DESIGNING A COMPOSITION FORMULATION OF SURFACE ACTIVE SUBSTANCES FOR THE PRETREATMENT OF KNITTED FABRIC

Knitwear industry is the largest sector of world production because knitted goods possess unique consumer properties. Important components of chemical-engineering process of the pretreatment of knitted fabric are textile auxiliaries (TA), whose application promotes the removal of oils, fats, waxlike substances and solid contaminants. Therefore, during the pretreatment of textile materials, there are a number of significant problems: selection of efficient and biodegradable surface-active surfactants (SAS); reduction in the destructive impact of the bleaching agents and TA; reduction in the volumes of water consumption and other forms of material resources; search for new, more efficient methods of pretreatment (biotechnology, treatment in the medium of low-temperature plasma and others) [1]. However, TA used in the Ukrainian knitted industry do not always ensure the required quality of the pretreatment of textile material, which subsequently affects negatively the quality of dyeing. At present, international quality standards place high demands to the textile products, which is predetermined by the need for creating and applying new ecologically safe TA for the provision of contemporary level of conducting technological processes, in particular, during the pretreatment of knitted fabric [2]. Improvement in the quality of the produced goods in the process of preliminary pretreatment of knitted fabrics is connected to designing highly efficient technologies with the use of new composition TA on the base of different classes of SAS [3, 4]. The need to create such preparations is predetermined by complex physical-chemical character of the treated material and by multistage nature of the processes of its treatment. The formulation of such compositions include the components that are compatible with each other, which either act additively or synergistically at one stage of the process or they are activated at its different stages. DESIGNING A COMPOSITION FORMULATION OF SURFACE ACTIVE SUBSTANCES FOR THE PRETREATMENT OF KNITTED FABRIC


Introduction
Knitwear industry is the largest sector of world production because knitted goods possess unique consumer properties.
Important components of chemical-engineering process of the pretreatment of knitted fabric are textile auxiliaries (TA), whose application promotes the removal of oils, fats, waxlike substances and solid contaminants.Therefore, during the pretreatment of textile materials, there are a number of significant problems: selection of efficient and biodegradable surface-active surfactants (SAS); reduction in the destructive impact of the bleaching agents and TA; reduction in the volumes of water consumption and other forms of material resources; search for new, more efficient methods of pretreatment (biotechnology, treatment in the medium of low-temperature plasma and others) [1].
However, TA used in the Ukrainian knitted industry do not always ensure the required quality of the pretreatment of textile material, which subsequently affects negatively the quality of dyeing.At present, international quality standards place high demands to the textile products, which is predetermined by the need for creating and applying new ecologically safe TA for the provision of contemporary level of conducting technological processes, in particular, during the pretreatment of knitted fabric [2].
Improvement in the quality of the produced goods in the process of preliminary pretreatment of knitted fabrics is connected to designing highly efficient technologies with the use of new composition TA on the base of different classes of SAS [3,4].The need to create such preparations is predetermined by complex physical-chemical character of the treated material and by multistage nature of the processes of its treatment.The formulation of such compositions include the components that are compatible with each other, which either act additively or synergistically at one stage of the process or they are activated at its different stages.
Unbleached linen is poorly wetted in the solutions as a result of the presence of hydrophobic natural impurities and greasing substances in the fibers, which leads to the reduction in capillarity of knitted fabric.The lowered capillarity of textile materials hampers bleaching, dyeing, printing and treatment of these materials in aqueous solutions, as well as causes defects when conducting these processes (spots, unevenness of dyeing and others).
The quality of the pretreatment of textile material also influences to a considerable degree the result of its dyeing, which must have increased wettability, capillarity, a capability for swelling and perception of the molecules of dye.
Those preparations, which are used at the knitted enterprises of Ukraine for washing knitted fabrics, are characterized by significant cost and are frequently non-ecological.The relevance of the work is defined by the need to seek and design new efficient and economically sound composition preparations of SAS for the pretreatment of knitted fabrics [5][6][7].

