Pearl wool coiled material continuous foaming composite technology and waste gas recovery system thereof

Abstract

The invention discloses a continuous foaming composite process for a pearl wool coiled material and a waste gas recovery system thereof, and belongs to the technical field of pearl wool processing. Aiming at the problems of low efficiency and waste gas pollution of a traditional intermittent process, the process realizes continuous production through raw material selection (the melt index of LDPE is 1.0-2.5 g / 10min), drying and mixing pretreatment, melting and plasticizing through a twin-screw extruder, injection of foaming agents such as butane under the pressure of 8-12MPa, extrusion foaming at a die head of 140-160 DEG C and combination of air-cooling and water-cooling shaping. The compounding link comprises multiple processes such as hot pressing and co-extrusion to adapt to different base materials, after-treatment is conducted through trimming, taper tension coiling and standing stress release, the product density fluctuation is + / -3%, and the peel strength is larger than or equal to 3 N / cm. According to the waste gas recovery system, negative pressure collection is conducted through a closed gas collecting hood, indirect cooling and alkali liquor spraying pretreatment are conducted, activated carbon adsorption concentration and catalytic combustion purification are conducted, the VOCs removal rate is larger than or equal to 98%, the emission concentration is smaller than or equal to 50 mg / m < 3 >, and efficient production and environmental protection benefits are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pearl wool roll processing, in particular to a pearl wool roll continuous foaming composite process and waste gas recovery system thereof. BACKGROUND

[0002] The continuous foaming composite process of pearl wool roll is an automatic production technology integrating foaming forming and material compounding, which realizes the foaming of low-density polyethylene material and the compounding of multi-layer structure through a continuous production line, and finally forms a roll product with buffering, heat insulation, moisture-proof and other properties. Pearl wool roll is widely used in the packaging field due to its buffering and shock-absorbing properties.

[0003] The traditional pearl wool roll foaming composite process mostly adopts an intermittent operation mode, which has problems such as energy waste caused by frequent start and stop of equipment, low production efficiency caused by poor process connection, and the like. In addition, the single-batch capacity is limited and cannot meet the needs of large-scale production. Moreover, VOCs waste gas generated by volatilization of butane and other foaming agents and adhesives used in the chemical foaming process is directly discharged, which not only increases the raw material loss and production cost, but also poses a threat to the atmospheric environment and the health of operators. With the increasingly strict environmental protection, the development of an intelligent production line integrating continuous production, precise temperature control and waste gas recycling has become a key direction for the transformation and upgrading of the industry. By integrating automatic unwinding, online compounding, multi-section temperature control foaming and other technologies, the process flow can be significantly shortened. The supporting condensation recovery, activated carbon adsorption and catalytic combustion combined treatment system can realize the recycling of more than 95% of organic waste gas, reduce the energy consumption of unit product by 15%-20%, and achieve the synergistic improvement of clean production and economic benefits. SUMMARY

[0004] The present application aims to provide a pearl wool roll continuous foaming composite process and waste gas recovery system to solve the problems raised in the background.

[0005] To solve the above technical problems, the present application provides the following technical solution: a pearl wool roll continuous foaming composite process, comprising the following steps:

[0006] S1, raw material and additive selection stage

[0007] Low-density polyethylene (LDPE) is the core raw material, and products with a melt index in the range of 1.0-2.5 g / 10 min should be selected. The index affects the flowability of the material. If the melt index is too high, the foam strength will be insufficient, and if it is too low, the extrusion forming will be affected. These particles will expand to form a pearl-like foam structure during the foaming process.

[0008] Foaming agents: Physical foaming agents such as butane, accounting for 3%-5%, need to be stored in high-pressure containers and transported through dedicated pipelines; chemical foaming agents such as azodicarbonamide (AC foaming agent), with an addition amount of 1%-2%, and their decomposition temperature needs to be precisely matched with the temperature of the extruder heating section.

[0009] Crosslinking agent: Dicumyl peroxide (DCP) with an addition amount of 0.5%-1% can crosslink the polyethylene molecular chains and enhance the stability of the foam structure. However, excessive amounts will cause the melt viscosity to rise sharply, affecting extrusion.

[0010] Anti-aging agent: Hindered phenolic anti-aging agent (such as 1010) is added at a ratio of 0.2%-0.5% to prevent pearl cotton from aging due to light and oxygen during storage and use;

[0011] Filler: The amount of calcium carbonate added is usually no more than 5% to adjust the hardness of pearl cotton, but too much will reduce the cushioning performance.

[0012] S2. Pretreatment of raw materials

[0013] Drying process: Put low-density polyethylene granules into a hot air circulating dryer and dry them at 60-80℃ for 2-4 hours. Insufficient drying will cause the moisture in the material to form large bubbles or voids during the foaming process, while excessive drying may lead to oxidation of the raw materials.

[0014] Mix evenly: Use a high-speed mixer, set the speed to 800-1200 r / min, and mix the main material and additives for 10-15 minutes. During the mixing process, ensure that the foaming agent is evenly dispersed to avoid uneven bubbles caused by excessively high local concentration.

[0015] S3, Continuous foaming molding process

[0016] Melt plasticizing: The process is carried out using a twin-screw extruder. Before starting, each heating section needs to be preheated. The dried and mixed raw material is fed into the extruder hopper through a metering feeder. Under the forward conveying and shearing action of the twin screw, the material gradually heats up and melts. The physical foaming agent is injected by a high-pressure metering pump in the melt homogenization section (pressure 8-12MPa), while the chemical foaming agent decomposes at high temperature to produce gas.

