Disperse Dyes (Full PDF) | Disperse Dye

Disperse Dyes (Full PDF) | Disperse Dye

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  1 DISPERSE DYES Introduction: Dyes arecolored unsaturated organic chemical compounds capable of giving color to a substrate (a textile), i e coloring or dyeing it. The term “disperse dye” have been applied to the organic coloring substances which are free from ionizing groups are or low water solubility and are suitable for dyeing hydrophobic fiber. The dye has derived its name for its insoluble aqueous properties and the need to apply it from in aqueous dispersion. Of all the dyes, they are of the smallest molecular size. Disperse dyes have substantivity for one or more hydrophobic fibers e g cellulose acetate nylon polyester acrylic and other synthetic fibers. The negative charge on the surface of one or more hydrophobic fibers like polyester cannot be that reduced by any means, so non-ionic dyes like disperse dyes are used which are not influenced by that surface charge. History: In 1922 Green and saunders made one type of coloured azo compound in which a solubilizing group (for example methyl sulphate ÑCH –So3H )is attached to amino group. In dye bath they are slowly hydrolyzed and produce azo compound and formaldehyde bi sulphate. In dye azo compound was capable of dyeing cellulose acetate fibers . This dye was named “ionamine” But this ion amine did not give satisfactory result in dyeing. Later in 1924 Baddlley and ells produced sulpho ricinoleie acid (SRA) for dyeing acetate fibers. This SRA was used as dispersing agent later it was seen that SRA was capable of dyeing Nylon , polyester, acrylic etc. In 1953 this dye was named as “Disperse Dye” Properties of Disperse Dyes: 1. Disperse dyes are nonionic dyes. So they are free from ionizing group. 2. They are ready made dyes and are insoluble in water or have very low water solubility. 3. They are organic colouring substances which are suitable for dyeing hydrophobic fibers.
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  2 4. Disperse dyesare used for dyeing man made cellulose ester and synthetic fibers specially acetate and polyester fibers and sometimes nylon and acrylic fibers. 5. Carrier or dispersing agent are required for dyeing with disperse dyes. 6. Disperse dyes have fair to good light fastness with rating about 3-5. 7. The wash fastness of these dyes is moderate to good with rating about 3-4. 8. Of all dyestuffs disperse dyes are of smallest molecular size. 9. Generally disperse dyes are derivatives of azo anthroquinone nitro and quinine groups. 10. They do not undergo any chemical change during dyeing. 11.In presence of nitrous oxide textile materials dyed with certain blue and violet disperse dyes with an anthraquinone structure will fade. this is called gas fading of disperse dyes which is a defect of this dye.] Classification of Disperse dye: According to chemical structure there are following of disperse dyes; 1. Nitro Dyes 2. Amino ketone dyes 3. Anthraquinonoid dyes 4. Mono azo dyes 5. Di-azo dye According to Fastness property: According to fastness property there are following 4types of disperse dyes: 1.Group A: These dyes have excellent dyeing and good fastness properties. 2. Group B : These dyes are excellent in high temperature and for carrier dyeing with moderate fastness . 3.Group C: These dyes are moderate for carrier and high temperature dyeing with higher fastness property than group B dyes. 4.Group D: These dyes are of excellent fastness to heat but for dyeing properties on carrier method
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  3 According to EnergyRequired: According to energy required for dyeing there are following 3 types of disperse dyes: 1. Low energy dyes : These dyes are used to dye with carrier For dyeing 77°C temperature is required . they have extremely poor resistance to sublimation. 2. Medium energy dyes : These dyes are used to dye mostly in between temperature 104°C-110°C which provides better sublimation fastness than that of low energy dyes. 3. High energy of dyes : These dyes are used to dye at temperature above 129°C and are suitable for continuous dyeing . they provide all round fastness properties. Chemical Groups in disperse dyes: The percentage of chemical groups in disperses dyes are as below: Mono azo dyes 50% Anthraquinonoid dyes 25% Di-azo dyes 10% Methyne dyes 03% Styryl dyes 03% Acrylene benzimidazol 03% Quinonaphthalon dyes 03% Amino naphthyl amide 01% Napthoquinone imine 01% Nitro disperse dyes 01% Total 100%
