1、Designation: D5523 10D5523 15Standard Test Method forPolyurethane Raw Materials: Acidity by ArgentometricDetermination of Hydrolyzable Chlorine in Monomeric,Aromatic Isocyanates1This standard is issued under the fixed designation D5523; the number immediately following the designation indicates the
2、year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method measures the hydrolyzable ch
3、lorine content of monomeric, aromatic isocyanates used as polyurethane rawmaterials and expresses it as HCl acidity. The test method is applicable to toluene diisocyanate (TDI) and monomeric methylenedi(phenylisocyanate), known as MDI. The main sources of hydrolyzable chlorine and, therefore, acidit
4、y in monomeric aromaticisocyanates are carbamyl chlorides, acid chlorides, and dissolved phosgene.All of these compounds react with alcohols and waterto form hydrochloric acid.1.2 This test method applies only to monomeric isocyanates in which all of the acidity is derived from species that generate
5、 HClon solvolysis.1.3 The values stated in SI units are to be regarded as the standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices
6、and determine the applicability of regulatorylimitations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to Plastics3. Terminology3.1 Definitions: DefinitionsFor definitions of terms used in this test method, s
7、ee Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 aciditythe acid strength of a sample expressed as parts per million hydrochloric acid (HCl) present.3.2.2 hydrolyzable chlorinethe amount of chlorine released as chloride ion under the conditions of the test, expressed as p
8、artsper million chlorine.4. Summary of Test Method4.1 The sample reacts with 2-propanol to form urethanes and hydrochloric acid, which is liberated from the labile carbamylchlorides, acid chlorides, and dissolved phosgene. The chlorides of the liberated acid are then determined potentiometrically us
9、ingstandard methanolic silver nitrate solution and calculated as parts per million HCl.5. Significance and Use5.1 This test method is suitable for research or for quality control to characterize TDI and MDI.1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the dir
10、ect responsibility of Subcommittee D20.22 on Cellular Materials - Plasticsand Elastomers.Current edition approved Aug. 1, 2010April 1, 2015. Published September 2010May 2015. Originally approved in 1994. Last previous edition approved in 20042010 asD5523 - 04D5523 - 10. 1. DOI: 10.1520/D5523-10.10.1
11、520/D5523-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is int
12、ended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the curr
13、ent versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 This test method was develo
14、ped to overcome problems with low-level acidity determinations that use glass electrodes in thepresence of reagent alcohol solvents. Reagent alcohols contain acidic and basic species, which complicate the glass electrodemethods at low levels of acidity.6. Interferences6.1 Acidic species that do not
15、generate chloride ions under the conditions of this test method will not be determined becauseacidity is determined indirectly from the chloride ion concentration.6.2 Acidic species that do not produce chloride ions are expected to be negligible at low levels of acidity and for the monomericisocyana
16、tes in this test method.6.3 Care must be taken to avoid chloride contamination of glassware and sample containers.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 b
17、e stored in 0.01 N methanolic silver nitrate solution in order to keep the electrode conditionedproperly. The use of chloride containing solutions must be avoided during storage and maintenance of the apparatus.NOTE 3Monomeric MDI samples can be solid when received in the laboratory. An oven is to b
18、e used to melt the sample prior to beginning the testprocedure.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the A
19、merican Chemical Society where suchspecifications are available.3 Other grades can be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the determination.8.2 Methanol.8.3 2-Propanol.8.4 Nitric Acid, concentrated,
20、 70 %.8.5 Silver Nitrate.8.6 Methanolic Silver Nitrate Solution (0.01 N)Prepare by dissolving 1.70 g AgNO3/L of solution. Potentiometricallystandardize with titration-grade sodium chloride frequently enough to detect changes of 0.00005 N.8.7 Methanolic Silver Nitrate Solution (0.001 N)Prepare by dis
21、solving 0.170 g AgNO3/L of solution. Potentiometricallystandardize with titration-grade sodium chloride frequently enough to detect changes of 0.000005 N.9. Sampling9.1 Since organic isocyanates react with atmospheric moisture, take special precautions in sampling. Usual sampling methods,even when c
22、onducted rapidly, can cause contamination of the sample with insoluble urea. Therefore, blanket the sample with dryair or nitrogen at all times. (WarningMany diisocyanates are known or suspected sensitizers. Over-exposure to diisocyanatescan lead to adverse health effects which include the developme
23、nt of occupational asthma and other respiratory, skin and eye effects.Engineering controls and/orDiisocyanates are eye, skin, and respiratory irritants at concentrations above the occupational exposurelimit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some peo
24、ple. Once sensitized, it isessential to limit further exposure to diisocyanates. Use a combination of engineering controls and personal protective equipment,including respiratory, skin and eye protection, are to be used when there is a potential for to prevent over-exposure to diisocyanates.The Cons
25、ult the product suppliersMaterialSafety Data Safety Sheet (MSDS) provides(SDS) for more detailed information aboutpotential adverse health effects and other importantspecific safety and handling information.Always follow the specific instructionsprovided on the MSDS.instructions for the product.)10.
