DE2910041A1 - Extruder with constant operation ejection zone - has revolving grooved feed regulator at hopper end barrel with speed adjusted relative to screw speed - Google Patents

Abstract

Extruder for plastics has a cylindrical barrel hopper and heaters; its revolving screw has axial zones for loading, consolidating and ejecting, the barrel has an inner grooved sleeve at the loading zone with a hole for the inlet hopper. Sleeve is a revolving feed regulator for the material and has a speed controller which has a number of circumferential holes successively aligning with the hopper inlet. Loading and ejecting zones are sharply delineated, and the ejection zone remains constant in operation.

Description

description

The invention relates to the field of processing plastics, more precisely on screw presses for processing polymeric materials.

The invention can be used in technological production lines of oriented and non-oriented sheet and film materials in production of cinema and photo films, of magnetic tapes for sound and image recording, of Films for the electronics industry and of plastic products made of linear dimensions, for example of pipes and profiles.

Increased demands are placed on the quality of such films: the films must be homogeneous, a high elastic limit in the direction of work, small differences in thickness and high strength, the quality of the manufactured Extrusions depends mainly on the steadiness of the work performance to the technological Production line belonging to screw press and the homogeneity and consistent Quality of the melt material it transports.

The currently known single-screw extrusion plants exist from a heated cylinder with a filling funnel and a screw - with a feeding zone, Compression zone and discharge zone (see E. Fischer "Extruziya plasticheskikh masse ' ("Extrusion of pastes"), publishing house "Khimiya", Moscow, 1970) 6 Many years of work experience have shown that the extrusion of granulated and powdered polymers with such screw presses of considerable fluctuations in performance, based on Time that j reach 50% is accompanied.

These fluctuations are connected with the discontinuity of the material feed in the feeding zone of the screw press and with the mismatch of the Performance in the feed and discharge zones of the screw.

The effect of the single screw presses is based in the loading zone on the difference in the frictional forces of the polymer on the surface of the cylinder and snail.

In this zone the solid polymer is conveyed, compressed and heated and pressed to a high pressure. It has been found that the coefficient of friction and consequently the working capacity of the screw press in the loading zone of many variable parameters depend: on the nature of the polymer, the processing quality the friction surfaces, the friction speed, the inclusion content of the polymer, Oligomers and volatiles, grain composition, etc.

The ejection zone is located in the area of the molten polymer. In this zone the process of conveying the polymer melt is significant depends on the flow properties of the same.

The feeding of the polymer is carried out in these screw presses Change of screw speed regulated.

This worsens the homogeneity of the melt and the length of the ejection zone changed resulting in the deterioration of the #hysikalisc1i-mechanical Properties of pressed products leads.

In production processes where there is an increased accuracy of the geometric Form of the product and a good quality of material processing required two-stage extrusion systems are used. Such a system includes two extruders connected in series, the first of which is the plasticizing one The extruder acts, while the second acts as a screw pump the melt is metered. The consistency of the work performance of the plasticizer and the metering extruder is controlled by maintaining a constant roe level of the polymer melt in the transfer hopper of the metering extruder (extrusion plants from Barmag for the production of biaxially oriented polyether and polypropylene sheets "Offic.

plast. et caoutch #, 1977, 24, No. 256, 824).

The disadvantage of the two-step extrusion process is its complexity of the equipment and automatics, increase of the metal requirement and the energy expenditure, Lengthening the residence time of the melt at high temperature, increasing the Number of standstill zones in which the polymer breaks down and burns.

In addition, there are technological and repair-related issues in the two-stage systems Equipment hold times elevated.

In connection with this, there was a need for a single-stage To create extrusion plant with increased performance stability. In addition, the achievement had to be of the feeding zone of the single screw press stabilized and with the performance in of the discharge zone, G. Menges ("Plastverarbeiter", Vol. 20, 1969, No. 2) in his work on a single screw press proposed with longitudinal grooves in the loading zone, which allowed the To avoid sliding of the polymer with respect to the cylinder in the direction of rotation of the screw and thereby to create a loading zone with a rigid characteristic curve.

In such a screw press, the coefficient of friction applies does not affect the performance in the loading zone.

The use of sleeves with longitudinal grooves leads to an increase the conveying capacity of the screw in the loading zone. The following sections of the screw are located in the cylinder with a smooth inner surface and bring consequently a lower work output, whereby they have a resistance to represent the material feed. As a result, the solid starting material becomes in these sections are excessively compacted, causing congestion of Worm drive has the consequence.

