DE2108047A1 - Method and device for determining the monomer content of a copolymer in the liquid stream of this copolymer - Google Patents

Description

DR.-ING. WALTER ABITZ DR. DIETER F. MORF DR. HANS-A. BROWN

Patent attorney

Drti. Pattnlanwältt Abili .. Morf, Brauns • Month. " U, PoiKodi IM 10"

February 19, I97I

Postal address 8 Munich 80, (»ottfach 86010?

Pienzenauerstraße Tel. 433225 and 486415 Telegram “i Chemindut Munich (O) 523992

ACS 8739

NATIONAL DISTILLERS AND CHEMICAL COIiPOKATION 99 Park Avenue, New York, New York

Method and device for determining the monomer content of a copolymer in the liquid stream of that copolymer

The invention relates to a method and apparatus for determining the proportion of a monomer ¹ in liquid stream opolymers this copolymer.

Laboratory tests have shown that the dielectric Constant of opolymer is composed of monomers with different dielectric constants and with the differences in the proportion of monomers of the co-

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polymers changes. The invention is based on the assumption that, firstly, the dielectric constant in connection with the kit changes of the monomer content in the copolymer and, secondly, that a capacitive test, which depends on the dielectric constant of the copolymer stands in any time interval, can be used as a guide for the composition (i.e. the monomer content 5 to find at this time, and finally, the invention thirdly assumes that capacitance measurements in connection with the monomer content in the copolymer stand.

The use of capacity checks in various flow processes is already known. For example, U.S. Patent 3,273,058 discloses a capacity test for determining the moisture content of coal on a conveyor. Reference should also be made to patents 3,067,305, 3,188, 565 and 3,233,452, which disclose the use of capacity samples in oil cushions to measure contamination. Finally, US Patents 2,540,146, 2,765,441 and 2,020 V87 show the use of capacitance measurements to determine the thickness and composition of cured plastic coatings on wire. While the disclosure of the use of the capacity probes for the purpose of measuring undesired impurities is hereby disclosed, none of the patents mentioned shows the use of a capacity probe in a liquid copo-

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polymer stream for the purpose of measuring the composition of this copolymer. These patents do not even disclose the need to conduct this test at a point in a liquid at which the temperature, pressure and condition of the end product remain essentially constant. As will be explained in the following, an arrangement of this type in a copolymer stream enables a precise analysis of the composition of an opolymer to be carried out. {

While the invention is described in connection with the capacitance measurement of a capacitive detector which is in contact with a polyethylene-vinyl acetate copolymer and therefore the vinyl acetate component is measured, it should be made clear that the invention is not limited to this. "It is thus noted that in Within the scope of the invention, other copolymers can be used which have different dielectric constants. These include copolymers of olefins and olefinically saturated acids and acids such as ethylene-vinyl acetate, ethylene-ethylene-acrylate, ethylene-methyl Methaerylates, propylene vinyl acetates, ethylene acrylic acid, styrene methyl methacrylates, butene f thy! Acrylates and the like, other copolymers.

Materials, the analysis of which in the context of the invention particularly It is easy to understand that the copolymers are of styrene or lower alkenes, namely those with two to four carbon atoms (e.g. ethylene, propylene and N-butene)

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with (1) vinyl esters of low alkaline and replaced alkaline acids, namely esters of alkaline acids with one to four carbon atoms (e.g. ant, vinegar, Chloroacetate, phenyl, propionic and isobutyric acid), (2) Cv-C * alkenic acids, i.e. acrylic and methacrylic acid or O) with alkyl esters of Cx-C ^ alkenic acids, i.e. Athy! Acrylates, methyl methacrylates and. like that.

The invention now relates to a method for determining the monomer content in a copolymer, wherein the monomers have different dielectric constants that come into contact with a capacitive detector, which react to the dielectric constant of the liquids in a flux of the copolymer, namely in a zone with relatively constant temperature and constant pressure, the capacity of the capacitive Detector is measured while it is in contact with the liquid flow, and then is the value of the capacitance measured in this way is compared with a certain reference value.

