1、Designation: D6099 13D6099 18Standard Test Method forPolyurethane Raw Materials: Determination of Acidity inModerate to High Acidity Aromatic Isocyanates1This standard is issued under the fixed designation D6099; the number immediately following the designation indicates the year oforiginal adoption
2、 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*1.1 This test method determines the acidity, expressed as parts per million (pp
3、m) of HCl, in aromatic isocyanate samples ofgreater than 100ppm acidity. The test method is applicable to products derived from toluene diisocyanate and methylene-bis-(4phenylisocyanate) (see Note 1).NOTE 1This test method is equivalent to ISO 14898, Test Method A.1.2 This international standard was
4、 developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced D
5、ocuments2.1 ASTM Standards:2D883 Terminology Relating to PlasticsE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals(Withdrawn 2009)3E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Metho
6、d2.2 ISO Standards:ISO 14898 PlasticsAromatic isocyanates for use in the production of polyurethaneDetermination of acidity43. Terminology3.1 DefinitionsTerms used in this test method are in accordance with Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 acidity, nthe acid
7、strength of a sample expressed in ppm HCl.4. Summary of Test Method4.1 The isocyanate is mixed with an excess of methanol and a cosolvent. Additional acid is released into the solvent systemduring urethane formation. The acid is titrated potentiometrically with methanolic KOH, and the acidity presen
8、t in the isocyanatesample is calculated from the titer.5. Significance and Use5.1 This test method can be used for research or for quality control to characterize aromatic isocyanates and prepolymers ofmoderate to high acidity. Acidity correlates with performance in some polyurethane systems.6. Appa
9、ratus6.1 250-mL Beakers.6.2 50-mL Pipet or Repipet, Class A volumetric.1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plasticsand Elastomers.Current edition approved Sept. 1, 2013Aug. 1, 2
10、018. Published September 2013August 2018. Originally approved in 1997. Last previous edition approved in 20082013as D6099 - 08.D6099 - 13. DOI: 10.1520/D6099-13.10.1520/D6099-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. F
11、or Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New Yor
12、k, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended 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 recomme
13、nds that users consult prior editions as appropriate. In all cases only the current 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,
14、 West Conshohocken, PA 19428-2959. United States16.3 100-mL Pipet or Repipet, Class A volumetric.6.4 Automatic Titration Equipment, capable of inflection detection and stirring the sample while, titrating, such as:6.4.1 Commerically-available Automatic Titration Apparatus,6.4.2 Reference Electrode,
15、with saturated LiCl/ethanol solution in both chambers.6.4.3 pH Glass Electrode, (see Note 2).NOTE 2A combination pH electrode with internal reference also may be used.6.5 Magnetic Stirrer.6.6 Stir Bars.6.7 Watch Glasses.6.8 Analytical Balance, capable of weighing to the nearest 1 mg.7. Reagents and
16、Materials7.1 0.02 N KOH in Methanol1.32 g KOH pellets (85 % KOH)/1000 mL methanol, standardized with potassium hydrogenphthalate (KHP).7.2 Toluene or 1,2,4Trichlorobenzene (TCB), dried for 24 h over molecular sieves.7.3 Anhydrous Methanol.8. Sampling8.1 Since organic isocyanates react with atmospher
17、ic moisture, take special precautions in sampling. Usual sampling methods,even when conducted rapidly, can cause contamination of the sample with insoluble urea. Therefore, blanket the sample with dryair or nitrogen at all times. (WarningDiisocyanates are eye, skin and respiratory irritants at conce
18、ntrations above theoccupational exposure limit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people.Once sensitized, it is essential to limit further exposure to diisocyanates. Use a combination of engineering controls and personalprotective equipment, inc
19、luding respiratory, skin and eye protection, to prevent over-exposure to diisocyanates. Consult the productsuppliers Safety Data Sheet (SDS) for more detailed information about potential health effects and other specific safety andhandling instructions for the product.)NOTE 3Many diisocyanates are k
20、nown or suspected sensitizers. Over-exposure to diisocyanates can lead to adverse health effects which may includethe development of occupational asthma and other respiratory, skin and eye effects. Engineering controls and/or personal protective equipment, includingrespiratory, skin and eye protecti
21、on, are to be used when there is a potential for over-exposure to diisocyanates. The product suppliers Material DataSafety Sheet (MSDS) provides more detailed information about potential adverse health effects and other important safety and handling information.Always follow the specific instruction
22、s provided on the MSDS.9. Calibration9.1 Calibrate the electrodes using pH 4 and pH 7 aqueous buffers.10. Test Conditions10.1 Since isocyanates react with moisture, It is essential that moisture be excluded from the sample by all means possible toensure the accuracy of measurements in this standard.
