JP4804912B2 - Racket string manufacturing method and apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for producing a synthetic string for rackets such as tennis, badminton, squash, and more specifically, to produce a string excellent in physical properties and quality stability as a continuous process without using a solvent. The present invention relates to a method and apparatus for manufacturing a synthetic string for a racket that can be used.

  Conventionally, as a string for rackets such as tennis, badminton, squash, so-called braided string (braided) type string that braided leather around the core yarn and especially surface-coated around the racket string especially for badminton use ing. The manufacturing method for this type of string includes (i) a braiding process in which a leather thread is braided around the core thread, (ii) a resin processing process to impart an adhesive resin, and (iii) a surface coating process by resin processing or melt coating. It is common to perform at least three steps.

  For example, in Japanese Examined Patent Publication No. 29-5819, after a nylon resin solution is applied to a nylon core yarn and dried, a nylon monofilament is braided as a core yarn, and then the obtained yarn is used as a nylon resin solution. Discloses a method (steps (ii)-(i)-(iii)) in which surface coating is carried out using, and the core yarn and leather yarn are fixed.

  Japanese Patent Laid-Open No. 2005-304678 discloses a method in which a polyamide multifilament core yarn is surface-coated with a copolymer thermoplastic resin solution, a leather yarn is braided on the core yarn, and then coated with a polyamide solution (step ( ii)-(i)-(iii)) is disclosed. Further, impregnation with a resin after braiding is also performed (steps (ii)-(i)-(iii)).

  The step (ii) is performed for bonding and integrating the core yarn and the leather yarn. According to the above prior art, a resin solution is used as the adhesive resin for resin processing.

  On the other hand, in Japanese Patent No. 3098702, an adhesive composition containing an ultraviolet or radiation curable adhesive and an anaerobic adhesive is applied to a multifilament core yarn, and these adhesives are cured, and thereafter The manufacturing method of the string for rackets which provides resin on the surface and forms a resin coating layer is disclosed.

Japanese Patent Publication No. 29-5819 JP 2005-304678 A Japanese Patent No. 3098702

  When processing with a resin solution when manufacturing a racket string, (i) environmental pollution due to evaporation and scattering of the solvent occurs, (ii) work environment measures and explosion-proof equipment measures are required, ( iii) There is a problem that due to a change in concentration due to solvent volatilization of the liquid bath during processing or a change in viscosity due to a change in liquid temperature, there is a concern that the physical properties of the product to be obtained increase and the strength may be lowered. Although equipment to reduce these problems is possible, very expensive capital investment is required. In addition, a drying time for drying the solvent is required, which is an obstacle to increasing the production efficiency. Furthermore, when phenol or cresols with high resin solubility are used as the solvent, the polyamide fiber, which is a constituent component of the core yarn and / or leather yarn, is dissolved, resulting in a problem that the strength of the obtained string is lowered. Cheap.

  An object of the present invention is to provide a method and an apparatus for producing a synthetic string for a racket that can produce a braided string type or a wound type string excellent in stability of physical properties and quality with high production efficiency without using a solvent. There is.

  As a result of studying the above problems, the present inventors have performed processing with a molten resin at each stage before and after braiding or winding the leather thread around the core thread, so that the core part, the skin part, and the surface part can be mutually connected. It has been found that a braided or wound string with good adhesion and good stretchability and durability can be stably produced by a dry process that does not use a solvent. Furthermore, the present inventors have also found that by using a dry process that does not use a solvent, it is possible to manufacture a braided string type or a wound type string in a continuous process with a compact manufacturing facility.

The present invention includes the following inventions.
(1) A step (A) of coating the surface of a multifilament and / or monofilament as a core yarn with a molten resin;
A step (B) of braiding or winding a plurality of monofilaments and / or multifilaments to be used as a leather thread around the core component, using the yarn coated with the resin obtained in step (A) as a core component;
A method for producing a string for a racket, comprising: a step (C) of forming a surface resin layer by coating a surface layer of the yarn obtained in the step (B) with a molten resin.

(2) The manufacturing method of the string for rackets as described in said (1) which performs a process (A), a process (B), and a process (C) continuously.

