DE2346054A1 - METHOD OF MANUFACTURING POLYMERS - Google Patents

Description

PATENT LAWYERS

DR.-ING. BY KREISLER DR.-ING. SCHÖNWALD 2346 0 DR.-ING. TH. MEYER DR. FUES DIPL.-CHEM. ALEK VON KREISLER DIPL.-CHEM. CAROLA KELLER DR.-ING. KLÖPSCH DIPL-ING. SELTING

COLOGNE 1, DEICHMANNHAUS

Kola, September 1st, 1973 AvK / IM

English Clays Loyering Pochin & Company Limited, John Keay House, St. Austell, Cornwall / Great Britain

Process for the production of polymers

The present invention relates to the production of polymers e.g. polyurethanes, from a prepolymer, e.g. a urethane elastomer, and a crosslinking agent therefor, and particularly relates to the manufacture of two reagents in a continuous manner.

The method of the invention is particular, but not exclusively, on the continuous production of polyurethane for lining the inside of steel pipes applicable by a centrifugal technique.

According to the invention is a method for producing Polymers, e.g. polyurethanes, made from prepolymers, e.g. a urethane elastomer, and a crosslinking agent intended for this purpose, which is characterized in that one

a) the prepolymer is heated to a temperature in the range in which the crosslinking agent is liquid with the prepolymer Form for networking the latter reacts,

b) the prepolymer. degassed,

c) the heated and degassed prepolymer is transferred to a first storage tank maintained at a substantially constant Temperature is kept in the specified range,

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d) / crosslinking agent in liquid form at a temperature /

with which it is able to do so. to crosslink the prepolymer and at a temperature at which the crosslinking agent decomposes, provides

e) storing the liquid crosslinking agent in a second storage tank which is at a substantially constant temperature is kept below the temperature at which the crosslinking agent decomposes,

f) the heated prepolymer and the liquid crosslinking agent continuously in circulation lines from the first or transferred from the second storage tank to separate lines in a mixing head and back to the respective storage tanks, whereby the mixing head can be operated continuously or discontinuously, as desired, in order to achieve the pre- to mix polymers and the crosslinking agent and to allow the mixture to flow out.

The liquid prepolymer is advantageously heated and degassed at the same time in a degassing apparatus. It understands that if the prepolymer is a solid or a very viscous liquid at normal air temperatures, - one it is preferably heated before it is put into the degassing apparatus is introduced to form a liquid that has a viscosity that allows the liquid to flow through and by stirring and preheating. Preferably, the amount of liquid prepolymer in the first storage tank is in a predetermined level range by automatically acting, iait the outlet opening of the degassing apparatus connected Devices held.

In the case that the prepolymer is a urethane elastomer, can it is a polyether with terminal isocyanate groups and that Crosslinking agent can be a diamine.

If the crosslinking agent is solid or a liquid with high viscosity at normal temperature, it is necessary to heating it to a temperature where it is liquid

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and in which it reacts with the prepolymer to crosslink the latter before the crosslinking agent enters the second Storage tank is introduced. An example of such a crosslinking agent which is solid at normal temperature is 4,4'-methylene-bis {2-chloroaniline) (MOCA). To get this to the required temperature at which it is liquid heat, it is preferred to use a suitable heating apparatus in which the in the second storage tank heated liquid crosslinking agent to be transferred is kept separate from the solid material. Some crosslinking agents are liquid at normal temperature and react satisfactorily with the prepolymer at ambient temperatures, i.e. normal temperatures, in which case heating of the crosslinking agent is not necessary. An example of one such crosslinking agent is CAYTUR-21, which is a 5o% dispersion of methylenedianiline / sodium chloride complex in dioctyl phthalate, and that when it is with the prepolymer is mixed, results in a processing time of 24 hours at room temperature.

In preparing a solid polymer from a prepolymer such as a urethane elastomer and a crosslinking agent the reagents are usually mixed in suitable proportions depending on the required qualities of the Final product, i.e. the crosslinked polymer, with a temperature selected which is within a suitable one Crosslinking or curing area lies. Once mixed, the reagents begin to mix together react and the crosslinking begins ^ the viscosity of the mixture then rises quite quickly during an initial Period until the mixture is almost solid. The crosslinking and curing of the polymer then takes place continues for a long period of time until the crosslinking reaction is completed.

