DE19607666C1 - Multiple screw compounding machine for thermoplastics - Google Patents

Abstract

A compounding machine for the melting, colouring, degassing and homogenising of thermoplastics, esp. high molecular weight polymers in solid form, has a number of closely intermeshing screws (3) arranged in a ring inside a closely fitting housing (2) so that they scrape material from the housing and from each other. The screws below the material entry section are placed symmetrically and, when viewed from above in the direction of material flow, for the case of screws pitched to the right, the right hand screw is reduced to the core diameter (3c) for at least part of the length of the material entry. Both screws are covered by a roof shaped filler piece (1n) in the inlet opening (1g), the lower width (1p) of the filler piece (1n) being larger than the distance (1q) between the screw axes.

Description

The invention relates to a screw machine for melting, Coloring, degassing and homogenizing thermoplastics, ins special high molecular polymers in solid form, with a fixed housing, around its horizontal axis in one fixed standing wreath with tight play to each other snails arranged are rotating in the same direction, parallel to the axis and one inside the other interlocking with their surfaces and that they with tight play surrounding housing or the one encased by them Inevitably scrape the housing with its combs.

Such machines have become known as so-called called thin-film reactors, which, however, with a polymer in Melt mold can be loaded under pressure, be it from one continuous polycondensation or from a reflow machine to ensure longer dwell times and thin To achieve layers in the presence of vacuum.

Since in these machines all gears, which advantageous Usually, the worm shafts are planet-like on both ends drive, run through the liquid processing material and are lubricated, they are for processing solid materials in powder or granular form unsuitable, especially since the feed gears would be destroyed.  

Assuming that the drive of the waves upstream of the Material addition is arranged and the associated seal material inlet problem is solved here, this is suitable Machine therefore not yet for processing solids, because the filling material to be processed only to the outer rim of the Screw conveyors and therefore the screw shafts from Solid in the melting part of the machines to their center axis would be pushed out and thus unusable.

So-called compounders are currently being used in the same direction rotating, interlocking, mutually scraping Twin screws, for melting, coloring, mixing and Homogenizing thermoplastic solids in powder or granular form used.

The present invention has set itself the task The 8-shaft machine also has the multi-shaft machine as Compounder to use and with thermoplastic solids to be able to load, with the same advantages, which the compounders listed above offer.

Because only interlocking, mutually scraping Snails for a defined mass transport and satisfied care self cleaning their surfaces and The invention has thus met the highest demands also given the task of self-cleaning the waves to get and the waves in the melting and homogenizing part from outside and inside at the same time with radial forces act upon, which cancel each other out.

According to the invention the object is achieved in that the two screws lying under the material inlet are axially symmetrical are arranged that in right-handed snails from above in Seen the direction of conveyance, the outer diameter of the right Auger, at least over part of the length of the material running, reduced to the core diameter and both screws so abge from a roof-shaped filler in the material inlet covers are that its lower width is larger than the axis  distance between the two snails below.

Due to the inventive design of the material inlet Multi-wave machine is achieved that two circular to their Center axis rotating material flows with opposite Rotation directions that center worm shafts between them. This also has twice the throughput per unit of time, based on the same diameter and machine length the twin screw. In addition, through the new design of the material inlet for solids with the Multi-wave machine for the first time completely new, from the melting plant independent process tasks can be fulfilled.

In the compounding machine according to the invention, the longitudinal ver Mix the processing material in the melt phase equally better than conventional machines of this type, because in the gusset area of the snails the material from the inside wreath very intensively mixed with the material from the outer wreath becomes. The material is based on 8 two-speed screws with 2 screw revolutions on the outer ring conveyed by 6 gears, on the inner rim, however, only by 2 courses, so that the longitudinal mix effect of the multi-shaft screw results from the fact that Workmanship on the outer rim with triple conveyor speed overhauled by the inner ring and at the same time is mixed with this.

