Polycarbonate diol and polyurethane using same
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Solution Overview
Problem
Conventional polycarbonate diols used in polyurethane production often exhibit inadequate low-temperature characteristics, chemical resistance, and heat resistance, with existing methods failing to achieve a balanced set of physical properties such as flexibility and elastic recovery performance.
Innovation Solution
A polycarbonate diol with a hydroxyl value of 20 to 40 mg-KOH/g and a glass transition temperature of -30°C or less, derived from aliphatic dihydroxy compounds with an average carbon number of 3 to 5.5, is produced through transesterification of dihydroxy compounds with diaryl carbonate, using a catalyst from Group 1 or Group 2 elements, to achieve a balanced set of properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polycarbonate diol synthesized from 1,6-hexanediol is used, then heat resistance and hydrolysis resistance are improved, but low-temperature characteristics such as flexibility and elongation deteriorate
Solution Approach 1:
The patent changes the chemical structure parameters of the polycarbonate diol by using dihydroxy compounds with average carbon numbers of 3 to 5.5 (such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol) instead of conventional 1,6-hexanediol. This structural parameter change achieves a glass transition temperature of -30°C or lower while maintaining adequate heat resistance, thereby improving low-temperature flexibility and elongation without sacrificing thermal stability.
Solution Approach 2:
The patent creates a composite molecular structure within the polycarbonate diol by copolymerizing multiple types of dihydroxy compounds (e.g., 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol) with specific molar ratios. This composite approach combines the beneficial effects of different chain lengths and structures, achieving both low glass transition temperature (improved flexibility) and sufficient heat resistance through synergistic molecular architecture.
2Ease of operation
If copolymerized polycarbonate diol using 1,6-hexanediol and other dihydroxy compounds is used, then low-temperature characteristics are improved, but chemical resistance deteriorates
Solution Approach 1:
The patent fundamentally changes the parameter of average carbon number of dihydroxy compounds from 6 (conventional) to 3-5.5 (invention). This parameter optimization achieves the counterintuitive result of improving both low-temperature characteristics (through lower glass transition temperature) and chemical resistance (through more stable carbonate bonds and optimized molecular packing), eliminating the trade-off present in conventional copolymerized materials.
3Reliability
If polycarbonate diol with higher molecular weight is synthesized, then heat resistance is improved, but low-temperature characteristics and flexibility deteriorate
Solution Approach 1:
The patent changes the primary parameter from molecular weight to chemical structure (average carbon number of dihydroxy compounds). By using dihydroxy compounds with average carbon numbers of 3 to 5.5, the invention achieves low glass transition temperature (improved flexibility) while maintaining heat resistance through optimized molecular structure and intermolecular interactions, proving that chemical structure parameters are more critical than molecular weight for achieving balanced performance.
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 resulting polyurethane exhibits excellent chemical resistance, low-temperature characteristics, heat resistance, and flexibility, making it suitable for applications in elastic fibers, synthetic leather, and high-performance elastomers.
Implementation Method 1
A polycarbonate diol with a hydroxyl value of 20 to 40 mg-KOH/g and a glass transition temperature of -30°C or less, derived from aliphatic dihydroxy compounds with an average carbon number of 3 to 5.5, is produced through transesterification of dihydroxy compounds with diaryl carbonate
Data Source
AI summary
The present invention relates to a polycarbonate diol comprising a structural unit derived from a compound represented by the following formula (A) and a structural unit derived from a compound represented by the following formula (B), wherein the hydroxyl value is from 20 to 450 mg-KOH/g: [Chem. 1] HO-R1-OH (A) HO-R2-OH (B) the glass transition temperature of said polycarbonate diol as measured by a differential operating calorimeter is -30 C or less and the average carbon number of a dihydroxy compound obtained by hydrolyzing said polycarbonate diol is from 3 to 5.5.