CN113878742A

CN113878742A - Processing technology of PE modified plastic particles

Info

Publication number: CN113878742A
Application number: CN202111082604.1A
Authority: CN
Inventors: 朱楠楠; 朱峰
Original assignee: Jieshou Tongda Plastic Industry Co ltd
Current assignee: Jieshou Tongda Plastic Industry Co ltd
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2022-01-04

Abstract

The invention discloses a processing technology of PE modified plastic particles, which comprises the steps of cleaning and sorting raw materials, removing dyed or polluted raw materials, cutting, stacking and finishing the cleaned and sorted raw materials through a material sorting mechanism, sending the finished raw materials into a screw extruder in batches and equivalently through a quantitative feeding mechanism for smelting and extruding, cooling and shaping the extruded plastic through a cooling mechanism, and crushing to obtain plastic particles; the guide conveying unit is used for automatically conveying the raw materials, and the rolling parts, the cutting parts and the cutting parts which are arranged on the conveying path are used for arranging and cutting the raw materials, so that the raw materials are formed into blocks with consistent sizes and shapes, and the subsequent conveying and smelting operations are facilitated; weigh raw materials weight through weighing the unit, then will satisfy the raw materials of weight demand and send into screw extruder for screw extruder's feed speed is more even stable, makes the plastics steady quality who extrudes.

Description

Processing technology of PE modified plastic particles

Technical Field

The invention relates to the field of plastic particle processing, in particular to a processing technology of PE modified plastic particles.

Background

Polyethylene is a thermoplastic resin obtained by polymerizing ethylene. The polyethylene is odorless, nontoxic, has wax-like hand feeling, excellent low-temperature resistance and good chemical stability, and can resist corrosion of most of acid and alkali. Is insoluble in common solvents at room temperature, has low water absorption and excellent electrical insulation. The use of polyethylene packaging materials in large quantities generates a large amount of non-degradable waste.

In PE plastic particle production enterprises, waste polyethylene films or packaging materials are recycled, and PE plastic particles are produced and processed again, so that the PE plastic is recycled.

The existing plastic particle processing technology is lack of effective sorting and finishing on raw materials for producing PE plastic particles, so that the quality of the raw materials is unstable, and the quality of the processed plastic particles is influenced; in the existing plastic particle processing process, the particle diameter is often directly determined by the output end of the screw extruder and cannot be flexibly adjusted.

Disclosure of Invention

The invention aims to provide a processing technology of PE modified plastic particles, which aims to solve the problems in the background technology:

(1) the existing processing technology of PE modified plastic particles lacks effective sorting and finishing on raw materials for producing PE plastic particles, so that the quality of the raw materials is unstable, and the quality of the processed plastic particles is influenced;

(2) the existing plastic particle processing technology generally adopts a manual feeding mode, so that the feeding speed of a screw extruder is unstable, the extrusion amount of plastic is not uniform, and the shape of the extruded plastic and the uniformity of the obtained plastic particles are further influenced;

(3) in the existing plastic particle processing process, the diameter of finished plastic particles is often directly determined by the output end of a screw extruder and cannot be flexibly adjusted.

In order to achieve the purpose, the invention provides the following technical scheme:

a processing technology of PE modified plastic particles comprises the following steps:

step S1: cleaning and sorting the raw materials to remove the dyed or polluted raw materials;

step S2: cutting, stacking and finishing the cleaned and sorted raw materials through a material arranging mechanism;

step S3: sending the raw materials after finishing into a screw extruder in batches and in equal quantity through a quantitative feeding mechanism for smelting and extruding;

step S4: and cooling and shaping the extruded plastic by a cooling mechanism, and crushing to obtain plastic particles.

As a further scheme of the invention: the working method of the monolith mechanism comprises the following steps:

step A1: the raw materials are fed through the guide unit and rolled through the rolling piece, so that the thicknesses of the raw materials are consistent;

step A2: cutting the edges of the two sides of the raw material through a cutting piece to enable the raw material to be formed into a strip shape with the same width, and putting the cut leftover materials back to the guide piece;

step A3: the raw materials are cut into blocks through the cutting parts, and the block raw materials are stacked and collected through the bearing unit.

