Sandwich composite wallboard produced based on plant straw and preparation method of sandwich composite wallboard

Abstract

The invention discloses a sandwich composite wallboard produced based on plant straws and a preparation method of the sandwich composite wallboard, and belongs to the technical field of composite wallboards. The preparation method comprises the following steps: crushing plant straws, and carrying out alkaline modification treatment to obtain modified plant straw powder; the modified plant straw powder is mixed with expanded perlite, a starch binder, a flame retardant and a composite plasticizer to prepare a core layer mixture, and the core layer mixture is mixed with glass fibers, a waterborne polyurethane binder, a silane coupling agent and talcum powder to prepare a panel mixture; after a panel-core layer-panel sandwich structure is laid, a finished product is obtained after hot press molding and maintenance. According to the invention, the interfacial compatibility of the straws is effectively improved through alkaline modification, and the wallboard has excellent mechanical strength, thermal insulation property and flame retardant property through sandwich structure design and reasonable compounding of functional aids, is free of formaldehyde release, and realizes high-valued utilization of agricultural wastes and collaborative optimization of green building functions.

Description

Technical Field

[0001] This invention belongs to the field of composite wall panel technology, and particularly relates to a sandwich composite wall panel based on plant straw and its preparation method. Background Technology

[0002] Straw, as a natural biomass material, is lightweight, porous, and has excellent thermal insulation properties. Furthermore, it is widely available and inexpensive, making it an ideal raw material for preparing green building wall panels. In recent years, straw-based composite wall panels have gradually become a research hotspot in the building materials field due to their combination of environmental friendliness and resource recycling value.

[0003] However, existing straw-based composite wall panels still face numerous technical bottlenecks: the surface of straw fibers is rich in lignin, hemicellulose, and wax layers, resulting in poor interfacial compatibility with binders and inorganic fillers, easily leading to delamination and cracking, which seriously affects the overall structural integrity and service life of the panels; product functional synergy is insufficient, with most wall panels failing to simultaneously meet multiple building requirements such as mechanical strength, thermal insulation, and flame retardancy; products that emphasize thermal insulation often have low mechanical strength and cannot withstand the load-bearing capacity of the wall or the needs of decorative construction, while products that increase strength by adding reinforcing materials often sacrifice thermal insulation effects, and their flame retardant performance generally fails to meet building safety standards, posing a significant fire hazard; and it is difficult to balance environmental protection and economy, as traditional straw-based engineered wood panels often use formaldehyde-containing binders such as urea-formaldehyde resin, which release toxic and harmful substances over a long period of time, endangering human health.

[0004] Therefore, developing a straw-based sandwich composite wall panel preparation technology that is mild, cost-controllable, environmentally friendly, and can achieve synergistic optimization of mechanical strength, thermal insulation, and flame retardant stability is of great practical significance for promoting the resource utilization of agricultural waste and upgrading the green building materials industry. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the present invention, by reasonably combining flame retardants, silane coupling agents, talc and other functional additives, enables the finished wall panels to have multiple functions such as heat insulation, flame retardancy, high mechanical strength and good stability.

[0006] To achieve the above objectives, the following technical solution is adopted: This invention provides a sandwich composite wall panel based on plant straw and its preparation method, the preparation method comprising the following steps:

[0007] S1. Plant straw is fed into a crusher and crushed into granules with a particle size of 2-5 mm. An 8%-12% sodium hydroxide solution is added to the crushed straw granules, and the mixture is stirred at a constant temperature of 50-60℃ for 40-60 min for alkali modification. After modification, the straw is washed with deionized water until neutral, and deionized water is added to adjust the moisture content to 45%-55%. The straw is placed in a sealed container and left to stand for 20-24 h. Finally, it is dried at 60-80℃ to constant weight, pulverized, and passed through an 80-mesh sieve to obtain modified plant straw powder.

[0008] S2. Add modified plant straw powder, expanded perlite, starch binder and flame retardant to a high-speed mixer and mix for 8-10 minutes; then add composite plasticizer and continue mixing for 15-20 minutes until uniform, and let stand for 30-40 minutes to allow the material to be fully impregnated to obtain straw-based core layer mixture.

