Preparation method of sepiolite modified flame-retardant E0-grade medium-density fiberboard
By using sepiolite modification technology, the problems of excessive formaldehyde emission and poor fire resistance of medium-density fiberboard have been solved, achieving low-cost E0-grade environmental protection and B1-grade flame retardant effects, and improving the physical properties and stability of fiberboard.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG JIANGSHANLIREN WOOD IND
- Filing Date
- 2025-12-22
- Publication Date
- 2026-04-14
AI Technical Summary
Existing medium-density fiberboard has problems such as excessive formaldehyde emission, poor fire resistance and high production cost during the manufacturing process, making it difficult to simultaneously achieve low cost, flame retardancy and E0 environmental protection requirements.
Using sepiolite modification technology, sepiolite is treated with acid activation, magnesium ion loading and organic surface modification, and then added to fiberboard as a functional additive to improve the compatibility and bonding force of adhesives, form Si-OC covalent bonds, enhance the synergistic toughening effect between fibers, capture formaldehyde molecules and catalyze their decomposition.
It significantly reduces formaldehyde emissions, achieving the E0 environmental standard, improves physical and mechanical properties and flame retardant properties, meets the B1 flame retardant requirements, and maintains controllable production costs.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of environmentally friendly material preparation technology, and in particular to a method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard. Background Technology
[0002] Medium-density fiberboard (MDF) is a common type of wood-based panel, widely used in construction, furniture, and other industries due to its high strength, lightweight, and good processing properties. However, traditional MDF has the following problems: According to the national standard GB / T39600-2021 "Classification of Formaldehyde Emission of Wood-based Panels and Their Products", the formaldehyde emission of E0 grade is ≤0.05mg / m³. The adhesive used in existing E0 grade medium-density fiberboard is urea-formaldehyde resin, which has problems such as high free formaldehyde, high production cost, long curing time, frequent excess of formaldehyde emission of the board, poor stability, and difficulty in meeting strict environmental protection standards. In addition, the board has poor fire resistance and is easy to burn and release harmful gases under high temperature or fire conditions.
[0003] Existing improvement technologies reduce formaldehyde emissions from boards by adding modifiers (such as melamine and phenol), but this increases production costs. Lowering the F / U (formaldehyde / urea) molar ratio reduces formaldehyde emissions, but leads to slower curing speed and lower bonding strength. Therefore, existing medium-density fiberboard (MDF) manufacturing methods cannot simultaneously achieve low cost, flame retardancy, and E0 environmental standards. Summary of the Invention
[0004] This invention proposes a method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard, in order to solve the problem mentioned in the background art that existing medium-density fiberboard preparation methods cannot simultaneously achieve low cost, flame retardancy, and E0-grade environmental protection requirements.
[0005] The technical solution of this invention is implemented as follows: A method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard includes the following steps: Step 1, Fiber Preparation: Wood raw materials are steamed and hot-milled to produce wood fibers; Step 2: Preparation of modified sepiolite: a. Acid activation treatment of sepiolite is carried out to remove impurities and increase specific surface area; b. Magnesium ion loading treatment on acid-activated sepiolite; c. Magnesium ion-loaded sepiolite is subjected to organic surface modification treatment to improve its compatibility with adhesives and its bonding force with wood fibers, thus obtaining modified sepiolite; Step 3: Fiber sizing and drying: Modified sepiolite was used as a functional additive and added to the wood fibers used for the surface and core layers for sizing. Step 4: Layered assembly of the board blank: The glued wood fibers are laid into a board blank according to the structure of surface layer-core layer-surface layer; Step 5, Hot pressing: The board blank is hot pressed to cure the adhesive and obtain medium density fiberboard; Step 6, Post-processing: Cool the board, saw the edges, and perform surface treatment.
[0006] Preferably, in step one, the wood raw material is poplar, eucalyptus, or pine; the wood raw material is steamed for 3-5 minutes at a steam temperature of 160-180℃ and a pressure of 0.6-0.8MPa.
