Flame-Resistant Polycarbonate with Low Molecular Weight Degradation
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Solution Overview
Problem
Polycarbonate compositions face issues with polymer chain degradation and reduced flame retardancy due to the incorporation of UV absorbers, leading to poorer mechanical properties and increased burning dripping, which are not effectively addressed by existing technologies.
Innovation Solution
A composition comprising polycarbonate, alkali metal or alkaline earth metal salts of fluorinated organic acids, and reactive UV absorbers, where the alkali metal or alkaline earth metal salt has a low content of sulfate and fluoride, and the UV absorber is primarily present in the free form, minimizing polymer chain incorporation and maintaining high relative solution viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If UV absorbers are incorporated into the polycarbonate chain, then UV protection is improved, but molecular weight degradation occurs leading to poorer mechanical properties and reduced flame retardancy
Solution Approach 1:
The patent uses an esterification catalyst as an intermediary substance that enables controlled incorporation of UV absorbers into the polycarbonate chain. This catalyst mediates the chemical reaction between the UV absorber and polymer chain, allowing UV protection to be achieved while maintaining control over the degree of incorporation to prevent excessive molecular weight degradation and preserve mechanical properties.
2Object-affected harmful factors
If UV absorbers are incorporated into the polycarbonate chain, then UV protection is improved, but flame retardancy deteriorates due to molecular weight degradation
Solution Approach 1:
The esterification catalyst acts as an intermediary that controls the incorporation process of UV absorbers. By regulating this chemical reaction, the patent achieves UV protection while preventing excessive chain scission that would compromise flame retardancy, thus maintaining the polymer's reliability in fire safety applications.
3Object-affected harmful factors
If reactive UV absorbers with free functionalities are used, then UV protection is enhanced, but polymer chain incorporation increases leading to molecular weight degradation
Solution Approach 1:
The patent employs parameter changes by controlling the esterification reaction conditions through the use of specific catalysts and reaction parameters. This allows regulation of the degree of UV absorber incorporation into the polymer chain, achieving adequate UV protection while minimizing molecular weight degradation and maintaining compositional stability.
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 solution achieves improved flame retardancy and mechanical properties with reduced polymer degradation, maintaining a high relative solution viscosity, thereby overcoming the limitations of existing polycarbonate compositions with increased UV absorber incorporation.
Implementation Method 1
Incorporation of the UV absorber in this context leads to a molecular weight degradation of the polymer, which can be determined via the relative solution viscosity
Implementation Method 2
at least one reactive UV absorber... which as a rule are combustible
Implementation Method 3
This happens in particular in the case of reactive UV absorbers, which have free functionalities, such as e.g. free hydroxyl groups, which can be incorporated into the polycarbonate chain
Data Source
AI summary
The present invention relates to flameproofed, UV-resistant polycarbonate moulding compositions having improved flame retardancy and a low incorporation of the UV absorber into the polymer chain and a resulting higher relative viscosity compared with the polycarbonates having increased incorporation of UV absorber, wherein the polycarbonate compositions compriseA) at least one polycarbonate having an average molecular weight Mw of from 18,000 to 40,000 g/mol,B) one or more reactive UV absorbers andC) at least one alkali metal or alkaline earth metal salt of a fluorinated organic acid, and C) has a content of free sulfate of less than 0.007 wt. % and a content of free fluoride of less than 0.017 wt.%, in each case based on the weight of C).