DE2744796A1 - FILTER MATERIAL, ITS PRODUCTION AND USE - Google Patents

Description

FROM KREISLER SCHÖNWALD MEYER EISHOLD FUES FROM KREISLER KELLER SELTING

27U796

PATENT LAWYERS Dr.-Ing. by Kreisler -f- 1973

Dr.-Ing. K. Schönwold, Cologne Dr.-Ing. Th. Meyer, Cologne Dr.-Ing. K. W. Eishold, Bad Soden Dr. J. F. Fues, Cologne Dipl.-Chem. Alek von Kreisler, Cologne Dipl.-Chem. Carola Keller, Cologne Dipl.-Ing. G. Selling, Cologne

Ke / To.
5 Cologne ι October 4, 1977

DEICHMANNHAUS AM HAUPTÜAHNHOF

CELANESE CORPORATION, Avenue of the Americas, New York, N.Y. 10036 (U.S.A.)

Filter material, its manufacture and use

809815/0708

Telephone: (0221] 23 4541 - 4 Telex: 8882307 dopo d T..lcqr _O , nm _: Dompotent Cologne

Filter material, its manufacture and use

The invention relates to a sheet-like material which is suitable, and in particular, as a filter material as a material for tobacco smoke filters. It also affects the filters that remove the harmful ingredients Effectively remove tobacco smoke, especially tar and nicotine, without creating an unpleasant one Cause the pull to rise to a high value. The invention also relates to methods of manufacture the filter material and the tobacco smoke filter.

The principle use of the material according to the invention is intended for a filter that is inhaled removes absorbable particles of any kind and can also be used in liquid filtration can. If the filter is used to remove inhalable particles, it can be used in In connection with cigarettes or other smoking articles, such as pipes, cigars, cigarettes or Cigar holders. From the following description results however, equally that the filter material according to the invention can also be used advantageously Can be used in surgical masks, for air filtration and in face masks for protection against fog, smog and dust.

Numerous types of filter materials have already been used, particularly to reduce the content of harmful ones Reduce the ingredients of tobacco smoke before it reaches the smoker's respiratory system. In addition to removing the harmful constituents

809815/070

27AA796

In large quantities, a satisfactory filter must also be effective without causing undesirable effects Way to impede the passage of air or smoke through the filter, so that too strong a draft is required will. When used in tobacco smoke filters, the filter material must not be Change the taste of tobacco smoke by adding its own taste. Another essential one A factor in making a satisfactory tobacco smoke filter is that its Production is not too expensive, so that the final price of the smoking article in which it is used does not rises too high. While a large number of fiber materials have come into use as filter material are, only cellulose fibers and fibers made of cellulose acetate could have a certain significance enforce commercially.

Pulp fibers are usually in the form of a paper used, which is fluted and / or compressed in the form of a rod and connected to a cigarette, while cellulose acetate is normally in the form of a strand of substantially longitudinal filaments is used, which are preferably crimped, so that short areas of each Filaments irregular in non-parallel, converging and diverging directions in comparison are arranged to the predominantly longitudinal direction of the strand.

Usual paper filters are generally characterized by a higher filter effect marked, which is determined by the effectiveness of smoke removal, but they affect also the taste and smell of the smoke. They also have a much lower selectivity for Phenol than the usual filters made of cellulose acetate

809815/0708

Filter rods. In addition, paper filters collapse while smoking, primarily because of them Tendency to absorb moisture from tobacco smoke and the smoker's mouth. Furthermore, the compressibility of paper filters for a given pressure drop are generally greater than the usual ones Line filters of comparable weight.

Compared to paper filters, the usual cellulose acetate line filters all of the above mentioned disadvantages of paper filters are overcome due to the lucky one Meeting of requirements for a good train and profitability. As a result, it is a big one Some of the filter cigarettes on the market are equipped with this filter material, despite the fact that cellulose acetate rope filters have smoke removal effectiveness on a given puff, which is comparatively lower than that of the paper filter.

Numerous types of filters have been proposed to overcome these drawbacks while maintaining them the advantages of the cellulose acetate filter in order to gain a filter that has the properties both filters combined in one filter, which both has a high effect in retaining smoke as well as an acceptable move. A commonly used suggestion to achieve this goal is is the combination of a cellulose acetate strand and paper in a single filter. This has been achieved by using a short paper stick and a short cellulose acetate stick at the same time in the filter usually called "dual filter". However, this filter is very expensive in comparison with the usual filter tip production as it requires the production of two separate rods and

809816/0708

their subsequent assembly in a single filter. According to US Pat. No. 3,396,061, in contrast proposed to this end, a web of a cellulose acetate strand and a paper web immediately before molding of the filter to unite with each other. The combined paper / acetate filter is only available through this process a small increase in the cost of conventional filter production. These filters are however not completely satisfactory, since an even distribution of the two filter materials over the Cross-section of the filter does not exist, and an undesirable arrangement because of the through a Part of the filter-drawn tobacco smoke only comes into contact with a filter material while passing through a Tobacco smoke drawn from the other part of the filter will only come into contact with the other filter material. It follows that no part of the smoke is affected by the filtration capacity of either material. In addition, the amount of paper used in the filter is that produced by a paper filter pronounced undesirable taste still present.

