A study has been made of the mechanism by which cotton is made wrinkle resistant by dimethylol ethyleneurea. Estimates are made of the length of cross-links and the relative effect of several factors, including processing conditions, cross-linkage, and acid damage, on the loss in strength of the fabric on treatment. ' Various methylol derivatives of ethyleneurea were used in the study of the effect on chemical and physical properties. It has been demonstrated that the methylol deriva tives of ethyleneurea react chemically with cellulose under the influence of acidic catalysts. Metallic salts are most efficient in promoting this reaction. Both mono functional and difunctional compounds react with the cellulose. The latter, however, cause cross-linkage, which effects marked changes in the physical properties of the treated cotton fabric, particularly wrinkle resistance. Dimethylol ethyleneurea forms cross-links averaging 1.4-1.5 ethyleneurea residues in length. These residues are con nected by methylene groups. The effects of variations in catalyst, composition of the finishing agent, and curing conditions are shown. Relation of the findings to practical finishing is discussed.

SynopsisAcetals that react with cotton to form cellulose crosslinks are derived from dialdehydes that can form five-or six-membered tetrahydrofuran or tetrahydrop-wan rings. These aldehydes themselves are reactive to cotton, but the acetals do not form the aldehyde to react. The acetals were less reactive than the aldehydes and formed crosslinks with a different structure. Intrinsic reactivity of acetals increased with increased branching in the alkoxy group, hut the increase was often hidden by the effect from changing solvents. In some instances a greater reactivity with methyl acetals was pronounced. Strength loss in cotton fabric from crosslinking was greater with acetals than with conventional crosslinking agents because even the most reactive acetals were less reactive and required more rigorous reaction conditions than conventional agents.

The cross-linking of cellulose in cotton fabric with three wrinkle-resistance finishing agents has been investigated. The three agents used were dimethylol urea, dimethylol ethyleneurea, and formaldehyde. With all three compounds, maximum crease recovery angles are obtained with a substitution of 0.04-0.05 cross links per anhydroglucose unit. As crease recovery angles increase, the elongation and permanent set caused by an 8-kg. tensile load on a 1-in. fabric strip decreases. Permanent set approaches zero near 135° warp crease recovery. Changes in the load-elongation curves indicate elastic modulus increases as crease recovery angles increase. Treatment of fabric to the same crease recovery angles with the three compounds reduces tearing and breaking strengths to different extents. The differences are due to different amounts of cellulose degradation caused by the aciclic catalyst systems and not to the structure of the cross links.

SynopsisThe relative effectiveness of several aldehydes in crosslinking cellulose of cotton fabric was determined using a pad-dry-cure treatment and a treatment by immersion in a solution at room temperature. Aldehydes ranked in the same order of ability to crosslink in both treatments. Factors related to crosslinking ability are discussed. The aldehydes crosslinking to the greater extent hydrated readily in water because the aldehyde group was activated or because cyclic hydrates could be formed.

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