(3) 50-100% by weight of monofilaments and / or multifilaments serving as core yarns are polyamide fibers, and 50-100% by weight of monofilaments and / or multifilaments serving as leather threads are polyamide fibers. (1) The manufacturing method of the string for rackets as described in (2).

(4) The manufacturing method of the string for rackets in any one of said (1)-(3) using a multifilament as a core yarn.

(5) The manufacturing method of the string for rackets in any one of said (1)-(4) using a monofilament as a leather thread.

(6) The melting point of the resin used in the step (A) and the melting point of the resin used in the step (C) are both 5 lower than the lowest melting point of the melting point of the filament used as the core yarn and the melting point of the filament used as the leather yarn. The method for producing a racket string according to any one of the above (1) to (5), which is lower by at least ° C.

(7) The resin used in the step (A) is selected from the group consisting of a polyamide resin, a polyurethane resin, and a polyolefin resin, and the resin used in the step (C) is a polyamide resin, a polyurethane resin, and a polyolefin. The manufacturing method of the string for rackets in any one of said (1)-(6) chosen from the group which consists of resin.

( 8 ) A melt coating apparatus that coats the surface of a filament that is a running core yarn with a molten resin, a braiding machine that braids a plurality of filaments that become a skin thread around a core component that is coated with a resin, or a winding machine that winds And a continuous manufacturing apparatus for a string for a racket, comprising a melt coating apparatus for forming a surface resin layer by coating a surface layer of a yarn with a molten resin.

  According to the present invention, the core portion, the skin portion, and the surface portion are bonded to each other at a stage before and after braiding or wrapping the skin yarn around the core yarn, thereby providing good adhesion between the core portion, the skin portion, and the surface portion. A string of a braided type or a wound type having good properties and durability can be stably manufactured by a dry process without using a solvent. Furthermore, according to the present invention, it is possible to manufacture a braided string type or a wound type string in a continuous process with a compact manufacturing facility.

Hereinafter, the present invention will be described in detail.
The racquet string produced by the present invention includes a multi-filament and / or monofilament core yarn, a multifilament and / or monofilament leather braided or wound around the core yarn, a core yarn and And a surface resin layer provided so as to cover the leather thread.

  In the present invention, the monofilament and / or multifilament fiber material constituting the core yarn and the leather yarn is not particularly limited, and polyamide-based fibers such as nylon 6 and nylon 66, which are conventionally used in racquet strings, are used. Other examples include polyester fibers and polyolefin fibers. Further, heat-resistant fibers such as polyphenylene sulfide, polyether ether ketone, aromatic polyamide, wholly aromatic polyester, and high-strength fibers can be used as components that can be mixed. As monofilaments and / or multifilaments, it is desirable to use 50% by weight or more of polyamide fiber as a main constituent.

  As the core yarn, specifically, a yarn (20 to 500 t / m) obtained by twisting high-strength nylon 6 or nylon 66 multifilament (single yarn of about 3 to 20 dtex) is preferably used. Thicker thread bundles, so-called monomultis, can also be used. In addition, other materials can be appropriately mixed in these, but as described above, it is desirable to use 50% by weight or more of the polyamide fiber as the main constituent component.

  A thin polyamide monofilament with a thickness of about 15 to 50 dtex is preferably used as the leather yarn when braiding on the surface of the core yarn. Although there is no limitation in the number of use, it is normally braided using about 16 to 64 pieces.

  Moreover, as a leather thread in the case of winding around the core yarn surface, a polyamide monofilament having a diameter of about 0.05 to 0.25 mm is preferably used. Although the number of winding is not limited, about 16 to 30 are usually used.

  Similar to the core yarn component, other fibers can also be used for the skin yarn component. However, as described above, it is desirable to use 50% by weight or more of the polyamide fiber as the main component.

