Flame-retardant wood-plastic composite material for pallets and preparation method thereof

Abstract

The present invention relates to the technical field of wood-plastic materials, and discloses a flame-retardant wood-plastic composite material for pallets and a preparation method thereof. The present invention uses (3-bromopropyl) trimethoxysilane and cardanol as raw materials, and under the catalysis of potassium carbonate, undergoes a substitution reaction to obtain a cardanol-containing silane intermediate, and then undergoes a polycondensation grafting reaction on its wood powder to obtain a cardanol-modified wood powder. Using DOPO, 4-vinylbenzaldehyde, and melamine as raw materials, a DOPO-containing melamine flame retardant is obtained by a phosphine hydrogenation reaction and a Schiff base reaction in sequence, and finally, cardanol-modified wood powder, polyethylene, a DOPO-containing melamine flame retardant, etc. are added to the wood powder, mixed evenly, and injection molding is performed to obtain a flame-retardant wood-plastic composite material for pallets. The flame-retardant wood-plastic composite material for pallets prepared by the present invention has excellent flame retardant properties and antibacterial properties.

Description

Technical Field

[0001] The invention relates to the technical field of wood-plastic materials, in particular to a flame-retardant wood-plastic composite material for a pallet and a preparation method thereof. Background Art

[0002] Wood-plastic composite material is a new type of environmentally friendly material with wood powder and plastic as the main raw materials. It is mainly used in building materials, automobiles, packaging materials, decorative materials and other fields. However, wood powder and plastic are both flammable materials. Therefore, it is of great practical significance to improve the flame retardant properties of wood-plastic composite materials.

[0003] Pallets are important carriers for mechanized loading and unloading, and are important tools for cargo storage and transportation. Wood-plastic composite materials are one of the important materials used in pallets. However, since plastic materials cannot completely seal wood materials and organic additives, they will also be attacked and damaged by mold and fungi. Therefore, the antibacterial modification of wood-plastic composite materials for pallets is also one of the research focuses.

[0004] For example, the patent with authorization announcement number CN105482484B discloses a method for preparing a flame-retardant wood-plastic composite material. The invention uses flame-retardant modified plant fibers, compatibilizers, plastics, etc. as raw materials. The prepared flame-retardant wood-plastic composite material has excellent flame retardant properties, but its antibacterial properties are not improved. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies of the prior art, the present invention provides a flame retardant wood-plastic composite material for a pallet and a preparation method thereof. The flame retardant wood-plastic composite material for a pallet prepared by the present invention has excellent flame retardant properties and antibacterial properties.

[0007] (II) Technical solution

[0008] A flame retardant wood-plastic composite material for pallets, the preparation method of which is as follows:

[0009] (1) Add the cardanol-containing silane intermediate to a 95% ethanol solution, add glacial acetic acid to adjust the pH to 3-4, stir evenly, and perform a hydrolysis reaction at 20-35°C for 1-3 hours. Then add wood powder, stir evenly, let it stand at room temperature for 10-16 hours, and then dry it in an oven at 100-110°C for 15-24 hours to obtain cardanol-modified wood powder.

[0010] (2) Adding cardanol-modified wood powder, polyethylene, maleic anhydride-grafted polyethylene, DOPO-containing melamine flame retardant, and antioxidant to the dried wood powder, mixing them evenly in a high-speed mixer at 1000-2000 r / min, and melting and kneading them evenly in a torque rheometer at 170-180°C. Finally, adding them to an injection molding machine at 180-190°C for injection molding to obtain a flame-retardant wood-plastic composite material for pallets.

[0011] Preferably, in step (1), the mass ratio of the cardanol silane intermediate to the wood powder is (1-5):100.

[0012] Preferably, in step (2), the mass ratio of wood powder, cardanol-modified wood powder, polyethylene, maleic anhydride-grafted polyethylene, DOPO-containing melamine flame retardant, and antioxidant is 100: (50-100): (120-180): (20-35): (15-20): (1-5).

[0013] Preferably, in the step (1), the preparation method of the cardanol-containing silane intermediate is: add (3-bromopropyl)trimethoxysilane to isopropanol solvent, stir and disperse, then add potassium carbonate and cardanol thereto, heat to 80-100° C., stir and react for 10-24 hours, filter after the reaction, and evaporate under reduced pressure to obtain the cardanol-containing silane intermediate.

[0014] Preferably, in the steps, the molar ratio of (3-bromopropyl)trimethoxysilane, potassium carbonate and cardanol is (4-8):(12-24):1.

