Non-stop screen changing device for fully biodegradable polymers

Abstract

A non-stop screen changing device for fully biodegradable polymers, characterized in that it comprises two groups of upper and lower cylindrical filter units which are installed in parallel in a hollow slideway of a shell in a sliding manner, wherein the cylindrical filter unit is composed of a cylinder and a filter assembly arranged on the cylinder; the filter assembly comprises a filter chamber with an oblate structure, a filter screen installed in the filter chamber and matching the shape of the filter chamber, a split special-shaped porous plate, a rear-net cavity located above the split special-shaped porous plate and a filter chamber outlet connected to a discharge channel, and a front-net cavity located below the filter screen and connected to a feed channel; the feed channel is located on the right side of the front-net cavity, and a material guide groove is provided on the right side of the front-net cavity, and the filter chamber outlet is located on the left side of the rear-net cavity; and a front-net exhaust groove and a rear-net exhaust groove are provided on the cylinder on the left side of the front-net cavity and the filter chamber outlet.

Description

Technical Field

[0001] The invention relates to melt filtration in pelletizing of various fully biodegradable polymer materials after polymerization and filtration of melt in secondary processing of the polymer, in particular to a non-stop screen changing device for fully biodegradable polymers. Background Art

[0002] Screen changers are needed in the pelletizing, downstream modification and product production of various fully biodegradable polymer materials after polymerization. The main purpose is to filter out impurities. Fully biodegradable materials are new materials and new processes that have emerged in recent years to meet environmental protection requirements. The various screen changers or filters currently in use have shortcomings, which are specifically manifested in the following aspects:

[0003] (1) Box filter, with candle wick structure inside, has a large filtration area, which solves the problem of frequent screen change. However, the cavity is too large, and there are many dead corners in the flow channel, which causes serious material stagnation. The characteristics of fully biodegradable polymers are easy to degrade and do not allow melt retention. This filter cannot be changed online without stopping the machine. Stopping the machine to change the filter screen is labor-intensive and causes greater losses.

[0004] (2) Multi-disc filters, although the large filtration area solves the problem of frequent filter changes, there are also problems with the cavity being too large and material stagnation (retention). They are also not suitable for filtering fully biodegradable polymers. If the filter is clogged, the filter cannot be replaced online without stopping the machine. The cost of using the filter and the cost of replacing the filter are both high.

[0005] (3) Ordinary dual-channel slide plate type, dual-channel cylindrical type, and dual-channel drum type screen changers are all circular or cylindrical screens. The circular screen is centrally fed and centrally discharged, while the drum type is side-fed and discharged after two 90-degree turns. In high-volume polymer production, as the diameter of the filter increases, the material flow return ratio is also large, and the edge of the filter is prone to retention (stagnation). Secondly, the structure of the porous plate of this type of screen changer cannot improve the consistency of the material flow rate, so this type of screen changer is not suitable for the filtration of fully biodegradable polymers. In particular, the flow resistance of the dual-channel cylindrical screen changer with side feeding is large and there are many dead corners. Even the smallest size is not suitable for the filtration of fully biodegradable polymers. Summary of the invention

[0006] The purpose of the present invention is to provide a non-stop screen changing device for fully biodegradable polymers with a more reasonable structure in view of the deficiencies existing in the above-mentioned prior art.

[0007] The purpose of the present invention can be achieved by the following technical measures:

[0008] The non-stop screen changing device for fully biodegradable polymers of the present invention comprises a shell having a feed port and a feed channel on one side and a discharge port and a discharge channel on the other side, and two groups of upper and lower cylindrical filter units are parallelly installed in a hollow slideway of the shell in a sliding manner, and the right ends of the upper and lower cylindrical filter units are respectively connected to the piston rods of hydraulic cylinders I and II for driving the cylindrical filter units to reciprocate along the hollow slideway of the device shell through connecting plates; the hydraulic cylinder is connected to the shell through upper, middle and lower double-headed positioning screws arranged at the right end of the shell and a cylinder mounting plate connected to the outer ends of the upper, middle and lower double-headed positioning screws; the cylindrical filter unit is It consists of a cylinder and a filter assembly arranged on the cylinder; the filter assembly includes a filter chamber with an oblate structure, a filter screen installed in the filter chamber and matching the shape of the filter chamber, a split special-shaped porous plate, a post-net cavity (post-filter cavity) located above the split special-shaped porous plate and a filter chamber outlet connected to the discharge channel, and a pre-net cavity (pre-filter cavity) located below the filter screen and connected to the feed channel; the feed channel is located on the right side of the pre-net cavity (close to the hydraulic cylinder side), and a material guide groove is provided on the right side of the pre-net cavity, and the filter chamber outlet is located on the left side of the post-net cavity (away from the hydraulic cylinder side); and a pre-net exhaust groove and a post-net exhaust groove are provided on the cylinder on the left side of the pre-net cavity and the filter chamber outlet.

