CHAPTER ONE: INTRODCTION1.1 GENERAL DISCUSSION: Now a day’s knit fabrics are used widespread in the world. The quality of a knit garment is mainly depends on the effective dyeing process. Considering the capability and demand our country has mainly cotton based industries. The knit products produced are mainly of cotton. So in the dyeing industries cotton is mainly dyed. For cotton dyeing there are many types of dyes are available such as direct dye, vat dye, reactive dye, azoic dye etc. To dye effectively, frankly saying considering all the facts like the application process, retention of the color during use and economy reactive is the most suited dye to dye cotton goods. Reactive dyes are used extensively in dyeing cotton in every factory of our country. Shades that can be produced by reactive dye is enormous, to produce a target shade perfectly monochromatic that means the primary color are used most frequently. But matching with the monochromatic color combination is not always suitable as some shades can’t be found. There are also some limitations about the reactivity and production of the color in a definite time. To remove this drawback, different dye manufacturers come with the idea of some dichromatic and tri-chromatic reactive dyes. These special types of dyes made for special shades. This dye is mainly bluish and some are yellowish. This dye is known as turquoise color. Turquoise color is a hot brand reactive dye. Usually reactive dye is applied to fabric at around 60 ◦C but turquoise color is applied to fabric at around 80◦C. These special dyes are made especially in comparison to normal reactive dye. They are introduced with metal complex structure; their reactive group activated at higher temperature, their molecular size is bigger than normal reactive dyes. Considering the above facts application process will definitely be different than normal reactive dye application. If process is not changed according to the structure of dyes achieving of proper shade is really an absurd. The special colors create different types of problems. 1 1.2 OBJECTIVES OF THE PROJECT WORK: The main object of this project work is to find out the suitable application process of turquoise color. Specially to find out the appropriate temperature and electrolyte concentration for applying the turquoise color on cotton. Also have some objects are mentioned below: To observe the effect of temperature on turquoise color. To observe the effect of electrolyte concentration. Finding out the difference between two different brand dyes. Finding out the variation in different fastness properties of sample dyed at different temperature and different electrolyte concentration. To watch the change of color strength of sample dyed at different temperature and different electrolyte concentration. CHAPTER TWO: LITERATURE REVIEW 2.1 REVIEW OF RECENT RESEARCH WORK: 1. Michel Hehlen [1] worked on “Effects of Dye Substantivity in Dyeing Cotton with Reactive Dyes”. It represents that, Fiber reactive dyes for cotton were shown to vary widely in their substantivity for the fiber. Substantivity also depended on dye bath temperature and salt concentration, as expected. The relative substantivities of the hydrolyzed forms of the reactive dyes were assessed in the laboratory by means of a simple, quick and inexpensive paper chromatography test. Correlation of the substantivity of the dye with the amount removed from the cotton under various washing conditions indicated that it should be possible to select higher or lower washing temperatures based on the substantivity of the dye to be removed. In addition, the paper chromatography test was useful for quick selection of dyes of about the same substantivity. Mixtures of such dyes dyed cotton with little change in hue during the dyeing process; dyes of different substantivity gave pronounced color changes. 2. M F H Arzu and M.M. Rahman[2] worked on “Effect of process parameters on cotton fabric dyeing with reactive dye especially on Green Color”. This paper presents the various effects on cotton fabric dyeing with reactive dyes. Most of the knitted cotton fabric was dyed with reactive dyes with a view of optimizing dyeing procedure of cotton fabrics by varying dyeing process and parameters. In isothermal process dyeing process has been completed at 60°C (for green color dyeing). Turquoise color cannot work at 60°C because of high dye affinity. But in migration process turquoise color can work at 80°C. Another side is dyeing procedure. Fixation and exhaustion has been completed at same temperature during isothermal process for green color dyeing, whereas color fixation 2 cannot be done properly due to turquoise color. In migration process, Fixation and exhaustion has been completed at varying temperature, so that dyeing procedure is done properly for green color dyeing. 3.D. Schimmel [3], K.C. Fagnan [3] , J.B. Oliveria dos Santos[3] , M.A.S.D. Barros [4] and E. Antonia da Silva [3] worked on “Adsorption of turquoise blue QG reactive dye on commercial activated carbon in batch reactor: Kinetic and Equilibrium studies”. The adsorption of reactive turquoise blue QG dye on commercial activated carbon was investigated in a batch reactor to obtain isotherm and kinetic data under different experimental conditions. The absorbent was characterized by FTIR method to analyze surface area and p h PZC and to identify functional groups. Experiments were conducted to obtain equilibrium data at 30◦C, within the ph effect being analyzed in the range of 2 to 8. Experiments were carried out under the optimal p h condition for dye removal to obtain equilibrium data at 30◦C, 45◦C, 60◦C. Maximum dye removal capacity was observed at a p h 2 and temperature 30◦C. The best fit for the kinetic data was obtained with the pseudo-second-order model. The adsorption of the dye on the activated carbon increased as the temperature decreased and the pH decreased. 4. J.Russell Ogle[5] worked on “The influence of the degree of preparation on shade consistency, wash fastness and crock fastness properties of a fibre reactive dyed 100% cotton woven fabric”. He states, the main objective of preparation is to remove all contaminants that could inhibit the uniform absorption of dyes and chemicals in subsequent treatment. 70% of all defects in the final finished cotton fabric are due to inadequate preparation. 5. Berger, Rebecca Riley[6]worked on “Fiber reactive dyes with improved affinity and fixation efficiency”. The investigation represents that, although fiber reactive dyes are widely used in the dyeing of cellulosic materials, several economical and environmental problems are associated with their application. Problems include residual color in wastewater, cost of wastewater treatment, raw material cost (salt, dye, and water), and quality of goods produced are examples of areas where improvements are needed. The afford mentioned costs could be reduced by increasing the fixation efficiency and exhaustion of reactive dyes. In turn, fixation efficiency and exhaustion could be increased by increasing dye-fiber affinity. This thesis pertains to an evaluation of four types of dye structures arising from novel but straight forward modifications of commercially available fiber reactive dyes to produce colorants designated by Proctor and Gamble as Teegafix Reactive dyes. Teegafix dyes are produced in 2 steps from dichlorotriazine (DCT) type reactive dyes, using either cysteamine or cysteine and then reacting the intermediate structures with either cyanuric chloride (cf. Type 1 and 2 yellow dyes) or a second molecule of the starting dye (cf. Types 3 and 4 yellow dyes). In the same way, red and blue DCT dyes were converted to the corresponding Teegafix structures. The resultant homo-bifunctional dyes vary in molecular size and reactivity and are designed to enhance dyefiber fixation efficiency and affinity. 3 CHAPTER THREE: THEORETICAL BACKGROUND 3.1.1 COTTON TEXTILES: Cotton fabrics are known to have been in use at least for 7000 years [7]. Although, numerous synthetic fibres such as polyesters, acrylics, polyamides and Polypropylenes have entered the market over the past 50 years, cotton has still maintained its strong consumer demand worldwide. Today, cotton textiles represent more than half of the global textile market [8], and the demand is expected to continue [9, 10]. This dominance of cotton fibre is mainly due to its natural comfort, performance and appearance. 