High-strength, durably flame retardant, seawater corrosion-resistant plastic-wood composite material and preparation method

Abstract

The present invention belongs to the technical field of composite materials, and specifically relates to a high-strength, durably flame retardant, seawater corrosion-resistant plastic-wood composite material, and a preparation method. The plastic-wood composite material of the present invention is primarily made of modified wood powder, a melamine formaldehyde resin, polyvinyl chloride and a binary hydroxyl-modified vinyl resin. The modified wood powder used in the present invention first undergoes a modification reaction using a melamine and formaldehyde solution on the surface of the wood powder under the catalytic action of citric acid, and is then dried. The modified wood powder enhances compatibility with the melamine formaldehyde resin. When preparing the plastic-wood composite material of the present invention, during a molding process, polyvinyl chloride partially self-crosslinks to form crosslinked polyvinyl chloride, causing the final product to have excellent static bending strength and tensile strength, and have durable flame retardancy. The flame retardancy performance does not significantly decrease after boiling in simulated seawater for 172 hours, and there is no obvious change on the surface. It is suitable for boardwalks in seaside scenic spots, etc.

Description

High-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material and preparation method Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to a high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material and a preparation method thereof. Background Art

[0002] Traditional flame-retardant wood-plastic composite materials basically use the method of adding flame retardants, such as those disclosed in CN200610039985.4 and CN201110231742.1, which add ammonium polyphosphate or flame retardants such as tris(dibromophenyl)phosphate and decabromodiphenyl ether. However, due to the poor binding force between the added flame retardants and wood powder and plastic, they are easily decomposed and lost with rainwater during outdoor use. As a result, the flame retardant properties of the wood-plastic composite materials used outdoors decrease rapidly until they disappear. In addition, as the added flame retardants are lost, the surface of the wood-plastic composite material becomes uneven, resulting in a sharp decrease in the mechanical properties of the wood-plastic composite material. Furthermore, conventional wood-plastic composites are made from thermoplastic resins, such as polyethylene, without the participation of thermosetting resins and cross-linking agents in the curing process. This results in low strength of the composites, making them prone to deformation when used on load-bearing objects such as floors and guardrails. Furthermore, the compatibility between the components is also unsatisfactory. This is especially true for wood-plastic composites used in seaside landscapes, such as floors and guardrails, which can be immersed in seawater at high tide, leading to rapid damage, such as cracking of the plastic wood and a decrease in flame retardancy. Therefore, to address the above issues, there is a need for a wood-plastic composite material that is high-strength, durable, flame-retardant, and resistant to seawater corrosion.

[0003] Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a high-strength, durable flame-retardant, and seawater-corrosion-resistant plastic-wood composite material;

[0005] The present invention also provides a method for preparing the above-mentioned wood-plastic composite material, which has the characteristics of simple process and easy industrialization.

[0006] The high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material provided by the present invention is mainly prepared from modified wood powder, melamine formaldehyde resin, polyvinyl chloride, dichlorovinyl resin, crosslinking agent, coupling agent, antioxidant, and ultraviolet absorber.

[0007] In the above-mentioned wood-plastic composite material, the weight proportions of the main raw materials are as follows:

[0008] Modified wood flour 20-35; melamine formaldehyde resin 15-28; polyvinyl chloride 28-40; dichlorovinyl resin 5-10; cross-linking agent 0.5-1.5; plasticizer 3-5; heat stabilizer 0.5-1.5; coupling agent 1-3; antioxidant 0.3-0.5; ultraviolet absorber 0.2-0.5.

[0009] Preferably, the modified wood flour comprises 21 to 35 parts, melamine formaldehyde resin comprises 16 to 28 parts, polyvinyl chloride comprises 29 to 40 parts, dichlorovinyl resin comprises 6 to 10 parts, cross-linking agent comprises 0.5 to 1.4 parts, plasticizer comprises 3 to 5 parts, heat stabilizer comprises 0.5 to 1.4 parts, coupling agent comprises 1 to 3 parts, antioxidant comprises 0.3 to 0.4 parts, and ultraviolet absorber comprises 0.2 to 0.4 parts.

[0010] Preferably, the modified wood flour comprises 22-35 parts, melamine formaldehyde resin comprises 17-28 parts, polyvinyl chloride comprises 30-40 parts, dichlorovinyl resin comprises 7-10 parts, cross-linking agent comprises 0.6-1.5 parts, plasticizer comprises 4-5 parts, heat stabilizer comprises 0.5-1.4 parts, coupling agent comprises 1-3 parts, antioxidant comprises 0.3-0.4 parts, and ultraviolet absorber comprises 0.2-0.3 parts.

[0011] Preferably, the modified wood flour is 23-35, the melamine formaldehyde resin is 18-28, the polyvinyl chloride is 31-40, the dichlorovinyl resin is 8-10, the crosslinking agent is 0.5-1.4, the plasticizer is 4-5, the heat stabilizer is 0.6-1.4, the coupling agent is 1-3, the antioxidant is 0.3-0.4, and the ultraviolet absorber is 0.2-0.3.

[0012] Preferably, the modified wood flour comprises 24-35 parts, melamine formaldehyde resin comprises 18-28 parts, polyvinyl chloride comprises 31-40 parts, dichlorovinyl resin comprises 8-10 parts, cross-linking agent comprises 0.6-1.3 parts, plasticizer comprises 4-5 parts, heat stabilizer comprises 0.6-1.3 parts, coupling agent comprises 1-3 parts, antioxidant comprises 0.3-0.4 parts, and ultraviolet absorber comprises 0.2-0.3 parts.

