Process for the production of water and solvent-free hydrogenated nitrile rubbers

Abstract

The present invention relates to a process for the production of water and solvent-free hydrogenated nitrile rubber polymers, to the hydrogenated nitrile rubbers and the use thereof.

Claims

1. A hydrogenated nitrile rubber comprising repeating units derived from at least one conjugated diene and at least one ,-unsaturated nitrile, wherein the hydrogenated nitrile rubber has a viscosity of a maximum of 1,000 Pa*s at 100 C. and a shear rate of 1/s, wherein the hydrogenated nitrile rubber has less than 0.2 wt % of volatile compounds, wherein the volatile compounds comprise both water and volatile organic compounds, wherein a proportion of the repeating units derived from the ,-unsaturated nitrile is greater than 43% b.w., based on a total weight of the hydrogenated nitrile rubber, and wherein the hydrogenated nitrile rubber has a weight average molecular weight Mw of 50,000 g/mol or less, and wherein apart from the conjugated diene and the at least one ,-unsaturated nitrile, the hydrogenated nitrile rubber comprises repeating units of one or more further copolymerizable monomers, and wherein the hydrogenated nitrile rubber has a polydispersity (Mw/Mn) of less than 2.0.

2. The hydrogenated nitrile rubber according to claim 1, wherein the nitrile rubber has less than 0.175 wt % of volatile compounds, with a residual water concentration less than 0.075 wt %, and a residual volatile organic compounds concentration less than 0.1 wt %.

3. The hydrogenated nitrile rubber according to claim 1, wherein: the hydrogenated nitrile rubber comprises 40 up to 57 wt % of the repeat units derived from at least one conjugated diene based on the total polymer, and the at least one conjugated diene comprises 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, piperylene, or mixtures thereof: the hydrogenated nitrile rubber comprises greater than 43 to 60 wt % of the repeat units derived from at least one ,-unsaturated nitrile based on the total polymer, and the at least one ,-unsaturated nitrile comprises acrylonitrile, methacrylonitrile, ethacrylonitrile, or mixtures thereof; and the hydrogenated nitrile rubber comprises 0.1 to 40 wt % of repeat units derived from at least one additional copolymerizable monomer based on the total polymer, and the at least one additional copolymerizable monomer comprises ,-unsaturated monocarboxylic acids, their esters or amides; ,-unsaturated dicarboxylic acids, their mono- or diesters, anhydrides or amides; or mixtures thereof.

Description

EXPLANATION OF FIGURES

(1) The equipment suitable to perform the process according to the invention will be described in more detail by means of schematic drawings in which:

(2) FIG. 1 shows a single-stage concentrator unit, a reheating unit and an extruder unit comprising one extruder degassing section, one accumulating section and one outlet section.

(3) FIG. 2 shows a single-stage concentrator unit, a reheating unit and an extruder unit comprising two extruder degassing sections, two accumulating sections and one outlet section.

(4) FIG. 3 shows a single-stage concentrator unit having a pressure relief valve, a reheating unit and an extruder unit having a pressure relief valve and further comprising two extruder degassing sections, two accumulating sections, a side feeder and an outlet section.

(5) FIG. 4 shows a double-stage concentrator unit, a reheating unit and an extruder unit comprising one extruder degassing section, one accumulating section and an outlet section.

(6) FIG. 5 shows a single-stage concentrator unit, a reheating unit and an extruder unit comprising three extruder degassing sections, three accumulating sections and one outlet section, whereby one extruder degassing section is a backward degassing section.

(7) FIG. 6 shows a single-stage concentrator unit comprising a pressure regulation device, a reheating unit and an extruder unit comprising a pressure regulation device, four extruder degassing sections, four accumulating sections and one outlet section, whereby one extruder degassing section is a backward degassing section.

(8) A bask and exemplary embodiment of the process step is shown in FIG. 1:

(9) In step a) Fluid F containing at least one non-volatile hydrogenated nitrile rubber polymer and at least one volatile compound is transferred via pump i to the heater 2, where the fluid F is heated.

