Recent work on the definition of synergistic effects has provided the basis for designing more efficient new approaches to flame-retardant cellulose. The synergistic role of nitrogen in enhancing flame-retardant characteristics has been confirmed for cotton and rayon fabrics modified with N-hydroxymethyl-3-(dialkylphosphono)propionamide (NMPA) and tris(hydroxymethyl)melamine (TMM). Results are compared with those reported previously for similar cellulose derivatives formed via the Arbuzov exchange of halogen precursors. Data are further compared for native and regenerated cellulose derivatives in which NMPA and TMM were applied from a single bath with acid curing, and for others in which TMM was subsequently polymerized by wet fixation in NMPA-modified cellulose. Satisfactory flame-retardant properties can be obtained in cotton at phosphorus contents as low as 0.8%, and the total amount of reagent required is lower as the NMPA/TMM ratio is decreased. An additional contribution of halogen, obtained by using the haloalkyl analog of NMPA, to the flame-retarding effectiveness of these systems is described.

The effect of anhydrous liquid ammonia in the durable press and flame-retardant finishing of cotton and polyester/ cotton blends was studied. The liquid ammonia treatment was carried out prior to, simultaneously with, and subsequent to the functional finishing treatments. The manner of the removal of the ammonia determines the morphological structure of the cellulose and thus the effectiveness of the treatment. Liquid ammonia apparently forms a less reactive aminated species with methylol compounds; therefore, liquid ammonia medium cannot be used for the application of such compounds. Liquid ammonia treatment prior to durable press and flame-retarding finishes is a viable approach to attain improved over-all fabric performance.

The Arbuzov reaction of cotton fabric containing the haloacetamidomethyl groups Cell-OCH 2 NHCOCH 2 X (X=I, Br, Cl) has been studied systematically to prepare new cellulose phosphonate ester derivatives. Comparison of flame-retardant properties of the phosphonate derivatives with those of fabric containing a deposited polymer of related structure showed that phosphorus is more efficient in the form of a cellulose derivative. Problems generally associated with fabrics containing flame-retardant finishes, notably stiffness, were also minimized in the case of derivative formation. Laundering durability was excellent.Further studies on the synergistic effect of nitrogen on flame retardant properties confirmed earlier results and showed that cotton sheeting fabric containing an N/P ratio of 3 at 2% P, 6 at 1.4% P, and about 12 at 0.9% P passed the vertical flame test.

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SynopsisThe reaction of cotton fabric with N-hydroxymethylacetylthioacetamide (HOCHp NHCOCH2SCOCH3) yields acetylthioacetamidomethylcellulose, which can be saponified under mild conditions to the corresponding thiol derivative, mercaptoacetamidomethylcellulose. Some reactions of the thiol group are discussed, including oxidation to disulfide, repeated reduction-oxidation cycles, and blocking with alkyl halides. Chemical methods were used in establishing the occurrence and extent of the predicted reactions and their dependence on specific variables in the system. Changes in the crease recovery and tensile strength of the cotton derivative obtained in the reactions were found to be qualitatively consistent with the expected structures. The results of this work show that crosslinks can be obtained reversibly in cotton by this sequence of reactions. Intervening side reactions produce a gradual decrease in the yield of the desired products, however, as the number of cycles increases. Mercaptoacetamidomethylcellulose provides a limited but useful model for the investigation of reversible crosslinks in cellulose.