1. INTRODUCTION Pulp Moulded Products is a certain concentration of pulp, adding appropriate amount of chemical additives to the fiber in the forming machine by vacuum or pressure to evenly distribute the fibers on the surface of the mold, thus forming a formulated geometry and size. The wet paper blank is further dehydrated and demolded, and the dried and shaped product is dried. The product is rich in raw materials, has no pollution during production and use, has light weight, high compressive strength, good cushioning properties and good recyclability, and has a wide range of applications as a packaging product. According to relevant information, the world's output of pulp molded products has reached more than 400,000 tons. With the increasing convergence of economic convergence between China and the rest of the world, the potential for the promotion and application of pulp molded products is undoubtedly enormous.
At the end of 1991, the 12 countries of the European Community issued a mandatory enforcement standard, the "New Packaging Rules." It is clearly stated that starting from 1992, the use of expanded polystyrene materials in transportation packaging and sales packaging will be prohibited and pulp molded products will be replaced. Later, in the Japanese trade community, it also designated some of China's electrical export manufacturers to use paper molded products instead of expanded polystyrene packaging. With regard to this major change in the inter-packaged market, China's Liaoning, Jiangsu, Guangdong, Zhejiang, and Fujian have made rapid responses in some areas. Although the development of China's pulp moulding products began in the 1980s, a certain scale of production has been established so far. However, the current production and operation situation is not very optimistic. There are still many areas where broken lines are worthy of deep research and improvement. The following issues are summarized and analyzed. .
2. Current production technology and equipment for pulp moulding products 2.1. Production technology for pulp mould products Production processes for paper mould products include waste paper sorting, shredded paper pulping, slurry preparation, pulp sizing, blended slurry (concentration), product forming, Cold extrusion of products, drying of products and finishing of products.
Waste paper is one of the main raw materials for the production of injection-molded products. It is necessary to carefully classify and eliminate various kinds of adulterants by using hydraulic attritors and sorters (waste newspapers, corrugated cardboard packaging, scraps, etc.). . Grinding waste paper can be realized either in an intermittent beater or in a continuous grinder or refiner. The sorted and purified waste paper is ground and smashed into a uniform pulp. In the grinding process, several raw materials can be quantitatively added to the slurry according to the designed slurry ratio. Pulp sizing is used to improve the resistance to liquid penetration of injection molded parts. For paper-type packaging products, the sizing agent is generally a loose period, paraffin emulsion or rosin paraffin paste. Tests have shown that in order to obtain high-quality articles, rosin gum equivalent to 3% of pulp dry fiber must be added to non-bonded waste paper pulp, and 1.5% should be added to bonded waste paper pulp. - 2% rosin gum.
Mix the concentration in an open water bath heater with a stirrer. After adding soda ash or caustic soda and dissolving it, slowly add the rosin block of appropriate size and heat the solution to a temperature of 100-105°C. Stirring is continued for 3-4 hours until carbon dioxide no longer escapes. The glue should be uniform and free of clots. When checking with eyesight, a wooden spatula is used to pick up the glue and the glue flows down into a sheet. After boiling, the gum should be oscillated in another intermediate container and slowly cooled, and then diluted with water to a suitable concentration. In the process of self-made pulp, the diluted glue is added to the pulp in the beater or agitating tank. In order to make the glue easy to adhere to the pulp fiber, an appropriate amount of aluminum sulfate solution having a concentration of 10% should be added. The degree of adherence of the rubber material to the pulp fibers is sufficient, depending on the pH of the medium. Generally, this value should be 4.5-5.0. If necessary, give the pulp a certain single color, because there are various kinds of printing content on the waste paper, so that the injection-type parts do not have a single color. Unlike cardboard production, pulp sizing concentrations for the production of molded products should be relatively high, approximately 1-2%.
Molded products can be molded in three ways: vacuum molding, hydraulic molding, and compressed air molding. In practice, one of the above methods or as much as possible a combined method can be used to increase the production efficiency.
