Method and apparatus for processing starting product

Abstract

A method for processing a starting product, preferably consisting of 5% to 30% polymer and 70% to 95% solvent, characterized by the following steps: supplying the starting product to a transport unit at a process temperature specific to each polymer, wherein the transport unit is generally a pump; passing the starting product through a one-way valve (9); heating and further pressurizing the starting product in a plate heat exchanger (2); adjusting the heated and pressurized starting product with a pressure-holding valve (8) and introducing it as a flash discharge into a kneader mixer (5) for processing as an intermediate product; and transporting it out as a product through a discharge section (7).

Description

Technical Field

[0001] The present invention relates to a method for processing a starting product according to the preamble of claim 1 and an apparatus according to the preamble of claim 6.

Background Art

[0002] Such methods are already known and are commonly used in a wide variety of forms and embodiments. For example, Patent Document 1 discloses that for processing a starting product, preliminary concentration or concentration is carried out between a stirred tank and an extruder, which is characterized by so-called flash evaporation. Flash evaporation is a thermal separation process in which part of the solvent in the product is directly transferred to the gas phase by a thermal flash due to a rapid pressure drop when the product enters the container. The term "flash" means rapid pressure reduction evaporation. This process has the advantage of having a high evaporation capacity as a result of the flash, resulting in a large vapor flow. However, it is also associated with cooling of the product, which, after flash evaporation, contains less solvent and is thus concentrated. Cooling is a direct result of the gas state equation and the energy extraction caused by the flash. Cooling also results in a decrease in the fluidity of the product. To empty the flash pot, the flash pot is usually characterized by sloping walls, which allows the product to flow by gravity towards the discharge opening of the flash pot. However, if the fluidity is too low, the flash pot will no longer empty, resulting in a fluidity limit. A larger flash will cool the product to such an extent that the fluidity limit is exceeded, the flash pot will not empty and will quickly clog. Therefore, as described in Patent Document 2, the fluidity limit of the product becomes the limit of the evaporation capacity in a conventional flash pot.

[0003] After the flash pod, a complex and energy-intensive reheating process must be carried out in the tubular heat exchanger. This carries a so-called fouling risk, which causes deposits to form on the surface of the heat exchange tubes before the starting product is fed to the extruder for residual degassing. This further increases labor input because the deposits must be removed from the tubes of the tubular heat exchanger, requiring the entire system to be shut down for this purpose, which again increases costs. Furthermore, due to its design, the tubular heat exchanger is not suitable for applying the desired pressure to the starting product so that a so-called explosive flash pod can occur inside the kneader mixer. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] European Patent No. 2328937 [Patent Document 2] European Patent No. 2328903 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a method and apparatus that improves upon the conventional kneader mixer to enable the processing of a starting product into a final product as cost-effectively as possible, the method and apparatus handling the processing of the product more efficiently, more compactly, less expensively, and more safely. [Means for solving the problem]

[0006] The features of claim 1 and the features of claim 6 are provided to solve the present objective.

[0007] Advantageous embodiments are described in the dependent claims.

[0008] A method for processing a starting product, preferably comprising 5% to 30% polymer and 70% to 95% solvent, according to the present invention, characterized by the following steps. - A step of supplying starting products to a transport unit at a process temperature specific to each polymer, wherein the transport unit is generally a pump. - A step of passing the starting product through a one-way valve in one direction in order to prevent a pressure drop resulting from backflow into the pump under any operating conditions. - A step of heating the starting product, preferably in a plate coil heat exchanger, to, for example, 180°C and then pressurizing it. The maximum temperature in this case depends on the type of polymer, the solvent, and the maximum allowable pressure in that part of the system. - A process in which the mixed, heated, and pressurized starting product is regulated by a pressure-holding valve and introduced into a kneader mixer as a flash release, and processed as an intermediate product. - A process of transporting the product through the discharge section.

[0009] The starting product may be, for example, rubber, thermoplastic elastomer, or thermoplastic resin. The composition of the starting product generally consists of 5% to 30% polymer and 70% to 95% solvent, but depending on the starting product, the component ratio of the starting product may fall outside this indicated range, and may take values ​​of 50% or slightly above.

[0010] The starting products are typically supplied to the feed pump from an intermediate container, ideally from a container equipped with a stirrer, to prevent separation.

[0011] The starting products pass through a one-way valve after leaving the supply pump. This is intended to prevent a pressure drop caused by backflow of the starting products through the pump, for example, when the pump is stopped.

