Let-off
It was mentioned earlier that there are two warp systems including ground warp and pile warp, and thus two warp beams are let off simultaneously in a terry weaving machine. The ground warp ends move forward slowly and under high tension as the ground warp beam turns slowly. At the same time, the pile warp ends move forward quickly and loosely as the pile warp beam turns faster than the ground warp beam. Ground and pile warp beams are propelled by two different independent motors. Rpm’s (revolution per minute) of the pile warp beams is proportional to the required pile height. The higher speed delivers more yarn to increase the pile height. During let- off, pile tension is controlled continuously. This decreases yarn breakages, and avoids out-of tolerance loop heights. In Figure the Terry Motion Control System® of Tsudakoma is shown. Here, pile tension is determined by pile tension roll which is propelled by a motor guided by electronic pile tension control system allows, so that it can hold the maximum length of pile warp. Keeping the pile beam’s diameter large avoids changing the beam frequently
Pile Tension Control System
Diagram of Pile Warp Tension during weaving pile, plain and border partsThe width of the pile beam is between 76 – 144 inches (190 - 360 cm) and the diameter of its flange can be up to 50 inches (125 cm), while the flange diameter of the ground beam is up to 40 inches (100 cm). The Pile beam can hold more than 130 cu ft of yarn, with a gross weight exceeding that of many automobiles
Diagram of Pile Warp Tension during weaving pile, plain and border parts
The two warp systems are evenly let- off by a system of constant tension control from full to empty beam. This is controlled by a highly sensitive electronic device. The tensions of the pile and ground warps are detected by force sensors and electronically regulated Elimination of unwanted increase of tension of warp tension during weaving high density border and/or plain section is achieved by reducing let-off speed the diagram of pile warp tension in Zax-e® Terry looms from Tsudakoma during weaving of pile, plain and border areas is shown. In Figure the diagram of loom rpm’s in Zax-e® Terry looms of Tsudakoma during pile weaving and border weaving is shown
The two warp systems are evenly let- off by a system of constant tension control from full to empty beam. This is controlled by a highly sensitive electronic device. The tensions of the pile and ground warps are detected by force sensors and electronically regulated Elimination of unwanted increase of tension of warp tension during weaving high density border and/or plain section is achieved by reducing let-off speed the diagram of pile warp tension in Zax-e® Terry looms from Tsudakoma during weaving of pile, plain and border areas is shown. In Figure the diagram of loom rpm’s in Zax-e® Terry looms of Tsudakoma during pile weaving and border weaving is shown
Diagram of Loom Rpm’s during weaving pile and border areasTo prevent starting marks or pulling back of the pile loops, the pile warp tension can be reduced during machine standstill. An automatic increase in tension can be programmed for weaving borders to achieve more compact weave construction in order to ensure a rigid border and/or to achieve nice visual effects via jacquard or dobby designs on the border. The way the back rest roller system is controlled depends on the weave. During insertion of the loose picks and during border or plain weaving the warp tension between the open and closed shed is compensated for by negative control. A warp tensioner with torsion bar is used for the ground warp, and a special tension compensating roll is used for the pile warp
Take-up:
The pick density is automatically controlled by synchronizing the take-up motor rotation with the loom speed. The take-up motor rotates the cloth pulling axle. The cloth pulling axle is covered with needles which pricks the terry fabric and assures that the thick fabric winds on the take-up roll evenly with a constant width. The electronically controlled cloth take-up guarantees exact weft densities in every terry towel and a faultless transition between pile and border. There are five elements of a take-up system. These are
1- Temple
The temple holds the width of the fabric as it is woven in front of the reed and assures the fabric to be firm at full width. A temple is seen on Figure.
2- Length Temple
Length temple is located on the center of loom width between two side temples. There are groves starting from the center and going to the left and right sides of the temple. It ensures the terry fabric is open to the sides and remains straight and tense throughout the fabric width.
3- Cloth pulling Axle with Needles
It ensures the thick terry fabric keep its tension and width while being transferred from the length temple to the cloth transfer axle.
4- Cloth Transfer Axle
It increases the contact angle between the terry fabric and cloth pulling axle with needles and transfers the fabric to take-up roll.
