Preparation method of molded wood-plastic composite material

Abstract

The invention relates to the technical field of wood-plastic composite materials, and discloses a preparation method of a molded wood-plastic composite material. According to the invention, dibenzoyl peroxide is used as an initiator, 4-glycidyl ether styrene phosphate is subjected to a polymerization reaction to obtain a flame-retardant polymer, and then the flame-retardant polymer is mixed with polystyrene, wood flour and an antioxidant to obtain the molded wood-plastic composite material with synchronously improved mechanical properties and flame retardancy. The flame-retardant polymer disclosed by the invention contains a polystyrene molecular chain and an epoxy group, and can be used as a compatilizer, so that the compatibility between polystyrene and wood flour is improved, and the mechanical properties such as tensile strength of a composite material are obviously improved. The flame-retardant polymer also contains a phosphate group, so that the combustion char-forming capability of polystyrene is improved, and the wood-plastic composite material has relatively high limit oxygen index and flame-retardant property.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood-plastic composites, in particular to a preparation method of a molded wood-plastic composite material. BACKGROUND

[0002] As an environmentally friendly material, wood-plastic composites combine the natural properties of wood fibers and the processing performance of plastics, and have wide applications in the fields of construction, packaging, furniture, etc. Among them, polystyrene wood-plastic composites are concerned due to their low cost and easy processing, but the interfacial bonding force between polystyrene and wood powder is weak, which leads to a decrease in the mechanical properties of the material, and the mechanical properties and flame retardant properties of wood-plastic composites are difficult to be improved simultaneously.

[0003] In order to make the composite material have high mechanical strength and high flame retardancy, it has become a research hotspot to design a multifunctional additive that can simultaneously act as a compatibilizer and a flame retardant. Patent CN118440433A discloses a wood-plastic board made of polystyrene and modified wood powder. The wood powder is modified twice by maleic anhydride and fluorine-containing unsaturated monomers, and the modified wood powder is mixed with polypropylene, polystyrene, etc. to obtain a wood-plastic board, which improves the mechanical properties and high-temperature resistance of the wood-plastic board. However, this patent does not solve the problem of poor flame retardant properties of wood-plastic composites. SUMMARY

[0004] (I) Technical problems solved:

[0005] In view of the deficiencies of the prior art, the present application provides a preparation method of a molded wood-plastic composite material, which solves the problems of poor interfacial compatibility and poor flame retardant properties of wood-plastic composites.

[0006] (II) Technical solution: A preparation method of a molded wood-plastic composite material is as follows:

[0007] S1, in a fume hood, a flask is added with cyclohexane and phosphorus pentachloride, 4-glycidyl ether styrene is added dropwise in an ice water bath, and sulfur dioxide gas is introduced until the reaction bottle is filled, then stirred at 20-30℃ for 1-1.5h, filtered, the filtrate is distilled under reduced pressure, the product is added to an alcohol solvent, pyridine is added, heated to 60-75℃, stirred and refluxed for 1-2h, distilled under reduced pressure, and the product is separated by silica gel column chromatography to obtain 4-glycidyl ether styrene phosphate, wherein the alcohol solvent is methanol or ethanol, and the reaction formula for preparation is:

[0008]

[0009] S2, to the flask is added toluene, isobutyl alcohol, 4-glycidyl ether styrene phosphate, heated to 75-85 DEG C under nitrogen atmosphere, then added diphenyl peroxide, stirred for 5-8h, after cooling, added n-hexane for determination, after filtration, n-hexane washing, drying, to obtain the flame-retardant polymer.

[0010] S3, to the high-speed mixer is added polystyrene, dried wood powder, flame-retardant polymer, antioxidant, after mixing, the material is extruded and granulated through a double-screw extruder, then molded in a molding machine to obtain the molded wood-plastic composite material, wherein the temperature of the double-screw extruder is 120-200 DEG C, the rotating speed is 50-100r / min, the temperature of the molding machine is 175-190 DEG C, and the pressure is 10-15MPa.

[0011] Further, the molar ratio of phosphorus pentachloride and 4-glycidyl ether styrene in S1 is (2.2-3):1.

[0012] Further, the molar ratio of 4-glycidyl ether styrene phosphate and diphenyl peroxide in S2 is 1:(0.012-0.016).

