Preparation method of flame-retardant recombined bamboo

Abstract

The invention discloses a preparation method of flame-retardant recombined bamboos. The preparation method comprises the steps that bamboo chips are put into an alkaline solution to be treated; immersing the bamboo chips into a NaIOO solution for reaction, and then putting the bamboo chips into a NaClO solution for reaction; the bamboo chips are put into a nano-cellulose, montmorillonite and sodium silicate ternary composite solution to be subjected to vacuum impregnation and normal-pressure impregnation; the bamboo chips are put into phenolic resin to be subjected to normal-pressure impregnation and vacuum impregnation, and then low-temperature drying is conducted; and the bamboo chips are laid in a mold in parallel in the grain direction, cold press forming is conducted, then hot pressing is conducted, and finally pressure reduction and cooling are conducted in stages till demolding is conducted. Nano montmorillonite is uniformly dispersed in a sodium silicate solution by using carboxylated nano cellulose, and inorganic components of montmorillonite and sodium silicate can be uniformly and firmly constructed on the surface of a bamboo chip which is pretreated by an alkaline solution and oxidized by NaIOO and NaClO solutions by abundant carboxyl groups under the action of hydrogen bonds, covalent bonds and the like, so that a compact layered network structure is formed; and the flame retardant property of the recombined bamboo is effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of bamboo material processing, and in particular relates to a method for preparing flame-retardant recombinant bamboo. Background Art

[0002] Bamboo boasts advantages such as a short growth cycle, high yield, and strong toughness. The development and utilization of bamboo resources is receiving increasing attention. However, due to its inherent hollow structure, raw bamboo is difficult to directly use in engineering projects. It requires specialized processing techniques to produce bamboo products, such as reconstituted bamboo. Reconstituted bamboo is already playing an important role in construction, interior design, and other fields.

[0003] Conventional reconstituted bamboo production involves rolling bamboo into strands, drying them, impregnating them with glue, and then drying them again before hot-pressing them into square lumber. To improve the flame retardancy of reconstituted bamboo, traditional, single flame retardants are often added directly to the adhesive, resulting in poor flame retardancy and limiting its application. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing flame-retardant recombinant bamboo in response to the deficiencies of the above-mentioned prior art. The method for preparing flame-retardant recombinant bamboo first uses an alkaline solution to pretreat the bamboo material to remove part of the lignin and hemicellulose, exposing the hydroxyl groups on the cellulose; then uses a NaIO4 solution to convert the hydroxyl groups into aldehyde groups, and further uses a NaClO2 solution to oxidize the aldehyde groups into carboxyl groups, so that the surface of the bamboo material is rich in hydroxyl and carboxyl functional groups; then the bamboo material is immersed in a nano-nanocellulose montmorillonite sodium silicate ternary composite solution with nanocellulose reinforced dispersion, and then impregnated with phenolic resin, directionally recombined and hot-pressed to densify to form flame-retardant recombinant bamboo, which can ultimately greatly improve the flame retardant performance.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] A method for preparing flame-retardant recombinant bamboo comprises the following steps:

[0007] Step 1: After removing the green and yellow bamboo, the bamboo is processed into bamboo slices of a certain width, and then dried;

[0008] Step 2: Place the bamboo chips treated in step 1 into a prepared alkaline solution and treat at a certain temperature to remove some hemicellulose and lignin;

[0009] Step 3: Immerse the bamboo slices treated in step 2 in a NaIO4 solution of a certain concentration and react for a period of time to convert the hydroxyl groups into aldehyde groups. Then, wash the bamboo slices with deionized water and place them in a NaClO2 solution to react for a period of time to oxidize the aldehyde groups into carboxyl groups.

