DE102023106829A1 - Method and device for treating a starting product - Google Patents

Abstract

A process for treating a starting product consisting preferably of 5 - 30% polymer and 70 - 95% solvent is characterized by the following steps:- the starting product is fed into a conveying unit, which is usually a pump, at a process temperature specific to the respective polymer.- the starting product passes through a one-way valve (9),- the starting product is heated in a plate heat exchanger (2) and additionally pressure-increased,- the heated and pressure-increased starting product is introduced into a mixer kneader (5) as a flash discharge under the control of a pressure-maintaining valve (8) and processed as an intermediate product, and- transported away as a product through a discharge (7).

Description

Technical area

The invention relates to a method for treating a starting product according to the preamble of claim 1 and a device according to the preamble of claim 6.

State of the art

Such processes are already known and in use in a variety of forms and designs. For example, in the EP 2 328 937 B discloses that in order to process a starting product, a pre-concentration or concentration takes place between a stirred tank and an extruder, which is characterized by so-called flash evaporation. Flash evaporation is a thermal separation process through a sudden drop in pressure when the product enters a container, so that part of the solvent in the product passes directly into the gas phase through a thermal flash. Flash is understood to mean sudden flash evaporation. This process has the advantage of a high evaporation capacity as a result of the flash, resulting in large vapor flows. However, it is also associated with cooling of the product, which contains less solvent after flash evaporation and is therefore more concentrated. The cooling is a direct result of the gas equation or the energy removal caused by the flash. The cooling in turn means a reduction in the flowability of the product. In order for flash pots to empty, they are typically characterized by inclined walls so that the product can flow gravimetrically against the outlet opening of the flash pot. If the flow strength is too low, the flash pot will no longer empty, which leads to a flow limit. A larger flash would cool the product so much that the flow limit is exceeded and the flash pot does not empty and quickly becomes clogged. The flow limit of the product therefore means a limitation of the evaporation capacity of classic flash pots, as in the EP 2 328 903 B1 described.

After the flash pot, a complex and energy-intensive reheating process must take place in a tubular heat exchanger. This involves the risk of fowling, whereby deposits form on the surfaces of the heat tubes before the starting product is fed to the extruder for residual degassing. This in turn leads to increased work because the deposits have to be removed from the tubes of the tubular heat exchanger and the entire system has to be stopped for this, which in turn leads to increased costs. In addition, tubular heat exchangers are not designed to apply the desired pressure to the starting product so that the so-called explosive flash discharge can take place inside the mixer kneader.

Object of the invention

The object of the invention is to improve the mixing kneaders according to the prior art in such a way that a method and a device are made available in which the processing of a starting product into a final product is achieved as inexpensively as possible, whereby the method and the device handle the processing of a product more efficiently, smaller, more cost-effectively and at the same time also more safely.

Solution to the task

The features according to claim 1 and the features according to claim 6 lead to the solution of the problem.

Advantageous embodiments are described in the subclaims.

• - das Ausgangsprodukt wird bei einer dem jeweiligen Polymer spezifischen Prozesstemperatur in ein Förderaggregat geleitet, welches in der Regel eine Pumpe darstellt.
• - das Ausgangsprodukt passiert ein Einwegventil, unidirektional um einen Druckabfall als Folge einer Rückströmung in die Pumpe bei jedwedem Betriebszustand zu verhindern.
• - das Ausgangsprodukt wird vorzugsweise in einem Spiralplattenwärmetauscher auf beispielsweise 180°C erhitzt und zusätzlich druckerhöht. Die maximale Temperatur richtet sich hierbei nach Art des Polymers, des Lösungsmittels, sowie dem maximal zulässigen Druck in diesem Teil der Anlage.
• - das gemischte, erhitzte und druckerhöhte Ausgangsprodukt wird geregelt durch ein Druckhalteventil als Flash-Entladung in einen Mischkneter eingebracht und als Zwischenprodukt verarbeitet, und
• - als Produkt durch einen Austrag abtransportiert.

