JP2012075513A - Modified cross section monofilament and string for racket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modified cross section monofilament which has excellent durability and impact absorption property and is suitable for obtaining a string for a racket at a low cost, and a string for racket.SOLUTION: The monofilament has a modified cross section shape comprising a center component including a fiber axis and at least four protruding parts formed on the peripheral edge of the center component. In the modified cross section monofilament, the length (A) of a contact boundary between the center component and the protruding parts and the maximum diameter (B) of the protruding parts satisfy relation of an equation A/B≤0.6. The string for the racket at least partially uses the modified cross section monofilament.

Description

  The present invention relates to a modified cross-section monofilament and a racquet string, and more particularly, to a modified cross-section monofilament and a racquet string which are excellent in durability and shock absorption and suitable for obtaining a racquet string at low cost. Is.

Conventionally, animal-derived strings (so-called natural guts) have been mainly used in the racket sports field such as tennis, squash, badminton, etc., but in recent years, the amount of synthetic fiber strings (so-called synthetic guts) is increasing. .

  The racket string must be highly durable, inexpensive, highly repulsive, good hitting sound, low burden on the elbow of the player, and soft feel Various characteristics are demanded, and the synthetic fiber string has been studied to satisfy these required characteristics.

  Among them, with regard to high resilience, hitting sound, etc., a certain effect has been obtained by studying the physical properties of the filament (for example, see Patent Document 1). It is difficult to achieve the properties, and a method of improving durability by arranging filaments called skin yarns and / or side yarns around the monofilament is generally adopted. However, in order to improve durability with leather yarn and / or side yarn, it is necessary to add a production process and a fiber type to be used, and as a result, there is a problem that production cost increases.

A technique for obtaining a string for a racket having excellent durability without using a leather thread and / or a side thread is disclosed in Patent Document 2 with respect to the problem of the leather thread and / or the side thread.
That is, the paragraph [0015] of Patent Document 2 states that “... a cross section with a large degree of deformation has a structure with no voids in the central part and that the groove in the outer peripheral part has a narrow opening width and a high fiber ratio”. As described in paragraph [0016] of Patent Document 2, “a cross-sectional shape is a cross-section approximated to a string in which a plurality of monofilaments are wound with an adhesive and converged. The point that improves durability is that the portion corresponding to the adhesive surface is integrated, so the adhesive strength is strong.

  However, in the invention described in Patent Document 2, since the core yarn and the leather yarn in the conventional string are firmly integrated, the impact at the time of hitting is large, and the burden on the elbow of the player is large. In addition, the string described in Patent Document 2 in which the portions corresponding to the core yarn and the leather yarn are firmly integrated has improved durability in terms of structural destruction, but the string receives the impact received at the time of hitting the ball. In other words, the load of the filament itself is large, that is, the string physical property deteriorates with time, and the yarn is broken.

JP 2008-029734 A JP 2002-239035 A

  The present invention has been achieved as a result of studying the solution of the problems in the prior art described above as an issue.

  Accordingly, an object of the present invention is to provide a modified cross-section monofilament and a racket string that are excellent in durability and shock absorption and are suitable for obtaining a racket string at low cost.

  In order to achieve the above object, according to the present invention, there is provided a monofilament having an atypical cross-sectional shape comprising a central component including a fiber axis and at least four or more protrusions formed on the periphery of the central component. Provided is a modified monofilament monofilament characterized in that the contact interface length (A) between the central component and the protrusion and the maximum diameter (B) of the protrusion satisfy the relationship of formula A / B ≦ 0.6 Is done.

In the modified cross-section monofilament of the present invention,
At least a part of the central component and the protrusion is peeled off,
The maximum diameter of the protrusion is 0.05 to 0.4 times the maximum diameter of the central component;
It is preferable that the resin forming the protruding portion is different from the resin forming the central component and that the resin is twisted.

  In addition, the racket string of the present invention is characterized in that the above-mentioned deformed cross-section monofilament is used at least in part.

  According to the present invention, as described below, it is possible to obtain a modified cross-section monofilament and a racket string that are excellent in durability and shock absorption and are suitable for obtaining a racket string at low cost.

