Low-formaldehyde integrated board

Abstract

The invention relates to the technical field of plate manufacturing, in particular to a low-formaldehyde integrated plate which comprises the following raw materials: a wood raw material, a modified MDI adhesive, a modified environment-friendly additive and modified nano silicon dioxide. According to the invention, the modified MDI adhesive is a formaldehyde-free bonding system modified by polyether polyol, and provides excellent basic bonding strength; the modified environment-friendly additive is a natural resin-vegetable oil composite system grafted and modified by maleic anhydride, and the water resistance and the flexibility of the board can be improved; the modified nano silicon dioxide is nano particles modified by a silane coupling agent KH-560, and interface gaps can be filled so as to enhance the mechanical property. The three modified materials and the wood raw materials are cooperatively matched, so that the low-formaldehyde and environment-friendly characteristics of the board are ensured, and good balance among the bonding strength, the water resistance and the mechanical property is realized, so that the board has the environment-friendly property and the practical property.

Description

Technical Field

[0001] This invention relates to the field of panel manufacturing technology, specifically to a low-formaldehyde integrated panel. Background Technology

[0002] Engineered wood panels are artificial boards made by bonding multiple pieces of wood raw materials with adhesives and hot pressing. They are divided into two categories: solid wood engineered wood and composite engineered wood. Their core function is to improve the utilization rate of wood, optimize performance, realize personalized size and function, and also take into account environmental protection and aesthetics. They are widely used in furniture manufacturing, interior decoration and construction engineering.

[0003] In existing technologies, engineered wood panels often use formaldehyde-based adhesives such as urea-formaldehyde resin. The formaldehyde emission level is difficult to meet the ultra-low environmental protection standards, posing a risk of indoor air pollution. Furthermore, the compatibility of environmentally friendly additives (such as ordinary natural resins and vegetable oils) with wood and adhesives is poor, resulting in poor water resistance and flexibility of the panels. They are prone to deformation and cracking in humid environments or during long-term use.

[0004] Based on this, the present invention provides a low-formaldehyde integrated panel. Summary of the Invention

[0005] The purpose of this invention is to provide a low-formaldehyde integrated panel. The integrated panel prepared by this invention not only has low formaldehyde emission, but also high static bending strength and modulus of elasticity.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a low-formaldehyde integrated board, comprising the following raw materials in parts by weight: 85-95 parts wood raw materials, 10-14 parts modified MDI adhesive, 3-6 parts modified environmentally friendly additives, and 1-3 parts modified nano-silica.

[0007] The modified MDI adhesive is a 4,4-diphenylmethane diisocyanate system modified with polyether polyol;

[0008] The modified environmentally friendly additive is a natural resin-vegetable oil composite system modified by maleic anhydride grafting.

[0009] The modified nano-silica is nano-silica modified with silane coupling agent KH-560.

[0010] Preferably, the preparation steps of the modified MDI adhesive are as follows: the polyether polyol is added to a four-necked flask and dehydrated for 1-1.5 hours under controlled temperature and vacuum; the dehydrated polyether polyol is cooled to 50-55°C, and pure MDI is slowly added while stirring at a speed of 150-200 rpm to ensure uniform mixing; the temperature is raised to 70-75°C and the reaction is maintained for 2-2.5 hours; after the reaction is completed, the temperature is lowered to 30-35°C, antioxidant 1010 is added, and stirring is continued for 15-20 minutes. After filtration, the modified MDI adhesive is obtained.

[0011] Preferably, the amount of polyether polyol added is 15-20 parts by weight; the amount of pure MDI added is 80-85 parts by weight; and the amount of antioxidant 1010 added is 0.1-0.2 parts by weight.

[0012] Preferably, the preparation steps of the modified environmentally friendly additive are as follows: natural rosin resin and linseed oil are added to a reaction vessel and heated and mixed at 90-95℃ with a stirring speed of 120-150 rpm for 30-40 minutes to form a homogeneous resin-oil system; maleic anhydride and initiator are added to the system, nitrogen gas is introduced for protection, the temperature is raised to 110-115℃, and the reaction is maintained for 3-3.5 hours for graft modification; after the reaction is completed, the temperature is lowered to 60-65℃, deionized water is added, the system viscosity is adjusted by stirring for 10-15 minutes, and the modified environmentally friendly additive is obtained after filtration.

[0013] Preferably, the amount of natural rosin resin added is 40-50 parts by weight, the amount of flaxseed oil added is 50-60 parts by weight, the amount of maleic anhydride added is 10-15 parts by weight, the initiator is benzoyl peroxide, and the amount used is 0.3-0.5 parts by weight; the amount of deionized water added is 10-15 parts by weight.

