Patent Publication Number: US-6984724-B2

Title: Pigmented 1-naphtholsulphonic acid-based monoazo pigments

Description:
The present invention relates to novel azo pigments based on naphtholsulfonic acids and a process for preparing them. 
     Laked monoazo pigments from the series of the naphtholsulfonic acids are known in principle, for example as Pigment Yellow 104, P. Orange 19, P. Red 60, 66 and 67. They are proposed for coloration of inks, including printing inks, and of plastics. But it is also known that these pigments have poor fastness properties, namely poor lightfastnesses and also insufficient color strengths. 
     Colorants of the aforementioned type that have improved fastness properties were described for example in WO 98/13425 or GB 1313147. However, the pigments described therein do not have both high lightfastnesses and high color strengths. 
     It is an object of the present invention to provide laked yellow, orange, brown and red azo pigments which have both high lightfastnesses and high color strengths. 
     We have found that this object is achieved, surprisingly, by laked monoazo pigments having the substitution pattern of the present invention. 
     The present invention accordingly provides compounds of the formula (1) 
                 
 
where
 
     R 1  is H, Cl or CH 3 , 
     R 2  is H or Cl, 
     M 2+  is Mg 2+ , Mn 2+  or Sr 2+ , 
     Y 1 =COO −  or SO 3   − , and 
     Y 2 =SO 3   − , Y 3 =Y 4 =Y 5 =H; or Y 3 =SO 3   − , Y 2 =Y 4 =Y 5 =H; or 
     Y 4 =SO 3   − , Y 2 =Y 3 =Y 5 =H; or Y 5 =SO 3   − , Y 2 =Y 3 =Y 4 =H. 
     Preferred compounds for the purposes of the present invention are: 
     compound (1a) where R 1 =Cl, R 2 =H, M 2+ =Sr 2+ , Y 1 =COO − , Y 2 =Y 3 =Y 5 =H, Y 4 =SO 3   − ; 
     compound (1b) where R 1 =Cl, R 2 =H, M 2+ =Mn 2+ , Y 1 =COO − , Y 2 =Y 3 =Y 4 =H, Y 5 =SO 3   − ; 
     compound (1c) where R 1 =H, R 2 =H, M 2+ =Sr 2+ , Y 1 =COO − , Y 3 =Y 4 =Y 5 =H, Y 2 =SO 3   − ; 
     compound (1d) where R 1 =CH 3 , R 2 =Cl, M 2+ =Mg 2+ , Y 1 =SO 3   − , Y 2 =Y 4 =Y 5 =H, Y 3 =SO 3   − . 
     The pigments of the present invention are preparable by diazotization of an amine of the formula (2) 
                 
 
subsequent coupling with a naphtholsulfonic acid of the formula (3) 
                 
 
and laking with a magnesium, manganese or strontium salt.
 
