JPH0584331A - Racket frame - Google Patents

Abstract

PURPOSE:To provide a racket frame of fiber reinforced thermoplastic resin free from a cavity and having uniform quality. CONSTITUTION:The whole or a part of a racket frame is made of a composite sheet comprising a fibrous aggregate with reinforcing filament substantially arrayed unidirectionally lengthwise, and a thermoplastic fibrous sheet. In addition, the thermoplastic fibrous sheet is caused to intervene in between the reinforcing filament constituting the sheet, and to interlace the filament for integration. Then, the composite sheet is melted and molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frame constituting a racket used for tennis, badminton, squash and the like.

[0002]

2. Description of the Related Art In recent years, racket frames made of fiber reinforced resin composite materials have become mainstream due to their features such as light weight, high rigidity, high strength and durability. The form of the reinforcing fiber used for it is long fiber, short fiber,
Whiskers and the like have mainly used thermosetting resins such as epoxy resins as matrix resins, but thermoplastic resins such as nylon and polyphenylene ether are partially used.

However, the conventional technique has the following problems. Usually, the racket frame is made of a thermosetting resin reinforced with high-strength and high-modulus fibers such as carbon fibers. In that case, a so-called loose prepreg in which reinforcing fibers are arranged in a sheet shape is used. Is manufactured using. A racket using a thermosetting resin requires a long time at 100 to 150 ° C. for 60 to 120 minutes for the curing reaction of the resin, so that the molding cycle is long and a large number of molds are required in mass production, resulting in a cost reduction. Becomes higher. Furthermore, since the viscosity of the resin temporarily drops during molding, the resin easily flows out of the mold, creating cavities on the surface and inside of the molded body, and it takes time for the post process to repair it and The resulting strength may not be achieved.

Further, as a characteristic of the thermosetting resin, since the toughness is inferior, the resin is likely to be worn or chipped due to the impact due to contact with the coated surface, and when the outer surface is scratched, stress is concentrated on that portion and cracks occur. If it occurs, there is a drawback that the frame will be damaged. When pursuing vibration damping, which is one of the important characteristics of the racket frame, the high rigidity of the thermosetting resin appears in the performance of the frame, making it a stiff and heavy frame, and its use was practically limited. ..

On the other hand, when a thermoplastic resin is used as a matrix, short fibers are mainly used as reinforcing fibers and are manufactured by an injection molding method. However, since the reinforcing fibers are short, the rigidity of the frame is increased. It is difficult to provide a racket frame that has a large striking surface and is lightweight, because the strength of the racket is low, and the cross-sectional area of the frame is large or the wall thickness is thick to make it heavy to compensate for it. It was

In recent years, some racket frames made of thermoplastic resin using long fibers as reinforcing fibers have been found.
It is expected that, due to the high toughness of the thermoplastic resin, characteristics such as impact resistance and vibration damping property, which cannot be achieved by the conventional thermosetting resin racket frame, can be exhibited. As a molding material for the racket frame made of the long fiber reinforced thermoplastic resin, a long fiber for reinforcement and a thermoplastic long fiber serving as a matrix resin are aligned (Japanese Patent Laid-Open No. 60-
56545) or mixed fibers (JP-A-60-20903).
No. 3 gazette) in the form of a braid, in the form of a comb, or in a weft with the reinforcing long fibers or the reinforcing long fibers and the thermoplastic long fibers aligned, or a mixed fiber. Manufactured by using a thermoplastic long fiber as a weft using the prepared fiber bundle (JP-A-60-28543)
A material having a relatively good drapability such as is used. However, among these, the ones in the shape of a blind or a woven fabric are
Since only relatively thick sheets can be formed, wrinkles and disorder of fiber orientation occur in the part of the material along the inner curved part of the mold when mounting these types of materials in the mold when molding the racket frame When a strong stress is applied to this portion of the racket frame, the fiber buckles and is easily broken.
Therefore, a braided material is often used because of its good conformability of the material shape along the curve of the mold and less wrinkling or disorder of the orientation of the fiber in the molded body together with the convenience of lamination.