[0014] Preferably, the preparation steps of the modified nano-silica are as follows: nano-silica is added to an ethanol-deionized water mixture with a volume ratio of 4:1, and ultrasonically dispersed in an ultrasonic cleaner for 20-25 minutes to ensure uniform dispersion of nanoparticles; silane coupling agent KH-560 is added to the dispersion, the temperature is raised to 60-65℃, and the mixture is stirred at 180-200 rpm for 2.5-3 hours to achieve coupling agent grafting; after the reaction is completed, the mixture is centrifuged to collect the precipitate; the precipitate is placed in a vacuum oven to dry for 2-2.5 hours, then pulverized and passed through a 200-mesh sieve to collect the sieve residue, thus obtaining modified nano-silica.

[0015] Preferably, the amount of silica added is 100 parts by weight, the amount of ethanol-deionized water mixture is 600-700 parts by weight, and the amount of silane coupling agent KH-560 added is 5-8 parts by weight.

[0016] Preferably, the wood raw material is either pine or poplar; if the wood raw material is pine, the amount of modified environmentally friendly additive added is 3-4 parts by weight; if it is poplar, the amount of modified environmentally friendly additive added is 5-6 parts by weight; when adding, contact with acidic substances should be avoided and the pH value should be controlled between 6.5 and 7.5.

[0017] Preferably, the preparation of the low-formaldehyde integrated panel specifically includes the following steps:

[0018] S1: Pretreatment of wood raw materials: The selected wood raw materials are debarked, cut, dried and sanded to obtain sized dried wood;

[0019] S2: Preparation of composite adhesive: First, add the modified MDI adhesive and modified environmentally friendly additives to a high-speed mixing tank according to the ratio, and stir at 40-45℃ and 250-300rpm for 3-5min; then add the modified nano-silica by stepwise addition method, and continue stirring for 2-4min; during the stirring process, monitor in real time with an online viscometer, and at the same time detect the pH value and compatibility;

[0020] S3: Gluing and splicing: Apply glue to the splicing surface of the sized dry wood using a double roller glue applicator. The amount of glue applied is adjusted according to the type of wood. After applying the glue, scrape it lightly with a scraper. Immediately splice the wood according to the preset size, align the edges with positioning clamps, and correct the flatness. Transfer the spliced ​​wood to the press within 15 minutes.

[0021] S4: Pressure curing: Place the assembled wood blanks into a cold press, set the pressure according to the type of wood, and hold the pressure for 12-15 minutes; after the pressure holding is completed, transfer them to a hot air curing chamber, set the temperature, wind speed 2.0-2.5 m / s, and cure for 8-10 minutes.

[0022] S5: Post-processing and testing: After curing, remove the board and place it in a ventilated area to cool to room temperature; use a precision edge trimmer to remove the burrs on the edges, and then use a wide-band sander to sand both sides of the board; finally, test the formaldehyde release, static bending strength and elastic modulus. Once all indicators are qualified, the low-formaldehyde integrated board is obtained.

[0023] Preferably, the amount of adhesive applied to the pine wood is 190-210 g / m², and the amount of adhesive applied to the poplar wood is 210-230 g / m²; the pressure set during the pressure curing process is 2.8-3.2 MPa for the pine wood and 3.3-3.5 MPa for the poplar wood; and the set temperature for the pine wood when it is transferred into the hot air curing chamber is 125-130℃, and the set temperature for the poplar wood is 130-135℃.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention uses MDI adhesive modified with polyether polyol, which contains no formaldehyde-based components, thus achieving extremely low formaldehyde emission from the source, reaching the ultra-environmentally friendly E0 level and above. It works synergistically with the active groups of wood raw materials, the grafting sites of modified environmentally friendly additives, and the surface functional groups of modified nano-silica to construct a dense and stable multiphase bonding and cross-linking system, which greatly improves the interlayer and interfacial bonding strength of the board, effectively avoiding delamination and separation during use, while ensuring the structural stability and long-term environmental friendliness of the board under complex working conditions.

[0026] 2. This invention uses a natural resin-vegetable oil composite environmentally friendly additive modified with maleic anhydride grafting. After modification, the compatibility with modified MDI adhesive and wood raw materials is significantly improved. The three work synergistically to reduce the water absorption thickness expansion rate of the board and greatly enhance its water resistance. At the same time, it gives the board excellent flexibility, alleviates the inherent brittleness of wood, reduces the risk of cracking caused by temperature and humidity changes, and ensures that the board can maintain good physical form and performance in long-term humid and shrinking / expanding environments.

[0027] 3. This invention uses nano-silica modified with silane coupling agent KH-560. Its surface functional groups fully react with modified MDI adhesive, modified environmentally friendly additives and active groups of wood fiber to achieve uniform dispersion and efficient filling of micro-pores at the interface. Under the synergistic effect of the three, the mechanical properties of the board, such as static bending strength and elastic modulus, are improved, which can meet the mechanical requirements of high load scenarios such as furniture and building decoration, while enhancing the dimensional stability and deformation resistance of the board. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application are described clearly and completely.

[0030] Example 1: A low-formaldehyde integrated board, comprising the following raw materials in parts by weight: 85 parts wood raw materials, 10 parts modified MDI adhesive, 3 parts modified environmentally friendly additives, and 1 part modified nano-silica.

