Abstract

A method for directly preparing a foamed polylactic acid (PLA) product from a PLA melt includes PLA melt preparation, feeding, and two-stage extrusion. In the two-stage extrusion, a pressure at an outlet of a first-stage twin-screw extruder is 15 MPa to 17 MPa, a PLA melt is fed at a rate of 250 kg/h, a foaming additive is fed at a rate of 7.5 kg/h to 10 kg/h, and a foaming gas is fed at a rate of 2.8 L/h to 7.5 L/h. The method can ensure both foamability and quality of a material and reduce more than ⅓ of energy consumption; and an obtained product has an adjustable foaming rate of 3 to 25, a crystallinity of 40.3% to 48.5%, a tensile strength of 8.7 MPa to 19.6 MPa, and an apparent density of 0.05 g/cm3 to 0.4 g/cm3.

IPC Classes  ?

• B29C 48/00 - Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired formApparatus therefor
• B29C 48/385 - Plasticisers, homogenisers or feeders comprising two or more stages using two or more serially arranged screws in separate barrels
• B29C 48/92 - Measuring, controlling or regulating
• B29C 48/395 - Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
• B29C 48/36 - Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
• C08J 9/14 - Working-up of macromolecular substances to porous or cellular articles or materialsAfter-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
• B29C 48/625 - Screws characterised by the ratio of the threaded length of the screw to its outside diameter [L/D ratio]

Abstract

The present invention provides a method for directly preparing a foamed polylactic acid article using a polylactic acid polymer melt, comprising: preparing a polylactic acid melt, feeding same, and performing dual extrusion treatment. In the dual extrusion treatment, the outlet pressure of the first stage twin screw extruder is 15 to 17 MPa, the feeding speed of the polylactic acid polymer melt is 250 kg/h, the feeding speed of a foaming aid is 7.5-10 kg/h, and the feeding speed of a foaming gas is 2.8-7.5 L/h. The method of the present invention does not need to undergo processes of water cooling and pelletizing, repeated drying and cooling, melt mixing at elevated temperature, etc. thereby avoiding the influence on foamability, can ensure not only the foamability of the material but also the quality, and saves energy consumption by 1/3 and more. The obtained product has an adjustable expansion ratio of 3-25 times, a crystallinity of 40.3-48.5%, a tensile strength of 8.7-19.6 MPa, and an apparent density of 0.05-0.4 g/cm3.

IPC Classes  ?

• C08J 9/14 - Working-up of macromolecular substances to porous or cellular articles or materialsAfter-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
• C08J 9/12 - Working-up of macromolecular substances to porous or cellular articles or materialsAfter-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
• C08G 63/08 - Lactones or lactides
• C08G 63/78 - Preparation processes
• C08K 3/34 - Silicon-containing compounds
• C08K 5/098 - Metal salts of carboxylic acids
• B29C 48/92 - Measuring, controlling or regulating
• B29C 48/385 - Plasticisers, homogenisers or feeders comprising two or more stages using two or more serially arranged screws in separate barrels