Note: Descriptions are shown in the official language in which they were submitted.
214199~
~.
~ 1316-804
RESEALABLE P.~CKAGING M,~TERIAL .~ND METHOD OF klAKING S.~E
CROSS-K~K~CE TO RELATED INV~NTIONS
Thls appllcatlon ls a Contlnuatlon-ln-Part of U.S.
Serlal No. 07/790,647, flled November 08, 1991, now abandoned,
whlch ls lnclude~ hereln by reference.
BACKGROUND OF TH~ INVFNTION
Field of the Inventlon
The present lnventlon relates ln general to packaging
materlals for use in flexlble bags. In particular, the present
lnvention relates to an lmproved packaging materials for use in
resealable bags, such as for food, and methods of making such
materials.
Descrlptlon of the Related .~rt
For many years lt has been known to package varlous
products, and ln part.lcular loose food products, ln flexlble
bags. In recent years lt has become lncreaslngly common to form
such bags uslng the so-called "form, fill and seal" technlque.
Thls technlque employs a roll of flexible packaglng materlal
whlch ls fed to an apparatus which forms the flexible bag
slmultaneously wlth placin~ the product wlthln the bag. Thls ls
an extremely fast and econorllical approach whlch produces quality
packages.
Regardless of the method em~loyed to form the package,
one perslstent problem wlth such flexlble bags is thelr poor
ablllty to be reclosed. It is common for a single flexible bag
to hold more product than is desired to be used in a slngle
214199~
application or use. This is often the case with food items such as
coffee, snack chips, etc. While such bags are provided with
adequate seals upon initial forming, once these seals are first
broken to open the package, it is difficult to reclose the bag to
the degree desired. In such situations it is often desired to
reclose the bag sufficiently to at least prevent the product from
inadvertently spilling from the bag, and often a greater seal is
desired to retain freshness of the product and/or prevent
contamination of the product.
Various devices have been proposed to attach to the bag
after opening to allow the bag to be reclosed. Certain of these
devices, such as clips, are only marginally adequate in their
ability to achieve the desired seal. Even where such devices work
properly, there is the additional expense to obtain such devices,
and the effort to find and properly employ the devices.
As an alternative, it has been proposed to form the
material of the bag with means for adhesive reclosure. One example
of this is shown in U.S. 3,454,210 to Spiegel et al. Spiegel et
al. propose a packaging material having a substrate (polyester and
polyethylene laminate) upon which is coated a layer of a tacky
adhesive. A further, thin layer of non-tacky material
(polyethylene) is then placed over the tacky layer. This sheet
material is then bonded to a standard package material, with the
outer, thin non-tacky layer providing an initial heat seal bond
with the standard sheet packaging material.
2I41994
-
61316-804
In use, the lnltlal heat seal ha~ a strength and
seallng quallty slmilar to standard bags. Upon opening, how-
ever, the thin non-tacky layer ruptures about the seal and is
retalned upon the sheet of standard packaglng material, thus
reveallng the tacky adheslve. The tacky adheslve at the seal
area may then be used to bond the sheets together numerous tlmes
to retaln freshness and prevent contamlnatlon.
Wlth the emergence of the use of "form, fill and seal"
machlnery, thls substrate/tacky adheslve/thln non-tacky layer
comblnatlon was proposed for use in such machinery. This is
shown in U.S. 5,089,320 to Strauss et al. The basic material is
substantially identical in both 5trauss et al. and Spiegel et
al., but in the Strauss et al. method the material is bonded to
itself, as is common in "form~ fill and seal" machinery, rather
than to a separate, standard, material.
SUMM~.RY OF THE IN~ENTION
An object of the present invention is to provide a
packaglng materlal for flexlble bags whlch allows the bags to be
reclosed.
Another object of the present lnventlon is to provide
such a materlal having localized areas of reclosability.
r. further ob~ect of the present invention is to
provide such a material having reduced thickness variations
despite such localization, to provide smoother rolllng and
unrolling of the material, and to reduce or elimlnate stretching
of the material
, 2141994
çaused by n lumps".
