A wood-plastic board based on hydrophobically modified wood powder and preparation method thereof

Abstract

The invention belongs to the field of composite materials, and discloses a wood-plastic board based on hydrophobically modified wood powder, comprising polypropylene, polystyrene, SBS elastomer, and wood powder; the wood powder is hydrophobically modified wood powder; the preparation method of the wood powder is as follows: untreated wood powder, maleic anhydride, and water are mixed for primary grafting; the wood powder after the primary grafting is secondary grafted with a fluorine-containing unsaturated monomer to obtain hydrophobically modified wood powder; the mass ratio of the polypropylene, polystyrene, SBS elastomer, and hydrophobically modified wood powder is 60-80:5-10:1-3:25. The wood-plastic board improves the compatibility of the wood powder and the polymer by hydrophobically modifying the wood powder, improves the mechanical properties of the board, and can also increase Tp and Tf, thereby improving the high temperature resistance of the wood-plastic board. At the same time, the invention also provides a preparation method of the wood-plastic board.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to a wood-plastic board based on hydrophobically modified wood powder and a preparation method thereof. Background Art

[0002] CN116694096A discloses an antistatic plastic-wood material and a preparation method thereof, which uses silane to hydrophobically modify kaolin to improve the anti-agglomeration performance of antimony tin oxide in paraffin, thereby improving the dispersion performance of the stabilizer of the wood-plastic material and improving the quality of the board.

[0003] CN110229537B discloses a flame-retardant plastic-wood composite material with excellent boiling resistance and a preparation method thereof. The composite material provided by the present invention is mainly prepared by using 15-35 weight parts of hydrophobic flame-retardant wood powder, 12-22 weight parts of polyperfluoroethylene-propylene resin, 10-20 weight parts of polyvinyl chloride resin, 15-32 weight parts of brominated epoxy resin, 8-18 weight parts of hydrophobic light calcium carbonate, 3-9 weight parts of compatibilizer and 0.5-3 weight parts of auxiliary agent.

[0004] Its hydrophobic flame-retardant wood powder is hydrophobically modified with trimethylolmelamine resin, 5-bromo-2-fluorobenzoic acid and catalyst tetrabutyl titanate, which gives the wood powder hydrophobicity and flame retardancy.

[0005] As is well known in the art, wood powder has a large amount of hydroxyl groups and is highly hydrophilic because it contains a large amount of cellulose and hemicellulose. The lignin in the wood powder is a hydrophobic material, but due to the limited content of lignin, the wood powder is generally hydrophilic.

[0006] The main material of wood-plastic materials is plastic, so improving the compatibility of wood powder and wood-plastic materials is an effective way to improve the performance of wood.

[0007] At the same time, wood-plastic materials also need to consider flame retardancy and high temperature resistance.

[0008] In this application project, the customer requires the wood-plastic material to have good high temperature resistance and mechanical properties. Summary of the invention

[0009] In view of the shortcomings of the prior art, the object of the present invention is to provide a wood-plastic board based on hydrophobically modified wood powder, which improves the compatibility of wood powder and polymer and improves the mechanical properties of the board by hydrophobically modifying the wood powder. At the same time, Tp and Tf can be increased, thereby improving the high temperature resistance of the wood-plastic board.

[0010] At the same time, the invention also provides a method for preparing the wood-plastic board.

[0011] To achieve the purpose of the invention, the present invention adopts the following technical scheme: a wood-plastic board based on hydrophobically modified wood powder, comprising polypropylene, polystyrene, SBS elastomer, and wood powder;

[0012] The wood powder is hydrophobically modified wood powder;

[0013] The preparation method of the wood powder is as follows:

[0014] Mix untreated wood powder, maleic anhydride and water for primary grafting;

[0015] The wood powder after the primary grafting is grafted with a fluorine-containing unsaturated monomer for a secondary grafting to obtain a hydrophobically modified wood powder;

[0016] The mass ratio of the polypropylene, polystyrene, SBS elastomer and hydrophobically modified wood powder is 60-80:5-10:1-3:25.

[0017] In the above-mentioned wood-plastic board based on hydrophobically modified wood powder, the fluorine-containing unsaturated monomer is one or more combinations of perfluorohexyl ethyl acrylate, 2-(perfluorohexyl)ethyl methacrylate, hexafluorobutyl methacrylate, and octafluoropentyl acrylate.

[0018] In the above-mentioned wood-plastic board based on hydrophobically modified wood powder, the primary grafting method is:

[0019] 100 parts by weight of wood powder, 1 to 5 parts by weight of maleic anhydride, and 100 to 300 g of water are mixed, heated to 60 to 80° C., stirred and mixed for 5 to 10 minutes, and then dried.

[0020] In the above-mentioned wood-plastic board based on hydrophobically modified wood powder, the secondary grafting method is:

[0021] The wood powder after the primary grafting, the organic solvent and the emulsifier are mixed, heated to the solvent reflux temperature, the fluorine-containing unsaturated monomer is added dropwise to the reaction system, and the mixture is stirred for 1 to 3 hours, and the solvent is recovered to obtain the hydrophobically modified wood powder.

