Preparation of grid multi-level structure by molded composite material of poplar wood powder mixed with phenolic resin

Abstract

The present invention relates to a poplar wood powder mixed with phenolic resin molded composite material for preparing a grid multi-level structure. The present invention adopts air-dried poplar wood powder to remove part of lignin and hemicellulose and then mixes with thermosetting phenolic resin, and the composite material prepared by molded integral molding is used as the core layer and panel material of the grid multi-level structure, and the core is embedded with the upper and lower panels to prepare the poplar wood powder mixed with phenolic resin molded composite material grid multi-level structure. The preparation method of the present invention includes seven steps: 1. Pre-treating the air-dried poplar wood powder to remove part of lignin and hemicellulose; 2. Preliminary stirring and mixing the phenolic resin and the treated poplar wood powder; 3. Drying the material obtained after preliminary stirring and mixing; 4. Grinding and mixing the dried material uniformly; 5. Applying demoulding lubricant oil to the mold; 6. Molding to obtain the core and panel material of the grid multi-level structure; 7. Assembling the core and the panel to obtain the poplar wood powder mixed with phenolic resin molded composite material grid multi-level structure. The poplar wood powder selected by the present invention can be obtained by crushing production waste, and is suitable for the technical field of preparation of new structures of biomass composite materials.

Description

Technical field:

[0001] The invention relates to a grid multi-level structure prepared from a poplar wood powder mixed with a phenolic resin molded composite material, belonging to the technical field of preparation of a new structure of a biomass composite material. Background technology:

[0002] With the improvement of national standards for wood structure buildings, the strengthening of policy support, and the needs of people's lives and leisure, wooden structures are appearing more and more in people's daily lives. However, my country currently lacks lightweight wooden engineering structures with good mechanical properties made of economic tree species.

[0003] Poplar is a widely planted fast-growing tree species in my country. It has a wide planting area and abundant reserves. However, due to its loose fiber structure and relatively poor material quality, it has not been well used in engineering structures. Thermosetting phenolic resin is a resin made by polycondensing phenol and formaldehyde under catalyst conditions, neutralizing and washing. Phenolic resin has good acid resistance, mechanical properties, heat resistance, good bonding properties for wood, and good fluidity and permeability.

[0004] Poplar wood is loose and soft, with poor mechanical properties. Treating poplar wood powder with a mixed aqueous solution of sodium hydroxide and sodium sulfite can remove some lignin and hemicellulose, creating pores on the surface and inside of the wood powder, making it rough, which is conducive to the infiltration of phenolic resin, increasing the interfacial bonding between the two, and improving the strength and modulus of the composite material. In addition, mixed molding of thermosetting phenolic resin and poplar wood powder can increase the density of poplar wood, enhance its mechanical properties and dimensional stability, and improve the anisotropy of wood. The mixed resin poplar wood molded composite material has heat and acid resistance and good mechanical properties, and is suitable for the preparation of grid structure engineering materials.

[0005] The grid structure has a simple spatial distribution, simple preparation process, and excellent mechanical properties. The lightweight multi-level grid structure prepared from biomass composite materials has the advantages of lightweight, good energy absorption, multifunctionality, and integrated design, and is considered to be the most promising new lightweight structure. The prepared grid structure has excellent mechanical properties and can be used as a sandwich panel for indoor walls, indoor floors, and other fields. The hollow configuration can provide sound absorption. Filling the hollow structure with sound insulation and thermal insulation materials can play a role in a variety of application scenarios. Summary of the invention:

[0006] The present invention proposes a poplar wood powder mixed with phenolic resin molded composite material to prepare a grid multi-level structure, and by utilizing the characteristics of different materials to complement each other for use in engineering structures, a grid multi-level structure with good stability, high strength and light weight is prepared.

