JP2006345924A - String - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide strings capable of being not only turned to a narrow gauge but also spread on a racket by high tension since strength per unit cross sectional area is high. <P>SOLUTION: The strings are composed by arranging at at least a part of core yarn of polyhexamethylene adipamide multifilaments, 95 mol% or more of which is composed of a hexamethylene adipamide unit and whose strength is 9-12 cN/dtex, fracture elongation is 16-24%, single yarn fineness is 1-20 dtex, the number of interengagements (CN value) is 5-40 and amorphous molecular orientation degree (fa) is 0.72-0.9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a string suitably used for racket applications such as tennis, squash, badminton and the like. More specifically, the present invention relates to a string that can be tensioned to a racket with high tension as well as being capable of making a fine gauge because of its high strength per unit cross-sectional area.

  In recent years, in the field of racket sports such as tennis, squash, badminton, and the like, synthetic fiber strings are generally used in place of animal fiber strings (so-called natural gut) because of the advantage of being inexpensive and excellent in durability.

  One of the required properties required for synthetic fiber strings is fine gauge. In other words, the fine gauge of the strings is a factor that reduces air resistance and reduces the weight of the string during the player's racket swing. .

  In recent years, the ball and shuttle firing speeds have been dramatically improved with the improvement of athlete technology. Depending on the player's playing style, especially in the badminton field, it is required to string the racket with the highest possible tension in order to improve the response from the collision of the shuttle or other strings to the launch. Therefore, there is a demand for a string having a high strength per unit cross-sectional area that can withstand such a high tension.

  Conventionally, various proposals have been made for the purpose of obtaining a string that satisfies the above-mentioned required characteristics. For example, a high-strength string can be obtained by using a so-called super fiber called a super-high-strength and high-modulus fiber. A technique (for example, see Patent Document 1) has been proposed. According to this technique, strings having high strength can be obtained by using super fibers, but the price of super fibers is high. There was a problem that the price of the strings to be raised. Also, because super fibers have low elongation, strings made using super fibers have low elongation, so there is little playable part of the strings when stringing the racket, and the tension applied when the racket is stretched There was a problem that the actual tension was different from that of the actual rack, and a problem that it was difficult to tie after being stretched on the racket.

  Further, a string core fiber is a core-sheath composite monofilament, and a resin having a lower elastic modulus than that of the core part is used for the sheath part of the sheath composite monofilament (see, for example, Patent Document 2). According to this technology, it is possible to obtain a string that satisfies the linear tensile strength and knot tensile strength in a balanced manner, but the monofilament composite fiber increases the price of the monofilament. In addition to having a problem, there were many concerns that the yarn-making property would be deteriorated due to complex abnormality or the like, and fiber diameter unevenness would occur.

In addition, the technique (for example, refer patent document 3) which uses a polyamide fiber for a string is already known, In this technique, "The polyamide type synthetic fiber used for a string is 5g / strength from a durable viewpoint. It is disclosed that the elongation is preferably about 10 to 30% for d or more. However, this technology does not suggest the use of ultra-high strength fibers, and the strength of polyamide fibers that are usually used in practice is at most 8.5 g / d (7.5 cN / dtex), generally high strength. Even in such a case, it was about 8.5 cN / dtex, and it did not satisfy the sufficient strength for tensioning the racket with high tension.
JP-A-6-238016 Japanese Patent Laid-Open No. 6-238017 JP-A-9-251936

The present invention has been achieved as a result of studying the solution of the above-described problems in the prior art, and is a string suitable for tennis, squash, and badminton applications, and has high strength per unit cross-sectional area. The object is to provide strings that can be gauged and can be stretched with high tension on a racket.

  In order to achieve the above object, according to the present invention, 95 mol% or more is composed of hexamethylene adipamide units, the strength is 9 to 12 cN / dtex, the breaking elongation is 16 to 24%, and the single yarn fineness is 1 to 1. A polyhexamethylene adipamide multifilament having 20 dtex, an entanglement number (CN value) of 5 to 40, and an amorphous molecular orientation degree (fa) of 0.72 to 0.9 is arranged on at least a part of the core yarn. A string is provided.

In the strings of the present invention,
At least the core yarn and the side yarn arranged around the core yarn are resin-coated,
A preferred condition is that at least two core yarns are combined.

