Details of cellulose in paints

What is paint made of?

Paint adds color to our lives. The core ingredients of paints can be briefly summarized into three categories: pigments, binders and solvents.

Pigments are finely ground particles that provide color, coverage and protective properties and can give paints different colors and opacities. They can be inorganic, such as titanium dioxide, iron oxide and carbon black, or organic compounds, such as phthalocyanines, quinacridones and perolefins.

Binders are film-forming components that act like “glue” to hold the pigments together and adhere the dried paint film to the substrate. Common binders include synthetic resins such as acrylics, vinyls, and polyurethanes, as well as natural polymers such as linseed oil and starch.

Solvents are volatile liquids that dissolve or disperse the binder, allowing the paint to be applied in thin, uniform layers. Water is the most common solvent used in latex paints, while oil-based paints use organic solvents such as mineral spirits. The solvents evaporate as the paint dries, leaving behind pigments that are held together by the binder to form a continuous film, which is what we are finally presented with.

In addition to these ingredients mentioned above, paints also contain various additives. Although additives make up only a small percentage of the formulation, they can give paints important qualities. Examples include film forming aids, surfactants, dispersants, preservatives, defoamers and thickeners.

The role of cellulose in paints

Cellulose is a key contributor to the smoothness and consistency of paints, and is a major component of the cell walls of green plants. Processed and modified, cellulose can be used to thicken and stabilize a variety of water-based products, including paints. Due to the complexity of each paint formulation, cellulose is required for efficient thickening while also providing good stability and compatibility with other additives. Cellulose has been used in paints and paints for generations.

In paint formulations, the main function of cellulose is to raise the viscosity of the paint to the desired level and to promote flow. This allows the paint to be easily brushed, rolled or sprayed onto a surface, allowing the paint film to spread evenly and form a consistent dry film. Cellulose also has water retention and suspension properties that help paints retain moisture during the drying process, allowing the pigment particles to be evenly suspended in the paint, which allows more time for the film to coalesce.

Why is HEC commonly used in paints?

As a paint thickener, hydroxyethyl cellulose offers several advantages:

High efficiency: HEC provides high viscosity at low concentrations (0.1-1.0% by weight of the paint). Formulation engineers do not need to add excessive amounts of thickeners to get the product to the desired consistency.

Compatibility: Hydroxyethyl cellulose solutions are clear and colorless, do not conflict with other chemical elements and are compatible with a wide range of paint ingredients. It can be used in both waterborne and solventborne systems.

Enzyme Resistance: Unlike some natural thickeners (e.g. starch), HEC is not easily degraded by microorganisms and has long-term stability.

pH Stability: HEC maintains its thickening efficiency over a wide pH range (4-11) and can be used in a variety of paint formulations.

Different viscosities: HEC is available in different viscosity grades, allowing formulators to select different viscosities for different application needs. Low viscosity hydroxyethyl cellulose provides better flow, while high viscosity hydroxyethyl cellulose creates a stronger thickening network.

Tips for using cellulose thickener in paints

Choose the right grade: Choose the thickener whose molecular weight and degree of substitution are suitable for the specific paint system.

Pre-dispersing the Thickener: To avoid agglomeration, add HEC powders slowly to a well-mixed system, possibly at high speeds, prior to incorporating the powder into the paint.

Allow Adequate Hydration Time: Cellulose thickeners require time to fully hydrate and reach maximum viscosity. This may range from 10 minutes to several hours after initial dispersion, depending on the grade and method of dispersion, so be sure to allow sufficient hydration time.

HEC is currently used in a large number of emulsions and façade paints, but has certain drawbacks, such as poor leveling and flow properties, poor splash resistance and a high price tag, which Kemox has improved with the development of its bonding thickener, HMHEC, which, in addition to improving performance, also blends well with VAE systems.

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