JP2015101687A - Method for preparing purified acrylic polymer solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing a purified acrylic polymer solution, in which an unreacted monomer is removed from an acrylic polymer solution obtained by solution polymerization, and temperature fluctuation of a heater, that is used for supplying the vapor of a solvent of the acrylic polymer solution, is reduced, and the energy consumption is made smaller than usual.SOLUTION: The method for preparing the purified acrylic polymer solution comprises the steps of: feeding an acrylic polymer solution, which is obtained by subjecting monomers containing acrylonitrile at the least to solution polymerization, to an evacuated distillation column (packed column) 1; feeding the vapor of the solvent of the acrylic polymer solution to the distillation column 1 so that the vapor thereof is brought into contacted with the fed acrylic polymer solution to remove the unreacted monomers; heating the solvent of the acrylic polymer solution to be fed to the distillation column 1 by the heat of the vapor of the solvent of the unreacted monomers-containing acrylic polymer solution; and feeding the solvent, which is heated at the above-mentioned heating step, to the heater 2, that is used for supplying the vapor of the solvent of the acrylic polymer solution to the distillation column.

Description

  The present invention relates to a method for producing a purified acrylic polymer solution.

  In general, the polymerization of acrylonitrile is radical polymerization, and processes for obtaining an acrylonitrile polymer industrially by the polymerization are roughly classified into solution polymerization as a homogeneous system and aqueous suspension polymerization as a heterogeneous system.

  Since the reaction rate of radical polymerization generally becomes slower as the progress of the reaction proceeds, in order to obtain a high conversion rate, a large apparatus or a long reaction time is required, which is industrially disadvantageous. It is economically advantageous to close it at around%. For this reason, since the polymer solution contains unreacted monomers, if the unreacted monomers are brought into the subsequent spinning process, the monomers are discharged into the atmosphere, causing a deterioration of the working environment, which is undesirable. It is necessary to efficiently and sufficiently remove the reactive monomer.

  Various proposals have been made so far for methods for producing purified acrylic polymer solutions that remove unreacted monomers. Patent Document 1 discloses a purified acrylic heavy polymer that can remove unreacted monomers from a polymer solution containing unreacted monomers in solution polymerization at an extremely high removal rate and simultaneously concentrate the polymer solution to an appropriate concentration in one step. In the method for producing a combined solution, Patent Document 2 discloses a method for removing unreacted monomers in solution polymerization at an extremely high removal rate, and simultaneously achieving concentration and cooling of the polymer solution to an appropriate concentration. Is disclosed. However, using these methods, the temperature of the heater for supplying the solvent vapor of the polymer solution fluctuates during the continuous production of the purified acrylic polymer solution. When the polymer concentration fluctuates, and when the production amount of the purified acrylic polymer solution is changed, the temperature of the heater for supplying the solvent vapor of the polymer solution fluctuates greatly. There was a problem that the polymer concentration fluctuated greatly and yarn breakage occurred in the subsequent spinning process. Further, as a method for reducing the temperature fluctuation of the heater for supplying the solvent vapor of the polymer solution, it is conceivable to enlarge the apparatus or introduce a heat exchanger for the polymer solution solvent. However, there are problems such as high equipment cost, energy disadvantage and high running cost.

JP 11-181019 JP2000-44606

  In view of the background of such prior art, the present invention removes unreacted monomers from a polymer solution in solution polymerization and has little temperature fluctuation of a heater for supplying a vapor of a solvent of the polymer solution. The present invention provides a method for producing a purified acrylic polymer solution obtained with less energy consumption.

  In the method for producing a purified acrylic polymer solution of the present invention, a polymer solution obtained by solution polymerization of a monomer containing at least acrylonitrile is supplied to a reduced-pressure distillation tower, and the solvent vapor of the polymer solution is supplied to the polymer solution. In the method for producing a purified polymer solution by removing the unreacted monomer from the polymer solution by supplying the polymer solution so as to contact with the polymer solution, the solvent vapor of the polymer solution containing the unreacted monomer which is waste heat is used. The latent heat of condensation is recovered with the solvent before being supplied to the heater for supplying the vapor of the solvent of the polymer solution.

  In the present invention, since the temperature variation of the heater for supplying the vapor of the solvent of the polymer solution is small as compared with the prior art, the problem such as yarn breakage in the spinning process is achieved by the above configuration. A purified acrylic polymer solution can be produced with a small amount of energy and less than the conventional amount.

It is the schematic which shows an example of the apparatus used for manufacture of the refinement | purification acrylic polymer solution of this invention. It is the schematic of the conventional apparatus.

    Hereinafter, the present invention will be described in more detail.

