U.S. patent application number 10/476920 was filed with the patent office on 2005-06-16 for filter tow.
This patent application is currently assigned to Rhodia Acetow GmbH. Invention is credited to Dollhopf, Rudiger, Kuner, Dieter, Leutner, Thomas, Teufel, Eberhard, Vogt, Christian.
Application Number | 20050126582 10/476920 |
Document ID | / |
Family ID | 7683354 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050126582 |
Kind Code |
A2 |
Dollhopf, Rudiger ; et
al. |
June 16, 2005 |
FILTER TOW
Abstract
The invention relates to a filter tow made from crimped endless
cellulose acetate filaments, whereby the filaments form at least
two connected fibre bundles with the same filament titre of at
least 600 filaments. The filament titres differ from bundle to
bundle by at least 1 dtex Furthermore a filter tow is disclosed
with a crimp ratio of more than 40%, said filaments comprising at
least 22 crimp turns per filament length.
Inventors: |
Dollhopf, Rudiger;
(Herbolzheim, DE) ; Teufel, Eberhard;
(Gundelfingen, DE) ; Leutner, Thomas;
(Herbolzheim, DE) ; Kuner, Dieter; (Merzhausen,
DE) ; Vogt, Christian; (Freiburg, DE) |
Correspondence
Address: |
DARBY & DARBY P.C.
P.O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Assignee: |
Rhodia Acetow GmbH
Engesserstrasse 8
Freiburg
DE
D-79108
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 0237982 A1 |
December 2, 2004 |
|
|
Family ID: |
7683354 |
Appl. No.: |
10/476920 |
Filed: |
May 4, 2004 |
Current U.S.
Class: |
131/331;
428/393 |
Current CPC
Class: |
A24D 3/10 20130101; Y10T
428/2965 20150115 |
Class at
Publication: |
131/331;
428/393 |
International
Class: |
A24D 003/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2001 |
DE |
101 21 310.7 |
Claims
What is Claimed is:
1. A filter tow of crimped, continuous cellulose acetate filaments,
wherein the filaments form at least two coherent fiber bundles of
the same filament dernier of at least 600 filaments which differ
from fiber bundle to fiber bundle in their filament dernier by at
least 1 dtex.
2. The filter tow of claim 1, wherein the filaments form more than
five coherent fiber bundles of the same filament dernier.
3. The filter of claim 1 or 2, wherein the individual fiber bundles
contain more than 1000 filaments.
4. The filter tow of one of claims 1 to 3, wherein the filament
derniers of the filaments differ from fiber bundle to fiber bundle
by more than 1.5 dtex.
5. The filter tow of one of claims 1 to 4, wherein the crimp ratio
is greater than 33%, and the number of crimps per cm is greater
than 15.
6. The filter tow of one of claims 1 to 5, wherein the crimp ratio
is greater than 35%
7. The filter tow of one of the above claims, wherein the crimp
ratio is greater than 40%, preferably greater than 42%, and the
number of crimps per cm exceeds a value of 22.
8. The filter tow of crimped, continuous cellulose acetate
filaments, wherein the filter tow has a crimp ratio of greater than
40% and the filaments have at least 22 crimps per cm filament
length.
9. The filter tow of claim 8, wherein the crimp ratio is greater
than 42% and the filaments have more than 25 crimps per cm.
10. The filter tow of claim 8 or 9, wherein the filament dernier is
greater than 3.3 dtex, and the total dernier is less than 44,000
dtex, preferably less than 40,000 dtex.
Description
Detailed Description of the Invention
DESCRIPTION
[0001] The invention relates to a filter tow used in the
manufacture of cigarette filters having a comparatively low
filtration performance whose draw resistance retention
characteristic was selected in such a way that their use in
full-flavor cigarettes with a ventilation degree of more than 25%
is possible while maintaining an acceptable draw resistance in the
cigarette and an acceptable filter plug weight.