[0009] The split special-shaped porous plate described in the present invention is made of stainless steel austenite and has an oblate structure; the bottom surface of the porous plate (facing the pre-filter cavity) matched with the filter screen is a flat structure, the top surface of the porous plate facing the outlet of the filter chamber is the thickest, the thickness at the edge is relatively thin, and the overall arc surface has a streamlined structure. The filter holes on the porous plate are composed of a number of small holes with the same cross-sectional area and a height that gradually increases from the edge to the middle.

[0010] In the present invention, the center lines of the feed port and the discharge port on the shell are arranged in a left-right staggered and parallel manner, and are perpendicularly intersected with the long axis of the split-type special-shaped porous plate. The distance between the center line of the feed channel and the center line of the filter chamber outlet is equal to the center distance of the semicircles at both ends of the split-type special-shaped porous plate with an oblate structure.

[0011] The material introduction trough arranged on the right side of the pre-net cavity of the present invention is in the shape of a wedge-shaped structure, located on the cylindrical surface where the pre-net cavity (pre-filter cavity) is located, and is at a 45-degree angle to the center line of the cylinder; the size of the material introduction trough of the wedge-shaped structure is arranged from right to left, from small to large. Heat medium channels are arranged on the inlet and outlet surfaces of the shell.

[0012] The beneficial effects of the present invention are as follows:

[0013] 1. Since the filter unit of the present invention adopts an integral cylindrical structure and a split-type special-shaped porous plate, when the filtration area is equal, the flow channel and cavity of the screen changing device of the present invention are more reasonable than those of the circular porous plate, and the flow rate is adjusted while changing the rheological behavior of the polymer to make it consistent, and stagnation is almost non-existent. The shell structure has better deformation resistance and is very suitable for filtration in the production of fully biodegradable polymer pellets.

[0014] 2. The unique parallel design of the feed channel and the discharge channel (filter chamber outlet) is that the distance between the parallel lines of the two channel centers is equal to the center distance of the semicircles at both ends of the special-shaped porous plate, which is very reasonable, making the polymer flow shortest and the flow return ratio the smallest. The design of this structure also further optimizes the size of the cylindrical filter unit and the shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the main view of the present invention (dual networks work normally).

[0016] Figure 2 yes Figure 1 A partial cross-sectional view of .

[0017] Figure 3 yes Figure 2 A-A section view.

[0018] Figure 4 It is a normal operation of one network, and one network launches the network change status diagram.

[0019] Figure 5 yes Figure 4 sectional view of .

[0020] Figure 6 This is a diagram of one network working normally and one network exhausting status.

[0021] Figure 7 yes Figure 6 A partial cross-sectional view of .

[0022] Figure 8 yes Figure 7 A-A section view.

[0023] Serial numbers in the figure: 1 is the feed port, 2 is the shell, 3 is the upper, middle and lower double-head positioning screws, 4 is the cylindrical filter unit, 5 is the connecting plate, 6 is the hydraulic cylinder I, 6-1 is the hydraulic cylinder II, 7 is the discharge port, 8 is the heat medium channel, 9 is the discharge channel, 10 is the exhaust groove behind the screen, 11 is the filter chamber outlet, 12 is the cavity behind the screen (cavity after filter), 13 is the split special-shaped porous plate, 14 is the filter screen, 15 is the cavity before the screen (cavity before filter), 16 is the exhaust groove before the screen, 17 is the material guide trough, and 18 is the feed channel. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with embodiments (attached drawings):

