WO2018207418A1

WO2018207418A1 - Racket string and production method therefor

Info

Publication number: WO2018207418A1
Application number: PCT/JP2018/004719
Authority: WO
Inventors: 海江田佳; 坂本樹; 大原淑行
Original assignee: 株式会社ゴーセン
Priority date: 2017-05-09
Filing date: 2018-02-09
Publication date: 2018-11-15
Also published as: TW201900249A; JP2018187163A

Abstract

This racket string comprises a core yarn 2, sheath yarns 4 provided outside same, and a surface resin layer 5 provided outside same. The core yarn 2 and sheath yarns 4 are integrated by fusion-bonding a hot-melt thread 3 interposed on the surface of the core yarn 2. The resin in the surface resin layer 5 is a solvent-free thermoplastic resin. The surface resin layer 5 has, on the surface thereof, protrusions and recesses formed along the sheath yarns 4. The sheath yarns 4 are preferably braids or wrap yarns. The difference in height between the protrusions and recesses on the surface of the surface resin layer 5 is preferably within the range of 1-100 µm. On the above basis is provided a racket string which has a low friction resistance and high durability.

Description

Racket string and manufacturing method thereof

The present invention relates to a synthetic string for rackets such as badminton, tennis and squash. In particular, the present invention relates to a racket string having a low frictional resistance suitable for badminton and high durability.

Conventionally, as a synthetic string for rackets such as tennis, badminton, squash, etc., many strings or braided strings made by winding the outer monofilament or multifilament with a thin monofilament have been proposed. For example, in a badminton string, a string in which thin monofilaments having a diameter of about 0.06 to 0.07 mm are braided (stringed) as a multi-filament at the core is generally used. Thin strings generally have a problem that they are excellent in feel and sound but inferior in durability, and development of a string that satisfies both is desired.

Patent Documents

1 and 2 propose coating a resin solution dissolved in a solvent as a surface resin. Patent Document 3 proposes electron beam crosslinking of the surface resin.

JP 2005-304678 A Japanese Patent No. 5593005 JP 7-148285 A

However, the methods of

Patent Documents

1 and 2 for coating a resin solution dissolved in a solvent as a surface resin have a problem in terms of environment because of the use of a solvent, and also have a problem that the surface is smooth and the frictional resistance value is increased. Further, the electron beam cross-linking method of the surface resin disclosed in Patent Document 3 has a problem that the surface is smooth and the frictional resistance value is increased. When the frictional resistance value is high, when the shuttlecock or the ball is hit with a racket in which the string is stretched, it is worn by friction between the strings, and the durability is lowered.

The present invention provides a string for a racket having a low frictional resistance value and high durability in order to solve the conventional problems.

The racquet string of the present invention is a racquet string including a core yarn, a sheath yarn outside the core yarn, and a surface resin layer outside the sheath yarn, wherein the core yarn and the sheath yarn are core yarns. It is integrated by fusing hot melt yarn interposed on the surface, the resin of the surface resin layer is a thermoplastic resin that does not contain a solvent, and the surface of the surface resin layer has an uneven shape along the sheath yarn Is formed.

The method for producing a string for a racket according to the present invention is a method for producing the above-described string for a racket, wherein a hot melt yarn is wound around a core yarn, and a sheath yarn is wound or wound around the surface of the core yarn. Heating to a temperature equal to or higher than the melting point, melting the hot melt yarn to thermally bond and integrate the core yarn and sheath yarn, and extruding a thermoplastic resin free of solvent outside the sheath yarn in a molten state Forming a surface resin layer, and then performing a surface treatment at a temperature equal to or higher than the melting point of the surface resin layer.

In the present invention, the surface of the surface resin layer has a rugged shape formed along the sheath yarn, so that the racquet string has a low frictional resistance value and high durability. In the method of the present invention, a thermoplastic resin that does not contain a solvent is extruded outside the sheath yarn in a molten state to form a surface resin layer, and then surface treatment (annealing treatment) at a temperature equal to or higher than the melting point of the surface resin layer. As a result, the surface resin is softened or melted to form a concavo-convex shape along the sheath yarn, crystallized upon cooling to become a glossy surface, the surface resin surface has a low frictional resistance value and high durability It can be a racket string. As a result, a tension loss when the string is stretched on the racket is small, a relatively hard feel and a comfortable hitting sound can be obtained at the time of hitting the ball, and a highly durable racket string can be provided.

