Plastic particle regeneration granulation treatment method

Abstract

The invention discloses a plastic particle regeneration granulation treatment method which comprises the following steps: collecting and classifying waste plastics, and respectively carrying out decoloring treatment according to classification conditions, so as to obtain colorless transparent plastics; the method comprises the following steps: crushing and melting colorless transparent plastic, and mixing the colorless transparent plastic with a supercritical foaming agent to obtain molten plastic containing bubbles; the plastic is preliminarily classified according to the color of the plastic and then classified according to the plastic material, the plastic material is divided into a PP material, a PE material and a PVC material, and if the color is dark, the plastic material is divided into light-color plastic, dark-color plastic and mixed-color plastic; compared with the prior art, the preparation method has the advantages that the color removal degree of the prepared plastic is effectively improved, and compared with the prior art, the color removal degree of the plastic is greatly improved and the plastic is protected by carrying out classification and then carrying out color removal treatment according to different characteristics of the plastic.

Description

Technical Field

[0001] The invention relates to a field related to a plastic particle preparation process, and in particular to a plastic particle regeneration granulation processing method. Background Art

[0002] As human beings become more and more dependent on plastic products, the problem of plastic waste is becoming more and more serious. A large amount of plastic waste has caused tremendous pressure on the environment and ecosystem. Therefore, it is urgent to develop an effective method for plastic waste treatment. In this context, the plastic granule recycling and granulation treatment method came into being, providing a new way for the resource utilization of plastic waste. The plastic granule recycling and granulation treatment method is a technology that converts waste plastics into reusable plastic granules through a series of processes. This treatment method can not only effectively solve the pollution problem caused by plastic waste to the environment, but also reduce the production cost of new plastics and promote the recycling of resources. In the traditional plastic granule recycling and granulation process, the waste plastics must first be pre-treated by washing, crushing and melting to remove non-plastic components such as oil, impurities and metals. Then, the molten plastic is processed into granules through specific granulation equipment, and these granules can be directly used to make new plastic products. In protective gear, especially the windshield in front of the helmet, it is required to have high transparency so as not to affect the rider's vision, and also to have high sturdiness to prevent sharp objects such as stones from flying and hitting the helmet during driving, thereby endangering the rider's personal safety. However, in the existing preparation process of plastic particle recycling and granulation, the strength of the obtained plastic is poor. Summary of the invention

[0003] The invention overcomes the shortcomings of the prior art and provides a plastic particle regeneration and granulation processing method.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a plastic granule regeneration and granulation processing method, comprising the following steps:

[0005] S1: Collect and classify waste plastics, and perform decolorization treatment according to the classification conditions to obtain colorless and transparent plastics;

[0006] S2: crushing the colorless and transparent plastic, melting it, and mixing it with a supercritical foaming agent to obtain a molten plastic containing bubbles;

[0007] S3: The molten plastic is extruded through an extruder and cooled through a high-speed spray cooling system, so that the basic plastic quickly forms a granular plastic containing a polycrystalline structure and bubbles.

[0008] In a preferred embodiment of the present invention, in S1, the classification is first performed according to the color of the plastic and then classified according to the material of the plastic, wherein the plastic material is divided into PP material, PE material and PVC material, and the color depth is divided into light plastic, dark plastic and mixed color plastic.

[0009] In a preferred embodiment of the present invention, the preliminary classification of plastics is divided into three situations according to their colors:

[0010] The first type is specifically for distinguishing light-colored plastics. White or gray samples are selected as references. If the color difference between the plastic to be classified and the standard sample is less than or equal to 4, it is identified as light-colored plastic.

[0011] The second type is specifically for distinguishing dark-colored plastics. Black or dark-colored samples are selected as references. If the color difference between the plastic to be classified and the standard sample is greater than 4, it is identified as light-colored plastic.

[0012] The third type is specifically the distinction between colored plastics. By using a spotlight, if the plastic to be tested contains heterochromatic plastic particles, and the area of ​​the particles accounts for more than 5% of the total area of ​​the plastic to be tested, it is identified as a heterochromatic plastic.

