JP2921560B2 - Racket string - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a string for rackets, such as tennis, badminton, and squash, which has excellent hitting characteristics and durability.

[0002]

2. Description of the Related Art Conventionally, strings for rackets such as tennis, badminton, squash and the like have been used in playability.
Because of its superiority, natural gut was used, but due to poor durability, strings made of synthetic fiber (Synsatech) mono- or multi-filaments are used. The playability and durability (Durab) which are important characteristics required for this racket string are
ility) is in inverse correlation and has the following relationship. (1) Durability; natural gut <multifilament synsatech string <monofilament synsatech string They were in conflict with each other and it was difficult to achieve both. In particular, a racket string composed of a polyamide-based synthetic fiber multifilament has a ball hitting property comparable to that of natural gut, but has a higher durability than a monofilament-made synsatech string (for example, JP-A-6-218081). Inferiorly, this improvement was requested. It is also known to mix potassium titanate whiskers on the surface of a string using a monofilament as a core.
As proposed above, the string using a monofilament has a basic problem that the hitting performance is inferior.

As a string for a racket comprising a multifilament made of a polyamide-based synthetic fiber, there is JP-A-1-135375 which has been already proposed by the present inventors.

[0004]

However, there is still a problem in the durability of the racket string made of a multifilament made of a polyamide-based synthetic fiber proposed in JP-A-1-135375.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multifilament synthatic string capable of improving the durability to the same level as a monofilament synthatic string in order to solve the conventional problems.
It is a second object of the present invention to provide a racket string which is excellent in stretchability which is an important characteristic of the racket string. A third object of the present invention is to provide an ideal racket string by adding low-cost elements to this.

[0006]

To achieve the above object, a racket string according to the present invention comprises a multifilament of a polyamide synthetic fiber having a single fiber fineness of 20 denier or less, and a resin coating layer on the surface. Wherein the multifilament is converged and integrated by an ultraviolet curable adhesive, and the surface resin coating layer contains an inorganic filler in a range of 1.0% by weight or more and 30.0% by weight or less. It is characterized by being contained.

[0007] In the above, the single fiber fineness of the constituent fibers is 0.1.
It is preferably from 1 denier to 15 denier, more preferably from 1 denier to 10 denier, and particularly preferably from 2 denier to 9 denier. The number of fibers constituting the multifilament is 500 to 5000
The number is preferably, and more preferably in the range of 1,000 to 2,000. The multifilament is converged and integrated by an ultraviolet curable adhesive. As the inorganic filler, at least one selected from barium titanate whiskers, aluminum borate whiskers, and aluminum borate particles can be used. In particular, at least one inorganic filler selected from highly transparent aluminum borate whiskers and aluminum borate particles is preferable. At least one inorganic filler selected from the aluminum borate whisker and the aluminum borate particles is subjected to a surface coupling treatment with a silane coupling agent, a titanate coupling agent, etc., and the resin of the resin coating layer on the surface. Excellent adhesion. As a resin coating layer on the surface,
Polyamide-based resins or urethane-based resins are preferred. As the whisker, one having an average fiber length of 1 to 320 μm, an average fiber diameter of 0.1 to 1.6 μm, and an aspect ratio (average fiber length / average fiber diameter) of 10 to 200 can be used as an example. More preferred whiskers have an average fiber length of 10
A range of 20 μm, an average fiber diameter of 0.2 to 0.5 μm, and an aspect ratio (average fiber length / average fiber diameter) of 20 to 55 is preferable. In the case of particles, the average particle diameter is 1 μm to 30 μm.
The surface coating resin is preferably a polyamide resin, a polyurethane resin, or the like, from the viewpoint of adhesion to a synthetic polyamide fiber constituting a string, abrasion resistance, and the like.

