DE19548136A1 - Low cost, monomer processing to give semi-finished plastic products - Google Patents

Abstract

During processing of plastic monomers the polymerisation is performed in an extruder and the obtd. polymer is further processed to produce a semi-finished product.

Description

The invention relates to a method for producing polymers from plastic and their Processing. Polymers are made from monomers. The polymerization occurs when Plastic monomers are brought into motion in a bath under heating. The Industrial polymer manufacturing sees extremely large, tempered for polymerization Containers with an agitator in front. The batches and are accordingly large the effort required to manufacture and operate the systems.

The invention has for its object to create small batches and the effort for to reduce the investments. The invention does not go the obvious way To scale plants down to scale. The goal of the smaller batches and the Reduction in construction effort achieved. However, the operational effort would be disproportionately large. The invention takes a different approach. According to the invention, the Polymerization takes place in an extruder. That the polymerization at all in an extruder can take place is somewhat surprising because the extruder is only a very small one Volume. Nevertheless, despite its relatively small volume, the extruder is suitable because it has a much higher efficiency than the previous systems.  

The efficiency of the extruder for the polymerization is due to the fact that the Extruder causes a much more advantageous movement of the monomers than the agitator a large container. In addition, the pressure in an extruder can vary widely can be designed arbitrarily. The polymerization can also be advantageously hard by pressure influence. In contrast to the extruder, pressure build-up is conventional Polymerization containers are not possible because, in this sense, these containers do not Are pressure vessels. The wall thicknesses of a large container would have to be the same pressure designed to be much thicker than that of an extruder. It follows that either a much greater structural effort is required to do the same in the large container Set up the operation as in an extruder or the operation in a large container cannot be the same as in the extruder.

The extruder pressure during the polymerization is preferably at least 20 bar.

In a further embodiment of the invention, the polymerization stage is a degassing stage downstream. The primary aim of the degassing is, with the gas components included, the Eliminate any remaining monomers from the mass. The degassing can be done by previous addition of a degassing agent can be made particularly effective. As Degassing agent is also suitable for water. Favorable conditions arise if that Degassing agent in an intermediate stage between the polymerization stage and the Degassing stage is added, the same if the degassing is a post-degassing is connected downstream.

According to the invention, an extruder is, in particular, a rotating multi-shaft extruder intended. The planetary roller extruder of this type is known in practice. Of the Planetary roller extruder has a driven central spindle. Run on the central spindle different planetary spindles around. The number varies with the size. The planetary spindles not only mesh with the teeth of the central spindle and therefore have one corresponding gearing. You also comb with an internal toothing of the Extruder housing or a socket seated in the extruder housing. The jack will preferred because it is easier to manufacture or process than the housing and because with Lighter cooling channels and / or heating channels can be represented in the extruder jacket with the aid of the socket are. The channels are preferably incorporated into the outer jacket of the socket. By  Cooling or heating the extruder is brought to a desired temperature or up the temperature kept.

The special advantage of the planetary roller extruder is its extreme impact on it processed insert material. The feed material is on the one hand in the planetary spindles the gap to the central spindle and on the other hand in the gap to the housing or the Rolled bushing. This results in a particularly large effective surface, increased through the interlocking of all planetary roller parts. The effect is used to relate to relative short machine length the necessary mixing of substances, dispersing and Homogenize and then achieve the required cooling. In the application this is a welcome effect on the polymerization according to the invention. This one more significant effect is the fact that such an extruder becomes an agitator, if all or part of the material he is promoting is prevented from escaping. Of the Leakage can be prevented by closing the extruder accordingly. As A blister is suitable for closure. It is a more or less sealing Collar on the central spindle and / or in the housing or in the socket if the Central spindle is of greater length, as will be explained below. If the Central spindle does not go beyond this extruder section, the extruder housing can be closed at the front.

The mass of the extruder closed by the collar or in some other way becomes over a pressure line pulled / drained. With a valve, the mass can escape being controlled. A pump also acts as a valve. The advantage of the pump is that with it a pressure can be built up within wide limits and the mass with the pressure in a further processing / extruder stage can be given.

The mass prevented from escaping is continuously pumped around in the planetary roller extruder. The pumping can be kept as long as desired. Pumping can be done by Enlargement of the spaces between the planetary roller spindles can be facilitated. The happens in a simple way by omitting or removing individual planetary spindles.

