Hinge Cap Having Biodegradability

Abstract

A hinge cap is provided which includes: a cap body having a top wall, a spout provided in the top wall and a side wall extending downward from a peripheral edge of the top wall; and an upper cap portion connected to the cap body via a hinge and capable of capping and uncapping the spout. The hinge cap is composed of a resin composition comprising polylactic acid and an aliphatic polyester resin other than the polylactic acid. The polylactic acid and the aliphatic polyester resin other than the polylactic acid are present in the resin composition in a mass ratio of (polylactic acid):(aliphatic polyester other than polylactic acid)=90:10 to 5:95.

1 . A biodegradable hinge cap comprising:
 a cap body having a top wall, a spout provided in the top wall and a side wall extending downward from a peripheral edge of the top wall; and   an upper cap portion connected to the cap body via a hinge and capable of capping and uncapping the spout;   the hinge cap being composed of a resin composition comprising polylactic acid and an aliphatic polyester resin other than the polylactic acid;   wherein the polylactic acid and the aliphatic polyester resin other than the polylactic acid are present in the resin composition in a mass ratio of (polylactic acid):(aliphatic polyester other than polylactic acid)=90:10 to 5:95.   
   
   
       2 . A biodegradable hinge cap as set forth in  claim 1 , wherein the mass ratio between the polylactic acid and the aliphatic polyester resin other than the polylactic acid in the resin composition is (polylactic acid):(aliphatic polyester other than polylactic acid)=60:40 to 10:90. 
   
   
       3 . A biodegradable hinge cap as set forth in  claim 1 , wherein the mass ratio between the polylactic acid and the aliphatic polyester resin other than the polylactic acid in the resin composition is (polylactic acid):(aliphatic polyester other than polylactic acid)=40:60 to 20:80. 
   
   
       4 . A biodegradable hinge cap as set forth in  claim 1 , wherein the resin composition has a flexural modulus of 700 to 3000 MPa. 
   
   
       5 . A biodegradable hinge cap as set forth in  claim 1 , wherein the resin composition has a flexural modulus of 1100 to 1800 MPa. 
   
   
       6 . A biodegradable hinge cap as set forth in  claim 1 , wherein the aliphatic polyester resin other than the polylactic acid is a polyalkylene alkanoate. 
   
   
       7 . A biodegradable hinge cap as set forth in  claim 6 , wherein the polyalkylene alkanoate is one of polybutylene succinate, a copolymer of polybutylene succinate and a mixture of polybutylene succinate and the polybutylene succinate copolymer. 
   
   
       8 . A biodegradable hinge cap as set forth in  claim 7 , wherein the polybutylene succinate copolymer is polybutylene succinate adipate. 
   
   
       9 . A biodegradable hinge cap as set forth in  claim 1 , wherein the resin composition further comprises 0.01 to 5 parts by mass of one of a fatty acid, a fatty amide and a mixture of the fatty acid and the fatty amide based on a total of 100 parts by mass of the polylactic acid and the aliphatic polyester resin other than the polylactic acid. 
   
   
       10 . A biodegradable hinge cap as set forth in  claim 1 , wherein the resin composition further comprises 1 to 10 parts by mass of an anti-blocking agent based on a total of 100 parts by mass of the polylactic acid and the aliphatic polyester resin other than the polylactic acid. 
   
   
       11 . A biodegradable hinge cap as set forth in  claim 1 , wherein the resin composition further comprises 0.1 to 10 parts by mass of a hydrolysis suppressing agent based on a total of 100 parts by mass of the polylactic acid and the aliphatic polyester resin other than the polylactic acid. 
   
   
       12 . A biodegradable hinge cap as set forth in  claim 1 , wherein the hinge has a snap function for opening and closing the upper cap portion with respect to the cap body. 
   
   
       13 . A biodegradable hinge cap as set forth in  claim 12 , wherein the hinge includes a thin hinge portion which connects the side wall of the cap body to a side wall of the upper cap portion, and a pair of resilient connection plates provided on opposite sides of the thin hinge portion to connect the side wall of the cap body to the side wall of the upper cap portion. 
   
   
       14 . A biodegradable hinge cap as set forth in  claim 1 , wherein the hinge has a tensile break stress retention ratio of not less than 20% after the upper cap portion is subjected to an opening/closing operation 1,000 times. 
   
   
       15 . A biodegradable hinge cap as set forth in  claim 1 , wherein the hinge has a tensile break stress retention ratio of not less than 40% after the upper cap portion is subjected to an opening/closing operation 1,000 times.