Method for producing adhesive polyacrylates using mercapto functional photoinitiators

Abstract

A process for preparing pressure-sensitively adhesive polyacrylates by free-radical addition polymerization, characterized in that mercapto-functionalized photoinitiators of the general formula (I) and/or (II). H—S—R   (I) R—S—S—R′  (II) are added to the monomer mixture or to the reaction mixture, R and R′ being chosen independently of one another from the following groups: a) benzophenone, acetophenone, benzil, benzoin, hydroxyalkylphenone, phenylcyclohexyl ketone, anthraquinone, thioxanthone, triazine, or fluorenone radicals, it being possible for each of these radicals to be substituted by one or more halogen atoms and/or one or more alkoxy groups and/or one or more amino groups or hydroxyl groups, b) radicals which comprise one or more of the substituted or unsubstituted radicals specified under a).

1 . A process for preparing pressure-sensitively adhesive polyacrylates by free-radical addition polymerization, characterized in that mercapto-functionalized photoinitiators of the general formula (I) and/or (II)  
       H—S—R   (I) R—S—S—R′  (II)  
       are added to the monomer mixture or to the reaction mixture, R and R′ being chosen independently of one another from the following groups: 
 a) benzophenone, acetophenone, benzil, benzoin, hydroxyalkylphenone, phenylcyclohexyl ketone, anthraquinone, thioxanthone, triazine, or fluorenone radicals, it being possible for each of these radicals to be substituted by one or more halogen atoms and/or one or more alkoxy groups and/or one or more amino groups or hydroxyl groups,  
 b) radicals which comprise one or more of the substituted or unsubstituted radicals specified under a).  
 
     
     
         2 . The process of  claim 1 , characterized in that the fraction of the compounds (I) and/or (II) is from 0.01 to 5% by weight, based on the monomers employed.  
     
     
         3 . The process of at least one of the preceding claims, characterized in that the polymerization takes place using a monomer mixture which comprises at least the following component: 
 a) acrylic and methacrylic acid monomers of the following structure                          where R 1 ═H or CH 3      and R 2 =an alkyl chain having 2-20 carbon atoms    with a fraction of from 65 to 100% by weight,    and which optionally comprises the following component:    b) vinyl compounds having functional groups    with a fraction of from 0 to 35% by weight,    it being possible optionally for further components to be present in the monomer mixture.    
     
     
         4 . The process of at least one of the preceding claims, characterized in that the pressure-sensitively adhesive polyacrylates are crosslinked by ultraviolet radiation in a wavelength range from 200 to 400 nm.  
     
     
         5 . The use of the pressure-sensitively adhesive polyacrylates of at least one of the preceding claims to produce PSA articles, particularly for producing an adhesive tape comprising an acrylic PSA applied to one or both sides of a backing.