EP0885321A1

EP0885321A1 - Melt-blown non woven fabric, process for producing same and the uses thereof

Info

Publication number: EP0885321A1
Application number: EP96944588A
Authority: EP
Inventors: Günter Maurer; Paul Rustemeyer; Eberhard Teufel
Original assignee: Rhodia Acetow GmbH
Current assignee: Cerdia Produktions GmbH
Priority date: 1996-03-08
Filing date: 1996-12-18
Publication date: 1998-12-23
Anticipated expiration: 2016-12-18
Also published as: ATE192789T1; DE59605210D1; JP3251018B2; US6207601B1; DE19609143C1; JPH11506175A; AU1302297A; WO1997033026A1; EP0885321B1

Abstract

The disclosure relates to a melt-blown non-woven fabric based on cellulose esters, with fibers of mean diameter less than about 10 microns. The fabric contains 0-10 wt. % extractable softener, has a reflection factor determined according to DIN 53 145 Part I (1992) of more than 60% and the cellulose ester has a degree of substitution DS of about 1.5-3.0. The softener is preferably water-extractable. A melt-blown non-woven fabric is produced with the cellulose ester as follows: a cellulose ester, cellulose acetate, with a DS of about 1.5-3.0, in particular 1.7-2.7, is mixed with softener in a weight ratio of about 2:1 to 1:4 and simultaneously heated and melted. The mixture of softener and cellulose ester has a melting index MFI (210/2.16) according to DIN 53 735 of about 400 to 5 g/10 min., in particular 300 to 50 g/10 min. The melt is worked in a melt-blown spinning device into a melt-blown non-woven fabric and the softener is then extracted with a softener solvent to leave a proportion of 0-10 wt. %. The melt-blown non-woven fabric is especially suitable as a filter material.

Description

Melt-blown fleece. Process for its production and its uses

The invention relates to a melt-blown nonwoven based on cellulose esters, in particular cellulose acetate. with fibers with an average fiber diameter of less than about 10 microns. a method which is particularly suitable for the production thereof and advantageous uses of the melt-blown nonwoven.

Melt-blown nonwovens follow the ISO definition for nonwovens (ISO 9092: 1988). According to this, a material is referred to as a nonwoven fabric if a) the fiber content is more than 50% by weight (except chemically digested vegetable fibers) and the fibers have a slenderness ratio of greater than 300 or b) the following conditions are met: 1) the fiber content is more than 30 % By weight (except chemically digested plant fibers) and the fibers have a slenderness ratio greater than 300 and 2) the density is less than 0.40 g / cm ³ .

This ISO regulation is also followed by the nonwovens explained in more detail below, these being produced by the melt-blown process or a melt-blowing technique. The melt-blown process can be represented as follows, without wishing to see any limitation here; i.e., the melt blown filaments, fibers and nonwovens are generally produced as follows:

The respective plastic is placed in an extruder in which it is melted. From the extruder, the melt reaches the spinning head, which contains the melt-blown nozzle, which is a central component of the process. Here the melt is brought to the required processing temperature. The nozzle itself contains a series of capillary holes. Openings for the pressurized primary process air are located on both sides of the nozzle bores. There is a deposit device below the nozzle. device arranged in the form of a driven screen belt or a screen drum through which the fibers are sucked in and deposited to form a fleece.

When the melt emerges from the nozzle holes, it comes into contact with the relaxing hot primary process air at high speed. Here, the melt of each capillary hole is torn and stretched to a large number of fine fibers. In this process, the filaments tear off predominantly into fibers. This is in contrast to other spunbonded processes in which fiber breakage must be prevented. Cold ambient air, which is referred to as secondary air, is drawn in by the primary process air flow and is drawn to the fibers and

Filaments. The filaments and fibers produced are thus cooled directly under the nozzle. Below are the fibers on the one mentioned above

Laying device laid down to a fleece and wound up. A melt bond between the fibers does not take place regularly. The fiber lengths are usually in the order of 5 to 50 cm. The fiber diameter is very small and, for example in connection with the invention described below, is less than about 10 μm.

