JPS6173743A - Method for continuously preparing stock solution of high-molecular polyolefin - Google Patents

Abstract

PURPOSE:To obtain a homogeneous high-viscosity polyolefin soln. continuously, by continuously dissolving a dispersion of a polyolefin in a solvent in a homogeneous stock soln. of a polyolefin. CONSTITUTION:A polyolefin (a) having a weight-average MW of 800,000 or above and a solvent (h) having a b.p. (TB) of 140 deg.C or above are fed to a slurry tank 1 and the mixture is stirred by heating at a temp. of not higher than the dissolution initiating temp. (TS) of component (a) to not lower than TS-50 deg.C to obtain a dispersion (A) having the predetermined concn. Component A is continuously added at a rate satisfying the formula [wherein VA is the quantity (kg/min) of component A to be added; LB is the quantity (kg) of component B] to a dissolving tank 2 contg. a stock soln. contg. component (a) dissolved in component (b) at the predetermined concn., which is stirred by heating at a temp. of not lower than TS+20 deg.C to not higher than TB under an internal pressure of 200-500Torr, to dissolve component (a). The soln. is continuously fed through a booster pump 4 to a kneader and/or extruder 4 at a temp. of not lower than TS+20 deg.C to homogeneously dissolve component (a) and dis charged through a metering pump 5 from a nozzle 6.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a method for preparing a spinning dope for producing molded products such as polyolefin fibers or films having extremely high tensile strength and modulus, and particularly relates to a method for preparing a spinning solution that is inexpensive and continuous. The purpose is to obtain a highly uniform high viscosity polyolefin solution.

<Prior Art> Generally, the molecular chain ends of a polymer become defects in the fiber microstructure, so it is expected that a polymer with a large molecular weight will have fewer molecular chain ends per unit volume and will have greater strength.

When spinning high-molecular-weight polyolefin using a ζ-rotation method, it is difficult to perform melt-spinning alone due to its high melt viscosity.Usually, a dilute solution of the high-molecular-weight polyolefin dissolved in a solvent is used and solidified by cooling during spinning. The so-called gel spinning method is disclosed in Japanese Patent Publication No. 44-26409 and Japanese Patent Application Laid-Open No. 55-1075.
This method is disclosed in Japanese Patent Application Laid-Open No. 06-06, Japanese Unexamined Patent Publication No. 58-5228, and the like.

However, these methods are not preferable because the polyolefin concentration is low, and in industrial production, solvent recovery costs and equipment costs due to decreased production are considered to increase.

In the case of increasing the concentration of polyolefin, the inventor's experiments show that when a dispersion of polyolefin and solvent is heated in a patch system to dissolve the polyolefin, the polymer aggregates at the point where dissolution has begun, resulting in extremely high viscosity. It has been found that this method is undesirable because it tends to create large lumps and result in a non-uniform solution, and it takes a long time to homogenize, resulting in high cost. In addition, the patch type had the disadvantage that some of the stock solution remained in the dissolver after discharging the stock solution, which required treatment and cleaning of the dissolver.

When considering scale-up of operations, it is advantageous to use a continuous method rather than a patch method to prepare a stock solution because equipment costs and power costs such as electric steam are lower, but the state of the stock solution changes suddenly at the temperature at which the polyolefin begins to dissolve It was thought that it would be difficult to make a homogeneous stock solution using a continuous method because it changes from a viscous dispersion to a highly viscous heterogeneous solution.

<Problems to be Solved by the Invention> In view of the above background, the present invention aims to provide a method for continuously preparing a polyolefin stock solution, which continuously obtains a uniform solution stock solution with a high polyolefin concentration.

Means to Solve the Problems〉 That is, the present invention provides a method for continuously obtaining a uniform solution of polyolefin, in which a dispersion of polyolefin and a solvent is added to a uniform solution of polyolefin B prepared in advance. It is adjusted by continuously adding and mixing A, and in this case, in particular, the temperature of the dispersion A at the time of addition and mixing, the temperature of the uniformly dissolved stock solution B, and more preferably the temperature of the dispersed adult solution with respect to the uniformly dissolved stock solution B. By selecting the amount added, etc., it is possible to continuously produce a uniformly dissolved stock solution of polyolefin.

