A multi-layer composite reinforced door and window casing and a method of manufacturing the same

Abstract

The application relates to the technical field of building materials, and discloses a multilayer composite reinforced door and window sleeve and a preparation method thereof. The multilayer composite reinforced door and window sleeve comprises a door and window sleeve base material and a composite coating layer covering the surface of the door and window sleeve base material; the composite coating layer comprises, from inside to outside, an adhesive layer, a reinforcing layer, a decorative layer and a weather-resistant layer; the reinforcing layer comprises modified bacterial cellulose and rubber particles. The three-dimensional nano network formed by the modified bacterial cellulose in the reinforcing layer and the rubber particles are synergistically toughened, and stress is efficiently dispersed, so that the anti-cracking property of the product at stress concentration positions such as corners is significantly better than that of traditional materials; the composite effect of the fluororesin weather-resistant layer and the decorative layer containing nano titanium dioxide enables the product to have excellent ultraviolet shielding, chemical corrosion resistance and anti-aging capacity, and the product is suitable for harsh outdoor environments; the compact epoxy tree reinforcing layer and the strong interface bonding design ensure the balance between low water absorption, high wet strength, flexibility and rigidity.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a multi-layer composite reinforced door and window frame and its preparation method. Background Technology

[0002] As an important component of building decoration, the covering technology and material selection of door and window frames directly affect the product's aesthetics, durability, and environmental friendliness. Traditional door and window frames are mostly made of materials such as solid wood, MDF, PVC, or aluminum alloy, and are covered with processes such as heat transfer printing, film application, or spraying. However, they still have a series of significant defects in practical applications. Solid wood door and window frames, while possessing good environmental friendliness and decorative effects, are expensive and easily cracked and deformed due to changes in temperature and humidity. MDF door and window frames, although cheaper, have poor waterproof and moisture-proof performance, are prone to absorbing moisture and expanding, and long-term use in humid environments can lead to the coating peeling off and mold growth. They also often contain harmful substances such as formaldehyde, which are detrimental to indoor environmental health. PVC door and window frames have poor weather resistance and are prone to aging and discoloration outdoors or under strong ultraviolet radiation, resulting in a short service life. Aluminum alloy door and window frames, while having high structural strength, are expensive and offer limited decorative effects, failing to meet diverse aesthetic needs.

[0003] In terms of cladding technology, existing techniques struggle to effectively address the challenge of cladding door and window frames at corners. Due to insufficient material flexibility, stress concentration easily occurs at corners, leading to cracking and peeling of the cladding layer, affecting overall aesthetics and structural integrity. Furthermore, traditional door and window frames lack sufficient weather resistance in outdoor or high-humidity environments, easily fading, deforming, and aging, limiting their application in outdoor or damp areas (such as kitchens and bathrooms). Simultaneously, existing door and window frames have poor adaptability to uneven walls, easily resulting in incomplete cladding, hollow areas, and gaps during installation, affecting construction quality and the final effect. Regarding environmental protection, formaldehyde release from engineered wood products such as MDF is increasingly concerning, while solid wood materials consume significant amounts of forest resources, contradicting sustainable development principles. Therefore, the market urgently needs a door and window frame and its cladding technology that meets requirements for high strength, high weather resistance, and crack resistance, while also possessing good waterproof and moisture-proof properties, being environmentally friendly and recyclable, and having strong installation adaptability. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide a multi-layered composite reinforced door and window frame.

[0005] The second objective of this invention is to provide a method for preparing this multi-layered composite reinforced door and window frame.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a multi-layer composite reinforced door and window frame, comprising a door and window frame substrate and a composite covering layer covering the surface of the door and window frame substrate; the composite covering layer comprises, from the inside to the outside, an adhesive layer, a reinforcing layer, a decorative layer and a weather-resistant layer; wherein the reinforcing layer comprises modified bacterial cellulose and rubber particles.

[0007] In some embodiments of the present invention, the raw materials for preparing the window frame substrate, by weight percentage, include: 40%-60% thermoplastic resin, 20%-40% glass fiber, and 3%-20% additives.

[0008] In some embodiments of the present invention, the additives include at least one of anti-hydrolysis agents, antioxidants, light stabilizers, and compatibilizers.