  According to the present invention, as described below, since the strength per unit cross-sectional area is high, it is possible not only to make a fine gauge, but also to obtain a string that can be stretched to a racket with high tension. The strings can be particularly suitably used as advanced strings.

  The present invention will be specifically described below.

  The strings of the present invention require that polyhexamethylene adipamide multifilaments comprising at least 95 mol% of hexamethylene adipamide units be used as at least a part of the core yarn.

  By using polyhexamethylene adipamide, which is a general-purpose resin, not only can strings be produced at low cost, but also high strength and wear resistance can be achieved by making 95 mol% or more hexamethylene adipamide units. Excellent strings can be obtained.

  The polyhexamethylene adipamide used in the present invention may contain a copolymer component as long as it is less than 5%. If the hexamethylene adipamide unit is less than 95 mol%, polyhexamethylene adipamide The crystallinity in the mid-multifilament is lowered, making it difficult to obtain high-strength strings. Examples of the copolymer component include ε-capramide, tetramethylene adipamide, hexamethylene sebacamide, hexamethylene isophthalamide, tetramethylene terephthalamide, and xylylene phthalamide.

  The polyhexamethylene adipamide multifilament according to the present invention preferably contains a copper compound in the amount of copper metal in an amount of 10 to 500 ppm, and more preferably in a range of 50 to 100 ppm. By making the amount of copper metal within the above range, excellent weather resistance and heat resistance are exhibited in actual use. Examples of the copper compound include copper iodide, copper chloride, copper bromide and the like, but are not limited thereto, and conventionally known inorganic and organic copper salts and simple copper metal can be used. . In addition to the copper compound, the polyhexamethylene adipamide multifilament may contain other heat-resistant agents such as an amine compound, a mercapto compound, a phosphorus compound, and a hindered phenol compound.

  The sulfuric acid relative viscosity of the polyhexamethylene adipamide multifilament is preferably 3 to 5.5, more preferably 3.5 to 5. When the relative viscosity of sulfuric acid is less than 3, high-strength polyhexamethylene adipamide multifilament tends not to be stably obtained. On the other hand, when the relative viscosity of sulfuric acid exceeds 5.5, the viscosity is too high, and it may be difficult to obtain a polyhexamethylene adipamide multifilament with good yarn production.

  The polyhexamethylene adipamide multifilament for strings of the present invention has a degree not impairing the effects of the present invention, specifically, 5% by weight or less, different polymers, various light-proofing agents, pigments, flame retardants, You may contain additives, such as a matting agent, a lubricant, and a pigment. Further, the single filament cross section of the multifilament may be an irregular cross section other than the round cross section, and the irregular cross sectional shape may be a flat type, a triangular type, a C type, a Y type, a dumpling type, a hollow type, or those Combinations and the like can be exemplified, but are not limited thereto.

  The strength of the polyhexamethylene adipamide multifilament for strings needs to be 9 to 12 cN / dtex, preferably 9.5 to 12 cN / dtex. The strength of nylon fibers used in ordinary strings is at most about 8.5 g / d (7.5 cN / dtex), and generally about 8.5 cN / dtex even when the strength is high. A polyhexamethylene adipamide multifilament for strings having a strength exceeding 9 cN / dtex and a string for rackets using the same have never existed, and a polyhexamethylene adipamide multifilament of 9 cN / dtex or more as in the present invention By arranging the in the core yarn, it is possible to obtain a string for a racket having a high strength per unit cross-sectional area and capable of being made into a fine gauge. When the strength is less than 9 cN / dtex, it is difficult to obtain high-strength strings per unit cross-sectional area targeted by the present invention. Moreover, it is difficult to obtain a polyhexamethylene adipamide multifilament having a strength of 12 cN / dtex or more with high productivity with the current technology.

  The breaking elongation of the polyhexamethylene adipamide multifilament needs to be 16 to 24%, preferably 16 to 22%. When the elongation at break is less than 16%, the play portion is small when the string is stretched to the racket, and the tension applied during the tension is different from the actual tension, or when the string is stretched There is a problem that it is difficult to tie. Further, when the elongation at break exceeds 24%, it is difficult to obtain a polyhexamethylene adipamide multifilament having a strength exceeding 9 cN / dtex. This is not preferable.