[0009] S3. Add modified plant straw powder, glass fiber, water-based polyurethane binder, silane coupling agent and talc to a high-speed mixer, mix for 10-12 minutes, add deionized water, stir and mix for 15 minutes until the system is a uniform paste, filter through a 100-mesh sieve to remove impurities, and obtain straw base panel mixture.

[0010] S4. Lay a layer of straw-based panel mixture with a thickness of 3-5mm at the bottom of the lamination mold as the bottom panel. Evenly lay a layer of straw-based core layer mixture with a thickness of 20-25mm on the bottom panel as the core layer. Lay another layer of straw-based panel mixture with the same thickness as the bottom panel on the surface of the core layer as the top panel. Send the mold into the hot press, preheat it at 130-150℃ for 15 minutes, then apply 9-12MPa pressure for hot pressing for 60-90 minutes. Finally, let it cool naturally to room temperature and take it out to obtain the rough product of sandwich composite wall panel.

[0011] S5. Trim and trim the rough sandwich composite wall panel to remove burrs and irregular parts, then place it in a constant temperature and humidity chamber at 25℃ and 50% humidity for 72 hours. After surface polishing, the finished plant straw sandwich composite wall panel is obtained.

[0012] Furthermore, in step S1, the solid-liquid ratio of straw particles to sodium hydroxide solution is 1:8.

[0013] Furthermore, in step S2, the mass ratio of modified plant straw powder, expanded perlite, starch binder, and flame retardant is 60:30:5:5.

[0014] Furthermore, in step S2, the composite plasticizer accounts for 40%-45% of the total mass of the core layer mixture, and the composite plasticizer is composed of glycerol and erythritol in a mass ratio of 60-80:40.

[0015] Furthermore, in step S3, the mass ratio of modified plant straw powder, glass fiber, waterborne polyurethane binder, silane coupling agent, and talc is 70:20:5:3:2.

[0016] Furthermore, in step S3, the deionized water accounts for 30%-35% of the total mass of the panel mixture.

[0017] Furthermore, the plant straw is at least one of corn straw or wheat straw.

[0018] Furthermore, the silane coupling agent is at least one of KH550, KH560, and KH570.

[0019] Furthermore, the flame retardant is at least one of magnesium hydroxide, aluminum hydroxide, and ammonium polyphosphate.

[0020] The beneficial effects of this invention are:

[0021] This invention enables the finished wall panel to possess multiple functions such as heat insulation, flame retardancy, high mechanical strength, and good stability by rationally combining flame retardants, silane coupling agents, talc, and other functional additives.

[0022] This invention uses agricultural waste such as corn stalks and wheat stalks as core raw materials, effectively solving the environmental pollution and resource waste problems caused by burning or discarding straw, and realizing the high-value recycling and utilization of agricultural waste. At the same time, starch binder, water-based polyurethane binder, inorganic flame retardant and environmentally friendly composite plasticizer are selected in the preparation process, and no formaldehyde or other toxic and harmful substances are released. The finished wall panels meet the green building materials environmental protection standards and are friendly to human health and the ecological environment.

[0023] This invention achieves synergistic optimization of the wall panel's mechanical strength and thermal insulation performance through a sandwich structure design of panel-core layer-panel: the addition of expanded perlite in the core layer significantly reduces the wall panel's density, improves thermal insulation, and meets the building energy conservation requirements; the composite of glass fiber and modified plant straw powder in the panel greatly enhances the wall panel's tensile strength, flexural strength, and wear resistance, meeting the requirements for wall load-bearing and decorative use; in addition, the introduction of flame retardants gives the wall panel excellent flame retardant properties, and the addition of silane coupling agents improves the interfacial compatibility of the components, further enhancing the product's structural stability and service life.

