1、BRITISH STANDARD BS EN ISO 3681:1998 BS 6782-2: 1996 Incorporating Amendment No. 1 to BS6782-2:1996 (renumbers the BS as BS EN ISO 3681:1998) Binders for paints and varnishes Determination of saponification value Titrimetric method The European Standard EN ISO3681:1998 has the status of a British St
2、andard ICS 87.060.20BSENISO3681:1998 This British Standard, having been prepared under the directionof the Sector Board for Materials and Chemicals, was published under the authority ofthe Standards Board and comesinto effect on 15November1996 BSI 06-1999 The following BSI references relate to the w
3、ork on this standard: Committee reference STI/3 Draft for comment 92/50270 DC ISBN 0 580 26476 9 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 w
4、ere represented: 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 10151 November 1998 Renumbers
5、 BS 6782-2:1996 as BSENISO3681:1998 with addition of EN ISO title page and foreword, and changes to national forewordBSENISO3681:1998 BSI 06-1999 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 1 Scope 3 2 Normative references 3 3 Definitions 3 4 Principle 3
6、 5 Reagents 3 6 Apparatus 3 7 Sampling 3 8 Preliminary test 4 9 Procedure 4 10 Expression of results 4 11 Test report 5 Annex A (normative) Binders which are saponifiable with difficulty Determination of saponification value 6 Annex ZA (normative) Normative references to internationalpublicationswit
7、htheir relevant European publications Inside back cover Table 1 Mass of test portion 4BSENISO3681:1998 ii BSI 06-1999 National foreword This Part of BS6782 has been prepared by Technical Committee STI/3 and is the English language version of ENISO3681:1998 Binders for paints and varnishes Determinat
8、ion of saponification value Titrimetric method, published by the European Committee for Standardization (CEN). It is identical with ISO3681:1996, published by the International Organization for Standardization (ISO). This British Standard supersedes BS6782-2:1987, which is withdrawn. Thedifference b
9、etween this British Standard and BS6782-2:1987 is that the saponification 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 this document m
10、ay 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. Attention is drawn to Annex ZA, which gives the European Standards that correspond to the international sta
11、ndards referred to. A British Standard does not purport to include all the necessary provisions of a contract. Users 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
12、 document comprises a front cover, an inside front cover, pagesi andii, theEN ISO title page, pages2 to6, an inside back cover and a back 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 f
13、ront cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 3681 April 1998 ICS 87.060.20 Descriptors: Paints, varnishes, binders (materials), tests, chemical tests, determination, saponification number, volumetric analysis English version Binders for paints and varnishes Determination of sa
14、ponification value Titrimetric method (ISO 3681:1996) Liants pour peintures et vernis Dtermination de lindice de saponification Mthode titrimtrique (ISO 3681:1996) Bindemittel fr Beschichtungsstoffe Bestimmung der Verseifungszahl Titrimetrisches Verfahren (ISO 3681:1996) This European Standard was a
15、pproved by CEN on 9 March 1998. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationa
16、l 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 version in any other language made by translation under the responsibility of a CEN member into its own language and notif
17、ied 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, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and
18、 UnitedKingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref. No. EN I
19、SO 3681:1998 EENISO3681:1998 BSI 06-1999 2 Foreword The text of the International Standard from Technical Committee ISO/TC35, Paints and varnishes, of the International Organization for Standardization (ISO) has been taken over as an European Standard by Technical Committee CEN/TC139, Paints and var
20、nishes, 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 endorsement, at the latest by month of October1998, and conflicting national standards shall be withdrawn at the latest by Octobe
21、r1998. According to CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, P
22、ortugal, Spain, Sweden, Switzerland and theUnitedKingdom. NOTENormative references to International Standards are listed in Annex ZA (normative).ENISO3681:1998 BSI 06-1999 3 1 Scope This International Standard specifies a titrimetric method for determining the esterified-acid content in binders for
23、paints and varnishes, free acids and acid anhydrides being necessarily included in the result obtained. Because different binders vary in their resistance to saponification, this International Standard is of limited applicability. If necessary, completeness of saponification may be checked by repeat
24、ing the test under more severe conditions achieved by the use of longer saponification time, more concentrated potassium hydroxide solution, or a higher-boiling alcohol as solvent. Annex A specifies a procedure suitable for binders that saponify with difficulty. The method is not applicable to those
25、 materials that show further reaction with alkalis beyond normal saponification. 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 vali
26、d. 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 Sta
27、ndards. ISO 385-1:1984, Laboratory glassware Burettes Part 1: General requirements. ISO 648:1977, Laboratory glassware One-mark pipettes. ISO 842:1984, Raw materials for paints and varnishes Sampling. ISO 3696:1987, Water for analytical laboratory use Specification and test methods. 3 Definitions Fo
28、r the purposes of this International Standard, the following definitions apply. 3.1 saponification the formation of the alkali metal salts of derivatives of organic acids 3.2 saponification value the number of milligrams of potassium hydroxide (KOH) required for the saponification of1g of the produc
29、t tested 4 Principle After a preliminary test to determine the saponification conditions (concentration of potassium hydroxide solution, saponification time,etc.) for the product to be tested, a test portion is boiled under reflux with potassium hydroxide solution under these conditions. The hot sol
