U.S. patent application number 12/617276 was filed with the patent office on 2010-03-04 for methods for making fasteners.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Dennis L. Becker, Lori-Ann S. Prioleau, Janet A. Venne, Zhiqun Zhang.
Application Number | 20100055326 12/617276 |
Document ID | / |
Family ID | 39168098 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100055326 |
Kind Code |
A1 |
Zhang; Zhiqun ; et
al. |
March 4, 2010 |
METHODS FOR MAKING FASTENERS
Abstract
A method for forming a fasteners is disclosed comprising
providing a multiplicity of suitable polymer particles, providing a
base with a front surface, and dispersing the particles onto at
least one discrete area of the contact release surface, forming a
predetermined shape. The dispersed particles are provided in a
semiliquid state of a suitable viscosity, at least some of the
particles in the discrete areas being in contact with the contact
release surface for a time sufficient to transform into preform
projections. The method further comprises conducting and fixing the
front surface of the base with the terminal ends of at least some
of the preform projections and removing the base from the contact
release surface to separate the preform projections fixed thereto
and form engaging projections projecting from the front surface of
the base in the form of a predetermined shape.
Inventors: |
Zhang; Zhiqun; (Roseville,
MN) ; Venne; Janet A.; (Roseville, MN) ;
Becker; Dennis L.; (Vadnais Heights, MN) ; Prioleau;
Lori-Ann S.; (St. Paul, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
39168098 |
Appl. No.: |
12/617276 |
Filed: |
November 12, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11530499 |
Sep 11, 2006 |
7636988 |
|
|
12617276 |
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Current U.S.
Class: |
427/272 |
Current CPC
Class: |
Y10T 24/2783 20150115;
Y10T 24/2708 20150115; A61F 13/625 20130101; A44B 18/0011 20130101;
Y10T 24/27 20150115 |
Class at
Publication: |
427/272 |
International
Class: |
B05D 1/32 20060101
B05D001/32 |
Claims
1. A method for forming a fastener comprising: providing a
multiplicity of suitable polymer particles; providing a base with a
front surface; dispersing onto a contact release surface a
multiplicity of polymers particles in at least one discrete area of
the contact release surface forming a predetermined shape;
providing the polymer particles, dispersed on the contact release
surface, in a semiliquid state of a suitable viscosity, at least
some of the particles in the discrete areas being in contact with
the contact release surface for a time sufficient to transform into
preform projections; conducting and fixing the front surface of the
base with the terminal ends of at least some of the preform
projections; removing the base from the contact release surface
thereby separating the preform projections fixed thereto, thereby
forming engaging projections projecting from the front surface of
the base in the form of a predetermined shape.
Description
TECHNICAL FIELD
[0001] The present invention relates to methods of manufacturing
fasteners, particularly male components for fasteners of the
touch-and-close type, also known as hook-and-loop type
fasteners.
BACKGROUND OF THE INVENTION
[0002] It is common to use certain types of hook-and-loop type
mechanical fasteners for fixing disposable diapers, training pants
and incontinence garments around a wearer. One approach is a thin,
molded male fastener with low loft loop materials, preferably
nonwoven, fabrics as the female components. For these uses
generally low cost, soft touch, appropriate strength and increasing
stretch in the waistline are important.
[0003] Hooks can be directly molded as disclosed for example in
U.S. Pat. No. 5,315,740, assigned to Velcro, which discloses molded
hooks with low displacement volumes so that it needs only to
displace a small volume of loop fabric in order to engage
therewith. The patent discloses a re-entrant hook, i.e., whose
tip-portion curves over and down toward the base sheet from the
upper end of the hook to define a fiber-retaining recess on the
underside of the hook.
[0004] It is also known to cap molded stems on webs.
Mushroom-shaped engaging projections obtained by this process are
disclosed in U.S. Pat. No. 5,679,302 and U.S. Pat. No. 5,879,604 in
which an extruded polymer layer is pressed against a mold with mold
cavities, the cavities producing projecting stems, integral with
the base. The terminal ends of the stems are then deformed with a
heated pressure roller, forming the loop engaging projections. U.S.
Pat. No. 6,054,091 discloses a similar method in which, however,
the heated deforming surface gives an essentially lateral
deformation to the stems during the deformation thereby forming
re-entrant, J-shaped hooks with flat top portions. The solution of
U.S. Pat. No. 6,627,133 differs from the previous ones in that the
stemmed web, to be capped with a heated pressure roller, is
manufactured with the method of U.S. Pat. No. 6,287,665, i.e., with
a special mold constituted by a cylindrical printing screen. All
documents mentioned in this paragraph are similar in that they
flatten preformed stems by a hot roll.
[0005] US Patent Application 2004/0031130A1 discloses a method in
which a product, comprising a polymer base and stems integral with
and projecting from a base is extrusion-molded with a mold roll
having a multiplicity of sophisticated mold cavities. The distal
ends of the stems are then heated and melted while their feet are
kept cold and solid. The melted ends are then flattened with a
deforming surface. The same approach, i.e., pre-heating and
successively flattening stems, appears in U.S. Pat. No. 6,592,800,
U.S. Pat. No. 6,248,276 and U.S. Pat. No. 6,708,378, the latter
ones also disclosing capping with a rough contact surface, creating
roughened flat tops of engaging projections.
[0006] U.S. Pat. No. 6,039,911 discloses a stem-deforming apparatus
comprising a long variable nip, e.g., a pair of co-operating
conveyors, which gradually compressively deform the stems, unitary
with the base.
[0007] U.S. Pat. No. 6,470,540 uses a hot extruded layer for
deforming stems, which results in semi-spherical mushroom
heads.
[0008] In U.S. Pat. No. 3,550,837 a male fastener member is
described whose each engaging projection is constituted by an
irregularly shaped granule with a special multifaceted surface,
adhesively adhered to the base. The fastener is suitable for
securing a flap of a disposable carton against opening. Engaging is
provided by the granules comprising a number of tiny flat planes
forming a multifaceted surface.
[0009] In U.S. Pat. No. 3,922,455 nibs of various shapes are
grafted onto linear filaments, the linear filaments, protruding
from a base, forming the engaging elements of a male fastener
component.
[0010] In PCT publication WO 01/33989, particles are, with a
scatter head of a scatter coater, randomly scattered, and fixed,
onto a base. Each engaging projection is constituted by several
agglomerated particles, though some individual particles may also
be left present.
[0011] It was therefore an object of the present invention to
provide low-cost male mechanical fasteners with advantageous
properties. It was another object of the present invention to
provide commercially attractive alternatives to the mechanical male
fastener systems available so far and methods for making them.
