JPH04218178A - Gut for racket - Google Patents

Abstract

PURPOSE:To provide a gut having excellent creep and weather resisting properties and improved shock and fatigue resisting properties by composing the gut of a molecular orientation body of super-high molecular weight ethylene/alpha- olefin copolymer containing a specified rate of alpha-olefin of at least three of the number of carbons. CONSTITUTION:For super-high molecular weight ethylene/alpha-olefin copolymer constituting a molecular orientation body are used for example ethylene like super-high molecular weight ethylene propylene copolymer, super-high molecular weight ethylene 1-buten copolymer, super-high molecular ethylene/1-desen copolymer etc., and alpha-olefin having 3-20, preferably 4-10 of carbon atoms. The copolymer includes 0.1-20, preferably 0.5-10, further preferably 1-7 of alpha-olefin having at least 3 of carbon atoms per 1000 of carbon atoms of the copolymer. The copolymer has at least 5dl/g, preferably 7-30dl/g of the limiting viscosity [eta].

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD OF THE INVENTION The present invention relates to racket strings, and more particularly, the present invention relates to strings for rackets, and more particularly, the strings are made of a molecularly oriented ultra-high molecular weight ethylene/α-olefin copolymer, have excellent creep resistance and weather resistance, and have excellent creep resistance and weather resistance. This invention relates to racket guts that have excellent impact resistance and fatigue resistance.

0002

[Technical Background of the Invention] Tennis or badminton rackets are strung with strings, and conventionally, sheep has been used as a natural material and nylon has been used as an artificial fiber for strings for such rackets. It is being However, as the technical level of competitions has become more sophisticated in recent years and batting methods have become more diverse in terms of technique, sheep and nylon guts are no longer compatible with these batting methods due to their material properties, and higher quality gut materials have been developed. is desired. In fact, recently, aromatic polyamide (aramid) fibers such as Kevlar have been used in high-level competitions. The key point in terms of material properties for applying this fiber to a gut material is its outstanding elastic modulus and strength compared to conventional materials. However, this aromatic polyamide fiber has a major problem in that it has poor weather resistance, water resistance, and fatigue resistance, and also requires a relatively small amount of energy to break, making it easy to break.

In order to solve these problems, racket strings made of ultra-high molecular weight polyethylene fibers have begun to be used. However, when racket strings made of ultra-high molecular weight polyethylene fibers are stretched onto rackets under high tension, they have poor creep resistance and become too tensioned, and are too hard, so only a few Although it is suitable for professional athletes, there was also the problem that it was not suitable for amateurs.

[0004] Therefore, the drawbacks of these aromatic polyamide fibers and ultra-high molecular weight polyethylene fibers as racket strings have been improved, and the performance has greatly exceeded that of conventional racket strings, and the fibers are suitable for all tennis and badminton enthusiasts. A material for racket gut is desired.

[0005] It is already known that by forming ultra-high molecular weight polyethylene into fibers, tapes, etc. and stretching this, a molecularly oriented molded article having a high modulus of elasticity and high tensile strength can be obtained. For example, JP-A-56-15408
The publication describes spinning a dilute solution of ultra-high molecular weight polyethylene and drawing the resulting filament. Furthermore, JP-A-59-130313 describes that ultra-high molecular weight polyethylene and wax are melt-kneaded, the kneaded product is extruded, and after cooling and solidifying, it is stretched.
Further, JP-A-59-187614 describes that the above-mentioned melt-kneaded product is extruded, drafted, cooled and solidified, and then stretched.

[0006]

OBJECT OF THE INVENTION The present invention aims to solve the problems associated with the prior art as described above, and has excellent creep resistance and weather resistance, as well as good impact resistance and fatigue resistance. Our aim is to provide superior racket guts.

[0007]

Summary of the Invention The racket string according to the present invention has an intrinsic viscosity [η] of at least 5 dl/g, and an average content of α-olefin having 3 or more carbon atoms of 0.1 to 1000 carbon atoms. Ultra-high molecular weight ethylene with 20 pieces
It is characterized by being composed of a molecularly oriented α-olefin copolymer.

The racket string according to the present invention is made of a molecularly oriented ultra-high molecular weight ethylene/α-olefin copolymer as described above, and has excellent creep resistance and weather resistance. It also has excellent impact resistance and fatigue resistance.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The racket string according to the present invention will be explained in detail below. First, the molecularly oriented ultra-high molecular weight ethylene/α-olefin copolymer constituting the racket string according to the present invention will be described in detail. I will explain about it.