[0013] Further, the mass ratio of polystyrene, wood powder, flame-retardant polymer and antioxidant in S3 is 100:(30-50):(10-25):(0.1-0.2).

[0014] (Three) beneficial technical effects: the present application uses diphenyl peroxide as an initiator, 4-glycidyl ether styrene phosphate is subjected to polymerization reaction to obtain a flame-retardant polymer, which is then added to a mixture of polystyrene and wood powder to obtain a molded wood-plastic composite material with synchronous improvement in mechanical strength and flame-retardant performance.

[0015] The flame-retardant polymer of the present application plays the role of an interfacial compatibilizer in the preparation process of the wood-plastic composite material, wherein the polystyrene molecular chain has good compatibility with the polystyrene matrix, and the epoxy group can react with the hydroxyl group on the surface of the wood powder, thereby significantly enhancing the binding force between the polystyrene and the wood powder, and obviously improving the mechanical strength of the wood-plastic composite material.

[0016] The 4-glycidyl ether styrene phosphate of the present application and the flame-retardant polymer prepared therefrom contain phosphate groups, which improve the flame-retardant performance of the composite material through charring effect, and improve the limiting oxygen index. DETAILED DESCRIPTION

[0017] The technical solutions of the present application are further illustrated by the specific embodiments below. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0018] 4-Vinylphenyl glycidyl ether was prepared according to the method of the article "4-Vinylphenyl Glycidyl Ether: Synthesis, RAFT Polymerization, and Postpolymerization Modifications with Alcohols" in Macromolecules 2016, 49, 4, 1135-1142, and its structure is as follows:

[0019]

[0020] The polystyrene with the following product number is 622P, which is from Shanghai U-Trust International Trading Co., Ltd.

[0021] Example 1: The preparation method of the molded wood-plastic composite material is as follows:

[0022] Step (1) In a fume hood, 500 mL of cyclohexane and 0.88 mol of phosphorus pentachloride were added to a flask, and 0.4 mol of 4-vinylphenyl glycidyl ether was added dropwise in an ice water bath. After stirring, sulfur dioxide gas was introduced until the reaction bottle was filled. The reaction was stirred at 30°C for 1 h, filtered, and the filtrate was distilled under reduced pressure. The product was added to 50 mL of ethanol, 42 mL of pyridine was added, heated to 60°C, and stirred to reflux for 2 h. The product was distilled under reduced pressure and separated by silica gel column chromatography to obtain 4-vinylphenyl glycidyl ether phosphate with the following structure:

[0023] Step (2) 600 mL of toluene and 150 mL of isobutyl alcohol were added to a flask, and 0.5 mol of 4-vinylphenyl glycidyl ether phosphate was added. The mixture was heated to 85°C under a nitrogen atmosphere, and 6 mmol of dibenzoyl peroxide was added. The mixture was stirred for 8 h, cooled, and then hexane was added for determination. After filtration and washing with hexane, the product was dried to obtain a flame-retardant polymer.

[0024] Step (3) 2 kg of polystyrene, 0.6 kg of dried wood powder (average particle size of 80 mesh), 200 g of flame-retardant polymer, and 4 g of antioxidant 1010 were added to a high-speed mixer. After mixing, the material was extruded and granulated by a twin-screw extruder with zone temperatures of 120°C, 150°C, 175°C, 190°C, and 200°C, and a rotation speed of 100 r / min. Then, the material was molded in a molding machine at a temperature of 175°C and a pressure of 15 MPa to obtain a molded wood-plastic composite material.

[0025] Example 2: The preparation method of the molded wood-plastic composite material is as follows:

[0026] Step (1) In a fume hood, 400 mL of cyclohexane, 1.2 mol of phosphorus pentachloride were added into a flask, 0.4 mol of 4-glycidyl ether styrene was added dropwise in an ice water bath, and then sulfur dioxide gas was bubbled into the reaction bottle until it was full. After stirring at 20°C for 1.5 h, filtration was performed, and the filtrate was distilled under reduced pressure. The product was added to 40 mL of methanol, 35 mL of pyridine was added, heated to 75°C, and stirred for 1 h under reflux. After distillation under reduced pressure, the product was separated by silica gel column chromatography to obtain 4-glycidyl ether styrene phosphate with the following structure:

[0027]

[0028] Step (2) 600 mL of toluene and 200 mL of isobutyl alcohol were added into a flask, 0.5 mol of 4-glycidyl ether styrene phosphate was added, heated to 75°C under nitrogen atmosphere, and then 8 mmol of dibenzoyl peroxide was added. After stirring for 5 h, n-hexane was added for determination after cooling. After filtration, n-hexane was used for washing and drying to obtain a flame-retardant polymer.

