A wood-plastic composite board and its preparation method and application

Abstract

The present application relates to the field of composite material technology, and specifically to a wood-plastic composite board and its preparation method and application. The wood-plastic composite board of the present application has a symmetrical structure of 5 layers, which are, in order, a first flame-retardant layer, a second flame-retardant layer, a core layer, a second flame-retardant layer, and a first flame-retardant layer. The layers are bonded together by an adhesive. The preparation method of the composite flame retardant of the first flame-retardant layer is to first immerse the attapulgite in an alcohol-alkali solution for hydroxyl modification, then add it to a chitosan solution for amino modification, and finally add it to a phosphoric acid solution to obtain a phosphorus-containing nano flame retardant. The composite flame retardant of the present application can release phosphoric acid during combustion, reduce the temperature and oxygen concentration on the surface of the combustible material, thereby achieving the purpose of flame retardancy. At the same time, the attapulgite contained in the composite flame retardant of the present application itself has excellent flame retardant properties, which can achieve a synergistic flame retardant effect with the phosphoric acid released during combustion.

Description

Technical Field

[0001] The present application relates to the technical field of composite materials, and in particular to a wood-plastic composite board and a preparation method and application thereof. Background Art

[0002] Wood-plastic composite (WPC), also known as WPC, has emerged in North America since the 1990s. It uses plastics such as polyethylene, polypropylene, and polyvinyl chloride to replace traditional resin adhesives, and mixes them with more than 50% waste plant fibers such as wood powder, rice husks, and straw to form a new wood material. This material can be processed into various boards or profiles through plastic processing techniques such as extrusion, molding, and injection molding for interior decoration, such as interior door panels. Compared with traditional fiberboard, particleboard, and plywood, WPC composite door panels are more processable and avoid the use of formaldehyde-containing adhesives that affect people's health. Therefore, they are becoming more and more popular. However, some problems have gradually been discovered in the process of using WPC composites, such as the poor flame retardancy of WPC composite panels.

[0003] The most common method for flame-retardant wood-plastic composites is to add flame retardants. This is because adding flame retardants to wood-plastic composites is the main method to improve the flame retardant properties of wood-plastic composites. Flame retardants can be divided into two categories: inorganic flame retardants and organic flame retardants. Inorganic flame retardants, such as aluminum hydroxide and magnesium hydroxide, have the advantages of high thermal stability, non-toxicity and pollution-free; organic flame retardants, such as phosphorus-based flame retardants and nitrogen-based flame retardants, can improve flame retardant properties by capturing free radicals and lowering combustion temperatures. In addition, the formula of the wood-plastic composite can be adjusted, the surface of the wood-plastic composite can be flame-retardant treated, or reasonable structural design can be adopted, such as increasing the thickness of the material and setting up fire isolation zones.

[0004] With the rise of nanomaterials, many researchers have begun studying their use as flame retardants. This is because nano-flame retardants typically possess excellent thermal and chemical stability, maintaining their integrity under high temperatures or flames, thereby slowing or preventing the spread of fire. Currently, nano-flame retardants are widely used in construction, transportation, electronics, textiles, and other fields, playing a vital role in improving the flame retardancy of materials and protecting people's lives and property.

[0005] Chinese patent publication number CN105566755B discloses a flame-retardant wood-plastic composite material with a synchronously co-extruded surface and core layer, and its manufacturing method. The flame-retardant wood-plastic composite material has a surface-core structure, with the surface layer made from polyolefin plastic, wood fiber, a nano-flame retardant, a lubricant, and a coupling agent, while the core layer is made from polyolefin plastic, wood fiber, nanocrystalline cellulose / ammonium polyphosphate colloid, a lubricant, and a coupling agent. The resulting flame-retardant wood-plastic composite material exhibits high flame retardancy and mechanical strength. However, the nanocrystalline cellulose / ammonium polyphosphate colloid, which has excellent flame retardancy, is placed in the core layer, potentially causing a delay in flame retardancy during the flame retardancy process. Chinese patent publication number CN103194075A discloses an inorganic nano-flame-retardant wood-plastic composite material and its preparation method. The application uses a nano-scale halogen-free environmentally friendly flame retardant and simply mechanically mixes components such as plastic, wood fiber, coupling agent, flame retardant, smoke suppressant, lubricant, and antioxidant. Although it has a certain flame retardant effect, the nano-scale halogen-free environmentally friendly flame retardant in the application is an inorganic substance such as aluminum hydroxide or magnesium hydroxide. These substances have poor compatibility with wood fiber and plastic, resulting in uneven dispersion and loose bonding of the flame retardant in the wood-plastic composite material, which may affect the mechanical strength or flame retardant effect of the wood-plastic composite material.

