Coinjection stretch blow molded container

Abstract

Multi-layered, coinjection stretch-blow molded containers are obtained by stretch-blow molding a preform prepared by coinjection molding a polyester resin and an EVOH resin blend in which one of the EVOH resins is dispersed as particles in an EVOH resin matrix. Containers prepared with this EVOH blend have good impact delamination resistance, good gas-barrier properties, and high transparency is high, even without an adhesive layer. The EVOH blend is composed of two EVOH resins having different ethylene contents and degrees of saponification. The blend exhibits at least two crystal fusion peaks by DSC.

What is claimed as new and is intended to be secured by Letters Patent is:  
     
         1 . A container comprising: 
 at least one layer comprising a thermoplastic polyester, and    at least one layer comprising a mixture of two ethylene-vinyl alcohol copolymers B1 and B2,    wherein said mixture of B1 and B2 has a morphology in which particles of B2 are dispersed in B1, said mixture of B1 and B2 exhibits at least two crystal fusion peaks in its differential scanning calorimetry (DSC) and satisfies the following formulae (1) to (7):   60/40≦WB1/WB2≦90/10  (1)25≦ETB1≦40  (2)99≦SDB1  (3)35≦ETB2≦48  (4)92≦SDB2≦99  (5)8≦ETB2−ETB1≦23  (6)1≦SDB1−SDB2≦8  (7)   and,    WB1 is the amount by weight of B1 in the mixture,    WB2 is the amount by weight of B2 in the mixture,    ETB1 is the mol % ethylene in B1,    ETB2 is the mol % ethylene in B2,    SDB1 is the % saponification of B1, and    SDB2 is the % saponification of B2.    
     
     
         2 . The container of  claim 1 , wherein one layer comprising B1 and B2 is contacted on each face thereof with a layer of said thermoplastic polyester.  
     
     
         3 . The container of  claim 1 , wherein pellets of the mixture are injection-molded, and the particles of B2 dispersed in B1 have a mean particle size of at most 0.8 μm.  
     
     
         4 . The container of  claim 1 , wherein B1 and B2 have melt indices (in units of g/10 min, measured at 190° C. under a load of 2160 g) MIB1 and MIB2, respectively, which satisfy formula (8): 
       0.1≦MIB1/MIB2≦10  (8). 
     
     
         5 . The container of  claim 1 , wherein the thermoplastic polyester has an intrinsic viscosity IV A (in units of dl/g) which satisfies the following formula (9) and the mixture of B1 and B2 has a melt index MIB (in units of g/10 min, measured at 190° C. under a load of 2160 g) which satisfies the following formula (10): 
       0.60≦IV A≦0.90  (9)0.1≦MIB≦10  (10). 
     
     
         6 . The container of  claim 1 , wherein the body of said container has a haze value of at most 5%.  
     
     
         7 . The container of  claim 1 , wherein said container is a stretch-blow molded container.  
     
     
         8 . The container of  claim 7 , wherein the capacity of said container is at most 800 ml.  
     
     
         9 . A preform for a container comprising: 
 at least one layer comprising a thermoplastic polyester, and    at least one layer comprising a mixture of two ethylene-vinyl alcohol copolymers B1 and B2,    wherein said mixture of B1 and B2 has a morphology in which particles of B2 are dispersed in B1, said mixture of B1 and B2 exhibits at least two crystal fusion peaks in its differential scanning calorimetry (DSC) and satisfies the following formulae (1) to (7):   60/40≦WB1/WB2≦90/10  (1)25≦ETB1≦40  (2)99≦SDB1  (3)35≦ETB2≦48  (4)92≦SDB2≦99  (5)8≦ETB2−ETB1≦23  (6)1≦SDB1−SDB2≦8  (7)   and,    WB1 is the amount by weight of B1 in the mixture,    WB2 is the amount by weight of B2 in the mixture,    ETB1 is the mol % ethylene in B1,    ETB2 is the mol % ethylene in B2,    SDB1 is the % saponification of B1, and    SDB2 is the % saponification of B2.    
     
     
         10 . The preform of  claim 9 , wherein one layer comprising B1 and B2 is contacted on each face thereof with a layer of said thermoplastic polyester.  
     
     
         11 . The preform of  claim 9 , wherein pellets of the mixture are injection-molded, and the particles of B2 dispersed in B1 have a mean particle size of at most 0.8 μm.  
     