As a further scheme of the invention: the cutting device comprises a middle guide and conveying unit, wherein the guide and conveying unit comprises a middle guide and conveying part, the cutting part comprises cutting knives symmetrically arranged on two sides of the middle guide and conveying part, the middle guide and conveying part comprises a middle guide and conveying frame, the inner wall of the middle guide and conveying frame is rotatably connected with a plurality of middle guide and conveying rollers, two sides of the middle guide and conveying frame are fixedly connected with side guide and conveying frames, the inner walls of the two side guide and conveying frames are rotatably connected with side guide and conveying rollers, a gap part is reserved between the two side guide and conveying frames and the middle guide and conveying frame, a cutting motor is fixedly arranged in the gap part, and the output end of the cutting motor is fixedly connected with the cutting knives;

the rolling part comprises a rolling support frame, a rolling motor is fixedly mounted on one side of the rolling support frame, a pressing roller is fixedly mounted at the output end of the rolling motor and arranged right above the middle guide part, the distance between the pressing rollers is smaller than the distance between the two cutting knives, and the height of the top surfaces of the cutting knives is slightly higher than that of the bottom surfaces of the pressing rollers; one side of the inner wall of the rolling support frame is fixedly connected with a scraping plate, and one side of the scraping plate is arranged to be an arc-shaped surface and is attached to one side of the pressing rotary roller;

one end of each of the two side edge guiding frames is fixedly connected with an edge guiding frame, one end of each edge guiding frame is arranged in a downward inclined mode, and a guiding conveying belt is fixedly installed on the inner wall of each edge guiding frame;

the cutting part comprises a cutting cover box, a cutting cylinder is fixedly mounted on one side of the inner wall of the cutting cover box, a cutting knife is fixedly connected to the output end of the cutting cylinder, a detection cylinder is fixedly mounted on the other side of the inner wall of the cutting cover box, a fixed-length detection plate is fixedly connected to the output end of the detection cylinder, and a pressure sensor is embedded on one side, close to the cutting cylinder, of the fixed-length detection plate.

As a further scheme of the invention: the end part of the middle guide piece is provided with a discharge opening, and a plurality of material receiving pieces are arranged in order on the blocky raw materials continuously through the bottom of the discharge opening.

The one end fixedly connected with spacing frame of middle part guide frame, the discharge opening has been seted up to spacing frame's inner wall, the bearing unit includes the bearing guide plate, the guide slide rail has been seted up at the top of bearing guide plate, the inner wall sliding connection of guide slide rail has a plurality of to connect the material piece, connect the material piece to include material receiving box. The size of the inner wall of the material receiving box is consistent with that of the discharge opening.

As a further scheme of the invention: the working mode of the quantitative delivery mechanism is as follows: firstly, the delivery of raw materials is guided and limited by the delivery guide piece, then the raw materials are lifted and transferred to the weighing unit, the weight of the raw materials is weighed by the weighing unit, and then the raw materials meeting the weight requirement are sent to the screw extruder.

The top of the spiral extruder is fixedly provided with a feeding workbench, the delivery guide part comprises a delivery frame which is rotationally connected with one end of the feeding workbench, the bottom of the delivery frame is arranged corresponding to one end of the bearing guide plate, and the width of the inner wall of the delivery frame is slightly larger than that of the material receiving box;

the weighing unit comprises a raw material scale embedded on one side of the top surface of the feeding workbench, the top surface of the raw material scale is flush with the top surface of the feeding workbench, an opening is formed in the other side of the top surface of the feeding workbench, and the bottom of the opening is communicated with a feed inlet of the screw extruder.

As a further scheme of the invention: the working method of the cooling mechanism comprises the following steps:

step B1: cooling the extruded plastic through a cooling pool;

step B2: the extruded plastic is dragged to move by the traction unit, and the diameter of the extruded plastic is adjusted by adjusting the traction speed of the traction unit;

step B3: and (3) crushing the plastic into granules by a crusher to obtain plastic granules.

