Document oZjabD2rqp9n1XR4dEYqvkyE

BUSINESS CONFIDENTIAL PROJECT REPORT VINYL RESINS ANALYSIS OF RESIDUAL VINYL CHLORIDE MONOMER BY HEAD-SPACE GAS CHROMATOGRAPHY AND COMPARISON TO THE EXISTING htu SOLUTION POLYMER GAS CHROMATOGRAPHIC METHOD JUN 1 o 1976 R N *WLE.<. i,<. AUTHORS* A. E. Gabany, Jr. (2) 0ATB* June 7, 1976 Work by: H. T. Bias PROJECT NO.) 910A20 SUPERVISOR) R. A. Bleidt (3) file Na> 22123 SUMMARY A head-space gas chromatographic analysis has been r ported for measurements of low levels of residual vinyl chlorld monomer in vinyl resins. The method is not applicable for polym rs in fused form, such as sheets or cubes. Likewise, the method was not de signed to accommodate latex samples. The results when compared to those obtained by the existing tetrahydrofuran solution polymer technique-gas chromatographic m tbod indicate that the method has good potential. However, the head spac method consistently gave lower results for both homopolymers and co polymers than the solution polymer method. Although the method is a good viable technique for measuring vinyl chloride monomer, it is not recommended at this time as a r place ment for our solution polymer technique-gas chromatographic method. The vinyl chloride monomer results obtained on various types of vinyl resins produced at Texas City are tabulated. INTRODUCTION The Environmental Protection Agency (EPA) issued proposed standards for the determination of vinyl chloride monomer (VCM) in in-process waste water samples and polyvinyl chloride (PVC) resin, slurry, wet cake and latex samples in the Federal Regist r of D c- ember 24, 1975. They have recommended for the analytical method of analy sis a relatively new technique, head space gas chromatography. The basis for the method relates to the vapor equilibrium which is established between VCM, PVC, resin, water, and air in a closed system. Supposedly, it has been demonstrated that the VCM in a PVC resin will equilibrate in a closed vessel quite rapidly, provided that the temp rature of the PVC resin is maintained above the glass transition temperatur of that specific resin. RESEARCH AND DEVELOPMENT DEPARTMENT CHEMICALS ANO PLASTICS UNION CARBIDE CORPORATION SOUTH CHARLESTON, WEST VIRGINIA I.JCC 038250 BISINESS CONFIDENTIAL 2 PROJECT NO. 910A20 Presently Perkin-Elmer Corporation markets a Model f-40 Head Space Analyzer for approximately $14,000-$16,000 which supposedly will do the required analysis, and this instrument is mentioned in the pro posal. However, it is stated in the proposed method that the m ntion of trade names on specific products does not constitute endorsement by the EPA. Furthermore, the proposed method of analysis is essentially that of B. F. Goodrich Chemical Company's Standart Test Procedure No. 1005-T-l. In light of the supposedly firm direction in which the EPA apparently is heading, Dr. J. J. Brezinski proposed that we investigat head space gas chromatography for the analysis of VCM in Union Carbide's various vinyl resin products and compare the data with that obtained from polymer solution gas chromatography. These products would include not only PVC homopolymers but also various copolymers each of which is . prepared by a separate process. To this end Mr. R. M. Arnold, Texas City, provided us with samples of the various types of vinyl resins pro duced at the Texas City Plant. DISCUSSION The most widely accepted procedure for determining r sidual vinyl chloride monomer in vinyl resins, powders, films and latexes is to dissolve the sample in a solvent and anaylze the solution by gas chromatographyf1). Recently, however, there has been a noted effort emerging which would change the analysis technique form solution- gas chromatography to head space-gas chromatography. The basis of the method relates