JP2013199518A - Acrylic polymer and method for producing acrylic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic polymer and a production method of an acrylic fiber without causing reduction of polymer qualities, and without diminishing productivity of fiber production actually, in a case of reutilizing recovered unreacted monomer containing impurities as the raw material monomer.SOLUTION: Solution polymerization is performed using a raw material monomer comprising 92 mass% or more acrylonitrile, dimethyl sulfoxide as the polymerization solvent and an azo compound as the polymerization initiator, respectively. The obtained polymer solution is subjected to vaporization/separation through counter contact with vapor of the polymerization solvent by way of a reduced-pressure distillation column. Thereafter, the polymer solution is mixed with a polymerization solvent containing moisture, and conducting reduced-pressure distillation again and the distillate is separated into a water phase and an organic phase to recover the unreacted monomer. The obtained recovered unreacted monomer is reutilized as the raw material monomer to produce the acrylic polymer by solution polymerization such that the charge amount of the recovered monomer is corrected according to concentration of containing impurities, and the usage rate of the recovered monomer is set to 1 to 50 mass% to acrylonitrile.

Description

  The present invention relates to a method for producing an acrylic polymer and a method for producing an acrylic fiber that effectively utilize recovered unreacted monomers.

  Acrylic fibers have excellent bulkiness similar to wool, texture and dyeing clarity, and have a wide range of uses in the clothing field such as knitwear and jerseys. In recent years, in addition to anti-pilling properties, there is an increasing demand for underwear applications, taking advantage of the soft texture and heat storage properties resulting from finer fineness.

  The acrylic fiber is obtained by spinning an acrylic polymer obtained by polymerizing a raw material monomer mainly composed of acrylonitrile by wet spinning. Acrylic polymer polymerization methods are roughly classified into solution polymerization and suspension polymerization. The acrylic polymer is polymerized by a radical polymerization reaction, but the reaction rate decreases as the reaction proceeds in solution polymerization. For this reason, from the production efficiency, the raw material monomer is polymerized at a polymerization rate of about 90%, and a polymer solution obtained by separating unreacted monomers from the obtained polymer stock solution is spun by a wet spinning method as a spinning stock solution.

  Generally, in order to remove unreacted monomers from a polymer solution, the unreacted monomers are separated and recovered from the polymer solution by bringing the polymer solution and solvent vapor into countercurrent contact using a vacuum packed tower. The solvent vapor from which the unreacted monomer has been recovered is liquefied using a heat exchanger, and is distilled again under reduced pressure under conditions where the unreacted monomer is preferentially distilled to separate and recover the solvent and the unreacted monomer.

  Discarding such unreacted monomer that can be used as a raw material for synthesis is not only economically problematic, but also because most of it is acrylonitrile, in order to reduce toxicity and safely dispose of it. Requires labor and equipment. Considering these, it is desirable to reuse the recovered unreacted monomer as a raw material monomer.

  Conventionally, a method has been proposed in which a polymer solution obtained by polymerization is distilled under reduced pressure to separate and recover an unreacted monomer and a solvent, and the recovered unreacted monomer is reused as a raw material monomer (Patent Document). 1). However, in this proposal, the recovered unreacted monomer contains, as impurities, a pyrolysis product obtained by distillation under reduced pressure at the time of recovery, in addition to by-products in the raw material monomer production process. There is a problem that the amount of monomer necessary for the production is insufficient, which causes deterioration of the quality of the polymer.

  In addition, regarding the technology for recovering unreacted monomers, when vaporizing and separating unreacted monomer components from the polymerization process, addition of a polymerization inhibitor for the purpose of suppressing polymerization of unreacted monomers, or aggregation by a polymer There are proposals such as automatically switching to another aggregator when the part is clogged (see Patent Documents 2 and 3). Both proposals show impurities in the unreacted monomer recovered and the unreacted monomer. There is no clear description of how to reuse the.

  Another method has been proposed in which unreacted monomer is distilled once or more under reduced pressure to be purified to a purity of 97% by mass or more and reused (see Patent Document 4). However, in the case of this proposal, a large amount of capital investment is required when a distillation column is connected in a continuous polymerization process, and when continuous distillation is performed with one distillation column as described, the result is high. There is a problem that purification becomes difficult.