More specifically, the present invention has the following features.

``10 In a method of homogeneously dissolving 3 to 30% by weight of a polyolefin having a weight average molecular weight of 800,000 or more in a solvent having a boiling point TB of 140°C or more, the polyolefin and the solvent are
The melting start temperature T of the polyolefin in the solvent at that time
A predetermined concentration of dispersed adults heated under stirring to a temperature lower than S and higher than T, −50° C. is preliminarily added to the TS +
Stock solution B of dissolving polyolefin and solvent at a predetermined concentration, heated with stirring at a temperature from 20°C to the above TS+
After continuously adding and dissolving the solution into the solution, the solution is continuously fed to a kneader and/or extruder at a temperature higher than TS + 20°C to obtain a uniformly dissolved stock solution. Continuous preparation method for polyolefin stock solution.

2. In claim 1, the amount of dispersion A to be added is determined by the following formula, %, with respect to the amount of stock solution B for dissolution. A method for continuously preparing a high molecular weight polyolefin stock solution, characterized by adding stock solution B in an amount (kg) that satisfies the amount of stock solution B.

3. A high molecular weight polyolefin according to claims 1 or 2, characterized in that the dispersion A added to the stock solution B is allowed to stay in the stock solution B for 3 minutes or more. Continuous preparation method of stock solution.

4. In claims 1 to 3, the internal pressure of the dissolving tank containing the dissolving stock solution B is set to 200 to 500 Torr, and at the same time defoaming is performed, extrusion is carried out using a screw system, and the dissolving solution B is continuously extruded using a kneader and/or extruder. A method for continuously preparing a high molecular weight polyolefin stock solution, characterized by supplying a stock solution of a high molecular weight polyolefin.

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The present invention will be explained in detail below.

The polyolefin referred to in the present invention refers to polyethylene, polypropylene, polybutene, polypropylene copolymer, or a polymer that has been modified by 20 mol% or less for the purpose of improving dyeing, antistatic, heat resistance, light resistance, flame retardance, etc. Copolymerized with quality agents, or glossy, colored, high specific gravity, conductive, magnetic,
It means a material containing 20% by weight or less of a filler for reinforcing purposes and/or 5% by weight or less of an antioxidant or ultraviolet absorber, or a mixture of two or more of these.

If the weight average molecular weight of the polyolefin is less than 800,000, it is difficult to obtain highly tenacious and highly modicolus fibers and molded products, and if it exceeds 60,000, the viscosity of the stock solution is high and it is difficult to obtain a highly concentrated and uniform stock solution. , 800,000 or more, preferably 1,300,000 to 5,000,000.

As the solvent for dissolving the polyolefin, one or more solvents having a boiling point of 140° C. or higher are used. When the boiling point of the solvent has a temperature range, the boiling point TB in the present invention means the lowest temperature in the temperature range. In addition, the solvent causes phase separation from the polyolefin when cooled, and the phase separation temperature (gelation temperature) is 70°C from the viewpoint of spinnability and drying.
It is preferable that the temperature is at least ℃. The phase separation temperature herein is defined as the temperature at which a 1% by weight polyolefin solution generates turbidity that can be detected with the naked eye when it is cooled in a stationary state at a cooling rate of 0.5° C./min.

Such solvents include, for example, nonane, decane, undecane, dodecane, paraffin, decalin, tetralin,
Examples include petroleum-based turbens whose main components are aliphatic or alicyclic reverted hydrogen such as naphthalene, aliphatic or aromatic hydrogen, or halogens such as dichlorobenzene (tl hydrogen).

In the present invention, the concentration of polyolefin produced by Fukagawa is 3 to 3.
It is 30% by weight. If it is less than 3% by weight, it is disadvantageous in terms of solvent recovery and a decrease in production, and if it exceeds 30% by weight, it is undesirable because high viscosity results in non-uniform dissolution, and at the same time, defoaming and liquid feeding are difficult. The viscosity of the stock solution is preferably 500 to 5000 voids in terms of defoaming, uniform dissolution, stable discharge, etc. Although the optimum concentration varies depending on the molecular weight of the polyolefin, in the case of polyethylene, a weight average molecular weight of 1.3 million to 5 million and a concentration of 5 to 15% by weight are preferred from the viewpoint of cost, uniform solubility, and fiber performance. In addition, in the case of a high concentration, raising the temperature to a high temperature in order to lower the viscosity tends to cause molecular chain scission and coloring due to thermal decomposition, so the preferred temperature is 150 to 200'C.