3.1.2 COTTON FIBRE: Cotton is the purest form of the natural cellulose polymers. The fibre is a single plant cell found as the seed hair of a genus of the plants called ‘gossypium’ [11]. Like all plant cells, a mature cotton fibre has a distinct cuticle, well developed primary and secondary walls and a lumen (Figure3.1) [12]. Figure 3.1 A morphological diagram of the cotton fibre (source: [12]) The cuticle is the very outside or ‘skin’ of the fibre. It is composed of pectins, protein and waxes. Therefore, it makes the fibre hydrophobic unless a wetting agent is used. The primary cell wall is immediately underneath the cuticle. The secondary wall, beneath the primary wall, forms the bulk of the fibre. Inadequate development of the secondary wall during the growth of cotton fibres on the plant creates ‘immature’ fibres. If there is no development of the secondary wall, then the fibre is referred to as a ‘dead’ cotton fibre. The immature and dead fibres tend to become entangled into small fibrous bundles, called neps, during the mechanical processes for producing yarns [13, 14]. The immature fibres cannot be dyed to shades as dark as mature fibres and the dead fibres remain undyed. Therefore, neps can be instantly seen on the surface of the dyed fabrics appearing as white and light spots. The color contrast between the dyed neps and mature fibres can be reduced by swelling of immature fibres during mercerizing (Section 1.2.2.2). The primary and secondary walls are composed of cellulose ‘fibrils’. The fibrils occur in the spiral form at certain angles to the fibre axis. The lumen is a longitudinally hollow canal in the centre of the fibre. Micrographs of the raw cotton fibres are shown in Figure 3.2. Mature cotton fibres are flattened tubes and are highly convoluted. The surface of such fibre enables inter-fibre friction (cohesiveness) which is helpful in producing fine spun 4 yarns of adequate strength. The appearance of the cross-section of cotton fibre is bean or kidney-shaped. The convolutions and bean-shaped cross section of the cotton fibre enable cotton apparel to be more comfortable. This is because the particular structure of cotton fibre is more compatible with human skin and makes apparel more moisture absorbent [12]. Figure 3.2: Scanning electron micrographs of raw cotton fibres (source: [11] 3.1.3 CHARATERISTICS OF COTTON: Cotton, as a natural cellulosic fiber, has a lot of characteristics, such as; Comfortable Soft hand. Good absorbency. Color retention. Prints well. Machine-washable. Dry-cleanable. Good strength. Drapes well. Easy to handle and sew. 3.1.4 COTTON POLYMER AND FIBRE POLYMER SYSTEM: Cotton fibres are composed of cellulose polymers, mostly α-cellulose [14]. The basic molecular structure of cotton cellulose is shown in Figure 3.3. Its repeating unit is cellobiose. The degree of polymerization of cotton cellulose is about 5000 based on cellobiose units [12]. Cotton polymer system is highly crystalline and oriented. Important groups on cotton polymer (cellulose) are hydroxyl and methylol groups. The presence of abundant hydroxyl groups and the polymer chain conformation cause intermolecular and intra-molecular hydrogen bonding that enhances the rigidity of the fibre structure. The existence of van der Waal’s forces is of little significance. 5 Figure 3.3 The chemical structure of cotton cellulose (source: [13]) REPEAT UNIT OF CELLULOSE: Figure 3.4 Repeat unit of cellulose. Typical composition of raw cotton (source: [13]): Components Cellulose Oils, waxes Pectins Carbohydrates Proteins Salts Water Other Main location Secondary wall Cuticle Primary wall Primary wall Lumen Lumen Amount% 86.8 0.7 1.0 0.5 1.2 1.0 6.8 2.0 Table 3.1: Typical composition of raw cotton 3.1.5 PROPERTIES OF COTTON FIBRE: HYGROSCOPIC PROPERTIES: The cotton fibre is hydrophilic and water absorbent [13]. This is because the polar hydroxyl groups of cellulose polymer attract the polar water molecules. Its porous structure allows ready penetration of water molecules between the fibrils and into the amorphous regions of the fibre where they can easily form hydrogen bonds with free cellulose hydroxyl groups. Even the typical cotton dyes, being quite large molecules, easily penetrate into the accessible interfibrillar and amorphous regions. The standard moisture regain of cotton fibre is about 8% and rises to around 25–30% at 100% relative humidity, at ambient temperature [13]. Cotton fibre swells with water absorption because of the swelling of the secondary wall. It is one of the few fibres which gains strength when wet [12]. This may be due to a temporary improvement in polymer alignment in the amorphous regions. 6 CHEMICAL PROPERTIES: The chemical reactions with cotton cellulose occur mainly due to the activity of hydroxyl groups and depend on the super molecular structure. Any reaction is initiated in the more accessible amorphous regions and at the surfaces of crystalline regions [14]. The reactions can be broadly classified into two categories: esterification and etherification. Esterification is usually carried out under acidic conditions. These reactions include nitration, acetylation, phosphorylation, and sulphation. Acidic conditions hydrolyse the cotton cellulose at the glucoside oxygen atom which links the two glucose units to form the cellobiose unit (Figure:3.4) [12]. Stronger acids hydrolyse the cellulose more rapidly. A cotton fibre dissolves completely in a 70% aqueous sulphuric acid [15]. Etherification, on the other hand, is favoured in an alkaline medium. This Zeaction is important for dyeing cotton with reactive dyes. In the presence of even dilute base, cellulose behaves as a weak acid and ionises to form a cellulosate anion according to the chemical equation given in Figure 1.4 [16]. This anion is capable of reacting with suitable dyes by nucleophilic substitution or addition to form covalent bonds [17]. Vickerstaff provided the evidence for reactive dyes forming covalent bond with the cellulosate anion (Cellulose-O–) [18]. Cellulose-OH + OH– (alkali) Cellulose-O– + H2O The dissociation of cellulose mercerizing is a treatment of cotton with strongly alkaline solutions where fibre lusture, tensile strength and dye uptake are improved [12, 19]. Such improvements are principally due to the swelling of cotton fibre and the alignment of poorly oriented fibre polymers during this treatment. The swelling is fundamentally due to the imbibitions of water as a consequence of the sorption of alkali by the cellulose [11]. Cellulose is readily attacked by oxidizing agents, such as hypochlorites, chlorous, chloric, and perchloric acids, peroxides, dichromates, permanganates, periodic acid, periodate salts, and nitrogen tetroxide [14]. Oxidation of cellulose can lead to two products: reducing and acidic oxycellulose. In reducing oxycellulose, the hydroxyl groups are converted to carbonyl groups or aldehydes, whereas in acidic oxycellulose, the hydroxyl groups are oxidised to carboxyl groups or acids. THERMAL PROPERTIES: Cotton fibres are heat conductive [12]. Excessive application of heat energy causes the cotton fibre to char and burn. Heating the fibre generally causes dehydration and decomposition of cellulose [14]. At temperatures above 150 °C, the extent of browning and hardening of the fibres increases [13]. If processing requires higher temperatures, shorter treatment times are set to avoid thermal damage. REACTIVE DYES 3.2.1 HISTORICAL DEVELOPMENT OF REACTIVE DYES: 7 A variety of attempts have been made in the struggle to obtain the covalent bond formation between a dye and a fibre. In 1895, Cross and Bevan achieved a covalent dye-cellulose bond with respect to the first approach [25]. They showed that cellulose (Cellulose-OH) treated with strong alkali was changed into ‘soda cellulose’ (Cellulose-ONa). The soda cellulose could be treated with benzoyl chloride to form benzoyl cellulose. The resultant benzoyl cellulose was nitrated where the nitro group was reduced and the amino group was diazotised. Coupling the diazo group with N, N-dimethylaniline gave ‘dyed’ fibres [26]. The idea of covalent bond formation between the reactive group of a dye molecule and a fibre polymer was initiated in the early 1900s [27]. Various reactive entities were found which could react with the hydroxyl groups of cellulose and eventually be converted into coloured cellulose. In 1954, Rattee and Stephen developed the reactive dyes for cotton fibre containing highly reactive dichloro-striazine groups with a dyeing procedure [28]. They established that dyeing cotton with these dyes under mild alkaline conditions resulted in a reactive chlorine atom on the triazine ring of the dye being substituted by an oxygen atom from a cellulose hydroxyl group. The role of the alkali was to cause dissociation of some of the hydroxyl groups in the cellulose to obtain cellulosate anion that reacts with the dye. This discovery led to the introduction of the first commercial reactive dye class for cellulose that was marketed by ICI in 1956 under the trade name of Procion M [17, 28, 29]. These dyes were introduced for the production of fast bright colors on cellulosic fibers using continuous dyeing methods [30]. Procion. Brilliant Red M-2B (CI Reactive Red 1) is one of the early dyes of this range [25]. The major factor contributing to the long delay in producing the first reactive dye for cellulose was the belief that cellulose was a relatively inert fibre. Further was the fear that the conditions required to effect a chemical reaction would cause serious fibre degradation [25, 29]. Therefore, in early studies, dyestuff chemists were led astray in thinking that they needed to convert cellulose to the more reactive soda cellulose which could make fiber reactivity possible [29, 31]. No one expected that any reactive group would prefer to react with a hydroxyl group of cellulose when cotton is immersed in an aqueous dye bath containing numerous competitive hydroxide ions of water [27]. However, a large number of reactive dyes with a variety of reactive groups have been developed. Today, the fiber-reactive dyes are the largest single dye class used for dyeing cotton. 3.2.2 GENERAL PROPERTIES OF REACTIVE DYES: Reactive dyes are anionic dyes. Reactive dyes are found in powder, liquid and print form. During dyeing the reactive group of this dye forms covalent bond with fiber polymer and becomes an integral part of fibers. Reactive dyes are soluble in water. They have very good light fastness with rating about 6. The dyes have very stable electron arrangement and can protect the degrading effect of ultra-violet ray. Textile materials dyed with reactive dyes have very good wash fastness with rating about 4-5 due to strong covalent bonds formed between fibre polymer and reactive group of dye. Reactive dyes give brighter shades and have moderate rubbing fastness. 8 Dyeing method of reactive dyes is easy. It requires less time and low temperature for dyeing. Reactive dyes are comparatively cheap. Fixation occurs in alkaline condition. Reactive dyes have good perspiration. A summary of the industrial history of commercial reactive dyes for cellulosic fibres. [25]. Year 1956 1957 1957 Commercial name Procion M Procion H Cibacron Company ICI ICI Ciba 1958 Remazol Hoechst 1959 1959 1959 1961 1963 1964 1964 1964 1966 1966 1968 1970 1970 1970 1977 1978 1979 1984 1987 1988 Levafix Reacton Drimarene Levafix E Elisiane Primazin P Solidazol Procilan Levafix EA, Levafix P Lanasol Reactofil Verofix Drimalan Procion HE, Procion Supra Procion T Cibacron F Sumifix Supra Kayacelon Procilene Cibacro Bayer Geigy Sandoz Bayer Francolour BASF Cassella ICI Bayer Ciba Geigy Bayer Sandoz ICI ICI Ciba Sumitomo Nippon Kayaku ICI Ciba Table 3.2 : A summary of the industrial history of commercial reactive dyes for cellulosic fibres. 3.2.3 CONSTITUTIONAL CHARACTERISTICS OF REACTIVE DYES: The four characteristic features of a typical reactive dye molecule are the chromophoric group, the water solubilising group(s) usually sulphonate (-SO3Na), the reactive group, and the bridging group that attaches the reactive group either directly to the chromophore or to some other part of the dye molecule. Each of these structural groups has an effect on the physical properties of the dye molecule. Today, the names of many companies have been changed because of the transfer, expansion, merger or division of the businesses. The names, mentioned here, are when the dyes were introduced to diffuse into fibres, migration within the fibre(s), colorfastness, and so on. Typical reactive dye chromophores include the azo, triphenodioxazine, 9 phthalocyanine, formazan and anthraquinone [27, 32]. Most commercial ranges of reactive dyes have a comprehensive color gamut, many of which are particularly bright. Figure 3.5 Molecular structure of CI Reactive Red 1 (source: [33]) 3.2.4 MECHANISMS OF DYE ATTACHMENT TO CELLULOSE: NUCLEOPHILIC SUBSTITUTION MECHANISM: Reactive groups based on carbon-nitrogen ring structures undergo nucleophilic substitution (Figure 3.5) [33]. They react with cellulose by the substitution of a labile chlorine, fluorine, methyl sulphone or nicotinyl leaving group. The adjacent nitrogen atom in a heterocyclic ring activates the system for nucleophilic attack. The attacking nucleophile can be either a cellulosate anion or a hydroxide ion of water. The reaction with cellulosate anion leads to ‘fixation’ of the dye on the fibre and that with hydroxide ion results in ‘hydrolysis’ of the reactive dye. Dichloro-s-triazine dye Transient species (D = Dye chromophore) Partly-hydrolysed dye (X = OH) or dyed fibre (x = O-Cellulose) Figure 3.6 Nucleophilic substitution mechanism (source: [33]) NUCLEOPHILIC ADDITION MECHANISM: Reactive groups based on masked vinyl sulphone structures undergo nucleophilic addition (Figure 3.6). They react with cellulose by addition to a carbon–carbon double bond, usually activated by an adjacent electron-attracting sulphone group. This type of group is usually generated in the dyebath by elimination of sulphate ion from a sulphatoethylsulphone precursor group in the presence of alkali. Again, the nucleophilic addition of hydroxide ion of water leads to dye hydrolysis. 10 Sulphatoethylsulphone dye Vinylsulphone dye (D = dye chromophore) Vinylsulphone dye Transient species Hydrolysed dye (X = OH) or dyed fibre (x = O-Cellulose) Figure 3.7 Nucleophilic addition mechanism (source: [33]). 3.2.4 CLASSIFICATION OF REACTIVE DYES On the basis of control parameters, there are 3 types: A. Alkali controllable dyes: These dyes have optimal fixation temperature between 40oc and 60oc. They are characterized by relative low exhaustion in the neutral salt solution before alkali is added. They have high relative and care should be taken to produce level dyeing. Typical example of this dye DCT, dichlorodifluropyrimidine, dichloroqinoxaline and VS d dyes. B. Salt controllable dyes: Dyes in this group low optimal fixation temperature between 80 oc and boil. Such dye exhibit comparatively high exhaustion at PH 7 that is neutral medium. So it is important to add salt a carefully to ensure level dyeing. Typical example of this class is Trichloropyrimidine, Aminochlorotriazine and bis (Aminochlorotriazine) etc. C. Temperature controllable reactive dyes: This group of dye reacts with cellulose above the boil in absence of alkali although this can be applied between 80oC and boil in alkali medium. Dyes of this group have self leveling characteristics. 11 There are no need additional auxiliaries to achieve level dyeing. Good result can be achieved by controlling the temperature only the kayacelon react (KYK) range of bis (Aminochlorotriazine) dyes belong to this group. On the basis of reactivity, there are three types: Lower reactive dyes: here PH is maintained 12-12.5 by using NaOH in bath. Medium reactive dyes: here PH is maintained 11-12 by using Na2CO3 in dye bath. Higher reactive dyes: here PH is maintained 10-11 by using NaHCO3 in dye ba On the basis of dyeing temperature and method, there are three types Cold brand: this type of dyes contains reactive groups of high reactivity. So dyeing can be done in lower temperature i.e. 32-60oC. For example Procion M, Levafix E. Medium brand: this type of dyes contains reactive groups of medium reactivity. So dyeing is done in higher temperature i.e. 60-70oC. For example Remazol, Levafix. Hot brand: this type of dyes contains reactive groups of low reactivity. So dyeing is done in higher temperature i.e. 72-93oC. For example Procion H, Cibacron. CHAPTER FOUR: MATERILAS AND METHODS 4.1.1 MATERIALS: 12 Reactive Turquoise Blue G-266% obtained from Indian dye Manufacturer Company and Turquoise Blue G (10) has been obtained from Chinese dye Manufacturer Company. Slub Single jersey was taken from Pantex Dress Ltd GSM of 150 and 100% cotton. Others auxiliaries such as glauber salt (electrolyte), soda (Na2CO3), leveling agent (ionactive PP-105), sequestering agent (kappaquest),acetic acid etc were used as dyeing auxiliaries. 