As a further scheme of the invention: a driving piece for driving cooling water to flow is arranged in the cooling pool, the driving piece comprises a driving water tank, a circulating water pump is fixedly mounted on the inner wall of the driving water tank, and the direction of the output end of the circulating water pump is consistent with the length direction of the cooling pool, so that the flow direction of the cooling water sent out by the circulating water pump is parallel to the conveying direction of extruded plastics;

the bottom fixedly connected with backward flow cooling bath of cooling bath, the water inlet has been seted up to one side bottom that the cooling bath is close to screw extruder, and the delivery port has been seted up to one side bottom of keeping away from screw extruder, the top of delivery port communicates with each other with driving water tank's inside, the middle part fixedly connected with division board of cooling backward flow groove, a plurality of fin of bottom fixedly connected with of division board, the vent has all been seted up to the both sides of cooling backward flow groove, a plurality of one side of vent is adjusted well with one side of a plurality of fin respectively and is set up.

As a further scheme of the invention: the traction unit comprises a plurality of traction rollers, and the diameter of the extruded plastic is adjusted by adjusting the rotating speed of the traction rollers to change the tensile force applied to the plastic;

the traction device comprises a traction mechanism, a traction mechanism and a traction mechanism, wherein the traction mechanism comprises two symmetrically arranged turntables which are fixedly connected through a plurality of connecting columns;

the top fixedly connected with lifting frame of driving water tank, the inner wall of lifting frame rotates and is connected with the lifting and changes the roller, a plurality of spacing groove has been seted up to the outer wall that the roller was changeed in the lifting, the clothing fixed mounting of lifting frame has the breaker, the stock guide that one side fixedly connected with slope of cooling bath set up.

Compared with the prior art, the invention has the beneficial effects that: the guide conveying unit is used for automatically conveying the raw materials, and the rolling parts, the cutting parts and the cutting parts which are arranged on the conveying path are used for arranging and cutting the raw materials, so that the raw materials are formed into blocks with consistent sizes and shapes, and the subsequent conveying and smelting operations are facilitated;

the material receiving parts are used for receiving blocky raw materials falling from the discharging opening, the feeding guide parts are used for guiding and limiting the feeding of the raw materials, the raw materials are lifted and transferred to the weighing unit, the weight of the raw materials is weighed through the weighing unit, and then the raw materials meeting the weight requirement are fed into the screw extruder, so that the feeding speed of the screw extruder is more uniform and stable, and the quality of extruded plastics is ensured to be stable;

the plastic is drawn by the rotation of a plurality of traction rollers, and the rotation speed difference is generated between the two traction rollers by adjusting the rotation speed of the two adjacent traction rollers, so that the diameter of the plastic between the two traction rollers is changed by stretching the plastic, the diameter of the plastic particles is adjusted, and the use flexibility is improved;

through setting up circulating water pump, the drive cooling level is on a line in the direction of delivery circulation flow of plastics, and the cooling water is cooled down heat dissipation and backward flow through setting up the cooling reflux groove simultaneously, has improved the cooling effect to extruding plastics.

Drawings

FIG. 1 is a block diagram of a process flow of the present invention;

FIG. 2 is a schematic perspective view of the quantitative delivery mechanism of the present invention;

FIG. 3 is a schematic perspective view of a monolith mechanism according to the present invention;

FIG. 4 is a cross-sectional view of a roll and cut piece of the present invention;

fig. 5 is a cross-sectional view of the cooling mechanism of the present invention.

In the figure: 1. a middle guide frame; 2. a side guide frame; 3. cutting knife; 4. a material pressing roller; 5. rolling the support frame; 6. a scraping plate; 7. a rim charge guide frame; 8. cutting off the cover box; 9. a cutting knife; 10. a fixed-length detection board; 11. a limiting frame; 12. supporting the guide plate; 13. a guide slide rail; 14. a material receiving box; 15. a screw extruder; 16. a feeding workbench; 17. a delivery frame; 18. raw material weighing; 19. a cooling pool; 20. a driving water tank; 21. a water circulating pump; 22. a reflux cooling tank; 23. a partition plate; 24. a heat sink; 25. a vent; 26. a traction roller; 27. a material guide plate; 28. a lifting frame; 29. lifting the roller; 30. a crusher.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-5, in an embodiment of the present invention, a processing method of PE modified plastic particles includes the following steps:

step S3: sending the raw materials after finishing into a screw extruder 15 in batches and in equal quantity through a quantitative feeding mechanism for smelting and extruding;

The raw materials which are mixed in the raw materials and are seriously stained or dyed are removed by cleaning and sorting the raw materials, so that the purity of the materials is improved, and the quality of processed plastic particles is ensured.

