JPH027322B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to polymeric substances, solutions, suspensions, etc. thereof (hereinafter referred to simply as polymeric substances).
It concerns energy savings in the production of.

[Prior art] Relatively low molecular weight by-products such as water, hydrogen chloride, ammonia, alcohol, carbon dioxide, etc. are produced by homopolymerization or copolymerization of at least one organic compound, or between molecules of at least one organic compound. BACKGROUND ART A method for producing a polymeric substance by a polycondensation reaction in which a polymeric substance is obtained by repeatedly causing a condensation reaction accompanied by the production of molecules is generally well known and has already been carried out on a large scale. It is also well known that a considerable number of these polymerization, copolymerization, and polycondensation reactions (hereinafter simply referred to as polymerization reactions) are highly exothermic reactions. The manufacturing process of polymeric substances based on the above basic principle includes a raw material storage tank, a process of uniformly mixing additives added as desired into the raw material, a polymerization process, a process of removing unreacted substances and/or unnecessary substances, and a process of removing unreacted substances and/or unnecessary substances. It consists of at least two unit processes, such as a waste material recovery process, a molding or pelletizing process, etc. Furthermore, among these unit processes, at least one polymerization reactor is used in the polymerization step, and in many cases more than two polymerization reactors are used in parallel or in series in the continuous production method.

[Problems to be solved by the invention] Conventionally, when carrying out a polymerization reaction, in order to remove the polymerization heat and maintain the reaction temperature at a desired appropriate temperature,
Heat transfer surfaces are installed inside and outside the polymerization reactor to cool the reactants with a cooling medium such as cooling water, and the polymerization heat transferred to the cooling medium is not used and requires cooling to about room temperature. as well as residual heat from unit processes are dumped into the environment. On the other hand, during a unit process, it is often necessary to cool the product to below room temperature. For example, some of the organic compounds (hereinafter referred to as monomers) that are the raw materials for the above polymerization reaction will undergo a slight polymerization reaction even at room temperature, so it is necessary to add a polymerization inhibitor or keep the temperature below room temperature. Preventing undesirable polymerization reactions before subjecting them to polymerization reactions by means such as
Or, because it is difficult to complete the polymerization reaction, the reaction product is kept at the pressure during polymerization or lower in order to remove and recover unreacted monomers, or remove and recover part or all of the additives. The unpolymerized monomers and additives to be removed and recovered are vaporized and separated from the reaction product by heating at a temperature below 200 mL, and the vaporized vapor is cooled down to room temperature or below, condensed, and recovered.

Conventionally, as a method of generating a cold heat source when cooling to below room temperature is required, the use of a compression refrigerator that requires energy to be introduced from the outside has become a universal method.

In the production of polymeric substances, the cold heat source required for the reasons described above is generated by an absorption refrigeration method in which the heat of polymerization generated during the polymerization reaction and/or residual heat generated from other unit processes is used as the heat source. This is a method for producing polymeric substances that uses a cold source to eliminate or significantly reduce the energy introduced from the outside, which is required when using a compression refrigerator.

[Means for Solving the Problems] The present invention involves polymerizing a polymerizable monomer or a mixture of at least two copolymerizable monomers at a temperature of 55° C. or higher in the presence of optionally added additives. However, in a method consisting of at least two unit processes for producing a polymeric substance or a liquid product containing a polymeric substance, the polymerization heat generated during the polymerization and/or residual heat from other unit processes is A polymeric substance and a liquid containing the same, characterized in that the cold energy obtained by absorption refrigeration as a heat source is used as a cold source for at least one other unit process that requires cooling to a temperature below room temperature. It provides the manufacturing method of the product.

The principle of this invention will be explained using FIG.

Figure 1 shows a continuous method for producing polymeric substances, using the absorption refrigeration method in which the residual heat of the polymeric substance after the heat of polymerization and the product of the polymerization reaction are further heated under reduced pressure to remove volatile matter is used as the heat source. FIG. 3 is a process diagram for explaining the principle of the present invention using an example in which the cold heat generated by is used for condensing the volatile matter under reduced pressure.