The molecularly oriented molded product used in the present invention is a molecularly oriented molded product of an ultra-high molecular weight ethylene/α-olefin copolymer. Molecularly oriented body used in the present invention (hereinafter referred to as
Ultra-high molecular weight ethylene/α-olefin copolymers constituting ultra-high molecular weight ethylene/α-olefin copolymers (also referred to as molecularly oriented molded products) include ultra-high molecular weight ethylene/propylene copolymers, ultra-high molecular weight ethylene/1-
Butene copolymer, ultra-high molecular weight ethylene/4-methyl-1
- Ethylene and 3 carbon atoms, such as pentene copolymers, ultra-high molecular weight ethylene/1-hexene copolymers, ultra-high molecular weight ethylene/1-octene copolymers, and ultra-high molecular weight ethylene/1-decene copolymers. Ultra-high molecular weight ethylene α-olefin with from 20 to 20, preferably from 4 to 10 α-olefins
An example is an olefin copolymer. In this ultra-high molecular weight ethylene/α-olefin copolymer, the α-olefin having 3 or more carbon atoms has 1000 carbon atoms in the polymer.
It is contained in an amount of 0.1 to 20 pieces, preferably 0.5 to 10 pieces, and more preferably 1 to 7 pieces.

[0011] The molecularly oriented molded product obtained from such an ultra-high molecular weight ethylene/α-olefin copolymer has particularly good impact resistance and creep resistance compared to the molecularly oriented molded product obtained from ultra-high molecular weight polyethylene. Are better. This ultra-high molecular weight ethylene/α-olefin copolymer is lightweight and has high strength, and has excellent abrasion resistance, impact resistance, and creep resistance, as well as weather resistance, water resistance, and salt water resistance.

The ultra-high molecular weight ethylene/α-olefin copolymer constituting the molecularly oriented molded article used in the present invention is
Its intrinsic viscosity [η] is 5 dl/g or more, preferably 7 to
It is in the range of 30 dl/g, and the molecularly oriented molded product obtained from this copolymer has excellent mechanical properties and heat resistance. That is, since molecular terminals do not contribute to fiber strength and the number of molecular terminals is the reciprocal of the molecular weight (viscosity), it can be seen that a material with a large intrinsic viscosity [η] gives high strength.

The density of the molecularly oriented molded product used in the present invention is 0.940 to 0.990 g/cm 3 , preferably 0.960 to 0.985 g/cm 3 . Here, the density was measured by the density gradient tube method according to a conventional method (ASTM D1505). The density gradient tube at this time was prepared by using carbon tetrachloride and toluene, and the measurement was performed at room temperature (23° C.).

The molecularly oriented molded product used in the present invention has a dielectric constant (1 KHz, 23° C.) of 1.4 to 3.0, preferably 1.8 to 2.4, and a positive electric loss tangent (1 KHz,
80°C) is 0.05 to 0.08%, preferably 0.08%.
0.040 to 0.010%. Here, the dielectric constant and positive electric dissipation tangent are determined by using a film-like sample made by closely arranging fibers and a tape-like molecularly oriented molded product in one direction.
Measured by STM D 150.

The stretching ratio of the molecularly oriented molded article used in the present invention is 5 to 80 times, preferably 10 to 50 times. The degree of molecular orientation in the molecularly oriented molded product used in the present invention can be determined by X-ray diffraction, birefringence, fluorescence polarization, and the like. When the ultra-high molecular weight polymer used in the present invention is a drawn filament, for example, the degree of orientation according to the half width as described in detail in Yukichi Go and Kiichiro Kubo: Industrial Chemistry Magazine Vol. 39, p. 992 (1939); The degree of orientation (F) defined by the formula (where H° is the half width (°) of the intensity distribution curve along the Debye ring of the strongest paratropic plane on the equator) is 0.90 or more, Especially 0.95
It is desirable for the molecules to be oriented in the above manner from the viewpoint of mechanical properties.

Furthermore, the molecularly oriented molded product of the ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention is
It also has excellent mechanical properties, for example, in the form of a drawn filament, it has an elastic modulus of 20 GPa or more, especially 30 GPa or more, and a tensile strength of 1.2 GPa or more, especially 1.5 GPa or more.

