Thread Content
I. Several basic concepts that must be established to improve the quality of printed and dyed products. Improving the quality of these products is now a common goal among printing and dyeing factories, but so far, efforts have been reactive – quality is given importance only due to customer demands – rather than proactive efforts to create brands by striving to enhance product quality. If improving quality were truly treated as a top priority, factories would not fall into the vicious cycle of price-cutting competition. To improve the quality of printing and dyeing, several basic principles should be adopted: 1. Water quality must be given priority attention – water quality is an important factor affecting the quality of the processing; it can be said that the difficulty in controlling printing and dyeing quality is largely due to poor water quality. Due to differences in water sources, there are significant variations in impurity content, hardness, levels of other metal ions, color, turbidity, and other pollutants. In terms of hardness alone, values below 100 ppm (100 mg/L) have little impact on dyeing and finishing processes. However, some factories use hard water with a hardness level above 300 ppm; even if such water is used only for washing, it can still reduce the color fastness. When used in scouring and bleaching processes, it causes calcium deposits, reduces whiteness, results in a rough texture, decreases fabric softness, and leads to uneven color absorption. Using hard water for dyeing lowers the solubility of dyes, causes staining, reduces color fastness, affects the vividness of colors, alters the evenness of coloring, and impacts color reproducibility. To pay attention to water quality, it is necessary to test the water used in the factory on a daily basis. In addition to analyzing hardness, it is also important to determine the levels of heavy metal ions such as copper, iron, and manganese, as their impact is greater than that of hardness. In addition, it is also necessary to determine whether there are reducing and oxidizing substances. After gaining a comprehensive understanding of the water quality, measures are taken to address the issues. Hardness and heavy metal ions can be treated using complexing agents or chelating dispersants. Different complexing agents have varying abilities to complex calcium, magnesium, iron, copper, and manganese ions; some are more effective at complexing calcium and magnesium ions while being less effective at complexing iron ions, and others are the reverse. This also depends on the pH value. Please refer to the overview section (number 15–001) in Chapter 15 on Chelating Agents in my book \"Manual of Analysis and Application of Chemical Auxiliaries\" (published by China Textile Press in 2001; hereinafter referred to as the Manual), as well as the various types of chelating agents, where all these topics are described in detail. For water with high turbidity and many impurities, water treatment agents must be used. Please refer to Chapter 14 of my manual on water treatment agents. Defects often occur during bleaching, dyeing, printing, and finishing due to changes in water quality. After understanding the water usage in the factory, in the absence of water treatment equipment, chelating agents or chelating dispersants can be added to the aforementioned processing solutions to address this issue. Chelating dispersants are usually copolymers of acrylic acid and maleic acid; they are capable of chelating calcium, magnesium, and other metal ions, and are suitable for use together with dyes. Unlike chelating agents, they have a lower chelation stability constant, so they generally do not remove the metal ions from dyes, whereas chelating agents may do so. The types of chelating dispersants are listed in Chapter 15 of the manual. There are also many domestic products available nowadays; for example, the chelating agents and chelating dispersants produced by Changzhou Chunjiang Chemical Factory, which are said to have good quality. 2. It is essential to pay close attention to the quality of fabric pretreatment: excellent pretreatment is a prerequisite for ensuring the quality of printed and dyed products. If the quality of preprocessing cannot be guaranteed, it is impossible to achieve stable quality in the final product. The quality of the pretreatment must be such that it results in a clean and uniform product. By \"clean,\" it is meant that impurities must be removed thoroughly; the slurry should also be cleaned as much as possible. More than 80% of fiber-associated substances such as oils, waxes, pectin, and proteins need to be removed, while the removal of pigments depends on the requirements of the processing process. Currently, textile printing and dyeing factories evaluate pretreatment quality based solely on the capillary effect, which is unscientific. Because if there are many surface activators with re-wetting properties remaining on the fabric, it can also lead to an artificial increase in the perceived fuzziness, resulting in higher values for fuzziness. Therefore, it is best to wash the fabric once with hot water and once with cold water before measuring fuzziness, in order to remove these re-wetting agents; after drying, the fabric should be kept at a constant humidity level before the fuzziness is measured. Evenness means that the pre-treatment should be uniform, with consistency across the left, center, and right sides of the fabric as well as in its front and back sections. In short, attention should be paid to pre-treatment; using high-quality additives is key to ensuring its quality, and thorough rinsing after pre-treatment is also necessary. 