WO1996021866A1 - Analyse par resonance magnetique nucleaire du polypropylene en temps reel - Google Patents

Analyse par resonance magnetique nucleaire du polypropylene en temps reel Download PDF

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Publication number
WO1996021866A1
WO1996021866A1 PCT/US1995/014646 US9514646W WO9621866A1 WO 1996021866 A1 WO1996021866 A1 WO 1996021866A1 US 9514646 W US9514646 W US 9514646W WO 9621866 A1 WO9621866 A1 WO 9621866A1
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WO
WIPO (PCT)
Prior art keywords
sample
time
components
measuring region
resonance
Prior art date
Application number
PCT/US1995/014646
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English (en)
Inventor
Ronald L. Dechene
Thomas B. Smith
Scott A. Marino
Ronald J. Tache
Ajoy K. Roy
Original Assignee
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 AU43644/96A priority Critical patent/AU4364496A/en
Publication of WO1996021866A1 publication Critical patent/WO1996021866A1/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
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/389—Field stabilisation, e.g. by field measurements and control means or indirectly by current stabilisation
    • 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
    • G01N24/085—Analysis of materials for the purpose of controlling industrial production systems
    • 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
    • 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

Definitions

  • the present invention relates to an instrument for measurement of the type and quantity of lattice bound and free magnetically active nuclei within successive samples of a process material flow through pulsed nuclear magnetic resonance (NMR) techniques and more particularly the application of such measurement to industrial process control of moisture content, polymer content, crystallinity fraction, oil/fat fraction and other percentages of components analysis and other parameters.
  • NMR pulsed nuclear magnetic resonance
  • NMR techniques have grown extensively over the past forty years, most notably in the medical instrumentation areas where in vivo examination of various parts of the human body can be seen, and in clinical research laboratory uses. In addition there has been some use and interest in the application of these techniques to industrial instrumentation and control tasks.
  • the present invention enables effective utilization (technically and economically) of pulsed NMR techniques in industrial areas to replace or complement existing optical and radiant energy-based instrumentation.
  • Pulsed NMR spectroscopy is described in our above- cited patent.
  • This technique uses a burst or pulse which is designed to excite the nuclei of a particular nuclear species of a sample being measured (the protons, or the like, of such sample having first been precessed in an essentially static magnetic field) ; in other words the precession is modified by the pulse.
  • FID free induction decay
  • Traditional Fourier Transform analysis generates a frequency domain spectrum which can be used to advantage in studying the nuclei of interest.
  • the duration of the pulses, the time between the pulses, the pulse phase angle and the composition of the sample are parameters which affect the sensitivity of this technique.
  • An object of this invention is an improved measurement system which leads to accurate, fast determination of the types and quantity of the nuclear species of interest.
  • a further object of this invention is its application to the industrial, on-line problems of measuring and calibrating the controlling processes per se.
  • Another object of this invention is to utilize time domain analysis in achieving such system.
  • the principal variables of interest are polymer crystallinity, tacticity and the molecular structure of polypropylene. But other parameters may be measured. It is an object of this invention to accommodate a variety of such measuring tasks.
  • Another object is to accommodate the dynamics of industrial on-line applications including variations of density, temperature, packing and size factors, friction and static electricity, vibrations and frequent, repetitive, cyclic and non-cyclic measurements.
  • a further object of the invention is to integrate all the features of accurate, fast determination of the types and quantity of the polymer molecular structure of interest, the use of time domain analysis in such a system, its application to the industrial, on-line problems of monitoring and controlling processes accommodating the dynamics of industrial on- line applications including variations of density, temperature, packing and size factors, friction and static electricity, vibration and frequent, repetitive, cyclic and non-cyclic measurements.
  • a further object of the invention is to use such magnetic resonance techniques in polypropylene analysis, including crystallinity, tacticity and density, all with enhanced accuracy and reliability of data obtained and while achieving the necessary practical economies.
  • a further object of the present invention is to extend those achievements further in relation to industrial on-line processing, and the like of NMR- active materials and more particularly to polypropylene wherein the tacticity of the material, and the concurrent molecular structure is determined on-line.