[0010] Step 4: Place the bamboo chips treated in step 3 into a nanocellulose, montmorillonite, and sodium silicate ternary composite solution for vacuum impregnation, followed by normal pressure impregnation, and allow the impregnated bamboo chips to air dry;

[0011] Step 5: Place the bamboo pieces treated in step 4 into the phenolic resin, completely immerse them below the liquid level of the phenolic resin, and perform normal pressure impregnation, followed by vacuum impregnation. After the impregnation is completed, dry the bamboo pieces at low temperature;

[0012] Step 6: Lay the bamboo pieces processed in step 5 in parallel with the grain direction in a mold, cold-press them into shape using a flat vulcanizer, then hot-press them, and finally depressurize them in stages and cool them until demolding, thereby preparing flame-retardant reconstituted bamboo.

[0013] As a further improved technical solution of the present invention, in the step 1, the bamboo material is processed into bamboo slices of a certain width after removing the green and yellow parts, and then dried to a moisture content of 8-10%.

[0014] As a further improved technical solution of the present invention, the step 2 specifically includes:

[0015] Prepare an alkaline solution with a concentration of 5% to 10%;

[0016] The bamboo chips dried in step 1 are placed in the prepared alkaline solution at a solid-liquid ratio of 1:5, and the alkaline solution is heated to 60-80°C for 1-2 hours. The bamboo chips are then taken out and washed with deionized water, and then dried to a moisture content of 8%-10%.

[0017] As a further improved technical solution of the present invention, the alkaline solution is NaOH, KOH or Ca(OH)2.

[0018] As a further improved technical solution of the present invention, the step 3 specifically includes:

[0019] Prepare a NaIO4 solution with a concentration of 1% to 5% and a NaClO2 solution with a concentration of 0.5%;

[0020] The alkali-treated bamboo slices were immersed in a 1%~5% NaIO4 solution for reaction for 1~2 hours, then the bamboo slices were taken out and washed with deionized water, and then dried to a moisture content of 8%~10%; the dried bamboo slices were then placed in a 0.5% concentration NaClO2 solution for reaction for 1~2 hours, then the bamboo slices were taken out and washed and dried with deionized water, and then dried to a moisture content of 8%~10%.

[0021] As a further improved technical solution of the present invention, the preparation method of the nanocellulose montmorillonite sodium silicate ternary composite solution in step 4 includes:

[0022] Nanocellulose and calcium-based nano-montmorillonite are mixed in a mass ratio of 1:1-3, and the mixture is then mixed with deionized water in a mass ratio of 1:100 to obtain a binary mixed solution. At the same time, sodium silicate and deionized water are mixed in a mass ratio of 1:100 to obtain a sodium silicate solution.

[0023] The binary mixed solution was ultrasonically dispersed at 800-1000 W for 60 min, then centrifuged at 3000 rpm for 10 min, and centrifuged at 9000-10000 rpm for 10-15 min before settling to obtain the upper suspension.

[0024] The upper suspension was mixed with the sodium silicate solution in a mass ratio of 5-20:100, heated to 60°C in an oil bath or water bath for 15-30 minutes, and naturally cooled to room temperature after the reaction to obtain a nanocellulose montmorillonite sodium silicate ternary composite solution.

[0025] As a further improved technical solution of the present invention, the nanocellulose is carboxylated nanocellulose.

[0026] As a further improved technical solution of the present invention, the step 4 specifically includes:

[0027] The bamboo strips treated in step 3 are immersed in a ternary composite solution of nanocellulose, montmorillonite and sodium silicate, and the vacuum impregnation is maintained for 30 to 45 minutes at a pressure of -0.1 MPa. Thereafter, the bamboo strips are immersed at room temperature and pressure for 30 to 45 minutes, and the immersed bamboo strips are allowed to air dry.

[0028] As a further improved technical solution of the present invention, the step 5 specifically includes:

[0029] Place the bamboo strips treated in step 4 into the phenolic resin and immerse them completely under the phenolic resin liquid surface for 10 to 15 minutes at normal pressure, or 6 to 10 minutes under vacuum. After the immersion is completed, dry the bamboo strips at low temperature until the moisture content is 10% to 15%.

