JPH0444563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drawn product of a crystalline polymer with high strength and high elastic modulus and a method for producing the same. More specifically, a novel method for obtaining a stretched crystalline polymer with high strength and high modulus by stretching a gel-like material (gel-like sheet or gel-like film made of gel-like particles) obtained by cooling a crystalline polymer solution. This method is particularly suitable industrially for obtaining drawn products with a large cross-sectional area or extremely thick circular filaments.

Conventionally, extremely thick steel filaments have been used for tensile strength wires for optical fiber cables, but
Electromagnetic interference during lightning strikes has become a problem, and as an alternative material, for example, rod-shaped plastic composite materials reinforced with Keplerian fibers are being developed.
In addition, extremely thick steel filaments have various uses other than tensile strength wires, but they have a fundamental problem in terms of weight reduction, and the above-mentioned plastic composite materials are attracting attention as an alternative material. . However, the plastic composite materials mentioned above are too expensive compared to steel filaments, so that they have not been widely used to replace steel filaments.

Therefore, it is expected that an ultra-thick organic material that is cheaper than the above-mentioned plastic composite materials, has high strength (preferably 1.5 GPa or more), and high elastic modulus (preferably 50 GPa or more) will emerge. The main purpose of the present invention is to provide a stretched crystalline polymer that meets these expectations and a method for producing the same, but it can also be widely used in all fields that require extremely thick, high strength, and high modulus of elasticity. I can do it.

(Prior technology) There has been much research into methods for producing fibers with high strength and high modulus of elasticity, but there are
A high-strength, high-modulus organic material with a diameter of 0.1 mm ² or more has not been produced industrially, nor is it known in the literature.

There have been many studies on methods for producing high-strength, high-modulus fibers made of flexible, crystalline polymers (T. Ohta, Polymer Eng., Sci., 23, 697,
1983) The following methods (1) to (4) are known as prior art relatively related to the present invention.

(1) A method of drawing gel-like fibers produced by spinning a crystalline polymer solution.

(2) A method in which a gel-like film obtained by casting a solution of a crystalline polymer is dried for a long time at room temperature to remove the shaking medium, and then stretched.

(3) A method in which a dilute solution of a drying polymer is cooled and a precipitated single crystal aggregate is ultra-stretched.

(4) A method of die-drawing a melt-molded crystalline polymer.

In the methods shown in (1) to (4) above, when trying to obtain a stretched crystalline polymer that is extremely thick, especially has a cross-sectional area of 0.1 mm ² or more and has high strength and high elastic modulus, many of the problems described below occur. A problem arises.

The key points of the technical content and problems associated with each of (1) to (4) will be explained below.

Regarding the method mentioned in (1), for example,
No. 107506 describes a method of spinning a polyethylene solution to form gel-like fibers and then hot stretching the fibers.

Further, JP-A-58-5228 describes a method for producing filaments or films by spinning or extruding a solution of a polymer such as polyethylene in the same manner as described above.

Furthermore, in Polymer Bulletin Vol. 2, pp. 775-783 (1980), etc., flaky gel obtained by cutting polyethylene gel containing paraffin oil is fed to an extruder.
A method of forming gel-like filaments by heating, spinning into a solution is described. What these methods all have in common is spinning or extruding a polymer solution. However, in these methods, the higher the content of the polymer in the solution, the lower the amount of solvent used, which is economically advantageous. Therefore, there is a problem that it becomes difficult to obtain a drawn product with high strength and high elastic modulus.

On the other hand, in these methods, the lower the polymer content in the solution, the slower the gelation rate becomes, making it difficult to roll up, the formed gel becomes soft and difficult to handle, and the cross section of the final drawn product becomes difficult to handle. There are other problems such as the tendency for the shape to become irregular. The latter problem is particularly serious when producing very thick filaments or drawn products with large cross-sectional areas. The reason for this is that, for example, in order to obtain a very thick filament with a final drawn product having a diameter of 1 mm, the diameter of the gel-like fibers formed by solution spinning must be 40 mm or more.

