Note: Descriptions are shown in the official language in which they were submitted.
~Z21~
Case V-5080
INFUSION BAG
The present invention is directed to infusion bags,
especially tea bags and the like, and more particularly to an
infusion bag constructed of a non-woven, fiber-free, perforated
thermoplastic film.
The invention is particularly concerned with an infusion
bag constructed of a coextruded multilayer perforated thermo-
plastic film having a plurality of uniform minute holes or
openings therein.
Thermoplastic films such as polyethylene and polypro-
pylene are common packaging materials. Multilayer films of
various types are also quite common packaging materials. The
films are generally non-porous and impervious to water and other
inert liquids. At least one of the layers of film has strong
adhesive qualities. Examples of such multilayer films may be
seen in U.S. 4,254,169; U.S. 4,239,826; U.S. 4,233,367; U.S.
3,908,070; U.S. 3,423,231; U.S. 2,817,124 and U.S. 2,817,123.
Perforated thermoplastic films have many useful applica-
tions, including packaging of food products such as cheese, gar~
dening and farming to prevent growth of weeds while permitting
moisture to be transmitted through the film to the soil beneath
and for making absorptive structures such as disposable diapers,
for example, see U.S. 3,814,101.
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Perforation of tharmoplastic films is generally achieved
by vacuum perforation of thin plastic films which involves the
e~trusion of molten polymeric materials such as polyethylene
through a slot die. The hot melt web of film exiting the die
5 impinges on a form through which a vacuum is drawn causing the
film web to be perforated and holes formed therein. Depending
upon the form used, films can be produced which have as few as
50 holes per square inch or which have thousands of holes per
square inch. One of the earlier methods for vacuum perforation
of plastic film is disclosed in U.S. 3,054,148.
Infusion-type tea bags are usually rectangular packets
or sachets made from single or multiple pieces of paper folded
in half and crimped or otherwise sealed along the edges. In
another type, a single strip of paper is folded twice longitu-
dinally to form an inner centrally disposed double fold joiningthe two meeting edges. In a type of flow-through tea bag, a
triple transverse fold intermediate the length of the folded
strip forms two pockets which are partially filled with tea
before the open ends thereof are folded over and stapled to a
20 strand of string usually having a tag on the end thereof.
Over the years, a wide variety of infusion packets or
bags, usually for containing tea for subsequent brewing, have
been developed. The bags are usually constructed of filter paper
or some other type of porous material such as cloth or the like.
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An infusion packet having two oppositely disposed,
rigidly separated pockets of tea joined together by two tapering
end portions which form a narrow, triangular shaped porous cup
is shown in U.S. 3,597,222.
U.S. 3,653,913 discloses an infusion bag made from a
rectangular strip of porous fibrous material, the longitudinal
margins of which are folded together so as to form a longitudinal
joint consisting of three layers which are knurled together.
The tube is divided by a transverse bend so as to form a 2air of
10 chambers for holding an infusible substance, and the opposite
ends of the tube are connected to each other so as to close the
bag.
An early type of tea bag or tea ball wherein the bag is
a triangularly-shaped pocket formed from a rectangular strip of
15 perforated aluminum foil is described in U.S. 1,581,578.
Other types of filter paper tea bags or the like with a
variety of handles are illustrated in U.S. 2,328,017; U.S.
2,359,292, U.S. 3,566,573; U.S. 4,153,153; and, Great sritain
2,087,350. British Patent 2,053,668 discloses a tea ba~ having
20 a somewhat accordion fold.
Infusion bags with positioning means and flotation means
are disclosed in U.S. 3,797,642 and U.S. 3,809,215, respectively.
The tea bags themselves may be made of various materials inclu-
ding paper, plastics such as nylon, perforated plastic film,
25 e.g., polyester, or woven or non-woven fabric oE natural or
synthetic origin.
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A percolatable porous bag constructed of a blend of
individualized textile or cellulosic fiber and a small amount of
thermoplastic fiber is disclosed in Canadian patent 802,720.
Various degrees of success have been achieved with the
foregoing infusion bags, with paper or fibrous bags presently
dominating the market place. One of the problems with paper
bags is lack of wet strength. This is even more of a problem
with the larger bags for tea brewing com~only used by the food
service industries.
