JP2016077743A - String for racket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a string for a racket in which polyoxymethylene (POM) filaments are arranged in a specific position, which has high resilience and low rigidity as string performance, and has durability posing no problem in practical use, and whose S-S curve is linear.SOLUTION: A string (10) for a racket is a string for a racket containing polyoxymethylene filaments and other synthetic fiber filaments. The string for a racket contains a plurality of core yarns (1), sheath yarns (2 and 3) coating the core yarns (1), and surface coating resin (4) outside the sheath yarns (2 and 3). At least part of the plurality of core yarns (1) are polyoxymethylene filaments, and at least part of the sheath yarns (2 and 3) are other synthetic fiber filaments.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a synthetic string for rackets (also called gut) used for hard tennis, soft tennis, squash, badminton and the like. In particular, it relates to a string for a racket that is excellent in feel at impact such as resilience and soft feeling.

  Conventionally, polyamides and polyesters are mainly used as materials for synthetic strings for rackets used in tennis, squash, badminton and the like. The main characteristics required for the string include a shot feeling, durability, and stretchability (ease of tension on a racket). Among them, the rebound characteristics (power), the soft feeling, the controllability, the spin property, the vibration absorption property, and the like are important characteristics as the feel at impact. Among the main characteristics, the feel at impact is particularly important. Regarding the feel at impact, natural gut made from the intestines of cattle and sheep has the characteristics of high resilience and low rigidity (soft), and it is evaluated as the gut with the best feel at impact. Conventionally, various studies have been made on the basis of nylon 6 and nylon 66 fibers in order to make a synthetic fiber string closer to the feel of a natural gut, but high resilience and low rigidity comparable to natural gut have not been obtained. This is thought to be due to limitations in terms of material properties.

  Polyoxymethylene (hereinafter also referred to as POM) is an example of a material that may provide a natural shot feeling. Patent documents 1-5 etc. are mentioned as an example in which POM was examined as a string for rackets. Patent Document 1 discloses a racket in which a polyacetal having a specific apparent density and tensile modulus (also known as POM) is stretched, and the gut's strength and elongation characteristics (SS curve) are linear and natural gut (natural sheep). ). In Patent Document 2, it is proposed to impregnate a void portion of a POM monofilament with a resin. Patent Document 3 proposes a string of twisted yarns obtained by converging twisted thin POM monofilaments. Patent Document 4 proposes a monofilament in which fisheye defects caused by voids and the like are reduced, and Patent Document 5 proposes a gut having a low friction coefficient with POM in the outermost layer.

JP-A-60-236670 JP 60-239514 A JP-A-61-146832 JP 2009-226108 A JP 2011-78581 A

  According to the study by the present inventors, the POM itself has high resilience and low rigidity, and the strong elongation curve is linear, and as a material characteristic, a characteristic close to natural gut can be expected, but as a problem, (1) Spinning stretchability of POM monofilament Particularly, it is difficult to stably stretch and stretch thick monofilament, and (2) poor adhesion. The former has a problem that in the case of a gut used as a single monofilament, it is difficult to stably produce a thick POM monofilament without voids or defects. On the other hand, in the case of the latter type of gut that is used as a bundle of thin filaments, there is a problem that the adhesion between the filaments is not sufficient, the filaments are scattered during use, and the durability is low. For this reason, no practical racket string using POM has been obtained.

  In order to solve the above-mentioned conventional problems, the present invention arranges the POM filament at a specific position, has high resilience and low rigidity as string performance, the SS curve is linear, and has no practical problem. A racket string having durability is provided.

  The racquet string of the present invention is a racquet string including polyoxymethylene filaments and other synthetic fiber filaments, and the racquet string includes a plurality of core yarns, and a leather yarn covering the core yarns, A surface coating resin is included outside the leather yarn, at least a part of the plurality of core yarns is a polyoxymethylene filament, and at least a part of the leather yarn is another synthetic fiber filament. .