Yet another object of the present invention is to provide
methods of making such material.
Another object of the present invention is to provide
such methods which result in precise localized areas of
reclosability.
Yet another object of the present invention is to provide
such a method which may be employed with standard, previously
manufactured, packaging material.
A further object of the present invention is a method of
making packaging material which may be employed without reclosable
features, or may be subject of further steps providing
reclosability.
These and other objects are achieved by a packaging
material for reclosable bags and methods for making same. The
material includes standard packaging material substrates typically
used for "form and fill" machinery. Such substrates include an
initial seal layer, typically for forming a heat seal. A layer of
a secondary seal material, typically a tacky material such as a
pressure sensitive adhesive, will be applied in localized areas
corresponding to the seal area for the bag. The initial seal layer
may have a reduced thickness in this localized area to reduce
thickness variation in the finished material. As the tacky
secondary seal material would foul the "form and fill" machinery,
an outer seal layer is provided over the secondary seal area. This
., =
2I4I 994
.
,
~1316-804
outer seal layer may be locallzed to cover only the secondary
seal layer. The outer seal layer- may ~dditionally or
alternatively have a reduced thickness in the localized area of
the secondary seal layer to again r-educe thickness varlation.
Various processes are available for providing the layers. In
one embodiment, the secondary and outer seal layers are applied
by use of a ribbon coater, providing precise control for
application area and thickness. This application may be
dlrectly upon the substrate, or upon a release sheet for later
1~ transfer to the substrate.
BRIEF DESCRIPTIQN OF THE DR~WING5
The objects and features of the invention noted above
are explained in more detail with reference to the drawlngs, in
whlch llke reference numerals denote llke elements, and ln
which:
Flg. 1 is a perspective view of a prior art "form,
fill and seal" process;
Fig. 2 is a perspective view of a resealable bag
according to the present invention;
Fig. 3 is a cross-sectional view of a top seal area of
the-bag of Fig. 2, in the sealed condition;
Fig. 4 is a cross-sectlonal vlew of a top seal area of
the bag of Flg. 2, ln the opened condltlon;
Fig. 5 is a top view of a web of packaging materlal
accordlng to a flrst embodlment;
Flg. 6 ls a cross-sectional view along line 6-6 of
Fig. 5;
214193'1
-
61316-804
Flg. 7 ls a schematlc vlew showing a process of maklng
the materlal of Flg. 5;
Flg. 8 ls a top view of a web of packaging materlal
accordlng to a second embodlment;
Fig. 9 ls a cross-sectlonal vlew along llne 9-9 of
Flg. 8;
Flg. 10 ls a schematlc vlew showlng a flrst process of
maklng the materlal of Flg. 8; and
Flg. 11 ls a schematlc vlew showlng a second process
of maklng the materlal of Flg. ~.
DET~.ILED DE~K~ 1ON OF THE INUENTION
Prlor to dlscusslng the materlals and processes of the
present lnventlon, prlor art bag formlng methods wlll be
descrlbed. Wlth reference to Flg. l, there ls shown an operatlng
"form, flll and seal" devlce or- machlne. The devlce recelves
web materlal 10 from a roll 12. In lts slmplest form, the web
rrlaterlal lncludes a substrate havlng an lnner face 11, wlth the
lnner face ll elther havlng sealable propertles to ltself, or
lncludlng a layer (not shown) havlng sealable propertles to
ltself. Thls seallng may be by several means, but ls most
typlcally a heat seal. r,ddltlonally, thls lnner face has a
sufflclently low coefflclent of frlctlon to allow the web to
smoothly pass through the "form, flll and seal" machlne
descrlbed below.
The web passes through varlous ldle and/or tenslon
rollers 14. The longltudlnal edges of the web l0 are then
caused
- - 2~1~19~4
-
to be wrapped about a tubular mandrel 16. The mandrel is sized
such that its diameter is slightly smaller than the width of the
web, so that the lateral edge portions of the web may be brought
together in abutting relation.
