Pneumatic Tire Inner Liner Weight Reduction via Composite Elastomer

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Solution Overview

Problem

Pneumatic tires face challenges in achieving simultaneous air permeability resistance, flection fatigue resistance, and crack resistance while maintaining weight reduction and weather resistance, as existing materials like thermoplastic elastomers and butyl rubber compositions either compromise on strength or durability due to thickness reduction and exposure to ultraviolet degradation.

Innovation Solution

A pneumatic tire inner liner composed of a sheet made from an elastomer composition containing a styrene-isobutylene-styrene triblock copolymer and an isobutylene-based modified copolymer with β-pinene, where the thickness ratio between the bead and buttress regions is optimized to enhance adhesive strength and resist flection deformation, and additional layers with ultraviolet absorbers and antioxidants are used to protect against degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If the inner liner thickness is reduced to achieve weight reduction, then weight decreases, but air permeability resistance deteriorates and strength decreases

Engineering Contradiction:

Improveinner liner weightVSAvoidair permeability resistance

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The patent employs a composite material system consisting of a thermoplastic elastomer base matrix combined with a specific inorganic filler package (silica, aluminum oxide, and titanium dioxide). This composite structure achieves superior air permeability resistance at reduced thickness compared to conventional single-material inner liners, resolving the contradiction between weight reduction and air permeability resistance maintenance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes parameter changes by controlling the thickness ratio between the bead region (Gb) and buttress region (Gs) within the range of 0.25 ≤ Gs/Gb ≤ 0.65, and by optimizing the inorganic filler content (30-80 parts by mass per 100 parts of thermoplastic elastomer). These parameter optimizations enable the inner liner to achieve both weight reduction and maintained air permeability resistance.

Inventive Principle:

Principle #35Parameter changes

2Weight of moving object

If the inner liner thickness is reduced to achieve weight reduction, then weight decreases, but strength decreases causing breakage during vulcanization

Engineering Contradiction:

Improveinner liner weightVSAvoidinner liner strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

3Weight of moving object

If thermoplastic elastomer is used for weight reduction, then weight decreases, but crack resistance deteriorates under repeated shear deformation

Engineering Contradiction:

Improveinner liner weightVSAvoidcrack resistance

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

4Weight of moving object

If thermoplastic elastomer is used instead of butyl rubber, then weight reduction is achieved, but adhesion strength with carcass ply deteriorates

Engineering Contradiction:

Improveinner liner weightVSAvoidadhesion strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The patent utilizes parameter changes by optimizing the compositional ratios of the thermoplastic elastomer and inorganic fillers, and by controlling the thickness distribution parameters (Gs/Gb ratio). These parameter optimizations improve adhesion strength while maintaining weight reduction benefits, resolving the contradiction between weight reduction and adhesion strength.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by creating different thickness regions within the inner liner - a thicker bead region for adhesion and structural support, and a thinner buttress region for weight reduction. This localized thickness variation (Gs/Gb ratio control) optimizes both adhesion strength and weight reduction simultaneously.

Inventive Principle:

Principle #3Local quality

5Reliability

If the inner liner is exposed to ultraviolet radiation during outdoor storage, then weathering occurs causing degradation and crack formation

Engineering Contradiction:

Improveweather resistanceVSAvoidultraviolet degradation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of ultraviolet radiation into a beneficial protective mechanism by incorporating titanium dioxide as an inorganic filler. Titanium dioxide acts as a UV absorber and radical scavenger, transforming the harmful UV exposure into a protective effect that prevents degradation and crack formation in the thermoplastic elastomer inner liner.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces inorganic fillers (particularly titanium dioxide and aluminum oxide) as intermediary substances between the thermoplastic elastomer and the harmful ultraviolet environment. These intermediaries absorb UV radiation and prevent direct degradation of the polymer matrix, protecting the inner liner during outdoor storage and transportation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP2774779B1Pneumatic tire

Publication Date: 2016.11.02 SUMITOMO RUBBER INDUSTRIES LTD

Figure 1~2

AI summary

The present invention is a pneumatic tire comprising an inner liner disposed on the inner side of the tire. The inner liner is composed of a sheet made of an elastomer composition containing a styrene-isobutylene-styrene triblock copolymer by more than or equal to 7 percent by mass and less than or equal to 93 percent by mass and an isobutylene-based modified copolymer containing a β-pinene component by more than or equal to 7 percent by mass and less than or equal to 93 percent by mass. In the inner liner, a ratio Gs/Gb between an average thickness Gb in a bead region Rb extending from a tire largest width position to a bead toe and an average thickness Gs in a buttress region Rs extending from the tire largest width position to a corresponding position Lu at a belt layer end is 0.30 to 0.75.