Halogen-Free Flame Retardant Polycarbonate via Composite Synergy

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Solution Overview

Problem

Existing polycarbonate compositions lack effective halogen-free flame retardance while maintaining impact strength, heat resistance, and moldability, which are crucial for thermoplastic molding applications.

Innovation Solution

A thermoplastic molding composition comprising 60-99% aromatic poly(ester) carbonate with a weight-average molecular weight of at least 25,000, 1-20 phr graft copolymer having a core-shell morphology with interpenetrated polyorganosiloxane and poly(meth)alkyl acrylate components, 2-20 phr phosphorus-containing compounds, and 0.1-15 phr boron compounds with an average particle diameter of 2-10 μm, all of which work together to provide halogen-free flame retardance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If halogen-free flame retardant composition is used, then flame retardance is improved, but impact strength deteriorates

Engineering Contradiction:

Improveflame retardanceVSAvoidimpact strength

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent employs a composite flame retardant system combining phosphorus-containing compounds (2-20 phr) with boron compounds (0.1-15 phr) and a specific graft copolymer (1-20 phr). This multi-component composite approach creates synergistic effects that achieve effective flame retardance while maintaining impact strength, resolving the contradiction between flame safety and mechanical properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The graft copolymer features a core-shell morphology with polyorganosiloxane and poly(meth)alkyl acrylate components distributed in specific phases. This local structural differentiation allows the flame retardant system to function effectively at flame fronts while preserving the bulk material's toughness and impact resistance.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If halogen-free flame retardant composition is used, then flame retardance is improved, but heat resistance deteriorates

Engineering Contradiction:

Improveflame retardanceVSAvoidheat resistance

Core Design Contradiction:

Object-affected harmful factorsVSTemperature

Solution Approach 1:

The synergistic combination of phosphorus compounds, boron compounds, and the specialized graft copolymer creates a composite system that forms protective char layers and suppresses heat release during combustion. This composite approach achieves flame retardance without compromising the base polycarbonate's inherent heat resistance.

Inventive Principle:

Principle #40Composite materials

3Object-affected harmful factors

If halogen-free flame retardant composition is used, then flame retardance is improved, but moldability deteriorates

Engineering Contradiction:

Improveflame retardanceVSAvoidmoldability

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The graft copolymer's specific composition parameters (core-shell morphology with polyorganosiloxane and poly(meth)alkyl acrylate) and controlled quantity (1-20 phr) modify the melt rheology of the flame retardant system. This parameter optimization ensures compatible processing behavior during injection molding while maintaining effective flame retardant performance.

Inventive Principle:

Principle #35Parameter changes

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 composition achieves excellent flame retardance, impact strength, heat resistance, and moldability without using halogens, ensuring long-term heat stability and reduced smoke formation in thermoplastic moldings.

Implementation Method 1

The composition achieves excellent flame retardance, impact strength, heat resistance, and moldability without using halogens

Methodology Applied

Scientific EffectFlame retardance: Combustion

Implementation Method 2

graft (co)polymer having a core-shell morphology, including a grafted shell that contains polymerized alkyl(meth)acrylate and a composite rubber core that contains interpenetrated and inseparable polyorganosiloxane and poly(meth)alkyl acrylate

Methodology Applied

Scientific EffectInterpenetrating polymer network: Cohesion

Data Source

PatentUS9856406B2Flame retardant polycarbonate

Publication Date: 2018.01.02 COVESTRO LLC

AI summary

The present invention provides a thermoplastic molding composition comprising A) 60 to 99 percent by weight (pbw) aromatic poly(ester) carbonate having a weight-average molecular weight of at least 25,000, B) 1 to 20 parts per 100 parts resin (phr) graft (co)polymer having a core-shell morphology, comprising a grafted shell that contains polymerized alkyl(meth)acrylate and a composite rubber core that contains interpenetrated and inseparable polyorganosiloxane and poly(meth)alkyl acrylate where the weight ratio of polyorganosiloxane/poly(meth)alkylacrylate/grafted shell is 70-90/5-15/5-15, C) 2 to 20 phr phosphorus-containing compound, and D) 0.1 to 15 phr boron compound having average particle diameter of 2 to 10 microns.