JP6634700B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball, and more particularly to a golf ball having a lower spin rate on driver shots than on approach shots.

  As a method of suppressing the spin amount of a driver shot, there is a method of controlling the hardness distribution of a golf ball. For example, by making the hardness distribution of the golf ball outer hard and inner soft, the spin rate of driver shots can be reduced, and the flight distance of driver shots can be increased.

  As a golf ball having a controlled hardness distribution, for example, Patent Document 1 discloses a golf ball having a core having two or more layers and a two-layer cover covering the core, and the outer cover having a hardness of Shore D40 to 60. A multi-piece solid golf ball having a structure of four or more layers, wherein the hardness of the inner cover is not more than 53 degrees Shore D and lower than the hardness of the outer cover.

  U.S. Pat. No. 5,077,087 discloses a single core having a mass, an outer surface, a geometric center, and an outermost transition adjacent to the outer surface, made from a substantially uniform composition. And a cover layer, the outermost transition being disposed between the outer surface of the core and the geometric center, the transition comprising an outer portion coinciding with the outer surface of the core. Having an outermost 45% or less of the volume of the core, and both the hardness of the outer surface of the core and the hardness in the outermost transition are less than the hardness of the geometric center; Golf balls that form a gradient are described.

JP-A-8-336617 JP 2009-233335 A

  By making the hardness distribution of the golf ball outer hard and inner soft, the spin rate of driver shots can be reduced. However, in this case, not only the spin rate of the driver shot but also the spin rate of the approach shot tends to decrease. Therefore, in the case of an outer-hard / soft-soft golf ball, although the flight distance of a driver shot is improved, the controllability in an approach shot tends to be reduced.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball having a small ratio of a spin amount of a driver shot to a spin amount of an approach shot.

  The golf ball of the present invention is a golf ball having a core and a cover, wherein the distance from the center of the golf ball is in the range of 36.0% to 65.0% of the radius of the golf ball, and the lowest in the core hardness distribution. It is characterized by having a hardness point. When a golf ball having a uniform hardness is hit with a driver, the strain is greatest in a region where the distance from the center of the golf ball is 36.0% to 65.0% of the radius of the golf ball. The present inventor has found that the presence of the lowest hardness point in the core hardness distribution in this region reduces the spin rate of driver shots independently, and completed the present invention. That is, according to the present invention, the spin amount of the driver shot can be reduced independently of the spin amount of the approach shot, so that a golf ball having a small ratio of the spin amount of the driver shot to the spin amount of the approach shot can be obtained. Can be

  ADVANTAGE OF THE INVENTION According to this invention, the golf ball with which hardness distribution was optimized and the ratio of the spin amount of a driver shot with respect to the spin amount of an approach shot is small is obtained. A golf ball having a small ratio of the spin amount of the driver shot to the spin amount of the approach shot has a large flight distance of the driver shot and is excellent in controllability of the approach shot.

FIG. 1 is a schematic sectional view showing a golf ball according to a preferred embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a hardness distribution of the golf ball of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a hardness distribution of the golf ball of the present invention. FIG. 1 is a partially cutaway sectional view showing a golf ball according to one embodiment of the present invention.

  The golf ball of the present invention is a golf ball having a core and a cover, wherein the minimum hardness in the core hardness distribution is in a range where the distance from the center of the golf ball is 36.0% to 65.0% of the golf ball radius. It is characterized by the presence of points.

(1) Structure and Hardness Distribution of Golf Ball Hereinafter, the golf ball of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings. As shown in FIG. 1, the golf ball of the present invention has a minimum hardness point in the core hardness distribution in a region S where the distance from the center of the golf ball is 36.0% to 65.0% of the radius of the golf ball. I do. The core hardness distribution is preferably evaluated by a cross-sectional hardness obtained by dividing the core into a hemispherical half. The section hardness may be obtained by cutting a golf ball into a hemisphere and measuring the hardness at the center of the cut surface and at a predetermined distance from the center. Further, when the portion for measuring the hardness is formed from the thermoplastic resin composition, the material hardness (slab hardness) of the thermoplastic resin composition can be regarded as the hardness of the portion. Further, when the portion for measuring the hardness is formed of the rubber composition, the hardness of the slab produced at the same temperature as the heat treatment temperature at the time of producing the golf ball can be regarded as the hardness of the portion. The hardness can be measured using an automatic rubber hardness meter P1 manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness meter Shore D specified in ASTM-D2240.

  When a golf ball having a uniform hardness is hit with a driver, the strain is greatest in a region S where the distance from the golf ball center is 36.0% to 65.0% of the golf ball radius. In a golf ball having a minimum hardness point in this region, the spin rate of a driver shot decreases independently. As a result, a golf ball having a small ratio of the spin rate of the driver shot to the spin rate of the approach shot is obtained. A golf ball having a small ratio of the spin amount of the driver shot to the spin amount of the approach shot has a large flight distance of the driver shot and has excellent controllability of the approach shot. The distance from the golf ball center in the region where the minimum hardness point exists is preferably 40.0% or more, more preferably 45.0% or more, and preferably 62.5% or less of the golf ball radius. Preferably, it is 60.0% or less. When the lowest hardness point exists in a layer having a uniform hardness distribution, it is sufficient that at least a part of this layer exists in the region S.

  The minimum hardness (Hs) at the minimum hardness point is preferably 40 or less in Shore D hardness, more preferably 35 or less, further preferably 30 or less, particularly preferably 25 or less, preferably 3 or more, more preferably 4 or less. The number is more preferably 5 or more. When the minimum hardness (Hs) is within the above range, the spin rate of a driver shot decreases independently. As a result, a golf ball having a small ratio of the spin rate of the driver shot to the spin rate of the approach shot is obtained.

  The golf ball has a center hardness (Ho) in Shore D hardness of preferably 15 or more, more preferably 20 or more, still more preferably 30 or more, preferably 55 or less, more preferably 50 or less, and even more preferably 45 or more. Is less than. When the center hardness (Ho) is within the above range, the resilience of the golf ball does not decrease.

  The golf ball preferably has an average descent gradient from the center of the golf ball to the lowest hardness point in Shore D hardness of -2.5 points / mm or more, more preferably -2.2 points / mm or more. And more preferably -1.9 point / mm or more, preferably -0.1 point / mm or less, more preferably -0.3 point / mm or less, and still more preferably -0.1 point / mm or less. is there. Here, the “average descending gradient” is a value (point / mm) calculated by (Hs−Ho) / (distance from the center of the golf ball to the minimum hardness point). When the lowest hardness point exists in a layer having a uniform hardness distribution, the center in the thickness direction of this layer is defined as the lowest hardness point.

  In the golf ball, the core hardness decreases at a gradient of -0.5 point / mm to -2 point / mm in Shore D hardness from the center of the golf ball toward the lowest hardness point. It is preferable that the distance reaches the minimum hardness in a range of 36.0% to 65.0% of the radius of the golf ball. This is because the minimum hardness point tends to exist in a region of 36.0% to 65.0% of the radius of the golf ball by decreasing the core hardness at a constant gradient from the center of the golf ball toward the surface. . The gradient is a change in hardness per unit distance.

  The core hardness is a hardness difference (Hy-1) between a hardness (Hy) at a point at a distance of Y mm from the center and a hardness (Hy-1) at a point at a distance of Y-1 mm in a range from the center to the lowest hardness point. Hy- (Hy-1)) is preferably 5 or less, more preferably 2 or less, further preferably 1 or less, particularly preferably 0 or less in Shore D hardness. In addition, the Y is 1 or more and is equal to or less than the distance (mm) from the center to the lowest hardness point.

  Further, it is preferable that the core hardness gradually decreases with Shore D hardness from the center of the golf ball toward the surface, and reaches the minimum hardness in the region S. Here, the term “gradual decrease in hardness” means that the hardness gradually decreases or gradually decreases from the core center to the region S without increasing the hardness.

  The golf ball preferably has a Shore D hardness of less than 45 in the entire area where the distance from the center of the golf ball is 36.0% to 50.0% of the radius of the golf ball. It is more preferably at most 35, more preferably at most 35. If the hardness of the entire region where the distance from the center of the golf ball is from 36.0% to 50.0% of the radius of the golf ball is less than 45 in Shore D hardness, a decrease in the spin rate of driver shots is caused. In addition, an increase in the spin amount of the approach shot can be realized at a higher level.

  The golf ball preferably has a Shore D hardness of 45 or less and a Shore D hardness of 40 or less in the entire region where the distance from the center of the golf ball is 0% to 50.0% of the golf ball radius. More preferably, it is more preferably 35 or less. If the hardness of the entire region where the distance from the center of the golf ball is 0% to 50.0% of the radius of the golf ball is 45 or less in Shore D hardness, a decrease in the spin rate of a driver shot and an approach shot Can be increased at a higher level.

  As shown in FIG. 2, the golf ball preferably has a highest hardness point in the core hardness distribution in a region H where the distance from the center of the golf ball is 85.0% to 99.5% of the radius of the golf ball. . This is because the presence of the highest hardness point in the core hardness distribution in the region H causes the golf ball to have an outer-hard / inner-soft structure, and the driver spin amount is further reduced. The distance from the core center of the region where the highest hardness point exists is preferably at least 87.5%, more preferably at least 90.0% of the golf ball radius, from the core center, It is preferably at most 99.0%, more preferably at most 98.0%. When the highest hardness point exists in a layer having a uniform hardness distribution, at least a part of this layer may be present in the region H.

  The highest hardness (Hh) at the highest hardness point is preferably 30 or more in Shore D hardness, more preferably 35 or more, further preferably 40 or more, preferably 85 or less, more preferably 80 or less, and even more preferably 77 or less. It is as follows. This is because if the maximum hardness (Hh) is within the above range, the degree of the outer-hard / inner-soft structure increases, and the driver spin amount further decreases.

  The golf ball preferably has an average rising gradient from the lowest hardness point to the highest hardness point in Shore D hardness of 2 points / mm or more, more preferably 3 points / mm or more, and still more preferably 4 points / mm. mm or more, preferably 10 points / mm or less, more preferably 8 points / mm or less, and still more preferably 6 points / mm or less. Here, the “average ascending gradient” is a value (point / mm) calculated by (Hh−Hs) / (distance from the lowest hardness point to the highest hardness point). When the highest hardness point exists in a layer having a uniform hardness distribution, the center in the thickness direction of this layer is defined as the highest hardness point.

  In the golf ball, it is preferable that the hardness of the core increases from 3 points / mm to 6 points / mm in Shore D hardness from the lowest hardness point to the highest hardness point. The lower limit of the hardness gradient is preferably 3.5 points / mm, more preferably 4 points / mm. The upper limit of the hardness gradient is preferably 5.5 points / mm, more preferably 5 points / mm. When the hardness gradient is within the above range, a core having a high degree of outer rigid inner soft structure can be obtained. As a result, the driver spin amount is further reduced.