[0029] Step (3) 2 kg of polystyrene, 0.7 kg of dried wood powder (average particle size of 80 mesh), 300 g of flame-retardant polymer, and 4 g of antioxidant 1010 were added into a high-speed mixer. After mixing, the materials were extruded and granulated by a twin-screw extruder with zone temperatures of 120°C, 150°C, 175°C, 190°C, and 200°C, and a rotation speed of 50 r / min. Then, the materials were molded into a wood-plastic composite material in a molding machine at a temperature of 190°C and a pressure of 10 Mpa.

[0030] Example 3: The preparation method of the molded wood-plastic composite material is as follows:

[0031] Step (1) 4-glycidyl ether styrene phosphate was prepared according to the method of Example 1.

[0032] Step (2) 600 mL of toluene and 175 mL of isobutyl alcohol were added into a flask, 0.5 mol of 4-glycidyl ether styrene phosphate was added, heated to 80°C under nitrogen atmosphere, and then 7 mmol of dibenzoyl peroxide was added. After stirring for 6.5 h, n-hexane was added for determination after cooling. After filtration, n-hexane was used for washing and drying to obtain a flame-retardant polymer.

[0033] Step (3) 2 kg of polystyrene, 0.85 kg of dried wood powder (average particle size of 80 mesh), 400 g of flame-retardant polymer, and 3 g of antioxidant 1010 were added into a high-speed mixer. After mixing, the materials were extruded and granulated by a twin-screw extruder with zone temperatures of 120°C, 150°C, 175°C, 190°C, and 200°C, and a rotation speed of 75 r / min. Then, the materials were molded into a wood-plastic composite material in a molding machine at a temperature of 180°C and a pressure of 15 Mpa.

[0034] Example 4: The preparation method of the molded wood plastic composite material is as follows:

[0035] Step (1) 4-glycidyl ether styrene phosphate was prepared by the method of Example 1.

[0036] Step (2) 600 mL of toluene, 200 mL of isobutyl alcohol, 0.5 mol of 4-glycidyl ether styrene phosphate, 7 mmol of dibenzoyl peroxide were added to a flask, heated to 85°C under nitrogen atmosphere, stirred for 6h, then added n-hexane for determination after cooling, washed with n-hexane after filtration, dried to obtain a flame-retardant polymer.

[0037] Step (3) 2 kg of polystyrene, 1 kg of dried wood powder (average particle size of 80 mesh), 500 g of flame-retardant polymer, 4 g of antioxidant 1010 were added to a high-speed mixer, mixed, and then the material was extruded and granulated through a twin-screw extruder, the temperature of each zone was 120°C, 150°C, 175°C, 190°C, 200°C, and the rotation speed was 50 r / min, then molded in a molding machine, the temperature was 190°C, and the pressure was 12 MPa, to obtain a molded wood plastic composite material.

[0038] The difference between Comparative Example 1 and Example 1 is that no flame-retardant polymer is added.

[0039] Step (1) 2 kg of polystyrene, 0.6 kg of dried wood powder (average particle size of 80 mesh), 4 g of antioxidant 1010 were added to a high-speed mixer, mixed, and then the material was extruded and granulated through a twin-screw extruder, the temperature of each zone was 120°C, 150°C, 175°C, 190°C, 200°C, and the rotation speed was 100 r / min, then molded in a molding machine, the temperature was 175°C, and the pressure was 15 MPa, to obtain a molded wood plastic composite material.

[0040] The difference between Comparative Example 2 and Example 1 is that glycidyl methacrylate is used instead of 4-glycidyl ether styrene phosphate for polymerization.