[0017] Foaming extrusion: Raw materials are fed into a foaming mold for processing. The mold lip width is set according to product specifications, generally 1-2m, and the lip temperature is maintained at 140-160℃. When the material is extruded from the mold, the pressure drops sharply to 0.5-1MPa. At this point, the bubbles rapidly expand to form foam melt. The size and density of the bubbles are controlled by adjusting the mold temperature and extrusion speed. Higher temperatures will decrease the melt viscosity, making bubbles more prone to coalescing and increasing in size; excessively high extrusion speeds may cause bubbles to burst.

[0018] Cooling and Shaping: The raw material is introduced into the mold for cooling and solidification. A combination of air cooling and water cooling is used. The air cooling device is located near the mold outlet, and the air temperature is controlled at 20-40℃ with adjustable air volume. The water cooling device further cools the foam sheet by circulating cooling water (water temperature 15-25℃). The movement of the foam sheet is controlled by traction. The traction roller group consists of multiple sets of rollers and pulls the foam sheet at a constant speed of 5-15m / min. The traction tension needs to be precisely controlled at 5-10N. Excessive tension will easily cause the sheet to stretch and deform, while insufficient tension will not be able to effectively shape it.

[0019] S4, Online Synchronous Foaming-Composite Processing

[0020] Hot-press lamination: When the temperature of the pearl cotton sheet drops to about 100℃, the composite substrate (such as PE film) is introduced into the hot-pressing zone through the guide roller system. It passes between the heating roller and the pressure roller simultaneously with the pearl cotton. The residual heat on the surface of the pearl cotton is used to melt the PE film and achieve adhesion. The surface temperature of the heating roller is set at 80-120℃ and is achieved by electric heating or heat transfer oil heating. The pressing pressure is 0.2-0.5MPa, which is provided by the hydraulic system.

[0021] Co-extrusion lamination: An auxiliary extruder is added to extrude hot melt adhesive (such as EVA, POE) or another layer of PE melt. The temperature of the auxiliary extruder is set 10-20℃ lower than that of the main extruder to ensure the matching of melt flow. The melt extruded by the auxiliary extruder and the pearl cotton sheet merge at the die exit. Co-extrusion lamination is achieved through the special flow channel design in the die to form a multi-layer structure.

[0022] S5, Post-processing Composite

[0023] Adhesive lamination: Water-based acrylic adhesive or hot melt adhesive is coated onto the surface of pearl cotton using roller coating or blade coating methods, with the coating amount controlled at 10-20 g / m². 2 The coating roller speed and traction speed must be matched to ensure uniform adhesive layer. After coating, the pearl cotton and composite substrate (such as kraft paper) are bonded by pressing roller (temperature 60-90℃, pressure 0.3-0.6MPa), and then enter the drying tunnel (temperature 100-120℃, residence time 2-5 minutes) to cure the adhesive.

[0024] High-frequency welding composite: After stacking pearl cotton and PVC materials, they are fed into a high-frequency welding machine. The frequency of the high-frequency electric field is generally 27.12MHz or 40.68MHz. The high-frequency electric field causes the molecules at the material interface to rapidly polarize and vibrate, generating heat. Under pressure (0.2-0.4MPa), glue-free bonding is achieved. The welding time is adjusted according to the material thickness, usually 1-3 seconds.

[0025] S6. Molding and Post-processing

[0026] Edge trimming: The traction roller group is driven by a servo motor, and the speed is monitored in real time by an encoder. The speed error is controlled within ±0.5%. During the traction process, the thickness of the pearl cotton roll can be adjusted by adjusting the roller gap, with an accuracy of ±0.1mm. The rough edges of the pearl cotton roll are removed by circular blades or hot cutting. The circular blades need to be sharpened regularly to ensure that the blades are sharp. The hot cutting temperature is controlled at 180-200℃ to prevent the cut edges from sticking together and to ensure the width accuracy is within ±1mm.

[0027] Winding: The finished product is wound up by a tension-controlled winding machine. The initial tension is set to 8-12N. As the roll diameter increases, the tension gradually decreases. A tapered tension control algorithm is used. The roll diameter is generally 1-2 meters. After winding, a PE protective film is wrapped around the surface of the roll. The rolled pearl cotton is placed in a room temperature warehouse and left to stand for 24-48 hours. During this process, the internal stress of the pearl cotton is released, the foam structure is further stabilized, and the density fluctuation range can be controlled within ±3%.

[0028] According to the above technical solution, in steps S5-S6, a density meter is used to monitor the density of the pearl cotton in real time, with an accuracy of ±0.5 kg / m³. 3 The infrared thermometer has an error of ±1℃ in monitoring the temperature of the sheet.

[0029] According to the above technical solution, in step S6, a series of inspections need to be carried out on the product. Physical properties such as density, tensile strength, and elongation at break need to be tested according to GB / T2918-1998 standard; the peel strength of the composite layer needs to be tested according to GB / T2791-1995 standard, which requires ≥3N / cm.

[0030] According to the above technical solution, in step S1, it is necessary to control the quality of low-density polyethylene and ensure that its density and purity meet the standards. Density deviation will affect the density uniformity and cushioning performance of the final product, while low purity will affect the appearance and performance of the product.

