1、BRITISH STANDARD BS ISO 8660:2002 Plastics Determination of permanganate absorption number of caprolactam Spectrometric method ICS 71.080.30; 83.080.01 BS ISO 8660:2002 This British Standard, having been prepared under the direction of the Sector Policy and Strategy Committee for Materials and Chemi
2、cals, was published under the authority of the Standards Policy and Strategy Committee on 15 July 2002 BSI 15 July 2002 ISBN 0 580 40029 8 National foreword This British Standard reproduces verbatim ISO 8660:2002 and implements it as the UK national standard. The UK participation in its preparation
3、was entrusted to Technical Committee PRI/21, Plastics test methods, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in thi
4、s document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a con
5、tract. Users are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposal
6、s for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 6, a blank page and a back c
7、over. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsINTERNATIONAL STANDARD ISO 8660 Second edition 2002-05-15 Reference number ISO 8660:2002(E) OSI 2002 Plastics Determination of permanganate a
8、bsorption number of caprolactam Spectrometric method Plastiques Dtermination de lindice dabsorption de permanganate du caprolactame Mthode spectromtriqueii ISO 8660:2002(E)iii Contents Page 1 Scope . 1 2 Term and definition . 1 3 Principle 1 4 Reagents 1 5 Apparatus . 2 6 Sample . 3 7 Procedure . 3
9、8 Calculation 4 9 Precision . 4 10 Test report 6ISO 8660:2002(E) iv 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 technica
10、l 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 wit
11、h the 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 3. Draft International Standards adopted by the technical committees are circulated to the
12、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 International Standard may be the subject of patent rights. ISO shall not be held respons
13、ible for identifying any or all such patent rights. International Standard ISO 8660 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-chemical properties. This second edition cancels and replaces the first edition (ISO 8660:1988), which has been technically revised
14、.ISO 8660:2002(E)v Introduction The permanganate index, expressed as the permanganate absorption number (PAN), defines the stability of a caprolactam sample to potassium permanganate in a buffered neutral aqueous solution and is a measure of the purity of the caprolactam in relation to the presence
15、of oxidizable impurities, e.g. unsaturated caprolactams. Permanganate in a neutral aqueous solution is a strong oxidizing agent, capable of oxidizing the impurities in caprolactam. The determination of the permanganate absorption number is based on measurement of the absorbance of a (by mass) aqueou
16、s caprolactam solution at a wavelength of . The measurement is carried out after adding a potassium permanganate solution of . To correct for the oxidation of water, a blank determination is carried out. In general, the oxidation reaction with unsaturated organic compounds is faster than with satura
17、ted organic compounds. Unsaturated caprolactam is oxidized at a faster rate than saturated caprolactam. The reaction speed depends upon the reducing agent and, in addition to other experimental conditions, strongly on the pH of the solution. The majority of the unsaturated impurities in caprolactam
18、are considered to react within a period of . The reaction does not end there, however, as the oxidation of slowly oxidizing compounds, e.g. caprolactam, will continue. The amount of manganese dioxide generated during the reaction is determined at a wavelength of . The contribution of caprolactam at
19、this wavelength in the method described here is less than of the total absorbance. The method is sensitive to external factors and therefore needs to be followed closely. The results obtained with the method in this edition of ISO 8660 are approximately lower than those obtained with ISO 8660:1988.
