JP2967935B2 - Method for producing polyethylene molded article and stretch molded article - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a novel method for producing a polyethylene molded article and a stretch molded article thereof. More specifically, the present invention relates to a method for producing a polyethylene molded article and a stretched polyethylene molded article which are excellent in strength and hardly decrease in tensile strength even when subjected to corona discharge treatment.

Technical background of the invention and its problems Polyethylene has a commonly used molecular weight of 50,0.
In addition to polyethylene of about 00 to 200,000 (general-purpose polyethylene), there are low-molecular-weight polyethylene (so-called wax), high-molecular-weight polyethylene, and ultra-high-molecular-weight polyethylene.

Among such polyethylene, ultra-high molecular weight polyethylene generally has a molecular weight of 1,000,000 or more,
It has completely different properties from general-purpose polyethylene. In other words, this ultra-high molecular weight polyethylene is extremely excellent in properties such as impact resistance, abrasion resistance, chemical resistance, and tensile strength, and new applications are being developed as engineering plastics utilizing such properties. is there.

Such ultra-high molecular weight polyethylene has the above-mentioned excellent properties, but has a very high intrinsic weight and an extremely high intrinsic viscosity. Therefore, the ultra-high molecular weight polyethylene has a remarkably low fluidity, and when producing a molded article of ultra-high molecular weight polyethylene, the extrusion method conventionally used in the production of molded articles using general-purpose polyethylene or the like has been used. The molding method and the injection molding method are hardly adopted.

When producing a molded article using such ultrahigh molecular weight polyethylene, a mixture in which a small amount of ultrahigh molecular weight polyethylene is added to a diluent in advance is prepared, and a molded article having a desired shape is prepared using this mixture. And then removing the diluent.

For example, Japanese Patent Application Laid-Open No. 58-81612 discloses that the weight average molecular weight is 400,000 or more, and the ratio of the weight average molecular weight to the number average molecular weight is
20 ethylene polymers or copolymers with Mw / Mn less than 5
A method for producing a filament having a tensile strength of 1.5 GPa or more using a solution containing the solvent in an amount of not more than 80% by weight and containing the solvent in an amount of not more than 80% by weight is disclosed.

However, in the polyethylene solution used in this method, since the molecular weight of polyethylene is high, the upper limit of the disclosed polyethylene concentration is 20% by weight. Specifically, for example, even when using a relatively low molecular weight polyethylene such as a weight average molecular weight of 500,000,
A solution having a low polyethylene concentration of 8% by weight is used. And even if such a solution is used, the tensile strength of the obtained filament is 1.9 Gpa (Mw / Mn = 2.9).
It is about. By this method, when producing a filament having a tensile strength of 2 GPa or more, the molecular weight is 110
A very high molecular weight polyethylene of the order of 10,000 must be used, and the solution using such a polyethylene is a solution having a polyethylene concentration of only about 2% by weight.

JP-A-61-167010 discloses that the weight average molecular weight is 20.
A solution is prepared by mixing 10,000 to 4 million polyethylene and a diluent, and by using this solution, at least 13
A method for producing a polyethylene molded article having a g / denier strength and a 350 g / denier modulus is disclosed. This method is basically the same as the technique disclosed in the above-mentioned JP-A-58-81612, and the concentration of the polyethylene solution actually used is only about 10% by weight.

As described above, a large amount of diluent must be used when producing a molded article from ultra-high molecular weight polyethylene, and it is difficult to significantly improve the working efficiency in producing the molded article.

Polyethylene having a molecular weight of about 200,000 to 1,000,000 has good moldability as compared with ultra-high molecular weight polyethylene, but has properties close to general-purpose polyethylene. Therefore, using such polyethylene having a high molecular weight, a molded article having extremely excellent properties such as impact resistance, abrasion resistance, chemical resistance, and tensile strength, such as a filament formed from ultra-high molecular weight polyethylene, is obtained. Was thought to be impossible.

In some cases, a molecularly oriented polymer of polyethylene is used as a fiber for reinforcing a composite material, and it is desired that such a composite fiber has excellent adhesion between the fiber and the matrix. However, polyethylene generally does not have a good adhesive property, and therefore, means for improving the adhesive property is employed. As one of the methods, corona discharge treatment is known.

In a conventionally known molecular orientation body of high molecular weight polyethylene, when a corona discharge treatment is performed, the adhesiveness is improved, but the tensile strength may be largely reduced.