[0031] The modified MDI adhesive is a 4,4-diphenylmethane diisocyanate system modified with polyether polyol;

[0032] The modified environmentally friendly additive is a natural resin-vegetable oil composite system modified by maleic anhydride grafting.

[0033] The modified nano-silica is nano-silica modified with silane coupling agent KH-560.

[0034] The preparation steps for modified MDI adhesive are as follows:

[0035] Step 1: Add the polyether polyol to a four-necked flask and dehydrate it for 1 hour at 80°C and a vacuum of -0.08MPa to remove moisture.

[0036] Step 2: Cool the dehydrated polyether polyol to 50°C, and slowly add pure MDI (purity ≥99.5%, free MDI content ≤0.5%) while stirring at 150 rpm to ensure uniform mixing.

[0037] Step 3: Heat to 70℃ and maintain the temperature for 2 hours. During this period, take samples every 30 minutes to test the viscosity of the adhesive.

[0038] Step 4: After the reaction is complete, cool down to 30°C, add antioxidant 1010, continue stirring for 15 minutes, and pass through a 100-mesh filter to obtain the modified MDI adhesive.

[0039] The amount of polyether polyol (specifically polyoxypropylene polyol) added is 15 parts by weight; the amount of pure MDI added is 80 parts by weight; and the amount of antioxidant 1010 added is 0.1 parts by weight.

[0040] The preparation steps of modified environmentally friendly additives are as follows:

[0041] Step 1: Take natural rosin resin and linseed oil, add them to the reaction vessel, and heat and mix them at 90℃ with a stirring speed of 120 rpm for 30 minutes to form a homogeneous resin-oil system.

[0042] Step 2: Add maleic anhydride and initiator to the system, purge with nitrogen for protection, heat to 110°C, maintain the temperature for 3 hours, and carry out grafting modification.

[0043] Step 3: After the reaction is complete, cool the temperature to 60°C, add deionized water, stir for 10 minutes to adjust the viscosity of the system, and then filter through a 120-mesh screen to obtain the modified environmentally friendly additive.

[0044] The amount of natural rosin resin added is 40 parts by weight, the amount of linseed oil added is 50 parts by weight, the amount of maleic anhydride added is 10 parts by weight, the initiator is benzoyl peroxide, the amount used is 0.3 parts by weight, and the amount of deionized water added is 10 parts by weight.

[0045] The preparation steps of modified nano-silica are as follows:

[0046] Step 1: Add nano-silica to an ethanol-deionized water mixture with a volume ratio of 4:1, place it in an ultrasonic cleaner, and ultrasonically disperse it for 20 minutes at a power of 300W and a frequency of 40kHz to ensure uniform dispersion of nanoparticles.

[0047] Step 2: Add silane coupling agent KH-560 to the dispersion, heat to 60℃, and react at a stirring speed of 180 rpm for 2.5 h to achieve coupling agent grafting.

[0048] Step 3: After the reaction is complete, transfer the mixture to a high-speed centrifuge and centrifuge at 6000 rpm for 15 minutes, then collect the precipitate.

[0049] Step 4: Place the precipitate in a vacuum oven and dry it at 105℃ and a vacuum of -0.08MPa for 2 hours. After drying, pulverize it using a planetary ball mill with a rotation speed of 300rpm and a ball-to-material ratio of 10:1. After pulverization, pass the precipitate through a 200-mesh sieve and collect the sieve-underfill material to obtain modified nano-silica.

[0050] The amount of silica added is 100 parts by weight, the amount of ethanol-deionized water mixture is 600 parts by weight, and the amount of silane coupling agent KH-560 added is 5 parts by weight.

[0051] The raw material is pine wood, and the amount of modified environmentally friendly additive added is 3 parts by weight; when adding, contact with acidic substances should be avoided and the pH value should be controlled at 6.5.

[0052] The preparation of low-formaldehyde integrated panels specifically includes the following steps:

[0053] S1: Pretreatment of wood raw materials: The selected wood raw materials are debarked, cut, dried and sanded to obtain dry wood of the specified specifications; after drying, 5 pieces of wood are randomly selected to test the moisture content. The pass rate must be ≥98%. Unqualified wood must be re-dried (drying time 1 hour) or sprayed with water (tested every 30 minutes) until qualified.

[0054] S2: Preparation of composite adhesive: Modified MDI adhesive and modified environmentally friendly additives were added to a high-speed mixing tank according to the specified ratio and stirred at 40°C and 250 rpm for 3 min; then modified nano-silica was added in steps and stirred for another 2 min; during the stirring process, an online viscometer was used to monitor the viscosity in real time to ensure that the adhesive viscosity was stable at 200 mPa・s (25°C), and the pH value (6.5) and compatibility (no stratification after standing for 30 min) were also tested.

[0055] S3: Gluing and splicing: Apply glue to the splicing surface of the sized dry wood using a double roller glue applicator. The amount of glue applied is adjusted according to the type of wood. After applying the glue, scrape it lightly with a scraper to ensure that the glue coverage of the splicing surface is ≥98%. Immediately splice the wood according to the preset size, align the edges with positioning clamps, and correct the flatness (deviation ≤0.3mm). Transfer the spliced ​​wood to the press within 15 minutes.

