Blocked-Polyisocyanate Resins for Stable 1K Dual-Cure Printing
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Solution Overview
Problem
Existing one-part (1K) dual cure resins for additive manufacturing suffer from inadequate shelf stability due to the use of latent hardeners, which can become active at elevated temperatures, reducing storage stability.
Innovation Solution
In situ generation of polyamine from a reactive blocked polyisocyanate in the resin, which reacts with water to form polyurea linkages, eliminating the need for a polyamine chain extender and allowing for 1K dual cure resins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If latent hardeners are used in 1K dual cure resins, then the resin can be provided as a one-part system eliminating mixing, but the shelf stability deteriorates because latent hardeners become active at elevated temperatures
Solution Approach 1:
The patent removes the latent hardener component from the resin system entirely. Instead of including a hardener that requires thermal activation (which causes shelf stability issues), the system uses only blocked isocyanate that remains dormant at storage temperatures and only reacts when unblocked during the curing process. This extraction of the problematic component resolves the contradiction between ease of use and storage stability.
Solution Approach 2:
The patent applies preliminary blocking to the isocyanate groups before resin formulation. By pre-blocking the isocyanate with compounds like carboxylic acids or phenols, the system creates a stable precursor that won't react during storage but can be selectively unblocked during curing. This preliminary modification allows the resin to maintain stability while still achieving complete cure, resolving the contradiction between operational simplicity and storage reliability.
2Adaptability or versatility
If polyamine chain extender is included in the resin, then polyurea structures can be formed, but the resin complexity increases and shelf stability decreases
Solution Approach 1:
The patent extracts the polyamine chain extender from the resin formulation. Instead of including polyamine as a separate reactive component (which would increase complexity and reduce shelf life), the system generates polyamine in situ by hydrolyzing the blocked isocyanate with water during the curing process. This eliminates the need to store and handle multiple reactive components while still achieving polyurea structure formation.
Solution Approach 2:
The patent enables the resin system to generate its own polyamine component through the hydrolysis of blocked isocyanate. Rather than requiring an external polyamine additive, the system self-produces the necessary amine groups from water and blocked isocyanate reactions during curing. This self-service approach simplifies the resin formulation while maintaining polyurea formation capability.
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 approach provides stable 1K dual cure resins with improved storage stability and efficient production of three-dimensional objects with polyurea structures, enabling flexible and rigid properties through mixed resins.
Implementation Method 1
additively manufacturing from said resin an intermediate object comprising the light polymerization product of said reactive blocked polyisocyanate
Implementation Method 2
the resin, the water, or both the resin and the water, contains a catalyst that catalyzes the reaction between isocyanate and water
Implementation Method 3
polyamine can be generated in situ in the product by contacting it with water, which polyamine can react with the remainder of the polymerization product to form polyurea linkages
Data Source
AI summary
Provided is method of making a three-dimensional object comprising polyurea, which may include: (a) dispensing a one part (1K) dual cure resin into a stereolithography apparatus, the resin comprising or consisting essentially of a photoinitiator, a reactive blocked polyisocyanate, optionally a catalyst such as a polyurethane blowing catalyst, and optionally a polyepoxide; (b) additively manufacturing from said resin an intermediate object comprising the light polymerization product of said reactive blocked polyisocyanate; (c) optionally cleaning said intermediate object; and (d) reacting said polymerization product in said intermediate with water in the presence of a catalyst such as a polyurethane blowing catalyst (which may be included in the resin, the water, or both) to generate polyamine in situ that sequentially reacts with the remainder of the polymerization product to form urea linkages and thereby produce a three-dimensional object comprising polyurea. Dual cure resins useful for the method are also provided.