Method of producing powdery coating material

Abstract

Disclosed is a method of producing a powdery coating material by using: a curable acrylic resin (A) having a number average molecular weight of from 2,000 to 20,000 and a glass transition temperature of from 30 to 90° C. obtained by polymerizing a starting monomer containing from 15 to 50 mol % of an unsaturated compound which contains at least a glycidyl group and/or a methylglycidyl group, and from 20 to 50 mol % of methyl methacrylate; a curing agent (B) capable of being reacted with the glycidyl group or the methylglycidyl group constituting the curable acrylic resin (A); and an alcohol solvent (C) having a boiling point under normal pressure of from 70 to 120° C.; said method comprising a kneading step of so kneading the curable acrylic resin (A), the curing agent (B) and the alcohol solvent (C) that at least the curing agent (B) is dissolved in the alcohol solvent (C) at a temperature of not higher than 130° C., and a vapor-removing step of continuously vapor-removing the alcohol solvent (C) under a reduced pressure at a temperature of not higher than 130° C.

1 . (canceled)  
   
   
       2 . (canceled)  
   
   
       3 . (canceled)  
   
   
       4 . (canceled)  
   
   
       5 . (canceled)  
   
   
       6 . (canceled)  
   
   
       7 . (canceled)  
   
   
       8 . (canceled)  
   
   
       9 . (canceled)  
   
   
       10 . (canceled)  
   
   
       11 . (canceled)  
   
   
       12 . (canceled)  
   
   
       13 . (canceled)  
   
   
       14 . (canceled)  
   
   
       15 . (canceled)  
   
   
       16 . A method of producing a powdery coating material by using: 
 a curable acrylic resin (A) having a number average molecular weight of from 2,000 to 20,000 and a glass transition temperature of from 30 to 90° C. obtained by polymerizing a starting monomer containing from 15 to 50 mol % of an unsaturated compound which contains at least a glycidyl group and/or a methylglycidyl group, and from 20 to 50 mol % of methyl methacrylate in a polymerization solvent selected from the group consisting of toluene, xylene and an alcohol solvent having a boiling point under normal pressure of from 70 to 120° C. such that when the toluene or the xylene is used as the polymerization solvent, said solvent is vapor-removed prior to being kneaded with the curable acrylic resin (A), a curing agent (B) and the alcohol solvent (D);    the curing agent (B) capable of being reacted with the glycidyl group or the methylglycidyl group consisting the curable acrylic resin (A); and    the alcohol solvent (D) having a boiling point under normal pressure of from 64 to 120° C.    wherein, the alcohol solvent (D) is used in an amount of from 10 to 200 parts by weight per 100 parts by weight of the curing agent (B);    said method comprising:    (I) the curable acrylic resin (A) and curing agent (B) are continuously fed to a kneading step while side-feeding the solvent (D) to said kneading step to continuously knead them together so that at least the effect of homogeneous kneading enhances at 50 to 130° C., or (II) the curable acrylic resin (A) is continuously fed to the kneading step while side-feeding, to said kneading step, a curing agent solution obtained by dissolving the curing agent (B) in the alcohol solvent (D) to continuously knead them together so that at least the effect of homogeneous kneading enhances at 50 to 130° C.;    the alcohol solvent (D) is continuously vapor-removed under a reduced pressure at 50 to 130° C. in a vapor-removing step; and    said kneading and said vapor-removing of the alcohol solvent (D) are executed at such rates that an average contact time between the curable acrylic resin (A) and the alcohol solvent (D) is not longer than 5 minutes,    wherein the powdery coating material is obtained by pulverizing a mixture of the curing agent (B) and the curable acrylic resin (A) obtained by removing the alcohol solvent (D) therefrom.    
   
   
       17 . A method of producing a powdery coating material according to  claim 16 , wherein the alcohol solvent (D) is an alcohol having 1 to 4 carbon atoms or a mixture thereof.  
   
   
       18 . A method of producing a powdery coating material according to  claim 16 , wherein the apparatus used in the kneading step is a monoaxial or biaxial extruder, or a monoaxial or biaxial kneader.  
   
   
       19 . A method of producing a powdery coating material according to  claim 16 , wherein the apparatus used in the vapor-removing step is a monoaxial or biaxial extruder, or a monoaxial or biaxial kneader having at least one vapor-removing port.  
   
   
       20 . A method of producing a powdery coating material according to  claim 16 , wherein the kneading and the vapor-removing of solvent are effected by using a single kneading/vapor-removing apparatus having at least one vapor-removing port.  
   
   
       21 . A method of producing a powdery coating material according to  claim 20 , wherein the kneading/vapor-removing apparatus is a monoaxial or biaxial extruder, or a monoaxial or biaxial kneader.