DE4330090A1 - Mixing and shear roller pair for plastic materials - has spiral grooves with pitch angle increasing along length together with shallow longitudinal grooves and two independent temperature control zones - Google Patents

Abstract

A mixing and shear roller pair for plastic materials has two temperature controlled rollers with sharp edged grooves and lands rotating in opposite directions at the same or different speeds. The helix angle of the grooves increases continuously from about 30 deg. at the material input end to about 45 deg. at the output end and the rolls are mirror images of each other. In addition there are esp. equispaced, longitudinal grooves running axially along the roll surfaces (4, 5). The rolls have independent temperature control. One roll has a zone at the input end running for about 2/3 of the roll length and the other roll has a zone at the input end of about 1.3 of the roll length. On each roll there is a second zone for the remainder of the roll length. USE/ADVANTAGE - For mixing materials of greatly differing viscosity. Produces controlled shear forces which improve mixing while avoiding material damage.

Description

The invention relates to a mixing and shearing mill for plasticizable Material with the features according to the preamble of protection claim 1.

In such rolling mills for continuous mixing, homogenizing, Plasticizing and transporting plastics, rubber, and others plasticizable materials, it is necessary that the materials regardless of the state of their viscosity at the time of posting on the Rolling mill, processed intensively and reliably by the rolling mill. Here it should be ensured that the shear and / or kneading pressures in the plastifi Decorative gap, especially between the two rollers, sufficiently small can be held. In addition, it must be ensured that the Adhesion of the material on the faster rotating and higher heated Roller is not too low to prevent unprocessed material the gap pressure build-up evades and above the second or counter roll longer, in the form of raw material tongues, lingers, resulting in quality fluctuations in the rolled product.

From EP-A-0 148 966 a mixing and shear rolling mill is known in which the two rollers are tempered from the inside and from the outside. The one on the The circumference of the rollers arranged sharp-edged grooves can be a slot ridge range from 5 ° to 45 °.

This rolling mill can handle materials with a certain brittle hardness  are used optimally because they generate enough gap pressure and there is narrowly limited by the material transport through the grooves. For soft plastic material, this rolling mill is unsuitable.

Furthermore, EP-A-0 231 398 is a continuous mixing and Shear rolling mill known, in which on the one hand the speed ratio of the at the rollers in a time rhythm of 5 to 50 seconds in the ratio of maximum 5: 1 to a maximum of 1: 5 is changed periodically and on the other hand in adaptation the two rollers on the melting behavior of the material via an In temperature control and external radiant heating to various Temperature levels along the bale length of the rollers is tempered.

In addition, from EP-A-0 324 800 a mixing and shearing mill for pla stififiable material known, in which grooves on both rollers with a The groove pitch is greater than 75 ° with respect to the roller axes are, the intermediate webs between the grooves at least twice as are wide, how the grooves are wide, and the ratio of the diameter of the rolls to the length of the rolls greater than 1 in 10 and less than 1 in 20 is.

Also put the rolling mills described in the last two documents not yet an optimal solution for processing each other in viscosity of very different materials, especially since the material transport in Plasticizing gap for the different material types is not yet available is established and the gap pressures at the gradients provided there are still too big.

The invention has for its object a rolling mill of the beginning ten kind so that in the rolling process not only an intensive but gentle shear of raw materials of all kinds and / or in various low-viscosity to hard-brittle Zu stand forms enabled and still a safe entry into the Plasti fication gap is guaranteed, but also that a sufficiently large Material adhesion factor on the roller in question is ensured to avoidance of the materials to be processed when building the gap exclude pressure.

This task is performed with the features in the characterizing part of the protection solved 1 and in the subclaims further features are bean speaks.

An advantage of this new rolling mill is not only the spatially clear type and limited course of the individual temperature zones T1 and T2 in the respective rollers, the flow rate of the bath liquid there in the individual temperature control circuits completely independently of each other bar, but also the specific, extremely effective groove course on the Shell surfaces of the rollers, in a combination of grooves with an esp special completely continuous, continuous increase in the groove pitch, with axially parallel grooves of relatively shallow depth. It is also advantageous a pair of rollers with a different number of grooves on the individual rollers.

