Note: Descriptions are shown in the official language in which they were submitted.
NON-INVASlVE ADHESIVE PROCESS
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Field of the Invention
This invention relates to a process for joining a sheet having at least one non-
planar surface to an item.
Back~round of the Invention
Releasablyengaging hookand loop type fasteners are well known
and may be obtained under the trade designation VELCRO~. These
fasteners are utilized in a wide variety of applications where two pieces
of material are to be releasably joined to each other. Typical
applications include shirt collar closures, on shoes as a substitute for
shoe laces, at the cuffs of garments such as pants and shirts and in
conjunction with the waist bands of garments for waist band
adjustment. As is well known, the hook and loop type fasteners
(sometimes referred to as hook and eye type fasteners) generally
include two elements. The first element is typically a sheet having a
multiplicity of fine hooks or their equivalents extending therefrom. The
second element is typically a sheet having a multiplicity of fine loops,
eyes or their equivalents extending upwardly therefrom. When the
sheets are brought into contact with each other so that the hooks
penetrate the eyes or loops, the hooks become ensnared within the
eyes or loops. This secures the two sheets together. The joining of
the two sheets or elements can be broken so as to again separate them
by application of sufficient force as is well known in the art. The two
2 5 sheets can be joined and unjoined many, many times before
degradation of the loops/eyes and/or hooks takes place to the extent
to appreciably affect the strength of the juncture.
Disposable garments are well known to those in the art. Such
garments include, for example, disposable diapers (see U.S. patent
numbers 5,192,606 to Proxmire and 5,176,672 to Bruemmer et al.);
adult incontinent garments (see U.S. patent numbers 4,886,512 to
Damico et al. and 4,747,846 to Boland et al.) and feminine hygiene
products (see U.S. patent numbers 5,221,275 to Van Iten and 5,219,341
to Serbiak et al.).
2122942
Disposable garments such as, for example, disposable diapers
have been manufactured for many years. Typically, the disposable
diaper is manufactured in an hour-glass configuration which can be
placed on an infant with the legs of the infant straddling the narrow
5 portion (the crotch portion) of the diaper and the top and bottom
portions co-operating together to form the waist portion of the diaper as
is well known in the art. Naturally, some means is necessary to join the
top and bottom portions together to secure the waist portion of the
diaper about the infant. In the past, a wide variety of adhesive tapes
have been used to perform this function. A drawback of using adhesive
tapes is that the number of times the tape can be removed and
resecured is limited because either the tape bonds to the diaper too
strongly and the tape tears the diaper upon its removal, or the tape
leaves adhesive behind after each use and, eventually, the adhesive
15 bond formed is too weak to successfully maintain the proper position
of the diaper on the baby, infant, or toddler.
The use of VELCRO~ fasteners with disposable diapers is known
to those of skill in the art. See, for example, U.S. patent number
5,176,670 to Rossler et al. However, a problem which has been
2U encountered by those in the art is in the attachment of the loop/eye
sheet to the disposable diaper. Typically, the loop/eye sheet is a
nonwoven fibrous web which is quite porous. Use of a liquid adhesive
to bond the porous sheet to the diaper body can lead to unsatisfactory
results because, to be cost effective, the loop/eye sheet must be
25 applied and joined to the disposable diaper at the rapid rates of
commercial manufacturing lines. Such an application involves an
application of pressure to the "diaper-adhesive-loop/eye" sheet
sandwich. This action, in many instances results in the adhesive being
pressed through the loop/eye sheet and out onto the outer surface of
- - 2122~2
the loop/eye sheet. Of course, the outer surface of the loop/eye sheet
is the surface which should be able to releasably engage and
disengage the hook laden sheet. The presence of the adhesive on the
outer surface of the loop/eye sheet tends to foul or clog up the loops
5 and eyes. Thus, the function of the arrangement may be severely
degraded, if not destroyed. Of course, this same problem exists when
adhesive attachment of a loop/eye sheet to any other type of product
is attempted. In like fashion, the problem is not solely limited to the
joining of loop/eye sheets by adhesive means but rather to any porous
10 sheet having a desired non-planar surface which could be degraded if
penetrated by an adhesive.
OBJECTS OF THE INVENTION
Accordingly, it is a general object of the present invention to
provide a process for joining a loop/eye sheet portion of a VELCRO~
fastener to an item without the function of the loop/eye sheet being
significantly adversely affected.
It is another general object of the present invention to provide a
20 process for joining a porous sheet having a non-planar outer functional
outer surface to an item without the function of the non-planar outer
surface being significantly adversely affected.
It is yet another object of the present invention to provide the
products which are formed by the aforementioned processes.