(A)-(d) is a cross-sectional schematic diagram which shows an example of the embodiment of the irregular cross-section monofilament of this invention. It is a cross-sectional schematic diagram explaining the interface component (A) of a center component and a projection part. (A)-(b) is a cross-sectional schematic diagram which shows an example of the interface peeling form of a projection part and a center component. It is explanatory drawing which shows an example of the manufacturing equipment of the irregular cross-section monofilament of this invention. (A)-(b) is a schematic diagram which shows an example of a nozzle | cap | die hole used in order to manufacture the irregular cross-section monofilament of this invention.

  Hereinafter, the present invention will be specifically described.

  The irregular cross-section monofilament of the present invention needs to have, in its cross section, a central component including a fiber axis and at least four, preferably ten or more protrusions formed on the periphery of the central component. is there. Here, when the number of protrusions is three or less, or when there are no protrusions, the protective effect of the central component by the protrusions is not exhibited, and the impact absorbability described later is insufficient. Therefore, it is not preferable.

  As shown in FIG. 1, the typical cross-sectional shape of the monofilament of the present invention is not limited to the shapes of the central component 1 and the protrusion 2 as long as the effects of the present invention are not impaired. The circle (a, d), the ellipse (b) or the polygon (c) shown in FIG. 1 is used, and the circle (a, b, c) or the polygon (d) shown in FIG. 1 is used as the protrusion. It can be illustrated. Moreover, as long as the effect of the present invention is not impaired, the central component and the protruding portion may be hollow or dumpling shaped irregular filaments.

As for the number of the protrusions 2, it is preferable that the center 1 is surrounded by the protrusions 2, that is, the number of the protrusions 2 is larger from the viewpoint of protection of the central component 1 and shock absorption. The number of the protrusions 2 may be set according to the diameter of the central part 1 and the diameter of the protrusions 2. For example, when the central component 1 is a circle with a radius R1 and the protrusion 2 is a circle with a radius R2, The obtained numerical value (rounded down after the decimal point) is the preferable upper limit of the protrusion 2.
{2 × (R1 + R2) × circumference} ÷ (2 × R2)

  In the modified cross-section monofilament of the present invention, the contact interface length (A) between the central component 1 and the protrusion 2 and the diameter of the protrusion (B) must satisfy the formula A / B ≦ 0.6. . At this time, the protrusion diameter (B) indicates the diameter of the longest portion in the protrusion section as shown in FIGS.

  Here, A / B is a value indicating the mobility of the protrusion arranged outside the central component, and the interface length (A) between the protrusion and the central component is relative to the diameter (B) of the protrusion. When it is small, the protrusion is easy to move around the central component. On the other hand, when (A) is large, the central component and the protrusion are firmly coupled.

  That is, the atypical cross-section monofilament of the present invention in which A / B ≦ 0.6 indicates that the protrusion is easy to move on the central component, and A / B ≦ 0.6, preferably A / B ≦ 0.55, more preferably A / B ≦ 0.35, in order to solve the two problems of the conventional string, the burden on the elbow of the player, and the deterioration of physical characteristics over time. It is an important point.

  Although the detailed mechanism by which the irregularly shaped monofilament of the present invention solves the above two problems simultaneously is not clear, the irregularly shaped monofilament satisfying A / B of 0.6 or less as in the present invention has a protrusion on the central component. Since the impact energy of the hit ball is dispersed by the movement of the protrusion, the burden on the elbow is reduced to the athlete, and the impact received by the monofilament by the hit ball is also reduced. It is thought that the physical property deterioration at the time can be suppressed.

  On the other hand, a monofilament with an irregular cross section with an A / B exceeding 0.6 cannot absorb and disperse impact energy such as a hit ball, so the burden on the player's elbow is heavy, and durability due to deterioration of physical characteristics over time Causes sex decline.

  In addition, A / B is preferably as small as possible from the viewpoint of shock absorption, but from the viewpoint of fiber production process and string production process passability, it is preferable that the central component and the protrusions maintain a certain level of bonding force, A specific A / B range is 0.01 or more, and a more preferable range is 0.15 or more.

  The diameter of the protrusion of the irregularly shaped monofilament of the present invention is preferably 0.05 to 0.4 times the maximum diameter of the central component, and more preferably 0.1 to 0.3 times. When the diameter of the protrusion satisfies the above range, it is possible to achieve both the spinning performance and the impact absorbing effect at an excellent level.

