EP1480532B1 - Device for the simultaneous, continuous measurement and regulation of the acetate and triacetine level in filter rods of the tobacco-processing industry - Google Patents

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

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

Cigarette filters are an essential, quality-relevant component of cigarettes, which is why great effort is made in the process of making the Filter rods to optimize quality. It is important to pay attention to the most goal-oriented Regulation of the procedure, which of course depends on one precise and fast characterization of the quality of the products in the In an optimal case, this is done using an online procedure.

For the characterization of filter rods in the cigarette industry, parameters, such as diameter, acetate weight and triacetine content and draw resistance. For the determination of acetate weight, draw resistance and Triacetingehalt are usually used off-line methods. The determination of the acetate weight takes place Gravimetric, by determining the gross weight of the bars and of which the Degradable mass of wrapping paper, glue and triacetin. Paper and glueing are also determined gravimetrically, this being largely is process-independent parameters. To determine the triacetin content Different methods are used. First, the weight a defined number of filter rods with and without triacetin. The difference from both measurements then gives the triacin content. This procedure has the Disadvantage that it can only rarely be used, or in case of frequent use, leads to high amounts of waste. There are also methods for triacetin determination on finished filter rods. Here are some examples of the extraction of the Triacetins with a suitable solvent and determination of triacetin content by a laboratory method, such as gas chromatography.

A further method, which may 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 Oberflächenmeßmethode and the infrared beam only a few wavelengths deep into the material to be measured. Thus, the measurement result is highly dependent on the migration behavior of the plasticizer, but also on the fiber fineness and the packing density of the filter material used.

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

For this reason, on - line determination methods of the Acetate weight used, which are also used to regulate the process can. For example, DE 28 15 025 describes the measurement of density and thus the mass of the finished filter strand by means of a beta emitter. This method So it makes it possible to determine the mass of the finished filter rod, wherein the Mass in this case additively composed of the acetate mass and the applied Triacetin. The determination of Triacetingestaltes takes place at this Method according to the off - line method already described above. The method is suitable with restrictions already for the regulation of the total mass of Filter rods, but with the restriction that the density determination using beta - Spotlight can not detect humidity fluctuations of the measured material.

Another, quasi, on-line determination is described in DE 31 49 670 A1. Here, the amount of acetate introduced is determined by the filter Tow bales are positioned on a scale and during the manufacturing process continuously recorded the consumption of material. With simultaneous determination of Number of sections (filter rod sections) per unit time can be combined close these two quantities to the amount of acetate consumed per filter rod.

In addition, if the final weight of the filter rods is determined by external weighing, results from the difference between consumed material and actual filter rod mass the applied triacetin amount. This method also has the disadvantage that it can only be described conditionally as an on - line procedure, since it is an additional one off - line weight determination of the finished filter rods required. The frequency the triacetin values obtainable by this method are determined by Frequency of externally determined gross weight determinations. As for this in turn Filter rods must be taken from the product flow, this provision is also associated with a non-negligible amount of waste. The scales also have the disadvantage that disturbances caused by certain tow defects are not can be detected. One of these disturbing factors would be e.g. the failure of one Spinneret during the production process of the filter Tows with the effect that briefly 2 to 5% of the nominal total titer is missing. This ultimately leads to for the same amount of consumption, measured by the weight loss of the bale, the filter rods become about 2.5% lighter. This would result in a too small triacetin content pretend. In addition, with the help of this method Short-term fluctuations in both the amount of acetate and triacetin do not determine.

Another disadvantage of this method is that when determining the amount of acetate the moisture of the acetate is not taken into account. The equilibrium moisture of cellulose acetate under normal conditions is about 5.5% by weight. Under normal production practice, the initial moisture of a filter may be conditional due to changed process parameters in the filter tow production between vary about 3.5 and 7 wt .-%. This variation leads to relative inaccuracy at the mentioned weight determinations for the amount of triacetin and acetate. For the sake of completeness, it should be mentioned here that, in addition, the final moisture, and thus the gross weight of the finished filter rods, significantly affected can be by changing process parameters in the filter rod production. By way of example, parameters such as the room climate, the processing speed are mentioned here and the temperature and humidity of the air at the spreader nozzles.

