EP1480532A1

EP1480532A1 - Device for the simultaneous, continuous measurement and regulation of the acetate and triacetine level in filter rods of the tobacco-processing industry

Info

Publication number: EP1480532A1
Application number: EP03706558A
Authority: EP
Inventors: Eberhard Teufel; Wolfgang Sexauer; Manfred Gerlitzki; Rainer Herrmann
Original assignee: Rhodia Acetow GmbH
Current assignee: Cerdia Produktions GmbH
Priority date: 2002-02-21
Filing date: 2003-02-21
Publication date: 2004-12-01
Anticipated expiration: 2023-02-21
Also published as: CN1635840A; CN100423660C; ATE300194T1; JP2005532040A; AU2003208749A1; WO2003070030A1; EP1480532B1; MXPA04008059A; JP3866714B2; DE10207357A1; US20050096202A1; DE50300871D1

Abstract

The invention relates to a device for producing cigarette filters, which comprises a conditioning section (AF) for conditioning the supplied filter tows, a formatting device (F) for producing a wrapped filter strand, a dosing device integrated into the conditioning section for dosing a softener. The device further comprises sensors that detect the mass flow of filter tow material M1 and sensors that detect the sum of the mass flow from filter tow material and softener compound M2. A measuring and regulation unit is coupled with the sensors for measuring the mass flows (M1 and M2) in such a manner that both the filter material and the softener compound can be measured and regulated independently.

Description

DEVICE FOR SIMULTANEOUS, CONTINUOUS MEASUREMENT AND CONTROL OF THE AMOUNT OF ACETATE AND TRIACETINE IN FILTER RODS IN THE CIGARETTE INDUSTRY

The invention relates to a device for the simultaneous, continuous measurement and control of the amount of acetate and triacetin in the manufacture of filter rods, in particular for use in the cigarette industry.

Cigarette filters are an essential, quality-relevant component of cigarettes, which is why great efforts are made to optimize the process for the production of the filter rods. It is important to ensure that the process is regulated as specifically as possible, which of course depends on the most precise and quick characterization of the quality of the products. In the best case, this is done using an online process.

To characterize filter rods in the cigarette industry, parameters such as diameter, acetate weight and triacetine content and tensile resistance are determined. Off-line methods are usually used to determine acetate weight, tensile strength and triacetine content. The acetate weight is determined gravimetrically by determining the gross weight of the rods and deducting the mass of wrapping paper, glue and triacetin from them. Paper and glue quantities are also determined gravimetrically, which are largely process-independent parameters. Different methods are used to determine the triacetine content. Firstly, the weight of a defined number of filter rods with and without triacetin is determined. The difference between the two measurements then gives the triacetine content. This method has the disadvantage that it can only be used rarely or, if used frequently, leads to high waste quantities. There are also methods for determining triacetin on finished filter rods. The extraction of the triacetin with a suitable solvent and determination of the triacetin content by a laboratory method, such as gas chromatography, are to be mentioned here as examples. Another method that should be mentioned is the determination of the plasticizer content by measuring the reflection of infrared rays in the near infrared range (see, for example: CANON AB; HUGHES IW: On-line measurement of triacetin in cigarette filter rods using near infrared reflectance spectroscopy;

Tob. Chem. Res. Conf., 1987.). This method has the considerable disadvantage that it is a surface measurement method and the infrared beam only enters the material to be measured a few wavelengths deep. The measurement result is thus strongly dependent on the migration behavior of the plasticizer, but also on the fineness of the fibers and the packing density of the filter material used.

All these methods have the disadvantage that, since they are carried out off-line, they only show snapshots of the current production.

For this reason, online determination methods of the

Acetate weight used, which can also be used for process control. For example, DE 28 15 025 describes the measurement of the density and thus the mass of the finished filter train using a beta emitter. This method therefore makes it possible to determine the mass of the finished filter rod, the mass in this case being additively composed of the acetate mass and the amount of triacetin applied. In this method, the triacetine content is determined in accordance with the offline methods already described above. The method is already suitable with restrictions for regulating the total mass of the filter rods, but with the restriction that the density determination by means of beta emitters cannot detect moisture fluctuations in the measured material.

