JPS60189420A - Manufacture of oriented article of ultra-high-molocular polyethylene - Google Patents

Abstract

PURPOSE:To manufacture an oriented article of ultra-high-molecular polyethylene whose tensile strength and an elastic modulus are both high, by a method wherein specific paraffin wax is added to the ultra-high-molecular polyethylene, which is oriented through fusing and extruding. CONSTITUTION:Paraffin wax whose fusing point is 40-120 deg.C and molecular weight is less than 2,000 is blended with ultra-high-molecular polyethylene (extreme viscosity is more than 5dl/g) at a ratio of 25:75, which is melted and kneaded within a screw extruder at the temperature of 180 deg.C of resin. Then the above molten article is extruded through the die for cooling and solidification. An obtained unoriented article is oriented at a ratio of orientation exceeding at least three times. As an obtained oriented article of the ultra-high-molecular polyethylene possesses high tensile strength, which is not obtainable through a conventional polyethylene oriented article, and a high elastic modulus, the oriented article can be used for various kinds of reinforcement materials for which lightweight properties are required.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for melt extrusion drawing of ultra-high molecular weight polyethylene. More specifically, the present invention relates to a method for producing a stretched ultra-high molecular weight polyethylene having high tensile strength and elastic modulus by melt-extruding and stretching a composition comprising ultra-high molecular weight polyethylene and a specific paraffin wax.

Ultra-high molecular weight polyethylene has superior impact resistance, abrasion resistance, chemical resistance, tensile strength, etc. compared to general-purpose polyethylene, and its use as an engineering plastic is expanding. However, compared to general-purpose polyethylene, it has an extremely high melt viscosity and poor fluidity, making it extremely difficult to mold by extrusion or 141 extrusion molding, and most of it is molded by compression molding. Currently, some rods and the like are extruded at extremely low speeds.

On the other hand, as a method for drawing high-density polyethylene monofilaments at a high magnification, additives with a high boiling point higher than the melting point of polyethylene are added at 20 to 150% by weight based on the weight of polyethylene.
%, a primary fibrous material is formed from the obtained high concentration dispersion, and then the 5
A method of hot stretching to 3 to 15 times the original length while leaving an amount equivalent to ~25% of the additive (Japanese Patent Publication No. 3'1-9765
Alternatively, a method has been proposed in which a solution of linear polyethylene having a molecular weight of 400,000 or more is spun and stretched at a temperature of at least 20 GPa. However, these methods specifically involve dispersing or dissolving in a solvent such as O-dichlorobenzene, xylene, or decalin and spinning using a specific method. Even if such a liquid solvent is used as a stretchability improver for ultra-high molecular weight polyethylene with a high molecular weight, the difference in viscosity between the solvent and the powder is too large, making it impossible to mix the solvent and the powder at all. It acts as a lubricant between the powder and the screw, causing the powder and screw to rotate together, making extrusion almost impossible. Further, even if it could be extruded, it would be completely impossible to draw it because it was not mixed uniformly, and it was currently impossible to perform continuous melt extrusion spinning using a screw extruder. Furthermore, since these solvents have low boiling points and are highly flammable, they are dangerous to use in screw extruders heated by electric heat, and special care must be taken when using them.

On the other hand, in order to improve the moldability of ultra-high molecular weight polyethylene, 10 to 60 parts by weight of low-molecular-weight polyethylene with a molecular weight of 5,000 to 20,000 is added to 100 parts by weight of ultra-high molecular weight polyethylene. Kaisho 57-1
77036), but in these compositions, the molecular weight of the added low molecular weight polyethylene is too large, making it impossible to draw the melt-extrusion-spun monofilament to a high magnification of 20 times or more, resulting in a high elastic modulus. , it is not possible to obtain monofilaments with high tensile strength.

