A wood-plastic composite environmental protection flame-retardant plywood and its preparation method

Abstract

The present invention relates to the technical field of plywood, and discloses a wood-plastic composite environmentally friendly flame-retardant plywood and a preparation method. The wood board is treated with a sodium hydroxide solution as a substrate, and phosphorus-containing maleic anhydride grafted polyethylene is used as an adhesive. After assembling the billets and hot pressing, the wood-plastic composite environmentally friendly flame-retardant plywood is obtained. During the surface treatment of the wood veneer with the sodium hydroxide solution, it can promote the reaction between the hydroxyl groups in the cellulose on the wood board surface and the anhydride groups of the phosphorus-containing maleic anhydride grafted polyethylene, thereby enhancing the interfacial interaction force between the polyethylene film adhesive and the wood veneer, improving the bonding strength of the wood-plastic composite plywood. Moreover, the phenyl phosphate group contained in the polyethylene film adhesive serves as a phosphorus-containing flame retardant, which can promote the dehydration and carbonization of the plywood substrate during combustion, reduce the heat release rate and total heat release amount during combustion, inhibit the combustion process, and play a good flame-retardant role.

Description

Technical Field

[0001] The present invention relates to the technical field of plywood, and specifically to a wood-plastic composite environmentally friendly flame-retardant plywood and a preparation method thereof. Background Art

[0002] Plywood has a wide range of applications in the fields of interior decoration, furniture building materials, construction industry, etc. Wood-plastic composite plywood is an environmentally friendly material manufactured on the basis of the traditional plywood production process, with wood veneer as the matrix and plastics such as polyethylene as the binder, through hot pressing and other methods. For example, the literature "Effect of Silane Coupling Agent on the Properties of High-Density Polyethylene Film / Poplar Plywood" reported that vinyltrimethoxysilane A-171 was used to pretreat poplar veneer, and then it was compounded with high-density polyethylene film to prepare plywood, which improved the interfacial compatibility between the veneer and HDPE and enhanced the bonding strength and other properties of the plywood.

[0003] Traditional plywood is a flammable material and is prone to causing fires. Therefore, improving the flame retardancy of plywood is of great significance. For example, the literature "Synthesis of Melamine-Modified Urea-Formaldehyde Resin and Its Application in Flame-Retardant Plywood" reported that a flame-retardant adhesive was obtained by blending melamine-modified urea-formaldehyde resin and ammonium polyphosphate, etc., and surface treatment of plywood had good flame-retardant properties. The present invention prepares a novel phosphorus-containing maleic anhydride-grafted polyethylene film as an adhesive, and through hot pressing with wood veneer treated with sodium hydroxide solution, a wood-plastic composite environmentally friendly flame-retardant plywood with high bonding strength and good flame-retardant properties is obtained. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a wood-plastic composite environmentally friendly flame-retardant plywood with high bonding strength and good flame-retardant properties.

[0006] (II) Technical Solutions

[0007] To achieve the above object, the present invention provides the following technical solutions: A wood-plastic composite environmentally friendly flame-retardant plywood, characterized in that: the wood-plastic composite environmentally friendly flame-retardant plywood is prepared by treating a wooden board with a sodium hydroxide solution, and then using a phosphorus-containing maleic anhydride-grafted polyethylene film as an adhesive, through assembling the billets and hot pressing.

[0008] Preferably, the ratio of the dosage of the phosphorus-containing maleic anhydride-grafted polyethylene film to the single-sided area of the wooden board is 100 - 250 g / m 2 .

[0009] Preferably, the preparation method of the wood-plastic composite environmentally friendly flame-retardant plywood is characterized in that: the preparation method includes the following steps:

[0010] S1: Immerse the wooden board in an aqueous sodium hydroxide solution, soak at room temperature and stir for 1 - 3 h, then wash the wooden board with water and dry it to obtain an alkali-treated wooden board.

[0011] S2: Use a phosphorus-containing maleic anhydride grafted polyethylene film as an adhesive, assemble and hot-press it with the alkali-treated wooden board, the pressure is 1 - 2 MPa, the hot-pressing temperature is 150 - 180 °C, and the hot-pressing time is 5 - 8 min to obtain a wood-plastic composite environmentally friendly flame-retardant plywood.

