Bamboo fiber composite layered material well lid and preparation method

Abstract

The application discloses a bamboo fiber composite layered material well lid and a preparation method thereof, and belongs to the technical field of bamboo fiber layered materials. The technical scheme in the application combines three-stage synergistic modification of bamboo fibers, a three-layer protection structure and a one-time die forming process to prepare a bamboo fiber composite well lid which has high strength, high toughness, excellent corrosion resistance, light weight and green environmental protection. The bamboo fiber composite well lid can replace existing cast iron or cement well lids and is applied to heavy load scenes such as main roads, ports and airports. The preparation cost is low, and the bamboo fiber composite well lid has good market application prospect.

Description

Technical Field

[0001] This invention relates to the field of bamboo fiber layered materials technology, and in particular to a bamboo fiber composite layered material manhole cover and its preparation method. Background Technology

[0002] Manhole covers used in urban construction facilities such as power, telecommunications, and municipal engineering are generally made of cast iron or reinforced concrete. Cast iron manhole covers have poor impact resistance, are prone to rust and breakage, and are easily stolen; while reinforced concrete manhole covers are heavy and have a short service life. Related technologies using fiberglass to make manhole covers are fragile and extremely environmentally unfriendly; a solution with high strength, good durability, and environmental friendliness is needed. Summary of the Invention

[0003] The main objective of this invention is to develop a high-strength layered material filled with bamboo fiber, replacing plastic or glass fiber, to meet the application requirements in fields such as manhole covers where both environmental protection and strength are needed.

[0004] This invention proposes a bamboo fiber composite layered material manhole cover, which includes a first protective layer, a bamboo fiber reinforcing layer, and a second protective layer stacked sequentially from top to bottom; the bamboo fiber reinforcing layer includes modified bamboo fiber and a resin matrix, wherein the mass fraction of the modified bamboo fiber is 30wt%~50wt%; the resin matrix is ​​selected from at least one of unsaturated polyester resin and epoxy resin.

[0005] In one embodiment, the method for preparing the modified bamboo fiber includes the following steps: Bamboo is pulverized into bamboo fiber by steam explosion, a coupling agent is added and stirred; then bio-enzymes and nano-silica are added, stirred and allowed to stand to complete the preparation of the modified bamboo fiber.

[0006] In one specific embodiment, the coupling agent includes at least one of a silane coupling agent and a titanate coupling agent.

[0007] In one specific embodiment, the weight ratio of the coupling agent to the bamboo fiber is 1:3 to 20.

[0008] In one embodiment, the bioenzyme includes at least one of cellulase, hemicellulase, laccase, and pectinase.

[0009] In one embodiment, the amount of the bio-enzyme is 0.5wt% to 1wt% of the bamboo fiber.

[0010] In one embodiment, the first protective layer includes reinforcing filler and the resin matrix; The reinforcing filler includes at least one of quartz sand and silicon carbide, and the particle size of the reinforcing filler is 0.1 mm to 0.5 mm, and the volume fraction of the reinforcing filler in the first protective layer is 10% to 20%.

[0011] In one embodiment, the upper surface of the first protective layer further includes a wear-resistant coating, the wear-resistant coating comprising 5wt% to 15wt% wear-resistant filler and 3wt% to 5wt% anti-slip particles; wherein the wear-resistant filler comprises at least one of alumina and silicon carbide, and the anti-slip particles comprise at least one of silicon carbide and zirconium oxide; and the particle size of the wear-resistant filler is 10μm to 50μm, and the particle size of the anti-slip particles is 0.2mm to 1mm.

[0012] In one embodiment, the second protective layer is any one of highly cross-linked epoxy resin, vinyl resin, and acrylate resin.

[0013] In one embodiment, the thickness of the first protective layer is 2mm to 4mm; and / or, the thickness of the bamboo fiber reinforcement layer is 10mm to 25mm; and / or, the thickness of the second protective layer is 1mm to 2mm.

