PIGMENT DISPERSANTS

Abstract: An acid terminated polyamide is reacted with an alkylene glycol, polyalkylene glycol, nitrogen base or an alkanol amine (followed by neutralization with an alkanoic acid) to provide a pigment dispersant. These dispersants are especially useful for preparing solvent-based packaging inks (i.e., packaging gravure and flexographic inks).

Description: -/- PIGMENT DISPERSANTS BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to pigment dispersants. Description of the Related Art Pigment dispersants have been used to improve the properties of inks. In general, dispersants promote the dispersion of the pigment in the ink and stabilize the dispersion. Lecithin is an example of such a dispersant. U. S. Patent No. 4,704,165 to Nakamura et al. discloses an example of another dispersant. This patent discloses a phosphate ester pigment dispersant for organic, inorganic and extender pigments in compositions wherein the pigment is present in high concentrations as a coloring agent (printing inks, paints, coating agents and synthetic resins) and compositions useful as a paint. U. S. Patent No. 4,350,535 to Ishijima et al. also discloses a phosphate ester dispersant that improves the long-term storage stability of aqueous coating compositions and adhesives containing a metallic powder pigment. SUMMARY OF THE INVENTION The invention relates to the reaction product of an acid terminated polyamide and either an alkylene glycol, a polyalkylene glycol, a nitrogen base, or an alkanol amine (followed by neutralization with an alkanoic acid) . The acid terminated polyamide is preferably the reaction product of a dimer acid and a tall oil fatty acid with an alkylene diamine, preferably ethylene diamine. The polyalkylene glycol is preferably polypropylene glycol. The reaction, at reaction temperatures of 140 - 300°C. of the polyamide with the alkylene glycol or polyalkylene glycol provides a nonionic reaction product, while reaction at reaction temperatures of up to 100°C. with the nitrogen base provides an anionic reaction product, and reaction at reaction temperatures of 140 - 300°C. with an alkanol amine and neutralization with the alkanoic acid provides a cationic reaction product. A pigment dispersion comprising a pigment, the reaction product (nonionic, anionic or cationic) and a dispersion vehicle as well as a solvent-based packaging ink comprising the pigment dispersion and a film-forming letdown varnish are also provided. The pigment may be any type that is useful for solvent-based packaging inks. Representative non-limiting examples of suitable pigments include Red Lake C, BON Red, Lithol Rubine, Permanent Red 2B, Naphthol Reds, Phthalocyanine Blue, Phthalocyanine Green, Monoarylide Yellows, Diarylide Yellows, Carbon Black, and the like. Generally, the reaction product is utilized in an amount of up to about 10 wt.%, preferably up to about 5 wt. %, based on the weight of the pigment dispersion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An acid terminated polyamide reacted with a reactant to provide either a nonionic, anionic or cationic product has been found to be an excellent dispersant for dispersing pigments in a variety of vehicles. The resultant pigment dispersions are especially useful for the preparation of solvent-based packaging inks (i.e., packaging gravure and flexographic inks). Such inks exhibit improved gloss, strength and transparency when printed on polymeric packaging such as high slip polyethylene, compared to inks prepared without the dispersants of the present invention. The polyamide is preferably formed by reacting a C- j g dimer acid and a tall oil fatty acid with an alkylene diamine to an acid value of between about 60 and 70. The dimer acid can be represented by the following formula: The particular components of the R- j _ - R^ moieties (which contain 5 - 14 carbon atoms) are governed by the type of condensation used to prepare the dimer acid. If head-to-head condensation took place, adjacent R groups (ej . R-^ and R , or Ro and R^) are terminated in carboxyl groups while the other two adjacent groups will be hydrocarbon terminated. If head-to-tail condensation took place, the R groups alternate in terminating carboxyl and hydrocarbon groups. The carboxy-terminating groups can have structures such as: -(CH 2 ) g C00H, -CH-CH(CH 2 ) g COOH, -(CH 2 ) 7 COOH, -CH^H-CH C^^COOH, etc. and the hydrocarbon-terminating group can be represented by: , CH 3 (CH 2 )7-, CH 3 (CH 2 ) 4 CH-CH- , etc. The dimer acid is preferably "Dimer 18"; this dimer acid contains 83% dimer acid species and 17% trimer acid species. A typical tall oil fatty acid is a mixture of fatty acids such as stearic acid, oleic or linoleic acid, rosin acids, and unsaponifiable materials. The alkylene diamine is preferably ethylene diamine. Other alkylene diamines may be used. The reaction product of the dimer acid, tall oil fatty acid and alkylene diamine is reacted with either: an alkylene glycol or polyalkylene glycol to provide a nonionic dispersant; a nitrogen base to provide an anionic dispersant; or an alkanol amine (followed by neutralization with an alkanoic acid) to provide