The web is drawn downward over the mandrel while it is
maintained in surrounding relation to the mandrel. This motion may
be effected by appropriate power belts 18 engaging the exterior of
the web. The abutting lateral edge portions of the web are then
sealed together to form a fin seal. This may be effected by
pressure or other means, but is preferably performed by a heated
fin sealer 20.
The lower end of the mandrel is located adjacent the fin
sealer. At this point the web has been formed into a tubular
configuration, and passes below the lower end of the mandrel.
Spaced below the fin sealer are a pair of end seal jaws 22 which
reciprocate between open and closed positions. The jaws may be
heated to form a heat seal in the packaging material, or may form
a seal by pressure, ultrasonic bonding, etc.
When in the closed position the jaws 20 will squeeze the
tube of packaging material into a flat configuration, and will bond
the packaging material to itself. The longitudinal length of this
bond is twice what is required for a single seal, and a lateral cut
is made at an intermediate line in the seal. Subsequent to forming
this seal the product to be packaged is passed from a hopper 24
through the tubular mandrel into the tube of packaging material.
21419~4
-
~he downward movement of the product is halted by the presence of
the end seal.
The jaws 22 are moved to the open position and the tube
of packaging material is then advanced by the length of one bag.
The jaws are then moved to the closed position to again form a seal
and a cut. As may be envisioned, this will seal the upper end of
the bag, and cut the bag from the tube of material.
Simultaneously, the lower seal of the next bag will be formed. The
product is then introduced into the next bag, the material
advanced, and another seal made to form the next bag, with this
process repeating itself.
A bag made according to this method typically has an
appearance as shown in Fig. 2, and is generally designated by
reference numeral 26. The bag 26 includes a body 28 formed of a
length of packaging material formed into a tube by fin seal 30, as
described above. Each longitudinal end of the bag has been
flattened radially (laterally) and the interior face of the
packaging material sealed to itself. This forms a top seal 32 and
a bottom seal 34.
It may be preferred to space the top seal 32
longitudinally inward of a top edge 36 of the bag. This will allow
the user to grasp the bag material at the top edge 36 and more
easily pull the bag open. As a further alternative, there may be
provided a secondary top seal (not shown) spaced from the top seal
32 in the longitudinal direction and including the top edge 36.
2 1 4 i 9 ~ ~
-
Indicia and/or perforations (not shown) would then extend laterally
across the bag at a longitudinal position intermediate the top seal
and secondary top seal. This may be employed to aid the user in
cutting or tearing the bag intermediate these seals. In this
manner the secondary top seal will act as a tamper indicating seal.
The above features are common to many prior art bags. To
make the bag 26 reclosable, however, the above-referenced patent to
Spiegel et al. teach that there is provided tacky material 38
within the periphery of the top seal 32 on the inner face 11 of the
web. As noted above, the inner face must have a low coefficient of
friction, and as such Spiegel et al. teach that a further layer 4-0
(Fig. 4) of low friction, sealable material is formed over the
tacky material.
The reclosable feature taught by Spiegel et al. is
illustrated in Figs. 3 and 4, which are cross-sectional side views
looking along the plane of the top seal 32. As may be seen in Fig.
3, the web 10 will have the layer of tacky material 38 in the area
of the top seal, with the layer 38 being covered with the further
layer 40, and the layer 40 sealed to itself. This provides a
standard initial seal similar to non-reclosable bags.
Upon the user applying a force to open the initial seal,
the layer 40 ruptures about the tacky layer 38, causing the tacky
layer to be exposed. Spiegel et al. notes several possible ways in
which the tacky layer may be disposed upon rupture. For example,
the tacky layer 38 may remain upon the substrate 10 in its original
214199~
. .