3. It is essential to strictly control the quality inspection of dyes and chemicals upon their arrival at the factory: The quality of these dyes and chemicals is key to minimizing the need for repairs and ensuring that re-dyeing is successful. Dyes and chemicals must be stored along with sample standards; for example, dye sample standards need to be prepared and stored, and new dyes are also inspected using these sample standards to check their color and dyeing strength. For additives, it is necessary to check whether their solid content, color, viscosity, pH value, and physical properties (such as refractive index, melting point, boiling point, and cloud point) match those of the standard samples. Although there are no complete testing criteria for additives at present, their quality stability can still be assessed based on their appearance and the aforementioned parameters. The practice of demanding compensation from additive or dye suppliers when defects occur is extremely irresponsible, as it is not possible to be certain that the problem lies with the dyes or chemicals. To be honest, any defect can arise if the water quality changes; so how can one determine that it is a problem with the dyes or chemicals? In fact, by ensuring proper quality control at the inspection stage, both parties benefit; counterfeit and substandard products are prevented from entering the market, which stops unethical practices from having a foothold. The quality of processing is guaranteed, the reproducibility of coloring improves, and delivery deadlines are also ensured. The testing methods for the above projects are described in detail in Chapters 5 and 6 of the Manual. 4. It is necessary to choose high-quality dyes and chemicals: The quality of dyes and chemicals does not necessarily mean that those with higher prices are of better quality. Some well-known companies these days resell domestic dyes and chemicals under their own brand names, charging more than double the original price; in fact, these chemicals are still produced domestically. The problem lies in our lack of information, our failure to conduct comparative tests, and our absence of a systematic screening process. In reality, if we learn paper chromatography, thin-layer chromatography, and column chromatography methods, we can quickly determine which domestic product a mixture of such chemicals actually comes from by using the Rt value, thereby reducing costs. To choose good dyes and chemical additives, the foundation is as follows: first, it is necessary to understand what structures exist for the same product in the domestic market, and what types of additives are available for each structure; in other words, such information is required, and this can be obtained by consulting relevant manuals or magazines. My book, \"Manual on the Analysis and Application of Chemical Additives,\" was written to meet this need. It covers all types of additives, with the exception of those developed and produced after the year 2000. Second, comparative process tests should be conducted; high-quality additives should be selected based on the equipment available in the factory, that is, effect tests should be carried out. For example, when selecting a leveling agent, tests for migration resistance, agglomeration tendency, foaming property, and leveling ability must be conducted (methods are provided in Manual 250-001) in order to identify high-quality leveling agents; it is not advisable to use them based solely on the information provided by the additive manufacturers. Thirdly, storage stability tests must be conducted; changes over a period of one week or one month should be observed. Some emulsion-type additives require testing for their emulsion stability through rapid centrifugation tests as well as actual storage tests. Special attention should be paid to the emulsion stability of defoamers. In the case of silicone-based defoamers, their emulsions tend to break down easily, and when used in overflow dyeing machines, silicon can precipitate, leading to silicon deposits and pipe blockages, which can cause serious problems. Fourth, on this basis, use cheaper varieties first. Care should be taken when changing varieties; foreign printing and dyeing factories often use a system of fixed suppliers and specific varieties, with the aim of ensuring that the quality of the finished printed products is not affected. 