ASTM D5523-04
(Test Method)Standard Test Method for Polyurethane Raw Materials Acidity by Argentometric Determination of Hydrolyzable Chlorine in Monomeric, Aromatic Isocyanates
Standard Test Method for Polyurethane Raw Materials Acidity by Argentometric Determination of Hydrolyzable Chlorine in Monomeric, Aromatic Isocyanates
SIGNIFICANCE AND USE
This test method can be used for research or for quality control to characterize TDI and MDI.
This test method was developed to overcome problems with low-level acidity determinations that use glass electrodes in the presence of reagent alcohol solvents. Reagent alcohols contain acidic and basic species, which complicate the glass electrode methods at low levels of acidity.
SCOPE
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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.
Note 1—There is no equivalent ISO standard.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D5523–04
Standard Test Method for
Polyurethane Raw Materials: Acidity by Argentometric
Determination of Hydrolyzable Chlorine in Monomeric,
1
Aromatic Isocyanates
This standard is issued under the fixed designation D5523; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 3.1.1 Discussion—Polyurethanes or urethanes, as they are
sometimes called, can be thermosetting, thermoplastic, rigid or
1.1 This test method measures the hydrolyzable chlorine
soft and flexible, or cellular or solid (see Terminology D883).
content of monomeric, aromatic isocyanates used as polyure-
3.2 Definitions of Terms Specific to This Standard:
thane raw materials and expresses it as HCl acidity. The test
3.2.1 acidity—the acid strength of a sample expressed as
method is applicable to toluene diisocyanate (TDI) and mono-
partspermillionhydrochloricacid(HCl)presentinthesample.
meric methylene-bis-(4-phenylisocyanate), known as MDI.
3.2.2 hydrolyzable chlorine—the amount of chlorine re-
The main sources of hydrolyzable chlorine and, therefore,
leased as chloride ion under the conditions of the test,
acidity in monomeric aromatic isocyanates are carbamyl chlo-
expressed in parts per million of chlorine in the sample.
rides, acid chlorides, and dissolved phosgene. All of these
compounds react with alcohols and water to form hydrochloric
4. Summary of Test Method
acid.
4.1 The sample reacts with 2-propanol to form urethanes
1.2 This test method applies only to monomeric isocyanates
and hydrochloric acid, which is liberated from the labile
in which all of the acidity is derived from species that generate
carbamyl chlorides, acid chlorides, and dissolved phosgene.
HCl on solvolysis.
The chlorides of the liberated acid are then determined
1.3 The values stated in SI units are to be regarded as the
potentiometrically using standard methanolic silver nitrate
standard.
solution and calculated as parts per million HCl.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
5. Significance and Use
responsibility of the user of this standard to establish appro-
5.1 This test method can be used for research or for quality
priate safety and health practices and determine the applica-
control to characterize TDI and MDI.
bility of regulatory limitations prior to use.
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
2.1 ASTM Standards:
electrode methods at low levels of acidity.
D883 Terminology Relating to Plastics
6. Interferences
3. Terminology
6.1 Any acidic species that does not generate chloride ion
3.1 Definitions—For definitions of terms used in this test
under the conditions of this test method will not be determined
method, see Terminology D883.
because acidity is determined indirectly from the chloride ion
concentration.
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
6.2 Acidic species not producing chloride ion are expected
and is the direct responsibility of Subcommittee D20.22 on Cellular Plastics.
to be negligible at low levels of acidity and for the monomeric
Current edition approved October 1, 2004. Published October 2004. Originally
´1 isocyanates in this test method.
approved in 1994. Last previous edition approved in 1999 as D5523 - 94(1999) .
6.3 Care must be taken to avoid chloride contamination of
DOI: 10.1520/D5523-04.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
glassware and sample containers.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
*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.
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D5523–04
7. Apparatus 11.2 Add100mLof2-propanoltothebeaker,cover,andstir
the sample for 10 min.
7.1 Potentiometric Titrator.
11.3 Add 100 mL of methanol, cover, and continue stirring
7.2 Combination Silver Billet Electrode (Note 2).
the sample solution for an additional 20 min (Note 5).
7.3 Oven, 70°C (Note 3).
11.4 Add ten drops of concentrated nitric acid solution to
7.4 Magnetic Stirrer.
the sample solution.
NOTE 2—The combin
...
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