4.1.2 DYEING AUXILLIARIES AND ITS FUNCTION: SALT: Salt plays crucial role of catalyst. Salt has an extremely high affinity for water. Broadly speaking, Salt is necessary in three ways, firstly, to drive dye into textile during the dyeing process in textile. Secondly, use of salt leads to maximum exhaustion of dye molecules during dyeing process in textiles. Thirdly it is used as an electrolyte for migration, adsorption and fixation of the dyestuff to the cellulose material. Salts plays important role in reactive dyeing by improving the affinity of the dyestuff towards the fibre and acceleration of the dyestuff's association and lowering its solubility. Normally, Glauber's salt is used for this purpose. The presence of chlorine ion in the common salt may cause corrosion of the equipment. Hence, Glauber's salt is always preferred over common salt. Glauber's salt is a common name for sodium sulfate decahydrate, Na2SO4.10H2O; it occurs as white or colorless monoclinic crystals Glauber's salt is water soluble, has a salty, bitter taste, and it is also widely used in dyeing[23]. FUNCTION OF SALT IN THE DYEING PROCESS: The salt in the reactive dyeing increases the affinity of the dye towards the Cellulosic substrate. Salt increases the exhaustion rate of reactive dyestuffs. As reactive dyestuffs have a lower affinity, more inorganic salt is required when using reactive dyestuffs in order to accelerate absorption. While the amount of inorganic salt used varies according to the type of dyestuff used, recently developed high-fixation dyestuffs with improved affinity allow the amount of inorganic salt to be reduced. ROLE OF SALT IN REACTIVE DYEING: Salts have two main functions in exhaustion dyeing with reactive dyestuffs: Improving the affinity of the dyestuff Acceleration of the dyestuff's association and lowering of its solubility. Generally reactive dyes contains sulphonic acid (-SO3H) group which is insoluble in water. During the manufacturing of the reactive dyes these sulphonic acid groups are converted into the sodium salt of sulphonic acid (-SO3Na) which is Reactive dye – SO3H + Na⁺ → Reactive dye SO3Na 13 soluble in water. Figure 4.1 Rule of salt in dyeing [23] Generally when the reactive dye goes in the water, it is solublised giving dye anions and sodium cations. Reactive dye – SO3Na + Water -- → Reactive dye – SO3⁻ + Na ⁺ (Dye anion) (Sodium cation) SODA ASH (SODIUM CARBONATE): The main function of soda ash is to react dye with fibre (fixation ). FIXATION: Fixation of dye means the reaction of reactive group of dye with terminal –OH group of fibre and thus forming strong covalent bond with the fibre. This is an important phase, which is controlled by maintaining proper pH by adding alkali. The alkali used for this purpose depends on brand of dye and dyeing temperature. soda ash or Na2CO3 is used as alkali. They created proper pH in dye bath and do as the dyefixing agent. [23] 4.2 METHODS: 4.2.1 EXHAUST DYEING PROCESS [24]: Exhaust dyeing also is known as batch, or discontinuous, dyeing. It is the process used for most commercial fabric dyeing. Dyeing: Essentially, the process involves loading fabric into a bath, originally known as a batch, and allowing it come into equilibrium with a solution, or suspension, of dye. Exhaust dyeing is the ability of the molecules to move from the solution onto the fabric fibers (substantivity). The substantivity of a dye can be influenced by temperature or additives, such as salt. 14 Rinsing: The exhaust dyeing process can take anywhere from a few minutes to a few hours. When the fabric has absorbed, or fixed, as much dye as it can, the bath is emptied and the fabric is rinsed to remove any excess dyestuff. Specific Liquor Ratio: An important concept in exhaust dyeing is what is known as the specific liquor ratio. This describes the ratio of the mass of the fabric to the volume of the dye bath and determines not only the depth of color obtained, but also the environmental impact of the process. DYEING RECIPE: Reactive Turquoise Blue G-266% or Turquoise Blue G (10) = 1% Fabric weight = 20 gm Glauber salt = 10 g/l, 20 g/l, 30 g/l, 40 g/l Na2CO3 = 6 g/l Kappaquest (Sequestering agent) = 1 g/l Ionactive PP-105 (Leveling agent) = 1g/l Temperature = 60◦C, 70◦C, 80◦C, 90◦C M:L = 1:10 Time = 1 hour. DYEING FLOW CHART: Dye + Leveling agent + Sequestering agent + Salt+ Water ↓ Fabric loading ↓ Raise temperature 50◦C ↓ Run 40 minutes at 50◦C (Migration) ↓ Add Soda ↓ Raise Temperature 80◦C ↓ Run 60 minutes at 80◦C ↓ Stop dyeing ↓ Rinsing ↓ Hot wash (90◦C x 10 min) ↓ Wash with Auxitech SN ↓ Rinsing Time 15 1 – Add dye, fabric and all auxiliaries. 2 – Migration (40X50◦C) 3 – Add soda 4 – Dyeing (60X80◦C) 5 – Rinsing (10X30◦C) 6 – Hot wash (10X90◦C) 7 – Chemical wash (10X80◦C) 8 – Rinsing (10X30◦C) At first the bleached fabric weighted and immersed into the fresh water. After that the fabric was dropped into the chemical liquor which contained all the necessary chemicals auxiliaries including dyes without soda. The ratio between the material and liquor was 1:10 and dyeing was performed by lab process in lab dip machine. Now the pot of lap dip machine was kept in the machine and run the machine. At first migration was completed at 50◦C for 40 minutes. After completing the migration calculated amount of is soda according to recipe was added in the dyeing liquor. It is mentioned here that before adding the soda ph of dye liquor was 7 that means neutral but after adding the soda into the liquor the p h became 10-12 that means alkaline. Now the dyeing temperature was raised at 80 ◦C and run for 60 minutes. After 60 minutes dyeing was stopped and cooling for 10 minutes. Now the fabric was rinsed with normal water after cold wash hot wash was done at 90◦C for 10 minutes. Completing hot wash chemical wash was done by wash chemical named Auxitech SN at 90◦C. Lastly fabric was ironed manually and collected for fastness test. 4.2.2 DETERMINATION OF COLOR STRENGTH (K/S): At first reflectance (R %) was determined by Data Color. Then color strength was measured by below mentioned formula. K/S value = (1-R) 2/2R 4.2.3 DETERMINATION OF DIFFERENT COLOR FASTNESS: COLOR FASTNESS TO WASH: The resistance to the loss of color of any dyed or printed material to washing is referred to as its wash fastness. Color fastness to wash was performed by using Wash fastness testing machine. The test was done at standard ISO 105 C06. Dyed fabric of 5 gm was taken and stapled with multi fibre. Recipe: Detergent : 4 g/l Steel ball : 10 M:L : 1:50 Temperature : 50◦C Time : 40 minutes As the fabric weight was 5 gm. So according to recipe the total water was 250 ml. Now 1 gm detergent added to the water and fabric was taken into the liquor. 10 steel balls dropped in the pot and pot containing fabric and liquor was set in machine. Run machine 40 minutes at 50 ◦C. After 40 minutes machine was 16 stopped and fabric was unloaded. Now the treated sample compared with the untreated sample and color change measured with the help of grey scale. Color staining was measured from the multi fibre according to grey scale comparison by ISO 105-A03. Color change and color staining was expressed by grading from 1 to 5 where 5 is best on the other hand 1 is worst. COLOR FASTNESS TO RUBBING: Rubbing fastness is the resistance to fading of dyed textiles when rubbed against a rough surface. Color fastness to rubbing was performed by standard of ISO 105-X12.Both wet and dry rubbing fastness was measured. ISO 105-X12 was followed to measure the fastness. The test was done by Crock master. The dyed sample was rubbed with a crocking cloth ten times. Crocking speed is 1 cycle per second at a weight of 9N. Color staining was measured at comparison by ISO105-A03 grey scale. Color staining is graded from 1 to 5. At the time of testing wet rubbing the crocking cloth was moisture by water. COLOR FASTNESS TO PERSPIRATION: Color fastness to perspiration is the ability of dyed textiles to resist the loss of color against perspiration. This test was performed as ISO 105-E04 and compared by ISO 105-A03 Grey Scale. Histidine mono For alkaline solution hydrochloride 0.5 g/l monohydrate Sodium chloride Disodium hydrogen orthophosphate Sodium dihydrogen orthophosphate 0.1 N sodium hydroxide 0.1 N acetic acid M:L=1:50 5 g/l 2.5 g/l Adjust PH to 8 Dip the fabric in the For acidic solution 0.5 g/l 5 g/l 2.2 g/l Adjust PH to 5.5 Dip the fabric in the above solution for 30 above solution for 30 min at room min at room