WO1995008777A1 - Viscometre en ligne par resonance magnetique nucleaire pour liquides et polymeres fondus - Google Patents

Viscometre en ligne par resonance magnetique nucleaire pour liquides et polymeres fondus Download PDF

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Publication number
WO1995008777A1
WO1995008777A1 PCT/US1994/010068 US9410068W WO9508777A1 WO 1995008777 A1 WO1995008777 A1 WO 1995008777A1 US 9410068 W US9410068 W US 9410068W WO 9508777 A1 WO9508777 A1 WO 9508777A1
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WIPO (PCT)
Prior art keywords
sample
nmr
viscosity
temperature
pulse sequence
Prior art date
Application number
PCT/US1994/010068
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English (en)
Inventor
Christian I. Tanzer
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Auburn International, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Auburn International, Inc. filed Critical Auburn International, Inc.
Priority to AU77221/94A priority Critical patent/AU7722194A/en
Publication of WO1995008777A1 publication Critical patent/WO1995008777A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/46—NMR spectroscopy
    • G01R33/4625—Processing of acquired signals, e.g. elimination of phase errors, baseline fitting, chemometric analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G01N2011/0006—Calibrating, controlling or cleaning viscometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
    • G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
    • G01N24/082—Measurement of solid, liquid or gas content
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/44—Resins; Plastics; Rubber; Leather
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/30—Sample handling arrangements, e.g. sample cells, spinning mechanisms
    • G01R33/31—Temperature control thereof