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  4 Commercial Names ofDisperse Dyes: Name of dye Manufacturer Origin Foron Sandoz Switzerland Terasil Ciba-Geigy Switzerland Dispersol ICI UK Samaron Hoechst Germany SRA British Celanese Ltd UK Setile ACNA Italy Application Method of disperse dyes: 1. Method N: Normal dyeing method dyeing temperature is 80-100°c. 2.Normal NC method :Method of dyeing at normal temperature with carriers dyeing temperature 80-100°C 3. Method HT: high temperature dyeing method . dyeing temperature 105- 140°c. 4. Method T : Thermasol dyeing method . dyeing temperature 180-220°C continuous method of dyeing 5. Pad roll method: Semi continuous dyeing method. 6. Pad steam method: continuous dyeing method . Factors considered for selection of a method: 1. Availability of dyeing machine. 2. Required color effect (dark medium /light) 3. Required color fastness. 4. Type of material to dye. 5. Cost of dye chemicals and auxiliaries. 6. Overall economy of the system. 7. Dyeing temperature. Theory of Dyeing with disperses dye: First step: One of the first obvious requirements of a dye is solubility. With regards to the disperse dyes, which are generally regarded as insoluble, their dissolution in the dye bath depends on their dispersability and solubility. Dispersability is aided by the presence of dispersing agents and the solubility by the rise in temperature. Neither of these characteristics is influenced by the fiber characteristics.
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  5 Second step: The secondstep, as has been described earlier, relates to the adsorption of the dye molecules on to the fiber surface. Dyestuff adsorption by the fiber surface is influenced by two characteristics, the solubility of the dye in the dye bath and that in the fiber. Third step: After adsorption, the next step in a dyeing process is penetration of the dyestuff molecules into the fiber structure. The overall rate of dyeing is governed by such penetration or diffusion of the dye from the fiber surface into the fiber. Under the normal dyeing conditions of time and temperature the rate of adsorption is always higher than the rate of diffusion and it is therefore the third step that governs the overall rate of dyeing. In any dye bath, when the amount of dye absorbed by the fiber equals the amount of dye desorbed by it (coming out of it), the dye bath is said to be in equilibrium. When equilibrium dyeing is reached, the following subsidiary equilibria are established: 1 Dye dispersed in the bath ↔ Dye dissolved in the dye bath. 2 Dye dissolved in the dye bath ↔ Dye adsorbed on the fiber surface 3 Dye adsorbed on the fiber surface ↔ Dye diffused into the fiber surface If the amount of dye present in the dye bath is not sufficient to saturate the fiber in the dyeing process, only the first two equilibria are established. If the fiber is saturated, the third equilibrium is attained and the dyeing is completed. Thus the aqueous solubility of the dye and the diffusion of the dye in the fiber are the two factors governing the dyeing process that are more important. If these factors are affected, the rate of dyeing, the percentage exhaustion of the dye bath and the level dyeing characteristics of the disperse dye are also affected. Auxiliaries used in polyester dyeing: Dispersing agents:  A dispersing agent assists the process of reducing the particle size of the dye.  It increases the solubility of the disperse dye in water.  It helps to avoid agglomeration of dyes during dyeing.  It influences the rate of exhaustion.
