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WO1996034269A1 - Nouveau viscometre capillaire a differentiel de pression et procede d'analyse - Google Patents

Nouveau viscometre capillaire a differentiel de pression et procede d'analyse Download PDF

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Publication number
WO1996034269A1
WO1996034269A1 PCT/US1996/004830 US9604830W WO9634269A1 WO 1996034269 A1 WO1996034269 A1 WO 1996034269A1 US 9604830 W US9604830 W US 9604830W WO 9634269 A1 WO9634269 A1 WO 9634269A1
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WO
WIPO (PCT)
Prior art keywords
die
capillary tube
measuring
pressure drop
solvent
Prior art date
Application number
PCT/US1996/004830
Other languages
English (en)
Inventor
Scot D. Abbott
Original Assignee
E.I. Du Pont De Nemours And Company
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 E.I. Du Pont De Nemours And Company filed Critical E.I. Du Pont De Nemours And Company
Publication of WO1996034269A1 publication Critical patent/WO1996034269A1/fr

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Classifications

    • 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
    • G01N11/02—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material
    • G01N11/04—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material through a restricted passage, e.g. tube, aperture
    • G01N11/08—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material through a restricted passage, e.g. tube, aperture by measuring pressure required to produce a known flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/50—Conditioning of the sorbent material or stationary liquid
    • G01N30/52—Physical parameters
    • G01N2030/524—Physical parameters structural properties
    • G01N2030/527—Physical parameters structural properties sorbent material in form of a membrane
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/62—Detectors specially adapted therefor
    • G01N2030/621—Detectors specially adapted therefor signal-to-noise ratio
    • G01N2030/625—Detectors specially adapted therefor signal-to-noise ratio by measuring reference material, e.g. carrier without sample
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • 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
    • G01N33/442—Resins; Plastics