23、 See Section 8keep laboratory humidity low, preferably around 50 % relativehumidity. of this standard for guidance on how to keep moisture out of the sample.11. Procedure11.1 All samples shall be done in duplicate.11.2 Accurately weigh to the nearest 1 mg, 10 g of sample into a 250-mL beaker.11.3 Ad
24、d 50 mL of dried toluene or TCB.NOTE 3THF has been used as a solvent for prepolymers.11.4 Add 100 mL of methanol into the solution.11.5 Add a stir bar, cover with a watch glass, and stir for 20 min.NOTE 4Samples must be at room temperature before titration. Warm samples cause more frequent electrode
25、 clogging.11.6 With uniform stitrring of the sample, automatically titrate the mixture with 0.02 N methanolic KOH through thepotentiometrically-determined inflection end point between apparent pH 4 and 9. Follow manufacturers instructions forinstrument-specific parameters for set-up, calibration and
26、 analysis of samples.NOTE 5If results indicate a drift in the data or a slow electrode response, the pH electrode should be cleaned by soaking in 2:1 sulfuric: nitric acidsfor 10 min, followed by soaking in water for 20 min, and then rinsing with acetone.clean or replace the pH electrode.D6099 18211
27、.7 Record the titrant volume for the potentiometric end point. If more than one potentiometric end point is found, record theone at highest apparent pH less than 7.NOTE 6The inflection point typically is at apparent pH between 4 and 5.11.7.1 If no clear end point can be identified, calculate results
28、 using the end point at apparent pH 7.0, and report the result asacidity at apparent pH 7.0.12. Calculation12.1 Calculate the acidity as ppm HCl as follows:Acidity ppm HCl!5 Vsam! 3N 3Fsample weightg!# (1)where:Vsam = volume of titrant needed for the sample, mL,N = normality of the titrant solution,
29、 andF = 36 465 (mol weight of HCl) 1000 (factor to change mg/g to g/g, that is, ppm).13. Report13.1 The result is reported as the average of duplicates, expressed as ppm HCl, to the nearest 1 ppm. Any unusual conditionsduring the operation shall also be reported, such as any heating required to effe
30、ct solution before titration, or end point identifieddifferent from that described in 11.7.14. Precision and Bias514.1 Table 1 is based on a round robin conducted in 1995 in accordance with Practice E180, involving two materials tested bytwelve laboratories. For each material, all the samples were p
31、repared at one source, but the individual specimens were preparedat the laboratories that tested them. Some laboratories generated a set of results for each of two solvents (toluene and TCB), andsome laboratories generated a set of results for each of two different electrode types. Neither change in
32、 experimental conditionswas found to be a significant source of increased variability. Each of these combinations of conditions was treated as a differentlaboratory for purposes of calculating the precision data. Each test result was the average of two individual determinations. Eachlaboratory obtai
33、ned two test results for each material for each combination of electrode and solvent used. (WarningThefollowing explanations of r and R (14.1.1 and 14.1.2) are intended only to present a meaningful way of considering theapproximate precision of this test method. The data in Table 1 should not be app
34、lied rigorously to the acceptance or rejection ofmaterial, as these data apply on to the materials tested in the round robin and may not be representative of other lots, conditions,materials, or laboratories. Users of this test method should apply the principles outlined in Practice E691 or E180 to
35、generate dataspecific to their laboratory and materials (or between specific laboratories). The principles of 14.1.1 through 14.1.2 would then bevalid for such data.)14.1.1 RepeatabilityPrecision under repeatability conditions.14.1.2 ReproducibilityPrecision under reproducibility conditions.14.1.3 A
36、ny judgment made in accordance with 14.1.1 and 14.1.2 would have an approximate 95 % (0.95) probability of beingcorrect.14.1.4 Repeatability, (r)Repeatability LimitComparing two replicates The value below which the absolute differencebetween two individual test results obtained under repeatability c
37、onditions may be expected to occur with a probability ofapproximately 0.95 (95 %). For the data generated above, the maximum expected differences between two test results for the same5 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Repor
38、t RR:D20-1195.TABLE 1 RoundRobin Acidity Data in Accordance With PracticeE180Values, ppm HClAverage SrA SR B r C R D n E df FRubinate M 189 5.8 13.5 16.2 37.9 11 23Mondur MR 414 3.4 27.5 9.5 76.9 11 20A Sr = within-laboratory standard deviation of the replicates.B SR = between-laboratory standard de
39、viation of the average.C r = within-laboratory repeatability limit = 2.8 Sr.D R = between-laboratory reproducibility limit = 2.8 SR.E n = number of laboratories contributing valid data for this material.F df = degrees of freedom in the data after incorporating multiple data sets frommost laboratorie
40、s due to different combinations of solvent and electrode.D6099 183material, obtained by the same operator using the same equipment on the same day, the two replicate results should be judged notequivalent if they differ by more than day in the same laboratory due solely to the rmethod is value for t
41、hat material.12.9 ppm asHCl.14.1.5 Reproducibility, (R)Reproducibility LimitComparing two results, each the mean of replicates,The value below whichthe absolute difference between two individual test results obtained under reproducibility conditions may be expected to occur witha probability of appr
42、oximately 0.95 (95 %). For the data generated above, the maximum expected differences between two testresults for the same material, obtained by different operators using different equipment in different laboratories on different days,the two test results should be judged not equivalent if they diff
43、er by more than the due solely to the method is 57.4 ppm as HCl.Rvalue for that material.14.1.3 Any judgment made in accordance with 14.1.1 and 14.1.2 would have an approximate 95 % (0.95) probability of beingcorrect.14.2 BiasThere are no recognized standards by which to estimate the bias of this te
44、st method.15. Keywords15.1 acidity; aromatic isocyanates; isocyanates; MDI; methylene diphenyldiisocyanate; polyurethane; raw materials; TDI;titration; toluene diisocyanateSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue(D6099D6099
45、 13 08) ) that may impact the use of this standard. (September(August 1, 2013)2018)(1) Updated Sampling and Test Conditions sections to be consistent with the other polyurethane raw material standards.(2) Revised 3.2.1,Precision 4.1, Note 3, Note 4, and theBias legend forsection toEq ply with that s
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