ASTM D6099-97

Standard Test Method for Polyurethane Raw Materials: Determination of Acidity in Moderate to High Acidity Aromatic Isocyanates

SCOPE
1.1 this test method determines the acidity, expressed as parts per million (ppm) of HCI, in aromatic isocyanate samples of greater than 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 is no similar or equivalent ISO standard.

General Information

• Status: Historical
• Publication Date: 09-Apr-1997
• ICS: 83.040.01 - Raw materials for rubber and plastics in general
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Replaced By: ASTM D6099-03 - Standard Test Method for Polyurethane Raw Materials: Determination of Acidity in Moderate to High Acidity Aromatic Isocyanates
• Effective Date: 10-Mar-2003
• Referred By: ASTM D5629-23 - Standard Test Method for Polyurethane Raw Materials: Determination of Acidity in Low-Acidity Aromatic Isocyanates and Polyurethane Prepolymers
• Effective Date: 10-Apr-1997

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 6099 – 97
Standard Test Method for
Polyurethane Raw Materials: Determination of Acidity in
Moderate to High Acidity Aromatic Isocyanates
This standard is issued under the fixed designation D 6099; 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 6. Apparatus
1.1 This test method determines the acidity, expressed as 6.1 250-mL Beakers.
parts per million (ppm) of HCl, in aromatic isocyanate samples 6.2 50-mL Pipet or Repipet, Class A volumetric.
of greater than 100–ppm acidity. The test method is applicable 6.3 100-mL Pipet or Repipet, Class A volumetric.
to products derived from toluene diisocyanate and methylene- 6.4 Automatic Titration Equipment, such as:
bis-(4–phenylisocyanate) (see Note 1). 6.4.1 Titroprocessor, and
6.4.2 Dosimat, with magnetic stirrer.
NOTE 1—There is no similar or equivalent ISO standard.
6.4.3 Reference Electrode, with saturated LiCl/ethanol
solution in both chambers.
2. Referenced Documents
6.4.4 pH Glass Electrode, (see Note 2).
2.1 ASTM Standards:
D 883 Terminology Relating to Plastics
NOTE 2—A combination pH electrode with internal reference also may
be used.
E 180 Practice for Determining the Precision of ASTM
Methods for Analysis and Testing of Industrial Chemicals
6.5 Magnetic Stirrer.
E 691 Practice for Conducting an Interlaboratory Study to
6.6 Stir Bars.
Determine the Precision of a Test Method
6.7 Watch Glasses.
6.8 Analytical Balance, capable of weighing to the nearest 1
3. Terminology
mg.
3.1 Definitions—Terms used in this test method are in
accordance with Terminology D 883. 7. Reagents and Materials
3.2 Definitions of Terms Specific to This Standard:
7.1 0.02 N KOH in Methanol—1.32 g KOH pellets (85 %
3.2.1 acidity, n—the acid strength of a sample expressed in
KOH)/1000 mL methanol, standardized with potassium hydro-
ppm hydrochloric acid.
gen phthalate (KHP).
7.2 Toluene or 1,2,4–Trichlorobenzene (TCB), dried for 24 h
4. Summary of Test Method
over molecular sieves.
4.1 The isocyanate is mixed with an excess of methanol and
7.3 Anhydrous Methanol.
a cosolvent. Additional acid is released into the solvent system
during urethane formation. The acid then is titrated potentio- 8. Sampling
metrically with methanolic KOH, and the acidity present in the
8.1 Since organic isocyanates react with atmospheric mois-
isocyanate sample is calculated from the titer.
ture, take special precautions in sampling (see Note 3: Warn-
ing and Note 4: Precaution). Usual sampling methods, for
5. Significance and Use
example, sampling an open drum thief, even when carried out
5.1 This test method can be used for research or for quality
rapidly, can cause contamination of the sample with insoluble
control to characterize aromatic isocyanates and prepolymers
urea. Blanket the sample, therefore, with dry air or nitrogen at
of moderate to high acidity. Acidity correlates with perfor-
all times.
mance in some polyurethane systems.
Instruments similar to and including the Metrohn 686 Titroprocessor with a
Metrohn 665 Dosimate/magnetic stirrer as supplied by Brinkman Instruments Co.,
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics Cantiague Road, Westbury, NY 11590-9974, or an equivalent instrument, have been
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials— found to be satisfactory for this analysis.
Plastics and Elastomers. The Brinkman CAT. #020-94-400-5, or its equivalent: bridge electrolyte
Current edition approved April 10, 1997. Published May 1998. (double junction), sleeve-type diaphragm, has been found satisfactory for this
Annual Book of ASTM Standards, Vol. 08.01. analysis. See Footnote 5 for the address to Brinkman Instruments Co.
3 7
Annual Book of ASTM Standards, Vol. 15.05. The Brinkman CAT. #020-91-012-7, or its equivalent, has been found satisfac-
Annual Book of ASTM Standards, Vol. 14.02. tory for this analysis. See Footnote 5 for the address to Brinkman Instruments Co.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 6099
NOTE 3—Warning: Organic isocyanates are toxic when they are ab-
as any heating required to effect solution before titration, or
sorbed through the skin or when the vapors are breathed.
end point identified different from that described in 11.7.
NOTE 4—Precaution: Provide adequate ventilation and wear protective
gloves and eyeglasses.
14. Precision and Bias
14.1 Table 1 is based on a round robin conducted in 1995 in
9. Calibration
accordance with Practice E 691, involving twelve laboratories.
9.1 Calibrate the electrodes using pH 4 and pH 7 aqueous
For each material, all the samples were prepared at one source,
buffer.
but the individual specimens were prepared at the laboratories
that tested them. Some laboratories generated a set of results
10. Test Conditions
for each of two solvents (toluene and TCB), and some
10.1 Since isocyanates react with moisture, keep laboratory
laboratories generated a set of results for each of two different
humidity low, preferably around 50 % relative humidity.
electrode types. Neither change in experimental conditions was
found to be a significant source of increased variability. Each
11. Procedure
of these combinations of conditions was treated as a different
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