Solid state polymerization method for preparing polylactic acid

A technology of solid phase polymerization and polylactic acid, which is applied in the field of preparation of high molecular weight polylactic acid, can solve the problems of prepolymer powder bonding, difficulty in water removal, affecting molecular weight and improving product quality, and achieve the effect of accelerating molecular weight growth

Active Publication Date: 2009-08-05
萘琪沃克有限责任公司
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0026] However, so far, there are still many problems to be overcome in the process of preparing polylactic acid by direct method melting + solid phase polymerization, such as: the amount of lactide produced in the reaction is large, resulting in too low yield; the polymerization time is too long and the efficiency Not high; the prepolymer powder is prone to sticking during solid state polymerization, making it difficult to remove water, affecting the increase in molecular weight and product quality

Method used

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  • Solid state polymerization method for preparing polylactic acid

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0067] Starting material: polylactic acid prepolymer powder (containing 0.3wt% stannous acetate / 0.2wt% methanesulfonic acid composite catalyst), particle size 150-250um, molecular weight Mw=11,000, crystallinity 15%, melting point Tm = 150°C; glass transition temperature Tg = 45°C.

[0068] Spread 5g of the above polylactic acid powder in a vacuum oven whose temperature is stable at Tq=90°C±0.1°C, turn on the vacuum pump, adjust the pressure at 200±10Pa, and raise the temperature to Tz at a heating rate of 0.2°C / min. = 150°C and solid phase polymerization at Ts = 150°C, 155°C and 160°C for 8 hours each. During the whole process, neither the formation of lactide nor the welding of powder was observed. When the product was taken out, the powder was still in a free state, and no agglomeration and discoloration were observed. The obtained polylactic acid had a weight-average molecular weight Mw of 154,000, a melting point Tm of 170°C, and a yield of 96%.

Embodiment 2

[0070] Starting material: polylactic acid prepolymer powder (containing 0.3wt% stannous acetate / 0.2wt% methanesulfonic acid composite catalyst), particle size 150-250um, molecular weight Mw=11,000, crystallinity 40%, melting point Tm = 152°C; glass transition temperature Tg = 45°C.

[0071] Spread 5g of the above polylactic acid powder in a vacuum oven whose temperature is stable at Tq=110°C±0.1°C, turn on the vacuum pump, adjust the pressure at 200±10Pa, and raise the temperature to Tz at a heating rate of 0.1°C / min. = 158°C and solid state polymerization at Ts = 158°C for 24 hours. During the whole process, neither the formation of lactide nor the welding of powder was observed. When the product was taken out, the powder was still in a free state, and no agglomeration and discoloration were observed. The obtained polylactic acid had a weight average molecular weight Mw of 175,000, a melting point Tm of 171°C, and a yield of 95%.

Embodiment 3

[0073] Starting material: polylactic acid prepolymer powder (containing 0.3wt% stannous acetate / 0.2wt% methanesulfonic acid composite catalyst), particle size 150-250um, molecular weight Mw=11,000, crystallinity 65%, melting point Tm = 158°C; glass transition temperature Tg = 45°C.

[0074] Spread 5g of the above-mentioned polylactic acid powder in a vacuum oven whose temperature is stable at Tq=139°C±0.1°C, turn on the vacuum pump, adjust the pressure at 200±10Pa, and raise the temperature to Tz at a heating rate of 0.05°C / min. = 160°C and solid phase polymerization at Ts = 160°C and 165°C for 8 hours each. During the whole process, neither the formation of lactide nor the welding of powder was observed. When the product was taken out, the powder was still in a free state, and no agglomeration and discoloration were observed. The obtained polylactic acid had a weight average molecular weight Mw of 195,000, a melting point Tm of 171°C, and a yield of 90%.

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Abstract

The invention relates to a solid phase polymerization method used for preparing polylactic acid. Low molecular weight lactic acid is taken as starting raw material, is heated to the final temperature from the starting temperature under the condition of vacuum or inertia atmosphere by the constant temperature rise, the staggered temperature rise or the combination way of the constant temperature rise and the staggered temperature rise and performs the solid phase polymerization reaction under one solid phase polymerization temperature or a plurality of solid phase polymerization temperatures. The invention inhibits the production of lactide and prevents preformed polymer from being melted by adjusting the constant temperature rise and the staggered temperature rise. The method effectively enhances the reaction efficiency by the control of the limiting temperature, has quick polymerization speed, has little subsidiary product such as the lactide after the reaction, and has high productive rate, simple equipment and lower cost.

Description

technical field [0001] The invention belongs to the field of macromolecular materials, and in particular relates to a method for preparing high-molecular-weight polylactic acid by a solid-phase polymerization method. Background technique [0002] With the development of science and society, people pay more and more attention to environmental and resource issues and become global issues. Petroleum-based plastic materials are widely used, and such materials are difficult to recycle after use, resulting in a relatively serious "white pollution" problem; moreover, resources such as petroleum are non-renewable resources, and a large number of unreasonable uses have brought human There is a serious shortage of resources. The emergence of degradable materials, especially the recyclability of raw materials for degradable materials, provides an effective means to solve this problem. [0003] Polylactic acid (PLA) is a degradable material that has been researched and applied relativ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08G63/80C08G63/06
Inventor 朱可新郭晓夏天成王枫何勇
Owner 萘琪沃克有限责任公司
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