5- Take-up Roll
The fabric which comes from the transfer axle is wound on take-up roll
Auxiliary Motions
Selvedge Forming
A length-wise edge of a woven fabric is called selvedge or selvage. The main purpose of the selvedge is to ensure that the edge of fabric will not tear when the cloth is undergoing the stresses and strains of the finishing process. This is achieved by making the selvedge area stronger than the body of the cloth using heavier and plied warp yarns, increasing warp yarns per inch, and applying different weaves. Two types of selvedge are formed during terry weaving
1-Leno Selvedge
A leno weave at the edges of the fabric locks in the warp yarns by twisting the last two warp yarns back and forth around each pick. They are made with special leno weaving harnesses. Leno selvedges predominate in terry weaving In below Figure, a leno selvedge forming system for terry weaving is shown.
Take-up:
The pick density is automatically controlled by synchronizing the take-up motor rotation with the loom speed. The take-up motor rotates the cloth pulling axle. The cloth pulling axle is covered with needles which pricks the terry fabric and assures that the thick fabric winds on the take-up roll evenly with a constant width. The electronically controlled cloth take-up guarantees exact weft densities in every terry towel and a faultless transition between pile and border. There are five elements of a take-up system. These are
1- Temple
The temple holds the width of the fabric as it is woven in front of the reed and assures the fabric to be firm at full width. A temple is seen on Figure.
2- Length Temple
Length temple is located on the center of loom width between two side temples. There are groves starting from the center and going to the left and right sides of the temple. It ensures the terry fabric is open to the sides and remains straight and tense throughout the fabric width.
3- Cloth pulling Axle with Needles
It ensures the thick terry fabric keep its tension and width while being transferred from the length temple to the cloth transfer axle.
4- Cloth Transfer Axle
It increases the contact angle between the terry fabric and cloth pulling axle with needles and transfers the fabric to take-up roll.
5- Take-up Roll
The fabric which comes from the transfer axle is wound on take-up roll
Auxiliary Motions
Selvedge Forming
A length-wise edge of a woven fabric is called selvedge or selvage. The main purpose of the selvedge is to ensure that the edge of fabric will not tear when the cloth is undergoing the stresses and strains of the finishing process. This is achieved by making the selvedge area stronger than the body of the cloth using heavier and plied warp yarns, increasing warp yarns per inch, and applying different weaves. Two types of selvedge are formed during terry weaving
1-Leno Selvedge
A leno weave at the edges of the fabric locks in the warp yarns by twisting the last two warp yarns back and forth around each pick. They are made with special leno weaving harnesses. Leno selvedges predominate in terry weaving In below Figure, a leno selvedge forming system for terry weaving is shown.
In Figure 20 (I), the diagram of a leno selvedge is shown.2-Tuck-in Selvedge
The fringed edges of the filling yarns are woven back into the body of the fabric using a special tuck-in device. As a result the filling density is doubled in the selvedge area. In below Figure, the ZTN™ needless tuck-in devices which are used in Zax- e™ terry looms from Tsudakoma is shown. In Figure 20 (II), the diagram of the tuck-in selvedge is shown
The fringed edges of the filling yarns are woven back into the body of the fabric using a special tuck-in device. As a result the filling density is doubled in the selvedge area. In below Figure, the ZTN™ needless tuck-in devices which are used in Zax- e™ terry looms from Tsudakoma is shown. In Figure 20 (II), the diagram of the tuck-in selvedge is shown
As the width of the towels is usually much narrower than that of the weaving machine
width, more than one towel may be woven at the same time. Thus, selvedges are formed not only at the sides but also several selvedges should be formed on the sides of each
width, more than one towel may be woven at the same time. Thus, selvedges are formed not only at the sides but also several selvedges should be formed on the sides of each
Leno Selvedge Tuck-in Selvedge
Figure 20 Selvedges in Towels
towel panels woven together. For this reason special selvedge forming systems are produced for terry weaving. One example is Dornier’s PneumaTuckers® for outside and center selvages, which are the selvedges of individual towel panels when they are woven on a loom side by side.
Weft Color Choosing Motion
There are special color selection systems for inserting the required pick color while weaving different filling colors. Terry weaving machines have weft maximum twelve different colors or type of filling to be woven, including novelty yarns like chenille.
Pick Control
The pick control mechanism or pick finder detects the weft breakage. At a filling break, the machine stops and moves at reverse slow motion – automatically – to free the broken pick. It has a significant role in reducing the down times for repairing filling breaks and thus the starting marks can be avoided
End Control
Drop wires which are hung individually on each warp end, fall down when a warp end is broken or is very loose, closes down the electric circuit and thus shutting down the weaving machine
Weft Measuring and Feeding Motion
During terry weaving in shuttle – less looms, the weft is inserted from one side with the help of rapiers, or air jet nozzles. A predetermined length of weft yarn under the necessary tension should be inserted during each picking. Before each picking motion, a definite length of weft pick is measure, stored usually on drum accumulators and released for picking. The weft feeders carry out this function. They pull the weft picks from the yarn packages and wind them helically over a turning cylinder. Winding speed determines the weft length.