Another problem with fibrous or paper bags is that as
they become wet, the fibers expand or swell. Such expansion or
swelling closes the openings in the bag material and removes the
permeability thereof. When placed in a water containing vessel
such as a cup or pot, the bags tend to float since the fibrous
structure is so closed or porosity so diminished that air is
trapped inside the bag.
An infusion bag for items such as tea, coffee or similar
food products for brewing must have a number of qualities. It
must have an inability to impart a taste factor to the liquid
2Q product after brewing. In effect, it must be substantially odor-
less and tasteless. It must also be sufficiently strong to con-
tain the brewing product in boiling water, e.g., in the steeping
of tea, coffee, and similar liquid beverages. The bag must also
be porous enough to permit liquid diffusion therethrough, but
25 the pores or openings must be of such size that migration of the
12~0~L
beverage material therethrough is inhibited, both when the bag
is dry and when the bag has been immersed in a liquid. It is
also important that infusion begins to take place within a few
seconds. In the brewing of tea, for example, it is desirable
that a change in color take place as rapidly as possible. It
is further desirable that a sachet, such as a tea sachet,
retain sufficient stability that it can be compressed after
brewing is completed without destruction of the container.
In the packaging of particulated, granule or powdered
products, especially items such as tea or coffee, it is import-
ant that the product does not cling to the packaging film or
otherwise interfere in the sealing of the bag. For example,
particles Df tea which are adhered to the film would prevent
an effective seal to be obtained during sealing operations.
The present invention provides an infusion bag or
sachet which meets all of these requirements.
More particularly, the present invention provides
an infusion bag for particulated or granular products such as
tea and coffee constructed of a vacuum perforated coextruded
dual layer thermoplastic film having a thickness of about 0.25
mil to 2 mils and having a heat resistant outer layer of resin
and a less heat resistant inner sealant layer of resin having
an antistatic agent blended therewith, the vacuum perforated
coextruded dual layer thermoplastic film having about 1800 to
4200 uniform perforations or holes per square inch of film,
the perforations or holes having been formed by vacuum
perforation, the vacuum formed perforations or holes
being about 2 mils to about 10 mils in diameter or
across the major axis, the vacuum formed perforations
or holes in the vacuum perforated coextruded
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dual layer thermoplastic film being tapered capillaries, with
the larger capillary opening being in the heat resistant outer
layer of the vacuum perforated coextruded dual layer thermo-
plastic film and the smaller capillary opening being in the
less heat resistant inner layer of the vacuum perforated co-
extruded dual layer thermoplastic film, and the perforated co-
extruded thermoplastic film having a porosity of about 100 to
about 500 cubic feet per minute.
Fig. 1 is a top plan view of one embodiment of the
invention;
Fig. 2 is a side view of the embodiment of Fig. l;
Fig. 3 is an end view of the embodiment of Fig. l;
Fig. 4 is an enlarged sectional view across line 4-4 of
Fig. l;~and
Fig. 5 is an enlarged top view of a portion of the
thermoplastic film of which the embodiment of Fig. 1 is
constructed.
Referring now to the drawings, an infusion bag of the
present invention is illustrated generally at 10. The bag or
packet 10 is constructed of a rectangular strip of a perforated
plastic film 11 which is described in more detail hereinafter.
jrc:
~L2;2~061
The strip of film 11 is folded at 12, sealed at edges 13 and 14
and filled with a particulated product P which can be seen
through the film ll. After the product P is inserted in the
sachet lO, the edge 15 is sealed, thereby encasing the product P
within the bag 10.
As best seen in Figs. 4 and S, the infusion bag lO is
constructed of a coextruded multilayer film ll comprising an
outer layer 21 of a heat resistant film forming thermoplastic
resin such as polyester~ polyolefin polycarbonate or nylon with
polyester being preferred, and an inner sealant layer 22 of a
somewhat less heat resistant film forming thermoplastic resin
such as polyethylene, polyester, polycarbonate or nylon with
polyethylene being preferred. The inner polyethylene layer or
less heat resistant layer also contains an effective amount of
an antistatic agent. The film ll has a multiplicity of fine
holes or capillaries 23 which are of a somewhat tapered con-
struction, being more or less in the form of a truncated cone.
