Polylactic acid-based film or sheet

Abstract

A method of producing a polylactic acid based film or sheet with improved heat resistance and comprised of a resin composition containing a polylactic acid according to a melt film forming method, wherein the resin composition comprises polylactic acid (A), an acidic functional group-denatured olefin based polymer (B) containing an acidic functional group, and having an acid number of 10-70 mg KOH/g and a weight average molecular weight of 10,000-80,000, and a tetrafluoroethylene based polymer (C), which method comprises performing melt film formation at a temperature of the resin composition between the crystallization temperature (Tc) in a decreasing temperature process of the resin composition +15° C. and the melting temperature (Tm) in a raising temperature process −5° C., or solidifying the resin composition melt-formed in a film state by cooling after a temperature controllable step at crystallization temperature (Tc) in the decreasing temperature process ±10° C.

1 . A method of producing a film or sheet of a resin composition containing a polylactic acid according to a melt film forming method, wherein the resin composition comprises polylactic acid (A), an acidic functional group-denatured olefin based polymer (B) containing an acidic functional group, and having an acid number of 10-70 mg KOH/g and a weight average molecular weight of 10,000-80,000, and a tetrafluoroethylene based polymer (C), which method comprises performing a melt film formation step at a temperature of the resin composition between the crystallization temperature (Tc) in a decreasing temperature process of the resin composition +15° C. and the melting temperature (Tm) in a raising temperature process −5° C., or solidifying the resin composition melt-formed in a film state by cooling after a crystallization promoting step at crystallization temperature (Tc) in a decreasing temperature process ±10° C. 
     
     
         2 . The production method according to  claim 1 , wherein the melt film formation step is performed at a temperature of the resin composition between the crystallization temperature (Tc) in a decreasing temperature process of the resin composition +15° C. and the melting temperature (Tm) in a raising temperature process −5° C., and the resin composition melt-formed in a film state is solidified by cooling after a crystallization promoting step at crystallization temperature (Tc) in the decreasing temperature process ±10° C. 
     
     
         3 - 4 . (canceled) 
     
     
         5 . The production method according to  claim 1 , wherein the melt film forming method is a technique comprising finally passing the resin composition in a molten state through a gap between two metal rolls to achieve a desired film thickness. 
     
     
         6 - 9 . (canceled) 
     
     
         10 . The production method according to  claim 1 , further comprising 0.1-5.0 parts by weight of crystallizing agent (D) per 100 parts by weight of the polylactic acid (A). 
     
     
         11 . The production method according to  claim 1 , wherein the aforementioned crystallization promoting step of the resin composition is achieved by a metal roll. 
     
     
         12 . A film or sheet comprising a polylactic acid, which is comprised of a resin composition comprising polylactic acid (A), an acidic functional group-denatured olefin based polymer (B) containing an acidic functional group, and having an acid number of 10-70 mg KOH/g and a weight average molecular weight of 10,000-80,000, and a tetrafluoroethylene based polymer (C), and shows a change ratio of not more than 40% when applied with a load of 10N for 30 min under an atmosphere of 150° C. according to the Heat deformation test method of JIS C 3005, and a relative crystallization ratio as determined by the following formula (1)
   relative crystallization ratio (%)=( ΔHm−ΔHc )/Δ Hm× 100  (1)
 
 wherein ΔHc is an amount of heat at an exothermic peak due to crystallization in a raising temperature process of a film sample after film formation, and ΔHm is an amount of heat due to melting, of not less than 50%. 
 
     
     
         13 . The film or sheet according to  claim 12 , further showing a heat shrinkage ratio as determined by the following formula (2)
   heat shrinkage ratio (%)=( L 1 −L 2)/ L 1×100  (2)
   wherein L1 is a gauge length before the test, and L2 is a gauge length after the test, of not more than 5% in both the machine direction (MD direction) and the width direction (TD direction) after preservation under a temperature atmosphere of 150° C. for 10 min.   
     
     
         14 . The film or sheet according to  claim 12 , wherein the acidic functional group-denatured olefin based polymer (B) is contained in a proportion of 0.1-5.0 parts by weight per 100 parts by weight of the polylactic acid (A). 
     
     
         15 . The film or sheet according to  claim 12 , wherein the tetrafluoroethylene based polymer (C) is contained in a proportion of 0.1-10.0 parts by weight per 100 parts by weight of the polylactic acid (A). 
     
     
         16 . The film or sheet according to  claim 12 , wherein the acidic functional group in the acidic functional group-denatured olefin based polymer is an acid anhydride. 
     
     
         17 . The film or sheet according to  claim 12 , further comprising 0.1-5.0 parts by weight of crystallizing agent (D) per 100 parts by weight of the polylactic acid (A). 
     
     
         18 . The film or sheet according to  claim 13 , wherein the acidic functional group-denatured olefin based polymer (B) is contained in a proportion of 0.1-5.0 parts by weight per 100 parts by weight of the polylactic acid (A). 
     
     
         19 . The film or sheet according to  claim 13 , wherein the tetrafluoroethylene based polymer (C) is contained in a proportion of 0.1-10.0 parts by weight per 100 parts by weight of the polylactic acid (A). 
     
     
         20 . The film or sheet according to  claim 13 , wherein the acidic functional group in the acidic functional group-denatured olefin based polymer is an acid anhydride. 
     
     
         21 . The film or sheet according to  claim 13 , further comprising 0.1-5.0 parts by weight of crystallizing agent (D) per 100 parts by weight of the polylactic acid (A).