5. It is essential to pay attention to and strengthen environmental protection awareness: Since joining the World Trade Organization, there have been frequent reports of foreign countries using technical barriers to restrict our exports. However, this may be just one aspect of the issue. In fact, as the standard of living improves, it is only natural to have higher requirements for textiles. The need for higher quality standards applies to both them and us. So why do they make such a fuss when it comes to us, while they seem able to tolerate those standards? It only shows that our standards are low; at least we haven’t paid enough attention to environmental protection requirements. Take free formaldehyde in fabrics as an example – it can cause skin diseases and is suspected to be a substance that may lead to skin cancer (though this has not been definitively proven yet). Therefore, it is important to note that the free formaldehyde content in children’s underwear should not exceed 20 ppm; in fact, it should be at a level where it cannot be detected at all, as this shows a commitment to human health. Dyeing and printing factories should make use of formaldehyde-free additives as much as possible, and avoid using those that contain formaldehyde. It is unfortunate that to date, fixing agent Y is still being used in large quantities, continuing to produce textiles that are harmful to the health of the Chinese people. Is it acceptable for harmful substances to be present in products sold domestically? This is an unethical act of sacrificing others’ well-being for profit. Due to a lack of environmental awareness, some factories use Pyrovatex CP for flame-retardant treatment, resulting in free formaldehyde levels in the fabrics exceeding 400 ppm. **This exceeds the allowed limits, causing the exported products to be rejected and leading to significant financial losses. Therefore, textile workers must enhance their environmental awareness and limit the use of environmentally unfriendly products as much as possible. Currently, formaldehyde-free color fixatives, formaldehyde-free adhesives, and formaldehyde-free anti-wrinkle finishing agents are being produced in China or are the subject of active research. 6. It is essential to adopt the approach of saving energy and water, improving the first-time success rate, and reducing the rate of rework: this is the only way to enhance the competitiveness of the printing and dyeing industry. Everyone who wants to achieve this goal will not object; the question is how to achieve it. Energy and water consumption account for a large proportion of the costs associated with dyeing and printing. In the past, the concepts of low-temperature, cold, and wet dyeing processes were merely slogans without any practical implementation methods, which is why they could not become a reality. It has now become a focus of research, depending on the development of additives. For example, cold-rolling pile finishing and bleaching, cold-rolling pile dyeing, and wet resin finishing have already been put into practice. But it has not yet been applied in all factories. The reason is that there is still a lack of consensus on it; cold rolling, stacking, and rinsing are carried out with the help of additives. It is already possible to achieve a quality level equivalent to that of hot-bleaching. The key is to choose high-quality additives; for example, Tinoclante Pb from Clariant (referenced as 24-053 in my manual) and MPF-1, a cold-rolling pile refining stabilizer from Zeng Qiuguo Factory in Yixing, are both excellent additives. The latter also contains components that help remove cottonseed hulls. If the pile-aging time is extended to 36 hours, a brightness level comparable to that of bleached fabric can be achieved. However, if ordinary penetrants are used in insufficient quantities, it will be difficult to ensure the desired quality, and the product might easily be mistaken for having substandard cold-rolling pile bleaching quality. Cold-rolling pile dyeing with reactive dyes has been adopted by some printing and dyeing factories; it is said that the process is kept secret. Some believe that it is difficult to ensure consistency in this process, but in fact the issue lies in the inappropriate choice of auxiliaries. To carry out this process successfully, leveling agents such as Ciba’s Uniso WL, catalysts, and appropriate mixed alkalis must be used. Unfortunately, no such leveling agents suitable for dyeing cotton with reactive dyes have yet been developed in China. The cold rolling stack process is an effective method for saving energy, and it is worth researching and developing. In addition, combining several processing steps into a single one is also a direction of recent research abroad. For example, there are publications on one-bath or two-bath methods for desizing, scouring, and even bleaching using enzymes; this