FIG. 1 is an exploded perspective view of a racket string in one embodiment of the present invention. 2A-C are cross-sectional views of a flat monofilament in one embodiment of the present invention. FIG. 3 is a schematic explanatory view of the orthogonal friction test apparatus used in the embodiment of the present invention. FIG. 4A is a schematic perspective view of a friction test apparatus on a string stretched on a racket used in the embodiment of the present invention, and FIG. 4B is a cross-sectional view thereof. FIG. 5 is an exploded perspective view of a racket string in a comparative example. FIG. 6 is a friction force comparison graph between Example 1 and Comparative Example 1 of the present invention.

The string for a racket according to the present invention includes a core yarn, a sheath yarn outside the core yarn, and a surface resin layer outside the sheath yarn. The core yarn and the sheath yarn are integrated by fusing hot melt yarn interposed on the surface of the core yarn. The resin of the surface resin layer is a thermoplastic resin that does not contain a solvent, and the surface of the surface resin layer has an uneven shape along the sheath yarn. This unevenness is a surface treatment (annealing treatment) at a temperature equal to or higher than the melting point of the surface resin layer, so that the surface resin is softened or melted and partially soaked into the sheath yarn, resulting in an uneven shape along the sheath yarn. It is.

The sheath yarn is preferably braided yarn or wound yarn. Among these, when the surface resin is softened or melted, the braided yarn partially soaks into the sheath yarn, and a clear uneven shape tends to appear along the braided yarn. In the case of a wound yarn, it may be S twist or Z twist, or S twist and Z twist.

The surface of the surface resin layer preferably has a gloss. The glossiness is because the surface resin is crystallized, and heat treatment to such an extent that the surface resin is crystallized is preferable.

The resin of the surface resin layer is preferably at least one selected from nylon resin and polyurethane resin. This is because nylon resin and polyurethane resin have good adhesion to the sheath yarn and are difficult to peel off.

The uneven shape on the surface of the surface resin layer is preferably such that the difference in height of the unevenness is 1 to 100 μm, more preferably 2 to 50 μm, particularly preferably 3 to 30 μm. With this degree of unevenness, the frictional resistance is low.

The abundance of the surface resin layer is preferably in the range of 5 to 22% by mass when the string is 100% by mass. More preferably, it is in the range of 5 to 15% by mass. If it is the said range, protection of a core yarn and a sheath yarn can fully be performed.

The hot melt yarn is preferably a flat monofilament yarn. Racket string.

The manufacturing method of the string for rackets of this invention includes the following processes.
(1) A process in which hot melt yarn is wound around a core yarn, and sheath yarn is wound or wound around the surface (string yarn assembling step).
(2) A process of heating to a temperature equal to or higher than the melting point of the hot melt yarn to melt the hot melt yarn and thermally bonding and integrating the core yarn and the sheath yarn (first heat treatment step)
(3) A step of extruding a thermoplastic resin not containing a solvent outside the sheath yarn in a molten state to form a surface resin layer (extrusion step)
(4) Thereafter, surface treatment at a temperature equal to or higher than the melting point of the surface resin layer (second heat treatment step)

The temperature of the surface treatment is preferably in the range of the melting point (Tm ° C.) of the surface resin layer to Tm + 25 ° C., more preferably in the range of Tm ° C. to Tm + 15 ° C. If it is the said temperature range, surface resin will soften or fuse | melt, it will soak in part in a sheath thread, and will become uneven | corrugated shape along a sheath thread.

An embodiment of the present invention is a braided string racket string including a core yarn, an outer sheath braid and an outer surface resin layer, and a hot melt flat monofilament is spirally formed on the core yarn. The core yarn and the sheath braid are integrated by thermal bonding. The proportion of the flat monofilament is preferably in the range of 2 to 12% by mass when the string mass is 100% by mass. More preferably, it is 2.5 to 8% by mass. If it is the said range, a thin and highly powerful string can be obtained.

In this embodiment, it is preferable that, in addition to heat bonding and integration of the core yarn and the sheath braid, the outer sheath braid is partially fused to each other by melting the flat monofilament. . As a result, the sheath braids are also bonded to each other, so that the hitting sound and the durability can be improved.

