Regarding chlorocyanuric acid products

This is some information I’ve found, which I’d like to share with you first. Sodium dichloroisocyanurate (abbreviated as NaDCC) is one of the important types of chloroisocyanurate products; it is also known as wool treatment agent DC or Opticlor. Its scientific name is sodium 1,3-dichloro-1,3,5-triazine. It appears as white powdery crystals with a slight chlorine odor. Its molecular formula is C3Cl2N3NaO3, with a molecular weight of 129.95. The theoretical effective chlorine content is 64.5%. Its melting point is 230–235°C (at which point it decomposes). At 25°C, 25 g of this substance can dissolve in every 100 ml of water. The pH value of a 1% aqueous solution is 6.5. The bulk density of the powdered form is 0.50–0.65 g/cm3, while that of the granular form is 0.90–0.96 g/cm3； When sodium dichloroisocyanurate crystals contain 2 molecules of crystal water, it is called sodium dichloroisocyanurate dihydrate (abbreviated as NaDCC•2H2O); its theoretical effective chlorine content is 55.4%, and its stability is greater than that of sodium dichloroisocyanurate without crystal water. Sodium dichloroisocyanurate can react with ammonia, ammonium salts, amides, and anilines at room temperature to release NCl3 gas; it can also undergo chemical reactions with metal oxides and acids, making it a relatively reactive strong oxidizing agent. 　　Sodium dichloroisocyanurate is a widely used, broad-spectrum, highly effective, and low-toxicity disinfectant and bactericide. It has a variety of applications in areas such as swimming pool disinfection, tableware disinfection, aquaculture disinfection, silkworm rearing disinfection, water treatment, industrial bleaching, wool shrinkage prevention, and cleaning products. It represents an ideal replacement for traditional disinfection agents such as sodium hypochlorite, bleaching powder, and chlorine bleach, offering great prospects for further development and utilization. 1 Production methods The main raw materials for producing sodium dichloroisocyanurate are cyanuric acid, caustic soda, and chlorine. The primary production methods include the neutralization method using dichloroisocyanurate, the sodium hypochlorite method, and the combined decomposition of trichloroisocyanurate. 1.1 Neutralization method using dichloroisocyanuric acid: First, cyanuric acid is mixed with caustic soda in a ratio of 1:2 (molar ratio) to form disodium cyanurate, which is then subjected to a chlorination reaction using chlorine gas to produce a dichloroisocyanuric acid slurry; centrifugation is used to separate out the wet dichloroisocyanuric acid ； It is then added to the sodium dichloroisocyanurate mother liquor, and caustic soda is added dropwise in a 1:1 molar ratio to carry out a neutralization reaction. After the reaction is complete, cooling, crystallization, and filtration yield wet sodium dichloroisocyanurate, which is dried to produce sodium dichloroisocyanurate or its dihydrate form. 　　The main advantages of the dichloroisocyanuric acid method are: (1) it enables the co-production of dichloroisocyanuric acid and sodium dichloroisocyanurate, with dichloroisocyanuric acid also being an important type of chloroisocyanuric acid derivative that can be used as a disinfectant ； (2) High product quality. Since the solubility of dichloroisocyanuric acid in water is only 0.7%, the sodium chloride produced as a byproduct of the reaction can be easily washed away, and no other impurities are formed during the neutralization reaction; as a result, the product has a high purity and low salt content ； (3) Lower raw material consumption. The disadvantages are: (1) Dichloroisocyanuric acid is highly corrosive, which requires high levels of corrosion resistance from the reaction vessels and centrifuge equipment, resulting in relatively high investment costs for such equipment ； (2) The absorption of chlorinated exhaust gases produces a significant amount of sodium hypochlorite as a by-product. 