Crosslinking cotton with formaldehyde in phosphoric acid

Cotton print cloth was treated with a solution of formaldehyde in concentrated orthophosphoric acid (a strong cellulose swelling agent). The treatment produces a crosslinked cotton with extremely high wet wrinkle recovery and moisture absorptivity, and very low dry wrinkle recovery. The variations in physical properties are explained in terms of crosslink distribution throughout the fiber and specifically by differences in interlamellar and intralamellar crosslinking. Data on the chemical and physical properties of the fabric as well as electron micrographs of fiber cross-sections are presented and compared or contrasted with data from similar treatments employing other solvents such as water (a moderate swelling agent), acetic acid (a weak swelling agent), and sulfuric acid (a solvent which restricts crosslinking to the periphery of the fiber). Although the treatment causes extensive fiber swelling, it produces very little change in crystallinity and no change in crystal lattice type. Also discussed are the effects of combining this wet crosslinking and conventional dry-cure crosslinking with methylol amides in a two-stage process, in which the wet crosslinking is used either as a pretreatment or as an aftertreatment.     

Degrees of heterogeneity of distribution of formaldehyde crosslinks in cotton cellulose

The distribution of formaldehyde crosslinks in cotton cellulose has been followed by electron micrographic analyses of fiber cross-sections and by kinetic analyses of rates of reactions of formaldehyde with cotton. Rapid and slow phases of the crosslinking reactions are indicated to extents which vary with the specific processes of reaction. A wide range in heterogeneity of distribution of crosslinks is found among the compositions investigated, the most heterogeneous distribution appearing in a high concentration of crosslinks in peripheral regions of the fiber. It is evident that additional substantial differences among the formaldehyde-crosslinked cottons are due to different extents of reaction of agent per accessible hydroxyl group.     

Absorption of phosphine in an aqueous solution of formaldehyde and hydrochloric acid

The absorption of phosphine in an aqueous solution of hydrochloric acid and formaldehyde was found to be kinetically controlled in the range of variables studied. The reaction was found to be first order with respect to phosphine and formaldehyde and approximately half-order with respect to hydrochloric acid. The reaction rate constants calculated were 2·34 × 10², 5·88 × 10², 1·84 × 10³, and 4·98 × 10³ [cm³/gmole]^1·5/sec at 4, 13, 27 and 40°C respectively and the activation energy 14740 cal/gmole.     

Grafting of cyclic carbonates onto cotton and modified cottons

Cyclic carbonates react with amines to form carbamates, with alcohols to form hydroxyalkylated products, and with dibasic acids or dibasic acids plus a glycol to form polyesters. These types of reactions between ethylene, propylene, or glycerine carbonate and cotton, either unmodified or modified to contain amine or carboxyl groups, were investigated. Effects of method of application, temperature, time of reaction, and pressure were studied. Temperature in excess of 100°C and reduced pressures were satisfactory for removing the water formed. Reaction between cyclic carbonates, dibasic acids, a glycol, and nonaqueously prepared carboxymethylated cotton in a vacuum oven yielded a fabric with conditioned and wet wrinkle recovery of approximately 300(W + F)°. Infrared spectra, wrinkle recovery, and weight gain indicated that crosslinks formed in reactions between unmodified or carboxymethylated cotton and the cyclic carbonate. Reactions with aminized or diethylaminoethylated cotton formed terminal grafts.     

Influence of reagent residues and catalysts on formaldehyde release from DMDHEU-treated cotton