Terry Designing
Terry fabrics are often very complex with different colored warp ends in combination with loop patterns. They are subject to changing fashions, and the market is constantly demanding new qualities and designs. The rapid development of electronics has enabled fabric designers to produce completely different patterns. Via a servo motor, the beat-up position for each pick, and, thus the type of terry and the pile height can be freely programmed from one pick group to another. In this way nearly 200 different loose pick distances, and hence the same number of pile heights, can be programmed in any order. For example, three- and four-pick terry and even fancy types of terry can be combined in the same fabric. This gives the fabric designer a broad range of patterning options and the weaving engineer the weaving structure for improving fabric performance, because transition from one pattern element to the next can be woven with greater precision With these capabilities, a new patterning method, called sculptured terry, has been developed. At each full beat -up, two pile loops of different heights can be formed in the filling direction. The secret of this method of pattern formation lies in the fact that two loose pick groups formed at distances corresponding to the pile heights are beaten up to the cloth fell together. For two short loops the pile yarns are woven into both loose pick groups and for one large loop into the second loose pick group only. The greatest challenge is to develop a basic weave which results in neat loops without excessive friction between warp and filling at full beat -up. The solution is found in a special seven pick weave combined with full beat -ups at the sixth and seventh pick. In this way, a second pile height is also formed in filling direction, making sculptured patterning possible by the difference in pile height in warp and filling direction. In Figure 21, a terry towel pattern which is produced with this technique is shown. In Figure 22, the diagram of seven pick terry design is shown. A requirement for this kind of pattern formation is a freely programmable sley traveling on a rapier weaving machine. Microprocessor control allows the loose pick distance to be
Figure 21 A terry pattern achieved by weaving two different heights of loops
programmed easily and individually for each pick. The loop formation system with full electronic control lets you alter the height of the loop by accompanying the electronic weft ratio variator device on jacquard looms to program different weft ratios like 3-pick terry, 4-pick terry and so. By this method, different heights of loops can be achieved in the same shed.
Special seven filling terry design with two-pick groups and full beat-up
Shearing is applied to the pile fabric, by passing it over a cylinder with blades like a giant cylindrical lawnmower. The velour fabric is then brushed with bristles set in a cylinder to remove cut bits of fiber. Brushing leaves the surface fiber lying in one direction so care must be taken to have all the fabrics in the same batch laid out in the same direction, or light will reflect off various pieces differently In above Figure, a simplified diagram of the shearing process is given. The pile fabric is guided across the shearing table and is sheared between the shearing blades mounted on a cylinder and a fixed blade.
Sculptured or carved design
Sculptured design is different from the one which is achieved during weaving by using long and short loops. This involves considerably more processing after weaving. The pile fabric which has been woven with single pile loop height I embossed, then the pile left upstanding is sheared off, and that which was flattened is brushed up, leaving the sculptured or carved design
Dyeing and Finishing of Terry Towel
As discussed earlier the main fiber which is used in towels is cotton. As cotton fiber is not sensitive to alkali or chlorine bleach but is to acids, all the dyeing and finishing processes must be planned with these conditions. Like other textile materials the dyeing and finishing stage of terry towels generally follow the workflow shown below
· Pretreatment
· Coloration (Dyeing or Printing)
Finishing
Pretreatment:
Fibrous textile materials need a pretreatment before dyeing. Fiber preparation ordinarily involves scouring to remove foreign material and thus ensures even access to dye liquor from the dye bath. Cotton must be boiled and bleached to remove pectin and cotton seeds Sizing substances also must be eliminated. The steps of pretreatment are shown below:
-Desizing
-Scouring
-Bleaching
Desizing:
Desizing is intended to remove size from the fabric to ensure even bleaching, level dyeing and soft handle Desizing processes differentiate according to the sizing agent used.
I- Enzymatic Desizing: This classical desizing process consists of removing the starch from towel fabric using enzymes. This desizing process simply involves liquefying the film of size on the product. Bacterial, malt and pancreas amylases are used as desizing agents. Enzymatic desizing is the classical desizing process of degrading starch size on cotton fabrics using enzymes. Enzymes are complex organic, soluble bio-catalysts, formed by living organisms that catalyze chemical reaction in biological processes. Enzymes are quite specific in their action on a particular substance. A small quantity of enzyme is able to decompose a large quantity of the substance it acts upon. Enzymes are usually named by the kind of substance degraded in the reaction it catalyzes.
