U.S. patent application number 11/563953 was filed with the patent office on 2007-05-31 for elastic laminates and methods of manufacturing same.
This patent application is currently assigned to Tredegar Film Products Corporation. Invention is credited to Bryan L. Matte, Jeffrey Alan Middlesworth.
Application Number | 20070123124 11/563953 |
Document ID | / |
Family ID | 37845313 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070123124 |
Kind Code |
A1 |
Middlesworth; Jeffrey Alan ;
et al. |
May 31, 2007 |
Elastic Laminates and Methods of Manufacturing Same
Abstract
A method for forming an elastic laminate comprising: bonding a
first nonwoven to an elastic film to form a laminate; activating
the laminate to form an activated laminate; and bonding a
consolidated nonwoven to the elastic film of the activated laminate
to form the elastic laminate.
Inventors: |
Middlesworth; Jeffrey Alan;
(Wauconda, IL) ; Matte; Bryan L.; (Kenosha,
WI) |
Correspondence
Address: |
JOSEPH A TESSARI;TREDEGAR FILM PRODUCTS
1100 BOULDERS PARKWAY
RICHMOND
VA
23225
US
|
Assignee: |
Tredegar Film Products
Corporation
Richmond
VA
23225
|
Family ID: |
37845313 |
Appl. No.: |
11/563953 |
Filed: |
November 28, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60740036 |
Nov 28, 2005 |
|
|
|
Current U.S.
Class: |
442/59 ; 442/149;
442/381 |
Current CPC
Class: |
B32B 2555/02 20130101;
B32B 37/144 20130101; Y10T 156/1054 20150115; B32B 38/1858
20130101; Y10T 442/659 20150401; B32B 5/04 20130101; B32B 37/02
20130101; B32B 5/26 20130101; B32B 37/10 20130101; B32B 27/12
20130101; B32B 33/00 20130101; B32B 2305/20 20130101; B32B 3/266
20130101; B32B 2310/028 20130101; B32B 5/022 20130101; B32B 2323/10
20130101; B32B 5/08 20130101; B32B 2307/724 20130101; B32B 2309/68
20130101; A61F 13/4902 20130101; B32B 37/153 20130101; Y10T
442/2738 20150401; B32B 27/32 20130101; B32B 38/0032 20130101; Y10T
156/10 20150115; Y10T 442/20 20150401; B32B 2307/51 20130101 |
Class at
Publication: |
442/059 ;
442/149; 442/381 |
International
Class: |
B32B 5/02 20060101
B32B005/02 |
Claims
1. A method for forming an elastic laminate comprising: bonding a
first nonwoven to an elastic film to form a laminate; activating
said laminate to form an activated laminate; and bonding a
consolidated nonwoven to said elastic film of said activated
laminate to form said elastic laminate.
2. The method of claim 1, wherein said elastic film is
apertured.
3. The method of claim 2, wherein said elastic film is bonded to
said first nonwoven and apertured essentially simultaneously.
4. The method of claim 3, wherein said first nonwoven and said
elastic film are apertured essentially simultaneously.
5. The method of claim 3, wherein vacuum lamination is used to bond
said first nonwoven to said elastic film and to aperture said
elastic film.
6. The method of claim 2 wherein the elastic film is apertured
after the first bonding step.
7. The method of claim 2, wherein the elastic film is apertured
before the first bonding step.
8. The method of claim 1, wherein activating said laminate
comprises activating said laminate in the cross direction.
9. The method of claim 8, wherein said laminate is activated using
intermeshing gear activation.
10. The method of claim 1, wherein said consolidated nonwoven is
extensible in said cross direction.
11. The method of claim 1, wherein at least one of said bonding
steps comprises ultrasonic bonding.
12. The method of claim 11, wherein said bonding of said
consolidated nonwoven is performed ultrasonically.
13. The method of claim 1, wherein said bonding of said
consolidated nonwoven is performed at essentially the same line
speed as said activation step.
