IL27459A - Tobacco smoke filter plugs made of paper and method for improving their taste qualites - Google Patents

Description

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The present invention relates to improvements in tobacco smoke filters made of paper, particularly for filter-tip cigarettes · and in methods for improving the taste qualities of such filters.

Filters containing paper in a wrapper are known and widely used for filter-tip cigarettes. One method, which is now practiced, for treating paper to make it into an efficient filtering material, i.e., filter paper for filter-tip cigarettes, included passing a web of smooth raw paper between at least one pair of intermeshing grooving or corrugating rolls provided with axially spaced circumferential ribs. The rolls form in the paper a corresponding number of parallel grooves, i.e. corrugate the paper. During treatment by the rolls, the engagement of the ribs with the paper prevents any substantial transverse shrinking or gathering thereof so that, as a result, the paper web is stretched laterally. Such stretching loosens the fibers of the paper to form fuzzy areas with numerous projecting fiber ends on the surfaces of the grooved web at locations where the fibers are at least partially separated or pulled apart. In some cases the stretching may be to such an extent as to cause haphazardly-located, discontinuous longitudinal tears which have frayed fuzzy edges, although the web for all practical purposes substantially retains its transverse continuity.

This method of treating paper to render it more effective as a tobacco smoke filter is well known, as well as filter paper produced by such treatment, and filter rods or plugs made by laterally gathering such filter paper into an endless string or cord which is wrapped and then cut into filter rods or plugs of any desired length. Such method and products are disclosed, for example, in the following patents: British patent s Nos . 796 , 679 ; 790 , 694 ; 801 , 391 and 832 , 087.

In accordance with the principal method used to date for roovin and laterall stretchin smooth raw a er to the extent needed for efficient filtering without completely destroying the lateral or transverse continuity of the web, it is necessary, prior to the grooving treatment, to make the paper web soft or yielding by a suitable treatment e.g. by moistening with water or any other suitable liquid. As a result, the grooved and laterally stretched web must be dried after the corrugating and stretching treatment before being wound up on spools or bobbins, or before being made directly into filter rods or plugs. This known treatment method includes before, during or after the drying treatment, further deformation or mechanical working of the corrugated and stretched web by any appropriate device, for example, by pinch rolls having smooth or knurled surfaces which partially compress or flatten the corrugations and so minimize the existence of unobstructed through passages in filters made of such paper or greatly restrict such passages. The thus produced filter paper may be wound on spools or bobbins to be fed later to filter rod machines of well known design, or may be fed directly into a filter rod machine. In the above-described known grooving and stretching method, it also is advantageous to heat the grooving and stretching rolls to a temperature up to several hundred °F though cold rolls are by no means insufficient.

Although the known treatment method, as described above, requires the paper to be quite moist during the grooving and stretching process, this moistening is not absolutely necessary. Smooth raw paper webs of sufficient types may be treated by passing pairs of intermeshing grooving or corrugating rolls with axially spaced circumferential ribs without an additional moistening. With this the treated paper web shows less distinctive or no longitudinal grooves but for lower grad demands of filtering qualities and of end face appearance also such paper web treatment is commercially applicable and offers the advantage to omit any drying devices.

It may be pointed out that other means than the above explained pairs of grooving rolls are known for treating a paper web to produce fiber loosening and projecting fiber ends. For example rolls provided with prongs of determined shape are sufficient for producing slot-like openings of desired shapes in a paper web passing such rolls whereby adhering struck out parts of the paper shows frayed edges with a multitude of projecting fiber ends. It has been suggested also to produce lacerations being haphazard in shape and size by passing a dry paper web through the nip between a pair of rolls provided with toothed discs as well as the nip between a smooth soft rubber roll and a metal roll provided with circumferential ribs.

All filter plugs made from paper webs, irrespective of their treatment to make into an efficient filtering material, show the disadvantage that such filter plugs used for cigarettes, especially cigarettes of light and fair tobacco mixtures, produce a taste in the smoke which is well known as "paper taste" with cigarette manufacturers-. No doubt this "paper taste" is not produced by substances given off from the paper filter plug into the smoke stream passing therethrough but rather by an absorption of smoke components in another degree as by other filter plugs, especially by Cellulose Acetate fiber filters. But the existence of a "paper taste" when using paper filter plugs with sensitive tobacco brands is a fact which is regarded occasionally by cigarette manufacturers as a deficiency.