[0056] S4: Pressure Curing: Place the assembled wood blank into a cold press, set the pressure according to the type of wood, and hold the pressure for 12 minutes; after the pressure holding is completed, transfer it to a hot air curing chamber, set the temperature, wind speed 2.0 m / s, and curing time 8 minutes; during the curing process, use a temperature sensor to monitor the center temperature of the blank to ensure that the temperature difference with the temperature inside the chamber is ≤ ±2℃.

[0057] S5: Post-processing and testing: After curing, remove the board and place it in a ventilated area to cool to room temperature (20℃, cooling time 2.5h); use a precision edge trimmer to remove the burrs (trimming width 8mm), and then use a wide-band sander (180-grit sandpaper, sanding speed 4m / min) to sand both sides of the board to make the surface roughness Ra≤2.5μm; finally, test the formaldehyde emission according to GB / T11718-2021 (requirement ≤0.02mg / m³), and test the static bending strength (requirement ≥16MPa) and elastic modulus (requirement ≥2800MPa) according to GB / T4897-2015. If all indicators are qualified, it is a low-formaldehyde integrated board.

[0058] The amount of adhesive applied to pine wood is 190 g / m², and the amount of adhesive applied to poplar wood is 210 g / m². During pressure curing, the set pressure for pine wood is 2.8 MPa, and the set pressure for poplar wood is 3.3 MPa. When transferred into the hot air curing chamber, the set temperature for pine wood is 125℃, and the set temperature for poplar wood is 130℃.

[0059] Example 2: A low-formaldehyde integrated board, comprising the following raw materials in parts by weight: 90 parts wood raw materials, 12 parts modified MDI adhesive, 5 parts modified environmentally friendly additives, and 2 parts modified nano-silica;

[0060] The modified MDI adhesive is a 4,4-diphenylmethane diisocyanate system modified with polyether polyol;

[0061] The modified environmentally friendly additive is a natural resin-vegetable oil composite system modified by maleic anhydride grafting.

[0062] The modified nano-silica is nano-silica modified with silane coupling agent KH-560.

[0063] The preparation steps for modified MDI adhesive are as follows:

[0064] Step 1: Add the polyether polyol to a four-necked flask and dehydrate it for 1.2 hours at 80-85℃ and a vacuum of -0.085MPa to remove moisture.

[0065] Step 2: Cool the dehydrated polyether polyol to 52°C, and slowly add pure MDI (purity ≥99.5%, free MDI content ≤0.5%) while stirring at 175 rpm to ensure uniform mixing.

[0066] Step 3: Heat to 72℃ and maintain the temperature for 2.2 hours. During this period, take samples every 30 minutes to test the viscosity of the adhesive.

[0067] Step 4: After the reaction is complete, cool down to 32°C, add antioxidant 1010, continue stirring for 17 minutes, and pass through a 100-mesh filter to obtain the modified MDI adhesive.

[0068] The amount of polyether polyol (specifically polyoxypropylene polyol) added is 17 parts by weight; the amount of pure MDI added is 82 parts by weight; and the amount of antioxidant 1010 added is 0.15 parts by weight.

[0069] The preparation steps of modified environmentally friendly additives are as follows:

[0070] Step 1: Take natural rosin resin and linseed oil, add them to the reaction vessel, and heat and mix them at 92℃ with a stirring speed of 135rpm for 35 minutes to form a homogeneous resin-oil system.

[0071] Step 2: Add maleic anhydride and initiator to the system, purge with nitrogen for protection, heat to 112°C, and maintain the temperature for 3.2 hours to carry out grafting modification;

[0072] Step 3: After the reaction is complete, cool the temperature to 62°C, add deionized water, stir for 12 minutes to adjust the viscosity of the system, and then filter through a 120-mesh screen to obtain the modified environmentally friendly additive.

[0073] The amount of natural rosin resin added is 45 parts by weight, the amount of linseed oil added is 55 parts by weight, the amount of maleic anhydride added is 12 parts by weight, the initiator is benzoyl peroxide, the amount used is 0.4 parts by weight, and the amount of deionized water added is 12 parts by weight.

[0074] The preparation steps of modified nano-silica are as follows:

[0075] Step 1: Add nano-silica to an ethanol-deionized water mixture with a volume ratio of 4:1, place it in an ultrasonic cleaner, and ultrasonically disperse it for 22 minutes at a power of 300W and a frequency of 40kHz to ensure uniform dispersion of nanoparticles.

[0076] Step 2: Add silane coupling agent KH-560 to the dispersion, heat to 62℃, and react at a stirring speed of 190 rpm for 2.7 h to achieve coupling agent grafting.

[0077] Step 3: After the reaction is complete, transfer the mixture to a high-speed centrifuge and centrifuge at 6000 rpm for 17 minutes, then collect the precipitate.