to the vapor equilibrium which is established betw en the sample and the atmosphere in a closed system. Furthermore, it has been observed(2) that at a temperature above the glass transition point of polyvinyl chloride (PVC), the solubility of vinyl chloride monom r (VCM) in PVC accurately follows Henry's law up to a VCM content of at 1 ast 4000 ppm. The analytical procedure involves sealing a weighed PVC sample containing VCM in a suitable vial at room temperature, heating the vial to 90C to establish VCM equilibrium between PVC and vapor pbas s, and analyzing a syringe sample of the "head space" vapor for its VCM cont nt. As one might expect, this procedure has been automated. The Perkin-Elmer Corporation is marketing a Model F-40 Head Space Analyz r. The package includes a gas chromatograph and a thermostated constant temperature bath which has an approximate range of 10-95C. A sampling turntable which holds 30 sealed sample vials (~20 ml each) is low red into the preset constant temperature bath and equilibrium is established. After reaching equilibrium, about 1 hour at 90C, the "head space" above the sample is automatically sampled and injected into the attached gas chromatograph. Needless to say, we do not have a F-40 Head Space Analyz r; therefore, we have used a Hewlett-Packard 5750 gas chromatograph equipped with a flame ionization detector. The chromatographic column used for the analysis was a 6-ft. x 1/4-in. stainless steel column packed with 80/100 mesh Porapak QS. The column oven was maintained at 140C Isothermal, ucc 038251 BUSINESS CONFIDENTIAL 3 PROJECT NO. 9I0A20 the detector at 250C and the injection port at 150C. Carrier gas (helium) flow was 30 cc/min. A retangular water bath filled with sili cone oil and maintained at 90C5C, with constant stirring, was used in the absence of a good constant temperature bath. In Table I are tabulated the results of the "head space" analyses obtained on various samples of vinyl resins produced at T xas City. The three different production processes as well as examples of both homopolymer and copolymer are included. In all of the gas chromat ograms obtained for these samples, there was an unidentified peak which eluted just prior to the VCM peak. The presence of this peak did not particularly interfere with the measurement of the VCM peak except for the VYHH sample. In this case the VCM peak appeared as a shoulder on the tailing side of the unknown peak, thereby ruling out even a r asonable estimate of its size, possibly the selection of another column could eliminate this for future analysis. From the data in Table II it is apparent that the "head spac " analyses are lower than the "solution" results obtained in our labora tory and the Texas City laboratory. It is possible that recalibration could correct the situation. But when the data are examined closely, it becomes apparent that the differences range from a low of 6 p rcent to a high of 38 percent and probably it is not due to calibration. Mor than likely, the data spread is a reflection of the poor temperature control in the silicone bath. The discrepancy between the South Charleston and Texas City data for QSAN-7 is thus far unexplained. It can, however, be assumed that the sample lost its VCM in transit. Since we are analyzing these samples by a manual technique, there are other factors which could effect the data. The loading of the sample vails, the sampling of the "head space" with a microsyring , and the injection of the sample into the chromatograph are just a f w of points to be considered. The sample vials we used were the same as Perkin-Elmer uses with their F-40 instrument. They are 23.5-ml Hypo-vials sealed with Teflon faced Tuf-Bond disks. The sample, approximately 2 gm, was quickly loaded into the tared