Object of the Invention The present invention is to solve the problems in the prior art as described above, having a high elastic modulus and high strength,
Moreover, it is an object of the present invention to provide a method for producing a polyethylene molded article and a stretched polyethylene molded article, which hardly decrease in tensile strength even when subjected to corona discharge treatment.

SUMMARY OF THE INVENTION The method for producing a polyethylene molded article according to the present invention comprises the steps of: mixing a molten mixture comprising a polyethylene having an intrinsic viscosity of 3.0 dl / g or more and a diluent at a shear rate of 20 sec ^-1 or more, and 1 × 10 ⁵
Extruding the polyethylene through a die nozzle while orienting the polyethylene in a die under application of a shear stress of ８8 × 10 ⁵ dyn / cm ² ,
It is characterized by producing a polyethylene molded body having an orientation degree of 0.7 or more.

Further, the method for producing a stretched polyethylene molded article according to the present invention is characterized in that a melt mixture comprising a polyethylene having an intrinsic viscosity of 3.0 dl / g or more and a diluent is subjected to a shear rate of 20 sec ^-1 or more, and 1 × 10 ⁵ to The polyethylene is extruded from a die nozzle while applying a shear stress of 8 × 10 ⁵ dyn / cm ² while orienting the polyethylene in the die to obtain a polyethylene molded body having a degree of orientation of 0.7 or more. It is characterized by being stretched three times or more.

In the method of the present invention, since the polyethylene is extruded while controlling the extrusion conditions, the polyethylene is oriented to some extent in the die when extruded. For this reason, it has become possible to produce a polyethylene molded body having a high degree of orientation, which has been conventionally difficult to obtain. And
The stretched molded article obtained by stretching such a molded article has an elastic modulus and strength almost equivalent to that of the ultra-high molecular weight polyethylene stretched molded article, even if the molecular weight of the raw polyethylene is 1,000,000 or less. Become.

According to the method of the present invention, by adjusting the extrusion conditions as described above, it is possible to produce a molded article and a stretch molded article having excellent properties, particularly using polyethylene. The present invention can also be applied to polyethylene having a relatively low molecular weight among high molecular weight polyethylenes, particularly ultrahigh molecular weight polyethylenes.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a method for producing a polyethylene molded article according to the present invention and a method for producing a stretch molded article using the molded article obtained by this method will be specifically described.

The present inventor studied a method for easily producing a molded article having excellent properties formed from ultra-high molecular weight polyethylene, and found that even a polyethylene having a lower molecular weight than ultra-high molecular weight polyethylene has a specific shear rate. It was found that polyethylene can be oriented in a die by adjusting the shear stress applied to the polyethylene during the extrusion. And this orientation state is favorably maintained even in the molded article by using a diluent having a low melting point. Therefore, by stretching such a molded body, high elasticity and
The inventors have found that a high-strength stretched polyethylene product can be manufactured, and have completed the present invention.

Manufacture of polyethylene molded article The polyethylene used in the present invention is
It is a polyethylene having an intrinsic viscosity [η] of 3.0 dl / g or more measured at 5 ° C. Therefore, in the present invention, so-called high molecular weight polyethylene or ultra high molecular weight polyethylene can be used. In particular, the method of the present invention has an intrinsic viscosity of 3.5 to 10 dl /
It is highly useful when using polyethylene in the range of g.

The polyethylene used in the present invention may be a homopolymer of ethylene or a copolymer of ethylene and a small amount of α-olefin.

When such a copolymer of ethylene and a small amount of α-olefin is used, a copolymer having an ethylene content of usually 95 mol% or more, preferably 98 mol% or more is used.

As the α-olefin forming such a copolymer, an α-olefin having 3 to 10 carbon atoms is usually used. Specific examples of such α-olefins include propylene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1- Octene and the like.

In addition to the above-mentioned α-olefin, other polymerizable components such as a cyclic olefin may be copolymerized within a range that does not impair the properties of the polyethylene used in the present invention.

In the present invention, the above polyethylene is melt-mixed with a diluent. As the diluent used here, a substance that is liquid at room temperature can be used, but it is desirable to use one having a melting point of 25 ° C. or higher. That is, by using a solid substance at room temperature (25 ° C),
Immediately after being extruded from the die nozzle, the diluent begins to solidify, the orientation state of the polyethylene oriented in the die is less likely to collapse, and the molecular orientation easily remains as a history in the obtained polyethylene molded body, so A polyethylene molded body having a degree of orientation F is obtained.

