JP2015160953A - Method for producing acrylonitrile-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an acrylonitrile-based polymer, in which the supply amount of acrylonitrile is reduced just after polymerization is initiated to prevent an acrylonitrile-rich polymer, that is produced at the initial stage of polymerization, from being produced so that the acrylonitrile-based polymer having excellent solubility can be produced.SOLUTION: The method for producing the acrylonitrile-based polymer comprises the steps of: continuously feeding monomers including acrylonitrile and (meth)acrylate, a redox polymerization initiator and water to a reactor; and continuously withdrawing a reaction solution from the reactor. Until X hours since a feed of the monomers to the reactor is started, the average value of the supply amounts of the (meth)acrylate for 10 minutes is controlled to be 1.1×A mass% to 2.0×A mass% of the supply amounts of all monomers. After X hours since the feed of the monomers to the reactor is started, the supply amount of the (meth)acrylate is controlled to be A mass% of the supply amounts of all monomers. On condition that A satisfies 3≤A≤10 and X satisfies 0.5≤X≤3.

Description

  The present invention relates to a method for producing an acrylonitrile-based polymer suitable for acrylic fibers.

  The acrylonitrile polymer used as a raw material for acrylic fibers is generally produced by aqueous precipitation polymerization or solution polymerization. In particular, the aqueous precipitation polymerization method enables continuous production with a shorter residence time than solution polymerization, and is extremely excellent in productivity because it uses a simple reactor.

  In general, the starting method for continuous production by aqueous precipitation polymerization is such that, at the start of polymerization, a predetermined amount of water and a polymerization initiator are charged in advance to the overflow start position of the reactor, and a polymerization initiator, a monomer and water are predetermined therein. The polymerization is started by continuously feeding at a ratio of

  The stability of the production process of polyacrylonitrile fiber and the quality of the fiber are affected by the solubility of the polyacrylonitrile polymer particles in the solvent. The solubility of the polymer particles is affected by the solubility of the individual particles and the dispersibility of the polymer particles. For example, if undissolved polymer particles are present in the spinning dope, it becomes a nucleus and a gel is generated, so that the stability of the dope is impaired, and thread breakage and fluff are caused. If the acrylonitrile monomer unit of the polyacrylonitrile polymer particles is less than 95% by mass, the solubility in the solvent is generally good, but if the acrylonitrile monomer unit is 95% by mass or more, the polymer particles The shape of has a great effect on solubility. In addition, when the dispersibility of the polymer particles is low, the polymer particles are fused.

As a solution to the above problem, in Patent Document 1, the polymer particle bulk density is controlled to 0.33 g / cm ³ or more and 0.50 g / cm ³ or less, and the volume average particle size is controlled to 15 μm or more and 30 μm or less. Discloses a method for producing acrylonitrile-based polymer particles, which are excellent in dispersibility and solubility in water and can improve the stability of the spinning process.

JP 2012-201739 A

  However, in the method described in Patent Document 1, polymer particles having an acrylonitrile monomer unit of 95% by mass or more may be generated at the initial stage of polymerization. If this is generated / mixed in the early stage of polymerization, the solubility may be affected.

  An object of the present invention is to reduce the acrylonitrile supply composition immediately after the start of polymerization, thereby preventing the formation of an acrylonitrile-rich polymer generated at the initial stage of polymerization, and producing an acrylonitrile-based polymer having excellent solubility. It is to provide a method for producing an acrylonitrile-based polymer.

The above problems are solved by the present invention.
The method for producing an acrylonitrile-based polymer of the present invention comprises continuously supplying acrylonitrile and a monomer containing a (meth) acrylic ester, a redox polymerization initiator and water to the reactor, and supplying the reaction liquid from the reactor. A process for producing an acrylonitrile-based polymer continuously taken out, wherein the average value of (meth) acrylic acid ester supply amount for 10 minutes is X 1.1 × A mass% to 2.0 × A mass% with respect to the supply amount, and after X hours from the start of supply, the (meth) acrylic ester supply amount is based on the supply amount of all monomers. It is a manufacturing method of the acrylonitrile-type polymer made into A mass%.
However, 3 ≦ A ≦ 10 and 0.5 ≦ X ≦ 3.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the acrylonitrile-type polymer which can manufacture the acrylonitrile-type polymer excellent in the solubility in the initial stage of superposition | polymerization is provided.

Details of the present invention will be described below.
<Reactor>
The reactor used in the present invention is, for example, a device having a device for stirring the reaction liquid in the reactor, a polymerization initiator, a supply port for supplying monomer and water, a polymerization heat removing means, and an overflow port.