Pumping is also optionally carried out in such a way that a for the polymerization stage Planetary roller extruder section is used, which is one of the general flow direction in the Extruder opposite conveying direction and also a leakage flow in the general direction of flow of the mass. This extruder section then conveys a blister. The mass flows in the spaces between the planetary roller spindles  against the conveying direction of the extruder section back in the general Direction of flow of the mass and later the melt.

In this way, the mass can be used as a leakage flow in a further processing stage reach.

The next stage of processing is preferably degassing. When degassing, the mass depressurized or the pressure significantly reduced, possibly even with negative pressure acted on, so that enclosed gases from the mass due to their internal pressure emerge.

Good degassing results are obtained when the extruder in the degassing stage has a conically widening spindle. In this embodiment, none are with the spindle meshing planet spindles provided. By simply enlarging the Passage cross section in the extruder, d. H. of the space surrounding the spindle in the extruder there is already a substantial reduction in pressure and calming of the melt flow, so that the desired degassing occurs. The still necessary Conveying effect on the mass is with a worm gear with relatively large / high Teeth ensured. These teeth can extend up to the housing / socket inner wall extend.

Optionally, an extruder is also used to first add a degassing agent to the mass to incorporate. This can be done in advance for post-degassing and / or in advance for Main degassing take place.

A common one can be used for the different processing stages of the planetary roller extruder Central spindle can be used. The individual processing stages can be viewed using Separate blisters and / or in another way.

When processing stages are separated

• - Feeding and mixing and
• - polymerization

by a blister or other means, both stages are preferably via a pump connected with each other.

The separation of the two stages and the use of one explained above Planetary roller extruder section with a general flow direction of the melt  opposite conveying direction open up the possibility of using the blister as a common Use thrust ring for both extruder stages, albeit for the material feed and the Mixing a planetary roller extruder is used.

It must be pointed out here that the planetary roller spindles roll on the central spindle and one on the internal teeth of the socket or the housing absorb considerable pressure in the axial direction by a so-called thrust ring is caught. The thrust ring is at the end of the planetary spindles on the conveying direction arranged so that the planetary spindles slide on its circular path with its end faces on it. By sharing a thrust ring on both axial as described above The end faces cancel each other out.

The mass reaches z. B. over a line with an intermediate static mixer from one Extruder section in the next. The static mixer is preceded by a pump downstream. The static mixer is used to even out the mass flow and allows the admixture of additives.

As far as provided, the post-degassing can go directly to the degassing stage connect. If a post-degassing agent is used, the Degassing agent in the mass preferably with a further extruder section. This Extruder section, like the other extruder sections, can be used as a planetary roller extruder be trained. The feed point of the post-degassing agent can be at some distance from the beginning of this extruder section to be selected on the way Effect sealing. The distance is then chosen so large that the resistance against an escape of degassing agent from the extruder section Degassing agent prevented in the degassing zone.

At this point, too, procedural advantages result from completing the Extruder section and withdrawal / discharge of the mass with one line. The post-degassing can be connected to this line. The degassing tank is optionally a simple container, preferably in the form of a funnel. Interposition of the container in the Line causes a substantial increase in the passage cross-section, thus a Pressure drop and a calming of the mass. Under these conditions, the crowd degas very advantageously, the process being included and now  leaking water is also accelerated and intensified considerably. The water ever falls according to temperature and pressure in the form of steam.

In the pressure line are in front of and / or behind the container and / or for the release Gas pumps provided. In terms of procedure, the best conditions result if both in A pump is provided in the inlet as well as in the outlet and in the gas outlet. With the help of Pumping creates a closed, also evacuable chamber. The pumps allow the chamber is essentially independent of the inlet pressure from the extruder section for the Addition of the degassing agent and regardless of the pressure required in the To drain line.

Another significant advantage of the above-described polymerization using an extruder is the possibility of the polymer mass emerging from the polymerization / post-degassing to be processed immediately in an extruder, to be melted. That can also be done in one common extruder. Then the polymerization emerges mass further extruder section fed. This extruder section has training as Planetary roller extruder with the previously explained extruder sections a common Central spindle.