20、The difference is due to buffering of the test solution and the blank at pH 7,0. Buffering the solution at a pH of 7,0 results in a significantly higher precision of the method, as fluctuations caused by the acidity/alkalinity of the sample are eliminated. 3 % 420 nm 10 min 0,002 mol/l 10 min 420 nm
21、 0,2 % 11 %blankINTERNATIONAL STANDARD ISO 8660:2002(E)1 Plastics Determination of permanganate absorption number of caprolactam Spectrometric method WARNING This International Standard may involve hazardous chemicals, materials or operations. This standard does not purport to address the safety pro
22、blems, if any, associated with its use. It is the responsibility of the user of this standard to establish proper safety and health practices and determine the applicability of regulatory limitations prior to use. 1 Scope This International Standard specifies a spectrometric method for the determina
23、tion of the permanganate absorption number of caprolactam for industrial use. The permanganate absorption number is a measure of the oxidizable impurities in caprolactam, determined in a buffered neutral aqueous medium under fixed conditions. The method is applicable to purified caprolactam (and int
24、ermediates in the caprolactam purification process) with an alkalinity or acidity lower than and a PAN value of up to 35. 2 Term and definition For the purposes of this International Standard, the following term and definition apply. 2.1 permanganate absorption number PAN index based on measurement
25、of the absorbance at of a (by mass) buffered neutral aqueous caprolactam solution in comparison with a blank consisting of buffered water, after addition of a standard solution of potassium permanganate, , to each and allowing each to stand for , the absorbance being measured in a cell of pathlength
26、 NOTE The P AN is the difference between the absorbance of the test solution and that of the blank, multiplied by 100/3 for a glass cell of pathlength . 3 Principle Equal amounts of potassium permanganate are added to a buffered caprolactam test solution and to a blank consisting of buffered water.
27、After a reaction time of , the absorbance at a wavelength of of the caprolactam test solution and the blank are compared in glass cells with a pathlength of . 4R e a g e n t s During the analysis, use only reagents of recognized analytical grade or of the grade specified. 4.1 Sulfuric acid, p.a., (b
28、y mass) to (by mass). 4.2 Hydrochloric acid, p.a., (by mass). 4.3 Oxalic acid dihydrate, . 0,50 mmol/kg 420 nm 3 % c = 0,002 mol/l 10 min 5cm 5cm 10 min 420 nm 5cm 95 % 97 % 37 % c = 0,1 mol/lISO 8660:2002(E) 2 4.4 Millipore-Q (or double-distilled) water. 4.5 pH7,0 buffer salt, exclusively composed
29、of potassium dihydrogen phosphate ( ) and disodium hydrogen phosphate ( ). The salt shall not contain impurities that influence the PAN analysis. Some commercially available buffer salts contain impurities and/or preservatives which influence the PAN analysis. The suitability of a commercially avail
30、able buffer salt shall always be tested by comparing the PAN results obtained with this buffer salt with those obtained with a buffer salt made of analytically pure components. The maximum storage time of a commercially available buffer salt or the pure components shall never be exceeded. 4.6 pH 7,0
31、 buffer solution. Dissolve of the buffer salt (4.5) in Millipore-Q water (4.4) in a volumetric flask and make up to the mark with Millipore-Q water. This solution shall be discarded 6 months after preparation (or sooner if any sediment is noticed). 4.7 PAN water. Add of buffer solution (4.6) to a sm
32、all quantity of Millipore-Q water in a volumetric flask, make up to the mark with Millipore-Q water and degas with helium (4.11). Prepare a fresh solution daily. The PAN value of a blank determination shall be . 4.8 Potassium permanganate, solid, p.a. 4.9 Potassium permanganate stock solution, . Sto
33、re in a brown bottle in the dark. Prepare a fresh solution every 4 weeks. Check the solution every day for manganese dioxide deposit on the walls of the bottle (see the note to 7.1). If any deposit is observed, the solution shall be discarded. 4.10 Potassium permanganate solution, . Store in brown b
34、ottle in the dark. Prepare a fresh solution weekly from the potassium permanganate solution (4.9). Before use check the solution for manganese dioxide deposit on the walls of the bottle. If any deposit is observed, the solution shall be discarded. 4.11 Helium. 5 Apparatus Ordinary laboratory apparat