  In the present invention, by placing the POM filament at a specific position, the string performance has high resilience and low rigidity, the SS curve is also linear, and a strong elongation characteristic close to natural gut is obtained. In addition, it is possible to provide a string for a racket having durability that has no practical problem.

FIG. 1 is a cross-sectional view of a racket string according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a racket string according to another embodiment of the present invention. FIG. 3 is a graph of a strong elongation curve (SS curve) of Example 3 of the present invention, Comparative Example 1, and Reference Example (natural gut). FIG. 4 is a graph of the strong elongation curve (SS curve) of Example 1 and Example 2 of the present invention.

The polyoxymethylene of the present invention refers to a homopolymer usually obtained by polymerizing formaldehyde or trioxane or a copolymer in which 90 mol% or more is polyoxymethylene, and is also referred to as a polyacetal resin. As a preferable copolymer, for example, a copolymer obtained by copolymerizing an alkylene oxide such as ethylene oxide in an amount of about 0.5 to 10 mol% can be mentioned. In the present invention, both homopolymers and copolymers can be used. Commercially available resins include “Dellin” (DuPont), “Duracon” (Polyplastics), “Tenac” (Asahi Kasei), “Iupital” (Mitsubishi Engineering Plastics), and the like.

The polyoxymethylene filament used in the present invention is a filament obtained by melt spinning and drawing the polyoxymethylene resin, and the preferred single yarn fineness is 10 to 1000 dtex, more preferably 20 to 700 dtex. If the single yarn is thick, stable spinning without voids or defects becomes difficult. Further, when the single yarn fineness is larger than the above range, there is a problem that the adhesion between the filaments is insufficient and the durability is lowered. When it is thin, high resilience is difficult to obtain.

  Moreover, as a preferable high elongation characteristic of a filament, a cutting elongation is about 15% to 40%, and the strength is 3 CN / dtex or more. Moreover, as a cross-sectional shape of the filament, an irregular cross-sectional shape such as an ellipse (flat) or a polygon may be used in addition to a normal round cross-section. Further, the POM filament may contain various additives and modified polymers as long as the effects of the present invention are not impaired.

  The present invention includes a plurality of core yarns, a leather yarn covering the core yarns, and a coating resin on the surface of the leather yarn, at least a part of the plurality of core yarns is a polyoxymethylene filament, At least a portion of the leather is other synthetic fiber filaments.

According to studies by the present inventors, POM filament is used as a raw material for a racket string, and in order to exhibit its high resilience and low rigidity properties and to obtain good string characteristics, the POM filament in the string Mixed rate is important. A preferable mixing ratio is 25 to 65% by weight. If the amount is less than 25% by weight, the effect of improving the feel of high resilience and low rigidity is insufficient. If the amount exceeds 65% by weight, POM filaments with poor adhesion tend to be scattered during use, resulting in insufficient durability. There is. More preferably, it is 30 to 60% by weight. More preferably, it is 33 to 55% by weight.

  The main component of the other synthetic fiber filament is preferably a polyamide filament. In the above, the main component means 50% by weight. Polyamide has higher resilience than polyester, is closer to natural, and has good adhesion.

  Polyamide filament materials include aliphatic polyamides such as nylon 6, nylon 66, nylon 46, nylon 56, nylon 11, nylon 12, nylon 610, nylon 612, and their copolymer polyamides, and semi-aromatics such as nylon 9T and nylon MXT6. Examples thereof include polyamide. In addition, heat-resistant aromatic polyamide fibers such as meta-aramid can be used by appropriately mixing as necessary.

  Although there is no restriction | limiting in particular as a single yarn thickness (fineness) of a polyamide filament, When using as a multifilament, about 20-2000 decitex is preferable when using as a monofilament.

  As a component of the racket string of the present invention, fibers other than the POM and polyamide can be used as long as they do not impair the object of the present invention. Although it does not specifically limit as a raw material, Polyester, polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyolefin, etc. are mentioned.