61316-804
posltlon, or lt may remaln upon the lnterlor face of the further
layer 40 (on the opposlte of the origlnal slde), or lt may shear
wlthln lts thlckness and adhere to both the substrate 10 and the
layer 40.
- Regardless of the partlcular flnal dlsposltlon of the
tacky layer, the tacky layer ls exposed, such that lt may be
used to form at least one, and preferably numerous, reclosures
of the bag 10.
Wlth the above background materlal outllned, attentlon
ls drawn to the lmprovements of the present lnventlon.
Flgs. 5 and 6 show a flrst embodlment of a packaglng
materlal, generally deslgnated 50, accordlng to the present
lnventlon. As ls best shown ln Flg. 5, the materlal ls ln the
form of a web elongated ln a longltudlnal dlrectlon (left to
rlght ln Flg. 5) and havlng a lateral extent. Thls lateral
extent ls shown ln the drawlngs as belng the wldth for a slngle
bag, but lt wlll be apparent that materlal havlng multlple bag
wldths may be produced and then cut or sllt to form slngle-bag
wldths.
Wlth partlcular reference to Flg. 6, the materlal wlll
lnclude a substrate 52. The substrate may be slngle or multl-
layer, but ls preferably rnultl-layer. The multlple layers wlll
typlcally be dlverse materlals, but may be multlple layers of an
ldentlcal materlal. The substrate may be formed by a varlety of
methods, lncludlng coextruslon, extruslon lamlnatlon, adheslve
lamlnatlon and comblnatlons thereof.
- 2141994
.
Where the substrate is formed of multiple diverse
materials, these materials typically serve particular functions
such as providing strength, vapor barriers, consumer-~isual
indicia, etc. Typical materials include metal foils, polyester,
cellophane, high density polyethylene, typical printing inks, etc.
As an example, the substrate 52 of Fig. 6 includes a base layer 54
acting as a support, and formed, for example, of cellophane. The
inner face of the base layer is then provided with an indicia layer
56 of an ink pattern providing advertising, product information,
etc. The inner face of the indicia layer is then provided with a
primer or adhesive layer 58 compatible with both the indicia layer
and the subsequent layer.
The inner face of the primer layer 58 is next provided
with an initial seal layer 60. The initial seal layer is formed of
a material having low friction to allow use in the "form and fill"
machine, and preferably is capable of forming a heat seal to
itself. For example, the initial heat seal layer may be
polyethylene, with the thickness being typical for forming a heat
seal in non-reclosable packages, i.e. between about 0.5 and 2.0
mils. Other possible materials include ethylene/vinyl acetate
copolymers or certain ionomers such as SURLYN~ available from
DUPONT~.
Each of the layers comprising the substrate 52 is
preferably coextensive. In other words, each layer extends the
full lateral width and the full longitudinal length of the
-- 21419~'1
material. As may be envisioned, this substrate could be used to
form standard non-reclosable bags, as will be discussed more below.
To allow the material to be used as a reclosable bag,
there is provided a secondary seal layer 62 formed of a tacky
material such as a pressure sensitive adhesive. Various tacky
materials may be employed for layer 62, although the preferred
methods according to the present invention limit these
possibilities, as explained more fully below. As the tacky
material inherently includes a high coefficient of friction,
allowing the tacky material to be exposed will foul the "form and
fill" machine.
To overcome this problem, there is provided an outer
layer of low friction seal material 64. This material is
preferably similar or identical to the initial seal layer. Again,
polyethylene is a good candidate at thickness in the range of about
0.2-0.7 mils (0.4 mil being preferred), although other materials
may be employed. The outer seal layer 64 typically will have a
lesser thickness than the initial seal layer, although material
properties of course affect this determination. In general, the
initial, secondary and outer seal layers must only meet the
criterion for bonding and rupturing as set forth by Spiegel et al.
