Polymers 2022 , 14 , 3309
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The performances were compared against a commercial CPAM and the initial non- functionalized cellulose fibers. The samples presenting the best flocculation performance in the LDS tests were incorporated into pulp and filler formulations and then analyzed in a dynamic drainage analyzer (DDA) to quantify the effects on drainability and the most effective filler retention capabilities. Due to the importance of filler retention in papermaking and the constantly increasing health and environmental concerns/restrictions, the present study aims to shed some light on the potential use of CCs as a retention agent and as a possible CPAM substitute.
2. Materials and Methods 2.1. Materials
The cationic celluloses were produced from industrial unrefined and never-dried BEKP (80–85 wt % cellulose, 14–19 wt % xylan, 0.3 wt % lignin and 0.4 wt % extractives) [23]. A commercial linear CPAM (from BASF, Ludwigshafen, Germany), with a Mw of 3.7 × 10 6 Da and a CD of 1.1 mmol/g, was used as the reference retention agent. An industrial scalenohedral form of PCC with a median diameter (d 50 ) of 4.8 μ m, determined by LDS, in a Mastersizer 2000 (Malvern Inst., Worcester City, UK), and a ZP of +9 mV (at pH 10), measured in a water suspension using electrophoretic light scattering (ELS–Zetasizer NanoZS, Malvern Inst., Malvern, Worcester City, UK), was used as filler in the flocculation tests. All chemicals employed in the cationization of cellulose were used as received, without further purification. The (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHPTAC) 60 wt % aqueous solution, sodium periodate (SP) and (carboxymethyl)trimethylammonium chloride hydrazide (Girard’s reagent T–GT) were obtained from Sigma-Aldrich (Schnell- dorf, Germany). Sodium hydroxide pellets and glacial acetic acid (AA) were purchased from VWR (Carnaxide, Portugal) and isopropanol (IPA) from Labsolve (Lisbon, Portugal). Distilled water was used throughout the work. 2.2. Cellulose Cationization The cationic celluloses were produced, following two previously reported proce- dures [23], and under the conditions presented in Table 1.
Table1. Reaction conditions used for the cationization of BEKP with CHPTAC and GT.
CHPTAC Method
Cellulose Activation
Cellulose Cationization
C 1 (wt%)
NaOH/AGU 2 (mol/mol)
CHPTAC/AGU 3 (mol/mol)
IPA (% v/v )
T ( ◦ C)
T ( ◦ C)
t (h)
t (h)
Sample
CH0.08 CH0.16
2 5
-
12 3.4
5
1 1
3 2 6
65 70 65
8 2 8
50
70 20
CH0.13_F 3
-
9
0.3
GTmethod
Cellulose Oxidation
Cellulose Cationization
SP/AGU 4 (mol/mol)
C 1 (wt%)
C 1 (wt%)
GT/ald. 6 (mol/mol)
AA (% v/v )
IPA (% v/v )
T ( ◦ C)
t (h)
t (h)
IPA (% v/v )
T ( ◦ C)
Sample
Dsa 5
- 7
0.50 1.50 0.10 0.20 0.55 0.65
0.50 1.59 0.11 0.19 0.48 0.85
GT0.32
-
GT1.06_P GT0.02_F GT0.04_F GT0.16_F GT0.36_FP
60
1
- - - -
2.5
10
70
5
70
1.5
4
10
0.7
0.6 1 Pulp consistency; 2 molar ratio of NaOH/Anhydroglucose unit; 3 molar ratio of CHPTAC/anhydroglucose unit; 4 molar ratio of sodium periodate/anhydroglucose unit; 5 degree of substitution of aldehyde groups; 6 molar ratio of Girard’s reagent T/aldehyde group; 7 pH adjusted to 4.5 with dilute HCl. Briefly, for the direct cationization with CHPTAC, BEKP was subjected to an activation step under alkaline conditions; then, a certain quantity of CHPTAC was added to the alkaline suspension. The cationic fibers were vacuum-filtered and thoroughly washed with distilled water. For the two-step cationization, BEKP was first subjected to an oxidation reaction with sodium periodate and was consequently converted into DAC. The obtained DACs, with
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