In another method, cellulose acetate staple fibers are in a pure cellulose acetate filter in the way used that the fiber direction in the filter as a function of the flow of the material to be filtered is oriented. Such filter materials are, however, whether they are in the form of nonwovens or folded cushions or in the form of cylindrical rods, not very dimensionally stable and require the use of a binder, to keep the filaments in the desired arrangement. In addition, these structures have a lower effectiveness than the usual paper filters because the surface area of the staple fibers is below the the paper fibers lies. In addition, the use

809816/0709

Formation of a binding agent poses further problems because this reduces the surface area available for filtration reduce, give an undesirable taste to the filtered smoke and moreover reduce the speed of filter manufacture due to the time it takes to complete a filter To achieve bond.

The object of the present invention was to provide a layer-like material with a staple fiber orientation to make available, which has a large surface area and can be used as a filter material can. Furthermore, a method for producing a binder-free layer-like material should be provided be created with a large surface area that can be used as a filter material, in particular a material suitable for the manufacture of tobacco smoke filters.

The solution to this problem is a binder-free, cohesive, self-supporting filter material the basis of a fiber fleece made of cellulose ester threads, which has a high filtration effect with an acceptable draw guaranteed and characterized in that it is about 5 to 35%, based on the weight of the fiber fleece existing staple fibers, a porous, fine fiber Contains cellulose ester material with a large surface area, which is called cellulose ester fibers or "cellulose ester fibrets" is referred to.

The term "fibrets" as used here denotes a fibrillated material made from a cellulose ester with a large surface area that has an upper

2
has an area of more than 5.0 m / g, a length of less than 1000 µm and a diameter of about 0.5 to 50 µm.

809815/0708

As used herein, the term "binder" denotes a non-solvent material that contains the Has the ability to attach fibrous material to this fibrous material with the formation of a foreign phase boundary layer tie. The definition of "binders" specifically does not include compounds that are partial solvents represent for the fibrous material and which can be more precisely defined as plasticizers, for example Triacetin, triethylene glycol diacetate and mixtures containing these and other plasticizer substances, such as polyethylene glycol and triacetene mixtures.

The phrase "large surface area" used here denotes products that have a surface area of 2
have more than 1 ir. / g. A comparison with regard to the surface areas is made possible by the fact that paper suitable for filtering purposes has a surface of

2
1.2 to 3.2 m / g, while cellulose acetate staple fibers of 6.35 mm length with a single denier of 1.8, 3.0 and 8.0 denotes a surface area of 0.35, 0.26

2
or 0.20 m / g.

The staple fibers used to make the web are expediently cellulose ester staple fibers of the usual type Type with a fiber length of about 3.175 to 15.875 mm and a single denier of about 1 to 8 den.

Preferably, the staple fibers have a length of 6.35 to 9.525 mm and a single denier of about 1.0 to 3.0 den. The layered material is in the moist state from an aqueous slurry of cellulose ester staple fibers and cellulose ester plates deposited using one suitable for the manufacture of nonwovens Device in a conventional process for laying down moist fiber combinations. The layered one Material preferably has a basis weight of 20 to

809815/0708

A / \

2 2

40 g / m, a surface area greater than 1 m / g and a breaking strength of 200 to 1000 g / 5 cm. The sheet-like material is preferably corrugated, before it is formed into a filter material for cigarettes in the form of a filter rod. The filter stick when cut to lengths customary for tobacco smoke filters has a draft that is in the range of 30 to 200 mm water column at a flow rate of 17.5 ml / second with a 20 mm filter length measured as the pressure drop across the filter.

The invention is explained in more detail below in connection with the drawings:

Fig. 1 is a schematic drawing of a system suitable for the production of fibrets according to the invention Can be used.

Figure 2 is a flow sheet of a process for making the sheet-like material according to the invention.

Fig. 3 is a side view of an arrangement for corrugating the sheet material according to the invention and for converting the corrugated material into a cylindrical filter rod.

Figure 4 is the photomicrograph of the cellulose acetate fibrets according to the invention.

Fig. 5 is the photomicrograph of the sheet material according to the invention.

In Fig. 1 is a schematic of the production of a highly fibrillated Acetate fiber according to the invention, i.e. a fibret. As shown in the drawing

809815/0708

27U796

a supply of cellulose acetate dissolved in acetone or optionally in acetic acid is passed through a capillary tube pumped. The end of the tube is arranged in the constriction of a Venturi tube through which a coagulating liquid, usually hot or cold water, is passed through. The high speed of the water flow in the area of the constriction ensures the weakening of the spinning solution flow and additionally extracts the solvent of this solution, whereby a fibret is formed. By Changing the concentration of the spinning solution, the water flow, the water temperature or by adding Other solvents to the aqueous stream can include particle size, degree of fibrillation and the length of the fibrets can be regulated. Special conditions for the device and the method for Production of the fibrets according to this method are explained in Example 2 below. The device according to Example 2 is also a venturi type device, but the spinning solution is extruded above the constriction of the venturi tube. Examples of fibrets obtained according to Example 2 4 represents the drawings in the form of a photomicrograph at 600X magnification Fibrets made by this method or by known methods can then may be incorporated into a sheet material as shown in Figure 2 of the drawings.