The object of the invention is the sheep sung in a screw press for the processing of polymeric materials, in which the charging and discharging zone have a rigid characteristic, whereby the performance of these zones is coordinated in such a way that that the length of the ejection zone remains constant during processing.

The problem posed is achieved in that in the screw press for processing polymeric materials that have a cylindrical housing with 'ulltriohter and contains heating elements, in the cavity of which a rotating screw with axially arranged zones for loading, compression and discharge as well as a sleeve which includes the screw in the loading zone and with grooves on its inner surface and with an opening for feeding the polymeric material through to the screw the hopper is provided, according to the invention, with a sleeve as a rotating metering device is designed for the material that is fed from the universal hopper to the screw is, and has a controller of the rotational speed of the feeder, on whose Circumferentially a group of openings is attached, one after the other with the outlet opening of the hopper are brought to cover.

The rotating feeder allows the work of the feeding and to coordinate the discharge zone. Run in the press according to the invention in connection with the fact that the material pressure in the cylindrical housing behind the metering device and the speed of rotation of the screw is always constant, all heating processes of melting and homogenizing without thermal fluctuations, and the melt becomes pressed out with constant temperature and viscosity. The construction according to the invention The screw press enables the products to be of high quality and lower To obtain thickness difference without heat fluctuations.

The attachment of openings of the dispenser on the circumference of the same allows the channels of the screw in the loading zone to be uniformly filled with material and prevents the material from getting stuck in the bunker.

The grooves on the inner surface of the dispenser, following a helical line run, which is opposite to the direction of the thread on the worm, makes it is possible to reduce the speed of rotation of the feeder and consequently the To reduce the power of the drive and to reduce the energy consumption.

The speed controller of the feeder enables the extrusion process to automate and favors the manufacture of a high-quality product.

Appropriately, the surface sections of the feeder, which separate the openings from one another, at an angle Y to the central axis of the Worm arranged, which is selected in the range arc tg f C R 900, where f is the coefficient of friction of the material to be processed on the screw surface means.

Such a version of the feeder allows the destruction (grinding) the material granules between the housing of the hopper and the surface of the To prevent dosing and consequently to reduce the energy consumption.

In one of the variants of the invention, the control of the rotational speed of the dispenser with the help of a pressure transducer for the polymer material to be processed take place, which is arranged in the cylindrical housing at the outlet from the dispenser.

In other embodiments of the invention, the speed control of the feeder with the help of a screw torque transmitter or a torque transmitter of the feeder.

The invention is illustrated by a detailed description of exemplary embodiments explained with reference to accompanying drawings; in the drawings shows: Fig. 1 screw press according to the invention (overall view in axial section) with a speed regulator the doser, with a pressure transducer for the polymeric material to be processed; FIG. 2 section along line II-II of FIG. 1; Fig. 3 View according to arrow D of Fig. 2; Fig. 4 Part of the screw press with a speed controller of the feeder, with a screw torque transducer; Fig. 5 part of the screw press with a speed controller of the feeder with a torque transmitter.

The screw press for processing polymeric materials contains a hopper 1, a cylindrical housing 2 with (not shown in Fig.) Heating elements, a rotating sleeve, which is designed as a dispenser 3, and a Screw 4 with loading zone A, compression zone B and discharge zone C. On the Longitudinal grooves "a" are provided on the inner surface of the dispenser 3. The depth of the grooves "a" decreases evenly in the direction of movement of the material. The doser 3 is stored in the housing 2 on bearings 5 and with a (not shown in the drawing) Control drive for its rotation with respect to the screw 4 is provided. The doser 3 has openings »b, which are attached to its circumference and with the outlet opening of the hopper 1 in succession as the doser rotates The surface portions of the dispenser 3 which the openings Bear "b" under each other (webs "c"), lie at an angle Y to the axis of the Screw 4 * The angle should be greater than the angle of friction of the polymeric material with steel and is limited by the range arc tg f <# <90 °, where f is the The coefficient of friction of the polymeric material with the surface of the dispenser 3 is.

The screw press has a speed controller of the doser 5 in with respect to the screw 4 This regulator consists of a pressure transducer 6 for the polymer Material (Fig. 1) that is in the cylindrical housing 2 at the exit from the dispenser 3 is appropriate. The grooves "a ': of the feeder @ can be found along a helical line run opposite to the direction of the thread on the worm 4, whereby inevitable Gliding of the polymer in the direction of rotation of the screw is ensured and in this way the speed of rotation of the screw 3 compared to the feeder with straight grooves is reduced.

In another embodiment, the speed controller contains the Doser 3 a torque transmitter 6 (Figo for the screw 4 and a controller 7, the one with the encoder 6 and the drive of the doser 3 is connected.

