U.S. patent application number 10/312241 was filed with the patent office on 2004-01-22 for beverage infusion packages and materials therefor.
Invention is credited to Rose, John Edward, Scott, Simon Mark, Whittaker, Nicholas Robin.
Application Number | 20040013831 10/312241 |
Document ID | / |
Family ID | 9894781 |
Filed Date | 2004-01-22 |
United States Patent
Application |
20040013831 |
Kind Code |
A1 |
Whittaker, Nicholas Robin ;
et al. |
January 22, 2004 |
Beverage infusion packages and materials therefor
Abstract
A non-woven porous, fibrous tissue for use in producing beverage
infusion packages comprises cellulose fibres and polylactic acid
(PLA) fibres to improve repulpability of waste materials.
Inventors: |
Whittaker, Nicholas Robin;
(Lancashire, GB) ; Rose, John Edward; (Lancashire,
GB) ; Scott, Simon Mark; (Manchester, GB) |
Correspondence
Address: |
Thomas Q Henry
Woodard Emhardt Naughton & McNett
Bank One Tower Suite 3700
111 Monument Circle
Indianapolis
IN
46204
US
|
Family ID: |
9894781 |
Appl. No.: |
10/312241 |
Filed: |
June 13, 2003 |
PCT Filed: |
June 19, 2001 |
PCT NO: |
PCT/GB01/02642 |
Current U.S.
Class: |
428/35.2 ;
206/205 |
Current CPC
Class: |
D21H 27/38 20130101;
D21H 27/10 20130101; D21H 27/08 20130101; Y10T 428/1334 20150115;
D21H 13/08 20130101; D21H 13/24 20130101 |
Class at
Publication: |
428/35.2 ;
206/205 |
International
Class: |
B65D 081/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2000 |
GB |
0016116.6 |
Claims
1. A non-woven porous, fibrous tissue for use in producing beverage
infusion packages, wherein said tissue comprises cellulose fibres
and polylactic acid PLA fibres to improve re-pulpability of waste
materials.
2. A tissue as claim 1 wherein the PLA fibres have a fibre length
of 2 mm to 8 mm.
3. A tissue as claimed in claim 2 wherein the PLA fibres have a
fibre length of 4 mm to 6 mm.
4. A tissue as claimed in claim 3 wherein the PLA fibres have a
fibre length of about 5 mm.
5. A tissue as claimed in any on claims 1 to 4 wherein the PLA
fibres are from 0.9 dcTex to 4.4 dcTex.
6. A tissue as claimed in claim 5 wherein the PLA fibres are from
1.4 dcTex to 3.3 dcTex.
7. A tissue as claimed in claim 6 wherein the PLA fibres are from
1.7 dcTex to 2.6 dcTex.
8. A tissue as claimed in claim 7 wherein the PLA fibres are from
1.9 dcTex to 2.3 dcTex
9. A tissue as claimed in any one of claims 1 to 8 having a basis
weight of 10 to 50 g m.sup.-2.
10. A tissue as claimed in claim 7 wherein the basis weight is 10
to 30 g m.sup.-2.
11. A tissue as claimed in claim 8 wherein the basis weight is 10
to 20 g m.sup.-2.
12. A tissue as claimed in claim 9 wherein the basis weight is 12
to 17 g m.sup.-2.
13. A tissue as claimed in any one of claims 1 to 12 wherein the
heat PLA fibres comprise 10% to 40% by weight of the thermally
active layer.
14. A tissue as claimed in claim 13 wherein the PLA fibres comprise
25% to 35% by weight of the thermally active layer.
15. A tissue as claimed in any one of claims 1 to 14 wherein at
least proportion of the PLA fibres are single component fibres.
16. A tissue as claimed in claim 15 wherein said single component
PLA fibres melt (soften) at a temperature of 145-175.degree. C.
17. A tissue as claimed in any one of claims 1 to 16 wherein at
least a proportion of the PLA fibres are bicomponent fibres
comprised of a PLA core and lower melting PLA sheath.