Another, quasi, on-line determination is described in DE 31 49 670 AI. The amount of acetate introduced is determined by positioning the filter tow bale on a balance and continuously recording the consumption of material during the manufacturing process. When the number of cuts (filter rod sections) per unit of time is determined at the same time, a combination of these two measured variables can be used to infer the amount of acetate used per filter rod. If the final weight of the filter rods is also determined by external weighing, the difference between the material used and the actual filter rod mass results in the amount of triacetin applied. This method also has the disadvantage that it can only be described to a limited extent as an on-line method, since it requires an additional off-line weight determination of the finished filter rods. The frequency of the triacetin values obtainable by this method is determined by the frequency of the externally determined gross weight determinations. Since filter rods have to be removed from the product flow for this purpose, this determination is also associated with a non-negligible amount of waste. The balance also has the disadvantage that disturbances which occur due to certain tow defects cannot be detected. One of these disturbing factors would be, for example, the failure of a spinneret during the manufacturing process of the filter tow, with the effect that 2 to 5% of the nominal total titre is missing for a short time. Ultimately, this means that with the same amount of consumption, measured by the weight loss of the bale, the filter rods become about 2.5% lighter. As a result, this would simulate a low triacetin content. In addition, short-term fluctuations in both the amount of acetate and the amount of triacetin cannot be determined using this method.

Another disadvantage of this method is that the moisture of the acetate is not taken into account when determining the amount of acetate. The equilibrium moisture content of cellulose acetate under normal conditions is about 5.5% by weight. Under normal production practice, the initial moisture of a filter tow can vary between about 3.5 and 7% by weight due to changed process parameters in filter tow production. This variation leads to a relative inaccuracy in the mentioned weight determinations for the amount of triacetin and acetate. For the sake of completeness, it should also be mentioned here that the final moisture, and thus the gross weight of the finished filter rods, can also be significantly influenced by changing process parameters during filter rod production. Examples include parameters such as the indoor climate, the processing speed and the temperature and humidity of the air at the spreader nozzles. The present invention is based on the object of eliminating the disadvantages of the prior art discussed above and of describing a device for the simultaneous, continuous measurement of the acetate and triacetin mass and the regulation of the production process.

According to the invention, this object is achieved by a device according to claim 1. The device according to the invention for the production of cigarette filters with simultaneous regulation of the filter material and plasticizer mass, comprising a processing part AF for processing the supplied filter tow, a format device F for forming a covered filter strand and a metering device integrated in the processing part for metering in plasticizer characterized in that sensors for detecting the mass flow of filter tow material Mi and sensors for detecting the sum of the mass flow of filter tow material and plasticizer mass M2 are present in the device, the device containing a measuring and control device which is compatible with the Sensors for measuring the mass flows Mi and M2 is coupled such that both the filter material and the plasticizer mass can be measured and controlled independently of one another.

In a preferred embodiment of the invention, as seen in the direction of travel of the filter train, are located before and after the metering device for the plasticizer sensors Smi; Sm2 for detecting the length-related mass im, πu of the continuous filter train and sensors Svi; Sv2 for detecting the current velocities vi and V2 of the continuous filter train, the respective mass flow resulting from the products of rm x vi = Mi and πu x V2 = M2.

The sensors Smi, Sm2, Sviund and. In principle, Sv2 can be arranged at various points in the overall device, it being essential for the invention that, viewed in each case in the running speed of the filter train, the sensors indicated with "1" are located in front of the metering device and the sensors indicated with "2" behind the same. The first mass sensor Smi and speed Svi can therefore be located anywhere between the bale drain and the

Dosing device.

