Polyester containers having a reduced coefficient of friction

Abstract

Polyester containers having a reduced coefficient of friction (“COF”) are produced by increasing the surface roughness of the polyester using either thermal crystallization or solvent crystallization. Because the low COF reduces or eliminates friction between polyester containers, the containers do not become entangled and disrupt the manufacturing process. As a result, the containers move easily through typical conveying and filling lines in manufacturing processes that use the containers.

1. A process for producing a polyester container having a reduced coefficient of friction, comprising:
 providing a polyester preform having an exterior surface;  
 treating the preform exterior surface to increase surface roughness using a process selected from the group consisting of thermal crystallization and chemical crystallization; and  
 stretch-blow molding the treated preform into a container.  
 
     
     
       2. The process of  claim 1  wherein the container has a surface roughness of from about 10 to about 80 nanometers, a coefficient of friction from about 0.01 to about 1.0, and a haze of from about 0.1% to about 5%. 
     
     
       3. The process of  claim 1  wherein the container has a surface roughness of from about 15 to about 60 nanometers, the coefficient of friction of the polyester in the container is from about 0.05 to about 0.5, and the haze level of the polyester container is from about 0.1% to about 3%. 
     
     
       4. The process of  claim 1  wherein the process for treating the exterior surface is thermal crystallization. 
     
     
       5. The process of  claim 4  wherein the preform exterior surface is heated to a temperature near or in the lower end of the thermal haze region for the polyester. 
     
     
       6. The process of  claim 4  wherein the temperature of the preform exterior surface is heated to a temperature about 10° C. above the pearlescent point of the polyester and the remainder of the preform is heated to a temperature about the pearlescent point of the polyester. 
     
     
       7. The process of  claim 4  wherein the temperature of the preform exterior surface is heated to above about 120° C. and the remainder of the preform is heated to below about 110° C. 
     
     
       8. The process of  claim 1  wherein the process for treating the exterior surface is chemical crystallization. 
     
     
       9. The process of  claim 8  wherein the exterior surface is treated with a chemical selected from the group consisting of ketones, esters, ethers, chlorinated solvents, nitrogen containing solvents, and mixtures thereof. 
     
     
       10. The process of  claim 8  wherein the exterior surface is treated with a chemical selected from the group consisting of acetone, methyl acetate, methyl ethyl ketone, tetrahydrofuran, cyclohexanone, ethyl acetate, N,N dimethylformamide, dioctyl phthalate, toluene, xylene, benzene, dimethylsulfoxide, and mixtures thereof. 
     
     
       11. The process of  claim 8  wherein the exterior surface is treated with a chemical selected from the group consisting of acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, dimethylsulfoxide, and mixtures thereof. 
     
     
       12. The process of  claim 8  wherein the exterior surface is treated with a chemical for from about 1 to about 10 seconds. 
     
     
       13. The process of  claim 8  wherein the exterior surface is treated with acetone. 
     
     
       14. The process of  claim 13  wherein the exterior surface is treated with acetone for from about 0.2 to about 3 seconds at room temperature. 
     
     
       15. A polyester container made according to the process of  claim 1 . 
     
     
       16. A polyester container having a reduced coefficient of friction, comprising:
 polyester that has been treated to increase the surface roughness of the polyester using a process selected from the group consisting of thermal crystallization and chemical crystallization.  
 
     
     
       17. The container of  claim 16  wherein the surface roughness of the polyester in the container is from about 10 to about 80 nanometers, the coefficient of friction of the polyester in the container is from about 0.01 to about 1.0, and the haze level of the polyester container is from about 0.1% to about 5%. 
     
     
       18. The container of  claim 16  wherein the surface roughness of the polyester in the container is from about 15 to about 60 nanometers, the coefficient of friction of the polyester in the container is from about 0.05 to about 0.5, and the haze level of the polyester container is from about 0.1% to about 3%. 
     
     
       19. The container of  claim 16  wherein the polyester is selected from the group consisting poly(ethyleneterephthalate), poly(ethylenenaphthalate), poly(ethyleneisophthalate), and poly(ethylenebutyleneterephthalate). 
     
     
       20. The container of  claim 16  wherein the polyester is poly(ethyleneterephthalate). 
     
     
       21. The container of  claim 16  wherein the polyester comprises only a portion of the container. 
     
     
       22. The container of  claim 16  wherein the polyester has been treated to increase the surface roughness of the polyester using thermal crystallization. 
     
     
       23. The container of  claim 16  wherein the polyester has been treated to increase the surface roughness of the polyester using chemical crystallization. 
     
     
       24. A polyester preform useful for producing a polyester container having a reduced coefficient of friction, comprising:
 a polyester preform that has been treated to increase the surface roughness of the polyester using a process selected from the group consisting of thermal crystallization and chemical crystallization.  
 
     
     
       25. A process for producing a polyester having a reduced coefficient of friction, comprising:
 treating the surface of the polyester to increase surface roughness using a process selected from the group consisting of thermal crystallization and chemical crystallization.