[0006] In summary, improving the flame retardant properties of wood-plastic composite materials can not only avoid some unnecessary economic losses, but also broaden the application fields of wood-plastic composite materials and have good prospects. In view of the problems that the current nano-composite flame retardant layer may have poor flame retardant effect due to unreasonable layer structure or loose combination of inorganic nano-flame retardant and wood-plastic material, this application proposes a wood-plastic composite board and its preparation method and application. Summary of the Invention

[0007] In view of the problems in the background technology of poor flame retardant effect caused by unreasonable layer structure or loose combination of inorganic nano flame retardant and wood-plastic material, this application proposes a wood-plastic composite board and its preparation method and application.

[0008] The technical solution of this application:

[0009] On the one hand, the present application provides a wood-plastic composite board,

[0010] The wood-plastic composite board has a symmetrical structure of five layers, which are, in order, a first flame retardant layer, a second flame retardant layer, a core layer, a second flame retardant layer and a first flame retardant layer, wherein the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer are bonded together by an adhesive;

[0011] The first flame retardant layer comprises the following raw materials by weight: 50-58 wt% wood flour, 10-14 wt% composite flame retardant, 27-34 wt% high-density polyethylene, 1-3 wt% lubricant, and 1-2 wt% antioxidant;

[0012] The core layer is of a corrugated type and comprises the following raw materials by weight: 50-58 wt% wood flour, 27-34 wt% high-density polyethylene, 10-14 wt% attapulgite, 1-3 wt% lubricant, and 1-2 wt% antioxidant;

[0013] The second flame retardant layer includes the following raw materials by weight: 50-58 wt% of wood flour, 27-34 wt% of high-density polyethylene, 2 wt% of nanocellulose, 8-12 wt% of attapulgite, 1-3 wt% of lubricant, and 1-2 wt% of antioxidant.

[0014] In a specific embodiment, the preparation method of the composite flame retardant is:

[0015] S1. The alkaline solution and the alcohol solution were ultrasonically dispersed for 30 to 40 minutes to obtain an alcohol-alkali solution, and then the attapulgite was added and ultrasonically dispersed for 30 to 40 minutes, and magnetically stirred for 3 to 5 hours to obtain a mixed solution A;

[0016] S2. The mixed solution A obtained in S1 was separated into solid and liquid, and the solid was dried to obtain a hydroxyl-modified attapulgite;

[0017] S3. The hydroxyl-modified attapulgite obtained in S2 was dispersed into the chitosan solution, ultrasonically dispersed for 30 to 40 minutes, and magnetically stirred for 3 to 5 hours to obtain a mixed solution B;

[0018] S4. The mixed solution B obtained in S3 was separated into solid and liquid, and the solid was dried to obtain an amino-modified attapulgite;

[0019] S5. The amino-modified attapulgite obtained in S4 is mixed with a phosphoric acid solution, stirred at 30-60° C. for 0.5-2 h to obtain a mixed solution C, the mixed solution C is separated into a solid and a liquid, and the solid is dried to obtain a composite flame retardant.

[0020] In a specific embodiment, the alkaline solution in S1 is sodium hydroxide or potassium hydroxide, with a concentration of 2 to 3 mol / L; the alcohol solution is any one of ethanol, ethylene glycol, propanol or isopropanol; the mass ratio of the alkaline solution to the alcohol solution is 1:(50 to 100); the mass ratio of the attapulgite in S1 to the alcohol-alkali solution is 1:(20 to 30).

[0021] In a specific embodiment, the mass fraction of the chitosan solution in S3 is 40-50%; the mass ratio of the hydroxyl-modified attapulgite to the chitosan solution is 1:(20-30).

[0022] In a specific embodiment, the mass fraction of the phosphoric acid solution in S5 is 35% to 40%; and the mass ratio of the amino-modified attapulgite to the phosphoric acid solution is 1:(20 to 30).

[0023] In a specific embodiment, the thickness ratio of the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer is 2:2:1:2:2.