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  6 Leveling agents:  Non-ionicleveling agents retard the rate of dyeing.  Carrier type leveling agents are used in high temperature dyeing to get uniform dyeing.  They also help to avoid the deposition of oligomers on the fiber surface. Antifoaming agents:  Antifoaming agents are used in a disperse dye bath to control the foam as excess foaming gives specky dyeing. Wetting agent:  A small quantity of wetting agent in the dye bath facilitates the dye liquor to be absorbed uniformly and quickly. PH and redox buffers:  These agents protect the dyes from degradation in a high temperature bath. Mechanism of disperses Dyeing on polyester: In this technique, the disperse dyes dissolves in the aqueous dye bath, the resulting dye in solution is adsorbed onto the fiber surface and the adsorbed dye diffuses into the fiber through the liquid phase. The boundary layer on the fiber surface remains a stationary liquid layer through which the dye has to diffuse in order to reach the fiber surface. In principle, the dye is adsorbed on the fiber surface from the diffusional boundary layer, which, in turn, receives the dye from the bulk of the agitated liquor. The thickness of the diffusional boundary layer under circulation conditions in different machines may vary, which, in turn, may vary the rate of dyeing from machine to machine. The rate of dye transfer through boundary layer depends on diffusion coefficient, fiber surface and the change in chemical potential in the process. In the polymer/water/disperse dye system there must be sufficiently large free volume. Carriers are often added which acts as plasticizers and increase the free volume of the system so that the diffusion rate is increased.
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  7 The mechanism ofdyeing is depicted schematically in figure: The diffusion boundary layer and the adsorption layer are clearly seen. Also seen is the diffusion of the dye molecules and the chemicals into the fiber. The various states of modification of the dispersed dye molecules are also clearly depicted. Methods of dyeing polyester with disperse dye:
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  8 Dispersing Agent: Disperse dyesare insoluble in water and form aqueous dispersion in water. At first these dye molecules are formed as large particles and they are made smaller particles by grinding .But as they are water insoluble they will give uneven dyeing if they are directly used in dye bath. So to ensure uniform and trouble free dyeing the dye should be present in dye bath in an uniform and very fine and should give at stable dispersion. This is the reason for which a special chemical is used in dye bath named dispersing agent. They should be effective under dyeing conditions stable to hard water high temperature and other dyeing assistants. For example soap power turkey Red oil alkali sulphates alkyl sulphonates etc. are some surface active agent which are recommended as dispersing agents in disperse dyeing . Function of Dispersing Agents : 1. It assists in the process of particle size reduction of dye. 2. It enables the dye to be formed in powder form. 3. It facilitates the recon version of the powder in to a dispersion which is required for dyeing. 4. It maintains the dispersion in a fine form in the dye bath throughout the process. 5. It increases the solubility of disperse dyes in water. 6. It affects on the rate of dyeing. Effect of Various conditions on disperse dyeing : 1. Effect of temperature: In case of dyeing with disperse dye temperature plays an important role. For the swelling of fibre temperature above 100°C is required if high temperature dyeing method is applied again in case of carrier dyeing method this swelling occurs at 85-90°C . In case of thermasol dyeing method if temperature is kept more fabric is kept for less time in thermasol unit .Because in higher temperature less time is enough for thermo fixation of dye . If it is kept for more time, then dye sublimation and lass of fabric strength may occur. Again though disperse dye is a water insoluble dye its solubility increases temperature.
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  9 2. Effect ofPH: For disperse dyeing the dye bath be should be acidic and PH should be in between 4.5-5.5. For maintaining this PH generally acetic acid is used. We may also use any mineral acid like H3 PO4. But those are strong and costly. So mild acid is used for controlling PH of the bath. At this PH dye Exhaustion is satisfactory. During colour development, correct PH should be maintained otherwise fastness will be inferior and colour will be unstable. Heat Setting Procedure of Polyester Fabric The process of heat setting is used to stabilize yarn twist remove residual shrinkage increase resistance and obtain durable pleat. Polyester may shrink 7% at boil and even more at higher temperature. The importance of heat setting is as below. 1. To modify crystalline structure. 2. To improve dimension stability. 3. To resist wet creasing during washing 4. To increase safe ironing temperature 5. To avoid shade variation 6. Affect water inhibition The disadvantages of heat setting are – 1. Some dyes sublime at higher temperature. 2. Heat setting reduces dye uptake Heat setting can be done before or after dyeing. If the fabric is heat set before dyeing the absorbency of fabric goes down and if it is done before scouring and bleaching then the dirt, dust may permanently deposit on the fabric. If heat setting is done after dyeing then some dye may sublime at high temperature and thus cause shad variation. The time of heat setting depends on the fabric state i. e grey scoured bleached etc. It also depends on count of yarn in fabric. For heat setting hot roller or radiant machine can be used. Super Heated Steaming: The features of this method of dye fixation are mentioned below: 1. It is a continuous process ofdye fixation. 2. This method is the best of the three methods.