Therefore, in these methods, there is a problem that the polymer concentration in the solution must be made as high as possible even if it sacrifices the strength and elastic modulus of the final drawn product to some extent.

Regarding the method mentioned in (2), PJ is a method in which a gel-like film obtained by casting a solution of ultra-high molecular weight polyethylene is dried for a long time at room temperature to remove the solvent, and the thus obtained film is hot-stretched.
Lemstra et al. (J. Polymer Sci., Polymer Phys.,
19, 877, 1981) and Matsuo et al. (Polymer
Preprints.Japan, 32, 841, 1983). According to this method, the maximum stretching ratio of the cast film depends on the polyethylene concentration in the solution, and the lower the concentration, the higher the maximum stretching ratio, which is convenient for obtaining a stretched product with high strength and high elastic modulus. It is shown. However, this method requires long drying time to remove the large amount of solvent contained in the gel-like film, and this is especially true when trying to obtain a final stretched product with a large cross-sectional area. Since the thickness needs to be increased, a longer drying time is required, and it is difficult to obtain a uniform cast film with little difference between the inner and outer layers.

Regarding the method mentioned in (3), a dilute solution of ultra-high molecular weight polyethylene is cooled, the precipitated single crystals are accumulated, the single crystal matte obtained by drying is compressed or solid-phase coextruded, and then Kanemoto et al. (Polymer
Preprints, Japan, 32, 741, 1983) and Miyasaka et al. (Polymer Preprints, Japan, 32, 874, 1983)
have been reported one after another. However, in this method, the steps of precipitating, accumulating, and drying the single crystal to form a single crystal mat are unproductive. Also
There is a problem in that super-stretching with a total stretching ratio of over 100 times is required to obtain a strength of 3.0 GPa or higher. The necessity of ultra-stretching exceeding 100 times in this method is thought to be due to the fact that the polyethylene concentration in the solution is so low that there are almost no molecules connecting single crystals. This problem can be said to be an essential problem in this method.

Regarding the method mentioned in (4), IMWard et al. (UK Patent GB 2060469) have shown a method for producing extremely thick stretched polyethylene with a high elastic modulus. It is a method in which a billet obtained by melt-molding polyethylene with a weight average molecular weight in the range of 5 x 10 ⁴ to 5 x 10 ⁵ is passed through a die and drawn.
102,000 and 135,000, the total stretching ratio is 15 to 24 times, and the flexural modulus of the stretched product (flexural youngs
modulue) has been shown to be 40 to 50 GPa. However, the weight average molecular weight of polyethylene is 3
When it is more than ×10 ⁵ , the total stretching ratio is halved to about 10 times, and as a result, the flexural modulus of the drawn product decreases to 14 GPa or less, and it cannot be said to be a high elastic modulus drawn product. Further, this document does not include any description regarding the strength of the drawn product, nor does it suggest a method for obtaining a drawn product with high strength and high elastic modulus. On the other hand, RSPorter et al. formed a billet from a polyethylene melt with a weight average molecular weight of 147,000 and solid-phase extruded it at a total stretching ratio of 52 times to obtain a drawn product with a high elastic modulus of about 70 GPa. , its strength is less than 0.7 GPa (Polymer Eng, Sci., 16, 200,
1976).

Therefore, since the method of IMWard et al. described above is very similar to Porter et al.'s method in terms of billet deformation, the strength achieved by that method is at most
It is estimated to be 1.0 GPa, which cannot be said to be high strength. As described above, the method of die-stretching a melt-molded product of a thermoplastic resin such as polyethylene has the problem that although a highly elastic stretched product can be obtained, it is difficult to obtain a high-strength stretched product.

(Problems to be Solved by the Invention) () Conventional technology has been unable to produce stretched crystalline polymers that simultaneously have a large cross-sectional area of 0.1 mm or more and high strength and high elastic modulus. is neither readily available nor known.

() In the case where a stretched crystalline polymer having a large cross-sectional area and high strength and high modulus is to be produced using the methods (1) to (4) mentioned above as the prior art, the above (1) ) to (4).

