JP6294281B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball, and more particularly to a golf ball provided with a cover mainly composed of polyurethane.

  Golf balls are required to have a flight distance and controllability. The flight distance of the golf ball is affected by the initial speed of the golf ball. The initial velocity of the golf ball is affected by the rebound of the golf ball. For this reason, ionomers are used for golf ball covers as a material with good resilience. However, since ionomers have high rigidity and hardness, they are difficult to be spun. Controllability is affected by the amount of spin. For this reason, polyurethane is used for golf ball covers as a material that is easily spun. However, there is a problem that the resilience of polyurethane is not good. In response to this problem, Japanese Patent No. 5371818 (Patent Document 1) proposes a cover material containing polyurethane having excellent resilience.

Japanese Patent No. 5371818

  As a result of intensive studies by the present inventors, it has been found that the flight distance of the golf ball does not improve even when the cover material described in the above publication is simply used for the golf ball.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a golf ball capable of improving a flight distance while maintaining the performance of being easily spun.

The golf ball of the present invention is a golf ball that includes a spherical core and a cover that covers the core. The cover includes polyurethane as a main component. The tan δ (loss tangent) of the cover is 0.11 or less at a measurement temperature of 23 ° C. and a frequency of 1000 Hz. The lift coefficient of the golf ball is 0.20 or more and 0.22 or less when the spin parameter is 0.1.

  The inventor of the present invention paid attention to the fact that the tan δ (loss tangent) of the polyurethane is larger than the tan δ of the ionomer as a reason why the resilience of the polyurethane is not good. Therefore, the use of polyurethane with a small tan δ for the cover was examined. However, it was found that when a polyurethane having a small tan δ is used as a cover, the polyurethane is likely to be spun, so that the trajectory of the golf ball blows up as the spin rate increases. This is noticeable on driver shots. As a result, it was found that the flight distance decreased. Accordingly, the inventor has earnestly studied a golf ball that can improve the flight distance while maintaining the performance that is likely to be spun, and has come up with the aerodynamic characteristics of the golf ball.

The present inventors have, tan [delta measurement temperature 23 ° C. cover comprising a polyurethane as a main component, at a frequency 1000 Hz, and 0.11 or less, when the lift coefficient of the golf ball spin parameter is 0.1, 0.20 It has been found that when the distance is 0.22 or less, the flight distance can be improved while maintaining the performance of being easily spun. That is, the present inventor has found that the performance of being easily spun by polyurethane can be maintained, and the flight distance can be improved by suppressing the rise of the golf ball trajectory due to the increase in the spin amount by the aerodynamic characteristics of the golf ball. .

  In the above golf ball, the difference between the surface hardness and the center hardness according to the JIS-C hardness of the core is preferably 14 or more and 40 or less. As a result, the present inventor has found that the effect of forcibly lowering the jumping spin amount due to the internal soft / external hard effect can be obtained.

  In the above golf ball, the Shore D hardness in the state of the cover sheet is 43 or more and 60 or less. As a result, the present inventor has found that an excellent feel can be obtained.

  In the above golf ball, the Shore D hardness in the state of the golf ball of the cover is 50 or more and 71 or less. As a result, the present inventor has found that an excellent feel can be obtained.

  In the above golf ball, the cover has a thickness of 0.4 mm or more and 2.3 mm or less. If the cover is too thin, the effect of polyurethane with good resilience cannot be brought out. Further, if the cover is too thin, it is difficult to manufacture and the manufacturing cost increases. On the other hand, if the cover is too thick, the material cost increases. On the other hand, if the cover is too thick, sink marks after the molding of the material become large, and designing for maintaining aerodynamic characteristics becomes difficult. When the cover thickness is 0.4 mm or more and 2.3 mm or less, the effect of polyurethane with good resilience can be brought out, the manufacturing cost is reduced, the material cost is reduced, and the design for maintaining the aerodynamic characteristics is easy. The present inventor has found that

  In the above golf ball, the compression of the golf ball is 63 or more and 121 or less. If the compression of the golf ball is too hard, too much spin will be applied. If the compression of the golf ball is too soft, a soft material will be used for the core. In this case, the rebound of the golf ball also decreases as the core rebound decreases. It has been found that when the compression of the golf ball is not less than 63 and not more than 121, it is possible to suppress excessive spin and to suppress a decrease in rebound of the golf ball.