[0012] In subsequent processes, the starting product is passed through / transported to / pushed through a plate coil heat exchanger by any means, heated to the maximum process temperature, and further pressurized. The plate coil heat exchanger may be a plate heat exchanger, which is determined by the size of the overall system and / or the total pressure resulting from the temperature rise.

[0013] Although using a plate coil heat exchanger as a pre-process for the kneader mixer is more economical and, depending on its design, allows for the accumulation of higher pressure in the starting product, this has not been considered in the prior art. In the prior art, plate heat exchangers have merely functioned as an intermediate process before supplying the starting product to pre-concentration or concentration in a so-called flashpot.

[0014] In the flashpot, some of the solvent had already evaporated in the initial step under high temperatures. However, a problem arose here: a pool formed in the funnel-shaped outlet of the flashpot, which needed to be kept flowable under all conditions. To ensure fluidity, the degree of concentration had to be limited depending on the viscosity of the resulting polymer solution. Subsequently, as known from the prior art, the concentrated starting product was transported by a gear pump to a tubular heat exchanger for reheating.

[0015] In the prior art, due to the pressure loss that occurs when the viscosity of the concentrated starting product increases, tubular heat exchangers were considered the only option for reheating. The drawback of tubular heat exchangers was that increasing the pressure of the concentrated starting product could only be achieved with considerable effort. However, increasing the pressure was, and still is, necessary to obtain effective flash release in the subsequent kneader mixer. The drawback of less effective flash release was compensated for in the prior art by placing an elaborate and expensive flash pod upstream.

[0016] Nowadays, it is possible to supply the starting product to the kneader mixer under high temperature and pressure conditions, particularly to achieve effective flash discharge in the kneader mixer through the use of a plate coil heat exchanger. This avoids the costs associated with flash pots, tubular heat exchangers, and the associated increased maintenance work and costs.

[0017] By omitting the flashpot and tubular heat exchanger, and by adapting the capabilities of the plate coil heat exchanger, it is possible to supply the starting product to the kneader mixer under high pressure and high temperature, thereby ensuring particularly effective, rapid, and safe flash release.

[0018] Plate heat exchangers play a crucial role here because the starting product is heated efficiently by the exchanger's geometric conditions, resulting in a shorter residence time for the starting product at high temperatures in the heat exchanger, thus eliminating the risk of polymer damage.

[0019] Another advantage of heated and pressurized starting products is that they allow pressure-holding valves to operate with fewer problems and failures. Pressure-holding valves, also known as equilibars, are configured to function as pressure-controlled capillaries. Two membranes pressed together by pressure are separated when the lateral pressure is greater than the set pressure between the two membranes. In plate coil heat exchangers, the advantage of pressurized starting products is that they always ensure sufficient lateral pressure to open the two membranes of the pressure-holding valve without causing uncontrolled pressure drops. Therefore, the user can intermittently supply the pressurized starting product in a desired manner to ensure controlled opening and closing of the two membranes. This was only possible in conventional tubular heat exchangers with considerable effort and additional steps, and was not always process-reliable.

[0020] A further advantage of the described method is that due to the high temperature and high pressure levels of the starting product, an effective flash discharge into the kneader mixer can be carried out. After the flash discharge in which a high proportion of the solvent is explosively discharged within the kneader mixer, an intermediate product is formed which is immediately cooled by flash evaporation upon entry into the kneader mixer. The intermediate product, which is now no longer dangerous with respect to the polymer temperature, can be subsequently processed just as effectively within the kneader mixer before being carried out as a product through the discharge section. This has the advantage that the kneader mixer can be optimally utilized according to its design. The high temperature and high pressure which correspondingly result in an effective flash discharge do not cause problems for the kneader mixer. Thus, in the prior art, the kneader mixer has not been able to optimally utilize its advantages.

[0021] In a preferred embodiment, the flash discharge is introduced into the kneader mixer in the process direction downstream of the vapor dome. In this case, there is a holding element within the kneader mixer which ensures the function of vapor removal by further conveying the intermediate product away from the vapor dome. Further, a processing element is arranged within the kneader mixer which converts the intermediate product into a product. The product is supplied to the discharge section by the discharge element within the kneader mixer.

[0022] The holding element, the processing element, and the discharge element are arranged on a shaft within the kneader mixer. On the shaft, the holding element is arranged first, then the processing element, and then the discharge element from the backplate of the kneader mixer towards the discharge section.

[0023] The device according to the invention is preferably provided for processing a starting product consisting of 5% to 30% polymer and 70% to 95% solvent, or, in exceptional cases as described above, a starting product consisting of more than 50% polymer at most. The polymer described above for the method equally applies to the device.