[0022] In the above-mentioned wood-plastic board based on hydrophobically modified wood powder, the organic solvent is one or more combinations of n-hexane, benzene, and cyclohexane; the emulsifier is one or more combinations of sorbitan fatty acid esters, polyglycerol fatty acid esters, and polyoxyethylene fatty acid esters.

[0023] In the above-mentioned wood-plastic board based on hydrophobically modified wood powder, the weight ratio of the untreated wood powder, the organic solvent, and the fluorine-containing unsaturated monomer is 100:500-1000:1-5; the weight ratio of the untreated wood powder and the emulsifier is 100:10-15.

[0024] The preparation method of the hydrophobically modified wood powder-based wood plastic board is as follows: polypropylene, polystyrene, SBS elastomer, and hydrophobically modified wood powder are added into a twin-screw extruder for extrusion granulation.

[0025] In the above-mentioned method for preparing a wood-plastic board based on hydrophobically modified wood powder, the temperature of the twin-screw extruder is 140 to 170°C, and the outlet die temperature is 175°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention improves the compatibility of wood powder and polymer by hydrophobic modification of wood powder, improves the mechanical properties of the board, and can also increase Tp and Tf, thereby improving the high temperature resistance of the wood-plastic board. In addition, by introducing a small amount of elastomeric material, the elastic modulus of wood can be effectively improved, the crystallization rate can be reduced, and the shrinkage resistance of the material can be improved. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0029] Part I: Hydrophobic modification of wood flour

[0030] Example

[0031] Step 1: Mix wood powder, maleic anhydride and water, heat to 70°C, stir at 800r / min for 10 minutes, and then dry.

[0032] Step 2: Mix the once grafted wood powder obtained in step 1 with n-hexane and an emulsifier, heat to the solvent reflux temperature (80-85°C), mix the fluorine-containing unsaturated monomer and part of the n-hexane and add dropwise to the reaction system, stir for 1 to 3 hours, recover the n-hexane, and then repeatedly wash the wood powder with n-hexane, dry the wood powder, and obtain hydrophobically modified wood powder.

[0033] The wood powder is poplar wood powder, with a particle size of 80 mesh and a moisture content of less than 3%;

[0034] The amounts of the substances in the examples are shown in Table 1 below, where the unit is g.

[0035] Table 1 Recipe

[0036]

[0037]

[0038] Comparative Example 1

[0039] Mix wood powder, maleic anhydride and water, heat to 70°C, stir at 800 r / min for 10 minutes, and then dry. The weight ratio of wood powder, maleic anhydride and water is 100:3:200; the wood powder raw material is the same as in the example.

[0040] Comparative Example 2

[0041] The process is substantially the same as Example 1, except that the fluorine-containing unsaturated monomer is replaced by methyl methacrylate.

[0042] Comparative Example 3

[0043] The method is substantially the same as Example 1, except that the fluorine-containing unsaturated monomer is replaced by octadecyl acrylate.

[0044] Part 2 Preparation of Wood Plastic Board

[0045] Plate Examples and Comparative Examples

[0046] Polypropylene, polystyrene, SBS elastomer, and hydrophobically modified wood flour are added into a twin-screw extruder for extrusion granulation. The temperature of the twin-screw extruder is 140 to 170° C., and the outlet die temperature is 175° C.

[0047] The granules obtained by granulation are re-melted and extruded through a single-screw extruder and matched with the shape of the outlet die required by the customer to extrude a sheet.

[0048] The specifications of polypropylene are: K7726, Sinopec Yanshan;

[0049] Polystyrene: 143E GPPS, Yangzi Petrochemical.

[0050] SBS elastomer: 4303, Yanshan Petrochemical.

[0051] The amounts of the various materials used in the plate examples and comparative examples are shown in Table 2 below, where the unit in Table 2 is g.

[0052] Table 2 Recipe

[0053]

[0054] Part III Performance Test

[0055] Performance test 1: flexural strength, test standard: GB / T 9341;

[0056] Performance test 2: Melting peak temperature Tp (melting peak temp)

[0057] Performance test 3: Viscous flow transition temperature Tf (return to baseline temp);

[0058] Performance tests 2 and 3 were conducted using the method shown in ASTM E794-06 (2018);

[0059] The test results refer to Table 3;

[0060] Table 3 Test results

[0061] Bending strength MPa Tp℃ Tf℃ Plate Example 1 109.6 165.1 178.3 Plate Example 2 106.7 163.2 176.6 Plate Example 3 108.8 158.0 171.3 Plate Example 4 112.4 169.7 180.5 Plate Example 5 115.3 168.9 181.4 Plate Comparison Example 1 98.1 159.4 170.2 Plate Comparison Example 2 98.5 167.3 178.8 Plate Comparison Example 3 101.2 156.7 168.9 Plate Comparison Example 4 95.9 156.2 169.1 Plate Comparison Example 5 98.2 159.2 172.4 Plate Comparative Example 6 102.3 158.3 171.4 Plate Comparison Example 7 83.1 152.4 166.8

