An Introduction To The Mercerized Cotton And Mercerizing Technology

I. Preface:

The mercerized cotton originally invented by Mercer was treated with strong caustic soda in cotton fabric without tension. The main purpose was to increase the strength of cotton fiber (Strength) and the affinity for dyes (Affinity). It was not until half a century later that the tension was added to cotton fabrics during alkaline treatment, resulting in luster fabrics.

Mercerizing Process, whether in tension or not, will increase the chemical activity (Chemical Reactivity) of cotton fabric, making it easier to absorb dyes and adapt to various chemical finishing. Recently, we have found that in some cases, the mercerization of cotton fabrics is mainly aimed at improving its affinity and chemical activity towards dyes. For some fabrics, the improvement of mercerizing works only improves the affinity of dyes and the chemical activity of cotton, and has little effect on the general appearance of fabrics.

Prudent control of mercerization can create a certain degree of stability. In many cases, the importance of this stability is almost the same as increasing the affinity for dyes. Increasing stability will result in a better yield of fabric after shrink proof treatment. Therefore, mercerization engineering is to obtain the appropriate stability, the necessary process.

In short, the current mercerizing project has the following purposes:

1. increase the affinity for dyes.

2. increase chemical activity.

3. increase stability.

4. increase the tensile strength.

5. gloss.

6. fabric smoothness.

Because mercerization works are applied to cloth and yarns at the same time, many of the same principles and techniques are applied to mercerization of cloth and yarns. We will first discuss the mercerization of cloth, and then discuss some basic differences between the two processes.

Two. Mercerization of cloth:

The mercerization works of cloth must be decided first by choosing the fabric in the condition of proembryo or pre-treatment, or partially pretreated. Since no method can be applied to the above three states, the fabric can be mercerized without any treatment in the case of proembryo, whether it is pre desizing or scouring or after scouring and bleaching.

Before making mercerizing works, the choice of materials before they need to be processed depends on the type of materials, the special plant and equipment, and the demand for mercerized fabrics. In theory, for most factories, the operation of the mercerization of the proembryo should be the simplest, because it can avoid drying or special pretreatment. However, because a large number of impurities are brought into the lye, these impurities will obstruct mercerizing or alkali recovery. However, under ideal conditions, the mercerization of the proembryo will result in satisfactory luster and affinity for dyes, and enhance toughness (Strength) and other excellent properties. Therefore, in the mercerizing engineering of the proembryo, in order to obtain satisfactory results, strong penetrant must be added to the lye.

The mercerization of the proembryo, or the desizing of the proembryo, or the mercerization of the scouring cotton, their respective luster, toughness, chemical activity and affinity to dye can not help us choose the good or bad. The choice can only be determined by the convenience of manufacturing machines, the effectiveness of alkali recovery equipment and the drying equipment. The material may have been completely scoured and bleached before mercerizing works, and many manufacturers are equipped with this equipment. In general, assuming that all mercerizing processes are controlled in the best case, the mercerization of materials after scouring and bleaching will give a better gloss and smoother appearance than that of bleached materials before mercerization.

There is a possible drawback of the bleaching of mercerizing bleached materials, that is, the adverse effects of excessive bleaching will not be shown under normal conditions, but will be manifested after mercerizing. Any excessive bleached fiber will be dissolved in alkaline solution, and at the same time, a certain degree of tensile strength will be destroyed.

Generally speaking, different mercerization pretreatment (Pretreatment) does not cause much difference between products. If the main purpose of mercerization is excellent luster and smoothness, the whole set of bleaching pretreatment is of course the best. If the maximum tensile strength must be maintained, bleaching should be done after mercerization.

All cotton, whether dry wet, proembryo or bleached, should be spread smoothly into mercerized lye. Wrinkles (Wrinkles), especially on thick cotton fabrics, will show traces on the finished dyed products. Therefore, before the cotton is placed in the lye, some tension should be applied to prevent wrinkling. If wet cotton is to be mercerized, they should be sent to the roller first (Mangle) to make the moisture content even. Usually, the smaller the moisture content is, the better. To get the best mercerizing effect, the cotton should be dried before entering the lye.

