Acid and alkali resistant medium density fiberboard

Abstract

The present application relates to the technical field of fiberboard, and discloses an acid and alkali resistant medium density fiberboard, which comprises a core layer located in the middle position and a protective layer tightly combined with the upper surface and the lower surface of the core layer. In the present application, the composite structure design of the core layer and the protective layer improves the use stability and durability of the board in a strong acid and strong alkali corrosive environment. The core layer is formed by hot pressing and curing of wood fibers and a modified phenolic resin adhesive. The modified phenolic resin is modified by end isocyanate group polyurethane prepolymer blending, which not only enhances the flexibility and weather resistance of the adhesive itself, but also improves the interfacial bonding strength with the wood fibers, so that the core has a good mechanical support foundation. At the same time, the evenly dispersed paraffin emulsion components in the core fill the micro-holes on the fiber surface, which can effectively block the penetration of water, and the triphenyl phosphate flame retardant is distributed in the cured crosslinked network in a molecular state, which gives the board excellent flame retardant performance.

Description

Technical Field

[0001] This invention relates to the field of fiberboard technology, and more specifically to an acid- and alkali-resistant medium-density fiberboard. Background Technology

[0002] Medium-density fiberboard (MDF) is a type of engineered wood product made from wood fibers or other plant fibers through processes such as fiber preparation, gluing and drying, and hot pressing. Due to its advantages such as uniform structure, dimensional stability, good machinability, and smooth surface, it is widely used in furniture manufacturing, building decoration, packaging and transportation, and automotive and ship interiors. However, traditional MDF faces several performance shortcomings in practical use, one of the most prominent being its insufficient corrosion resistance. Because wood fibers themselves contain a large number of hydrophilic hydroxyl groups, and the cross-linked network formed after the curing of conventional urea-formaldehyde resin or phenolic resin adhesives still has a certain number of hydrophilic groups and micropores, fiberboard is extremely prone to absorbing moisture and swelling in humid environments or under conditions of direct contact with water. This leads to a decrease in the dimensional stability of the board and a deterioration in its mechanical properties. More seriously, when fiberboard is used in special environments with strong acid and alkali corrosive media, such as chemical plants, electroplating workshops, laboratory workbenches, battery production sites, or coastal high-salt spray environments, acidic and alkaline substances will quickly penetrate into the interior of the board through the exposed pores on the surface and sides. On the one hand, this directly catalyzes the degradation of the lignocellulose molecular chains, causing irreversible damage to the fiber skeleton. On the other hand, it corrodes the cross-linked structure of the phenolic resin adhesive, leading to a sharp decrease in bonding strength. Ultimately, this manifests as powdering of the board surface, delamination and peeling, edge cracking, or even loosening and collapse of the overall structure, severely limiting the applicability and service life of medium-density fiberboard in corrosive environments.

[0003] To address these issues, existing technologies have attempted to coat the fiberboard surface with ordinary paint, polyurethane varnish, or epoxy resin coatings to provide physical isolation. However, these conventional coatings exhibit weak interfacial bonding with the wood substrate, and the coatings themselves are prone to swelling, blistering, discoloration, or even complete dissolution and failure when exposed to strong acids and alkalis over extended periods, making it difficult to achieve long-term reliable protection for the core material. Furthermore, some technical solutions involve adding small amounts of hydrophobic additives or nanofillers to the adhesive during the gluing process to improve the core's impermeability and corrosion resistance. However, due to the difficulty in ensuring the uniformity of filler dispersion and the limitation of the addition amount by the adhesive's viscosity and curing reactivity, these methods offer very limited improvement to the overall acid and alkali resistance of the fiberboard, failing to meet the high corrosion resistance standards required in industrial applications. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides an acid and alkali resistant medium density fiberboard to solve the problems existing in the background art.

[0005] The present invention provides the following technical solution: an acid and alkali resistant medium density fiberboard, comprising a core layer located in the middle and a protective layer tightly bonded to the upper and lower surfaces of the core layer; The core layer is an integral, dense board formed by uniformly mixing wood fibers and modified phenolic resin adhesive and then hot-pressing and curing. The modified phenolic resin adhesive is a blended modified adhesive obtained by blending phenolic resin and isocyanate-terminated polyurethane prepolymer. The protective layer is a corrosion-resistant coating layer with polytetrafluoroethylene emulsion as the main film-forming material and nano-silica particles and organosilicon hydrophobic agents dispersed inside. The protective layer continuously covers all exposed surfaces of the core layer, and part of the protective layer penetrates into the fiber pores of the core layer surface and forms an interface fusion and anchoring structure with the core layer.