While the cause of such taste is not known, it has been thought that the above-described moistening and drying steps, and the engagement of the moist paper with the hot metallic rolls, may possibly be somewhat responsible. Tests have been shown, however, that paper filter plugs made from a paper web treated, when dry, by non metallic means to make it into an effective filter paper for tobacco smoke have met with failure in respect to the "paper taste".

Additionally, prior to this invention attempts have been made along other lines to reduce or eliminate the so-called "paper taste" attendant cigarette filters made of paper. Such efforts have included the addition of acid substances to the fluid used to moisten the a er as a reliminar to the roovin and or subsequent to the grooving treatment, and in some instances have been sprinkled on the grooved web after it has. been dried. Such substances have included acetic acid, formic acid, aluminous water and other acidic substances. All such attempts have met with failure, however, because paper webs treated with such substances, have a disagreeable odor and, moreover, tend to corrode metal parts of the grooving or lacerating apparatus or otherwise deleteriously affect its operation. Unsuccessful earlier efforts to reduce or eliminate the "paper taste" also have included the use of raw paper having a pH value lower than its normal value of 6.1 to 6.3. All such papers heretofore used, however, have not been satisfactory because they frequently have a yellow color, which is most unattractive to smokers, or have a reduced flexibility that renders them somewhat brittle and of a straw-like character. The brittle characteristic makes such paper completely unsatisfactory for a fiber loosening treatment, as aforesaid, so that such paper webs usually are ineffective as a filter material for tobacco smoke and showed no remarkable reduction of the "paper taste" .

It is, therefore, an object of the present invention to provide a method for improving the taste qualities of tobacco filters containing paper in a wrapper.

It is another object of this invention to provide an improved method which embodies the foregoing object and in which a paper web is made of sulphur free pulp into which is added a sulphur free metallic compound of an acid from the group comprehending acetic acid, propionic acid and- formic acid in an amount to achieve a pH-value less than 6/0 m the water container of the last screen of the paper-making machine, whereupon the paper web is corrugated and lacerated in a controled manner, wrapped up, reshaped into an endless paper rope of approximative round sectional shape and subdivided into filter portions of desired lenghts.

Another object of this invention is a tobacco smoke filter plug, especially for filter-tip cigarettes, which is made by subdividing an endless filter rope containing paper in a wrapper and having an approximative round sectional shape.

The filter plug is improved in that the paper is free from sulphureous compounds and contains a metallic compound of an acid from the group comprehending acetic acid, propionic acid and formic acid.

Other objects and advantages of the invention v/ill become apparent from the following description.

Known tobacco smoke paper filter plugs are normally accomplished through the use of raw paper, preferably of a weight of about 20 to 40 grams per square meter. During the manufacture thereof aluminium sulfate is incorporated into the paper pulp in order to increase the tensile strength of the dried paper. Aluminium sulfate has the property of somewhat increasing the coherence of the fibers constituting the paper web. Used with filter-tip cigarettes containing light and fair tobacco mixtures such paper filter plugs impart the tobacco smoke the undesired so-called "paper taste" .

It has been discovered and proved by a multitude of tests that the "paper taste" of paper filter plugs is reduced or completely omitted by producing the filter plugs according to the present method. To this end a paper web should be produced from a pulp being substantially free from su fu ic compounds and containing no aluminium sulfate. To achieve the necessary glueing and fiber coherence in the paper web other suitable compounds have to be added to the pulp which possess the same desired property as aluminium sulfat but no sulphureous components. It has been found out that ¾luminium acetate Al^ (OH) 2 (CH^COO) , for example, is suitable when added in an amount that the pH-value of the water in the container of the last screen of the paper-making machine is reduced to a value less than 6/0 or preferably less than 5/δ. Such a paper web, substantially free of sulphurous compounds and having a higher acid content than normally, can be corrugated or lacerated in dry or moistened condition to any desired extent and wound up on spools or bobbins which are made up into filter plugs later n, or ma be fed directl into a filter rod machine for wra in into filter plugs of desired lengths.