As such a diluent, an aliphatic hydrocarbon compound which is solid at room temperature or an aliphatic hydrocarbon compound derivative which is solid at room temperature is preferably used.

Here, as the aliphatic hydrocarbon compound, usually, the molecular weight is 2000 or less, preferably 1000 or less, more preferably 80 or less
0 or less compounds are used. Specifically, n-alkanes having 22 or more carbon atoms such as docosan, trichosane, tetracosane, and triacontan or a mixture with lower n-alkanes containing these as a main component, paraffin wax separated and refined from petroleum, ethylene or ethylene Medium-low pressure polyethylene wax, high pressure polyethylene wax, ethylene copolymer wax, which is a low molecular weight polymer obtained by copolymerizing A wax whose molecular weight has been reduced by degradation or the like can be given.

Such an aliphatic hydrocarbon wax may be used after being subjected to an oxidation treatment or a maleic acid modification, if necessary.

As the diluent other than the aliphatic hydrocarbon compound, a derivative of the aliphatic hydrocarbon compound is used. Such compounds include, for example, one or more, preferably one or two, particularly preferably one carboxyl group, hydroxyl group, carbamoyl group at the terminal or inside of an aliphatic hydrocarbon group (alkyl group, alkenyl group). Group, ester group,
Examples thereof include compounds having a functional group such as a mercapto group and a carbonyl group. The aliphatic hydrocarbon compound derivative has 8 or more carbon atoms, preferably 12 to 50 carbon atoms.
And fatty acids, fatty alcohols, fatty acid amides, fatty acid esters, fatty mercaptans, fatty aldehydes, and fatty ketones having a molecular weight of 130 to 2,000, preferably 200 to 800.

Specific examples of these compounds include, as fatty acids, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; as aliphatic alcohols, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol; , Caprinamide, laurinamide, palmitamide, stearylamide; and stearyl acetate esters as fatty acid esters.

The polyethylene and the diluent as described above are mixed in a molten state. The mixing concentration at this time depends on the type of polyethylene and diluent used, but is usually 160 to 250.
° C.

In the present invention, when polyethylene having an intrinsic viscosity of 3.0 dl / g or more is used, the content of the polyethylene in the mixture is usually 20% by weight or more, preferably 25% by weight or more, and more preferably 30% by weight or more. can do. By using such a high concentration mixture, the oriented state of the polyethylene oriented in the die is maintained even in the molded body.

The melt mixture prepared as described above may further contain components such as an antioxidant and a lubricant.

The molten mixture of polyethylene and diluent thus prepared is extruded from a die nozzle at a specific shear rate and while applying a specific shear stress.

By extruding the molten mixture from the die nozzle using such a high concentration of the mixture and under specific extrusion conditions, at least a portion of the polyethylene in the molten mixture is oriented in the die.

Then, when extruding the molten mixture through a die nozzle in the present invention, the shear rate, 20sec ^-1 or more, preferably 25 sec ^-1 or more, and particularly preferably 30 sec ^-1 or more. The upper limit of the shear rate is not particularly limited from the viewpoint of the orientation of the molded body, but if the shear rate is too high, melt fracture is likely to occur. Is set. This upper limit is usually 200 sec ^-1 , preferably 150 sec ^-1 .

When extrusion molding is performed at the above shear rate, the shear stress applied to the melt in the die nozzle is 1 × 10 ⁵ to 8
× 10 ⁵ dyn / cm ² , preferably 1.5 × 10 ⁵ to 8 × 10 ⁵ dyn / cm ² ,
More preferably, it is set in the range of 2 × 10 ⁵ to 8 × 10 ⁵ dyn / cm ² .

When the shear stress is smaller than the above range, effective in-die orientation cannot be given to polyethylene, and when the shear stress exceeds the upper limit, the orientation state of the molded body is not improved due to turbulence such as melt fracture.

Such values of the shear rate and the shear stress depend on the mixing ratio between the polyethylene and the diluent as described above,
It is also affected by the melt extrusion temperature. Therefore,
The extrusion temperature is set so that the shear rate and the shear stress are within the above ranges in consideration of the mixing ratio of the polyethylene and the diluent, but generally, 160 to 250 ° C., preferably
It is set within the range of 160 to 200 ° C.

Here, in the present invention, the “shear rate” means that when the molten material is discharged to the atmosphere, the molten mixture is extruded by forming a subsidiary flow corresponding to the shape of the die nozzle.
It refers to the velocity gradient of the molten mixture at the die nozzle wall relative to the nozzle. Further, the “shear stress” can be determined based on a flow curve under specific conditions predetermined for the above-mentioned shear rate.