  Further, it is preferable that the core hardness gradually increases in Shore D hardness from the lowest hardness point to the highest hardness point. The term “gradual increase” means that the hardness gradually increases or gradually increases without decreasing the hardness from the lowest hardness point to the highest hardness point.

  The ratio (Hh / Ho) between the maximum hardness Hh and the center hardness (Ho) of the golf ball is preferably 1.1 or more, more preferably 1.2 or more, still more preferably 1.3 or more, and 45 or less. Is more preferable, more preferably 35 or less, and still more preferably 30 or less. If the ratio (Hh / Ho) is 1.1 or more, the spin rate of driver shots tends to decrease. Also, if the ratio (Hh / Ho) is 80 or less, the shot feeling at the time of shot is improved.

  The hardness difference (Hh-Ho) between the maximum hardness (Hh) and the center hardness (Ho) of the golf ball is preferably 1 or more, more preferably 5 or more, and still more preferably 10 or more in Shore D hardness, It is preferably at most 70, more preferably at most 65, even more preferably at most 60. If the hardness difference (Hh-Ho) is 1 or more in Shore D hardness, the spin rate of driver shots tends to decrease. If the hardness difference (Hh-Ho) is 70 or less in Shore D hardness, the resilience of the golf ball does not decrease.

  The hardness difference (Hh-Hs) between the maximum hardness (Hh) and the minimum hardness (Hs) is preferably 30 or more in Shore D hardness, more preferably 32 or more, still more preferably 34 or more, and 80 or less. Preferably, it is 75 or less, more preferably, 70 or less. If the hardness difference (Hh-Hs) is 30 or more in Shore D hardness, the spin rate of driver shots tends to decrease. Also, if the hardness difference (Hh-Hs) is 80 or less in Shore D hardness, the shot feeling at the time of shot is improved.

  The thickness of the cover is preferably 2.0 mm or less, more preferably 1.6 mm or less, further preferably 1.2 mm or less, particularly preferably 1.0 mm or less. If the thickness of the cover is 2.0 mm or less, the resilience and shot feeling of the obtained golf ball will be better. The thickness of the cover is preferably 0.1 mm or more, more preferably 0.2 mm or more, and still more preferably 0.3 mm or more. If the thickness of the cover is less than 0.1 mm, it may be difficult to form the cover, and the durability and wear resistance of the cover may be reduced.

  The material hardness (Hc) of the cover is preferably 5 or more, more preferably 7 or more, and still more preferably 10 or more, preferably 55 or less, more preferably 53 or less, and still more preferably 50 or less in Shore D hardness. It is. This is because if the material hardness (Hc) of the cover is within the above range, the spin amount of the approach shot becomes higher.

  The diameter of the golf ball is preferably 40 mm to 45 mm. The diameter is particularly preferably equal to or greater than 42.67 mm from the viewpoint that the standards of the United States Golf Association (USGA) are satisfied. In light of suppression of air resistance, the diameter is more preferably equal to or less than 44 mm, and particularly preferably equal to or less than 42.80 mm. The weight of the golf ball of the present invention is preferably 40 g or more and 50 g or less. In light of attaining a large inertia, the mass is more preferably equal to or greater than 44 g, and particularly preferably equal to or greater than 45.00 g. In light of satisfying the USGA standard, the mass is particularly preferably equal to or less than 45.93 g.

  When the golf ball has a diameter of 40 mm to 45 mm, the amount of compressive deformation (the amount of compression of the golf ball in the compression direction) when a final load of 1275 N is applied from an initial load of 98 N is 2.0 mm or more. Is more preferably 2.2 mm or more, preferably 4.0 mm or less, and more preferably 3.5 mm or less. The golf ball having a compression deformation of 2.0 mm or more does not become too hard and has a good shot feeling. On the other hand, by setting the amount of compressive deformation to 4.0 mm or less, the resilience increases.

  The structure of the golf ball of the present invention is such that the minimum hardness point in the core hardness distribution exists in a region S where the distance from the center of the golf ball is 36.0% to 65.0% of the radius of the golf ball. If so, it is not particularly limited. For example, a two-piece golf ball having a core and a single-layer cover covering the core; a core comprising a center and an envelope layer covering the center; and a single layer covering the core. And multi-piece golf balls (including three-piece golf balls).

  Although the present invention can be used for golf balls having any of the above structures, the golf ball of the present invention includes a spherical center and an n-layer (n: It is preferable that the golf ball is a multi-piece golf ball having a core composed of a surrounding layer of (a natural number of 2 or more) and a single-layer cover covering the core. Hereinafter, the present invention relates to a multi-piece golf ball having a core comprising a center, an n-layer (n is a natural number of 2 or more) surrounding layer covering the center, and a single-layer cover covering the core. It will be described in detail based on the embodiment.

  FIG. 3 is a sectional view schematically showing the structure of a multi-piece golf ball according to a preferred embodiment of the present invention. In FIG. 3, a multi-piece golf ball has a core B including a center C and an n-layer surrounding layer (n is a natural number of 2 or more) covering the center C, and a single-layer cover A covering the core B. Are formed. The surrounding layers are, in order from the center side, the first surrounding layer 1, the second surrounding layer 2, the third surrounding layer 3, the fourth surrounding layer 4,..., The (n-1) th surrounding layer n-1, the n-th surrounding layer. Called layer n.

  N is preferably a natural number of 2 or more, more preferably a natural number of 3 or more, and further preferably a natural number of 4 or more. Further, n is preferably a natural number of 9 or less, more preferably a natural number of 8 or less, and further preferably a natural number of 7 or less. When the number of the surrounding layers is two or more, it becomes easy to provide an appropriate hardness distribution to the golf ball. On the other hand, if the number of the surrounding layers is too large, the moldability of the surrounding layers is reduced. The reinforcing layer (adhesive layer) provided to enhance the adhesion between the surrounding layers is not included in the surrounding layer. The reinforcing layer (adhesive layer) and the surrounding layer have different thickness ranges. The thickness of the reinforcing layer (adhesive layer) is usually 50 μm or less.

  In the multi-piece golf ball according to a preferred embodiment of the present invention, the minimum hardness point in the core hardness distribution exists in a region S in which the distance from the center of the golf ball is 36.0% to 65.0% of the radius of the golf ball. It is preferable that the surrounding layer (hereinafter, may be simply referred to as “minimum hardness surrounding layer (Es)”) is formed. That is, it is preferable that the minimum hardness surrounding layer (Es) is formed of a resin material having the lowest Shore D hardness among the resin materials constituting the core. Further, in this case, it is preferable that the entire minimum hardness surrounding layer (Es) is disposed in a region S in which the distance from the center of the golf ball is 36.0% to 65.0% of the radius of the golf ball. In the region where the minimum hardness surrounding layer (Es) is disposed, the distance from the golf ball center is preferably 40.0% or more, more preferably 45.0% or more, and 62.5% or more of the golf ball radius. % Or less, more preferably 60.0% or less.

  The thickness of the minimum hardness surrounding layer (Es) is preferably 0.2 mm or more, more preferably 0.5 mm or more, further preferably 1 mm or more, preferably 20 mm or less, more preferably 17 mm or less, and still more preferably 15 mm or less. It is as follows. If the thickness of the minimum hardness surrounding layer (Es) is 0.2 mm or more, the spin rate of driver shots tends to decrease. If the thickness of the minimum hardness surrounding layer (Es) is 20 mm or less, the resilience of the golf ball does not decrease.

  The hardness (Hs) of the minimum hardness surrounding layer (Es) is, in Shore D hardness, preferably 40 or less, more preferably 35 or less, still more preferably 30 or less, particularly preferably 25 or less, and preferably 3 or more, It is more preferably 4 or more, and further preferably 5 or more. When the material hardness (Hs) of the minimum hardness surrounding layer (Es) is within the above range, the spin rate of the driver shot is independently reduced. As a result, a golf ball having a small ratio of the spin rate of the driver shot to the spin rate of the approach shot is obtained.

  In a preferred aspect of the multi-piece golf ball of the present invention, the material hardness of the constituent members of the core is from -0.5 point / mm to -2 point / mm in Shore D hardness from the center of the golf ball toward the surface. It is preferable that the hardness gradually decreases with the gradient and reaches the minimum hardness in the region S. Because the core hardness gradually decreases at a constant gradient from the center of the golf ball toward the surface, a minimum hardness point is likely to exist in a region of 36.0% to 65.0% of the radius of the golf ball. is there. Here, the term “gradual decrease in hardness” means that the hardness gradually decreases or gradually decreases from the core center to the region S without increasing the hardness. The “gradient” is a value calculated by (minimum hardness−center hardness of golf ball) / (distance from center of golf ball to minimum hardness point). The minimum hardness point is located at the middle point in the thickness direction of the minimum hardness surrounding layer (Es), and the distance from the core center to the minimum hardness point is the thickness direction of the minimum hardness surrounding layer (Es) from the core center. Is the distance to the midpoint.

  In the preferred embodiment of the multi-piece golf ball of the present invention, as shown in FIG. 2, the distance from the center of the golf ball is the highest in the core hardness distribution in a region H of 85.0% to 99.5% of the radius of the golf ball. It is preferable that an envelope layer having a hardness point (hereinafter sometimes simply referred to as “maximum hardness envelope layer (Eh)”) is formed. That is, the highest hardness surrounding layer (Eh) is preferably formed of the resin material having the highest Shore D hardness among the resin materials constituting the core. Further, in this case, it is preferable that the whole of the highest hardness surrounding layer (Eh) is arranged in a region H where the distance from the center of the golf ball is 85.0% to 99.5% of the golf ball radius. .

  In the region where the highest hardness surrounding layer (Eh) is arranged, the distance from the center of the core is preferably 87.5% or more of the radius of the golf ball, more preferably 90.0% or more, and 99% or more. 0.0% or less, and more preferably 98.0% or less. This is because, by arranging the highest hardness layer (Eh) in the core hardness distribution in the above-mentioned region of the golf ball radius, the golf ball has an outer-hard / inner-soft structure, and the driver spin amount is further reduced.

  The thickness of the highest hardness surrounding layer (Eh) is preferably 0.1 mm or more, more preferably 0.2 mm or more, still more preferably 0.5 mm or more, preferably 5 mm or less, more preferably 4 mm or less, and still more preferably. Is 3 mm or less. If the thickness of the highest hardness surrounding layer (Eh) is 0.1 mm or more, the durability of the golf ball is improved. This is because if the thickness of the highest hardness surrounding layer (Eh) is 5 mm or less, the shot feeling at the time of shot is improved.