[0013] In a preferred embodiment of the present invention, in S1, the decolorization process is specifically as follows:

[0014] S11: Select different chemical solvents according to the classification of plastics, soak the plastics, take them out and rinse them;

[0015] S12: Take out the dark-colored plastic and the multicolored plastic, soak them again in bleach, take them out and rinse them;

[0016] S13: Take out all the plastics in S11 and S12, and perform high temperature treatment to decompose the internal pigment molecules.

[0017] In a preferred embodiment of the present invention, in S11, the selection of chemical solvents is divided into two cases:

[0018] In the first case, for light-colored plastics, the chemical solvent is selected from an organic solvent such as acetone with a concentration of 50%-80% or butanone with a concentration of 30%-50%;

[0019] The second case is dark or variegated plastics, and the chemical solvent is selected from an organic solvent such as chloroform with a concentration of 5%-10% or chlorobenzene with a concentration of 1%-5%;

[0020] The soaking time in both cases was 8 min-14 min.

[0021] In a preferred embodiment of the present invention, in S12, the bleaching agent is selected from sodium hypochlorite or hydrogen peroxide solution, the concentration is 8%-11%, the soaking time is 17min-25min, and the temperature is 40°C-45°C.

[0022] In a preferred embodiment of the present invention, in S13, the high temperature treatment is performed by baking at a temperature of 180°C-200°C for 30min-40min.

[0023] In a preferred embodiment of the present invention, in S2, crushing is carried out in a crusher, the rotation speed is 300-500rpm, the melting temperature is 150℃-300℃, the supercritical foaming agent is selected from one of carbon dioxide or nitrogen dioxide, the mixing pressure is 0.2MPa-2.5MPa, and the rotation speed is 25Hz-50Hz.

[0024] In a preferred embodiment of the present invention, in S3, the high-speed spray cooling system can quickly perform graded cooling on the extruded plastic, and the polycrystalline structure is specifically two different crystallization regions.

[0025] In a preferred embodiment of the present invention, the graded cooling is specifically an initial cooling stage and a deep cooling stage, the crystallization zone is specifically a narrow crystallization zone and a larger crystallization zone, the cooling temperature in the initial cooling stage is 5°C-12°C, and the temperature in the deep cooling stage is 15°C-25°C.

[0026] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0027] (1) The present invention provides a method for recycling and granulating plastic particles, by classifying waste plastics into multiple levels according to color and material and then performing decolorization treatment, thereby performing decolorization treatment according to the different conditions of each plastic, effectively improving the decolorization degree of the prepared plastic. Compared with the prior art, the present application greatly improves the decolorization degree of the plastic and protects the plastic by classifying the plastics according to their different characteristics and then performing decolorization treatment, and effectively avoids the situation in the prior art where the same chemical reagent is used to directly decolorize the plastics due to the different characteristics of each plastic, resulting in damage to the plastics that are easier to decolorize and failure to achieve the desired effect for the plastics that are more difficult to decolorize.

[0028] (2) The present invention provides a method for recycling and granulating plastic particles, by using a high-speed spray cooling system to perform graded cooling on the extruded molten plastic, thereby forming different crystallization zones on the surface and inside of the hardened plastic, thereby improving the strength and transparency again. Compared with the prior art, the present invention uses a high-speed spray cooling system to perform graded cooling on the extruded molten plastic, instead of cooling the granulation under water in the prior art, to form different crystallization zones, thereby greatly improving the transparency and strength of the plastic while avoiding stickiness. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a three-dimensional structural diagram of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in 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.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0034] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0035] As shown in the figure, a plastic granule recycling and granulation processing method comprises the following steps:

[0036] S1: Collect and classify waste plastics, and decolorize them according to the classification conditions to obtain colorless and transparent plastics;

[0037] S2: crushing the colorless and transparent plastic, melting it, and mixing it with a supercritical foaming agent to obtain a molten plastic containing bubbles;

[0038] S3: The molten plastic is extruded through an extruder and cooled through a high-speed spray cooling system, so that the basic plastic quickly forms a granular plastic containing a polycrystalline structure and bubbles.

[0039] In a preferred embodiment of the present invention, in S1, the classification is first performed according to the color of the plastic and then classified according to the material of the plastic, wherein the plastic material is divided into PP material, PE material and PVC material, and the color depth is divided into light plastic, dark plastic and mixed color plastic.