Melt molding is generally performed using a melt extrusion molding machine. For example, a filament for drawing can be obtained by melt extrusion through a spinneret (nozzle), and a film, sheet or tape for drawing can be obtained by extrusion through a flat die or a ring die, and further extruded through a circular die. Thus, a stretch blow molding pipe (parison) is obtained.
By performing extrusion molding under the above conditions, a molded body having an orientation degree F of 0.7 or more can be obtained. By setting more suitable conditions, a molded article having a degree of orientation F of 0.8 or more, more preferably 0.90 or more, can be obtained.

The degree of orientation F of the molded article, that is, the degree of molecular orientation, can be measured by an X-ray diffraction method.

In the present invention, in the case of a filament for polyethylene drawing, the orientation degree F is calculated by the half-width method described in detail in, for example, Yukichi Kure and Teruichiro Kubo: Industrial Science Magazine, Vol. 39, pp. 992 (1939). Degree of orientation, ie, the formula; (Where H ゜ is the half-width (゜) of the intensity distribution curve formed along the Debye ring of the strongest paratropic plane on the equator).

The polyethylene molded body produced by the method according to the present invention is highly oriented even though the stretching operation is not actively performed.

Further, the degree of orientation is further increased by performing a drafting operation on this molded body, for example, an undrawn filament.

The draft ratio in the case of performing the draft operation depends on the temperature of the mixture, the molecular weight of polyethylene, the composition ratio with the diluent, and the like, but is usually 3 or more, preferably 6 or more.

However, the reason why the degree of orientation of the molded article is improved by the drafting operation is that polyethylene oriented in the die is extruded under specific conditions, and the
If the extrusion conditions at the nozzle are out of the above-mentioned range of the shear rate and the shear stress, good results cannot be obtained in the subsequent stretching operation even if the draft operation is performed.

Here, the draft ratio is determined by measuring the extrusion speed V ₀ of the melt in the die / nozzle and the winding speed V of the unstretched material that has been cooled and solidified, and substituting these values into the following equation. be able to.

Draft ratio = V / V ₀ The polyethylene molded article thus obtained can be used as it is after removing the diluent contained in the molded article by using a method described later, but is further stretched. Thereby, characteristics such as elastic modulus and strength are further improved.

Production of Stretched Polyethylene Product The stretched polyethylene product having an intrinsic viscosity of 3.0 dl / g or more according to the present invention can be produced by stretching the polyethylene molded product obtained by the above-described method. That is, by stretching the polyethylene molded body at least in the uniaxial direction, the degree of molecular orientation in the molded body is further improved.

Such a stretching treatment is generally performed by heating and holding the object to be stretched at a temperature of 40 to 160 ° C, preferably 80 to 145 ° C. As a heat medium for heating, any of air, steam, and an organic solvent can be used. Among these heating media, it is preferable to use an organic solvent. By using such an organic solvent, the above-mentioned diluent can be eluted and removed. Therefore, it is preferable that the organic solvent used here has a boiling point higher than the melting point of the molded article. Specific examples of such an organic solvent include aliphatic hydrocarbons such as decalin, decane, and kerosene. By performing a stretching operation using such a heat medium, the diluent described above can be uniformly removed, and the occurrence of stretching unevenness during stretching is reduced. Therefore, a stretching operation with a higher stretching ratio can be performed.

The diluent can be removed at the time of stretching as described above, but before the stretching operation, the unstretched material is immersed in a solvent such as hexane, heptane, hot ethanol, chloroform or benzene to remove the diluent. After performing the stretching operation, or the stretching operation, the obtained stretched product is hexane, heptane,
A method of immersing in a solvent such as hot ethanol, chloroform, benzene or the like for treatment may be employed. Further, these methods can be used in combination.

In the present invention, the stretching operation is performed in one stage or in two or more stages. The stretching ratio depends on the degree of molecular orientation and the degree of increase in the melting temperature accompanying the degree of molecular orientation.
It can be set within the range of 8 times, preferably 10 to 50 times. This stretching ratio is an area stretching ratio.

In the present invention, the stretching operation is preferably performed in two or more stages, and in this case, the first-stage stretching operation is performed in 80 stages.
At a relatively low temperature of ~ 120 ° C while removing the diluent in the extruded product.
It is preferable to carry out at a temperature of ° C, and at a temperature higher than the stretching temperature of the first stage.