The invention also relates to a device for measuring the monomer content in an olefin ester or acidic copolymer in liquid plastic composition. The invention consists initially in that a device for measuring capacitance and a device for introducing this device into this assembly

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■ ACS 8739

settlement · is present, so that the plastic fluid comes into contact with the I / Inge of this device, and wherein a device is coupled to the capacitance measurement which indicates an output which is the mono "' concerns in the copolymer.

The invention also relates to a process for the production of a copolymer from monomers with ver j • Different dielectric constants, with an improvement the control of the proportion of monomers in the copolymer it is provided that a continuous recording of changes from a certain reference value of the capacity of the liquid flow in the copolymer into a zone. ■; iit relatively constant temperature and constant Pressure includes, a device for transmitting these changes to a control device for control of the supplied Konomer share and a facility for 'control of the changes to the

■ - ■ - j position of the added monomer portion is provided, | so that the capacity is brought closer to the reference value will.

Further advantages and details of the invention emerge from the description that now follows of some exemplary embodiments referring to the drawing. In this aeigen:

θΙώθ devicej which does not need to scale to 3ztü , according to the invention, partially

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ACS 8731? *

for measuring the composition of liquid copolymers and
t

Fig. 2 shows a device (which is not to scale needs to be) with a further embodiment, the invention, partially cut, for ■ Measurement of the composition of copolymer liquids.

According to FIG. 1-, a housing arrangement 10 and a capacitance treadmill 12 of a known type with a linear flow scale are illustrated. The housing 10 can comprise the continuously graduated unit typically used in the manufacture of polyvinyl acetate copolymers. But it is of course clear that the capacitance measurement can be made at any point in the process sequence where the temperature, pressure and the stage of the end product remain essentially constant. The housing 10 here shows a channel 14 at which point the liquid plastic is fed into the housing from a source 15 of copolymeric material. The channel 14 leads to a suitable pump 16, which is driven by the drive 1? is set in motion, which may be an electric motor, so that the plastic material is introduced into the channel 18 of the body 10 with controlled pressure. Preferably, the pressure in channel 18 'will be between 1.03 and 21.1 kg / cm ² (100 to 300 psi)

ACS 8759

a corresponding control of the speed of the drive 17, or by a not illustrated Gear transmission held, which connects the motor 17 to the pump 16. The speed control can of course can also be done in a different way. The liquid plastic now reaches the end 18 of the capacity test VJ in channel 20 and then flows to the outlet channel 21 and into a next section of the procedure.

The capacitance sample 19 is made of stainless steel, which can be lightweight and coated with polytetrafluoroethylene to prevent possible sticking of the copolymer to the sample. This can be a problem with the ethylene-vinyl acetate polymer which contains 35 ^c ß> and more vinyl acetate. The sample is attached to the housing 10 by means of an insulating sleeve 22 which isolates the sample 19 from the housing 10.

A suitable heating body, which is formed, for example, by the heating coil 25 ′, is attached to the body 10. Of course, any desired radiator can be used. This heating coil 25 is with a appropriate temperature control device 24 connected to the the electrical energy supplied to the heating coil 25 controls. A temperature and pressure sensor 25 is connected to »

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finally attached in the channel 20, and the exit from this controls the pump drive 17 and the temperature controller 24 in order to keep pressure and temperature within certain limits keep constant. Any suitable control system for temperature control can be used, and one can also use an independent system for pressure control when controlling pressure and temperature are not an integral part of the process selected to produce the capacitance measurement.

The electrode end part 26 of the sample 19 is connected to the input of a protective or coaxial cable 27 which connects the capacitance meter 12 with the unit 19. The other input of the cable is connected to the housing 10 at point 28. A display instrument 30 is connected to the measuring device 12 in order to convert the read capacitance values into a percentage of the monomer and then to enable a reading. If desired, the units 12 and 30 can be used for. For the purposes of measurement, display and data transfer to a recording device or a process control device, a capacity Dynalog (manufactured by the Foxboro Company, Poxboro, Mass.) Can be exchanged.