JP 2000-336115 A JP 2003-292528 A JP 2006-241648 A JP 2011-063553 A

  Therefore, an object of the present invention is to provide a method for producing an acrylic polymer which does not substantially impair the productivity of fiber production without reducing the polymer quality when the recovered unreacted monomer containing impurities is reused as a raw material monomer. It is providing the manufacturing method of an acrylic fiber.

  The present invention is obtained by performing solution polymerization using a raw material monomer comprising at least 92% by mass of acrylonitrile, dimethyl sulfoxide (hereinafter sometimes referred to as DMSO) as a polymerization solvent and an azo compound as a polymerization initiator. The polymer solution was vaporized and separated by countercurrent contact with the polymerization solvent vapor using a vacuum distillation column, then mixed with a water-containing polymerization solvent, and the fraction distilled again under reduced pressure was separated into an aqueous phase and an organic phase, and unreacted. The monomer is recovered, and the recovered unreacted monomer is reused as a raw material monomer. The monomer input amount is corrected according to the concentration of impurities contained therein, and the usage rate is 1 to 50% by mass with respect to acrylonitrile. A method for producing an acrylic polymer, characterized by polymerization.

  In the present invention, when a recovered unreacted monomer containing impurities is used, the amount of impurities contained can be specified, and the raw material monomer deficient in the polymerization reaction system can be corrected. At this time, the input amount of the polymerization solvent is changed according to the corrected monomer amount, and the total amount of the input solution to the polymerization reaction system is made constant. Thereby, it is possible to supply the amount of monomers required for the polymerization reaction to the reaction tank without being influenced by the amount of impurities, and the deterioration of the quality of the polymerized acrylic polymer can be suppressed.

  Moreover, the unreacted monomer and water form an azeotrope by mixing the recovered unreacted monomer recovered with a water-containing polymerization solvent. The fraction obtained by distilling this mixed solution under reduced pressure is flocculated and liquefied by a heat exchanger, and the aqueous phase separated by decantation is discharged to remove dissolved impurities. It is possible to suppress accumulation of impurities.

  In this invention, the acrylic fiber which suppressed the deterioration of quality can be manufactured by carrying out wet spinning using the solution of the acrylic polymer obtained by the manufacturing method of said acrylic polymer as a spinning dope.

  ADVANTAGE OF THE INVENTION According to this invention, the acrylic polymer and acrylic fiber which suppressed the deterioration of quality can be manufactured even if the collect | recovered unreacted monomer containing the impurity is reused for a polymerization reaction. Since there is no problem even if impurities are contained, it is not necessary to purify the recovered unreacted monomer with high purity, and it is possible to reduce the operating cost of the distillation tower. High reuse becomes possible.

  In the method for producing an acrylic polymer of the present invention, 92% by mass or more of a raw material monomer consisting of acrylonitrile, DMSO as a polymerization solvent and an azo compound as a polymerization initiator are used for solution polymerization, and the obtained polymer solution is obtained. It is vaporized and separated by countercurrent contact with the polymerization solvent vapor by a vacuum distillation column, then mixed with a water-containing polymerization solvent, and the fraction distilled again under reduced pressure is separated into an aqueous phase and an organic phase to recover unreacted monomers, The amount of monomer input is corrected according to the concentration of impurities contained in recycling the recovered unreacted monomer obtained as a raw material monomer, and solution polymerization is carried out at a usage rate of 1 to 50% by mass with respect to acrylonitrile. It is what.

  The present invention relates to a method for producing an acrylic polymer, in which a raw material monomer that has not contributed to the reaction is reused as a raw material monomer in a polymer solution that is an acrylic fiber spinning dope.

  As a raw material monomer, in addition to acrylonitrile as a main component, 2.8 to 7.0% by mass of a copolymerizable ethylenic vinyl monomer and 1.0 to 5.2% by mass of a sulfonic acid-containing vinyl monomer, It is preferable to contain. An acrylic fiber having good quality and excellent color developability can be obtained by wet spinning the obtained polymer. When the content of acrylonitrile is less than 92% by mass, the heat setting property in a tension state applied in advance in the yarn forming process may be remarkably deteriorated by dyeing or steam heat treatment in a higher processing step, which is not preferable.

