Polymers 2022 , 14 , 3309
8of 18
The drainage times were recorded in a dynamic drainage analyzer (DDA, AB Akribi Kemikonsulter, Sweden) for formulations with pulp, filler and retention agent (CPAM or cationic cellulose) [8]. The formulations were prepared in order to obtain sheets with a nominal filler content of 20 wt %. For reference, tests using only pulp and PCC (80 BEKP: 20 PCC) and without a retention agent were performed. Contents of 0.02, 0.2 and 0.4 wt % of cationic cellulose (corresponding to 1, 10 and 20 mg of cationic cellulose per gram of PCC) were tested and compared to samples with the addition of 0.02 wt % of CPAM. The pulp was disintegrated in the DDA vessel at 1200 rpm for 60 s. The filler, pre- flocculated with the retention agent for 60 s in an external beaker with magnetic stirring (700 rpm), was then added to the pulp suspension inside the equipment vessel, reaching a total solids concentration of 5 g/L and a final volume of 500 mL (extra water was added to the pulp during disintegration to achieve the final desired volume). The final suspension was kept at 800 rpm for 60 s and was subsequently drained. The DDA vessel was equipped with a 60-mesh (250 μ m pore size) screen and a vacuum of 30 kPa was maintained in the equipment. After drainage, the formed wet pads were removed from the forming screen and dried at 105 ◦ C. The dried pads were subsequently calcinated at 525 ◦ C (according to the TAPPI standard, T211) to determine the effective filler content and the corresponding filler retention.
3. Results and Discussion 3.1. Chemical Analysis
As mentioned before, cationic celluloses with distinct morphologies and levels of cationization were obtained by the incorporation of quaternary ammonium groups into the BEKP structure via direct cationization with CHPTAC or by a two-step reaction (periodate oxidation + Girard’s reagent T) and the submission of some of the samples for treatment in an HPH. The successful cationization was confirmed by the ZP (Table 2) and FTIR (Figure 3) results, and the extent of the cationization was assessed by the determination of the DS and CD (Table 2).
Table2. Characterization of the original BEKP and celluloses cationized with CHPTAC and GT.
ZP (mV) 1
avgMw(Da) 2,3 /PDI 4
DS
YF (%)
SF (%)
CD (mmol/g) 0.14 ± 0.01 5 0.46 ± 0.04 0.92 ± 0.04 0.78 ± 0.01 1.62 ± 0.09 3.44 ± 0.00 0.23 ± 0.04 0.32 ± 0.03 0.90 ± 0.02 1.68 ± 0.04
BEKP CH0.08 CH0.16
-
− 23 ± 5 +29 ± 3 +18 ± 4 +26 ± 3 +21 ± 4 +35 ± 2 +24 ± 2 +29 ± 5 +27 ± 2 +30 ± 3
- - - - -
- - -
- - - - -
0.08 ± 0.02 0.16 ± 0.00 0.13 ± 0.01 0.32 ± 0.01 1.06 ± 0.00 0.02 ± 0.01 0.04 ± 0.01 0.16 ± 0.01 0.36 ± 0.01
CH0.13_F 6
29.0 ± 0.4
0.0 ± 0.0
GT0.32
-
2150 ± 12/1.01 ± 0.00 972 ± 8.5/1.02 ± 0.00
100.0 ± 0.0 6.1 ± 1.0 6.5 ± 1.6 39.9 ± 1.4 99.6 ± 0.4
GT1.06_P GT0.02_F 6 GT0.04_F 6 GT0.16_F 6 GT0.36_FP 6
6.4 ± 0.6 11.5 ± 1.0 98.4 ± 0.5 100.0 ± 0.0
- -
1081 ± 3.5/1.11 ± 0.00 526 ± 0.5/1.02 ± 0.00 1025 ± 43/1.06 ± 0.02 543 ± 4.5/1.01 ± 0.00
1 Determined at ca. pH 7; 2 bimodal distributions; 3 measured for the soluble fraction of the sample; 4 polydis- persity index; 5 carboxyl content of the initial BEKP, determined by conductometric titration [47]; 6 Data from [23]. The negative ZP ( − 23 mV) of BEKP shifted to positive values for all the CCs, with the ZP values ranging between +18 and +35 mV, indicating the successful incorporation of cationic moieties into the cellulose structure.
Made with FlippingBook - Online magazine maker