing particleboard that can replace veneer, comprising the following steps:

[0010] S1. Prepare wood shavings;

[0011] Process wood into shavings;

[0012] S2, applying adhesive to wood shavings;

[0013] Wood shavings were soaked in a magnesium salt composite aqueous solution and then mixed with magnesium oxide to obtain a paving material with magnesium cementitious material as inorganic adhesive.

[0014] S3, Paving;

[0015] The amount of paving material laid in a single instance shall not exceed one-third of the total amount laid, and paving shall be carried out in small quantities and multiple times to obtain paving slabs.

[0016] S4, hot pressing;

[0017] The paving slab is hot-pressed at a temperature of 90℃~120℃ and a unit pressure of 5MPa~6MPa for 15min~20min. After hot pressing, the pressure is gradually reduced. After the unit pressure drops to no more than 0.1MPa and is maintained for at least 10min, the pressure is released and the slab is removed to obtain the blank.

[0018] S5, Maintenance;

[0019] The two sides of the slab are clamped and locked with a hard plate mold, and cured for at least 7 days in a gradient manner within a humidity range of 80% to 90% to 20% to 30% to obtain a particleboard with a thickness of 3mm to 5mm.

[0020] Specifically, in step S1, the particle size of the wood shavings is 4 to 10 mesh, and their moisture content is controlled to be 2% to 8%.

[0021] Because this manufacturing method produces particleboard of a specific thickness between 3mm and 5mm, excessively large particle sizes result in poor surface smoothness and uneven density due to uneven distribution of particle and adhesive, leading to unstable mechanical properties. Conversely, excessively small particle sizes result in lower mechanical properties, making it unsuitable as a substitute for veneer, since the strength is primarily provided by large-diameter particleboard. Furthermore, excessively small particle sizes significantly increase the contact area between the inorganic adhesive and the particleboard, leading to an increase in weak phase structures in the inorganic adhesive, affecting mechanical properties, significantly reducing water resistance, and making it prone to water absorption and swelling, which is detrimental to actual production.

[0022] The aforementioned control range of particle moisture content ensures that the pressed particleboard after adding inorganic adhesive will not experience board bursting due to high moisture content, nor will it suffer from dusting and uneven mixing problems caused by excessively dry materials. This control of the initial particle moisture content ensures that the moisture content of the substrate after adhesive application is between 20% and 23%, which determines the shape control of the final particleboard sheet. This is because a higher substrate moisture content leads to more water vapor evaporating from the particleboard sheet after high-temperature pressing, resulting in greater deformation. Therefore, substrate moisture content is more important in the particleboard preparation process. Furthermore, the particleboard produced by this invention is only 3mm to 5mm thick, which has stricter substrate moisture content requirements compared to conventional particleboard with a thickness of 6mm or more, because under the same stress conditions, the deformation of a thinner sheet is much greater than that of a thicker sheet.

[0023] To save timber and reduce production costs, poplar branches and processing residues are preferred as raw materials for processing into wood shavings.

[0024] Specifically, in step S2, the magnesium cementitious material refers to magnesium sulfate-magnesium oxychloride cement or magnesium chloride-magnesium oxychloride cement. Thus, the magnesium salt in the magnesium salt composite aqueous solution corresponds to magnesium sulfate or magnesium chloride, and is composited with a water-resistant agent.

[0025] Water-resistant agents refer to additives commonly used in any magnesium oxysulfate cement or magnesium oxychloride cement to improve water resistance, such as at least one of phosphoric acid, citric acid, glycolic acid, and tartaric acid. Water-resistant agents can reduce the dissolution of ions in the inorganic adhesive and ensure the integrity of the structure of the strength phase (referring to the main strength phase 518 phase in magnesium oxysulfate cement and the main strength phase 518 phase in magnesium oxychloride cement). When used as a water-resistant additive, it can effectively improve the water resistance of particleboard.

[0026] Furthermore, the usage range of each raw material in the above paving materials is as follows (by mass parts):

[0027]

[0028] Furthermore, the aforementioned paving material may also include 2 to 4 parts by weight of a thickening modifier; specifically, the thickening modifier is at least one of 1 to 2 parts by weight of polyacrylamide and 1 to 2 parts by weight of sodium carboxymethyl cellulose.

[0029] Furthermore, the polyacrylamide is selected from any one of nonionic, cationic, anionic, and biionic types, with a molecular weight of 5 million to 12 million; sodium carboxymethyl cellulose is an anionic polymer compound obtained by reacting natural cellulose with caustic alkali and monochloroacetic acid; polyacrylamide and sodium carboxymethyl cellulose, as tackifiers, can improve the bonding strength and toughness of the inorganic adhesive, thereby improving the mechanical properties of the final particleboard.