The impulse voltage breakdown value of the molecularly oriented molded article used in the present invention is 110 to 250 kV/mm, preferably 150 to 220 kV/mm. The impulse voltage breakdown value was measured by using the same sample as in the case of the dielectric constant, and increasing the voltage while applying a negative impulse in steps of 2 kV/3 times on a copper plate using a brass (25 mmφ) JIS type electrode.

When the molecularly oriented molded product used in the present invention is a molecularly oriented molded product of an ultra-high molecular weight ethylene/α-olefin polymer, this molecularly oriented molded product has good impact resistance, breaking energy and creep resistance. It has the characteristic of being extremely superior. These ultra-high molecular weight ethylene
The characteristics of the molecularly oriented molded product of α-olefin copolymer are expressed by the following physical properties.

Ultra-high molecular weight ethylene α- used in the present invention
The breaking energy of the molecularly oriented molded product of the olefin copolymer is 8 kg·m/g or more, preferably 10 kg·m/g or more.

Furthermore, the molecularly oriented molded product of the ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention has excellent creep resistance. In particular, it has outstanding creep resistance at high temperatures, which corresponds to the conditions that promote room-temperature creep, and is determined as elongation (%) after 90 seconds at a 30% breaking load and an ambient temperature of 70°C. creep is 7% or less, especially 5% or less, and the creep rate (ε, sec-1) after 90 seconds to 180 seconds is 4×1
It is 0-4 sec-1 or less, especially 5x10-5 sec-1 or less.

Among the molecularly oriented materials used in the present invention, the molecularly oriented materials of ultra-high molecular weight ethylene/α-olefin copolymers have the above-mentioned room temperature properties, but in addition to these room temperature properties, they also have the following properties: It is preferable to have the above thermal properties because the above-mentioned physical properties are further improved and the heat resistance is also excellent.

Ultra-high molecular weight ethylene used in the present invention
The molecularly oriented molded product of the α-olefin copolymer is at least 20°C higher than the original crystal melting temperature (Tm) of the copolymer.
At high temperature, at least one crystalline melting peak (Tp)
The heat of fusion is 15% or more, preferably 20% or more, particularly 30% or more.

The original crystal melting temperature (Tm) of the ultra-high molecular weight ethylene copolymer can be determined by completely melting the molded product, cooling it, relaxing the molecular orientation in the molded product, and raising the temperature again. can be determined in a second run using a so-called differential scanning calorimeter.

To explain further, in the molecularly oriented molded product used in the present invention, there is no crystal melting peak at all in the above-mentioned crystal melting temperature range inherent to the copolymer, or even if it exists, there is very little tailing. It just exists. The crystal melting peak (Tp) is generally within the temperature range Tm
+20℃~Tm+50℃, especially Tm+20℃~Tm+1
It is usually expressed in the 00° C. region, and this peak (Tp) often appears as a plurality of peaks within the above temperature range. That is, this crystal melting peak (Tp
) is the high temperature side melting peak (Tp1) in the temperature range Tm + 35°C to Tm + 100°C and the temperature range Tm + 20°C
It often appears as two separate peaks, the melting peak (Tp2) on the low temperature side at ~Tm+35°C, and depending on the manufacturing conditions of the molecularly oriented molded product, Tp1 and Tp2 may further consist of a plurality of peaks.

These high crystal melting peaks (Tp1,
Tp2) significantly improves the heat resistance of molecularly oriented molded products of ultra-high molecular weight ethylene/α-olefin copolymers, and contributes to strength retention or elastic modulus retention after high-temperature thermal history. I think that the.

[0026] Also, the temperature range Tm+35°C to Tm+100
It is desirable that the total amount of heat of fusion based on the high temperature side melting peak (Tp1) of °C is at least 1.5%, particularly at least 3.0%, based on the total heat of fusion.

Furthermore, as long as the sum of the heat of fusion based on the high-temperature side melting peak (Tp1) satisfies the above-mentioned value, if the high-temperature side melting peak (Tp1) does not stand out as a main peak, that is, a small peak Even if it becomes an aggregate or a broad peak, the heat resistance may be slightly lost, but the creep resistance is excellent.