  In the present invention, a molten resin is used in each of the step (A) and the step (C). In order to avoid the influence of heat on the core yarn and the leather yarn, all of these resins have a melting point equal to or lower than the lowest melting point of the melting point of the filament used as the core yarn and the melting point of the filament used as the leather yarn, Preferably, a resin having a melting point lower by 5 ° C. or more, more preferably a melting point lower by 15 ° C. or more is used. If the melting point of the resin is higher than the melting point of any one of the filaments used, the fiber material itself or a part thereof melts at the melting temperature of the resin during coating processing, although depending on the contact time, and this is not preferable. That is, it is preferable that the temperature of the molten resin is equal to or lower than the melting point of the fiber material in contact.

  The type of resin used in the step (A) and / or the step (C) is not limited, but it is preferable to use a resin having good adhesion to the fiber material.

  Specifically, for example, when the fiber is nylon 66 (melting point: 255 ° C.), a resin having a melting point of preferably 250 ° C. or lower, more preferably 240 ° C. or lower is used as the molten resin. Specific examples of such resins include nylon 6, nylon 610, nylon 612, nylon 12, nylon 6/66 copolymer resin, nylon 6/12 copolymer resin, and nylon 6/66/12. Examples thereof include polyamide resins such as resins and nylon elastomers. Examples of the polyurethane resin include thermoplastic polyester polyurethane and polyether polyurethane. Examples of polyolefin resins include polyethylene resins, polypropylene resins, and other copolymers and modified products thereof. Various resins known as hot melt resins can also be used.

  When the fiber is nylon 6 (melting point: 215 ° C.), a resin having a melting point of preferably 210 ° C. or lower, more preferably 200 ° C. or lower is used. Such a resin can be selected from the above resins.

  In the present invention, the resin applied to the core yarn in the step (A) and the resin that covers the core yarn component and the skin yarn component and forms the surface resin layer in the step (C) may be different even if they are the same resin. Although it may be a resin, the melting point of the resin used in the step (A) is preferably the same or lower than the melting point of the resin used in the step (C).

  In the step (A) and / or the step (C), in order to apply the molten resin to the traveling yarn, there is no particular limitation and a known coating apparatus may be used. For example, what is necessary is just to select suitably from a well-known apparatus according to the thickness of the string to obtain, a use, a surface state, etc. Usually, it is preferable to use a coating apparatus provided with a resin heating and melting part such as a small extruder, a measuring part such as a gear pump, and a coating head part for uniformly applying the molten resin to the target yarn surface. In some cases, the gear pump can be omitted.

  In the step (B), the yarn coated with the resin obtained in the step (A) is used as a core component, and a plurality of preferably monofilaments that become leather yarn are braided or wound around the core component. The braiding or winding is not particularly limited as long as it is a device capable of braiding or winding the leather around the traveling yarn, and a known braiding machine or winding machine may be used. For example, as the braiding machine, a horizontal high-speed stringing machine can be used, and as the winding machine, a device for winding a leather thread around a core thread while rotating a plurality of bobbins in a certain direction can be used.

  In the production method of the present invention, (i) the adhesive resin is applied to the yarn in a molten state at each stage (steps (A) and (C)) before and after the braiding or winding step (B) of the core yarn to the core yarn. It is characterized in that (ii) no solvent is used, and (iii) step (A), step (B) and step (C) can be carried out continuously.

  First, the present invention is characterized in that (i) the adhesive resin is applied to the yarn in a molten state at each stage before and after the braiding or winding step (B) of the leather around the core yarn. Only by melt coating after braiding or wrapping, it is difficult to impregnate the molten resin into the inside, so that the adhesion between the core yarn and the leather yarn is insufficient, and the resulting string tends to be broken. On the other hand, if the molten resin is simply applied to the core yarn, the surface of the leather yarn is hardly covered with the resin, so that the obtained string has insufficient durability. By applying a molten resin before braiding or winding and at each stage after braiding or winding, a string satisfying the resistance to folding back and durability can be obtained. Conventionally, it is known to coat the core yarn with a solvent-based resin (resin solution). However, since the drying step is not required by coating the molten resin, the core yarn covering step (A) and the braiding or winding step Since (B) can be directly connected, continuous processing is possible and the quality is stabilized. Furthermore, since there is no restriction | limiting of the solubility of resin with respect to a solvent, there also exists an advantage which can use various resin. Furthermore, by applying the molten resin even after the braiding or winding step (B), the entire string can be integrated, and the durability is improved in addition to the resistance to folding at the time of stretching.