temperature. Allow it temperature. Allow it dwell for 4 hrs at 37◦C dwell for 4 hrs at 37◦C temp under 5 kg weight temp under 5 kg weight of the perspirometer. of the perspirometer. After above mentioned process the sample was compared with untreated sample and color change was graded. Now the multi fibre which was attached with the sample is observed for color staining and graded from 1 to 5. Yarn related defects Barriness 17 Thick & Thin lines Dark or Light horizontal lines (due to the difference in dye pick up) Imperfections Contaminations Snarling Spirality Knitting Elements related defects Needle & Sinker Lines Drop Stitches etc Machine Settings related Defects Drop Stitches Yarn Streaks Barriness Fabric press off Broken Ends Spirality Finishing related defects High Shrinkage Skewing Spirality Surface Hairiness & Pilling Tonal variation Dyeing related defects Dyeing patches, Softener Marks Shade variation Tonal variation Color fading (Poor Color Fastness) Dull shade Crease or rope Marks CHAPTER FIVE Category of Defects: 18 Yarn related defects Almost all the defects appearing in the horizontal direction, in the knitted fabric are, yarn related. These defects are mainly; Barriness Thick & Thin lines Dark or Light horizontal lines (due to the difference in dye pick up) Imperfections Contaminations Snarling Spirality Knitting Elements related defects Almost all the defects appearing in the vertical direction, in the knitted fabrics, are as a cause of bad Knitting Elements. These defects are mainly; Needle & Sinker Lines Drop Stitches etc. Machine Settings related Defects These defects appear randomly in the knitted fabrics, due to the wrong knitting machine settings & that of the machine parts. The defects are mainly; Drop Stitches Yarn Streaks Barriness Fabric press off Broken Ends Spirality Dyeing related defects The Dyeing related defects are, as follows; Dyeing patches, Softener Marks Shade variation Tonal variation Color fading (Poor Color Fastness) Dull shade Crease or rope Marks Finishing related defects 19 Defects caused, mainly due to the wrong process parameters are; High Shrinkage Skewing Spirality Surface Hairiness & Pilling Tonal variation Snagging (Sharp points in the dyeing machine or trolley etc) Fold Marks Wet Squeezer Marks GSM variation Fabric Width variation Curling of S.J. Fabrics 5.1 Yarn related defects Barriness Definition: Barriness defect appears in the Knitted fabric, in the form of horizontal stripes of uniform or variable width. Causes: High Yarn Tension Count Variation Mixing of the yarn lots Package hardness variation Remedies: Ensure uniform Yarn Tension on all the feeders. The average Count variation in the lot, should not be more than + 0.3 Ensure that the yarn being used for Knitting is of the same Lot / Merge no. Ensure that the hardness of, all the yarn packages, is uniform, using a hardness tester. Streakiness Definition: Streaks in the Knitted fabrics appear as; feeble, irregularly spaced & sized, thin horizontal lines. 20 Causes: Yarn slippage on the IRO Pulley, due to the yarn slipping in & out from underneath the IRO Belt, due to a tilted IRO Pulley. Worn out IRO belts, yarn guides & eyelets etc. Faulty winding of the yarn packages. Yarn running out of the belt, on the IRO Pulley. Remedies: Ensure very smooth, clean & obstruction free passage of the yarn, through the eyelets, yarn & tension discs etc. No cuts or rough surfaces, in the Porcelain Eyelets, Yarn Guides & the Yarn Feeder holes etc. Flawless winding of the, Yarn Package (The yarn coils should unwind smoothly, without any obstruction). The yarn should be running under the IRO belt, between the belt & around the IRO pulley Imperfections Definition: Imperfections appear on the fabric surface, in the form of unevenly placed or randomly appearing, Knots, Slubs & Neps, Thick & Thin places in the yarn. Causes: Big Knots, Slubs & Neps in the yarn, Thick & Thin yarn (Uneven USTER) Remedies: Specify the quality parameters of the yarns, to be used for production, to the yarn supplier. Specify the number of acceptable Imperfections / Km. of the yarn & the USTER evenness %, while ordering the yarn. Snarls Definition: Snarls appear on the fabric surface, in the form of big loops of yarn getting twisted, due to the high twist in the yarn (Unbalanced twist yarn). Causes: High, twist in the, yarn. Hosiery yarns are soft twisted. High, twist in the yarn, is the cause of snarling. (Snarls cause, fabric defects & needle breakages) Remedies: Ensure using Hosiery Yarns, of the recommended T.P.M. only. 21 (Hold a few inches of the yarn in both the hands, in the form of a ‘U’. The yarn has a balanced twist, if it doesn’t tend to rotate or turn, in the form of a snarl. (Such yarn can be used for Hosiery applications.) Contaminations Definition: Contaminations appear, in the form of foreign matter, such as; dyed fibers, husk, dead fibers etc., in the staple spun yarn or embedded in the knitted fabric structure. Causes: Presence of dead fibers & other foreign materials, such as; dyed fibers, husk & synthetic fibers etc. Dead Fibers appear in the fabric, as a result of the, presence of excessive immature Cotton fibers, in the Cotton fiber crop. Dead fibers do not pick up color during Dyeing. Presence of the foreign materials, in the, staple fiber mixing (Kitty, Husk, Broken Seeds, dyed fibers & fibers like Poly Propylene, Polyester, Viscose etc) Dyed & other types of fibers flying from the adjacent Knitting machines cling, to the yarn being used for knitting & get, embedded in the Grey Fabric. Remedies: Use rich fiber mixing for the yarns, to be used for Knitting, in order to have less dead fibers, appearing in the fabric. Rigid control measures in the Blow Room, to prevent the mixing of foreign matters in the Cotton mixing. Segregate the Spinning & Knitting Machines, with Plastic Curtains or Mosquito Nets, to prevent the fibers flying from the neighboring machines, from getting embedded in the yarn / fabric. Spirality Definition: Spirality appears in the form of a twisted garment, after washing. The seams on both the sides of the garment displace, from their position & appear on the front & back of the garment. Causes: High T.P.M. of the Hosiery Yarn (Spirality is caused, by the Twisting Torque as a result, of the high yarn T.P.M.) (Hosiery yarns are soft twisted, whereas the Warp yarns are hard twisted) 22 Uneven Fabric Take down tension, on the Knitting machine. Unequal rate of Fabric feed on the Stenter, Calender & Compactor machines. Remedies: Use the Hosiery yarns of the recommended TPM level for Knitting (Hosiery yarns are soft twisted, in comparison to the Warp yarns) Fabric pull or the Take Down tension, on both sides of the grey fabric tube, on the knitting machine, should be equal. Ensure uniform rate of feed of the dyed fabric, on both the edges, while feeding the fabric to the Calander, Compactor or Stenter machines. 5.2 Knitting Elements related defects Needle Lines Definition: Needle lines are prominent, vertical lines, along the length of the fabric, which are easily visible in the grey as well as finished fabric. Causes: Bent Latches, Needle Hooks & Needle stems Tight Needles in the grooves Wrong Needle selection (Wrong sequence of needles, put in the Cylinder or Dial) Remedies: Inspect the grey fabric on the knitting machine for any Needle lines. Replace all the defective needles having, bent latches, hooks or stems. Remove the fibers accumulated in, the Needle tricks (grooves). Replace any bent Needles, running tight in the tricks. Check the Needle filling sequence in the Cylinder / Dial grooves (tricks). Sinker Lines Definitions Sinker lines are prominent or feeble vertical lines, appearing parallel to the Wales, along the length of the knitted fabric tube. Causes: Bent or Worn out Sinkers Sinkers being tight in, the Sinker Ring grooves Remedies: Replace, all the worn out or bent sinkers, causing Sinker lines in the fabric. 