The present invention is based on the object discussed above Disadvantages of the prior art remedy and a device for simultaneous, continuous measurement of acetate and triacetin mass and regulation of Describe manufacturing 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 control of the filter material and plasticizer mass, comprising a processing part AF for processing the supplied filter Tows, a format device F for forming a wrapped filter strand and an integrated in the processing part metering device for metering plasticizer, characterized in that sensors for detecting the mass flow of filter tow material M ₁ , as well as sensors for detecting the sum of the mass flow of filter tow material and plasticizer mass M ₂ , are present in the device, the device comprising a measuring and control device which is connected to the Sensors for measuring the mass flows M ₁ and M _{2 is} coupled such that both the filter material and the plasticizer mass can be measured and controlled independently.

In a preferred embodiment of the invention are, seen in the direction of the filter strand, before and after the metering device for the plasticizer sensors S _m1 ; S _m2 for detecting the length-related mass m ₁ , m _{2 of} the continuous filter strand and sensors S _v1 ; S _v2 for detecting the current velocities v ₁ and v _{2 of} the continuous filter train, wherein the respective mass flow from the products of m ₁ xv ₁ = M ₁ and m ₂ xv ₂ = M ₂ results.

The sensors used S _m1 , S _m2 , S _v1 and and. S _v2 can in principle be arranged at different points of the overall apparatus, wherein it is essential for the invention that, viewed in each case at running speed of the filter strand, the sensors marked "1" are located in front of the metering device and the sensors labeled "2" are located after the same , The first mass sensor S _m1 and speed sensor S _v1 can thus be located at any point between the ball outlet and metering device.

In an advantageous embodiment, the sensor S _v1 for detecting the speed v ₁ and the sensor S _m1 for detecting the length-related mass m ₁ are arranged directly adjacent.

By "immediately adjacent" is meant that they are in the direction of the course of the filter strand are directly behind each other, without being between them another element of the device is located. If the sensors work without contact, it may also be possible to measure in the same place. This ensures that speed and length-related mass at a point of the filter strand detected on the identical overall conditions with respect to the state of stretching of the filter Tows.

For reasons of measuring sensitivity, in particular the sensor S _{m1 concerned} , it has been found to be particularly advantageous if the mass flow M _{1 is determined} before entering the filter Tows in the processing part AF.

In a further advantageous embodiment of the invention, the sensor S _m2 , seen in the direction of the filter strand, arranged immediately in front of the cutting device, and as a sensor S _v2 , the measuring device is used for the tape speed.

The speeds v ₁ and v ₂ are preferably detected via optical sensors. Such optical sensors have the advantage that the relative velocity between two objects can be measured without contact. Thus, no mechanical interference takes place in the barrel of the filter string by the measurement. In such optical sensors, the surface structures of the filter strand are usually imaged on a grating where they produce a light modulation. With the aid of a photoelectric device, this light modulation is converted into a frequency proportional to the relative velocity. Other possibilities for non-contact measurement of the speed of a continuous material strand can be used, but remain unmentioned here.

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

It is particularly advantageous if, in addition to the length-related mass, at the same time and regardless of the mass determination, even the moisture content of the measured material can be determined, since only a complete mass balance in the Processing process (moisture, acetate - Triacetinmasse) can be determined.

Preferably, the length-related masses m ₁ and m _{2 are} therefore determined by means of microwave resonators as mass sensors.

