Amorphous Polycarbonate Diol for Flexible Polyurethane
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Solution Overview
Problem
Conventional polycarbonate diols used in polyurethanes face challenges in achieving a balance of physical properties such as oil resistance, flexibility, hydrolysis resistance, and weather resistance, with issues like crystallization, poor low-temperature properties, and insufficient oil resistance, particularly when used as soft segments in thermoplastic elastomers.
Innovation Solution
A polycarbonate diol comprising specific repeating units with a 99:1 to 1:99 ratio of formula (A) to formula (B) by mol, and a number-average molecular weight of 300 to 10,000, which is amorphous and provides excellent physical property balance when used in polyurethanes or thermoplastic elastomers, is developed. This diol is synthesized using 2-methyl-1,3-propanediol and other diols like 1,4-butanediol or 1,6-hexanediol, with a controlled amount of 5-methyl-1,3-dioxan-2-one impurity to enhance flexibility and processing ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polycarbonate polyol of 1,6-hexanediol is used to improve hydrolysis resistance and weather resistance, then the polyurethane shows good resistance to hydrolysis and weathering, but the polyurethane suffers from poor flexibility and low-temperature properties due to crystallization tendency
Solution Approach 1:
The patent introduces asymmetric structural units (odd-numbered methylene groups between carbonate bonds) into the polycarbonate diol chain. This asymmetry disrupts the regularity of the polymer structure, preventing efficient packing and crystallization. As a result, the material maintains an amorphous state at room temperature while preserving the stable carbonate bonds that provide hydrolysis and weather resistance.
Solution Approach 2:
The patent changes the structural parameters of the polycarbonate diol by controlling the number of methylene groups between carbonate bonds to be an odd number (3, 5, 7, or 9). This parameter change fundamentally alters the crystallization behavior of the polymer, transitioning it from a crystalline to an amorphous state, thereby improving flexibility and low-temperature properties while maintaining chemical stability.
2Ease of operation
If copolymerized polycarbonate diol from 1,6-hexanediol and 1,5-pentanediol is used to reduce crystallinity, then flexibility is improved, but oil resistance becomes insufficient
Solution Approach 1:
The patent applies local quality by maintaining long segments of regular carbonate bonds (providing oil resistance) while intermittently introducing asymmetric units (odd-numbered methylene groups) that disrupt crystallization. This localized asymmetry within an otherwise regular structure allows the material to simultaneously achieve flexibility and oil resistance.
Solution Approach 2:
The patent creates a composite molecular structure within the polycarbonate diol, combining regular carbonate linkages (which provide oil resistance) with asymmetric methylene sequences (which prevent crystallization). This molecular-level composite structure enables the material to exhibit both flexibility and oil resistance properties.
3Reliability
If polycarbonate diol with high regularity is used to achieve high oil resistance, then the polyurethane shows excellent oil resistance, but the polyurethane becomes crystalline and loses flexibility
Solution Approach 1:
The patent introduces asymmetric structural units (odd-numbered methylene groups) into the polycarbonate diol chain. This asymmetry disrupts the regularity of the polymer structure, preventing efficient packing and crystallization. As a result, the material maintains an amorphous state at room temperature while preserving the stable carbonate bonds that provide hydrolysis and weather resistance.
Solution Approach 2:
The patent changes the structural parameters of the polycarbonate diol by controlling the number of methylene groups between carbonate bonds to be an odd number (3, 5, 7, or 9). This parameter change fundamentally alters the crystallization behavior of the polymer, transitioning it from a crystalline to an amorphous state, thereby improving flexibility and low-temperature properties while maintaining chemical stability.
Data Source
AI summary
A polycarbonate diol which is useful as a raw material compound for producing a polycarbonate-based polyurethane having a sufficient mechanical strength and excellent in a balance of physical properties such as oil resistance, hydrolysis resistance, and weather resistance and which is amorphous. The polycarbonate diol includes repeating units of the below-shown formula (A) and the below-shown formula (B), wherein both terminal groups are hydroxyl groups, the ratio of the below-shown formula (A) to the below-shown formula (B) is 99:1 to 1:99 by mol, and number-average molecular weight is 300 to 10,000.