After filling the pulp with the model and the upper volume of the housing, the water will be discharged through the metal mesh wall of the model, and the fibers are attached to the surface of the mesh model. After molding is completed, the model is raised by means of a hydraulic cylinder, the product is taken out after compaction and transferred to the drying process. The compaction of the parts is achieved in special presses organized by upper and lower dies. The structure of the press machine should ensure that the parts are not stretched in real time, otherwise it will cause the wall rupture. This equipment works on the principle that the parts are only compressed during the entire pressing process. In order to discharge the water from the place where it is pressed, it is necessary to have vacuum suction equipment. Due to the different degree of extrusion, the moisture content of the parts is 50%-75%, and the moisture content should be reduced to 10%-12% through the drying process, and can be reduced to 3%-4% in some cases. Drying of the product is carried out in a drying oven that operates on a continuous or continuous basis. The product is placed on a shrink-proof model and fed into a drying oven. The product is dried with hot air. The temperature starts at 250-300°C (the product has a 50% reduction in moisture content within 7-10 seconds), and then the temperature drops to 100-105. °C. The continuous drying furnace has a conveying device. The pieces pass through different temperature zones in the furnace and are finally dried to a moisture content of about 10% to about 12%. The production process of paper molding products has been accompanied by dehydration, from gravity dehydration, vacuum dehydration, press dehydration, to the final thermal dehydration, ie drying. Vacuum dehydration and press dewatering remove most of the water from the product. The remaining water must be dehydrated by heating and drying.
After drying, the use of extrusion on the hot post-forming machine is more compact, which is necessary for uniform thickness of the wall of the injection-type packaging product, smooth outer surface, and increased wall strength. Paper mouldings can be used after drying, but sometimes special treatments such as calendering, paint baking, or pattern printing on the surface are required.
Pulp molded products are used in the production of fast food products and packaging products are different in the process. Such as: disposable fast food requirements require water and oil, to meet the stiffness requirements, in line with health standards, the appearance of printing trademarks, smooth surface inside and outside clean. The general shape of the packaging products is relatively large and complex, and requires a bearing capacity, a buffer function, and a positioning function. Based on these special requirements, it is determined that the process characteristics of paper-type packaging products are: regardless of the complexity of the shape of the products, the wall thickness of the same product must be the same. Only in this way can the requirements of molding and shaping (or drying) of the products in the production process be met. . The packaging of industrial products is sometimes not too high in size and shape accuracy, and requires certain strength and cushioning. Therefore, industrial packaging of pulp molded products seldom requires stereotypes. After the molding machine is down, it is dried and molded by the dryer. This kind of drying method changes the shape and size of the product due to the precipitation of moisture from the wet paper blank. Accumulating empirical data and grasping the change law in this regard can be used as the basis for future mold design.
2.2. Production equipment for pulp moulding products According to the technological requirements, the main equipments for the production of paper moulding products are the hydraulic crushed prize machine, the distribution pool, the forming machine, the drying machine and the setting machine.
The function of the hydraulic pulper is to disintegrate the waste paperboard and turn it into pulp, which can be divided into two types, vertical and horizontal. The horizontal hydraulic pulper is commonly used in the production line of industrial packaging products. Its advantages have only dispersion effect on the paper fiber, no cutting effect, high fragmentation efficiency, short disintegration time, low power consumption, simple structure, and can handle large Miscellaneous, metal debris waste paper. The machine is mainly composed of a horizontal tank body and a working impeller. There is a feeding port on the top and a row of slurry and slag discharge port on the bottom. The working impeller is fixed on the shaft end extending from one end into the tank body. The diameter of the impeller is generally 1/2 or 1/3 of the diameter of the tank body, and the linear speed of the impeller rotation is generally 15 to 17.7 meters/second. When the impeller rotates during operation, a high-speed rotating water flow is generated, and the cardboard begins to disintegrate under the action of high-speed water flow and centrifugal force. The disintegrated pulp can be discharged through the discharge port from the mesh plate outside the impeller. The debris that cannot be disintegrated is attached to the wall of the tank under the effect of centrifugal force to rotate. When the machine stops, these impurities settle in the slagging outlet of the bottom wall of the tank, and the slag discharge port can open the slag. The thick slurry is discharged to the slurry pool and diluted in the slurry pool to a working degree. At the same time, some process aids and functional auxiliaries are added. The distribution tank is equipped with a propeller so that the slurry always maintains a rotation cycle in the working system to avoid fiber precipitation.