EP 0 468 023 B1 describes how, by measuring two physical effects, the length-related mass and the humidity of a product which is located in the microwave field of a microwave resonator can be determined independently of one another. Microwave resonators form a standing wave at the resonant frequency, through which, with the aid of special openings and with dielectric material lined product guides, the acetate or filter material to be measured is moved. The special interaction between the standing microwave and the product changes the resonance characteristics of the microwave resonators. A great advantage of these resonators is that you can adapt by geometric design to a wide variety of applications and so achieved a large measuring effect and a large penetration into the product. In addition, unlike measurement techniques that do not use the resonance principle (such as the transmission or scattering techniques), the measurement of the losses of microwave energy due to absorption into the product has the quality of an exact measurement, which is not the case with transmission measurements due to the undetectable leakage is. A large number of exemplary embodiments of such resonators are listed in the cited patent specification: For planar material forms, as represented by the filter tow strand in the entire region of the processing section (AF) in front of the metering device, a sensor type whose microwave measuring field is in one embodiment is particularly suitable up to 3 cm wide and up to 30 cm long measuring gap can be made very homogeneous, so that the position of the product in the sensor is indifferent to the strength of the interaction between microwave and product. This "fork resonator" is an excited in the basic mode E ₀₁₀ resonator, which has been cut in the direction of the wall currents, so that there is a measuring zone with extremely homogeneous measuring field.

For a lateral one-sided measurement of the acetate strand before the plasticizer application Also suitable is a planar sensor with a standing wave above a planar one Surface, whose stray field starting from the sensor surface in the room decreases exponentially up to a maximum extension of 10 cm. One such sensor is described in EP 0 908 718.

Before the first spreader nozzle, before the filter tow material to a flat Strand is also aligned, the use of a closed, by a plastic - Sampling openwork resonator possible in E010 basic mode is excited and thus in the sample area a maximum measuring field, i. a maximum Has sensitivity.

In the area of the formed filter strand after the plasticizer application, the position Sm ₂ , the profile sensor is particularly suitable, with which, in particular, a high spatial resolution of less than 3 mm in the direction of the filter strand can be achieved, and which is also very good for measuring the homogeneity of the plasticizer application suitable is. Such a profile sensor is disclosed for example in EP 0 889 321. This sensor has a through hole perpendicular to its planar extension. The throughbore is bounded by metallic, longitudinally extending walls and substantially flat. This resonator is preferably filled with a dielectric. Its thickness is much smaller than its length, that is smaller than the thickness perpendicular to the transverse dimension.

The particular advantages of a microwave sensor with regard to the advantageous Embodiment according to claim 8 will be explained in more detail here. As direct measurands fall in the microwave resonator two techniques: the change the resonance frequency A and the increase of the half width B of the resonance curve to the empty state of the resonator. The first effect of the resonance frequency detuning A depends mainly on the shortening of the wavelength by the dielectric product, which is currently in the measuring field of the resonator (ie from the so-called real part of the dielectric constant). The second effect B stems from the Conversion of the microwave energy into heat, which only in Resonatorverfahren can be accurately measured (the "microwave oven effect" or the so-called. Imaginary part of the dielectric constant). Because both sizes are proportional in the same way are to the mass of the product in the measuring field, they are both suitable for Mass measurement. As a rule, parameter A is used for this purpose. on the other hand Both measured variables are dependent on the humidity in different ways. Consequently Thus, the quotient of both quantities B / A provides a mass - independent, only from the Humidity-dependent measured variable that can be calibrated against the moisture content of the material. With this size, on the other hand, the moisture influence on the mass value A can be compensated be so that two independent measures can be output: The moisture-independent mass and mass independent of moisture. In addition, the moisture information of the incoming acetate strand can be used be to moisture variations between different acetate bales like even within the bale by regulating the mass flow to compensate.

A big advantage of the microwave measuring method is the constancy of the once calibration, and their independence from variations in material parameters, such as changing the manufacturing parameters of the acetate, e.g. its total titre or thread size. The measuring technique has been on recently the achievement of a high measuring speed and precision optimized so that each after 0.1 milliseconds, a new humidity and mass value are output can, that is 10,000 values per second.

