JPS6187730A - Preparation of polymer solution - Google Patents

Abstract

PURPOSE:To obtain a polymer solution having a low content of bubbles within a short time, by deaerating a polymer and its solvent separately in a specified atmosphere of a reduced pressure and dissolving the former in the latter by mixing. CONSTITUTION:A polymer such as PE or polycaproamide is fed to a deaeration tank 1 and a solvent therefore is fed to a deaeration tank 2. The polymer and the solvent in the tanks 1 and 2 and a dissolution tank 3 are deaerated by decreasing the pressures in the tanks to a pressure which is at most three times as high as the vapor pressure of the solvent at a predetermined deaeration temperature by means of a vacuum pump 5. The polymer and the solvent in this atmosphere of reduced pressure are transferred to the tank 3 and mixed and dissolved by agitation. EFFECT:A polymer solution which has excellent curability and can give a molding excellent in mechanical properties and uniformity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for preparing polymer baths. More specifically, it relates to a method for preparing a polymer solution (hereinafter simply referred to as dope) for producing molded products with excellent moldability, mechanical properties, and homogeneity in the molding of films, fibers, etc. .

BACKGROUND OF THE INVENTION It is known that dope is prepared by mixing a polymer and a solvent for the polymer and stirring and dissolving the mixture. , contains a large amount of air bubbles. When subjected to dope molding containing air bubbles, during the molding process, for example, in the case of fiber manufacturing, not only yarn breakage occurs at the spinneret discharge surface, but also yarn breakage occurs during coagulation, water washing, etc., and fuzz occurs. This results in frequent process troubles. Furthermore, as a result of the inclusion of air bubbles in the resulting molded products such as films and fibers, the mechanical properties and homogeneity of the products are significantly reduced. Therefore, in order to obtain molded products with excellent moldability and high quality, it is technically extremely important how to prepare a molding dope that does not contain air bubbles.

On the other hand, the conventional method is to mix the polymer and the d-medium under normal pressure, stir and soften the mixture to form a dope, and then hold it under reduced pressure to remove air bubbles (hereinafter referred to as defoaming). In order to shorten the defoaming time, a method has been adopted in which the polymer and solvent are mixed under normal pressure, then stirred and dissolved under reduced pressure, and then defoamed under reduced pressure. In such a method, due to the viscosity of the dope, the bubbles formed during stirring and relaxation require a long time to be defoamed sufficiently to obtain a molded product with good moldability and high quality. In order to improve product performance, when increasing the polymer concentration in the dope (hereinafter simply referred to as dope concentration), it takes a longer time or a dope with insufficient defoaming is obtained, resulting in the molding process C.
Second, it caused process troubles and deterioration of product properties, which was extremely undesirable.

Problems to be Solved by the Invention In view of these drawbacks, the present inventor has created a polymer that can be easily degassed or that does not require degassing from a polymer and a solvent that can substantially decompose the double-stranded polymer. The method for preparing dope is fundamentally different from the conventional method of removing air bubbles from the dope once it has been formed, and the dope is prepared in the absence of gases that cause air bubbles during dope formation. As a result of intensive research into this method, we have developed a dope with excellent moldability and extremely low bubble inclusion by deaerating the polymer and solvent separately and then mixing and softening them while maintaining the degassed state. The present inventors have completed the method of the present invention by discovering that this can be obtained and that the relaxation itself can be achieved in a short period of time.

Means for Solving the Problems The present invention (2) A method for preparing a polymer bath solution is to prepare a polymer bath solution for molding by dissolving a polymer in a solvent that can substantially soften the polymer. In doing so, prior to decomposition, both the polymer and the solvent are degassed under a reduced pressure atmosphere at a temperature of 2 times or less than the vapor pressure of the solvent, and then while maintaining the reduced pressure atmosphere. A method for preparing a polymer solution, which comprises mixing the two and stirring and dissolving them under a reduced pressure atmosphere.

And, in preparing a polymer solution for molding by dissolving the polymer in a solvent that can substantially dissolve the polymerization body,
Prior to relaxation, both the polymer and the solvent are degassed in a reduced pressure atmosphere of 3 times or less the vapor pressure of the solvent at the degassing temperature, and then both are continuously heated while maintaining the reduced pressure atmosphere. This is a method for preparing a polymer solution, which is characterized by supplying, mixing, stirring under a reduced pressure atmosphere, stirring, and then taking out continuously.

° In the present invention, the polymer may be any natural or synthetic polymer as long as it can form molded products such as fibers and films, and there are no particular restrictions. do not have.