[0040] It should be noted that for light-colored plastics, since their colors are relatively light, decolorization is relatively easy. Through appropriate chemical or physical treatment, the surface color can be effectively removed, making it appear colorless or nearly colorless and transparent.

[0041] Decolorization is more difficult for dark-colored plastics than for lighter-colored ones. Because dark plastics are darker in color, they may require stronger chemical treatments or longer physical treatments to remove.

[0042] For variegated plastics, the decolorization process is more complicated than the first two. Because the color of variegated plastics is uneven or contains multiple colors, different treatment methods may be used to remove all colors.

[0043] For PP (polypropylene) plastics:

[0044] When decolorizing plastics made of PP, due to its good chemical stability and heat resistance, a stronger chemical treatment method can be used.

[0045] For PE (polyethylene) plastics:

[0046] PE plastic is relatively soft and slightly less resistant to chemical corrosion than PP. Therefore, when performing decolorization, a milder chemical agent needs to be selected.

[0047] In a preferred embodiment of the present invention, the preliminary classification of plastics is divided into three situations according to their colors:

[0048] The first type is specifically for distinguishing light-colored plastics. White or gray samples are selected as references. If the color difference between the plastic to be classified and the standard sample is less than or equal to 4, it is identified as light-colored plastic.

[0049] The second type is specifically for distinguishing dark-colored plastics. Black or dark-colored samples are selected as references. If the color difference between the plastic to be classified and the standard sample is greater than 4, it is identified as light-colored plastic.

[0050] The third type is specifically the distinction between colored plastics. By using a spotlight, if the plastic to be tested contains heterochromatic plastic particles, and the area of ​​the particles accounts for more than 5% of the total area of ​​the plastic to be tested, it is identified as a heterochromatic plastic.

[0051] It should be noted that, for the first type: differentiation of light-colored plastics, the selected standard samples are white or gray plastic samples as reference standards for light-colored plastics.

[0052] Colorimeter measurement: A colorimeter is a device that can quantify color differences. Here, it is used to measure the color difference between the plastic sample to be classified and a standard sample.

[0053] Color difference threshold: By setting the threshold, that is, the color difference value, the color difference value is specifically the difference between the plastic to be classified and the standard sample, which is the color difference value. The color difference value in light-colored plastics is considered to be less than or equal to 4, and the color difference value in dark-colored plastics is considered to be greater than 4.

[0054] The second type: To distinguish dark plastics, select black or dark samples as the reference standard for dark plastics. Use a colorimeter to measure the color difference between the plastic to be classified and the dark standard sample. If the color difference is greater than 4, the plastic is identified as dark plastic.

[0055] The third type: the distinction between colored plastics relies on visual inspection under spotlight, by checking the different colored particles in it. If under the spotlight, the plastic to be tested contains particles with a different color from other parts, and the area of ​​these particles accounts for more than 5% of the entire plastic sample, then this piece of plastic is identified as colored plastic.

[0056] In a preferred embodiment of the present invention, in S1, the decolorization process is specifically as follows:

[0057] S11: Select different chemical solvents according to the classification of plastics, soak the plastics, take them out and rinse them;

[0058] S12: Take out the dark-colored plastic and the multicolored plastic, soak them again in bleach, take them out and rinse them;

[0059] S13: Take out all the plastics in S11 and S12, and perform high temperature treatment to decompose the internal pigment molecules.

[0060] In a preferred embodiment of the present invention, in S11, the selection of chemical solvents is divided into two cases:

[0061] In the first case, for light-colored plastics, the chemical solvent is selected from an organic solvent such as acetone with a concentration of 50%-80% or butanone with a concentration of 30%-50%;

[0062] The second case is dark or variegated plastics, and the chemical solvent is selected from an organic solvent such as chloroform with a concentration of 5%-10% or chlorobenzene with a concentration of 1%-5%;

[0063] The soaking time in both cases was 8 min-14 min.

[0064] In a preferred embodiment of the present invention, in S12, the bleaching agent is selected from sodium hypochlorite or hydrogen peroxide solution, the concentration is 8%-11%, the soaking time is 17min-25min, and the temperature is 40°C-45°C.

