Production process of high-strength weather-proof bamboo-plastic container bottom plate

Abstract

The invention discloses a production process of a high-strength weather-proof bamboo-plastic container bottom plate. The production process comprises the four steps of bamboo base material pretreatment, composite raw material preparation, injection molding composite forming and gradient cooling post-treatment. The bamboo base material is subjected to high-temperature and high-pressure cooking, gradient drying, two-longitudinal and one-transverse assembly and aging treatment, and a bamboo-based blank with the water content being 8-10% is obtained; the composite raw materials comprise bamboo powder, thermoplastic resin, vegetable acid modified calcium carbonate, a compatilizer and the like, and are mixed and dried for later use; a customized mold with a vacuum exhaust structure is adopted, interface permeation compounding of the bamboo-based green body and the composite raw material is achieved through specific injection molding parameters, and then a finished product is obtained through gradient cooling, trimming and sanding, cutting and coating and other treatment. The problems that the bamboo-plastic interface compatibility is poor and the product defect rate is high are solved, the static bending intensity of the product is larger than or equal to 85 MPa, the elastic modulus is larger than or equal to 6000 MPa, and the bamboo-plastic composite material is high in weather resistance, environmentally friendly, free of pollution, high in production efficiency and suitable for large-scale industrial production and has remarkable economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of container floor manufacturing technology, specifically to a production process for a high-strength, weather-resistant bamboo-plastic container floor. Background Technology

[0002] As the core load-bearing component of a container, the container floor must possess excellent properties such as high strength, high toughness, weather resistance, and resistance to insects and mildew. Traditional container flooring mostly uses hardwood plywood or bamboo plywood. Hardwood resources are becoming increasingly scarce due to over-harvesting and face environmental trade barriers in regions such as the EU and the US. Bamboo plywood, on the other hand, suffers from problems such as high glue consumption, susceptibility to mildew, insufficient interlayer bonding, and short service life. Its production process often involves hot-pressing adhesive bonding, which poses a risk of formaldehyde release and has low production efficiency.

[0003] While existing bamboo-plastic composite processes have addressed environmental concerns to some extent, they generally suffer from technical challenges such as poor compatibility between bamboo fiber and plastic interfaces, insufficient venting during molding leading to product defects, and unstable mechanical properties. For example, some processes employ simple mixing molding, resulting in loose bonding between the bamboo and plastic layers and insufficient interlayer shear strength; the lack of targeted venting structures in mold design leads to defects such as air bubbles and shrinkage cavities within the product; and incomplete pretreatment of the bamboo substrate leaves residual sugar and moisture, making it susceptible to mold and insect infestation, thus affecting product lifespan. Therefore, developing a production process for bamboo-plastic container flooring that features strong interfacial bonding, excellent mechanical properties, high weather resistance, and environmental friendliness and efficiency has become a pressing technical challenge for the industry. Summary of the Invention

[0004] To address the technical deficiencies of existing technologies, this invention provides a production process for high-strength, weather-resistant bamboo-plastic container flooring. By optimizing the bamboo substrate pretreatment process, innovating the composite raw material formula, and using injection molding technology, it solves problems such as poor compatibility of bamboo-plastic interfaces, high product defect rate, and insufficient weather resistance, resulting in container flooring products that meet mechanical performance standards, have a long service life, and are environmentally friendly and pollution-free.

[0005] The technical solution adopted in this invention is: a production process for high-strength, weather-resistant bamboo-plastic container flooring, characterized by the following steps:

[0006] (1) Bamboo substrate pretreatment: Select 3-5 year old moso bamboo, which has the best mechanical properties and moderate fiber density. After cutting and splitting, bamboo strips with a width of 20-30 mm and a thickness of 3-5 mm are obtained. They are then subjected to high-temperature and high-pressure steaming, gradient drying, two-longitudinal and one-transverse assembly, and aging treatment to obtain bamboo substrate blanks with a moisture content of 8-10%. (2) Preparation of composite raw materials: By mass, 60-65 parts bamboo powder, 30-35 parts thermoplastic resin, 3-5 parts plant acid modified calcium carbonate, 2-3 parts compatibilizer, 1-2 parts antioxidant and 0.5-1 parts mildew inhibitor are mixed and the composite raw materials are obtained after high-speed stirring and vacuum drying. The ratio of bamboo powder to thermoplastic resin is controlled at 60-65:30-35 to ensure product strength and take into account molding processability. Plant acid modified calcium carbonate is used to replace the traditional silane coupling agent. Through the synergistic effect of carboxyl bonding and hydrogen bond network, the compatibility of the multiphase interface of "bamboo fiber-filler-polymer" is improved, while reducing cost and improving environmental protection. The addition of compatibilizer further enhances the bonding force between bamboo fiber and plastic. Antioxidant and mildew inhibitor improve the product's aging resistance and anti-insect and mildew resistance. Vacuum drying treatment ensures that the moisture content of the composite raw materials is ≤0.5% to avoid the generation of bubbles during injection molding. (3) Injection Molding Composite Molding: The bamboo-based preform is embedded in a customized mold with a vacuum venting structure, preheated to 80-100℃, and molten composite material is injected. The clamping force is controlled at 800-1200 tons, the injection pressure at 80-100MPa, the holding pressure at 60-80MPa, and the holding time at 2-3 minutes. At the same time, the vacuum is evacuated to below -0.095MPa through the mold venting hole to achieve bamboo-plastic interface penetration composite. The customized mold with a vacuum venting structure extracts the air inside the cavity through multiple venting holes, solving the problem of insufficient venting in traditional injection molding and reducing the product defect rate. The preheating treatment of the bamboo-based preform promotes the interface penetration between the composite material and the bamboo pieces. The specific clamping force, injection pressure, and holding pressure parameters ensure that the plastic fully fills the mold cavity and penetrates into the gaps between the bamboo pieces to form a strong mechanical interlocking structure. This process replaces the traditional hot-press adhesive composite, increasing production efficiency by more than 30% and releasing no formaldehyde. (4) Gradient cooling and post-processing: The segmented cooling process is adopted. First, the mold temperature is reduced to 60-70℃ and kept at that temperature for 1-1.5 minutes. Then, it is cooled to below 40℃ and the mold is removed. After automatic trimming, sanding, length cutting and performance testing, the finished bamboo-plastic container floor is obtained. The segmented cooling process avoids internal stress caused by the sudden drop in temperature, reducing the risk of deformation and cracking. The trimming, sanding and cutting accuracy are precisely controlled to ensure that the product size meets the container assembly requirements. The surface is coated with a water-based wear-resistant coating to further improve the wear resistance and weather resistance of the product surface and adapt to the complex environment during the sea transport process.

[0007] The high-temperature and high-pressure cooking parameters in step (1) are: temperature 120-140℃, pressure 2.0-2.2MPa, and time 3-5 hours, to achieve desugaring and degreasing of bamboo strips.

[0008] In step (1), 0.3-0.5% of plant extract antifungal agent is added to the cooking liquid during high-temperature and high-pressure steaming to replace traditional chemical insecticides and improve environmental friendliness.

[0009] In step (1), the gradient drying is carried out in three stages: the first stage is drying at 60-70℃ for 2-3 hours, the second stage is drying at 80-90℃ for 3-4 hours, and the third stage is drying at 100-110℃ for 1-2 hours. This avoids cracking and deformation of the bamboo strips due to rapid drying and accurately controls the moisture content at 8-10%, providing a good foundation for subsequent injection molding and composite.

