FI89775B - Mixing and injection moulding device and method and application of the device - Google Patents

Abstract

Device for mixing or transfer moulding of polymer and/or highly viscous liquids, comprising a cylindrical mixing vessel 1, a mixing piston 2, which rotates in the mixing vessel and is axially moveable, at least one auxiliary cylinder connected to the mixing vessel, and an auxiliary piston, which moves in each auxiliary cylinder in order to return the mixture at least to the mixing vessel. On the surface of the mixing piston 2 there is a toothing 3 corresponding to the length of the mixing vessel 1, in order to form a mixing screw known in the art. There are at least two auxiliary cylinders 5, 6 in which the auxiliary pistons 7, 8 are arranged to perform an oscillatory mixing cycle in essentially separate stages, in order to transfer the mixed material between the auxiliary cylinders 5, 6 and the mixing vessel 1. <IMAGE>

Description

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Mixing and injection molding equipment and method and use of the equipment - Blandnings- och formsprutningsanordning och -förfa-rande samt användning av anordningen 5

The invention relates to an apparatus and method for mixing or injection molding polymers and / or high viscosity liquids, the apparatus comprising a cylindrical mixing housing, a mixing piston rotating and axially movable in the mixing housing, at least one auxiliary cylinder connected to the mixing housing and at least one auxiliary piston moving in each auxiliary cylinder.

Finnish patent 83843 describes an apparatus in which the mixing takes place alternately by pumping and shear mixing and which is particularly suitable for mixing small plastic rolls and in particular for the production of conductive polymers. Mixers with a piston-like mixing element, in which several mixing methods are combined, are also known from U.S. Pat. No. 3,623,703, WO-89/00536 and U.S. Pat. No. 3,370,754. In addition, it is known to mix the melt with a mixing screw, especially for melting polymers. .

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The real problem in mixing polymers and high viscosity liquids is e.g. in that the substances in question · often behave like non-Newtonian liquids, forming a film on the surface layers of the mixers in which .30 all mixing takes place without leaving most of the raw material unmixed. In this case, the mass obtained from the mixing device or the injection press, respectively, is not sufficiently mixed and homogeneous or is not at a uniform temperature. Another problem with conventional equipment for mixing plastics, such as said screw mixer, is that a fairly large batch of plastic is usually required to fill the device, since the mixing screw must be very long to achieve effective mixing. 2 - \ - r- · r— ι r-

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available in public areas. This poses problems in the case of a small sample batch, when a special polymer is mixed or the raw materials used are expensive. A third problem occurs when the mass to be mixed, or at least some of its components, is either a solid or a very high viscosity liquid. In this case, the passage of the pulp in the manner intended in the mixer, often through rather small-diameter holes or channels, is made more difficult or does not take place at all, or the pressure due to the increase in force inside the device becomes unreasonably high.

It is an object of the invention to provide an apparatus and method for using it for efficiently mixing high-viscosity liquids, such as plastic raw materials, or even solid state polymers or solid and liquid ingredients. It is also an object of the invention to provide such an apparatus and method by which a polymer or mixture of polymers can be brought into a molten state and into a homogeneous mass for melt processing, such as injection molding. In addition, it is an object of the invention to provide such a device in which the proportion of material wasted would be relatively small.

The objects defined above are achieved and the disadvantages described above are eliminated by the device according to the invention, which is characterized by what is defined in the characterizing part of claim 1, and by the method characterized by what is defined in the characterizing part of claim 16 and by the use characterized by what is defined in the characterizing part of claim 14.

The main advantage of the invention is that with the device and method according to it, two or more material components can be mixed, which can be liquids or: solid. Another advantage is that with the same device, the mixture can be melted to a uniform temperature and fed into a cross mold. A further advantage of the invention is that the mixing can be carried out efficiently at the same time as the pressure in the mixing space can be maintained at the desired level. Another advantage of the invention is that the device is relatively simple and thus inexpensive.

The invention will now be described in detail with reference to the accompanying drawings.

