Flame-retardant surface layer oriented strand board based on interfacial penetration anchoring and method of making the same
By constructing an interface anchoring structure catalyzed by acid-base reaction and a core layer chelating group in oriented strand board through interface penetration anchoring technology, the problems of low interface bonding strength and metal corrosion are solved, achieving high strength and flame retardancy, and meeting building safety requirements.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF WOOD INDUDTRY CHINESE ACAD OF FORESTRY
- Filing Date
- 2026-04-07
- Publication Date
- 2026-06-09
AI Technical Summary
The bonding strength between the fine core layer and the large particle surface layer of oriented strand board is low, and traditional flame retardants cause corrosion of metal connectors, affecting the long-term safety of building structures.
The interfacial penetration anchoring technology is adopted. By creating a slightly acidic environment on the surface of the wood shavings and forming a weakly alkaline mixture in the core layer, the acid-base reaction catalyzes the rapid reaction of the isocyanate adhesive, forming an interfacial anchoring structure of physical penetration and chemical bonding. At the same time, the active chelating groups in the core layer capture metal ions and form coordination crosslinking.
It improves the internal bond strength and nail-holding power of the board, meets the GB 8624 B1 flame retardant standard, and maintains excellent nail-holding power in humid environments, preventing metal corrosion.
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Figure CN122165519A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to engineered wood products manufacturing technology, specifically to a flame-retardant surface-coated oriented strand board based on interfacial penetration anchoring and its preparation method. Background Technology
[0002] Oriented strand board (OSB) typically requires both the core and surface layers to use large-sized oriented strands to ensure mechanical strength. To reduce costs and improve resource utilization, the industry has experimented with a structure of "large oriented strands on the surface and fine, non-oriented strands in the core." However, this structure has two main drawbacks: First, the interfacial bonding is poor. The contact between the fine core layer and the surface layer of large wood shavings is a "point-to-surface" contact, lacking the physical interweaving between the large wood shavings, resulting in low internal bonding strength and easy delamination.
[0003] Second, there is the issue of metal corrosion. Traditional flame retardants (such as ammonium salts) added for flame retardancy are prone to moisture absorption and can cause corrosion of metal connectors (screws). Corrosion products damage the wood fiber structure, leading to a significant decrease in nail-holding power over time, thus affecting the long-term safety of the building structure. Summary of the Invention
[0004] In view of the above-mentioned research and development issues, this invention addresses the problems of low interlayer bonding strength and easy corrosion of metal connectors in previously unresolved fine core oriented strand board (OSB) by providing a flame-retardant surface OSB based on interfacial penetration anchoring and its preparation method.
[0005] The specific technical solution is as follows: A method for preparing flame-retardant surface oriented strand board based on interfacial penetration anchoring includes the following steps.
[0006] Step 1: Under the condition of hot air flow, the long wood shavings and the acidic adhesive system composed of 1,6-hexanediamine aqueous solution, 2-hydroxyphosphonic acid acetic acid aqueous solution and diphenylmethane diisocyanate are stirred by a mixing machine. When the pH value of the shaving surface reaches 4.0-6.0, the pretreated surface layer large wood shavings are discharged.
[0007] Long wood shavings are wood shavings that are 40-70mm long, 5-20mm wide, and 0.3-0.7mm thick. The wood can be at least one of pine, poplar, or fir.
[0008] The concentration of the 1,6-hexanediamine aqueous solution is 40-65 wt%.
[0009] The concentration of the aqueous solution of 2-hydroxyphosphonic acid is 45-65 wt%.
[0010] The mass ratio of oven-dried long wood shavings, 1,6-hexanediamine aqueous solution, 2-hydroxyphosphonic acid acetic acid aqueous solution, and diphenylmethane diisocyanate is 100 : 5-7 : 2.5-3.5 : 3-5.
[0011] The stirring process includes stirring the reaction at a speed of 150-400 rpm for 1-1.5 minutes.
[0012] The hot air flow is a compressed hot air flow with a temperature of 50-60℃ and a pressure of 0.2-0.3MPa.