A process according to the invention for treating a starting product, which preferably consists of 5 - 30% polymer and 70 - 95% solvent, is characterized by the following steps:

• - the starting product is fed into a conveying unit, which is usually a pump, at a process temperature specific to the respective polymer.
• - the output product passes through a one-way valve, unidirectional, to prevent a drop in pressure due to backflow into the pump in any operating condition.
• - the starting product is preferably heated in a spiral plate heat exchanger to, for example, 180°C and the pressure is additionally increased. The maximum temperature depends on the type of polymer, the solvent and the maximum permissible pressure in this part of the system.
• - the mixed, heated and pressurised starting product is fed into a mixer kneader as a flash discharge controlled by a pressure control valve and processed as an intermediate product, and
• - transported away as a product through a discharge.

The starting product can be, for example, rubber or thermoplastic Elastomers or thermoplastics. The composition of the starting product usually consists of 5 - 30% polymer and 70 - 95% solvent, but depending on the starting product, it can also fall outside this proportion window of the components of the starting product and assume values of 50% or slightly more.

The starting product is fed to a feed pump, usually from an intermediate tank, ideally with an agitator to prevent segregation.

The starting product passes through a one-way valve after it has left the feed pump. This is intended to prevent a drop in pressure of the starting product in the pump, for example when the pump is in operation.

In a subsequent step, the starting product is guided/conducted/pressed or transported through a spiral plate heat exchanger in whatever form and is heated to the maximum process temperature and the pressure is also increased. Spiral plate heat exchangers can also be heat plate exchangers. This depends on the size of the entire system and/or the total pressure resulting from the increase in temperature.

The use of the spiral plate heat exchanger in the preliminary step to a mixer kneader has not been considered in the state of the art to date, although it is cheaper and, due to its design, more pressure can be built up in the starting product. The plate heat exchangers used in the state of the art to date only served as an intermediate step before the starting product could be fed to a pre-concentration or concentration in a so-called flash pot.

In the flash pot, part of the solvent was evaporated in a first step at elevated temperatures. This again presented the problem that a sump formed in the funnel-shaped outlet of the flash pot, which had to be kept flowable under all circumstances. In order to ensure flowability, the degree of concentration had to be limited depending on the viscosity of the polymer solution. A gear pump then pumped the starting product, which had been concentrated using the state of the art, to a tubular heat exchanger to reheat it there.

In the prior art, tubular heat exchangers were considered the only option for reheating due to the pressure loss that occurs with higher viscosity of the concentrated starting product. The disadvantage of tubular heat exchangers was that increasing the pressure of the concentrated starting product was very complex. However, increasing the pressure was and is necessary in order to achieve an effective flash discharge in the subsequent mixer kneader. The disadvantage of a less effective flash discharge was compensated in the prior art by installing the flash pot upstream, which was complex and expensive.

Now, by using the spiral plate heat exchanger, it is possible to feed a starting product at high temperature and high pressure to the mixer kneader in order to achieve a particularly effective flash discharge in the mixer kneader. This avoids the costs for the flash pot, the tubular heat exchanger and the associated increased maintenance work and costs.

By omitting the flash pot and the tubular heat exchanger and by adjusting the capacity of the spiral plate heat exchanger, it is possible to feed the starting product to the mixer kneader under high pressure and at high temperatures and to ensure a particularly effective, fast and safe flash discharge there.

The plate heat exchanger plays an important role here, since the starting product is heated highly efficiently due to the geometric conditions of the exchanger and the resulting short residence time of the starting product in the heat exchanger at high temperature means that the risk of polymer damage can be excluded.

Another advantage of the heated and pressure-increased starting product is that the pressure-maintaining valve can be operated with fewer problems and failures. The pressure-maintaining valve, also known as an equilibar, is designed in such a way that it is a pressure-controlled capillary. Two membranes that are closed to each other by pressure are spaced apart when the side pressure is greater than the preset pressure of the two membranes to each other. The advantage of the pressure-increased starting product in the spiral plate heat exchanger always ensures sufficient side pressure to open the two membranes of the pressure-maintaining valve without an uncontrolled drop in pressure occurring. The user can therefore pulse the pressure-increased starting product in the desired manner to ensure controlled opening and closing of the two membranes. With the state-of-the-art tube heat exchangers, this was very complex to achieve with additional steps and was not always process-reliable.

