DE4013304A1 - METHOD FOR PRODUCING CIGARETTE FILTERS - Google Patents

Abstract

A process for manufacturing a cigarette filter from a section of a transverse-axially compacted fibre strand is described, in which the fibre strand consists of randomly oriented individual fibres of PHB (polyhydroxybutyric acid) or of a copolymer of PHB and PHV (polyhydroxyvaleric acid). The fibres spun in a centrifuge device are combined as a fibre strand and fed to the format device of the cigarette filter machine. The invention also relates to a cigarette filter manufactured in this way and to the use of spun PHB or of a copolymer of PHB and PHV for cigarette filters. <IMAGE>

Description

The invention relates to a method for producing Cigarette filters according to the preamble of claim 1 as well a filter thus produced according to the preamble of Claim 8.

It is common today to use cellulose acetate cigarette filters to manufacture. To manufacture the cigarette filters two independent process steps are required. First of all the fiber material by a nozzle spinning process with a Variety of spinnerets made. The individual continuous fibers are after spinning in a number of several Thousand combined into a fiber bundle and in one Crimping device crimped. The bundle is then crimped Tape stored and pressed together, for example in block form. For further processing of the fiber material the crimped tape is pulled off the block and initially opened by a stretching arrangement that causes that the individual fibers are shifted in their position against each other be, so that it is as voluminous, 3-dimensional Strand forms. The one in a format setup the desired diameter compressed with paper wrapped and processed into cylindrical filter rods becomes.

The manufacturing process for forming such a cigarette filter is relatively complex and requires a number of work steps. The main disadvantage of cellulose acetate Filtering, however, is that the filter material remains stable over long periods of time and therefore below Environmental protection issues disposal problems.  

Because a cigarette filter with good filter properties should be neutral in terms of taste, natural materials come under normal environmental conditions would allow easy disposal, as a rule not considered as base material. It is also difficult with natural materials the high demands on the To achieve tobacco smoke filtering that are being put in place today.

EP 01 77 207 A2 already describes medical applications a fiber material has become known, the individual fibers from PHB (polyhydroxybutyric acid) or copolymers PHB / PHV (Polyhydroxyvaleric acid) are produced. This fiber material is produced microbiologically and is suitable for Spinning out of a centrifugal spinning device. The generated Fibers form cloths that are suitable for the intended purpose can be pressed together or molded. At the specified Intended use of these materials for medicine, veterinary or dental medicine comes the special property the fiber materials, namely their biodegradability, especially to wear, because those made with these fibers Products, such as wound sutures, are broken down in the body itself so that later removal of the materials from the body is not required.

This material is a polyester with 4-5 carbon atoms per basic building block. For the production of the polymer is usually a microorganism in one aqueous medium on a suitable substrate, such as. B. Carbohydrates or methanol, which energy and carbon for Provides, cultivated. The substrate has to pass through the microorganism be assimilable. To accumulate the Promoting polymers becomes at least part of the cultivation carried out under the limitation of the nutrient required for  Growth of the microorganism is required, however is not necessary for polymer accumulation. Examples for suitable processes are in EP-PS 15 669 and 46 344 described.

In general, it is desirable to separate the polymer from the rest of the cell material to separate. This separation can be done by breaking up the Cells are made by treatment with acetone, which is the extraction of the polymer from the broken cells by treatment with a solvent in which the polymer is soluble, succeeds. Such methods are for example in the US 30 36 959 and 30 44 942 described in which as a solvent Pyridine or mixtures of methylene chloride and ethanol are specified. Other extraction solutions for the polymer in the form in which it is generated in the cells are, for example cyclic carbonates such as 1,2-propylene carbonate (US 41 01 533) or chloroform (US 32 75 610) and 1,2-dichloroethane (EP 15 123).

The prior art knows other materials and processes to break up the cells, for example ultrasonic vibration, Freeze drying, etc. Copolymers can also be made be the other hydroxycarboxylic acids such. B. Hydroxyvaleric acid and / or units derived from a diol, e.g. B. Contain ethylene glycol and / or dicarboxylic acids, e.g. B. isophthalic acid. There is an ester exchange, if that is microbiological produced polymer or copolymer with a Hydroxycarboxylic acid, or its lactone, e.g. B. pivalolactones, a diol, a dicarboxylic acid and / or one made therefrom Polyester is melted.