  According to the method for producing a purified acrylic polymer solution of the present invention, a polymer solution obtained by solution polymerization of a monomer containing at least acrylonitrile is supplied to a vacuum distillation column, and the solvent vapor of the polymer solution is supplied. The unreacted monomer generated from the distillation column is supplied to the distillation column reduced in pressure so as to come into contact with the polymer solution, and the unreacted monomer in the polymer solution is removed to produce a purified acrylic polymer solution. Using the solvent of the polymer solution before being supplied to a heater for supplying the vapor of the contained solvent to a distillation column whose pressure is reduced so that the solvent vapor of the polymer solution is in contact with the polymer solution Then, the solvent of the polymer solution before being supplied to the heater used as the refrigerant is introduced into the heater as it is.

  By adopting such a configuration, the temperature variation of the heater for supplying the solvent vapor of the polymer solution is less than that of the conventional technique, so that it is not necessary in the spinning process and purified with less energy consumption than in the past. An acrylic polymer solution can be produced. In the present invention, in the monomer containing at least acrylonitrile, the content of acrylonitrile in all monomers is preferably 80 mol% or more. One or more other monomers having an ethylenic double bond may be contained. Examples of other monomers having an ethylenic double bond include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate; acrylic acid, methacrylic acid, and esters or salts thereof; maleic acid, fumaric acid, and These esters or anhydrides; diene monomers such as butadiene, chloroprene, isoprene; styrene, acrylonitrile, vinylidene halide, vinyl ether, and the like can be used.

  In the present invention, an organic solvent such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide is preferably used as the solvent for the polymer solution.

  The polymerization method may be either batch polymerization or continuous polymerization, and the polymer solution supplied to the distillation column preferably has a viscosity at 45 ° C. of 50 to 1000 poise. If it is lower than 50 poise, the residence time in the distillation column is shortened, so that the contact time with the solvent is shortened. If it is higher than 1000 poise, the residence time in the distillation column is increased, but the polymer solution Less surface renewal. If it is 50-1000 poise, an unreacted monomer can be removed efficiently.

  Further, it is preferable to use a polymer solution supplied to the distillation column having a polymer concentration of 15 to 30% by weight and containing an unreacted monomer concentration of 1 to 8% by weight. If the polymer concentration is lower than 15% by weight, the reaction rate of the polymer in the process of polymerization is slow, which causes problems such as high running costs.If the polymer concentration is higher than 30% by weight, the reaction rate is high. However, it is difficult to control the polymer concentration. In addition, if the unreacted monomer concentration is lower than 1% by weight, there is a problem that the running cost is high because a large amount of solvent is required to be supplied to the heater. There are problems such as becoming expensive. In the present invention, the distillation column may be a hollow column, a plate column, or a packed column packed with a packing, but the presence of the packing renews the surface of the polymer solution. Since removal of unreacted monomers is promoted, it is preferable to use a packed tower.

  In the present invention, in a distillation column that has been depressurized, the lower the column pressure, the more advantageous it is to increase the removal rate of unreacted monomers and to concentrate the polymer solution, but to maintain a high vacuum. There are also problems such as the need for expensive equipment and high running costs, and 30 to 5 Torr is preferably employed industrially.

  In the present invention, the polymer solution is supplied to a distillation column reduced in pressure and supplied to a distillation column reduced in pressure so that the solvent vapor of the polymer solution is brought into contact with the polymer solution. The contacting direction is not particularly limited, but the polymer solution is supplied from the upper part of the distillation column, and the solvent vapor of the polymer solution is supplied from the lower part of the distillation column so as to be in countercurrent contact with the polymer solution. preferable. That is, in the distillation column, it is preferable to supply the solvent vapor so that the moving direction of the polymer solution is substantially opposite to the moving direction of the solvent vapor.

  The solvent of the polymer solution supplied to the distillation tower is heated with a heater such as a reboiler. What is necessary is just to use the heater called the reboiler of the distillation tower generally used industrially as a heater. Further, the amount of the solvent supplied to the heater is preferably large, but 1 to 50% by weight is preferable with respect to the weight of the polymer solution supplied to the distillation column from the viewpoint of the apparatus and running cost.

  In the present invention, the vapor of the solvent containing the unreacted monomer generated from the distillation tower is cooled in the condenser using the solvent of the polymer solution before being supplied to the heater. As the condenser, a condenser called a condenser of a distillation column that is generally used industrially may be used. Further, the vapor of the solvent containing unreacted monomer generated from the distillation column was depressurized so that the vapor of the solvent of the polymer solution was brought into contact with the polymer solution depending on the amount of the solvent supplied to the heater. Since the solvent of the polymer solution before being supplied to the heater for supplying to the distillation column is not completely condensed and cooled, the vapor of the solvent containing unreacted monomers generated from the distillation column is used as the polymer. After cooling in the condenser using the solvent of the polymer solution before being supplied to the heater for supplying the vapor of the solvent of the solution to the distillation column whose pressure has been reduced so as to contact the polymer solution, It is preferable to use a condenser for complete condensation and cooling.