  In the present invention, in order to obtain a string having high resilience, low rigidity, and sufficient durability, it is preferable that the POM filament is arranged in a straight line mainly in the center of the string, that is, in the core, parallel to the axis of the string. I understood it.

  When the POM filament is placed on the surface layer of the string, the POM adhesion is low, so there is a problem that the POM part is easily peeled off early during use and the durability is lowered, but it is possible to place a small amount partially. It is.

  In the present invention, the number of core POM filaments is not limited, but preferably one or more, more preferably seven or more. These core yarns are preferably used as a non-twisted alignment or a low twist filament of 50 times / m or less in terms of feel. As the core component, in addition to the POM filament, other filaments can be used in combination as required. The filaments are preferably arranged symmetrically in the cross section, and the resulting string may be coiled in an asymmetrical or eccentric arrangement.

  The core POM filament is then preferably coated and bonded with a polyamide multifilament to focus the filament. Polyamide multifilaments are (1) impregnated with an adhesive together with POM filaments and focused and fixed, or (2) a plurality of multifilament yarns are wound and bonded around the outer periphery of a bundle of POM core yarns without any gaps. Can be obtained at The latter method of wrapping and bonding is preferably used because the core yarn can be focused and fixed more firmly.

  The single yarn fineness of the polyamide multifilament yarn to be coated is preferably smaller than the single yarn fineness of the POM filament of the core yarn because it can easily enter the uneven space between the core yarns and has good adhesion. The preferred single yarn fineness of the polyamide multifilament is about 2 to 20 dtex. As the polyamide multifilament, a twisted yarn or a sweet twisted yarn having a twist of 50 times / m or less is preferably used from the viewpoint of coverage.

  The adhesive is not particularly limited, and in addition to a solution in which a nylon resin is dissolved in a solvent such as phenol, a urethane resin, a UV curable resin, or the like can be used. In addition, it is also possible to mix and / or coat the heat-adhesive fiber with the POM filament and heat-seal it.

  In the present invention, it is particularly preferable from the viewpoint of durability that the outer periphery of the multifilament coating is wound and bonded using nylon monofilament as a leather. As for the thickness of the nylon monofilament to be used, a plurality of filaments having a diameter of about 0.05 to 0.25 mm (20 to 500 dtex) are used so that there is no gap as in the normal string manufacturing process. Can be wound and bonded evenly. Normally, monofilaments are wound around bobbins one by one and wound around the core using a plurality of bobbins, but multifilaments with a small single yarn fineness are aligned and bobbed together (around 2 to 4). Can be wrapped around the core.

  A part of the nylon monofilament used as the leather thread can be replaced with a POM filament having the same diameter as the monofilament or slightly thinner. Although a part of the yarn can be replaced with a yarn made of other materials such as meta-aramid fiber yarn, it is preferable that 50% by weight or more of the leather yarn is polyamide monofilament.

  According to the study by the present inventors, the multifilament is coated on the outer side of the core yarn, and the outer monofilament coating and the string coated with two layers are significantly more durable than the above-mentioned one layer. This is particularly preferable.

  The string of the present invention preferably has a resin-coated surface portion. Here, the coating method of the surface resin is not particularly limited, and a coating method by a melt coating method of various thermoplastic resins or a resin processing method using a resin solvent solution or dispersion is employed. Although it does not specifically limit as resin, A polyamide-type resin, a polyurethane-type resin, a polyolefin-type resin, a polyacetal-type resin etc. are mentioned. Of these, polyamide resins such as nylon 6, nylon 66, nylon 46, nylon 610, nylon 612, nylon 11, nylon 12 and copolymers thereof are particularly preferably used. Other examples include semi-aromatic thermoplastic polyamides such as nylon 9T. In addition to the resin component, the surface layer resin of the present invention may optionally contain additives such as inorganic particles, dyes / pigments, glossy pigments, heat-resistant agents, light-proofing agents, friction / wear modifiers, and modifiers as appropriate. it can.

