Golf Ball Core Rubber Composition Hardness Gradient
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Solution Overview
Problem
Existing golf ball core compositions struggle to achieve a large hardness difference between the core surface and center while maintaining desired core hardness, which limits the reduction of spin rate on full shots and thus the distance traveled by the golf ball.
Innovation Solution
A rubber composition for golf ball cores incorporating a base rubber, an α,β-unsaturated carboxylic acid or its metal salt, a crosslinking initiator, and an alcohol with a molecular weight divided by the number of hydroxyl groups of 70 or less, which promotes decomposition of organic peroxide and creates a distinct crosslinked structure with varying radical reactions, resulting in a significant hardness difference between the core surface and center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the cross-sectional hardness of the core is increased to reduce spin rate on full shots, then the distance traveled by the golf ball is improved, but the feel of the ball on impact deteriorates
Solution Approach 1:
The patent applies local quality by creating a hardness gradient within the core, where the surface hardness is higher than the center hardness. This is achieved by controlling the vulcanization process and composition distribution, resulting in a core with surface hardness of 70-95 Shore D and center hardness of 40-70 Shore D. The harder surface reduces spin rate for distance, while the softer center maintains comfortable feel on impact.
2Speed
If the hardness difference between core surface and center is enlarged to reduce spin rate, then the distance traveled is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent employs parameter changes by adjusting the vulcanization temperature profile and composition parameters to achieve the desired hardness gradient. Specifically, the core composition includes organic peroxide (1-5 parts by weight per 100 parts by weight of rubber composition) and the vulcanization is conducted at temperatures and times that create differential crosslinking between surface and center, achieving the hardness difference without complex multi-layer construction.
3Manufacturing precision
If a two-layer core structure is used to enlarge hardness difference, then the spin properties are optimized, but the number of manufacturing operations increases
Solution Approach 1:
The patent applies segmentation by dividing the core into functional zones (surface layer and center region) with different hardness properties, achieved through controlled composition and vulcanization rather than physical layering. The core composition is segmented into regions with different crosslinking densities, creating the hardness gradient needed for optimized spin properties while maintaining a single-layer structure for manufacturing efficiency.
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
This composition effectively reduces spin rates on golf ball shots, enhancing flight performance by maintaining desired core hardness and achieving a large hardness difference, thereby improving the ball's distance and durability.
Implementation Method 1
an alcohol having a value obtained by dividing the molecular weight of the alcohol by the number of hydroxyl groups which is 70 or less, the hardness difference in the hardness profile at the interior of the core can be set to a large value
Implementation Method 2
a co-crosslinking agent that is an α,β-unsaturated carboxylic acid and/or a metal salt thereof, (c) a crosslinking initiator
Data Source
AI summary
A rubber composition for golf balls includes (a) a base rubber, (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid and/or a metal salt thereof, (c) a crosslinking initiator, and (d) an alcohol having a value obtained by dividing the molecular weight of the alcohol by the number of hydroxyl groups thereon which is 70 or less. When the rubber composition is used in a golf ball having a core and a cover of one or more layers encasing the core, by setting the hardness difference in the core interior hardness profile to a large value while maintaining a desired core hardness, low spin properties can be manifested on golf ball shots, enabling the flight performance of the ball to be improved.