Process for production of polylactic acid resin composition

Abstract

A method for producing a polylactic acid resin composition, including the following steps (1) and (2): step (1): subjecting an organic crystal nucleating agent to a wet pulverization in the presence of a carboxylic acid ester having a weight-average molecular weight of from 150 to 600 and a viscosity at 23° C. of from 1 to 500 mP·s and/or a phosphoric ester having a weight-average molecular weight of from 150 to 600 and a viscosity at 23° C. of from 1 to 500 mPa·s to give a finely pulverized organic crystal nucleating agent composition; and step (2): melt-kneading a raw material for a polylactic acid resin composition comprising the finely pulverized organic crystal nucleating agent composition obtained in the step (1) and a polylactic acid resin. The polylactic acid resin composition obtainable by the method of the present invention can be suitably used in various industrial applications, such as daily sundries, household electric appliance parts, packaging materials for household electric appliance parts, and automobile parts.

1 . A method for producing a polylactic acid resin composition, comprising the following steps (1) and (2):
 step (1): subjecting an organic crystal nucleating agent to a wet pulverization in the presence of a carboxylic acid ester having a weight-average molecular weight of from 150 to 600 and a viscosity at 23° C. of from 1 to 500 mPa·s to give a finely pulverized organic crystal nucleating agent composition; and   step (2): melt-kneading a raw material for a polylactic acid resin composition comprising the finely pulverized organic crystal nucleating agent composition obtained in the step (1) and a polylactic acid resin.   
     
     
         2 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the organic crystal nucleating agent comprises at least one organic compound selected from the group consisting of metal salts of dialkyl aromatic sulfonates, metal salts of phosphoric esters, metal salts of phenylphosphonic acids, metal salts of rosin acids, aromatic carboxylic acid amides, and rosin acid amides. 
     
     
         3 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the organic crystal nucleating agent comprises a metal salt of a phenylphosphonic acid. 
     
     
         4 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the finely pulverized organic crystal nucleating agent composition has a volume-median particle size (D 50 ) of from 50 to 700 nm. 
     
     
         5 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the step (1) comprises subjecting the organic crystal nucleating agent to a wet pulverization in the presence of the carboxylic acid ester, within a range satisfying a ratio of the weight of the organic crystal nucleating agent and a total weight of the carboxylic acid ester, that is the organic crystal nucleating agent/the carboxylic acid ester, of from 1/99 to 50/50. 
     
     
         6 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the carboxylic acid ester is a carboxylic acid ester having two or more ester groups in the molecule, wherein an alcohol component constituting the carboxylic acid ester comprises an alcohol with addition of an alkylene oxide having 2 to 3 carbon atoms in an amount of from 0.5 to 5 mol per one hydroxyl group in average. 
     
     
         7 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the carboxylic acid esters are one or more members selected from the group consisting of carboxylic acid esters formed between acetic acid and an ethylene oxide adduct of glycerol, an ethylene oxide moiety of which is added in an amount of from 3 to 6 mol in average, carboxylic acid esters formed between acetic acid and an ethylene oxide adduct of a polyethylene glycol, an ethylene oxide moiety of which is added in an amount of from 4 to 6 mol in average, carboxylic acid esters formed between succinic acid and an ethylene oxide adduct of a polyethylene glycol monomethyl ether, an ethylene oxide moiety of which is added in an amount of from 2 to 3 mol in average, carboxylic acid esters formed between adipic acid and diethylene glycol monomethyl ether, and carboxylic acid esters formed between 1,3,6-hexanetricarboxylic acid and diethylene glycol monomethyl ether. 
     
     
         8 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the organic crystal nucleating agent subjected to the wet pulverization has a volume-median particle size (D 50 ) of from 500 nm to 5 μm. 
     
     
         9 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the treatment temperature for the wet pulverization is from 5° to 250° C. 
     
     
         10 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the pulverizer used in the wet pulverization is a media pulverizer. 
     
     
         11 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein in the step (2) the finely pulverized organic crystal nucleating agent composition obtained in the step (1) is contained in an amount of from 1 to 50 parts by weight, based on 100 parts by weight of the polylactic acid resin. 
     
     
         12 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the carboxylic acid esters are one or more members selected from the group consisting of carboxylic acid esters formed between acetic acid and an ethylene oxide adduct of glycerol, an ethylene oxide moiety of which is added in an amount of from 3 to 6 mol in average. 
     
     
         13 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the carboxylic acid esters are one or more members selected from the group consisting of carboxylic acid esters formed between acetic acid and an ethylene oxide adduct of a polyethylene glycol, an ethylene oxide moiety of which is added in an amount of from 4 to 6 mol in average. 
     
     
         14 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the carboxylic acid esters are one or more members selected from the group consisting of carboxylic acid esters formed between succinic acid and an ethylene oxide adduct of a polyethylene glycol monomethyl ether, an ethylene oxide moiety of which is added in an amount of from 2 to 3 mol in average. 
     
     
         15 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the carboxylic acid esters are one or more members selected from the group consisting of carboxylic acid esters formed between adipic acid and diethylene glycol monomethyl ether. 
     
     
         16 . The method for producing a polylactic acid resin composition according to  claim 1 , wherein the carboxylic acid esters are one or more members selected from the group consisting of carboxylic acid esters formed between 1,3,6-hexanetricarboxylic acid and diethylene glycol monomethyl ether. 
     
     
         17 . A polylactic acid resin composition obtained by the method as defined in  claim 1 .