(Means for Solving the Problems) Means for solving the above-mentioned problems, that is, the structure of the present invention is to cast a gel-like film (A) obtained by casting a solution of a crystalline polymer. Film (A)
A stretched crystalline polymer characterized in that the solvent and a portion contained in (A) are removed by compression at a temperature below the melting temperature of (A), and the compression-molded film (B) thus obtained is stretched through a drawing die. This is the manufacturing method.

The crystalline polymer used in the present invention may be any crystalline polymer that has fiber-forming properties, such as polyethylene, polypropylene, ethylene-propylene copolymer, polyoxymethylene, polyethylene oxide, etc. Polyolefin, polyacrylonitrile, poly(fluoride)
Examples include various polyesters such as vinylidene, polyvinyl alcohol, various polyamides, polyethylene terehetalate, and polybutylene terephthalate. The higher the molecular weight of these polymers, the better from the viewpoint of high strength and high modularity, and usually the weight average molecular weight is 1×
¹⁰⁵ or more is better.

The present invention is particularly effective when applied to polyethylene polymers.

In particular, when the crystalline polymer is a polyethylene polymer, higher strength and higher modulus can be obtained by setting the viscosity average molecular weight to 3 x 10 ⁵ or more, more preferably 1 x 10 ⁶ or more.

The solvent used to prepare the solution in the present invention is one that can be obtained as a solution by dissolving each of the above-mentioned polymers, and that can form a gel-like substance when the solution is cooled. It is. In order to satisfy this condition, one type of solvent may be used alone, or a mixture of two or more types of solvents or a mixture of a solvent and a non-solvent may be used. Such solvents vary depending on the type of crystalline polymer to be dissolved therein, but for example, when the polymer is polyolefin such as polyethylene or polypropylene, solvents such as octene, notene, decane, undecane, dotecan, or isomers thereof may be used. Aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons with a boiling point of at least 100°C or higher, higher straight chain hydrocarbons or higher branched hydrocarbons, with a boiling point of at least 100℃ or higher
Petroleum fractions at temperatures above 100℃, toluene, xylene, naphthalene, tetralin, decalin, etc.
Halogenated hydrocarbons and other solvents can also be used. When the polymer is polyacrylonitrile, solvents such as dimethyl formamide, dimethyl sulfoxide, and γ-butyrolactone can be used.
It will be clear to those skilled in the art that suitable solvents, known or unknown, can be used for other polymers as well.

When forming a gel-like film (A) in the present invention, it is necessary to select a polymer concentration suitable for forming a gel-like film. Here, the minimum concentration at which a gel-like film is formed needs to be higher than the critical concentration at which the crystalline polymers begin to entangle with each other during dissolution. The critical concentration at which crystalline polymers begin to entangle with each other in solution can be known as the concentration at which the relationship between solution concentration and zero shear viscosity changes. Generally, if the polymer concentration is too low, no gel-like film will be formed. In general, if the polymer concentration is too high, it tends to become difficult to stretch at a high magnification in the stretching process. For example, especially when the crystalline polymer is a polyethylene polymer with a viscosity average molecular weight of 2×10 ⁶ , the concentration of the polymer in the solution is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight, and still more preferably 2% by weight. ~
It is 8% by weight.

Such a crystalline polymer solution can be obtained, for example, as follows. That is, a crystalline polymer suitable for the solvent is added to the selected solvent in an appropriate weight ratio, heated to a temperature equal to or lower than the decomposition temperature of the final polymer, and stirred using a stirrer. It is obtained by dissolving the crystalline polymer by mixing.

The solution thus obtained is used to prepare the gel film (A). To produce a gel-like film by casting a solution of a crystalline polymer, the solution obtained by the above method is casted so that its thickness becomes thin, and the solution is cooled to directly form a gel-like film.

As an apparatus for forming a gel-like film, for example, an ordinary film forming apparatus equipped with a slit can be used. The gel-like film obtained here contains the solvent in almost the same proportion as the casting solution.
The thickness is not particularly limited, but it is important that it is not too thick so that it can be easily compressed in the next compression step.