1. Sodium hypochlorite method 1.2.1 Low-concentration sodium hypochlorite method: Chlorine reacts with caustic soda to produce an aqueous solution of sodium hypochlorite at a concentration of 10%~11%; this sodium hypochlorite then undergoes a chlorination reaction with cyanuric acid to yield sodium dichloroisocyanurate and sodium chloride as products. To control the pH value during the reaction process, chlorine can be added to ensure full utilization of the reaction materials. However, since chlorine is required for the chlorination reaction, strict controls are necessary over the cyanuric acid raw materials and the operating conditions of the reaction; otherwise, nitrogen trichloride explosions may occur ； It is also possible to use inorganic acids (such as hydrochloric acid) for neutralization; this method does not involve chlorine directly in the reaction, making it easy to control, but it does not make full use of the sodium hypochlorite raw material. The chemical reaction equation is as follows: Or it can be expressed as follows: A 10%-12% sodium hypochlorite solution contains 7%-8% sodium chloride; the sodium hydroxide produced as a result of the reaction between sodium hypochlorite and cyanuric acid is also converted into sodium chloride. The high sodium chloride content in sodium dichloroisocyanurate slurry leads to a high sodium chloride content in the filter cake. If the salt is not removed by washing, the product quality will be poor. To remove sodium chloride from the filter cake, plain water cannot be used for washing; only a saturated aqueous solution of sodium dichloroisocyanurate can be employed. Both the mother liquor and wash liquid obtained after filtering sodium dichloroisocyanurate need to be treated; otherwise, the consumption of product will be high. The common method for treating the mother liquor is to add acid; sodium dichloroisocyanurate reacts with the acid to form a dichloroisocyanuric acid slurry, which is then filtered to isolate dichloroisocyanuric acid. Dichloroisocyanuric acid can be directly dried to obtain the product, or it can be mixed with water to form a slurry, and then neutralized with an alkali to yield sodium dichloroisocyanurate. The sodium dichloroisocyanurate solution obtained through neutralization can be used as a washing liquid for the salt-containing filter cake. Mother liquor and washing liquid can also be chlorinated to produce trichloroisocyanuric acid. The advantage of this process is that the reaction takes place in a nearly neutral solution, so there are no high requirements regarding the material of the equipment; ordinary enamel-lined equipment and stainless steel centrifuges can be used ； No nitrogen trichloride is generated, making the production process relatively safe. The downside is that the quality of the product is slightly poor; it generally contains 3%–4% sodium chloride, and the effective chlorine content in the dried product is only around 60% ； The amount of mother liquor is large; if the sodium dichloroisocyanurate filter cake is not washed, the purity of the product will be low ； The mother liquor contains a high amount of sodium dichloroisocyanurate; due to its high salt content, it cannot be recycled, which results in higher raw material consumption ； When using chlorine to neutralize the caustic soda produced by the reaction between cyanuric acid and sodium hypochlorite, the amount of chlorine applied must be precisely measured; it cannot be excessive, otherwise trichloroisocyanuric acid will be formed. Since this process consumes large amounts of sodium hypochlorite solution, it can be used in chlor-alkali plants that generate significant quantities of sodium hypochlorite as a by-product for production purposes. To address the problems existing in the production of this process, the following methods are currently primarily used to improve the production process, thereby enhancing product quality and reducing raw material consumption. (1) High-concentration sodium hypochlorite (such as 25%~30%) is used to produce sodium dichloroisocyanurate, which helps reduce the salt content in the product and improves its quality ； (2) Utilize the sodium dichloroisocyanurate mother liquor to produce trichloroisocyanurate, thereby improving the utilization rate of raw materials. 2.2.2 High-concentration sodium hypochlorite method: After sodium chloride is separated from sodium hypochlorite with an effective chlorine content of 23%-25%, the salt content is only 5%-7%. The method of producing sodium dichloroisocyanurate by reacting such sodium hypochlorite with cyanuric acid is known as the high-concentration sodium hypochlorite method. The advantage of using high-concentration sodium hypochlorite to produce sodium dichloroisocyanurate is less mother liquor and a lower salt content in the filter cake. High-concentration sodium hypochlorite cannot be produced by directly introducing chlorine into high-concentration liquid alkali, as the high viscosity of such liquid alkali hinders