A process for making a packaging board for steel coils using fiberboard and recycled plastic particles

Abstract

The application discloses a process for manufacturing a packaging board for steel coils by using wood fibers and recycled plastic particles, and belongs to the technical field of steel packaging materials. The recycled wood fibers obtained by dissociating waste wet hard fiber boards and industrial recycled plastic particles are used as main raw materials, and a compatible agent, a flame retardant and an anti-aging agent are additionally used, so that the packaging board for steel coils is prepared through drying, mixing, hot-pressing, cooling and shaping and post-processing. The application makes full use of solid waste resources, and the prepared packaging board has the advantages of high rigidity, moisture resistance, impact resistance, steel coil weight pressure resistance, water resistance and crack resistance, and meets the protection requirements of steel coil external packaging of a steel plant. The application solves the problem of high cost of the all-plastic board, realizes solid waste resource utilization, reduces the packaging cost of the steel coil, and is suitable for industrialized batch production.

Description

Technical Field

[0001] This invention relates to the production process of steel packaging materials. Background Technology

[0002] In the steel industry, hot-rolled and cold-rolled steel coils require end face pads and outer ring guards for transportation to provide pressure resistance, isolation, and protection against impacts. All-plastic pads offer good waterproofing, but their raw material costs are high, their rigidity is insufficient, and they are prone to creep deformation under heavy pressure.

[0003] Wood-plastic composites possess the dual advantages of high strength from wood fibers and waterproof, corrosion-resistant properties from plastics. However, most existing wood-plastic composites use virgin wood flour, resulting in high costs; they rarely utilize recycled fibers from waste wet-process hardboard; and the impact resistance and pressure bearing capacity of ordinary wood-plastic composite boards cannot directly meet the heavy pressure and lifting impact conditions of steel coils. Waste wet-process hardboard is mostly incinerated and landfilled. If recycled wood fibers could be obtained by separating it and combining them with recycled plastic granules to prepare special packaging boards for steel coils, it would both dispose of industrial solid waste and reduce the packaging material costs for steel mills, demonstrating significant application value. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing steel coil packaging boards and to provide a process for producing steel coil packaging boards using wood fiber and recycled plastic granules. The technical solution adopted by the present invention to achieve the above objectives is as follows: A process for producing packaging plates for steel coils using fiberboard and recycled plastic granules, comprising the following steps: 1) Preparation of recycled wood fiber: Recycled wood fiber is obtained by processing waste wet-process hardboard; 2) Raw material ratio: by weight: 45-65 parts recycled wood fiber, 25-45 parts recycled plastic granules, 3-8 parts compatibilizer, 2-5 parts flame retardant, 0.5-2 parts anti-aging agent, and 0.3-1.5 parts lubricant; 3) High-speed mixing: Dry recycled wood fiber, recycled plastic granules and additives are put into a high-speed mixer, the mixing temperature is 85-110℃, the mixing time is 5-12 minutes, and a uniform mixture is obtained. 4) Pre-compression laying: The mixture is laid into the steel mold and pre-compressed. The pre-compression pressure is 1.5-3.5MPa and the pre-compression time is 1-3min to obtain the slab. 5) High-temperature hot pressing molding: hot pressing of the slab, hot pressing temperature 160-190℃, hot pressing pressure 6-12MPa, holding time 8-18min; so that the plastic melts and coats the wood fiber, and the interface is bonded. 6) Cooling and shaping: After hot pressing, maintain pressure and cool to 45-65℃ to demold and obtain the raw board.

[0005] 7) Post-processing: trimming and sanding, the surface can be coated with a waterproof protective coating to obtain a packaging plate for steel coils. The finished packaging plate is used as a protective pad for the end face and outer ring of steel coils in steel plants. The plate thickness is 8-22mm.

