Overview[1]
Sodium monofluorophosphate (“MFP” for short) is a white powdery solid with a melting point of about 626°C. It is easily soluble in water and has strong hygroscopicity. Its solubility in water at 25°C is 42%. There is no rusting effect. The pH value of 2% aqueous solution is 6.5 to 8.0. The aqueous solution undergoes slow hydrolysis when boiling, which can lead to a decrease in bound fluorine and an increase in free fluorine, so the purity is reduced. Acidic substances can catalyze the hydrolysis of MFP; in alkaline or very acidic solutions, or when there are cations that can form insoluble fluoride or low-solubility orthophosphate, the hydrolysis will be accelerated. Decahydrate can be obtained by crystallization from an aqueous solution at 0°C. If the crystal water is removed by heating, it will cause hydrolysis. Anhydrous sodium monofluorophosphate can be obtained by multiple extractions with ethanol or other organic solvents.
Apply[2]
Sodium monofluorophosphate is widely used and is mainly used in toothpaste additives, concrete corrosion inhibitors, food, medical treatment, etc.
1. Application in toothpaste
Sodium monofluorophosphate is the most widely used toothpaste additive in the world. It is an excellent anti-caries agent and tooth desensitizing agent. Its mass fraction in toothpaste is 0.7% to 0.8%. According to the ingredients contained, it is mainly divided into two categories: nursing toothpaste and biological toothpaste.
1) Nursing toothpaste: Nursing toothpaste has the functions of preventing caries, desensitizing, anti-inflammation, and preventing dental calculus. The developed Grass Coral full-effect nursing toothpaste has this multi-effect function. The most important thing for effective prevention and treatment of tooth and periodontal tissue diseases is to eliminate bacteria in the oral cavity that are harmful to dental health. Herbal plant extracts have been widely recognized in preventing and eliminating general inflammation of the gums and oral mucosa. The fluoride in Grass Coral Total Care Toothpaste has antibacterial and bactericidal properties. According to relevant research, low concentrations of fluoride ions (0.8% sodium monofluorophosphate in grass corals) have a good antibacterial effect. Fluoride is used as an anti-caries additive. It not only has a health-care effect on acid-resistant desensitization of teeth, but also interacts with tooth enamel to form fluoroapatite on the surface of tooth enamel, improving the hardness of tooth enamel.
2) Biological toothpaste: Biological toothpaste is to add substances with specific active functions to biological organisms into toothpaste. Currently, biological toothpaste mainly contains enzyme preparations, antibody preparations and other biologically active preparations. Toothpaste containing enzyme preparations mainly contains protease and glucanase. Proteolytic enzyme toothpaste can quickly hydrolyze and break the long protein polypeptide chains, softening the food residue attached to the tooth surface, making it easy to clean the mouth, and has the function of softening blood vessels, which can make inflammation and edema of the gums subside, and the phenomenon of tooth bleeding is obvious. Industrial additives are improved or eliminated.
Contains glucanase to help remove tartar. Toothpaste containing antibody preparations is generally divided into: toothpaste containing milk antibodies and toothpaste containing genetically modified preparations. Toothpaste containing milk antibodies extracts antibodies from milk and adds them to the toothpaste to fight against certain diseases. Toothpaste containing genetically modified antibody preparations is the product of human oral disease vaccine genes in genetically modified potato tubers added to the toothpaste, which can produce corresponding preventive effects on oral diseases. The fluorine in sodium monofluorophosphate is stable, and the fluorine content remains at 84.4% in PVC resin within one year, effectively ensuring the anti-caries effect; its pH value is 5.5 to 6.5, neutral; and it has good compatibility with abrasives. These advantages determine the single Sodium fluorophosphate is very suitable as a toothpaste additive and is now mass-produced in my country. The Beijing Department of Stomatology used fluoride toothpaste to observe the anti-caries effect for two and a half years and found that dental caries were reduced by 42.95%.
2. Application in food
1) Used as a food additive: From long-term clinical experiments, it is known that sodium monofluorophosphate is a better source of fluorine than other common fluoride raw materials (such as sodium fluoride). Sodium monofluorophosphate can be used as a food additive to increase food nutrition, but if it exceeds the standard, it is unsafe. Sodium monofluorophosphate is added to food, which can supplement 0.25 to 5 mg of fluoride every day, which is equivalent to the intake of 2.5 to 16 mg of sodium monofluorophosphate. According to data, it is unsafe to consume fluoride-containing sodium salt (1.7 to 14 mg) and phosphate (1.1 to 8.8 mg) every day. In Europe, the levels of additives in food are generally below maximum limits. For adults, if you consume 2mg of fluoride-containing food every day, it will not exceed the standard. Therefore, while we pay attention to sodium monofluorophosphate to enhance the nutritional value of food, we should also pay attention to its safety.
