Preparation method of modified plastic

Abstract

The invention discloses a preparation method of modified plastic, and relates to the technical field of modified plastic preparation, and the preparation method comprises the following steps: S1, raw material preparation: selecting 30-40 parts by weight of polypropylene, 25-35 parts by weight of polyethylene, 20-30 parts by weight of polystyrene, 3-5 parts by weight of a reinforcing agent, 2-4 parts by weight of a flame retardant and 3-6 parts by weight of an antistatic agent; s2, premixing: adding the plastic raw materials and the additives into a mixer according to the proportion, and premixing; s3, melt blending: adding the premixed materials into a double-screw extruder for melt blending; s4, extrusion and granulation: extruding the melt-blended material through an extruder to form plastic strips, and then cutting the plastic strips into particles with the length of 3-5mm through a granulator; the modified plastic particles are dried and packaged, moisture in the particles is removed, and the quality and stability of the particles are improved; through the adsorption barrel and the staggered magnetic rods, iron chips in plastic raw materials can be adsorbed, and the content of metal impurities in the plastic raw materials is reduced.

Description

Technical Field

[0001] The invention relates to the technical field related to the preparation of modified plastics, and in particular to a method for preparing modified plastics. Background Art

[0002] Modified plastics refer to plastic products that are modified on the basis of general-purpose plastics and engineering plastics through filling, blending, reinforcement and other methods to improve their flame retardancy, strength, impact resistance, toughness and other properties.

[0003] In the preparation process of modified plastics, the required plastic raw materials and some additives need to be placed in a mixing tank for blending. The existing method is usually to place the plastic raw materials in the mixing tank first, and then add various additives one by one. This will cause the added additives to accumulate on the top of the plastic raw materials. Since the amount of additives used is small, it is easy to cause uneven mixing with the plastic raw materials in the subsequent mixing, affecting the quality of the modified plastics. In addition, since there will be some metal impurities in the plastic raw materials, if they are not treated, it will also affect the quality of the modified plastics. Summary of the invention

[0004] In order to solve the defects in the prior art, the present invention provides a method for preparing a modified plastic.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a modified plastic, comprising the following steps:

[0007] S1 Raw material preparation: select 30-40 parts of polypropylene, 25-35 parts of polyethylene, 20-30 parts of polystyrene, 3-5 parts of reinforcing agent, 2-4 parts of flame retardant, and 3-6 parts of antistatic agent in parts by weight;

[0008] S2 premixing: adding the plastic raw material and the additive into the mixer according to the above ratio for premixing, so that the additive is evenly dispersed in the plastic raw material;

[0009] S3 melt blending: add the premixed materials into a twin-screw extruder for melt blending. In the extruder, the materials are subjected to high temperature and shear force, so that the additives and plastic raw materials are fully mixed and chemically react to form modified plastics;

[0010] S4 extrusion granulation: the melt blended material is extruded through an extruder to form a plastic strip, and then the plastic strip is cut into particles of 3-5 mm in length by a pelletizer to obtain modified plastic particles;

[0011] S5 post-processing: drying and packaging the modified plastic particles, removing moisture from the particles, and improving the quality and stability of the particles;

[0012] The premixing device used in the above-mentioned preparation method comprises a premixing tank, one side of the top of the premixing tank is connected to a plastic raw material channel, at least one additive channel is respectively provided on both sides of the plastic raw material channel, and a magnetic adsorption processing mechanism for removing metal impurities in the plastic raw material is provided at the top of the plastic raw material channel;

[0013] A premixing assembly for premixing the plastic raw material and the additive is arranged at the bottom of the plastic raw material channel and the additive channel in the premixing tank body, the premixing assembly is fixed on the top of the stirring shaft, a mixing blade is arranged at the bottom of the stirring shaft, and a mixing motor for driving the stirring shaft is arranged at the top of the premixing tank body.

[0014] As a preferred technical solution of the present invention, the magnetic adsorption processing mechanism includes a processing cylinder connected to the plastic raw material channel, the top of the processing cylinder is detachably provided with an end cover by bolts, the inner wall of the processing cylinder is fitted with an adsorption cylinder with open ends and magnetic properties, and at least one positioning guide block is equidistantly arranged on the outer wall of the top of the adsorption cylinder in the circumferential direction, and the positioning guide block is matched and placed in a positioning guide groove opened on the edge of the top of the processing cylinder.