The enzymes generally employed for desizing are:
· α – amylase
· β – amylase
· amyloglucosidase
Amylase is the enzyme that hydrolyses and reduced the molecular weight of amylose and amylopectin molecules in starch, rendering it water soluble enough to be washed off the fabric. Effective enzymatic desizing requires strict control of pH, temperature, water hardness, electrolyte addition and choice of surfactant. Enzyme sources are either from animal origin (slaughter house waste – pancreas, clotted blood, liver etc.), vegetable origin (malt extract – made from germinated barley), and bacterial (produced by growing cultures of certain micro organisms). Bacterial enzymes are preferred because of their activity over a wider pH range and tolerance to variations in pH. Since desizing is carried out on grey fabric, which is essentially non-absorbent, a wetting and penetrating agent is incorporated into the desizing liquor. Bacterial enzymes are commercially available in three grades:
Next, longitudinal hemming is achieved by lengthwise hemming machines, most of which are usually equipped with two 401 chain stitch sewing machines, one on the right side and one on the left side, for the longitudinal hemming of towels. Labels can be attached during lengthwise hemming. In a longitudinal hemming machine is shown.
Figure 20 Selvedges in Towelstowel panels woven together. For this reason special selvedge forming systems are produced for terry weaving. One example is Dornier’s PneumaTuckers® for outside and center selvages, which are the selvedges of individual towel panels when they are woven on a loom side by side.
Weft Color Choosing Motion
There are special color selection systems for inserting the required pick color while weaving different filling colors. Terry weaving machines have weft maximum twelve different colors or type of filling to be woven, including novelty yarns like chenille.
Pick Control
The pick control mechanism or pick finder detects the weft breakage. At a filling break, the machine stops and moves at reverse slow motion – automatically – to free the broken pick. It has a significant role in reducing the down times for repairing filling breaks and thus the starting marks can be avoided
End Control
Drop wires which are hung individually on each warp end, fall down when a warp end is broken or is very loose, closes down the electric circuit and thus shutting down the weaving machine
Weft Measuring and Feeding Motion
During terry weaving in shuttle – less looms, the weft is inserted from one side with the help of rapiers, or air jet nozzles. A predetermined length of weft yarn under the necessary tension should be inserted during each picking. Before each picking motion, a definite length of weft pick is measure, stored usually on drum accumulators and released for picking. The weft feeders carry out this function. They pull the weft picks from the yarn packages and wind them helically over a turning cylinder. Winding speed determines the weft length.
Terry Designing
Terry fabrics are often very complex with different colored warp ends in combination with loop patterns. They are subject to changing fashions, and the market is constantly demanding new qualities and designs. The rapid development of electronics has enabled fabric designers to produce completely different patterns. Via a servo motor, the beat-up position for each pick, and, thus the type of terry and the pile height can be freely programmed from one pick group to another. In this way nearly 200 different loose pick distances, and hence the same number of pile heights, can be programmed in any order. For example, three- and four-pick terry and even fancy types of terry can be combined in the same fabric. This gives the fabric designer a broad range of patterning options and the weaving engineer the weaving structure for improving fabric performance, because transition from one pattern element to the next can be woven with greater precision With these capabilities, a new patterning method, called sculptured terry, has been developed. At each full beat -up, two pile loops of different heights can be formed in the filling direction. The secret of this method of pattern formation lies in the fact that two loose pick groups formed at distances corresponding to the pile heights are beaten up to the cloth fell together. For two short loops the pile yarns are woven into both loose pick groups and for one large loop into the second loose pick group only. The greatest challenge is to develop a basic weave which results in neat loops without excessive friction between warp and filling at full beat -up. The solution is found in a special seven pick weave combined with full beat -ups at the sixth and seventh pick. In this way, a second pile height is also formed in filling direction, making sculptured patterning possible by the difference in pile height in warp and filling direction. In Figure 21, a terry towel pattern which is produced with this technique is shown. In Figure 22, the diagram of seven pick terry design is shown. A requirement for this kind of pattern formation is a freely programmable sley traveling on a rapier weaving machine. Microprocessor control allows the loose pick distance to be
Figure 21 A terry pattern achieved by weaving two different heights of loopsprogrammed easily and individually for each pick. The loop formation system with full electronic control lets you alter the height of the loop by accompanying the electronic weft ratio variator device on jacquard looms to program different weft ratios like 3-pick terry, 4-pick terry and so. By this method, different heights of loops can be achieved in the same shed.