[0006] Preferably, a transition adhesive layer is provided between the upper surface of the core layer and the protective layer, and a transition adhesive layer is also provided between the lower surface of the core layer and the protective layer. The transition adhesive layer is a thin film layer formed after the thermosetting epoxy resin adhesive is cured. One side of the transition adhesive layer is bonded to the surface of the core layer, and the other side of the transition adhesive layer is bonded to the inner surface of the protective layer.

[0007] Preferably, the modified phenolic resin adhesive further disperses nano-montmorillonite sheet material and silane coupling agent. The nano-montmorillonite sheet material is distributed in the cross-linking network of the modified phenolic resin adhesive in an intercalation form, and the silane coupling agent is used to bridge the interface between the nano-montmorillonite sheet material and the phenolic resin matrix.

[0008] Preferably, the wood fiber is poplar fiber, and the length direction of the poplar fiber is randomly laid out along the surface direction of the core layer, and adjacent fibers are bonded together by modified phenolic resin adhesive to form a three-dimensional interwoven network skeleton.

[0009] Preferably, the core layer also contains uniformly dispersed paraffin emulsion and triphenyl phosphate flame retardant components.

[0010] Preferably, the paraffin emulsion component fills the micropores on the surface of the wood fiber, and the triphenyl phosphate flame retardant component is uniformly distributed in the cured cross-linked network of the modified phenolic resin adhesive in a molecular state.

[0011] Preferably, the polytetrafluoroethylene coating of the protective layer also contains dispersed short glass fiber filaments, the length direction of which is consistent with the extension direction of the protective layer, and multiple short glass fiber filaments are randomly distributed in a planar manner inside the protective layer to form a local reinforcement network.

[0012] Preferably, the protective layer is further laminated with a decorative surface layer on the side away from the core layer. The decorative surface layer is a decorative paper layer impregnated with melamine-formaldehyde resin. The decorative paper layer is bonded and fixed to the outer surface of the protective layer by melamine-formaldehyde resin under hot pressing conditions.

[0013] Preferably, a planar reinforcing mesh is embedded in the middle of the core layer, and the mesh direction of the planar reinforcing mesh is parallel to the board surface direction of the core layer.

[0014] Preferably, the planar reinforced mesh is a glass fiber woven mesh, and the mesh of the glass fiber woven mesh is filled with a mixture of wood fiber and modified phenolic resin adhesive.

[0015] The beneficial effects of this invention are: In this invention, the composite structure design of the core layer and the protective layer enhances the stability and durability of the board in environments with strong acid and alkali corrosion. The core layer is formed by hot-pressing and curing wood fibers and modified phenolic resin adhesive. The modified phenolic resin is blended with isocyanate-terminated polyurethane prepolymer, which not only enhances the flexibility and weather resistance of the adhesive itself, but also improves the interfacial bonding strength with the wood fibers, giving the core a good mechanical support foundation. At the same time, the paraffin emulsion component uniformly dispersed inside the core fills the micropores on the fiber surface, which can effectively block moisture penetration. Triphenyl phosphate flame retardant is distributed in molecular form in the cured cross-linked network, giving the board excellent flame retardant properties. The protective layer uses polytetrafluoroethylene emulsion as the main film-forming material, which has excellent chemical inertness and low surface energy characteristics. Combined with internally dispersed nano-silica particles and organosilicon hydrophobic agents, it further enhances the coating's density, hydrophobicity, oleophobicity, and impermeability. This allows the protective layer to effectively resist the erosion of acid and alkali media. Moreover, the protective layer continuously covers all exposed surfaces of the core board and partially penetrates into the surface fiber pores to form an interface fusion and anchoring structure. This solves the problems of weak adhesion between traditional coatings and substrates and easy peeling and detachment, ensuring the integrity and reliability of the protective layer during long-term use.