[0031] According to the above technical solution, the waste gas recovery system of the continuous foaming composite process of high-strength pearl cotton rolls as described in any one of claims 1-4 is characterized by comprising the following steps:

[0032] S1. Install a gas collection hood

[0033] Sealed gas collection hoods are installed at exhaust gas generation points such as the extruder outlet, composite pressure roller, and drying tunnel. Negative pressure ventilation is used to ensure that exhaust gas does not leak out. For example, an annular gas collection hood is installed at the extruder die head, with the wind speed controlled at 0.8-1.2 m / s to prevent material splashing while efficiently collecting exhaust gas. For areas that are difficult to completely seal (such as near the traction roller), an umbrella-shaped gas collection hood combined with a barrier is used to increase collection efficiency. Corrosion-resistant PP or stainless steel pipes are selected, with a pipe slope of ≥3% to prevent condensate accumulation. The pipe diameter is designed according to the exhaust gas flow rate to ensure that the flow velocity inside the pipe is 15-20 m / s, reducing residue inside the pipe.

[0034] S2, Exhaust Gas Pretreatment

[0035] The exhaust gas temperature typically reaches 60-120℃. It is first cooled to below 40℃ using an indirect cooler (such as a plate heat exchanger) to prevent damage to subsequent treatment equipment. Circulating cooling water is used as the cooling medium, with the water temperature controlled at 20-25℃. A cyclone spray tower is installed, utilizing a circulating alkaline absorbent liquid (such as NaOH solution, concentration 5-10%) to remove oil mist, particulate matter, and water-soluble organic matter from the exhaust gas. The spray liquid flow rate is controlled at 8-12 L / m³. 2 The gas-liquid contact time is ≥2s. The sprayed exhaust gas contains a large amount of moisture. The moisture is further removed by a wire mesh demister + desiccant adsorption tower (filled with silica gel or molecular sieve), so that the humidity of the exhaust gas is reduced to below 80% to prevent it from affecting the adsorption or catalytic efficiency.

[0036] S3, Exhaust Gas Purification Treatment

[0037] The waste gas is introduced into the purification structure for treatment, using a honeycomb activated carbon adsorption tower with a specific surface area ≥1000m². 2 / g, the filling amount is calculated based on the waste gas flow rate and VOCs concentration to ensure a residence time ≥1.5s. When the activated carbon adsorption saturation reaches 80%, the hot air desorption and regeneration program is started. The desorption temperature is 120-150℃, which concentrates the low-concentration waste gas into high-concentration, low-flow-rate waste gas (concentration ratio 5-15 times). Then, the waste gas undergoes catalytic combustion treatment. The desorbed high-concentration waste gas is sent to the catalytic combustion furnace, which uses precious metal catalysts (such as Pt, Pd) at a reaction temperature of 250-350℃ to decompose VOCs into CO2 and H2O. The purification efficiency is ≥98%. The high-temperature exhaust gas generated by combustion recovers heat through a waste heat exchanger and is used to preheat the waste gas to be treated or for activated carbon desorption, thereby reducing energy consumption.

[0038] After purification, the exhaust gas can be discharged from the system once it meets the emission standards. The emission indicators must comply with the "Integrated Emission Standard for Air Pollutants" (GB 16297-1996), with VOCs emission concentration ≤50mg / m³. 3 Benzene series compounds ≤10mg / m³ 3 .

[0039] According to the above technical solution, activated carbon needs to be replaced regularly (generally every 3-6 months), and the spray tower nozzles and packing need to be cleaned to prevent clogging. The catalyst activity should be tested every quarter, and it should be replaced when the purification efficiency drops below 90%.

[0040] According to the above technical solution, in step S3, it is necessary to monitor the concentration of non-methane total hydrocarbons and benzene series compounds in real time; temperature, humidity, pressure and flow sensors are required, and the data is connected to the environmental protection supervision platform, and an alarm is automatically triggered in case of abnormality.

[0041] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0042] 1. The beneficial effects of this continuous foaming composite process for high-strength pearl cotton rolls are as follows: Firstly, it enables continuous production, changing the traditional intermittent operation mode, reducing energy waste from equipment start-up and shutdown, improving production efficiency, and meeting the needs of large-scale production. Secondly, it precisely controls the raw material ratio and process parameters, such as LDPE melt index, additive dosage, and drying and mixing time, ensuring material flowability and uniformity, and avoiding problems such as uneven bubble distribution and unstable structure. Thirdly, through a twin-screw extruder, a precise temperature-controlled die, and a combination of air-cooling and water-cooling for shaping, coupled with traction tension control, the foam structure is made uniform, and density fluctuations can be controlled within ± Within 3%, improving physical indicators such as buffer performance; fourth, the composite process is flexible and diverse, covering hot pressing, co-extrusion, adhesive bonding and high-frequency welding, etc., which can be adapted to various substrates such as PE film, kraft paper, PVC, etc., expanding the application scenarios of products; fifth, the post-processing stage uses servo motor to drive edge cutting, tapered tension winding and static stress release to ensure width accuracy of ±1mm, and product density, peel strength and other indicators meet national standards; sixth, the supporting waste gas recovery system, through gas collection, pretreatment, activated carbon adsorption and catalytic combustion, the purification efficiency is ≥98%, which meets environmental protection standards, and at the same time recovers waste heat to reduce energy consumption.

