1、BRITISH STANDARD BS EN ISO 3682:1998 BS 6782-3: 1996 Incorporating Amendment No. 1 to BS6782-3:1996 (renumbers the BS as BSENISO 3682:1998) Binders for paints and varnishes Determination of acid value Titrimetric method The European Standard EN ISO 3682:1998 has the status of a British Standard ICS
2、87.060.20BSEN ISO 3682:1998 This British Standard, having been prepared under the directionof the Sector Board forMaterials and Chemicals, waspublished under the authorityof the Standards Boardand comes into effect on 15 November1996 BSI 06-1999 The following BSI references relate to the work on thi
3、s standard: Committee reference STI/3 Draft for comment 92/50271 DC ISBN 0580264750 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee STI/3, Paints, media and related products, upon which the following bodies were represent
4、ed: British Coatings Federation Ltd. European Resin Manufacturers Association FOSFA International Ministry of Defence Oil and Colour Chemists Association Seed Crushers and Oil Processors Association Amendments issued since publication Amd. No. Date Comments 10150 November 1998 Renumbers BS 6782-3:19
5、96 as BSENISO3682:1998, with addition of EN ISO title page and foreword, and changes to national forewordBSENISO3682:1998 BSI 06-1999 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 1 Scope 3 2 Normative references 3 3 Definition 3 4 Principle 3 5 Reagents 3
6、 6 Apparatus 3 7 Sampling 3 8 Procedure 3 9 Expression of results 4 10 Test report 5 Table 1 Mass of test portion 3BS EN ISO 3682:1998 ii BSI 06-1999 National foreword This Part of BS 6782 has been prepared by Technical Committee STI/3 and is the English language version of ENISO3682:1998 Binders fo
7、r paints and varnishes Determination of acid value Titrimetric method, published by the European Committee for Standardization (CEN). It is identical with ISO3682:1996, published by the International Organization for Standardization (ISO). This British Standard supersedes BS6782-3:1987, which is wit
8、hdrawn. The difference between this British Standard and BS6782-3:1987 is that the acid value is no longer related to1g of non-volatile matter of the product but to1g of the product itself. Cross-references The British Standards which implement international or European publications referred to in t
9、his document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Us
10、ers of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theENISO title page, pages2to5 and a back
11、 cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 3682 April 1998 ICS 87.060.20 Descriptors: Paints, varnishes, binders
12、(materials), tests, chemical tests, determination, acid number, volumetric analysis English version Binders for paints and varnishes Determination of acid value Titrimetric method (ISO 3682:1996) Liants pour peintures et vernis Dtermination de lindice dacide Mthode titrimtrique (ISO3682:1996) Bindem
13、ittel fr Beschichtungsstoffe Bestimmung der Surezahl Titrimetrisches Verfahren (ISO3682:1996) This European Standard was approved by CEN on9 March1998. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the statu
14、s of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A ve
15、rsion in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, CzechRepublic, Denmark, Finland, Fra
16、nce, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 19
17、98 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref. No. EN ISO 3682:1998 EEN ISO 3682:1998 BSI 06-1999 2 Foreword The text of the International Standard from Technical Committee ISO/TC35, Paints and varnishes, of the International Organizat
18、ion for Standardization (ISO) has been taken over as an European Standard by Technical Committee CEN/TC139, Paints and varnishes, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorse
19、ment, at the latest by month of October1998, and conflicting national standards shall be withdrawn at the latest by October1998. According to CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belg
20、ium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and theUnitedKingdom.ENISO3682:1998 BSI 06-1999 3 1 Scope This International Standard specifies a titrimetric method for determining the acid
21、value of binders for paints and varnishes. It is not applicable to phenolic resins. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were v
22、alid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International
23、Standards. ISO 385-1:1984, Laboratory glassware Burettes Part 1: General requirements. ISO 842:1984, Raw materials for paints and varnishes Sampling. 3 Definition For the purposes of this International Standard, the following definition applies: 3.1 acid value the number of milligrams of potassium h
24、ydroxide (KOH) required to neutralize the free acids in1g of the product tested 4 Principle The free acids contained in a test portion are titrated with potassium hydroxide solution, either in the presence of a colour indicator or potentiometrically. 5 Reagents During the analysis, use only reagents
25、 of recognized analytical grade. 5.1 Solvent mixture, consisting of2 parts by volume of toluene and1 part by volume of at least95%(V/V) ethanol (see note4 to 8.2), unless otherwise agreed or specified. If denaturated alcohol, or alcohol of another quality, is used, its suitability for the test shall
26、 be checked. Neutralize, using phenolphthalein as indicator, the solvent mixture with potassium hydroxide solution (5.2) prior to use. 5.2 Potassium hydroxide, standard volumetric solution, c(KOH) = 0,1 mol/l, in95% (V/V) ethanol (see 5.1) or in methanol, free from carbonates, standardized against p
27、otassium hydrogen phthalate. NOTE 1A 0,5 mol/l standard volumetric solution of potassium hydroxide may also be used in cases when more than50ml of titrant would be required with a0,1mol/l solution, thus avoiding the additional errors involved in refilling the50ml burette. Check the concentration of