Special seven filling terry design with two-pick groups and full beat-upShearing:
It is quite common practice to shear the terry loops after manufacture in order to create a cut-pile effect. Many hand towels are sold with one face showing the traditional terry loop, whilst the other side shorn to give the velour effect
It is quite common practice to shear the terry loops after manufacture in order to create a cut-pile effect. Many hand towels are sold with one face showing the traditional terry loop, whilst the other side shorn to give the velour effect
Shearing is applied to the pile fabric, by passing it over a cylinder with blades like a giant cylindrical lawnmower. The velour fabric is then brushed with bristles set in a cylinder to remove cut bits of fiber. Brushing leaves the surface fiber lying in one direction so care must be taken to have all the fabrics in the same batch laid out in the same direction, or light will reflect off various pieces differently In above Figure, a simplified diagram of the shearing process is given. The pile fabric is guided across the shearing table and is sheared between the shearing blades mounted on a cylinder and a fixed blade.Sculptured or carved design
Sculptured design is different from the one which is achieved during weaving by using long and short loops. This involves considerably more processing after weaving. The pile fabric which has been woven with single pile loop height I embossed, then the pile left upstanding is sheared off, and that which was flattened is brushed up, leaving the sculptured or carved design
Dyeing and Finishing of Terry Towel
As discussed earlier the main fiber which is used in towels is cotton. As cotton fiber is not sensitive to alkali or chlorine bleach but is to acids, all the dyeing and finishing processes must be planned with these conditions. Like other textile materials the dyeing and finishing stage of terry towels generally follow the workflow shown below
· Pretreatment
· Coloration (Dyeing or Printing)
Finishing
Pretreatment:
Fibrous textile materials need a pretreatment before dyeing. Fiber preparation ordinarily involves scouring to remove foreign material and thus ensures even access to dye liquor from the dye bath. Cotton must be boiled and bleached to remove pectin and cotton seeds Sizing substances also must be eliminated. The steps of pretreatment are shown below:
-Desizing
-Scouring
-Bleaching
Desizing:
Desizing is intended to remove size from the fabric to ensure even bleaching, level dyeing and soft handle Desizing processes differentiate according to the sizing agent used.
I- Enzymatic Desizing: This classical desizing process consists of removing the starch from towel fabric using enzymes. This desizing process simply involves liquefying the film of size on the product. Bacterial, malt and pancreas amylases are used as desizing agents. Enzymatic desizing is the classical desizing process of degrading starch size on cotton fabrics using enzymes. Enzymes are complex organic, soluble bio-catalysts, formed by living organisms that catalyze chemical reaction in biological processes. Enzymes are quite specific in their action on a particular substance. A small quantity of enzyme is able to decompose a large quantity of the substance it acts upon. Enzymes are usually named by the kind of substance degraded in the reaction it catalyzes.The enzymes generally employed for desizing are:
· α – amylase
· β – amylase
· amyloglucosidase
Amylase is the enzyme that hydrolyses and reduced the molecular weight of amylose and amylopectin molecules in starch, rendering it water soluble enough to be washed off the fabric. Effective enzymatic desizing requires strict control of pH, temperature, water hardness, electrolyte addition and choice of surfactant. Enzyme sources are either from animal origin (slaughter house waste – pancreas, clotted blood, liver etc.), vegetable origin (malt extract – made from germinated barley), and bacterial (produced by growing cultures of certain micro organisms). Bacterial enzymes are preferred because of their activity over a wider pH range and tolerance to variations in pH. Since desizing is carried out on grey fabric, which is essentially non-absorbent, a wetting and penetrating agent is incorporated into the desizing liquor. Bacterial enzymes are commercially available in three grades:
JUSTIFICATION FOR THE USE OF REACTIVE DYES IN THE DYEING OF TOWEL
It is over thirty years since reactive dyes for cellulose were introduced and they now account for about 25% of the total dye consumption on that fibre. There emerged after the results of the work on the mechanisms of organic reactions were in place and their enabled their development to be characterized by the study and application of reaction mechanisms involved in the dye-fibre reaction. This factor has paid handsome dividends. The work continues, increasingly gaining cost-effectiveness by enhancing reaction mechanisms, such as polymerization, have met with little success and the simple nucleophilic substitution and addition mechanisms of dye fixation remain totally dominant.
The following factors rightly justify the usage of reactive dyes world wide
Bright shades
Good Fastness properties
Easy application
Moderate cost
Eco-friendliness
Bright shades
The reactive dyes are the brightest dyes available for the cellulosic fibres and have a full range of shades.