BRIEF DESCRIPTION OF THE INVENTION
[0012] The present invention provides a hook fastener capable of
engaging a suitable loop fabric comprising a base with a front
surface and a back surface, where at least one surface has a
multiplicity of engaging projections having a top surface and an
attached end. The attached end is fixed to the surface of the base
where a plurality of said projections are arranged in a region to
form one or more shapes.
[0013] In a preferred method polymer particles are dispersed onto a
contact release surface using electrostatic attraction to impact
the particles onto the contact release surface.
[0014] In more detail the present invention provides a fastener for
engaging with a loop fabric comprising a base with a front surface
and a back surface, where at least one surface has a multiplicity
of engaging projections having a top surface and an attached end,
which attached end is fused to the surface of the base where a
plurality of said projections are arranged to form one or more
shapes. (Thereafter herein, the engaging projections are referred
to as being attached to the "front" surface of the base. This is
done for purposes of illustration and encompasses attachment of
engaging projections to either surface). The engaging projections
are arranged in a nonuniform distribution in a region so as to
collectively form one or more predetermined shapes on the base.
These shapes are preferably discrete and can create functional hook
regions adjacent nonfunctional or lower functional hook containing
regions. The shapes can be determined by functional or artistic
considerations and can extend continuously along a dimension of the
base or be discrete islands within a front or back surface of the
base. Preferably the at least some engaging projections top surface
ends form an edge angle surrounding the projections, with a mantle
surface extending from the top surface edge to the attached end; at
least one contour line of a side view of the mantle surface being
strictly convex from a top surface edge to the attached end.
[0015] The present invention furthermore provides a fastener, as
described above, for engaging with a loop fabric, comprising a base
having a front surface with a multiplicity of engaging projections
at least some of the engaging projections having a top surface end
and an attached end. The engaging projections attached ends are
fixed or preferably fused to the front surface of the base and the
top surface forming an edge at least partially surrounding the
projection.
[0016] The present invention also provides a first subset method
for forming a fastener comprising:
[0017] providing a multiplicity of suitable polymer particles;
[0018] providing a base with a front surface;
[0019] dispersing onto a contact release surface a multiplicity of
polymers particles in at least one discrete area of the contact
release surface forming a predetermined shape;
[0020] providing the polymer particles, dispersed on the contact
release surface, in a semiliquid state of a suitable viscosity, at
least some of the particles in the discrete regions or areas being
in contact with the contact release surface for a time sufficient
to transform into preform projections;
[0021] conducting and fixing the front surface of the base with the
terminal ends of at least some of the preform projections;
[0022] removing the base from the contact release surface thereby
separating the preform projections fixed thereto,
[0023] thereby forming engaging projections projecting from the
front surface of the base in the form of a predetermined shape.
[0024] The polymer particles are generally dispersed into a
predetermined shape as preform projections by use of a masking
surface where particles impact the masking surface and those
particles passing though the masking surface forming the
predetermine shapes. The polymer particles can be impacted onto the
masking surface by gravity, electrostatic attraction, impaction or
other suitable forces or any combination thereof. The preform
projections on the contact release surface are then transferred to
the base, retaining approximately the same predetermined shape, so
as to form engaging projections approximately of the predetermined
shape.
[0025] In a preferred method polymer particles are dispersed onto a
contact release surface using electrostatic attraction to impact
the particles onto the contact release surface. [0026] The present
invention also provides a second subset method for forming a
fastener comprising: [0027] providing a multiplicity of suitable
polymer particles; [0028] providing a base with a front surface;
[0029] dispersing onto a contact release surface a multiplicity of
polymers particles; [0030] providing the polymer particles,
dispersed on the contact release surface, in a semiliquid state of
a suitable viscosity, at least some of the particles in discrete
regions or areas being in contact with the contact release surface
for a time sufficient to transform into preform projections; [0031]
conducting and fixing the front surface of the base with the
terminal ends of at least some of the preform projections in a
predetermined region or area of the base; [0032] removing the base
from the contact release surface thereby separating the preform
projections fixed thereto, thereby forming engaging projections
projecting from the front surface of the base in the form of a
predetermined shape.
[0033] The polymer particles can be selectively adhered in these
predetermined regions or areas by providing for preferential
adhesion to the base in these predetermined areas. Preferential
adhesion could be accomplished by providing areas with adhesion
promoting layers or treatments, or providing areas with adhesion
deterring layers or treatments, including a removable mask. It is
also possible to combine the two methods; that is by depositing the
particles onto the contact release surface in a predetermined area,
thereafter transferring the particles onto the base in a
predetermined area with preferential adhesion to the particles.
[0034] The present invention also encompasses the use of adhesives
in various methods and configurations. Such adhesives can include
any of the wide variety of adhesives (hot melt, UV cure, etc.) that
are known in the art, but preferably include pressure sensitive
adhesives, as described herein and referred to hereafter by the
term PSAs. A PSA can be provided on the base front surface for
example in discrete areas adjacent to the predetermined regions of
engaging projections described above or on the base back surface or
both.
[0035] The male mechanical fasteners of the invention can also be
used in disposable diapers. In a preferred embodiment the fastener
is capable of engaging with the nonwoven outer shell of a diaper
strongly enough to securely keep the soiled diaper in a folded
state. Further, preferably the engagement with the nonwoven outer
shell of a diaper is strong enough to secure the diaper around a
wearer during use, thereby making a separate frontal tape, of a
special loop fabric, in the landing zone unnecessary, which can
provide considerable cost saving.
[0036] The male mechanical fasteners of the present invention can
also be used to form a so-called back-to-back wrapping tape that
has the fastener of the present invention on one face thereof
thereby offering such new possibilities, deriving from the
invention, such as an inexpensive, highly flexible still strong,
very thin or easily cut wrapping tape. In a preferred embodiment,
the wrapping tape can be easily written upon with a pen. In another
preferred embodiment the wrapping tape may be elastically
stretchable and can be advantageously used for packaging or
technical (e.g. cable wrap) applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1a is a schematic side view of the apparatus for
manufacturing a fastener of the invention.
[0038] FIG. 1b is a segmented top view of a masking surface used in
the apparatus of FIG. 1a.
[0039] FIG. 1c is an enlarged cross sectional view of the fastener
of FIG. 1a.
[0040] FIG. 2a is a schematic side view of a second apparatus for
manufacturing a fastener of the invention.
