DE102009007641A1 - Separating material mixtures, particularly solutions, suspensions and emulsion, involves dividing main vaporization and degasification, where main vaporization and degasification are performed in separate mixing kneader - Google Patents

Abstract

Material mixtures separation involves dividing main vaporization and a degasification, where the main vaporization and the degasification are performed in separate mixing kneader (4,12). The material mixture is concentrated before the main vaporization. The concentrated mixture is fed into a pre-concentrating kneading machine and evaporated residual content of volatile components, where the material mixture is concentrated over a discharge (8).

Description

The The invention relates to a process for continuous thermal Separation of mixtures, in particular of solutions, Suspensions and emulsions.

STATE OF THE ART

The industrial production of mixtures, but in particular by no means limiting the production of polymers, in particular of homo- and co-polymeric elastomers, carried out by Polymerization reactions in the so-called solution polymerization process, being for better mixing through use Solvent lowered the viscosity in the stirred tank reactor becomes. From the resulting polymer solution must Solvents are separated. The removal of this diluent takes place today in the coagulation and stripping process, with large Quantities of energy in the form of stripping steam (wet process) used become. After this step, the polymer must be replaced by a mechanothermal Drying consuming to be separated from the stripping medium. The distance the stripping medium is carried out in two stages via a mechanical Squeezing and atmospheric drying. While These processes are very much energy in the form of water vapor and a lot of washing water is needed, resulting in high wastewater volumes and, due to the large open aggregates, high emissions leads. In parallel, the stripping agent and the solvent must again very expensive to be separated from each other. The existing one Procedure is thus a very energy efficient, one of high emission and investment costs characterized ineffective Technology. The existing technology is aware of the risks are low and the catalyst systems as well as the processing are tailored to this technology.

In the US Pat. No. 3,683,511 describes a method which has been specially developed for the degassing of polybutadiene-containing polymer solutions and solutions where more than 50% of butadiene is polymerized in the polymer. According to the invention, the removal of the solvent is achieved by adding water into the extruder.

Similar solutions are also used in the US 4,909,898 A and the EP 0 262 594 B1 presented. In these publications, the polymer solution is placed in the mixer / kneader zone and the solvent is evaporated at the temperature at which the surface of the heat transfer surface has a higher temperature than the boiling temperature of the lowest-boiling solvent. In this case, a immiscible with the polymer liquid is also added, in this case water.

In the US 6 150 498 A and the EP 0 910 588 B1 A method for degassing EPDM and similar polymers such as polyethylene, polypropylene, ethylene propylene rubber and polystyrene with a thermal dryer is presented. In this case, the thermal dryer consists of a horizontal shell and a rotating shaft within the shell, disc elements which are arranged on the shaft and having stationary counter-pins which are mounted on the inside of the shell. The application of such a technology is limited to polymer solutions that can absorb larger amounts of dissipation energy, otherwise the polymer will overheat or the degassing performance will be insufficient.

Next the energetic aspects and the high emissions are above all the high cost of water separation for the modern water-sensitive anionic polymerization and the processing of extremely temperature-sensitive products Driving force to modernize the process.

task

task It is the object of the present invention to reduce the energy or water vapor and reduce water consumption to the energy balance of the process improve the efficiency of new processes. In parallel, temperature-sensitive mixtures can which are not compatible with existing technology or can be produced only with the addition of special antioxidants. The new treatment process (dry process) has the goal of the Process more energy efficient, greener and more flexible too do.

Solution of the task

to Solution to the task that leads to the continuous Treatment of the mixtures in a main evaporation and degassing is divided, with the main evaporation and the degassing in each take place a separate mixing kneader.

It is particularly and preferably a method and an apparatus for the continuous treatment of a polymer solution by direct evaporation of solvent, monomer, catalyst, initiator or reaction residues from the polymerization of elastomer-containing polymer solutions in mixing kneaders with one or two stirrer shafts. In this case, a low-viscosity polymer solution is firstly treated in an evaporation loop, secondly in an evaporative mixing kneader and thirdly in a degassing kneader. This method is especially suitable for temperature-sensitive polymers that may be treated up to a maximum of 160 ° C. It However, it should be expressly stated that the method according to the invention relates to the corresponding treatment of other mixtures, irrespective of whether they are solutions, suspensions or emulsions. All corresponding mixtures of substances are intended to be encompassed by the present invention.

