Stabilization of fluorescent dyes in vinyl articles using hindered amine light stabilizers

Abstract

A durable colored article having fluorescent properties comprises a substantially solventless polyvinyl chloride matrix, a thioxanthene fluorescent dye, and a secondary or tertiary hindered amine light stabilizer having a molecular weight less than about 1000 grams/mole. The invention has the advantage in that it provides a flexible polyvinyl chloride film that exhibits durable fluorescent colors.

1 . An article exhibiting durable color and fluorescent properties comprising: 
 (a) a polymeric matrix that contains a substantially solventless polyvinyl chloride resin;    (b) a thioxanthene fluorescent dye; and    (c) a hindered amine light stabilizer comprising at least one secondary or tertiary amine groups and having a molecular weight less than about 1000 grams/mole.    
   
   
       2 . The article of  claim 1 , wherein the polymeric matrix further comprises plasticized polyvinyl chloride resin.  
   
   
       3 . The article of  claim 1 , wherein the article contains at most about 2 weight percent of the thioxanthene fluorescent dye based on the total weight of the article.  
   
   
       4 . The article of  claim 1 , wherein the article contains about 0.01 to at about 1 weight percent of the thioxanthene fluorescent dye based on the total weight of the article.  
   
   
       5 . The article of  claim 1 , wherein the article contains at most about 2 weight percent of the hindered amine light stabilizer based on the total weight of the article.  
   
   
       6 . The article of  claim 1 , wherein the article contains about 0.05 to about 1 weight percent of the hindered amine light stabilizer based on the total weight of the article.  
   
   
       7 . The article of  claim 1 , wherein the hindered amine light stabilizer is selected from at least one of the group consisting of bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)-2-n-butyl-2-(3,5-di-tert-butyl-4-hydroxybenzyl)malonate, and prpanedloic acid, [(4-methoxyphenyl)-methylene]-bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)ester.  
   
   
       8 . A fluorescent retroreflective article that comprises the article of  claim 1 .  
   
   
       9 . The article of  claim 1 , wherein the article is a film.  
   
   
       10 . The article of  claim 1 , wherein the article is a retroreflective cube film.  
   
   
       11 . The article of  claim 1  further comprising a protective overlay.  
   
   
       12 . A retroreflective sheeting exhibiting durable color and fluorescent properties comprising: 
 (a) a retroreflective base sheet having a front surface; and    (b) a body layer disposed on the frong surface of the base sheet, the body layer comprising the article of  claim 1 .    
   
   
       13 . The sheeting of  claim 12 , wherein the retroreflective base sheet is a cube corner based sheeting or a microsphere based sheeting.  
   
   
       14 . The sheeting of  claim 12 , wherein the sheeting is sufficiently flexible to be wound about a mandrel having a diameter of 3 millimeters without cracking.  
   
   
       15 . A method of making an article exhibiting durable color and fluorescent properties comprising: 
 (a) combining substantially solventless polyvinyl chloride resin, a thioxanthene fluorescent dye, and a hindered amine light stabilizer comprising at least one secondary or tertiary amine groups having a molecular weight less than 1000 grams/mole into a mixture; and    (b) forming the article from the mixture.    
   
   
       16 . The method of  claim 15 , wherein the article is formed by either extrusion or calendaring.  
   
   
       17 . The method of  claim 15 , wherein the extrusion temperature or calendaring temperature is about 175° C. to about 205° C.  
   
   
       18 . The method of  claim 15 , wherein the article contains at most about 2 weight percent of the thioxanthene fluorescent dye based on the total weight of the article.  
   
   
       19 . The method of  claim 15 , wherein the article contains about 0.01 to about 1 weight percent of the thioxanthene fluorescent dye based on the total weight of the article.  
   
   
       20 . The method of  claim 15 , wherein the article contains at most about 2 weight percent of the hindered amine light stabilizer based on the total weight of the article.  
   
   
       21 . The method of  claim 15 , wherein the article contains about 0.05 to about 1 weight percent of the hindered amine light stabilizer based on the total weight of the article.  
   
   
       22 . The method of  claim 15 , wherein the article is disposed on a front surface of a retroreflective base sheet.  
   
   
       23 . The method of  claim 22 , wherein the retroreflective base sheet is cube corner based or microsphere based.  
   
   
       24 . A fluorescence-stabilized polymeric composition comprising: 
 a) polyvinyl chloride;    b) a fluorescent dye;    c) an ultraviolet absorber; and    d) a hindered amine light stabilizer compound.    
   
   
       25 . A fluorescence-stabilized polymeric composition of  claim 24  wherein said fluorescent dye is a thioxanthene.  
   
   
       26 . A fluorescence-stabilized polymeric composition of  claim 24  wherein said ultraviolet absorber is a benzophenone.  
   
   
       27 . A retroreflective structure comprising the polymeric composition of  claim 24.