[0030] As a further improved technical solution of the present invention, the step 6 specifically includes:

[0031] The bamboo slices treated in step 5 are laid parallel to the grain direction in a mold, placed in a flat vulcanizer and cold-pressed at 0.5 MPa for 15 to 20 minutes to form, then hot-pressed at a temperature of 130 to 140°C and a pressure of 4.0 MPa for 5 to 10 minutes, and finally depressurized in stages and cooled to 40 to 50°C for demolding to prepare flame-retardant recombinant bamboo.

[0032] The beneficial effects of the present invention are:

[0033] (1) In the prior art, montmorillonite directly dispersed in adhesives has poor dispersibility and low interfacial bonding strength. In the present invention, nanocellulose is used as a dispersant to evenly disperse the nano-montmorillonite in a sodium silicate solution. Furthermore, the hydroxyl groups on the surface of the carboxylated nanocellulose, combined with the montmorillonite and the Si-O-Si residue from the hydrolysis of the sodium silicate, form a stable three-dimensional network structure through hydrogen, covalent, and ionic bonding. This improves interfacial bonding strength and enhances the stability of the flame retardant component.

[0034] (2) Components such as SiO2 and Al2O3 in montmorillonite can accelerate the solidification of sodium silicate solution in the air. At the same time, sodium aluminate and calcium ions generated in the flame retardant system will slowly form aluminum hydroxide and calcium carbonate precipitation in the air, which can form a dense and uniform inorganic mineral film on the surface of bamboo together with the solidified sodium silicate solution.

[0035] (3) The present invention first exposes the hydroxyl groups on the cellulose by treating the bamboo with alkali. The hydroxyl groups are then converted into aldehyde groups using a NaIO4 solution. The aldehyde groups are further oxidized into carboxyl groups using a NaClO2 solution, resulting in a surface rich in hydroxyl and carboxyl functional groups. Hydrogen bonding is then used to bridge the carboxylated nanocellulose, firmly bonding inorganic components such as nano-montmorillonite and sodium silicate to the bamboo surface to form a layered network structure, achieving physical barrier properties and enhancing the bamboo's flame retardancy. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are further described below:

[0037] Example 1:

[0038] A method for preparing flame-retardant recombinant bamboo comprises the following steps:

[0039] Step 1: Remove the green and yellow bamboo and process it into 20mm wide bamboo strips. Dry the bamboo strips at 100°C to a moisture content of about 8%. Finally, place them in a climate chamber at 25°C and 65% relative humidity for equilibrium treatment.

[0040] Step 2: prepare an alkaline solution (NaOH, KOH or Ca(OH)2, etc.) with a concentration of 5%; place the bamboo chips dried in step 1 into the prepared alkaline solution at a solid-liquid ratio of 1:5, heat the alkaline solution to 80°C and react for 2 hours to remove part of the hemicellulose and lignin; then take out the bamboo chips and wash them with deionized water, and then dry them until the moisture content is about 8%.

[0041] Step 3, prepare a NaIO4 solution with a concentration of 5% and a NaClO2 solution with a concentration of 0.5%; immerse the bamboo slices after the alkali treatment in step 2 in a 5% NaIO4 solution (protected from light, pH 3-5) for 2 hours to convert the hydroxyl groups into aldehyde groups, then remove the bamboo slices and wash them with deionized water, and then dry the bamboo slices to a moisture content of about 8%; then place the dried bamboo slices in a 0.5% NaClO2 solution for 2 hours to oxidize the aldehyde groups into carboxyl groups, then remove the bamboo slices and wash and dry them with deionized water, and then dry them to a moisture content of about 8%.

[0042] Step 4: Immerse the bamboo chips oxidized in step 3 into the nanocellulose, montmorillonite, sodium silicate ternary composite solution, maintain vacuum impregnation for 45 minutes, and the pressure is -0.1 MPa. Then, continue to immerse in the nanocellulose, montmorillonite, sodium silicate ternary composite solution at room temperature and pressure for 45 minutes, and let the impregnated bamboo chips air-dry.