  The golf ball further includes a paint layer that covers the cover. The paint layer is composed of one or two coating films. Since polyurethane turns yellow, in order to maintain the quality of the appearance over time, there are usually those having three or more coating films. If the coating film increases, the coating film may become thicker than intended, and if so, the depth of the dimples becomes shallow and the lift may increase more than necessary. Moreover, since the variation of a coating film will increase when a coating film increases, the dispersion | variation in an aerodynamic characteristic will become large. The inventor has found that the paint layer can be either one layer or two layers. Thus, the inventor has found that the aerodynamic characteristics can be maintained and the aerodynamic characteristics can be stabilized.

  In the above golf ball, the cover is a cover material containing polyurethane obtained by reacting an isocyanate component and an active hydrogen compound component, and the isocyanate component contains 1,4-bis (isocyanatomethyl) cyclohexane. It is characterized by. Thereby, a cover with good resilience can be obtained.

  In the above golf ball, the cover is made of a polyurethane obtained by reacting an isocyanate component containing 1,4-bis (isocyanatomethyl) cyclohexane and an active hydrogen compound component, a thermoplastic elastomer, and 1,4- Bis (isocyanatomethyl) cyclohexane is kneaded and molded. Thereby, a cover with good resilience can be obtained.

  As described above, it is possible to provide a golf ball capable of improving the flight distance while maintaining the performance of being easily spun.

1 is a schematic front view of a golf ball according to an embodiment of the present invention. It is sectional drawing which follows the II-II line | wire of FIG. It is a figure for demonstrating the state of the golf ball in flight. It is sectional drawing of the golf ball of the modification 1 of one embodiment of this invention. It is sectional drawing of the golf ball of the modification 2 of one embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the structure of the golf ball in the present embodiment will be described.

  Referring to FIGS. 1 and 2, golf ball 1 includes dimple 2, land 3, spherical core 4, and cover 5 that covers core 4. A large number of dimples 2 are provided on the surface of the cover 5. A portion of the surface of the cover 5 other than the plurality of dimples 2 is a land 3. The golf ball 1 includes a paint layer and a mark layer on the outside of the cover 5, but these layers are not shown.

  Here, regarding the flight distance of the golf ball, the in-flight golf ball 1 struck by the club has a gravity 11, an air resistance (drag) 12, and the golf ball 1 has a spin as shown in FIG. 3. It is known to receive the lift 13 that occurs in The golf ball 1 moves in the flight direction 14 and rotates in the arrow direction 16 about the ball center 15.

In this case, the force acting on the golf ball 1 is represented by the following ballistic equation (1).
F = FL + FD + Mg (1)
F: Force acting on the golf ball, FL: Lift, FD: Drag, Mg: Gravity Further, lift FL and drag FD in the ballistic equation (1) are expressed by the following formulas (2) and (3), respectively.

FL = 0.5 × CL × ρ × A × V ² (2)
FD = 0.5 × CD × ρ × A × V ² (3)
CL: lift coefficient, CD: drag coefficient, ρ: air density, A: golf ball maximum cross-sectional area, V: golf ball air velocity The lift coefficient CL of the golf ball 1 is obtained when the spin parameter Sp is 0.1. It is 0.15 or more and 0.22 or less.

  The drag coefficient CD and the lift coefficient CL affect the trajectory of the golf ball. The American Golf Association (USGA) has published a manual for the ballistic calculation program. By inputting the drag coefficient CD and the lift coefficient CL into the program according to this manual, the flight distance of the golf ball can be predicted. The drag coefficient CD and the lift coefficient CL are measured by ITR (Indoor Test Range) defined in USGA rules.

  Note that the lift coefficient CL is calculated by using a pneumatic force measuring device as disclosed in Japanese Patent No. 498148, and blowing the wind on the rotated golf ball to generate a three-component force (drag, lift, lateral force). Force).

