Hydroxy Propyl Methyl Cellulose (HPMC) is a common ingredient used in the formulation of paints and coatings. It is a water-soluble polymer that acts as a thickener, rheology modifier, and binder in paint formulations.

Here are some of the ways that HPMC is used in paint:

1. Improving viscosity: HPMC is used as a thickener to increase the viscosity of paint. This helps to prevent settling and sagging, and can also improve the ease of application.
2. Enhancing workability: HPMC can improve the workability of paint by providing better leveling, dispersion, and flow properties. This can result in a smoother and more even finish.
3. Controlling water retention: HPMC can help to control the water retention of paint by absorbing water and releasing it slowly over time. This can help to prevent cracking and improve the durability of the paint.
4. Providing binding properties: HPMC can act as a binder in paint formulations, helping to bind the pigment and other ingredients together. This can improve the adhesion and durability of the paint.
5. Reducing foaming: HPMC can help to reduce the amount of foam that is produced during the mixing and application of paint. This can improve the appearance of the paint and reduce the amount of time needed for surface preparation.

Overall, HPMC is a useful ingredient in the formulation of paints and coatings. Its properties can help to improve the performance and appearance of the paint, making it a popular choice in the industry.