The HB polymer used below does not mean only 3-hydroxybutyric acid homopolymers, but also copolymers,  as described, provided the 3-hydroxybutyric acid units form at least part of the polymer chain.

The invention has for its object a method for Specify the manufacture of cigarette filters and cigarette filters, the relative under the influence of environmental influences are quickly decomposable, but still have good filter properties exhibit.

This object is achieved by that specified in claims 1 and 8 Invention solved. Advantageous developments of the invention are specified in subclaims.

The filter material according to the invention has the special Property on that within a short period of time, in particular in months to become completely harmless products, such as Converts carbon dioxide and water. The one with cigarette filters previously required disposal, such as incineration or landfill is only required to a limited extent, since the material according to the invention under the influence of Microorganisms decompose themselves.

The new material for the purpose of the invention has improved compared to conventional cellulose acetate filters Filter properties, especially with filter-ventilated Cigarettes improved the taste properties are or with the same taste intensity an increased Dilution of cigarette smoke is possible.

The invention is described below using an exemplary embodiment explained in more detail. Show it:

Fig. 1 is a longitudinal sectional view through a cigarette filters,

Fig. 2 is a schematic view of a device for the production of the filter material,

Fig. 3 is a schematic view of a plant for the production of the filter material with subsequent formatting device,

Fig. 4 is an electron micrograph of a cloth manufactured with a volume ratio of 2: 1 cold to warm air,

Fig. 5 is an electron micrograph of a yarn produced with a volume ratio of 1:10 cold to warm air,

Fig. 6 is an electron micrograph of a strand produced with a volume ratio of 1: 3 cold to warm air,

Fig. 7 is a comparison of smoke concentrate, nicotine and CO in dependence on the degree of ventilation

Fig. 8 shows the result of a headspace analysis,

Fig. 9, three chromatograms

Fig. 10 is a normalized headspace analysis,

Fig. 11 shows the result of a sensory evaluation.

A filter 17 according to FIG. 1 has a filter material 19 which is surrounded by a paper wrapper 18 . The filter material 19 consists of tangled layers of a fiber material, the individual fibers of which are generally longer than the filter section. The individual fibers of the material are generally at an angle of 30-40 ° to the longitudinal axis of the filter 17 , the fibers being generally oriented in the axial direction of the filter.

The filter materials are produced by spinning of the polymer into fibers. That described in EP 01 77 207 Centrifugal spinning is for the purposes of the invention basically applicable, but the process parameters differ. The use of centrifuge spinning technology has increased led to the surprising realization that in this way direct filter rod production is possible. By the utilization of the rotational symmetry of the spinning arrangement. the resulting confusion of the individual fibers in this process and the rotational symmetry of the final product as Cigarette filters, it is not necessary to have a 2-dimensional one To manufacture intermediate. The centrifuge spinning process enables immediate production a 3-dimensional strand with an approximately round cross-sectional shape, by radial compression into the desired one Shape and size of a filter rod are brought can.

Fig. 2 shows a device for producing a fiber strand according to the invention.

A spinning solution with 10-20% weight concentration per volume solution (W / V) consists of PHB or copolymer PHB-PHV with a molecular weight of greater than 300,000 in a solvent such as. B. chloroform or methylene chloride. The solution is in a solution container 14 .

The solution is fed to the spinning head via a pump 15 . This preferably contains a hollow shaft 1 , which leads to a spinning cup 2 , on which the cup bead 4 is axially continued. Through the hollow shaft 1 , the spinning solution is pressed under pressure onto the top of the cup bead 4 . The spinning head rotates at a speed of 8000 rpm, for example. This rotation causes the spinning solution to fly to the outside of the bead and is broken up into individual filaments.