Further information on the melt-blown process can be found in US Pat. No. 3,825,379 (from Exxon Research and Engineering Co.) and US Pat. No. 4,714,647 (from Kimberly Clark Corp.).

US Pat. No. 4,869,275 also addresses the melt-blown process for producing a nonwoven from various starting materials. Suitable starting materials are polyolefins (polypropylene, polyethylene and ethylene / propylene copolymers), polystyrene, polyester (polyethylene terephthalate), nylon (6, 66 and 610), polymethylene methacrylates and generally also cellulose acetate. This patent does not contain any statements as to what degree of substitution this cellulose acetate has when it is used in the process described. Even the unusual hint that even cellulose acetate is suitable ("even cellulose acetate" / see Sp. 5, Paragraph 1), indicates that this is only suitable to a limited extent. This is also in accordance with the expert knowledge that the narrow temperature interval between the melting temperature and the decomposition range converts the cellulose esters into processable melts, for example in the case of cellulose triacetate. largely excludes and is still associated with the beginning of product damage in the case of low-melting cellulose acetopropionates (cf. plastics manual 3/1 Hansa-Verlag, 1992, p. 411). If cellulose acetate were actually processed into a melt-blown fleece at a high "melting temperature" to be taken as a basis, then this would be associated with an undesirable, strong degradation. The degradation products would have a very disadvantageous effect in various uses, in particular when used as filter materials in tobacco smoke filters. This purpose is highlighted in U.S. Patent 4,869,275. However, cellulose acetate is not taken into account in the description of the particularly practical embodiments. Due to the decomposition of cellulose acetate, which can be expected by the known method, the quality of the melt-blown nonwoven obtained would also deteriorate insofar as a satisfactory degree of whiteness does not develop. With regard to the decomposition of cellulose acetates at higher temperatures, it should be noted that a noticeable chemical decomposition occurs from 180 ° C., which can be recognized by the formation of furfural, among other things.

According to Example 5 of US Pat. No. 3,509,009, a part of cellulose acetate and a part of diethyl phthalate (as a plasticizer) are melt-spun at a temperature of 170 ° C. As a result, decomposition of the cellulose ester used is largely ruled out, but the product properties are undesirably dominated by the plasticizer. Such a high plasticizer content limits the use properties to the extent that the melting point is too low and plasticizer migration or exudation and evaporation can occur.

Proceeding from the prior art described above, the invention is based on the object of further developing a melt-blown fleece of the type described at the outset. form that it is not thermoplastic up to a temperature of about 180 ° C, has a desirably high reflection factor or whiteness and, if desired, advantageous filter materials, in particular filter materials of cigarettes and the filtration of gases or liquids, especially of Blood. In addition, the invention proposes a particularly advantageous method for producing such a melt-blown nonwoven.

According to the invention this object is achieved in that it contains about 0 to 10% by mass of an extractable plasticizer, a reflection factor (R∞), determined according to DIN 53 145 Part 1 (1992), of more than about 60% and the cellulose ester one

Degree of substitution DS of about 1.5 to 3.0.

The invention thus provides access to melt-blown nonwovens made of cellulose ester which contain little or no plasticizer, which could not previously be considered possible.

The melt-blown fleece according to the invention contains fibers from cellulose esters. This can be, for example, cellulose acetate, acetobutyrate, acetopropionate and propionate and the like. Cellulose acetate is preferred.

The degree of substitution DS of the cellulose esters used according to the invention is between about 1.5 to 3.0, in particular between about 1.7 and 2.7, the range from about 2.2 to 2.6 being very particularly preferred. If the value falls below 1.5, damage to the polymer structure through dehydration is to be feared. Although the desired success can also be achieved with a degree of substitution of approximately 3.0, undesired crystallization and phase separation can already occur at this value. These undesirable disadvantages can be countered with a higher extractable plasticizer content of up to about 10% by mass. However, if a lower plasticizer content is desired, then it is advantageous to simultaneously increase the degree of substitution DS to at least about 2.7, in particular lower at least about 2.6.