  Next, the present invention is characterized in that (ii) no solvent is used. As an advantage of manufacturing without using a solvent, there is naturally an advantage that there is no environmental pollution due to evaporation / scattering of the solvent, and there is no concern about quality variation and strength reduction due to the use of the solvent as described above. There are advantages. In addition, products processed with conventional solvent-based resins (resin solutions) contain residual solvent even if only a small amount (usually several ppm to several tens of ppm), which may cause odor and discoloration, In the present invention, since no solvent is used in the production process, these problems do not occur. Specifically, the string produced in the present invention includes phenolic solvents such as phenol and cresol conventionally used as resin solvents, alcoholic solvents such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, trichrene, and ethane dichloride. There is an advantage that the product does not contain chlorinated solvents such as toluene, aromatic solvents such as toluene and xylene, and solvents such as dimethylformamide. Furthermore, the equipment and time for solvent drying which were conventionally required are unnecessary, and production efficiency can be improved.

  Furthermore, the present invention is characterized in that (iii) step (A), step (B) and step (C) can be carried out continuously. When a string is manufactured using the steps (A), (B), and (C) as a continuous process, the overall processing line speed becomes slow because the processing speed of the line becomes the rate of braiding (string) or the winding speed. However, since it can be manufactured continuously to the product state substantially, there is no need to make it long for passing through processes such as resin processing as in the past, and the time required for commercialization can be extremely shortened. The required space can be greatly reduced. For example, in order to obtain a long product of about 2000 m, for example, for resin processing, the present situation is that it takes two weeks or more only in the braiding process. In the present invention, when a high-speed stringing machine is used, a long product of 2000 m can be produced in two days, and quality and performance can be confirmed and initial products can be collected 30 minutes after starting the processing line. It becomes. In addition, since a series of steps of adhesion-braiding-coating is completed in a short time under the same tension in the apparatus arranged in series, the obtained string has few voids in the string, and is dense and integrated. Excellent in physical properties and good physical properties. In addition, quality changes and variations have occurred in the past due to moisture absorption and inner / outer layer differences of the yarn wound on the bobbin between processes, but such quality changes and variations have been made by using a continuous process. Therefore, there is an advantage that a string excellent in physical properties and quality stability can be obtained.

  The continuous production apparatus for strings for carrying out the production method of the present invention includes a continuous running apparatus for yarn, a melt coating apparatus for coating the surface of a filament that is a running core yarn with a molten resin, and a resin coating. A braiding machine for braiding a plurality of filaments to be used as a leather thread on the core component or a winding machine for winding, and a melt coating apparatus for coating a surface layer of the yarn with a molten resin to form a surface resin layer.

  FIG. 1 shows a configuration example of a continuous production apparatus for strings. In FIG. 1, a continuous production apparatus for strings includes a continuous running apparatus for yarn (not shown), a melt coating apparatus A for coating the surface of a filament that is a running core thread with a molten resin, and a core coated with a resin. A horizontal type high-speed cord making machine B that braids a plurality of filaments that become leather threads as components and a melt coating apparatus C that coats the surface layer of the yarn with a molten resin to form a surface resin layer are provided.

  The melt coating apparatus A includes a small extruder 11 that melts and extrudes the resin a, a gear pump 12 that quantitatively sends the molten resin a sent from the extruder 11, and a filament that melts the molten resin a sent from the gear pump 12. The coating head 13 provided with the nozzle hole provided to 1 surface is provided. In the example shown in the figure, a horizontal high-speed stringing machine B is shown as a braiding machine, and a predetermined number of tube bobbins 21 around which a braided thread b is wound and guides 22 are arranged. In the high-speed stringing machine B, the bobbin 21 and the guide 22 are rotatable about the traveling direction of the yarn so that the braided yarn b can be braided around the yarn 2. The melt coating apparatus C includes a small extruder 31 that melts and extrudes the resin c, a gear pump 32 that quantitatively sends the molten resin c sent from the extruder 31, and a molten resin c sent from the gear pump 32. 3 and a coating head 33 having nozzle holes to be applied to the surface layer.