[0024] The alkaline method for modifying plant straw is a mild process with low energy consumption and simple operation, making it more suitable for large-scale production compared to harsher treatments such as steam explosion. The modified straw has exposed surface active groups, significantly enhancing its interfacial bonding with binders and fillers. This effectively solves the technical problems of poor compatibility and easy delamination between unmodified straw and polymer materials, ensuring the structural integrity and performance stability of the finished wall panels. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used in the following examples are all purchased from commercial channels.

[0028] Example 1:

[0029] A sandwich composite wall panel based on plant straw and its preparation method, the preparation method comprising the following steps:

[0030] S1. Plant straw is fed into a crusher and crushed into granules with a particle size of 2 mm. An 8% sodium hydroxide solution is added to the crushed straw granules, and the mixture is stirred at a constant temperature of 50°C for 40 min for alkaline modification. After modification, the straw is washed with deionized water until neutral, and deionized water is added to adjust the moisture content to 45%. The mixture is placed in a sealed container and left to stand for 20 h. Finally, it is dried at 60°C to constant weight, pulverized, and passed through an 80-mesh sieve to obtain modified plant straw powder.

[0031] S2. Add modified plant straw powder, expanded perlite, starch binder and flame retardant to a high-speed mixer and mix for 8 minutes; then add composite plasticizer and continue mixing for 15 minutes until uniform, and let stand for 30 minutes to allow the material to be fully impregnated to obtain straw-based core layer mixture;

[0032] S3. Add modified plant straw powder, glass fiber, water-based polyurethane binder, silane coupling agent and talc to a high-speed mixer, mix for 10 minutes, add deionized water, stir and mix for 15 minutes until the system is a uniform paste, filter through a 100-mesh sieve to remove impurities, and obtain straw base panel mixture.

[0033] S4. Lay a 3mm thick layer of straw-based panel mixture at the bottom of the lamination mold as the bottom panel. Evenly lay a 20mm thick layer of straw-based core mixture on the bottom panel as the core layer. Lay another layer of straw-based panel mixture of the same thickness as the bottom panel on the surface of the core layer as the top panel. Send the mold into the hot press, preheat it at 130℃ for 15 minutes, then apply 9MPa pressure for hot pressing for 60 minutes. Finally, let it cool naturally to room temperature and take it out to obtain the rough product of the sandwich composite wall panel.

[0034] S5. Trim and trim the rough sandwich composite wall panel to remove burrs and irregular parts, then place it in a constant temperature and humidity chamber at 25℃ and 50% humidity for 72 hours. After surface polishing, the finished plant straw sandwich composite wall panel is obtained.

[0035] In step S1, the solid-liquid ratio of straw particles to sodium hydroxide solution is 1:8; in step S2, the mass ratio of modified plant straw powder, expanded perlite, starch binder, and flame retardant is 60:30:5:5; in step S2, the composite plasticizer accounts for 40% of the total mass of the core layer mixture, and the composite plasticizer is composed of glycerol and erythritol in a mass ratio of 60:40; in step S3, the mass ratio of modified plant straw powder, glass fiber, waterborne polyurethane binder, silane coupling agent, and talc is 70:20:5:3:2; in step S3, the deionized water accounts for 30% of the total mass of the panel mixture; the plant straw is corn straw; the silane coupling agent is KH550 and KH560, and their mass ratio is 1:1; the flame retardant is magnesium hydroxide and aluminum hydroxide, and their mass ratio is 1:1.

[0036] Example 2:

[0037] A sandwich composite wall panel based on plant straw and its preparation method, the preparation method comprising the following steps:

[0038] S1. Plant straw is fed into a crusher and crushed into granules with a particle size of 5 mm. A 12% sodium hydroxide solution is added to the crushed straw granules, and the mixture is stirred at a constant temperature of 60°C for 60 min to carry out alkaline modification. After modification, the straw is washed with deionized water until neutral, and deionized water is added to adjust the moisture content to 55%. The straw is placed in a sealed container and left to stand for 24 h. Finally, it is dried at 80°C to constant weight, pulverized, and passed through an 80-mesh sieve to obtain modified plant straw powder.