Generally speaking, the curing or curing is faster at higher temperatures and the initial period of time

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23460B4

in which the mixture can still be processed - called processing time - increases with the rise in temperature. shorter. This is an important consideration when making a polymer that is to be cast or molded, as the processing of the mixture into the final form must be carried out during the processing time.

Another important consideration is viscosity of both reagents and the mixture during the processing time. The viscosity decreases at higher temperatures of the reagents and allows the reagents to be mixed more quickly and intimately can. However, once heated, most polyurethane reagents are subject to degradation, and degradation takes place faster at elevated temperatures.

Furthermore, the temperature of the mixed reagents will, to some extent, determine the viscosity during the processing time the mixture, i.e. the higher the temperature, the lower the viscosity.

The choice of the mixing temperature is therefore based on the required the processing time that should be sufficient for processing the polymer, and also according to the Viscosity of the mixture, which should be such that the polymer is molded, cast, or otherwise within the available processing time can be determined.

The temperature of the reagents prior to mixing is also determined by two factors, namely viscosity the reagents for adequate mixing and the risk of degradation of the reagents. On the one hand, the reagents must be kept at a selected temperature for sufficient mixing and, on the other hand, the reagents cannot at temperatures that are too high, as they can degrade to an undesirable state before they are

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be turned.

In one application of the invention, a process for the production of polyurethanes _from urethane elastomers and crosslinking agents has been developed which is suitable for the continuous production of polyurethane for the lining of pipes or conduits or other objects in a continuous manner, wherein the liquid urethane elastomer and its crosslinking agent are mixed and injected into the preheated tubes or lines during the processing time. As soon as a predetermined amount of the mixture has been injected, the pipe is rotated about its longitudinal axis in order to distribute the still processable mixture evenly on the inside of the pipe wall. Rotation of the tube is continued at a given temperature until the polyurethane hardens to a rubbery solid. After that, the spinning is stopped and the tube is held at a given temperature until the hardening is almost complete.

In practice the invention can be carried out in a number of ways. A special embodiment will be described as an example with reference to the drawings.

Fig. 1 is a flow sheet showing a method of making polyurethane reagents;

Fig. 2 shows the sketch of a degassing and heating apparatus for urethane elastomers;

Fig. 3 is a section showing details of parts of the degassing apparatus of Fig. 2;

Fig. 4 is a sectional view of an uncured heated urethane elastomer storage tank;

Fig. 5 is a section through a combined heating and storage apparatus for the crosslinking agent;

6 and 7 show a mixing head for mixing

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heated urethane elastomer and crosslinking agent; FIG. 8 is a sketch illustrating an application of the according to FIG

Invention produced polyurethane shows; Figure 9 is a viscosity versus time graph for the blended

Urethane and crosslinking agent of the specific embodiment.

For many uses, especially in mining / it is necessary to highly abrasive or abrasive slurries and other liquids containing mineral solids To pump pipes or lines over longer distances. It turns out that normal steel tubes or -pipes suffer from severe wear and tear due to the abrasion caused by the mineral solids.

In order to reduce the exceptionally high level of wear suggested the steel pipes and lines with a suitable Lining polyurethane that is crosslinked and cured Condition has high tensile strength, rebound resilience and high resistance to abrasion. A Polyurethane, which has been shown to be completely satisfactory in tests, is implemented by a Isocyanate-terminated polyethers made with a diamine crosslinking agent. The present invention mainly concerns the preparation and pretreatment of the raactants in such a way that the Lining of steel pipes and lines can be done almost continuously.

In the special process to be described is the polyether with terminal isocyanate groups an adiprene and the crosslinking agent is 4,4'-methylenebis (2-chloroaniline) (M.O.C.A.) The adipren, preferably Adipren-L-1oo, is with the MOCA crosslinking agent converted to a linear, high molecular weight To give polyurethane, the mixing and curing temperatures are selected so that the Lining technology can be carried out and a high-

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stable product is obtained.

The lining technique generally involves injection a predetermined amount of mixed reagents, into one end of a preheated tube which is inclined to allow the mixed liquid to enter the tube at a given speed, which depends on the viscosity of the mixture, can flow down. The angle of the slope of the tube, and the speed of injection will be according to the total amount of the injected Polyurethane and its viscosity chosen in such a way that when the first injected part of the Mixture reaches the bottom of the tube, poured the right amount of mixture into the tube and evenly is distributed along the length of the tube. The tube is then immediately brought into a horizontal position and rotated, so that the mixture through the centrifugal force evenly all around on the entire inside of the Tubing is distributed to provide a complete liner of substantially constant inner diameter result. The turning is continued until the mixture has crosslinked and hardened and then turning is carried out completed. After that, the tube is kept at a given temperature for final curing and crosslinking of the polyurethane to complete.