In the above-described stretching operation, for example, in the case of a uniaxial stretching operation performed on a filament, a tape, or the like, the stretching may be performed between rollers having different peripheral speeds, or performed on a stretched film or the like. In the case of the biaxial stretching operation, the stretching may be performed in the longitudinal direction between rollers having different peripheral speeds, or after the stretching, the stretching may be performed in the transverse direction by a tender or the like. Biaxial stretching by the inflation method is also possible.
Furthermore, in the case of a three-dimensional molded product such as a container, a biaxially stretched molded product can be obtained by a combination of tensile stretching in the axial direction and expansion stretching in the circumferential direction.

The oriented stretched product obtained in this manner may be subjected to a heat treatment (heat set treatment) while being fixed, if necessary. This heat treatment is generally performed at a temperature of 140 to 180 ° C, preferably 150 to 175 ° C, for 1 to 20 minutes, preferably 3 to 20 minutes.
Performed for 10 minutes. By performing the above-described heat treatment on the stretched molded body, the crystallization of the oriented stretched molded body further proceeds, and the crystal melting temperature shifts to a high temperature side, so that the strength and elastic modulus of the molded body are improved. .

As described above, in the method for producing a stretched polyethylene article according to the present invention, the polyethylene molded article is provided with a molecular orientation in a die at the time of production, and the stretched article is further stretched to have a tensile strength of 2 GPa or more. And a stretched polyethylene molded article having an elastic modulus of 50 GPa or more. Moreover, in the production method of the present invention, it is possible to obtain a stretched polyethylene molded article having the same elastic modulus and strength as when ultra-high molecular weight polyethylene is used, without using a high molecular weight polyethylene such as ultra-high molecular weight polyethylene. it can.

The degree of orientation of the stretched polyethylene molded article thus obtained is preferably 0.95 or more, more preferably 0.96 or more.
0.97 or more.

In the present invention, the intrinsic viscosity is extruded at a specific shear rate and shear stress of a molten mixture of polyethylene and a diluent having a viscosity of 3.0 dl / g or more, and the reason why molecular orientation is imparted to the obtained molded article is as follows. Although not disclosed until now, the present inventor believes that the reason is as follows.

It is generally known that the orientation of molecules occurs when the molecules flow through the die / nozzle. However, in the case of a polymer having a relatively low molecular weight, the relaxation rate of the molecular orientation is high even once oriented. Therefore, at the moment when it is extruded from the die nozzle into the atmosphere, the orientation state is relaxed together with the swell phenomenon, and the orientation of the molecules imparted in the die nozzle hardly remains in the molded body as a history.

However, in the case of a high molecular weight polymer, when a certain level of shear stress is applied in the presence of a diluent in a die nozzle,
The molecules are elongated in the direction of flow. In order to extend a molecule by a stretching operation or a drafting operation as in the related art, it is necessary that the molecular chains are entangled to some extent. However, such entanglement of molecules causes structural defects when the extended chains are crystallized after elongation of the molecules. Therefore, it has been considered that this method is not a preferable method for a relatively low-molecular polymer that requires a large amount of molecular entanglement.

On the other hand, by applying a shear stress, at the molecular level, the molecules are fully extended, and the degree of orientation of the molecules is improved. Therefore, if this state can be maintained even after molding, characteristics such as elastic modulus and strength of the stretched molded body are improved, and even when a polyethylene having a relatively low molecular weight is used, it is comparable to a molded body made of ultra-high molecular weight polyethylene. It is thought to have characteristics. .

However, Japanese Patent Application Laid-Open No. 58-81612 exemplified as prior art.
In the gazette and JP-A-61-167010, the orientation in the die / nozzle hardly occurs due to the low concentration of polyethylene, and the solvent used is a good solvent for polyethylene. This is necessary, and during this time, the state of molecular orientation is relaxed, and the history of molecular orientation in the die cannot be brought into the molded product. Further, since the solvent is a liquid, the solvent does not have the ability to prevent the relaxation of the molecular orientation state. For this reason, it is considered that the orientation in the die nozzle cannot be used effectively.

However, in the present invention, polyethylene having a relatively high molecular weight is extruded under specific conditions,
The diluent solidifies in a relatively short time in the melt discharged from the die nozzle into the atmosphere by using a diluent that is solid at room temperature without causing the orientation state of polyethylene in the die nozzle to collapse so much. By doing
The alignment state of the molecules is less likely to collapse.