[0007] Preferably, in step two, the sepiolite used for acid activation treatment has a water content of less than 10%, and the acid activation treatment method is to treat it with dilute hydrochloric acid with a mass concentration of 1%-3% to remove carbonate impurities and increase the specific surface area of sepiolite to more than 300m² / g.
[0008] Preferably, in step two, the magnesium ion loading treatment of the acid-activated sepiolite is carried out by filtration to remove the hydrochloric acid solution, followed by impregnation with a 5%-8% MgCl2 solution to achieve a Mg²⁺ loading of 8%-12wt%.
[0009] Preferably, in step two, the organic surface modification treatment of the magnesium ion-loaded sepiolite is carried out by filtration to remove the magnesium chloride solution, obtaining sepiolite slurry, and then adding 0.3%-0.5% hexadecyltrimethylammonium chloride surfactant and 1.0%-1.5% silane coupling agent KH550, which are equal to the total amount of sepiolite, and stirring thoroughly to coat the slurry, thereby obtaining modified sepiolite.
[0010] Preferably, in step three, modified sepiolite is used as a functional additive. 10%-12% functionalized sepiolite is added to the surface fiber at a glue content of 12%-15%, and 8%-10% functionalized sepiolite is added to the core fiber at a glue content of 9%-12%. The fiber is then dried using a pipeline to achieve a moisture content of 8-12% after drying.
[0011] Preferably, in step four, the weight ratio of the surface layer-core layer-surface sizing fiber is 1:3:1.
[0012] Preferably, in step five, the hot pressing method for the slab is to feed a single slab into a hot press via a loading machine for hot pressing, with a hot pressing temperature of 180℃-210℃, a hot pressing unit pressure of 2.8Mpa-2.5Mpa, and a hot pressing time of 15s-20s per 1mm plate.
[0013] By adopting the above technical solution, the beneficial effects of the present invention are as follows: 1. This invention introduces acid-activated and organically modified sepiolite into the urea-formaldehyde resin system, thereby significantly reducing the free formaldehyde release of the board while maintaining the feasibility of the original process. The formaldehyde release of the resulting medium-density fiberboard can be stably controlled at ≤0.05mg / m³ (climate chamber method), which meets and exceeds the E0 environmental protection level requirements. 2. This invention utilizes the nanoporous structure of modified sepiolite, the enhanced interfacial interaction, and the synergistic toughening effect between fibers to give the resulting medium-density fiberboard excellent physical and mechanical properties. Its static bending strength ≥19MPa, elastic modulus ≥3500MPa, and internal bond strength ≥0.50MPa meet national standards and have high structural stability. 3. This invention significantly improves the flame retardant properties of the product through metal ion loading and the action of sepiolite itself. The resulting medium-density fiberboard can meet the B1 flame retardant requirements and has higher safety and material reliability under fire conditions. Detailed Implementation
[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.
[0015] The relevant mechanism of this application is: (1) Sepiolite is a natural fibrous silicate mineral with a huge specific surface area and nanoscale pore structure (pore size 0.37nm×1.06nm), which precisely matches the molecular dynamics diameter of formaldehyde (0.45nm). After acid activation and organic modification, its surface hydrophobicity is enhanced, and it can be more uniformly dispersed in the adhesive matrix. Through its adsorption properties, it can capture trace amounts of free formaldehyde released by the board to a certain extent. When the material is subjected to external force, these micro- and nano-scale fibers can effectively transfer stress, induce silver streaks and shear bands, thereby consuming a lot of energy and improving the strength and toughness of the board. (2) Sepiolite is rich in magnesium ions, which can catalyze the decomposition of formaldehyde into formic acid; the nanopores of sepiolite capture formaldehyde molecules; (3) Modified sepiolite was introduced into E0 grade medium density fiberboard to increase the density of the board, reduce the amount of adhesive used, and improve the flame retardant performance of medium density fiberboard.