[0025] like Figure 1 , 2 As shown in Figures 3 and 4, the non-stop screen changing device for fully biodegradable polymers of the present invention comprises a shell 2 with a feed port 1 and a feed channel 18 on one side and a discharge port 7 and a discharge channel 9 on the other side, and two upper and lower groups of cylindrical filter units 4 are parallelly installed in the hollow slideway of the shell in a sliding manner, and the right ends of the upper and lower groups of cylindrical filter units 4 are respectively connected to the piston rods of hydraulic cylinders Ⅰ, Ⅱ6, and 6-1 for driving the cylindrical filter units 4 to reciprocate along the hollow slideway of the device shell through connecting plates 5; the hydraulic cylinders are connected to the shell through upper, middle, and lower double-headed positioning screws 3 arranged at the right end of the shell and cylinder mounting plates connected to the outer ends of the upper, middle, and lower double-headed positioning screws 3; the cylindrical filter units are composed of a cylinder and a device. The filter assembly is arranged on a cylinder; the filter assembly comprises a filter chamber with an oblate structure, a filter screen 14 matched with the shape of the filter chamber installed in the filter chamber, a split special-shaped porous plate 13, a post-net cavity (post-filter cavity) 12 located above the split special-shaped porous plate 13 and a filter chamber outlet 11 connected to a discharge channel 9, and a pre-net cavity (pre-filter cavity) 15 connected to a feed channel 18 located below the filter screen 14; the feed channel 18 is located on the right side of the pre-net cavity 15 (close to the hydraulic cylinder side), and a guide groove 17 is provided on the right side of the pre-net cavity, and the filter chamber outlet 11 is located on the left side of the post-net cavity 12 (away from the hydraulic cylinder side); and a pre-net exhaust groove 16 and a post-net exhaust groove 10 are provided on the cylinder on the left side of the pre-net cavity 15 and the filter chamber outlet 11.

[0026] The split special-shaped porous plate 13 is made of stainless steel austenite and has an oblate structure; the bottom surface of the porous plate (facing the pre-filter cavity) matched with the filter screen 14 is a flat structure, the top surface of the porous plate facing the filter chamber outlet 11 is the thickest, and the thickness at the edge is relatively thin, and its overall arc surface has a streamlined structure, and the filter holes on the porous plate are composed of a plurality of small holes with the same cross-sectional area and a height that gradually increases from the edge to the middle.

[0027] In the present invention, the center lines of the feed port 1 and the discharge port 7 on the shell are arranged in a left-right offset and parallel manner, and perpendicularly intersect with the long axis of the split special-shaped porous plate 13. The distance between the center line of the feed channel 18 and the center line of the filter chamber outlet 11 is equal to the center distance between the two end semicircles of the split special-shaped porous plate 13 with an oblate structure.

[0028] The material introduction trough 17 arranged on the right side of the pre-net cavity is in the shape of a wedge-shaped structure, located on the cylindrical surface where the pre-net cavity (pre-filter cavity) 15 is located, and at a 45-degree angle to the center line of the cylinder; the size of the material introduction trough of the wedge-shaped structure is arranged from right to left, from small to large. Heat medium channels 8 are arranged on the inlet and outlet surfaces of the shell.

[0029] More specifically, the present invention designs the porous plate in the filter chamber into a split type, which not only allows the split porous plate (filter carrier) to be quickly replaced, but also allows the porous plate to be designed and processed into a special shape according to the rheological characteristics of the fully biodegradable polymer. Specifically, the conventional circular shape is designed to be an oblate shape, with the aim of reducing the flow return ratio of the polymer and thereby reducing retention.

[0030] In order to adjust and improve the consistency of the flow rate of the fully biodegradable polymer in the filter chamber, the present invention slows down the flow rate in the fast place and speeds up the stagnant flow place according to the rheological behavior of the polymer. For this reason, the present invention designs a porous plate filter hole with the same cross-sectional area but different lengths. The porous plate is thickened in the middle part of the porous plate, especially in the part facing the feed channel and the discharge channel (that is, the height (length) of the porous plate filter hole gradually increases from the edge to the part facing the feed channel and the discharge channel). The part facing the discharge channel is the thickest, the flow resistance is large, and the polymer flow rate will be slightly slowed down, while the thickness at the edge of the porous plate is relatively thin, and the result is the opposite. The thickness change of the porous plate is strictly designed according to the distribution of the flow rate of the polymer in the pre-filter cavity or the post-filter cavity of the filter chamber. Therefore, the thickness change of the porous plate is also streamlined, but the main function of the porous plate is still the filter screen carrier. Considering the installation and use of the filter screen, the porous plate should be designed to be flat towards the pre-filter cavity or the feed port side.