Definitions

  • the present invention relates generally to pulsed NMR spectroscopy and spin-spin relaxation process theory as applied for determining viscosity of liquids and polymer melts .
  • Pulsed NMR technology produces free induction decay (FID) signals generated in samples under test.
  • FIDs have decay time constants (T2's) which are dependent upon the viscosity of the liquid samples. As viscosity increases, either through composition changes or temperature changes, the T2 values decrease; and as viscosity decreases, T2 *s increase.
  • a pulse sequence known in the art as the Carr-Purcell-Meiboom-Gill (CPMG) Sequence, has been developed for the accurate measurement of Spin-Spin or transverse relaxation times (T2's) .
  • Measuring T2 's by line-width or directly from free induction decay (FID) is inaccurate if the magnet and sample inhomogeneity factors are major contributors to the decay of the NMR signal, i.e. the magnet and sample inhomogeneity factor is comparable to or greater than the actual T2 of the sample. This is particularly the case with low-field time domain instrumentation used for on-line measurement applications.
  • the effect of the CPMG pulse sequence is to remove effects due to magnet inhomogeneities as well as pulse imperfections such that the measured NMR response reflects the true T2 of the spins.
  • relatively low resolution magnets may be employed to measure signals with very long time constants.
  • the NMR technique has not yet been applied to on-line viscosity measurement, and present on-line viscosity equipment has significant maintenance and calibration problems, particularly when used for polymer melts and when large shifts in viscosity occur.
  • An object of this invention is to overcome the above illustrated limitations and problems with an on-line NMR approach.
  • means may be provided for temperature control of said sample during NMR -. measuring, wherein the sample temperature is stable and at a known temperature compared to the flowing liquid or the polymer melt. Typically that known temperature is about equal to the temperature of the flowing liquid or the polymer melt.
  • FIG. 1 is a functional block diagram/schematic in cross section
  • FIG. 2 is a block diagram used with heated samples
  • FIG. 3 is a graphical representation of a preferred pulse sequence
  • FIG. 4 is a graph of the echo response from motor oils
  • FIG. 5 is graph of a least squares curve fit
  • FIG. 6 is a calibration plot
  • FIG. 7 is a graph of temperature effects. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
  • FIG. 1 shows an on-line, liquid flow- through system highlighting the basic elements of a preferred embodiment.
  • the above incorporated references describe in detail a basic apparatus for an industrial NMR system suitable for carrying out the present invention when combined with the added elements described herein.
  • a liquid 2 flows through conduits in an industrial system.
  • the liquid is continuously pumped through the sample measurement chamber 4 located between the poles of a jnagnet 6.
  • the sample chamber is surrounded by a temperature controlled air curtain which maintains the sample in the chamber at the same temperature as that of the flowing liquid 2.
  • the air curtain description is found in detail in the above incorporated patent application references.
  • the sample temperature in the chamber must be stable and equal to that of the flowing liquid since the viscosity is highly temperature dependent .
  • the actual temperature value of the flowing liquid may be used to adjust the viscosity measurements. This is accomplished by making calibration measurements of the specific sample material and developing correlation data between the temperature and t a viscosity of that material.
  • a control valve 10 is opened allowing the sample chamber to be filled by new liquid material.
  • the valve 10 is closed, and the NMR measurement is made.
  • the temperature of the sample is maintained equal to that of the flowing liquid.
  • the bypass loop ensures that a fresh sample is available at all times.
  • the control valve 12 is typically operated in a complementary fashion with the valve 10; when one valve is opened the other is closed. In other preferred embodiments valve 12 may be always opened or always closed or partially opened.
  • the RF (radio frequency) coils provide the NMR pulse source and pick up. These are described in more detail in the incorporated patent applications above.
  • FIG. 2 shows the modifications needed for utilizing the present invention with a polymer melt flow.
  • the flow circuit of FIG. 1 is replaced by a vertically mounted single screw extruder 14 driven by a motor 16.
  • Multi-stage heating units 18, attached to the walls of the extruder melt the material and the extruder forces the melt into the measurement chamber 20.
  • Solid samples are introduced into the extruder feed hopper 22 where the screw 14 forces the material through the extruder where it is melted.
  • the final stage of the extruder and the sample chamber are thermally regulated at a predetermined temperature value specific for the material.
  • the air curtain provides the sample chamber temperature required. The sample is driven into the chamber by the screw; the screw stops and the sample in the chamber is measured; then the screw drives out the old sample while introducing a new sample.
  • FIG. 3 shows the CPMG pulse sequence used in this preferred embodiment, and the sequence is P90(x) " ( t -Pl80(y) ⁇ t ) n .
  • an excitation pulse P90(x) is generated and transmitted to the sample followed by a Pi80 (y) excitation pulse at an interval of t and a series of Pl80(y) pulses at intervals of 2t .
  • the P90(x) and P180 (y) represent pulses with relative phase orientation.
  • Excitation by the Pi80 (y) pulses causes echo responses to occur.
  • the falling portions of the echoes (B in FIG. 3) have the same general pattern as the original FID (A in FIG. 3) excepting that the intensities at the echo maxima are attenuated according to the time constant T2. Measurement of the intensities of the echoes is taken, and a curve plotted of echo intensity as a function of time is made.
  • the curve is decomposed into component curves, and these curves are fitted to the data by an iterative process based upon a Marquardt- Levenberg (M-L) approximation technique applied automatically through a structured realization in software.
  • M-L Marquardt- Levenberg
  • This technique is used to determine the magnitude of all the parameters, constants, frequencies, etc. which best fit the FID curve.
  • This is an iterative technique where the entire curve is determined at once.
  • the M-L iteration process performs the curve fitting by attempting to minimize the Chi-Squared error function (the sum of the squared differences between the measured data points and the data points from the derived equation) .
  • the results of the M-L approximation are accepted if t ' he Chi Squared error is small enough, if not, the M-L fitting procedure may be reapplied with a different set of starting guesses. If this process also fails, the sample is discarded and a new sample obtained.
  • the M-L technique is documented in the following references: Ind. Appl . Math . , vol. 11, pp. 431-441 by D. . Marquardt, 1963; Data Reduction and Error Analysis for the Physical Sciences (New York, McGraw Hill) , Chapter 11 by Philip R. Bevington, 1969; and The State of the Art in Numerical Analysis (London: Academic Press, David A.H. Jacobs, ed 1977), chapter III.2 by J.E. Dennis.
  • the selected parameters taken from the derived curves are the y-axis intercept ratios, time constants (T*s), frequency terms and other parameters.
  • Calibration is accomplished by measuring T2 values for a number of samples with known viscosity values. Regression analysis is then performed to derive the coefficients relating the T2 values to the viscosities . For an unknown sample, the T2 values are determined and the viscosity is calculated from the known coefficients.
  • FIG. 4 shows the echo response train obtained from four motor oil samples with known relative viscosities (commercial grade 30, 40,. 50 and 60 wt motor oils) .
  • FIG. 5 shows the result of a least square exponential curve fit on one oil sample with the resulting T2 value.
  • FIG. 6 shows the calibration plot of T2 values with the known relative viscosity.
  • the temperature dependence of viscosity is well established, as shown in FIG. 7.
  • This temperature effect, as seen by NMR, is graphed as performed on one of the oil samples .
  • the effect of a decrease in temperature on the echo train response of one oil sample results in a shorter T2 value consistent with the higher viscosity value.
  • different groupings of the echoes may be used to generate a plot of intensities versus time.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Analytical Chemistry (AREA)
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  • Pathology (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)

Abstract

Dispositif (figures 1 et 2) et procédé servant à mesurer la viscosité en ligne d'échantillons liquides (2) et de polymères fondus (figure 2) au moyen d'une séquence Carr-Purcell-Meiboom Gill (CPMG) (figure 3) ou d'une autre séquence d'impulsions appropriée dans laquelle apparaît un train d'échos de signaux de précession libre (FID) (A et B) et où les FID sont analysés, de manière à obtenir les constantes de temps (T2) et d'autres informations. Les T2 sont étalonnées par l'intermédiaire de normes connues, afin d'obtenir la viscosité de l'échantillon de matériau. L'invention comporte un système de régulation de température (24), étant donné que la viscosité dépend de la température.
PCT/US1994/010068 1993-09-23 1994-09-09 Viscometre en ligne par resonance magnetique nucleaire pour liquides et polymeres fondus WO1995008777A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU77221/94A AU7722194A (en) 1993-09-23 1994-09-09 Nmr on-line viscometer for liquids or polymer melts

Applications Claiming Priority (2)

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US12591193A 1993-09-23 1993-09-23
US08/125,911 1993-09-23