Despite the unusually good degree of whiteness, which will be discussed further, the melt-blown nonwoven according to the invention contains only up to about 10% by mass, in particular about 2 to 8% by mass, of an extractable plasticizer, in particular in the form of a water-extractable plasticizer. The invention thus takes account of the relevant uses in which the plasticizer content must not be too high, since otherwise the product is undesirably dominated by the plasticizer. Rather, the product properties should largely go back to the cellulose ester. The exact setting of the plasticizer content within the specified range of about 0 to 10% by mass depends on the particular intended use of the fleece. Accordingly, it is left to the person skilled in the art to quantitatively optimize the amount of plasticizer in the scope of the invention in individual cases. Thus, when using the melt-blown nonwoven in filter cigarettes, it has been found desirable to set a plasticizer content of about 5 to 10% by mass, especially if triacetin is used as the plasticizer. It is known that triacetin has a positive effect on the taste of tobacco smoke and the specific retentions of cellulose acetate. A plasticizer content exceeding 10% by mass would limit the use properties to such an extent that the melting point is too low, and plasticizer migration or exudation and exhalation and, moreover, undesirable sticking can occur. Furthermore, if used in filter rods, a high plasticizer content would have a negative influence on the filter rod hardness. In the case of applications which are subject to the provisions of food law, the plasticizer content is kept as low as possible within the scope of the invention, in particular set to near 0. The same applies to medical applications, such as in blood filters.

The plasticizer used in the invention does not only have to have a plasticizing effect. Rather, the plasticizer made from the melt-blown fleece, which, after the completion of the production process, has a plasticizer content of more than 10% by mass, can be extracted with a suitable solvent to such an extent that the scope according to the invention is adjusted from about 0 to 10% by mass. The chemical and physical structure of the cellulose ester fibers should remain largely unchanged. Triacetin, ethylene and propylene carbonate, citric acid triethyl ester have proven suitable as plasticizers. Triethylene glycol diacetate, Carbowax ^® (polyethylene glycols with a MW of 200 to 14000, manufactured by UCC, USA) and / or sulfolane (tetrahydrothiophene-l, l-dioxide). Triacetin is particularly useful because it can be extracted quickly and effectively with water.

The degree of polymerization DP of the cellulose esters mentioned, in particular of the cellulose acetate, is not critical and can be in a relatively wide range. However, particularly advantageous results are achieved if it is between about 150 to 400, in particular between about 180 to 350. If the degree of polymerization fell below about 150, the proportion of oligomers would be too high, so that when the plasticizer was extracted, a large part of the cellulose ester would be extracted at the same time. If the upper limit value of approximately 400 is exceeded, the melt index in the melt-blown process explained below becomes too high, which would have a disadvantageous effect. Although this problem could be reduced in individual cases by increasing the plasticizer content, this would mean additional effort in realizing the invention, in particular in connection with the removal or recovery of the plasticizer.

A minimum reflection factor, also called whiteness, of the fleece is of critical importance in the context of the invention with regard to the various fields of application in which the melt-blown fleece according to the invention can be used. The reflection factor or whiteness is measured in accordance with DIN 53 145 Part 1 (1992) in accordance with ISO 2469 (1977). Here, an Elrepho device from Zeiss used. A fleece sample placed on top of each other in 8 layers is diffusely exposed and measured perpendicular to the sample plane (measurement geometry d / 0) at 457 nm (using a spectral band filter). Here reference is made to the barium sulfate white standard. The reflection factor or whiteness in the context of the invention is more than 60%, in particular more than 70% or even about 90%. The degree of whiteness is in particular a measure of the purity of the product according to the invention. If this were brownish or yellowish, then this means that undesired and uncontrollable decomposition products have been produced. Customers would therefore reject such a product if it was used in the cigarette industry. Surprisingly, the disadvantage of an unsatisfactory degree of whiteness cannot be remedied by the incorporation of white pigments, such as titanium dioxide, during the production process. It is therefore a particularly clear statement about the chemical purity of the cellulose ester fibers. This aspect plays an outstanding role in various areas, for example in the use of the fleece in the bio-medical area, in particular in blood filtration.