A first air chamber 5 is provided around the hollow shaft, to which cold air is supplied via an air inlet 6 . The cold air supplied blows onto the spinning head in the axial direction and combs and separates the fibers as they emerge from the spinning cup 2 . The speed of the cold air counteracts the rotation or the swirl which the fibers have been impressed by the spinning cup 2 . A change in the cold air speed influences the degree of crosslinking in the fiber stream. A further air chamber 7 is provided which is concentric with the air chamber 5 and to which hot air is supplied via the air inlet 8 . The hot air blown out of the chamber 7 in the axial direction of the device downward from the air outlet 9 evaporates the solvent of the spinning solution and forms the network-like connected polymer fibers.

The spinning head rotates at about 4000-15,000 rpm, in particular 8000-12,000 rpm. The spinning head diameter is typically 10-15 cm. The warm air temperature at the entrance to air chamber 7 is approximately 160-200 ° C. The individual filaments are deflected downwards by the air streams blowing in the axial direction and can be combined there into a strand. At a certain distance below the spinning head, an extractor operating with an air stream is provided, which detects the fiber bundle and extracts it to the outside. The excess air and solvent vapor are discharged to the outside through an opening 11 and a vent 12 .

By varying the flow of cold air to warm air otherwise same conditions, the shape of the spun Material can be influenced. If the volume ratio is cold: warm larger than 2: 1, you get an open fleece. It's smaller 0.1: 1 is a compact, twisted thread. In the intermediate area, a fiber bundle or a fiber strand can be produce. It has been found that for the further Forming and processing into cigarette filter rods Ratio of 0.5: 1 to 0.2: 1 is the most favorable strand formation ratio represents.

FIG. 4 shows an electron micrograph of a cloth produced with a volume ratio of 2: 1 cold air to warm air, FIG. 5 shows a corresponding image of a thread in which the volume ratio was 0.1: 1 and FIG. 6 shows an image of a Stranges, which was produced with a volume ratio of 0.33: 1 and which can be used for the purposes of the invention.

The temperature at the exit of the evaporation section should be in Range 60-100 ° C. Align the absolute air volumes according to the mass flow of the spinning fluid, taking heat amounts per gram of fibers in the above Solvents for PHB in the range of 4000-8000 J are required.

The air extraction which combines the downward blown fiber bundle at the end of the evaporation path through an annular nozzle 16 exerts a minimal pulling force on the fiber bundle and nevertheless brings the bundle together well. Too large a pull-off force would rather cause an excessive fiber orientation in the axial direction, which negatively affects the filter properties. The ring nozzle used with a diameter of 50 mm, an air flow of 0.012-0.016 m / s and an air pressure of 0.21-0.28 bar acts practically as a fixed point for the twisting of the fibers, which results from the rotation of the spinning head. At the exit of the ring nozzle 16 , the strand diameter is set to approximately 30-50 mm. Arranged around the spinning core and the surrounding air chambers is a container 10 which extends far downwards and has the opening 11 at the lower end, at the end of which an outlet 12 is provided, to which a suction device can be connected.

The polymers made according to the invention are thermoplastic Properties. Many properties match those of polyolefins. In contrast to conventional plastics PHB and the copolymers are characterized by this from that they are biodegradable.

Instead of using a spinning solution at ambient temperature a hot spinning solution can also be used to remove the Avoid gelling of the HB polymer at high concentration. For PHB with a molecular weight of approximately 600,000 is a spinning solution with 10-15% concentration (weight per Volume) PHB in chloroform or methylene chloride.

example

It became a spinning head with a diameter of 10 cm and a rotational speed of 10,000 rpm is used. The Solution concentration was 13% weight PHB per unit volume  Solution dissolved in chloroform. The molecular weight was about 600 000. Hot air of 190 ° C was used, the volume ratio between cold and warm air was 1: 1-0.3: 1. 6.4 g per second of polymer material was spun out. The solution temperature was 20 ° C. The length of the evaporation zone was 1.2 m. There were filaments with a diameter of 2-20 microns (the majority of the fibers had a diameter of 5-7 micrometers), which with at a speed of 10 m per minute. The strand density was approximately 500 mg per decimeter of run length.

To avoid adhesion of the fibers to the metallic At least surfaces of the device should be vented 1.2 m below the spinning head.