[0043] 2. By installing sealed gas collection hoods at exhaust gas generation points such as the extruder outlet, negative pressure ventilation is used, combined with umbrella-shaped gas collection hoods and enclosures, to efficiently collect exhaust gas and prevent leakage. In the exhaust gas pretreatment stage, the temperature is reduced to below 40℃ using an indirect cooler to avoid high-temperature damage to subsequent equipment. A cyclone spray tower is used to remove oil mist, particulate matter, and water-soluble organic matter. Then, a wire mesh demister and a desiccant adsorption tower are used to reduce humidity, laying the foundation for subsequent purification. The purification process uses a honeycomb activated carbon adsorption tower. After adsorption saturation, hot air desorption and regeneration are used to concentrate the exhaust gas. Finally, VOCs are decomposed in a catalytic combustion furnace, achieving a purification efficiency of ≥98%. Waste heat from combustion is recovered, reducing energy consumption. Emission indicators comply with the "Integrated Emission Standard for Air Pollutants," with VOCs emission concentration ≤50mg / m³. 3 Benzene series compounds ≤10mg / m³ 3It boasts excellent environmental performance, with sensors equipped to monitor concentration, temperature, humidity, and other data in real time and connect to an environmental protection platform. It also features alarms for abnormalities and regular maintenance operations such as replacing activated carbon and cleaning the spray tower to ensure stable system operation. Detailed Implementation

[0044] 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. 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.

[0045] This invention provides the following technical solutions:

[0046] Example 1

[0047] This invention provides a technical solution: a continuous foaming and composite process for pearl cotton rolls, including the S1 stage of raw material and additive selection.

[0048] Low-density polyethylene (LDPE) is the core raw material. Products with a melt index in the range of 1.0-2.5 g / 10 min should be selected. This index affects the flowability of the material. If the melt index is too high, the foam strength will be insufficient. If it is too low, it will affect the extrusion molding. These particles will expand during the foaming process to form a pearl-like foam structure.

[0049] Foaming agents: Physical foaming agents such as butane, accounting for 3%-5%, need to be stored in high-pressure containers and transported through dedicated pipelines; chemical foaming agents such as azodicarbonamide (AC foaming agent), with an addition amount of 1%-2%, and their decomposition temperature needs to be precisely matched with the temperature of the extruder heating section.

[0050] Crosslinking agent: Dicumyl peroxide (DCP) with an addition amount of 0.5%-1% can crosslink the polyethylene molecular chains and enhance the stability of the foam structure. However, excessive amounts will cause the melt viscosity to rise sharply, affecting extrusion.

[0051] Anti-aging agent: Hindered phenolic anti-aging agent (such as 1010) is added at a ratio of 0.2%-0.5% to prevent pearl cotton from aging due to light and oxygen during storage and use;

[0052] Filler: The amount of calcium carbonate added is usually no more than 5% to adjust the hardness of pearl cotton, but too much will reduce the cushioning performance.

[0053] S2. Pretreatment of raw materials

[0054] Drying process: Put low-density polyethylene granules into a hot air circulating dryer and dry them at 60-80℃ for 2-4 hours. Insufficient drying will cause the moisture in the material to form large bubbles or voids during the foaming process, while excessive drying may lead to oxidation of the raw materials.

[0055] Mix evenly: Use a high-speed mixer, set the speed to 800-1200 r / min, and mix the main material and additives for 10-15 minutes. During the mixing process, ensure that the foaming agent is evenly dispersed to avoid uneven bubbles caused by excessively high local concentration.

[0056] S3, Continuous foaming molding process

[0057] Melt plasticizing: The process is carried out using a twin-screw extruder. Before starting, each heating section needs to be preheated. The dried and mixed raw material is fed into the extruder hopper through a metering feeder. Under the forward conveying and shearing action of the twin screw, the material gradually heats up and melts. The physical foaming agent is injected by a high-pressure metering pump in the melt homogenization section (pressure 8-12MPa), while the chemical foaming agent decomposes at high temperature to produce gas.

[0058] Foaming extrusion: Raw materials are fed into a foaming mold for processing. The mold lip width is set according to product specifications, generally 1-2m, and the lip temperature is maintained at 140-160℃. When the material is extruded from the mold, the pressure drops sharply to 0.5-1MPa. At this point, the bubbles rapidly expand to form foam melt. The size and density of the bubbles are controlled by adjusting the mold temperature and extrusion speed. Higher temperatures will decrease the melt viscosity, making bubbles more prone to coalescing and increasing in size; excessively high extrusion speeds may cause bubbles to burst.

[0059] Cooling and Shaping: The raw material is introduced into the mold for cooling and solidification. A combination of air cooling and water cooling is used. The air cooling device is located near the mold outlet, and the air temperature is controlled at 20-40℃ with adjustable air volume. The water cooling device further cools the foam sheet by circulating cooling water (water temperature 15-25℃). The movement of the foam sheet is controlled by traction. The traction roller group consists of multiple sets of rollers and pulls the foam sheet at a constant speed of 5-15m / min. The traction tension needs to be precisely controlled at 5-10N. Excessive tension will easily cause the sheet to stretch and deform, while insufficient tension will not be able to effectively shape it.

