Rayon Yarns Research Articles

Processing of rayon waste effluent for the recovery of zinc and separation of calcium using thiophosphinic extractant

Zinc is used in various metallurgical, chemical and textile industries. In textile industries, waste effluent containing zinc is generated during the manufacture of rayon yarn. Due to the strict environmental regulations and the presence of toxic metallic and other constituents, the discharge of effluents in sewage is restricted. In view of above a process has been developed for the recovery of zinc from rayon waste effluent following solvent extraction technique using thiophosphinic extractants Cyanex 272 and 302. Before recycling of zinc sulphate solution in spinning bath, solution must be free from calcium, which is deleterious to the process as gypsum precipitates and forms scale. The extractant Cyanex 302 has been found selective for the recovery of 99.99% of zinc in the form of [R 2Zn] org from the effluent above equilibrium pH 3.4 maintaining the O/A ratio of 1/30 leaving all the calcium in the raffinate. The zinc from the loaded Cyanex 302 can be stripped with 10% sulphuric acid at even O/A ratio of 10. The stripped solution thus obtained could be recycled in the spinning bath of the rayon plant and raffinate could be disposed safely without affecting environment.

Studies on Leaching and Recycling of Zinc from Rayon Waste Sludge

Zinc is an important nonferrous metal used in various metallurgical, chemical, and textile industries. In textile industries, a waste sludge containing zinc hydroxide is generated during the manufacture of rayon yarn. The two sludge samples were used for the experimental work. The National rayon contained a high value of zinc (18.90%), 13.0% Ca, and 7.63% Si, whereas the sample from Baroda rayon contained a low value of zinc (5.12%), 19.2% Ca, and 5.60% Si. The impurities present in both of the samples are iron, aluminum, magnesium, silica, etc. The leaching studies were carried out using alkaline, ammoniacal, and acidic solutions at different concentrations of the lixiviants at room temperature. Sulfuric acid has been found to be the suitable reagent for complete dissolution of zinc. On the basis of the results of kinetic studies of the leaching in sulfuric acid medium, a chemical reaction control dense constant size cylindrical model has been proposed as the experimental data that fit most satisfactorily with the equation 1 − (1 − X)1/2 = Kct for both the sludge samples. The solution could be purified for subsequent metal recovery. The residue produced after zinc recovery could be disposed of safely without affecting the environment.

Changes in Breaking Strength and Water Retention of Cellulosic Fibers hydrolyzed by Commercial Cellulases.

The changes in weight loss, breaking strength and water retention of the cellulosic fibers; cotton, viscose rayon filament and cuprammonium rayon filament yarns, by the enzymatic hydrolysis were investigated with the commercial cellulase A and cellulase B from Aspergillus niger and from Trichoderma viride, respectively. Under the hydrolysis conditions used in this study, the surface fibrils of cotton and rayon yarns did not easily eliminated. The cellulase B lost weight at faster rate than the cellulase A for all samples: the weight loss increased in the order viscose rayon < cotton < cuprammonium rayon. In all cases, although the fall in breaking strength was totally progressive with increasing weight loss, the relationship between the breaking strength and weight loss appears to be markedly affected by the fine structure of cellulosic fiber. Retention of strength after 240 min incubation time increased in the order cotton < cuprammonium rayon < viscose rayon. It was especially noted, in the case of cellulase B, that there was the range of weight loss which the strength remains constant for all samples. Water retention value of hydrolyzed yarns was found to reach a minimum at initial stages of hydrolysis and then increase at more advanced stages of hydrolysis in all cases.

Multi-level lot-sizing in a rayon yarn company: A case study

This paper presents a case study conducted at a rayon-yarn plant. (For commercial reasons, the identity of the company is concealed.) This study deals with the economic lot-sizing problem in a multi-stage, multi-facility and multi-product production-inventory system. The multi-level lot-sizing model suggested by Gunasekaran et al. (1990a) is used for the application. The application of the model helped to reduce the set-up and in-process inventory carrying costs. The consequences of implementing economic batch sizes obtained from the model are presented and compared with present practice.

A Study of the Micropore Structure of Carbonized Rayon Yarn by Nitrogen Adsorption and Nonane Pre-Adsorption

Adsorption isotherms of nitrogen have been determined at 77 K on three samples of carbonized rayon yarn, both before and after the pre-adsorption of n-nonane. In their original state the three samples were all highly microporous. Application of the αs-method of isotherm analysis reveals that their micropore volumes were 0·17–0·19 cm3g−1 and their external surface areas 20–27 m2g−1 (the corresponding BET areas being 427–483 m2g−1). Nonane pre-adsorption resulted in blockage of the entire micropore structure only in the case of one sample: micropore volumes ∼0·1 cm3g−1 were still available for nitrogen adsorption in the other two samples. It appears that nitrogen molecules were able to gain access to some parts of these micropore structures through wider pore entrances which were not completely blocked by the pre-adsorbed nonane. The work has shown that the nonane pre-adsorption method requires further investigation before it can be used with confidence for the assessment of microporosity.