[0013] Step 2: The copolymer CS-HH, wood fines, diphenylmethane diisocyanate and an appropriate amount of water are mixed. When the pH value of the wood fines reaches 7.7-8.5, the mixture is discharged to obtain pretreated core fines.
[0014] The copolymer CS-HH was prepared by reacting chitosan acetic acid solution, 1,6-hexanediamine aqueous solution and 2-hydroxyphosphonic acid, and controlling the excess of amine functional groups to make the product weakly basic.
[0015] Chitosan-acetic acid solution is obtained by mixing chitosan and acetic acid aqueous solution with a mass ratio of 1:7-10 at a mass ratio and stirring for 30-50 minutes.
[0016] An aqueous solution of 1,6-hexanediamine is obtained by mixing 1,6-hexanediamine and water in a mass ratio of 1:9-13 and stirring for 20-40 minutes.
[0017] The mass ratio of 2-hydroxyphosphonic acid, chitosan acetic acid solution, and 1,6-hexanediamine aqueous solution is 1:0.8-1.2:2.5-6.0.
[0018] The preparation of copolymer CS-HH specifically includes: mixing 2-hydroxyphosphonic acid acetic acid, chitosan acetic acid solution and 1,6-hexanediamine aqueous solution in a mass ratio of 1:0.8-1.2:2.5-6.0, slowly heating to 55-65℃, reacting for 60-90 min, obtaining a brown precipitate, and obtaining CS-HH after filtration and washing.
[0019] Slow heating means heating at a rate of 1-3℃ / min.
[0020] Wood scraps are waste wood or small wood shavings that are 3-15mm long, 0.5-1.5mm wide, and 0.2-0.4mm thick.
[0021] The mass ratio of copolymer CS-HH to oven-dried wood fines is 10-25:100.
[0022] Diphenylmethane diisocyanate accounts for 3-5 wt% of the total mass of the above copolymer CS-HH and oven-dried wood particles.
[0023] The appropriate amount of water is 1.5-2 wt% of the total mass of the copolymer CS-HH and the oven-dried wood fibers.
[0024] The mixing process includes stirring at 150-400 rpm for 0.5-2 minutes.
[0025] Step 3: The pretreated materials are laid out in the following order: large surface wood chips, fine core material, and large surface wood chips again as the lower surface layer, core layer, and upper surface layer. A hot-pressing process is then performed to obtain the flame-retardant surface oriented strand board.
[0026] The hot pressing process includes a hot pressing temperature of 190-220℃ and a pressure of 5.5-8.0MPa.
[0027] The paving ratio of the lower surface layer, core layer, and upper surface layer is 2:6-8:2.
[0028] Hot pressing employs a slow closing and rapid pressurization method.
[0029] Slow closing involves controlling the closing speed to 0.5-2.0 mm / s during the initial 15-40 seconds of contact between the hot press plate and the slab.
[0030] Rapid pressurization involves slow closure followed by rapid pressurization to 5.5-8.0 MPa for pressure holding and curing for 5-10 minutes.
[0031] A preferred solution includes: The concentration of the aqueous solution of 2-hydroxyphosphonic acid is 55-65 wt%. During the synthesis of CS-HH, the mass ratio of 2-hydroxyphosphonic acid, chitosan acetic acid solution, and 1,6-hexanediamine aqueous solution is 1:0.8-1.2:3-6.
[0032] Another preferred option includes: The hot-pressing temperature is 210-220℃, and the pressure is 6.5-8.0MPa.