A racket frame using these materials is basically formed by an internal pressure or an external pressure forming method as in the case of a prepreg of a long fiber reinforced thermosetting resin, but it is formed by heating in a mold. At the same time as shaping, it is necessary to melt the thermoplastic fibers and impregnate them between the reinforcing fibers. This point is that the reinforcing fibers have already been uniformly impregnated with the resin when the material (prepreg) is not attached to the mold. This is a big difference from the case of the thermosetting resin used.

It is extremely important to uniformly impregnate the reinforcing fibers with the matrix resin from the viewpoint of physical properties such as strength and rigidity of the racket frame. This good or bad is reflected in the performance, quality of the frame and the yield at the time of manufacturing. .. However, the melt viscosity of the thermoplastic resin is much higher than the viscosity of the thermosetting resin in the monomer or prepolymer state, so that the resin is melted and fluidized uniformly and impregnated uniformly between the reinforcing fibers without unevenness. difficult.

Since the reinforcing fibers in the above-described conventional racket frame molding material in a braided form, or in the form of a blind or a woven fabric exist in the state of a bundled fiber bundle and their positions are restrained from each other, they are in a difficult state to move. It is difficult to uniformly impregnate the resin obtained by melting the thermoplastic fiber between the reinforcing fibers without unevenness, and it is necessary to increase the heating temperature and pressure during the forming and to lengthen the heating time. Therefore, there is a problem that productivity decreases and it is necessary to use an expensive internal pressure tube material that withstands high temperature and high pressure, resulting in cost increase and deterioration of physical properties of the molded product due to decomposition of the matrix resin. It was

Furthermore, as described above, since the reinforcing fibers are bound and bundled with each other, the reinforcing fibers move and spread and become uniform as the thermoplastic fiber resin melts and diffuses during molding. Since it is difficult to reinforce, the reinforcing fiber-rich portion that exists in a bundled state of the reinforcing fibers in the molded body and the resin-rich portion with few reinforcing fibers coexist, that is, molding with large unevenness of the reinforcing fiber content. It became a body and caused deterioration of the physical properties of the product and variation.

[0011]

It is an object of the present invention to provide a racket frame which has good resin impregnation property, excellent moldability, and is less likely to cause disorder of fiber orientation and has high strength and rigidity.

[0012]

In the racket frame of the present invention, the whole or a part thereof is a fiber assembly in which reinforcing long fibers are substantially aligned in one direction of the fiber length and a thermoplastic fiber. A racket characterized in that the thermoplastic fiber is melt-molded into a composite sheet in which the thermoplastic fibers are interlaced and integrated with each other by interposing between the reinforcing long fibers constituting the composite sheet. It is a frame.

Details of the composite sheet used are described in JP-A-3-47.
An example of the method for producing a composite sheet of the preferred embodiment described in Japanese Patent Publication No. 73 is as follows. That is, disperse the short fibers obtained by cutting the thermoplastic long fibers in the liquid,
The dispersion is made into paper to make a thermoplastic fiber sheet in which the fibers are randomly oriented. On the other hand, a sheet is prepared by separately arranging reinforcing long fibers in a plane direction in one direction. Thermoplastic fiber sheets are arranged on the upper and lower surfaces of the sheet, and the reinforcing long fiber sheets are sandwiched. Then, by applying a water jet fluid from the upper and lower surfaces of this sandwich-like sheet, the short fibers constituting the thermoplastic fiber sheet are made to interlace into the reinforcing long fibers constituting the reinforcing long fiber sheet to be entangled and integrated. Get a composite sheet.

The reinforcing long-fiber sheet constituting the composite sheet of the present invention is required to have the reinforcing long-fibers aligned substantially in one direction in the fiber length direction. That is, the mechanical performance of the fiber-reinforced resin composite material is most prominently expressed in the fiber length direction. Therefore, the reinforcing long fibers can exhibit mechanical performance more efficiently when the respective fiber length directions are aligned.

