KR20190060431A - Method for preparing acrylonitrile based polymer - Google Patents

Abstract

The present invention relates to a continuous production method which includes a reaction system comprising two or more reactors. The present invention includes: a step of primarily polymerizing a raw material mixture containing an acrylonitrile monomer in the presence of a polymerization initiator in a first reactor while controlling residence time within 8 to 15 hours; and a step of producing a final polymer by transferring the primarily polymerized raw material mixture to a second reactor, secondarily polymerizing in a second reactor, and controlling residence time within 1.5 to 6 hours. The present invention: has the ratio of the residence time of the first reactor to the residence time of the second reactor to be 2:1 to 6:1; suppresses physical properties, improves a conversion rate, thereby increasing productivity when using the production method; and is able to produce an acrylonitrile-based copolymer having uniform physical properties.

Description

METHOD FOR PREPARING ACRYLONITRILE BASED POLYMER [0002]

The present invention relates to a process for preparing an acrylonitrile-based copolymer for use in the production of carbon fibers, and more particularly to a process for controlling the residence time of a reactor in a polymerization reaction.

The carbon fiber is a fibrous carbon material having a carbon element content of 90 wt% or more based on the total weight of the carbon fiber. The carbon fiber is preferably a polyacrylonitrile (PAN), a pitch which is a residue of a petroleum-based hydrocarbon residue, Quot; means a fiber obtained by pyrolyzing a precursor of the polymer in an inert atmosphere.

The carbon fiber is a fiber type material having the structural and structural characteristics of the carbon which is a constituent, and is a material having a fiber shape. It is a material having heat resistance, chemical stability, electric thermal conductivity, dimensional stability due to low thermal expansion, low density, frictional wear characteristics, , Biocompatibility, and flexibility, and it is also possible to impart very good adsorption characteristics depending on the activation conditions.

On the other hand, acrylonitrile-based polymers are widely used as raw materials for carbon fiber precursors. Solution polymerization is mainly used as a method for producing an acrylonitrile-based polymer. The solution polymerization is advantageous in that it is unnecessary to dissolve the polymer in a spinning solvent since the polymer solution can be used as a spinning solution as it is by a method using a monomer, an initiator and a reaction solvent.

On the other hand, efforts to improve the productivity of PAN-based carbon fibers have been made in all processes of spinning, chlorination or carbonization of carbon fiber precursor fibers. Among them, the productivity improvement of the spinning side of the PAN-based carbon fiber precursor fibers has a problem in that the productivity is limited due to the limiting radiation drag ratio depending on the characteristics of the PAN-based polymer solution during spinning and the draw ratio depending on the solidification structure. If the spinning speed is increased to improve the productivity, the spinnability is lowered. If the spinning speed is lowered, the productivity is lowered.

In this effort, when a small amount of ultrahigh molecular weight component is contained in the PAN-based polymer solution, precursor fibers having good durability without damaging the fiber can be obtained even at a high radiation draft rate, which makes it possible to mass-produce carbon fibers , And a batch type solution polymerization method is proposed by this method (Patent Document 1)

Specifically, the polymerization of ultrahigh molecular weight components and the polymerization of ordinary molecular weight components are carried out in the same reaction solution by introducing a reagent such as a polymerization initiator in two divided doses, whereby a PAN-based polymer solution having excellent prospective properties can be easily obtained Is proposed.

However, in order to obtain a polymerization rate of a predetermined ultrahigh molecular weight component, precise control of the injection timing of the reagent is required, and when the polymerization is repeatedly performed in the same reactor, the residual reagent affects the polymerization specification and the viscosity is high, It is necessary to separately wash the reactor. Therefore, the PAN-based polymer produced by the batch method has a problem of quality deviation because the uniformity of physical properties is greatly lowered, The achievement is still in need of improvement.

JP 2008-248219A

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a method of controlling a retention time in a first reactor and a retention time ratio in a second reactor, The present invention provides a method for producing an acrylonitrile-based copolymer which can greatly improve productivity and thereby greatly increase productivity.

According to one embodiment of the present invention, there is provided a continuous production method comprising a reaction system comprising at least two reactors, wherein the polymerization is carried out in the presence of a polymerization initiator in a first reactor, Polymerizing the raw material mixture while controlling the retention time to 8 to 15 hours by first polymerizing the raw material mixture; And transferring the first polymerized raw material mixture to a second reactor and performing a secondary polymerization in a second reactor and controlling a retention time to be 1.5 to 6 hours to prepare a final polymerized product, And the residence time of the second reactor is from 2: 1 to 6: 1.