is made possible by the application of genetic engineering in the production of enzyme preparations, which allows for modifications to enzymes that were not possible in the past. The integration of multiple processing steps is also reflected in the use of effective additives, which enclose the dirty water resulting from the scouring process, preventing it from sticking to the fabric. This allows the wastewater to be removed after scouring and bleaching, after which dyes can be added for coloring. It reduces the need for intermediate washing steps as well as processes related to temperature adjustment, thereby saving energy and water. The total time required for scouring and dyeing is reduced by half, with more than half less water being used. Another combination process is to carry out oil removal before polyester dyeing in the same bath as dyeing, as well as soap washing after dyeing in the same bath, which also **saves energy and water**. To increase the success rate of each sampling process, it is essential to strictly control the manufacturing processes and operating procedures. All necessary dyes and chemicals should be used in sufficient quantities; one should not try to save costs by using less of them. For example, the normal dosage of a leveling agent is 1 g/L, and it should not be reduced to 0.5 g/L. Do not overuse defoamers by increasing their dosage arbitrarily; the appropriate dosage is 0.05-0.1 g/L. Strictly control parameters such as the amount of dye used, the rate of temperature increase, the dyeing temperature, and the time. With the right dye selection and stable water quality, the success rate for a single attempt can exceed 90%. The rate of defective fabric needing rework is an indicator of technical proficiency and the quality of technical management; factories with high standards can keep this rate below 3%, and reliance on rework to solve problems should never be accepted. It is abnormal for the sales volume of color corrector L to be so high at the moment. To reduce the costs of printing and dyeing factories, it is necessary to address these aspects mentioned above. It is absolutely unacceptable to cut corners by using low-quality, inexpensive additives, or to engage in price competition by lowering processing costs, as this will lead to competition among peers and ultimately harm those businesses themselves. Second, what should be considered when choosing additives? When selecting additives to help improve the quality of printed and dyed products, the following points must be taken into account: 1. Technical personnel must have a basic understanding of additives; this is a prerequisite for choosing the right additives. To make good use of additives, it is necessary to have a basic understanding of their fundamental concepts, structure, properties, and usage characteristics; this allows one to identify the causes of any abnormalities and take timely action to address them. To this end, I have included an overview section at the beginning of each chapter in my manual, explaining the principle of action, basic properties, structural classification, usage methods, application testing methods, and precautions for using such additives. This helps readers gain a basic understanding of these additives and lays a foundation for their proper use. In the subsequent sections dedicated to each individual additive, its basic structure, characteristics (factory standards), uses, and usage methods are described in detail. If the structural types are similar, the usage methods and performance characteristics tend to be similar as well, allowing for generalizations based on one example. For varieties not covered in the manual, as long as one knows their basic structure, they can be understood easily. Therefore, when using new additives, manufacturers must have the supplier inform them of the structural category of that additive; for example, it is important for the manufacturer to know whether the softener being used belongs to the category of amino silicone-based softeners, hydroxysilicone-based softeners, fatty amide-based softeners, imidazoline-based softeners, or fatty acid paraffin-based softeners. Only in this way can its basic performance be understood, preventing blind use. 2. There should be a basic understanding of the solubility of additives and their stability in hard water and metal ions. For example, anionic surfactants have higher solubility in alkaline environments than in acidic ones, while cationic surfactants exhibit the opposite behavior. Amphoteric surfactants possess characteristics of both anionic and cationic surfactants, whereas non-ionic surfactants have a lesser impact. The solubility of the first three types of surfactants increases as the temperature rises, whereas the solubility of non-ionic surfactants decreases with rising temperature; as a result, a cloud point is formed. This cloud point must be higher than the operating temperature, otherwise these surfactants will lose their effectiveness