Patent Number: 045254966
Section: description

EXAMPLE 1 A water-in-oil emulsion of an acrylamide/acrylic acid copolymer is prepared by dissolving 125 g of acrylamide and 54 g of acrylic acid in 100 g of water. The pH of the resulting aqueous solution is adjusted to 6.5 by the addition of a 50 percent aqueous solution of NaOH. To this solution is added 0.04 g of the pentasodium salt of diethylenetriaminepentaacetic acid and 2 g of a polyethylene glycol ether of a secondary alcohol sold by Union Carbide under the trade name Tergitol 15-S-9. The total weight of this aqueous phase is adjusted to 490 g by the addition of water. This aqueous phase is then dispersed in an oil phase which contains 182 g of liquid hydrocarbon, 4 g of isopropanolamide of oleic acid and 4 g of sorbitan monooleate. The resulting emulsion is placed into a liter glass resin kettle equipped with a stirrer, a nitrogen sparger, a thermometer, a water bath and gas exit. The kettle containing the emulsion is sparged with nitrogen for about 1 hour to remove oxygen. The emulsion is then subjected to polymerization conditions as described in U.S. Pat. No. 3,284,393 to form a water-in-oil emulsion of acrylamide/acrylic acid copolymer. After polymerization, 90 g of an aqueous solution of 16 g of Na.sub.2 CO.sub.3 is added to the water-in-oil emulsion. To this emulsion is then added 7 g of Tergitol 15-S-9 (inverting surfactant) with stirring. The resulting emulsion is then tested for invertibility by the following procedure. To a 473 ml bottle equipped with a three-bladed stirrer is added 300 g of an aqueous solution containing 3 percent NaCl and 0.05 percent CaCl.sub.2. A 1.5 g portion of the aforementioned emulsion is then rapidly added to the bottle while stirring the solution at 400 rpm for 30 minutes. The viscosity of the resultant solution is measured using a Brookfield RVT viscometer using a No. 1 spindle and operating at 20 rpm and 25.degree. C. Several additional emulsions are prepared using different amounts of inverting surfactants and different inverting surfactants in accordance with the foregoing procedure. These emulsions are also tested for invertibility. The results of these tests are reported in Table I, Sample Nos. 1-12. For purposes of comparison, several emulsions are prepared following the foregoing procedure except that all of the inverting surfactant is added subsequent to polymerization. These emulsions are similarly tested for invertibility and the results are reported in Table I, Sample Nos. C.sub.1 -C.sub.4. TABLE I ______________________________________ Pre-Added Post-Added Sam- Emulsifier (1) Surfactant (2) Surfactant (3) ple Amt, Amt, Amt, Inverti- No. Type % Type % Type % bility (4), % ______________________________________ 1 IPO 2 15-S-9 1 15-S-9 2.5 51 SMO 2 C.sub.1 * IPO 2 0 15-S-9 3.5 34 SMO 2 2 IPO 2 15-S-9 1 15-S-9 4.0 65 SMO 2 C.sub.2 * IPO 3 0 15-S-9 5.0 20 SMO 2 3 IPO 2 15-S-9 1 DN-14 2.0 77 SMO 2 C.sub.3 * IPO 2 0 DN-14 3.5 &lt;5 SMO 2 4 IPO 2 15-S-9 1 DN-14 4.0 &gt;90 SMO 2 C.sub.4 * IPO 2 0 DN-14 6.0 58 SMO 2 5 IPO 2 15-S-9 0.2 DN-14 4.8 74 SMO 2 6 IPO 2 15-S-9 0.5 DN-14 4.5 82 SMO 2 7 IPO 2 15-S-9 2.0 DN-14 3.0 96 SMO 2 8 IPO 2 15-S-5 1 DN-14 4.0 &gt;90 SMO 2 9 IPO 2 15-S-7 1 DN-14 4.0 &gt;90 SMO 2 10 IPO 2 15-S-12 1 DN-14 4.0 60 SMO 2 11 IPO 2 STO 1 DN-14 4.0 47 SMO 2 12 IPO 2 DN-14 0.5 DN-14 4.0 &gt;90 SMO 2 ______________________________________ *Not an example of the invention. (1) Weight percent of waterin-oil emulsifier based on total monomers wherein: IPO -- isopropanolamide of oleic acid SMO -- sorbitan monooleate (2) Weight percent based on total monomers of inverting surfactant added to the waterin-oil emulsion prior to polymerization wherein: 15S-9 Tergitol 15S-9 (HLB = 13.5) DN14 alkyl polyether alcohol (Triton DN14 sold by Rohm and Haas) 15S-5 polyethylene glycol ether of secondary alcohol (HLB = 10.5) (Tergitol 15S-5 sold by Union Carbide) 15S-7 polyethylene glycol ether of secondary alcohol (HLB = 12.1) (Tergitol 15S-7 sold by Union Carbide) 15S-12 polyethylene glycol ether of secondary alcohol (HLB = 14.5) (Tergitol 15S-12 sold by Union Carbide) STO -- Sorbitan trioleate having 20 polyoxyethylene units (HLB = 11) (3) Weight percent based on total monomers added to the waterin-oil emulsion after polymerization wherein 15S-9 and DN14 are as defined in (2). (4) Invertibility is determined from the following equation: ##STR1## wherein .eta. sample is the Brookfield viscosity of the sample as determined by the procedure described hereinbefore, .eta. blank is the Brookfield viscosity of the aqueous solution containing 3 percent NaCl an 0.05 percent CaCl.sub.2 and .eta. max. is the Brookfield viscosity of a control sample. This control sample is prepared by (1) adding 0.15 percen of polymer in emulsion form to deionized water containing 0.15 percent of inverting surfactant that is postadded in the preparation of the particular sample (.eta. sample), (2) stirring the control sample at 400 rpm for 30 minutes as described hereinbefore and (3) adding 3 percent NaC and 0.15 percent CaCl.sub.2. In each case viscosity is measured soon afte preparation and then after standing overnight. In Sample Nos. 1-12, the viscosities develop more rapidly and to higher values when compared to .eta. max. In Sample Nos. C.sub.1 -C.sub.4, the viscosities do not fully develop when compared to the values for .eta. max. As evidenced by the data of Table I, samples in which a part of the inverting surfactant is added prior to polymerization (Sample Nos. 1-4) invert to a greater degree (percent of inversion) than when the entire amount of the inverting surfactant is added after polymerization as in Sample Nos. C.sub.1 -C.sub.4.