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Use of a Twin‐Screw Extruder as a Chemical Reactor for Starch Cationization
Author(s) -
Valle Guy Della,
Colonna Paul,
Tayeb Jean
Publication year - 1991
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.19910430804
Subject(s) - starch , reagent , cationic polymerization , extrusion , sodium hydroxide , chemical engineering , chemistry , plastics extrusion , ammonium hydroxide , materials science , chromatography , polymer chemistry , organic chemistry , composite material , engineering
The objective of this work was to study the obtaining of cationic starch by using a pilot scale twin‐screw extruder Clextral BC45 as a chemical reactor. The reagent was 3‐chloro 2‐hydroxypropyltrimethyl ammonium chloride (CHPTMA) and catalyst was sodium hydroxide (NaOH). In a first set of experiments extruded starch gave higher chemical efficiencies than native starch (+15%) both being fed at the same location of the barrel. Influence of extrusion conditions on reaction kinetics was studied starting from extruded starch in order to optimize the reaction without interfering with starch melting phenomenon. In a second set of experiments, a special screw design was implemented in order to obtain a homogeneous starch molten phase in a first stage, and to achieve starch modification in a second stage. Changes of reacting conditions were performed through the modification of reagent quantities and molar ratios related to starch and NaOH, location of reagent injection, temperature of reaction and Specific Mechanical Energy input. Samples were evaluated through their degree of substitution (final DS < 0,09); their homogeneity and rheological behavior were studied by ion exchange chromatography and Brabender viscoamylograph. resp., Reaction efficiency was computed to optimize the process, leading to values up to 82%. Extruded samples were then compared to commercial cationic starches.