[0014] This invention also proposes a method for preparing the bamboo fiber composite layered material well cover, comprising the following steps: S1. Coat the lower surface of the mold with raw material and cure to form a second protective layer. Then, lay modified bamboo fiber and add resin on the upper surface of the second protective layer and pre-cur it to form a bamboo fiber reinforcement layer. Coat the upper surface of the bamboo fiber reinforcement layer obtained in step S1 with raw material and cure it to form a first protective layer. S2. Perform molding to complete the preparation of the bamboo fiber composite layered material manhole cover.

[0015] In one embodiment, in step S2, the molding temperature is 180℃~220℃, the pressure is 10MPa~20MPa, and the molding time increases by 5min~10min for every 1mm increase in the thickness of the bamboo fiber composite layered material manhole cover.

[0016] The technical solution of this invention utilizes a three-stage synergistic modification of bamboo fiber combined with a three-layer protective structure and a one-time molding process to produce bamboo fiber composite manhole covers that possess high strength, high toughness, excellent corrosion resistance, lightweight, and environmental friendliness. These covers can replace existing cast iron or cement manhole covers in heavy-duty applications such as main roads, ports, and airports; moreover, their manufacturing cost is low, indicating promising market application prospects. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0019] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0020] The technical problem addressed by this invention is that manhole covers used in urban construction facilities such as power, telecommunications, and municipal engineering are generally made of cast iron or reinforced concrete. Cast iron manhole covers have poor impact resistance, are prone to corrosion and breakage, and are easily stolen; while reinforced concrete manhole covers are heavy and have a short service life. Related technologies use fiberglass manhole covers, which are fragile and extremely environmentally unfriendly; therefore, a solution with high strength, good durability, and environmental friendliness is needed.

[0021] It should be noted that cast iron manhole covers have drawbacks such as being heavy, prone to rust, easily stolen, and generating significant noise when driven over them; cement manhole covers are brittle, have poor impact resistance, are easily weathered and damaged, and have a low recycling rate; conventional composite material manhole covers are mostly reinforced with glass fiber, but glass fiber production is highly polluting and difficult to degrade after disposal, failing to meet green environmental protection requirements, while conventional plant fiber reinforced manhole covers have problems such as insufficient strength, easy water absorption and mold growth, and poor weather resistance, failing to meet municipal load-bearing standards.

[0022] To address the aforementioned technical problems, this invention proposes a bamboo fiber composite layered material manhole cover, comprising a first protective layer, a bamboo fiber reinforcing layer, and a second protective layer stacked sequentially from top to bottom; the bamboo fiber reinforcing layer comprises modified bamboo fiber and a resin matrix, wherein the mass fraction of the modified bamboo fiber is 30wt%~50wt%; the resin matrix is ​​selected from at least one of unsaturated polyester resin and epoxy resin.

[0023] Specifically, the bamboo fiber composite layered material manhole cover provided by this invention adopts a sandwich layered structure of "upper protective layer - bamboo fiber reinforcement layer - lower protective layer". Among them, the bamboo fiber reinforcement layer serves as a load-bearing skeleton, utilizing the high specific strength and toughness of modified bamboo fiber to provide the main mechanical support; the first protective layer directly bears wear and impact, protecting the internal bamboo fiber; the second protective layer serves as a sealing layer to isolate groundwater vapor and corrosive media; through the synergistic effect of the three layers, the problems of bamboo fiber being easily worn, easily corroded, and having weak interfacial bonding are systematically solved.

[0024] It should also be noted that when the modified bamboo fiber content is less than 30 wt%, the bamboo fiber cannot form a continuous and effective reinforcing skeleton. The composite material is dominated by the resin matrix, exhibiting brittle fracture, and its impact resistance and load-bearing capacity are significantly reduced. When the modified bamboo fiber content is higher than 50 wt%, the resin matrix is ​​insufficient to fully impregnate and encapsulate all the fibers, resulting in a large number of pores and defects inside the composite material. This leads to a decrease in mechanical properties and a decrease in processing fluidity, making it difficult to mold.

