A method for preparing a molded wood plastic composite

Abstract

The present application relates to the technical field of wood-plastic composite materials, and discloses a preparation method of a molded wood-plastic composite material. In the present application, 4-glycidyl ether styrene phosphate is subjected to a polymerization reaction to obtain a flame-retardant polymer by using diphenyl benzene peroxide as an initiator, and then the flame-retardant polymer is mixed with polystyrene, wood powder and an antioxidant to obtain a molded wood-plastic composite material with synchronous improvement in mechanical properties and flame-retardant properties. The flame-retardant polymer contains polystyrene molecular chains and epoxy groups, and can be used as a compatibilizer to improve the compatibility between polystyrene and wood powder, so that the mechanical properties such as tensile strength of the composite material are obviously improved. The flame-retardant polymer also contains phosphate groups, which improves the carbonization capacity of polystyrene during combustion, so that the wood-plastic composite material has a high limiting oxygen index and flame-retardant properties.

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 in a nitrogen atmosphere, then added diphenyl peroxide, stirring for 5-8h, after cooling, add 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 twin-screw extruder, and then molded into a molded wood-plastic composite material in a molding machine, wherein the temperature of the twin-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, and 4-glycidyl ether styrene phosphate is subjected to a 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 simultaneous 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 bonding 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 specific embodiments. 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, add 400 mL of cyclohexane and 1.2 mol of phosphorus pentachloride to a flask. Add 0.4 mol of 4-glycidyl ether styrene dropwise in an ice-water bath. After stirring, purge with sulfur dioxide gas until the reaction flask is full. Stir and react at 20°C for 1.5 h. Filter, fractionate the filtrate under reduced pressure, add the product to 40 mL of methanol, add 35 mL of pyridine, heat to 75°C, stir and reflux for 1 h, distill under reduced pressure, and separate the product by silica gel column chromatography to obtain 4-glycidyl ether styrene phosphate, with the following structural formula:

[0027]

[0028] Step (2) Add 600 mL toluene, 200 mL isobutanol, and 0.5 mol 4-glycidyl ether styrene phosphate to the flask, heat to 75 °C in a nitrogen atmosphere, then add 8 mmol benzoyl peroxide, stir and react for 5 h, cool and add n-hexane for determination, filter, wash with n-hexane, dry, and obtain flame retardant polymer.

[0029] Step (3) Add 2kg of polystyrene, 0.7kg of dried wood powder (average particle size of 80 mesh), 300g of flame retardant polymer, and 4g of antioxidant 1010 to a high-speed mixer. After mixing, the material is extruded and granulated through a twin-screw extruder. The temperatures of each zone are 120℃, 150℃, 175℃, 190℃, and 200℃, and the rotation speed is 50r / min. Then, it is molded in a molding press at a temperature of 190℃ and a pressure of 10MPa to obtain a molded wood-plastic composite material.

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

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

[0032] Step (2) Add 600 mL toluene, 175 mL isobutanol, and 0.5 mol 4-glycidyl ether styrene phosphate to the flask, heat to 80 °C in a nitrogen atmosphere, add 7 mmol benzoyl peroxide, stir for 6.5 h, cool, add n-hexane for determination, filter, wash with n-hexane, dry, and obtain flame retardant polymer.

[0033] Step (3) Add 2kg of polystyrene, 0.85kg of dried wood powder (average particle size of 80 mesh), 400g of flame retardant polymer, and 3g of antioxidant 1010 to a high-speed mixer. After mixing, the material is extruded and granulated through a twin-screw extruder. The temperatures of each zone are 120℃, 150℃, 175℃, 190℃, and 200℃, and the rotation speed is 75r / min. Then, it is molded in a molding press at a temperature of 180℃ and a pressure of 15MPa to obtain a molded wood-plastic composite material.

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

[0035] Step (1) Prepare 4-glycidyl ether styrene phosphate according to the method of Example 1.

[0036] Step (2) Add 600 mL toluene, 200 mL isobutanol, and 0.5 mol 4-glycidyl ether styrene phosphate to the flask, heat to 85 °C in a nitrogen atmosphere, add 7 mmol benzoyl peroxide, stir for 6 h, cool, add n-hexane for determination, filter, wash with n-hexane, dry, and obtain flame retardant polymer.