The melting points of the core yarn, the sheath braid and the flat monofilament are preferably represented by the following formula. With the following formula, it is possible to prevent a decrease in strength of the core yarn and the sheath braid when the flat monofilament is thermally melted, and to obtain a thin and high-strength string.
TM3 <TM2 ≦ TM1
However, TM1: melting point of core yarn, TM2: melting point of sheath braid, TM3: melting point of flat monofilament.

In one embodiment of the present invention, a hot-melt flat monofilament is spirally wound around a core yarn, a sheath braid is formed on the surface of the core yarn, and the obtained string is used as a flat monofilament. Heating to a temperature equal to or higher than the melting point (TM3), the core yarn and the sheath braid are integrated by thermal bonding by melting the flat monofilament. The temperature for thermal bonding is preferably TM3 + 30 ° C. or higher and TM2 + 15 ° C. or lower. More preferably, the temperature is TM3 + 40 ° C. or higher and TM2 + 10 ° C. or lower. If it is the said range, a core thread and a sheath part braid can be heat-bonded, and also a sheath part braid can be partly melted.

The draw ratio of the string yarn during heat bonding is preferably 0.95 to 1.20 times. A more preferable draw ratio is 1.00 to 1.10 times. When heat-bonding at the above draw ratio, heat shrinkage can be prevented under tension, and a thin and high-strength string can be obtained.

The thickness of the flat monofilament is preferably 0.015 to 0.06 mm, more preferably 0.02 to 0.05 mm. The flatness (width / thickness) of the flat monofilament is preferably 1.5 to 100, more preferably 2.5 to 80. If the thickness and flatness of the flat monofilament are within the above ranges, the core yarn and the sheath braid can be thermally bonded and the sheath braid can be partially fused.

In order to wind a flat monofilament spirally around the surface of the core yarn, the following precautions are necessary.
(1) When producing a flat monofilament, it is wound without being twisted with a horizontal winder, and when it is wound around a core yarn, it is pulled out from the horizontal wound body so that no twist is generated.
(2) When a flat monofilament is manufactured, if it is wound by a vertical winder, the winding is twisted, and when winding around the core yarn, it is pulled out from the wound body in the same direction and no twisting is entered. Like that.

The coverage of the flat monofilament wound around the core yarn on the surface of the core yarn is preferably 15 to 70%, more preferably 20 to 50%. Within this range, the core yarn and the sheath braid can be thermally bonded and the sheath braid can be partially fused.

The cross-sectional shape of the flat monofilament wound around the core yarn is preferably a flat shape having irregularities. If the cross-sectional shape is uneven, when the sheath monofilament is laced from the flat monofilament wrapped around the core yarn, friction can be generated to produce a strong string, and the adhesive strength can be increased with a small amount. is there.

The core yarn material is not particularly limited, but is preferably a high-strength polyamide filament yarn. Polyamides include nylon 6, nylon 66, nylon 610, nylon 612, nylon 46, nylon 56, nylon 410, nylon 12 and other aliphatic polyamide resins, nylon 9T, nylon MXD6, nylon 6T and other semi-aromatic polyamide resins. Is mentioned. Particularly preferred are high-strength multifilament yarns of nylon 6 and nylon 66. High-strength polyamide yarns are generally known for industrial materials such as tire cords.

The preferred single yarn fineness of the core yarn is 2 to 10 decitex, and the total fineness is 1500 to 7000 decitex. The preferred number of filaments constituting the core yarn is 150-3500.

When the melting point of the core yarn is TM1, TM1 is preferably 170 ° C. or higher, more preferably 200 ° C. or higher. In the present invention, the melting point is a value indicated by a peak temperature when measured with a differential scanning calorimeter (DSC) at a heating rate of 20 ° C./min. The physical properties of the core yarn greatly affect the physical properties of the string. A preferred multifilament has a strength of 5.0 to 12.0 cN / decitex and an elongation of about 16 to 25%. The core yarn can be used together or mixed with other filaments as required.