The corrugated and lacerated paper webs produced continuously by the described method can be easily made up into filter plugs and possesses mechanical qualities, for example tensile strength and dimensional stability, at least equivalent to the corresponding qualities of hitherto used paper webs. Also the raw paper has been found to possess mechanical qualities at least equivalent, and possibly better, than corresponding qualities of hitherto used raw paper webs. The following table compares relevant characteristics of the best quality raw paper used heretofore for making filter paper according to the above-described known process with raw paper embodying this method.

COMPARISON OF QUALITIES OF RAW PAPER USED HERETOFORE TO MAKE FILTER PLUGS WITH RAW PAPER ACCORDING TO THIS METHOD.

Prior Paper according Paper to this method Example I Example II White color content in % 89/s 88% Weight in grams per square meter 35?/θ 35/fa Thickness in millimeters 0^060 0^060 Tension length in meters lengthwise 3500 5000 (length of a depending strip necessary to cause laterally 1460 2593 rupture by its own weight) ratio in % 4l v 5l/9 pH value in screen water container 6*/3 s s - 1.0 - It is evident from the foregoing table that raw paper for filters according to the present method has better mechanical qualities than raw paper used heretofore for tobacco smoke filter plugs.

Tobacco smoke filter plugs for filter-tip cigarettes have been prepared from longitudinal grooved, mutilated and lacerated paper webs produced from paper according to the present method and the above table for so called blind smoking tests by experts.

It has been proved that the "paper taste" hitherto common to cigarettes having paper filter plugs is noticeable only to a negligible extent or not at all. Further tests have shown that this phenomenon probably results from the fact, that in the paper and xts collulose fibers the %^Lluminium sulfate is a. replaced by Aluminium acetate and at the same time the grooved and lacerated paper web is provided with higher acid content. Without doubts the described filter plugs prove a noticeable improvement in taste qualities compared to all other known paper filter plugs for cigarettes.

Other tests have proved that a further reduction of the pH-value below 5/8 to i/4 does completely remove all eventual existing remainders of the "paper taste" and is followed by a further taste improvement. An increaseae-at- of the acid content in this paper up to pH = 5 2 to 5/0 does not produce any taste disadvantage; the preferred range of pH values with this kind Extended tests have been made with filter plugs containing paper webs with a complete replacement of the hitherto used Aluminium sulfate by Aluminium acetate according to the following Examples III and IV, respectively.

Example III: Into the beater containing pulp prepared, according to well known methods but without any Aluminium sulfate has been passed liquid Aluminium acetate Al^(OH) ^ (CH^COO) in small amounts whilst monitoring the pH value of the water in the container of the last screen of the paper-making machine. The addition of has been continued until further addition did no longer reduce the pH value which condition was reached in the range of pH = 5^3 to 5*/S . A raw paper web of about 32 to 34 grams weight per square meter and with a "cloudy" structure was produced from such pulp and wound up into a raw paper roll.

From this raw paper roll a paper web was continuously wound on with a speed of about 60 to 100 cm per second, mdstened, passed through the nip between a pair of heated rotating steel rolls provided with interfitting circumferential The treated paper web was provided with narrow longitudinal ridges, intermediate longitudinal grooves and a multitude of irregular distributed disconnected longitudinal tears and fe iied- into a filter rod machine of known design, gathered laterally to an endless rope of about 8/3 mm diameter, wrapped in and subdivided into filter- rods of desired length.

The filter plugs prodiced according to Example III has been checked in respect to the nicotine and tars absorption as well as to the taste quality and compared to filter plugs having a the same draw resistance and being made from ^fluminium acetate containing raw paper of the same weight by the same treatment. The filtering effect of the acetate containing paper filter plugs is at least of the same value and according to many test results even higher. The taste improvment of this acetate containing paper filter plugs compared to sulfate containing paper filter plugs has been proved beyond any doubts by so-called blind smoking tests of experts.

Example IV: The pulp in the beater has been prepared as in Example III and ¾luminium acetate Al^(OH) ^ (CH^COO) added up to a pH-value in the water of the container of the last screen of about 5/8 to 5^6.