Furthermore, one can be used in the extruder section used for polymer processing Planetary roller extruder with the opposite direction to the general flow of the melt Direction of flow and leakage flow in the general flow direction can be used. in the In principle, this extruder section corresponds to the extruder section of the polymerization stage. This achieves two advantages. One advantage is the possibility to use it a common thrust ring. The other, bigger advantage is the particularly intense one Processing the melt. This allows all the necessary additives to be obtained in the shortest possible way and mix the blowing agent into the melt. The additives can be lubricants, Act stabilizers or crosslinking agents.

The blowing agents can be added in liquid and / or gaseous form.

Optionally, additives and blowing agents are added to several above the The length of the extruder section is distributed and follows the above Extruder section with opposite conveying direction an extruder section with the same Conveying direction. This further extruder section can also be mixed, Dispersion and homogenization are used.  

In addition, there is also regularly an extruder section for setting one controlled outlet temperature provided.

The last extruder section can also be closed, so that the melt as in Transition to polymer processing withdrawn / derived via a line and via a Pump with a defined pressure, independent of the extruder operation. B. in a Extrusion tool can be directed to the production of a plastic foam strand.

The closure of the extruder housing at the end of the extruder finally opens the Possibility of an advantageous spindle bearing at the end of the extruder. That relieves the Spindles, reduces wear and extends the service life.

Heating / cooling liquid can be led through the end of the central spindle on the outlet side will or exit. This means that the outlet end of the spindle can also be thermally controlled will. This is especially true in the case of a separate liquid supply. So far, the Liquid supply only from the drive end of the spindle. Even if only liquid is drained through the outlet end of the spindle, Structural simplification of the spindle has considerable advantages.

In the drawing, an embodiment of the invention is shown.

It is an extruder for the polymerization and the subsequent processing of the polymers. The extruder consists of sections I, II, III, IV, V and VI. Each extruder section has its own housing 1 , 10 , 20 , 30 , 40 and 50 . All extruder sections have a common spindle 60 . The common spindle 60 is provided with a toothing 2 for section I or forms a planetary roller extruder section with planetary roller spindles 3 and an internal toothing 4 of the housing 1 .

In section I feed materials 5 and 6 are fed through the feed openings. These are low or highly viscous monomer plastic compounds. The feed materials enter the space enclosed by the planetary spindles 3 , the central spindle 60 and the housing 1 . The room is closed and can be tempered from the outside and inside. For heating 1 channels 7 are provided in the housing and a channel 61 in the central spindle. The feed materials are mixed in the room due to the dwell time, the mechanical mixing process and with heating. Polymerization of the monomers can already start. In the event that further components are required for the polymerization, they can be input via a feed line 8 and pump 9 .

The reaction space in section I is delimited by a blister lock 62 on the central spindle 60 . The blister lock is a collar of the central spindle 60 , which at this point completely fills the bore for the central spindle except for the play necessary for the rotary movement. The bore for the central spindle 60 is formed at this point by two adjacent rings. In addition to a task to be explained below, both rings have the advantageous effect of centering the central spindle. As a result, the central spindle runs more smoothly, its wear is reduced and the service life is increased.

The ring on the left in the drawing also has the task of absorbing the forces occurring from the planetary spindles 3 in the general direction of flow of the melt in the extruder (from left to right in the drawing).

The melt obtained at the end in the reaction space of section I is drawn off via a line 63 . A static mixer 66 is arranged in line 63 , which serves to even out the mass and allows additives to be added. Pumps 64 and 65 are provided in front of and behind the static mixer 66 , with which the pressure conditions can be controlled as desired.

The line coming from the ring arranged on the left in the drawing with an inlet opening in front of the blister lock 62 leads into the ring arranged on the right in the drawing with an outlet opening behind the blister block 62 . As a result, the mass passes from line 63 into section II.

Section II includes a further planetary roller extruder section with a toothing 12 of the central spindle 60 , planetary roller spindles 13 and an internal toothing 14 . These parts act in the same way as in the planetary roller extruder section of section I. The temperature of the associated housing 10 is the same as that of the housing 1 . The associated channels are designated 17 .

However, the planetary roller extruder section of section II differs from that of section I in that the conveying direction is opposite to the general flow direction of the mass. The geometry, ie the slope of the planetary system, is directed against the general flow direction. At the same time, the mass cannot run out at the end. Because there is a higher pressure, a leakage flow is formed. The mass flows back in the space between the planetary roller spindles against the conveying direction of the planetary roller extruder section. This is increased by suitably large distances between the planetary roller spindles 13 . The distances increase by reducing the number of planetary spindles. The number of planetary roller spindles 13 in section II is at least 1 less than that of planetary roller spindles 3 in section I.