  • the present invention provides a materials measurement system using magnetic resonance hardware, controls (and related data capture and data reduction means and steps) and techniques, preferably in the time domain.
  • the system can be used to capture data from a continuous production line or like repetitive measurements system.
  • the NMR system effects a reliable extraction of free induction decay data in a way that is practical in an industrial on-line context and economically practical.
  • the system is characterized by provision of a base magnetic field homogeneity to a reasonable degree and offset of inhomogeneity effects, temperature stabilization to a reasonable degree and offsets of thermal drift effects and use of multiple runs (10-50) for each measurement with digital data reduction and use of statistical methods or other data manipulation for industrially effective measurement.
  • a very fast Gaussian, a slower unmodified Gaussian, and an even slower exponential are used.
  • These different components are representative of proton relaxation after an initial excitation by a pulse of transmitted and resonant or near resonant coupled radio frequency energy that induces a modification of the precession of protons in the sample being measured in a high static magnetic field.
  • the calibration system including the M-L technique (described below) will still be applicable.
  • the fast Gaussian FID portion is based on measurement data points of magnetization decay of a relatively immobile structure present in the polypropylene sample and picked up at the NMR system's receiver. This component can be related to the isotactic polypropylene structure.
  • the slower modified Gaussian or slower Gaussian component is a transition zone between the constrained and the more mobile structures.
  • the slow exponential FID portion is usually based on mobile structure. This component can be related to the atactic polypropylene structure.
  • the fast Gaussian, the slower modified Gaussian or slower Gaussian, and exponential FID portions and the FID as a whole can be extrapolated to a decay origin usually set close to the time center of the excitation pulse.
  • Zero time intercepts of these curves provide ratio data using the FID intercept and/or intercepts of one or more of the curve portions to determine polymer tacticity or crystallinity. Density can also be determined through the invention because the FID varies predictably as a function of tacticity/crystallinity and density.
  • the measuring system of the invention comprises economically scaled down and industrially hardened portions, relative to the widely used laboratory systems.
  • a magnetic essentially fixed field comprises closely spaced pole pieces with a 4,000 - 8,000 Gauss field (about 4,700 Gauss, nominally).
  • Helmholtz coils are provided which are adjustable to provide rapid adjustments for the precise, correct field and overlaid with coarse, slower adjustments to thermal environment. This is to assure that the product of a materials related constant (gamma) multiplied by the magnetic field strength, which is resonant frequency, will match excitation frequency either exactly (on- resonance condition, no offset) or by a selected offset. Still further fine adjustment is made in signal processing as described below.
  • the present invention accommodates great streams of data in practical ways through features, described below, which are inter-related to the thermal controls to provide a measuring system meeting the foregoing objects.
  • the materials of construction are also integrated into the reliability considerations, as described below. Measurement of a sample is often accomplished in approximately a minute (in contrast to hours-long measurements of many prior art systems) .
  • the measurements made through the present invention based on ratios of intercept, delay time constants and/or integrated areas under curves and/or peak analysis are independent of weight or volume of sample in the measuring region or gain of the system whereas precise weight measurement is a necessary feature -- and limitation of -- many prior art systems.
  • FIGS. 1 and 2 are lateral and cross-sections of a preferred embodiment of the invention including electrical block diagram components
  • FIG. 3 shows the voltage-time waveforms of the free induction decay (FID) of the embodiment of FIGS. 1-2 in the course of operation
  • FID free induction decay
  • FIG. 4 is a flow chart of measuring steps utilizing the FIGS. 1-2 apparatus including its signal processing elements, (the activity of which is illustrated by the FIG. 3 waveforms) ,-
  • FIG. 5 is a voltage-time trace for FID curves derived from samples of polypropylene with different isotactic indices (xylene or hexane solubles) ; and FIG. 6 is a polypropylene calibration chart.
  • FIGS. 1-2 show transverse and cross sections with block diagram inserts of a first embodiment of the apparatus and method of the invention.
  • An industrial process line IPL has material flowing as indicated by arrow A. Some of the material is captured by a probe
