JPS59223307A - Preparation of stock solution for polyolefin yarn - Google Patents

Abstract

PURPOSE:To obtain the titled uniform and inexpensive stock solution for providing yarn having extremely high tensile strength and modulus, by blending a high-molecular-weight polyolefin with a solvent having a specific phase separation temperature at a given temperature, cooling the blend to remove the solvent, concentrating it, dissolving it under heating. CONSTITUTION:A polyolefin (e.g., polyethylene, etc.0 having >=400,000 weight- average molecular weight is blended with a solvent (e.g., decalin, etc.) having >=80 deg.C phase separation temparature (Ts) at a concentration to satisfy the formula (C1 is polyolefin concentration of wt%, and Mw is weight-average molecular weight) at solution temperature of Ts+10 deg.C-boiling point of the solvent -20 deg.C with stirring, cooled to >=15 deg.C and <Ts of the solvent, concentrated to 6-60wt% polyolefin concentration, and redissolved under heating in the range of the above-mentioned solution temperature, to give the desired stock solution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing a bulk solution for producing polyolefin fibers with extremely high tensile strength and modulus. In particular, the present invention relates to a method for preparing a uniform high-concentration polyolefin solution at a low cost and with good spinning drawability when spinning an ultra-high molecular weight polyolefin solution to obtain high-strength, high-modulus fibers.

Generally, when an organic polymer is solid, the molecular chain terminals become a type of microstructural defect. Therefore, when manufacturing artificial fibers from organic polymers, it is expected that a polymer with fewer molecular chain ends and a higher molecular weight will provide greater strength. However, in the actual M4 fiber manufacturing process, when the molecular weight increases beyond a certain level, a non-uniform structure occurs inside the fiber and the strength tends to decrease. Furthermore, as the molecular weight increases, the viscosity increases rapidly, making spinning operations difficult.

For example, when trying to melt-spun a polymer with a molecular weight of about 1 million, the melt viscosity ranges from several hundreds of poise to several billion poise, making it difficult to thin the fiber during spinning, and also to reduce the feed speed, which is an advantage of melt-spinning. It gets lost. on the other hand,
In order to solve the problem of high viscosity, when dry spinning is performed by dissolving it in a solvent, the concentration of the solution needs to be lower than that of a polymer with a normal molecular weight, making drying difficult and making spinning unstable. Furthermore, even when wet spinning is performed, the coagulation rate becomes extremely low, making uniform coagulation difficult, resulting in unstable spinning.

Conventionally, as a method for making fibers from polymers with very large molecular weights, there is a method using a solvent that solidifies without substantially removing the solvent by simply cooling the solution.
It is shown in the publication No. 4-26409. This method is an extremely excellent method for stably spinning and forming fibers from a dilute polymer solution, but because the solution concentration is low, production costs increase rapidly due to drying and recovery of the solvent, and a decrease in production. rise to In order to solve these drawbacks, it is possible to increase the concentration of the spinning dope, but it is extremely difficult to prepare a highly concentrated solution of so-called ultra-high molecular weight polyolefins having a weight average molecular weight of 400,000 or more. When dissolving in a tank-type dissolver equipped with a stirrer, the polymer aggregates at the point where dissolution begins, creating a lump with extremely high viscosity. Especially when the molecular weight is 1.5 million or more, the critical concentration for making a uniform solution is It is 4-5%. In addition, if large shear is applied to a high concentration and high viscosity part in an attempt to crush it into small pieces, a fibrous solid substance with entangled polymers or a large amount of air bubbles may be generated, resulting in properties that are not suitable for use as a spinning dope. Becomes the property of It was found that the spun yarn obtained from such a non-uniform stock solution has extremely poor drawability and has many polymer entanglement points, making it difficult to obtain fibers with high strength and high modulus.
child.