The gel-like film (A) thus obtained is then compressed at a temperature below the melting temperature of (A) to remove a portion of the solvent and form a film (B).

It is important that the device for compressing the gel-like film (A) used in the present invention is capable of molding while removing the solvent that separates during compression. To achieve this purpose, it is suitable to use two rollers with a constant gap. It is also possible to use a pressure roller that applies a constant load. At this time, compression molding is not possible in this case because the liquid will not be removed even if pressure is applied in a sealed state. The compression molding temperature must be below the temperature at which the gel-like film (A) melts. This is because compression molding at a temperature above the melting temperature makes it impossible to achieve a high stretching ratio in the subsequent stretching process, and it is not possible to obtain a stretched product with high strength and high elastic modulus. The greater the thickness of the compression molded layer, the greater the pressure required to remove the liquid. Therefore, when it is desired to obtain a compressed product with a high polymer concentration, it is preferable that the layer thickness be small.

In the present invention, pressure is applied to the film surface of the gel-like film (A), which is the starting material, at a temperature below the melting temperature of (A) to remove a portion of the large amount of solvent contained in (A). B) is different from conventional technology in that it is molded.

In the conventional method, that is, the method of stretching a gel-like fiber or gel-like film obtained by spinning or casting a solution of a crystalline polymer, it is either stretched while containing a melting point, or the solvent is replaced with another low-boiling point solvent. Methods of replacing the film with an organic solvent, drying it, and stretching it, or drying the solvent as it is, and then stretching it, are adopted, and mechanical removal of the solvent is avoided.

Although the gel-like film (A) in the present invention can be stretched without being compressed, removing the solvent by compression reduces the voids in the unstretched product and provides a stretched product with a denser structure. It was also found that stretching could be performed more smoothly. For example, small-angle and wide-angle X-ray diffraction photographs (Figure 3) of compression molded products obtained by compressing a gel-like material from a polyethylene solution at room temperature using a flat plate press device show that the molecular chain axis is perpendicular to the pressing surface. The structure of the compression molded product can be expressed as a structural model as shown in Figure 4. That is, the lamellar surfaces tend to be aligned parallel to the pressed surface, and it can be said that the structure is similar to that of a single crystal laminate. This tendency of lamella arrangement is thought to be due to a compression force couple acting on the flat camera before compression. Compression molded products having such a structure can be super-stretched at a total stretching ratio of more than 50 times, as will be described later, and as a result, a stretched product with high strength and high elastic modulus can be obtained. In addition, with conventional techniques, it takes a long time to remove the solvent, but it takes even longer to obtain a stretched product with a particularly large cross-sectional area, and it is also disadvantageous industrially when recovering the solvent. Seem.

The temperature when compressing the gel-like film (A) should be below the temperature at which the polymer forming the gel-like film is dissolved by the solvent contained in a large amount in the gel-like film (A), but it should be higher than room temperature. is more preferable. still,
The dissolution temperature mainly depends on the amount of solvent in the gel film (A).

The compression method of the present invention requires that the solvent can be removed during compression;
Even if (A) is put into an extruder and extruded by applying pressure below the melting temperature of (A), the solvent will only phase separate from the crystalline polymer and the voids in (A) will not decrease and the solvent cannot be removed. , this method is not adopted in the present invention.

The compressed film (B) thus obtained is then stretched to obtain a stretched product having the required strength. The compressed product in the present invention can be stretched by being heated and stretched using a known method. In this case, a stretched product in the form of a tape or a flat cross-sectional shape or an arbitrary cross-sectional shape can be produced.

In order to produce a stretched product with a circular cross section from a compressed product in the present invention, drawing and stretching is performed through a die having a hole with a circular cross section. Similarly, it is also possible to use a die with any cross-sectional shape other than circular to produce a stretched product with any cross-sectional shape other than circular.