and fail to serve as additives. The cloud point increases as the EO number rises. It increases with the amount of anionic additive added. But it decreases as the electrolyte content increases. If Pingenjia is used as a leveling agent or dispersant in high-temperature and high-pressure dyeing, the use temperature **exceeding its cloud point (usually around 75°C) will cause it to precipitate out of the dye solution; it will not be effective at all, and instead it will cause the dyes to aggregate, resulting in color spots. Silicone defoamers are emulsions formed by emulsifying methyl silicone oil or ethyl silicone oil with non-ionic surfactants and silica. If emulsifiers with a low cloud point are used, the same problems will arise. Auxiliary manufacturers often fail to pay attention to this issue, which poses a serious threat to printing and dyeing factories. The method for determining the cloud point is outlined in my manual 5-013, while the method for measuring the solubility of surfactants is described in 6-035. 3. The acid and alkali resistance of the additives must be determined: this helps to determine whether the additives can meet the requirements of the manufacturing process. The acid and alkali resistance of these additives varies greatly. Anionic surfactants are generally resistant to alkalis but not to acids; among them, phosphate esters have the best alkali resistance, while carboxylic acids have the worst acid resistance. Cationic surfactants are generally acid-resistant but not alkali-resistant. Non-ionic surfactants can withstand weak acids and bases, but not strong acids and bases. Textile dyeing factories must first test, in accordance with the process requirements, whether the additives used will cause turbidity or precipitation when applied. One factory used imported additives for submersed belt bleaching; no problems were observed at first, but later wrinkles appeared on the fabric, and irregular color spots appeared on its surface after dyeing. Upon checking, solid substances of varying thicknesses were found accumulated on the guide rollers – these were actually precipitates formed due to the additives’ inability to withstand alkalis, and they stuck to the fabric, resulting in color spots during dyeing. Therefore, the alkali and acid resistance when using additives must be determined. This should be taken even more into account during cold rolling, stacking, and bleaching. Many additives hydrolyze in alkaline and acidic media; the methods for their determination are provided in manuals 6-017 and 6-018. 4. It is necessary to understand the ionicity of additives. There are four types of additives: anionic, cationic, non-ionic, and amphoteric; the first three are commonly used. Anionic additives cannot be used together with cationic additives, as they will form flocculent precipitates, which not only prevent these additives from functioning but also cause staining defects. Non-ionic additives can be used together with both cationic and anionic additives. These principles are well known to everyone, but in actual production they are often inadvertently ignored. For example, fixing agents are cationic and cannot come into contact with anionic auxiliaries; yet many factories use anionic soap detergents for washing after dyeing with direct, acidic, or reactive dyes. Without removing these detergents first, they then apply fixing agents, which bind to the detergents remaining on the fabric. This not only wastes the fixing agent and reduces its effectiveness, but it also affects the wash fastness and rubbing fastness of the dyed fabric due to the precipitates formed by the interaction between the soap detergent and the fixing agent. 5. Do not reduce the amount of additives used arbitrarily: The components of printing and dyeing additives can be roughly divided into two categories, namely functional additives and surfactant-based additives. The former uses different compounds to exert functional effects during processing, such as oxygen bleach stabilizers, color fixatives, color correctors, defoamers, softeners, greening agents, water- and oil-repellent finishing agents, flame retardants, anti-wrinkle finishing agents, and so on; these compounds only achieve the desired effects when used in appropriate amounts. Another category consists of surfactants used as auxiliaries in dyeing and printing, such as penetrants, cleaning agents, leveling agents, scouring agents, soaking agents, dispersants, emulsifiers, etc. Their functions actually rely on the wetting, emulsifying, dispersing, and solubilizing properties of surfactants; they represent either the combined effects of these functions or specific manifestations of individual effects. Therefore, they are fully in line with the theory of surfactants, which is why it is necessary to learn about surfactants. Surfactants form micelles in solution, and the concentration at which these micelles appear is known as the critical micelle concentration, abbreviated as CMC. As