In order to solve these problems, the present inventors conducted various studies and found that ultra-high molecular weight polyolefin is first dissolved in a solvent by stirring and mixing at a dilute concentration within a predetermined temperature range, and then cooled. It has been found that a homogeneous solution can be obtained by concentrating the polyolefin solution and removing the solvent to obtain a highly concentrated polyolefin solution. As a prior art related to the present invention, a dilute polyolefin solution having a concentration of 05% is used after being concentrated to 5 to 10%, as reported in the Journal.
of Materials8science 15 (1
980), but the concentration conditions are not specifically described therein, and the optimum concentration and temperature are set as in the present invention, and in particular, a uniform high concentration polyolefin solution of 10% or more is prepared. A method for obtaining it at low cost is not disclosed.

The present invention will be explained in detail below. The polyolefin used in the present invention refers to polyethylene, polypropylene, polybutene, ethylene propylene, car body base, dyeing, antistatic, etc.
2 is added to the polymer for the purpose of improving heat resistance, light resistance, flame retardancy, etc.
Copolymerized with 0 mol% or less of a modifier, or gloss,
A filler for the purpose of coloring, high specific gravity, conductivity, magnetism, reinforcement, etc. is added in an amount of 20M<Mt% or less, or a mixture of two or more of these is used.

Next, the solvent for dissolving the polyolefin has a phase separation temperature (TS) of 80°C or higher, and Ts is 80°C or higher.
If the temperature is less than 0.degree. C., solidification by cooling is slow and the cooling temperature needs to be very low, which is not preferable. Furthermore, unless the drying temperature of the solvent is lowered, spinning atoms will stick together and denier unevenness will occur, so it is also necessary to lengthen the drying time. Examples of the solvent include aliphatic or cyclic hydrocarbons such as nonane, decane, undecane, dodecane, decalin, xylene, and naphthalene, or petroleum-based solvents mainly composed of aliphatic hydrocarbons, or halogenated hydrocarbons such as dichlorobenzene. Alternatively, the solvent may be a mixed solvent of two or more of these, but the present invention is not limited thereto. In addition, the phase separation temperature T
s is the temperature at which turbidity that can be detected with the naked eye occurs when a solution is cooled in a stationary state at a cooling rate of 0.59 q min, and when the solution is kept below this temperature, it swells with the solvent. Separates into a polymer gel. The phase separation temperature increases little by little as the dissolved iV concentration increases, so
In the present invention, the phase separation temperature when measured at a concentration of 0.5% is shortened. Further, the boiling point of the solvent is preferably 120 to 200°C from the viewpoint of solvent evaporation during stock solution preparation and spinning, and dry recovery of the solvent.

In the present invention, a dilute solution of polyolefin is first prepared, and in this case, the polyolefin concentration (0
It was found that the relationship between the weight average molecular weight Mw of the polyolefin (+% by weight) and the weight average molecular weight Mw of the polyolefin must be set to C, -3,7 If the solution is made too large, the viscosity of the solution becomes high, making it difficult to stir and mix thoroughly, which tends to cause concentration unevenness.Also, when stirring and mixing vigorously, molecular chains become entangled, making it impossible to obtain high-strength fibers. , C7 is less than the range given by the above formula, sufficient crosstalk is possible, but this is not preferable since the subsequent cooling, removal of solvent, and concentration will result in lower efficiency and higher costs due to solvent recovery.

1. of such dilute solutions in the present invention. The melting temperature IW during production must be between Ts + 10°C and the boiling point of the solvent - 20°C. Here, at a temperature lower than Ts + 10°C, the polymer tends to gel and solidify, making it difficult to create a uniform solution, and at a temperature higher than the boiling point -20°C, the polymer may become colored.
Concentration unevenness is likely to occur due to intense evaporation and condensation of the solvent during decomposition and dissolution, and energy consumption when converting from heating to cooling is undesirable. Stirring and mixing to obtain a dilute solution of polyolefin is performed using a heat-sealed tank-type melter or a mixer that rotates and revolves, using shearing force to obtain a uniform solution with less entanglement of molecular chains. A mixer that is not too strong will suffice. There is no problem even if the cooling and solvent removal operations that will be performed next can be performed at the same time.

