Method for producing lactic acid and method for producing polylactic acid

Patent metadata

Field	Value
Publication number	US-10683254-B2
Application number	US-200913142062-A
Country	US
Kind code	B2
Filing date	Dec 25, 2009
Priority date	Dec 26, 2008
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

Lactic acid is obtained by a method including (A) a step of continuous fermentation wherein a fermentation culture medium of a microorganism having an ability of lactic acid fermentation is filtered through a porous membrane having an average pore size of not less than 0.01 μm and less than 1 μm with a transmembrane pressure difference within the range of 0.1 to 20 kPa, and the permeate is collected, while retaining the non-permeated liquid in or returning the non-permeated liquid to the culture, and adding a fermentation feedstock to the culture; (B) a step of filtering the permeate obtained in Step (A) through a nanofiltration membrane; and (C) a step of distilling the permeate obtained in Step (B) under a pressure of not less than 1 Pa and not more than atmospheric pressure, at 25° C. to 200° C. to recover lactic acid.

First claim

The invention claimed is:

1. A method of producing a lactide, comprising heating under reduced pressure a purified lactic acid composition comprising lactic acid having optical purity of not less than 95%, wherein the lactic acid composition contains methanol at a concentration of not more than 0.007778 wt % (weight/lactic acid weight), pyruvic acid at a concentration of 0.022222 to 0.05556 wt % (weight/lactic acid weight), furfural at a concentration of 0.0003333 to 0.001667 (weight/lactic acid weight), 5-hydroxymethylfurfural at a concentration of 0.00022222 to 0.001667 wt % (weight/lactic acid weight), methyl lactate at a concentration of not more than 0.04444 wt % (weight/lactic acid weight), acetic acid at a concentration of not more than 0.04444 wt % (weight/lactic acid weight), and 2-hydroxybutyric acid at a concentration of 0.011111 to 0.02222 wt % (weight/lactic acid weight) to produce lactic acid oligomers and depolymerizing the lactic acid oligomers to produce the lactide.

2. The method according to claim 1 , wherein the purified lactic acid composition has an optical purity of not less than 99%.

3. The method according to claim 1 , wherein the purified lactic acid composition contains acetic acid at a concentration of 0.022222 to 0.04444 wt % (weight/lactic acid weight).

4. A method of producing a polylactic acid, comprising heating under reduced pressure a purified lactic acid composition comprising lactic acid having optical purity of not less than 95%, wherein the lactic acid composition contains methanol at a concentration of not more than 0.007778 wt % (weight/lactic acid weight), pyruvic acid at a concentration of 0.022222 to 0.05556 wt % (weight/lactic acid weight), furfural at a concentration of 0.0003333 to 0.001667 (weight/lactic acid weight), 5-hydroxymethylfurfural at a concentration of 0.00022222 to 0.001667 wt % (weight/lactic acid weight), methyl lactate at a concentration of not more than 0.04444 wt % (weight/lactic acid weight), acetic acid at a concentration of not more than 0.04444 wt % (weight/lactic acid weight), and 2-hydroxybutyric acid at a concentration of 0.011111 to 0.02222 wt % (weight/lactic acid weight) to produce lactic acid oligomers and depolymerizing the lactic acid oligomers to produce a lactide, and subjecting the lactide to ring opening polymerization.

5. A method of producing a polylactic acid, comprising polymerizing a purified lactic acid composition comprising lactic acid having optical purity of not less than 95%, wherein the lactic acid composition contains methanol at a concentration of not more than 0.007778 wt % (weight/lactic acid weight), pyruvic acid at a concentration of 0.022222 to 0.05556 wt % (weight/lactic acid weight), furfural at a concentration of 0.0003333 to 0.001667 (weight/lactic acid weight), 5-hydroxymethylfurfural at a concentration of 0.00022222 to 0.001667 wt % (weight/lactic acid weight), methyl lactate at a concentration of not more than 0.04444 wt % (weight/lactic acid weight), acetic acid at a concentration of not more than 0.04444 wt % (weight/lactic acid weight), and 2-hydroxybutyric acid at a concentration of 0.011111 to 0.02222 wt % (weight/lactic acid weight) by direct dehydration polycondensation.

6. The method according to claim 5 , wherein the purified lactic acid composition has an optical purity of not less than 99%.

7. The method according to claim 5 , wherein the purified lactic acid composition contains acetic acid at a concentration of 0.022222 to 0.04444 wt % (weight/lactic acid weight).

Assignees

• Sawai Kenji
• Sawai Hideki
• Mimitsuka Takashi
• Masateru Ito
• Yamada Katsushige
• Kawamura Kenji
• Minegishi Shin Ichi
• Nakagawa Izumi
• Nagano Tatsuya
• Toray Industries

Inventors

• Sawai Kenji
• Sawai Hideki
• Mimitsuka Takashi
• Masateru Ito
• Yamada Katsushige
• Kawamura Kenji
• Minegishi Shin-Ichi
• Nakagawa Izumi
• Nagano Tatsuya

Classifications

• C12P7/56 Primary

  Lactic acid · CPC title

• C07C59/08 Primary

  Lactic acid · CPC title

• C08G63/08

  Lactones or lactides · CPC title

• C08G63/06

  derived from hydroxycarboxylic acids · CPC title

• C07C51/42 Primary

  Separation; Purification; Stabilisation; Use of additives · CPC title