In this embodiment of the invention the Capacitance meter 12 provides a reading which is a linear function of the capacitance of the sample 19 on the housing 10, the

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consists of He tall ". This reading may similarly Yi ei se to the dielectric constant of the liquid polymeric material be tuned to provide an indication to maintain the monomer content of the polymeric material and also to a direct relationship to the monomer component of to produce flowing polymeric material through the entire length of the sample, since changes in the vinyl acetate content of the polyvinyl acetate copolymer correspond to changes in the

Creating capacity is using the capacity pro | be .19 an effective means by which changes in the composition of the liquid plastic can be determined. What is more important is that the capacity probe 19 forms a device by means of which the direction and extent of the changes in the composition can be easily and continuously determined. In such an analysis of a polyethylene-vinyl-acetate copolymer it was found that the measured vinyl-acetate content was between a low value of 24 i ^a and a high fourth of 31 1 ^{a for} 36 hours. Through the

Invention may be changes in the vinyl acetate content in the copolymer of i a certain amount will be determined on slightly, and the settings required for stabilization of the portion can be easily performed.

In this regard, it should be noted that the Measurement accuracy due to temperature and pressure changes

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is easily influenced. Because of this, the sample 19 according to FIG. 1 preferably arranged in the stepped unit of the device forming the liquid plastic, in the known manner temperature and pressure kept within narrow limits and the polymerization reaction is essentially terminated. But it is clear that the sample is placed at some point in the process flow at which the temperature and, to a certain extent, the pressure as well, is properly controlled or the control can be made by an auxiliary device, and this results in a Stage of the end product that remains essentially constant.

A further exemplary embodiment of the invention is illustrated in FIG. The housing has dimensions of about 2 cm (3/4 ^M ) χ β cm C2 1/2 ") with couplings 31 of about 1.2 cm (1/2") which are welded to the opposite sides of the housing · Connecting rods 32 penetrate these couplings 31 and protrude through openings 33 into the housing 30. These rods 32 are isolated from the housing 30 by spacer seals 34 and can be sheathed with couplings 35 in the couplings 31. The rods 32 are connected with threaded bores 37 with right-angled condenser plates 36, which cut parallel to one another in the housing 30 at a certain distance, sB 0.5 cm (0.125 ") from one another.

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which are arranged. The rectangular capacitor plates can be made of stainless steel with a thickness of 0.3 cm (0.125 "), a width of 1.27 cm (0.5") and a length 6.35 cm (2.5 ").

The connecting rods 32 are at the ends 38 with two Lines 39 and 40 of a shielded or coaxial cable connected. This coaxial cable is then used connected to a capacitance meter (not shown) or an equivalent instrument, as already described in " Zuüamrjenhang with the device of Figure 1 described has been.

The housing 30 can be continuous in the sample line Separation device can be installed in a device for producing iithylenevinyl acetate copolymer. The direction of flow through this separation system is indicated in FIG. The rods 32 and the lines 39 and 40 are sheathed by pipes, not shown, to protect them from the environment. Here, the capacity is i The rate of copolymeric flow in the housing between the plates 36 was measured. It is preferred that the inner surface of the housing 30 with a polytetrafluoroethylene or a similar material cooperates to the flow of the copolymer through the housing 30 to facilitate

The device according to the invention can work together be used with a process control device,

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in order to continuously measure the proportion of monomer fed into the process for producing the copolymer. The invention The device registers changes in the composition of the copolymer and displays them Changes can be made visible for handling the control device, so that corresponding settings of the added monomer content can be carried out.

