Cycloaliphatic Diepoxide Resin for Stereolithography

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Solution Overview

Problem

Current stereolithographic resin compositions face challenges in achieving high reactivity, green strength, low viscosity, low humidity sensitivity, and high temperature resistance while maintaining mechanical and chemical properties desired for complex three-dimensional article fabrication.

Innovation Solution

A radiation-curable composition comprising 50-70 wt% cycloaliphatic diepoxide, 5-15 wt% polyol, 5-15 wt% oxetane, 10-20 wt% aromatic diacrylate, a radical photoinitiator, and a cationic photoinitiator, which improves flexibility, accuracy, and green strength, and is suitable for high-powered stereolithography machines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high-powered lasers with fast scanning speeds are used to increase productivity, then the fabrication speed increases, but the temperature rises causing part distortion and excessive color development

Engineering Contradiction:

Improvefabrication speedVSAvoidpart temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent converts the harmful effect of polymerization exotherm (temperature rise) into a beneficial dual-cure mechanism. The resin composition is designed to undergo both free-radical polymerization (initiated by UV light) and cationic polymerization (initiated by the heat from laser scanning), transforming the unwanted thermal effect into a useful curing mechanism that improves green strength and reduces distortion.

Inventive Principle:

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

Solution Approach 2:

The patent employs a composite resin system containing multiple polymerizable components: (meth)acrylates for free-radical polymerization, epoxy resins for cationic polymerization, and oxetane compounds as reactive modifiers. This composite material system allows simultaneous or sequential activation of different polymerization mechanisms, balancing cure speed, green strength, and thermal management.

Inventive Principle:

Principle #40Composite materials

2Productivity

If the resin composition is made more reactive to decrease build time, then the fabrication speed increases, but the green strength and accuracy decrease due to excessive curling and deformation

Engineering Contradiction:

Improvebuild timeVSAvoidgreen model accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent modifies the chemical parameters of the resin system by incorporating epoxy resins and oxetane compounds that undergo cationic polymerization. This changes the curing kinetics and mechanical properties of the green model, reducing curling and deformation while maintaining acceptable build times through the dual-cure mechanism.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces oxetane compounds as intermediary reactive modifiers that bridge the two polymerization systems. These compounds contain both cationic and radical polymerizable groups, allowing them to participate in both polymerization mechanisms and mediate between the fast-curing but low-strength free-radical system and the slow-curing but high-strength cationic system.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If a single polymerization system is used to simplify the composition, then the device complexity decreases, but the balance of properties (green strength, temperature resistance, mechanical properties) cannot be achieved

Engineering Contradiction:

Improveresin composition complexityVSAvoidproperty balance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent creates a universal resin composition that performs multiple functions: free-radical polymerization for initial layer adhesion and fast curing, cationic polymerization for green strength development and thermal resistance, and oxetane modification for enhanced mechanical properties. This multi-functional system replaces what would otherwise require multiple separate resin compositions or post-processing steps.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 composition enhances the mechanical properties of the resulting three-dimensional articles with improved green strength, accuracy, and temperature resistance, reducing curling and deformation during fabrication.

Implementation Method 1

a radiation curable composition comprising 50-70 wt% cycloaliphatic diepoxide, 5-15 wt% polyol, 5-15 wt% oxetane, 10-20 wt% aromatic diacrylate, a radical photoinitiator, and a cationic photoinitiator

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

In step (a), a layer of the radiation-curable composition, one boundary of which is the surface of the composition, is cured with the aid of appropriate imaging radiation, preferably imaging radiation from a computer-controlled scanning laser beam

Methodology Applied

Scientific EffectPhotoinitiation: Photopolymerisation

Data Source

PatentEP1918316B1Photo-curable resin composition

Publication Date: 2015.09.16 DSM IP ASSETS BV

AI summary

The invention relates to a radiation curable composition comprising from about 50 wt% to about 70 wt% of a cycloaliphatic diepoxide, from about 5 wt% to about 15 wt% of a polyol, from about 5 wt% to about 15 wt% of an oxetane, from about 10 wt% to about 20 wt% of an aromatic diacrylate, a radical photoinitiator and a cationic photoinitiator. The invention further relates to a process for making a three dimensional article from the resin composition of the invention, to the three-dimensional article itself and to the use of the composition of the invention.