Block Copolymer Hot Melt Adhesive Softening Agent Bleeding
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Solution Overview
Problem
Hot melt adhesives using aromatic vinyl-conjugated diene-aromatic vinyl triblock copolymers face issues with softening agent bleeding, heat resistance, and transparency, particularly when used under high temperature conditions or for labeling applications.
Innovation Solution
A block copolymer composition comprising an asymmetric aromatic vinyl-conjugated diene-aromatic vinyl triblock copolymer with specific molecular weight ranges and ratios of aromatic vinyl and conjugated diene polymer blocks, along with a tackifying resin and softening agent, is developed to enhance softening agent holding properties, heat resistance, and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the amount of softening agent is increased, then coatable temperature is lowered and tackiness is increased, but the softening agent bleeds out and contaminates the object to be adhered
Solution Approach 1:
The patent changes the molecular weight parameters of the polymer blocks (specifically setting the weight average molecular weight of the aromatic vinyl blocks to 10,000-50,000 and the conjugated diene block to 50,000-100,000) to optimize the interaction with the softening agent, allowing higher softening agent content without bleeding
Solution Approach 2:
The patent uses a composite block copolymer structure combining aromatic vinyl and conjugated diene blocks in specific ratios (aromatic vinyl content: 20-40 mass%) to create a material that can hold softening agents effectively while maintaining adhesive properties
2Productivity
If adhesion is conducted under high temperature conditions, then adhesion speed is improved, but detachment of the object to be adhered occurs
Solution Approach 1:
The patent optimizes the molecular weight parameters and composition ratios of the block copolymer to achieve a balance between initial tack and heat resistance, allowing high-temperature application without detachment
3Productivity
If adhesion is conducted under high temperature conditions, then adhesion speed is improved, but flowing out of the adhesive composition occurs
Solution Approach 1:
The patent sets specific molecular weight ranges and composition ratios for the block copolymer components to control the viscosity-temperature relationship, preventing adhesive flow at application temperatures while maintaining quick setting
4Reliability
If the block copolymer structure is optimized for softening agent holding, then softening agent holding properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent divides the polymer into distinct functional blocks (aromatic vinyl blocks and conjugated diene blocks) with specific molecular weight ranges, where each block contributes specific properties that together achieve softening agent holding without excessive complexity
Data Source
AI summary
Provided is a block copolymer composition for a hot melt adhesive, which can provide a hot melt adhesive composition having excellent softening agent holding properties, heat resistance and transparency. Disclosed is a block copolymer composition for a hot melt adhesive, comprising a block copolymer A and a block copolymer B each having a particular structure, characterized in that the aromatic vinyl monomer unit content of the block copolymer A is 30% to 50% by weight; the aromatic vinyl monomer unit content of the block copolymer B is 15% to 25% by weight; a content of the aromatic vinyl monomer units relative to all polymer components of the block copolymer composition is 18% to 45% by weight; the weight ratio (A/B) of the block copolymer A with respect to the block copolymer B is 20/80 to 80/20; and the ratio (MwA/MwB) of the weight average molecular weight of the block copolymer A (MwA) with respect to the weight average molecular weight of the block copolymer B (MwB) is 0.65 to 1.5.