The lining technique gives a satisfactory product, when the mixing and curing temperatures are maintained within the range of 88 to 115 ° C. Therefore, in a special embodiment, the injection, the turning and subsequent curing are carried out at 11o + 5 ° C, and the tubes are heated to 11o + 5 ° C Preheated for about 1 hour before injection.

According to the invention, the preparation of the adiprene and MOCA reactants carried out so that the reactants

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at temperatures and viscosities that are on the one hand suitable for mixing and pouring, on the other hand with match the optimal temperature ranges for handling adiprene and MOCA, taking into account that that the degradation with increased storage temperature of the reactants before mixing to an increased extent in shorter Periods occurs.

The recommended range for the use and handling of Adipren L - 100 is 70 to 100 ° C. Within this Temperature, the polymer has good stability, low viscosity and can be easily degassed. At the upper limit of the temperature range, the adiprene is degraded to an unusable state when it is kept at this temperature for more than 8 hours ". The lower limit of the temperature can be reached the adiprene can be held for up to 14o hours before it is broken down too much.

The recommended usage and handling temperature for MOCA is around 12o ° C, but it should not be heated above 14o ° C, otherwise degradation will occur. . _t

In Fig. 1 a flow diagram is shown graphically, which shows the preparation of the two reactants according to the invention. The system generally comprises three separate supply lines, one Adipren L-100 supply line ± - tion indicated generally at 1, a MOCA supply line indicated at 2 and a methylene chloride solvent £ supply line, indicated at 3. The three supply lines are fed into a mixing and emptying head 4 whose function is to mix the adiprene and MOCA when needed and add the mixture to the Discharge tubes to perform the tube lining process.

First, reference is made to the adiprene supply line system 1

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taken, with essentially a preheating and mixing room 8, a degassing and heating apparatus 11 and a storage tank 3o is provided / the one with the mixing head 4 connected is.

The adiprene raw material is obtained in drums 7 containing 26 to 45 gallons (about 118.2 to 2o4 _f 6 liters), which are stored at outside temperature until used. The first stage in the preparation of the adiprene is in the preheating and stirring room 8, in which a number of drums, e.g. 6, are stored on a suitable roller conveyor for up to 1 1/2 days, the room being kept at 40 ° C. so that the adiprene slowly melts (the melting point of the adiprene is 1 1/2 ° C) and heated to the temperature at which adiprene has a sufficiently low viscosity to enable it to be stirred. The preheated drums are then placed in sequence in two stirring stations 9 in the room 8. Here the drums 7 are continuously rolled in order to stir and mix the adiprene through and through.

After the drums 7 have been rolled for a few hours, they are placed on stands within the room 8 mounted and connected to the supply line 1o to the To supply adiprene to the degassing and heating apparatus 11. Two drums 7 are connected to the supply line Io with a suitable shuttle valve so that if a drum is empty, the supply line immediately to the second drum can be switched while the empty first drum is replaced by another from the stirring station 9 will. The switching of the valve can be done automatically for the continuous supply of adiprene to ensure degassing apparatus 11.

Each drum has a drying tube that is attached to the drum before the adiprene runs. That

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-1ο-

Drying tube contains e.g. anhydrous calcium sulfate in order to remove the moisture from the air that replaces the adiprene when the latter is withdrawn for use. Without a drying tube, moisture would get to the adiprene and adversely affect the end product.

The degassing and heating apparatus 11 is a standard apparatus, the construction of which is shown graphically in Fig. 2 and 3 is shown. It essentially comprises an outer glass tube 15 which extends between an upper Closure 16 and a base 17 expands, and an inner coaxially arranged tube 18 extending from the Base extends out upwards. The inner tube 18 is shorter than the outer tube 15, has an open top and is through for most of its length Heating coils 19 circled. By a not shown The vacuum pump applies a vacuum of 2 to 5 mm Hg to the inside of the outer tube 15 through a gas extraction outlet 2o applied, up, the upper end piece 16 an air motor 21 is mounted, which via a shaft 22, extending downwardly through the inner tube 18, a screw pump 23 of the Moyno type drives the the base 17 is mounted. The base also contains an inlet 24 for adiprene through the supply line 10 with the supply drums 7 in the preheating space 8 is connected to To supply adiprene to the annular space 27 between the inner tube 18 and the outer tube 15. Farther an outlet 25 is provided on the base 17 through which the adiprene can be directed to the storage tank 3o by the pump 23. The outlet 25 is operated by a solenoid Valve 26 controls that to close the outlet 25 and to recycle the adiprene can be operated in the degassing apparatus.