Alternatively, a density measurement can be done via beta radiation. Finally comes as mass sensor and an optical sensor in question, in which the Density is detected by scattered light measurements with infrared radiation. These sensors are well known to those skilled in the field of metrology and are therefore intended here will not be discussed further. However, the latter two methods have the Disadvantage that they do not detect the moisture of the filter Tows, which is why in particular the Triacetin determination is associated with a higher degree of inaccuracy, as in the microwave method.

According to a further preferred embodiment of the invention, the mass flow M _{1 can} also be determined by means of a baling scale according to DE 31 49 670 A1; whereby the already mentioned restrictions on moisture balance apply.

According to the invention, the output signals of all sensors are either a control device and / or supplied to a display device. If a control device is present, an automatic control of the device according to the invention carried out procedure, resulting in production conditions proves to be particularly advantageous. Alternatively, it is also possible an operator displays the signals displayed on the display device self-determined and executes the corresponding regulation. If both of the above Facilities are present, via the display device, a control of automatic regulation.

The control device is coupled in an advantageous embodiment with the drive of the processing part (AF) and the gear pump that the metering the required Triacetinmenge supplies.

The operation of the device according to the invention will be exemplified below with reference to the accompanying drawings. The only figure The drawing shows an embodiment of a device according to the invention for Production of cigarette filters.

A conventional filter rod machine, as known in the art, operates as follows:
The filter tow machine supplied filter tow is withdrawn from a bale 8 and introduced via a so-called gallows 9 from there into the processing device (AF). In front of the spreader nozzle 3 ", the sensors S _v1 and S _m1 are arranged side by side in the order.

The processing device (AF) generally comprises two spreader nozzles 3 and 3 ', a pair of brake rollers 1, through which the filter train is given a pre-stretch As well as draw roller pairs 2, which run at different speeds and subject the filter strand to drawing. The draw rolls can with be provided a thread-like surface, so that only parts of the spread continuous filter strand are detected and stretched. That way the individual filament groups, which make up the filter strand, shifted against each other. Furthermore, the processing device at its output a Deflection roller pair 5, by means of which the processed filter strand in one direction which is deflected for entry into the inlet nozzle and the inlet finger of the after-arranged format device F is suitable.

The drafting rollers 2, as well as the guide roller 5 are driven rollers, which with a Fixed speed ratio are operated to each other.

In the downstream format device F, the filter strand is gathered to the diameter of the future cigarette filter, wrapped with paper, and then cut the filter rods in a cutter 7 to the required length. Directly in front of the cutting device 7, the sensor S _{m2 is} arranged. As a means of transport for the filter strand, as already mentioned, a textile tape called a format tape is used, which tightly encloses the filter strand during the bonding process. As already mentioned, the speed of this conveyor 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 S _v2 .

The dosage of the acetate mass takes place in the filter rod machines according to the state of Technique in that the speed difference between processing part (AF) and format part (F) is changed, wherein usually the format part (F) is constant is held.

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

The metering device 4 is preferably between the drafting rollers and the deflecting rollers arranged in the processing device. The order of the plasticizer thus takes place on the completely spread filter strand. Usually the metering device consists of a spray box in which, for example, rotating Brushes are attached, which serve to finely atomize the plasticizer and to fling on the spreading fiber strand. As a softening agent usually triacetin or TEGDA (triethylene glycol diaceate) used. A A complete list of possible plasticizers can be found in DE 19951062 A1.

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

With the device according to the invention, it is possible in the production of Filter rods at the same time the amount of filter material or acetate and the amount of plasticizer to regulate.

In general, the mass flow of filter tow material is constant at all points of the device. For the products M ₁ and M ₂ from mass and speed applies, as long as without plasticizer is used: M 1 = M 2

And once you work with plasticizer: M 1 <M 2 . wherein the difference between M ₁ and M _{2 represents} a measure of the amount of plasticizer per filter rod.