(10) Fluid F, also called cement, contains for example from 3 to 50 wt % of a non-volatile hydrogenated nitrile rubber polymer (I) and from 50 to 97 wt % volatile compounds (ii), this being in particular an organic solvent, whereby the aforementioned components (i) and (ii) add up to 90 to 100, preferably 95 to 100 wt % of the total mass of fluid F.

(11) The volatile compounds) comprise preferably organic solvents, more preferably selected from the group comprising dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichlorethane, monochlorobenzene, dichlorobenzene, trichlorobenzene, benzene, toluene, xylene, methyl ethyl ketone, ethyl acetate, acetone, tetrahydrofuran, tetrahydropyran and dioxane.

(12) In a preferred embodiment of the invention, fluid F contains a non-volatile hydrogenated nitrile rubber polymer in the range from 3 to 50 wt % volative organic compound(s), in particular one or more organic solvents, in a range front 50 to 95 wt % and water in a range from 0.5 to 20 wt % whereby the aforementioned components add up to 95 to l00 wt % of the total mass of fluid F.

(13) As outlined above the fluid F is typically obtained from the hydrogenation reaction, Very small amounts of water may result from the organic solvent used during hydrogenation. or the preceding metathesis reaction, or from the NBR, the co-catalyst used during hydrogenation, if any, or the co-olefin used for metathesis, if any. In the alternative water in Fluid F may result from the addition of pure water or by the addition of aqueous solutions of appropriate additives after hydrogenation. Appropriate additives are inorganic or organic bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, urea, guanidines etc. It may be advisable to add such aqueous solutions of inorganic or organic bases bases in order to neutralize hydrochloric acid which is formed as a by product during the hydrogenation of NBR, especially when monochlorobenzene is used as a solvent.

(14) Temperature of Fluid F:

(15) Fluid F entering the heater typically and preferably has a temperature of 10 C. to 100 C., preferably of 20 C. to 80 C. The viscosity of fluid F is for example in the range of 100 mPa*s to 75,000 mPa*s, preferably in the range of 500 mPa*s to 5000 mPa*s

(16) A heater may be any device that is able to raise the temperature of Fluid F. In a preferred embodiment, heater 2 is a heat exchanger. The heating medium is selected from the group consisting of steam, heating oil or hot pressurized water. The heat exchanger is for example of shell-and-tube type, where the fluid F is inside the tubes and the heating medium is on the shell side. Special inserts in the tubes may be applied to enhance heat transfer. Another type of heat exchanger may also be used, in which fluid F is on the outside of the heat exchanger tubes. The advantage of the aforementioned types of heat exchangers is the avoidance of maldistribution and easy maintenance as well as good heat transfer. Said heat exchangers are well known and commercially available. In a less preferred embodiment Plate type heat exchangers may also be applied.

(17) Temperature of Heated Fluid G:

(18) Upon heating, heated fluid G is obtained. The heated fluid G has a higher temperature than fluid F, preferably a temperature of 100 to 250 C., more preferably 110 C. to 200 C. and even mom preferably 120 C. to 190 C.

(19) The heated fluid G is there conveyed further into a degassing vessel 4. In the degassing vessel, the volatile compounds at least partially evaporate. The vapors are separated and removed from the heated fluid G by a vacuum line 4.1. The pressure in the degassing vessel 4 is for example h the range of 100 hPa to 4,000 hPa, preferably in the range of 200 hPa and 2,000 hPa and more preferred in the map of 230 to 1,100 hPa.

(20) The vapors removed via the vacuum line 4, are preferably condensed and recycled into the process for preparation of fluid F. After degassing and separation a concentrated fluid H is obtained, which is removed from the degassing vessel 4 by means of a pump 4.2.

(21) In a preferred embodiment of the invention the degassing vessel is designed in the shape of a cyclone to further aid separation of vapor from heated fluid a In another preferred embodiment of the invention the degassing vessel 4 has a conical or at least torisperical shaped bottom, to allow the vessel being emptied completely or substantially complete.