Embodiments with these and other advantageous features are shown in the drawings and are explained in more detail below. It  demonstrate

Fig. 1 is a perspective view of a roller pair for a mixing and shearing rolling mill with the respective temperature control circuits in the individual rollers and related to the individual rollers diagrams over the temperature profile of the bath depending on the length of the roller,

Fig. 2 is a roller pair for a mixing and shearing rolling mill with a mirror-image opposing relatively flat slope of increase of the grooves,

Fig. 3 is a perspective view of a roller pair in the region of the cutout Plastifizierungsspaltes,

Fig. 4 is a roller pair for a mixing and shearing rolling mill with a mirror-image opposing relatively steep slope increase of the grooves,

Fig. 5 is a roller pair for a mixing and shearing rolling mill with an opposing mirror image, completely steplessly continuous, relatively shallow slope increase of the grooves and having axially extending rela tively shallow grooves,

Fig. 6 is a roller pair for a mixing and shearing rolling mill with an opposing mirror image, completely steplessly continuous, relatively steep pitch of the grooves increase with axialverlaufen relatively shallow grooves,

Fig. 7 is a perspective view of a roller pair in the region of the cutout Plastifizierungsspaltes,

Fig. 8 is a diagrammatic cross-sectional view through a pair of rollers without axial grooves and

Fig. 9 is a diagrammatic cross sectional view through a pair of rolls with Axialnutrillen.

Fig. 1 shows in detail the two axially parallel angeord Neten, rotatably mounted rollers 1 and 2nd The roller 1 acts as a so-called work roller and the roller 2 as a so-called counter roller.

On the roller 1 , 13 a denotes a temperature control channel of the temperature control zone T1, which begins on the side of the material feed 9 and extends over approximately 2/3 of the total length of the roller 1 . The remaining third, towards the material decrease 10 , corresponding to the intended tempering zone T2, is tempered by a tempering channel 13 b.

On the roller 2 13 c denotes a temperature control channel of the tempering zone T1 there, which runs on the side of the material feed 9 over about 1/3 of the total length of the roller 2 . The remaining 2/3 of the total length of the roller 2 , towards the material take-off 10 , corresponding to the tempering zone T2 provided there, is tempered by the tempering duct 13 d.

From, the individual rolls 1 and 2 associated diagrams is ersicht Lich, that in the heating zone T1 of the roll 1, the supply temperature of the bath in the area of material supply 9 is approximately 200 ° C. As a result, the cold material is quickly warmed up in the melting area. Accordingly, the bath liquid cools down to approx. 160 ° C towards the end of the bath zone T1. In this way, the material temperature during the machining process in the plasticizing gap 3 is sufficiently stabilized over approximately 2/3 of the roll length. The tempering liquid then leaves the system via the inside of the roll and the rotary union 14 in the area of the roll bearing 15 . It is heated in a temperature control device not shown and pumped back into the circuit. The course of the temperature curve over the length of the roll is set by controlling the quantity of the Temperler liquid. With a corresponding throttling to a third, the temperature difference between the flow and return temperatures can reach up to 40 ° C.

On the material take-off side 10 , in the area of the tempering zone 2 , the bath liquid is heated at relatively low temperatures, e.g. B. at 130 ° C, but throttled to a small amount, countercurrent to the product supplied. There, the product on the roller 1 is locally removed from the local temperature until it no longer sticks to the outer surface 4 , is tough and can be easily removed as a strip, or after passing through a granular perforated drum as a cylindrical granule, it can be removed dry.

While the material cools on the roller 1 , the tempering liquid heats up in countercurrent to the extent that it no longer has a temperature jump in comparison to the return flow of the temperature control zone T1. In this way, the observed melting the jam in the Materialknet Plastifizierungsspaltes 3 avoided otherwise in large temperature differences during the transition from the first tempering step T1 in the second tempering or cooling step T2.

The material-free counter roll, or roll 2 , must be tempered so that, despite high shear energy in the plasticizing gap 3, the jacket surface 5 is tempered everywhere, but remains sufficiently outside of the adhesive area of the material.

Since there is the greatest energy turnover in the middle of the roller length, a different division of the temperature zones T1 and T2 is seen on the roller 2 , compared to the roller 1 . The temperature zone T1 of the roller 2 extends at the longest to the middle of the roller. In particular, it is advantageous to extend the temperature zone T1 only over approximately 1/3 of the roll length. Also in this zone T1, a relatively high temperature bath fluid of approx. 180 ° C with in particular throttled volume flow is supplied in advance, in direct current to the material, in order to bring as much cold material as possible to the processing temperature while releasing heat.