  In addition, what is necessary is just to change suitably according to uses, such as for badminton use, squash use, and tennis use, and the maximum diameter of the center component of the irregular cross-section monofilament of this invention can illustrate the range of 0.05-1.70 mm.

  The irregularly shaped monofilament of the present invention is preferably formed by peeling off at least a part of the protrusion and the central component. Atypical cross-section monofilaments having a small A / B, that is, with easy movement of the projections as in the present invention, may cause the projections to get caught in the production apparatus in the monofilament or string production process and deteriorate the process passability. For this reason, in the monofilament manufacturing process, A / B is 0.2, preferably 0.4, more preferably more than 0.6. After providing, it is preferable to peel off the interface between the central component and the protrusion as shown in FIG. 3 to obtain a desired A / B. Regarding the interface length to be peeled off, it is preferable that 20% or more of the interface between the central component and the protrusion is peeled off, and a more preferable range is 20 to 90%, and a further preferable range is 50 to 90%.

  The deformed cross-section monofilament of the present invention is preferably twisted, and a preferable twist number is 0.1 to 20.0 T / 10 cm, and a more preferable range is 0.5 to 10.0 T / 10 cm. The monofilament satisfying the number of twists has a protrusion portion spirally arranged around the central component by twisted yarn, and the convergence is improved, so that it is resistant to crushing by a hit ball and the like, and the durability of the irregular cross-section monofilament of the present invention It is possible to further improve the performance. The twisting may be carried out with a monofilament single wire, or a plurality of monofilaments may be twisted.

  The resin used for the modified cross-section monofilament of the present invention is not particularly limited, and as long as the present invention is satisfied, both the central component and the protrusion are aliphatic and / or aromatic polyester, aliphatic and / or aromatic. Normally known resins such as nylon, polyolefin, fluororesin and the like can be used. Further, if the effect of the present invention is not impaired, specifically 5% by weight or less, various kinds of resins can be blended. It can contain additives such as weathering agents, pigments, flame retardants, matting agents, lubricants, pigments and the like.

  As described above, the resin used in the modified monofilament of the present invention is not particularly limited, and the central component and the protrusion can be formed of the same resin, but the resin forming the protrusion is a resin that forms the central component. In the case of being different, it is possible to obtain a more versatile modified cross-section monofilament and string.

  For example, “By using a resin with a high initial elastic modulus, such as polyethylene terephthalate, as the central component and using a resin with a low initial elastic modulus, such as nylon, polybutylene terephthalate, polypropylene terephthalate, or elastomer, for the protrusion, high rebound and soft hitting `` To obtain a string with a high level of feeling '', `` If the center component is made of a resin with high breaking strength such as polyethylene terephthalate or nylon, and the protrusion is made of a low friction resin such as fluorine resin, it is fine. “To obtain a gauge and high-spin string”, “When a plant-derived resin such as polylactic acid resin is used as the central component, and a resin with excellent wear resistance such as nylon or fluorine-based resin is used for the protrusion. To obtain an environmentally friendly string with excellent durability, "or" the core component and / or protrusions Using a resin to obtain a lightweight string ”,“ A high specific gravity resin with a specific gravity of 1.5 or more containing a metal oxide or the like as the central component, and a polyamide or fluorine-based material different from the central component in the protrusion By using a resin or polyester resin, it is possible to obtain a string that is easy to swing out and has excellent wear resistance. Further, by using an incompatible resin for the protrusion and the central component, it is possible to facilitate the interfacial peeling between the protrusion and the central component.

  However, from the viewpoint of durability, processability, and economy, it is possible to use nylon 6, nylon 66, polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polyolefin resin as the central component, and nylon 6, Nylon 66, polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polyolefin, and fluorine resin are preferably used.

  The deformed cross-sectional monofilament of the present invention preferably has a strength of 2.5 to 8 cN / dtex, and a more preferable range is exemplified by a range of 3.2 to 6.0 cN / dtex. When the strength satisfies the above range, it is possible to obtain a monofilament having the strength required as a string with good spinning properties.