Section II serves for further dynamic mixing through the mode of action of Planetary roller system. The in this extruder section under pressure and temperature Monomers pumped around constantly become polymers. The degree of implementation stands depending on the adjustable residence time of the melt in section II.

Section III provides for the input of a liquid degassing agent by means of a pump 67 and via a line 68 . The degassing agent is water. The water is mixed in the mass by means of a third planetary roller extruder section. The third planetary roller extruder section consists of one of the central spindles 60 with the toothing 22 , the planetary roller spindles 23 and the inner toothing 24 in the housing 20 . As in the other planetary roller sections, channels 27 are provided in the housing for temperature control. Likewise, the heating / coolant guide in the channel 61 of the central spindle 60 acts on the temperature control.

In Section III, the focus is on dispersing the blowing agent well while maintaining the solution pressure for water in the mass. The option that the number of spindles and the core diameter of the central spindle can be selected also applies here. Added to this is the control of the process step by means of targeted liquid temperature control in the housing 20 and in the central spindle 60 as well as the pressure superimposition or dwell time of the mass depending on the conveying speed of the pump 64 and a pump 34 connected downstream.

In section IV, a blister lock 69 in turn forces the mass flow into a line 35 with the pump 34 . The housing 30 of the section IV surrounds the collar forming the blister lock 69 like the rings between the sections I and II with the same advantageous effect. The pump 34 is a gear pump. It has the function of a pressure control valve for sections II, III and IV and is required for the further transport of the resulting polymer mixture into a gas-tight expansion space which is designed as a funnel 31 . In the funnel 31 , residual monomer portions that are still present are degassed using the expansion principle. In order to achieve high degassing efficiency, the mass flow is injected vertically from above into the funnel, which is under vacuum, via a nozzle bar equipped with a large number of outlet bores. The drop in pressure causes the liquid monomer residues still in solution to emerge from the polymer mass to the surface. This effect is reinforced by the liquid medium entered in the section, referred to as the flash medium.

The polymer mass collecting at the bottom of the funnel 31 is subsequently fed back into the planetary roller system via a pump 32 designed as a gear pump. The associated end of the line 35 opens behind the blister block 69 in the general flow direction.

The polymer mass enters section V, which begins with a first planetary roller extruder part. The first planetary roller extruder part includes the central spindle 60 with a toothing 602 , planetary roller spindles 43 and an internal toothing 44 of the housing 40 . This planetary roller extruder part, like the extruder part of section H, has a conveying direction opposite to the general flow direction with a particularly high efficiency. This planetary roller extruder part is arranged in the same arrangement with the extruder part of section III as the extruder part of section II with the extruder part of section 1 . The housing 30 of section IV forms a common thrust ring for the planetary roller spindles of both parts, like the two rings between the sections I and II. Here, the starting forces of the planetary roller spindles are also canceled.

The housing 40 is heated to the same temperature as the other housings. For this purpose, channels 47 are provided in the housing and another channel 601 is used in the central spindle. While the channel 61 leads to the blister lock 69 on the inlet side, the channel 601 in the central spindle 60 leads from the other end to the blister lock 69 . The blister lock 69 is located at the transition from the polymerization part of the extruder to the polymer processing part of the extruder.

In section V liquid processing aids such. B. internal lubricants, stabilizers or crosslinking agents via a pump 42 with the associated line. The pump 42 forms a metering system. The processing aids added are dispersed in the melt by the first planetary roller extruder section.

A liquid blowing agent of the polymer melt can optionally be supplied selectively via the pump 45 as a further metering system.

In the subsequent, second planetary roller extruder section of section V, the melt is effectively mixed and tempered or cooled. The cooling takes place from the outside via the housing 40 and from the inside via the heat transfer on the central spindle. The special feature of the tempering of the central spindle is the division of the tempering areas into two parts via a separate supply and discharge of the liquid tempering medium at the respective central spindle end. Central spindle 60 with teeth 603 and planetary roller spindles 604 belong to the second planetary roller extruder section of section V. The temperature control belonging to the first planetary roller extruder section also serves for temperature control in the second planetary roller extruder section of section V.