In the present invention, the phrase "substantially aligned with the fiber length direction aligned in one direction" means that the respective fibers are arranged substantially parallel to the averaged fiber length direction of the entire sheet. Means that As the reinforcing fiber, known high-strength, high-modulus fibers such as carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, and alumina fiber are used alone or in combination, but carbon fiber is used from the viewpoint of reinforcing efficiency and weight saving. Is most preferably used.

The other thermoplastic fiber sheet constituting the composite sheet is formed by arranging thermoplastic short fibers randomly or loosely in one direction or by arranging thermoplastic long fibers in a meandering or swirl shape. Any of the above can be used. The thermoplastic fiber is preferably low in rigidity of the fiber itself in view of easiness of entanglement and integration with the reinforcing long-fiber sheet and flexibility of the obtained composite sheet,
Although it depends on the kind of the polymer raw material used, the fiber diameter is generally 200 μm or less, preferably 100 μm or less, more preferably 50 μm or less. When using short fibers, the length is 100 cm or less, preferably 10 c.
m or less, more preferably 5 cm or less, 0.1c
When it is m or less, it is not preferable because it is difficult to entangle with the reinforcing long fiber sheet.

Examples of the polymer raw material of the thermoplastic fiber include polyolefin, polyester, polyamide, acrylic resin, polyoxymethylene, polycarbonate, polyphenylene ether, polystyrene, polyether ketone, polyether ether ketone, polyether sulfone and polyphenylene sulfide. Polymers such as polyether imide can be used. These may be alloyed in the fiber, or 2 as long as the effect is not impaired.
Although more than one kind of thermoplastic fiber may be mixed, nylon-6 and nylon-6 are used in view of the molding temperature and the physical properties of the molded body.
6 or polyester (polyethylene terephthalate) or the like is preferable.

The volume ratio of the reinforcing fibers to the volume of all the fibers in the composite sheet (representing the volume content, hereinafter abbreviated as Vf) is the required physical properties of the racket frame, the reinforcing fibers to be combined and the thermoplastic polymer. Generally, the range of 30 to 70% is preferable, and the range of 40 to 60% is more preferable, though it depends on the kind of the above. The characteristic of the thermoplastic resin racket frame that uses long fibers as reinforcing fibers is that it has excellent vibration damping properties, that is, it absorbs the vibration of the hit ball quickly and secures a stable hit ball, and the vibration is difficult to transmit to the hand. Since it is effective in preventing so-called loose tennis elbows, strong against stress cracks, and excellent in shock resistance, it is difficult to scratch when the racket comes into contact with the court surface or drops the racket, even if scratches Even if stress is concentrated on that portion, it is excellent in durability because it is difficult for cracks to develop and cracks occur between the laminated plies of the reinforcing fibers that form the frame, and for cracks to occur.

In addition to the general features described above, in the racket frame of the present invention, the composite sheet to be used is a sheet of fibers in which reinforcing long fibers are opened and aligned substantially in one direction to be arranged in a plane. In the meantime, the fibers constituting the thermoplastic fiber sheet are bent to enter and intertwine with the reinforcing long fibers so that the composite sheet has large flexibility and low rigidity, and In the manufacturing process, the reinforcing fibers are subjected to the opening action and the rubbing action by the energy of the fluid jet in order to cause the fluid jet to act on the sheet, and one of the sizing agents and sizing agents attached to the reinforcing fibers and the thermoplastic fibers. Part or most of it is inevitably removed to form a composite sheet that is flexible and rich in drape, so the composite sheet is attached to the mold when the racket frame is formed. When, with the features a small racket frame of reduction or variation in strength for can be mounted without difficulty to fit along the curved shape of wrinkles enters hardly mold the composite sheet.