In FIG. 1, reference numeral 1 denotes a supply pipe for raw material monomer, and this pipe and/or a desired number of other pipes (not shown) that similarly open into the polymerization reactor 2 are used to supply the raw material monomer and desired amount. Additives such as a polymerization catalyst, a molecular weight regulator, a solvent, and other auxiliary raw materials are supplied to the polymerization reactor 2. In this figure, only one polymerization reactor 2 is shown, but in both batch polymerization method and continuous polymerization method, one polymerization reactor is usually used in which one or more polymerization reactors are arranged in parallel or in series. Although a reactor is used as a representative example, the present invention can be applied regardless of the arrangement method of such polymerization reactors. The inside of the polymerization reactor 2 is usually stirred and mixed using a stirrer (not shown). The polymerization reactor 2 is equipped with a heat transfer surface 3 for removing polymerization heat, and the refrigerant and absorption liquid of the absorption refrigeration method described later are heated through this heat transfer surface, and the polymerization heat is removed, causing the polymerization reaction to proceed. The temperature inside the vessel 2 is maintained at a desired temperature. The polymerization product after the polymerization reaction is transported through a tube 4 into a devolatilizer 5 having a heat transfer surface 6, where the tube is heated under approximately the same pressure as the polymerization reactor 2 or a desired pressure lower than this. It is heated via the heat transfer surface 6 by an external heat source supplied by 7, and unpolymerized monomers and volatile substances contained in the product are removed as vapor. The volatile matter vaporized by heating is sent through a pipe 8 to a condenser 9 under approximately the same pressure as the volatile matter remover 5, and a heat transfer surface 10 attached to this condenser 9
It is cooled and condensed by a cold heat source by an absorption refrigeration method supplied via a pipe 11, and is extracted from a pipe 12 to be used as a raw material for polymerization or for a desired purpose such as a purification process. On the other hand, the polymerization product from which the volatile matter has been removed in the volatile matter remover 5 is extracted through the tube 13, cooled in the heat exchanger 14 in the same manner as in the case of the polymerization reactor 2, and then cooled in the tube 15.
It is sent to the next process. In the above series of processes, the devolatilizers are removed in multiple stages with different pressures and/or temperatures, and each of these multiple stages of devolatilizers is often equipped with a single condenser. As in the case of the polymerization reactor 2, a set of volatile matter remover 5 and condenser 9 is used as a representative example. In addition, the polymerization product sent to the devolatilizer 5 through the pipe 4 is often a highly viscous liquid, and in order to increase the devolatilization effect, the polymerization product is transferred onto the heat transfer surface 6 of the devolatilizer 5. The heat transfer surface is usually installed so that the material flows in a thin film. Furthermore, other steps not directly related to the present invention may be installed between the polymerization reactor 2 and the volatile matter remover 5, but these steps have been omitted.

In the example shown in FIG. 1, an absorption freezing method is combined with the series of polymerization steps described above as follows. In the well-known absorption refrigeration method, two types of refrigerant are used: a refrigerant whose boiling temperature under atmospheric pressure is below room temperature, and an absorption liquid that easily dissolves this refrigerant and whose boiling point under atmospheric pressure is 50°C or more higher than that of the refrigerant. A fluid is used.