The tempering zone T2, which begins after the tempering zone T1, for dissipating the shear energy is required over approximately 2/3 of the roller length in order to enable the introduction of a large amount of dispersing energy into the material 11 without increasing the material temperature.

The removal of shear energy via this second temperature control zone T2 of the roller 2 takes place, as in the temperature control zone T2 of the roller 1 , in countercurrent to the material to be processed. The temperatures of the outer surface 5 of the roller 2 must remain close to below the adhesive temperature of the material everywhere.

Therefore, it is necessary that a relatively large volume flow of tempering liquid flows in this temperature zone T2 of the roller 2 .

The quantity control can be used in all temperature control circuits speed-controlled pumps or via throttle controllers, which take place in the rear of the respective temperature control circuit.

The measures described above, in particular the extension of the temperature zone T1 of the roller 1 to approximately 2/3 of the roller length based on the material task 9 , and at the same time the extension of the cooling zone from the temperature zone T2 of the roller 2, based on the material removal 10 , serve to enlarge the working area of such a rolling mill. In particular, a substantial increase in the quantity output and the dispersion quality is achieved by the lengthening of the roller length known from the prior art and the present special division of the temperature zones T1 and T2, as well as the individual quantity control of the temperature liquids.

In order to adequately exclude a mutual influence of the pipes provided for the individual temperature control channels 13 a, 13 b, 13 c and 13 d and to achieve a completely free choice of the individual temperature levels, the supply and discharge lines of the individual temperature control channels are used by both End faces of the roll neck 16 of the rolls 1 and 2 forth. In particular, the individual temperature control channels 13 a, 13 b, 13 c, 13 d are designed as single spiral channels. Thus, the temperature curve adapted to the material along the plasticizing gap 3 is achieved in a geous manner by further throttling or increasing the volume flow of the bath fluid there.

Fig. 2 shows in detail the two rollers 1 and 2. 12 indicates there grooves on the lateral surfaces 4 and 5 of the rollers 1 and 2 , the Stei supply completely stepless from about 30 ° to the roller axis 17 , to about 45 °, with a particularly mirror-image arrangement of the grooves 12 on the lateral surfaces 4th and 5 .

This measure, in particular in the case of rubber-like stretchable plastic materials, in conjunction with the specific temperature control described above, according to FIG. 1, achieves an advantageous material processing.

Due to the mirror-image opposite slope and the slope increase of the grooves 12 , a uniform transport thrust of the material develops from the material feed 9 to the material take-off 10 along the plasticizing gap 3 . At the same time, the material kneading and the material fur on the roller 1 are stretched in the axial direction. The grooved grooves grooving over the material knead and produce a large volume rotating material layer in the plasticizing gap 3 . When coincidence of the non-grooved roll surfaces, of the intermediate webs 8 of Wal zen 1 and 2 there develops in the very small Plastifizierungsspalt 3, a relatively high nip pressure. The material under high pressure al 11 deviates in the direction of the grooves 12 and preferably flows in the axial direction from the bottom of the groove 18 , as can be seen clearly from FIG. 3.

On the other hand, plasticizable materials 11 are also to be processed, which have only a low structural strength in different states. Due to strong differences in the axial thrust behavior of the various groove pitches, the fur formation on these materials on the work roller 1 is hindered. The pieces of material of the so-called roller skin do not adhere sufficiently or are torn apart by the different slopes of the grooves 12 . These materials 11 are known te, relatively long rollers 1 and 2 with very smooth grooves 12 is inserted. In the heating area of the material 11 , only a small radial shear component and a larger axial trans component are introduced by the steep groove angle. Therefore, to achieve an experience in accordance with optimal material processing, the steeper grooves 12 , in the order of 75 ° to 89 °, the material receiving area 9 , and the less steep grooves 12 in the order of 75 ° to 85 °, the melted material state in the ge Assigned to the area of material removal 10 , as can be seen from FIG. 4. With this arrangement of the nu th 12 a continuous change of the slopes is advantageous.