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  10 3. Dye isfixed at 1000-1800C for 2-1 minutes by radiators. 4. Higher productivity. 5. No loss of colour. 6. Dyes with medium sublimation fastness can be applied. 7. The fabric handle is very soft. High Pressure Steaming: The features of this method of dye fixation are mentioned below:- 1. Discontinuous process ofdye fixation 2. Low productivity. 3. Dye fixation is done by high pressuresteam. 4. Low productionso costly process. 5. Dyes with low sublimation fastness can be applied. 6. It gives good Colour yield and bright print & smoothness. Reduction Cleaning In case of dark shade dyeing, we have to use more amounts of dye and chemicals. But these chemicals should be removed from fabric after dyeing. For this reason a special process is used in case of disperse dyeing. This cleaning process is called reduction cleaning. A typical recipe for reduction cleaning is given below 1. Caustic Soda : 2 gm/litre 2. Hydrosulphite : 2 gm/litre 3. Datergent : 2 gm/litre 4. M : L Ratio : 1:5 5. Time : 30 Minutes By reduction cleaning surface dye molecules or unfixed dye molecules are stripped and this in turn results in level dyeing. Reduction cleaning also impoves wash fastess property of textile material. CARRIER DYEING METHOD Carriers : It has been established that certain hydrocarbons phenols amino acids amides, alcohols , esters ketones nitriles etc. accelerate the rate of dyeing polyester fibre with disperse dyes from aqueous medium at temperature up to 100 C . These
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  11 dyeing assistants alterthe disperse dyes from of the dyes and the physical characteristics of t5he fibre so that more dye can be transferred from the dye bath to the fibre. these are called carriers and are necessary for dyeing polyester fibres at the normal within the fibre and level dyeing of disperse dyes depend on the migration power of the dye which is affected by nature and amount of carrier dyeing time temperature and the shade Some commercial carriers : Commercial Name Manufacturer Chemical Class Solvent op Franco O-phenyl phenol Tumescal D ICI Diphenyl Palanil carrier A BASF Aromatic Ether Carrier PDC TCC Emulsifiable solvents Dilatin TCR Sandoz Chlorinated aromatic compound Butyl oleate HAR Ester Factors considered for selecting a carrier: 1. High carrier efficiency 2. Availability at low cost 3. Little or no effect on light fastness of final dyeing 4. Non toxicity 5. No degradation or discoloration of fiber 6. Ease of removal after dyeing 7. High stability under dyeing conditions 8. Compatibility with dyestuffs 9. Ease of dispersion in the dye bath 10. Low volatility of the carrier including low volatility in the steam 11. Uniform absorption by the fiber Mechanism of carrier Action In carrier method of polyester dyeing is used. Carrier swells the fiber and ultimately causes relaxation. They may operate by opening up the internal fiber structure and allow the dye molecules to diffuse more rapidly. They act as molecular lubricants reducing inter-molecular forces operating in the fiber there by following the dye molecule to force its way in its action may be described as below. 1. It creates dye film on fiber surface
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  12 2. Carrier takesdye inside the fiber from dye carrier association 3. It increases the solubility of dye in the bath 4. Carrier penetrates inside the fiber polymer chain and thereby reduces inter-chain attraction. thus polymer chains become movable and so dye molecules may enter the polymer system of fiber 5. It increases fiber swelling 6. The absorbency power of fiber 7. The absorbed carrier increases therate of dyeuptakeby creating liquid co-fiber 8. It lubricates the thermally agitated fiber molecules 9. 2-10 gm/lit carrier is used depending on material and liquor ratio and depth of shade 10. The automatic of it attracts water 11. With increasing molecular weight the carrier efficiency also increases up to a certain limit Dyeing of polyester Fabric with Disperse Dye in carrier method: The extreme crystalline nature of polyester fibres creates problems in obtaining dark shades by conventional dyeing method even at high temperature. The carrier are found to assist the disperse dye to enter the polyester polymer enabling dark shades to9 be produced. The carrier swell the polyester fibres, increase inter polymer space and let the dye molecules to enter the polymer system easily RECIPE: Dye - For light shade < 0.5% - For medium shade 0.5-1.5% - For deep shade > 1.5% - Carrier (phenol) : 3gm/lit - Acetic acid : 1gm/lit - Disperse agent : 2gm/lit - Salt (NH ) SO : 1-2gm/lit - PH : 4-5.5 - M:L : 1:10 - Time : 60 min - Temperature : 90 C PROCEDURE: 1. At first, a paste of dye and dispersing agent is prepared and then water is added to it.