The speed controller of the doser 3 can have a torque transmitter 6 (Fig. 5) of the doser 3 and a controller 17, which with the encoder 6 and the drive of the doser 3 is connected.

The screw press works as follows: A thermoplastic polymeric material in granulated, comminuted or powdered state through the hopper 1 and the openings "b" of the rotating dispenser 3 to the housing 2 fed to the screw press.

As a result of the fact that the webs II "c" between the openings "b" of the Doser 3 arranged at an angle r with respect to the axis of the screw that is greater than the angle of friction of the polymer with steel (the angle Y is limited by the range arc tg f <Lk 900), the slide between the housing 2 and the webs c passing polymer granules and are not crushed (destroyed). This allows a low power drive for the dispenser 3 and the uniform Filling of the channel of the screw 4 in the loading zone with material.

The most effective is an incline of the webs, the f = 15 to 450 amounts to. Almost all polymeric materials show at these values of the angle r a good slide through. Beyond 450, the rigidity of the Construction because the bars act as springs. With CP 900 goes The S.i- ~ n of the construction is lost the screw 4 is advanced in the direction of the grooves "a" of the metering device 3. The doser 3 with longitudinal grooves is used when processing the granulated or comminuted polymer Material in order to match the work performance of the screw in the feeding and the discharge zone are driven at a speed which is 0.6 to 0.9 the speed the screw 4 is. Such a high speed of the dispenser 3 leads to a Drive the feeder 3 of increased power, since the drive power according to the Equation N = M.n 71620 x 1.36 is calculated, where mean: M - torque (kp / cm), n - speed of rotation of the feeder (rpm).

With the aim of reducing energy consumption and improving the performance of the To reduce metering drive, you can the grooves a of the metering device 3 according to a Execute the helical line opposite to the direction of the thread of the worm 4, the inevitable sliding of the polymer in the direction of rotation of the screw 4 bring about and thereby the speed of rotation of the dispenser 3 in comparison with the dispenser 3 which has straight grooves. The reduction Twice the speed of the doser allows the output of the doser drive to be reduced to half, which follows from the equation given above.

The performance in the feed zone of the screw 4 depends on the relative speed of the screw 4 and the metering device 3, which at the constant The speed of the screw 4 can be changed by changing the speed of the feeder 3 can. From the dispenser 3, the polymeric material passes into the heated housing 2, in which it is heated, compressed, melted and homogenized as it moves is transformed into a homogeneous viscous mass and by the screw 4 for profiling of a product.

The performance in the discharge zone depends on the speed of the screw and the feeding of the polymer in the feeding zone of the screw 4.

At a given angular speed of the screw 4, the is constant in all sections of the screw press, so is the continuity the work performance of the screw press from the steadiness of the material feed in the feed zone of the screw 4 depending.

For the continuity of the material feed in the feeding zone of the screw 4, the grooves "a" on the inner surface of the meter 3 contribute. However, the Material feed due to changes in the bulk density of the polymer fluctuate over time. Depending on its size, the performance in the loading zone the screw 4 at constant speed of the screw is greater or less than be the power in the discharge zone of the screw 4. About the performance in the loading zone of the screw 4 to the power in the discharge zone of the screw 4 # the direction of rotation and the speed of the feeder 3 are selected. #enn yourself doing it the metering device 3 rotates at an angular speed which is the same as the rotational speed the screw 4 is the same, so in this case is the power in the loading zone of the screw 4 is zero because the relative speed of the screw 4 and of the doser 3 is zero. The increase in the supply of the pourable polymer Material is processed by increasing the relative speed of auger 4 and feeder 3 made. About the consistency of the work performance of the screw in the The feed and discharge zones are judged by the pressure sensor displays 6, which is mounted in the cylindrical housing 2 at the outlet from the doser. if the pressure is absent, it means that the power in the feed zone of the screw is less than the output in the discharge zone and the screw press is in its operating state Ieis has not yet reached an increase in the loading zone of the screw man the relative speed of the feeder 3 in relation to the screw 4 until on the appendix of the smooth section of the inner surface of the cylindrical housing 2 / i.e. a pressure is created at the outlet of the dosing device 3 /. The pressure is being asked for Level increased by further changing the speed of the feeder 3.

The specified pressure level is then automatically set to the following Maintain way: The pressure transducer 6 / Fig. 1 / transmits the signal to the controller 7, which ensures the maintenance of a constant material pressure at the outlet of the feeder 3 supervised. When increasing or decreasing the bulk density of the starting polymer decreased, or. enlarges the control device based on the principle of pressure stabilization is built in the smooth cylindrical housing 2, the material feed in the loading zone the screw 4 by constantly changing the speed of the metering device 3 with respect to the screw 4 and in this way maintains a balanced operating state of the Extrusion upright.