[0009] In some embodiments of the present invention, the raw materials for preparing the window frame substrate, by weight percentage, include: 40%-60% thermoplastic resin, 20%-40% glass fiber, 3%-6% anti-hydrolysis agent, 0.2%-2% antioxidant, 0.2%-2% light stabilizer, and 0-10% compatibilizer.

[0010] In some preferred embodiments of the present invention, the raw materials for preparing the window frame substrate, by weight percentage, include: 45%-55% thermoplastic resin, 30%-40% glass fiber, 3%-5% anti-hydrolysis agent, 0.5%-1.5% antioxidant, 0.5%-1.5% light stabilizer, and 5-8% compatibilizer.

[0011] In some embodiments of the present invention, the melt index of the thermoplastic resin at test conditions of 190°C / 2.16kg is 1g / 10min-10g / 10min.

[0012] In some embodiments of the present invention, the melt index of the thermoplastic resin at test conditions of 190°C / 2.16kg is 5g / 10min-10g / 10min.

[0013] In some preferred embodiments of the present invention, the thermoplastic resin includes at least one of high-density polyethylene resin and polypropylene resin.

[0014] In some embodiments of the present invention, the glass fiber has a single filament diameter of 10-14 μm and a length of 1-3 mm.

[0015] In some embodiments of the present invention, the antioxidant is selected from at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0016] In some preferred embodiments of the present invention, the antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant in a mass ratio of (1.5-2.5):1.

[0017] In some embodiments of the present invention, the hindered phenolic antioxidant is selected from 2,6 di-tert-butyl-p-methylphenol (BHT), β (3,5) Second Uncle Ding Ji 4 Octadecyl hydroxyphenyl propionate (antioxidant 1076), tetra[β-hydroxyphenyl]prop ... (3,5) Second Uncle Ding Ji 4 [Hydroxyphenyl]propionic acid pentaerythritol ester (antioxidant 1010), N,N' pair (3 (3,5) Second Uncle Ding Ji 4 Hydroxyphenyl)propionyl)hexanediamine (antioxidant 1098), triethylene glycol bis[β] (3 tert-butyl 4 hydroxyl 5 At least one of [methylphenyl]propionate (antioxidant 245).

[0018] In some embodiments of the present invention, the phosphite antioxidants include diphenyl isooctyl phosphite (ODPP), tris[2,4]... At least one of the following: di-tert-butylphenyl phosphite (antioxidant 168), bisphenol A phosphite, and triphenyl phosphite (TPP).

[0019] In some preferred embodiments of the present invention, the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of (2-3):1.

[0020] In some embodiments of the present invention, the anti-hydrolysis agent includes a carbodiimide-type anti-hydrolysis stabilizer.

[0021] In some embodiments of the present invention, the light stabilizer includes hindered amine light stabilizers.

[0022] In some embodiments of the present invention, the compatibilizer includes maleic anhydride grafted reactive compatibilizers.

[0023] In some preferred embodiments of the present invention, the compatibilizer is selected from maleic anhydride-grafted polypropylene (PP). g MAH), maleic anhydride grafted polyolefin elastomer (POE) g MAH), maleic anhydride-grafted ethylene propylene diene monomer (EPDM) g At least one of MAH).

[0024] In some embodiments of the present invention, the reinforcing layer comprises, by weight percentage, the following raw materials: 70%-80% epoxy resin, 3%-5% modified bacterial cellulose, 2-4% curing agent, 10%-15% rubber particles, and 2%-6% silane coupling agent.

[0025] In some embodiments of the present invention, the epoxy equivalent of the epoxy resin is 210-240 g / eq.

[0026] In some embodiments of the present invention, the modified bacterial cellulose is selected from bacterial cellulose that has been surface-grafted with a silane coupling agent or bacterial cellulose that has been esterified and hydrophobically modified.

[0027] Specifically, unmodified bacterial cellulose is highly hydrophilic and has poor compatibility with hydrophobic epoxy resin. By grafting with silane coupling agents or esterifying and hydrophobically modifying it, organic functional groups are introduced on its surface, which significantly reduces its surface energy and enhances its interfacial compatibility with the resin matrix.