The molding machine is a machine that guarantees the operation of the molds for the pulping, dewatering, and removal of wet paper blanks. Its main structure includes: racks, pulp boxes, lift cylinders, guide columns, upper and lower formworks, and chlorine chambers that are attached to the formwork (although they communicate with the vacuum system and the air compressor). During work, the punch of the forming die is fixed on the lower die plate, and a large number of small holes are communicated with the air chamber on the die. The punch die is lined with a net die that completely fits the surface of the irregular punch die, and the current die plate is pushed under the chlorine cylinder. Carry the punch into the slurry in the slurry tank. At this time, the chlorine in the lower mold generates negative pressure from the vacuum pump. The water in the slurry flows through the inlet of the screen and is filtered through the gas chamber and the pipeline. The fiber is retained on the screen. Wet paper blank; then the lower die starts to ascend, and after the slurry surface is lifted, the wet paper blank on the net mold is continuously dehydrated under vacuum adsorption. At this point, the lower die continues to ascend and the female die fixed on the upper die plate is closed and mechanically dewatered. Then, the vacuum is cut off in the lower mold air chamber to enter the compressed air, and the vacuum is turned on in the upper mold air chamber. The negative pressure is transmitted to the wet paper blank through the small hole on the die, and the wet paper blank is under the action of “push†and “pullâ€. The lower die is passed to the upper die and the upper die begins to descend again. Manually push the tray under the upper mold, touch the upper model chlorine chamber pneumatic reversing valve, the upper mold air chamber cuts the vacuum to enter the compressed air, the wet paper blank is blown onto the tray, and manually put the tray together with the wet paper blank to dry On the conveyor belt, this is a complete working section of the molding machine. Although there are many forms of pulp molding machines, there are two molding processes: in-mold quantitative grouting and out-mold adsorption molding. The principle is that the pulp flows through the net mold, the water is filtered out, and the fibers are intercepted on the net mold to form a wet paper blank. In-mold grouting is to ensure the thickness of products through a certain amount of pulp, while the outside of the mold is to ensure the thickness of the product by controlling the pulp degree and adsorption time. Most of the paper mold industrial packaging products use reciprocating mold adsorption molding. This molding machine can produce large area products with strong adaptability and can form an automated production line.
The dryer is recommended to use the heating method of the fuel stove. The drying structure includes the head, tail, transition section, intermediate heating section, burner, induced draft fan, transmission belt and automatic control box. During operation, the combustion furnace atomizes the diesel fuel and sprays it into the combustion chamber for combustion.
If the product shape and size requirements are very strict, the wet paper blank needs to be shaped, and the wet paper blank to be dried to a certain degree is put into the shaping die to be pressurized and heated to dry the product in the die. The setting machine is actually a small four-column press (hydraulic or pneumatic). The only difference is that the fixed mold fixed to the upper and lower platens is equipped with heating elements. The three elements of the stereotypes for pulp mouldings are: 1 pressure, which requires a projected area unit pressure of 0.4-0.6 MPa; 2 temperature, mold cavity temperature generally required in the 180-200 °C; 3 is the environment, depending on the shape and thickness of the product to determine, generally In 30-50 seconds. In practice, the final thickness of the product is approximately 70% of the thickness of the mold cavity.
3. Problems and Development Countermeasures in the Production and Management of Pulp Molded Products According to relevant statistics, China produces about 20 million color TV sets each year, of which about 4 million are exported; 40 million color picture tubes are produced annually, of which 1,244 are exported. In these two years, it takes about 20,000 tons of foamed material, which translates into a volume of 1 million cubic meters. Although the number of foamed plastic materials consumed every year in other household appliances, industrial instruments, and mechanical and electrical products is difficult to have a certain amount of statistics, it is undoubtedly a terrible figure. The replacement of pulp molded products is a general trend. It can be said that the prospects for the development of paper molded products are very good, but there are still some problems in the promotion and application in our country.