     Useful amines are preferably anthranilic acid, 4-chloroanthranilic acid, 4-methylanthranilic acid, 2-amino-5-chloro-4-methylbenzenesulfonic acid and 2-amino-4-methylbenzenesulfonic acid. 
     The diazotization reaction is suitably carried out with alkali metal nitrites or the alkyl nitrites of short-chain alkanes together with strong mineral acids. Sodium nitrite and hydrochloric acid are particularly suitable. The reaction can be carried out in a temperature range of −5° C. to +30° C., preferably between 0° C. and 10° C. Although not necessary, the diazotization can be carried out in the presence of nonionic, anionic or cationic surface-active substances. It is optionally also possible to use other auxiliaries, such as natural or synthetic resins or resin derivatives. 
     The naphtholsulfonic acids of the formula (3) can be used as free acids or as salts, such as alkali metal or ammonium salts for example. Coupling is possible by the direct or inverse method, but preferably is carried out directly, i.e., the diazonium salt is added to the initially charged coupling component. The coupling reaction can be carried out in a temperature range between −5° C. and 80° C., preferably between 5° C. and 25° C., and at a pH between pH 4 and pH 14, especially between pH 9 and pH 12. Like the diazotization reaction, the coupling can be carried out in the presence of surface-active substances, resins and also resin derivatives or customary additives. In general, the coupling component is used in a small excess over the diazonium compound, and preferably 1 equivalent of diazo component is reacted with 1.02 to 1.10 equivalents of the coupling components. It is known that coupling with the coupling components 1-naphthol-3-sulfonic acid, 1-naphthol-5-sulfonic acid and 1-naphthol-8-sulfonic acid will by-produce the para-coupled product to a minor extent as well as producing the ortho-coupled main component. The fraction of by-produced components can be in the range from 0% to 20%. 
     The addition of alkali-soluble resinous auxiliaries or mixtures thereof during or after coupling and also before or during laking improves pigment dispersibility. Advantageously, the resinous auxiliaries or mixtures thereof are used in the form of their aqueous alkaline solutions. Useful resinous auxiliaries include natural and synthetic resins. Rosin, disproportionated or hydrogenated rosin and also rosin derivatives are advantageous. Preference is given to natural resin acids, such as abietic acid, dihydroabietic acid, tetrahydroabietic acid, laevopimaric acid, dextropimaric acid and isodextropimaric acid, as present in commercially available rosin varieties. Particular preference is given to the commercially available resin Rosin N, which contains the resin acids abietic acid, dehydroabetic acid, neoabietic acid, palustric acid, isopimaric acid, pimaric acid and sandaracopimaric acid, or to a commercial product which is equivalent to Rosin N. As well as the enumerated resins and their derivatives it is also possible to use alkyd resins or synthetic hydrocarbon resins having a high acid number. The resins mentioned are preferably added to the reaction mixture following the coupling reaction. 
     The coupling products prepared are laked by adding magnesium, manganese or strontium salts or aqueous solutions thereof. Preference is given to using an aqueous solution of one of the metal salts mentioned. Examples of suitable metal salts are magnesium chloride, magnesium nitrate, strontium chloride, strontium nitrate, manganese(II) sulfate and manganese(II) chloride, aqueous metal salt solutions of magnesium chloride, strontium chloride or manganese(II) sulfate being particularly suitable. The laking advantageously takes place at a temperature between 25 and 80° C. and preferably between 50 and 60° C. 
     After laking, the compounds of the present invention are preferably subjected to a heat treatment in an aqueous, aqueous-organic or organic medium at temperatures between 80 and 200° C., under atmospheric or superatmospheric pressure, and advantageously for 1 to 6 hours, especially in the presence of the aforementioned resinous auxiliaries. The pigment suspensions obtained can subsequently be filtered in the usual way and the presscake washed salt-free with water, dried and ground. 