[0031] The present invention designs the special-shaped porous plate into a split oblate shape, and the material thereof is selected from stainless steel austenite, which has the greatest characteristic of being corrosion-resistant, thereby meeting the corrosion-resistant requirements in the polymerization pelletizing, modification and production of fully biodegradable polymers.

[0032] In the present invention, the center lines of the feed port 1 and the discharge port 7 on the shell are arranged in a left-right offset and parallel manner, and are perpendicularly intersected with the long axis of the split-type special-shaped porous plate 13. The distance between the center line of the feed channel 18 and the center line of the filter chamber outlet 11 is equal to the center distance of the semicircles at both ends of the split-type special-shaped porous plate 13 with an oblate structure. That is, the center line of the feed channel of each cylindrical filter unit and the center line of the filter chamber outlet are respectively extensions of the centers of the semicircles at both ends of the special-shaped porous plate. In this way, the polymer flow at both ends of the oblate circle of the porous plate is consistent, and the flow return ratio is small. At the same time, there is no flow return between the center of the feed channel and the center of the filter chamber outlet of the polymer, and the entire cross-section flows directly without stagnation and retention. According to this rule, in the production of large or extra-large polymers, a special-shaped porous plate of a similar shape can be designed in its screen changing device. The special-shaped porous plate has a large area, the filter screen is also large year-on-year, and the throughput is naturally large. If the traditional screen changing device increases the diameter of the circular porous plate to increase the filtration volume, there will be side effects, because the center lines of the feed port and the discharge port of the traditional screen changing device are extensions of the center of the circular porous plate. The larger the diameter of the circular porous plate, the greater the flow return ratio of the polymer. In addition, the porous plate does not have the function of adjusting the flow rate, so the polymer will stagnate or be retained, which is not allowed for fully biodegradable polymers with poor stability.

[0033] The feed trough 17 arranged on the right side of the pre-net cavity in the present invention is in the shape of a wedge-shaped structure, located on the cylindrical surface where the pre-net cavity (pre-filter cavity) 15 is located, and at a 45-degree angle to the center line of the cylinder; the size of the feed trough of the wedge-shaped structure is set from right to left and from small to large. The feed amount and exhaust time can be adjusted when changing the net and exhausting. At the same time, due to the angle, the feed trough is deeper and wider near the pre-net cavity. When exhausting, the incoming polymer will flow to the bottom of the pre-net cavity at the same time, forcing the air at the corner of the pre-net cavity to be quickly discharged. Since the porous plate of the present invention is a special-shaped oblate circle, the pre-net cavity formed is an "oblong", and the depth is shallower than the pre-net cavity formed by the circular porous plate of the same area, and the corner in the cavity is also shallow. Although the two have equivalent volumes, the pre-net cavity and its corner in the shape of a special-shaped "oblong" are more conducive to exhaust.

[0034] The housing and cylindrical filter unit of the non-stop screen changing device for fully biodegradable polymers of the present invention can be designed to be smaller than those of the non-stop screen changing device for fully biodegradable polymers of the same filtration area. Since the feed port and the discharge port of the device are not on the same center line, the eccentric design makes the screen changing stroke short, that is, the flow channel closing stroke is short when changing the screen, so that the length of the housing can be reduced. Since the special-shaped porous plate is oblate, the increase in length is offset by the shortened screen changing stroke. Moreover, the diameter of the cylindrical carrier where the special-shaped porous plate is located can be designed to be smaller, so overall, the non-stop screen changing device for fully biodegradable polymers of the same filtration area has a smaller external size.

[0035] The purpose of opening the liquid phase heat medium channel of the present invention is as follows: due to the strict temperature requirements of the fully biodegradable polymer, overheating or large temperature fluctuations are strictly prohibited. Therefore, the best solution is to use liquid phase heat medium for heat preservation, and the heat medium channel should be distributed on the inlet and outlet surfaces of the shell. The reasons are as follows: first, the proximity to the feed channel and the discharge channel is conducive to heat transfer, second, the inlet and outlet surfaces of the shell are relatively thick, which is conducive to the opening of the heat medium channel, and third, due to the need to open the feed channel and the discharge channel, the inlet and outlet surfaces of the shell must be thick, and the thickness is conducive to pressure bearing, so that the hollow slideway in the middle of the shell will not be deformed under the pressure of the external force generated by the connecting flange, and the movement of the cylindrical filter unit in the hollow slideway will not be affected. Fourth, the upper and lower surfaces of the shell (the cross-sectional view is left and right) are also the thinnest places of the shell cross-sectional dimensions. It is forbidden to open the heat medium channel, which will directly affect the thermal expansion coefficient of the shell, resulting in the instability of the hollow slideway in the middle of the shell, affecting the movement of the cylindrical filter unit or polymer leakage.

