Golf Ball Core Hardness Gradient via Thioether Antioxidant
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Solution Overview
Problem
Current golf ball core compositions struggle to achieve a large hardness gradient while maintaining durability and low spin properties, often leading to early collapse due to foreign matter contamination during manufacturing.
Innovation Solution
A rubber composition for golf ball cores incorporating a base rubber, α,β-unsaturated carboxylic acid or its metal salt, a crosslinking initiator, an alcohol, and a hindered phenol-type antioxidant with a thioether structure, which enhances heat resistance and durability, allowing for a significant hardness gradient and reduced spin rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hardness difference between core surface and center is enlarged to reduce spin rate and increase distance, then the spin properties and distance are improved, but the durability of the golf ball to impact is likely to decline
Solution Approach 1:
The patent applies local quality by creating a hardness gradient within the core where the surface hardness and center hardness are deliberately different. The surface layer has higher hardness to reduce spin rate on full shots, while the center maintains appropriate hardness for energy storage and release. This localized variation in material property allows simultaneous optimization of distance (through reduced spin) and durability (through controlled hardness distribution that prevents stress concentration).
Solution Approach 2:
The patent employs parameter changes by systematically adjusting the hardness values at different core locations. Specifically, the surface hardness is set to 70-95 on the JIS-C scale while the center hardness is set to 50-75, creating a controlled gradient. This parameter optimization enables the core to achieve both low spin properties (improving distance) and adequate impact resistance (maintaining durability).
2Speed
If a two-layer rubber core structure is used to enlarge hardness difference, then the spin properties are improved, but the number of manufacturing operations increases
Solution Approach 1:
The patent achieves local quality differentiation within a single-layer core by controlling the hardness gradient from surface to center through specific rubber composition formulation and vulcanization parameters. This eliminates the need for multiple physical layers while still creating distinct hardness zones (surface: 70-95 JIS-C, center: 50-75 JIS-C) necessary for optimizing spin rate and distance.
Solution Approach 2:
The patent merges the functions of multiple layers into a single-layer structure by creating a continuous hardness gradient within one rubber core. This consolidation maintains the spin-controlling benefits of differentiated hardness zones while simplifying the core structure and reducing manufacturing complexity compared to multi-layer alternatives.
3Speed
If the core hardness is increased to reduce spin rate, then the distance is improved, but the feel of the ball on impact deteriorates
Solution Approach 1:
The patent applies local quality by differentiating hardness between core surface and center. The surface layer (70-95 JIS-C hardness) provides the hardness needed to reduce spin rate and increase distance, while the softer center (50-75 JIS-C hardness) maintains good feel on impact by allowing appropriate deformation and energy absorption during ball-club interaction.
Solution Approach 2:
The patent optimizes the feel-distance tradeoff by carefully controlling the hardness parameter gradient. The surface hardness is set high enough (70-95) to reduce spin and extend distance, while the center hardness is kept lower (50-75) to preserve feel. This parameter differentiation allows independent optimization of distance performance and impact feel.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves improved durability and low spin properties, preventing core collapse and enhancing flight performance even when foreign matter is present, while maintaining desired core hardness profiles.
Implementation Method 1
a hindered phenol-type antioxidant including a substituent having thioether structure, wherein the content of component (e) is at least 0.2 part by weight per 100 parts by weight of component (a)
Implementation Method 2
enhances heat resistance and durability, allowing for a significant hardness gradient and reduced spin rates
Implementation Method 3
a crosslinking initiator
Implementation Method 4
the core accounts for most of the golf ball volume and exerts a large influence on ball properties such as rebound, feel and durability
Implementation Method 5
the cross-sectional hardness of the core is suitably adjusted so as to achieve a specific core hardness gradient, thereby optimizing the spin properties of the ball on full shots with a driver or an iron and enabling the ball to travel an increased distance
Data Source
AI summary
The present invention provides the rubber composition for a golf ball comprising (a) a base rubber, (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid or a metal salt thereof or both, (c) a crosslinking initiator, and (d) an alcohol, in which further (e) a hindered phenol-type antioxidant including a substituent having thioether structure is included and the content of component (e) is at least 0.2 part by weight per 100 parts by weight of component (a), and a golf ball using the rubber composition, in order to achieve the object that good durability of the golf ball to impact is maintained.