Prefers is, a low-viscosity mixture first in Pre-concentrate an evaporation loop with contact heat and then as a viscous solution in a Verdampfungsmischkneter so dose that viscosity in this aggregate is sufficient to the majority about friction the evaporation energy ready to provide over 90% of the solution supplied fluids (eg solvent) to evaporate. The registered thermal and mechanical energy is directly used for the evaporation of the solvent, the pressure level is set so that the maximum mixture temperature due to the evaporative cooling of the solvent is not exceeded becomes.

Out This evaporation kneader is a mixture of about 10% residual moisture (For example, solvent) discharged and in a degassing dosed, there to the final desired residual moisture (eg, residual solvent concentration) to be evaporated.

to Improving the degassing process will be small amounts of a fluid (For example, water) dosed into the degassing, by evaporation on the surface of the substance mixture for a surface renewal registered mechanical energy remove again, so that the substance mixture temperature exactly can be adjusted, for. B. overheating and thermal To avoid damage.

Parallel The resulting fluid vapor (eg water vapor) in the vapor space helps to do this as a stripping medium, partial pressure lowering and can, in contrast to contaminated hot air (hot air) of the existing Process, be completely condensed with the solvent.

The found method is suitable for high temperature sensitive and less sensitive mixtures, such as for the direct evaporation of butadiene- and butyl-based elastomers, such as BR, SBR, SBS, SIS, SBM HBR, NBR or EPDM-derived Elastomers and for evaporation of copolymer solutions, which are directly co-polymerized or from two polymer solutions be mixed before direct evaporation, such. B. polymer solutions from mixed SBS and SBR solutions, ie difficult to mix elastomers and plastomers.

by virtue of of the closed system of the dry process can over 98% of the solvent in the circulation without expensive water separation recycled and the solvent emissions or the polluted wastewater and exhaust gas quantity are enormously reduced.

opposite The cited prior art makes it possible for the invention elastomer-containing polymer solutions by means of extruders or kneaders especially pure polybutadiene solutions, directly and without further Auxiliary components, to any residual solvent contents to degas.

The mixing kneaders with which the present invention has been tested are one or two-wave, equal or opposite, and are described in the patents DE 2 349 106 C . EP 0 517 068 A1 . EP 0 853 491 . DE 101 50 900 C1 ( PTC / EP 02/11578 ; WO 03 / 035235A1 ) described in detail. They are produced up to a size of 25,000 liters of free volume and can be used for direct evaporation.

The Subclaims describe advantageous embodiments of the inventive method.

figure description

Further Advantages, features and details of the invention will become apparent the following description of a preferred embodiment as well as from the drawing; this shows in her single figure a block diagram representation of a process structure of a inventive multi-stage system for continuous thermal Separation of mixtures, in particular for the treatment of polymer solutions.

Any polymer solution 1 Becomes first an evaporator 2 fed. In this evaporator 2 it may, for example, be an evaporation tube loop. In the evaporator 2 takes place a pre-concentration. The low-viscosity, mostly directly from the solvent polymerization polymer solution having about 5 to 50% polymer content is concentrated by a thermal treatment to about 20 to 80%. The vaporized volatiles (vapors) are withdrawn from the evaporator and a condenser 3 fed.

The concentrated polymer solution then passes out of the evaporator 2 in an evaporation kneader 4 , This is preferably a horizontal mixing kneader with one or more horizontally arranged kneading shafts, on which there are corresponding kneading elements. This kneading shafts is a drive 5 assigned.

The concentrated polymer solution may be attached to one or more Make successive or simultaneous dosing. there should the metered amount of the polymer solution in each case by a predetermined product temperature can be controlled.

The evaporation kneader 4 again sits a Brüdendom 6 to deduct the volatile constituents, which in turn are in a condenser 7 condensed and discharged.

The now in the evaporation kneader 4 concentrated polymer solution is via a polymer discharge 8th continuously discharged. It should be from the evaporation kneader 4 discharged polymer solution by a pressure build-up, preferably by a gear pump 9 be brought to a pressure of more than 10 bar. If necessary, a liquid or gaseous additive is metered into the pressurized polymer solution and placed in a mixing tube 10 , a static or dynamic mixer mixed as homogeneously as possible in the polymer solution. This mixture is then in the present embodiment by a nozzle plate 11 in a downstream degassing kneader 12 vented for degassing, whereby an increase of the particle surface takes place by a sudden evaporation of the volatile constituents and the additives. This happens analogously to the so-called popcorn effect.