[0036] The shell of the present invention is more pressure-bearing. The melt material filtered by the non-stop screen changing device for fully biodegradable polymers is input and output through high-pressure pipelines, and is connected to the feed port and the discharge port of the shell of the present invention by flanges. The external force generated by the connecting flange presses the shell, which will cause the hollow slide to be deformed by force, thereby affecting the movement of the cylindrical filter unit. In order to enhance the bearing capacity of the plane where the feed port and the discharge port of the shell are located, the wall thickness between the two hollow slides of the shell is designed to be increased. From the cross-section of the shell, the size of this part is larger than the upper and lower surfaces of the shell (the cross-section diagram shows left and right). In this way, the external force generated by the connection between the flange and the feed port and the discharge port of the shell of the present invention is basically borne by the thick wall between the two hollow slides, and the hollow slide is subjected to very little force, which does not affect the movement of the cylindrical filter unit.

[0037] The working principle of the present invention is as follows:

[0038] (1) When the dual-net filtering of this device is normal (see Figure 1 , 2 、3)

[0039] The fully biodegradable polymer melt enters from the feed port of the shell. The plane where the feed port of the shell is located is provided with a double feed channel in an "eight" shape. Under the action of the melt pressure, the material passes through the feed port and enters the respective feed channels to reach the front-net cavity. A "wedge"-shaped feed trough is designed near the oil cylinder end of the front-net cavity, and a front-net exhaust trough is designed near the net-exchange end of the front-net cavity. The position is roughly obliquely symmetrical with the feed trough, and is designed to be tangent to the position of the oblate front-net cavity as shown in the figure.

[0040] The fully biodegradable polymer melt instantly fills the filter chamber after entering the front cavity of the net. It passes through the oblate filter screen and the split special-shaped porous plate, and then enters the back cavity of the net. Since the special-shaped porous plate is streamlined and has different thicknesses, the melt flow rate is forcibly adjusted, so that the melt with a long flow path and a large flow return ratio has a small flow resistance and a fast flow rate. The stagnation caused by the filter chamber cavity and flow channel is minimized.

[0041] After the polymer melt reaches the cavity behind the screen, its rheological behavior is changed again. The front end of the cavity behind the screen is also oblate like the split-type special-shaped porous plate, and its inner cavity shape changes with the streamline of the porous plate, in order to facilitate the rapid flow of the polymer melt and reduce unnecessary cavity space. The cavity behind the screen is a "funnel-shaped" design, which transitions the large area of ​​the split-type special-shaped porous plate into a small-diameter filter chamber outlet, which is equivalent to the feed channel in size. The filtered polymer melt is "concentrated" and flows through the filter chamber outlet to the discharge channel on the shell. Finally, the melt coming out of the discharge channels of the two filter units converges at the shell outlet, thereby completing the filtration of the entire material.

[0042] (2) This device works normally with one net and exhausts and changes the net (see Figures 4 to 8 )

[0043] After a long period of operation, the impurities on the filter surface increase, and the pressure difference before and after the filter increases. The decrease in filtration volume will affect the quality of downstream products. There are also very few impurities that escape under high pressure difference. The most important thing is that the strength of the filter will decrease under high pressure difference, and it is easy to break. In this case, a new filter needs to be replaced:

[0044] Unit I oil cylinder starts to work, the cylindrical filter unit starts to move, the filter chamber is also pushed out of the screen changing position outside the shell, the contaminated filter screen is removed (the split special-shaped porous plate is not removed unless there is a special case) and a new filter screen is installed, and then the cylindrical filter unit moves back to the exhaust position under the action of the oil cylinder. After reaching this position, it stops moving, and the front-net cavity at the entrance of the filter chamber is connected to the feed channel 1 through the "wedge" shaped feed trough. The polymer melt quickly fills the filter chamber, and the feed amount and the exhaust time can be adjusted by moving the position of the cylindrical filter unit. In particular, the 45-degree "wedge" shaped feed trough is more conducive to the polymer melt filling the corner of the front-net cavity. The gas inside the filter chamber is discharged as the polymer melt is filled, the air in the front-net cavity is discharged through the front-net exhaust trough, and the air in the back-net cavity and the filter chamber outlet is discharged through the back-net exhaust trough. When polymer melt comes out of the two exhaust grooves, it proves that the gas inside the filter chamber is completely discharged. The cylinder continues to move back, and the cylindrical filter unit is pulled back to normal working state. The filter screen of a cylindrical filter unit is replaced.