the concentration exceeds the CMC, the number of micelles increases and they become larger. The wetting effect of surfactants can occur at concentrations below the CMC, while emulsification, solubilization, dispersion, and cleaning are all effects mediated by micelles; therefore, these effects can only be achieved at concentrations above the CMC. Generally, the C.M.C. value of pure surfactants does not exceed 0.2 g/L. In most commercial products, the amount of surfactant active ingredients is only 15–20%; together with other additives, the total solid content is 40%. Therefore, the C.M.C. value of these commercial products is likely to be no more than 1 g/L. In other words, a concentration of additives of at least 0.5 g/L is required for gel formation to occur; only above this concentration does the amount of gel increase significantly, yielding noticeable effects. Thus, the amount of additives cannot be reduced arbitrarily, especially in inexpensive commercial detergents, where the effective ingredient concentration is as low as 5%, with the remainder being substances such as calcium sulfate. Using too little of such additives results in no effective cleaning effect. This is why national and ISO standards specify a dosage of 3 g/L for soap in wash fastness tests. Wetting penetration is achieved not by micelles but by monomeric surfactants; therefore, it can occur below the CMC, and the concentration in the processing fluid does not need to exceed 1 g/L. 6. Aditives must first be dissolved and diluted before being added to the processing solution. Due to the different specific gravities of their components, composite aditives have varying solubilities; as a result, commercial aditive solutions often develop upper and lower layers with different compositions, which can affect their effectiveness. Over time or in cold weather, changes in solubility can cause turbidity or even stratification. This phenomenon is acceptable as long as it does not involve emulsions. However, before use, it is essential that the operator stir the mixture thoroughly before measuring the ingredients. Emulsions, on the other hand, must not exhibit any turbidity or stratification. This indicates that the emulsion has been demulsified and can no longer be used; either it must be reemulsified through rapid stirring, or it can only be used if high-speed centrifugation tests prove that it is still usable. It must never be used after merely stirring it by hand. Solid additives should be completely dissolved in hot water before use, while liquid additives must first be diluted with warm water. Additives with very high viscosity need to be gradually diluted by adding water while stirring. For additives that are prone to mold growth, such as fatty softeners and pastes, as long as they have not become too thin and there is not excessive mold, the upper layer can be removed; the remaining additive can still be used. If it has become too thin, it should be returned. The addition of the dissolved and diluted auxiliaries to the treatment bath depends on the process requirements; generally, they are added to the treatment solution before the fabric is introduced into it, and after the solution has circulated to ensure uniform distribution, the fabric is then added. In the case of leveling agents, the fabric is first immersed in the leveling agent for a few minutes before the dye solution is added. 7. Shift from passive to active selection: From the perspective of additive manufacturers, textile printing factories are considered their \"gods.\" There are thousands of such manufacturers in China today, and in order to compete for market share, they use various tactics such as delivering samples directly to the factories and seeking connections to get access to them. As a result, textile printing factories are overwhelmed with so many samples that they don’t have time to process them all. The negative consequence of this is that these factories tend to remain confined to what’s available locally and avoid seeking alternatives; they prefer to choose additives from those offered by these manufacturers. Yet, there are countless high-quality additives available worldwide, which can help improve product quality. Therefore, textile printing factories need to change this approach and stop relying solely on what’s locally available, instead seeking out additives that offer good quality at reasonable prices. In today’s era of increasing information availability, it’s easy to find the samples needed. The manual lists 4,000 types of additives that were developed and produced by 2000 for selection. III. Process Analysis: There are numerous dyeing and printing processes, and it is too much to analyze them from the perspective of additives alone. Some of these aspects have already been discussed earlier; here, only a few processes are presented for analysis as a reference. 