  The hardness (Hh) of the highest hardness layer (Eh) is preferably 30 or more in Shore D hardness, more preferably 35 or more, still more preferably 40 or more, preferably 85 or less, more preferably 80 or less, and still more preferably. Is 77 or less. If the hardness (Hh) of the highest hardness layer (Eh) is within the above range, the driver spin amount is further reduced.

  In a preferred aspect of the multi-piece golf ball of the present invention, the hardness of the constituent members of the core gradually increases from the lowest hardness point to the highest hardness point at a gradient of 3 points / mm to 6 points / mm in Shore D hardness. It is preferred to increase. The term “gradual increase” means that the hardness gradually increases or gradually increases without decreasing the hardness from the lowest hardness point to the highest hardness point. The lower limit of the hardness gradient is preferably 3.5 points / mm, more preferably 4 points / mm. The upper limit of the hardness gradient is preferably 5.5 points / mm, more preferably 5 points / mm. When the hardness gradient is within the above range, a core having a high degree of outer rigid inner soft structure can be obtained. As a result, the driver spin amount is further reduced. Here, the “gradient” is a value calculated by (maximum hardness−minimum hardness) / (distance from core center to maximum hardness point−distance from core center to minimum hardness point). Note that the highest hardness point is located at the midpoint in the thickness direction of the highest hardness surrounding layer (Eh), and the distance from the core center to the highest hardness point is the thickness direction of the highest hardness surrounding layer (Eh) from the core center. Is the distance to the midpoint.

  In the multi-piece golf ball according to a preferred embodiment of the present invention, the hardness of the constituent members arranged in the entire region where the distance from the center of the golf ball is 34.0% to 65.0% of the radius of the golf ball has a high hardness. , Shore D hardness is preferably less than 45, more preferably 40 or less, and even more preferably 35 or less. If the hardness of the components arranged in the entire region where the distance from the center of the golf ball is 34.0% to 65.0% of the radius of the golf ball is less than 45 in Shore D hardness, the driver shot , The spin amount of the approach shot can be increased at a higher level. In addition, the components having a Shore D hardness of less than 45 arranged in the entire region where the distance from the center of the golf ball is 34.0% to 65.0% of the radius of the golf ball are entirely formed of the golf ball. It is assumed that the distance from the center exists in an area of 34.0% to 65.0% of the radius of the golf ball.

  In a multi-piece golf ball according to another preferred embodiment of the present invention, the hardness of a component disposed in a region where the distance from the center of the golf ball is 0% to 50.0% of the radius of the golf ball has a hardness of: The Shore D hardness is preferably 45 or less, more preferably 40 or less, and even more preferably 35 or less. If the hardness of a component disposed in a region where the distance from the center of the golf ball is 0% to 50.0% of the radius of the golf ball is 45 or less in Shore D hardness, the spin rate of driver shots , And an increase in the spin amount of the approach shot can be realized at a higher level. In addition, the component members having a Shore D hardness of 45 or less arranged in a region where the distance from the center of the golf ball is 0% to 50.0% of the radius of the golf ball are entirely the distance from the center of the golf ball. Exist in a region of 0% to 50.0% of the radius of the golf ball.

  In the multi-piece golf ball according to a preferred embodiment of the present invention, the center hardness (Ho) of the spherical center is preferably 15 or more, more preferably 20 or more, further preferably 30 or more, and preferably 55 or less in Shore D hardness. , More preferably 50 or less, even more preferably less than 45. If the center hardness (Ho) of the spherical center is less than 15 in Shore D hardness, the center becomes too soft and rebound may be reduced. If the center hardness (Ho) of the spherical center exceeds 55 in Shore D hardness, the center becomes too hard and the shot feeling tends to decrease.

  The diameter of the spherical center is preferably 5 mm or more, more preferably 7 mm or more, still more preferably 10 mm or more, preferably 25 mm or less, more preferably 22 mm or less, and still more preferably 20 mm or less. If the diameter of the spherical center is 5 mm or more, the driver spin amount is further reduced. On the other hand, if the diameter of the spherical center is 25 mm or less, the approach spin amount is less likely to decrease. Further, by having such a spherical center having a small diameter, a large number of surrounding layers can be provided, and it becomes easy to provide a golf ball with an appropriate hardness distribution.

  When the spherical center has a diameter of 5 mm to 25 mm, the amount of compressive deformation from the state of applying an initial load of 98 N to the time of applying a final load of 1275 N (the amount of the center shrinking in the compression direction) is preferably 1.5 mm or more, It is more preferably at least 1.7 mm, further preferably at least 2.0 mm, preferably at most 5.0 mm, more preferably at most 4.7 mm, even more preferably at most 4.5 mm. If the amount of compressive deformation is 1.5 mm or more, the shot feeling is better, and if it is 5.0 mm or less, the resilience is better.

  The thickness of the surrounding layers other than the lowest hardness surrounding layer (Es) and the highest hardness surrounding layer (Eh) is not particularly limited, but is preferably 0.1 mm or more, more preferably 0.2 mm or more, and further preferably 0.3 mm or more. Preferably, it is 15 mm or less, more preferably 13 mm or less, even more preferably 10 mm or less.

  The thickness of the cover is preferably 2.0 mm or less, more preferably 1.6 mm or less, further preferably 1.2 mm or less, particularly preferably 1.0 mm or less. If the thickness of the cover is 2.0 mm or less, the resilience and shot feeling of the obtained golf ball will be better. The thickness of the cover is preferably 0.1 mm or more, more preferably 0.2 mm or more, and still more preferably 0.3 mm or more. If the thickness of the cover is less than 0.1 mm, it may be difficult to form the cover, and the durability and wear resistance of the cover may be reduced.

  The material hardness Hc of the cover is preferably 5 or more, more preferably 7 or more, still more preferably 10 or more, preferably 55 or less, more preferably 53 or less, and still more preferably 50 or less in Shore D hardness. . This is because if the material hardness of the cover is within the above range, the spin amount of the approach shot becomes higher.

  Specific examples of the multi-piece golf ball of the present invention include a four-piece golf ball, a five-piece golf ball, a six-piece golf ball, and a seven-piece golf ball.

(2) Material for Constituting Golf Ball The material for constituting the golf ball of the present invention will be described. Examples of the constituent material of the golf ball of the present invention include a thermoplastic resin composition and a rubber composition. These materials can be used to form spherical centers, envelope layers, and covers. The material hardness of each material can be adjusted by changing the composition of the raw material.

First, the thermoplastic resin composition used in the present invention will be described. The resin component (A) contained in the thermoplastic resin composition is not particularly limited as long as it is a thermoplastic resin. As the thermoplastic resin, for example, an ionomer resin, a thermoplastic olefin copolymer, a thermoplastic polyurethane resin, a thermoplastic polyamide resin, a thermoplastic styrene resin, a thermoplastic polyester resin, a thermoplastic resin such as a thermoplastic acrylic resin. Can be mentioned. Among thermoplastic resins, a thermoplastic elastomer having rubber elasticity is preferable. Examples of the thermoplastic elastomer include a thermoplastic polyurethane elastomer, a thermoplastic polyamide elastomer, a thermoplastic styrene-based elastomer, a thermoplastic polyester elastomer, and a thermoplastic acrylic elastomer.

(2-1) Ionomer resin As the ionomer resin, an ionomer resin comprising a metal ion neutralized product of a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms; olefin An ionomer resin comprising a metal ion neutralized product of a terpolymer of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester; or a mixture thereof. Can be mentioned.

  In the present invention, "an ionomer resin comprising a metal ion neutralized product of a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms" is simply referred to as a "binary ionomer resin." "Ionomer resin comprising a metal ion neutralized product of a terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester” May simply be referred to as “ternary ionomer resin”.

  The olefin is preferably an olefin having 2 to 8 carbon atoms, and examples thereof include ethylene, propylene, butene, pentene, hexene, heptene, octene, and the like, and particularly preferably ethylene. Examples of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like, and acrylic acid or methacrylic acid is particularly preferable. As the α, β-unsaturated carboxylic acid ester, for example, methyl, ethyl, propyl, n-butyl, isobutyl ester and the like such as acrylic acid, methacrylic acid, fumaric acid and maleic acid are used. Or a methacrylic acid ester is preferable.

  As the binary ionomer resin, a metal ion neutralized product of an ethylene- (meth) acrylic acid binary copolymer is preferable. As the ternary ionomer resin, a metal ion neutralized product of a ternary copolymer of ethylene, (meth) acrylic acid and (meth) acrylate is preferable. Here, (meth) acrylic acid means acrylic acid and / or methacrylic acid.

  The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the binary ionomer resin is preferably 15% by mass or more, more preferably 16% by mass or more, and further preferably 17% by mass or more. It is preferably at most 30% by mass, more preferably at most 25% by mass. If the content of the [alpha], [beta] -unsaturated carboxylic acid component having 3 to 8 carbon atoms is 15% by mass or more, it is easy to obtain the desired hardness of the resulting component. When the content of the [alpha], [beta] -unsaturated carboxylic acid component having 3 to 8 carbon atoms is 30% by mass or less, the hardness of the resulting component does not become too high, and the durability and shot feeling are good. Because it becomes.

  The neutralization degree of the carboxyl group of the binary ionomer resin is preferably 15 mol% or more, more preferably 20 mol% or more, and preferably 100 mol% or less. When the degree of neutralization is at least 15 mol%, the resilience and durability of the obtained golf ball will be good. In addition, the neutralization degree of the carboxyl group of the said binary ionomer resin can be calculated | required by the following formula. Further, the metal component may be contained so that the theoretical degree of neutralization of the carboxyl group in the ionomer resin exceeds 100 mol%.

  Degree of neutralization (mol%) of binary ionomer resin = 100 x number of moles of neutralized carboxyl groups in binary ionomer resin / total number of carboxyl groups in binary ionomer resin

  Examples of the metal ion that neutralizes at least a part of the carboxyl group of the binary ionomer resin include monovalent metal ions such as sodium, potassium, and lithium; and divalent metals such as magnesium, calcium, zinc, barium, and cadmium. Ions; trivalent metal ions such as aluminum; and other ions such as tin and zirconium.

  When a specific example of the binary ionomer resin is exemplified by a trade name, "Himilan (registered trademark)" (for example, Himilan 1555 (Na), Himilan 1557) which is commercially available from Mitsui-DuPont Polychemical Co., Ltd. (Zn), Himilan 1605 (Na), Himilan 1706 (Zn), Himilan 1707 (Na), Himilan AM7311 (Mg), Himilan AM7329 (Zn), etc. ".

  Further, Surlyn (registered trademark) commercially available from DuPont (for example, Surlyn 8945 (Na), Surlyn 9945 (Zn), Surlyn 8140 (Na), Surlyn 8150 (Na), Surlyn 9120 (Zn), Surlyn 9150 (Zn), Surlyn 6910 (Mg), Surlyn 6120 (Mg), Surlyn 7930 (Li), Surlyn 7940 (Li), Surlyn AD8546 (Li)) and the like.