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997009601A1 (fr) * 1995-09-07 1997-03-13 Micro Motion, Inc. Systeme et procede pour calibrer un viscosimetre
US5650722A (en) * 1991-11-20 1997-07-22 Auburn International, Inc. Using resin age factor to obtain measurements of improved accuracy of one or more polymer properties with an on-line NMR system
WO2005124324A1 (fr) * 2004-06-18 2005-12-29 Basell Polyolefine Gmbh Procede rmn pour determiner et reguler la composition de melanges de polymeres en polymerisation
EP1750128A3 (fr) * 2005-08-04 2007-08-29 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Methode et appareil pour la mesure du durcissement d'un matériau duroplastique

Citations (11)

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US4321538A (en) * 1978-08-31 1982-03-23 Hitachi, Ltd. Nuclear gyromagnetic resonance apparatus
US4546317A (en) * 1983-07-01 1985-10-08 The United States Of America As Represented By The Secretary Of The Navy Free nuclear precession gradiometer system
US4728892A (en) * 1985-08-13 1988-03-01 Shell Oil Company NMR imaging of materials
US4769601A (en) * 1985-08-22 1988-09-06 Amoco Corporation Method of and apparatus for determining cement strength and extent of setting with a pulsed nuclear magnetic resonance spectrometer
US4940942A (en) * 1989-04-14 1990-07-10 Bartuska Victor J Method and apparatus for conducting variable-temperature solid state magnetic resonance spectroscopy
US5023551A (en) * 1986-08-27 1991-06-11 Schlumberger-Doll Research Nuclear magnetic resonance pulse sequences for use with borehole logging tools
US5049819A (en) * 1989-06-30 1991-09-17 Auburn International, Inc. Magnetic resonance analysis in real time, industrial usage mode
JPH04157354A (ja) * 1990-10-19 1992-05-29 Nkk Corp 熱可塑性樹脂の核磁気共鳴スペクトルの測定方法
US5192910A (en) * 1990-06-12 1993-03-09 Spectrospin Ag Temperature-control device for samples
US5306640A (en) * 1987-10-28 1994-04-26 Shell Oil Company Method for determining preselected properties of a crude oil
US5321358A (en) * 1993-03-01 1994-06-14 General Electric Company Embedded NMR sensors for cure monitoring and control of composite structures

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4321538A (en) * 1978-08-31 1982-03-23 Hitachi, Ltd. Nuclear gyromagnetic resonance apparatus
US4546317A (en) * 1983-07-01 1985-10-08 The United States Of America As Represented By The Secretary Of The Navy Free nuclear precession gradiometer system
US4728892A (en) * 1985-08-13 1988-03-01 Shell Oil Company NMR imaging of materials
US4769601A (en) * 1985-08-22 1988-09-06 Amoco Corporation Method of and apparatus for determining cement strength and extent of setting with a pulsed nuclear magnetic resonance spectrometer
US5023551A (en) * 1986-08-27 1991-06-11 Schlumberger-Doll Research Nuclear magnetic resonance pulse sequences for use with borehole logging tools
US5306640A (en) * 1987-10-28 1994-04-26 Shell Oil Company Method for determining preselected properties of a crude oil
US4940942A (en) * 1989-04-14 1990-07-10 Bartuska Victor J Method and apparatus for conducting variable-temperature solid state magnetic resonance spectroscopy
US5049819A (en) * 1989-06-30 1991-09-17 Auburn International, Inc. Magnetic resonance analysis in real time, industrial usage mode
US5192910A (en) * 1990-06-12 1993-03-09 Spectrospin Ag Temperature-control device for samples
JPH04157354A (ja) * 1990-10-19 1992-05-29 Nkk Corp 熱可塑性樹脂の核磁気共鳴スペクトルの測定方法
US5321358A (en) * 1993-03-01 1994-06-14 General Electric Company Embedded NMR sensors for cure monitoring and control of composite structures

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ACS SYMPOSIUM SERIES, Volume 475, issued 26 August 1990, A. CHARLESBY, "Characterization of Macromolecular Morphology by Pulsed NMR Spectroscopy", pages 193-217. *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5650722A (en) * 1991-11-20 1997-07-22 Auburn International, Inc. Using resin age factor to obtain measurements of improved accuracy of one or more polymer properties with an on-line NMR system
WO1997009601A1 (fr) * 1995-09-07 1997-03-13 Micro Motion, Inc. Systeme et procede pour calibrer un viscosimetre
WO2005124324A1 (fr) * 2004-06-18 2005-12-29 Basell Polyolefine Gmbh Procede rmn pour determiner et reguler la composition de melanges de polymeres en polymerisation
US7737230B2 (en) 2004-06-18 2010-06-15 Basell Polyolefine Gmbh NMR method of determining and regulating the composition of polymer mixtures in polymerization
KR101118939B1 (ko) 2004-06-18 2012-02-27 바젤 폴리올레핀 게엠베하 중합반응에서 중합체 혼합물의 조성을 결정 및 조절하는ｎｍｒ 방법
EP1750128A3 (fr) * 2005-08-04 2007-08-29 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Methode et appareil pour la mesure du durcissement d'un matériau duroplastique

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