Resin composition of good long-run workability comprising ethylene-vinyl alcohol copolymer

Abstract

The present invention relates to a resin composition having an ethylene-vinyl alcohol copolymer (EVOH) component and a multi-layered structure containing the resin composition.

What is claimed is:  
     
         1 . A resin composition comprising an ethylene-vinyl alcohol copolymer, which is characterized in that, when it is heated in a nitrogen atmosphere at 220° C., its MFR (at 230° C. under a load of 10.9 kg) shows a minimum value within 10 hours after the start of heating it, and shows a maximum value (MFRmax) within 100 hours after showing its minimum value, that it contains from 0.05 to 4 μmols/g of a carboxylic acid (A), and that it satisfies the following formulae (1) and (2):  
       0.5 ≦MFRmax/MFR 0≦45  (1) 0.1≦( a 1)/( A )≦1.0  (2)  
       wherein MFRmax indicates the maximum value of MFR (at 230° C. under a load of 10.9 kg) of the resin composition heated in a nitrogen atmosphere at 220° C.; 
 MFR0 indicates MFR (at 230° C. under a load of 10.9 kg) of the resin composition not heated;  
 (A) indicates the total content (mol/g) of the carboxylic acid (A) and its salt in the resin composition;  
 (a1) indicates the content (μmol/g) of a carboxylic acid (a1) having a molecular weight of at least 75 and its salt in the resin composition.  
 
     
     
         2 . The resin composition as claimed in  claim 1 , which contains from 50 to 500 ppm, in terms of the metal element, of an alkali metal salt (B).  
     
     
         3 . The resin composition as claimed in  claim 1 , which contains from 10 to 120 ppm, in terms of the metal element, of an alkaline earth metal salt (C).  
     
     
         4 . The resin composition as claimed in  claim 1 , which contains from 10 to 500 ppm, in terms of the phosphate radical, of a phosphate compound (D).  
     
     
         5 . The resin composition as claimed in  claim 1 , which contains from 50 to 2000 ppm, in terms of the boron element, of a boron compound (E).  
     
     
         6 . The resin composition as claimed in  claim 1 , wherein the carboxylic acid (a1) having a molecular weight of at least 75 is a hydroxycarboxylic acid.  
     
     
         7 . The resin composition as claimed in  claim 1 , wherein the carboxylic acid (a1) having a molecular weight of at least 75 is a lactic acid.  
     
     
         8 . The resin composition as claimed in  claim 1 , which satisfies the following formula (3):  
       2 ≦[B (μ mol/g )+ C (μ mol/g )]/[ A (μ mol/g )+ D (μ mol/g )]≦9  (3)  
       wherein A indicates the content (μmol/g) of the carboxylic acid (A) in the resin composition per the unit weight of the composition; 
 B indicates the content (μmol/g, in terms of the metal element) of the alkali metal salt (B) in the resin composition per the unit weight of the composition;  
 C indicates the content (μmol/g, in terms of the metal element) of the alkaline earth metal salt (C) in the resin composition per the unit weight of the composition;  
 D indicates the content (μmol/g, in terms of the phosphate radical) of the phosphate compound (D) in the resin composition per the unit weight of the composition.  
 
     
     
         9 . The resin composition as claimed in  claim 1 , which contains from 0.005 to 1 part by weight, relative to 100 parts by weight of the ethylene-vinyl alcohol copolymer therein, of a lubricant.  
     
     
         10 . Pellets of the resin composition of  claim 1 , which have from 0.005 to 0.5 parts by weight, relative to 100 parts by weight of the resin composition, of a lubricant adhered on their outer surfaces.  
     
     
         11 . A multi-layered structure comprising at least one layer of the resin composition of  claim 1 .  
     
     
         12 . A resin composition comprising an ethylene-vinyl alcohol copolymer, which is characterized in that, when it is heated in a nitrogen atmosphere at 220° C., its MFR (at 230° C. under a load of 10.9 kg) shows a minimum value within 10 hours after the start of heating it, and shows a maximum value (MFRmax) within 100 hours after showing its minimum value, that it contains from 50 to 500 ppm of a carboxylic acid (a2) having a molecular weight of smaller than 75, from 50 to 500 ppm, in terms of the metal element, of an alkali metal salt (B), from 10 to 120 ppm, in terms of the metal element, of an alkaline earth metal salt (C), from 10 to 200 ppm, in terms of the phosphate radical, of a phosphate compound (D), and from 50 to 2000 ppm, in terms of the boron element, of a boron compound (E), and that it satisfies the following formula (1):  
       0.5 ≦MFRmax/MFR 0≦45  (1)  
       wherein MFRmax indicates the maximum value of MFR (at 230° C. under a load of 10.9 kg) of the resin composition heated in a nitrogen atmosphere at 220° C.; 
 MFR0 indicates MFR (at 230° C. under a load of 10.9 kg) of the resin composition not heated.  
 
     
     
         13 . The resin composition as claimed in  claim 12 , wherein the carboxylic acid (a2) having a molecular weight of smaller than 75 is an acetic acid.  
     
     
         14 . The resin composition as claimed in  claim 12 , which satisfies the following formula (4):  
       1 ≦[B (μ mol/g )+ C (μ mol/g )]/[ D (μ mol/g )+( a 2)(μ mol/g )]≦15  (4)  
       wherein (a2) indicates the content (μmol/g) of the carboxylic acid (a2) having a molecular weight of smaller than 75 in the resin composition per the unit weight of the composition; 
 B indicates the content (μmol/g, in terms of the metal element) of the alkali metal salt (B) in the resin composition per the unit weight of the composition;  
 C indicates the content (μmol/g, in terms of the metal element) of the alkaline earth metal salt (C) in the resin composition per the unit weight of the composition;  
 D indicates the content (μmol/g, in terms of the phosphate radical) of the phosphate compound (D) in the resin composition per the unit weight of the composition.  
 
     
     
         15 . The resin composition as claimed in  claim 12 , which contains from 0.005 to 1 part by weight, relative to 100 parts by weight of the ethylene-vinyl alcohol copolymer therein, of a lubricant.  
     
     
         16 . Pellets of the resin composition of  claim 12 , which have from 0.005 to 0.5 parts by weight, relative to 100 parts by weight of the resin composition, of a lubricant adhered on their outer surfaces.  
     
     
         17 . A multi-layered structure comprising at least one layer of the resin composition of any of  claim 12.