Fig. 2 of the drawings is a flow chart depicting a typical process employing a Apparatus for moist laying down of a fiber fleece for the production of a layered material according to the invention. As can be seen from the flow sheet, a slurry of fibret is produced from a delivery point for fibrets by a Dutchman in a storage

809815/0708

_ / ₂ . 27U796

transferred vessel into which a slurry of staple fibers from a staple fiber supply is entered. In the mixing device is used to move the flowing mass that forms in order to ensure the uniform dispersion of the To reach solids, and the amount of liquid present is adjusted. The mixing device supplies the head container of the Fourdrinier machine, where the aqueous layer is deposited, then through the dryer is guided and finally transported on to the product reel. An example of this way The sheet-like material obtained is shown in Fig. 5 of the drawings in a photograph at 10O magnification shown. It can be seen in Fig. 5 that the fibrets with themselves and the staple fibers are intertwined and interlock to form a physical bond. This binding effect is evidenced by the fact that on similar Wise produced nonwovens from staple fibers have essentially no tear strength.

The layer material located on the spool is then processed further by means of that shown in FIG. 3 Arrangement. A web 2 cut to a suitable width is fed from the delivery roller 1 in the gap of a driven pair of corrugating rollers out, the corrugating rollers 3 are designed so that they cause folds, grooves and partial tears along the running direction of the web 2. One device 4 to prevent electrostatic charges is arranged in connection with the corrugated rollers 3 to prevent sticking the web 2 to prevent one of the corrugating rollers 3. The corrugated sheet material 2 is then Continued via a drive roller 5 into the inlet tunnel 6 of a filter rod production machine with a wrapping strip 7 which is fed from the supply roll 8. The one curled in the transverse direction

809815/0708

and in the longitudinal direction corrugated layer material leaves with a cylindrical envelope the channel 6, its protruding Edge 9 is provided with an adhesive by means of an applicator 10, whereupon the adhesive provided filter rods then passed through the heated mold 11 and the final Filter rod 12 molded from. The entire apparatus for producing the filter rods is suitable Way driven by means of an endless conveyor belt 13, which moves itself through the drive shafts 14 will. The filter rod material 12 obtained in this way can then be adapted in a suitable manner Length sections are divided, which are then cut into cigarette filter sticks will.

As stated earlier, the layer material according to the invention contains a coherent one Nonwoven made of cellulose ester staple fibers and about 5 to 35% cellulose ester fibrets, based on weight of the finished layer material. Preferably, the filter material according to the invention contains about 10 to 20% cellulose ester fibrets. It is also preferred that both the staple fibers and the fibrets consist of cellulose acetate. The filter material according to the Invention is further characterized by an upper

2
area between about 1 and 5 m / g, a permeability

Δ P having a diameter of 25.4 mm

round disc between about 1 and 70 mm for a

Flow rate of 200 ml / minute. Preferential

However, the filter material has a surface area between about 2 and 5 m / g.

As stated earlier, the fibrets used in the filter material according to the invention can prior art methods known per se

809815/0708

be prepared, for example by the method of US Patents 3,342,991 and 3,441,473, according to which a dilute spinning solution of a cellulose ester is sprayed into the atmosphere by means of air and then in a Hydraulic engineering are quenched or by the method described in US Pat. No. 2,988,469, according to which a Cellulose acetate spinning solution into a free-flowing one that is only unidirectional at high speed The gas jet is extruded with fiber formation without the formation of spheres. The manufacture of the fibrets, which are used in the filter material according to the invention is preferably carried out in accordance with the teaching the description of Fig. 1 or in accordance with the teaching of US application 6 38 242 dated December 8, 1975, which describes a rotary spinning process. This procedure has the following procedural steps: 1) A spinning solution of a cellulose ester is formed, which is preferably 5 to 15% by weight of cellulose ester contains, in a solvent that contains about 2 to 20 wt .-% of a non-solvent liquid, which is miscible with the solvent for the cellulose ester and also 80 to 98% by weight of a solvent for the cellulose ester, which is miscible with the nonsolvent.

2) This cellulose ester spinning solution is by suitable means, for example by pumping, by a rotating Unit passed to the spinning orifice.

3) A substantially cylindrical disc rotating on its axis is placed in a heated coagulation bath arranged, and this bath contains essentially a nonsolvent for the cellulose ester and up to 10% by weight of an organic solvent which is miscible with the nonsolvent.

4) The coagulation bath is at a temperature of about 60 ° C to a temperature below the boiling point of the nonsolvent contained therein,

B09815 / 0708

, 274Α798

/ lip

preferably at a temperature of up to 95 ° C.

5) Additional liquid, regarding its composition essentially corresponds to the composition of the coagulating bath, is used in this Coagulating bath and pumped out over the circumference of the rotating disc at a flow rate of at least 0.5 l / minute per spinning opening, preferably with at least 1 l / minute per spinning nozzle opening.

6) The spinning solution is extruded through one or more spinning orifices or capillary needles, which are located on the circumference of the rotating disk or alternatively in a viand or plate that extends the circumference of the Surrounding rotating disk, where appropriate, the dope from spinning orifices on the wall or are arranged on the circumference of the disc, is extruded into the coagulation bath, the Spinning orifices have a diameter on the order of 0.12 to 1 mm.

7) The cellulose ester dope is precipitated in the coagulating bath, whereupon the precipitated out removed from the bathroom.

8) The precipitated fibrets are subjected to boiling, preferably in water, for at least 5 minutes, preferably for 10 to 30 minutes to remove residual organic solvent and to prevent puffing and bring about the fixation of the porous fibril structure.

9) The fibrets are then homogenized and the particle size of the cellulose ester fibrets is reduced.

lo) Finally, the cellulose ester fibrets are optionally subjected to a drying process in order to produce the filter material according to the invention to partially or completely dry the fibrets used.