[0033] The inventors constructed a mixture of a slightly acidic surface layer of wood chips and a weakly alkaline core layer. They discovered that the rheological properties and the difference in chemical potential between acids and bases during hot pressing allowed for the core layer components to induced permeation into the surface micropores. At the interface, the acid-base environment catalyzes a rapid reaction of the isocyanate adhesive, forming an interfacial anchoring structure that combines physical penetration and chemical bonding, with the effect increasing with the gradient. The resulting board meets the GB 8624 B1 flame-retardant standard. Simultaneously, the active chelating groups in the core layer can form coordination crosslinks with metal ions generated during corrosion, enabling the board to exhibit excellent nail-holding power retention in humid and corrosive environments. Detailed Implementation
[0034] Unless otherwise stated, the numerical range "A~B" in this invention refers to A or above (greater than or equal to A) and B or below (less than or equal to B). When referring to the concept of room temperature, it usually means between 22 and 25°C, and sometimes between 20 and 28°C depending on the process. In actual industry, different fields have different understandings of room temperature or room temperature. However, from the perspective of the implementation and application of patent law, it should be regarded as limited to achieving the purpose of the invention, and should not be limited to a narrow empirical range in a certain field.
[0035] In this invention, if some processes do not specify a temperature or room temperature limit, they should generally be considered to be carried out at room temperature or room temperature. Those skilled in the art can control the process conditions without special knowledge, unless otherwise specified or should be understood by those skilled in the art.
[0036] This invention specifically designs a surface-oriented strand board (OSB), defined as a novel OSB structured particleboard with a surface layer of large, oriented wood shavings and a core layer of fine wood shavings / fine wood particles laid out non-oriented. Specifically, large-sized wood shavings of a specified geometric shape are glued together and laid out in a specific direction as the surface layer. Fine wood shavings, commonly used in ordinary particleboard, are then laid out as the core layer, followed by hot pressing to solidify the mixture.
[0037] The preparation method of flame-retardant surface oriented strand board based on interfacial penetration anchoring of the present invention includes the following steps.
[0038] Step 1: Under the condition of hot air flow, the long wood shavings and the acidic adhesive system composed of 1,6-hexanediamine aqueous solution, 2-hydroxyphosphonic acid acetic acid aqueous solution and diphenylmethane diisocyanate are stirred by a mixing machine. When the pH value of the shaving surface reaches 4.0-6.0, the pretreated surface layer large wood shavings are discharged.
[0039] Long wood shavings are wood shavings that are 40-70mm long, 5-20mm wide, and 0.3-0.7mm thick. The wood is at least one of pine, poplar, or fir.
[0040] The concentration of the 1,6-hexanediamine aqueous solution is 40-65 wt%.
[0041] The concentration of the aqueous solution of 2-hydroxyphosphonic acid is 45-65 wt%.
[0042] The mass ratio of oven-dried long wood shavings, 1,6-hexanediamine aqueous solution, 2-hydroxyphosphonic acid acetic acid aqueous solution, and diphenylmethane diisocyanate is 100 : 5-7 : 2.5-3.5 : 3-5.
[0043] The mixing machine is not particularly limited, but it is preferable to have separate channels for placing wood shavings and adhesive in the feed area. The acidic adhesive system can be premixed or applied from different feed channels.
[0044] There are no special restrictions on stirring speed and time, as long as the output is uniform and the pH value reaches 4.0-6.0.
[0045] pH value can be determined, for example, by sampling and monitoring. In the case of a continuous feeding mixer, a sampling hole can be set along the feeding route. In this case, the mixing time is determined by a combination of the mixing speed and the feeding length, but before sampling, the mixing reaction should be carried out at a speed of at least 150-400 rpm for 1-1.5 minutes.
[0046] The hot air flow is a compressed hot air flow with a temperature of 50-60℃ and a pressure of 0.2-0.3MPa.
[0047] In this process, 2-hydroxyphosphonic acid, 1,6-hexanediamine, and the surface of the wood shavings undergo a chemical grafting reaction as shown in the following formula.
[0048]
[0049] 2-Hydroxyphosphonic acid and 1,6-hexanediamine undergo a grafting reaction with the hydroxyl groups of wood under the action of hot air, introducing phosphate ester bonds and carboxyl groups on the wood surface to construct a slightly acidic surface (pH 4.0-6.5). This not only imparts flame retardancy to the surface layer but also inhibits the pre-curing of diphenylmethane diisocyanate at room temperature, thus preserving its reactivity.
[0050] Step 2: The copolymer CS-HH, wood fibers, diphenylmethane diisocyanate, and an appropriate amount of water were mixed to obtain a weakly alkaline pretreated core layer fiber.