30、ution is titrated with standard volumetric hydrochloric acid, either in the presence of a colour indicator or potentiometrically. 5 Reagents During the analysis, use only reagents of recognized analytical grade, and only water of at least grade3 purity as defined in ISO3696. 5.1 Toluene, or other su
31、itable unsaponifiable solvent. 5.2 Potassium hydroxide solution, in isopropanol, ethanol or methanol, c(KOH) = 0,5 mol/l. NOTE 1If more severe conditions for saponification are needed,2 mol/l ethanolic potassium hydroxide solution may be used, or1,2-ethanediol (ethylene glycol) or2,2- oxydiethanol (
32、diethylene glycol) may be used as the solvent (see clause 8 andAnnex A). Where isopropanol can be used instead of ethanol or methanol, it shall be used. The applicability of the solution in isopropanol is comparable to that of an ethanolic solution and its toxicity is less than that of a methanolic
33、solution. 5.3 Hydrochloric acid, standard volumetric solution,c(HCl) = 0,5 mol/l, in a mixture of4 parts by volume of methanol and1 part by volume of water or in water. 5.4 Phenolphthalein or thymolphthalein, 10 g/l solution in95% (V/V) ethanol, in methanol or in isopropanol (see note1). 6 Apparatus
34、 Ordinary laboratory apparatus and glassware, complying with the requirements of ISO385-1 and ISO648, together with the following: 6.1 Conical flask, of capacity250 ml, with a ground-glass joint. 6.2 Reflux condenser, with a ground-glass joint. 6.3 Burette or pipette, of capacity25 ml or50 ml. 6.4 P
35、otentiometric titration apparatus, fitted with a glass electrode and a reference electrode. The use of this apparatus is an optional alternative (see 9.2). 6.5 Magnetic stirrer 6.6 Water bath or oil bath 7 Sampling Take a representative sample of the product to be tested, as described in ISO842.ENIS
36、O3681:1998 4 BSI 06-1999 8 Preliminary test If no special saponification conditions are specified or agreed, carry out the procedure specified in clause9 using25ml of potassium hydroxide solution (5.2) and a boiling time of1h. To test whether the saponification value can be determined under these co
37、nditions, intensify the conditions by increasing the saponification time to at least2h and/or by using a2 mol/l potassium hydroxide solution or a solution of potassium hydroxide in an alcohol that has a boiling point distinctly higher than that of ethanol, for example1,2-ethanediol (ethylene glycol)
38、 or2,2-oxydiethanol (diethyleneglycol). If no increase in the final (i.e.mean) result (see10.1) is obtained using the more intense conditions, the test may be carried out using this International Standard. If a higher value is obtained which is not further increased by again intensifying the test co
39、nditions, this International Standard may be followed but using and noting the intensified conditions applied. If a constant result is not obtained even under the most severe conditions of saponification, the method to be used shall be agreed between the interested parties. 9 Procedure Carry out the
40、 determination in duplicate. 9.1 Test portion By reference to Table 1, select the appropriate mass of test portion to be taken. This mass shall be chosen so that less than half of the volume of potassium hydroxide solution added is sufficient to saponify the test portion. Table 1 Mass of test portio
41、n Weigh, to the nearest 1 mg, the test portion into the conical flask (6.1). 9.2 Determination Dissolve the test portion, if necessary, in a measured volume of toluene or other suitable, unsaponifiable solvent (5.1), warming, if necessary, under the reflux condenser (6.2). Add, from the burette or p
42、ipette (6.3), one of the following: a) 25 ml of 0,5 mol/l potassium hydroxide solution(5.2); b) 25 ml of a different potassium hydroxide solution (see clause 8 and note 1 to 5.2); c) the specified or agreed volume of a potassium hydroxide solution. Heat, while stirring, the contents of the flask to
43、boiling in a water bath or oil bath (6.6) and reflux for1h or the specified or agreed time, or the time found necessary in the preliminary test (seeclause8). Titrate the hot solution with hydrochloric acid (5.3) after addition of3 drops of phenolphthalein or thymolphthalein solution (5.4). If the po
44、tentiometric titration is used, the glass electrode shall have a suitable response time. If precipitation occurs, bring the precipitate back into solution by the addition of water, which acts as a solvent. 9.3 Blank test Carry out a blank test, following the same procedure but omitting the test port
45、ion. 10 Expression of results 10.1 Calculation Calculate the saponification value SV, in milligrams of KOH per gram of product, using the equation Expected saponification value mg KOH/g Approximate mass oftestportion g up to 10 above 10 to 20 above 20 to 50 above 50 to 100 above 100 to 200 above 200
46、 to 300 above 300 to 500 above 500 20 10 5 2,5 1,5 1 0,5 0,2 where V 0 is the volume, in millilitres, of hydrochloric acid (5.3) required for the blank test (9.3); V 1 is the volume, in millilitres, of hydrochloric acid (5.3) required for the determination(9.2); c is the actual concentration, in mol
47、es per litre, of the hydrochloric acid (5.3); 56,1 is the factor for the conversion of millilitres of hydrochloric acid, c(HCl)= 1 mol/l, to milligrams of potassium hydroxide; m is the mass, in grams, of the test portion(9.1). SV V 0 V 1 ()c 56,1 m - =ENISO3681:1998 BSI 06-1999 5 If the two results
48、(duplicates) differ by more than3% (relative to the mean), repeat the procedure described in clause 9. Report as the final result the mean, rounded to the nearest0,1mg KOH/g, of two valid results (replicates). 10.2 Precision No precision data are currently available. 11 Test report The test report s
49、hall contain at least the following information: a) all details necessary to identify the product tested; b) a reference to this International Standard (ISO3681); c) the result of the test as indicated in 10.1; d) the solvent and the concentration and volume of the potassium hydroxide solution used; e) the period of boiling; f) the type of titration: in the presence of a colour indicator (phenolphthalein or thymolphthalein) or potentiometric; g) any deviation from the test