  The fracture elongation of the modified cross-section monofilament of the present invention is preferably 16 to 45%. When the breaking elongation satisfies the above range, it is possible to obtain a monofilament having a good shot feeling when formed into a string and good stretchability. On the other hand, when the elongation at break is less than 16%, there is a problem that a play portion is small when a string made of a monofilament having a modified cross section of the present invention is stretched on a racket, and the target tension and actual tension at the time of tension are different. This causes a problem that it is difficult to tie the racket. Further, when the elongation at break exceeds 45%, vibration at the time of hitting the ball is large, and the hit feeling may be inferior.

  The racket string of the present invention needs to use at least a part of the above-mentioned modified cross-section monofilament of the present invention. By using the modified cross-section monofilament of the present invention, as described above, durability and impact absorption can be simultaneously achieved. A satisfactory string can be obtained.

  The racket string using the modified monofilament monofilament of the present invention has a great durability improvement effect, so there is no need to use a core yarn protecting component such as leather, and the string manufacturing cost can be greatly reduced. It also has a feature that can be simplified. Moreover, since the racket string of the present invention has a long life, the load on the environment is small.

  The structure of the racket string of the present invention is not particularly limited, and a protective component such as leather may be wound or a coating layer may be provided as necessary for further improving durability. When a protective component such as leather is used, conventionally known fibers such as multifilaments, monofilaments, spun yarns, and film yarns can be used as the protective component. In addition, the material used for the protective component and the coating layer is not particularly limited, and may be aliphatic and / or aromatic polyester, aliphatic and / or aromatic polyamide, polyolefin, etc., as long as the effects of the present invention are not impaired. Usually known resins can be used. In addition, the material used for the protective component and the coating layer may be a different resin or various weathering agents as long as the effect of the present invention is not impaired, specifically, 5% by weight or less based on the total amount of the filament and the additive. , Pigments, flame retardants, matting agents, lubricants, pigments and other additives. The single yarn cross section of the protective component filament may be a round cross section as well as an irregular 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 a combination thereof. However, the present invention is not limited to this.

The strength of the racket string of the present invention is not particularly limited, and may be appropriately changed depending on the target competition, but is generally designed to be 300 to 800 N / mm ² .

Although the tension of the racket string of the present invention to the racket has an optimum value depending on the competition to be used, in order to obtain the above-mentioned effect of the string of the present invention to the maximum, a tension of 70 to 400 N / mm ² is used. It is preferable to stretch. If the tension is less than 70N / mm ² is resilience, will racket inferior in hitting sound due tension is too low, if the tension設張force exceeds 400 N / mm ² is contained in the string tension is too high There is a possibility that the mobility of the monofilament protrusions to be reduced is reduced, and the effect of the modified cross-section monofilament of the present invention cannot be maximized.

  Next, taking a tennis string as an example, an example of a method for manufacturing a modified cross-section monofilament of the present invention (hereinafter sometimes simply referred to as a monofilament) and a racket string will be described with reference to FIG. The method is not limited to this.

  The monofilament of the present invention can be obtained by a melt spinning method in which melt-spun unstretched monofilaments are cooled and then stretched between rollers. In order to obtain a high-strength monofilament, it is preferable to employ a multistage drawing method, and the number of drawing stages is preferably 2 to 4 from the viewpoint of increasing the strength of the monofilament and simplifying the equipment. Hereinafter, a production method by the melt spinning two-stage drawing method will be described.

  The raw material resin used for melt spinning is supplied from the raw material storage hopper 4 shown in the figure to the extruder 5, and the moisture content of this raw material resin is controlled by the generation of bubbles during melting, and when using a polyester raw material, it is hydrolyzed. From the viewpoint of suppression, it is preferably 0 to 200 ppm. The moisture content may be measured by a generally known method. For example, it can be measured by a coulometric titration method using a Karl Fischer moisture meter (AQ-2100) manufactured by Hiranuma Sangyo Co., Ltd.

  There is no particular rule on the method of melting the raw material resin, and it may be melted using a pressure melter, an extruder or the like. The melting temperature may be appropriately changed depending on the raw material type, but in FIG. 4, a uniaxial extruder 5 is used. Usually, from the viewpoint of melt moldability and suppression of thermal decomposition, it is usually set in the range of melting point + 10 ° C. to melting point + 60 ° C. of the raw material resin.