  The spin parameter Sp is defined by the following equation (4). The spin parameter is expressed as peripheral speed / speed.

Sp = πdN / U (4)
Each symbol in Expression (4) will be described. d is the diameter (m), N is the rotational speed (rps), and U is the ball speed (m / s). For example, when the ball speed (ball speed) is 60 m / s and the rotation speed is 2684 rpm, the spin parameter Sp≈0.1.

  Further, the spin parameter Sp is related to the Reynolds number Re through the following equation (5) through U.

Re = UL / ν (5)
Re: Reynolds number, U: Flow velocity (m / s) (ball velocity), L: Representative length (m) (ball diameter), ν: Kinematic viscosity coefficient Air (1 atm, 20 ° C.): 1.51 × 10 ^-5 (m ² / s)
Using equation (5), for example, when the Reynolds number is 17000 and the spin amount is 2684 rpm, the spin parameter Sp≈0.1.

  It is preferable that the compression of the golf ball is 63 or more and 121 or less. Compression refers to the force required to deform a ball by a predetermined size with a compression tester. Specifically, it is the load when a compression tester is used and the ball is compressed and deformed by 2.54 mm at 10 mm / min.

  The diameter of the golf ball 1 is required to be 42.67 mm or more according to rules (see R & A and USGA). However, in consideration of aerodynamic characteristics and the like, it is preferable to make the ball diameter as small as possible, for example, 42.7 to 43.7 mm. The weight is also required to be 45.93 g or less according to the rules. Considering the flight distance performance of the ball, the weight is preferably as large as possible, and can be 45.2 g to 45.93 g or less.

  In the golf ball 1 of the present embodiment, one or more intermediate layers may be provided between the core 4 and the cover 5. Referring to FIG. 4, in golf ball 1 of Modification 1 of the present embodiment, intermediate layer 6 is provided between core 4 and cover 5.

  In the golf ball 1 of the present embodiment, the paint layer 7 covering the cover 5 may have two or less coating films. Referring to FIG. 5, golf ball 1 of Modification 2 of the present embodiment includes paint layer 7. The paint layer 7 is composed of one or two coating films.

  The shape of the core 4 is generally spherical, but for example, protrusions may be provided so as to divide the surface of the spherical core 4 evenly, or recesses that are evenly distributed are provided. May be. In the case of providing the ridge, the concave portion partitioned by the ridge is filled with a plurality of envelope layers or a single envelope layer covering each of the recesses, so that the core 4 and the envelope layer are formed. The shape of the molded body is preferably spherical. When providing a recessed part, it is shape | molded so that a recessed part may be filled with the outer-layer material which coat | covers the core 4, and it is preferable to make a shape spherical.

  The core 4 is formed in a spherical shape and is formed of a rubber composition. The diameter of the core 4 is preferably 33.0 mm to 41.0 mm, and particularly preferably 38.5 mm to 40.0 mm. If the core 4 is small, the resilience performance is lowered, and if the core 4 is too large, the cover 5 covering the core 4 is too thin and the durability is lowered, or the ball becomes too soft and the resilience performance is lowered. .

  The core 4 can be manufactured from a known rubber composition containing a base rubber, a cross-linking material, a metal salt of an unsaturated carboxylic acid, a filler, and the like. As the base rubber, natural rubber, polyisobrene rubber, styrene butadiene rubber, EPDM and the like can be used, but high cis polybutadiene having at least 40% or more, preferably 80% or more of cis 1,4 bonds should be used. Is particularly preferred.

  As the crosslinking agent, for example, organic peroxides such as dicumyl peroxide and t-butyl peroxide can be used, but it is particularly preferable to use dicumyl peroxide.

  As the metal salt of the unsaturated carboxylic acid, it is preferable to use a metal salt of a monovalent or divalent unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid, but zinc acrylate is used. Then, the resilience performance of the ball can be improved, which is particularly preferable.

  What is normally mix | blended with a core can be used for a filler, for example, a zinc oxide, barium sulfate, a calcium carbonate etc. can be used. Moreover, you may mix | blend an organic sulfur compound, an antioxidant, a peptizer, etc. as needed.