Observations and conclusions drawn from a model N-methylol reactant system have been used to study formaldehyde release from cotton fabric treated with N,N′-dimethylol-4,5-dihydroxy-ethyleneurea (DMDHEU). Reagent residues produced by DMDHEU in the presence of sodium bisulfate or zinc nitrate were found to be more complex than those formed from the N-methylolpyrrolidone (NMP) reactant system, and the exact nature of some of the residues from DMDHEU could not be established. Zinc nitrate produces higher fixation of DMDHEU on cotton as compared to sodium bisulfate and also reduces formaldehyde release. As is the case with the NMP system, the lower amount of formaldehyde release with zinc nitrate catalyst is believed to be at least partially due to the formation of a complex between the N-methylol reactant, DMDHEU, and zinc nitrate. The C? OCell bonds in both finishes resist acid-catalyzed cleavage but cleavage of the N? C bonds in N-methylol groups (to release formadehyde) in the presence of acid is greater for the DMDHEU system than for the NMP system. Results with the DMDHEU and NMP systems are similar, but because of the complex nature of the products formed in the DMDHEU system it is very difficult to correlated formaldehyde release with specific chemical structures of residues or reactants.     

Influence of structure of cyclic urea derivatives on their reactivities with cotton

The structure of the cyclic urea influenced the rate of reaction with cotton cellulose and the mechanism by which reaction occurred. Reaction of N, N′-dimethylolethylene-urea (DMEU) and N, N′-dimethylolpropyleneurea (DMPU) with cellulose in presence of inorganic salt catalysts proceeded through methylol hydroxyls and at the same rate; but reaction mechanism differed. With DMEU, N → metal ion coordination occurred and S_N2 mechanism prevailed. With DMPU, O → metal ion coordination resulted. Reaction of dihydroxyethylene urea (DHEU), N, N′-dimethyldihydroxyethyleneurea (DMeDHEU), and N, N′-dimethyloldihydroxyethyleneurea (DMDHEU) with cotton cellulose proceeded through ring hydroxyls with the formation of a carbonium ion, indicating an S_N1 mechanism. The much faster rate of reaction with DMeDHEU than with DHEU was attributed to the more electronegative environment of its ring hydroxyl, while the much slower rate of reaction of DMDHEU was attributed to hydrogen bonding between its methylol and ring hydroxyls.     

Absorption and rheological phenomena during foam application on textiles.

A simple rheological model has been used to describe foam flow through moving textile assemblies. The validity of this model was tested, and the nature and the relative magnitude of deviations from the model evaluated for several different substrates. Neglecting foam degeneration during transport, the model was found to represent a valuable means of evaluating some rheological and geometrical deviations. The model can be used in a semi-quantitative way to describe absorbency during foam application. Liquid absorption experiments done off-line, absorption during foam application and some earlier results could be described using different theoretical approaches. Some rheological anomalies have been discussed.     

Carboxyethylation of cotton by treatment with acrylamide

New methods for the treatment of cotton with acrylamide have been studied which permit the preparation of modified fabrics with relatively high degrees of carboxyethyl substitution. Wet treatment with acrylamide and sodium hydroxide can be used to produce cottons bearing both carboxyethyl and carbamoylethyl ether substituents. Adjustment of reaction conditions controls the amount and ratio of these substituents. The effects of varying the concentrations of the reactants, the time and the temperature of reaction, and the solvent media employed have been determined. Some elucidation of the chemical mechanisms is provided. Previous work has shown that dry heat treatments of cotton impregnated with acrylamide and alkali can be used to produce high carbamoylethyl substitutions with little or no carboxyethyl substitution. The present work provides an extension of the cotton-acrylamide treatment whereby fabrics can be produced with only carboxyethyl or carbamoylethyl groups, or with mixtures of the two.     

Catalytic oxidation of methanol to formaldehyde: an example of kinetics with transport phenomena in a packed-bed reactor

In the present work the partial oxidation of methanol to formaldehyde has been studied as an example of strongly exothermic reaction affected by internal diffusion in order to deep the topic of mass and heat transfer in packed-bed catalytic reactors both at particle level, introducing the calculation of the effectiveness factor for complex reactions network, and at reactor level, for what concerns long range gradients of composition and temperature. The aim of the work is to stress the impact of the use of rigorous numerical methods, today possible for the high performances reached by the computers, in the solution of a simultaneous set of many differential equations that are necessary to describe completely the mentioned system. A complete mathematical model of the particle and the reactor is presented and a solution strategy is reported for the chosen reaction by considering a reliable kinetic law and evaluating related parameters from experimental data reported by the literature. Calculation results are reported for both particle internal profiles and reactor simulation. The described approach can easily be extended to many other devices and reactors geometry such as, e.g., the ones used in the field of environmental catalysis.     

