CHEMISTRY AND TEXTILES

By Academician Aleksei KUTEPOV, Andrei MORYGANOV, Dr. Sc. (Tech.); Anatoly ZAKHAROV, Dr. Sc. (Tech.), RAS Institute of Chemistry of Solutions

A major condition for giving Russia's textile industry a new lease on life is to make its products more competitive on the world market by improving their quality and ecological effect. And what matters most, fabrics should have a cost affordable for consumers and be produced in a most environment-friendly way. It is impossible in principle to solve such interlinked and quite often incompatible tasks by upgrading technological processes based on the extensive improvement of processing parameters, expanding assortment, and increasing the concentration of chemical reagents.

What deserves special attention for textile producers nowadays is the use of non-traditional physical and chemical methods of modification of solutions of auxiliary preparations and dyes, ways of regulating the processes of heat and mass transfer in textiles, ensuring better technological and consumer qualities of production and intensive dressing production processes. Scientists in the town of Ivanovo do well in this respect largely thanks to the lucky merger of academic science and industry there. The practical result of their activity- 168 machines and conveyor lines, applying new technologies at 50 enterprises of Russia and CIS and at two enterprises in Italy (certified by 43 licenses and patents).

Natural fibrous materials (cotton, flax, wool) contain 6-25 percent impurities (wax-like, pectic, nitrogen bearing, dye-stuffs, vegetative). They do not stand in the way of such mechanical operations as the making of yarn out of fibres and out of it or chemical threads- fabrics. However, at this stage, fabric, called grey or unprepared cloth because of wax-like substances availability, dressing(*) and oil is actually non-capillary; it is poorly moistened and cannot be dyed or added any properties, improving its consumer qualities (non-crease, small shrinkage, etc.).

Carried out in dressing production, these operations are based on various physical and chemical processes under way in fibrous materials-the elimination of natural and artificial impurities and their removal from fabric, diffusion deep inside fibre and the fixation of dye- stuffs in it (in the process of uniform dyeing or pattern dyeing) and the putting of special textile auxiliary substances on fabric, for instance, to sew cellulose

* Dressing-a mixture of starch or synthetic preparations with water.- Ed.

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macro-molecules together, which ensures non-crease and non-shrinkage, wear and fire resistance, etc.

The general shortcoming of the existing chemical-technological processes in dressing production is the need to apply huge amounts of chemicals, oxidizers, reducers, alkalis, and dyes. Regrettably, they cannot be fully used for their direct purpose, and a significant part of them gets into the working zone air and in sewage quite often with an adverse effect on the technological properties of fabrics and their quality.

Proceeding from what has been said above, the use of non-traditional physical and physical- chemical methods in the textile industry is the task of prime importance. The methods should improve technological and consumer properties, make dressing processes less dangerous for environment, and intensify the processes of improving fibrous materials.

As has been said, grey cloth stands out for low capillarity and poor moistening, impeding the penetration of solution in the material structure, adversely affecting ready-made products' quality. For this reason, the creation of technologies and equipment to intensify the impregnation of textile materials has become the main trend in industrial production today.

By using specially developed methods, a relative assessment of the effect of various ways of intensifying the impregnation of poorly moistened textile materials was carried out experimentally for the first time. As a result, an activating effect of the short-term preliminary steaming of a textile material in the course of its impregnation was established. Several modifications of industrial installations, implementing the preliminary steaming of poorly moistened textile materials before impregnation were created by taking into account the peculiarities of their dressing and dyeing treatment. The essence of the effect is the formation of a vacuum in the pores of a material at its entry into the impregnating liquid under the condensation of the steam squeezing out the air from the fibrous material's pores.

The modifications of the updated impregnation equipment, unmatched elsewhere in the world, went through extensive industrial testing and was applied in technological processes at more than 30 textile mills of Russia and CIS countries both as separately manufactured chambers and as machines and lines, serially produced by the Ivtekmash association.

The last few years have seen yet another untraditional way of raising the effect of the processes of liquid treatment of poorly moistened textile materials, based on the notions of the simultaneous impact on colloid systems of chemical and mechanical factors, expressed in the Rebinder effect(*). Using a specially designed gas dynamic unit, the developed technology mercerization(*) saved ten tons of 44 percent alkali solution for 1 million meters of processed satin, making fabrics' quality much better.

In another trend, fabrics' drying and thermal treatment are intensified by infra-red heating, cutting the thermal treatment duration scores of times as compared with connective heating. The intensifying infra-red radiation factor stems from the high penetrating and heating effect of a material on its entire thickness, the reduced period of fabric heating, and the increased reactivity of the fibrous materials, dyes, and the precondensates of thermosetting resins.