[0015] As a preferred technical solution of the present invention, a fixed base is fixedly provided at the bottom of the treatment cylinder, and a clamping groove for clamping and limiting the bottom of the adsorption cylinder is formed between the outer wall of the fixed base and the inner wall of the treatment cylinder;

[0016] At least three lifting springs are arranged on the fixed base at the bottom of the adsorption cylinder, and the lifting springs are fixedly arranged in spring grooves opened on the fixed base.

[0017] As a preferred technical solution of the present invention, both ends of the fixed base are open, and the inner wall of the fixed base is arranged to slope downward.

[0018] As a preferred technical solution of the present invention, a plurality of magnetic rods are staggered at different levels inside the adsorption cylinder, one end of the magnetic rod is provided with a connecting rod rotatably arranged through a connecting shaft, and one end of the connecting rod is passed through the through holes opened on the adsorption cylinder and the treatment cylinder in turn and a shifting block is fixed thereon.

[0019] As a preferred technical solution of the present invention, the outer wall of the adsorption cylinder is located on the external thread connection limit holder of the connecting rod, and the limit holder is provided with a circular hole corresponding to the perforation for the connecting rod and the magnetic rod to pass through;

[0020] A limiting clamping column is fixedly arranged at one end of the connecting rod close to the shifting block, and a limiting clamping groove which is matched with the limiting clamping column and is in an inverted L shape is opened on the limiting clamping seat.

[0021] As a preferred technical solution of the present invention, the premixing assembly includes a conical rotating table, and a plurality of magnetic protrusions are arranged on the outer wall of the rotating table at equal intervals along the circumferential direction. The magnetic protrusions are inverted T-shaped and are matched and limited in T-slots provided on the rotating table. A sliding slope is formed between the top of the rotating table and two adjacent magnetic protrusions.

[0022] As a preferred technical solution of the present invention, the bottom of the T-slot is communicated with the side wall of the rotating table, and the bottom of the rotating table is threadedly connected with a threaded cylinder for limiting the magnetic protrusion in the T-slot.

[0023] As a preferred technical solution of the present invention, the top and bottom of the rotating table are both provided with threaded sleeves for fixing the position of the rotating table, and the threaded sleeves are threadedly connected to the stirring shaft.

[0024] As a preferred technical solution of the present invention, the bottom of the additive channel is arranged to be inclined downward and toward the plastic raw material channel.

[0025] The beneficial effects of the present invention are:

[0026] 1. The preparation method of the modified plastic can adsorb iron filings in the plastic raw material through the adsorption cylinder and the staggered magnetic rods, thereby reducing the content of metal impurities in the plastic raw material, and the magnetic rods are rotatably connected to the connecting rods through the connecting shaft. When the magnetic rods are impacted by the falling plastic raw material in the treatment cylinder, they will rotate, so that the iron filings in the plastic raw material can be adsorbed on the outer surface of the magnetic rod, and will not be simply adsorbed on the upper outer surface, which can increase the adsorption area of ​​the magnetic rod.

[0027] 2. The preparation method of this modified plastic is as follows: when it is necessary to process the metal iron filings adsorbed on the surface of the magnetic suction rod, the shift block can be rotated to remove the limit of the limit slot on the limit column, and then the shift block is pulled to pull the magnetic suction rod out of the processing tube. In the process of moving the magnetic suction rod out of the processing tube, the iron filings adsorbed on the outer surface of the magnetic suction rod will be scraped off by the adsorption tube and the perforation and adsorbed on the adsorption tube. After all the magnetic suction rods are removed from the processing tube, the adsorbed and processed iron filings will all be concentrated on the inner wall of the adsorption tube. Finally, the end cover is opened, and the adsorption tube is pushed upward by the elastic action of the lifting spring. Then the adsorption tube is taken out to process the iron filings adsorbed on the inner wall.

[0028] 3. The preparation method of the modified plastic can mix the plastic raw materials falling along the plastic raw material channel and the additives falling in the additive channel through the cooperation of the rotating boss and the magnetic boss when the two rotate. Since the plastic raw materials and multiple additives are added simultaneously through the plastic raw material channel and the additive channel respectively, after contacting and colliding with the magnetic boss and mixing, they will slide along the sliding slope on the rotating boss to the bottom of the premixing tank, and then be further stirred and mixed by the mixing blade, which can improve the mixing effect between the additives and the plastic raw materials, and thus improve the quality of the modified plastic.

