Plastics -- Aromatic isocyanates for use in the production of polyurethanes -- Determination of total chlorine
ISO 26603:2008 is used to determine 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.
Plastiques -- Isocyanates aromatiques utilisés pour la production de polyuréthannes -- Dosage du chlore total
Standards Content (sample)
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
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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
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established has the right to be represented on that committee. International organizations, governmental and
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International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 26603 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosettingmaterials.
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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 International Standard 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 usefultool for assessing product quality.
iv © ISO 2008 – All rights reserved
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INTERNATIONAL STANDARD ISO 26603:2008(E)
Plastics — Aromatic isocyanates for use in the production of
polyurethanes — Determination of total chlorine
SAFETY PRECAUTIONS — Persons using this International Standard should be familiar with normal
laboratory practice, if applicable. This International Standard 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 International Standard is used to determine 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 International Standard is technically equivalent to ASTM D 4661-03.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenceddocument (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 series3 Terms and definitions
For the purposes of this document, the following definitions apply.
organic compounds containing one or more NCO groups
polymer prepared by the reaction of an organic di- or polyisocyanate with compounds containing two or morehydroxyl groups
organic or inorganic chlorine compounds formed in the production of isocyanates that react with methanolunder the conditions of ISO 15028 to liberate hydrogen chloride
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inorganic and organically bound chlorine present in isocyanates that is converted to titratable chlorides underthe combustion conditions of the test
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 bytitration with silver nitrate (AgNO ) solution.
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, refer to Reference .
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 thevapours are breathed.
CAUTION — Provide adequate ventilation and wear protective gloves and eyeglasses.7 Test Method A ─ Total chlorine by oxygen bomb
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 ofISO 6353-2 and ISO 6353-3.
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7.1.2 Purity of water
Unless otherwise indicated, references to water shall be understood to mean grade 2 water as defined byISO 3696.
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 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 nitrate (AgNO ) solution, and
check frequently enough to detect changes of 0,000 5 M, either gravimetrically or potentiometrically, usingstandard hydrochloric acid (HCl).
7.1.7 Sodium carbonate solution (50 g/l) ─ Dissolve 135 g of sodium carbonate decahydrate(Na CO 10H O) in water and dilute to 1 l.
2 3 2
7.2.1 Weighing bottle and balance ─ suitable for weighing a liquid sample by difference to the nearest0,5 mg.
7.2.2 Oxygen bomb apparatus ─ A corrosion-resistant steel reactor capable of being pressurized to 40
atmospheres of pure oxygen, followed by electrical ignition of the sample by use of an internal fuse wire. The
bomb must be capable of withstanding the pressure build-up caused by the combustion of the sample. Parr
Bomb No. 1108 is a suitable device (see Figure 1). Equivalent apparatus may be substituted with appropriatechanges in the procedure.
7.2.3 Fuse wire ─ iron-nickel-chromium, No. 34 B & S gage.
7.2.4 Titrimeter ─ automatic (preferred) or manual, equipped with a silver/silver chloride electrode pair anda 10 ml capacity microburette.
7.2.5 Bubble counter ─ a 100 ml graduate and delivery tube, or a bent “L” glass tube connected to a piece
of rubber tubing. The graduate is filled to the 50 ml mark with water to which 3 ml of 0,1 M AgNO and 1 drop
of concentrated nitric acid have been added. Any turbidity that develops indicates that HCl gas is being lostwhen venting the bomb.
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Figure 1 — Parr oxygen bomb
7.3.1 Make certain that the bomb, oxygen lines, and fittings are free of oil and grease.
WARNING — Small quantities of either oil or grease may cause a violent explosion.
When the bomb is used repeatedly, a film may form on its inner surface. Remove this film by rotating the
bomb on a lathe at about 300 rpm and polishing the inside surface with Grit No. 2/0 or equivalent paper
coated with light machine oil, then with a paste made from grit-free chromic oxide and water. This procedure
will remove all but very deep pits while polishing the surface. Before using the bomb, wash it with soap and
water to remove residual cutting oil or paste. Bombs with pitted surfaces should not be used because they willretain chlorine from sample to sample.
7.3.2 Weigh a 0,9 g sample by difference to ± 0,000 5g into the combustion capsule.WARNING — A severe safety hazard exists if more than 1 g of sample is used.
7.3.3 Fit a 100 mm, iron-nickel fuse wire (7.2.3) onto the two electrodes. Place the combustion capsule on
the loop electrode and adjust the fuse wire in the capsule so that it is under the surface of the sample but does
not touch the capsule. Place about 5 ml of Na CO solution (7.1.7) in the bomb and, with a small rubber2 3
spatula, wet the interior surface of the bomb, including the head, as thoroughly as possible. Put the bomb
head in the bomb cylinder and the contact ring on top of the bomb head, screwing the cap down finger-tight.Close the outlet v