Hot-melt coating is a modern technique that eliminates the need for solvents by applying the coating material in a molten state directly onto the substrate. Unlike traditional methods that rely on organic solvents or water, this process avoids solvent evaporation, reducing processing time and environmental impact. Over the past decade, researchers have explored its potential, and it has gained significant traction in industries such as pharmaceuticals, food, and metal coatings abroad. In contrast, domestic research in this area remains limited.
One of the key advantages of hot-melt coating is its eco-friendly nature, as no solvents are used. This not only reduces waste but also minimizes energy consumption. While water-based coatings are more common in some regions, they face challenges like microbial contamination and incompatibility with certain drugs that are prone to hydrolysis. Hot-melt technology overcomes these limitations, offering better stability and controlled drug release.
Compritol 888ATO, a commonly used hot-melt coating material, was tested in experiments using theophylline as a model drug. Researchers optimized parameters such as air flow, temperature, and spray rate to study how these factors influence coating efficiency and drug release. They found that the coating temperature plays a critical role: too high, and the material may not adhere; too low, and the coating may not spread evenly, affecting drug release profiles.
In one experiment, theophylline particles were coated under specific conditions, including an inlet air temperature of 75–78°C and a coating material temperature of 120°C. The results showed that a coating temperature of 67°C produced sustained release, while lower temperatures resulted in minimal improvement. Additionally, the size and uniformity of the coating droplets influenced the effectiveness of the process. Smaller droplets led to better coverage and higher coating efficiency.
The study also revealed that the amount of coating material significantly impacted drug release. Higher weight gain led to slower initial release, demonstrating the importance of optimizing the coating formulation. Furthermore, particle size affected release behavior—smaller particles required more coating material to achieve the same effect, resulting in slower drug release compared to larger particles.
Overall, hot-melt coating offers a promising alternative to conventional techniques, with benefits in cost, efficiency, and environmental sustainability. As research continues, its application in the pharmaceutical industry is expected to expand.
A special reactive surfactant compound, with excellent diffusion and dispersion property, very strong migrating power to disperse dyes, under the condition of high temperature and high pressure, dyestuffs are allowed to migrate from high concentration to low concentration, until all areas are dyed uniformly, thus the levelling out of the unlevel dyeing can be achieve.
migrating power, dye specks, unlevel dyeing, high temperature and high pressure, Simple application
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