[0008] Whiskers described below are mixed with these resins in a heat-melted state. Currently known whiskers include: Aluminum borate (9Al ₂ O ₃
・ 2B ₂ O ₃ , white needle-like crystals), potassium titanate (K ₂
O.6TiO ₂ , white needle-like crystals), barium titanate (BaTiO ₃ , white needle-like crystals), silicon carbide (Si
C, green needle-like crystals), silicon nitride (Si ₃ N ₄ , white needle-like crystals), zinc oxide (ZnO, tetrapot-like crystals), basic magnesium sulfate, graphite, magnesia, calcium sulfate (Na ₂ C ₂ aP) ₂ O ₁₈ ), magnesium borate, α-alumina, chrysotile, wollastonite and the like.

Among these whiskers, those that are particularly useful for strings for rackets are effective in improving durability.
Moreover, it is an aluminum borate whisker excellent in transparency similar to natural gut. Aluminum borate particles are also excellent in transparency. Aluminum borate whiskers and particles have a relatively low refractive index of 1.60 to 1.63. When mixed with a polyamide resin or a polyurethane resin, the refractive indices are close to each other, and the whisker and the particles have high translucency and high transparency. Property is obtained.

The content of the inorganic filler is 1.0% by weight.
If it is less than 3, the effect of improving durability is not sufficient. On the other hand, if the content exceeds 30% by weight, the elasticity of the coating layer is reduced, and it is impossible to follow the expansion and contraction of the string for each hit ball, cracks are generated, and the hardness of the coating layer is increased to increase the abrasion resistance and the durability is adversely affected. It has been observed to decrease.

It is not limited that the coating resin contains other additives such as a smoothing agent, a coloring agent and a stabilizer in addition to the whiskers. According to the present invention, the hitting property is good, and the durability can be improved to the same level as a monofilament-made synthatic string. This is due to the presence of the UV curable adhesive in the inner layer and the inorganic filler in the coating resin coating layer. In addition, the racket string has excellent stretchability, which is an important characteristic, and can be realized at low cost.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyamide-based synthetic fiber used in the present invention, nylon 6, nylon 66 or a copolymer thereof is particularly preferred because high strength is easily obtained. In order to obtain a soft feeling at the time of hitting the ball, it is desirable that the fiber showing the thickness of the single fiber be 2 to 9 denier. The strength is 5 g / denier or more and the elongation is 10 from the viewpoint of durability.
About 30% is desirable. Furthermore, in order to obtain a strong, round cross-sectional shape and a soft feeling, the number of twists applied to the entire yarn is 50 to
It is preferably about 300 turns / m.

As the UV-curable adhesive, basically, any UV-curable adhesive is used. The ultraviolet curable adhesive may be any one containing a photopolymerizable prepolymer, a photopolymerizable monomer and a photopolymerization initiator, and in addition, a sensitizer, a pigment, a filler, an inert organic polymer, a leveling agent, It may contain a thixotropic agent, a thermal polymerization inhibitor, a solvent and the like.

Examples of the photopolymerizable prepolymer include polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, oligoacrylate, alkyd acrylate and polyol acrylate.
Polyurethane acrylates and epoxy acrylates are desirable, and polyurethane acrylates are most desirable from the viewpoint of softness and resilience. This polyurethane acrylate can be obtained by reacting a compound having an isocyanate group such as tolylene diisocyanate with an acrylate having a hydroxy group such as a 2-hydroxy group. In addition, a characteristic urethane acrylate can be obtained by a combination of a diisocyanate, a diol, a dibasic acid, and an acrylate compound.

The photopolymerizable monomer is useful as a crosslinking agent and a diluent, and various acrylates are mainly used. The above-mentioned various acrylates become a polymer having a urethane binding group having an excellent affinity for polyamide in a very short time upon irradiation with ultraviolet light, and thus exhibit an excellent adhesive with various nylons which are polyamide-based synthetic fibers.