[0015] Preferably, in step (2), the preparation method of the DOPO melamine flame retardant is:

[0016] S1. Under nitrogen conditions, DOPO is dispersed in toluene solvent, and then azobisisobutyronitrile and 4-vinylbenzaldehyde are added thereto, stirred and dispersed, and the temperature is raised to 80-90°C, and the reaction is carried out for 6-12 hours. After the reaction is completed, the reaction is performed by rotary evaporation and drying to obtain intermediate 1.

[0017] S2. Under nitrogen conditions, add intermediate 1 and melamine to dimethyl sulfoxide solvent, stir and disperse, heat to 170-190°C, react for 60-100 hours, and after the reaction is completed, cool to room temperature, filter, wash with tetrahydrofuran and deionized water in turn, and dry to obtain a DOPO-containing melamine flame retardant.

[0018] Preferably, in step S1, the molar ratio of DOPO, azobisisobutyronitrile and 4-vinylbenzaldehyde is 1:(0.01-0.1):(1-1.5).

[0019] Preferably, in step S2, the molar ratio of intermediate 1 to melamine is (3-5):1.

[0020] 3. Beneficial technical effects

[0021] The present invention uses (3-bromopropyl)trimethoxysilane and cardanol as raw materials, and obtains a cardanol-containing silane intermediate through a substitution reaction under the catalysis of potassium carbonate, and then performs a polycondensation grafting reaction on the wood powder to obtain a cardanol-modified wood powder. Using DOPO, 4-vinylbenzaldehyde, and melamine as raw materials, sequentially undergoes a phosphine hydrogenation reaction and a Schiff base reaction to obtain a DOPO-containing melamine flame retardant, and finally adds cardanol-modified wood powder, polyethylene, and a DOPO-containing melamine flame retardant to the wood powder, mixes them evenly, and performs injection molding to obtain a flame-retardant wood-plastic composite material for a pallet.

[0022] The flame-retardant wood-plastic composite material for pallets prepared by the present invention contains a DOPO structure and a melamine structure, both of which are good flame-retardant structures. Adding them to the wood-plastic composite material has excellent flame-retardant effect. In addition, it contains silicon elements, which can produce a glass-like substance when heated, adhere to the surface of the material, prevent the material from transporting substances and transferring energy with the outside world, and assist the DOPO structure and the melamine structure to jointly improve the flame-retardant performance of the material.

[0023] The flame-retardant wood-plastic composite material for pallets prepared by the present invention contains a cardanol structure, which contains a long chain and can pierce the bacterial cell membrane, causing the bacterial cytoplasm to flow out, thereby killing the bacteria. Adding the cardanol structure to the wood-plastic composite material can improve the antibacterial property of the wood-plastic composite material. The flame-retardant wood-plastic composite material for pallets prepared by the present invention has excellent flame-retardant and antibacterial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a preparation route for cardanol-containing silane intermediates;

[0025] Figure 2 The invention is a preparation route of DOPO-containing melamine flame retardant. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0027] The preparation method of maleic anhydride grafted polyethylene is as follows: under nitrogen conditions, 10g of polyethylene, 2.5g of maleic anhydride, and 0.2g of diisopropylbenzene peroxide are added to toluene solvent, stirred and dispersed, heated to 105°C, reacted for 2.5h, and after the reaction is completed, cooled to room temperature, the solvent was extracted, washed with benzene and ether in turn, and dried to obtain maleic anhydride grafted polyethylene.

[0028] The antioxidant was antioxidant 1010.

[0029] Example 1

[0030] (1) Add 4 mmol of (3-bromopropyl)trimethoxysilane to isopropanol solvent, stir and disperse, then add 20 mmol of potassium carbonate and 1 mmol of cardanol, raise the temperature to 90°C, stir and react for 12 hours. After the reaction is completed, filter and evaporate under reduced pressure to obtain a cardanol-containing silane intermediate.

[0031] (2) Add 0.2 g of the cardanol-containing silane intermediate to a 95% ethanol solution, add glacial acetic acid to adjust the pH to 3, stir evenly, and perform a hydrolysis reaction at 30°C for 2 h. Then add 20 g of wood powder, stir evenly, let it stand at room temperature for 12 h, and then dry it in an oven at 110°C for 24 h to obtain cardanol-modified wood powder.

[0032] (3) Under nitrogen conditions, 6 mmol of DOPO was dispersed in toluene solvent, and then 0.1 mmol of azobisisobutyronitrile and 8 mmol of 4-vinylbenzaldehyde were added thereto. The mixture was stirred and dispersed, and the temperature was raised to 85 °C. The reaction was carried out for 8 h. After the reaction was completed, the mixture was rotary evaporated and dried to obtain intermediate 1.