The working method of the monolith mechanism comprises the following steps:

The guide and delivery unit comprises a middle guide and delivery part, the cutting part comprises cutting knives 3 symmetrically arranged on two sides of the middle guide and delivery part, the middle guide and delivery part comprises a middle guide and delivery frame 1, the inner wall of the middle guide and delivery frame 1 is rotatably connected with a plurality of middle guide and delivery rollers, two sides of the middle guide and delivery frame 1 are fixedly connected with side guide and delivery frames 2, the inner walls of the two side guide and delivery frames 2 are rotatably connected with side guide and delivery rollers, gap parts are reserved between the two side guide and delivery frames 2 and the middle guide and delivery frame 1, cutting motors are fixedly arranged in the gap parts, and the output ends of the cutting motors are fixedly connected with the cutting knives 3; one end of each of the two side edge guide frames 2 is fixedly connected with an edge guide frame 7, one end of each edge guide frame 7 is arranged in a downward inclined mode, and a guide conveying belt is fixedly installed on the inner wall of each edge guide frame 7; the cutting parts arranged on the two sides of the middle guide part are used for cutting the edges of the two sides of the raw material in the plastic conveying process, so that the raw material is formed into a strip shape with equal width, and the subsequent cutting and dividing operation is facilitated;

the rolling piece comprises a rolling support frame 5, a rolling motor is fixedly mounted on one side of the rolling support frame 5, a pressing roller 4 is fixedly mounted at the output end of the rolling motor, the pressing roller 4 is arranged right above the middle guide piece, the distance between the pressing rollers 4 is smaller than the distance between the two cutting knives 3, and the height of the top surface of each cutting knife 3 is slightly higher than the height of the bottom surface of the corresponding pressing roller 4; one side of the inner wall of the rolling support frame 5 is fixedly connected with a scraping plate 6, one side of the scraping plate 6 is arranged to be an arc-shaped surface and is attached to one side of the pressing rotary roller 4, the rolled plastics are consistent in height through the rolling operation of the pressing rotary roller 4, the subsequent cutting and transportation operation is facilitated, and the stable cutting is ensured by providing a pushing force for the cutting belt; plastics adhered to the surface of the material pressing rotary roller 4 are scraped and separated from the material pressing rotary roller by arranging a scraping plate 6;

cut the piece including cutting cover box 8, cut one side fixed mounting that 8 inner walls of cover box have and cut the cylinder, the output fixedly connected with of cutting the cylinder cuts sword 9, the opposite side fixed mounting that cuts 8 inner walls of cover box has the detection cylinder, the output fixedly connected with constant length detection board 10 that detects the cylinder, constant length detection board 10 inlays near one side of cutting the cylinder and is equipped with pressure sensor, through constant length detection board 10 and pressure sensor, guarantee to cut the plastics length that the groove is interrupted unanimous, make plastics take shape for the even massive of size, conveniently connect material with transportation and subsequent ration and the operation of smelting.

The tip of middle part guide piece is provided with the discharge opening, connects the material piece to put things in good order the arrangement to blocky raw materials through making a plurality of in succession through realizing the bottom of the discharge opening.

One end of the middle guide frame 1 is fixedly connected with a limiting frame 11, a discharge opening is formed in the inner wall of the limiting frame 11, the bearing unit comprises a bearing guide plate 12, a guide sliding rail 13 is formed in the top of the bearing guide plate 12, a plurality of material receiving parts are connected to the inner wall of the guide sliding rail 13 in a sliding mode, and each material receiving part comprises a material receiving box 14; the size of the inner wall of the material receiving box 14 is consistent with the size of the discharge opening, and the material receiving pieces are driven to stably receive plastic raw materials through the material receiving openings by the aid of the bearing guide plate 12 and the guide slide rail 13.

The working mode of the quantitative delivery mechanism is as follows: firstly, the delivery of the raw materials is guided and limited by the delivery guide piece, then the raw materials are lifted and transferred to the weighing unit, the weight of the raw materials is weighed by the weighing unit, and then the raw materials meeting the weight requirement are sent to the screw extruder 15.