the formation of sodium chloride crystals; as a result, fine sodium chloride crystals are formed and it is difficult to separate them from the sodium hypochlorite solution. High-viscosity liquid caustic also affects the dispersion of chlorine in the solution, leading to localized hyperchlorination that causes the generated sodium hypochlorite to decompose, thereby reducing the yield. To produce high-concentration sodium hypochlorite, 25% caustic soda must first be reacted with chlorine, with the pH value being carefully controlled, to obtain sodium hypochlorite at a concentration of 190 g/L. Next, 50% caustic soda is added, mixed and chlorine is introduced; the precipitated sodium chloride is separated, thereby obtaining sodium hypochlorite with an effective chlorine content of 25%. 1.3 Double-displacement method using trichloroisocyanuric acid: Cyanuric acid and sodium hydroxide are combined in a ratio of 1:3 (molar ratio) to form trisodium cyanurate, which is then chlorinated with chlorine at a certain temperature; subsequent centrifugal filtration yields wet trichloroisocyanuric acid ； It is then subjected to a double displacement reaction with cyanuric acid and sodium hydroxide solution in a molar ratio of 2:1:3, at a temperature of 30–40°C. After cooling, crystallization, filtration, and drying, the sodium dichloroisocyanurate product in powder form is obtained. 　　The advantages of the triple chloride isocyanuric acid double-displacement method are: (1) it enables the simultaneous production of two main types of chloroisocyanuric acid products, namely triple chloride isocyanuric acid and sodium dichloroisocyanurate, and the production volume of these two products can be adjusted as needed based on market demands ； (2) In double-displacement reactions, a 50% sodium hydroxide solution is used, which allows the entire amount of dichloro mother liquor to be reused without any discharge, resulting in minimal environmental pollution ； (3) The reaction yields are high, the product quality is good, and the salt content is low; the effective chlorine content in sodium dichloroisocyanurate products can reach over 62%, while that in the dihydrate form can also reach 55% ； (4) The synthesis of trichloroisocyanuric acid can employ a continuous chlorination process, ensuring safe and reliable production ； The disadvantages are: (1) The process for synthesizing trichloroisocyanuric acid requires high-performance reaction and centrifugation equipment, resulting in high capital investment ； (1) In the production of trichloroisocyanuric acid, the chlorination off-gases contain large amounts of unreacted chlorine gas; this gas is generally absorbed using sodium hydroxide to produce sodium hypochlorite, resulting in a significant amount of sodium hypochlorite as a by-product. Foreign manufacturers of sodium dichloroisocyanurate generally use this process technology for production. 　　The three sodium dichloroisocyanurate production methods mentioned above are all employed by manufacturers of this product in China. Each of these methods has its own characteristics; when comparing them in terms of product structure, quality, consumption, and the versatility of the equipment used, the production process that involves co-producing sodium dichloroisocyanurate from trichloroisocyanuric acid is currently the most advanced method for manufacturing sodium dichloroisocyanurate. 2 Domestic and International Production Status Research and development of chloroisocyanuric acid-based products began in the 1950s, with the first industrial production facility coming online in the United States in 1962. Since then, many research institutions and manufacturers have conducted in-depth technical studies on the production technology of cyanuric acid, the main raw material for such products, as well as the process of chlorinating cyanuric acid. They developed various viable industrial production methods and built their own industrial facilities for production. It was not until the early 1980s, when industrial production facilities for producing trichloroisocyanuric acid along with sodium dichloroisocyanurate were successfully developed, that the chlorination process of cyanuric acid became continuous, safety issues in production were resolved, and the yield of the products improved; only then did chloroisocyanuric acid-based products truly see development. 　　