From this point of view, the present inventors conducted various studies aimed at developing a continuous extrusion molding method for drawn products of ultra-high molecular weight polyethylene having high elastic modulus and high tensile strength using a screw extruder, and as a result, they identified ultra-high molecular weight polyethylene. The object of the present invention can be achieved by using a composition containing paraffin wax, which was previously disclosed in Japanese Patent Application No. 57-2274
47 and Japanese Patent Application No. 58-59976. As a result of further investigation, the temperature of the screw extruder was 190.
It has been found that ultra-high molecular weight polyethylene and paraffin wax can be stably and continuously extruded using a screw extruder even if the temperature is below ℃ by increasing the residence time in the screw extruder, that is, by lowering the extrusion speed of the molten resin. Understood, we have completed the present invention.

That is, in the present invention, the intrinsic viscosity [η] is at least 5d1
/g or more ultra-high molecular weight polyethylene (A): 15 to 80 parts by weight and a paraffinic wax having a melting point of 40 to 120°C and a molecular weight of 2.000 or less (B185 to 20 parts by weight). Melt-kneading in a screw extruder at a temperature of from above to below 190°C,
This paper proposes a method for producing a stretched product of ultra-high molecular weight polyethylene with high tensile strength and elastic modulus, which is characterized by extruding an unstretched product through a die and then stretching it at a small (more than 3 times) stretching ratio. .

The ultra-high molecular weight polyethylene (A) used in the method of the present invention has an intrinsic viscosity [η] of 5 at 135°C in decalin solvent.
dl/g or more, preferably in the range of F to 30 a/g.

If [η] is less than 5 dl/g, a stretched product with excellent tensile strength cannot be obtained even if stretched. The upper limit of [η] is not particularly limited, but if it exceeds 30 dl/g, the melt viscosity is high even if paraffin wax (B) described below is added, and melt spinning using a screw extruder in the temperature range described below is difficult. inferior to sex.

Paraffin wax used in the method of the present invention.

(B) has a melting point of 40 to 120°C, preferably 40°C.
It is a paraffin wax having a temperature of 5 to 110°C and a molecular weight of 2,000 or less, preferably 1,000 or less, particularly preferably 800 or less. If a material with a melting point of less than 40° C. or liquid paraffin is used, the ultra-high molecular weight polyethylene (A) and the screw will rotate together, making uniform melt spinning impossible. On the other hand, if the melting point exceeds 120°C and the molecular weight exceeds 2,000, drafting before cooling and solidification will cause stretching breakage, making it impossible to obtain a stretched product with high elastic modulus and high tensile strength. It is also impossible to extract excess paraffin wax from the drawn product.

In addition, when using a material with a molecular weight of 800 or less, a drawn product with a sufficiently high elastic modulus can be obtained even at a drawing ratio of more than 3 times by applying a draft before cooling and solidifying.
When using a paraffin wax of 0.00 to 2,000, it is preferable to apply a draft and stretch at a stretching ratio of 5 times, preferably 10 times or more, before cooling and solidifying.

The melting point in the present invention is a value measured using a differential scanning calorimeter (D SC) according to ASTM D 3417. The molecular weight is the weight average molecular weight (nail) measured by GPC method (gel permeation chromatography) under the following conditions.

Equipment: 150C type column manufactured by Waters Co., Ltd. TSK GMH-6 manufactured by Toyo Soda Co., Ltd. (6 mmφ x 600 m
m) Solvent: orthodichlorobenzene (ODCB) temperature;
135℃ Flow rate: 1.0m7! /min Injection concentration: 30mg/20ml1.0DCB (Injection amount 400μI2) In addition, Toyo Soda Co., Ltd. and Pressure Chemical? ! ,
Column elution volumes were calibrated by the universal method using standard polyethylene.

The paraffin wax (B) used in the method of the present invention is not particularly limited to a compound consisting only of carbon and hydrogen, as long as it has a melting point and molecular weight within the above range, and may contain a small amount of oxygen or other elements. May contain.