[0078] Step 4: Place the precipitate in a vacuum oven and dry it at 107℃ and a vacuum of -0.085MPa for 2.2 hours. After drying, pulverize it using a planetary ball mill with a speed of 300rpm and a ball-to-material ratio of 10:1. After pulverization, pass the precipitate through a 200-mesh sieve and collect the sieve-less material to obtain modified nano-silica.

[0079] The amount of silica added is 100 parts by weight, the amount of ethanol-deionized water mixture is 650 parts by weight, and the amount of silane coupling agent KH-560 added is 6.5 parts by weight.

[0080] The raw material is poplar wood, and the amount of modified environmentally friendly additive added is 5 parts by weight. When adding, contact with acidic substances should be avoided and the pH value should be controlled at 7.0.

[0081] The preparation of low-formaldehyde integrated panels specifically includes the following steps:

[0082] S1: Pre-treatment of timber raw materials: The selected timber raw materials are debarked, cut, dried and sanded to obtain sized dry timber; after drying, 5 pieces of timber are randomly selected to test the moisture content. The pass rate must be ≥98%. Unqualified timber must be re-dried (additional drying time 1.5h) or sprayed with water (tested every 30min) until qualified.

[0083] S2: Preparation of composite adhesive: Modified MDI adhesive and modified environmentally friendly additives were added to a high-speed mixing tank according to the specified ratio and stirred at 42°C and 275 rpm for 4 min; then modified nano-silica was added in steps and stirred for another 3 min; during the stirring process, an online viscometer was used to monitor the viscosity in real time to ensure that the adhesive viscosity was stable at 215 mPa・s (25°C), and the pH value (7.0) and compatibility (no stratification after standing for 30 min) were also tested.

[0084] S3: Gluing and splicing: Apply glue to the splicing surface of the sized dry wood using a double roller glue applicator. The amount of glue applied is adjusted according to the type of wood. After applying the glue, scrape it lightly with a scraper to ensure that the glue coverage of the splicing surface is ≥98%. Immediately splice the wood according to the preset size, align the edges with positioning clamps, and correct the flatness (deviation ≤0.3mm). Transfer the spliced ​​wood to the press within 15 minutes.

[0085] S4: Pressure Curing: Place the assembled wood blank into a cold press, set the pressure according to the type of wood, and hold the pressure for 13 minutes; after the pressure holding is completed, transfer it to a hot air curing chamber, set the temperature, wind speed 2.2 m / s, and curing time 9 minutes; during the curing process, use a temperature sensor to monitor the center temperature of the blank to ensure that the temperature difference with the temperature inside the chamber is ≤ ±2℃.

[0086] S5: Post-processing and testing: After curing, remove the board and place it in a ventilated area to cool to room temperature (22℃, cooling time 2.7h); use a precision edge trimmer to remove the burrs (trimming width 9mm), and then use a wide-band sander (180-grit sandpaper, sanding speed 5m / min) to sand both sides of the board to make the surface roughness Ra≤2.5μm; finally, test the formaldehyde emission according to GB / T11718-2021 (requirement ≤0.02mg / m³), and test the static bending strength (requirement ≥16MPa) and elastic modulus (requirement ≥2800MPa) according to GB / T4897-2015. If all indicators are qualified, it is a low-formaldehyde integrated board.

[0087] The amount of adhesive applied to pine wood is 200g / m², and the amount of adhesive applied to poplar wood is 220g / m². During pressure curing, the set pressure for pine wood is 3.0MPa, and the set pressure for poplar wood is 3.4MPa. When transferred into the hot air curing chamber, the set temperature for pine wood is 127℃, and the set temperature for poplar wood is 132℃.

[0088] Example 3: A low-formaldehyde integrated board, comprising the following raw materials in parts by weight: 95 parts wood raw materials, 14 parts modified MDI adhesive, 6 parts modified environmentally friendly additives, and 3 parts modified nano-silica;

[0089] The modified MDI adhesive is a 4,4-diphenylmethane diisocyanate system modified with polyether polyol;

[0090] The modified environmentally friendly additive is a natural resin-vegetable oil composite system modified by maleic anhydride grafting.

[0091] The modified nano-silica is nano-silica modified with silane coupling agent KH-560.

[0092] The preparation steps for modified MDI adhesive are as follows:

[0093] Step 1: Add the polyether polyol to a four-necked flask and dehydrate it for 1.5 hours at 85°C and a vacuum of -0.09 MPa to remove moisture.

[0094] Step 2: Cool the dehydrated polyether polyol to 55°C, and slowly add pure MDI (purity ≥99.5%, free MDI content ≤0.5%) while stirring at 200 rpm to ensure uniform mixing.

[0095] Step 3: Heat to 75℃ and maintain the temperature for 2.5 hours. During this period, take samples every 30 minutes to test the viscosity of the adhesive.

[0096] Step 4: After the reaction is complete, cool down to 35°C, add antioxidant 1010, continue stirring for 20 minutes, and pass through a 100-mesh filter to obtain the modified MDI adhesive.