18. A tissue as claimed in claim 17 wherein the thermally active
layer comprises single component PLA fibres and bicomponent PLA
fibres.
19. A tissue as claimed in claim 18 wherein the single component
fibres have a, melting (softening) point of 145 to 175.degree. C.
and the bicomponent fibres have a sheath with a melting (softening)
temperature in the range 105.degree. C. to 165.degree. C. but lower
than the melting (softening) temperature of the single component
fibres.
20. A tissue as claimed in any one of claims 1 to 19 additionally
comprising an insulating layer incorporating only thermally
inactive fibres.
21. A tissue as claimed in claim 20 wherein the thermally active
layer comprises 65% to 97% by weight and the insulating layer
comprises 3% to 35% by weight, the percentages being based on the
weight of the tissue.
22. A tissue as claimed in claim 21 wherein the thermally active
layer comprises 79% to 93% by weight and the insulating layer
comprises 7% to 21% by weight, the percentages being based on the
weight of the tissue.
23. A tissue as claimed in claim to 22 wherein the thermally active
layer comprises 83% to 90% by weight and the insulating layer
comprises 10% to 17% by weight, the percentages being based on the
weight of the tissue.
24. A tissue as claimed in any one of claims 20 to 23 wherein the
insulating layer comprises wood pulp and lyocell or viscose rayon
fibres.
25. A tissue as claimed in claim 24 wherein the insulating layer
comprises 70% to 95% by weight wood pulp and 5% to 30% by weight
lyocell or viscose rayon.
26. A tissue as claimed in claim 23 wherein the insulating layer
comprises about 100% by weight wood pulp.
27. A tissue as claimed in any one of claims 20 to 26 wherein the
cellulosic fibres of the insulating layer have a length shorter
than those of the thermally active layer.
28. A tissue as claimed in any one of claims 20 to 27 wherein the
cellulosic fibres of the insulating layer have a length of 0.5 mm
to 5 mm.
29. A tissue as claimed in claim 38 wherein the cellulosic fibres
of the insulating layer have a length of 1 mm to 3 mm.
30. A beverage infusion package comprising a bag of a tissue as
claimed in any one of the previous claims and a beverage precursor
material contained within the bag.
31. A package as claimed in claim 30 which is a tea bag.
32. A package as claimed in claim 30 which us a coffee bag.
Description
[0001] The present invention relates to porous, fibrous web
materials of the heat seal type for use in producing beverage
infusion packages (e.g. tea bags, coffee bags and the like) as well
as to beverage infusion packages produced using such materials.
[0002] Beverage infusion packages comprise a particulate beverage
precursor material, e.g. tea leaves or ground coffee, in a bag,
sachet, pouch or the like (all conveniently referred to herein as a
bag) of a porous, fibrous (usually cellulosic) material. This
material typically has a basis weight of 10 to 30 g m.sup.-2 and is
often referred to as "tissue" or "tissue paper".
[0003] To produce a beverage, the package is infused with hot
water. This may be done, for example, by immersing the package in
hot water, pouring hot water onto the package, or heating water and
the bag in a microwave oven.
[0004] The infusion package may be of a size, and contain an amount
of the beverage precursor material, so as to be intended for
producing a single cup of the beverage. Alternatively the package
may be of a "catering size" and as such intended to produce a
plurality of servings of the beverage. Such a "catering size"
package may for example contain ground coffee as the beverage
precursor material and be used in a commercial coffee-making
machine.
[0005] "Heat seal" tissue usually (but not necessarily) comprises
two or more layers wet-laid in succession one on top of the other.
One layer incorporates thermoplastic fibres (e.g. polypropylene)
and the other incorporates only thermally inactive materials. The
tissue will generally also incorporate a wet strength agent and is
typically manufactured by a wet laid process on an inclined wire
paper making machine.
[0006] A beverage infusion package is produced from the heat seal
such tissue by forming the bag such that layers of the tissue
incorporating thermoplastic fibres are juxtaposed and then heat
sealed.
