How is Polyanionic Cellulose manufactured?
2026-04-14 09:52:46
Polyanionic Cellulose(PAC)is produced via a multi-step chemical modification process of high-purity natural cellulose(cotton linters or wood pulp),involving alkalization,etherification/carboxymethylation,purification,and finishing.It is a high-purity,high-performance derivative of CMC(Carboxymethyl Cellulose).
1.Raw Material Preparation&Activation
Raw Material:High-purity cellulose(cotton linters or bleached wood pulp)with high Degree of Polymerization(DP≥2600).
Mechanical Treatment:Shredded to increase surface area.
Alkalization(Key Activation Step):
Cellulose is mixed with concentrated NaOH(sodium hydroxide)in an alcohol solvent(ethanol/isopropanol)at 8–15°C.
Reaction:Cell-OH+NaOH→Cell-ONa+H₂O
Forms alkali cellulose(activated,reactive intermediate).
Low temperature prevents chain cleavage and viscosity loss.
2.Etherification/Carboxymethylation(Core Reaction)
Etherifying Agent:Monochloroacetic Acid(MCA)or Sodium Monochloroacetate(SMCA).
Process:
MCA/SMCA is added to alkali cellulose.
Heated to 60–75°C for 90–120 minutes.
Nucleophilic substitution replaces–OH with carboxymethyl groups(–CH₂COONa).
Reaction:Cell-ONa+ClCH₂COONa→Cell-O-CH₂COONa+NaCl
PAC vs CMC Difference:PAC uses higher purity,controlled DS(Degree of Substitution),uniform substitution,and often secondary anionic modification(e.g.,sulfonation)for enhanced salt/thermal stability.
3.Neutralization&Washing(Purification)
Neutralization:Acid(HCl)added to reach pH 7.
Washing:
Alcohol/water solution removes impurities:NaCl,excess NaOH,unreacted MCA.
Centrifugation for solid-liquid separation.
Critical for high purity(≥90%)(vs lower purity CMC).
4.Drying&Finishing
Drying:Vacuum rake drying to remove moisture/solvents.
Milling&Screening:Ground to fine powder(standard mesh sizes).
Quality Control:Tests for DS,viscosity,purity,salt resistance,pH.
Packaging:Sealed moisture-proof bags.
Simplified Flowchart
Raw Cellulose→Alkalization→Etherification→Neutralization→Washing→Drying→Milling→PAC Product
References
GB/T 7714
Zhang G,Yang N,Du G,et al.Preparation method of polyanionic cellulose:CN109929041A[P].2019-06-25.
MLA
Zhang,Guifeng,et al."Preparation Method of Polyanionic Cellulose."Chinese Patent,CN109929041A,25 June 2019.
APA
Zhang,G.,Yang,N.,Du,G.,&Yang,B.(2019).Preparation method of polyanionic cellulose(Patent No.CN109929041A).China National Intellectual Property Administration.