[0012] Preferably, the mass fraction of the aqueous sodium hydroxide solution is 5 - 15%.

[0013] Preferably, the preparation method of the phosphorus-containing maleic anhydride grafted polyethylene film includes the following steps:

[0014] S3: Dissolve 5-hydroxyisophthalic acid and dimethylphosphoryl chloride in a solvent, then dropwise add triethylamine, stir and react at room temperature for 4 - 12 h, filter and concentrate under reduced pressure after the reaction, wash with petroleum ether, and recrystallize the crude product in ethanol to obtain 5-phosphorylisophthalic acid;

[0015]

[0016] S4: Add 5-phosphorylisophthalic acid, allyl bromide and cesium carbonate to N,N-dimethylformamide, stir evenly and react at 20 - 40 °C for 18 - 48 h, add distilled water and ethyl acetate for extraction after the reaction, concentrate the organic phase under reduced pressure, wash with petroleum ether, and recrystallize the crude product in ethyl acetate to obtain 5-phosphorylisophthalic acid bis(allyl methyl ester);

[0017]

[0018] S5: Add phosphorus-containing isophthalic acid bis(allyl methyl ester), maleic anhydride, styrene, diisopropylbenzene peroxide, and polyethylene resin with a mass ratio of 2 - 8:3 - 8:5 - 12:0.3 - 0.8:100 to an extruder, melt-graft, extrude, and blow into a film to obtain a phosphorus-containing maleic anhydride grafted polyethylene.

[0019] Preferably, the molar ratio of 5-hydroxyisophthalic acid, methylphosphoryl chloride, and triethylamine in S3 is 1:1 - 1.4:2 - 3.

[0020] Preferably, the solvent in S3 includes toluene, tetrahydrofuran, ethyl acetate, dichloromethane or chloroform.

[0021] Preferably, the molar ratio of 5-phosphorylisophthalic acid, allyl bromide and cesium carbonate in S4 is 1:2 - 2.5:2.5 - 4.

[0022] (III) Beneficial technical effects

[0023] Using 5-hydroxyisophthalic acid and dimethylphosphoryl chloride as raw materials, a 5-phosphoryl group isophthalic acid intermediate is synthesized. Then, under the catalysis of cesium carbonate, it reacts with allyl bromide to obtain a 5-phosphoryl group isophthalic acid bis(allyl methyl ester) monomer. It undergoes melt grafting with styrene, maleic anhydride, and polyethylene. The 5-phosphoryl group isophthalic acid bis(allyl methyl ester) contains diallyl functional groups, which can increase the grafting sites with polyethylene, improve the reaction rate and grafting rate, and thus obtain a phosphorus-containing maleic anhydride grafted polyethylene with a high grafting rate.

[0024] Treating a wooden board with a sodium hydroxide solution as the substrate and using phosphorus-containing maleic anhydride grafted polyethylene as the adhesive, through blanketing and hot pressing treatments, a wood-plastic composite environmentally friendly flame-retardant plywood is obtained. During the surface treatment of the wood veneer with a sodium hydroxide solution, it can promote the reaction between the hydroxyl groups in the cellulose on the wood board surface and the anhydride groups of the phosphorus-containing maleic anhydride grafted polyethylene, thereby enhancing the interfacial interaction force between the polyethylene film adhesive and the wood veneer, improving the bonding strength of the wood-plastic composite plywood. Moreover, the phenyl phosphate group contained in the polyethylene film adhesive as a phosphorus-containing flame retardant can promote the dehydration and carbonization of the plywood substrate during combustion, reduce the heat release rate and total heat release amount during combustion, inhibit the combustion process, and play a good flame-retardant role. Specific embodiments

[0025] Example 1

[0026] (1) Dissolve 2 mmol of 5-hydroxyisophthalic acid and 2 mmol of dimethylphosphoryl chloride in dichloromethane solvent, then dropwise add 5 mmol of triethylamine, stir and react at room temperature for 12 h. After the reaction, filter and concentrate under reduced pressure, wash with petroleum ether, and recrystallize the crude product in ethanol to obtain 5-phosphoryl group isophthalic acid.