[0028] In some embodiments of the present invention, the surface grafting modification specifically includes the following steps: 1) Place the bacterial cellulose membrane in deionized water and homogenize it to form a bacterial cellulose aqueous dispersion; 2) Mix the silane coupling agent with an aqueous ethanol solution, adjust the pH to 4-5, and hydrolyze to form a silane hydrolysate; 3) Mix the bacterial cellulose aqueous dispersion with the silane hydrolysate, react, separate the solid phase by solid-liquid separation, wash, and dry to obtain the modified bacterial cellulose.

[0029] In some embodiments of the present invention, the solid content of the bacterial cellulose aqueous dispersion is 1%-2%.

[0030] In some embodiments of the present invention, the volume ratio of ethanol to water in the aqueous ethanol solution is (3-5):1.

[0031] In some embodiments of the present invention, the solid-liquid ratio of the silane coupling agent to the aqueous ethanol solution is (1-5) g: 100 mL.

[0032] In some embodiments of the present invention, the amount of the silane coupling agent is 5%-20% of the dry weight of bacterial cellulose.

[0033] In some embodiments of the present invention, the surface grafting modification includes the use of γ-glycidoxypropyltrimethoxysilane (KH-560) or γ-aminopropyltriethoxysilane (KH-550).

[0034] In some embodiments of the present invention, the reaction temperature is 60-80°C and the time is 2-6 hours.

[0035] In some embodiments of the present invention, the esterification hydrophobic modification specifically includes the following steps: 1) The bacterial cellulose hydrogel was replaced with ethanol and placed in N,N-dimethylformamide to obtain a dispersion; 2) Under anhydrous and inert gas protection, esterifying agent and catalyst are added to the dispersion, the reaction is carried out, the solid phase is collected by solid-liquid separation, washed, and dried to obtain the modified bacterial cellulose.

[0036] In some embodiments of the present invention, the amount of the esterifying agent is 1-5 times the number of molar hydroxyl groups of the bacterial cellulose dry weight.

[0037] In some embodiments of the present invention, the esterifying agent is selected from acetic anhydride, succinic anhydride or maleic anhydride.

[0038] In some embodiments of the present invention, the catalyst comprises 4-dimethylaminopyridine.

[0039] In some embodiments of the present invention, the reaction temperature is 60-110°C and the time is 4-12 hours.

[0040] In some embodiments of the present invention, the curing agent includes at least one of hexamethylene diisocyanate trimer (HDI trimer) and diphenylmethane diisocyanate (MDI polymer).

[0041] In some embodiments of the present invention, the silane coupling agent includes at least one of 3-aminopropyltrimethoxysilane (KH-540), γ-aminopropyltriethoxysilane (KH-550), and γ-glycidoxypropyltrimethoxysilane (KH-560).

[0042] In some embodiments of the present invention, the particle size of the rubber particles is 125-280 μm.

[0043] In some preferred embodiments of the present invention, the particle size of the rubber particles is 150-200 μm.

[0044] In some embodiments of the present invention, the weather-resistant layer comprises, by weight percentage, the following raw materials: 20%-30% fluororesin, 60%-70% solvent, 1%-3% UV absorber, 1%-3% antioxidant, and 0.5%-5% other additives.

[0045] In some embodiments of the present invention, the other additives include at least one of leveling agents, wetting and dispersing agents, and defoamers.

[0046] In some preferred embodiments of the present invention, the weather-resistant layer comprises, by weight percentage, the following raw materials: 25%-30% fluororesin, 65%-70% solvent, 1%-2% UV absorber, 1%-2% antioxidant, 0.5%-1% leveling agent, 0.5%-2% wetting and dispersing agent, and 0.1%-0.5% defoamer.

[0047] In some embodiments of the present invention, the fluororesin includes at least one of polyvinylidene fluoride (PVDF) resin and acrylic fluorocarbon resin.

[0048] In some embodiments of the present invention, the solvent includes at least one of N-methylpyrrolidone (NMP) and dimethylacetamide (DMAC).

[0049] In some embodiments of the present invention, the ultraviolet absorber includes benzotriazole ultraviolet absorbers.

[0050] In some embodiments of the present invention, the antioxidant is selected from at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0051] In some embodiments of the present invention, the leveling agent comprises an organosilicon leveling agent.

[0052] In some embodiments of the present invention, the adhesive layer comprises a polyurethane adhesive.