Specifically, for example, natural fibrous polymer substances such as wood pulp and linters, cellulose polymer derivatives such as cellulose diacetate, triacetate, and anoethyl cellulose, and acrylonitrile polymers obtained using acrylonitrile as a main component. and copolymers, vinyl polymers such as polyethylene and polypropylene, polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, etc., aliphatic polyamides typified by polycaproamide, polyhequinamethylene adipamide, etc., and polymetaphenylene. isophthalamide, aromatic polyamides, aliphatic and/or
Alternatively, examples thereof include aromatic polyamideimide, phrethane polymers and copolymers whose main components are aromatic and/or aliphatic diisocyanate components and diol components.

The intrinsic viscosity of these polymers used in the present invention is
There are no particular limitations, and the point is that they may be selected and determined as appropriate in accordance with the required characteristics of the intended molded product. Further, the shape of these polymers may be ordinary chips, powder, fibers, pulp, or the like.

The solvent for the polymer used in the present invention is not particularly limited as long as it can dissolve the above-mentioned polymer, and can be selected from conventionally known solvent groups depending on the polymer used. The solvent may be appropriately selected, and may be either an organic solvent or an inorganic solvent. In addition, it is also possible to form a mixture of two or more types if necessary, and for the purpose of adjusting the solubility or changing the appearance of the molded product, such as an inorganic salt or an organic acid salt Additives such as metal oxides may be added.Furthermore, although these solvents are usually liquid, there is no problem even if they are solid during deaeration and mixing, which will be explained in detail later.

Specifically, for example, water, aqueous caustic soda solution, organic acids such as formic acid and acetic acid, nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, fluorosulfuric acid, chlorosulfuric acid, and these, such as sodium nitrate,
Calcium nitrate, sodium sulfate, sodium phosphate,
Water bath of seven or more solutions containing inorganic salts such as ammonium phosphate, so-called rhodan salts such as zinc chloride, sodium thiocyanate, potassium thiocyanate, and calcicum thiocyanate, inorganic salts such as magnesium chloride, and lucicum chloride. liquid, N,N-dimethylformamide, N,N-
Dimethylacetamide, N-methyl-cobyrolidone,
So-called amide solvents such as N, N, N', N'-tetramethylurea, N, N'-dimedelimidazolidinone, dimethyl sulfoxide, acetotolyl, ethylene carbonate, ethylene cyanohydrin, γ- butyrolactone,
Examples include halogenated hydrocarbon solvents represented by methylene chloride, chloroform, carbon tetrachloride, dichloroethane, etc., fluorine solvents, phenol solvents such as phenol and cresol, and the like.

In order for the method of the present invention to fully exhibit its effects, it is important to sufficiently degas both the polymer and the solvent for the polymer prior to dissolution. In particular, polymers are usually used in the form of chips, granules, fibers, or pulp, and these contain sufficient air to form bubbles during dope formation. It is. Similarly, even if no air bubbles are present in the solvent of the polymer when observed simply with the naked eye, common gases may cause the formation of air bubbles during dope formation.

For the above reasons, it is preferable to degas the polymer and the solvent for the polymer at as high a degree of vacuum as possible, and according to detailed studies by the present inventors, at least the solvent used for dissolution is It is necessary to perform degassing at a degree of vacuum that is three times or less the vapor pressure of the solvent at the degassing temperature. The reason for this is that under a reduced pressure atmosphere of three times or more the vapor pressure of the solvent, there is still a large amount of gas brought in from the polymer and the solvent, making it impossible to prepare a dope free of bubbles. When degassing in a reduced pressure atmosphere with a pressure less than 3 times the vapor pressure of the solvent, the gases that cause bubbles are still not completely removed.In particular, gases such as air and nitrogen brought in by the polymer Although not completely removed during the degassing process, the vapor of the solvent of the polymer (secondarily, the air present in a reduced pressure atmosphere,
By easily displacing and evacuating gases such as oxygen, the dope becomes bubble-free after the dope is formed, or an additional defoaming operation is performed after the dope preparation (=therefore, the dope can be easily defoamed. The degassing of the polymer and the solvent for the polymer in the invention method is carried out at least 3 times the vapor pressure of the solvent used for dissolution.
It is necessary to carry out the process under a reduced pressure atmosphere which is twice as high or less, and preferably under a reduced pressure atmosphere which is twice or less. In some cases, degassing while boiling the solvent under the vapor pressure of the solvent is also permitted and included in the embodiment of the dope preparation method of the present invention. The degree of vacuum for degassing the polymer and the degree of vacuum for degassing the solvent do not necessarily have to be the same degree of vacuum, but from the standpoint of equipment and operability in mixing described later, it is recommended that the degree of vacuum be the same. It is preferable to do so. In order to make the degree of vacuum the same, depending on the case, after each deaeration is completed in advance, the decompression exhaust system of both may be connected to equalize the pressure in the present invention, but this may not impair the effect in any way. It's not a thing.