The knot rotation which is also formed there in the plasticizing gap 3 with a so-called backflow vortex inside the material kneading, as can be seen in more detail in FIG. 8, is constantly disturbed by the shear grooves 12 of the rollers 1 and 2 entering the plasticizing gap 3 because the gap pressure swings up and down in a ratio of 5 to 1 and more in accordance with the respective groove depths and gap distances. The level of the developing greatest gap pressure essentially determines the quality of the dispersion.

In addition, the pressure in the plasticizing gap 3 increases exponentially if the effective distance between the intermediate webs 8 of the rollers 1 and 2 is reduced. The pressure also increases with the length of the narrowest gap section, in particular with a smaller material feed angle, larger roller diameters and greater adhesion factors between the material 11 on the one hand and the lateral surface 4 , 5 of the rollers 1 and 2 . on the other hand. The size of the adhesive factor depends on the material type and the effective temperature of the jacket surfaces 4 and 5 , but also on the structure of the jacket surfaces 4 and 5 of the rollers 1 and 2 .

These requirements are met by an advantageous further development of the innovation, in that, on the one hand, relatively shallow grooves 12 a are provided in the intermediate webs 8 running between the grooves 12, which run at the same pitch as the grooves 12 .

A further advantageous improvement is achieved when the relatively flat grooves 12 a, in addition to the grooves 12 , are arranged parallel to the rollers and against each other on the lateral surfaces 4 and 5 of the rollers 1 and 2 .

With this new and advantageous groove profile on the lateral surfaces 4 and 5 of the rollers 1 and 2 , the force transmission of the boundary layer is most effectively increased particularly by the flat, axially parallel grooves 12 a. The depth of the grooves 12 a is expediently 0.1 mm to 2 mm, in particular 0.3 mm to 1.3 mm, but at most approximately half the depth of the grooves 12 . The width of these grooves 12 a must on the one hand cause mechanical clipping of the boundary layers, but on the other hand enable material eddies and interchangeable effects by cutting effects of the sharp edges. The most appropriate widths of the axially extending grooves 12 a are between two to eight times, in particular four to six times the above-mentioned groove depth. The length of these grooves 12 a be between five to fifty times their width. This length is specified in particular by the spacing of the grooves 12 . In addition, it is necessary there that the spatial distance between the individual grooves 12 a to each other is chosen large enough so that when the intermediate webs 8 meet sufficiently large lateral surfaces 4 and 5 remain on the rollers 1 and 2 .

Running Figs. 5, 6 and 7 show pairs of rolls with the new advantageous Nutver. Specifically, 1 and 2 designate the two rollers. 4 and 5 the man telflächen of the rollers 1 and 2 . 12 denotes the shear grooves and 12 a the axially extending, relatively flat grooves. 3 shows the plasticizing gap.

The new axially extending grooves 12 a pull the clamped material 11 into the plasticizing gap 3 with great force. Since the slip friction in the boundary layer area is hindered by this, the pressure build-up in front of the narrowest point of the plasticizing gap 3 can reach twice the value compared to completely smooth outer surfaces 4 , 5 of the rollers 1 , 2 . Since it is expedient that on the roller 1 , the so-called work roller, significantly fewer grooves 12 a are provided than on the material-free roller 2 .

When voluminous, powdery or granulated material 11 is incorporated into the plasticized material layer on the roller 1 , the roller 2 receives about 30% more grooves 12 a than the roller 1 . This results in a bulk volume that is approximately 30% larger. The axially extending grooves 12 a on the rollers 1 and 2 press approximately equal amounts of solid material into the plasticizing gap 3 . This method has the effect that, instead of the known kneading swirl, two stable symmetrical kneading swirls are formed in the plasticizing gap 3 , as can also be seen from FIG. 9.

Each of the two rollers 1 and 2 inevitably drags the same amounts of material into the plasticizing gap 3 , of which about half the amount of material cannot pass through the gap 3 and must therefore flow back into the upper part of the material core.

The axially extending grooves 12 a of the material-free roller 2 also manage the venting of the material in these grooves 12 a after both sides in the adjacent large, thread-like shear and trans port grooves 12 and press the solid content in the lower half of the wedge-shaped kneading bead into the plastic mass, as can be seen schematically from FIG. 9.

