Block Copolymer Adhesive Composition Balancing Tack and Viscosity
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Solution Overview
Problem
Conventional adhesive compositions based on vinyl aromatic monomer-conjugated diene monomer block copolymers lack sufficient balance between retentivity, tack strength, and low-viscosity properties, as well as contamination resistance on adherends.
Innovation Solution
A block copolymer composition comprising a hydrogenated block copolymer with specific molecular weight ranges and hydrogenation ratios, combined with a tackifier and optional softening agents, to enhance tack strength, retentivity, and low-viscosity properties while minimizing contamination on adherends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional vinyl aromatic monomer-conjugated diene monomer block copolymers are used as base polymers for hot melt viscous adhesives, then the adhesive composition can be formulated, but the balance among retentivity, tack strength, and low-viscosity properties is insufficient
Solution Approach 1:
The patent applies parameter changes by controlling the hydrogenation ratio of conjugated diene monomer units within 10-80% by mol and specifying weight-average molecular weights for components (A) and (B) within particular ranges. It also defines the ratio of weight-average molecular weight of component (B) to component (A) as 1.3 to 10, and sets content ratios of components (A) and (B) at 20-90% by mass and 10-80% by mass respectively. These parameter optimizations resolve the contradiction by achieving balanced adhesive properties through precise compositional control
Solution Approach 2:
The patent uses composite materials by formulating an adhesive composition that combines block copolymer composition (comprising components A and B) with tackifiers and optional softening agents. This composite approach allows the synergistic combination of different materials to achieve balanced retentivity, tack strength, low-viscosity properties, and contamination resistance that cannot be obtained with single polymers alone
2Strength
If the hydrogenation ratio of conjugated diene monomer units is increased to improve retentivity and tack strength, then adhesive properties are enhanced, but the low-viscosity property and contamination resistance may deteriorate
Solution Approach 1:
The patent resolves this contradiction by optimizing the hydrogenation ratio parameter within 10-80% by mol range. This controlled hydrogenation level achieves enhanced tack strength and retentivity while maintaining low-viscosity properties and contamination resistance. The specific molecular weight ranges and component ratios further fine-tune this balance
3Strength
If the weight-average molecular weight of block copolymers is increased to improve retentivity, then adhesive strength is enhanced, but the low-viscosity property deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the block copolymer system into two distinct components: component (A) with weight-average molecular weight of 30,000-190,000 and component (B) with weight-average molecular weight of 60,000-500,000. This segmentation allows each component to contribute different properties - component (A) provides lower viscosity while component (B) enhances retentivity - and their combined ratio (1.3 to 10) achieves the optimal balance between strength and flow properties
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 proposed solution achieves excellent tack strength, retentivity, and low-viscosity properties while maintaining a balance with adhesive properties and reducing contamination on adherends, thereby improving the overall performance of the adhesive composition.
Implementation Method 1
a hydrogenation ratio of the conjugated diene monomer units in the component (A) and the component (B) is 10 to 80% by mol
Data Source
AI summary
Disclosure provides a block copolymer composition having 20% by mass or more and 90% by mass or less of a component (A) and 10% by mass or more and 80% by mass or less of a component (B), wherein the component (A) is a block copolymer having a polymer block mainly comprising a vinyl aromatic monomer unit and a polymer block mainly comprising a conjugated diene monomer unit, and having a weight-average molecular weight of 30,000 or higher and 190,000 or lower; and the component (B) is a block copolymer having a polymer block mainly comprising a vinyl aromatic monomer unit and a polymer block mainly comprising a conjugated diene monomer unit, and having a weight-average molecular weight of 60,000 or higher and 500,000 or lower.