Tapered holes help to speed infusion. The somewhat cone shape
of the holes effectively channels liquid into the bag and into
contact with the particles contained therein.
Por simplicity of illustration, the holes or openings
are shown as being circular or round. It can be appreciated
that the openings may be of any desired shape such as oval, pen-
tagonal, hexagonal or other geometric configuration. It is im-
portant that the holes be uniform and that they be sufficiently
12Z106~
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large in size and number to provide adequate infusion and besufficiently small in size to prevent the migration of particles
therethrough such as the particulated product P.
In the packaging of an item such as tea, a preferred
S hole ~ize is from two to 10 mils, in diameter or across the
opening, with a size of three to four mils being most pre-
ferred. The film has a base thickness of 0~25 mil to two mils
and about 500 holes per square inch or more. From 1800 to 4200
holes per square inch are preferred, with about 2900 holes per
0 square inch being most preferred. The porosity of the film is
50 to 500 cubic feet per minute (CFM).
The outer layer of the coaxial or coextruded perforated
thermoplastic film of the bag is preferably a heat resistant
polyester film having a melting temperature of 425F to 600F
with about 525F being most preferred. The inner sealant layer
of the coextruded perforated thermoplastic film of the bag is
preferably a somewhat less heat resistant polyethylene film
having a melting temperature of 180F to 250F with 220F being
most preferred. The use of an outer polyester layer enables a
sealing/melting temperature differential of about 150F to be
obtained. The film has a desired seal strength of 3/4 lb. per
inch width.
A temperature of about 240F is required to melt the
polyethylene film for sealing. To prevent sticking of the outer
layer of thermoplastic film to the steel jaws of the sealing
~221C!6~
g
device or heat sealing machine, it is important that the melting
temperature of the polyethylene inner layer be kept below about
260F. It can be appreciated that particular polyolefin resins
or other film forming resins may hzve higher or lower melting
temperatures; however, it is essential that a melting
temperature differential be obtained between each layer to
achieve the desired seal without a deleterious effect on the
film.
The edges of the film are heat sealed to complete the
package. The melting temperature of the outer layer of the bag
must be sufficiently high to prevellt the film from sticking to
the sealant jaws. The melting temperature of the inner sealant
layer of the bag must be less than the melting temperature of
the outer layer.
The edges of the bags may be readily heat sealed using
standard sealing and automatic bag making machines. The edges
may also be effectively sealed with use of impulse or band type
sealers, hot wires, hot air or other suitable apparatuses or
techniques.
During heat sealing, the static-free surface of the
polyethylene film permits the particulated products to be direc-
ted away from the sealant area. For example, in a typical pac-
kaging operation, a rectangular strip of film is folded and
sealed on the two sides adjacent to or at right angles to the
fold, thereby forming a container or bag. A desired amount of
~2;;~06~
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particulated product is inserted in the bag while the bag is
held in a vertical or upright position. The product particles
immediately fall to the bottom of the container away from the
top~edge. The top edge is then sealed without any inhibition of
the fine particles.
For the packaging of a typical commercial tea for brew-
ing, a VisQueen~ Vispore~ film identified as X-6040 is especially
suitable for constructing the infusion bag. The film is a coex-
truded polypropylene/polyethylene perforated thermoplastic film
0 formed from a high density polyethylene resin to which about
2000 ppm of an anti-static agent, identified by the manufacturer
* *
as Atmul 84 or ATMUL 84R, has been added and a polypropylene
resin. The resins and antistatic agent are odorless and taste-
less and approved for food packaging.
The antistatic agent is added to the polyethylene resin
in an amount of S00-10,000 parts 2er million (ppm). The agent
must meet the requirements of the U.S. Food and Drug
Administration or any other applicable government specifications.