Definitions

  • This invention relates to capillary viscometers. More specifically, it relates to differential pressure capillary viscometers which may be used alone to measure the viscosity of fluids or in combination with a chromatograph to obtain molecular size distribution information,
  • a capillary viscometer is often used to measure the absolute viscosity of a given fluid. For many purposes, however, it is necessary to know the relative viscosity of two fluids.
  • the viscosity measuring means may also be used to measure the relative viscosity of a sample liquid and a reference liquid or to determine the viscosity of the sample liquid independent of flow rate and temperature fluctuations.
  • Relative viscosity is of particular importance in polymer research and manufacturing since it can be used to measure molecular weights and to determine molecular weight distributions, which provide important information relating to the physical properties of polymers.
  • a comparison of the viscosity behavior of two polymers of the same molecular weight, for example, is used as a measure of the degree of branching.
  • One of the oldest means used to obtain such information is to measure the viscosity of a known concentration of a polymer in a solvent.
  • Inherent and intrinsic viscosities are important polymer characterization parameters.
  • the intrinsic viscosity provides an indication of the size of the polymer molecules.
  • the value of [ ⁇ ] is not a function of polymer concentration or the viscosity of the solvent medium.
  • K and a are Mark-Houwink viscosity constants, some of which are available in polymer handbooks.
  • Viscosity measuring means may also be used together with size exclusion chromatography to determine the molecular weight distribution of polymer materials.
  • Relative viscosity is often determined experimentally by measuring the absolute viscosity of each fluid separately with a viscometer and then calculating the ratio of the absolute viscosities.
  • Prior art viscometers have been designed to measure viscosities in a number of ways.
  • U.S. Pat. No. 4,627,271 and U.S. 4,578,990 assigned to the same assignee as the present application, disclose a method and apparatus for measuring either intrinsic or inherent viscosity of a solute in solution with a solvent which is independent of flowrate and temperature fluctuations.
  • the solution is passed through a first capillary tube and the solvent through a second capillary tube, which are in series and subject to the same flowrate, while the pressure drop across each is measured by a pressure sensor.
  • Signals corresponding to each pressure drop measurement are fed to an amplification means, such as a logarithmic amplifier, analog divider or high speed computer, where they are processed to determine either the mtrinsic or inherent viscosity of the solute independent of flowrate and temperature fluctuations.
  • T e disclosed method and apparatus can usually achieve a precision of about 1/1000.
  • the pressure signals for the first (sample) capillary tube Si and the second (reference) capillary tube S2 can be expressed as follows:
  • the relative viscosity ⁇ r obtained is thus independent of flowrate, since the flowrates through each capillary are designed to be the same.
  • the method and apparatus disclosed in these patents are subject to limitations regarding the pressure sensors themselves, typically pressure transducers.
  • fluctuations or errors in the no-flow zero values, Zi and Z2, for the pressure transducers can significantly affect the precision of the relative viscosity measurements, especially when small changes in relative viscosity need to be detected.
  • the no-flow zeroes are measured for die sample and reference transducers at no flow through the capillaries.
  • Most transducers are sensitive to absolute pressure, and since the absolute pressure measured is a function of flowrate, the no-flow zero values are also a function of flowrate. This means the no-flow zero values are only accurate within a limited flowrate range, causing error in the signals outside that flowrate range.
  • An objective of the present invention is to provide a method and means for measuring intrinsic or inherent viscosity of a solute in solution independently of flowrate and temperature fluctuations, in order to overcome problems due to variations in actual flowrate through a sample and reference capillary, thereby improving the precision of the viscosity measurements.
  • Another objective of this invention is to provide continuous flow control in an apparatus for accomplishing the above process in order to improve d e precision of the viscosity measurements.
  • the present invention provides a method for measuring the relative viscosity of a first and second fluid or liquid independently of flow rate and temperature fluctuations, which method comprises die steps of:
  • d e signal processor may be based on real time signal processing which processes die ratio of DPp/DP s in real time.
  • d e first fluid is a solvent
  • the second fluid is a ⁇ solution of a solute in said solvent.
  • the solute is a polymer or polymer composition, for example, having an molecular weight distribution. A measurement of the intrinsic or inherent viscosity of the solute can be obtained based on die relative viscosity.
  • the solute may be a fluid or a solid in pure form.
  • the present invention also provides an apparatus for accomplishing the above process, comprising: (a) a first capillary tube through which the first fluid can flow;
  • a second supply means for supplying the second fluid to flow through the second capillary tube comprising a means for introducing a sample material into the first fluid
  • a signal processor for receiving and processing the ratio of the pressure drop signals of DPp DP s for use in measuring either said relative viscosity or the intrinsic or inherent viscosity of the sample material independent of the flow rate and temperature fluctuations of the solution and solvent; wherein the improvement comprises
