Differences between Surface Treated and Non-Surface Treated Melacoll HPMC Products

MelaColl Hydroxypropyl Methylcellulose (HPMC) can be divided into two types: surface-treated HPMC and non-surface-treated HPMC. Surface treatment type, also known as delayed dissolution/hydration HPMC, refers to the use of cross-linking agents to treat its surface during the production process, so that HPMC can be quickly dispersed in cold water, but will not dissolve in this step. By stirring evenly, it will dissolve and the viscosity will slowly increase.

In contrast, HPMC without surface treatment clumps in cold water but disperses quickly when mixed with hot water. By stirring, the temperature of the solution will drop to a certain temperature (in our company, the gel formation temperature of the resulting product is about 65°C-75°C). The viscosity will slowly increase until a clear, viscous gel forms.

Non-surface treated HPMC:

When HPMC products with untreated surfaces are dissolved alone, their particles quickly dissolve and form a film, causing water to no longer enter other particles, causing agglomeration and agglomeration.

Untreated HPMC is characterized by rapid dissolution of individual particles in neutral, alkaline and acidic states. Still, it cannot disperse between particles in the liquid, leading to agglomeration and clumping.

In actual operation, after this series of products are physically dispersed with solid particles such as rubber powder, cement, and sand, they dissolve very quickly without aggregation or agglomeration. Therefore, HPMC without surface treatment can be used for cement-based and gypsum-grade tile adhesives, but cannot be used for paste emulsion-based tile adhesives.

Surface treatment HPMC:

After surface treatment, HPMC product particles can be dispersed in neutral water without agglomeration, but will not become sticky immediately. After a certain period of soaking and the chemical structure of the surface treatment is destroyed, water can dissolve the HPMC particles. At this point the product particles have been fully dispersed and absorbed enough moisture so that the product will not clump or clump after dissolving.

The characteristic of surface-treated HPMC products is that the particles can disperse with each other in aqueous solution. It dissolves quickly in alkaline state and slowly in neutral and acidic state.

In actual production operations, this series of products are often dispersed and dissolved with other solid particulate matter under alkaline conditions. Its dissolution rate is no different from the untreated product. During the construction process, both cement tile adhesive and gypsum-based tile adhesive are alkaline systems, and the amount of HPMC added is very small. It can be evenly dispersed among these particles. HPMC dissolves rapidly when water is added. Paste-based emulsion adhesive tile adhesives are typically neutral or slightly acidic products. Although the use of this series of products requires a certain dissolution time, it is impossible to use HPMC without surface treatment to accelerate dissolution.

The physical and chemical indicators of surface-treated and non-surface-treated HPMC are the same, but the application fields are different. In short, delayed dissolution is generally used for water-based substances, such as detergents, cement, wet mortars, etc. Slow-dissolving hpmc needs to be added to the cement matrix with a content of 2%. Non-delayed dissolving hpmc is our company's leading product. Delayed dissolution does not become viscous in neutral aqueous solutions for one to two hours, while non-delayed dissolution becomes immediately viscous in aqueous solutions. In one case, the viscosity onset time of slow-dissolving HPMC and non-slow-dissolving HPMC is the same, that is, in an alkaline solution with a pH value less than 9. At this point, the application areas of the two types of HPMC may overlap.