Carbomer Interpolymer
(kar' boe mer in'' ter pol' i mer).
» Carbomer Interpolymer is a carbomer homopolymer or copolymer that contains a block copolymer of polyethylene glycol and a long chain alkyl acid ester.
Packaging and storage— Preserve in tight containers, at a temperature not exceeding 45.
Labeling— Label it to indicate whether it is Type A, B, or C. Also label it to state the measured viscosity, giving the viscosity measurement parameters, the concentration of the solution, and the type of equipment used; the solvent or solvents used in the polymerization process; and the nominal and measured residual solvent levels for each solvent.
Identification—
A: Infrared Absorption 197K—The IR absorption spectrum exhibits bands at or near (±5) wave numbers (cm1) 1710, 1454, 1414, 1245, 1172, 1115, and 801, with the strongest band at 1710.
B: Without mixing, add 2.5 g of Carbomer Interpolymer to 500 mL of water in an 800-mL beaker, and allow to stand. The powders wet out in not more than 60 minutes.
C: Add about 5 g of Carbomer Interpolymer to 500 mL of water, stir, and adjust with 1 N sodium hydroxide to a pH of about 7.5. It forms a viscous gel.
Viscosity 911
Carbomer Interpolymer A— Proceed as directed for Viscosity under Carbomer Copolymer, except to perform the test on a 0.5% aqueous dispersion prepared by using 2.50 g instead of 5.00 g of copolymer.
Carbomer Interpolymer B— Proceed as directed for Viscosity under Carbomer Copolymer, except to adjust the pH of the dispersion to a range of 5.8 to 6.3 instead of 7.3 to 7.8.
Carbomer Interpolymer C— Proceed as directed for Viscosity under Carbomer Copolymer, except to perform the test on a 0.5% aqueous dispersion prepared by using 2.50 g instead of 5.00 g of copolymer and to adjust the pH of the dispersion to a range of 5.8 to 6.3 instead of 7.3 to 7.8. The viscosity values, determined by the conditions specified herein, are within the limits specified in the accompanying table.
Carbomer Interpolymer Viscosity Specifications
(mPa·s)
A 45,000–65,000
B 47,000–77,000
C 8,500–16,500
Loss on drying 731 Dry it in vacuum at 80 for 1 hour: it loses not more than 2.0% of its weight.
Limit of ethyl acetate and cyclohexane— [note—This test is required only for those Carbomer Interpolymers where the labeling indicates that ethyl acetate or a mixture of ethyl acetate and cyclohexane was used in the polymerization process. ]
Standard stock solution— Proceed as directed in the test for Limit of ethyl acetate and cyclohexane under Carbomer Copolymer, except to use 20 µL of ethyl acetate and 10 µL of cyclohexane.
Standard solution— Proceed as directed in the test for Limit of ethyl acetate and cyclohexane under Carbomer Copolymer to obtain a solution containing 0.18 mg of ethyl acetate and 0.078 mg of cyclohexane.
Test solution and Chromatographic system— Proceed as directed in the test for Limit of ethyl acetate and cyclohexane under Carbomer Copolymer.
Procedure— Proceed as directed in the test for Limit of ethyl acetate and cyclohexane under Carbomer Copolymer, except to calculate the percentages of ethyl acetate and cyclohexane in the portion of Carbomer Interpolymer taken by the formula:
100(WS / WT)(RU / RS)
in which WT is the weight, in mg, of Carbomer Interpolymer taken to prepare the Test solution; and the other terms are as defined therein: not more than 0.35% of ethyl acetate and not more than 0.15% of cyclohexane is found.
Limit of benzene—
Solvent solution— Quantitatively dissolve an accurately weighed quantity of benzene in dimethyl sulfoxide to obtain a solution having a concentration of about 1.0 mg per mL. Dilute this solution quantitatively, and stepwise if necessary, with organic-free water (see Residual Solvents 467) to obtain a solution having a concentration of about 0.1 µg per mL.
Test solution— Transfer about 50 mg of Carbomer Interpolymer, accurately weighed, to a 10-mL volumetric flask. Add about 7.5 mL of sodium chloride solution (2 in 100), and mix by mechanical means until homogeneous (usually about 30 minutes). Dilute with sodium chloride solution (2 in 100) to volume, and mix until homogeneous (usually less than 1 minute). [note—This preparation must be analyzed within 3 hours of preparation. ]
Reference solution— Transfer about 50 mg of Carbomer Interpolymer, accurately weighed, to a 10-mL volumetric flask. Add about 7.5 mL of sodium chloride solution (2 in 100), and mix by mechanical means until homogeneous (usually about 30 minutes). Add 1.0 mL of the Solvent solution, dilute with sodium chloride solution (2 in 100) to volume, and mix until homogeneous (usually less than 1 minute). This solution contains about 0.01 µg of benzene per mL.
Chromatographic system— Proceed as directed in the test for Limit of benzene under Carbomer Copolymer.
Procedure— Proceed as directed in the test for Limit of benzene under Carbomer Copolymer. The benzene peak response obtained from the Test solution is not greater than half of the benzene peak response obtained from the Reference solution: not more than 0.0002% is found.
Limit of acrylic acid—
pH 3.0 Phosphate buffer, Mobile phase, Standard solution, Test solution, and Chromatographic system— Proceed as directed in the test for Limit of acrylic acid under Carbomer Copolymer.
Procedure— Proceed as directed in the test for Limit of acrylic acid under Carbomer Copolymer, except to calculate the percentage of free acrylic acid in the portion of Carbomer Interpolymer taken by the formula:
100(V / 1000)(C/W)(rU / rS)
in which V is the volume, in mL, of the Test solution; 1000 is a factor converting mg to µg; W is the weight, in mg, of Carbomer Interpolymer taken to prepare the Test solution; and the other terms are as defined therein: not more than 0.25% is found.
Content of carboxylic acid— Proceed as directed in the test for Content of carboxylic acid under Carbomer Copolymer, except to calculate the percentage of carboxylic acid in the portion of Carbomer Interpolymer taken by the formula:
100(45.02VN/W)
in which W is the weight, in mg, of the portion of Carbomer Interpolymer taken; and the other terms are as defined therein. The carboxylic acid content is not less than 52.0% and not more than 62.0%.
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