  Examples of the ionomer resin commercially available from ExxonMobil Chemical Co., Ltd. include “Iotek (registered trademark)” (for example, Iotek 8000 (Na), Iotek 8030 (Na), Iotek 7010 (Zn), and Iotek 7030 ( Zn)) ”and the like.

  As the binary ionomer resin, those exemplified above may be used alone or as a mixture of two or more. Na, Zn, Li, Mg, etc. described in parentheses after the trade name indicate the metal species of these neutralizing metal ions.

  The bending rigidity of the binary ionomer resin is preferably 140 MPa or more, more preferably 150 MPa or more, still more preferably 160 MPa or more, preferably 550 MPa or less, more preferably 500 MPa or less, and even more preferably 450 MPa or less. If the flexural rigidity of the binary ionomer resin is too low, the spin amount of the golf ball tends to increase and the flight distance tends to decrease.If the flexural rigidity is too high, the durability of the golf ball decreases. There is.

  The melt flow rate (190 ° C., 2.16 kg load) of the binary ionomer resin is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, and still more preferably 1.0 g / 10 min or more. Yes, it is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 15 g / 10 min or less. When the melt flow rate of the binary ionomer resin (190 ° C., 2.16 kg load) is 0.1 g / 10 min or more, the fluidity of the thermoplastic resin composition becomes good, and for example, a thin layer can be formed. Becomes When the melt flow rate of the binary ionomer resin (190 ° C., 2.16 kg load) is 30 g / 10 min or less, the durability of the obtained golf ball becomes better.

  The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the ternary ionomer resin is preferably 2% by mass or more, more preferably 3% by mass or more, and 30% by mass or less. And more preferably 25% by mass or less.

The degree of neutralization of the carboxyl group of the ternary ionomer resin is preferably 20 mol% or more, more preferably 30 mol% or more, and preferably 100 mol% or less. When the degree of neutralization is at least 20 mol%, the resilience and durability of a golf ball obtained using the thermoplastic resin composition will be good. In addition, the neutralization degree of the carboxyl group of the ionomer resin can be obtained by the following equation. Further, the metal component may be contained so that the theoretical degree of neutralization of the carboxyl group in the ionomer resin exceeds 100 mol%.
Degree of neutralization of ionomer resin (mol%) = 100 × moles of neutralized carboxyl groups in ionomer resin / total mol number of carboxyl groups in ionomer resin

  Examples of the metal ion that neutralizes at least a part of the carboxyl group of the ternary ionomer resin include monovalent metal ions such as sodium, potassium, and lithium; and divalent metals such as magnesium, calcium, zinc, barium, and cadmium. Ions; trivalent metal ions such as aluminum; and other ions such as tin and zirconium.

  When a specific example of the ternary ionomer resin is exemplified by a trade name, "Himilan (for example, Himilan AM7327 (Zn), Himilan 1855 (Zn)," which is commercially available from Mitsui DuPont Polychemical Co., Ltd .; Himilan 1856 (Na), Himilan AM7331 (Na), etc.). Further, as ternary ionomer resins commercially available from DuPont, "Surlyn 6320 (Mg), Surlyn 8120 (Na), Surlyn 8320 (Na), Surlyn 9320 (Zn), Surlyn 9320W (Zn), HPF1000 (Mg ), HPF2000 (Mg)). Examples of a ternary ionomer resin commercially available from ExxonMobil Chemical Co., Ltd. include "Iotek 7510 (Zn), Iotek 7520 (Zn)" and the like. In addition, Na, Zn, Mg, etc. described in parentheses after the trade name indicate types of neutralized metal ions. The ternary ionomer resins may be used alone or in combination of two or more.

  The flexural rigidity of the ternary ionomer resin is preferably 10 MPa or more, more preferably 11 MPa or more, still more preferably 12 MPa or more, preferably 100 MPa or less, more preferably 97 MPa or less, and even more preferably 95 MPa or less. If the flexural rigidity of the ternary ionomer resin is too low, the spin distance of the golf ball tends to increase and the flight distance tends to decrease.If the flexural rigidity is too high, the durability of the golf ball decreases. There is.

  The melt flow rate (190 ° C., 2.16 kg load) of the ternary ionomer resin is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, and further preferably 0.5 g / 10 min or more. Yes, it is preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, and even more preferably 10 g / 10 min or less. When the ternary ionomer resin has a melt flow rate (at 190 ° C. and a load of 2.16 kg) of 0.1 g / 10 min or more, the fluidity of the thermoplastic resin composition becomes good and the thin envelope layer can be easily formed. Become. If the melt flow rate (at 190 ° C., a load of 2.16 kg) of the ternary ionomer resin is 20 g / 10 min or less, the durability of the obtained golf ball will be better.

  The slab hardness of the ternary ionomer resin is preferably 20 or more, more preferably 25 or more, still more preferably 30 or more, preferably 70 or less, more preferably 65 or less, even more preferably 60 or less in Shore D hardness. It is. When the slab hardness is 20 or more in Shore D hardness, the resulting component does not become too soft, and the resilience of the golf ball is improved. When the slab hardness is 70 or less in Shore D hardness, the resulting component does not become too hard, and the durability of the golf ball is further improved.

(2-2) Thermoplastic olefin copolymer Examples of the thermoplastic olefin copolymer include a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms; And a ternary copolymer of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester; or a mixture thereof. The thermoplastic olefin copolymer is a nonionic one whose carboxyl group is not neutralized.

  In the present invention, “binary copolymer of olefin and α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms” is simply referred to as “binary copolymer”, A ternary copolymer of ８8 α, β-unsaturated carboxylic acids and α, β-unsaturated carboxylic acid esters may be simply referred to as a “ternary copolymer”.

  Examples of the olefin include the same olefins as those constituting the ionomer resin, and ethylene is particularly preferable. The α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and the ester thereof are the same as the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and the ester thereof which constitute the ionomer resin. Can be mentioned.

  The binary copolymer is preferably a binary copolymer of ethylene and (meth) acrylic acid. The terpolymer is preferably a terpolymer of ethylene, (meth) acrylic acid and (meth) acrylate. Here, (meth) acrylic acid means acrylic acid and / or methacrylic acid.

  The content of the α, β-unsaturated carboxylic acid component having 3 to 8 carbon atoms in the binary copolymer or terpolymer is preferably 4% by mass or more, more preferably 5% by mass or more. The content is preferably 30% by mass or less, more preferably 25% by mass or less.

  The melt flow rate (190 ° C., 2.16 kg load) of the binary copolymer or ternary copolymer is preferably at least 5 g / 10 min, more preferably at least 10 g / 10 min, even more preferably at least 15 g / 10 min. And it is preferably 1700 g / 10 min or less, more preferably 1500 g / 10 min or less, and still more preferably 1300 g / 10 min or less. When the melt flow rate (190 ° C., 2.16 kg load) of the binary copolymer or the ternary copolymer is 5 g / 10 min or more, the fluidity of the thermoplastic resin composition becomes good, and the molding of the constituent members is performed. Becomes easier. Further, if the melt flow rate (190 ° C., 2.16 kg load) of the binary copolymer or ternary copolymer is 1700 g / 10 min or less, the durability of the obtained golf ball becomes better.

  When a specific example of the binary copolymer is exemplified by a trade name, for example, a trade name “NUCREL (registered trademark)” (for example, “Nucrel N1050H”, “Nucrel N2050H” from Mitsui DuPont Polychemicals, Inc. "Nucrel N1110H", "Nucrel N0200H"), an ethylene-methacrylic acid copolymer commercially available from Dow Chemical Company under the trade name "PRIMACOR (registered trademark) 5980I". Acid copolymers and the like can be mentioned.

  When a specific example of the terpolymer is exemplified by a trade name, a trade name “NUCREL” (for example, “Nucrel AN4318” or “Nucrel AN4319”) commercially available from Mitsui-Dupont Polychemicals, Dupont Trade name “NUCREL” (for example, “Nucrel AE”) commercially available from Dow Chemical Company, and “PRIMACOR” (for example, “PRIMACOR AT310”, “PRIMACOR AT320”) commercially available from Dow Chemical Company. ")" And the like. The binary copolymer or ternary copolymer may be used alone or in combination of two or more.

(2-3) Thermoplastic polyurethane resin and thermoplastic polyurethane elastomer Examples of the thermoplastic polyurethane resin and the thermoplastic polyurethane elastomer include a thermoplastic resin and a thermoplastic elastomer having a plurality of urethane bonds in a main chain of a molecule. The polyurethane is preferably obtained by reacting a polyisocyanate component and a polyol component. Examples of the thermoplastic polyurethane elastomer include “Elastolane (registered trademark) XNY85A”, “Elastolane XNY90A”, “Elastolane XNY97A”, “Elastolane ET885”, and “Elastoran XNY85A” manufactured by BASF Japan Ltd. Last Run ET890 ".

(2-4) Thermoplastic styrene-based elastomer As the thermoplastic styrene-based elastomer, a thermoplastic elastomer containing a styrene block can be suitably used. The styrene block-containing thermoplastic elastomer includes a polystyrene block as a hard segment and a soft segment. A typical soft segment is a diene block. Examples of the constituent components of the diene block include butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. Butadiene and isoprene are preferred. Two or more components may be used in combination.

  Styrene block-containing thermoplastic elastomers include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-isoprene-butadiene-styrene block copolymer (SIBS), It includes hydrogenated SBS, hydrogenated SIS, and hydrogenated SIBS. Examples of hydrogenated SBS include styrene-ethylene-butylene-styrene block copolymer (SEBS). Examples of hydrogenated SIS include styrene-ethylene-propylene-styrene block copolymer (SEPS). Examples of the hydrogenated product of SIBS include styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS).

  The content of the styrene component in the styrene block-containing thermoplastic elastomer is preferably 10% by mass or more, more preferably 12% by mass or more, and particularly preferably 15% by mass or more. In light of the feel at impact of the obtained golf ball, the content is preferably equal to or less than 50% by mass, more preferably equal to or less than 47% by mass, and particularly preferably equal to or less than 45% by mass.

  The styrene block-containing thermoplastic elastomer includes an alloy of SBS, SIS, SIBS, SEBS, SEPS, and SEEPS, and one or more selected from the group consisting of hydrogenated products thereof and a polyolefin. It is. It is presumed that the olefin component in the alloy contributes to the improvement of compatibility with the ionomer resin. By using this alloy, the resilience performance of the golf ball is improved. Preferably, an olefin having 2 to 10 carbon atoms is used. Suitable olefins include ethylene, propylene, butene and pentene. Ethylene and propylene are particularly preferred.

