Softened Multicomponent Rubber Composition for Crack-Resistant Processing

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Solution Overview

Problem

Rubber compositions containing multicomponent copolymers with conjugated diene, non-conjugated olefin, and aromatic vinyl units exhibit poor processability and adhesion, leading to decreased productivity in rubber products like tires and hoses due to their hard state at room temperature and low tackiness.

Innovation Solution

Incorporating a softener into the rubber composition with a multicomponent copolymer containing a conjugated diene, non-conjugated olefin, and aromatic vinyl units, where the non-conjugated olefin content is 40 mol% or more, and adjusting the molecular weight and crystallinity to improve crack resistance and processability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a multicomponent copolymer containing conjugated diene unit, non-conjugated olefin unit, and aromatic vinyl unit is used as rubber component, then crack resistance is improved, but processability deteriorates due to hard state at room temperature and low tackiness

Engineering Contradiction:

Improvecrack resistanceVSAvoidprocessability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the chemical composition parameters of the rubber component by specifying that the non-conjugated olefin unit content must be 40 mol% or more. This parameter adjustment modifies the molecular structure to reduce crystallinity and hardness, thereby improving processability while maintaining crack resistance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite rubber composition by combining the multicomponent copolymer with specific additives including zinc oxide (5-50 parts by mass), stearic acid (3-30 parts by mass), and sulfur (1-5 parts by mass). This composite formulation balances the hard, crack-resistant properties of the copolymer with the softening and tackifying effects of the additives, resolving the contradiction between crack resistance and processability

Inventive Principle:

Principle #40Composite materials

2Reliability

Engineering Contradiction:

Improvecrack resistanceVSAvoidadhesion

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent adjusts the compositional parameters by requiring the non-conjugated olefin unit content to be 40 mol% or more, which reduces the glass transition temperature and increases molecular chain flexibility. This parameter change enhances tackiness and adhesion while preserving the crack resistance provided by the multicomponent structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent formulates a composite system incorporating the multicomponent copolymer with zinc oxide (5-50 parts by mass), stearic acid (3-30 parts by mass), and sulfur (1-5 parts by mass). The zinc oxide and stearic acid act as softening agents that increase surface tackiness and adhesion, while the sulfur provides crosslinking for crack resistance, thus resolving the adhesion-crack resistance contradiction

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP3725841B1Tire, rubber crawler, seismic isolation device, and hose

Publication Date: 2024.08.07 BRIDGESTONE CORP

AI summary

Provided is a rubber composition having excellent crack resistance and processability. A rubber composition comprises: a rubber component (a) containing a multicomponent copolymer (a1) that contains a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit; and a softener (b), wherein a content of the softener (b) is 30 parts to 150 parts by mass with respect to 100 parts by mass of the rubber component (a).