As a cellulose ester, the spinning solution contains, for example

809815/0708

^ _ 27U796

ff

wise cellulose acetate, cellulose triacetate, cellulose acetate butyrate, benzyl cellulose or mixtures thereof. The fibrets are preferably made from cellulose acetate which is dissolved in a solvent consisting of two miscible components; an organic solvent such as acetone, methyl ethyl ketone, acetaldehyde or ethyl acetate, and a liquid non-solvent for the cellulose ester such as water, methanol or ethanol. The liquid nonsolvent makes up about 2 to 20% by weight of the solvent mixture. The preferred organic solvent is acetone, which is miscible with the preferred nonsolvent, namely water. The concentration of the cellulose ester in the solvent mixture should be about 5 to 15% by weight, preferably 5 to 8% by weight. If the cellulose ester content is less than 5% by weight, the process is economically unattractive. Since the organic solvents evaporate during the process and can cause various problems with regard to the recovery of the solvent and with regard to the presence of a flammable volatile solvent in the atmosphere, it is desirable to keep the amount of the organic solvent as low as possible on the one hand and on the other hand to win the desired product. In addition, by setting the solids content of the spinning solution to comparatively low values, a spinning solution is obtained which also has a relatively low viscosity and is much easier to handle and also to extrude without the spinning orifices becoming significantly clogged. Mineral additives such as TiO _? , BaSO. and Al ₂ O- can be added to the spinning solution if desired. If such additives are present, they can be incorporated into the spinning solution in amounts up to 50% by weight of the cellulose acetate as part of the total solids

8098 15/0708

a small particle size obtained by ball milling.

The cellulose esters according to the invention are preferably obtained from an acetylation wood pulp with greater than 90% by weight hemicellulose. However, lower grades of wood pulp can also be used find, i.e. wood pulp with a hemicellulose content of 5 to 10% by weight. Accordingly, are preferred Cellulose ester of high purity used. The purity is to be equated with the filterability, which represents the number of kilograms of dissolved ester that can be filtered through typical for this purpose Filtration media before the media clogs to an undesirable extent. Filter range values between

126.418 and 252.837 kg.dm ² (30 to 60 Ib.ft. ² ) are characteristic of commercially available esters tailored for the textile sector. For the production of the fibrets used according to the invention, however, cellulose esters with filter range values below 2 are also suitable

126.418 kg.dm suitable. This means that the fibrets according to the invention can also be produced from cellulose esters whose degree of purity is lower than that which is normally considered acceptable for filament formation.

The fibrets used for use in the filter material according to the invention are obtained by the spray spinning process prepared in accordance with the description of FIG. 1 of the drawings, water is preferably used by high pressure used as the spray medium. When using water, a gently flowing, the spinning opening Achieved non-clogging spray process, and the dimensions of the precipitated product seem to be finer than that of the product made in accordance with the teaching of U.S. Application 638,242 dated December 8, 1975

809815/0708

V19

is obtained. The length of the fibrets can be varied by changing the water flow and the temperature. Cold water and / or high flow rates reduce the length of the fibrets. The spinning solution preferably contains 10% solids dissolved in a solvent consisting of 90% acetone and 10% water. Solids concentrations between 5 and 12% can be used, with higher concentrations a coarser fiber material is obtained, while lower concentrations are economically undesirable. The solvent mixture can be between 100% acetone and 60% acetone and 40% water without significantly affecting the product properties. It should be understood, however, that any cellulose ester dope composition may be used in the spray spinning process as described in FIG. 1, identified in the process of U.S. Application 638,242 dated December 8, 1975 as being useful. Mineral tracers such as TiO ₂ , BaSO. and Al ₃ O ₃ may also be contained in the spinning solutions, if desired.

The preferred fibrets according to the invention have a particularly large surface area per unit weight. While common cellulose acetate filaments have a surface area of The cellulose ester fibrets, which are used for the production of the filter material, have about 0.25 m / g used in accordance with the invention, in most cases surfaces in the range of about 12 to 25 m / g but essentially always have surfaces of

2
more than 5.0 m / g.

as has already been mentioned, it is used in the Celluloseester staple fibers useful for a material of the conventional type having a fiber length of about 3.175 to 15.875 mm length and a denier of about 1.0 to 8.0 to. Preferably the stacking

809815/0708

fibers a length of 6.35 to 9.525 mm in length and a single denier of about 1.4 to 3.0 den. The fiber cross-section can have the normal round shape, as it is formed by a round spinning opening during spinning, or can have other cross-sectional shapes such as those formed in extrusion by non-round spinning orifices are, for example, cross-sections in the form of a Y, an X or a dumbbell (dog bone). The cellulose ester staple fibers can be made from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose benzoate, cellulose acetate formate, Cellulose acetate propionate, cellulose acetate butyrate or mixtures thereof exist. The esters can be ripened and acetone soluble, like common cellulose acetate, or they can be substantially full be esterified, i.e. contain less than 0.29 free hydroxyl groups per anhydroglucose unit, such as Cellulose triacetate. The preferred cellulose ester staple fibers are cellulose acetate fibers.

As explained in connection with Figure 2 of the drawings has been, the sheet-like material according to the invention can be made from a slurry of cellulose ester staple fibers and the cellulose ester fibrets are made in water. Between 5 and 35%, preferably between 10 and 20% fibrets, based on the weight of the fiber material used, should be present be. Solids can be between 0.005 and 0.1%, and preferably between 0.01 and 0.03% in the slurry be included.