[0002] The great majority of cigarette filters currently in use are
manufactured from filter tow, which consists of continuous
cellulose 2,5-acetate filaments. These filters are referred to as
acetate filters. The cigarettes that are manufactured and sold in
the European Union can be classified as follows based on their
condensate contents in smoke:
[0003] Full-flavor
[0004] Medium
[0005] Light, and
[0006] Ultralight cigarettes
[0007] Because of the maximum-content regulations (90/239/EEC)
applying to condensate content, all of these cigarettes are
ventilated. The degree of ventilation depends on the condensate
target value and on the filtration performance of the filter being
used.
[0008] The following table summarizes the typical current
values:
[0009] [0009.1]
[0010]
1 Class mg Condensate Filament Dernier % Ventilation Full Flavor
<12 2.8-3.3 dtex <25 Medium 8-10 .ltoreq.3.3 dtex <35
Light 4-8 2.1-2.8 dtex 30-50 Ultralight <41 1.7-8.8 >50
[0011]
[0012] Most of products currently sold have a diameter of
7.8.+-.0.2 mm and a cigarette length of 85-120 mm. In addition,
there are niche products whose design characteristics differ
significantly from the most commonly sold products. In response to
this wide variety of product requirements, the filter tow industry
supplies a multitude of different tow types that can essentially be
described by the following characteristics: filament dernier (dtex)
1.6-8.8; total dernier (dtex) 17,000-60,000; crimp index (%) 25
max. 38; number of crimps per cm: 10 max. 20.
[0013] The following description of the object of the invention
exclusively relates to the class of full-flavor products. A typical
filter cigarette of the full-flavor class has the following typical
characteristics (these values are approximate typical values). They
serve simply as a basis for calculations for further
embodiments.
[0014] Lengths:Cigarette:84 mmFilter:24 mmTobacco rod:63
mmTipping:26 mmDiameters:Filter:7.80 mmCigarette:7.85 mm Draw
resistance:Filter:66 mm water column Tobacco rod:50 mm water column
Cigarette:100 mm water column Filter tow specification: 3.0 Y 35
(filament dernier: 3.33 dtex; total dernier: 38.900,
cross-sectional shape of the filaments: Y)Tobacco mixture: American
BlendVentilation:Degree of ventilation:20%Position of ventilation
zone:11 mm from the mouth endSmoke values:Condensate:12
mgNicotine:0.9 mgCarbon monoxide (CO): 14 mgRetention
values:Condensate:42%Nicotine:38%Carbon monoxide (CO):None
[0015] As a consequence of the new maximum-content regulation
(2000/C 150E/03) of the European Union, full-flavor products in
particular will have to undergo drastic changes in their design
features, since effective Jan. 1, 2004 not only the condensate
value, but also the nicotine value--and in particular the CO
value--will be regulated with respect to their maximum limits. The
challenge involving the modification of the products to meet the
new EU regulations will be that the permitted maximum amounts with
an optimal smoke flavor will need to hit the values 10 mg
condensate, 1 mg nicotine, and 10 mg CO per cigarette as precisely
as possible. In other words, in the future a 1:1 ratio of CO/tar
must be targeted for full-flavor products. As the above table
shows, the ratio in this example is 1.17.
[0016] Based on the model calculations that solely take a change in
filter ventilation into account, it can be assumed that a filter
ventilation of approximately 35% will be required to reduce the CO
from the current value in the above calculation example of 14 mg to
a future value of 10 mg per cigarette. An increase in the degree of
ventilation in an otherwise unchanged product will unavoidably
necessitate a decrease in the cigarette draw resistance.
[0017] For consumers however, an optimal smoke flavor means that
the draw resistance of the cigarette must not fall significantly
below the current value of approximately 100 mm water column.