[0041] FIG. 2b is a segmented top view of a masking surface used in
the apparatus of FIG. 2a.
[0042] FIG. 3a is a schematic side view of a third apparatus for
manufacturing a fastener of the invention.
[0043] FIG. 3b is a segmented top view of a first masking surface
used in the apparatus of FIG. 3a.
[0044] FIG. 3c is a segmented top view of a second masking surface
used in the apparatus of FIG. 3a.
[0045] FIG. 4a is a schematic side view of a fourth apparatus for
manufacturing a fastener of the invention.
[0046] FIG. 4b is a segmented top view of a masking surface used in
the apparatus of FIG. 4a.
[0047] FIG. 5a is a schematic side view of a fifth apparatus for
manufacturing a fastener of the invention.
[0048] FIG. 5b is segmented top view of a patterned electrode belt
used in the apparatus of FIG. 5a.
[0049] FIG. 6a is a schematic side view of a sixth apparatus for
manufacturing a fastener of the invention.
[0050] FIG. 6b is a segmented top view of a base film with regions
of preferential adhesion used in the apparatus of FIG. 6a.
[0051] FIG. 7a is a schematic side view of a seventh apparatus for
manufacturing a fastener of the invention.
[0052] FIG. 7b is a segmented top view of a masking surface used in
the apparatus of FIG. 7a.
[0053] FIGS. 8a-8d are segmented top views of alternative shapes
possible using methods of the invention.
[0054] FIGS. 9a and 9b are segmented top views of alternative
design shapes possible using methods of the invention.
[0055] FIG. 10 is a segmented top view of a fastener possible using
methods of the invention having adhesive areas adjacent hook
containing regions.
DETAILED DESCRIPTION OF THE INVENTION
[0056] The present invention provides a fastener for engaging with
a loop fabric. The fastener comprises a base having a front surface
with a multiplicity of engaging projections arranged into
predetermined patterns or shapes formed by a multitude of the
engaging projections. Namely a plurality of engaging projections
together create a shape on a base based on their size and/or
density being different than in adjacent areas of the base, the
shape is one that is generally clearly visible to the naked eye. As
shown in FIG. 1c, at least some of the engaging projections 13 have
a top surface end 14, where at least some engaging projections top
surface ends 14 form an edge angle 18 surrounding the projections
13. Opposite the top surface end 14 is an attached end 16, which is
attached to the front surface 20 of the base 4. There can be a
mantle surface 17 extending from the top surface 14 edge 15 to the
attached end 16. The mantle surface 17 in some embodiments has at
least one contour line of a side view of the mantle surface 17 that
is strictly convex from a top surface edge 15 to the attached end
16, as shown in FIG. 1c.
[0057] The present invention furthermore provides a fastener for
engaging with a loop fabric, comprising a base 4 having a front
surface 20 with a multiplicity of engaging projections 13 arranged
in to predetermined patterns or shapes at least some of the
engaging projections having a top surface end 14 and an attached
end 16, which attached end 16 is fixed or fused to the front
surface 20 of the base 4 and the top surface 14 forming an edge 15
at least partially surrounding the projection 13.
[0058] The hook fastener can have plurality of engaging projections
form a discrete or continuous shape. Shape is defined as a
plurality of the engaging projections that are organized into a
specific area or region, where there are more or less, or different
types or sizes, of engaging projections outside this region. A
shape does not need to have defined edges but rather could have a
gradual change in the density or distribution of the engaging
projections from, e.g., a high density engaging projection area to
an adjacent low density engaging projection area. This low density
engaging projection area could have little or no hook engaging
projections. Preferably the shape is formed by the plurality of
engaging projections in a region having a relatively high density
of engaging projections. The plurality of engaging projections
forming a shape can extend substantially continuously in one
dimension of the base as shown in FIG. 8a. The shapes in most
embodiments will have a minimum width dimension less than the width
of the base as it should not cover the entire surface of the base
The shapes could be surrounded by secondary areas having a either a
different type and/or density of engaging projections. In a
preferred embodiment the shapes are relatively high density regions
having an average density of engaging projection of at least 1 gram
per square meter (gsm) of particles, or at least 2 gsm of particles
which are of a general average size of about 50 to 1000 microns or
generally 50 to 500 microns. (Note that the engaging projection
average size, and density of the engaging projection material, can
be used to convert this measurement to the number of engaging
projections per area). In another alternative the secondary regions
have an average density of engaging projections of less than about
50 percent of the average density of engaging projections in the
shape region, or less than about 25 percent of the average density
of engaging projections in the shape region. In a preferred
embodiment at least one region will have little or no engaging
projections. For those shapes that extend continuously in one
dimension of the base the shapes generally will have a minimum
width dimension less than the width of the base. The shapes
generally would have a minimum width dimension of greater than 1 mm
or greater than 4 mm.
[0059] The shaped regions of engaging projections may be provided
on a base layer that is a continuous web. The regions of engaging
projections can be present as a plurality of regions on the surface
of the continuous web, for example in a repeating or nonrepeating
pattern of regions bearing engaging projections, partially or
completely surrounded by regions lacking any engaging projections
(or, as discussed herein, bearing engaging projections that are
present at a lower density, or that differ in some property such as
size, height, color, aspect ratio, etc.). Various potential shapes
that engaging projection regions 77 may form on a base film 4 are
illustrated in FIGS. 8a-8d. The shaped regions bearing engaging
projections may be present as discrete regions within a contiguous
area that has no engaging projections (or, that have differing
engaging projections as discussed above); or, the engaging
projections may be present in a contiguous area that has regions of
no (or fewer, or different) engaging projections interspersed
therein.
[0060] The engaging projection regions or areas can serve a wide
variety of functions. The basic premise is that of providing one or
more sets of engaging projections only in the regions in which they
are desired to be present on the substrate (base). Such regions of
engaging projections may provide benefits in terms of adhesion,
cost, ornamental or visual effect, or some other factor. A example
is the placement of a hook containing region (strip, rectangle, or
shape as desired) on an article in a predetermined desired
location. This is customarily done by making a uniform hook
material on a backing, such as a film, and cutting discrete pieces
of this hook material and bonding it to the article where fastening
functionality is desired (for example onto a sheet of material that
is to be used as a diaper side panel, ear, or backsheet). This is
typically done by use of adhesives or melt bonding. The current
method allows regions of engaging projections to be formed directly
on the desired article in the size and location desired. For
example, engaging projections may be placed in desired regions on a
continuous web, intended to be used as a diaper side panel, ear or
backsheet, etc. from which individual pieces bearing the engaging
projections may then be taken (for example by die-cutting), to form
a diaper side panel, ear or backsheet, etc.