[0045] Repeat the above steps to replace the filter screen in the cylindrical filter unit where the oil cylinder of unit II is located. The two units can be replaced in turn to achieve online filter replacement without stopping the machine.

[0046] (3) The wedge-shaped feed trough has different widths and depths, and the exhaust speed is adjustable. The depth of the feed trough is inclined toward the bottom and corner of the cavity in front of the screen. The exhaust is thorough without dead corners, the time for replacing the filter is short, and there are no bubbles in the polymer melt.

[0047] (4) Dual-channel setting. During normal operation, two units filter at the same time. The filter screen can be replaced online without stopping the machine. When changing the screen, one unit is offline while the other unit works normally. The pressure fluctuation is small, and continuous production can be achieved. There is no loss caused by stopping for changing the screen.

Claims

1. A non-stop screen changing device for fully biodegradable polymers, characterized by: It comprises a shell (2) having a feed port (1) and a feed channel (18) on one side and a discharge port (7) and a discharge channel (9) on the other side, and two upper and lower groups of cylindrical filter units (4) which are installed in parallel in a hollow slideway of the shell in a sliding manner, and the right ends of the upper and lower groups of cylindrical filter units (4) are respectively connected to the piston rods of hydraulic cylinders I and II (6, 6-1) for driving the cylindrical filter units (4) to reciprocate along the hollow slideway of the device shell through a connecting plate (5); the hydraulic cylinders are connected to the upper, middle and lower double-headed positioning screws (3) arranged at the right end of the shell and connected to the upper, middle and lower double-headed positioning screws (5). The cylinder mounting plate at the outer end of the screw rod is connected to the housing; the cylindrical filter unit is composed of a cylinder and a filter assembly arranged on the cylinder; the filter assembly includes a filter chamber with an oblate structure, a filter screen (14) installed in the filter chamber and matching the shape of the filter chamber, a split-type special-shaped porous plate (13), a rear-net cavity (12) located above the split-type special-shaped porous plate and a filter chamber outlet (11) connected to the discharge channel (9), and a front-net cavity (15) located below the filter screen (14) and connected to the feed channel (18); the feed channel (18) is located on the right side of the front-net cavity (15), and a feed guide groove (18) is provided on the right side of the front-net cavity 17), the filter chamber outlet (11) is located on the left side of the rear-net cavity (12); and the front-net exhaust groove (16) and the rear-net exhaust groove (10) are provided on the cylinder on the left side of the front-net cavity (15) and the filter chamber outlet; the split-type special-shaped porous plate (13) is made of stainless steel austenite and has an oblate structure; the bottom surface of the porous plate and the filter screen (14) are in a flat structure, the top surface of the split-type special-shaped porous plate facing the filter chamber outlet (11) is the thickest, and the thickness at the edge is relatively thin, and the overall arc surface is a streamlined structure, and the filter holes on the split-type special-shaped porous plate have the same cross-sectional area and the height gradually increases from the edge to the middle. The feed port (1) and the discharge port (7) on the housing are arranged in a left-right offset and parallel manner, and perpendicularly intersect with the long axis of the split-type special-shaped porous plate (13); the distance between the center line of the feed channel (18) and the center line of the filter chamber outlet (11) is equal to the center distance of the semicircles at both ends of the split-type special-shaped porous plate (13) with an oblate structure; the feed guide trough (17) arranged on the right side of the net front cavity is in the shape of a wedge-shaped structure, located on the surface of the cylinder where the net front cavity (15) is located, and forms an angle of 45 degrees with the center line of the cylinder; the size of the feed guide trough of the wedge-shaped structure is arranged from right to left, from small to large.

2. The non-stop screen changing device for fully biodegradable polymers according to claim 1, characterized in that: Heat medium channels (8) are provided on both the inlet surface and the outlet surface of the shell.

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