STABILIZED AQUEOUS SOLUTION

Abstract: What is provided herein is a stabilized aqueous solution of a C1-C5 alkyl vinyl ether and maleic acid copolymer which includes about 100 to 1,000 ppm of (1) an additive mixture of (a) about 30-70 % by weight of ethylenediaminetetraacetic acid EDTA and (b) about 30-70 % by weight of a secondary additive which is an organic antioxidant and/or free radical scavenger selected from t-butylhydroquinone, propyl gallate and N,N-diethylhydroxylamine; or (2) 10-500 ppm of an inorganic reducing agent such as sulfur dioxide and salts derived from sulfur dioxide and alkali metals such as sodium or potassium bisulfite, sodium or potassium metabisulfite, sodium or potassium thiosulfite, or sodium or potassium sulfite, said stabilized solution exhibiting a retention of at least about 85-90 % of its original viscosity after 3 months.

Description: STABILIZED AQUEOUS SOLUTION What is provided herein is a colorless, stabilized aqueous solution of a C^Ce j alkyl vinyl ether and maleic acid copolymer which includes about 100 to 1,000 ppm of (1) an additive mixture of (a) about 30-70% by weight of ethylenediaminetetraacetic acid and (b) about 30-70% by weight of a secondary additive which is an organic antioxidant and/or free radical scavenger selected from t-butylhydroquinone, propyl gallate and N,N-diethyl- hydroxylamine, or (2) 10-500 ppm of an inorganic reducing agent such as sulfur dioxide and salts derived from sulfur dioxide and alkali metals such as, sodium or potassium bisulfite, sodium or potassium metabisulfite, sodium or potassium thiosulfite, or sodium or potassium sulfite, said stabilized solution exhibiting a retention of at least about 85-90% of its original viscosity after 3 months. Preferably, the stabilized solution is prepared by hydrolyzing the corresponding anhydride in the presence of said additive mixture. In one embodiment, copolymers of maleic anhydride and a C^Cg alkyl vinyl ether are dissolved in water containing about 100-1,000 ppm of an additive mixture of (a) about 30-70% by weight of ethylenediaminetetraacetic acid and (b) about 30-70% by weight of a secondary additive which is an organic antioxidant and/or free radical scavenger selected from t-butylhydroguinone, propyl gallate and N,N-diethylhydroxylamine. The polymer reaction solution containing the predetermined additive then is hydrolyzed to the corresponding acid form of the polymer to provide the desired colorless, stabilized aqueous solution of maleic acid-C 1 -C 5 alkyl vinyl ether copolymer which includes the additive mixture. While the additive mixture could be added after hydrolysis, it is much preferred to add it directly to the anhydride copolymer before hydrolysis. In this manner, solution relative viscosities of 11-14 measured 1% in water at 25°C, are obtained for a typical high molecular weight maleic aσid-C 1 -C 5 -alkyl vinyl ether copolymer instead of the value of 9 when untreated and 9-11 when the additive is included in the solution after hydrolysis. The secondary additive of the additive mixture of the invention has the following particular attributes: (1) effective in stabilizing the viscosity of the interpolymer; (2) useful in small amounts; (3) soluble in water; (4) does not discolor the solution; (5) an effective antioxidant and/or free radical scavenger; and (6) t-butylhydroquinone and propyl gallate are suitable for use in denture additives and other personal care products. COMPARATIVE EXAMPLES 1. Untreated Copolymer A 1-liter resin kettle equipped with an agitator, a reflux condenser and a water bath was charged with 22.0 g. of methyl vinyl ether/maleic anhydride copolymer (Gantrez • AN-169, International Specialty Products, Inc.) of specific viscosity of 2.83 (as determined in methyl ethyl ketone at a concentration of 1% at 25°C.) and 178.0 g. of deionized water. While agitating, the mixture was heated to 85°C. and maintained at this temperature for 1.5 hours. During this period the anhydride groups of the copolymer were converted to carboxylic acid groups generating a methyl vinyl ether/maleic acid copolymer. The clear solution which contained 13.02% solids was cooled to room temperature and maintained, in the dark, for 3 months. The stability of the solution was determined by measuring its specific viscosity (1% in H 2 0, at 25°C.) and Brookfield viscosity (Spindle # 3, 5 rp , 25°C). The results were the following: The data shows that a solution of methyl vinyl ether/maleic acid copolymer, which did not contain any stabilizer, deteriorated to only 40% of its initial specific viscosity, and to about 28% of its initial Brookfield viscosity, after a period of only 3 months. 2. Individual Additives To the solution prepared in Example 1, a number of different additives were added after dissolution of the polymer. The following data show the stabilizing effect of these additives: TABLE 2 The data above shows that the addition of a stabilizing amount of either a transition metal chelating agent, (EDTA) , or of an antioxidant, (TBHQ, PG) , or a radical chaser, (DEHA) , substantially increased the stability of the acidic copolymer; and, particularly, it degraded to a significantly lesser degree than a nonstabilized copolymer solution of Example 1. INVENTION EXAMPLES 1. Additive Mixture After Hydrolysis . To the solution of Example 1 various stabilizer blends were added. The stabilizing effect is apparent in the data in Table 3 below. Additive Blend/ppm None TBHQ/500 + EDTA/200 The data shows an improvement over the individual components of Example 2. Specifically, the specific viscosity of the copolymer decreased by only 7.6% and the Brookfield viscosity of the copolymer solution was substantially unchanged after standing for 3 months at room temperature. 2. Additive Mixture Before Hydrolysis A copolymer solution as in Example 1 was prepared by dissolving Gantrez* AN-169 in an additive blend of various stabilizers and water prior to beginning of heating. The acid copolymer was made by heating as in Example 1. The results are shown in Table 4 below. Additive Blend/ppm TBHQ/75+ EDTA/75 DEHA/75+ EDTA/75 The data above demonstrates the advantage of adding the stabilizers during dissolution of copolymer. Accordingly, both the specific viscosity and the Brookfield viscosity values of the solution were at least 90% of its initial values after 3 months, and with much higher initial and final viscosities with much lower concentrations of the mixture, than the same additive mixture used after hydrolysis. In another embodiment, copolymers of maleic anhydride and a C±-C ζ alkyl vinyl ether, e.g. methyl vinyl ether, are dissolved in water containing about 10-500 ppm of a stabilizer additive which is an inorganic reducing agent such as sulfur dioxide, sodium or potassium bisulfite, sodium or potassium metabisulfite, sodium or potassium sulfite or sodium or potassium thiosulfite. The copolymer reaction solution containing the predetermined amount of the reducing additive then is hydrolyzed to the corresponding acid form of the copolymer to provide the desired colorless, stabilized aqueous solution of maleic acid-C^-Cg alkyl vinyl ether copolymer which includes the reducing additive. The resultant copolymer solution contained about 11-13% solids therein. While the additive could be added after hydrolysis, it is much preferred to add it directly to the anhydride copolymer before hydrolysis. The relative viscosity of the copolymer solution of Gantrez* AN-169 (methyl vinyl ether/maleic anhydride copolymer) from International Specialty Products Inc. thus obtained is much improved as compared to either the untreated copolymer or the treated copolymer after hydrolysis. The specific viscosity of the resultant copolymer solutions is about 8-13, as determined in water at a concentration of 1% at 25°C. COMPARATIVE EXAMPLES 1. Untreated Copolymer A 1-liter resin kettle equipped with an agitator, a reflux condenser and a water bath was charged with 22.0 g. of methyl vinyl ether/maleic anhydride copolymer (Gantrez* AN-169, International Specialty Products Inc.) of specific viscosity of 2.6 (as determined in methyl ethyl ketone at a concentration of 1%. at 25°C.) and 178.0 g. of deionized water. While agitating, the mixture was heated to 85°C. and maintained at this temperature for 1.5 hours. During this period the anhydride groups of the copolymer were converted to carboxylic acid groups generating a methyl vinyl ether/maleic acid copolymer. The clear solution which contained 12.4% solids was cooled to room temperature and maintained, in the dark, for 2 months. The stability of the solution was determined by measuring its specific viscosity (1% in H 2 0, at 25°C.) and Brookfield viscosity (Spindle # 3, 5 rpm, 25°C). The results were the following: The data shows that a solution of methyl vinyl ether/maleic acid copolymer, which did not contain any stabilizer, deteriorated to about 24% of its initial specific viscosity, and to about 29% of its initial Brookfield viscosity, after a period of 2 months. INVENTION EXAMPLES 1. Additive After Hydrolysis To the solution of Example 1 various stabilizers were added. The stabilizing effect is apparent in the data in Table 6 below. Additive/ PP m None NaHS0 3 /100 The data shows an improvement over the untreated copolymer of Example 1. Specifically, the specific viscosity of the copolymer decreased by only 13% and the Brookfield viscosity of the copolymer solution decreased by only about 10% after standing for 2 months at room temperature. 2. Additive Before Hydrolysis A copolymer solution as in Example 1 was prepared by dissolving Gantrez* AN-169 in an inorganic reducing additive and water prior to beginning of heating. The acid copolymer was made by heating as in Example 1. The results are shown in Table 7 below. TABLE 7 The data above demonstrates the advantage of adding the reducing additive during dissolution of copolymer. Accordingly, both the specific viscosity and the Brookfield viscosity values of the solution were at least 85% of its initial values after 2 months, and with much higher initial and final viscosities than when the same additive was used after hydrolysis.