[0043] The preparation method of the nanocellulose montmorillonite sodium silicate ternary composite solution in step 4 comprises:

[0044] Carboxylated nanocellulose and calcium-based nano-montmorillonite are mixed in a mass ratio of 1:1, and the mixture is then mixed with deionized water in a mass ratio of 1:100 to obtain a binary mixed solution. At the same time, sodium silicate and deionized water are mixed in a mass ratio of 1:100 to obtain a sodium silicate solution.

[0045] The binary mixed solution was ultrasonically dispersed at 1000 W for 60 min, then centrifuged at 3000 rpm for 10 min, and centrifuged at 9000 rpm for 15 min before settling to obtain the upper suspension.

[0046] The upper suspension was mixed with the sodium silicate solution in a mass ratio of 15:100, heated to 60°C in an oil bath or water bath for 30 minutes, and naturally cooled to room temperature after the reaction to obtain a nanocellulose montmorillonite sodium silicate ternary composite solution.

[0047] Step 5: Place the impregnated and dried bamboo strips into phenolic resin and immerse them completely under normal pressure for 15 minutes. Then, immerse them completely under vacuum for 10 minutes. After the impregnation is completed, dry the bamboo strips at low temperature until the moisture content is about 10%.

[0048] Step 6: Lay multiple low-temperature dried bamboo slices parallel to the grain direction in a mold, place them in a flat vulcanizer, cold-press them at 0.5 MPa for 20 minutes, and then hot-press them at a temperature of 130°C and a pressure of 4.0 MPa for 10 minutes. Finally, reduce the pressure in stages and cool them to 40°C for demolding to prepare flame-retardant recombinant bamboo.

[0049] The density of the reconstituted bamboo prepared was 1.22 g / cm 3 The water absorption rate is 1.6%, the thickness expansion rate is 1.5%, the width expansion rate is 1.3%, the limiting oxygen index LOI is 40.5%, the heat release rate and total heat release are 300kW / m 2 and 16MJ / m 2 The smoke release rate and smoke release volume are 0.017m 2 / s and 0.8m 2 / kg, and the flame retardant grade can reach B1.

[0050] Example 2:

[0051] A method for preparing flame-retardant recombinant bamboo comprises the following steps:

[0052] Step 1: Remove the green and yellow bamboo and process it into 20mm wide bamboo strips. Dry the bamboo strips at 100°C to a moisture content of about 10%. Finally, place them in a climate chamber at 25°C and 65% relative humidity for equilibrium treatment.

[0053] Step 2: prepare an alkaline solution (NaOH, KOH or Ca(OH)2, etc.) with a concentration of 10%; place the bamboo chips dried in step 1 into the prepared alkaline solution at a solid-liquid ratio of 1:5, heat the alkaline solution to 60°C and react for 1 hour to remove part of the hemicellulose and lignin; then take out the bamboo chips and wash them with deionized water, and then dry them until the moisture content is about 10%.

[0054] Step 3, prepare a NaIO4 solution with a concentration of 1% and a NaClO2 solution with a concentration of 0.5%; immerse the bamboo slices treated with alkali in step 2 in a 1% NaIO4 solution (protected from light, pH 3-5) for 1 hour to convert the hydroxyl groups into aldehyde groups, then remove the bamboo slices and wash them with deionized water, and then dry the bamboo slices to a moisture content of about 10%; then place the dried bamboo slices in a 0.5% NaClO2 solution for 1 hour to oxidize the aldehyde groups into carboxyl groups, then remove the bamboo slices and wash and dry them with deionized water, and then dry them to a moisture content of about 10%.

[0055] Step 4: Immerse the bamboo chips oxidized in step 3 into the nanocellulose, montmorillonite, sodium silicate ternary composite solution, maintain vacuum impregnation for 30 minutes, and the pressure is -0.1 MPa. Then, continue to immerse in the nanocellulose, montmorillonite, sodium silicate ternary composite solution at room temperature and pressure for 30 minutes, and let the impregnated bamboo chips air-dry.