14. An elastic laminate comprising: an elastic layer having a first
side and a second side; an activated nonwoven layer bonded to said
elastic layer on said first side; and a consolidated nonwoven layer
bonded to said elastic layer on said second side.
15. The elastic laminate of claim 14, wherein said elastic layer is
breathable.
16. The elastic laminate of claim 15, wherein said elastic layer is
apertured.
17. The elastic laminate of claim 14, wherein said activated
nonwoven layer is a carded nonwoven.
18. The elastic laminate of claim 17, wherein said activated
nonwoven layer is polypropylene.
19. The elastic laminate of claim 14, wherein said activated
nonwoven layer is extensible in a first direction, and said
consolidated nonwoven layer is extensible in said first direction.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 60/740,036, filed Nov. 28, 2005, which is hereby
incorporated by reference.
FIELD OF INVENTION
[0002] The present invention relates generally to elastic laminates
and their methods of manufacture, and, more particularly, to
breathable elastic laminates having nonwoven surfaces on both
sides.
BACKGROUND OF INVENTION
[0003] Breathable elastic laminates are used in the manufacture of
many goods, including, for example, disposable articles such as
diapers, feminine sanitary articles, and bandages. These
applications require that the laminate be strong, stretchable, and
soft to the touch. Improving one of these features, however, tends
to diminish the others. Consequently, previously-introduced
laminates tend to represent a compromise among softness,
elasticity, and strength.
[0004] For example, one prior art laminate comprises an apertured
elastic laminate produced by vacuum laminating a carded
polypropylene nonwoven to a multilayer coextruded elastic film. The
laminate is then activated in the cross direction using
intermeshing gears. This construction has the advantage of a soft
feel, but is limited to two layers (nonwoven and film) and lacks
high peel strength.
[0005] Another prior art product comprises an apertured elastic
film which is activated in the cross direction (CD) and is
ultrasonically bonded on each side to a consolidated nonwoven.
Although this laminate tends to be strong, it has a harsher feel
than desired, requires substantial ultrasonic energy to bond the
layers, and, because it has three layers, it tends to lack the
level of stretch obtainable from a laminate with just a single
layer of nonwoven.
[0006] Therefore, there is a need for a breathable laminate that is
soft on either side yet stretchable and strong. The present
invention fulfills this need among others.
SUMMARY OF INVENTION
[0007] The invention relates to an elastic laminate having soft,
nonwoven surfaces on both sides, yet is stretchable and strong.
Specifically, the elastic laminate comprises an elastic inner layer
and two outer nonwoven layers, in which each nonwoven layer is
rendered extensible through a different method. That is, one
nonwoven layer is activated, while the other is consolidated.
[0008] Applicants have discovered unexpectedly that the laminate of
the present invention has an exceptional degree of cross direction
stretch, offers a pleasant, soft feel, and can be bonded
ultrasonically at full line speed to obtain an exceptionally strong
interlayer bond. Without being bound to any particular theory,
applicants hypothesize that the high level of stretch results from
"elasticizing" the two nonwoven layers using two different
techniques--i.e., activation and consolidation. This approach
synergistically combines the strengths of the two technologies,
resulting in a laminate having the high tensile strength and a
strong bond characteristic of a consolidated/ultrasonically bonded
nonwoven, and the softness and tear resistance characteristic of an
activated nonwoven. Furthermore, this approach appears to minimize
the observed tendency of one nonwoven layer to constrain the
extensibility of the other nonwoven layer in the same laminate.
[0009] Accordingly, one aspect of the invention is an elastic
laminate having two outer nonwoven layers which are rendered
extensible using two different techniques. In a preferred
embodiment, the elastic laminate comprises: (1) an elastic layer
having a first and second side; (2) an activated nonwoven layer
bonded to the elastic layer on the first side; and (3) a
consolidated nonwoven layer bonded to the elastic layer on the
second side.
[0010] Another aspect of the invention is a method for producing
the laminate described above. In a preferred embodiment, the method
comprises: (1) bonding a first nonwoven to an elastic film to form
a laminate; (2) activating the laminate to form an activated
laminate; and (3) bonding a consolidated nonwoven to the elastic
film of the activated laminate to form the elastic laminate.