[0006] In step 1), the preparation of recycled wood fiber includes the following steps: S1: Crushing: Crushing waste wet-process hardboard; S2: Humidity conditioning and curing: Temperature 45-65℃, relative humidity 90%-92%RH, curing time 3-4h; S3: Hydrothermal steaming: Hydrothermal steaming temperature 120-140℃; holding time 30-50min, corresponding to saturated steam pressure 0.4-0.5MPa; S4: Flash steaming and puffing: The pressure is released and flash steaming occurs at the end of the cooking process, causing the water vapor inside the rigid board to expand rapidly and break down into loose fiber clumps; S5: Low-speed gentle mechanical carding: Low-speed fiber carding machine cardes fibers at low speed to obtain fiber slurry; S6: Adhesive removal and purification: a) Hot water washing: After combing, the fibers are sent into a hot water washing tank with a water temperature of 60-85℃ and a solid-liquid ratio of 1:4-1:6. The hot water dissolves the hydrolyzed small molecules of gums and some of the degradation extracts. Stir and wash for 5-12 minutes. The gum residue is partially dissolved into the liquid phase. b) Solid-liquid separation: Screw extrusion dewatering removes washing wastewater carrying colloidal substances, and the fiber moisture content after extrusion is 45-60%; the wastewater is treated and recycled. c) Dry purification: After initial drying, the dehydrated fibers enter an air classifier; using density difference, denser rubber particles and sand impurities are separated from the heavy wood fibers; then, they pass through a 12-20 mesh vibrating screen to remove residual rubber lumps and hard particle impurities, resulting in purified regenerated wood fibers, which are then dehydrated and dried to a moisture content of 2-6%.

[0007] The recycled plastic granules are one or a mixture of two of the recycled HDPE and PP granules, with a melt flow index of 5-15 g / 10 min.

[0008] The compatibilizer is maleic anhydride-grafted polypropylene or maleic anhydride-grafted polyethylene; the flame retardant is a halogen-free phosphorus-nitrogen flame retardant; the anti-aging agent is a combination of hindered phenolic antioxidant and light stabilizer, with antioxidant 1010:HALS (944) = 1:2.

[0009] In step 3), the preferred temperature is 95-105℃ and the mixing time is 7-10 min.

[0010] In step 5), the preferred hot pressing temperature is 170-180℃, the pressure is 8-10MPa, and the holding time is 10-14min.

[0011] In step 6), the prepared raw board has a density of 1.05-1.35 g / cm³, a static bending strength ≥28 MPa, and a 24-hour water absorption thickness expansion rate ≤2.5%.

[0012] The raw plate prepared by the process is used for the end face and outer protective pad of steel coil packaging in steel plants.

[0013] The present invention has the following advantages: 1. The raw materials are recycled wood fibers from waste wet-process hardboard + recycled plastic pellets, which disposes of a large amount of solid waste, reduces raw material costs, and reduces the consumption of logs. 2. The use of compatibilizers improves the interfacial bonding force between the wood and plastic phases, resulting in high static bending strength of the board, resistance to heavy pressure, and ability to withstand the self-weight load of the steel coil, making it suitable for steel coil end face pad applications. 3. The continuous plastic coating of wood fiber has a low water absorption and swelling rate, is moisture-resistant and mildew-resistant, and can meet the requirements of open-air storage and high-humidity salt spray environment in sea transportation, with no formaldehyde release; 4. Compound flame retardants and anti-aging additives to improve weather resistance and extend the number of times packaging boards can be reused; 5. The entire process can be integrated with waste wet-process hard fiberboard decomposition production lines for continuous production, making it suitable for bulk supply of packaging materials to steel mills. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the present invention for producing packaging plates for steel coils using fiberboard and recycled plastic granules. Detailed Implementation