In an advantageous embodiment, the sensor Svi for detecting the speed vi and the sensor Smi for detecting the length-related mass mi are arranged immediately adjacent.

“Immediately adjacent” is to be understood to mean that they are located one behind the other in the direction of the course of the filter strand, without another element of the device being located between them. If the sensors work without contact, it may also be possible to measure at the same point. This ensures that the speed and length-related mass are recorded at a point on the filter strand at which identical overall conditions with regard to the drawing state of the filter tow prevail.

For reasons of measurement sensitivity, in particular relating to the sensor Smi, it has turned out to be particularly advantageous if the mass flow Mi is determined before the filter tow enters the preparation part AF.

In a further advantageous embodiment of the invention, the sensor Sm2, viewed in the direction of travel of the filter strand, is arranged directly in front of the cutting device, and the measuring device for the format tape speed is used as the sensor Sv2.

The speeds vi and V2 are preferably detected via optical sensors. Such optical sensors have the advantage that the measurement of the relative speed between two objects can take place without contact. As a result, there is no mechanical intervention in the course of the filter train due to the measurement. With such optical sensors, the surface structures of the filter strand are usually imaged on a grid, where they generate light modulation. With the help of a photoelectric component, this light modulation is converted into a frequency proportional to the relative speed. Other ways to Non-contact measurement of the speed of a continuous strand of material can be used, but are not mentioned here.

In principle, any sensors can be used as "mass sensors" with which it is possible to directly or indirectly measure the length-related mass of a continuous strand of material.

It is particularly advantageous if, in addition to the length-related mass, the moisture content of the material to be measured can be determined simultaneously and independently of the mass determination, since this is the only way to determine a complete mass balance during the processing process (moisture, acetate - triacetin mass).

The length-related masses mi and rr are therefore preferably determined with the aid of microwave resonators as mass sensors.

EP 0 468 023 B1 explains how the length-related mass and the moisture of a product located in the microwave field of a microwave resonator can be determined independently of one another by measuring two physical effects. At the resonance frequency, microwave resonators form a standing wave through which the acetate or filter material to be measured is moved with the aid of special openings and product guides lined with dielectric material. The special interaction between the standing microwave and the product changes the resonance properties of the microwave resonators. A great advantage of these resonators is that one can adapt to a wide variety of applications by means of a geometrical design and thus achieve a large measuring effect and a great depth of penetration into the product. In addition, in contrast to measurement techniques that do not use the resonance principle (such as the transmission or scatter measurement techniques), the measurement of the losses of microwave energy due to absorption into the product has the quality of an exact measured variable, which is not the case with radiation measurements due to the undetectable leakage losses is. A whole series of exemplary embodiments for resonators of this type are listed in the cited patent specification: forms, as represented by the filter tow strand in the entire area of the preparation part (AF) in front of the metering device, a sensor type is particularly suitable, the microwave measuring field of which can be formed very homogeneously in a measuring gap up to 3 cm wide and up to 30 cm long , so that the position of the product in the sensor is indifferent to the strength of the interaction between the microwave and the product.

This "fork resonator" is a resonator excited in the basic mode Eoio, which has been cut open in the direction of the wall currents, so that a measuring zone with an extremely homogeneous measuring field results.

A planar sensor with a standing wave above a planar surface, whose stray field decreases exponentially from the sensor surface into the room up to a maximum extension of 10 cm, is also suitable for a lateral one-sided measurement of the acetate strand before the plasticizer is applied. Such a sensor is described in EP 0 908 718.

In front of the first spreader nozzle, before the filter tow material is aligned to a flat strand, it is also possible to use a closed resonator, which is broken through by a plastic sample guide, which is excited in the E010 basic mode and thus a maximum measuring field in the sample area, i.e. has maximum sensitivity.