[0029] 4. The preparation method of this modified plastic, by setting the magnetic boss with magnetism, can further adsorb the iron filings remaining in the plastic raw material while premixing the plastic raw material and the additive, thereby reducing the impact of the high content of metal impurities in the plastic raw material on the quality of the modified plastic.

[0030] 5. The preparation method of this modified plastic can achieve that the additives are offset from the plastic raw material when being discharged from the outlet by directing the bottom outlet of the additive channel toward the plastic raw material channel, thereby improving the mixing effect between the plastic raw material and the additives.

[0031] 6. The preparation method of the modified plastic facilitates the connection of the magnetic protrusion with the rotating table through the setting of the T-slot, and then the threaded barrel is threadedly fixed to the rotating table, so that multiple magnetic protrusions can be limited in the T-slot at the same time without fixing them one by one. When the magnetic protrusion needs to be disassembled, it is only necessary to separate the threaded barrel from the rotating table and then slide the magnetic protrusion out of the T-slot. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 is a front perspective view of the present invention;

[0034] Figure 2 It is a schematic diagram of the internal structure of the premix tank of the present invention;

[0035] Figure 3 It is a schematic diagram of the external structure of the treatment tube of the present invention;

[0036] Figure 4 It is a schematic diagram of the internal structure of the treatment cylinder of the present invention;

[0037] Figure 5 It is a schematic diagram of the connection structure between the fixed base and the processing cylinder of the present invention;

[0038] Figure 6 The present invention Figure 5 A local enlarged view of point A;

[0039] Figure 7 It is a schematic diagram of the position structure of the adsorption cylinder and the fixed base of the present invention;

[0040] Figure 8 It is a schematic diagram of the structure when the limit clamping column of the present invention is clamped in the limit clamping groove;

[0041] Fig. 9 It is a schematic structural diagram of the limiting clamping column of the present invention when it is moved out of the limiting clamping slot;

[0042] Fig.10 It is a schematic diagram of the position structure of the rotating table of the present invention inside the premixing tank;

[0043] Fig.11 It is a schematic diagram of the structure of the premixing component of the present invention;

[0044] Fig.12 It is a schematic structural diagram of the threaded barrel and the rotating table when they are separated.

[0045] In the figure: 10, premixing tank; 11, plastic raw material channel; 12, additive channel; 13, stirring shaft; 14, mixing blade; 15, mixing motor; 20, magnetic adsorption processing mechanism; 21, processing cylinder; 22, end cover; 23, adsorption cylinder; 24, positioning guide block; 25, positioning guide groove; 26, fixed base; 27, clamping groove; 28, lifting spring; 29, spring groove; 210, magnetic attraction rod; 211, connecting shaft; 212, connecting rod; 213, perforation; 214, shifting block; 215, limit card seat; 216, limit card column; 217, limit card groove; 30, premixing component; 31, rotating table; 32, magnetic protrusion; 33, T-slot; 34, threaded cylinder; 35, threaded sleeve; 36, sliding slope. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0047] Example: Figure 1-Figure 12 As shown, a method for preparing a modified plastic of the present invention comprises the following steps:

[0048] S1 Raw material preparation: select 30-40 parts of polypropylene, 25-35 parts of polyethylene, 20-30 parts of polystyrene, 3-5 parts of reinforcing agent, 2-4 parts of flame retardant, and 3-6 parts of antistatic agent in parts by weight;

[0049] S2 premixing: adding the plastic raw material and the additive into the mixer according to the above ratio for premixing, so that the additive is evenly dispersed in the plastic raw material;

[0050] S3 melt blending: add the premixed materials into a twin-screw extruder for melt blending. In the extruder, the materials are subjected to high temperature and shear force, so that the additives and plastic raw materials are fully mixed and chemically react to form modified plastics;

[0051] S4 extrusion granulation: the melt blended material is extruded through an extruder to form a plastic strip, and then the plastic strip is cut into particles of 3-5 mm in length by a pelletizer to obtain modified plastic particles;

[0052] S5 post-processing: drying and packaging the modified plastic particles, removing moisture from the particles, and improving the quality and stability of the particles;