[0024] In a specific embodiment, the attapulgite is calcined at 300-350° C. for 2-3 hours.

[0025] In a specific embodiment, the lubricant is sodium stearate, and the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecanol.

[0026] In a second aspect, the present application provides a method for preparing a wood-plastic composite board, comprising the following steps:

[0027] Step 1: Mix wood flour, composite flame retardant, high-density polyethylene, lubricant and antioxidant in proportion by mass, and then feed into a twin-screw extruder for melt extrusion to obtain a first flame retardant layer for later use;

[0028] Step 2: Mix wood flour, high-density polyethylene, nanocellulose, attapulgite, lubricant and antioxidant in percentage by mass and then feed into a twin-screw extruder for melt extrusion to obtain a second flame retardant layer for later use;

[0029] Step 3: Mix wood flour, high-density polyethylene, attapulgite, lubricant and antioxidant in proportion to mass percentage, and then feed into a press for melt extrusion to obtain a core layer for later use;

[0030] Step 4: Bonding the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer with an adhesive to obtain a wood-plastic composite board.

[0031] In a third aspect, the present application provides an application of a wood-plastic composite board for interior door panels.

[0032] Beneficial effects of this application:

[0033] (1) In the present application, the attapulgite is first modified with an alcohol-base solution to obtain a hydroxyl-modified attapulgite, which is then added to a chitosan solution to obtain an amino-modified attapulgite, and finally added to a phosphoric acid solution to obtain the composite flame retardant required by the present application. In the present application, the phosphorus-containing substance is attached to the surface of the attapulgite by chemical action to form a phosphorus-containing nano flame retardant, which can release phosphoric acid during the combustion process, reduce the temperature and oxygen concentration on the surface of the combustible material, and thus achieve the purpose of flame retardancy. At the same time, the attapulgite contained in the composite flame retardant of the present application itself has excellent flame retardant properties, which can achieve a synergistic flame retardant effect with the phosphoric acid released during the combustion process. On the other hand, the attapulgite of the present application is modified with hydroxyl and amino groups, which increases the compatibility and dispersibility of the attapulgite in the wood-plastic composite material, further improving the flame retardant effect.

[0034] (2) The attapulgite in the second flame retardant layer and the core layer of the present application is activated by calcination, and the attapulgite loses adsorbed water, zeolite water, and part of the crystal water and structural water, and can be transformed into a porous haystack-like structure, thereby increasing the porosity and specific surface area, and improving the dispersibility and adsorption. On the one hand, the compatibility in the wood-plastic composite material is improved, and the mechanical strength of the material is further improved. On the other hand, the attapulgite in the second flame retardant layer and the core layer can cooperate with the composite flame retardant of the first flame retardant layer to achieve a flame retardant effect.

[0035] (3) The core layer of the present application is processed into a corrugated type, and the layer thickness ratio of the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer is controlled to be 2:2:1:2:2. The corrugated type of the core layer and the second flame retardant layer form a hollow structure, which can not only achieve a flame retardant effect in physical space, but also achieve a sound insulation effect. At the same time, the thickness of the corrugated layer is small, which avoids affecting the mechanical properties of the wood-plastic composite board.

[0036] (4) The wood-plastic composite board of the present application has a symmetrical structure of 5 layers, which are arranged in the order of the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer. The layers work together to achieve a common flame retardant effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the structure of the wood-plastic composite panel in this application;

[0038] Reference numerals: 1, first flame retardant layer; 2, second flame retardant layer; 3, core layer; 4, second flame retardant layer; 5, first flame retardant layer. DETAILED DESCRIPTION

[0039] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0040] Example 1

[0041] S1. A 3 mol / L sodium hydroxide solution and an ethanol solution were ultrasonically dispersed at a mass ratio of 1:75 for 25 min to obtain an alcohol-base solution, followed by ultrasonic dispersion of attapulgite for 35 min, controlling the mass ratio of attapulgite to the alcohol-base solution to be 1:25, and magnetically stirred for 4 h to obtain a mixed solution A;

[0042] S2. The mixed solution A obtained in S1 was centrifuged at a speed of 300 r / min for 5 min for solid-liquid separation, the upper liquid was removed, and the solid was taken out and dried in a blast drying oven at 110 ° C for 12 h, and then ground through a 300 mesh sieve to obtain a hydroxyl-modified attapulgite;

