JP3956068B2 - Multi-piece solid golf ball - Google Patents

Description

【００４２】
得られたソリッドコアを金型内に配備し、表２，３に示す内層カバー材を射出して、内層カバーを形成した後、金型から取り出して該内層カバーの表面をバレル研磨にて粗面化した。
【００４３】
上記粗面化した面を表２，３に示す接着剤にて形成されたシート（厚さ５０μｍ）で包み、余剰部分をカットして接着剤層を形成した後、更に金型内に配備して、表２，３に示す外層カバー材を射出し、総数４３２個、表面占有率７０％、体積率（ディンプル部分を考慮しないボールの仮想球体積に対するディンプル総容積の割合）０．９％のディンプルを有するマルチピースソリッドゴルフボールを作成した。
【００４４】
また、比較例１は、表１のソリッドコアに表３で示されるカバー材を１層被覆形成してなるツーピースソリッドゴルフボール、比較例２〜４は、表１のソリッドコアに表３の内層カバーを被覆すると共に、この上に接着剤層を形成せずに外層カバーを被覆してなるスリーピースソリッドゴルフボールで、粗面化した内層カバーに外層カバーを被覆形成したもので、ディンプル個数及び態様は上記と同様である。
【００４５】
製造した各ソリッドゴルフボールに対して、下記方法により、飛び性能、スピン性能、コントロール性、耐擦過傷性、繰り返し打撃耐久性を評価した。結果を表２，３に併記する。なお、表中、中間ボールとはソリッドコアに内層カバーを形成したものをいう。
【００４６】
飛び性能
ツルー・テンパー（Ｔｒｕｅ Ｔｅｍｐｅｒ）社製のスウィングロボットを用い、ドライバーを用いてヘッドスピード５０ｍ／ｓｅｃ（ＨＳ＝５０）でショットしたときのスピン量、初速度、キャリー、トータル飛距離を測定した。
スピン性能
上記と同様のスウィングロボットにて、ピッチングウェッジを用いて、ヘッドスピード２０ｍ／ｓｅｃ（ＨＳ＝２０）でショットした時のスピン量を測定した。
コントロール性
上級のアマチュアプレーヤー（いわゆるシングルプレーヤー）１０人により、ピッチングウェッジを用いてアプローチショットを行った時のコントロール性を下記基準にて官能評価した。
○：大変優れる
△：良好
×：悪い
耐擦過傷性
飛び性能と同様のスウィングロボットにて、ピッチングウェッジを用いて、ヘッドスピード３０ｍ／ｓｅｃ（ＨＳ＝３０）で、同一ボールにつき３回繰り返し打撃した後にボールの表面状態を目視にて観察し、点数評価した（１０点が満点で、点数が高い程、良好であることを示す）。
繰り返し打撃耐久性
飛び性能と同様のスウィングロボットにて、ドライバーを用いて、ヘッドスピード４５ｍ／ｓｅｃ（ＨＳ＝４５）で、同一ボールにつき３００回繰り返し打撃した後にボールの状態を目視にて観察し、比較例１を基準値１００として、各ボールについて比較評価した。
【００４７】
【表２】

【００４８】
【表３】

１）デュポン社製，酸含量１８％，亜鉛系アイオノマー（Ｄ６５）
２）デュポン社製，酸含量１８％，ナトリウム系アイオノマー（Ｄ６６）
３）デュポン社製，酸含量２０％，亜鉛系アイオノマー（Ｄ６７）
４）デュポン社製，酸含量２０％，ナトリウム系アイオノマー（Ｄ６８）
５）三井・デュポンポリケミカル社製，酸含量１５％，亜鉛系アイオノマー（Ｄ６２）
６）三井・デュポンポリケミカル社製，酸含量１５％，ナトリウム系アイオノマー（Ｄ６３）
７）住友化学工業社製，エチレン−グリシジルメタクリレート共重合体，ＧＭＡ含量６重量％
８）三井・デュポンポリケミカル社製，エチレン−エチルアクリレートの無水マレイン酸グラフト変性物
９）エクソン社製，エチレン−メタアクリレート−アクリル酸三元共重合体
１０）東レ・デュポン社製，ポリエステルエラストマー（Ｄ４０）
１１）アトケム社製，ポリアミドエラストマー（Ｄ４０）
１２）大日本インキ化学工業社製，ポリウレタンエラストマー（Ｄ４０）
＊（Ｄ）はショアＤ硬度を示す。
１３）１００ｋｇ荷重負荷時のボールの変形量
１４）ゴルフボール公認機関（ＵＳＧＡ）の測定法に従い測定した初速度
【００４９】
本発明のマルチピースソリッドゴルフボールは、接着剤層が内層カバーと外層カバーとに強固に接着しているので、アプローチショット時のスピン量が多く、ドライバーショット時のスピン量が少なく、コントロール性に優れ、かつ飛距離の増大化が図れる優れたスピン量を有する上、アイアンショットに対する擦過傷が発生しにくく、繰り返し打撃耐久性に優れたものであることが認められた。
【００５０】
これに対して、比較例の接着剤層のないゴルフボールは、いずれも本発明の性能に勝るものはなかった。特に、比較例１のツーピースソリッドゴルフボールは、ドライバー、アイアンショット時におけるスピン性能のすべてにおいて少なすぎ、コントロール性が悪く、耐久性が劣るものであり、また比較例２〜４の接着剤層を有していない以外は本発明と同様の内外層カバーを有するスリーピースソリッドゴルフボールは、耐久性及び耐擦過傷性が極端に劣るものであった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-piece solid golf ball that is excellent in durability against repeated hitting, can increase a flight distance, and has excellent controllability and scratch resistance.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, for low-handy players, the spin control performance of the ball when shot with a short iron has been important, especially for the two-piece golf ball made of ionomer resin with a hard cover, excellent flying distance unique to the ball Improving spin control performance without compromising performance is a major issue in development, and various studies have been conducted.
[0003]
