EP3072405A1 - Cigarette filter - Google Patents

Abstract

There are proposed filaments of regenerated cellulose for tobacco smoke filter, in particular for cigarette filters, wherein the filaments contain additives, which are characterized in that the additives are oligomeric or low-polymer saccharides. In addition, the invention provides a method for producing such filaments.

Description

The invention relates to cellulosic filaments, such as e.g. Rayon, for tobacco smoke filters, in particular cigarette filters, and a method for producing such cellulosic filaments for tobacco smoke filters.

Usually one starts in the production of the base of cigarette filters of cellulose. The technical acetate production is carried out essentially by reaction of pulp with acetic anhydride in acetic acid under sulfuric acid catalysis. In this case, the three partial steps, pre-activation of the pulp, complete acetylation to cellulose triacetate and partial hydrolysis (saponification) to the desired cellulose-2,5-acetate, go through. After the saponification step, the cellulose 2,5-acetate is dissolved in acetone and spun into long multifilament yarns by dry spinning. The diameter of the filaments is 30-50 microns. Very many threads (3000 to 35000) are brought together to form an endless band and this band is then crimped into stuffer boxes. The product is dried and is then ready to be presented in the next process step as a filter tow. To produce the cigarette filter, the filter tow is placed in filter rod machines, wherein the filter tow is first stretched and then charged with an adhesive triggering additive. After forming a three-dimensional sliver, the filter tow is introduced by means of an inlet funnel in a format part, there transversely compressed axially, wrapped in paper and cut to the length of the filter rods.

This conventional manufacturing method involves some problems and disadvantages, such as e.g. often insufficient pre-activation. This can lead to the formation of gel particles due to the different acetone solubility of the partially hydrolyzed cellulose-2,5-acetate. Another disadvantage is the use of sulfuric acid as a catalyst. In the case of too slow a reaction due to insufficient activation or use of too low molecular weight pulp, cellulose chain degradation may become critical. In addition, sulfuric acid ester groups in the cellulose also cause gel particles in the solution of cellulose 2,5-acetate and the thermal instability of the final product.

There has been no lack of attempts to carry out the process described above with cellulosic fibers or regenerated cellulose fibers (instead of cellulose acetate (also referred to simply as acetate).) Cellulose is the most common and important naturally occurring polymer in the world, cellulosic fibers, filaments and multifilaments As is known, one can perform a classification according to the manufacturing process, in which a distinction is made between the direct dissolving process and the regenerating process, the fibers or filaments resulting from these processes - The terms "fibers" or "filaments" are used synonymously in the context of this invention - are referred to below and regardless of the preparation process as underivatized or non-acetylated cellulose - in contrast, for example to their acetates.

As a direct dissolving process, inter alia, processes are known in which the recovery of cellulosic fibers from solutions in tertiary amine oxides, such as N-methylmorpholine N-oxide (NMMO), ionic liquids (ionic liquids) or phosphoric acid and subsequent precipitation into suitable coagulation occurs.

Other common processes for the production of cellulosic filaments, which are used for yarn or Kordherstellung, Regeneratverfahren in which cellulose is first reacted to be chemically soluble derivatives (xanthates or carbamates) and dissolved. The solution is pumped through spinnerets and finally regenerated in the precipitation bath to cellulosic filaments. Such filaments are i.a. known as rayon.

The production of cigarette filters directly from the cellulosic filaments would also bring an additional environmental benefit. Cellulose, like rayon, has a much better digestibility than acetate and with an annual production of around 6.000 billion cigarettes, of which the vast majority are filter cigarettes, the better digestibility of the remaining filters would be a decisive ecological as well as economic advantage and certainly promoting the image of the industry.

Accordingly, efforts have been underway for quite some time now to develop cigarette filters made of cellulosic filaments, e.g. from the regenerated cellulose, and not from the acetate.

The main drawbacks according to literature, which have led to the fact that, for example, the use of rayon in cigarette filters has not prevailed, on the one hand the fact that - due to the smoother surface of rayon filaments - the components of the smoke are filtered insufficiently. The GB 749,340 Therefore, it tries to give the rayon increased porosity by adding gas in the spinning bath. This gas is introduced into the viscose in finely divided form, the gas-containing spinning solution pressed through a nozzle with a plurality of holes in a spin bath and then withdrawn the coagulated threads at a speed which is less than the exit velocity of the spinning solution from the nozzle (nozzle delay ).