[0051] The copolymer CS-HH was prepared by reacting chitosan acetic acid solution, 1,6-hexanediamine aqueous solution and 2-hydroxyphosphonic acid, and controlling the excess of amine functional groups to make the product weakly basic.
[0052] The preparation reaction formula is as follows.
[0053]
[0054] Chitosan-acetic acid solution is obtained by mixing chitosan and acetic acid aqueous solution with a mass ratio of 1:7-10 at a mass ratio and stirring for 30-50 minutes.
[0055] An aqueous solution of 1,6-hexanediamine is obtained by mixing 1,6-hexanediamine and water in a mass ratio of 1:9-13 and stirring for 20-40 minutes.
[0056] The chitosan acetic acid solution involved in the following embodiments and comparative examples of the present invention was obtained by mixing chitosan and acetic acid aqueous solution with a mass ratio of 1:8.5 and stirring for 30 min; the 1,6-hexanediamine aqueous solution was obtained by mixing 1,6-hexanediamine and water with a mass ratio of 1:11 and stirring for 20 min.
[0057] 2-Hydroxyphosphonic acid is a solid powder.
[0058] The mass ratio of 2-hydroxyphosphonic acid, chitosan acetic acid solution, and 1,6-hexanediamine aqueous solution is 1:0.8-1.2:2.5-6.0.
[0059] The preparation of copolymer CS-HH specifically includes: mixing 2-hydroxyphosphonic acid, chitosan acetic acid solution and 1,6-hexanediamine aqueous solution in a mass ratio of 1:0.8-1.2:2.5-6.0, slowly heating to 55-65℃, reacting for 60-90 min, obtaining a brown precipitate, and obtaining CS-HH after filtration and washing.
[0060] Slow heating means heating at a rate of 1-3℃ / min.
[0061] After filtration, the process also includes washing with deionized water.
[0062] Wood scraps are waste wood or small wood shavings that are 3-15mm long, 0.5-1.5mm wide, and 0.2-0.4mm thick.
[0063] The copolymer CS-HH is preferably ground.
[0064] The copolymer CS-HH, wood fibers, diphenylmethane diisocyanate and an appropriate amount of water are preferably mixed by a mixing machine to obtain pretreated core layer shavings that are weakly alkaline and have thermal thixotropic properties.
[0065] When the pH value of the wood pulp reaches 7.7-8.5, a weakly alkaline pretreated core layer is obtained. The pH value of the wood shavings can be determined, for example, by sampling and monitoring. In the case of a continuous feeding mixer, a sampling hole can be set along the feeding route. In this case, the mixing time is determined by a combination of the mixing speed and the feeding length, but before sampling, the mixing reaction should be carried out at a speed of at least 150-400 rpm for 0.5-2 minutes.
[0066] The mass ratio of copolymer CS-HH to oven-dried wood fines is 10-25:100.
[0067] Diphenylmethane diisocyanate accounts for 3-5 wt% of the total mass of the copolymer CS-HH and the oven-dried wood fines.
[0068] The appropriate amount of water is 1.5-2 wt% of the total mass of the copolymer CS-HH and the oven-dried wood fibers.
[0069] The mixer is not particularly limited, but it is preferable to have separate channels for placing wood shavings and fillers in the feed area. The copolymer CS-HH and diphenylmethane diisocyanate can be premixed or applied from different feed channels.
[0070] The mixing conditions are to stir at 150-400 rpm for 0.5-2 min to ensure that diphenylmethane diisocyanate is evenly distributed on the surface of the mixture.
[0071] During the synthesis of CS-HH, an excess of amino groups is controlled. The chitosan (CS) backbone is grafted with 2-hydroxyphosphonic acid and 1,6-hexanediamine to form a three-dimensional network structure. This structure is rich in unreacted amino groups (-NH2), making it weakly basic.
[0072] In steps 1 and 2, the pH value of the surface of the large wood shavings in the pre-treatment layer before discharge is controlled to be greater than or equal to 1.7 and the pH value of the surface of the fine material in the pre-treatment core layer is controlled to be greater than or equal to 1.7 and less than or equal to 4.8.