2) Used as chewing gum raw material: Chewing gum has always been favored by the public. However, the current chewing gum does not have health care functions such as preventing caries, desensitizing, bacteriostatic and sterilizing, and preventing colds. Although general medicated toothpaste has one or more functions, it cannot replace the chewing function and taste of chewing gum. In 1998, Li Guohua developed a chewing gum with multiple functions. This chewing gum was added with 0.5% sodium monofluorophosphate, so it had a good anti-caries effect.
3. Application in medical treatment
1) Used to regulate menopause: Women’s blood lipids and lipoprotein metabolism Sodium monofluorophosphate can be used to regulate the blood lipids and lipoprotein metabolism of menopausal women.
2) Used to increase bone mass and alleviate osteoporosis: Sodium monofluorophosphate promotes the differentiation and proliferation of osteoblasts and increases bone mass. This effect is caused by the fluorine in acid phosphatase that inhibits growth. produce. MFP can exert its function through other signaling mechanisms. Although sodium fluoride also has the function of increasing bone mass, when consuming the same amount of MFP and NaF, MFP increases bone mass more. Sodium monofluorophosphate can increase bone mass and alleviate osteoporosis, but it cannot change the mineralization of bone tissue.
4. Used as corrosion inhibitor�When steel corrodes, a range of protection and repair methods can strengthen the concrete structure, with corrosion inhibitors being the most attractive replacement. MFP acts as a rust inhibitor to slow down the corrosion of steel bars.
Preparation[1, 3]
There are many preparation methods for sodium monofluorophosphate, but they are mainly divided into three categories: ①melting method and molten salt process; ②liquid phase neutralization method; ③vapor phase fluorination method. Among them, the melting method is a more traditional and commonly used method, both in terms of research focus and industrial application status. The various processes will be introduced and compared in more detail below.
1. Melting method: The melting method mainly refers to the use of sodium metaphosphate (or ortho, pyro, sodium polyphosphate, etc.) and sodium fluoride as raw materials. After pretreatment such as drying and mixing, it is heated in a reactor made of special materials ( Generally, platinum, graphite, silver, platinum-rhodium alloy, etc. are used as the lining) and heated to 600-800°C in the molten state to react to obtain sodium monofluorophosphate. The process flow is shown in the figure.
The melting process was first developed and patented by Carl O. Anderson and others in 1947 (Patent No. US2481807), and commercial production began in 1949 by Ozark-Mahoning Company. This process uses sodium metaphosphate and sodium fluoride as raw materials, and heats and melts them in a closed platinum container at a temperature of 650 to 800°C. After cooling, the finished product of sodium monofluorophosphate is obtained, with a purity of nearly 100%. The reaction formula is:
2. Liquid phase neutralization method: American Hans-Walter Swidersky et al. obtained a patent in 1995 (US5393506), and proposed the use of liquid phase neutralization method to prepare monofluorophosphate M2PO3F (M refers to the first main group metal in the periodic table cation, such as Na+). The process is shown in the figure:
This method uses phosphoric acid, hydrofluoric acid, sodium carbonate or sodium hydroxide as raw materials for liquid phase neutralization. As the neutralized liquid evaporates, concentrates, crystallizes, and dries, the sodium monofluorophosphate product can be obtained. However, because fluorophosphoric acid is extremely corrosive, it requires special equipment structure and materials, and the production process is difficult to control. The investment in production equipment is high, and the corrosion products can easily introduce impurities into the product.
Main reference materials
[1] Preparation method of sodium monofluorophosphate
[2] Analysis of the application status of sodium monofluorophosphate
[3] Research on new preparation process of sodium monofluorophosphate
Strong, it has special requirements for equipment structure and materials, and the production process control is difficult. The investment in production equipment is high, and corrosion products can easily introduce impurities into the product.
Main reference materials
[1] Preparation method of sodium monofluorophosphate
[2] Analysis of the application status of sodium monofluorophosphate
[3] Research on new preparation process of sodium monofluorophosphate