The melting point and heat of crystal fusion in the present invention were measured by the following method. The melting point was determined using a differential scanning calorimeter as follows. Differential scanning calorimeter is DSC II
A mold (manufactured by PerkinElmer) was used. The sample is approximately 3mg
was restrained in the orientation direction by wrapping it around an aluminum plate of 4 mm x 4 mm and 0.2 mm thick. Next, the sample wrapped around an aluminum plate was sealed in an aluminum pan and used as a measurement sample. In addition, the same aluminum plate used for the sample was sealed in the normally empty aluminum pan placed in the reference holder to maintain heat balance. First, the sample was held at 30° C. for about 1 minute, and then the temperature was raised to 250° C. at a rate of 10° C./min, and the melting point measurement at the first heating was completed. Subsequently, the temperature was held at 250°C for 10 minutes, then the temperature was lowered at a rate of 20°C/min, and the sample was further held at 30°C for 10 minutes. Then, the second temperature increase was carried out at a temperature increase rate of 10°C/min.
The temperature was raised to 50° C., and at this time, the melting point measurement was completed during the second temperature increase (second run). At this time, the maximum value of the melting peak was taken as the melting point. When it appears as a shoulder, a tangent is drawn at the inflection point immediately on the low-temperature side and the inflection point immediately on the high-temperature side of the shoulder, and the intersection is taken as the melting point.

[0029] Furthermore, by connecting the points of 60°C and 240°C on the endothermic curve, the straight line (baseline) and the original crystal melting temperature (Tm ) and draw a perpendicular line to a point 20°C higher than The heat of fusion of each crystal was calculated from these areas. In addition, the heat of fusion based on the melting of Tp1 and Tp2 is determined by the above-mentioned method.
The heat of fusion is based on the melting of , and the high temperature side part is Tp
The heat of fusion was calculated in the same way based on the melting of 1.

Ultra-high molecular weight ethylene used in the present invention
The drawn filament of α-olefin copolymer is 170
Strength retention rate is 95% after 5 minutes of heat history at °C
As described above, the elastic modulus retention is 90% or more, particularly 95% or more, and has excellent heat resistance that is completely unrecognizable in conventional drawn polyethylene filaments.

Method for producing a molecularly oriented molded product of ultra-high molecular weight polyolefin A method for obtaining the above-mentioned drawn ultra-high molecular weight polyolefin product having high elasticity and high tensile strength is disclosed in, for example, JP-A-56
-15408, JP 58-5228, JP 59-130313, JP 59-1876
As detailed in Publication No. 14, etc., the stretchability of ultra-high molecular weight polyethylene can be improved by making ultra-high molecular weight polyethylene into a dilute solution or by adding a low molecular weight compound such as paraffin wax to ultra-high molecular weight polyethylene. An example of an improved method for stretching to a high magnification can be given.

Method for producing a molecularly oriented molded product of ultra-high molecular weight ethylene/α-olefin copolymer Next, the present invention will be explained below in order of raw materials and production method for easy understanding.

Raw Materials The ultra-high molecular weight ethylene/α-olefin copolymer used in the present invention is prepared by slurry polymerizing ethylene and an α-olefin having 3 or more carbon atoms in an organic solvent using a Ziegler catalyst. It can be obtained by

[0034] As the α-olefin having 3 or more carbon atoms,
Propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, heptene-1, octene-1
Among these, butene-1, 4-
Preferred are methylpentene-1, hexene-1, octene-1, and the like. Such α-olefins are copolymerized with ethylene in the amount stated above per 1000 carbon atoms of the resulting copolymer. In addition, the ultra-high molecular weight ethylene/α-olefin copolymer used as a base when producing the molecularly oriented material in the present invention has the above-mentioned intrinsic viscosity [
η].

Ultra-high molecular weight ethylene used in the present invention
The α-olefin component in the α-olefin copolymer is quantitatively determined using an infrared spectrophotometer (manufactured by JASCO Corporation). Specifically, α- incorporated into the ethylene chain
1378cm representing the bending vibration of the methyl group of olefin
The absorbance of -1 was measured using an infrared spectrophotometer, and this value was converted into the number of methyl branches per 1000 carbon atoms using a calibration curve prepared in advance using a model compound using a 13C nuclear magnetic resonance apparatus. By doing so, the amount of α-olefin in the ultra-high molecular weight ethylene/α-olefin copolymer is determined.

Production Method In the present invention, when producing a molecularly oriented product from the ultra-high molecular weight ethylene/α-olefin copolymer, a diluent is blended into the copolymer. As such a diluent, a solvent for the ultra-high molecular weight ethylene copolymer or various wax-like substances having dispersibility for the ultra-high molecular weight ethylene copolymer are used.

