System and method for industrially producing PGA product

Abstract

The invention discloses a system and a method for industrially producing a PGA product. The system comprises a polymerization reaction unit and a solvent treatment unit, the polymerization reaction unit comprises a PGA storage tank, a polymerization reactor, a PGA devolatilization device, a PGA crystallizer, a PGA melter, a PGA cold-set granulator and a PGA packaging stacker which are connected insequence according to a material conveying direction; and the solvent treatment unit comprises a solvent recovery tower, a solvent regenerator and a solvent refining tower. According to the system, the glycolide raw material is used for producing the PGA product, meanwhile, the solvent recovery tower, the solvent regenerator and the solvent refining tower are arranged to treat the solvent and recycle the solvent; a PGA molten material and a cooling water are subjected to indirect heat exchange, so that direct contact can be avoided, and the PGA loss is reduced. According to the system and method, the phenomenon of PGA granule product loss caused by hydrolytic degradation of the PGA in the production process is avoided, the total yield of the PGA product is increased from 73.80-75.60 wt% to 74.00-76.60 wt%; and the system and method can be applied to large-scale continuous production of PGA.

Description

technical field [0001] The invention relates to the industrial production of polyglycolide products, in particular to a system and method for producing polyglycolide products, which are degradable materials, using glycolide as a raw material through steps such as polymerization, devolatilization, and granulation. Background technique [0002] Polyglycolide, also known as polyglycolic acid, English abbreviation PGA, under high temperature and low pressure reaction conditions, using metal organic compounds or Lewis acids as the main catalyst, C3-C7 alcohols as co-catalysts, ethanol as molecular weight and reaction rate control agent, the glycolide raw material is subjected to a two-step polymerization reaction to generate polyglycolide / polyglycolic acid / PGA products. Its products mainly include low molecular weight PGA products and high molecular weight PGA products. The PGA product is a linear aliphatic polyester with a regular linear molecular structure, high crystallinity,...

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Problems solved by technology

In addition, the present invention can adopt the usual solution polymerization method, by controlling the polymerization reaction temperature to 20-110°C, and the polymerization reaction time to 20-720 minutes, 2.16-4.47 grams of polyglycolide finished product can be obtained after the polymerization reaction, and the yield is 67.3- 98.1wt%, molecular weight 13,000-276,000, the polymerization reaction process is simple, the molecular weight of the polymer can be adjusted, the selectivity is wide, and the molecular weight distribution of the obtained polymer is narrow, with excellent physical and chemical properties, but it is only a laboratory scale, intermittent The method of preparing polyglycolide products, the polymerization reaction takes 20-720 minutes to obtain 2.16-4.47 grams of polyglycolide. Once applied to large-scale continuous industrial polyglycolide production equipment, there is a problem of "amplification effect"

The invention patent with the application number CN202010625774.9 discloses a rotating cylinder water cooling device, including a mounting frame, a first cylinder is fixedly connected to the mounting frame, a second cylinder is sleeved in the first cylinder, and the first cylinder A pipe group structure is sleeved between the second cylinder body, the top of the first cylinder body is provided with a water tank, the bottom of the water tank is provided with a first water spray hole, the bottom of the first cylinder body is provided with a water collection tank, and the second cylinder body Connected to the water supply source, the outer wall of the second cylinder is provided with a second water spray hole; the pipe group structure includes two symmetrically arranged liquid distribution boxes, and the two liquid separation boxes are respectively connected with the first hollow shaft and the second hollow shaft. One hollow shaft is connected to the liquid inlet rotary joint, and the second hollow shaft is connected to the liquid discharge rotary joint. There are several connecting pipes on the side of the liquid distribution box, and a heat dissipation pipe is connected between the connecting pipes facing each other on the two liquid distribution boxes. Thus greatly improving the utilization rate of cooling water and improving heat dissipation efficiency, but the device is provided with a first water spray hole and a second water spray hole, and the cooling water is in contact with polyglycolide, which is prone to degradation reactions. It is a hydrolysis degradation reaction. Water molecules are particularly easy to attack the terminal ester groups of polyglycolide polymers. Once the terminal ester groups undergo hydrolysis reactions to generate glycolic acid monomers, the free glycolic acid monomers will quickly undergo a self-catalyzed reaction under the action of water molecules. , to accelerate the process of polyglycolide hydrolysis degradation, resulting in the loss of the final polyglycolide pellet product

Therefore, in the process of using glycolide as raw material to prepare polyglycolide products in the prior art, there is an "amplification effect" in laboratory technology and cannot be applied to large-scale commercial continuous production of polyglycolide industrial devices. Polyglycolide The hydrolysis and degradation reaction of glycolide in contact with cooling water will lead to the problem of large loss of pellet products

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