     The compounds of the formula (1) are useful for pigmenting macromolecular organic materials of natural or synthetic origin, for example plastics, resins, varnishes, paints or electrophotographic toners and developers, and also inks including printing inks. 
     Macromolecular organic materials pigmentable with the compounds of the present invention include for example cellulose ethers and esters, such as ethylcellulose, nitrocellulose, cellulose acetate or cellulose butyrate, natural resins or synthetic resins, such as addition polymerization resins or condensation resins, for example amino resins, especially urea- and melamine-formaldehyde resins, alkyd resins, acrylic resins, phenolic resins, polycarbonates, polyolefins, such as polystyrene, polyvinyl chloride, polyethylene, polypropylene, polyacrylonitrile, polyacrylic esters, polyamides, polyurethanes or polyesters, rubber, casein, silicone and silicone resins, individually or in mixtures. 
     It is immaterial in this connection whether the macromolecular organic compounds mentioned are present as plastically deformable masses, melts or in the form of dopes, varnishes, paints or printing inks. Depending on the intended use, it will be advantageous to use the compounds of the present invention as a blend or in the form of preparations or dispersions. Based on the macromolecular organic material to be pigmented, the compounds of the present invention are used in an amount of 0.05% to 30% by weight and preferably 0.1% to 15% by weight. 
     The compounds of the present invention are also useful as colorants in electrophotographic toners and developers, such as for example one- or two-component powder toners (also known as one- or two-component developers), magnetic toners, liquid toners, addition polymerization toners and also specialty toners. 
     Typical toner binders are addition polymerization, polyaddition and polycondensation resins, such as styrene, styrene acrylate, styrene butadiene, acrylate, polyester, phenol-epoxy resins, polysulfones, polyurethanes, individually or in combination, and also polyethylene and polypropylene, which may each contain further ingredients, such as charge control agents, waxes or flow auxiliaries, or may be subsequently modified with these additives. 
     Furthermore, the compounds of the present invention are useful as colorants in powders and powder coatings, especially in triboelectrically or electrokinetically sprayable powder coatings used for surface coating of objects composed for example of metal, wood, plastic, glass, ceramic, concrete, textile material, paper or rubber. 
     Powder coating resins used are typically epoxy resins, carboxyl- and hydroxyl-containing polyester resins, polyurethane and acrylic resins together with customary hardeners. Combinations of resins are also used. For instance, epoxy resins are frequently used in combination with carboxyl- and hydroxyl-containing polyester resins. Typical hardener components (depending on the resin system) are for example acid anhydrides, imidazoles and also dicyandiamide and derivatives thereof, blocked isocyanates, bisacylurethanes, phenolic and melamine resins, triglycidyl isocyanurates, oxazolines and dicarboxylic acids. 
     The compounds of the present invention are also useful as colorants in ink-jet inks based on aqueous and nonaqueous systems and also in such inks which are processed according to the hot-melt process. 
     The compounds of the present invention are further useful as colorants for color filters not only for additive but also for subtractive color generation. 
     To evaluate the coating properties of the pigments prepared according to the invention, a selection was made, from among the multiplicity of known varnishes, of an alkyd-melamine (AM) resin varnish containing aromatic components and based on a medium-oil, nondrying alkyd resin. 
     The pigments of the present invention are notable for excellent fastness properties; more particularly, they have both high lightfastnesses and high color strengths. They do not contain any environmentally unsafe heavy metals. The properties mentioned qualify the pigments of the present invention for use in particular as colorants in the printing sector (especially solventborne printing inks, production of ink-jet inks) and also for use in varnishes and in plastics, color filters, toners and for coloration of seed. 
     Parts in the inventive and comparative examples which follow are by weight. 
    