35、us and additionally: 5.1 Spectrometer, suitable for monochromatic analyses at , bandwith . 5.2 Glass cells, pathlength . 5.3 Water bath, capable of being maintained at . 5.4 Stopwatch, accurate to at least . 5.5 Glassware, extremely clean and suitable for PAN analyses (see 7.1). NOTE Disposable syri
36、nges and other plastic devices are not suitable because of the extraction capacity of caprolactam. Additives extracted from plastic devices such as syringes have a negative effect on the PAN determination. 5.6 Pipette, made of glass (e.g. a Pasteur pipette), chemically clean (see 7.1). NOTE Plastic
37、pipettes are not suitable (see note to 5.5). 40,30 % 59,70 % 3,3 g 500 ml 2,5 ml/l 1 l 0,67 c = 0,020 mol/l c = 0,002 mol/l 0,020 mol/l 420 nm 2nm 5cm 25,0 C 0,5 C 0,5 sISO 8660:2002(E)3 6S a m p l e Caprolactam samples shall be stored in chemically clean, preferably glass, containers. If plastic fl
38、asks or containers are used, contact with hot, liquid caprolactam shall be avoided. Caprolactam solutions shall not be stored in plastic containers and any contact with e.g. plastic stoppers shall be avoided (see 5.5). Samples can consist of pure solid caprolactam or caprolactam solutions. The prefe
39、rred sample is a solution containing (by mass) of caprolactam in Millipore-Q water. NOTE Sampling of pure liquid caprolactam may result in an increase in the PAN value, as a result of oxidation of caprolactam in the presence of air. 7 Procedure 7.1 Cleaning of the glassware Glassware used for the fi
40、rst time in PAN analysis shall be cleaned successively with concentrated sulfuric acid (4.1), tap water, concentrated hydrochloric acid (4.2), Millipore-Q water (4.4). Glassware used for PAN analysis shall be used for that purpose only and shall be cleaned at least once every 6 months using the abov
41、e procedure. Glassware shall be rinsed with tap water (3 times) immediately after the analysis, followed by rinsing 3 times with Millipore-Q water (4.4). Glassware shall be stored closed. NOTE If the glassware is not rinsed immediately after the analysis, manganese dioxide will settle on the inside
42、surface of the glass. Manganese dioxide catalyses the reaction and has a negative effect on the PAN determination. Manganese dioxide can be removed from the glassware by rinsing with oxalic acid (4.3). 7.2 Purity of the PAN water Check the PAN water (4.7) by carrying out a blank determination in acc
43、ordance with 7.3 and calculate its PAN value (see clause 8). If the PAN value is , the PAN water is acceptable. For e.g. production control, the blank determination carried out to check the PAN water should preferably be combined with a determination carried out on a control sample. Analysis of furt
44、her samples should only be carried out if both the blank and the control sample meet the specifications. If the PAN value of the PAN water is , repeat the blank determination with a freshly prepared solution of potassium permanganate (4.10) and, if necessary, a fresh stock solution of potassium perm
45、anganate (4.9). If the PAN value is still , purify the Millipore-Q water by dissolving of potassium permanganate (4.8) in each litre of Millipore-Q water, storing the solution for and then distilling with a Vigreux column, collecting the first three-quarters of the solution to distill over. Use this
46、 purified Millipore-Q water to prepare a fresh solution of PAN water. If the PAN water still does not meet the specification of (for a glass cell of in length, this corresponds to an absorbance of 0,020), the potassium permanganate may be contaminated with manganese dioxide or the PAN water may have
47、 too high an impurity content. 50 %0,67 0,002 mol/l 0,020 mol/l 0,67 1 g 24 h 600 mm 0,67 PAN units 5 cmISO 8660:2002(E) 4 7.3 Determination Weigh of solid caprolactam or of (by mass) caprolactam solution in Millipore-Q water into a volumetric flask, transferring the solution with a glass pipette. I
48、f the concentration of the caprolactam solution is not , determine the mass of the test portion by dividing by the concentration of the caprolactam solution, expressed as a percentage by mass, and multiplying by 100. In the case of solid caprolactam, add of PAN water (4.7) and dissolve the caprolact
49、am. Make up to the mark with PAN water and mix. Place the flask in a water bath at for at least . Add of permanganate solution (4.10) and start the stopwatch immediately. Mix carefully, minimizing the amount of oxygen entering the mixture, and put the flask back in the water bath. After , fill two glass spectrometer cells with the test solution and with Millipore-Q water, respectively. Determine the absorbance of the solution after in comparison with the Millipore-Q water at a
