Cotton cellulose commercial reactions

Figure 1 shows the repeating glucose units of cellulose with the carbons labeled, including those with the reactive 2, 3, and 6 hydroxyls. Ihe most important reactions of cotton cellulose commercially are esterification and etherification, with the products of etherification ranking first. It is generally agreed today among textile scientists that durable press cellulosic textiles ow their smooth-drying and resilient properties to the reactivity of formaldehyde and its amide derivatives with cellulose to produce crosslinks between adjacent cellulose chains (Figure 2). Hovever, the theory that crosslinking was responsible for increased resiliency developed only after the treatmaits were in wide use.

Another important commercial utilization of cotton etherification is in coloration of fabrics with reactive dyes [338 340]. Reactive dyes contain chromophoric groups attached to moieties that have functions capable of reaction with cotton cellulose by nucleophilic addition or nucleophilic substitution to form covalent bonds. In the nucleophilic addition reaction, an alkaline media transforms the reactive dye to an active species by converting the sulfatoethyl-... 

Etherification. The accessible, available hydroxyl groups on the 2, 3, and 6 positions of the anhydroglucose residue are quite reactive (96) and provide sites for much of the current modification of cotton cellulose to impart special or value-added properties. The two most common classes into which modifications fall, include etherification and esterification of the cotton cellulose hydroxyls as well as addition reactions with certain unsaturated compounds to produce cellulose ethers (see Cellulose Ethers). One large class of cellulose-reactive dyestuffs in commercial use attaches to the cellulose through an alkali-catalyzed etherification by nucleophilic attack of the chlorotriazine moiety of the dyestuff ... 

Phosphoric Acid-Based Systems for Cellulosics. Semidurable flame-retardant treatments for cotton (qv) or wood (qv) can be attained by phosphorylation of cellulose, preferably in the presence of a nitrogenous compound. Commercial leach-resistant flame-retardant treatments for wood have been developed based on a reaction product of phosphoric acid with urea—formaldehyde and dicyandiamide resins (59,60). 

CP esters are generally prepared as the ammonium salt [9038-38-4] by the reaction of cellulose with phosphoric acid and urea at elevated temperatures (130—150°C). The effects of temperature and urea/H PO /cellulose composition on product analysis have been investigated (33). One of the first commercially feasible dameproofing procedures for cotton fabric, the Ban-Flame process (34,35), was based on this chemistry. It consists of mixing cellulose with a mixture of 50% urea, 18% H PO, and 32% water. It is then pressed to remove excess solution, heated to 150—175°C for 5—30 minutes, and thoroughly washed (36). 

Cotton Ammonium phosphates are the most effective FRs for cotton as first identified by Gay-Lussac in 1821 and still widely used. All phosphates on heating release phosphoric acid, which catalyses dehydration reactions of cellulose to yield char at the expense of volatiles formation reactions.50 However, ammonium phosphates like mono- or diammonium phosphates are water soluble, hence applicable as nondurable treatments only. Ammonium bromide can be used in combination with ammonium phosphates to provide some vapor-phase FR action. Other examples include borax and boric acid, ammonium sulfamate, and sulfates. These nondurable finishes are useful for disposable fabrics, insulation, wall boards, theatrical scenery, packaging material, paper, etc. Ammonium polyphosphates (APPs) are used in combination with urea to provide semidurable finishes and by curing at 160°C, when some phosphorylation can occur. Semidurable finishes are very useful for materials that may not need frequent washings, e.g., mattresses, drapes, upholstery, carpets, etc. Some commercial examples of semidurable finishes include Flammentin FMB (Thor Specialities), Pyrovatim PBS (Ciba, now marketed by Huntsman), etc.26... 

The chemical name of this reagent is l,3-bis(hydroxymethyl)-4,5-dihydroxy-imidazolidinone-2 but it is usually called DMDHEU or the glyoxal reactant because it is prepared from glyoxal, urea, and formaldehyde. Other methylolamide agents that have been used for producing wrinkle resistance in cotton include the aforementioned urea formaldehyde, dimethylolurea, dimethylolethyleneurea, and formaldehyde adducts of melamines (triazines), acetylenediurea, propyleneurea, uron, triazones, and alkyl carbamates. Reactions between methylolamides and cellulose occur in the presence of acid (or Lewis acid) catalysts and are very fast at elevated temperatures—sufficiently so that they are adaptable to the requirements of rapid, commercial processing of cotton fabrics. 

Many important fibers, including cotton and wool, are naturally occurring polymers. The first commercially successful synthetic polymers were made not by polymerization reactions but through the chemical regeneration of the natural polymer cellulose, a condensation polymer of the sugar glucose that is made by plants ... 

Cotton linters were swollen to an increasing extent by means of phosphoric acid of increasing concentration, Using a number of simple sugars plus a series of dextran molecules ranging in M.W. from 180 to 2,4 X 107 and diameter from 8 to 1600 A, it was possible to measure the pore volume and calculate the surface area within the swollen fibres accessible to all the molecules within this range. The substrates reacted with a commercial cellulose enzyme preparation, and the initial rate of reaction was compared with the accessibility of the substrate to molecules of various sizes. There was found to be a linear relationship between the initial reaction rate and the surface area within the cellulose gel which was accessible to a molecule of 40 A, diameter. 

As cotton fabrics are cellulose-based, the dyeing of polysaccharides has been studied as an art for centuries, but the underlying reactions have now been studied. Although this Section is concerned with the covalent dye derivatives of purified polysaccharides, and not general dyeing of fibers, it is not always possible to deduce from the literature the exact structures of the derivatives. This situation arises because attention has mainly been paid to the dyeing of polysaccharides simply to color them, and because commercially available dyes whose overall structures have not necessarily been disclosed are usually used. 

Flame-Retardant Finishes on Cellulosic Substrates. The flame retarding of cotton and viscose-rayon fabrics has been the object of a large worldwide effort on phosphorus-containing finishes (217-219). The commercial cotton finishes are based on tetrakis(hydroxymethyl)phosphonium salts, usually the chloride or sulfate (220). These salts are prepared by reaction of formaldehyde with phosphine in the presence of an acid. 

Cotton is almost pure cellulose. Both rayon and acetate rayon are made from chemically modified cellulose and were the first commercially important synthetic textile fibers. In the production of rayon, cellulose-containing materials are treated with carbon disulfide, CSj, in aqueous sodium hydroxide. In this reaction, some of the —OH groups on a cellulose fiber are converted to the sodium salts of a xanthate ester, which causes the fibers to dissolve in alkali as a viscous colloidal dispersion. 

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