Increasing the degree of ventilation, however, will mean that
maintaining the other filter parameters such as draw resistance,
diameter, position of the ventilation zone, and the filter length
will significantly reduce the draw resistance of the cigarette. The
resulting cigarette draw resistance can be calculated using the
following equation, which is based on a laminar flow model:
P.sub.v=P.sub.o-V.sub.x(P.sub.o-P.sub.fxL.sub.v/L.sub.f),
where:
[0018] P.sub.v: Draw resistance of the ventilated cigarette (mm
water column)
[0019] P.sub.o: Draw resistance of unventilated cigarette: =draw
resistance [filter+tobacco rod] (mm water column)
[0020] P.sub.f: Filter draw resistance (mm water column)
[0021] V: Ventilation degree of filter (%)/100
[0022] L.sub.v: Distance of the ventilation zone from the mouth end
(mm)
[0023] L.sub.f: Filter length
[0024] Thus, the open draw resistance will then only be 88 mm water
column (instead of the original 100 mm water column) for the stated
sample cigarette at a ventilation degree of 35%. Such a drop in the
cigarette draw resistance is clearly perceivable for the smoker and
it must be offset by an increase in the filter resistance (in the
above example to approximately 80 mm water column) in order to
maintain the consumer's smoke feel. This increase in the filter
draw resistance results in an unavoidable increase in the CO/tar
ratio, since the tar values, but not the CO values, are influenced
by the filter draw resistance (an increase in the filter draw
resistance results in a decrease in the tar values).
[0025] Therefore, the draw resistance/retention ratios must be
redefined for future products in the "full-flavor" category. The
adjustment to a 1:1 CO/tar ratio and the filter tow used to
manufacture the filter needed to achieve an acceptable product with
regard to cigarette draw resistance must be modified to meet these
requirements. In this regard, the following specifications may be
defined:
[0026] 1. The filter tow must be suitable for producing the draw
resistance values that are typical today (however preferably even
higher values).
[0027] 2. The filtration performance of the filter made with the
filter tow of the invention must, with the given filter draw
resistance, be significantly lower than the current typical
retention values in order to achieve the 1:1 CO/tar ratio.
[0028] 3. The additional material consumption that results from the
increase of the filament dernier must be kept within acceptable
limits.
[0029] With a given filter diameter and length, the retention of a
filter depends exclusively on the draw resistance and the filament
dernier. For example, an increase in the filament dernier and a
decrease in the draw resistance results in a drop in filtration
performance (and vice-versa). Since the interrelationships are of a
very complex nature, filter calculation programs are used to
estimate the extent of such changes. One example of such
calculation programs is Cabled (Capability Line Expert; copyright
Rhodia Acetow GmbH 1998, Freiburg, Germany) from the firm of Rhodia
Acetow.
[0030] In the prior art, therefore, the retention of a filter is
reduced by increasing the filament dernier. Model calculations
suggest that in the future the filament dernier will need to be
increased by at least 0.5-1.5 dtex in order to meet the
requirements for filtration performance. However, the filter tow
specifications commonly encountered in the market (the mean total
dernier of all specifications is approximately 35 ktex) are not
suitable for also covering the required draw resistance range with
the required minimum filament dernier (retention) (Cable.COPYRGT.
calculation program from Rhodia Acetow GmbH). In the prior art,
this problem can only be solved with a monoacetate filter by
drastically increasing the filter dernier to well above 45,000
dtex.
[0031] Such solutions, for example a filter tow of the type 4.5 Y
55 (see FIG. 2) in the prior art would then meet the draw
resistance and retention specifications, but would result in an
increase in the consumption of filter tow of >35% compared with
current products.
[0032] The above discussion was limited to a description of the
full-flavor group of cigarettes. If, however, a CO/tar ratio of 1:1
is generally sought, the discussion regarding the widening of the
filter resistance ranges would apply to all filament derniers. This
means that the object of the invention described below will
generally comprise the currently standard filament dernier spectrum
of 1.6-8.8 dtex.
[0033] Therefore, the object of the invention is to disclose a
filter tow with which it is possible to manufacture filters that
have a filtration performance achieving a CO/tar ratio of 1:1.
[0034] In order to meet the above requirements, the invention
proposes two approaches that are basically independent of each
other and whose elements can, if desired, be combined.