[0007] There are currently available many thermoplastics which can
be used as fibres for producing heat seal tissue and, when used for
producing beverage infusion packages, give more than adequate
performance. However the tissue has a disadvantage in that the
waste material ("broke") generated during manufacture of the tissue
(e.g. as a result of reeling operations) cannot successfully be
reused. This is because the tissue will not break down during
standard alkaline conditions used in fibre recovery processes. To
recover a proportion of the cellulose fibre, non standard chemicals
and high levels of mechanical energy have to be used, and these
result in a low grade recovered fibre source, still containing
thermoplastic material, which is undesirable. Also the fibre length
of the resultant material is dramatically reduced from a virgin
mean fibre range of typically 3.5-6 mm down to 0.96-1.65 mm. This
reduction in fibre length and retention of thermoplastic material
within the "broke" results in only a small level of "broke" being
able to be accommodated within the tissue. This is due to the very
short fibre length reducing the pore size of the web, as it forms
on the moving belt of the paper machine, which negatively impacts
on the water removal process, production rate, costs and physical
properties of mechanical strength and seal strength. For these
reasons, the "broke" is predominantly disposed of in landfill sites
or by incineration.
[0008] To the extent that the "broke" is disposed of in a land fill
site, there is an additional disadvantage in that the thermoplastic
fibres are generally not biodegradable and therefore remain in the
environment. This disadvantage also applies to the disposal of used
beverage infusion packages (produced form the tissue) in land fill
sites.
[0009] It will thus be appreciated that the inability to recycle
"broke" in the production of heat seal tissue gives rise to two
disadvantages. Firstly, the need to produce the heat seal tissue
from "broke" free virgin materials increases cost. Secondly, the
need to dispose of the broke give rise to environmental
disadvantages, particularly in the case of disposal in a land fill
site. The ability to recycle the "broke" would have a positive
impact both on the cost base for the production of tissue and for
the environment but due to the above mentioned limitations these
advantages are not currently realised.
[0010] It is therefore an object of the present invention to
obviate or mitigate the above mentioned disadvantages.
[0011] According to the present invention there is provided a
non-woven porous, fibrous tissue for use in producing beverage
infusion packages, wherein said tissue comprises fibres produced
from polylactic acid (PLA).
[0012] According to a second aspect of the invention there is
provided a beverage infusion package comprising a bag of a
non-woven porous, fibrous tissue as defined in the previous
paragraph, and a beverage precursor material contained within the
bag.
[0013] The PLA fibres in the tissue are thermoplastic and serve as
heat seal fibres for the purposes of thermally bonding two layers
of the tissue together.
[0014] We have found that the inclusion of PLA fibres in tissue to
be used for producing beverage infusion bags significantly improves
the "re-pulpabilty" of the tissue. Material produced using PLA will
re-pulp under alkaline condition as the PLA readily hydrolyses.
This method of removing the PLA fibres fits with the process for
removing the typical wet strength systems used in the production of
the aforementioned porous tissue. The ability to "peel" the PLA
fibres away from the de-wet strengthened cellulose matrix enables
the fibre length of the recovered pulp to be maximised to a
typically mean fibre range of 2.5-3.5 mm. This increase in overall
mean fibre length range and the removal of thermoplastic fibres
enables more waste material to be utilised in both the "parent"
product, without detracting from product performance or production
efficiencies, and other non related NHSTB products without the
problem of inclusion of a small percentage of thermoplastic from
the inclusion of broke. These factors result in a significant
reduction in the requirement for the use of landfill or
incineration of waste "broke" materials.
[0015] Furthermore, as is known, PLA polymers degrade in the
environment into lactic acid (monomer). Thus tissue disposed of to
a typical landfill site (e.g. in the form of a "used beverage
infusion package") will ultimately completely degrade. In this way
the impact on the environment is significantly reduced compared to
the current thermoplastic containing materials.