  As a preferable material composition ratio of the string for the racket of the present invention, the polyoxymethylene filament is 25 to 65% by weight and the polyamide component (including the filament, the surface coating resin, and the adhesive component) is 35 to 100% by weight. 75% by weight and other components (including filament component, surface coating resin component and adhesive component) are about 0 to 30% by weight.

  A preferred string structure in the present invention is a structure in which at least one or more POM filaments are arranged in the core, polyamide multifilaments are wound around the outside, and polyamide monofilaments are wound around the outside, and the resin is coated as the surface layer. It is done.

  Examples of such a cross-sectional structure of the string of the present invention are shown in FIGS. In the drawings, the same reference numerals indicate the same items. Nylon multifilament is wound around the outer side of the POM monofilament of the core yarn 1 (seven examples are shown in FIG. 1) as the lower wound thread 2, and the nylon monofilament is wound as the upper wound thread 3 on the outer side. 4 is coated. FIG. 2 shows an example of the core yarn 1 in which a number of thinner POM filaments are bundled. The twist direction of the lower wound leather 2 and the upper wound leather 3 is preferably different. For example, when the lower wound leather 2 is S-twisted, the upper wound leather 3 is preferably Z-twisted. If it does in this way, twist of a string does not occur easily. In the case of the same twist direction, the string is likely to be twisted, which is not preferable.

  The racket string of the present invention can be applied to hard tennis, soft tennis, badminton, squash, etc., and is particularly suitable as a soft tennis string.

  This will be specifically described below with reference to examples. In addition, this invention is not limited to the following Example. In the following examples, evaluation was performed by the following method.

<Physical properties>
The string strength and elongation were measured with a tensile tester (Shimadzu Corporation, Autograph AGS-100NX) according to JIS L1013. The diameter was measured using a micrometer. The number of measurements showed the average value of N = 5.

<Mixed ratio>
The string was accurately cut to 1.00 m and weighed, and the basis weight per m was measured. The weight per meter of the mixed POM filament yarn was calculated from the fineness and number of yarns.
Mixed rate = 100 × (weight of mixed POM filament (g / m) / string weight (g / m))

<Durability>
To evaluate the durability of the string, the string was stretched on a hard tennis racket at 40 pounds, left for 24 hours, and then a hard tennis ball was launched into this racket (conditions: ball speed 100 km / hour, launch interval 15 times / minute) The ball was hit at four points on the racket at a launch distance of 50 cm and a launch angle of 40 degrees), and the number of strikes until the string was cut was measured. The average value in a total of three tests is shown.

<Repulsion / Rigidity>
One string is pulled with 50 pound tension and clamped at both ends (grip spacing 30 cm). Using a pendulum hammer, swing down from a fixed position so that it strikes the center of the string at a right angle to the string in the horizontal direction, and the movement (displacement) and stress of the string after the collision are 1/1000 second intervals. The rigidity (pound / inch) and the rebound rate (%) were determined by the following methods.
Rigidity (pound / inch) = maximum stress P (pound) / maximum displacement L (horizontal direction, inch)
Rebound rate (%) = (S2 / S1) × 100
However, S1: Area of the portion from the collision to the maximum displacement (forward portion) in the stress-strain (displacement) curve (reciprocation) S2: Area from the maximum displacement position to the zero displacement (return portion) of the stress-strain curve Rigidity The higher the numerical value, the harder the hit feeling is when stretched on the racket, and the lower the numerical value, the softer (soft feeling).
The higher the rebound rate, the less energy loss in collision and the greater the rebound. The restitution rate and the stiffness rate are explained in detail in the reference; Rod Cross "Laboratory testing of tennis string" Sports Engineering (2000) 3,219-230).