<Monomer>
In the case of producing an acrylonitrile-based polymer, it is preferable that the acrylonitrile unit is contained in an amount of 40% by mass or more, and considering the heat resistance of fibers produced from the polymer, the acrylonitrile unit is 90% by mass. More preferably, it is contained. Further, other vinyl monomers copolymerizable with acrylonitrile can be included. Examples of other copolymerizable vinyl monomers include (meth) acrylic acid such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and hexyl (meth) acrylate. Esters, vinyl halides such as vinyl chloride, vinyl bromide, vinylidene chloride, acids such as (meth) acrylic acid, itaconic acid, crotonic acid and their salts, maleic imide, phenylmaleimide, (meth) acrylamide, Examples include styrene, α-methylstyrene, vinyl acetate, sodium (meth) allylsulfonate, sodium (meth) allyloxybenzenesulfonate, sodium styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and salts thereof. It is done.

<Polymerization initiator>
In redox aqueous precipitation polymerization, as an oxidizing agent, generally, an inorganic oxidizing agent such as ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide, methyl ethyl ketone peroxide, t-butyl hydroperoxide, di-t Organic peroxides such as butyl peroxide, cumene hydroperoxide, succinic acid peroxide, and di (2-ethoxyethyl) peroxydicarbonate are used.

As the reducing agent, sodium sulfite, ammonium sulfite, sodium bisulfite, ammonium bisulfite, sodium thiosulfate, ammonium thiosulfate, sodium dithionite, sodium formaldehyde sulfoxylate, L-alcorbic acid, dextro -Etc. are used.
Moreover, it is preferable to use a redox-type auxiliary agent together with the oxidizing agent and the reducing agent. Examples of the auxiliary agent include ferrous sulfate and copper sulfate. The concentration of the auxiliary agent is not particularly defined, but is preferably 0.01 ppm or more from the viewpoint of more efficient polymerization, and preferably 1000 ppm or less from the viewpoint of preventing excessive remaining in the polymer particles.
In particular, it is preferable to use a combination of ammonium persulfate-ammonium hydrogen sulfite-ferrous sulfate.

<Polymerization reaction>
Since the present invention is a method of continuously polymerizing monomers by an aqueous precipitation polymerization method, a known method can be used. For example, deionized water (polymerization medium) is charged in the reactor in advance, and oxidant, reducing agent, redox system auxiliary, deionized water, and monomer are continuously supplied to the reactor and stirred. The polymerization reaction is preferably allowed to proceed.

<Aqueous solution in which initiator is dissolved>
Immediately after starting to supply the monomer into the reactor, the monomer concentration is very dilute. Furthermore, when the concentration of the initiator is also dilute, the polymerization may not start quickly. Therefore, in order to start the polymerization reaction promptly, it is preferable to charge the initiator in advance before starting to supply the monomer. The initiator concentration charged in advance is preferably 1% by mass or less, and more preferably 0.8% by mass or less from the viewpoint of suppressing a large amount of oligomer formation. The concentration is preferably 0.01% by mass or more, more preferably 0.1% by mass or more from the viewpoint of promptly starting the polymerization reaction.

<Start supplying continuously into the reactor stored up to the specified position>
Immediately after starting to supply the monomer, polymer particles are rapidly precipitated, and the concentration of the polymer particles increases. If the concentration of the polymer particles becomes too high, the reaction solution becomes viscous, resulting in poor stirring, and the heat removal from the polymerization heat may be locally insufficient. Therefore, in order to suppress the rapid increase in the polymer particle concentration as much as possible, it is preferable to take out the reaction solution from the reactor at the same time as the start of the monomer supply.

  The polymer composition differs between the initial state (unsteady state) and the steady state. However, in the continuous polymerization method, it is necessary to take out the same amount of the reaction liquid at the same time as the supply of monomers and initiators. The produced polymer may directly affect the subsequent process. Therefore, it is preferable from the viewpoint of solubility that the acrylonitrile unit in the polymer in the initial stage of polymerization is not more than the acrylonitrile unit in the steady state. On the other hand, if there are too few polymer acrylonitrile units in the polymer, there is a concern that the performance of the carbon fiber will be lowered. Therefore, the lower limit of the acrylonitrile units at the initial stage of polymerization must not be significantly lower than that in the steady state.

  In view of the above, in order to prevent the acrylonitrile unit of the polymer in the initial stage of polymerization from being lower than the acrylonitrile unit in the steady state and not significantly lower, it is effective to make the acrylonitrile supply amount in the initial stage of polymerization lower than the steady state.

  In the present invention, the (meth) acrylic acid ester unit supplied to the steady state is A mass% by mass. A is not particularly limited as long as acrylonitrile-based polymer can be obtained. However, since a decrease in acrylonitrile units may cause a decrease in carbon fiber performance, A is preferably 10% by mass or less. Further, if the acrylonitrile unit is too high, the solubility of the polymer is deteriorated, which may cause a problem in passing through the spinning process. Therefore, A is preferably 3% by mass or more.