Figure 1 shows a longitudinal section of one embodiment of a mixing device according to the invention.

Figures 2a-2f schematically illustrate a process step chain of a device according to the invention.

Figures 3a-3f illustrate another method step chain of the device according to the invention.

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In the following description, the same or equivalent components are used with the same reference numerals. The device for mixing or injection molding materials comprises a cylindrical mixing housing 1 and a mixing piston 2 rotating in this mixing housing and moving in the direction of its axis 10.

According to the invention, the surface of the mixing piston 2 has a notch 3 extending along the length L of the mixing housing 1 to form a mixing piston into a mixing screw known per se. This agitation of the mixing piston 3 may consist of a single or intermittent spiral, single or multi-headed continuous or discontinuous screw threads or non-screw-like pins, ridges or grooves, possibly also holes or combinations thereof. Thus, the notch 3 typically conforms in shape to, but may deviate from, the shapes used in the feed or mixing screws or spreaders of the extruders 30. In the case that the screw piston of the mixing piston is right-handed, as shown in the figures, one direction of rotation R1 of the piston is preferably counterclockwise, the mixing screw tending to move 35 masses in the mixing housing 4 towards the free end 20 away from the actuators of the mixing piston, and the other direction of rotation R2 to move the mass 4 in the opposite direction. Invent- 4 L. The mixing piston 3 is thus rotatable in both directions R1 and R2. In addition, according to the invention the device has at least two auxiliary cylinders 5, 6 with auxiliary pistons 7, 8. The auxiliary cylinders 5, 6 can be located either 5 perpendicular to the axis 10 of the mixing housing. as in Figures 2 and 3 or may be at a substantial angle 9 with respect to this mixing housing axis 10, as in Figure 1. Alternatively, the auxiliary cylinders 5, 6 may also be at least approximately parallel to the axis 10, an embodiment not shown in the figures.

According to the invention, the auxiliary pistons 7 and 8 are arranged to make their reciprocating working cycle in substantially different stages for transferring the mass 4 to be stirred between the auxiliary cylinders 5 and 6 15 and the mixing housing 1 while the mixing piston rotates in the mixing housing. In the step illustrated in Fig. 2A, the mass 4 to be mixed is in the first auxiliary cylinder 5 and the mixing piston 2 rotates in the direction R1. The auxiliary piston 7 of the first auxiliary cylinder is then pressed in the forward pushing direction E, whereby the mass to be mixed is pushed through the notch 3 into the mixing housing 1 while the mixing piston 2 retracts in the direction T of the stroke length 16 by the volume required by the mass. In the next step, the mixing piston 2 rotates in the direction R2 and is pushed forward in the direction S, whereby the mass 4 to be mixed protrudes from the mixing housing 1 through the notch 3 into the second auxiliary cylinder 6 while the auxiliary piston 8 of this second auxiliary cylinder retracts in the direction P. This step is shown in Figure 2C. The mixing continues .30 by pushing the second auxiliary piston 8 forward in the direction E, whereby the mixing piston 2 retracts in the direction T, whereby the mass moves from the second auxiliary cylinder to the mixing housing, not shown in the figures. The mixing piston then pushes forward again in the direction S and presses the mass to be mixed into the first auxiliary cylinder 5 as described above via the mixing piston - notch 3 while the second auxiliary piston 7 retracts in the direction P by a dimension 15, as shown in Fig. 2D. These described steps from the state of Figure 2A to the same initial state .- /. The corresponding state of Fig. 2D is called the mixing period and is repeated as many times as necessary to effectively mix the mixture in question, to carry out the desired reaction or to bring about the melting of the mass. In some cases, one such mixing cycle may be sufficient to mix, carry out the reaction or melt the pulp, but in most cases it is necessary to use at least three mixing cycles and usually five or more. The maximum number of mixing cycles used in the experiments was 20.

