UV-Curable Pressure-Sensitive Adhesive Composition
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Solution Overview
Problem
Current pressure-sensitive adhesives (PSAs) face challenges in achieving high adhesion and cohesion when cured by ultraviolet radiation, particularly due to the inhibitory effects of traditional tackifiers like rosin resins, which absorb UV radiation and lead to phase separation and poor performance.
Innovation Solution
A pressure-sensitive adhesive composition comprising an acid-functionalized (meth)acrylate copolymer, a high glass transition temperature (meth)acrylate polymer tackifier, and a low glass transition temperature (meth)acrylate polymer tackifier, formed through a reaction mixture with a non-tertiary alkyl acrylate and an acid-functionalized ethylenically unsaturated monomer, and cured using ultraviolet photoinitiators, minimizing organic solvent use and optimizing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional tackifiers like rosin resins are used to enhance adhesion, then adhesion performance is improved, but ultraviolet radiation absorption increases and polymerization reaction is inhibited
Solution Approach 1:
The patent removes traditional tackifiers (rosin resins, terpene resins, petroleum resins, aromatic resins) from the adhesive formulation. These tackifiers are extracted/eliminated because they absorb UV radiation and inhibit polymerization. Instead, the invention uses acrylic-based polymers with specific molecular weights and glass transition temperatures to provide both adhesion and enable successful UV curing.
Solution Approach 2:
The patent changes the chemical composition parameters by using specific acrylic-based polymers with controlled molecular weights (10,000-1,000,000 g/mol) and glass transition temperatures (-50°C to 50°C). It also controls the ratio of polymer to monomer (1:4 to 4:1) and uses specific UV photoinitiators (0.1-10% by weight) to enable polymerization without traditional tackifiers, thereby resolving the contradiction between adhesion and UV curing compatibility.
2Ease of manufacture
If organic solvents are used in PSA compositions, then processing and application are facilitated, but pollution and energy consumption increase
Solution Approach 1:
The patent eliminates organic solvents from the adhesive composition. Instead of using solvent-based systems that require evaporation and energy-intensive drying processes, the invention employs a solvent-free or water-based acrylic polymer system that cures through UV photopolymerization. This extraction of harmful solvents reduces pollution and energy consumption while maintaining ease of application through the low-viscosity monomer mixture.
Solution Approach 2:
The patent replaces the thermal drying process (mechanical evaporation of solvents requiring high energy input) with UV photopolymerization (photochemical curing). This substitution eliminates the need for high-temperature drying ovens and reduces energy consumption significantly, while also eliminating VOC emissions associated with organic solvent evaporation.
3Use of energy by moving object
If UV curing is used to reduce energy consumption and increase speed, then energy efficiency and productivity are improved, but adhesion performance deteriorates due to tackifier inhibition
Solution Approach 1:
The patent removes traditional UV-inhibiting tackifiers from the formulation, enabling effective UV curing. The adhesion performance is maintained through the selection of specific acrylic polymers with appropriate glass transition temperatures and molecular weights, plus the use of sufficient UV photoinitiator (0.1-10% by weight) to ensure complete polymerization and bond strength.
Solution Approach 2:
The patent creates a composite adhesive system combining acrylic-based polymers (for adhesion), monomers (for low viscosity and reactivity), and UV photoinitiators (for curing). This composite formulation achieves both high adhesion performance and UV curability without the inhibitory effects of traditional tackifiers, resolving the contradiction between energy efficiency and adhesion strength.
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 solution enables the production of PSAs with enhanced adhesiveness and high temperature shearing properties, achieved through low energy consumption and high-speed processing without significant organic solvent use, while avoiding the limitations of traditional tackifiers.
Implementation Method 1
cured using ultraviolet photoinitiators
Data Source
AI summary
Curable adhesive compositions that can be used to prepare the pressure-sensitive adhesives, and methods of making the pressure-sensitive adhesives are provided. More particularly, the pressure-sensitive adhesives contain (a) a (meth)acrylate copolymer having a weight average molecular weight greater than 500,000 grams/mole (Daltons), (b) a high glass transition temperature (meth)acrylate polymer tackifier having a Tg of at least 5° C. and (c) a low glass transition temperature (meth)acrylate polymer tackifier having a Tg no greater than 0° C. The pressure-sensitive adhesives advantageously are prepared by ultraviolet (UV) curing a curable adhesive composition that contains minimal or no organic solvents.