[0016] (4) Strength enhancement mechanism: KH550 coupling agent enables sepiolite to form Si-OC covalent bonds with fibers; layered addition avoids excessive weakening of the core layer, and the surface sepiolite fills the fiber gaps.
[0017] Example 1
[0018] The specific method is as follows: 1. Material Preparation: A drum chipper is used to process small-diameter timber and branches into wood chips with dimensions of 12-25mm in length, 12-20mm in width, and 2-5mm in thickness. The wood chips are then purified using a roller screen to remove substandard wood chips and bark. 2. Fiber Preparation: Qualified wood chips are conveyed to a wood chip digester via a belt conveyor. Saturated steam is then introduced into the digester to soften the wood chips. The pressure inside the digester is 0.8 MPa, the temperature is 180℃, and the processing time is 4 minutes. The preheated wood chips are then fed into a thermal mill via a feed screw for mechanical separation to prepare wood fibers. 3. Preparation of modified sepiolite: The sample was treated with dilute hydrochloric acid (2% by mass) solution to remove carbonate impurities and increase the specific surface area to ≥300m² / g. Then, it was impregnated with MgCl2 solution (5% by mass) to achieve a Mg²⁺ loading of 12wt%. The magnesium chloride solution was removed by filtration to obtain sepiolite slurry. Then, 0.3% cetyltrimethylammonium chloride surfactant and 1.5% silane coupling agent KH550 were added to the total amount of sepiolite and stirred thoroughly to coat the sample, thus obtaining modified sepiolite.
[0019] 4. Fiber sizing and drying: A production process with different sizing and drying methods is adopted for the core layer and the surface layer. 12% modified sepiolite is added to the surface layer fibers (12% sizing), and 8% modified sepiolite is added to the core layer fibers (9% sizing). Pipe drying is used, and the moisture content of the fibers after drying is 8-12%. 5. Layered board assembly and forming: A vacuum airflow assembling machine is used to lay the glued and dried wood fibers into a continuous board strip of a certain thickness. The continuous board strip is pre-compressed by a pre-pressing machine to achieve initial compaction, and then sawn into individual board blanks of the required specifications by a trim saw and a cross-cut saw. 6. Hot pressing: Single slab blanks are fed into the hot press by the loading machine for hot pressing. Under the combined action of heat and pressure, the moisture in the slab blanks vaporizes and evaporates, the density increases, the adhesive cures, and the waterproofing agent redistributes. The components in the raw materials undergo a series of physicochemical changes, forming various bonding forces between the fibers. The hot pressing temperature is 180℃, the hot pressing unit pressure is 2.5Mpa, and the hot pressing time is 20s per 1mm of board.
[0020] 7. Post-processing: After the boards from the press are cooled by the cooling machine, the edges are sawn to cut them into standard sizes. Finally, they are sent to the sander for surface treatment and then put into storage.
[0021] Example 2
[0022] The specific method is as follows: 1. Material Preparation: A drum chipper is used to process small-diameter timber and branches into wood chips with dimensions of 12-25mm in length, 12-20mm in width, and 2-5mm in thickness. The wood chips are then purified using a roller screen to remove substandard wood chips and bark. 2. Fiber Preparation: Qualified wood chips are conveyed to a wood chip digester via a belt conveyor. Saturated steam is then introduced into the digester to soften the wood chips. The pressure inside the digester is 0.7 MPa, the temperature is 160℃, and the processing time is 5 minutes. The preheated wood chips are then fed into a thermal mill via a feed screw for mechanical separation to prepare wood fibers. 3. Preparation of modified sepiolite: The sample was treated with dilute hydrochloric acid (1% by mass) solution to remove carbonate impurities and increase the specific surface area to ≥300m² / g. Then, it was impregnated with MgCl2 solution (6.5% by mass) to achieve a Mg²⁺ loading of 10wt%. The magnesium chloride solution was removed by filtration to obtain sepiolite slurry. Then, 0.4% hexadecyltrimethylammonium chloride surfactant and 1.2% silane coupling agent KH550 were added to the total amount of sepiolite and stirred thoroughly to coat the sample, thus obtaining modified sepiolite.