(22) In another embodiment the inner surface of the degassing, vessel cast be heated.

(23) The pump 4.2 is preferably directly connected to the outlet of the degassing vessel 4. In general, the connection piece between pump and vessel is preferably as short as possible.

(24) Due to the high viscosity of the concentrated fluid H at this stage, the inlet of the pump is preferably designed with a large inlet, thereby reducing the pressure drop at the inlet,

(25) The pump 4.2 may be selected from the group consisting of positive displacement type pumps, gear pumps, piston pumps, membrane pumps, screw type pumps, extruder type pumps like counter-rotating or co-rotating single or twin screw extruders or kneader type pumps. Positive displacement type pumps and gear pumps are preferred, gear pumps are even more preferred.

(26) to another preferred embodiment the pump 4.2 comprises a combination of an extruder or a kneader and a gear pump whereby the gear pomp is fed from the extruder or kneader.

(27) The amount of volatile compounds that is removed in this step a) is for example dependent on the temperature of fluid G and the pressure in the degassing vessel 4. In a preferred embodiment of the invention the temperature of fluid G and the pressure in the degassing vessel 4 are chosen so that the concentrated fluid H is still free-flowing as defined above and comprises for example from 10 to 60, preferably from 25 to 60 wt % of a non-volatile hydrogenated nitrile rubber polymer and from about 40 to about 90, preferably from 40 to 75 wt % volatile compounds whereby the aforementioned components non-volatile hydrogenated nitrile rubber polymer, volatile organic compound and water add up to 90 to 100 wt %, preferably to 95 to 100 wt % of the total mass of fluid H.

(28) In a preferred embodiment and where the feedstock fluid F comprises water, fluid H for example comprises from 10 to 60, preferably from 25 to 60 wt % of the non-volatile hydrogenated nitrile rubber, from about 25 to about 90, preferably from 25 to 75 wt % volatile organic compounds, in particular a solvent, and about 0.5 to about 15 wt % water, whereby the aforementioned components non-volatile polymer, volatile organic compound and water add up to 90 to 100 wt %, preferably 95 to 100 wt % of the total mass of fluid H.

(29) Temperature of Concentrated fluid H:

(30) The temperature of the concentrated fluid H is lower than that of heated fluid G and is for example in the range of 15 to 150 C., preferably in the range of 20 to 120 C. The concentrated fluid H is stilt free-flowing as defined above.

(31) Step b) of the Process According to the Invention:

(32) In step b), the concentrated fluid H obtained in step a) is then passed through a reheating unit 6 to obtain a reheated concentrated fluid L. In a preferred embodiment the reheating unit comprises a heat exchanger, whereby the same disclosure including the preferences with regard to heating media and heat exchanger types apply as described above for heat exchanger 2.

(33) The temperature of the reheated concentrated fluid L is higher than that of the concentrated fluid H and is for example in the range 50 C. to 250 C., preferably in the range of 90 C. to 180 C. The reheated concentrated fluid L is still free-flowing with the viscosity in the ranges as defined above.,

(34) Step c) of the Process According to the Invention:

(35) In step c), the reheated concentrated fluid L obtained in step b) is passed on to a extruder unit and fed into the conveying section 36 of the extruder degassing section at the feeding point 12.

(36) Suitable extruder types include single screw and multiscrew extruders comprising any number of barrels and types of screw elements and other single or multishaft conveying kneaders. Possible embodiments of multiscrew extruders are twin-screw extruders, ring extruders or planetary roller extruders, whereby twin-screw extruders and planetary roller extruders are preferred.

(37) Single screw extruders include the having an axial oscillating screw. Twin screw extruders are for example counter-rotating intermeshing, counter-rotating non-intermeshing, co-rotating intermeshing and co-rotating non-intermeshing twin screw extruders are preferred.

(38) In a further embodiment of the present process it is also possible to use two or more of the above described extruders in a consecutive manner.