The paraffinic wax (B) is mainly composed of saturated aliphatic hydrocarbon compounds, specifically n-alkanes having 22 or more carbon atoms such as tocosane, 1... lycosane, tetracosane, triacontane, or these. mixture with lower n-alkanes mainly composed of , so-called paraffin wax separated and purified from petroleum, and low molecular weight polymers obtained by copolymerizing ethylene or ethylene and other α-olefins. polyethylene wax,
High-pressure polyethylene wax, ethylene copolymer wax, medium/low-pressure polyethylene, high-pressure polyethylene, and other polyethylene waxes whose molecular weight has been lowered by thermal degradation, and oxidized Fuchs such as oxides of these Fuchs or maleic acid-modified products. , maleic acid-modified wax, and the like.

Other hydrocarbon compounds that fall within the melting point and molecular weight range of the paraffinic wax (B) used in the present invention include aromatic hydrocarbon compounds such as naphthalene and dimethylnaphthalene, but unlike paraffinic waxes, these It has poor compatibility with high molecular weight polyethylene (A), and when used in the method of the present invention, it has poor compatibility with ultra high molecular weight polyethylene (A).
), and it is difficult to achieve uniform stretching or a high stretching ratio.

A specific example of a method for examining the compatibility between ultra-high molecular weight polyethylene (A) and paraffin wax (B) is a method of observing the cross section of an undrawn yarn using a high-magnification scanning electron microscope. That is, ultra-high molecular weight polyethylene (A
) and paraffin wax (B), etc., are melt-blended and then melt-spun. Next, the obtained undrawn yarn is cut with a sharp blade such as a microtome so as to be perpendicular to the longitudinal direction of the yarn. A cross section cut out by the same process as the cross section is roughly immersed in a nonpolar solvent such as hexane or hebutane at room temperature for at least 1 hour to extract and remove baraf, in-based wax (B), etc. Comparative observation is made using a scanning electron microscope at a magnification of at least a, ooo times or more. Paraffin wax (B) of the present invention
Because it has good compatibility with ultra-high molecular weight polyethylene (A), depressions of 0.1 μ or more are rarely observed,
When naphthalene is used instead of paraffin wax (B), poor dispersion occurs, and 0.1. Countless depressions larger than μ are observed.

The method of the present invention comprises the ultra-high molecular weight polyethylene (A)+1
5 to 80 parts by weight, preferably 30 to 50 parts by weight, and the paraffin wax (B): 85 to 20 parts by weight.
parts by weight, preferably 70 to 50 parts by weight, is melt-kneaded in a screw extruder at a temperature from the melting point of the mixture to less than 190°C, preferably from the melting point of the mixture +10°C to less than 190°C. This is a method in which an unstretched product is extruded through a goo at a temperature above its melting point, and then stretched at a stretching ratio of at least 3 times, preferably 5 times or more.

If the amount of ultra-high molecular weight polyethylene (A) is less than 15 parts by weight, it will be difficult to melt and knead it in a screw extruder, and the extruded product will have poor drawability, causing breakage and making it difficult to draw at high magnification or draft. Can not. On the other hand 8
If the amount exceeds 0 parts by weight, the melt viscosity becomes high, making melt extrusion difficult, and the extruded unstretched product (strand) has a rough surface and is likely to break during stretching.

If the temperature of the screw extruder is lower than the melting point of the mixture, the ultra-high molecular weight polyethylene (A) and paraffin wax (B) will not be well dispersed, and a uniform strand that can withstand stretching cannot be extruded from the die orifice. . In addition, ultra-high molecular weight polyethylene (A) and paraffin wax (
The mixture with B) can be carried out by mixing using a Henschel mixer, (1)-blender, etc., or by melt-kneading and granulating with a single-screw or multi-screw extruder after mixing.

When the unstretched material is extruded from the die, the molten material undergoes at least 1. Preferably, by applying a draft of more than 2, a drawn product having a higher modulus of elasticity and higher tensile strength can be obtained than a drawn product that is not subjected to drafting.

