Process for producing environment-friendly expandable polystyrene by extrusion method

Abstract

The invention provides an extrusion method environment-friendly expandable polystyrene production process which comprises the following steps: (1) optimizing a pretreatment process according to characteristics of polystyrene and historical processing data of a historical processing process to obtain an optimal pretreatment process, and processing the polystyrene by using the optimal pretreatment process; (2) mixing polystyrene and an additive by using a first process to form a mixed material; (3) mixing and plasticizing the mixed material by using a second process to form a plasticized material; (4) molding a plasticized material by using a third process; and (5) post-processing the plasticized material by using a fourth process. According to the process, the pretreatment process is optimized according to the characteristics of the polystyrene material and historical processing data, and different pretreatment processes are used for recycled polystyrene materials with different characteristics, so that the process is more accurate, the recycling stability is improved, the cost is saved, and the dependence on artificial experience is reduced.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to an extrusion method environmentally friendly expandable polystyrene production process. Background Art

[0002] Due to its excellent properties, polystyrene materials are widely used in electronic device shell packaging, daily necessities, toy products, foam materials, home appliance packaging and exterior wall insulation. However, in 2022, the global amount of polystyrene waste plastics reached 63 million tons, of which only 18.9 million tons were recycled, landfill and incineration accounted for 32% and 31% respectively, and direct abandonment accounted for about 7%. These waste plastics are not easy to recycle and biodegrade, and take a long time to decompose, resulting in environmental pollution and waste of resources, which is not in line with the sustainable development strategy of low-carbon emissions. Waste polystyrene plastics come from many aspects, including industrial sources (waste materials and waste industrial products in plastic molding processing), agricultural sources (waste agricultural mulch, agricultural pipes, etc.), medical sources (disposable plastic products such as protective clothing, goggles, etc.) and daily sources (disposable tableware, home appliance shells, etc.).

[0003] The quality and impurity content of recycled polystyrene vary significantly depending on the source, which requires different treatment methods and process parameters for different types of materials during recycling and reuse. However, many current recycling processes still rely on the experience and habits of operators and lack unified standards and processes, resulting in unstable treatment results and affecting the quality of recycled products. Summary of the invention

[0004] The embodiment of the present invention provides an environmentally friendly expandable polystyrene production process by extrusion, comprising the following steps: (1) optimizing the pre-treatment process according to the characteristics of polystyrene and the historical processing data of the historical processing process to obtain the best pre-treatment process, and treating the polystyrene using the best pre-treatment process; (2) mixing the polystyrene and the additive by the first process to form a mixed material; (3) kneading and plasticizing the mixed material by the second process to form a plasticized material; (4) shaping the plasticized material by the third process; and (5) treating the plasticized material by the fourth process.

[0005] Further, the characteristics of the polystyrene include the type of polystyrene, particle size, impurity content and impurity category.

[0006] Furthermore, the historical processing data includes historical processing flow, historical processing time, historical processing frequency and historical processing effect.

[0007] Furthermore, optimizing the pre-treatment process includes selecting a corresponding historical treatment process according to the type, particle size, impurity content or impurity category of polystyrene, selecting a first set of detection time nodes in the historical treatment process, obtaining the historical treatment effects corresponding to the first set of detection time nodes, treating the polystyrene according to the historical treatment process, detecting the actual treatment effect at the first set of detection time nodes, comparing the actual treatment effect with the historical treatment effect, and obtaining the effect difference. When the effect difference is less than a preset difference, the historical treatment process remains unchanged. When the effect difference is greater than the preset difference, the historical treatment process is adjusted so that the effect difference is less than the preset difference.

[0008] Furthermore, optimizing the pre-processing process includes selecting a corresponding historical processing process according to the type, particle size, impurity content or impurity category of polystyrene, processing the polystyrene according to the historical processing process, detecting the actual processing effect at a second set of detection time nodes, calculating the node detection values ​​at the second set of detection time nodes according to the actual processing effect, comparing the node detection values, and the detection time node corresponding to the largest node detection value is the key node, and adjusting the historical processing process according to the time position of the key node.

[0009] Furthermore, the node detection value is the difference in actual processing effect per unit time before and after the node is detected.

[0010] Further, the first process includes mixing polystyrene and additives by weight, wherein the weight proportion of polystyrene is 20% to 95% and the weight proportion of the additive is 5% to 80%.

[0011] Further, the second process includes melting the mixed material in an extruder and then extruding the mixed material, wherein the operating temperature of the extruder is 80° C. to 220° C. and the operating pressure of the extruder is 3 MPa to 20 MPa.

