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1、 Reference number ISO 14896:2006(E) ISO 2006 INTERNATIONAL STANDARD ISO 14896 Second edition 2006-06-01 Plastics Polyurethane raw materials Determination of isocyanate content Plastiques Matires premires des polyurthannes Dtermination de la teneur en isocyanate ISO 14896:2006(E) PDF disclaimer This
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4、 PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. ISO 2006 All rights reserv
5、ed. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requeste
6、r. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2006 All rights reserved -,-,- ISO 14896:2006(E) ISO 2006 All rights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Nor
7、mative references. 1 3 Terms and definitions. 2 4 Principle. 2 5 Application 2 6 Interferences . 2 7 Sampling 3 8 Test conditions . 3 9 Reagents 3 10 Apparatus 4 11 Method A Toluene/dibutylamine with aqueous HCI . 4 12 Method B Toluene/TCB/DBA with methanolic HCI . 7 -,-,- ISO 14896:2006(E) iv ISO 2
8、006 All rights reserved 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
9、 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 Commiss
10、ion (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
11、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
12、not be held responsible for identifying any or all such patent rights. ISO 14896 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting materials. This second edition cancels and replaces the first edition (ISO 14896:2000), of which it constitutes a minor revision
13、 the purpose of which was to combine the standard with its Technical Corrigendum ISO 14896:2000/Cor.1:2005. -,-,- INTERNATIONAL STANDARD ISO 14896:2006(E) ISO 2006 All rights reserved 1 Plastics Polyurethane raw materials Determination of isocyanate content SAFETY STATEMENT Persons using this docume
14、nt 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 reg
15、ulatory requirements. 1 Scope This lnternational Standard specifies two methods for the measurement of the isocyanate content of aromatic isoocyanates used as polyurethane raw materials. Method A is primarily applicable to refined toluene diisocyanate (TDI), methylene-bis-(4-phenylisocyanate) (MDI)
16、and their prepolymers. Method B is applicable to refined, crude or modified isocyanates derived from toluene diisocyanate, methylene-bis- (4-phenylisocyanate) and polymethylene polyphenylisocyanate. It can also be used for isomer mixtures of toluene diisocyanate, methylene-bis-(4-phenylisocyanate) a
17、nd polymethylene polyphenylisocyanate. Other aromatic isocyanates may be analysed by this method if precautions are taken to verify suitability. It is not applicable to blocked isocyanates. 2 Normative references The following referenced documents are indispensable for the application of this docume
18、nt. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 385, Laboratory glassware Burettes ISO 648, Laboratory glassware One-mark pipettes ISO 3696, Water for analytical laboratory use Spe
19、cification and test methods ISO 4787, Laboratory glassware Volumetric glassware Methods for use and testing of capacity ISO 4788, Laboratory glassware Graduated measuring cylinders ISO 6353-1, Reagents for chemical analysis Part 1: General test methods ISO 6353-2, Reagents for chemical analysis Part
20、 2: Specifications First series ISO 6353-3, Reagents for chemical analysis Part 3: Specifications Second series ISO 14898:1999, Plastics Aromatic isocyanates for use in the production of polyurethane Determination of acidity -,-,- ISO 14896:2006(E) 2 ISO 2006 All rights reserved 3 Terms and definiti
21、ons For the purposes of this document, the following terms and definitions apply. 3.1 polyurethane polymer prepared by the reaction of an organic di- or polyisocyanate with compounds containing two or more hydroxyl groups NOTE Polyurethanes may be thermosetting, thermoplastic, rigid or soft and flex