[0073] Step 3: The pretreated materials are laid out in the following order: large surface wood chips, fine core material, and large surface wood chips again as the lower surface layer, core layer, and upper surface layer. The materials are then pre-pressed to obtain a pre-pressed slab. The pre-pressed slab is then hot-pressed at a temperature of 190-220℃, a pressure of 5.5-8.0MPa, and a time of 5-10 minutes.
[0074] The paving ratio of the lower surface layer, core layer, and upper surface layer is 2:6-8:2.
[0075] The high specific surface area and fluidity of the fine material allow the core layer mixture to fill the pores between the large shavings of the upper and lower surface layers. Driven by the steam pressure generated by hot pressing, the alkaline core layer components undergo micro-convection permeation to the acidic interface between the upper and lower surface layers, forming a physically-chemically locked interface pinning layer.
[0076] Hot pressing employs a slow closing and rapid pressurization method.
[0077] Slow closing involves controlling the closing speed to 0.5-2.0 mm / s during the initial 15-40 seconds of contact between the hot press plate and the slab.
[0078] Thus, heat and pressure are used to liquefy the core layer mixture and force it into the gaps between the large shavings on the surface layer.
[0079] Rapid pressurization involves slow closure followed by rapid pressurization to 5.5-8.0 MPa for pressure holding and curing for 5-10 minutes.
[0080] Thus, the interface is solidified by acid-base reaction, forming a physically-chemically locked interface pinning layer.
[0081] Before the hot pressing process, a pre-pressing process can be carried out to obtain a pre-pressed slab, and then the hot pressing process can be carried out on the pre-pressed slab.
[0082] A preferred solution includes: The concentration of the aqueous solution of 2-hydroxyphosphonic acid is 55-65 wt%. During the synthesis of CS-HH, the mass ratio of 2-hydroxyphosphonic acid, chitosan acetic acid solution, and 1,6-hexanediamine aqueous solution is 1: 0.8-1.2: 3.5-6.
[0083] A preferred solution includes: The hot pressing temperature is 210-220℃, and the pressure is 6.5-8.0MPa.
[0084] This allows CS-HH powder to form a more uniform paste on the surface of fine materials, improving the fluidity during the initial stage of hot pressing.
[0085] During the hot pressing process, the free amine groups (-NH2) carried by CS-HH in the core layer migrate to the surface interface with water vapor, and undergo an exothermic neutralization reaction with the acidic 2-hydroxyphosphonic acid and diphenylmethane diisocyanate enriched on the surface. This induces the diphenylmethane diisocyanate adhesive at the interface to rapidly form a polyurea / polyurethane rigid network under the infiltration state.
[0086] In other words, the core layer liquefies upon heating and permeates to the surface interface. The basic amine groups in the core layer attack the acidic groups in the surface layer, resulting in a neutralization reaction that is exothermic. This enhances the nucleophilic activity of the amine groups in the modified surface wood shavings, promoting a reaction with diphenylmethane diisocyanate at the core-surface interface to generate a high-strength polyurea structure. This instantly activates the curing reaction of the diphenylmethane diisocyanate at the interface, generating high-strength polyurea bonds. This "acid-base catalysis-in-situ curing" mechanism firmly locks the physically permeated core layer "roots" within the surface framework.
[0087] In the preparation of layered particleboard, to ensure consistent adhesive curing and maintain internal bond strength, the pH value of the core and surface particleboard layers must be kept constant after adhesive application. Furthermore, to minimize the negative impact of pH differences, during the typical hot-pressing process, the pressure must be increased to the required level as quickly as possible after pre-pressing to reduce the negative effects of inconsistent curing.
[0088] In this invention, a core and surface layer of wood shavings with pH differences are designed. During hot pressing, the amine groups of the core layer react with the phosphorus hydroxyl groups of the surface layer at the molecular interface level, releasing heat and improving the nucleophilic activity of the amine groups of the modified surface layer wood shavings. This promotes the reaction with diphenylmethane diisocyanate at the core-surface interface to generate a high-strength polyurea structure.
