ISO 26603:2017

INTERNATIONAL ISO
STANDARD 26603
Second edition
2017-03
Plastics — Aromatic isocyanates for
use in the production of polyurethanes
— Determination of total chlorine
Plastiques — Isocyanates aromatiques utilisés pour la production de
polyuréthannes — Dosage du chlore total
Reference number
ISO 26603:2017(E)
©
ISO 2017

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ISO 26603:2017(E)

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ISO 26603:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
4.1 Test Method A . 2
4.2 Test Method B . 2
5 Interferences . 2
6 Sampling . 2
7 Test Method A — Total chlorine by oxygen bomb . 2
7.1 Reagents. 2
7.2 Apparatus . 3
7.3 Procedure . 4
7.4 Calculation . 5
7.5 Precision and bias . 6
7.5.1 Precision. 6
7.5.2 Bias . 6
8 Test Method B — Total chlorine by Schöniger oxygen flask . 6
8.1 Reagents. 6
8.2 Apparatus . 6
8.3 Procedure . 7
8.4 Calculation . 8
8.5 Precision and bias . 8
8.5.1 Precision. 8
8.5.2 Bias . 8
9 Test report . 8
Bibliography . 9
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ISO 26603:2017(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www . i so .org/ iso/ foreword .html.
The committee responsible for this document is ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting
materials.
This second edition cancels and replaces the first edition (ISO 26603:2008), of which it constitutes a
minor revision. The changes compared to the previous edition are as follows:
— a key has been added to Figure 1.
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ISO 26603:2017(E)

Introduction
Isocyanates are typically produced by phosgenation of an aromatic amine using chlorine-substituted
benzenes (e.g. o-dichlorobenzene) as reaction solvents. ISO 15028 is used to determine the hydrolyzable
chlorine content of the isocyanates. The test methods in this document are used to determine the total
chlorine content of aromatic isocyanates. The difference between the total chlorine content and the
hydrolyzable chlorine content is a measure of the reaction solvents left in the product, and therefore is
a useful tool for assessing product quality.
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INTERNATIONAL STANDARD ISO 26603:2017(E)
Plastics — Aromatic isocyanates for use in the production
of polyurethanes — Determination of total chlorine
SAFETY PRECAUTIONS — Persons using this document should be familiar with normal laboratory
practice, if applicable. This document does not purport to address all of the safety concerns, if
any, associated with its use. It is the responsibility of the user to establish appropriate safety
and health practices and to ensure compliance with any regulatory requirements.
1 Scope
This document specifies the determination of the total chlorine content of aromatic isocyanates
used in the preparation of polyurethanes. The difference between the total chlorine content and the
hydrolyzable chlorine content (see ISO 15028) is a measure of the process solvents left in the product.
Both test methods are applicable to a variety of organic compounds, including aliphatic isocyanates, but
the amount of sample used might need to be adjusted. These test methods can be used for research or
for quality control.
NOTE This document is technically equivalent to ASTM D4661–03.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
isocyanate
organic compound containing one or more NCO groups
3.2
polyurethane
polymer prepared by the reaction of an organic di- or polyisocyanate with compounds containing two
or more hydroxyl groups
3.3
hydrolyzable chlorine
organic or inorganic chlorine compounds formed in the production of isocyanates that react with
methanol under the conditions of ISO 15028 to liberate hydrogen chloride
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ISO 26603:2017(E)

3.4
total chlorine
inorganic and organically bound chlorine present in isocyanates that is converted to titratable chlorides
under the combustion conditions of the test
4 Principle
In each test method, the organic matter in the sample is destroyed by combustion with oxygen,
thus converting the organically combined chlorine to ionic chloride. The chloride is determined
potentiometrically by titration with silver nitrate (AgNO ) solution.
3
4.1 Test Method A
Combustion of the sample is done in a pressurized oxygen bomb.
4.2 Test Method B
Combustion is done at atmospheric pressure in a Schöniger oxygen flask.
NOTE For information on the Schöniger flask, see Reference [6].
5 Interferences
Thiocyanate, cyanide, sulphide, bromide, iodide or other substances capable of reacting with silver
ion, as well as substances capable of reducing silver ion in acid solution, will interfere with the
determination.
6 Sampling
Since organic isocyanates react with atmospheric moisture, take special precautions in sampling. Usual
sampling methods, even when conducted rapidly, can expose the isocyanate to moisture and cause
contamination of the sample with insoluble ureas; therefore, blanket the sample with a dry inert gas
(e.g. nitrogen, argon or dried air) at all times.
WARNING — Organic isocyanates are hazardous when absorbed through the skin, or when the
vapours are breathed.
CAUTION — Provide adequate ventilation and wear protective gloves and eyeglasses.
7 Test Method A — Total chlorine by oxygen bomb
7.1 Reagents
7.1.1 Purity of reagents
Reagent-grade chemicals shall be used in all tests. Other grades may be used, provided that it is first
determined that the reagent is of sufficiently high purity to permit its use without lessening the
accuracy of the determination. Unless otherwise indicated, it is intended that all reagents shall conform
to the specifications of ISO 6353-2 and ISO 6353-3.
7.1.2 Purity of water
Unless otherwise indicated, references to water shall be understood to mean grade 2 water as defined
by ISO 3696.
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ISO 26603:2017(E)

7.1.3 Ethyl alcohol, conforming to ISO 6353-2.
7.1.4 Nitric acid (diluted). While stirring vigorously, add 100 ml of nitric acid (HNO specific gravity
3,
1,42) to 100 ml of water cooled in an ice bath.
7.1.5 Oxygen, free of combustible materials and halogen compounds.
7.1.6 Silver nitrate, standard solution (0,01 M). Prepare a 0,01 M silver
...