[0053] In some embodiments of the present invention, the polyurethane adhesive is selected from water-based polyurethane adhesives or reactive hot-melt polyurethane adhesives.

[0054] In some embodiments of the present invention, the decorative layer comprises a decorative base paper as a substrate, impregnated with melamine-formaldehyde resin, wherein the amount of resin impregnation is 120%-130% of the dry weight of the decorative base paper.

[0055] In some embodiments of the present invention, the basis weight of the decorative base paper is 80-150 g / m². 2 .

[0056] In some embodiments of the present invention, the decorative layer further includes nano-titanium dioxide with a particle size of 10-50 nm.

[0057] In some embodiments of the present invention, the width of the door and window frame substrate is 80-200mm, the thickness is 15-30mm, and the shape includes L-shaped, U-shaped, and T-shaped.

[0058] In some embodiments of the present invention, the thicknesses of the adhesive layer, reinforcing layer, decorative layer and weather-resistant layer in the composite coating layer are 0.05-0.1 mm, 0.15-0.3 mm, 0.1-0.2 mm and 0.05-0.1 mm, respectively.

[0059] A second aspect of the present invention provides a method for preparing the multi-layer composite reinforced door and window frame described in the first aspect of the present invention, comprising the following steps: S1. Mix the various raw materials for preparing the door and window frame substrate and extrude them into shape using a twin-screw extruder; S2. Impregnate the decorative base paper with melamine-formaldehyde resin impregnation solution, pre-cur it, and then print the decorative pattern on the front to form a decorative layer. S3. Mix the raw materials for the reinforcement layer and apply them to the back of the decorative layer; after applying an adhesive layer to the surface of the door and window frame substrate, bond the back of the decorative layer to the adhesive layer and hot-press to form a composite blank. S4. Mix the raw materials for preparing the weather-resistant layer, apply them to the decorative layer surface of the composite blank, and dry to obtain the multi-layer composite reinforced door and window frame.

[0060] In some embodiments of the present invention, in step S1, the extrusion temperature is 180-220°C.

[0061] In some embodiments of the present invention, after the extrusion molding in step S1, the process further includes corona treatment or plasma treatment of the surface of the door and window frame substrate.

[0062] In some embodiments of the present invention, in step S2, the content of melamine-formaldehyde resin in the melamine-formaldehyde resin impregnation solution is 50%-60%.

[0063] In some embodiments of the present invention, in step S2, the melamine-formaldehyde resin impregnation solution further includes nano-titanium dioxide, with a content of 1%-3%.

[0064] In some embodiments of the present invention, in step S2, the pre-curing temperature is 70-80°C and the time is 12-15 hours.

[0065] In some embodiments of the present invention, in step S2, the printing includes using alkyd resin ink or UV-curable ink.

[0066] In some embodiments of the present invention, in step S2, the decorative pattern includes wood grain and stone grain.

[0067] In some embodiments of the present invention, in step S3, the pre-composite temperature is 80-100℃, the pressure is 0.3-0.5MPa, and the time is 1-5min; the hot-press composite temperature is 100-120℃, the pressure is 0.5-0.8MPa, and the time is 20-40min.

[0068] In some embodiments of the present invention, in step S4, the drying includes: first evaporating the solvent at 80-120°C, and then baking at 200-240°C for 3-5 minutes.