For example, US Pat. No. 4,431,193 discloses a three-piece solid golf ball in which an inner layer cover is formed of a hard ionomer resin and an outer layer cover is formed of a soft ionomer resin, thereby improving the respective spin amounts when shot with a driver and a short iron. It has been proposed to plan.
[0004]
However, since this golf ball is inferior to the two-piece solid golf ball in abrasion resistance and flight distance performance, improvement thereof has been demanded.
[0005]
JP-A-6-343718 discloses a heat which does not contain a low modulus ionomer resin or an ionomer resin having a relatively low acid content while forming an inner layer cover with a high modulus ionomer resin having a relatively high acid content. A three-piece solid golf ball made of a plastic elastomer has been proposed.
[0006]
However, this golf ball has a problem that when the outer layer cover is formed of a thermoplastic elastomer resin, the rebound and durability of the ball may be significantly impaired due to poor adhesion of the inner layer cover to the ionomer resin. ing.
[0007]
The present invention has been made in view of the above circumstances, and has excellent flight distance performance over conventional two-piece solid golf balls, and is resistant to repeated hitting, such as controllability with a short iron, spin performance, abrasion resistance, etc. An object of the present invention is to provide a multi-piece solid golf ball capable of improving playability.
[0008]
Means for Solving the Problem and Embodiment of the Invention
In order to achieve the above object, the present inventors
(1) In a multi-piece solid golf ball in which a solid core and a cover having a two-layer structure consisting of an inner layer and an outer layer are coated on the solid core , glycidyl methacrylate or an organic acid is grafted onto the olefin compound on the inner layer cover. An adhesive layer composed mainly of a copolymerized or random copolymerized polymer is formed, and an outer layer cover is laminated on the adhesive layer, and the inner layer cover is at least 15% by weight of α, β-uncoated. A multi-piece solid golf ball characterized in that an ionomer resin containing a saturated carboxylic acid is a main material, and an outer layer cover is a thermoplastic elastomer containing no ionomer resin.
(2) The hardness of the inner layer cover is Shore D hardness 60 to 75, the outer layer cover is mainly made of one or more of polyurethane elastomer, polyester elastomer and polyamide elastomer, and the hardness is Shore D hardness 35 to 55. A multi-piece solid golf ball according to (1),
(3) The multi-piece solid golf ball according to (1 ), wherein the adhesive is an ethylene-glycidyl methacrylate copolymer, an ethylene-ethyl acrylate maleic anhydride graft-modified product, or an ethylene-methacrylate-acrylic acid terpolymer; 4) The multi-piece solid golf ball according to any one of (1) to (3), wherein the adhesive layer has a thickness of 10 μm to 1.5 mm.