In individual cases it may be advantageous for the cellulose acetate to be in the form of a polymer blend, in particular with aliphatic polyesters and / or acetylated starches. Not only can this optimize the desired properties, for example the biodegradability in connection with aliphatic polyesters (cf. DE-C-39 14 022), but there is also the possibility of cost savings. In another area of application, this results from EP-A-0 622 407, to which reference is made.

In order to achieve the effects desired with the invention, the fiber diameter, as is generally obtained by the melt-blown process, must be below approximately 10 μm, in particular between approximately 2 to 8 μm. In contrast, the standard diameter of a filament obtained by the dry spinning process is generally between about 15 and 40 μm. Fibers of a smaller diameter have the advantage that they deliver a larger specific surface area and thus also a greater activity in the desired fields of application, in particular in the filtration. Within the scope of the invention, fibers with an average fiber diameter of less than approximately 8 μm can be adjusted without further notice. The particularly advantageous practical range is between approximately 5 and 8 μm. The fiber diameter is the average diameter. Here, a number of fibers are measured by scanning electron microscopy and then the average is formed.

In principle, if desired, active substances can be added to the melt obtained by the melt-blown process according to the invention described below, e.g. Agroactive ingredients, pharmaceutical active ingredients, selective and other filtration aids, e.g. for selective retention, flavorings, additives for biodegradability, etc. They are preferably compatible with the melt.

The melt-blown nonwoven according to the invention can advantageously be produced in that a cellulose ester, in particular cellulose acetate, with a degree of substitution DS of approximately 1.5 to 3.0, in particular approximately 1.7 to 2.7, with a plasticizer in one mass Ratio of about 2: 1 to 1: 4 mixed with heating and transferred to a melt, the mixture of plasticizer and cellulose ester having a melt index MFI (210 / 2.16) according to DIN 53 735 of about 400 to 5 g / 10 min, in particular 300 to 50 g / 10 min, the melt processed in a melt-blown spinning device to form a melt-blown fleece and then the plasticizer to a proportion of about 0 to 10% by mass with a solvent for the plasticizer is extracted. In order to convert the starting materials into a melt, they are preferably heated to a temperature of more than about 100 ° C. The particularly suitable melting temperature depends on the individual case and can be determined purely by a person skilled in the art. However, a temperature of 240 ° C should not be exceeded, since otherwise undesirable signs of decomposition occur. As shown, the melt-blown nonwoven obtained according to the invention has a low proportion of extractable plasticizer of about 0 to 10% by mass. Decomposition of the cellulose ester used is largely ruled out by the process according to the invention. It is not necessary to work in a protective gas atmosphere to avoid undesirable oxidative processes. It is advantageous if the melt is subjected to the melt-blown process immediately after its production, since otherwise undesirable degradation reactions can occur. Thus, a particular advantage of the method according to the invention is that it can be carried out continuously. Mixing and spinning are advantageously carried out in a single operation, in that the mixture of the extruder is immediately fed to the melt-blown nozzle. The method according to the invention thus represents a significant simplification in terms of the methodology.

To carry out the melt-blown process according to the invention, it is advantageous if the mass ratio of plasticizer to cellulose ester is set to about 3: 2 to 2: 3, consequently in the practical embodiment preferably to about 1: 1, which is also the case Requirement of US Pat. No. 3,509,009 corresponds. However, the present invention differs in the course of the process from the teaching according to US Pat. No. 3,509,009 in that it requires the use of a suitable solvent for the plasticizer. Accordingly, according to the invention, a solvent is used to extract the plasticizer, which, however, does not adversely affect the chemical and physical structure of the cellulose ester fibers.