An antistatic agent found to be particularly effective is ATMUL~
84 or AT~UL~ 84R, identified by the manufacturer to be mono- and
diglycerides (edible fats glycerolysis). It is Generally Recog-
nized As Safe (~RAS) food additive per FDA 121.101. The agent
is in the form of ivory white beads or flakes and is blended or
otherwise mixed with the polyethylene resin prior to extrusion.
*Trade Mark
,
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ATMUL~ 84 is a well known commercially available anti-
stat or antistatic agent for polyolefins such as low density
polyethylene (LDPE), medium density polyethylene (MDPE) and poly-
propylene (PP), but said by the manufacturer not to be suffi-
ciently effective in high density polyethylene (~DPE). The agentis comprised mainly of mono- and diglycerides and contains a
minimum of about 40 weight percent alpha monoglyceride with a
maximum content of one weight percent of each water, free fatty
acid and free glycerides.
Unexpectedly, it has been discovered that the anti-
static agent not only is effective in HDPE, but also substan-
tially increases the infusion rate of tea bags having an inner
sealant layer of perforated polyethylene film when a small amount
of the agent has been blended with the ~DPE resin prior to
extrusion.
The female side or surface of the thermoplastic film to
be on the outside of the bag is also preferably flame or corona
discharge treated. Such treatment enhances the flow of water
into the bag and thus accelerates the infusion process.
The antistatic agent can be activated or further acti-
vated by corona discharge treatment of the film surface.
Although a coextruded multilayer polyester/polyethylene
film is preferred, other combinations of multilayer films are
suitable. Using the following designations:
o~
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Polypropylene PP
Polyethylene PE
Crystalline polyester CPE
Amorphous polyester ~PE
Polycarbonate PC
Nylon N
some examples of other suitable multilayer films are as follows:
PP/PE PC~PE N/PP
CPE/PP PC/PP N/PE
0 CPE/APE PC/APE N/APE
It can readily be appreciated that other film forming
resins can be used providing they can be effectively perforated
and provided that there is an adequate melt differential between
the outer layer of the bag and the inner sealant layer of the
bag.
With some resins, it may be necessary or desirable to
provide multilayer films of more than two layers. For example,
a triple layer film is suitable. Regardless of the number of
layers of film, it is essential that the melting temperature
differential be maintained between the ooter layer of the bag
and the inner sealant layer of the bag. The layers of a sheet
of film must also, of course, not be subject to separation or
delamination. The inner layer of film must also be made from a
film forming resin with which a suitable antistatic agent can be
mixed or blended.
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The film is preferably clear in color, but may be manu-
factured in its natural color or a variety of colors as desired
or permitted by governmental regulations, etc.
~ The film has a dry surface and has no tendency to stick,
cling or ~block~.
Vacuum perforated thermoplastic films have a "male~
side or surface and a ~female~ side or surface. In the con-
struction of infusion bags, the male side of the film is on the
inside of the bag.
0 The invention is illustrated in its simplest form, and
as a typical small size infusion bag for the packaging of indi-
vidual servings of tea for brewing. Larger size packages, such
as those customarily used in the food services industry can also
be constructed. Such larger bags can be similarly constructed
or constructed of two rectangular strips of film and sealed on
all four edges. The bags or packages can, of course, be con-
structed in other geometrical configurations as desired.
Rectangular packages are generally more suitable for boxing or
other group packaging.
Although the invention is particularly suitable for the
packaging of tea, it can be used for packaging of other types of
finely ground or particulated food products such as coffee and
grits. The bags of the invention are also suitable for packaging
items such as tobacco, snuff and the like. The bags may be used
for packaging of any items in vhich infusion of liquids is
desired.
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The infusion bags of the present invention have excel-
lent wet strength and will not deteriorate in boiling water.
The bags themselves are odorless and tasteless and do not impart
any foreign taste to the item being packaged. They are, in
effect, substantially inert~
~n antistatic agent or antistat as used herein is an
internal material blended with a polyolefin resin to reduce
static-electrical charges on film made from the resin by allowing
the charge to leakoff or otherwise inhibits the clinging of par-
0 ticles to the film and which is approved by appropriate regula-
tory agency as a food additive or suitable for use in packaging
of foods~
The effectiveness of the infusion bags of the present
invention is illustrated by the following comparative tests using
regular Tetley and Lipton teas available at any supermarket.