When we consider that the equipment is most suitable for caustic soda impregnation, we should pay attention to the reaction between cotton and lye when mercerizing. When cotton is very dry and can be used as absorbent, it will be inhaled into every fiber after contact with caustic soda. Then the fiber will expand due to the absorption of sodium hydroxide. The swollen cotton fiber becomes plastic and can change shape arbitrarily. Mercerization is produced instantaneously. Mercerization has a time factor. Even a very small factor can not be ignored. It is not enough for a small amount of lye to be extruded into the fiber. Caustic soda must react with cotton fibers. If the fiber is absorbent, extrusion or pressure will not accelerate the reaction. If cotton is not dried into the lye, mercerization will take a long time, because the real mercerization will take place until some of the water in the cotton is replaced by the lye.

Obviously, it takes a lot of time to choose the impregnation equipment. We know that when cotton is full of lye, the process of mercerization does not require cotton soaking in lye, so we only need a long storage tank to make cotton full of lye. If cotton is in a completely dry absorbent state and has enough time after the upper rack is washed before washing, there is a very simple suction operation, that is, a process of immersion in alkali bath. However, if the cotton contains water, the lye will be diluted by water because of this alkali leaching operation, and the real lye concentration is only 1/2 to 1/3. Therefore, if cotton is water content into the mercerizing soda tank, its impregnation equipment must be long enough or deep enough, so that the cotton after leaving the lye is completely saturated, and the alkalinity is the same as that in the alkali bath. Under normal circumstances, wet cotton should be mercerized, and its impregnation trough should be designed to allow cotton to enter the alkali solution and to pour the strong alkali from the opposite side. The correct time for contact between cotton and lye can not be fully known. About 30 seconds will be enough. Although longer contact time or longer storage tanks will not be harmful, they will be detrimental to economy and protection.

Three. Mercerizing pressure:

The amount of extruded cotton after leaving the caustic soda equipment is very important. Lack of knowledge of this factor is one of the main reasons for the failure to get all the advantages of mercerization. In general, most factories operate when cotton is removed from mercerized lye, the smaller the amount of lye. In some cases, heavy suction cylinders are often required and adjusted to reduce the alkali content of cotton to 60%. Factory managers believe that high grouting pressure can help to save the consumption of lye and improve the efficiency of cleaning cotton later on the machine (Tenterframe) in two aspects. Low alkali content does mean that alkali consumption is less and easy to clean, but in many cases, it also hints at possible consequences such as incomplete mercerization, insufficient stability, poor gloss, or all three elements.

When the alkali treated cotton is in plastic state, there must be a certain amount of lye near each fiber so that the fiber can be changed to form suitable lubrication. I have visited many factories, and their cotton leaves very little sodium hydroxide when they leave the lye, so that there is no need to worry about cracks in the process of widening. It is not known that the content of cotton that is about to leave the lye is at least 100% cotton weight. For many light fabrics that require good operation and certain gloss, cotton must be soaked in lye when leaving the alkali bath. By trial and error method, the pressure on cotton that is about to leave lye can be adjusted. It can be connected with Frame operation, so that the best mercerizing effect can be obtained. This operation method must be tested on a series of materials before implementing each factory.

Four, Lye Concentration:

Most of the fabric silk is photochemical in the concentration of 28~31 Be`. Although there are also some operations under 19~22 Be`, the aim is to improve the affinity of dyes. Our experience is the range of 28~31 Be`, which is most suitable for most situations. Alkalinity higher than 31 Be` does not increase gloss or improve other properties. Less than 28 Be` alkalinity will reduce gloss and cause poor appearance. The range of 28~31 Be` is particularly good because the range can still provide good results when there are temperature changes or impurities in the lye. Unless the temperature changes too much or the impurities are too much, it will affect the finished products. Usually, we recommend that the plant set alkalinity in the range of 29~30 Be`, and this standard is satisfactory from the viewpoint of control technology and finished product effect. If any factory adopts this standard range, there will be no difference in the final result if the Twaddel is raised or lowered to this standard. In addition, the temperature change caused by climate also does not affect mercerization in the operation of this alkalinity range.

