1、Designation: D 5523 04Standard Test Method forPolyurethane Raw Materials: Acidity by ArgentometricDetermination of Hydrolyzable Chlorine in Monomeric,Aromatic Isocyanates1This standard is issued under the fixed designation D 5523; the number immediately following the designation indicates the year o
2、foriginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method measures the hydrolyzable chlorineconte
3、nt of monomeric, aromatic isocyanates used as polyure-thane raw materials and expresses it as HCl acidity. The testmethod is applicable to toluene diisocyanate (TDI) and mono-meric methylene-bis-(4-phenylisocyanate), known as MDI.The main sources of hydrolyzable chlorine and, therefore,acidity in mo
4、nomeric aromatic isocyanates are carbamyl chlo-rides, acid chlorides, and dissolved phosgene. All of thesecompounds react with alcohols and water to form hydrochloricacid.1.2 This test method applies only to monomeric isocyanatesin which all of the acidity is derived from species that generateHCl on
5、 solvolysis.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and det
6、ermine the applica-bility of regulatory limitations prior to use.NOTE 1There is no equivalent ISO standard.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to Plastics3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, see Terminology D 883.3.1.1 Discu
7、ssionPolyurethanes or urethanes, as they aresometimes called, can be thermosetting, thermoplastic, rigid orsoft and flexible, or cellular or solid (see Terminology D 883).3.2 Definitions of Terms Specific to This Standard:3.2.1 aciditythe acid strength of a sample expressed asparts per million hydro
8、chloric acid (HCl) present in the sample.3.2.2 hydrolyzable chlorinethe amount of chlorine re-leased as chloride ion under the conditions of the test,expressed in parts per million of chlorine in the sample.4. Summary of Test Method4.1 The sample reacts with 2-propanol to form urethanesand hydrochlo
9、ric acid, which is liberated from the labilecarbamyl chlorides, acid chlorides, and dissolved phosgene.The chlorides of the liberated acid are then determinedpotentiometrically using standard methanolic silver nitratesolution and calculated as parts per million HCl.5. Significance and Use5.1 This te
10、st method can be used for research or for qualitycontrol to characterize TDI and MDI.5.2 This test method was developed to overcome problemswith low-level acidity determinations that use glass electrodesin the presence of reagent alcohol solvents. Reagent alcoholscontain acidic and basic species, wh
11、ich complicate the glasselectrode methods at low levels of acidity.6. Interferences6.1 Any acidic species that does not generate chloride ionunder the conditions of this test method will not be determinedbecause acidity is determined indirectly from the chloride ionconcentration.6.2 Acidic species n
12、ot producing chloride ion are expectedto be negligible at low levels of acidity and for the monomericisocyanates in this test method.6.3 Care must be taken to avoid chloride contamination ofglassware and sample containers.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsa
13、nd is the direct responsibility of Subcommittee D20.22 on Cellular Plastics.Current edition approved October 1, 2004. Published October 2004. Originallyapproved in 1994. Last previous edition approved in 1999 as D 5523 - 94(1999)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org
14、, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C7
15、00, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 Potentiometric Titrator.7.2 Combination Silver Billet Electrode (Note 2).7.3 Oven, 70C (Note 3).7.4 Magnetic Stirrer.NOTE 2The combination silver billet electrode is to be stored in 0.01N methanolic silver nitrate solution in order
16、to keep the electrodeconditioned properly.NOTE 3Monomeric MDI samples can be solid when received in thelaboratory. An oven is to be used to melt the sample prior to beginning thetest procedure.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless ot
17、herwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.3Other grades can be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to
18、 permit its use without lessening the accuracy ofthe determination.8.2 Methanol.8.3 2-Propanol.8.4 Nitric Acid, concentrated, 70 %.8.5 Silver Nitrate.8.6 Methanolic Silver Nitrate Solution (0.01 N)Prepareby dissolving 1.70 g AgNO3/L of solution. Potentiometricallystandardize with titration-grade sod
19、ium chloride frequentlyenough to detect changes of 0.00005 N.8.7 Methanolic Silver Nitrate Solution (0.001 N)Prepareby dissolving 0.170 g AgNO3/L of solution. Potentiometricallystandardize with titration-grade sodium chloride frequentlyenough to detect changes of 0.000005 N.9. Sampling9.1 Take speci
20、al precautions in sampling since organicisocyanates react with atmospheric moisture. Even when con-ducted rapidly, usual sampling methods (for example, samplingan open drum with a thief) can cause contamination of thesample with moisture that results in the formation of insolubleureas. Therefore, bl