A number of machines have been designed on this basis for fabric drying and thermal treatment by using infra-red heating, involving quartz tube radiators with an Ni-Cr alloy spiral and halogenous radiators and heaters with heat-resistant mica components. The radiation-contact and radiative -convective drying machines

* The Rebinder effect-solid body strength decline in adsorptive-active media; discovered by Academician P. Rebinder in WS.-Ed.

* Mercerization-treatment of cotton thread or fabric with caustic soda solution.-Ed.

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and thermal treatment installations are part of the equipment at many enterprises in Russia and CIS countries.

To make fabrics more attractive and add new consumer qualities to them, theoretical and applied research is under way in using low-temperature plasma. These studies have gained recognition both in Russia and abroad. What particularly matters is that the results were used to develop a plasmatic fabrics' modification technology. Laboratory installations development paved the way for high-tech industrial plasmatic chemical equipment(*). The use of plasmatic chemical technologies developed for the textile and light industries in the 21st century is very prospective thanks to pollution-free processes and processed materials' quality since other methods will in many cases hardly bring such a result.

Another remarkable trend in the intensification of fabrics dying and dressing is the use of magnetic-chemical effects. It involves the intentional change of the physical and chemical state and reactive capability of various liquid phase systems by inhomogeneous magnetic field treatment. It made up the basis of a magnetic-chemical method of solutions and alloys control, essential for the creation of new auxiliary textile preparations, technologies of dying and dressing fabrics from cellulose and polyester fibres. Experimental models of equipment for uninterrupted fabrics dressing under the impact of inhomogeneous magnetic fields at the stages of fabric impregnation, drying, and thermal treatment have been designed and installed at a number of enterprises already.

The use of the suggested modified compositions, technologies, and equipment reduces the specific expenditure of chemical materials by 10-30 percent and cuts the power intensity of processes 1.3-1.5 times. For instance, in thermo-magnetic treatment with the use of the combined infra-red radiation and magnetic field impact, the optimal temperature of the dressing preparations' fixation drops 40-60C. The economic effect extends to an all-round improvement in the consumer properties of ready-made production thanks to the unique effects of initiating changes in the system "fibrous material-solution or melt of textile modifiers and dyes".

The importance of the mechano-chemical modification of natural polysaccharides stems from their broad applications in various branches of industry.

If abroad, only chemically modified polysaccharides are applied, and in the United States, for instance, the annual production of modified starches exceeds 800,000 tons,

* See:. A. Kutepov et al., "Solutions and Plasma", Science in Russia, No. 5, 1998. -Ed.

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in Russia, their output amounts to only 40,000 tons a year while about 200,000 tons are required per annum.

The mechanochemical technologies developed at the RAS Institute of Chemistry of Solutions solve the problem of polysaccharides' modification right at the application sites. The newly-obtained properties are a summarized consequence to physical effects on the water-polymeric system (high-rate sheer deformations, the mechanical oscillations of the sound and ultrasound bands of frequencies and cavitations) and mechanically catalyzed chemical transformations into a substratum under the impact of chemical reagents. Institute researchers have developed and produced laboratory and industrial devices of a rotor- impulse type. Such a solution is economic because it excludes the intensive power capacity operations of extracting and drying the ready-made product, making the obtained materials eventually several time cheaper.

The summed up theoretical and technological research data provide the basis of energy and resources' saving mechanochemical technologies of producing dressing and thickening agents from cheap domestic raw material (starch and flour). Their application allowed to cut the expenditure of steam two-three times or do away with it in full, significantly reduce the specific expenditure of the thickening preparation, exclude ecologically harmful chemical splitters, improve the quality of dressed yarn and printed fabrics, and in some cases replace imported raw material.

The technologies developed by specialists from the RAS Institute of Chemistry of Solutions open broad opportunities for obtaining principally new composite materials with regulated structure and properties, superior to their well-known foreign counterparts (silvitoza, solvitex, prisulon) and suitable not only for textile making but also for the construction, food, paper, and oil processing industries.

Institute scientists working in conjunction with experts from specialized and teaching Institutes of Ivanovo created a set of technological processes, covering a whole cycle of gracing textiles: dressing, mercerization, preparation for dyeing and printing, making adhesive qualities better, drying, and the thermofixation of dyers and precondensates ofther- moreactive resins, the creation of a semi-transparent lace effect on fabrics and methods of producing new auxiliary preparations (dressing and thickening components on the basis ofmechanochemically modified starch, low formaldehyde dressing preparations, the stabilizers of solutions of restorers in the processes of their making and use). Engineering calculation methods were spelled out and equipment was designed for putting the developed technologies into practice.