JPS5910384B2 - Method for producing molding solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention refers to the use of acrylonitrile polymers for molding (spinning and molding).

The present invention relates to a method for producing a solution (the same applies hereinafter), and more specifically to a method for producing a solution for use in spinning or molding from a wet acrylonitrile polymer produced by aqueous precipitation polymerization. Acrylonitrile polymers are often manufactured in an aqueous medium.

The reasons for this are (a) water, which is the solvent, is cheap;
(1) The reaction rate in the aqueous medium in which the produced polymer precipitates is much faster than in organic solvents such as dimethylformamide, dimethyl sulfoxide, dimethylformamide, and ethylene carbonate, so the productivity of the polymer increases. In addition to azobis-based organic catalysts that are soluble in high 17 → monomers, water-soluble redox initiators can also be used.
It has a wide selection range of catalysts, it is easy to remove the heat of polymerization reaction, the viscosity of the reaction liquid is low, so the equipment used is simple, and the H-generating polymer is easy to separate. This is because it has many advantages. On the other hand, the spinning solution produced from this polymer needs to have a water content of 3% by weight or less.

This is because if the water content exceeds 3% by weight, problems such as so-called blockage of the spinning nozzle holes, a decrease in the stretching ratio, devitrification of the yarn, and instability of the yarn quality occur. However, when producing a spinning solution by conventional methods from a wet polymer obtained by polymerization in an aqueous medium, there are many problems in terms of equipment, operation, quality, economy, etc., as explained below. Contains problems.

Generally, in order to reduce the water content of a spinning solution to a predetermined concentration or less, a slurry with a water content of 90 to 80% obtained by a polymerization reaction is passed through P to reduce the water content to 60 to 80%, and then the water content is reduced to 1. A widely used method is to dry to below 0% and then add a solvent. In order to operate the drying step in this method industrially advantageously, it is necessary to treat the wet polymer at relatively high temperatures. However, when a polymer is treated at high temperatures, this causes coloring of the polymer and chemical changes in the polymer, making it difficult to obtain a satisfactory spinning solution. As described above, treating the polymer at high temperatures is a contributing factor to the decrease in the spinnability of the resulting solution (for example, an increase in thread breakage and an increase in P overpressure). In addition, in order to evaporate the water adsorbed and occluded within the polymer particles, it is necessary to blow dry air through the particles at a relatively high temperature, which results in extremely large heat loss, which is also economically disadvantageous. It is.

Moreover, since the drying process itself requires a minimum amount of heat commensurate with the latent heat of vaporization of water, conventional methods employing a drying process are very disadvantageous. On the other hand, a technology for producing a spinning solution from a wet acrylonitrile polymer produced in an aqueous medium, avoiding the conventional drying process, has already been published in Japanese Patent Publication No. 37-17665.
Publication No. 16142, Special Publication No. 16142, Special Publication No. 16142, Special Publication No. 16142-
It has been reported in US Patent No. 18820, US Patent No. 3.313.758, US Patent No. 3.630.986, etc.
As a result of various studies on these techniques, it has become clear that they all have essential drawbacks and are inadequate from an industrial standpoint.

That is, the technique disclosed in Japanese Patent Publication No. 37-17765 involves filtering a polymer slurry produced in an aqueous medium to obtain a wet P mass, washing it with a concentrated aqueous solution containing dimethylformamide, dimethylacetamide, or dimethyl sulfoxide, and filtration. to obtain a composition containing about 50 to 60% by weight of solids and about 5 to 15% by weight of water, and further add about 25 to 15% of water to this composition.
In this method, 65% by weight of the solvent is mixed. In this technique, F-filtration operation becomes impossible in the condition range in which even a portion of the polymer dissolves during the ▲ filtration operation. On the other hand, in order to operate in a range where the polymer does not dissolve at all, the water content in the washed F mass must be reduced to about 5% or more (solid content 50 to 60% by weight).
), but even if this ▲ mass is then further mixed with approximately 25 to 65% by weight of solvent, it is almost impossible industrially to reduce the water content of the resulting solution to 3% by weight or less. It's impossible.

Furthermore, it is necessary to recover the solvent used for cleaning, which is disadvantageous both in terms of equipment and heat. Special Public Service 1977-16142
No. 42-18820, U.S. Patent No. 3.313.
The technology of No. 758 is such that the wet polymer is treated with acetone,
This technology involves washing with a non-solvent such as ethylene glycol and then washing with a solvent, but it requires a step to recover the used non-solvent and is difficult to control. When the amount of solvent decreases, some of the polymer begins to dissolve as described above, and filtration cannot be carried out smoothly.On the other hand, if the operation is performed at low temperatures to prevent dissolution of the polymer, the extraction efficiency decreases, causing problems. However, there are problems such as the need for large amounts of non-solvents and solvents, and
From the viewpoint of extraction efficiency, it is impossible to reduce the amount of water and non-solvent in the spinning solution to almost zero, so it is disadvantageous to industrialize this process from various viewpoints.