  In addition, the material which comprises the core 4 can use a well-known elastomer other than the said rubber composition.

  The difference between the surface hardness and the center hardness according to the JIS-C hardness of the core 4 is preferably 14 or more and 40 or less. The JIS-C hardness is a hardness measured according to the spring hardness test type C test method referred to in JIS K 7312 Appendix 2.

  The cover 5 is made of an elastomer. The cover 5 contains polyurethane as a main component. The cover 5 contains 50% by mass or more of polyurethane. The tan δ (loss tangent) of the cover 5 is 0.11 or less at a measurement temperature of 23 ° C. and a frequency of 1000 Hz. The loss tangent is a ratio of the loss elastic modulus E ″ (G ″) and the storage elastic modulus E ′ (G ′) in the viscoelasticity measurement, as shown in the following formula (6).

tanδ = E ″ / E ′ (= G ″ / G ′) (6)
Here, the characteristic of the elastic body (individual property) of the material is expressed by E ′ (G ′), and the characteristic of the viscous body (liquid property) of the material is expressed by E ″ (G ″). Here, it is considered that the rebound characteristics of the material are better as E ′ (G ′) is larger and E ″ (G ″) is smaller. Therefore, it is considered that smaller tan δ is more advantageous.

  The Shore D hardness of the cover 5 in the sheet state is preferably 43 or more and 60 or less. Shore D hardness is a hardness measured according to JIS K 7215.

  The Shore D hardness of the cover 5 in the state of the golf ball 1 is preferably 50 or more and 71 or less.

  The thickness (layer thickness) of the cover 5 is preferably 0.4 mm or more and 2.3 mm or less. The thickness of the cover 5 is particularly preferably 0.9 mm or more and 1.99 mm or less. In general, since the resilience of polyurethane is not good, the thickness of the cover 5 made of polyurethane is made thin. In the present embodiment, since the resilience of polyurethane is good, the thickness of the cover 5 can be increased.

  The cover 5 is a cover material containing polyurethane obtained by reacting an isocyanate component and an active hydrogen compound component, and the isocyanate component contains 1,4-bis (isocyanatomethyl) cyclohexane.

  The cover 5 is made of polyurethane obtained by reacting an isocyanate component containing 1,4-bis (isocyanatomethyl) cyclohexane and an active hydrogen compound component, a thermoplastic elastomer, and 1,4-bis (isocyanato). Methyl) cyclohexane may be kneaded and molded. The cover 5 can use what was described in the patent 5371818 gazette, and can be manufactured by the method described in this gazette.

  When the cover 5 contains the other resin component of the polyurethane, the polyurethane content is, for example, 50% by mass or more, preferably 60% by mass with respect to the total amount of the polyurethane and the other resin components. As mentioned above, More preferably, it is 70 mass% or more. Furthermore, it is also a preferable aspect that it consists only of the said polyurethane.

  In addition to the above resin component, the cover 5 is within a range that does not impair the performance of the cover material, for example, pigment components such as zinc oxide, titanium oxide, and blue pigment, for example, specific gravity adjusting agents such as calcium carbonate and barium sulfate, Furthermore, for example, an anti-aging agent, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent whitening agent, and the like can be contained.

Examples of the pigment component include titanium oxide as a white pigment.
When titanium oxide is blended, the content thereof is, for example, 0. 100 parts by mass with respect to 100 parts by mass of a resin component (polyurethane as an essential component and other resin components as an optional component, the same shall apply hereinafter). 5 parts by mass or more, preferably 1 part by mass or more, and usually 8 parts by mass or less.

  When the content of titanium oxide is within the above range, it is possible to ensure concealability, rebound resilience, and durability of physical properties as a cover material.