a cationic dispersant. Preferably, the polyalkylene glycol is polypropylene glycol. The nitrogen base is preferably an amine, most preferably ammonium hydroxide or methyldiethanol amine. The alkanol amine and alkanoic acid are preferably methyldiethanol amine and propionic acid, respectively. Of the three classes of dispersants (nonionic, anionic and cationic) , the nonionic dispersant is preferred. The reaction ratios to provide the acid terminated polyamide backbone are about 0.6 - 1.0 equivalent dimer acid to about 0.5 - 0.9 equivalent tall oil fatty acid to about 0.7 - 1.0 equivalent ethylene diamine. About 0.5 carboxyl equivalent of the polyamide is reacted with either about 0.5 equivalent of alkylene glycol or about 0.5 equivalent of polypropylene glycol, about 0.50 equivalent of ammonium hydroxide or methyldiethanol amine, or about 0.125 equivalents of methyldiethanol amine followed by 0.125 equivalents of propionic acid. The dispersant has an acid value between about 20 and 5, preferably between 15 and 10. The following structures generally illustrate the three classes of dispersants prepared in accordance with the invention: nonionic The pigment dispersion is readily prepared by conventional methods (e.g., a 3-roll mill) in which pigment, solvent(s) and dispersant are combined. As a general rule, the dispersant will comprise not more than about 10 wt. %, preferably not more than 5 wt. %, based on the weight of the dispersion. The pigment may be any type that is useful for solvent-based packaging inks such as those listed above and is typically present in an amount of about 30 to 70 wt. %, based on the weight of the dispersion. The solvent(s), i.e., the dispersion vehicles (3), may be any of those typically used to prepare pigment dispersions useful for solvent-based packaging inks. The solvent(s) is (are) generally utilized in amounts of about 20 - 60 wt. %, based on the weight of the dispersion. Suitable solvents include C-. - C 7 straight or branched chain alkyl, aryl or heterocyclic alcohols, esters or hydrocarbons such as isopropanol, ethyl acetate, n-heptane, n-hexane, toluene, cyclohexane, etc. As a general rule, such solvents will have boiling points of up to about 120"C. The solvent-based packaging ink is readily prepared by mixing the pigment dispersion with a film-forming letdown varnish such as nitrocellulose, polyamides, ketone resins, acid-modified rosin esters, polyvinyl butyral and the like. As a general rule, about 40 to 70 parts of the dispersion will be mixed with 100 parts of the varnish together with optional adjuvants such as extenders, waxes, opacifiers, antioxidants, etc. The finished ink will typically contain 10 - 30 wt. % pigment, based on the weight of the ink. The following Examples 1 - 6 generally illustrate how a dispersant and a pigment composition in accordance with the invention may be prepared. Example 1 illustrates preparation of a nonionic dispersant. Example 2 illustrates preparation of a cationic dispersant. Example 3 illustrates preparation of an anionic dispersant. Example 4 illustrates an ink formulation prepared using the dispersant of Example 1. Example 5 illustrates in tabular form the components of several additional ink formulations prepared utilizing the dispersant of the invention. Example 6 is to the same effect as Example 5, except the pigment is carbon black. Example 1 (Nonionic Dispersant) 259.9 parts of a dimer acid (Chemtall C36 -18) and 177.3 parts of a tall oil fatty acid (Sylfat 95-Sylvachem) were charged into a 4-neck, 1 liter round bottom flask equipped with a reflux condenser, mechanical agitator, thermometer, and nitrogen blanket. The contents were heated to 60°C. where 30.0 parts of ethylene diamine were added slowly through an addition funnel over 5 minutes. The temperature was raised to 115°C. , held for 1 hour, and was then increased to 200"C. and held for 1 hour while removing water of reaction as it was formed. The batch was cooled to 140°C. and 262.2 parts of a polypropylene glycol (Pluracol 1010-BASF) were added slowly through an addition funnel over 20 minutes. The temperature was gradually increased to 270°C, removing water of reaction as it was formed. hen an acid value below 8.0 was obtained, the batch was cooled to 200°C. and discharged. Forty parts of this batch were combined with 48 parts n-heptane and 12 parts of n-butanol in a 4-neck, 1 liter flask equipped as described above. The contents were heated to 70°C. until the resin was completely solubilized. It was then cooled to 30°C. and discharged. Example 2 (Cationic Dispersant) The procedure of Example 1 was repeated up to the addition of the polypropylene glycol. At this point, 44.4 parts of methyldiethanol amine were added and the contents slowly heated to 250°C. , removing water of reaction as it was formed. An acid value of 4.2 and amine value of 25.2 were obtained after 2 hours. The batch was cooled to 100°C. and 15.5 parts of propionic acid were added. The reaction was held for 30 minutes and discharged. Example 3 (Anionic Dispersant) The procedure of Example 1 was repeated up to the addition of the polypropylene glycol. At this point, the batch was