[0010] In step (1), the two-longitudinal-one-transverse assembly method is as follows: the surface and bottom bamboo strips are arranged longitudinally, and the middle bamboo strips are arranged transversely. After assembly, the bamboo strips are pre-pressed at a pressure of 1.5-2MPa for 30-60 minutes and aged for 24-48 hours. The aging environment has a humidity of 50-60% and a temperature of 20-25℃. This fully utilizes the high longitudinal strength of bamboo fiber to improve the overall mechanical properties of the base plate. The pre-pressing and aging treatments ensure the stability of the bamboo base body structure.

[0011] In step (2), the thermoplastic resin is HDPE or PP, the bamboo powder particle size is 80-120 mesh, and the moisture content is ≤0.5%; the plant acid modified calcium carbonate is citric acid modified or DL-malic acid modified, and the amount of modifier added is 5-15% of the mass of calcium carbonate; the compatibilizer is maleic anhydride grafted PP or maleic anhydride grafted PE.

[0012] In step (3), the melting temperature of the composite raw material is 160-190℃, and the customized mold has 8-12 evenly distributed venting holes that are connected to the molding tank to achieve full-area venting.

[0013] In step (4), the automatic trimming accuracy is controlled within ±0.2mm, the surface roughness Ra after sanding is ≤3.2μm, the cutting size tolerance is ±0.5mm, and the finished product inspection includes static bending strength, elastic modulus, interlaminar shear strength and moisture content detection, wherein the static bending strength is ≥85MPa, the elastic modulus is ≥6000MPa, and the interlaminar shear strength is ≥6.0MPa.

[0014] It also includes post-processing steps: the cut base plate is coated with a water-based wear-resistant coating at a rate of 80-100g / m², and dried at 60-70℃ for 30-60 minutes to improve surface wear resistance and weather resistance.

[0015] The beneficial effects of this invention are as follows: (1) Excellent mechanical properties: The static bending strength of the product of this invention is ≥85MPa, the elastic modulus is ≥6000MPa, and the interlaminar shear strength is ≥6.0MPa, all of which exceed the national standard requirements for container flooring. The interlaminar shear strength is 20-30% higher than that of traditional bamboo plywood, thanks to the tight bonding of the bamboo-plastic interface. (2) Strong weather resistance: The bamboo substrate is desugared and degreased, and combined with the anti-mildew and antioxidant components in the composite raw materials, the product has a water absorption rate of ≤1.5%, a mildew resistance level of 0, and a weather resistance that meets the requirements of 8-10 years of service life in the marine environment. (3) Environmentally friendly and pollution-free: No formaldehyde or other harmful gases are released during the production process. Bamboo is a renewable resource and can be harvested in 3-5 years, which meets the requirements of the "replacing plastic with bamboo" and "double carbon" policies and avoids environmental trade barriers. (4) High production efficiency: The injection molding process enables continuous production, with a daily output of over 100m³, which is 30% more efficient than the traditional hot pressing process, and the product qualification rate is ≥98%; (5) Significant cost advantage: Local procurement of raw materials, the cost of plant acid modified calcium carbonate is 10-15% lower than that of silane coupling agent, and the unit cost can be controlled at RMB3600-4200 / m³ under mass production, which is 15-20% lower than that of hardwood plywood. Attached Figure Description

[0016] Figure 1 This is a flowchart of the production process of the present invention; Figure 2 This is a schematic diagram of the vacuum venting structure of an injection mold.

[0017] Figure 3 This is a cross-sectional view of the finished high-strength, weather-resistant bamboo-plastic container floor.

[0018] Among them, 1-base plate blank cavity, 2-feed inlet, 3-pressure sealing edge, 4-positioning hole, 5-fluorocarbon weather-resistant coating, and 6-modified bamboo-plastic composite substrate layer. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: (1) Bamboo substrate pretreatment: Select 3-year-old moso bamboo and cut it into 25mm×4mm bamboo strips; put the bamboo strips into a high temperature and high pressure cooking tank, add 0.3% of Artemisia argyi extract antifungal agent, and cook for 3 hours at 120℃ and 2.0MPa; use gradient drying: dry at 60℃ for 2 hours, dry at 80℃ for 3 hours, dry at 100℃ for 1 hour, and control the moisture content to 8%; assemble the blanks in two longitudinal and one transverse directions, pre-press at 1.5MPa for 30 minutes, and age for 24 hours at 50% humidity and 20℃ to obtain bamboo substrate blanks.