[0069] The basic principles of this invention are explained as follows: The multi-layer composite reinforced door and window frame provided by this invention uses glass fiber reinforced polyolefin composite material as the base material. Utilizing the high strength and high modulus of glass fiber, it is composited with polyolefin resin to provide a skeleton for the entire door and window frame, ensuring its basic structural strength, dimensional stability, and lightweight. The extrusion molding process ensures that it can be processed into various required profile sections. The composite coating layer includes an adhesive layer, a reinforcing layer, a decorative layer, and a weather-resistant layer, wherein: 1) The adhesive layer firmly bonds the substrate to the remaining covering layers through chemical bonding force; 2) The reinforcing layer is the core functional layer for crack prevention. It uses epoxy resin as the continuous matrix and modified bacterial cellulose and rubber particles as reinforcing phases. Through synergy with a silane coupling agent, it forms a strong interfacial bond, achieving efficient stress transfer. The modified bacterial cellulose has an extremely high aspect ratio and, during preparation, randomly orients, cross-links, and entangles within the epoxy resin matrix, forming a continuous, interpenetrating three-dimensional nanofiber network that runs throughout the entire reinforcing layer. When the composite material is subjected to external forces (such as bending, impact, especially complex stresses at the corners of door and window frames), the stress first acts on the continuous epoxy resin matrix, and then... Through strong interfacial bonding between the modified bacterial cellulose network and the resin matrix, stress can be efficiently transferred from the relatively weak resin matrix to the rigid nanofiber network, achieving stress dispersion and preventing crack initiation and propagation. The rubber particles act as stress concentration points. When the material is subjected to impact or bending stress, the matrix around the rubber particles generates crazing and shear bands, consuming a large amount of energy. At the same time, the elastic deformation capacity of the rubber particles can effectively blunt the crack tip and prevent crack propagation. The modified bacterial cellulose and rubber particles form a soft and hard synergistic toughening system, with the former providing rigid support and the latter providing toughness, achieving a balance between strength and toughness. 3) The decorative layer is used to provide decorative effects such as wood grain and stone grain. The addition of nano titanium dioxide can enhance the hiding power and protect the underlying resin and ink through its excellent ultraviolet shielding ability and high refractive index, and delay fading. 4) The weather-resistant layer utilizes the extremely high chemical inertness, extremely low surface energy, and excellent UV resistance of fluoropolymers to form a dense protective layer outside the decorative layer, effectively blocking the erosion of internal materials by moisture, ultraviolet rays, pollutants, and temperature changes.

[0070] During the preparation process, hot-pressing is performed at 100-120℃ and 0.5-0.8MPa for 20-40 minutes, which allows the hot melt adhesive film of the adhesive layer to melt, flow, and wet the substrate, and undergo a moisture curing reaction. The epoxy resin of the reinforcing layer undergoes a cross-linking reaction with the curing agent, and is completely cured and shaped. The melamine resin in the decorative layer is further cured. This integrated hot-pressing and simultaneous curing avoids the problems of interlayer thermal stress, interface contamination and low efficiency caused by step curing, and ensures that the interfaces of each layer are tightly bonded at the molecular level.

[0071] Compared with the prior art, the beneficial effects of the present invention are: The multi-layer composite reinforced door and window casing provided by this invention utilizes the synergistic toughening effect of a three-dimensional nano-network constructed from modified bacterial cellulose in the reinforcing layer and rubber particles to efficiently disperse stress, making the product significantly more resistant to cracking than traditional materials at stress concentration points such as corners. The composite effect of the fluororesin weather-resistant layer and the internal decorative layer containing nano-titanium dioxide gives the product excellent UV shielding, chemical corrosion resistance, and anti-aging capabilities, making it suitable for harsh outdoor environments. The dense epoxy resin reinforcing layer and strong interface bonding design ensure low water absorption, high wet strength, and a balance between flexibility and rigidity. Using a low-formaldehyde system and recyclable substrate, the product also has good flexibility and dimensional stability, easily adapting to various irregular wall shapes and uneven base surfaces, achieving a firm and aesthetically pleasing covering effect, solving the problems of traditional products being prone to cracking, aging, moisture susceptibility, and difficult installation. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the multi-layer composite reinforced door and window frame in Example 1; Figure 2 This is a schematic diagram of the main door frame in the multi-layer composite reinforced door and window frame in Example 1; Figure 3 This is a schematic diagram of the structure of the multi-layer composite reinforced door and window frame in Example 1; Among them, ①-weather-resistant layer, ②-decorative layer, ③-adhesive layer, ④-reinforcing layer, and ⑤-door and window frame substrate. Detailed Implementation