In the present invention, when a stock solution is continuously prepared, there are roughly three steps as shown in FIG.

The first is the preparation process of polyolefin and solvent dispersion A in slurry tank 1, and the second is the dissolution stock solution B in dissolution tank 2.
The third step is the step of preparing a uniform stock solution in the kneader and/or extruder 3. In all steps, it is preferable to replace oxygen in the system with nitrogen or an inert gas in order to prevent oxidative decomposition of the polymer.

The predetermined concentration dispersion of polyolefin and solvent in the first step needs to be heated under stirring to a temperature lower than the polyolefin's dissolution start temperature T8 and higher than TS50°C. If dispersion A is not heated and the temperature is lower than TS50°C, adding the dispersion Ronin to the solution B will take time to dissolve the polyolefin in the dispersion, and the polyolefin powder will aggregate. It tends to form white lumps and create density spots. Further, a temperature higher than TB is not preferable because it becomes a highly viscous and heterogeneous solution, making it difficult to add it to the stock solution B in the second step, or even if it is added, the concentration fluctuates.

Note that the melting start temperature of polyx y V :/ varies depending on the solvent used, but the melting start temperature of polyethylene referred to in the present invention is the temperature at which 1% polyolefin changes from white powder to partially transparent under stirring. This is the temperature when making a high viscosity stock solution.

As mentioned above, the temperature of dispersion A needs to be lower than TI and higher than TS50°C, and
Temperatures lower than 0 to 30°C are preferred.

In addition, in the continuous adjustment method of the present application in which the dispersion liquid A is continuously added to the dissolution stock solution B, it is natural that the mixing ratio of both is selected so that the polyolefin concentration matches the polyolefin concentration of the dissolution stock solution B. .

If dispersion A is not stirred, the polyolefin tends to settle immediately, so it is necessary to add it to the stock solution B while stirring so that there is no stagnation in the piping.

The stock solution B in the second step needs to be heated and stirred at a temperature from TS + 20°C to TS. If the temperature of the stock solution B is lower than TS +20° C., it takes time to dissolve the added dispersion A, which tends to cause concentration unevenness.

Further, at a temperature exceeding TB, the solvent boils, degassing becomes insufficient under pressure, and concentration unevenness is likely to occur due to evaporation and condensation of the solvent, which is not preferable.

In addition, in dissolution tank 2, addition of dispersion liquid A tends to cause temperature and concentration unevenness, so the shape and stirring rotation of the stirrer should be optimized to avoid excessive swirling of the stock solution to increase the stirring effect and add it little by little. is preferable.

In the case of a steady state, it is particularly preferable that the amount of dispersion A added and the amount of stock solution B satisfy the following formula.

0, I X 10-2≦VA / La ≦3 X j
O-2VA/Ls is 0. If it is less than lX10', the amount added is small and it is advantageous in terms of uniform dissolution, but if you try to increase the amount added, it is necessary to increase the value of LB, and the equipment cost and driving cost will be reduced due to the increase in the capacity of the dissolution tank. This is undesirable as it causes an increase.

If VA/Le exceeds 3 X l O-2, non-uniform undissolved polyolefin lumps are likely to be formed, which is not preferable.

In addition, in the steady state, the amount of dispersion A added is determined by the kneader and/or
Or, it is equal to the amount of sugar (discharge i) discharged from the extruder with a metering pump during spinning.

Furthermore, in order for the dispersion liquid A to dissolve, it is desirable that the dispersion liquid A has a residence time of at least 3 minutes or more in the dissolution stock solution B without short-passing in the dissolution tank, and preferably, in the dissolution tank 2 shown in FIG. It is preferable to configure the structure so that the path of the dispersion liquid A is a curved path, like the structure of the stirring blade. Although the solution stock solution B may be a partially (microscopically) non-uniform solution, it is preferable that the polyolefin in the dispersion solution A be dissolved and transparent and macroscopically uniform.