[0037] As such a solvent, a solvent having a boiling point higher than the melting point of the copolymer, more preferably a boiling point higher than the melting point of the copolymer by 20°C or more is used. Specifically, such solvents include n-nonane, n-
- Decane, n-undecane, n-dodecane, n-tetradecane, n-octadecane or aliphatic hydrocarbon solvents such as liquid paraffin and kerosene; xylene, naphthalene,
Tetralin, butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene, benzylbenzene,
Aromatic hydrocarbon solvents such as dodecylbenzene, bicyclohexyl, decalin, methylnaphthalene, ethylnaphthalene, etc. or hydrogenated derivatives thereof; 1,1,2,2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,2,3- Examples include halogenated hydrocarbon solvents such as trichloropropane, dichlorobenzene, 1,2,4-trichlorobenzene, and bromobenzene; mineral oils such as paraffinic process oil, naphthenic process oil, and aromatic process oil.

[0038] Waxes as diluents include:
Specifically, aliphatic hydrocarbon compounds or derivatives thereof are used. As such an aliphatic hydrocarbon compound, a compound called paraffin wax, which is mainly composed of a saturated aliphatic hydrocarbon compound and has a molecular weight of 2000 or less, preferably 1000 or less, more preferably 800 or less, is used.

[0039] Specific examples of such aliphatic hydrocarbon compounds include docosane, tricosane, tetracosane,
N-alkanes with 22 or more carbon atoms such as triacontane or mixtures with lower n-alkanes containing these as main components, so-called paraffin wax separated and refined from petroleum, copolymerization of ethylene or ethylene and other α-olefins. Low molecular weight polymers such as medium/low pressure polyethylene wax, high pressure polyethylene wax, ethylene copolymer wax, medium/low pressure polyethylene, high pressure polyethylene, etc. are lowered in molecular weight by thermal degradation, etc. Waxes, oxides of these waxes, oxidized waxes modified with maleic acid, waxes modified with maleic acid, etc. are used.

Further, as the aliphatic hydrocarbon compound derivative, for example, one or more, preferably one to two, particularly preferably one, aliphatic hydrocarbon group (alkyl group, alkenyl group) has one or more, preferably one or more, at the end or inside the aliphatic hydrocarbon group (alkyl group, alkenyl group). carboxyl group,
A compound having a functional group such as a hydroxyl group, a carbamoyl group, an ester group, a meltcapto group, or a carbonyl group with a carbon number of 8 or more, preferably a carbon number of 12 to 50, or a molecular weight of 13
0 to 2000, preferably 200 to 800, fatty acids, aliphatic alcohols, fatty acid amides, fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, aliphatic ketones, etc. are used.

Examples of such aliphatic hydrocarbon compound derivatives include fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, lauric alcohol, myristyl alcohol, cetyl alcohol, fatty alcohols such as stearyl alcohol; fatty acid amides such as caprinamide, lauramide, palmitinamide, stearylamide;
Fatty acid esters such as stearyl acetate are used.

[0042] The ultra-high molecular weight ethylene/α-olefin copolymer and diluent differ depending on their type, but generally the ratio is 3:97 to 80:20, particularly 15:85 to 6.
A weight ratio of 0:40 is used. If the amount of the diluent is less than the above range, the melt viscosity will become too high, making melt kneading and melt molding difficult, and the resulting molded product will have a markedly rough surface and is prone to stretch breakage. On the other hand, if the amount of the diluent is larger than the above range, melt-kneading will become difficult, and the resulting molded product will have poor stretchability.

Melt-kneading is generally carried out at a temperature of 150 to 300°C, particularly 170 to 270°C. If the temperature is lower than the above range, the melt viscosity will be too high and melt molding will be difficult, and if the temperature is higher than the above range, the molecular weight of the ultra-high molecular weight ethylene/α-olefin copolymer will decrease due to thermal degradation. However, it becomes difficult to obtain a molded article having excellent high elastic modulus and high strength. The blending may be carried out by dry blending using a Henschel mixer, a V-type blender, or the like, or may be carried out using a single-screw extruder or a multi-screw extruder.

[0044] Melt molding of a dope (spinning stock solution) comprising an ultra-high molecular weight ethylene/α-olefin copolymer and a diluent is generally carried out by melt extrusion molding. Specifically, by melt-extruding the dope through a spinneret,
A filament for drawing is obtained. At this time, the molten material extruded from the spinneret may be drafted, that is, drawn in the molten state. The draft ratio can be defined as the ratio of the extrusion speed V0 of the molten resin within the die orifice and the winding speed V of the unstretched material cooled and solidified.