[0021] (2) Preparation of composite raw materials: By mass, take 60 parts of 80-mesh bamboo powder (moisture content 0.4%), 35 parts of HDPE, 3 parts of citric acid modified calcium carbonate (citric acid added at 10% of the mass of calcium carbonate), 2 parts of maleic anhydride grafted PE, 1 part of antioxidant 1010, and 0.5 parts of tea polyphenol antifungal agent; put them into a high-speed mixer and stir for 15 minutes, then dry them in a vacuum dryer at 80°C for 2 hours to obtain composite raw materials.

[0022] (3) Injection molding composite molding: The bamboo-based blank is embedded into a customized mold and preheated to 80°C; the composite material is melted at 160°C and injected into the mold, with the clamping force controlled at 800 tons, the injection pressure at 80MPa, the holding pressure at 60MPa, and the holding time at 2 minutes, while simultaneously vacuuming to -0.095MPa; the mold cavity size is 2400×1200×28mm, and it has 8 vacuum holes.

[0023] (4) Gradient cooling and post-processing: First, cool the mold to 60℃, keep it warm for 1 minute, and then cool it to 38℃ to remove the mold; after automatic trimming and sanding, cut it to standard size, coat the surface with water-based fluorocarbon wear-resistant coating (coating amount 80g / m²), and dry it at 60℃ for 30 minutes; finished product inspection: static bending strength 85MPa, elastic modulus 6200MPa, interlaminar shear strength 6.0MPa, moisture content 8.5%, which meet the national standard requirements.

[0024] Example 2: (1) Bamboo substrate pretreatment: Select 5-year-old moso bamboo, cut it into 30mm×5mm bamboo strips; add 0.5% camphor leaf extract antifungal agent, and steam for 5 hours at 140℃ and 2.2MPa; gradient drying: dry at 70℃ for 3 hours, dry at 90℃ for 4 hours, dry at 110℃ for 2 hours, and control the moisture content to 10%; assemble the two longitudinal and one transverse sections, pre-press at 2MPa for 60 minutes, and age for 48 hours at 60% humidity and 25℃.

[0025] (2) Preparation of composite raw materials: By mass, take 65 parts of 120-mesh bamboo powder (moisture content 0.3%), 30 parts of PP, 5 parts of DL-malic acid modified calcium carbonate (DL-malic acid added amount is 15% of the mass of calcium carbonate), 3 parts of maleic anhydride grafted PP, 2 parts of antioxidant 1076, and 1 part of Coptis chinensis extract antifungal agent; stir at high speed for 20 minutes, and vacuum dry at 85℃ for 3 hours.

[0026] (3) Injection molding composite molding: The bamboo-based blank is preheated to 100°C, the composite material is melted at 190°C and injected into the mold. The clamping force is 1200 tons, the injection pressure is 100MPa, the holding pressure is 80MPa, the holding time is 3 minutes, and the vacuum degree is -0.098MPa. The mold is equipped with 12 vacuum holes.

[0027] (4) Gradient cooling and post-treatment: The mold is first cooled to 70℃ and kept at that temperature for 1.5 minutes, then cooled to 35℃ and demolded; after trimming and sanding, a water-based wear-resistant coating is applied (coating amount 100g / m²), and dried at 70℃ for 60 minutes; finished product testing: static bending strength 92MPa, elastic modulus 6800MPa, interlaminar shear strength 6.5MPa, moisture content 9.2%, performance better than national standard requirements.

[0028] Please note to all technical personnel: Although the present invention has been described according to the specific embodiments above, the inventive concept of the present invention is not limited to this invention. Any modifications that utilize the inventive concept will be included within the scope of patent protection of this patent.