  The polyhexamethylene adipamide multifilament needs to have a single yarn fineness of 1 to 20 dtex. If the single yarn fineness is less than 1 dtex, the single yarn fineness is too thin, the strength per single yarn is insufficient, and the process passability deteriorates in the string manufacturing process. Also, when the single yarn fineness exceeds 20 dtex, uniform cooling during spinning and uniform drawing are difficult, and not only the yarn-making property is deteriorated, but also polyhexamethylene adipamide multifilament with single yarn fineness exceeding 20 dtex is used as the string core. When arranged on the yarn, the durability of the strings is reduced. That is, when the single yarn fineness exceeds 20 dtex, there is a concern that the fatigue properties of the strings are deteriorated because the outer portion of the portion subjected to the bending of each single yarn and the inner portion of the single yarn are greatly bent. The single yarn fineness is preferably in the range of 1 to 15 dtex, more preferably in the range of 1 to 10 dtex.

  The total fineness of the polyhexamethylene adipamide multifilament is preferably 420 to 3600 dtex. When the total fineness is less than 420 dtex, there is a problem in that the productivity at the time of producing the polyhexamethylene adipamide multifilament is poor and the cost increases. When the total fineness exceeds 3600 dtex, the polyhexamethylene adipamide has a problem. In the cooling step of the pamide multifilament manufacturing process, uniform cooling is difficult to obtain, and it is difficult to obtain polyhexamethylene adipamide multifilaments with good yarn forming properties.

  The polyhexamethylene adipamide multifilament needs to have an entanglement number (CN value) of 5 to 40. When the CN value is less than 5, not only the filaments are not well-converged, but there is a problem that the single yarn is caught on the apparatus in the string manufacturing process, and the single yarn is exposed on the string surface, so that the productivity is deteriorated. There is a risk. In addition, when trying to entangle the CN value exceeding 40, the single yarn appears on the surface of the multifilament as a loop, and there is a risk that the string productivity deteriorates as in the case where the number of entanglement is small. ing.

Entanglement can be imparted by injecting high-pressure air in a direction substantially perpendicular to the running yarn in the entanglement imparting device immediately before winding the yarn during spinning of polyhexamethylene adipamide multifilament. . Not determined particularly in air pressure in this ^case, but can be exemplified range of ^{0.5kg / cm 2 ~4.5kg / cm 2} .

  The degree of amorphous molecular orientation (fa) of the polyhexamethylene adipamide multifilament used for the strings needs to be 0.72 to 0.9, preferably 0.75 to 0.85. The degree of amorphous molecular orientation (fa) indicates the orientation of tie molecules connecting crystal molecules in polyhexamethylene adipamide multifilament, and the degree of amorphous molecular orientation (fa) is less than 0.7. When adipamide multifilaments are used for strings, it is difficult to obtain high-strength strings because the orientation of tie molecules in polyhexamethylene adipamide multifilaments is poor. Moreover, it is difficult to obtain a polyhexamethylene adipamide multifilament having an amorphous molecular orientation altitude of more than 0.9 with good spinning properties.

  In the strings of the present invention, it is necessary to arrange the polyhexamethylene adipamide multifilament at least in a part of the core yarn. By using the above-described polyhexamethylene adipamide multifilament, it is possible to obtain a string having high strength per unit area and good processability.

  Moreover, it is preferable that the boiling water shrinkage rate of the polyhexamethylene adipamide multifilament used for the strings of the present invention is 2 to 5%. The strings have an opportunity to be heated during the melting dip of the coating resin in the manufacturing process. When the boiling water shrinkage rate satisfies the above range, it is preferable because the dimensional change of the strings when subjected to heating is small. On the other hand, when the boiling water shrinkage rate exceeds 5%, since the shrinkage during heating is large, there is a possibility that only strings with poor quality can be obtained. In addition, it is difficult to obtain a polyhexamethylene adipamide multifilament having a boiling water shrinkage of less than 2% at low cost and with good yarn production.

  The strings of the present invention are preferably composed of a core yarn, a side yarn, and a coating resin. In addition to the core yarn mainly responsible for strength, it is composed of side yarns that protect the core yarns, and coating resin that covers and protects the side yarns and adjusts friction, so that strings that satisfy durability and high strength in a well-balanced manner Can be obtained.

