Polyolefin container having certain shrink characteristics and method of making such containers

Abstract

The two stage production of clear, low-haze, injection stretch blow molded polypropylene container articles with advantageous free shrink characteristics is disclosed. In the first processing stage, a preform article is manufactured on an injection molding machine. In a second and subsequent step, which may occur remotely from apparatus used in the first step, the preform article is heated and stretch blown into a container. The process may employ the selection of processing parameters to produce preform articles that facilitate stretch blow molding at relatively high rates of speed, while still maintaining an appropriate polypropylene polymer morphology that results in clear, low haze containers. Free shrink may be improved and measured. Furthermore, a haze, MFI, and wall thickness of containers subjected to a free shrinkage test following manufacture may be used to estimate or predict the processing parameters used to manufacture the container.

1 . A polypropylene container made by an injection stretch blow molding two stage process, said container having a side wall, wherein: 
 a) said side wall provides a haze value of less than about 3 according to ASTM D 1003,    b) said polypropylene provides an MFI between about 6 g/10 min and about 50 g/10 min according to ASTM D 1238;    c) wherein the average wall thickness of said container after subjecting said container to the free shrinkage test is less than about 1.8 mm.    
   
   
       2 . The polypropylene container according to  claim 1  wherein said haze of said side wall of the polypropylene container is less than about 2, measured according to ASTM D 1003.  
   
   
       3 . A polypropylene container according to  claim 1  wherein the haze of the side wall of the polypropylene container is less than about 1, measured according to ASTM D 1003.  
   
   
       4 . A polypropylene container according to  claim 1  wherein the wall thickness of the container after subjecting the container to the free shrinkage test is less than about 1.6 mm.  
   
   
       5 . A polypropylene container according to  claim 1  wherein the wall thickness of the container after subjecting the container to the free shrinkage test is less than about 1.5 mm.  
   
   
       6 . A polypropylene container according to  claim 1  wherein the wall thickness of the bottle after subject to the free shrinkage test is less than 1.4 mm.  
   
   
       7 . A polypropylene container according to  claim 1  wherein the wall thickness of the bottle after subject to the free shrinkage test is less than about 1.2 mm.  
   
   
       8 . A polypropylene container according to  claim 1  wherein the wall thickness of the bottle after subject to the free shrinkage test is less than about 1.0 mm.  
   
   
       9 . A polypropylene container according to  claim 2  wherein the wall thickness of the bottle after subject to the free shrinkage test is less than about 1.6 mm.  
   
   
       10 . A polypropylene container according to  claim 2  wherein the wall thickness of the bottle after subject to the free shrinkage test is less than about 1.4 mm.  
   
   
       11 . A polypropylene container according to  claim 2  wherein the wall thickness of the bottle after subject to the free shrinkage test is less than about 1.2 mm.  
   
   
       12 . A polypropylene resin container made by injection stretch blow molding two stage process with the following characteristics: 
 a) haze of the side wall of the polypropylene resin container of less than about 3 according to ASTM D 1003,    b) MFI of the polypropylene resin is between 6 g/10 min and 50 g/10 min according to ASTM D 1238,    c) the average wall thickness of the container is less than 0.8 mm,    d) the axial free shrinkage ratio (% FSA) is no more than about 50%.    
   
   
       13 . A polypropylene container according to  claim 12  wherein the haze of the side wall of the polypropylene container is less than about 2 according to ASTM D 1003.  
   
   
       14 . A polypropylene container according to  claim 12  wherein the haze of the side wall of the polypropylene container is less than about 1 according to ASTM D 1003.  
   
   
       15 . A polypropylene container according to  claim 12  wherein the wall thickness of the container is less than about 0.7 mm.  
   
   
       16 . A polypropylene container according to  claim 12  wherein the wall thickness of the container is less than about 0.6 mm.  
   
   
       17 . A polypropylene container according to  claim 12  wherein the wall thickness of the container is less than 0.5 mm.  
   
   
       18 . A polypropylene container according to  claim 12  wherein the shrinkage ratio is no more than 45%.  
   
   
       19 . A polypropylene container according to  claim 12  wherein the shrinkage ratio is no more than 40%.  
   
   
       20 . A polypropylene container according to  claim 13  wherein the wall thickness of the container is less than 0.7 mm.  
   
   
       21 . A polypropylene container according to  claim 13  wherein the wall thickness of the container is less than 0.6 mm.  
   
   
       22 . A polypropylene container according to  claim 13  wherein the shrinkage ratio is no more than 45%.  
   
   
       23 . A polypropylene container according to  claim 13  wherein the shrinkage ratio is no more than 40%.