[0030] Specifically, in step S3, the material is generally laid in small, multiple applications, with each application not exceeding one-third of the total material volume. This is because, compared to conventional thick particleboard (6mm or more), thin particleboard requires a higher density to meet standard mechanical performance indicators. The density of the particleboard in this invention is controlled at 1.2 g / cm³. 3 ~1.35g / cm 3 Between these two types of boards, the thickness of thin boards is much smaller than that of thick boards, making them more prone to uneven installation. Uneven installation can lead to a sharp decline in mechanical properties and water resistance. Therefore, the production of particleboard requires a higher degree of uniformity in installation.

[0031] In step S4, too little hot pressing pressure will reduce the density of the board, thus affecting its mechanical properties; while too much hot pressing pressure means that the particleboard has a higher density and better performance, but the resulting high cost, including increased energy consumption and raw material costs, is meaningless for actual production.

[0032] Specifically, in step S5, the clamping pressure is controlled at 0.1 MPa to 0.2 MPa, and the humidity gradient reduction rule is to control the initial humidity at 80% to 90%, with no less than three gradients, an average humidity change of no less than 20% between adjacent gradients, and finally curing at 20% to 30% humidity for at least 4 days. Mold clamping of the slab aims to prevent warping and deformation due to drastic temperature changes. Combined with the humidity gradient reduction curing method, compared to conventional curing methods (generally curing for 7 days under high humidity, normal temperature, and normal pressure or normal humidity, normal temperature, and normal pressure), this avoids the problem of excessively low mechanical properties caused by excessively high moisture content in particleboard under high humidity and normal pressure. Furthermore, under normal humidity conditions and sudden drops in humidity, the internal moisture content of the particleboard drops rapidly from a high level to a low level, thus causing deformation problems. Therefore, the curing process adopted in this invention can prevent uneven stress and strain caused by drastic changes in internal moisture content and temperature, thus preventing warping and deformation of the thin plate. Under this curing process, the shape of the thin plate does not change.

[0033] This invention, through the control of particle size and initial moisture content, and with the magnesium cementing system as the inorganic adhesive, combined with special improvements in hot pressing and curing processes, not only ensures that the obtained particleboard avoids the problem of warping and deformation, and has a high degree of surface flatness, but also achieves mechanical properties close to those of veneer. It can be used as a substitute for veneer, significantly reducing the production cost of plywood. Furthermore, it can effectively utilize wood branches and processing residues as raw materials, and can use conventional particleboard installation equipment, avoiding the manual installation of traditional plywood (made of veneer glued together), further reducing production costs. Attached Figure Description

[0034] Figure 1 This is a photograph of a particleboard according to Embodiment 1 of the present invention;

[0035] Figure 2 This is a photograph of the third comparative particleboard according to Comparative Example 3 of the present invention;

[0036] Figure 3 This is a photograph of the fourth comparative particleboard according to Comparative Example 4 of the present invention. Detailed Implementation

[0037] The following specific embodiments describe the method for manufacturing the particleboard that can replace veneer provided by the present invention. However, those skilled in the art will understand that the following embodiments are merely specific examples of the method for manufacturing particleboard according to the present invention and are not intended to limit all of them. Rather, these embodiments are provided to explain the principles of the present invention and its practical application, thereby enabling other those skilled in the art to understand the various embodiments of the present invention and various modifications suitable for specific intended applications.

[0038] It should be noted that in the following embodiments, the steel plate mold used for clamping and pressurizing the slab is achieved by using a cold press on the production line to clamp the entire slab and apply pressure for a certain period of time.

[0039] Example 1

[0040] This embodiment provides a method for manufacturing particleboard, and correspondingly obtains a particleboard that can replace veneer applications. The specific manufacturing process is as follows:

[0041] First, the wood shavings left over from wood processing are sieved through 4-mesh and 10-mesh screens to obtain wood shavings with a size of 4-10 mesh and a moisture content of about 5%.

[0042] Next, add 2g of diionic polyacrylamide with a molecular weight of about 8 million and 2g of sodium carboxymethyl cellulose to 57.76g of water and stir manually for 5min to 10min until the polyacrylamide is completely dissolved; then add 1g of glycolic acid as a water-resistant agent and stir manually for 5min to 10min until the glycolic acid is completely dissolved; then add 54.37g of magnesium chloride hexahydrate and stir until completely dissolved to obtain a magnesium salt aqueous solution.

[0043] The third step is to add the above magnesium salt aqueous solution to 201.81g of wood shavings and stir it in a mixing tank until it is evenly mixed. Then, weigh out 89.14g of active magnesium oxide and add it to the stirred wood shavings and continue stirring until it is evenly mixed to obtain the paving material (magnesium oxychloride cement as an inorganic adhesive).

[0044] Specifically, the moisture content of the paving material was 21.13%.