Good Fastness properties
Colour Fastness may be defined as”the resistance of a material to change in any of its color characteristics, to transfer its colorant(s) to adjacent materials, or both, as a result of the exposure of the material to any environment that might be encountered during the processing, testing, storage, or use of the material”
Wash Fastness:
Textile materials coloured with reactive dyes have very good wash fastness properties. The wash fastness rating is about 4-5. This is attributed to the very stable covalent bond that exists between the dye molecule and the fibre.
Light Fastness:
Textile materials coloured with reactive dyes have very good light fastness. The light fastness rating being about 6. These dyes have a very stable electron arrangement and provide very good resistence to the degrading effect of the U.V component of sunlight. There are, however, some reactive dyes with only fair light fastness
Bleaching fastness:
The reactive dyes are stable to peroxide bleaching and so are suitable for dyeing cotton yarns to be used as effect threads. Strong reducing agents and chlorine, however, destroy the chromogens.
Easy application
Reactive dyes offer a great flexibility in application methods with a wide choice of equipment and process sequences and so have become very popular. These are applied through exhaust and continuous systems both very comfortably. Following is the list of equipments used for the application of these dyes:
a) Exhaust/Batch/Dis-Continuous Dyeing Systems
Jigger Open Width 3-5:1
Winch Rope Form 20:1
Jet/Soft Flow Rope Form 15:1
Beam Dyeing Open Width 10:1
Star Frame Open Width
b) Semi-Continuous Dyeing Systems
Pad-Batch
Pad-Jig
Pad-Roll
c) Continuous Dyeing Systems
Pad-Thermosol
Pad-Steam
It is over thirty years since reactive dyes for cellulose were introduced and they now account for about 25% of the total dye consumption on that fibre. There emerged after the results of the work on the mechanisms of organic reactions were in place and their enabled their development to be characterized by the study and application of reaction mechanisms involved in the dye-fibre reaction. This factor has paid handsome dividends. The work continues, increasingly gaining cost-effectiveness by enhancing reaction mechanisms, such as polymerization, have met with little success and the simple nucleophilic substitution and addition mechanisms of dye fixation remain totally dominant.
The following factors rightly justify the usage of reactive dyes world wide
Bright shades
Good Fastness properties
Easy application
Moderate cost
Eco-friendliness
Bright shades
The reactive dyes are the brightest dyes available for the cellulosic fibres and have a full range of shades.
Good Fastness properties
Colour Fastness may be defined as”the resistance of a material to change in any of its color characteristics, to transfer its colorant(s) to adjacent materials, or both, as a result of the exposure of the material to any environment that might be encountered during the processing, testing, storage, or use of the material”
Wash Fastness:
Textile materials coloured with reactive dyes have very good wash fastness properties. The wash fastness rating is about 4-5. This is attributed to the very stable covalent bond that exists between the dye molecule and the fibre.
Light Fastness:
Textile materials coloured with reactive dyes have very good light fastness. The light fastness rating being about 6. These dyes have a very stable electron arrangement and provide very good resistence to the degrading effect of the U.V component of sunlight. There are, however, some reactive dyes with only fair light fastness
Bleaching fastness:
The reactive dyes are stable to peroxide bleaching and so are suitable for dyeing cotton yarns to be used as effect threads. Strong reducing agents and chlorine, however, destroy the chromogens.
Easy application
Reactive dyes offer a great flexibility in application methods with a wide choice of equipment and process sequences and so have become very popular. These are applied through exhaust and continuous systems both very comfortably. Following is the list of equipments used for the application of these dyes:
a) Exhaust/Batch/Dis-Continuous Dyeing Systems
Jigger Open Width 3-5:1
Winch Rope Form 20:1
Jet/Soft Flow Rope Form 15:1
Beam Dyeing Open Width 10:1
Star Frame Open Width
b) Semi-Continuous Dyeing Systems
Pad-Batch
Pad-Jig
Pad-Roll
c) Continuous Dyeing Systems
Pad-Thermosol
Pad-Steam
Moderate cost
Reactive dyes as compared to vats are of lesser costs considering the fastness properties of both. The dyeing process involved in vat dyeing is also costly which involves certain steps like reduction and oxidation. On the other hand reactive dyeing is free from these steps.
Eco-friendliness
Many consumers also appreciate the eco-friendliness of fiber reactive dyes. Some companies process the dyes with natural ingredients and materials, focusing on creating a product with a minimum of harmful waste. Since the dyes are colorfast, they will not bleed into wash water, leading to a reduction in dye-laden water runoff, which can be harmful for the environment.
