Polylactic acid and method for producing the same

A technology of polylactic acid and lactic acid, which is applied in the field of polylactic acid and its preparation, can solve the problems of large molecular weight, easy residue, and high crystal melting point

Inactive Publication Date: 2009-09-02
TEIJIN LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This method is to suppress the evaporation of lactide and carry out the reaction under pressure. Unreacted lactide tends to remain in the reaction system, which may lower the melting point of the obtained stereocomplex polylactic acid.
[0012] As mentioned above, the production method of stereocomplex polylactic acid, which has a large molecular weight, a high crystal melting point, and only stereocomplex crystals grown even after repeated melting and crystallization, has not yet been proposed.

Method used

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  • Polylactic acid and method for producing the same
  • Polylactic acid and method for producing the same
  • Polylactic acid and method for producing the same

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0093] Step (1): Preparation of the first polylactic acid

[0094]Under nitrogen flow, 100 parts by weight of L-lactide (Musashino Chemical L-lactide, optical purity 99% or more) and 0.15 parts by weight of stearin were added from the feed port of a polymerization reaction vessel equipped with a condensation distillation tube. alcohol. Next, the inside of the reaction container was replaced with nitrogen five times to melt L-lactide at 190°C. When L-lactide was completely melted, 0.05 parts by weight of tin 2-ethylhexanoate and 500 μL of toluene were simultaneously added from the feed port, and polymerized at 190° C. for 1 hour to obtain the first polylactic acid.

[0095] Step (2): Removal of Lactide

[0096] Next, the inside of the reaction vessel was depressurized to 1.33 kPa to remove excess lactide to obtain purified first polylactic acid. The Mw and lactide content of the obtained purified first polylactic acid are shown in Table 1.

[0097] Step (3): Preparati...

Embodiment 2

[0102] Steps (1) and (2)

[0103] Except having changed 0.15 weight part of stearyl alcohols into 0.2 weight part, the same operation as the step (1) of Example 1 was performed, and the purified 1st polylactic acid was obtained. The Mw and lactide content of the purified first polylactic acid are shown in Table 1.

[0104] Steps (3) and (4)

[0105] The same operation as in Example 1 was carried out to obtain the purified second polylactic acid. The Mw, lactide content and L / D of the purified second polylactic acid are shown in Table 1. The crystal melting enthalpy, stereocomplex crystal content (S) and crystal melting point are shown in Table 2.

Synthetic example 1

[0107] (Synthesis of PDLA)

[0108] Under a nitrogen stream, 100 parts by weight of D-lactide (manufactured by Musashino Chemical Research Laboratories) and 0.15 parts by weight of stearyl alcohol were added from the feed port of a polymerization reaction vessel equipped with a condensing distillation tube. Next, the inside of the reaction vessel was replaced with nitrogen five times to melt D-lactide at 190°C. When D-lactide was completely melted, 0.05 parts by weight of tin 2-ethylhexanoate and 500 μL of toluene were simultaneously added from the feed port, and polymerized at 190° C. for 1 hour. Next, the pressure in the reaction container was reduced to 1.33 kPa to remove excess lactide. The Mw of the obtained PDLA was 198,422.

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Abstract

A method of producing a stereocomplex polylactic acid having a high melting point and a high molecular weight, wherein only stereocomplex crystals are grown even when melting and crystallization are repeated. The method comprises the steps of: (1) obtaining a first polylactic acid by the ring-opening polymerization of a first lactide composed of lactic acid units of the same chirality; (2) obtaining a purified first polylactic acid by removing the lactide from the first polylactic acid in a molten state under reduced pressure; (3) obtaining a second polylactic acid by the ring-opening polymerization of a second lactide which differs from the first lactide in chirality in the presence of the purified first polylactic acid; and (4) obtaining a purified second polylactic acid by removing the lactide from the second polylactic acid in a molten state under reduced pressure.

Description

technical field [0001] The present invention relates to polylactic acid and its preparation method. Background technique [0002] Most of the plastics derived from petroleum are light, strong, durable, and can be molded easily and arbitrarily. They are mass-produced and support our lives in many ways. However, the above-mentioned plastics are not easily decomposed and accumulated when they are disposed of in the environment. In addition, a large amount of carbon dioxide is released during incineration, which accelerates global warming. [0003] In view of the above-mentioned status quo, there has been vigorous research into resins formed from de-oiled raw materials or biodegradable plastics to be decomposed by microorganisms. Almost all the biodegradable plastics studied now contain aliphatic carboxylate units, which are easily decomposed by microorganisms. On the other hand, the above-mentioned biodegradable plastics lack thermal stability, and the molecular weight decre...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08G63/08C08G63/90C08L101/16
CPCC08G63/90C08G63/08C08L67/04C08G63/78C08L2205/02C08L2666/18C08L101/16
Inventor 铃木启高高田昌幸
Owner TEIJIN LTD
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