(39) In one embodiment of the invention the extruders can either be heated via the harms to temperatures up to 300 C. or cooled.

(40) In a preferred embodiment, the extruder comprises means to operate separate zones independently of each other at different temperatures so that the zones can either be heated, unheated or cooled. In another preferred embodiment the extruder comprises for each conveying section at least one separate zone, which can be operated independently at different temperatures.

(41) Preferred extruder materials should be non-corrosive and should substantially prevent the reheated concentrated fluid L and the Product P from being contaminated with metal or metal ions. Preferred extruder materials include nitrided steel, duplex steel, stainless steel, nickel-based alloys, composite materials Hite sintered metals, hot isostatic pressed materials, hard wear resistant materials like Stellite, coated metals with coatings for example made from ceramics, titanium nitride, chromium nitride and diamond-like carbon (DLC).

(42) The conveying section 16 is open to a vent port 15. In the conveying section 16 a part of the solvent is evaporated and separated from the reheated concentrated fluid L. The vapors are removed through the vent port 15 via a vapor line 15.1.

(43) Since the evaporation volatile compounds have at tendency to entrain the reheated concentrated fluid L or the Product P towards the vent ports, in a preferred embodiment of the invention the vent ports 15 are designed to prevent the material, in particular the reheated concentrated fluid L or the Product P, from coming out of the vent ports.

(44) Suitable means to accomplish that purpose are stuffer screws, that are mounted on the vent ports and convey any material back into the extruder, or rollers or belts, that are applied to the inside of the vent ports to push deposited material back into the extruder. As an alternative or in addition to the aforementioned, coatings of the vent ports may be applied which reduce or prevent sticking of the material to the surface. Suitable coatings include DLC (Diamond like carbon), Ethylene-Tetrafluoroethylene (ETFE), Polytetrafluoroethylene (PTFE) and Nickel-Alloys.

(45) The pressure at the vent port 15 is for example between hPa and 2,000 hPa, preferably between 5 hPa and 900 hPa. The vapor line 15.1 may be and is preferably connected to a condensing system, fit general, the purpose of the condensing system is to collect volatile compounds removed by the vent ports via the vapour lines and typically comprises a condenser and a vacuum pomp. Any condensing system known in the art may be used to effect the recovery of volatile compounds.

(46) Generally, it is preferred to recycle the condensed volatile compounds, optionally after carrying out a phase separation to separate the volatile organic compounds from water, into a process for the preparation of fluid F.

(47) The conveying section 16 is terminated by a accumulating section 20. The purpose of the accumulation is to assure a certain pressure level in the vent port 15 and to introduce mechanical energy into the material to facilitate evaporation of volatile compounds. The accumulating section 20 may comprise any means that enable the accumulation of the material. It may be designed to include for example kneading or throttling elements, blister discs or die plates.

(48) Examples of throttling elements are conical or cylindrical flow paths or other throttling means.

(49) The application of kneading elements, blister discs or die plates within the accumulating section is preferred, kneading elements are even more preferred. Examples of kneading elements include kneading blocks, which may be designed as double or triple flighted forward, backward or neutral conveying kneading blocks; single or double flighted screw mixing elements with grooves, single flighted tooth mixing elements, blister plates and single, double or triple flighted eccentric discs. The kneading elements may be assembled in any combination on the screw shafts of the extruder, in particular of an twin screw counter rotating or co-rotating twin screw extruder,

(50) A typical accumulating section comprises of 2 to 10 kneading blocks, oftentimes terminated by a back conveying type of kneading element. For mixing in of a stripping anent, tooth type elements or screw elements with grooves may be applied.

(51) Eccentric discs are preferably applied the last section of the extruder, where the product P highly viewers and substantially free of volatile compounds.

(52) For planetary miler extruders, kneading elements like tooth shaped milers are or milers with grooves and clearances are preferred.

(53) Generally the extruder unit may comprise OEM Or MOM conveying sections and one or MOM accumulating sections, whereby the number is only limited by constructional constraints. A typical number of conveying sections and accumulating sections is 1 to 30 preferably 2 to 20 and more preferably 3 to 15.