1) There is a lack of certain policy guidance and regulation on the macro level. Production and applications are mostly self-distribution of enterprises and society, and there are no mandatory policies and regulations for protection. The relevant equipment and products also have no formal special standards, making it difficult for paper mold enterprises to become a dominant industry with grouping, industrialization, and standardization;
2) The problem of scattered management in the industry. Paper mold products and equipment manufacturers are more than 200 companies involved in packaging, light industry, chemical industry, machinery, electronics, military, railway, transportation and education and other departments. There is no shortage of competent ministries
At the end of 1991, the 12 countries of the European Community issued a mandatory enforcement standard, the "New Packaging Rules." It is clearly stated that starting from 1992, the use of expanded polystyrene materials in transportation packaging and sales packaging will be prohibited and pulp molded products will be replaced. Later, in the Japanese trade community, it also designated some of China's electrical export manufacturers to use paper molded products instead of expanded polystyrene packaging. With regard to this major change in the inter-packaged market, China's Liaoning, Jiangsu, Guangdong, Zhejiang, and Fujian have made rapid responses in some areas. Although the development of China's pulp moulding products began in the 1980s, a certain scale of production has been established so far. However, the current production and operation situation is not very optimistic. There are still many areas where broken lines are worthy of deep research and improvement. The following issues are summarized and analyzed. .
2. Current production technology and equipment for pulp moulding products 2.1. Production technology for pulp mould products Production processes for paper mould products include waste paper sorting, shredded paper pulping, slurry preparation, pulp sizing, blended slurry (concentration), product forming, Cold extrusion of products, drying of products and finishing of products.
Waste paper is one of the main raw materials for the production of injection-molded products. It is necessary to carefully classify and eliminate various kinds of adulterants by using hydraulic attritors and sorters (waste newspapers, corrugated cardboard packaging, scraps, etc.). . Grinding waste paper can be realized either in an intermittent beater or in a continuous grinder or refiner. The sorted and purified waste paper is ground and smashed into a uniform pulp. In the grinding process, several raw materials can be quantitatively added to the slurry according to the designed slurry ratio. Pulp sizing is used to improve the resistance to liquid penetration of injection molded parts. For paper-type packaging products, the sizing agent is generally a loose period, paraffin emulsion or rosin paraffin paste. Tests have shown that in order to obtain high-quality articles, rosin gum equivalent to 3% of pulp dry fiber must be added to non-bonded waste paper pulp, and 1.5% should be added to bonded waste paper pulp. - 2% rosin gum.
Mix the concentration in an open water bath heater with a stirrer. After adding soda ash or caustic soda and dissolving it, slowly add the rosin block of appropriate size and heat the solution to a temperature of 100-105°C. Stirring is continued for 3-4 hours until carbon dioxide no longer escapes. The glue should be uniform and free of clots. When checking with eyesight, a wooden spatula is used to pick up the glue and the glue flows down into a sheet. After boiling, the gum should be oscillated in another intermediate container and slowly cooled, and then diluted with water to a suitable concentration. In the process of self-made pulp, the diluted glue is added to the pulp in the beater or agitating tank. In order to make the glue easy to adhere to the pulp fiber, an appropriate amount of aluminum sulfate solution having a concentration of 10% should be added. The degree of adherence of the rubber material to the pulp fibers is sufficient, depending on the pH of the medium. Generally, this value should be 4.5-5.0. If necessary, give the pulp a certain single color, because there are various kinds of printing content on the waste paper, so that the injection-type parts do not have a single color. Unlike cardboard production, pulp sizing concentrations for the production of molded products should be relatively high, approximately 1-2%.
Molded products can be molded in three ways: vacuum molding, hydraulic molding, and compressed air molding. In practice, one of the above methods or as much as possible a combined method can be used to increase the production efficiency.