DESCRIPTION OF DRAWINGS
[0011] FIG. 1 shows a schematic view of an elastic laminate of the
present invention.
[0012] FIG. 2 shows a schematic of a manufacturing line for making
the elastic laminate of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] The present invention relates to an elastic laminate and a
method for making it. Briefly, referring to FIG. 1, the elastic
laminate 10 comprises an elastic layer 12 having a first and second
side, 14, and 15. Preferably, but not necessarily, the elastic
layer has apertures 13 or is otherwise modified to be breathable.
On the first side 14 is an activated nonwoven layer 16 bonded to
the elastic film material 12. As used herein the terms "activated"
or "activation" refer to a method or state in which a laminate
comprising an elastic layer and at least one less-elastic layer is
stretched to an extension limit beyond the deformation point of the
less-elastic layer to allow the elastic layer to elongate to the
extension limit essentially unimpeded by the less-elastic layer.
Activation is a well-known technique. On the second side 15 is a
consolidated nonwoven layer 17 bonded to the elastomer film 12. As
used herein, the terms "consolidated" or "consolidation" refer to a
method or state in which the fibers or fiber-like elements of the
nonwoven are aligned, thereby allowing the nonwoven to elongate in
a direction perpendicular to the alignment. Consolidation, like
activation, is a well-known technique for imparting extensibility
to a nonwoven.
[0014] Referring to FIG. 2, the method 100 of preparing the
laminate 10 is described in connection with a preferred
manufacturing apparatus. The method comprises bonding a first
nonwoven 50 to an elastic film 60 to form a laminate 65. The
elastic film is optionally breathable. Once the laminate 65 is
formed, it is activated to form an activated laminate 75. A
consolidated nonwoven 55 is then bonded to the elastic film 50 of
the activated laminate 75 to form the elastic laminate 95. The
elastic laminate 95, its uses, and the method of preparing it are
described in detail below.
[0015] Referring back to FIG. 1, the elastic layer 12 provides
elasticity to the laminate. The elastic layer comprises at least
one elastic material. Suitable elastic materials include any
material that is capable of being formed into a thin sheet,
rendered breathable and bonded to nonwovens. For example, elastic
materials include natural and/or synthetic polymeric materials
including isoprenes, butadiene-styrene materials, styrene block
copolymers (e.g., styrene/isoprene/styrene (SIS),
styrene/butadiene/styrene (SBS), or
styrene/ethylene-butadiene/styrene (SEBS)), olefinic elastomers,
polyether esters, polyurethanes, etc. In certain preferred
embodiments, the elastic materials may comprise high performance
elastic material such as Kraton.RTM. elastic resins from Kraton
Polymers, LLC, which are elastic block copolymers.
[0016] The form of an elastic layer 12 can vary and may include,
for example, elastic strands, elastic nonwoven, elastic film,
elastic adhesive, elastic tacky polymeric web, elastic scrim, etc.
For the sake of simplicity, unless otherwise noted, these different
forms are referred to collectively herein as "elastic film." In
certain preferred embodiments, a monolayer elastic film is used. It
should be understood, however, that the present invention in not
limited to a monolayer film and, in certain applications, a film
having multiple layers may be used. For example, it may be
advantageous to have an elastic core between two skin layers to
enhance bonding to the nonwoven layers or to facilitate
processability. Suitable skin layers are well known and include,
for example, polyethylene which may be more or less elastic than
the elastic material. The thickness of the elastic film may vary
according to the application, although the individual layers of the
films are typically thin (e.g., the elastic core is usually, but
not necessarily, less than 100 microns, and skin layers, if used,
are usually less than 20 microns).
[0017] Preferably, the elastic film is breathable or is modified to
be breathable in conventional ways. Such ways include, for example,
aperturing, slitting, or impregnating with granular particles to
create microvoids upon stretching of the elastic film.