  The type of side yarn is not particularly limited. As the resin used, known resins such as aromatic polyester, aliphatic polyester, polyamide, aramid, and polyolefin can be used, and as the form, known fibers such as multifilament, monofilament, spun yarn, slit yarn are used. Can do. Moreover, in order to adjust the thickness of the strings, the thickness and processing form of the fibers used can be freely changed, and a layer made of fibers or resin may be provided on the outer layer of the side yarn.

  The core yarn and / or the side yarn may be impregnated with an adhesive or the like, and the side yarn and the core yarn may be bonded with an adhesive.

  The strings of the present invention are not particularly defined as to the coating resin to be used. As the coating resin, not only synthetic resins such as polyamide, polyester, and polyurethane, but natural resins may be used, and additives such as different polymers, various light-proofing agents, pigments, matting agents, lubricants, pigments and the like may be used. It may be contained.

  The present invention does not lose its effect due to the string diameter, and the thickness may be appropriately changed according to the application.

  The string core yarn is preferably twisted. By twisting, the convergence property of the multifilament is improved and the process passability is stabilized. As long as the effect of the present invention is not impaired, the number of twists is not particularly limited. For example, a range of 10 to 1000 T / m can be exemplified.

  Furthermore, the string core yarn of the present invention is preferably formed by combining at least two polyhexamethylene adipamide multifilaments. Examples of the method of combining yarns include a method of twisting a plurality of polyhexamethylene adipamide multifilaments while aligning them. By twisting multiple polyhexamethylene adipamide multifilaments, not only the convergence is further improved, but also the fine irregularities between the multifilaments formed by the twisting cause friction between the strings and the ball or shuttle. Higher, so-called hooked strings. There is no particular upper limit to the number of polyhexamethylene adipamide multifilaments to be combined, but in consideration of productivity, it is preferably 10 or less.

  Although an example of the manufacturing method of the polyhexamethylene adipamide multifilament for strings is shown below, a manufacturing method is not restricted to this.

  In the strings of the present invention, the polyhexamethylene adipamide multifilament used for the core yarn is obtained by cooling and solidifying the melt-spun yarn and then applying an oil agent and stretching the yarn between rollers. In order to obtain a high-strength fiber as in the present invention, it is preferable to employ a 3-5 multistage drawing method.

  The polyhexamethylene adipamide polymer used in the production of the polyhexamethylene adipamide multifilament of the present invention is preferably a high viscosity polymer having a relative viscosity of 3 to 5. When the relative viscosity of sulfuric acid is less than 3, the molecular weight of the polymer is low, and a high-strength polyhexamethylene adipamide multifilament cannot be obtained stably. On the other hand, when the relative viscosity of sulfuric acid exceeds 5, the melt viscosity is too high, and it is difficult to obtain polyhexamethylene adipamide multifilaments with good spinning properties.

  The water content of the polymer used for melt spinning is preferably 0 to 200 ppm.

  The spinning temperature can be changed depending on the presence or absence of a copolymer component, but is usually set to 250 to 300 ° C.

  Immediately below the spinneret, the upper end is 0 to 15 cm from the spinneret surface, and a range of 5 to 100 cm from the upper end is surrounded by a heating tube and / or a heat insulating tube, and the spinning yarn is placed in a high temperature atmosphere of 200 to 280 ° C. Passing through is a preferred form. The orientation of the spun yarn is relaxed by slow cooling through the high temperature atmosphere surrounded by the heating tube and / or the heat insulation tube without immediately cooling the spun yarn, and the molecular orientation between the single fibers Since the uniformity can be improved, the strength of the polyhexamethylene adipamide multifilament can be increased. On the other hand, if it cools immediately without letting it pass in a high temperature atmosphere, the orientation of an undrawn yarn will increase and the orientation degree distribution between single fibers will become large. When such an undrawn yarn is heat-drawn, there is a possibility that a polyhexamethylene adipamide multifilament having high strength and excellent heat resistance may not be obtained as a result.