Scientific literature analysis and the problem statement
In the production of knitted fabrics, with the purpose of increasing operational stability of knitting machines, the threads are treated with the greasing substances.The removal of greasing substances, as well as natural substances associated with cotton (nitrogen containing, pectic, waxlike substances, sugars, ash and coloring substances), from the knitted fabrics in the process of pretreatment presents great difficulties.
If technological and natural contaminants of cotton knitted fabric are not removed completely or their resorption occurs during washing, then this will lead to the reduction in its capillary properties and, during subsequent dyeing, to the incomplete dyeing in the places of contaminants deposition.
The studies [8] examined in detail the properties of SAS, produced in Ukraine, and demonstrated the peculiarities of the development of composition SAS for the treatment of textile materials [9].In the papers [10][11][12], the composition for the pretreatment of cellulose-containing fabrics was designed, based on efficient emulsifiers and moisteners, which facilitate the removal of wax substances and remains of cuticular film from the surface of cotton fiber.
In the work [13], the authors assessed a washing action of a three-component mixture of SAS, based on determining the parameters of washing action, and proposed a washing formulation for cleaning woolen goods.
It was shown in the paper [14] that the binary mixtures and complex multicomponent systems based on SAS possess a higher wetting and washing capacity as compared to individual SAS that are contained in the mixtures.
The authors of [15] selected optimum parameters for the pretreatment of knitted fabric with the application of ferments: pH, temperature, concentration of a ferment.
The researchers in the [16] experimentally studied synergism of different affinity of both the individual SAS and those contained in the mixture.It was established that the wetting properties of the mixture of SAS are higher than the individual solutions of SAS.
The mixture of nonionogenic SAS with anionic SAS were investigated in the paper [17].The measurement of surface tension was used for determining the values of CCMF and other parameters of adsorption.It was established that the formation of chain increases in the mixture of SAS.
The authors of [18] carried out studies of determining a washing capacity depending on the structure of nonionogenic and anion-active SAS on textile materials in non-aqueous medium (perchlorethylene).It was established that the best washing capacity is possessed by anion-active substances (alkylsulfates), which increase considerably a washing capacity of the pure solvent; introduction of nonionogenic hydrophilic groups to hydrocarbon radicals is accompanied by the decrease in washing capacity.
Analysis of scientific and technical information testifies to the lack of the purposeful and systematic studies in Ukraine with regard to the development of preparations for washing knitted fabrics.The Ukrainian knitted factories (PAO "Trikotazhnaya fabrika "Roza", Kiev, OOO "T-Style", Rovno) use washing imported preparations in the process of pretreatment, which is not always economically efficient.
Taking into account a continuous growth in the production of knitted fabrics and the goods made of them, it is promising at present to search for and design new compositions of SAS and the technologies of pretreatment, which will take into account peculiarities of the structure of knitted fabric and of conducting the processes of its pretreatment and which will make it possible to ensure improvement in the quality of the obtained raw material with the efficiency of technologies.

The purpose and objectives of the study
The purpose of this work was to develop composition formulation of SAS for the pretreatment of knitted fabric by the method of mathematical planning of the experiment and to study efficiency of applying the designed composition in the process of washing and its influence on the subsequent dyeing of knitted fabric.
To achieve the set goal, the following tasks were to be solved: -to conduct optimization of single mathematical models "composition-property" according to a series of selected initial parameters of optimization of the composition; -to determine optimal composition of the SAS formulation for pretreatment of knitted fabric by the Scheffe's simplex lattice method of the second order; -to determine capillarity and dyeability of the knitted fabric, prepared with the application of the designed composition of SAS.
Determining of wetting capacity of SAS was carried out by the Draves immersion method, which involves alternating immersion of the samples of knitted fabrics into prepared aqueous solutions of SAS with subsequent recording of time before their complete immersion [18].
For determining washing capacity of the examined SAS, the samples of knitted fabric were weighed accurate to four significant figures.Then the samples underwent boiling in the aqueous solutions of the examined SAS (0,2-5 g/l) at M=50, T=80 о С for 30 minutes with subsequent washing by warm water and repeated determining of the mass.Washing capacity of SAS was determined by the formula: ( ) where m 1 is the mass of the sample before boiling, g; m 2 is the mass of the sample after boiling, g [19].
For determining foaming capacity of the composition of SAS and stability of the foam, 20 ml of the solution with concentration 5 g/l at the temperature of 20 °С was put to a graduated cylinder with capacity of 100 ml with a ground stopper.The cylinder with the solution was then shaken vigorously for 10 s.The volume of the formed foam was measured immediately after the shaking, as well as in 5, 10, 30 and 60 min [20].
The foaming capacity (F) and the stability of foam over specific time (Y) were calculated by the formulas: where V 1 is the volume of foam after shaking, ml; V 0 is the initial volume of the solution, ml; V 2 is the volume of foam after specific time after shaking, ml [20].Surface tension of the solutions was determined by the du Noüy ring method, which is based on determining the force, necessary for detachment of the liquid, which wets the ring of the radius R, from the surface of the liquid.The force, necessary for lifting the ring, was determined with the aid of the du Noüy scale by the formula: is the surface tension of distilled water [21][22][23].
Determining of capillarity of plain and prepared knitted fabrics was carried out according to GOST 3816-81 "Textile fabrics.Methods of determining hygroscopic and water-repellent properties".
Dyeing of the prepared fabric was performed by a periodic way at temperature 60 °С, for 170 min with the use of bifunctional active dye Auxicolor Red ARD 2B («Auxicolor», Spain).
Determining of the degree of fixation of the dye was carried out based on the spectrophotometric analysis of the initial dyeing solution, residual after dyeing of the solution and wash baths.The degree of fixation DF, %, was calculated by the formula [24]: where D den is the optical density of the solution, residual after dyeing; D res is the optical density of washing solution; D init is the optical density of initial dyeing solution.
The optimum formulation of the SAS composition was determined with the help of the Scheffe's simplex lattice method of the second order [25,26].