[0024] Furthermore, a plate heat exchanger is positioned between the conveying unit and the kneader mixer. This wording is intended to clarify that no tubular heat exchanger, flashpot, or any other concentration device is involved.

[0025] The starting product is of equal concentration between the conveying unit and the kneader mixer. Equivalent concentration means that the composition of the starting product remains essentially the same throughout the path from the conveying unit to the kneader mixer. Minor variations caused by existing safety devices, such as valves, are excluded from this.

[0026] A one-way valve, as described above, is positioned between the transport unit and the plate heat exchanger. The above description also applies to the apparatus.

[0027] A pressure-holding valve is positioned between the plate heat exchanger and the kneader mixer. The above description also applies to the apparatus.

[0028] The flash inlet is positioned between the steam dome and the discharge port of the kneader mixer. The above description also applies to the apparatus. This positioning of the flash inlet between the steam dome and the discharge port allows for advantageous use of the kneader mixer's structure. There are no elements such as a steam dome between the flash inlet and the discharge port that would weaken the kneader mixer's structure. The steam dome is positioned on the backplate side of the kneader mixer. The discharge port is positioned on the frontplate of the kneader mixer, opposite the steam dome. This gives the kneader mixer a barrel shape, which ensures further safety and process stability, especially in the case of flash discharge.

[0029] Furthermore, the use of a plate heat exchanger or a plate coil heat exchanger is requested for the apparatus according to the present invention described above.

[0030] In embodiments of the present invention, flash introduction may be performed at one or more locations in the kneader mixer. Flash introduction is defined as the immediate release of the starting product, which is under excessive pressure and temperature, upon entry into the process chamber or working chamber of the kneader mixer, resulting in the release of some of the solvent contained in the solution. Here, excessive pressure and temperature refer to the pressure and temperature of the starting product before entry into the kneader mixer, compared to the pressure and temperature inside the process chamber of the kneader mixer. Simultaneously with the pressure release, cooling of the starting product also occurs. This results in an explosive expansion of the starting product, thereby allowing the solvent to escape particularly well. This results in polymer particles. In the prior art, these polymer particles are then drawn into the vapor dome along with the solvent and accumulate on the dome walls. This leads to clogging of the vapor dome. Furthermore, the polymer accumulated on the dome walls is subjected to a permanent heat load, resulting in thermal damage to the polymer. If such thermally damaged particles fall back into the normal product in the kneader mixer, it can lead to undesirable contamination of the product, which in turn can lead to a decrease in the quality of the product. In the steam dome configuration described herein, this is prevented, allowing the kneader mixer to operate for longer periods without interference.

[0031] The flash inlet is operationally connected to a pressure-holding valve. By positioning the pressure-holding valve directly upstream of the flash inlet, it becomes possible to introduce the starting product into the kneader mixer in batches for explosive expansion, and then introduce the starting product of the next batch into the kneader mixer for explosive expansion. Of course, the batch introduction can be repeated.

[0032] Regardless of the dominant pressure and temperature within the kneader mixer, the starting products will have excess pressure and high temperature relative to them. This can lead to a flash that generates bubbles, but these bubbles are prevented from rising into the vapor dome by the retaining elements.

[0033] The steam dome is positioned within the area of ​​the backplate, or, in exceptional cases, flush with the backplate. The main consideration here is that the area below the steam dome within the kneader mixer housing should be kept as open as possible. In the configuration where the steam dome is positioned flush with the backplate, the area to be kept as small as possible. In embodiments where the steam dome is offset from the backplate toward the frontplate, cost reductions can be achieved in manufacturing, so both variations equally realize the concept of the present invention.

[0034] The closer the steam dome is positioned to the backplate, the less empty space is required within the kneader mixer. Less empty space allows for more efficient use of the kneader mixer. While a configuration where the steam dome is flush with the backplate optimally minimizes empty space, this is offset by increased manufacturing costs. Therefore, the decision of whether to position the steam dome relative to the backplate, and at what distance, is left to those skilled in the art.

[0035] Naturally, the kneader mixer according to the present invention is longer in its axial length than a kneader mixer that does not have a steam dome on the side of the first flash inlet opposite to the product flow direction. The compartment between the steam dome and the first flash inlet contains little to no product and is therefore used for steam removal but not for product processing that generates steam. However, in the kneader mixer according to the present invention, this cost disadvantage can be reduced by designing the steam dome not to be circular and by making its axial length shorter than its radial length. This minimizes the compartment between the backplate and the first flash inlet in the kneader mixer. Thus, the size difference is minimized when compared to a kneader mixer for a similar process but without embodiments of the present invention. The number of flash inlets may vary.

