JP2007330772A - String for racket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide string which has smaller loosening by stress relaxation compared to conventional strings for a racket, excellent durability, and ball hitting performance similar to natural gut strings. <P>SOLUTION: The string for a racket comprises a sea island type composite monofilament. The island components comprise polyester based resin and the sea component comprises at least one thermoplastic synthetic resin selected from polyamide based resin, fluorine based resin and polyolefine based resin. Further, the string is characterized by having 7-25 island components. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a racket gut that is stretched around a sports racket such as tennis, badminton, or squash. More specifically, the present invention relates to a racket gut that has less sag due to stress relaxation than the conventional racket gut, has excellent durability, and has a hitting property comparable to that of a natural gut.

  In general, there are three functions required for a racket gut: durability, hitting performance, and stretchability. In other words, durability refers to the degree of slack due to stress relaxation after tensioning and ease of cutting due to wear for each hit ball. Hitability refers to resilience, ball control, and ease of rotation on the ball. In addition to the above, the feeling at the time of hitting the ball and the feeling of hitting the ball, such as the sound of hitting the ball, and the stretchability means the ease of tensioning the racket.

  These three performances have different degrees of importance, and the importance is positioned in the order of hitting performance, durability, and stretchability. However, no matter how excellent the hitability and durability, there is a problem with stretchability. For example, it is a racket gut that lacks practicality.

  As a gut to be stretched on a sports racket such as tennis, badminton, and squash, natural gut obtained from animal fibers represented by sheep intestine, whale muscle and the like has been used for a long time.

  However, natural gut is excellent in resilience, ball control and impact resistance, but since it is inferior in water resistance, its service life is short and expensive, so in recent years it has improved durability, mass productivity, economy, etc. Many excellent synthetic resin guts are used.

  As a synthetic resin gut using a monofilament or multifilament of synthetic resin, for example, a gut using polyamide for both the core yarn and the wound yarn (for example, refer to Patent Document 1), or a gut using a polyester monofilament (for example, Patent Document 2) has been proposed.

  These synthetic resin guts have the advantages of superior durability and stable supply of materials compared to natural guts, but there is a problem that it is difficult to obtain a soft shot feeling similar to natural guts. It was.

  Further, a gut (see, for example, Patent Document 3) in which a synthetic resin core-sheath composite monofilament is used as a core yarn and the synthetic resin monofilament is wound as a wound yarn has been proposed.

  This gut is excellent in resilience and durability while maintaining high knot strength. However, when actually used, the elastic modulus of the core yarn is different from that of the wound yarn. There was a problem that the yarn peeled off, leading to a decrease in durability and inferior tension.

As described above, the conventional racket gut has the three characteristics of durability, ball hitting property, and stretchability in a well-balanced manner, and it has been difficult to obtain a product having the same performance as a natural gut. It was rare.
JP 7-178203 A Japanese Patent No. 2826055 Japanese Patent No. 3581158

  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.

  That is, an object of the present invention is to provide a racket gut which has less slack due to stress relaxation than the conventional racket gut, is excellent in durability and has a hitting property comparable to that of a natural gut.

  In order to achieve the above object, according to the present invention, there is provided a racket gut composed of a sea-island type composite monofilament, wherein the island component of the composite monofilament is mainly composed of a polyester-based resin, and the sea component is a polyamide-based resin. A racket gut is provided, which is made of at least one thermoplastic synthetic resin selected from fluororesins and polyolefin resins, and has 7 to 25 island components.

In the racket gut of the present invention,
The island component is a mixture of 99 to 60% by weight of a polyester-based resin and 1 to 40% by weight of the same thermoplastic synthetic resin as the sea component;
It is composed of 10 to 40% by weight of sea component and 90 to 60% by weight of island component, and the composite monofilament has a diameter of 0.5 to 1.5 mm and a tensile strength of 3.0 to 8.0 cN / dtex. And that the thermoplastic synthetic resin constituting the sea component is a polyamide-based resin, both of which are mentioned as preferable conditions, and further satisfying effects can be obtained by satisfying these conditions.

  The racket gut of the present invention has less slack due to stress relaxation than conventional racket guts, is excellent in durability, and has a hitting property comparable to that of a natural gut, such as tennis, badminton and squash. When used in sports rackets, these effects are exhibited in a well-balanced manner.

  The present invention is described in detail below.

  The racket gut of the present invention is a racket gut made of a sea-island type composite monofilament, wherein the island component of the composite monofilament is mainly made of a polyester resin, and the sea component is a polyamide resin, a fluorine resin and a polyolefin resin. And at least one kind of thermoplastic synthetic resin selected from the above, and the number of island components is 7 to 25.