  The (meth) acrylic acid ester unit supplied from the start of polymerization to X hours is not particularly limited as long as an acrylonitrile-based polymer can be obtained, but the decrease in the acrylonitrile unit may cause a decrease in carbon fiber performance. It is preferable that it is A * 2.0 or less. Further, if the acrylonitrile unit at the initial stage of polymerization is too high, the solubility of the polymer is deteriorated, which may cause a problem in passing through the spinning process. Therefore, it is preferably A × 1.1 or more.

  It is preferable that the acrylonitrile unit, which has been temporarily lowered at the stage when the steady state is changed from the unsteady state where there is a concern that a polymer having a high acrylonitrile unit is formed, be brought into a steady state. X time is defined as the time from the start of polymerization until the ratio of the monomer to the initiator reaches a steady state. X is preferably 0.5 ≦ X ≦ 3. X is more preferably 1.5 or less.

The temperature of the reaction liquid in the reactor is not particularly limited as long as the monomer can be polymerized. However, it is preferably 80 ° C. or less, more preferably 60 ° C. or less, from the viewpoint of preventing acrylonitrile from evaporating and being dispersed outside the reaction system. In order for the polymerization reaction to proceed rapidly, it is necessary to be 30 ° C. or higher. Moreover, it is preferable to keep the temperature of the reaction liquid constant from the viewpoint of stabilizing the molecular weight of the polymer.
The average residence time of the monomer in the reactor is not particularly limited, and may be a time conventionally employed when producing an acrylonitrile-based polymer by aqueous precipitation polymerization. The average residence time is preferably 200 minutes or less from the viewpoint of productivity, and preferably 20 minutes or more from the viewpoint of sufficiently completing the polymerization. The hydrogen ion concentration in the reactor may be a concentration such that the initiator promptly causes an oxidation / reduction reaction, and an acidic region having a pH of 2.0 to 3.5 is preferable.

<Removal of reaction solution>
In the present invention, while the monomer is polymerized in the reactor as described above, the reaction liquid containing the polymer particles is continuously taken out from, for example, the overflow port of the reactor.
The polymerization is stopped by adding, for example, a polymerization terminator dissolved in deionized exchange water to the reaction solution. As the polymerization terminator, a polymerization terminator conventionally used when producing an acrylonitrile-based polymer by aqueous precipitation polymerization can be used without limitation. Subsequently, the unreacted monomer is recovered from the aqueous polymer solution. As a method for recovering the unreacted monomer, there is a method of directly distilling the polymer aqueous solution, or a method of once dehydrating and separating the unreacted monomer from the polymer, followed by distillation. Both can be adopted. As the dehydration washer used in the latter method, a generally known filter dehydrator can be used. For example, a rotary vacuum filter, a centrifugal dehydrator, or the like can be used. From the viewpoint of efficiency, a flocculant such as ammonium sulfate, aluminum sulfate, or sodium sulfate can be added when separating the polymer from the reaction solution using these apparatuses, and further from the viewpoint of promoting the aggregation of the polymer. Operations such as raising the temperature of the aqueous polymer solution can also be performed. Further, water remaining in the polymer can be removed by a normal drying method.

  The above acrylonitrile polymer is dissolved in an amide solvent to obtain a spinning dope. As the amide solvent, dimethylacetamide and dimethylformamide capable of obtaining highly dense acrylonitrile copolymer fibers are preferable, and dimethylacetamide is particularly preferable.

  In the present invention, aqueous precipitation polymerization using a redox initiator is adopted because it is excellent in productivity and can reduce the amount of unnecessary components such as residual monomers, but the polymerization method is aqueous precipitation polymerization. , Suspension polymerization, solution polymerization, emulsion polymerization and the like are not particularly limited. In the aqueous precipitation polymerization using the redox initiator in the present invention, the monomer is polymerized by continuously supplying a monomer mainly composed of acrylonitrile, a redox initiator and deionized water in the reactor. Is the method.

<Pressure degree: Evaluation of solubility of polymer particles>
Polymer particles are uniformly dispersed at a solid content of 21% by mass in dimethylacedamide cooled to −15 ° C. to obtain a dispersion. This dispersion is passed through a pipe with an inner diameter of 11 mm with a jacket through which the heat medium can be circulated, and dissolved by heating to 110 ° C. with a residence time of 4.2 minutes to obtain a polymer solution. When the polymer solution is passed through a metal non-woven fabric filter (manufactured by Nippon Seisen: NF-05S) with a 90% collection efficiency of 5 μm at 330 g at 11 g / min, the value of the differential pressure increase is expressed as the degree of pressure increase (MPa ) As an index of solubility of polymer particles. The smaller the value of the pressurization degree, the less the undissolved substance captured by the filter, and the better the solubility.