In addition, the multi-wave machine compared to the double snail still advantages when melting such substances, which cannot yet be estimated in their dimensions. So the multi-wave machine has 4 times more waves to offer what means that a surface 3 times larger is processing good for surface renewal and therefore better mixing is offered.

Whether the machine is fed in doses or from the full hopper is driven, in both cases it is intended that the Half of the total amount reaches the outer and inner ring and certainly bridging in the material inlet  is avoided.

The number of teeth on the worm shafts must therefore be divisible by four be preferred because in such compounding machines two-speed snails are used because they are axially symmetrical are equally loaded with radial forces, which cancel each other out, so that, for this reason, every Schnec core shaft rotated by 90 ° to its neighboring shaft got to.

To the upstream seals to the transmission from To keep dust and solids free and to relieve them, there are all worm shafts at least on a length of their Diameter again formed with its full diameter, in order to achieve forced support at this point and ensure that even with a full funnel no feast fabrics on the end wall penetrated by the worm shafts and get their sealants.

Because in current compounding machines not enough heat from can be supplied externally due to insufficient heat transfer surface to the product, the very expensive energy becomes from the drive used for melting, so that the melting process as a result the conversion of this mechanical energy into heat the Ver wear on the screws and casings in this zone Consequence and therefore uneconomical.

According to the invention, it is of immense importance for this Design of a compounding machine that enough heat from outside and inside of the melting part of the processed material is carried out, especially since on the one hand double per time unit Amount of material can be melted and on the other hand the Melting process should only take place with cheaper heating energy and therefore at the same time better coloring results can be achieved.

That is why it is particularly advantageous shortly after the material one heater each on the outer and inner housing,  so that the screws enclosed by both casings of two sides can be supplied with appropriate heating energy can. This complies with the fact that it faces the snails outer heating surface is twice as large as that of the Double screw existing total heating area and in addition that An interior housing heating surface is offered, which is not available with the twin screw.

The stationary inner housing is heated in such a way that advantageously the material leakage is not, as in Screw machines usual, is arranged in the center of the axis, but according to the invention the axial material outlet channel of each Schnec kenwelle opens into an annular melt channel, the cross cut enlarged from snail to snail, so that on largest cross section radially offset to the central axis, the materi al outlet occurs longitudinally or radially outwards.

According to the invention, it is therefore also possible to use rod heating indispensable heating of the inner housing introduce there and their current conductors and thermocouple lines gene lead out, so that the worm shafts of two heated around 60% of their surface with tight play the, trough-shaped housing surfaces can be tempered.

It has proven to be advantageous when feeding powder or pearls proven at a suitable distance downstream of the material inlet - at which the material has already melted - one Evaporation opening for the air drawn in with the powder or for the moisture absorbed with the pearls and the resultant Arrange forming water vapor so that the gases present can be conveyed with the processed goods and not contrary to the direction of conveyance, the flights of the screws are empty blow.

According to the invention, this opening is created in that between the two housings to be connected on the fasteners spacer rings are pushed on and thus on the short very effective degassing opening is created in the  which vents the snails a full 360 ° around the crown axis, thereby feeding the material into the downstream housing is favored that the housing inner holes at this point which open obliquely, which the upstream ones Cover the conically tapered, molded housing spout.

To the very expensive dosing systems for such machines too avoid, it is advantageous to drive with a full funnel to be preferred, especially since such interlocking snail systems make a very precise allocation of materials. To do this enable without having to convert the machine or over load, two inlet openings can be provided in the inlet part be, which each closed with a slide can be, with a small under the drive-side opening incline adapted to the specific weight of the granulate of the snails and below the second downstream Opening, large, for the specific weight of powder or Bead suitable slope, is provided.

In practice have been used to seal shafts in gearboxes so-called radially resilient, axially closed lamella rings proven to remove dust, dirt or foreign objects from the gear unit hold especially if they are in a thin film of fat encircle and several lamella rings to each other a labyrinth form, with at least three such rings radially resilient in intended, spaced-apart shaft grooves sit, of which 2 rings clamped radially resiliently on the surrounding housing stuck and between these another ring on the off sealing shaft groove is stuck and rotates.

