JPS6136003B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a dimethyl formamide solution of acrylonitrile alone or a polymer containing acrylonitrile as a main component. More specifically, we will efficiently manufacture dimethyl formamide solutions of acrylonitrile polymers with a high degree of polymerization necessary for manufacturing acrylic fibers, polyacrylonitrile films, polyacrylonitrile semipermeable membranes, etc., continuously from the polymerization process. It's about how to do it.

Conventionally, aqueous suspension polymerization, emulsion polymerization, and solution polymerization have been industrially employed as methods for producing acrylonitrile-based polymers containing acrylonitrile as a main component. In addition, since acrylonitrile polymer itself is difficult to melt by heating and easily carbonizes, the general method for molding is to dissolve it in a solvent, shape it, and then remove the solvent. Among the various polymerization methods mentioned above, the solution polymerization method is said to be the most advantageous in terms of process.

However, since acrylonitrile polymer is a highly polar polymer, the solvent that dissolves it is
Dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, concentrated nitric acid aqueous solution,
It is limited to very special solvents such as concentrated zinc chloride aqueous solution and concentrated sodium thiocyanate aqueous solution. Among these various solvents, organic solvents are widely used industrially as solvents for shaping acrylonitrile polymers because they have a relatively low viscosity compared to inorganic solvents even at high concentrations. However, when these organic solvents are used as a homogeneous solution polymerization solvent, the chain transfer system number in the polymerization reaction is large,
Only dimethyl sulfoxide, which has a relatively small chain transfer coefficient, is used. Dimethyl formamide gives a high molecular weight polymer only when polymerized at a very high monomer concentration, but the entire polymerization system tends to gel at the end of the polymerization, which poses problems such as difficulty in removing heat. has, and also
It is said that dimethylacetamide cannot be used as a polymerization solvent because its molecular weight cannot be sufficiently increased even when solution polymerization is carried out with high concentration monomers.

Therefore, the inventors of the present invention selected the amount of solvent, amount of monomer, polymerization rate, etc. as a result of intensive studies to improve the above-mentioned drawbacks and obtain an acrylonitrile polymer with a high molecular weight in a solvent with a large chain transfer coefficient. The present invention has been completed based on the discovery that the object can be achieved by this method.

That is, the present invention provides a mixed solvent with a water/dimethylformamide ratio of 0/100 to 40/60 by weight.
A raw material mixture consisting of ~85% by weight of acrylonitrile alone or a mixture of acrylonitrile and a monomer capable of copolymerizing it with 15% to 45% by weight is continuously fed to a polymerization tank, and a radical generating catalyst is heated at 30 to 80°C. dimethyl formamide heated to 100°C to below the boiling point was added to the resulting polymerization reaction mixture, and the mixture was fed to a screw extruder 4 with a vent, and the unused material was removed from the vent. Part of the reaction monomer and solvent are recovered in gaseous form under reduced pressure, cooled and liquefied, and then reused as raw materials, while acrylonitrile polymers 15 to 35 are collected from the tip of the extruder 4.
wt%, water 0-3 wt%, residual monomer 0-3 wt% and dimethylformamide 59-85 wt%
A method for producing an acrylonitrile polymer solution, characterized by obtaining a polymer solution comprising:

In the present invention, monomers copolymerizable with acrylonitrile include methacrylonitrile, methacrylic acid and its esters, acrylic acid and its esters, itaconic acid and its esters, vinyl chloride, vinylidene chloride, vinyl bromide, Vinylidene bromide, vinyl acetate, vinyl propionate, styrene, α-methylstyrene, α-chloroacrylonitrile, α-hydroxyacrylonitrile, allylsulfonic acid and its salts, methallylsulfonic acid and its salts, 2-acrylamido-2-methyl Propanesulfonic acid and its salts, 2-methacrylamido-2-methylpropanesulfonic acid and its salts, vinylbenzenesulfonic acid and its salts, vinylbenzylsulfonic acid and its salts, alkali sulfoxyphenyl (meth)allyl ether, vinyl pyridine, methylvinylpyridine,
Examples include N,N-dialkylaminoethyl (meth)acrylate. In this case, since dimethylformamide used as a solvent has a large dissolving power, the amount of copolymerization of these copolymerization components can be selected from a wide range. Note that when producing normal acrylic fibers, the amount is about 10% by weight, but for modacrylic fibers, it is about 50% by weight.