Adsorption characteristics of carbonized rayon yarn: Effect of outgassing temperature

It is shown that the outgassing temperature has a pronounced effect on the adsorption characteristics of a carbonized rayon yarn. The results of the present study reveal that after outgassing the carbon yarn at 350°C the pores become easily accessible to nitrogen molecules at liquid nitrogen temperature. Earlier, these samples, outgassed at 200°C, showed hardly any accessibility to nitrogen molecules at 77 K.

Characterisation of the pore structure of carbonised viscose rayon yarn: Analysis of adsorption isotherms of nitrogen and carbon dioxide

Viscose rayon yarn was carbonise under various conditions. Adsorption of nitrogen and carbon dioxide was measured at 77 K and 195 K respectively on the carbonised yarn samples. The adsorption data was analysed using the BET method, α s method and an empirical method for Type I isotherms. The results of the present study suggest that the carbonised fibres are predominantly microporous with a significant contribution of the external surface to the total adsorption.

Dyeing High Wet Modulus Rayon Yarns with Fiber Reactive Dyes

Dyeing behavior of four selected high wet modulus (HWM) rayon yarns, regular viscose rayon yarn, and cotton yarn were compared. After being dyed with a variety of fiber reactive dyes, yarns of each fiber were evaluated for quantity of dye taken up by the fiber and for apparent color yield. Dye sorption was quantified through spectrophotometric analysis; color and shade evaluation were done instrumentally, using a colorimeter, as well as visually. All forms of rayon studied were found to exhaust more dye than did cotton. Dye take-up of HWM rayon yarns was similar to that o f viscose. Depth of color o f dyed cotton yarns was consistently lower than that o f any o f the rayon yarns studied. Small variations in depth of shade among HWM and viscose yarns were attributed to the presence or absence o f delustrant.

Adsorption characteristics of carbonised rayon yarn

Carbonisation of indigenous rayon yarn was carried out at various maximum heat treatment temperatures. Results of the present study suggest the possibility of making carbon fibres with molecular sieve properties by suitably adjusting the conditions of pyrolysis. Maximum adsorption capacity for carbon dioxide was estimated to be 28% by weight provided the adsorption is carried out at 273°K and under a pressure of 2614 cm of mercury.

Studies of pyrolysis and air heating of rayon by inverse gas chromatography

Inverse gas chromatography using water probing at 110°C was carried out to characterize rayon yarns after prior heating at 200 and 250°C in both inert (nitrogen) and oxidative (dry air) atmospheres for successively longer time intervals. During the early stages of heating in either atmosphere, the affinity of the rayon for water drops rapidly. However, whereas continued heating in N 2 results in a further loss of activity, data have been obtained showing that after an initial period yarns heated in air at 250°C exhibit an increasing attraction for water even while losing more weight.

The Use of Textile Yarns in Separation Processes

A new method has been developed for preparing chromatography columns quickly, uniformly, and with high reproduci bility, using textile yarns as the solid adsorbent. Gas-chromatography experiments using columns packed in this way have revealed that rayon yarns have a high affinity for water vapor but allow other species, even those quite similar to water in size and chemistry, to pass through essentially unretarded. The degree of water retardation by rayon yam- filled columns has been found to depend on a number of controllable factors: charge volume and frequency of injection, column pressure and temperature, and yarn packing density. To demonstrate the usefulness of the rayon-water specificity for removing water from mixtures, two novel devices have been built that are capable of producing dry ethanol from aqueous mixtures on a laboratory scale at modest energy cost. One of these designs, taking advantage of the high tensile strength of yarn, makes use of a moving yarn loop to achieve almost continuous separation and a high yield of ethanol. Even if such processes do not turn out to be economically practicable for large-scale ethanol production, the concept of gas or liquid chromatography using bundles of yarns with suitable chemical properties should find application in many practical separation problems.