In addition, from the point of view of defoaming, the internal pressure of the dissolving tank 2 containing the dissolving stock solution B was set at 2.
It is preferable to set it to 00 to 500'porr, but 2
If the temperature is less than 0.00 Torr, it becomes difficult to raise the level of the raw liquid and to extrude it to the next step.

When the internal pressure is 200 to 500 Torr, the stock solution B is extruded using a screw system and the pressure is increased, and in some cases, the external pressure pump 4 is used to flow the stock solution in the piping to the supply port of the kneader and/or extruder 3. is good.

The kneader and/or extruder 3 in the third step must be a device that ultimately converts the stock solution B into a uniform solution, and is preferably a twin-screw kneader or a twin-screw kneading extruder.

In addition, when the dissolving stock solution B is a substantially uniform dissolving stock solution, a single screw extruder alone may be used as long as the degassed uniform dissolving stock solution is discharged from the spinning nozzle without any problem.

The stock solution temperature in the kneader and/or extruder is TS +2
The temperature is higher than 0°C, and preferably 150°C to 200°C from the viewpoint of uniform dissolution, defoaming, and decomposition of polyolefin.

<Function> As explained above, the present invention is a method in which a dispersion of polyolefin and a solvent is added to a pre-made stock solution for dissolving both, in order to produce a stock solution for uniformly dissolving high molecular weight polyolefin in a continuous manner. Regulating the respective temperatures of the dispersion liquid and the dissolution stock solution, preferably regulating the addition lid to the dissolution stock solution of the dispersion liquid, and more preferably regulating the residence time of the dispersion liquid in the dissolution stock solution, the internal pressure of the dissolution tank, etc. This eliminates the problems of non-uniformity of the stock solution and residual liquid that were observed in batch-type systems.

<Example> The present invention will be specifically explained below using examples. .

Example 1 Polyethylene powder with a weight average molecular weight of 1.5 million and an antioxidant (1% by weight based on polyethylene) were mixed at a boiling point of 185~
A petroleum-based solvent whose main component is aliphatic at 210°C is poured into a slurry tank so that the polyethylene concentration is 10% by weight, and after vacuum defoaming and N2 substitution with stirring, it is heated to 110°C. , 30 kg of Dispersion A was prepared. The dissolution start temperature of the polyethylene in the petroleum solvent was 119°C, and the polyethylene in 11 Dispersion A was in the state of white powder. Note that 1.35 kg of solvent preheated to 110°C and 0.15 g of polyethylene powder are added to each slurry tank every hour, and the amount of dispersion A in each slurry tank does not change at all due to mass balance. I did it like that.

On the other hand, using the same polyethylene and petroleum solvent at a concentration of 10% by weight, 175
The mixture was stirred at ℃ for 4 hours to prepare 9 to 20 diluted stock solutions B.

The temperature inside the dissolution tank in which the stock solution B was dissolved was 400 Torr.
Then, 0.251 g of the dispersion A was added to the dissolution tank in 7' portions. Note that the supply port of the dissolution tank was cooled with tap water to prevent polyethylene from fusing.

As shown in Figure 1, the stirring blades of the dissolution tank are anchor-shaped and in contact with the tank wall, and at the same time there is a shelf plate between the rotating shaft and the anchor, so that the residence time of the dispersion liquid A is at least 10 minutes. did. In addition, the tip of the stirring blade was of a screw type, and the stock solution B was extruded and supplied to the next twin-screw kneading extruder in the same direction. The stirring rotation speed during the addition of dispersion A was 25 rpm.

The solution stock B before adding the dispersion A is macroscopically a homogeneous solution, and the dispersion A is added thereto at a rate of 0.25 kti/min (■mu/LB=1.25 XI 0-2) Immediately after addition, white powder of polyethylene was seen, but 1-2
The solution became transparent after a few minutes, and when the stock solution was observed at the outlet of the dissolving tank, it was found that the clear solution and some small swollen transparent polyethylene particles were mixed together. Also, because it was under vacuum, there were almost no bubbles containing polyethylene (no coloring or decomposition was observed even after 10 hours. Furthermore, when I looked at the stock solution extruded from the kneading extruder, I did not see any small swollen transparent particles of polyethylene. It was a homogeneous, transparent solution with a viscosity of about 1500 voids.

