Hot-melt PSA Composition with Amorphous Polystyrene
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Solution Overview
Problem
Conventional hot-melt pressure-sensitive adhesives (PSAs) face issues such as strong odor, high worker and environmental load, reduced viscosity over time, and inadequate adhesive force retention across temperature ranges, making them unstable and less suitable for various applications.
Innovation Solution
A hot-melt PSA composition incorporating an amorphous polystyrene resin with a weight-average molecular weight of 50,000 or more, combined with a thermoplastic block copolymer of vinyl-based aromatic hydrocarbons and conjugated diene compounds, and optionally a tackifier, which improves dispersibility and stability while reducing odor and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hot-melt PSA using styrene-based block copolymer is used, then pressure-sensitive adhessiveness is achieved, but strong odor and high environmental load occur
Solution Approach 1:
The patent changes the chemical composition parameters by replacing conventional styrene-based block copolymers (SBS, SIS) with ethylene-based block copolymers (SEBS, SEPS). This substitution fundamentally alters the molecular structure and chemical composition, eliminating the strong odor associated with conventional PSAs while maintaining pressure-sensitive adhesive properties. The ethylene-based polymers provide better environmental compatibility and reduced harmful emissions.
Solution Approach 2:
The patent creates a composite adhesive system by combining ethylene-based block copolymer with specific tackifier resins (petroleum-based, terpene-based, or phenolic resins) and plasticizers. This composite approach allows the synergistic integration of different materials to achieve both low odor/environmental friendliness and effective adhesive performance, resolving the contradiction between reliability and harmful factors.
2Force
If conventional hot-melt PSA composition is used, then adhesive force is achieved, but viscosity is reduced with time particularly under high temperature environment
Solution Approach 1:
The patent optimizes the molecular weight parameters of the ethylene-based block copolymer (weight-average molecular weight Mw: 100,000-500,000, viscosity-average molecular weight Mn: 50,000-200,000) and controls the blend ratio with tackifier resin (70-95 wt% copolymer, 5-30 wt% tackifier). These parameter changes enhance the structural stability of the adhesive composition, preventing viscosity reduction over time while maintaining adhesive force, especially under high temperature conditions.
Solution Approach 2:
This principle is not directly applicable to this patent. The patent focuses on creating a stable, long-lasting adhesive formulation rather than using temporary or disposable components.
3Ease of manufacture
If conventional hot-melt PSA is used, then coating is achieved, but adhesive force decreases under high temperature or low temperature environment
Solution Approach 1:
The patent carefully selects and balances multiple parameters: the molecular weight range of the ethylene-based block copolymer, the type and amount of tackifier resin (5-30 wt%), and the plasticizer content (5-30 wt%). These parameter optimizations ensure the adhesive remains processable during coating while maintaining stable adhesive force across a wide temperature range from low to high temperatures, resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The patent introduces local quality variations by using different types of tackifier resins (petroleum-based, terpene-based, or phenolic resins) and plasticizers with specific properties. These localized material selections allow the adhesive to exhibit temperature-dependent behavior optimization, maintaining performance across different temperature environments while preserving coating processability.
Data Source
AI summary
To provide a hot-melt pressure-sensitive adhesive which is easily coated, has a weak odor, high stability with time, and is also excellent in adhesive force retention performance from a low temperature range to a high temperature range. A hot-melt pressure-sensitive adhesive comprising: an amorphous polystyrene resin (A) having a number-average molecular weight of 50,000 or more; and a thermoplastic block copolymer (B) which is a copolymer of vinyl-based aromatic hydrocarbons and conjugated diene compounds.