Novel methine dyes

Abstract

The present invention relates to novel methine dyes, methods for the preparation thereof and use thereof for dyeing plastics, especially polyamides, so as to obtain yellow to orange colourings with improved light fastness and improved thermal stability.

What is claimed is: 
     
         1 . A method for the bulk colouration of plastic, the method comprising:
 adding to plastic as colorants for the plastic one or more dyes of formula (I)   
       
         
           
           
               
               
           
         
         in which
 R 1  is hydrogen, halogen, C 1 -C 4 -alkyl, which is optionally mono- to trisubstituted, identically or differently, by halogen, COOH or COOR 9 , 
 R 2  is oxygen or sulfur, 
 R 3  is hydrogen, halogen, COOR 10  or CN, 
 R 4  is C 1 -C 4 -alkyl or phenyl, 
 R 5  and R 6  are each independently C 1 -C 4 -alkyl, 
 R 7  and R 8  are each independently hydrogen, halogen, C 1 -C 4 -alkyl, which is optionally mono- to trisubstituted, identically or differently, by methoxy or ethoxy, or COOR 11 , and 
 R 9 , R 10  and R 11  are each independently C 1 -C 4 -alkyl, and 
 where R 1  and R 3  are not both hydrogen. 
 
       
     
     
         2 . The method of  claim 1 , wherein in formula (I)
 R 1  is hydrogen, fluorine, chlorine, CF 3  or COOR 9 ,   R 2  is oxygen or sulfur,   R 3  is hydrogen, fluorine, chlorine or CN,   R 4 , R 5  and R 6  are each independently methyl or ethyl,   R 7  and R 8  are each independently hydrogen, each independently unsubstituted methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl; or methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl in each case mono- or disubstituted, identically or differently, by methoxy or ethoxy, and   R 9  is methyl or ethyl,   where R 1  and R 3  are not both hydrogen.   
     
     
         3 . The method of  claim 1 , wherein in formula (I)
 R 1  is fluorine, chlorine, CF 3  or COOR 9 ,   R 2  is oxygen or sulfur,   R 3  is hydrogen,   R 4 , R 5  and R 6  are each methyl,   R 7  and R 8  are each independently hydrogen, each independently unsubstituted methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl or 1-methyl-2-methoxyethyl, and   R 9  is methyl.   
     
     
         4 . The method of  claim 1 , wherein the plastic is selected from the group consisting of vinyl polymers, polyesters, polyolefins, polycarbonates, and polyamides. 
     
     
         5 . The method of  claim 1 , wherein the plastic is nylon-6 and/or nylon-6.6. 
     
     
         6 . The method of  claim 1 , wherein the method further comprises adding to the plastic an amount of 0.0001 to 1 percent by weight of the dyes, based on the amount of plastic. 
     
     
         7 . The method of  claim 1 , wherein the method further comprises adding to the plastic an amount of 0.01 to 0.5 percent by weight of the dyes, based on the amount of plastic. 
     
     
         8 . A method for the bulk colouration of plastic, comprising the steps:
 mixing one or more dyes of formula (I) of  claim 1  in dry form with one or more plastics, or, grinding the one or more dyes in dry form with one or more plastics, to produce a mixture, and melting and homogenizing the mixture.   
     
     
         9 . The method of  claim 8 , wherein the one or more plastics are in the form of granules. 
     
     
         10 . A method for the bulk colouration of plastics, the method comprising adding the one or more dyes of formula (I) of  claim 1  to a molten plastic material comprising one or more plastics to form a mixture, and then homogenizing the mixture. 
     
     
         11 . A method for the bulk colouration of plastics, the method comprising mixing the one or more dyes of formula (I) of  claim 1  with monomeric starting components for producing one or more plastics, and subsequently polymerizing the monomeric components. 
     
     
         12 . A method for the bulk colouration of polymethyl methacrylate (PMMA), the method comprising mixing the one or more dyes of formula (I) of  claim 1  with one or more methyl methacrylate monomers to form a mixture, or dissolving the one or more dyes therein to form a solution, and polymerizing the monomers in the mixture or solution in the presence of one or more polymerization catalysts. 
     
     
         13 . A plastic composition comprising the one or more dyes of formula (I) of  claim 1 . 
     
     
         14 . The plastic composition of  claim 13 , wherein the plastic composition is a polyamide composition or a polymethyl methacrylate. 
     
     
         15 . A moulding comprising one or more plastic compositions of  claim 13 .