Method for reducing plate-out in a stretch blow molded container

Abstract

A method for reducing or eliminating plate-out during the process used to produce stretch blow molded containers from polyester preforms by crystallizing the low molecular weight polyester molecules in or on the preform exterior surface before stretch blow molding the preform into a container. The molecules are crystallized using a crystallization process selected from (1) treating the outer surface of the preform with a solvent that is capable of crystallizing low molecular weight polyester molecules in polyester or (2) heating the outer surface of the preform to a temperature and for a time suitable for crystallizing low molecular weight polyester molecules in polyester. Plate-out is reduced because the crystallized molecules do not migrate out of the preform and form plate-out deposits on the mold.

We claim:  
     
       1. A method for reducing or eliminating plate-out during the process used to produce stretch blow molded containers from polyester preforms comprising crystallizing at least a portion of the low molecular weight polyester molecules at the exterior surface of the preform before stretch blow molding the preform into a container. 
     
     
       2. The method of  claim 1  wherein the low molecular weight polyester molecules are crystallized using a process selected from the group consisting of treating the outer surface of the preform with a solvent that is capable of crystallizing low molecular weight polyester molecules in polyester and heating the outer surface of the preform to a temperature and for a time suitable for crystallizing low molecular weight polyester molecules in polyester. 
     
     
       3. The method of  claim 1  wherein the low molecular weight polyester molecules are crystallized by treating the outer surface of the preform with a solvent that is capable of crystallizing low molecular weight polyester molecules in polyester. 
     
     
       4. The method of  claim 3  wherein the solvent is selected from the group consisting of ketones, esters, ethers, chlorinated solvents, nitrogen containing solvents, and mixtures thereof. 
     
     
       5. The method of  claim 3  wherein the solvent is 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. 
     
     
       6. The method of  claim 3  wherein the solvent is selected from the group consisting of acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, dimethylsulfoxide, and mixtures thereof. 
     
     
       7. The method of  claim 3  wherein the outer surface of the preform is treated with a solvent for from about 0.1 to about 20 seconds. 
     
     
       8. The method of  claim 3  wherein the solvent is acetone. 
     
     
       9. The method of  claim 8  wherein the outer surface of the preform is treated with acetone for from about 0.2 to about 3 seconds. 
     
     
       10. The method of  claim 3  further comprising the step of removing residual solvent from the preform prior to stretch blow molding. 
     
     
       11. The method of  claim 1  wherein the low molecular weight polyester molecules are crystallized by heating the outer surface of the preform to a temperature and for a time suitable for crystallizing low molecular weight polyester molecules in polyester. 
     
     
       12. The method of  claim 11  wherein the preform surface is heated to a temperature of from about 100° C. to about 150° C. for a period of from about 1 to about 26 seconds. 
     
     
       13. The method of  claim 1  wherein the polyester preform contains from about 0.01% to about 2% low molecular weight polyester molecules in the preform. 
     
     
       14. The method of  claim 1  further comprising blow molding the preform into a container. 
     
     
       15. A container made using the method of  claim 14 . 
     
     
       16. A method for making a polyester preform useful for reducing or eliminating plate-out during the process used to produce stretch blow molded containers from polyester preforms comprising crystallizing low molecular weight polyester molecules at the preform exterior surface. 
     
     
       17. The method of  claim 16  wherein the low molecular weight polyester molecules are crystallized using a process selected from the group consisting of treating the outer surface of the preform with a solvent that is capable of crystallizing low molecular weight polyester molecules in polyester and heating the outer surface of the preform to a temperature and for a time suitable for crystallizing low molecular weight polyester molecules in polyester. 
     
     
       18. The method of  claim 16  wherein the low molecular weight polyester molecules are crystallized by treating the outer surface of the preform with a solvent that is capable of crystallizing low molecular weight polyester molecules in polyester. 
     
     
       19. The method of  claim 16  wherein the low molecular weight polyester molecules are crystallized by heating the outer surface of the preform to a temperature and for a time suitable for crystallizing low molecular weight polyester molecules in polyester. 
     
     
       20. A polyester preform made using the method of  claim 16 . 
     
     
       21. A polyester preform useful for reducing or eliminating plate-out during the process used to produce stretch blow molded containers from polyester preforms comprising a polyester preform having crystallized low molecular weight polyester molecules in or on the preform exterior surface. 
     
     
       22. The preform of  claim 21  wherein the low molecular weight polyester molecules have been crystallized using a process selected from the group consisting of treating the outer surface of the preform with a solvent that is capable of crystallizing low molecular weight polyester molecules in polyester and heating the outer surface of the preform to a temperature and for a time suitable for crystallizing low molecular weight polyester molecules in polyester. 
     
     
       23. The preform of  claim 21  wherein the low molecular weight polyester molecules have been crystallized by treating the outer surface of the preform with a solvent that is capable of crystallizing low molecular weight polyester molecules in polyester. 
     
     
       24. The preform of  claim 21  wherein the low molecular weight polyester molecules have been crystallized by heating the outer surface of the preform to a temperature and for a time suitable for crystallizing low molecular weight polyester molecules in polyester.