Next, a method for manufacturing the golf ball of the present embodiment will be described.
First, the core 4 is formed. In the formulation of Table 1 described in the examples, the kneaded rubber was kneaded with a kneader and the kneaded with a roll using a kneader, and the kneaded rubber was cut (preliminarily molded) to a predetermined mass. (Preliminary product) is set in the mold. This die is molded in the range of 140 to 170 ° C., and the molding time is set as a time that can be appropriately molded at that temperature to obtain the core 4. The shape of the core 4 is generally formed in a spherical shape. A protrusion or a recess may be formed on the surface of the core 4. Since the obtained core 4 may still have burrs and footwear, it may be obtained by polishing with a predetermined polishing machine. When forming a mantle layer, this core is set in an injection molding machine, molded at an injection temperature and pressure suitable for the material used for the mantle, and then polished for the purpose of removing gates, burrs, etc. . Subsequently, the cover 5 is formed so as to cover the core 4. Moreover, when forming a mantle layer, the cover 5 is shape | molded so that a mantle layer may be coat | covered.

  The cover 5 is manufactured by thermoforming a resin component mainly composed of the above polyurethane. For example, it is possible to cite heat compression molding using a specific mold or injection molding directly on the core layer.

  The thermoforming temperature is, for example, 180 to 240 ° C, preferably 185 to 230 ° C. The molding pressure is, for example, 0.5 to 25 MPa, or preferably 1 to 20 MPa. The cover 5 having a uniform thickness can be obtained by thermoforming under the above conditions.

  When the cover 5 is molded, the dimples 2 are formed on the cover surface. After forming the cover 5, deburring, cleaning, polishing, painting, and mark printing are performed as necessary, and the golf ball 1 is completed. At that time, by appropriately polishing the molded product using a wet vibration barrel or the like, the dimple depth can be adjusted to obtain a desired lift coefficient CL.

Next, the function and effect of the golf ball of the present embodiment will be described.
The inventor has found the aerodynamic characteristics of the golf ball 1 that can improve the flight distance while maintaining the performance of being easily spun.

  When the tan δ of the cover 5 containing polyurethane as a main component is 0.11 or less at a measurement temperature of 23 ° C. and a frequency of 1000 Hz, and the lift coefficient Sp of the golf ball 1 is 0.1, It has been found that the flight distance can be improved while maintaining the performance of being easily spun by being 0.15 or more and 0.22 or less. That is, the present inventor can maintain the performance that is easy to be spun by polyurethane, and can improve the flight distance by suppressing the rising of the trajectory of the golf ball 1 due to the increase of the spin amount by the aerodynamic characteristics of the golf ball 1. I found it.

  In addition, since the difference between the surface hardness and the center hardness according to JIS-C of the core 4 is not less than 14 and not more than 40, it is possible to obtain the effect of forcibly reducing the jump spin amount due to the internal / external hard / hard effect. Found.

  Further, the present inventor has found that an excellent feel can be obtained when the Shore D hardness of the cover 5 in the sheet state is 43 or more and 60 or less.

  Further, the present inventors have found that an excellent feel can be obtained when the Shore D hardness of the cover 5 in the state of the golf ball 1 is 50 or more and 71 or less.

  In addition, when the thickness of the cover 5 is 0.4 mm or more and 2.3 mm or less, the effect of polyurethane with good resilience can be brought out, the manufacturing cost can be suppressed, the material cost can be suppressed, and the aerodynamic characteristics can be maintained. The present inventor has found that this is easy.

  In addition, it has been found that, when the compression of the golf ball 1 is 63 or more and 121 or less, it is possible to suppress excessive spin and to suppress a reduction in rebound of the golf ball 1.

  The paint layer 7 is composed of one or two coating films. Usually, the coating film has three or more layers. As the coating film increases, the aerodynamic characteristics deteriorate because the coating film becomes thicker. Moreover, since the variation of a coating film will increase when a coating film increases, the dispersion | variation in an aerodynamic characteristic will become large. The inventor has found that the paint layer can be either one layer or two layers. Thus, the inventor has found that the aerodynamic characteristics can be maintained and the aerodynamic characteristics can be stabilized.

  In the golf ball 1, the cover 5 is a cover material containing polyurethane obtained by reacting an isocyanate component and an active hydrogen compound component, and the isocyanate component contains 1,4-bis (isocyanatomethyl) cyclohexane. It is characterized by including.