  The molten resin passes through the gear pump 6 and is removed from the nozzle holes illustrated in FIG. The shape and size of the pores may be appropriately changed according to the melt viscosity of the resin, the target monofilament diameter, and the like. Needless to say, the design is such that the discharge pressure of the protrusions is higher than the discharge pressure of the central component, and the pore length / hole diameter of the pores discharging the protrusions is the fineness of discharging the central component. It is preferably larger than the hole length / hole diameter.

  Although the detailed reason is unknown, since the discharge pressure of the resin forming the protrusion is increased, the measurement property of the protrusion resin is improved and the bending / deformation of the unstretched monofilament is suppressed, and the hole This may be because the elastic energy received by the polymer when flowing into the die hole due to the large length / hole diameter is easily relaxed in the die hole, and the swelling immediately after the discharge of the polymer forming the protrusion is reduced.

  A heating cylinder can be installed just below the spinneret 8 as necessary. By passing the spun monofilament through a heating cylinder kept at 200 to 300 ° C., the orientation of the discharged monofilament is relaxed, and a monofilament having uniform physical properties can be obtained with good stretchability.

  The discharged monofilament is then cooled and solidified in a cooling bath 9 filled with a solvent having a glass transition temperature or lower of the discharged resin. There is no particular rule on the type of the solvent, and examples of the cooling solvent include water and polyethylene glycol.

  At this time, in order to obtain the monofilament of the present invention, it is necessary to set the distance from the spinneret surface to the cooling bath 9 to 1 to 10 cm. When the distance to the cooling bath 9 exceeds 10 cm, a lot of microcrystals are generated in the discharged resin and not only the stretchability is deteriorated, but also the peelability between the central component and the protruding portion may be deteriorated. On the other hand, when the distance to the cooling bath 9 is less than 1 cm, the cooling in the air layer is insufficient and the cooling solvent bumps, making it difficult to obtain a monofilament having a desired cross section.

  Next, the cooled and solidified unstretched monofilament is taken up by the first GR10. The surface speed of the first GR10 may be set according to the spinnability of the resin to be spun, but is usually set in the range of 1 to 50 m / min.

  The unstretched monofilament taken up at the above-mentioned speed is subjected to a stretching process after being wound up or continuously without being wound up. That is, in the case of the two-stage stretching method, the first stage stretching is performed between the first GR10 and the second GR11, and then the second stage stretching is performed between the second GR11 and the third GR12. The monofilament after stretching is taken up by the winder 15 after removing the strain generated in the stretching process by the relaxation heat treatment performed between the third GR 12 and the fourth GR 13.

  The method for applying heat to the monofilament during the stretching and relaxation treatment is not particularly limited, and may be appropriately selected from a heating roll, dry hot air, steam, a heating medium bath, etc. depending on the resin type and monofilament diameter. In FIG. 4, a dry oven 14 with a lid is disposed between the GRs.

  Moreover, although it can change suitably also with respect to the resin kind to be used regarding the heat amount provided at the time of extending | stretching and a relaxation | loosening process, it is preferable to set it as the range of glass transition temperature-melting | fusing point +20 degreeC of resin at the time of an extending | stretching process and a relaxation | loosening process.

  Furthermore, it is preferable that the monofilament of the present invention is provided with 0.1 to 1.5% by weight of an oil agent during the production of the monofilament from the viewpoint of improving process passability and removing static electricity. If the amount of oil adhesion is less than 0.1% by weight, the effect of imparting the oil agent is hardly exhibited. On the other hand, if the amount of oil agent adhesion exceeds 1.5% by weight, the guide of the next process etc. is soiled and the process passability deteriorates There is a possibility to make it.

  Next, a method for forming the peeling portion 3 (see FIG. 3) by peeling off the interface between the central component 1 and the protrusion 2 in the monofilament cross section will be described.

  As a first method, a method of applying a physical external force such as compression, striking, bending, and twisting directly to a monofilament or after processing to a string will be exemplified. Specifically, the monofilament after spinning is moved between two rollers that rotate at the same speed, and the monofilament is pressed against a square bar or a round bar so that the bending angle of the monofilament is about 20 to 60 °. What is necessary is just to employ a method of applying pressure to the string from the top. In addition, when the method is used, cracks on the monofilament surface and significant physical property degradation occur, the resin of the central component and the protruding portion is used so that peeling easily occurs due to physical external force. Incompatibility is preferred. As a combination of incompatible resins, when one resin selected from polyamide, polyester, polyolefin, and fluororesin is used as the central component, the central component of polyamide, polyester, polyolefin, and fluororesin is used as the protrusion resin. Resins other than those used in the above may be used. A combination of polyester and polyamide is most preferable from the viewpoint of processability and production cost.