Designing a SAS composition for the pretreatment of knitted fabric by the method of mathematical planning
In the previously cited work [27], the washing and wetting capacities of different classes of SAS were determined and preparations that ensure optimum capillary properties in the pretreatment of knitted fabric were selected based on this.It was established that nonionogenic, anion-active SAS have the best washing capacity while nonionogenic ones possess the best wetting capacity.
For creating efficient washing formulation, it is necessary to define their optimum ratio.Usually the formulation of compositions is selected by empirical way based on the results of trial washings or removal of the contamination, for the washing of which this substance was created.
The most promising for designing multicomponent compositions is considered to be the use of methods of mathematical planning of experiment, which make it possible to considerably reduce the volume of experiment, exclude the need for a spatial representation of complex surfaces because the properties of compositions may be presented in the form of equations.
At present, for optimization of calculation of the formulations of compositions based on the mathematical model "composition-property", the simplex lattice plans proposed by Scheffe are the ones most widely applied [28].
In the study of properties of the mixture, which depend only on the ratios of components, factor space is a correct (q-1) -measured simplex.The following ration is fulfilled for such systems: where x i ≥0 is the concentration of component; q is the quantity of components.
The Scheffe's plans ensure the uniform spread of experimental points on (q-1) -measured simplex.Experimental points present {q, n} -lattice on the simplex, where n is the degree of polynomial.
Since the designed composition will consist of four components (q=4), then a correct simplex will be presented as a tetrahedron, each apex of which corresponds to clean com-ponents.Each edge of the tetrahedron is a two-component system and the face -three-component.Each point inside the tetrahedron corresponds to a four-component system (Fig. 1).

Fig. 1. Correct simplex -tetrahedron of a four-component system
Thus, component х 1 is absent from the edge х 2 , х 3 and х 4 , and along the sections of the tetrahedron, approaching the apex х 1 , the content of the component х 1 increases.
Graphically this system is presented in the form of the sections of a tetrahedron by the planes, perpendicular to one of the axes.The formulation of a four-component mixture, which lies at the plane of the section, is determined in this case by a two-dimensional plane that it makes it possible to present a change in the properties of the system in the form of contour curves.
The rate of change in the properties of a multicomponent formulation is characterized by the inclination of the magnitude of the expected response for the i-th component at the point х 1 : where For a q-component formulation, the expression (6) corresponds to gradient of the (q-1)-th surface along the axis of the i-th component [25].
I. e., the field of research represented a polygon with eight apexes and sides, which was reduced to a simplex with the number of apexes m•n=q.Since a simplex-study is small in comparison with the entire area of research, it is necessary to make transition from the components x i to the pseudo-components z i .
The Scheffe's simplex lattice plan of the second order for a four-component formulation is presented in Table 2.
Determining the optimum formulation of a composition comes down to optimization of the system of mathematical models, each of which describes the selected properties of the compositions.In this case, the optimization problem may be formulated as follows: to find in the area of the allowed values of factors Ω those values, for which the output parameters take minimum or maximum values.The output parameters are evaluated by the scalar optimization criteria, which form the vector of efficiency: wet. wash.
Y T ,T , ,F,Y = σ and they are connected by the dependency Y=F(z 1 , z 2 , z 3 , z 4 ) through the factors with a generalized optimization criterion.This expression is the system of mathematical equations, which must be optimized with the limitations by the factors 0≤z 1 ≤1.
The system of equations can be represented as follows: As the calculations show, the joint solution to the system for the obtained model "composition-properties" is lacking (16).Consequently, for finding the optimum results, the system ( 16) must be slightly changed.
For obtaining reliable data on optimization of the SAS composition formulation, it is necessary to conduct the optimization of single models "composition-properties".
From the point of view of the treatment of textile material in the aqueous solutions of SAS, foaming and foam stability influence the efficiency of the process by not more than 10 % [28].
For efficient conducting of the process of treatment of textile materials in the aqueous solutions of SAS, their surface tension must be lower than the surface tension of water by 20 units and amount to about 52 mN/m.
Results represented in Table 3 show that the values of the surface tension of the compositions vary in the range from 45 to 52 mN/m.Therefore, these models can be excluded from the optimization.
That is why, with the purpose of determining optimum formulation of the composition, it is expedient to conduct optimization of the models "composition-properties" by wetting and washing capacities.
For the wetting capacity, it is necessary to determine the optimum formulation of the composition at the minimum values of the time of wetting: Т wet.→min, 0≤z i ≤1. ( For the washing capacity, it is necessary to determine the optimum formulation of the composition at the maximum value of the degree of removal of contamination: Т wash.→max, 0≤z i ≤1. ( Results of optimization are presented in Table 4.
The optimum values of natural components for the models of wetting and washing capacities are presented in Table 6.
In making up the composition, it is necessary to adhere to conditions of the formula (6): the sum of the shares of components must equal one.
The application of this formulation ensures maximum indicators of wetting (130 s) and washing capacity (0,98 %).

