What is Cellulose Ether application？

It introduces the cellulose ether preparation, cellulose ether performance and cellulose ether application , especially the application in coatings.
Key words: cellulose ether, performance, application
Cellulose is a natural macromolecular compound. Its chemical structure is a polysaccharide macromolecule with anhydrous β-glucose as the base ring. There is one primary hydroxyl group and two secondary hydroxyl groups on each base ring. Through its chemical modification, a series of cellulose derivatives can be obtained, and cellulose ether is one of them. Cellulose ethers are widely used in many industries.

1.Preparation

Cellulose ether is obtained by reacting cellulose with NaOH, then reacting with various functional monomers such as monochloromethane, ethylene oxide, propylene oxide, etc., and washing the by-product salt and cellulose sodium.

2.Performance

2.1 Appearance: Cellulose ether is white or milky white, odorless, non-toxic, fibrous powder with fluidity, easy to absorb moisture, and dissolves into a transparent viscous stable colloid in water.
2.2 Ionicity: MC, MHEC, MHPC, HEC are nonionic; NaCMC, NaCMHEC are anionic.
2.3 Etherification: The characteristics and degree of etherification of etherification will affect the performance of cellulose ether during etherification, such as solubility, film-forming ability, bonding strength and salt resistance.
2.4 Solubility: (1) MC is soluble in cold water, insoluble in hot water, and also soluble in some solvents; MHEC is soluble in cold water, insoluble in hot water and organic solvents. However, when the aqueous solution of MC and MHEC is heated, MC and MHEC will precipitate. MC precipitates at 45-60°C, while the precipitation temperature of mixed etherified MHEC rises to 65-80°C. When the temperature is lowered, the precipitate redissolves. (2) HEC, NaCMC, and NaCMHEC are soluble in water at any temperature, but insoluble in organic solvents (with a few exceptions).
2.5 Delayed swelling: Cellulose ether has a certain delayed swelling in neutral pH water, but it can overcome this delayed swelling in alkaline pH water.
2.6 Viscosity: Cellulose ether dissolves in water in the form of colloid, and its viscosity depends on the degree of polymerization of cellulose ether. The solution contains hydrated macromolecules. Due to the entanglement of macromolecules, the flow behavior of solutions differs from that of Newtonian fluids, but exhibits a behavior that changes with shear force. Due to the macromolecular structure of cellulose ether, the viscosity of the solution increases rapidly with the increase of concentration and decreases rapidly with the increase of temperature.
2.7 Biological stability: Cellulose ether is used in the water phase. As long as water is present, bacteria will grow. The growth of bacteria leads to the production of enzyme bacteria. The enzyme breaks the unsubstituted anhydroglucose unit bonds adjacent to the cellulose ether, reducing the molecular weight of the polymer. Therefore, if the cellulose ether aqueous solution is to be preserved for a long time, a preservative must be added to it. This is true even with antimicrobial cellulose ethers.

