Hydroxypropyl methylcellulose (HPMC) is a water-soluble non-ionic cellulose ether widely used in building materials, pharmaceuticals, food, personal care products and coatings. In industrial coatings and paints, HPMC has become an important additive due to its unique physical and chemical properties. Its main function is to serve as a thickener, stabilizer, film-forming agent and rheology control agent to improve the workability, storage stability and coating quality of coatings and paints.
1. Basic characteristics of HPMC
HPMC is a compound obtained by chemically modifying natural cellulose. It has the following significant physical and chemical properties, making it widely used in industrial coatings and paints:
Water solubility: HPMC has good solubility in cold water, forming a transparent viscous solution that helps improve the viscosity of the paint.
Thermal gelability: At a certain temperature, HPMC will form a gel and return to a solution state after cooling. This characteristic allows it to provide better coating performance under specific construction conditions.
Good film-forming properties: HPMC can form a continuous film when the paint dries, improving the adhesion and durability of the coating.
Stability: It has high resistance to acids, bases and electrolytes, ensuring the stability of the coating under different storage and use conditions.
2. Main functions of HPMC in industrial coatings and paints
2.1 Thickener
In industrial coatings, the thickening effect of HPMC is particularly important. Its solution has high viscosity and good shear thinning properties, that is, during the stirring or painting process, the viscosity will temporarily decrease, thereby facilitating the construction of the paint, and the viscosity will quickly recover after the construction is stopped to prevent the paint from sagging. This property ensures even coating application and reduces sagging.
2.2 Rheology control
HPMC has a significant impact on the rheology of coatings. It maintains the proper viscosity of coatings during storage and prevents coatings from delaminating or settling. During application, HPMC provides appropriate leveling properties to help the paint distribute evenly over the application surface and form a smooth coating. In addition, its shear thinning properties can reduce brush marks or roll marks produced during the application process and improve the appearance quality of the final coating film.
2.3 Film-forming agent
The film-forming properties of HPMC help improve the adhesion and film strength of coatings. During the drying process, the film formed by HPMC has good toughness and elasticity, which can enhance the crack resistance and wear resistance of the coating, especially in some high-demand industrial coating applications, such as ships, automobiles, etc., HPMC The film-forming properties can effectively improve the durability of the coating.
2.4 Stabilizer
As a stabilizer, HPMC can prevent the precipitation of pigments, fillers and other solid particles in coating formulations, thereby improving the storage stability of coatings. This is especially critical for water-based coatings. HPMC can inhibit delamination or agglomeration of coatings during storage and ensure product quality consistency over a long storage period.
3. Application of HPMC in different coatings
3.1 Water-based coatings
Water-based coatings have received considerable attention in recent years due to their environmental friendliness and low volatile organic compound (VOC) emissions. HPMC is widely used in water-based coatings. As a thickener and stabilizer, HPMC can effectively improve the storage stability and workability of water-based coatings. It provides excellent flow control in low or high temperature environments, making paint smoother when sprayed, brushed or rolled.
3.2 Latex paint
Latex paint is one of the most widely used architectural coatings today. HPMC is used as a rheology control agent and thickener in latex paint, which can adjust the viscosity of latex paint, enhance its spreadability, and prevent the paint film from sagging. In addition, HPMC has a better regulating effect on the dispersion of latex paint and prevents the paint components from settling or stratifying during storage.
3.3 Oil-based paint
Although the application of oil-based coatings has decreased today with increasingly stringent environmental protection requirements, they are still widely used in some specific industrial fields, such as metal protective coatings. HPMC acts as a suspending agent and rheology control agent in oil-based coatings to prevent pigment settling and help the coating have better leveling and adhesion during application.
4. How to use and dosage of HPMC
The amount of HPMC used in coatings is usually determined by the type of coating and specific application needs. Generally speaking, the addition amount of HPMC is usually controlled between 0.1% and 0.5% of the total mass of the coating. The adding method is mostly direct dry powder addition or pre-prepared solution and then added. The solubility and viscosity adjustment effect of HPMC are affected by temperature, water quality and stirring conditions. Therefore, the usage method needs to be adjusted according to the actual process conditions.
Hydroxypropyl methylcellulose (HPMC) is used as a thickener, rheology control agent, film-forming agent and stabilizer in industrial coatings and paints, significantly improving the construction performance, storage stability and final coating film of the coating. quality. With the promotion of environmentally friendly coatings and the increasing market demand for high-performance coatings, HPMC will continue to play an important role in future industrial coatings. Through the rational use of HPMC, the physical and chemical properties of the coating can be effectively improved, and the durability and decorative effect of the coating can be enhanced.