  Alternatively, in the golf ball 1, the cover 5 includes a polyurethane obtained by reacting an isocyanate component containing 1,4-bis (isocyanatomethyl) cyclohexane and an active hydrogen compound component, a thermoplastic elastomer, It may be formed by kneading and molding 4-bis (isocyanatomethyl) cyclohexane. Thereby, the cover 5 with good resilience can be obtained.

  Examples of the present invention will be described below.

  With reference to Table 1 and Table 2, Examples 1-21 are examples of the present invention, and Comparative Examples 1-9 are comparative examples for the present invention.

  The inventor prepared golf balls of Examples 1 to 21 and Comparative Examples 1 to 9 having configurations shown in Tables 1 and 2. And the ball performance of each of these golf balls was measured.

  The measurement results are shown in Tables 1 and 2. Each item in Table 1 and Table 2 will be described. The structure shows two-piece (2P) or three-piece (3P). The core formulation indicates the formulation of the core material.

  The compression is a value obtained by measuring a load when a ball is compressed and deformed by 2.54 mm at 10 mm / min using a precision universal testing machine (Autograph AG-5000D (manufactured by Shimadzu Corporation)) as a compression testing machine. . The core, mantle and golf ball were all measured by the above method. The number of measurements was over half a dozen (six), and the value was averaged. The measurement was performed immediately after taking out what was stored in a constant temperature bath of about 23 ° C. from the day before the measurement.

  The JIS-C hardness was measured immediately after taking out what was stored in a thermostat of about 23 ° C. from the day before the measurement. JIS-C hardness (surface) measured the surface of the core. As for JIS-C hardness (center), the core was cut into two and the center hardness was measured. Regarding the surface hardness of the core, the surface hardness was measured (in the direction from the core surface toward the core center). For the center hardness, the core was divided into two and the center of the cross section was measured. Further, in consideration of the variation in the measured values, the surface hardness was measured at five locations spaced at approximately equal intervals, and the average value was obtained. The center hardness was determined by measuring five golf balls and averaging them. In addition, as a measuring instrument, ASKER CL-150 (manufactured by Kobunshi Keiki Co., Ltd.) was used. In this case, the measurement was performed after the object to be measured was firmly fixed so as not to be displaced by the weight of the needle.

  The Shore D hardness was measured for a mantle, a cover (sheet), and a cover (Golball). As for the surface hardness of the mantle, the surface hardness was measured (in the direction from the core surface toward the core center). Further, in consideration of the variation in the measured values, the surface hardness was measured at five locations spaced at approximately equal intervals, and the average value was obtained. Regarding the surface hardness of the cover (sheet), a sheet having a thickness of about 2 mm was prepared, and three sheets were stacked to measure the total thickness of about 6 mm. The surface hardness was measured 5 times, and the average value was taken.

  Regarding the surface hardness (ball state) of the golf ball, the surface hardness was measured (in the direction from the core surface toward the core center). The hardness of the land between dimples was measured as a measurement point. Further, in consideration of the variation in the measured values, the surface hardness was measured at five locations spaced at approximately equal intervals, and the average value was obtained.

  Tan δ (loss tangent) was measured by a viscoelasticity test. As a test piece, a test piece having a width of about 3 mm, a height of about 30 mm (20 mm between chucks), and a thickness of about 2 mm was prepared. Rheogel-E4000 manufactured by UBM Co., Ltd. was used as a testing machine. As test conditions, synthetic waves having measurement frequencies of 1 Hz, 2 Hz, 4 Hz, 8 Hz, 16 Hz, 32 Hz, and 64 Hz were used. Further, the start temperature was set to −40 ° C., the step temperature = 2 ° C., the end temperature = 50 ° C., and the rate of temperature increase = 1 ° C./min. Measured in tensile mode. As the master curve (synthetic curve), a calculation method (n = 3) to a WMF method was used. Then, tan δ (loss tangent) of the material at a measurement temperature of 23 ° C. and a frequency of 1000 Hz was obtained.