  • the said region is defined by a tube 98 typically about 30 cm long made of an essentially non-magnetic, nonconducting material which does not itself generate substantially interfering FID signals (glass, certain ceramics, certain plastics or hybrids) .
  • the sample region is defined between inlet and outlet valves VI and V2. Gas jets J are also provided. These are pulsed on/off repeatedly to agitate fluent sample materials during sample admission and expulsion.
  • the region S2 is the critical portion of the sample. It is surrounded by a sample coil 100 tuned to resonance and driven by a tuning circuit 102 and related transmitter/receiver controller 104.
  • Grounded loops 101 are Lenz Law shields which are provided above and below coil 100 to help shape the field of coil 100 -- i.e., contain the field established by an excitation pulse.
  • the controller 104 includes an on-board microprocessor and required power supply elements, memory, program and I/O decoding suitable to interconnect to the hardware shown and to an external microcomputer 106 with keyboard 108, monitor (or other display) 110, recorder 112 and/or process controller 114 (to control the process at IPL) .
  • the operator initiates and controls operation from the display keyboard 108 and the resulting data and signals are subsequently shown on the display 100 and utilized in 110, 112, and/or 114.
  • the computer 106 also controls instrument operation conditions.
  • the region S2 of tube 98 and coil 100 are in a static, but adjustable, crossing magnetic field defined by a magnetic assembly 116 which comprises a yoke 118, pole pieces 120, surrounding Helmholtz coils 124, and a coil current generator 117.
  • the critical sample region S2 of the tube 98 and magnet are contained in a metallic (but non-ferromagnetic) box 126 with highly thermally conductive face-plates 128 and internal partitions 130 and over-all mass related to each other to minimize harmonics and other interferences with a signal emitted from coil 100 to a sample and/or returned from the sample for pick-up by coil 100 and its tuned circuit 102 and transmit/receive controller 104.
  • a thermal controller 140 processes temperature signals from 138 to adjust heating/circulation at 134/136 as a coarse control and to adjust current through the Helmholtz coils 124 at magnet pole pieces 120 as a sensitive and fast fine control, as well as implementing general control instructions of computer 106.
  • thermal stabilization may be provided by a closed loop heat exchanger 142 having pump 144 and coils 146 attached to yoke 118 and coils 148 attached to the plates 128 of box 126. Still further thermal stabilization may be provided by directing temperature controlled air (controller not shown) into an annular region defined by collar 134A around the sample. The strength, consistency and constancy of the magnetic field between poles 120 in the region S2 of the sample is thus controlled by a uniform base magnetic field in the entire region S2.
  • the Helmholtz coils 124 are energized by the coil current controller 117 to accurately trim the final magnitude of the field in which the sample is placed. This field is the vector addition of the fields due to the magnet poles 120 and the Helmholtz coils 124.
  • the controller 117 sets the current through the Helmholtz coils 124 using current generators.
  • the coils 124 are wound around the magnet pole pieces such that the magnetic field created by the current in the coils 124 can add to or subtract from the field created by the magnet pole pieces.
  • the magnitude of the current through the coils 124 determines the strength of the field added to or subtracted from the field due to the magnet pole pieces (and related yoke structure) alone.
  • the actual determination of the current through the Helmholtz coils is accomplished by carrying out the magnetic energy and resonance techniques hereinafter described in preliminary runs and adjusting Helmholtz current until the maximum sensitive resonance is achieved. In some cases, the Helmholtz current is then adjusted to offset the system from resonance by about 1-3 KHz.
  • tuner 102 including coils 100 and 101 and variable capacitors 102-1 and 102-2, resistor 102-3 and diodes 102-4 and constructed for tuning to Q of twenty to fifty to achieve coil 100 resonance, and control 104 including a transmit/receive switch 104-1, a transmitter 104-2 and receiver 104-3, a crystal oscillator 104-4, gated pulse generator (GPG) 104-5, and phase shifter 104-6.
  • the crystal provides a nominal twenty megahertz carrier which is phase modulated or demodulated by the MOD, DEMOD elements of transmitter 104-2 and receiver 104-3.
  • the receiver includes variable gain amplifier elements 104-31 and 104-32 for operation.
  • the analog signals received are fed to a high speed at least 12 bit flash A/D converter 105-1 and internal (to the instrument) CPU element 105-2, which provides data to an external computer 106 which has a keyboard 108, monitor 110, modem 109, recording elements 112 and process controller elements 114, e.g., for control of valves VI, V2 via valve controls 115 and/or to coil current controls 122, all via digital-analog converters (not shown) .
  • the analog signal FID curve is conditioned by a Bessel filter which acts as a pre-filter and an anti ⁇ aliasing filter.