Five. Temperature effect:

For many years, the temperature effect of lye has been deeply misunderstood. Many factories attach great importance to the temperature control of lye. In fact, it is improper from the viewpoint of cost or quality. In fact, many lye factories are equipped with cooling systems only. In recent years only a lot of factories have abandoned cooling equipment. In fact, if a factory uses the lye in the range of 28~31 Be`, the larger temperature changes will not cause any variation of the final product of the filament. Through the study of actual operation and proper control, it is shown that there is no difference in the temperature of the alkali liquor in the range of 28~31 Be` for 70 ~ 100 (21 ~ 38 C). Once the temperature exceeds 110 (43), the gloss of the finished mercerized product is obviously worse. When the temperature drops below 70 (21 degrees), there is no obvious improvement. Therefore, it is no doubt a waste to provide cooling equipment for a large quantity of lye. However, the temperature effect of low concentration lye is particularly noteworthy. If a 19 Be` alkali solution is used, slight changes in temperature will lead to obvious differences between the appearance of fabric and the affinity of dyes to two. The alkali liquor of 25~27 Be` is also between the low alkali and high alkali liquor. Therefore, the variation allowed by temperature is just in between.

Perhaps the misconception of temperature in mercerization is derived from the concept of the first in merley, that is, if weakly caustic soda is to be satisfactorily mercerized, the lye must be cooled. At present, many factories have been designed to avoid caustic bath temperature rising too high. In some special cases, the material will be mercerized in the bath lye and its temperature will exceed 100 (38 degrees). If the material is dried or converted to large bath lye or completely cooled by the newly prepared caustic solution, either method can solve the problem of high temperature. The so-called hot wire photochemical treatment is very interesting, it is to soak the lye cloth under pressure to heat up to boiling point. Because the silk cotton will not change its physical properties and chemical properties at the beginning of the contact with the alkali solution. When the fabric is removed from the pressure supply and cooled, it will change its physical properties and chemical properties when it enters the mercerization of Fu Tong. Therefore, hot wire photochemistry is only the mercerization before alkali refining. Another advantage of this treatment is the increase in the amount of lye infiltrated into cotton due to the increase in the temperature of the lye. However, adding chemical osmosis to the lye at room temperature can also achieve the same effect.

Six. Mercerizing tension:

After the cotton has been infiltrated by the lye, this procedure is the most difficult part of the silk dyeing process. No matter how perfect the cotton pretreatment is, no matter how well the lye penetrated through the cotton, it will not guarantee that the mercerizing effect will be good. Unless the cotton is properly handled and evenly washed and thoroughly cleaned on the stretching machine, the mercerizing effect will be satisfied. In other words, the improper operation and cleaning process of the cloth machine is the main reason for the poor mercerizing effect. When the cotton is treated with mercerizing, the state of the cloth is semi plastic, unless the cotton is fixed to the right width by the cloth machine and properly cleaned by leaving the cloth machine, otherwise it will cause poor luster, poor shrinkage and even uneven dyeing.

Theoretically, the operation of the cloth machine should be done as soon as possible before the cotton is cleaned. The actual operation must be compromised, and the cotton will gradually be pulled to the set width. About how long the time is, or how long it will take for cotton to reach the predetermined width, it is not available here. But they are related to the length of the cloth machine and the subsequent cleaning process. The compromise made before is also caused by unsatisfactory cleaning. The width of cloth is also a controversial issue. Usually, most of the operations that require excellent gloss and shrinkage should be pulled to the width of the original embryo, and if possible, pull 1 inches more. If the width of the cotton is wider than the width of the proembryo, the gloss of the finished product will be lost and its shrinkage and stability will be reduced. Many factories have a fear of pulling cotton into the width of the original embryo. In fact, the cracks appear after the cotton is stretched, because the cotton is too dry. This drawback can be made up of cotton by removing some lye before leaving the lye.

Another factor that sometimes prevents the factory from pulling the cotton width is the effect of cotton gin due to the increased tension on the Clip and the machine. This effect can offset the lubricating effect of the lye slowly dropping on the cloth and prevent knot formation.