  The creation of a master curve (composite curve) will be described in detail. The measuring frequency of one measuring device is in the range of about three digits (Hz), and it is difficult to examine the wide range of properties of substances. In a polymer, a viscoelastic function obtained at an arbitrary temperature T can be converted into a reference temperature value by converting it into a unit of time (frequency). This property is called a temperature-time conversion rule, and the obtained curve is called a master curve (synthetic curve). For example, dynamic storage elastic modulus (E ′, G ′) data obtained when a sample is measured at different temperatures (for example, 25 ° C., 100 ° C., 125 ° C.) while changing the frequency as described above. (Relationship between storage elastic modulus and frequency) is plotted with storage elastic modulus on the vertical axis and frequency on the horizontal axis. For example, when the reference temperature is 100 ° C., the data on 25 ° C. and the data on 125 ° C. are plotted on the horizontal axis ( By shifting the frequency so as to overlap with 100 ° C., data having different temperatures can be converted into data having different frequencies with respect to the reference temperature (temperature time conversion).

  Here, the calculation method is to calculate how much the data to be overlapped should be shifted to the reference data, and apply it to 2 to 3 types of functions, and select the one with the best fitting condition. This is a method of shifting and superimposing data. Specifically, a composite line is applied to a linear equation and a quadratic equation, and a solution of an equation having a high correlation coefficient is obtained, and the first point (low frequency), the middle point, and the last point of the data to be superimposed The distance of the composite curve is calculated at three points (high frequency). The average value of the distances of these three points is used as the shift amount. This is repeated for data measured at a plurality of temperatures to obtain a master curve. The WMF method is an empirically obtained technique for polymer materials proposed by William, Landel, Ferry and others.

  The measurement method of the coefficient of restitution will be described. First, the air gun is directed to a steel plate having a fixed surface of about 5 cm in thickness, which is vertically installed at a distance of 2 m in the horizontal direction from the air gun launch port, and a smooth surface. Golf balls according to the examples and comparative examples were launched at a speed before collision of 43.51 m / s (e = 43.51). Then, the velocity of the golf ball before and after the collision of each golf ball that collided with the iron plate was measured, and the ratio of the velocity after the collision to the velocity before the collision was defined as the coefficient of restitution.

  The difference due to the coating shows a change in the coefficient of restitution due to the further increase in the coating of golf balls having the same configuration except for the number of times of coating. Specifically, the change in the coefficient of restitution of Examples 14 and 15 relative to Example 13 is shown. Moreover, the change of the coefficient of restitution of Examples 17 and 18 with respect to Example 16 is shown. From this change, it was found that the coefficient of restitution decreases as the coating is further increased.

  The lift coefficient is an average of values measured with the golf ball set direction set to PP (Poles over Pole) and PH (Poles Horizontal).

  No. 1 Wood (1W: MP CRAFFT H4 10.5 ° C Quad H4 carbon shaft #S manufactured by Mizuno Co., Ltd.), Sand Wedge (SW: MP-T10 Loft 58 manufactured by Mizuno Co., Ltd.) ° Drum test using Dynamic Gold). For No. 1 wood (driver), initial speed, launch angle (not shown), spin rate, and flight distance (carry) were measured. For the sand wedge, the jump angle (not shown) and the spin amount were measured. Here, the head speed (HS) of No. 1 wood (1W) was 40 m / s, and the head speed of the sand wedge (SW) was 20 m / s. Measurement was performed using a Trackman manufactured by Trackman as a measuring instrument. And the initial speed difference of Examples 1-21 and Comparative Examples 2-9 and Comparative Example 1 was examined. Moreover, the spin difference of Examples 1-21 and Comparative Examples 2-9 and Comparative Example 1 was examined.

  Comparative Examples 1 to 7 have a two-piece (2P) structure including a core and a cover. The cover material of Comparative Example 1 is an ionomer. The cover material of Comparative Examples 2-9 is polyurethane. In Tables 1 and 2, polyurethane is expressed as urethane. In Comparative Examples 2 to 7, the flight distance was shorter than that of Comparative Example 1. Comparative Examples 8 and 9 have a three-piece (3P) structure including a core, a mantle, and a cover. In Comparative Example 8, tan δ (loss tangent) was larger than those in Comparative Examples 2-7. The lift coefficient of Comparative Example 9 was smaller than that of Comparative Example 8.

