Recently, biodegradable plastics are very popular, and various levels of plastic ban orders have been introduced. As one of the main types of biodegradable plastics, PLA is naturally a rising tide lifting all boats. As the intermediate raw material of PLA two-step production, lactide is in short supply.

I. Introduction of PLA materials

PLA is short for Polylactic Acid, its full English name is Polylactic acid or Polylactide, which is the product of α-hydroxypropionic acid condensation and belongs to a kind of thermoplastic aliphatic polyester.

The emergence of PLA was derived from the direct condensation of lactic acid in vacuum by Dupont scientist Wallace Carothers in 1932. Due to the low molecular weight of the resulting polymer and the high production cost, it could not be commercially produced at that time.

It was not until 1987 that the food company Cargill began to invest in the research and development of a new PLA manufacturing process, and in 2001, Cargill established NatureWorks, a joint venture with Dow, for commercial production of PLA, that PLA officially entered into every aspect of our lives in large numbers.

Ii. PLA material synthesis technology

1. Preparation of PLA monomer raw materials

PLA's monomer raw material is lactic acid, which is generally ground corn and other shell crops, from which starch is extracted, and then the starch is made into unrefined glucose. The glucose is then fermented in a process similar to beer or alcohol production, and the lactic monomers are purified.

2. Polymerization method of PLA

There are two main synthesis methods of PLA, namely direct lactic acid polycondensation and lactide ring opening polymerization (also known as two-step method). The two-step method is commonly used. The process is to first produce lactide (LA) by decompression distillation of lactic acid, and then use lactide as monomer to prepare PLA under the conditions of initiator, high temperature and high vacuum for several hours.

Iii. Material properties and processing technology of PLA

PLA is light yellow transparent solid, good thermal stability, processing temperature 170 ~ 230℃, has good solvent resistance, can be processed in a variety of ways, such as extrusion, spinning, biaxial stretching, injection blow molding.

Fourth, the application of PLA

Polylactic acid (PLA) is a new kind of biodegradable material, suitable for extrusion, injection molding, film drawing, spinning and other processing methods, easy processing, so it can be used in food packaging, fast food lunch boxes, non-woven fabrics, industrial and civil fabrics, agricultural fabrics, 3D printing and other fields. PLA materials in food packaging and tableware applications accounted for more than 66%, followed by medical and personal care, accounting for 28%.

Five, the current mainstream PLA resin synthesis manufacturers inventory

Although the annual production capacity of polylactic acid in the world is more than 250,000 tons at present, according to the market situation, it is basically in a state of short supply, 40,000 yuan/ton can not get the goods.