cooled to 5 100°C. with 63.5 parts of methyldiethanol amine being added. The material was held for 30 minutes at 100 β C. Example 4 (Ink Formulation) 25.0 parts of a varnish consisting of 40% (wt.) Example 1 Q dispersant, 48% heptane, and 12% n-butanol, 1.0 part heptane, 13.0 parts n-propylacetate and 10.0 parts n-butanol were added together and placed in an attriter. To this was added 1.0 part lecithin and 50.0 parts cyan blue pigment. This was milled until no seed or scratches were observed on a grind gauge. This portion is called 5 pigment dispersion or the base. To 31.8 parts of this base were added 3.0 parts of a high viscosity nitrocellulose, 4.7 parts of an alcohol soluble nitrocellulose, 1.0 part dioctylphthalate, 4.0 parts of a wax compound, 1.0 part of a silicone solution, 1.0 part of a citric acid solution, 38.2 parts of a polyamide solution, 2.0 0 parts n-propanol, and 13.3 parts ethanol. They were mixed in a blender for 10 minutes. The ink had an uncut viscosity of 30 seconds on a number 3 Zahn cup. The ink was cut with a 90/10 (wt.) n-propanol to n-propylacetate mixture and printed with a 165 anilox hand proofer on high slip polyethylene film. The prints exhibited 5 superior gloss, transparency, and strength compared to a standard polyamide/nitrocellulose ink prepared without the dispersant. Example 5 (Additional Ink Formulations) The following pigment dispersions were prepared utilizing the 0 dispersant of the invention. The compositions were as follows: Dispersion Component Percentage (wt.) of dispersion Nonionic dispersant 25.0 25.0 25.0 of Example 1 Heptane n-Propylacetate n-Butanol Lecithin AAOT Yellow Pigment BON Red Pigment 50.0 Phthalo Blue Pigment 50.0 These dispersions were letdown to inks in the following manner: Ink Component Percentage (wt. ) of ink Yellow Dispersion 33.5 Red Dispersion 32.7 Blue Dispersion Nitrocellulose S. S. Nitrocellulose A. S. Dioctylphthalate Waxes Citric Acid Solution Silicone Solution SK 1487 (polyamide) Polyamide Solution Ethanol n-Propylacetate Heptane i-Propanol n-Propanol 2.0 The inks were cut to printing viscosity with 90/10 n-propanol/n-propylacetate and printed on high slip polyethylene. Inks made from the above bases are superior in strength, gloss and transparency than equivalent dry grind base standards without the dispersant of the invention. Example 6 A solvent-based packaging ink was prepared in the same manner as in Example 5, using carbon black as the pigment. the pigment dispersion was prepared from the following components: Dispersion Component Percentage (wt.) of dispersion Nonionic dispersant of Example 1 14.2 Heptane 26.7 n-Butanol 7.0 Lecithin 2.0 Carbon Black 50.0 The resultant dispersion was letdown to an ink in the following manner: Ink Component Percentage (wt.) of ink Dispersion 33.5 Nitrocellulose A. S. 7.6 Wax 4.0 Citric Acid Solution 1.0 Silicone Solution 1.0 SK 1487 (polyamide) 8.9 Polyamide Solution 44.0 The ink was cut to printing viscosity with 90/10 n-propanol/n-propyl acetate and printed on high-slip polyethylene. The results were comparable to those achieved in Example 5.

Claims: WHAT IS CLAIMED IS: 1. The reaction product of an acid terminated polyamide and a reactant selected from the group consisting of an alkylene glycol, a polyalkylene glycol, a nitrogen base and an alkanol amine. 2. The reaction product of claim 1, wherein the acid terminated polyamide comprises the reaction product of a dimer acid and a tall oil fatty acid with an alkylene diamine. 3. The reaction product of claim 2, wherein the alkylene diamine is ethylene diamine. 4. The reaction product of claim 1 wherein the polyalkylene glycol is polypropylene glycol. 5. The reaction product of claim 2, wherein the dimer acid is prepared by head-to-head condensation and has the general formula where R-^ and R 2 represent carboxy-terminating groups containing 5 to 14 carbon atoms and R3 and R^ represent hydrocarbon-terminating groups containing 5 to 14 carbon atoms, or R^ and R 2 represent such hydrocarbon-terminating groups and R- j and R^ represent such carboxy-terminating groups. 6. The reaction product of claim 2, wherein the dimer acid is prepared by head-to-tail condensation and has the general formula wherein R-. and R β represent carboxy-terminating groups containing 5 to 14 carbon atoms and R and R^ represent hydrocarbon-terminating groups containing 5 to 14 carbon atoms or R-^ and R3 represent such hydrocarbon-terminating groups and R 2 and R^ represent such carboxy-terminating groups. 7. The reaction product of claim 1, wherein the nitrogen base is an amine or ammonium hydroxide. 8. The reaction product of claim 1, wherein the reactant is an alkanol amine. 9. A pigment dispersion comprising pigment, a solvent and a pigment dispersing effective amount of the reaction product of claim 1. 10. A solvent-based packaging ink comprising the dispersion of claim 9 and a film-forming letdown varnish.

Inventors: CATENA ROBERT J, KVEGLIS ALBERT A, CATENA, ROBERT, J., KVEGLIS, ALBERT, A.
Applicants: SUN CHEMICAL CORP, SUN CHEMICAL CORPORATION
Application year: 1990
Main classification: C08G69
IPC codes: B01F17, B01J13, C08G69, C09C3, C09D11, C09D17