A further advantage of the process described is that, due to the high temperature and pressure levels of the starting product, an effective flash discharge can take place in the mixer kneader. After the flash discharge, in which a high percentage of the solvent is explosively released in the mixer kneader, an intermediate product is created which is immediately cooled by flash evaporation upon entering the mixer kneader. The intermediate product, which is now non-critical in terms of polymer temperature, can also be effectively processed further in the mixer kneader before it is transported away as a product through a discharge. This has the advantage that the mixer kneader can be used more optimally due to its design. High temperatures and pressures, which lead to a correspondingly effective flash discharge, are not a problem for a mixer kneader. In the prior art, the mixer kneader could therefore not make optimal use of its advantages.

In a preferred embodiment, the flash discharge is introduced into the mixing kneader in a process direction after the vapor dome. In this case, there are holding elements in the mixing kneader that additionally transport the intermediate product away from the vapor dome so that the vapor removal function is reliably guaranteed. Furthermore, processing elements are arranged in the mixing kneader that convert the intermediate product into the product. The product is fed to the discharge by means of discharge elements in the mixing kneader.

The clearance elements, the processing elements and the discharge elements are arranged on a shaft in the mixer kneader. On the shaft, from a rear plate of the mixer kneader to the discharge, first the clearance elements, then the processing elements and then the discharge elements are arranged.

A device according to the invention serves to treat a starting product consisting preferably of 5 - 30% polymer and 70 - 95% solvent or, in exceptional cases as mentioned above, up to over 50% polymer. The polymers mentioned above for the process also apply to this device.

Furthermore, the plate heat exchanger is arranged between the conveying unit and the mixer kneader. This wording is intended to clarify that no tubular heat exchanger or flash pot or other concentration device is installed in between.

The starting product has the same concentration between the conveyor unit and the mixer kneader. Equal concentration means that the composition of the starting product remains essentially the same on the way from the conveyor unit to the mixer kneader. This excludes minor fluctuations that arise, for example, from existing safety devices such as valves or the like.

The unidirectional valve described above is arranged between the conveyor unit and the plate heat exchanger. The statements above should also apply to the device.

A pressure holding valve is arranged between the plate heat exchanger and the mixer kneader. The statements above should also apply to the device.

The flash inlet is arranged between a vapor dome and the discharge of the mixer kneader. The statements above should also apply to the device. This arrangement of the flash inlet between the vapor dome and the discharge allows the design of the mixer kneader to be advantageously used. There is no element between the flash inlet and the outlet that weakens the structure of the mixer kneader, such as the vapor dome. The vapor dome is arranged towards the rear plate of the mixer kneader. The discharge is arranged opposite on a front plate of the mixer kneader. This creates a cannon barrel shape for the mixer kneader, which ensures additional safety and process stability, especially in the case of flash discharges.

In addition, the use of a plate heat exchanger or spiral plate heat exchanger is claimed for the device according to the invention described above.

In the embodiment according to the invention, the flash entry can take place via one or more points in the mixer-kneader. A flash entry is defined by the fact that a starting product under excess pressure and excess temperature immediately relaxes when it enters a process chamber or working chamber of the mixer-kneader and, as a result, part of the solvent contained in a solution is released. The excess pressure and excess temperature refer to the pressure and temperature of the starting product before entering the mixer-kneader, compared to the pressure and temperature in the process chamber of the mixer-kneader. At the same time as the pressure is relaxed, the starting product also cools down. This leads to an explosive expansion of the starting product, which allows the solvent to escape particularly well. This causes the polymer to atomize. This atomization of the polymer is in turn State of the art technology draws the solvent into the vapor dome and settles on the wall of the dome. This can even lead to the vapor dome becoming blocked. The polymer that settles on the wall of the dome is also subject to permanent temperature stress, which results in thermal damage to this polymer. If such thermally damaged particles fall back into the regular product in the mixer kneader, this results in undesirable contamination of the product, which in turn can result in a reduction in product quality. This is prevented by the vapor dome arrangement described here, so that the mixer kneader can operate trouble-free for longer with this vapor dome arrangement.