[0013] Preferably, the modified wood flour is 25-35, the melamine formaldehyde resin is 19-28, the polyvinyl chloride is 32-40, the dichlorovinyl resin is 9-10, the crosslinking agent is 0.7-1.3, the plasticizer is 4-5, the heat stabilizer is 0.7-1.2, the coupling agent is 1-3, the antioxidant is 0.3-0.4, and the ultraviolet absorber is 0.2-0.3.

[0014] Preferably, the modified wood flour comprises 26-35 parts, melamine formaldehyde resin 20-28 parts, polyvinyl chloride 33-40 parts, dichlorovinyl resin 7-10 parts, crosslinking agent 0.7-1.3 parts, plasticizer 4-5 parts, heat stabilizer 0.5-1.1 parts, coupling agent 1-3 parts, antioxidant 0.3-0.4 parts, and ultraviolet absorber 0.2-0.3 parts.

[0015] Preferably, the modified wood flour is 27-35, the melamine formaldehyde resin is 21-28, the polyvinyl chloride is 34-40, the dichlorovinyl resin is 7-10, the crosslinking agent is 0.8-1.3, the plasticizer is 4-5, the heat stabilizer is 0.5-1.4, the coupling agent is 1-3, the antioxidant is 0.3-0.4, and the ultraviolet absorber is 0.2-0.3.

[0016] Preferably, the modified wood flour is 28-35, the melamine formaldehyde resin is 18-28, the polyvinyl chloride is 35-40, the dichlorovinyl resin is 7-10, the crosslinking agent is 0.8-1.3, the plasticizer is 4-5, the heat stabilizer is 0.5-1.4, the coupling agent is 1-3, the antioxidant is 0.3-0.4, and the ultraviolet absorber is 0.2-0.3.

[0017] Preferably, the modified wood flour comprises 29-35 parts, 19-28 parts of melamine formaldehyde resin, 36-40 parts of polyvinyl chloride, 7-10 parts of dichlorovinyl resin, 0.8-1.3 parts of cross-linking agent, 4-5 parts of plasticizer, 0.5-1.4 parts of heat stabilizer, 1-3 parts of coupling agent, 0.3-0.4 parts of antioxidant, and 0.2-0.3 parts of ultraviolet absorber.

[0018] Preferably, the modified wood flour is 30-35, the melamine formaldehyde resin is 20-28, the polyvinyl chloride is 37-40, the dichlorovinyl resin is 7-10, the crosslinking agent is 0.8-1.2, the plasticizer is 4-5, the heat stabilizer is 0.5-1.4, the coupling agent is 1-3, the antioxidant is 0.3-0.4, and the ultraviolet absorber is 0.2-0.3.

[0019] Preferably, the modified wood flour comprises 31-35 parts, 21-28 parts melamine formaldehyde resin, 38-40 parts polyvinyl chloride, 7-10 parts dichlorovinyl resin, 0.8-1.3 parts crosslinking agent, 4-5 parts plasticizer, 0.5-1.4 parts heat stabilizer, 1-3 parts coupling agent, 0.3-0.4 parts antioxidant and 0.2-0.3 parts ultraviolet absorber.

[0020] Preferably, the modified wood flour comprises 20 to 34 parts; melamine formaldehyde resin comprises 15 to 27 parts; polyvinyl chloride comprises 28 to 39 parts; dichlorovinyl resin comprises 7 to 9 parts; crosslinking agent comprises 0.8 to 1.2 parts; plasticizer comprises 4 to 5 parts; heat stabilizer comprises 0.5 to 1.4 parts; coupling agent comprises 1 to 3 parts; antioxidant comprises 0.3 to 0.4 parts; and ultraviolet absorber comprises 0.2 to 0.4 parts.

[0021] Preferably, the modified wood flour comprises 20-33 parts, melamine formaldehyde resin comprises 15-26 parts, polyvinyl chloride comprises 28-38 parts, dichlorovinyl resin comprises 7-9 parts, cross-linking agent comprises 0.8-1.3 parts, plasticizer comprises 4-5 parts, heat stabilizer comprises 0.5-1.4 parts, coupling agent comprises 1-3 parts, antioxidant comprises 0.3-0.4 parts, and ultraviolet absorber comprises 0.2-0.4 parts.

[0022] Preferably, the modified wood flour comprises 20-33 parts, melamine formaldehyde resin comprises 15-26 parts, polyvinyl chloride comprises 28-38 parts, dichlorovinyl resin comprises 7-9 parts, cross-linking agent comprises 0.8-1.3 parts, plasticizer comprises 4-5 parts, heat stabilizer comprises 0.5-1.4 parts, coupling agent comprises 1-3 parts, antioxidant comprises 0.3-0.4 parts, and ultraviolet absorber comprises 0.2-0.4 parts.

[0023] Preferably, the modified wood flour comprises 20-32 parts, 15-26 parts of melamine formaldehyde resin, 28-37 parts of polyvinyl chloride, 7-9 parts of dichlorovinyl resin, 0.8-1.3 parts of crosslinking agent, 4-5 parts of plasticizer, 0.5-1.4 parts of heat stabilizer, 1-3 parts of coupling agent, 0.3-0.4 parts of antioxidant, and 0.2-0.4 parts of ultraviolet absorber.

[0024] Preferably, the modified wood flour comprises 20-31 parts, 15-25 parts of melamine formaldehyde resin, 28-38 parts of polyvinyl chloride, 7-9 parts of dichlorovinyl resin, 0.8-1.3 parts of crosslinking agent, 4-5 parts of plasticizer, 0.5-1.4 parts of heat stabilizer, 1-3 parts of coupling agent, 0.3-0.4 parts of antioxidant, and 0.2-0.4 parts of ultraviolet absorber.