  The core yarn 1 is caused to travel, and when passing through the coating head 13 of the melt coating apparatus A, the surface of the yarn 1 is coated with the molten resin a. The resin a is heated and melted in the extruder 11, measured by the gear pump 12, supplied to the coating head 13, and coated in a molten state on the surface of the core yarn 1 from the nozzle hole. The surface-coated yarn 2 is air-cooled, and then the braided yarn b is assembled by the string making machine B using the yarn 2 as a core. The braided yarn b wound around the bobbin (for example, 16 in the case of 16 strokes) is braided while rotating about the traveling direction of the yarn by the rotation of the bobbin 21 and the guide 22. Subsequently, when the braided yarn 3 passes through the coating head 33 of the melt coating apparatus C, the surface of the braided yarn is coated with the molten resin c to obtain the string 4. The adhesion between the resin a applied to the core yarn surface in the melt coating apparatus A and the braided leather thread b is insufficient at the stage of the yarn 3, but the resin during the melt coating of the yarn surface in the melt coating apparatus C. At least the surface layer portion of the resin a is heated and re-melted by the heat of c and bonded to the leather yarn b, so that the core yarn, the leather yarn, the resin a and the resin c are firmly integrated, and a strong and excellent string 4 is obtained. It is done.

  Although not shown in the figure, the string 4 is then cooled (water-cooled or air-cooled), and is commercialized by performing steps such as drying after water cooling, printing, and oiling as necessary. Since these steps do not have a great influence on the string structure itself, they can be performed continuously but may be performed in separate steps.

  Furthermore, in the present invention, if necessary, it is possible to form two or more multilayer coating layers as the surface resin layer by disposing a melt coating apparatus D of another resin d in the downstream of the melt coating apparatus C. It is. It is also possible to change the surface resin in the length direction (for example, change the color of the surface) by alternately switching the melt coating apparatus C and the melt coating apparatus D.

  In FIG. 1, the example using the braiding machine of the yarn filament was illustrated. If a wrapping machine is arranged instead of the braiding machine B, a wrapping type string can be manufactured. Even in this case, at the stage of the yarn 3 after winding, the adhesion between the resin a applied to the core yarn surface by the melt coating apparatus A and the wound leather yarn is insufficient, but the yarn in the melt coating apparatus C Due to the heat of the resin c at the time of the melt coating on the surface, at least the surface layer portion of the resin a is heated and re-melted and adheres to the leather thread, so that the integration of the core thread, the leather thread, the resin a and the resin c becomes strong and strong. An excellent string 4 can be obtained.

  As described above, the method of manufacturing the string by continuously performing the steps (A), (B), and (C) is exemplified. Processes (A), (B), and (C) can be performed discontinuously, or processes (A) and (B), processes (B), and (C) can be performed continuously. However, a continuous process is particularly preferable in order to maximize the effects of the present invention. The term “non-continuous” means that the steps are not continuous, for example, by winding the yarn once.

  Hereinafter, the production of braided string for badminton will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Example 1)
The apparatus shown in FIG. 1 was used. As the extruder 11 of the melt coating apparatus A and the extruder 31 of the melt coating apparatus C, a small extruder having a screw diameter of 12 mmφ and a gear pump of 0.1 cc / rotation was used. As the braiding machine B, a 16-stroke horizontal high-speed braiding machine with a speed of 0.5 to 1.5 m / min was used.

  Nylon 66 multifilament (Toray Co., Ltd., Promiran 1400T-204-T1781) single twisted yarn (300 t / m) is used as the core yarn, and low-melting copolymer nylon (Toray Co., Ltd., Amilan CM8000) is used as the molten resin in Step A. , Melting point 140 ° C.) and core yarn coating at a melting temperature of 180 ° C. Next, as the process B, a 16-pitch braiding was performed using a three-piece product of nylon 66 monofilament 0.06 mm (speed 1 m / min; braiding pitch 40 pieces / inch). Subsequently, nylon 6 (Toray Industries, Inc., Amilan CM1007, melting point 215 ° C.) was coated as a molten resin in Step C at a melt extrusion temperature of 245 ° C. (nozzle diameter 0.80 mm). Immediately after exiting the nozzle, it was cooled with water and dried to obtain a string.