  The racket gut also has a complex in which the wound yarn is wound spirally around the outer periphery of the core yarn, but even if it is not made into a complex, the reason that it can exhibit excellent durability and hitting performance Therefore, the racket gut of the present invention needs to be a sea-island type composite monofilament.

  In the present invention, if necessary, a sea-island type composite monofilament can be used as a core yarn, and a wound yarn can be wound around the outer periphery of the core yarn or a surface coating can be applied.

  Further, the sea component of the sea-island type composite monofilament used in the racket gut of the present invention must be composed of at least one thermoplastic synthetic resin selected from polyamide resin, fluorine resin and polyolefin resin. is there.

  This is because the sea component is at least one thermoplastic synthetic resin selected from polyamide resin, fluorine resin and polyolefin resin, preferably a thermoplastic synthetic resin having a lower elastic modulus than the polyester resin contained in the island component. This is because, by using it, the durability of the polyester resin contained in the island component is covered, and excellent durability can be obtained by reducing slack due to stress relaxation.

  The type of polyester resin contained in the island component used in the present invention is not particularly limited as long as it can be melt-spun. For example, aromatic resins such as polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, and polyethylene naphthalate. Examples thereof include aliphatic polyesters such as polyester, polylactic acid, and polybutylene succinate.

  On the other hand, at least one thermoplastic synthetic resin selected from polyamide-based resin, fluorine-based resin and polyolefin-based resin used as a sea component is not particularly limited as long as it is a thermoplastic resin that can be melt-spun, For example, in the case of a polyamide-based resin, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, and various copolymers of these nylons can be used.

  In the present invention, it is possible to cover the rigidity of the polyester resin of the island component, reduce the slack due to stress relaxation, and improve the durability even under conditions where the sea component is relatively small. It is particularly preferred to use a resin.

  In the case of a fluorine resin, polyvinylidene fluoride, an ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, a tetrafluoroethylene-vinylidene fluoride copolymer, and the like can be given.

  In the case of polyolefin resin, polyethylene, polypropylene, polybutene-1, polypentene-1, polymethylhexene and the like can be mentioned.

  Furthermore, in the present invention, additives such as various colorants, crystallization inhibitors, light proofing agents, fillers, antistatic agents, flame retardants, and plasticizers are added to the above-mentioned thermoplastic synthetic resin to achieve the effects of the present invention. It is also possible to add in the range which does not inhibit.

  Further, by adding at least one selected from the same thermoplastic synthetic resin as the sea component, that is, a polyamide resin, a fluorine resin, and a polyolefin resin, to the polyester resin as the island component, the island component and the sea component are added. Is effectively suppressed, and a highly durable racket gut is obtained. When the content of the sea component resin added to the island component is 1 to 40% by weight, more preferably 5 to 30% by weight, it is particularly preferable because a racket with higher durability can be obtained.

  If the amount of the sea component resin added to the island component is less than 1% by weight, the effect of suppressing the separation of the island component and the sea component cannot be obtained. This is because it occurs and results in a loss of durability as a gut.

  The island component of the sea-island type composite monofilament used for the racket gut, the greater the number, the smaller the diameter of the island component thermoplastic synthetic resin, the lower the individual rigidity, and the shot feel close to that of a multifilament. Obtainable.

  However, the number of island components of the sea-island type composite monofilament used for the racket gut of the present invention needs to be 7 to 25, and more preferably 13 to 21.

  This is because, when the number of island components is below the above range, the contact interface area between the island components and the sea component becomes small, and the island component and the sea component peel off during repeated hitting, resulting in a decrease in durability. On the contrary, if the number of island components exceeds the above range, the thermoplastic synthetic resin of the island components is too thin and the durability becomes inferior.

  In addition, the arrangement of the island component in the sea component can be appropriately selected according to the function required for the racket gut as well as the rotation symmetry arrangement generally adopted as the racket gut.

  In addition, the cross-sectional shape of the island component of the sea-island type composite monofilament is not particularly limited. It can be selected as appropriate according to the function to be performed.

  Furthermore, as a preferable condition of the racket gut of the present invention, the sea component is composed of 10 to 40% by weight and the island component 90 to 60% by weight, and further, the sea component 20 to 35% by weight and the island component 80 to 65% by weight. A composite monofilament having a diameter of 0.5 to 1.5 mm, further a diameter of 0.7 to 1.4 mm, and a tensile strength of 3.0 to 8.0 cN / dtex, further 3.5 to 7.5 cN / dtex. It is mentioned that.

  This is because when the diameter is below the above range, it is difficult to obtain sufficient strength as a racket gut, and conversely, when the diameter is above the above range, the hitting performance is likely to be reduced. is there.

  In addition, when the weight ratio of the sea component is below the above range, it becomes difficult to obtain a hit feeling due to slackness due to stress relaxation. Since it becomes small, it becomes difficult to obtain sufficient strength. As a result, it is difficult to obtain a preferable tensile strength of 3.0 cN / dtex or more as a racket gut.