22、ible, cellular or non-cellular. 3.2 assay percent by mass of a specific isocyanate present in a sample 3.3 isocyanate content NCO content percent by mass of the NCO groups present in a sample 3.4 amine equivalent mass of sample that will combine with 1 gram-equivalent of dibutylamine 4 Principle 4.1
23、 Method A The isocyanate sample is reacted with an excess of dibutylamine in toluene to form the corresponding substituted urea. After cooling to room temperature, acetone is added as a co-solvent, then the reaction mixture is back-titrated with standardized aqueous HCI using potentiometric or color
24、imetric end point determination. 4.2 Method B The isocyanate sample is reacted with an excess of dibutylamine in a toluene/trichlorobenzene solvent to form the corresponding substituted urea. After cooling to room temperature, the reaction mixture is diluted with methanol and back-titrated potentiom
25、etrically or colorimetrically with methanolic hydrochloric acid. 5 Application These test methods can be used for research or for quality control purposes to characterize isocyanates used in polyurethane products. 6 Interferences Phosgene, the carbamyl chloride of the isocyanate, hydrogen chloride a
26、nd any other acidic or basic compounds will interfere. In refined isocyanates, these impurities are usually present in such small amounts that they do not affect the determination; however, some crude or modified isocyanates may contain acidities of up to approximately 0,3 %, so the value reported f
27、or the NCO content of unrefined isocyanates should preferably be designated as “corrected” or “uncorrected” for acidity. ISO 14896:2006(E) ISO 2006 All rights reserved 3 7 Sampling Since organic isocyanates react with atmospheric moisture, take special precautions in sampling (see warning). Usual sa
28、mpling methods (for example, sampling an open drum with a thief), even when conducted rapidly, can 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 wh
29、en absorbed through the skin, or when the vapours are breathed. Provide adequate ventilation and wear protective gloves and eyeglasses. 8 Test conditions Since isocyanates react with moisture, keep the laboratory humidity low, preferably below 50 % relative humidity. 9 Reagents Use reagent-grade che
30、micals in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of ISO 6353-1, ISO 63535-2 and ISO 6353-3. Other grades may be used, provided that it is first determined that the reagent is of sufficiently high purity to permit its use without le
31、ssening the accuracy of the determination. Unless otherwise indicated, references to water shall be understood to mean grade 3 water as defined in ISO 3696. 9.1 Acetone (method A). 9.2 Toluene, dried over type 4A molecular sieve. 9.3 di-n-butylamine solution, 1 mol/l (method A). Dilute 129 g of di-n
32、-butylamine to 1 litre with toluene. 9.4 di-n-butylamine solution, 2 mol/l (method B). Dilute 258 g of di-n-butylamine to 1 litre with toluene. 9.5 Aqueous hydrochloric acid, 1 mol/l (method A). Prepare 1 mol/l aqueous hydrochloric acid and standardize frequently enough to detect changes of 0,001 mo
33、l/l. 9.6 Methanolic hydrochloric acid, 1 mol/l (method B). Prepare 1 mol/l hydrochloric acid in methanol and standardize frequently enough to detect changes of 0,001 mol/l. NOTE In order to have homogeneous solutions, it is recommended that methanolic HCI be used in this procedure. If desired, aqueo
34、us HCI can be used; however, turbidity will be encountered in some titrations. It is recommended that 200 ml to 250 rnl of methanol be added to the reacted product to minimize the formation of two layers. Experience has shown that, if the mixtures are agitated vigorously, inhomogeneity can be tolera
35、ted without adversely affecting the results. 9.7 Bromophenol blue indicator solution, for colorimetric titration: 0,04 % aqueous solution of bromophenol blue sodium salt, reagent grade, or 0,04 % solution of bromophenol blue in acetone. 9.8 1,2,4-Trichlorobenzene (TCB), dried over type 4A molecular