The co-directional twin-screw kneading extruder 3 has two kneading sections and three extrusion sections.
Divided into 5 sections, screw rotation speed is 20
The temperature was kept constant at 175° C. in each section at 0 rpm. The residence time in the kneading extruder was approximately 15 minutes. The screw tip pressure was 38 kt)/d, needles were added using a metering pump (gear pump) 5, and the material was extruded from a spinning head (nozzle) 6 at a discharge rate of 150 f/min, cooled, solidified, and made into fibers.

Spinning was carried out for 5 consecutive days using a 40-hole nozzle at a discharge rate of 2'501/min and a winding speed of 20/min, but there was no yarn breakage, and no increase in spinning head pressure due to filter clogging occurred. 1 I couldn't see it at all. The discharged stock solution was collected, and the polyethylene concentration for 5 days was calculated by weight measurement before and after the solvent scattering, and it was found to be approximately constant at 100.09%. Furthermore, when the denier fluctuation rate of the obtained spun yarn was measured, it was found that it was low within 2.5% and that a uniform stock solution was obtained. Furthermore, we observed fluctuations in stretchability and fiber performance due to molecular chain scission and differences in the degree of entanglement.
There was fluffing twice during the day-long drawing, but there was no yarn breakage, and the strength of the drawn yarn was 20 f/r1 or more, and the modulus was 700.
It has been found that Vd or higher can be stably obtained.

Example 2 12% by weight of polyethylene having a weight average molecular weight of 3 million, 1% by weight of an antioxidant and 0.2% by weight of an ultraviolet absorber based on the polyethylene were dispersed in decalin having a boiling point of 187 to 196°C, and heated at 100°C. 15 kg of Dispersion A was prepared. This was added at a rate of 30y/min into 10kg of a previously prepared solution B of the same composition at 185°C (VA
/LB = 0.3 x 10-2).

The dissolution tank was stirred by a hook that rotated and revolved and a scraper that was in contact with the tank wall.The hook was rotated at 39 rpm, the revolution was at 15 rpm, the scraper was rotated at 15 rpm, and the residence time of dispersion A was 5 minutes. That was it.

The temperature at which the polyethylene begins to dissolve in decalin is 11
When dispersion A was added to dissolution stock solution B at 5°C, the stock solution state was similar to that in Example 1, but because the amount added was small, the swollen transparent particles of polyethylene were slightly visible and almost uniform. The clarity of the dissolution was.

Although the temperature inside the dissolution tank was set to 300 TOrr, the viscosity of the stock solution was as high as about 4000 torr, so it contained some air bubbles.

However, when the material is fed to the next single-screw extruder using an external pressure pump and extruded, the air bubbles are pushed back to the rear of the extruder screw and are completely defoamed within the extruder because the tip pressure is as high as so kg/d. There was found. The screw diameter is 25s.
+ m, the rotation speed is 3 Q rpm, and the temperature is 185°C.
It was set to

Spinning was carried out for two days using a 12-hole nozzle at a discharge rate of 30 g/min and a winding speed of 10 ml/min, but there was no yarn breakage.
The spinning head pressure was constant at 65 to 7 s kg/d, and no filter clogging was observed.

In addition, the polyethylene concentration was measured every hour, and it was 12 ± 0.
．． It turned out that there was almost no change at 11%. The obtained spun yarn was dried to a solvent content of 5% or less, and was stretched for 10 days between rollers at a rate of 31 times, equivalent to 85% of the maximum stretching ratio, using a heater, but fluff and yarn breakage were 2. It was confirmed that the spun yarn was almost uniform just because of the number of times. In addition, the performance of the drawn yarn is that the strength and elongation is 23 f/
The modulus was 980 Vd at -4.2%.

Example 3 Polypropylene with a weight average publication of 1 million at a concentration of 7% by weight
It was added to a petroleum solvent having a boiling point of 215 to 242°C so that the dispersion liquid A was prepared at 120°C. Next, add 1 to 5 kg of a pre-prepared solution of the same composition at 195°C.
Dispersion A was added at a rate of 00 f/min, and the stirring blade and rotation speed were set so that the residence time was 4 minutes or more (Va
/ Lm = 2 x 10-”).