[0025] In one embodiment, the method for preparing the modified bamboo fiber includes the following steps: pulverizing bamboo into bamboo fiber by steam explosion, adding a coupling agent, and stirring; then adding bio-enzymes and nano-silica, stirring and letting stand to complete the preparation of the modified bamboo fiber.

[0026] Furthermore, during steam explosion, the steam pressure is 0.8MPa~1.2MPa, and the steam explosion time is 15min~20min.

[0027] Furthermore, the average length of the bamboo fiber is not less than 5mm. It is understandable that by further limiting the bamboo fiber to long fibers, the high strength of the bamboo fiber can be fully utilized.

[0028] Specifically, this invention employs a three-tiered synergistic modification strategy involving physical, chemical, and biological processes to treat bamboo fibers. First, steam explosion instantly destroys the lignin structure of bamboo under high temperature and pressure, making the fibers easier to separate and retaining a longer length, avoiding the excessively short and weak fibers resulting from traditional mechanical crushing. Next, a coupling agent is blended with the bamboo fibers to introduce hydrophobic groups onto the fiber surface, addressing its strong hydrophilicity and hygroscopicity. Finally, bio-enzymes and nano-silica are added. Bio-enzyme treatment gently etches the fiber surface, improving its flexibility and reactivity, while nano-silica fills the fiber micropores, further blocking moisture and enhancing fatigue resistance. This synergistic effect of the three-tiered treatment endows the modified bamboo fibers with hydrophobicity, high interfacial bonding strength, and excellent fatigue resistance.

[0029] In one specific embodiment, the coupling agent includes at least one of a silane coupling agent and a titanate coupling agent. Specifically, the silane coupling agent may be KH-550, KH-560, or KH-570; the titanate coupling agent may be, for example, isopropyltris(dioctylpyrophosphonooxy) titanate or isopropyltris(dioctylpyrophosphonooxy) titanate.

[0030] In one embodiment, the weight ratio of the coupling agent to the bamboo fiber is 1:3 to 20.

[0031] In one specific embodiment, the bamboo fiber obtained by steam explosion treatment is dried at 80℃~105℃ for 2h~4h. The silane coupling agent and / or titanate coupling agent are dissolved in an ethanol / water mixed solvent (ethanol:water volume ratio of 90:10~70:30) to prepare a coupling agent solution with a mass concentration of 0.5wt%~3.0wt%. The pH of the solution is adjusted to 3.5~5.0, and the solution is stirred at room temperature for 5min~30min. The bamboo fiber is then immersed in the above solution for 60min~120min and vacuum dried for 30min to obtain the bamboo fiber modified in the first step.

[0032] In one embodiment, the bioenzyme includes at least one of cellulase, hemicellulase, laccase, and pectinase.

[0033] In one embodiment, the amount of the bio-enzyme is 0.5wt% to 1wt% of the bamboo fiber.

[0034] In one embodiment, the amount of nano-silica used is 1wt% to 3wt% of the bamboo fiber.

[0035] In one embodiment, the particle size of the nano-silica is 50nm~200nm.

[0036] In one specific embodiment, a biological enzyme is dissolved in a pH buffer solution to prepare an enzyme treatment solution. Nano-silica powder is dispersed in deionized water, and a dispersant of 1wt%–3wt% of the nano-silica mass is added. The mixture is stirred at 1000–3000 rpm for 20–40 minutes, followed by ultrasonic dispersion at 300–500 W for 15–30 minutes to obtain a nano-silica dispersion. Bamboo fibers modified in the first step are immersed in the enzyme treatment solution at a bath ratio of 1:10–1:20, a treatment temperature of 40–60°C, and a treatment time of 1–4 hours, during which gentle stirring (50–100 rpm) or shaking may be used. Then, the nano-silica dispersion is added to the same reaction system, with the amount of nano-silica being 1wt%–5wt% of the dry weight of the bamboo fibers. The mixture is then stirred or shaken at 40–60°C for 30 minutes–2 hours. Afterwards, remove the bamboo fiber and soak it in hot water at 80℃~90℃ for 5min~10min to inactivate the biological enzymes. Rinse it gently with deionized water 1~2 times, dry it at 60℃~70℃ for 2h, and then raise the temperature to 100℃~105℃ and dry it for 10min~20min to complete the preparation of modified bamboo fiber.

