Methacrylic Adhesive Composition for High-Strength UV Curing
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Solution Overview
Problem
Existing adhesive compositions cured by active energy rays face challenges in achieving excellent adhesive force due to issues with solvent pollution, energy consumption, odor from unreacted compounds, and difficulties in synthesizing oligomers with large molecular weights, leading to adhesives with low adhesive strength.
Innovation Solution
An adhesive composition comprising a (meth)acrylic polymer with specific terminal groups, isobornyl acrylate, and a photoradical polymerization initiator, where the (meth)acrylic polymer has a weight average molecular weight to number average molecular weight ratio less than 1.8, and a weight ratio of n-butyl acrylate to 2-ethylhexyl acrylate of 20/80 to 80/20, is used, which is cured using high-pressure mercury lamps, metal halide lamps, or UV-LED light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a low molecular compound having a (meth)acryloyl group is used for photopolymerizable composition, then the adhesive can be cured by active energy rays, but odor due to volatilization of unreacted compound from cured product becomes a serious problem
Solution Approach 1:
The patent changes the molecular weight parameter of the (meth)acrylic polymer from low molecular weight to high molecular weight (weight average molecular weight of 10,000 to 1,000,000), which eliminates volatilization and odor while maintaining photopolymerizability. The high molecular weight polymer contains (meth)acryloyl groups that can undergo photopolymerization but do not volatilize due to their large molecular size.
Solution Approach 2:
Instead of using low molecular weight compounds that are easy to polymerize but cause odor, the patent inverts the approach by using high molecular weight polymers that are traditionally difficult to polymerize completely. This inversion solves the odor problem while the patent addresses the polymerization difficulty through specific compositional ratios and photoinitiator selection.
2Object-generated harmful factors
If an oligomer having a (meth)acryloyl group is used to solve odor problem, then volatilization is reduced, but it tends to be difficult to obtain oligomers with large molecular weight due to synthesis problems
Solution Approach 1:
The patent changes the molecular weight parameter from oligomer range to high polymer range (weight average molecular weight of 10,000 to 1,000,000), which naturally eliminates the need for difficult oligomer synthesis while maintaining the odor-free advantage. The high molecular weight is achieved through conventional polymerization of (meth)acrylic monomers followed by terminal functionalization.
Solution Approach 2:
The patent uses commercially available high molecular weight (meth)acrylic polymers as starting materials, copying the successful synthesis of these polymers and then introducing (meth)acryloyl groups at the terminals. This approach avoids the difficulty of synthesizing high molecular weight oligomers from scratch by using existing high molecular weight polymers as the base structure.
3Ease of manufacture
If a vinyl polymer having a (meth)acryloyl group at molecular terminal and having large molecular weight is used, then synthesis is simplified, but the adhesive tends to have low adhesive force
Solution Approach 1:
The patent creates a composite adhesive system combining high molecular weight (meth)acrylic polymer with (meth)acryloyl terminal groups and a cyclic vinyl monomer. The high molecular weight polymer provides the backbone structure and rubber elasticity, while the cyclic vinyl monomer (5-100 parts by weight per 100 parts polymer) contributes to adhesive force through its cyclic structure and reactivity, creating a synergistic composite that overcomes the low adhesive force problem.
Solution Approach 2:
The patent applies local quality by concentrating the adhesive force-generating components at specific locations: the (meth)acryloyl groups are placed at the molecular terminals of the high molecular weight polymer, and cyclic vinyl monomers are added as separate reactive components. This localized placement of functional groups ensures that the bulk polymer provides structural integrity while the terminal and added cyclic components provide adhesion.
4Ease of operation
If solvent type acrylic adhesive is used, then the adhesive can be applied easily, but air pollution due to solvents occurs
Solution Approach 1:
The patent extracts and removes the solvent component from the adhesive system entirely, creating a 100% solid photopolymerizable composition. The adhesive is applied in uncured state and then cured by active energy rays (UV or electron beam irradiation), eliminating the need for solvents that would cause air pollution while maintaining ease of application through the liquid or paste-like consistency of the uncured composition.
5Ease of operation
If emulsion type acrylic adhesive is used, then the adhesive can be applied easily, but a large amount of energy is required to evaporate water
Solution Approach 1:
The patent extracts and removes the water component from the adhesive system, creating a solvent-free photopolymerizable composition. The adhesive is applied in uncured state and cured by active energy rays, eliminating the need for water evaporation and the associated high energy consumption while maintaining ease of application.
Solution Approach 2:
The patent replaces the thermal evaporation mechanism (heating to evaporate water) with a photopolymerization mechanism (UV or electron beam irradiation to cure the adhesive). This substitution eliminates the need for high energy input for water evaporation while achieving the same goal of transitioning from applyable state to bonded state.
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 adhesive composition achieves an excellent adhesive force, as demonstrated by a 180° peeling test, with improved rubber elasticity and handling properties, while minimizing environmental impact and odor issues.
Implementation Method 1
an adhesive composition containing a (meth)acrylic polymer curable by active energy rays
Data Source
AI summary
The present invention provides an adhesive composition which is cured by active energy rays and exhibits an excellent adhesive force. An adhesive composition containing the following components (A) to (C): 100 parts by weight of a (meth)acrylic polymer (A) having at least one group represented by the general formula (1) per molecule at a molecular terminal: -OC(O)C(R1)=CH2 (1) in which R1 represents hydrogen or an organic group containing 1 to 20 carbon atoms; 45 to 65 parts by weight of isoboronyl acrylate (B), and 0.1 to 10 parts by weight of a photoradical polymerization initiator (C).