In addition, the two counter-rotating symmetrical kneading vortexes described above double the accumulation effect and thus the local pressure in the plasticizing gap 3 , with the same mechanically predetermined size of the gap 3 .

The doubled number of shear flows in the interior of the kneading, which take place particularly effectively in the area of the grooves 12 a as flows of clamped material against flowing material 11 , lead to a considerable increase in performance with regard to the amount and the dispersion quality of the plasticizing gap 3 .

The proposed improvement features in the mantle surface tempering and the surface profiling of such continuous rolls 1 and 2 not only double the working pressure in the gap 3 without the effective intermediate webs 8 still having to be reduced in the constructively critical area of the rolls, but also make it possible for if the bulk densities of the materials to be machined are known, the volume ratio of all the grooves 12 a of the roller 1 to all the grooves 12 a of the roller 2 can be calculated via the number and shape of the groove an equally strong material input into the plasticizing gap 3 without this the stepless speed control of rollers 1 and 2 a product-specific friction ratio must be set. This means that it is possible to drive the two rollers 1 and 2 with only one common drive and at the same speed if the material-specific material entry into the plasticizing gap 3 is ensured by the unequal number and shape of the grooves 12 a.

Claims (6)

1. Mixing and shear rolling mill for plasticizable material with two, with the same or different peripheral speed, to each other against continuously running, internally tempered rollers ( 1 and 2 ), which form a plasticizing gap ( 3 ) between them, over their entire length, and on their lateral surfaces ( 4 and 5 ) at an angle of inclination (StW) obliquely to the roller axes ( 6 ), sharp-edged grooves ( 12 ) and intermediate webs ( 8 ) are arranged in opposite directions to one another and with material feed ( 9 ) and removal devices ( 10 ), which are suitable for the different materials ( 11 ) are suitable, characterized in that the pitch angle (StW) of the grooves ( 12 ) from approx. 30 ° on the side of the material feed ( 9 ) to approx. 45 ° towards the side of the material take-off ( 10 ) continuously increases that the grooves ( 12 ) on the rollers ( 1 and 2 ) are arranged in mirror image to each other, that on the lateral surfaces ( 4 and 5 ) of the rollers ( 1 and 2 ), plus ch to the grooves ( 12 ), in particular at equal pitches to each other on the lateral surfaces ( 4 and 5 ), axially extending grooves ( 12 a) are provided that the rollers ( 1 and 2 ) each with two, independently fed, tempering zones (T1 and T2) are provided that on the roller ( 1 ) the first tempering zone (T1) beginning in the area of the material feed ( 9 ) extends over approximately 2/3 of the total length of the roller ( 1 ), that the second , over the remaining third of the total length of the roller ( 1 ), the tempering zone (T2) connects indirectly to the tempering zone (T1), and that on the roller ( 2 ) the first tempering zone (T1) starting in the area of the material feed ( 9 ) ) runs over approx. 1/3 of the total length of the roller ( 2 ), to which the second tempering zone (T2) is connected indirectly, which runs over the remaining 2/3 of the total length of the roller ( 2 ). 2. Mixing and shearing mill according to claim 1, characterized in that the grooves ( 12 a) are dimensioned approximately 5 mm to 200 mm long, that between the individual grooves ( 12 a) a groove-free roll surface of approximately 0.3 mm up to 100 mm is provided, and that the number of grooves ( 12 a) on the roller ( 1 ) is approximately 10 to 60% smaller than the number of grooves ( 12 a) on the roller ( 2 ). 3. Mixing and shearing mill according to claim 1 and 2, characterized in that the grooves ( 12 a) are about 0.1 mm to 2 mm deep and about 0.4 mm to 16 mm wide. 4. Mixing and shear rolling mill according to claim 1 to 3, characterized in that the lateral surfaces ( 4 and 5 ) of the rollers ( 1 and 2 ) with the grooves ( 12 and 12 a) are integrally formed. 5. Mixing and shearing mill according to claim 1 to 4, characterized in that for tempering the tempering zones (T1 and T2) on the jacket surfaces ( 4 and 5 ) coaxially arranged, helical channels for the per perfluids in the rollers ( 1 and 2 ) are provided. 6. Mixing and shearing mill according to claim 1 to 5, characterized net that the flow rate of the bath liquid per tempering zone (T1 and T2) can be regulated independently of one another.