[0016] The production of polylactic acid (PLA) for use in forming
the fibres employed in this invention is described for example in
U.S. Pat. No. 5,142,023 (Cargill, Incorporated). Briefly however
PLA is produced by condensation of lactic acid. By adjusting the
ratio of the D(+) and L(-) isomers used in the polycondensation
reaction, it is possible to significantly affect the degree of
crystallinity of the PLA and therefore adjust properties such as
melting/softening point. In broad terms a 100% L(-) isomer would
give a melt flow temperature of circa 170.degree. C., while a
combination of 88% L(-) and 12% D(+) isomers would produce a melt
flow value of circa 120.degree. C. PLA fibres for use in the
invention may be obtained from Unitika Fibre of Japan under the
trade name of Terramac.
[0017] Beverage infusion packages (e.g. tea bags) may be produced
from tissue in, accordance with the invention on standard
converting machinery at throughput rates commensurate with those
achieved using conventional tissue with seals of adequate
strength.
[0018] The PLA fibres will preferably have a fibre length of 2 mm
to 8 mm, more preferably 4 mm to 6 mm, and ideally about 5 mm.
[0019] Preferably the PLA fibres are from 0.9 dcTex to 4.4 dcTex,
more preferably from 1.4 dcTex to 3.3 dcTex, even more preferably
1.7 dcTex to 2.6 dcTex and most preferably from 1.9 dcTex to 2.2
dcTex for optimum fibre coverage.
[0020] The PLA fibres preferably melt (soften) at a temperature of
140-175.degree. C. and have an MFI (WFR) value of 10-14
(230.degree. C., 2.16 kgs).
[0021] The PLA fibres may be single component fibres. It is however
also possible for at least a portion of the PLA fibres to be
bicomponent fibres comprised of a PLA core and an outer PLA sheath
of significantly lower melting point than the core. Thus, for
example, the PLA core may have a melting point of about 260.degree.
C. whereas that of the PLA sheath may be 105.degree. C. to
175.degree. C. It is possible that the bicomponent fibres may be
the sole PLA fibres in the tissue. In this case, the sheath of the
bicomponent fibres will generally be such as to melt (soften) at a
temperature of 140-175.degree. C. and have an MFI (MFR) value of
10-14 (230.degree. C., 2.16 kgs), i.e. the same properties for the
single component, heat seal PLA fibres. It is however also possible
that the tissue incorporates single component PLA fibres as the
heat seal fibres and bicomponent fibres having a sheath with a
lower melting (softening) temperature than the single component
fibres. Thus, in this case the sheath of the bicomponent fibres may
have a melting/softening temperature in the range 105.degree. C. to
165.degree. C. but lower than the melting (softening) temperature
of the single component fibres. In all cases, the core of the
bicomponent fibres may have a melting (softening) temperature of
about 260.degree. C. with the core providing for added strength of
the tissue.
[0022] If PLA bicomponent fibres are incorporated in the tissue
then these may be thermally bonded to each other at the cross-over
points of these fibres during manufacture of the tissue (see infra)
to give a significant increase in both dry and wet tensile
strength, again with no affect on total tissue re-pulpability and
product biodegradability. The incorporation of bicomponent (sheath
and core) fibres in the tissue allows optionally for a string and
tag to be thermally bonded to the beverage infusion bag.
[0023] Tissue in accordance with the invention will generally have
a basis weight of 10 to 50 g m.sup.-2 more preferably 10 to 30 g
m.sup.-2, even more preferably 10 to 20 g m.sup.-2 and still more
preferably 10 to 18 g m.sup.-2, e.g. 12 to 17 .mu.m.sup.-2. For
preference the tissue will be a wet-laid material although
production of the tissue as a dry laid material is also
possible.
[0024] A heat seal tissue in accordance with the invention may
comprise only a single layer which is the thermally active layer
and which incorporates the PLA fibres and also cellulosic material
as conventionally used in the formation of tissue. The heat seal
tissue may also comprise an insulating layer incorporating only
thermally inactive fibres.
[0025] It is preferred that the heat seal tissue incorporates a
total of 10% to 40%, more preferably 15% to 35% by weight of the
PLA fibres based on the weight of the thermally active layer. If
the PLA fibres are comprised of both single component and
bicomponent fibres then it is preferred that 60-80% by weight of
the PLA fibres are single component fibres and correspondingly
20-40% by weight (of the PLA fibres) are bicomponent fibres.