(54) The last accumulating section 20 is typically designed to form a product plug at the outlet of the extruder, thereby preventing surrounding air from entering the extruder. While passing from the conveying section 16 and the accumulating section 20 to the outlet section 22 the reheated concentrated fluid L undergoes a transition from the free-flowing reheated concentrated fluid L to the product P, which typically has depending on the molecular weight a honey-like, waxy or solid appearance.

(55) In case the hydrogenated nitrile polymer rubber, i.e. the product P has a solid appearance the outlet section 22 typically comprises means to allow the product to exit the extruder and optionally but preferably product processing equipment. Examples of suitable product processing equipment includes combinations of die plates and cutters; die plates und underwater-pelletizing means: means for crumb formation like screw elements with teeth and holes; turbulators which may be designed as cylinders with holes in it, whereby the product is pressed from the outside to the inside of the cylinder, and whereby a rotating knife inside the cylinder cuts the product into pieces; fixed knifes placed at the end plate of the extruder, whereby the screw rotation causes the cutting action, which preferably is applied when working with twin screw co-rotating, single screw and planetary roller extruders.

(56) To reduce the mechanical and thermal stress to the product, in a preferred embodiment of the invention the product processing equipment is combined with cooling means.

(57) The cooling means comprises any means that allow the removal of heat from the product. Examples of cooling means include heat exchangers (in particular tube bundle heat exchangers), pneumatic crumb conveyers with convective air cooling, vibrating crumb conveyers with convective air cooling, vibrating crumb conveyer with cooled contact surfaces, belt conveyer with convective air cooling, belt conveyer with cooled belts, water spraying ors hot crumbs upon outlet of the extruder end as already mentioned underwater-pelletizing means, whereby water serves as the coolant.

(58) In case the nitrile polymer rubber, i.e. the product P, does not have a crumbly, but more honey like or waxy appearance, i.e. when having a viscosity of of at maximum 20,000 Pa*s, preferably at maximum 10,000 Pa*s, more preferably at maximum 5,000 Pa*s and most preferably at maximum 1,000 Pa*s and a weight average molecular weight Mw of 50,000 g/mol or less, preferably 10,000 to 50,000 g/mol, more preferably 12,000 to 40,000 g/mol and a polydispersity (Mw/Mn) of leas than 2.0 the outlet section 22 typically comprises means to allow the product to exit the extender and optionally product cooling equipment. The cooling equipment comprises any means that allow the removal of heat from the product. Examples of cooling equipment include heat exchangers (in particular tube bundle heat exchangers), belt conveyors with convective air cooling, belt conveyors with cooled belts, water spaying on hot product or as water bath, whereby water serves as the coolant.

(59) The Product P may then be processed further for final packing and shipping: Therefore, crumbly like hydrogenated nitrite rubber is formed into hales e.g. by a hydraulic press, and then packed into boxes or crates for shipment. For so-called liquid grades of hydrogenated nitrile rubber (having a honeylike or waxy appearance) appropriate containers have to be used.

(60) In general, an increasing feed rate of the reheated concentrated fluid L at the feeding point 12 requires a corresponding increase in the screw speed of the extruder. Moreover, the screw speed determines the residence time of fluid L. Thus, the screw speed, feed rate and the extruder diameter are typically interdependent. Typically the extruder is operated in such a manner that the dimensionless throughput V/n*d.sup.3, wherein V denotes the Volume flow rate, n the screw speed expressed in revolutions per minute and d the effective diameter of the extruder, is adjusted to about 0.01 to about 0.2 preferably to about 0.015 to about 0.1. The maximum and minimum teed rates and extruder screw speeds are determined by for example the size of the extruder, the physical properties of the synthetic rubber product contained in Fluid L and the target values of remaining volatile compounds. Given these properties, however, the operating parameters can be determined by one skilled in the art by some initial experiments.