[0009]
That is, the present inventors have conducted intensive studies on a golf ball in which a solid core and a cover having a two-layer structure consisting of an inner layer and an outer layer are coated on the solid core. In addition, an adhesive layer mainly composed of a polymer obtained by graft copolymerization or random copolymerization of glycidyl methacrylate or an organic acid with an olefin compound is formed, and a multilayer structure in which an outer cover is laminated on the adhesive layer is formed. In addition, by specifying the material of the inner layer cover and outer layer cover that are bonded to the above adhesive layer, the durability by repeated hits is dramatically improved, and when driving a driver, the flight distance is increased with a low spin rate In addition, when taking an approach shot with a short iron or the like, the spin rate is large and the controllability is excellent. It was found to be also good.
[0010]
In order to further improve the performance of the multi-piece solid golf ball, the Shore D hardness of the inner layer and the outer layer cover is optimized and the main material of the outer layer cover is specified, the material of the adhesive is specified, Furthermore, it has been found that it is more effective to optimize the thickness of the adhesive layer to the above-described range, and the present invention has been made.
[0011]
Hereinafter, the present invention will be described in more detail. As described above, the multi-piece solid golf ball of the present invention is formed by covering a solid core and a cover having a two-layer structure of an inner layer and an outer layer on the solid core. An adhesive layer is interposed between the inner layer and the outer layer cover.
[0012]
Here, the solid core will be described in detail. The solid core of the present invention can be formed using a known material, and a known rubber in which a base rubber is blended with a co-crosslinking agent, a peroxide, an inert filler, and the like. This rubber composition can be obtained by heating, pressing and molding.
[0013]
In this case, as the base rubber, polybutadiene conventionally used for solid cores or a mixture of polybutadiene and polyisoprene rubber can be used. In particular, in order to obtain high resilience, a cis structure 90 is used. It is preferable to use cis-1,4-polybutadiene having at least%.
[0014]
As the co-crosslinking agent, for example, zinc salts of unsaturated fatty acids such as methacrylic acid and acrylic acid, and ester compounds such as magnesium salts and trimethylpropane trimethacrylate can be used. Can be suitably used. The compounding amount of these co-crosslinking agents is not limited, but can be 10 to 50 parts by weight with respect to 100 parts by weight of the base rubber.
[0015]
As the peroxide, for example, dicumyl peroxide or a mixture of dicumyl peroxide and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane is preferably used. The blending amount is preferably 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the base rubber.
[0016]
Examples of the inert filler include zinc white, barium sulfate, silica, calcium carbonate and zinc carbonate. In general, zinc white and barium sulfate are preferably used, and the blending amount thereof is appropriately adjusted. In particular, in order to improve the resilience of the solid core, it is recommended that the zinc white be blended so as to be 30% by weight or more of the total filler.
[0017]
Moreover, additives, such as anti-aging agent, can be added to the core material as necessary.
[0018]
In order to obtain a solid core with the above material, it can be produced according to a known method. After kneading using a kneader such as a Banbury mixer or a roll, the material is put into a core mold, and a co-crosslinking agent and It can be cured by heating to a temperature sufficient for the peroxide to act.
[0019]
The solid core of the present invention has a diameter of 27 to 40 mm, particularly 32 to 39 mm, a weight of 10 to 35 g, particularly 15 to 32 g, and a deformation amount of 2.5 to 5.5 mm, particularly 3.0 to 30 kg. It can be formed to be 5.0 mm.
[0020]
The inner layer cover of the present invention is mainly composed of an ionomer resin containing α, β-unsaturated carboxylic acid at a high concentration of 15% by weight or more.
[0021]
Here, examples of the α, β-unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid and fumaric acid, and methacrylic acid and acrylic acid are particularly preferable.
[0022]
The ionomer resin used as the inner layer cover material of the present invention contains the above α, β-unsaturated carboxylic acid in the resin at a high concentration of 15% by weight or more, and the content is particularly 15 to 25% by weight. It is recommended that the content be 17 to 25% by weight, and more preferably 18.5 to 21.5% by weight. If it is less than 15% by weight, the rigidity is low and the resilience is also poor. In addition, when it exceeds 25 weight%, rigidity may become high too much and resin may become fragile.