Study of the influence of the developed composition of SAS on the capillarity of knitted fabric and its dyeability
For exploring the influence of the designed composition on the quality of the pretreatment of knitted fabric, we carried out a study of capillarity of the knitted fabric, pretreated by applying the developed formulation (proposed mode) of concentration from 0,5 to 2 g/l and under the conditions of an enterprise (basic mode) (Fig. 2).
Results presented in Fig. 2 demonstrate that the application of the developed composition of SAS provides reaching high indicators of capillarity of knitted fabric.Thus, maximum capillarity of the knitted fabric, pretreated in the basic mode, is 60 mm.The textile material, washed with the application of the designed composition of SAS, capillarity of 60 mm is reached in 3 min while maximum one is 180 mm (at the concentration of the developed SAS composition from 1,2 to 2,0 g/l).
The influence of the mode of pretreatment of knitted fabric on its dyeability by an active dye was further determined.Fig. 3 presents the results of determining the degree of fixation of the active dye Auxicolor Red ARD 2B of the knitted fabric, prepared in the basic and designed modes.Obtained results (Fig. 3) make it possible to conclude that the SAS composition, developed for the pretreatment of knitted fabric, provides obtaining high-quality coloration in the subsequent process of dyeing the knitted material.This is explained by the fact that the recommended SAS possess maximal wetting and washing capacity, which makes it possible to efficiently remove hydrophobic impurities and contaminations and they are characterized by minimal capacity to form foam, which facilitates conducting and increases the rate of technological processes of pretreatment and subsequent dyeing.
Based on determining the influence of the developed SAS composition on the capillarity of knitted fabric and its dyeability, it is possible to draw a conclusion that the proposed composition of SAS is most efficient at the concentration of 1,2 g/l, an increase in the concentration of SAS composition to 2 g/l insignificantly influences the indicators of indicated parameters and it is not rational from the economic point of view.

Conclusions
1.It was found that for the pretreatment of cotton knitted fabric in the aqueous solutions of SAS, foam formation, foam stability, surface tension have little influence on the efficiency of the process.The wetting and washing capacity of SAS are the main indicators for optimization of composition formulation.With the purpose of determining the optimum formulation of composition, we carried out optimization of mathematical models "composition-property" by the wetting and washing SAS capacities.
3. Composition formulation of SAS, designed for the pretreatment of knitted fabric, possesses maximal wetting and washing capacity, as well as ensures obtaining high quality coloring in the subsequent process of dyeing the knitted material, which is confirmed by an increase in the capillarity (by 3 times) and the degree of fixation of active dye (by 7,5 %).
the force of lifting the ring from distilled water and from the examined solution; 2 H O σ

Table 1
Characteristic of the examined SAS

Table 3
Value of the initial parameters according to the Scheffe's simplex lattice plan of the second order for a four-component formulation