[0007] The technical solution of the present invention:

[0008] 1. A method for preparing a multi-level grid structure by using a poplar wood powder mixed with a phenolic resin molded composite material, comprising: removing part of lignin and hemicellulose from air-dried poplar wood powder by using a mixed aqueous solution of sodium hydroxide and sodium sulfite as a reagent; placing the treated poplar wood powder and a uniformly mixed phenolic resin powder in a mold of a multi-level grid core for hot pressing, so that the structural core is integrally formed, and the upper and lower panels of the structure are integrally formed; the composite material prepared by mixed phenolic resin molding is used as the core layer and upper and lower panel materials of the multi-level grid structure; an appropriate amount of adhesive epoxy resin is injected into the grooves of the upper and lower panels; the integrally molded core is positioned in the upper and lower panels with grooves; the three are assembled; and after the interlocking is stable and the adhesive at the connection is cured, a poplar wood powder mixed with a phenolic resin molded composite material grid multi-level structure is obtained.

[0009] 2. The core prepared from the poplar wood powder mixed with phenolic resin molded composite material has a thickness of 20 mm and a height of 60 mm, and there are a series of linearly distributed square holes with a side length of 15 mm and a height throughout the core. The thickness of the panel is 25 mm, the groove depth is 5 mm, the spacing of the grooves is the same as the rib spacing of the core, and the width of the grooves is the thickness of the core. The size and arrangement can be adapted and adjusted according to the usage scenario.

[0010] 3. The epoxy resin and its curing agent used to bond the multi-level grille core layer to the panel, the diluent ratio is 10:4:1, and the curing conditions of the adhesive used to bond the components are: standing for 6 hours at room temperature.

[0011] 4. The preparation process is:

[0012] 5. Step 1: air-dry the poplar wood and crush it into powder, remove part of the lignin and hemicellulose from the poplar wood powder using a mixed aqueous solution of sodium hydroxide and sodium sulfite, and hydrothermally treat the wood powder for 2 hours under boiling conditions;

[0013] 6. Step 2: Rinse and dry the chemically treated poplar wood powder, use the poplar wood powder after removing part of the lignin and hemicellulose as a matrix and mix it with a thermosetting phenolic resin with a solid content of 65%, and the ratio of poplar wood powder to phenolic resin is 10:1. Stir it manually in a container to form a small ball, and then stir it with a high-speed universal grinder (25000r / min) to mix the poplar wood powder and liquid phenolic resin evenly to obtain a semi-finished product;

[0014] 7. Step 3: After the poplar wood powder and the liquid phenolic resin are mixed, in order to avoid glue penetration, the poplar wood powder and the liquid phenolic resin mixture is placed in a vacuum drying oven for drying. At the same time, a proper amount of P2O5 solid powder is placed in the drying oven to help remove moisture quickly. The vacuum drying oven is vacuumed and dried at room temperature for 24 hours to make its moisture content below 10%;

[0015] 8. Step 4: Use a ball mill to crush and mix the dried poplar wood powder and phenolic resin mixture evenly. The ball mill crushes and mixes the dried poplar wood powder and phenolic resin mixture by the impact of the falling grinding body and the grinding effect of the grinding body and the inner wall of the ball mill. The ball mill speed is set to 100 r / min and the grinding time is 10 h. After the ball milling, a powder of the poplar wood powder and the phenolic resin evenly mixed is obtained for preparing a grid multi-level structure.

[0016] 9. Step 5: Apply demoulding lubricant methyl silicone oil evenly to the contact surface of the core mold and the grooved panel mold;

[0017] 10. Step 6: Fill the uniformly mixed powder of poplar wood powder and phenolic resin obtained in step 4 into a mold and place it in a hot press. Heat the upper and lower plates of the hot press to 150° C., pressurize to 10 MPa in stages, and stop heating after 15 minutes of hot pressing. Wait for the grille core structure and the grooved panel to be formed, and release the pressure after cooling naturally to room temperature.

[0018] 11. Step seven, assembling the multi-level grille structure, injecting an appropriate amount of epoxy resin adhesive into the grooves of the upper and lower panels of the multi-level grille structure of the molded composite material of poplar wood powder mixed with phenolic resin obtained after molding, embedding the integrally molded core into the grooved upper and lower panels along the grooves, assembling the three, and waiting for them to be stably embedded and the adhesive at the connection to cure to obtain the multi-level structure of the molded composite material grille of poplar wood powder mixed with phenolic resin.