Ways of reducing the consumption of materials in the production of viscose rayon

of the viscose. The investigations described in this article were carried out relative to the textile rayon technology used at the Klin Man-Made Fibre Combine so that the experiments were carried out by a procedure in which the viscosity of the viscose is not increased. There are three methods of lowering the viscosity of viscose, viz. by increasing its temperature [2], by greatly increasing the gradient of the flow velocity of the viscose in the pipelines and through the spinneret holes [3], and by reducing the degree of polymerization (DP) of the cellulose for the textile rayon [4-6]. The first two methods are not used extensively in the industry because they require equipment modification and the reconstruction of the viscose department of the chemical section, and the third method is of limited use because it may result in a decrease of the tenacity of the textile rayon yarn. In view of the production conditions obtained in the Klin Combine the choice fell on the third method of reducing the viscosity of the viscose. It was necessary, therefore, to determine the limit to which the DP of the cellulose can be lowered without producing an adverse effect on the quality indices of the yarn. An analysis of imported and Soviet-produced textile viscose rayons showed that at many Soviet establishments the DPof the cellulose in textile rayon is on a higher level than the DP of the imported specimens, by about 20-40 units. Experimental batches of textile rayons with a DP of 258-340 were next produced on semiindustrlal equipment.

Postdecrystallization rates of grafted fibers and their effect on fiber elasticity. I. Effect of zinc chloride concentration

AbstractRayon yarns grafted with poly(ethyl acrylate) become highly elastic following decrystallization in aqueous zinc chloride solutions. An increase in temperature speeds up the decrystallization rate but does not have a substantial effect on the ultimate elongation properties of the grafted fiber. Increasing the concentration of zinc chloride does not have a marked change in the extension properties of the grafted fiber until 70% zinc chloride. At this saturated concentration, there is a sudden and dramatic change in the elastic properties of the grafted fiber. In fact, the grafted fibers after decrystallization in 70% zinc chloride have elongations in excess of 800%.

Composition of the viscose and the parameters of the precipitation liquor as factors in the spinning conditions for viscose rayon yarn

Composition of the viscose and the parameters of the precipitation liquor as factors in the spinning conditions for viscose rayon yarn

The Optimum Twist in Conventional and Open-end-spun Staple-fibre Viscose Rayon Yarns

The Optimum Twist in Conventional and Open-end-spun Staple-fibre Viscose Rayon Yarns

The Effect of Repeated Winding on the Hairiness of Open-end-spun and Conventional Cotton and Staple-fibre Viscose Rayon Yarns

The Effect of Repeated Winding on the Hairiness of Open-end-spun and Conventional Cotton and Staple-fibre Viscose Rayon Yarns

50—SOME ASPECTS OF WORSTED-YARN STRUCTURE. PART III: THE FIBRE-PACKING DENSITY IN THE CROSS-SECTION OF SOME WORSTED YARNS

Measurement of the fibre-packing density in the cross-section of a range of wool worsted yarns indicates that these are slightly hollow at the core, with the maximum packing density occurring about one-quarter of the yarn radius from the yarn axis. A comparison of these results with those obtained on cotton-viscose rayon yarns by other workers is also made.

Processing rayon and acetate yarns at textile mills

Processing rayon and acetate yarns at textile mills

The market for polyester, nylon, and rayon yarns in tire applications

AbstractThe use of rayon, nylon, and polyester in various tire applications is described, and the relative merits of each are defined. Future development objectives and expectations are outlined. Volume projections for polyester, nylon, and rayon in tire reinforcement are given as a function of tire type. Product life cycles of tire reinforcement materials are analyzed in terms of market share. Polyester is expected to become dominant in 1973.

43—FIBRE MIGRATION IN OPEN-END-SPUN YARNS

A study of the migration of fibres in open-end-spun yarns is reported. Samples of viscose rayon yarns were produced by the drum and air-vortex methods, and the results obtained on them were compared with those for a ring-spun yarn made from the same fibre. Migration was studied by determining three parameters: the helix profile, the mean fibre position, and the r.m.s. deviation, i.e., the root-mean-square value of the radial deviation of the helix profile from the mean fibre position. The geometry of fibre-packing in the yarn cross-section and the fibre extent were also studied. It is shown that open-end-spun yarns are somewhat different in character from ring-spun yarns and that the most basic structural differences are found in the fibre extent, fibre migration, and fibre-packing density. The fibre migration in an open-end-spun yarn is shown to be as little as one-sixth of that in a typical ring-spun yam, and the difference in structure is important in that it can affect the yarn properties. It is concluded that the observed low strength of most open-end-spun yarns can be attributed to the poor fibre extent and inferior fibre migration within the yarn body and that their relatively high elongation can be explained in terms of the folded and entangled nature of the fibres. An examination of the fibre geometry in the yarn shows that the design features of drum spinners are important with regard to the determination of the fibre extent, a tangential feed being preferable to an axial one. The yarn cross-sections demonstrate that open-end spun yarns generally have a lower fibre-packing density than ring-spun yarns, which tends to give the yarn a more bulky nature; this is consistent with what might be expected from an assembly of tangled fibres.