Next, in the present invention, the dilute solution obtained as described above is cooled and the solvent is removed to obtain a highly concentrated solution, and the cooling temperature (toC) is set to 15°C or higher and lower than Ts, preferably t=Ts-a. , 6 呵 + 1o (where C2 is the polyolefin concentration after concentration in weight %). Here, if t is below the range of the above formula, a lot of energy will be wasted when remelting the shellfish, and if the temperature is lower than 15°C, the polymer will be hard and it will be difficult to remove the solvent from the shellfish. Undesirable. There is no problem in concentrating the polyolefin solution by any method such as centrifugal dehydration, squeezing, or removing the solvent when solidifying the dilute solution into pellets or blocks by extrusion.

The polyolefin concentration after concentration in the present invention is 6 to 60
Heavy spring % is preferably 10 to 40 M amount %,
If the molecular weight is high, the concentration will be low due to the viscosity of the solution during subsequent redissolution. It is difficult to concentrate more than 60% by weight, and if it is less than 6% by weight, there is no cost advantage in terms of solvent recovery and reduced production.

In the present invention, depending on the viscosity of the solution after concentration, the polymer is heated and dissolved using a melting grid type general dissolution system, a tank type low-rotation mixing system, a ram type extruder, a single screw extruder, etc. For the same reason as above, Ts + 10℃ ~ boiling point -
It is preferable to heat and melt at a temperature of 20°C.

The reheated and dissolved solution thus obtained is sent to a spinning machine and discharged from a spinneret to form fibers.

From this point of view, it has become possible to operationally obtain a uniform and highly concentrated polyolefin solution, and it has become possible to obtain polyolefin fibers with high strength and high modulus at low cost.

The present invention will be specifically explained below using examples.

Example 1 Polyethylene powder with a weight average molecular weight of 1.9 million was mixed with decalin at a concentration of 5% by weight (the phase separation temperature (Ts) of decalin at a boiling point of 187% by weight was 88°C. Put the solution into a press-type squeezer 4
After cooling to 0 to 50°C, it was compressed to obtain a solid having a polyethylene concentration of 26% by weight. Next, the solid material was placed in a mixed-wire melting machine that rotates and revolves, and after standing to dissolve at 170° C., it was stirred at a low speed to prepare a uniform stock solution. Next, common sense! The raw solution is sent from the bottom of the S machine to the spinneret using a gear pump system, and the raw yarn is wound at a discharge rate of 2597 minutes and a spinning speed of 20 strokes through the spinning holes with a nozzle diameter of 1.5 mm and length of 12 Tfgn, 1 small number of spindles. I took it. Then, when the raw yarn with a tekarin content of 40 to 50 threads was stretched 37 times in a drawing furnace at 130°C, the strength was 34.5 p/d, the elongation was 4.6%, and the tensile modulus was 7.
10 g/d of fiber was obtained.

In addition, when the polyethylene concentration of the polymer discharged after continuous spinning for 10 hours was measured, it was 25.6 to 26.1ii.
%, and troubles such as yarn wobbling, yarn breakage, and nozzle pack pressure fluctuations never occurred during spinning, indicating that the spinning dope was uniform. Furthermore, changes over time in the denier and strength/elongation of the drawn yarn were examined, and it was found that both fluctuations were within ±5%, indicating that there were no large irregularities in the entanglement of polyethylene molecular chains.

Example 2 Polyethylene powder with an average molecular weight of 80 Kameya was mixed with a petroleum-based insecticidal solvent (boiling point 200~) to a concentration of 5% by weight.
250°C), and a solution at 160°C was prepared using a hook-type mixer that rotates and revolves. Here, the phase separation temperature (Ts) of the insecticidal solvent at 0.5% by weight was 93°C. The sheet was then cooled to 60 to 58 DEG C., rolled, and cut to obtain 4 mm cube-shaped chips having a polyethylene concentration of 42% by weight. Then, the chips were melted and kneaded using a screw extruder and spun using a spinning machine.

Extruder cylinder temperature 170'C1 spinning rod temperature 180
Spinning was carried out continuously for 5 days at ℃, and the spinning condition was good.
There was almost no clogging of the 5-mesh filter, and the variation in polyethylene concentration was almost constant at ±6%. Also,
Daily measurements of the polyethylene molecular weight distribution of the spun fibers and measurements of the viscosity of a solution of completely dried fibers dissolved in decalin revealed that the raw material polyethylene was hardly decomposed. In this Example 1ζ, insecticidal solvent content area 1
% or less at 140°C, the maximum stretching ratio was 28 to 32 times, and the yarns spun under the same conditions for 5 days showed almost the same drawability, proving that it was a uniform stock solution. Ta.