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  13 2. Dye bathis kept at 60°C temperature and all the chemicals along with the material are added to it. Then the bath is kept for 15 min without raising the temperature. 3. pH of bath is controlled by acetic acid at 4-5.5. 4. Now temperature of dye bath is raised to 90°C and at that temperature the bath is kept for 60 min. 5. Then temperature is lowered to 60°C and resist and reduction cleaning is done if required. Reduction cleaning is done only to improve the wash fastness. 6. Material is again rinsed well after reduction cleaning and then dried. Advantages of carrier dyeing: 1. In conventional dyeing method the extremely crystalline polyester fibres can not be dyed in deep shade. But by using carrier we can get medium to dark shade in boiling temperature. 2. Materials can be dyed with simple equipments at atmospheric pressure and temperature below 100 c . 3. Moderate level dyeing of polyester fabric can be done. 4. Some carrier reduce the staining of wool while dyeing polyester –wool blends . 5. Rate of dyeing can be increased by using carrier . 6. Improves fastness properties of fabric except light fastness .
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  14 Disadvantages of carrierDyeing: 1. Carrier add to production cost of dyeing. Firstly, for dyeing it is used which is costly and secondly for its removal alkali is required. 2. Carriers are unhygienic and toxic. It creates skin diseases. 3. Some dyeing machine may create carrier spot. 4. Carriers affect the light fastness property of dyed material. This effect may be reduced by treating the material with hot air for 30 min. 5. Some carriers are dyed specific. They possess different efferent dyes, others have compatibility with certain dyes. High Temperature Dyeing Method: Dyeing of polyester fabric in high temp Dyeing method : In high temperature dyeing method either material or liquor should circulate. otherwise dye molecules will not penetrate inside the material. they will stay on surface only. In this method temperature is kept in between 105 -140 c and pressure is kept from 0 to 170 kpa. this method is also known as pressure dyeing which is used for highly crystalline synthetic fibres and their blends. This technique causes the fibre to swell even more than which achieved at 100 c temperature. so that dye molecules penetrate the fibre polymer system. It eliminates the need of carrier. RECIPE: Dye : 3% Disperse agent : 1gm/lit Acetic acid : 1gm/lit PH : 4-5.5 M:L : 1:10 Time : 60 min Temperature:130 C Procedure: Ø At first a paste of dye and dispersing agent is prepared and water is added to it. Ø PH is controlled by adding acetic acid. Ø This condition is kept for 15 minutes at temperature 60°C. Ø Then the dye bath temperature is raised to 130°C and this temperature is maintained for 1 hour. Within this time, dye is diffused in dye bath, adsorbed by
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  15 the fibre andthus required shade is obtained. Ø The dye bath is cooled as early as possible after dyeing at 60°C. Ø The fabric is hot rinsed and reduction cleaning is done if required. Ø Then the fabric is finally rinsed and dried. Dyeing Curve Types of HTHP dyeing machines:  Pressure jigger  Pressure winch  Package dyeing machine  Beam dyeing machine  Jet dyeing machine Thermosol Dyeing Method: Dyeing of polyester fabric in thermasol dyeing method : Thermosol method is continuous method of dyeing with disperse dye. Here dyeing is performed at high temperature like 180-220 C in a close vessel. Here time of dyeing should be maintained very carefully to get required fabric strength. Sequence: The dyeing process is developed by du pont corporation in 1949. here at sufficient temperature the fibres are soften and their internal structure is opened polymer macromolecules vibrates vigorously and dye molecules diffuse in fibre. It requires only a few seconds to 1 min and temperature about 200-230° C . Sequence: Pading-Drying-Thermofixing-Aftertreatment