[0041] Step (1) 600 mL of toluene, 150 mL of isobutyl alcohol, 0.5 mol of glycidyl methacrylate were added to a flask, heated to 85°C under nitrogen atmosphere, then 6 mmol of dibenzoyl peroxide was added, stirred for 8h, then added n-hexane for determination after cooling, washed with n-hexane after filtration, dried to obtain a glycidyl methacrylate polymer.

[0042] Step (2) 2 kg of polystyrene, 0.6 kg of dried wood powder (average particle size of 80 mesh), 200 g of polyglycidyl methacrylate, and 4 g of antioxidant 1010 were added to a high-speed mixer, and after mixing, the material was extruded and pelletized by a twin-screw extruder, with the temperature of each zone being 120℃, 150℃, 175℃, 190℃, and 200℃, and the rotation speed being 100 r / min, and then molded into a compression wood-plastic composite material in a compression molding machine at a temperature of 175℃ and a pressure of 15 MPa.

[0043] Comparative Example 3 differs from Example 1 in that 4-glycidylstyrene phosphate ester is replaced by 4-glycidylstyrene, and a polymerization reaction is performed.

[0044] Step (1) 600 mL of toluene, 150 mL of isobutyl alcohol, and 0.5 mol of 4-glycidylstyrene were added to a flask, heated to 85℃ in a nitrogen atmosphere, and then 6 mmol of dibenzoyl peroxide was added, and stirred for 8 h. After cooling, n-hexane was added for determination, and after filtration, n-hexane was washed and dried to obtain polyglycidylstyrene.

[0045] Step (2) 2 kg of polystyrene, 0.6 kg of dried wood powder (average particle size of 80 mesh), 200 g of polyglycidylstyrene, and 4 g of antioxidant 1010 were added to a high-speed mixer, and after mixing, the material was extruded and pelletized by a twin-screw extruder, with the temperature of each zone being 120℃, 150℃, 175℃, 190℃, and 200℃, and the rotation speed being 100 r / min, and then molded into a compression wood-plastic composite material in a compression molding machine at a temperature of 175℃ and a pressure of 15 MPa.

[0046] Comparative Example 4 differs from Example 1 in that 4-glycidylstyrene phosphate ester is replaced by 2-(oxyethylene phosphoryl oxygen) ethyl acrylate, and a polymerization reaction is performed.

[0047] 2-(oxyethylene phosphoryl oxygen) ethyl acrylate was prepared according to the method of the journal “South China Normal University Journal” in September 2014, Volume 46, Issue 5, Literature “Synthesis and Application of New High Molecular Flame Retardant Antistatic Agent”

[0048] Step (1) 600 mL of toluene, 150 mL of isobutyl alcohol, and 0.5 mol of 2-(oxyethylene phosphoryl oxygen) ethyl acrylate were added to a flask, heated to 85℃ in a nitrogen atmosphere, and then 6 mmol of dibenzoyl peroxide was added, and stirred for 8 h. After cooling, n-hexane was added for determination, and after filtration, n-hexane was washed and dried to obtain a flame-retardant polymer.

[0049] Step (2) 2 kg of polystyrene, 0.6 kg of dried wood powder (average particle size of 80 mesh), 200 g of the flame-retardant polymer, 4 g of antioxidant 1010 were added into a high-speed mixer, and after mixing, the materials were extruded and pelletized by a twin-screw extruder, the temperature of each zone was 120℃, 150℃, 175℃, 190℃, 200℃, and the rotation speed was 100 r / min, then the materials were molded into a wood-plastic composite material by a molding machine, the temperature was 175℃, and the pressure was 15 MPa.

[0050] The tensile strength of the wood-plastic composite material was tested according to GB / T 1040.1-2008. The bending strength was tested according to GB / T 9341-2008. The flame-retardant property was tested according to GB / T 2406.2-2009.