As is apparent from comparison of Figs. 5 and 6, the
initial and outer seal layers in this embodiment are coextensive,
while the secondary seal layer of tacky material is localized. In
particular, the secondary seal layer is localized to areas which
- 2141~
,
~correspond to the full lateral extent of one side of the top seal
32 only (in other words, only that area which needs to be
reclosable). While the secondary seal layer could be coextensive,
the illustrated, localized, embodiment uses less of the tacky
material to reduce cost, and results in only the typical firm seal
at the bottom of the bag. To aid in placement of the localized
tacky material, the indicia layer 56 may include locating strips 65
and/or 66.
The material 50 may be formed in many ways. For example,
the substrate may be formed by standard methods such as extrusion
lamination or coextrusion. Where the secondary and outer seal
layers are coextensive these same methods may be employed to form
the entire material 50 in a "single" step. However, where the
secondary seal layer is localized, these localized areas may be
placed by various methods, such as Meyer rod, rotogravure, etc.
In the preferred embodiment, however, the localized areas
of secondary seal 62 are formed by use of a ribbon coater for
improved accuracy and uniformity. A suitable ribbon coater is
available from Graco LTI of Monterey, California, or from Accumeter
of Marlborough, Massachusetts. Such ribbon coaters provide very
good continuous or intermittent pattern coatings at relatively high
speeds, but are limited as to the types of materials which may be
applied. In particular, ribbon coaters are known to be limited to
materials having a relatively narrow range of viscosities,
typically between about 1,000.-5,000 cP (mPa/s).
13
21~ 1 99 4
`
As typical hot melt pressure sensitive adhesives have
viscosities at application temperature much greater than this range
(typically many tens of thousands to hundreds of thousands cP),
standard hot melt pressure sensitive adhesives clearly can not be
employed with ribbon coaters. However, a small number of hot melt
pressure sensitive adhesives having viscosities at application
temperature falling within the range of ribbon coaters have
recently become commercially available. For example, one preferred
pressure sensitive adhesive is commercially available from the H.B.
Fuller Co. of St. Paul Minnesota under product no. HL-2115-X. This
adhesive has a viscosity at application temperature (approx. 162-C)
of 1,100 cP, and a melt index of greater than 100. It is only
through use of such adhesives that the use of ribbon coaters is
possible.
With reference to Fig. 7 there is schematically shown an
apparatus 68 for forming the material 50, and with reference to
this apparatus the preferred method will be described.
First, the substrate 52 is formed by prior art methods.
As illustrated by the dashed rollers and substrate 52 in Fig. 7,
this step may be part of a continuous process for forming the
material 50. However, the substrate 52 may be formed and rolled,
and then stored in rolled condition until it is desired to produce
the material 50. It is noted that the substrate 52 will often be
capable of use in forming standard non-reclosable bags. As such,
the amount of inventory may be reduced by using this same substrate
14
2141994
for both end uses.
In any event, the substrate 52 will pass through various
idle and/or tensioning rollers 70. A ribbon coater head 72 will be
located in position to apply the secondary seal layer to the inner
face of layer 60, and appropriate control apparatus for the ribbon
coater head will also be provided. In particular, there may be
provided a valve 74, melt delivery equipment 76 and a pattern
controller t8. The pattern controller 78 is preferably operatively
connected to a sensor 80 which will sense the eye or locator spots
65 or 66. The thickness of the secondary seal layer will typically
be within the range of 0.5 and 1.5 mils, with 1.0 mils being
preferred for the adhesive noted above. Different adhesive
materials having different properties will of course require
different thicknesses.
After application of the localized secondary seal layer
there is applie~ the outer seal layer 64. This application may be
by standard extrusion lamination, with the material then passing by
a chill and cool pincA roller assembly 82 to set the layers 62 and
64. The material 50 is then rolled for shipping or storage.
From the above description it should be apparent that
this method may be an integral part of a larger continuous process
of making packaging material, or may be a separate method performed
upon substrate material previously formed. As noted above, this
permits substrate material useful for both standard (non-
reclosable) and reclosable bags to be produced, with this substrate
214193~
~,
61316-804
materlal only later belng provlded wlth the addltlonal layers
necessary for reclosable bags. Thls of course reduces lnventory
requlrements.