  As specific examples of the polymer alloy, “Lavalon (registered trademark) T3221C”, “Lavalon T3339C”, “Lavalon SJ4400N”, “Lavalon SJ5400N”, “Lavalon SJ6400N”, “Lavalon SJ7400N”, “Lavalon SJ8400N” manufactured by Mitsubishi Chemical Corporation. , “Lavalon SJ9400N” and “Lavalon SR04”. Other specific examples of the styrene block-containing thermoplastic elastomer include "Epofriend A1010" manufactured by Daicel Chemical Industries, Ltd. and "Septon HG-252" manufactured by Kuraray Co., Ltd.

(2-5) Thermoplastic polyamide resin and thermoplastic polyamide elastomer The thermoplastic polyamide is not particularly limited as long as it is a thermoplastic resin having a plurality of amide bonds (—NH—CO—) in a main chain of the molecule. For example, a product in which an amide bond is formed in a molecule by ring-opening polymerization of a lactam or reacting a diamine component with a dicarboxylic acid component is exemplified.

  Examples of the polyamide resin include aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 6I, polyamide 9T, polyamide M5T, and polyamide 612; poly-p-phenylene terephthalate Aromatic polyamides such as amides and poly-m-phenylene isophthalamide are exemplified. These may be used alone or in combination of two or more. Among these, aliphatic polyamides such as polyamide 6, polyamide 66, polyamide 11, and polyamide 12 are preferred.

  When a specific example of the polyamide resin is represented by a trade name, for example, “Rilsan (registered trademark) B (for example, Rilsan BESN TL, Rilsan BESN P20 TL, Rilsan BESN P40 TL, Rilsan MB3610, Rilsan MB3610) commercially available from Arkema Co., Ltd. BMF O, Rilsan BMN O, Rilsan BMN O TLD, Rilsan BMN BK TLD, Rilsan BMN P20 D, Rilsan BMN P40 D, etc.).

  The polyamide elastomer has a hard segment portion and a soft segment portion made of a polyamide component. Examples of the soft segment portion of the polyamide elastomer include a polyetherester component or a polyether component. Examples of the polyamide elastomer include a polyetherester amide obtained by reacting a polyamide component (hard segment component) with a polyetherester component (soft segment component) composed of polyoxyalkylene glycol and dicarboxylic acid; And a polyether amide obtained by reacting a polyoxyalkylene glycol with aminated or carboxylated both terminals and a polyether (soft segment component) comprising a dicarboxylic acid or a diamine.

  Examples of the polyamide elastomer include “PEBAX (registered trademark) 2533”, “Pebax 3533”, “Pebax 4033”, and “Pebax 5533” manufactured by Arkema.

(2-6) Thermoplastic polyester resin and thermoplastic polyester elastomer The thermoplastic polyester resin is not particularly limited as long as it has a plurality of ester bonds in the main chain of the molecule. For example, a dicarboxylic acid is reacted with a diol. What is obtained by this is preferable. Examples of the thermoplastic polyester elastomer include a block copolymer having a hard segment composed of a polyester component and a soft segment. Examples of the polyester component constituting the hard segment include an aromatic polyester. Examples of the soft segment component include an aliphatic polyether and an aliphatic polyester.

  Specific examples of the polyester elastomer include "Hytrel (registered trademark) 3548" and "Hytrel 4047" manufactured by Toray DuPont, "Primalloy (registered trademark) A1606", "Primalloy B1600", and "Primalloy" manufactured by Mitsubishi Chemical Corporation. B1700 ".

(2-7) Thermoplastic (meth) acrylic elastomer The thermoplastic (meth) acrylic elastomer includes a thermoplastic elastomer obtained by copolymerizing ethylene and a (meth) acrylate. Specific examples of the thermoplastic (meth) acrylic elastomer include, for example, "Kuraray (a block copolymer of methyl methacrylate and butyl acrylate)" manufactured by Kuraray Co., Ltd.

  The thermoplastic resin composition, as a resin component, an ionomer resin, a thermoplastic olefin copolymer, a thermoplastic styrene-based elastomer, a thermoplastic polyester elastomer, a thermoplastic polyurethane elastomer, a thermoplastic polyamide elastomer, at least a thermoplastic acrylic elastomer. It is preferable to contain one type. It becomes easy to form a constituent member having a desired hardness.

  In the present invention, when an ionomer resin or a thermoplastic olefin copolymer is used as a resin component contained in the thermoplastic resin composition, the thermoplastic resin composition further includes (B) a basic fatty acid metal salt described below. May be contained. By containing the basic fatty acid metal salt (B), the degree of neutralization of the ionomer resin and the thermoplastic olefin copolymer can be increased. Increasing the degree of neutralization increases the resilience of the resulting component.

  (B) The basic fatty acid metal salt can be obtained by a known production method in which a fatty acid is reacted with a metal oxide or hydroxide. On the other hand, (B) a metal salt of a basic fatty acid is obtained by adding a metal oxide or hydroxide in excess of a reaction equivalent to a fatty acid, and the metal content of the product is as follows: The melting point and the like are different from those of general fatty acid metal salts.

As the basic fatty acid metal salt (B), for example, those represented by the following general formula (1) are preferable.
mM ¹ O · M ² (RCOO) ₂ (1)
In the formula (1), m represents the number of moles of the metal oxide or metal hydroxide in the basic fatty acid metal salt represented by the formula (1). m is preferably from 0.1 to 2.0, and more preferably from 0.2 to 1.5. If m is less than 0.1, the resilience of the obtained resin composition may decrease, and if m exceeds 2.0, the melting point of the basic fatty acid metal salt becomes too high, and May be difficult to disperse. M ¹ and M ² are each preferably a metal belonging to Group 2 or 12 of the periodic table. M ¹ and M ² may be the same or different. Examples of metals belonging to Group 2 include beryllium, magnesium, calcium, strontium, and barium. Examples of the metal belonging to Group 12 include zinc, cadmium, and mercury. The metal M ¹ and ^{M 2,} for example, magnesium, calcium, barium, zinc are preferable, magnesium is more preferable.

  In the formula (1), RCOO represents a residue of a saturated fatty acid or an unsaturated fatty acid. (B) Specific examples (IUPAC name) of the saturated fatty acid component of the basic fatty acid metal salt include butanoic acid (C4), pentanoic acid (C5), hexanoic acid (C6), heptanoic acid (C7), and octanoic acid (C8). ), Nonanoic acid (C9), decanoic acid (C10), undecanoic acid (C11), dodecanoic acid (C12), tridecanoic acid (C13), tetradecanoic acid (C14), pentadecanoic acid (C15), hexadecanoic acid (C16), Heptadecanoic acid (C17), Octadecanoic acid (C18), Nonadecanoic acid (C19), Icosanoic acid (C20), Henicosanoic acid (C21), Docosanoic acid (C22), Trichosanoic acid (C23), Tetracosanoic acid (C24), Pentacosanoic acid (C25), hexacosanoic acid (C26), heptacosanoic acid (C27), octacosanoic acid (C28), nonacosa Acid (C29), triacontanoic acid (C30).

  (B) Specific examples (IUPAC name) of the unsaturated fatty acid component of the basic fatty acid metal salt include butenoic acid (C4), pentenoic acid (C5), hexenoic acid (C6), heptenoic acid (C7), and octenoic acid ( C8), nonenoic acid (C9), decenoic acid (C10), undecenoic acid (C11), dodecenoic acid (C12), tridecenoic acid (C13), tetradecenoic acid (C14), pentadecenoic acid (C15), hexadecenoic acid (C16) Heptadecenoic acid (C17), octadecenoic acid (C18), nonadecenoic acid (C19), eicosenoic acid (C20), henicicosenoic acid (C21), docosenoic acid (C22), trichosenoic acid (C23), tetracosenoic acid (C24), pentacocene Acid (C25), hexacosenoic acid (C26), heptacosenoic acid (C27), octacosenoic acid (C28), nonaco Phosphate (C29), and the like triacontene acid (C30).

  (B) Specific examples (common names) of the fatty acid component of the basic fatty acid metal salt include, for example, butyric acid (C4), valeric acid (C5), caproic acid (C6), enanthic acid (C7), and caprylic acid (C8). ), Pelargonic acid (C9), capric acid (C10), lauric acid (C12), myristic acid (C14), myristoleic acid (C14), pentadecylic acid (C15), palmitic acid (C16), palmitoleic acid (C16) , Margaric acid (C17), stearic acid (C18), elaidic acid (C18), vaccenic acid (C18), oleic acid (C18), linoleic acid (C18), linolenic acid (C18), 12-hydroxystearic acid (C18) ), Arachidic acid (C20), gadolinic acid (C20), arachidonic acid (C20), eicosenoic acid (C20), behenic acid ( 22), erucic acid (C22), lignoceric acid (C24), nervonic acid (C24), cerotic acid (C26), montanic acid (C28), be mentioned melissic acid (C30).

  (B) The basic fatty acid metal salt is preferably a basic unsaturated fatty acid metal salt. Examples of the unsaturated fatty acid component include oleic acid (C18), erucic acid (C22), linoleic acid (C18), linolenic acid (C18), arachidonic acid (C20), eicosapentaenoic acid (C20), and docosahexaenoic acid (C22). , Stearidonic acid (C18), nervonic acid (C24), vaccenic acid (C18), gadoleic acid (C20), elaidic acid (C18), eicosenoic acid (C20), eicosadienoic acid (C20), docosadienoic acid (C22), pinolene A group consisting of acid (C18), eleostearic acid (C18), mead acid (C20), adrenic acid (C22), succinic acid (C22), nisinic acid (C24), and tetracosapentaenoic acid (C24) It is preferably at least one selected from

  (B) The basic fatty acid metal salt is preferably a basic fatty acid metal salt having 8 to 30 carbon atoms, and more preferably a basic fatty acid metal salt having 12 to 24 carbon atoms. (B) Specific examples of basic fatty acid metal salts include basic magnesium laurate, basic calcium laurate, basic zinc laurate, basic magnesium myristate, basic calcium myristate, basic zinc myristate, and base. Basic magnesium palmitate, basic calcium palmitate, basic zinc palmitate, basic magnesium oleate, basic calcium oleate, basic zinc oleate, basic magnesium stearate, basic calcium stearate, basic stearic acid Zinc, basic magnesium 12-hydroxystearate, basic calcium 12-hydroxystearate, basic zinc 12-hydroxystearate, basic magnesium behenate, basic calcium behenate, basic behenin Zinc, and the like. (B) The basic fatty acid metal salt is preferably a basic fatty acid magnesium, and more preferably a basic magnesium stearate, a basic magnesium behenate, a basic magnesium laurate, and a basic magnesium oleate. The basic fatty acids can be used alone or as a mixture of two or more.