28、this solution on the day of use. 5.3 Phenolphthalein, 10 g/l solution in95% (V/V) ethanol, in methanol or in isopropanol. NOTE 2Other suitable indicators may be used, for example a10g/l solution of bromothymol blue in95% (V/V) ethanol, in methanol or in isopropanol. 6 Apparatus Ordinary laboratory a
29、pparatus and glassware, together with the following: 6.1 Conical flask, capacity250 ml. 6.2 Burette, capacity50ml, complying with the requirements of ISO385-1. 6.3 Potentiometric titration apparatus, fitted with a glass electrode and a reference electrode. The use of this apparatus is an optional al
30、ternative (see note3 to 8.2). 6.4 Magnetic stirrer 7 Sampling Take a representative sample of the product to be tested, as described in ISO842. 8 Procedure Carry out the determination in duplicate. 8.1 Test portion By reference to Table 1, select the appropriate mass of test portion to be taken. Thi
31、s mass shall be chosen so that the volume of potassium hydroxide solution(5.2) used is in the range10 ml to30 ml. Table 1 Mass of test portion Weigh, to the nearest 1 mg, the test portion into the conical flask (6.1). Expected acid value mg KOH/g Approximate mass of test portion g up to 10 above 10
32、to 25 above 25 to 50 above 50 to 150 above 150 10 5 2,5 1 0,5ENISO3682:1998 4 BSI 06-1999 8.2 Determination Dissolve the test portion (8.1), with stirring, in 50 ml of the solvent mixture (5.1). If free acid anhydrides are present in the binder, as in the case of certain polyester resins, the alcoho
33、lic potassium hydroxide solution reacts only partially with the anhydrides. This, however, is generally of little importance with most binders because of the small amount of free anhydrides present. If it is suspected that significant amounts of free anhydrides are present, an aqueous potassium hydr
34、oxide solution shall be used. Warm, if necessary, but cool the solution to room temperature before carrying out the titration. CAUTIONIf the solution is warmed, this shall be carried out in a fume cupboard or well ventilated atmosphere. Avoid overheating. Add 2 or 3 drops of phenolphthalein solution
35、 (5.3) and titrate rapidly with potassium hydroxide solution (5.2) until a red coloration just appears and is stable for at least 10 s while the solution is being stirred. NOTE 3With some substances, for example certain polyester resins, no very definite colour change will be obtained with phenolpht
36、halein. In such cases, another indicator, for example bromothymol blue (see note 2 to 5.3) may be used. In all cases of doubt, and especially when the solutions are coloured, a potentiometric titration to pH 7 is to be preferred, using glass electrodes with a suitable response time. In the case of p
37、olybasic acids, there may also be points of inflection above pH 7. In such cases, the point of inflection in the most basic range shall be taken as the end point. If a precipitate is formed during the titration which interferes with the determination of the end point, add additional solvent as indic
38、ated in note 4. When a suitable solvent mixture has been found, repeat the titration using the same solvent mixture. NOTE 4The type and volume of solvent mixture to be used depend on whether precipitation occurs during the titration. Thevolume of solvent mixture may be increased up to 150 ml, or25ml
39、 of acetone may be added. The purpose of the solvent is to prevent precipitation during titration and not to dissolve the resin initially. Use the same solvent mixture for the blank test (8.3) and record the type and volume of the solvent mixture in the test report (clause 10). 8.3 Blank test Carry
40、out a blank test following the same procedure, but omitting the test portion. NOTE 5Theoretically, if the neutralization of the solvent mixture (5.1) has been carried out correctly, the result of the blank test will be zero. 9 Expression of results 9.1 Calculation Calculate the acid value AV, in mil
41、ligrams of KOH per gram of product, using the equation the two results (duplicates) differ by more than 3% (relative to the mean), repeat the procedure described in clause 8. Report as the final result the mean, rounded to the nearest 0,1 mg KOH/g, of two valid results (replicates). 9.2 Precision 9.
42、2.1 Repeatability, r The value below which the absolute difference between two test results, each the mean of duplicates, obtained on identical material by one operator in one laboratory using the same equipment within a short interval of time using the standardized test method, may be expected to l
43、ie with a 95% probability is 3%. 9.2.2 Reproducibility, R The value below which the absolute difference between two test results, each the mean of duplicates, obtained on identical material by operators in different laboratories using the standardized test method, may be expected to lie with a 95 %
44、probability is 5 %. where V 0 is the volume, in millilitres, of potassium hydroxide solution (5.2) required for the blank test (8.3); V 1 is the volume, in millilitres, of potassium hydroxide solution (5.2) required for the determination (8.2); c is the actual concentration, in moles per litre, of t
45、he potassium hydroxide solution(5.2); 56,1 is the factor for the conversion of millilitres of potassium hydroxide solution, c(KOH) = 1 mol/l, to milligrams of potassium hydroxide; m is the mass, in grams, of the test portion(8.1).AV V 1 V 0 ()c 56,1 m - =ENISO3682:1998 BSI 06-1999 5 10 Test report T
46、he test report shall contain at least the following information: a) all details necessary to identify the product tested; b) a reference to this International Standard (ISO 3682); c) the result of the test as indicated in 9.1; d) the type and volume of solvent mixture used (see 8.2); e) the type of
47、titration: in the presence of a colour indicator (phenolphthalein, bromothymol blue or other) or potentiometric; f) any deviation from the test method specified; g) the date of the test.BSENISO 3682:1998 BS6782-3: 1996 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is th
48、e independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that
49、 they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that
