FR2518374A1 - VENTILATED FILTER WITH NON-HOMOGENEOUS STRUCTURE FOR TOBACCO SMOKE - Google Patents

Abstract

TOBACCO SMOKE FILTER WHICH REDUCES THE TAR CONTENT PRIMARILY BY AIR DILUTION RATHER THAN BY MECHANICAL FILTRATION WHILE MAINTAINING A RELATIVELY HIGH PRESSURE LOSS, IN WHICH THE FILTER MATERIAL FORMS A LAYER AROUND A MORE DENSE FIBROUS OR FILAMENTARY OBSTACLE TO THE FLOW OF SMOKE AND IS ITSELF SURROUNDED BY AN ENVELOPE PERMEABLE TO AIR. THE FILTER MATERIAL IS FOR EXAMPLE IN CELLULOSE CELLULOSE ACETATE LINKED FILAMENTS AND THE CORE IS FOR EXAMPLE A STRETCH OF LOW OR NULL PERMEABILITY OF SUBSTANTIALLY DECREPPED FILAMENTS, FOR EXAMPLE IN CELLULOSE ACETATE. THE FILTER IS INCORPORATED IN A FILTER CIGARETTE USING A VENTILATION END CAP (FOR EXAMPLE WITH PERFORATIONS) WHICH MAY CONSTITUTE THE SAME.

Description

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  The present invention relates to filters for tobacco smoke.

  It relates to a new non-homogeneous filter, for tobacco smoke, rod-shaped, and a ventilated filter for tobacco smoke, which comprises a rod of the same general type and which reduces the tar content mainly by dilution by air rather than by mechanical filtration, while maintaining a loss of-

  relatively high filter load (PC) compared to that of a conventional filter

  sic with the same tar retention and air dilution; such a conventional filter can for example be made homogeneously with cellulose acetate filaments of 12 to 15 DPFF (deniers per filament), thus providing a low filtration efficiency -when such filters are used in combination with levels high air dilution, however, too low pressure drop (PC) of filter and filter cigarette. The present invention comprises the use of a filter rod in which the filtering material forms a layer around a denser fibrous or filamentary nucleus constituting an obstacle for the passage of smoke;

  the latter may be impermeable or of very low permeability to smoke.

  According to a first aspect, the present invention relates to a tigefilter for tobacco smoke comprising a layer of filtering material

  for tobacco smoke arranged around a denser and drawn core of fila-

  linked, obstructing the flow of smoke.

  According to another aspect, the invention relates to a ventilated filter for cigarette smoke which reduces the content of tar diluted more by air dilution than by mechanical filtration, in which the smoke filtration material forms a layer around a denser core obstructing the flow of smoke, fibrous or filamentary, and is itself surrounded by an air-permeable envelope, in a filter cigarette employing such a ventilated filter the percentage of dilution by air through the filter is preferably greater than the percentage of tar retention "without ventilation" of the filter, that is to say the percentage measured with an equivalent filter and cigarette by pocketing the dilution by air at

through the filter.

  The filter according to the invention naturally has an air permeable outer envelope, for example a substantially waterproof paper provided with perforations; when in use, the air dilution of the smoke is preferably at least 50% Cigarettes fitted with such filters

  the invention can give a CO / tar ratio lower than that of ciga-

  rettes using the conventional highly ventilated filter (for which said ratio is generally close to unity) but with a draft resistance similar to that of cigarettes with conventional filters; non-ventilated or

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poorly ventilated.

  The pressure loss (CC) of the complete filter e 8 t-maintained at a reasonably high level because of the narrowed cross-sectional area of the filter material The mechanical efficiency of the filter is low due to this narrowed cross-sectional area, and also in reason for the low

  intrinsic efficiency of said filtration material.

  The percentage of air dilution is defined here as the percentage

  tage by volume of the ventilation air added through the filter into the total mixture leaving the filter; thus a dilution by air or ventilation of 50% means that in each puff, there is a volume ratio 50/50 of air added compared to the starting smoke, and a dilution by air of

  % means this ratio is 40/60, and so on.

  Preferably, the closed filter (i.e. with dilution by air prevented) will have a pressure drop (PC) of at least 90 m of water and a mechanical tar retention of at most 45% The filtration material can be a conventional material having a low filtration efficiency, for example cellulose acetate or other fibers of 8 dpf or more (in the form of bundles of filaments or fibers in strands) or under the shape of an assembly of corrugated sheet material or

waffle.

