Polyester Hybrid Resin Casting with Controlled Curing
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Solution Overview
Problem
Polyester hybrid resins used in casting large parts, such as boat bodies or swimming pool parts, experience excessively rapid curing speeds, which limits the casting process, and secondary hydroxyl group containing polyesters are less efficient in polyesterification, leading to unsatisfactory pot life and increased processing time.
Innovation Solution
A two-pack polyester urethane hybrid resin composition is developed, comprising an unsaturated polyester dissolved in a radically copolymerizable compound and a polyfunctional isocyanate with a radical initiator, where the polyester is formed by reacting alcohols with olefinically unsaturated carboxylic acids and a monoepoxide to predominantly produce secondary hydroxyl groups, allowing for controlled curing and extended pot life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If secondary hydroxyl group containing polyesters are used to delay polyaddition reaction, then pot life is extended, but polyesterification becomes much slower and more time-consuming
Solution Approach 1:
The patent changes the chemical structure parameter of the polyester by ensuring it contains both primary and secondary hydroxyl groups in specific proportions (at least 20% primary hydroxyl groups by weight), rather than using only secondary hydroxyl groups. This parameter adjustment allows the polyesterification reaction to proceed at acceptable speeds while still providing sufficient pot life for processing.
2Productivity
If polyesterification is accelerated to improve production efficiency, then productivity increases, but curing speed becomes too high for casting large parts
Solution Approach 1:
The patent segments the curing mechanism into two distinct pathways: polyaddition reaction (controlled by hydroxyl group composition) and radical copolymerization (controlled by olefinic unsaturation and initiator). This segmentation allows independent optimization of polyesterification speed and curing speed, enabling fast production without compromising the ability to cast large parts.
Solution Approach 2:
The patent creates a composite resin system combining polyester with olefinically unsaturated compounds and isocyanates. This composite material approach allows the polyesterification and curing reactions to proceed at different rates through different mechanisms, resolving the contradiction between production efficiency and processing time for large parts.
3Productivity
If high filling is achieved to improve productivity, then casting efficiency increases, but control over curing process becomes more difficult
Solution Approach 1:
The patent introduces dynamic control of the curing process through the two-stage reaction mechanism. The polyaddition reaction provides initial structure formation with controllable speed via hydroxyl group composition, while the subsequent radical copolymerization provides final crosslinking. This dynamic, multi-stage approach maintains ease of operation even with high filling applications.
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 solution provides a hybrid resin with reduced curing speed, maintaining favorable properties like tensile strength, impact resistance, and heat distortion temperature, while allowing for high filling and versatility in composition, enabling the casting of larger parts with improved processing efficiency.
Implementation Method 1
Formation of the crosslinked polymer occurs via radically initiated copolymerisation of the unsaturated solvent and the polyester
Implementation Method 2
via polyaddition of the hydroxy functional polymers to the diisocyanate
Data Source
AI summary
This invention relates to a polyester urethane hybrid resin casting resin composition which comprises a mixture ABCD of an unsaturated polyester ABC which has moieties derived from at least one alcohol A, moieties derived from a mixture B of carboxylic acids, wherein at least 10% of the mass of at least one of the said carboxylic acids B or of the said alcohols A have at least one olefinic unsaturation in their molecules, and moieties derived from a monoepoxide C having at least four carbon atoms, which polyester ABC is dissolved in a compound D, and which has at least one olefinic unsaturation and which is radically copolymerizable with the unsaturated polyester oligomer ABC and a second liquid component EF comprising a polyfunctional isocyanate E and a radical initiator F, a process for its production, and a method of use thereof to form large moulded parts.