[0035] The solution of the invention relates to a filter tow of
crimped, continuous cellulose acetate filaments, in which the
filaments form at least two coherent fiber bundles that have the
same filament dernier and have at least 600 filaments and that
differ in their filament dernier from fiber bundle to fiber bundle
by at least 1 dtex. In particular, this solution produces
outstanding results with regard to filtration performance, since it
was unexpectedly found that a filter that is manufactured from such
a non-homogeneously distributed mixed tow exhibits a significantly
lower tar retention than does a product made of a conventional tow
with a uniform filament dernier distribution or a mixed tow having
a homogeneous filament distribution (see FIG. 3).
[0036] The second solution is accomplished by a filter tow that has
a more intensive and at the same time markedly finer crimp
structure than the typical products encountered today. Claim 4
recites a filter tow having a crimp index of more than 40%, in
which the filaments have at least 22 curls per cm filament length.
In particular, this filter tow fulfills the maximum requirements
with regard to filter draw resistance. The values that are achieved
are even exceeded if the crimp index is more than 42%, whereby the
filaments preferably have more than 25 curls per cm.
[0037] In order at the same time to achieve optimal filtration
performance by the filters, a filter tow having a filament dernier
of more than 3.33 dtex and a total dernier of less than 44,000
dtex, preferably less than 40,000 dtex is proposed. The limitation
on the total dernier results in an increased filter tow consumption
that is still acceptable.
[0038] The design and the advantages of the two solutions of the
invention may be described as follows: The crimp index Ix is a
measure of the intensity of curling. The crimp index of a filter
tow is determined by means of the tensile test (load/elongation
relationship). It is defined as the ratio of the elongated length
L2 under the test load minus the initial length over the initial
length under preload L.sub.1:
I.sub.x=(L.sub.2-L.sub.1)/L.sub.1*100(%)
[0039] Here, the test load is 25 N and the preload is 2.5 N. The
length between the jaws of the tensile test machine is 250 mm. The
curling index is determined in a tensile test at a constant
traverse rate of 300 mm/min on a G02 test machine manufactured by
Borgwaldt GmbH, Hamburg. 10 individual readings were taken per
measurement. Testing is performed in a standard climate: 20.degree.
C. and 60% relative humidity. (The test method for determining the
crimp ratio is described in the Cable program under the "Help"
button).
[0040] The crimp ratio values of current filter tow specifications
normally lie between 25 and 35%. The firm of Rhodia Acetow is the
sole manufacturer that offers worldwide specifications under the
designation SK in a filament dernier range of <2.78 dtex that
covers a crimp ratio range of from greater than 35% to a maximum of
38%.
[0041] As already stated, the crimp ratio is a measure of the
intensity of crimping and, thus, the position of the performance
curve. In this context, a performance curve is understood to mean a
performance range of a filter tow, which states the draw resistance
range in which a filter tow can be processed with a given diameter
and filter rod length under typical processing conditions. For this
working range, the performance curve describes the relationship
between the draw resistance and weight. The relationship between
the position of the performance curve and the crimp ratio is shown
using the example of a filter tow of type 2.1 Y 35 HK (filament
dernier: 2.33 dtex; total demier: 38,900; cross-sectional shape of
the filaments: Y; crimp ratio: 32%) and a 2.1 Y 35 SK (filament
dernier: 2.33 dtex; total demier: 38,900, cross-sectional shape of
the filament: Y; crimp ratio: 36%) in FIG. 1.
[0042] The above object is accomplished by manufacturing a filter
tow that has a crimp ratio of more than 40%, preferably more than
42%. This ratio is absolutely necessary in order to cover the
corresponding draw resistance range. The crimp ratio is affected by
the frequency and the amplitude of the crimps. The number of crimps
provides a measure of the fineness of crimping. Currently, typical
values range from 10 to max. 20 crimps per cm filament length. The
SK tows referred to above normally have 15-18 crimps per cm.
[0043] It was unexpectedly discovered that such an index can only
be achieved with an acceptable filter tow tensile strength if the
crimping is hyper-fine. Therefore, the filter tow of the invention
has, in addition to an index of more than 40% in the filaments, on
average more than 22 crimps per cm, preferably more than 25. Such a
filter tow can be processed on conventional filter rod machines
into cigarette filters that have a draw resistance level comparable
to filters manufactured using the currently typical specifications.