In the above description, the cold source supplied to the heat transfer surface 10 of the condenser 9 through the tube 11 is the refrigerant liquid after being depressurized. This refrigerant liquid cools and condenses the volatile vapor sent from the devolatilizer 5 through the pipe 8 via the heat transfer surface 10 of the condenser 9, and the refrigerant liquid itself evaporates to become refrigerant gas. This refrigerant gas is sent to the absorber 17 through the pipe 16, where it comes into contact with an absorption liquid with a low refrigerant content (hereinafter referred to as "poor absorption liquid") sent into the absorber 17 through the pipe 18, and absorbs poorly. The absorbent liquid becomes a rich absorbent liquid with a high refrigerant content. The heat generated during this melting is indirectly removed by cooling water at approximately room temperature supplied through the pipe 19. The rich absorption liquid generated in the absorber 17 is extracted, pressurized by a pump 20, passed through a pipe 21, and further divided into pipes 24a and 24b.
is heated by the heat of polymerization through the tube 24.
The one via b is heated in the heat exchanger 14 by the residual heat of the polymerization product after removing volatile components,
Both tubes 25 are boiling and in a gas-liquid mixed phase state.
a and 25b, join together at pipe 26, and enter distiller 29. In the distiller 29, the rich absorption liquid is subjected to a distillation action under approximately the same pressure as the outlet pressure of the pump 20, and refrigerant gas under pressure is taken out from the upper pipe 30, which is cooled to approximately room temperature in the cooler 31. It is indirectly cooled by water and liquefied to become a refrigerant liquid, and a part of it is passed through a pipe 32 as necessary to the distiller 2.
Most of the remaining liquid is used as the reflux liquid of the condenser 9 through the pipe 11 after being depressurized, as described above.

On the other hand, the remaining rich absorption liquid from which the refrigerant gas has been separated in the distiller 29 becomes a poor absorption liquid and is taken out from the lower part of the distiller 29, and is then depressurized and recirculated to the absorber 17 through the pipe 18.

In the example of this FIG. As shown in Fig. 2, a heat exchanger 34 is installed separately below the pump 33 and distiller 29, and a part of the piping is changed to connect these devices as shown in Fig. 2. is supplied to the distiller 29 via the pipe 21.

In FIG. 2, the pressure is increased by a pump 33, and the flow is then divided into a pipe 24a and a pipe 24b. The water that passes through the pipe 24b becomes high temperature through the heat exchanger 14, joins the pipe 26 through the pipes 25a and 25b, heats the bottom of the distiller 29 in the heat exchanger 34, and then becomes low temperature. The distiller 29 is circulated by the circulation of a heat medium for conveying polymerization heat and residual heat different from the refrigerant which is circulated to the pump 33 by a pipe 38.
It is also possible to thermally combine the polymerization reactor 2 and the residual heat generating section with the absorption refrigeration method by heating the bottom of the reactor 2 to configure the absorption refrigeration method.

By using the absorption freezing method as shown in Figure 2,
The surface temperature of the polymerization product side of the heat transfer surface attached to the unit process that serves as a heat source such as heat transfer surface 3 and heat transfer surface 6 decreases too much, and the polymerization product that comes into contact with this surface solidifies.
Alternatively, it is possible to prevent undesirable phenomena such as a decrease in the overall heat transfer coefficient of the heat transfer surface due to adhesion.

In the absorption refrigeration method, it is also possible to use the heating methods shown in FIGS. 1 and 2 in a single absorption refrigeration apparatus for multiple unit processes that serve as heat sources in a series of polymer substance manufacturing processes. Conversely, it is also possible to use the heating method of FIG. 1 and the heating method of FIG. 2 separately in separate absorption refrigeration methods.

Even in the method of this invention, some power is required for the pump 20 for the absorption refrigeration method shown in Figure 1 or the pump 33 for the usage method shown in Figure 2, but the power required for these pumps is the same amount This is extremely small, being only a fraction of the power required when using a compression refrigerator to obtain cold heat. Therefore, even if the power required for the pump 20 or the pump 33 is introduced from outside the system, the advantages of the present invention, which will be described later, will not be impaired.

If the total amount of polymerization heat and other heat sources for absorption refrigeration is excessive compared to the required amount of cooling heat, this excess heat source can be used to expand the refrigerant using the well-known Rankine cycle. It is also possible to generate power with a turbine, drive the pump with the generated power, and use no externally introduced power.

