JPH01234424A - Novel, continuous preparation of polymer solution - Google Patents

Abstract

PURPOSE:To obtain a polymer solution free from discoloration for use as a spinning stock solution using a small-scale unit, by heating to a specified temperature, using an engaging type multiple screw extruder, a high-molecular weight copolymer from acrylonitrile, a halogen-contg. monomer and comonomer followed by mixing with a solvent. CONSTITUTION:An acrylonitrile-based polymer 1 with a weight-average molecular weight of 30,000 to 130,000 produced by polymerization between 25-70wt.% of acrylonitrile, 75-30wt.% of a halogen-contg. unsaturated monomer and 0-10wt.% of another unsaturated monomer copolymerizable therewith is fed, via a quantitable feeder 2, into the resin feed section 11 in an engaging type multiple screw extruder followed by mix dispersion while a solvent 3 is charging into a solvent feed section 12 using a quantitable pump 4, and the resultant dispersion is heated so as to be brought to a temperature either at or higher than the boiling point of said solvent or at or higher than that lower than the glass transition temperature (Tg) of said polymer 1 by 10 deg.C in the earlier stage 14 of the kneading section, followed by blending said polymer with said solvent in the middle and the later stages 15, 16 to make a shearing and kneading into a homogeneous solution, which is then extruded, via the extruding section 17, thus continuously preparing the objective polymer solution.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a method for preparing a polymer stock solution for use in the production of synthetic fibers and films by wet and dry methods, in which a polymer stock solution is prepared using an intermeshing multi-screw extruder. This invention relates to a novel method for obtaining a polymer solution by mixing and kneading with a solvent.

<Prior art and problems to be solved by the invention> Polymers mainly composed of two components: acrylonitrile component and a halogen-containing unsaturated monomer component represented by vinyl chloride or vinylidene chloride ) is a useful polymer that is used in large quantities in the production of fibers and films. In order to produce fibers and films from such polymers, a wet method or a dry method is usually used instead of a melt method. In these methods, a polymer stock solution is first prepared by dissolving a halogen-containing acrylic polymer in a solvent, and this stock solution is extruded through a spinning nozzle or die to form fibers or films.

Conventionally, the method used industrially to prepare such a stock solution is to put a solid (e.g., powder, flakes, pellets, etc.) polymer together with a solvent into a tank equipped with a mixing means such as a stirrer. The basic method was to dissolve it. As a method for dissolving halogen-containing acrylic polymers in solvents, which have been conventionally produced in large quantities, there is almost no alternative to this method, and this method has been used for a long time.

However, since the above method takes time to dissolve the polymer, the capacity of the tank becomes large, and depending on the amount of processing, a large-scale apparatus is required, and furthermore, it is not economical in terms of energy consumption. In addition, undissolved gel and concentration unevenness occur, making it difficult to obtain a homogeneous stock solution. Also,
In such a method, a batch method or a semi-continuous method using a combination of tanks has to be used, making continuous processing difficult. Furthermore, because it takes time to dissolve, and in some cases the residence time is long in the semi-continuous method, unfavorable phenomena in terms of quality such as coloring of the solution, decrease in the degree of polymerization, and generation of deteriorating reaction products occur. It was easy.

Furthermore, halogen-containing acrylic polymers are also soluble in solvents such as acetone and acetonitrile, which have relatively low boiling points and can be easily recovered and reused, but when such solvents are used, the concentration of the polymer in the solution is low. The upper limit is about 30% by weight, and if the concentration is increased more than this, it becomes an agar-like substance (gelled substance) when dissolved, and there is a problem that stirring becomes virtually impossible.

As a dissolution method other than the above-mentioned tank method, JP-A-61143439 discloses a method for preparing a polymer solution using a twin-screw kneading extruder. This method is a method for dissolving special polymers having a weight average molecular weight of 200,000 or more, but it is described that it is not very suitable for low boiling point solvents that can be easily recovered and reused. However, the present inventors have discovered that it is also possible to use a twin-screw kneading extruder to dissolve a halogen-containing acrylic polymer of ordinary molecular weight manufactured by Okawa in a solvent. However, it has been found that this method can be used without any problems even with solvents with low boiling points, which had been thought to be undesirable, and that it is particularly effective to carry out the dissolution above the boiling point. Furthermore, by using this method, it is possible to easily produce a polymer solution with a high concentration exceeding 30% by weight, which was previously impossible. According to this method, it is possible to overcome all the drawbacks of the conventional tank-based dissolution method described above.