23 Sinker lines are very fine & feeble vertical lines, appearing in the fabric. Remove the fibers, clogging the Sinker tricks (Grooves) Drop Stitches (Holes) Definition: Drop Stitches are randomly appearing small or big holes of the, same or different size, which appear as defects, in the Knitted fabrics. Major Causes: High Yarn Tension Yarn Overfeed or Underfeed High Fabric Take Down Tension Obstructions in the yarn passage, due to the clogging of eyelets, yarn guides & tension discs, with wax & fluff etc. Defects like; Slubs, Neps, Knots etc. Incorrect gap between the Dial & Cylinder rings. Remedies: Ensure uniform yarn tension on all the feeders, with a Tension Meter. Rate of yarn feed should be strictly regulated, as per the required Stitch Length. The fabric tube should be just like a fully inflated balloon, not too tight or too slack. Eyelets & the Yarn Guides, should not have, any fibers, fluff & wax etc. stuck in them. The yarn being used, should have no imperfections, like; Slubs, Neps & big knots etc The gap between the Cylinder & the Dial should, be correctly adjusted, as per the knitted loop size. 24 5.3 Machine Settings related Defects Broken Needles Definition: Defects caused by the broken needles, show prominently, as vertical lines parallel to the Wales. There are no loops formed in the Wale, which has a broken needle. Causes: High Yarn Tension Bad Setting of the Yarn Feeders Old & Worn out Needle set Remedies: Ensure uniform & the right Yarn tension on all the feeders. Keep the recommended gap, between the Yarn Feeders & the Needles. Periodically change the complete set of needles. Oil Lines Definitions: Oil lines are prominent vertical lines, which appear along the length of the knitted fabric tube. The lines become permanent, if the needle oil used is not washable & gets baked, due to the heat, during the finishing of the fabric. Causes: Fibers & fluff accumulated in the needle tricks, which remain soaked with oil. Excessive oiling of the, needle beds. Remedies: Fibers, accumulated in the needle tricks, cause the oil to seep into the Fabric. Some lubricating oils are not washable & can not be removed during Scouring. Oil lines appear in the fabric, in the lengthwise direction, even after dyeing. Remove all the Needles & the Sinkers of the machine, periodically. Clean the grooves of the Cylinder & Dial of the machine thoroughly, with petrol. Blow the grooves of the Cylinder, Dial & Sinker ring, with dry air after cleaning. 25 Broken Ends Definition: Broken ends appear as equidistant, prominent horizontal lines, along the width of the fabric tube, when a yarn breaks or is exhausted. Causes: High Yarn Tension Yarn exhausted on the Cones. Remedies: Ensure correct yarn tension on all the feeders. Ensure that the Yarn detectors on all the feeders are working properly. Depute a skilled & alert machine operator, on the knitting machine. Streakiness Definition: Streaks in the Knitted fabrics appear as; feeble, irregularly spaced & sized, thin horizontal lines. Causes: Yarn slippage on the IRO Pulley, due to the yarn slipping in & out from underneath the IRO Belt, due to a tilted IRO Pulley. Worn out IRO belts, yarn guides & eyelets etc. Faulty winding of the yarn packages Yarn running out of the belt, on the IRO Pulley Remedies: Ensure very smooth, clean & obstruction free passage of the yarn, through the eyelets, yarn & tension discs etc. No cuts or rough surfaces, in the Porcelain Eyelets, Yarn Guides & the Yarn Feeder holes etc. Flawless winding of the, Yarn Package (The yarn coils should unwind smoothly, without any obstruction) The yarn should be running under the IRO belt, between the belt & around the IRO pulley 26 Fabric Press Off Definition: [ Fabric press off appears, as a big or small hole in the fabric, caused due to the interruption of the, loop forming process, as a result of the yarn breakage, or closed needle hooks. Press off takes place, when the yarn feeding to both the short butt & long butt needles, suddenly stops, due to the yarn breakage. At times, complete fabric tube can fall off the needles, if the needle detectors are not functioning, or are not properly set. Causes: End breakage on feeders, with all needles knitting. Yarn feeder remaining in lifted up position, due to which, the yarn doesn’t get fed in the hooks of the needles. Remedies: Needle detectors, should be set precisely, to detect the closed needles & prevent the fabric tube from completely pressing off. Proper yarn tension should be maintained, on all the feeders. Surface Hairiness & Piling Definition: Surface hairiness appears in the form of excess superfluous fibers, on the surface of the knitted fabrics, which have either been reprocessed, or tumble dried. Pilling appears as, small fiber balls formed on the fabric surface, due to the entanglement of loose surface fibers. Factors such as, the fiber staple length, low T.P.M. & fabric construction (with long yarn floats) etc. also contribute to pilling. Causes: Abrasion due to the contact with rough surfaces Excessive surface hairiness caused, due to the abrasive tumbling action (Fabric friction in the Tumble Dryer) Rough Dyeing process & abrasive machine surfaces (Soft Flow Machine tubes, Tumble Dryer drum etc.) Reprocessing of the fabric is, also a major cause of piling. Remedies: 27 Avoid using the Tumble Dryer. (Control shrinkage by maximum fabric relaxation & over feed in the processing) Regularly inspect the fabric contact points on all the machines, for any rough & sharp surfaces. (Rectify, if found rough) Avoid repeated reprocessing of the fabrics. Use anti pilling chemical treatments for the fabrics, prone to pilling. Snagging Definition: Snagging appears on the knitted fabric surface, as a pulled up yarn float, showing up in the form of a large loop. Causes: Caused by the pulling or the plucking of yarn from the, fabric surface, by sharp objects. Remedies: Inspect & rectify the fabric contact points on all the machines (Soft Flow Dyeing, Tumble Dryer & Centrifuge etc), on which snagging is taking place. Bowing Definition: Bowing appears as, rows of courses or yarn dyed stripes, forming a bow shape, along the fabric width. Causes: Uneven distribution of tensions, across the fabric width while, dyeing or finishing the fabric. Remedies: Bowing can be corrected, by reprocessing the fabric, by feeding it from the opposite end. A special machine (MAHLO) is also available for, correcting the bowing in the knitted fabrics. 5.4 Dyeing faults Dyeing faults and their remedies Uneven dyeing Causes 28 • • • Due to improper pretreatment. Very rapid addition of dyes and chemicals. Lack of controlling dyeing parameters figure: 5.1 Remedies Check addition of dyes and chemicals are at a steadily increasing rate. Proper pretreatments. Check the rope turnover time. Proper washing after dyeing. Running shade Causes • Machine loading is higher. • Running at lower nozzle pressure. • High bath draining temperature. • • • • Figure: 5.2 • • • Remedies Proper cycle time should be ensured. Nozzle pressure should be accurate. Bath draining temperature should be moderate. Crease mark Causes • Excessive loading of fabric during dyeing. • Sudden change in temperature during cooling. • Due to lack of synchronization of winch speed and pump pressure. figure: 5.3 Remedies 29 • • • Follow the temperature gradation during the whole cycle of dyeing. Fabric must be loaded according to loop length. Maintaining the proper synchronization between the winch speed and pump pressure. Pin hole Causes • Due to presence of traces of Fe+ and Cu+ ions in the process bath. • If soda dosing is done at high temperature then in presence of oxygen pin hole is created. • Inadequate amount of stabilizer im H2O2 bleaching. figure: 5.4 Remedies The water used in dyeing should be free from water hardness. Soda dosing should be done at low temperature (not more than 600C) Dye spot Causes • Improper mixing and dissolving of dyestuff. • Dye bath hardness. • • figure: 5.5 Remedies Mixing and dosing of dyestuffs should be done properly. Water of dye bath should hardness free. Soda spot Causes • If soaping start before wash • CaCO3 or MgCO3 in soaping bath • Quick soda dosing • • 30 figure: 5.6 • • • • • • Remedies Soda particles should be dissolved properly. After pre-treatment and dyeing, proper neutralization should be done. Fly dye stains Causes If dye is mixed in the dyeing floor then flying dust particles may come in contact with the dissolved dyestuffs. If dyeing floor is too dirty. Remedies Dyes should be dissolved in separate drum and in separate room. Dyeing floor must be neat and clean. Trims shade not match with the body Causes • Different types of yarns used in fabric and trims. • Dye lot is different for trims and body. • Improper recipe setting for trims and fabric. figure: 5.7 • • • • • • • • Remedies Same type of yarn, dye lot, recipe, nozzle pressure ,uniform distribution to each nozzle etc. should be used for both fabric and trims. Softener Marks Causes If pH is not maintained Poor emulsification of softener