[0037] Step (3) Add 2kg of polystyrene, 1kg of dried wood powder (average particle size of 80 mesh), 500g of flame retardant polymer, and 4g of antioxidant 1010 to a high-speed mixer. After mixing, the material is extruded and granulated through a twin-screw extruder. The temperatures of each zone are 120℃, 150℃, 175℃, 190℃, and 200℃, and the rotation speed is 50r / min. Then, it is molded in a molding press at a temperature of 190℃ and a pressure of 12MPa 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) Add 2kg of polystyrene, 0.6kg of dried wood powder (average particle size of 80 mesh) and 4g of antioxidant 1010 to a high-speed mixer. After mixing, the material is extruded and granulated through a twin-screw extruder. The temperatures of each zone are 120℃, 150℃, 175℃, 190℃ and 200℃, and the rotation speed is 100r / min. Then, it is molded in a molding press at a temperature of 175℃ and a pressure of 15MPa to obtain a molded wood-plastic composite material.

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

[0041] Step (1) Add 600 mL toluene, 150 mL isobutanol and 0.5 mol glycidyl methacrylate to the flask, heat to 85 °C in a nitrogen atmosphere, add 6 mmol benzoyl peroxide, stir for 8 h, cool and add n-hexane for determination, filter, wash with n-hexane, dry to obtain polyglycidyl methacrylate.

[0042] Step (2) Add 2kg of polystyrene, 0.6kg of dried wood flour (average particle size of 80 mesh), 200g of polymethyl methacrylate and 4g of antioxidant 1010 to a high-speed mixer. After mixing, the material is extruded and granulated through a twin-screw extruder. The temperatures of each zone are 120℃, 150℃, 175℃, 190℃ and 200℃, and the rotation speed is 100r / min. Then, it is molded in a molding press at a temperature of 175℃ and a pressure of 15MPa to obtain a molded wood-plastic composite material.

[0043] The difference between Comparative Example 3 and Example 1 is that 4-glycidyl ether styrene was used instead of 4-glycidyl ether styrene phosphate for the polymerization reaction.

[0044] Step (1) Add 600 mL toluene, 150 mL isobutanol and 0.5 mol 4-glycidyl ether styrene to the flask, heat to 85 °C in a nitrogen atmosphere, add 6 mmol benzoyl peroxide, stir for 8 h, cool and add n-hexane for determination, filter, wash with n-hexane, dry to obtain polyglycidyl ether styrene.

[0045] Step (2) Add 2kg of polystyrene, 0.6kg of dried wood powder (average particle size of 80 mesh), 200g of polyglycidyl ether styrene, and 4g of antioxidant 1010 to a high-speed mixer. After mixing, the material is extruded and granulated through a twin-screw extruder. The temperatures of each zone are 120℃, 150℃, 175℃, 190℃, and 200℃, and the rotation speed is 100r / min. Then, it is molded in a molding press at a temperature of 175℃ and a pressure of 15MPa to obtain a molded wood-plastic composite material.

[0046] The difference between Comparative Example 4 and Example 1 is that ethyl 2-(oxyvinylphosphooxy)acrylate was used instead of 4-glycidyl ether styrene phosphate for the polymerization reaction.

[0047] 2-(oxyvinylphosphoyloxy)acrylate was prepared according to the method described in the article "Synthesis and Application of Novel Polymer Flame Retardant and Antistatic Agent" published in the September 2014 issue of the Journal of South China Normal University (Vol. 46, No. 5).

[0048] Step (1) Add 600 mL toluene, 150 mL isobutanol, and 0.5 mol ethyl 2-(oxyvinylphosphooxy)acrylate to the flask, heat to 85 °C in a nitrogen atmosphere, add 6 mmol benzoyl peroxide, stir and react for 8 h, cool and add n-hexane for determination, filter, wash with n-hexane, dry to obtain flame retardant polymer.

[0049] Step (2) Add 2kg of polystyrene, 0.6kg of dried wood powder (average particle size of 80 mesh), 200g of flame retardant polymer, and 4g of antioxidant 1010 to a high-speed mixer. After mixing, the material is extruded and granulated through a twin-screw extruder. The temperatures of each zone are 120℃, 150℃, 175℃, 190℃, and 200℃, and the rotation speed is 100r / min. Then, it is molded in a molding press at a temperature of 175℃ and a pressure of 15MPa to obtain a molded wood-plastic composite material.

