Dual Cure Resin With Volatile Blocking Groups For Additive Manufacturing

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Solution Overview

Problem

Conventional additive manufacturing techniques, including stereolithography and CLIP, face limitations in producing parts with a wide range of mechanical properties, as ingredients that facilitate easy processing can hinder strength, and those enhancing strength can compromise final mechanical properties.

Innovation Solution

A dual cure resin method involving a light polymerizable first component and a heat polymerizable second component, where the heat polymerizable component includes a blocked reactive constituent with a volatile blocking group that degrades upon heating to contribute to the final polymer's mechanical properties, allowing for tuning of glass transition temperatures and mechanical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If ingredients that provide low viscosity for easy processing are used, then ease of manufacture is improved, but strength of the green part deteriorates

Engineering Contradiction:

Improveease of processingVSAvoidstrength of green part

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent segments the curing process into two distinct stages: light-induced polymerization for shape formation and heat-induced curing for mechanical property development. This allows optimization of resin composition for each stage independently, resolving the contradiction between processability and green part strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs blocked isocyanates that are pre-prepared with blocking groups to prevent premature reaction. These blocked groups are removed during the heat curing stage, allowing the isocyanate to participate in the second curing phase and contribute to final mechanical properties without interfering with the initial light curing process.

Inventive Principle:

Principle #10Preliminary action

2Strength

If ingredients that provide strong green parts are used, then strength is improved, but mechanical properties of the finished part deteriorate

Engineering Contradiction:

Improvestrength of green partVSAvoidmechanical properties of finished part

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent utilizes temperature-dependent parameter changes to activate different curing mechanisms. The blocked isocyanates remain inactive during light curing but become active during heat curing, allowing the system to provide strength at the green part stage while ensuring proper mechanical properties in the finished part through subsequent thermal processing.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The blocking groups act as intermediaries that temporarily prevent isocyanate reactivity during light curing. These blocking groups are subsequently removed through heat treatment, allowing the isocyanate to participate in the second curing phase and contribute to the final mechanical properties of the part.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If UV-reactive blocking agents are used to block NCO groups, then light polymerization is improved, but polyurethane/polyurea weight fraction is reduced

Engineering Contradiction:

Improvelight polymerization performanceVSAvoidpolyurethane/polyurea weight fraction

Core Design Contradiction:

Ease of manufactureVSQuantity of substance

Solution Approach 1:

The patent converts the potential harm of UV-reactive blocking groups (which may remain in the final product and reduce polyurethane content) into a benefit by designing blocking groups that are specifically removed during heat curing. This ensures complete elimination of the blocking groups while maximizing polyurethane/polyurea formation in the second curing stage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 enables the production of three-dimensional objects with tailored mechanical properties, including elastomeric and rigid materials with desired glass transition temperatures, by controlling the polyurethane/polyurea and UV-network percentages, thereby overcoming the limitations of existing methods.

Implementation Method 1

irradiating the build region with light through the optically transparent member to form a solid polymer scaffold from the first component

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

heating the three-dimensional intermediate sufficiently to (i) cleave the volatile blocking group from the reactive constituent

Methodology Applied

Scientific EffectThermal decomposition: Pyrolysis

Data Source

PatentUS11226559B2Blocking groups for light polymerizable resins useful in additive manufacturing

Publication Date: 2022.01.18 CARBON INC

AI summary

Provided herein is a method of forming a three-dimensional object in which the polymerizable liquid includes a mixture of (i) a light polymerizable first component, and (ii) a heat polymerizable second component; the heat polymerizable second component comprising (i) a first blocked reactive constituent that is blocked with a volatile blocking group, and optionally (ii) a curative. Upon heating a formed three-dimensional intermediate sufficiently, the volatile blocking group is cleaved and vaporizes out of the three-dimensional intermediate, to form the three-dimensional object. Also provided is a three-dimensional object produced by the method. Further provided is a polymerizable liquid composition useful for carrying out the method, and prepolymers and monomers useful for the polymerizable liquid composition.