36、sieve (method B). 9.9 Methanol (method B). -,-,- ISO 14896:2006(E) 4 ISO 2006 All rights reserved 10 Apparatus 10.1 Potentiometric titrator or pH-meter, accurate to 0,1 mV or better, equipped with a pair of electrodes or a combination glass-calomel electrode (filled with a 1 mol/l lithium chloride s
37、olution in methanol, or an equivalent solution) and a piston burette having a 20 ml capacity. 10.2 Syringes, 2 ml and 5 ml, and syringes with a large orifice suitable for weighing viscous prepolymers by difference to the nearest 1 mg. 10.3 Magnetic stirrer. 10.4 Analytical balance, accurate to 0,1 m
38、g. 10.5 Iodine flask, 500 ml capacity, with ground-glass neck (method A). 10.6 Conical flask, 250 ml, wide-mouth (method B). 10.7 Volumetric pipettes, 25 ml (method A) and 20 ml (method B), conforming to ISO 4787. 10.8 Measuring pipette, 1 ml, conforming to ISO 648. 10.9 Graduated cylinders, 250 ml
39、(method A) and 100 ml (method B), conforming to ISO 4788. 10.10 Beaker, 500 ml. 10.11 Burette, 50 ml, for colorimetric titration, conforming to ISO 385. 11 Method A Toluene/dibutylamine with aqueous HCI 11.1 Procedure 11.1.1 Using a volumetric pipette (10.7), add 25 ml of 1 mol/l dibutylamine soluti
40、on (9.3) to an iodine flask (10.5). Rinse the walls of the flask with 10 ml of toluene (9.2). 11.1.2 Weigh a sample of the product to be analysed to the nearest 0,1 mg using a suitable syringe (10.2). The sample used for analysis shall be completely liquid; if it contains crystallized isocyanates, h
41、eat it carefully until a homogeneous liquid phase is obtained. Add m0 grams of the product to the dibutylamine solution in the iodine flask. The mass (m0) in grams of the product to be analysed shall contain (15 5) milliequivalents of isocyanate or, in the case of TDI, about 1,5 g or, in the case of
42、 MDI, about 2,5 g. In the event that the isocyanate equivalent is not known, a preliminary test should be run to determine the proper sample size to be used. 11.1.3 After complete dissolution, allow to react for 15 min at ambient temperature. The reaction will cause some warming of the solution. Let
43、 the solution stand until it reaches room temperature (an additional 5 min to 10 min). 11.1.4 Using a graduated cylinder (10.9), add 150 ml of acetone (9.1), taking care to rinse the flask walls and stopper. 11.1.5 Titrate the excess dibutylamine using one of the two following procedures: 11.1.5.1 P
44、otentiometric titration (recommended) Pour the contents of the iodine flask into the titration beaker (10.10), rinsing with 25 ml of acetone (9.1). Place the beaker on the magnetic stirrer (10.3) and stir the contents. ISO 14896:2006(E) ISO 2006 All rights reserved 5 Immerse the electrodes in the re
45、action mixture and titrate with 1 mol/l hydrochloric acid (9.5), using the potentiometer (10.1) to determine the equivalence point. 11.1.5.2 Colorimetric titration Place the iodine flask on the magnetic stirrer and stir the reaction mixture. Using a graduated 1 ml pipette (10.8), add 0,8 ml of bromo
46、phenol blue solution (9.7). Titrate using the burette containing 1 mol/l aqueous hydrochloric acid until the indicator changes from blue to yellow, and remains stable for 15 s. The solution will change from a blue colour at the start of the titration to a bluish-green intermediate colour and to a ye
47、llow colour at the end point. Recognition of the end point is a matter of experience, but better defined colour changes are obtained when the acid is titrated rapidly into the solution until the first flash of yellow colour is observed. This flash of colour appears within a few tenths of a millilitr
48、e of the end point. 11.1.6 Conduct a blank determination under identical conditions, except omit the test portion. 11.2 Expression results 11.2.1 Calculate the % NCO as follows: () 12 0 4,202 % NCO VVc m = where V1 is the volume of HCI required for titration of the blank, in ml, to the nearest 0,01 ml; V2 is the volume of HCI required for titration of the test portion, in ml, to the nearest 0,01 ml; c is the concentration of the HCI, in mol/l; m0 is the mass of the test portion, in g; 4,202 is a constant combining the equivalent mass of NCO (42,02 mg/mequiv), conversion of