According to the method for producing an acrylonitrile-based copolymer of the present invention, the retention time in the first reactor can be controlled and the ratio of the residence time with the second reactor can be controlled to suppress the deterioration of the physical properties of the polymer, It is possible to maximize productivity and to provide an acrylonitrile-based copolymer having uniform physical properties.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

A method for producing an acrylonitrile-based copolymer according to an embodiment of the present invention is a continuous production method comprising a reaction system comprising two or more reactors, wherein in the presence of a polymerization initiator in the first reactor, the acrylonitrile- , And polymerizing the first mixture by controlling the residence time to 8 to 15 hours; And transferring the first polymerized raw material mixture to a second reactor and performing a secondary polymerization in a second reactor and controlling a retention time to be 1.5 to 6 hours to prepare a final polymerized product, And the residence time of the second reactor is from 2: 1 to 6: 1.

According to the above production method of the present invention, it is possible to obtain an acrylonitrile-based copolymer having uniform physical properties as compared with the batch polymerization method, to shorten the reaction time, to improve the conversion rate, So that the productivity can be greatly improved.

Hereinafter, the production method according to the present invention will be described in detail.

The production method is a continuous solution polymerization method using two or more reactors, and preferably two reactors are used to carry out the polymerization.

First, in the first reactor, the polymerization reaction is carried out in the presence of the polymerization initiator in the raw material mixture containing the acrylonitrile-based monomer. The primary polymerization in the first reactor is characterized in that the residence time control of the reactor is important, and is particularly controlled to be 8 to 15 hours.

If the residence time of the first reactor is excessively longer than 15 hours, the conversion rate may increase. However, since the conversion rate is increased, there is a problem that the reactor size must be increased in order to increase the residence time. The operation ratio may increase exponentially, and the productivity may be significantly lowered.

In addition, when the residence time in the first reactor is too short as less than 8 hours, the conversion rate may be too low, and accordingly, the residence time in the second reactor must be long, and the residence time in the second reactor It may cause a problem that the physical properties of the final polymer may be greatly lowered.

Therefore, the control of the residence time in the first reactor can serve as an important factor in the preparation of the acrylonitrile-based copolymer. From the viewpoint of the yield, the conversion rate, the design of the reactor, etc., Hour, more preferably 10 hours to 13 hours, and most preferably 11 hours to 12 hours.

The raw material mixture may include an acrylonitrile-based monomer and an organic solvent.

The acrylonitrile-based monomer may be at least one member selected from the group consisting of acrylonitrile and methacrylonitrile, and acrylonitrile may be preferable.

The organic solvent may be at least one selected from the group consisting of dimethylsulfoxide, dimethylformamide and dimethylacetamide, of which dimethylsulfoxide may be preferred.

The raw material mixture may preferably contain 200 to 500 parts by weight, preferably 300 to 450 parts by weight, more preferably 320 to 380 parts by weight of the organic solvent per 100 parts by weight of the acrylonitrile monomer When this range is satisfied, the viscosity of the raw material mixture is appropriate, so that the polymerization conversion ratio and the weight average molecular weight of the solution polymerization can be increased.

Meanwhile, the raw material mixture may further include an additional monomer as a comonomer in addition to the acrylonitrile monomer. The comonomer may be at least one member selected from the group consisting of, for example, a carboxylic acid-based monomer and a (meth) acrylate-based monomer.

The carboxylic acid-based monomer may be at least one member selected from the group consisting of acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid and mesaconic acid, among which itaconic acid is preferable. The (meth) acrylate-based monomer may be at least one member selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate and propyl methacrylate, Methyl acrylate is preferred.

The comonomer may be contained in an amount of 1 to 10 parts by weight, preferably 1 to 7 parts by weight, more preferably 1 to 4 parts by weight based on 100 parts by weight of the acrylonitrile-based monomer. When the above-mentioned range is satisfied, not only the initiation temperature of the oxidation stabilization reaction can be lowered in the acrylonitrile-based fiber production process, but also suitable stretchability can be imparted to the acrylonitrile-based fiber.

The polymerization reaction may be carried out in the presence of a polymerization initiator, and the polymerization initiator is used for initiating polymerization of monomers in the raw material mixture. For example, azobisisobutyronitrile, 2,2'-azobis ( Azobis (2, 4-dimethylvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 1 Azobis [cyclohexane-1-carbonitrile], 2,2'-azobis [N- (2-propenyl) -2- methylpropionamide, [(cyano- (N-butyl-2-methylpropionamide), 2,2'-azobis (N-cyclohexyl-2-methylpropionamide) and the like can be used. Of these, azo Bisisobutyronitrile is particularly preferred.