Draft ratio=V/V0 Such a draft ratio varies depending on the temperature of the mixture, the molecular weight of the ultra-high molecular weight ethylene copolymer, etc., but it can usually be 3 or more, preferably 6 or more.

Next, the unstretched molded product of the ultra-high molecular weight ethylene/α-olefin copolymer thus obtained was
Stretch. Stretching is carried out so as to effectively impart at least uniaxial molecular orientation to the unstretched molded article obtained from the ultra-high molecular weight ethylene/α-olefin copolymer.

[0047] The stretching of the unstretched molded product obtained from the ultra-high molecular weight ethylene/α-olefin copolymer is generally 40 to
It is carried out at a temperature of 160°C, in particular from 80 to 145°C. As a heat medium for heating and maintaining the unstretched molded body at the above-mentioned temperature, any of air, water vapor, and a liquid medium can be used. However, as a heating medium, a liquid medium that is a solvent capable of eluting and removing the diluent described above and whose boiling point is higher than the melting point of the molded body composition, specifically, is used.
It is preferable to carry out the stretching operation using decalin, decane, kerosene, etc., since this makes it possible to remove the diluent described above, prevents uneven stretching during stretching, and allows a high stretching ratio to be achieved.

Means for removing the diluent from the ultra-high molecular weight ethylene/α-olefin copolymer are not limited to the above method,
A method in which an unstretched product is treated with a solvent such as hexane, heptane, hot ethanol, chloroform, benzene, etc., or a method in which a stretched product is treated with a solvent such as hexane, heptane, hot ethanol, chloroform, benzene, etc. By removing the diluent, a stretched product with high elastic modulus and high strength can be obtained.

[0049] The stretching operation can be carried out in one stage or in multiple stages of two or more stages. The stretching ratio is generally 5 to 80 times, preferably 10 to 50 times, although it depends on the desired molecular orientation and the accompanying effect of increasing the melting temperature.

Generally, it is preferable to carry out the stretching operation by two or more stages of stretching, with the first stage stretching at 80 to 120
The stretching operation is performed while extracting the diluent in the extruded product at a relatively low temperature of 120 to 160 °C.
It is preferable to carry out the stretching operation of the molded body at a temperature of .degree. C. and at a temperature higher than the first-stage stretching temperature.

In the case of uniaxial stretching, tension stretching may be performed between rollers having different circumferential speeds. The molecularly oriented molded product thus obtained can be heat-treated under restrictive conditions if desired. This heat treatment generally ranges from 140 to 18
1-20 at a temperature of 0°C, preferably 150-175°C.
It can be carried out for 3 to 10 minutes, preferably 3 to 10 minutes. The heat treatment further advances the crystallization of the oriented crystal parts, shifts the crystal melting temperature to a higher temperature side, improves the strength and elastic modulus, and further improves the creep resistance at high temperatures.

In the present invention, a racket string is formed from a filament-like molecularly oriented molded product of such an ultra-high molecular weight ethylene/α-olefin copolymer. Conventionally known methods are used to manufacture racket strings from filament-like molecularly oriented bodies.

[0053] In this case, the molecularly oriented ultra-high molecular weight ethylene/α-olefin copolymer has moderate elongation and high knot strength compared to the molecularly oriented ultra-high molecular weight polyethylene. , can be knitted in a wide range of ways.

[0054]

Effects of the Invention As described above, the present invention uses a racket string made of a molecularly oriented molded product of ultra-high molecular weight ethylene/α-olefin copolymer, so it has excellent creep resistance and weather resistance. Moreover, it also has excellent impact resistance and fatigue resistance.

Claims (3)

[Claims] Claim 1: The intrinsic viscosity [η] is at least 5 dl/
g, and the content of α-olefins having 3 or more carbon atoms is on average 0.1 to 20 per 1000 carbon atoms. Gut for. Claim 2: The α-olefin is butene-1,4-
The racket gut according to claim 1, which is methylpentene-1, hexene-1, octene-1 or decene-1. Claim 3: The α-olefin content is 10 carbon atoms.
The racket gut according to claim 1, wherein the number of strings per 00 pieces is 0.5 to 10 pieces on average.