The flash inlet is operatively connected to the pressure-maintaining valve. The arrangement of the pressure-maintaining valve immediately before the flash inlet makes it possible to introduce the starting product into the mixer kneader in tranches and to enable explosive expansion and then to introduce the next tranche of the starting product into the mixer kneader for explosive expansion, whereby the introduction of the tranches can of course also overlap.

Regardless of the pressure and temperature in the mixer kneader, the starting product has an excess pressure and an increased temperature relative to it. This can lead to a flash that generates foam that is prevented from rising into the vapor dome by the release elements.

The vapor dome is arranged in an area of the back plate or, in exceptional cases, flush with the back plate. The main aim here is to keep the area below the vapor dome in the mixer housing as free as possible. If the vapor dome is arranged flush with the back plate, the area to be kept free is kept as small as possible. In the version in which the vapor dome is arranged offset from the back plate in the direction of the front plate, cost savings can be achieved during production, so that both variants implement the invention idea on an equal footing.

The closer the vapor dome is to the back plate, the less space in the mixer kneader that needs to be kept free. The less space that needs to be kept free, the better the mixer kneader can be used. If the vapor dome is arranged flush with the back plate, the space that needs to be kept free is optimally reduced, but this is offset by the higher manufacturing costs. Consequently, the specialist must determine whether and how far the vapor dome should be from the back plate.

Naturally, the mixing kneader according to the invention is longer in its axial extension than mixing kneaders without a vapor dome on the side facing away from the first flash inlet in the direction of product flow. The section between the vapor dome and the first flash inlet contains little or no product and is thus used for vapor removal but not for vapor-generating product processing. However, this cost disadvantage can be reduced in the mixing kneader according to the invention by making the vapor dome shorter in its axial extension than in its radial extension, rather than circular. This minimizes the section between the back plate and the first flash inlet in the mixing kneader. This minimizes the size difference compared to a mixing kneader for similar processes but without the inventive design. The number of flash inlets can vary.

"Product" always refers to the polymer-containing part of the product stream, which is enriched with more and more polymer as intended, while the solvent content is reduced as intended. The product must therefore be defined in such a way that a certain ratio of polymer to solvent is achieved. The proportion of solvent can also be 0.

In one embodiment, the vapor dome and the flash inlet are arranged next to one another in a north pole area of the mixing kneader in a longitudinal extension. The north pole area is assumed to be the area of the mixing kneader that opposes the direction of gravitational force in the upper area. A south pole area would therefore be the area of the mixing kneader arranged in the direction of gravitational force.

In a further embodiment, the vapor dome is arranged in the north pole region of the mixing kneader and the flash entry is arranged in an equatorial region of the mixing kneader.

The equatorial region here means that it is approximately the region whose center is arranged in the middle of the surface of the mixer kneader, running from the north pole region to the south pole region. Half of the path from the center to the north pole region and to the south pole region is covered by the equatorial region. In this embodiment, the shaft is arranged in such a way that the starting product introduced by the flash feed is transported away. The clearance elements arranged on the shaft, as described above, are used for this purpose.

The vapor dome can be designed to be heated. This allows better use of the mixer and prevents unwanted condensation of the vapor in the vapor dome. Preferably, the temperature can be set independently of the temperature in the mixer or in a housing shell or in the shaft of the mixer. This makes it possible to ensure, by means of a specifically selected temperature in a wall of the vapor dome, a condensation such that the resulting condensate flow (also called reflux) along the walls of the vapor dome downwards into the intermediate product in the mixer and cleans it of fine particles that settle there.