[0037] In one specific embodiment, the resin matrix includes at least one of an unsaturated polyester resin and an epoxy resin; the unsaturated polyester resin is preferably an orthophthalic or isophthalic unsaturated polyester resin; more preferably, the unsaturated polyester resin is an isophthalic unsaturated polyester resin. The epoxy resin is preferably a bisphenol A type epoxy resin or a bisphenol F type epoxy resin.

[0038] In one embodiment, the first protective layer includes reinforcing filler and the resin matrix; wherein the reinforcing filler includes at least one of quartz sand and silicon carbide, and the particle size of the reinforcing filler is 0.1 mm to 0.5 mm, and the volume fraction of the reinforcing filler in the first protective layer is 10% to 20%.

[0039] Specifically, the substrate of the first protective layer uses the same resin as the bamboo fiber reinforcement layer, including at least one of unsaturated polyester resin and epoxy resin. By introducing high-hardness inorganic particles into the first protective layer, surface wear is transformed into impact on hard particles, significantly improving wear resistance. Quartz sand or silicon carbide has extremely high hardness, which can significantly improve the surface wear resistance and disperse impact force, thereby mitigating the problem of breakage and wear of the bamboo fiber reinforcement layer due to sudden stress. Furthermore, this embodiment further limits the amount and particle size of reinforcing fillers to form a uniform and dense reinforced wear-resistant skeleton in the first protective layer.

[0040] In a preferred embodiment, two fillers with different particle size ranges are used in combination: 60wt%~80wt% of 0.2mm~0.3mm particles are mixed with 20wt%~40wt% of 0.3mm~0.5mm particles to achieve higher bulk density and better wear resistance.

[0041] In a preferred embodiment, the upper surface of the first protective layer further includes a wear-resistant coating, the wear-resistant coating comprising 5wt% to 15wt% wear-resistant filler and 3wt% to 5wt% anti-slip particles; wherein the wear-resistant filler comprises at least one of alumina and silicon carbide, and the anti-slip particles comprise at least one of silicon carbide and zirconium oxide; and the particle size of the wear-resistant filler is 10μm to 50μm, and the particle size of the anti-slip particles is 0.2mm to 1mm.

[0042] Specifically, the wear-resistant coating is formed as an independent sacrificial protective layer through a secondary coating process. Nanoscale alumina or silicon carbide fillers significantly increase the surface hardness of the coating, while micron-sized anti-slip particles form protrusions on the coating surface, providing macroscopic anti-slip texture. Its anti-slip effect far exceeds the microscopic roughness of the first protective layer itself, effectively preventing vehicles and pedestrians from slipping.

[0043] In one embodiment, the base material of the wear-resistant coating is polyurethane and / or epoxy resin; and it is cured on the surface of the first protective layer by room temperature curing or low temperature baking. It is understood that low temperature curing avoids thermal stress damage to the formed bamboo fiber composite structure caused by high temperatures.

[0044] In one specific embodiment, the substrate material of the wear-resistant coating is a two-component polyurethane, which is cured at 25°C to 40°C for 24 to 48 hours; if acceleration is required, it can be baked at 60°C to 80°C for 2 to 4 hours.

[0045] In one embodiment, a wear-resistant coating is formed on the surface of the first protective layer using high-pressure airless spraying or scraping; preferably, the upper surface of the first protective layer is sandblasted or polished to increase roughness and improve coating adhesion.

[0046] In one specific embodiment, the dry film thickness of the wear-resistant coating is 0.5 mm to 2 mm.