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  16 Procedure: Ø At firstthe fabric is padded with dye solution using above recipe in a three bowl padding mangle. Ø Then the fabric is dried at 100°C temperature in dryer. Fordyeing, infra red drying method is an ideal method by which water is evaporated from fabric in vapor form. This eliminates the migration of dye particles. Ø Then the fabric is passed through thermasol unit where thermo fixing is done at about 205°C temp for 60-90 seconds depending on type of fibre, dye and depth of shade. In thermasol process about75-90% dye is fixed on fabric. Ø After thermo fixing the unfixed dyes are washed off along with thickener and other chemicals by warm water. Ø Then soap wash or reduction cleaning is done if required. And finally the fabric is washed . Advantage of Thermosol process:  No carrier is required and hence problems associated with carrier do not arise.  Excellent dye utilization is achieved.  Simultaneously heat setting and dyeing can be carried out.  The dyeing is unaffected by pre heat setting.  High uniformity of shade can be obtained throughout the fabric. Comparison among high temperature, Carrier & Thermosol method: Carrier method high temperature method Thermosol method Lower dyeing temp (80- 100 C) Higher dyeing temp (105- 140 C) Very high dyeing temp (180-220 C) Production less More carfulness required Very much carfulness required Costly as carrier is used Not costly costly as special m/c used Less bright shade More bright shade Very bright shade Batch wise process Batch wise process continuous process Toxic & unhygienic process Non –Toxic &hygienic process Non –Toxic &hygienic process More shrinkage Less shrinkage Less shrinkage Less production Less production Higher production Carrier Removal is difficult & alkali is used Not Applicable Not Applicable No change is shade No change in shade Change in shade may occur due to sublimation
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  17 Dyeing of polyester/cottonblends: Different effects can be produced while dyeing these blends: Solid phase dyeing: Both the components of the blends are dyed to the same tone and depth of shade. Contrast dyeing: Two components of the blend are dyed in different shade. Reserve dyeing: Only one component of the blend is dyed whereas the second component is left un-dyed. Two tone dyeing: The same dyeing effect and tone is produced in different depths of shade percentage in the two fibers.
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  18 Printing with DisperseDye Introduction : Disperse dyes are most suitable dyes for printing polyester fabric. Selected dyes with good steaming & thermofixation fastness are suitable for printing. The washing fastness of disperse dyes on polyester are much higher than acetate triacetate or nylon disperse dyes have high degree of dispersibility and the disperse dyes marketed in liquid form are easy to make in to stock thickening without predispersing. The printing paste should contain a dispersing agent. **Thickener used in printing with disperse dyes Proper selection of thickener is important in printing polyester fabric with disperse dyes. It depends on method of printing (i.e- Roller printing, screen printing ) and method of fixation of dye. The kind of fabric to be printed also influences the thickener choice. suitable thickener should adhere well to be fabric and should produce an elastic flum to prevent cracking. The thickener should be easily removal in the after treatments. Thickening with a high solid content bring less water on hydrophobic and produce sulpher and more level prints than those with low solid content. But the thickening with low solid content behave better with respect to cracking and in thermosol process for better colour yeild. But its sharpness in prints is not good as with high solid contents thickenings. The most commonly used thickeners used in printing with disperse dyes are below 1. Starch ethers (best) 2. Natural Gums 3. Locust Bean Gum 4. Meyprogum 5. CMC (car boxy methyl cellulose)
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