The type of mixing of plasticizer and cellulose ester, if appropriate with further additives, is not subject to any significant restrictions. It has been shown that the cellulose ester and plasticizer are particularly advantageously mixed in a twin-screw extruder. This achieves the shear necessary for optimal mixing of the starting materials, which leads to a particularly advantageous homogenization of the starting materials. It is preferred to use a co-rotating twin screw extruder. The process according to the invention is controlled particularly advantageously in the melt-blown spinning device when a temperature of approximately 180 to 240 ° C., in particular approximately 200 to 230 ° C., is set on the spinneret and the spinning head of the spinning device. If the value falls below about 180 ° C, this can lead to insufficient fineness of the process product. If the upper limit of 240 ° C is exceeded, undesired degradation begins.

The plasticizers which can be used in the context of the invention have already been discussed above, in particular the advantageous use of the water-extractable

Plasticizer in the form of triacetin. In the case of a water-extractable plasticizer, the melt-blown fleece obtained is simply passed into a water bath to extract the plasticizer. The process according to the invention can be carried out here with the particular advantage that a normal water bath (about room temperature), i.e. can be used for extraction without heating. If the plasticizer content is high, the use of a hot extraction bath is even disadvantageous because the melt-blown nonwoven then has such a melting range that its structure is impaired or even destroyed.

It is particularly advantageous if the fleece leaving the melt-blown spinning device is transferred to a depositing device, in particular in the form of a sieve or sieve belt or a sieve drum, pressed to set the desired strength and then the plasticizer is extracted. In principle, it is also possible to carry out the extraction before pressing. If desired, the melt-blown fleece can also be structured during pressing. The structuring is done in order for the later

To obtain advantageous structure use, for example in the case of use in cigarette filters, a longitudinal corrugation, combined with an increase in surface area.

Finally, it can be advantageous in individual cases to simultaneously form filaments when forming the melt-blown fleece. in particular to introduce cellulose acetate filaments. There are basically two options here, which are described in detail in DE 35 21 221. In this regard, reference is expressly made to these. In general, the incorporation of filaments leads to an improvement in the mechanical properties, in particular the tensile strength, of the material.

It is also particularly advantageous if the meltblown fleece leaving the spinning device is deposited on a carrier to form a composite structure, in particular in the form of a fleece made of a cellulose acetate filter tow, a flatly prepared filter tow or paper. If a carrier fleece is used, the person skilled in the art can easily determine the suitable fleece, depending on the end use. For example, in the case of further use of the melt-blown fleece according to the invention in filter cigarettes, a cellulose acetate fleece would preferably be assumed. However, any closed supports are also possible, such as the paper already mentioned. The composite structures obtained in each case can advantageously be pressed and / or structured to regulate their strength.

A particular advantage of the method according to the invention is that the desired melt-blown nonwoven can be produced without the need for special additives, such as any processing aids.

Because of the properties mentioned, the meltblown nonwoven according to the invention is particularly advantageously suitable as a filter material. The fleece is e.g. in tobacco smoke filters, in particular in cigarette filters, and here in particular in double filters for ultralight cigarettes, for the filtration of gases and liquids, for example sterile filtration of beverages and very particularly advantageously for the filtration of blood.

If the melt-blown fleece according to the invention is used in cigarette filters, these can be easily disintegrated. Furthermore, a low degree of substitution DS leads Cellulose esters, especially cellulose acetate, to a particularly favorable biodegradability.

The filter materials according to the invention not only show a better filter effect than the previously known materials, but they also fully meet the taste requirements. This applies in particular to cellulose acetate in connection with a residual content of triacetin plasticizer.