After filling the pulp with the model and the upper volume of the housing, the water will be discharged through the metal mesh wall of the model, and the fibers are attached to the surface of the mesh model. After molding is completed, the model is raised by means of a hydraulic cylinder, the product is taken out after compaction and transferred to the drying process. The compaction of the parts is achieved in special presses organized by upper and lower dies. The structure of the press machine should ensure that the parts are not stretched in real time, otherwise it will cause the wall rupture. This equipment works on the principle that the parts are only compressed during the entire pressing process. In order to discharge the water from the place where it is pressed, it is necessary to have vacuum suction equipment. Due to the different degree of extrusion, the moisture content of the parts is 50%-75%, and the moisture content should be reduced to 10%-12% through the drying process, and can be reduced to 3%-4% in some cases. Drying of the product is carried out in a drying oven that operates on a continuous or continuous basis. The product is placed on a shrink-proof model and fed into a drying oven. The product is dried with hot air. The temperature starts at 250-300°C (the product has a 50% reduction in moisture content within 7-10 seconds), and then the temperature drops to 100-105. °C. The continuous drying furnace has a conveying device. The pieces pass through different temperature zones in the furnace and are finally dried to a moisture content of about 10% to about 12%. The production process of paper molding products has been accompanied by dehydration, from gravity dehydration, vacuum dehydration, press dehydration, to the final thermal dehydration, ie drying. Vacuum dehydration and press dewatering remove most of the water from the product. The remaining water must be dehydrated by heating and drying.
After drying, the use of extrusion on the hot post-forming machine is more compact, which is necessary for uniform thickness of the wall of the injection-type packaging product, smooth outer surface, and increased wall strength. Paper mouldings can be used after drying, but sometimes special treatments such as calendering, paint baking, or pattern printing on the surface are required.
Pulp molded products are used in the production of fast food products and packaging products are different in the process. Such as: disposable fast food requirements require water and oil, to meet the stiffness requirements, in line with health standards, the appearance of printing trademarks, smooth surface inside and outside clean. The general shape of the packaging products is relatively large and complex, and requires a bearing capacity, a buffer function, and a positioning function. Based on these special requirements, it is determined that the process characteristics of paper-type packaging products are: regardless of the complexity of the shape of the products, the wall thickness of the same product must be the same. Only in this way can the requirements of molding and shaping (or drying) of the products in the production process be met. . The packaging of industrial products is sometimes not too high in size and shape accuracy, and requires certain strength and cushioning. Therefore, industrial packaging of pulp molded products seldom requires stereotypes. After the molding machine is down, it is dried and molded by the dryer. This kind of drying method changes the shape and size of the product due to the precipitation of moisture from the wet paper blank. Accumulating empirical data and grasping the change law in this regard can be used as the basis for future mold design.
2.2. Production equipment for pulp moulding products According to the technological requirements, the main equipments for the production of paper moulding products are the hydraulic crushed prize machine, the distribution pool, the forming machine, the drying machine and the setting machine.
The function of the hydraulic pulper is to disintegrate the waste paperboard and turn it into pulp, which can be divided into two types, vertical and horizontal. The horizontal hydraulic pulper is commonly used in the production line of industrial packaging products. Its advantages have only dispersion effect on the paper fiber, no cutting effect, high fragmentation efficiency, short disintegration time, low power consumption, simple structure, and can handle large Miscellaneous, metal debris waste paper. The machine is mainly composed of a horizontal tank body and a working impeller. There is a feeding port on the top and a row of slurry and slag discharge port on the bottom. The working impeller is fixed on the shaft end extending from one end into the tank body. The diameter of the impeller is generally 1/2 or 1/3 of the diameter of the tank body, and the linear speed of the impeller rotation is generally 15 to 17.7 meters/second. When the impeller rotates during operation, a high-speed rotating water flow is generated, and the cardboard begins to disintegrate under the action of high-speed water flow and centrifugal force. The disintegrated pulp can be discharged through the discharge port from the mesh plate outside the impeller. The debris that cannot be disintegrated is attached to the wall of the tank under the effect of centrifugal force to rotate. When the machine stops, these impurities settle in the slagging outlet of the bottom wall of the tank, and the slag discharge port can open the slag. The thick slurry is discharged to the slurry pool and diluted in the slurry pool to a working degree. At the same time, some process aids and functional auxiliaries are added. The distribution tank is equipped with a propeller so that the slurry always maintains a rotation cycle in the working system to avoid fiber precipitation.