  The unstretched yarn that has passed through the high temperature atmosphere is then preferably cooled and solidified by blowing air at 10 to 100 ° C., preferably 10 to 75 ° C. When the cooling air is less than 10 ° C., a large cooling device is required separately from the normal device, which is not preferable. Further, when the cooling air exceeds 100 ° C., the single fiber sway during spinning becomes large, so that the single fibers collide with each other, and it becomes difficult to produce the fibers with good yarn forming properties. The air cooling device may be a horizontal blowing type or an annular blowing type.

  The oil agent is then applied to the cooled and solidified unstretched yarn. The oil agent is preferably a non-aqueous oil agent containing a smoothing agent as a main component and containing a surfactant, an antistatic agent, an extreme pressure agent component and the like.

  The unstretched yarn to which the oil is applied is wound around a take-up roller (1FR) and taken up. The surface speed of 1FR, that is, the take-up speed is preferably 300 m / min or more, more preferably 500 m / min or more. If the take-up speed is less than 300 m / min, the production efficiency is low and it is difficult to adopt. Although there is no particular upper limit to the take-up speed, the take-up speed is preferably 2000 m / min or less for industrially stable production.

  The undrawn yarn taken up at the take-up speed is drawn after being wound once or continuously without being taken up. A Nelson type roller having two rollers as one unit includes a yarn feeding roller (2FR), a first stretching roller (1DR), a second stretching roller (2DR), a third stretching roller (3DR), and a relaxation roller (RR). ) Are arranged side by side, and the yarn is sequentially wound around these rollers to perform a drawing heat treatment. Usually, stretching is performed between 1FR and 2FR to focus the yarn. A preferable stretch ratio is 1 to 7%, and more preferably 1 to 5%.

  Stretching is performed between 2FR and 1DR, between 1DR and 2DR, and between 2DR and 3DR. At this time, in the stretching between 2FR and 1DR, it is preferable that the draw point, that is, the point where the yarn is sharply thinned by the stretching does not exist on 2FR. The draw point is more preferably within 10 cm from the 2FR exit. By setting the position of the draw point within the above range, it is possible to obtain a high-strength polyhexamethylene adipamide multifilament. The position of the draw point can be adjusted by changing the draw ratio, roller temperature, and roller surface friction according to the degree of orientation of the fiber.

  The first stage of stretching is performed between 2FR and 1DR, the temperature of 2FR is 30-80 ° C, the temperature of 1DR is 80-150 ° C, and the total number of stretching stages is three, the first stage draw ratio is It is set to 20 to 90%, preferably 20 to 50% of the total draw ratio.

  The second stage stretching is performed between 1DR and 2DR, but the 2DR temperature is preferably 180 to 240 ° C. In the case of three-stage stretching, the remaining stretching ratio is divided into two stages. The temperature of 3DR when performing three-stage stretching is preferably 180 to 250 ° C. The finished yarn is subjected to a relaxation treatment of 0 to 5% between 3DR and RR, and then wound up by a winder. By the relaxation treatment, not only the strain caused by the thermal stretching can be removed, but also the highly oriented structure achieved by the stretching can be fixed, the orientation of the amorphous region can be relaxed, and the thermal shrinkage rate can be lowered. RR uses a non-heated roller or a roller heated to 160 ° C. or less. Usually, RR becomes a temperature of 90 to 150 ° C. regardless of the presence or absence of heating due to the heat brought in by the yarn heated at the time of hot drawing.

  Next, the string manufacturing method of the present invention will be described by taking badminton strings as an example, but the string manufacturing method is not limited to this.

  First, a polyhexamethylene adipamide multifilament satisfying the above properties is twisted to obtain a core yarn. At this time, the number of polyhexamethylene adipamide multifilaments to be used may be adjusted so that the fineness required for the core yarn is obtained, and twisting may be performed while combining the yarns as necessary. At this time, the core yarn may be impregnated with an adhesive or the like, but it is preferable not to impregnate the core yarn with an adhesive or the like in order to improve the durability of the strings.

  Next, side yarn is arranged on the obtained core yarn, and resin coating is applied. When arranging the side yarn on the core yarn, the side yarn can be fixed with an adhesive as necessary. The side yarn to be used is not limited, and a plurality of types of fibers may be used, or the side yarns to be used may be arranged in a plurality of layers depending on the thickness of the strings that require the side yarn to be used. . Moreover, as a method for arranging the side yarns, a known method such as braiding or winding can be employed. Examples of the resin coating method include a dipping method and a melt coating method.