These lamellar rings have the advantage that they absolutely ver are wear and maintenance-free as well as being radially very small need space what with the shaft couplings used here Requirement is. These lamellar rings are for this application Reverse function used to avoid any dust to let out so that the free space to the distributor gearbox, wear-free and therefore maintenance-free sealed is.  

The worm shafts are with the pinion shafts of the distribution gear drives in this free space connected via couplings in which easily accessible from the outside, radially arranged, with cones ver see studs are provided, which the axial Ver tension of the shafts to each other in the conical shaft grooves generate and include the couplings on both ends the outer circumference of said lamellar rings.

In the drawing is an embodiment of the object presented the invention. Show it:

Fig. 1 is a longitudinal section through the part of a method for decoding machine Kompoun granules without drive motor, reducer gearbox and transfer gearbox,

Fig. 2 shows the cross section through the inventive material inlet according to the line II of FIG. 1 or 4,

Fig. 3 shows a cross section through the melting zone of the machine,

Fig. 4 shows the longitudinal section through the material inlet for pearls or powders with ventilation.

The process part shown in Fig. 1 for melting granules, consists of the air-cooled inlet casing 1, the inner housing 2, the screw 3, the outer casing 4 and the extrusion member 5.

The grooves 1b pierced in the air-cooled inlet housing 1 form the cooling fins 1 a, which are combined by means of longitudinal axis fractions 1 c, 1 d ( FIG. 2) to form axially symmetrical parallel cooling groups. The sheet metal jacket 1 e and the connecting plate 1 f with the correspondingly lengthened inlet hole 1 g are welded together, the air supply via an unillustrated solenoid valve in countercurrent via the threaded connection 1 h and the air outlet is denoted by 1 i.

As worm shaft 3 , preferably hammered shafts according to DIN 5480 made of a high-strength, stainless steel are used by the meter, the number of teeth of which is divisible by 4.

The number of teeth on the worm shafts must therefore be an integer be divisible by 4, because in such machines 1, 2 and 3-speed screw bushes for different processes were used and so the 2-way bushings 90 ° ver sets must be arranged to their neighboring rifles.

At the exit end of the shafts, a fine thread for receiving the screw tips 3 d is provided, the thread diameter of which is equal to or smaller than the wel lengrundkreisdiameter the toothing and its direction of slope - with a right-hand slope of the Schneckenbüch sen 3 a - must be left-handed, so that the tips tighten during operation due to the friction effect of the material being processed. At the end of the coupling, only a groove 31 is inserted, for receiving a split ring on which the screw bushes are supported.

The inlet opening is covered over its entire length by a roof-shaped filler 1 n and welded to the intermediate plate 1 f, the lower width 1 p is kept larger than the center distance 1 g of the screws below.

In Fig. 2, the left screw 3 c is reduced to its core diameter under the roof-shaped filling piece 1 n, so that the processing material in the intermediate screw created for the left screw can fall through to the inner ring. Since there is no space between the right snail and its neighboring snail, the material must remain in the outer ring.

In the space between the rear edge of the inlet opening and the intermediate plate 1 k conveyor bushings with a small pitch are provided on all screws, so that at this point absolute constraint even with a full funnel, the intermediate plate and the sealant located in it 3 e keeps free of material.

The screws in the melting part for granules are designed so that left-handed kneading blocks 3 b are spaced 3 h apart by short screw bushes between them, so that a safe melting of the granules is ensured.

Each screw follows in the extrusion part 5 its own melt bore 5 a, which b in an annular melt channel 5 Mün the whose cross-section tapers from screw to screw and c either axially or radially outward downstream to a greatest cross-section in a bore 5, not shown Darge nozzle or another following machine is performed.

Within the melt channel 5 is therefore fen b so much space geschaf that necessary for heating the inner casing 2 heating elements 2 a and for which the current conductor and thermocouple wires 2 can be led out b.

