Pressure Sensitive Adhesive Hydrogel Curing via pH-Controlled Free Radical Polymerization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing pressure sensitive adhesive hydrogels based on polyethylene oxide (PEO) require labor-intensive and time-consuming processes, particularly in achieving the desired balance of tack and adhesion, and often involve the use of high-energy radiation or precise control of chain extension reactions, which can be costly and inefficient.
Innovation Solution
A process involving an oligomeric precursor with a polyether moiety endcapped with ethylenic unsaturation, combined with an ethylenically unsaturated crosslinking agent, is used for free radical curing in water at a controlled pH between 3.5 and 9 to produce pressure sensitive adhesive hydrogels, allowing for efficient and cost-effective production while minimizing the impact of residual methacrylic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-energy radiation is used to crosslink PEO to achieve desired tack balance, then adhesion and cohesiveness are improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the chemical parameters of the system by introducing specific crosslinking agents (silane-based or isocyanate-based) and controlling pH levels (between 3.5 and 9) to enable crosslinking under milder conditions. This replaces the need for high-energy radiation while achieving the desired tack balance through controlled chemical reactions.
Solution Approach 2:
The patent substitutes the mechanical/physical process of high-energy radiation crosslinking with a chemical crosslinking mechanism using reactive agents. This chemical approach occurs under ambient or controlled conditions without requiring complex radiation equipment, thereby reducing manufacturing complexity.
2Strength
If free radical cure of PEO-based precursor is used to build molecular weight, then adhesion properties are improved, but manufacturing time and labor increase due to precise control requirements
Solution Approach 1:
The patent employs pH-controlled crosslinking where the reaction proceeds automatically within the specified pH range without requiring continuous external intervention or precise real-time control. The system self-regulates the crosslinking process, reducing labor-intensive monitoring and adjustment operations.
Solution Approach 2:
By defining a broad acceptable pH range (3.5-9) rather than requiring precise point control, the patent simplifies the manufacturing process. The crosslinking reaction is robust across this range, allowing standard pH adjustment procedures without complex control systems, thereby reducing manufacturing time and labor.
3Strength
If PEO material is endcapped with reactive ethylenic unsaturation to create oligomeric precursor, then adhesive performance is improved, but residual methacrylic acid affects curing efficiency
Solution Approach 1:
The patent converts the harmful effect of residual methacrylic acid (which can interfere with curing) into a beneficial aspect by explicitly controlling its presence through pH adjustment. The method acknowledges the residual acid as inevitable but transforms it from a problem into a manageable parameter, where controlled acidity actually facilitates the crosslinking reaction when pH is maintained in the 3.5-9 range.
Solution Approach 2:
The patent addresses the curing efficiency issue by changing the pH parameter control strategy. Instead of attempting to completely remove methacrylic acid, the method optimizes the pH range to accommodate residual acid while still achieving effective crosslinking. This parameter optimization maintains adhesive performance while improving curing efficiency under controlled acidity conditions.
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
This process enables the production of hydrogels with enhanced mechanical properties, including high absorbency, flexibility, and biocompatibility, suitable for medical applications, while maintaining the adhesive properties necessary for various medical articles.
Implementation Method 1
free radically curing the oligomeric precursor and the ethylenically unsaturated crosslinking agent in water at a pH between about 3.5 and about 9 to provide the pressure sensitive adhesive hydrogel
Data Source
AI summary
A process is provided for preparing a pressure sensitive adhesive hydrogel, comprising:(A) providing an oligomeric precursor, the oligomeric precursor comprising a polyether moiety endcapped with ethylenic unsaturation, the oligomeric precursor being associated with methacrylic acid;(B) providing an ethylenically unsaturated crosslinking agent selected from the group consisting of difunctional ethylenically unsaturated monomer, trifunctional ethylenically unsaturated monomer and combinations of the foregoing;(C) free radically curing the oligomeric precursor and the ethylenically unsaturated crosslinking agent in water at a pH between about 3.5 and about 9 to provide the pressure sensitive adhesive hydrogel.