HG/T 2709-1995 Determination of hydroxyl value in polyester polyols HG/T2709-1995 Standard download decompression password: www.bzxz.net

Chemical Industry Standard of the People's Republic of China
Determination of Hydroxyl Value in Polyester Polyols
1 Subject Content and Application
This standard specifies the method for determining the hydroxyl value in ester polyols by acetylation. This standard is applicable to polyester polyols prepared by the condensation reaction of adipic acid and low molecular weight polyols. 2 Reference standards
GB/T601 Preparation of standard solutions for titration analysis (volumetric analysis) of chemical reagents 3 Definition
Hydroxy value: the number of grams of potassium hydroxide equivalent to the hydroxyl content in each gram of sample. 4 Principle
HG/T 2709-95
Acetylation method The acetic anhydride in the acetylation reagent undergoes acylation reaction with the hydroxyl groups in the sample. The remaining acetic anhydride is decomposed by adding water. The generated acetic anhydride is titrated with a standard potassium hydroxide ethanol solution. A blank test is also performed. The hydroxyl value of the sample is calculated from the difference. 5 Reagents
5.1 n-Butanol (GB/T 12590).
5.2 Acetic anhydride (GB/T 677)-pyridine (GB/T 689) solution, 1+23 (V/V). Shake the prepared solution and stick it in a brown bottle (prepare it for each use).
5.3 Potassium hydroxide ethanol standard solution, (KOH) = 0.5mol/L, calibrated once every two weeks, 5.3.1 Preparation: Referring to the method specified in GB/T601, weigh 36g potassium hydroxide (GB/T2306), dissolve in 20mL water, and dilute to 1000mL with ethanol (GB/T 679). Leave for one week, take the upper clear liquid for use 5.3.2 Calibration: Use the method specified in 4.1.2 of GB/T 601 for calibration 5.4 Phenolic acid indicator solution, 10mol/L ethanol solution. 6 Instruments
6.1 Reflux device, 250mL Erlenmeyer flask, with self-ground condenser, condenser length greater than 60cm, 6.2 Constant oil bath, 115±5℃.
6.3 Burette, 50 mL, basic type
6 4 Pipette, 25 mL.
6. 5 Analytical balance, sensitivity 0. 1 mg
Analysis steps
Weigh an appropriate amount of sample (accurate to 0.2 mg) into a conical flask as specified in Table 1, add 25 mL of pyridine acetate solution, quickly install the reflux condenser, and slowly shake the conical flask to completely dissolve the sample. Place the flask in the oil bath, make the sample liquid level below the oil level, and reflux at 115±5℃ for 1h. Hold the flask out of the oil, add 10mL of water from the top of the condenser, and then immerse the flask in the moistening bath for 10min, and keep stirring. Take out the reflux device, cool to room temperature, and then add 15mL of n-butanol from the top of the condenser to rinse the inner wall of the condenser and the flask, add 10 drops of phenolic acid indicator solution, and titrate with potassium hydroxide ethanol standard titration solution until the reddish color remains unchanged for 30s, which is the end point. At the same time, make a blank test, requiring that the volume of the standard titration solution consumed by the sample is greater than three-quarters of the volume of the solution consumed in the blank test. Table 1
Hydroxy value, mgKOH/g
60 ~ 80
80~120
120~200
8Calculation and expression of analysis results
8. 1 Hydroxyl value X, is calculated according to formula (1):
Wherein: X,-
Hydroxy value, mgKOH/g
(V/ - V,) ·c × 56. 10
-Amount of potassium hydroxide ethanol standard titration solution used in blank test, mL;-Amount of potassium hydroxide ethanol standard titration solution used in titration of sample, mL;-Concentration of potassium hydroxide ethanol standard titration solution, mD/L;-Mass of sample, g
-Mol weight of potassium hydroxide: mg/mal;-Acid value of polyester polyol, mgKOH/g+weighing weight, Meng
The test result is expressed as the arithmetic mean of two measurements, accurate to the second decimal place, when the hydroxyl value is greater than 80mgKOH/g, accurate to the first decimal place, 8.2 allowable error
The difference between the results of two parallel measurements is not more than 0.5mgKOH/g. Test report
The test report should include the following items:
Indicate reference to this industry standard;
Sample name, model, grade. Batch number; Sample sending unit;
Results expressed in accordance with Article 8:
Test personnel:
Test date.
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-HG / T 2709 —95
This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Plastics Resin Products Branch of the National Plastics Standardization Technical Committee (TC15/SC4). This standard was drafted by Jiangsu Chemical Research Institute. The main drafters of this standard are Chen Zhaolian and Zeng Yaoling. 13
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