<Example 1>
Deionized exchange water in which 0.0000097 mass% ferrous sulfate, 0.098 mass% ammonium persulfate, and 0.15 mass% ammonium bisulfite were dissolved in an aluminum reactor equipped with a 76.5 liter disc turbine stirring blade Was charged until the reactor was full and the internal temperature of the reactor was raised to 57 ° C., then acrylonitrile 259 g / min, 2-hydroxyethyl methacrylate 25% by weight aqueous solution 56 g / min, deionized water 578 g / min, ammonium persulfate 2. A 75 mass% aqueous solution 55 g / min, an ammonium bisulfite 5 mass% aqueous solution 45 g / min, a ferrous sulfate 0.0002 mass% aqueous solution 41 g / min, and a sulfuric acid 0.5 mass% aqueous solution 63 g / min were simultaneously and continuously used as fluids. Supply started.

After the generation of polymerization heat was confirmed, the temperature of the reaction solution was gradually lowered to 50 ° C. about 1 hour after the start of the monomer supply. Furthermore, at the time of 1 hour after starting the supply of the monomer, among the supply fluid, 262 g / min of acrylonitrile, 45 g / min of 2-hydroxyethyl methacrylate, 612 g / min of deionized water, 46 g / min of an aqueous ammonium persulfate solution, The supply flow rate was quickly changed so that the aqueous solution of ammonium hydrogen sulfite was 38 g / min and the aqueous solution of sulfuric acid 53 / min.

  Through the polymerization reaction, the polymerization reaction was continuously carried out while stirring, and the reaction solution was continuously taken out from the reactor overflow port so that the average residence time of the monomers was 70 minutes. The reaction liquid in the reactor was polymerized while adjusting the sulfuric acid aqueous solution supply amount so that the pH was 3.0. The reaction solution for measuring the pressure increase was collected from the overflow port 7 hours after the start of polymerization.

  A polymerization stopper aqueous solution in which 0.5% by mass of sodium oxalate and 1.8% by mass of sodium bicarbonate were dissolved in deionized water was added to the removed reaction solution, and the pH of the reaction solution was adjusted to 5.5 to 6.0. In addition, the mixture was filtered with a centrifugal dehydrator to separate unreacted monomers and surplus polymerization surplus from the polymer.

  The obtained wet polymer was dried with a ventilation band type dryer to obtain an acrylonitrile-based polymer. Table 1 shows the polymer composition and the pressure increase degree of the polymer 7 hours after the start of the polymerization.

  The acrylonitrile unit in the polymer 7 hours after the start of the polymerization was 95% by mass or more, and the pressurization degree was kept low.

<Example 2>
As in Table 1, the supply rate of acrylonitrile was changed to 92.85% by mass before 1 hour from the start of polymerization and 95.85% by mass after 1 hour. Acrylonitrile-based polymer was obtained.
The acrylonitrile unit in the polymer 7 hours after the start of the polymerization was 95% by mass or more, and the pressurization degree was kept low.

<Comparative Example 1>
As in Table 1, the supply ratio of acrylonitrile was not changed from the start of polymerization, but the supply flow rate was changed so that it was 95.85% by mass before 1 hour and after 1 hour. As a result, an acrylonitrile-based polymer was obtained.
The acrylonitrile unit in the polymer 7 hours after the start of polymerization was the same as in the examples, but the degree of pressurization increased.

<Comparative Example 2>
As in Table 1, the supply rate of acrylonitrile was changed to 96.54% by mass before 1 hour from the start of polymerization and 95.85% by mass after 1 hour. Acrylonitrile-based polymer was obtained.
The acrylonitrile unit in the polymer 7 hours after the start of polymerization was the same as in the examples, but the degree of pressurization increased.

Claims (2)

Each of acrylonitrile and a monomer containing (meth) acrylic acid ester, a redox polymerization initiator and water are continuously supplied to a reactor in which the polymerization initiator and water are stored, and a polymerization reaction is started. A method for producing an acrylonitrile-based polymer in which a reaction liquid containing a polymer is continuously taken out from a reactor, wherein (meth) acrylic acid ester is supplied until X hours from the start of supplying the monomer to the reactor. The average value of the amount for 10 minutes is 1.1 × A mass% to 2.0 × A mass% with respect to the supply amount of all monomers, and after X hours from the start of supply, (meth) acrylic acid ester A method for producing an acrylonitrile-based polymer in which the supply amount is A mass% with respect to the supply amount of all monomers.
However, 3 ≦ A ≦ 10 and 0.5 ≦ X ≦ 3.   From the start of supplying the monomer to the reactor until the X hour, the average value of the (meth) acrylic acid ester supply amount for 10 minutes is 1.2 × A mass% with respect to the total monomer supply amount. It is -1.8 * A mass%, The manufacturing method of the acrylonitrile-type polymer of Claim 1.