[0027] (2) Add 4 mmol of 5-phosphoryl group isophthalic acid, 8 mmol of allyl bromide, and 10 mmol of cesium carbonate to N,N-dimethylformamide, stir evenly and react at 40 °C for 24 h. After the reaction, add distilled water and ethyl acetate for extraction, concentrate the organic phase under reduced pressure, wash with petroleum ether, and recrystallize the crude product in ethyl acetate to obtain 5-phosphoryl group isophthalic acid bis(allyl methyl ester).

[0028] (3) Add 1 g of phosphoryl group isophthalic acid bis(allyl methyl ester), 1.5 g of maleic anhydride, 2.5 g of styrene, 0.15 g of diisopropylbenzene peroxide, and 50 g of polyethylene resin to an extruder, melt graft at 180 °C for 6 min, extrude, and blow into a film to obtain phosphorus-containing maleic anhydride grafted polyethylene.

[0029] (4) Immerse the poplar board with dimensions of 2000 mm × 1200 mm × 2 mm into a 15% sodium hydroxide aqueous solution, soak at room temperature and stir for 2 h, then wash the board with water and dry it to obtain the alkali-treated board.

[0030] (5) Use the phosphorus-containing maleic anhydride grafted polyethylene film as the adhesive, perform blanketing and hot pressing with the alkali-treated board, the pressure is 1 MPa, the hot pressing temperature is 180 °C, and the hot pressing time is 5 min to make a three-layer structured wood-plastic composite environmentally friendly flame-retardant plywood, where the dosage ratio of the phosphorus-containing maleic anhydride grafted polyethylene film to the single-sided area of the board is 100 g / m 2 .

[0031] Example 2

[0032] (1) Dissolve 2 mmol of 5-hydroxyisophthalic acid and 2.8 mmol of dimethylphosphoryl chloride in toluene solvent, then dropwise add 6 mmol of triethylamine, stir and react at room temperature for 4 h, filter and concentrate under reduced pressure after the reaction, wash with petroleum ether, and recrystallize the crude product in ethanol to obtain 5-phosphorylisophthalic acid.

[0033] (2) Add 4 mmol of 5-phosphorylisophthalic acid, 10 mmol of allyl bromide and 12 mmol of cesium carbonate to N,N-dimethylformamide, stir evenly and react at 30 °C for 18 h, add distilled water and ethyl acetate for extraction after the reaction, concentrate the organic phase under reduced pressure, wash with petroleum ether, and recrystallize the crude product in ethyl acetate to obtain 5-phosphorylisophthalic acid bis(allyl methyl ester).

[0034] (3) Add 2 g of phosphorylisophthalic acid bis(allyl methyl ester), 2 g of maleic anhydride, 4 g of styrene, 0.3 g of diisopropylbenzene peroxide, and 50 g of polyethylene resin to an extruder, melt and graft at 180 °C for 6 min, extrude and blow into a film to obtain phosphorus-containing maleic anhydride grafted polyethylene.

[0035] (4) Immerse the poplar board with dimensions of 2000 mm × 1200 mm × 2 mm into a 5% sodium hydroxide aqueous solution, soak at room temperature and stir for 3 h, then wash the board with water and dry it to obtain the alkali-treated board.

[0036] (5) Use the phosphorus-containing maleic anhydride grafted polyethylene film as the adhesive, perform blanketing and hot pressing with the alkali-treated board, the pressure is 2 MPa, the hot pressing temperature is 160 °C, and the hot pressing time is 8 min to make a three-layer structured wood-plastic composite environmentally friendly flame-retardant plywood, where the dosage ratio of the phosphorus-containing maleic anhydride grafted polyethylene film to the single-sided area of the board is 200 g / m 2 .

[0037] Example 3

[0038] (1) Dissolve 2 mmol of 5-hydroxyisophthalic acid and 2.8 mmol of dimethylphosphoryl chloride in a tetrahydrofuran solvent, then add dropwise 6 mmol of triethylamine, stir and react at room temperature for 4 h. After the reaction, filter and concentrate under reduced pressure, wash with petroleum ether, and recrystallize the crude product in ethanol to obtain 5-phosphatylisophthalic acid.

[0039] (2) Add 4 mmol of 5-phosphatylisophthalic acid, 8 mmol of allyl bromide, and 10 mmol of cesium carbonate to N,N-dimethylformamide, stir evenly and react at 40 °C for 18 h. After the reaction, add distilled water and extract with ethyl acetate. Concentrate the organic phase under reduced pressure, wash with petroleum ether, and recrystallize the crude product in ethyl acetate to obtain 5-phosphatylisophthalic acid bis(allyl methyl ester).