The term "draft" in the present invention refers to the drawing of the melt extruded from the screw extruder during melting, and refers to the drawing down of the melt. That is, the extrusion speed υ of the molten resin within the die orifice. The ratio of the winding speed υ of the cooled and solidified fiber to the draft ratio was defined as the following equation.

Draft ratio - υ/υO Further, the cooling may be performed by either air cooling or water cooling.

The temperature during stretching is usually 60℃ or the melting point of the mixture → -20℃
If the temperature is below 60°C, high-stretching may not be achieved, whereas if the temperature exceeds the melting point of the mixture + 20°C, the ultra-high molecular weight polyethylene (A) will soften, and although it may be stretched, high-stretching may not be achieved. There is a possibility that a stretched product with a modulus of elasticity may be obtained.

A stretched product with a high elastic modulus can be obtained by using air, water vapor, or a solvent as a heating medium during the above-mentioned stretching process. By using a solvent with a boiling point higher than the melting point of the mixture, specifically, for example, decalin, decane, or kerosene, it is possible to extract excess paraffin wax (B) or remove exuded wax during stretching, and the stretching during stretching This is preferable because it makes it possible to reduce unevenness and achieve a high stretching ratio. In addition, methods for removing excess paraffin wax (B) from a stretched product of ultra-high molecular weight polyethylene (A) are not limited to the above-mentioned method, but include a method in which an unstretched product is treated with a solvent such as hexane or heptane, and then stretched. The paraffin wax (B) can also be extracted and removed by treating the product with a solvent such as hexane or heptane, and a stretched product with high elastic modulus and high strength can be obtained.

When extracting the paraffin wax (B) with the above solvent or solvent, the paraffin wax (B) in the stretched product
By reducing the remaining amount of B) to 10% by weight or less, microporous fibers are obtained, and the fibers are brand new by weight conversion.For both the elastic modulus and strength obtained from the method of calculating the area, use the values of the stretched product before extraction. It is preferable without any problems.

When the stretching ratio in the solvent is less than 3 times, the degree of high tensile strength and high elastic modulus is small, and the stretched product is accompanied by uneven stretching, which often impairs the appearance. In the case of drafting, the final stretching ratio may be at least 3 times, preferably at least 5 times, and may be one-stage stretching or multi-stage stretching of two or more stages. Further, when no drafting is applied, high strength and high elastic modulus can be achieved by increasing the final stretching ratio to 10 times or more.

Further, the final stretching speed during stretching is not particularly limited, but from the viewpoint of productivity it is 3 m/min or more, preferably 5 m/min.
It is better to have n or more.

The ultra-high molecular weight polyethylene (A>) used in the present invention contains additives that can be normally added to polyolefin, such as heat stabilizers, weather stabilizers, pigments, dyes, and inorganic fillers, within a range that does not impair the purpose of the present invention. It may be added in advance.

The drawn product of ultra-high molecular weight polyethylene obtained by the method of the present invention has high tensile strength and high elastic modulus that cannot be obtained with conventional drawn products of ordinary polyethylene. In addition to the field of drawn yarn, it can be used in the field of high modulus and high strength fibers, and can be used in various reinforcing materials that require lightness. Furthermore, it is suitable for functional materials such as selective membranes and electrets that utilize the highly aligned crystal arrangement achieved by ultra-high stretching and the micropores that are generated as a by-product by extracting excess paraffin wax (B). is also excellent.

Next, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to these embodiments unless it goes beyond the gist of the invention.

Experimental example 1 Ultra-high molecular weight polyethylene ([η]-8゜20di/g)
and paraffin wax (melting point -69℃, molecular weight -460
) was melt-spun and drawn under the following conditions. After mixing ultra-high molecular weight polyethylene powder and crushed paraffin wax, 20 mmφ, L/D=
Melt kneading was carried out using a 20 mm screw extruder at a resin temperature of 180°C. Next, the melt was extruded through a die with an orifice diameter of 4 mm and a die temperature of 210°C, and an air gap of 5 cm was set at 0°C.
It was solidified in ice water at ℃. At this time, the extrusion speed of the molten resin was 6. Ocm/min, winding speed is 0.3m
I made a withdrawal so that the amount would be /min.