[0061] It is also possible to provide the regions of engaging
projections so as to impart unique or novel mechanical performance.
For example, the engaging projections can be present in the form of
regions (for example, strips), separated by regions without
engaging projections, or with a lower density (that is, the number
of engaging projections per unit area of the base film), of
engaging projections, or with larger or smaller engaging
projections, etc. Such configurations may provide enhanced or
tailored properties, for example in peel or shear behavior. For
example, regions of low shear or peel properties can be interposed
with regions of high shear or peel properties, which might serve to
provide more uniform performance when a fastener is disengaged from
a loop substrate. Or, a region with a lower density of engaging
projections (which, again, includes regions of no engaging
projections) may serve as a fingerlift zone, for example in use as
a diaper closure. If engaging projections are applied in regions in
a multistep process the regions can overlap in whole or in part
which can result in a certain number of "stacked" projections
resulting from the deposition of preform projections onto existing
preform projections. The presence and amount of stacked projections
can also be tailored to achieve desired engagement properties.
[0062] The engaging projection regions can also be provided so as
to impart novel and unique visual or ornamental effects. The
engaging projections can be provided in a region that is shaped so
as to form a recognizable image or shape, e.g. an object, a letter,
or the like, as exemplified in FIG. 9a. Multiple shapes could be
provided to create a more complex image or shape or be repeated in
simple patterns. These visual effects can be augmented by providing
the engaging projections in one or more colors (via use of
pigmented materials, etc.), or by the use of reflective additives,
and so on.
[0063] One alternative embodiment of providing unique visual or
ornamental effects is to provide the engaging projections on a base
that has preprinted graphic elements. (The preprinted graphic
elements can be present on the top surface or bottom surface of the
base layer, depending on whether or not the base layer is
transparent.). The region of engaging projections could be used as
a graphic element in conjunction with the preprinted graphic
elements. For example, the base layer can be preprinted with a
visual image or scene (e.g. a garden), and the region of the
engaging projections can then be deposited in the shape of a
flower. The shaped engaging element region may be placed at random
in the preprinted visual image. Or the shaped engaging element
region may be placed into a predetermined location in the
preprinted visual image, as shown for example in FIG. 9b, in which
a shaped engaging projection region 77 is placed in a preprinted
visual image 78 on a base film 4. The engaging projections can also
be provided so as to comprise a background in a predetermined
region (for example, the engaging projections could appear to be
individual snowflakes in a landscape scene).
[0064] The engaging projections are provided by means of depositing
preform projections onto a surface of a preprinted base. The
preform projections may be deposited in areas, which are not imaged
(i.e. do not bear ink, pigment, metalized coating, etc).
Alternatively the preform projections can be deposited onto imaged
areas as long as the imaging layer is such that the preform
projection can be bonded satisfactorily to it. Or, if the imaging
layer is sufficiently thin, it may be possible to fuse the preform
projection to the underlying base front surface, through the
imaging layer, by deforming, melting, or otherwise displacing the
imaging layer.
[0065] As mentioned, the polymer particles used to form the
engaging projections can be colored, tinted, pigmented, etc., for
specific visual purposes. Multiple regions can be provided with
different color engaging projections, or different densities or
sizes of engaging projections, for specific visual effects.
[0066] The present invention also encompasses the use of adhesives,
preferably pressure sensitive adhesives (PSAs). Such PSAs include a
wide variety of materials known in the art, for example, natural
rubber adhesives, block copolymer-based PSA's (for example, those
based on elastomers available from Kraton Polymers, of Houston
Tex.), acrylate-based PSA's, and silicone-based PSA's. PSA's may be
chosen so as to bond well to polyolefinic thermoplastic materials
(e.g. polypropylene, polyethylene, and copolymers and blends of the
same), and might include, for example, the family of PSAs available
from 3M Company under the designation LSE (e.g., LSE 300). Other
suitable compositions may be based on silicone-polyurea based
pressure sensitive adhesives. Such compositions are described in
U.S. Pat. No. 5,461,134 and U.S. Pat. No. 6,007,914, for
example.
[0067] In one embodiment, the PSA may be provided in an area
adjacent the region bearing engaging projections. Either or both
the PSA and engaging projection regions may be present as discrete
or continuous regions. For example, in FIG. 10 is pictured downweb
stripes 91 of PSA adjacent to downweb stripes 92 of engaging
projections.
[0068] The base used in the methods of the invention can be any
suitable continuous or discontinuous base web such as a porous or
nonporous polymer film, a laminate film, a non-woven web, a paper
web, a metal films and foils or the like. The base could be
modified by any known method such as by being printed, embossed,
flame treated, laminated, particle coated, colored, or the like. A
polymer film used as a base can be oriented or unoriented. In
conjunction with the methods described later, the base film can be
provided such that it possesses areas that vary in the ability to
bond to the preform projection, which is yet another way of
providing a substrate with engaging projection regions present in
discrete shapes, patterns, and the like. The base film surface can
be smooth, or can be provided with features such as projections or
valleys molded into the base which could be used as ripstops, tear
propagation lines or other features, which could be on the front or
rear face of the base.
[0069] The surface of the base can also be roughened, for example
with particles previously scattered and fixed thereon. The
particles should be brought and fixed on the base 4 in a way that
at least the terminal ends of the projections can be formed from
the particles. Projections can consist completely of the particles
without any further modification of said particles. For bringing
and fixing the particles to the (smooth or roughened) front
surface, several methods are taught, e.g., random scattering and
adhering, for example, in the cited PCT publication WO 01133989,
the entire disclosure of which is hereby incorporated by
reference.
[0070] The word "particle", as used herein, refers to a solid,
liquid or semi-liquid particle, including, for example, granules,
pellets, powders and droplets. Appropriate particles can be
selected based on the discussions herein. If the embodiment of this
invention relying on electrostatic deposition of particles (as
described later herein) is used, the particles should be chosen so
as to be compatible with this process. In electrostatic deposition,
particles are moved under the influence of an electric field so as
to impinge on the base (whether onto selected regions or uniformly
onto all regions of the base). Thus, in this instance the particles
must be susceptible to having an electric charge imparted to them
(otherwise they would not move under the influence of the electric
field). Such methods are well known in the art and the selection of
such particles is straightforward.
[0071] In terms of the properties of the engaging projections that
are formed from the particles, it is preferable if at least some
engaging projections are provided with a side view which strictly
tapers from the top surface or top surface edge to the attached end
at the front surface of the base. As used herein, a side view means
a view taken perpendicular to the front surface of the base.