In the degassing kneader produces a plug flow for the polymer solution, which gives a continuous active surface renewal subject and thereby mechanical dissipation energy in the polymer solution is absorbed.

During degassing, the polymer solution temperature in the degassing kneader is maintained below the polymer degradation temperature by the addition of readily volatilizable, non-polymer soluble additives in the degasifier at one or more locations. This is through the arrows 13 shown. The whole thing is controlled by temperature measuring instruments, over which also the corresponding metered amount of additive for evaporative cooling is controlled.

On the degassing kneader 12 another brother dome is sitting 14 on, in turn, the volatile constituents are discharged from the degassing.

To the degassing kneader 12 closes another polymer discharge 15 at, wherein the now finished polymer composition by a further pressure build-up, preferably by a further gear pump 16 , is brought to a pressure of more than 10 bar.

This polymer mass then passes into a cutting device 17 in which it is preferably granulated or brought to some other desired shape. This granulate is then discharged. LIST OF REFERENCE NUMBERS 1 polymer solution 2 Evaporator 3 capacitor 4 Verdampfungskneter 5 drive 6 vapor dome 7 capacitor 8th polymer discharge 9 gear pump 10 mixing tube 11 nozzle plate 12 Entgasungskneter 13 arrow 14 vapor dome 15 discharge 16 gear pump 17 cutter

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 3683511 A [0003]
• - US 4909898 A [0004]
• EP 0262594 B1 [0004]
• - US 6150498 A [0005]
• - EP 0910588 B1 [0005]
• - DE 2349106 C [0017]
• EP 0517068 A1 [0017]
• EP 0853491 [0017]
• DE 10150900 C1 [0017]
• - EP 02/11578 [0017]
• WO 03/035235 A1 [0017]

Claims (66)