[0039] S2. Add modified plant straw powder, expanded perlite, starch binder and flame retardant to a high-speed mixer and mix for 10 minutes; then add composite plasticizer and continue mixing for 20 minutes until uniform, and let stand for 40 minutes to allow the material to be fully impregnated to obtain straw-based core layer mixture;

[0040] S3. Add modified plant straw powder, glass fiber, water-based polyurethane binder, silane coupling agent and talc powder to a high-speed mixer, mix for 12 minutes, add deionized water, stir and mix for 15 minutes until the system is a uniform paste, filter through a 100-mesh sieve to remove impurities, and obtain straw base panel mixture.

[0041] S4. Lay a 5mm thick layer of straw-based panel mixture at the bottom of the lamination mold as the bottom panel. Evenly lay a 25mm thick layer of straw-based core mixture on the bottom panel as the core layer. Lay another layer of straw-based panel mixture of the same thickness as the bottom panel on the surface of the core layer as the top panel. Send the mold into the hot press, preheat it at 150℃ for 15 minutes, then apply 12MPa pressure for hot pressing for 90 minutes. Finally, let it cool naturally to room temperature and take it out to obtain the rough product of sandwich composite wall panel.

[0042] S5. Trim and trim the rough sandwich composite wall panel to remove burrs and irregular parts, then place it in a constant temperature and humidity chamber at 25℃ and 50% humidity for 72 hours. After surface polishing, the finished plant straw sandwich composite wall panel is obtained.

[0043] In step S1, the solid-liquid ratio of straw particles to sodium hydroxide solution is 1:8; in step S2, the mass ratio of modified plant straw powder, expanded perlite, starch binder, and flame retardant is 60:30:5:5; in step S2, the composite plasticizer accounts for 45% of the total mass of the core layer mixture, and the composite plasticizer is composed of glycerol and erythritol in a mass ratio of 80:40; in step S3, the mass ratio of modified plant straw powder, glass fiber, water-based polyurethane binder, silane coupling agent, and talc is 70:20:5:3:2; in step S3, the deionized water accounts for 35% of the total mass of the panel mixture; the plant straw is wheat straw; the silane coupling agent is KH560 and KH570, and their mass ratio is 1:1; the flame retardant is magnesium hydroxide and ammonium polyphosphate, and their mass ratio is 1:1.

[0044] Example 3:

[0045] A sandwich composite wall panel based on plant straw and its preparation method, the preparation method comprising the following steps:

[0046] S1. Plant straw is fed into a crusher and crushed into granules with a particle size of 3mm. A 10% sodium hydroxide solution is added to the crushed straw granules, and the mixture is stirred at a constant temperature of 55℃ for 50 minutes for alkaline modification. After modification, the straw is washed with deionized water until neutral, and deionized water is added to adjust the moisture content to 50%. The mixture is placed in a sealed container and left to stand for 22 hours. Finally, it is dried at 70℃ to constant weight, pulverized, and passed through an 80-mesh sieve to obtain modified plant straw powder.

[0047] S2. Add modified plant straw powder, expanded perlite, starch binder and flame retardant to a high-speed mixer and mix for 9 minutes; then add composite plasticizer and continue mixing for 18 minutes until uniform, and let stand for 35 minutes to allow the material to be fully impregnated to obtain straw-based core layer mixture;

[0048] S3. Add modified plant straw powder, glass fiber, water-based polyurethane binder, silane coupling agent and talc to a high-speed mixer, mix for 11 min, add deionized water, stir and mix for 15 min until the system is a uniform paste, filter through a 100-mesh sieve to remove impurities, and obtain straw base panel mixture.

[0049] S4. Lay a 4mm thick layer of straw-based panel mixture at the bottom of the lamination mold as the bottom panel. Evenly lay a 23mm thick layer of straw-based core mixture on the bottom panel as the core layer. Lay another layer of straw-based panel mixture of the same thickness as the bottom panel on the surface of the core layer as the top panel. Send the mold into the hot press, preheat it at 140℃ for 15 minutes, apply 10.5MPa pressure for hot pressing for 75 minutes, and finally let it cool naturally to room temperature. Take it out to obtain the rough product of sandwich composite wall panel.