It is almost unnecessary to give excess tension along the warp. Generally speaking, the Tenter should move at the same speed as the alkali, so that the cotton will not stretch along the warp and will not shrink. When we want a good glossy warp, the cloth machine operates at a speed greater than that of the alkali, so that the warp can be stretched extra. Usually the maximum differential wing volume between the cloth and the alkali hydraulic suction is 5%.

Seven, cleaning:

When the cotton is pulled to a suitable width, the lye must be removed immediately from cotton so as to achieve the best results. Once the cotton leaves the cloth stretches, any cleaning or stretching will not affect the mercerizing effect in the fabric. We know that at room temperature, cotton will wrinkle in 3.5 Be` lye, indicating that the content of lye in each cotton fiber should be reduced to 3.5 Be` before leaving. If there is a large amount of lye in the fiber, cotton will wrinkle after leaving the cloth machine, and at the same time, it will also cause luster and poor stability.

One common mistake is that the washing under the end of the washing machine can be regarded as the true alkali content of the fiber, but in fact, the washing water may contain only 5% of the alkali content. Some measurements of the cleaning efficiency of the cloth cloth can be done by measuring the width taken away from the end of the cotton cloth machine. If there is a lot of cleaning, the width of the cotton self drawn machine will only decrease slightly after the cloth is lowered.

Eight. The mercerization of raw billet:

When Greige is to be mercerized, it is very important to add strong penetrant in alkali hydraulic suction to make caustic soda enter cotton fiber and react with cotton fiber. When the pretreatment of cotton before mercerization has been completed, including bleaching, cotton can be saturated without penetration. The early mercerizing osmosis agent on the market is mostly used to help the lye penetrate into the proembryo. They are generally designed in the range of 28~30 Be`, and are effective penetrant, but they often lose their osmotic force at low alkalinity.

Recently, mercerized osmotic agents have developed in a new way. Mercerizing osmosis agents have the use of osmotic agents in the range of mercerizing alkalinity. However, they can be used as surfactants at low alkalinity. The use of mercerizing osmosis agent or the interface activator, which is able to operate in a large alkalinity range, will affect the cleaning work on the machine. The auxiliaries can help to remove alkali from cotton in Zhang Bu, and because of their surfactants, cotton can be used for scouring machine.

Nine. Polyester / cotton blended mercerization:

Now we are going to discuss some special problems of mercerization on cotton blending. The purpose of mercerization is to improve the properties of other fibers other than cotton. Polyester and cotton are two completely different fibers. Cotton is water sensitive fiber. Polyester is just the opposite, and only when it is immersed in high concentration alkali liquor for a long time at high temperature. Fortunately, the best condition for silk actinization is to impregnate in strong alkali at low temperature for a short time.

Therefore, there is little danger of damage to polyester in mercerizing, and the mercerization of normal cotton can also meet the demand of cotton and polyester blend. On the contrary, cotton fibers in cotton and polyester blend often do not exist as absorbent bears, because the pre scouring and bleaching of all cotton fabrics are not exactly the same. Therefore, it is necessary to add special penetrant in the mercerized lye.

Because there is no special improvement in the mercerization of cotton and polyester, and because the operation of the blended mercerization and the finished product are almost the same as that of cotton, we will no longer repeat and will continue to explore the blend of cotton and viscose rayon (Viscose).

Ten, cotton viscose blended mercerization:

The High Wet Modulus viscose rayon (Viscose Rayon) and the cotton mercerizing and blending project, as well as cotton and ordinary viscose rayon mercerized blend, have brought us some special problems. In the process of mercerization, we hope to improve the properties of cotton without affecting viscosity. This involves two aspects of theory and practice, because all rayon rayons will expand in caustic soda (Swelling). When we make another viscose rayon which is not easy to expand in lye, they will be more sensitive than cotton in some cases. Therefore, unless the operation is in the right condition, the blended products after mercerization may have many disadvantages, such as hard, brittle, low tensile strength or wool paper effect.