  • die means for measuring flowrate comprises the means for measuring the pressure DP S across the first capillary tube and the amplification means.
  • the sample material may comprise, for example, a compound, composition, or solution of a solute.
  • This invention may also be employed wim GPC (Gel Permeation
  • Fig. 1 is a schematic diagram of one embodiment of the viscometer of die present invention.
  • Fig. 2 is a schematic of another embodiment of die viscometer when used in connection witii GPC analysis. DETAILED DESCRIPTION OF THE INVENTION
  • the present invention employs two capillary tubes, preferably arranged in series, as described in U.S. Patents No. 4,578,990 and 4,627,271, incorporated by reference herein.
  • a pressure transducer is connected across each capillary to monitor simultaneously the pressure drop of fluid flowing through each tube.
  • the pressure drop measured across the first, or reference, capillary tube will correspond to a reference fluid, such as a solvent and will be designated as DP S .
  • the pressure drop across the second, or sample, capillary tube will correspond to a sample fluid, such as a polymer solution, and will be designated as DP p .
  • These measured pressure drops, DP S and DP p are men used to determine the inherent or intrinsic viscosity of the sample polymer and to determine the flowrate of the fluids.
  • the signals generated by the pressure transducers are fed to an analogue or digital signal processor, alternatively referred to as an amplifier.
  • the signal processor can be an analog divider, but is preferably a high speed computer. In the process and apparatus of this invention, the signal processor processes the pressure drop differentials in two ways: (1) as a ratio DPp/DP s and (2) as a flowrate based, for example, on DP S .
  • the signal processor can perform these functions in real time. Real time signal processing of die simultaneous pressure drops across die analytical and reference capillaries assists in eliminating die effects of flow rate and temperature fluctuations in the capillaries. It also eliminates the need to match die dimensions of d e capillaries.
  • the output of the signal processor is then a real time measure of die natural logarithmic of the relative viscosity, In ⁇ r .
  • the pressure measurement from the reference transducer can also be a real time measure of flowrate.
  • the signal processor can also store the calculated variables for post-processing.
  • the pressure drop DP signal generated by die pressure transducer is related to the viscosity of fluid flowing through the capillary in accordance widi the following relationship:
  • K is the instrument constant which is proportional to the capillary's length, 1, and diameter, d, as follows: 1/d 4
  • h r is e relative viscosity T
  • G j and G2 are the electronic gains in the DP signal, measured across die analytical and reference capillary, respectively.
  • the first term is a flow rate and temperature independent instrument constant of the capillary mismatch that can easily be eliminated by suitable zero offset calibration in the instrument electronics.
  • die solvent and sample capillaries are preferably arranged in a series fashion. It has now been found that controlling the flowrate of d e solvent and sample fluid flowing through the reference and sample capillary tubes, respectively, can very significandy and surprisingly increase the precision of the viscosity measurements obtained.
  • the flowrate control system employs a pressure measurement to determine the flowrate at a given point in combination with a controller which compares the measured flowrate to a predetermined setpoint and then determines the correct adjustment to the flow. This adjustment would be transmitted to die pump and the pump speed would be adjusted accordingly.
  • the flowrate can men be maintained within a predetermined limited range.
  • the flowrate of the solvent and sample are essentially equivalent.
  • the flowrate, dierefore, need only be measured at one point.
  • the pressure measurements from the reference pressure transducer, DP S is preferably employed for this purpose, since the material flowing through the capillary would not change and die transducer does not experience hydraulic upsets due to sample introduction.
  • a suitable pressure transducer is me Validyne ⁇ ! DP15-32-22- 66 differential pressure transducer commercially available from Validyne Corp. (Northridge, CA).
  • the signal processor is preferably micro-processor based, capable of manipulating the pressure measurement to obtain a flowrate.
  • a personal computer suitably modified may be employed as die signal processor, adapted with an A/D board such as Data Translation Corp. Model DT 2800/5716A A/D board.
  • the calculated flowrate is then transmitted to a flow controller.
  • the amplifying means may transmit signals pneumatically, electronically, or digitally, depending on the configuration of the recipient controller. Many flow controllers are known in the art.
  • Any flow controller which serves to control the rate of the solvent and polymer within about five percent of a given setpoint is suitable for use in the invention herein.
  • Various types of controllers can be used.
  • the controller receives die flowrate measurement from the amplifier, compares it with a pre-determined setpoint, and determines the needed adjustment to d e pump speed.
  • the needed adjustment to me flowrate may be determined in various ways.
  • Controllers may use model-predictive control or proportional-plus-integral control schemes, among others, to determine d e necessary adjustment to d e pump speed.
  • Suitable control software is commercially available, for example, Asyst®version 4.1 software commercially available from Kiedily Instruments Corp. A Maxon Corp. MMC ⁇ Linear servor controller can be employed to adjust d e pump speed.