(61) In one embodiment a the invention the extruder is operated at a feed rate of 5 to 25,000, preferably of 5 to 6,000 kilograms per hour.

(62) Additionally a stripping agent is added to the extruder unit which is then removed together with other volatile compounds, Such stripping agent substantially improves the degassing achievable in the extruder. Even though the stripping agent may be added anywhere in the extruder unit, the addition in one or more accumulating sections is preferred. In a more preferred embodiment a stripping agent is added in one or more accumulating sections except the at one (20).

(63) Suitable snipping agents are substances that are inert to the reheated concentrated fluid (L) and/or the product (P) and have a vapor pressure greater than 100 hPa at 100 C.

(64) In the context of the invention, the term inert means that the stripping agent does not or virtually not react with the hydrogenated nitrile polymer contained in the reheated concentrated fluid (L) and the product (P). Suitable stripping agents are nitrogen, carbon dioxide, carbon monoxide, noble gases, methane, ethane, propane, butane, isobutane, pentane, hexane, cyclohexane, ethlylene, propene, isobutene, butadiene, natural gas, acetone, methylethylketone, methanol, ethanol, diethylether, tetrahydrofurane, water or a mixture of the aforementioned substances. The amount of stripping agent may be chosen in the range from 0.0001 to 10, preferably 0.001 to 5 and more preferably 01. to 2 wt-% based on the amount of the hydrogenated nitrite rubber obtained at the outlet section.

(65) The process according to the present can be performed in a device comprising a least one concentrating unit comprising a heater (2) in communication with a degassing vessel (4), whereby the bottom part of the degassing vessel (4) is in communication with a pump (4.2) the upper part of the degassing vessel (4) is in communication with at least one vapour line (4.1) one heating unit (6) in communication with the pump (4,2) of the concentrating unit and a feeding point (12) on an extruder unit one extruder unit comprising at least one feeding point (12), one extruder degassing section (16), one accumulating section (20) and one outlet section (22), whereby the extruder degassing section (16) further comprises at least one vent port (15) connected to a vapour line (15.1).

(66) In the context of this invention the term in communication includes direct or indirect connections whereby indirect connections may be accomplished for example via tubes or pipes. The term in communication further includes the option that between the units or means in communication further units or means are arranged.

(67) One Embodiment or How to Perform the Present Process is Shown in FIG. 2.

(68) FIG. 2 shows another flow chart and suitable device for the accomplishment of the process according to the invention comprising a concentrator unit with a pump 1, a heater 2, a degassing vessel 4, a vapour line 4.1 and a pump 4.2, a reheating Lath comprising a heater 6 and as extruder unit comprising two extruder degassing sections having two conveying sections 16A and 16B each connected to a vent port 15 A and 15 B and a vapour line 15.1A and 15.1.B, two accumulating sections 18 and 20 terminating the conveying sections 16 A and 16 B a an outlet section 22. In addition to that the extruder unit further comprises a side feeder 24.

(69) Generally, the extruder unit may comprise one or more side feeders, which may positioned anywhere in the extruder, preferably in close proximity to the feeding point or the outlet suction 22. Side feeders are suitable for the addition of additives to the polymer.

(70) Examples of additives, in particular for hydrogenated nitrile rubber products include stabilizing agents, acid scavengers like ESBO (epoxidized soy bean oil), stearates like calcium-stearate antioxidants and the him Examples of suitable antioxidants include sterically hindered phenols like butythydroxytoluenes and its derivatives like Irganox 1010, 1076, Vulkanox KB, Vulkanox BKF, and Wingstay L, amines, mercapto-benzimidazoles, Methyl-2-mercaptobenzimidazol, alkylated diphenylamines like butylated and octlyated diphenylamine, polymerized 2,2,4-trimethyl-1,2-dihydrochinolin (Vulkanox HS) certain phosphites like tris(nonylphenyl)phosphite and the like.