[0053] The premixing device used in the above preparation method includes a premixing tank 10, a plastic raw material channel 11 is provided on one side of the top of the premixing tank 10, at least one additive channel 12 is provided on both sides of the plastic raw material channel 11, and a magnetic adsorption processing mechanism 20 for removing metal impurities in the plastic raw material is provided on the top of the plastic raw material channel 11;

[0054] A premixing assembly 30 for premixing the plastic raw material and the additive is provided at the bottom of the plastic raw material channel 11 and the additive channel 12 in the premixing tank 10. The premixing assembly 30 is fixed to the top of the stirring shaft 13. A mixing blade 14 is provided at the bottom of the stirring shaft 13. A mixing motor 15 for driving the stirring shaft 13 is provided at the top of the premixing tank 10.

[0055] Among them, Figure 3-Figure 9 As shown, the magnetic adsorption processing mechanism 20 includes a processing cylinder 21 which is connected to the plastic raw material channel 11. The top of the processing cylinder 21 is detachably provided with an end cover 22 by bolts. The inner wall of the processing cylinder 21 is fitted with an adsorption cylinder 23 which is open at both ends and has magnetic properties. On the outer wall of the top of the adsorption cylinder 23, at least one positioning guide block 24 is equidistantly arranged in the circumferential direction. The positioning guide block 24 is matched and placed in a positioning guide groove 25 opened on the edge of the top of the processing cylinder 21.

[0056] It should be noted that, through the setting of the adsorption cylinder 23, some iron filings present in the plastic raw materials passing through the inside of the processing cylinder 21 can be adsorbed, thereby reducing the content of metal impurities in the plastic raw materials, and through the setting of the positioning guide block 24 and the positioning guide groove 25, the position of the adsorption cylinder 23 placed in the processing cylinder 21 can be positioned.

[0057] Among them, Figure 5 and Figure 6As shown, a fixed base 26 is fixedly provided at the bottom position in the processing cylinder 21, and a snap-in groove 27 for snapping and limiting the bottom of the adsorption cylinder 23 is formed between the outer wall of the fixed base 26 and the inner wall of the processing cylinder 21; at least three lifting springs 28 are provided on the fixed base 26 at the bottom of the adsorption cylinder 23, and the lifting springs 28 are fixedly provided in spring grooves 29 opened on the fixed base 26.

[0058] Furthermore, the adsorption cylinder 23 is positioned in the processing cylinder 21 by cooperating with the positioning guide block 24 and the positioning guide groove 25. At this time, the bottom of the adsorption cylinder 23 will be limited in the clamping groove 27, and the bottom of the adsorption cylinder 23 will contact the top of the lifting spring 28. When the end cover 22 and the processing cylinder 21 are fixed by bolts, the bottom surface of the end cover 22 will give the adsorption cylinder 23 a downward squeezing effect. The downward movement of the adsorption cylinder 23 will push the lifting spring 28 to shrink and be in a compressed state.

[0059] In detail, when the adsorption cylinder 23 needs to be taken out from the processing cylinder 21, the end cover 22 can be removed. After the end cover 22 is removed, the force on the adsorption cylinder 23 will be removed. At this time, through the elastic action of the lifting spring 28, the top of the adsorption cylinder 23 can be pushed out from the processing cylinder 21, making it convenient to take the adsorption cylinder 23 out of the processing cylinder 21.

[0060] Among them, Figure 5 As shown, both ends of the fixed base 26 are open, and the inner wall of the fixed base 26 is inclined downward.

[0061] Specifically, by setting the fixed base 26, it can cooperate with the inner wall of the processing cylinder 21 to limit the bottom of the adsorption cylinder 23 in the clamping groove 27, and by setting the inner wall of the fixed base 26 to be a downward slope, it is convenient to drop the plastic raw materials in the processing cylinder 21.

[0062] Among them, Figure 4 , Figure 7-Figure 9 As shown, the interior of the adsorption cylinder 23 is provided with a plurality of magnetic rods 210 which are staggered at different levels, one end of the magnetic rod 210 is rotatably provided with a connecting rod 212 through a connecting shaft 211, one end of the connecting rod 212 passes through the through holes 213 provided on the adsorption cylinder 23 and the processing cylinder 21 in turn, and is fixed with a shift block 214; the outer wall of the adsorption cylinder 23 is located at an external threaded connection limit holder 215 of the connecting rod 212, and a circular hole for the connecting rod 212 and the magnetic rod 210 to pass through is provided on the limit holder 215 corresponding to the through hole 213; a limit column 216 is fixedly provided on one end of the connecting rod 212 close to the shift block 214, and a limit slot 217 which is adapted to the limit column 216 and is in an inverted L shape is provided on the limit holder 215.