Fig. 3 shows the device in connection with a format device. The fiber strand 20 emerging from the air vent 16 is transferred via a deflection 23 directly into the inlet 24 of the format device. Here, the strand is radially compressed to the desired diameter and wrapped with filter wrapping paper 25 , which is fed to the strand 20 via a format belt 27 . The filter strand produced can be cut to length in a cutting device 26 , so that the finished filter rods 22 then result.

A finished filter shows a pressure drop (tensile resistance at a standard flow of 17.5 cm / s) of about 20-50 mm water column per cm. The weight of the filter is 30-80 mg per cm for common diameters of 7.84 mm.

Differentiate due to the material properties of the filter the filter properties differ from those of conventional cellulose acetate  Filter. This difference is due to the different Chemical structure of the polymer surfaces of cellulose acetate and attributed to PHB. This leads to changed adhesion properties of the particles to be filtered, so that the amount the unfiltered medium-volatile components of cigarette smoke different from conventional cigarettes. This is particularly due to the usual in the cigarette industry Headspace analysis recognizable on the gas chromatograph.

example

Filters made from PHB fiber material were made using standard filters Comparing cellulose acetate. The focus of the investigations was to find out how the sensory and smoke analysis of the Compare the influence of filter ventilation in both systems leaves.

Two sets of filter-ventilated cigarettes were used. The tobacco rod was the same every time, the ventilation levels were immediately hired. One series contained cellulose acetate Filters (CA filters), the other series filters made of polyhydroxybutyric acid (PHB filter). The filter dimensions were constant.

The two series were laser-perforated. By setting the laser line and the pulse frequency were the following degrees of ventilation  achieved:

24%, 51%, 73%.

The unventilated version served as a zero test.

Fig. 7 shows a comparison of the nicotine free, dry smoke condensate (PMWNF), nicotine and CO for PHB in dependence on the degree of ventilation, based in relative units to CA filter.

A headspace analysis of the smoke has been carried out. The sum over all peaks of the chromatogram as the total headspace amount is shown in FIG. 8 for both series.

In Fig. 9, the chromatograms have been divided into three areas. The relative proportions of the volatile substances (boiling point range less than 100 ° C), the medium volatile substances (boiling point range 100 ° C-200 ° C, here are the taste-relevant substances), and the non-volatile range (boiling points greater than 200 ° C) are against Ventilation shown for both types of filter (total headspace amount = 100%).

If the amount of headspace is related to the amount of wet condensate (TPM), the course shown in FIG. 10 is obtained if the headspace areas per TPM are normalized to the corresponding CA values.

In Fig. 11 sensory rating of a test group are shown. The grading is plotted on the Y axis in an absolute scale that ranges from -5 to +5. Since the samples are graded in comparison to the standard CA filters, a negative sign means "weaker" or "worse", a positive sign means "stronger" or "better". The terms used mean the following:

Difference = summary assessment on a scale of 0-10
Mouth irritation = scratchiness
Mouthfull feeling = fullness, content
Aroma quality = taste of tobacco smoke
Acceptance = evaluation, preference.

Although the physical filtering properties of PHB and CA are similar, the PHB filters used have a slightly higher Filtration performance than the CA filter, so that the filter smoke and nicotine levels are lower in PHB than at CA. The reason is essentially that the single fiber diameter the PHB filter polydispers with a right high proportion of fine fibers, while the CA fibers are monodisperse are.

At higher ventilation levels, the PHB filter holds disproportionately more condensate, and nicotine gets disproportionately more into the smoke compared to CA ( Fig. 7). Since CO remains comparable in all cases, this is not a dilution effect, but stems from the material properties.

It is striking that the headspace analysis has changed behavior comes to light. As expected, the total quantities will decrease with increasing degree of ventilation. However, while the amounts of smoke with PHB filters are lower than with CA filters the opposite behavior for the total headspace amount. Because the headspace analyzes on the condensate leaving the cigarette this means that the condensate of PHB filter cigarettes is much more headspace than that of standard filter cigarettes.  

The main shift is in the central area of the chromatograms, where the medium-volatile, flavor-intensive substances are detected. If these areas are related to the condensate (TPM) and the PHB values are normalized to the CA values, the course shown in FIG. 10 is included. The proportion of medium volatile substances is significantly higher than the comparatively large proportion of volatile and low volatility substances.