The core yarn is preferably twisted and used in view of the bundle bundle's converging property, roundness, elongation, etc., and the twist number is preferably about 30 to 300 times / m. Resin processing may be performed with an adhesive resin in order to enhance the adhesion between the core yarns and to impart an appropriate hardness to the core yarns. Moreover, a low-melting-point heat-adhesive fiber can be mixed with the core yarn.

As the sheath braid (melting point: TM2), a filament made of a resin having a melting point which is preferably the same as or lower than the melting point of the core yarn and higher than the low melting point resin wound around the core is used. As the material, the same polyamide-based resin as that of the core yarn is preferably exemplified. Examples thereof include aliphatic polyamides such as nylon 6, nylon 66, nylon 610, nylon 612, nylon 46, nylon 56, nylon 410, nylon 11, and nylon 12. These copolyamides are preferably used. When the core yarn component is nylon 66 or nylon 6, nylon 6, nylon 6/66 copolymer, nylon 6/12 copolymer or the like is used as a preferable sheath braid. Further, it may be a filament obtained by blending about 5 to 80% of copolymer nylon having a low melting point with nylon 6.

As the sheath braid, it is preferable that the single yarn fineness is larger than the single filament fineness of the multifilament of the core yarn, and it is preferable to use one monofilament or a filament in which about 2 to 4 monofilaments are arranged as the braid. When the single yarn fineness is too thick or the number of filaments is too large, the diameter after stringing becomes large, which is not preferable. Moreover, the cross-sectional shape of a filament can use an ellipse or a flat cross section. A connected cross-section filament disclosed in Japanese Patent Application Laid-Open No. 2008-48867 filed by the present applicant is also preferably used. The preferred single yarn fineness of the sheath braid is about 10 to 100 decitex. It is preferable to use 8 to 32 braids of this single yarn fineness to form a string to form a sheath.

ホット A hot melt type flat monofilament is wound around the outside of the core yarn in a spiral, and then the sheath braid is made. A known method can be adopted for the string making. For example, it is preferable to use a 16-placing machine. The step of winding the flat monofilament and the step of forming the sheath braiding may be separate steps or may be continued.

As the hot-melt type flat monofilament, a material having a lower melting point than that of the filament yarn of the core yarn and the sheath braid and having good adhesion to the constituent filament fiber of the core yarn and the braid of the sheath portion is preferably used. A preferable melting point (TM3) is 100 ° C. to 180 ° C., and a resin having a melting point lower than that of a resin of TM3 <TM2 ≦ TM1, that is, a core yarn fiber and a sheath braided fiber is selected. Examples of such resins include copolymerized polyamide resins and polyurethane resins obtained by copolymerizing two or more selected from aliphatic nylons such as nylon 6, nylon 66, nylon 12, nylon 11, nylon 610, and nylon 612. Can be mentioned. More preferably, the resin is lower by 30 ° C. or more than the melting point of the sheath braided fiber. Specifically, nylon 6/12, nylon 6/66/610, nylon 6/66/12, nylon 6/12/610, nylon 6/12/612, nylon 12/612, nylon 6/66/610/12 Nylon 6/66/610/612 copolymer and the like can be mentioned, but the copolymer is not limited to these, and can be appropriately selected from known copolymer nylon as a heat-fusible resin and a heat-fusible fiber.

According to the study by the present inventors, in order to obtain a durable string even when the feel and sound are fine, the amount and the applied state of the adhesive component are important as described above, and sufficient adhesiveness is obtained. It is important to reduce the applied amount as much as possible while applying the. For this reason, a flat monofilament is used as the form of the material to be wound. In the case of a multi-fragment with a large number of filaments, it is difficult to uniformly control the thickness and width of the yarn in the wound state, and it is not preferable because a portion having a large string diameter or a void is formed.

The preferred single yarn fineness of the flat monofilament is 10 to 150 decitex. A more preferable single yarn fineness is 20 to 100 decitex. A flat monofilament is preferably wound spirally around a core thread, but a plurality of bobbins may be used for winding.

After melting the flat monofilament, the core yarn and the sheath braid are heat bonded and integrated, and then a surface resin layer is formed on the outside of the sheath braid. The surface resin layer is formed by dipping or melt coating a nylon resin dissolved in a solvent. Nylon resin is not particularly limited, but aliphatic polyamides such as nylon 6, nylon 66, nylon 46, nylon 610, nylon 612, nylon 11 and nylon 12, and their copolyamides and semi-aromatic polyamides such as nylon 9T can be used. . Dipping or coating can improve color, appearance, durability, and the like. Furthermore, coloring, heat treatment, printing, oiling and the like can be performed as necessary.