[0018] The first nonwoven layer 16 provides a soft and breathable
surface once activated (discussed below) on the first side 14 of
the elastic layer. Suitable nonwovens are capable of being
activated and are less elastic than the elastic layer 12. Suitable
nonwovens include loose fibers and webs prepared using know
techniques such as, for example, air laying, spun bond, spun lace,
bonded melt blown, thermobond, bonded carded. The nonwoven material
may be homogeneous or contain a variety of woven materials
including bi-component fibers (e.g. having an inner core of one
material and an outer core of a second material), fibers of
different morphologies, geometries, and surface finishes. Suitable
nonwovens materials include, for example, fibrous polyolefins such
as polyethylenes and polypropylenes, and natural fibers such as
cotton and cellulose.
[0019] The consolidated nonwoven 17, like the first nonwoven 16,
provides a soft and breathable covering to the second side 15 of
the elastic layer 12. Unlike the first nonwoven, the consolidated
nonwoven is rendered extensible through a consolidation method
rather than an activation method. The consolidation method is
discussed in detail below.
[0020] The laminate 10 may be used in any application requiring a
soft, stretchable, breathable material, and especially well suited
for disposable articles given its relatively low cost. Suitable
applications include, for example, absorbent articles, including
adult, child or infant incontinent products (diapers, including
parts such as diaper ears, tabs, and/or side panels, briefs, etc.);
wraps, including sterile and nonsterile (e.g. bandages with and
without absorbent sections,) as well as other disposable and/or
multiple use products; e.g., articles proximate to a human or
animal body, such as (e.g., garments, apparel, including
undergarments, under- and outer-wear, for example, undershirts,
bras, briefs, panties, etc., bathing suits, overalls, socks, head
coverings and bands, hats, mitten and glove liners, medical
clothing, etc.) bed sheets; medical drapes; packaging materials;
protective covers; household; office; medical or construction
materials; wrapping materials; etc. therapeutic devices and
wraps.
[0021] The method of making the laminate is described below with
reference to FIG. 2. FIG. 2 shows elastic source 20 for providing
elastic film 60. In this embodiment, the elastic source 20
comprises a slot die or blown die for extruding molten or
semimolten elastic material or coextruding multiple layer film
structure in which one or more of the layers are elastic. It should
be understood, however, that any conventional elastic source may be
used, including, for example, a roll of elastic material.
[0022] The first nonwoven source 70 provides the first nonwoven 50.
In this embodiment, the first nonwoven source 70 comprises a roll
of material, however, any suitable source may be used, including
forming the material in situ.
[0023] The first nonwoven 50 is brought into contact with elastic
film 60 and bonded thereto. In this embodiment, the molten or
semimolten phase of elastic film 60 facilitates bonding with the
first nonwoven 50. The first nonwoven 50 may also be bound, in
whole or part, to the elastic layer using other conventional
methods, such as hot pin aperturing, adhesive bonding, thermal
bonding, ultrasonic bonding, and combination thereof.
[0024] Optionally, the elastic film 60 is modified to render it
breathable. One preferred approach for aperturing the elastic layer
is shown in FIG. 2 in which a pressure differential source 30 is
used. Specifically, the first nonwoven 50 and the elastic film 60
are provided to pressure differential source 30 such that the
elastic film 60 is interposed between the pressure differential
source 30 and the first nonwoven 50. Pressure differential source
30 creates a pressure differential across the thickness of the
laminate which is high enough to cause ruptures (i.e., apertures)
in the elastic film 60. This method creates three-dimensional
apertures which are especially preferred where breathability or
permeability of the laminate is desired.
[0025] The pressure differential source 30 is well known. In a
preferred embodiment, the pressure differential source 30 comprises
a vacuum (not shown) and an aperture definition device 120. In this
embodiment, aperture definition device 120 comprises a screen with
20 apertures per linear inch in a square pattern, referred to
herein as 20 square. Other screen geometries may be used to vary
the amount of open area, aperture size, geometries, patterns, and
other attributes. Furthermore, more than one aperture definition
device may be used, for example, a device in one area may provide
one pattern of apertures, and a device in another area may provide
another desired pattern.