[0016] Based on this, the transition bonding layer between the core and the protective layer, formed by curing a thermosetting epoxy resin adhesive into a thin film, effectively buffers the internal stress caused by the difference in thermal expansion coefficients between the core and the protective layer. It also enhances the chemical bonding and physical anchoring between the heterogeneous material layers, preventing delamination failure. The nano-montmorillonite sheets dispersed in the modified phenolic resin adhesive are intercalated within the cross-linked network, and, in conjunction with the interfacial bridging effect of the silane coupling agent, improve the mechanical strength and thermal stability of the adhesive. Simultaneously, it extends the penetration path of corrosive media, providing a physical barrier effect. Poplar fibers are randomly laid out to form a three-dimensional interwoven network skeleton, reducing the anisotropy of the core and improving dimensional stability. The protective layer contains... The loosely chopped glass fibers form a planar localized reinforcing network, significantly improving the crack resistance and impact resistance of the protective layer without affecting the coating's density. The decorative surface layer is bonded and fixed to the outer surface of the protective layer with melamine-formaldehyde resin under hot-pressing conditions, satisfying both aesthetic requirements and further enhancing the surface scratch resistance and stain resistance of the board by utilizing the high hardness and high wear resistance formed after the melamine-formaldehyde resin cures. The planar reinforcing mesh fabric embedded inside the core is parallel to the board surface, and the mesh is filled with a mixture of wood fiber and modified phenolic resin adhesive, improving the overall bending strength and deformation resistance of the core and preventing warping, cracking, and other failures of the board under long-term use or temperature and humidity changes.

[0017] This invention, through the synergistic effect of a multi-level structure, endows medium-density fiberboard with excellent acid and alkali corrosion resistance, waterproof and moisture-proof properties, flame retardant properties, and dimensional stability, while ensuring good mechanical properties. It is particularly suitable for applications with stringent requirements for material corrosion resistance, such as chemical plants, laboratory countertops, areas around electroplating tanks, and coastal high-humidity and high-salt-spray environments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a cross-sectional view of the entire invention.

[0020] Figure 2 This is a partially enlarged view of the surface interface and material composition of the present invention.

[0021] Figure 3 This is an exploded view of the present invention.

[0022] The attached diagram is labeled as follows: 1. Core layer; 2. Protective layer; 3. Transition adhesive layer; 4. Decorative surface layer; 5. Planar reinforcing mesh. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] Reference Figures 1 to 3 The present invention provides an acid and alkali resistant medium density fiberboard, comprising a core layer 1 located in the middle and a protective layer 2 tightly bonded to the upper and lower surfaces of the core layer 1; The core layer 1 is an integral, dense board formed by uniformly mixing wood fibers and modified phenolic resin adhesive and then hot-pressing and curing. The modified phenolic resin adhesive is a blended modified adhesive obtained by blending phenolic resin and isocyanate-terminated polyurethane prepolymer. The protective layer 2 is a corrosion-resistant coating layer with polytetrafluoroethylene emulsion as the main film-forming material and nano-silica particles and organosilicon hydrophobic agents dispersed inside. The protective layer 2 continuously covers all exposed surfaces of the core layer 1, and part of the protective layer 2 penetrates into the fiber pores of the surface layer of the core layer 1 and forms an interface fusion and anchoring structure with the core layer 1.

[0025] By using isocyanate-terminated polyurethane prepolymer blended with modified phenolic resin in the core layer 1, the flexibility and weather resistance of the adhesive are enhanced. Meanwhile, the protective layer 2 is based on polytetrafluoroethylene and compounded with nano-silica and organosilicon hydrophobic agents, giving the coating excellent chemical inertness, density and hydrophobic and oleophobic properties. The protective layer 2 penetrates into the surface fiber to form an anchoring structure, which effectively solves the problem of weak adhesion between the coating and the substrate and easy peeling and falling off, thus ensuring the long-term structural integrity and protective reliability of the board in the corrosive environment of strong acids and alkalis.

[0026] A transition adhesive layer 3 is provided between the upper surface of the core layer 1 and the protective layer 2, and a transition adhesive layer 3 is also provided between the lower surface of the core layer 1 and the protective layer 2. The transition adhesive layer 3 is a thin film layer formed after the thermosetting epoxy resin adhesive is cured. One side of the transition adhesive layer 3 is bonded to the surface of the core layer 1, and the other side of the transition adhesive layer 3 is bonded to the inner surface of the protective layer 2.

[0027] By setting a transitional bonding layer 3 formed by the curing of thermosetting epoxy resin adhesive, the internal stress caused by the difference in thermal expansion coefficient between the core layer 1 and the protective layer 2 can be effectively buffered. At the same time, the polar groups formed after the epoxy resin is cured can form chemical bonds and physical anchoring effects with the hydroxyl groups on the surface of the core fiber and the fluorine-containing groups in the protective layer 2, respectively, thereby significantly enhancing the interfacial bonding strength between heterogeneous material layers, avoiding interlayer delamination failure, and improving the overall durability and peel resistance of the composite board.