Therefore, by stretching such a molded product, the degree of molecular orientation is further improved, and even when a polyethylene having a lower molecular weight than the ultra-high molecular weight polyethylene is used, the elastic modulus is comparable to that of the ultra-high molecular weight polyolefin. In addition, a stretched molded product having tensile strength can be produced.

Therefore, by employing the method of the present invention, the polyethylene molded article and the stretch molded article produced by the method of the present invention are used for applications in which the ultrahigh molecular weight polyolefin molded article or the stretch molded article has been used exclusively in the past. Will be able to do it.

Further, the polyethylene molded article and the stretched polyethylene molded article obtained according to the present invention have a property that when subjected to a corona discharge treatment, the adhesion is greatly improved, but the tensile strength is hardly reduced.

Effect of the Invention In the present invention, the melt mixture composed of a specific polyethylene and a diluent is melt-extruded at a specific shear rate and a specific shear stress, whereby the orientation state of the polyethylene in the molten mixture oriented in the die is changed. It is maintained even in the molded body.
Therefore, a polyethylene molded article having a high degree of orientation can be obtained by employing the method of the present invention. Then, by stretching the molded article obtained in this way, it is possible to obtain a stretched polyethylene molded article having a high modulus of elasticity and high strength and exhibiting almost no decrease in tensile strength even when subjected to corona discharge treatment.

[Examples] Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Ethylene-propylene copolymer having an intrinsic viscosity of 5.6 dl / g measured in decalin at 135 ° C. (ethylene content: 99.9%)
And paraffin wax (melting point 69 ° C., molecular weight 490) were mixed at a weight ratio of 30:70 and melt-spun under the following conditions. That is, 3,5-
Dimethyl-tert-butyl-4-hydroxytoluene was added to 100 parts by weight of the ethylene-propylene copolymer.
0.1 part by weight was blended.

Then, using a screw type extruder, the mixture was melt-kneaded at a set temperature of 190 ° C., and the melt was continuously passed through a spinning die having an orifice diameter of 2 mm attached to the extruder, at a shear rate of 25 sec ⁻¹ and a shear stress of 2.6 ×. 10 ⁵ dyn / cm ² , die temperature 180
Melt spinning was performed under the condition of ° C. At this time, the spun fiber was taken out at a draft ratio of 33 times with an air gap of 180 cm, cooled and solidified in air to obtain an undrawn fiber. The degree of orientation F of the undrawn fiber was 0.9.

Further, the undrawn fiber was drawn under the following conditions to obtain an oriented fiber. The stretching operation was performed using four codet rolls.
This was performed by step stretching. At this time, n-decane was used as a heat medium for the first stretching tank and the second stretching tank.
The temperature was set to 0 ° C. and 120 ° C., and triethylene glycol was used as a heat medium for the third stretching tank, and the temperature was set to 143 ° C. The effective length of each tank was 50 cm. At the time of stretching, the rotation speed of the first codet roll was 0.5 m / min,
By changing the rotation speed of the fourth codet roll, a fiber having a desired draw ratio was obtained. At this time, the rotation speeds of the second and third codet rolls were appropriately selected within a range where stable stretching was possible. The initially mixed paraffin wax was mostly extracted in the first draw tank and the second draw tank. The stretching ratio was determined by calculating from the rotation speed ratio between the first codet roll and the fourth codet roll.

The elastic modulus, tensile strength and elongation at break were measured at room temperature (23 ° C.) using a Tensilon RTM-100 type tensile tester manufactured by Orientec. At this time, the sample length between the clamps was 100 mm, and the pulling speed was 100 mm / min. The elastic modulus referred to herein means an initial elastic modulus, and was determined from a slope of a tangent of a stress-strain curve. The fiber cross-sectional area required for the calculation was calculated from the weight with the density set to 0.960 g / cc.

Table 1 shows the tensile properties and the degree of orientation of the obtained drawn fibers.

Example 2 A molten mixture similar to that described in Example 1 was subjected to a shear rate of 41 sec ^-1 , a shear stress of 3.1 × 10 ⁵ dyn / cm ² and a die temperature of 170.
Spinning and stretching were performed in the same manner as in Example 1 except that the temperature was changed to ° C. The degree of orientation F of the undrawn fiber was 0.93.

Table 2 shows the tensile properties and the degree of orientation of the drawn fibers obtained.