The staple fibers and the fibrets should be raked together mixed and evenly distributed throughout the slurry. This can be done by stirring or mixing, either manually or with any conventional mixing apparatus. The staple fibers and fibrets can can be added to the water individually and mixed. Are

809815/070

SI

however, the fibrets using water as a boiling medium for expansion and stabilization the porous fibrillar structure has been produced, the cake consisting of fibrets and water, optionally with the addition of additional water, if necessary, as a base for slurrying the staple fibers and the fibrets in water are used, in which case the slurry is made by simply adding a sufficient amount of staple fibers to the fibret-water mixture.

As mentioned above, the slurry is then fed onto a standard paper machine to make the to form layer-like material that is to be used as a filter material, for example in layer form for use as face masks or gas masks or in corrugated and compressed form for use as a cigarette filter. Cigarette filter sticks from the corrugated filter material according to the invention show the same or higher filter efficiency at a given pressure drop as a rod from correspondingly corrugated paper webs with significantly improved taste at the same time.

The invention is illustrated in more detail by the following examples, where, unless otherwise stated, all parts are parts by weight and all percentages are percentages by weight and all temperatures are given in ^° C.

example 1

For the production of rotation-spun fibrets for the sheet-like material according to the invention, a 75% solids spinning solution of cellulose acetate suitable for fiber manufacture having an acetyl value of about 55, the 90.5 parts by weight of cellulose acetate

809815/0708

27U796

flakes, containing 1080.0 parts by weight of acetone and 120.0 parts by weight of water, prepared by first mixing acetone and water and then adding the cellulose acetate flakes. The mixture is gently agitated until the cellulose acetate is completely dissolved. Then 20 wt .-% TiO are added as an indicator material, based on the solids weight of the spinning solution. Using the device described in US application 608,416, the spinning solution is introduced into a storage container and then pumped by means of a gear pump through a conduit to the through-going hollow shaft of a rotating unit into the interior of a hollow disk having a diameter of 15.24 cm and rotates at 2900 rpm (peripheral speed 1390 m / minute). The disk is immersed in a coagulation bath for the spinning solution, which essentially consists of water heated to a temperature between 75 ° and 85 ° C. The hollow rotating disk has three openings, each 0.35 mm in diameter, arranged on its circumferential surface. The disc rotates within a circular wall or ring at a distance of about 4.762 mm from its peripheral surface. Water kept at a temperature between 75 ° and 85 ° C is pumped into the coagulation tank and flows through the annular space between the wall and the disc circumference at a rate of 6.7 l / minute / opening. The rapid precipitation of the cellulose acetate and the shearing and high stretching effects on the stream of spinning solution emerging from the spinning orifices result in the formation of short, porous fibers with a high degree of fibrillation.

The material is then directed to the surface of the coagulation bath and flows onto a collecting screen about where some of the water and acetone is separated from the fibrous material. The collected

809815/0708

274A796

fr

Material is then heated to boiling for about 20 minutes at a pressure of 1.05 atmospheres to remove any remaining solvent to remove and to consolidate the porous structure. The fibrillated material is then put in water again dispersed and through a Gaulin 15M homogenizer (Manufacturer Gaulin Corporation, Everett, Massachusetts, USA) where the length of the fibrets at a pressure

reduced from about 211 kg / cm to about 500 µm or less will. The fibrillated material is then aspirated to form a filter cake which is about 12% by weight Contains cellulose acetate fibrets and 88% water. The fibrets obtained from the coagulation bath have a relative slack structure and a relatively short mean fiber length. After homogenization and heat treatment if the fibrets are no longer slack, they are firm and have a certain amount of puffiness porous structure. The fibrets are generally irregularly shaped and have a length that is between varies about 1 and 500 jam, and a diameter of about 1 to 50 pm. The fibrets and staple fibers of 6.35 mm in length and a single denier of 1.8, 3.0 and 8.0 denier having a Y cross section becomes a sheet material on a laboratory apparatus for manufacturing formed by nonwovens. For this purpose, the fibrets 5 are in a Waring mixer in a concentration of 0.5% dispersed, and this slurry is further dispersed in 946 l of water, the 227 g of staple fibers contain. This slurry is pumped onto a 60 χ 40 mesh brass screen, that moves at 1.68 m / minute. Vacuum (203 to 254 mmHg) is applied to the grid to keep the water in remove; the layer formed is then placed on a felt belt and finally to two steam dryers out, which are under a vapor pressure of 9.07 to 13.6 kg. The finally obtained in this way Layers 30.5 cm wide have a thickness of

809815/0708

0.094 to 0.097 now and are characterized by those in the properties given in Table I below:

the on Table I. Fibrets Tear-resistant Singles- bad layer in the speed titer mung to weight Final layer the joined g / 5 cm
Stripes stack Fibrets fibers G % 300 101 g / m 16.5 459 1.8 216 37.3 17.6 755 3.0 309 33.0 20.1 8.0 32.1

Strips of the width given below were cut from the layers and passed through heated corrugated rollers which had 25 grooves per 25.4 mm and a surface temperature of about 120 ^° C. The rolled strips were gathered into a stick and wrapped with paper to form a filter 90 mm long and 25 mm in circumference. These rods were cut into 20 mm long filters and attached to 65 mm long tobacco columns in order to determine the filter effect, that is, the percentage by the filter ent fernton, in relation to the smoke removal, the nicotine removal and the tar removal, the readjusting as smoke removal efficiency REW, nicotine removal efficiency NEW and tar removal efficiency TEW. The results achieved here are given in Table II below:

809815/0708

Streak Tabel II Efficiency at TEW Singles- window weight mitt 6 O mm Pressure drop titer broad of ler 64.9 the Filters pressure 57.2 stack
fibers cm of 20 mm
length waste REW 57.5 19.5 mg mm WS 1.8 22.9 0.118 43 6 8.0 NEW 3.0 25.4 0.167 62 62, 1 8.0 0.204 70 62.5 65, 58 56, , 7 ,8th , 7

The layer material with fibers of lower single titre appears to be better for various reasons. In the sheet material manufacturing process, the Fibrets are better stored and a softer, more easily corrugated layer is formed. The resulting weight of the filter and the pressure drop are reduced, and in the case of a single titer of 1.8 den, a considerable increase in efficiency achieved.

Example 2

To produce injection-spun fibrets for the filter material according to the invention, the im Example 1 described spinning solution used. A nozzle and a bell spinning machine are used from Spraying Systems Company Set-up 22B, 3201 Randolph Street, Bellwood, Illinois 60104, USA. The spinning solution is filled into a storage container and then pumped through a centrally located 10.3 mm spinneret at a rate of 420 g / minute. The water from 60 ° to 65 ° C used for precipitating and refining is passed through three nozzles that surround the spinneret, at a rate of 9 to 10 l / minute at one pressure

8098 1 5/0708

274Λ796

2έ / "

from 12.6 atm. The mixture of spinning solution and water passes through an opening with a diameter of 2.8 mm, which is arranged 3.5 mm below the spinneret, into a tube filled with water, where the fibrets are precipitated. The fibrets are then collected and cleaned and according to the example 1 wrapped in paper with the exception that the material is at atmospheric pressure heated to boiling and the homogenization is omitted.

Example 3

The procedure of Example 2 was repeated with the exception that the injection-spun fibret material brought to the boil at atmospheric pressure and then passed through a Gaulin homogenizer became.

Example 4

The procedure of Example 2 was repeated with the exception that the injection spun material was under Pressure boiled at 120 ° C and then homogenized by passing through a Gaulin homogenizer.

The samples of Examples 2, 3 and 4 were made into layer-like Lanes and gave the values given in Table III below:

809815/0708

27AA796

Table 111

Bo i - layer % Fibrets , 3 Tear filter Smoke removal game weight , 0 firm weight nungswi r- , 6 speed * + efficiency at 50 mm g / m 24 g / 5 cm 9 Pressure drop 2 32.1 16 1300 0.181 54 3 37.1 23 1300 0.182 55 4th 32.1 1018 0.195 58

Inter- or extra-polished from higher or lower Pressure drop values.

The greater strength of the layer material results from the drying carried out at higher temperatures by means of steam at pressures of 2.15 ^r J and 3.15 atm.

As can be seen from the information in Table 111, By cooking under pressure and by homogenizing a finer material obtained that is softer and forms a layer that is easier to corrugate, which in turn has a better effect at a given pressure drop shows in terms of smoke removal.

In order to determine the effect of the amount of fibrets in the layer-like material according to the invention, the rofation-spun fibrets from Example 1 and the injection-molded fibrets from Hei game 4 were combined with staple fibers and Zi: 1 1 st, ο Γ fibers to form layers, those between 5 and 10O Ί fibrets (kept up. The relevant data are given in the next table! Y v. '. i given':

0 9 H 1 5/0708

Fi stack Spinning board fibers ver lot (Singles- travel titer χ % Length now)

as

Table IV

Layer-FiI- compressive- strength waste

weight filters g / 5 cm g mm WS

Efficiency

REW NEW TEW

5 1.8x6.35 spray

11.9 3.0x6.35 rotary

15.8 3.0x6.35 rotary

17.6 3.0x6.35 rotary 23.1 3.0x6.35 rotary

27.7 1.8x6.35 rotary 30 * 1.8x6.35 spray

50 + rotational

75 + rotational

- rotational

182 0.115 60 71.1 63.7 68.0 228 0.121 58 62.2 60.0 59.5 354 0.119 58 62.6 59.7 59.8 459 0.160 60 62.1 58.8 57.2 505 0.127 60 62.0 61.1 59.5 771 0.124 60 63.0 57.5 61.4 767 0.114 60 58.3 50.9 51.3 - 0.168 56 54.2 50.0 49.0 - 0.222 60 43.2 32.3 37.8 0.230 56 37.2 27.2 29.5

Manufactured on a hand-operated Noble Woods machine, Amount of fibret determined from the concentration of fibret in the slurry and the amount remaining on the sieve.

Pulp fibers instead of staple fibers

10

As can be seen from Table IV, the values given show that the amount of fibret depends on the strength of the layer is correlated but is subject to smoke removal efficiency at levels of fibret 30% not particularly affected. When fibrets are present in an amount of 30% or more, the layer strength is reduced high enough so that the corrugation process does not open the structure enough to allow a get good filter. As a result, there is an increasing decrease in efficiency when the The amount of fibret increases over 30%. In addition, the

809815/0708

- -Λ - 29

To recognize signs of an increase in the filter weight with increasing amount of fibrets, so that high amounts of fibrets are undesirable from an economic point of view. At the low level of 5% fibrets, the smoke removal efficiency values are high, partly because of the low single denier staple fibers used and partly because of the openness of the layer chosen. The layer strength is very low and the material is difficult to handle both as a layer and to make filter rods from it.