The temperature for degassing gases such as air dissolved in the interior of the polymer and the solvent is not particularly limited in the method of the present invention, and generally a higher temperature is preferable as the main degassing agent. However, at high temperatures, the polymer and solvent deteriorate and become colored, so it is preferable to set the temperature in a range where these deteriorations do not occur, and the temperature is usually from room temperature to 0°C.

In the method of the present invention, the means for degassing may be any conventional reduced pressure generating device such as a vacuum pump, ejector, or aspirator.

To prepare the dope according to the method of the present invention, as described above,
It is necessary to mix a previously degassed polymer and a solvent for the polymer while maintaining a degassed, reduced-pressure atmosphere, and to stir and dissolve them. If a degassed and reduced pressure atmosphere is not maintained and gases such as air or nitrogen enter from the outside (:ha,
This is because these gases are taken into the interior of the polymer or into the solvent and are dissolved (=in some cases, causing the formation of bubbles).

Specifically, to mix the two while maintaining a reduced pressure atmosphere,
A dissolver connected to a storage tank for degassing the polymer and the solvent of the polymer by a connection means such as piping is depressurized in advance to a predetermined degree of vacuum, and then the polymer and the solvent of the polymer are degassed. of,
Sending it to a melter through a connecting means and mixing it (this is done twice, but it is not limited to this method; in short, it is a method of bringing the two into contact and mixing while maintaining a degassed and reduced pressure atmosphere. If present, Special C: Does not impair the effects of the present invention.

Mixing 1: In the method of the present invention, it is possible to mix both at once, or to divide parts of both and mix them alternately, without causing any problems. The two may be mixed so that the dope to be prepared has a predetermined doping concentration.

In the method of the present invention, the dope concentration is not particularly limited and can be arbitrarily set depending on the purpose of the product to be molded and the ability to dissolve the polymer and the solvent.
In the method of the present invention (Part 2), since the gas that causes bubbles is removed in advance, the effect becomes remarkable in the high-speed dope preparation that was difficult to prepare using the conventional method.

Stirring for dissolution may be carried out in accordance with a conventional method, except that stirring is carried out under a reduced pressure atmosphere (2). In the dope preparation method of the present invention, the polymer and the solvent for the polymer are degassed in advance Since the polymer is dissolved in a degassed and reduced pressure atmosphere, the solvent and polymer are effectively mixed in contact with each other, resulting in faster dissolution compared to conventional methods. I can do it.

In the present invention, the dope can be prepared by supplying a previously degassed polymer and a solvent for the polymer in a batch manner, or by continuously supplying a polymer and a solvent for the polymer. Continuous adjustment can also be carried out by feeding and mixing. The purpose of the present invention can be achieved with either of these methods,
The obtained dope can be used directly in the process of manufacturing molded products such as films and fibers as it is or by easily performing additional defoaming if necessary.

In order to manufacture molded products such as films and fibers from the dope prepared by the method of the present invention, conventionally known film forming, spinning techniques, etc. may be used.

EXAMPLES The present invention will be explained in more detail with reference to Examples (2), but unless otherwise specified, it percentages are shown.

Example 1 A dissolution tank (8) equipped with a hot water jacket and a stirrer as shown in FIG. Stir and dissolve. After dissolving, the inside of the dope tank is evacuated with a vacuum pump (5) and confirmed! It was kept at i Torr and degassed for 20 minutes. On the other hand, the polymer deaeration tank (
1) Poly-metaphenylene isophthalamide 74#f
Similarly, the vacuum pump (5) was used to degas the inside of the degassing tank at 2.3 Torr for about 7 hours.

Next, 21. While maintaining the reduced pressure state of f Torr,
The polymer degassing tank (1) and the dissolving tank (3) are connected and the pulp is gradually opened (-), and it takes about 70 minutes to drop the polymetaphenylene isophthalamide into the dissolving tank. The stirrer installed in (3) was operated to stir and dissolve for about 2 hours. After stirring and dissolving, the pressure inside the melting tank was returned to normal pressure by introducing nitrogen. The resulting dope contained bubbles and No residual poly-metaphenylene isophthalamide grains were observed, and the dope was highly transparent.