On the other hand, the technology of U.S. Patent No. 3,630,986 is related to a method in which water is distilled out by adding a solvent such as dimethylformamide to a wet polymer and then performing a high temperature vacuum treatment. As the particles decrease, some of the particles gradually dissolve and are left in an incompletely dissolved state for a long time, so the resulting solution is heterogeneous and, therefore, when the solution is subjected to spinning, Stability, deterioration of spinnability due to non-uniformity, etc. are significant, which is an industrial problem.

In addition, a large amount of solvent is required to distill water,
Therefore, it is industrially disadvantageous in terms of new installation of solvent recovery equipment and the heat required for recovery. As mentioned above, Tokuko Sho 37-17665
It can be said that the methods disclosed in No. 1 and the other four patents are impossible to implement from an industrial standpoint. In view of the current situation, the present inventors have developed a technology for producing a molding solution from a wet acrylonitrile polymer obtained by polymerization in an aqueous medium, from the viewpoints of process simplification, labor saving, energy saving, quality improvement, etc. As a result of intensive studies, we have arrived at the present invention.
That is, in the present invention, an acrylonitrile polymer containing a large amount of water obtained by aqueous precipitation polymerization is heated to a water content of 40 kg/Cii or more under a pressure of 100 kg/Cii or more without adding a solvent.
% by weight or less, preferably 20% by weight or less, solids content 60
The polymer is compressed and dehydrated until it becomes at least 80% by weight, and then a solvent for the polymer is added to dissolve it (
Alternatively, the polymer is added and dissolved in a solvent), and this solution is further treated under reduced pressure at 30 to 120°C and 500 to 0.1 Torr to obtain a water content of 3% by weight or less and a polymer concentration of 15 to 30%.
The present invention relates to a method for producing a molding solution of an acrylonitrile polymer, which is characterized by obtaining a solution with a weight percent solution.

The most important point of the present invention is that in order to mechanically reduce the water content of an acrylonitrile polymer obtained by polymerization in an aqueous medium, conventional solid-liquid separation equipment can be used to mechanically reduce the solid content. The limit was 40 to 50% by weight, but when this wet polymer was mechanically compressed and dehydrated under a pressure of 1001<g/Cd or more, the solid content was 80% by weight or more and the water content was 2.
This is surprising since less than 0% by weight of wet polymer was obtained.

Generally, in order to reduce the water content of a polymer to 20% by weight or less,
(b) As mentioned above, the polymer slurry is filtered to form a wet mass with a solid content of 50 to 60% by weight and a water content of up to 40% by weight, and a solvent is added to this to remove the water in the mass. Either the method of replacing the liquid with a solvent and filtering it to obtain a wet mass with a solid content of 50 to 60% by weight and moisture of 5 to 15% by weight, or drying by (oral) ventilation is used. It will be done. However, according to the present invention, complicated processes can be avoided and a process that saves labor and energy can be easily assembled, which is important.

Further, according to the present invention, a solvent is then added to the composition thus obtained, and the polymer is uniformly dissolved at once to obtain a molding solution, and then the water distilled from this solution and the accompanying solvent are removed. It is also important that the amount of distillate is small.

A concrete list of these industrial advantages is as follows. 1) Energy saving Conventional drying methods require a minimum amount of heat to match the latent heat of vaporization of the water contained, but in reality they require a large amount of heat to compensate for the drop in drying efficiency. In order to remove moisture, it is necessary to collect and separate the washing liquid after washing, which requires heat corresponding to the latent heat of vaporization of water.

However, in the method of mechanically dehydrating water to a solid content of 80% by weight or more as in the present invention, there is no need to change the phase of water from liquid to gas, so only the energy of squeezing pressure for solid-liquid separation is used. is necessary. This energy is orders of magnitude lower than the energy required for recovery and separation through drying and washing methods, and is 10 to 20 times lower than the conventional energy requirement, including the heat required for the process of reducing pressure after adding the solvent.
01). 2) Process simplification and investment savings Eliminating the need for complicated processes such as ventilation production equipment, post-drying exhaust air processing equipment, and large areas required for drying beds, which are unavoidable in conventional drying processes. It can be covered by just the machine.