Surface treatment of cotton fabrics with chitosan

Antibacterial activities of cotton and polyester/cotton fabrics treated with chitosan or chitosan/DMDHEU have been investigated. The washing durability properties of the aforementioned fabrics were also studied. Another group of fabric samples produced from mature and immature cotton fibres were dyed with reactive dyes and the colour yields and colour differences of the dyed fabrics assessed. The surfaces of the treated and untreated cotton fabrics were observed by scanning electron microscopy to compare the morphology.     

一种新型甲醛处理装置及处理效果研究

针对目前室内装修甲醛严重超标,严重危害人体健康的现状,设计了一个可以在线检测甲醛浓度并采用光触媒技术进行处理的系统装置,并进行了探索性试验.结果表明,在一定的时间和浓度范围内,光照强度越强、甲醛初始浓度越低、光触媒用量越多,甲醛的去除率越高.在实际应用中,考虑时间和成本的因素,可以选择光照强度31 W,甲醛的初始浓度1.6 ppm,光触媒的用量为2.5％,此时甲醛的去除率较高.     

Amine-catalyzed polymer encapsulation of cotton fibers by vapor phase application of formaldehyde

A process for encapsulating cotton fibers in the form of woven clothes at ambient temperatures with polyoxymethylene is described. It involves pretreatment of the cotton with a carbon tetrachloride solution of tributylamine and diphenylamine to deposit the basic catalyst on the surface of the fibers. Subsequent exposure to dry, purified vapors of monomeric formaldehyde at 25°C results in the encapsulation of individual fibers with high molecular weight polyoxymethylene. The process is relatively fast (30% fiber weight gain in approx. 20 min) with the polymer located only at the fiber surfaces. Fiber cementation does not become pronounced for weight increases below approximately 60%–65% based upon the weight of the fibers. Thickness of the polymer sheath increases with the time of the polymerization reaction. Because of the uniformity of the polymer layer deposition, the encapsulated cotton cellulose fibers can be expected to exhibit substantially different physical and chemical surface properties even at low polymer add-on. The tensile and tear strengths of the polyoxymethylene-encapsulated cotton fibers are generally improved, with some gains in abrasion resistance also noted. Differential staining techniques and polarized light microscopy have shown the location and uniformity of the polymer sheaths.     

A study of the ageing and deactivation phenomena occurring during operation of an iron molybdate catalyst in formaldehyde production

Catalyst from a Perstorp Formox formaldehyde plant, operating with high inlet concentration of methanol (10.2 vol.%), was discharged from single tubes of a multi-tube reactor after half the expected lifetime of the catalyst and again after termination of the load. Each tube was filled with two different layers of catalyst. From the inlet of the reactor the first layer was a catalyst mixed with inert rings, which was followed by a second layer of pure catalyst extending from the middle to the outlet of the reactor. Catalyst fractions from the two layers were characterized with various techniques including BET, Fourier transform Raman (FT-Raman) spectroscopy, X-ray diffraction (XRD), elemental analysis with atomic absorption spectroscopy (AAS) and activity measurements. It was found that the surface area of the catalyst in the mixed layer increases during operation while a small decrease is noticeable for the catalyst below in the pure layer. Elemental analysis, XRD and FT-Raman show that during operation of the catalyst there is migration of Mo species from the upper part of the reactor towards the outlet. Activity measurements reveal severe deactivation of the catalyst in the mixed layer. It is concluded that the deactivation primarily is due to formation of volatile species formed by the MoO₃ surface reacting methanol, causing a decrease of the MoO₃/Fe₂(MoO₄)₃ mole ratio in the catalyst. Concerning the catalyst in the pure layer, the condensation of needle-like crystals of MoO₃ mainly occurs on the external surface of the catalyst ring.     