  Thus, the strings of the present invention can be obtained.

  Hereinafter, embodiments of the present invention will be described in more detail by way of examples. The definition and measurement method of the characteristics used in the specification text and examples are as follows.

[Relative viscosity]:
1 g of a sample was dissolved in 100 ml of 98% sulfuric acid and measured at 25 ° C. with an Ostwald viscometer. The average value of the number of executions 2 times was used.

[Multifilament fineness]:
It was measured according to JIS L1090.

[Single yarn fineness]:
A value obtained by dividing the fineness measured according to JIS L1090 by the number of single fibers constituting the fiber was adopted.

[Fiber strength and elongation]:
It measured by the method of JIS L1013. Using a Tensilon tensile tester manufactured by Orientec Co., Ltd., measurement was performed under the conditions of a test length of 250 mm and a tensile speed of 300 mm / min. Each sample was measured 5 times, and the average value was obtained.

[Boiling water shrinkage]:
The sample is allowed to stand for 24 hours in the air at a temperature of 20 ° C. and a humidity of 65% without tension, and the length when measured under a load of 0.1 g / d is defined as L1. The measured sample was treated in boiling water for 30 minutes, left unattended in air at a temperature of 20 ° C. and a humidity of 65% for 4 hours, and then measured at a load of 0.1 g / d as L2. It was determined according to the following formula.
Boiling water shrinkage = (L1-L2) / L1 × 100
Note that an average value of two trials was adopted.

[Amorphous molecular ash direction (fa)]:
Using the crystallinity, birefringence, and crystal orientation obtained from the density, the following R.D. S. Stein et al. Polymer Sci. , 21, 381, (1956).
Δ = XfcΔ0c + (1-X) faΔ0a
Here, Δ = birefringence, X: crystallinity, fc: crystal orientation, fa: amorphous molecular orientation, Δ0c: intrinsic birefringence of crystal part, Δ0a: intrinsic birefringence of amorphous part, (Δ0c = Δ0a = 0.73)

[Birefringence]:
Using a POH polarizing microscope manufactured by Nihon Kogyo Kogyo Co., Ltd., the measurement was performed by the Belek Compensator method. In addition, the value employ | adopted the average value of 5 times of trials.

[Crystal orientation (fc)]:
Using an X-ray generator (4036A2 type) manufactured by Rigaku Denki Co., Ltd., measurement was performed using CuKα (using a Ni filter) as a radiation source (output 35 KV, 15 mA, slit 2 mmφ). It calculated | required using the following formula from the half value width H ° of the intensity distribution obtained by scanning the (100) plane observed in the vicinity of 2Θ = 20.6 ° in the circumferential direction.
fc = (180 ° −H °) / 180 °

[density]:
It was measured at 25 ° C. by a density gradient tube method using toluene as a light liquid and carbon tetrachloride as a heavy liquid. An average value of 5 trials was adopted.

[Polyhexamethylene adipamide multifilament spinning]:
The evaluation was made in the following three stages from the occurrence of yarn breakage and fluff when continuous spinning was performed.
○: Good and stable long-time yarn production is possible. Fluff incidence is less than 1 / 10,000m,
Δ: Unstable. Fluff incidence is 1 / 10,000m or more,
×: Many yarn breaks occur, making long-time yarn production difficult.

[Draw Point]:
Using a laser Doppler velocimeter (LS-50M, manufactured by TSI), the yarn speed from 2FR to 1DR was measured, and the point at which the speed rapidly increased to near the 1DR surface speed was taken as the draw point.

[Number of confounding (CN value)]:
Noncontact optical measurement was performed using EIB-E manufactured by LAWSON-HEMPHILL. The measurement was carried out at a speed of 100 m / min by adjusting the hysteresis brake roll of the apparatus and the plate tensioner of the yarn feeding unit so that the tension at the CCD camera unit was 0.04 ± 0.01 cN / dtex. In the measurement, the number of entanglements per meter was measured continuously for 100 m, that is, the average value was determined as the number of entanglements from the result of measuring the number of entanglements of N = 100.