  The denser fibrous or filamentary nucleus obstructing the flow of smoke may be an impermeable or low permeability material, for example a filamentary or fibrous material with low permeability such as that sold under the registered trademark "Transorb",

  a dense, stretched rod of bonded cellulose acetate filaments

  of the Transorh stems and the methods for preparing them (which can eliminate the initial creping of the filament) are described in the patent

  British No. 970 817 to which the reader is referred for further details.

  In the case of a core with low permeability, the radial flow of smoke or air between the core blocking the flow and the filtering material can be prevented with a sleeve or an envelope (for example made of non-porous paper or in waterproof film) or with a skin integrated around the core. The core obstructing the flow of smoke surrounded by the filtration material may extend over the entire length or over a part

  the length of the filter In cases where the core obstructs the flow

  lement does not extend from one end to the other of the filter, it can start from one end or be separated from each end The core obstructing the flow will normally be parallel to the axis of the filter and

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  preference will be coaxial with the filter but this is not absolutely essential

  The filter according to the invention can, of course, have two cores which obstruct the flow as described above, or more.

  filters according to the invention are easily produced by advancing long

  continuously tudinally - a sheet or strip of smoke filtration material, by continuously placing on it a continuous core obstructing the flow of smoke or by depositing thereon at regularly spaced intervals, core elements, tightening continuously the assembly in a rod with the filtering material surrounding the core obstructing the smoke, by continuously enveloping said rod with the air-permeable envelope, and

  by continuously cutting the continuous product obtained into individual elements.

  In the case there is an end cap with perforations and a

  core of length less than that of the filter, the latter can advantageously-

  ment be arranged downstream or upstream of the cap perforations, that is

  say respectively at the mouth end of the filter or distant from the end

filter mouthpiece.

  The filters according to the invention can be used alone or as components of a multiple filter in combination with at least one buffer

  additional low pressure drop and low tar retention.

  The retention pressure drop and air dilution values mentioned here are measured according to the procedures recommended by CORESTA

  (Cooperation Center for Scientific Research Relating to Tobacco).

  When the entire core obstructing the flow of the

  smoke and the filter material that surrounds it as manufactured is self-supporting

  as long as the air permeable casing can be put in place after the

  seems to be made continuously has been cut into individual pieces - this may be

  for example the cap cap joining the filter to a cylinder of tobacco

  loped up in a filter cigarette.

  It is also possible to put in place an air permeable envelope as said assembly is produced continuously; then the filter can be incorporated into a cigarette by an annular nozzle, or the dilution by air in use can be carried out through this envelope and a cap cap. As indicated above, the core obstructing the flow of smoke can be totally or intrinsically impermeable to smoke or it can be of a structure and composition such that it has a certain permeability to smoke but contributes only slightly or not at all

  all to the smoke permeability of the filter as a whole.

  The core (s) obstructing the flow of smoke may for example be made up of a body of filaments or fibers linked

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  having a certain permeability which is however clearly lower, during

  from the use of the filter, to that of the smoke filtration material

  rotating When the core (s) obstructing the flow of smoke have a certain intrinsic permeability to smoke, they may have a shell or a skin impermeable to smoke 9 e separating them from the material of

  filtration of smoke surrounding them.

  In a preferred embodiment of the invention, the core or each core obstructing the flow of smoke is a "Transorb" rod of cellulose acetate in bonded filaments and is surrounded by a conventional smoke filtration material , with if d 9 sirg a waterproof envelope between

both.

  In particular embodiments, the core rod obstructing the flow of smoke is an unwrapped "Transorh" rod made of substantially creped cellulose acetate filaments, manufactured according to a process described in the patent. British No. 970 817, and the filter material arranged around it consists of creped filaments of cell acetate

  lose linked The core rod and the filter rod which surrounds it extend each

  cune over the entire length of the filter which has a highly permeable envelope (150 K) For the efficiency tests of the filter cigarette exposed below, such wrapped filter tips are connected to conventional wrapped tobacco cylinders (with loss of load of 45 mm of water) by a classic cap cap which is made of waterproof material but with perforations to give the required degree of dilution by air in the filtering tip during normal smoking Details of three examples specific are given in

table 1.

