Metallic Plastic Parts with NIR-Sortable Pigment Compositions
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Solution Overview
Problem
Plastics containing metal effect pigments are difficult to detect and identify using Near Infrared (NIR) spectroscopy due to high reflection of infrared rays by aluminum pigments, leading to inadequate penetration and masking of IR radiation, which hampers accurate sorting in automated systems.
Innovation Solution
A plastic part with a specific mixture of flaky aluminum pigments and silvery, absorbing pearlescent pigments, where the concentration and particle size distribution are optimized to ensure adequate IR penetration and detection, maintaining a metallic appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If flaky aluminum pigments are added to plastic to achieve metallic appearance, then opacity and brightness are improved, but detection accuracy by NIR spectroscopy deteriorates due to high reflection and masking of IR radiation
Solution Approach 1:
The patent changes the concentration parameter of aluminum pigments from conventional high levels (0.5-5 wt%) to optimized low levels (0.01-0.5 wt%), specifically controlling the product of concentration and thickness (cAl×tpl) to enable sufficient IR penetration while maintaining acceptable metallic appearance
Solution Approach 2:
The patent creates a composite pigment system combining flaky aluminum pigments with silvery pearlescent pigments in specific ratios, where the aluminum provides brightness and the pearlescent pigments provide detection capability, achieving both metallic appearance and NIR detectability
2Object-generated harmful factors
If high concentration of aluminum pigments is used to enhance metallic effect, then hiding power is improved, but IR radiation penetration is reduced, preventing accurate plastic identification
Solution Approach 1:
The patent optimizes the concentration parameter by establishing specific ranges for cAl×tpl (0.005-0.5 wt.% cm for D10≥7.0 μm pigments, 0.003-0.1 wt.% cm for D10<7.0 μm pigments), balancing hiding power with IR penetration capability
Solution Approach 2:
The patent applies different pigment concentrations and types to different applications based on plastic part thickness, using higher concentrations for thinner parts and lower concentrations for thicker parts to maintain detection capability across various geometries
3Ease of manufacture
If conventional pigment concentrations are used to achieve cost-effective metallic appearance, then manufacturing cost is reduced, but automated sorting capability is lost
Solution Approach 1:
The patent establishes specific concentration ranges and cAl×tpl product limits that enable both cost-effective production (using minimal aluminum pigment) and automated sorting capability (maintaining sufficient IR transmission), creating a new parameter regime that satisfies both requirements
Solution Approach 2:
The patent introduces silvery pearlescent pigments as an intermediary that bridges the conflict between aluminum pigment concentration and detection capability, allowing reduced aluminum content while maintaining metallic appearance and enabling NIR detection
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 enables reliable detection and sorting of plastics with a metallic look in automated systems, balancing cost-effectiveness and process stability while maintaining opacity and brightness.
Implementation Method 1
silvery, absorbing pearlescent pigments
Implementation Method 2
aluminum pigments exhibit a masking effect of the plastic part against IR radiation penetration
Data Source
AI summary
Plastic part having a mean thickness tpl containing a mixture of effect pigments comprising flaky aluminum pigments obtained by milling of aluminum or aluminum-based alloy powder in a concentration cAl and silvery, absorbing pearlescent pigments in a concentration cP, wherein i) for flaky aluminium pigments having a D10≥7.0 μm: cAl*tpl is in a range of 0.0 to 0.20 wt. % cm, or ii) for flaky aluminium pigments having a D10<7.0 μm: cAl*tpl is in a range of 0.0 to 0.036 wt. % cm, wherein each concentration refers in wt. % to the total plastic part.