[0045] The fourth step is to lay the paving material in three layers, ensuring that the amount laid each time is approximately the same. Precise weighing is not required to obtain the paving material.

[0046] The fifth step is to place the paving material into a hot press and hot press it at a temperature of 120°C and a unit pressure of 6MPa for 15 minutes. After hot pressing, the pressure is gradually reduced until the unit pressure drops to no more than 0.1MPa and is maintained for at least 10 minutes. Then, the pressure is released and the slab is removed to obtain the blank.

[0047] Finally, the slab is clamped and pressurized using a steel plate mold, with the clamping pressure controlled between 0.1MPa and 0.2MPa; the humidity in the curing chamber is adjusted, and the humidity is controlled to decrease gradually according to the following pattern: "85% to 90% for one day, 60% to 65% for one day, 37% to 40% for one day, and 20% to 23% for four days" to obtain a particleboard with a thickness of 3.0mm.

[0048] A physical image of the particleboard obtained by the above manufacturing method is shown below. Figure 1 As shown. From Figure 1 It can be seen that the surface of the particleboard is flat and there are no curls or bends.

[0049] Example 2

[0050] This embodiment provides a method for manufacturing particleboard, and correspondingly obtains a particleboard that can replace veneer applications. The specific manufacturing process is as follows:

[0051] First, the wood shavings left over from wood processing are sieved through 4-mesh and 10-mesh screens to obtain wood shavings with a size of 4-10 mesh and a moisture content of about 5%.

[0052] Next, add 2g of diionic polyacrylamide with a molecular weight of about 8 million and 2g of sodium carboxymethyl cellulose to 60.50g of water and stir manually for 5min to 10min until the polyacrylamide is completely dissolved; then add 1g of glycolic acid as a water-resistant agent and stir manually for 5min to 10min until the glycolic acid is completely dissolved; then add 47.38g of magnesium chloride hexahydrate and stir until completely dissolved to obtain a magnesium salt aqueous solution.

[0053] The third step is to add the above magnesium salt aqueous solution to 201.81g of wood shavings and stir it in a mixing tank until it is evenly mixed. Then, weigh out 93.37g of active magnesium oxide and add it to the stirred wood shavings and continue stirring until it is evenly mixed to obtain the paving material (magnesium oxychloride cement as an inorganic adhesive).

[0054] Specifically, the moisture content of the paving material was 21.42%.

[0055] The fourth step is to lay the paving material in three layers, ensuring that the amount laid each time is approximately the same. Precise weighing is not required to obtain the paving material.

[0056] The fifth step is to place the paving material into a hot press and hot press it at a temperature of 120°C and a unit pressure of 6MPa for 15 minutes. After hot pressing, the pressure is gradually reduced until the unit pressure drops to no more than 0.1MPa and is maintained for at least 10 minutes. Then, the pressure is released and the slab is removed to obtain the blank.

[0057] Finally, the slab is clamped and pressurized using a steel plate mold, with the clamping pressure controlled between 0.1MPa and 0.2MPa; the humidity in the curing chamber is adjusted, and the humidity is controlled to decrease gradually according to the following pattern: "80% to 83% for one day, 55% to 60% for one day, 40% to 42% for one day, and 20% to 25% for four days" to obtain a particleboard with a thickness of 3.0mm.

[0058] Example 3

[0059] This embodiment provides a method for manufacturing particleboard, and correspondingly obtains a particleboard that can replace veneer applications. The specific manufacturing process is as follows:

[0060] First, the wood shavings left over from wood processing are sieved through 4-mesh and 10-mesh screens to obtain wood shavings with a size of 4-10 mesh and a moisture content of about 5%.

[0061] Add 1g of glycolic acid as a water-resistant agent to 62.2g of water and stir manually for 5min to 10min until the glycolic acid is completely dissolved; then add 42.02g of magnesium chloride hexahydrate and stir until completely dissolved to obtain a magnesium salt aqueous solution.

[0062] The third step is to add the above magnesium salt aqueous solution to 201.81g of wood shavings and stir it in a mixing tank until it is evenly mixed. Then, weigh out 96.61g of active magnesium oxide and add it to the stirred wood shavings and continue stirring until it is evenly mixed to obtain the paving material (magnesium oxychloride cement as an inorganic adhesive).

[0063] Specifically, the moisture content of the paving material was 22.06%.

[0064] The fourth step is to lay the paving material in three layers, ensuring that the amount laid each time is approximately the same. Precise weighing is not required to obtain the paving material.

[0065] The fifth step is to place the paving material into a hot press and hot press it at a temperature of 120°C and a unit pressure of 6MPa for 15 minutes. After hot pressing, the pressure is gradually reduced until the unit pressure drops to no more than 0.1MPa and is maintained for at least 10 minutes. Then, the pressure is released and the slab is removed to obtain the blank.