The dope solution viscosity is 37! The temperature was θ voids (7°C).

This dope as it is, pore size 0. Hemethyl-2-pyrrolidone 3! The product was extruded into a coagulation bath consisting of calcium chloride 23-'A and 4 tots of water, and the resulting filament was taken up with a take-up roll at a speed of 4 trnZ, and then washed with water. Next, the water-washed yarn was stretched 3.7 times on a hot plate heated to θ° C. to obtain fibers.

The physical properties of the obtained fibers are shown in Table 1 together with the results of Comparative Examples.

Table 7 Fibers obtained from the dope obtained by the method of the present invention are:
Fiber # obtained by the conventional method: (Comparative example/) It showed superior strength and elongation physical properties and was recognized as an excellent dope.

Comparative Example'/Example/(2) The same polymer, same solvent and An N-methyl-λ-pyrrolidone/calcium chloride dope of poly-metaphenylene isophthalamide was obtained under these conditions.The dope obtained was opaque due to the presence of a large amount of air bubbles.In order to defoam this dope, Then, it was transferred to a tank that can be depressurized and evacuated, and the pressure was decompressed using Utah Torrl to degas it.
It took 5 hours. Although the dope obtained using Cl does not contain any air bubbles, it has poor transparency and is somewhat cloudy due to the presence of many traces of dissolved poly-metaphenylene isophthalamide. Ta. This dope was spun under the same conditions as in Example/1, but during spinning, single yarns were broken several times on the spinneret surface. The physical properties of the obtained fibers are also listed in Table 1.

Example core acrylonitrile/methyl acrylate/acrylamide = 9,! /t, s//, acrylonitrile copolymer (θ, J-t//θ
θω-7θ Nitric acid/j00ml was placed in a jacketed solvent degassing tank (2), and a vacuum pump was used to drain both tanks and the second dissolution tank (3), which was connected to the same vacuum pump.
The pressure was reduced to the degree of vacuum shown in the table and degassed for 20 minutes.

At this time, cold water was passed through the jackets of the solvent degassing tank (2) and the dissolution tank (3) to maintain a temperature of about /θ°C.

Next, the degassed polymer and nitric acid were transferred to a dissolution tank +8) while being evacuated under reduced pressure, mixed, and dissolved for about 1.5" hours. Bubbles in each dope obtained by breaking the reduced pressure The amounts were as shown in Table 2.

Using these doped spinnerets, pore diameter θ, /o, and pore number ioo, 4
The thread was wound up at a speed of 4 tm/m in a coagulation bath consisting of an aqueous nitric acid solution (two leads, separated by a space of 111 m), then passed through a 5 m water washing bath, and then washed through a 2.j m water bath. The fibers were drawn in a boiling water bath and stretched to ♂ times to obtain fibers.

This fiber was then dried in a relaxed state in a hot air atmosphere at 700°C, and then drawn in the same boiling water bath for an average residence time of approximately Jj.
3. Introduce at a speed of 2.41 m7- seconds so that
The yarn was drawn at a rate of 3 m/m and drawn at 4 t, 4 times (3 times the undrawn yarn at 4 t).

The fibers thus obtained were then dried at 70°C.
The fibers were subjected to relaxation heat treatment with saturated steam at /♂°C to obtain final fibers.

The results are shown in Table 2.

142 Table = (Note 1) Place a small amount of dope between glass plates, θ,! Number of bubbles observed with the naked eye in 7CIIN when the thickness was set to Akebono (Note 2) Number of times single yarn breakage occurred in the spinneret and spinning bath during a spinning time of approximately 3 hours As is clear from the table s2 It was found that the dope degassed under a high degree of vacuum had a small amount of bubbles and had high spinning stability. Note that the dope shown in Experiment 44' is outside the scope of the present invention (the degree of vacuum is 3.7 To
rr), and the amount of bubbles is much smaller than AJ's conventional dope, which is dissolved in a normal pressure atmosphere without degassing. I couldn't.

Example 3 It was placed in an air tank (1), and the pressure was reduced to 3 Torr, and the air was degassed for 3 tons. On the other hand, 4J-1 aqueous solution of agglomerated zinc 7 no 9θ1
was placed in the solvent degassing tank 12), and after opening the piping valve between the tank (1) and the solvent degassing tank (2) to equalize the pressure at room temperature (Kog °C), the melting tank (which had been previously depressurized to J Torr) was 8) and stirred and dissolved for 2 hours.