[0036] The term "product" always refers to the polymer-containing portion of the product stream, which is concentrated with increasing amounts of polymer as intended, while the solvent portion decreases as intended. Therefore, the product should be defined such that a constant ratio of polymer to solvent is achieved. The solvent portion may be zero.

[0037] In one embodiment, the steam dome and flash inlet are arranged adjacent to each other longitudinally in the Arctic region of the kneader mixer. The Arctic region should be considered as the upper region of the kneader mixer opposite the direction of gravity. Thus, the Antarctic region is the region of the kneader mixer arranged in the direction of gravity.

[0038] In another embodiment, the steam dome is located in the Arctic region of the kneader mixer, and the flash introduction section is located in the equatorial region of the kneader mixer.

[0039] Here, the equatorial region refers to the region where the center of the kneader mixer is located roughly midway along the surface extending from the Arctic region to the Antarctic region. In this case, the equatorial region is the starting point, and half the distance from the center to the Arctic region and half the distance to the Antarctic region are included. In this embodiment, the shaft is positioned so that the starting product introduced through the flash introduction section is discharged. For this purpose, as already described above, a retaining element positioned on the shaft is used.

[0040] The steam dome may be configured to be heatable. This allows for better use of the kneader mixer and prevents undesirable condensation of steam within the steam dome. Preferably, the temperature can be set independently of the temperature inside the kneader mixer, the temperature inside the housing jacket, or the temperature inside the shaft of the kneader mixer. This allows a specially selected temperature inside the walls of the steam dome to provide condensation designed to allow the resulting condensate flow (also called reflux) to flow down the walls of the steam dome into the intermediate products in the kneader mixer below, washing away any particulate matter that accumulates on the walls.

[0041] The steam dome compartment of the working chamber may include a temperature sensor, which can be used to measure the product temperature.

[0042] Further advantages, features, and details of the present invention are derived from the following description of preferred embodiments and drawings. [Brief explanation of the drawing]

[0043] [Figure 1] This figure shows the conventional device Vs. [Figure 2] This figure shows the apparatus Ve according to the present invention. [Modes for carrying out the invention]

[0044] Figure 1 shows the conventional device V. s This is shown. The device V s The starting product is subjected to processing between the container 18 and the kneader mixer 5. In this case, pre-concentration or concentration is performed. This pre-concentration is first carried out by heating in the plate heat exchanger 15. The starting product is then supplied to the pre-concentrator or flashpot 3. There, some of the starting product, especially the solvent, has already evaporated, resulting in a temperature drop of the starting product.

[0045] The resulting temperature drop is then compensated for again in the tubular heat exchanger 4. The reheated starting product is then supplied to the kneader mixer 5 via a throttle valve.

[0046] The resulting increase in the viscosity of the starting product is characteristic of the prior art. In this case, further attention must be paid to the fluidity of the starting product during the concentration process at the funnel-shaped outlet 16 of the flashpot 3.

[0047] A pool of material forms inside the funnel-shaped outlet 16. This pool must always maintain fluidity to prevent clogging of the outlet 16. Fluidity is hindered by evaporation and cooling that occur in the flashpot 3. If fluidity is not maintained, some of the pool may accumulate in the outlet 16 in the form of sediment, which will then have to be cleaned again at high cost. The flashpot must also have a sufficiently large volume because there is a risk of foam formation during the flash process. If the foam does not have a sufficient volume, there is a risk that the flash process cannot be maintained. In the prior art, this risk of foam formation is counteracted by the addition of additives, which further increases costs. A gear pump (not shown in detail) is connected to the outlet 16, which supplies the concentrated starting product to the complex and energy-intensive reheating in the tubular heat exchanger 4.

[0048] The tubular heat exchanger 4, in turn, presents a so-called fouling risk, which causes deposits to repeatedly form in the heat exchange tubes before the concentrated starting product is supplied to the kneader mixer 5. This further increases labor input because the deposits must be removed from the tubes of the tubular heat exchanger 4, requiring the entire system to be shut down for this purpose, which again increases costs.

[0049] Figure 2 shows the apparatus V according to the present invention. e This diagram shows a transport unit 1, followed by a one-way valve 9. The one-way valve 9 is connected to a plate heat exchanger 2 and a pressure holding valve 8, after which a kneader mixer 5 is positioned.

[0050] The kneader mixer 5 includes a back plate 14 and a front plate 17, with a shaft 13 positioned between them. On the shaft 13, in the direction of production flow, a holding element 10 is positioned first, followed by a processing element 11, and then a discharge element 12. The production direction refers to the direction extending from the back plate 14 to the front plate 17.