[0097] The amount of polyether polyol (specifically polyoxypropylene polyol) added is 20 parts by weight; the amount of pure MDI added is 85 parts by weight; and the amount of antioxidant 1010 added is 0.2 parts by weight.

[0098] The preparation steps of modified environmentally friendly additives are as follows:

[0099] Step 1: Take natural rosin resin and linseed oil, add them to the reaction vessel, and heat and mix them at 95°C with a stirring speed of 150 rpm for 40 minutes to form a homogeneous resin-oil system.

[0100] Step 2: Add maleic anhydride and initiator to the system, purge with nitrogen for protection, heat to 115°C, and maintain the temperature for 3.5 hours to carry out grafting modification;

[0101] Step 3: After the reaction is complete, cool the temperature to 65°C, add deionized water, stir for 15 minutes to adjust the viscosity of the system, and then filter through a 120-mesh screen to obtain the modified environmentally friendly additive.

[0102] The amount of natural rosin resin added is 50 parts by weight, the amount of flaxseed oil added is 60 parts by weight, the amount of maleic anhydride added is 15 parts by weight, the initiator is benzoyl peroxide, the amount used is 0.5 parts by weight, and the amount of deionized water added is 15 parts by weight.

[0103] The preparation steps of modified nano-silica are as follows:

[0104] Step 1: Add nano-silica to an ethanol-deionized water mixture with a volume ratio of 4:1, place it in an ultrasonic cleaner, and ultrasonically disperse it for 25 minutes at a power of 300W and a frequency of 40kHz to ensure uniform dispersion of nanoparticles.

[0105] Step 2: Add silane coupling agent KH-560 to the dispersion, heat to 65℃, and react for 3 hours with stirring at 200 rpm to achieve coupling agent grafting.

[0106] Step 3: After the reaction is complete, transfer the mixture to a high-speed centrifuge and centrifuge at 6000 rpm for 20 minutes, then collect the precipitate.

[0107] Step 4: Place the precipitate in a vacuum oven and dry it at 110℃ and a vacuum of -0.09MPa for 2.5 hours. After drying, pulverize it using a planetary ball mill with a rotation speed of 300 rpm and a ball-to-material ratio of 10:1. After pulverization, pass the precipitate through a 200-mesh sieve and collect the sieve-underfill material to obtain modified nano-silica.

[0108] The amount of silica added is 100 parts by weight, the amount of ethanol-deionized water mixture is 700 parts by weight, and the amount of silane coupling agent KH-560 added is 8 parts by weight.

[0109] The wood raw material is either pine or poplar. If the wood raw material is pine, the amount of modified environmentally friendly additive added is 4 parts by weight; if it is poplar, the amount of modified environmentally friendly additive added is 6 parts by weight. When adding, contact with acidic substances should be avoided and the pH value should be controlled at 7.5.

[0110] The preparation of low-formaldehyde integrated panels specifically includes the following steps:

[0111] S1: Pre-treatment of wood raw materials: The selected wood raw materials are debarked, cut, dried and sanded to obtain dry wood of the specified size; after drying, 5 pieces of wood are randomly selected to test the moisture content. The pass rate must be ≥98%. Unqualified wood must be re-dried (additional drying time 2 hours) or sprayed with water (tested every 30 minutes) until qualified.

[0112] S2: Preparation of composite adhesive: Modified MDI adhesive and modified environmentally friendly additives were added to a high-speed mixing tank according to the specified ratio and stirred at 45°C and 300 rpm for 5 min; then modified nano-silica was added in steps and stirred for another 4 min; during the stirring process, an online viscometer was used to monitor the viscosity in real time to ensure that the adhesive viscosity was stable at 230 mPa・s (25°C), and the pH value (7.5) and compatibility (no stratification after standing for 30 min) were also tested.

[0113] S3: Gluing and splicing: Apply glue to the splicing surface of the sized dry wood using a double roller glue applicator. The amount of glue applied is adjusted according to the type of wood. After applying the glue, scrape it lightly with a scraper to ensure that the glue coverage of the splicing surface is ≥98%. Immediately splice the wood according to the preset size, align the edges with positioning clamps, and correct the flatness (deviation ≤0.3mm). Transfer the spliced ​​wood to the press within 15 minutes.

[0114] S4: Pressure Curing: Place the assembled wood blank into a cold press, set the pressure according to the type of wood, and hold the pressure for 15 minutes; after the pressure holding is completed, transfer it to a hot air curing chamber, set the temperature, wind speed 2.5 m / s, and curing time 10 minutes; during the curing process, use a temperature sensor to monitor the center temperature of the blank to ensure that the temperature difference with the temperature inside the chamber is ≤ ±2℃.

