ACS Omega
http://pubs.acs.org/journal/acsodf
Article
Table 8. Operation Conditions of DDA Vacuum Drainage a
start − 90 pulp 400
drainage
fi nish
− 70
− 50
− 31
− 11
− 1
time (s)
0
+30
furnish
+AKD
+ fi ller
+PAM
+bentonite
stirring rate (rpm)
400
400
800
400
0
0
a Vacuum pressure, 250 mbar; delay time, 1 s; forming time, 30 s.
to give a total weight of 50 g, and the resulting mixture was stirred. An aliquot of this mixture was analyzed using a UV/vis spectrophotometer (Varian, Mulgrave Victoria, Australia) at wavelengths of 450 and 338 nm, using chloroform as a reference. To explore the e ff ect of the DMAP/AKD ratio on the reaction, the amount of DMAP added to the 0.1% AKD solution of chloroform was changed from 30 to 180 times of the AKD weight, the mixture was diluted further with chloroform, as before, and the resulting mixture was stirred for 2 h. Next, samples of the mixture were analyzed by UV/vis spectrometry. A calibration line was determined for the quantitative analysis of AKD by UV/vis spectrometry. Thus, 100 g of AKD emulsion at a concentration of 40 − 160 mg/L and 100 g of chloroform were placed in a separation funnel, and the funnel was then vigorously shaken to extract AKD. Next, DMAP was added in a weight ratio of 120:1 of AKD weight, and the resulting mixture was reacted for 2 h. After this, an aliquot of the mixture was analyzed by UV/vis spectrometry, as before. AKD calibration lines were determined for AKD-I and AKD-II emulsions. To evaluate AKD retention, an extraction method using chloroform as a solvent was used to determine the amount of AKD in white water. To determine the extraction time required for the complete extraction of AKD, 500 g of AKD emulsion at a concentration of 50 ppm was placed in a separation funnel and 500 g of chloroform was added. After shaking the funnel for 5 − 180 min, the UV/vis absorption of an aliquot was observed. The ratio of DMAP/AKD was fi xed at 120:1 to ensure the complete reaction of AKD, and the mixture was allowed to react for 2 h. To investigate the e ff ect of pulp fi ber and fi llers on AKD extraction, slurries of hardwood BKP, BCTMP, GCC, and PCC at 0.1% consistency were prepared. Next, 10 wt % AKD (with respect to the dry weight of the pulp or fi ller) was added to each slurry, and each of the resulting mixtures was subject to an extraction and quanti fi cation procedure, as above. 4.2.2. E ff ects of Pulp and Filler Types on AKD Retention. To investigate the e ff ects of pulp type, hardwood BKP, BCTMP, and a 50/50 mixture of these two pulps were used. Thus, 500 mL of a prepared stock of one of the above pulps at 0.5% consistency was placed in a dynamic drainage analyzer (DDA; AB Akribi Kemikonsulter, Sundsvall, Sweden) and
Table 9. Seven Factors Examined for Their E ff ect on AKD Retention
no.
variable
type of variable
1 2 3 4 5 6 7
pulp type
BCTMP 20% BCTMP 40%
fi xing agent type fi xing agent dosage
PAM
PAE
0.025% AKD-I
0.050% AKD-II
AKD type fi ller type fi ller dosage
GCC
PCC 30%
15%
PAM/bentonite dosage
0.025/0.125% 0.050/0.250%
tronics, Hirakata, Japan), respectively. The two AKDs were very similar in most properties except the ζ -potential: AKD-I was positively charged, while AKD-II was negatively charged. Eucalyptus hardwood bleached kraft pulp (BKP; CMPC Celulosa, Brazil) and bleached chemithermomechanical pulp (BCTMP; Temcell, Tembec Inc., Québec, Canada) were used for papermaking. Hardwood BKP was beaten in a Valley beater to450 ± 10 mL Canadian standard freeness (CSF) and diluted to a consistency 0.5%. Aspen BCTMP was simply disintegrated and diluted to 0.5%. Chloroform (Sigma-Aldrich) was used for AKD extraction, and 4-dimethyl aminopyridine (DMAP; Sigma-Aldrich) was used as a reactant for the UV/vis spectrometric analysis of AKD. 24 Ground calcium carbonate (GCC; Omya Korea, Jeongseon, Korea) and on-site precipitated calcium carbonate (PCC; Omya Korea, Ulsan) with average particle sizes of 1.1 and 2.4 μ m, respectively, were used as fi llers. Cationic starch (Samyang Genex, Incheon, Korea) with a 0.06 degree of substitution was used as an internal additive. Two retention systems were used: one consisted of cationic poly(acrylamide) (PAM; Percol63) and bentonite (Hydrocol OTK; Ciba Specialty Chemicals Korea, Seoul, Korea), which is often referred to as a Hydrocol retention system, 33,34 and the other consisted of poly aluminum chloride (PAC), anionic PAM, and anionic micropolymer, denoted a PerForm system (PerForm SP; Solenis Korea, Kimcheon, Korea). 4.2. Methods. 4.2.1. Quantitative Analysis and Retention Measurement of AKD. First, we identi fi ed the required reaction time for AKD and DMAP. In a round-bottom fl ask, 4.8 g of DMAP was added to 4 g of a 0.1% AKD solution of chloroform. This mixture was diluted further with chloroform
Figure 8. Flow diagram of the gap-former paper machine used for examining the e ff ect of certain variables and showing the points of introduction of additives. Fixing, fi xing agent; A-PAM, anionic poly(acrylamide); MP, micropolymer..
11232
https://dx.doi.org/10.1021/acsomega.0c01374 ACS Omega 2020, 5, 11227 − 11234
Made with FlippingBook - Online catalogs