Application of Lactic Acid in Chemical Industry

Lactic acid, also known as 2-hydroxypropionic acid, is a light yellow thick liquid with strong acidity and hygroscopicity. It is widely used in medicine, food, leather, cigarettes, chemical industry, printing and dyeing and other industries. It is recognized as the three major organic acids in the world. One of them can be produced from starchy substances by fermentation or chemical synthesis.

Lactic acid is a hydroxycarboxylic acid with a hydroxyl group and a carboxyl group in the molecule, so it can carry out the typical reaction of these two functional groups to produce a series of lactic acid derivatives such as lactate, lactate, lactic acid amide and their polymers . This paper focuses on the properties and applications of several important lactic acid derivatives and lactic acid polymers.

1 Lactic acid derivatives

1.1 Calcium Lactate

Calcium lactate is white or off-white crystalline granules or powder.The molecular formula is C₆H₁₀CaO₅·5H₂O, the molecular weight is 308.40, non-toxic and odorless, easily soluble in hot water, insoluble in alcohol, and loses crystal water at 120°C.The product can be obtained by reacting 80% lactic acid with calcium oxide (or calcium carbonate), and the content of calcium lactate is >98%.

Another method is to add calcium phosphate as a neutralizing agent during lactic acid fermentation to obtain crude calcium lactate, and then refine it to obtain finished calcium lactate.

Calcium lactate is a newly developed calcium nutrition enhancer. Widely used in food and pharmaceutical industries. As a calcium nutrition enhancer, it can be used in bread, milk powder, tofu, sauce, pickles, etc.

1.2 Ferrous lactate

Ferrous lactate is light green or yellow crystalline powder or crystal block, its molecular formula is C₆H₁₀FeO₆ 3H₂O, its molecular weight is 288.04, it has a special odor and slightly sweet rusty smell, it is soluble in water and slightly soluble in ethanol, and it needs to be stored away from light in an airtight container.

Ferrous lactate is mainly used as an iron fortifier for food (such as flour, milk powder, biscuits, etc.). Using iron-fortified food or beverage is the most effective, convenient and economical way to prevent and treat iron deficiency anemia. It is used in medicine as a drug for treating anemia. Ferrous lactate can also be used as a feed iron fortifier.

1.3 Ethyl lactate

Ethyl lactate is a colorless volatile liquid with a special aroma of rum, fruit and cream. The molecular formula is C₅H₁₀O₃, the molecular weight is 118.13, and the specific gravity is 1.042 (14/4°C, boiling point 154°C, flash point 46°C, miscible in Water, alcohols, ketones, ethers, chloroform and oils.

Ethyl lactate is one of the commonly used food spices. It can be used to prepare rum, milk, cream, grape, fruit wine, coconut flavor, ethyl lactate is also used as a solvent for nitrocellulose and cellulose acetate, an advanced solvent for artificial pearls, and pharmaceuticals. Lubricants for industrially compressed pharmaceutical tablets.Used as a flavoring agent in the feed industry.

1.4  Butyl lactate

Butyl lactate is a water-white stable liquid with a sweet creamy and milky aroma. The molecular formula is C₇H₁₄O₃, the molecular weight is 146.22, the specific gravity is 0.974~0.984 (20/20°C), the boiling point is 188°C, and the melting point is -49°C. It is slightly soluble in water and miscible In various paint solvents and vegetable oils.

As a high boiling point solvent, butyl lactate has a very high allowable limit for non-solvents and thinners. It can be used as a solvent for nitrocellulose, ethyl cellulose and alkaline pigments. It can be used in dry printing inks and spray paints to provide coatings Good flow and appearance quality. Butyl lactate can also be used as a food flavor in dairy products, cheese, and butter.

Lactic acid polymer has become the focus of development and production in the world today because of its biodegradability. Therefore, the development and production of the above-mentioned products will play a positive role in increasing new chemical products, broadening the application field of lactic acid, making more effective use of my country’s rich crop resources, and promoting the development of my country’s lactic acid industry.