[0025] Preferably, the modified wood flour comprises 20 to 30 parts; melamine formaldehyde resin comprises 15 to 26 parts; polyvinyl chloride comprises 28 to 37 parts; dichlorovinyl resin comprises 7 to 9 parts; crosslinking agent comprises 0.8 to 1.3 parts; plasticizer comprises 4 to 5 parts; heat stabilizer comprises 0.5 to 1.5 parts; coupling agent comprises 1 to 3 parts; antioxidant comprises 0.3 to 0.4 parts; and ultraviolet absorber comprises 0.2 to 0.4 parts.

[0026] Preferably, the modified wood flour comprises 20-29 parts; melamine formaldehyde resin comprises 15-25 parts; polyvinyl chloride comprises 28-36 parts; dichlorovinyl resin comprises 7-9 parts; crosslinking agent comprises 0.8-1.3 parts; plasticizer comprises 4-5 parts; heat stabilizer comprises 0.5-1.4 parts; coupling agent comprises 1-3 parts; antioxidant comprises 0.3-0.4 parts; and ultraviolet absorber comprises 0.2-0.4 parts.

[0027] Preferably, the modified wood flour comprises 20-28 parts, melamine formaldehyde resin comprises 15-24 parts, polyvinyl chloride comprises 28-35 parts, dichlorovinyl resin comprises 7-9 parts, crosslinking agent comprises 0.8-1.3 parts, plasticizer comprises 4-5 parts, heat stabilizer comprises 0.5-1.4 parts, coupling agent comprises 1-3 parts, antioxidant comprises 0.3-0.4 parts, and ultraviolet absorber comprises 0.2-0.4 parts.

[0028] Preferably, the modified wood flour comprises 20-27 parts, melamine formaldehyde resin comprises 15-23 parts, polyvinyl chloride comprises 28-34 parts, dichlorovinyl resin comprises 7-9 parts, cross-linking agent comprises 0.8-1.3 parts, plasticizer comprises 4-5 parts, heat stabilizer comprises 0.5-1.4 parts, coupling agent comprises 1-3 parts, antioxidant comprises 0.3-0.4 parts, and ultraviolet absorber comprises 0.2-0.4 parts.

[0029] Preferably, the modified wood flour comprises 20-26 parts; melamine formaldehyde resin comprises 15-22 parts; polyvinyl chloride comprises 28-33 parts; dichlorovinyl resin comprises 7-9 parts; crosslinking agent comprises 0.8-1.3 parts; plasticizer comprises 4-5 parts; heat stabilizer comprises 0.5-1.4 parts; coupling agent comprises 1-3 parts; antioxidant comprises 0.3-0.4 parts; and ultraviolet absorber comprises 0.2-0.4 parts.

[0030] Preferably, the modified wood flour comprises 20-25 parts, melamine formaldehyde resin comprises 15-21 parts, polyvinyl chloride comprises 28-32 parts, dichlorovinyl resin comprises 7-9 parts, cross-linking agent comprises 0.8-1.2 parts, plasticizer comprises 4-5 parts, heat stabilizer comprises 0.5-1.4 parts, coupling agent comprises 1-3 parts, antioxidant comprises 0.3-0.4 parts, and ultraviolet absorber comprises 0.2-0.4 parts.

[0031] Preferably, the modified wood flour is 20-24, the melamine formaldehyde resin is 15-20, the polyvinyl chloride is 28-31, the dichlorovinyl resin is 7-9, the crosslinking agent is 0.8-1.2, the plasticizer is 4-5, the heat stabilizer is 0.5-1.4, the coupling agent is 1-3, the antioxidant is 0.3-0.4, and the ultraviolet absorber is 0.2-0.4.

[0032] Preferably, the modified wood flour comprises 20-23 parts, melamine formaldehyde resin 15-20 parts, polyvinyl chloride 28-30 parts, dichlorovinyl resin 7-9 parts, crosslinking agent 0.8-1.2 parts, plasticizer 4-5 parts, heat stabilizer 0.5-1.4 parts, coupling agent 1-3 parts, antioxidant 0.3-0.4 parts, and ultraviolet absorber 0.2-0.4 parts.

[0033] Preferably, the weight proportions of the main raw materials are as follows: 22-33 parts of modified wood flour; 16-26 parts of melamine formaldehyde resin; 30-38 parts of polyvinyl chloride; 6-9 parts of dichlorovinyl resin; 0.8-1.2 parts of crosslinking agent; 3-5 parts of plasticizer; 0.5-1.2 parts of heat stabilizer; 1-2.5 parts of coupling agent; 0.3-0.4 parts of antioxidant; and 0.2-0.4 parts of ultraviolet absorber.

[0034] Preferably, the weight proportions of the main raw materials are as follows: 23-32 parts of modified wood flour; 17-25 parts of melamine formaldehyde resin; 31-37 parts of polyvinyl chloride; 6-9 parts of dichlorovinyl resin; 0.8-1.2 parts of crosslinking agent; 3-5 parts of plasticizer; 0.5-1.2 parts of heat stabilizer; 1-2.5 parts of coupling agent; 0.3-0.4 parts of antioxidant; and 0.2-0.4 parts of ultraviolet absorber.

[0035] Preferably, the weight proportions of the main raw materials are as follows: 24-31 parts of modified wood flour; 18-24 parts of melamine formaldehyde resin; 32-36 parts of polyvinyl chloride; 6-9 parts of dichlorovinyl resin; 0.8-1.2 parts of crosslinking agent; 3-5 parts of plasticizer; 0.5-1.2 parts of heat stabilizer; 1-2.5 parts of coupling agent; 0.3-0.4 parts of antioxidant; and 0.2-0.4 parts of ultraviolet absorber.