[0015] Example 1: A process for producing packaging plates for steel coils using wood fiber and recycled plastic granules, as follows: Figure 1 As shown: 1) Waste wet-process hardboard is processed according to the following decomposition process to obtain recycled wood fiber, which is then dried with hot air to a moisture content of 3.2%. The preparation of recycled wood fiber includes the following steps: S1: Crushing: The waste wet-process hardboard is crushed into 20-40mm pieces; S2: Humidity conditioning and curing: Temperature 50℃, relative humidity 90%RH, curing time 4h; S3: Hydrothermal steam: Hydrothermal steam temperature 135℃; holding time 38min, corresponding to saturated steam pressure 0.4MPa; S4: Flash Expansion: The pressure is released and flash evaporation occurs instantly after the cooking process ends. The water vapor inside the rigid board expands rapidly and breaks down into loose fiber clumps. S5: Low-speed gentle mechanical carding: The low-speed fiber carding machine cardes the fiber pulp at a low speed, with the carding machine speed at 200 r / min for 9 min; S6: Adhesive removal and purification: a) Hot water washing: After combing, the fibers are sent into a hot water washing tank at 80°C and a solid-liquid ratio of 1:5. The hot water dissolves the hydrolyzed small molecules of gums and some of the degradation extracts. Stir and wash for 10 minutes. The gum residue is partially dissolved into the liquid phase. b) Solid-liquid separation: Screw extrusion dewatering removes washing wastewater carrying colloidal substances, and the fiber moisture content is 50% after extrusion; the wastewater is treated and recycled. c) Dry purification: After initial drying, the dehydrated fibers enter an air separator; using density difference, denser rubber particles and sand impurities are separated from the heavy wood fibers; then, after passing through a 15-mesh vibrating screen, residual rubber blocks and hard particle impurities are removed to obtain purified regenerated wood fibers, which are then dehydrated and dried to a moisture content of 3.2%.

[0016] 2) Component ratio by weight: 55 parts recycled wood fiber, 34 parts recycled PP granules, 5 parts maleic anhydride grafted PP compatibilizer, 3 parts phosphorus and nitrogen halogen-free flame retardant, 1.2 parts anti-aging compound agent, and 0.8 parts lubricant. 3) Mix at 100℃ for 8 minutes using a high-speed mixer; 4) Lay out the steel mold, pre-compress at a pressure of 2.5 MPa for 2 minutes, and form the slab; 5) Hot pressing temperature 175℃, pressure 9MPa, holding pressure for 12min; 6) Hold pressure and cool to 52℃ before demolding; 7) Trim and sand the edges, and apply a waterproof protective coating to the surface to obtain a packaging board for steel coils, and prepare a 14mm thick steel coil packaging pad.

[0017] Performance testing: density 1.22g / cm³, static bending strength 34.6MPa, 24h water absorption thickness expansion rate 1.8%, no formaldehyde release, pressure resistance meets the requirements for use as end face pads for cold-rolled steel coils.

[0018] Example 2: By weight: 48 parts recycled wood fiber, 42 parts recycled HDPE granules, 4 parts compatibilizer, 3.5 parts flame retardant, 1 part anti-aging agent, 1.5 parts lubricant; the remaining process conditions are the same as in Example 1.

[0019] Sheet material properties: density 1.16g / cm³, static bending strength 30.2MPa, 24h water absorption thickness expansion rate 2.1%, suitable for outer ring lining of marine steel coils.

[0020] Comparative example: Ordinary plywood, with a thickness expansion rate of 11.3% after 24 hours of water absorption, is extremely prone to delamination and mold growth in humid environments, and releases formaldehyde.

[0021] This invention uses recycled wood fibers from waste wet-process hardboard and recycled plastic granules as main raw materials, combined with functional additives, and hot-pressed to prepare a special packaging board for steel coils. The board has high rigidity, pressure resistance, low water absorption, and aging resistance, making it suitable for steel coil storage in steel mills and for protection during sea transportation, thus realizing the resource utilization of solid waste.

[0022] This invention has been described through embodiments. Those skilled in the art will understand that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this invention.