When the plant is in operation, the adiprene is in the annular space 27 with the help of the reduced pressure

drawn inside the outer tube 15 and while the 409813/1088

Adiprene rises in the annular space, it is heated to 95 ° C. by the heating beats 19. The combination the heating and vacuum inside the apparatus causes the adiprene to foam while the trapped Gas is removed and withdrawn through gas extraction outlet 2o. The degassed and heated adiprene then flows over the top of the inner tube 18 and is collected at the bottom of that tube. From there the adiprene is fed through the screw pump 23 either to the storage tank 3o through the outlet 25 and an insulated line, or returned in the circuit through the annular opening 27 depending on the position of the Valve 26, which is automatically controlled by level sensors in the storage tank 3o, as will be explained later.

The storage tank 3o, the one with heated adiprene from the degassing apparatus 11 is filled is shown in detail in FIG. The storage device comprises a one Cylindrical tank with a capacity of 110 liters, surrounded by an insulated jacket 36 containing oil which contains 50 gallons of heated oil to keep the temperature of the adiprene essentially constant To keep 9o ° C + 2 ° C. The inlet 31 coming from the degassing apparatus 11 comprises a tube which extends under extend the level of adiprene in the tank to close to the bottom of the tank to prevent air from entering the tank Adiprene becomes trapped, the inflowing liquid causing the adiprene in the tank to continue is moved to avoid overheating zones in the adiprene. .

The tank 3o is provided with high and low level sensors 32 and 33 (see FIG. 1), which are equipped with the automatic Valve 26 of the degassing apparatus 11 are connected. When the level of adiprene in the tank is below the level of the low level sensor 33 (40 liters) falls, it actuates the valve 26 to remove more adiprene from the discharge.

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Gassing apparatus 11 to bring up until the level reaches the upper level sensor 32 (90 liters), which then in turn actuates valve 26 to cut off the supply of adiprene to the tank. A sensor 34 in one particular There is also a low level, which corresponds to 18 liters and is connected to an alarm device serves as a warning system for a very low level.

From the bottom of the storage tank 3o, on which a filter 35 provided outlet is provided, the adiprene with

2
at a pressure of 1.96 kg / cm to the mixing head and back to the tank through a closed loop line receiving lines 37 and 38, the return line 38 being attached to the bottom of the storage tank so that the recirculating liquid also serves to carry the adiprene through and keep it in the tank by stirring.

The supply and return lines 37 and 38 are flexible hoses, each of which is slightly through a diameter larger coaxial tubing, thereby obtaining an annular conduit connecting each of the two Lines 37 and 38 surrounds to hot oil from the oil jacket 36 of the storage tank 3o to the mixing head 4 and back to to circulate oil jacket 36, the oil flow in the Countercurrent to the flow of adiprene goes. The purpose of continuously circulating adiprene to and from the mixing head 4 and the oil counterflow, it must be ensured that that the adiprene is continuously present in the mixing head whenever it is needed and to ensure that that the adiprene and the adiprene lines in the mixing head 4 are kept at constant temperatures of 9o + 2 ° C.

Reference will next be made to the MOCA delivery system 2. A continuous MOCA melter is planned and a storage tank 4o, which tank is connected to the mixing head 4 by lines 41 and 42, as explained below. The MOCA raw material lies

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in the form of beads or granules, as needed be melted in a special melting device and in liquid form in a temperature-controlled Storage reservoir can be brought below the melting apparatus.

The details of the MOCA melting and storage equipment will be shown in fig. The tank 4o is a cylindrical 11o 1-capacity tank, which is filled with an oil ' holding insulated jacket 45 is surrounded by an oil reservoir 46 represents around the tank 4o and contains 35 gallons of oil held at 12o + 15 ° C. Inside the upper Part of the tank 14 is a cylindrical wire basket

available
/ which is mounted at its lower end on a heatable base 48 which is provided with electrical heating elements 49 which are controlled at 140 ° C. by an on / off thyristor control device. A temperature sensor, not shown, is attached near the top of the heating floor to sense the temperature of the molten MOCA. If the temperature rises too much, the temperature sensor activates the thyristor control device to switch off the heating elements. The wire basket and the heating floor fill about the upper half of the tank 4o, while the lower half serves as a storage tank for the melted and heated MOCA.