  In the present invention, the lower the temperature of the solvent of the polymer solution supplied to the condenser, the more advantageous it is for condensing the vapor of the solvent containing unreacted monomers generated from the distillation column. A cooling device is newly required for cooling, and a normal temperature of 5 ° C. to 35 ° C. is preferable from the viewpoint of running cost.

  In this invention, the solvent of this polymer solution before supplying to the heater used as a refrigerant | coolant is introduce | transduced into a heater as it is. In order to reduce heat loss, the shorter the distance between the condenser and the heater, the better. It is also preferable to keep the condenser, the heater body, and the introduction pipe warm.

  A preferred embodiment of the method for producing a purified acrylic polymer solution of the present invention will be described below with reference to FIG.

  FIG. 1 is a schematic flow diagram showing an example of an apparatus used in the method for producing a purified acrylic polymer solution of the present invention. A polymer solution containing unreacted monomers is fed into the column from the top of the distillation column 1. The solvent is heated by the reboiler 2 and the vapor is supplied into the distillation column 1, and the vapor of the unreacted monomer in the polymer solution and the vapor of the solvent are brought into countercurrent contact with the vapor of the solvent and the polymer solution. The mixture is cooled in the first condenser 3. At this time, the solvent of the polymer solution is used as the cooling liquid in the first condenser 3. The solvent used as the cooling liquid in the first condenser 3 is heated as it is in the reboiler 2 and its vapor is supplied to the distillation column 1. The mixture of the unreacted monomer vapor and the solvent vapor in the polymer solution cooled in the first condenser 3 is cooled in the second condenser 4 with water to be completely condensed. Cooling.

  The purified acrylic polymer solution from which the unreacted monomer has been removed by the above method is extracted from the lower part of the packed tower 1 with a pump and spun in the subsequent spinning step. On the other hand, the mixture of the completely condensed and cooled solvent vapor and the removed monomer separates and purifies the monomer and the solvent in a later distillation step.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
93.8 mol% of acrylonitrile, 6 mol% of methyl acrylate, 0.2 mol% of sodium methallyl sulfonate were polymerized using dimethyl sulfoxide (hereinafter referred to as DMSO) as a solvent, and an acrylonitrile having a polymer concentration of 21.6% by weight containing 2.7% by weight of unreacted monomers. In the embodiment shown in FIG. 1, the system polymer DMSO solution was heated to 70 ° C. with the heat exchanger 5 and continuously supplied at 8500 kg / Hr from the upper part of the packed tower with a vacuum degree of 10 Torr. At the same time, DMSO at 20 ° C. as the cooling liquid of the first condenser 3 is continuously supplied at 25% by weight to the acrylic polymer DMSO solution continuously supplied from the upper part of the packed tower, and the DMSO is directly supplied to the heater 2. Introduced. DMSO is heated to 80 ° C in heater 2, and 80 ° C DMSO vapor is continuously supplied from the bottom of packed column 1 at 25 wt% to the acrylic polymer DMSO solution continuously supplied from the top of the packed column. From the upper part of packed column 1, 1929.5 kg / Hr of DMSO vapor containing unreacted monomer at 70 ° C. was generated, and 8270.5 kg / Hr of a purified acrylic polymer DMSO solution was continuously produced. Further, the DMSO vapor containing unreacted monomer at 70 ° C. generated from the upper part of the packed tower 1 is condensed in DMSO at 20 ° C. continuously supplied as a cooling liquid in the first condenser 3, and then condensed in the second condenser 4 And cooled to 20 ° C. with 10 ° C. water in the second condenser 4. At this time, 0.49 ton / Hr of water vapor for heating DMSO in the heater 2 was used, and 11.2 ton / Hr of water for cooling DMSO containing unreacted monomer was used in the second condenser 4. At this time, the polymer concentration of the purified acrylic polymer DMSO solution was 22.2 wt%, and the temperature of the heater 2 was constant at 80 ° C.

Example 2
In the embodiment of Example 1, the continuous supply amount of the acrylic polymer DMSO solution was increased by 20% by weight. At the same time, DMSO at 20 ° C. is continuously supplied as a cooling liquid of the first condenser 3 at 25% by weight to the acrylic polymer DMSO solution continuously supplied from the upper part of the packed tower, and the DMSO is directly supplied to the heater 2 as it is. The DMSO was heated to 80 ° C. with the heater 2 and the DMSO vapor at 80 ° C. was supplied from the lower part of the packed tower 1 to the acrylic polymer DMSO solution continuously supplied from the upper part of the packed tower at 25% by weight. Continuous supply. 2315.4 kg / Hr of DMSO vapor containing unreacted monomer at 70 ° C. was generated from the top of packed column 1 to continuously produce a 9924.6 kg / Hr purified acrylic polymer DMSO solution. Further, the DMSO vapor containing unreacted monomer at 70 ° C. generated from the upper part of the packed tower 1 is condensed in DMSO at 20 ° C. continuously supplied as a cooling liquid in the first condenser 3, and then condensed in the second condenser 4 And cooled to 20 ° C. with 10 ° C. water in the second condenser 4. At this time, 0.59 ton / Hr of water vapor for heating DMSO in the heater 2 was used, and 13.4 ton / Hr of water for cooling DMSO containing unreacted monomer was used in the second condenser 4. At this time, the polymer concentration of the purified acrylic polymer DMSO solution was 22.2 wt%, and the temperature of the heater 2 was constant at 80 ° C.