[Strings productivity]:
The following two stages were evaluated from the situation when continuous production was performed.
○: Stable production for a long time is possible.
X: The rejected product rate is high due to the fact that multifilament loops and fluff are exposed on the surface.

[Strong string for racket]:
Using a Tensilon tensile tester manufactured by Orientec Co., Ltd., measurement was performed under the conditions of a test length of 250 mm and a tensile speed of 300 mm / min. Each sample was measured 5 times, and the average value was obtained.

[Example 1]
(Method for producing polyhexamethylene adipamide multifilament)
A polyhexamethylene adipamide polymer having a relative viscosity of 3.9 was melt-spun at 280 ° C. using an extruder-type spinning machine. The molten polymer was weighed with a gear pump so as to have a fineness of 1050 dtex, filtered through a 20 μm metal nonwoven fabric filter in a spinning pack, and spun from a 210-hole die with a hole diameter of 0.3φ. A 15 cm heating cylinder and a 15 cm heat insulating cylinder were attached 3 cm below the base surface, and heated so that the in-cylinder atmosphere temperature was 250 ° C. Here, the in-cylinder atmosphere temperature is an air layer temperature in a central portion of the heating cylinder length and a portion 1 cm away from the inner wall.

  An annular blow-off chimney was attached immediately below the heating cylinder, and cold air of 30 ° C. was blown onto the yarn at a rate of 35 m / min to cool and solidify, and then an oil agent was applied to the yarn.

Two unstretched yarns provided with an oil agent were combined, wound around 1FR rotating at a surface speed of 370 m / min, and then drawn at 5.95 times. The take-up yarn was stretched 5% continuously between the take-up roller and 2FR without being wound once, and subsequently subjected to three-stage heat drawing and wound at a speed of 2200 m / min. 1FR was unheated, 2FR was 60 ° C, 1DR was 115 ° C, 2DR was 200 ° C, 3DR was 210 ° C, and RR was unheated. The number of times the yarn was wound around the roller was 3, 4, 4, 4, 5, and 4, respectively. An entanglement imparting nozzle was installed between the RR and the winder to entangle the fibers. Entangling was performed by injecting ² kg / cm ² of high-pressure air in a direction substantially perpendicular to the running yarn in the entanglement imparting device to obtain a polyhexamethylene adipamide multifilament. The obtained fiber properties were evaluated and shown in Table 1. The first stage draw ratio was 40% of the total draw ratio, the second stage draw ratio was 35%, and the third stage draw ratio was set to 25%.

(Side yarn manufacturing method)
A polyhexamethylene adipamide polymer having a relative viscosity of 3.5 was melt-spun at 280 ° C. with an extruder-type spinning machine. The molten polymer was weighed by a gear pump, and the spun yarn melt-extruded from a nozzle having a discharge hole diameter of 0.25 mm was immediately introduced into a 75 ° C. cooling water bath. The unstretched yarn after cooling was taken up at 40 m / min, and then steam-stretched by 5.5 times between rollers without being wound once, and a polyhexamethylene adipamide monofilament having an average wire diameter of 60 μm was spun at a speed of 200 m. Winded up at / min. The linear strength of the obtained monofilament was 2.3N.

(Strings manufacturing method)
The above-mentioned polyhexamethylene adipamide multifilament is wound in a spiral shape with 16 polyhexamethylene adipamide monofilaments as side threads on a core yarn twisted at 200 T / m while combining two yarns. After fixing with a phenol aqueous solution adhesive, the polycapramide resin was coated by a melt dipping method to obtain strings having a diameter of 0.7 mm. The physical properties of the obtained strings were evaluated and shown in Table 1.

[Example 2]
The same procedure as in Example 1 was performed except that the discharge amount was adjusted so that the fineness was 525 dtex during spinning of the polyhexamethylene adipamide multifilament and the total draw ratio was 6.8 times. The RR speed is fixed, and the stretching ratio in each stretching step is the same as in Example 1.

[Example 3]
A polyhexamethylene adipamide multifilament was spun at the time of spinning using a 140-hole die, the discharge amount was adjusted so that the fineness was 2100 dtex, and the total draw ratio was 5.7 times, The same operation as in Example 1 was performed. The RR speed is fixed, and the stretching ratio in each stretching step is the same as in Example 1.