[0073] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0074] Example 1 This embodiment prepares a multi-layer composite reinforced door and window frame, which consists of a door and window frame substrate and a composite covering layer covering the surface of the substrate. The composite covering layer, from the inside out, comprises an adhesive layer, a reinforcing layer, a decorative layer, and a weather-resistant layer. The preparation steps are as follows: S11. Mix 55wt% polypropylene resin, 30wt% glass fiber, 4wt% carbodiimide-type hydrolysis stabilizer, 1.5wt% antioxidant 1010, 0.5wt% antioxidant 168, 1wt% light stabilizer 770, and 8wt% maleic anhydride-grafted polypropylene, and extrude the mixture through a twin-screw extruder at 180-220℃ to obtain a door and window frame substrate. S21. The decorative base paper is passed at a uniform speed through an impregnation tank containing melamine-formaldehyde resin impregnation solution. The impregnation solution contains 55wt% melamine-formaldehyde resin and 2wt% nano-titanium dioxide (20-30nm). The amount of resin adhering is precisely controlled by the extrusion roller to make the resin solid content reach 120% of the dry weight of the base paper. The impregnated wet paper is sent into a drying oven and pre-cured at 75℃ for 12 hours. Subsequently, a wood grain pattern is printed on the surface of the pre-cured impregnated paper using a gravure printing machine to form a decorative layer. S31. Mix 75wt% bisphenol A type epoxy resin, 5wt% modified bacterial cellulose, 3wt% HDI trimer, 12wt% rubber particles, and 5wt% KH-560, apply the mixture to the back of the decorative layer (the side without pattern), and press it through a hot press roller assembly at a temperature of 80℃, a pressure of 0.4MPa, and a time of 5min. S32. Apply reactive hot melt polyurethane adhesive to the surface of the door and window frame substrate, then bond the back of the decorative layer to the adhesive layer, and hot press the composite material at 120°C and 0.8MPa for 30 minutes to form a composite blank. S41. Mix 30wt% acrylic fluorocarbon resin, 65wt% N-methylpyrrolidone, 1wt% UV326, 1.5wt% antioxidant 1010, 0.5wt% organosilicon leveling agent BYK-333, 1.5wt% BYK-163, and 0.5wt% BYK-066N, and apply the mixture to the decorative layer surface of the composite preform. First, evaporate the solvent at 100℃, and then bake at 220℃ for 5 minutes to level and form a film, thus obtaining the main door frame or casing of the multi-layer composite reinforced door and window casing.

[0075] The polypropylene resin is PP EP300M, with a melt flow index of 9 g / 10 min at 190℃ / 2.16 kg. The glass fiber has a monofilament diameter of 10-14 μm and a length of 1-3 mm. The bisphenol A epoxy resin has an epoxy equivalent of 220 g / eq. The rubber granules have a particle size of 150-200 μm. The decorative base paper has a basis weight of 100 g / m². 2The modified bacterial cellulose is KH-560 surface-grafted modified bacterial cellulose, and the modification steps are as follows: Bacterial cellulose membranes were placed in deionized water and homogenized to form a bacterial cellulose aqueous dispersion (2% solid content). KH-560 was mixed with an ethanol-water (4:1, v / v) solution, and the pH was adjusted to 4-5 with acetic acid to hydrolyze the mixture to form a silane hydrolysate. The bacterial cellulose aqueous dispersion and the silane hydrolysate were mixed and reacted at 60°C for 5 hours. The solid phase was collected by solid-liquid separation, washed, and dried to obtain modified bacterial cellulose. The amount of KH-560 used was 15% of the dry weight of the bacterial cellulose.

[0076] The main door frame and trim are prepared through the above steps and then assembled to form the door and window frames. Figure 1 This is a schematic diagram of the multi-layer composite reinforced door and window frame in Example 1. Figure 2 This is a schematic diagram of the main door frame in the multi-layer composite reinforced door and window frame in Example 1. Figure 3 The diagram shows the structure of the sleeve in the multi-layer composite reinforced door and window frame in Example 1. In the diagram, ① is the weather-resistant layer, ② is the decorative layer, ③ is the adhesive layer, ④ is the reinforcement layer, and ⑤ is the door and window frame substrate. The thicknesses of the adhesive layer, reinforcement layer, decorative layer, and weather-resistant layer are 0.1 mm, 0.3 mm, 0.2 mm, and 0.1 mm, respectively.