[0065] In a preferred embodiment of the present invention, in S13, the high temperature treatment is performed by baking at a temperature of 180°C-200°C for 30min-40min.

[0066] It should be noted that in this decolorization treatment part, a series of chemical and physical methods are used to remove the color of the plastic to make the plastic transparent or translucent. In S11, the chemical solvent immersion method is used to achieve the purpose of using chemical solvents to preliminarily remove the plastic pigment. Light-colored plastic: select an organic solvent with a concentration of 50%-80% acetone or a concentration of 30%-50% butanone. These two solvents have good solubility for the pigment of light-colored plastics and will not cause excessive damage to the plastic substrate. Dark plastic and variegated plastic: select an organic solvent with a concentration of 5%-10% chloroform or a concentration of 1%-5% chlorobenzene. These solvents have strong solubility for the pigment in dark and variegated plastics. Soaking time and effect: The soaking time is 8min-14min, ensuring that the solvent is in full contact with the plastic surface so that the pigment molecules are dissolved in the solvent. Rinse after taking out to remove the residual solvent and dissolved pigment on the surface.

[0067] In S12, the purpose of further removing the stubborn pigments in the dark and variegated plastics is achieved by soaking in bleach again. The bleach is selected from sodium hypochlorite or hydrogen peroxide solution with a concentration of 8%-11%. These bleaches are highly oxidizing and can oxidize and decompose pigment molecules. The soaking time is 17min-25min to ensure that the bleach fully reacts with the plastic surface. The temperature is controlled to be 40℃-45℃ to promote the oxidation reaction of the bleach. In S13, the high temperature treatment method is used to decompose the pigment molecules inside the plastic by high temperature, thereby achieving the purpose of decolorization. The high temperature treatment is carried out by baking at a temperature of 180℃-200℃. This temperature range is sufficient to decompose the pigment molecules inside most plastics. The treatment time is 30min-40min to ensure that the pigment inside the plastic is fully decomposed. Therefore, the pigment on the plastic surface can be preliminarily removed by soaking in the chemical solvent in S11. The bleach soaking in S12 further removes the stubborn pigments in the dark and variegated plastics. The high temperature treatment of S13 ensures that the pigment molecules inside the plastic are also fully decomposed. Through the combined action of the above three steps, the plastic is decolorized and transparent, making the originally colored plastic transparent or translucent.

[0068] In a preferred embodiment of the present invention, in S2, crushing is carried out in a crusher, the rotation speed is 300-500rpm, the melting temperature is 150℃-300℃, the supercritical foaming agent is selected from one of carbon dioxide or nitrogen dioxide, the mixing pressure is 0.2MPa-2.5MPa, and the rotation speed is 25Hz-50Hz.

[0069] In a preferred embodiment of the present invention, in S3, the high-speed spray cooling system can quickly perform graded cooling on the extruded plastic, and the polycrystalline structure is specifically two different crystallization regions.

[0070] In a preferred embodiment of the present invention, the graded cooling is specifically an initial cooling stage and a deep cooling stage, the crystallization zone is specifically a narrow crystallization zone and a larger crystallization zone, the cooling temperature in the initial cooling stage is 5°C-12°C, and the temperature in the deep cooling stage is 15°C-25°C. The initial cooling stage forms a fine crystallization zone on the surface of the plastic particles, and the deep cooling stage forms a larger crystallization zone in the plastic particles.

[0071] It should be noted that the high-speed spray cooling system is a cooling device that uses high-speed spray technology to spray coolant evenly and quickly onto the surface of the object to be cooled. In plastic processing, this system is mainly used to quickly cool the extruded plastic particles to control the crystallization process of the plastic. In the initial stage, the plastic has just entered the mold from a molten state and the temperature is very high. At this time, the temperature of the plastic needs to be quickly reduced to start the crystallization process and prevent the plastic from excessively flowing or deforming in the mold. Rapid cooling helps to form fine crystalline areas on the surface of the plastic, thereby improving transparency and toughness. The cooling water temperature is set in a lower range of 5℃-12℃ to ensure sufficient temperature difference for rapid heat exchange. In the deep cooling stage, the plastic is close to its solidification temperature and requires longer cooling to ensure complete solidification. At this time, too fast a cooling rate may cause stress or deformation inside the plastic, so the cooling rate needs to be slowed down. Further increasing the cooling water temperature to 15℃-25℃ can further slow down the cooling rate, thereby ensuring uniform solidification of the plastic and reducing stress.