[0089] Meanwhile, the core layer mixture has metal ion-induced self-reinforcing properties. When the metal connectors in contact with the plate corrode and release metal ions, the chitosan-polyamine network in the core layer captures the metal ions in situ and forms coordination crosslinking nodes.
[0090] In other words, the abundant hydroxyl and amine groups in the CS-HH structure are excellent chelating ligands. When the screw corrodes, Fe is released... 2 + / Fe 3+ or Zn 2+ When ions are present, they are captured by the core network and form coordination bonds, increasing the crosslinking density of the polymer network and thus achieving a counter-intuitive increase in nail-holding force.
[0091] Example 1
[0092] (1) Surface preparation: Pine wood shavings with a length of 40-70 mm, a width of 5-20 mm, and a thickness of 0.3-0.7 mm were placed in a glue mixer. 7 wt% of the surface shavings were added to a 40% aqueous solution of 1,6-hexanediamine, 3.5% to a 45% aqueous solution of 2-hydroxyphosphonic acid acetic acid, and 5% to diphenylmethane diisocyanate. Compressed hot air at 60°C and 0.3 MPa was introduced and stirred at 400 rpm for 1.5 minutes. Pretreated surface shavings were obtained, with a pH of approximately 4.8.
[0093] (2) Core layer preparation: CS-HH synthesis: 2-hydroxyphosphonic acid, chitosan acetic acid solution and 1,6-hexanediamine aqueous solution were mixed evenly at a mass ratio of 1:1.2:2.5, heated to 65℃ at a rate of 3℃ / min, and reacted for 90min to obtain a brown precipitate. After filtration and washing, CS-HH was obtained. Poplar wood fines with a length of 3-15mm, a width of 0.5-1.5mm and a thickness of 0.2-0.4mm were mixed with CS-HH powder accounting for 25% of the mass of poplar wood fines, diphenylmethane diisocyanate accounting for 5% of the total mass of fines and CS-HH, and water accounting for 2wt% of the total mass of fines and CS-HH. The mixture was stirred at a speed of 400 rpm for 2min to obtain a core layer mixture with a pH of about 8.0.
[0094] (3) Hot pressing: The pretreated materials are laid in the following order: large surface wood chips, fine core material, and large surface wood chips again as the lower surface layer, core layer, and upper surface layer, with a mass ratio of 2:8:2. The hot pressing temperature is 190℃ and the pressure is 5.5MPa. A slow closing process is adopted: the closing speed is controlled at 2mm / s within the first 40 seconds of the pressure plate contacting the board blank, and then the pressure is rapidly increased to 8MPa and held for 10min. A flame-retardant surface oriented strand board is obtained.
[0095] Example 2
[0096] (1) Surface preparation: Pine wood shavings with a length of 40-70 mm, a width of 5-20 mm, and a thickness of 0.3-0.7 mm were placed in a glue mixer. 5% (by weight) of 1,6-hexanediamine aqueous solution (40% concentration), 2.5% (by weight) of 2-hydroxyphosphonic acid acetic acid aqueous solution (45% concentration), and 3% (by weight) of diphenylmethane diisocyanate were applied. Compressed hot air at 50°C and 0.2 MPa was introduced and stirred at 150 rpm for 1 minute. Pretreated surface wood shavings were obtained, with a pH of approximately 6.0.
[0097] (2) Core layer preparation: CS-HH synthesis: 2-hydroxyphosphonic acid, chitosan acetic acid solution and 1,6-hexanediamine aqueous solution were mixed evenly at a mass ratio of 1:0.8:2.5, heated to 55℃ at a rate of 1℃ / min, and reacted for 60min to obtain a brown precipitate. After filtration and washing, CS-HH was obtained. Poplar wood fines with a length of 3-15mm, a width of 0.5-1.5mm and a thickness of 0.2-0.4mm were mixed with 10% of the mass of poplar wood fines, 3wt% of the total mass of fines and CS-HH, diphenylmethane diisocyanate, and 1.5wt% of the total mass of fines and CS-HH, and stirred at a speed of 150 rpm for 0.5min to obtain a core layer mixture with a pH of about 7.7.