[0051] Table 1 Mechanical properties and flame-retardant properties of the wood-plastic composite material

[0052]

[0053] Compared with Comparative Example 1, the flame-retardant polymer prepared by the polymerization reaction of 4-glycidyl ether styrene phosphate and dibenzoyl peroxide in Examples 1-4 was added into the mixture of polystyrene and wood powder, which greatly improved the flame-retardant property and mechanical properties such as tensile strength and bending strength of the wood-plastic composite material. This is mainly because the 4-glycidyl ether styrene phosphate and the flame-retardant polymer prepared therefrom contain phosphate groups, epoxy groups and polystyrene molecular chains. The phosphate groups have flame-retardant function, promote the formation of carbon by polystyrene and wood powder, and significantly improve the limiting oxygen index of the wood-plastic material. In addition, the flame-retardant polymer plays the role of a compatibilizer in the preparation of the wood-plastic composite material. The polystyrene molecular chains have good compatibility with the polystyrene matrix, and the epoxy groups can react with the hydroxyl groups on the surface of the wood powder, thereby improving the interfacial bonding force and compatibility between the wood powder and the polystyrene matrix, and making the wood-plastic material have high tensile strength and bending strength.

[0054] In Comparative Examples 2 and 3, glycidyl methacrylate and 4-glycidyl ether styrene were respectively used instead of 4-glycidyl ether styrene phosphate to prepare polymers by polymerization reaction. The polymers prepared by the two methods both do not contain phosphate groups, resulting in poor flame retardancy and low limiting oxygen index of the composite materials. In addition, the polymer prepared in Comparative Example 2 does not contain polystyrene molecular chains, and has poor compatibility with polystyrene, which cannot be used as a good compatibilizer to improve the compatibility between polystyrene and wood powder, resulting in low mechanical properties such as bending strength of the composite material.

[0055] The flame-retardant polymer prepared in Comparative Example 4 does not contain epoxy groups, which cannot react with the hydroxyl groups on the surface of the wood powder, and cannot be used as a compatibilizer to improve the compatibility between polystyrene and wood powder, resulting in poor mechanical strength of the wood-plastic material.

[0056] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. The application is defined by the claims and their equivalents.

Claims

1. A method for producing a molded wood plastic composite, characterized in that The preparation method is as follows: Step (1), adding toluene, isobutyl alcohol, 4-glycidyl ether styrene phosphate in a flask, heating to reaction temperature under nitrogen atmosphere, then adding dibenzoyl peroxide, stirring reaction, adding n-hexane after cooling, filtering after n-hexane washing, drying, obtaining flame-retardant polymer; Step (2), adding polystyrene, dried wood powder, flame-retardant polymer, antioxidant in a high-speed mixer, mixing, then extruding and granulating the material through a twin-screw extruder, then molding in a molding machine, obtaining molded wood-plastic composite material.

2. The method for preparing molded wood-plastic composite material according to claim 1, characterized in that, The molar ratio of 4-glycidyl ether styrene phosphate and dibenzoyl peroxide in step (1) is 1:(0.012-0.016).

3. The method for preparing molded wood-plastic composite material according to claim 1, characterized in that, The reaction temperature in step (1) is 75-85℃, and the reaction time is 5-8h.

4. The method for preparing molded wood-plastic composite material according to claim 1, characterized in that, The preparation method of 4-glycidyl ether styrene phosphate is as follows: adding cyclohexane, phosphorus pentachloride in a flask, adding 4-glycidyl ether styrene dropwise in an ice water bath, then passing sulfur dioxide gas, stirring at 20-30℃ for 1-1.5h, filtering, distilling the filtrate under reduced pressure, adding the product to an alcohol solvent, adding pyridine, heating to 60-75℃, stirring refluxing for 1-2h, distilling under reduced pressure, separating the product through silica gel column chromatography, obtaining 4-glycidyl ether styrene phosphate.

5. The method for preparing molded wood-plastic composite material according to claim 4, characterized in that, The molar ratio of phosphorus pentachloride and 4-glycidyl ether styrene is (2.2-3):

1.

6. The method for preparing molded wood-plastic composite material according to claim 4, characterized in that, The alcohol solvent is methanol or ethanol.

7. The method of claim 1, wherein the wood-plastic composite is compression molded. The mass ratio of polystyrene, wood powder, flame-retardant polymer, antioxidant in step (2) is 100:(30-50):(10-25):(0.1-0.2).

8. The method of claim 1, wherein the wood-plastic composite is compression molded. The temperature of the twin-screw extruder in step (2) is 120-200℃, and the rotation speed is 50-100r / min.

9. The method of claim 1, wherein, The temperature of the molding machine in step (2) is 175-190℃, and the pressure is 10-15MPa.

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