The invention is explained in more detail below with the aid of examples.

example 1

Cellulose acetate with a DP of 220 and a DS of 2.5 was added by means of a gravimetric metering device into the filling opening of the 1st zone of a co-rotating 2-screw laboratory extruder with a screw diameter of 25 mm, a length of 48 D and 15 zones . In the 2nd zone, triacetin was supplied as a plasticizer in a ratio of 2: 3 (1: 1.5) using a reciprocating pump. The temperatures of the zones in the 1st and 2nd zone 30 in the 3rd 110th in the 4th were 150 ° C. The temperatures of zones 5-11 were 150 and zones 12-15 175 ° C. A homogeneous melt was obtained at a screw speed of 150 rpm. The melt obtained in this way was continuously transferred into a strand via a round die, and the strand was cooled below the melting temperature and comminuted into cylindrical granules of 2 mm in diameter and 3 mm in length with the aid of a strand granulator. The granules obtained in this way were fed to a melt-blown laboratory spinning device consisting of extruder, intermediate block, melting tube, spinneret nozzle, hot air device, tray and winder. The temperatures in the extruder of the melt-blown laboratory spinning device were increased from 100 ° C. at the inlet to 170 ° C. at the extruder outlet. The intermediate block and the melting tube were set to 200 ° C. The temperature in the spinning head was 230 ° C. The air temperature was 265 ° C. The air volume was set to 70 m ³ / h. With these process parameters a melt pressure of 125 bar was established. The mass throughput was 7.7 kg / h. The fibers produced with the spinning device were placed on a storage belt and continuously drawn off under the spinning device in such a way that a weight per unit area of 132 g / m ^{2 was} obtained. The fleece was wound up into a roll by means of a winding device. The fleece roll was then fed to a washing device filled with water consisting of two troughs connected in series and the plasticizer contained in the fleece was washed out to a residual content of 0.3%. The fleece was then dried with a drying device at 160 ° C. to a residual moisture content of 4.8%. The average fiber diameter of the fleece thus obtained was 8.4 μm. The reflection factor (R∞) was 65% based on the barium sulfate white standard.

Example 2

Cellulose acetate with a DP of 220 and a DS of 2.5 was added by means of a gravimetric metering device into the filling opening of the 1st zone of a co-rotating 2-screw laboratory extruder with a screw diameter of 25 mm, a length of 48 D and 15 zones. In the 3rd zone, triacetin was supplied as a plasticizer in a ratio of 3: 2 (1.5: 1, 0) by means of a reciprocating pump. The temperatures in the 1st and 2nd zone were 50 in the 3rd 100 and in the 4th zone 120 ° C. The temperatures of zones 5-10 were 140 and zones 1 1-15 150 ° C. The mass throughput was 3.2 kg / h. A homogeneous melt was obtained at a screw speed of 190 rpm. The melt obtained in this way was fed directly to a laboratory melt-blown spinning device described in Example 1, which, in contrast to Example 1, no longer required an extruder, since the material to be processed was already in the form of a melt. In this case, the melt-blown spinning unit was connected directly after the co-rotating 2-screw laboratory extruder. The intermediate block and the melting tube were set to 170 ° C. The temperature in the spinneret nozzle

3 was 210 ° C, air temperature 255 ° C. The air volume was set to 60 m / h. With these process parameters, a melt pressure of only 73 bar was established. The Fibers produced with the spinning device were placed on a storage belt and continuously drawn off under the spinning device in such a way that a weight per unit area of 176 g / m ² resulted. The fleece obtained in this way was fed directly into a washing device as described in Example 1 and the plasticizer contained in the fleece was washed out to a residual content of 5.5%. The fleece was then dried with a drying device at 150 ° C. to a residual moisture content of 6.3%. The average fiber diameter of the fleece thus obtained was 5.7 μm. The reflection factor (R∞) was 74% based on the barium sulfate white standard.

***

Claims

claims

1. Melt-blown fleece based on cellulose esters, in particular cellulose acetate, with fibers with an average fiber diameter of less than about 10 μm, characterized in that it contains about 0 to 10% by mass of an extractable plasticizer, a reflection factor (R ∞), determined according to DIN 53 145 Part 1 (1992), of more than about 60% and the cellulose ester has a degree of substitution DS of about 1.5 to 3.0.

