| 摘要 |
PROBLEM TO BE SOLVED: To provide a tennis ball 1 having seam portions 4 of a right width and a good appearance. SOLUTION: The tennis ball 1 has a core 2, two felts 3, and seam portions 4. In the manufacturing method of the tennis ball 1, a plurality of dumbbell- shaped felts 3 is superposed one on top of another and compressed in the direction of superposition so as to set the compression ratio y at 0.4 or higher and 0.9 or lower. Subsequently the felts 3 are dipped into a liquid adhesive having a solid content ratio x of 20% or higher. Dipping makes an adhesive adhere to the sides of the felts 3. Subsequently, the felts 3 are drawn out and dried. Drying makes a solvent contained in the adhesive sticking thereto volatilize. Subsequently, the two felts 3 are pasted to the core 2. Subsequently the adhesive is cross-linked, and forms the seam portions 4. The solid content ratio x and the compression ratio y satisfy the relation shown in the following mathematical formula (10/x)<=y<=(28/x) (1).
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