Abstract:
Polymeric products of styrene, an acrylate, acrylic or methacrylic acid and polyethylene oxide, prepared in contact with a cobalt compound, are hydrophobic and can be used as rheology control agents in printing ink.

Description:
TECHNICAL FIELD 
     This invention relates to a new class of polymeric products containing cobalt. It is more particularly directed to the polymeric products obtained by polymerizing styrene, an acrylate, acrylic or methacrylic acid and polyethylene oxide in contact with a cobalt compound, and to inks containing the products as rheology control agents. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Ethyl hydroxyethylcellulose is commonly used as an additive for printing ink. This cellulose ester not only extends the ink but also provides rheological control at printing viscosities and gives an ink whose print has enhanced abrasion resistance. It is, however, quite expensive and tends to degrade the gloss of print. 
     It has now been found that blending such a cellulose ester with a polymeric product of the invention not only provides a less expensive additive without loss of abrasion resistance, but also gives an ink whose print has improved gloss and enhanced color intensity, especially at the red end of the spectrum. 
     In addition, the polymeric product of the invention, when laid down as a film on a substrate, demonstrates dramatic hydrophobicity, which makes it useful as a water-repellant coating for glass and metal wherever such things are employed. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The polymeric products of the invention can be made by bringing the following components together, under conditions suitable for polymerization: 
     (1) Styrene, at a concentration of 50-85%, preferably 55-70%, most preferably about 63%, by weight of the total charge. 
     (2) 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate or butyl acrylate, at a concentration of 10-40%, preferably 20-35%, most preferably about 30%. 
     (3) Acrylic or methacrylic acid, at a concentration of 2-10%, preferably 4-8%, most preferably about 5%. 
     (4) Polyethylene oxide, at a concentration of 0.5-10%, preferably 1-5%, most preferably about 2%. The polyethylene oxide should have a molecular weight Mn of 20,000-400,000, preferably 100,000-300,000. Such a product is commercially available. 
     (5) A cobalt compound, at a concentration of 10-150 ppm, preferably 25-75 ppm, most preferably about 50 ppm. This compound can be any which provides Co+2 or Co+3 ions and is soluble in the system, but is preferably a product sold by Manchem Incorporated of Princeton NJ as Manosec Cobalt 18. This product is proprietary and its composition is therefore unknown to the public, but it is believed to be a cobalt-boron soap modified with C8-C13 fatty acids. 
     To prepare a polymer product of the invention, one takes an appropriate amount of cobalt compound, as a solution in toluene or another suitable organic liquid, and mixes it with (A) the desired amount of polyethylene oxide and (B) an inert organic liquid such as xylene, and then brings the mixture to reflux temperature. To this mixture is then added a mixture of (1), (2) and (3), as described above, together with an appropriate amount of a conventional polymerization initiator such as ditertiary butyl peroxide The resulting mixture is held at reflux temperature until polymerization is substantially complete, as determined by conventional viscosity measurements. 
     The resulting mass, a solution of polymer product in the organic liquid, can be concentrated by evaporation or can be laid down on a substrate and dried to give a hydrophobic film. 
     To use the polymer product of the invention as an ink additive, it is mixed with a cellulose ester, preferably ethyl hyroxyethylcellulose, in product/ester weight ratios of 20-80/8020, preferably about 50/50, to give a concentrate. This concentrate can then be added to conventional ink at a concentration of 0.5-4% by weight, preferably about 2%, as needed. 
     EXAMPLE 
     Those skilled in the art will be able to practice this invention more easily after referring to the following illustrative example. 
     These artisans will no doubt be able to compose numerous variations on the theme disclosed, such as changing the amounts of components slightly but insignificantly from those shown, adding innocuous substances, or substituting equivalent or nearly equivalent components for those shown. All such variations are considered to be within the inventive concept. 
     In the Example, all parts are by weight. 
     A mixture was prepared to contain 
     
         ______________________________________Xylene               1190.00 partsManosec 18           5.01 parts(10% in toluene)Polyethylene oxide   36.00 partsMW = 300,00______________________________________ 
    
     This mixture was heated to reflux temperature and held there, with stirring, while the following mixture was added over a four-hour period: 
     
         ______________________________________Styrene              1134.00 parts2-ethylhexyl         540.00 partsacrylateAcrylic acid         90.00 partsDitertiary butyl     52.92 partsperoxide______________________________________ 
    
     To the resulting mixture was then added a mixture of 
     
         ______________________________________t.butyl        18.00 partsperoxyacetateXylene         10.00 parts______________________________________ 
    
     The reaction mass was then held at reflux temperature, with stirring, for two hours, to give the polymer product styrene/2-ethylhexyl acrylate/acrylic Acid/polyethylene oxide, 63/30/5/2, which was a clear light tan solution, 59.5% solids, with a Gardner-Holdt viscosity of Z-4. 
     This solution was diluted to a concentration of 10% with toluene, and was then mixed in equal proportions with a 10% solution of ethyl hydroxyethyl cellulose (Hercules HE 350), to give a concentrate. 
     Forty parts of this concentrate was then mixed with 160 parts of ink (R1909-148, General Printing Ink Division, Sun Chemical Corp.) and the product drawn on a glass plate and dried. The resulting film was glossy and not readily wettable with water.