[0012] Furthermore, the third process includes cooling the plasticized material using circulating water, wherein the temperature of the circulating water is 30°C to 60°C.

[0013] Furthermore, the fourth process includes drying the plasticized material.

[0014] The environmentally friendly expandable polystyrene production process by extrusion of the present invention optimizes the pre-treatment process according to the characteristics of the polystyrene material and historical processing data, and uses different pre-treatment processes for recycled polystyrene materials with different characteristics, so that the process is more accurate, the recycling stability is improved, the cost is saved, and the reliance on manual experience is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A process flow chart showing an environmentally friendly expandable polystyrene production process using an extrusion method according to an embodiment of the present invention DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] For the recycling and reuse of polystyrene materials, a pre-treatment process is required before reuse. Due to the different recycled polystyrene materials, the pre-treatment processes used are also different. Generally speaking, technicians skilled in the art have certain corresponding treatment methods for various recycled materials, but these treatment methods are too dependent on personnel experience and habits, and the material recovery output is unstable and the difference is large.

[0018] Characteristics of the recycled polystyrene material may include: type of polystyrene material, particle size, impurity content or impurity category.

[0019] Generally, according to historical experience, different polystyrene recycled materials will form historical processing processes after a large number of pre-processing processes, and retain a large amount of historical processing data. Among them, historical processing data includes historical processing flow, historical processing time, historical processing frequency and historical processing effect.

[0020] Specifically, the historical treatment process includes water washing, acid washing, alkali washing or organic washing, etc. The historical treatment time is the treatment time used by different historical treatment processes. The historical treatment frequency is the number of treatments corresponding to different historical treatment processes or the number of treatments per unit time. The historical treatment effect is the recovery rate or impurity rate of polystyrene recovered after the pre-treatment process, etc.

[0021] Example 1 In this embodiment, the polystyrene pretreatment process is described in detail. By optimizing the pretreatment process, the best pretreatment process is obtained to refine the pretreatment process, avoid poor pretreatment effects due to differences in the recycled materials, and avoid relying on personnel experience and habits. The material recovery output is unstable and the difference is large. Therefore, the pretreatment process needs to be optimized. The pretreatment process is optimized according to the characteristics of polystyrene and historical processing data to obtain the best pretreatment process, and the polystyrene material is processed using the best pretreatment process.

[0022] In the first step, based on the characteristics of the recycled polystyrene, the historical processing process with the highest frequency of use of this type of recycled polystyrene in the historical processing process is selected as a reference process.

[0023] The recycled polystyrene may include different types of polystyrene, for example, general-purpose polystyrene, high-impact polystyrene, expanded polystyrene, and the like.

[0024] In this embodiment, the general-purpose polystyrene alkali washing, acid washing, organic washing and water washing are used as the historical treatment process, the cleaning time of each step in the process is used as the treatment time, and the recovery rate of the general-purpose polystyrene is used as the treatment effect. The optimization of the pre-treatment process is achieved by optimizing the treatment process, the treatment time and the treatment effect.

[0025] The second step is to insert detection time nodes into the historical processing flow, and evaluate the historical processing effect at each time node based on the historical processing data corresponding to different time nodes.

[0026] The detection time nodes are determined according to the historical processing time, and generally the initial time, the first period, the middle period, the last period and the last period of the historical processing flow are used as the five detection time nodes. Of course, other time nodes can also be selected as the detection time nodes, and this is not limited here.

[0027] By selecting the historical pre-processing process, a set of detection time nodes are found. For example, the detection time nodes are T1, T2, T3, T4 and T5, and the corresponding historical processing effects are R1, R2, R3, R4 and R5. For example, the corresponding historical processing effect is the recovery rate of polystyrene.

[0028] The third step is to pre-treat the recycled polystyrene material according to the historical processing technology. During the processing, samples are taken and tested according to the detection time nodes in turn to obtain the actual processing effect at each time node. For example, the actual processing effect is that the actual recovery rates of polystyrene are R1', R2', R3', R4' and R5' respectively.

[0029] The fourth step is to compare the data of the actual treatment effect and the historical treatment effect to obtain the effect difference, where the effect difference values ​​are R1-R1', R2-R2', R3-R3', R4-R4' and R5-R5' respectively.

