How is Carboxymethyl Cellulose (CMC) produced?
2026-04-13 10:23:42
Carboxymethyl Cellulose(CMC,sodium carboxymethyl cellulose)is a cellulose ether synthesized via a two-step chemical process(alkalization+etherification)on purified natural cellulose,typically using the solvent(slurry)method for high-quality food/pharma grades.Below is the industrial production process:
1.Raw Material Preparation
Cellulose Source:High-purity cotton linters or wood pulp(bleached,α-cellulose>90%).
Chemicals:Sodium hydroxide(NaOH,30–50%solution),monochloroacetic acid(MCA)or sodium chloroacetate(etherifying agent),aqueous ethanol/isopropanol(reaction medium),hydrochloric/acetic acid(neutralization),and water.
2.Alkalization(Activation)
Cellulose is soaked in concentrated NaOH in an organic solvent(ethanol/water mix)at 25–40°C for 30–90 min.
Reaction:Cell-OH+NaOH→Cell-ONa+H₂O
Effect:Swells cellulose fibers,activates hydroxyl(-OH)to reactive alkoxide(-ONa)groups.
3.Etherification(Carboxymethylation)
Chloroacetic acid/sodium chloroacetate is added;heated to 55–75°C for 60–120 min.
Core reaction:Cell-ONa+ClCH₂COONa→Cell-O-CH₂COONa+NaCl
Forms sodium CMC;controls Degree of Substitution(DS,0.6–1.5)for solubility/viscosity.
4.Neutralization&Washing
Crude CMC is neutralized with HCl/acetic acid to pH 6–8.
Washed with aqueous alcohol to remove byproducts(NaCl,sodium glycolate)and unreacted chemicals.
Centrifuged to separate solids;solvent recycled.
5.Drying&Milling
Washed cake dried(vacuum/rake dryer,80–100°C)to moisture<10%.
Ground/pulverized to fine powder;sieved to grade(particle size/viscosity).
6.Quality Control&Packaging
Tests:DS,viscosity,pH,purity,moisture,heavy metals.
Packaged as food/pharma/industrial grade CMC.
Key Production Methods
Solvent Method(Slurry):Organic solvent medium;uniform reaction,high DS(0.8–1.5),high purity→food/pharma grades.
Water Media Method:Water-based;lower cost,lower DS/purity→industrial grades(detergents/textiles).
Dry Process:Solid-state mixing;simple,low cost→low‑purity industrial CMC.
References
GB/T 7714:
Horst F,Rånby B.Carboxymethyl Cellulose:Synthesis,Properties,and Applications[J].Progress in Polymer Science,1981,7(3–4):249–277.
MLA:
Horst,Frieder,and Bengt Rånby."Carboxymethyl Cellulose:Synthesis,Properties,and Applications."Progress in Polymer Science,vol.7,nos.3–4,1981,pp.249–277.
APA:
Horst,F.,&Rånby,B.(1981).Carboxymethyl cellulose:Synthesis,properties,and applications.Progress in Polymer Science,7(3–4),249–277.