[0040] (3) Add 4 g of phosphatylisophthalic acid bis(allyl methyl ester), 4 g of maleic anhydride, 6 g of styrene, 0.4 g of diisopropylbenzene peroxide, and 50 g of polyethylene resin to an extruder, melt and graft at 180 °C for 6 min, extrude, and blow into a film to obtain phosphorus-containing maleic anhydride grafted polyethylene.

[0041] (4) Immerse a poplar board with dimensions of 2000 mm×1200 mm×2 mm in a 10% aqueous sodium hydroxide solution, soak and stir at room temperature for 2 h, then wash the board with water and dry to obtain an alkali-treated board.

[0042] (5) Use the phosphorus-containing maleic anhydride grafted polyethylene film as an adhesive, perform blanking and hot pressing with the alkali-treated board, the pressure is 2 MPa, the hot pressing temperature is 150 °C, and the hot pressing time is 8 min to make a three-layer structured wood-plastic composite environmentally friendly flame-retardant plywood, where the dosage of the phosphorus-containing maleic anhydride grafted polyethylene film and the single-sided area of the board is 200 g / m 2 .

[0043] Example 4

[0044] (1) Dissolve 2 mmol of 5-hydroxyisophthalic acid and 2.5 mmol of dimethylphosphoryl chloride in an ethyl acetate solvent, then add dropwise 5 mmol of triethylamine, stir and react at room temperature for 4 h. After the reaction, filter and concentrate under reduced pressure, wash with petroleum ether, and recrystallize the crude product in ethanol to obtain 5-phosphatylisophthalic acid.

[0045] (2) 4 mmol of 5-phosphonatoisophthalic acid, 9 mmol of allyl bromide, and 16 mmol of cesium carbonate were added to N,N-dimethylformamide. After stirring evenly, the reaction was carried out at 30 °C for 48 h. After the reaction, distilled water and ethyl acetate were added for extraction. The organic phase was concentrated under reduced pressure, washed with petroleum ether, and the crude product was recrystallized in ethyl acetate to obtain 5-phosphonatoisophthalic acid bis(allyl methyl ester).

[0046] (3) 4 g of phosphonatoisophthalic acid bis(allyl methyl ester), 3.2 g of maleic anhydride, 5 g of styrene, 0.3 g of diisopropylbenzene peroxide, and 50 g of polyethylene resin were added to an extruder. The mixture was melt-grafted at 180 °C for 6 min, extruded, and blown into a film to obtain phosphorus-containing maleic anhydride-grafted polyethylene.

[0047] (4) Poplar boards with dimensions of 2000 mm × 1200 mm × 2 mm were immersed in a 5-15% aqueous sodium hydroxide solution, soaked at room temperature and stirred for 1 h, then the boards were washed with water and dried to obtain alkali-treated boards.

[0048] (5) Using the phosphorus-containing maleic anhydride-grafted polyethylene film as an adhesive, it was assembled with the alkali-treated boards and subjected to hot pressing. The pressure was 2 MPa, the hot pressing temperature was 160 °C, and the hot pressing time was 8 min to make a three-layer-structured wood-plastic composite environmentally friendly flame-retardant plywood. The dosage of the phosphorus-containing maleic anhydride-grafted polyethylene film was in a ratio of 250 g / m to the single-sided area of the board. 2 。

[0049] Comparative Example 1

[0050] (1) Using a polyethylene film as an adhesive, it was assembled with poplar boards with dimensions of 2000 mm × 1200 mm × 2 mm and subjected to hot pressing. The pressure was 1.5 MPa, the hot pressing temperature was 170 °C, and the hot pressing time was 8 min to make a three-layer-structured plywood. The dosage of the polyethylene film was in a ratio of 200 g / m to the single-sided area of the board. 2 。

[0051] Referring to the GB / T 9846-2015 "General Plywood" standard, a CM12-type plywood universal testing machine was used to measure the bonding strength of the plywood.