Next, explanation will be made with reference to the drawings. FIG. 1 is an exploded perspective view of a racket string 1 according to an embodiment of the present invention. In the racket string 1, a hot-melt flat monofilament 3 is spirally wound around a core yarn 2, and the core yarn 2 and the sheath braid 4 are integrated by thermal bonding. For the sake of clarity, FIG. 1 shows the shape of the three flat monofilaments before melting. A surface resin layer 5 is formed on the surface of the sheath braid 4. The surface resin layer 5 is partially immersed in the sheath braid 4 and has an uneven shape along the sheath thread.

In FIG. 1, the core yarn 2 is an example of a multifilament, but it may be a monofilament. The number of multifilaments can also be arbitrarily selected. The sheath braiding 4 is an example of a 4-connected monofilament having a circular cross section, but it may be 2-8 connected. Alternatively, 2 to 4 monofilaments may be arranged in parallel.

In the present invention, the flat monofilament is preferably at least one selected from a shape in which a plurality of cross-sectional circles are connected in a row, a concavo-convex shape in which a plurality of cross-sectional circles are connected and the surface is smooth, and an oval shape. For example, the cross-sectional shape shown in FIGS. 2A-C. FIG. 2A shows a flat monofilament 6 having five cross-sectional circles connected, and the flatness L / D is about 5. FIG. However, L shows a width | variety and D shows thickness. For example, L = 0.165 mm and D = 0.035 mm. FIG. 2B shows a flat monofilament 7 having an uneven surface. FIG. 2C shows an oblong flat monofilament 8 having no irregularities on the surface.

FIG. 5 is an exploded perspective view of the racket string in the comparative example. The difference from FIG. 1 is that the surface of the surface resin layer 5 is smooth.

Hereinafter, a specific description will be given using examples. In addition, this invention is not limited to the following Example. In the following Examples, monofilaments and strings were evaluated by the following methods.

<Physical property test>
Strength, knot strength, and elongation were in accordance with the measurement method of JIS L1013. The diameter was measured five times using a micrometer while rotating the monofilament little by little, and the average value was taken as the diameter.

<Friction Test 1> Orthogonal Friction The orthogonal friction test apparatus 10 shown in FIG. Both ends of the string 11 were fixed in the horizontal direction of the arrow P with a tension of 30 pounds applied (13a, 13b). The same string 12 crossed the string 11 in the horizontal direction at right angles, one end 12a was fixed, and the other end 12b was hung with a load 14 of 2 kg. The string 12 is hung at a right angle on the same horizontal plane on the string 11 with both ends fixed, and is pulled downward in the vertical direction by the weight of the load. With the load applied to the string 12, as shown by the arrow Q, the string 12 was reciprocated 10 mm at a speed of 1 reciprocation per second in the direction perpendicular to the horizontal. Evaluation was performed in the state of fluff of the string 12 after reciprocating friction. The number of times that the string (12) was cut or fluffed was evaluated. When the fluff was small after 200 times of friction, it was set to 200 times or more.

<Friction Test 2> Friction Test on String FIG. 4A is a schematic perspective view of a friction test apparatus 15 on a string stretched on a racket used in an embodiment of the present invention, and FIG. 4B is a cross-sectional view thereof. As shown in FIGS. 4A and 4B, the string 17 was lifted to the racket 16 at 25 pounds, a shuttle cork 18 was placed on the surface of the string 17, and a 500 g weight 19 was placed thereon. A chuck (hook) 20 was attached to the side surface of the shuttle cork 18 and the string 21 was hung and pulled in the direction of the arrow 22 at a speed of 100 mm / min. At this time, the shuttle was pulled with an autograph (Shimadzu Corporation), and the frictional resistance was measured.