[0047] Specifically, the method for preparing the wear-resistant coating includes the following steps: The surface of the first protective layer is roughened by sandblasting or mechanical grinding to achieve a surface roughness Ra of 3μm~10μm. The dried wear-resistant filler and anti-slip particles are mixed, and then 1wt%~3wt% of dispersant and solvent (by weight of the total filler) are added. The mixture is stirred in a high-speed disperser at 1000r / min~2000r / min for 15min~30min to obtain a pre-dispersed filler slurry. The resin matrix and solvent are mixed at a weight ratio of 10:1~10:3, and the viscosity is adjusted to 20s~40s (Ford Cup 4 viscosity). The filler slurry and additives are added, and stirring continues for 20min~30min until homogeneous. Before use, a curing agent is added and stirring continues for 3min~5min. The mixture is allowed to stand for 5min~10min to degas, and then evenly coated onto the pre-treated first protective layer surface of the manhole cover.

[0048] In one embodiment, the second protective layer is any one of highly cross-linked epoxy resin, vinyl resin, and acrylate resin. Specifically, the second protective layer is dense and non-porous, serving a sealing function to cut off the path for moisture to penetrate from the bottom and protect the bamboo fiber reinforcement layer from erosion by groundwater and acidic or alkaline media.

[0049] In one specific embodiment, the second protective layer can be a highly cross-linked epoxy resin, preferably a bisphenol A type epoxy resin combined with an aromatic amine curing agent or an anhydride curing agent to achieve a high degree of cross-linking. It can also be a vinyl resin, obtained by reacting epoxy resin with an unsaturated monobasic acid, combining the excellent mechanical properties of epoxy resin with the good processability of unsaturated polyester resin. Bisphenol A type epoxy vinyl resin or phenolic epoxy vinyl resin is preferred. Alternatively, it can be a highly cross-linked acrylate resin obtained by polymerizing multifunctional acrylate monomers.

[0050] In one embodiment, the thickness of the first protective layer is 2mm to 4mm; and / or, the thickness of the bamboo fiber reinforcement layer is 10mm to 25mm; and / or, the thickness of the second protective layer is 1mm to 2mm.

[0051] This invention also proposes a method for preparing the bamboo fiber composite layered material well cover, comprising the following steps: S1. Coat the lower surface of the mold with raw material and cure to form a second protective layer. Then, lay modified bamboo fiber and add resin on the upper surface of the second protective layer and pre-cur it to form a bamboo fiber reinforcement layer. Coat the upper surface of the bamboo fiber reinforcement layer obtained in step S1 with raw material and cure it to form a first protective layer. S2. Perform molding to complete the preparation of the bamboo fiber composite layered material manhole cover.

[0052] In a specific embodiment, in step S2, the molding temperature is 180℃~220℃, the pressure is 10MPa~20MPa, and the molding time increases by 5min~10min for every 1mm increase in the thickness of the bamboo fiber composite layered material manhole cover.

[0053] Specifically, excessively high molding temperatures can lead to thermal decomposition and strength loss in bamboo fibers, while excessively low temperatures can result in incomplete resin curing.

[0054] In one specific embodiment, the method for preparing a bamboo fiber composite layered material manhole cover includes the following steps: S1. Apply the pre-prepared second protective layer mixture to the inner bottom surface of the mold and pre-cur it at 60℃~80℃ for 15min~30min; lay the pre-prepared modified bamboo fiber on the upper surface of the pre-cured second protective layer; add the prepared resin matrix adhesive into the bamboo fiber to ensure complete impregnation of the bamboo fiber without producing excessive adhesive, and then pre-cur it at 80℃~100℃ for 15min~30min to obtain a semi-cured bamboo fiber reinforced layer; then apply the pre-prepared first protective layer mixture and pre-cur it at 60℃~80℃ for 10min~20min to obtain a semi-cured manhole cover; S2. The semi-cured manhole cover is molded and pressure is applied for high-temperature and high-pressure molding. After molding, the pressure is maintained and the mold is allowed to cool naturally to below 80°C. After cooling to room temperature, the mold is opened and the manhole cover product is removed to complete the preparation.

[0055] The technical solution of the present invention will be further described below through specific embodiments.