Next, as the radical polymerization catalyst, any ordinary one can be used without particular limitation, and since it is also possible to add water to the polymerization system of the present invention, either a water-soluble initiator or an oil-soluble initiator can be used. I can do things,
Examples include azo compounds such as azobisisobutyronitrile, azobisvaleronitrile, azobisamidinopropane hydrochloride, percarboxylic compounds such as benzoyl peroxide, lauryl peroxide, t-butyl peroxypivalate, isopropyl peroxycarbonate, etc. Acids and their esters, di-t
- Peroxide ethers such as butyl, t-butyl hydroperoxide, cumene hydroperoxide,
Amines, peroxides such as persulfates and hydrogen peroxide alone, or in the presence or absence of these transition metal salts;
Redox initiators with various sulfoxy compounds and various reducing agents are used.

As a solvent, dimethyl formamide = 0/
Use one consisting of 100 to 40/60. Adding water improves the polymerization rate and the polymerization rate is approximately 50%.
When the polymer is in the form of a thin emulsion, starch paste, or soft cream, the molecular weight is significantly improved, and the polymer is sufficiently strong and flexible to produce fibers and films. However, if water is added in excess of the limit amount, the polymerization system will become cake-like or crumb-like as the polymerization progresses, making stirring and heat removal impossible. It is necessary to use water, especially water/
Dimethyl formamide ratio is 0/100 to 60/80
It is preferable that it is a weight ratio.

Regarding the monomer concentration, if it is less than 15% by weight, the polymerization rate is slow and industrially undesirable.
If it exceeds % by weight, the polymerization rate will increase and the polymerized liquid phase will become cake-like or crumb-like, making stirring impossible.

Polymerization temperature also has a large effect on polymerization. The polymerization temperature naturally varies depending on the type of catalyst, but below 30℃ the polymerization system becomes viscous and difficult to stir;
If the temperature is higher than 0.degree. C., the polymer will become noticeably colored, which is not preferable, and the temperature should be in the range of 40 to 60.degree.

When actually producing an acrylonitrile-based polymer solution, it is best to use an apparatus as shown in Figure 1, for example. First, (a) acrylonitrile and oil-soluble monomer, (b) the necessary In this case, water, water-soluble monomers, and (c) dimethylformamide will be added, but in continuous operation, these will be All you have to do is adjust the input amount of raw materials. Next, when supplying to the polymerization tank 3, it may be supplied at the same temperature, but it is preferable to cool it in advance to a necessary and sufficient temperature in the cooler 2 in order to facilitate the removal of reaction heat. The raw material mixture e prepared in this way is added to the polymerization tank 3 together with the radical polymerization catalyst d.
The polymerization reaction mixture f was heated to 80℃~80℃ using heater 2' in advance.
It is fed to a vented screw type extruder 4 together with the solvent c dimethylformamide heated to its boiling point. The polymer mixture supplied to the extruder 4 is heated by the amount of heat brought in during mixing and the amount of heat from heating from outside the extruder, and is heated at the vent port of the extruder 4 where the pressure is reduced by the ejector 5. Part of the remaining monomer and solvent is evaporated. The raw material recovered here is liquefied in a cooler 2', extracted from the lower part of the separator 8 by a pump 9, and recycled to the raw material preparation tank 1. On the other hand, from the tip of the extruder 4, a dimethyl formamide solution P containing an acrylonitrile polymer as a main component, whose concentration has been adjusted and which has become uniformly transparent after removing the necessary amount of non-solvent such as water, is released.
is discharged.

As described above, in the present invention, it is possible to continuously produce a dimethylformamide mixture of an acrylonitrile-based polymer polymerized to have a molecular weight high enough to be made into fibers and films, and whose concentration is adjusted. Features.