[0056] The preparation method of the nanocellulose montmorillonite sodium silicate ternary composite solution in step 4 comprises:

[0057] Carboxylated nanocellulose and calcium-based nano-montmorillonite are mixed in a mass ratio of 1:3, and the mixture is then mixed with deionized water in a mass ratio of 1:100 to obtain a binary mixed solution. At the same time, sodium silicate and deionized water are mixed in a mass ratio of 1:100 to obtain a sodium silicate solution.

[0058] The binary mixed solution was ultrasonically dispersed at 800 W for 60 min, then centrifuged at 3000 rpm for 10 min, centrifuged at 10000 rpm for 10 min, and allowed to settle to obtain the upper suspension.

[0059] The upper suspension was mixed with the sodium silicate solution in a mass ratio of 5:100, heated to 60°C in an oil bath or water bath for 15 minutes, and naturally cooled to room temperature after the reaction to obtain a nanocellulose montmorillonite sodium silicate ternary composite solution.

[0060] Step 5: Place the impregnated and dried bamboo strips into phenolic resin and immerse them completely under the phenolic resin liquid surface for 10 minutes at normal pressure. Then, immerse the bamboo strips completely under the phenolic resin liquid surface for 6 minutes under vacuum. After the impregnation is completed, dry the bamboo strips at low temperature until the moisture content is about 15%.

[0061] Step 6: Lay multiple low-temperature dried bamboo slices parallel to the grain direction in a mold, place them in a flat vulcanizer, cold-press them at 0.5 MPa for 15 minutes, and then hot-press them at a temperature of 140°C and a pressure of 4.0 MPa for 5 minutes. Finally, reduce the pressure in stages and cool them to 50°C for demolding to prepare flame-retardant recombinant bamboo.

[0062] The density of the prepared reconstructed bamboo is 1.20 g / cm 3 The water absorption rate is 3.1%, the thickness expansion rate is 2.8%, the width expansion rate is 1.8%, the heat release rate and total heat release are 390kW / m 2 and 25 MJ / m 2 The smoke release rate and smoke release volume are 0.030m 2 / s and 1.8m 2 / kg, flame retardant grade reaches B1.

[0063] Example 3:

[0064] A method for preparing flame-retardant recombinant bamboo comprises the following steps:

[0065] Step 1: Remove the green and yellow bamboo and process it into 20mm wide bamboo strips. Dry the bamboo strips at 100°C to a moisture content of about 10%. Finally, place them in a climate chamber at 25°C and 65% relative humidity for equilibrium treatment.

[0066] Step 2: prepare an alkaline solution (NaOH, KOH or Ca(OH)2, etc.) with a concentration of 8%; place the bamboo chips dried in step 1 into the prepared alkaline solution at a solid-liquid ratio of 1:5, heat the alkaline solution to 70°C and react for 1 hour to remove part of the hemicellulose and lignin; then take out the bamboo chips and wash them with deionized water, and then dry them until the moisture content is about 10%.

[0067] Step 3, prepare a 3% NaIO4 solution and a 0.5% NaClO2 solution; immerse the bamboo slices treated with alkali in step 2 in a 3% NaIO4 solution (protected from light, pH 3-5) for 2 hours to convert the hydroxyl groups into aldehyde groups, then remove the bamboo slices and wash them with deionized water, and then dry them until the moisture content is about 10%; then place the dried bamboo slices in a 0.5% NaClO2 solution for 2 hours to oxidize the aldehyde groups into carboxyl groups, then remove the bamboo slices and wash and dry them with deionized water, and then dry them until the moisture content is about 10%.

[0068] Step 4: Immerse the bamboo chips oxidized in step 3 into the nanocellulose, montmorillonite, sodium silicate ternary composite solution, maintain vacuum impregnation for 35 minutes, and a pressure of -0.1 MPa. Then, continue to immerse in the nanocellulose, montmorillonite, sodium silicate ternary composite solution at room temperature and pressure for 35 minutes, and let the impregnated bamboo chips air-dry.