(71) In particular, hydrogenated nitrile rubbers may be mixed e.g. with 0.0001 to 4 phr epoxidized soy bean oil (ESBO), 0.0001 to 5 phr calcium-stearate and 0.0001 to 0.5 phr of antioxidants (phr parts per hundred rubber with respect to rubber weight). Other additives am also applicable, dependent on the application of the hydrogenated nitrile rubber product, i.e. fillers or colorants.

(72) As an alternative or in addition to that, additives may also already be added to the fluid F or, as far as they are liquid together with the stripping agent.

(73) A Further Embodiment of the Process Pursuant to the Invention is Shown in FIG. 4.

(74) In this embodiment step a) is repeated a least once, preferably once or twice. The advantage of repeating step a) is that the total energy consumption to produce the concentrated fluid H can be significantly reduced due to easier operation by parameter optimization for each concentration unit. The repetition of step a) is preferably accomplished by connecting the respective number of concentrating units in series.

(75) FIG. 4 shows the flow chart and suitable device for such accomplishment of the process according to the invention comprising a double-stage concentrator unit with a pump 1, a lion concentrator unit comprising heater 2A, degassing vessel 4A equipped with a vapour line 4.1A and a pump 4.2A, a second concentrator unit comprising heater 2B, degassing vessel 4B equipped with a vapour line 4.1B and a pump 4.2B, a reheating unit romping a heater 6 and an extruder coil comprising two extruder degassing sections having two conveying sections 16A and 16B each connected to a vent port 15 A and 15 B and a vapour line 15.1A and 15.1B, two accumulating sectional and 20 terminating the conveying sections 16 A and 16 B a an outlet section 22. The heated fluid G is subjected to the first concentration stage, thereby obtaining pre-concentrated field which is then reheated by heater 2B to obtain the reheated pre-concentrated fluid K, which is then subjected to the second concentration stage, whereby concentrated fluid H is obtained. Concentrated fluid H is then processed further as described above. in a preferred embodiment of the process according to the invention the concentration unit, the reheating unit or the extruder unit may independently of each other be equipped with one or more pressure regulation devices which allow the very precise operation of the units under predefined conditions.

(76) The pressure regulation devices may be active or passive, whereby active pressure regulation devices are preferred. Examples of active pressure regulation devices include control valves like a pressure relief valve, examples of passive pressure regulation devices include nozzles and dies or orifice plates. Suitable valves may be selected from ball, piston, gate or needle valves.

(77) In case of as passive pressure control device, it is preferred to calculate an orifice to cause a certain pressure drop. The calculation is based on viscosity of the fluid at that point and the throughput. Anyone skilled in the art can perform this calculation.

(78) Active pressure control devices are typically controlled by a pressure measurement upstream of the device. The pressure is for example measured and compared to the set point. The pressure control device is then adjusted according to the offset recognized.

(79) Alternatively the pressure drop across the device is measured instead of the absolute pressure upstream of the pressure control device. The valve position is adjusted manually, electrically, pneumatically or hydraulically. The control of the valve position, i.e. adjustment to the set point pressure, can for example be made manually or from any automated process control system.

(80) Another Embodiment of the Present Process Having Additional Pressure Control Devices is Shown in FIG. 3.

(81) Apart from the pressure control devices such embodiment is very similar to FIG. 2. The pressure of heated fluid G is controlled by the pressure control device 3, the pressure of reheated, concentrated fluid L entering the extruder is controlled by the pressure control device 7.

(82) In a preferred embodiment of the process according to the invention the reheated concentrated fluid (L) is injected into the first extruder degassing section of the extruder unit, whereby the first extruder degassing section comprises one or more rear vent ports in upstream direction each connected to a vapor line.

(83) The advantage rear vent ports is that the volatile compounds present in the reheated concentrated fluid L undergo sudden and rapid evaporation, thereby effecting at least partial separation of the synthetic robber product and the volatile compounds, the vapors emerging through the rear vents in upstream direction. Generally, from about 50 to about 99 wt.-%, of the volatile compounds present in the fluid L is removed through the upstream vents.

(84) Art Example of this Embodiment is Shown in FIG. 5.