Infusion rating tests were conducted illustrating the
effectiveness of the infusion bags of the present invention in
comparison with samples of tea bags of the leading domestic tea
manufacturers readily available in a supermarket.
Test ~aterials and Equipment
2 boxes of commercial Tetley*pillow type tea bags (100
bags per box) - orange pekoe tea
1 box of commercial Lipton Flo-Thru~ tea bags (100 bags
per box) - orange pekoe*tea
Sheet of Vispore~ X-6005 coextruded perforated thermo-
plastic film [PP/MDPE, 40 mesh, 10 mil hexagonal holes,
1.2S mils thick (0.8 mil PP + 0.45 mil MDPE - calcula-
ted) and having a porosity of 225 CFM].
*Trade Mark
.:~^,.
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Sheet af Vispore~ X-6018 coextruded perforated thermo-
plastic film (PP/MDP2 ~ ATMU~ 84), 40 mesh, 10 mil
hexagonal holesr*l.25 mils thick tO.75 mil PP + 0.50
mil MDPE + ATI~L 84) and having a porosity of 225 CFM.
Color ~radient chart of three colors as follows:
Yellow - Flair ~ot Line
Pink - Carter's ~i-Liter
orange - Sanford's No. 1500
Electrical hot plate
0 Mr. Coffee or iike Purex breaker for boiling water
Pyrex No. 1000 - 400 mL beaker
Distilled Water
Stop watch
Sealine hand held heat sealer, Model 70
Razor blades, glass cutting plate, paperboard template
1-11/16 inches x 11 inches, and ruler.
Sample Pree~ tion
Perforated thermoQlastic film tea bags wera individually
prepared by hand from each film sample as follows:
The male surface of a strip of film was sandwiched
and/or snugged around the paperboard template. The hand sealer
was set at 270F and the film sealed along the open end. ~p-
proximately 1/8 inch film overhang was left from the outer sealed
area. Excess film was cut from the fabricated tube. The paper-
board template was removed leaving a tube of film having an
*Trade Mark
.,
.
\
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inside diameter of 1-11/16 inches. Three specimens, each 2-10/16
inches long were cut from the fabricated tube. One edge of each
specimen was sealed ~ith the hand sealer. A distance of 2-2/16
inches was measured from the inside edse seal and marked. The
tea from a Tetley tea bag was poured into the fabricated perfo-
rated film bag. The fabricated film bag was sealed with th~
hand sealer along the 2-2/16 inches measured area. Additional
bags as needed were similarly fabricated.
Ten Tetley bags and ten Lipton bags were randomly
selected for tea weight loading measurements. The bags had sub-
stantially the same weight loading an a~eraged 2.2 grams of tea
per bag. Weight loading measurements are set forth in Table I
hereinafter.
Tetley and Lipton*tea bags were tested as regularly
packaged.
Procedure and Testing
Twenty-five bags of each of the four types of bags were
used for each series of tests. Six and eight ounce cups were
selected. The 400 mL beaker was set at eye level. The color
gradient chart was adjusted two inches in back of the beaker.
The Mr. Coffee container or pyrex beaker was filled with dis-
tilled water, placed on the hot plate and the water was heated
to a full rolling boil. A tea bag was placed in the bottom of
the 400 mL beaker. The stop watch was started as six or eight
*Trade Mark
, . ,
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ounces of boiling water was poured over the tea bag. The tea
bag was lightly stirred or spooned. Visual inspection was made
for infusion at a distance of eight to ten inches from the brew-
ing tea looking through the liquid to the color gradient chart.
Time intervals of elapsed time were recorded at each instance
where the yellow, pink and orange colors were no longer visible
on the color gradient. Averages for 25 bags were calculated.
The results are set forth hereinafter in Tables II-VII.