[0019] The beneficial effects of the present invention compared with the prior art are as follows:

[0020] 1. The present invention proposes to use poplar wood powder mixed with phenolic resin molded composite materials to prepare a multi-level grid structure, which realizes the optimal utilization of materials, and the advantages are cross-complementary, integrated, and infiltrated. A new structure with light weight, high strength, high specific modulus, heat preservation, heat insulation and sound absorption is prepared, realizing the high added value utilization of low-quality fast-growing materials. In addition, the preparation process of the structural material is simple and the preparation process is short. It only needs one step of chemical treatment and one step of integrated molding process to realize the structural material. The structural material can be used in indoor walls, indoor floors and other fields. The hollow structure is not conducive to the linear propagation of sound and can provide sound absorption. In addition, the hollow structure is conducive to the filling of materials such as sound insulation and heat preservation, and can play a role in a variety of application scenarios. Description of the drawings:

[0021] Figure 1 This is a schematic diagram of the core layer mold of the poplar wood powder mixed with phenolic resin molded composite material grid multi-level structure of the present invention

[0022] Figure 2This is a schematic diagram of a grooved panel mold of a poplar wood powder mixed with phenolic resin molded composite material grid multi-level structure of the present invention.

[0023] Figure 3 The core layer plane and side view of the multi-level structure of the poplar wood powder mixed with phenolic resin molded composite grid of the present invention

[0024] Figure 4 The plan and side schematic diagram of the upper and lower panels with grooves of the multi-level structure of the poplar wood powder mixed with phenolic resin molded composite grille of the present invention

[0025] Figure 5 This is a three-dimensional schematic diagram of the core layer of the poplar wood powder mixed with phenolic resin molded composite material grid multi-level structure integrally formed by the present invention.

[0026] Figure 6 This is a three-dimensional schematic diagram of the poplar wood powder mixed with phenolic resin molded composite material grid multi-level structure integrally formed with grooved upper and lower panels of the present invention.

[0027] Figure 7 This is a schematic diagram of the multi-level sandwich structure of the poplar wood powder mixed with phenolic resin molded composite material grid of the present invention Specific implementation plan:

[0028] The present invention is described in detail below in conjunction with specific embodiments and accompanying drawings:

[0029] Specific implementation method 1: This example uses air-dried poplar wood powder with a particle size of less than 80 mesh under the national standard and phenolic resin with a solid content of 65% as raw materials. The wood powder is hydrothermally boiled in a mixed solution of sodium hydroxide with a concentration of 2 mol / L and sodium sulfite with a concentration of 0.32 mol / L for two hours to remove about 40% of lignin and hemicellulose, and then washed to a neutral pH value and dried; the poplar wood powder after drying to remove part of the lignin and hemicellulose is used as a matrix and mixed with a thermosetting phenolic resin with a solid content of 65%, and the ratio of poplar wood powder to phenolic resin is 10:1. First, it is manually stirred in a container to form a small ball, and then stirred with a high-speed universal grinder (25000r / min) to mix the poplar wood powder and liquid phenolic resin evenly to obtain a semi-finished product; after the poplar wood powder and liquid phenolic resin are mixed, in order to avoid glue penetration, the poplar wood powder and liquid phenolic resin mixture is placed in a vacuum drying oven for drying, and the dry A proper amount of P2O5 solid powder is placed in a drying box to help remove moisture quickly. The mixture is dried in a vacuum drying box at room temperature for 24 hours to keep its moisture content below 10%. A ball mill is used to crush and mix the dried mixture of poplar wood powder and phenolic resin. The ball mill crushes and mixes the dried mixture of poplar wood powder and phenolic resin by the impact of the falling grinding body and the grinding effect of the grinding body and the inner wall of the ball mill. The ball mill speed is set to 100r / min and the grinding time is 10h. After the ball milling, a powder uniformly mixed with poplar wood powder and phenolic resin is obtained for preparing a grid multi-level structure. Methyl silicone oil, a demoulding lubricant, is evenly applied to the contact surface of the core mold and the grooved panel mold. The prepared powder uniformly mixed with poplar wood powder and phenolic resin is poured into the core mold of the grid multi-level structure ( Figure 1 ) and grooved panel molds ( Figure 2 ) and control the amount of powder material so that the density of the material after molding is 1.366 (± 0.61) g / cm3, place the mold in a hot press, fill the mold with a uniform mixture of poplar wood powder and phenolic resin into the mold, place it in a hot press and pressurize it in sections, which is divided into five stages: the first stage is 6MPa pressure to heat the upper and lower plates of the hot press to 150°C at a rate of 3.3°C / min, the second stage is 6MPa hot pressing for 5 minutes and then exhausting, the third stage is 10MPa hot pressing for 5 minutes and then exhausting, the fourth stage is 10MPa hot pressing for 5 minutes, the fifth stage is to maintain 10MPa pressure to close the temperature, wait for the grille core structure and the grooved panel to be formed, wait for it to naturally cool to room temperature at a cooling rate of 0.55°C / min, then release the pressure and take it out to obtain the above-mentioned core and panel.