Addltlonally, thls method need not be performed at the
slte of manufacture of the substrate material. In partlcular,
the method of addlng the layers 62 and 64 to the substrate may
be performed on the slte havlng the "form, flll and seal" equlp-
ment. Thls allows the manufacturer of the consumer product to
qulckly lmplement productlon of consumer product ln reclosable
bags, wlthout the need to walt for, or store, separate materlal
50.
As may be envlsloned, the materlal 50 descrlbed above,
wlth the locallzed areas of secondary seal layer 62, results ln
a lumpy roll upon wlndlng for shlpplng or storage, due to the
thlckness varlatlons ln the materlal 50. Whlle thls is
unslghtly, lt also may result ln speed varlatlon durlng wlndlng
at the end of the apparatus 68, whlch could cause mlsplacement
of the locallzed areas 62 and/or thlckness varlatlon ln the
extruded outer layer 64. Slmllar speed varlatlons and/or cycllc
stresses may be lnduced upon unwlndlng at the "form, flll and
seal" machlne. These "lumps" ln the roll may also cause the
materlal to be stretched over the lump, deformlng the materlal.
To reduce or ellmlnate these posslble problems lt ls
posslble to form one or both of the lnltlal and outer layers 60
and 64 wlth thlckness varlatlon ln the lateral dlrectlon to
provlde a reduced thlckness ln the lateral extent of the
secondary seal layer
16
21gl994
~62. Such thickness variation may be achieved by appropriate
variation in the outlet of the extruder for the layer(s). Fig. 6
shows an example where both layer 60 and 64 include a reduced
thickness area corresponding to the lateral extent of the layer 62,
such that the thickness of the material 50 is substantially
constant in the lateral direction at the localized areas 62.
It is noted that this thickness variation in the layer 60
and/or 64 extends the full longitudinal length of the material 50.
As such, in the sections of material 50 which are longitudinally
between the localized layers 62, there will be a reduced thickness
compared to the material 50 within the periphery of a layer 62.
This is illustrated by dashed lines 84 in Fig. 5. While there is
such a thickness variation laterally within the lines 84, the
sections of the material 50 laterally exterior of lines 84 have a
substantially constant thickness. This should result in a roll
having a smooth appearance and winding/unwinding characteristics.
While Fig. 6 shows an example where both layers 60 and 64
include a thickness variation, only one of these layers may have
such variation. Where such variation is present, the smallest
thickness of the layer should of course still be sufficiently thick
to provide the required bond. As an example, the outer layer 64
should have a minimum thickness of approx. 0.3 mil in the example
given. Additionally, while the layers 60 and 64 are varied
sufficiently to result in a substantially constant thickness in
Fig. 6, a lesser variation in their thicknesses would reduce
~ 17
21~199~
-
~problems associated with uneven winding, while not eliminating them
to the degree illustrated in Fig. 6.
With reference to Figs 8 and 9 there is shown a second
embodiment of the present invention. This embodiment is
substantially similar to the first embodiment, and thus has similar
reference numerals, with the exception that the outer layer 64 is
not coextensive, but is localized in a manner similar to layer 62.
Since the outer layer 64 provides the low friction
necessary to allow passage through packaging machinery, the outer
layer 64 must at least fully cover the secondary seal layer 62. In
practice, the outer layer will typically extend peripherally beyond
the entire area of the layer 62 to ensure coverage in case of
slight misalignment. As shown in Fig. 8, if the outer layer 64 is
an opaque material, it may be used to cover and obscure one or both
of the spots 65 and 66 to provide improved appearance on the
interior of the package.
As may be envisioned, the thickness variation with this
second embodiment would be even greater than the first embodiment,
as the lateral edges of the material 10 will have a thickness
corresponding to only the substrate, without the outer layer 64.