That is, the draft ratio was set to 5. Subsequently, the film was stretched using two pairs of godet rolls in a stretching bath using n-decane as a heating medium (temperature inside the bath was -130° C., length of the bath was 40 cm).

During stretching, the rotational speed of the first godet roll is set to 0.
5m/min, the second godet troll and the third
By appropriately changing the rotational speed of the godet roll, fibers with different drawing ratios were obtained. For stretching, the film was first stretched to a stretching ratio of 4.0 times using a second godet roll, and then a second stage of stretching was performed at a predetermined stretching ratio using a third godet roll.

However, the stretching ratio was calculated from the rotation ratio of the godet roll. Table 1 shows the tensile modulus, tensile strength, and elongation at break at each stretching ratio. The tensile modulus, tensile strength, and elongation at break were measured at room temperature (23°C) using an Instron universal testing machine model 1123 (manufactured by Instron). At this time, the sample length between the clamps was 100 mm, and the tensile speed was 100 mm/min. However, the tensile modulus was calculated using stress at 2% strain. The fiber cross-sectional area required for calculation was determined by measuring the weight and length of the fiber, assuming the density of polyethylene as 0.96 g/cd.

Table 1 Experimental example 2 Ultra high molecular weight polyethylene ([η) -8,20 dl/g
) and paraffin wax (melting point -69°C, weight = 460) was melt-spun and stretched under the same conditions as in Experimental Example 1. However, the melt was extruded through a die with an orifice diameter of 4 mm and solidified in ice water at 0° C. with an air gap of 5 cm.

At this time, the extrusion speed of the molten resin was 6.0 cm/min, and the withdrawal was performed so that the winding speed was 0.6 m/min. That is, the draft ratio was set to 10. For stretching, the film was first stretched to a stretching ratio of 3.0 times using a second godet roll, and then a second stage of stretching was performed at a predetermined stretching ratio using a third godet roll. Table 2 shows the tensile modulus, tensile strength, and elongation at break at each stretching ratio. By increasing the draft ratio, the tensile strength of 8 Table 2 Experimental Example 3 Ultra-high molecular weight polyethylene ([η) = 8.20 dl/g
) and paraffin wax (melting point -69℃, molecular weight = 4
A 25:75 blend with 60) was subjected to melt-spinning and drawing under the same conditions as in Experimental Example 1. However, the melt was extruded through a die with an orifice diameter of 4 nm and solidified in ice water at 0° C. with an air gap of 5 cm.

At this time, the extrusion speed of the molten resin was 6.0 cm/min, and the withdrawal was performed so that the winding speed was 3.0 m/1 line. That is, the draft ratio was set to 50. For stretching, the film was first stretched by 9 times with a second godet roll at a stretching ratio of 3.0 times, and then a second stage of stretching was performed at a predetermined stretching ratio with a third godet roll. Table 3 shows the tensile modulus, tensile strength, and elongation at break at each stretching ratio. It can be seen that by increasing the draft ratio, a drawn product with high tensile strength can be obtained.

Table 3 Experimental example 4 Ultra high molecular weight polyethylene ([η) -8,20 dl/g
) and paraffin wax (melting point = 69°C, molecular weight -46
A 25:75 blend of 0) was melt-spun and drawn under the same conditions as in Experimental Example 1. However, the melt was extruded through a die with a diameter of 4 mm and solidified in air at room temperature with an air gap of 20 cm.

At this time, the extrusion speed of the molten resin was 6.0 cm/min, and the withdrawal was performed so that the winding speed was 0.3111/min. That is, the draft ratio was set to 5.