  • filtering can be performed to change the analog signal FID curve in a variety of ways. After digitization the signal may be time smoothed by a fast Fourier transform filter program. The combination of these filters results in a relative improvement in signal to noise ratios which enhance the accuracy of the system.
  • the excitation of coil 100 and excitation- precession of the sample's proton content and subsequent relaxation/decay produces a received signal that, after demodulation, controlled gain amplification, A/D conversion and plotting of points has the free induction decay (FID) curve shape C shown in FIG. 3.
  • FIG. 3 voltage-time trace, shows the elements of a "cycle" of excitation of a sample and free induction decay.
  • the excitation pulse center is taken as to.
  • the transceiver 104 electronic components do not receive effectively until saturation effects are overcome at tl. Then a useable curve is developed.
  • the signal processing equipment can add or subtract consecutive waveforms for useful adjustment as described below.
  • the FID curve data are stored in the external computer 106 where a program finds the best curve to fit each stored FID curve.
  • the FID curve has three primary component parts shown as A, B and E in FIG. 3.
  • the A curve which dominates the first part of the FID curve is a Gaussian
  • the B curve that dominates the middle part of the curve is a slower modified Gaussian or a slower Gaussian
  • E that dominates the later part of the FID curve is a exponential decay.
  • the Gaussian and exponential portions are associated with the relatively immobile and mobile portions, respectively, of the polypropylene samples.
  • the slower modified Gaussian or slower Gaussian is a transition interface or a transition zone between the two.
  • the determination of the types of curves which make up the FID curve is important because once the curves are known they can be extended back to a time origin (shown as AQ, BQ and En at tO, i.e., excitation of a Cycle 1) , which is close to the center of the transmitted burst signal. This is important since the saturation effects of the instrument's electronic components (which occur during and a short time after the burst signal to tl) make direct measurements of the intercepts inaccurate.
  • the portion of the curve of interest extends from to to t4 beyond which the curve is too small to matter and the electronics needs recovery time to prepare for the next cycle (beginning with a pulse centered at t0#2) .
  • the received signal is the product of the in-resonance FID and a cosine term at the offset frequency.
  • the near resonance operation of the system still yields good results since physical variations cause only minor secondary effects. In suitable cases, operation at resonance is carried out.
  • Each (sub) cycle goes on to t5 to allow for recovery i.e., essentially full relaxation of the protons of the sample before beginning a new transmit signal burst (t0#2) .
  • an excitation pulse interval is five to ten microseconds
  • the tO-tl time is five to fifteen microseconds (the shorter the better)
  • tl-t2 where effects due to the relatively immobile structure are predominant
  • - t2-t3 is a transition/interfacial region of fifteen to twenty- five microseconds duration, also characterized by phase cancellation effects
  • - and t3-t4 is a region of fifty to five hundred microseconds, where more mobile (exponential) structure predominates.
  • There is a final t4-t5 region to allow recovery (re- equilibration) of the sample material, which is usually on the order of hundreds of milliseconds up to several seconds.
  • the entire FID curve is composed of several major components as shown in Equation Eq. 1 as applied to polypropylene and like materials, although as described there may be fewer components on some occasions.
  • the selected parameters are the y-axis intercept ratios and time constants, sample temperature, frequency terms and other parameters described below.
  • the resulting data utilized in the computer 106 is the equation for the FID curve as composed of the three (excluding the cosine term) components shown in Eq. 1.
  • Each of these curves (and their intercepts) has been experimentally related to the same nuclei of interest.
  • the FID curve equation is determined, the following ratios of the y-axis intercepts of the indicated curves are formed: the exponential/fast Gaussian, (Rl) , and the modified Gaussian/fast Gaussian, (R2) .
  • the ratios (Rl) and (R2) , the cross product (R12) , together with the squares of these ratios (Rll) and (R22) , the decay times for each of the three curve components, the product temperature and the cosine frequency term of the modified Gaussian form a ten dimensional model.
  • a nine dimensional model is used.
  • a regression analysis relates these ten terms to the isotactic index (xylene solubles) of the polypropylene. The results are independent of the amount of sample, and the gain of the system, which obviates the need to measure these physical quantities.
  • the M-L iteration process performs the curve fitting by minimizing the Chi-Squared function (the sum of the squared differences between the measured data points and the data points from the derived equation) , a technique well known in the art.