[0063] In detail, the limiting card seat 215 is firstly threadedly connected with the processing cylinder 21, and then one end of the magnetic suction rod 210 is passed through the through holes 213 on the processing cylinder 21 and the adsorption cylinder 23 along the circular hole in turn, and the magnetic suction rod 210 is inserted into the interior of the processing cylinder 21, and the limiting card column 216 is followed to enter the limiting card slot 217, and then the dial block 214 is driven to drive the connecting rod 212 to rotate, and the rotation of the connecting rod 212 will drive the limiting card column 216 to rotate together, so that the limiting card column 216 is limited and fixed in the limiting card slot 217, and then the magnetic suction rod 210 can be limited in the processing cylinder 21;

[0064] Furthermore, the magnetic rod 210 is rotatably connected to the connecting rod 212 through the connecting shaft 211. When the magnetic rod 210 is impacted by the falling plastic material in the processing cylinder 21, it will rotate, so that the iron filings in the plastic material can be adsorbed on the outer surface of the magnetic rod 210, and will not be simply adsorbed on the outer surface at the top, which can increase the adsorption area of ​​the magnetic rod 210.

[0065] It should also be noted that the aperture of the perforation 213 is compatible with the diameter of the magnetic rod 210. When it is necessary to process the metal iron filings adsorbed on the surface of the magnetic rod 210, the shift block 214 can be rotated to remove the limit of the limit slot 217 on the limit column 216, and then the shift block 214 can be pulled to pull the magnetic rod 210 out of the processing tube 21. In the process of moving the magnetic rod 210 out of the processing tube 21, the iron filings adsorbed on the outer surface of the magnetic rod 210 will be scraped off and adsorbed on the adsorption tube 23 and the perforation 213. After all the magnetic rods 210 are removed from the processing tube 21, the adsorbed and processed iron filings will all be concentrated on the inner wall of the adsorption tube 23. Finally, the end cover 22 is opened, and the adsorption tube 23 is pushed upward by the elastic action of the lifting spring 28. Then the adsorption tube 23 is taken out to process the iron filings adsorbed on the inner wall.

[0066] Among them, Figure 10-12 As shown, the premixing assembly 30 includes a conical rotating table 31, and a plurality of magnetic protrusions 32 are arranged on the outer wall of the rotating table 31 at equal intervals along the circumferential direction. The magnetic protrusions 32 are inverted T-shaped and are matched and limited in T-slots 33 provided on the rotating table 31. A sliding slope 36 is formed between the top of the rotating table 31 and two adjacent magnetic protrusions 32.

[0067] It should be noted that, through the cooperation between the rotating table 31 and the magnetic protrusion 32, when the two rotate, the plastic raw material falling along the plastic raw material channel 11 and the additive falling in the additive channel 12 can be mixed. Since the plastic raw material and multiple additives are added simultaneously through the plastic raw material channel 11 and the additive channel 12 respectively, after contacting and colliding with the magnetic protrusion 32 and mixing, they will slide along the sliding slope 36 on the rotating table 31 to the bottom of the premixing tank 10, and then further stirred and mixed by the mixing blade 14, which can improve the mixing effect between the additive and the plastic raw material, and thus improve the quality of the modified plastic.

[0068] Furthermore, by providing the magnetic protrusion 32 with magnetism, the iron filings remaining in the plastic raw material can be further adsorbed while the plastic raw material and the additive are premixed, thereby reducing the impact of the high content of metal impurities in the plastic raw material on the quality of the modified plastic.

[0069] Among them, Fig.12 As shown, the bottom of the T-slot 33 is connected to the side wall of the rotating table 31, and the bottom of the rotating table 31 is threadedly connected with a threaded cylinder 34 for limiting the magnetic protrusion 32 in the T-slot 33, and the top and bottom of the rotating table 31 are provided with a threaded sleeve 35 for fixing the position of the rotating table 31, and the threaded sleeve 35 is threadedly connected to the stirring shaft 13.