Still further objects and the broad scope of applicability of the
present invention will become apparent to those of skill in the art from
the details given hereinafter. However, it should be understood that the
detailed description of the preferred embodiment of the present
invention is given only by way of illustration because various changes
and modifications well within the spirit and scope of the invention
212~2
should become apparent to those of skiil in that art in view of the
following detailed description.
SUMMARY OF THE INVENTION
In response to the aforementioned difficulties encountered by those
of skill in the art, we have devised a process for joining a porous sheet
having at least one non-planar surface to an item without fouling the
non-planar surface. The process includes the steps of: providing the
10 item; providing the porous sheet having a first and second surface
where at least the second surface has a non-planar configuration;
providing a material adapted, upon application of sufficient temperature,
to substantially melt prior to either the item or the porous sheet
significantly melting and which, when melted, forms an adhesive bond
15 with both the item and the porous sheet; placing the material on a
surface of the item; placing the first surface of the porous sheet on the
material to form an item-material-poroussheet sandwich configuration;
applying sufficient heat to the sandwich configuration to melt the
material without significantly melting the item or the porous sheet and
20 applying sufficient pressure to the sandwich configuration to distribute
the melted material on the surface of the item and into, but not through,
the pores of the porous material. As a result of this process, the first
surface of the porous sheet is joined to the item without the non-planar
configuration of the second surface of the porous sheet being adversely
25 affected as by interpenetration of adhesive there into or through. Thus,
the functionality of the non-planar second surface is preserved.
The number of items to which the present invention is applicable
is virtually limitless. For example, the item may be a piece of wearing
apparel, a disposable garment such as a diaper, a shoe or shoes, an
30 adult incontinent garment, a feminine hygiene product, furniture covers,
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automobile covers, luggage and sporting equipment. The diaper may
be disposable.
The porous sheet may be selected from a wide variety of such
sheets well known to those of skill in the art. For example, the porous
sheet may be selected from the group including meltblown webs,
apertured films, spunbonded webs, dry laid webs and wet laid webs.
Furthermore, the porous sheet may be formed from any conventional
substance which can be formed into a porous sheet. For example, the
porous sheet may be formed from a substance selected from the group
including polyolefins, nylons and polyesters. The polyolefin may be
polyethylene, polypropylene or copolymers of either ethylene or
propylene with other monomers. In one embodiment the non-planar
configuration of the second surface of the porous sheet is formed by a
plurality of loops adapted to releas~hly engage a plurality of hooks.
That is, the porous sheet is the loop or eye sheet of a VELCRO~ hook
and loop/eye type of fastening system.
The material adapted, upon application of sufficient temperature,
to substantially melt prior to either the item or the porous sheet
significantly melting may be selected, in some embodiments, from the
group including meltblown webs, films, spunbonded webs, dry laid
webs and wet laid webs.
In some embodiments the sandwich configuration may be heated
to at least about 155 degrees Centigrade (311 degrees F.). For
example, the sandwich configuration may be heated to at least about
160 degrees Centigrade (320 degrees F.). More particularly, the
sandwich configuration may be heated to at least about 177 degrees
Centigrade (350 degrees F.).
- - 2122942
- THE FIGURE
Figure 1 is a schematic rendering of a process for carrying out the
present invention.
DETAILED DISCLOSURE
Turning now to the figure where like features are represented by
like numerical reference numbers, and, in particular, it can be seen that
Figure 1 is a schematic illustration o~ a process 10 for joining a porous
sheet having a functional non-planar surface to an item without
significantly adversely affecting the function of the non-planar surface
of the sheet. Figure 1 illustrates an in-line process for this attachment
where the item is, for example, the outer cover of a disposable diaper.
Of course, the item can be selected from a wide variety of structures
such as, for example, wearing apparel, disposable garments, shoes,
furniture, car covers, luggage, feminine hygiene products, adult
incontinent products and safety equipment. Initially, the diaper outer
cover material 12 is provided by a roll 14 and is transported to the nip
16 formed b~ two nip rollers 18 and 20. It may be necessary to support
the outer cover material 12 by a conventional arrangement such as, for
example, transport roller 22.
The porous sheet material having a functional non-planar surface
24 is provided by a ro!l 26. The porous sheet material 24 may be a
sheet of the loop/eye material which is used in the manufacture of
VELCRO~ type fastening systems. That is to say, the non-planar
configuration of the surface of the porous sheet 24 can include a
plurality of loops/eyes configured to releasably engage a plurality of
hooks or equivalents thereto. Other examples of such porous sheets
include meltblown webs, spunbonded webs, apertured films, dry laid
webs and wet laid webs. All of these materials may be porous and
212Z9~2
have a non-planar surface or surfaces. If either one or both of these
surfaces is formed to perform a function that would be degraded or
ruined if an adhesive interpenetrated the surface, such a material would
be a candidate for use in the present invention. The porous sheet 24
can be formed from a wide variety of material such as, for example,
polyolefins, nylons and polyesters. Exemplary polyolefins include
polyethylene and polypropylene. An exemplary polyethylene is linear
low density polyethylene. The porous sheet 24 is, likewise, guided to
the nip 16 of the nip rollers 18 and 20. Transport rolls 22 may be
utilized to accomplish this guidance.