[0066] Finally, the slab is clamped and pressurized using a steel plate mold, with the clamping pressure controlled between 0.1MPa and 0.2MPa; the humidity in the curing chamber is adjusted, and the humidity is controlled to decrease gradually according to the following pattern: "80% to 85% for one day, 60% to 63% for one day, 40% to 44% for one day, and 25% to 30% for four days" to obtain a particleboard with a thickness of 3.0mm.

[0067] Example 4

[0068] This embodiment provides a method for manufacturing particleboard, and correspondingly obtains a particleboard that can replace veneer applications. The specific manufacturing process is as follows:

[0069] First, the wood shavings left over from wood processing are sieved through 4-mesh and 10-mesh screens to obtain wood shavings with a size of 4-10 mesh and a moisture content of about 5%.

[0070] Next, add 2g of sodium carboxymethyl cellulose to 60.50g of water and stir manually for 5min to 10min until the polyacrylamide is completely dissolved; then add 1g of glycolic acid as a water-resistant agent and stir manually for 5min to 10min until the glycolic acid is completely dissolved; then add 47.38g of magnesium chloride hexahydrate and stir until completely dissolved to obtain a magnesium salt aqueous solution.

[0071] The third step is to add the above magnesium salt aqueous solution to 201.81g of wood shavings and stir it in a mixing tank until it is evenly mixed. Then, weigh out 93.37g of active magnesium oxide and add it to the stirred wood shavings and continue stirring until it is evenly mixed to obtain the paving material (magnesium oxychloride cement as an inorganic adhesive).

[0072] Specifically, the moisture content of the paving material was 21.52%.

[0073] The fourth step is to lay the paving material in three layers, ensuring that the amount laid each time is approximately the same. Precise weighing is not required to obtain the paving material.

[0074] The fifth step is to place the paving material into a hot press and hot press it at a temperature of 90℃ and a unit pressure of 6MPa for 20 minutes. After hot pressing, the pressure is gradually reduced until the unit pressure drops to no more than 0.1MPa and is maintained for at least 10 minutes. Then, the pressure is released and the slab is removed to obtain the blank.

[0075] Finally, the slab is clamped and pressurized using a steel plate mold, with the clamping pressure controlled between 0.1MPa and 0.2MPa; the humidity in the curing chamber is adjusted, and the humidity is controlled to decrease gradually according to the following pattern: "80% to 85% for one day, 60% to 63% for one day, 35% to 40% for one day, and 20% to 23% for four days" to obtain a particleboard with a thickness of 3.0mm.

[0076] Example 5

[0077] This embodiment provides a method for manufacturing particleboard, and correspondingly obtains a particleboard that can replace veneer applications. The specific manufacturing process is as follows:

[0078] First, the wood shavings left over from wood processing are sieved through 4-mesh and 10-mesh screens to obtain wood shavings with a size of 4-10 mesh and a moisture content of about 5%.

[0079] Next, add 2g of diionic polyacrylamide with a molecular weight of about 8 million to 60.50g of water and stir manually for 5min to 10min until the polyacrylamide is completely dissolved; then add 1g of glycolic acid as a water-resistant agent and stir manually for 5min to 10min until the glycolic acid is completely dissolved; then add 47.38g of magnesium chloride hexahydrate and stir until completely dissolved to obtain a magnesium salt aqueous solution.

[0080] The third step is to add the above magnesium salt aqueous solution to 201.81g of wood shavings and stir it in a mixing tank until it is evenly mixed. Then, weigh out 93.37g of active magnesium oxide and add it to the stirred wood shavings and continue stirring until it is evenly mixed to obtain the paving material (magnesium oxychloride cement as an inorganic adhesive).

[0081] Specifically, the moisture content of the paving material was 21.43%.

[0082] The fourth step is to lay the paving material in three layers, ensuring that the amount laid each time is approximately the same. Precise weighing is not required to obtain the paving material.

[0083] The fifth step is to place the paving material into a hot press and hot press it at a temperature of 120°C and a unit pressure of 5MPa for 15 minutes. After hot pressing, the pressure is gradually reduced until the unit pressure drops to no more than 0.1MPa and is maintained for at least 10 minutes. Then, the pressure is released and the slab is removed to obtain the blank.

[0084] Finally, the slab is clamped and pressurized using a steel plate mold, with the clamping pressure controlled between 0.1MPa and 0.2MPa; the humidity in the curing chamber is adjusted, and the humidity is controlled to decrease gradually according to the following pattern: "80% to 83% for one day, 58% to 63% for one day, 35% to 40% for one day, and 20% to 25% for four days" to obtain a particleboard with a thickness of 3.0mm.