Example 5

Cellulose acetate staple fibers were mm having a denier of 3 deniers and a length of 6.35 used together with the Celluloseacetatfibrets of Example 4 to prepare a sheet-like material. A 30.5 cm wide laboratory Fourdrinier machine with a 90 χ 100 mesh screen was used, and the drying conditions were chosen so that uncoated layers were obtained (use of drying rollers at a steam pressure of 0.7 atm.). The sheet-like material was then converted into cigarette filters as shown in Figure 3 of the drawings. The results of this example are given in Table V below:

Table V

Layer Fi- Tear Pressure Filter Efficiency weight boards solid waste weight

REW NEW TEW

g / m% g / 5 cm mm WS g %%%

20.0 13.6 100 39.5 0.126 54.8 50.0 53.1 35.5 11.9 228 40.5 0.116 57.2 51.5 54.0

41.1 13.2 325 40 0.139 56.6 50.0 52.0

809815/0708

2744798

Example 6

Cellulose acetate staple fibers of 6.35 mm in length and a single denier of 1.8 den were together with the Cellulose acetate fibrets according to Example 4 used to produce a layer-like material. The quantities the staple fibers and fibrets in the starting slurry were reduced to 113 and 32 g per each 946 1 water. A 30.5 cm wide laboratory Fourdrinier machine with a 90 χ 100 mesh screen was used Application, and the drying conditions were such that uncoated layers were obtained (use of drying rollers at a steam pressure of 0.7 atm.). The results obtained in this example are in in Table VI below:

Table VI

Layer fi- mitt- mitt efficiency at

weight brets leres lerer 60 mm pressure drop

Filter pressure

weight of waste REW NEW TEW

g / _m % g mm WS

26.8 17.3 0.148 52 71.0 66.5 68.4 37.3 16.5 0.118 43 68.0 65.7 64.9

The results of Tables V and VI show that an optimal layer weight for filters made from the layer-like material according to the invention

2 represents, exists in the range between 26 and 36 g / m. Of course, this is to be understood as that this optimal layer weight also depends on other physical parameters of the layer is.

To improve the efficiency of the cigarette filter from the to compare layer-like web according to the invention with cigarette filter materials of known type,

809815/0708

27U796

became a sheet-like sheet according to the following Example 7 made:

example

The procedure of Example 6 was repeated using a sufficient amount of fibrets to produce a layer containing 17.3% fibrets and

2
had a layer weight of 26.8 g / m 2. The sheet was then corrugated lengthways and hand rolled into a cigarette filter. This filter was then compared to commercially available filters. The main data are given in the table below

VII listed:

Tabel VII Filter structure pressure filter waste weight (mm WS) (G) Cellulose acetate single strand titer 1, 8 den, Total titre 4 3000 80 0.116

Smoke removal efficiency

Cellulose acetate strand, single titre 3.3 denier, total titer 44,000 77 0.138

Corrugated cellu-

loose paper 80 0.208

Corrugated cellulose acetate fleece (17.3% fibrets) 80 0.158

56.5

53.0 70.7

77.6

30 As can be seen from the data in Table VII, it is evident that the corrugated sheet-like Celluloseacetatmateria ¹ of the smoke removal than other structures has a higher efficiency with respect to and thus represents the preferred embodiment. If

809815/0708

27U796

39

However, if for various purposes, for example if preferred by smokers, it is desirable to use the The layer-like material can change the manufacture of the filter or reduce the filtration efficiency chopped or needled instead of curled before rolling into a filter. Besides, it is possible to use pulp, the mixture of cellulose fibrets and cellulose staple fibers, which are used to produce the layer-like material are used according to the invention to be mixed. To the aforementioned reduction To demonstrate the filter effect, the layer-like material of Example 7 was before Hand rolls needled, carved before hand rolls and stretched with cellulose. The essential data for this are given in the following table VIII:

Table VIII

Filter structure pressure filter smoke removal waste weight efficiency

(mm WS) (g)

Needled cellu-

loose acetate fleece 81 0.126 69.5

Corrugated fleece
from cellulose acetate chips 81 0.138 67.0

Cellulose acetate fleece with
a single titer
of 1.8 den and
17.5% cellulose fibers 80 0.147 66.0

Most preferred means of adjusting the smoke removal efficiency of the sheet-like material according to the invention, the corrugated sheet-like material is coated with a cellulose acetate strand before the formation of the filter rods. The production of such coated filters is

809815/0708

described in U.S. Patent 3,396,061. However, it is preferred the coated material corrugated at the same time. For example, if the corrugated sheet material of the Example 7 is coated and at the same time corrugated with a cellulose acetate strand with a single titer of 3.3 denier on a 50:50 weight basis, a cigarette filter is found to weigh 0.154 g and a pressure drop of 78 mm WS has a smoke removal efficiency of 65.9%.