[0028] The modified phenolic resin adhesive also contains nano-montmorillonite sheet material and silane coupling agent. The nano-montmorillonite sheet material is distributed in the cross-linking network of the modified phenolic resin adhesive in the form of intercalation, and the silane coupling agent is used to bridge the interface between the nano-montmorillonite sheet material and the phenolic resin matrix.

[0029] By distributing nano-montmorillonite sheets in the phenolic resin crosslinking network in an intercalated form, the physical barrier effect of its two-dimensional sheet structure extends the penetration path of corrosive media and heat. At the same time, the silane coupling agent improves the interfacial compatibility between the montmorillonite sheets and the resin matrix through chemical bridging, thereby synergistically improving the mechanical strength, thermal stability and resistance to media penetration of the adhesive, and further enhancing the structural stability and corrosion resistance of the core board.

[0030] The wood fiber is poplar fiber, and the length direction of the poplar fiber is randomly laid out along the surface direction of the core layer 1. Adjacent fibers are bonded together by modified phenolic resin adhesive to form a three-dimensional interwoven network skeleton.

[0031] Poplar fibers are randomly laid out along the board surface along their length and bonded together with modified phenolic resin adhesive to form a three-dimensional interwoven network skeleton. This makes the mechanical properties of the core material more uniform in all directions, effectively reducing the anisotropy and warping tendency of the board. At the same time, the three-dimensional interwoven structure provides a stable mechanical support foundation for the core material, improving the overall bending strength and dimensional stability of the board.

[0032] The core layer 1 also contains uniformly dispersed paraffin emulsion and triphenyl phosphate flame retardant components. The paraffin emulsion component fills the micropores on the surface of the wood fibers, and the triphenyl phosphate flame retardant component is uniformly distributed in molecular form in the cured cross-linked network of the modified phenolic resin adhesive.

[0033] By filling the micropores on the surface of wood fibers with paraffin emulsion, the capillary penetration channels of moisture and corrosive media are effectively sealed, giving the core board excellent waterproof and moisture-proof properties. Triphenyl phosphate is uniformly dispersed in the molecular state in the phenolic resin cross-linking network. When heated, it can inhibit the combustion chain reaction through the gas phase flame retardant mechanism. The synergistic effect of the two makes the core board have both excellent waterproof and flame retardant safety without affecting its mechanical properties.

[0034] The protective layer 2 also contains dispersed glass fiber chopped strands inside the polytetrafluoroethylene coating. The length direction of the glass fiber chopped strands is consistent with the extension direction of the protective layer 2, and multiple glass fiber chopped strands are randomly distributed in a planar manner inside the protective layer 2 to form a local reinforcement network.

[0035] By dispersing short glass fiber filaments inside the polytetrafluoroethylene coating and making them randomly distributed in a plane, the high modulus and high strength of the glass fiber are used to form a local reinforcing network without affecting the density and chemical inertness of the coating. This significantly improves the crack resistance, impact resistance and wear resistance of the protective layer 2, and avoids the formation of microcracks in the coating due to external impact or temperature changes, thereby ensuring the long-term integrity and corrosion resistance of the protective layer 2.

[0036] The protective layer 2 is further reinforced with a decorative surface layer 4 on the side away from the core layer 1. The decorative surface layer 4 is a decorative paper layer impregnated with melamine-formaldehyde resin. The decorative paper layer is bonded and fixed to the outer surface of the protective layer 2 by melamine-formaldehyde resin under hot pressing conditions.

[0037] By bonding and fixing the decorative paper layer impregnated with melamine-formaldehyde resin to the outer surface of the protective layer 2 under hot pressing, the board is given a variety of decorative effects to meet the aesthetic needs of different application scenarios. At the same time, the high hardness and high wear resistance surface layer formed after the melamine-formaldehyde resin is cured further improves the scratch resistance, stain resistance and aging resistance of the board surface. In addition, the decorative layer and the protective layer 2 undergo a chemical cross-linking reaction during hot pressing, ensuring the long-term adhesion of the decorative surface.