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The forward pushing movement E of the auxiliary pistons means the direction of movement of the auxiliary pistons in which they press the mass 4 towards the mixing housing 1 and the retraction movement P correspondingly the direction of movement of the auxiliary pistons in which they receive the mass 4 from the mixing housing 1. In the case of Figures 2 and 3, the forward pushing movements E of the first and second auxiliary pistons are thus directed against each other and the reversing movements away from each other, respectively. In the structure of Figure 1, the directions are basically of the same type only at an angle 9 with respect to the axis 20 20 of the mixing housing. The forward pushing movement S of the mixing piston 2, on the other hand, is directed in the direction of the free end 20 of the mixing piston, i.e. towards the end 17 of the mixing housing 1 in which the mixed mass outlet 18a or alternatively the extrusion nozzle 18b is formed. The retraction direction T of the mixing piston, on the other hand, is directed away from said end 17, i.e. towards the actuators of the mixing piston 2. The forward pushing movement E, S of the auxiliary pistons 7 and 8 and the mixing piston 2 described above, and in particular the reversing movement P, T, is controlled by hydraulic or pneumatic means, not shown in the figures, including pressure control means for maintaining a preset pressure during the return of the respective piston 2, 7, 8. For example, when the first piston 7 presses the mass 4 into the mixing housing 1, the mixing piston is returned, whereby the pressure control means of the mixing piston maintain the desired pressure in the mixing housing 35. For example, when the mixing piston presses the mass 4 into the second auxiliary cylinder 6, the pressure control means associated with the second auxiliary piston 8 maintain the pressure in this second auxiliary cylinder at the desired level. Correspondingly, the mixing piston 6 '·' ~ r

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when the mass is pressed into the first auxiliary cylinder 5, the pressure control means associated with the first auxiliary piston 7 maintain the pressure in this first auxiliary cylinder at the desired value. In the other operating steps, the operation of the mixing piston and the auxiliary pistons 5 is similar. This also applies to the slightly different type of mixing cycle explained below.

In the operating cycle described above in connection with Figures 2A-2D, the mixing piston 2 is rotated in the first direction R1 or 10 in the second direction R2, depending on whether the mass to be mixed flows into or out of the mixing housing 1. The preferred direction of rotation in each case depends, for example, on the type of notching 3, which in the case of Figures 2A-2D is of the screw thread type, and on the fluidity of the mass. The direction of rotation can thus be used to promote the above-mentioned transfer of the mass, but also at the same time or alternatively to promote the mixing of the mass. It is clear that the mixing piston can be made to rotate in only one direction during the whole mixing period or operation, as in the case of Figures 3A-3D.

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The mixing cycle illustrated in Figures 3A-3C differs from the mixing cycle described in Figures 2A-2D in that the mixing piston 2 does not make any retraction movement during that time and thus of course no forward pushing movement, but only rotates in the direction R1 during the mixing period. In the operating mode of Fig. 3A, the mass 4 must be agitated in the first auxiliary cylinder 5. When the first auxiliary piston 7 is pushed forward in the direction E, the agitating piston in this case remains rotating and

sa protrudes through the notch 3 of the mixing piston into the second auxiliary cylinder 30 while its auxiliary piston 8 retracts in the direction P by the dimension 15 required by the required volume, as can be seen in Fig. 3B. In the next operating step of Fig. 3C, the second auxiliary piston 8 in the second cylinder 6 makes a forward pushing movement E and at the same time the auxiliary piston 7 of the first auxiliary cylinder 35 makes a reciprocating movement P of a corresponding dimension 15, the mass moving from the second auxiliary cylinder to the mixing piston 3. Thus, one mixing cycle is formed and in Figure 3D

'' 11 * -, - • - J 7 describes the next operating step of the next mixing cycle. The movements and back pressure of the auxiliary pistons and mixing pistons are controlled as described in the previous paragraph by hydraulic or pneumatic means and the pressure control means included therein.