[0115] S5: Post-processing and testing: After curing, remove the board and place it in a ventilated area to cool to room temperature (25℃, cooling time 3h); use a precision edge trimmer to remove the burrs on the edges (trimming width 10mm), and then use a wide-band sander (180-grit sandpaper, sanding speed 6m / min) to sand both sides of the board to make the surface roughness Ra≤2.5μm; finally, test the formaldehyde emission according to GB / T11718-2021 (requirement ≤0.02mg / m³), and test the static bending strength (requirement ≥16MPa) and elastic modulus (requirement ≥2800MPa) according to GB / T4897-2015. If all indicators are qualified, it is a low-formaldehyde integrated board.

[0116] The amount of glue applied to pine wood is 210g / m², and the amount of glue applied to poplar wood is 230g / m². During pressure curing, the set pressure for pine wood is 3.2MPa, and the set pressure for poplar wood is 3.5MPa. When transferred into the hot air curing chamber, the set temperature for pine wood is 130℃, and the set temperature for poplar wood is 135℃.

[0117] Comparative Example 1 differs from Example 1 in that it uses a commercially available MDI adhesive that has not been modified with polyether polyol.

[0118] Comparative Example 2 differs from Example 1 in that it uses a commercially available ordinary rosin-linseed oil mixture that has not undergone maleic anhydride grafting modification.

[0119] Comparative Example 3 differs from Example 1 in that it uses commercially available nano-silica that has not been modified by silane coupling agent KH-560.

[0120] Performance testing: Performance tests were conducted on the products prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3.

[0121] Formaldehyde emission test: First, cut the integrated board into samples of specified size, pre-treat the climate chamber to a temperature of 23℃±0.5℃, relative humidity of 45%±5%, and formaldehyde background concentration ≤0.005mg / m³; then place the samples in the chamber with spacing, seal it, and collect air samples from the chamber at regular intervals. After capturing formaldehyde with an absorption liquid, determine the concentration by spectrophotometry or high performance liquid chromatography. Finally, calculate the formaldehyde emission by combining the climate chamber parameters and the sample surface area. Test standard: GB / T 11718-2021;

[0122] Static bending strength test: The three-point bending test method is adopted. The integrated panel is cut into specimens of specified size, and a three-point bending device is assembled on a universal testing machine. The span is set to 20 times the specimen thickness, the test speed is 10 mm / min, and a vertical load is applied to the midpoint of the specimen until fracture. After recording the maximum load, the strength is determined by the formula. Calculate the static bending strength and take the arithmetic mean as the result. Test standard: GB / T 17657-2013;

[0123] Elastic modulus test: Cut the integrated board into specimens with a length ≥300mm, width 50mm, and thickness equal to the actual thickness. Use a universal testing machine equipped with a displacement sensor and a three-point bending device. Set the span to 20 times the specimen thickness and the test speed to 10mm / min. Calibrate the sensor to ensure displacement accuracy ≤0.01mm. First, preload 5% of the maximum estimated load to eliminate gaps, then apply 4-stage loading at 4bh increments until the maximum load reaches 40%-50%. Simultaneously record the displacement at each load level and the corresponding midpoint. After selecting the linear segment and calculating the slope, use the formula... Calculate the elastic modulus of a single specimen, and finally take the arithmetic mean of all qualified specimens as the result. The test is based on GB / T 17657-2013.

[0124] The obtained test data are recorded in Table 1 below:

[0125] Testing items Formaldehyde emission (mg / m³) Static bending strength (MPa) Elastic modulus (MPa) Example 1 0.018 16 2800 Example 2 0.017 17 2830 Example 3 0.015 19 2870 Comparative Example 1 0.055 11 2350 Comparative Example 2 0.052 13 2420 Comparative Example 3 0.048 14 2470

[0126] By comparing and analyzing the relevant data in Table 1, it can be seen that the integrated panel prepared by the present invention using a low-formaldehyde integrated panel not only has low formaldehyde emission but also high static bending strength and modulus of elasticity. This indicates that the low-formaldehyde integrated panel provided by the present invention has a broader market prospect and is more suitable for promotion.

[0127] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0128] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-formaldehyde integrated panel, characterized in that, It includes the following raw materials by weight: 85-95 parts wood raw materials, 10-14 parts modified MDI adhesive, 3-6 parts modified environmentally friendly additives, and 1-3 parts modified nano-silica; The modified MDI adhesive is a 4,4-diphenylmethane diisocyanate system modified with polyether polyol; The modified environmentally friendly additive is a natural resin-vegetable oil composite system modified by maleic anhydride grafting. The modified nano-silica is nano-silica modified with silane coupling agent KH-560.

2. The low-formaldehyde integrated panel according to claim 1, characterized in that, The preparation steps of the modified MDI adhesive are as follows: the polyether polyol is added to a four-necked flask and dehydrated for 1-1.5 hours under controlled temperature and vacuum; the dehydrated polyether polyol is cooled to 50-55°C, and pure MDI is slowly added while stirring at a speed of 150-200 rpm to ensure uniform mixing; the temperature is raised to 70-75°C and the reaction is maintained for 2-2.5 hours; after the reaction is completed, the temperature is lowered to 30-35°C, antioxidant 1010 is added, and stirring is continued for 15-20 minutes. After filtration, the modified MDI adhesive is obtained.