The intermediate plate 1 k is screwed to the material inlet via the screws 1 r and is screwed or centered to the gearbox together with the pins 1 l, the screws 1 m and the spacer sleeves 1 s to the gearbox. Also, the outer housing 4 with its heaters 4 a is screwed and fixed in position axially via screws and pins to the material inlet and the extrusion part.

In Fig. 4, a melting part for powder or pearls is provided, in which after the material inlet 1 , the housing 4 with its heaters 4 a as two partial halves are screwed together axially by means of screws 6 a, the pins 6 b and the spacers 6 c or are centered relative to each other, so that by means of the spacer sleeves 6 c between the housing halves 4 a 360 ° effective evaporation opening 6 d is formed, which is formed by the upstream, conically tapering housing part 4 b and the downstream, conically widening housing part 4 c det and is overlapped.

The kneading blocks 3 f are in this case right-handed and also spaced apart by means of the interposed short screw bushes 3 g. These kneading blocks are therefore right-handed so that the air in the powder or the gases in the pearls reach the evaporation opening unhindered.

In the inlet housing 1 two axially spaced inlet openings can be provided, which can be worn independently with sliders, whereby under the upstream opening suitable for granulate screw bushings are arranged and under the downstream opening for powders or pearls suitable screw bushes are provided, whose Effective length extend into the heated on melted part, so that the machine can be used for powder or granules with a full funnel without screw modification, without being overloaded and the very expensive dosing systems are not required.

If there is only one type of material on such a machine Lich their specific weight comes to processing it is advisable to provide only one inlet opening.

Claims (6)

1. Compounding machine for melting, coloring, degassing and homogenizing thermoplastics, in particular high-molecular polymers in solid form, with a fixed housing, around the horizontal axis of which are arranged in a fixed ring with tight play to each other, the screws rotating in the same direction, parallel to the axis and interlocking mutually scraping with their surfaces and the housing surrounding them with tight play or the housing encased by them with their combs is characterized in that the two screws below the material inlet are arranged axially symmetrically in such a way that with right-handed screws, from above in Seen flow direction, the outer diameter of the right-hand screw is reduced to at least part of the length of the material inlet to the core diameter ( 3 c), both screws being covered by a roof-shaped filler ( 1 n) in the inlet opening ( 1 g) so that the lower one Width ( 1 p) of the filler ( 1 n) is greater than the center distance ( 1 g) of the two screws below. 2. Compounding machine according to claim 1, characterized in that the material exit from the individual screws in its axis via bores ( 5 a) which open into a ring-shaped channel ( 5 b), the cross section of which increases from screw to screw and is largest Cross section ( 5 c) is continued. 3. Compounding machine according to claim 1 or 2, characterized in that in the central region of the shaft ring from the tread end of the inner, fixed housing accessible rod heater ( 2 a) are arranged, the current conductor ( 2 b) and thermocouples from the inner housing ( 2 ) are brought out. 4. Compounding machine according to one of claims 1 to 3, characterized in that the melting part after the Materialein run of two housings ( 4 ) is formed, which screws by means of screws ( 6 a), dowel pins ( 6 b) and spacers ( 6 c) or are fixed to each other, so that by means of the spacer sleeves ( 6 c) between the two housing halves ( 4 ) a 360 ° effective evaporation opening ( 6 d) is formed, which is conical from the upstream. tapered housing part ( 4 b) and the downstream, flared housing part ( 6 c) is formed and overlapped. 5. Compounding machine according to one of claims 1 to 4 thereby characterized in that the material inlet consists of 2 openings which is spaced in the longitudinal direction of the machine are and can be closed independently with sliders with the snails under the upstream opening a small slope intended for granulate and below that downstream opening one for powder or pearls have a suitable slope. 6. Compounding machine according to one of claims 1 to 5, characterized in that a sealing plate ( 1 k) penetrated by the shaft couplings ( 3 k) is arranged between the output-side shafts of the transfer case and the inlet-side worm shafts, the sealing points of which are formed by sealing means ( 3 e) which consist of radially resilient and axially closed lamellar rings.