This invention will be explained more specifically. For example, the second
In the apparatus shown in the figure, 4353 kg/hour of styrene monomer is supplied from tube 1 to polymerization reactor 2.
75% of the supplied styrene monomer was polymerized at
In the volatile matter remover 5, 25% of the styrene monomer remaining unpolymerized is heated and evaporated under high vacuum.
The case of producing polystyrene in which the styrene monomer that has become a vapor is cooled to about +2° C. and liquefied in the condenser 9 will be explained.

In this case, Dowtherm liquid is used as the heat medium circulated by the pump 33, and in the absorption refrigeration method, water is used as the refrigerant and ammonia is used as the absorption liquid.

In order to cool and liquefy the styrene monomer under high vacuum in the evaporator 9, 216,600 Kcal/hour is required as a cold heat source at a temperature of at most -4°C. In order to obtain this cold heat source, if we use a compression refrigerator using electric power in the conventional method,
Consumes 60.7KWH/hour of electricity. In contrast to such conventional methods, the total of 562,200 Kcal/hour of the polymerization heat of the polymerization reaction carried out at 100°C or higher and the residual heat held by the residual polystyrene liquid after unpolymerized monomers are removed in the volatile matter remover 5 is reduced. When used as a heat source in absorption refrigeration as described above, this absorption refrigeration process can generate 216,600 Kcal/hour of cold heat at -4°C. In this case, the power consumption required for pump 20 and pump 33 is 9.24KWH/
Since the time is approximately 51Kwh/hour, the electricity savings is approximately 51KWh/hour. The amount of polystyrene produced in this example is approximately 3260 kg/hour, so per 1000 kg of polystyrene, approximately
This resulted in a power saving of 15.7KWH, compared to the conventional power consumption of 86KWH for manufacturing 1000Kg of polystyrene.
This is actually equivalent to 18% of the total, which is a very large effect.

In the method of this invention as well, the condenser 9
It does not require any particular explanation that the cooling and liquefaction of the volatile matter in can be carried out in exactly the same manner as in the conventional method.

The above is an example of producing polystyrene using styrene monomer as a raw material, but the process is substantially the same in the production of polymeric substances other than polystyrene. These polymeric materials include polypropylene, high-density and low-density polyethylene, polyvinyl chloride, polyvinyl acetate, polyacetal, polymethyl methacrylate, polyethylene terephthalate, polycaprolactam, polyacrylonitrile, polymethyl acrylate, polycarbonate, polybutadiene, polyisoprene. , polychloroprene, and copolymers of two or more of these monomers. Also,
The final product can be in many states such as solid filaments, pellets, and plates at room temperature, and liquid emulsion, suspension, solution, or paste at room temperature.

On the other hand, polymerization methods for producing these polymeric substances by polymerizing raw material monomers include bulk polymerization methods that do not use any additives that give a diluting effect to the monomers, as described in the example of polystyrene, and Suspension polymerization or emulsion polymerization, in which small monomers are dispersed in water and polymerized;
There are various polymerization methods such as a solution polymerization method in which monomers are diluted and dissolved in a solvent as an additive.

These polymerization methods can often be carried out either continuously or batchwise.

In addition, in these polymerization methods, not only additives that do not have a diluting effect on the monomer, such as polymerization catalysts, molecular weight regulators, suspension stabilizers, emulsion stabilizers, etc., but also additives that have a diluting effect on the monomer are not used at all. Although there are cases where polymerization can be carried out without additives, in many cases at least one of these additives is used.