[0036] Preferably, the weight proportions of the main raw materials are as follows: 25-30 parts of modified wood flour; 19-23 parts of melamine formaldehyde resin; 33-35 parts of polyvinyl chloride; 6-9 parts of dichlorovinyl resin; 0.8-1.2 parts of crosslinking agent; 3-5 parts of plasticizer; 0.5-1.2 parts of heat stabilizer; 1-2.5 parts of coupling agent; 0.3-0.4 parts of antioxidant; and 0.2-0.4 parts of ultraviolet absorber.

[0037] Preferably, the weight proportions of the main raw materials are as follows: 26-29 parts of modified wood flour; 20-22 parts of melamine formaldehyde resin; 33-35 parts of polyvinyl chloride; 6-9 parts of dichlorovinyl resin; 0.8-1.2 parts of crosslinking agent; 3-5 parts of plasticizer; 0.5-1.2 parts of heat stabilizer; 1-2.5 parts of coupling agent; 0.3-0.4 parts of antioxidant; and 0.2-0.4 parts of ultraviolet absorber.

[0038] Preferably, the modified wood flour comprises 23 to 31 parts, melamine formaldehyde resin comprises 17 to 25 parts, polyvinyl chloride comprises 31 to 37 parts, dichlorovinyl resin comprises 6 to 8 parts, cross-linking agent comprises 0.8 to 1.2 parts, plasticizer comprises 3 to 4.5 parts, heat stabilizer comprises 0.5 to 1.0 parts, coupling agent comprises 1 to 2.3 parts, antioxidant comprises 0.3 to 0.4 parts, and ultraviolet absorber comprises 0.2 to 0.4 parts.

[0039] Preferably, modified wood flour 24; melamine formaldehyde resin 22; polyvinyl chloride 34; dichlorovinyl resin 7; crosslinking agent 1.0; plasticizer 4; heat stabilizer 0.8; coupling agent 1.8; antioxidant 0.35; ultraviolet absorber 0.3.

[0040] Preferably, modified wood flour 22; melamine formaldehyde resin 24; polyvinyl chloride 32; dichlorovinyl resin 8; crosslinking agent 1.1; plasticizer 3.5; heat stabilizer 0.8; coupling agent 1.8; antioxidant 0.35; ultraviolet absorber 0.3.

[0041] The particle size of the modified wood flour is 80-100 mesh.

[0042] The melamine formaldehyde resin is in powder form and has a solid content greater than or equal to 99%.

[0043] The binary chloroacetic acid resin is polyvinyl chloride-vinyl acetate, model CP-710.

[0044] The plasticizer is selected from at least one of dioctyl phthalate and dibutyl phthalate;

[0045] The crosslinking agent is a mixture of vinyl triethoxysilane and dibenzoyl peroxide, and the mass ratio of vinyl triethoxysilane to dibenzoyl peroxide is 20 to 25:1.

[0046] Preferably, the heat stabilizer is a calcium-zinc composite heat stabilizer;

[0047] Preferably, the polyvinyl chloride is a standard polyvinyl chloride resin, brand S-1000;

[0048] Preferably, the coupling agent is selected from silane coupling agent KH550 or silane coupling agent KH570;

[0049] Preferably, the antioxidant is antioxidant 1010;

[0050] Preferably, the ultraviolet absorber is ultraviolet absorber UV-531.

[0051] The preparation steps of modified wood flour are as follows:

[0052] Sodium hydroxide is added to the formaldehyde solution to adjust the solution to alkaline, and then melamine is added. After stirring evenly, the temperature is increased, the temperature is kept for reaction, and then the temperature is lowered. Citric acid is added to adjust the material to acidic, and then wood powder is added. After stirring and mixing, the mixture is thoroughly mixed and then dried to obtain modified wood powder.

[0053] Preferably, a sodium hydroxide solution with a mass concentration of 40-60% is added to a formaldehyde solution with a mass concentration of 35-40% to adjust the pH to 8.5-9.5, then melamine is added, stirred evenly, and then the temperature is raised to 90-98° C. and kept warm for reaction for 1-3 hours, then cooled to room temperature, citric acid is added, the pH is adjusted to 3-4.5, and then wood powder is added, stirred and mixed for 1-2 hours, thoroughly mixed, and placed in a vacuum oven at 60-80° C. to fully dry until the volatile matter is less than 4%, thereby obtaining modified wood powder;

[0054] Preferably, a 50% sodium hydroxide solution is added to a 37% formaldehyde solution to adjust the pH to 9, and then melamine is added. After stirring evenly, the temperature is raised to 95° C. and kept warm for 2 hours. The temperature is then lowered to room temperature, citric acid is added to adjust the pH to 4, and then wood powder is added. The mixture is stirred for 1.5 hours, thoroughly mixed, and dried in a vacuum oven at 70° C. until the volatile matter is less than 4%, thereby obtaining modified wood powder.

[0055] Preferably, the molar ratio of melamine to formaldehyde is 1:2-4;

[0056] Preferably, the molar ratio of melamine to formaldehyde is 1:3;

[0057] Preferably, the mass ratio of melamine to wood powder is 0.1 to 0.3:1;

[0058] Preferably, the mass ratio of melamine to wood powder is 0.2:1.

