Pneumatic Tire Inner Liner Polymer Stack Adhesion
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Solution Overview
Problem
Current pneumatic tire inner liners face challenges in achieving optimal adhesiveness, flex fatigue resistance, air permeability, weight saving, operation stability, and braking stability due to issues with adhesiveness between the inner liner and carcass ply, as well as complications in manufacturing processes such as sticking to bladders during vulcanization.
Innovation Solution
A polymer layer stack for the inner liner comprising a first layer of styrene-isobutylene-styrene triblock copolymer and a second layer of styrene-isoprene-styrene triblock copolymer or styrene-isobutylene diblock copolymer, with specific rubber components and additives, dynamically vulcanized to enhance adhesiveness and maintain thin thickness for improved air permeability resistance and rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive layers are provided on both sides of the inner liner layer to improve adhesiveness, then adhesiveness between inner liner and rubber layer is improved, but the adhesive layers stick and adhere to the bladder during vulcanization
Solution Approach 1:
The harmful adhesive function is extracted and removed from the inner liner structure. Instead of providing adhesive layers on both sides of the inner liner, the patent eliminates the need for adhesive layers by using a thermoplastic resin film that bonds to the rubber layer through heat and pressure during vulcanization, preventing sticking to the bladder while maintaining necessary adhesiveness.
Solution Approach 2:
The patent changes the bonding mechanism parameter from chemical adhesion (adhesive layers) to thermal-mechanical bonding (thermoplastic resin film activated by heat and pressure). This parameter change allows the inner liner to bond to the rubber layer during vulcanization without the adhesive layers sticking to the bladder, as the thermoplastic resin film remains stable under vulcanization conditions.
2Strength
If a thermoplastic resin film with high Young's modulus is used to improve rigidity, then rigidity is improved, but stress is concentrated on the film causing detachment and cracks during long-time running
Solution Approach 1:
The patent optimizes the Young's modulus parameter of the thermoplastic resin film to balance rigidity and flexibility. By selecting a resin with moderate Young's modulus (not excessively high), the film maintains sufficient rigidity while reducing stress concentration during running, thereby preventing detachment and cracks and improving long-term reliability.
Solution Approach 2:
The patent creates a composite structure by bonding the thermoplastic resin film to the rubber layer. This composite material combines the rigidity benefits of the thermoplastic resin with the flexibility and stress-absorbing properties of the rubber layer, distributing stress more evenly and preventing concentration on the film alone, thus improving durability.
3Reliability
If inner liner thickness is increased to improve air permeation resistance, then air permeation resistance is improved, but weight saving is reduced
Solution Approach 1:
The patent changes the material parameter by using a thermoplastic resin film with superior air permeation resistance properties compared to traditional butyl-based rubber. This allows the inner liner to achieve the required air permeation resistance at a reduced thickness, thereby reducing weight while maintaining the necessary barrier function.
Solution Approach 2:
The patent employs a thin film structure (thermoplastic resin film) that provides effective air permeation resistance despite its reduced thickness. The thin film design, combined with the inherent low permeability of the thermoplastic resin material, achieves the required air retention performance while minimizing weight, eliminating the need for thick inner liners.
4Reliability
If nylon film layer is used for inner liner to improve air permeability, then air permeability is improved, but manufacturing process becomes complicated and nylon film sticks to bladder during vulcanization
Solution Approach 1:
The patent removes the harmful RFL treatment step and rubber cement application process from the manufacturing sequence. By using a thermoplastic resin film that can be directly bonded to the rubber layer through heat and pressure during vulcanization, the patent eliminates the need for RFL treatment and rubber cement, simplifying the manufacturing process while maintaining air permeability performance.
Solution Approach 2:
The patent changes the material parameter from nylon (requiring RFL treatment) to thermoplastic resin (bondable through heat and pressure). This parameter change eliminates the need for complex RFL treatment and rubber cement application steps, simplifying the manufacturing process while achieving the required air permeability resistance without sticking to the bladder during vulcanization.
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 solution improves adhesive strength with the carcass ply rubber, maintains air permeability resistance, enhances flex fatigue resistance, and increases braking stability while allowing for weight saving and improved operation stability through dynamic vulcanization and strategic layer thickness.
Implementation Method 1
dynamically vulcanized to enhance adhesiveness and maintain thin thickness for improved air permeability resistance and rigidity
Implementation Method 2
the SIBS, which is a thermoplastic elastomer, serves as the matrix phase... the SIBS is restrained from being deteriorated and hardened and therefore has excellent durability
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention is a pneumatic tire (1) including an inner liner (9) and a carcass ply (6) provided adjacent to the inner liner (9) and having a cord (K) embedded in a rubber layer. The inner liner (9) is composed of a polymer layer stack including a first layer of a polymer composition containing SIBS and at least one kind of rubber component selected from among natural rubber, isoprene rubber and butyl rubber, the first layer having a thickness of 0.05 mm to 0.6 mm, and a second layer of a polymer composition containing at least either one of SIS and SIB as well as at least one kind of rubber component selected from among natural rubber, isoprene rubber and butyl rubber, the second layer having a thickness of 0.01 mm to 0.3 mm. The second layer is arranged so as to be in contact with the rubber layer of the carcass ply (6). A distance L from a plane passing through the center of cross section of the cord to the second layer is more than or equal to 0 and less than or equal to (1+D/2) mm where D denotes the diameter of the cord.