[0023]
As such an ionomer resin, specifically, Himiran 1706, 1605 (Mitsui / DuPont Polychemical), Surlyn 8220, AM7317, 7318, 7315 (DuPont), etc. can be used. Can be used alone or in admixture of two or more, but in particular, the combination of two or more ionomer resins with different neutralizing metal ions is recommended. As an example of the combination of neutralizing metal ions, Zn / Na, Mg / Li, Mg / Na and the like.
[0024]
In the present invention, the inner layer cover hardness is not particularly limited, but a Shore D hardness of 60 to 75, particularly a Shore D hardness of 62 to 70 is recommended, and a Shore D hardness of less than 60 is sufficient as a ball. The rebound can not be obtained, and it will not fly, and if it is higher than 75, the feel at impact will be very hard and the feeling may be poor. The specific gravity of the inner layer cover is preferably 0.8 to 1.5.
[0025]
Moreover, the thickness of the inner layer cover can usually be formed to 0.5 to 3.0 mm, particularly 1.0 to 2.0 mm, and if it is thinner than 0.5 mm, the effect of controlling the deformation of the core and increasing the resilience However, if it is thicker than 3.0 mm, the resilience of the core may not be fully utilized.
[0026]
The outer layer cover of the present invention is mainly composed of a thermoplastic elastomer that does not contain an ionomer resin. Examples of such a thermoplastic elastomer include polyurethane elastomers, polyester elastomers, and polyamide elastomers. Hytrel 4047 (polyester elastomer manufactured by Toray DuPont), Pebax 4033SA00 (polyamide elastomer manufactured by Atochem), Pandex T7890 (polyurethane elastomer manufactured by Dainippon Ink & Chemicals, Inc.) and the like can be suitably used. The seeds can be used alone or in admixture of two or more. The specific gravity of the outer cover is usually 1.0 to 1.5.
[0027]
In the present invention, the hardness of the outer layer cover is not particularly limited, but the Shore D hardness is 35 to 55, particularly 45 to 55, and is preferably formed to have a lower hardness than the inner layer cover described above.
[0028]
Further, the thickness of the outer layer cover is not particularly limited, and can be generally 0.6 to 1.6 mm, particularly 0.8 to 1.6 mm. If the outer layer cover is too thin, If the ball is too thick, the resilience of the ball will be reduced and good flight performance may not be obtained.
[0029]
As described above, the adhesive layer is interposed between the inner layer cover and the outer layer cover, thereby firmly bonding the ionomer resin of the inner layer cover and the thermoplastic elastomer of the outer layer cover, and durability by repeated hitting of the ball. In addition to improving the performance, the spin performance suitable for various club hits, the increase in the flight distance, the controllability, and the abrasion resistance can be improved.
[0030]
In the present invention, the adhesive layer is formed by using an adhesive mainly composed of a polymer obtained by graft copolymerization or random copolymerization of olefin compound with glycidyl methacrylate or organic acid. In this case, examples of the olefinic compound include ethylene, a mixture of ethylene and ethyl acrylate, methacrylate, and the like, and these may be used in combination. Examples of the organic acid include maleic anhydride and acrylic acid. Specifically, ethylene-glycidyl methacrylate copolymer, ethylene-ethyl acrylate maleic anhydride graft-modified product, ethylene-methacrylate-acrylic acid terpolymer, and the like are commercially available. 2C (ethylene-glycidyl methacrylate copolymer manufactured by Sumitomo Chemical Co., Ltd.), AR-201 (methylene anhydride-modified maleic anhydride grafted product of Mitsui DuPont Polychemical), ESCOR-ATX325 (ethylene-meta manufactured by Exxon) An acrylate-acrylic acid terpolymer can be preferably used.
[0031]
Further, the mode of the adhesive is not particularly limited, and can be adjusted to a state in which an adhesive layer can be easily formed on the inner cover, for example, any of liquid, paste, solid sheet, etc. There may be. Therefore, as a method for forming the adhesive layer, in addition to general application methods such as injection, molding, and hot melt, when a sheet-like adhesive is used, a method of wrapping the inner layer cover or the like can be employed.
[0032]
In the present invention, the thickness of the adhesive layer is appropriately selected and is not particularly limited, but is usually 10 μm to 1.5 mm, particularly preferably 10 μm to 1.0 mm, and if less than 10 μm If the effect is not sufficiently obtained and the thickness exceeds 1.5 mm, the resilience is lowered.