FIG. 2 shows the working range of a tow of type 4.5 Y 35 of the
invention (filament dernier: 5.0 dtex; total demier: 38,900 dtex)
in comparison with a conventional filter tow of type 3.0 Y 35
(filament dernier 3.33 dtex: total dernier: 38,900 dtex)
respectively a conventional 4.5 Y 55 and a conventional 4.5 Y
35.
[0044] FIG. 2 clearly shows that, compared with the current
situation (3.0 Y 35) significantly more material is consumed with
the solution of the invention (Example 1: 4.5 Y 35) as a result of
the increase of the filament dernier, but that this additional
consumption ends up being significantly less than with a
traditional prior-art solution (4.5 Y 55).
[0045] In order to produce hyper-fine crimping without being overly
aggressive, certain basic conditions must be met in the
manufacturing process. Prior to the crimping process, the filter
tow band contains the following components that soften the acetate
filaments: water, acetone, and softening components. It is known
that these softening components have a lasting effect on the
crimping process. For example, U.S. Pat. No. 5,225,277 describes
the effect of acetone and tow band temperatures on the stability of
crimping. Products having up to 19.7 crimps per cm can be
manufactured using the method described therein. This document does
not make any statements with regard to the crimp ratio. However,
using the data stated therein (draw resistance, tow specification
and machine settings) a crimp ratio that is clearly below 35% can
be estimated with the help of the Cable software referred to
above.
[0046] JP unexamined patent document 56-53223 describes the effects
of steam-treating the toll band before it enters the crimping
machine. Products having 16 crimps per cm are described. No
information on the crimp ratio is provided. It has now been
unexpectedly discovered that hyper-fine crimping can be achieved
effectively and without all-too drastic damage to the filaments if
the total amount of the plasticizing components exceeds a value of
25 weight % at the time the crimping process occurs. The
concentrations in which the individual components are present does
not matter. The total content of the individual components is
determined experimentally using a gravimetric method by taking a
sample at 150.degree. C. (20 min.) directly downstream from the
crimping machine.
[0047] As already noted, one of the solutions to the object of the
invention relates to a filter tow that has a so-called mixed
dernier.
[0048] DE 29 16 062 describes such a filter tow and the cigarette
filters made from it. In contrast to the filter tow of the
invention, in this citation the most uniform possible distribution
of the filaments is provided (see column 2, lines 22 ff. in DE 29
16 062). In the embodiment of DE 29 16 062, the effect of this is
that the amount of material used in the filters that are to be
produced is decreased with the same draw resistance, but as a
consequence of the uniform distribution of the filaments the
retentions in the filters increase significantly.
[0049] The object of the described invention is also to save
material, but at the same time the retention in the filters made
from the filter tow should be significantly less than that which is
achieved when corresponding filters are made from a filter tow
having a uniform filter dernier. This is achieved when measures are
taken to ensure that in the product of the invention the filaments
of the coherent fiber bundles of the same filament dernier are
formed of at least 600 filaments, preferably more than 1000
filaments, that differ in their filament demier from fiber bundle
to fiber bundle by at least 1 dtex, preferably by more than 1.5
dtex. The filter tow contains at least two, preferably more than
five areas of filament bundles having the same filament dernier.
The advantage of this embodiment is that the filament bundles of
the same filament dernier agglomerate in the filter and thus form
areas of low, respectively high, draw resistance. A filter
manufactured from such a mixed-dernier tow accordingly has similar
properties with respect to draw resistance and retention as those
described, for example, in JP2000000085 for a classical core-jacket
filter. There are no restrictions with regard to crimp ratio and
number of crimps per cm for this tow filter. However, in a
preferred embodiment of the invention, a product having a crimp
ratio of more than 33%, preferably more than 35%, is made.
[0050] The advantages of the invention set forth in claims 8 to 10
may be summarized as follows: Based on the combination of materials
set forth in the invention, working ranges with respect to draw
resistance that are not currently available may be achieved. By
applying the teachings of claim 10 with the given draw resistance,
the filament demier can be increased so that the products can
achieve a significantly lower filtration performance. As a result
of the cited restriction with regard to the total demier, the
consumption of material can be limited in manufacturing the
filters. However, a combination of the embodiments of at least one
of claims 1 to 7 with one or more of claims 8 to 10 is especially
advantageous. This embodiment permits a further significant
reduction of the total dernier to be used and, thus, results in
further savings potential with regard to material consumption.