That is, since the residual monomer can be easily removed and recovered from the vent port of the extruder 4,
It is not necessary for the polymerization reaction in 100% completion. Therefore, in the present invention, the residence time in the polymerization tank 3 is selected to provide a high polymerization rate and high productivity. In the method of the present invention, the highest polymerization rate is 5.
It is in the range of ~70%. Also, it takes about 8 hours to achieve a polymerization rate of 95% or more, whereas the polymerization rate is 98%.
%, it takes more than 24 hours to achieve this, so take into consideration polymerization efficiency, coloring of the polymer, etc.
It is necessary to keep it below 95%.

Next, it is necessary to feed the polymerization reaction mixture f and the heated solvent c' together to the extruder 4. If the polymerization reaction mixture f is fed as it is to the extruder 4, evaporation occurs with rapid foaming near the vent port, and a portion of the remaining monomer, water, and solvent are vaporized. The amount of heat from the heating medium supplied to the jacket of the extruder 4 is not sufficient to remove the residual monomer and solvent from the polymerization reaction mixture f. Therefore, in the present invention, heated solvent c' is used to adjust the concentration of the acrylonitrile polymer solution, and is added to the polymerization reaction mixture f as a heating medium for removing residual monomers and non-solvent. It supplies the The temperature of the heated solvent c′ added here should be determined by considering the amount of evaporation at the vent and the amount of supplied solvent c′.
℃~boiling point allows smooth evaporation at the vent port. Note that the solvent c' may contain chemicals necessary for post-treatment, such as a polymerization terminator and a coloring inhibitor.

The desired acrylonitrile polymer solution is obtained from the tip of the extruder, but the concentration and temperature of the weight, residual monomer, and residual water must be maintained to keep the polymer solution uniform and ready for the next fiber to be used. It is preferable to match the process conditions of oxidation and film formation. That is, the polymer concentration is 15-35% by weight, the residual monomer and water are each 3% or less, and the temperature of the polymer solution p discharged from the tip of the extruder is 10-60°C.
It is preferable that it falls within the range of .

Although the matters explained above with reference to FIG. 1 are essential requirements of the present invention, it is within the scope of the present invention to incorporate conventionally known unit techniques in addition to these.

For example, in order to sufficiently remove residual monomers or residual water in the obtained polymer solution P, if the polymer concentration does not necessarily match the next fiberization or film formation step, the obtained polymer solution P may be further treated with a solvent. A mixing tank for adjusting by dilution etc. may be provided.

Furthermore, the polymerization tank may be multi-tubed for the purpose of removing polymerization heat, as is conventionally known. As an example, as shown in Figure 2, the initial stage of polymerization, where the polymerization rate is high and heat generation is significant, is divided into two tanks (3 and 3') to facilitate heat removal, and the polymerization rate is 50, when the polymerization rate begins to decrease.
It is also possible to continue increasing the polymerization rate by transferring the polymerization rate from ~70% to the third tank 3'', or as this often results in heterogeneous solution polymerization, scrape off the polymer to ensure sufficient stirring as shown in Figure 3. Alternatively, as shown in Fig. 3, the vent vapor from the extruder 4 is introduced into the distillation column 7, where the high boiling point solvent dimethylacetamide or dimethylformamide is distilled. It can also be fractionated and used as a heating solvent c' or c'' for adjusting the concentration of the product acrylonitrile polymer solution p.

Furthermore, before the polymerization reaction mixture is introduced into the extruder 4, a heating mixer 6 may be installed and the mixture may be passed through to promote mixing with the heated solvent c' and to heat the mixture sufficiently.

In the apparatus of the present invention, solution polymerization is performed in a high monomer concentration or in a heterogeneous system with water addition, so polymerization is improved and the polymerization time, which used to be 12 to 50 hours, can be reduced to 2.
The process can be shortened to ~7 hours, and since residual monomers and water are vaporized and recovered using a vented extruder, the processing speed is high and productivity is extremely high. Further, although the reaction mixture discharged from the polymerization tank is often heterogeneous, since it is sufficiently kneaded in the screw type extruder, there are no undissolved polymer particles, and the process of forming powder threads or films can be maintained stably.