The vapor dome section of the working chamber can have a temperature sensor. This can be used to measure the product temperature.

Character description

• 1 zeigt eine Vorrichtung V_s nach dem Stand der Technik;
• 2 zeigt eine erfindungsgemässe Vorrichtung V_e.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings, which show in:

• 1 shows a device V _s according to the prior art;
• 2 shows a device V _e according to the invention.

Example

In 1 a device V _s according to the prior art is described. This device Vs is used to process a starting product between a container 18 and a mixer kneader 5. A pre-concentration or concentration takes place. This pre-concentration is initially carried out by heating in a plate heat exchanger 15. The starting product is then fed to a pre-con or a flash pot 3. There, part of the starting product, in particular the solvent, evaporates, resulting in a drop in the temperature of the starting product.

This temperature drop is then compensated for in a tubular heat exchanger 4. The reheated starting product is then fed to the mixer kneader 5 via a dosing valve.

The resulting increase in the viscosity of the starting product is characteristic of the state of the art. In addition, attention must be paid to the flowability of the starting product during concentration in a funnel-shaped outlet 16 of the flash pot 3.

A sump forms in the funnel-shaped outlet 16. This sump must always remain fluid so that the outlet 16 does not become blocked. The evaporation and cooling that takes place in the flash pot 3 counteracts the flowability. If this does not happen, parts of the sump can settle in the outlet 16 in the form of deposits, which then have to be cleaned again at great expense. The flash pot must also be provided with a sufficiently large volume, as there is a risk of foam formation during the flash process. If the foam does not have sufficient volume, there is a risk that the flash process cannot be maintained. This risk of foam formation is additionally counteracted in the prior art by adding cost-increasing additives. The outlet 16 is connected to a gear pump (not shown in detail), which feeds the concentrated starting product to a complex and energy-intensive reheating process in a tubular heat exchanger 4.

The tubular heat exchanger 4, in turn, involves the so-called fowling risk, whereby a coating repeatedly forms on the heat tubes before the concentrated starting product is fed to the mixing kneader 5. This in turn leads to increased work input because the coating has to be removed from the tubes of the tubular heat exchanger 4 and the entire system has to be stopped for this, which in turn leads to increased costs.

2 shows a device V _e according to the invention. The conveying unit 1 is shown there, to which a one-way valve 9 is connected. A plate heat exchanger 2 and a pressure holding valve 8 are connected to the one-way valve 9, before the mixing kneader 5 is then arranged.

The mixing kneader 5 has a rear plate 14 and a front plate 17, between which a shaft 13 is arranged. On the shaft 13, first of all, clearance elements 10, processing elements 11 and discharge elements 12 are arranged in the production direction. Production direction means the direction starting from the rear plate 14 to the front plate 17.

A flash inlet, not shown in more detail, is arranged between a vapor dome 6 and a discharge 7 on the front plate 17 of the mixing kneader 5. “Between the vapor dome 6 and the discharge 7” means that the flash inlet can be arranged over an entire surface of the mixing kneader 5, as long as the clearance elements 10 fulfill their function of keeping a vapor function area clear. area of the vapor dome 6. In this context, it should also be noted that the same applies to the function of the discharge elements 12. In fact, the flash entry must be provided regularly in the area of the processing elements 11 so that the processing elements 11 can process the intermediate product into a product.

• Zunächst wird das Ausgangsprodukt in dem Förderaggregat 1 bei maximal 120°C vermischt. Das gemischte Ausgangsprodukt passiert das Einwegventil 9 und wird in dem Spiralplattenwärmetauscher 2 auf 180°C erhitzt und zusätzlich druckerhöht. Das gemischte, erhitzte und druckerhöhte Ausgangsprodukt wird geregelt durch das Druckhalteventil 8 als Flash-Entladung in den Mischkneter 5 eingebracht, als Zwischenprodukt verarbeitet und zuletzt als Produkt durch den Austrag 7 abtransportiert.