[0023] 4. Fiber sizing and drying: A production process with different sizing and drying methods is adopted for the core layer and the surface layer. 10% modified sepiolite is added to the surface layer fibers (15% sizing), and 9% modified sepiolite is added to the core layer fibers (11% sizing). Pipe drying is used, and the moisture content of the fibers after drying is 8-12%. 5. Layered board assembly and forming: A vacuum airflow assembling machine is used to lay the glued and dried wood fibers into a continuous board strip of a certain thickness. The continuous board strip is pre-compressed by a pre-pressing machine to achieve initial compaction, and then sawn into individual board blanks of the required specifications by a trim saw and a cross-cut saw. 6. Hot pressing: Single slab blanks are fed into the hot press by the loading machine for hot pressing. Under the combined action of heat and pressure, the moisture in the slab blanks vaporizes and evaporates, the density increases, the adhesive cures, and the waterproofing agent redistributes. The components in the raw materials undergo a series of physicochemical changes, which form various bonding forces between the fibers. The hot pressing temperature is 200℃, the hot pressing unit pressure is 2.6Mpa, and the hot pressing time is 18s per 1mm of board.
[0024] 7. Post-processing: After the boards from the press are cooled by the cooling machine, the edges are sawn to cut them into standard sizes. Finally, they are sent to the sander for surface treatment and then put into storage.
[0025] Example 3
[0026] The specific method is as follows: 1. Material Preparation: A drum chipper is used to process small-diameter timber and branches into wood chips with dimensions of 12-25mm in length, 12-20mm in width, and 2-5mm in thickness. The wood chips are then purified using a roller screen to remove substandard wood chips and bark. 2. Fiber Preparation: Qualified wood chips are conveyed to a wood chip digester via a belt conveyor. Saturated steam is then introduced into the digester to soften the wood chips. The pressure inside the digester is 0.6 MPa, the temperature is 170℃, and the processing time is 3 minutes. The preheated wood chips are then fed into a thermal mill via a feed screw for mechanical separation to prepare wood fibers. 3. Preparation of modified sepiolite: The sample was treated with dilute hydrochloric acid (3% by mass) solution to remove carbonate impurities and increase the specific surface area to ≥300m² / g. Then, it was impregnated with MgCl2 solution (8% by mass) to achieve a Mg²⁺ loading of 8wt%. The magnesium chloride solution was removed by filtration to obtain sepiolite slurry. Then, 0.5% cetyltrimethylammonium chloride surfactant and 1.0% silane coupling agent KH550 were added to the total amount of sepiolite and stirred thoroughly to coat the sample, thus obtaining modified sepiolite.
[0027] 4. Fiber sizing and drying: A production process with different sizing and drying methods is adopted for the core layer and the surface layer. 11% modified sepiolite is added to the surface layer fibers (13% sizing), and 10% modified sepiolite is added to the core layer fibers (12% sizing). Pipe drying is used, and the moisture content of the fibers after drying is 8-12%. 5. Layered board assembly and forming: A vacuum airflow assembling machine is used to lay the glued and dried wood fibers into a continuous board strip of a certain thickness. The continuous board strip is pre-compressed by a pre-pressing machine to achieve initial compaction, and then sawn into individual board blanks of the required specifications by a trim saw and a cross-cut saw. 6. Hot pressing: Single slab blanks are fed into the hot press by the loading machine for hot pressing. Under the combined action of heat and pressure, the moisture in the slab blanks vaporizes and evaporates, the density increases, the adhesive cures, and the waterproofing agent redistributes. The components in the raw materials undergo a series of physicochemical changes, forming various bonding forces between the fibers. The hot pressing temperature is 210℃, the hot pressing unit pressure is 2.8Mpa, and the hot pressing time is 15s per 1mm of board.