Example 3 Ethylene-1-butene copolymer having an intrinsic viscosity of 5.7 dl / g measured in decalin at 135 ° C. (ethylene content 99.8%)
And the paraffin wax used in Example 1 is 30: 7 by weight.
The mixture mixed at 0 was melt-spun in the same manner as in Example 1. However, at this time, the shear rate was 33 sec ⁻¹ , the shear stress was 2.9 × 10 ⁵ dyn / cm ² , and the die temperature was 170 ° C. The degree of orientation F of the undrawn fiber was 0.91. Further, the undrawn fiber was drawn by the method described in Example 1 to obtain a drawn fiber.

Table 3 shows the tensile properties and the degree of orientation of the drawn fibers obtained.

Example 4 A mixture of a high-molecular-weight polyethylene having an intrinsic viscosity of 7.4 dl / g measured in decalin at 135 ° C. and the paraffin wax used in Example 1 at a weight ratio of 20:80 was prepared in the same manner as in Example 1. And melt spun. However, the draft ratio at this time is 40, the shear rate is 41 sec ⁻¹ , and the shear stress is 2.5 × 10 ⁵ dyn / cm ²
Met. The degree of orientation F of the undrawn fiber was 0.94.
Further, the undrawn fiber was drawn by the method described in Example 1 to obtain a drawn fiber.

Table 4 shows the tensile properties and the degree of orientation F of the drawn fibers obtained.
Is shown.

Example 5 Ethylene-propylene copolymer having an intrinsic viscosity of 8.5 dl / g measured in decalin at 135 ° C. (ethylene content 99.8%)
And the paraffin wax used in Example 1 was in a weight ratio of 20: 8.
The mixture mixed at 0 was melt-spun in the same manner as in Example 1. However, the draft ratio at this time is 47, and the shear rate is 72.
sec ^-1 , shear stress 3.1 × 10 ⁵ dyn / cm ² , die temperature 175 ° C
Met. The degree of orientation F of the undrawn fiber was 0.94.
Further, the undrawn fiber was drawn by the method described in Example 1 to obtain a drawn fiber.

Table 5 shows the tensile properties and the degree of orientation of the obtained drawn fibers.

Comparative Example 1 A mixture of polyethylene having an intrinsic viscosity of 2.8 dl / g measured in decalin at 135 ° C. and the paraffin wax used in Example 1 at a weight ratio of 50:50 was melted in the same manner as in Example 1. Spun. However, the shear rate at this time is 25se
c ⁻¹ and the shear stress were 1.9 × 10 ⁵ dyn / cm ² . The degree of orientation F of the undrawn fiber was 0.85. Further, the undrawn fiber was drawn by the method described in Example 1 to obtain a drawn fiber.

Table 6 shows the tensile properties and the degree of orientation of the drawn fibers obtained.

Comparative Example 2 A mixture of polyethylene having an intrinsic viscosity of 5.6 dl / g measured in decalin at 135 ° C. and the paraffin wax used in Example 1 at a weight ratio of 30:70 was prepared in the same manner as in Example 1. It was melt spun. However, the shear rate at this time is 10
The sec ^-1 and the shear stress were 1.5 × 10 ⁵ dyn / cm ² . The degree of orientation F of the undrawn fiber was 0.88. Further, the undrawn fiber was drawn by the method described in Example 1 to obtain a drawn fiber.

Table 7 shows the tensile properties and the degree of orientation of the drawn fibers obtained.

Example 6 Using a corona discharge treatment device manufactured by Tomoe Kogyo Co., Ltd., 1 m between the bar-shaped electrodes was applied to the drawn fiber (sample-9) obtained in Example 4.
The corona discharge treatment was performed once under the conditions of m, irradiation amount of 75 W / m ² · min.

The tensile strength of the treated fiber is 2.92 GPa (strength retention 94
%)Met.

Comparative Example 3 Polyethylene having a molecular weight of 2.2 × 10 ⁶ (17.0 dl / g in intrinsic viscosity measured in decalin at 135 ° C.) and decalin 5:
A 95 (weight ratio) mixture was spun under the following conditions.

First, 0.1 part by weight of 3,5-dimethyl-tert-butyl-4-hydroxytoluene was blended as a process stabilizer with respect to 100 parts by weight of the mixture, and charged into a nitrogen-sealed separable flask, and heated at 180 ° C. Stir for 1 hour to form a homogeneous solution.

