Rheology modifiers for modifying the rheological behaviour of coating compositions

Abstract

The present invention provides rheology modifiers, which are water-soluble polymers having a weight average molecular weight (Mw) of at least 1′000′000 g/mol and an intrinsic viscosity of at least 2.5 dl/g, both as determined by size exclusion chromatography, and wherein the water-soluble polymers are in the form of solid particles. It also provides mixtures of rheology modifiers comprising a first rheology modifier, which is a water-soluble polymer having a weight average molecular weight (Mw) of at least 1′000′000 g/mol and an intrinsic viscosity of at least 2.5 dl/g, both as determined by size exclusion chromatography, and a second rheology modifier, which has a weight average molecular weight of from 2′000 g/mol to 800′000 g/mol. It also provides coating composition containing the rheology modifiers, respectively, mixtures of rheology modifiers, a process for their preparation, a process for coating a substrate using these coating compositions and substrates coated with these coating compositions.

1 - 4 . (canceled) 
     
     
         5 . A process for preparing a coating composition comprising the steps of
 (i) providing a rheology modifier, wherein the rheology modifier is a water-soluble polymer having a weight average molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic viscosity of at least 2.5 dl/g, both as determined by size exclusion chromatography, and wherein the water-soluble polymer is in the form of solid particles,   (ii) optionally forming an aqueous solution or inverse (water-in-oil) emulsion of the rheology modifiers of claim  1 , and   (iii) mixing the rheology modifiers of step (i) or the aqueous solution or inverse emulsion of the rheology modifiers obtained in step (ii) with a binder, a pigment, a carrier solvent and optional additives in order to form a coating composition.   
     
     
         6 . A coating composition obtainable by the process of  claim 5 . 
     
     
         7 . A process for coating a substrate comprising the steps of
 (i) providing a rheology modifier, wherein the rheology modifier is a water-soluble polymer having a weight average molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic viscosity of at least 2.5 dl/g, both as determined by size exclusion chromatography, and wherein the water-soluble polymer is in the form of solid particles,   (ii) optionally forming an aqueous solution or inverse (water-in-oil) emulsion of the rheology modifier,   (iii) mixing the rheology modifier of step (i) or the aqueous solution or inverse emulsion of the rheology modifier obtained in step (ii) with a binder, a pigment, a carrier solvent and optional additives in order to form a coating composition, and   (iv) applying the coating composition obtained in step (iii) onto a substrate.   
     
     
         8 . The process of  claim 7  wherein the substrate is made from paper, cardboard or polymer. 
     
     
         9 . The process of  claim 8 , wherein the substrate is made from paper. 
     
     
         10 . The process of  claim 7 , wherein the coating composition is applied by curtain coating onto the substrate. 
     
     
         11 . A substrate coated by the process of  claim 7 . 
     
     
         12 - 13 . (canceled) 
     
     
         14 . A mixture of rheology modifiers comprising a first rheology modifier, which is a water-soluble polymer having a weight average molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic viscosity of at least 2.5 dl/g, both as determined by size exclusion chromatography, and a second rheology modifier, which has a weight average molecular weight of from 2,000 g/mol to 800,000 g/mol, as determined by size exclusion chromatography. 
     
     
         15 . The mixture of rheology modifiers of  claim 14 , wherein the first rheology modifier is a polymer composed of monomer units derived from
 (i) at least one monomer of formula I   
       
         
           
           
               
               
           
         
         whereby 
         R 1  and R 2  can be the same or different and are hydrogen, C 1-6 -alkyl or C 5-8 -cycloalkyl, or R 1  and R 2  can together with the nitrogen to which they are attached form a heterocyclic 5- or 6-membered ring, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
         R 3  and R 4  can be the same or different and are hydrogen, C 1-6 -alkyl, C 5-8 -cycloalkyl, halogen, aryl or NHCOC 1-4 -alkyl, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
         (ii) optional other ethylenically unsaturated monomers. 
       
     
     
         16 . The mixture of rheology modifiers of  claim 15 , wherein the optional other ethylenically unsaturated monomers comprise at least one monomer of formula II 
       
         
           
           
               
               
           
         
         whereby 
         R 5  and R 6  can be the same or different and are hydrogen, C 1-6 -alkyl, C 5-8 -cycloalkyl, halogen, aryl or NHCOC 1-4 -alkyl, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
         M is hydrogen, ammonium, mono-, di-, tri- or tetraC 1-4 -alkylammonium, alkali metal or earth alkaline metal. 
       