  Furthermore, when the tensile strength exceeds the above range, since the film is stretched at a high magnification, the elongation at break is reduced, and the gut is easily cut during tensioning.

  The racket gut of the present invention can be efficiently manufactured by the method described below.

  First, when melt-spinning a sea-island type composite monofilament, a known composite spinning machine can be used. The conditions include, for example, a polymer temperature of 200 to 350 ° C., an extrusion pressure of 1 to 50 MPa, and a die hole diameter. Ordinary conditions such as 0.1 to 5 mm and spinning speed of 0.3 to 200 m / min can be employed.

  First, at least one thermoplastic synthetic resin selected from a polyester resin, which is an island component, and a polyamide resin, a fluorine resin, and a polyolefin resin, which are sea components, is supplied to a compound spinning machine. After melt-kneading in a spinning machine, it is compounded into a sea-island structure in a die of a compound spinning machine and spun from a die.

  Thereafter, the spun composite monofilament passes through a short gas zone and is then cooled in the cooling bath. The cooling temperature here prevents the meandering of the composite monofilament in the cooling bath, and the roundness of the composite monofilament In order to improve property, it is preferable to set it as 5-90 degreeC.

  Examples of the cooling medium include a liquid inert to the polymer, usually water, polyethylene glycol and glycerin.

  Next, the cooled and solidified composite monofilament is continuously sent to the first or second drawing step. Here, in order to obtain a composite monofilament having high strength and excellent stress relaxation, it is preferable to perform the first-stage stretching under relatively low temperature and low magnification conditions, specifically, a temperature of 60 to 120 ° C. It is preferable to stretch 2.0 to 4.5 times.

  Furthermore, the composite monofilament that has undergone the stretching process may be subjected to moderate constant length and / or relaxation heat treatment for the purpose of removing stretching strain and the like.

  In addition, as the atmosphere (bath) in the stretching process and the constant length / relaxation heat treatment process, a heated heat medium bath such as warm water, polyethylene glycol, glycerin and silicone oil, a dry heat gas bath, and a steam bath can be used. .

  The racket gut thus obtained has less slack due to stress relaxation than conventional racket guts, has excellent durability, and has a hitting property similar to that of natural guts, so tennis, badminton, squash, etc. When used in a sports racket, these effects can be exhibited.

  Hereinafter, the racket gut of the present invention will be described more specifically. However, the racket gut of the present invention is not limited to the following examples unless it exceeds the gist thereof.

  The evaluation tennis racket used was a tennis racket frame having a face area of 115 inches and an obtained racket gut stretched with a tension of 60 Lb, and evaluation was performed according to the following criteria.

[Test method for evaluating interfacial debonding between sea and island components]
The composite monofilament was crushed at the tip (circular flat cross section) of a stainless steel round bar having a diameter of 5.5 mmφ until the width of the crushed portion was about 2.5 times the thickness of the yarn. Thereafter, the crushed portion was observed with an optical microscope (magnification 40 times), and the degree of interface peeling between the sea component and the island component was determined according to the following criteria.
○: No peeling was observed.
Δ: Partial peeling was observed.
X: It peeled entirely.

[Thread diameter]
The measurement was performed using a laser outer diameter measuring machine manufactured by Anritsu Corporation.

[Tensile strength]
Measurement was performed at a test length of 25 cm and a tensile speed of 30 cm / min under a standard condition of a temperature of 20 ° C. and a relative humidity of 65% in accordance with JIS L1013, and the tensile strength (N) at break was measured.

  The measured tensile strength (N) was divided by the positive fineness (dtex) of the composite monofilament calculated from the equilibrium moisture content, and the value was defined as the tensile strength (cN / dtex).

[Evaluation of racket gut characteristics]
A. Surface pressure retention Using a surface pressure measurement device (Swiss RaTest), the surface pressure was measured immediately after tensioning and one week after tensioning, and evaluated by the retention rate (%) relative to the surface pressure immediately after tensioning. . The larger the retention rate, the better the surface pressure retention.
B. Durability Durability was evaluated by hitting the tennis ball against the tennis racket face at a speed of 100 km / h, a launch interval of 15 times / minute, a launch distance of 50 cm, and a launch angle of 40 degrees until the gut was cut. .
C. Striking performance A tennis player with an advanced level actually uses a tennis racket to try out a tennis ball. Compared to a tennis racket using a natural gut and a conventional polyester resin gut, the ball has a ball control, resilience and resistance. The impact property was evaluated by sensitivity in the following three stages.
A: Equivalent to natural gut.
○: Inferior to natural gut, but equivalent to polyester resin gut.
X: Inferior to polyester resin gut.
D. Tensionability The ease of tension when producing a tennis racket by stretching a racket gut was evaluated in the following two stages compared to the case of stretching a natural gut.
○: Good.
X: It was inferior.