In this way, porous rayon is used as a filter, which shows a correspondingly increased retention capacity for the pollutants contained in tobacco smoke.

Another - but still unsolved - disadvantage in the use of cellulose instead of the acetate, is the lower hardness of the filter strand to be processed in the filter production; this causes problems during the continuous process of cigarette production on the filter rod machine and on the cutting machine, but restricts v. a. also the performance characteristics of the filter crucial, as too soft a filter is sensitive to the senses. Theoretically, this could be compensated by a firmer filter cover paper, which would still take some getting used to sensory. Another possibility would be to increase the filter hardness by higher material compression of the filter material in the given filter volume. However, the latter would in turn have undesirable effects on the filter density and the suction power requirement to achieve the desired smoke flow.

In addition, unlike acetate, underivatized cellulose does not cut well due to poorer cure in the process. Furthermore, it is difficult to obtain exactly round filter cross sections, which comply with the specified very tight tolerance limits.

It is therefore an object of the present invention to provide cellulosic filaments which are suitable for the production of cigarette filters and which do not or to a lesser extent have the disadvantages described above. In addition, a method for producing such filaments to be proposed.

It has now surprisingly been found that the above-mentioned problems of the prior art can be solved by substantially non-acetylated cellulosic filaments, which filaments contain additives which are oligomeric or low-polymer saccharides according to the invention.

Unexpectedly, the tows of such cellulosic filaments thus obtained exhibit quite sufficient hardness during filter production so that the uniformity of the circular cross-sections of the filters is maintained even after cutting the tows.

By the term "substantially non-acetylated" is meant those cellulosic filaments that have virtually no actetate groups, more preferably that the filaments have no acetate groups at all, and in particular no O-acetylation, and most preferably that all of the filaments are OH Groups are free within the chain.

The preparation of the cellulosic filaments is therefore not limited to a particular method per se. Thus, for example, the cellulosic filaments of the present invention may be prepared by both a direct dissolving process such as the NNMO process and by regenerating processes such as e.g. the viscose or rayon process are obtained. However, in the context of the present invention, the rayon process is particularly preferred as the starting process for the claimed cellulosic filaments.

In principle, it is preferred if the degree of polymerization of the oligomeric or low-polymer saccharides used is greater than about 20, preferably greater than about 50, and more preferably greater than about 100.

In the context of the present invention, the term "saccharides" is to be understood as meaning not only the substances which fall under the gross formula C _n (H ₂ O) _m (often also carbohydrates in the narrower sense, that is to say hydrates of the carbon), but also Representatives of this class, which differ significantly from this gross formula and contain other functional groups and heteroatoms such as nitrogen or sulfur. Oligomeric or low-polymer representatives of saccharides with heteroatoms are also referred to below as "heterosaccharides".

The use of the oligomeric or low polymer saccharides during the spinning process of the rayon filaments causes their water solubility, preferably at room temperature or at temperatures between 20 and 35 ° C.

It is very particularly preferred in the product according to the invention if it is in the saccharides to be used are xylans or xylene derivatives. Xylans are known to those skilled in the art as the most important representatives of hemicelluloses or polyoses. Although the xylans are per se water-insoluble, the water solubility can be adjusted by appropriate adjustment of the degree of polymerization and by targeted influencing of the side groups of the xylan chains. In addition, for example, a high degree of acetylation of xylan is favorable for water solubility.

In this context, it is also preferred if starch or starch derivatives or also cellulose or cellulose derivatives are used as saccharides.

Again, care should be taken that the desired water solubility of the saccharides is adjusted by a suitable pretreatment. Natural starch is hardly soluble in water. However, aqueous starch solutions are obtained, for example, with hot water, which solidify on cooling to a gel and form a starch paste. The production of wallpaper paste is also based on this principle. In contrast to natural starch, gelatinization in the case of the methylcellulose of the wallpaper pasteuriser already takes place with cold water. Measures for this purpose are known to the expert.