Fortunately, the alkalinity affecting viscose rayon is not the same as that affecting cotton alkalinity. For a long time, it has been known that the lower the temperature of alkali solution is, the better the expansion effect of cotton will be. However, for viscosity, temperature will have a great influence, and in some cases, it will be dissolved in caustic soda. The time factor of alkali leaching is also different from viscose rayon. For cotton, most of the mercerizing effect starts at the beginning of alkali leaching, and it will soon reach the equilibrium expansion state. However, for viscose rayon, the lye will take a long time to achieve equilibrium. Therefore, we know that the time factor of alkali leaching is not very important to cotton, but it is very important for viscose rayon. Finally, because viscose rayon fibers are more absorbent than cotton, some alkali solutions must be infiltrated into cotton.

Based on the above discussion, we know that in the mercerization of cotton and viscose rayon blended fabrics, we must consider the following points:

1. alkali concentration.

2. alkali temperature.

3. contact with lye.

4. the penetration of lye.

5. cleaning methods.

We have suggested that the mercerization of all cotton fabrics should be carried out in the concentration range of 28~31 Be`, not only to increase gloss, to promote the affinity and stability of dyes, but also to improve other properties. At the same time, this range has the least adverse effect on viscose rayon. Therefore, if the gloss of cotton and the affinity and stability of dyes are the targets of our improvement, the 28~31 Be` lye bath can indeed achieve good results in the mercerization of cotton and viscose rayon blended yarn.

We also recommend the use of mercerizing equipment without cooling system, but the temperature of the lye can not be higher than 110 (43 C). We also give the same suggestion for the mercerization of cotton / viscose rayon blended yarn. However, if the temperature is kept at a temperature of 110 degrees below 43 degrees Celsius, the minimum swelling will be achieved. Because cotton fiber is the main place of reaction and the absorption of viscose rayon is very strong, it is very important to increase the rate of alkali penetration into cotton and to facilitate the reaction of cotton and lye as soon as possible. Using some newly developed auxiliaries on the market can help us achieve this requirement. Due to the prolonged contact time between cotton and lye, it is sometimes beneficial. Therefore, for all cotton textiles, we recommend two times of caustic soda operation. The aim is just as air oxidation operation is to give enough time to make alkali and cotton react completely. However, long time immersion in lye will have adverse effects on viscose rayon. Therefore, a compromise must be envisaged in the mercerizing technology of cotton and viscose rayon blended fabrics. Air oxidation and alkali bath two times are not applicable now. Instead, cotton must pass the lye quickly. Usually, simply remake the standard mercerizing machine. The use of special auxiliaries in the mercerizing lye can also cause the reaction between alkali and cotton to occur quickly. If we do not consider the improvement of gloss, as long as the affinity of cotton fabric to dye is enhanced, the method of operation in many factories is to design the lye in the range of 16~22 Be`. Unfortunately, the concentration of alkali liquor which is most harmful to viscose rayon blended with cotton is in the vicinity of this range. On the other hand, some experienced mercerizing technicians also operate in the same concentration range, but keep the lye temperature near 100, allowing cotton to pass the lye quickly. Finally, the cleaning steps are carried out with special caution. Generally speaking, we still feel that it is better to operate in the range of 28~31 Be` than in the sensitive range of 16~22 Be`.

For blending, if it is not possible to provide special caustic soda equipment other than standard equipment, it must be specially adjusted for the importance of adjusting cotton pressure suction when cotton is away from alkali leaching. For all cotton cloth, we propose to leave some alkali solution in cotton for lubrication when stretching Frame. In theory, cotton and viscose rayon blending can also be adopted. If there is no proper cleaning equipment, there is no need to consider this. If the cleaning is not ideal, when the cotton leaves the lye, the best pressure can be applied.

Or, when stretching machine is stretched, the way of giving maximum tension to cotton can be a little easier. This is also helpful. The operators must keep these details in mind so that the cotton can be stretched to a predetermined width or wider after being expanded, leaving some alkaline solution in cotton to lubricate the stretches. From another point of view, the alkali must be washed out as soon as it is entangled, otherwise it will cause breakage or tensile strength loss.

In the mercerization of cotton or cotton / polyester fabric, the ideal arrangement is to give the cloth machine a longer operation time after soaking in alkali, so that cotton can slowly be pulled to the desired width and then rinse with a lot of cold or warm water. However, the blending with viscose rayon must be handled in the opposite case. It is not only necessary to wash out the alkali as soon as possible, but also to clean it with lots of extremely hot water at the beginning of the job.