[0028] 7. Post-processing: After the boards from the press are cooled by the cooling machine, the edges are sawn to cut them into standard sizes. Finally, they are sent to the sander for surface treatment and then put into storage.
[0029] The following is a table comparing the performance of medium-density fiberboard (MDF) obtained using the three embodiments described above with those obtained using traditional methods: As shown in the table above, the medium-density fiberboard produced by this method has significant improvements in formaldehyde emission, static bending strength, modulus of elasticity, and flame retardant properties. The formaldehyde emission reaches E0 level (≤0.05mg / m³), the flame retardant properties reach B1 level, and the static bending strength and modulus of elasticity meet the relevant national standards.
[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard, characterized in that, Includes the following steps: Step 1, Fiber Preparation: Wood raw materials are steamed and hot-milled to produce wood fibers; Step 2: Preparation of modified sepiolite: a. Acid activation treatment of sepiolite is carried out to remove impurities and increase specific surface area; b. Magnesium ion loading treatment on acid-activated sepiolite; c. Magnesium ion-loaded sepiolite is subjected to organic surface modification treatment to improve its compatibility with adhesives and its bonding force with wood fibers, thus obtaining modified sepiolite; Step 3: Fiber sizing and drying: Modified sepiolite was used as a functional additive and added to the wood fibers used for the surface and core layers for sizing. Step 4: Layered assembly of the board blank: The glued wood fibers are laid into a board blank according to the structure of surface layer-core layer-surface layer; Step 5, Hot pressing: The board blank is hot pressed to cure the adhesive and obtain medium density fiberboard; Step 6, Post-processing: Cool the board, saw the edges, and perform surface treatment.
2. The method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard according to claim 1, characterized in that, In step one, the wood raw material is poplar, eucalyptus, or pine; the wood raw material is steamed for 3-5 minutes at a steam temperature of 160-180℃ and a pressure of 0.6-0.8MPa.
3. The method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard according to claim 1, characterized in that, In step two, the sepiolite used for acid activation treatment has a water content of less than 10%, and the acid activation treatment method is to treat it with dilute hydrochloric acid with a mass concentration of 1%-3% to remove carbonate impurities and increase the specific surface area of sepiolite to more than 300m² / g.
4. The method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard according to claim 3, characterized in that, In step two, the method for treating the acid-activated sepiolite with magnesium ion loading is to remove the hydrochloric acid solution by filtration, and then add a 5%-8% MgCl2 solution for impregnation treatment, so that the Mg²⁺ loading reaches 8%-12wt%.
5. The method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard according to claim 4, characterized in that, In step two, the organic surface modification treatment of the magnesium ion-loaded sepiolite is carried out by filtration to remove the magnesium chloride solution, obtaining sepiolite slurry, and then adding 0.3%-0.5% hexadecyltrimethylammonium chloride surfactant and 1.0%-1.5% silane coupling agent KH550, which are equal to the total amount of sepiolite, and stirring thoroughly to coat the slurry, thereby obtaining modified sepiolite.
6. The method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard according to claim 1, characterized in that, In step three, modified sepiolite is used as a functional additive. 10%-12% functionalized sepiolite is added to the surface fiber at a glue content of 12%-15%, and 8%-10% functionalized sepiolite is added to the core fiber at a glue content of 9%-12%. The fiber is then dried using a pipeline to achieve a moisture content of 8-12% after drying.
7. The method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard according to claim 1, characterized in that, In step four, the weight ratio of the surface layer, core layer, and surface sizing fiber is 1:3:
1.
8. The method for preparing sepiolite-modified flame-retardant E0-grade medium-density fiberboard according to claim 1, characterized in that, In step five, the hot pressing method for the slab is to feed a single slab into a hot press through a loading machine for hot pressing. The hot pressing temperature is 180℃-210℃, the hot pressing unit pressure is 2.8Mpa-2.5Mpa, and the hot pressing time is 15s-20s per 1mm plate.