[0060] S4, Online Synchronous Foaming-Composite Processing

[0061] Hot-press lamination: When the temperature of the pearl cotton sheet drops to about 100℃, the composite substrate (such as PE film) is introduced into the hot-pressing zone through the guide roller system. It passes between the heating roller and the pressure roller simultaneously with the pearl cotton. The residual heat on the surface of the pearl cotton is used to melt the PE film and achieve adhesion. The surface temperature of the heating roller is set at 80-120℃ and is achieved by electric heating or heat transfer oil heating. The pressing pressure is 0.2-0.5MPa, which is provided by the hydraulic system.

[0062] Co-extrusion lamination: An auxiliary extruder is added to extrude hot melt adhesive (such as EVA, POE) or another layer of PE melt. The temperature of the auxiliary extruder is set 10-20℃ lower than that of the main extruder to ensure the matching of melt flow. The melt extruded by the auxiliary extruder and the pearl cotton sheet merge at the die exit. Co-extrusion lamination is achieved through the special flow channel design in the die to form a multi-layer structure.

[0063] S5, Post-processing Composite

[0064] Adhesive lamination: Water-based acrylic adhesive or hot melt adhesive is coated onto the surface of pearl cotton using roller coating or blade coating methods, with the coating amount controlled at 10-20 g / m². 2 The coating roller speed and traction speed must be matched to ensure uniform adhesive layer. After coating, the pearl cotton and composite substrate (such as kraft paper) are bonded by pressing roller (temperature 60-90℃, pressure 0.3-0.6MPa), and then enter the drying tunnel (temperature 100-120℃, residence time 2-5 minutes) to cure the adhesive.

[0065] High-frequency welding composite: After stacking pearl cotton and PVC materials, they are fed into a high-frequency welding machine. The frequency of the high-frequency electric field is generally 27.12MHz or 40.68MHz. The high-frequency electric field causes the molecules at the material interface to rapidly polarize and vibrate, generating heat. Under pressure (0.2-0.4MPa), glue-free bonding is achieved. The welding time is adjusted according to the material thickness, usually 1-3 seconds.

[0066] S6. Molding and Post-processing

[0067] Edge trimming: The traction roller group is driven by a servo motor, and the speed is monitored in real time by an encoder. The speed error is controlled within ±0.5%. During the traction process, the thickness of the pearl cotton roll can be adjusted by adjusting the roller gap, with an accuracy of ±0.1mm. The rough edges of the pearl cotton roll are removed by circular blades or hot cutting. The circular blades need to be sharpened regularly to ensure that the blades are sharp. The hot cutting temperature is controlled at 180-200℃ to prevent the cut edges from sticking together and to ensure the width accuracy is within ±1mm.

[0068] Winding: The finished product is wound up by a tension-controlled winding machine. The initial tension is set to 8-12N. As the roll diameter increases, the tension gradually decreases. A tapered tension control algorithm is used. The roll diameter is generally 1-2 meters. After winding, a PE protective film is wrapped around the surface of the roll. The rolled pearl cotton is placed in a room temperature warehouse and left to stand for 24-48 hours. During this process, the internal stress of the pearl cotton is released, the foam structure is further stabilized, and the density fluctuation range can be controlled within ±3%.

[0069] In steps S5 and S6, a density meter was used to monitor the density of the pearl cotton in real time, with an accuracy of ±0.5 kg / m³. 3 The infrared thermometer has an error of ±1℃ in monitoring the temperature of the sheet.

[0070] In step S6, a series of inspections need to be carried out on the product. According to GB / T2918-1998 standard, physical properties such as density, tensile strength, and elongation at break need to be tested; the peel strength of the composite layer needs to be tested according to GB / T2791-1995 standard, which requires ≥3N / cm.

[0071] In step S1, it is necessary to control the quality of low-density polyethylene and ensure that its density and purity meet the standards. Density deviation will affect the density uniformity and cushioning performance of the final product, while low purity will affect the appearance and performance of the product.

[0072] Example 2

[0073] Based on Example 1, a waste gas recovery system for the continuous foaming composite process of high-strength pearl cotton rolls is further obtained, characterized by comprising the following steps:

[0074] S1. Install a gas collection hood

[0075] Sealed gas collection hoods are installed at exhaust gas generation points such as the extruder outlet, composite pressure roller, and drying tunnel. Negative pressure ventilation is used to ensure that exhaust gas does not leak out. For example, an annular gas collection hood is installed at the extruder die head, with the wind speed controlled at 0.8-1.2 m / s to prevent material splashing while efficiently collecting exhaust gas. For areas that are difficult to completely seal (such as near the traction roller), an umbrella-shaped gas collection hood combined with a barrier is used to increase collection efficiency. Corrosion-resistant PP or stainless steel pipes are selected, with a pipe slope of ≥3% to prevent condensate accumulation. The pipe diameter is designed according to the exhaust gas flow rate to ensure that the flow velocity inside the pipe is 15-20 m / s, reducing residue inside the pipe.

[0076] S2, Exhaust Gas Pretreatment

[0077] The exhaust gas temperature typically reaches 60-120℃. It is first cooled to below 40℃ using an indirect cooler (such as a plate heat exchanger) to prevent damage to subsequent treatment equipment. Circulating cooling water is used as the cooling medium, with the water temperature controlled at 20-25℃. A cyclone spray tower is installed, utilizing a circulating alkaline absorbent liquid (such as NaOH solution, concentration 5-10%) to remove oil mist, particulate matter, and water-soluble organic matter from the exhaust gas. The spray liquid flow rate is controlled at 8-12 L / m³. 2 The gas-liquid contact time is ≥2s. The sprayed exhaust gas contains a large amount of moisture. The moisture is further removed by a wire mesh demister + desiccant adsorption tower (filled with silica gel or molecular sieve), so that the humidity of the exhaust gas is reduced to below 80% to prevent it from affecting the adsorption or catalytic efficiency.