  Examples of the ethylenic vinyl monomer of the copolymer component include vinyl halides, vinyl esters, acrylic acid, methacrylic acid and esters or salts thereof, maleic acid, fumaric acid and esters or anhydrides thereof, butadiene, chloroprene, and styrene. Is mentioned. When the copolymerization rate of the ethylenic vinyl monomer is less than 2.8% by mass, the stretchability is poor and stable production may be difficult. On the other hand, when the copolymerization ratio of the ethylenic vinyl monomer is more than 7.0% by mass, it becomes difficult to drop off the pills generated in the cloth fabric spun and knitted from the knitted acrylic fiber, which leads to a decrease in product quality. Sometimes.

  In addition, examples of the sulfonic acid-containing vinyl monomer include unsaturated sulfonic acids such as vinyl sulfonic acid, acrylic sulfonic acid, methallyl sulfonic acid, and P-styrene sulfonic acid, or acidic monomers such as salts thereof. When the copolymerization rate of the sulfonic acid-containing vinyl monomer is less than 1% by mass, sufficient dyeing performance cannot be obtained. When the copolymerization ratio exceeds 5.2% by mass, the dyeing performance increases, but the coagulation is slow and the fibers are separated in the spinning process. Adhesion tends to occur. Moreover, the obtained fiber may also cause dyeing spots such as ring dyeing.

  The polymerization reaction in the present invention is carried out by a solution polymerization method in which dimethyl sulfoxide is selected as a polymerization solvent from the viewpoint of chain transfer constant and low toxicity. Since the polymer concentration obtained by the polymerization reaction is preferably 21 to 24% by mass, the amount of DMSO to be used is preferably 2.88 to 3.36 by mass ratio with respect to the raw material monomer. The conditions for the solution polymerization may be those usually carried out, but regarding the polymerization rate, it is advantageous in terms of production efficiency and economy to set the raw material monomers to 85 mass% to 95 mass%.

  Further, although an azo compound is used as the polymerization initiator, relatively low temperature decomposable azobisdimethylvaleronitrile that does not remain in the recovered unreacted monomer is 0.052 to 0.066 with respect to the polymerization solution. It is a preferable aspect to use the mass%.

  An acrylic fiber is obtained by wet spinning using a polymer solution obtained by polymerization as a spinning dope. Wet spinning is a spinning method in which a spinning solution is directly discharged into a coagulation bath from a spinneret to form a fiber.

  Next, a method for recovering unreacted monomers will be described.

  The polymer solution having a polymerization rate of preferably about 90% by mass is sent to a vacuum packed column and brought into countercurrent contact with solvent vapor, whereby unreacted monomers are vaporized and separated from the polymer solution. After separation, it is liquefied by a heat exchanger and stored in a recovery tank. At this time, a polymerization solvent containing water is supplied to the tank to obtain a recovered liquid. As a polymerization solvent containing water to be supplied, it is preferable to use a coagulation bath liquid used in wet spinning. Thus, the recovered solution is distilled under reduced pressure, whereby the polymerization solvent can be separated and purified from water while the unreacted monomer is vaporized and separated, which is efficient. The fraction obtained by distilling the recovered liquid under reduced pressure is condensed and liquefied by a heat exchanger and separated into an unreacted monomer and an aqueous phase, which are organic phases, by decantation. The separated monomer is reused in the polymerization reaction as a recovered unreacted monomer. In addition, since an azeotrope with unreacted monomers is formed in the aqueous phase, accumulation of impurities in the recovery system can be suppressed by discharging them. Impurities generated at this time include acrylonitrile-derived acetone, acetonitrile, and dimethylsulfoxide-derived dimethyl sulfide.

  The recovered unreacted monomer is reused as a raw material monomer for the polymerization reaction. The ratio of the recovered unreacted monomer in the raw material monomer acrylonitrile is colored yellow when the impurities are concentrated, and is 1 to 50% by mass in consideration of the influence on the color tone of the acrylic fiber after spinning, preferably 1 -30 mass%.

  Next, a method for reusing recovered unreacted monomers will be described.