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T A B L E A U 1

  Filter material Diameter material Length Circumfused Pressure drop Core nucleus rate in filter rence of without ventilation retention mm in mm filter in mm tar water%

without ventilation

  lation Example 1 wick 8/54 wick 1.6 / 7 (4.5 25 24.61 101 42 Example 2 wick 8/54 wick 1.6 / 7 4.6 25 24.61 118 45 Example 3 wick 8/54 wick 1, 6/7 4.5 25 24.61 92

_ _ _-

I t.n I -N Co w

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  In Table 1, the expression "wick 8/54" means a bundle of

  filaments or wick of 8 denier filament and in total 54 x X 03 denier the express-

  sion "wick 1.6 / 70" has a similar meaning, and the "pressure drop without ventilation" is that of the filter end alone, measured in mm of water preventing the lateral entry of air The "rate tar retention without ventilation "is that obtained with the filter cigarette as described above in

  standardized conditions on a Filtrona 300 smoking machine with the perfo-

  plug cap rations.

  Table 2 compares the pressure drop characteristics of the filter alone and of the ventilated filter cigarette of the example with that of the filters and filter cigarettes in which the filter consists of a uniform buffer of coarse or conventional filaments d crgpgs ligs cellulose acetate The comparative results as for Example 1 refer to a filter length of 25 mm, to a tar retention rate (without ventilation) of 42% and to a pressure drop for the cylinder. 45 tobacco

mm of water.

TABLE 2

  Table 3 gives the results of the tests for Examples 1 to 3; the smoking tests are carried out under standardized conditions on a Filtrona 300 smoking machine with the perforations of the cap cap open. Example 1 of Table 3 differs from that indicated in Table 2.

  only by the fact that in this last test the dilution by air (ventila-

  tion) was limited 50%; in each example, the filterless cigarette has a pressure drop of 45 mm of water, a tar retention rate of 29 mg, and a CO level of 15.7 mg. The ventilated filter cigarette of example 1 has a

pressure drop of 95 mm of water.

, r

  Pressure drop Example I Cell acetate Cell acetate

  mm of water lose coarse lose classic (12 dpf) (2.5-5 dpf) Closed filter 10 l 67 35-60 (without ventilation) Cigarette with open filter 102 84.5 50-70 with ventilation

at 50%

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TABLE 3

  TPM (WNF) means: Total particulate material t (free of water and nicotine).

  In Table 4 below, a commercial filter cigarette and its conventional ventilated filter (wick) of bonded homogeneous cellulose acetate are compared with a filter (of the same size) and a filter cigarette (example 4) according to l 'invention; the tobacco cylinders of example 4 and in the

  commercial reference product are of course identical.

  Example 1 2 3 Closed filter (without ventilation) 101 118 92 Pressure drop mm of water TPM content (WNF) mg 5.5 6.2 9.7 CO content mg 4.1 4.8 5.85 CO / ratio TPM (WNF) 0.75 0.77 0.6 Filter ventilation in% 62 58 50 -8-

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TABLE 4 -

  An air permeability of n K here represents an air permeability of N x 1000 mls / minute / 10 cm / 100 mm of pressure water - determined by measuring the pressure "p" in mm d water generated by a current of 1050 mls of air per minute through 10 cm of the paper and calculated according to the equation: Air permeability = 1050 x-00 P The invention also relates to a rod of smoke filter

  tobacco comprising a layer of filter material for tobacco smoke available

  sge around a denser core drawn from linked filaments constituting an obstacle to the flow of smoke, constituting the preferred form of the filter rod for use according to the invention, with a cap of ventilation nozzle in a filter cigarette The core filaments, for example of cellulose acetate, are of substantially non-creped p 6 eference, having been

  for example d 9 crimped by the stretching of the core material during its formation.

  The filter mat 6 is suitably made up of 6-fold bonded filaments, for example cellulose acetate. The composite rod can be

  surrounded by an envelope of high air permeability (for example 150 K).