[0043] S3. The hydroxyl-modified attapulgite obtained in S2 was mixed with a 45% chitosan solution in a mass ratio of 1:25, and then ultrasonically dispersed for 35 min and magnetically stirred for 4 h to obtain a mixed solution B;

[0044] S4. The mixed solution B obtained in S3 was separated into solid and liquid, and the solid was separated by centrifugation at a speed of 300 r / min for 5 min. The upper liquid was removed, and the solid was removed and placed in a blast drying oven at 110 ° C for 12 h, and then ground through a 300 mesh sieve to obtain an amino-modified attapulgite;

[0045] S5. The amino-modified attapulgite obtained in S4 was mixed with a 37% by mass phosphoric acid solution in a mass ratio of 1:25. The mixture was stirred at 45°C for 1.5 hours to obtain a mixed solution C. The mixed solution C was centrifuged at 300 r / min for 5 minutes for solid-liquid separation. The upper liquid was removed, and the solid was taken out and dried in a forced air drying oven at 110°C for 12 hours. The solid was then ground through a 300-mesh sieve to obtain a composite flame retardant.

[0046] Example 2

[0047] S1. A 3 mol / L potassium hydroxide solution and an ethylene glycol solution were ultrasonically dispersed for 40 min in a mass ratio of 1:50 to obtain an alcohol-base solution, followed by ultrasonic dispersion of attapulgite for 30 min, controlling the mass ratio of attapulgite to the alcohol-base solution to be 1:20, and magnetically stirred for 5 h to obtain a mixed solution A;

[0048] S2. The mixed solution A obtained in S1 was centrifuged at a speed of 300 r / min for 5 min for solid-liquid separation, the upper liquid was removed, and the solid was taken out and dried in a blast drying oven at 110 ° C for 12 h, and then ground through a 300 mesh sieve to obtain a hydroxyl-modified attapulgite;

[0049] S3. The hydroxyl-modified attapulgite obtained in S2 was mixed with a 40% chitosan solution in a mass ratio of 1:30, and then ultrasonically dispersed for 40 min and magnetically stirred for 3 h to obtain a mixed solution B;

[0050] S4. The mixed solution B obtained in S3 was separated into solid and liquid, and the solid was separated by centrifugation at a speed of 300 r / min for 5 min. The upper liquid was removed, and the solid was removed and placed in a blast drying oven at 110 ° C for 12 h, and then ground through a 300 mesh sieve to obtain an amino-modified attapulgite;

[0051] S5. The amino-modified attapulgite obtained in S4 was mixed with a 40% by mass phosphoric acid solution in a mass ratio of 1:20. The mixture was stirred at 60°C for 0.5 h to obtain a mixed solution C. The mixed solution C was centrifuged at 300 r / min for 5 min for solid-liquid separation. The upper liquid was removed, and the solid was taken out and dried in a forced air drying oven at 110°C for 12 h. It was then ground and passed through a 300-mesh sieve to obtain a composite flame retardant.

[0052] Example 3

[0053] S1. A 3 mol / L sodium hydroxide solution and a propanol solution were ultrasonically dispersed at a mass ratio of 1:100 for 30 min to obtain an alcohol-base solution, followed by ultrasonic dispersion of attapulgite for 40 min, controlling the mass ratio of attapulgite to the alcohol-base solution to be 1:30, and magnetically stirred for 3 h to obtain a mixed solution A;

[0054] S2. The mixed solution A obtained in S1 was centrifuged at a speed of 300 r / min for 5 min for solid-liquid separation, the upper liquid was removed, and the solid was taken out and dried in a blast drying oven at 110 ° C for 12 h, and then ground through a 300 mesh sieve to obtain a hydroxyl-modified attapulgite;

[0055] S3. The hydroxyl-modified attapulgite obtained in S2 was mixed with a 50% chitosan solution in a mass ratio of 1:20, and then ultrasonically dispersed for 30 min and magnetically stirred for 5 h to obtain a mixed solution B;

[0056] S4. The mixed solution B obtained in S3 was separated into solid and liquid, and the solid was separated by centrifugation at a speed of 300 r / min for 5 min. The upper liquid was removed, and the solid was removed and placed in a blast drying oven at 110 ° C for 12 h, and then ground through a 300 mesh sieve to obtain an amino-modified attapulgite;

[0057] S5. The amino-modified attapulgite obtained in S4 was mixed with a 35% by mass phosphoric acid solution in a mass ratio of 1:30. The mixture was stirred at 30°C for 2 h to obtain a mixed solution C. The mixed solution C was centrifuged at 300 r / min for 5 min for solid-liquid separation. The upper liquid was removed, and the solid was taken out and dried in a forced air drying oven at 110°C for 12 h. It was then ground and passed through a 300-mesh sieve to obtain a composite flame retardant.