[0072] Among them, the specific high-speed spray cooling system cools plastics as follows: Initial cooling stage:

[0073] When the extruded hot plastic pellets enter the high-speed spray cooling system, they first encounter a large amount of low-temperature coolant, which quickly lowers the surface temperature of the plastic pellets and forms a thin cooling layer.

[0074] Due to the rapid cooling effect of the coolant, the plastic molecules on the surface layer of the plastic particles begin to gradually arrange in order to form fine crystalline areas. These fine crystalline areas are mainly distributed on the surface of the plastic particles and the area close to the surface. When the plastic is just extruded from the molten state and enters the cooling system, it immediately encounters the coolant, causing rapid cooling. The surface of the plastic and the area close to the surface will cool rapidly. Due to the rapid decrease in temperature, the molecular chains do not have enough time to move and rearrange over long distances, so only small, local, and orderly crystal structures can be formed, namely fine crystalline areas.

[0075] Deep cooling stage:

[0076] As the cooling process progresses, the temperature inside the plastic particles gradually decreases. At this time, due to the poor thermal conductivity of plastic materials, the cooling rate inside the plastic particles is relatively slow. At this stage, the plastic molecules inside the plastic particles begin to gradually arrange into an orderly crystal structure, forming a larger crystallization area. These larger crystallization areas are mainly distributed in the interior and central areas of the plastic particles. The high-speed spray cooling system can be used to grade the extruded plastic particles to effectively control the crystallization area. In the initial cooling stage, rapid cooling helps to form fine crystallization areas; in the deep cooling stage, a slower cooling rate is conducive to the formation of larger crystallization areas.

[0077] Embodiment 1:

[0078] Waste plastics are collected and classified according to their colors and then classified according to their materials. The materials are divided into PP materials, PE materials and PVC materials. The colors are divided into light-colored plastics, dark-colored plastics and mixed-colored plastics. The classification is divided into three situations: the first is the distinction of light-colored plastics. White or gray samples are selected as references. The color difference between the plastic to be classified and the standard sample is measured by a colorimeter. If the color difference is less than or equal to 4, it is considered light-colored plastic; the second is the distinction of dark-colored plastics. Black or dark samples are selected as references. The color difference between the plastic to be classified and the standard sample is measured by a colorimeter. If the color difference is greater than 4, it is identified as light-colored plastic: The third type is specifically the distinction of mixed-color plastics. By using a spotlight to illuminate, if the plastic to be tested contains heterochromatic plastic particles, and the area of ​​the particles accounts for more than 5% of the total plastic to be tested, it is identified as mixed-color plastic, and decolorization treatment is performed according to the classification to obtain colorless and transparent plastics; in the decolorization process: for light-colored plastics, the chemical solvent is selected to be 60% acetone organic solvent; for dark plastics and mixed-color plastics, the chemical solvent is selected to be 8% chloroform organic solvent, the immersion time is 12 minutes, take out and rinse; take out the dark plastic and mixed-color plastic and use bleach again Soaking, the bleaching agent is sodium hypochlorite, the concentration is 10%, the soaking time is 20 minutes, the temperature is 42°C, and then taken out for rinsing; all the plastics in the first two steps are taken out and subjected to high-temperature baking treatment, the temperature is 200°C, and the time is 35 minutes, so that the internal pigment molecules are decomposed; the colorless and transparent plastic is crushed in a crusher at a speed of 380rpm, melted, and the melting temperature is 230°C, and mixed with a carbon dioxide supercritical foaming agent at a mixing pressure of 2.3MPa and a stirring speed of 33Hz to obtain a molten plastic containing bubbles; the molten plastic is extruded through an extruder, and The high-speed spray cooling system performs graded cooling, which is specifically divided into an initial cooling stage and a deep cooling stage, so that the basic plastic quickly forms a granular plastic containing a polycrystalline structure and bubbles. The polycrystalline structure is specifically divided into two different crystallization zones, and the crystallization zones are specifically divided into a fine crystallization zone and a larger crystallization zone. Specifically, a fine crystallization zone is formed on the surface of the plastic particles and a larger crystallization zone is formed inside the plastic particles in the deep cooling stage. The cooling temperature in the initial cooling stage is 7°C to cool the plastic particles, so that a fine crystallization zone is quickly formed on the surface of the plastic particles. The temperature in the deep cooling stage is 25°C, so that a larger crystallization zone is formed inside the plastic particles.