In the area of the formed filter strand after the plasticizer application, the position Srm, the profile sensor is particularly suitable, with which in particular a high spatial resolution of less than 3mm in the direction of the filter strand can be achieved, and which is also very suitable for measuring the homogeneity of the plasticizer application is. Such a profile sensor is disclosed, for example, in EP 0 889 321. This sensor has a through hole perpendicular to its areal extent. The through hole is delimited by metallic, longitudinally extending walls and is essentially flat. This resonator is preferably filled with a dielectric. Its thickness is much smaller than its length, that is smaller than the transverse dimension perpendicular to the thickness. The particular advantages of a microwave sensor with regard to the advantageous embodiment according to claim 8 will be explained again in more detail here. In microwave resonator measurement technology, two quantities are the direct measurement variables: the change in the resonance frequency A and the increase in the half-width B of the resonance curve compared to the empty state of the resonator. The first effect of the resonance frequency detuning A mainly depends on the shortening of the wavelength due to the dielectric product which is currently in the measuring field of the resonator (i.e. on the so-called real part of the dielectric constant). The second effect B results from the conversion of the microwave energy into heat, which can only be measured precisely in the resonator method (the "microwave oven effect" or the so-called imaginary part of the dielectric constant). Since both quantities are equally proportional to the mass of the Products are in the measuring field, they are both suitable for mass measurement. Usually parameter A is used for this. On the other hand, both measured variables are dependent on moisture in different ways. So the quotient of both variables B / A provides a mass - independent, This parameter can be used to compensate for the influence of moisture on the mass value A, so that two independent measured variables can be output: The moisture independent of the mass and that independent of the moisture In addition, the moisture information of the can shrink the acetate strands are used to compensate for moisture fluctuations between different acetate bales as well as within the bale by regulating the mass flow.

A great advantage of the microwave measuring method is the constancy of the calibration once carried out, and its independence from fluctuations in material parameters, such as the change in the production parameters of the acetate, for example its total titer or its thread size. The measuring technique has recently been optimized to achieve a high measuring speed and precision, so that a new moisture and mass value can be output after 0.1 milliseconds, ie 10,000 values per second. Alternatively, a density measurement can also be carried out using beta radiation.

Finally, an optical sensor can also be used as the mass sensor, in which the density is detected by means of scattered light measurements with infrared radiation. These sensors are well known to experts in the field of measurement technology and are therefore not to be discussed in more detail here. However, the latter two have the

Disadvantage that they do not record the moisture of the filter tow, which is why the triacetin determination in particular is more inaccurate than in the microwave method.

According to a further preferred embodiment of the invention, the mass flow Mi can also be determined by means of a bale scale according to DE 31 49 670 AI, the restrictions mentioned above relating to the moisture balance applying.

According to the invention, the output signals of all sensors are either fed to a control device and / or a display device. If a control device is present, the process carried out with the device according to the invention can be controlled automatically, which proves to be particularly advantageous under production conditions. As an alternative to this, it is also possible for an operator to detect the signals displayed on the display device himself and to carry out the corresponding control. If both of the devices mentioned are present, the automatic control can be checked via the display device.

In an advantageous embodiment, the control device is coupled to the drive of the processing part (AF) and the gear pump, which supplies the metering device with the required amount of triacetin.

The mode of operation of the device according to the invention is described in more detail below by way of example with reference to the accompanying drawing. The only figure in the drawing shows an embodiment of a device according to the invention for producing cigarette filters. A conventional filter rod machine, as is known from the prior art, works as follows:

The filter tow fed to the filter rod machine is drawn off from a bale 8 and introduced from there into the processing device (AF) via a so-called gallows 9. In front of the spreader nozzle 3 ", the sensors Svi and Smi are arranged side by side in the order.

The conditioning device (AF) generally comprises two spreader nozzles 3 and 3 ', a pair of brake rollers 1, by means of which the filter strand is pre-stretched, and pair of stretching rollers 2, which run at different speeds and subject the filter strand to stretching. The stretching rollers can be provided with a thread-like surface, so that only parts of the extended continuous filter strand are grasped and stretched. In this way, the individual filament groups that make up the filter strand are shifted against each other. Furthermore, the processing device has at its outlet a pair of deflecting rollers 5, by means of which the processed filter strand is deflected in a direction that is suitable for entry into the inlet nozzle and the inlet finger of the downstream format device F.