  Before supplying the recovered unreacted monomer to the polymerization reaction tank, the solution is fed to the adjustment tank, and the content of impurities is grasped by gas chromatography. When the recovered unreacted monomer is fed from the adjustment tank to the polymerization reaction tank, the amount of acrylonitrile is corrected according to the amount of impurities, and the amount of raw material monomer necessary for the reaction is adjusted to be constant in the reaction tank. At this time, the total amount of liquid charged into the reaction tank increases by the amount of impurities, but the amount of liquid input in the reaction tank is made constant by decreasing the amount of polymerization solvent by the amount of impurities. Thus, the required amount of monomer is charged into the reaction vessel without depending on the amount of impurities, and proper polymer polymerization proceeds. The polymer concentration in the polymer solution is preferably 20 to 25% by mass, and the viscosity at a temperature of 45 ° C. is preferably 180 to 240 poise.

  The obtained polymer solution is wet-spun by spinning from a spinneret into a bath using DMSO aqueous solution as a coagulating liquid as a spinning solution after evaporating and separating unreacted monomers by distillation under reduced pressure. When spinning, the spinning dope temperature is preferably 60 to 80 ° C, more preferably 65 to 75 ° C, and the spinning draft is preferably 1.7 to 2.2, more preferably 1.8 to 2.1. Is defined as the yarn production condition. When the spinning dope temperature is less than 60 ° C., not only the spinning property of the spinning dope is insufficient, but also the viscosity is high, which may cause equipment damage such as an increase in nozzle pressure. On the other hand, when the temperature of the stock solution for spinning is higher than 80 ° C., it often causes modification such as gelation of the stock solution for spinning, and stable spinning may not be expected.

  Also, if the spinning draft is less than 1.7, the yarn from the base to the take-up roller is loosened, the yarn is shaken by the turbulent flow of the coagulation bath liquid, and the yarn is cut at the base, and if the spinning draft exceeds 2.2, the tension is May break the thread on the base.

  The coagulated fiber bundle is desolvated in a bath of several stages where the DMSO concentration sequentially decreases, and after passing through the stretching step and the water washing step, DMSO is completely removed, and then preferably at 165 ° C. or more, more preferably 170 While maintaining a shrinkage of 5% or less, more preferably 1 to 3% under dry heat at a temperature of ˜175 ° C., drying and densification tension heat treatment are performed to obtain an acrylic fiber. As a result, it is possible to produce acrylic fibers having good quality and excellent color developability while effectively utilizing recovered unreacted monomers.

  Next, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The impurity concentration, polymer concentration and viscosity in the examples were based on the following method. Further, the dry strength and elongation of acrylic fibers were measured by the JIS L1015 chemical fiber staple test method. About dry strength elongation, each 35 points | pieces were measured and the average value was made into the measured value.

(Impurity concentration)
Using a microsyringe, 1 μL of recovered unreacted monomer sampled from the liquid storage tank was collected and measured by gas chromatography. The impurity amount was calculated from the detected component ratio. GC-17A manufactured by Shimadzu Corporation was used as gas chromatography.

(Polymer concentration)
It is the weight% of the polymer contained in the polymer solution sampled from the polymerization reaction tank. Specifically, the measurement is performed as follows.
Weigh the sampled polymer solution. ... Mass (1)
The polymer solution is dissolved in a liquid that does not dissolve the polymerized polymer and is compatible with the polymerization solvent, and then the mass of the polymer is weighed. ... Mass (2)
(In the present invention, DMSO was used as a polymerization solvent, and water was used as a compatible liquid.)
The polymer concentration is calculated from the following formula.
Mass (2) ÷ mass (1) × 100 = polymer concentration (%).

(Polymer viscosity)
The polymer solution sampled from the polymerization reaction vessel was measured with a B-type viscometer at a liquid temperature of 45 ° C. in a constant temperature bath.