The following applies: W = K x (M 2 - M 1 ) + C where W is the amount of plasticizer in mg per filter rod, and K and C are factors determined by calibration. These calibration factors are quantities that result from the sensor characteristic.

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

The same applies to the mass of spent filter tow material M per filter rod. This is linearly dependent on the product M ₁ .

The following applies: M = K 1 M 1 + C 1 where K ₁ and C ₁ in turn must be determined by calibration according to the sensor characteristic.
A control carried out with the device according to the invention is to be carried out so that the products M ₁ and M ₂ are kept constant in each case.

1. Bei gleichbleibender Geschwindigkeit von Aufbereitungsteil (AF) und Formatteil (F) verändert sich das Produkt M₂, wobei M₁ gleich bleibt. Dies ist ein Anzeichen dafür, daß zuwenig oder zuviel Weichmacher zudosiert wird. In diesem Fall ist die Drehzahl der Zahnradpumpe der Dosiereinrichtung so zu regeln, daß das Produkt M₂ auf den ursprünglichen Wert zurückgeführt wird.

2. Es ändert sich sowohl das Produkt M₁ als auch das Produkt M₂, und das Signal des Geschwindigkeitssensors S_v1 bleibt konstant, wobei sich das Signal S_m1 ändert. In diesem Fall handelt es sich um einen Fadenbruch. Hierunter versteht man den Ausfall einer Spinndüse beim Herstellungsprozess des Filter Tows mit der Auswirkung, daß kurzzeitig 2 bis 5 % des nominalen Gesamtfilters fehlen. Für den Fachmann sind die Auswirkungen eines solchen Störfalles klar vorhersehbar. Ohne Regelung führt dies zu einem Abfall von Acetatmenge im Filterstab, verbunden mit einer Verminderung des Zugwiderstandes.

3. Es ändert sich sowohl das Produkt M₁ als auch das Produkt M₂. wobei sich das Signal des Geschwindigkeitssensors S_v1 ändert und S_m1 konstant bleibt. In diesem Fall liegt als Ursache eine Änderung des Kräuselindex des Filterstranges vor. Auch dieser Störfall führt ohne Regelung, für den Fachmann klar erkennbar, zu einer Veränderung von Acetatmenge im Filterstab und Zugwiderstand.

In practice, it has been found that there are essentially three possible situations in the scheme:

1. At constant speed of processing part (AF) and format part (F), the product M _{2 changes} , with M ₁ remains 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 is to be controlled so that the product M _{2 is returned} to its original value.

2. Both the product M ₁ and the product M _{2 change} , and the signal of the speed _sensor S _v1 remains constant, with the signal S _m1 changing. In this case, it is a thread break. This refers to the failure of a spinneret during the manufacturing process of the filter Tows with the effect that briefly missing 2 to 5% of the nominal total filter. For the skilled person, the effects of such an accident are clearly predictable. Without regulation, this leads to a decrease in the amount of acetate in the filter rod, associated with a reduction in draw resistance.

3. It changes both the product M ₁ and the product M ₂ . wherein the signal of the speed _sensor S _v1 changes and S _m1 remains constant. In this case, there is a cause of a change in the Kräuselindex the filter strand. Also, this fault leads without regulation, clearly recognizable to the skilled person, to a change in the amount of acetate in the filter rod and draw resistance.

In both latter cases, the speed of the processing part (AF) is to be regulated so that the product M _{1 is returned} to its original value.

Of course, theoretically, all three cases can occur simultaneously. In this very unlikely case, first of all M _{1 is} returned to the original value as described, and then M _{2 is} readjusted as described in Case 1.
With some additional computational effort, when using microwave sensors, as already mentioned, it is also possible to carry out a product and process-related moisture correction. However, it is necessary to create sensor-specific calibration curves. However, a more detailed description of the procedure is omitted here.
In the case of a thread break (Case 2), can be interpreted, also with some computational effort, the scheme so that not a constant acetate weight as a target size, but a constant draw resistance is achieved. This type of control requires that the dependence on draw resistance, acetate weight and total titre be known. Such computational models exist. One of them is distributed by Rhodia Acetow under the name "Cable ©".