Therefore, the amount of investment is also small. 3) Labor saving The number of personnel required for operation and maintenance is reduced because the process is simplified.

4) Advantages in terms of operability and stability Since the water contained in a wet polymer depends uniquely on the squeezing pressure during solid-liquid separation, the moisture content can be very stable if only the pressure is controlled accurately. be.

Also, the pressure is extremely easy to control. 5) Improved spinning stability and improved whiteness of raw cotton Because the process is simplified and the operation is stable, the resulting molding solution is extremely homogeneous and can be exposed to high temperatures during drying. As a result, the color tone of the obtained fibers is also very good.

The present invention will be further explained.

The solvent used in the present invention is an organic solvent known as a solvent for acrylonitrile polymers, and has a boiling point higher than that of water. N-dimethylformamide, N. N
Dimethylacetamide, N-methylpyrrolidone, N. N
-dimethylmethoxyacetamide, N. N. N″.N′
-tetramethyloxyamide, benzaldimethylamide, N. N. N'. N″-tetramethylphthalamide 6ε
1-caprolactam, 2-oxazolidone, N-formylhexamethyleneimino, N. N″-diformylpiperazine, 4-formylmorpholine, N-formylpyrrolidine, N-formylpiperidine, 4-acetylmorpholine,
4-acetylpyrrolidine, nitrile compounds such as arononitrile, succinonitrile, adiponitrile, bis(β-cyanocochel)ether, bis(β-cyanoethyl sulfide), sulfone, and sulfoxide compounds such as dimethylsulfoxide, dimethylsulfone,
Ethylmethylsulfone, sulfolane, thiocyanate compounds, methylene dithiocyanate, trimethylene dithiocyanate, nitro compounds m- or P-nitrophenol, 4-nitrosomorpholine, phosphorus compounds, tris(dimethylamide) phosphate, carbonate compounds Examples include γ-butyrolactone and ethylene carbonate.

Among these, dimethylacetamide, dimethylformamide, dimethyl sulfoxide and the like are particularly preferred solvents for the purpose of the present invention. The polymer used in the present invention includes not only a polymer of acrylonitrile alone but also a polymer of 50% by weight.
Copolymers of the above acrylonitrile and other copolymerizable monomers are included.

Examples of copolymerizable monomers include ethylenically unsaturated compounds, vinyl acetate, ethyl acrylate, methyl acrylate, methyl methacrylate, methacrylonitrile, methyleneglutaronitrile, vinyl bromide, vinyl chloride, and chloride. vinylidene, acrylamide, N. Examples include N''-substituted acrylamide, methacrylamide, acrylic acid, and methacrylic acid.Of course, it also includes copolymers made by copolymerizing appropriate amounts of basic or strongly acidic monomers for the purpose of improving dyeing properties. Examples of basic or strongly acidic monomers include vinylpyridines, dimethylaminoethyl acrylate, methacrylsulfonic acid or its salts, etc.For dehydration of wet polymers, conventional batch presses do not require much pressure. It is several tens of kg/Cd, which means that the water content is 40 kg/Cd.
Since it is not possible to compress the material to less than % by weight, a conventional press is used in the present invention, especially designed to withstand ultra-high pressure.

However, when squeezing at LllOO~400kg/d, a water pressure f
It is possible to use an overexpeller. As explained above, the feature of the present invention is that a wet polymer with a solid content of 40 to 50% by weight is dehydrated under a pressure of 100 kg/Cd or more to reduce the solid content to 60% or more, preferably 80 (F6 or more). , has established an industrially very advantageous method for producing a molding solution by adding a solvent to the solution and then distilling off water.

The present invention will be explained in more detail below using practical examples.

In addition, unless otherwise specified, parts and percentages in the examples are based on weight. Whiteness is measured using Hitachi self-recording spectrophotometer EPU-
The value is determined from the reflectance of the fiber surface using Type 2, and the value is taken as 100 for a white plate of magnesium oxide. Also, the pressure unit is 1 Torr - 1? It is H9. Example 1 A polymer slurry consisting of 100 parts of a copolymer consisting of 93% acrylonitrile and 7 (fl) vinyl acetate, 800 parts of water, and 5 parts of unreacted acrylonitrile was separated into solid and liquid using a centrifuge to obtain 100 parts of a copolymer. , 100 parts of water, and 1 part of acrylonitrile to obtain a wet polymer (about 50% water content).