[0030] Assuming that the preset difference is M, that is, according to the characteristics of recycled polystyrene, the effect difference between the actual polystyrene recovery rate and the historical polystyrene recovery rate at each detection time node is compared with the preset difference M. When the effect difference is less than the preset difference, there is no need to adjust the historical treatment process, and the historical treatment process can be used as the optimal pre-treatment process to continue to use the process to treat polystyrene. When the effect difference is greater than the preset difference, it means that the historical treatment process cannot meet the existing pre-treatment of recycled polystyrene, and the historical pre-treatment process needs to be adjusted until the effect difference is less than the preset difference.

[0031] Specifically, for example, when the effect difference at T2 is greater than the preset difference M, it is necessary to increase the time of the processing step at the time node, or to increase the reagent in the process step at the time node to ensure that the impurities to be cleaned in the polystyrene material are fully cleaned and increase the recovery rate of polystyrene.

[0032] Through the above steps, the pre-treatment process is optimized. The optimized pre-treatment process is more suitable for this batch of recycled polystyrene materials. Therefore, the optimized pre-treatment process is the optimal pre-treatment process, and the optimal pre-treatment process is then used to treat this batch of polystyrene materials.

[0033] Example 2 In this embodiment, the pre-treatment process of polystyrene materials is described in detail. By optimizing the pre-treatment process, key nodes are found, and the pre-treatment process is adjusted according to the positions of the key nodes in the historical processing flow, so as to obtain the best pre-treatment process.

[0034] In the first step, based on the characteristics of the recycled polystyrene, the historical processing process with the highest frequency of use of this type of recycled polystyrene in the historical processing process is selected as a reference process.

[0035] The recycled polystyrene may include different types of polystyrene materials, such as general-purpose polystyrene, high-impact polystyrene, expanded polystyrene, etc.

[0036] In this embodiment, alkali washing, acid washing, organic washing and water washing in the recovery of general-purpose polystyrene are used as the processing flow, the cleaning time of each step in the process is used as the processing time, and the recovery rate of general-purpose polystyrene is used as the processing effect. The optimization of the pre-treatment process is achieved by optimizing the processing flow, processing time and processing effect.

[0037] The second step is to insert detection time nodes into the historical processing flow, and evaluate the historical processing effect at each time node based on the historical processing data corresponding to different time nodes.

[0038] The detection time nodes are determined according to the historical processing time, and generally the initial time, the first period, the middle period, the last period and the last period of the historical processing flow are used as the five detection time nodes. Of course, other time nodes can also be selected as the detection time nodes, and this is not limited here.

[0039] By selecting the historical pre-treatment process, a set of detection time nodes are found. For example, the detection time nodes are T10, T20, T30, T40 and T50, and the corresponding actual treatment effects are R10, R20, R30, R40 and R50. For example, the corresponding historical treatment effect is the recovery rate of polystyrene.

[0040] The detection time nodes are determined according to the time of the processing step, and generally the initial time T10, the first time T20, the middle time T30, the second time T40 and the last time T50 of the processing step are used as the five detection time nodes. Of course, other time nodes can also be selected as the detection time nodes, which is not limited here.

[0041] The fourth step is to calculate the node detection value at the detection time node according to the actual processing effect, compare the node detection values, and the detection time node corresponding to the largest node detection value is the key node. Adjust the historical processing process according to the time position of the key node.

[0042] In one embodiment, the node detection value is the difference between the actual processing effect in the unit time before and after the detection node. For example, when the node detection value at T10 is T10-d1, the actual effect is R10-f1, and when the time node is T10+d1, the actual effect is R10+f1. Wherein, d1 is the change value per unit time, and f1 is the change value of the actual effect per unit time, then the node detection value at T10 is 2f1. When the node detection value at T20 is T20-d1, the actual effect is R20-f2, when the time node is T20+d1, the actual effect is R20+f2, and the node detection value at T20 is 2f2. By analogy, the node detection value at T30 is 2f3, the node detection value at T40 is 2f4, and the node detection value at T50 is 2f5. If f2 is the maximum value, the T20 detection time node is a critical node.

[0043] In another embodiment, according to the time of the detection time node and the actual processing effect, a curve of the actual processing effect with respect to time is fitted, and the time node where the curve has the maximum curvature is used as the key node. Finding the key node according to the curve is more intuitive and improves the operation efficiency.

[0044] Specifically, if the detection time node corresponding to the key node is in the first half of the step, the amount of medicine added in the step is increased; if the detection time node corresponding to the key node is in the second half of the step, the processing time of the step is increased. The maximum curvature indicates that the reaction before the time node is more intense, and the reaction after the time node is balanced. If the treatment effect is not up to standard and the reaction force is insufficient in the first half, the medicine needs to be increased; if it is in the second half, it means that the reaction time is insufficient and the reaction time needs to be increased.

