ASTM D4660-00
(Test Method)Standard Test Methods for Polyurethane Raw Materials: Determination of the Isomer Content of Toluenediisocyanate
Standard Test Methods for Polyurethane Raw Materials: Determination of the Isomer Content of Toluenediisocyanate
SCOPE
1.1 These test methods measure the amount of toluene-2,6-diisocyanate (TDI) in mixtures of the 2,4- and 2,6-isomers. Two test methods are required to give accurate results over a broad range of isomer concentrations.
1.1.1 Test Method A -Applicable to TDI samples containing 5 to 95% 2,6-isomer.
1.1.2 Test Method B -Applicable to TDI samples containing 0 to 5% 2,6-isomer.
Note 1--There are no equivalent ISO standards.
1.2 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. For specific warning and precautionary statements see Note 3.
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Designation:D4660–00
Standard Test Methods for
Polyurethane Raw Materials: Determination of the Isomer
Content of Toluenediisocyanate
This standard is issued under the fixed designation D4660; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.1 isomer—a compound having the same percentage
composition and molecular weight as another compound but
1.1 These test methods measure the amount of toluene-2,6-
differs in chemical or physical properties.
diisocyanate (TDI) or toluene–2,4–diisocyanate in mixtures of
3.2.2 isomer content—theamountofanisomerexpressedas
the 2,4– and 2,6–isomers. Two test methods are required to
a percentage of total isomer amount.
give accurate results over a broad range of isomer concentra-
tions.
4. Summary of Test Methods
1.1.1 Test Method A—Applicable to TDI samples contain-
4.1 Both test methods are based on the quantitative mea-
ing 5 to 95% 2,6–isomer (95 to 5% 2,4–isomer).
surement of absorption bands arising from out-of-plane C–H
1.1.2 Test Method B—Applicable to TDI samples contain-
deformation vibrations of the aromatic ring at 810 and 782
ing 0 to 5% 2,6–isomer (95 to 100% 2,4–isomer).
−1
cm (12.3 and 13.8 µm).
NOTE 1—There are no equivalent ISO standards.
4.2 In Test MethodA, the infrared spectrum of a cyclohex-
−1
ane solution of the sample is recorded in the 770 to 840-cm
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the (12 to 13-µm) region. The absorbance ratio of the 810 and
−1
782-cm bands is measured and converted to percent toluene-
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 2,6-diisocyanate from a previously established calibration
curve.
bility of regulatory limitations prior to use. For specific
−1
warning and precautionary statements see Note 3. 4.3 InTestMethodB,theabsorbanceofthe782-cm band
is measured from an infrared spectrum of an undiluted sample
2. Referenced Documents
and then converted to percent 2,6-isomer from a previously
2.1 ASTM Standards: established calibration curve.
D883 Terminology Relating to Plastics
5. Significance and Use
E180 Practice for Determining the Precision of ASTM
Methods for Analysis and Testing of Industrial and Spe- 5.1 These test methods can be used for research or for
quality control to determine the isomer ratios of toluene
cialty Chemicals
diisocyanates.
3. Terminology
5.2 The isomer ratio of a toluene diisocyanate relates to its
3.1 Terminologyinthesetestmethodsisinaccordancewith reactivity.
Terminology D883.
6. Apparatus
3.2 Definitions of Terms Specific to This Standard:
6.1 Spectrophotometer—Any single- or double-beam re-
cordinginfraredspectrophotometeraccurateto0.2%transmis-
sion and capable of resolving the two peaks of the 2,4-isomer
−1
These test methods are under the jurisdiction of ASTM Committee D20 on
doublet at 810 cm .
Plastics and are the direct responsibility of Subcommittee D20.22 on Cellular
6.2 Cells, sealed sodium chloride (NaCl) liquid absorption
Plastics.
cells with 0.2-mm (Test MethodA) and 0.1-mm (Test Method
Current edition approved Nov. 10, 2000. Published February 2001. Originally
published as part of D1638–59 T. Last previous edition D1638–95.
