5 Must-Have Features in a Texanol

Author: Evelyn y

May. 27, 2024

Key Features of Texanol for Effortless Latex Paint Coalescence

It's unfortunate that latex paint must undergo a drying phase. Regardless of its stability or precise formulation, this paint must transition through the critical drying phase to form a functional film. At this pivotal moment of changing from liquid to solid, known as coalescence, Texanol Ester-Alcohol from Eastman Chemical Co. ensures success rather than failure.

To delve into the role of coalescing aids, it's essential to examine the film formation process in latex paint. The emulsified polymers destined to form the paint film are tiny droplets of solid material dispersed in water. On a porous surface, some water, and potentially some coalescent, depending on solubility, will migrate into the substrate. As water content decreases during drying, the latex particles draw closer. When the surface repulsive forces can no longer keep them apart, the emulsion collapses and solidifies.

If the latex particles are sufficiently soft, they merge upon collapse to form a film. Conversely, if they are too hard, no merging occurs, and the coating may crack, flake, or pulverize. The coalescing aid in the formulation ensures the latex particles are pliable enough at the point of coalescence to create a continuous film.

The ability for a polymer to form a film is highly temperature-dependent. Each polymer has a specific minimum film-formation temperature (MFFT) below which film formation ceases. Usually measured using an MFFT bar apparatus according to ASTM Method D, polymers with low MFFT values form films easily, but the films typically lack desirable properties like durability or low surface tack. Paint formulation polymers generally have MFFT values in the 15-45°C range, forming durable, nontacky films above the MFFT. However, applying latex paint at temperatures close to 0°C necessitates adding a coalescing aid to achieve an optimal film below the MFFT of the base emulsion.

A coalescing aid acts as a temporary plasticizer for film-forming polymers. Its purpose is to soften the polymer during critical fusion, allowing individual particles to combine and form a continuous film. The coalescing aid must evaporate slowly, enabling the paint film to attain maximum durability and aesthetic properties. An ideal coalescing aid must meet three criteria: actively dissolve the base polymer, efficiently reduce the system's MFFT, and have a significantly lower evaporation rate than water. Additionally, low water solubility is highly desirable. The ensuing discussion shows how Texanol Ester-Alcohol (E-A) meets these requirements and why it's the most widely used coalescent for latex paint globally.

Ensures Compatibility with Base Polymers

Compatibility with the base polymer is essential for a coalescing aid, determined by its polymer solubility. Texanol E-A, chemically 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, contains both hydroxyl and ester functional groups, making it structurally similar to most paint formulation polymers. This similarity renders Texanol a robust solvent for acrylic, polyvinyl acetate, and polyvinyl chloride polymers, commonly used in paint formulations. Moreover, Texanol's hydrophobicity ensures it is absorbed directly into the emulsified polymer particles, effectively reducing the system's MFFT.

Delivers High-Efficiency Performance

Efficiency is a key attribute distinguishing coalescing aids. Every polymer has a distinct glass-transition (Tg) temperature, defining its baseline MFFT. When combined with a compatible coalescing aid, the system's MFFT lowers as the coalescent concentration increases, reaching the desired performance level. The efficiency is sensitive to the polymer structure, affecting the needed concentration of a coalescent to achieve desired performance levels.

The efficient coalescing aid is a critical cost determinant, with the cost/benefit ratio varying per formulation. Despite Texanol not always being the most efficient, considering total cost/benefit and other factors, it remains the preferred coalescent globally.

Features Optimal Evaporation Rate

An effective coalescing aid must have a slower evaporation rate than water under any drying condition. The slow evaporation rate of Texanol ensures it remains in the drying paint film long enough for proper film formation, making it ideal for most flat or semi-gloss paint applications. However, for high-gloss paints, Eastman EEH may be preferable due to its faster evaporation rate and higher efficiency.

Exhibits Low Water Solubility

Low water solubility is crucial for a coalescing aid's final performance in paint formulations, affecting how it's partitioned within the paint system. A water-insoluble coalescent concentrates inside and on the emulsion particles' surface, softening the polymer effectively. Conversely, water-soluble coalescents may migrate during application or evaporate prematurely, causing application problems despite positive laboratory results.

Enhances Durability, Gloss, and Color Development

Although a major function of coalescing aids is improving low-temperature drying, they also impact other paint properties like gloss, scrub resistance, and color development. Studies show that Texanol outperforms other coalescing aids, including Eastman EEH and Eastman DB, in gloss and scrub resistance, particularly under demanding conditions. Additionally, Texanol improves color development by affecting the paint film's surface roughness, enhancing light reflectance and resulting in more vibrant colors.

In summary, the majority of emulsions used in paint production require coalescing aids to develop durable and aesthetically pleasing films across all application conditions. Texanol Ester-Alcohol has proven to be an invaluable tool in the paint industry, ensuring consistent performance whether in the manufacturing lab or the hands of the end-user.

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