Closed-Cell Foamed Rubber Sealing Material

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Solution Overview

Problem

Conventional waterproof/watertight sealing materials made from foamed rubber suffer from poor long-term interface adherence and waterproof performance due to relaxation of repulsive force over time, leading to water leakage issues.

Innovation Solution

A closed-cell foamed rubber sheet with specific apparent density and compression set ranges, achieved through crosslinking and foaming treatments of a nitrile-butadiene rubber composition, combined with physical crosslinking by ionizing radiation and the addition of organic peroxides, ensures excellent interface adherence and dimensional stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If cells in foam are changed to open cells by breaking the cells, then compression flexibility is improved remarkably, but waterproof property decreases

Engineering Contradiction:

Improvecompression flexibilityVSAvoidwaterproof property

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies local quality by creating different cell structures in different regions of the foam. The skin layer has a different cell structure (with both closed and open cells) compared to the inner layer (mainly closed cells), allowing the skin to provide flexibility while the inner layer maintains waterproofing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining foam structures with different cell characteristics. The multi-layer foam structure integrates regions with closed cells (for waterproofing) and open cells (for flexibility), achieving both requirements simultaneously.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If a foamed structure having both closed cells and open cells is used, then easiness in filling work and waterproof property are expected, but repulsive force relaxes with time causing water leakage

Engineering Contradiction:

Improvefilling work easinessVSAvoidlong-term interface adherence

Core Design Contradiction:

Ease of operationVSDuration of action of stationary object

Solution Approach 1:

The patent applies parameter changes by optimizing the ratio of closed cells to open cells, controlling cell size distribution, and adjusting foam density parameters to maintain stable repulsive force over time while preserving filling capabilities.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements beforehand cushioning by designing a foam structure with sufficient initial repulsive force and stability to prevent water leakage throughout the service life, accounting for long-term deformation and aging effects in advance.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If closed cells are used in foam structure, then waterproof action is expected, but compression flexibility deteriorates

Engineering Contradiction:

Improvewaterproof actionVSAvoidcompression flexibility

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent applies segmentation by dividing the foam into multiple layers with different cell structures. The inner layer contains mainly closed cells for waterproofing, while the skin layer contains both closed and open cells for flexibility, with each layer performing its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements local quality by creating region-specific cell structures where the skin layer has a different composition (more open cells) compared to the inner layer (mostly closed cells), allowing each region to optimize for its specific requirement.

Inventive Principle:

Principle #3Local quality

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 provides a high-performance waterproof/watertight sealing material with improved long-term reliability and dimensional stability, maintaining excellent interface adherence and waterproof properties.

Implementation Method 1

physical crosslinking by ionizing radiation

Methodology Applied

Scientific EffectPhysical crosslinking by ionizing radiation: Ionisation

Implementation Method 2

addition of organic peroxides

Methodology Applied

Scientific EffectCrosslinking reaction: Chemical Bonding

Implementation Method 3

foaming treatment

Methodology Applied

Scientific EffectFoaming: Foam

Implementation Method 4

maintaining excellent interface adherence and waterproof properties

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP1970403B1Closed cell foam rubber sheet, laminate, and waterproof/watertight sealing material using the sheet or lamiante

Publication Date: 2012.02.08 SEKISUI CHEMICAL CO LTD

AI summary

A high-performance foamed structure which is formed of a foamed structure having closed cells and which exhibits excellent interface adherence to an element to be sealed (i.e., a structural element to which waterproofing is to be applied) even when used for a long time in use as a waterproof sealing material, and a high-performance waterproof/watertight sealing material made of the same are provided. The closed-cell foamed rubber sheet of the present invention is characterized in that it is obtained by subjecting a foamable raw material composition composed mainly of a rubber-based resin to crosslinking treatment and foaming treatment and that it has an apparent density of from 30 to 100 kg/m3 as measured in accordance with JIS K7222 and a compression set of 60% or less as measured under the conditions of 70°C for 24 hours in accordance with JIS K6262.