For stretching, the film was first stretched to a stretching ratio of 4.0 times using a second godet roll, and then a second stage of stretching was performed at a predetermined stretching ratio using a third godet roll. Table 4 shows the tensile modulus, tensile strength, and elongation at break at each stretching ratio. By increasing the draft ratio,
) and paraffin wax (melting point = 69°C, molecular weight -46
A 25:75 blend of 0) was melt-spun and drawn under the same conditions as in Experimental Example 1. However, if the orifice diameter is 4
The molten material was inserted through the tube of III and solidified in air at room temperature with an air gap of 20 cm. At this time, the extrusion speed of the molten resin was 6.0 cm/min, and the withdrawal was performed so that the winding speed was 0.6 m/n+in. That is, the draft ratio was set to 10.

For stretching, the film was first stretched to a stretching ratio of 3.0 times using a second godet roll, and then a second stage of stretching was performed at a predetermined stretching ratio using a third godet roll. Table 5 shows the tensile modulus, tensile strength, and elongation at break at each stretching ratio. Table 5 Experimental Example 6 Ultra-high molecular weight polyethylene ((η) -8,20dl/g
) and paraffin wax (melting point = 69℃, molecular weight = 4
A 25:75 blend with 60) was subjected to melt-spinning and drawing under the same conditions as in Experimental Example 1. However, the molten material is extruded through a goo with an orifice diameter of 4 mm, and the air gap:
It was solidified at 20 cm in air at room temperature. At this time, the extrusion speed of the molten resin was 6.0 cm/min, and the winding speed was 3.0 cm/min. (The draft ratio was set to 50.)

For stretching, the film was first drawn to a drawing ratio of 3.0 times A with a second godet roll, and then a second stage of drawing was performed at a predetermined drawing ratio with a third godet roll. Table 6 shows the tensile modulus, tensile strength, and elongation at break at each stretching ratio. It can be seen that by increasing the draft ratio, a drawn product with high tensile strength can be obtained.

Table 6 Experimental Example 7 Ultra-high molecular weight polyethylene ((η) = 8.20 dl/g
) and paraffin wax (melting point = 69°C, molecular weight -46
0) and 25! The 75 blend was melt-spun and drawn under the same conditions as in Experimental Example 1. However, the melt was extruded through a gouey with a diameter of 4 mm and solidified in ice water at O'C with an air gap of 50.

At this time, the extrusion speed of the molten resin was 6.0 cm/min, and the withdrawal was performed so that the winding speed was 3.0 cm/min. That is, the draft ratio was set to 0.5.
For stretching, the film was first stretched to a stretching ratio of 3.0 times using a second godet roll, and then a second stage of stretching was carried out using an i3 godet roll at a predetermined stretching ratio. Table 7 shows the tensile modulus, tensile strength, and elongation at break at each stretching ratio G2.

Table 7 6 Experimental example 8 Ultra high molecular weight polyethylene ([η) -8.20 dl/g
) and paraffin wax (melting point -69℃, molecular weight -46
A 25:75 blend of 0) was melt-spun and drawn under the same conditions as in Experimental Example 1. However, if the orifice diameter is 4
Extrude the melt through a mm die, air gap: 2
It was solidified in air at room temperature at 0 cm. At this time, the extrusion speed of the molten resin was 6.0 cm/min, and the withdrawal was performed so that the winding speed was 3.0 cm/min. That is, the draft ratio was set to 0.5. For stretching, the film was first stretched to a stretching ratio of 3.0 times using a second godet roll, and then a second stage of stretching was performed at a predetermined stretching ratio using a third godet roll. Tensile modulus, tensile strength and breaking point 7 at each stretching ratio Table 8 Experimental example 9 Ultra high molecular weight polyethylene ((η) -8,20di/g
) and paraffin wax (melting point -69℃, molecular weight -46
A 50:50 blend of T-0) with T-
After die film molding, stretching was performed. After mixing the ultra-high molecular weight polyethylene powder and the pulverized paraffin wax, they were melted and mixed in a screw extruder with a diameter of 20 mm and L/D=20 at a resin temperature of 180° C. to beretinate. Next, the pellets were passed through a coat hanger type die at 220°C (
Lip length -300+nm.