<Example 1>
Polyoxymethylene monofilament (diameter 0.20 mm; manufactured by Toray Monofilament, fineness 440 dtex, strength 25 N, elongation 20%) and nylon 6 monofilament (diameter 0.115 mm; manufactured by Toray Monofilament, product number) “120Y0.115WX”) was prepared. Nylon 6 multifilament manufactured by Toray Industries, Inc. (trade name “122T-30F-T100”) was used for the lower wound thread.
Using an adhesive in which nylon is dissolved in a phenolic solvent, 11 POM filament yarns are drawn together to form a core material. The adhesive was applied to the surface of the core material, and 20 nylon 6 multifilament yarns for lower winding leather were wound around the outer periphery of the core material without gaps and dried. The lower wound leather was S-twisted and the number of twists was 91 times / m.
Next, 25 nylon 6 monofilaments for upper winding yarn were wound around the outer side of the multifilament-coated yarn for lower winding yarn and dried by using the adhesive. The upper wound yarn was Z-twisted, and the number of twists was 92 times / m.
The resulting yarn was melt coated with nylon 6 resin as a surface coating resin to obtain a tennis string having a diameter of about 1.27 mm. 33% by weight of this string was POM filament. Table 1 shows the physical properties and gut characteristics.

<Example 2>
The same process was used except that 14 POM monofilaments used in Example 1 were used as the core yarn. The obtained string had a diameter of 1.28 mm and a POM content of 40%. Table 1 shows the physical properties and gut characteristics.

<Example 3>
As the core yarn, 20 POM monofilaments of Example 1 are aligned, and the outside is used as a lower wound yarn for untwisted N66 multifilament (manufactured by Toray Industries, trade name Promilan, product number “122T-30F-T1100”, no twisted yarn ) And wrapped and adhered. The lower wound leather was S-twisted, and the number of twists was 92 times / m.
Subsequently, 18 bobbins obtained by winding three thin N6 monofilaments (0.065 mm in diameter) for the upper wound thread were wound on the outside for 54 total yarns and bonded. The upper wound yarn was Z-twisted, and the number of twists was 92 times / m.
The obtained yarn was melt coated with nylon 6 resin as a surface coating resin. The obtained string had a diameter of 1.29 mm and a POM content of 55%. Table 1 shows the physical properties and gut characteristics.

<Comparative Example 1>
A single nylon 6 monofilament (diameter 0.78 mm) was used in place of the polyoxymethylene filament of the core yarn of Example 1, and the other processing was performed in the same manner as in Example 1. The obtained string had a diameter of 1.25 mm and a POM filament content of 0%. Table 1 shows the physical properties and gut characteristics.

<Reference Example 1>
Four of the 11 POM filaments of the core yarn of Example 1 were replaced with nylon 6 monofilaments (diameter 0.19 mm) having substantially the same diameter, and the core yarn was processed in the same manner as in Example 1. The obtained string had a diameter of 1.28 mm and a POM content of 22% by weight. Table 1 shows the physical properties and gut characteristics.

<Reference Example 2>
Twenty-six POM monofilaments of Example 3 were aligned as the core yarn, and the outer side was used for the lower wound leather yarn with non-twisted N66 multifilament (trade name Promilan, 122T-30F-T1100, no twisted yarn manufactured by Toray Industries, Inc.) Wrapped and glued. The lower wound leather was S-twisted, and the number of twists was 92 times / m.
In order to increase the POM ratio with strings having substantially the same diameter, the nylon component has to be reduced. Therefore, the nylon 6 resin was melt coated on the obtained yarn without winding the upper wound leather. That is, when the upper winding is performed as in Example 3, the POM ratio is decreased and the diameter is increased, so that comparison is not possible and the upper winding is omitted. The obtained string had a diameter of 1.28 mm and a POM content of 68%. Table 1 shows the physical properties and gut characteristics.

<Example 4>
The core yarn is composed of seven core POM monofilaments (diameter 0.26 mm, fineness 740 dtex, strength 40 N, elongation 21%) thicker than the POM monofilament of Example 1, and the others are the same as in Example 1. processed. The string had a diameter of 1.27 mm and a POM content of 34% by weight. Table 1 shows the physical properties and gut characteristics.