[0029] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A production process for high-strength, weather-resistant bamboo-plastic container floor panels, characterized in that, Includes the following steps: (1) Bamboo substrate pretreatment: Select 3-5 year old moso bamboo, cut and split it to obtain bamboo strips with a width of 20-30 mm and a thickness of 3-5 mm, and then perform high temperature and high pressure cooking, gradient drying, two longitudinal and one transverse assembly and aging treatment to obtain bamboo substrate blanks with a moisture content of 8-10%. (2) Preparation of composite raw materials: By mass, 60-65 parts of bamboo powder, 30-35 parts of thermoplastic resin, 3-5 parts of plant acid modified calcium carbonate, 2-3 parts of compatibilizer, 1-2 parts of antioxidant and 0.5-1 parts of mildew inhibitor are mixed and then dried under vacuum to obtain composite raw materials; (3) Injection molding composite molding: The bamboo-based blank is embedded into a customized mold with a vacuum exhaust structure, preheated to 80-100℃, and molten composite raw material is injected. The clamping force is controlled at 800-1200 tons, the injection pressure at 80-100MPa, the holding pressure at 60-80MPa, and the holding time at 2-3 minutes. At the same time, the vacuum is evacuated through the mold evacuation hole to below -0.095MPa to achieve bamboo-plastic interface penetration composite. (4) Gradient cooling and post-processing: The segmented cooling process is adopted. First, the mold temperature is reduced to 60-70℃ and kept warm for 1-1.5 minutes. Then, it is cooled to below 40℃ and the mold is removed. After automatic trimming, sanding, fixed-length cutting and performance testing, the finished bamboo-plastic container floor is obtained.

2. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, The high-temperature and high-pressure cooking parameters in step (1) are: temperature 120-140℃, pressure 2.0-2.2MPa, and time 3-5 hours.

3. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, In step (1), 0.3-0.5% of plant extract antifungal agent is added to the cooking liquid during high-temperature and high-pressure steaming.

4. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, In step (1), the gradient drying is carried out in three stages: the first stage is drying at 60-70℃ for 2-3 hours, the second stage is drying at 80-90℃ for 3-4 hours, and the third stage is drying at 100-110℃ for 1-2 hours.

5. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, In step (1), the two-longitudinal-one-transverse assembly method is as follows: the surface and bottom bamboo strips are arranged longitudinally, and the middle bamboo strips are arranged transversely. After assembly, the bamboo strips are pre-pressed at a pressure of 1.5-2MPa for 30-60 minutes, aged for 24-48 hours, and aged in an environment with a humidity of 50-60% and a temperature of 20-25℃.

6. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, In step (2), the thermoplastic resin is HDPE or PP, the bamboo powder particle size is 80-120 mesh, and the moisture content is ≤0.5%; the plant acid modified calcium carbonate is citric acid modified or DL-malic acid modified, and the amount of modifier added is 5-15% of the mass of calcium carbonate; the compatibilizer is maleic anhydride grafted PP or maleic anhydride grafted PE.

7. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, In step (3), the melting temperature of the composite raw material is 160-190℃, and the customized mold has 8-12 evenly distributed venting holes that are connected to the molding tank to achieve full-area venting.

8. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, In step (4), the automatic trimming accuracy is controlled within ±0.2mm, the surface roughness Ra after sanding is ≤3.2μm, the cutting size tolerance is ±0.5mm, and the finished product inspection includes static bending strength, elastic modulus, interlaminar shear strength and moisture content detection, wherein the static bending strength is ≥85MPa, the elastic modulus is ≥6000MPa, and the interlaminar shear strength is ≥6.0MPa.

9. The production process of a high-strength, weather-resistant bamboo-plastic container floor according to claim 1, characterized in that, It also includes post-processing steps: the cut base plate is coated with a water-based wear-resistant coating at a rate of 80-100g / m², and dried at 60-70℃ for 30-60 minutes to improve surface wear resistance and weather resistance.

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