vial and subsequently capped using a vial capper. After calculating the weight of the sample, the vial was then placed in the temperature bath and allowed to equilibrate at 90C5C for 1 hour. The "head space" was sampled using a 500-ml Hamilton gas tight syring and injected into the gas chromatograph. Vinyl chloride eluted at 4.2 minutes. The system was calibrated using a 100-ppm VCM in air sample prepared and checked by members of the Environmental Health Group. Two additional pieces of data are required for "head spac " analysis which are not encountered in solution-gas chromatographic methods. The complex equation used for calculating VCM requires both ucc 038252 BUSINESS CONFIDENTIAL 4 PROJECT NO. 910A20 the barometric pressure and air temperature at the time of the measure ment. Certain other values must also be known, such as Henry's Law Constant for VCM in PVC at 90C and the gas constant. Both of these values are known and become constants if the equilibrium temperatur is maintained at 90C. The equation for calculating VCM is as follows: ppm VCM 2]Aspa fMvVg Rffi P*5" + KT where As pa Rf Tl Mv M R K t2 Area counts for sample VCM peak Atmospheric pressure, mm Hg Response factor for VCM standard (counts per ppm) Room temperature, K Molecular weight VCM (62.5) Total vial volume less volume of PVC, cc's Sample weight, gms Gas constant (62,400) Henry's Law Constant for VCM in PVC at 90C Equilibration temperature, 363K (90C) / An example calculation would be as follows: ppm VCM As 21,200 pa 745 Rf 119.93 Ti 297 Mv VS 62.5 (23.5 - 5_L6233) M 2.6233 R K 62,400 6.52 x 10 -6 T2 - 363 (21.200)(745 ) (liOS) (2977 re2.5(: 2.6233A [ 2.523;|3<ta74d6)4 (6.52 x 10'6)(363)] 4.70 Notebook Reference 6HTB1 BUSINESS CONFIDENTIAL 5 PROJECT NO. 910A20 BIBLIOGRAPHY 1) "Determination of Residual Vinyl Chloride Monomer in Vinyl Resins", Union Carbide Standard Testing Method, WC-326-G-1, October 15, 1975. 2) Berens, A. R., et al, "Analysis for Vinyl Chloride in PVC Powd rs by Head-Space Gas Chromatography", Journal of Applied Polymer Sci nee. Vol. 19, 3169-3172, 1972. MANUSCRIPT DATE: May 26, 1976 Date Typed: June 2, 1976 AEG:gcf Ay Ef Gabany UCc 038254 BUSINESS CONFIDENTIAL PROJECT NO. 910A: TABLE I RESIDUAL VINYL CHLORIDE ANALYSIS OF VINYL RESINS BY HEAD-SPACE GAS CHROMATOGRAPHY Resin Type QYNL VYNW Process Non-Solvent Composition PVC VC1-VA Residual VCM, ppm 2.9 2.9 VYHH VSKK-10 QSQH-7 QSAN-7 QSAL Solvent Suspension ft tt M VC1-VA VC1-VA VCl-Ethylene PVC PVC 0 197.1 11.5 10.6 4.7 ucc 038255 BUSINESS CONFIDENTIAL PROJECT NO. 910A20 TABLE II COMPARISON OF RESIDUAL VINYL CHLORIDE ANALYSIS BY HEAD-SPACE-GAS CHROMATOGRAPHY WITH SOLUTION-GAS CHROMATOGRAPHY Resin Type QYNL VYNW VYHH VSKK-10 QSQH-7 QSAN-7 QSAL Head Space 2.9 2.9 0 197.1 11.5 10.6 4.7 Residual VCM . PP_____ _____________ Solution S. C. Tech Center T xas City 4.3 5.1 3.7 3.6 0.13 0.2 241 237 18.7 20.2 11.3 40.2 ' 5.3 6.6 038256 4 BUSINESS CONFIDENTIAL DISTRIBUTION Dr. W. B. Ackart, 312 Mr. R. L. Anderson, 511 Mr. R. M. Arnold, 515 Dr. R. K. Barnes, 511 Mr. J. J. Behen, Jr., 525 Mr. G. P. Bigelow, NYO-32 Dr. J. J. Brezinski, 511 Mr. G. W. Buttrick, 511 Dr. M. A. Carey, 511 Mr. J. L. Davidson, 513 Dr. T. L. Dawson, 511 Mr. M. E. Eisenhour, 515 Mr. W. S. Engle, 511 Mr. J. W. Fields, 515 Mr. C. E. Fry, 514 Miss 0. M. Garty, 312 Mr. U. H. Gibson, 511 Mr. M. E. Griffith, 514 Mr. H. C. Gunst, 312 Mr. R. J. Hanna, 511 Mr. D. E. Hardman, NYO-33 Dr. L. P. McMaster, 312 Dr. C. N. Merriam, 312 Dr. C. E. Moyer, Jr., 515 Mr. H. E. Persinger, 511 Mr. Q. Quick, 511 Mr. K. E. Ross, 515 Mr. J. E. Ruch, 511 Mr. J. J. Smith, 511 Mr. G. F. Tacquard, 515 iMr. R. N. Wheeler, 514 Mr. W. E. Whitehurst, 511 Dr. F. G. Willeboordse, 312 Information Retrieval Librarian, 525 File: 300-44B PROJECT NO. 910A20 ucc 038257