Example 3 4 parts of polypropylene having an average molecular weight of 10,000 yen, a phase separation temperature (Ts) of 78°C, and a boiling point of 180°C. U1
0 The mixture was placed in a dissolver equipped with a stirrer and mixed at a temperature of Nakateraso°C.

Then, the mixture was cooled to 50 to 60° C. and centrifuged to remove liquid, thereby obtaining a solid material having a polypropylene concentration of 10% by weight.

A170 The solid material was placed in a stock solution tank at 1-44°C and dissolved by standing for spinning and drawing, but there was no fuzz or yarn breakage, and the strength and elongation of the drawn yarn was 21 Q/, 1.7 on average. .8%, the variation rate was 11.4% for strength, 6.8% for elongation, and almost uniform fibers were obtained. In addition, the variation rate (CV) is UV-Σcx-xP7<N
-1)+xx1on (X: measured value, also: average value,
N: The number of measurements was calculated from 30).

In addition, the concentration of the discharged polymer after the spinning nozzle is 9.8 to 1
The concentration was 0.1%, which was within the measurement error range, and no coloration was observed.

Example 4 M, ilt Polyethylene having an average molecular weight of 2.7 million and 1% by weight of a red pigment were added to decalin to prepare a 0.8 quintillion star-shaped polyethylene solution at 160°C. Then, the solution was
The gel was cooled to 5 to 75°C and compressed to obtain a gel having a polyethylene concentration of 8% by weight, then dissolved at 150°C and spun for 10 hours. The obtained spun yarn was 890d/6f and contained 150% decalin, but the hollow heater 120'
Stretched at C1 supply rate of 50, 1st stage drawing ratio 12x, 2nd stage stretching ratio 2.8x, strength 28.5 ff/d
A spun-dyed high-strength polyethylene fiber having an elongation of 5.1% was obtained.

The spun-dyed yarn was knitted into a tube and the pigment content was evaluated between single fibers by checking the hue unevenness and absorbance, and it was found that the pigment was uniformly dispersed and the high concentration polyethylene solution was uniform in both cases. . Further, there was little variation in the strength and elongation of the drawn fibers depending on the spinning time, and the single fiber denier was almost constant.

Comparative Examples 1 to 2 As Comparative Example 1, the polyethylene of Example 1 was used at a concentration of 7 tJ.
I tried to directly prepare a high concentration polyethylene solution at 170°C by putting iL%C together with decalin in a crosstalk dissolver, but the viscosity became extremely high during dissolution and the solution became unstirable midway through, resulting in a solution with large concentration irregularities.

As Comparative Example 2, when heating and dissolving the 26% polyethylene solution of Example 1 at 90°C, it took a long time to dissolve and the polymer wrapped around the stirring rod of the mixer was cooled. It turned out to be a white solid with uneven density.

Reference Example 1 The 5% by weight polyethylene solution of Example 2 was cooled to 70°C, but it was quite difficult to concentrate it to a concentration of 42% by weight due to the small amount of solvent produced during phase separation.

Patent applicant: Kuraray Co., Ltd. Representative Patent Attorney Ken Honda

Claims (3)

[Claims] (1) Polyolefin with a weight average molecular weight of 400,000 or more,
In a solvent whose phase separation temperature (Ts) is 80°C or higher, c, =
Add so that s, y After that, the stock solution for polyolefin fibers is characterized in that it is cooled to a temperature of 15° C. or higher and lower than the Ts of the solvent, concentrated to a polyolefin concentration of 6 to 60% by weight, and then heated and dissolved again in the solution temperature range. Preparation method. (2) Cooling temperature (t'C) is t=Ts '8-3V6
-±10 (where C2 is the polyolefin concentration after concentration, weight %). (3) Polyolefin concentration after concentration is 10 to 40% by weight
A method for preparing a stock solution for polyolefin fibers according to item 1 or 2.