Strictly tapering means that the nearer the engaging projection
gets to the base, the narrower the projection becomes. For example,
a cylinder is not a strictly tapering shape. This type of tapering
will pull engaged fibers down to the front surface of the base when
a shear load is applied to the fastener without the fibers being
caught at a nontapered portion displaced from the front surface of
the base. Thus the torque on the engaging projection is minimal so
the base can be weaker, i.e., can be cheaper, more flexible, more
skin friendly, thinner etc. Furthermore, the fastener may have a
relatively large surface area formed by the projection tops, making
the fastener smooth to the touch, while also having a relatively
low total surface area of the projection attached ends connected to
the base, increasing the flexibility and skin-friendliness of the
fastener. The engaging projections can also be characterized by a
ratio of the perimeter of area of the engaging top to the height of
the engaging projection, which is generally 1.1 to 50, and is
preferably 1.2 to 20. The engaging projection also generally forms
an overhanging rim, which generally is the difference between the
top surface area and the area of the attached end.
[0072] Turning from the materials used to the methods of the
invention, a preferred general set of methods for manufacturing a
male fastener component with predetermined shapes of engaging
projections in accordance with the invention generally comprises
the basic steps of:
[0073] providing a base with a front surface;
[0074] providing particles of polymer material;
[0075] providing a contact release surface of a suitable surface
energy;
[0076] dispersing, on the contact release surface, a multiplicity
of the polymer particles;
[0077] bringing or providing the polymer particles into an at least
semi-liquid or softened state of a suitable viscosity, providing
preform projections (preform projection signifies a projection that
to at least some extent has been preformed into the shape of the
final engaging projection) sitting on and projecting from the
release surface. The preform projections along their edges
contacting the contact release surface will form contact angles,
which contact angle is influenced by the surface energies of the
polymer particles and the contact release surface. The polymer
particles are maintained in a semiliquid state for a suitable
period of time so that they form an acute contact angle;
[0078] the preform projections can then be at least partially
solidified for contacting and fixing to the front surface of the
base with the terminal ends of at least some of preform
projections, while essentially maintaining the shape of the edge
formed by the contact release surface;
[0079] the preform projections are then further solidified
sufficient to separate and remove the preform projections from the
contact release surface thereby forming engaging projections
attached to the base. These formed engaging projections project
from the front surface of the base to flattened tops, which tops
were formed on the contact release surface. The flattened tops at
least partially overhang the base forming a rim, and are bordered,
at least partly, by an edge having an angle which is influenced by
the acute contact angle.
[0080] As mentioned above, there are two generic subsets of methods
that allow the formation of predetermined shapes of engaging
projections. In the first subset method the polymer particles are
deposited onto the contact release surface in a predetermined
pattern that defines the shape to be formed. The particles are
delivered to the contact release surface in selected patterns or
shapes by a variety of methods. In a first method the particles are
projected against a mask having cutout portions that define the
shape to be formed. The mask can be fixed in position, with the
result that particles that go through the cutout portion of the
mask are deposited as preform projections onto the (moving) contact
release surface in stripes. An exemplary engaging projection area
configuration resulting from this approach (upon transfer of the
preform projections to a base film) is shown in FIG. 8a. The
deposition of particles can be stopped and started so as to provide
interrupted downweb stripes. Alternatively, the mask can move with
and at about the same speed as the contact release surface. In this
case, the particles that go through the cutout portion of the mask
are deposited on the contact release surface in the shape defined
by the cutout. Some exemplary engaging projection area
configurations resulting from this approach are shown in FIGS. 8b,
8c and 8d. The mask can comprise a disposable film, for example a
plastic film with appropriately shaped cutouts. In a preferable
embodiment, the mask comprises an endless belt (as discussed later
with regard to the embodiment of FIG. 2a).
[0081] The particles are projected onto or through the mask by any
of a variety of means. First, gravity could be used where particles
are simply allowed to fall onto the mask. This method however
suffers from the problem of how to remove the particles that land
on the non-cut out portions of the mask. These particles could be
removed by vacuum, contact removal, air jets or the like, but there
remains the possibility that some of these particles later fall
through the apertures of the mask in areas not intended to have
particles, or at the wrong time in regions intended to have
particles.
[0082] Another way to bring particles onto or through a mask is
electrostatic deposition. In this method the polymer particles are
directed toward the mask by an electrostatic driving force. This is
performed by providing two electrodes so as to establish an
electric field therebetween. A first electrode is positioned so
that the mask is between the first electrode and the contact
release surface. A second electrode is positioned behind the
contact release surface. A voltage is applied to the electrodes so
as to establish an electric field therebetween. Upon the
introduction of suitable particles into the gap between the first
electrode and the mask, the particles are changed then driven under
the influence of the electric field in the direction of the second
electrode. Thus, the particles encounter the mask, with the result
that some hit the solid portion of the mask and some pass through
the cutout regions and impinge on the contact release surface so as
to collectively form the desired shape.
[0083] Electrostatic deposition is most advantageously performed in
a vertical configuration with the second electrode positioned above
the first electrode. In this arrangement the particles are driven
upwards, against gravity, thus the particles that hit the mask fall
back down and may be collected and/or recycled, or are otherwise
less likely to accidentally fall onto the contact release surface,
which is present behind the mask and the contact release surface.
This method also has the advantage of providing for more uniform
distribution of particles onto the contact release surface. All the
particles will be like charged and repel one another. This will
tend to keep the particles evenly distributed and keep individual
particles from forming large number of unified preform projections.
This method is advantageous for providing either uniform
distributions of particles in the discrete regions or over the
contact release surface as a whole with a uniform distribution of
particles to be formed into preform projections.
[0084] As previously described herein, the mask may be stationary
or moving in tandem with the contact release surface. (An
embodiment of the latter is discussed in detail later with regard
to the embodiment of FIG. 2a). In electrostatic coating, ideally
the mask material is such that the particles that hit the mask do
not stick to it via electrostatic attraction.
[0085] The polymer particles must also be chosen for their
suitability for electrostatic coating. The primary requirement is
that under the influence of the imposed electric field, the
particle develop sufficient induced charge such that sufficient
force is placed on the particle by the electric field that the
particle moves between the two electrodes. Preferably, the electric
force should overcome gravity such that the above-described
vertical configuration can be used. Fortunately, most of the
materials that are appropriate for forming preform projections
(namely, thermoplastic powders such as polypropylene and the like)
are dielectric materials (that is, capable of having a charge
induced upon being placed in an electric field). Suitable particles
for forming the preform projections are also generally small and of
low density (thus light in weight) making them easier to be driven
via electrostatic force upward against the force of gravity.