3. The low-formaldehyde integrated panel according to claim 2, characterized in that: The amount of the polyether polyol added is 15-20 parts by weight; the amount of the pure MDI added is 80-85 parts by weight; and the amount of the antioxidant 1010 added is 0.1-0.2 parts by weight.

4. The low-formaldehyde integrated panel according to claim 1, characterized in that, The preparation steps of the modified environmentally friendly additive are as follows: natural rosin resin and linseed oil are added to a reaction vessel and heated and mixed at 90-95℃ with a stirring speed of 120-150rpm for 30-40 minutes to form a homogeneous resin-oil system; maleic anhydride and initiator are added to the system, nitrogen gas is introduced for protection, the temperature is raised to 110-115℃, and the reaction is maintained for 3-3.5 hours for grafting modification; after the reaction is completed, the temperature is lowered to 60-65℃, deionized water is added, the system viscosity is adjusted by stirring for 10-15 minutes, and the modified environmentally friendly additive is obtained after filtration.

5. The low-formaldehyde integrated panel according to claim 4, characterized in that: The amount of natural rosin resin added is 40-50 parts by weight, the amount of flaxseed oil added is 50-60 parts by weight, the amount of maleic anhydride added is 10-15 parts by weight, the initiator is benzoyl peroxide, and the amount used is 0.3-0.5 parts by weight; the amount of deionized water added is 10-15 parts by weight.

6. The low-formaldehyde integrated panel according to claim 1, characterized in that, The preparation steps of the modified nano-silica are as follows: nano-silica is added to an ethanol-deionized water mixture with a volume ratio of 4:1, and ultrasonically dispersed in an ultrasonic cleaner for 20-25 minutes to ensure uniform dispersion of nanoparticles; silane coupling agent KH-560 is added to the dispersion, the temperature is raised to 60-65℃, and the mixture is stirred at 180-200 rpm for 2.5-3 hours to achieve coupling agent grafting; after the reaction is completed, the mixture is centrifuged to collect the precipitate; the precipitate is placed in a vacuum oven to dry for 2-2.5 hours, then pulverized and passed through a 200-mesh sieve to collect the sieve-passing material to obtain modified nano-silica.

7. A low-formaldehyde integrated panel according to claim 6, characterized in that: The amount of silica added is 100 parts by weight, the amount of ethanol-deionized water mixture is 600-700 parts by weight, and the amount of silane coupling agent KH-560 added is 5-8 parts by weight.

8. The low-formaldehyde integrated panel according to claim 1, characterized in that: The wood raw material is either pine or poplar. If the wood raw material is pine, the amount of modified environmentally friendly additive added is 3-4 parts by weight; if it is poplar, the amount of modified environmentally friendly additive added is 5-6 parts by weight. When adding, contact with acidic substances should be avoided and the pH value should be controlled between 6.5 and 7.

5.

9. A low-formaldehyde integrated panel according to claim 1, characterized in that, The preparation of the low-formaldehyde integrated panel specifically includes the following steps: S1: Pretreatment of wood raw materials: The selected wood raw materials are debarked, cut, dried and sanded to obtain sized dried wood; S2: Preparation of composite adhesive: First, add the modified MDI adhesive and modified environmentally friendly additives to a high-speed mixing tank according to the ratio, and stir at 40-45℃ and 250-300rpm for 3-5min; then add the modified nano-silica by stepwise addition method, and continue stirring for 2-4min; during the stirring process, monitor in real time with an online viscometer, and at the same time detect the pH value and compatibility; S3: Gluing and splicing: Apply glue to the splicing surface of the sized dry wood using a double roller glue applicator. The amount of glue applied is adjusted according to the type of wood. After applying the glue, scrape it lightly with a scraper. Immediately splice the wood according to the preset size, align the edges with positioning clamps, and correct the flatness. Transfer the spliced ​​wood to the press within 15 minutes. S4: Pressure curing: Place the assembled wood blanks into a cold press, set the pressure according to the type of wood, and hold the pressure for 12-15 minutes; after the pressure holding is completed, transfer them to a hot air curing chamber, set the temperature, wind speed 2.0-2.5 m / s, and cure for 8-10 minutes. S5: Post-processing and testing: After curing, remove the board and place it in a ventilated area to cool to room temperature; use a precision edge trimmer to remove the burrs on the edges, and then use a wide-band sander to sand both sides of the board; finally, test the formaldehyde release, static bending strength and elastic modulus. Once all indicators are qualified, the low-formaldehyde integrated board is obtained.

10. A low-formaldehyde integrated panel according to claim 9, characterized in that: The amount of glue applied to the pine wood is 190-210 g / m², and the amount of glue applied to the poplar wood is 210-230 g / m². During the pressure curing process, the set pressure for the pine wood is 2.8-3.2 MPa, and the set pressure for the poplar wood is 3.3-3.5 MPa. When the wood is transferred to the hot air curing chamber, the set temperature for the pine wood is 125-130℃, and the set temperature for the poplar wood is 130-135℃.