It is necessary that the cross-sectional area of the hole in the die used in the present invention is smaller than the cross-sectional area of the compressed material to be supplied.
However, if the cross-sectional area of the die hole is too small, breakage will occur during drawing and stretching, and the objective will not be achieved. By providing the die with a conical introduction section, drawing is performed smoothly. The angle of inclination of the conical introduction part is preferably from 7° to 15°. Die drawing is performed at a temperature below the melting point of the die feed. Proper heating of the die facilitates drawing and stretching using the die. For polyethylene compacts, a die temperature of 90°C to 130°C is preferred. If a suitable drawing temperature cannot be maintained by heating the die alone, a preheating zone may be provided. The film (B) is fed to the die as it is, or after being slit along its length to a suitable width, or without being slit. If the compressed material is folded or rolled into a cylindrical shape and then fed to the die, it will be fed into a more cylindrical shape.

According to the present invention, it is possible to convert a thin sheet-like or film-like compressed product into a stretched product with a circular cross section by die drawing and stretching. It has been found that there is no evidence that it was formed from compacted material.

During stretching, it is possible to pass through one die and then further stretch through another die with a smaller opening area. In particular, when obtaining an ultra-thick stretched product with a cross-sectional area of 0.5 mm ² or more, two or more dies may be used. Preferably, multistage drawing is carried out through a die. In order to obtain a stretched product with sufficiently high strength or modulus of elasticity, it is preferable to carry out heat-pulling stretching without using a die after die drawing stretching. in this case,
The temperature of the heating tension stretching is preferably the same as or higher than the temperature of the die drawing stretching. Here, first pultrusion stretching is performed through a die, and then when performing tensile stretching, the total stretching ratio is 20 times or more,
In particular, it is a preferable condition to make it 40 times or more in order to obtain a stretched crystalline polymer with high strength and high elastic modulus.

When the polymer is polyethylene, the polymer concentration of the compressed film (B) supplied to the drawing die is preferably 40% to 60% by weight (60% to 40% by weight in terms of solvent concentration). range. Most of the solvent contained in the compressed film (B) is naturally removed from the stretched product during passing through a die and during subsequent heating and stretching.

If necessary, the solvent contained in the object to be stretched may be extracted with another volatile solvent or removed by evaporation by heating, but this must be done within a range that does not impede reshaping or fusion using a die.

In the present invention, high strength and high elastic modulus refer to the range of strength and elastic modulus of a type of drawn material that has particularly high strength and high elastic modulus among conventionally known drawn products, and the range exceeding the range. The tensile strength varies depending on the type of polymer or stretched material.
15g/d or more, preferably 20g/d or more, initial tensile resistance 300g/d or more, preferably 500g/d
As mentioned above, especially when the stretched product is a polyethylene polymer, the tensile strength is 20 g/d or more, preferably
30g/d or more, initial tensile resistance 500g/d or more,
Preferably, it is set at 800 g/d or more.

The stretched crystalline polymer obtained by the present invention has high strength, high elastic modulus, and is extremely thick, especially having a large cross-sectional area of 0.1 mm ² or more. A stretched crystalline polymer having such a large thickness, high strength, and high elastic modulus has not been known so far.

In the present invention, the viscosity average molecular weight of polyethylene
Mv was calculated by measuring the viscosity of a decalin solution at 135°C according to ASTM D2857 to obtain the intrinsic viscosity product [η], and then substituting [η] into the following equation.

Mv=3.64×10 ⁴ [η] _1.39 The strength and initial tensile resistance of the drawn product are JIS
-L-1013 (1981), it was measured according to the constant rate elongation method.

The gel dissolution temperature of the gel-like material was determined as follows. In other words, manufactured by Rigaku Denki Co., Ltd.
Measurement was carried out using THERMOFLEX DSC-10A in a sealed container with a sample amount of 10 mg and a heating rate of 5° C./min, and the endothermic peak temperature was taken as the dissolution temperature.

Example 1 Polyethylene having a viscosity average molecular weight Mv of 3.5×10 ⁶ was mixed with decalin and dissolved by heating to 160° C. to prepare a solution having a polyethylene content of 2% by weight.
This solution was passed through a slit and rapidly cooled to form a gel-like film.