[0086] An alternative embodiment of electrostatic discrete
deposition uses a second electrode that is in the form of a
patterned conductive belt. Such a patterned belt, placed behind the
contact release surface (above the release surface, if in the
vertical configuration), moving in tandem with the release surface,
would result in particles being moved toward the contact release
surface primarily in the regions of the release surface that have a
solid area of the patterned electrode behind them. This eliminates
the need for a physical mask interposed between the particle source
and the contact release surface. Such a patterned belt most
conveniently takes the form of a continuous metal belt with holes
provided therein, which can be connected to a voltage source and
maintained at a desired voltage even while moving in an endless
loop. (Such an embodiment is discussed in more detail with regard
to the embodiment of FIG. 5a) This arrangement is most suited for
deposition of preform projections in a contiguous pattern with
discrete empty areas therebetween. If it is desired to provide the
preform projections in discrete regions surrounded by contiguous
empty areas, it is possible to use a nonconductive belt with
conductive regions provided thereon (for example, a nonconductive
polymeric film with areas of conductive ink screen printed
thereon). It would of course be necessary to provide electrical
connection between the conductive areas, which could be done with
very thin lines of conductive material.
As described previously, the particles are introduced into the
space between the first electrode and the mask (if present).
Alternatively, in the absence of a mask, the particles are
introduced into the space between the first electrode and the
contact release surface. The particles should be placed in the gap
in whatever manner will allow them to come under the influence of
the electric field and be driven toward the contact release
surface. Ideally, this is performed in a uniform manner. The
particles may be sprayed, dropped, blown, or otherwise injected
into the gap by methods well known in the art. In the
above-described vertical configuration, the particles may be
injected laterally into the gap by spraying. Alternatively, the
particles can be brought into the gap by means of a carrier belt
which, bearing the particles on its top surface, comes into the gap
such that the particles are free to move toward the contact release
surface by the applied electric field.
[0087] Other methods besides the afore-mentioned electrostatic
deposition and gravity-assisted deposition are possible.
Alternative methods to selectively bringing particles to a contact
release surface in predetermined shapes or patterns include
impacting the particles onto a mask by a forced airstream,
mechanical projection or conveying, and the like.
[0088] These first generic subset methods are amenable to multistep
deposition of particles as preform projections. That is, it may be
advantageous to provide different discrete regions that comprise
engaging projections that differ in some feature (for example,
color, size, aspect ratio, modulus, etc.). One such way to provide
such a product is to process a base film to attach one set of
engaging projections, then send the film through an additional
processing step to attach a second set. However, this may involve
cumbersome handling of the base film. A preferred method is to
provide a processing line with multiple deposition stations. That
is, it is possible to deposit a given set of preform projections
onto the contact release surface, and thereafter deposit another
set of preform projections. The second set may be deposited in
(separate) discrete regions, or may be deposited throughout the
contact release surface (which will of course result in some degree
of "stacked") projections. Such a configuration may be provided by
means of a processing line that has two deposition stations
positioned sequentially such that the moving contact release
surface passes through one station, then through the other station.
After passing through the deposition stations, the preform
projections are transferred to the (same) base film. (An example of
this is discussed in additional detail with reference to the
embodiment of FIG. 3a). In an alternate configuration, the first
set of preform projections may be deposited on the contact release
surface then transferred to the base film, which is then fed into
the second deposition station for deposition and subsequent
attachment of the second set of preform projections.
[0089] In a second generic subset of methods the polymer particles
are deposited onto the contact release surface, which could be
uniformly. The predetermined pattern or shape of engaging
projections is provided by selectively transferring and attaching
polymer particles on the contact release surface onto predetermined
regions of the base. This selective attachment can be done by
making predetermined regions of the base more or less receptive to
bonding the preform projection polymers. Two basic approaches
exist. The first is to provide a base film that has little or no
ability to bond to the polymer particles used to form the preform
projections, and then imparting regions of higher bonding ability
onto the surface of the base film. In the use of an adhesive such
as a PSA to bond the preform projections to the base, it would be
straightforward to provide the PSA on the base only in selected
regions (by pattern coating, stripe coating, and the like). In the
case of fusing (i.e. melt bonding), dissimilar polymeric materials
may not bond well to each other. Thus, for example, the placement
of preform projections of polystyrene onto a base film of
polypropylene, (or vice versa) may result in little or no bond
formation. However, if a compatibilizing layer is placed upon a
selected area of the polypropylene base film, an enhanced bond may
be achieved. Such compatibilizing layers can be applied to the base
in a patterned or discrete or discontinuous manner by a wide
variety of methods of the art, including pattern coating, screen
printing, vapor coating, plasma coating, photolithography, chemical
vapor deposition, and the like.
[0090] Compatibilizing layers may comprise any of the widely known
tie layers and bonding layers that are available in the art. All
that is necessary is that the compatibilizing tie layer have
sufficient adhesion to the base and sufficient adhesion to the
polymer particle used to form the preform projection. In this
approach, the polymer particles and base film may no longer need to
be formed of the exact same material, or materials that are
extremely close or similar in composition. This allows the base and
the polymer particles to be chosen based on the physical properties
most desired for each. For example, it may be desirable to chose a
base film that is extremely soft and flexible, and a polymer
particle that is extremely hard and rigid (or vice versa). The use
of compatibilizing layers on the base film allows this to be done.
An example of this approach is discussed later with regard to the
embodiment of FIG. 6a.
[0091] The other approach is to use a base and polymer particles
that bond well to each other, and to apply a masking layer to
selected regions of the base. In one embodiment the masking layer
is a permanent layer that is retained on the base and that does not
bond to the polymer particles. Such masking layers could be
polymeric (for example, coatings such as silicone, fluorosilicone,
or Paralene) or metal or metal oxides, for example. All that is
necessary is that the layer does not bond well to the particles nor
is it sufficiently displaceable to permit bonding to occur through
it. Such layers can be applied to the base in a patterned or
discrete or discontinuous manner by a wide variety of methods of
the art, including pattern coating, screen printing, vapor coating,
plasma coating, photolithography, chemical vapor deposition, and
the like. It is also possible to deposit the masking layer
everywhere on the surface and to remove it in selected regions, via
etching, ablating, and the like.
