Solvent-Free Polyester Adhesive via Molecular Weight Control
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Solution Overview
Problem
Conventional polyester-based adhesive compositions face challenges in achieving good coatability and adhesion performance without using organic solvents, as they often require high molecular weight polyesters that are difficult to process and result in adhesives with poor tackiness at room temperature.
Innovation Solution
A solvent-free polyester-based adhesive composition with a weight-average molecular weight of 1 × 10^3 to 20 × 10^3 and a trifunctional or more polyepoxy compound as a crosslinking agent, maintaining viscosity below 80 Pa·s at 23°C to ensure coatability and adhesion performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyester with high molecular weight is used to ensure adhesion performance, then adhesive force is improved, but viscosity becomes too high for coating
Solution Approach 1:
The patent changes the molecular weight parameter of the polyester from conventional high values (10,000-200,000) to a lower range (1,000-20,000), which simultaneously reduces viscosity for better coatability while maintaining adhesion performance through optimized molecular weight control and crosslinking
2Ease of operation
If a polyester with low molecular weight is used to improve coatability, then viscosity is reduced, but adhesion performance becomes insufficient
Solution Approach 1:
The patent creates a composite system combining low molecular weight polyester with specific crosslinking agents (isocyanate compounds and/or epoxy compounds) in defined ratios, where the crosslinking network compensates for the lower molecular weight to maintain adhesion while the low molecular weight ensures coatability
Solution Approach 2:
The patent optimizes multiple parameters simultaneously: molecular weight (1,000-20,000), crosslinking agent ratios (isocyanate 1-10 parts, epoxy 0.1-5 parts per 100 parts polyester), and functional group ratios (mOH/mCOOH: 0.5-0.98), creating a coordinated parameter set that achieves both coatability and adhesion
3Ease of operation
If organic solvent is added to reduce viscosity and improve coatability, then coatability is enhanced, but environmental impact increases and solvent-free requirement is violated
Solution Approach 1:
The patent changes the molecular weight parameter to a lower range (1,000-20,000) and controls the mOH/mCOOH ratio (0.5-0.98) to achieve sufficient reactivity and flow at room temperature without solvents, eliminating the need for organic solvents while maintaining coatability
Solution Approach 2:
The patent replaces expensive and environmentally problematic organic solvents with a simple molecular weight control strategy and crosslinking system, achieving solvent-free formulation that is both environmentally friendly and cost-effective
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 composition achieves excellent coatability and adhesion performance at room temperature without organic solvents, reducing environmental impact and enabling the production of pressure-sensitive adhesive sheets with improved adhesive force and heat resistance.
Implementation Method 1
a trifunctional or more polyepoxy compound as a crosslinking agent for the polyester having the above-mentioned Mw
Data Source
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Figure 4~6
AI summary
The present invention has an object to provide a solvent-free polyester-based adhesive composition having good coatability and capable of forming an adhesive that shows good adhesion performance. The present invention provides a polyester-based adhesive composition containing a polyester having Mw of from 1 × 103 to 20 × 103 as a main component and a trifunctional or more polyepoxy compound as a crosslinking agent, and containing substantially no organic solvent. The molar number, mOH, of hydroxyl group contained in a polyalcohol component constituting the polyester is from 0.5 to 0.98 times of the molar number, mCOOH, of carboxyl group contained in a polycarboxylic acid component. The composition has a viscosity at 23°C of at most 80 Pa·s.