Balls the feeding of the polymeric material in the loading zone the worm is regulated according to the torque of the worm / Fig, 4 /, is given by the torque transmitter 6 the screw 4 sends a signal to the controller 7, the maintenance of a constant Torque on the screw 4 is monitored. When changing the torque on the screw 4th decreases or increases the control system based on the principle the stabilization of the torque of the screw 4 is built up, depending on the ion change the supply of material in the loading zone by constantly changing the speed of the doser 3 with respect to the screw 4 and thus maintains a balanced Operating state of extrusion upright.

In the case of the feeding of the polymeric material in the feed zone the screw according to the torque of the feeder / Fig. 5 / is regulated, gives the Torque transmitter 6 of the doser 3 sends a signal to the controller 7, which is the preservation a constant torque of the doser 3 is monitored. When changing the torque of the doser 3 reduces or increases the control system. Based on the principle the stabilization of the torque of the worm 4 is built up, depending on the change in torque the material feed in the loading zone by constantly changing the speed of rotation of the doser 3 with respect to the screw 4 and thus maintains a balanced -Operating state of extrusion upright.

In connection with the fact that the speed of the screw 4 and the power are constant in the feeding zone of the screw, run in the inventive Screw press all heat processes and the homogenization of the melt without heat fluctuations, and the melt is at a constant temperature and viscosity pressed out, which leads to the production of a high-quality product contributes.

The application of the invention offers the possibility of the performance the loading and ejecting zones on one screw when processing different polymeric materials regardless of the changes in the bulk weight of the starting polymer to match. The screw press according to the invention is suitable for with the screw high-quality processing into products of practically all pourable polymeric materials, regardless of the grain composition Carry out change range of the bulk density of the polymers.

The fact that the openings "b" of the meter 3 on the circumference of the same are attached and with the outlet opening of the hopper when rotating the Doser are successively brought to congruence, it is made possible the Filling of the helical channel of the screw 4 with the polymer in the feed zone to stabilize.

The arrangement of the surface portions of the dispenser containing the openings Separate "b" from each other, at an angle f to the screw axis, which angle is selected within the limits arc tg f ## <900, prevents the grinding the Polymer granules, whereby the power of the rotary drive of the doser 3 is considerable can be reduced.

The grooves "a" of the metering device 3, executed according to a helical line in the opposite direction to the direction of the thread on the worm 4, allow it to reduce the speed of the doser 3 and consequently the power of the drive to reduce as well as to reduce the energy consumption.

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Claims (6)

SCREW PRESS FOR PROCESSING POLYMER MATERIALS Claims 1 screw press for processing polymer materials, containing a cylindrical one Housing with filling funnel and heating elements, in its cavity a rotating screw with axially arranged zones for loading, compression and discharge as well as one Sleeve are housed, which includes the screw in the loading zone and with Grooves on its inner surface as well as with an opening for the supply of the polymer Material is provided to the screw through the hopper, d a -d u r c h g e k It is noted that the sleeve acts as a rotating metering device (3) for the material is executed, which is fed from the hopper t1) of the screw (4) will, and a speed controller of the dosing device (3), on the circumference of which a group of openings (b) is attached, which successively with the outlet opening of the filling funnel (must be brought to cover. 2. Screw press according to claim 1, d a d u r c h g ek e n n z e i c h n e t that the surface sections of the feeder (3), which the openings (b) Separate from each other, arranged at an angle Y to the central axis of the screw (4) which is selected in the range arc g f <~ <900, where f is the coefficient of friction of the material to be processed with the screw surface means. 3. Screw press according to claim 1 or 2, d a d u r c h g e k e n It is noted that in the rotating dosing device (3) the grooves (a) on his Inner surface following a helical line in the direction opposite to the direction of the Screw thread of the worm (4) are executed and a continuously decreasing Have depth in the direction of movement of the material. 4. Screw press according to claim 1, 2 or 3, d a -d u r c h g e k It is noted that the speed controller of the dosing device (3) has a pressure transducer (6) is provided for the polymer material to be processed, which is in the cylindrical Housing (2) is arranged at the outlet from the dosing device (3). 5. Screw press according to claim 1, 2 or 3> d a d u r c h g e It is not possible to state that the speed controller of the feeder (3) has a torque transmitter (6) the screw (4) is provided. 6. screw press according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that the speed controller of the doser (3) with a torque transmitter (6) of the dispenser (3) is provided.