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Method for producing polylactic acid with low lactide monomer content

A monomer content, lactide technology, used in the production of high molecular weight polylactic acid with low lactide monomer content, can solve the problem of hindering operation, reducing the glass transition temperature and melt viscosity of the polymer, formability and heat. Stability deterioration and other problems, to achieve the effect of simple and convenient operation, good formability and thermal stability, and conducive to industrial production

Active Publication Date: 2014-05-28
CHINA PETROLEUM & CHEM CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These residual lactide monomers tend to sublime during injection molding or spinning of polylactic acid used as a raw material, sticking to the mold or nozzle, thereby hindering the operation
In addition, residual lactide lowers the glass transition temperature and melt viscosity of the polymer, resulting in poor formability and thermal stability

Method used

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  • Method for producing polylactic acid with low lactide monomer content
  • Method for producing polylactic acid with low lactide monomer content
  • Method for producing polylactic acid with low lactide monomer content

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0048] Add 200kg of L-lactide to a 500L melting tank that has been exhausted with nitrogen and has a temperature of 130°C. After the L-lactide is completely melted, 20L of L-lactide is continuously supplied by a melt metering pump at a mass flow rate of 5kg / h. A vertical polymerization kettle, at the same time, the catalyst stannous octoate was continuously supplied to a 20L vertical polymerization kettle at a mass flow rate of 1.5g / h through a catalyst pump, and polymerized at a temperature of 160°C and a pressure of 0.4MPa for 0.9 hours. The conversion rate of lactide reaches 30%. The obtained polymer was sent to a tubular reactor with a melt metering pump, and polymerized at a polymerization temperature of 160-190° C. and a pressure of 0.8 MPa for 2.5 hours. The conversion rate of lactide reached 91%, and the weight average molecular weight of the obtained polylactic acid was 161000.

[0049] The polymer obtained from the tubular reactor was fed into a twin-screw extruder ...

Embodiment 2

[0052] The steps are the same as in Example 1, except that the temperature of the melting tank is 120° C.; the mass flow rate of the catalyst stannous octoate is 2.5 g / h; two tubular reactors connected in series are used; the polylactic acid particles diced after water cooling The weight is 1.0g; the nitrogen gas enters the degassing tower from the lower part of the degassing tower, and the polylactic acid particles and nitrogen gas are heated to 140°C by using the heat transfer oil in the jacket of the degassing tower, and the polylactic acid particles are in countercurrent contact with the nitrogen gas for 3 hours; cool in the cooling kettle The temperature of the obtained polylactic acid particles is about 30°C. The data are shown in Table 1.

Embodiment 3

[0054] The steps are the same as in Example 1, except that the temperature of the melting tank is 140° C.; the raw material D, L-lactide monomer is continuously supplied to the vertical polymerization tank at a mass flow rate of 4.0 kg / h after melting, and the catalyst octanoic acid sub- The mass flow rate of tin is 3.2g / h; the weight of the pelletized polylactic acid particles after water cooling is 2.0g; the temperature of hot nitrogen is 100°C, and the countercurrent contact is 5h. The data are shown in Table 1.

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Abstract

The invention discloses a method for producing polylactic acid with low lactide monomer content. The method comprises the following steps: a) under the action of a catalyst, polymerizing molten lactide, wherein the conversion rate of the lactide is 10-30 percent; b) polymerizing a product in the step a) to obtain the polylactic acid, wherein the conversion rate of the lactide is greater than 90 percent; c) removing the lactide remained in the polylactic acid in the step b) under reduced pressure, and then granulating the polylactic acid, wherein the reduced pressure is minus 0.07MPa to minus 0.09MPa, and the content of the lactide remained in polylactic acid granulates is less than 5 weight percent; d) reversely contacting granulated polylactic acid in the step c) with inert gas under normal pressure, and removing a lactide monomer to obtain the polylactic acid with the low lactide monomer content, wherein the content of the lactide monomer in the polylactic acid is less than 0.1 weight percent. According to the method and equipment provided by the invention, the polylactic acid with lower remained lactide monomer content can be produced, and the obtained polylactic acid is better in formability and thermal stability.

Description

technical field [0001] The present invention relates to a production method of high molecular weight polylactic acid, more particularly, relates to the production method of high molecular weight polylactic acid with low lactide monomer content. Background technique [0002] In recent years, with the widespread use of plastic products such as polyethylene, polypropylene, polystyrene and polyvinyl chloride, the disposal of waste after use has become one of the increasingly serious environmental problems. These wastes are usually disposed of by incineration and landfill. Incineration will produce harmful gases. Due to the high chemical stability of the above-mentioned plastic products, microbial decomposition hardly occurs after landfill treatment, but remains in a semi-permanent state. [0003] In order to solve the above problems, researchers have vigorously developed environmentally friendly biodegradable polymers, one of which is polylactic acid. Polylactic acid can be p...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08G63/08C08G63/90C08G63/78
Inventor 孟伟娟杜影赵丽娜闫岩齐可非刘铭唐伟刚
Owner CHINA PETROLEUM & CHEM CORP
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