Claims: WHAT IS CLAIMED IS: 1. A colorless, stabilized aqueous solution of a copolymer of a C-^Cg alkyl vinyl ether and maleic acid suitable for use in denture adhesives which includes (1) about 100 to 1,000 ppm of an additive mixture of (a) about 30-70% by weight of ethylenediaminetetraacetic acid and (b) about 30-70% by weight of a secondary additive which is an organic antioxidant and/or free radical scavenger selected from t-butylhydroquinone, propyl gallate and N,N-diethylhydroxylamine, or (2) 10-500 ppm of an inorganic reducing agent, said stabilized solution exhibiting a retention of at least 85-90% of its original viscosity after a period of at least 3 months. 2. A solution according to claim 1 wherein said solution is prepared by hydrolyzing a copolymer of a C^-C 5 alkyl vinyl ether and maleic anhydride in the presence of said additive mixture. 3. A solution according to claim 2 which includes about 500 ppm of said additive mixture. 4. A solution according to claim 1 which includes about 50% each of (a) and (b) . 5. A solution according to claim 1 wherein said inorganic reducing additive is sulfur dioxide, or a salt derived from sulfur dioxide and alkali metal such as sodium or potassium bisulfite, sodium or potassium metabisulfite, sodium or potassium thiosulfite or sodium or potassium sulfite.

Inventors: CHUANG JUI-CHANG, LOGIN ROBERT B, PLOCHOCKA KRYSTYNA, CHUANG, JUI-CHANG, LOGIN, ROBERT, B., PLOCHOCKA, KRYSTYNA
Applicants: ISP INVESTMENTS INC, ISP INVESTMENTS INC.
Application year: 1992
Main classification: C08K5
IPC codes: A61C13, A61K6, C08K3, C08K5