As such, it may be preferred to provide a thickness variation in
the layer 60 and/or 64 in a manner similar to that discussed above.
As an example, Fig. 9 shows the initial seal layer 60 having a
reduced thickness area laterally corresponding to the position of
the secondary seal layer 62. As before, this reduced thickness in
~8
21419g4
61316-804
layer 60 wlll extend the full longltudlnal length of the
materlal 50 where the layer 6n is extruded. The lllustrated
arrangement serves to lessen the amount of thlckness varlatlon
lrl the materlal 50 to reduce the problems assoclated with a
lumpy roll.
Other arrangements are of course possible to further
reduce thlckness varlatlon. For example, the lateral extent of
the thlckness varlatlon in layer 60 could be extended to encom-
pass the lateral extent of outer seal layer 64. If thlckness
varlatlon ln the layer 60 were set to equal the comblned
thlckness of the layers 62 and ~4, thls would result ln an
arrangement equlvalent to that sho~n ln Flg. 6.
As wlth the layer 62, the locallzed appllcatlon of the
outer layer 64 may be achleved by several methods, such as roto-
gravure, flexographlc prlntlng, etc. However, lt ls preferred
to employ a rlbbon coater as used for the layer 6Z. Agaln,
rlbbon coaters requlre materlals havlng a vlscoslty wlthln about
1,000-5,000 cP at appllcat.lon temperature. One sultable rnater-
lal havlng the deslred low frlctlon, heat sealablllty, and
vlscoslty ls commerclally avallable from the H.B. Fuller Co. of
St. Paul Mlnnesota under product No. HL-7068-X. Thls materlal
has a vlscoslty at appllcatlon temperature (approx. 162C) of
approxlmately 2,000 cP. As may be seen, thls heat seal materlal
therefore has a viscosity (at applicatlon temperature) which
would not permlt extruslon.
lg
- 21419~
`
With reference to Fig. 10 there is schematically shown an
apparatus 68' for forming the material 50 of the second embodiment,
and with reference to this apparatus the preferred method for
forming this embodiment will be described.
The formation of the substrate and application of the
localized secondary seal layer 62 by use of a ribbon coater is as
described above in the first embodiment, and as such has like
reference numerals.
After the application of the layer 62 the material may be
fed through a chill and cooI pinch roller assembly 82 to set the
layer 62. Since the layer 62 is inherently a tac~y material, the
assembly 82 must be formed with Teflon~ or other low friction
rollers. While this may be employed, it is preferred to simply do
without the assembly 82. In other words, upon application of the
layer 62, the material is guided directly to a second ribbon coater
for application of the layer 64.
This second ribbon coater is very similar to the first,
and thus may include a head 72' to apply the layer 64, a valve 74',
melt delivery equipment 76 ' and a pattern controller 78 ' . The
pattern controller 78 ' is preferably operatively connected to a
sensor 80' which will sense the eye or locator spots 65 or 66. The
thickness of the outer layer 64 will typically be within the range
of 0.2 and 0.7 mils, with 0.4 mils being preferred for the material
noted above. Different materials having different properties will
of course require different thicknesses.
.
. .
., ., ~ ,.
2 1 4 1 9 9 4
`
After application of the localized outer seal layer 64
the material is passed by a chill and cool pinch roller assembly 82
to set the layers 62 and 64. The material 50 is then rolled for
shipping or storage.
This method of course has the same advantages as
described above with regard to Fig. 7.
A second method for forming the material of Figs. 8 and
9 is now described with reference to Figs. lO and ll. With
reference to Fig. lO, where the above-described process stands
alone and is performed upon existing rolled substrate material, the
general steps are to simply apply the two layers 62 and 64 to the
substrate in the correct position. In this second method, these
general steps are still performed, but are performed upon a double
sided release sheet 86, and in the opposite order.
lS In other words, the roll of substrate 52 at the far right
in Fig. lO is replaced with a roll of sheet material 86 having a
low friction release coating, such as silicone, on both faces. The
release sheet 86 passes through the same rollers and under the same
ribbon coaters, with the sole further exception being that the
outer layer 64 is first applied to the release sheet 86, and then
the secondary seal layer 62 is applied upon the layer 64. The
relative sizes of the layers re~ the same as above, and in
particular the layer 64 extends outwardly of the layer 62.