It is striking that the levels of oral irritation are getting lower become, d. H. from "stronger than the reference" to the reference approach. With "aroma quality" one sees an upside down Behavior. Here is found at higher ventilation levels a change of sign from "weaker / worse" to "stronger / better ". A similar trend can also be seen in the acceptance values. Because the summary "difference" is always rough is constantly graded, this means that the PHB samples with increasing ventilation not the correspondingly ventilated CA samples will be similar, but that one with the material coherent taste impression assessed more positively becomes.

As with PHB filters, even with highly diluted smoke Headspace amount is larger than in the comparison case of the CA filter, a stronger one is created with the same ventilation Taste impression.

From the measured values you can see that with higher ventilation the ratio of headspace quantity to condensate for PHB filter samples to values that fall within the range of CA filters lower ventilation or the unventilated version.  PHB samples are therefore used from a certain degree of ventilation better accepted by sensors than the corresponding CA samples.

Overall, this example results from ventilation a positive overall impression of approx. 50% of PHB filters.

Reference symbol list

1 hollow shaft
2 spinning cups
3 page
4 cup beads
5 air chamber (cold)
6 air inlet (cold)
7 air chamber (hot)
8 air inlet (hot)
9 outlet
10 containers
11 opening
12 outlet
13 tube
14 autoclave
15 pump
16 air vent
17 filters
18 wrapping
19 fiber material
20 fiber strand
21 individual fibers
22 filters
23 leadership
24 inlet
25 wrapping paper
26 cutting device
27 format tape

Claims (12)

1. A process for the production of cigarette filters by cross-axial compression and sheathing a strand of essentially axially structured fiber material, characterized in that PHB (polyhydroxybutyric acid) or a copolymer of PHB / PHV (polyhydroxyvaleric acid) is discharged in a centrifuge spinning device and the network-connected single fibers produced merges into a fiber strand, which is fed to the format device of a cigarette filter machine. 2. The method according to claim 1, characterized in that a PHB solution or a PHB / PHV copolymer solution a rotating spinning head is pressed that a concentric Cold air flow supplied coaxially to the spinning head with ambient temperature that emerging at the spin pool The fibers are combed and separated to keep the twist Fibers to counteract that one around the cold air flow concentrically arranged hot air flow the used Solvent evaporates and that the polymer fibers formed are brought together to form a fiber strand. 3. The method according to claim 2, characterized in that the spinning head with a speed of 4000-15 000 rpm rotates at a spinner head diameter of 10-15 cm and that the temperature of the hot air flow 160-200 ° C is. 4. The method according to claim 2 or 3, characterized in that that by adjusting the ratio of air volumes the cold to the warm air flow formed a strand shape will be even after radial compression  Has diameter. 5. The method according to claim 3 or 4, characterized in that the ratio of air volumes from cold to warm Airflow is 0.5: 1 to 0.2: 1. 6. The method according to claim 4, characterized in that radial compression takes place through an annular nozzle, whose longitudinal tensile force goes to zero and that the diameter of the fiber strand leaving the nozzle Is 30-50 mm. 7. The method according to one or more of the preceding claims, characterized in that from the spinning device emerging fiber strand directly into the Format device of the cigarette filter machine introduced becomes. 8. cigarette filter, produced by a method according to claim 1, consisting of a section of a cross-axially compressed fiber strand ( 20 ) of randomly oriented individual fibers made of spun PHB (polyhydroxybutyric acid) or a copolymer of PHB and PHV (polyhydroxyvaleric acid). 9. Cigarette filter according to claim 8, characterized in that the diameter of the single fiber is 2-20 microns is. 10. Cigarette filter according to claim 8 or 9, characterized in that the individual fibers in a main Lateral position of 30-45 ° to the longitudinal axis of the filter.   11. Cigarette filter according to one of claims 8-10, characterized characterized in that the individual fibers are usually a have a greater length than the cigarette filter. 12. Cigarette filter according to one of claims 8-11, characterized characterized in that the filter has a degree of ventilation of over 40%.