ASTM D5523-94(1999)e1

Standard Test Method for Polyurethane Raw Materials Acidity by Argentometric Determination of Hydrolyzable Chlorine in Monomeric, Aromatic Isocyanates

SCOPE
1.1 This test method measures the hydrolyzable chlorine content of monomeric, aromatic isocyanates used as polyurethane raw materials and expresses it as HCl acidity. The test method is applicable to toluene diisocyanate (TDI) and monomeric methylene-bis-(4-phenylisocyanate), known as MDI. The main sources of hydrolyzable chlorine and, therefore, acidity in monomeric aromatic isocyanates are carbamyl chlorides, acid chlorides, and dissolved phosgene. All of these compounds react with alcohols and water to form hydrochloric acid.  
1.2 This test method applies only to monomeric isocyanates in which all of the acidity is derived from species that generate HCl on solvolysis.  
1.3 The values stated in SI units are to be regarded as the standard.  
1.4 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. Specific warning and precautionary statements are given in Note 4.  Note 1-There is no equivalent ISO standard.

General Information

• Status: Historical
• Publication Date: 09-Jul-1999
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Replaced By: ASTM D5523-04 - Standard Test Method for Polyurethane Raw Materials Acidity by Argentometric Determination of Hydrolyzable Chlorine in Monomeric, Aromatic Isocyanates
• Effective Date: 01-Oct-2004

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
e1
Designation: D 5523 – 94 (Reapproved 1999)
Standard Test Method for
Polyurethane Raw Materials: Acidity by Argentometric
Determination of Hydrolyzable Chlorine in Monomeric,
Aromatic Isocyanates
This standard is issued under the fixed designation D 5523; 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.
e NOTE—ASTM Headquarter’s address in 13.1 was corrected editorially in April 2000.
1. Scope 3.1.1 Discussion—Polyurethanes or urethanes, as they are
sometimes called, may be thermosetting, thermoplastic, rigid
1.1 This test method measures the hydrolyzable chlorine
or soft and flexible, or cellular or solid (see Terminology
content of monomeric, aromatic isocyanates used as polyure-
D 883).
thane raw materials and expresses it as HCl acidity. The test
3.2 Definitions of Terms Specific to This Standard:
method is applicable to toluene diisocyanate (TDI) and mono-
3.2.1 acidity—the acid strength of a sample expressed as
meric methylene-bis-(4-phenylisocyanate), known as MDI.
parts per million hydrochloric acid (HCl) present in the sample.
The main sources of hydrolyzable chlorine and, therefore,
3.2.2 hydrolyzable chlorine—the amount of chlorine re-
acidity in monomeric aromatic isocyanates are carbamyl chlo-
leased as chloride ion under the conditions of the test,
rides, acid chlorides, and dissolved phosgene. All of these
expressed in parts per million of chlorine in the sample.
compounds react with alcohols and water to form hydrochloric
acid.
4. Summary of Test Method
1.2 This test method applies only to monomeric isocyanates
4.1 The sample reacts with 2-propanol to form urethanes
in which all of the acidity is derived from species that generate
and hydrochloric acid, which is liberated from the labile
HCl on solvolysis.
carbamyl chlorides, acid chlorides, and dissolved phosgene.
1.3 The values stated in SI units are to be regarded as the
The chlorides of the liberated acid are then determined
standard.
potentiometrically using standard methanolic silver nitrate
1.4 This standard does not purport to address all of the
solution and calculated as parts per million HCl.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety and health practices and determine the applica-
5.1 This test method can be used for research or for quality
bility of regulatory limitations prior to use. Specific warning
control to characterize TDI and MDI.
and precautionary statements are given in Note 4.
5.2 This test method was developed to overcome problems
NOTE 1—There is no equivalent ISO standard.
with low-level acidity determinations that use glass electrodes
in the presence of reagent alcohol solvents. Reagent alcohols
2. Referenced Documents
contain acidic and basic species, which complicate the glass
2.1 ASTM Standards:
electrode methods at low levels of acidity.
D 883 Terminology Relating to Plastics
D 1193 Specification for Reagent Water 6. Interferences
6.1 Any acidic species that does not generate chloride ion
3. Terminology
under the conditions of this test method will not be determined
3.1 Definitions—For definitions of terms used in this test
because acidity is determined indirectly from the chloride ion
method, see Terminology D 883.
concentration.
6.2 Acidic species not producing chloride ion are expected
to be negligible at low levels of acidity and for the monomeric
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
and is the direct responsibility of Subcommittee D20.22 on Cellular Plastics.
isocyanates in this test method.
Current edition approved March 15, 1994. Published May 1994.
6.3 Care must be taken to avoid chloride contamination of
Annual Book of ASTM Standards, Vol 08.01.
3 glassware and sample containers.
Annual Book of ASTM Standards, Vol 11.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5523
7. Apparatus 11. Procedure
7.1 Potentiometric Titrator. 11.1 Weigh 10.0 g of the sample into a beaker and record the
7.2 Combination Silver Billet Electrode (Note 2). weight to the nearest 0.0001 g (Note 5).
7.3 Oven, 70°C (Note 3). 11.2 Add 100 mL of 2-propanol to the beaker, cover, and stir
7.4 Magnetic Stirrer. the sample for 10 min.
11.3 Add 100 mL of methanol, cover, and continue stirring
NOTE 2—The combination silver billet electrode should be stored in
the sample solution for an additional 20 min (Note 6).
0.01 N methanolic silver nitrate solution in order to keep the electrode
11.4 Add ten drops of concentrated nitric acid solution to
conditioned properly.
the sample solution.
NOTE 3—Monomeric MDI samples may be solid when received in the
laboratory. An oven may be used to melt the sample prior to beginning the
11.5 Cool the sample solution to room temperature in an ice
test procedure.
bath if necessary.
11.6 Titrate the sample solution potentiometrically with the
8. Reagents and Materials
appropriate methanolic silver nitrate solution (Note 7).
8.1 Purity of Reagents—Reagent grade chemicals shall be
11.7 Record the volume of titrant used to reach the end point
used in all tests. Unless otherwise indicated, it is intended that
to at least the nearest 0.001 mL.
all reagents conform to the specifications of the Committee on
NOTE 5—The beaker must be of such size to accommodate approxi-
Analytical Reagents of the American Chemical Society where
mately 300 mL of solution, and it must be of a shape to allow the proper
such specifications are available. Other grades may be used,
coverage for the electrode. For monomeric MDI, the beaker may be
provided it
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