  As a second method, the surface of the protrusion and / or the central component is eluted with a solvent, that is, the difference in the solubility of the resin used for the protrusion or the central component in the specific solvent is used to determine the protrusion or the central component. A method for elution of either or both of the above and peeling the interface is illustrated. The solvent to be eluted may be appropriately selected depending on the type of resin used, and formic acid and sulfuric acid can be exemplified as a solvent for eluting polyamide, and an aqueous sodium hydroxide solution can be exemplified as a solvent for eluting polyester. According to the second method, interfacial peeling can be caused without causing cracks or the like in the central component or the protrusion. Specifically, in the case of a modified cross-section monofilament using a polyester resin for the central component and / or the protrusion, it may be treated with a 5% aqueous sodium hydroxide solution at a temperature of 70 ° C. for 10 minutes and then repeatedly washed with pure water.

  As a third method, a method of peeling the interface between the protrusion and the central component in the yarn forming process is exemplified. Specifically, after heat-treating the monofilament subjected to stretching of about 30% of the total stretching ratio in the first stage of the multi-stage stretching process at the crystallization temperature of the resin forming the central component and / or the protrusion, ± 20 ° C. A method of performing the second stage stretching can be exemplified. Although the mechanism by which the central component and the protrusion are easily peeled by the third method is not clear, either the central component or the protrusion is sufficiently crystallized, and the other is not sufficiently caused to crystallize. It is considered that a difference occurs in the stretchability of the film, and the central component and the protrusion are peeled off during the stretching, relaxation, and winding processes.

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

  Next, a method for obtaining the string of the present invention will be described.

  The string of the present invention can be obtained by twisting the monofilament of the present invention as necessary, winding a protective component such as leather, and coating with a resin. When arranging the leather thread on the monofilament of the present invention, it is also possible to fix the protective component and the monofilament as the core component with an adhesive as necessary. Examples of the method for arranging the leather include braiding and winding, and examples of the resin coating method include a dipping method and a melt coating method. Furthermore, it is preferable to perform a tension or relaxation heat treatment in the string manufacturing process in order to adjust the string physical properties.

  Further, as described above, the interface between the central component of the monofilament of the present invention and the protrusion can be peeled off in the string manufacturing process.

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

  Hereinafter, embodiments of the present invention will be described in more detail by way of examples. In addition, the definition and the measuring method of the characteristic used for the specification text and the Example are as follows.

  [Central Component Diameter and Protrusion Diameter]: Using a microscope VHX-500 manufactured by Keyence Corporation, the diameter of the central component and the longest portion of the protrusion was defined as the central component diameter and the protrusion diameter, respectively. The measurement magnification may be appropriately changed depending on the sample size.

  [Interface length between central component and protrusion]: Measured using a microscope VHX-500 manufactured by Keyence Corporation. 2 and 3, the length of the straight line connecting the contact end point from the contact start point of the central component and the protrusion is defined as the interface length.

  [Break strength and elongation of monofilament]: Tensile tester manufactured by Orientec Co., Ltd., tensile test was performed according to the method of JIS L1013 under the conditions of a test length of 250 mm and a tensile speed of 300 mm / min. Further, the breaking strength and breaking elongation were determined. According to JIS L1013, fineness measurement was performed using a METTLER AE240 manufactured by Siebel Machinery Co., Ltd. The breaking strength was obtained by dividing the obtained breaking strength by the fineness. Each sample was measured five times, and the average value was obtained.