[0033]
The multi-piece solid golf ball of the present invention can be obtained by forming each layer on a solid core prepared in advance using a material of each layer described above by a known method. The method for forming each layer is not particularly limited. For example, a method in which a solid core is disposed in a mold and an inner layer cover material, an adhesive, and an outer layer cover material are sequentially injected and molded, and an inner layer and an outer layer cover material are previously formed. A pair of hemispherical bowl-shaped half cups were respectively prepared, and an adhesive layer was formed on the surface of the inner layer cover, and then an outer layer cover was superimposed thereon to obtain a pair of half cups. A method of compression molding at 110 to 160 ° C. for 2 to 10 minutes, a pair of half cups formed only by the inner layer cover, and a solid core being encapsulated at 110 to 160 ° C. for 2 to 10 minutes. After that, an adhesive layer is formed on the surface of the inner layer, and an outer layer cover material is injection-molded from this, but the adhesive layer is more stable. To form, it is recommended to roughen the surface subjected to such pre-barrel polishing to the inner cover.
[0034]
The total thickness of the inner layer cover, the adhesive layer, and the outer layer cover formed as described above is usually 2.0 to 7.5 mm, particularly preferably 2.5 to 3.5 mm. The ratio of inner layer cover: adhesive layer: outer layer cover is preferably 50: 1: 50 to 2: 1: 2.
[0035]
Further, the deformation amount of the ball when a load of 100 kg is applied is normally 2.3 to 4.5 mm, particularly preferably 2.5 to 4.0 mm.
[0036]
The multi-piece solid golf ball of the present invention is formed by forming a large number of dimples on the surface in the same manner as a normal golf ball, and the number of dimples is not particularly limited, but is usually 350 to 500, preferably May be 370 to 480, more preferably 390 to 450, and the dimples may be two or more types having different diameters and depths. The diameter is usually adjusted to 1.4 to 4.5 mm, particularly 2.0 to 4.3 mm, and the depth is preferably 0.15 to 0.25 mm, particularly 0.17 to 0.23 mm. .
[0037]
The golf ball of the present invention can be appropriately set according to the golf rules as long as it does not deviate from the above range, and can be formed to have a weight of 45.93 g or less and a diameter of 42.67 mm or more.
[0038]
【The invention's effect】
The multi-piece solid golf ball of the present invention has durability against repeated hits, has an excellent spin performance with a high spin rate on approach shots, and a low spin rate on driver shots, and has excellent controllability and flying performance. The distance can be increased and the scuff resistance is excellent.
[0039]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[0040]
[Examples and comparative examples]
The composition shown in Table 1 is obtained by kneading the rubber composition of the composition shown in Table 1 (all units in parts by weight) with a kneader, placing it in a mold, and heat-pressing it at 150 ° C. for 15 minutes. Created a solid core.
[0041]
[Table 1]

[0042]
The obtained solid core is placed in a mold, and the inner layer cover materials shown in Tables 2 and 3 are injected to form the inner layer cover. Then, the inner layer cover is taken out and roughened by barrel polishing on the surface of the inner layer cover. Faced.
[0043]
After wrapping the roughened surface with a sheet (thickness 50 μm) formed of the adhesive shown in Tables 2 and 3, the surplus portion is cut to form an adhesive layer, and then placed in a mold. The outer layer cover materials shown in Tables 2 and 3 were injected, the total number was 432, the surface occupancy was 70%, and the volume ratio (the ratio of the total dimple volume to the phantom sphere volume of the ball not considering the dimple portion) was 0.9%. A multi-piece solid golf ball having dimples was prepared.
[0044]
Comparative Example 1 is a two-piece solid golf ball in which the solid core shown in Table 1 is covered with one layer of the cover material shown in Table 3, and Comparative Examples 2 to 4 are the inner core shown in Table 3 on the solid core shown in Table 1. A three-piece solid golf ball that covers a cover and covers an outer layer cover without forming an adhesive layer thereon. The three-piece solid golf ball is formed by coating an outer layer cover on a roughened inner layer cover. Is the same as above.
[0045]
With respect to each manufactured solid golf ball, flying performance, spin performance, controllability, scratch resistance, and repeated impact durability were evaluated by the following methods. The results are also shown in Tables 2 and 3. In the table, the intermediate ball means a solid core formed with an inner layer cover.