The solution viscosity of the obtained dope was 34too boys/2! ℃
Met. As a result of measuring the air bubbles in this dope by the method shown in Example C, it was found that no air bubbles were contained.

Example 2. Transfer the same acrylonitrile copolymer 2.73 (,4) as that used in Example λ to the polymer degassing tank (1) shown in Figure 2, and add N,N-dimethylacetamide/,2
．． 4 into the solvent degassing tank (2) shown in Figure 2,
It was degassed in advance for 10 minutes using a θTart. While maintaining the reduced pressure, the degassed copolymer was heated at 0.4t f/li.
n,N,N-dimethylacetamide 7. , g 1
At a speed of 7 m, the feed was fed to a continuous kneader (7) kept at 20°C and having an internal volume/l as shown in Fig. 2, and kneaded under the reduced pressure. ) to produce a homogeneous dope with no air bubbles and the dope concentration/♂wt%! ! ? , obtained continuously at a speed of ^. The viscosity of this dope was /♂Poise (2θ°C).

No air bubbles were observed in this dope. The pore diameter θ, /4tm (73X
E, / , gc using a / 00 hole spinneret
C/min, 3.76 m/min, discharge linear velocity via jwm space, column length/, 3 m, bath temperature kept at 3/~36°C! Discharge into an aqueous solution of methylacetamide, then ';1
The undrawn yarn was drawn at a speed of 1 m/min and was washed by introducing it into a 1 m water washing bath, then stretched 9 times in a boiling water bath, and then 720
Dry in a hot air dryer at °C. Thereafter, a relaxation treatment was performed with saturated steam at ♂°C to obtain a final fiber. The obtained fiber is a single yarn, 7! Denier, strength 3.1. P/d,
The elongation was 3 Otsu and 6 Chi.

Effects of the present invention In the dope preparation method of the present invention, as mentioned above, by removing the gas that causes bubbles in advance,
The defoaming process, which conventionally required a long time, can be omitted or skipped, resulting in an easy and short defoaming operation.

This not only has the effect of omitting and simplifying car manufacturing processes, but also has the extremely important effect of preventing polymer deterioration during dope preparation and making it possible to obtain high-performance, high-quality molded products. It is something. In particular, the dope preparation method of the present invention requires high-concentration dope and defoaming in a short period of time, which is difficult to dissolve and subsequently defoam using conventional methods. Since it can be prepared without any process, it is possible to easily produce molded products with higher performance and higher quality than ever before.

Furthermore, when manufacturing molded products such as fibers or films from the dope obtained by the method of the present invention, fiber breakage occurs at the spinneret discharge surface, coagulation, washing, etc. compared to dope prepared by conventionally known methods. This significantly reduces process troubles such as the occurrence of fuzz.

Molded articles such as fibers or films obtained by the method of the present invention can be used not only in conventional fields of application but also in a wide range of other fields due to their high quality and excellent performance.

[Brief explanation of drawings]

1 and 2 show seven examples of preferred embodiments used in the dope preparation method of the present invention, in which FIG. 1 shows a batch-type dope preparation apparatus, and FIG. 2 shows a continuous-type dope preparation apparatus. This is an example. The main symbols in the drawings are as follows. 1... Polymer deaeration tank, 2... Solvent deaeration tank, 3... Melt-resistant tank, 4... Vacuum gear pump, 5
... Vacuum pump, 6... Stirring motor, 7...
Continuous kneader Patent applicant Asahi Kasei Corporation Figure 1

Claims (2)

[Claims] (1) When preparing a polymer solution for molding by dissolving a polymer in a solvent that can substantially dissolve the polymer, both the polymer and the solvent are degassed in advance before dissolution. Preparation of a polymer solution characterized by degassing in a reduced pressure atmosphere at a temperature of 3 times or less than the vapor pressure of the solvent, mixing the two while maintaining the reduced pressure atmosphere, and stirring and dissolving in the reduced pressure atmosphere. law (2) When preparing a polymer solution for molding by dissolving a polymer in a solvent that can substantially dissolve the polymer, both the polymer and the solvent are degassed in advance before dissolution. After degassing under a reduced pressure atmosphere of 3 times or less the vapor pressure of the solvent at a temperature of
A method for preparing a polymer solution characterized by continuous extraction