Comparative Example 1
FIG. 2 is the same as in Example 1 except that there is no condenser for recovering the latent heat of condensation, which is the waste heat of the solvent vapor of the polymer solution containing unreacted monomer, and DMSO is continuously supplied directly to the heater 2. It was set as the aspect. The same acrylic polymer DMSO solution containing unreacted monomer as in Example 1 was heated to 70 ° C. with the heat exchanger 5 and continuously supplied at 8500 kg / Hr from the top of the packed tower with a vacuum degree of 10 Torr. At the same time, DMSO at 20 ° C. is continuously supplied to the heater 2 at 25 wt% with respect to the acrylic polymer DMSO solution continuously supplied from the top of the packed tower, and DMSO is heated to 80 ° C. with the heater 2, Continuously supply DMSO vapor of 80 ° C from the lower part of packed tower 1 to the acrylic polymer DMSO solution continuously supplied from the upper part of packed tower at 25 wt%, and 70 ° C unreacted from the upper part of packed tower 1 1929.5 kg / Hr of DMSO vapor containing monomer was generated, and a purified acrylic polymer DMSO solution of 8270.5 kg / Hr was continuously produced. Further, DMSO vapor containing unreacted monomer at 70 ° C. generated from the top of packed column 1 was cooled to 20 ° C. with 10 ° C. water in condenser 6. At this time, 0.67 ton / Hr of water vapor for heating DMSO with the heater 2 and 17.0 ton / Hr of water for cooling DMSO containing unreacted monomer were used with the condenser 6. At this time, the polymer concentration of the purified acrylic polymer DMSO solution varied from 21.8 to 22.4% by weight, and the temperature of the heater 2 varied from 79 to 81 ° C.

Comparative Example 2
In the embodiment of Comparative Example 1, the continuous supply amount of the acrylic polymer DMSO solution was increased by 20% by weight. At the same time, DMSO at 20 ° C. is continuously supplied to the heater 2 at 25 wt% with respect to the acrylic polymer DMSO solution continuously supplied from the top of the packed tower, and DMSO is heated to 80 ° C. with the heater 2, Continuous supply of DMSO vapor of 80 ° C from the lower part of packed column 1 to the acrylic polymer DMSO solution continuously supplied from the upper part of packed column at 25% by weight, and 70 ° C unreacted monomer from the upper part of packed column 1 A DMSO vapor containing 2315.4 kg / Hr was generated, and a 9924.6 kg / Hr purified acrylic polymer DMSO solution was continuously produced. Further, DMSO vapor containing unreacted monomer at 70 ° C. generated from the top of packed column 1 was cooled to 20 ° C. with 10 ° C. water in condenser 6. At this time, 0.80 ton / Hr of water vapor for heating DMSO with the heater 2 was used, and 20.4 ton / Hr of water for cooling DMSO containing unreacted monomer was used with the condenser 6. Further, the polymer concentration of the purified acrylic polymer DMSO solution at this time varied from 21.6 to 22.6% by weight, and the temperature of the heater 2 varied from 78 to 82 ° C., and yarn breakage occurred in the subsequent spinning step.

1: packed tower
2: Heater 3: First condenser 4: Second condenser 5: Heat exchanger 6: Condenser

Claims (2)

Supplying a polymer solution obtained by solution polymerization of a monomer containing at least acrylonitrile to a distillation column whose pressure has been reduced, and supplying the solvent vapor of the polymer solution to the distillation column so as to come into contact with the polymer solution In the method for producing a purified polymer solution by removing unreacted monomer from the polymer solution, the polymer solution before being supplied to the distillation column by the heat of the solvent vapor of the polymer solution containing the unreacted monomer A method for producing a purified acrylic polymer solution, comprising: heating a solvent of the polymer solution; and supplying the solvent to a heater for supplying a vapor of the solvent of the polymer solution to the distillation column. There are at least two condensers for liquefying the solvent vapor of the polymer solution containing the unreacted monomer, and at least one of the condensers contains the solvent vapor of the polymer solution containing the unreacted monomer. 2. The method for producing a purified acrylic polymer solution according to claim 1, wherein the liquid is liquefied.

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