  (B) The melting point of the basic fatty acid metal salt is not particularly limited. For example, when the metal is magnesium, the melting point is preferably 100 ° C or higher, preferably 300 ° C or lower, more preferably 290 ° C or lower, Those having a temperature of 280 ° C. or lower are more preferred. If the melting point is in the above range, the dispersibility in the resin component becomes good.

  (B) The content of the metal component of the basic fatty acid metal salt is preferably 1 mol% or more, more preferably 1.1 mol% or more, preferably 2 mol% or less, and more preferably 1.9 mol% or less. If the content of the metal component is within the above range, the resilience of the resulting golf ball component is further improved. In addition, the content of the metal component of the basic fatty acid metal salt (B) is a value obtained by dividing the amount g of the metal contained per mole of the metal salt by the atomic weight of the metal, and is expressed in mol%.

  The content of the (B) basic fatty acid metal salt in the thermoplastic resin composition used in the present invention is preferably 5 parts by mass or more, more preferably 8 parts by mass or more based on 100 parts by mass of the (A) resin component. Preferably, it is 10 parts by mass or more, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less. (B) By setting the content of the basic fatty acid metal salt to 5 parts by mass or more, the resilience of the golf ball constituent member is improved, and by setting the content to 100 parts by mass or less, golf accompanied by an increase in low molecular weight components. This is because a decrease in the durability of the ball constituent member can be suppressed.

  In the golf ball of the present invention having a center, two or more surrounding layers for covering the center, and a cover for covering the surrounding layer, as the resin component constituting the center or the surrounding layer, an ionomer resin, Plastic olefin copolymers, thermoplastic styrenic elastomers, or mixtures thereof are preferred. The resin component preferably contains a thermoplastic styrene-based elastomer. As the thermoplastic styrene-based elastomer, an alloy of a polyolefin and one or more selected from the group consisting of SBS, SIS, SIBS, SEBS, SEPS, SEEPS and hydrogenated products thereof is preferable. The content of the thermoplastic styrene-based elastomer in the resin component constituting the center is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 100% by mass or less, and more preferably 80% by mass or less.

Preferred embodiments of the resin component constituting the center or the surrounding layer include the following embodiments.
(1) An embodiment containing an ionomer resin and a thermoplastic styrene-based elastomer as resin components. In a more preferred embodiment, an ternary ionomer resin, an alloy of a polyolefin and one or more selected from the group consisting of SBS, SIS, SIBS, SEBS, SEPS and SEEPS, and hydrogenated products thereof. contains.

(2) An embodiment containing an ionomer resin and a thermoplastic styrene-based elastomer, and further containing a metal salt of a basic fatty acid for increasing the degree of neutralization of the ionomer resin. In a more preferred embodiment, an ternary ionomer resin, an alloy of a polyolefin and one or more selected from the group consisting of SBS, SIS, SIBS, SEBS, SEPS and SEEPS, and hydrogenated products thereof. And further contains a metal salt of a basic fatty acid in order to increase the degree of neutralization of the ionomer resin.

(3) An embodiment which contains a thermoplastic olefin copolymer and a thermoplastic styrene-based elastomer, and further contains a basic fatty acid metal salt for increasing the degree of neutralization of the thermoplastic olefin copolymer. Examples of the thermoplastic olefin copolymer include a binary copolymer of an olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and / or an α-olefin having 3 to 8 carbon atoms. Terpolymers of α, β-unsaturated carboxylic acid esters and α, β-unsaturated carboxylic acid esters are preferred, and the thermoplastic styrene-based elastomers include SBS, SIS, SIBS, SEBS, SEPS, SEEPS and waters thereof. An alloy of one or more selected from the group consisting of additives and a polyolefin is preferred.

  The resin component constituting the minimum hardness surrounding layer contains an ionomer resin and a thermoplastic styrene-based elastomer, and preferably has a total content of 50% by mass or more, more preferably 70% by mass or more, and furthermore Preferably it is 90 mass% or more. In this case, the ratio of the ionomer resin to the thermoplastic styrene-based elastomer (ionomer resin / thermoplastic styrene-based elastomer) is preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.3 or more. And preferably 3.0 or less, more preferably 1.7 or less, and still more preferably 1.2 or less.

  The resin component constituting the highest hardness surrounding layer contains an ionomer resin, and the content of the ionomer resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. is there.

  The resin component forming the cover preferably contains an ionomer resin, a thermoplastic polyurethane resin (including a thermoplastic polyurethane elastomer), or a mixture thereof. When the resin component constituting the cover contains an ionomer resin, a golf ball having excellent durability and a long flight distance can be obtained. When the resin component constituting the cover contains a thermoplastic polyurethane resin (including a thermoplastic polyurethane elastomer), a golf ball excellent in shot feeling and controllability can be obtained.

  The resin component constituting the cover contains a thermoplastic polyurethane resin, and the content of the thermoplastic polyurethane resin is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more. It is.

  The thermoplastic resin composition used in the present invention may further contain (C) an additive. (C) Examples of the additive include pigment components such as white pigments (for example, titanium oxide) and blue pigments, weight adjusters, dispersants, antioxidants, ultraviolet absorbers, light stabilizers, fluorescent materials, and fluorescent brighteners. Agents and the like. Examples of the weight adjusting agent include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder.

  The content of the white pigment (for example, titanium oxide) is preferably at least 0.5 part by mass, more preferably at least 1 part by mass, and preferably at most 10 parts by mass, based on 100 parts by mass of the resin component (A). It is more preferably at most 8 parts by mass. By setting the content of the white pigment to 0.5 parts by mass or more, hiding properties can be imparted to the obtained golf ball component. Also, if the content of the white pigment exceeds 10 parts by mass, the durability of the resulting golf ball component may decrease.

  The thermoplastic resin composition used in the present invention is obtained, for example, by dry-blending (A) a resin component and (C) an additive. (B) The basic fatty acid metal salt is blended if necessary. Further, the dry-blended mixture may be extruded into pellets. For the dry blending, for example, it is preferable to use a mixer capable of blending a pellet-shaped raw material, and more preferably to use a tumbler type mixer. For the extrusion, a known extruder such as a single-screw extruder, a twin-screw extruder, or a twin-screw single-screw extruder can be used.

Next, the rubber composition that can be used in the present invention will be described. Examples of the rubber composition include those containing a base rubber, a crosslinking initiator, a co-crosslinking agent, and a filler.

  As the base rubber, natural rubber and / or synthetic rubber can be used, and for example, polybutadiene rubber, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like can be used. These may be used alone or in combination of two or more. Among these, high cis polybutadiene having at least 40% by mass, preferably at least 80% by mass, more preferably at least 90% by mass of a cis-1,4-bond that is advantageous for repulsion is particularly suitable.

  The high cis polybutadiene preferably has a 1,2-vinyl bond content of 2% by mass or less, more preferably 1.7% by mass or less, and even more preferably 1.5% by mass or less. If the content of the 1,2-vinyl bond is too large, the resilience may decrease.

  The high cis polybutadiene is preferably synthesized using a rare earth element-based catalyst. In particular, the use of a neodymium-based catalyst using a neodymium compound, which is a lanthanum series rare-earth element compound, has a high content of 1,4-cis bonds. , 1,2-vinyl bonds are preferred because polybutadiene rubber having a low content can be obtained with excellent polymerization activity.

The high cis polybutadiene preferably has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 30 or more, more preferably 32 or more, still more preferably 35 or more, and preferably 140 or less, more preferably It is 120 or less, more preferably 100 or less, and most preferably 80 or less. The Mooney viscosity (ML _{1 + 4} (100 ° C.)) referred to in the present invention refers to a condition in which an L rotor is used according to JIS K6300, preheating time is 1 minute, rotor rotation time is 4 minutes, and 100 ° C. These are the values measured below.

  The high cis polybutadiene preferably has a molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of 2.0 or more, more preferably 2.2 or more, and still more preferably 2. It is 4 or more, most preferably 2.6 or more, preferably 6.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less, and most preferably 3.4 or less. If the molecular weight distribution (Mw / Mn) of the high cis polybutadiene is too small, the workability is reduced, and if it is too large, the resilience may be reduced. The molecular weight distribution was determined by gel permeation chromatography ("HLC-8120GPC", manufactured by Tosoh Corporation) using a differential refractometer as a detector, column: GMHHXL (manufactured by Tosoh Corporation), column temperature: 40 ° C, mobile phase. : A value measured under the condition of tetrahydrofuran and calculated as a standard polystyrene equivalent value.

  The crosslinking initiator is blended for crosslinking the base rubber component. As the crosslinking initiator, an organic peroxide is preferable. Specifically, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) Organic peroxides such as hexane and di-t-butyl peroxide are exemplified, and among them, dicumyl peroxide is preferably used. The compounding amount of the crosslinking initiator is preferably at least 0.3 part by mass, more preferably at least 0.4 part by mass, and preferably at most 5 parts by mass, more preferably at most 5 parts by mass, based on 100 parts by mass of the base rubber. Not more than 3 parts by mass. If the amount is less than 0.3 parts by mass, the resulting envelope layer becomes too soft, and the resilience tends to decrease.If the amount exceeds 5 parts by mass, the amount of the co-crosslinking agent used is reduced in order to obtain appropriate hardness. It needs to be reduced, and the resilience tends to be insufficient.

  It is considered that the co-crosslinking agent has a function of crosslinking rubber molecules by graft polymerization to a base rubber molecular chain. As the co-crosslinking agent, for example, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof can be used. Preferably, acrylic acid, methacrylic acid or a metal salt thereof is used. Can be mentioned. Examples of the metal constituting the metal salt include zinc, magnesium, calcium, aluminum, and sodium. It is preferable to use zinc because the resilience increases.

  The use amount of the co-crosslinking agent is preferably at least 10 parts by mass, more preferably at least 15 parts by mass, even more preferably at least 20 parts by mass, and preferably at most 55 parts by mass, based on 100 parts by mass of the base rubber. , More preferably 50 parts by mass or less, even more preferably 48 parts by mass or less. When the use amount of the co-crosslinking agent is less than 10 parts by mass, the amount of the crosslinking initiator must be increased in order to obtain appropriate hardness, and the resilience tends to decrease. On the other hand, when the use amount of the co-crosslinking agent exceeds 55 parts by mass, the resulting envelope layer becomes too hard, and the shot feeling may be reduced.

  The filler contained in the rubber composition is mainly used as a weight adjuster for adjusting the weight of a golf ball obtained as a final product, and may be added as needed. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder. The compounding amount of the filler is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass, based on 100 parts by mass of the base rubber. Part or less. If the amount of the filler is less than 0.5 part by mass, it is difficult to adjust the weight. If the amount exceeds 30 parts by mass, the weight fraction of the rubber component tends to be small, and the resilience tends to decrease.