[0078] S3, Exhaust Gas Purification Treatment

[0079] The waste gas is introduced into the purification structure for treatment, using a honeycomb activated carbon adsorption tower with a specific surface area ≥1000m².2 / g, the filling amount is calculated based on the waste gas flow rate and VOCs concentration to ensure a residence time ≥1.5s. When the activated carbon adsorption saturation reaches 80%, the hot air desorption and regeneration program is started. The desorption temperature is 120-150℃, which concentrates the low-concentration waste gas into high-concentration, low-flow-rate waste gas (concentration ratio 5-15 times). Then, the waste gas undergoes catalytic combustion treatment. The desorbed high-concentration waste gas is sent to the catalytic combustion furnace, which uses precious metal catalysts (such as Pt, Pd) at a reaction temperature of 250-350℃ to decompose VOCs into CO2 and H2O. The purification efficiency is ≥98%. The high-temperature exhaust gas generated by combustion recovers heat through a waste heat exchanger and is used to preheat the waste gas to be treated or for activated carbon desorption, thereby reducing energy consumption.

[0080] After purification, the exhaust gas can be discharged from the system once it meets the emission standards. The emission indicators must comply with the "Integrated Emission Standard for Air Pollutants" (GB 16297-1996), with VOCs emission concentration ≤50mg / m³. 3 Benzene series compounds ≤10mg / m³ 3 .

[0081] Activated carbon needs to be replaced regularly (generally every 3-6 months), and the spray tower nozzles and packing should be cleaned to prevent clogging. The catalyst activity should be tested quarterly, and it should be replaced when the purification efficiency drops below 90%.

[0082] In step S3, it is necessary to monitor the concentration of non-methane total hydrocarbons and benzene series compounds in real time; temperature, humidity, pressure and flow sensors are required, and the data is connected to the environmental protection supervision platform, with automatic alarms for abnormal situations.

[0083] In actual operation, when this device is used, the working principle of the continuous foaming and composite process of pearl cotton rolls is to achieve continuous foaming and composite molding of low-density polyethylene (LDPE) by precisely controlling the raw material ratio and process parameters. The core raw material LDPE is selected as a product with a melt index of 1.0-2.5g / 10min. After being mixed and dried with butane (3%-5%), azodicarbonamide (1%-2%) and other additives, it is melted and plasticized by a twin-screw extruder. The physical foaming agent is injected under a pressure of 8-12MPa, and the chemical foaming agent decomposes at high temperature to generate gas, forming a gas-containing melt.

[0084] When the gas-containing melt is extruded through the die lip (temperature 140-160℃), the pressure drops sharply to 0.5-1MPa, and the bubbles expand to form foam melt. The bubble size is controlled by adjusting the die temperature and extrusion speed. Subsequently, air cooling (20-40℃) and water cooling (15-25℃) are used for shaping, and the traction roller pulls the sheet at a speed of 5-15m / min and a tension of 5-10N.

[0085] The lamination process is divided into online hot pressing and co-extrusion. Hot pressing utilizes the residual heat of the sheet at 100℃ to melt the PE film, which is then bonded to the sheet using 80-120℃ heated rollers and 0.2-0.5MPa pressure rollers. Co-extrusion uses a secondary extruder (10-20℃ lower temperature than the main extruder) to extrude hot melt adhesive and co-extrude it to the sheet. Post-processing lamination uses either adhesives or high-frequency welding; the former is coated with 10-20g / m². 2 After gluing, the adhesive is pressed at 60-90℃ and dried at 100-120℃. The latter is achieved by using a high-frequency electric field of 27.12MHz or 40.68MHz to polarize the molecules and generate heat to bond them together.

[0086] After forming, the edge trimming accuracy is ±1mm. The initial tension during winding is 8-12N, with taper control of tension. The structure stabilizes after 24-48 hours of resting. The entire process is verified using a density meter (±0.5kg / m³). 3 The physical properties and peel strength (≥3N / cm) were monitored by an infrared thermometer (±1℃) and tested according to GB / T2918-1998 and GB / T2791-1995 standards.