When the plant is in operation, the MOCA granules or -balls 5o placed in the wire basket 47. If the ' Heating elements 49 in the heating floor 48 are switched on, the MOCA on the bottom of the wire basket and the liquid melts MOCA is collected on the bottom and flows out of the bottom and falls into the lower half of the tank 4o. There the liquid MOCA is held at temperatures of 12o + 5 ° C by the oil jacket. The tank 4o is with a Provided level sensor 5o, which can be connected to a display device, so that the operator of the apparatus knows when the heating floor should be switched on

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to heat more MüCA granules. With the help of others Feelers and other suitable devices can control the tray-shaped heating floor and reload it of the wire basket 4 7 with MOCA beads completely can be made automatically so that the level of the liquid MOCA is between the predetermined level lines lies. An extra low-level sensor can be provided in the lower part of the tank to give a warning signal triggered when the level of the liquid MOCA falls too low.

From the bottom of the tank 4o, the liquid MOCA is passed through a filter 51 and an outlet 52 at about 120 ° C and a Pressure of 1.96 kg / cm is pumped to the mixing head 4 and back to the tank 4o, taking it through the closed loop of the circulation lines 41 and 42, the return line 42 being attached to the bottom of the tank 4o is that the recirculated liquid MOCA serves to keep the liquid MOCA in motion in the tank to avoid overheated zones in the liquid MOCA.

The supply and return lines 41 and 42 are flexible Hoses, with each hose lying within oil lines, not shown, in exactly the same way as described for the adiprene tubes 37 and 38.

The mixing head 4 is a standard apparatus for mixing polyurethane reagents and its construction is used shown in detail in Figs. Referring to Figure 6, the mixing head 4 generally comprises a housing 6o, which has a centrally located shaft 61, which is connected by a quick release connection 66 at its upper end mounted and driven by an oil motor 65. The lower end of the shaft carries the mixing device 62, which is located in a nozzle 63, which is attached to the main

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housing 60 by means of a quickly releasable screw connection 67 is mounted.

6 openings 68 are provided on the bottom of the main housing 60, some of which are used to discharge adiprene and MOCA reagents, the openings with their centers are arranged on a circle around the central axis of the shaft 61. In the current design there are two orifices used for adiprene and one for MOCA.

Above each opening 68 for the discharge of adiprene and MOCA is a passage 7o containing a longitudinally movable plunger valve 71, wherein the plunger piston valves 71 for each opening with one common piston 72 are connected, which can be set in alternating motion with the aid of compressed air, so that the plunger piston valves 71 can all be opened or closed at the same time.

The passage 70 above each port connects a reactant inlet port 74 and a reactant outlet port 75 to which the supply and return circuit lines 37 and 38 in the case of the adiprene cycle and 41 and 42 in the Case of the MOCA circuit are connected.

In operation, the adiprene and MOCA are simply circulated through the mixing head when each plunger valve is up 71 is in its lower position and its lower end closes the openings. For mixing and Unloading the reactants, the agitator shaft 61 is driven at about 45oo rpm and the plunger piston valves 71 with it Opened with the aid of compressed air to open the adiprene and MOCAr openings 68 and to close the outlet openings 75 close so that adiprene and MOCA are directed through openings 68 rather than back to their respective storage tanks will. The rotating mixer 62 on the shaft

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61 mixes the reactants quickly and completely and then they are passed through the lower end of the nozzle 6 3 carried out. The shaft 61 is lubricated through a lubrication inlet connection 67.

In the present construction, the diameters for the adiprene and MOCA supply lines are the pressure for the feed pumps from the storage tanks and the sizes of the openings 68 arranged so that there is a mixing ratio of adiprene: MOCA of 8: 1 yields.