According to the invention, the auxiliary cylinders 5 and 6 are connected to the mixing housing 1 at least approximately completely at the end edge 21 of the notching of the mixing screw 3, if from 10 to the drive the sealing portion 22 and the shaft to the drive follow. The stroke length 16 of the mixing piston is such that the auxiliary cylinders 5 and 6 remain at the pitch length L during the entire reversing movement T and the forward pushing movement S of the mixing piston 2. The length of the notch 3 as well as the length of the mixing housing 1 thus correspond to the length of the notch at its free end 20 to the edge 17 of the mixing crossing of the auxiliary cylinders away from the end 17 of the mixing housing. The dimension of the mixing housing is typically the same as the dimensioning of the notch, because the free end 20 of the mixing piston is substantially closed at the end of the mixing housing 17 in the fully forward-pushed position 17. In the embodiment of Figure 1, the auxiliary cylinders 5 and 6 are connected to the mixing housing 1 by chokes or constrictions. Such a structure is suitable for mixing liquid materials. According to the invention, the auxiliary cylinders 25 can also be connected to the mixing housing 1 along the entire diameter 12 of the auxiliary cylinders, as schematically illustrated in Figures 2 and 3.

The structure described above has two auxiliary cylinders, but there may also be a larger number and preferably an even number. In this case, each of the first auxiliary cylinders has in its own way a second counter-cylinder into which and from which the mass to be mixed can be pushed through the notching 3. It is, of course, conceivable that there are also an odd number of auxiliary cylinders 35 if the cylinders are either of different diameters or of different stroke lengths so that the mass to be mixed passes from some auxiliary cylinders to other auxiliary cylinders and back again. In the circumferential direction of the mixing housing, the auxiliary cylinders are typically always located opposite each other, i.e. at a circumferential angle of 180 ° from each other. However, the auxiliary cylinders can also be arranged one-sided in the circumferential direction, even side by side in the circumferential direction. A possible embodiment not shown in the figures is one in which the auxiliary cylinders are successively in the direction of the axis 10 of the mixing housing, i.e. the center lines of the auxiliary cylinders are spaced apart in the direction of the axis 10. In this case, the auxiliary cylinders can be at the same point in the circumferential direction 10, in which case they can be said to be adjacent in the axial direction, or they can be at some circumferential angle from each other.

Figures 2E-2F and 3E-3F illustrate the removal of the mixed mass from the mixing device. Whether it is a mixing cycle according to Figures 2A-2D or 3A-3D, the pulp is removed by the same operations of the mixer. It can be seen from Figures 2E and 3E that in both auxiliary cylinders 5 and 6 the auxiliary pistons 7 and 8 are pushed forward in the direction E, whereby there is no mass 4 in the auxiliary cylinders. In this case, the mixing piston 2 makes a retraction in the direction T of 16 the amount of material required. In Fig. 3F, the end 17 on the free end 20 of the mixing piston is formed as a pulp outlet 18a, 25 which is opened, for example, by a valve pin 19. The pulp can be removed from the mixing device by a mixing piston forward movement S, whereby the pulp is discharged into a free space. Figures 2F and 1 ... illustrate the use of the device as an extruder. In this case, the free end 20 on the free end 20 side of the mixing piston 30 is formed as an extrusion nozzle 18b and a mold structure 23 known per se is arranged on its outlet side. 18b to the mold structure 23. The operation of the device in this respect otherwise corresponds to conventional extrusion, so it will not be described in more detail here.