     
     
         17 . The mixture of rheology modifiers of  claim 14 , wherein the second theology modifier is prepared from a monomer mixture comprising at least one acrylic monomer. 
     
     
         18 . A process for preparing a coating composition which comprises the steps of
 (i) providing the mixture of rheology modifiers of  claim 14     (ii) mixing the mixture of rheology modifiers of step (i) with a binder, a pigment, a carrier solvent and optional additives in order to form a coating composition.   
     
     
         19 . A coating composition obtainable by the process of  claim 18 . 
     
     
         20 . A process for coating a substrate comprising the steps of
 (i) providing the mixture of rheology modifiers of  claim 14 ,   (ii) mixing the mixture of rheology modifiers of step (i) with a binder, a pigment, a carrier solvent and optional additives in order to form a coating composition, and   (iii) applying the coating composition obtained in step (iii) onto the substrate.   
     
     
         21 . The process of  claim 20  wherein the substrate is made from paper, cardboard or polymer. 
     
     
         22 . The process of  claim 21 , wherein the substrate is made from paper. 
     
     
         23 . The process of  claim 20 , wherein the coating composition is applied by blade coating onto the substrate. 
     
     
         24 . A substrate coated by the process of  claim 20 . 
     
     
         25 - 26 . (canceled) 
     
     
         27 . A method for reducing white pitch in the production of coated paper comprising the step of coating the paper with a coating composition comprising the mixture of rheology modifiers of  claim 14 . 
     
     
         28 . The process of  claim 5 , wherein the water-soluble polymer is composed of monomer units derived from
 (i) at least one monomer of formula I   
       
         
           
           
               
               
           
         
         whereby
 R 1  and R 2  can be the same or different and are hydrogen, C 1-6 -alkyl or C 5-8 -cycloalkyl, or R 1  and R 2  can together with the nitrogen to which they are attached form a heterocyclic 5- or 6-membered ring, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
 R 3  and R 4  can be the same or different and are hydrogen, C 1-6 -alkyl, C 5-8 -cycloalkyl, halogen, aryl or NHCOC 1-4 -alkyl, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
 
         (ii) optional other ethylenically unsaturated monomers. 
       
     
     
         29 . The process of  claim 28 , wherein the optional other ethylenically unsaturated monomers comprise at least one monomer of formula II 
       
         
           
           
               
               
           
         
         whereby
 R 5  and R 6  can be the same or different and are hydrogen, C 1-6 -alkyl, C 5-8 -cycloalkyl, halogen, aryl or NHCOC 1-4 -alkyl, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
 
         M is hydrogen, ammonium, mono-, di-, tri- or tetraC 1-4 -alkylammonium, alkali metal or earth alkaline metal. 
       
     
     
         30 . The process of  claim 7 , wherein the water-soluble polymer is composed of monomer units derived from
 (i) at least one monomer of formula I   
       
         
           
           
               
               
           
         
         whereby
 R 1  and R 2  can be the same or different and are hydrogen, C 1-6 -alkyl or C 5-8 -cycloalkyl, or R 1  and R 2  can together with the nitrogen to which they are attached form a heterocyclic 5- or 6-membered ring, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
 R 3  and R 4  can be the same or different and are hydrogen, C 1-6 -alkyl, C 5-8 -cycloalkyl, halogen, aryl or NHCOC 1-4 -alkyl, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
 
         (ii) optional other ethylenically unsaturated monomers. 
       
     
     
         31 . The process of  claim 28 , wherein the optional other ethylenically unsaturated monomers comprise at least one monomer of formula II 
       
         
           
           
               
               
           
         
         whereby
 R 5  and R 6  can be the same or different and are hydrogen, C 1-6 -alkyl, C 5-8 -cycloalkyl, halogen, aryl or NHCOC 1-4 -alkyl, whereby C 1-6 -alkyl may be substituted with amino, hydroxyl, halogen, C 1-4 -alkoxy, aryl or mono- or diC 1-4 -alkylamino, and 
 M is hydrogen, ammonium, mono-, di-, tri- or tetraC 1-4 -alkylammonium, alkali metal or earth alkaline metal.