Unsaturated Polyester-Urethane Prepolymer for SMC Viscosity Control
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Solution Overview
Problem
Conventional two-component systems based on unsaturated polyester polyol and polyisocyanate in SMC or BMC applications face issues such as exothermicity leading to temperature rises, low viscosity resulting in resin overflow, and the need for specialized cooling and handling precautions due to the use of large amounts of polyisocyanates, which are harmful and require ventilated areas.
Innovation Solution
The use of prepolymers with hydroxyl and/or amine or free isocyanate end functional groups, where a portion of the isocyanate is pre-reacted with the unsaturated polyester to form a urethane polyol prepolymer, reducing the need for isocyanate at the final formulation stage, thereby controlling reaction exothermicity and viscosity, and minimizing the amount of isocyanate required, thus enhancing handling safety and reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a two-component system based on unsaturated polyester polyol and polyisocyanate is used in SMC or BMC applications, then the mechanical properties of the molded components are improved, but the reaction exothermicity causes significant temperature rise during manufacture
Solution Approach 1:
The patent applies preliminary action by pre-reacting a portion of the isocyanate with the unsaturated polyester polyol to form a urethane polyol prepolymer before the final formulation. This preliminary reaction reduces the amount of free isocyanate available for exothermic reaction during SMC/BMC manufacturing, thereby controlling temperature rise while still achieving the desired mechanical properties through the pre-formed urethane bonds and remaining reactive groups.
2Strength
If polyisocyanate is added at the time of formulating SMC or BMC, then the mechanical properties are enhanced, but the viscosity of the hybrid paste becomes too low causing resin drainage and overflow
Solution Approach 1:
The patent uses preliminary action by forming a urethane polyol prepolymer in advance, which has inherently higher viscosity than the original polyol and isocyanate components. This prepolymer serves as the base for the hybrid paste, providing adequate viscosity for proper impregnation without drainage or overflow, while still containing reactive groups that will form the crosslinked network for enhanced mechanical properties.
3Strength
If large amounts of polyisocyanate are used in the formulation, then the crosslinking density and mechanical performance are improved, but the handling becomes hazardous requiring specialized precautions and ventilated areas
Solution Approach 1:
The patent applies preliminary action by pre-consumption of a portion of the isocyanate through reaction with the polyester polyol to form the urethane polyol prepolymer. This reduces the amount of free, hazardous isocyanate that needs to be handled by the final formulator by up to 50%, while maintaining the necessary crosslinking density and mechanical performance through the pre-formed urethane bonds and remaining reactive groups.
Solution Approach 2:
The patent converts the potentially harmful excess isocyanate into a beneficial pre-reacted state. By deliberately reacting a portion of the isocyanate with the polyester polyol under controlled conditions to form the urethane polyol prepolymer, the patent transforms the hazardous material into a more stable intermediate that is easier and safer to handle, while still achieving the desired crosslinking and mechanical properties.
4Strength
If isocyanate modification is carried out at the time of formulating, then the mechanical properties are improved, but the equipment complexity increases due to the need for specialized cooling systems
Solution Approach 1:
The patent applies preliminary action by performing a portion of the isocyanate modification in advance during the preparation of the urethane polyol prepolymer. This preliminary modification reduces the exothermicity of the subsequent reaction during SMC/BMC manufacturing, eliminating the need for specialized cooling systems and allowing the use of standard equipment while still achieving the desired mechanical properties.
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 decreases exothermicity during impregnation, eliminates the need for cooling systems, improves viscosity control, reduces isocyanate usage by up to half, and simplifies handling, making the process less polluting and safer while maintaining or improving the mechanical performance of molded components.
Implementation Method 1
an unsaturated polyester component having a high NOH with an isocyanate... which react together to give a semi-finished product... The modification by the isocyanate, with results in the formation of urethane groups
Implementation Method 2
the exothermicity of the reaction between the isocyanate and the unsaturated polyester brings about a significant rise in temperature
Data Source
AI summary
An ethylenically unsaturated prepolymer comprising an ending X which reacts by condensation being a hydroxyl and/or amine or free isocyanate group and optionally an ending X′ having ethylenic unsaturation, the prepolymer being the reaction product of a first component A comprising a mixture of i) a first ethylenically unsaturated resin carrying specific hydroxyl and/or amine reactive endings, and/or ii) optionally a second resin different from resin i), being an ethylenically unsaturated hydroxylated resin and/or a hydroxylated and/or aminated saturated resin, and/or iii) optionally a third reactive saturated resin, iv) optionally an unsaturated monoalcohol up to 30% in equivalents of the OH+NH2 total, and a second component B comprising a polyisocyanate with a functionality equal to 2 or greater than 2, A and B being in proportions to effectively avoid any gelling by crosslinking.