Polylactic acid composition

Abstract

An object of the present invention is to provide a composition containing polylactic acid and having improved blow moldability and a blow molded product thereof. The polylactic acid composition meets the following requirements (a) to (g) at the same time: (a) the weight average molecular weight must be 70,000 to 700,000; (b) the total content (metal content) of Sn atom, Ti atom, Al atom and Ca atom must be 3 to 20 ppm; (c) the content of P atom must be 3 to 3,000 ppm; (d) the (total number of gram-atoms of Sn, Ti, Al and Ca)/(number of gram-atoms of P) value must be 0.01 to 5; (e) the content of a compound having a molecular weight of 150 or less must be not more than 0.2 wt %; (f) the COOH terminal group concentration must be not more than 30 equivalents/ton; and (g) the following expressions (1) and (2) must be satisfied: 10 Pa·s<P<100 Pa·s  (1) 10 MPa<S  (2) (P is a melt viscosity at 230° C. and S is a stress at 150° C.).

1 . A polylactic acid composition which comprises:
 (A) 30 to 70 parts by weight of polylactic acid (A) comprising not less than 90 mol % of an L-lactic acid unit and less than 10 mol % of a D-lactic acid unit and/or a comonomer unit except for lactic acid; and   (B) 70 to 30 parts by weight of polylactic acid (B) comprising not less than 90 mol % of a D-lactic acid unit and less than 10 mol % of an L-lactic acid unit and/or a comonomer unit except for lactic acid,   
     and which meets the following requirements (a) to (g) at the same time:
 (a) the weight average molecular weight must be 70,000 to 700,000; 
 (b) the total content (metal content) of Sn atom, Ti atom, Al atom and Ca atom must be 3 to 20 ppm based on the total weight of the polylactic acid composition; 
 (c) the content of P atom must be 3 to 3,000 ppm; 
 (d) the (total number of gram-atoms of Sn, Ti, Al and Ca)/(number of gram-atoms of P) value must be 0.01 to 5; 
 (e) the content of a compound having a molecular weight of 150 or less must be not more than 0.2 wt %; 
 (f) the COOH terminal group concentration must be not more than 30 equivalents/ton; and 
 (g) the following expressions (1) and (2) must be satisfied:
   10 Pa·s<P<100 Pa·s  (1) 
   10 MPa<S  (2) 
 
 (P is a melt viscosity at 230° C. and S is a stress at 150° C.). 
 
   
   
       2 . A blow molded product which comprises:
 (A) 30 to 70 parts by weight of polylactic acid (A) comprising not less than 90 mol % of an L-lactic acid unit and less than 10 mol % of a D-lactic acid unit and/or a comonomer unit except for lactic acid; and   (B) 70 to 30 parts by weight of polylactic acid (B) comprising not less than 90 mol % of a D-lactic acid unit and less than 10 mol % of an L-lactic acid unit and/or a comonomer unit except for lactic acid,   
     and which meets the following requirements (a) to (g) at the same time:
 (a) the weight average molecular weight must be 100,000 to 500,000; 
 (b) the total content (metal content) of Sn atom, Ti atom, Al atom and Ca atom must be 3 to 20 ppm based on the total weight of the blow molded product; 
 (c) the content of P atom must be 20 to 5,000 ppm; 
 (d) the (total number of gram-atoms of Sn, Ti, Al and Ca)/(number of gram-atoms of P) value must be 0.1 to 5; 
 (e) the content of a compound having a molecular weight of 150 or less must be not more than 0.1 wt %; 
 (f) the COON terminal group concentration must be not more than 30 equivalents/ton; and 
 (g) the following expressions (1) and (2) must be satisfied:
   10 Pa·s<P<100 Pa·s  (1) 
   10 MPa<S  (2) 
 
 (P is a melt viscosity at 230° C. and S is a stress at 150° C.). 
 
   
   
       3 . The blow molded product according to  claim 2 , wherein the polylactic acid (A) and the polylactic acid (B) form a stereocomplex crystal in the blow molded product.