[0077] Performance testing In this invention, the reinforcing layer is the core functional layer for crack prevention; therefore, its performance is verified as follows: Preparation of ordinary glass fiber mesh reinforcement layer: using alkali-free glass fiber mesh (area density approximately 80-100 g / m²) 2 Using a pore size of approximately 2-4 mm as the reinforcing phase, cut the appropriate number of glass fiber mesh layers, with a mass of 10 wt% of the total mass of the raw materials. Combine 75 wt% bisphenol A type epoxy resin and 15 wt% HDI trimer to form an epoxy resin mixture. Apply a layer of epoxy resin mixture to the mold, lay a layer of glass fiber mesh, and press it flat with a roller to impregnate it. Repeat this process until the required number of layers is reached, ensuring that the resin is fully impregnated. Then, hot-press the composite at 120°C and 0.8 MPa for 30 minutes to obtain a common glass fiber mesh reinforcement layer.

[0078] Preparation of pure epoxy resin layer: Bisphenol A type epoxy resin and HDI trimer were mixed at a mass ratio of 5:1, stirred evenly at room temperature, degassed under vacuum, coated onto a mold, and then hot-pressed at 120℃ and 0.8MPa for 30 min to obtain pure epoxy resin layer.

[0079] Preparation of modified bacterial cellulose reinforcement layer: Modified bacterial cellulose was prepared according to the method in Example 1. Then, 75 wt% bisphenol A type epoxy resin, 5 wt% modified bacterial cellulose, 3 wt% HDI trimer, 12 wt% rubber particles, and 5 wt% KH-560 were mixed and coated onto a mold. Then, the mixture was hot-pressed at 120°C and 0.8 MPa for 30 min to obtain the modified bacterial cellulose reinforcement layer.

[0080] 1. Flexibility test: The test was conducted in accordance with BS EN ISO 10619-2:2021 "Measurement of flexibility and stiffness of rubber and plastic hoses and pipes".

[0081] Table 1. Flexibility test results of different materials

[0082] 2. Crack resistance test: A horizontal folding endurance tester was used for folding tests. The folding tension was 0.75 kg. The fold was first folded clockwise by 180° and then counterclockwise by 180°. The folds were scanned and the crack area percentage was analyzed using ImageJ software.

[0083] Table 2. Test results of crack resistance of different materials

[0084] 3. Peel strength test: A 180° peel test was conducted according to BS EN ISO 29862:2024 "Determination of peel and adhesion properties of self-adhesive tapes", with a peel rate of 100 mm / min and a test temperature of 23±2℃.

[0085] Table 3. Peel strength test results for different materials

[0086] 4. Mechanical property testing: 1) Tensile strength: Refer to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", conduct a three-point bending test at a speed of 50 mm / min on a universal testing machine, and the test temperature is 23±2℃; 2) Heat distortion temperature: Tested according to ASTM D648-18, "Standard Test Method for Temperature of Plastic Deformation under Bending Load"; 3) Impact toughness: Tested according to GB / T 1843-2008 "Determination of impact strength of plastic cantilever beams"; 4) Interlaminar shear strength: Tested according to ASTM D 2344-2016, "Standard Test Method for Strength of Polymer-Based Composite Materials and Their Laminates as Short Beams".

[0087] Table 4. Test results of mechanical properties of different materials

[0088] Table 1 shows the flexibility test results of different materials, Table 2 shows the crack resistance test results of different materials, Table 3 shows the peel strength test results of different materials, and Table 4 shows the mechanical property test results of different materials. As can be seen from Tables 1-4, the modified bacterial cellulose reinforced layer is comprehensively and significantly superior to the traditional glass fiber reinforced and pure epoxy resin systems in terms of overall performance, especially achieving an ideal balance between strength and toughness, durability and processability. Specifically: 1) Significant advantages in key crack resistance and flexibility: The modified layer has the smallest bending radius (R=1-3mm) and the highest elongation at break (40.6%), far exceeding the control sample. In the simulated corner test, its... The lowest crack area percentage (2.9%) and crack propagation length (0.5mm), with microcrack arrest as the failure mode, demonstrate that its three-dimensional network stress dispersion mechanism can effectively inhibit crack initiation and propagation, fundamentally solving the problem of corner cracking; 2) It possesses both excellent mechanical strength and interfacial bonding: its tensile strength (≥300MPa) and interlaminar shear strength (38MPa) are the highest, and its peel strength (≥2.8N / cm) and heat aging retention rate (92%) are also the best, indicating that it has the strongest and most durable bonding with the upper and lower layers; 3) Significantly improved heat resistance and impact resistance: heat distortion temperature ≥200℃, impact toughness reaches 25kJ / m 2 This demonstrates that it maintains its shape at high temperatures and can effectively absorb impact energy. Therefore, this invention uses a modified bacterial cellulose reinforcement layer as the main functional layer, which can integrate the high strength, high toughness, high heat resistance and high interfacial bonding force that are difficult to achieve with traditional reinforcement materials, thus significantly improving the overall performance of door and window frames.