[0062] Result analysis:

[0063] 1. It can be seen from the above-mentioned board examples 1-5 and board comparative examples 4-7 that the hydrophobic modification of the wood powder of the present invention improves the strength and high temperature resistance of the board. The reason is that more effective hydrophobic modification and whether hydrophobic modification affects the performance of the product. It can be seen from board comparative examples 5 and 6 that the performance of the board using short-chain or long-chain hydrophobic groups is improved compared with blank wood powder or wood powder that has been modified once, but the improvement is not as good as the improvement of using unsaturated fluorine-containing monomers. The possible reason is that in the secondary modification process, the modification process is a free radical polymerization reaction initiated under high temperature. By adopting the dripping method, the added monomer can be partially polymerized and grafted with the maleic anhydride on the wood powder, and part of the subsequently added monomer continues to polymerize to increase the molecular weight; by constructing a long-chain fluorine-containing structure, the wood powder can be given a super-hydrophobic effect. Compared with other hydrophobic monomers, its hydrophobic property is more excellent and can be better compatible with polymer materials; particularly preferably, the hydrophobic modifier with a F atom content of less than 10 has a more obvious effect on the bending strength and high temperature resistance. The possible reason is that too many F atoms are not conducive to continuous polymerization and grafting, resulting in the theoretical hydrophobicity of the board examples 1-3 being inferior to that of examples 4 and 5;

[0064] Polystyrene plays an auxiliary role in reinforcing many plastics, so adding polystyrene to wood-plastic boards can improve the strength of the boards;

[0065] SBS elastomer material can not only improve the elastic modulus of the board, but also improve the structural strength of polypropylene when used in combination with polystyrene. At the same time, due to its triblock structure, SBS is better compatible with organic fluorine than polystyrene and polypropylene, thereby enhancing the compatibility of wood powder and polypropylene. The compatibility of hydrophobically modified wood powder is significantly improved compared to that of non-hydrophobically modified wood powder. Under the action of SBS elastomer, its compatibility is better, which is ultimately manifested in that in the absence of SBS, the bending strength of the board of Example 3 is significantly reduced.

[0066] 2. In the tests of Tp and Tf, board comparison example 7 showed a lower temperature. Due to the poor compatibility between wood powder and polypropylene, it showed a lower temperature characteristic. In the relevant tests of the present invention, the relevant temperature characteristics and structural strength are correlated. Therefore, it can be considered that the compatibility of wood powder and polymer determines the temperature performance and strength performance.

Claims

1. A wood-plastic board based on hydrophobically modified wood powder, characterized in that: Including polypropylene, polystyrene, SBS elastomer, wood flour; The wood powder is hydrophobically modified wood powder; The preparation method of the wood powder is as follows: Mix untreated wood powder, maleic anhydride and water for primary grafting; The wood powder after the primary grafting is grafted with a fluorine-containing unsaturated monomer for a secondary grafting to obtain a hydrophobically modified wood powder; The mass ratio of the polypropylene, polystyrene, SBS elastomer and hydrophobically modified wood powder is 60-80:5-10:1-3:25; The fluorine-containing unsaturated monomer is one or more combinations of perfluorohexyl ethyl acrylate, 2-(perfluorohexyl) ethyl methacrylate, hexafluorobutyl methacrylate, and octafluoropentyl acrylate; The method of the primary grafting is: Mix 100 parts by weight of wood flour, 1 to 5 parts by weight of maleic anhydride, and 100 to 300 g of water, heat to 60 to 80° C., stir and mix for 5 to 10 minutes, and then dry; The method of the secondary grafting is: The wood powder after the primary grafting, the organic solvent and the emulsifier are mixed, heated to the solvent reflux temperature, the fluorine-containing unsaturated monomer is added dropwise to the reaction system, and the mixture is stirred for 1 to 3 hours, and the solvent is recovered to obtain the hydrophobically modified wood powder.

2. The wood-plastic board based on hydrophobically modified wood powder according to claim 1, characterized in that: The organic solvent is one or more combinations of n-hexane, benzene and cyclohexane; the emulsifier is one or more combinations of sorbitan fatty acid ester, polyglycerol fatty acid ester and polyoxyethylene fatty acid ester.

3. The wood-plastic board based on hydrophobically modified wood powder according to claim 1, characterized in that: The weight ratio of the untreated wood powder, the organic solvent and the fluorine-containing unsaturated monomer is 100:500-1000:1-5; the weight ratio of the untreated wood powder and the emulsifier is 100:10-15.

4. The method for preparing a wood-plastic board according to any one of claims 1 to 3, characterized in that: The method specifically comprises the following steps: adding polypropylene, polystyrene, SBS elastomer and hydrophobically modified wood powder into a twin-screw extruder for extrusion granulation.

5. The method for preparing the wood-plastic board according to claim 4, characterized in that: The temperature of the twin-screw extruder was 140 to 170°C, and the exit die temperature was 175°C.

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