Pressure Sensitive Adhesive Purification via Redox Scavenging
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Solution Overview
Problem
Conventional free radical solution polymerization methods for adhesive compositions result in high levels of residual monomers and impurities, which are difficult to remove and can degrade the polymer, leading to unwanted properties in medical adhesives.
Innovation Solution
A method involving the addition of an oxidizing agent and a reducing agent to the initial reaction product to further react unreacted polymerizable reactants, followed by precipitation, to reduce the levels of residual monomers and impurities in the adhesive polymer, resulting in a purified copolymer with significantly lower impurity content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional free radical solution polymerization is used to manufacture adhesive polymers, then the manufacturing process is simple and fast, but the adhesive polymer contains high levels of residual monomers and impurities that are difficult to remove
Solution Approach 1:
The patent applies preliminary action by adding scavenger monomers and performing purification steps during the polymerization process itself, before the adhesive polymer is finalized. The scavenger monomers are introduced in advance to react with residual monomers, and purification steps including precipitation and washing are performed during manufacturing to remove impurities before the product is completed.
Solution Approach 2:
The patent converts the harmful effect of residual monomers and impurities into a benefit by using scavenger monomers that specifically react with these impurities. The harmful residual monomers are transformed into useful polymer chains through the scavenging reaction, while impurities are converted into removable byproducts that can be washed away during the purification process.
2Manufacturing precision
If scavenger monomers are used to remove residual monomers from adhesive polymer, then residual monomer levels are reduced, but the adhesive polymer structure is altered and scavenger monomer must also be removed
Solution Approach 1:
The patent merges multiple functions into the scavenger monomer: it serves as both a purification agent that reacts with residual monomers and as a component of the final adhesive polymer formulation. The scavenger monomer is incorporated into the adhesive at controlled levels (0.1-10% by weight) where it continues to provide purification benefits while contributing to the adhesive's performance characteristics.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the amount of scavenger monomer added (0.1-10% by weight of total monomers) and the reaction conditions (temperature, time, solvent) to optimize the balance between residual monomer removal and preservation of adhesive polymer properties. The purification parameters such as precipitation solvent choice and washing conditions are adjusted to remove impurities while maintaining polymer integrity.
3Manufacturing precision
If multiple heating and evaporation steps are used to remove volatile impurities from adhesive polymer, then volatile components are removed, but the polymer may crosslink, gel or degrade and the process is time consuming and costly
Solution Approach 1:
The patent replaces the mechanical/thermal system of heating and evaporation with a chemical system using scavenger monomers and precipitation. Instead of applying heat to evaporate volatile impurities, the method uses chemical reactions to transform impurities into non-volatile forms that can be removed through precipitation and washing at lower temperatures, thereby avoiding polymer degradation.
Solution Approach 2:
The patent utilizes phase transitions in the purification process by precipitating the adhesive polymer from solution using non-solvents. The polymer transitions from a dissolved state to a precipitated state, allowing separation from impurities that remain in the supernatant. This phase transition-based purification occurs at low temperatures and avoids the thermal degradation associated with evaporation methods.
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 effectively reduces residual monomer levels to below 10 ppm and non-polymerizable material levels, producing a clean adhesive suitable for medical applications with enhanced adhesion and cohesion properties.
Implementation Method 1
Purifying the initial reaction product by adding an oxidizing agent and a reducing agent to the initial reaction product and allowing the unreacted polymerizable reactant in the initial reaction product to further react
Implementation Method 2
Precipitating the polymer from the second reaction product to provide a precipitated polymer
Data Source
AI summary
A method for the manufacture of an adhesive id described, comprising: (A) Providing an initial reaction product of a solution polymerization reaction, the initial reaction product comprising polymer, unreacted polymerizable reactant, non-polymerizable material, and solvent; and (B) Purifying the initial reaction product by adding an oxidizing agent and a reducing agent to the initial reaction product and allowing the unreacted polymerizable reactant in the initial reaction product to further react, thereby providing a second reaction product comprising additional polymer and a lower level of unreacted polymerizable reactant than was present in the initial reaction product. Optionally, the method of the invention may further comprise: Precipitating the polymer from the second reaction product to provide a precipitated polymer, and separating the precipitated polymer from the remainder of the second reaction product, the precipitated polymer comprising a lower level of non-polymerizable material or unreacted polymerizable reactant or both non-polymerizable material and unreacted polymerizable reactant than was present in the second reaction product.