[0026] Cellulosic fibres for incorporation in the thermally active
layer may be conventionally woody and/or non-woody materials, e.g.
Manila hemp, sisal, jute? bleached and unbleached soft wood and
hard wood species. Alternatively or additionally the cellulose
fibres may be of a regenerated or reconstituted cellulose such as
viscose rayon or lyocell. Typically the cellulosic fibres in the
thermally active layer will have a length of 1 mm to 5 mm.
[0027] Cellulosic fibres preferably provide 30% to 65% by weight of
the thermally active layer.
[0028] It is preferred that the tissue incorporates 1% to 20%, more
preferably 7% to 15% by weight of floc based on the weight on the
thermally active layer.
[0029] Flocs for use in the invention are heavily fibrillated
fibres and for materials produced by a wet-laying technique on a
papermaling machine (e.g. an inclined wire machine) act as an
effective binder to provide "classic" wet web strength prior to
drying and removing the non-woven tissue from the inclined wire
forming fabric and provide dry web strength after drying the
non-woven web. The floc will generally have a fibre length within
the range 0.1 mm to 1.5 mm but preferably about 1.0 mm. At this
fibre length, the area coverage of the fibre is significantly
increased, compared to a typical fibrillated 5 mm fibre, by a
combination of internal and external "cleaving" of the fibre wall
surface. Generally the floc will have a SR value in the range
60.degree. to 100.degree., more preferably 70.degree. to
95.degree..
[0030] The heat seal tissue may optionally comprise both a
thermally active layer (i.e. one incorporating the heat seal
fibres) and a thermally inactive or insulating layer. In this case,
the former preferably comprises 60% to 80% by weight of the heat
seal tissue and he latter 20% to 40% on the same basis. More
preferably the former comprises 60% to 75% and the latter 25% to
40% on the same basis. Most preferably the heat seal tissue
comprises 65% to 75% by weight of the thermally active layer and
25% to 35% by weight of the insulating layer.
[0031] If the heat seal tissue incorporates a thermally inactive
layer then this preferably comprises natural cellulosic fibres.
Although it can also contain regenerated cellulose such as viscose
rayon or lyocell in the order of 70% to 95% by weight of wood pulp
and 5% to 30% by weight of synthetic cellulose, most preferably
about 85% by weight wood pulp and about 15% by weight synthetic
cellulose.
[0032] For the insulating layer, the synthetic cellulose fibres are
preferably shorter than those in the thermally active layer and may
have a length of 0.5 mm to 5 mm, preferably 1 mm to 3 mm.
[0033] Tissue in accordance with the invention is most preferably
produced by wet-laying employing technique well established in this
field. The tissue may for example be produced on an inclined wire
papermaking machine.
[0034] If the tissue comprises a thermally active layer and an
insulating layer then these may be laid in either order. If
biocomponent fibres are included then they may be thermally bonded
during drying of the tissue on the paper making machine giving a
significant increase in both dry and wet tensile strength.
[0035] The dry tensile strength of a wet laid tissue can be
increased by coating (e.g. using a size press, blade coater,
gravure printing press etc.) with a solution of a starch, or
poly(vinyl)alcohol (95-99% hydrolysed) or latex (preferably a food
approved SBR) or a cellulose ether, e.g. selected from methyl
cellulose, ethyl cellulose, hydroxyethyl cellulose, propyl
cellulose, hydroxypropyl cellulose but most preferably
carboxymethyl cellulose, at a level of 0.5% to 3%, more preferably
1% to 2% by weight of the tissue, to improve mechanical
strengths.
[0036] Wet strength may be enhanced by the use of melamine.
[0037] Tissue in accordance with the invention may alternatively be
produced by a dry-laying technique, in which case it will be
preferred that the tissue incorporate bicomponent fibres.
[0038] Beverage infusion packages (e.g. tea bags or coffee bags)
may be produced from tissue in accordance with the invention on
standard converting machinery at throughput rates commensurate with
those achieved using conventional tissue.