There are over 20 manufacturing plants, with the main ones including Jiangsu Changzhou Chemical Factory (with a production capacity of 10kt/a), Hebei Jiheng Group Co., Ltd. (with a production capacity of 3kt/a), Tengzhou Yinfeng Chemical Co., Ltd. (with a production capacity of 2kt/a), Jiangsu Xuzhou Kweisi Disinfectant Co., Ltd. (with a production capacity of 2kt/a), Liaocheng Chemical Factory of Shandong Luxi Chemical Group Corporation (with a production capacity of 2kt/a), Shandong Linju County No.1 Chemical Factory (with a production capacity of 1.5kt/a), and Hebei Shijiazhuang Synthetic Chemicals Corporation (with a production capacity of 0.5kt/a), among others. 3 Applications 3.1 Wool shrinkage prevention agents: Aqueous solutions of sodium dichloroisocyanurate can release hypochlorous acid in a uniform manner, which reacts with the protein molecules in the wool scales, breaking some of the bonds within these protein molecules and thereby preventing shrinkage. Furthermore, treating woolen products with a sodium dichloroisocyanurate solution also prevents sticking during washing of the wool, that is, the occurrence of \"pilling\". Wool that has been treated to prevent shrinkage shows almost no shrinkage, has a vibrant color, and a pleasant texture ； Immerging wool or wool-blended fibers and fabrics in a 2%~3% sodium dichloroisocyanurate solution along with other additives can prevent wool and its products from pilling or felting. Typical formulations include: (1) 0.5 parts by mass of sodium dichloroisocyanurate, 0.15 parts of acetic acid, 0.02 parts of a wetting agent, 600 parts of water, and 200 parts of woolen fabric; the soaking time at room temperature is 0.5 hours ； (2) 0.5 parts of sodium dichloroisocyanurate, 0.15 parts of peracetic acid, 0.02 parts of wetting agent, 600 parts of water, and 200 parts of woolen fabric. 3.2 Bleaching in the textile industry In the textile industry, sodium dichloroisocyanurate is primarily used as a bleaching agent for natural and synthetic fibers. The bleaching of natural and synthetic fibers involves destroying the pigments contained in the fibers. Sodium dichloroisocyanurate produces hypochlorous acid in water; this hypochlorous acid can undergo an addition reaction with the conjugate bonds of the chromophoric groups in the fibers, altering the wavelength at which the fibers absorb light and destroying the pigments within them, thereby achieving the purpose of bleaching. Compared to traditional bleaching agents, sodium dichloroisocyanurate has many unique advantages. For example, while conventional bleaching agents need to be used at high temperatures, such high temperatures increase the erosive effect of the bleaching agent on fibers and reduce their strength; whereas sodium dichloroisocyanurate can achieve good bleaching results even at lower temperatures ； Furthermore, bleaching natural and synthetic fibers with sodium dichloroisocyanurate not only yields good bleaching results with minimal damage to the fibers, but it also improves their tensile strength and elongation. For cotton fabrics, it helps to remove cotton linters, enhance water affinity, and prevent cellulose degradation. 3.3 Sterilization and Disinfection in Aquaculture 3.3.1 Sterilization and Disinfection in Sericulture Silkworms are highly susceptible to pests, diseases, and bacteria; without proper care, they can easily die. Sodium dichloroisocyanurate is an excellent disinfectant for silkworm rearing areas, equipment, and the silkworms themselves. By spraying or fumigating with a water solution of sodium dichloroisocyanurate, or with a disinfectant formulated using sodium dichloroisocyanurate along with stabilizers and accelerants, it is possible to disinfect the rearing areas, equipment, and silkworms, thereby preventing silkworm diseases. It not only has a strong killing effect on the pathogens of viral, fungal, bacterial, and protozoal diseases in silkworms, but also exhibits significant efficacy against agents such as gastrointestinal pyoplasma, gastrointestinal pyovirus, and hemagglutinating pyoplasma. Compared with the disinfectants currently used for silkworms, it features rapid dissolution, good stability, a long duration of efficacy, and no adverse effects on the growth and development of silkworms or their quality; it is thus one of the best disinfectants for the silkworm farming industry today. 