GB/T 7383-2020 Non-ionic surface active agents - Determination of hydroxyl value
1 Scope
This standard specifies the determination of hydroxyl value in non-ionic surface active agents.
This standard is applicable to the determination of the hydroxyl value of aliphatic and alicyclic polyalkoxy compounds (in particular, of adducts of ethylene oxide, propylene oxide and their mixtures of primary fatty alcohols, of alkylphenols and of fatty acids) and can be used for the determination of hydroxyl values from 10 to 1,000.
Phthalic anhydride method is suitable for the determination of the hydroxyl value of the adducts of ethylene oxide, propylene oxide and their mixtures of primary and secondary fatty alcohols, alkylphenols and fatty acids.
Acetic anhydride method is suitable for the determination of the hydroxyl value of the ethylene oxide adducts of primary and secondary fatty alcohols, alkylphenols and fatty acids, but not for the determination of the hydroxyl value of propoxylated products.
Near infrared spectroscopy is suitable for the determination of hydroxyl value of non-ionic surface active agents by phthalic anhydride method or acetic anhydride method.
The possible interferences are detailed below:
——Primary and secondary amines, amides, tertiary alcohols, thiols and epoxides undergo side reactions which affect the accuracy of the method.
——Long-chain fatty acids and esters may interfere by forming anhydrides which are more stable than phthalic anhydride and acetic anhydride and are not completely decomposed at the end of the method.
——Other free acids interfere by reacting with the sodium hydroxide standard volumetric solution; bases, including some tertiary amines, interfere by reacting with the phthalic acid and acetic acid produced.
Epoxides are known to interfere, but the method can still be used if it is possible to eliminate them, by cold vacuum distillation, without affecting the hydroxyl value. By this means, free ethylene oxide, which interferes at levels above 0.5% can be eliminated.
The presence of water in the specimen is revealed by reaction with the phthalic anhydride and acetic anhydride, but the method may nevertheless be used without risk if the precautions described in the procedure are followed.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 601 Chemical reagent - Preparations of reference titration solutions
GB/T 2384 Dyes intermediates - General method for the determination of melting range
GB/T 3143 Color determination method of liquid chemicals (Hazen unit - Platinum-cobalt scale)
GB/T 6365 Surface active agents - Determination of free alkalinity or free acidity - Titrimetric method (GB/T 6365-2006, ISO 4314: 1977, IDT)
GB/T 6372 Surface active agents and detergents — Methods of sample division (GB/T 6372-2006, ISO 607: 1977, IDT)
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
GB/T 11275 Surface active agents - Determination of water content (GB/T 11275-2007, ISO 4317: 1991, MOD)
GB/T 29858 Standard guidelines for molecular spectroscopy multivariate calibration quantitative analysis
ISO 4327 Non-ionic surface active agents - Polyalkoxylated derivatives - Determination of hydroxyl value - Phthalic anhydride method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
hydroxyl value (OH)
the number of milligrams of potassium hydroxide needed to neutralize the phthalic anhydride or acetic anhydride required to acetylate the hydroxyl groups in 1g of the specimen, or the number of milligrams of potassium hydroxide corresponding to the hydroxyl groups in 1g of the specimen
3.2
modeling samples
a series of representative samples selected to build a calibration model
3.3
validation samples
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Method A - Phthalic anhydride method (arbitration method)
5 Method B - Acetic anhydride method (arbitration method)
6 Method C - Near infrared spectroscopy
7 Arbitration methods
8 Test report
Annex A (Informative) Structural changes of this standard with respect to ISO 4326: 1980
Annex B (Normative) Determination for purity of phthalic anhydride
Annex C (Normative) Determination of hydroxyl value outside the fume hood
Annex D (Informative) Mass range of specimens with different water contents and hydroxyl values
Annex E (Informative) Example of calibration model building