About the effectiveness of the nonwovens made of fibrets and staple fibers in layered filtration applications to investigate, samples of layers were prepared according to the procedure of Example 1 with the exception that a hand-operated film forming apparatus (Nobel and Woods) was used. Cellulose acetate and polyester staple fibers containing varying amounts of fibret were used to make the layers used. These were cut into 1 3/4 diameter disks and placed in Cambridge filter pad holders hitched to test its tobacco smoke removal efficiency, which in this case is regarded as a representative aerosol for a particle range between 0.1 and 1.0. Two kinds of Samples were made, one made from normal thin layers (0.1 to 1.2 mm thick) and the other made from thick layers (1.4 to 1.6 mm thick) consisted of what in corresponds approximately to the pressure drop of a commercially available filter material for face masks. In the event of of the thin layers, the pressure drop comparison was carried out through stacked layers in the Cambridge pillow holder. The commercially available material used for the purposes of comparison existed from disks cut from face mask material. One consisted of a dust and Fog mask pillows manufactured by the Mine Safety Appliances Co. of Pittsburg, Pennsylvania, USA, and

8098 15/0708

27U796

2k

the other made of a bonded fiber material known as a molded face mask TC-21C-132 (No. 8710) sold by the Minnesota Mining and Manufacturing Co. of Minneapolis, Minnesota, USA will. The results are given in Table IX below:

7C-21C-132 number Singles- Tabel 5 IX pressure Smoking % Cushion material Il the titer Fi 5 Kis- waste distance Kis the brets 5 sen- effective 70.9 sen stack ge Degree 79.2 fibers 10 weight 85.8 and 10 length 31.7 (mm) (mm WS) 62.9 % 10 (G) thick cellu- 1 8.0x6.35 10 7th loose acetate fleece 1 3.3x6.35 - 0.890 11 30.4 1 3.3x6.35 - 0.780 12th 77.4 If - 0.802 39.5 thin cellu- 1 1.8x6.35 - 3 40.3 loose acetate fleece 3 1.8x6.35 - 0.091 8th 44.8 Il - 0.324 43.3 Poly fleece 74.6 ester staple fibers 1 1.5x6.35 2 68.8 and fibrets 5 1.5x6.35 0.126 6th Il 1 - 0.626 3 BM 2166, 1 1 - 0.687 3 1 1 - 0.695 7th 2 1 - 0.695 9 2 1 - 0.712 7th 1 - 0.400 9 0.400

10

It can be clearly seen that the nonwovens consisting of staple fibers are suitable for tobacco smoke particles both in thick ^ .Is as well as in thin pillow arrangements

809815/0708

3S

successfully remove. It was found that the pillows formed as a fleece according to the invention have the same or a greater effectiveness than that Prior art materials in the high pressure drop area.

809815/0708

Blank page

Claims (16)

Claims (1.! Filter material based on a fiber fleece ^ - / cellulose ester threads, characterized in that it about 5 to 35% cellulose ester fibrets contains. 2. Filter material according to claim 1, characterized in that it contains 65 to 95% cellulose ester staple fibers and contains 5 to 35% cellulose ester fibrets. 3. Filter material according to claim 1 and 2, characterized in that it contains 10 to 25% cellulose ester fibrets contains. 4. Filter material according to claim 1 to 3, characterized in that the cellulose ester fibrets made of cellulose acetate, Cellulose triacetate, cellulose acetate butyrate, cellulose benzoate or mixtures thereof exist. 5. Filter material according to claim 1 to 4, characterized in that the cellulose ester staple fibers Cellulose acetate, cellulose propionate, cellulose butyrate, Cellulose benzoate, cellulose acetate formate, cellulose acetate propionate, Cellulose acetate butyrate or mixtures thereof. 6. Filter material according to claim 1 to 5, characterized in that the staple fibers have a single titre of about 1 to 8 denier and about 3.175 to 15.875 mm in length. 7. Process for the production of a cohesive, self-supporting filter material on the basis of a Nonwoven made of cellulose ester staple fibers according to claim 809015/0708 ORIGINAL INSPECTED to 6, characterized in that about 5 to 35% cellulose ester fibrets are incorporated into it. 8. The method according to claim 7, characterized in that the staple fibers and the fibrets in water slurries, the slurry homogenized and on applies a porous surface causing the drainage, the fiber structure dries and as a fleece of the surface stands out. 9. Use of the filter material according to claim 1 to 8 for the production of a tobacco smoke filter. 10. Use of the filter material according to claim 1 to 8 for the purpose mentioned in claim 9 such that the fiber fleece is corrugated, folded into a filter rod and this is provided with a cover. 11. Use of the filter material according to claims 1 to 8 for the purpose mentioned in claim 9 in such a way that the corrugated fleece before folding with a a strand of cellulose acetate threads covered web. 12. A process for the preparation of the cellulose ester fibrets mentioned in claim 1, characterized in that one a cellulose ester in a solvent containing a nonsolvent for the cellulose ester with which the Non-solvent is miscible, releases this spinning solution leads to a spinning opening that is in or above the constriction a Venturi tube is arranged, through which one essentially consists of a nonsolvent for the Cellulose ester existing coagulating liquid, which contains a miscible organic solvent, passed through and the cellulose ester as Fibrets is precipitated. 009815/0700 13. The method according to claim 12, characterized in that that cellulose acetate is used as the cellulose ester. 14. The method according to claim 12 and 13, characterized in that water is used as the coagulating liquid . 15. The method according to claim 12 to 14, characterized in that the particle size of the fibrets is homogenized the precipitation is reduced. 16. The method according to claim 15, characterized in that the homogenized precipitate is at least 5 minutes heated to boiling. 8098 15/0708