20mmφ with sump thickness -0.5mm), ■, /
A film was formed using a D=208 screw extruder. Using a roll cooled with cold water at 20° C., the film width and thickness were adjusted to 300 mm and 0.5n+n+. Next, use two pairs of snap rolls to roll n-
Stretching was performed in a stretching bath using decane as a heating medium (tank temperature: 130° C., bath length: 80 cm).

During stretching, the rotational speed of the first snap roll was set to 0.
5 m/1 nin, the tapes were previously stretched to a stretching ratio of 8.0 times using the second snap roll, and then the rotational speed of the third snap roll was appropriately changed to obtain stretched tapes having different stretching ratios. However, the stretching ratio was calculated from the rotation ratio of the first and third snack rolls. Tensile modulus, tensile strength, and elongation at break of stretched tape at each stretching ratio 9 3.0 Comparative Example 1 Ultra-high molecular weight polyethylene ([η) = 8.20 dl/g
) and paraffin wax (melting point -69°C8 molecular weight -4
A 25:75 blend with 60) was subjected to melt-spinning and drawing under the same conditions as in Experimental Example 1. However, the resin temperature inside the screw extruder was set to 100°C. However, because the mixture co-rotated in the screw extruder, it was not possible to obtain a uniform molten strand even when the die temperature was set at 200°C.

Comparative Example 2 Ultra-high molecular weight polyethylene ([η) = 8.20 dl/g
) and n-hexadecane were melt-kneaded under the same conditions as in Experimental Example 1.

However, the melt was extruded through a die with an orifice diameter of 2 mm. However, since the mixture co-rotates within the screw extruder, uniform molten strands could not be obtained, and uniform drawn fibers could not be obtained.

1 The drawn fibers obtained in this experimental example were ASTM D
DSC measurement using No. 3417 revealed that no paraffin wax remained.

In this experimental example, in order to examine the influence of draft, the tensile modulus and tensile strength according to different cooling conditions during the preparation of unstretched products are plotted against the stretching ratio in FIGS. 1 and 2.

Furthermore, the tensile strength was plotted against the tensile modulus in FIG. As is clear from the figure, no particular influence by the cooling conditions was observed during the preparation of the unstretched material.

The tensile modulus and tensile strength are influenced by draft and show a markedly different dependence on the draw ratio. It is clear from FIG. 3 that when a drawdown is applied during melting, a drawn product having a higher elastic modulus and higher strength can be obtained than when a drawdown is not applied. That is, high elastic modulus and high strength fibers can be obtained by applying a draft before cooling and solidifying.2

[Brief explanation of drawings]

FIG. 1 shows the relationship between tensile modulus and stretching ratio, FIG. 2 shows the relationship between tensile strength and stretching ratio, and FIG. 3 shows the relationship between tensile strength and tensile modulus. Applicant Mitsui Petrochemical Industries Co., Ltd. Agent Kazu3 Yamaguchi (ηd'o)ma″@Decoration 1β

Claims (1)

[Claims] (11) 15 to 80 parts by weight of ultra-high molecular weight polyethylene (A) having an intrinsic viscosity of at least 5 dl/g and a melting point of 4
A mixture with 85 to 20 parts by weight of paraffin wax (B) having a molecular weight of 2000 or less is melt-kneaded in a screw extruder at a temperature of 0 to 120°C and a temperature of from the melting point of the mixture to less than 190°C, and then unstretched through a die. 1. A method for producing a stretched product of ultra-high molecular weight polyethylene, which comprises extruding the product and then stretching the product at a stretching ratio of at least 3 times.