  • Calibration of the system is accomplished by measuring a number of known samples and using the M-L technique to derive the model equation constants associated with each known sample. Regression analysis is then performed to derive the coefficients relating the various model equation constants to the desired measured quantity or quantities. A calibration equation is then prepared using these coefficients. In operation, a FID is obtained from the test sample and by the M-L technique the constants of the model equation are determined. These constants are then input to the calibration equation and the desired parameters are calculated.
  • FIG. 5 shows FIDs taken for polypropylene samples of varying isotactic indices. The curves are sufficiently distinct and the resulting three component parts found (by M-L) for each curve result, after regression, in values from which actual polypropylene isotactic index (xylene solubles) is computed from the calibration equation.
  • the data can be used as a QC type measurement or as an on-line control parameter which is fed back to control a process, back in line IPL (FIG. 1) or related equipment.
  • the form of the input operating parameters of the system can be wide reaching to include previously stored parameters in PROMs or ROMs or in magnetic storage media such as disks or tapes or inputs sent in over telephone line and modem 109.
  • the generation of the excitation pulse can be accomplished with many techniques including a coil or antenna arrangement.
  • the steady magnetic field can be generated by electromagnets, permanent magnets, electromagnets with superconducting winding or other standard techniques of generating magnetic fields.
  • FIG. 4 is an expanded flow chart showing the steps of measurement to establish effective industrial measurement.
  • First a single free induction decay curve C is established to see if the sample area is clear (Quick FID) in an abbreviated cycle of attempting to establish a curve C. If the sample region is not clear (N) , measurement is interrupted to allow valve V2 (re)opening and operation of jets J and gravity to clear the region. A new Quick FID step establishes clearance. Then a sample is admitted by closing valve V2, opening valve VI and making such adjustments of probe P and line LI as may be necessary (if any) to assure sample acquisition. Jets J adjust and stabilize the new sample.
  • Temperature controls 134-138 and 142-146 described above, establish very coarse and less coarse thermal controls countering sample temperature variations.
  • the heater 134 and/or the fan 136 may be disabled, thereby reducing interference, when performing high sensitivity measurements.
  • An electronic signal processing apparatus baseline is established in 3-4 cycles (each having (+) and (-) sub-cycles with addition of (C+) and (C-) to detect a baseline offset and compensate for it) . It would be feasible to avoid this baseline offset determination and simply deal with it as an additional (i.e., eleventh) dimension in the M-L analysis, but this would increase iteration time.
  • Each cycle involves a transmission/reception/flash A-D conversion, and storage of data. The curves are then averaged for M-L curve fitting, and the above listed intercepts and ratios are established. Similar cycles, but somewhat abbreviated can be applied for Quick FID, field check and baseline correction purposes.
  • Each of the sub- cycles [(+) and (-)] of each such cycle involves a capture and utilization of thousands of FID points in data reduction.
  • Each sub-cycle occurs on the order of a second and the number of such sub-cycles employed depends on the desired smoothing and signal to noise ratio (S/N) ; generally S/N improves in a square root relationship to the number of cycles accumulated.
  • S/N smoothing and signal to noise ratio
  • sample tube composition can distort readings. If glass is not used (and it is preferred to avoid glass in industrial usage) , then the replacement should not contain hydrogen. But fluorocarbons can be effective in several applications since signals from fluorine appear far from resonance. These signals can be distinguished from hydrogen at the levels of sensitivity required and if desired can be filtered (or distinguished) . In other cases of higher sensitivity measurements, e.g., for gauging relative proportions of amorphous and crystalline species in mixtures thereof, the sample container should be glass or non-protonic ceramic. In some instances, however, fluorocarbon or reinforced fluorocarbon can be used acceptably for polymer measurements.
  • the point is to avoid sample containers with species that can couple with transmitted energy and generate a FID decay curve mimicking the samples. Since the regression analysis involves ten variables residing in an eleven dimensional space (or nine variables residing in a ten dimensional space for the case when the slower modified Gaussian function is replaced by the slower Gaussian function) , the results cannot be graphed. But the measurements obtained from the model represented in the present invention can be favorably compared to the results obtained from accepted off-line measuring techniques.
  • FIG. 6 shows a calibration curve of such polypropylene xylene solubles, as measured by the present invention (y axis) vs. standard methods, illustrating the efficacy of the present invention.