  In addition to the base rubber, the crosslinking initiator, the co-crosslinking agent, and the filler, the rubber composition may further appropriately contain an organic sulfur compound, an antioxidant, a peptizer, and the like.

  Examples of the organic sulfur compound include thiophenols, thionaphthols, polysulfides, thiocarboxylic acids, dithiocarboxylic acids, sulfenamides, thiurams, dithiocarbamates, and thiazoles. Among these, diphenyl disulfides can be suitably used as the organic sulfur compound. Examples of the diphenyl disulfides include diphenyl disulfide; bis (4-chlorophenyl) disulfide, bis (3-chlorophenyl) disulfide, bis (4-bromophenyl) disulfide, bis (3-bromophenyl) disulfide, and bis (4- Monosubstituted products such as fluorophenyl) disulfide, bis (4-iodophenyl) disulfide, bis (4-cyanophenyl) disulfide; bis (2,5-dichlorophenyl) disulfide, bis (3,5-dichlorophenyl) disulfide, bis ( 2,6-dichlorophenyl) disulfide, bis (2,5-dibromophenyl) disulfide, bis (3,5-dibromophenyl) disulfide, bis (2-chloro-5-bromophenyl) disulfide, bis (2-cyano Di-substituted products such as 5-bromophenyl) disulfide; bis (2,4,5-trichlorophenyl) disulfide, bis (2,4,6-trichlorophenyl) disulfide, bis (2-cyano-4-chloro-6- Tri-substituted products such as bromophenyl) disulfide; tetra-substituted products such as bis (2,3,5,6-tetrachlorophenyl) disulfide; bis (2,3,4,5,6-pentachlorophenyl) disulfide, bis (2 Penta-substituted compounds such as (3,4,5,6-pentabromophenyl) disulfide. These diphenyl disulfides have some effect on the vulcanized state of the rubber vulcanizate, and can enhance the resilience. Among these, diphenyl disulfide and bis (pentabromophenyl) disulfide are preferably used from the viewpoint that a particularly high resilience golf ball can be obtained. The compounding amount of the organic sulfur compound is preferably at least 0.1 part by mass, more preferably at least 0.3 part by mass, and preferably at most 5.0 parts by mass, based on 100 parts by mass of the base rubber. More preferably, it is 3.0 parts by mass or less.

  The compounding amount of the antioxidant is preferably 0.1 part by mass or more and 1 part by mass or less based on 100 parts by mass of the base rubber. Further, the compounding amount of the peptizing agent is preferably 0.1 part by mass or more and 5 parts by mass or less based on 100 parts by mass of the base rubber.

  The rubber composition can be formed into an envelope layer by mixing and kneading the respective raw materials and forming the mixture in a mold. The method for molding the envelope layer made of the rubber composition is not particularly limited. For example, the rubber composition is molded in advance into a hemispherical shell-like half shell, and two pieces of the shell are used to wrap the sphere at 130 ° C. A method of press-molding at a temperature of 170 ° C. for 5 minutes to 30 minutes, and a method of injection-molding a rubber composition are exemplified.

  As a structure of the golf ball of the present invention, a four-piece golf ball having a spherical center, two surrounding layers covering the spherical center, and a cover covering the surrounding layer; covering the spherical center and the spherical center 5-piece golf ball having three surrounding layers and a cover covering the surrounding layer; a six-piece golf ball having a spherical center, four surrounding layers covering the spherical center, and a cover covering the surrounding layer Golf ball; a seven-piece golf ball having a spherical center, five surrounding layers covering the spherical center, and a cover covering the surrounding layer.

  As a combination of the constituent materials of the golf ball, an embodiment in which the spherical center and the minimum hardness surrounding layer (Es) are formed from a thermoplastic resin composition; an embodiment in which the spherical center and the minimum hardness surrounding layer (Es) are formed from a rubber composition An embodiment in which the spherical center is formed from a thermoplastic resin composition and the lowest hardness surrounding layer (Es) is formed from a rubber composition; the spherical center is formed from a rubber composition and the lowest hardness surrounding layer (Es) is formed from a thermoplastic resin; Embodiments formed from the composition are exemplified. The highest hardness surrounding layer (Eh) is preferably formed from a thermoplastic resin composition.

  FIG. 4 is a partially cutaway sectional view showing a golf ball 1 according to one embodiment of the present invention. The golf ball 1 includes a spherical center C, a first surrounding layer 1 provided outside the spherical center C, a second surrounding layer 2 provided outside the first surrounding layer 1, (2) a third surrounding layer 3 provided outside the surrounding layer 2, a fourth surrounding layer 4 provided outside the third surrounding layer 3, and provided outside the fourth surrounding layer 4 And a cover A disposed outside the fifth surrounding layer 5. Many dimples 81 are formed on the surface of the cover A. Portions of the surface of the cover A other than the dimples 81 are lands 82. In the case of a seven-piece golf ball, it is preferable that the second surrounding layer be the lowest hardness surrounding layer (Es) and the fifth surrounding layer be the highest hardness surrounding layer (Eh).

(3) Manufacturing Method of Golf Ball Hereinafter, the manufacturing method of the golf ball of the present invention will be described based on an embodiment of a golf ball having a spherical center, an envelope layer covering the spherical center, and a cover covering the envelope layer. Although described, the manufacturing method of the golf ball of the present invention is not limited to the following manufacturing method.

Spherical center As the constituent material of the spherical center, a thermoplastic resin composition or a rubber composition can be used. When the spherical center is formed using a thermoplastic resin composition, the spherical center is obtained, for example, by injection molding the thermoplastic resin composition. Specifically, the thermoplastic resin composition heated and melted at 160 ° C. to 260 ° C. is injected into the mold clamped at a pressure of 1 MPa to 100 MPa for 1 second to 100 seconds, and cooled for 30 seconds to 300 seconds. It is preferable to open the mold.

  When the spherical center is formed using a rubber composition, the spherical center can be obtained by molding the kneaded rubber composition in a mold. The temperature for molding into a spherical core is preferably from 120C to 170C. Further, the pressure during molding is preferably from 2.9 MPa to 11.8 MPa. The molding time is preferably from 10 minutes to 60 minutes.

Envelope layer A thermoplastic resin composition or a rubber composition can be used as a constituent material of the envelope layer. When the surrounding layer is formed using a thermoplastic resin composition, for example, the thermoplastic resin composition is previously formed into a hemispherical shell-shaped half shell, and the two wrapped spheres are used. Press molding at 1 ° C. for 1 to 5 minutes, or a method in which the thermoplastic resin composition is directly injection molded on a sphere to wrap the center is used.

  When the thermoplastic resin composition is injection-molded on a sphere to form the envelope layer, it is preferable to use a molding die having a hemispherical cavity and having a hold pin as the upper and lower molds. The molding of the envelope layer by injection molding is to project the hold pin, throw in the sphere to be coated, hold it, then inject the thermoplastic resin composition that has been heated and melted, and cool to form the envelope layer. Can be.

  When the envelope layer is formed by the compression molding method, the half shell can be formed by either the compression molding method or the injection molding method, but the compression molding method is preferable. The conditions for compression molding the thermoplastic resin composition to form a half shell include, for example, a pressure of 1 MPa or more and 20 MPa or less, with respect to the flow start temperature of the thermoplastic resin composition, -20 ° C. or more and + 70 ° C. The following molding temperatures can be mentioned. By setting the molding conditions, a half shell having a uniform thickness can be molded. As a method of forming the envelope layer using the half shell, for example, a method of covering a sphere with two half shells and performing compression molding can be exemplified. The conditions for compression-molding the half shell into an envelope layer include, for example, at a molding pressure of 0.5 MPa or more and 25 MPa or less, -20 ° C. or more and + 70 ° C. with respect to the flow start temperature of the thermoplastic resin composition. The following molding temperatures can be mentioned. By setting the molding conditions, the surrounding layer having a uniform thickness can be molded.

The molding temperature means a maximum temperature at which the surface of the concave portion of the lower mold reaches between the mold clamping and the mold opening. The flow start temperature of the thermoplastic resin composition was determined by using a flow tester CFT-500 manufactured by Shimadzu Corporation and pelletizing the thermoplastic resin composition into a plunger area of 1 cm ² , a DIE LENGTH of 1 mm, and a DIE DIA. 1 mm, load: 588.399 N, starting temperature: 30 ° C., heating rate: 3 ° C./min.

  When the surrounding layer is formed using a rubber composition, for example, the rubber composition is preliminarily formed into a hemispherical shell-like half shell, and two pieces of the shell are used to wrap the sphere, and the temperature is 130 ° C. to 170 ° C. for 5 minutes. Pressure molding for up to 30 minutes can be mentioned. Alternatively, the rubber composition may be injection molded to form an envelope layer.

Cover A thermoplastic resin composition can be used as a constituent material of the cover. As a method for forming the cover using the thermoplastic resin composition, the method for forming the envelope layer using the above-described thermoplastic resin composition can be adopted. As the upper and lower molds for molding, it is preferable to use a mold having hemispherical cavities, having pimples, and having a part of the pimples also serving as a hold pin that can be advanced and retracted.

  The cover usually has a depression called a dimple on the surface. The total number of dimples formed on the cover is preferably 200 or more and 500 or less. If the total number of dimples is less than 200, it is difficult to obtain the effect of dimples. If the total number of the dimples exceeds 500, the size of each dimple becomes small, and it is difficult to obtain the effect of the dimple. The shape (planar shape) of the dimple to be formed is not particularly limited, and may be a circle; a polygon such as a substantially triangle, a substantially square, a substantially pentagon, or a substantially hexagon; Or two or more of them may be used in combination.

  It is preferable that the golf ball body having the cover formed thereon is removed from the mold and subjected to surface treatment such as deburring, washing, and sand blasting as necessary. Further, if desired, a coating film or a mark can be formed. The thickness of the coating film is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, preferably 50 μm or less, more preferably 40 μm or less, and still more preferably 30 μm or less. When the film thickness is less than 5 μm, the coating film is liable to be worn out by continuous use, and when the film thickness exceeds 50 μm, the effect of dimples is reduced and the flight performance of the golf ball is reduced.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and changes in a range that does not depart from the gist of the present invention and embodiments of the present invention are all described in the present invention. Included in the range.

(1) Core hardness distribution (Shore D hardness)
The core of the golf ball was cut into a hemisphere, and the cross-sectional hardness (Ho, Hs, Hh) at the center of the cut surface and at a point at a predetermined distance from the center was measured. The hardness at each point was determined by measuring the cross-sectional hardness at any four points at a predetermined distance from the center, and averaging the measured values. The measurement was performed using an automatic rubber hardness meter P1 manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore D type spring hardness meter specified in ASTM-D2240.