[Example 1]
Using DMSO as a polymerization solvent and azobisdimethylvaleronitrile as a polymerization initiator, 92% by mass of acrylonitrile, 7% by mass of methyl acrylate, and 1% by mass of sodium methallylsulfonate were polymerized to obtain a polymer solution. . The DMSO used was 2.93 times the mass ratio of the raw material monomers, and the amount of initiator added was 0.058% by mass relative to the raw material monomers. The polymer concentration at this time was 22.0% by mass. The obtained polymer solution was sent to a vacuum packed tower to recover unreacted monomers. The recovered monomer was mixed with the coagulation bath solution obtained by spinning the polymer solution, and the fraction obtained by distillation under reduced pressure was decanted again to obtain recovered unreacted monomer from the organic phase. The impurity concentration of the recovered unreacted monomer obtained was 3.6% by mass, acrylonitrile 94.4% by mass, and water 2% by mass. The breakdown of impurities was 1.50% dimethyl sulfide, 0.40% acetone, and 1.70% acetonitrile. The usage rate of the recovered unreacted monomer with respect to acrylonitrile was set to 30% by mass, and the recovered unreacted monomer was charged instead of acrylonitrile. When substituting 30% by mass of acrylonitrile with recovered unreacted monomer, the monomer correction was performed by introducing 31.12% by mass of recovered unreacted monomer in consideration of the impurity being 3.6% by mass. By reducing the amount of DMSO input, the total amount of liquid input to the reaction tank becomes constant even if recovered unreacted monomer is used for the amount of liquid input to the polymerization reaction tank increased by this correction. I did it. Similarly, solution polymerization was carried out, and unreacted monomers were collected and reused repeatedly. Even when this polymerization cycle was carried out 50 times, there was no significant difference between the polymer concentration obtained and the high elongation of the spun acrylic fiber. The results are shown in Table 1.

[Comparative Example 1]
The same polymerization cycle as in Example 1 was carried out 50 times except that monomer correction was not performed. Regarding the results, as shown in Table 1, a decrease in the polymer concentration and a decrease in the strength and elongation of the spun acrylic fiber were observed.

[Comparative Example 2]
The same polymerization cycle as in Example 1 was carried out 50 times except that the recovered unreacted monomer was used without mixing with the coagulation liquid. As a result, as shown in Table 1, the impurity concentration increased and the viscosity increased with the decrease in DMSO.

[Comparative Example 3]
The same polymerization cycle as in Example 1 was carried out 50 times, except that the usage rate of the recovered unreacted monomer was 80% by mass. As a result, as shown in Table 1, it was confirmed that the color tone of the spun acrylic fiber was yellowed by visual evaluation.

  Compared to Example 1, in Comparative Example 1, monomer correction was not performed, so that the polymer concentration after the polymerization reaction was 16.05% (Comparative Example 1) versus 22.05% (Example 1). The dry strength and elongation of the acrylic fiber obtained were 2.40 cN / dtex / 28.7%, and 2.40 cN / dtex / 18.7%, both values being low.

  Further, in Comparative Example 2, since rectification was not performed after mixing with moisture, impurities accumulated in the reaction system along with the polymerization cycle, and the impurity concentration exceeded 20 mass% allowed. In using unreacted monomer having a high impurity concentration, the amount of DMSO was insufficient due to monomer correction, which affected the chain transfer of the polymer in the reaction system, leading to an increase in the viscosity of the polymerized polymer.

  Moreover, in the comparative example 3, it resulted in yellowing of the color tone of the fibrillated acrylic fiber by using 50 mass% or more which accept | permits a usage rate.

Claims (5)

  Solution polymerization was carried out using a raw material monomer comprising 92% by mass or more of acrylonitrile, dimethyl sulfoxide as a polymerization solvent and an azo compound as a polymerization initiator, and the resulting polymer solution was converted to a polymerization solvent vapor by a vacuum distillation column. Vaporized and separated by fluid contact, then mixed with a water-containing polymerization solvent, and the fraction distilled again under reduced pressure is separated into an aqueous phase and an organic phase to recover unreacted monomers, and the recovered unreacted monomers obtained are used as raw materials. A method for producing an acrylic polymer, wherein the monomer charge is corrected according to the concentration of impurities contained in reusing as a monomer, and solution polymerization is carried out at a usage rate of 1 to 50% by mass relative to acrylonitrile.   2. The method for producing an acrylic polymer according to claim 1, wherein the polymerization is carried out by correcting the shortage of the raw material monomer introduced into the polymerization tank with respect to the amount of impurities in the recovered unreacted monomer.   3. The acrylic polymer according to claim 2, wherein in the monomer correction, the polymerization is performed with the total amount of liquid charged into the reaction system being constant by changing the amount of polymerization solvent charged into the reaction system according to the correction amount. Production method.   The method for producing an acrylic polymer according to claim 2 or 3, wherein the amount of impurities contained in the recovered unreacted monomer is 0% to 20% by mass with respect to the recovered unreacted monomer.   A method for producing acrylic fibers, characterized in that wet spinning is performed using a solution of an acrylic polymer obtained by the method for producing an acrylic polymer according to any one of claims 1 to 4 as a spinning dope.