  Table 1 summarizes the evaluation results of Examples, Comparative Examples, and Reference Examples. FIG. 3 shows an SS curve example of the string obtained in Example 3, Comparative Example 1 (POM 0%), and a commercially available natural gut SS curve example as a reference example. FIG. 4 shows a graph of the strong elongation curve (SS curve) of Example 1 and Example 2 of the present invention. 3 and 4 are graphs obtained by measuring one sample, and Table 1 is slightly different because the number of measurement samples is an average value of N = 5 as described above.

These results show the following.
(1) By using POM for the core yarn, the gut's rigidity tends to be lower and the rebound rate tends to be higher than when it is not used. Natural gut (rebound rate 87%, stiffness 16.5 pounds / inch) ).
(2) There is no significant difference in the rebound rate and rigidity at the POM mixed rate of 33-55%. The SS curve is almost linear with a content of 33% or more. As shown in FIG. 3, the string obtained in Example 3 was very close to the natural gut in the linearity and slope of the SS curve. This means that even if the tension is changed, the feel at impact such as rebound and rigidity is almost constant. Also in FIG. 4, it can be seen that the linearity and slope of the SS curves of Examples 1 and 2 are very close to natural gut.
(3) When the POM mixture ratio is 65% or more, the other fiber (nylon) layer becomes thin and the durability of the string is greatly reduced, which causes a problem in physical properties such as a decrease in knot strength.

  Next, a trial evaluation was performed. Trial hits were made by four senior soft tennis players, and the hit feeling was evaluated on a five-point scale for each of the resilience, softness, controllability, and spin characteristics. The comparison product was 3 points (normal), 5 points; good, 4 points; slightly good, 2 points; slightly bad, 1 point; The results are shown in Table 2.

  As is clear from Table 2, the strings of Examples 1 to 4 are superior in resilience, soft feeling, controllability, and spin characteristics as compared with the strings of Comparative Example 1 and Reference Examples 1 and 2, and the feel at impact is high. I was able to confirm.

DESCRIPTION OF SYMBOLS 1, 5: Core yarn 2, 6: Lower winding leather thread 3, 7: Upper winding leather thread 4, 8: Surface coating resin layer 10, 11: String

Claims (9)

A string for rackets comprising polyoxymethylene filaments and other synthetic fiber filaments,
The string for the racket includes a plurality of core yarns, a skin yarn covering the core yarns, and a surface coating resin on the outside of the leather yarn, and at least a part of the plurality of core yarns is a polyoxymethylene filament. And
A racquet string, wherein at least a part of the leather thread is other synthetic fiber filaments.   The racket string according to claim 1, wherein the weight of the polyoxymethylene filament is 25 to 65% when the weight of the racket string is 100%.   The string for rackets according to claim 1 or 2, wherein a single yarn fineness of the polyoxymethylene filaments is 10 to 1000 dtex.   The racquet string according to any one of claims 1 to 3, wherein the polyoxymethylene filament is untwisted or twisted 50 times / m or less.   The racquet string according to any one of claims 1 to 4, wherein a main component of the other synthetic fiber filaments is a polyamide filament.   The racket string according to any one of claims 1 to 5, wherein the leather yarn is wound around the core yarn.   The racket string according to any one of claims 1 to 6, wherein at least one polyoxymethylene filament is disposed in a core portion of the racket string, and an outer peripheral portion thereof is coated and bonded with a polyamide multifilament.   In the racket string, at least one polyoxymethylene filament is disposed at the core, polyamide multifilament is coated and bonded as a lower wound thread on the outer periphery, and polyamide monofilament is wound as an upper wound thread on the outer side. The racket string according to any one of claims 1 to 7, wherein the string is attached and the surface layer is resin-coated.   The racket string according to claim 8, wherein the twist direction of the lower wound leather is different from that of the upper wound thread.

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