Reactive dyes as compared to vats are of lesser costs considering the fastness properties of both. The dyeing process involved in vat dyeing is also costly which involves certain steps like reduction and oxidation. On the other hand reactive dyeing is free from these steps.
Eco-friendliness
Many consumers also appreciate the eco-friendliness of fiber reactive dyes. Some companies process the dyes with natural ingredients and materials, focusing on creating a product with a minimum of harmful waste. Since the dyes are colorfast, they will not bleed into wash water, leading to a reduction in dye-laden water runoff, which can be harmful for the environment.
Printing:
Printing is local dyeing in zones according to patterns. Thickeners ensure that these zones defined by the engraved pattern are adhered to. The type and size of the artistic design determine the printing process and method of dye paste application. Various printing types like direct printing, discharge printing and resist printing and techniques like roller printing and full screen printing are available for the colorist to realize the print idea.
Package Dyeing:For package dyeing, yarn is wound on dye tubes as packages, each with a hollow center that allows liquid to flow through it. The packages are stacked on perforated, hollow posts, and dye liquor is pumped through these. Package machines are enclosed and can be pressurized so dye liquor can reach temperatures above atmospheric boiling point (100 C) for faster dyeing. The term yarn-dyed is associated with quality in woven fabrics. A pattern with dyed yarns looks sharper than one printed. The fabric will probably be more colorfast, and it is also reversible. The yarn dyeing process takes place between spinning and weaving steps
Printing is local dyeing in zones according to patterns. Thickeners ensure that these zones defined by the engraved pattern are adhered to. The type and size of the artistic design determine the printing process and method of dye paste application. Various printing types like direct printing, discharge printing and resist printing and techniques like roller printing and full screen printing are available for the colorist to realize the print idea.
Package Dyeing:For package dyeing, yarn is wound on dye tubes as packages, each with a hollow center that allows liquid to flow through it. The packages are stacked on perforated, hollow posts, and dye liquor is pumped through these. Package machines are enclosed and can be pressurized so dye liquor can reach temperatures above atmospheric boiling point (100 C) for faster dyeing. The term yarn-dyed is associated with quality in woven fabrics. A pattern with dyed yarns looks sharper than one printed. The fabric will probably be more colorfast, and it is also reversible. The yarn dyeing process takes place between spinning and weaving steps
Final Finishing of Terry Towels:
Final finishing includes all the finishing treatments applied to the fabric after dyeing and printing it can be divided into two:
1- Chemical (or Wet) Treatments
2-Mechanical (or Decorative), Treatments
Chemical Treatments:
Softening, hydrophilling and antimicrobial treatments are among the chemical finishing processes of terry towels
Hydrophilic Treatment:
Silicones are added to the towel to give hydrophilic properties. It is also used to give a soft handle.
Softening:
The three basic types of softeners which are used on towels are cationic softeners, non- ionic softeners and silicones. Cationic softeners give good softness, but also some yellowness, so are only used for colored towels. Non-ionic softeners have less softening effect but are used in white towels due to the colorlessness of the chemicals. Silicones are the best and the most expensive of the softeners Hydrophilic silicones also affect the hydrophility of the towel positively. There are also applications of enzymatic softening using cellulases.
Antimicrobial Treatment:
Towels can be treated with antimicrobial finishes in order to prevent mold and mildew, reduce odor and minimize spread of harmful organisms Two types of antibacterial and deodorant finishes are available The first is applied during fiber-forming process, whereas the other is incorporated into the finishing process. The second approach is more versatile and widely adapted. Chemical entities are responsible for imparting antibacterial attributes including fungicides and bactericides. Obtaining antimicrobial properties by using antimicrobial fibers is achieved by anchoring the antimicrobial agent in the fiber. Trevira Bioactive (R) is an example of antimicrobial fiber used in towels which has proven to fully retain its antimicrobial effect after 100 domestic or 50 commercial wash cycles.
Mechanical Treatments:
The main aims of dry treatments are to give the towels fuller volume, and dimensional stability and dryness
Tumble Drying:
The towel is given a fluffy and soft hand, and some particles are removed during drying. The common way is to use continuous tumbler dryer generally called Turbang®, which is the brand name of the machine brand. The second way is to use tumble dryers which are a huge version of domestic tumble dryers.
