Mary Ann F. Brannan

Introduction of Ester Cross Links into Cotton Cellulose by a Rapid Curing Process

The reaction of polycarboxylic acids with cotton at elevated temperature has been investigated as a function of partial neutralization of the carboxylic acid with sodium carbonate or triethylamine. A high level of cellulose cross-linking was realized with a variety of polycarboxylic acids having three or more carboxyl groups per molecule, although only partial esterihcation of the carboxyl groups occurs in this process. The use of polycarhoxylic acids in the form of their partial salts results in broader applicability of this rapid esterification process of cross-linking, in improved add-ons and performance characteristics of the modified cotton, and in reduced acid tendering of the treated fabrics.

Mobile Ester Cross Links for Thermal Creasing of Wrinkle-Resistant Cotton Fabrics

Ester cross linkages in cotton cellulose have been investigated for mobility (trans esterification) at elevated temperature. Cotton cellulose polycarboxylates were prepared by reaction of cotton print cloth with polycarboxylic acids having 3-6 carboxyl groups per molecule, at least two of the carboxyl groups being on adjacent carbon atoms. Durable creases were developed to various degrees when these fabrics were subjected to thermal creasing treatments subsequent to the cross-linking reaction. Thermal mobil ity of ester linkages in selected model compounds has been shown to result from participation of the unesterified carboxyl group adjacent to the ester linkage. The cyclic anhydride was detected from dissociation of model ester compounds at elevated tempera tures; similar cyclic anhydrides are the probable intermediates in transesterification of ester linkages in cotton cellulose polycarboxylates.

The Relative Reactivities of the Hydroxyl Groups of Cotton Cellulose—A Progress Report1

Major preceding studies of the distribution of substituents in cellulose have been reviewed. Over-all results indicate that the highest degree of reaction occurs at the hydroxyl group on C-2 in the case of the irreversible Williamson syntheses involving reagents of small molecular size. Pronounced preferential reaction occurs at the hy droxyl group on C-6 in the case of reversible reactions and with increasing molecular size of reagent. The relative reactivities of the hydroxyl groups on C-2, C-3, and C-6 of the D(1→4)- β-glucopyranosyl unit of cotton cellulose have been explored with three chemical agents. Predominant reaction of cotton cellulose occurs at the primary hydroxyl group on C-6 in the case of the reversible Michael addition of methyl vinyl sulfone (i.e., 2-0- : 3-0- : 6-0- = 0.20: 0.03: 1.00), at the hydroxyl groups on C-2 and C-6 in the case of the irreversible reaction with diethylaminoethyl chloride (1.27 : 0.35 : 1.00), and at the hydroxyl groups on C-6 and C-2 in the case of the irreversible Williamson synthesis with sodium allyl sulfate (0.7:0.2:1.0). The D-(1→4)-α-glucopyranosyl unit of dextrin (employed as a soluble model compound for cellulose) undergoes reversible esterification with formic acid most rapidly and to the highest equilibrium level at the primary hydroxyl group on C-6.

Introduction and Removal of Durable Creases in Wrinkle-Resistant Cotton Fabric

Internally catalyzed, cross-linked cotton fabrics have provided the basis for an exploratory study of the introduction and removal of creases by thermal treatment. Durable creases having ratings of 4.0-5.0 have been developed in these cross-linked compositions which are characterized by conditioned and wet wrinkle recovery angles (W + F) as high as 300°. Creases are introduced by extended heat treatment or by multiple ironings of the wet fabric. By similar treatments of the creased fabric in the flat state, creases may be reduced substantially and, in some-cases, they may be reduced to the same extent as in unmodified cotton fabric. The study is based on cotton fabrics cross-linked with divinyl sulfone; the internal catalysis is provided by quaternary ammonium substituents introduced into the cellulose via ether linkages.

Recent Developments in the Chemistry of Cellulose which Pertain to the Cross-Linking of Cotton1

The distributions of sites of attachment of substituents or cross linkages (a) at the 2–0-, 3–0-, and 6–0-positions of the d-glucopyranosyl units, (b) along the molecular chains of cellulose, (c) on or in the microstructural units, and (d) within the fiber cross sections are reviewed in order to develop perspective for the factors that influence and control these distributions. Among the factors determining the site of attachment in the d-glucopyranosyl unit are: (1) the type of reaction (e.g., reversible or nonreversible), (2) the specific nature of the reagent (e.g., molecular size), and (3) the medium from which the reagent is introduced. Means of controlling this distribution are discussed. There is no available information on the distributions of linkages introduced along the molecular chains of cellulose from reactions that occur without disruption of the crystalline order. It is evident, however, that, even under these conditions, every molecule in the cellulose matrix has one or more accessible segments along its chain. Measurements that are specific to the distribution of substituents among the total d-glucopyranosyl units, but which are applicable, in first-order approximation, to the units along the molecular chain, are discussed in connection with reactions conducted in mercerizing media. Evidence indicative of reactions occurring on the surfaces of highly ordered micro-structural units (microfibrils or bundles of microfibrils) has been obtained from measurement of the distribution of substituents introduced into the d-glucopyranosyl units of cotton cellulose under nonmercerizing conditions. Penetration within these units is evident under mercerizing conditions of reaction. An interrelationship between the site of attachment in the d-glucopyranosyl unit and the site of reaction in the microstructural unit is discussed. At the fiber level of structure, the complex interplay between rate of chemical reaction and rate of diffusion into the fibers is considered. Gross variations of distribution of substituents or cross linkages in the fiber cross section (from peripheral to uniform) result from changes in the two rates noted. In a case examined in some detail, wrinkle-recovery angles benefit from the more uniform distribution of cross linkages.