[0050] S5. Trim and trim the rough sandwich composite wall panel to remove burrs and irregular parts, then place it in a constant temperature and humidity chamber at 25℃ and 50% humidity for 72 hours. After surface polishing, the finished plant straw sandwich composite wall panel is obtained.

[0051] In step S1, the solid-liquid ratio of straw particles to sodium hydroxide solution is 1:8; in step S2, the mass ratio of modified plant straw powder, expanded perlite, starch binder, and flame retardant is 60:30:5:5; in step S2, the composite plasticizer accounts for 42.5% of the total mass of the core layer mixture, and the composite plasticizer is composed of glycerol and erythritol in a mass ratio of 70:40; in step S3, the modified plant straw powder, glass fiber, waterborne polyurethane binder, and silane coupling agent... The mass ratio of the agent and talc is 70:20:5:3:2; in step S3, the deionized water accounts for 32.5% of the total mass of the panel mixture; the plant straw is corn straw and wheat straw, with a mass ratio of 1:1; the silane coupling agent is KH550, KH560, and KH570, with a mass ratio of 1:1:1; the flame retardant is aluminum hydroxide and ammonium polyphosphate, with a mass ratio of 1:1.

[0052] Comparative Example 1:

[0053] Compared with Example 3, this comparative example only changed step S1: after crushing the plant straw into granules with a particle size of 3 mm, without alkaline modification treatment, the moisture content was directly adjusted to 50% using deionized water, placed in a sealed container and left to stand for 22 hours, dried at 70°C to constant weight, pulverized and passed through an 80-mesh sieve to obtain unmodified plant straw powder. The other steps were exactly the same as in Example 3.

[0054] Comparative Example 2:

[0055] Compared with Example 3, this comparative example changes step S4: instead of using a sandwich structure, the straw-based core layer mixture is laid separately in the lamination mold with a thickness of 30mm and directly hot-pressed. The other steps are the same as in Example 3.

[0056] Comparative Example 3:

[0057] Compared with Example 3, this comparative example differs in step S2: the mass ratio of modified plant straw powder, expanded perlite, starch binder, and flame retardant is adjusted to 40:50:5:5. All other steps are the same as in Example 3.

[0058] Results Analysis

[0059] To verify the comprehensive performance of the plant straw sandwich composite wall panel of the present invention, performance tests were conducted on the wall panel samples prepared in Examples 1-3 and Comparative Examples 1-3 according to relevant national standards. The test items and methods included: apparent density (GB / T5486), flexural strength (GB / T 7019), thermal conductivity (GB / T 10294), flame retardant rating (GB 8624), and formaldehyde emission (GB 18580). The test results are shown in Table 1.

[0060] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Apparent density / kg / m 3 > 585 605 595 610 820 450 Flexural strength / MPa 8.5 9.2 8.9 5.1 11.5 3.8 Thermal conductivity / W / (m·K) 0.082 0.078 0.080 0.091 0.195 0.073 Flame retardant rating B1 level B1 level B1 level B2 level B2 level B1 level Formaldehyde release / mg / L Not detected Not detected Not detected Not detected Not detected Not detected Interface integration status Dense, without layers Dense, without layers Dense, without layers Obvious layering and cracking Dense, without layers Loose structure, fragile