Claims

1. A multi-layer composite reinforced door and window frame, characterized in that, It includes a door and window frame substrate and a composite coating layer covering the surface of the door and window frame substrate; the composite coating layer includes, from the inside out, an adhesive layer, a reinforcing layer, a decorative layer and a weather-resistant layer; wherein, the reinforcing layer contains modified bacterial cellulose and rubber particles.

2. The multi-layer composite reinforced door and window frame according to claim 1, characterized in that, The raw materials for preparing the window frame substrate, by weight percentage, include: 40%-60% thermoplastic resin, 20%-40% glass fiber, and 3%-20% additives.

3. The multi-layer composite reinforced door and window frame according to claim 2, characterized in that, The melt flow index of the thermoplastic resin under test conditions of 190℃ / 2.16kg is 1g / 10min-10g / 10min; And / or, the glass fiber has a single filament diameter of 10-14 μm and a length of 1-3 mm.

4. The multi-layer composite reinforced door and window frame according to claim 1, characterized in that, The reinforcing layer comprises the following raw materials by weight percentage: 70%-80% epoxy resin, 3%-5% modified bacterial cellulose, 2-4% curing agent, 10%-15% rubber particles, and 2%-6% silane coupling agent.

5. The multi-layer composite reinforced door and window frame according to claim 4, characterized in that, The modified bacterial cellulose is selected from bacterial cellulose that has been surface-grafted with a silane coupling agent or bacterial cellulose that has been esterified and hydrophobically modified. And / or, the particle size of the rubber particles is 125-280 μm.

6. The multi-layer composite reinforced door and window frame according to claim 1, characterized in that, The weather-resistant layer comprises the following raw materials by weight percentage: 20%-30% fluororesin, 60%-70% solvent, 1%-3% UV absorber, 1%-3% antioxidant, and 0.5%-5% other additives.

7. The multi-layer composite reinforced door and window frame according to claim 1, characterized in that, The adhesive layer includes a polyurethane adhesive. And / or, the decorative layer comprises a decorative base paper as the substrate, impregnated with melamine-formaldehyde resin, the impregnation amount being 120%-130% of the dry weight of the decorative base paper.

8. The multi-layer composite reinforced door and window frame according to any one of claims 1-7, characterized in that, The width of the door and window frame substrate is 80-200mm, the thickness is 15-30mm, and the shape includes L-shaped, U-shaped, and T-shaped. And / or, in the composite coating layer, the thicknesses of the adhesive layer, the reinforcing layer, the decorative layer and the weather-resistant layer are 0.05-0.1 mm, 0.15-0.3 mm, 0.1-0.2 mm and 0.05-0.1 mm, respectively.

9. The method for preparing the multi-layer composite reinforced door and window frame according to claim 8, characterized in that, Includes the following steps: S1. Mix the various raw materials for preparing the door and window frame substrate and extrude them into shape using a twin-screw extruder; S2. Impregnate the decorative base paper with melamine-formaldehyde resin impregnation solution, pre-cur it, and then print the decorative pattern on the front to form a decorative layer. S3. Mix the raw materials for the reinforcement layer and apply them to the back of the decorative layer for pre-composite bonding; after applying an adhesive layer to the surface of the door and window frame substrate, bond the back of the decorative layer to the adhesive layer and hot-press to form a composite blank. S4. Mix the raw materials for preparing the weather-resistant layer, apply them to the decorative layer surface of the composite blank, and dry to obtain the multi-layer composite reinforced door and window frame.

10. The preparation method according to claim 9, characterized in that, In step S3, the pre-composite temperature is 80-100℃, the pressure is 0.3-0.5MPa, and the time is 1-5min; the hot-pressing composite temperature is 100-120℃, the pressure is 0.5-0.8MPa, and the time is 20-40min.

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