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Polylactic Acid (PLA) – A New Industrial Revolution in the Field of Polymers
In 2003, eSUN decided to focus on developing polylactic acid (PLA) bioplastics. This material, derived from biological sources and capable of biodegradation, is hailed as "a new industrial revolution in the field of polymer materials."
Why recycle polylactic acid (PLA)?
In 2006, a customer asked us,
"Degradation also means a form of waste.
Why not consider recycling and reusing it?"
This perspective struck a chord with us.
Recycling: Biodegradable Materials
Recycling Process:
A. Raw Material Pretreatment: Crush PLA plastic, wash with water, filter to remove impurities, and dry to remove moisture.
B. Melting: Use twin-screw extrusion for chain scission, resulting in PLA melt.
C. Chain Scission: The melt undergoes a chain scission reaction under certain conditions, reducing the number-average molecular weight to below 5000.
D. Depolymerization: The melt is pumped into the depolymerization system, producing crude lactide.
E. Purification: The crude lactide is pumped into the purification process, where it is separated through melt crystallization to obtain refined lactide (with optical purity reaching over 99.9%).
F. During production, the disproportionation products and polymers from the bottom of the depolymerization reactor are decolorized and purified, then undergo alcoholysis to produce ethyl lactate.
G. Oligomers and meso-lactide produced in the lactide purification process undergo alcoholysis in the presence of a catalyst to produce lactate esters.
H. High optical purity L-lactide is used to produce polyols or their copolymers.
Research and Industrialization Achievements of Chemical Recycling
Summary of Achievements:
01
1.Initial Research and Pilot Trials:
2009: Commenced related small-scale trials.
2011: Established a PLA chemical recycling facility in Xiaogan.
2011-2013: Recycled approximately 2000 tons of PLA film, fiber, and pellet materials, producing around 100 tons of lactide (using solvent recrystallization process) and approximately 3000 tons of ethyl lactate. Successfully demonstrated the process of recycling PLA for the production of lactide and lactate esters, achieving significant economic benefits.
02
2.Expansion and Stabilization:
2013: Built a 2000 tons/year PLA facility in Xiaogan, which has been operating stably for a long period.
03
3.Scale-Up and Integration:
2014: Constructed a 5000 tons/year lactide facility.
2018: Launched the facility using lactic acid and recycled PLA as primary raw materials to produce lactide and ethyl lactate. From 2018 to 2021, conducted trial operations in three phases, recycling a total of approximately 120 tons of PLA and producing around 133.5 tons of lactide and 40 tons of ethyl lactate.
04
4.Product Development and Market Applications:
Various grades of poly(lactic acid) polyols have been practically applied by customers, leading to stable sales.
Achieved widespread application in downstream industries such as biobased material additives, UV curing, and green foaming.
05
5.New Production Line:
2020: Established a 10 kg/hour lactide copolymer pilot production line in Xiaogan, targeting high-value small products, mainly for medical and other high-value applications.
06
6.Patents and Standards:
Throughout the project implementation, developed a series of process and equipment patents.
Led or participated in drafting relevant industry and national standards.
Specific Achievements Display
Patents
| No. | Patent Number | Title | Type | Legal Status | Authorization Date |
| 1 | ZL201010262372.3 | Method for producing high-content and high-optical-purity ethyl lactate by a two-step process | Invention Patent (China) | Authorized | 2013.07.10 |
| 2 | ZL201010262356.4 | Method for producing high-content and high-optical-purity butyl lactate by a two-step process | Invention Patent (China) | Authorized | 2013.06.05 |
| 3 | ZL201010262384.6 | Method for producing high-content and high-optical-purity methyl lactate by a two-step process | Invention Patent (China) | Authorized | 2013.08.21 |
| 4 | ZL201010261047.5 | Method for producing high-content and high-optical-purity lactate esters by a two-step process | Invention Patent (China) | Authorized | 2013.10.23 |
| 5 | ZL201010261242.8 | Method for producing high-content and high-optical-purity propyl lactate by a two-step process | Invention Patent (China) | Authorized | 2013.07.10 |
| 6 | ZL201210221914.1 | Method for recovering polylactic acid to prepare refined-grade lactide | Invention Patent (China) | Authorized | 2014.06.11 |
| 7 | ZL201510063085.2 | Method for preparing electronic-grade ethyl lactate | Invention Patent (China) | Authorized | 2016.09.28 |
| 8 | US9475790 B2 | Method for recovering polylactic acid to prepare refined-grade lactide | Invention Patent (USA) | Authorized | 2016.10.25 |
| 9 | ZL201010239065.3 | Method for foaming polylactic acid | Invention Patent (China) | Authorized | 2011.12.28 |
| 10 | ZL201510054929.7 | Method for preparing low-acid-value polylactic acid polyol | Invention Patent (China) | Authorized | 2019.01.15 |
| 11 | ZL201711191894.7 | Process equipment and method for refining lactide | Invention Patent (China) | Authorized | 2020.09.25 |
| 12 | ZL202210188084.0 | Bimetallic aluminum alkyl complex catalyst, preparation method and application in the preparation of lactide and ε-caprolactone random copolymer | Invention Patent (China) | Authorized | 2022.10.21 |
| 13 | 201811623355.0 | Method for preparing electronic-grade propyl propionate | Invention Patent (China) | Pending | |
| 14 | 202010281112.4 | Process method for preparing glycolide from glycolic acid ester | Invention Patent (China) | Pending | |
| 15 | 2022 10237218.3 | Method and device for preparing high-purity L-lactide | Invention Patent (China) | Pending | |
| 16 | 2022 10276619.X | Method and application for preparing urethane-modified polyester acrylate | Invention Patent (China) | Pending |
Application Number/Patent Number: 201210221914.1
Application Date: June 29, 2012
Authorization Date: June 11, 2014
Application Number/Patent Number: US9475790 B2
Application Date: June 29, 2012
Authorization Date: October 25, 2016
Standard
| No. | Standard Name | Standard Number | Standard Type | Standard Release Date | Standard Status | Participating Unit |
| 1 | Polycaprolactone Diol | Q/XYS 007-2017 | Corporate Standard | 2017.7.28 | Currently Effective | eSUN |
| 2 | Polycaprolactone Triol | Q/XYS 008-2017 | Corporate Standard | 2017.7.28 | Currently Effective | eSUN |
| 3 | L-Lactide | Q/XYS 006-2022 | Corporate Standard | 2022.6.13 | Currently Effective | eSUN |
| 4 | Polycaprolactone, Polylactide Polyol | Q/XYS 001-2021 | Corporate Standard | 2022.5.18 | Currently Effective | eSUN |
| 5 | Ethyl Lactate | Q/XGYS013-2021 | Corporate Standard | 2022.5.18 | Currently Effective | eSUN |
| 6 | Polylactic Acid (PLA2201) | Q/XYS 005-2022 | Corporate Standard | 2022.6.15 | Currently Effective | eSUN |
Industrialization Achievements: Recycling Facilities
eSUN Solution Approach
Biobased | Recycling | Biodegradable
Benefits of PLA Chemical Recycling:
1.Resource Recycling: Converts waste PLA materials into reusable raw materials, reducing resource waste.
2.Reduction of Environmental Pollution: This prevents pollution caused by discarded PLA, helping to protect the environment.
3.Sustainable Development: Promotes the sustainable use of PLA materials, aligning with environmental protection and sustainable development goals.
