Solvent-Free Polyurethane Transdermal Patch Reactive Coating
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Solution Overview
Problem
Existing transdermal patches face issues with residual solvents causing fluctuations in active ingredient concentration and layer thickness, leading to inaccurate dosing and potential skin occlusions, which are difficult to control and monitor.
Innovation Solution
A method for producing a solvent-free polyurethane patch using reactive coating on an elastic backing film supported by an inextensible auxiliary film, ensuring complete solvent evaporation and stable adhesion, with the polyurethane composition being mixed and applied immediately to prevent mechanical stress and layer thickness fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solvent-containing polymer mixtures are applied to a backing film and the solvent is removed by drying, then the polymer matrix can be formed for active ingredient delivery, but residual solvents remain in the matrix causing fluctuations in active ingredient concentration and prolonged solvent vapor emission
Solution Approach 1:
The invention extracts and eliminates the solvent component from the transdermal patch manufacturing process entirely. Instead of using solvent-containing polymer mixtures and attempting to remove solvents through drying, the patent employs a solvent-free polymerization process where the polymer matrix is formed directly without any solvent, thereby completely avoiding residual solvent issues and their associated problems with active ingredient concentration fluctuations
Solution Approach 2:
The invention changes the fundamental parameter of solvent content from present to absent. By transitioning from a solvent-based manufacturing approach to a solvent-free approach, the patent fundamentally alters the manufacturing process parameters to eliminate the source of concentration fluctuations and solvent vapor emission issues
2Adaptability or versatility
If the backing film remains elastic during coating, then the coating process can accommodate film flexibility, but mechanical stress during application causes fluctuations in layer thickness and active ingredient concentration
Solution Approach 1:
The invention applies preliminary action by making the backing film inelastic specifically in the processing direction before the coating process begins. This pre-treatment ensures that when the coating is applied, the film cannot deform or stretch, thereby preventing layer thickness fluctuations. After coating, the film can regain its elasticity for application to the skin
Solution Approach 2:
The invention applies local quality by differentiating the mechanical properties of the backing film in different directions and at different stages. The film is made inelastic only in the processing direction during coating, while maintaining flexibility in other aspects for eventual skin application. This localized property modification solves the contradiction between flexibility and coating precision
3Productivity
If a conveyor belt is used to support the backing film during coating, then the coating process can proceed efficiently, but detachment of the patch from the belt causes quality fluctuations that are difficult to monitor
Solution Approach 1:
The invention introduces an intermediary auxiliary film between the backing film and the conveyor belt. This auxiliary film serves as a mediator that remains connected to the backing film throughout the coating process and until polyaddition is complete, preventing direct detachment issues between the patch and conveyor belt while still enabling efficient processing
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 method ensures accurate and consistent delivery of active ingredients with reduced solvent exposure, improved adhesion, and controlled release, maintaining therapeutic efficacy while avoiding skin occlusions and metering inaccuracies.
Implementation Method 1
By 'reactive coating' here is meant that all of the constituents envisioned for the polyurethane are mixed and immediately applied, so that the polyaddition reaction takes place during the coating operation and on the coated backing.
Implementation Method 2
an inextensible, underlying auxiliary film (30) which provides support for the elastic backing film (20) to be coated, and which remains connected thereto until the polyaddition is virtually at an end
Data Source
AI summary
A method for producing an active substance-containing polyurethane plaster for transdermal application is described, said plaster containing at least one active substance at a highly accurate declared dose. In the described method, a solvent-free active substance-containing polyurethane is produced by reactively coating a solvent-free active substance-containing polyurethane material (40), which is mixed in a coating unit (60) immediately before or during the application process, onto an elastic backing foil (20) that has been rendered non-extensible at least in the direction in which the applied polyurethane material is processed by means of a supporting, adhering auxiliary foil (30) which is at least mono-axially non-extensible.