[0085] Example 6

[0086] The similarities between this embodiment and Embodiment 2 will not be repeated here; only the differences from Embodiment 2 will be described. The difference between this embodiment and Embodiment 2 is that, in this embodiment, in the second step, only 1g each of diionic polyacrylamide and sodium carboxymethyl cellulose are added; the rest is as described in Embodiment 2, to obtain a 3.0mm particleboard.

[0087] Example 7

[0088] The similarities between this embodiment and Embodiment 2 will not be repeated here; only the differences from Embodiment 2 will be described. The difference between this embodiment and Embodiment 2 is that, in this embodiment, 0.5g of glycolic acid is added as a water-resistant agent in the second step; the rest is the same as described in Embodiment 2, to obtain a 3.0mm particleboard.

[0089] Example 8

[0090] First, the wood shavings left over from wood processing are sieved through 4-mesh and 10-mesh screens to obtain wood shavings with a size of 4-10 mesh and a moisture content of about 5%.

[0091] Next, add 2g of diionic polyacrylamide with a molecular weight of about 8 million and 2g of sodium carboxymethyl cellulose to 64.97g of water and stir manually for 5min to 10min until the polyacrylamide is completely dissolved; then add 1g of glycolic acid as a water-resistant agent and stir manually for 5min to 10min until the glycolic acid is completely dissolved; then add 27.18g of magnesium chloride hexahydrate and 27.456g of magnesium sulfate heptahydrate and stir until completely dissolved to obtain a magnesium salt aqueous solution.

[0092] The third step is to add the above magnesium salt aqueous solution to 201.81g of wood shavings and stir it in a mixing tank until it is evenly mixed. Then, weigh out 81.703g of active magnesium oxide and add it to the stirred wood shavings and continue stirring until it is evenly mixed to obtain the paving material (equal amounts of magnesium oxychloride cement and magnesium oxysulfide cement are mixed as inorganic adhesive).

[0093] Specifically, the moisture content of the paving material was 22.67%.

[0094] The fourth step is to lay the paving material in three layers, ensuring that the amount laid each time is approximately the same. Precise weighing is not required to obtain the paving material.

[0095] The fifth step is to place the paving material into a hot press and hot press it at a temperature of 120°C and a unit pressure of 6MPa for 15 minutes. After hot pressing, the pressure is gradually reduced until the unit pressure drops to no more than 0.1MPa and is maintained for at least 10 minutes. Then, the pressure is released and the slab is removed to obtain the blank.

[0096] Finally, the slab is clamped and pressurized using a steel plate mold, with the clamping pressure controlled between 0.1MPa and 0.2MPa; the humidity in the curing chamber is adjusted, and the humidity is controlled to decrease gradually according to the following pattern: "80% to 83% for one day, 58% to 63% for one day, 35% to 40% for one day, and 20% to 25% for four days" to obtain a particleboard with a thickness of 3.0mm.

[0097] Example 9

[0098] The similarities between this embodiment and Embodiment 2 will not be repeated here; only the differences will be described. The difference between this embodiment and Embodiment 2 is that in this embodiment, during the fourth step of installation, the installation is performed in five equal steps, while the rest is the same as described in Embodiment 2, resulting in a particleboard with a thickness of 3.0 mm.

[0099] Example 10

[0100] The similarities between this embodiment and Embodiment 2 will not be repeated here; only the differences from Embodiment 2 will be described. The difference between this embodiment and Embodiment 2 is that, in this embodiment, the wood shavings remaining after processing are first sieved through 4-mesh and 10-mesh screens to obtain wood shavings with a size of 4-mesh to 10-mesh and a moisture content of about 5%.

[0101] Next, 2.67g of diionic polyacrylamide with a molecular weight of approximately 8 million and 2.67g of sodium carboxymethyl cellulose were added to 100.83g of water and stirred manually for 5 to 10 minutes until the polyacrylamide was completely dissolved. Then, 1.33g of glycolic acid was added as a water-resistant agent and stirred manually for 5 to 10 minutes until the glycolic acid was completely dissolved. Then, 78.97g of magnesium chloride hexahydrate was added and stirred until completely dissolved to obtain a magnesium salt aqueous solution.

[0102] The third step is to add the above magnesium salt aqueous solution to 336.35g of wood shavings and stir it in a mixing tank until it is evenly mixed. Then, weigh out 155.62g of active magnesium oxide and add it to the stirred wood shavings and continue stirring until it is evenly mixed to obtain the paving material (magnesium oxychloride cement as an inorganic adhesive).

[0103] Specifically, the moisture content of the paving material was 21.69%.

[0104] The fourth step is to lay the paving material in three layers, ensuring that the amount laid each time is approximately the same. Precise weighing is not required to obtain the paving material.

[0105] The fifth step is to place the paving material into a hot press and hot press it at a temperature of 120°C and a unit pressure of 6MPa for 15 minutes. After hot pressing, the pressure is gradually reduced until the unit pressure drops to no more than 0.1MPa and is maintained for at least 10 minutes. Then, the pressure is released and the slab is removed to obtain the blank.