Means for Solving the Problems〉 To describe the method of the present invention in detail, the acrylonitrile component is 25 to 70% by weight, and the halogen-containing unsaturated monomer component is 75% by weight.
When dissolving in a solvent an acrylonitrile-based polymer having a weight average molecular weight of 30,000 to 30,000 I obtained by polymerizing 0 to 10% by weight of an unsaturated monomer component copolymerizable with these, interdigitating type Using a multi-screw extruder, at least a portion of the extruder is heated to a temperature above the boiling point of the solvent or 10°C above the glass transition temperature (Tg) of the polymer, at which the main chain of the polymer begins thermal movement and softens. In this method, a polymer solution is continuously prepared by heating to a low temperature or higher and mixing the polymer and a solvent.

Acrylonitrile component used in the present invention 25~
70% by weight, halogen-containing unsaturated monomer component 75-30
Weight% and unsaturated monomer component copolymerizable with these: 0
The polymer consisting of ~IO% by weight is a raw material polymer for so-called modacrylic fibers. Examples of the halogen-containing unsaturated monomer component used in this polymer include chlorine-containing unsaturated monomers such as vinyl chloride and vinylidene chloride, and bromine-containing unsaturated monomers such as vinyl bromide and vinylidene bromide. can be mentioned. Since the polymer of the present invention contains such a monomer component, it becomes soluble in a low boiling point solvent such as acetone and acetonitrile.

In addition to acrylonitrile and halogen-containing unsaturated monomers, the polymer of the present invention may contain other monomer components copolymerizable with these. Unsaturated compounds that generate acidic groups, such as sodium styrene sulfonate and sodium methacryl sulfonate, are used to improve dyeability, and unsaturated monomers, such as methyl methacrylate and vinyl acetate, are used to improve the physical properties of polymers. Quantities can be mentioned.

The weight average molecular weight of the polymer is 30,000 to 130,000.
The molecular weight of the halogen-containing acrylic polymers that have been produced in large quantities is within this range. A more preferable molecular weight range is 4,0000 to 5oooo.

Examples of organic solvents include organic solvents that can dissolve the polymer, such as dimethylformamide, dimethylacetamide, dimethylsulfoquine, acetonitrile, acetone,
2-methylvinylpyridine, ethylene carbonate, succinonitrile, γ-butyrolactone, nitromethane,
Cyclohexanone etc. are used.

In the present invention, various additives such as stabilizers, pigments, and dyes may be added to the solvent in addition to the halogen-containing acrylic polymer. Such additives may be introduced into the extruder together with the polymer, or may be injected into the extruder in a state in which they have been previously dissolved or dispersed in a solvent.

The intermeshing multi-screw extruder used in the method of the present invention is well known and is often used for resin processing. There are two types of extruders: a co-directional type and a non-directional type, and both can be used, but the co-directional extruder is preferred because it has a self-cleaning function. Among the two-sleeved extruders, a high-speed shearing type extruder, that is, a shearing type extruder in which the outer peripheral speed of the extrusion screw is at a high speed of 400 m/sheet or more is preferable. An example of such an extruder is the co-rotating twin-screw extruder TEM model manufactured by Toshiba Machine Co., Ltd., which can handle mixing, pressurization, heating, and kneading depending on the type of screw and barrel combination unit. , extrusion, etc., and can be performed continuously. The extruder used must have at least one kneading section and one extrusion section, and more preferably has units with basic functions such as a resin supply section, a solvent mixing and dispersion section, a heating kneading section, and an extrusion section. It is an extruder. In particular, in the mixing and dispersing section and the heating and kneading section, it is important to combine a plurality of units and appropriately set cooling, heating, and pressurizing conditions in order to dissolve the polymer homogeneously and efficiently.

