Method for utilizing potentiometric titration method to measure polyhydric alcohol acid value

Abstract

The invention relates to polyhydric alcohol value determination, in particular to a method for utilizing potentiometric titration method to measure a polyhydric alcohol acid value. The method comprises the steps of accurately weighing a polyhydric alcohol sample and utilizing an organic solvent without acid to dissolve the polyhydric alcohol sample, setting an acid value calculation formula for a potentiometric titrator, wherein an acid value AV is equal to (V1-V2)*C*56.1 / M; using a potassium hydroxide-alcoholic solution to titrate the sample, enabling the potentiometric titrator to automatically stop working when a terminal point is reached, and an acid value result is given. The polyhydric alcohol contains aromatic polyester polyol prepared by raw materials including polypropylene oxide ether polyhydric alcohol, phenyl anhydride polyester polyol and waste PET and the polyhydric alcohol which needs a special assistant in a production process and accordingly cannot normally develop color in acid value determination. The problem that a titration end point is unobvious in color development and inaccurate in titration result due to deep color of a detected material and other reasons can be solved through potentiometric titration, and the method is simple, and a determination result is accurate and reliable.

Description

technical field

[0001] The invention relates to the determination of the acid value of polyalcohols, in particular to a method for determining the acid value of polyalcohols by means of potentiometric titration. Background technique

[0002] In the field of polyurethane polymer materials, polyol is an important chemical intermediate. During the synthesis of polyurethane, the pH of polyol directly affects the reactivity of isocyanate. The pH may also have a high or low impact on the determination of the hydroxyl value.

[0003] In the synthesis process of some polyether polyols, since the use of catalysts may bring or generate alkaline substances, polyols should avoid alkaline residues to prevent many unpredictable side reactions from being promoted in the synthesis of polyurethane materials, so Measurements of pH and acidity are required to quickly determine the extent of alkaline treatment.

[0004] Phthalic anhydride polyester polyols use phthalic anhydride as a raw mat...