Next, the solution was put into a spinning cylinder, and was heated to 180 ° C under a nitrogen atmosphere.
At room temperature for 2 hours to defoam the solution. The solution was passed through a spinning die having a diameter of 2 mm, at a shear rate of 30 sec ^-1 and a shear stress of
At 1.2 × 10 ⁵ dyn / cm ² and a die temperature of 130 ° C., the mixture was extruded into a coagulation tank (water bath) located 30 cm below without drafting twice or more to obtain a gel filament. After winding the gel filament on a bobbin at a speed of 1 m / min, the bobbin is n-
It was immersed in a hexane tank at room temperature to replace decalin, which is a liquid component of the gel filament, with n-hexane. further,
It was taken out of the n-hexane tank and sufficiently dried under a vacuum of 50 ° C. The degree of orientation F of the obtained undrawn fiber was 0.6.

Subsequently, dry fiber is placed in a nitrogen sealed heat tube at 50 cm / min.
And three-stage stretching was performed using four codet rolls. The effective length of each of the heat tubes was 50 cm. At this time, the temperature in the first heat tube was 110 ° C., the temperature in the second heat tube was 130 ° C., and the temperature in the third heat tube was 140 ° C. The stretching ratio is determined by the rotation ratio of the first codet roll and the fourth codet roll.
It was 60 times. The rotation speeds of the second and third codet rolls were appropriately selected within a range where stable movement was possible. Physical properties of the obtained polyethylene fiber were an intrinsic viscosity of 14.0 dl / g, a fiber of 21 denier, and a tensile strength of 2.85 GPa.

The polyethylene fiber was subjected to corona discharge treatment under the same conditions as in Example 6. The tensile strength of the treated fiber is 1.75
GPa (retention: 61%).

Example 7 40:60 of an ethylene-butene-1 copolymer (ethylene content: 99.9%) having an intrinsic viscosity of 6.0 dl / g (molecular weight: 5.0 × 10 ⁵ ) and paraffin wax (melting point: 69 ° C., molecular weight: 490)
(Weight ratio) of the mixture was melt-spun under the following conditions. First, 3,5-dimethyl-t was added to this mixture as a process stabilizer.
0.1 part by weight of ert-butyl-4-hydroxytoluene was added to 100 parts by weight of a high-molecular-weight ethylene-propylene copolymer. Next, using a screw type extruder, the mixture was melt-kneaded at a set temperature of 190 ° C., and the melt was continuously passed through a spinning die having an orifice diameter of 2 mm attached to the extruder at a shear rate of 25 sec ⁻¹ and a die temperature of 170 ° C. It was melt spun under conditions. The spun fiber was taken out at a draft ratio of 60 times with an air gap of 180 cm, cooled and solidified in air to obtain an undrawn fiber. The degree of orientation of the undrawn fiber was 0.91.

The undrawn fiber thus obtained was drawn in the same manner as in Example 1.

Table 8 shows the tensile strength and degree of orientation of the obtained drawn fibers.

Continuation of the front page (56) References JP-A-57-193319 (JP, A) JP-A-60-100102 (JP, A) JP 7-64015 (JP, B2) JP 4-30904 (JP) , B2) JP 6-252312 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 47/00-47/96

Claims (4)

(57) [Claims] 1. A melt mixture comprising a polyethylene having an intrinsic viscosity of 3.0 dl / g or more and a diluent is subjected to a shear rate of 20 sec ^-1 or more and a shear rate of 1 × 10 ⁵ to 8 × 10 ⁵ dyn / cm ² . A method of producing a polyethylene molded article having a degree of orientation of 0.7 or more by extruding the polyethylene from a die nozzle while orienting the polyethylene in a die while applying stress. 2. A molten mixture comprising a polyethylene having an intrinsic viscosity of 3.0 dl / g or more and a diluent is sheared at a shear rate of 20 sec ^-1 or more and 1 × 10 ⁵ to 8 × 10 ⁵ dyn / cm ² . Under the application of stress, the polyethylene is extruded from a die nozzle while orienting the polyethylene in a die to obtain a polyethylene molded body having a degree of orientation of 0.7 or more, and then stretching the polyethylene molded body three times or more. Manufacturing method. 3. The method according to claim 1, wherein the content of the polyethylene in a mixture of a polyethylene having an intrinsic viscosity of 3.0 dl / g or more and a diluent is 20% by weight or more. 4. The method according to claim 1, wherein the melting point of the diluent is 25 ° C. or higher.
Item 3. The method according to item 2 or 2.