Polycarbonate Flame-Retardant Sheet for Battery Pack Cases

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Solution Overview

Problem

Polycarbonate resin compositions face challenges in achieving high flame retardancy, especially in thin sheets or films, and in producing battery pack cases with balanced fluidity, strength, and heat resistance, as existing phosphorus-containing flame retardants compromise impact resistance and fluidity.

Innovation Solution

A polycarbonate resin composition containing 7 to 30 parts by mass of a specific phosphorus-containing flame retardant, carbon black, and optional inorganic fillers or stabilizers, extruded into a sheet or film with controlled thickness distribution, providing excellent flame retardancy and light-blocking properties, and processed into thin-walled battery pack cases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If phosphorus-containing flame retardants are blended with polycarbonate resins to achieve flame retardancy, then flame retardancy is improved, but impact resistance is greatly reduced

Engineering Contradiction:

Improveflame retardancyVSAvoidimpact resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent changes the chemical structure parameters of phosphorus-containing compounds by specifying precise structural formulas (Formula 1 and Formula 2) with defined molecular weights and structural characteristics. This parameter optimization allows achieving flame retardancy while minimizing the negative impact on impact resistance, resolving the contradiction between these two properties.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite material system by blending polycarbonate resin with specifically structured phosphorus-containing compounds. The composite achieves synergistic effects where the optimized phosphorus compound structure provides flame retardancy without severely compromising the polycarbonate's impact resistance, thus resolving the contradiction.

Inventive Principle:

Principle #40Composite materials

2Reliability

If phosphorus-containing flame retardants are used to achieve high flame retardancy, then flame retardancy is improved, but fluidity is reduced

Engineering Contradiction:

Improveflame retardancyVSAvoidfluidity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent optimizes physical parameters of the phosphorus-containing compounds by specifying molecular weight ranges and structural configurations. These parameter changes ensure the flame retardants maintain appropriate melt flow characteristics, preserving fluidity while achieving high flame retardancy in the molded products.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If halogen-containing flame retardants are used to achieve flame retardancy, then flame retardancy is improved, but heat stability is reduced and corrosion of screws and dies occurs

Engineering Contradiction:

Improveflame retardancyVSAvoidheat stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent extracts and eliminates halogen elements from the flame retardant system, replacing them with phosphorus-containing compounds having specific non-halogen structures (Formula 1 and Formula 2). This extraction of harmful halogen components resolves the contradiction by maintaining flame retardancy through phosphorus chemistry while eliminating heat stability degradation and corrosion issues associated with halogens.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the potential harm of using flame retardants (which can cause heat stability issues and corrosion) into a benefit by carefully selecting phosphorus-containing compounds with optimized structures. The specific molecular weight ranges and structural features transform what could be harmful interactions into beneficial effects, maintaining both flame retardancy and heat stability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Reliability

If halogen-containing flame retardants are used to achieve flame retardancy, then flame retardancy is improved, but environmental pollution is caused

Engineering Contradiction:

Improveflame retardancyVSAvoidenvironmental pollution

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes halogen elements from the flame retardant composition, replacing them with environmentally benign phosphorus-containing compounds. This extraction eliminates the generation of harmful halogenated dioxins and furans during combustion, resolving the environmental pollution issue while maintaining effective flame retardancy.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS10263225B2Flame-retardant sheet or film, products comprising the same and process for production thereof

Publication Date: 2019.04.16 MITSUBISHI GAS CHEM CO INC

AI summary

A thin sheet or film excellent in flame retardancy and light-blocking properties is provided. A battery pack case and others with high flame retardancy are each molded from this thin film. A thin sheet or film Including a specific phosphorus-containing flame retardant in a polycarbonate resin is excellent in thickness accuracy, flame retardancy and appearance. A thin sheet or film excellent in flame retardancy and also having a thickness of 0.01 to 0.25 mm was formed when controlling its thickness uniformly during sheet or film molding. Further, upon addition of carbon black, the resulting sheet or film was found to have good light-blocking properties and higher flame retardancy. Moreover, when used as a film packaging material for battery packs, the sheet or film of the present invention was found to be excellent in film strength and ultrasonic weldability.