Use of aldehydes other than formaldehyde in THPOH/ammonia flame-retardant finishes for cotton

Several aldehydes have been tested as substitutes for the lachrymator formaldehyde in the THPOH/ammonia process. Aldehydes such as acetaldehyde or butyraldehyde promote rapid polymer formation without being incorporated into the finish. Chloral is incorporated to a limited extent, but the finish is sensitive to base. To gain further insight into the polymer-forming process, the reactions of THP and its aldehyde derivatives with ammonia have been investigated in vitro. There is evidence that THP acts as a difunctional reagent, regardless of the aldehyde, forming a linear polymer with a single phosphorus, nitrogen, and oxygen atom in each repeating unit.     

Absorption of water by graft copolymers of cotton with methyl methacrylate using high-resolution NMR

Graft cotton fibers containing poly(methyl methacrylate) were initiated by ultraviolet radiation. High-resolution NMR was used to study the nature of water absorption by these graft copolymers and also by mixtures of cotton fibers with the corresponding homopolymers. Results obtained help in investigating the structure of the copolymers and to differentiate, in a simple way, between true graft copolymers and mechanical mixtures or coated fibers.     

Studies of some basic aspects in easy-care cotton finishing,IV. Effect of acid scavengers on free formaldehyde in and strength of crosslinked cotton

When cotton fabric was padded with a solution containing dimethylol dihydroxy ethylene urea (DMDHEU) (200 g/l) at pH 2.5, batched for one hour, given a wash through padding with water, dried and cured, the crosslinked cotton showed a crease recovery of 287° and 307° in the dry and wet state respectively and a retained strength of ca. 68%. Incorporation of sodium hydroxide in the washing pad accentuates the retaining strength. The latter attained a value of ca. 90% without seriously affecting the dry and wet crease recovery. However, the amount of free formaldehyde in the crosslinked cotton was quite substantial. Increasing the concentration of NaOH up to 2 g/l in the washing pad caused a significant decrease in crease recovery of and a considerable increase in the amount of free formaldehyde in the crosslinked cotton fabric. Replacement of sodium hydroxide by sodium carbonate at a concentration of up to 2 g/l reduced the amount of free formaldehyde without adversely affecting the crease recovery. Utilization of urea in the washing pad at a concentration of up to 16 g/l provided advantages in terms of lesser amount of free formaldehyde (388 ppm), higher retaining strength (ca. 80%)and excellent crease recovery (above 280°). On the other hand, addition of sodium sulphite at a concentration of up to 8 g/l in the washing pad was accompanied by a significant decrease in crease recovery, and a significant increase in the amount of free formaldehyde. Nevertheless the role of sodium sulphite as acid and formaldehyde scavanger could be ameliorated through lowering the pH of DMDHEU padding bath or addition of sodium chloride or sodium dihydrogen phosphate to this bath.     

Single-step dyeing and finishing treatment of cotton with 1,2,3,4-butanetetracarboxylic acid

A single-step dyeing and finishing (SDF) process was developed to eliminate dyeing problems associated with cotton crosslinked by polycarboxylic acid such as 1,2,3,4-butanetetracarboxylic acid (BTCA). This process consisted of several steps: (a) impregnation of the fabric by the bath containing BTCA, dye, and catalyst; (b) drying; and (c) curing at high temperature. Color strength (K/S) and dye fixation of cotton treated by the SDF process were excellent, especially with reactive dyes containing mono- or dichlorotriazinyl compounds and, in some cases, were higher than those of the sample dyed by a conventional batch process without finishing treatment. The presence of dye in the SDF process did not interfere with crosslinking of cotton. We believed that the reaction occurred between carboxyl groups of BTCA and s-triazinyl groups in reactive dyes in the presence of imidazole and other catalyst. FTIR, Raman, and X-ray fluorescence spectroscopies were used to confirm the mechanism of dye fixation. Elemental analysis also supported this mechanism. The SDF process can be an excellent way to dye fabric that also requires crosslinking treatment for smooth drying appearance. © 1994 John Wiley & Sons, Inc.