[Spinning property]: Evaluated based on the number of yarn breaks per 10,000 m of the length of the yarn when continuous spinning was performed.
A: Excellent in productivity (number of yarn breaks <0.01 times / 10,000 m)
○: Excellent in productivity (number of yarn breaks = 0.01 to 0.05 times / 10,000 m)
Δ: Stable production possible (number of yarn breaks = 0.05 to 0.2 times / 10,000m)
×: Stable production is not possible (number of yarn breaks> 0.2 times / 10,000m)

[String productivity]: Evaluated by the number of yarn breaks per 10,000 m of processing length when continuous production was performed.
A: Excellent in productivity (number of yarn breakage <0.01 times / 10,000 m)
○: Excellent productivity (number of yarn breaks = 0.01 to 0.03 times / 10,000 m)
Δ: Stable production possible (number of yarn breaks> 0.03-0.05 times / 10,000 m)
×: Stable production is not possible (number of yarn breaks> 0.05 times / 10,000 m)

[Monitor test]: A two-hour actual hit test on the feel at impact was conducted by three athletes with a 10-year history and two athletes with an 8-year calendar. Each person made the following five-step evaluation with the hit feeling when using the string using the normal round cross section yarn described in Comparative Example 1 as three points, and the average was used as the monitor test result. The score was calculated to one decimal place by rounding off.
5: very soft, 4: soft, 3: normal, 2: hard, 1: very hard

  [Durability test]: Trial hits (2 hours / day) were performed by 3 athletes with 10 years of competition and 2 athletes with 8 years of competition calendar, and the number of days until the string was broken was measured. In addition, a trial was performed twice per person for each sample, and a relative comparison was performed when the number of days until the string of Comparative Example 1 made of a normal round cross-section monofilament broke was “1”. The numerical value was calculated to the first decimal place by rounding off the score, and the average value of 5 athletes was used as the test result.

(Production example)
[String Manufacturing Method] Amylan T-100L (manufactured by Toray Industries, Inc.) melted at 220 ° C. was coated by a melt dipping method on a monofilament in a state where a stretch of 1.02 times was applied. The coated filament was heat set in a state where a stretch of 1.05 times was applied in a 230 ° C. dry heat oven, followed by 1% relaxation treatment in a 230 ° C. dry heat oven to obtain a diameter of 1.33 mm. Got the string.

  [Stretching method of string on racket]: A string was stretched on a racket (Six.One BLX 105 manufactured by Wilson) using an electric string machine manufactured by TOALSON.

Example 1
A polyethylene terephthalate resin (J055 manufactured by Mitsui Chemicals, Inc.) was dried with a vacuum dryer at 110 ° C. so that the moisture content was 60 ± 30 ppm, and then a uniaxial extruder with a diameter of 30 mm (L / D = 25) (center) For components) and fed to a two-component composite melt spinning apparatus having a uniaxial extruder (for projections) of φ25 mm (L / D = 25) and melted at a spinning temperature of 285 ° C.

  The melted resin is weighed with a gear pump so that the center component after stretching and the diameter of the protrusions are as shown in Table 1, and then filtered through a 50 μm metal nonwoven fabric filter in a spinning pack, and then spun from the die shown in FIG. I put it out. The distance between the central component discharge hole and the protrusion discharge hole was designed to be the interface length shown in Table 1.

  The spun strand was cooled and solidified with cold water at 10 ° C., and then taken up by the first GR rotating at a surface speed of 8 m / min by the first roller to obtain an unstretched filament. The unstretched monofilament taken up was continuously stretched between the first GR and the second GR without being wound once, and then stretched at the second stage between the second GR and the third GR. At this time, for the first stage stretching and the second stage stretching, dry ovens with lids of 100 ° C. and 225 ° C. were used, respectively, and the first stage and second stage stretching ratios were set to 3 respectively. Stretched at 5 times and 1.5 times.

  The drawn filament was subjected to a relaxation heat treatment of 0.95 times between the third GR and the fourth GR, and then wound up with a winder. In addition, the heat processing used the dry oven with a lid | cover of 250 degreeC. Table 1 shows the physical properties of the obtained monofilament.

  Table 1 shows the string productivity when a string is manufactured using the obtained filament according to the above-described string manufacturing method. The obtained string was stretched with the tension shown in Table 1 according to the above-described stretching method. Table 1 shows the string evaluation results using the obtained racket.

(Example 2)
The same procedure as in Example 1 was performed except that polybutylene terephthalate resin (hereinafter referred to as PBT) was used as the resin for forming the protrusions, and the melting temperature of the protrusion extruder was 270 ° C. As PBT, Toraycon 1200S manufactured by Toray Industries, Inc. was used and dried with a vacuum dryer at 100 ° C. so that the moisture content was 100 ± 30 ppm. Table 1 shows the properties of the obtained monofilament, string productivity, and string evaluation results after racquet stretching.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the resin was not supplied to the protrusion extruder. Table 2 shows the characteristics of the obtained monofilament, string productivity, and string evaluation results after racquet stretching.

