Hydroxypropyl Methylcellulose (HPMC), as a semi-synthetic nonionic cellulose ether, plays an irreplaceable role in the formulation of modern liquid detergents due to its unique physical and chemical properties.
1. Rheological modification: building an ideal rheological system
HPMC forms a three-dimensional network structure through the entanglement of molecular chains, effectively improving the apparent viscosity of liquid detergents (0.5-2% addition can make the viscosity reach 1000-5000 mPa·s). Its shear-thinning properties give the product ideal rheological behavior: it maintains high viscosity when standing to prevent stratification, and the viscosity drops sharply when pouring or pumping to ensure ease of use. Compared with acrylic thickeners, the viscosity of HPMC is less affected by electrolytes, and is particularly suitable for concentrated formulas with high surfactant content. The research and development data of a certain brand of super concentrated laundry detergent shows that the viscosity decay rate of the composite system of HPMC and hydrophobically modified polyurethane (HEUR) is less than 5% after storage at 40°C for 30 days, which is significantly better than that of a single thickening system.
2. Multiphase system stability: synergistic effect at the molecular level
Suspension stability: HPMC prevents the sedimentation of solid particles with a particle size >1μm (such as enzyme preparations, abrasives) through steric hindrance effect. In a certain automatic dishwashing agent formula, 0.3% HPMC can increase the Zeta potential of calcium carbonate particles to -35mV and reduce the sedimentation rate by 78%.
Emulsion stability: In laundry detergent containing silicone oil softener, HPMC and polyoxyethylene ether emulsifiers form a composite interfacial film, the interfacial tension drops to below 2.5mN/m, and the emulsion particle size D50 is stable in the range of 150nm.
Foam control: By adjusting the degree of substitution of HPMC (DS=1.8-2.0), the precise design of high-foaming dishwashing detergents and low-foaming machine detergents can be achieved, and the dynamic foaming height difference can reach more than 300%.
3. Functional enhancement: chemical synergy beyond physical stability
Anti-redeposition: The linear molecular structure of HPMC forms a directional adsorption layer on the fiber surface. Experiments show that the secondary adsorption of carbon black particles by cotton fabrics can be reduced by 60-70%.
Enzyme activity protection: A comparative study shows that the protease activity retention rate of liquid detergents containing HPMC after storage at 50°C for 8 weeks is 92%, which is better than the traditional carboxymethyl cellulose system.
Low-temperature stability: By adjusting the methoxy/hydroxypropoxy ratio (such as type 228), the detergent can remain in a flowing state at -5°C, and the phase change temperature is 8-10°C lower than that of conventional formulas.
4. Green innovation: responding to the needs of sustainable development
Biodegradability: OECD 301B test confirms that the biodegradation rate of HPMC within 28 days can reach more than 75%, which meets the requirements of EU EC/648/2004 regulations.
Renewable raw materials: Cellulose raw materials derived from wood or cotton linters have a carbon footprint 40-60% lower than petroleum-based polymers.
Skin-friendliness: The human patch test verified that the irritation index (TEWL value) of the HPMC-containing formula product is 30% lower than that of the SLES system, which is suitable for sensitive skin care products.
Development trends and challenges:
As liquid detergents develop towards super-concentration and multifunctionality, the modification research of HPMC continues to deepen. Hydrophobic modified HPMC (HMHPMC) introduces long-chain alkyl groups to improve the surfactant tolerance by more than 50% while maintaining thickening performance. The application of nanocellulose/HPMC composite system in transparent formulas achieves the synergistic optimization of transmittance>90% and viscosity>3000mPa·s. However, the stability of HPMC under extreme pH (pH>12) conditions still needs to be improved through structural modification. At present, studies have been conducted to improve the alkali resistance to pH13.5 by grafting propylene oxide segments.
The application of HPMC in liquid detergents has developed from a single thickener to a multifunctional platform additive. Its technical value is not only reflected in the improvement of physical properties, but also in the molecular-level synergy with detergent active ingredients, which promotes the development of products towards high efficiency, environmental protection and intelligence. With the advancement of green chemistry and precision manufacturing technology, the innovative application of HPMC will continue to lead the technological innovation of liquid detergent formulations.
Post time: Apr-15-2025