Innerliner Compound Mixing With Lignin for High Tyre Impermeability
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Solution Overview
Problem
The pneumatic tyre industry faces challenges in achieving high impermeability in the innerliner layer to prevent air diffusion and oxidative degradation, while also seeking to reduce tyre weight and maintain mechanical integrity, particularly in the belt pack region.
Innovation Solution
A method for producing an innerliner compound that includes a first mixing step with a cross-linkable unsaturated chain polymer base and a filler system, followed by an intermediate mixing step where lignin is added, and a final mixing step with a vulcanization system, specifically using Kraft lignin with particles of less than 400 µm² average surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the innerliner layer is increased to improve impermeability, then air diffusion is reduced, but the weight of the pneumatic tyre increases
Solution Approach 1:
The patent changes the chemical composition parameters of the innerliner compound by incorporating specific additives and fillers (lignin, zinc oxide, stearic acid, sulfur) in optimized proportions. This modifies the molecular structure and density of the rubber compound, enabling high impermeability at reduced thickness. The parameter change transforms the material properties rather than simply increasing quantity
Solution Approach 2:
The patent creates a composite rubber compound by combining natural rubber or synthetic polybutadiene with lignin, carbon black, zinc oxide, stearic acid, and sulfur. This composite formulation leverages the complementary properties of each component: lignin provides barrier properties against gas permeation, carbon black enhances structural integrity, and the vulcanization system creates cross-linked networks. The synergistic effect achieves superior impermeability-to-weight ratio compared to homogeneous rubber
2Reliability
If the thickness of the innerliner layer is increased to improve impermeability, then air diffusion is reduced, but the manufacturing cost increases
Solution Approach 1:
The patent optimizes the concentration parameters of compound ingredients to achieve maximum impermeability per unit thickness. By precisely controlling the proportions of lignin (5-20 phr), zinc oxide (2-5 phr), sulfur (1-3 phr), and other additives, the formulation achieves high performance with minimal material quantity. This parameter optimization reduces both material cost and processing requirements
Solution Approach 2:
The patent incorporates lignin, a low-cost byproduct of the paper and pulp industry, as a key functional ingredient. Lignin provides excellent gas barrier properties at low cost, replacing more expensive conventional additives. This substitution maintains impermeability performance while significantly reducing the quantity of expensive materials required in the compound formulation
3Reliability
If conventional mixing procedures are used without intermediate mixing, then the production process is simpler, but the impermeability characteristics are insufficient
Solution Approach 1:
The patent segments the mixing process into three distinct stages: (1) initial mixing of rubber with carbon black and lignin, (2) intermediate mixing with zinc oxide, stearic acid, and other additives, and (3) final mixing with sulfur and vulcanization agents. Each stage ensures thorough incorporation of specific ingredient groups, creating a homogeneous compound with optimized distribution of impermeability-enhancing components. This segmentation achieves superior mixing quality without requiring complex equipment
Solution Approach 2:
The patent performs preliminary mixing of rubber with lignin and carbon black before adding other additives. This preliminary action ensures that the key impermeability-providing components (lignin and carbon black) are uniformly distributed in the rubber matrix before subsequent additives are incorporated. This sequencing prevents aggregation and ensures optimal performance in the final vulcanized product
Data Source
AI summary
Method for the manufacture of the innerliner compound comprising: - a first mixing step wherein at least one cross-linkable unsaturated chain polymeric base and one filler system are mixed together; - a final mixing step wherein a vulcanization system is added and mixed with the mixture deriving from an earlier mixing step; and - an intermediate mixing step, interposed between said first mixing step and the final mixing step, and wherein lignin is added and mixed into the mixture deriving from a previous mixing step.