The specific polymerization conditions for producing the various polymeric substances mentioned above vary widely depending on the characteristics of the raw material monomers and the intended use of the polymeric substance, but the general polymerization temperature is -30°C to 300°C, Pressure is high vacuum ~ 2000
Up to Kg/cm ² G. There is also a large difference in the amount of heat generated during polymerization, but in general, polymerization in which the production of by-product molecules during the polymerization reaction can be determined is superior to polymerization that does not involve the production of by-product molecules, such as the polymerization of vinyl monomers. The polymerization of vinyl monomers often produces about 22 Kcal per gram mole of monomer. In this invention, this amount of heat is effectively utilized. Furthermore, when operations such as heating or cooling are performed in unit processes other than the polymerization process as described above, residual heat generated from these operations can be used as a heat source in the present invention in the same way as the polymerization heat. . As is clear from the above explanation, the principle of this invention is that none of the refrigerant, absorption liquid, heat medium, etc. used in this invention come into direct contact with the raw material monomer, polymerization product, or product polymer substance. It is possible to apply this method to all cases of producing the above-mentioned polymeric substances.

However, in the absorption refrigeration method used in this invention, it is necessary to use cooling water at approximately room temperature in the cooling pipe 19 and cooler 31 of the absorber in both FIGS. 1 and 2. The temperature of room-temperature cooling water varies depending on the region, but it often rises to around 40 degrees Celsius in the summer.

In this invention, it is necessary that the temperature of the polymerization heat and other residual heat, which serve as the heat source in the absorption freezing method, be higher than the temperature of the cooling water at approximately room temperature. Therefore, if the temperature of the polymerization heat and other residual heat is lower than 55°C, the ability of the absorption freezing method to generate cold heat will be reduced.

Further, in the present invention, examples of unit processes in which the cold heat generated by the absorption freezing method can be used include a storage tank for methyl methacrylate monomer, and a cooling and condensation process for evaporated unreacted monomers and/or diluent solvent vapor, such as the polystyrene example. ,spinning,
It can be used to produce cold air or cooling water at or below room temperature for rapidly cooling molded products during molding of polymeric substances such as pelletization.

As an embodiment of this invention, a simple process diagram for explaining the principle as shown in FIGS. 1 and 2 can be implemented, but in both FIGS. (not shown) can increase the cooling output of absorption refrigeration.

As an additional heat exchanger in such a case, for example, as shown in FIG. 2, the poor absorbent liquid is transferred under reduced pressure from the distiller 29 to the absorber 17 through the pipe 18, and after leaving the distiller 29, the pressure is reduced. After cooling by heat exchange with the rich absorption liquid transferred from the pump 20 to the distiller 29 through the pipe 21 without any heat exchange, and further cooling the poor absorption liquid after the heat exchange with cooling water at approximately room temperature,
Either the refrigerant liquid is depressurized and supplied to the absorber 17, or the refrigerant liquid that is cooled by cooling water at room temperature in the cooler 31 and condensed into liquid is heat exchanged with the refrigerant gas sent to the absorber 17 through the pipe 16 without depressurizing the refrigerant liquid. After that, it is depressurized and supplied to the heat transfer surface 10 of the condenser 9 through the pipe 11.

In this sense, the detailed embodiments of the invention are not limited to the examples shown in FIGS. 1 or 2.

The degree of energy saving that can be achieved in the production of polymeric substances by the method of the present invention is that, as in the case of polystyrene production, the amount of generated cold heat obtained by using all the polymerization heat and other residual heat in the absorption freezing method is The case where the total amount of cooling energy required for all unit processes that require cooling is equal to the following is the largest. On the other hand, if the amount of cold energy generated and the amount of cold energy required do not substantially match, the amount of cold energy generated or the amount of cold energy required will be Excessive amounts of either of these reduce the amount of energy savings possible in the production of polymeric materials.

If the amount of cold energy generated is excessive, the absorption refrigeration method can be made smaller, and the surplus polymerization heat and other residual heat that is generated after the amount of cold energy generated is approximately equal to the required amount of cold energy can be used as in the conventional method. It can be easily disposed of in the environment or used as described above. On the other hand, if the amount of cold heat generated is too small, as shown by the dotted line in FIG. The compressor is suctioned and compressed into the cooler 40.
In step 1, the refrigerant is cooled and liquefied using cooling water at approximately room temperature, and after the pressure of this liquefied refrigerant is reduced, it is merged with that produced by the absorption refrigeration method through a pipe 11, thereby making it possible to compensate for the deficiency in the amount of cold heat generated.