The polypropylene in dispersion A was a white powder, and when it was added to the stock solution B, white lumps were produced.
It became a transparent swollen grain in minutes. The stock solution extruded from the dissolution tank was partially non-uniform and contained some air bubbles, but 2
A homogeneous stock solution without air bubbles was observed after passing through the axial kneader and twin-screw extruder. Note that the polypropylene concentration was Huff ±0.05%. Spinning and drawing was carried out just in case, but there was almost no denier variation (#1), the drawing ratio was stable, and a high-strength polypropylene fiber was obtained.

Comparative Example 1 The same operation as in Example 1 was performed except that the concentration of dispersed Ronin was set to room temperature. However, because the temperature of dispersion liquid A is low, the temperature of the stock solution at the addition part in the dissolution tank drops, and large white lumps of polyethylene are formed and it does not dissolve transparently, and the stock solution discharged from the twin-screw extruder in the same direction does not Swollen transparent grains of polyethylene were present, and filter clogging and yarn breakage occurred frequently during spinning.

Comparative Example 2 In Example 1, the amount of dispersion A was added in large amounts of 1 kg over 7 minutes (VA/Ln = 5 x 10')
The same operation as in Example was performed except for this point. In this case, the amount of dispersion added was large, and as in Comparative Example 1, white lumps were produced, resulting in a slightly non-uniform stock solution.

Comparative Example 3 In Example 1, the temperature of the dissolution stock solution was set to 130°C, which was 11°C higher than the dissolution start temperature TS. However, the heating temperature of this dissolved stock solution was too low, and when dispersion A was added to the dissolved stock solution, large white lumps of polyethylene were formed. Filter clogging and thread breakage occurred frequently.

<Effects of the Invention> As shown in the examples, the present invention allows a continuous solution to obtain a uniform solution with a high concentration of polyolefin, resulting in a more uniform solution, lower equipment costs, and less residual liquid than a batch method. It has many advantages such as no processing required.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the continuous preparation process of a high molecular weight polyolefin stock solution according to the present invention, where l is a slurry tank of dispersion liquid A, 2 is a dissolution tank, 3 is a kneading extruder, 4 is a booster pump, 5 indicates a metering pump, and 6 indicates a spinning head.

Claims (1)

[Claims] 1. A polyolefin with a weight average molecular weight of 800,000 or more,
In a method of uniformly dissolving 3 to 30% by weight in a solvent with a boiling point T_B of 140°C or higher, the polyolefin and the solvent are lower than the dissolution start temperature T_S of the polyolefin in the solvent at that time, and T_S
Dispersion A with a predetermined concentration heated under stirring to a temperature higher than -50°C is a stock solution of a polyolefin and a solvent with a predetermined concentration, which has been previously heated with stirring at a temperature between the above T_S+20°C and the above T_B. A high molecular weight polyolefin characterized in that after being continuously added and dissolved in B, the dissolved solution is continuously supplied to a kneader and/or an extruder at a temperature higher than T_S + 20°C to obtain a uniformly dissolved stock solution. Continuous preparation method of stock solution. 2. In claim 1, the amount of dispersion A to be added is determined by the following formula: 0.1×10^-^2≦V_A/L_B≦3×10^-
^2 However, V_A: Addition amount of dispersion A (kg/min) L_
B: A method for continuously preparing a high molecular weight polyolefin stock solution, which is characterized by adding the solution stock solution B in an amount (kg) that satisfies the amount. 3. A high molecular weight polyolefin according to claims 1 or 2, characterized in that the dispersion A added to the stock solution B is allowed to stay in the stock solution B for 3 minutes or more. Continuous preparation method of stock solution. 4. In claims 1 to 3, the internal pressure of the dissolving tank containing the dissolving stock solution B is set to 200 to 500 Torr, and at the same time defoaming is performed, extrusion is carried out using a screw system, and the dissolving solution B is continuously extruded using a kneader and/or extruder. A method for continuously preparing a high molecular weight polyolefin stock solution, characterized by supplying a stock solution of a high molecular weight polyolefin.