Stentering:
Stentering or tentering is a controlled straightening and stretching process of cloth which has been pulled out of shape due to the many vigorous finishing processes. The selvedges of the cloth are attached to a series of pins/hooks/clips as it is fed through a stenter machine which is an oven of controlled temperature. During the process, as the pins/hooks/clips are gradually placed further apart width ways, the cloth is slowly and permanently brought out to the desired width. Stentering gives the fabric particular dimensions of length and width, and eliminates creasing.
Cutting and Sewing:
In this stage, towels pass through four steps
- Longitudinal cutting
- Longitudinal hemming
- Cross cutting
- Cross hemmingThese processes are achieved by scissors and standard sewing machines by workers or by machines specialized in towel cutting or sewing or even by automatic machines which can carry out some of or all of the mentioned processes Lengthwise cutting machines are used for the first step of this stage, longitudinal cutting of towels which have been produced on the weaving loom as several panels joined side by side. In these machines, there are several cutters which cut lengthwise between adjacent towel panels in order to separate them. The cutting process can be carried out by means of a pressing blade on a motorized roll in the lengthwise cutter. a longitudinal cutting machine is shown
Final finishing includes all the finishing treatments applied to the fabric after dyeing and printing it can be divided into two:
1- Chemical (or Wet) Treatments
2-Mechanical (or Decorative), Treatments
Chemical Treatments:
Softening, hydrophilling and antimicrobial treatments are among the chemical finishing processes of terry towels
Hydrophilic Treatment:
Silicones are added to the towel to give hydrophilic properties. It is also used to give a soft handle.
Softening:
The three basic types of softeners which are used on towels are cationic softeners, non- ionic softeners and silicones. Cationic softeners give good softness, but also some yellowness, so are only used for colored towels. Non-ionic softeners have less softening effect but are used in white towels due to the colorlessness of the chemicals. Silicones are the best and the most expensive of the softeners Hydrophilic silicones also affect the hydrophility of the towel positively. There are also applications of enzymatic softening using cellulases.
Antimicrobial Treatment:
Towels can be treated with antimicrobial finishes in order to prevent mold and mildew, reduce odor and minimize spread of harmful organisms Two types of antibacterial and deodorant finishes are available The first is applied during fiber-forming process, whereas the other is incorporated into the finishing process. The second approach is more versatile and widely adapted. Chemical entities are responsible for imparting antibacterial attributes including fungicides and bactericides. Obtaining antimicrobial properties by using antimicrobial fibers is achieved by anchoring the antimicrobial agent in the fiber. Trevira Bioactive (R) is an example of antimicrobial fiber used in towels which has proven to fully retain its antimicrobial effect after 100 domestic or 50 commercial wash cycles.
Mechanical Treatments:
The main aims of dry treatments are to give the towels fuller volume, and dimensional stability and dryness
Tumble Drying:
The towel is given a fluffy and soft hand, and some particles are removed during drying. The common way is to use continuous tumbler dryer generally called Turbang®, which is the brand name of the machine brand. The second way is to use tumble dryers which are a huge version of domestic tumble dryers.
Stentering:
Stentering or tentering is a controlled straightening and stretching process of cloth which has been pulled out of shape due to the many vigorous finishing processes. The selvedges of the cloth are attached to a series of pins/hooks/clips as it is fed through a stenter machine which is an oven of controlled temperature. During the process, as the pins/hooks/clips are gradually placed further apart width ways, the cloth is slowly and permanently brought out to the desired width. Stentering gives the fabric particular dimensions of length and width, and eliminates creasing.
Cutting and Sewing:
In this stage, towels pass through four steps
- Longitudinal cutting
- Longitudinal hemming
- Cross cutting
- Cross hemmingThese processes are achieved by scissors and standard sewing machines by workers or by machines specialized in towel cutting or sewing or even by automatic machines which can carry out some of or all of the mentioned processes Lengthwise cutting machines are used for the first step of this stage, longitudinal cutting of towels which have been produced on the weaving loom as several panels joined side by side. In these machines, there are several cutters which cut lengthwise between adjacent towel panels in order to separate them. The cutting process can be carried out by means of a pressing blade on a motorized roll in the lengthwise cutter. a longitudinal cutting machine is shown
Next, longitudinal hemming is achieved by lengthwise hemming machines, most of which are usually equipped with two 401 chain stitch sewing machines, one on the right side and one on the left side, for the longitudinal hemming of towels. Labels can be attached during lengthwise hemming. In a longitudinal hemming machine is shown.
After lengthwise hemming, towels pass through cross cutting as the third step. Transversal cutting machines carry out product stacking and automatic discharge.
The cut product is stacked in layers one on the other.
The cut product is stacked in layers one on the other.
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