[0050] The tensile strength of molded wood-plastic composites shall be tested according to GB / T 1040.1-2008. The flexural strength shall be tested according to GB / T9341-2008. The flame retardant properties shall be tested according to GB / T 2406.2-2009.

[0051] Table 1 Mechanical and flame retardant properties of molded wood-plastic composites

[0052]

[0053] Compared to Comparative Example 1, Examples 1-4 used 4-glycidyl ether styrene phosphate and benzoyl peroxide to polymerize a flame-retardant polymer, which was then added to a mixture of polystyrene and wood flour. This significantly improved the flame-retardant properties and mechanical properties such as tensile strength and flexural strength of the wood-plastic composite material. This is mainly because 4-glycidyl ether styrene phosphate and the resulting flame-retardant polymer contain phosphate groups, epoxy groups, and polystyrene molecular chains. The phosphate groups have flame-retardant properties, promote charring between polystyrene and wood flour, and significantly improve the limiting oxygen index of the wood-plastic composite material. Furthermore, this flame-retardant polymer acts as a compatibilizer in the preparation of the wood-plastic composite material. The polystyrene molecular chains have excellent compatibility with the polystyrene matrix, and the epoxy groups can react with the hydroxyl groups on the surface of the wood flour, thereby improving the interfacial bonding and compatibility between the wood flour and the polystyrene matrix, resulting in higher tensile and flexural strength in the wood-plastic composite material.

[0054] Comparative Examples 2 and 3 used glycidyl methacrylate and 4-glycidyl ether styrene instead of 4-glycidyl ether styrene phosphate, respectively, in the polymerization reaction. Neither polymer contained phosphate groups, resulting in poor flame retardancy and a low limiting oxygen index in the composite materials. Furthermore, the polymer obtained in Comparative Example 2 lacked polystyrene molecular chains, exhibiting poor compatibility with polystyrene and failing to act as a good compatibilizer to improve the compatibility between polystyrene and wood flour, leading to lower mechanical properties such as flexural strength in the composite material.

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

[0056] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a molded wood-plastic composite material, characterized in that, The preparation method is as follows: Step (1): Toluene, isobutanol, and 4-glycidyl ether styrene phosphate were added to the flask and heated to the reaction temperature in a nitrogen atmosphere. Then, benzoyl peroxide was added and the mixture was stirred to react. After cooling, hexane was added for determination. After filtration, the mixture was washed with hexane and dried to obtain the flame-retardant polymer. Step (2): Add polystyrene, dried wood powder, flame retardant polymer and antioxidant to a high-speed mixer. After mixing, granulate the material through a twin-screw extruder and then mold it in a molding press to obtain a molded wood-plastic composite material.

2. The method for preparing molded wood-plastic composite material according to claim 1, characterized in that, In step (1), the molar ratio of 4-glycidyl ether styrene phosphate and benzoyl peroxide 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 the 4-glycidyl ether styrene phosphate is as follows: cyclohexane and phosphorus pentachloride are added to a flask, and 4-glycidyl ether styrene is added dropwise in an ice-water bath. After stirring, sulfur dioxide gas is introduced, and the mixture is stirred and reacted at 20-30℃ for 1-1.5 h. The mixture is filtered, and the filtrate is fractionated under reduced pressure. The product is added to an alcohol solvent, pyridine is added, and the mixture is heated to 60-75℃ and stirred under reflux for 1-2 h. The mixture is then distilled under reduced pressure, and the product is separated by silica gel column chromatography to obtain 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 to 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 for preparing molded wood-plastic composite material according to claim 1, characterized in that, In step (2), the mass ratio of polystyrene, wood flour, flame retardant polymer, and antioxidant is 100:(30-50):(10-25):(0.1-0.2).

8. The method for preparing molded wood-plastic composite material according to claim 1, characterized in that, In step (2), the temperature of the twin-screw extruder is 120-200℃ and the rotation speed is 50-100r / min.

9. The method for preparing molded wood-plastic composite material according to claim 1, characterized in that, In step (2), the temperature of the molding press is 175-190℃ and the pressure is 10-15MPa.

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