Now more than ever, there is an increased need to clean surfaces frequently. Many solvent- and water-based cleaning solutions used to clean highly trafficked, often contaminated surfaces are strongly acidic or alkaline. For these cleaners to work optimally, an extended dwell time on surfaces is usually required. These facts pose a unique challenge for formulators, as they need to produce a cleaning solution with stable viscosity at extreme pH.
Xanthan Gum Thickeners
Xanthan gums are often used as rheology modifiers in water-based cleaners due to their inexpensive nature and stability in a wide pH range. However, they do not offer good compatibility and performance in cleaners and detergent formulations that contain organic solvents. In addition, the anionic nature of xanthan gum makes it incompatible in formulations that contain cations.
METHOCEL™ hydroxypropyl methylcellulose (HPMC) polymers are nonionic, bio-based polymers that serve as excellent thickeners for water-based and solvent-based household and industrial cleaners as well as detergents. Like xanthan gum, they are resilient in highly acidic and alkaline systems and produce consistent, stable viscosity from pH 2 to 13. Unlike xanthan gum, however, METHOCEL™ HPMC polymers are compatible with cationic materials and a variety of solvents commonly used in cleaner and detergent formulations. Some of the typical organic solvents used with METHOCEL™ are listed below.
METHOCEL™ polymers are also pseudoplastic and impart a shear-thinning nature to solutions. Adding pseudoplasticity to a cleaning solution will allow it to be sprayed onto surfaces easily. Once applied to the surface and at rest, the solution's viscosity will build up, holding the cleaner in place more effectively under the force of gravity. This is useful for cleaning solutions that need to be applied onto angled or overhead surfaces.
Besides providing thickening and pseudoplasticity to solvent-based and water-based cleaning products in a wide pH range, METHOCEL™ will also add soil antiredeposition properties on surfaces. This extends the utility of the cleaner, making recleaning surfaces easier. METHOCEL™ also functions as a surfactant to help stabilize emulsions and different phases that may be present within cleaners. Below are grade recommendations for METHOCEL™ in cleaning and detergent applications.
METHOCEL™ polymers are very hygroscopic and must be completely dispersed in solution prior to hydration and thickening; otherwise, lumps will form. Proper dispersion can be carried out in a few different ways. These methods are covered in the sections below or, alternatively, in this video.
Dispersion in Hot Water
Dispersing in hot water, also called the "hot/cold" technique, takes advantage of the fact that METHOCEL™ is insoluble in hot water and highly soluble in cool water. METHOCEL™ is first dispersed by mixing with one-third of the total required volume of water heated to 90°C. Once all METHOCEL™ particles are wetted and dispersed, the remaining volume of cold water or ice is added. Once the dispersion temperature reaches the point where METHOCEL™ is soluble, the particles will hydrate and begin thickening the solution.
Dry METHOCEL™ powders can be mixed with other dry ingredients before adding them to the water component. Dry blending ensures METHOCEL™ particles are separated and can be completely wetted out and hydrated when water is added. The recommended ratio of dry ingredients to METHOCEL™ powder varies from 7:1 to 3:1.
Dispersion in Nonaqueous Solvents
Direct solubility of most METHOCEL™ grades in nonaqueous solvents is limited. In formulations that utilize water-miscible organic solvents, METHOCEL™ powder can first be dispersed in the organic solvent before adding water. At least 5 to 8 parts of solvent should be used to every 1 part of METHOCEL™ when preparing dispersions. The addition of water will then trigger hydration and thickening.
Rheology modifiers are particularly useful in many household, industrial, and institutional cleaning and detergent formulations. In these formulations, rheology modifiers control viscosity to provide sufficient coverage on many surfaces, including those that are angled or overhead.
Many of these formulations use traditional thickening agents like xanthan gum, which limits the versatility of cleaners that can be made. METHOCEL™ polymers are naturally derived thickeners with great stability in extreme pH as well as organic solvents, both of which are common in many cleaners used today. METHOCEL™ also provides value beyond thickening by adding soil antiredeposition and solution stabilization for cleaners.
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