[0051] The invention is described in greater detail below based on
the examples.
[0052] COMPARISON EXAMPLE (TOW OF TYPE 4.5 Y 55)
[0053] A spinning solution having a concentration of 30 weight
percent cellulose acetate in acetone is prepared, filtered, and
then extruded through spinnerets. The water content of the spinning
solution is 1.5%. The spinnerets are selected with regard to the
number of holes, hole size, and number of spinnerets so that
ultimately a tow of type 4.5 Y 55 is made. The application of
softening agent is set so that an oil coating of 0.5% results. The
tow band is crimped with a conventional stuffer box crimping
machine so that after drying and packing, a filter tow having a
crimp ratio of 30.5% results. The total content of plasticizing
components is 22.3%. The tensile strength of the tow is 143 N. The
number of crimps is 15.8 per cm filament length.
[0054] The product is processed into filter rods having a length of
126 mm and a diameter of 7.8 mm on a conventional filter rod
machine, model KDF2/AF2, make: Hauni, Hamburg. The generation of
lint during the processing of the product is insignificant and
amounts to 0.5 g/ton for the estimated consumption of one ton of
material. The performance curve of the product shown in FIG. 2
covers a draw resistance of 310-460 mm water column.
[0055] EXAMPLE 1
[0056] A spinning solution having a concentration of 30 weight
parts cellulose acetate is prepared in acetone, filtered, and then
extruded through spinnerets. The water content of the spinning
solution is 3%. The spinnerets are selected with regard to number
of holes, hole size, and number of spinnerets so that ultimately a
filter tow of the type 4.5 Y 35 is produced. The application of
softening agent is adjusted so that an oil coating of 1.3% results.
The resulting tow band is crimped with a conventional stuffer box
crimping machine so that, after drying and packaging, a filter tow
having a crimp ratio of 43.5% results.
[0057] The total content of plasticizing components is 29%. The
tensile strength of the tow is 111 N. The number of crimps is 26
per cm filament length.
[0058] The product is processed into filter rods having a length of
126 mm and a diameter of 7.8 mm on a conventional filter rod
machine, model KDF2/AF2, make: Hauni, Hamburg. The generation of
lint during the processing of the product is insignificant and
amounts to 2.8 g/ton for the estimated consumption of one ton of
material. The performance curve of the product, shown in FIG. 2,
covers a draw resistance range of 298-505 mm water column.
[0059] EXAMPLE 2
[0060] A spinning solution having a concentration of 30 weight
parts cellulose acetate is prepared in acetone, filtered, and then
extruded through spinnerets. The water content of the spinning
solution is 3%. The spinnerets are selected with regard to number
of holes, hole size, and number of spinnerets so that ultimately a
filter tow of the type 4.5 Y 32 is produced. Unlike in the above
examples, the spinning machine is divided into six zones, and
alternating zone by zone, a higher filament dernier (1185 filaments
6.9 den=7.65 dtex per zone) and a lower filament dernier (1185
filaments 2.1 den=2.3 dtex per zone) is spun. The application of
softening agent is adjusted so that an oil coating of 1.3%
results.
[0061] The resulting tow band is crimped using a conventional
stuffer box crimping machine so that after drying and packaging, a
filter tow having a crimp ratio of 39.8% results. The total content
of plasticizing components is 27.5%. The tensile strength of the
tow is 129 N. The number of crimps is 23.1 per cm filament
length.
[0062] The product is processed into filter rods having a length of
126 mm and a diameter of 7.8 mm on a conventional filter rod
machine, model KDF2/AF2, make: Hauni. The generation of lint during
the processing of the product is insignificant and amounts to 0.9
g/ton for the estimated consumption of one ton of material. The
performance curve of the product covers a draw resistance range of
267-487 mm water column.
* * * * *