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Possible heating means 13 and / or 14 of the mass to be mixed are arranged at least in the jacket of the mixing housing 1 and preferably also in the jacket of the auxiliary cylinders 5, 6 so that heat spreads over the travel 15 of the auxiliary pistons 7, 8 and the length L and at least approximately the stroke length 16 for the total length. Figure 2F shows a structure in which the heating means are disposed, to these lengths, and Figure 1 structure, in which a single heating means 13, whereby a sufficient lämmönjohtu 10 takes care of the fact that the heat spreads to the portion of the auxiliary cylinders. The portions of the auxiliary pistons and the mixing piston away from said mixing housing 1 of these lengths are in cooled jacket structures, which ensures the tightness of the structure despite very high mixing and injection pressing pressures, up to more than 15 1000 bar. In particular, the sealing portion 22 of the mixing piston, but preferably also the sealing portions of the auxiliary pistons, extend at least in part to the cold or cooled areas of the jacket structure 24 of the device. In this case, the mass 4 possibly flowing from the hot area solidifies on this cold section, forming a sealing material zone. Sealing of pistons is particularly important in the manufacture, mixing and processing of electrically conductive plastics, since the materials used in this case are at least partially corrosive or otherwise harmful. Conventional plastics, on the other hand, are harmless, so that, for example, in their injection molding, it has not been necessary to pay much attention to sealing. In the device according to the invention, special attention must be paid to the sealing of the mixing piston, since it makes both a reciprocating movement 30 S, T and a rotating movement R1 and / or R2. Em. the sealing can be further enhanced by using a very small clearance of 0.01 mm -2 mm between the mixing piston 22 and the jacket structure 24.

The device according to the invention is excellently suited for use in the manufacture, mixing and processing of electrically conductive plastics, and in particular for the mixing of a conductive polymer and its dopant, for the heat treatment of this mixture. - - 7, - 10 '' '' 'and for blending the solidified conductive polymer and the matrix plastic. The device is therefore particularly suitable for handling the materials described in Finnish patent application 915760 and in particular by the methods described therein. Thus, in particular, it is a reaction product of polyaniline and a sulfonic acid, such as dodecylbenzenesulfonic acid, but the use of the device according to the invention is not in itself limited in this way. The device according to the invention is further suitable for the melt processing of the pulp obtained as described above, as well as other corresponding pulps, into an injection molding product.

Claims (18)