[0087] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0088] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A continuous foaming composite process for pearl cotton rolls, characterized in that: Includes the following steps: S1. Raw material and auxiliary agent selection stage Low-density polyethylene (LDPE) is the core raw material. Products with a melt index in the range of 1.0-2.5 g / 10 min should be selected. This index affects the flowability of the material. If the melt index is too high, the foam strength will be insufficient. If it is too low, it will affect the extrusion molding. These particles will expand during the foaming process to form a pearl-like foam structure. Foaming agents: Physical foaming agents such as butane, accounting for 3%-5%, need to be stored in high-pressure containers and transported through dedicated pipelines; chemical foaming agents such as azodicarbonamide (AC foaming agent), with an addition amount of 1%-2%, and their decomposition temperature needs to be precisely matched with the temperature of the extruder heating section. Crosslinking agent: Dicumyl peroxide (DCP) with an addition amount of 0.5%-1% can crosslink the polyethylene molecular chains and enhance the stability of the foam structure. However, excessive amounts will cause the melt viscosity to rise sharply, affecting extrusion. Anti-aging agent: Hindered phenolic anti-aging agent (such as 1010) is added at a ratio of 0.2%-0.5% to prevent pearl cotton from aging due to light and oxygen during storage and use; Filler: The amount of calcium carbonate added is usually no more than 5% to adjust the hardness of pearl cotton, but too much will reduce the cushioning performance. S2. Pretreatment of raw materials Drying process: Put low-density polyethylene granules into a hot air circulating dryer and dry them at 60-80℃ for 2-4 hours. Insufficient drying will cause the moisture in the material to form large bubbles or voids during the foaming process, while excessive drying may lead to oxidation of the raw materials. Mix evenly: Use a high-speed mixer, set the speed to 800-1200 r / min, and mix the main material and additives for 10-15 minutes. During the mixing process, ensure that the foaming agent is evenly dispersed to avoid uneven bubbles caused by excessively high local concentration. S3, Continuous foaming molding process Melt plasticizing: The process is carried out using a twin-screw extruder. Before starting, each heating section needs to be preheated. The dried and mixed raw material is fed into the extruder hopper through a metering feeder. Under the forward conveying and shearing action of the twin screw, the material gradually heats up and melts. The physical foaming agent is injected by a high-pressure metering pump in the melt homogenization section (pressure 8-12MPa), while the chemical foaming agent decomposes at high temperature to produce gas. Foaming extrusion: The raw material is fed into the foaming mold for processing. The width of the mold lip is set according to the product specifications, generally 1-2m, and the mold lip temperature is maintained at 140-160℃. When the material is extruded from the die, the pressure drops sharply to 0.5-1 MPa. At this point, the bubbles rapidly expand to form a foam melt. The size and density of the bubbles are controlled by adjusting the die temperature and extrusion speed. Increasing the temperature will reduce the melt viscosity, making the bubbles more likely to merge and grow larger; excessively high extrusion speed may cause the bubbles to burst. Cooling and Shaping: The raw material is introduced into the mold for cooling and solidification. A combination of air cooling and water cooling is used. The air cooling device is located near the mold outlet, and the air temperature is controlled at 20-40℃ with adjustable air volume. The water cooling device further cools the foam sheet by circulating cooling water (water temperature 15-25℃). The movement of the foam sheet is controlled by traction. The traction roller group consists of multiple sets of rollers and pulls the foam sheet at a constant speed of 5-15m / min. The traction tension needs to be precisely controlled at 5-10N. Excessive tension will easily cause the sheet to stretch and deform, while insufficient tension will not be able to effectively shape it. S4, Online Synchronous Foaming-Composite Processing Hot-press lamination: When the temperature of the pearl cotton sheet drops to about 100℃, the composite substrate (such as PE film) is introduced into the hot-pressing zone through the guide roller system. It passes between the heating roller and the pressure roller simultaneously with the pearl cotton. The residual heat on the surface of the pearl cotton is used to melt the PE film and achieve adhesion. The surface temperature of the heating roller is set at 80-120℃ and is achieved by electric heating or heat transfer oil heating. The pressing pressure is 0.2-0.5MPa, which is provided by the hydraulic system. Co-extrusion lamination: An auxiliary extruder is added to extrude hot melt adhesive (such as EVA, POE) or another layer of PE melt. The temperature of the auxiliary extruder is set 10-20℃ lower than that of the main extruder to ensure the matching of melt flow. The melt extruded by the auxiliary extruder and the pearl cotton sheet merge at the die exit. Co-extrusion lamination is achieved through the special flow channel design in the die to form a multi-layer structure. S5, Post-processing Composite Adhesive lamination: Water-based acrylic adhesive or hot melt adhesive is coated onto the surface of pearl cotton using roller coating or blade coating methods, with the coating amount controlled at 10-20 g / m². 2 The coating roller speed and traction speed must be matched to ensure uniform adhesive layer. After coating, the pearl cotton and composite substrate (such as kraft paper) are bonded by pressing roller (temperature 60-90℃, pressure 0.3-0.6MPa), and then enter the drying tunnel (temperature 100-120℃, residence time 2-5 minutes) to cure the adhesive. High-frequency welding composite: After stacking pearl cotton and PVC materials, they are fed into a high-frequency welding machine. The frequency of the high-frequency electric field is generally 27.12MHz or 40.68MHz. The high-frequency electric field causes the molecules at the material interface to rapidly polarize and vibrate, generating heat. Under pressure (0.2-0.4MPa), glue-free bonding is achieved. The welding time is adjusted according to the material thickness, usually 1-3 seconds. S6. Molding and Post-processing Edge trimming: The traction roller group is driven by a servo motor, and the speed is monitored in real time by an encoder. The speed error is controlled within ±0.5%. During the traction process, the thickness of the pearl cotton roll can be adjusted by adjusting the roller gap, with an accuracy of ±0.1mm. The rough edges of the pearl cotton roll are removed by circular blades or hot cutting. The circular blades need to be sharpened regularly to ensure that the blades are sharp. The hot cutting temperature is controlled at 180-200℃ to prevent the cut edges from sticking together and to ensure the width accuracy is within ±1mm. Winding: The finished product is wound up by a tension-controlled winding machine. The initial tension is set to 8-12N. As the roll diameter increases, the tension gradually decreases. A tapered tension control algorithm is used. The roll diameter is generally 1-2 meters. After winding, a PE protective film is wrapped around the surface of the roll. The rolled pearl cotton is placed in a room temperature warehouse and left to stand for 24-48 hours. During this process, the internal stress of the pearl cotton is released, the foam structure is further stabilized, and the density fluctuation range can be controlled within ±3%.

