Heat Resistant Shield Layer for Golf Ball Compression Molding
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Solution Overview
Problem
Existing golf ball manufacturing techniques face difficulties in compression molding a thermosetting polybutadiene-comprising layer over a thermoplastic core due to temperature-related melting and distortion of the thermoplastic material, which results in inconsistent properties and poor durability.
Innovation Solution
A multi-layer golf ball design featuring a low melting point thermoplastic inner core surrounded by a high melting point thermoplastic shield layer, allowing for the successful compression molding of a thermosetting polybutadiene outer core without material leakage, using high vicat softening point materials like Hytrel and Surlyn to maintain core integrity during curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermosetting polybutadiene-comprising layer is compression molded over a thermoplastic core layer, then the desired playing characteristics (spin rate, resiliency) are achieved, but the thermoplastic core layer melts, distorts and flows into the surrounding rubber layer due to high temperature exposure
Solution Approach 1:
A heat resistant shield layer comprising a thermoplastic material with a melting point at least 20°C greater than the underlying thermoplastic core layer is introduced as an intermediary between the thermoplastic core and the thermosetting polybutadiene layer. This shield layer protects the core from excessive heat during compression molding, preventing melting and distortion while allowing the thermoset layer to cure properly.
Solution Approach 2:
The invention changes the melting point parameter of the intermediate shield layer material to be significantly higher than that of the core layer. By selecting materials with appropriate melting point differences (at least 20°C), the process enables temperature control during compression molding, allowing the thermoset layer to achieve proper cure without causing the thermoplastic core to melt.
2Reliability
If high temperature (315-350°F) and extended time (11-15 minutes) are used to cure the thermosetting rubber layer, then thorough curing is achieved, but the thermoplastic layer undergoes significant melting and flow
Solution Approach 1:
The heat resistant shield layer acts as a thermal barrier that allows extended curing times and higher temperatures to be applied to the thermoset layer without proportionally increasing the thermal exposure of the thermoplastic core. This intermediary layer absorbs and buffers the thermal energy, enabling thorough curing while protecting the core from excessive heat accumulation.
3Ease of manufacture
If the melting temperature of the thermoplastic core layer is below the curing temperature of the rubber layer, then the thermoplastic material can be processed, but the core layer melts and distorts during rubber layer compression molding
Solution Approach 1:
The golf ball core structure is segmented into multiple layers with different thermal properties: an inner thermoplastic core layer that provides desired playing characteristics, and an outer heat resistant shield layer with higher melting point that protects the core during processing. This segmentation allows each layer to be optimized for its specific function while resolving the temperature conflict.
Solution Approach 2:
The invention uses a composite structure combining thermoplastic and thermosetting materials with significantly different melting/curing temperatures. The shield layer material is specifically selected to have a melting point at least 20°C greater than the core layer, creating a composite system that can withstand the high temperatures required for thermoset curing without compromising the thermoplastic core integrity.
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 minimizes the exposure of the inner core to excessive temperature and time, preventing melting and flow, thereby enhancing the durability and consistency of the golf ball while maintaining desired playing characteristics such as spin rate and distance.
Implementation Method 1
an outer adjacent layer (shield layer) is a high melting point thermoplastic material. This combination facilitates the compression molding of a thermosetting polybutadiene-comprising layer over a thermoplastic layer without significant flow of the thermoplastic layer into the thermoset layer.
Implementation Method 2
Additionally, the exotherm generated from the curing reaction of a 11-15 minute cure can elevate the rubber temperature even higher.
Data Source
AI summary
The present invention is directed to a golf ball comprising a shield layer having heat resistant properties to facilitate compression molding of a thermosetting polybutadiene-comprising layer over at least one thermoplastic layer. The invention utilizes a thermoplastic inner core comprising of a low vicat highly neutralized ionomer material having a low melting point of less than 100° C., and a Shore C surface hardness of less than 80 and a compression of less than 70, wherein a shield layer is placed around the low vicat softening point temperature thermoplastic to shield it from the high heat necessary to mold a thermoset material about it.