1. Brief Introduction of Carboxymethyl Cellulose
English name: Carboxyl methyl Cellulose
Abbreviation: CMC
The molecular formula is variable: [C6H7O2(OH)2CH2COONa]n
Appearance: white or light yellow fibrous granular powder.
Water solubility: easily soluble in water, forming a transparent viscous colloid, and the solution is neutral or slightly alkaline.
Features: High molecular compound of surface active colloid, odorless, tasteless and non-toxic.
Natural cellulose is widely distributed in nature and is the most abundant polysaccharide. But in production, cellulose usually exists in the form of sodium carboxymethyl cellulose, so the full name should be sodium carboxymethyl cellulose, or CMC-Na. Widely used in industry, construction, medicine, food, textile, ceramics and other fields.
2. Carboxymethyl cellulose technology
The modification technology of cellulose includes: etherification and esterification.
Transformation of carboxymethyl cellulose: carboxymethylation reaction in etherification technology, cellulose is carboxymethylated to obtain carboxymethyl cellulose, referred to as CMC.
Functions of carboxymethyl cellulose aqueous solution: thickening, film forming, bonding, water retention, colloid protection, emulsification and suspension.
3. Chemical reaction of carboxymethyl cellulose
Cellulose alkalization reaction:
[C6H7O2(OH) 3]n + nNaOH→[C6H7O2(OH) 2ONa ]n + nH2O
The etherification reaction of monochloroacetic acid after alkali cellulose:
[C6H7O2(OH) 2ONa ]n + nClCH2COONa →[C6H7O2(OH) 2OCH2COONa ]n + nNaC
Therefore: the chemical formula for forming carboxymethyl cellulose is: Cell-O-CH2-COONa NaCMC
Sodium carboxymethyl cellulose (NaCMC or CMC for short) is a water-soluble cellulose ether that can make the viscosity of most commonly used aqueous solution formulations vary from a few cP to several thousand cP.
4. Product characteristics of carboxymethyl cellulose
1. Storage of CMC aqueous solution: It is stable under low temperature or sunlight, but the acidity and alkalinity of the solution will change due to temperature changes. Under the influence of ultraviolet rays or microorganisms, the viscosity of the solution will decrease or even become corrupted. If long-term storage is required, a suitable preservative should be added.
2. Preparation method of CMC aqueous solution: make the particles uniformly wet first, which can significantly increase the dissolution rate.
3. CMC is hygroscopic and should be protected from moisture during storage.
4. Heavy metal salts such as zinc, copper, lead, aluminum, silver, iron, tin, and chromium can cause CMC to precipitate.
5. Precipitation occurs in the aqueous solution below PH2.5, which can be recovered after neutralization by adding alkali.
6. Although salts such as calcium, magnesium and table salt do not have a precipitation effect on CMC, they will reduce the viscosity of the solution.
7. CMC is compatible with other water-soluble glues, softeners and resins.
8. Due to different processing, the appearance of CMC can be fine powder, coarse grain or fibrous, which has nothing to do with physical and chemical properties.
9. The method of using CMC powder is simple. It can be directly added and dissolved in cold water or warm water at 40-50°C.
5. Degree of substitution and solubility of carboxymethyl cellulose
The degree of substitution refers to the average number of sodium carboxymethyl groups attached to each cellulose unit; the maximum value of the degree of substitution is 3, but the most industrially useful is NaCMC with a degree of substitution varying from 0.5 to 1.2. The properties of NaCMC with a degree of substitution of 0.2-0.3 are quite different from those of NaCMC with a degree of substitution of 0.7-0.8. The former is only partially soluble in pH 7 water, but the latter is completely soluble. The opposite is true under alkaline conditions.
6. Polymerization degree and viscosity of carboxymethyl cellulose
Polymerization degree: refers to the length of the cellulose chain, which determines the viscosity. The longer the cellulose chain, the greater the viscosity, and so is the NaCMC solution.
Viscosity: NaCMC solution is a non-Newtonian liquid, and its apparent viscosity decreases when the shear force increases. After stirring was stopped, the viscosity increased proportionally until it remained stable. That is, the solution is thixotropic.
7. Application range of carboxymethyl cellulose
1. Construction and ceramic industry
(1) Architectural coatings: good dispersion, uniform coating distribution; no layering, good stability; good thickening effect, adjustable coating viscosity.
(2) Ceramic industry: used as blank binder to improve the plasticity of pottery clay; durable glaze.
2. Washing, cosmetics, tobacco, textile printing and dyeing industries
(1) Washing: CMC is added to the detergent to prevent the washed dirt from re-depositing on the fabric.
(2) Cosmetics: thickening, dispersing, suspending, stabilizing, etc. It is beneficial to give full play to the various properties of cosmetics.
(3) Tobacco: CMC is used for bonding tobacco sheets, which can effectively use chips and reduce the amount of raw tobacco leaves.
(4) Textile: As a finishing agent for fabrics, CMC can reduce yarn skipping and end breakage on high-speed looms.
(5) Printing and dyeing: It is used in printing paste, which can enhance the hydrophilic and penetrating ability of dyes, make dyeing uniform and reduce color difference.
3. Mosquito coil and welding rod industry
(1) Mosquito coils: CMC is used in mosquito coils to enhance the toughness of mosquito coils and make them less likely to break and break.
(2) Electrode: CMC is used as a glaze agent to make the ceramic coating better bonded and formed, with better brushing performance, and it also has burnout performance at high temperatures.
4. Toothpaste industry
(1) CMC has good compatibility with various raw materials in toothpaste;
(2) The paste is delicate, does not separate water, does not peel off, does not thicken, and has rich foam;
(3) Good stability and suitable consistency, which can give toothpaste good shape, retention and particularly comfortable taste;
(4) Resistant to temperature changes, moisturizing and fragrance-fixing.
(5) Small shearing and tailing in cans.
5. Food industry
(1) Acidic beverages: As a stabilizer, for example, to prevent precipitation and stratification of proteins in yogurt due to aggregation; better taste after dissolving in water; good substitution uniformity.
(2) Ice cream: Make water, fat, protein, etc. form a uniform, dispersed and stable mixture to avoid ice crystals.
(3) Bread and pastry: CMC can control the viscosity of the batter, enhance the moisture retention and shelf life of the product.
(4) Instant noodles: increase the toughness and cooking resistance of noodles; it has good formability in biscuits and pancakes, and the cake surface is smooth and not easy to break.
(5) Instant paste: as a gum base.
(6) CMC is physiologically inert and has no calorific value. Therefore, low-calorie foods can be produced.
6. Paper industry
CMC is used for paper sizing, which makes the paper have high density, good ink penetration resistance, high wax collection and smoothness. In the process of paper coloring, it helps to control the rollability of the color paste; it can improve the stickiness state between fibers inside the paper, thereby improving the strength and folding resistance of the paper.
7. Petroleum industry
CMC is used in oil and gas drilling, well digging and other projects.
8. Others
Adhesives for shoes, hats, pencils, etc., polishes and colorants for leather, stabilizers for foam fire extinguishers, etc.
Post time: Jan-04-2023