[0092] In another embodiment the masking layer is provided
temporarily, so as to constitute a physical barrier in certain
locations to prevent polymer particles from contacting the base
during transfer from the release surface. In this case the masking
layer may be a film which is used temporarily but does not become
part of the final product, as described later with reference to the
embodiment of FIG. 7a.
[0093] The skilled person, familiar with the field of surface
energy, surface tension and wetting, can select a combination of a
suitable polymer for the particles and a contact release surface of
a suitable surface energy, and also select particles having a
suitable viscosity at the temperature of the contact release
surface that will wet the contact release surface within a suitable
time. The surface energy of the contact release surface may be
formed by known materials and methods, such as siliconized
surfaces, fluorochemicals, corona discharge, flame or the like. The
contact release surface must be able to release the particular
polymer particles used, semi-liquefied and solidified. It is known
that certain release surfaces can release certain polymers but are
unable to release other polymers. For example, a polyethylene
release surface can release suitable polypropylene particles but
cannot release certain polyethylene particles as they tend to weld
or fuse to each other. The word "release" as used herein refers to
the phenomenon where the particles are detached from the contact
release surface without (unacceptable) damage or loss of material
of the particles or preform projections.
[0094] Dispersing of the particles onto the contact release surface
by gravity can be performed in any suitable way, for example, by
scattering the particles with a scatter unit. Other methods have
been mentioned herein. The particles should be dispersed at a rate
per unit surface area so that they form preform projections where
one particle can form one preform projection, which may merge as
discussed above. The particles can be brought into the at least
semi-liquid state before, during and/or after dispersing of the
particles onto the contact release surface. "At least semi-liquid"
means liquid or semi-liquid. A suitable way of liquefying will
depend on the properties of the selected polymer, and can include,
for example, heating, thinning, solving, emulsifying, dispersing
etc.
[0095] A solidity (degree or extent of solidification) suitable for
contacting and fixing the preform projections on the contact
release surface with the front surface of the base can be decided
by the skilled person, depending on the particular circumstances.
It will usually, but not necessarily, mean a more solid state than
the one in which the preform projections have been formed on the
contact release surface. Preferably the preform projections should
be solid enough to keep, at least partly, their shape while being
contacted with the front surface of the base. It usually primarily
means keeping at least a minimum free height and also a suitable
edge angle of the preform projections. Setting the necessary
solidity in the preform projections will be material-dependent, and
can include cooling, drying, heating, crosslinking, curing,
chemical treatment etc. The preform projections of suitable
solidity, sitting on the contact release surface, can be covered by
the base front surface such that the front surface of the base can
contact and fix with the preform projection terminal ends. The
terminal ends are the ends farthest from the contact release
surface. Before contacting with the front surface of the base, the
preform projections can be provided, or supplemented, with further
added dispersed particles or the like, which will attach to the
preform projections. It is possible that the front surface of the
base is contacted with the preform projections when the preform
projections are in a semiliquid state. In this case it is possible
that after the contacting, and before a final solidification, the
preform projections are somewhat lengthened by stretching while the
preform projections are removed from the release surface thereby
causing the preform projections to get slimmer in their middles. A
skilled person can also choose a base flexible enough to permit
contacting preform projections of possibly non-uniform heights. The
front surface of the base can be smooth but it can also be suitably
rough, for example roughened with particles or projections
previously scattered and fixed on the base. The fixing of the
terminal ends of the preform projections to the front surface of
the base can be obtained for example by, adhering with an added
adhesive (for example, a pressure sensitive adhesive, hot melt
adhesive, or UV-cure adhesive), crosslinking with ultraviolet
irradiation, or it can utilize the inherent adhesion of the
contacting materials (the base front surface or the preform
projections) or fusing. Fixing with fusing will be discussed in
detail later herein. While fixing, care should be taken in order
that the free overhangs or rims, and the actual heights of the
preform projections are sufficiently preserved. For example, an
exaggerated sinking or compression of the projections into the
front surface of the base should be avoided. The proper solidity of
the preform projections and the base, suitable for a separating and
removing both from the release surface can be decided by the
skilled person, depending on the particular circumstances. The
solidity of the preform projections when they are removed from the
release surface will usually, but not necessarily, be a more solid
state than when they are initially contacted with the front surface
of the base. Preferably the preform projections should be solid
enough to keep, at least partly, their shape during the separation
from the release surface. It usually primarily means keeping a
suitable overall shape, with particular respect to the edge angle
formed, but preserving a suitably strong bond with the front
surface of the base is also an important factor. The base generally
should be solid enough to keep its form and separate the preform
projections from the release surface. The top surface as formed can
be smooth but can also be somewhat roughened, e.g., sandpaper-like
or grooved, as known from the art. The top surface structure will
be largely determined by the contact release surface, which may be
essentially flat, even if naturally not planar in the true
geometrical sense. Post treatments could however be used that would
make the top surface not essentially flat, such as a noncontact
heat treatment. If small numerous projections are advantageous it
is preferable if, in the methods, that at least some of the
separate preform projections comprise exactly one polymer particle
per preform projection.
[0096] It is preferable if, in the methods, at least some of the
preform projections are provided with contact angles 38 of between
10.degree. and 85.degree., preferably 30.degree. and 80.degree..
This would be the range of contact angles for most of the
individual preform projections. For a preferred embodiment this
range would be the mean contact angle for the preform
projections.
[0097] It is preferable if, in the methods, at least some engaging
projections are provided with a profile in which, in each side view
thereof, the engaging projection strictly tapers (preferably is
strictly convex) from the flattened top or top edge to the front
surface of the base. This is usually very easy to achieve by this
method which typically creates semi-lenticular preform projections,
like water drops sitting on a suitable surface. In the methods,
non-thermoplastic and thermoplastic polymer particles can be used,
the selection being based on necessary strength, required surface
energy, cost etc. However it is preferable if, in the methods the
polymer particles are thermoplastic polymers.
[0098] If drops of liquids are deposited onto a solid contact
release surface and if the surface energy of the release surface is
somewhat higher than the surface energy (or surface tension) of the
liquid, the liquid will typically perfectly wet the solid, with a
contact angle of zero. With liquids, each "solid-liquid" pair has a
contact angle, between zero and 180.degree., with which the liquid
drop will, approximately, wet the solid. With semi-liquid, e.g.,
softened thermoplastic, particles, the process of forming a contact
angle is a time-temperature phenomenon. With solid contact release
surfaces of high surface energy a liquid polymer will wet perfectly
if given enough time. If this high surface energy solid contact
release surface is kept hot, and a cold solid particle is placed
thereon, a process is started in which the contact angle transforms
over time, from an initial obtuse angle towards the final zero
contact angle. By interrupting this transformation process, e.g.,
by a suitable cooling, one can achieve any desired contact angle.