Examples of the photopolymerization initiator include sulfur compounds, acetophenones, and carbonyl compounds such as benzophenone. UV light is about 100nm to 400n
Although light of a wavelength in the range of m is useful, light of a wavelength in the range of about 200 nm to 400 nm is particularly useful for curing the resin. Examples of the light source include a mercury lamp, a xenon lamp, a carbon arc, a plasma arc, and a metal halide lamp, and a high-pressure mercury lamp and a metal halide lamp are particularly useful from the viewpoint of curing efficiency. Although a metal halide lamp is more suitable for curing a thick film, it is not sufficient to achieve the object of the present invention. As the ultraviolet irradiation device, a commercially available device including a lamp and a light collector for increasing efficiency can be used.

In the present invention, when a number of filaments are twisted to form a string, each filament is impregnated with the above-mentioned adhesive in advance, and the impregnated resin is cured in a short time by irradiating ultraviolet rays while twisting. In the method of impregnating the ultraviolet curable adhesive after the twisting, the adhesive does not sufficiently penetrate into each filament inside the twisted bundle, and therefore, the filaments do not adhere with sufficient strength. For this reason, the durability of the string cannot be obtained.

[0018] Then the preferred borate made of aluminum whiskers or particles used in the present invention, if Shimese by Formula is _{9AL 2 O 3 · 2B 2 O} 3, whiskers average fiber length 10 to 30 [mu] m, average fiber The diameter is 0.5-1.
0 μm, and the particles have an average particle diameter of 3 to 100 μm.

When the amount is less than 1% by weight, the effect is hardly obtained, and preferably 3% by weight or more. On the other hand, if the amount exceeds 30% by weight, the entire string becomes hard, which is not suitable for the soft ring as the object of the present invention, and is 30% by weight or less, preferably 15% by weight or less. These effects not only improve the durability of the string, but also improve the stretchability, probably due to the smoothing of the surface. Aluminum borate is particularly useful because it has a lower index of refraction than other materials and can provide a transparent string.

Finally, a resin having a thickness of 30 μm or more and 150 μm or less after drying is coated by an ordinary method in order to improve the durability at the time of stretching and hitting the ball. As the resin in this case, nylon, polyurethane or the like is desirable from the viewpoint of durability.

Further, when a whisker made of aluminum borate or the like is blended in the above coating resin, the durability is further improved. Further, a smoothing agent composed of waxes, silicone oil, or the like is applied to obtain a final product.

FIG. 1 schematically shows an example of a cross section of a racket string 1 according to one embodiment of the present invention. FIG.
In the racket string 1, the multifilament fiber 2 of a plurality of polyamide-based synthetic fibers is twisted up, and an adhesive is used at the time of twisting up. Reference numeral 3 denotes an adhesive resin layer used for twisting. The surface resin coating layer 4 to which an inorganic filler (for example, whisker) is added is formed thereon.

[0023]

The present invention will be described more specifically with reference to the following examples. (Example 1) A multifilament of nylon 6 having a single yarn fineness of 6 denier and 1224 single yarns was twisted to a number of turns of 80 turns /
While twisting with m, the resin was impregnated with a UV-curable resin composed of a UV-curable urethane acrylic polymer, a monomer and a photoinitiator, and squeezed through a nozzle having a diameter of 1.1 mm. Thereafter, this was irradiated with ultraviolet rays using a high-pressure mercury lamp and cured to obtain a linear body having a diameter of 1.14 mm.

An aluminum borate whisker surface-treated with an alkylsilane coupling agent (average fiber length 20 μm, average fiber diameter 0.75 μm, aspect ratio (average fiber length / average fiber diameter) 27) on the outer periphery of the linear body Pellets 30 of nylon 6,6 containing 30 parts by weight of
Parts by weight and 70 parts by weight of ordinary nylon 6,6 pellets were mixed to obtain hot-melt nylon (whisker content 9
% By weight) to obtain a racket string.

The obtained racket string has a diameter of 1.
315mm, tensile strength 75.3Kg, knot strength 37.8
kg and elongation were 19.8%. The thickness of the coating was 100μ. The resulting string was transparent and had a luxurious feel.