[0058] Comparative Example 1

[0059] The main difference between this comparative example and Example 1 is that the attapulgite in this comparative example is not subjected to hydroxyl modification treatment and amino modification treatment, and is directly mixed with the phosphoric acid solution.

[0060] Example 4

[0061] This embodiment provides a method for preparing a wood-plastic composite board, which is as follows:

[0062] Step 1: 55 wt% of wood flour, 10 wt% of the composite flame retardant prepared in Example 1, 30 wt% of high-density polyethylene, 3 wt% of a lubricant, and 2 wt% of an antioxidant were mixed, and an SJSZ-65 conical twin-screw extruder was used to control the head temperature at 180° C., the body temperature at 155° C., and the mold temperature at 165° C. to obtain a first flame retardant layer for later use;

[0063] Step 2: 55wt% wood flour, 30wt% high-density polyethylene, 2wt% nanocellulose, 8wt% attapulgite, 3wt% lubricant and 2wt% antioxidant are mixed, and an SJSZ-65 conical twin-screw extruder is used to control the head temperature at 180°C, the body temperature at 155°C, and the mold temperature at 165°C to obtain a second flame retardant layer for standby use;

[0064] Step 3: First, calcine the convex rods at 325°C in a muffle furnace for 2.5 hours, then mix 55wt% wood powder, 30wt% high-density polyethylene, 10wt% convex rods, 3wt% lubricant and 2wt% antioxidant, and use a SJSZ-65-conical twin-screw extruder to control the head temperature at 180°C, the body temperature at 155°C, and the mold temperature at 165°C to obtain the core layer for use, wherein the distance between two adjacent corrugated peaks or corrugated valleys is controlled to be 15mm.

[0065] Step 4: Use MDI adhesive to glue the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer in sequence, with an adhesive amount of 150g / m 2 , the cold pressing pressure is 0.5 MPa, and the wood-plastic composite board of the present application is obtained.

[0066] Example 5

[0067] This embodiment provides a method for preparing a wood-plastic composite board, which is as follows:

[0068] Step 1: 58 wt% of wood flour, 12 wt% of the composite flame retardant prepared in Example 2, 27 wt% of high-density polyethylene, 2 wt% of a lubricant, and 1 wt% of an antioxidant were mixed, and an SJSZ-65 conical twin-screw extruder was used to control the head temperature at 180° C., the body temperature at 155° C., and the mold temperature at 165° C. to obtain a first flame retardant layer for later use;

[0069] Step 2: 58 wt% wood flour, 27 wt% high-density polyethylene, 2 wt% nanocellulose, 10 wt% attapulgite, 2 wt% lubricant and 1 wt% antioxidant are mixed, and an SJSZ-65 conical twin-screw extruder is used to control the head temperature at 180° C., the body temperature at 155° C., and the mold temperature at 165° C. to obtain a second flame retardant layer for standby use;

[0070] Step 3: First, calcine the convexograph at 350°C in a muffle furnace for 2h, then mix 58wt% wood powder, 27wt% high-density polyethylene, 12wt% convexograph, 2wt% lubricant and 1wt% antioxidant, and use a SJSZ-65-conical twin-screw extruder to control the head temperature at 180°C, the body temperature at 155°C, and the mold temperature at 165°C to obtain the core layer for use, wherein the distance between two adjacent corrugated peaks or corrugated valleys is controlled to be 15mm.

[0071] Step 4: Use MDI adhesive to glue the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer in sequence, with an adhesive amount of 150g / m 2 , the cold pressing pressure is 0.5 MPa, and the wood-plastic composite board of the present application is obtained.