[0046]
Flying performance Spin amount, initial speed, carry and total flying when using a swing robot made by True Temper with a head speed of 50m / sec (HS = 50) using a driver The distance was measured.
Spin performance Using a swinging robot similar to the above, the amount of spin when shot at a head speed of 20 m / sec (HS = 20) was measured using a pitching wedge.
Controllability 10 senior amateur players (so-called single players) performed a sensory evaluation on the controllability of an approach shot using a pitching wedge based on the following criteria.
○: Excellent △: Good ×: Bad
Scratch resistance Using a swinging robot similar to flying performance, using a pitching wedge, with a head speed of 30 m / sec (HS = 30), hitting the same ball three times repeatedly, visually inspecting the surface state of the ball And scored (10 points are perfect, the higher the score, the better).
Repeated hitting durability Using a swing robot similar to the flying performance, using a screwdriver with a head speed of 45 m / sec (HS = 45), hitting the same ball 300 times repeatedly, visually checking the state of the ball Each ball was comparatively evaluated using Comparative Example 1 as a reference value of 100.
[0047]
[Table 2]

[0048]
[Table 3]

1) Product made by DuPont, acid content 18%, zinc ionomer (D65)
2) DuPont, acid content 18%, sodium ionomer (D66)
3) DuPont, acid content 20%, zinc ionomer (D67)
4) DuPont, acid content 20%, sodium ionomer (D68)
5) 15% acid content, Mitsui DuPont Polychemicals, zinc ionomer (D62)
6) Mitsui-DuPont Polychemicals, acid content 15%, sodium ionomer (D63)
7) Sumitomo Chemical Co., Ltd., ethylene-glycidyl methacrylate copolymer, GMA content 6% by weight
8) Mitsui-DuPont Polychemical Co., Ltd., Ethylene-ethyl acrylate maleic anhydride graft modified 9) Exxon, ethylene-methacrylate-acrylic acid terpolymer 10) Toray DuPont, polyester elastomer ( D40)
11) Polyamide elastomer (D40) manufactured by Atchem
12) Dainippon Ink & Chemicals, polyurethane elastomer (D40)
* (D) indicates Shore D hardness.
13) Amount of deformation of the ball under a load of 100 kg 14) Initial velocity measured in accordance with a measurement method of a golf ball official agency (USGA)
In the multi-piece solid golf ball of the present invention, since the adhesive layer is firmly adhered to the inner layer cover and the outer layer cover, the spin amount at the approach shot is large, the spin amount at the driver shot is small, and controllability is increased. It was confirmed that it had excellent spin amount that could improve the flight distance, was not easily scratched against iron shots, and had excellent repeated hitting durability.
[0050]
On the other hand, none of the golf balls without the adhesive layer of the comparative example surpassed the performance of the present invention. In particular, the two-piece solid golf ball of Comparative Example 1 has too little spin performance at the time of driver and iron shot, has poor controllability, and is inferior in durability. The three-piece solid golf ball having the same inner and outer layer cover as that of the present invention except that it does not have the durability and scratch resistance was extremely inferior.

Claims (4)

In a multi-piece solid golf ball in which a solid core and a cover having a two-layer structure consisting of an inner layer and an outer layer are coated on the solid core , a glycidyl methacrylate or an organic acid is graft-copolymerized on the inner layer cover on the inner layer cover An adhesive layer mainly composed of a polymer obtained by random copolymerization is formed, an outer layer cover is laminated on the adhesive layer, and the inner layer cover is at least 15% by weight of an α, β-unsaturated carboxylic acid. A multi-piece solid golf ball comprising an ionomer resin containing a main material and an outer layer cover comprising a thermoplastic elastomer containing no ionomer resin as a main material.   The hardness of the inner layer cover is Shore D hardness 60 to 75, and the outer layer cover is mainly composed of one or more of polyurethane elastomer, polyester elastomer and polyamide elastomer, and the hardness is Shore D hardness 35 to 55. The multi-piece solid golf ball according to 1. 2. The multi-piece solid golf ball according to claim 1, wherein the adhesive is an ethylene-glycidyl methacrylate copolymer, an ethylene-ethyl acrylate maleic anhydride graft-modified product, or an ethylene-methacrylate-acrylic acid terpolymer. The multi-piece solid golf ball according to claim 1 , wherein the adhesive layer has a thickness of 10 μm to 1.5 mm.