[Example 1]
Polyethylene terephthalate (J055 made by Mitsui Chemicals, hereinafter referred to as PET) was used as the island component, and nylon 6 (M1041, manufactured by Toray, hereinafter referred to as nylon 6) was used as the sea component.

  First, these raw materials were supplied to an extruder type composite spinning machine, melted and kneaded at 300 ° C., spun through a die having a pore diameter of 4.5 mm and 19 islands, and further cooled and solidified in a hot water bath at 70 ° C., An undrawn yarn was obtained.

  Next, this undrawn yarn was drawn 3.0 times in a 90 ° C. hot water drawing bath, and further drawn in a 230 ° C. dry heat bath.

  Subsequently, a heat treatment at a relaxation rate of 0.95 times was performed in a dry heat bath at 200 ° C., and a sea-island type monofilament having a diameter of 1.25 mm, a sea component of 20% by weight and an island component of 80% by weight was obtained. Obtained. The composite monofilament was used as a racket gut.

[Example 2]
A sea-island type composite monofilament was obtained under the same conditions as in Example 1 except that the island component was changed to a mixture of 90% by weight of PET and 10% by weight of nylon 6. The composite monofilament was used as a racket gut.

[Example 3]
A sea-island type composite monofilament was obtained under the same conditions as in Example 2 except that nylon 6 used as part of the sea component and island component in Example 2 was changed to polyethylene (manufactured by Nippon Polyethylene, Kernel KC-580S). . The composite monofilament was used as a racket gut.

[Example 4]
A sea-island type composite monofilament was obtained under the same conditions as in Example 2 except that the island component was changed to a mixture of 55% by weight of PET and 45% by weight of nylon 6. The composite monofilament was used as a racket gut.

[Example 5]
A sea-island type composite monofilament was obtained under the same conditions as in Example 2 except that the spinning conditions were changed so that the island component was 60% by weight with respect to 40% by weight of the sea component. This composite also used a monofilament as a racket gut.

[Comparative Example 1]
A sea-island type composite monofilament was obtained under the same conditions as in Example 2 except that the number of island components was three. The composite monofilament was used as a racket gut.

[Comparative Example 2]
A sea-island type composite monofilament was obtained under the same conditions as in Example 2 except that the number of island components was 30. The composite monofilament was used as a racket gut.

[Comparative Example 3]
A sea-island type composite monofilament was obtained under the same conditions as in Example 2 except that nylon 6 used for a part of the sea component and the island component was changed to polyethylene naphthalate (TN8065S manufactured by Teijin Chemicals). The composite monofilament was used as a racket gut.

  As is clear from the results in Table 1, the racket guts (Examples 1 to 5) that satisfy the conditions of the present invention are compared to the racket guts (Comparative Examples 1 to 3) that do not satisfy the conditions of the present invention. It can be seen that, since there is little loosening due to stress relaxation, the surface pressure retention is good, the durability is excellent, and the ball hitting property is comparable to that of natural gut.

  In particular, the racket gut (Examples 2, 3 and 5) in which an appropriate amount of the sea component is blended with the island component effectively suppresses the separation of the island component and the sea component, and provides a highly durable racket gut.

  On the other hand, the racket gut (Comparative Example 3) made of polyester resin having the same sea component and island component is rigid when trying to be stretched with a tension of 60 Lb, not only lacking stretchability but also resilience, It was a racket gut with poor ball control and impact resistance and low utility.

  The racket gut of the present invention is less slack due to stress relaxation than conventional racket guts, has excellent durability, and has a hitting property similar to that of natural guts, so sports such as tennis, badminton and squash When used for a racket, these effects can be exhibited.

Claims (4)

A racket gut composed of a sea-island type composite monofilament, wherein the island component of the composite monofilament is mainly composed of a polyester resin, and the sea component is at least one selected from a polyamide-based resin, a fluorine-based resin, and a polyolefin-based resin A racket gut comprising the thermoplastic synthetic resin and the number of island components of 7 to 25. 2. The racket gut according to claim 1, wherein the island component is a mixture of 99 to 60% by weight of a polyester resin and 1 to 40% by weight of the same thermoplastic synthetic resin as the sea component. The composite monofilament is composed of 10 to 40% by weight of sea component and 90 to 60% by weight of island component, and the composite monofilament has a diameter of 0.5 to 1.5 mm and a tensile strength of 3.0 to 8.0 cN / The racket gut according to claim 1, wherein the racket gut is dtex. The thermoplastic synthetic resin which comprises the said sea component is a polyamide-type resin, The gut for rackets of any one of Claims 1-3 characterized by the above-mentioned.