[0106] Finally, the slab is clamped and pressurized using a steel plate mold, with the clamping pressure controlled between 0.1MPa and 0.2MPa; the humidity in the curing chamber is adjusted, and the humidity is controlled to decrease gradually according to the following pattern: "80% to 83% for one day, 58% to 63% for one day, 35% to 40% for one day, and 20% to 25% for four days" to obtain a particleboard with a thickness of 5.0mm.

[0107] It should be noted that in the above embodiments, the water-resistant agent is a conventional functional additive in magnesium cementitious materials, specifically glycolic acid, but it can also be selected from phosphoric acid, citric acid and tartaric acid, etc., which will not be elaborated here.

[0108] To demonstrate the necessity of the hot pressing pressure, laying method, and curing method in the above-mentioned method for manufacturing particleboard of the present invention, several comparative experiments were conducted.

[0109] Comparative Example 1

[0110] The similarities between this comparative example and Example 2 will not be repeated here; only the differences between them will be described. The difference between this comparative example and Example 2 is that, in this comparative example, a unit pressure of 3 MPa is used during the fifth step of hot pressing; the rest is the same as described in Example 2, resulting in a first comparative particleboard.

[0111] Comparative Example 2

[0112] The similarities between this comparative example and Example 2 will not be repeated here; only the differences between them will be described. The difference between this comparative example and Example 2 is that, in this comparative example, during the fourth step of installation, a one-time installation method similar to that of conventional particleboard (thickness greater than 6mm) is used; the rest is as described in Example 2, resulting in a second comparative particleboard.

[0113] Comparative Example 3

[0114] The similarities between this comparative example and Example 2 will not be repeated here; only the differences from Example 2 will be described. The difference between this comparative example and Example 2 is that, in the final curing step, conventional curing methods for particleboard (thickness greater than 6 mm) are used, i.e., steel plate clamping and pressure are not used; instead, the particleboard is directly placed in a curing box and cured at 80%–90% humidity. The rest of the process is the same as described in Example 2, resulting in a third comparative particleboard.

[0115] The physical image of the third comparative particleboard obtained by the above manufacturing method is shown below. Figure 2 As shown. From Figure 2 It can be seen that the surface of the particleboard is extremely bent, indicating a serious deformation problem.

[0116] Comparative Example 4

[0117] The similarities between this comparative example and Example 2 will not be repeated here; only the differences between them will be described. The difference between this comparative example and Example 2 is that, in this comparative example, the clamping pressure is controlled at 0.05 MPa during the final curing step; the rest is the same as described in Example 2, resulting in a fourth comparative particleboard.

[0118] The physical image of the fourth comparative particleboard obtained by the above manufacturing method is shown below. Figure 3 As shown. From Figure 3 It can be seen that the surface of the particleboard has a slight deformation problem.

[0119] Comparative Example 5

[0120] The similarities between this comparative example and Example 2 will not be repeated here; only the differences between them will be described. The difference between this comparative example and Example 2 is that in this comparative example, the final curing step is carried out at normal temperature and humidity (around 50% humidity); the rest is as described in Example 2, resulting in the fifth comparative particleboard.

[0121] Comparative Example 6

[0122] The similarities between this comparative example and Example 2 will not be repeated here; only the differences between them will be described. The difference between this comparative example and Example 2 is that in this comparative example, during the final curing step, the humidity was controlled to decrease rapidly (without a gradient decrease) in the manner of "80% to 83% for three days - 20% to 25% for four days"; the rest was the same as described in Example 2, resulting in the sixth comparative particleboard.

[0123] Comparative Example 7

[0124] The similarities between this comparative example and Example 2 will not be repeated here; only the differences between them will be described. The difference between this comparative example and Example 2 is that in this comparative example, during the final curing step, the humidity was controlled to decrease rapidly (without a gradient decrease) from 80% to 83% for one day to 20% to 25% for six days; the rest was the same as described in Example 2, resulting in the seventh comparative particleboard.

[0125] Comparative Example 8

[0126] The similarities between this comparative example and Example 2 will not be repeated here; only the differences from Example 2 will be described. The difference between this comparative example and Example 2 is that the particle size used is less than 4 mesh; otherwise, it is the same as described in Example 2, resulting in an eighth comparative particleboard.

[0127] Comparative Example 9

[0128] The similarities between this comparative example and Example 2 will not be repeated here; only the differences from Example 2 will be described. The difference between this comparative example and Example 2 is that the particle size used is greater than 10; otherwise, it is the same as described in Example 2, resulting in the ninth comparative particleboard.