As explained above, the adiprene and MOCA intake and - Return lines 37, 38 and 41, 42 surrounded by oil lines in which hot oil is removed from the oil jackets of the storage tanks 3o and 4o to the mixing head 4 and back to the tanks. This ensures that the lines 37, and 41, 42 and the mixing head are maintained at the temperatures required for the reactants. The oil will circulated through the side of the mixing head 4 as shown in Fig. 7, on the side on which the adiprene arrives, through lines 8o and 81, and on the side where the MOCA arrives through lines 82 and 83.

After the reactants have been mixed and drained, it is necessary to close the mixing head and nozzle 6 3 with a solvent rinsing to prevent any of the mixture from remaining in the nozzle 63 and on the mixer 62, solidifies and contaminates the mixer. For this purpose, one of the openings 68, namely the opening 68A provided with an inlet port 85 for cleaning solvent (Methylene chloride) feed. As shown in Fig. 1, this is fed from a drum 86, which feeds a solvent tank 87 from which the solvent can be pumped into the mixing head 4.

In the final stages of the specific embodiment described the polyurethane from the nozzle 63 of the

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Mixing head 4 guided into the pipe to be lined. The lining technique is briefly described above and illustrated graphically in FIG. The tubes 9o are cleaned first and then preheated in an oven 91 to 11o + 5 ° C. After preheating, the tubes are moved one after the other to an injection and turning station 9 3 where the Pipes first inclined at a small angle and the polyurethane mixture at a speed of 10 kg / min. is injected. After injecting the required amount of the mixture, the injection is stopped and that Tube 9o is brought into a horizontal position and rotated at 8oo - 9oo rpm to wrap the polyurethane all around inside of the pipe to distribute. Turning is continued for about 1/2 hour to allow the polyurethane to set can. After turning, the lined pipes are held in furnace 91 for a further 21/2 to 3 hours, to complete the curing and crosslinking of the polyurethane lining.

Since the lining technique is not the main subject of the present invention, it is not in greater detail Details described. '

The viscosity of adiprene and MOCA mixed is a important factor in lining technology. The pot life of the mixture at around 100 ° C is around 1o - 12 Minutes. It is therefore necessary to ensure that the mixture is injected within 5 minutes at the most after mixing is completely finished, so that the turning of the pipe to distribute the liner is carried out while the polyurethane is still processable. A typical graph of viscosity variations of adiprene / MOCA mixtures over time will become 9 shown.

In the reactant preparation system described above 40981 3/1 088

the adiprene is stored in the tank 3o at about 9o ° C. This means that the adiprene held on for about up to 16 hours before it starts to degrade. This is an adequate time to ensure that it is continuous Processing can be carried out because the adiprene, when used continuously, does not last longer than Remains in the storage tank for 16 hours. For example, if the system is shut down overnight, the adiprene is left in the The storage tank is allowed to cool and the storage tank is covered with a nitrogen blanket to ensure that none humid air acts on the adiprene. When the plant is put back into operation, the cold Adipren be heated in the storage tank 3o to 9o ° C within 3 hours by heating the oil in the surrounding tank A coat. The preferred temperature range for storing the adiprene in the storage tank 3o and supplying it to the Mixing head 4 during operation is at 85 to 100 C, although it is assumed that the adiprene is still satisfactory is when it is stored and supplied in a temperature range of 75 to 11o ° C.

The MOCA is kept in the storage tank 4o at 12o ± 5 ° C, the preferred range is 11o to 130 ° C, although it is also stored between 105 and 14o ° C and fed to the mix head can be.

During the shutdown, the MOCA is allowed to cool down in the storage tank 4o '. It can return to its processing temperature in about 3 hours be heated by heating the oil in the jacket surrounding the tank 4o.

It is clearly evident that the method according to the Invention for preparing the reactants using the degassing and heating apparatus and the storage tanks for Adipren and MOCA makes the system very suitable for almost completely automatic operation. In the

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Not only can the preparation of the reactants, but also the mixing and delivery of the polyurethane to the pipes, the lining technology and the Curing and crosslinking stages are just as easy for one automatic continuous production can be customized.