Preferably, the concentration of the saccharides is chosen so that they are present in the filaments between 5000 and 100,000 ppm, preferably between 10,000 and 50,000 ppm, based on the cellulosic filaments. This concentration is usually quite sufficient to achieve and maintain the desired properties in the resulting cigarette filter. Without wishing to be bound by theory, it is believed that increasing the hardness of the tow (for example, rayon), which has a beneficial effect on subsequent filter production and dimensional stability, is due to gluing of the filaments ("gelatinization") the saccharides present in the cellulosic filaments. The effect of the gluing, or gelatinization of the saccharide-modified Cellulosic filaments can be achieved by moistening the correspondingly equipped cellulosic filaments in the process of filter production and then drying them again.

The present invention is also directed to a process for producing substantially non-acetylated cellulosic filaments for tobacco smoke filters, in particular cigarette filters, wherein additives are added to the spinning solution in aqueous solution immediately before or during the spinning process, and wherein the additives are oligomeric or lower polymer saccharides.

Rayon is particularly preferably treated as regenerated cellulose by means of these additives.

The process for producing rayon is known per se. Usually, first of all, e.g. made of wood through a digestion process pulp, a fine-fiber mass consisting mainly of cellulose.

The pulp obtained is first treated with 18 to 22% sodium hydroxide solution, whereupon the alkali cellulose (Na salt of cellulose) is formed. The alkali cellulose is then reacted with carbon disulfide (CS ₂ ) to cellulose xanthate. By dissolving this xanthate in sodium hydroxide solution, the "spinning solution", the so-called viscose is obtained, which must "ripen" for 2 - 3 days before spinning. The ripened spinning solution is forced through fine nozzles into a "precipitation bath" or "spin bath", ie a solution of sulfuric acid (H ₂ SO ₄ ) and sulfates such as sodium sulfate (Na ₂ SO ₄ ) and zinc sulfate (ZnSO ₄ ). In the precipitation bath, the carbon disulfide molecules that are bound to the cellulose are split off again, resulting in the viscose filaments or rayon filaments, which consist of almost pure cellulose.

Also in the process it is preferred if the degree of polymerization of the saccharides is greater than about 20, preferably greater than about 50 and more preferably greater than about 100.

The addition of the saccharides is conveniently carried out by adding in aqueous alkaline solution (pH = 10-14) either by injection directly into the viscose line or into the spinning bath.

Again, heterosaccharides are preferably used and particularly preferably xylans or xylene derivatives.

Claims (14)

Filaments of substantially non-acetylated cellulosic filaments for tobacco smoke filters, in particular for cigarette filters, the filaments containing additives, characterized in that the additives are oligomeric or low-polymer saccharides. The filaments according to claim 1, characterized in that the filaments are cellulosic filaments obtained by means of a regenerating process, particularly preferably by the viscose process. The filaments according to claim 1 or 2, characterized in that the degree of polymerization of the saccharides is greater than about 20. The filaments according to one or more of the preceding claims, characterized in that the saccharides are heterosaccharides. The filaments according to one or more of the preceding claims, characterized in that the saccharides are water-soluble at room temperature. The filaments according to one or more of the preceding claims, characterized in that the saccharides are xylans or xylene derivatives. The filaments according to one or more of the preceding claims 1-5, characterized in that the saccharides are starch or starch derivatives. The filaments according to one or more of the preceding claims 1-5, characterized in that the saccharides are cellulose or cellulose derivatives. The filaments according to one or more of the preceding claims 1-5, characterized in that the saccharides are present in a concentration between 500 and 10,000 ppm based on the cellulosic filaments. A process for the preparation of substantially non-acetylated cellulosic filaments for tobacco smoke filters, in particular cigarette filters, wherein the spin solution additives are added in aqueous solution immediately before or during the spinning process, characterized in that the additives are oligomeric or low-polymer saccharides. The method of claim 10, characterized in that the degree of polymerization of the saccharides is greater than about 20. The method according to claim 10 or 11, characterized in that the saccharides are heterosaccharides. The method according to one or more of claims 10 to 12, characterized in that the saccharides are heterosaccharides. The method according to one or more of claims 10 to 12, characterized in that the saccharides are xylans or xylene derivatives.