It has been mentioned before that viscose rayon is quite sensitive to the weak base of 12~19 Be`. To be clear, cotton / viscose rayon blended fabric must be quickly passed through lye and cleaned with very large quantities of water. Secondly, the alkaline content of these cleaning water is low. In the use of countercurrent washing equipment in the mercerizing of cotton fabrics, washing water contains fairly high alkali content. Such cleaning water is quite dangerous, especially when they are not hot enough. Fortunately, high temperature is beneficial to the effect of lye on rayon. In other words, it's 18 to 30. TW in cold or slightly warm alkali liquor is more suitable for expansion than that in the same concentration, but the temperature is higher than 180 (82 degrees). Therefore, with a large quantity of washing water, the alkalinity of the washing water can be as low as possible, and the best temperature of the washing water is more than 180 (82 degrees).

Finally, adding proper mercerizing aids to the original alkali bath can also accelerate the rate of washing the alkali from viscose rayon.

The newest mercerizing AIDS have the functions of osmotic and surfactant, and can be used in a wide range of basicity. It is very important for the mercerization of cotton / rayon blended fabrics, because even if cotton is in the absorption state, the lye can rapidly infiltrate into cotton. At the same time, they will also accelerate the reaction of cotton and alkali. Another important thing is that because they can remain active in any alkalinity, they can also function even when washed. With their presence, lye can be removed very quickly, and their high activity prevents the possible damage of lye and quickly washes water to every part of the fiber.

Eleven. Mercerization of yarns:

The mercerization of warp can not be discussed without discussing the mercerization of warp yarn (Warp Mercerizing). Like many of the items we discussed in the photochemistry of cloth, such as alkali bath concentration and cleaning parameters can be applied to warp yarn photochemistry. Therefore, we discuss only those areas of different or other special technologies.

The question is why the mercerization of warp yarn can achieve the greatest benefit we require, and become the first choice to replace cloth yarn. There are many answers, most of which can be directly observed. First, yarns can be used for knitting. Obviously, unless there is a special case, it is almost impossible to make full mercerization of the fabric. Besides, cotton thread is often knitted with silk, wool, rayon and other fibers. There are also technical difficulties in processing this kind of fabric. Therefore, the mercerization of yarn is the only reasonable method for the significant development of the finished products of mercerized cotton. Similarly, fiber can also be applied to the above statement.

The answer to yarn is easy to doubt. The mercerization of weaving is faster than yarn yarn, and the rate is faster and more economical. It is the most reasonable way to obtain good results. However, the mercerization of yarns is not only flexible in operation, but also has potential for development in terms of toughness such as the mercerization of yarns made of the same yarns. Even by mercerizing some weak yarn, it can improve its toughness and increase the benefit of weaving.

The yarn will be knitted into cotton yarn to be silk, so that the product will have a number of special effects. For example, warp yarn can be shredded and made of yarns made of other fibers, woven into a fabric. Finally, for maximum toughness and best luster two, the best results can be obtained by replacing the mercerization of finished products with yarns.

In the process of mercerizing yarn, there are many advantages in warp processing. First, it allows continuous yarn mercerization for yarns up to 6000 yards or more and can handle thousands of yarns at the same time, which is quite economical. This method of mercerization is the most economical in management, because the yarn will automatically be made from the yarn rack to the spherical warp, continuous filament actinization, continuous drying, and then spinning around the bobbin or the bobbin. Lastly, the warp process itself has a characteristic that the chemicals used in this process will not be consumed. In addition, because the warp yarn is allowed to be washed by counter current, the caustic liquor can be recovered. If the amount of yarn used in silk is large, it is better to use warp yarn.

Because of the early warp yarn practitioners, several warp yarns were tied into a single yarn and loosely tied together by clues or raw yarns, called Water Ribbon. Recently, some operators have abandoned the single yarn system and made the yarn mercerized in free state, thus obtaining a similar continuous warp Sheet.