21、anket the sample with dry air or nitrogen atall times.WarningOrganic isocyanates are toxic when ab-sorbed through the skin, or when the vapors are breathed.Provide adequate ventilation and wear protective gloves andeyeglasses.10. Test Conditions10.1 Since isocyanates react with moisture, keep the la
22、bo-ratory humidity low, preferably below 50 % relative humidity.11. Procedure11.1 Weigh 10.0 g of the sample into a beaker and record theweight to the nearest 0.0001 g (Note 4).11.2 Add 100 mL of 2-propanol to the beaker, cover, and stirthe sample for 10 min.11.3 Add 100 mL of methanol, cover, and c
23、ontinue stirringthe sample solution for an additional 20 min (Note 5).11.4 Add ten drops of concentrated nitric acid solution tothe sample solution.11.5 Cool the sample solution to room temperature in an icebath if necessary.11.6 Titrate the sample solution potentiometrically with theappropriate met
24、hanolic silver nitrate solution (Note 6).11.7 Record the volume of titrant used to reach the end pointto at least the nearest 0.001 mL.NOTE 4The beaker must be of such size to accommodate approxi-mately 300 mL of solution, and it must be of a shape to allow the propercoverage for the electrode. For
25、monomeric MDI, the beaker can bewarmed on a hot plate to melt the sample prior to the addition of2-propanol. This will assist in dissolution of the sample in 2-propanol.NOTE 5The stir times were chosen to ensure an adequate reactiontime for material that has been adjusted with an acid chloride. Inmo
26、nomeric, unadjusted material, the stirring times can be reduced to thoserequired to obtain uniform solutions and stable electrode responses(approximately 2 min).NOTE 6For expected acidities or hydrolyzable chlorines below 20ppm, use the 0.001 N methanolic silver nitrate solution as the titrant.12. C
27、alculation12.1 Calculate the acidity, as ppm HCl, as follows:acidity 5S 3 N 3 36.465 3 106W 3 1000(1)where:S = AgNO3required for titration of the sample, mL,N = normality of AgNO3solution, meq/mL,W = sample weight, g,36.465 = equivalent weight of HCl, mg/meq,1000 = factor for converting milligrams t
28、o grams, and106= factor for converting to parts per million.12.2 Because hydrolyzable chlorine is measured, the ppmhydrolyzable chlorine can be calculated as follows:hydrolyzable chlorine 5S 3 N 3 35.465 3 106W 3 10000(2)where:S = AgNO3required for titration of the sample, mL,N = normality of AgNO3s
29、olution, meq/mL,W = sample weight, g,35.465 = equivalent weight of Cl, mg/meq,1000 = factor for converting milligrams to grams, and106= factor for converting to parts per million.13. Precision and Bias413.1 Attempts to develop a precision and bias statement forthis test method have not been successf
30、ul due to the limitednumber of laboratories participating in round-robin tests. Dataon precision and bias cannot be given for this reason. Contactthe Chairman, Subcommittee D20.22 (Section D20.22.01),3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington,
31、DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.4Supporting data
32、 are available from ASTM Headquarters. Request RR:D-20-1181.D5523042ASTM, 100 Barr Harbor Drive, PO Box C700, West Consho-hocken, PA 194282959, if you are interested in participatingin the development of precision and bias data for this testmethod.13.2 A limited round robin was conducted with nine l
33、abo-ratories.13.2.1 It has been estimated that duplicate results for eitheracidity or hydrolyzable chlorine by the same analyst are to beconsidered suspect if they differ by 63.9 ppm for resultsgreater than 10 ppm and 60.6 ppm for results less than 10ppm.13.2.2 It has been estimated that results rep
34、orted by differentlaboratories for either acidity or hydrolyzable chlorine are to beconsidered suspect if they differ by 615.5 ppm for resultsgreater than 10 ppm and 63.5 ppm for results less than 10ppm.14. Keywords14.1 acidity; HC; hydrolyzable chlorine; isocyanates; isocy-anates aromatic; MDI; met
35、hylene-bis-(4-phenylisocyanate);polyurethane; raw materials; TDI; test method; titration; tolu-ene diisocyanateSUMMARY OF CHANGESThis section identifies the location of selected changes to this test method. For the convenience of the user,Committee D20 has highlighted those changes that impact the u
36、se of this test method. This section also includesdescriptions of the changes or reasons for the changes, or both.D 5523 - 04:(1) Subsection 2.1: Removed reference to D 1193, water,because water is not used.(2) Subsections: 3.1.1, 8.1, 13.1, 13.2.1, and 13.2.2; Notes 2, 3,5, and 6: Editorial changes
37、 to remove non-mandatory language.(3) Subsection 8.2: Removed because water is not used.(4) Subsections 8.3 through 8.8: Renumbered as required byremoving 8.2.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this stand
38、ard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be review
39、ed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible
40、 technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D5523043
