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Method for disaggregation of waste and old PET

A depolymerization and waste technology, applied in organic chemistry, plastic recycling, bulk chemical production, etc., can solve the problems of low purity of TPA, slow reaction, difficult recovery of ethylene glycol, etc., and achieve high reaction efficiency and short reaction cycle , The effect of simple process

Inactive Publication Date: 2009-06-17
CHINESE ACADEMY OF SCI THE JIAXING MATERIALS & CHEM TECH ENG CENT
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The disadvantages of this method are: the large amount of concentrated acid and strong alkali consumed by the reaction are difficult to recycle, which is easy to cause environmental pollution, and the ethylene glycol produced is also difficult to recycle.
Aiming at the problems of low purity and slow reaction of TPA produced by alkaline hydrolysis, researchers have made continuous improvements.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0014] Add 10 grams of colorless transparent polyethylene terephthalate beverage bottle fragments and 100 grams of processed (crushed, washed, dried) in a high-pressure reactor equipped with an electromagnetic stirrer, thermocouple, and programmed temperature controller. gram of water, purged with nitrogen to remove the oxygen in the reactor, then started the stirrer and heated. The temperature of the reaction system was raised to 375°C, and the pressure was raised to 30.0Mpa. After the reaction was carried out at this temperature for 30 minutes, it was cooled to room temperature, crystallized, filtered, washed, and the obtained solid product was dried, and the filtrate was separated by rectification. The recovery rate of terephthalic acid was 90.3%, the recovery rate of ethylene glycol was 70.1%, and the decomposition rate of PET was 100%.

Embodiment 2

[0016] Depolymerization step and condition are carried out by embodiment 1, add 10 grams of colored transparent polyethylene terephthalate beverage bottle fragments and 110 grams of water through processing (crushing, washing, drying) in the high-pressure reactor, blow with nitrogen Sweep to remove the oxygen in the reactor, then start the stirrer and heat. The temperature of the reaction system was raised to 450°C, and the pressure was raised to 40.0Mpa. After the reaction was carried out at this temperature for 20 minutes, it was cooled to room temperature, crystallized, filtered, washed, and the obtained solid product was dried, and the filtrate was separated by rectification. The recovery rate of terephthalic acid was 97.5%, the recovery rate of ethylene glycol was 80.4%, and the decomposition rate of PET was 100%.

Embodiment 3

[0018] Depolymerization steps and conditions are carried out according to Example 1, add 10 grams of polyethylene terephthalate fibers and 105 grams of water through processing (crushing, washing, drying) in the high pressure reactor, with nitrogen purging, remove reaction Oxygen in the tank, then start the stirrer and heat. The temperature of the reaction system was raised to 400°C, and the pressure was raised to 35.0Mpa. After the reaction was carried out at this temperature for 15 minutes, it was cooled to room temperature, crystallized, filtered, washed, and the obtained solid product was dried, and the filtrate was separated by rectification. The recovery rate of terephthalic acid was 90.0%, the recovery rate of ethylene glycol was 70.2%, and the decomposition rate of PET was 100%.

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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...

Claims

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Application Information

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IPC IPC(8): C07C63/26C07C31/20C07C51/09C08J11/14
CPCY02P20/54Y02W30/62
Inventor 简令奇徐寒松王建民
Owner CHINESE ACADEMY OF SCI THE JIAXING MATERIALS & CHEM TECH ENG CENT
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