The stretching rollers 2 and the deflection roller 5 are driven rollers which are operated at a fixed speed ratio to one another.

In the downstream format device F, the filter strand is gathered to the diameter of the future cigarette filter, coated with paper, and the filter rods are then cut to the required length in a cutting device 7. The sensor Sm2 is arranged directly in front of the cutting device 7. As already mentioned, a conveyor belt for the filter strand is a textile belt, known as a format belt, which wraps the filter strand tightly during the gluing process. As already mentioned, the speed of this means of transport corresponds to the speed of the filter strand in the format part and thus after the metering device 4. This speed is measured by means of the sensor Sv2. The metering of the acetate mass takes place in the filter rod machines according to the prior art by changing the speed difference between the preparation part (AF) and the format part (F), with that of the format part (F) generally being kept constant.

The acetate mass can also be changed by other measures. For example, EP 0 629 356 B1 describes the regulation of the acetate mass by changing the brake roller pressure on the brake roller pair 1.

The metering device 4 is preferably arranged between the stretching rollers and the deflecting rollers in the processing device. The application of the plasticizer thus takes place on the completely spread out filter strand. The metering device usually consists of a spray box in which, for example, rotating brushes are attached, which serve to atomize the plasticizer finely and to spin it onto the spread fiber strand. Triacetin or TEGDA (triethylene glycol diaceate) are usually used as plasticizers. A complete list of possible plasticizers can be found in DE 19951062 AI.

The amount of plasticizer required for the process is usually supplied to the metering device 4 by means of a gear pump. The amount of plasticizer is dosed by changing the speed of the drive of this gear pump.

With the device according to the invention it is possible to control the amount of filter material or acetate and the amount of plasticizer at the same time in the manufacture of filter rods.

In general, the mass flow of filter tow material is constant at all points in the device. The following applies to the Mi and M2 products from mass and speed as long as you are working without plasticizer:

Mi = M2 And as soon as plasticizers are used:

where the difference between Mi and M2 is a measure of the amount of plasticizer per

Filter bar represents.

The following applies:

where W is the amount of plasticizer in mg per filter rod, and K and C are factors that are determined by calibration. These calibration factors are quantities that result from the sensor characteristics.

This calibration makes it possible not only to regulate the plasticizer content per filter rod, but also to measure it quantitatively and continuously, regardless of the filter tow specification used.

The same applies to the mass of filter tow material M used per filter rod. This is linearly dependent on the product Mi

The following applies:

Ki and Ci in turn must be determined by calibration according to the sensor characteristics.

A control implemented with the device according to the invention is to be carried out so that the products Mi and M2 are kept constant.

In practice, it has been found that there can be three main cases in the regulation: 1. If the speed of the preparation part (AF) and format part (F) remains the same, the product M2 changes, with Mi remaining the same. This is an indication that too little or too much plasticizer is being added. In this case, the speed of the gear pump of the metering device should be regulated so that the product M2 is returned to the original value.

2. Both the product Mi and the product M2 change. and the signal from the speed sensor Svi remains constant with the signal Smi changing. In this case it is a thread break. This means the failure of a spinneret in the manufacturing process of the filter tow with the effect that 2 to 5% of the nominal total filter is missing for a short time. The effects of such an accident are clearly predictable for the person skilled in the art. Without regulation, this leads to a drop in the amount of acetate in the filter rod, combined with a reduction in the tensile resistance.

3. Both the product Mi and the product M2 change, the signal from the speed sensor Svi changing and Smi remaining constant. In this case, the cause is a change in the ripple index of the filter train. This malfunction also leads to a change in the amount of acetate in the filter rod and tensile resistance without control, which can be clearly recognized by the person skilled in the art.

