ASTM D5629-99

Standard Test Method for Polyurethane Raw Materials Determination of Acidity in Low-Acidity Aromatic Isocyanates and Polyurethane Prepolymers

SCOPE
1.1 This test method covers the acidity, expressed as ppm of hydrochloric acid, in aromatic isocyanate or polyurethane prepolymer samples of below 100 ppm acidity. The test method is applicable to products derived from toluene diisocyanate and methylene-bis-(4-phenylisocyanate) (see Note 1).  Note 1-There are no equivalent ISO standards.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Nov-1999
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Replaced By: ASTM D5629-05 - Standard Test Method for Polyurethane Raw Materials Determination of Acidity in Low-Acidity Aromatic Isocyanates and Polyurethane Prepolymers
• Effective Date: 01-Mar-2005
• Referred By: ASTM D1786-21 - Standard Specification for Toluene Diisocyanate
• Effective Date: 10-Nov-1999

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D5629–99
Standard Test Method for
Polyurethane Raw Materials: Determination of Acidity in
Low-Acidity Aromatic Isocyanates and Polyurethane
Prepolymers
This standard is issued under the fixed designation D 5629; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope * andthedifferenceintiterisusedtocalculatetheaciditypresent
in the isocyanate sample.
1.1 This test method covers the acidity, expressed as ppm of
hydrochloric acid, in aromatic isocyanate or polyurethane
5. Significance and Use
prepolymersamplesofbelow100ppmacidity.Thetestmethod
5.1 This test method can be used for research or for quality
isapplicabletoproductsderivedfromtoluenediisocyanateand
control to characterize aromatic isocyanates and low-acidity
methylene-bis-(4-phenylisocyanate) (see Note 1).
prepolymers. Acidity correlates with performance in some
NOTE 1—There are no equivalent ISO standards.
polyurethane systems.
1.2 The values stated in SI units are to be regarded as the
6. Apparatus
standard.
6.1 Disposable Beakers, 250 mL.
1.3 This standard does not purport to address all of the
6.2 Repipet,50mL.
safety concerns, if any, associated with its use. It is the
6.3 Pipet, 100 mL, class A volumetric; or a 50-mL buret
responsibility of the user of this standard to establish appro-
dosimat unit, and a dosimat; or a 100-mL repipet, class A
priate safety and health practices and determine the applica-
volumetric.
bility of regulatory limitations prior to use.
6.4 Automatic Titration Equipment, such as the following:
2. Referenced Documents
6.4.1 Titroprocessor.
6.4.2 Dosimat, with magnetic stirrer.
2.1 ASTM Standards:
D 883 Terminology Relating to Plastics 6.4.3 Reference Electrode (Brinkman Catalogue No. 020-
94-400-5 or equivalent: bridge electrolyte (double junction),
E 180 Practice for Determining the Precision of ASTM
sleeve-typediaphragm),havingsaturatedLiCl/ethanolsolution
Methods forAnalysis and Testing of Industrial Chemicals
in both chambers.
3. Terminology
6.4.4 pH Glass Electrode (Brinkman Catalogue No. 020-
3.1 Definitions—The terminology in this test method fol- 91-012-7 or equivalent) (see Note 2).
lows the standard terminology defined in Terminology D 883.
NOTE 2—Acombination pH electrode with internal reference may also
3.2 Definitions of Terms Specific to This Standard:
be used.
3.2.1 acidity, n—the acid strength of a sample expressed in
6.5 Magnetic Stirrer.
ppm HCl.
6.6 Polytetrafluoroethylene-Coated Stir Bars.
6.7 Watch Glasses.
4. Summary of Test Method
6.8 Analytical Balance, capable of weighing to the nearest
4.1 The isocyanate is mixed with an excess of n-propanol, a
0.1 mg.
cosolvent, and a known amount of HCl. Additional acid is
released into the solvent system during urethane formation.
7. Reagents and Materials
The acid is then titrated potentiometrically with methanolic
7.1 KOH in Methanol, 0.01 N: 0.66 g 87.7 % KOH/1000
KOH. The same procedure is performed with a blank solution,
mLmethanol, standardized with potassium hydrogen phthalate
(KHP).
ThistestmethodisunderthejurisdictionofASTMCommitteeD-20onPlastics
and is the direct responsibility of Subcommittee D20.22 on Cellular Plastics.
Current edition approved Nov. 10, 1999. Published February 2000. Originally Instruments similar to and including the Metrohn 686 Titroprocessor with a
published as D 5629 – 94. Last previous edition D 5629 – 94. Metrohn 665 Dosimat/magnetic stirrer as supplied by Brinkman Instruments
Annual Book of ASTM Standards, Vol 08.01. Company, Division of Sybron Corporation, Cantiague Road, Westbury, NY 11590-
Annual Book of ASTM Standards, Vol 15.05. 9974, have been found to be satisfactory for this analysis.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5629
7.2 Toluene or THF (dried for 24 h over 5 A sieves). 12. Calculation
7.3 n-Propanol, acidified with 120 µL concentrated hydro-
12.1 Calculate the acidity, as ppm HCl, as follows:
chloric acid per 4-L bottle. This solution should be allowed to
~V 2 V ! 3 ~KOH ! 3 F
sam blank normality
stand for at least 24 h before use to allow equilibration. The
acidity 5 (1)
sample weight ~g!
solution should be mixed well before dispensing.
where:
8. Sampling V = volume of titrant needed for the sample,
sam
mL,
8.1 Since organic isocyanates react with atmospheric mois-
V = volume of titrant needed for the blank,
blank
ture, take special precautions in sampling (Warning—Organic
mL,
isocyanates are toxic when they are absorbed through the skin
KOH = normality of the titrant solution, and
normality
or when the vapors are breathed. Provide adequate ventilation,
F = 36465 = 36.456 (mol weight of HCl) 3
and wear protective gloves and eye glasses.). Usual sampling
1000 (factor to change mg/g to µg/g, that
methods (for example, sampling an open drum thief), even
is, ppm).
when conducted rapidly, can cause contamination of the
sample with insoluble urea.Therefore, blanket the sample with
NOTE 8—Acidity is typically calculated as meq/Kg for prepolymers.
For this calculation, F = 1000.
dry air or nitrogen at all times.
13. Report
9. Calibration
13.1 Report the result as the average of duplicates, ex-
9.1 Calibrate the electrodes using pH 4 and 7 aqueous
pressed as ppm HCl, to the nearest 1 ppm. See also Note 8.
buffers.
14. Precision and Bias
10. Test Conditions
14.1 Precision—Table 1 is based on a round robin con-
10.1 Since isocyanates react with moisture, keep the labo-
ducted in 1993 per Practice E 180, involving six materials
ratory humidity low, preferably at approximately 50 % relative
tested by nine laboratories.All of the samples for each material
humidity.
werepreparedatonesource,butthein
...