Next, this polymer was compressed using a press at a pressure of 400 kg/Cd to squeeze out the liquid, resulting in a copolymer of 100 kg/Cd.
50 parts of water was obtained. When 950 parts of dimethylacetamide was added to this wet polymer and the temperature was raised to 60°C, the polymer instantly dissolved and a homogeneous solution was obtained. This solution was then distilled for about 120 minutes under a reduced pressure of 20 torr to remove water and solvent, yielding a spinning solution with a polymer concentration of 24%. The amount of water in this solution was measured and found to be 0.02q6. This solution was poured into 2,000 holes.
When wet spinning was carried out in a conventional manner using a spinning nozzle with a hole diameter of 0.075, there was almost no nozzle clogging or yarn breakage for 3 days, and the f overpressure before spinning remained constant. As a comparative example,
A wet polymer with a moisture content of approximately 50% in this example was subjected to aeration drying treatment and spun under the same conditions as in this example.2
During 4 hours, there were 1 to 3 nozzle blockages and 2 to 4 thread breaks.

In addition, the yarn bundle obtained by spinning was drawn, washed, treated with oil, dried, and relaxed at 140°C, and then the whiteness of the fibers obtained in this practical example was measured. is 98
．． 6, which was significantly higher than the whiteness of the fiber of the comparative example, which was 94.0. In addition, the energy used in this example was only 40% of that in the 6 comparative examples, contributing to energy saving. Example 2 100 parts of a copolymer consisting of 95% acrylonitrile, 45% methyl acrylate, and 0.5% sodium vinylbenzenesulfonate, 6, and a wet polymer consisting of 200 parts of water and 1 part of unreacted acrylonitrile were mixed in a compressor for 2,001 hours. When a pressure of <g/Cd was applied and six liquids were squeezed out, a wet polymer containing 100 parts of copolymer and 60 parts of water (water content 37.5% by weight) was obtained.

Adding 700 parts of dimethylformamide to the wet polymer;
The temperature was raised to 70° C. to uniformly dissolve the polymer, and then distilled for about 150 minutes under a reduced pressure of 50 torr to remove water.
A spinning stock solution having a copolymer concentration of 29q6 and a water content of 2% was obtained.
This solution was heated to 125°C and dry spun in air at 180°C, then stretched 4 times in boiling water, washed with water, and
It was dried at 20°C. No yarn breakage during spinning, whiteness 98
．． A good fiber of No. 5 was obtained. Example 3 Acrylonitrile 94 (F6, vinyl acetate 5.896,
100 parts of copolymer consisting of 0.2% sodium vinylbenzenesulfonate, 900 parts of water, 5 parts of unreacted acrylonitrile
% of the polymer slurry was filtered under reduced pressure P, and the obtained wet polymer was dehydrated by pressing the liquid by applying a pressure of 8001<g/Cd with a press machine, resulting in 100 parts of copolymer and 21.4 parts of water.
% (moisture content: 17.6%).

Add 500 parts of dimethylacetamide to this composition,
When the temperature was raised to 0°C, the polymer was instantly dissolved to obtain a homogeneous solution. This solution was then heated under a vacuum of 20 torr to approximately 3
Distillation was performed for 0 minutes to remove water. The resulting spinning solution had a polymer concentration of 23.8% and a viscosity of 450 poise (50°C).
And its water content is 0.020! ). The stability of this spinning solution was very good, with almost no change in the viscosity of the solution even after one week, for example. Next, this solution was passed through a nozzle with a hole diameter of 0.075 mm into a spinning bath consisting of a 53% dimethylacetamide aqueous solution at 43°C, stretched 5 times in boiling water, washed with water, dried at 120°C, and further Relaxed in saturated steam at ℃. Even after continuous spinning for 3 days, there were no problems such as yarn breakage.

The whiteness of the obtained fiber was 98.8, which was an extremely superior value compared to conventional fibers. In addition, almost 100% of the water, dimethylacetamide, unreacted monomers, etc. resulting from the treatment in this example were recovered by rectification separation, so there was no escape to the outside of the system, and there was no concern about pollution. .

Claims (1)

[Claims] 1 An acrylonitrile polymer containing a large amount of water obtained by aqueous precipitation polymerization is dehydrated under a pressure of 100 kg/cm^2 or more until the water content is 40% by weight or less and the solid content is 60% or more. Then, a solvent for the polymer is added and dissolved, and this solution is further heated at 30-120°C, 50°C.
Water content is 3% by weight after vacuum treatment under conditions of 0 to 0.1 Torr.
The following is a method for producing a molding solution of an acrylonitrile polymer, which is characterized by obtaining a solution having a polymer concentration of 15 to 30% by weight.