(Examples 3 to 10, Comparative Example 2, Comparative Example 3)
The same procedure as in Example 1 was performed except that a polyamide resin (hereinafter referred to as PA) was used as a resin for forming the protrusions, and the melting temperature of the protrusion extruder was 280 ° C. As PA, a blend of 70% by weight of nylon 6 / nylon 66 copolymer chip (M6241 manufactured by Toray Industries, Inc.) and 30% by weight of homonylon 6 chip (M1021 manufactured by Toray Industries, Inc.) was used. It dried with the vacuum dryer so that the moisture content might be set to 100 +/- 30 ppm. Table 1 or 2 shows the characteristics of the obtained monofilament, string productivity, and string evaluation results after racquet stretching.

  As is clear from Tables 1 and 2, the monofilaments and strings of Comparative Examples 1 to 3 in which the number of protrusions and A / B were outside the scope of the present invention were low in durability and had poor monitor evaluation results. On the other hand, the monofilament of the present invention satisfies not only the yarn-making property and process passability, but also a soft feel at impact and excellent durability at the same time.

  Moreover, in the monitor test, there was a comment that the strings of Example 2 and Example 3 were better in catching balls than the string of Example 1. This is thought to be because the resin used for the monofilament protrusions constituting the strings of Example 2 and Example 3 is more easily crushed than the resin of Example 1.

(Example 11)
The same procedure as in Example 2 was performed, except that the obtained monofilament was twisted at 8 T / 10 cm using a ring twisting machine. Table 3 shows the properties of the obtained monofilament, string productivity, and string evaluation results after racquet stretching.

(Example 12)
After spinning, the monofilament was dissolved in 98% sulfuric acid in a state wound on a metal bobbin until the protrusion diameter shown in Table 3 was reached, then washed with running water and dried at room temperature for 2 days. Performed as in Example 3. Table 3 shows the properties of the obtained monofilament, string productivity, and string evaluation results after racquet stretching.

  As is apparent from Table 3, the filaments from which the central component and the protrusions were peeled off by twisting or solvent treatment, and the strings using the filaments were excellent in string productivity as well as filament production, In addition, the shot feeling and durability were excellent.

  The deformed cross-section monofilament and the racket string of the present invention are obtained with high productivity and have excellent shock absorption, so that the burden on the elbow of the player is small compared to conventional strings. Have. In addition, the string of the present invention has durability that can withstand practical use even when there is no leather that has been used as a string protecting component in conventional strings, and therefore, any string such as tennis, badminton, squash, soft tennis, etc. Applicable to the racket sports field.

1: Central component of irregular cross-section monofilament 2: Projection part of monofilament monofilament 3: Central component and separation part of projection part 4: Raw material storage hopper 5: Single shaft extruder 6: Gear pump 7: Spin pack 8: Base 9: Cooling Bath 10: 1st GR
11: Second GR
12: 3rd GR
13: 4th GR
14: Dry oven with lid 15: Winder 16: Central component discharge hole 17: Projection discharge hole A: Interface length B: Projection diameter

Claims (6)

A monofilament having an atypical cross-sectional shape including a central component including a fiber axis and at least four or more protrusions formed on the periphery of the center component, and a contact interface length between the central component and the protrusion ( A) and the maximum diameter (B) of the protrusion satisfy the relationship of the formula A / B ≦ 0.6. The deformed cross-sectional monofilament according to claim 1, wherein at least a part of the central component and the protrusion is peeled off. The deformed cross-section monofilament according to claim 1 or 2, wherein the maximum diameter of the protrusion is 0.05 to 0.4 times the maximum diameter of the central component. The deformed cross-sectional monofilament according to any one of claims 1 to 3, wherein a resin forming the protrusion is different from a resin forming the central component. The irregular cross-section monofilament according to any one of claims 1 to 4, wherein the monofilament is twisted. A racket string, wherein the irregularly shaped monofilament according to any one of claims 1 to 5 is used at least in part.

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