[0059] The method for preparing the above-mentioned high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material comprises the following steps:

[0060] (1) polyvinyl chloride, a cross-linking agent, a plasticizer, and a heat stabilizer are thoroughly mixed at room temperature to obtain a first premix;

[0061] (2) adding the first premix to a parallel twin-screw extruder for extrusion and granulation to obtain composite cross-linked polyvinyl chloride pellets;

[0062] (3) fully mixing the composite cross-linked polyvinyl chloride pellets obtained in (2), the dichlorovinyl resin, the melamine formaldehyde resin, the modified wood flour, the coupling agent, the antioxidant, and the ultraviolet absorber, and then cooling the mixture to obtain a second premix;

[0063] (4) adding the second premix to a parallel twin-screw extruder for extrusion and granulation to obtain formed composite pellets;

[0064] (5) conveying the pellets obtained in (4) to a conical twin-screw plastic wood profile extruder for extrusion molding;

[0065] (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material.

[0066] The method for preparing the above-mentioned high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material comprises the following steps:

[0067] (1) polyvinyl chloride, a cross-linking agent, a plasticizer, and a heat stabilizer are thoroughly mixed at room temperature to obtain a first premix;

[0068] (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; the process conditions for extrusion granulation are: barrel temperature of 170-180° C., screw speed of 200-250 rpm;

[0069] (3) The composite cross-linked polyvinyl chloride pellets obtained in (2), dichlorovinyl resin, melamine formaldehyde resin, modified wood flour, coupling agent, antioxidant, and ultraviolet absorber are first fully mixed at 100-120° C., and then cooled to below 70° C. to obtain a second premix;

[0070] (4) adding the second premix to a parallel twin-screw extruder for extrusion granulation to obtain formed composite pellets, wherein the process conditions for extrusion granulation are: a barrel temperature of 180-200° C. and a screw speed of 250-300 rpm;

[0071] (5) conveying the pellets prepared in (4) to a conical twin-screw plastic wood profile extruder, and the extrusion process conditions are: barrel temperature of 190-210°C, screw speed of 5-15 rpm;

[0072] (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material;

[0073] Preferably, the method for preparing the above-mentioned high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material comprises the following steps:

[0074] (1) polyvinyl chloride, a cross-linking agent, a plasticizer, and a heat stabilizer are thoroughly mixed at room temperature to obtain a first premix;

[0075] (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; the extrusion granulation process conditions are: barrel temperature of 175° C., screw speed of 220 rpm;

[0076] (3) The composite cross-linked polyvinyl chloride pellets obtained in (2), dichlorovinyl resin, melamine formaldehyde resin, modified wood flour, coupling agent, antioxidant, and ultraviolet absorber are first fully mixed at 110° C., and then cooled to below 70° C. to obtain a second premix;

[0077] (4) adding the second premix to a parallel twin-screw extruder for extrusion granulation to obtain formed composite pellets. The extrusion granulation process conditions are: barrel temperature of 190° C., screw speed of 280 rpm;

[0078] (5) The pellets prepared in (4) were conveyed to a conical twin-screw plastic wood profile extruder. The extrusion process conditions were: barrel temperature of 200°C and screw speed of 10 rpm;

[0079] (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material.

[0080] The beneficial effects of the present invention are:

[0081] (1) Modified wood powder is used, and the modified wood powder has enhanced compatibility with melamine formaldehyde resin. The binary chloroacetic acid resin (polyvinyl chloride-vinyl acetate) has excellent bonding properties. The use of binary chloroacetic acid resin (polyvinyl chloride-vinyl acetate) can increase the compatibility of polyvinyl chloride, modified wood powder and melamine formaldehyde resin, play a bonding role, and has a significant effect on improving the strength and long-lasting flame resistance of the final product; polyvinyl chloride is cross-linked with the cross-linking agent during the molding process to form partially cross-linked polyvinyl chloride, which also further enhances the static bending strength and seawater resistance of the plastic wood composite material;

[0082] (2) The plastic-wood composite material has flame retardant properties, and the melamine formaldehyde resin is cross-linked and cured at high temperature to obtain a high cross-link density profile. The static bending strength and tensile strength of the product are greatly improved, and the flame retardancy is long-lasting. After being boiled in simulated seawater (3.5% sodium chloride solution) for 172 hours, the flame retardant performance will not be significantly reduced, and there is no obvious change on the surface. It is especially suitable for use in plank roads in seaside scenic areas;

[0083] (3) The preparation process of the product of the present invention is simple and easy to industrialize. DETAILED DESCRIPTION

[0084] In order to enable those skilled in the art to better understand the present invention, the present invention will be further explained in conjunction with specific embodiments.

[0085] The models and manufacturers of some raw materials in the present invention are as follows:

[0086] Melamine formaldehyde resin was in powder form with a solid content of 99% and was purchased from Shandong Wangsheng New Material Technology Co., Ltd.

[0087] Polyvinyl chloride is standard polyvinyl chloride resin, brand S-1000, purchased from Sinopec Qilu Branch;

[0088] Dichlorovinyl acetate resin (polyvinyl chloride-vinyl acetate), brand CP-710, was purchased from Hanwha Group, South Korea;

[0089] The plasticizer was dioctyl phthalate (DOP) or dibutyl phthalate (DBP), purchased from Shandong Kexing Chemical Co., Ltd.

[0090] The crosslinking agent is a mixture of vinyl triethoxysilane and dibenzoyl peroxide, and the mass ratio of vinyl triethoxysilane to dibenzoyl peroxide is 20 to 25:1.

[0091] The heat stabilizer was a calcium zinc composite heat stabilizer, brand G0102W, purchased from Jiangsu Aiteen Polymer Materials Co., Ltd.

[0092] The coupling agent is silane coupling agent KH550 or silane coupling agent KH570, purchased from Guangzhou Zhongjie Chemical Technology Co., Ltd.