Example 1
The badminton string was manufactured in the next step.
(1) Core yarn As the core yarn, a filament yarn (melting point 260 ° C., fineness of 1400 decitex and 940 decitex, total fineness of 2340 decitex) manufactured by Toray Industries, Inc., Z twist 120 times / m Thread was used. A nylon emulsion was adhered to the core yarn at an adhesion rate of 6 to 12% by mass.
(2) Hot-melt flat monofilament and winding process A shape in which five cross-sectional circles are connected as shown in FIG. 2A using Ube Industries, Ltd., low-melting point copolymer nylon, product name “7128B” (melting point 130 ° C.) A flat monofilament was prepared by melt spinning. The flatness L / D was about 5, L = 0.165 mm, D = 0.035 mm, and the fineness was 55 decitex. One flat monofilament was spirally wound around the core yarn surface. The winding machine was attached to the core yarn supply part of the string making machine, and the winding and string making were continuously performed.
(3) Sheath braiding and string making process (string yarn assembling process)
A cross-section in which four circles are connected by using nylon 6 and nylon 66 copolymer nylon (trade name “2320J”, nylon 6/66 = 95/5; melting point 215 ° C.) manufactured by DSM as the sheath braid Shaped monofilaments were made by melt spinning. The flatness L / D was about 4, L = 0.04 mm, D = 0.16 mm, the fineness was 64 deci tex, the strength was 4.8 N, and the elongation was 31.5%. A total of 16 monofilaments were used one by one, and the flat monofilament was spirally wound around the surface of the core yarn with a round 16 punching machine.
(4) Thermal bonding process (first heat treatment process)
The string after the stringing was heat-treated for 40 seconds with a hot air drying apparatus having a temperature of 215 ° C. The draw ratio was 1.03. By this heat treatment, the low melting point flat monofilament was melted, and the core yarn and the sheath braid were thermally bonded and integrated. In addition, fusion of the sheath braid (leather thread) was also observed. Table 1 shows the physical properties after the heat treatment. Increase in strength and decrease in elongation were observed by heat treatment.
(5) Surface resin layer forming process (extrusion process)
A product name “7034T” (melting point Tm: 201 ° C., glass transition point Tg: 45 ° C.) manufactured by Ube Industries, Ltd. was extruded at a maximum temperature of 330 ° C. using an extruder and coated on the surface of the string after the thermal bonding. . The mass of the string before coating was 0.3877 g / m, and the mass of the string after coating was 0.4500 g / m. The amount of the surface resin layer applied was 0.0623 g / m, and the ratio when the string was 100% by mass was 13.8% by mass.
(6) Surface heat treatment step (second heat treatment step)
The string on which the surface resin layer was formed was heat-treated for 40 seconds with a hot air dryer at a temperature of 215 ° C. to obtain a string for badminton. An exploded perspective view of the obtained string is shown in FIG. However, for easy understanding of the structure, the core winding state in FIG. 1 shows the winding state before the heat treatment.
Conditions and results are summarized in Tables 1 and 2.

(Comparative Example 1)
A string was prepared in the same manner as in Example 1 except that the surface heat treatment step (second heat treatment step) was not performed. FIG. 5 shows an exploded perspective view of the obtained string. The surface of the surface resin layer 5 was smooth. However, for easy understanding of the structure, the core winding state in FIG. 5 shows the winding state before the heat treatment.
The result of the friction test of the strings of Example 1 and Comparative Example 1 is shown in FIG. As is clear from FIG. 6, the frictional force of Example 1 was low. That is, when the surface heat treatment step (second heat treatment step), a part of the resin film coated in advance penetrates into the braid of the sheath part, and the resin film becomes uneven along the braid, and the friction resistance is increased. Lower. As a result, the string was easily misaligned, the spin was applied well, the shot feeling was soft, and the durability was good.

(Example 2)
The experiment was performed in the same manner as in Example 1 except for the following items.
(1) As a sheath braiding yarn, a nylon 6 and nylon 66 copolymer nylon (made by DSM, trade name “1020J”, nylon 6; melting point 220 ° C.) is melt-spun and has a cross-sectional shape in which four circles are connected. A monofilament was made and used.
(2) In the surface heat treatment step (second heat treatment step), heat treatment was performed for 40 seconds with a hot air drying apparatus having a temperature of 225 ° C.
The obtained string was spun well, the feel at impact was soft, and the durability was good.