  • Figure 1 illustrates one embodiment of the viscometer of the present invention which can be used in batch, or if a fractionating column is used to supply die sample capillary tube, continuous, sample viscosity determinations.
  • Two capillaries are arranged in series. The first is the reference capillary 10 through which only solvent flows. The second is die sample capillary 12 through which the solute-solvent solution will flow. As one example, this solute may be a polymer.
  • the capillaries are long tubes of small internal diameter formed of glass, metal or any odier suitable material. Connected across each respective capillary are pressure transducers 14 and
  • Each transducer will generate an electrical signal corresponding to me pressure drop across its capillary. These signals are fed to a signal processor 17.
  • Solvent is introduced from a reservoir 18 via a pump 20.
  • the pump speed is controlled by a flow controller 19 which adjusts die speed based on input from the process controller 17.
  • the pump can be of various types but is preferably a gear pump. When a relatively pulseless gear pump is used with feedback flow control, a constant, pulseless, flowrate of fluid results.
  • the polymer sample is injected into die solvent stream from a sample loop 22 via a sample injection valve 24, which may be a two-position 6-port valve.
  • a sample injection valve 24 which may be a two-position 6-port valve.
  • Valco CV6UHPA Valco CV6UHPA
  • the sample loop is located downstream from the reference capillary 10 but before the sample capillary 12.
  • Solvent is pumped to the reference capillary.
  • a flow resistor 32 provides a solvent flow by-pass around the sample injection valve 24. This ensures continuous flow during sample injection and reduces flow rate upsets caused by die valve switching during sample injection.
  • a concentration detector 34 such as a differential refractometer is placed at the end of die stream.
  • concentration detectors such as ultraviolet or infrared devices may be used depending upon die particular type of sample used. After it passes die concentration detector 34, the sample stream empties into a waste receptacle 36. Where die concentration of d e sample is known, a concentration detector is not needed in order to calculate either die inherent or intrinsic viscosity of me polymer.
  • the viscometer of Figure 1 will generate two separate signal detector traces for recording.
  • the signals from pressure transducers 14 and 16 by employing a signal processor such as an analog divider or high speed computer, will be processed to generate a viscosity (ln ⁇ r ) trace.
  • the signal from pressure transducer 14 will also be processed by die signal processor to generate a direct indication of flowrate. This flowrate is fed to die flow controller 19 and is used to determine needed adjustments to die pump speed.
  • the concentration detector 34 will generate a concentration trace.
  • the signals from the pressure transducers can be processed in real-time or stored for further processing at a later time.
  • FIG. 2 illustrates a second embodiment of the viscometer of the present invention where like elements are designated by the same reference numerals.
  • the viscometer here is used as a GPC-viscosity detector, but it should be understood that other separation devices could also be used.
  • a GPC column set 40 is located between die sample loop 22 and injection valve 24 and d e sample capillary 12. It should be noted that the relative positions of the sample (for example, polymer solution) capillary 12 and reference (solvent) capillary 10 have been reversed in this embodiment.
  • a large depository column 42 has been added and die concentration detector 24 is located between the analytical and reference capillary. The purpose of the column 42 is to dilute the polymer-solvent solution with solvent so tiiat die reference capillary 10 essentially has only solvent passing through it during die detection operation.
  • GPC-viscosity detector While the operation of the GPC-viscosity detector will be described with reference to the schematic of Figure 2, it should be understood d at die viscometer of Figure 1 could have been used also, modified only by adding a GPC or other SEC column set between the sample injection loop 22 and die sample capillary 12. Likewise, widi the arrangement of Figure 1, column 42 is not necessary.
  • a multicomponent polymer mixture sample is injected through sample loop 22 and valve 24. The sample is carried by the solvent and is introduced into the GPC column 40 where the polymer molecules are separated according to size. The large molecules are eluted first at die other end as described earlier.
  • the concentration detector 34 detects each polymer component and provides a concentration signal at the elution time corresponding to each successively smaller molecular weight polymer component.
  • the DP viscosity detection traces will also occur at the corresponding retention time since each component will generate a pressure drop signal across the sample capillary 12 as it is eluted from die GPC column set 40.
  • the DP signals are fed to a signal processor or amplifier, preferably a computer, which will process them as explained above.
  • the DP S signal is fed to the computer or other signal processor, and resulting flowrate measurements are fed to die flow controller 19.
  • the foregoing also improves the independence of die present invention to temperature fluctuations.
  • temperature control is important in conventional capillary viscometers since small temperature variations in d e liquids can gready effect the accuracy of the viscosity measurements.
  • the invention herein provides a much more stable heat flux experience for each parcel of fluid as it passes dirough the system, and thus produces more nearly identical temperatures for d e fluids in me sample and reference zones of the instrument.
  • the measurements yielded an average standard deviation of 0.0224, and an average relative standard deviation of 0.0166.