[0056] Example 1 The preparation of modified bamboo fiber in Example 1 includes the following steps: T1. Take bamboo strips with a length of 5cm~10cm and a width of 1cm~2cm. Put the bamboo strips into a steam explosion tank, introduce saturated steam, control the pressure at 1.0MPa, maintain the pressure for 18min, and then release the pressure instantly to obtain fluffy bamboo fibers, and dry them at 95℃ for 3h; T2. Dissolve 20g of silane coupling agent KH-560 in a mixed solvent of 800mL ethanol and 200mL deionized water, adjust the pH to 4.2 with glacial acetic acid, stir at room temperature for 15min, then immerse bamboo fiber in the solution at a bath ratio of 1:15, soak in a 45℃ water bath for 90min, then filter out the bamboo fiber and dry at 80℃ for 45min. T3. Cellulase (10000 U / g) and laccase (8000 U / g) were mixed at a mass ratio of 1:1, with the total enzyme amount being 0.5% of the dry weight of bamboo fiber. The mixture was dissolved in 0.1 M acetate-sodium acetate buffer to prepare an enzyme treatment solution with a total volume of 15 L. The bamboo fiber was then immersed in the solution at a bath ratio of 1:15 and treated in a 50°C water bath shaker (80 rpm) for 2.5 h. Afterward, the solution was removed and placed in a nano-silica dispersion, and further treated with shaking at 50°C for 1 h. The silica content was 2 wt% of the dry weight of the bamboo fiber, and the bath ratio was 1:10. The bamboo fiber was then removed and immersed in 85°C hot water for 8 min to inactivate the enzyme, followed by gentle rinsing twice with deionized water. The wet fiber was then placed in an oven and dried at 65°C for 2 h to obtain modified bamboo fiber.

[0057] The raw materials for the manhole cover in Example 1 are as follows: The second protective layer includes: Bisphenol A type epoxy resin E-51: 100 parts; Methylhexahydrophthalic anhydride curing agent: 35 parts; Diluent: 10 parts; Silane coupling agent KH-560: 1.5 parts.

[0058] The above raw materials, excluding the curing agent, are stirred in a 50°C water bath for 15 minutes until homogeneous. The curing agent is added just before use, and stirring is continued for 3 minutes. Vacuum degassing is then performed for 5 minutes to obtain the second protective layer mixture.

[0059] The raw materials for the resin matrix of the bamboo fiber reinforcement layer include: Isophthalic unsaturated polyester resin (A400TV-957S): 100 parts; Methyl ethyl ketone peroxide curing agent: 1.5 parts; Cobalt naphthenate accelerator: 0.8 parts; Zinc stearate release agent: 1 part.

[0060] Mix the above raw materials except for the curing agent for 5 minutes. Add the curing agent just before use, stir for 2 minutes, and then vacuum degas for 3 minutes to obtain the bamboo fiber reinforced layer resin mixture.

[0061] The first protective layer includes: The resin matrix uses 100 parts of bamboo fiber reinforced resin mixture; the reinforcing filler is quartz sand (particle size about 0.2mm~0.4mm), with a volume fraction of about 10%.

[0062] Abrasion-resistant coatings include: Polyester polyol: 100 parts; HDI trimer: 20 parts; Butyl acetate: 20 parts; Alumina (average particle size 25μm): 12 parts; Silicon carbide anti-slip particles (average particle size 0.5mm): 5 parts; Polyether modified siloxane leveling agent: 0.5 parts; Organosilicon defoamer: 0.3 parts; Ultraviolet absorber UV-531: 1 part; Silane coupling agent KH-560: 1 part.

[0063] Mix the above raw materials except for HDI trimer for 20 minutes, add HDI trimer just before use, and stir rapidly for 5 minutes to obtain the coating.