applied Inferior quality of softener Remedies Ensure that the softener is uniformly dissolved in the water Use the right softener and the correct procedure for the application. Maintain the correct pH. Barrie Causes High yarn tension 31 • • Count variation Mixing of the yarn lots figure: 5.8 • • Remedies Ensure uniform yarn tension to all the feeders. Ensure that the yarn being used for knitting is from the same lot. Metamerism Causes • This is because, dye class is not same for all ropes in a batch or when collar/cuff is dyed using dyes from one lot and body fabric is dyed using dyes from different lot. figure: 5.8 • Remedies To overcome this, one has to choose same dye class which will give same shade at least under primary and secondary light source. Hand feel problem Causes • Use of harsh metal chemicals for processing. • Insufficient softeners application in dyeing machine. Remedies It can be easily reduced by demineralization Dyeing related defects The Dyeing related defects are, as follows; Dyeing patches, Softener Marks Shade variation 32 Tonal variation Color fading (Poor Color Fastness) Dull shade Crease or rope Marks Dyeing patches Definition: Dyeing patches appear, as random irregular patches on the surface of dyed fabrics. Causes: (Scouring, Dyeing recipe, Dyeing Machine stoppage, Softener) Inadequate Scouring of the grey fabric is one of the primary causes of the dyeing patches. Improper leveling agent is also one of the causes of dyeing patches. Correct pH value not maintained. Dyeing machine stoppage, due to power failure, or the fabric entanglement, in the, dyeing machine are, a major cause of the dyeing patches. Remedies: Scour the grey fabric thoroughly, to remove all the impurities from the fabric, before dyeing. Use appropriate leveling agents, to prevent patchy dyeing. Maintain the correct pH value, during the course of dyeing. Use a power back up (Inverter) for the dyeing operation to be completed, uninterrupted. Softener Marks Definition: Softener marks appear as distinct irregular patches in the dried fabric, after the application of softener. Causes: Softener not being uniformly dissolved in water Remedies: Scour the grey fabric thoroughly, to remove all the impurities from the fabric, before dyeing. Ensure that the softener is uniformly dissolved in the water & doesn’t remain un-dissolved as, lumps or suspension. Use the right softener & the correct procedure for the application. Maintain the correct pH value of the softener, before application. Stains Definition: 33 Stains appear as spots or patches of grease, oil or dyes of different color, in a neat & clean finished fabric surface. Causes: Dyeing Machine not cleaned thoroughly, after dyeing a lot. Grease & Oil stains from the unguarded moving machine parts, like; Gears, Shafts, Driving Pulleys & Trolley wheels etc. Fabric touching the floors & other soiled places, during transportation, in the trolleys. Handling of the fabric, with soiled hands & stepping onto the stored fabric with dirty feet or shoes on. Remedies: Wash & clean the dyeing machine thoroughly, after dyeing every dye lot. Follow the dyeing cycle of Light- Medium- Dark shades & then the reverse the cycle, while dyeing the fabric. All the lubricated moving machine parts, should be protected, with safety guards Make sure that the fabric is neatly packed in or covered with Polythene sheets, while transporting or in storage. Handle the fabric carefully, with clean hands & do not let anyone step onto the stored fabric. Color Fading (Poor Color Fastness) Definition: The color of the garment or the fabric appears, lighter & pale, in comparison to the original color of the product, after a few uses. Causes: (Washing, Crocking, Chlorine, Light, Perspiration) Dyeing recipe i.e. the poor fixing of the dyes is a major cause, of color fading. Using the wrong combination of colors in a, secondary or tertiary shade. Use of strong detergents & the quality of water are also the common causes for color fading. Prolonged exposure to strong light will, also cause the colors to fade. High level of acidity or alkalinity in the perspiration of individuals also, causes color fading. Remedies: Use the correct dyeing recipe i.e. the appropriate leveling, fixing agents & the correct combination of dyes. Follow the wash care instructions rigidly. Use mild detergents & soft water for washing the garments. Don’t soak the garments for more than 10- 15 minutes, in the detergent, prior to washing Turn the wet garments, inside out, while drying. 34 Dry in shade & not in direct sunlight Protect the garments against prolonged direct exposure to strong lights (show rooms or exhibitions etc.). Shade variation (Roll to roll & within the same roll) Definition: Sometimes, there appears to be a difference in the depth of shade, between the roll to roll & from place to place, in the same roll. The defect will show up clearly, in the garments, manufactured from such fabric. Causes: Shade variation can be as a result of mixing of the, fabrics of two different lots. Shade variation is also caused, by the variation in the process parameters i.e. Time, Temperature & Speed etc. from one fabric roll, to the other. Shade variation can appear to be, in fabrics with GSM variation, caused due to the uneven stretching, unequal fabric overfeed % etc. Remedies: Ensure that the grey fabric used for one shade, is knitted from the same lot of the yarn. Ensure that the same process parameters (Width, Overfeed, Temperature & Machine Speed etc.) are used, for each roll of a dye lot. Tonal variation Definition: Roll to roll or within the same roll difference in the color perception i.e. Greenish, Bluish, Reddish or Yellowish etc., is attributed as tonal variation in the shade. Causes: Wrong Dyeing recipe (Wrong leveling agent selection or wrong dyes combinations) Improper fabric Scouring (Impurities like, Oil & Wax etc. not being completely removed in Scouring) Level dyeing not being done, due to the inappropriate leveling agents. Variation in the process parameters, e.g. Temperature, Time & Speed etc 35 (Tonal variation in the fabric is caused, due to the variations, in the fabric processing parameters i.e. Temperature, Time & Speed etc. of the Shrink Dryer & Stenter, especially if, the machine is repeatedly stopped.) Remedies: Use appropriate leveling agents, to ensure uniform & level dyeing. Scour the grey fabric thoroughly, to ensure the removal of all the impurities. Ensure that the whole lot of the dyed fabric is processed, under uniform process parameters. Wet Squeezer Marks Definition: The fabric on the edges of the fabric tube gets, permanent pressure marks, due to the, hard pressing by the squeezer rolls. These marks appear as distinct lines, along the length of the fabric & can’t be corrected. Causes: These marks are caused due to the excessive pressure, of the squeezer rolls of the Padding Mangle, on the wet fabric, while rinsing. Remedies: Use the Padding mangle, only for the application of the softener. Use a hydro extractor (Centrifuge) for the extraction, to avoid the squeezer roll marks. Soon after extraction, open the fabric manually, to prevent crease marks in the damp fabric. Folding Marks Definition: Fold marks appear as distinct pressure marks, along the length of the fabric Causes: High pressure of the fabric Take Down rollers of the Knitting machine, on the grey fabric, is one of the main causes. Too much pressure of the feeding rolls of the Calander & Compactor is, the primary cause of the folding marks, in the knitted fabric. Remedies: Adjust the gap between the two rolls, as per the thickness of the fabric sheet (Pique, S.J. etc.) 36 Gap between the two Calander rolls should be just enough, to let the rolls remove, the wrinkles in the fabric, but put no pressure on the fabric sheet, especially in the case of Pique & structured fabrics. Crease Marks Definition: Crease marks appear in the knitted fabric, as dark haphazard broken or continuous lines. Causes: Damp fabric moving at high speed in twisted form, in the Hydro extractor (Centrifuge) Remedies: Use anti Crease, during the Scouring & the Dyeing process (The use of anti Crease, swells the Cellulose & prevents the formation of Crease marks) Spread the fabric in loose & open form & not in the rope form, in the Hydro Extractor. Finishing related defects Surface Hairiness & Piling Definition: Surface hairiness appears in the form of excess superfluous fibers, on the surface of the knitted fabrics, which have