[0045] Through the above steps, the pre-treatment process is optimized to obtain the best pre-treatment process, and then the best pre-treatment process is used to treat the batch of polystyrene materials.

[0046] Example 3 The polystyrene material and the additive are mixed to form a mixed material using a first process. The first process specifically includes:

[0047] The recycled polystyrene is mixed with an additive, wherein the recycled polystyrene is made into granules, the weight proportion of the polystyrene is 20% to 95%, and the weight proportion of the additive is 5% to 80%.

[0048] In a specific embodiment, the additive includes one or more of a nucleating agent, pentane and a colorant, wherein the weight proportion of the nucleating agent may be 0.5% to 10%, the weight proportion of the pentane may be 3% to 10%, and the weight proportion of the colorant may be 0.1% to 20%.

[0049] Specifically, the nucleating agent includes one or more of talc, polyethylene wax, kaolin, white carbon black, calcium carbonate, silicon dioxide, and precipitated silica.

[0050] Nucleating agents can help polystyrene form tiny crystal nuclei during the recycling process. These crystal nuclei can serve as the starting point of the polymerization reaction, thereby promoting the extrusion polymerization reaction. It can also improve the physical and mechanical properties of recycled polystyrene, such as impact resistance, transparency and weather resistance. In addition, it can promote the crystallization of polymers and control the morphology and size of polymers. In recycled polystyrene, this helps to obtain a more uniform and stable polymer structure, thereby further improving the performance of the material.

[0051] The pentane may be one or more of n-pentane and isopentane. If n-pentane and isopentane are included, the ratio is preferably 1:9 to 9:1. Pentane is used as a solvent or diluent in the recovery of polystyrene, promotes foaming, regulates reaction speed and temperature, and affects the physical properties and processing properties of the material. These functions jointly promote the effective recovery and reuse of polystyrene.

[0052] Example 4 The second process includes melting the mixed material in an extruder and then extruding the mixed material, wherein the operating temperature of the extruder is 80° C. to 220° C. and the operating pressure of the extruder is 3 MPa to 20 MPa.

[0053] Specifically, the compounding and plasticizing process of polystyrene is mainly carried out by an extruder, which achieves effective melting, mixing and plasticizing of the material by precisely controlling the working temperature and pressure.

[0054] In one embodiment, the apparatus may be a twin screw extruder or a single screw extruder.

[0055] For a twin-screw extruder, the machine operating temperature can be 130°C to 200°C, specifically 130°C, 150°C, 180°C and 200°C, and different operating temperatures are related to the characteristics of polystyrene. The working pressure can be 3MPa to 20MPa. Under this working condition, it can ensure that the material is fully melted and mixed evenly, and at the same time ensure that the material is subjected to sufficient shear force and mixing plasticization effect during the melting process.

[0056] For a single screw extruder, the machine operating temperature can be 80°C to 220°C, specifically 80°C, 130°C, 180°C and 220°C, and different operating temperatures are related to the characteristics of polystyrene. The working pressure can be 4MPa to 10MPa, under which the material can be fully melted and mixed evenly, and the material can be subjected to sufficient shear force and mixing effect during the melting process.

[0057] Example 5 The third process includes molding the plasticized material. Specifically, the plasticized material is extruded from the head of the extruder and enters the circulating water for underwater pelletizing. The particles are cut into particles of the required particle size according to the product specifications, and the particle size can be 0.4cm to 3.0cm. This process is usually operated under pressure, and the working pressure is 0.1Mpa to 2Mpa. The temperature of the circulating water is between 30℃ and 60℃ to ensure the stability of the pelletizing process and the quality of the product. The polystyrene particles after underwater pelletizing and centrifugal drying have the advantages of uniform particle size, good dispersibility and fluidity.

[0058] Example 6 The fourth process includes drying the plasticized material. Specifically, after the underwater pelletizing process of the plasticized material, the particles with water will enter the integrated dehydration dryer for further drying treatment, and the optional drying method is one or both of the lower dehydration method and the upper exhaust method.

[0059] For the bottom dehydration method, a dehydration dryer is preferred to remove the residual water in the particles by mechanical or physical means, usually by vibrating the screen plate or centrifugal force, so that the particles roll or jump on the screen plate, thereby throwing off the water attached to the surface.