[0064] The method for preparing the manhole cover in Example 1 includes the following steps: S1. A circular manhole cover steel mold with a diameter of 700mm and a thickness of 25mm is used. The inner surface of the mold is sprayed with silicone oil release agent; the second protective layer mixture is evenly scraped onto the bottom surface of the mold and placed in a 70℃ oven for pre-curing for 20 minutes to obtain a semi-cured second protective layer with a dry film thickness of about 1.5mm. Modified bamboo fibers are cross-laid on the upper surface of the second protective layer. Then, the bamboo fiber reinforcement layer resin mixture is evenly poured onto the bamboo fiber layer and repeatedly rolled with rollers to remove air bubbles, so that the resin fully impregnates the fiber. After that, it is placed in a 90℃ oven for pre-curing for 20 minutes to obtain a semi-cured bamboo fiber reinforcement layer with a dry film thickness of about 20mm. The first protective layer mixture is evenly coated onto the surface of the bamboo fiber reinforcement layer. An anti-slip texture is embossed on the surface using a diamond-patterned press plate. The mixture is then placed in a 70℃ oven for pre-curing for 15 minutes to obtain a semi-cured first protective layer with a dry film thickness of approximately 3 mm. S2. Place the mold with the three-layer semi-cured structure into the hydraulic hot press and close the mold. Set the molding temperature to 185℃, the pressure to 15MPa, and the molding time to 140min. After the heat preservation and pressure holding are completed, cool it with water to below 70℃, open the mold and take out the manhole cover; S3. Roughen the upper surface of the first protective layer of the molded manhole cover by sandblasting with 60-mesh quartz sand, clean it with compressed air, spray the coating, and cure it at room temperature for 48 hours to obtain a wear-resistant coating with a total dry film thickness of about 0.9 mm, thus completing the preparation of the manhole cover.

[0065] Comparative Example 1 Comparative Example 1 is based on Example 1, except that the preparation of bamboo fiber in Comparative Example 1 includes the following steps: T1. Take bamboo strips with a length of 5cm~10cm and a width of 1cm~2cm. Put the bamboo strips into a steam explosion tank, introduce saturated steam, control the pressure at 1.0MPa, maintain the pressure for 18min, and then release the pressure instantly to obtain fluffy bamboo fibers, and dry them at 95℃ for 3h; T2. Dissolve 20g of silane coupling agent KH-560 in a mixed solvent of 800mL ethanol and 200mL deionized water, adjust the pH to 4.2 with glacial acetic acid, stir at room temperature for 15min, then immerse bamboo fiber in the solution at a bath ratio of 1:15, soak in a 45℃ water bath for 90min, then filter out the bamboo fiber and dry at 80℃ for 45min; thus obtaining modified bamboo fiber.

[0066] The performance data of the manhole covers obtained in Example 1 and Comparative Example 1 are shown in Table 1.

[0067] Table 1

[0068] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A bamboo fiber composite layered material manhole cover, characterized in that, The bamboo fiber composite layered material manhole cover includes a first protective layer, a bamboo fiber reinforcing layer, and a second protective layer stacked from top to bottom. The bamboo fiber reinforcement layer comprises modified bamboo fiber and a resin matrix, wherein the mass fraction of the modified bamboo fiber is 30wt%~50wt%. The resin matrix is ​​selected from at least one of unsaturated polyester resin and epoxy resin; The method for preparing the modified bamboo fiber includes the following steps: The bamboo fiber obtained by steam explosion treatment is dried at 80℃~105℃ for 2h~4h. The silane coupling agent and / or titanate coupling agent are dissolved in a mixed solvent of ethanol and water to prepare a coupling agent solution with a mass concentration of 0.5wt%~3.0wt%. The pH of the solution is adjusted to 3.5~5.