(85) FIG. 5 shows another flow chart and suitable device for the accomplishment of the process according to the invention comprising a single-stage concentrator unit with a pump 1, a concentrator unit comprising heater 2, degassing vessel 4 equipped with a vapour line 4.1 and a pump 4.2, a reheating unit comprising a heater 6 and an extruder unit comprising three extruder degassing sections, whereby the feeding point 12 is located at the first extruder degassing section, comprising a conveying section 16A, a rear vent port 13 connected to a vapor line 13.1 in upstream direction and whereby the extruder Unit further comprises two downstream extruder degassing sections each comprising a conveying section 16 B and 16 C, a vent, port, 15 A and 15B, whereby the vent ports 15A and 15B are each connected to a vapour line 15.A and 15.1B, and whereby each of the conveying sections 16A, 16B and 16C is terminated by a accumulating section 18A, 18B and 20 and whereby the extruder unit further comprises an outlet section 22. Generally the streams are processed as described above with the difference being that large amounts of fluid compounds present in the reheated concentrated fluid L are already removed via vent port 13 and the vapour line 13.1 connected thereto.

(86) Another Example of this embodiment is shown in FIG. 6.

(87) FIG. 6 shows another flow chart and suitable device for the accomplishment of the process according to the invention comprising a single-stage concentrator unit with a pump 1, a concentrator nth comprising a pressure control device 3, a heater 2, a degassing vessel 4 equipped with a vapour line 4.1 and a pump 4.2, a reheating unit. comprising a heater 6 and an extruder unit comprising a pressure control device 7 Upstream the fettling point 12 of the extruder, four extruder degassing sections, whereby the feeding point 12 located at the first extruder degassing section, whereby the first extruder degassing section comprises a conveying section 16A, a rear vent port 13 connected to a vapor line 13.1 in upstream. direction and whereby the extruder unit farther comprises dime downstream extruder degassing sections each comprising a conveying section, 16 B, 16 C and 16D, a vent port, 15A, 15B and 15C, whereby the vent ports 15A, 15B and 15C are each connected to a vapour line 15.1A, 15.1B and 15C, and whereby each of the conveying sections 16A, 16B, 16C and 16D is laminated by a accumulating section 18A, 18B, 18C and 20 and whereby the extruder unit further comprises an outlet section 22. Generally, the streams are processed as described above.

(88) Fluid F, which is fed into the heater 2 typically, and as already disclosed above, contains for example from 3 to 50 wt % of a non-volatile hydrogenated nitrile rubber polymer and from 50 to 97 wt % volatile compounds, in particular at least an organic solvent, whereby the aforementioned components add up to 90 to 100, preferably 95 to 100 wt % of the total mass of fluid F and in a preferred embodiment from 3 to 50 wt % of a non-volatile hydrogenated nitrile rubber polymer from 50 to 95 wt % volatile organic compounds, in particular at least an organic solvent, and from 0.5 to 20 wt % water, whereby the aforementioned components add up to 95 to 100 wt % of the total mass of fluid F.

(89) The invention is in particular advantageous in view of energy and fresh water consumption. The products obtained are free of volatile compounds.

(90) The reference numerals used hereinbefore are summarized below: 1 pump 2, 2A, 2B heater 3 pressure control device 4, 4A, 4B degassing vessel 4.1, 4.1A, 4.1B vapor line 4.2, 42.A, 4,2B pump 6 reheating unit 7 pressure control device 12 feeding point 13 rear vent port (upstream) 13.1 vapor line 5, 15A, 15B, 15B, 15C vent port (downstream) 15.1, 15.1A, 15.1B, 15.1C vapor line 16, 16A, 16B, 16B, 16C conveying section (downstream) 18, 18A, 18B, 18B, 18C accumulating section 20 last accumulating section 22 outlet section F fluid F G heated fluid H H concentrated fluid H J pre-concentrated fluid J K reheated pre-concentrated fluid K L reheated concentrated fluid L P hydrogenated nitrile rubber polymer obtained by the process according to the invention.