[0129] It should be noted that in the above embodiments and comparative examples, the humidity range under each humidity gradient represents a small range of slight fluctuations, while the average humidity change between different gradients is not less than 20%.

[0130] The performance of each particleboard provided in the above embodiments and comparative examples was tested;

[0131] 1) The fire resistance rating of each particleboard was tested according to the test method of GB 8624-2012 "Classification of Combustion Performance of Building Materials and Products";

[0132] 2) The performance of each particleboard was tested according to the methods in GB / T 17657-2013 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels";

[0133] 3) Refer to the standard for furniture-type particleboard (P2 type) used in dry condition in GB / T4897-2015 "Particleboard".

[0134] The test results are shown in Table 1 below.

[0135] Table 1. Performance test results of particleboard in each embodiment and comparative example.

[0136]

[0137]

[0138] The test results above show that the particleboard produced by the various embodiments of the present invention does not have warping or deformation problems, and its mechanical properties reach the level of 7mm to 9mm thick plywood; it also has better water resistance, internal bond strength and nail holding power than general low-thickness particleboard standards.

[0139] In each pair of proportions, warping and deformation are very likely to occur. Even if abnormal warping does not occur, there will be a significant reduction in mechanical properties and / or poor or even drastic decrease in water resistance.

[0140] Specifically, the difference between Examples 1 to 3 lies in the mass ratio of magnesium oxide to magnesium chloride. In the three examples, the molar ratios of magnesium oxide to magnesium chloride hexahydrate are 5:1, 6:1, and 7:1, respectively. From the mechanical property data, within a certain range, the mechanical properties gradually increase with the increase of the amount of magnesium oxide and magnesium chloride hexahydrate. However, after exceeding a certain value, the strength decreases. The reason for the increase is that the material system requires excess magnesium oxide to react with magnesium chloride hexahydrate to form the strength phase 5Mg(OH)₂·MgCl₂·8H₂O. At this point, the amount of the strength phase is high, hence the high mechanical properties. When the ratio exceeds a certain point, the amount of the strength phase decreases. Furthermore, with the increase of magnesium oxide content, the water absorption thickness expansion test rate is higher during water resistance testing due to the expansion of unreacted magnesium oxide. In addition, Example 3 did not include the tackifier sodium carboxymethyl cellulose and polyacrylamide, resulting in slightly weaker bonding forces between the strength phases, which is also one of the reasons for its decreased strength.

[0141] In Example 4, the hot-pressing temperature was 90°C, but the hot-pressing time was extended to 20 minutes, which allowed the substances in the system to react fully. However, only sodium carboxymethyl cellulose was added, and no tackifier polyacrylamide was added to synergistically enhance the connection between the strength phases. Therefore, its performance was slightly lower than that of Example 2.

[0142] In Example 5, the unit pressure of hot pressing was 5 MPa, which directly affected the density of the particleboard, resulting in a reduction in its mechanical properties. Furthermore, the absence of sodium carboxymethyl cellulose as a tackifier led to insufficient bonding force between the strength phases. In addition, during the water resistance test, because its density was lower than that of Examples 1-4, the five-phase structure 5Mg(OH)2·MgCl2·8H2O between the boards was more easily eroded by water, thus absorbing water and swelling. However, its mechanical properties and water resistance still met the requirements of national standards.

[0143] In Example 6, the addition of less polyacrylamide and sodium carboxymethyl cellulose resulted in a slight decrease in mechanical strength. This is because polyacrylamide and sodium carboxymethyl cellulose can better crosslink the five-phase structure, thereby enhancing its mechanical strength.

[0144] In Example 7, the amount of water-resistant agent added was relatively small, which caused the ions in the inorganic adhesive to dissolve when immersed in water, ultimately resulting in a slight decrease in water resistance.

[0145] In Example 8, the mass ratio of magnesium oxychloride cement to magnesium oxysulfide cement was 1:1 as an inorganic adhesive. Although magnesium oxysulfide cement had better water resistance than magnesium oxychloride cement, its mechanical strength was slightly lower.

[0146] In Example 9, the paving was carried out in five stages, which made the wood shavings more evenly distributed. However, the degree of evenness was not much different from that of three stages, and the performance indicators were similar to those of Example 2, only slightly better than those of Example 2.

[0147] In Example 10, the amount of raw materials was adjusted (compared to 5 / 3 times that in Example 2), and a particleboard with a thickness of 5 mm was pressed. The mechanical properties were not much different from those in Example 2.

[0148] In Comparative Example 1, the unit pressure of the hot press was set to 3 MPa, and it was found that neither the mechanical properties nor the water resistance met the national standards. This is because excessively low hot pressing pressure leads to a low density of the resulting particleboard, making its main strength phase, 5Mg(OH)2·MgCl2·8H2O, more susceptible to water erosion, causing water absorption and swelling, and ultimately resulting in a significant reduction in both mechanical properties and water resistance.