Then diluted acetic acid CH_COOH was admixed up to a pH- alue in the water from the last screen of about .5,4. The production of paper webs and filter plugs has been carried out as described in Example III.

Filter plugs of 20 mm length prepared according to Example IV and attached to a tobacco column of 65 mm length have been tested and compared to filter plugs of the same length and identical draw resistance made from ^ellulose Acetate fibers (TypaESTRON 3.3-40) connected to identical tobacco columns.

The filter plugs containing ellulose-^icetate fibers have been prepared in known manner together with Driacetin as a softening agent whilst the filter plugs according to Example IV have been used without any additional preparation. The filtering efficiency of the two filter plug types has been checked and the following values of components in the smoke stream of one cigarette has been found: Milligrams Milligrams Nicotine solid substances ■ Cigarette with filter Example IV o/s 16 c, a Cigarette with Accordingly a chemical analysis to ascertain the critical substances in the raw paper or filter rods is rather difficult but suitable methods for a qualitativ examination are available.

For a detection of ¾ft.uminium sulfate normally contained in paper filter plugs but not allowable according to the present method an examination using is preferred which shows in known manner a deposit of Baryt ¾arium sulfate) if sulfate compounds are contained in the paper. The qualitative detection of acetic compounds in filter plugs is more difficult c p but ossible usin the known iadod l check or the Potassium reaction of Jirsenic trioxyd and the presence of acetates is indicated by an odor of f?arlic. The second mentioned check results in a typical acetic acid odor.

Consequently the lack of sulfates and the presence of acetates in a paper web and in filter plugs can be positively substantiated and constitute material features of the products with satisfactory distinctness.

The above described Examples and embodiments of the present method as well as the' products therefrom relate to a replacement of ffluminium sulfate normally contained in paper webs by uminium acetate with or without additional acetic acid. It may be pointed out, however, that the present method and the products therefrom are not restricted to the mentioned replacing substances. An improvement of paper filter plug taste qualities can be achieved also by replacing Aluminium sulfate in paper webs by other ¾Luminium compound of sulphur free monovalent organic carbon acids as for example formic acid HCOOH or propionic acid C^H^COOH. The taste qualities of paper filter plugs are also improved whena luminium sulfate c m is replaced by ^!alcium acetate e.nd ^fagnesium acetate or other c , ¾ (alcium and i^agnesium compounds of sulphur free monovalent carbon acids, but such a replacement is influencing also the mechanical and other properties of the paper.

Claims (1)

1. smote filter plug tip produced by subdividing of endless rope of round sectional sha e in a characterized that the paper is tially free u compounds and contains an aluminium acid propionic acid and 2 A tobacco smoke filter according to Claim characterised in the co said in small percentage of weight by filter o Claim characterized in that the of the paper less A tobacco to characterized that of the paper is 1 tobacco smoke filter according to Claim characterized that the of the is in the to tobacco smoke filter to G characterized the paper a weight of 20 to 40 grams per square A tobacco smoke filter according to Claim characterised the paper is 17 end ip by that the provided with a of longitudinal for the taste of filters containing in a characterised in that a paper web of substantial sulphur pulp into which is added a sulphur free aluminium compound of an acid from the group comprehending acetic propionic acid and formic in an amount to achieve a less than in the water container the last screen of the making whereupon the said paper web Is corrugated lacerated in a controlled wrapped reshaped into an endless paper rope of approximative round sectional shape and subdivided into filter portions of desired Method according to characterized that the said pulp is substantially free of aluminium that into said acetate added to Claim in that acetate added to a in of to the screen of the 18 Method to Claims that dilated is to salt to a further decrease of the Method to Claim 9 aad that la adjusted up to a of to Method to Claiia 10 to characterized the said paper web is advanced between at least pair of rotating rolls ribs stretched up to an producing a tude of discontinuous longitudinal mutilations and that the the paper is and Tilth projecting 9 la that the aid paper web is moistened prior to ment of said pair of rolls and the moistened web the t Method to of to that the said paper web is provided with a multitude of openings pierced out the web haying projecting are whole of web according to any desired pattern and haphazard in respect to the Applicants insufficientOCRQuality