3.3.2 Sterilization and disinfection in aquaculture: Sodium dichloroisocyanurate is effective in preventing and treating fish diseases caused by bacteria, fungi, and algae; it also shows significant efficacy against viral diseases in fish. It can be used for cleaning ponds, disinfecting fish fry, disinfecting water bodies, and disinfecting fishing equipment in aquaculture practices involving various species of fish, shrimps, river crabs, bullfrogs, etc. 3.4 Additives for cleaning products: Sodium dichloroisocyanurate can be used as an additive in household dry bleach, bleaching laundry powder, scouring powders, and dishwashing liquids. It serves to bleach and sterilize, enhancing the functionality of these cleaning products; it is particularly effective in removing proteins and fruit juices. 3.5 Civilian hygiene and disinfection: When disinfecting tableware, add 400–800 mg of sodium dichloroisocyanurate per 1 L of water; soaking for 2 minutes is sufficient to eliminate E. coli completely. After 8 minutes, the elimination rate of bacilli can reach over 98%, and 15 minutes is enough to completely destroy the surface antigen of hepatitis B virus. In addition, sodium dichloroisocyanurate can also be used for disinfecting the surfaces of fruits and poultry eggs, as well as for sterilizing and deodorizing refrigerators and toilets. 3.6 Disinfection of swimming pool water: If the water in a swimming pool is not disinfected, germs can easily multiply. A layer of slippery and dirty microbial algae adheres to the pool walls, and the water takes on an unpleasant odor. Swimmers find these slippery algae annoying, and contaminated water can cause infections in swimmers; in mild cases this leads to skin infections, while in more severe cases it can affect the eyes and respiratory organs. By adding sodium dichloroisocyanurate to the swimming pool water, not only does the water become blue, clear, and shiny, with smooth pool walls free from any deposits, allowing swimmers to feel comfortable, but it is also harmless to the human body at the used concentrations. It has a high efficiency in killing bacteria, which is very beneficial for protecting people’s health. 3.7 Drinking water disinfection: Sodium dichloroisocyanurate, when used in drinking water, can effectively kill various algae and microorganisms, as well as eliminate the color and odor caused by pollutants such as hydrogen sulfide in the water. At a concentration of 2×106, the killing rate against E. coli, osteomyelitis virus, dysentery pathogens, hepatitis viruses, and others can reach 100%. 3.8 Industrial circulating water treatment: Many industrial sectors (such as thermal power plants, oil refineries, chemical plants, etc.) require large amounts of cooling water to remove the heat generated during manufacturing processes. In various equipment such as heat exchangers, condensers, circulation pipes, cooling towers, and pump systems, rapid algae growth leads to the accumulation of significant amounts of dirt. Treating cooling water with fungicides is one of the very effective methods, among which sodium dichloroisocyanurate is an important fungicide. Sodium dichloroisocyanurate is used in industrial circulating water treatment systems. As an important component of water treatment agents for industrial cooling towers, it can effectively prevent the growth of algae and microorganisms, does not cause corrosion to industrial equipment, and helps maintain the water quality in the circulating water system for an extended period of time. 3.9 Food industry and cleaning and disinfection in public places: Sodium dichloroisocyanurate is being used increasingly widely in the fields of cleaning and disinfection in food processing plants, dairy processing plants, beer factories, and soft drink manufacturers. Not only must the equipment used in the production and processing processes (storage tanks, pipes, containers, utensils, tools, equipment, and work areas) be cleaned and disinfected, but also the utensils in cafes, ice cream shops, tea houses, restaurants, and buffets (trays, plates, bowls, tablecloths, towels, etc.) should frequently be cleaned and disinfected using sodium dichloroisocyanurate. This is done to prevent the spread of diseases, eliminate stains, mold, and unpleasant odors caused by proteins, and to maintain the shine of the utensils. In these fields, sodium dichloroisocyanurate is often used in combination with phosphates, silicates, surfactants, acid salts, basic salts, and neutral salts to enhance its ability to chelate calcium, its control over water hardness, its cleaning power, as well as its acidity or alkalinity. The amounts of active chlorine and other compounds required for cleaning and disinfection products