A Delayed-Curing Cotton Fabric Based on an Internally Catalyzed Cotton Cellulose and Divinyl Sulfone

2-(Diethylamino)ethyl cotton celluloses in the form of print cloth and at three levels of nitrogen have been quaternized and converted to the strong bases. Studies were made of internally catalyzed reactions of these cotton cellulose quaternary ammonium hydroxides with divinyl sulfone at room temperature in a “wet-cure” and with bis-(2-hydroxyethyl) sulfone in a “bake-cure.” Moderate levels of conditioned wrinkle-recovery angles and high levels of wet wrinkle-recovery angles result from the “wet-cure” reaction. The wrinkle-recovery angles of these modified cotton celluloses are compared to those of the corresponding cotton celluloses cross-linked by conventional external catalysis. The internally catalyzed fabrics from the “wet-cure” are particularly interesting among these compositions with regard to (a) the developed levels of wrinkle-recovery angle, (b) the capability of these compositions to develop high conditioned wrinkle-recovery angles as a result of recure in a “bake-cure” in the absence of external catalysis, and (c) the evidence of mobility of the cross links (i.e., reversibility of the cross-linking reaction followed by reformation of new or old cross linkages) at elevated temperature.

A kinetic analysis of the reactivities of the hydroxyl groups in formylation of the D-glucopyranosyl residues in dextrin

Abstract The kinetics of the homogeneous formylation of dextrin with 90% formic acid have been analyzed as the composite of four, simultaneous, independent, reversible reactions at the C-2, C-3, and C-6 hydroxyl groups of each D -glucopyranosyl residue and the C-4 hydroxyl group on the terminal D -glucopyranosyl group of each molecule. The velocity coefficient and the equilibrium constant for the primary hydroxyl group are higher than the values for the (secondary) C-2 and C-3 hydroxyl groups. Results of the kinetic analysis suggest that one secondary hydroxyl group is esterified rapidly to a low level of equilibrium, whereas the other secondary hydroxyl group is slowly esterified to a higher level of equilibrium. These results are shown to be qualitatively consistent with the behavior of other carbohydrates on esterification or de-esterification.

An Exploratory Characterization of Cotton Cellulose Modified with Tris (2-chloroethyl)phosphoramide

Tris(2-chloroethyl)phosphoramide prepared from ethylenimine and phosphorus oxychloride was reacted with cotton cellulose in the form of print cloth by a pad-dry-cure process involving a base such as sodium carbonate. Relatively low levels of reaction were achieved with this reagent (less than 10% add-on). Conditioned wrinkle recovery angles of the fabric and structural features of the cross links and reagent residues in the cotton cellulose modified with tris(2-chloroethyl)phosphoramide are compared with those of cotton cellulose modified with tris(1-aziridinyl)phosphine oxide.

Nature and Proportion of Cross Links in a Chemically Modified Cotton Cellulose

Cotton fabric was reacted with sodium N-methyl-bis (2-sulfatoethyl) amine in hake-cure reactions and with N-methyl-bis (2-chloroethyl) amine in wet-cure reactions. These reagents were selected so that the cross linkages and substituent groups in the chemically modified cotton would be amenable to analysis by current chemical techniques. The structural units developed by the reagent residues were isolated and identified by means of gas-liquid chromatography and electro- , phoresis. The nature and amount of the structural components of the reagent residues are related to the specific reagent and to the process of reaction. Simple cross linkages involving a single reagent unit constitute a small fraction (about 11-26%) of the total reagent residues. The predominating simple cross link develops between the 2-O- and 6-O-positions of D-glucopyranosyl units.

Variations in a Delayed-Curing Cotton Via Internal Catalysis of Reaction With Divinyl Sulfone

Cotton cellulose fabrics containing quaternary ammonium hydroxide groups at three levels of substitution were prepared directly from reaction of print cloth with 3-chloro- 2-hydroxypropyltrimethylammonium chloride or with glycidyltrimethylammonium chlo ride. The reactions involved sodium hydroxide solutions of mecerizing strength. The chemically-modified fabrics were characterized for primary physical performance proper ties and for self-catalyzed reactions with divinyl sulfone and bis-(2-hydroxyethyl) sul fone. The results extend information already reported for unmercerized cotton cellulose containing quaternary ammonium hydroxide groups generated by quaternization of 2-diethylaminoethyl substituents. The nature of the quaternary ammonium substituent and the mercerized or unmercerized state of the cotton fibers are shown to have a bearing on the efficiency of this self-catalyzed reaction and on the wrinkle recovery angles and other properties developed in the products.