3. Purpose

3.1 Oilfield: NaCMC is mainly used in oilfield exploitation, and it is used in making mud to increase viscosity and reduce water loss. It can resist various soluble salt pollution and improve oil recovery. Sodium carboxymethyl hydroxypropyl cellulose and sodium carboxymethyl hydroxyethyl cellulose are good drilling mud treatment agents and materials for preparing completion fluids, with high pulping rate, good salt and calcium resistance, It has good viscosity-increasing ability and temperature resistance (160°C). It is suitable for preparing completion fluids of fresh water, sea water and saturated salt water. It can be formulated into completion fluids of various densities (1.03-1.279/Cm3) under the weight of calcium chloride, and it has a certain viscosity. And lower fluid loss, its viscosity increasing ability and fluid loss reducing ability are better than hydroxyethyl cellulose, it is a good additive for increasing oil production.
3.2 Building ceramics: NaCMC can be used as retarder, water retaining agent, thickener and binder, so that the produced ceramic products have good appearance and no defects and bubbles.
3.3 Papermaking: NaCMC is used for internal and external sizing and filling and retention of paper surface, and can replace casein, so that printing ink can easily penetrate and the edges are clear. In wallpaper making, it can be used as pigment dispersant, tackifier, stabilizer and sizing agent.
3.4 Textile: NaCMC is used as a substitute for grain and sizing in the textile industry, and it is not easy to deteriorate and become moldy. When printing and dyeing, there is no need to desizing, and the dye can obtain a uniform colloid in water, which enhances the hydrophilicity and penetration of the dye. At the same time, due to the small change in viscosity, it is easy to adjust the color difference. CMHEC is used as a thickener for printing and dyeing pulp, with small residue and high color yield, and the printing and dyeing quality is much higher than its single ionic and non-ionic cellulose ether products.
3.5 Tobacco: NaCMC is used for the bonding of tobacco. It dissolves quickly and has strong bonding force, which is beneficial to improve the quality of cigarettes and reduce costs.
3.6 Cosmetics: NaCMC plays the role of dispersing, suspending and stabilizing the paste products of solid silty raw materials, and plays the role of thickening, dispersing and homogenizing in liquid or emulsion cosmetics. It can also be used as an emulsifier, thickener and stabilizer for ointment and shampoo.
3.7 Batteries: NaCMC has high purity, good acid and salt resistance, especially low iron and heavy metal content, and the colloid is very stable, suitable for alkaline batteries and zinc-manganese batteries.
3.8 Water-based paints: HEC and MHEC can be used as stabilizers, thickeners and water-retaining agents for latex paints. In addition, they can also be used as dispersants, tackifiers and film-forming agents for colored cement paints.
3.9 Building materials: it can be used as dispersant, water retaining agent and thickener for plaster and mortar of gypsum bottom layer and cement bottom layer, and ground plastering materials.
3.10 Glaze: It can be used as the adhesive of glaze.
3.11 Detergent: It can be used as an anti-adhesion agent for thickening dirt.
3.12 Emulsion dispersion: it can be used as stabilizer and thickener.
3.13 Toothpaste: NaCMHPC can be used as a stabilizer for toothpaste adhesives. It has good thixotropic properties, making the toothpaste good in shape, long-term without deformation, and has a uniform and delicate taste. NaCMHPC has superior salt resistance and acid resistance, and its effect is far superior to that of CMC.

4. Application in coatings and pastes

Cellulose ether plays a very important role in coatings and pastes. Only add the total amount of formula O. 2% to 0.5% can thicken, retain water, prevent pigments and fillers from settling, and increase adhesion and bonding strength.
4.1 Viscosity: The viscosity of cellulose ether aqueous solution changes with shear force, and the paint and paste thickened with cellulose ether also have this characteristic. For ease of application of the coating, the type and amount of cellulose ether must be carefully selected. For coatings, when using cellulose ether, medium viscosity products can be selected.
4.2 Water retention: Cellulose ether can prevent moisture from quickly entering the porous substrate, so that it can form a uniform coating during the entire construction process without drying it too quickly. When the content of the emulsion is high, the requirement of water retention can be met by using less cellulose ether. The water retention of paints and slurries depends on the concentration of cellulose ether and the temperature of the coated substrate.
4.3 Stable pigments and fillers: Pigments and fillers tend to precipitate. To keep the paint uniform and stable, the pigment fillers must be in a suspended state. The use of cellulose ether can make the paint have a certain viscosity, and no precipitation will occur during storage.
4.4 Adhesion and bonding strength: Due to the good water retention and adhesion of cellulose ether, good adhesion between the coating and the substrate can be guaranteed. MHEC and NaCMC have excellent dry adhesion and adhesion, so they are especially suitable for paper pulp, while HEC is not suitable for this purpose.
4.5 Protective colloid function: Due to the hydrophilicity of cellulose ether, it can be used as a protective colloid for coatings.
4.6 Thickener: Cellulose ether is widely used in latex paint as a thickener to adjust the construction viscosity. Medium and high viscosity hydroxyethyl cellulose and methyl hydroxyethyl cellulose are mainly used in emulsion paints. Sometimes cellulose ether can also be used together with synthetic thickeners (such as polyacrylate, polyurethane, etc.) to improve some properties of latex paint and give latex paint uniform stability.
Cellulose ethers all have excellent water retention and thickening properties, but some properties are different. Anionic cellulose ether, easy to form water-insoluble salts with divalent and trivalent cations. Therefore, compared with methyl hydroxyethyl cellulose and hydroxyethyl fiber, sodium carboxymethyl cellulose has poor scrub resistance. So sodium carboxymethyl cellulose can only be used in cheap latex paint formulations.
Methyl hydroxyethyl cellulose and methyl hydroxypropyl cellulose have lower shear viscosity and higher surfactant properties than hydroxyethyl cellulose, thus reducing the tendency of latex paints to splatter. And carboxymethyl cellulose has no surfactant effect.
Hydroxyethyl cellulose has the characteristics of good fluidity, low brushing resistance and easy construction in latex paint. Compared with methyl hydroxyethyl and methyl hydroxypropyl cellulose, it has better compatibility with pigments, so It is recommended for silk latex paint, colored latex paint, color paste, etc.