[0061] As can be seen from Table 1, the sandwich composite wall panels prepared in Examples 1-3 of the present invention exhibit excellent comprehensive performance, with an apparent density of 585-605 kg / m³. 3 These materials are lightweight; their flexural strength reaches 8.5-9.2 MPa, meeting the basic mechanical performance requirements for wall materials; their thermal conductivity is as low as 0.078-0.082 W / (m·K), exhibiting excellent thermal insulation performance; their flame retardancy rating reaches B1 level, and formaldehyde emission was undetectable. These data indicate that this invention has successfully prepared a lightweight, high-strength, thermally insulating, flame-retardant, and environmentally friendly composite wall panel.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0063] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a sandwich composite wall panel based on plant straw, characterized in that: Includes the following steps: S1. Plant straw is fed into a crusher and crushed into granules with a particle size of 2-5 mm. An 8%-12% sodium hydroxide solution is added to the crushed straw granules, and the mixture is stirred at a constant temperature of 50-60℃ for 40-60 min for alkali modification. After modification, the straw is washed with deionized water until neutral, and deionized water is added to adjust the moisture content to 45%-55%. The straw is placed in a sealed container and left to stand for 20-24 h. Finally, it is dried at 60-80℃ to constant weight, pulverized, and passed through an 80-mesh sieve to obtain modified plant straw powder. S2. Add modified plant straw powder, expanded perlite, starch binder and flame retardant to a high-speed mixer and mix for 8-10 minutes; then add composite plasticizer and continue mixing for 15-20 minutes until uniform, and let stand for 30-40 minutes to allow the material to be fully impregnated to obtain straw-based core layer mixture. S3. Add modified plant straw powder, glass fiber, water-based polyurethane binder, silane coupling agent and talc to a high-speed mixer, mix for 10-12 minutes, add deionized water, stir and mix for 15 minutes until the system is a uniform paste, filter through a 100-mesh sieve to remove impurities, and obtain straw base panel mixture. S4. Lay a layer of straw-based panel mixture with a thickness of 3-5mm at the bottom of the lamination mold as the bottom panel. Evenly lay a layer of straw-based core layer mixture with a thickness of 20-25mm on the bottom panel as the core layer. Lay another layer of straw-based panel mixture with the same thickness as the bottom panel on the surface of the core layer as the top panel. Send the mold into the hot press, preheat it at 130-150℃ for 15 minutes, then apply 9-12MPa pressure for hot pressing for 60-90 minutes. Finally, let it cool naturally to room temperature and take it out to obtain the rough product of sandwich composite wall panel. S5. Trim and trim the rough sandwich composite wall panel to remove burrs and irregular parts, then place it in a constant temperature and humidity chamber at 25℃ and 50% humidity for 72 hours. After surface polishing, the finished plant straw sandwich composite wall panel is obtained.

2. The method for preparing sandwich composite wall panels based on plant straw production according to claim 1, characterized in that: In step S1, the solid-liquid ratio of straw particles to sodium hydroxide solution is 1:

8.

3. The method for preparing sandwich composite wall panels based on plant straw production according to claim 2, characterized in that: In step S2, the mass ratio of modified plant straw powder, expanded perlite, starch binder, and flame retardant is 60:30:5:

5.

4. The method for preparing sandwich composite wall panels based on plant straw production according to claim 3, characterized in that: In step S2, the composite plasticizer accounts for 40%-45% of the total mass of the core layer mixture, and the composite plasticizer is composed of glycerol and erythritol in a mass ratio of 60-80:

40.

5. The method for preparing sandwich composite wall panels based on plant straw production according to claim 4, characterized in that: In step S3, the mass ratio of modified plant straw powder, glass fiber, water-based polyurethane binder, silane coupling agent, and talc is 70:20:5:3:

2.

6. The method for preparing sandwich composite wall panels based on plant straw production according to claim 5, characterized in that: In step S3, the deionized water accounts for 30%-35% of the total mass of the panel mixture.

7. The method for preparing sandwich composite wall panels based on plant straw production according to claim 6, characterized in that: The plant straw is at least one of corn straw or wheat straw.

8. The method for preparing sandwich composite wall panels based on plant straw production according to claim 7, characterized in that: The silane coupling agent is at least one of KH550, KH560, and KH570.

9. The method for preparing sandwich composite wall panels based on plant straw production according to claim 8, characterized in that: The flame retardant is at least one of magnesium hydroxide, aluminum hydroxide, and ammonium polyphosphate.

10. A sandwich composite wall panel based on plant straw production, characterized in that: It is prepared according to any one of claims 1-9.