Further, the racket frame of the present invention has two other great advantages, that is, the composite sheet used is a composite sheet in which thermoplastic fibers are sandwiched between reinforcing long fibers and entangled and integrated to form a racket frame. Sometimes the thermoplastic fiber resin that is heated and melted is easily and uniformly impregnated between the fibers of the reinforcing fiber sheet, and the reinforcing long fibers in the composite sheet (reinforcement in the case of thermosetting resin prepreg Since the reinforcing fiber is already formed in a sheet shape in which the fiber length directions are aligned in one direction, the reinforcing frame fiber has an advantage that the racket frame has a small Vf unevenness.

The advantages of excellent impregnation with the above resin are that the temperature, pressure, time during molding of the racket frame are low, low pressure,
This can be done in a short time, which in turn results in the formation of molded products with high physical properties due to the low decomposition of the thermoplastic resin due to thermal history, and the use of expensive internal pressure tube materials that can withstand high temperatures and pressures. It is possible to reduce the molding cost because the molding can be performed without a short molding cycle.

That is, by using the composite sheet of the present invention which is excellent in flexibility, drapeability and resin impregnation property, it is possible to fit well to the curved shape of the mold of the racket frame at the time of molding and to make the mold uneven. The reinforcing fiber impregnated with the resin is evenly distributed throughout the portion or the stepped portion, and a low-cost, high-quality racket frame having a uniform Vf without voids can be stably obtained.

In obtaining the racket frame, the flexibility and drapeability of the composite sheet are not impaired, for example,
The composite sheet may be used by heating it with or without applying heat and consolidating it with a means such as a press or a press roll. The cross section of the racket frame is solid or hollow.In the former, the composite sheet wound around the core material of the foam is attached to the mold and pressed by the pressure when the foam foams during heat molding. The composite sheet is formed by pressing the composite sheet against the inner wall surface of the mold.The latter is a heat-resistant tube for pressurization (for example, a rubber tube with a large elongation such as silicone rubber or fluorine rubber, or a heat-resistant tube such as polyimide or aramid). A composite sheet wrapped around a polymer tube) is attached to the mold, and the tube is pressed from the inside with a fluid such as air to press the composite sheet against the inner wall surface of the mold during heat molding. To shape.
The latter method is preferable in terms of weight reduction of the racket frame and ease of laminating work at the time of molding, but depending on the shape of the racket frame, both methods may be combined for molding.

The method of wrapping the composite sheet around the foam or tube and laminating it in molding is not particularly limited. For example, a method of winding a wide composite sheet by a sheet winding method, or a tape-shaped composite sheet The composite sheet may be processed into a cylindrical braided shape from the method of winding by a method or the convenience of lamination and then inserted into the foam or tube.

The braid is a general term for strings produced by a braiding machine. It is a group of sheets that intersect in two directions opposite to each other to form a string, and the sheet groups are mutually connected. While interlacing, they are oriented obliquely with respect to the axis at a constant angle, and when such a braid is attached to a curved mold, the sheet itself becomes curved by shifting the orientation direction and follows the mold shape. It fits comfortably.

The braid of the composite sheet can be obtained by processing the composite sheet with a narrow width by a braiding machine. At this time, it is better to take care not to twist the composite sheet. The narrow width composite sheet used for the braid may be manufactured by arranging the reinforcing long fibers in one direction to have a width of a required size from the beginning at the time of manufacturing the composite sheet. After making a wide composite sheet,
It is preferable to cut (slit) it in parallel with the direction of alignment of the reinforcing long fibers to form a tape-shaped composite sheet having a required width.

The composite sheet in this case can be obtained by sequentially cutting while feeding the sheet using a shear type cutter or an ultrasonic type cutter. At that time, the blade of the slitter or the sheet is heated to form the composite sheet. It is also possible to cut the thermoplastic fiber while melting or softening it.
As another method, for example, the composite sheet once wound into a roll shape can be obtained by cutting the composite sheet as it is into a required width in a sliced manner.