The molding machine is a machine that guarantees the operation of the molds for the pulping, dewatering, and removal of wet paper blanks. Its main structure includes: racks, pulp boxes, lift cylinders, guide columns, upper and lower formworks, and chlorine chambers that are attached to the formwork (although they communicate with the vacuum system and the air compressor). During work, the punch of the forming die is fixed on the lower die plate, and a large number of small holes are communicated with the air chamber on the die. The punch die is lined with a net die that completely fits the surface of the irregular punch die, and the current die plate is pushed under the chlorine cylinder. Carry the punch into the slurry in the slurry tank. At this time, the chlorine in the lower mold generates negative pressure from the vacuum pump. The water in the slurry flows through the inlet of the screen and is filtered through the gas chamber and the pipeline. The fiber is retained on the screen. Wet paper blank; then the lower die starts to ascend, and after the slurry surface is lifted, the wet paper blank on the net mold is continuously dehydrated under vacuum adsorption. At this point, the lower die continues to ascend and the female die fixed on the upper die plate is closed and mechanically dewatered. Then, the vacuum is cut off in the lower mold air chamber to enter the compressed air, and the vacuum is turned on in the upper mold air chamber. The negative pressure is transmitted to the wet paper blank through the small hole on the die, and the wet paper blank is under the action of “push†and “pullâ€. The lower die is passed to the upper die and the upper die begins to descend again. Manually push the tray under the upper mold, touch the upper model chlorine chamber pneumatic reversing valve, the upper mold air chamber cuts the vacuum to enter the compressed air, the wet paper blank is blown onto the tray, and manually put the tray together with the wet paper blank to dry On the conveyor belt, this is a complete working section of the molding machine. Although there are many forms of pulp molding machines, there are two molding processes: in-mold quantitative grouting and out-mold adsorption molding. The principle is that the pulp flows through the net mold, the water is filtered out, and the fibers are intercepted on the net mold to form a wet paper blank. In-mold grouting is to ensure the thickness of products through a certain amount of pulp, while the outside of the mold is to ensure the thickness of the product by controlling the pulp degree and adsorption time. Most of the paper mold industrial packaging products use reciprocating mold adsorption molding. This molding machine can produce large area products with strong adaptability and can form an automated production line.
The dryer is recommended to use the heating method of the fuel stove. The drying structure includes the head, tail, transition section, intermediate heating section, burner, induced draft fan, transmission belt and automatic control box. During operation, the combustion furnace atomizes the diesel fuel and sprays it into the combustion chamber for combustion.
If the product shape and size requirements are very strict, the wet paper blank needs to be shaped, and the wet paper blank to be dried to a certain degree is put into the shaping die to be pressurized and heated to dry the product in the die. The setting machine is actually a small four-column press (hydraulic or pneumatic). The only difference is that the fixed mold fixed to the upper and lower platens is equipped with heating elements. The three elements of the stereotypes for pulp mouldings are: 1 pressure, which requires a projected area unit pressure of 0.4-0.6 MPa; 2 temperature, mold cavity temperature generally required in the 180-200 °C; 3 is the environment, depending on the shape and thickness of the product to determine, generally In 30-50 seconds. In practice, the final thickness of the product is approximately 70% of the thickness of the mold cavity.
3. Problems and Development Countermeasures in the Production and Management of Pulp Molded Products According to relevant statistics, China produces about 20 million color TV sets each year, of which about 4 million are exported; 40 million color picture tubes are produced annually, of which 1,244 are exported. In these two years, it takes about 20,000 tons of foamed material, which translates into a volume of 1 million cubic meters. Although the number of foamed plastic materials consumed every year in other household appliances, industrial instruments, and mechanical and electrical products is difficult to have a certain amount of statistics, it is undoubtedly a terrible figure. The replacement of pulp molded products is a general trend. It can be said that the prospects for the development of paper molded products are very good, but there are still some problems in the promotion and application in our country.
1) There is a lack of certain policy guidance and regulation on the macro level. Production and applications are mostly self-distribution of enterprises and society, and there are no mandatory policies and regulations for protection. The relevant equipment and products also have no formal special standards, making it difficult for paper mold enterprises to become a dominant industry with grouping, industrialization, and standardization;
2) The problem of scattered management in the industry. Paper mold products and equipment manufacturers are more than 200 companies involved in packaging, light industry, chemical industry, machinery, electronics, military, railway, transportation and education and other departments. There is no shortage of competent ministries
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