This string was stretched on a racket made of carbon fiber reinforced resin having a face area of 110 square inches together with a warp / weft thread with a tension of 60 pounds. String tension and waist are moderate, surface hardness is moderate and slipperiness is good,
The stretchability was very good as compared with the natural gut, and was also better as compared with the comparative example containing no whisker.

In addition, an actual tennis ball is launched,
Striking was continued at a speed of 127 km / h, at a launch interval of 15 times / min, and at a launch distance of 50 cm until the string was cut. In a total of two tests, the number of punches before cutting was 991 and 907, respectively.

As a comparative example, a string obtained by exactly the same method except that the whisker of the above-mentioned example was not included was examined for durability by the same method. As a result, it was 576 times.

As a reference example, the natural gut of the same gauge is 543 times, and the monofilament Synsatech is 80 times.
It was about 0 to 1100 times. (Example 2) The linear body of Example 1 was coated on its outer periphery with hot melt nylon 6 containing 6% by weight of aluminum borate particles (average particle diameter: 3 μm) by a conventional method. I got a racket string.

The diameter of the obtained racket string
310 mm, tensile strength 75.1 kg, knot strength 36.5
kg and elongation were 19.0%. The coating thickness is
It was about 100μ.

The durability of this string was examined in the same manner as in the above embodiment. The tension and waist and surface hardness of the string were moderate, the slipperiness was good, and the stretchability was very good. In a total of two tests, the number of punches before cutting was 995 and 992, respectively.

Example 3 The linear body of Example 1 was coated on its outer periphery with hot-melt nylon 6 containing 6% by weight of barium titanate whiskers by a conventional method to form a string for racket. Obtained.

The diameter of the obtained racket string
305mm, tensile strength 74.9kg, knot strength 34.9
kg and the elongation were 18.6%. The coating thickness is
It was about 80μ.

The durability of this string was examined in the same manner as in the above embodiment. The tension and waist and surface hardness of the string were moderate, the slipperiness was good, and the stretchability was very good. In a total of two tests, the number of hits before cutting was 993 and 1012, respectively.

[0035]

As described above, according to the present invention, there is provided a racket string comprising a multifilament of a polyamide synthetic fiber having a single fiber fineness of 20 denier or less and having a resin coating layer on its surface.
The multifilament is converged and integrated by an ultraviolet curable adhesive, and the surface resin coating layer contains an inorganic filler in a range of 1.0% by weight or more and 30.0% by weight or less. It has good properties and durability can be improved to the same level as a monofilament synthatic string. In addition, the racket string has excellent stretchability, which is an important characteristic, and can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a racket string according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 String for racket 2 Multifilament fiber of a plurality of polyamide synthetic fibers 3 Adhesive resin layer used for twisting 4 Surface resin coating layer with whisker added

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-103458 (JP, A) JP-A-61-103459 (JP, A) JP-A-4-109972 (JP, A) JP-A-6-103458 296712 (JP, A) JP-A-7-148285 (JP, A) JP-A-3-205070 (JP, A) JP-A-7-194744 (JP, A) JP-A-7-185046 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) A63B 51/02

Claims (4)

(57) [Claims] 1. A racket string comprising a polyamide-based synthetic fiber having a single-fiber fineness of 20 denier or less and having a resin coating layer on its surface, wherein the multi-filament is converged by an ultraviolet-curable adhesive. A racket string which is integrated, and wherein the surface resin coating layer contains an inorganic filler in a range of 1.0% by weight or more and 30.0% by weight or less. 2. The racket string according to claim 1, wherein the inorganic filler is at least one inorganic filler selected from barium titanate whiskers, aluminum borate whiskers, and aluminum borate particles. 3. The racket string according to claim 1, wherein at least one inorganic filler selected from aluminum borate whiskers and aluminum borate particles has been subjected to a surface coupling treatment. 4. The racket string according to claim 1, wherein the resin coating layer on the surface is a polyamide resin or a urethane resin.