1. Desizing: There are a great variety of sizing agents used at present. Manual 20-039 provides a detailed explanation of the types, properties, simple identification methods, and most suitable desizing methods for textile sizing agents, so it is unnecessary to repeat this information here. The problem is that there are many types of sizing agents used on poor-quality fabric, and it is not possible to determine their exact composition, which makes it difficult for printing and dyeing factories to decide on the appropriate method for removing the sizing. But they can be roughly divided into several categories: the first is based on PVA, the second on OMO and cellulose derivatives, the third on acrylate copolymers, and the fourth on starch and its derivatives or sodium alginate. An approximate assessment can be made through an iodine test; the method is described in manual 20-039. The third type of pulp can be delignified using hot water, the second type can be delignified with cellulase, the first type with oxidants, and the fourth type with amylase. Therefore, the delignification methods include enzyme-based delignification, hydrogen peroxide-based delignification, and dilute alkali solution-based delignification. The required degree of delignification depends on the type of pulp; even if the third type of pulp is not fully delignified, it will not affect subsequent processing, and a starch residue of around 10% is not a problem. However, if a small amount of PVA remains, it can cause serious issues. Thus, the best delignification process involves adding hydrogen peroxide to the delignification solution. When using enzyme desizing, choosing enzymes with high efficiency and activity is key to cost savings. Thanks to advances in genetic engineering, amylases that can function at various temperatures and complete desizing within just a few seconds of steaming have been developed – these are the so-called third-generation enzymes. Some of our factories still use first- and second-generation enzymes; for more information, please refer to Chapter 17 on enzyme preparations in my manual, 17-001, which provides a comprehensive overview of the development of new enzyme preparations as well as methods for measuring their activity. Whether the desizing is complete or not is an indicator of the quality of the desizing process, and it can be determined using simple testing methods, as described in 20-039. 2. Bleaching processing: The one-bath process of cooking, bleaching has become a mature technology; currently, there are three such processes: hot cooking-bleaching, cold rolling-heap cooking-bleaching, and enzyme cooking-bleaching. They all depend on the use of additives. The hot scouring method uses caustic soda, hydrogen peroxide, a scouring agent, and an oxygen bleaching stabilizer, in relatively low concentrations; high temperatures are employed to remove impurities from cottonseed hulls and fibers. With the use of a good scouring agent, a high quality of scouring and bleaching can be achieved. Cold-rolling pile scouring and bleaching utilizes high-concentration caustic soda, hydrogen peroxide, and scouring stabilizers, with the scouring and bleaching effect being achieved through prolonged stacking. The key lies in selecting the right additives; some factories mistakenly believe that the cold-rolling pile process has limitations due to the use of inadequate additives. This is because the reaction rate depends on the concentration of the reactants and the temperature: at lower temperatures, the reaction rate is slow, and this can be compensated for by increasing the concentration or extending the reaction time, thereby still reaching the end of the reaction. Because the reaction rate is proportional to the concentration of the reactants. However, cold rolling reduces energy consumption while ensuring the flatness of the fabric, which are its advantages. According to measurements, during hot scouring and bleaching, the decomposition rate of hydrogen peroxide is between 60-70%; if it were to be completely decomposed, the whiteness would actually decrease, due to the re-contamination by impurities left over from the scouring and bleaching process. During cold rolling and stacking, the decomposition rate of hydrogen peroxide is only 20–30%; therefore, if the stacking time is extended to 36 hours, the brightness and softness of the fabric can **increase, reaching the level of bleached fabric. Some experiments have shown that using catalysts to accelerate the decomposition of hydrogen peroxide can speed up the scouring and bleaching process, with significant results. In Europe, TAED is commonly used as a catalyst, while in the United States, NOBS is preferred. With 40 g/L of caustic soda, 40 g/L of 35% hydrogen peroxide, 15 g/L of scouring stabilizer, and a catalyst amount equal to 1/5 of the molar amount of hydrogen peroxide, cold rolling and stacking for 24 hours resulted in a GIE brightness of 75.5, compared to 66.1 when no NOBS was used; the fiber strength and copper hydrogen conductivity remained the same in both cases. So now many people are researching