Multifunctional polycarboxylic acids have been used as nonformaldehyde cross linking agents for cotton fabrics to replace the traditional N-methylol reagents. Ester ification of cotton cellulose by seventeen aliphatic and aromatic polycarboxylic acids is studied using Fourier transform infrared spectroscopy. Five-membered cyclic an hydride intermediates formed under the curing conditions are identified on cotton fabrics treated with these acids. Only those polycarboxylic acids that form cyclic an hydride intermediates esterify cotton cellulose. Formation of the cyclic anhydride intermediates and esterification of cotton cellulose take place in the same curing tem perature regions. The infrared spectroscopy data also indicate that the second carboxyl group in a bifunctional carboxylic acid is not able to esterify cotton cellulose effectively. Therefore, we can conclude that a polycarboxylic acid esterifies cotton cellulose through the formation of a cyclic anhydride intermediate. The infrared spectroscopy data also reveal that 1,2,3,4-butanetetracarboxylic acid is the most effective crosslinking agent for cotton cellulose among the acids studied.

Polycarboxylic acids appear to be the most promising nonformaldehyde durable press finishing agents to replace the traditional N-methylol reagents, 1,2,3,4-Butanetetracarboxylic acid (btca) is the most effective crosslinking agent among the acids investigated, but its exceedingly high cost has prevented its use in the textile industry on a commercial scale. In this research, we evaluate the effectiveness of two polymers of maleic acid, i.e., the homopolymer (pma) and the terpolymer (tpma), along with citric acid (ca) for crosslinking cotton cellulose., pma, tpma, and ca have molecular structures similar to btca, but are more cost effective. We have found that pma and tpma are less effective crosslinking agents for cotton than btca, probably due to the low mobility of the anhydride intermediate formed by pma or tpma to access the cellulosic hydroxyl during the curing process. We have found that the hydroxyl of ca and other α-hydroxylpolycarboxylic acids hinder the esterification of those acids with cellulose. The infrared spectroscopy data indicate that ca esterifies the anhydride intermediates of pma and tpma on cotton fabric under curing conditions. Consequently, ca is transformed from a trifunctional acid to a tetrafunctional one with the formation of an ester linkage with pma or tpma.

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Butanetetracarboxylic acid (BTCA) has been used as the most effective nonformaldehyde crosslinking agent for cotton and wood pulp cellulose. Our previous research has indicated that a polycarboxylic acid esterifies cellulose in two steps: the formation of a five-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl groups, and the reaction between cellulose and the anhydride intermediate to form an ester linkage. In this research, we investigated the formation of carboxylic anhydrides by BTCA and other polycarboxylic acids in powder forms, and as finishes applied to cotton fabric using thermal gravimetry, differential scanning calorimetry, and Fourier transform infrared spectroscopy. We found that BTCA and other polycarboxylic acids in powder forms start to form five-membered cyclic carboxylic anhydrides when the temperature reaches the vicinity of their melting points. The formation of carboxylic anhydride is accelerated above the melting points. We also found that BTCA forms anhydrides at lower temperatures when it is applied to cotton fabric as a finish. An increase in temperature increases both the amount of anhydride and the amount of ester formed on the cotton fabric.

Polycarboxylic acids have been used as nonformaldehyde crosslinking agents for cotton fabrics to replace the traditional N‐methylol reagents. In this research, we compared 1,2,3,4‐butanetetracarboxylic acid (BTCA) with poly(maleic acid) (PMA) as crosslinking agents for cotton cellulose. BTCA and PMA have similar molecular structures with carboxyl groups bonded to their molecular backbones, and both form five‐membered cyclic anhydride intermediates during a curing process. However, BTCA is a more effective crosslinking agent for cotton cellulose than PMA. This is mainly attributed to the differences in the mobility of the anhydride intermediates to access the cellulosic hydroxyl groups during a curing process. The mobility of the anhydride intermediate of PMA is reduced due to its molecular size and multiple bonding between a PMA molecule and cellulose. Consequently, more anhydride and less ester are detected on the cotton fabric treated with PMA than on the fabric treated with BTCA. The amount of the unreacted anhydride intermediate on the fabric treated with PMA is reduced whereas the amount of ester is increased when another hydroxyl‐containing compound of low molecular weight is present. Thus, the infrared spectroscopy data show a clear link between the molecular weight of a polycarboxylic acid and its effectiveness for crosslinking cotton cellulose. © 1997 John Wiley & Sons, Inc.