[0052] The plywood was made into square specimens with a length of 2 cm and a width of 2 cm, and a microcalorimeter was used to measure the flame retardancy. The heat radiation power was 35 kW / m 2 。

[0053] Gluing strength (MPa) <![CDATA[Peak heat release rate HRR (kW / m 2 ).]]> <![CDATA[Total Heat Release THR (MJ / m 2 )]]> Example 1 1.21 102.4 13.6 Example 2 1.32 85.8 12.9 Example 3 1.06 80.6 12.5 Example 4 0.95 78.0 12.2 Comparative Example 1 0.83 130.5 15.8

[0054] After the poplar board is treated with sodium hydroxide solution, using the phosphorus-containing maleic anhydride grafted polyethylene film as an adhesive, the maximum gluing strength of the obtained plywood is 1.12 MPa, the peak value of the heat release rate drops to 78.0 kW / m 2 , and the total heat release amount drops to 12.2 MJ / m 2 .

Claims

1. A wood-plastic composite environmentally friendly flame-retardant plywood, characterized in that: The wood-plastic composite environmentally friendly flame-retardant plywood is prepared by treating wooden boards with sodium hydroxide solution, and then using a phosphorus-containing maleic anhydride grafted polyethylene film as an adhesive, followed by assembling the billets and hot pressing. The preparation method of the wood-plastic composite environmentally friendly flame-retardant plywood includes the following steps: S1: Immerse the wooden boards in an aqueous sodium hydroxide solution, soak and stir at room temperature for 1 - 3 h, then wash and dry the wooden boards with water to obtain alkali-treated wooden boards. S2: Use a phosphorus-containing maleic anhydride grafted polyethylene film as an adhesive, perform billet assembly and hot pressing treatment with the alkali-treated wooden boards, the pressure is 1 - 2 MPa, the hot pressing temperature is 150 - 180 °C, and the hot pressing time is 5 - 8 min to obtain the wood-plastic composite environmentally friendly flame-retardant plywood. The preparation method of the phosphorus-containing maleic anhydride grafted polyethylene film includes the following steps: S3: Dissolve 5-hydroxyisophthalic acid and dimethylphosphoryl chloride in a solvent, then dropwise add triethylamine, stir and react at room temperature for 4 - 12 h. After the reaction, filter, concentrate under reduced pressure, wash, and recrystallize to obtain 5-phosphatoxyisophthalic acid. S4: Add 5-phosphatoxyisophthalic acid, allyl bromide, and cesium carbonate to N,N-dimethylformamide, stir evenly and react at 20 - 40 °C for 18 - 48 h. After the reaction, extract and recrystallize to obtain 5-phosphatoxyisophthalic acid bis(allyl methyl ester). S5: Add 5-phosphatoxyisophthalic acid bis(allyl methyl ester), maleic anhydride, styrene, diisopropylbenzene peroxide, and polyethylene resin with a mass ratio of 2 - 8:3 - 8:5 - 12:0.3 - 0.8:100 to an extruder, perform melt grafting, extrusion, and blow molding to form a film to obtain the phosphorus-containing maleic anhydride grafted polyethylene.

2. The wood-plastic composite environmentally friendly flame-retardant plywood according to claim 1, characterized in that: The ratio of the dosage of the phosphorus-containing maleic anhydride grafted polyethylene film to the single-sided area of the wooden board is 100 - 250 g / m 2 .

3. The preparation method of the wood-plastic composite environmentally friendly flame-retardant plywood according to claim 1, characterized in that: The mass fraction of the aqueous sodium hydroxide solution is 5 - 15%.

4. The preparation method of the wood-plastic composite environmentally friendly flame-retardant plywood according to claim 1, characterized in that: In S3, the molar ratio of 5-hydroxyisophthalic acid, dimethylphosphoryl chloride, and triethylamine is 1:1 - 1.4:2 - 3.

5. The preparation method of the wood-plastic composite environmentally friendly flame-retardant plywood according to claim 1, characterized in that: The solvent in S3 includes toluene, tetrahydrofuran, ethyl acetate, dichloromethane, or chloroform.

6. The preparation method of the wood-plastic composite environmentally friendly flame-retardant plywood according to claim 1, characterized in that: In S4, the molar ratio of 5-phosphatoxyisophthalic acid, allyl bromide, and cesium carbonate is 1:2 - 2.5:2.5 - 4.

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