It is not necessary to consider whether the yarn should be bleached before or after mercerization in the process of yarn actinization. All mercerizing with proto yarn, if the yarn has been scoured or soaked, then we must control the yarn in the best case in order to make the yarn get a good effect in mercerization. The problem between wet mercerization and dry mercerization is the theme. First, because this is the earliest and the most primitive process in the earliest technology, of course, there are people who support it. When Mercer first discovered the mercerizing process, he found that in order to make alkali and cotton react, cotton must be thoroughly soaked.

When he knew that he was trying to get the alkali to permeate himself, the early mercerizing technology first cooked their yarns, then extracted the excess water, and then treated them with silk. Many of today's warp mercerizing technologies still insist on adopting the old process, but they have also been improved.

The bitter experience of foaming in lye evaporator is caused by some earlier poor mercerizing osmosis agents and some ineffective osmotic agents. They make many operators refuse to use dry mercerization. In most cases, wet type has more disadvantages than dry type. The latter is mainly used to soak the yarn directly in lye. Wet mercerization has few advantages and is not important, so it is often neglected. One of its small advantages is the pre soaking process before soaking, filtering out impurities in some yarns, thus preventing the contamination of lye. If the yarn is exposed to the air for a long time, it contains a lot of impurities.

Kiering before mercerization has long been outdated and expensive. It may have been the earliest method of immersion. In fact, it has long been abandoned by the industry. Today, the so-called wet dry type problem is that the first one is pre soaking the mercerizing machine before alkali treatment, which is directly immersed in the alkali solution added with a special penetrating agent compared to another yarn. If soaking is done only by boiling the yarn in hot water without adding any chemicals, the only cost is steam, but if it is to be thoroughly soaked thoroughly, it is almost impossible to achieve the goal without boiling a yarn on a very long operation line. In this method, the cost of steam is quite large. However, the operator who uses this method usually adds two devices to the mercerizing apparatus before the lye impregnation, so that the yarn is completely soaked through wetting agents. In this method, the cost of chemicals is also considerable. In addition, in order to provide uniform and constant penetration, the Wetting Bath should be carefully controlled.

One disadvantage of immersion treatment is that cotton has insoluble waxes, which amount to considerable accumulation and float in alkaline bath. The wax is also carried away by some yarns, leaving Resist Spot or even uneven dyeing. However, the biggest drawback of immersion treatment is the considerable amount of water that the yarn carries into the lye, which is about 70 to 140% of the yarn weight. That means that if silk irradiation must be carried out under a fixed alkalinity, for example, 29Be`, then alkali solution must be added frequently to the alkali bath to make up for the dilution caused by the yarn. At the same time, the wet yarn immersed in alkali bath must be replaced by a certain amount of water after the alkali solution is replaced. It means that the wet type is longer and slower than the dry process.

The new mercerizing osmosis agent and auxiliaries used in dry treatment can bring us many advantages which make the wet method even inferior.

The first is that the use of osmotic agents not only causes the lye to soak the yarn of the embryo very quickly, but also accelerates the catalytic effect of silk irradiation. The addition of penetrant also causes the caustic liquor to be washed into the recovery system without washing. In addition, by immersing yarn in alkaline bath with proper penetrant, it can make silk actinization start immediately and make the whole yarn at the same time. Therefore, uneven wetting in wet process can not occur on dry method.

Second: because the yarn does not bring the water into the alkali bath, the alkalinity in the alkali bath is easier to control. At the same time, as the alkalinity in alkaline bath is maintained only a small amount of high alkalinity liquid is added, in other words, the alkalinity change of alkali bath is very small. Therefore, in the washing water recovery system, the recovery of low alkali content can be simplified, and the high concentration alkali liquor must be evaporated without washing the water like wet process. In dry process, because the yarn is not rinsed, some impurities are added to the lye. These impurities can be easily removed by circulating filters in the wet mercerizing plant. In terms of dry method, it costs much less of the additives used in the process of silk production than the cost of wetting agents, steam supply and evaporation in wet process.

The last thing to mention is the quality of finished yarn after photochemical treatment. The dry mercerized finished product is able to absorb more tension, and because the length of the yarn has no different water content on the special end, it has an average reaction with lye. Therefore, dry method is easier to produce uniform dyed yarn than wet method. We must assume that all other factors remain unchanged.