[0070] Specifically, through the setting of the T-slot 33, it is convenient to connect the magnetic protrusion 32 to the rotating table 31, and then screw it to the rotating table 31 through the threaded tube 34, so that multiple magnetic protrusions 32 can be limited in the T-slot 33 at the same time, without the need to fix them one by one, and when the magnetic protrusion 32 needs to be disassembled, it is only necessary to separate the threaded tube 34 from the rotating table 31, and then slide the magnetic protrusion 32 out of the T-slot 33.

[0071] It should also be noted that, by providing two threaded sleeves 35 and threadedly connecting with the stirring shaft 13 , the rotating table 31 can be fixed on the stirring shaft 13 , and the disassembly of the rotating table 31 is also convenient.

[0072] Among them, Figure 2 As shown, the bottom of the additive channel 12 is tilted downward and toward the plastic raw material channel 11. By directing the bottom outlet of the additive channel 12 toward the plastic raw material channel 11, the additive can be offset against the plastic raw material when discharged from the outlet, thereby improving the mixing effect between the plastic raw material and the additive.

[0073] Working principle:

[0074] The plastic raw material and the additive are added into the premixing tank 10 along the processing cylinder 21 and the additive channel 12 respectively. After entering the processing cylinder 21, the plastic raw material will be disturbed and contacted by the magnetic suction rods 210 staggered inside and then fall downward. The iron filings inside the plastic raw material will be adsorbed and filtered out after contacting the magnetic suction rods 210 and the adsorption cylinder 23. The filtered plastic raw material will continue to fall into the premixing tank 10 along the plastic raw material channel 11;

[0075] When the additives falling through the additive channel 12 enter the premixing tank 10, they will collide with the additives falling along the plastic raw material channel 11 and fall onto the rotating table 31. The mixing motor 15 will drive the stirring shaft 13, the rotating table 31 and the mixing blade 14 to rotate. The plastic raw material and the additives can be mixed by the rotating cooperation between the rotating table 31 and the magnetic protrusion 32. The mixed plastic raw material and the additives will fall to the bottom along the gap between the rotating table 31 and the inner wall of the premixing tank 10, and continue to mix under the stirring of the mixing blade 14, which can improve the mixing effect between the plastic raw material and the additives.

[0076] When it is necessary to process the metal iron filings adsorbed on the surface of the magnetic rod 210, the shift block 214 can be rotated to remove the limit of the limit slot 217 on the limit column 216, and then the shift block 214 can be pulled to pull the magnetic rod 210 out of the processing tube 21. In the process of moving the magnetic rod 210 out of the processing tube 21, the iron filings adsorbed on the outer surface of the magnetic rod 210 will be scraped off and adsorbed on the adsorption tube 23 and the perforation 213. After all the magnetic rods 210 are removed from the processing tube 21, all the adsorbed and processed iron filings will be concentrated on the inner wall of the adsorption tube 23. Finally, the end cover 22 is opened, and the adsorption tube 23 is pushed upward by the elastic action of the lifting spring 28. Then the adsorption tube 23 is taken out to process the iron filings adsorbed on the inner wall.

[0077] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified plastic, characterized in that: The following steps are involved: S1 Raw material preparation: select 30-40 parts of polypropylene, 25-35 parts of polyethylene, 20-30 parts of polystyrene, 3-5 parts of reinforcing agent, 2-4 parts of flame retardant, and 3-6 parts of antistatic agent by weight; S2 premixing: adding the plastic raw materials and additives into the mixer according to the above ratio for premixing, so that the additives are evenly dispersed in the plastic raw materials; S3 melt blending: add the premixed materials into a twin-screw extruder for melt blending. In the extruder, the materials are subjected to high temperature and shear force, so that the additives and plastic raw materials are fully mixed and chemically react to form modified plastics; S4 extrusion granulation: the melt blended material is extruded through an extruder to form a plastic strip, and then the plastic strip is cut into particles of 3-5 mm in length by a pelletizer to obtain modified plastic particles; S5 post-processing: drying and packaging the modified plastic particles, removing moisture from the particles, and improving the quality and stability of the particles; The premixing device used in the preparation method comprises a premixing tank (10), a plastic raw material channel (11) is provided on one side of the top of the premixing tank (10), at least one additive channel (12) is provided on both sides of the plastic raw material channel (11), and a magnetic adsorption processing mechanism (20) for removing metal impurities in the plastic raw material is provided at the top of the plastic raw material channel (11); A premixing assembly (30) for premixing the plastic raw material and the additive is arranged at the bottom of the plastic raw material channel (11) and the additive channel (12) in the premixing tank (10), the premixing assembly (30) is fixed on the top of a stirring shaft (13), a mixing blade (14) is arranged at the bottom of the stirring shaft (13), and a mixing motor (15) for driving the stirring shaft (13) is arranged at the top of the premixing tank (10).