[0026] In certain embodiments, it may be desired to modify the
elastic layer to make it breathable before it is bonded to the
first nonwoven layer. Furthermore, it may preferable to use other
known aperturing techniques such as pin rolls, slitting, hydrojets,
or lasers, instead of or in addition to a pressure differential
source to impart permeability or breathability to the laminate. It
should also be understood that modifying the elastic film to render
it breathable is not required if the elastic film comprises elastic
strands or scrim in which case it is already breathable.
[0027] Pressure source 35 provides pressure to the materials. A nip
roll is used in the preferred embodiments, although any suitable
source may be used as a pressure source. Additionally, some
embodiments may dispense with a pressure source, or use a pressure
differential source as a pressure source as well. Moreover,
pressure source 35 is shown here upstream of the pressure
differential source, although it may be located adjacent to the
pressure differential source 30 or down stream of the pressure
differential source 30.
[0028] Once the elastic layer is bound to the first nonwoven, it is
activated. Referring back to FIG. 2, the laminate 65 is activated
in an activation area 40. The activation area 40, in a preferred
embodiment, involves intermeshing gear ("IMG") activation, although
any conventional activation technique may be used. In the
embodiment shown in FIG. 2, activation occurs in the transverse or
cross direction (CD), although activation may be in any direction
desired, e.g., machine direction (MD), diagonally, or a combination
of directions. Further, activation may occur along the entire
laminate or only in predetermined areas of the laminate. In other
embodiments, the degree of activation may be varied, for example, a
lightly activated area may be used to give a laminate low
elasticity, while a heavily activated area may be used to give a
laminate high elasticity. Of course, activated regions may be
interposed with nonactivated regions as well, to provide zones or
regions of extensibility to the laminate.
[0029] Returning now to the embodiment of FIG. 1, second nonwoven
source 80 provides a second nonwoven 55. In this embodiment, the
second nonwoven source 80 comprises a roll of material, although
any suitable nonwoven source may be used, such as forming the
material in situ.
[0030] In one embodiment, the second nonwoven 55 is consolidated
on-line. Consolidation may be performed using various techniques
such as heat consolation, cold drawing, or combing. Preferably,
heat consolidation is used which is disclosed, for example, in U.S.
Pat. No. RE 35,206, which is hereby incorporated by reference. As
shown in FIG. 2, the second nonwoven 55 passes through heat
application area 45, where heat is applied, and the fibers of the
web are oriented in the machine direction, thereby providing for
elongation in the cross direction. Although consolidation is
performed on-line in this embodiment, it should be understood that
the consolidation may be performed ahead of time, and a source of
consolidated nonwoven be provided to the line.
[0031] The consolidated nonwoven 91 is brought into contact with
activated laminate 75 through rollers 81 and 82 and bonded using
known techniques. Preferably, the consolidated nonwoven 91 and
laminate 75 are bonded ultrasonically in the ultrasonic bonding
area 85. It has been found that this bonding can be performed
quickly at normal line speeds, e.g., 70 mpm.
[0032] Varying the materials and method conditions may vary the
characteristics of the laminate. For example, selection of
particular elastic and/or nonwovens, or selective processing of
those materials, can result in optimization of desired properties
such as bond strength, softness, elasticity, breathability, etc.
Examples of method variables that may be used to modify laminate
characteristics include modifying the phase of the elastic layer
prior to bonding; modifying the pressure differential applied by a
pressure differential source; modifying pressure imposed by a
pressure source; modifying apertures in a nonwoven; modifying
apertures provided in an aperture definition device; various
secondary treatments of the laminate and/or components of the
laminate (e.g. plasma treatment), modifying stretching of a
laminate following lamination, and combinations thereof. A laminate
may also be modified in any suitable fashion, for example, a
laminate may be sewn, bonded, printed, cut, shaped, glued, fluted,
sterilized, etc.
[0033] Although the present invention has been described with
respect to various specific embodiments, various modifications will
be apparent from the present disclosure and are intended to be
within the scope of the following claims.
* * * * *