B) path lengths. The actual thicknesses of the cells should be
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
known to 60.002 mm.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
6.3 Glassware, 25-mL, glass-stoppered, volumetric flasks,
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 0.80-mL pipet, and an all-glass syringe.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4660–00
7. Reagents and Materials 10.1.1 Approximate standard mixtures for wide-range cali-
bration are given in Table 1.
7.1 Purity of Reagents—Use reagent grade chemicals in all
10.1.2 Approximate standard mixtures for short-range cali-
tests. Unless otherwise noted, all reagents conform to the
brations (see Note 4) are given in Tables 2 and 3 (see Figs. 1
specifications of the Committee onAnalytical Reagents of the
and 2).
American Chemical Society where such specifications are
available. Othergradesmaybeused,provideditisascertained
NOTE 4—Calibrationoveranarrowrangecoveringtheexpectedisomer
that the reagent is of sufficiently high purity to permit its use
ratio gives more accurate results than a wide-range calibration.
without lessening the accuracy of the determination.
10.2 Preparation of Standard Solutions— Using a pipet,
7.2 Cyclohexane, distilled and stored over silica gel to
transfer0.80mL(0.98g)ofstandardmixtureintoadry,25-mL
remove traces of moisture.
glass-stoppered, volumetric flask. Dilute to volume with cy-
7.3 Diisocyanate Standards—Pure samples of 2,4-TDI and
clohexane and mix thoroughly.
2,6-TDI are required for calibration (Note 2). The following
10.3 Filltwo0.2-mmsealed,liquidabsorptioncells(onefor
criteria can be used to judge purity:
a single-beam instrument) with cyclohexane and record its
−1
spectrum from 770 to 840 cm (12 to 13 µm). Refill the
2,4–TDI—freezingpoint 522.0°C,n 51.56781, (1)
D
sample cell with a solution from 10.2 and record the spectrum
d 51.2186,and2,6–TDI—freezingpoint
superimposing it over the previously recorded solvent spec-
20 20
518.2°C,n 51.57111,d 51.2270.
D 4 trum.Theinstrumentcontrolsmustremainunchangedbetween
samples of a given series. Repeat the process for each solution
NOTE 2—The diisocyanates can be prepared by phosgenating the
from 10.2.
corresponding pure amines and vacuum-distilling the products. Since
these diisocyanates will react with moisture and may discolor in the 10.4 Using the solvent spectrum as the baseline, measure
−1
presence of air, store them under dry nitrogen.
the absorbance of each standard solution sample at 810 cm
−1
(2,4-TDI) and 782 cm (2,6-TDI) and calculate the 810/
8. Sampling
−1
782-cm absorbance ratio. Construct a calibration curve (see
8.1 Since organic isocyanates react with atmospheric mois-
Fig. 3) by plotting absorbance ratio (ordinate) versus weight
ture, take special precautions in sampling. See 8.1.1. Usual
ratio of 2,4- to 2,6-TDI (abscissa).
sampling methods (for example, sampling an open drum with
10.5 For convenience in short-range calibrations, the absor-
a thief), even when carried out rapidly, can cause contamina-
banceratiomaybeplottedagainsttheconcentration,expressed
tion of the sample with insoluble urea. Therefore, blanket the
in weight percent, of each isomer (see Figs. 1 and 2). This
sample with dry air or nitrogen at all times.
allows direct determination of composition without equations,
8.1.1 Warning: Organic isocyanates are toxic when they
however, the relationship is not linear and the shape of the
areabsorbedthroughtheskin,orwhenthevaporsarebreathed.
calibration curve must be carefully determined.
Provide adequate ventilation and wear protective gloves and
11. Procedure
eyeglasses.
11.1 Using a pipet, transfer 0.8 mL (0.98 g) of sample into
9. Test Conditions
a dry, 25-mL, glass-stoppered, volumetric flask. Dilute to
9.1 Since isocyanates react with moisture, keep laboratory volume with cyclohexane and mix thoroughly. Fill the 0.2-mm
humidity low, preferably around 50% relative humidity. cell with the solution and record the spectrum from 770 to 840
−1
cm (12 to 13 µm), and without changing instrument settings,
TEST METHOD A—SAMPLES CONTAINING 5 TO
refill the sample cell with pure solvent and record its spectrum
...
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