Opacifying Pigment Particles with Segmented Polymer Shell
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Solution Overview
Problem
Existing opacifying coatings and plastics face challenges in achieving high opacity with minimal pigment usage, as the refractive index difference between pigments and polymers is not adequately exploited, leading to suboptimal light scattering efficiency.
Innovation Solution
Pigment particles with a refractive index of at least 1.8 are encapsulated in a polymeric shell with a thickness of 25 nm to 200 nm, comprising two polymer phases where the first phase has a refractive index 0.03 units less than the second phase, optimizing light scattering and maintaining desirable polymer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a low refractive index polymer is used to maximize light scattering efficiency, then opacity is improved, but desirable coating properties such as gloss, water resistance, and stain resistance deteriorate
Solution Approach 1:
The polymer shell is segmented into two distinct phases: an inner low refractive index polymer phase (RI 1.40-1.55) for light scattering, and an outer high refractive index polymer phase (RI 1.55-1.70) for maintaining coating properties. This segmentation allows each phase to perform its specialized function without compromising the other.
Solution Approach 2:
Different regions of the polymer shell have different refractive indices tailored to specific functions: the inner phase optimizes for light scattering efficiency while the outer phase optimizes for gloss and water resistance. This local differentiation of optical properties resolves the contradiction between opacity and coating quality.
2Illumination intensity
If more opacifying pigment is used to increase hiding performance, then opacity is improved, but the amount of pigment required increases
Solution Approach 1:
The refractive index parameter of the polymer shell is optimized to maximize the difference with the pigment particle (RI ≥1.8), thereby maximizing light scattering efficiency per unit pigment. This parameter optimization reduces the quantity of pigment needed to achieve target hiding performance.
Solution Approach 2:
The encapsulated pigment structure creates a composite material with enhanced optical properties. The combination of high RI pigment core and low RI polymer shell generates superior light scattering compared to bare pigment, reducing the overall pigment quantity required in the coating formulation.
3Illumination intensity
If the thickness of the low refractive index polymer shell is increased to enhance light scattering, then opacity is improved, but the shell thickness exceeds the optimal range
Solution Approach 1:
Rather than using a uniformly thick low RI shell, the invention applies a relatively thin inner low RI phase (25-200 nm) that provides sufficient light scattering enhancement, combined with an outer high RI phase that maintains coating properties. This partial action approach achieves opacity improvement without excessive total shell thickness.
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
This approach enhances light scattering efficiency and opacity while maintaining properties like gloss and water resistance, achieving better hiding performance with reduced pigment content.
Implementation Method 1
Higher light scattering efficiency occurs when the difference in refractive indexes of the opacifying pigment particles and the polymeric components of the coating or plastic are larger
Data Source
AI summary
. An opacifying particle including a pigment particle having an average particle diameter of from 0.15 micron to 1.0 micron and a refractive index of at least 1.8, the pigment particle being at least partially encapsulated in a polymeric shell having a calculated thickness of from 35 nm to 200 nm, wherein the polymeric shell includes at least a first polymer phase and a second polymer phase, wherein the first polymer is substantially in contact with the surface of the pigment particle providing a calculated shell thickness of at least 25 mm. and wherein the first polymer has a refractive index of at least 0.03 units less than the refractive index of the second polymer is provided as is a composition such as, for example, a coating or a plastic including the opacifying particle. Further provided is a composition including pigment particles having an average particle diameter of from 0.15 micron to 1.0 micron and a refractive index of at least 1.8, the pigment particles being at least partially encapsulated in a shell of a first polymer having a calculated thickness of from 25 nm to 200 nm, and the encapsulated pigment particles in contact with from 10% to 600% by weight, based on the weight of the first polymer, second polymer, wherein the first polymer has a refractive index of at least 0.03 units less than the refractive index of the second polymer.