[0060] For the upper exhaust method, an exhaust system is installed above the dehydration area. Through the negative pressure, the air containing moisture is extracted, and natural cold air is introduced as circulating air. After being filtered, the natural cold air comes into contact with the particles containing moisture, taking away the moisture on the surface of the particles, achieving the drying effect.

[0061] In other embodiments, a normal temperature drying method may be selected, wherein the dehydration and drying process is performed at normal temperature, thereby avoiding the damage to the particle performance caused by high temperature. At the same time, normal temperature drying also reduces energy consumption and production costs.

[0062] In another embodiment, a natural cold air circulation method is adopted, and natural cold air is used as the circulating air, and no additional refrigeration equipment is required, thereby reducing energy consumption. At the same time, natural cold air can also ensure the cleanliness of the air during the drying process, avoiding secondary pollution of particles.

[0063] In another embodiment, the combination of lower dehydration and upper ventilation achieves efficient dehydration of the particles. This process not only removes moisture on the surface of the particles, but also gradually discharges moisture inside the particles, achieving an ideal drying effect.

[0064] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any changes that adopt the design principles of the present invention and are made through non-creative work on this basis should fall within the protection scope of the present invention.

Claims

1. A process for producing environmentally friendly expandable polystyrene by extrusion, comprising the following steps: (1) Optimizing the pretreatment process according to the characteristics of polystyrene and the historical processing data of the historical processing process to obtain the best pretreatment process, and using the best pretreatment process to treat the polystyrene; (2) Using the first process to mix the polystyrene and the additive to form a mixed material; (3) Using the second process to mix and plasticize the mixed material to form a plasticized material; (4) Using the third process to shape the plasticized material; (5) Using the fourth process to treat the plasticized material.

2. The process for producing environmentally friendly expandable polystyrene by extrusion according to claim 1, wherein the characteristics of the polystyrene include the type, particle size, impurity content and impurity category of the polystyrene.

3. According to the extrusion method environmentally friendly expandable polystyrene production process described in claim 1, the historical processing data includes historical processing flow, historical processing time, historical processing frequency and historical processing effect.

4. According to the extrusion method environmentally friendly expandable polystyrene production process as described in any one of claims 1 to 3, the optimized pre-treatment process includes selecting a corresponding historical treatment process according to the type, particle size, impurity content or impurity category of the polystyrene, selecting a first set of detection time nodes in the historical treatment process, obtaining the historical treatment effects corresponding to the first set of detection time nodes, treating the polystyrene according to the historical treatment process, detecting the actual treatment effect at the first set of detection time nodes, comparing the actual treatment effect with the historical treatment effect, obtaining an effect difference, when the effect difference is less than a preset difference, the historical treatment process remains unchanged, and when the effect difference is greater than the preset difference, adjusting the historical treatment process so that the effect difference is less than the preset difference.

5. According to the extrusion method environmentally friendly expandable polystyrene production process as described in any one of claims 1 to 3, the optimized pre-treatment process includes selecting a corresponding historical treatment process according to the type, particle size, impurity content or impurity category of the polystyrene, treating the polystyrene according to the historical treatment process, detecting the actual treatment effect at a second set of detection time nodes, calculating the node detection values ​​at the second set of detection time nodes according to the actual treatment effect, comparing the node detection values, the detection time node corresponding to the largest node detection value is the key node, and adjusting the historical treatment process according to the time position of the key node.

6. According to the extrusion method environmentally friendly expandable polystyrene production process of claim 5, the node detection value is the difference in actual processing effect per unit time before and after the detection node.

7. The process for producing environmentally friendly expandable polystyrene by extrusion according to claim 1, wherein the first process comprises mixing polystyrene and additives by weight, wherein: The weight proportion of the polystyrene is 20% to 95%, and the weight proportion of the additive is 5% to 80%.

8. The process for producing environmentally friendly expandable polystyrene by extrusion according to claim 1, wherein the second process comprises melting the mixed material in an extruder and then extruding the mixed material, wherein: The working temperature of the extruder is 80° C. to 220° C., and the working pressure of the extruder is 3 MPa to 20 MPa.

9. The process for producing environmentally friendly expandable polystyrene by extrusion according to claim 1, wherein the third process comprises cooling the plasticized material by circulating water, wherein: The temperature of the circulating water is 30°C to 60°C.

10. The process for producing environmentally friendly expandable polystyrene by extrusion according to claim 1, wherein the fourth process comprises drying the plasticized material.

Images