[Example 4]
When spinning the polyhexamethylene adipamide multifilament, it was carried out in the same manner as in Example 1 except that 1 kg / cm ² of high-pressure air was injected in a direction substantially perpendicular to the running yarn in the entanglement device.

[Example 5]
When spinning polyhexamethylene adipamide multifilament, it was carried out in the same manner as in Example 1 except that 3.5 kg / cm ² of high-pressure air was injected in a direction substantially perpendicular to the running yarn in the entanglement device. .

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the total draw ratio was 5.1 times during spinning of the polyhexamethylene adipamide multifilament. The RR speed is fixed, and the stretching ratio in each stretching step is the same as in Example 1.

[Comparative Example 2]
When spinning the polyhexamethylene adipamide multifilament, it was carried out in the same manner as in Example 1 except that 0.2 kg / cm ² of high-pressure air was injected in a direction substantially perpendicular to the running yarn in the entanglement device. .

[Comparative Example 3]
When polyhexamethylene adipamide multifilament was spun, it was carried out in the same manner as in Example 1 except that 5 kg / cm ² of high-pressure air was injected in a direction substantially perpendicular to the running yarn in the entanglement device.

[Comparative Example 4]
The same procedure as in Example 1 was performed except that an 84-hole die was used during spinning of polyhexamethylene adipamide multifilament and the discharge amount was adjusted to 2100 dtex.

[Comparative Example 5]
The same procedure as in Example 1 was performed except that the total draw ratio was 7.3 times during spinning of the polyhexamethylene adipamide multifilament. The RR speed is fixed, and the stretching ratio in each stretching step is the same as in Example 1. In this case, there was a strong tendency to break the yarn, making it impossible to produce a multifilament.

  Using these polyhexamethylene adipamide multifilaments obtained in Examples 2 to 5 and Comparative Examples 1 to 4, strings were produced in the same manner as in Example 1, and the physical properties of the obtained strings were evaluated. The results are also shown in Table 1.

  As is apparent from Table 1, the polyhexamethylene adipamide multifilament and strings for strings of the present invention can be produced with very high productivity.

  In addition, the strings of the present invention have a higher strength per unit cross-sectional area than the strings of Comparative Example 1 as the prior art, so that the racket can be stretched with a high tension, and a high resilience and a play speed. In addition to the improvement, it is possible to make a fine gauge when obtaining a string having the desired strength.

  On the other hand, when the CN value is out of the range of the present invention as in Comparative Example 2 or Comparative Example 3, even when the fiber strength satisfies the range of the present invention, the process passability in the strings manufacturing process is high. Deteriorating, it is impossible to obtain strings with good productivity.

  In addition, when the single yarn fineness is outside the range of the present invention as in Comparative Example 4, it is difficult to obtain polyhexamethylene adipamide multifilaments with good yarn production properties, and fluff generated in the yarn production process is also difficult. Because of this, the productivity of strings was also bad.

  When trying to obtain a polyhexamethylene adipamide multifilament having a strength exceeding 12 cN / dtex as in Comparative Example 5, it is difficult to stably sample the polyhexamethylene adipamide multifilament. there were.

  In addition, the strings obtained in Examples 1 to 3 were subjected to trial hitting by an advanced player with a competition history of 20 years. As a result, the strings of the polyhexamethylene adipamide multifilaments in descending order, that is, the strings of Example 2 were used. It was evaluated that the hit feeling was excellent in the order of the strings of Example 1 and the strings of Example 3.

  The string of the present invention has the advantage that it can be made fine gauge because of its high strength per unit cross-sectional area, and it can be stretched on a racket with high tension. It can be used suitably for rackets such as tennis, squash, badminton, etc.

Claims (3)

95 mol% or more is composed of hexamethylene adipamide units, the strength is 9-12 cN / dtex, the elongation at break is 16-24%, the single yarn fineness is 1-20 dtex, the number of entanglements (CN value) is 5-40, A string formed by arranging polyhexamethylene adipamide multifilament having an amorphous molecular orientation degree (fa) of 0.72 to 0.9 on at least a part of a core yarn. The strings according to claim 2, wherein at least the core yarn and side yarns arranged around the core yarn are resin-coated. The strings according to claim 1 or 2, wherein at least two core yarns are combined.