Process for the continuous thermal separation of mixtures, in particular solutions, suspensions and emulsions, characterized in that the continuous treatment of the mixtures is subdivided into a main evaporation and a degassing, wherein the main evaporation and the degassing take place in a separate mixing kneader. Method according to claim 1, characterized in that that the main evaporation is preceded by a pre-concentration. A method according to claim 1 or 2, characterized in that the volatile constituents of the substance mixture ( 3 ) are almost completely separated with the addition of small amounts of additives which are metered in over the length of the mixing kneader. Method according to claim 3, characterized that the amount of additives is adjusted so that the energy balance from dissipated kneading energy, contact heating or cooling through shaft and housing of the mixing kneader and evaporative cooling of the additive and other volatile components Temperature yield, which is an efficient removal of the unwanted Volatile components from a pasty mixture ensures. Method according to claim 3 or 4, characterized that the mixing of the additive, the emergence of germs for Favored microbubbles in the mixture of substances, the unwanted volatiles record and z. B. by a rotating shaft to the substance mixture surface be transported, whereby the degassing power to unwanted Volatiles significantly favored becomes. Method according to one of claims 3 to 5, characterized in that the addition of the additives more favorable Product behavior, in particular with regard to surfaces, Viscosity od. Like. Produced. Method according to at least one of the claims 3 to 6, characterized in that the added additive evenly over the length or punctually distributed over the mixture or over the length of the mixing kneader is metered. Method according to at least one of the claims 1 to 7, characterized in that the pressure in a gas space of the kneader is varied periodically to the creation of microbubbles in addition to favoring in the melt and thus additionally increasing the degassing performance. Method according to at least one of the claims 3 to 8, characterized in that by the addition of small Quantities of additives does not chemically change the substance mixture, no application-related damage and change the substance mixture properties occur. Method according to one of claims 1 to 9, characterized in that it is in the mixtures elastomer-containing and plastomer-containing homo-polymer solutions, Polymer solution mixtures or copolymer solutions from solution polymerization, such as butadiene or butyl homopolymer or copolymer polymer solutions, Polyisoprene or polyethylene propylene solutions. Method according to claim 10, characterized in that that the polymer solutions are after solvent polymerization in any ratio mixed polymer solutions is. Method according to claim 10 or 11, characterized that at least one polymer solution is a Solution of an elastomeric polymer is. Method according to at least one of the claims 1 to 12, characterized in that it is in the mixture is a temperature-sensitive polymer. Method according to at least one of the claims 1 to 13, characterized in that it is to be separated at the Volatile components to solvents or solvent systems or unreacted monomers, catalysts, initiators, stabilizers, Antioxidant or polymerization residues. Method according to at least one of claims 2 to 14, characterized in that the preconcentration of the low-viscosity substance mixture with 5 to 50% substance content by a thermal treatment, preferably, but not necessarily, in an evaporation tube loop ( 2 ) is concentrated to a still pumpable, with higher concentrated mixture of 20 to 80%. A method according to claim 15, characterized in that the concentrated substance mixture in one of the pre-concentration downstream evaporation kneader ( 4 ) is metered to the main evaporation and evaporated to a residual content of volatile components of less than 20%, preferably from 2 to 12%. A method according to claim 16, characterized in that the concentrated Stoffge mixed into the evaporation kneader ( 4 ) is metered at one or more points at the same time. Method according to claim 16 or 17, characterized that the metered amount of the mixture in each case by a temperature is controlled. Method according to one of claims 16 to 18, characterized in that by the distribution of the concentrated substance mixture in the evaporation kneader ( 4 ) creates a homogeneous highly viscous mixture in which large amounts of mechanical dissipation energy can be entered by friction. Method according to one of claims 16 to 19, characterized characterized in that by the distribution of the concentrated Substance mixture in the evaporation kneader foam formation is suppressed and very high specific contact heat per heating surface unit is reached. Method according to at least one of claims 1 to 20, characterized in that the evaporated volatiles, called vapors, withdrawn via a Brüdenstutzen from the evaporation kneader, in the Brüdendom ( 6 ) and condensable components in a condenser connected via a vapor tube ( 7 ), preferably a spray condenser or an air-cooled condenser, almost completely precipitated and discharged from the closed system and the non-condensable components are supplied to the technological further treatment. Method according to at least one of the claims 1 to 21, characterized in that a process pressure is selected is that the evaporative cooling of the volatile Ingredients damage to the mixture due to overheating prevents, preferably between 10 and 2000 mbar abs. Method according to at least one of claims 1 to 22, characterized in that a heating temperature of the evaporation kneader ( 4 ) and the maximum substance mixture temperature at any point in time to reach or exceed the damage temperature and preferably between 60 ° C and 160 ° C are set. Method according to at least one of claims 1 to 23, characterized in that in the evaporation kneader ( 4 ) concentrated mixture via a directly integrated in the evaporation kneader discharge ( 8th ) is continuously discharged. A method according to claim 24, characterized in that the from the evaporation kneader ( 4 ) discharged substance mixture by a pressure build-up, preferably by a gear pump ( 9 ), to a pressure of more than 1 bar. Method according to claim 25, characterized in that that the mass balance in the mixing kneader by means of the speed of Gear pump is kept constant, so the output from the kneader and the constancy of the mass flow are separated, the gear pump responsible for the constancy of the mass balance. Method according to claim 25 or 26, characterized that the discharge integrated directly in the mixing kneader produces so much pressure builds up that the gear pump has sufficient form and approximate is uniformly filled, as well as this connection is regulated, but does not necessarily have to be regulated. Method according to at least one of the claims 25 to 27, characterized in that in the pressurized Mixture of a liquid or gaseous additive is dosed. A method according to claim 28, characterized in that the dosed in the mixture additive in a mixing tube ( 10 ), a static or dynamic mixer is mixed as homogeneously as possible in the mixture. Method according to claim 28 or 29, characterized that the liquid additive is a freely selectable temperature has, preferably between 10 ° C and 160 ° C, and preferably water, alcohol or a liquefied gas, preferably carbon dioxide or butane. Method according to one of claims 28 to 30, characterized in that the gaseous additive is a has freely selectable temperature, preferably between 10 ° C. and 160 ° C, and preferably carbon dioxide, nitrogen or Air is. Process according to at least one of claims 27 to 31, characterized in that the mixture of substances standing under pressure of more than 1 bar and homogeneously mixed with additives is passed through a nozzle plate ( 11 ) in a downstream degassing ( 12 ) is relieved for degassing, wherein an increase in the particle surface takes place by a sudden evaporation of the volatile constituents and the additives, analogous to the popcorn effect. A method according to claim 32, characterized in that the nozzle shape, the nozzle arrangement tion, the number of holes and the distance between the holes in the nozzle plate ( 11 ) are optimally tuned to the shortening of the diffusion path, the possibility of free gas removal and the extension of the diffusion time. Method according to at least one of claims 1 to 33, characterized in that the substance mixture in plug flow in the degassing ( 12 ) is subject to a continuous active surface renewal and thereby mechanical dissipation energy is absorbed into the mixture. Method according to at least one of claims 1 to 34, characterized in that the substance mixture temperature during degassing in degassing ( 12 ) by the addition of easily evaporable or gaseous, in the mixture not soluble additives at one or more points in the degassing ( 12 ) is kept below the damage temperature for the mixture of substances. A method according to claim 35, characterized in that in the degassing ( 12 ) additives are for example water, alcohols or gases. A method according to claim 35 or 36, characterized in that by the addition of readily volatile additives in the degassing ( 12 ) is limited by evaporative cooling the material mixture temperature. A method according to claim 37, characterized in that the limitation of the temperature increase of the substance mixture by the mechanically registered dissipation energy for the surface renewal in Entgasungskneter ( 12 ) is controlled by temperature measuring instruments and the appropriately metered amount of additive for evaporative cooling is controlled. Method according to at least one of the claims 35 to 38, characterized in that by the evaporation of the easily evaporable or gaseous additives of the partial pressure in the gas phase to be removed from the mixture volatile Components is significantly lowered, thereby increasing the diffusion accelerating stripping effect arises. Process according to at least one of claims 35 to 39, characterized in that the volatile constituents from the mixture of substances in the degasification kneader ( 12 ) are lowered below the desired residual contents, preferably 10 to 10,000 ppm. Method according to at least one of claims 35 to 40, characterized in that the evaporated volatiles, called vapor, withdrawn via a Brüdenstutzen from the degassing, in Brüdendom ( 14 ) and the condensable components in a connected via a vapor tube condenser, preferably a spray condenser, almost completely precipitated and discharged from the closed system and the non-condensable components of the technological further treatment are supplied. Method according to at least one of the claims 35 to 41, characterized in that the process pressure is selected is that the evaporative cooling of the volatile Ingredients and the added vaporizable additives damage prevent the mixture by overheating, preferably between 10 and 2000 mbar abs. Method according to at least one of claims 35 to 42, characterized in that the heating temperature of the degassing ( 12 ) and the maximum substance mixture temperature at any point in time to reach or exceed the damage temperature and preferably between 60 ° C and 160 ° C are set. Method according to at least one of claims 35 to 43, characterized in that the in the degassing ( 12 ) concentrated mixture via a directly integrated in the degassing ( 15 ) is continuously discharged. Method according to at least one of claims 1 to 44, characterized in that the from the degassing ( 12 ) discharged, removed from the volatile components mixture, now referred to as mass, by a further pressure build-up, preferably by a gear pump ( 16 ), to a pressure of more than 1 bar. A method according to claim 45, characterized in that the mass through a nozzle plate with an upstream cutting device ( 17 ), preferably a granulator, is brought into a form which makes sense for the further processing of the measure, and preferably, but not necessarily, fed to a baler. Method according to at least one of claims 1 to 46, characterized in that the evaporation kneader ( 4 ) and the degassing kneader ( 12 ) for the treatment of mixtures and polymer compositions of different composition, the homogeneous mixing, the removal of volatile components and the processing