  Examples 1 to 7 have a two-piece (2P) structure including a core and a cover. Examples 8 to 21 have a three-piece (3P) structure including a core, a mantle, and a cover. The cover material of Examples 1-21 is polyurethane. In Examples 1 to 21, tan δ was 0.11 or less, the lift coefficient was 0.15 or more and 0.22 or less, and the flight distance was longer than that of Comparative Example 1. In Examples 1 to 21, the difference between the surface hardness and the center hardness according to JIS-C of the core was 14 or more and 40 or less. Further, the Shore D hardness in the state of the cover sheet was 42.7 or more and 60.0 or less. Further, the Shore D hardness of the cover golf ball was 49.5 or more and 71.0 or less. Further, the compression of the golf ball was 63 or more and 121 or less.

  Referring to Tables 1 and 2, the tan δ of the cover 5 containing polyurethane as a main component is 0.11 or less at a measurement temperature of 23 ° C. and a frequency of 1000 Hz, and the lift coefficient of the golf ball 1 is 0. It was found that the flight distance can be improved while maintaining the performance of being easy to be spun by being 0.15 or more and 0.22 or less when 1.

  Further, it was found that the effect of forcibly reducing the jumping spin amount due to the internal / external hardness effect can be obtained because the difference between the surface hardness and the center hardness according to JIS-C of the core 4 is 14 or more and 40 or less. .

  Further, it was found that the Shore D hardness of the cover 5 in the state of the sheet is 43 or more and 60 or less, whereby an excellent hit feeling can be obtained.

  Further, it was found that when the Shore D hardness of the cover 5 in the state of the golf ball 1 is 50 or more and 71 or less, an excellent hit feeling can be obtained.

  In addition, when the thickness of the cover 5 is 0.4 mm or more and 2.3 mm or less, the effect of polyurethane with good resilience can be brought out, the manufacturing cost can be suppressed, the material cost can be suppressed, and the aerodynamic characteristics can be maintained. It turns out that it becomes easier.

  Further, it has been found that when the compression of the golf ball 1 is 63 or more and 121 or less, it is possible to suppress the spin from being excessively applied, and it is possible to suppress the decrease in the rebound of the golf ball 1.

  It was also found that the aerodynamic characteristics can be maintained and the aerodynamic characteristics can be stabilized when the paint layer 7 is composed of one or two coating layers.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 golf ball, 2 dimples, 3 lands, 4 cores, 5 covers, 6 intermediate layers, 7 paint layers.

Claims (9)

A spherical core,
A golf ball comprising a cover covering the core,
The cover includes polyurethane as a main component,
The tan δ of the cover is 0.11 or less at a measurement temperature of 23 ° C. and a frequency of 1000 Hz,
The golf ball has a lift coefficient of 0.20 or more and 0.22 or less when the spin parameter is 0.1.   The golf ball according to claim 1, wherein a difference between a surface hardness and a center hardness according to JIS-C hardness of the core is 14 or more and 40 or less.   The golf ball according to claim 1, wherein a Shore D hardness in a state of the cover sheet is 43 or more and 60 or less.   The golf ball according to claim 1, wherein a Shore D hardness of the cover in the state of the golf ball is 50 or more and 71 or less.   The golf ball according to claim 1, wherein the cover has a thickness of 0.4 mm or more and 2.3 mm or less.   The golf ball according to claim 1, wherein the compression of the golf ball is 63 or more and 121 or less. A paint layer covering the cover;
The golf ball according to claim 1, wherein the paint layer is formed of a coating film of one layer or two layers.   The cover is a cover material containing polyurethane obtained by reacting an isocyanate component and an active hydrogen compound component, wherein the isocyanate component contains 1,4-bis (isocyanatomethyl) cyclohexane, The golf ball according to claim 1.   The cover includes a polyurethane obtained by reacting an isocyanate component containing 1,4-bis (isocyanatomethyl) cyclohexane and an active hydrogen compound component, a thermoplastic elastomer, and 1,4-bis (isocyanatomethyl). The golf ball according to claim 1, wherein the golf ball is kneaded and molded with cyclohexane.