  The obtained string had a diameter of 0.75 mm, a strength of 24.8 kg, an elongation of 24.4%, and a hook strength of 30.7 kg (average value of 10 samples). The maximum value-minimum value (variation) in 10 samples was 0.8 kg strength, 2.1% elongation, and 2.2 kg hook strength.

(Comparative Example 1)
16 punching string machine (16 punching string manufactured by Kokbun Limited), which is usually used so as to have the same set pitch as in Example 1, using the same core yarn and leather as used in Example 1. Machine). Next, the yarn was dipped in a 20% by weight methanol-based (solvent: methanol / phenol = 85/15 (volume ratio)) solution of Alamine CM8000 resin, and then squeezed and dried by a nozzle (resin processing). ). Thereafter, nylon 6 resin (Amilan CM1007) was melt coated at 250 ° C. using a coating apparatus (processing speed: 70 m / min).

  The obtained string had a diameter of 0.77 mm, a strength of 23.1 kg, an elongation of 25.5%, and a hook strength of 28.5 kg (average value of 10 samples). The maximum value-minimum value (variation) in 10 samples was 1.8 kg strength, 4.6% elongation, and 5.0 kg hook strength. Although the string obtained in Comparative Example 1 is basically composed of the same material as Example 1, the physical properties are slightly lower and the variation tends to be larger than that of Example 1. there were.

(Comparative Example 2)
The same core yarn as used in Example 1 was immersed in a 20 wt% methanol-based (solvent; methanol / phenol = 85/15 (volume ratio)) solution of Alamine CM8000 resin, followed by squeezing and drying with a nozzle. Winded up (core yarn resin processing). Next, the resin-processed yarn was used as a core and braided with a 16-placing string machine (16-punch stringing machine manufactured by Kokbun Limited) that is usually used so as to have the same pitch as in Example 1. Thereafter, the surface resin was processed with a solution of nylon 6 resin (Amilan CM1007) (25 wt% phenol solution).

  The obtained string had a diameter of 0.78 mm, a strength of 23.2 kg, an elongation of 26.3%, and a hook strength of 28.1 kg (average value of 10 samples). The maximum value-minimum value (variation) in 10 samples was a strength of 2.0 kg, an elongation of 5.4%, and a hook strength of 5.8 kg. Although the string obtained in Comparative Example 2 is basically made of the same material as Example 1, the physical properties are slightly lower and the variation tends to be larger than that of Example 1. there were.

  Each of the strings obtained in Example 1 and Comparative Examples 1 and 2 was stretched as badminton gut (23 pounds) and subjected to trial hitting (5 people). The string of Example 1 was more resistant to bending than those of Comparative Examples 1 and 2, and could be lifted up satisfactorily. The string of Comparative Example 1 was evaluated to be somewhat easily broken. In the trial hits, 4 out of 5 people showed that the results of Example 1 were better than those of Comparative Examples 1 and 2 in terms of both taste and durability. Moreover, although the thing of Example 1 did not have an odor, the thing of the comparative example 1 felt the phenol odor, and the thing of the comparative example 2 felt the odor clearly.

(Example 2)
The same apparatus as in Example 1 was used. Nylon 6 multifilament (Toray Co., Ltd. Amilan 1400T-204-T781) single twisted yarn (300 t / m) is used as the core yarn, and low melting copolymer nylon (Toray Co., Ltd., Amilan CM8000, And a core yarn coating at a melting temperature of 180 ° C. Next, as the process B, 16 punches were braided using a three-piece product of nylon 6 monofilament 0.06 mm (speed 1 m / min). Subsequently, the same resin (Amilan CM8000) as that in Step A was coated as a resin in Step C at a melt extrusion temperature of 180 ° C. (nozzle diameter 0.80 mm). Immediately after exiting the nozzle, it was cooled with water and dried to obtain a string.