of highly viscous mixtures or polymer compositions are suitable. Method according to at least one of claims 1 to 47, characterized in that in the evaporation kneader ( 4 ) and the degassing kneader ( 12 ) a screw system for the discharge of mixtures and polymer compositions of different composition is integrated. Method according to at least one of claims 1 to 48, characterized in that the evaporation kneader ( 4 ) and the degassing kneader ( 12 ) are large-volume, self-cleaning, single or multi-shaft mixing kneader, the housing side (preferably with double jacket) and / or kneader shaft side (independently) are temperature controlled. Method according to at least one of claims 1 to 49, characterized in that the evaporation kneader ( 4 ) and the degassing kneader ( 12 ) at different pressures, preferably at 10 mbar abs to 2000 mbar abs, and temperatures, preferably at 60 to 250 ° C, with different degrees of filling, preferably from 20 to 80%, are operated continuously. Process according to at least one of claims 1 to 50, characterized in that the described mixing kneaders ( 4 . 12 ) can be operated at different speeds and torques, preferably at speeds of 5 to 150 rpm and specific, relative to the apparatus volume torques of 1 Nm / l to 100 Nm / l. Method according to at least one of claims 1 to 51, characterized in that the residence time of the substance mixture in the evaporation kneader ( 4 ) and the degassing kneader ( 12 ) is as short as possible, preferably 5 minutes to a maximum of 2 hours per apparatus. Method according to at least one of claims 1 to 52, characterized in that the evaporation kneader ( 4 ) and the degassing kneader ( 12 ) have a free volume of 2 liters to 25,000 liters. Method according to at least one of claims 1 to 53, characterized in that the technological arrangement of the process-relevant elements, the configuration of the mixing kneaders ( 4 . 12 ) and the process parameters are chosen so that foaming is avoided and, if undesirable foam is formed, he reduced by suitable means or. can be destroyed / eliminated. Method according to at least one of the claims 1 to 54, characterized in that in all technological Stages enough interfaces for one optimum mass transfer within the substance mixture or the mass and the transition of volatiles to the gas phase is created. Method according to at least one of the claims 1 to 55, characterized in that the technological path of the Vapors at least partially with non-stick coated material is lined to adhere or caking of mixture to avoid. Process according to at least one of Claims 1 to 56, characterized in that the evaporation of volatile constituents in the evaporation kneader ( 4 ) is controlled by the speed of the kneader shaft as a function of the outlet temperature. Method according to at least one of claims 1 to 57, characterized in that at constant speed of the kneader shafts into the evaporation kneader ( 4 ) metered substance mixture quantity adapted to the respective evaporation performance and thus regulated in dependence on the product temperature. Method according to at least one of the claims 1 to 58, characterized in that an increase of Throughput by increasing the speed of the kneader shafts and the resulting higher dissipation energy input higher evaporation performance in a rising temperature noticeable and therefore due to the linkage of Temperature and metering a throughput increase and as well conversely, a reduction in throughput takes place when the speed is reduced. Method according to at least one of the claims 3 to 59, characterized in that the substance mixture temperature at constant speed with the appropriate amount of addition to light vaporizable additives is regulated. Method according to at least one of the claims 3 to 60, characterized in that the hold up in the degassing over the discharged mass is regulated, whereby the mechanically registered Dissipation energy and evaporative cooling of the additive almost equalize and overheat the mixture prevent. Method according to at least one of the claims 1 to 61, characterized in that one in each case in the mixing kneader integrated discharge device discharges the substance mixture from the process space, a form for the downstream pressure increase built, preferably for a gear pump, and this keeps constant. Method according to at least one of Claims 1 to 62, characterized in that the concentrated mixture is transported from the integrated in the mixing kneader Austragsorgan directly through a pressure-resistant pipe to the downstream pressure increase or is transported by the pressure increase, preferably a gear pump, also through a pressure-resistant pipe to the next process stage, without experiencing any product damage. Method according to at least one of Claims 1 to 63, characterized in that the high torques, high rotational speeds and high powers for the dissipation energy to be introduced into the evaporation stage take place via a special drive concept in which a frequency-controlled electric motor drives a very large hydraulic motor as an oil quantity supplier, as it were Pump, and this large amount of oil directly to the hydraulic motor of the evaporator ( 4 ), without additional flow adjustment. Method according to at least one of claims 1 to 64, characterized in that a degree of filling in the evaporation kneader ( 4 ) As a function of the torque of the mixing kneader on the discharge, so the speed of the discharge or the amount of entry, so reducing or increasing the registered mixture amount is regulated. Process according to Claims 1 to 65, characterized that a higher speed in the mixing kneader, preferably in degassing, to a higher surface renewal leads, which accelerates the mass transfer and increases the mechanically recorded dissipation energy, why the mass temperature rises and the corresponding to be added Additive amount for evaporative cooling increases, not to overheat or damage the elastomer, wherein at the same time increases the partial pressure of the additive in the gas space to reduce the partial pressure of the components to be removed which in turn gives a higher driving force for the mass transfer occurs and the degassing effect of undesirable components is reduced.