Tension (Tension) is the basic factor in the photochemical process of warp yarn (Factor). Therefore, the control of tension is also very important. Strictly speaking, the term "tension" has been misused in the same industry. Tension is a force acting on yarn. In the warp yarn actinic machine, we can only control tension by stretching, shrinking or expanding the ability of the lye. If the lye keeps a constant basicity, the tension in the mercerizing machine will be controlled by the relative speed of the Squeeze Roll in the alkali bath and the yarn slippage (Slippage) phenomenon in the suction roller.

Therefore, from the point of view of mercerization, we are concerned that yarn enters into mercerized lye until the alkali liquor is washed out of the yarn, and the yarn is contracted or stretched on the yarn. From the general point of view of quality and efficiency, we are concerned with Boiloff, water washing, scouring, even stretching or shrinking during drying. Stretching and shrinking in all these steps will affect yarn quality in all respects. However, we will first discuss the extension or contraction of lye. For most yarns, it is a very simple and very common practice to keep yarns in the process of alkali treatment and pre cleaning. Under these conditions, satisfactory gloss, shrinkage and dye affinity can be developed. However, some special properties of mercerized yarns will be improved with increasing stretching, while others will weaken.

If the yarns are not allowed to shrink before washing, the gloss is directly related to extension during alkali treatment. Even if the elongation is as high as 10 degrees Celsius, the conclusion is true. However, under the same circumstances, the increase of elongation will lead to the weakening of the affinity of dyes and the decrease of their elasticity. According to the nature of yarns, the increase in elongation during alkaline treatment will increase the Breaking Strength to a certain extent, and then increase the elongation to reduce the strength of the cut. For twisted yarns with standard mercerization, the twist range is from 20s / Z to 90s / Z, which is equivalent to 4% of the extension of the alkali solution. It can be safely applied without worrying about the extension of yarn finished products. Moreover, the gloss will increase greatly and the tensile strength will also be improved. For single yarns, any excess stretch can cause danger, so single yarn should best avoid shrinkage.

For special dyeing effects, such as very high affinity for dyes, yarns can allow up to 10% shrinkage in alkaline treatment. If the yarn is stretched or contracted during this process, the total number of yarns will not equal the total number of original yarn used. Under normal circumstances, because of the loss of some colloid and impurities in the mercerizing process, the yarn will have one or two total, but the main reason for the change in yarn number is the large shrinkage or extension.

During the mercerizing period, any difference in elongation or shrinkage will result in uneven dyeing of finished yarn, though we can not see any changes in their luster and intensity. In order to control these tensions, the most important thing is to have a precise way to control the speed of the suction cylinder and the speed at which it leaves the final cleaning process. These sucking cylinders maintain a true and average density, so that the end of the warp yarn can achieve the same effect. Obviously, it is also important to control the uniformity of warp tension when making warp yarns. When the tension is increased at both ends of the yarn, if there are slight differences, we can not see a distinct difference in gloss and intensity, but we will notice the difference in affinity for dyes. Therefore, in order to obtain the maximum evenness of the warp yarn, the tension or elongation at both ends of the yarn must be very similar.

If the scouring or soaking system is used before mercerization, the shrinkage of 2~4% is usually caused when the yarn is not applied to tension during immersion treatment. If you want the best luster, it is best to make the yarn shrink a little while soaking, and then extend it to make up for the loss.

If there is a slight relaxation (Slack) in the yarn, the penetration will become more complete and the yarn will be soaked. For how to choose to be soaked in tension and to maintain the same elongation when mercerizing, or to allow a little shrinkage during wetting, then extend it in alkaline solution, depending on the existing equipment.

Finally, during the cleaning process, when a certain amount of alkali liquor is removed, the yarn will increase its length. At this point, it is best to speed up the cylinder that is leaving the lotion so as to keep the least amount of relaxation in the yarn. Too much relaxation will break the ends of the yarn and cause some trouble in the final winding process.

From the above discussions about the latest development of some mercerization in recent years, it is clear that good mercerization is still the basis for the rational application of the basic practices exposed in the first process developed by muse.