[0098] (3) Hot pressing: The pretreated materials are laid in the following order: large surface wood chips, fine core material, and large surface wood chips again as the lower surface layer, core layer, and upper surface layer, with a mass ratio of 2:6:2. The hot pressing temperature is 190℃ and the pressure is 5.5MPa. A slow closing process is adopted: the closing speed is controlled at 0.5mm / s within the first 15 seconds of the pressure plate contacting the board blank, and then the pressure is rapidly increased to 5.5MPa and held for 5 minutes. A flame-retardant surface oriented strand board is obtained.
[0099] Example 3
[0100] Based on Example 1, only the following process is changed: In the preparation of the surface layer (1), the concentration of the aqueous solution of 2-hydroxyphosphonic acid was 55 wt%, and pretreated surface layer shavings were obtained. The pH of the surface layer shavings was about 4.2. In the preparation of the core layer (2), the preparation of CS-HH includes a mass ratio of 2-hydroxyphosphonic acid, chitosan acetic acid solution and 1,6-hexanediamine aqueous solution of 1:1.2:3.5 to obtain a core layer mixture with a pH of about 7.8.
[0101] Example 4
[0102] Based on Example 1, only the following process is changed: In the preparation of the surface layer (1), the concentration of the aqueous solution of 2-hydroxyphosphonic acid is 65wt%, and pretreated surface layer shavings are obtained. The pH of the surface layer shavings is about 4.0. In the preparation of the core layer (2), the preparation of CS-HH includes a mass ratio of 2-hydroxyphosphonic acid, chitosan acetic acid solution and 1,6-hexanediamine aqueous solution of 1:1.2:6, to obtain a core layer mixture with a pH of about 8.5.
[0103] Example 5
[0104] Based on Example 1, only the following process is changed: In step (3), the hot pressing temperature is 210℃ and the hot pressing pressure is 6.5MPa.
[0105] Example 6
[0106] Based on Example 1, only the following process is changed: In (3), the hot pressing temperature is 220℃ and the hot pressing pressure is 8MPa.
[0107] Comparative Example 1
[0108] Based on Example 1, only the following process is changed: In the preparation of the core layer (2), poplar wood fines with a length of 3-15 mm, a width of 0.5-1.5 mm, and a thickness of 0.2-0.4 mm are mixed with 5% of the mass of poplar wood fines in an aqueous solution of 1,6-hexanediamine (concentration 40%), 2.5% of the mass of 2-hydroxyphosphonic acid acetic acid (concentration 45%), 3% of diphenylmethane diisocyanate, and 1.5 wt% of the total mass of the fines and CS-HH, and stirred at a speed of 150 rpm for 0.5 min to obtain the core layer mixture.
[0109] Comparative Example 2
[0110] Based on Example 1, only the following process is changed: In the surface preparation (1), 1 wt% of water by weight of the oven-dried long wood shavings was added to obtain pretreated surface wood shavings with a pH of approximately 6.5. In the preparation of the core layer (2), the added water accounts for 3wt% of the total mass of the fine material and CS-HH, and a core layer mixture with a pH of about 7.5 is obtained.
[0111] Table 1 Performance test data of the examples and comparative examples
Claims
1. A method for preparing flame-retardant oriented strand board with a surface layer based on interfacial penetration anchoring, characterized in that, include: (1) Under the condition of hot air flow, the long wood shavings and the acidic adhesive system composed of 1,6-hexanediamine aqueous solution, 2-hydroxyphosphonic acid acetic acid aqueous solution and diphenylmethane diisocyanate are stirred by a mixing machine. When the pH value of the shaving surface reaches 4.0-6.0, the material is discharged to obtain pretreated surface large wood shavings. (2) The copolymer CS-HH, wood fines, diphenylmethane diisocyanate, and an appropriate amount of water are mixed. When the pH value of the wood fines surface reaches 7.7-8.5, the mixture is discharged to obtain pretreated core fines. The copolymer CS-HH is prepared by reacting a mixture of chitosan acetic acid solution, 1,6-hexanediamine aqueous solution, and 2-hydroxyphosphonic acid acetic acid, controlling the excess of amine functional groups to make the product weakly basic. The preparation reaction formula is as follows: ； (3) The pretreated materials are laid in the order of surface large wood chips, core fine material, and surface large wood chips as the lower surface layer, core layer, and upper surface layer, and hot pressing process is carried out to obtain the flame-retardant surface oriented strand board.