Claims

1. A process for producing packaging plates for steel coils using fiberboard and recycled plastic granules, characterized in that: It includes the following steps: 1) Preparation of recycled wood fiber: Recycled wood fiber is obtained by processing waste wet-process hardboard; 2) Raw material ratio: by weight: 45-65 parts recycled wood fiber, 25-45 parts recycled plastic granules, 3-8 parts compatibilizer, 2-5 parts flame retardant, 0.5-2 parts anti-aging agent, and 0.3-1.5 parts lubricant; 3) High-speed mixing: Dry recycled wood fiber, recycled plastic granules and additives are put into a high-speed mixer, the mixing temperature is 85-110℃, the mixing time is 5-12 minutes, and a uniform mixture is obtained. 4) Pre-compression laying: The mixture is laid into the steel mold and pre-compressed. The pre-compression pressure is 1.5-3.5MPa and the pre-compression time is 1-3min to obtain the slab. 5) High-temperature hot pressing: hot pressing of slabs, hot pressing temperature 160-190℃, hot pressing pressure 6-12MPa, holding time 8-18min; This process involves melting and coating wood fibers with plastic, creating an interfacial bond. 6) Cooling and shaping: After hot pressing, maintain pressure and cool to 45-65℃ to demold and obtain the raw board.

2. The process for producing packaging plates for steel coils using fiberboard and recycled plastic granules according to claim 1, characterized in that: In step 1), the preparation of recycled wood fiber Includes the following steps: S1: Crushing: Crushing waste wet-process hardboard; S2: Humidity conditioning and curing: Temperature 45-65℃, relative humidity 90%-92%RH, curing time 3-4h; S3: Hydrothermal steaming: Hydrothermal steaming temperature 120-140℃; holding time 30-50min, corresponding to saturated steam pressure 0.4-0.5MPa; S4: Flash steaming and puffing: The pressure is released and flash steaming occurs at the end of the cooking process, causing the water vapor inside the rigid board to expand rapidly and break down into loose fiber clumps; S5: Low-speed gentle mechanical carding: Low-speed fiber carding machine cardes fibers at low speed to obtain fiber slurry; S6: Adhesive removal and purification: a) Hot water washing: After combing, the fibers are sent into a hot water washing tank with a water temperature of 60-85℃ and a solid-liquid ratio of 1:4-1:

6. The hot water dissolves the hydrolyzed small molecules of gums and some of the degradation extracts. Stir and wash for 5-12 minutes. The gum residue is partially dissolved into the liquid phase. b) Solid-liquid separation: Screw extrusion dewatering removes washing wastewater carrying colloidal substances, and the fiber moisture content after extrusion is 45-60%; Wastewater is treated and then recycled. c) Dry purification: After initial drying, the dehydrated fibers enter an air classifier; using density difference, denser rubber particles and sand impurities are separated from the heavy wood fibers; then, they pass through a 12-20 mesh vibrating screen to remove residual rubber lumps and hard particle impurities, resulting in purified regenerated wood fibers, which are then dehydrated and dried to a moisture content of 2-6%.

3. The process for producing packaging plates for steel coils using fiberboard and recycled plastic granules according to claim 1, characterized in that: The recycled plastic granules are one or a mixture of two of the recycled HDPE and PP granules, with a melt flow index of 5-15 g / 10 min.

4. The process for producing packaging plates for steel coils using fiberboard and recycled plastic granules according to claim 1, characterized in that: The compatibilizer is maleic anhydride-grafted polypropylene or maleic anhydride-grafted polyethylene; the flame retardant is a halogen-free phosphorus-nitrogen flame retardant; the anti-aging agent is a mixture of hindered phenolic antioxidant and light stabilizer: antioxidant 1010: HALS (944) = 1:

2.

5. The process for producing packaging plates for steel coils using fiberboard and recycled plastic granules according to claim 1, characterized in that: In step 3), the preferred temperature is 95-105℃ and the mixing time is 7-10 min.

6. The process for producing packaging plates for steel coils using fiberboard and recycled plastic granules according to claim 1, characterized in that: In step 5), the preferred hot pressing temperature is 170-180℃, the pressure is 8-10MPa, and the holding time is 10-14min.

7. The process for producing packaging plates for steel coils using fiberboard and recycled plastic granules according to claim 1, characterized in that: In step 6), the prepared raw board has a density of 1.05-1.35 g / cm³, a static bending strength ≥28 MPa, and a 24-hour water absorption thickness expansion rate ≤2.5%.

8. The raw plate prepared by the process according to any one of claims 1 to 7 is used as the end face and outer ring protective pad for steel coil packaging in steel plants.

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