Furthermore, a method that is completely different from the two methods described above and in which the required amount of cooling energy and the generated amount of cooling energy are made to substantially match can be implemented. That is, in many processes for producing polymeric substances, the heat of polymerization often accounts for most of the heat of polymerization and other residual heat that serve as the heat source in the absorption freezing method. Therefore,
When the polymerization rate is slightly increased or decreased, the amount of heat that becomes the heat source in absorption refrigeration increases or decreases by a wide range, and along with this, the cold heat generated by absorption refrigeration also increases or decreases by a wide range. On the other hand, an increase or decrease in the polymerization rate results in a decrease or increase in the amount of cooling energy required for the condenser 9, respectively, as in the examples of FIGS. 1 and 2. If there is a quantitative discrepancy between the amount of cold heat generated and the amount of required cold heat for such reasons, the discrepancy in the amount of cold heat can be made approximately equal by changing the polymerization rate of the monomer supplied to the polymerization reactor. Can be done. This method can be carried out very easily in cases where a large amount of polymerization heat is generated, such as the polymerization of monomers having double bonds, and it can be operated under conditions of minimal energy consumption during the production of polymeric substances. This is an extremely desirable method because of its results. In addition, in batch polymerization, if the timing when polymerization heat and other residual heat is generated does not coincide with the timing when cooling heat is required,
Producing and storing a low-temperature refrigerant when heat of polymerization and other residual heat is generated, and taking it out and using it when cold heat is required can be easily carried out by conventionally known methods.

The absorption freezing method that can be used in this invention is:
In addition to the above-mentioned method using ammonia as the refrigerant and water as the absorption liquid, absorption freezing methods using any known combination of refrigerant and absorption liquid can be used. These include, for example, water-lithium chloride,
There are absorption refrigeration methods such as combinations of water-lithium bromide, ethyl chloride-tetrachloroethane, methylene chloride-tetraethylene glycol dimethyl ether, or Freon 21-tetraethylene glycol dimethyl ether (all of the foregoing are refrigerants).

[Effects of the Invention] The effects of this invention are achieved by utilizing polymerization heat and other residual heat during the production of polymeric substances, which were dumped into the atmosphere, natural waterways, etc. in conventional methods, as a heat source for absorption refrigeration. The reason is that it has become possible to save a large amount of energy during the production of polymeric substances, and the extent of the savings has already been explained.

[Brief explanation of drawings]

FIG. 1 is a process diagram for explaining the principle of this invention.
FIG. 2 is a diagram of one embodiment of the invention. 2... Polymerization reactor, 3... Heat transfer device, 5... Volatile remover, 6, 10... Heat transfer surface, 9... Condenser,
14, 34... Heat exchanger, 17... Absorber, 2
0,33... pump, 29... distiller, 31...
Cooler, 40... Compressor, 41... Cooler.

Claims (1)

[Claims] 1. Polymerizing a polymerizable monomer or a mixture of at least two copolymerizable monomers at a temperature of 55°C or higher in the presence of additives added as desired,
In a method consisting of at least two unit processes for producing a polymeric substance or a liquid product containing a polymeric substance, the heat of polymerization generated during polymerization and/or residual heat from other unit processes is used as the heat source. A polymer substance or a liquid product containing the same, characterized in that the cold energy obtained by the absorption freezing method is used as a cold source for at least one other unit process that requires cooling to a temperature below room temperature. Manufacturing method. 2 The amount of cold energy generated by increasing or decreasing the polymerization rate of the monomer or monomer mixture supplied as a raw material by absorption freezing method and the amount of cold energy required for at least one other unit process that requires cooling to a temperature below room temperature. The method according to claim 1, which substantially coincides with the following.