(Example 3)
The experiment was performed in the same manner as in Example 1 except for the following items.
(1) As the core yarn, a filament yarn (melting point 260 ° C., total fineness 2100 decitex) made by Toray Industries, Inc., trade name “Promiran” (nylon 66) was used with a Z twist of 150 times / m.
(2) In the surface resin layer forming step (extrusion step), the mass of the string before coating was 0.3603 g / m, and the mass of the string after coating was 0.4240 g / m. The amount of the surface resin layer applied was 0.0637 g / m, and the ratio when the string was 100% by mass was 15.0% by mass.
The obtained string was spun well, the feel at impact was soft, and the durability was good.

Example 4
The experiment was performed in the same manner as in Example 3 except for the following items.
(1) As a sheath braiding yarn, a nylon 6 and nylon 66 copolymer nylon (made by DSM, trade name “1020J”, nylon 6; melting point 220 ° C.) is melt-spun and has a cross-sectional shape in which four circles are connected. A monofilament was made and used.
(2) In the surface heat treatment step (second heat treatment step), heat treatment was performed for 40 seconds with a hot air drying apparatus having a temperature of 225 ° C.
The obtained string was spun well, the feel at impact was soft, and the durability was good.
The above conditions and results are summarized in Tables 1 and 2.

The string of each example and comparative example was stretched on a badminton racket and subjected to a ball hitting test. The strings of examples 1 to 4 were superior in durability, tension retention, and hitting sound as compared with comparative example 1. .

The string of the present invention is suitable for badminton. In addition, it is useful for rackets such as hard tennis, soft tennis and squash.

DESCRIPTION OF SYMBOLS 1 String for rackets 2

Core yarn

3, 6, 7, 8 Flat monofilament 4 Sheath braiding 5 Surface resin layer 10 Orthogonal

friction test apparatus

11, 12, 17

String

13a, 13b, String fixing tool 14 Load 15 On string Friction test equipment 16 Racket 18 Shuttle cork 19 Weight 20 Chuck (hook)
21 String

Claims

A string for a racket including a core yarn, a sheath yarn outside the core yarn, and a surface resin layer outside the sheath yarn,
The core yarn and sheath yarn are integrated by fusion of hot melt yarn interposed on the surface of the core yarn,
The resin of the surface resin layer is a thermoplastic resin containing no solvent,
A racquet string, wherein the surface of the surface resin layer has a concavo-convex shape formed along the sheath yarn.
The racket string according to claim 1, wherein the sheath yarn is a braided yarn or a wound yarn.
The racket string according to claim 1 or 2, wherein the surface of the surface resin layer has gloss.
The racket string according to any one of claims 1 to 3, wherein the resin of the surface resin layer is at least one selected from a nylon resin and a polyurethane resin.
The racket string according to any one of claims 1 to 4, wherein the uneven shape on the surface of the surface resin layer has a difference in height of the unevenness in the range of 1 to 100 µm.
The racket string according to any one of claims 1 to 5, wherein the abundance of the surface resin layer is in the range of 5 to 22 mass% when the string is 100 mass%.
The racket string according to any one of claims 1 to 6, wherein the hot melt yarn is a flat monofilament yarn.
The racket string according to any one of claims 1 to 7, wherein a ratio of the monofilament yarn is 2 to 12% by mass of the string mass.
The racket string according to any one of claims 1 to 8, wherein the outer filament yarn is partly fused together with the fusion of the monofilament yarn.
10. The flat monofilament is at least one selected from a shape in which a plurality of cross-sectional circles are connected in a row, a concavo-convex shape in which a plurality of cross-sectional circles are connected and the surface is smooth, and an oval shape. String for racket as described in.
A method for manufacturing a racket string according to any one of claims 1 to 10,
Winding the hot melt yarn around the core yarn and winding or winding the sheath yarn around the surface;
Heating to a temperature equal to or higher than the melting point of the hot melt yarn, melting the hot melt yarn and thermally bonding and integrating the core yarn and the sheath yarn;
Forming a surface resin layer by extruding a thermoplastic resin containing no solvent outside the sheath yarn in a molten state;
Then, the manufacturing method of the string for rackets characterized by including the process of surface-treating at the temperature more than melting | fusing point of the said surface resin layer.
The method for producing a string for a racket according to claim 11, wherein the temperature of the surface treatment is in the range of not less than the melting point (Tm ° C) of the surface resin layer and Tm + 25 ° C.