Method for disaggregation of waste and old PET

Abstract

The invention discloses a method for depolymerizing waste PET (polyethylene terephthalate). The method comprises: taking the waste PET as raw material and water as a supercritical medium, and depolymerizing the polyethylene terephthalate in the supercritical state to obtain depolymerization products of terephthalic acid and glycol, wherein the weight ration between the polyethylene terephthalate and the water is between 1:5 and 1:20, the depolymerizing temperature is between 375 and 450 DEG C, the pressure is between 22.12 and 50MPa, and the depolymerizing time is 5 to 60 minutes. The method has the advantages of short reaction period, simple process, high reaction efficiency, unnecessary catalyst and high monomer content of the product.

Description

technical field

[0001] The invention relates to a method for depolymerizing waste PET, that is, polyethylene terephthalate waste. Background technique

[0002] Polyethylene terephthalate (PET) resin has excellent physical and chemical properties, so it is widely used in food, beverage, medicine, photosensitive film, decorative materials, engineering materials, tapes in the electronics industry, and polyester fibers in the clothing industry. PET-related products usually become waste after one-time use, which not only consumes a lot of petroleum resources, but also becomes one of the white pollution sources of the environment. The ways to recycle waste PET can be divided into two categories. One is the physical method of direct recycling, which is to prepare recycled materials through melting, purification or modification. Another type of method is the chemical method of degradation and reuse. The commonly used methods are as follows: acidic hydrolysis, alkaline hydrolysis, m...