In the latter two cases, the speed of the processing section (AF) should be controlled so that the product Mi is returned to the original value.

Of course, all three cases can theoretically occur simultaneously. In this very unlikely case, Mi is first returned to the original value as described and then readjusted as described in case 1M∑. With some additional computing effort, when using microwave sensors, as already mentioned, a product and process-related moisture correction can also be carried out. However, this requires sensor-specific calibration to create curves. However, the procedure is not described in more detail here.

In the event of a thread break (case 2), the control can also be designed, with some computation, so that not a constant acetate weight as the target variable but a constant draw resistance is achieved. This type of regulation presupposes that the dependency on tensile resistance, acetate weight and total titer is known. Such calculation models exist. One of them is sold by Rhodia Acetow under the name "Cable ^® ".

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Claims

1. Device for producing cigarette filters, comprising a processing part (AF) for processing the supplied filter tow, a format device (F) for forming a coated filter strand and a metering device (4) integrated in the processing part for metering in plasticizers, characterized thereby that sensors for detecting the mass flow of filter tow material Mi as well as sensors for detecting the sum of the mass flow of filter tow material and plasticizer mass M2 are present in the device, the device including a measuring and control device which is used with the sensors for measuring the Mass flows (Mi and M2) is coupled such that both the filter material and the plasticizer mass can be measured and controlled independently of one another.

2. Device according to claim 1, characterized in that, seen in the direction of the filter train, before and after the metering device (4) for the Weichma- rather sensors (Smi; Sm2) for detecting the length-related mass mi, r of the continuous filter train and sensors (Svi; Sv2) are available for detecting the current velocities vi and V2 of the continuous filter train, the respective mass flow being obtained from the products of mi x vι = Mi and πu x V2 = M2.

3. Device according to one of claims 1 or 2, that the sensor (Svi) for detecting the speed vi and the sensor (Smi) for detecting the length-related mass mi are arranged immediately adjacent.

4. Device according to at least one of the preceding claims 1 to 3, characterized in that the sensors (Smi; Svi) for detecting the length-related mass rm or the speed vi are arranged before entering the processing part (AF).

5. Device according to one of the preceding claims, characterized in that the format device (F) has a cutting device and the sensor (Sm2), seen in the running direction of the filter strand, is arranged immediately before the cutting device and as a sensor (Sv2) the measuring device for Format tape speed is used.

6. The device according to at least one of the preceding claims, characterized in that the sensors (Svi; Sv2) for detecting the current speed vi and V2 of the continuous fiber strand are optical speed sensors.

7. Device according to one of the preceding claims, characterized in that a sensor is selected as the sensor (Smi and / or Smi) for detecting the length-related mass mi and / or rm, which is suitable, in addition to the length-related masses, the moisture content of the current Measure good to determine.

8. Device according to one of the preceding claims, characterized in that the sensor (Smi and / or Sπώ) is a microwave sensor.

9. The device according to claim 8, characterized in that the microwave sensor comprises a fork resonator.

10. The device according to claim 8, characterized in that the microwave sensor comprises a closed, tubular, through a plastic sample guide broken resonator.

11. The device according to claim 8, characterized in that the microwave sensor is designed as a planar sensor.

12. The apparatus according to claim 8, characterized in that the microwave sensor is designed as a profile sensor.

13. The device according to at least one of claims 1 to 5, characterized in that the sensor (Smi and / or Sπώ) for detecting the length-related mass mi and / or rm of the continuous filter strand is a ß radiation source and a ß radiation detector.

14. The device according to at least one of the preceding claims, characterized in that a bale balance is used as a sensor for determining the mass flow Mi.

15. The device according to at least one of claims 1 to 13, characterized in that it contains a control device for automatic control of the filter material and plasticizer mass, which is coupled at its output both to the processing part (AF) and to the metering device (4) is.

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