[0093] Example 1

[0094] A method for preparing a high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material comprises the following steps:

[0095] (1) polyvinyl chloride, a cross-linking agent, a plasticizer, and a heat stabilizer are thoroughly mixed at room temperature to obtain a first premix;

[0096] The mass ratio of vinyltriethoxysilane to dibenzoyl peroxide is 22:1;

[0097] (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; the extrusion granulation process conditions are: barrel temperature of 175° C., screw speed of 220 rpm;

[0098] (3) The composite cross-linked polyvinyl chloride pellets obtained in (2), dichlorovinyl resin, melamine formaldehyde resin, modified wood flour, coupling agent, antioxidant, and ultraviolet absorber are first fully mixed at 110° C., and then cooled to below 70° C. to obtain a second premix;

[0099] (4) adding the second premix to a parallel twin-screw extruder for extrusion granulation to obtain formed composite pellets. The extrusion granulation process conditions are: barrel temperature of 190° C., screw speed of 280 rpm;

[0100] (5) The pellets prepared in (4) were conveyed to a conical twin-screw plastic wood profile extruder. The extrusion process conditions were: barrel temperature of 200°C and screw speed of 10 rpm;

[0101] (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material.

[0102] The preparation method of the modified wood flour is as follows:

[0103] A 50% sodium hydroxide solution is added to a 37% formaldehyde solution to adjust the pH to 9, and then melamine is added. After stirring evenly, the temperature is raised to 95°C and kept warm for reaction for 2 hours. The temperature is then lowered to room temperature, and citric acid is added to adjust the pH to 4. Then, wood powder is added, stirred and mixed for 1 to 2 hours, and thoroughly mixed. The mixture is placed in a vacuum oven at 70°C and dried until the volatile matter is less than 4% to obtain modified wood powder. The molar ratio of melamine to formaldehyde is 1:3, and the mass ratio of melamine to wood powder is 0.2:1.

[0104] The process parameters of Examples 2 to 3 are slightly different from those of Example 1, but the amounts of raw materials used are exactly the same, as follows:

[0105] Example 2

[0106] A method for preparing a high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material comprises the following steps:

[0107] (1) polyvinyl chloride, a cross-linking agent, a plasticizer, and a heat stabilizer are thoroughly mixed at room temperature to obtain a first premix;

[0108] (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; the extrusion granulation process conditions are: barrel temperature of 170° C., screw speed of 200 rpm;

[0109] (3) The composite cross-linked polyvinyl chloride pellets obtained in (2), dichlorovinyl resin, melamine formaldehyde resin, modified wood flour, coupling agent, antioxidant, and ultraviolet absorber are first fully mixed at 100° C., and then cooled to below 70° C. to obtain a second premix;

[0110] (4) adding the second premix to a parallel twin-screw extruder for extrusion granulation to obtain formed composite pellets. The extrusion granulation process conditions are: barrel temperature of 180° C., screw speed of 250 rpm;

[0111] (5) The pellets prepared in (4) were conveyed to a conical twin-screw plastic wood profile extruder. The extrusion process conditions were: barrel temperature of 190°C and screw speed of 5 rpm;

[0112] (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material.

[0113] The preparation method of the modified wood flour is the same as that in Example 1.

[0114] Example 3

[0115] A method for preparing a high-strength, long-lasting flame-retardant, seawater-corrosion-resistant plastic-wood composite material comprises the following steps:

[0116] (1) polyvinyl chloride, a cross-linking agent, a plasticizer, and a heat stabilizer are thoroughly mixed at room temperature to obtain a first premix;

[0117] (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; the extrusion granulation process conditions are: barrel temperature of 180° C., screw speed of 250 rpm;

[0118] (3) The composite cross-linked polyvinyl chloride pellets obtained in (2), dichlorovinyl resin, melamine formaldehyde resin, modified wood flour, coupling agent, antioxidant, and ultraviolet absorber are first fully mixed at 120° C., and then cooled to below 70° C. to obtain a second premix;

[0119] (4) adding the second premix to a parallel twin-screw extruder for extrusion granulation to obtain formed composite pellets. The process conditions for extrusion granulation are: barrel temperature of 200° C., screw speed of 300 rpm;

[0120] (5) The pellets prepared in (4) were conveyed to a conical twin-screw plastic wood profile extruder. The extrusion process conditions were: barrel temperature of 210°C, screw speed of 15 rpm;

[0121] (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material.

[0122] In Examples 4 to 8, the amounts of raw materials used are different from those in Example 1, as shown in Table 1 below:

[0123] Table 1 Dosage of products in each embodiment

[0124] Comparative Example 1

[0125] Other conditions were the same as in Example 1, except that ordinary wood flour was used instead of modified wood flour;

[0126] Comparative Example 2

[0127] Other conditions are the same as in Example 1, except that melamine formaldehyde resin is not used. The rest are the same as in Example 1;

[0128] Comparative Example 3

[0129] Other conditions are the same as in Example 1, except that binary vinyl chloride resin (polyvinyl chloride-vinyl acetate) is not used. The rest are the same as in Example 1;

[0130] Comparative Example 4

[0131] Commercially available outdoor plastic wood flooring, model 150S25-H, was purchased from Huangshan Huasu New Materials Co., Ltd.

[0132] Example 9

[0133] The product performance in each embodiment and comparative example was tested using the following method:

[0134] The static bending strength (three-point bend), tensile strength, and seawater corrosion resistance (3.5% sodium chloride) of the present invention were all tested in accordance with GB / T17657-2013, "Test Methods for Physical and Chemical Properties of Wood-Based Panels and Veneered Wood-Based Panels." The static bending strength (three-point bend) was tested according to Section 4.7, the tensile strength was tested according to Section 4.24, and the seawater corrosion resistance was tested according to Section 4.50, using 3.5% sodium chloride solution instead of ordinary tap water. The combustion grade of the flame retardant performance was tested in accordance with GB / T8624-2012, "Classification of Combustion Performance of Building Materials and Products."