This gel-like film contained a large amount of decalin, maintained a uniform shape, and had a thickness of 11.5 mm. This gel-like film was successively passed through gaps between three sets of two rolls rotating at a constant speed, and the liquid was squeezed out while being compressed to form a compressed sheet.
At that time, the diameter of the rotating rollers was 300 mm, and the roller gaps were 5 mm, 1.2 mm, and 0.3 mm in order from the first set. Compression was performed at room temperature of 27°C without heating. The compressed sheet obtained by squeezing out the liquid during compression contains 71% by weight polyethylene.
Its thickness was 0.32 mm, and it was strong enough to not break even when folded.

This compressed sheet was slit in the length direction to a width of 200 mm, and while being folded to a width of about 15 mm, it was fed to a drawing die and taken out through the drawing die at a speed of 1.0 m/min. The drawing die used had a hole with a circular cross section of 4 mm in diameter and 5 mm in length, and had a conical introduction part with a half angle of 10°. In addition, the drawing die is heated to 120
The temperature was maintained at ℃.

By passing through this drawing die, the diameter of the compressed sheet is
An extension with a circular cross section of 8.2 mm was formed.
There were almost no cracks in the cross section of the stretched product, and no evidence that it was formed from a sheet-like material was observed. This stretched product was further stretched in a heated air bath at 135° C. while heating using stretching rollers at different speeds to form a rigid final stretched product.

The total stretching ratio from the compressed sheet to the final stretched product was 92 times. The final drawn product had a circular cross section with a diameter of 0.8 mm, a tensile strength of 23 g/d, and an initial tensile resistance of 760 g/d.

Comparative Example 1 Thickness 11.5 formed by exactly the same method as Example 1
mm gel-like film was subjected to stretching without compression and squeezing using rollers. 1st stage 70℃ 2nd stage so that the stretching temperature is below the melting point of the stretched feed.
Three stages of stretching were carried out in sequence at 110℃ and the third stage at 135℃, but the total stretching ratio was a maximum of 12 times, and the tensile strength was 8.
The g/d initial tensile resistance tension was 180 g/d.

Example 2 Polyethylene having a viscosity average molecular weight Mv of 2×10 ⁶ was mixed with decalin and heated to 160° C. to dissolve it, thereby preparing a solution having a polyethylene content of 4%. This solution was passed through a slit and rapidly cooled to form a gel-like film. This gel-like film contained a large amount of decalin, maintained a uniform shape, and had a thickness of 7 mm.

This shell-shaped film was formed into a compressed sheet in the same manner as in Example 1, and then stretched with a drawing die and in a heated air bath at the following stretching ratios to form a final stretched sheet. The respective characteristic values of the obtained final stretched product are shown below.

Compressed sheet thickness Polyethylene content 0.8 mm 72% by weight Figure 3 shows (a) small-angle and (b) wide-angle X-ray photographs of the compressed sheet.

Stretching ratio by drawing die 6.5x Stretching ratio by air bath 7.1x Final drawn product diameter Tensile strength Initial tensile resistance 1.3mm 21g/d 640g/d Example 3 Polypropylene with an intrinsic viscosity (in decalin at 135°C) of 18 was mixed with p-xylene and dissolved by heating to 135°C to prepare a solution containing 3% polypropylene.

This solution was allowed to flow out from the slit and then rapidly cooled to form a gel-like film. This gel-like film contained a large amount of p-xylene and maintained a uniform shape, and its thickness was about 7 mm.

This gel-like film was compressed between rotating rollers and the liquid was squeezed out to form a compression-molded sheet. This compressed sheet was rolled into a cylindrical shape and stretched at the following stretching ratio through a heated drawing die having a circular cross section, and further stretched in a heated air bath to form a final stretched product. The characteristic values of each object are shown below.

Compressed sheet thickness Polyethylene content 0.5mm 51% by weight Stretching ratio by drawing die 6.0x Stretching ratio by air tank 6.3x Final stretched product diameter Tensile strength Initial tensile resistance 0.4mm 10g/d 210g/d (Effects of the invention) According to the present invention, it has become possible to produce a crystalline polymer stretched product, particularly a polyethylene stretched product, which has a large cross-sectional area (0.1 mm ² or more), high strength, and high elastic modulus.
In addition, the conventional method of die drawing or solid phase extrusion of a molten crystallized crystalline polymer yields a drawn product with a high elastic modulus, but it solves the problem that a drawn product with high strength and high elastic modulus cannot be obtained. did it.

