Abstract

Controlled-release capsule systems are disclosed for delivering pigment paste into coating agents such as paints and plasters, improving on prior-art capsules having a fixed-thickness, passively dissolving polyvinyl alcohol (PVA) wall. Dissolution is engineered through crosslinked, co-polymer-blended or grafted PVA films and can be made responsive to pH, temperature or mechanical shear, including two-phase delay-then-burst release. Capsule architectures include variable wall thickness within one capsule, surface-area-maximising geometries, multi-layer walls, engineered rupture points, capsule-in-capsule and two-component formats, microporous membrane walls and automation-compatible cylindrical formats. The dissolved wall can act as an active material in the coating, providing pigment dispersion, rheology modification, self-healing, biocide release, UV protection or thermal management. Pigment engineering and manufacturing aspects include double micro-encapsulation of pigment particles, thermochromic and photochromic pigments, dissolution indicators and conductivity-based endpoint detection, and manufacture by thermoforming, filling and sealing with in-line pneumatic and optical integrity testing and automated dosing calibration. Disclosed in South African provisional patent application No. 2026/04448, filed 24 April 2026. Parties interested in collaboration, licensing or development during the priority period are invited to contact the author at [email protected].

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This work is licensed under a Creative Commons Attribution 4.0 License.

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