[0135] Table 2 Performance comparison of the products in each embodiment and comparative example (before boiling seawater (3.5% sodium chloride solution))

[0136] Table 3 Performance comparison of the products in the examples and comparative examples (after boiling simulated seawater (3.5% sodium chloride solution) for 172 hours)

[0137] As can be seen from Tables 2 and 3 above, Examples 1-8 all exhibit excellent overall performance, including outstanding mechanical properties, excellent static flexural strength, and tensile strength. Furthermore, their flame retardancy is generally A1, indicating good flame retardancy. After being boiled in simulated seawater (3.5% sodium chloride) for 172 hours, the composite material's surface showed little noticeable change, and its static flexural strength and tensile strength showed no significant decrease. Flame retardancy was also largely maintained, demonstrating that the present invention exhibits excellent seawater corrosion resistance.

[0138] From the performance of the product in Comparative Example 1, it can be seen that after ordinary wood flour is used instead of modified wood flour, the compatibility of wood flour with the system becomes worse, resulting in a slight decrease in mechanical properties, especially after being boiled in simulated seawater (3.5% sodium chloride solution) for 172 hours, cracking occurs on the surface, and the mechanical properties also show a slight decline;

[0139] Comparative Example 2 lacks thermosetting melamine formaldehyde resin, resulting in the inability of the entire system to effectively cure, resulting in poor seawater corrosion resistance, and flame retardancy due to the mere effect of cross-linked polyvinyl chloride, which significantly deteriorates.

[0140] Comparative Example 3 lacks binary chloroacetic acid resin, which leads to poor compatibility of polyvinyl chloride with components such as modified wood flour and melamine formaldehyde resin, resulting in a decrease in performance after boiling in simulated seawater (3.5% sodium chloride solution) for 172 hours.

[0141] Comparative Example 4 is a conventional wood-plastic composite material, which has rather ordinary mechanical and flame retardant properties. After being boiled in simulated seawater (3.5% sodium chloride solution) for 172 hours, its properties deteriorated significantly.

Claims

1. High-strength, long-lasting flame retardant, seawater corrosion-resistant plastic-wood composite material, characterized in that: The wood-plastic composite material is mainly prepared from modified wood powder, melamine formaldehyde resin, polyvinyl chloride and dichlorovinyl resin.

2. The high-strength, durable flame-retardant, seawater corrosion-resistant plastic-wood composite material according to claim 1, characterized in that: The plastic-wood composite material further comprises at least one of a cross-linking agent, a plasticizer, a heat stabilizer, a coupling agent, an antioxidant, and an ultraviolet absorber; preferably, in the plastic-wood composite material, the weight proportions of the main raw materials are as follows: Modified wood flour 20-35; melamine formaldehyde resin 15-28; polyvinyl chloride 28-40; binary chloroacetic acid resin 5-10; Preferably, in the plastic-wood composite material, the cross-linking agent is 0.5-1.5; the plasticizer is 3-5; the heat stabilizer is 0.5-1.5; the coupling agent is 1-3; the antioxidant is 0.3-0.5; the ultraviolet absorber is 0.2-0.5; Preferably, in the plastic-wood composite material, the weight proportions of the main raw materials are as follows: 20-35 parts of modified wood flour; 15-28 parts of melamine formaldehyde resin; 28-40 parts of polyvinyl chloride; 5-10 parts of dichlorovinyl resin; 0.5-1.5 parts of cross-linking agent; 3-5 parts of plasticizer; 0.5-1.5 parts of heat stabilizer; 1-3 parts of coupling agent; 0.3-0.5 parts of antioxidant; and 0.2-0.5 parts of ultraviolet absorber.

3. The high-strength, durable flame-retardant, seawater-corrosion-resistant plastic-wood composite material according to claim 1, characterized in that: In the wood-plastic composite material, the weight proportions of the main raw materials are as follows: Modified wood flour 22-33; melamine formaldehyde resin 16-26; polyvinyl chloride 30-38; dichlorovinyl resin 6-9; cross-linking agent 0.8-1.5; plasticizer 3-5; heat stabilizer 0.5-1.2; coupling agent 1-2.5; antioxidant 0.3-0.4; ultraviolet absorber 0.2-0.

4.

4. The high-strength, durable flame-retardant, seawater-corrosion-resistant plastic-wood composite material according to claim 1, characterized in that: In the wood-plastic composite material, the weight proportions of the main raw materials are as follows: Modified wood flour 23-31; melamine formaldehyde resin 17-25; polyvinyl chloride 31-37; dichlorovinyl resin 6-8; cross-linking agent 1-1.5; plasticizer 3-4.5; heat stabilizer 0.5-1.0; coupling agent 1-2.3; antioxidant 0.3-0.4; ultraviolet absorber 0.2-0.

4.

5. The high-strength, durable flame-retardant, seawater corrosion-resistant plastic-wood composite material according to claim 2, characterized in that: The particle size of the modified wood powder is 80-100 meshes.

6. The high-strength, durable flame-retardant, seawater-corrosion-resistant plastic-wood composite material according to claim 2, characterized in that: The melamine formaldehyde resin is in powder form, and the solid content is greater than or equal to 99%; the binary chloroacetic acid resin is polyvinyl chloride-vinyl acetate, and the model is CP-710.