2. The continuous foaming composite process for pearl cotton rolls and its waste gas recovery system according to claim 1, characterized in that: In steps S5 and S6, a density meter is used to monitor the density of the pearl cotton in real time, with an accuracy of ±0.5 kg / m³. 3 The infrared thermometer has an error of ±1℃ in monitoring the temperature of the sheet.

3. The continuous foaming composite process for pearl cotton rolls and its waste gas recovery system according to claim 1, characterized in that: In step S6, a series of inspections need to be carried out on the product. According to the GB / T2918-1998 standard, physical properties such as density, tensile strength, and elongation at break need to be tested; the peel strength of the composite layer needs to be tested according to the GB / T2791-1995 standard, which requires ≥3N / cm.

4. The continuous foaming composite process for pearl cotton rolls and its waste gas recovery system according to claim 1, characterized in that: In step S1, it is necessary to control the quality of low-density polyethylene and ensure that its density and purity meet the standards. Density deviation will affect the density uniformity and cushioning performance of the final product, while low purity will affect the appearance and performance of the product.

5. A waste gas recovery system for a continuous foaming and composite process of high-strength pearl cotton rolls as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Install a gas collection hood Sealed gas collection hoods are installed at exhaust gas generation points such as the extruder outlet, composite pressure roller, and drying tunnel. Negative pressure ventilation is used to ensure that exhaust gas does not leak out. For example, an annular gas collection hood is installed at the extruder die head, with the wind speed controlled at 0.8-1.2 m / s to prevent material splashing while efficiently collecting exhaust gas. For areas that are difficult to completely seal (such as near the traction roller), an umbrella-shaped gas collection hood combined with a barrier is used to increase collection efficiency. Corrosion-resistant PP or stainless steel pipes are selected, with a pipe slope of ≥3% to prevent condensate accumulation. The pipe diameter is designed according to the exhaust gas flow rate to ensure that the flow velocity inside the pipe is 15-20 m / s, reducing residue inside the pipe. S2, Exhaust Gas Pretreatment The exhaust gas temperature typically reaches 60-120℃. It is first cooled to below 40℃ using an indirect cooler (such as a plate heat exchanger) to prevent damage to subsequent treatment equipment. Circulating cooling water is used as the cooling medium, with the water temperature controlled at 20-25℃. A cyclone spray tower is installed, utilizing a circulating alkaline absorbent liquid (such as NaOH solution, concentration 5-10%) to remove oil mist, particulate matter, and water-soluble organic matter from the exhaust gas. The spray liquid flow rate is controlled at 8-12 L / m³. 2 The gas-liquid contact time is ≥2s. The sprayed exhaust gas contains a large amount of moisture. The moisture is further removed by a wire mesh demister + desiccant adsorption tower (filled with silica gel or molecular sieve), so that the humidity of the exhaust gas is reduced to below 80% to prevent it from affecting the adsorption or catalytic efficiency. S3, Exhaust Gas Purification Treatment The waste gas is introduced into the purification structure for treatment, using a honeycomb activated carbon adsorption tower with a specific surface area ≥1000m². 2 / g, the filling amount is calculated based on the waste gas flow rate and VOCs concentration to ensure a residence time ≥1.5s. When the activated carbon adsorption saturation reaches 80%, the hot air desorption and regeneration program is started. The desorption temperature is 120-150℃, which concentrates the low-concentration waste gas into high-concentration, low-flow-rate waste gas (concentration ratio 5-15 times). Then, the waste gas undergoes catalytic combustion treatment. The desorbed high-concentration waste gas is sent to the catalytic combustion furnace, which uses precious metal catalysts (such as Pt, Pd) at a reaction temperature of 250-350℃ to decompose VOCs into CO2 and H2O. The purification efficiency is ≥98%. The high-temperature exhaust gas generated by combustion recovers heat through a waste heat exchanger and is used to preheat the waste gas to be treated or for activated carbon desorption, thereby reducing energy consumption. After purification, the exhaust gas can be discharged from the system once it meets the emission standards. The emission indicators must comply with the "Integrated Emission Standard for Air Pollutants" (GB 16297-1996), with VOCs emission concentration ≤50mg / m³. 3 Benzene series compounds ≤10mg / m³ 3 .

6. The continuous foaming composite process for pearl cotton rolls and its waste gas recovery system according to claim 5, characterized in that: Activated carbon needs to be replaced regularly (generally every 3-6 months), and the spray tower nozzles and packing should be cleaned to prevent clogging. The catalyst activity should be tested quarterly, and it should be replaced when the purification efficiency drops below 90%.

7. The continuous foaming composite process for pearl cotton rolls and its waste gas recovery system according to claim 5, characterized in that: In step S3, it is necessary to monitor the concentration of non-methane total hydrocarbons and benzene series compounds in real time; temperature, humidity, pressure, and flow sensors are required, and the data is connected to the environmental protection supervision platform, with automatic alarms for abnormal situations.