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Abstract

On décrit un système de résonance magnétique nucléaire (NMR) pulsée conçu pour des mesures industrielles, comprenant un système de traitement d'échantillons (P, LI, V1, V2) et des commandes (104) du système utilisateur afin d'établir des courbes numérisées (C) de la désintégration par induction libre (FID), à partir desquelles sont déterminées les composantes gaussiennes rapides, les composantes gaussiennes modifiées moins rapides ou, de préférence, les composantes gaussiennes moins rapides et les composantes exponentielles à l'aide de la technique d'itération Marquardt-Levenberg et à l'aide de techniques de régression de sorte qu'une corrélation puisse être établie entre les composantes des courbes et les quantités physiques des noyaux cibles.
PCT/US1995/014646 1995-01-10 1995-11-09 Analyse par resonance magnetique nucleaire du polypropylene en temps reel WO1996021866A1 (fr)

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AU43644/96A AU4364496A (en) 1995-01-10 1995-11-09 Nmr analysis of polypropylene in real time

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US08/371,091 1995-01-10

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107389719A (zh) * 2017-06-08 2017-11-24 内蒙古中煤蒙大新能源化工有限公司 一种聚丙烯粉料中二甲苯可溶物含量测定的方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993010468A1 (fr) * 1991-11-20 1993-05-27 Auburn International, Inc. Analyse amelioree par resonance magnetique en temps reel, a usage industriel
US5302897A (en) * 1992-05-19 1994-04-12 Auburn International, Inc. NMR analysis of polypropylene in real time

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993010468A1 (fr) * 1991-11-20 1993-05-27 Auburn International, Inc. Analyse amelioree par resonance magnetique en temps reel, a usage industriel
US5302897A (en) * 1992-05-19 1994-04-12 Auburn International, Inc. NMR analysis of polypropylene in real time

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107389719A (zh) * 2017-06-08 2017-11-24 内蒙古中煤蒙大新能源化工有限公司 一种聚丙烯粉料中二甲苯可溶物含量测定的方法

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