either been reprocessed, or tumble dried. Pilling appears as, small fiber balls formed on the fabric surface, due to the entanglement of loose surface fibers. Factors such as, the fiber staple length, low T.P.M. & fabric construction (with long yarn floats) etc. also contribute to pilling. Causes: Abrasion due to the contact with rough surfaces Excessive surface hairiness caused, due to the abrasive tumbling action (Fabric friction in the Tumble Dryer) Rough Dyeing process & abrasive machine surfaces (Soft Flow Machine tubes, Tumble Dryer drum etc.) Reprocessing of the fabric is, also a major cause of piling. Remedies: Avoid using the Tumble Dryer. (Control shrinkage by maximum fabric relaxation & over feed in the processing) 37 Regularly inspect the fabric contact points on all the machines, for any rough & sharp surfaces. (Rectify, if found rough) Avoid repeated reprocessing of the fabrics. Use anti pilling chemical treatments for the fabrics, prone to pilling. Tonal variation Definition: Roll to roll or within the same roll difference in the color perception i.e. Greenish, Bluish, Reddish or Yellowish etc., is attributed as tonal variation in the shade. Causes: Wrong Dyeing recipe (Wrong leveling agent selection or wrong dyes combinations) Improper fabric Scouring (Impurities like, Oil & Wax etc. not being completely removed in Scouring) Level dyeing not being done, due to the inappropriate leveling agents. Variation in the process parameters, e.g. Temperature, Time & Speed etc (Tonal variation in the fabric is caused, due to the variations, in the fabric processing parameters i.e. Temperature, Time & Speed etc. of the Shrink Dryer & Stenter, especially if, the machine is repeatedly stopped.) Remedies: Use appropriate leveling agents, to ensure uniform & level dyeing. Scour the grey fabric thoroughly, to ensure the removal of all the impurities. Ensure that the whole lot of the dyed fabric is processed, under uniform process parameters. Folding Marks Definition: Fold marks appear as distinct pressure marks, along the length of the fabric Causes: High pressure of the fabric Take Down rollers of the Knitting machine, on the grey fabric, is one of the main causes. Too much pressure of the feeding rolls of the Calander & Compactor is, the primary cause of the folding marks, in the knitted fabric. Remedies: Adjust the gap between the two rolls, as per the thickness of the fabric sheet (Pique, S.J. etc.) 38 Gap between the two Calander rolls should be just enough, to let the rolls remove, the wrinkles in the fabric, but put no pressure on the fabric sheet, especially in the case of Pique & structured fabrics. Wet Squeezer Marks Definition: The fabric on the edges of the fabric tube gets, permanent pressure marks, due to the, hard pressing by the squeezer rolls. These marks appear as distinct lines, along the length of the fabric & can’t be corrected. Causes: These marks are caused due to the excessive pressure, of the squeezer rolls of the Padding Mangle, on the wet fabric, while rinsing. Remedies: Use the Padding mangle, only for the application of the softener. Use a hydro extractor (Centrifuge) for the extraction, to avoid the squeezer roll marks. Soon after extraction, open the fabric manually, to prevent crease marks in the damp fabric. Snagging Definition: Snagging appears on the knitted fabric surface, as a pulled up yarn float, showing up in the form of a large loop. Causes: Caused by the pulling or the plucking of yarn from the, fabric surface, by sharp objects. Remedies: Inspect & rectify the fabric contact points on all the machines (Soft Flow Dyeing, Tumble Dryer & Centrifuge etc), on which snagging is taking place. Skewing or Diagonal Grain Lines (Wales) Definition: Fabric Wales appear in the diagonal direction, to the edges of the fabric, instead of being parallel. Causes: Improper feeding of the fabric, while Calandering & Compacting. Remedies: 39 Keep a slit line on one side of the tubular fabric. Use the slit line, as a reference line, to keep the grain lines straight, while feeding the fabric slowly, on the Calander, or the Compactor machines. High Shrinkage Definition: The original intended measurements of the Garment go, haywire, during storage or after the very first wash. Causes: High Stresses & strains exerted on the fabric, during Knitting, Dyeing & Processing & the fabric not being allowed to relax properly, thereafter. (High shrinkage is primarily due to the fabric being subject to high tension, during the Knitting, Dyeing & the Finishing processes) Remedies: Keep the Grey Fabric in loose plated form, immediately after the roll is cut. Store the finished fabric also in the plated form & not in the roll form. Allow the fabric to relax properly, before it is cut. Give maximum overfeed to the fabric, during the processing, on the Stenter, Compactor & the Calandering machines. GSM Variation Definition: The fabric will appear to have a visible variation in the density, from roll to roll or within the same roll of, the same dye lot. Causes: Roll to roll variation in the, process parameters, of the fabric, like; Overfeed & Widthwise stretching of the dyed fabric, on the Stenter, Calander & Compactor machines. Roll to roll variation in the fabric stitch length. Remedies: Make sure that all the fabric rolls in a lot, are processed under the same process parameters. The Knitting Machine settings, like; the Quality Pulley diameter etc. should never be disturbed. 40 Fabric Width Variation Definition: Different rolls of the same fabric lot, having difference in the finished width of the fabric. Causes: Grey fabric of the same lot, knitted on different makes of Knitting Machines, having varying number of Needles in the Cylinder. Roll to roll difference, in the Dyed Fabric stretched width, while feeding the fabric on the Stenter, Calander & Compactor. Remedies: THE WHOLE LOT OF THE GREY FABRIC SHOULD BE KNITTED ON THE SAME MAKE OF KNITTING MACHINES. FOR THE SAME GAUGE & DIAMETER OF THE KNITTING MACHINES, THERE CAN BE A DIFFERENCE OF AS HIGH AS 40 NEEDLES, FROM ONE MAKE TO THE OTHER MAKE OF THE MACHINE. THIS DIFFERENCE, IN THE NUMBER OF NEEDLES, CAUSES A DIFFERENCE OF UPTO 2”- 3” IN THE FINISHED WIDTH OF THE FABRIC. THE STRETCHED WIDTH OF THE GREY FABRIC SHOULD REMAIN CONSTANT, DURING FINISHING ON THE STENTER. Problems faced in Knits on the Cutting Table (Curling of the Single Jersey Fabrics) Definition: Single Jersey fabrics, when layered on the cutting table tend to, curl at the edges. Causes: Dimensional instability of the Single Jersey knitted fabrics The face side of the fabric has loops, whereas the back side has only yarn floats. So, there is an imbalance, between the face & the back side of the fabric. Remedies: Gumming on both the edges of the S.J. fabrics, while Stentering, can control the curling. Measurement Problems Definition: 41 The measurements of the garments totally change after, a few hours of relaxation & after the first wash. The arm lengths or the front & back lengths of the garments may vary, due to the mix up of the parts. Causes: Shrinkage caused due to the inadequate relaxation of the knitted fabrics, before cutting. Mixing of the garment parts cut from, different layers or different rolls of the knitted fabric. Remedies: Use a trolley, for laying the fabric on the table, to facilitate a tension free, laying. Let the fabric relax for a few hours, before cutting, especially the Lycra fabrics. Ensure the numbering of the different layers of the fabric, to prevent the mix up of the components. CHAPTER SIX: CONCLUSION Due to the increasing demand for quality dyed fabrics, high quality requirements are today greater since customer has become more aware of “Non quality” problems. In order to avoid fabric rejection, knik dyeing mills have to dye fabrics of high quality,constantly. Detection of faults during production of knit dyeing fabric with dyeing machine is crucial for improved quality and productivity. Any variation to the knit dyeing process needs to be investigated and corrected. The high quality standard can beguaranteed by incorporating appropriate quality assurance. Industrial analysis indicate that product quality can be improved, and defect cost minimised, by monitoring of dyeing process. Dyed knitted fabric faults are very different in nature and appearance and are often superimposed. They can be attributed not only to the dyeing, but also to thequality of dyeing finishing. 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