the use of complexes containing transition metal elements as catalysts; then why not reduce the amount of hydrogen peroxide used? This is because doing so will reduce the reaction rate due to the decrease in reactant concentration, failing to achieve the desired effect. Enzymatic scouring is another focus of current research and development; many new DNA recombinases have been developed that can break down pectin to enable cotton scouring. When used in combination with laccase, these enzymes can bleach pigments, thus achieving the purpose of scouring, as laccase is capable of breaking down pigments. In China, pectinase and lipase have been used for cotton refining, achieving excellent results as well. The characteristics of enzyme scouring and bleaching are mild reaction conditions, relatively fast reaction speed, no damage to the fibers, low wastewater generation, and low washing requirements. 3. Fixing: Fixing agents are used to improve the wash fastness, rubbing fastness, steam fastness, and sweat fastness of fabrics dyed with direct, acid, or reactive dyes. The previously used formaldehyde-containing fixing agent Y should be phased out, as the formaldehyde content in fabrics produced with it reached 200–300 ppm, which does not meet environmental standards; therefore, formaldehyde-free fixing agents must be used in its place. After years of development, the quality of these formaldehyde-free fixing agents has now reached or even surpassed that of fixing agent Y, and their prices have also decreased gradually, being only twice as expensive as fixing agent Y—a cost that printing and dyeing factories can easily afford. There are roughly three structural types of formaldehyde-free fixing agents: homopolymers or copolymers of N-methylbisacrylammonium or NN-dimethylbisacrylammonium, as well as homopolymers or copolymers of NN-dimethylacrylammonium. Examples of such products include fixing agents DUR and OS-1, OS-11, OS-111; refer to manuals 2-029 and 26-021 for more details. These agents can improve wash fastness but do not enhance chlorine fastness. The second type of structure consists of the reaction products of dichloramine, diethylenetriamine condensates, and epichlorohydrin; they possess cationic properties and reactivity, which improves soap-fastness, but cause color change. The third category consists of polyene polyamines condensed with ethylene amine and epichlorohydrin; they also possess reactive groups and cationic groups, which enable an improvement in soap wash fastness as well as in wet heat and chlorine fastness, although the degree of improvement for dyes with phthalocyanine structures is reduced. These three types of color fixatives are currently the auxiliaries that perform well in various factories. In addition, there are also condensates of dimethylamine or diethylenetriamine with epichlorohydrin; these offer only a modest increase in wash fastness and have gradually been phased out. The fixing processes for these types of color fixatives are basically similar. Manufacturers have very different requirements regarding color fixatives; aside from consistent wash fastness, some manufacturers place particular emphasis on wet ironing fastness, while others require chlorine resistance, and still others pay special attention to wet rubbing fastness. Unfortunately, these three types of color fixatives provide little improvement in wet rubbing fastness; enhanced post-dyeing soaping and washing using anti-stain agents are required to achieve a level of 2-3. 4. Finishing: Finishing is usually of a functional nature; the quality of the printed and dyed products varies depending on the additives used, and there are significant differences in the processing techniques as well. For example, 2D resins are commonly used for anti-wrinkle finishing, but due to the issue of formaldehyde release, non-formaldehyde finishing agents have been adopted instead. Currently, the most researched compounds are polycarboxylic acids such as BTOA, citric acid, acrylic acid, maleic acid, and other such carboxylic acid-based finishing agents. Research is also being done on silicone elastomers as well as compounds formed by the condensation of glyoxal and urea, but it remains difficult to replace 2D resins with these alternatives. The yellowing of BTCA after cellulose esterification can be resolved through chlorine bleaching, while the catalyst, hypophosphite, is relatively expensive. Flame-retardant finishing agents such as THPC, THPOH, Pyrovatex OP, and TMM result in extremely high levels of free formaldehyde when used for finishing; therefore, it is necessary to find flame-retardant agents that do not contain aldehydes. Although there are numerous patents on this topic, no commercial products are currently available. With the use of fluoropropionic acid polymers, the problem associated with water-repellent finishing agents based on hexamethylenetrimine has been largely resolved; unfortunately, more discussion on this topic is not possible.