2. Melt-blown fleece according to claim 1, characterized in that the plasticizer is water-extractable.

3. Melt-blown fleece according to claim 1 or 2, characterized in that the plasticizer is in the form of triacetin, ethylene and propylene carbonate, citric acid triethyl ester, triethylene glycol diacetate, polyethylene glycol with low molecular weight and / or sulfolane.

4. Melt-blown nonwoven according to at least one of the preceding claims, characterized in that the degree of substitution DS is approximately 1.7 to 2.7, in particular approximately 2.2 to 2.6.

5. Melt-blown fleece according to at least one of the preceding claims, characterized in that the cellulose ester has a degree of polymerization DP of about 150 to 400, in particular about 180 to 350.

6. melt-blown nonwoven according to at least one of claims 1 to 5, characterized in that the content of plasticizer is about 2 to 8% by mass.

7. melt-blown fleece according to at least one of claims 1 to 6, characterized in that the reflection factor (R∞) is more than about 70%.

8. melt-blown fleece according to at least one of claims 1 to 7, characterized in that the cellulose acetate is in the form of a polymer blend, in particular with aliphatic polyesters and / or acetylated starches.

9. A process for producing a melt-blown nonwoven according to at least one of the preceding claims, characterized in that a cellulose ester, in particular cellulose acetate, has a degree of substitution DS of approximately 1.5 to 3.0, in particular approximately 1.7 to 2, 7, is mixed with a plasticizer in a mass ratio of about 2: 1 to 1: 4 with heating and transferred to a melt, the mixture of plasticizer and cellulose ester having a melt index MFI (210 / 2.16) according to DIN 53 735 of about 400 to 5 g / 10 min, in particular 300 to 50 g / 10 min, the melt processed in a melt-blown spinning device to form a melt-blown fleece and then the plasticizer to a proportion of about 0 to 10 mass -% is extracted with a solvent for the plasticizer.

10. The method according to claim 9, characterized in that the mass ratio of plasticizer to cellulose ester is set to about 3: 2 to 2: 3.

11. The method according to claim 9 or 10, characterized in that the temperature when mixing the plasticizer with the cellulose ester is set to about 140 to 180 ° C.

12. The method according to any one of claims 9 to 11, characterized in that the temperature at the spinning head and the nozzle of the melt-blown spinning device is set to approximately 180 to 240 ° C, in particular approximately 200 to 230 ° C.

13. The method according to at least one of claims 9 to 12, characterized in that the mixing of cellulose and plasticizer is carried out in a co-rotating twin-screw extruder.

14. The method according to at least one of claims 9 to 13, characterized in that a water-extractable plasticizer is used.

15. The method according to claim 14, characterized in that the melt-blown fleece obtained for extracting the plasticizer is passed into a water bath.

16. The method according to at least one of claims 9 to 15, characterized in that the fleece leaving the melt-blown spinning device is transferred to a depositing device, pressed to adjust the desired thickness and then extracted.

17. The method according to claim 16, characterized in that the melt-blown fleece is structured during pressing.

18. The method according to claim 16 or 17, characterized in that the melt-blown fleece is placed on a sieve or a belt or a sieve drum.

19. The method according to at least one of claims 9 to 18, characterized in that during the formation of the melt-blown fleece filaments, in particular cellulose acetate filaments, are introduced simultaneously.

20. The method according to at least one of the preceding claims, characterized in that the melt-blown fleece leaving the spinning device is deposited on a carrier to form a composite structure.

21. The method according to claim 20, characterized in that the carrier is a fleece made of a cellulose acetate filter tow. a flat filter filter or made of paper

22. The method according to claim 20 or 21, characterized in that the composite structure is pressed and / or structured to regulate its strength.

23. Use of a melt-blown fleece according to at least one of claims 1 to 8 as a filter material.

24. Use of a melt-blown fleece according to claim 23 in tobacco smoke filters. especially in cigarette filters.

25. Use of a melt-blown fleece according to claim 24 in double filters for ultralight cigarettes.

26. Use of a melt-blown fleece according to claim 23 for the filtration of gases or liquids.

27. Use of a melt-blown fleece according to claim 26 for the filtration of blood.