A halogen-containing acryl-based acrylic polymer is supplied from the supply section into the extruder, and then a solvent is mixed at a certain ratio, heated, pressurized, and kneaded, and extruded from the tip as a homogeneous polymer solution. Be able to do it. The mixing ratio (
You can choose the solution concentration), temperature, pressure conditions, and combinations thereof.

In the present invention, when a polymer and a solvent are supplied to a multi-screw extruder, they may be supplied separately or both may be supplied in a mixed state, but they may be supplied in a mixed state. Then, if the temperature of the resin supply section is high, the solvent may volatilize, so it is preferable to supply it separately.

When using a solvent with a boiling point of 100° C. or lower in the method of the present invention, the temperature inside the extruder must be set to at least a portion of the extruder at a temperature equal to or higher than the boiling point of the organic solvent used. Since such a low boiling point solvent has a weak dissolving power, the dissolution rate of the polymer decreases at temperatures below the boiling point. Specifically, in an example using acetone (boiling point 566C), a temperature range of 56 to 150C, particularly 60 to 120C is preferred.

When the temperature inside the extruder exceeds the boiling point of the solvent, problems such as the boiling solvent evaporating from the resin supply section and the formation of bubbles in the polymer solution are expected, but the method of the present invention unexpectedly solves these problems. However, such a phenomenon does not exist at all. It is desirable that as many locations as possible within the extruder be at the above temperature. There is no problem even if the temperature is particularly high at the location where the solvent and polymer are mixed. However, if the vapor pressure of the solvent used becomes too high, the pressure balance within the system is likely to collapse, causing solvent vapor to flow backwards or creating vapor voids, making normal operation difficult. vapor pressure l
It is desirable to keep it below 0 kg/cm'.

The residence time of the polymer in the barrel of the extruder is 1 to 10 minutes;
Preferably it is 3 to 6 minutes. If the residence time is less than 1 minute, dissolution and kneading will be insufficient and it will be difficult to obtain a uniform solution.On the other hand, if the residence time exceeds IO, drawbacks will appear such as deterioration of the polymer and a decrease in productivity due to a decrease in discharge m. Factors that affect residence time include the number of kneading sections, the shape of the screw element, the feed rate, and the ratio of screw diameter to length (L/D).
etc. are possible.

The polymer strength of the polymer solution produced in the present invention is arbitrary, but is generally preferably 20 to 90% by weight. In particular, with the method of the present invention, it is possible to prepare solutions with a concentration of 30% by weight or more, which was previously impossible, and it is possible to easily obtain a uniform solution containing no insoluble matter even if the concentration is 50% by weight or more. Can be done.

The polymer solution obtained by the present invention can be fed as it is to a spinning nozzle or die to form filaments or films. It is also possible to dilute the highly concentrated solution once to about 30% by weight and supply it to existing spinning equipment.

<Examples> Hereinafter, the present invention will be specifically explained in detail with reference to Examples, but it goes without saying that the present invention is not limited thereto. In addition, unless otherwise specified in the examples, % is weight %.

Examples and Comparative Examples An acrylonitrile copolymer consisting of 50% acrylonitrile and 50% vinyl chloride with an average degree of polymerization of about 1000 (weight average molecular weight 5°80,000) was used, using acetone as a solvent, and intermeshing twin-screw extrusion. A polymer solution was prepared using a machine.

The intermeshing twin-screw extruder used was a co-rotating twin-screw extruder TEM-35 model manufactured by Toshiba Machine Co., Ltd., and 10 barrel units were connected in series. The parts that have a melting function, consisting of a barrel and a screw, can be broadly divided into the resin (powder) supply part, the solvent supply part, and the dispersion mixing part.1. It consisted of a kneading section and an extruder, and the kneading section mainly used a shear force-enhancing screw element, and the other parts used ordinary screw elements. The temperature of the kneading section was controlled by dividing it into three sections: a front stage, a middle stage, and a rear stage, and the temperature of the central part was set to be the highest.