     
         12 . The preform of  claim 9 , wherein B1 and B2 have melt indices (in units of g/10 min, measured at 190° C. under a load of 2160 g) MIB1 and MIB2, respectively, which satisfy formula (8): 
       0.1≦MIB1/MIB2≦10  (8). 
     
     
         13 . The preform of  claim 9 , wherein the thermoplastic polyester has an intrinsic viscosity IV A (in units of dl/g) which satisfies the following formula (9) and the mixture of B1 and B2 has a melt index MIB (in units of g/10 min, measured at 190° C. under a load of 2160 g) which satisfies the following formula (10): 
       0.60≦IV A≦0.90  (9)0.1≦MIB≦10  (10). 
     
     
         14 . A polymer blend comprising two ethylene-vinyl alcohol copolymers B1 and B2, 
 wherein said blend of B1 and B2 has a morphology in which particles of B2 are dispersed in B1, said mixture of B1 and B2 exhibits at least two crystal fusion peaks in its differential scanning calorimetry (DSC) and satisfies the following formulae (1) to (7):   60/40≦WB1/WB2≦90/10  (1)25≦ETB1≦40  (2)99≦SDB1  (3)35≦ETB2≦48  (4) 92 ≦SDB2≦99  (5)8≦ETB2−ETB1≦23  (6)1≦SDB1−SDB2≦8  (7)   and,    WB1 is the amount by weight of B1 in the blend,    WB2 is the amount by weight of B2 in the blend,    ETB1 is the mol % ethylene in B1,    ETB2 is the mol % ethylene in B2,    SDB1 is the % saponification of B1, and    SDB2 is the % saponification of B2.    
     
     
         15 . The polymer blend of  claim 14 , wherein the particles of B2 dispersed in B1 have a mean particle size of at most 0.8 μm.  
     
     
         16 . The polymer blend of  claim 14 , wherein B1 and B2 have melt indices (in units of g/10 min, measured at 190° C. under a load of 2160 g) MIB1 and MIB2, respectively, which satisfy formula (8): 
       0.1≦MIB1/MIB2≦10  (8). 
     
     
         17 . The polymer blend of  claim 14 , wherein the blend has a melt index MIB (in units of g/10 min, measured at 190° C. under a load of 2160 g) which satisfies the following formula (10): 
       0.1≦MIB≦10  (10). 
     
     
         18 . A process for preparing a stretch-blow molded container comprising: 
 coinjection molding a preform, and    stretch-blow molding said preform, thereby forming a stretch-blow molded container, wherein said preform comprises: 
 at least one layer comprising a thermoplastic polyester, and  
 at least one layer comprising a mixture of two ethylene-vinyl alcohol copolymers B1 and B2,  
 wherein said mixture of B1 and B2 has a morphology in which particles of B2 are dispersed in B1, said mixture of B1 and B2 exhibits at least two crystal fusion peaks in its differential scanning calorimetry (DSC) and satisfies the following formulae (1) to (7): 
 60/40≦WB1/WB2≦90/10  (1)25≦ETB1≦40  (2)99≦SDB1  (3)35≦ETB2≦48  (4)92≦SDB2≦99  (5)8≦ETB2−ETB1≦23  (6)1≦SDB1−SDB2≦8  (7) 
 and,  
 WB1 is the amount by weight of B1 in the mixture,  
 WB2 is the amount by weight of B2 in the mixture,  
 ETB1 is the mol % ethylene in B1,  
 ETB2 is the mol % ethylene in B2,  
 SDB1 is the % saponification of B1, and  
 SDB2 is the % saponification of B2.  
   
     
     
         19 . The process of  claim 18 , wherein the particles of B2 dispersed in B1 have a mean particle size of at most 0.8 μm.  
     
     
         20 . The process of  claim 18 , wherein B1 and B2 have melt indices (in units of g/10 min, measured at 190° C. under a load of 2160 g) MIB1 and MIB2, respectively, which satisfy formula (8): 
       0.1≦MIB1/MIB2≦10  (8). 
     
     
         21 . The process of  claim 18 , wherein the thermoplastic polyester has an intrinsic viscosity IV A (in units of dl/g) which satisfies the following formula (9) and the mixture of B1 and B2 has a melt index MIB (in units of g/10 min, measured at 190° C. under a load of 2160 g) which satisfies the following formula (10): 
       0.60≦IV A≦0.90  (9)0.1≦MIB≦10  (10). 
     
     
         22 . The process of  claim 18 , wherein the body of said container has a haze value of at most 5%.