The method according to the invention is carried out by means of the device according to the invention described. It is clear that the method comprises a method for determining the monomer content of a copolymer, the monomers having different dielectric constants . The method comprises measuring the capacitance of a capacitive detector while it is in contact with a copolymeric current in a zone with a relatively constant temperature and constant pressure, and a comparison is made between the capacitance thus measured and a specific reference value. The specific reference values can be determined in various ways who the · One of these methods is. Prepare samples of a copolymeric liquid with known monomer proportions, keeping the temperature and pressure conditions similar to those that prevailed during the capacitance measurement of the capacitive detector, while contact is made with six different types of copolymeric liquid, which is an as yet unknown problem. Contains portion, whereby the capacitance of the capacitive detector is measured, väh-

rend this is in contact with various samples of the liquid, whereupon the so obtained Capacity values of each sample tested are recorded and related to the values of the samples set with the known monomer content.

Having established the reference values for any copolymer, it is relatively easy to use the Mone- 'J to determine iner fraction of the copolymer. As in Figure 3 shown can be the percentage of vinyl / acetate "in the case of a polyethylene vinyl acetate copolymer by the Contact of the capacitive detector described with this liquid take place, whereupon the capacity enjoyed and. is compared with the capacity of the reference liquid a

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Claims (10)

ACS 8739 Fattonal Distillers and Chemical February 19, 1971 Corporation Claims [1. ! Procedure for determining the monomer content of a Copolymers, the copolymer having different dielectric constants, characterized in that a capacitive detector, responsive to the dielectric constant of the liquid, with a liquid . Stream of the copolymer in a zone with relatively constant temperature and constant pressure is brought into contact, whereupon the capacitance of the detector is measured while it is still in contact with the desi * liquid current is located, after which the value of the thus measured capacity is compared with a certain reference value will. 2. The method according to claim 1, characterized in that, a copolymer of (a) styrene or an alkene with two up to four carbon atoms, and (b) an alkene acid, an alkyXester of an alkene acid or a vinyl ester an alkenoic acid is used. 3. The method according to claims 1 or 2, characterized in that » that the copolymer of an ethylene vinyl acetate is used. ACS 8739 4. Apparatus for measuring the monomer content of an olefin-olefinic ester or acid copolymer in a liquid-plastic state, characterized in that a capacitance measuring instrument and a device for introducing this instrument into the composition is provided so that the liquid plastic comes into contact with it over the length of the instrument, with a Coupling device for the instrument and a j device are provided to an output signal al to produce, which indicates the monomer content of the copolymer. · 5. The device according to claim 4, characterized in that the capacitance measuring instrument in a cell-shaped Housing is arranged through which the liquid plastic flows, and wherein, the capacitance measuring instrument is located at a point which is at substantially constant temperature and constant pressure is held. i 6. Apparatus according to claim 4 or 5, characterized in that the device for emitting electrical signals which represent changes in the dielectric constant, and wherein another device is provided, which interacts with the last mentioned, and also for the conversion *, * The electrical signals are formed into a visible signal of the monomer part, which the liquid plastic.composition at any time 109838/1537 shows. . ...... lh ■ ACS 873? 7. The device according to claim 6, characterized in that it has a capacitance meter with the capacitance measuring instrument is coupled by means of a coaxial cable. 8. Device "according to one of claims 4 to 7, characterized characterized in that the capacitance measuring instrument has a probe. 9. Device according to one of claims 4 to 7 »characterized in that the capacitance measuring instrument is a Has pair of plates that are substantially parallel to each other and to the direction of flow of the liquid Plastic are arranged. 10. Process for the preparation of one from monomers with different dielectric constant existing copolymer, characterized in that the monomer portion of the copolymer is controlled so that a continuous determination of the deviations from a certain reference value the capacity of the copolymeric liquid flow in a zone with a relatively constant Has temperature and constant pressure, whereupon the changes to the control device for controlling the added monomer portion are transferred, and also, depending on the changes, the added • adjusted monomer content so that the capacity comes closer to the reference value. - 16 109838/1537 Blank page