A roll 28 provides a sheet of strip 30 of a material adapted, upon
application of sufficient temperature to substantially melt prior to either
the item, such as the outer cover of the disposable diaper 12, or the
porous sheet 24 significantly melting or heat degrading. The strip 30
also has the ability to, upon melting, form an adhesive bond with both
the item 12 and the sheet 24. Exemplary forms of the strip 30 are films,
meltblown webs, spunbonded webs, wet laid webs and dry laid webs.
It should be noted that the strip 30 need only be formed from a material
having the aforementioned characteristics. Of course, the melting point
characteristics required of the strip 30 will vary with the material from
which the item 12 and the porous sheet 24 are formed. Exemplary
materials from which the strip 30 can be formed include polyolefins,
urethanes, Krayton0, Hytrel0, Arnitel~ and various compounded mixtures
of these polymers with other materials.
Figure 1 illuslra~es that the nip 16 forms the item 12, the strip 30
and the porous sheet 24 into a "sandwich" configuration. Thereafter,
the sandwich configuration is heated to a temperature high enough to
substantially melt the strip 30 but not so high as to significantly melt or
otherwise degrade the item 12 or the porous sheet 24. The heating of
the sandwich is accomplished by a conventional heating element 32.
As has been previously stated, the degree of heating to which the
212294Z
sandwich need be subjected for the present invention to effectively
operate will vary greatly with the materials from which strip 30 is made.
Naturally, the upper temperature to which the sandwich should be
subjected will depend upon the melting point/degeneration point(s) of
5 the item 12 and the porous sheet 24. The upper limit will be the lower
of these later two points. An exemplary temperature to which the
sandwich can be heated if the strip 30 is formed from Krayton~D, the
porous sheet 24 is formed from polyester and the item 12 is formed
from polyethylene is at least about 155 degrees Centigrade (at least
10 about 311 degrees F.) For example, the sandwich may be heated to at
least about 160 degrees Centigrade (at least about 320 degrees F.)
More particularly, the sandwich may be heated to at least about 177
degrees Centigrade. (at least about 350 degrees F.)
There are, no doubt, numerous mechanisms by which the strip 30
15 can be designed or formed so that it preferentially achieves a melted or,
at least, a semi-molten state at a temperature which is less than the
melting or degradation temperature of the item 12 and the porous sheet
24. The most readily recognizable way of achieving this result is for the
material from which the strip 30 is formed to have a melting point which
20 is less than the melting point of either the item 12 or the porous sheet
24. For example, the melting point differential may be at least 10
degrees Centigrade (C.), (50 degrees F.) More particularly, the melting
point differential may be at least 100 degrees C. (212 degrees F.) Even
more particularly, the melting point differential may be at least 200
25 degrees C. (392 degrees F.)
Once the sandwich has been heated to substantially melt the strip
30, and while the strip 30 is still in a semi-liquid state, pressure is
applied to the sandwich by a pair of nip rollers 34 and 36. Passing the
sandwich through the nip 38 formed by the nip rollers 34 and 36 forces
30 the semi-liquid strip 30 to slightly interpenetrate the porous sheet 24
without penetrating through the porous sheet 24 and onto the outer
21~29~
surface of the porous sheet 24. That is, the non-planar surface of the
porous sheet 24 which does not face the strip 30 is not interpenetrated
by the flowing strip 30. Thus, the function of this non-planar surface is
not adversely affected by interpenetration of the flowing strip 30. Those
of skill in the art will readily recognize that the amount of pressure
applied by the nip rollers 34 and 36 will have to vary with a number of
parameters including, for example, temperature applied and dwell time
in the nip 38.
Because the strip material 30 also has the characteristic of being
able to form an adhesive bond with both the item 12 and the porous
sheet material 24, bonding of the porous sheet 24 to the item is effected
by this process. Importantly, the function of the non-planar outer
surface of the porous sheet material 24 is not adversely affected by
interpenetration of the strip 30. Accordingly, in the situation where the
item 12 is the outer cover of a disposable diaper and the porous sheet
24 is the loop/eye sheet of a VELCRO~ type fastening system, the
loop/eye sheet is joined to the outercover material in such a manner
that its function in co-operating with a hook sheet is not significantly
affected.