2. The preparation method according to claim 1, wherein, In (2), The preparation of copolymer CS-HH includes: Chitosan-acetic acid solution is obtained by mixing chitosan and acetic acid aqueous solution with a mass ratio of 1:7-10 at a mass ratio and stirring for 30-50 minutes. An aqueous solution of 1,6-hexanediamine is obtained by mixing 1,6-hexanediamine and water in a mass ratio of 1:9-13 and stirring for 20-40 minutes. A solution of 2-hydroxyphosphonic acid, chitosan acetic acid, and 1,6-hexanediamine in a mass ratio of 1:0.8-1.2:2.5-6.0 was mixed evenly, and the mixture was slowly heated to 55-65℃ and reacted for 60-90 min to obtain a brown precipitate. After filtration and washing, CS-HH was obtained.
3. The preparation method according to claim 2, wherein, In (1), The concentration of the 1,6-hexanediamine aqueous solution is 40-65 wt%. The concentration of the aqueous solution of 2-hydroxyphosphonic acid is 45-65 wt%. The mass ratio of oven-dried long wood shavings, 1,6-hexanediamine aqueous solution, 2-hydroxyphosphonic acid acetic acid aqueous solution, and diphenylmethane diisocyanate is 100 : 5-7 : 2.5-3.5 : 3-5; In (2), The mass ratio of copolymer CS-HH to oven-dried wood fines is 10-25:100; Diphenylmethane diisocyanate constitutes 3-5 wt% of the total mass of copolymer CS-HH and oven-dried wood particles; The appropriate amount of water is 1.5-2 wt% of the total mass of the copolymer CS-HH and the oven-dried wood fibers.
4. The preparation method according to claim 1, wherein, In (1), The hot air flow is a compressed hot air flow with a temperature of 50-60℃ and a pressure of 0.2-0.3MPa.
5. The preparation method according to claim 1, wherein, In (3), The hot pressing process includes a hot pressing temperature of 190-220℃ and a hot pressing pressure of 5.5-8.0 MPa. It also adopts a slow closing and fast voltage boosting method: Slow closing means controlling the closing speed to 0.5-2.0 mm / s during the first 15-40 seconds of contact between the hot press plate and the slab. The rapid pressurization process involves first closing the device slowly, then rapidly increasing the pressure to the aforementioned hot-pressing pressure and holding it under pressure for 5-10 minutes to cure.
6. The preparation method according to claim 1, wherein, Long wood shavings are wood shavings that are 40-70mm long, 5-20mm wide, and 0.3-0.7mm thick. Wood scraps are waste wood or small wood shavings that are 3-15mm long, 0.5-1.5mm wide, and 0.2-0.4mm thick.
7. The preparation method according to claim 3, wherein, In (1), the concentration of the aqueous solution of 2-hydroxyphosphonic acid is 55-65 wt%; In step (2), the mass ratio of 2-hydroxyphosphonic acid, chitosan acetic acid solution, and 1,6-hexanediamine aqueous solution in the preparation of CS-HH is 1: 0.8-1.2: 3.5-6.
8. The preparation method according to claim 5, wherein, In (3), the hot pressing temperature is 210-220℃ and the hot pressing pressure is 6.5-8.0MPa.
9. The preparation method according to claim 1, wherein, In (1), the stirring process includes stirring the reaction at a speed of 150-400 rpm for 1-1.5 min; In step (2), the mixing process includes stirring at a speed of 150-400 rpm for 0.5-2 min.
10. A flame-retardant surface-coated oriented strand board prepared by the preparation method according to any one of claims 1-9.