FT-IR Spectroscopy Study of the Polycarboxylic Acids Used for Paper Wet Strength Improvement

Abstract

Polycarboxylic acids have been used as cross-linking agents for cellulose to increase the wet strength of paper. In this research, we applied Fourier transform infrared (FT-IR) spectroscopy to study the kraft paper treated with poly(maleic acid) and 1,2,3,4-butanetetracarboxylic acid. FT-IR spectroscopy is used to measure the carboxyl of a polycarboxylic acid and ester on the treated paper. The ester carbonyl band intensity and the carbonyl band intensity ratio (ester/carboxylate) are used for the evaluation of the effectiveness of a polycarboxylic acid for cross-linking cellulose on the paper. The correlation between the ester carbonyl band intensity and the wet strength improvement of the treated paper reveals that the increase in the paper wet strength by a polycarboxylic acid is the result of ester cross-linking of cellulosic fibers and molecules. We identified a five-membered cyclic anhydride intermediate formed on the paper during the curing processes. The infrared spectroscopy data support the reaction mechanism that a polycarboxylic acid esterifies cellulose through the formation of a five-membered cyclic anhydride as a reactive intermediate. We also studied the catalysis effects of sodium hypophosphite on the formation of the anhydride intermediate and the esterification of wood cellulose by a poly(carboxylic acid).

Combination of bifunctional aldehydes and poly(vinyl alcohol) as the crosslinking systems to improve paper wet strength

“…This result indicates that Zn(NO 3 ) 2 is the most effective catalyst for the acetalization of glutaraldehyde by cellulose and PVA. For the purpose of comparison, NH 4 Cl is also included in the study. We find that NH 4 Cl provided a relatively constant W/D ratio around 30% in the pH range from 3.5 to 6.1 (Fig.…”

“…For the purpose of comparison, NH 4 Cl is also included in the study. We find that NH 4 Cl provided a relatively constant W/D ratio around 30% in the pH range from 3.5 to 6.1 (Fig. 5).…”

“…Both PVA samples were supplied by Airproducts (Allentown, PA). The catalysts [Zn(NO 3 ) 2 , AlCl 3, MgCl 2 , and NH 4 Cl], citric acid, sodium hydroxide, and glyoxal were all reagent grade chemicals supplied by Aldrich (Milwaukee, WI).…”

“…[1][2][3][4] In our previous research, we found that polycarboxylic acids of small molecular sizes, such as 1,2,3,4-butanetetracarboxylic acids and poly(maleic acid) (PMA) with M w of 800, improve wet strength but also diminish folding endurance of the treated paper. [5][6] We also found that the use of copolymers of maleic acid with high M w as the crosslinking agents improves both wet strength and folding endurance.…”

DSC-FTIR microspectroscopy used to investigate the heat-induced intramolecular cyclic anhydride formation between Eudragit E and PVA copolymer

“…24,25 It has been reported that the symmetric C¼O stretching band at high frequency is stronger than the asymmetric C¼O stretching band at low frequency for a noncyclic anhydride, and that the opposite is true for a cyclic anhydride. 25 In the present study, the peak intensity ratios of 1763 cm À1 /1801 cm À1 for Eudragit E and 1759 cm À1 /1799 cm À1 for the PVA copolymer were about 2.47 and 2.02, respectively. A high peak intensity ratio (41.0) implies that the cyclization due to intramolecular ester condensation was predominantly responsible for the cyclic anhydride formation occurring in the film of Eudragit E or PVA copolymer.…”