[0072] Example 6

[0073] This embodiment provides a method for preparing a wood-plastic composite board, which is as follows:

[0074] Step 1: 50 wt% of wood flour, 14 wt% of the composite flame retardant prepared in Example 3, 34 wt% of high-density polyethylene, 1 wt% of a lubricant, and 1 wt% of an antioxidant were mixed, and an SJSZ-65 conical twin-screw extruder was used to control the head temperature at 180° C., the body temperature at 155° C., and the mold temperature at 165° C. to obtain a first flame retardant layer for later use;

[0075] Step 2: 50 wt% wood flour, 34 wt% high-density polyethylene, 2 wt% nanocellulose, 12 wt% attapulgite, 1 wt% lubricant, and 1 wt% antioxidant were mixed, and an SJSZ-65 conical twin-screw extruder was used to control the head temperature at 180° C., the body temperature at 155° C., and the mold temperature at 165° C. to obtain a second flame retardant layer for standby use;

[0076] Step 3: First, calcine the convexograph at 300°C in a muffle furnace for 3h, then mix 50wt% wood powder, 34wt% high-density polyethylene, 14wt% convexograph, 1wt% lubricant and 1wt% antioxidant, and use a SJSZ-65-conical twin-screw extruder to control the head temperature at 180°C, the body temperature at 155°C, and the mold temperature at 165°C to obtain the core layer for use, wherein the distance between two adjacent corrugated peaks or corrugated valleys is controlled to be 15mm.

[0077] Step 4: Use MDI adhesive to glue the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer in sequence, with an adhesive amount of 150g / m 2 , the cold pressing pressure is 0.5 MPa, and the wood-plastic composite board of the present application is obtained.

[0078] Comparative Example 2

[0079] The main difference between this comparative example and Example 5 is that the composite flame retardant selected is the composite flame retardant prepared in Comparative Example 1.

[0080] Comparative Example 3

[0081] The main difference between this comparative example and Example 5 is that the core layer is planar.

[0082] Comparative Example 4

[0083] The main difference between this comparative example and Example 5 is that the arrangement order of the wood-plastic composite board is the second flame retardant layer, the first flame retardant layer, the core layer, the first flame retardant layer and the second flame retardant layer.

[0084] Comparative Example 5

[0085] The main difference between this comparative example and Example 5 is that the attapulgite of the second flame retardant layer has not been calcined and activated.

[0086] Performance testing

[0087] (1) Flame retardant performance: The flame retardant performance of the wood plastic composite board was tested using a cone calorimeter in accordance with the international standard ISO5660-1-2002, with a radiation power of 50Kw / m 2 The flame retardant performance test results are shown in Table 1. (2) Mechanical properties: The tensile performance test was carried out according to ASTM D638 standard, the tensile speed was 5mm / min, and the bending performance test was carried out according to ASTM D790 standard, three-point bending mode, span was 64mm, and load loading speed was 1.9mmm / min. The mechanical performance test results are shown in Table 2.

[0088] (3) The sound insulation performance was tested according to the method of GB / T 5266-2006. The average sound absorption coefficient is shown in Table 2.

[0089] Table 1

[0090]

[0091] Table 2

[0092]

[0093]

[0094] Result Analysis

[0095] Combining Examples 4 to 6 and Comparative Examples 2 to 5 and Tables 1 and 2, it can be seen that the composite flame retardant prepared by the method of the present application can achieve a good flame retardant effect, wherein the ignition time is 27 to 30 seconds and the average heat release rate is 69.9 to 78.4 km / m 2 The total heat release is 253.6~271.4MJ / m 2 This is because the present invention first modifies the attapulgite with an alcohol-base solution to obtain hydroxyl-modified attapulgite, which is then added to a chitosan solution to obtain amino-modified attapulgite, and finally added to a phosphoric acid solution to form a phosphorus-containing nano flame retardant. The first flame-retardant layer, the second flame-retardant layer, and the core layer of the present invention all contain attapulgite, which itself has excellent flame retardant properties. Therefore, the various layers can synergize with each other to achieve a flame retardant effect.

[0096] In combination with Examples 4 to 6, Comparative Examples 2 to 5, and Table 2, it can be seen that the corrugated type of the core layer of the present application and the flame retardant layer form a hollow structure, which can not only achieve a flame retardant effect in physical space, but also achieve a sound insulation effect. The thickness ratio of the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer, and the first flame retardant layer is controlled to be 2:2:1:2:2. The thickness of the corrugated layer is small, which avoids affecting the mechanical properties of the board.