    
     INVENTIVE EXAMPLE 1 
     a) Preparation of Rosin N Solution 
     To 4000 parts of water add 88 parts of an aqueous sodium hydroxide solution (40% w/w) and heat to 90° C. Add 800 parts of solid Rosin N (from Dujadwala and Company, Mumbai, India) a little at a time in the course of about 1 hour. 
     Then heat to the boil for about 30 minutes until a solution is obtained and make up with water to a total amount of 8000 parts of Rosin N solution. 
     b) Diazotization 
     Suspend 51.5 parts of 4-chloroanthranilic acid in 350 parts of water, add 48.4 parts of aqueous sodium hydroxide solution (40% w/w) and stir until all the amine has dissolved. Cool the resultant solution to 10° C. and add 51.8 parts of aqueous sodium nitrite solution (40% w/w). 
     Charge 300 parts of water and 108.8 parts of hydrochloric acid (30 w/w) to a second vessel and add ice to cool to 5° C. Add the alkaline solution of 4-chloroanthranilic acid to the acid/ice initial charge dropwise at a temperature between 0 and 5° C. in the course of 10 to 15 minutes with stirring. Add the sodium nitrite solution and stir at a temperature between 5 and 10° C. for 1 hour. Then destroy excess nitrite by adding sulfamic acid. 
     c) Coupling 
     Provide a mixture of 200 parts of water and 500 parts of ice as an initial charge. To this initial charge add with stirring 70.6 parts of 1-hydroxynaphthalene-5-sulfonic acid (L-acid) and then aqueous sodium hydroxide solution (40% w/w) to set a pH of 12 to 13. To the resultant solution add the diazonium salt of 4-chloroanthranilic acid from a) dropwise at a temperature between 5 and 10° C. in the course of 15 to 20 minutes and subsequently stir for 1 hour. Allow the temperature of the reaction mixture to rise from about 10° C. to about 20° C. during the subsequent stirring time. Once no diazonium compound and only traces of the coupling component are detectable, add 150 parts of the Rosin N solution prepared as per a) with stirring and stir for a further 10 to 15 minutes. Then adjust the pH with hydrochloric acid (10% w/w) to pH 5 to 6. 
     d) Laking 
     Heat the reaction mixture to 55° C. At this temperature, add a solution of 95.1 parts of strontium chloride in 300 parts of water dropwise in the course of about 10 minutes and stir until laking is complete (about half an hour). 
     e) Aftertreatment of Crude Pigment 
     Adjust the resultant suspension of the crude pigment with hydrochloric acid (30% w/w) to pH 4.0, then heat to 95° C. over one hour and stir at 95° C. for a further hour. Thereafter, allow to cool down to about 30° C. and filter the pigment off, before washing the filter cake salt-free with water. Dry the filter cake and grind to obtain 138 parts of a red pigment: compound (1a). 
     The pigment provides on incorporation into AM varnish a coating which is fast to overcoating, strong in color and high in lightfastness. The overcoating fastness is 5 on the 5 point “staining” gray scale of DIN 54002. 
     INVENTIVE EXAMPLE 2 
     Inventive Example 1 is repeated except for the following points: 
     The coupling component used is 70.6 parts of 1-hydroxynaphthalene-8-sulfonic acid. 
     Laking is effected using a solution of 90.6 parts of manganese(II) sulfate in 300 parts of water. 
     The pigment obtained is slurried up in a mixture of 1 800 parts of isobutanol and 800 parts of water. The suspension obtained is heated to 89° C. in the course of an hour and maintained at 89° C. for a further two hours. Thereafter, it is allowed to cool down to about 30° C. and the pigment is filtered off. The filter cake is dried and ground to obtain 115 parts of a brown pigment: compound (1 b). 
     INVENTIVE EXAMPLE 3 
     Inventive Example 1 is repeated except for the following points: 
     Diazotization: 41.1 parts of anthranilic acid and 360 parts of water are introduced as an initial charge and admixed with 121.0 parts of hydrochloric acid (30% w/w) with stirring. This is followed by cooling to 2 to 5° C. by adding ice and the dropwise addition of 62.2 parts of an aqueous sodium nitrite solution (40% w/w) in the course of 10 to 15 minutes. This is followed by stirring at 5° C. for an hour. Subsequently, excess nitrite is destroyed by addition of sulfamic acid. 
     The coupling component used is 77.5 parts of the sodium salt of 1-hydroxynaphthalene-3-sulfonic acid (sodium salt of Armstrong Wynne acid). The pigment obtained is slurried up in 1 250 parts of N-methylpyrrolidone. The suspension obtained is heated to 155° C. in the course of an hour and maintained at 155° C. for a further hour. Thereafter, the suspension is cooled down to about 30° C. and the pigment is filtered off. The filter cake is dried at 80° C. under reduced pressure overnight and ground to obtain 136 parts of an orange pigment: compound (1c). 
     INVENTIVE EXAMPLE 4 
     Inventive Example 1 is repeated except for the following points: 
     The diazo component used is 66.4 parts of 2-amino-5-chloro-4-methylbenzenesulfonic acid (CLT acid). 
     The coupling component used is 70.6 parts of 1-hydroxynaphthalene-4-sulfonic acid (Nevile Winther acid). 
     Laking is effected using a solution of 57.1 parts of magnesium chloride in 300 parts of water. 
     This gives 144 parts of an orange pigment: compound (1d). 
     COMPARATIVE EXAMPLES 1 to 3 
     COMPARATIVE EXAMPLE 1 
     Example 2 of WO 98/13425 is followed to couple 2-amino-5-chloro-4-methylbenzenesulfonic acid (CLT acid) onto the potassium salt of 2-hydroxy-naphthalene-6-sulfonic acid (potassium salt of Schäffer&#39;s acid) and lake with strontium. 
     COMPARATIVE EXAMPLE 2 
     Example 4 of WO 98/13425 is followed to couple 2-amino-5-chloro-4-ethylbenzenesulfonic acid (homo CLT acid) onto the potassium salt of 2-hydroxy-naphthalene-6-sulfonic acid (potassium salt of Schäffer&#39;s acid) and lake with strontium. 
     COMPARATIVE EXAMPLE 3 
     The pigments described in Example 2 of GB 1 313 147 are prepared as follows:
     a) Diazotization of 2-amino-5-methylbenzenesulfonic acid, subsequent coupling onto 1-naphthol-4-sulfonic acid and laking of the resulting coupled product with calcium.   b) Diazotization of 2-amino-5-methylbenzenesulfonic acid, subsequent coupling onto 2-hydroxynaphthalene-3-carboxylic acid and laking of the resulting coupled product with calcium.   