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Abstract

Dispositif permettant de mesurer la viscosité intrinsèque ou inhérente d'un soluté en solution avec un solvant, viscosité indépendante des variations de débit et de température. Le solvant passe par un tube capillaire (10) et la solution passe par un deuxième tube capillaire (12) en série par rapport au premier et la chute de pression se produisant le long de chacun de ces tubes est mesurée. Des signaux correspondant au rapport des mesures de la chute de pression et du débit (dérivés de la chute de pression dans le premier capillaire) sont transmis à un dispositif de traitement des signaux dans lequel ils sont traités pour déterminer soit la viscosité intrinsèque soit la viscosité inhérente du soluté indépendamment des variations de débit et de température. Ce dispositif de mesure de la viscosité peut également être utilisé conjointement avec une chromatographie par perméation sur gel pour déterminer la répartition du poids moléculaire des matériaux polymères.
PCT/US1996/004830 1995-04-28 1996-04-10 Nouveau viscometre capillaire a differentiel de pression et procede d'analyse WO1996034269A1 (fr)

Applications Claiming Priority (2)

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US43136595A 1995-04-28 1995-04-28
US08/431,365 1995-04-28

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1949060A4 (fr) * 2005-10-12 2013-12-04 Malvern Instr Inc Viscosimetre multicapillaire ameliore et procede
EP2885621A4 (fr) * 2012-08-20 2016-04-27 Us Health Viscosimètre à capillaire et dispositif de mesure différentielle multi-échelle de la pression
CN106501127A (zh) * 2016-10-17 2017-03-15 大港油田集团有限责任公司 调剖用凝胶动态性能评价方法及装置
WO2019060716A1 (fr) * 2017-09-25 2019-03-28 Freenome Holdings, Inc. Méthodes et systèmes d'extraction d'échantillon
CN113634027A (zh) * 2021-07-04 2021-11-12 林哲鑫 一种抽滤实验装置及方法
CN114486630A (zh) * 2021-12-23 2022-05-13 西安交通大学 一种测量装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3548638A (en) * 1967-10-05 1970-12-22 Toray Industries Apparatus and method for continuously determining viscosity
JPS5838837A (ja) * 1981-08-31 1983-03-07 Toray Ind Inc 細管式粘度計
US4578990A (en) * 1984-11-07 1986-04-01 E. I. Du Pont De Nemours And Company Differential pressure capillary viscometer for measuring viscosity independent of flow rate and temperature fluctuations
US4790668A (en) * 1988-01-19 1988-12-13 Westvaco Corporation Viscometric thermometer

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3548638A (en) * 1967-10-05 1970-12-22 Toray Industries Apparatus and method for continuously determining viscosity
JPS5838837A (ja) * 1981-08-31 1983-03-07 Toray Ind Inc 細管式粘度計
US4578990A (en) * 1984-11-07 1986-04-01 E. I. Du Pont De Nemours And Company Differential pressure capillary viscometer for measuring viscosity independent of flow rate and temperature fluctuations
US4790668A (en) * 1988-01-19 1988-12-13 Westvaco Corporation Viscometric thermometer

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 007, no. 121 (P - 199) 25 May 1983 (1983-05-25) *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1949060A4 (fr) * 2005-10-12 2013-12-04 Malvern Instr Inc Viscosimetre multicapillaire ameliore et procede
EP2885621A4 (fr) * 2012-08-20 2016-04-27 Us Health Viscosimètre à capillaire et dispositif de mesure différentielle multi-échelle de la pression
CN106501127A (zh) * 2016-10-17 2017-03-15 大港油田集团有限责任公司 调剖用凝胶动态性能评价方法及装置
CN106501127B (zh) * 2016-10-17 2019-04-12 大港油田集团有限责任公司 调剖用凝胶动态性能评价方法及装置
WO2019060716A1 (fr) * 2017-09-25 2019-03-28 Freenome Holdings, Inc. Méthodes et systèmes d'extraction d'échantillon
US11781959B2 (en) 2017-09-25 2023-10-10 Freenome Holdings, Inc. Methods and systems for sample extraction
US12247905B2 (en) 2017-09-25 2025-03-11 Freenome Holdings, Inc. Methods and systems for sample extraction
CN113634027A (zh) * 2021-07-04 2021-11-12 林哲鑫 一种抽滤实验装置及方法
CN114486630A (zh) * 2021-12-23 2022-05-13 西安交通大学 一种测量装置

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