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Claims (16)

Claims ι _J / · Process for the production of polymers from Prepolymers and crosslinking agents therefor, characterized in that one a) the prepolymer heated to a temperature in the range in which the crosslinking agent with the prepolymer reacts in liquid form to cross-link the latter, b) the prepolymer is degassed, c) the heated and degassed prepolymer transferred to a first storage tank, which on a substantially constant temperature is kept in the specified range, " d) the crosslinking agent in liquid form at a temperature at which it is capable of forming the prepolymer to crosslink and provide at a temperature at which the crosslinking agent decomposes, e) the liquid crosslinking agent is stored in a second storage tank which is at a substantially constant Temperature is maintained below the temperature at which the crosslinking agent decomposes, f) the heated prepolymer and the liquid crosslinking agent continuously in circulation lines from the first and the second storage tank to separate lines transferred to a mixing head and back to the respective storage tanks, with the mixing head as desired can be operated continuously or discontinuously to the prepolymer and the crosslinking agent mix and allow the mixture to flow out. 2. The method according to claim 1, characterized in that the liquid prepolymer simultaneously in a degassing apparatus is heated and degassed. 409813/1088 3. The method according to claims 1 and 2, characterized in that that the amount of the liquid prepolymer in the first storage tank is within predetermined level ranges is held by automatically acting devices / which are connected to the outlet of the degassing apparatus, 4.. Method according to claims 1-3, characterized in that that the prepolymer is a solid or a highly viscous liquid at normal temperature and the prepolymer is heated prior to introduction into the degassing apparatus. 5. The method according to claims 1-4, characterized in that the crosslinking agent at normal temperature is solid and is liquefied by heating before it is introduced into the second storage tank. 6. The method according to claims 1-5, characterized in that the heating of the solid crosslinking agent is carried out in a heating apparatus in which the heated liquid crosslinking agent to the second Storage tank is to be transferred, is kept separate from the solid material. 7. The method according to claims 1-6, characterized in that that the prepolymer is a urethane elastomer which when mixed with a suitable crosslinking agent forms a polyurethane. 8. The method according to claims 1- 7, characterized in that the urethane elastomer is a polyether with terminal Isocyanate groups. 9. The method according to claims 1-8, characterized in that that the crosslinking agent is a diamine, for example 4,4'-methylene-bis- (2-chloroaniline). 40981 3/1 088 7346054 10. The method according to claim 8, characterized in that that the crosslinking agent is a 5o% dispersion of methylenedianiline / sodium chloride complex in dioctyl phthalate is. 11. The method according to claims 1 - 1o, characterized in that the first and the second storage tank on im substantially constant temperatures are maintained by means of jackets containing oil around each tank. 12. The method according to claims 1 - ti, characterized in that that the prepolymer and the crosslinking agent from the first and second storage tanks to the mixing head and returned back to the tanks in lines - / ground that are surrounded by oil lines through which oil from the oil-filled jackets of the first and second storage tanks, respectively is circulated. 13. The method according to claim 12, characterized in that that the oil circulating in the oil lines is also passed through separate oil lines in the mixing head to keep the lines for the prepolymer and the crosslinking agent in the mixing head at predetermined temperatures. 14. The method according to claims 12 and 13, characterized in that that the circulating oil flows in countercurrent to the flow of the prepolymer and the crosslinking agent. 15. Process for lining pipes, tubes, molds or other tubular or hollow cylindrical Articles with a curable polymer which are introduced into the articles in liquid form can and has been prepared according to claims 1-14, characterized in that following the steps a) to f) according to claim 1 g) a tube or a tube-like object is arranged so that it passes with its longitudinal axis in a 09813/1088 are inclined at a certain angle to the horizontal, h) the mixture of prepolymer and crosslinking agent from the mixing head at a predetermined speed in a selected amount into the top of the tubular article introduces, the angle of inclination of the tube and the rate of introduction of the polymer mixture is chosen so that the portion of the polymer mixture which is first introduced into the pipe, along the inner wall of the pipe to a previously determined lower part of the pipe in the same The time required for the completion of the introduction of the entire amount of the polymer mixture flows, wherein the polymer blend along the length of the pipe is distributed, i) then brings the tube into a horizontal position and rotates it around its longitudinal axis, around the polymer mixture around the inside of the tube wall, continuing turning until the Polymer has set. 16. The method according to claim 15, characterized in that after carrying out steps a) to g) h) the curable mixture of prepolymer and crosslinking agent from the mixing head into the upper end of the inclined tube, the angle of inclination of the tube according to the viscosity of the liquid is chosen so that as the liquid flows down the tube, the liquid polymer mixture is along it is distributed along the length of the pipe, i) the supply of polymer mixture from the mixing head is prevented and j) the tube rotates around its longitudinal axis, around the liquid polymer mixture evenly all around on the inside the pipe wall, continuing rotating until the polymer is solid. 40981 3/1088 Blank page