Plastics - Aromatic isocyanates for use in the production of polyurethane - Part 2: Determination of hydrolysable chlorine
WARNING: Persons using this standard shall be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions prior to use.
1 Scope
This part of GB/T 12009 specifies a method for determination of hydrolysable chlorine in aromatic isocyanates for use in the production of polyurethane by potentiometric titration.
This part is applicable to the determination of hydrolysable chlorine in toluenediisocyanate (TDI), 4,4'-diphenyl-methane-diisocyanate (MDI), polymethylene polyphenyl isocyanate and other soluble isocyanates.
This part is not applicable to substances containing thiocyanate, cyanide, sulfide, bromide, iodide and other substances capable of reacting with silver ions, as well as substances capable of reducing silver ions in acid solution.
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 6682 Water for analytical laboratory use - Specification and test methods (GB/T 6682-2008; ISO 3696:1987, MOD)
3 Interference
Thiocyanate, cyanide, sulfide, bromide, iodide and other substances capable of reacting with silver ions, as well as substances capable of reducing silver ions in acid solution, will interfere with the determination.
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4 Principle
The hydrolysable chlorine mainly comes from carbamoyl chloride and dissolved phosgene in the production process. These two substances react with alcohol and water to produce urea, carbamate, carbon dioxide and hydrochloric acid, and the hydrochloric acid produced is determined by potentiometric titration with silver nitrate standard solution.
5 Sampling
Since organic isocyanates react with moisture in the air, take special precautions in sampling. Usual sampling methods (for example, sampling from an open container), even when conducted rapidly, can cause contamination of the sample with insoluble urea; therefore, blanket the sample with a dry inert gas (e.g. nitrogen, argon or dry air) at all times.
Foreword i
1 Scope
2 Normative references
3 Interference
4 Principle
5 Sampling
6 Reagents and solutions
7 Apparatus
8 Determination steps
9 Result calculation
10 Precision
11 Test report
Annex A (Informative) Precision specified in ISO 15028:2004 Plastics - Aromatic isocyanates for use in the production of polyurethanes - Determination of hydrolysable chlorine