26、 Test Conditions10.1 Samples are to remain sealed against moisture until immediately before testing.Since isocyanates react with moisture, keeplaboratory humidity low, preferably around 50 % relative humidity. See warning statement in 9.1.3 Reagent Chemicals, American Chemical Society Specifications
27、, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmaceutical Convention,
28、Inc. (USPC), Rockville, MD.D5523 15211. Procedure11.1 Weigh 10.0 g of the sample into a beaker and record the weight to the nearest 0.0001 g (Note 4).11.2 Add 100 mL of 2-propanol to the beaker, cover, and stir the sample for 10 min.11.3 Add 100 mL of methanol, cover, and continue stirring the sampl
29、e solution for an additional 20 min (Note 5).11.4 Add ten drops of concentrated nitric acid solution to the sample solution.11.5 Cool the sample solution to room temperature in an ice bath if necessary.11.6 Titrate the sample solution potentiometrically with the appropriate methanolic silver nitrate
30、 solution (Note 6).11.7 Record the volume of titrant used to reach the end point to at least the nearest 0.001 mL.11.8 If the chloride content of the reagents is in question, run a blank (steps 11.1 to 11.7 with no isocyanate sample added) toensure that the reagents are free of chloride interference
31、s. If chloride is detected, subtract the volume (mL) of AgNO3 required totitrate the blank from the volume (mL) of AgNO3 required to titrate the sample.NOTE 4The beaker must be of such size to accommodate approximately 300 mL of solution, and it must be of a shape to allow the proper coveragefor the
32、 electrode. For monomeric MDI, it is acceptable to gently warm the beaker on a hot plate to keep the sample molten prior to the addition of2-propanol. This will assist in dissolution of the sample. Once 2-propanol has been added, remove the beaker from the hot plate.NOTE 5The stirring times were cho
33、sen to ensure an adequate reaction time for material that has been adjusted with an acid chloride. In monomeric,unadjusted material, it is acceptable to reduce the stirring times to those required to obtain uniform solutions and stable electrode responses (approximately2 min).NOTE 6For expected acid
34、ities or hydrolyzable chlorines below 20 ppm, use the 0.001 N methanolic silver nitrate solution as the titrant. For expectedacidities or hydrolyzable chlorines above 20 ppm, use the 0.01 N methanolic silver nitrate solution as the titrant.12. Calculation12.1 Calculate the acidity, as ppm HCl, as fo
35、llows:acidity5S3N336.4653106W31000 (1)where:S = AgNO3 required for titration of the sample, mL,S = AgNO3 required for titration of the sample, mL (If a blank is run, subtract the volume in mL of AgNO3 required totitrate the blank from the volume (mL) of AgNO3 required to titrate the sample),N = norm
36、ality of AgNO3 solution, meq/mL,W = sample weight, g,36.465 = equivalent weight of HCl, mg/meq,1000 = factor for converting milligrams to grams, and106 = factor for converting to parts per million.12.2 Because hydrolyzable chlorine is measured, the ppm hydrolyzable chlorine can be calculated as foll
37、ows:hydrolyzable chlorine5S3N335.4653106W31000 (2)where:S = AgNO3 required for titration of the sample, mL,S = AgNO3 required for titration of the sample, mL (If a blank is run, subtract the volume in mL of AgNO3 required totitrate the blank from the volume (mL) of AgNO3 required to titrate the samp
38、le),N = normality of AgNO3 solution, 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 for this test
39、 method have not been successful due to the limited numberof laboratories participating in round-robin tests. Data on precision and bias cannot be given for this reason. Contact the Chairman,Subcommittee D20.22 (Section D20.22.01),ASTM, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA194282
40、959,if you are interested in participating in the development of precision and bias data for this test method.13.2 A limited round robin was conducted with nine laboratories.4 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D20-
41、1181.D5523 15313.2.1 It has been estimated that duplicate results for either acidity or hydrolyzable chlorine by the same analyst are to beconsidered suspect if they differ by 63.9 ppm for results greater than 10 ppm and 60.6 ppm for results less than 10 ppm.13.2.2 It has been estimated that results
42、 reported by different laboratories for either acidity or hydrolyzable chlorine are to beconsidered suspect if they differ by 615.5 ppm for results greater than 10 ppm and 63.5 ppm for results less than 10 ppm.14. Keywords14.1 acidity; HC; hydrolyzable chlorine; isocyanates; isocyanates aromatic; MD
43、I; methylene-bis-(4-phenylisocyanate);methylene-4,4-di(phenylisocyanate); methylene di(phenylisocyanate); polyurethane; raw materials; TDI; test method; titration;toluene diisocyanateSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue
44、 (D5523 10) that may impact the use of this standard. (April 1, 2015)(1) Subsection 9.1: SamplingThe previous warning statement was edited to remove non-mandatory language and updated withinput from the Center for the Polyurethanes Industrys (CPI) Product Stewardship Committee.(2) Section 10: Test C
45、onditionsRemoved redundant information.(3) Section 12: CalculationsAdded calculations to perform if a blank is used.(4) Section 14: KeywordsChanged keyword for MDI to be consistent with that used in the other polyurethane raw materialanalysis methods.ASTM International takes no position respecting t
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