Claims (15)

1. Apparatus for manufacturing cigarette filters including a treatment portion (AF) for treating the supplied filter tow, a formatting device (F) for forming a sheathed filter strand and a metering device (4) integrated into the treatment portion for adding metered amounts of plasticizer, characterised in that provided in the apparatus there are sensors for detecting the mass flow of filter tow material M₁ and sensors for detecting the sum of the mass flow of filter tow material and plasticizer composition M₂, the apparatus including a measuring and regulating device, which is so coupled to the sensors for measuring the mass flows (M₁ and M₂) that both the filter material and the plasticizer composition can be measured and regulated independently from one another.
2. Apparatus as claimed in Claim 1, characterised in that provided upstream and downstream, seen in the direction of movement of the filter strand, of the metering device (4) for the plasticizer there are sensors (S_m1; S_m2) for detecting the mass with respect to length m₁, m₂ of the continuous filter strand and sensors (S_v1; S_v2) for detecting the actual speeds v₁ and v₂ of the continuous filter strand, the respective mass flow being given by the products of m₁ x v₁ = M₁ and m₂ x v₂ = M₂.
3. Apparatus as claimed in one of Claims 1 or 2, characterised in that the sensor (S_v1) for detecting the speed v₁ and the sensor (S_m1) for detecting the mass m₁ with respect to length are arranged directly adjacent one another.
4. Apparatus as claimed in at least one of the preceding Claims 1 to 3, characterised in that the sensors (S_m1; S_v1) for detecting the mass m₁ with respect to length and the speed v₁ are arranged before the entry into the treatment portion (AF).
5. Apparatus as claimed in one of the preceding claims, characterised in that the formatting device (F) has a cutting device and the sensor (S_m2) is arranged directly before the cutting device, seen in the direction of movement of the filter strand, and the measuring device for the formatting band speed is used as the sensor (S_v2).
6. Apparatus as claimed in at least one of the preceding claims, characterised in that the sensors (S_v1; S_v2) for detecting the actual speed v₁ and v₂ of the continuous fibre strand are optical speed sensors.
7. Apparatus as claimed in one of the preceding claims, characterised in that a sensor is selected for the sensor (S_m1 and/or S_m2) for detecting the mass with respect to length m₁ and/or m₂ which is suitable for determining the moisture content of the current material to be measured in addition to the masses with respect to length.
8. Apparatus as claimed in one of the preceding claims, characterised in that the sensor (S_m1 and/or S_m2) is a microwave sensor.
9. Apparatus as claimed in Claim 8, characterised in that the microwave sensor includes a fork resonator.
10. Apparatus as claimed in Claim 8, characterised in that the microwave sensor includes a closed, tubular resonator pierced by a plastic sample guide.
11. Apparatus as claimed in Claim 8, characterised in that the microwave sensor is in the form of a planar sensor.
12. Apparatus as claimed in Claim 8, characterised in that the microwave sensor is in the form of a profile sensor.
13. Apparatus as claimed in at least one of Claims 1 to 5, characterised in that the sensor (S_m1 and/or S_m2) for detecting the mass with respect to the length m₁ and/or m₂ of the continuous filter strand is a β radiation source and a β radiation detector.
14. Apparatus as claimed in at least one of the preceding claims, characterised in that a ball weighing machine is used as the sensor for determining the mass flow M₁.
15. Apparatus as claimed in at least one of Claims 1 to 13, characterised in that it includes a regulating device for automatically regulating the mass of filter material and plasticizer, the output of which is coupled both to the treatment portion (AF) and to the metering device (4).

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