[0033] (4) Under nitrogen conditions, 15 mmol of the intermediate 1 and 5 mmol of melamine were added to a dimethyl sulfoxide solvent, the mixture was dispersed with stirring, the temperature was raised to 180°C, and the reaction was carried out for 80 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with tetrahydrofuran and deionized water in turn, and dried to obtain a DOPO-containing melamine flame retardant.

[0034] (5) Add 25 g of cardanol-modified wood powder, 80 g of polyethylene, 10 g of maleic anhydride-grafted polyethylene, 7.5 g of DOPO-containing melamine flame retardant, and 2.5 g of antioxidant to 50 g of dried wood powder, mix them evenly in a high-speed mixer at 1000 r / min, melt-knead them evenly in a torque rheometer at 180°C, and finally add them to an injection molding machine at 185°C for injection molding to obtain a flame-retardant wood-plastic composite material for pallets.

[0035] Example 2

[0036] (1) Add 5 mmol of (3-bromopropyl)trimethoxysilane to isopropanol solvent, stir and disperse, then add 24 mmol of potassium carbonate and 1 mmol of cardanol, raise the temperature to 100°C, stir and react for 10 hours. After the reaction is completed, filter and evaporate under reduced pressure to obtain a cardanol-containing silane intermediate.

[0037] (2) Add 0.4 g of the cardanol-containing silane intermediate to a 95% ethanol solution, add glacial acetic acid to adjust the pH to 4, stir evenly, and perform a hydrolysis reaction at 35°C for 3 h. Then add 20 g of wood powder, stir evenly, let it stand at room temperature for 14 h, and then dry it in an oven at 100°C for 18 h to obtain cardanol-modified wood powder.

[0038] (3) Under nitrogen conditions, 6 mmol of DOPO was dispersed in toluene solvent, and then 0.5 mmol of azobisisobutyronitrile and 8 mmol of 4-vinylbenzaldehyde were added thereto. The mixture was stirred and dispersed, and the temperature was raised to 85 °C. The reaction was carried out for 10 h. After the reaction was completed, the mixture was rotary evaporated and dried to obtain intermediate 1.

[0039] (4) Under nitrogen conditions, 24 mmol of the intermediate 1 and 5 mmol of melamine were added to a dimethyl sulfoxide solvent, the mixture was dispersed with stirring, the temperature was raised to 190°C, and the reaction was carried out for 100 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with tetrahydrofuran and deionized water in turn, and dried to obtain a DOPO-containing melamine flame retardant.

[0040] (5) Add 30 g of cardanol-modified wood powder, 80 g of polyethylene, 16 g of maleic anhydride-grafted polyethylene, 8 g of DOPO-containing melamine flame retardant, and 2 g of antioxidant to 50 g of dried wood powder, mix them evenly in a high-speed mixer at 1500 r / min, melt-knead them evenly in a torque rheometer at 175°C, and finally add them to an injection molding machine at 185°C for injection molding to obtain a flame-retardant wood-plastic composite material for pallets.

[0041] Example 3

[0042] (1) Add 6 mmol of (3-bromopropyl)trimethoxysilane to isopropanol solvent, stir and disperse, then add 16 mmol of potassium carbonate and 1 mmol of cardanol, raise the temperature to 90°C, stir and react for 18 hours. After the reaction is completed, filter and evaporate under reduced pressure to obtain a cardanol-containing silane intermediate.

[0043] (2) Add 0.6 g of the cardanol-containing silane intermediate to a 95% ethanol solution, add glacial acetic acid to adjust the pH to 4, stir evenly, and perform a hydrolysis reaction at 35°C for 2 h. Then add 20 g of wood powder and stir evenly. Let it stand at room temperature for 14 h, and then dry it in an oven at 110°C for 16 h to obtain cardanol-modified wood powder.

[0044] (3) Under nitrogen conditions, 6 mmol of DOPO was dispersed in toluene solvent, and then 0.4 mmol of azobisisobutyronitrile and 8 mmol of 4-vinylbenzaldehyde were added thereto. The mixture was stirred and dispersed, and the temperature was raised to 90 °C. The reaction was carried out for 10 h. After the reaction was completed, the mixture was rotary evaporated and dried to obtain intermediate 1.