In this method, however, the longitudinal spacing of the
layers on the sheet 86 need not correspond to the length of a final
21
21~19~4
`
61316-804
bag. In fact, it ls preferred that the locallzed layers are
spaced closely together, although not touchlng. Upon settlng of
the layer by the chlll assembly 82 Iformed of a low frlctlon
rr,aterial due to the exterior placement of layer 62 in this
embodlment~, the sheet 86 ls rolled. Agaln, slnce the layer 62
is exterior in this embodiment lt is lmportant to employ double
slded release sheet.
The roll of sheet 86 wlth locallzed layers thereon
wlll at some later time be used as a transfer sheet as shown in
Fig. 11. In particular, substrate rnaterial 52 will be fed from a
roll (or as the output from the process formlng the substrate)
across a pair of idler rollers 7Q which define an application
area. The release sheet 86 wlth the layers adhered thereto will
also be fed from a roll across a palr of rollers 88 which are
connected to a reciprocating plston assembly 90. The layers 63
and 64 are orlented to face the substrate 52 as shown, and the
rollers 88 are opposlte the appllcatlon area deflned by rollers
70.
The release sheet is fed an appropriate distance to
bring a set of layers 62 and 64 between the rollers 80, and the
substrate 52 ls fed the length of a bag. As noted above, these
dlstances may be, but are not necessarlly, equal. Once the
sheet 86 and substrate 52 are ln the proper posltion the piston
assembly 90 ls extended to press the set of layers 62 and 64
ayalnst the substrate to transfer the layers to the substrate.
The plston ls then retracted and the sheet 86 and substrate 52
advanced to the next. position for application of the next set of
layers. There may be
~ 2I~I9~
61316-804
provlded a pressure nip or heated roller assembly to ald ln
transfer elther durlng OL^ afteL-- extension of the piston
assembly.
This will result in the tacky secondary seal layer 62
belng secured to the substrate 52 wlth the outer layer 64 ln
coverlng relatlon. As suchl the su~strate 52 wlth applled
locallzed layers may be rolled as ln the prevlous embodlments.
It ls noted that the appllcatlon of the layers to the
substrate ln thls second method ls generally qulte fast, but
rnore lmportantly is not unduly affected by lntermlttent stop-
pages. Thls ls not the case wlth processes lncluding extruslonl
and ls difficult in processes lncludlng ribbon coating. Because
thls appllcatlon can accommodate such stoppagesl lt ls posslble
to lncorporate the transfer steE~ of Flg. 11 lnto a "form/ flll
and seal" machlnel such that the substrate and applled layers
are not rolledl but lnstead are fed directly lnto the packaglng
machlnery.
From the foregolng it wlll be seen that this invention
is one well adapted to attain all ends and ob~ects hereinabove
set forth together with the other advantages which are obvious
and which are inherent to the structure.
It will be understood that certain features and sub-
comblnations are of utility and may be employed wlthout refer-
ence to other features and subcomblnatlons. For example/ the
process of Flg. 10 could feed dlrectly lnto the packaglng
machlnery. Thls ls contemplated by and ls within the scope of
the claims.
- 2141994
~`
Various modifications can also be made. For example, the
secondary seal layer 62 may be formed with a color contrasting with
the initial and outer seal layers 60 and 64, to therefore prove a
tamper-indicating feature. The various embodiments and processes
may also be useful in other combinations.
Since many possible embodiments may be made of the
invention without departing from the scope thereof, it is to be
understood that all matter herein set forth or shown in the
accompanying drawings is to be interpreted as illustrative, and not
in a limiting sense.
24