[0051] A flash inlet (not shown in more detail) is located between the steam dome 6 and the discharge 7 on the front plate 17 of the kneader mixer 5. "Between the steam dome 6 and the discharge 7" means that the flash inlet may be located across the entire surface of the kneader mixer 5, as long as the retaining element 10 can maintain its function of keeping the steam functional area of ​​the steam dome 6 open. It should be noted that the same applies to the function of the discharge element 12 in this context. In practice, the flash inlet should usually be located in the area of ​​the processing element 11 so that the processing element 11 can process the intermediate product into the product.

[0052] Referring to Figure 2, the operating method of the device according to the present invention will be described as follows.

[0053] First, the starting materials are mixed in the conveying unit 1 at a maximum temperature of 120°C. The mixed starting materials pass through a one-way valve 9 and are heated to 180°C and further pressurized in the plate coil heat exchanger 2. The mixed, heated, and pressurized starting materials are regulated by a pressure-holding valve 8 and introduced into the kneader mixer 5 as a flash discharge, where they are processed as an intermediate product and finally discharged as the final product through the discharge section 7.

[0054] Here, the flash release is introduced into the kneader mixer 5 between the steam dome 6 and the discharge section 7. After the flash release, the steam is drawn towards the steam dome 6, and the intermediate product is transported by the retaining element 10 away from the steam dome 6 or the steam functional area. Here, controlled spatial separation of the steam and intermediate product after the flash release takes place.

[0055] The processing element 11 located within the kneader mixer 5 is positioned between the holding element 10 and the discharge element 12, and converts the intermediate product into the final product.

[0056] The discharge element 12 then supplies the product to the discharge section 7, thereby enabling further flash discharge to continue in the region of the processing element 11. [Explanation of symbols]

[0057] 1. Conveyor Unit 2 Plate coil heat exchanger 3 Flashpot 4 tube heat exchanger 5. Kneader Mixer 6. Steam dome 7 Discharge section 8. Pressure holding valve 9. One-way valve 10 Retention elements 11 Processing elements 12 Emission elements 13 shafts 14 Backplate 15 Plate heat exchanger 16 Outlet 17 Front plate 18 Container V s Conventional technology apparatus V e Apparatus according to the present invention

Claims

1. A method for processing a starting product, preferably comprising 5% to 30% polymer and 70% to 95% solvent, characterized by the following steps: - A step of supplying the starting product to a transport unit at a process temperature specific to each polymer, wherein the transport unit is generally a pump, - A step of passing the starting product through a one-way valve (9), - A step of heating the mixed starting product in a plate heat exchanger and further pressurizing it, - A step of adjusting the mixed, heated, and pressurized starting product with a pressure-holding valve (8), introducing it into a kneader mixer (5) as a flash release, and processing it as an intermediate product, - A process of transporting the product out through the discharge section (7).

2. The method according to claim 1, characterized in that the flash discharge is introduced into the kneader mixer (5) between the steam dome (6) and the discharge section (7).

3. The method according to claim 1 or 2, characterized in that the holding element (10) in the kneader mixer (5) transports the intermediate product away from the steam functional area.

4. The method according to any one of claims 1 to 3, characterized in that the processing element (11) in the kneader mixer (5) converts the intermediate product into the product.

5. The method according to any one of claims 1 to 4, characterized in that the discharge element (12) in the kneader mixer (5) supplies the product to the discharge section (7).

6. An apparatus for processing a starting product preferably comprising 5% to 30% polymer and 70% to 95% solvent, characterized in that a plate heat exchanger (2) is positioned between a transport unit (1) and a kneader mixer (5), and the starting product is of equal concentration between the transport unit (1) and the kneader mixer (5).

7. The apparatus according to claim 6, characterized in that a one-way valve (9) is arranged between the transport unit (1) and the plate coil heat exchanger (2).

8. The apparatus according to claim 6 or 7, characterized in that a pressure-holding valve (8) is arranged between the plate coil heat exchanger (2) and the kneader mixer (5).

9. The apparatus according to any one of claims 1 to 8, characterized in that a flash introduction section is arranged between the steam dome (6) and the discharge section (7) of the kneader mixer (5).

10. The apparatus according to any one of claims 1 to 9, characterized in that the kneader mixer (5) includes a holding element (10), a processing element (11), and a discharge element (12) in the shaft (13).

11. The apparatus of claim 10, characterized in that, from the back plate (14) of the kneader mixer (5) toward the discharge section (7), the holding element (10) is first, then the processing element (11), and then the discharge element (12) is arranged on the shaft (13).

12. Use of a plate heat exchanger (2) for the apparatus according to any one of claims 6 to 11.

Images