[0079] Experiment 1:

[0080] The plastic particles prepared in Example 1 were used as a control group. On the basis of the preparation method of the control group, that is, on the basis of Example 1, experimental group 1 and experimental group 2 were set. The preparation method of experimental group 1 specifically canceled the classification in Example 1, and directly used 8% chloroform and 60% acetone organic solvents to decolorize the plastics after the collection was completed, wherein the decolorization and subsequent steps were the same as those in Example 1; the preparation method of experimental group 2 specifically classified only according to the material but not according to the color in the classification step of Example 1, and then used 8% chloroform organic solvent and 60% acetone organic solvent to decolorize the plastics, wherein the decolorization and subsequent steps were the same as those in Example 1; the control group, experimental group 1 and experimental group 2 were tested for transparency, and the specific operation was to use a beam of light of the same intensity to irradiate from one side of the control group, experimental group 1 and experimental group 2, and set a spectrophotometer on the other side of the control group, experimental group 1 and experimental group 2, and use a luminescence photometer to receive the projected light, and then detect the light transmittance of the plastic particles prepared by the control group, experimental group 1 and experimental group 2, as shown in Table 1:

[0081] Table 1:

[0082]

[0083] It can be seen from Table 1 that the light transmittance of the plastic particles prepared by the control group reached a maximum of 70%, while the maximum light transmittance of the experimental group could only reach 56%. In the process of decolorization using chloroform organic solvent in Experimental Group 2, the plastic particles were over-treated, resulting in a rough surface. It can be seen that only by performing preliminary classification according to color depth before decolorization and then classifying according to material, can the appropriate solvent be selected for decolorization according to material and color depth during the decolorization process, thereby improving the degree of color extraction and further improving the light transmittance of the prepared plastic particles.

[0084] Experiment 2:

[0085] The plastic particles prepared in Example 1 were used as a control group. On the basis of the preparation method of the control group, experimental groups 3, 4 and 5 were set up on the basis of Example 1. The specific preparation method of experimental group 3 was to change the cooling of the extruded plastic particles using a high-speed spray cooling system to underwater extrusion cooling in the prior art on the basis of Example 1, and the other steps were the same; experimental groups 4 to 5 changed the cooling temperatures in the initial cooling stage and the deep cooling stage, respectively, and then performed transmittance detection and pressure detection, wherein the specific operation of the transmittance detection was to use a beam of light of the same intensity to irradiate from one side of the control group and the experimental group respectively, and set a spectrophotometer on the other side of the control group and the experimental group, and use the spectrophotometer to receive the projected light, and then detect the transmittance of the plastic particles prepared by the control group and the experimental group; the specific operation of the pressure detection was to place the plastic particles on a metal platform and use a press to apply pressure to observe the pressure value when it is deformed, as shown in Table 2:

[0086] Table 2:

[0087]

[0088] As can be seen from Table 2, by comparing the control group and the experimental group 3, it can be seen that the plastic particles prepared by the high-speed spray cooling system are better than the cooling in water in the prior art in terms of light transmittance and pressure value. The optimal temperature of the high-speed spray cooling system in the initial stage is 7°C, and the optimal temperature in the deep stage is 25°C. The plastic particles prepared at this temperature have a higher fine crystallization area, and the crystal particles are small, smaller than the visible light wavelength range, which does not hinder the transmission of visible light and near-infrared light in the sunlight spectrum, can reduce light scattering, and improve the transparency of plastic products. At the same time, there is a higher larger crystallization area. In the deep cooling stage, the temperature difference is reduced, the cooling is slow, and the residence time of the plastic in the crystallization area is prolonged, which is conducive to crystal growth and the formation of a larger crystallization area. More molecular segments are fixed in the lattice, which reduces the mobility of the segments, making it more difficult to deform when subjected to external forces, thereby increasing the hardness of the plastic.

