Carboxymethyl hydroxyethyl cellulose
[CAS# 9004-30-2]

Identification

• Classification: Catalysts and additives >> Polymer
• Name: Carboxymethyl hydroxyethyl cellulose
• Synonyms: CMHEC; Cellulose, carboxymethyl 2-hydroxyethyl ether
• Molecular Formula: [C6?H7?O2?(OH)_3-x-y?(_OCH2?COOH)_x?(_OCH2?CH2?OH)_y?]_n
• CAS Registry Number: 9004-30-2
• EC Number: 618-377-0
• SMILES: OC(CO)COC1[C@@H]([C@H]([C@@H]([C@H](O1)COC(=O)O)O)O)O

Properties

• Solubility: readily soluble in sea water (Expl.)

Discovory and Applicatios

Carboxymethyl hydroxyethyl cellulose (CMHEC) is a water-soluble, anionic cellulose ether derived from cellulose by introducing both carboxymethyl (–CH₂COO⁻) and hydroxyethyl (–CH₂CH₂OH) substituents onto the cellulose backbone. This dual substitution imparts a unique combination of properties, including enhanced solubility, stability across a wide pH range, improved thickening ability, and resistance to salt, heat, and shear. CMHEC is widely used in a variety of industrial and consumer applications, especially in the construction, paint, personal care, and oilfield sectors.

The development of CMHEC was part of broader research into multifunctional cellulose derivatives that combine the properties of individual substituents. Carboxymethyl cellulose (CMC) is known for its solubility and anionic character, while hydroxyethyl cellulose (HEC) offers thickening, film-forming, and water retention properties. The synthesis of CMHEC involves the sequential or simultaneous etherification of cellulose with chloroacetic acid (or its salts) and ethylene oxide in an alkaline medium. The resulting polymer contains both ionic and nonionic functional groups, which confer improved performance in demanding formulations.

CMHEC is used extensively in water-based paint and coating formulations as a thickener, stabilizer, and rheology modifier. Its presence ensures appropriate viscosity for application, sag resistance, and pigment suspension. Unlike some other thickeners, CMHEC is stable in systems containing divalent and trivalent metal ions, making it suitable for high-performance architectural and industrial coatings.

In construction materials, CMHEC is employed in dry-mix mortars, tile adhesives, joint compounds, and cement-based renders. It enhances workability, water retention, and adhesion, and it helps control setting time. Its ability to function effectively in alkaline environments and under variable temperature and shear conditions makes it a valuable additive in construction products.

CMHEC is also used in oilfield applications, particularly in drilling fluids and fracturing gels, where it acts as a viscosifier and fluid-loss control agent. Its performance under high-salinity and high-temperature conditions supports its use in complex subsurface environments. It helps stabilize the borehole, transport drill cuttings, and reduce water loss to the formation.

In personal care and cosmetic products, CMHEC functions as a thickening agent, film-former, and stabilizer in shampoos, lotions, creams, and gels. It contributes to texture, product stability, and ease of application. Its mildness, non-toxic nature, and compatibility with surfactants and electrolytes make it suitable for sensitive skin formulations.

The properties of CMHEC can be tailored by adjusting the degree of substitution (DS) for carboxymethyl groups and the molar substitution (MS) for hydroxyethyl groups. Higher DS values increase water solubility and anionic character, while higher MS values improve thickening and tolerance to electrolytes. CMHEC is available in various molecular weights and viscosity grades to meet specific formulation requirements.

CMHEC is typically supplied as a free-flowing white to off-white powder or granule that readily dissolves in cold or hot water to form clear to slightly hazy solutions. It is insoluble in most organic solvents but is compatible with water-alcohol mixtures and certain polar solvents. It exhibits pseudoplastic (shear-thinning) flow behavior, which is beneficial in applications that require ease of application or pumping.

In summary, carboxymethyl hydroxyethyl cellulose is a dual-modified cellulose ether known for its excellent solubility, rheological performance, and stability in a wide range of formulations. It is widely used in paints, construction materials, personal care products, and oilfield chemicals due to its combined ionic and nonionic characteristics, which provide enhanced functionality, robustness, and versatility.