[0069] The preparation method of the nanocellulose montmorillonite sodium silicate ternary composite solution in step 4 comprises:

[0070] Carboxylated nanocellulose and calcium-based nano-montmorillonite are mixed in a mass ratio of 1:2, and the mixture is then mixed with deionized water in a mass ratio of 1:100 to obtain a binary mixed solution. At the same time, sodium silicate and deionized water are mixed in a mass ratio of 1:100 to obtain a sodium silicate solution.

[0071] The binary mixed solution was ultrasonically dispersed at 900 W for 60 min, then centrifuged at 3000 rpm for 10 min, and centrifuged at 10000 rpm for 12 min before settling to obtain the upper suspension.

[0072] The upper suspension was mixed with the sodium silicate solution in a mass ratio of 20:100, heated to 60°C in an oil bath or water bath for 20 minutes, and naturally cooled to room temperature after the reaction to obtain a nanocellulose montmorillonite sodium silicate ternary composite solution.

[0073] Step 5: Place the impregnated and dried bamboo strips into phenolic resin and immerse them completely under normal pressure for 12 minutes. Then, immerse them completely under vacuum for 8 minutes. After the impregnation is completed, dry the bamboo strips at low temperature until the moisture content is about 15%.

[0074] Step 6: Lay multiple low-temperature dried bamboo slices parallel to the grain direction in a mold, place them in a flat vulcanizer, cold-press them at 0.5 MPa for 20 minutes, and then hot-press them at a temperature of 140°C and a pressure of 4.0 MPa for 10 minutes. Finally, reduce the pressure in stages and cool them to 50°C for demolding to prepare flame-retardant recombinant bamboo.

[0075] The density of the reconstructed bamboo was 1.22 g / cm 3 The water absorption rate is 2.9%, the thickness expansion rate is 2.7%, the width expansion rate is 1.9%, the heat release rate and total heat release are 312kW / m 2 and 21 MJ / m 2 The smoke release rate and smoke release volume are 0.028m 2 / s and 0.9m 2 / kg, flame retardant grade reaches B1.

[0076] Example 4:

[0077] A method for preparing flame-retardant recombinant bamboo comprises the following steps:

[0078] Step 1: Remove the green and yellow bamboo from the bamboo and process it into 20mm wide bamboo strips. Dry the bamboo strips at 100°C to a moisture content of about 9%. Finally, place them in a climate chamber at 25°C and 65% relative humidity for equilibrium treatment.

[0079] Step 2: prepare an alkaline solution (NaOH, KOH or Ca(OH)2, etc.) with a concentration of 8%; place the bamboo chips dried in step 1 into the prepared alkaline solution at a solid-liquid ratio of 1:5, heat the alkaline solution to 60°C and react for 2 hours to remove part of the hemicellulose and lignin; then take out the bamboo chips and wash them with deionized water, and then dry them until the moisture content is about 9%.

[0080] Step 3: Prepare a 1% NaIO4 solution and a 0.5% NaClO2 solution; immerse the bamboo slices treated with alkali in step 2 in a 1% NaIO4 solution (protected from light, pH 3-5) for 2 hours to convert the hydroxyl groups into aldehyde groups, remove the bamboo slices, wash them with deionized water, and then dry them until the moisture content is about 9%; then place the dried bamboo slices in a 0.5% NaClO2 solution for 2 hours to oxidize the aldehyde groups into carboxyl groups, remove the bamboo slices, wash them with deionized water, and dry them, and then dry them until the moisture content is about 9%.

[0081] Step 4: Immerse the bamboo strips treated in step 3 into the nanocellulose, montmorillonite, sodium silicate ternary composite solution, maintain vacuum impregnation for 30 minutes, and a pressure of -0.1 MPa. Then, continue to immerse in the nanocellulose, montmorillonite, sodium silicate ternary composite solution at room temperature and pressure for 30 minutes, and let the impregnated bamboo strips air-dry.