Next, a more detailed and specific explanation will be given with reference to Examples. In the examples, % simply means % by weight.

Example 1 In the apparatus shown in Fig. 1, monomer a consisting of 92% acrylonitrile and 8% methyl acrylate and dimethyl formamide (hereinafter referred to as DMF) c were introduced into the raw material mixing tank 1 so that the monomers were constantly maintained. The concentration was adjusted to 44.345%, and this mixed solution e was added to 9.02 kg/hr in polymerization tank 3.
On the other hand, 2% DMF concentration d1.0Kg/hr of polymerization catalyst azobisvaleronitrile was supplied to 3 and 50
Polymerization was carried out at ℃. After a residence time of 6 hours, the polymerization reaction mixture f overflows from 3.
It was a slightly yellowish transparent viscous liquid with a polymerization rate of 63% and a viscosity of 400 poise.

The polymerization reaction mixture f was then heated to 130°C.
DMFe'2.95 Kg/hr was supplied to the extruder 4, where it was heated and the remaining monomer was recovered from the vent port under reduced pressure. When the recovered gas at the vent port is cooled, the recovered liquid
g' was obtained at 2.89Kg/hr, and the composition was 40.0% acrylonitrile, 8.8% methyl acrylate,
The DMF was 51.2% and was recycled to the raw material adjustment tank 1. From the tip of the extruder 4, a homogeneous and transparent acrylonitrile polymer solution p having a polymer concentration of 25%, a residual monomer concentration of 0.9%, and a DMF of 74.1% was obtained at a rate of 10.1 Kg/hr. The intrinsic viscosity of the polymer is DMF at 25°C.
I operated it continuously for 12 hours at 1.40 to 1.50, but there was almost no change.

When this polymer solution was cast on a glass plate and a film with a thickness of about 20 microns was produced using a dry method, a strong film was obtained, and it was found that it could be sufficiently used for fibers.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a polymerization apparatus used in the present invention, and FIG. 2 is a diagram of an apparatus in which a part of the polymerization apparatus shown in FIG. 1 is made into a multi-vessel polymerization tank. . Figure 3 shows the polymerization apparatus shown in Figure 1, with a scraped-type stirring blade in the polymerization tank 3, a kneader for mixing the polymerization reaction mixture and heating solvent before entering the extruder 4, and an extruder. 4 is a diagram in which a distillation column is added to separate the solvent from the vent gas emitted from No. 4. 1... Raw material preparation tank, 2, 2', 2''... Heating or cooler, 3, 3', 3''... Polymerization tank, 4... Extruder with vent, 5... Ejector, 6... Heating kneader, 7...
Distillation melt, 8...decanter, 9,9'...pump, a
...monomer such as acrylonitrile, b...water and raw materials dissolved therein, c, c', c''...dimethylacetamide or dimethylformamide solvent or the solvent and raw materials dissolved therein, d...polymerization initiator, e...
Preparation raw material, f...polymerization reaction mixture, g, g'...vent gas or recovered raw material, p...acrylonitrile polymer solution, x...refrigerant, y...heating medium.

Claims (1)

[Claims] 1 The weight ratio of water/dimethyl formamide is 0/
Continuously feeding a raw material mixture consisting of 55 to 85% by weight of a mixed solvent of 100 to 40/60 and 15 to 45% by weight of acrylonitrile alone or a mixture of a monomer copolymerizable with acrylonitrile to a polymerization tank, 30~80
Polymerization rate of 50-95% using a radical generating catalyst at °C
Heated dimethyl formamide was added to the resulting polymerization reaction mixture, and the mixture was fed to a screw-type extruder with a vent, and unreacted monomers and a portion of the solvent were removed from the vent under reduced pressure. The acrylonitrile polymer 15
~35% by weight, residual monomer 0-3% by weight, water 0-3%
1. A method for producing an acrylonitrile polymer solution, which comprises obtaining a polymer solution containing 59 to 85% by weight of dimethyl formamide.