Apparatus for mixing or injection molding polymers and / or high viscosity liquids, the apparatus comprising a cylindrical mixing housing (1), a mixing piston (2) rotating in the mixing housing and moving axially, at least one auxiliary cylinder connected to the mixing housing and a return cylinder moving in each auxiliary cylinder to the mixing housing, characterized in that the surface of the mixing piston (2) has a notch (3) along the length (2) of the mixing housing (1) to form a mixing screw known per se, that there are at least two auxiliary cylinders (5, 6) with auxiliary pistons (7, 8) is arranged to make its reciprocating mixing cycle at substantially different stages for transferring the mass (4) to be mixed between the auxiliary cylinders (5, 6) and the mixing housing (1), in which the mixing piston (2) simultaneously rotates (R1, R2). 1. b 11 Device according to Claim 1, characterized in that the pistons (7, 8) of the auxiliary cylinders (5, 6) are arranged to retract (P) and protrude (E), respectively, and the mixing piston (2) to rotate substantially substantially in place (R1, R2) that when the mass (4) to be mixed is pushed forward by pushing the auxiliary piston (7 or 8) of the first (5) or second auxiliary cylinder (6) through the mixing housing (1) to the second (6) or first auxiliary cylinder (5), respectively, this an auxiliary piston (8 or 7) of the latter cylinder, maintaining a preset pressure for the required volume. Device according to Claim 1, characterized in that the pistons (7, 8) of the auxiliary cylinders (5, 6) and the mixing piston (2) are arranged to alternate (P, T) and protrude (E, S) in such a way that when the mass (4) to be mixed is pressed forward by pushing the auxiliary piston (7 or 8) of the first (5) or second auxiliary cylinder (6) into the mixing housing 35 (1), the mixing piston (2) retracts above a preset pressure, passing the required volume so that when the mixing piston (2) is pushed forward, the piston of the second (6) or first (5) auxiliary cylinder, respectively (8 or 12 f **. * · * «·" '- /. ·' D or 7) is maintained at the preset pressure, maintaining the required volume about. Device according to Claim 1, characterized in that the auxiliary cylinders (5, 6) are located either at a substantially angle (9) to the axis line (10) of the mixing housing or alternatively at least approximately parallel to the axis line (10). Device according to Claim 1, characterized in that the auxiliary cylinders are located in the direction of the axis line (10) of the mixing housing at a distance from each other and at an essential angle to the axis line. Device according to Claim 1, characterized in that the auxiliary cylinders (5, 6) are connected to the mixing housing (1) either by a throttle (11) or, alternatively, along the entire diameter (12) of the auxiliary cylinder. Device according to Claim 1, characterized in that the first (5) and second auxiliary cylinders (6) are arranged at least approximately opposite one another with respect to the axis line (10) of the mixing housing. Device according to Claim 1 or 7, characterized in. : 25 that there are an even number of auxiliary cylinders. Device according to Claim 1, characterized in that the possible heating means (13, 14) for the mass to be mixed are preferably arranged in the jacket 30 of the auxiliary cylinders (5, 6) so that the heat is due to their piston travel (15) from the mixing housing and / or 1) the jacket so that the heat is due to the combined length of the piston length (L) and the stroke length (16) of the mixing piston (2), the portions of the auxiliary pistons (7, 8) and the mixing piston (2) 35 away from the mixing housing being in cooled jacket structures. i '. ·. · b 13 Device according to Claim 1 or 9, characterized in that at least the sealing section (22) of the mixing piston (2) extends at least partially to the cold jacket structures, whereby the mixing mass (4) which may have leaked from the hot area solidifies in this cold area. Device according to claim 1, characterized in that in the mixing housing (1) the end (17) on the free end (20) of the mixing piston (2) is formed as an outlet (18a) for the mixed mass or alternatively as an extrusion die (18b) and that the end includes a valve (19) or similar structure controlled for this purpose. Device according to one of Claims 1 to 3, characterized in that the reversing movement (P, T) and the forward pushing movement (E, S) of the auxiliary pistons (7, 8) and the mixing piston (2) are controlled by hydraulic or pneumatic means comprising pressure control means. to maintain the set pressure during the reversing movement (P, T). Device according to one of Claims 1 to 3, characterized in that the mixing piston is arranged to rotate alternately in the first direction (R1) and in the second direction: 2 (R2). Use of a device according to claim 1 for mixing or injection molding polymers and / or high viscosity liquids, the device comprising a cylindrical mixing housing (1), a mixing piston (2) rotating in the mixing housing and moving axially, at least one auxiliary cylinder connected to the mixing housing and a return cylinder moving in each auxiliary cylinder at least in a mixing housing, characterized in that the use is for the production of electrically conductive polymers, in particular for mixing the conductive polymer and its dopant, for heat treating the mixture and for mixing the solidified conductive polymer 14 into a matrix plastic and injection molding the resulting mass. Use according to Claim 14, characterized in that the electrically conductive polymer is the reaction product of polyaniline and a sulfonic acid, such as dodecylbenzenesulfonic acid. A method for mixing or injection molding polymers and / or high viscosity liquids with a device according to claim 1, comprising a cylindrical mixing housing (1), a mixing piston (2) rotating in the mixing housing and moving axially, at least one auxiliary cylinder connected to each mixing housing and to return the mixture of the auxiliary piston moving in the auxiliary cylinder to at least the mixing housing, characterized in that the mass (4) to be agitated is pressed from the first auxiliary cylinder (5) through the mixing housing (1) in which the mixing piston (2) rotates (R1, R2); (7) and / or by means of a mixing piston and the like back to the first auxiliary cylinder (5) by means of a second auxiliary piston (8) and / or a mixing piston and that this mixing cycle is repeated to mix the mixture effectively or to obtain a uniform temperature in the pulp or desired reaction. the number of times required to implement Action 25. Method according to claim 16, characterized in that said mixing periods are at least three, preferably at least five. 30 Method according to Claim 16, characterized in that during each mixing cycle the mixing piston (2) is rotated between the auxiliary cylinders (5, 6) and the mixing housing (1) between the auxiliary cylinders (5, 6) and the first (R1) promoting mass transfer and / or mixing. ) or in the other direction (R2). '-, Γ-. -, - f ϋ 15