[0082] The preparation method of the nanocellulose montmorillonite sodium silicate ternary composite solution in step 4 comprises:

[0083] Carboxylated nanocellulose and calcium-based nano-montmorillonite are mixed in a mass ratio of 1:1, and the mixture is then mixed with deionized water in a mass ratio of 1:100 to obtain a binary mixed solution. At the same time, sodium silicate and deionized water are mixed in a mass ratio of 1:100 to obtain a sodium silicate solution.

[0084] The binary mixed solution was ultrasonically dispersed at 800 W for 60 min, then centrifuged at 3000 rpm for 10 min, centrifuged at 9000 rpm for 10 min, and allowed to settle to obtain the upper suspension.

[0085] The upper suspension was mixed with the sodium silicate solution in a mass ratio of 15:100, heated to 60°C in an oil bath or water bath for 15 minutes, and naturally cooled to room temperature after the reaction to obtain a nanocellulose montmorillonite sodium silicate ternary composite solution.

[0086] Step 5: Place the impregnated and dried bamboo strips into phenolic resin and immerse them completely under the phenolic resin liquid surface for 10 minutes at normal pressure. Then, immerse the bamboo strips completely under the phenolic resin liquid surface for 6 minutes under vacuum. After the impregnation is completed, dry the bamboo strips at low temperature until the moisture content is about 15%.

[0087] Step 6: Lay multiple low-temperature dried bamboo slices parallel to the grain direction in a mold, place them in a flat vulcanizer, cold-press them at 0.5 MPa for 15 minutes, and then hot-press them at a temperature of 130°C and a pressure of 4.0 MPa for 5 minutes. Finally, reduce the pressure in stages and cool them to 40°C for demolding to prepare flame-retardant recombinant bamboo.

[0088] The density of the reconstructed bamboo was 1.23 g / cm 3 The water absorption rate is 1.9%, the thickness expansion rate is 1.8%, the width expansion rate is 1.6%, the heat release rate and total heat release are 293kW / m 2 and 13 MJ / m 2 The smoke release rate and smoke release volume are 0.019m 2 / s and 0.65m 2 / kg, flame retardant grade reaches B1.

[0089] The protection scope of the present invention includes but is not limited to the above embodiments. The protection scope of the present invention is based on the claims. Any replacement, deformation, and improvement of the technology that can be easily thought of by those skilled in the art fall within the protection scope of the present invention.

Claims

1. A method for preparing flame-retardant recombinant bamboo, characterized in that: The following steps are involved: Step 1: After removing the green and yellow bamboo, the bamboo is processed into bamboo slices of a certain width, and then dried; Step 2: Place the bamboo chips treated in step 1 into a prepared alkaline solution and treat at a certain temperature to remove some hemicellulose and lignin; Step 3: Immerse the bamboo slices treated in step 2 in a NaIO4 solution of a certain concentration and react for a period of time to convert the hydroxyl groups into aldehyde groups. Then, wash the bamboo slices with deionized water and place them in a NaClO2 solution to react for a period of time to oxidize the aldehyde groups into carboxyl groups. Step 4: Place the bamboo chips treated in step 3 into a nanocellulose, montmorillonite, and sodium silicate ternary composite solution for vacuum impregnation, followed by normal pressure impregnation, and allow the impregnated bamboo chips to air dry; Step 5: Place the bamboo pieces treated in step 4 into the phenolic resin, completely immerse them below the liquid level of the phenolic resin, and perform normal pressure impregnation, followed by vacuum impregnation. After the impregnation is completed, dry the bamboo pieces at low temperature; Step 6: Lay the bamboo pieces processed in step 5 in parallel with the grain direction in a mold, cold-press them into shape using a flat vulcanizer, then hot-press them, and finally depressurize them in stages and cool them until demolding, thereby preparing flame-retardant reconstituted bamboo.

2. The method for preparing flame-retardant recombinant bamboo according to claim 1, characterized in that: In the step 1, the bamboo material is processed into bamboo slices of a certain width after removing the green and yellow parts, and then dried to a moisture content of 8-10%.