7. The high-strength, durable flame-retardant, seawater corrosion-resistant plastic-wood composite material according to claim 2, characterized in that: The plasticizer is selected from at least one of dioctyl phthalate and dibutyl phthalate; Preferably, the crosslinking agent is a mixture of vinyl triethoxysilane and dibenzoyl peroxide, and the mass ratio of vinyl triethoxysilane to dibenzoyl peroxide is 20 to 25:1; Preferably, the heat stabilizer is a calcium-zinc composite heat stabilizer; Preferably, the polyvinyl chloride is a standard polyvinyl chloride resin, grade S-1000; Preferably, the coupling agent is selected from silane coupling agent KH550 or silane coupling agent KH570; Preferably, the antioxidant is antioxidant 1010; Preferably, the ultraviolet absorber is ultraviolet absorber UV-531.

8. The high-strength, durable flame-retardant, seawater-corrosion-resistant plastic-wood composite material according to claim 2, characterized in that: The preparation steps of modified wood flour are as follows: Adding sodium hydroxide to the formaldehyde solution to adjust the solution to alkalinity, then adding melamine, stirring evenly, heating, keeping the temperature for reaction, then cooling, adding citric acid, adjusting the material to acidity, then adding wood powder, stirring and mixing, fully mixing and drying to obtain modified wood powder; Preferably, a sodium hydroxide solution with a mass concentration of 40 to 60% is added to a formaldehyde solution with a mass concentration of 35 to 40%, the pH is adjusted to 8.5 to 9.5, and then melamine is added, stirred evenly, and then heated to 90 to 98° C. and kept warm for 1 to 3 hours, and then cooled to room temperature. Add citric acid to adjust the pH to 3-4.5, then add wood powder, stir and mix for 1-2 hours, mix thoroughly and evenly, place in a vacuum oven at 60-80°C and fully dry until the volatile matter is less than 4%, to obtain modified wood powder; Preferably, a sodium hydroxide solution with a mass concentration of 50% is added to a formaldehyde solution with a mass concentration of 37%, the pH is adjusted to 9, and then melamine is added, stirred evenly, the temperature is raised to 95°C and kept warm for reaction for 2 hours, then the temperature is lowered to room temperature, citric acid is added, the pH is adjusted to 4, and then wood powder is added, stirred and mixed for 1.5 hours, fully mixed, and placed in a vacuum oven at 70°C to fully dry until the volatile matter is less than 4%, to obtain modified wood powder; Preferably, the molar ratio of melamine to formaldehyde is 1:2 to 4; Preferably, the molar ratio of melamine to formaldehyde is 1:3; Preferably, the mass ratio of melamine to wood powder is 0.1 to 0.3:1; Preferably, the mass ratio of melamine to wood powder is 0.2:

1.

9. The method for preparing the high-strength, durable flame-retardant, seawater-corrosion-resistant plastic-wood composite material according to claim 2 comprises the following steps: (1) polyvinyl chloride, a crosslinking agent, a plasticizer, and a thermal stabilizer are fully mixed at room temperature to obtain a first premix; (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; (3) fully mixing the composite cross-linked polyvinyl chloride pellets obtained in (2), the dichloroacetic acid resin, the melamine formaldehyde resin, the modified wood powder, the coupling agent, the antioxidant, and the ultraviolet absorber, and then cooling the mixture to obtain a second premix; (4) adding the second premix to a parallel twin-screw extruder for extrusion and granulation to obtain a formed composite granule; (5) conveying the pellets obtained in (4) to a conical twin-screw plastic wood profile extruder for extrusion molding; (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material.

10. The method for preparing the high-strength, durable flame-retardant, seawater-corrosion-resistant plastic-wood composite material according to claim 2, comprising the following steps: (1) polyvinyl chloride, a crosslinking agent, a plasticizer, and a thermal stabilizer are fully mixed at room temperature to obtain a first premix; (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; the process conditions for extrusion granulation are: a barrel temperature of 170 to 180° C. and a screw speed of 300 to 350 rpm; (3) The composite cross-linked polyvinyl chloride pellets obtained in (2), the dichlorovinyl resin, the melamine formaldehyde resin, the modified wood powder, the coupling agent, the antioxidant, and the ultraviolet absorber are first mixed thoroughly at 100 to 120° C., and then cooled to below 70° C. to obtain a second premix; (4) adding the second premix to a parallel twin-screw extruder for extrusion granulation to obtain a shaped composite granule, wherein the process conditions for the extrusion granulation are: a barrel temperature of 180 to 200° C. and a screw speed of 250 to 300 rpm; (5) conveying the pellets prepared in (4) to a conical twin-screw plastic wood profile extruder, and the extrusion process conditions are: a barrel temperature of 190 to 210° C. and a screw speed of 5 to 15 rpm; (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material; Preferably, (1) polyvinyl chloride, a crosslinking agent, a plasticizer, and a thermal stabilizer are first fully mixed at room temperature to obtain a first premix; (2) adding the first premix to a parallel twin-screw extruder for extrusion granulation to obtain composite cross-linked polyvinyl chloride pellets; The process conditions for extrusion granulation were: barrel temperature 175 °C, screw speed 320 rpm; (3) The composite cross-linked polyvinyl chloride pellets obtained in (2), the dichlorovinyl resin, the melamine formaldehyde resin, the modified wood powder, the coupling agent, the antioxidant, and the ultraviolet absorber are first mixed thoroughly at 110° C., and then cooled to below 70° C. to obtain a second premix; (4) Adding the second premix to a parallel twin-screw extruder for extrusion granulation to obtain a composite granule. The process conditions for extrusion granulation are: barrel temperature of 190°C, screw speed of 280 rpm; (5) conveying the pellets prepared in (4) to a conical twin-screw plastic wood profile extruder, and the extrusion process conditions are: barrel temperature of 200° C., screw speed of 10 rpm; (6) The extruded profile is cooled, shaped, and cut to a fixed length to obtain a finished plastic-wood composite material.

Images