[0030] It should be noted that although wood flour appears to be powder when observed with the naked eye, it is essentially a short-fiber wood product and is very easy to absorb moisture, resulting in an excessively high water content. Therefore, it must be dried before use. Otherwise, the preparation time will be prolonged and many defective materials will be produced. The particle size of wood flour is required to be less than 80 mesh because the surface area is negatively correlated with the volume. The finer the wood flour, the larger its outer surface, the higher the degree of adhesion, the larger the resin infiltration area, and the more ideal the finished product. However, the particle size of wood flour cannot be too fine, which will result in excessive resin consumption, labor-intensive preparation process, and other consumption.

[0031] Specific implementation method 2: The poplar wood powder mixed with phenolic resin molded composite grid multi-level structure, its structural components include a core layer structure, an upper panel, a lower panel, and the following combination Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 Specifically describe this implementation mode:

[0032] (1) A composite material core and a grooved panel are prepared by mixing molded poplar wood powder with phenolic resin. The detailed preparation method is shown in Specific Implementation Method 1;

[0033] (2) The dimensions of the molded core and its grooved panel are as follows: Figure 3 , Figure 4 As shown, the unit is mm;

[0034] (3) Preparation of a multi-level grid structure by molding a composite material of poplar wood powder and phenolic resin In the first step of assembling, the core prepared in (2) is demoulded to obtain a core layer structure, such as Figure 5 As shown, the grooved panel prepared in (2) is demoulded to obtain upper and lower panels, as shown in FIG. Figure 6 As shown;

[0035] (4) The second step of assembling the multi-level grid structure made of poplar wood powder mixed with phenolic resin molded composite material is to inject appropriate epoxy resin adhesive along the grooves of the upper and lower panels, and the ratio of epoxy resin and its curing agent and diluent is 10:4:1, and the core layer structure completed in (3) is assembled with the grooved upper and lower panels in the second step to prepare the poplar wood powder mixed with phenolic resin molded composite material to prepare the multi-level grid sandwich structure, such as Figure 7 As shown, place it in a cool place indoors and let it stand for 6 hours. After the adhesive at the joint is cured, the poplar wood powder mixed with phenolic resin molded composite material is used to prepare the grid multi-level sandwich structure.

Claims

1. A method for preparing a grid multi-level structure by using a poplar wood powder mixed with a phenolic resin molded composite material, characterized in that: A composite material prepared by molding air-dried poplar wood powder after removing part of lignin and hemicellulose and then mixing with thermosetting phenolic resin is used as the core layer and panel material of the multi-level grid structure. The poplar wood powder and phenolic resin mixture is placed in a mold of the multi-level grid core and hot-pressed to form the structural core and the panel in one piece. The core is embedded with the upper and lower panels, and an adhesive is used to reinforce the joint between the core structure and the panel. The preparation process of the poplar wood powder mixed with phenolic resin molded composite grid multi-level structure is as follows: Step 1: air-dry the poplar wood and grind it into powder, remove part of the lignin and hemicellulose from the poplar wood powder using a mixed aqueous solution of sodium hydroxide and sodium sulfite as a reagent, and hydrothermally treat the poplar wood powder for 2 hours under boiling conditions; Step 2: Rinse and dry the chemically treated poplar wood powder, use the poplar wood powder after removing part of the lignin and hemicellulose as a matrix and mix it with a thermosetting phenolic resin with a solid content of 65%, and the ratio of the poplar wood powder to the phenolic resin is 10:

1. First, stir it manually in a container to form a small ball, and then stir it with a high-speed universal grinder to mix the poplar wood powder and the liquid phenolic resin evenly to obtain a semi-finished product; Step 3: After the poplar wood powder and the liquid phenolic resin are mixed, in order to avoid glue penetration, the poplar wood powder and the liquid phenolic resin mixture is placed in a vacuum drying oven for drying. At the same time, a proper amount of P2O5 solid powder is placed in the drying oven to help remove moisture faster. The vacuum drying oven is vacuumed and dried at room temperature for 24 hours to make its moisture content below 10%; Step 4: Use a ball mill to crush and mix the dried poplar wood powder and phenolic resin mixture evenly. The ball mill crushes and mixes the dried poplar wood powder and phenolic resin mixture by the impact of the falling grinding body and the grinding effect of the grinding body and the inner wall of the ball mill. The ball mill speed is set to 100 r / min and the grinding time is 10 hours. After the ball milling, a powder of the poplar wood powder and the phenolic resin evenly mixed is obtained for preparing a grid multi-level structure. Step 5: Apply demoulding lubricant methyl silicone oil evenly to the contact surface of the core mold and the grooved panel mold; Step 6: Fill the uniformly mixed powder of poplar wood powder and phenolic resin prepared in step 4 into a mold and place it in a hot press, heat the upper and lower plates of the hot press to 150°C, pressurize to 10MPa in stages, and stop heating after 15 minutes of hot pressing, wait for the grid core structure and the grooved panel to be formed, and release the pressure after cooling naturally to room temperature; Step seven, assembling the multi-level grille structure, injecting an appropriate amount of epoxy resin adhesive into the grooves of the upper and lower panels of the multi-level grille structure of the molded composite material of poplar wood powder mixed with phenolic resin obtained after molding, embedding the integrally molded core into the grooved upper and lower panels along the grooves, assembling the three, and waiting for them to be stably embedded and the adhesive at the connection to cure to obtain the multi-level structure of the molded composite material grille of poplar wood powder mixed with phenolic resin.

2. The preparation method according to claim 1, characterized in that: The core made of poplar wood powder mixed with phenolic resin molded composite material has a thickness of 20mm and a height of 60mm. There are a series of linearly distributed square holes with a side length of 15mm and a height throughout the core. The thickness of the panel is 25mm and the groove depth is 5mm. The spacing between the grooves is the same as the rib spacing of the core. The width of the groove is the thickness of the core. The size and arrangement can be adapted and adjusted according to the usage scenario.

3. The preparation method according to claim 1, characterized in that: In the preparation step 1, the maximum particle size of the poplar wood powder is 80 meshes, the concentration of sodium hydroxide in the hydrothermal chemical treatment is 2 mol / L, and the concentration of sodium sulfite is 0.32 mol / L.

4. The preparation method according to claim 1, characterized in that: In preparation step six, the powder uniformly mixed with poplar wood powder and phenolic resin is filled into a mold and placed in a hot press for staged pressurization, which is divided into five stages: the first stage is 6MPa pressure to heat the upper and lower plates of the hot press to 150°C at a rate of 3.3°C / min, the second stage is 6MPa hot pressing for 5 minutes and then exhausting, the third stage is 10MPa hot pressing for 5 minutes and then exhausting, the fourth stage is 10MPa hot pressing for 5 minutes, and the fifth stage is to maintain the 10MPa pressure to close the temperature, and wait for the sample temperature to gradually cool to room temperature at a cooling rate of 0.55°C / min.

5. The preparation method according to claim 1, characterized in that: In preparation step six, the epoxy resin and its curing agent used to bond the multi-level grid core layer to the panel, and the diluent ratio is 10:4:

1. The curing conditions of the adhesive that combines the components are: standing for 6 hours at room temperature.

Images