vary; given specific conditions, different combinations of formulations can be selected. The cleaning of tableware requires high detergency, sterilization capability, water softening ability, and a certain dissolution rate, while also protecting metals from corrosion. Typical formulations include: 3.5% sodium dichloroisocyanurate (by mass, the same below), 30% sodium tripolyphosphate, 5%–10% hydrated sodium silicate, 5% cationic surfactant, and an appropriate amount of soda ash. In general use, the effective chlorine concentration in the solution is kept between 7.5×10-5 and 10×10-5; in important applications, this concentration can be increased to 2×10-4. Typical formulations include: (1) 25% sodium dichloroisocyanurate (by mass), 15% sodium silicate, 5% soda ash, 10% sodium bicarbonate, and 20% trisodium bicarbonate ； (2) Sodium dichloroisocyanurate 6%, sodium tripolyphosphate 36%, sodium silicate 8%, sodium sulfate 50%, with an effective chlorine content of 3.3%. For cotton fabrics used in hotels and restaurants, such as pillowcases, towels, bed sheets, tablecloths, and other items, the disinfection formula is as follows: sodium dichloroisocyanurate at 18% (by weight), sodium tripolyphosphate at 20%, sodium dodecylbenzenesulfonate at 3%, sodium sulfate at 34%, sodium carbonate at 25%, and 10% effective chlorine. The disinfection formula under alkaline conditions is: sodium dichloroisocyanurate 25% (by mass, the same below), trisodium phosphate 10%, sodium sulfate 65%, and available chlorine 13.9 ； The washing and disinfection formula under acidic conditions is: sodium dichloroisocyanurate 28% (by mass, the same below), sodium sulfate 42%, sodium hydrogen phosphate 30%, and available chlorine 15.5% ； Neutral cleaning and surface disinfection formula: sodium dichloroisocyanurate 34%~40% (by mass, the same below), sodium sulfate 60%~66%, available chlorine 18.9%~22.4%. Li Jiguo. Research on the synthesis process of sodium dichloroisocyanurate. Journal of Shenyang Institute of Chemical Technology (Natural Sciences Edition), 1998, 12. Xu Yanfeng. Production and applications of sodium dichloroisocyanurate. China Chlor-Alkali, 2002, 2: 28–31. Lu Zeyao. Production and applications of chloroisocyanurate-based products. Shijiazhuang Chemical Industry, 1997, 3: 18–22. Shao Ming, Yang Wenwei, Ge Min. Properties and applications of chloroisocyanurates. Chlor-Alkali Industry, 1999, 8: 27–29.

Table 1: Some domestic manufacturers of chlorinated isocyanuric acids (information from the Internet)
Manufacturer | Cyanuric acid (tons/year) | Sodium dichloroisocyanurate (tons/year) | Trichloroisocyanuric acid (tons/year)
Liaocheng Aile Chemical Disinfection Co., Ltd. | 5,000 | 5,000 | 3,000
Liaocheng Zhonglian Industrial Co., Ltd. | 8,000 | 12,000 | 6,000
Heze Huayi Chemical Co., Ltd. | 20,000 | 8,000 | 15,000
Juancheng Kangtai Chemical Co., Ltd. | 8,000 | 6,000 | 6,000
Juancheng Mingjiang Chemical Co., Ltd. | 5,000 | 6,000 | 4,000
Juancheng Eurasia Chemical Co., Ltd. | 20,000 | 6,000 | 3,000
Juancheng Shengheng Chemical Co., Ltd. | 10,000 | 6,000 | 4,000
Suzhou Saidefu Chemical Co., Ltd. | 6,000 | 3,000 | 6,000
Handan Guangzheng Disinfectant Co., Ltd. | 10,000 | 4,500 | 5,000
Tai’an Huawei Disinfectant Co., Ltd. | 25,000 | 9,000 | 6,000
Guangwei Disinfectant Co., Ltd. | 9,000 | 10,000 | 8,000
Jinfulai (Handan) Chemical Co., Ltd. | 10,000 | 5,000 | 10,000
Jiangsu Shenan Fine Chemical Co., Ltd. | 12,000 | 3,000 | 3,000
Jiangsu Jiangdong Chemical Co., Ltd. – | 10,000 | 20,000
Hebei Kongxiang Chemical Group Co., Ltd. | 15,000 – | 3,000

Our company produces chloroisocyanuric acid products. This product is an excellent item in the chlor-alkali industry chain, as it makes use of both chlorine and alkali. However, due to anti-dumping measures in Europe and the United States, exports have been low in recent years. At present, the biggest issue with this product is environmental protection; there is still no effective solution for dealing with the large amount of high-concentration saline wastewater it generates.

This product is best manufactured by the sea, where the saline wastewater can be discharged directly into the ocean or into salt pans for evaporation. Inland areas can also be used for salt production, but special design is required. The ideal design is to refine the brine with P and then electrolyze it again to produce chlorine and caustic soda, thereby achieving a circular production process with no waste emissions. Feel free to continue the discussion: P