A feeding workbench 16 is fixedly arranged at the top of the screw extruder 15, the delivery guide part comprises a delivery frame 17 which is rotatably connected with one end of the feeding workbench 16, the bottom of the delivery frame 17 is arranged corresponding to one end of the bearing guide plate 12, and the width of the inner wall of the delivery frame 17 is slightly larger than that of the material receiving box 14; the receiving box 14 is guided to the feeding workbench 16 by the supporting and guiding plate 12 through the delivery frame 17, so that the feeding operation of the screw extruder 15 is more convenient; a raw material scale 18 is embedded in one side of the top surface of the feeding workbench 16, the top surface of the raw material scale 18 is flush with the top surface of the feeding workbench 16, a through hole is formed in the other side of the top surface of the feeding workbench 16, and the bottom of the through hole is communicated with a feeding hole of the screw extruder 15.

The working method of the cooling mechanism comprises the following steps:

step B1: cooling the extruded plastic by a cooling tank 19;

step B3: the plastic is crushed into granules by the crusher 30 to obtain plastic granules.

A driving piece for driving cooling water to flow is arranged in the cooling pool 19, the driving piece comprises a driving water tank 20, a circulating water pump 21 is fixedly installed on the inner wall of the driving water tank 20, the direction of the output end of the circulating water pump 21 is consistent with the length direction of the cooling pool 19, so that the flow direction of the cooling water sent out by the circulating water pump 21 is parallel to the conveying direction of extruded plastics, and the cooling effect of the extruded plastics is improved by driving the cooling water to flow circularly;

bottom fixedly connected with backward flow cooling bath 22 of cooling bath 19, the water inlet has been seted up to one side bottom that cooling bath 19 is close to screw extruder 15, keep away from one side bottom of screw extruder 15 and seted up the delivery port, the top of delivery port communicates with each other with driving water tank 20's inside, the middle part fixedly connected with division board 23 of cooling backward flow bath, a plurality of fin 24 of the bottom fixedly connected with of division board 23, vent 25 has all been seted up to the both sides of cooling backward flow bath, one side of a plurality of vent 25 is set up well with one side of a plurality of fin 24 respectively, cool down the heat dissipation and the backward flow to the cooling water through setting up the cooling backward flow bath, improve the cooling effect of cooling water.

The traction unit comprises a plurality of traction rollers 26, and the diameter of the extruded plastic is adjusted by adjusting the rotating speed of the traction rollers 26 to change the tensile force applied to the plastic;

the traction device comprises two symmetrically arranged turntables which are fixedly connected through a plurality of connecting columns; through the traction roller 26 of carousel with a plurality of spliced pole structure, when the rotation through a plurality of spliced pole realizes plastics tractive guide, reduce the contact surface of traction roller 26 outer wall and the plastics of not cooling completely, and then reduce plastics and the adhesion of traction roller 26, the rotation through a plurality of traction roller 26 realizes the tractive to plastics, through making two adjacent traction rollers 26's rotational speed, make the traction roller 26 who keeps away from screw extruder 15, its rotational speed is greater than the rotational speed of the traction roller 26 who is close to screw extruder 15 one side, make to produce the difference in rotational speed between the two, make plastics between the two elongated.

The top of the driving water tank 20 is fixedly connected with a lifting frame 28, the inner wall of the lifting frame 28 is rotatably connected with a lifting roller 29, the outer wall of the lifting roller 29 is provided with a plurality of limiting grooves, cooled plastics are fished out of the cooling pool 19 through the lifting roller 29, the fished plastics are limited through the limiting grooves, and the position stability of the plastic in the continuous conveying process is ensured; a crusher 30 is fixedly arranged on the clothes of the lifting frame 28, and a guide plate 27 which is obliquely arranged is fixedly connected to one side of the cooling pool 19.