Section VI serves to further equalize the temperature or cool the polymer melt to its dimensional stability. Section VI is formed by an extruder section with a single screw. The single screw consists of teeth on the central spindle 601 . For the temperature control of section VI, channels 57 in the housing 50 and 601 in the central spindle 60 belong.

The extruder is closed on the entry side with a cover 52 . The discharge takes place via a line 53 with a pump 54 . The pump 54 is designed as a gear pump. It in turn serves to regulate the pressure, to influence the dwell time and thus to influence the flow in section V and VI.

The extruder / pump system can be a pelletizing system or Tools for the production of profiles, sheets, flat foils or blown foils or be unfoamed.

Claims (28)

1. A process for processing plastic monomers, in particular olefins, into a semifinished product, a polymerization initially taking place and the polymers being further processed, characterized in that the polymerization takes place in an extruder (I, II, III, IV, V, VI). 2. The method according to claim 1, characterized by a pressure of at least 20 bar in the polymerization stage. 3. The method according to claim 1 or 2, characterized in that the polymerization stage a degassing stage is connected downstream. 4. The method according to claim 3, characterized in that a degassing agent is used becomes. 5. The method according to claim 4, characterized in that the degassing agent after the Polymerization is added in an intermediate stage before the degassing stage. 6. The method according to claim 4 or 5, characterized by a second degassing stage Post-degassing. 7. The method according to one or more of claims 1 to 6, characterized by the Use of a rotating multi-shaft extruder. 8. The method according to claim 7, characterized by a planetary roller extruder (I, II, III, IV, V, VI). 9. The method according to claim 8, characterized by the use of a Planetary roller section (II) for the polymerization stage, which is one of the general  Direction of flow of the melt through the extruder with the opposite conveying direction Has leakage flow in the direction of flow of the mass. 10. The method according to claim 9, characterized in that the number of planetary spindles Generation of the leakage flow is reduced. 11. The method according to claim 8 or 9, characterized by the use of a common central spindle ( 60 ) for several processing stages and the separation of the processing stages by blisters ( 62 , 69 ). 12. The method according to one or more of claims 8 to 11, characterized by a first, divided stage (I) for material intake and mixing, which is connected to the polymerization stage via a pump ( 64 , 65 ) and / or a mixer ( 66 ) . 13. The method according to one or more of claims 9 to 12, characterized by a common thrust ring for the planetary spindles ( 3 , 13 ) of the first stage (I) and the polymerization stage (II, III). 14. The method according to one or more of claims 8 to 13, characterized by the Use of a screw part between the polymerization stage (II) and the Degassing stage (III). 15. The method according to claim 9 or 14, characterized in that the extruder for Degassing completed with a blister and the degassing to the extruder housing a line is connected. 16. The method according to claim 15, characterized in that the degassing is formed by a container ( 31 ) to which a pump ( 32 , 34 ) is connected upstream and downstream. 17. The method according to claim 16, characterized in that the container ( 31 ) is provided with a gas suction pump. 18. The method according to claim 16 or 17, characterized by the use of a funnel-shaped container ( 31 ). 19. The method according to one or more of claims 1 to 18, characterized by additional material feed after material removal. 20. The method according to claim 19, characterized by a material feed by means of a Static mixers in a pump line between two processing stages. 21. The method according to claim 19, characterized by feeding a degassing agent. 22. The method according to one or more of claims 1 to 21, characterized in that polymerization and further processing in a common extruder (I, II, III, IV, V, VI) take place. 23. The method according to claim 22, characterized by the use of at least one Extruder section (V) for further processing, the one for general Flow direction of the melt in the opposite direction of flow and a leakage flow in has a general direction of flow. 24. The method according to claim 23, characterized in that the further processing a mixing and dispersing stage (V) and a cooling and homogenizing stage (VI) consists. 25. The method according to claim 23 and one or more of claims 1 to 22 and 25, characterized in that the extruder section for further processing and the extruder for degassing are designed as planetary roller extruders and the planetary spindles ( 23 , 43 ) of both extruders have common thrust rings . 26. The method according to one or more of claims 1 to 25, characterized by a melt discharge by means of a pump ( 54 ). 27. The method according to one or more of claims 1 to 26, characterized by an outlet-side mounting of the central spindle ( 60 ). 28. The method according to one or more of claims 1 to 26, characterized by different coolant and heating agent loading of the central spindle ( 60 ) in the polymerization area and processing area.