The polymerization initiator can be added after raising the temperature of the raw material mixture to 50 to 70. When the polymerization initiator is added after the temperature rise as described above, the polymerization yield can be prevented from being lowered due to vaporization of the monomers in the raw material mixture, The initiation of polymerization by the initiator can be effectively carried out and the polymerization rate can be excellent.

The polymerization initiator may be added in an amount of 0.2 to 2.0 parts by weight, preferably 0.3 to 1.0 part by weight, more preferably 0.4 to 0.8 part by weight based on 100 parts by weight of the acrylonitrile monomer. When the above-mentioned range is satisfied, the final polymerization conversion ratio of the obtained polymer can be increased.

After the addition of the polymerization initiator, as described above, the residence time of the first reactor may be controlled to 10 to 15 hours. After completion of the first polymerization in the first reactor, The mixture is transferred. In this case, the viscosity of the raw material mixture may be 40,000 cP to 50,000 cP when measured at 45, and when the polymerization is carried out in the first reactor to such a viscosity range, the polymerization conversion and the molecular weight distribution of the final polymer may be excellent, Gel formation in the reactor can be greatly suppressed.

After the first polymerization is completed as described above, the raw material mixture may be transferred from the first reactor to the second reactor so that the secondary polymerization may be performed, and the secondary polymerization in the second reactor may be performed for 1.5 to 6 hours , Preferably 3 to 6 hours.

The residence time in the second reactor needs to be controlled to be shorter than the residence time of the first reactor, which can be an important factor for improving the physical properties of the final polymer and improving the polymerization conversion rate.

In particular, the residence time in the second reactor and the residence time in the first reactor need to be adjusted, and the ratio of the residence time of the first reactor to the residence time of the second reactor is from 2: 1 to 6: 1 < / RTI >

If the residence time ratio is lower than 2: 1, the residence time of the first reactor is shorter and the residence time of the second reactor is longer, the conversion rate is too low as described above, There is a concern that the physical properties of the polymer may be deteriorated due to an increase in the residence time of the second reactor.

Also, if the residence time ratio is greater than 6: 1 and the residence time of the first reactor is longer and the residence time of the second reactor is shorter, the contamination of the reactor may become serious due to the formation of gel in the first reactor, There is a problem that the size of the reactor must be increased in order to increase the reaction volume. In addition, since the viscosity of the raw material mixture in the first reactor may increase, difficulties may occur in the heat treatment, have.

Particularly, the above-mentioned heat-removing efficiency can be maximized by introducing a second reactor at the rear end of the first reactor, and it is possible to increase the heat amount by distinguishing the polymerization reaction distinction between the first reactor and the second reactor by viscosity, The productivity can be improved.

Therefore, in order to satisfy such an effect, it is necessary to control the residence time ratio in the first reactor and the second reactor to be in the range of 2: 1 to 6: 1, more preferably 2: 1 to 4: 1 .

On the other hand, a polymerization initiator to be added to the second reactor may be added secondarily. In this case, the polymerization initiator to be added in the second reactor may be the same as or different from the polymerization initiator used in initiating polymerization in the first reactor , The above-described types of polymerization initiators can be used equally. As described above, when the polymerization initiator is added in the second place, the final polymerization conversion rate can also be increased.

The second introduced polymerization initiator may be mixed with an organic solvent, and the organic solvent may be the same as that used in the raw material mixture to be fed into the first reactor. When the second charged polymerization initiator is put in a state mixed with an organic solvent, it can be more uniformly mixed with the raw material mixture transferred in the first reactor.

At this time, the secondary polymerization initiator and the organic solvent may be mixed in a weight ratio of 1:15 to 1:35, preferably 1:20 to 1:30, and more preferably 1:23 to 1:27 have. When mixed in the above-mentioned range, the viscosity of the obtained polymer solution can be controlled, and can be used as a spinning solution in the production of polyacrylonitrile-based fibers without any additional post-treatment.

The total amount of the first charge and the second charge of the polymerization initiator may be 0.1 to 2.0 parts by weight, preferably 0.5 to 1.5 parts by weight, more preferably 0.6 to 1.2 parts by weight based on 100 parts by weight of the raw material mixture. When the above-mentioned range is satisfied, solution polymerization can be easily carried out without lowering the polymerization conversion ratio of the obtained polymer.

The secondary polymerization in the second reactor may also require control of the reaction temperature in some cases. For example, the reaction temperature of the second reactor may be preferably from 60 to 80, and if the above range is satisfied, the molecular weight distribution can be narrowed (can be made small), thereby suppressing deterioration of physical properties And the conversion rate can be increased.

