Pneumatic Tire Tread Antioxidant Formulation for Discoloration
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Solution Overview
Problem
Pneumatic tires with reduced sub-tread thickness at the base of the tread main groove are prone to tread groove cracking (TGC) and discoloration, especially when stored under strained conditions or in high ozone environments, and existing solutions fail to effectively prevent discoloration while maintaining good TGC resistance.
Innovation Solution
A pneumatic tire design featuring a tread portion with a jointless band, cap tread, and undertread, where the rubber compositions for these components include phenylenediamine antioxidants in specific amounts, sulfur, and naturally occurring waxes, ensuring moderate blooming and enhanced ozone resistance, thereby preventing discoloration and TGC even with reduced sub-tread thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antioxidants and petroleum wax are excessively added beyond the solubility of the rubber, then crack formation is suppressed, but white discoloration and brown discoloration occur due to excessive blooming
Solution Approach 1:
The invention changes the chemical composition parameters of the rubber compound by incorporating specific antioxidants (6PPD and TMDQ) in controlled amounts along with petroleum wax and sulfur. This parameter optimization allows the compound to achieve both crack suppression and discoloration resistance by balancing the blooming characteristics of these additives
Solution Approach 2:
The invention uses a composite rubber compound containing multiple additives (6PPD, TMDQ, petroleum wax, sulfur) working synergistically. This composite approach allows the different materials to complement each other's functions while mitigating their individual drawbacks, particularly in controlling blooming and preventing discoloration
2Weight of moving object
If sub-tread thickness at the base of the tread main groove is reduced to reduce tire weight, then tire weight is decreased, but TGC resistance deteriorates during storage
Solution Approach 1:
The invention changes the chemical composition parameters of the rubber compound to enhance its resistance to ozone and cracking. By optimizing the ratios of antioxidants, petroleum wax, and sulfur, the compound achieves superior TGC resistance that compensates for the reduced physical thickness of the sub-tread
Solution Approach 2:
The invention converts the potential harm of reduced sub-tread thickness into a benefit by developing a rubber compound with enhanced chemical resistance. The specially formulated compound provides such superior protection against ozone and cracking that the thinner sub-tread performs as well as or better than thicker designs using conventional compounds
3Adaptability or versatility
If tires are stored in high ozone environments or strained conditions, then storage flexibility is maintained, but TGC occurrence increases due to rubber strain at reduced sub-tread thickness
Solution Approach 1:
The invention modifies the chemical parameters of the rubber compound by incorporating specific antioxidants and sulfur in optimized amounts. This enhances the rubber's resistance to oxidative degradation from ozone, allowing the tire to maintain flexibility during storage while resisting TGC even in high ozone environments
Solution Approach 2:
The invention applies beforehand cushioning by pre-equipping the rubber compound with antioxidants and protective additives before the tire encounters storage conditions. This preventive approach ensures the rubber is already protected against ozone and strain-induced cracking before exposure to harsh storage environments
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 tire effectively prevents discoloration and exhibits good TGC resistance over a wide temperature range, maintaining performance even with minimal sub-tread thickness at the base of the tread main groove.
Implementation Method 1
the antioxidants oxidized by ozone cause brown discoloration
Implementation Method 2
degradation of such tires is accelerated at high ozone concentrations
Implementation Method 3
The antioxidants and petroleum wax in rubber vulcanizates migrate (bloom) to the rubber surface
Data Source
Figure 1(a)~1(c)
AI summary
The present invention provides a pneumatic tire capable of preventing discoloration while exhibiting good TGC resistance even after the tire having a reduced sub-tread thickness at the base of the tread main groove is stored. The present invention relates to a pneumatic tire including a tread portion, the tread portion including a jointless band and at least two tire components selected from the group consisting of a cap tread, a base tread, and an undertread, the rubber composition for cap treads having an amount of phenylenediamine antioxidant of a specific value or less, the cap tread, the base tread, the undertread, and the upper layer of the jointless band having amounts of phenylenediamine antioxidant satisfying a specific relational expression, the rubber composition for undertreads containing a specific amount of sulfur, the pneumatic tire having a sub-tread thickness at the base of the tread main groove of 0.5 to 2.0 mm.