Viscous Epoxy Syrup Production via Partial Polymerization
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Solution Overview
Problem
There is a need for a method to increase the viscosity of epoxy resins beyond what is achievable via the epichlorohydrin route, as most epoxies used in liquid form have low viscosity and high molecular weight, leading to insoluble crosslinked deposits when polymerized, limiting their use in pressure-sensitive adhesives.
Innovation Solution
A process involving the addition of an initiator, such as electron-poor monoisocyanates or photoinitiators, to multifunctional epoxies to polymerize them into high molecular weight polyepoxies without premature crosslinking, resulting in a viscous epoxy syrup with viscosities at least twice that of the unreacted state, suitable for pressure-sensitive adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If liquid multifunctional epoxy is polymerized to increase viscosity, then adhesive bond strength increases, but crosslinked insoluble deposits are formed making the epoxy unusable for pressure-sensitive tapes
Solution Approach 1:
The patent applies preliminary action by adding the initiator and performing partial polymerization in advance, but stopping before crosslinking occurs. This creates a viscous intermediate state that maintains solubility while achieving the desired viscosity increase, allowing subsequent processing into pressure-sensitive tapes without premature crosslinking
Solution Approach 2:
The patent employs partial action by performing only partial polymerization rather than complete crosslinking. The epoxy is polymerized to a specific viscosity level (at least twice the original viscosity) but stopped before reaching the crosslinking point, maintaining the balance between viscosity increase and solubility preservation
2Ease of operation
If epoxies are polymerized to increase molecular weight and viscosity, then pressure-sensitive adhesive properties are achieved, but premature crosslinking occurs forming insoluble deposits
Solution Approach 1:
The patent uses an initiator as an intermediary to control the polymerization process. The initiator enables controlled chain growth to achieve desired viscosity while preventing uncontrolled crosslinking. The initiator is selected and used in specific amounts (0.01-5 wt%) to mediate between polymerization and crosslinking, ensuring storage stability while achieving pressure-sensitive adhesive properties
Solution Approach 2:
The patent applies parameter changes by carefully controlling the initiator amount (0.01-5 wt%), reaction temperature (20-80°C), and reaction time to achieve the target viscosity range. These parameter adjustments ensure polymerization reaches the desired viscosity without triggering crosslinking, maintaining both operability and storage stability
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 process effectively increases the viscosity of epoxy resins, maintaining their solubility and preventing premature crosslinking, enabling the production of high-viscosity, pressure-sensitive adhesives with improved storage stability and handling properties.
Implementation Method 1
adding an initiator selected from the group consisting of electron-poor monoisocyanate, photoinitiator and thermal initiator to at least one liquid multifunctional epoxy and polymerizing the multifunctional epoxy
Data Source
AI summary
A process for producing a viscous epoxy syrup from at least one liquid multifunctional epoxy, comprising the steps of:adding an initiator selected from the group consisting of electron-poor monoisocyanate, photoinitiator and thermal initiator to at least one liquid multifunctional epoxy;mixing the components;polymerizing the multifunctional epoxy such that the viscosity of the resulting epoxy syrup is at least twice as high, preferably at least four times as high and in particular at least ten times as high as the viscosity of the employed epoxy in the unreacted statemakes it possible to produce epoxy adhesives having pressure-sensitive properties.