Referring to the 2 The functioning of the device according to the invention is explained as follows:

• First, the starting product is mixed in the conveyor unit 1 at a maximum of 120°C. The mixed starting product passes through the one-way valve 9 and is heated to 180°C in the spiral plate heat exchanger 2 and additionally pressure-increased. The mixed, heated and pressure-increased starting product is introduced into the mixing kneader 5 as a flash discharge controlled by the pressure-maintaining valve 8, processed as an intermediate product and finally transported away as a product through the discharge 7.

The flash discharge is introduced between a vapor dome 6 and the discharge 7 into the mixing kneader 5. After the flash discharge, the vapors are drawn in the direction of the vapor dome 6 and the intermediate product is transported away from the vapor dome 6 or the vapor function area by the clearance elements 10. A controlled spatial separation of vapors and intermediate product takes place here after the flash discharge.

The processing elements 11 present in the mixing kneader 5, which are arranged between the holding elements 10 and the discharge elements 12, convert the intermediate product into the product.

The discharge elements 12 in turn feed the product to the discharge 7, so that further flash discharges can occur in the area of the processing elements 11.

List of reference symbols

1

Conveyor unit

2

Spiral plate heat exchanger

3

Flash Pot

4

Tubular heat exchanger

5

Mixer kneader

6

Brüdendom

7

Discharge

8

Pressure holding valve

9

One-way valve

10

Clearance elements

11

Processing elements

12

Discharge elements

13

Wave

14

Back plate

15

Heat plate exchanger

16

Sequence

17

Front panel

18

container

vs

State of the art device

Ve

device

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 2328937 B [0002]
• EP 2328903 B1 [0002]

Claims (12)

A process for treating a starting product, which preferably consists of 5 - 30% polymer and 70 - 95% solvent, is characterized by the following steps: - the starting product is fed into a conveying unit, which is usually a pump, at a process temperature specific to the respective polymer; - the starting product passes through a one-way valve (9), - the mixed starting product is heated in a plate heat exchanger and the pressure is additionally increased. - the mixed, heated and pressure-increased starting product is introduced into a mixer kneader (5) as a flash discharge under the control of a pressure-maintaining valve (8) and processed as an intermediate product, and - transported away as a product through a discharge (7). Procedure according to Claim 1 , characterized in that the flash discharge is introduced into the mixing kneader (5) between a vapor dome (6) and the discharge (7). Procedure according to Claim 1 or 2 , characterized in that in the mixing kneader (5) clearance elements (10) transport the intermediate product away from a vapor discharge area. Method according to one of the preceding claims, characterized in that in the mixing kneader (5) processing elements (11) convert the intermediate product into the product. Method according to one of the preceding claims, characterized in that in the mixing kneader (5) discharge elements (12) feed the product to the discharge (7). Device for treating a starting product consisting of preferably 5 - 30% polymer and 70 - 95% solvent, characterized in that a plate heat exchanger (2) is arranged between a conveying unit (1) and a mixing kneader (5), the starting product having the same concentration between the conveying unit (1) and the mixing kneader (5). Device according to Claim 6 , characterized in that a one-way valve (9) is arranged between the conveyor unit (1) and the spiral plate heat exchanger (2). Device according to Claim 6 or 7 , characterized in that a pressure holding valve (8) is arranged between the spiral plate heat exchanger (2) and the mixing kneader (5). Device according to one of the preceding claims, characterized in that a flash inlet is arranged between a vapor dome (6) and a discharge (7) of the mixing kneader (5). Device according to one of the preceding claims, characterized in that the mixing kneader (5) has clearance elements (10), processing elements (11) and discharge elements (12) on a shaft (13). Device according to Claim 10 , characterized in that from a rear plate (14) of the mixing kneader (5) to the discharge (7), first the clearance elements (10), then the processing elements (11) and subsequently the discharge elements (12) are arranged on the shaft (13). Use of a plate heat exchanger (2) for a device according to the Claims 6 until 11 .

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