[0097] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A wood-plastic composite board, characterized in that: The wood-plastic composite board has a symmetrical structure of five layers, which are, in order, a first flame retardant layer, a second flame retardant layer, a core layer, a second flame retardant layer and a first flame retardant layer, wherein the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer are bonded together by an adhesive; The first flame retardant layer comprises the following raw materials by weight: 50-58 wt% wood flour, 10-14 wt% composite flame retardant, 27-34 wt% high-density polyethylene, 1-3 wt% lubricant, and 1-2 wt% antioxidant; The core layer is of a corrugated type and comprises the following raw materials by weight: 50-58 wt% wood flour, 27-34 wt% high-density polyethylene, 10-14 wt% attapulgite, 1-3 wt% lubricant, and 1-2 wt% antioxidant; The second flame retardant layer includes the following raw materials by weight: 50-58 wt% of wood flour, 27-34 wt% of high-density polyethylene, 2 wt% of nanocellulose, 8-12 wt% of attapulgite, 1-3 wt% of lubricant, and 1-2 wt% of antioxidant.

2. A wood-plastic composite board according to claim 1, characterized in that: The preparation method of the composite flame retardant is: S1. The alkaline solution and the alcohol solution were ultrasonically dispersed for 30 to 40 minutes to obtain an alcohol-alkali solution, and then the attapulgite was added and ultrasonically dispersed for 30 to 40 minutes, and magnetically stirred for 3 to 5 hours to obtain a mixed solution A; S2. The mixed solution A obtained in S1 was separated into solid and liquid, and the solid was dried to obtain a hydroxyl-modified attapulgite; S3. The hydroxyl-modified attapulgite obtained in S2 was dispersed into the chitosan solution, ultrasonically dispersed for 30 to 40 minutes, and magnetically stirred for 3 to 5 hours to obtain a mixed solution B; S4. The mixed solution B obtained in S3 was separated into solid and liquid, and the solid was dried to obtain an amino-modified attapulgite; S5. The amino-modified attapulgite obtained in S4 is mixed with a phosphoric acid solution, stirred at 30-60° C. for 0.5-2 h to obtain a mixed solution C, the mixed solution C is separated into a solid and a liquid, and the solid is dried to obtain a composite flame retardant.

3. A wood-plastic composite board according to claim 2, characterized in that: The alkaline solution in S1 is sodium hydroxide or potassium hydroxide, with a concentration of 2 to 3 mol / L; the alcohol solution is any one of ethanol, ethylene glycol, propanol or isopropanol; the mass ratio of the alkaline solution to the alcohol solution is 1:(50 to 100); the mass ratio of the attapulgite in S1 to the alcohol-alkali solution is 1:(20 to 30).

4. A wood-plastic composite board according to claim 2, characterized in that: The mass fraction of the chitosan solution in S3 is 40-50%; the mass ratio of the hydroxyl-modified attapulgite to the chitosan solution is 1:(20-30).

5. The wood-plastic composite board according to claim 2, characterized in that: The mass fraction of the phosphoric acid solution in S5 is 35% to 40%; the mass ratio of the amino-modified attapulgite to the phosphoric acid solution is 1:(20 to 30).

6. The wood-plastic composite board according to claim 1, characterized in that: The thickness ratio of the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer is 2:2:1:2:

2.

7. The wood-plastic composite board according to claim 1, characterized in that: The attapulgite is calcined at 300-350° C. for 2-3 hours.

8. The wood-plastic composite board according to claim 1, characterized in that: The lubricant is sodium stearate, and the antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecanol.

9. The method for preparing a wood-plastic composite board according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Mix wood flour, composite flame retardant, high-density polyethylene, lubricant and antioxidant in proportion by mass, and then feed into a twin-screw extruder for melt extrusion to obtain a first flame retardant layer for later use; Step 2: Mix wood flour, high-density polyethylene, nanocellulose, attapulgite, lubricant and antioxidant in percentage by mass and then feed into a twin-screw extruder for melt extrusion to obtain a second flame retardant layer for later use; Step 3: Mix wood flour, high-density polyethylene, attapulgite, lubricant and antioxidant in proportion to mass percentage, and then feed into a press for melt extrusion to obtain a core layer for later use; Step 4: Bonding the first flame retardant layer, the second flame retardant layer, the core layer, the second flame retardant layer and the first flame retardant layer with an adhesive to obtain a wood-plastic composite board.

10. The use of a wood-plastic composite board according to any one of claims 1 to 8, characterized in that: For interior door panels.

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