[0089] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for regenerating and granulating plastic particles, characterized in that: The following steps are involved: S1: Collect and classify waste plastics, and perform decolorization treatment according to the classification conditions to obtain colorless and transparent plastics; S2: crushing the colorless and transparent plastic, melting it, and mixing it with a supercritical foaming agent to obtain a molten plastic containing bubbles; S3: The molten plastic is extruded through an extruder and cooled through a high-speed spray cooling system, so that the basic plastic quickly forms a granular plastic containing a polycrystalline structure and bubbles.

2. A plastic granule regeneration and granulation processing method according to claim 1, characterized in that: In S1, the classification is first performed according to the color of the plastic and then classified according to the material of the plastic, wherein the plastic material is divided into PP material, PE material and PVC material, and the color depth is divided into light plastic, dark plastic and mixed color plastic.

3. A plastic granule regeneration and granulation processing method according to claim 2, characterized in that: The preliminary classification according to the color of plastics is divided into three situations: The first type is specifically for distinguishing light-colored plastics. White or gray samples are selected as references. If the color difference between the plastic to be classified and the standard sample is less than or equal to 4, it is identified as light-colored plastic. The second type is specifically for distinguishing dark-colored plastics. Black or dark-colored samples are selected as references. If the color difference between the plastic to be classified and the standard sample is greater than 4, it is identified as light-colored plastic. The third type is specifically the distinction between colored plastics. By using a spotlight, if the plastic to be tested contains heterochromatic plastic particles, and the area of ​​the particles accounts for more than 5% of the total area of ​​the plastic to be tested, it is identified as a heterochromatic plastic.

4. A plastic granule regeneration and granulation processing method according to claim 2, characterized in that: In S1, the decolorization process is specifically as follows: S11: Select different chemical solvents according to the classification of plastics, soak the plastics, take them out and rinse them; S12: Take out the dark-colored plastic and the multicolored plastic, soak them again in bleach, take them out and rinse them; S13: Take out all the plastics in S11 and S12, and perform high temperature treatment to decompose the internal pigment molecules.

5. A plastic granule regeneration and granulation processing method according to claim 4, characterized in that: In S11, the selection of chemical solvents is divided into two cases: In the first case, for light-colored plastics, the chemical solvent is selected from an organic solvent such as acetone with a concentration of 50%-80% or butanone with a concentration of 30%-50%; The second case is dark or variegated plastics, and the chemical solvent is selected from an organic solvent such as chloroform with a concentration of 5%-10% or chlorobenzene with a concentration of 1%-5%; The soaking time in both cases was 8 min-14 min.

6. A plastic granule regeneration and granulation processing method according to claim 4, characterized in that: In S12, the bleaching agent is selected from sodium hypochlorite or hydrogen peroxide solution, the concentration is 8%-11%, the soaking time is 17min-25min, and the temperature is 40°C-45°C.

7. A plastic granule regeneration and granulation processing method according to claim 4, characterized in that: In S13, the high temperature treatment is performed by baking at a temperature of 180°C-200°C for 30min-40min.

8. A plastic granule regeneration and granulation processing method according to claim 1, characterized in that: In S2, the crushing is carried out in a crusher with a rotation speed of 300-500rpm, a melting temperature of 150°C-300°C, a supercritical foaming agent selected from carbon dioxide or nitrogen dioxide, a mixing pressure of 0.2MPa-2.5MPa, and a rotation speed of 25Hz-50Hz.

9. A plastic granule regeneration and granulation processing method according to claim 1, characterized in that: In S3, the high-speed spray cooling system can rapidly perform graded cooling on the extruded plastic, and the polycrystalline structure is specifically two different crystallization regions.

10. A plastic granule regeneration and granulation processing method according to claim 9, characterized in that: The graded cooling specifically includes an initial cooling stage and a deep cooling stage, the crystallization zone specifically includes a narrow crystallization zone and a larger crystallization zone, the cooling temperature in the initial cooling stage is 5°C-12°C, and the temperature in the deep cooling stage is 15°C-25°C.

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