[0045] (4) Under nitrogen conditions, 18 mmol of the intermediate 1 and 5 mmol of melamine were added to a dimethyl sulfoxide solvent, the mixture was dispersed with stirring, the temperature was raised to 190°C, and the reaction was carried out for 60 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with tetrahydrofuran and deionized water in turn, and dried to obtain a DOPO-containing melamine flame retardant.

[0046] (5) Add 40 g of cardanol-modified wood powder, 90 g of polyethylene, 17 g of maleic anhydride-grafted polyethylene, 9 g of DOPO-containing melamine flame retardant, and 2.5 g of antioxidant to 50 g of dried wood powder, mix them evenly in a high-speed mixer at 2000 r / min, melt-knead them evenly in a torque rheometer at 180°C, and finally add them to an injection molding machine at 190°C for injection molding to obtain a flame-retardant wood-plastic composite material for pallets.

[0047] Example 4

[0048] (1) Add 7 mmol of (3-bromopropyl)trimethoxysilane to isopropanol solvent, stir and disperse, then add 12 mmol of potassium carbonate and 1 mmol of cardanol, raise the temperature to 100°C, stir and react for 22 hours. After the reaction is completed, filter and evaporate under reduced pressure to obtain a cardanol-containing silane intermediate.

[0049] (2) Add 0.8 g of the cardanol-containing silane intermediate to a 95% ethanol solution, add glacial acetic acid to adjust the pH to 4, stir evenly, and perform a hydrolysis reaction at 20°C for 3 h. Then add 20 g of wood powder, stir evenly, let it stand at room temperature for 14 h, and then dry it in an oven at 100°C for 24 h to obtain cardanol-modified wood powder.

[0050] (3) Under nitrogen conditions, 6 mmol of DOPO was dispersed in toluene solvent, and then 0.2 mmol of azobisisobutyronitrile and 8 mmol of 4-vinylbenzaldehyde were added thereto. The mixture was stirred and dispersed, and the temperature was raised to 85 °C. The reaction was carried out for 12 h. After the reaction was completed, the mixture was rotary evaporated and dried to obtain intermediate 1.

[0051] (4) Under nitrogen conditions, 20 mmol of the intermediate 1 and 5 mmol of melamine were added to a dimethyl sulfoxide solvent, the mixture was dispersed with stirring, the temperature was raised to 180°C, and the reaction was carried out for 90 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with tetrahydrofuran and deionized water in turn, and dried to obtain a DOPO-containing melamine flame retardant.

[0052] (5) Add 45 g of cardanol-modified wood powder, 70 g of polyethylene, 15 g of maleic anhydride-grafted polyethylene, 9.5 g of DOPO-containing melamine flame retardant, and 2 g of antioxidant to 50 g of dried wood powder, mix them evenly in a high-speed mixer at 2000 r / min, melt-knead them evenly in a torque rheometer at 180°C, and finally add them to an injection molding machine at 185°C for injection molding to obtain a flame-retardant wood-plastic composite material for pallets.

[0053] Example 5

[0054] (1) Add 8 mmol of (3-bromopropyl)trimethoxysilane to isopropanol solvent, stir and disperse, then add 24 mmol of potassium carbonate and 1 mmol of cardanol, raise the temperature to 80°C, stir and react for 24 hours. After the reaction is completed, filter and evaporate under reduced pressure to obtain a cardanol-containing silane intermediate.

[0055] (2) Add 1 g of the cardanol-containing silane intermediate to a 95% ethanol solution, add glacial acetic acid to adjust the pH to 3, stir evenly, and perform a hydrolysis reaction at 35°C for 3 h. Then add 20 g of wood powder, stir evenly, let it stand at room temperature for 10 h, and then dry it in an oven at 110°C for 20 h to obtain cardanol-modified wood powder.

[0056] (3) Under nitrogen conditions, 6 mmol of DOPO was dispersed in toluene solvent, and then 0.6 mmol of azobisisobutyronitrile and 8 mmol of 4-vinylbenzaldehyde were added thereto. The mixture was stirred and dispersed, and the temperature was raised to 90 °C. The reaction was carried out for 10 h. After the reaction was completed, the mixture was rotary evaporated and dried to obtain intermediate 1.

[0057] (4) Under nitrogen conditions, 18 mmol of the intermediate 1 and 5 mmol of melamine were added to a dimethyl sulfoxide solvent, the mixture was dispersed with stirring, the temperature was raised to 180°C, and the reaction was carried out for 100 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with tetrahydrofuran and deionized water in turn, and dried to obtain a DOPO-containing melamine flame retardant.