[0149] In Comparative Example 2, the same one-time laying and molding process as conventional thick particleboard was used. For thin particleboard, uneven density occurred in some areas, resulting in lower mechanical strength and poorer water resistance in some test samples.

[0150] In Comparative Example 3, the particleboard was not subjected to steel plate clamping and pressure, and thus, during the curing process, which was in a dynamic process, severe deformation occurred.

[0151] In Comparative Example 4, although the particleboard was pressurized by a steel plate clamping mold, the pressure of the steel plate clamping mold was only 0.05 MPa. Slight deformation still occurred during the curing process, which could not meet the application requirements.

[0152] In Comparative Example 5, the particleboard was cured at normal temperature and humidity. Under normal temperature and humidity, the moisture inside the particleboard would evaporate violently. Although no deformation occurred under the pressure of the steel plate clamping mold, the stress inside did not disappear. Since it was not cured under balanced conditions, deformation still occurred after the pressure was released.

[0153] In Comparative Example 6, without a gradual pressure reduction, the stress in the internal structure did not disappear. Therefore, warping deformation still occurred after the pressure was released.

[0154] In Comparative Example 7, the pressure was not reduced by gradient and the high humidity curing time was too short, which was not conducive to the occurrence of hydration reaction in its internal structure. Therefore, its mechanical properties were lower than those of Example 2.

[0155] In Comparative Example 8, wood shavings with a mesh size of less than 4 were selected for testing. Although the mechanical properties were better (because the larger particle size of the wood shavings provided some strength, resulting in improved mechanical properties), the larger particle size of the wood shavings resulted in larger wood shaving particles on the surface, making the surface of the wood shavings rougher and less practical, especially when used to replace veneer.

[0156] In Comparative Example 9, wood shavings with a mesh size greater than 10 were selected for the test. Although the surface became smoother due to their smaller particle size compared to the original wood shavings, the mechanical properties deteriorated. This is because the effect of small wood shavings on mechanical properties is not beneficial, thus leading to a decrease in strength.

[0157] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing particleboard that can replace veneer, characterized in that, Includes the following steps: S1. Wood shavings preparation: Processing wood into wood shavings; S2. Wood shavings sizing: The wood shavings are soaked in a magnesium salt composite aqueous solution and then magnesium oxide is mixed evenly to obtain a paving material with magnesium cementitious material as inorganic adhesive. S3. Paving: Control the amount of paving material to be paved at one time to not exceed one-third of the total paving amount. Pave according to the principle of small amount and multiple times to obtain paving slabs. S4. Hot pressing: The paving board is hot-pressed at a temperature of 90℃~120℃ and a unit pressure of 5MPa~6MPa for 15min~20min. After hot pressing, the pressure is gradually reduced. After the unit pressure drops to no more than 0.1MPa and is maintained for at least 10min, the pressure is released and the board is removed to obtain the slab blank. S5. Curing: The two sides of the slab are clamped and locked with a hard plate mold, and cured for at least 7 days in a gradient decreasing manner within a humidity range of 80% to 90% to 20% to 30% to obtain a particleboard with a thickness of 3mm to 5mm; wherein the gradient decreasing manner is no less than three gradients, the average humidity change of adjacent gradients is not less than 20%, and the final curing is carried out at a humidity of 20% to 30% for at least 4 days.

2. The manufacturing method according to claim 1, characterized in that, In step S1, the particle size of the wood shavings is 4 mesh to 10 mesh, and their moisture content is controlled to be 2% to 8%.

3. The manufacturing method according to claim 1, characterized in that, In step S5, the clamping pressure is controlled to be 0.1MPa to 0.2MPa.

4. The manufacturing method according to any one of claims 1 to 3, characterized in that, In step S2, the magnesium cementitious material is magnesium sulfate-magnesium oxychloride cement and / or magnesium chloride-magnesium oxychloride cement; the magnesium salt in the magnesium salt composite aqueous solution is magnesium sulfate and / or magnesium chloride, and it is composited with a water-resistant agent.

5. The manufacturing method according to claim 4, characterized in that, The water-resistant agent is selected from at least one of phosphoric acid, citric acid, glycolic acid, and tartaric acid.

6. The manufacturing method according to claim 4, characterized in that, The specific composition of the paving material is as follows: By weight parts.

7. The manufacturing method according to claim 6, characterized in that, The paving material further includes 2 to 4 parts by weight of a thickening modifier; wherein the thickening modifier is 1 to 2 parts by weight of polyacrylamide and / or 1 to 2 parts by weight of sodium carboxymethyl cellulose.

8. The manufacturing method according to claim 7, characterized in that, The polyacrylamide is selected from any one of nonionic, cationic, anionic, and biionic types, and its molecular weight is 5 million to 12 million.

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