[0039] The invention is illustrated by the following non-limiting
Examples.
EXAMPLE 1
[0040] A wet-laid heat seal tissue having a basis weight of 16.5 g
m.sup.-2 was prepared from a furnish comprising
1 Component % by weight Manila fibres (5 mm, 2.4 dcTex) 41.0%
.sup.1PLA fibres (5 mm, 2.2 dcTex) 21.0% Bleached Softwood Floc
33.0% Moisture 5.0% .sup.1ex Unitika of Japan under the trade name
Terrammac
[0041] The fibrous web was treated with 3.0% by weight melamine
applied at the wet end of the paper machine.
[0042] The resultant product converted at satisfactory speeds on
standard tea-bag manufacturing machinery and gave tea bags with
adequate seal strengths.
EXAMPLE 2
[0043] A wet-laid heat seal tissue having a basis weight of 16.5
gsm was prepared from a furnish comprising
2 Component % by weight Manila fibres (5 mm, 2.4 dcTex) 40.0%
.sup.1PLA (5 mm, 2.2 dcTex) 10.0% .sup.2PLA Sheath and Core fibres
(5 mm, 2 denier) 15.0% Lyocell fibres (3 mm, 2.4 dcTex) 21.0%
Bleached Softwood Floc 9.0% Moisture 5.0%
[0044] Unitika of Japan under the trade name TerrammacUnitika of
Japan under the trade name Terrammac
[0045] The melting point for the single PLA fibre was 170.degree.
C.
[0046] The melting points for the bi-component PLA fibre were
130.degree. C. sheath and 170.degree. C. core
[0047] The product obtained also again converted well on standard
tea bag manufacturing apparatus to give tea bags with adequate seal
strength to with stand brewing by microwave method.
EXAMPLE 3
[0048] The tissue produced in Examples 1 and 2 was under laboratory
conditions to replicate the typical production scale re-pulping
process. The re-pulping procedure was also carried out on a
standard polypropylene-containing tissue.
[0049] The results obtained were as shown in Table 1.
3TABLE 1 BROKE TREATMENT OF MATERIAL TEMPERA- SOAK BROKE CONDITION
CHEMICAL TURE TIME 4% w/w NaOH 80.degree. 60 MIN WET WET TENSILE
TENSILE Before After % TEST METHOD Treatment Treatment Difference
PLA (Example 1&2) 15 kN/m 0.065 kN/m -99.5 No Mechanical Action
Std Polypropylene Control 16 kN/m 9.1 kN/m -43.1 No Mechanical
Action Std Polypropylene Control 16 kN/m 0.06 kN/m -99.6 With
Mechanical Action Beaten under full load 1 hour
[0050] It will be seen from Table 1 that the wet strength tensile
reduction of the PLA material was the same as for the polypropylene
control thus confirming the removal of the melamine wet strength
chemical. However, in the case of the control, the polypropylene
"web" was still place and the tissue would only disperse with
significant mechanical action, which was supplied by traditional,
Hollander Beta under full load for 1 hour. In contrast, the PLA
material readily dispersed without mechanical action
[0051] The impact on the quality of the final "broke" material due
to the need for significant mechanical action to disperse the
polypropylene containing web can be seen from table 2 which
compares the initial (Virgin) product fibre lengths to the chemical
and mechanically treated fibre lengths of a "broke" treated product
web, for both the PLA and polypropylene containing materials.
4TABLE 2 FIBRE LENGTH ANALYSIS OF PRODUCT BY KAJAANI 100 POLYPROPY-
PLA/PP PLA LENE Initial Stock Broke Treated Broke Treated Weighted
AVE Fibre length mm Fibre length mm Fibre length mm D1 0.58 1.04
0.36 Q1 1.15 1.44 0.59 Q2 3.07 4.33 0.96 Q3 4.99 4.92 1.49 D9 5.33
5.22 2.18 AVE 3.07 3.39 1.14 Wt AVE 4.26 4.25 1.65
* * * * *