3. The method for preparing flame-retardant recombinant bamboo according to claim 1, characterized in that: The step 2 specifically includes: Prepare an alkaline solution with a concentration of 5% to 10%; The bamboo chips dried in step 1 are placed in the prepared alkaline solution at a solid-liquid ratio of 1:5, and the alkaline solution is heated to 60-80°C for 1-2 hours. The bamboo chips are then taken out and washed with deionized water, and then dried to a moisture content of 8%-10%.

4. The method for preparing flame-retardant recombinant bamboo according to claim 3, characterized in that: The alkaline solution is NaOH, KOH or Ca(OH)2.

5. The method for preparing flame-retardant recombinant bamboo according to claim 1, characterized in that: The step 3 specifically includes: Prepare a NaIO4 solution with a concentration of 1% to 5% and a NaClO2 solution with a concentration of 0.5%; The alkali-treated bamboo slices were immersed in a 1%~5% NaIO4 solution for reaction for 1~2 hours, then the bamboo slices were taken out and washed with deionized water, and then dried to a moisture content of 8%~10%; the dried bamboo slices were then placed in a 0.5% concentration NaClO2 solution for reaction for 1~2 hours, then the bamboo slices were taken out and washed and dried with deionized water, and then dried to a moisture content of 8%~10%.

6. The method for preparing flame-retardant recombinant bamboo according to claim 1, characterized in that: The preparation method of the nanocellulose, montmorillonite and sodium silicate ternary composite solution in step 4 comprises: Nanocellulose and calcium-based nano-montmorillonite are mixed in a mass ratio of 1:1-3, and the mixture is then mixed with deionized water in a mass ratio of 1:100 to obtain a binary mixed solution. At the same time, sodium silicate and deionized water are mixed in a mass ratio of 1:100 to obtain a sodium silicate solution. The binary mixed solution was ultrasonically dispersed at 800-1000 W for 60 min, then centrifuged at 3000 rpm for 10 min, and centrifuged at 9000-10000 rpm for 10-15 min before settling to obtain the upper suspension. The upper suspension was mixed with the sodium silicate solution in a mass ratio of 5-20:100, heated to 60°C in an oil bath or water bath for 15-30 minutes, and naturally cooled to room temperature after the reaction to obtain a nanocellulose montmorillonite sodium silicate ternary composite solution.

7. The method for preparing flame-retardant recombinant bamboo according to claim 6, characterized in that: The nanocellulose is carboxylated nanocellulose.

8. The method for preparing flame-retardant recombinant bamboo according to claim 1, characterized in that: The step 4 specifically includes: The bamboo strips treated in step 3 are immersed in a ternary composite solution of nanocellulose, montmorillonite and sodium silicate, and the vacuum impregnation is maintained for 30 to 45 minutes at a pressure of -0.1 MPa. Thereafter, the bamboo strips are immersed at room temperature and pressure for 30 to 45 minutes, and the immersed bamboo strips are allowed to air dry.

9. The method for preparing flame-retardant recombinant bamboo according to claim 1, characterized in that: The step 5 specifically includes: Place the bamboo strips treated in step 4 into the phenolic resin and immerse them completely under the phenolic resin liquid surface for 10 to 15 minutes at normal pressure, or 6 to 10 minutes under vacuum. After the immersion is completed, dry the bamboo strips at low temperature until the moisture content is 10% to 15%.

10. The method for preparing flame-retardant recombinant bamboo according to claim 1, characterized in that: The step 6 specifically includes: The bamboo slices treated in step 5 are laid parallel to the grain direction in a mold, placed in a flat vulcanizer and cold-pressed at 0.5 MPa for 15 to 20 minutes to form, then hot-pressed at a temperature of 130 to 140°C and a pressure of 4.0 MPa for 5 to 10 minutes, and finally depressurized in stages and cooled to 40 to 50°C for demolding to prepare flame-retardant recombinant bamboo.