     The color strength and lightfastness of the pigments prepared in the preceding examples and comparative examples are reported in tables 1 and 2. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 (Inventive Examples 1 to 4): 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Coupling 
                   
                   
                   
                   
                   
               
               
                   
                   
                 com- 
                   
                   
                   
                 LiE/ 
                 LiE/ 
               
               
                 Ex. 
                 Amine: 
                 ponent: 
                 Color: 
                 M 
                 FST 
                 VT 
                 AH 
               
               
                   
               
               
                 1 
                 4-Chloro- 
                 1-Naphthol- 
                 red 
                 Sr 2+   
                 1:2.41 
                 8 
                 6 
               
               
                   
                 anthranilic 
                 5-sulfonic 
               
               
                   
                 acid 
                 acid 
               
               
                 2 
                 4-Chloro- 
                 1-Naphthol- 
                 brown 
                 Mn 2   
                 1:3.55 
                 7-8 
                 6 
               
               
                   
                 anthranilic 
                 8-sulfonic 
               
               
                   
                 acid 
                 acid 
               
               
                 3 
                 Anthranilic 
                 1-Naphthol- 
                 orange 
                 Sr 2+   
                 1:2.52 
                 8 
                 6-7 
               
               
                   
                 acid 
                 3-sulfonic 
               
               
                   
                   
                 acid 
               
               
                 4 
                 CLT acid 
                 1-Naphthol- 
                 orange 
                 Mg 2+   
                 1:2.17 
                 8 
                 5 
               
               
                   
                   
                 4-sulfonic 
               
               
                   
                   
                 acid 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 (Comparative Examples 1 to 3): 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Coupling 
                   
                   
                   
                 LiE/ 
                 LiE/ 
               
               
                 Ex. 
                 Amine: 
                 component: 
                 Color: 
                 M 
                 FST 
                 VT 
                 AH 
               
               
                   
               
               
                 1 
                 CLT acid 
                 2-Naphthol- 
                 orange 
                 Sr 2+   
                 1:192 
                 6 
                 4 
               
               
                   
                   
                 6-sulfonic 
               
               
                   
                   
                 acid 
               
               
                 2 
                 Homo CLT 
                 2-Naphthol- 
                 red 
                 Sr 2+   
                 1:1.96 
                 6-7 
                 3-4 
               
               
                   
                 acid 
                 6-sulfonic 
               
               
                   
                   
                 acid 
               
               
                 3a 
                 2-Amino-5- 
                 1-Naphthol- 
                 red 
                 Ca 2+   
                 1:2.68 
                 6 
                 3-4 
               
               
                   
                 methyl- 
                 4-sulfonic 
               
               
                   
                 benzene- 
                 acid 
               
               
                   
                 sulfonic acid 
               
               
                 3b 
                 2-Amino-5- 
                 2-Naphthol- 
                 red 
                 Ca 2+   
                 1:0.89 
                 6 
                 2-3 
               
               
                   
                 methyl- 
                 3-carboxylic 
               
               
                   
                 benzene- 
                 acid 
               
               
                   
                 sulfonic acid 
               
               
                   
               
               
                 M = metal cation  
               
               
                 FST = color strength  
               
               
                 LiE/VT = full-shade lightfastness  
               
               
                 LiE/AH = reduction lightfastness  
               
            
           
         
       
     
     Color strength (FST) indicates how many parts of TiO 2  are needed to adjust 1 part of color pigment to ⅓ standard depth of shade (DIN 53235): 1:x TiO 2 . 
     Lightfastness was determined in full shade and in reduction against the 8 point blue scale on the lines of DIN 54003. “8” corresponds to the highest lightfastness, “1” to the lowest.