According to the present invention, (1) the conventional method of drawing gel-like fibers obtained by solution spinning, and (2) the conventional method of drawing gel-like fibers obtained by casting a solution, have a large cross-sectional area, high strength, high The problem of difficulty in obtaining elastic modulus stretched products has been solved. Compared to the conventional techniques (1) and (2) and (3) the conventional method of ultra-stretching a single crystal mat, solvent recovery has become industrially more advantageous. Furthermore, compared to the above-mentioned prior art (3), it has become possible to industrially produce a stretched product with high strength and high elastic modulus with remarkable advantage.

According to the present invention, since the film is started from a solution with a relatively low polymer concentration, it is easier to stretch to a higher magnification than when starting from a solution with a higher polymer concentration. Furthermore, compared to a method in which a single crystal is produced starting from a solution with a particularly low polymer concentration, the gel-like material is produced faster and more efficient stretching is possible.

Furthermore, since the melting temperature is not exceeded during the time from a solution with a relatively low polymer concentration to an unstretched product with a high polymer concentration, the property of being able to stretch to a high magnification is not impaired.

According to the present invention, it has become possible to obtain a very thick drawn product with high strength and high elasticity modulus having an arbitrary cross-sectional shape of the final drawn product.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a method for compression molding a gel-like film (A) by passing it between rotating rollers (R) and (R'). FIG. 2 is a schematic view showing an example of a method of folding a compression-molded film (B) and supplying the film to a drawing die D having a conical inlet and passing the film to obtain a stretched product having a circular cross section. In the figure, O indicates the moving direction of the material, and d indicates the hole diameter of the drawing die. Figure 3 is an X-ray diffraction photograph of a compressed sheet after compression molding the gel-like material obtained in Example 2, (a) is a small-sized X-ray diffraction photograph, and (b)
is a wide-angle X-ray diffraction photograph. FIG. 4 shows a structural model of a compression molded product obtained by compression molding a gel-like material made from a polyethylene solution. A: gel-like film, B: film, D: drawing die, O: moving direction of material, R, R': rotating roller, d: hole diameter of drawing die, I: compression direction,
J: Pressed surface, K: Lamellar surface, L: Lamellar, M:
molecular chain axis.

Claims (1)

[Claims] 1 A gel-like film (A) obtained by casting a solution of a crystalline polymer is compressed at a temperature below the melting temperature of the gel-like film (A). 1. A method for producing a stretched crystalline polymer product, which comprises removing a portion of the solvent and stretching the compression-molded film (B) thus obtained through a drawing die. 2. The method for producing a stretched crystalline polymer product according to claim 1, wherein the crystalline polymer is a polyethylene polymer having a viscosity average molecular weight of 3×10 ⁵ or more. 3. The method for producing a stretched crystalline polymer product according to claim 1 or 2, wherein the compression molded film (B) is stretched by first drawing it through a die and then stretching it by tension. . 4. The method for producing a stretched crystalline polymer product according to claim 3, wherein in the method of first drawing and stretching through a die and then tensile stretching, the total stretching ratio is 20 times or more. 5. The method for producing a stretched crystalline polymer product according to claim 3, wherein in the method of first drawing and stretching through a die and then tensile stretching, the total stretching ratio is 40 times or more. 6. The stretched crystalline polymer according to claim 1, wherein the concentration of the crystalline polymer solution is higher than the critical concentration at which the crystalline polymers start to become entangled with each other in the solution. Manufacturing method. 7. The method for producing a stretched crystalline polymer product according to claim 1, wherein the proportion of the solvent contained in the compression-molded film (B) is 60% by weight or less based on (B). 8. The method for producing a stretched crystalline polymer product according to claim 1, wherein the proportion of the solvent contained in the compression-molded film (B) is 40% by weight or less based on (B).