Hydroxyl value detection method

Abstract

The invention relates to a chemical detection method, particularly to a method for detecting the hydroxyl value of a high molecular weight organic compound containing active hydroxyl. The hydroxyl value detection method includes the steps of: weighing sample in a container, and taking another empty container; pipetting an acetic anhydride-imidazole-pyridine solution into the sample loaded container and the empty container respectively, shaking the solution well, sealing the containers and placing them in a water bath to undergo reaction under certain temperature; at the end of the reaction, pulling out corks, adding distilled water quickly, then sealing bottlenecks, and placing the containers in a water tank to undergo hydrolysis reaction; at the end of the hydrolysis reaction, taking the two containers out of the water bath, and performing cooling; adding several drops of a phenolphthalein indicator dropwise into the two containers respectively after cooling to room temperature; titrating the container solutions to pink respectively by an alcoholic solution of inorganic base, and calculating the hydroxyl value of the sample according to a formula. The method provided by the invention has the advantages of simple analysis steps, high precision, and good accuracy.

Description

Technical field [0001] The invention relates to a chemical detection method, in particular to a method for detecting the hydroxyl value of a high molecular weight organic compound containing active hydroxyl groups. Background technique [0002] The hydroxyl value generally used in industry refers to the number of milligrams of potassium hydroxide (KOH) equivalent to the hydroxyl group in 1g sample, expressed in mgKOH / g. At present, the current detection methods of hydroxyl value mostly use phthalic anhydride-pyridine method or acetic anhydride-pyridine method. The principle of detection is to first allow excess and quantitative acid anhydride to react with the hydroxyl group of the test object, and then use KOH solution to titrate the excess acid anhydride. Use the formula to calculate the hydroxyl value of the test substance. [0003] The disadvantages of the current detection methods are: 1. The temperature of the acylation reaction is too high, which may cause personal safety o...

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Problems solved by technology

[0003] The shortcomings of the current detection method are: 1. The acylation reaction temperature is too high, which may easily cause personal safety or accidents; 2. The acylation reaction is not complete if phthalic anhydride is used; 3. There will be acetic anhydride in the acylation reaction process if acetic anhydride is used. Volatility, resulting in inaccurate results; 4. During the titration process, the reaction between acid anhydride and water at room temperature is slow, and the titration end point is not clear

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