[0038] A planar reinforcing mesh 5 is also embedded in the middle of the core layer 1. The mesh direction of the planar reinforcing mesh 5 is parallel to the board surface direction of the core layer 1. The planar reinforcing mesh 5 is a glass fiber woven mesh, and the mesh of the glass fiber woven mesh is filled with a mixture of wood fiber and modified phenolic resin adhesive.

[0039] By embedding a fiberglass woven mesh in the middle of the core, with the mesh surface parallel to the board surface, the high tensile strength of the fiberglass mesh significantly improves the overall bending strength and deformation resistance of the core. At the same time, the mesh is filled with a mixture of wood fiber and modified phenolic resin adhesive, which creates a good mechanical interlock and integrated structure between the mesh and the core matrix, avoiding interface defects. This effectively prevents structural failures such as warping and cracking of the board under long-term use or temperature and humidity changes, and greatly improves the load-bearing capacity and stability of the board.

[0040] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An acid- and alkali-resistant medium-density fiberboard, characterized in that, It includes a core layer (1) located in the middle and a protective layer (2) tightly bonded to the upper and lower surfaces of the core layer (1). The core layer (1) is an integral, dense board formed by uniformly mixing wood fibers and modified phenolic resin adhesive and then hot-pressing and curing it. The protective layer (2) is a corrosion-resistant coating layer with polytetrafluoroethylene emulsion as the main film-forming material and nano-silica particles and organosilicon hydrophobic agent dispersed inside. The protective layer (2) continuously covers all exposed surfaces of the core layer (1), and part of the protective layer (2) penetrates into the fiber pores of the surface layer of the core layer (1) and forms an interface fusion and anchoring structure with the core layer (1).

2. The acid- and alkali-resistant medium-density fiberboard according to claim 1, characterized in that, A transition adhesive layer (3) is provided between the upper surface of the core layer (1) and the protective layer (2), and a transition adhesive layer (3) is also provided between the lower surface of the core layer (1) and the protective layer (2). The transition adhesive layer (3) is a thin film layer formed after the thermosetting epoxy resin adhesive is cured.

3. The acid- and alkali-resistant medium-density fiberboard according to claim 1, characterized in that, The modified phenolic resin adhesive also contains nano-montmorillonite sheet material and silane coupling agent. The nano-montmorillonite sheet material is distributed in the cross-linking network of the modified phenolic resin adhesive in an intercalation form, and the silane coupling agent is used to bridge the interface between the nano-montmorillonite sheet material and the phenolic resin matrix.

4. The acid- and alkali-resistant medium-density fiberboard according to claim 1, characterized in that, The wood fiber is poplar fiber, and the length direction of the poplar fiber is randomly laid out along the board surface direction of the core layer (1).

5. The acid- and alkali-resistant medium-density fiberboard according to claim 1, characterized in that, The core layer (1) also contains uniformly dispersed paraffin emulsion and triphenyl phosphate flame retardant components.

6. The acid- and alkali-resistant medium-density fiberboard according to claim 5, characterized in that, The paraffin emulsion component fills the micropores on the surface of the wood fiber, and the triphenyl phosphate flame retardant component is uniformly distributed in the cured cross-linking network of the modified phenolic resin adhesive in a molecular state.

7. The acid- and alkali-resistant medium-density fiberboard according to claim 1, characterized in that, The protective layer (2) also contains chopped glass fibers dispersed inside the polytetrafluoroethylene coating. The length direction of the chopped glass fibers is consistent with the extension direction of the protective layer (2), and multiple chopped glass fibers are randomly distributed in a planar manner inside the protective layer (2) to form a local reinforcement network.

8. The acid- and alkali-resistant medium-density fiberboard according to claim 1, characterized in that, The protective layer (2) is further reinforced with a decorative surface layer (4) on the side away from the core layer (1). The decorative surface layer (4) is a decorative paper layer impregnated with melamine-formaldehyde resin. The decorative paper layer is bonded and fixed to the outer surface of the protective layer (2) by melamine-formaldehyde resin under hot pressing conditions.

9. The acid- and alkali-resistant medium-density fiberboard according to claim 1, characterized in that, The core layer (1) is also embedded with a planar reinforcing mesh (5) in the middle position, and the mesh direction of the planar reinforcing mesh (5) is parallel to the board surface direction of the core layer (1).

10. The acid- and alkali-resistant medium-density fiberboard according to claim 9, characterized in that, The planar reinforced mesh (5) is a glass fiber woven mesh, and the mesh of the glass fiber woven mesh is filled with a mixture of wood fiber and modified phenolic resin adhesive.

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