Golf Ball Core Hardness Uniformity via Water Vapor Barrier
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Solution Overview
Problem
The existing golf ball cores exhibit a hardness difference between the surface and center, leading to reduced spin rates and longer flight distances, while attempts to minimize this difference result in longer production times due to lower temperature heat molding.
Innovation Solution
A golf ball design featuring a spherical core with an inner core layer composed of a rubber composition including high-cis polybutadiene rubber, α,β-unsaturated carboxylic acid, a crosslinking initiator, and a terpene-based resin, which is molded at elevated temperatures to achieve a low hardness difference between the surface and center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heat molding is performed at high temperature (150-170°C) for short time (10-30 min), then production efficiency is improved, but a hardness difference is generated between surface and center of the core
Solution Approach 1:
The patent applies local quality by introducing a water vapor barrier layer with specific properties (low water vapor permeability) at the center region of the core. This localized modification allows the center to cure at a different effective rate than the surface, enabling uniform hardness throughout the core even when processed at high temperatures for short durations. The barrier layer creates a localized microenvironment that controls the curing process spatially.
Solution Approach 2:
The water vapor barrier layer acts as an intermediary element between the curing initiator and the center region of the core. It mediates the water vapor transfer during heat molding, controlling the rate at which moisture moves through the core material. This intermediary layer enables precise control over the curing kinetics, allowing the surface to cure quickly while the center cures uniformly, thus achieving both high productivity and hardness uniformity.
2Manufacturing precision
If heat molding is performed at low temperature (120-130°C) for long time (60-90 min), then hardness difference between surface and center is reduced, but production time increases
Solution Approach 1:
The water vapor barrier layer creates a localized environment at the core center that accelerates water vapor removal during low-temperature curing. This localized modification allows the center region to cure efficiently even at lower temperatures, reducing the overall curing time while maintaining uniform hardness distribution throughout the core.
Solution Approach 2:
The patent changes the water vapor permeability parameter of the core material by introducing the barrier layer with specific permeability characteristics. This parameter change enables the core to achieve uniform curing at lower temperatures by controlling moisture transport, thereby reducing production time while maintaining hardness uniformity.
3Speed
If a hardness difference exists between surface and center of the core, then spin rate of the golf ball is reduced, but durability is compromised
Solution Approach 1:
The water vapor barrier layer creates a localized curing environment that ensures uniform hardness throughout the core. This uniform hardness distribution optimizes the spin rate of the golf ball by eliminating the hardness difference that would otherwise reduce spin performance. Simultaneously, the uniform structure enhances durability by preventing weak points that could arise from hardness variations.
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 design enhances the production efficiency of golf balls with improved durability and spin rates while maintaining a low hardness difference, resulting in better shot performance and reduced production time.
Implementation Method 1
a difference in the curing reaction of the rubber composition occurs at the core surface portion and the core center portion
Implementation Method 2
heating a core rubber composition at a temperature of about 150° C. to 170° C. for about 10 min to 30 min
Implementation Method 3
a temperature distribution is generated inside the spherical core such that a difference in the curing reaction of the rubber composition occurs
Data Source
AI summary
An object of the present invention is to provide a golf ball having excellent durability. The present invention provides a golf ball comprising a spherical core composed of an inner core layer and an outer core layer, and at least one cover covering the spherical core, wherein the inner core layer is formed from an inner core layer rubber composition containing (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a terpene-based resin.