  If the rod does not have an envelope, it will be incorporated into a cigarette with a ventilated filter Cigarette Example 4 Commercial comparison product Pressure drop (PC) 80 89 mm of water Filter ventilation in% 65.3 56 , 4 TPM content (WNF) mg 5.7 5.0 CO content mg 2.94 4.09 CO / TPM ratio (WNF) 0.52 0.82 Non-ventilated filter 126 98 Pressure drop mm of water,? ,,% tar retention 42 53 (without ventilation)

  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __-

  -9- filter by means of a ventilation end cap; if the stem has a

  envelope permeable to air, then it can be incorporated into a cigar

  filter rette, by an annular nozzle or by a cap of ventilating nozzle

  tion, most often thanks to the latter solution.

  The filters according to the invention can be designed, by the choice of

  the length, the core and filter material that surrounds it, the structure

  ture, relative density and cross-sections, and percentage of air dilution, to provide with any given tobacco cylinder an acceptable ventilated filter cigarette having a total pressure drop of about 80 to 120 mm d water, generally preferably about 80 or about 90 or about 100 mm of water However, significantly higher or significantly lower pressure drops of ventilated filter cigarettes (e.g. 70, 60 , 50, 40, 30 or even 25 mm of water) can be obtained, if

  this is required, in each case more satisfactorily than with structures

conventional filter sizes.

  The present invention therefore relates to a smoke filter for

  tobacco with a new non-homogeneous structure which reduces preferential CO-

  compared to tar This is achieved by a filter with relatively low mechanical efficiency in combination with air dilution

relatively high.

  Conventional filters, constructed in a homogeneous manner, with for example cellulose acetate at 12 dpf or 15 dpf, which have a relatively low mechanical efficiency, have the disadvantage that, when used in combination with high levels dilution by air, we

  obtains pressure drop of filter or filter cigarette unacceptable-

  The filters manufactured according to the present invention have low mechanical retention while maintaining a relatively high pressure drop

  by comparison with conventional homogeneous filters.

  It can therefore be seen that the invention relates to a ventilated filter for tobacco smoke which preferentially reduces CO with respect to tar, and in which the filtering material for smoke forms a layer around a

  denser fibrous or filamentary nucleus constituting an obstacle to the flow-

smoke.

  Cigarettes fitted with such filters according to the invention have a lower CO / tar ratio than that of cigarettes having the same tar ratio using conventional ventilated filters (for which said ratio is generally close to unity), increasing the contribution of ventilation and decreasing the contribution of mechanical retention for tar reduction, but can maintain resistance to draft

similar to cigarettes.

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REYEND 1 C AT O NS

  l Ventilated tobacco smoke filter which reduces the tar content more by air dilution than by mechanical filtration, in which the smoke filtration material forms a layer around a denser fibrous or filamentary nucleus constituting an obstacle for smoke flow

  and is itself surrounded by an air permeable envelope.

  2 Filter according to claim 1, in which the percentage of dilution by air is higher than the percentage of mechanical retention of tar without ventilation, these two values being measured in combination with

  equivalent tobacco cylinders.

  3 Filter according to claim 1, characterized in that it has a pressure drop without ventilation of at least 90 mm of water and a

  mechanical tar retention without ventilation of up to 45%.

  4 Filter according to claim I or 2, characterized in that it has an envelope or a sleeve separating the core of the filtering material

which surrounds it.

  Filter according to any one of the preceding claims,

  characterized by the fact that the core consists of a drawn rod of cellulose acetate filaments bonded substantially dgcrépgs, and that the material

  filter is made of linked filaments of cellulose acetate pancakes.

  6 Filter according to any one of the preceding claims,

  characterized by the fact that the envelope comprises a cap cap incorporating

  the filter in a filter cigarette.

  7 Tobacco smoke filter rod, comprising a layer of tobacco smoke filter material arranged around a denser core

  stretched, obstructing the flow of smoke, bound filaments.

  8 Filter according to claim 7, characterized in that the core filaments are substantially dgcrêpgs, the filtering material being

  preferably made of creped tied filaments.

  9 Filter according to claim 7 or 8, characterized in that

  the filaments are made of cellulose acetate.

  Filter or filter rod according to any one of the claims

  1 to 5 and 7 to 9, characterized in that it is incorporated in a cigarette

  filter with a cap of ventilation cap.

  11 Ventilated tobacco smoke filter, characterized by the fact that it preferentially reduces CO in relation to tar and by the fact that the filter material for smoke forms a layer around a denser fibrous or filamentary core constituting an obstacle to the flow of smoke.