ISO 26603:2008 download free.Plastics Aromatic isocyanates for use in the production of polyurethanes Determination of total chlorine.
Isocyanates are typically produced by phosgenatiori 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 isocyariates. The test methods in ISO 26603 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.
ISO 26603 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 apphcable 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
ISO 26603 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 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 ISO 26603, the following definitions apply.
isocyanates
organic compounds 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
Combustion is done at atmospheric pressure in a Schöniger oxygen flask. NOTE For information on the Schôniger flask, refer to Reference [6J.
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.
7.1.3 Ethyl Alcohol — Conforming to ISO 6353-2.
7.1.4 Nitric acid (diluted) — While stirring vigorously, add 100 ml of nitric acid (HNO3, 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 (AgNO3) solution, and check frequently enough to detect changes of 0,000 5 M, either gravimetrically or potentiometrically, using standard hydrochloric acid (HCI).
7.1.7 Sodium carbonate solution (50 g/l) — Dissolve 135 g of sodium carbonate decatiydrate (Na2CO3 10H20) in water and dilute to 11.
7.2 Apparatus
7.2.1 WeIghing bottle and balance — suitable for weighing a liquid sample by difference to the nearest
0,5 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 appropriate changes in the procedure.
7.2.3 Fuse wire — iron-nickel-chromium, No. 34 B & S gage.
7.2.4 Titrlmeter — automatic (preferred) or manual, equipped with a silver/silver chloride electrode pair and a 10 ml capacity microburette.
7.2.5 Bubble counter — a 100 ml graduate and delivery tube, or a bent I” 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 AgNO3 and 1 drop of concentrated nitric acid have been added. Any turbidity that develops indicates that HCI gas is being lost when venting the bomb.
7.3 Procedure
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 will retain chlorine from sample to sample.
7.3.2 Weigh a 0,9 g samp’e by difference to ± 0,000 5g into the combustion capsule. WARNING — A severe safety hazard exists if more than 1 9 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 Na2CO3 solution (7.1.7) in the bomb and, with a small rubber 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 valve securely with the special wrench provided and open the main oxygen cylinder slightly. Place the bomb in its bench-mounted holder and tighten the holder with a suitably sized hex wrench. Attach the union on the oxygen-filling connection to the inlet valve of the bomb. Admit oxygen slowly (to prevent blowing the sample from the cup) to 20 to 25 atmospheres (2,03 MPa to 2,53 MPa). Close the operating valve of the oxygen cylinder and observe the pressure on the bomb gage. If a leak is indicated by a gradual pressure drop, inspect and tighten all connections. Do not continue with the test until the leak is stopped and the bomb holds pressure. Release the pressure from the oxygen tank and disconnect the bomb, Place the valve thumb nut on the oxygen inlet valve and tighten finger-tight.
WARNING — Exercise extreme caution from this point on until the bomb has been fired, cooled, and bled free of oxygen.
8.5.1 PrecIsion
8.5.1.1 Duplicate results by the same analyst should be considered suspect if they differ by more than
0,015 % total chlorine.
8.5.1.2 Results reported by different laboratories should be considered suspect if they differ by more than
0,03 % total chlorine.
8.5.2 Bias
Bias is the difference between the expectation of the test results and an accepted reference value. There are no recognized standards by which to estimate the bias of this test method.
9 Test report
The test report shall include the following information:
a) a reference to this International Standard;
b) all details necessary to identify the product analysed (such as manufacturer, product type, lot or notebook numbers, date of manufacture, as required):
C) the results obtained, expressed as percent total chlorine to the nearest 0.000 1 %;
d) the date of the analysis;
e) any incident or detail not stipulated in this International Standard which may have influenced the result.