The working principle of the invention is as follows: firstly, cleaning and sorting raw materials through manual work or external equipment, and removing the raw materials which are mixed in the raw materials and seriously stained or dyed;

the cleaned raw materials are placed on a guide piece, the raw materials are uniformly stacked on the guide piece as much as possible through manual adjustment, a middle guide roller and a side guide roller rotate to drive the raw materials to move, the top of the raw materials is flattened through the rotating rolling of a pressing roller 4 after the raw materials pass through the bottom of the pressing roller 4, a cutting motor is started to drive a cutting knife 3 to rotate to cut the raw materials, the middle of the raw materials form a strip with the same height and the same width, the edge part of the cut raw materials is provided with a guide conveying belt in an edge material guide frame 7 to be sent out, and then the raw materials are manually sent back to the guide piece again;

the rolled strip raw materials are continuously transferred by a middle guide roller, when the raw materials are contacted with a pressure sensor on a fixed-length detection plate 10, the conveying is stopped, a cutoff cylinder drives a cutoff knife 9 to press down, the raw materials are cut, the strip raw materials are changed into blocks, then a detection cylinder drives the fixed-length detection plate 10 to lift up, the middle guide roller is continuously transferred, the block raw materials fall from a discharge opening and fall into a material receiving box 14, when the raw materials contained in the material receiving box 14 reach a preset amount, the material receiving box 14 is pushed to move to the bottom of a delivery frame 17 along a bearing guide plate 12, then the material receiving and delivery frame 17 is transferred to a feeding workbench 16 by a manual external driving device, the raw materials are weighed by a raw material scale 18, and when the original weight meets the requirement, the raw materials are sent to a screw extruder 15 from the feed opening to be smelted and extruded;

the strip-shaped plastic obtained by smelting and extrusion is guided by a plurality of traction rollers 26 to be immersed into cooling water for cooling, then the cooled plastic is fished out from the cooling pool 19 by the lifting rollers 29, and the fished strip-shaped plastic is limited by a limiting groove, so that the position stability of the plastic in the continuous conveying process is ensured; then, crushing the fished strip-shaped plastic by a crusher 30 to obtain plastic particles;

when the cooling device is used, the circulating water pump 21 is started to drive cooling water to circularly flow, so that plastics in the cooling pool 19 are cooled, and the cooling water in the reflux tank is cooled through the ventilation opening 25 and the cooling fins 24, so that the cooling effect of the cooling water is improved.

Although the present invention has been described with reference to the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications, equivalents and alternatives falling within the spirit and scope of the invention.

Claims

1. A processing technology of PE modified plastic particles is characterized by comprising the following steps:

step S3: sending the raw materials after finishing into a screw extruder (15) in batches and in equal quantity through a quantitative feeding mechanism for smelting and extruding;

2. The processing technology of PE modified plastic particles as claimed in claim 1, wherein the working method of the monolith mechanism comprises the following steps:

3. The processing technology of PE modified plastic particles as claimed in claim 2, wherein the guiding and feeding unit comprises a middle guiding and feeding member, the cutting member comprises cutting blades (3) symmetrically arranged at two sides of the middle guiding and feeding member, the rolling member comprises a nip roller (4), the nip roller (4) is arranged right above the middle guiding and feeding member, and the distance between the nip roller (4) is smaller than the distance between the two cutting blades (3).

4. The process for preparing PE modified plastic particles as claimed in claim 3, wherein the middle conveying member has a discharge opening at its end, and the arrangement of the block-shaped raw materials is realized by passing a plurality of receiving members continuously from the bottom of the discharge opening.

5. The processing technology of PE modified plastic particles as claimed in claim 1, wherein the quantitative delivery mechanism works in a manner that: the feeding of the raw materials is guided and limited through the feeding guide piece, then the raw materials are lifted and transferred to the weighing unit, the weight of the raw materials is weighed through the weighing unit, and then the raw materials meeting the weight requirement are fed into the screw extruder (15).

6. The processing technology of PE modified plastic particles as claimed in claim 1, wherein the working method of the cooling mechanism comprises the following steps:

step B1: cooling the extruded plastic by a cooling tank (19);

step B3: the plastic is crushed into granules by a crusher (30) to obtain plastic granules.

7. A processing technology of PE modified plastic particles as claimed in claim 6, wherein a driving member for driving the cooling water to flow is arranged in the cooling tank (19), and the flow direction of the cooling water is parallel to the conveying direction of the extruded plastic.

8. The processing technology of PE modified plastic particles as claimed in claim 6, wherein the drawing unit comprises a plurality of drawing rollers (26), and the diameter of the extruded plastic is adjusted by adjusting the rotating speed of the plurality of drawing rollers (26) to change the drawing force applied to the plastic.