Table I
0 Tea Weight and/or Loading ~easurements
(Net ~.~eight of Tea in Grams)
Tetley Pillow 3agsLipton Flo-Thru Ba~s
2.2955 2.2143
2.0705 2.2190
2.1832 2.1653
2.3338 2.1694
2.1138 2.1588
2.2946 2.1252
2.2821 2.2562
2.2424 2.2211
2.2173 2.2082
2.1651 2.2156
Average = 2.2198 grams/bagAverage = 2.1954 grams/bag
- /; *Trade Mark
1~:2~Q6~L
Table II
6 oz. Cup - Yellow Color
(Number of Tea Bags)
Elapsed * Perforated Film Bags
5 Time in Tetley Lipton with Tetley Tea
Seconds Tea BagFlo-Thru Bag X-5005 X-6018
0 40 7
2 1 5 4
3 2 8 4
25 ~ 12 3 1 15
6 18 2
Average No. Seconds
25 Bags 2~.16 24.00 39.4030.10
*Trade Mark
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Table III
6 Oz. Cup - Pink Color
tNumber of Tea aa~s~
Elapsed * Perforated Fi*lm Bags
5 Time in Tetley Lipton with Tetley Tea *
Seconds Tea Ba~ Flo Thru Bag X-6005 X-6018
~5 2
l 2
4 7 2
~ 1 2 7 3
4 l 5
12 9 1 14
530 3 9
Average No. Seconds
25 Bags 39.92 38.00 53.50 40.40
*Trade Mark
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Table IV
6 oz. Cu? - orange Color
(Number of T~a aags)
Elapsed Perforated Film Bags
5 Time in Tetley Liptonwith*Tetley Tea *
Seconds Tea Ba~ Flo-Thru Ba~X-6005 X-6018
130
12S 2 2
120 3
115 1 2
0110 3 3
105 1 6
100 ~ 4 2
4 3
4 5 3
585 2 3
7 4 4
3 1 8
2 3
20 Average No. Seconds
25 8ags 87.72 110.80 97.00 77.90
*Trade Mark
"~' '
- 21 -
Table V
8 Oz. Cu~ - Yellow Color
(Number of Tea Bags)
~lapsed Perforated Fi*m Bags
5 Time inTetley * Lipto*nwith*Tetley Tea *
Seconds Tea 3agFlo-Thru BagX-6005 X-6018
2 5
1 4 7
l 8 6 2
_ 3 4 4 8
~7 5 1 10
9 2 4
15 Average No. Seconds
25 Bags 39.76 49.08 56.00 44.50
*Trade Mark
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Table VI
8 Oz. Cup - Pink Color
(Number of Tea Bags)
Elapsed Perforated Fi*m Bags
5 Time in Tetley Liptonwith Tetley Tea
Seconds Tea Bag Flo-Thru 3agX-6005 X-5018
2 3
2 3
6 2
0 70 1 8 8
3 4 6
~ 8 1 2 3
2 13
5 45 4
~0 2
Average No. Seconds
25 Bags 56.32 75,60 74.2 58.20
*Trade Mark
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Table VII
8 oz. Cuo - Orange Color
(Number of Tea 3ags)
Elapsed Perforated Film Bags
5 Time in Tetley* Liptonwith*Tetley Tea
Seconds Tea Bag Flo-Thr~*BagX-6005 X-6018
-
215
210
205
0 200 2
195
190
185 5 2
180 - l l
175 ~ 2
170 2
165 3
160 l 2
155
20 150 2 3 5
145 1 1 4
140 3
135 5 2
130 1 2 2
25 125 2 1 5
120 6 2
115 2 4
110 5 5
105 1 3
30 100 2
Average No. Seconds
25 Bags 125.72 177.16 147.20 121.20
*Trade Mark
~ ~ .
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From the foregoing, it is readily seen that the infusion
rates of the perforated plastic film bags incorporating an anti-
static agent with the resin are substantially greater than the
infusion rates of the perforated plastic film bags made from film
in which no antistatic agent was used. The former bags also
have an infusion rate comparable to that of the regular commer-
cial Tetley tea bags.
The blend of monoglycerides and diglycerides also pro-
vides a film surface which does not tend to block. This is
0 important in the rapid production of large quantities of perfo-
rated thermoplastic film.
Corona discharge treatment of the perforated plastic
film prior to bag fabrication further assures a cling free~
film. A treatment level of about 33 to 44 dynes provides maximum
functionality.