What is possible for them is that the composite sheet for producing the racket frame of the present invention is a sheet in which the thermoplastic fibers are mixed into the sheet in which the reinforcing long fibers are aligned in one direction and arranged and entangled and integrated. Therefore, even if cut according to the usage form, the cut surface is frayed or disturbed, and the cut composite sheet can maintain the integral shape without the reinforcing long fibers or the thermoplastic fibers falling off, that is, This is because the sheet has excellent shape retention and handleability.

The width of the composite sheet used for the braid is not particularly limited, and the diameter of the braid and the arrangement of the reinforcing fibers, which are required from the design of the racket frame, that is, the size, rigidity, and strength of the cross section of the frame. It is determined from the angle and the number of sheets to be driven, but generally 3 mm to 10
A width of 5 mm, preferably a width of 5 mm to 7 mm is used.

The assembling angle of the tape-shaped composite sheet when it is made into a braid is not particularly limited and is determined by the design condition of the racket frame and the width of the composite sheet. Generally, for example, the width of the composite sheet is 5 mm. For 7 mm, an angle of 20 ° to 35 ° is used. The rigidity and strength of the racket frame can be arbitrarily adjusted by the type and orientation angle (laminating angle) of the reinforcing long fibers of the composite sheet to be used, and the reinforcing long fibers Vf. However, only the braids constitute the reinforcing long fibers. Since the fibers themselves are arranged at an angle, the strength of the racket frame in the pipe axis direction may be insufficient.
In that case, a composite sheet in which reinforcing fibers are aligned in one direction can be arranged in parallel with the tube axis direction and used in combination.

[0031]

EXAMPLES The present invention will be described below with reference to examples.

[0032]

Reference Example 1 Nylon 6 polymer was spun to obtain 770 denier / 770 filament filaments. A large number of these long fibers were collected and cut into a length of 10 mm with a guillotine cutter to obtain short fibers. Next, this short fiber is put into water and polyacrylic amide is added to form a slurry liquid.
Continuously papermaking on 0 mesh wire mesh and basis weight 33g /
to obtain a papermaking sheet of m ^2.

Separately, polyacrylonitrile-based carbon fiber
(New Asahi Kasei Carbon Fiber, Hiker Boron
1.2Kf) 130 charcoal continuously drawn from krill
100 g / m basis weight in which elementary fibers are aligned in one direction²Collection of
The unit weight is 33g / m.²of
Place the papermaking sheet and sandwich the carbon fiber aggregate.
It's like a chi. 200 sheets of this sandwich sheet
Riding on a wire net that moves at a speed of 4 m / min of the mesh
5mm from the front and back of this sandwich sheet
500 nozzles with a diameter of 0.2 mm arranged at equal intervals
With a reciprocating motion of 5 mm in the width direction of the net, 150c
30 Kg / cm with a water jet device at pm ²Water pressure
Nylon 6 short fibers enter between the carbon fibers by applying the vertical flow.
The total weight is 166g / m.²With carbon fiber
A composite sheet having a Vf of 50% was obtained. Get in this way
Dry the resulting composite sheet in a hot air dryer at 110 ° C for 2 hours.
Let it dry.

[0034]

[Reference Example 2] A total basis weight of 250 g / m ² in the same manner as in Reference Example except that the basis weight of the papermaking sheet was 50 g / m ² and the number of carbon fibers drawn from the krill was 195 and the basis weight of the carbon fiber sheet was 150 g / m ^2. Vf of carbon fiber at m ²
Of 50% was obtained.

[0035]

Example 1 The composite sheet of Reference Example 1 was cut so that the carbon fiber array angles were 0 °, 20 °, and 45 °. This sheet was placed on a silicone rubber tube with an outer diameter of 10 mmφ and a wall thickness of 1 mm and a length of 2 m, and sheets with an arrangement angle of 45 °, 20 °, 0 ° were arranged from the inside in the manner of sheet winding.
It was mounted on a 3,2 ply wound racket frame mold.