0. The solution is stirred at room temperature for 5min~30min. The bamboo fiber is immersed in the above solution for 60min~120min and vacuum dried for 30min to obtain the bamboo fiber modified in the first step. The bio-enzyme was dissolved in a pH buffer solution to prepare an enzyme treatment solution. Nano-silica powder was dispersed in deionized water, and a dispersant of 1wt%–3wt% (by weight of the nano-silica) was added. The mixture was stirred at 1000–3000 rpm for 20–40 minutes, followed by ultrasonic dispersion at 300–500 W for 15–30 minutes to obtain a nano-silica dispersion. Bamboo fibers modified in the first step were immersed in the enzyme treatment solution at a bath ratio of 1:10–1:20 and a treatment temperature of 40–60°C. The treatment time is 1 to 4 hours, during which gentle stirring or shaking can be used as an auxiliary method. Then, the nano-silica dispersion is added, so that the amount of nano-silica is 1 wt% to 5 wt% of the dry weight of bamboo fiber. Stirring or shaking is continued at 40℃ to 60℃ for 30 minutes to 2 hours. After that, the bamboo fiber is taken out and soaked in hot water at 80℃ to 90℃ for 5 minutes to 10 minutes to inactivate the biological enzymes. It is then gently rinsed 1 to 2 times with deionized water, dried at 60℃ to 70℃ for 2 hours, and then heated to 100℃ to 105℃ for 10 minutes to 20 minutes to complete the preparation of the modified bamboo fiber.

2. The bamboo fiber composite layered material well cover as described in claim 1, characterized in that, The method for preparing the modified bamboo fiber includes the following steps: Bamboo is pulverized into bamboo fiber by steam explosion, a coupling agent is added and stirred; then bio-enzymes and nano-silica are added, stirred and allowed to stand to complete the preparation of the modified bamboo fiber.

3. The bamboo fiber composite layered material well cover as described in claim 2, characterized in that, The coupling agent includes at least one of a silane coupling agent and a titanate coupling agent; And / or, the weight ratio of the coupling agent to the bamboo fiber is 1:3~20.

4. The bamboo fiber composite layered material well cover as described in claim 2, characterized in that, The bioenzyme includes at least one of cellulase, hemicellulase, laccase, and pectinase. And / or, the amount of the bio-enzyme is 0.5wt% to 1wt% of the bamboo fiber.

5. The bamboo fiber composite layered material well cover as described in claim 1, characterized in that, The first protective layer includes reinforcing filler and the resin matrix; The reinforcing filler includes at least one of quartz sand and silicon carbide, and the particle size of the reinforcing filler is 0.1 mm to 0.5 mm, and the volume fraction of the reinforcing filler in the first protective layer is 10% to 20%.

6. The bamboo fiber composite layered material well cover as described in claim 1, characterized in that, The upper surface of the first protective layer also includes a wear-resistant coating, which comprises 5wt% to 15wt% wear-resistant filler and 3wt% to 5wt% anti-slip particles; The wear-resistant filler includes at least one of alumina and silicon carbide, and the anti-slip particles include at least one of silicon carbide and zirconium oxide. Furthermore, the wear-resistant filler has a particle size of 10μm to 50μm, and the anti-slip particles have a particle size of 0.2mm to 1mm.

7. The bamboo fiber composite layered material well cover as described in claim 1, characterized in that, The second protective layer is any one of highly cross-linked epoxy resin, vinyl resin, and acrylate resin.

8. The bamboo fiber composite layered material well cover as described in claim 1, characterized in that, The thickness of the first protective layer is 2mm to 4mm; And / or, the thickness of the bamboo fiber reinforcement layer is 10mm~25mm; And / or, the thickness of the second protective layer is 1mm to 2mm.

9. A method for preparing a bamboo fiber composite layered material well cover according to any one of claims 1 to 8, characterized in that, The method for preparing the bamboo fiber composite layered material manhole cover includes the following steps: S1. Coat the lower surface of the mold with raw material and cure to form a second protective layer. Then, lay modified bamboo fiber and add resin on the upper surface of the second protective layer and pre-cur it to form a bamboo fiber reinforcement layer. Coat the upper surface of the bamboo fiber reinforcement layer obtained in step S1 with raw material and cure it to form a first protective layer. S2. Perform molding to complete the preparation of the bamboo fiber composite layered material manhole cover.

10. The method for preparing a bamboo fiber composite layered material well cover as described in claim 9, characterized in that, In step S2, the molding temperature is 180℃~220℃, the pressure is 10MPa~20MPa, and the molding time increases by 5min~10min for every 1mm increase in the thickness of the bamboo fiber composite layered material well cover.

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