The acrylonitrile-based copolymer produced according to the present invention may have a molecular weight distribution (PDI), that is, a value obtained by dividing the weight average molecular weight by the number average molecular weight of about 1.5 to 3.5, preferably 2.0 to 3.0. In the case of producing the acrylonitrile-based copolymer according to an embodiment of the present invention, it is advantageous in that the conversion rate is excellent but the lowering of the molecular weight distribution value is suppressed and the deterioration of the properties is suppressed.

When the second polymerization reaction is carried out in the second reactor, the viscosity of the final polymer may be about 70,000 cP to 80,000 cP as measured at 45 ° C. Such a viscosity range is a range of viscosity suitable for application to a spinning process as a post-process for producing acrylonitrile-based fibers, and can be carried out by a spinning process without any additional treatment to perform spinning, and clogging or stretching The radiation can be performed without deteriorating physical properties such as deterioration.

According to an embodiment of the present invention, it is preferable that the first reactor and the second reactor are mutually different reactors, and the first reactor may have a relatively excellent heat- It is preferable that a reactor equipped with a stirrer and a jacket is applied, and in the second reactor, a reactor used when there is no gaseous reactant, such as a static mixer, is preferably applied because the reactant has a high viscosity.

In contrast, when the static mixer is used as the first reactor, the physical properties may be degraded due to the temperature gradient in the front portion of the reactor. In the case of using the continuous stirred tank type reactor as the second reactor, May occur.

Example

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example  One

For the evaluation of the continuous process in the steady state, the following reactions were preferentially performed up to a certain conversion rate in order to meet the steady state conditions.

100 parts by weight of a mixture of acrylonitrile, methyl acrylate and itaconic acid in a molar ratio of 97.24: 2.2: 0.54 was uniformly dissolved in 256.5 parts by weight of dimethyl sulfoxide to prepare a reaction solution. And 0.6 part by weight of azobisisobutyronitrile as a radical polymerization initiator were uniformly dissolved in 30 parts by weight of dimethylsulfoxide to prepare a radical polymerization initiator solution.

The reaction solution was poured into a reactor equipped with a stirrer, purged with nitrogen, and then the internal temperature of the reactor was raised to 65 ° C. The radical polymerization initiator solution was added all at once and solution polymerization was carried out for 4 hours.

A mixture of the same components / composition as that of the reaction solution and the polymerization initiator solution was prepared and charged into a container equipped with a stirrer. (This container is referred to as a raw material mixing vessel, and this mixture is referred to as a CSTR raw material.) The CSTR raw material was purged with nitrogen, and the internal temperature was cooled to 5 캜 to be in a steady state.

Thereafter, the CSTR raw material was pumped into the reactor at a flow rate of 12 hours with a pump at the time point of 4 hours of the reactor polymerization (when the polymerization conversion ratio was 70%). At the same time, the polymer in the reactor was pumped out at the same flow rate, and a part of the same was put into a static mixer. The flow rate into the static mixer was such that the residence time in the static mixer was 3 hours.

When the temperature of the reactor, the flow rate, the load of the stirrer, and the static mixer pressure become constant, it can be judged that the steady state has been reached. After reaching the normal state, an acrylonitrile-based copolymer solution was obtained at the end of the static mixer.

Example  2

The acrylonitrile-based copolymer was prepared in the same manner as in Example 1, except that the flow rate was adjusted so that the residence time in the static mixer was 4 hours.

Example  3

The acrylonitrile-based copolymer was prepared in the same manner as in Example 1, except that the flow rate was adjusted so that the residence time in the static mixer was 6 hours.

Comparative Example  One

The acrylonitrile-based copolymer was prepared in the same manner as in Example 1 except that the flow rate was adjusted so that the residence time in the static mixer was 0.83 hours.

Comparative Example  2

The acrylonitrile-based copolymer was prepared in the same manner as in Example 1 except that the flow rate was adjusted so that the residence time in the static mixer was 1.5 hours.

Comparative Example  3

The acrylonitrile-based copolymer was prepared in the same manner as in Example 1 except that the flow rate was adjusted so that the residence time in the CSTR was 6 hours and the residence time in the static mixer was 1.5 hours.

Experimental Example  One

Polymerization conversion and molecular weight distribution (PDI: Mw / Mn) of the acrylonitrile-based copolymer prepared in Examples and Comparative Examples were measured and reported in Table 1 below.

1) Polymerization Conversion Ratio

1 g of the obtained polymer solution was precipitated in water, washed with warm water and dried at 70 for 4 hours. The weight of the dried resin was measured, the content of the solid content was measured, and the polymerization conversion ratio was measured by the following formula.