As shown in FIG. 1, the polymer 1 is supplied from the quantitative feeder 2 to the resin supply section 11, and a solvent 3 (acetone) is added to the resin supply section 11.
were mixed and dispersed while being injected into the solvent supply section 12 of the second section using the metering pump 4, and further heated and heated in the pre-kneading section 14 of the third section. The melted mixture rapidly progresses in dissolution in the middle stage I5 of the kneading section kept at a high temperature, and is uniformly mixed by shearing force, resulting in a decrease in viscosity. The solution, which has almost completely dissolved, passes through the latter part of the kneading section I6 while further lowering the temperature.
A homogeneous solution is prepared by shearing and mixing, cooled to a required temperature in the final extrusion section 17, and extruded. Table 1 shows the results of experiments conducted under typical conditions.

The solutions obtained in all of the above experiments were free of coloration and undissolved gel, and were sufficiently usable for practical use, demonstrating that the present invention is industrially very useful.

Experiment 1 was an example in which the concentration was comparable to that of the solution obtained by the conventional method, but it had the advantage that the solution was less colored because the dissolution was completed in a short time. However, since the viscosity is low, it is difficult for the shearing force to work effectively, and the present invention was found to be suitable for dissolving higher concentrations and higher viscosity.

Experiment 2 is an example of dissolution to a concentration of 50%.

The temperature of the shearing section was set higher than in Experiment 1 to facilitate dissolution. It was possible to obtain a highly concentrated homogeneous solution with a concentration of 50% and a viscosity of 400'O poise, which could not be achieved using conventional methods. In addition, a nozzle of 1 mmφ x 200 holes was attached to the extruder, and a test was conducted to wind the yarn at a take-up speed of +00IIlZ, but there was no yarn breakage and the machine could operate smoothly for 3 hours.

Experiment 3 was conducted at an even higher concentration, 70-% dissolution, by lowering the screw rotation speed and increasing the residence time. The resulting solution had a high viscosity, and was close to the state obtained by extruding a molten material, and solidified immediately after extrusion.

<Effect of the invention> The effects of the present invention can be summarized as follows.

(1) The dissolution process becomes more compact. Especially on an industrial production scale, the installation area is reduced to 1 for the same capacity (kg/hour).
15 to 1/10 or less.

(2) Since the device can be made compact, the amount of solution stagnant inside is small (1/10 to 1150), so there is less loss when starting and stopping, and product changeover loss and time loss are greatly reduced. .

(3) Short time required for dissolution <(115-1150),
It can be completed in a few minutes, and the heating temperature can be lower than in conventional methods due to the kneading effect of strong shearing force. Therefore, the quality of the solution is improved, with less thermal history and less thermal coloring.

(4) It is also possible to increase the concentration of the resulting solution to a high concentration (30 to 90%) that cannot be obtained by conventional methods, which is preferable in terms of quality and productivity of fibers and films manufactured from this method.

(5) Compared to conventional methods, energy is saved by making the device more compact and relaxing heating conditions.

(6) Stabilizers, additives, etc. can be added in either liquid or solid form.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of an intermeshing multi-screw extruder used in the method for continuously preparing a polymer solution of the present invention. l...polymer, 2...quantitative feeder, 3
...solvent, 4...metering pump, 11...
Resin supply section, 12... Solvent supply section, 13... Dispersion mixing section, 14... Kneading seat front stage, 15... Kneading section middle stage, 1
6... Kneading section latter stage, 17... Extrusion section. Patent applicant Kanekabuchi Kagaku Kogyo Co., Ltd. Representative Patent Attorney Aoyama Aoyama and I others

Claims (1)

[Claims] 1. Weight average molecular weight obtained by polymerizing 25 to 70% by weight of an acrylonitrile component, 75 to 30% by weight of a halogen-containing unsaturated monomer component, and 0 to 10% by weight of an unsaturated monomer component copolymerizable with these. When dissolving an acrylonitrile-based polymer having a molecular weight of 30,000 to 130,000 in a solvent, an intermeshing multi-screw extruder is used, and at least a portion of the extruder is heated to a temperature higher than the boiling point of the solvent, or lower than the glass transition temperature (Tg) of the polymer. A method for continuously preparing a polymer solution, which comprises heating the polymer and a solvent to a temperature that is 10° C. lower or higher, and mixing the polymer and a solvent.