This mold is sandwiched by a hot press heated to 250 ° C. and 10 kg / c from both ends of the silicon tube.
After applying air pressure of m ² for 35 minutes, the mold was transferred to a cooling press, cooled for 10 minutes with air pressure applied, and the mold was taken out from the press to form a racket frame. This racket frame had almost no wrinkles in the curved portion of the frame, and had no resin-impregnated portion and voids, and the nylon 6 resin was uniformly impregnated between carbon fibers.

[0037]

[Example 2] The composite sheet of Reference Example 1 was cut in parallel with the carbon fiber arraying direction to have a fiber array angle of 0 ° and a width of 25 mm.
To obtain a tape-shaped composite sheet. This tape-like sheet was wound on the same silicone rubber tube as used in Example 1 so that the tape was wound in the same manner as tape winding without any overlap or blinding, and the first and third layers of the laminated ply were angled. , 5th and 7th layers are plus direction, 2nd, 4th, 6th
The racket frame was molded in the same manner as in Example 1 by mounting it on a racket frame mold with 8 plies wound so that the eighth layer was in the negative direction.

Similar to Example 1, this racket frame was one in which nylon 6 resin was uniformly impregnated between carbon fibers having almost no wrinkles in the curved portion of the frame.

[0039]

Example 3 Two kinds of composite sheets having a width of 6 mm and a width of 5.3 mm were obtained by slitting the composite sheet of Reference Example 2 continuously with a shear slitter in parallel with the arrangement direction of carbon fibers. The slit composite sheet had no frayed cut surface, no turbulence, and no falling of fibers.

These two types of slit composite sheets were made into a cylindrical braid of 16 azireth lines by a twisting machine so that the sheet was not twisted. At this time, the assembly angle of the slit composite sheet is 25 °, the inner diameter (gauge) of the braid is 14.0 mmφ when the width is 6 mm, and 11.1 when the width is 5.3 mm.
It was mmφ. The braid thus obtained was placed on the outside of a silicone rubber tube of the same size as that used in Example 1, and had a width of 5.3 mm as the first and second layers and a width as the third layer. A 6 mm piece was put on and the braids were arranged so as to have a total of 3 plies.

Next, a silicone tube covered with 3 plies of this braid was attached to a racket frame mold and a racket frame was molded in the same manner as in Example 1. In the obtained racket frame, wrinkles were not observed at all in the curved portion of the frame, the carbon fibers were not disordered, and the nylon 6 resin was uniformly impregnated between the carbon fibers and the Vf spots were few.

[0042]

[Comparative example] Two kinds of fibers obtained by opening and mixing one carbon fiber yarn of 12 kf used in Comparative Example 1 and six nylon 6 fiber yarns of 770 denier / 770 filament by air jet. Mixed carbon fiber Vf
A fiber bundle of 50% was obtained. This fiber bundle is 24
This braid has the same cylindrical shape as the braid. At this time, the braid angle of the fiber bundle is 25 °, and the inner diameter (gauge) of the braid is 15.8.
It was mmφ.

This braid was used as a braid in the same manner as in Example 3, and a silicon tube was covered with 3 plies and then mounted on a mold to obtain a racket frame. In this racket frame, no wrinkles were observed in the curved portion of the frame, but the arrangement of the carbon fibers was disturbed and meandered, and there was a part where the nylon 6 resin was not completely impregnated between the carbon fibers. Moreover, the carbon fiber was poorly dispersed, and the carbon fiber-rich portion and the resin-rich portion, that is, the carbon fiber had a large Vf unevenness.

[0044]

EFFECT OF THE INVENTION The racket frame made of the composite material of the present invention has a uniform impregnation of the resin into the reinforcing fibers, a high homogeneity without cavities, and a small variation in strength, as compared with the conventional racket frame. It is a thing.

Claims (1)

[Claims] 1. A composite sheet comprising a thermoplastic fiber sheet and a fiber assembly in which all or part of the racket frame has reinforcing long fibers substantially aligned in one direction in the fiber length direction. A racket frame formed by melt-molding a composite sheet in which the thermoplastic fibers are interlaced and integrated by interposing between reinforcing long fibers constituting the composite sheet.