(2) Material hardness (Shore D)
The material hardness of each layer can be measured as follows. In the case of a thermoplastic resin composition, a sheet having a thickness of about 2 mm was prepared by injection molding. In the case of a rubber composition, it was pressed at 170 ° C. for 25 minutes to produce a sheet having a thickness of about 2 mm. This sheet is stored at 23 ° C. for 2 weeks, and in a state where three or more sheets are stacked so that the influence of the measurement substrate and the like does not appear, a polymer meter equipped with a spring hardness meter Shore D type specified in ASTM-D2240. It is measured by using an automatic rubber hardness tester Model P1 manufactured by Sharp.

(3) Compression deformation (mm)
The amount of deformation in the compression direction (the amount of compression of the golf ball in the compression direction) from when the initial load of 98 N was applied to when the final load of 1275 N was applied to the golf ball was measured.

(4) Spin amount of approach shot A sand wedge (CG15 forged dough (58 °) manufactured by Cleveland Golf Co., Ltd.) was attached to a swing machine manufactured by True Temper, and the golf ball was hit at a head speed of 10 m / sec. The spin amount (rpm) was measured by taking continuous photographs of the ball. The measurement was performed 10 times for each golf ball, and the average value was defined as the spin amount.

(5) Driver spin amount (rpm)
A golf head W # 1 driver (manufactured by Dunlop Sports, XXIOS loft 11 °) is attached to a swing robot M / C manufactured by Golf Laboratory, and the golf ball is hit at a head speed of 50 m / sec. The spin rate of the ball was measured. The measurement was performed 12 times for each golf ball, and the average value was taken as the measured value of the golf ball. The spin rate of the golf ball immediately after hitting was measured by taking continuous shots of the hit golf ball.

[Production of golf ball]
(1) Preparation of thermoplastic resin composition As shown in Table 1, the blended materials were dry-blended, mixed by a twin-screw kneading extruder, and extruded into strands into cold water. The extruded strand was cut with a pelletizer to prepare a pellet-shaped thermoplastic resin composition. The extrusion conditions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D = 35, and the compound was heated to 160 to 230 ° C. at the die position of the extruder.

The raw materials used in Table 1 are as follows.
Himilan AM7327: Zinc ion-neutralized ethylene-methacrylic acid-butyl acrylate terpolymer ionomer resin (manufactured by Mitsui DuPont Polychemicals) (melt flow rate (190 ° C. × 2.16 kgf): 0.7 g / 10 min, Flexural rigidity: 35 MPa)
Nuclell AN4319: Mitsui-Dupont Polychemical Co., Ltd., ethylene / methacrylic acid / butyl acrylate copolymer (melt flow rate (190 ° C. × 2.16 kgf): 55 g / 10 min, flexural rigidity: 21 MPa)
Himilan 1605: manufactured by Mitsui DuPont Polychemicals Co., Ltd., sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C × 2.16 kgf): 2.8 g / 10 min, flexural rigidity: 320 MPa)
Himilan AM7329: manufactured by Mitsui-Dupont Polychemical Co., Ltd., zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin (melt flow rate (190 ° C. × 2.16 kgf): 5 g / 10 min, flexural rigidity: 221 MPa)
HPF2000: Magnesium ion-neutralized terpolymer ionomer resin manufactured by DuPont (melt flow rate (190 ° C. × 2.16 kgf): 1.0 g / 10 min, flexural rigidity: 64 MPa)
HPF1000: Magnesium ion-neutralized terpolymer copolymer ionomer resin manufactured by DuPont (melt flow rate (190 ° C. × 2.16 kgf): 0.7 g / 10 min, flexural rigidity: 190 MPa)
Lavalon T3221C: manufactured by Mitsubishi Chemical Corporation, thermoplastic styrene elastomer (SBS, SIS, SIBS, SEBS, SEPS and SEEPS, and one or more selected from the group consisting of hydrogenated products thereof, and polyolefin Alloy)
Elastran XNY84A: thermoplastic polyurethane elastomer manufactured by BASF Japan Ltd. Basic magnesium oleate: manufactured by Nitto Kasei Kogyo Co., Ltd. (metal content: 1.7 mol%, in the formula (1), M ¹ = M ² = Mg, R = Carbon number 17)
Titanium dioxide: Ishihara Sangyo A220

(2) Preparation of rubber composition The materials shown in Table 2 were kneaded to prepare a rubber composition.

The raw materials used in Table 2 are as follows.
Polybutadiene rubber: manufactured by JSR, BR730 (high cis polybutadiene, cis-1,4-bond content = 96% by mass, 1,2-vinyl bond content = 1.3% by mass, Mooney viscosity (ML _{1 + 4} (100 ° C.)) = 55, molecular weight distribution (Mw / Mn) = 3) ”
Zinc acrylate: "ZNDA-90S" manufactured by Nippon Distillery
Zinc oxide: “Ginrei (registered trademark) R” manufactured by Toho Zinc Co., Ltd.
Diphenyl disulfide: Bis (pentabromophenyl) disulfide manufactured by Sumitomo Seika: Dicumyl peroxide manufactured by Sankyo Kasei Co., Ltd .: “Park Mill (registered trademark) D” manufactured by NOF Corporation
Barium sulfate: “Barium sulfate BD” manufactured by Sakai Chemical Co., Ltd.

(3) Production of Spherical Center The thermoplastic resin composition obtained above was injection molded at 200 ° C. as shown in Tables 3 and 5 to produce a spherical center. Further, the rubber composition obtained above was pressed at 170 ° C. for 25 minutes as shown in Tables 4 and 6, to produce a spherical center. The golf ball No. About 5-1, the rubber composition No. shown in Table 2 was used. A was pressed at 170 ° C. for 25 minutes to form a spherical center.

(4) Production of Envelope Layer Made of Thermoplastic Resin Composition Each envelope layer was molded by injection molding the thermoplastic resin composition obtained above at 200 ° C. as shown in Tables 3 to 6.

(5) Production of Envelope Layer Made of Rubber Composition As shown in Tables 4 and 5, half shells were molded from the rubber composition shown in Table 2. The sphere was covered with two half shells. The sphere and the half shell were put into a mold including upper and lower molds each having a hemispherical cavity, and heated at 170 ° C. for 25 minutes to produce an envelope layer made of a rubber composition. Golf ball No. About 5-1, the rubber composition No. shown in Table 2 was used. Using B, a two-layer core made of the rubber composition was molded.

(6) Production of Cover Made of Thermoplastic Resin Composition A cover was formed by compression-molding the thermoplastic resin composition obtained above. In the compression molding of the half shell, the obtained thermoplastic resin composition in the form of a pellet was charged one by one into each concave portion of the lower mold of the half shell molding die and pressurized. The compression molding was performed at a molding temperature of 160 ° C., a molding time of 2 minutes, and a molding pressure of 11 MPa. The sphere on which the n-th surrounding layer was formed was concentrically covered with two half shells, put into a mold having a large number of pimples on the cavity surface, and a cover was formed by compression molding. The compression molding was performed at a molding temperature of 150 ° C., a molding time of 3 minutes, and a molding pressure of 13 MPa. A large number of dimples having the inverted shape of the pimples were formed on the cover after molding.

  After the surface of the obtained golf ball body is sandblasted and marked, a clear paint is applied, and the paint is dried in an oven at 40 ° C. to obtain a golf ball having a diameter of 42.8 mm and a mass of 45.4 g. Was. The results of evaluating the obtained golf balls are also shown in Tables 3 to 6.

  According to the results of Tables 3 to 6, the golf ball having the core and the cover has a core hardness distribution in a region where the distance from the center of the golf ball is 36.0% to 65.0% of the radius of the golf ball. In the golf ball having the lowest hardness point, the spin rate of the driver shot is lower than the spin rate of the approach shot. As a result, the golf ball of the present invention flies well on driver shots and stops well on approach shots.

  INDUSTRIAL APPLICABILITY The present invention is useful as a golf ball that flies well on a driver shot and stops well on an approach shot. The golf ball of the present invention is suitable as a golf ball for golfers having a head speed of 40 m / S or more.

100: golf ball, C: spherical center, 1: first surrounding layer, 2: second surrounding layer, 3: third surrounding layer, 4: fourth surrounding layer, 5: fifth surrounding layer, A: cover, B : A core, 81: dimples, 82: land, S: a region whose distance from the center of the golf ball is 36.0% to 65.0% of the radius, H: a distance from the center of the golf ball of 85.5% of the radius. 0% to 99.5% area

Claims (10)

A multi-piece golf ball having a core including a spherical center, an n-layer (n is a natural number of 2 or more) surrounding layers covering the spherical center, and a single-layer cover covering the core.
The minimum hardness point in the core hardness distribution exists in a region where the distance from the center of the golf ball is 36.0% to 65.0% of the radius of the golf ball, and the minimum hardness point corresponds to a layer having a uniform hardness distribution. The minimum hardness is 3 or more and 27 or less in Shore D hardness, and the hardness of the entire region in which the distance from the golf ball center is 0% to 50.0% of the golf ball radius is the Shore D hardness. A multi-piece golf ball having a diameter of 40 or less.   2. The multi-piece golf ball according to claim 1, wherein the minimum hardness point in the core hardness distribution exists in a region where the distance from the golf ball center is 40.0% to 62.5% of the radius of the golf ball.   From the center of the golf ball toward the lowest hardness point, the core hardness decreases in Shore D hardness with an average descending gradient of -2.5 points / mm to -0.3 points / mm, and the distance from the center of the golf ball 3. The multi-piece golf ball according to claim 1, wherein the minimum hardness reaches the minimum hardness in a range of 36.0% to 65.0% of a radius of the golf ball. 4.   The multi-piece golf ball according to any one of claims 1 to 3, wherein the minimum hardness is 3 to 23 in Shore D hardness.   The mulch according to any one of claims 1 to 4, wherein the highest hardness point in the core hardness distribution exists in a region where the distance from the center of the golf ball is 85.0% to 99.5% of the radius of the golf ball. Peace golf ball.   6. The multi-piece golf ball according to claim 5, wherein the hardness increases from the lowest hardness point to the highest hardness point at an average ascending gradient of 2 points / mm to 10 points / mm in Shore D hardness.   The multi-piece golf ball according to claim 5, wherein the maximum hardness is 30 to 85 in Shore D hardness. The multi-piece golf ball according to claim 5 , wherein the highest hardness point exists in a layer having a uniform hardness distribution. The multi-piece golf ball according to any one of claims 5 to 8 , wherein a hardness difference between the maximum hardness and the minimum hardness is 30 or more and 80 or less in Shore D hardness. The diameter of the spherical center is 20 mm or less, the diameter of the golf ball is 42.67 mm or more, and the distance from the center of the golf ball is 90.0% to 99.5% of the radius of the golf ball. The multi-piece golf ball according to any one of claims 1 to 9 , wherein a maximum hardness point in the distribution exists.

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