2. The method for preparing a modified plastic according to claim 1, characterized in that: The magnetic adsorption processing mechanism (20) comprises a processing cylinder (21) connected to the plastic raw material channel (11), the top of the processing cylinder (21) is detachably provided with an end cover (22) by means of bolts, the inner wall of the processing cylinder (21) is fitted with an adsorption cylinder (23) with open ends and possessing magnetic properties, at least one positioning guide block (24) is equidistantly provided on the outer wall of the top of the adsorption cylinder (23) along the circumferential direction, and the positioning guide block (24) is matched and placed in a positioning guide groove (25) provided on the edge of the top of the processing cylinder (21).

3. The method for preparing a modified plastic according to claim 2, characterized in that: A fixed base (26) is fixedly arranged at the bottom of the treatment cylinder (21), and a clamping groove (27) for clamping and limiting the bottom of the adsorption cylinder (23) is formed between the outer wall of the fixed base (26) and the inner wall of the treatment cylinder (21); At least three lifting springs (28) are arranged on the fixed base (26) at the bottom of the adsorption cylinder (23), and the lifting springs (28) are fixedly arranged in spring grooves (29) provided on the fixed base (26).

4. The method for preparing a modified plastic according to claim 3, characterized in that: Both ends of the fixed base (26) are open, and the inner wall of the fixed base (26) is arranged in a sloped manner and tilted downward.

5. The method for preparing a modified plastic according to claim 2, characterized in that: A plurality of magnetic rods (210) are arranged in an interlaced manner at different levels inside the adsorption cylinder (23); one end of the magnetic rod (210) is rotatably provided with a connecting rod (212) via a connecting shaft (211); one end of the connecting rod (212) passes through through holes (213) provided on the adsorption cylinder (23) and the processing cylinder (21) in sequence and is fixedly provided with a shifting block (214).

6. The method for preparing a modified plastic according to claim 5, characterized in that: The outer wall of the adsorption cylinder (23) is located on the outer thread connection of the connecting rod (212) and is provided with a limit clamping seat (215), and a circular hole for the connecting rod (212) and the magnetic attraction rod (210) to pass through is provided on the limit clamping seat (215) corresponding to the through hole (213); A limiting clamping column (216) is fixedly provided at one end of the connecting rod (212) close to the shifting block (214), and a limiting clamping groove (217) in an inverted L shape and matching with the limiting clamping column (216) is provided on the limiting clamping seat (215).

7. The method for preparing a modified plastic according to claim 1, characterized in that: The premixing assembly (30) comprises a conical rotating table (31), the outer wall of the rotating table (31) is provided with a plurality of magnetic protrusions (32) equidistantly arranged along the circumferential direction, the magnetic protrusions (32) are in an inverted T-shape and are matched and limited in a T-slot (33) provided on the rotating table (31), and a sliding slope (36) is formed between the top end of the rotating table (31) and two adjacent magnetic protrusions (32).

8. The method for preparing a modified plastic according to claim 7, characterized in that: The bottom of the T-shaped slot (33) is in communication with the side wall of the rotating platform (31), and the bottom of the rotating platform (31) is threadedly connected with a threaded cylinder (34) for limiting the position of the magnetic protrusion (32) in the T-shaped slot (33).

9. The method for preparing a modified plastic according to claim 7, characterized in that: The top and bottom of the rotating table (31) are both provided with threaded sleeves (35) for fixing the position of the rotating table (31), and the threaded sleeves (35) are threadedly connected to the stirring shaft (13).

10. The method for preparing a modified plastic according to claim 1, characterized in that: The bottom of the additive channel (12) is arranged to be inclined downward and toward the plastic raw material channel (11).

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