  The obtained string had a diameter of 0.75 mm, a strength of 24.9 kg, an elongation of 25.4%, and a hook strength of 30.9 kg (average value of 10 samples). The maximum value-minimum value (variation) in 10 samples was 1.1 kg strength, 2.0% elongation, and 1.5 kg hook strength.

(Example 3)
The braiding machine B in the apparatus shown in FIG. 1 was replaced with a winding apparatus. As the extruder 11 of the melt coating apparatus A and the extruder 31 of the melt coating apparatus C, a small extruder having a screw diameter of 12 mmφ and a gear pump of 0.1 cc / rotation was used.

  Nylon 6 multifilament single twisted yarn (four Amilan 1400T-204-T781 from Toray Industries, Inc., combined to give a single twist of 200 times / m) is used as the core yarn component. Using a melting point polyamide resin (Toray Industries, Inc., Amilan CM8000, melting point 140 ° C.), coating was performed at a melting temperature of 185 ° C. Next, as the process B, 20 nylon 6 monofilaments 0.155 mm were wound so that there was no gap on the surface (speed: 3 m / min). Subsequently, nylon 12 (Ube Industries, 3014B) was coated at a melt extrusion temperature of 200 ° C. (nozzle diameter 1.35 mm) as a resin for the C process. Immediately after exiting the nozzle, it was cooled with water and dried to obtain a string.

  The obtained string had a diameter of 1.31 mm, a strength of 72.9 kg, and an elongation of 25.8%. This string had good punch and durability for hard tennis.

It is a figure which shows schematic structure of the continuous manufacturing apparatus of the string of this invention.

Explanation of symbols

A: Melt coating apparatus 11: Extruder 12: Gear pump 13: Coating head B: Braiding machine 21: Tube bobbin 22: Guide C: Melt coating apparatus 31: Extruder 32: Gear pump 33: Coating head 1: Core yarn 2: Core yarn 3 after coating: String 4 after braiding 4: String after surface coating a: Resin for core yarn coating b: Leather yarn for braiding c: Resin for surface coating

Claims (8)

A step (A) of coating the surface of the multifilament and / or monofilament as a core yarn with a molten resin;
A step (B) of braiding or winding a plurality of monofilaments and / or multifilaments to be used as a leather thread around the core component, using the yarn coated with the resin obtained in step (A) as a core component;
A method for producing a string for a racket, comprising: a step (C) of forming a surface resin layer by coating a surface layer of the yarn obtained in the step (B) with a molten resin.   The manufacturing method of the string for rackets of Claim 1 which performs a process (A), a process (B), and a process (C) continuously.   The monofilament and / or multifilament used as the core yarn is 50 to 100% by weight of the polyamide fiber, and the monofilament and / or multifilament used as the skin yarn is 50 to 100% by weight of the polyamide fiber. The manufacturing method of the string for rackets of Claim 2.   The manufacturing method of the string for rackets in any one of Claims 1-3 which uses a multifilament as a core yarn.   The manufacturing method of the string for rackets in any one of Claims 1-4 which uses a monofilament as a leather thread.   The melting point of the resin used in step (A) and the melting point of the resin used in step (C) are both 5 ° C. or more lower than the lowest melting point of the melting point of the filament used as the core yarn and the melting point of the filament used as the leather yarn. The manufacturing method of the string for rackets in any one of Claims 1-5.   The resin used in the step (A) is selected from the group consisting of a polyamide resin, a polyurethane resin, and a polyolefin resin, and the resin used in the step (C) is selected from a polyamide resin, a polyurethane resin, and a polyolefin resin. The manufacturing method of the string for rackets in any one of Claims 1-6 selected from the group which consists of.   A melt coating apparatus that coats the surface of a filament that is a running core yarn with a molten resin, a braiding machine that braids a plurality of filaments that are leather threads around a core component that is coated with a resin, or a winding machine that winds; A continuous manufacturing apparatus for a string for a racket, comprising: a melt coating apparatus for forming a surface resin layer by coating the surface layer of the rack with a molten resin.

Images