Polymerization Conversion (%): (content of solid content measured) / (content of solid content per gram of reaction solution calculated as ratio of solid content and solvent introduced into the reactor) x 100

2) Molecular weight distribution ( PDI )

1 g of the obtained polymer solution was measured for weight average molecular weight (Mw) and number average molecular weight (Mn) using GPC (Gel Permeation Chromatography) under the following conditions, and the molecular weight distribution was calculated.

Column: PLmixed B × 2, solvent: DMF / 0.05 M LiBr (0.45 μm Filtered), flow rate: 1.0 ml / min, sample concentration: 4.0 mg / , Standard: PS)

The first reactor residence time Second reactor residence time Residence time ratio Polymerization conversion rate
(%) Molecular weight distribution
(Mw / Mn) Example 1 12 3 4: 1 84.84 2.55 Example 2 12 4 3: 1 85.40 2.67 Example 3 12 6 2: 1 86.51 2.80 Comparative Example 1 12 0.83 14.4: 1 77.76 2.29 Comparative Example 2 12 1.5 8: 1 80.64 2.46 Comparative Example 3 6 1.5 4: 1 79.59 2.54

Referring to Table 1, it can be seen that the retention time in the first reactor and the second reactor and the residence time ratio of the two reactors were suitably controlled in Examples 1 to 3, In the case of Comparative Examples 1 to 3, it was confirmed that the retention time or residence time ratio was not appropriately controlled, and the conversion ran around at a value of 80% or less.

Specifically, in the case of Comparative Example 1, the residence time in the second reactor was too short to satisfy the residence time, and the residence time ratio was too large, resulting in a poor conversion rate. In Comparative Example 2, It can be seen that the conversion ratio is a large value and the conversion ratio is low. In Comparative Example 3, the residence time ratio is at an appropriate level, but the residence time in the first reactor is too short, have.

In addition, it can be seen from the molecular weight distribution values that Comparative Examples 1 to 3 and Examples 1 to 3 are almost at the same level. As described above, when the retention time and the like are controlled, deterioration of physical properties is prevented At the same time, it is confirmed that the conversion ratio is improved and a superior acrylonitrile-based copolymer can be provided.

Experimental Example  2

The effects of addition of an initiator to the second reactor and the addition of an initiator to Example 1 and Comparative Example 2 are shown in Table 2 below.

The addition of the initiator was carried out by dissolving 0.6 parts by weight of azobisisobutyronitrile in 20.6 parts by weight of dimethylsulfoxide to prepare a radical polymerization initiator solution. After nitrogen replacement, the mixture was poured into a static mixer for 10 minutes 1 at a flow rate of 1 ml / min. The procedure of Example 1 and Comparative Example 2 was repeated.

If no additional initiator is added If additional initiator is added Example 1 84.84% 90.17% Comparative Example 2 80.64% 84.67%

Referring to Table 2 above, it can be confirmed that the conversion rate greatly increased when the initiator was further added to the second reactor. Specifically, in the case of Example 1, the ratio of the residence time and the residence time in each reactor was controlled, so that the conversion rate was increased to about 5.5% even with the addition of the initiator. In the comparative example, however, the conversion rate was only about 4% , The regulation of residence time and the ratio of residence time also affect the increase in conversion rate due to the addition of initiator.

Claims (8)

A continuous production process comprising a reaction system comprising at least two reactors,
Polymerizing the raw material mixture containing the acrylonitrile monomer in the presence of the polymerization initiator in the first reactor while controlling the residence time to 8 to 15 hours;
Transferring the first polymerized raw material mixture to a second reactor and performing a secondary polymerization in a second reactor and controlling the retention time to be 1.5 to 6 hours to prepare a final polymerized product,
Wherein the ratio of the residence time of the first reactor to the residence time of the second reactor is from 2: 1 to 6: 1.
The method according to claim 1,
Wherein the residence time of the first reactor is 10 to 13 hours.
The method according to claim 1,
Wherein the ratio of the residence time of the first reactor to the residence time of the second reactor is from 2: 1 to 4: 1.
The method according to claim 1,
And the residence time of the second reactor is 3 to 6 hours.
The method according to claim 1,
Wherein the first reactor comprises any one selected from the group consisting of a continuous stirred tank reactor, a tubular reactor, and an extruder.
The method according to claim 1,
Wherein the second reactor comprises any one selected from the group consisting of a static mixer, a tubular reactor, and an extruder.
The method according to claim 1,
Wherein a polymerization initiator is further added to the second reactor, and 0.1 to 2.0 parts by weight of the polymerization initiator is added to 100 parts by weight of the first polymerized raw material mixture.
The method according to claim 1,
And the reaction temperature of the second reactor is 60 to 80 占 폚.