Polycarbonate Diol Composition for Low-Temperature Polyurethane
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Solution Overview
Problem
Conventional polycarbonate diols used in polyurethane production exhibit inadequate low-temperature characteristics, chemical resistance, and heat resistance, limiting their applications due to high crystallinity and poor flexibility.
Innovation Solution
A polycarbonate diol is developed with a specific structural unit derived from compounds represented by formulas (A) and (B), with a hydroxyl value of 20 to 450 mg-KOH/g, and a glass transition temperature of -30°C or less, achieving a balanced combination of chemical resistance, low-temperature characteristics, and heat resistance by controlling the molar ratio and carbon number of the dihydroxy compound.
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 and flexibility deteriorate due to high crystallinity
Solution Approach 1:
The patent uses a composite structure comprising a polycarbonate diol main chain with pendant ester groups introduced through specific dihydroxy compounds (formula A). This composite molecular structure combines the advantages of polycarbonate (heat and hydrolysis resistance) with the flexibility provided by ester groups, while the pendant structure disrupts crystallinity to improve low-temperature characteristics
Solution Approach 2:
The patent introduces ester groups at specific local positions along the polycarbonate chain through the use of dihydroxy compounds with formula (A). This local modification allows the majority of the chain to maintain polycarbonate properties (heat and hydrolysis resistance) while specific segments provide flexibility and reduce crystallinity
2Reliability
If polycarbonate diol with higher molecular weight is used, then heat resistance is improved, but low-temperature characteristics and flexibility deteriorate
Solution Approach 1:
The patent introduces pendant ester groups at specific intervals along the polycarbonate chain through dihydroxy compounds (formula A). This local structural modification creates flexible segments that maintain low-temperature characteristics even in higher molecular weight polymers, while the overall polycarbonate structure preserves heat resistance
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.