Those of skill in the art will readily recognize that the heating and
pressure applying steps can be performed simultaneously or the
pressure applying step can be performed shortly after the heating step
while the strip 30 is still in a semi-liquid state. After these steps have
been performed, the item 12 with the porous sheet 24 attached thereto
by way of the strip 30 is fed through a pair of transport rollers 40 and
42 and the composite sandwich is rolled up onto a supply roll 44.
Additionally, it should be recognized that certain of the process steps
do not have to be done in an in-line fashion. For example, the strip 30
can first be joined to the porous sheet 24 so that a liquid impermeable
backing for the porous sheet 24 is formed. This material can be wound
up and stored until such time as it is desired to attach the porous sheet
- 21229~2
24 to an item 12. Because the porous sheet 12 has now been provided
with a liquid impermeable backing, a variety of different ways of
attaching the porous sheet 24 to the item 12 are possible. Typically,
the porous sheet 24 will be attached to the item 12 by heat sealing the
backing strip 30 to the item 12. Alternatively, an adhesive can be
utilized between the backing strip 30 and the item 12. Because of the
presence of the liquid impermeable backing strip 30, the adhesive
cannot interpenetrate through the porous sheet 24.
Further clarification of the present invention is afforded by reference
to the following examples.
EXAMPLE I
In order to apply sufficient heat and pressure to the samples to be
treated, an inverted hot plate was fabricated. The platen was provided
with wooden handles and a 1/4 inch by 12 inch by 12 inch stainless
steel plate was attached to the bottom of the assembly to act as the
soleplate. Power to heat the soleplate was regulated by a variable
autotransformer and the temperature of the soleplate was read by a
contact thermocouple inserted through a well area of the platen.
A heat sink and working surface was provided by an aluminum
plate approximately 20 inches by 15 inches by 5/8 inches in dimer~ion.
A sheet of silicon rubber about 1/32nd inch thick, 50 Shore A
durometer was placed over the plate. The sample to be treated was
placed on the silicone sheet with the non-planar surface of the porous
sheet against the silicone sheet. A sheet of ~.003 inch thick Teflon~
impregnated woven fiberglass cloth was placed over the sample to be
treated and the heating platen was then passed over the cloth with an
"ironing" motion.
A layer of loop/eye material (polyester 1.64 ounces per square yard
(osy/, 55.o grams per square metertgsm)) obtained from the Gilford
Mills Company of Greensboro, North Carolina, was placed on the
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silicone sheet with the loop surface of the materiai against the silicone
sheet. A layer of polypropylene meltblown web with a basis weight of
0.5 ounce per square yard (osy),16.95 grams per square meter (gsm)
was placed over the loop material, and the fiberglass sheet placed over
the combined sample. The platen was heated to 365 degrees F.,185
degrees C. and passed over the sample. The fiberglass sheet was
removed leaving a composite material with one surface of engaging
loops, and a second surface of smooth film-like nature. A stamp of
VELCROh hook material one (1) inch by two (2) inches was repeatedly
engaged and disengaged with the loop surface with no diminution in
holding strength, and no visible deterioration in the integrity of the loop
surface.
EXAMPLE ll
This sample consisted of a layer of Gilford loop material (polyester
1.64 osy, 55.6 gsm) and a layer of polyethylene meltblown web (Dow
Aspun 6814A) with a basis weight of 1.55 osy, 52.7 gsm. The sample
was assembled and treated as described in Example I at 350 degrees
F., 177 degrees C. for one (1) second. The sample after treatment
showed the same properties as described in Example 1.
EXAMPLE lll
In this sample the Gilford loop material (polyester 1.64 osy, 55.6
gsm~ was placed loop side on the silicone sheet. A layer of Krayton D
meltblown web (Shell Chemical 2.86 osy, 97.0 gsm) was placed over
the loop material, and a layer of polyethylene film (Edison Plastic S/E
702) having a thickness of 0.5 mil (.0005 inch) placed over the
meltblown web. The sample was treated as described in Example 1.
The sample after treatment at 350 degrees F.,177 degrees C. for one
(1) second (as described in Example 1), was found to be a composite
structure with the loop material securely bonded to the diaper film. The
21229~2
VELCRO~ hook stamp was engaged and disengaged as in Example 1.
In addition to the properties noted before, there was no separation of
the bond between the loop material and the film.
While the invention has been described in detail with respect to
5 specific embodiments thereof, it will be appreciated that those skilled
in the art, upon attaining an understanding of the foregoing, may readily
conceive of alterations to, variations of and equivalents to these
embodiments. Accordingly, the scope of the present invention should
be assessed as that of the appended claims and all equivalents thereto.