[0058] (5) Add 50 g of cardanol-modified wood powder, 80 g of polyethylene, 10 g of maleic anhydride-grafted polyethylene, 10 g of DOPO-containing melamine flame retardant, and 2 g of antioxidant to 50 g of dried wood powder, mix them evenly in a high-speed mixer at 2000 r / min, melt-knead them evenly in a torque rheometer at 175°C, and finally add them to an injection molding machine at 190°C for injection molding to obtain a flame-retardant wood-plastic composite material for pallets.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that no cardanol-modified wood powder is added in step (5).

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that no DOPO-containing melamine flame retardant is added in step (5).

[0063] The material is tested to UL-94 using a vertical burning tester.

[0064] Use an oxygen index tester to test the LOI of a material.

[0065]

[0066] It can be seen from the table that the wood-plastic composite material prepared by the present invention has excellent flame retardant effect.

[0067] The mechanical properties of materials were tested using an electronic universal testing machine.

[0068]

[0069] It can be seen from the table that the mechanical properties of the wood-plastic composite materials of Examples 1-5 and Comparative Example 2 are better than those of the wood-plastic composite material of Comparative Example 1. This is because they contain cardanol-modified wood powder, and the cardanol contained therein is a flexible long chain that can improve the mechanical properties of the material. In addition, the cardanol-modified wood powder can improve the compatibility of wood powder with polyethylene, thereby further improving the mechanical properties of the material.

[0070] The antibacterial properties of the materials were tested according to GB / T31402-2015 standard, and the tested bacteria were Escherichia coli and Staphylococcus aureus.

[0071]

[0072] It can be seen from the table that the wood-plastic composite material prepared by the present invention has relatively excellent antibacterial properties.

[0073] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A flame retardant wood-plastic composite material for pallets, characterized in that: The preparation method is as follows: (1) Add the cardanol-containing silane intermediate to a 95% ethanol solution, add glacial acetic acid thereto to adjust the pH to 3-4, stir evenly, carry out a hydrolysis reaction at 20-35°C for 1-3 hours, then add wood powder thereto and stir evenly, wherein the mass ratio of the cardanol-containing silane intermediate to the wood powder is (1-5):100, let stand at room temperature for 10-16 hours, and then place in an oven at 100-110°C to dry for 15-24 hours to obtain cardanol-modified wood powder. The preparation method of the cardanol-containing silane intermediate comprises: adding (3-bromopropyl)trimethoxysilane to an isopropanol solvent, stirring and dispersing, and then adding potassium carbonate and cardanol thereto, wherein the molar ratio of (3-bromopropyl)trimethoxysilane, potassium carbonate, and cardanol is (4-8): (12-24): 1, heating to 80-100° C., stirring and reacting for 10-24 hours, filtering after the reaction is completed, and performing vacuum rotary evaporation to obtain the cardanol-containing silane intermediate; (2) Adding cardanol modified wood powder, polyethylene, maleic anhydride grafted polyethylene, DOPO melamine flame retardant, and antioxidant to the dried wood powder, wherein the mass ratio of wood powder, cardanol modified wood powder, polyethylene, maleic anhydride grafted polyethylene, DOPO melamine flame retardant, and antioxidant is 100: (50-100): (120-180): (20-35): (15-20): (1-5), mixing uniformly in a high-speed mixer at 1000-2000 r / min, melting and kneading uniformly in a torque rheometer at 170-180° C., and finally adding it to an injection molding machine at 180-190° C. for injection molding to obtain a flame-retardant wood-plastic composite material for a pallet. The preparation method of the DOPO melamine flame retardant is as follows: S1. Under nitrogen conditions, DOPO is dispersed in a toluene solvent, and then azobisisobutyronitrile and 4-vinylbenzaldehyde are added thereto, wherein the molar ratio of DOPO, azobisisobutyronitrile and 4-vinylbenzaldehyde is 1:(0.01-0.1):(1-1.5), and the mixture is stirred and dispersed, and the temperature is raised to 80-90°C, and the reaction is carried out for 6-12 hours. After the reaction is completed, the mixture is rotary evaporated and dried to obtain an intermediate 1; S2. Under nitrogen conditions, add intermediate 1 and melamine to dimethyl sulfoxide solvent, wherein the molar ratio of intermediate 1 to melamine is (3-5):1, stir and disperse, heat to 170-190°C, react for 60-100 hours, and after the reaction is completed, cool to room temperature, filter, wash with tetrahydrofuran and deionized water in turn, and dry to obtain a DOPO-containing melamine flame retardant.

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