High Tg Copolycarbonate Suppresses Crystallization
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Solution Overview
Problem
There is a need for polycarbonate compositions with very high glass transition temperatures (Tg) suitable for high-performance film applications, such as OLEDs and flexible printed circuits, that also exhibit high optical transparency, low shrinkage, and low coefficient of thermal expansion, as existing high Tg copolycarbonates derived from 3,3-Bis-(4-hydroxyphenyl)-2-phenyl-2,3-dihydroisoindol-1-one (BHPD) tend to crystallize during film formation.
Innovation Solution
A copolycarbonate composition comprising units derived from 70 to 99.5 mole percent of a dihydroxy compound like BHPD and 0.5 to 30 mole percent of another dihydroxy compound, formed using a bischloroformate manufacturing process, which prevents crystallization and achieves high molecular weights, optical clarity, and desired thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polycarbonate is derived from BHPD to achieve high glass transition temperature, then thermal stability is improved, but crystallization occurs during film formation reducing optical clarity
Solution Approach 1:
The patent modifies the chemical composition parameters of the polycarbonate by incorporating specific ratios of BHPD (70-99.5 mole percent) combined with other dihydric phenols, thereby changing the polymer's crystallization behavior and optical properties while maintaining high Tg
Solution Approach 2:
The invention creates a composite polycarbonate system by combining BHPD-derived units with other dihydric phenol units in specific proportions, resulting in a material that achieves both high thermal stability and suppressed crystallization during film formation
2Temperature
If high Tg copolycarbonate is used to achieve very high glass transition temperature, then thermal resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent establishes specific compositional parameters (70-99.5 mole percent BHPD, 0.5-30 mole percent other dihydric phenols) that simplify the manufacturing process by defining clear synthesis guidelines while achieving the desired high Tg property
3Illumination intensity
If polycarbonate composition is optimized for high optical transparency, then clarity is improved, but thermal stability may be compromised
Solution Approach 1:
The invention optimizes the compositional parameters by selecting specific dihydric phenols with particular molecular structures that maintain optical clarity while supporting high glass transition temperatures through their contribution to polymer chain rigidity
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 copolycarbonates have glass transition temperatures of 250° C. or higher, maintaining optical clarity, low shrinkage, and low thermal expansion, making them suitable for high-performance film applications.
Implementation Method 1
existing high Tg copolycarbonates derived from 3,3-Bis-(4-hydroxyphenyl)-2-phenyl-2,3-dihydroisoindol-1-one (BHPD) tend to crystallize during film formation
Implementation Method 2
polycarbonates with very high Tg and high temperature process compatibility. Other desirable features include high optical transparency, high color neutrality, low shrinkage, and low CTE
Data Source
AI summary
A copolycarbonate is discloses, comprising units of the formula (1)wherein 70 to 99.5 mole percent of the total number of R1 groups are derived from a dihydroxy compound of formula (2)wherein R2 and R3 are each independently a halogen or a C1-6 alkyl group, R4 is a methyl or a phenyl group, and c is independently 0 to 4; and 0.5 to 30 mole percent of the total number of R1 groups are derived from a dihydroxy compound of formula (3)HO—R5—OH (3)wherein at least 60% of the R5 groups are aromatic, and the dihydroxy compound of formula (3) is not the same as the dihydroxy compound of formula (2), and wherein the copolycarbonate has a glass transition temperature of 250° C. or higher.