Therefore high surface energy solid contact release surfaces are
useful in the process of the invention. However, the higher the
contact release surface's surface energy, the more difficult it is
to finally separate the release surface from the preform
projections. Also if the surface energy of the contact release
surface is too high in relation to that of the polymer particles
there is greater opportunity for unintentional operator error
forming a preform projection that is excessively wets the contact
release surface. The danger of overwetting the contact release
surface is lower if the surface energy of the contact release
surface is not higher than the surface energy of the particle plus
60 mJ/m.sup.2.
[0099] High surface energy contact release surfaces also might
cause the engaging projection's edge angles being too sharp
creating rims that are too thin and which might possibly break off
during later use, creating undesired contamination. It is likely
sometimes better to accept larger contact or edge angles to provide
enhanced security against engaging projections forming with thin
weak edges and rims. Therefore it can be preferable if the methods
comprise providing a contact release surface whose surface energy
is lower than the first surface energy (that of the particle). In
this case the edge angle in the product can be determined by
material selection rather than by on-line operating parameters.
Also the lower the surface energy of the contact release surface,
the easier it is to finally detach the preform projections
therefrom. However a certain degree of force needed for detaching
preform projections from the contact release surface can be
beneficial. Some preform projections can be weakly fixed to the
front surface of the base. Namely the fixing strength is lower than
desired for its intended end use resulting in some engaging
projections possibly breaking loose during use. This is a difficult
to detect defect. Therefore it is preferable if the contact release
surface's surface energy is higher than the first surface energy
(that of the particle) minus 23 mJ/m.sup.2. With a contact release
surface of this level the separation force for detaching preform
projections from the contact release surface may be high enough to
remove projections weakly fixed to the base front surface thereby
providing an on-line fault-detection and correction mechanism.
[0100] It is preferable if, in the methods described hereinabove
for thermoplastic preform projections (which can also be termed
protrusions throughout), the fixing of the front surface of the
base with the terminal ends of at least some of the preform
projections comprises fixing by heat or fusing.
[0101] Fixing by heat can include melting one or the other of the
preform projections or the base front surface, depending on the
materials and pressure etc. Preferably both the preform projections
and the front surface of the base are allowed to potentially melt,
and are thereby fused. Fusing is a fixing of the preform
projections to the front surface of the base by heat. In this case
the preform projections are made up of particles well suited for
both sharpening by the release surface, from below, and the
covering and fixing to the base by fusing, above. The particles
must be liquefied enough during the fusing to suitably form the
contact angle, but must remain solid enough, to permit keeping
their edge angles. It is preferred that the thermoplastic polymer
particles have a melt flow rate of between 1 and 90 grams per 10
minutes at the conditions appropriate for the selected polymer.
[0102] In the subsequent step of the above method, the fixing by
heat comprises maintaining the contact release surface at a
temperature lower than the softening temperature of the polymer
particles or preform projections while contacting the front surface
of the base with the attachment ends of at least some of the
preform projections. The back surface of the base is preferably
heated by subjecting it to a heated gas. However, other heating
methods such as radiant or IR heat may be used. If heated gas is
used, the gas pressure at the back surface of the heated base is
typically higher than the pressure (e.g. a gas pressure) at the
front surface of the heated base, thereby pressing the heated base
against the attachment ends of at least some of the preform
projections to enhance the fixing thereof to the base. The pressure
difference may be enhanced, for example, by applying vacuum from
beneath the contact release surface or the front surface of the
base.
[0103] Also, in these methods it is not a great problem if the
preform projections are of different heights, as long as a
sufficiently pliable base, capable of bending down to reach the
lower preform projections, is provided. It is especially useful if
the whole base is thermoplastic and is actually softened, thereby
made soft and flexible, easily bending or even stretching when hot
(This may be advantageous particularly if regions of preform
projections differing in height are present, as discussed
previously). If desired the base can be fully softened, where fully
softening means softening of all components, layers thereof, e.g.
in case of a composite, above a softening temperature.
[0104] After the separation of the base from the release surface,
some preform projections, not fixed to the base, may remain on the
contact release surface. These are usually very tiny residual
polymer particles, which may melt into, and go away with, particles
dispersed later on the contact release surface. Still by regularly
providing for their removal from the contact release surface, the
process can be made more uniform and secure. Therefore it is
preferable if the method further comprises:
[0105] before the dispersing of the multiplicity of polymer
particles on the contact release surface;
[0106] heating the contact release surface to a temperature higher
than the softening temperature of both the polymer particles and
the front surface of the base;
[0107] contacting the front surface of the base with the heated
contact release surface thereby softening the front surface;
[0108] suitably pressing the softened front surface against the
heated contact release surface thereby fusing the polymer particle
contamination residue into the front surface of the base;
[0109] providing, for the contact release surface and the base,
temperatures suitable for separating the base from the contact
release surface;
[0110] separating the base from the release surface, thereby
cleaning the contact release surface.
[0111] This method uses the thermoplastic character of both the
particles and the front surface of the base for cleaning the
contact release surface. During the steps above, the small amount
of residual polymer contamination goes away with, and usually
disappears in the front surface of the base. The base can then be
utilized as usual. In a continuous operation, e.g. comprising rolls
or conveyors, the release surface can be cleaned with every
revolution, before each dispersing of particles, thus always
keeping the cumulative contact release surface contamination at low
levels.
[0112] While the preform projections are being fused to the front
surface of the base, the base is typically above the release
surface where it is supported by the preform projections and
bridges the space between them. If the front surface of the base is
above its softening temperature, any molecular orientation therein
may cause problems by shrinking at least the bridging portions of
the sheet-form base. That can be avoided, for example, with using a
composite base with a suitable backing resistant to shrinking. For
example a base, comprising a polyester film, or paper, backing and
a polyethylene layer coated thereon as front surface, can
potentially withstand the shrinking that may occur in the base.
However if shrinkage is a problem it is preferable if the base is
free of molecular orientation when fusing the preform projections
or particles. Molecularly oriented films can be pretreated by
contacting the front surface of the base with a heated release
surface (which could be the contact release surface), thereby
rendering the front surface of the base essentially molecularly
un-oriented.
[0113] Heated gas (preferably air) at an elevated pressure can best
be provided with gas nozzles ejecting heated gas. If the base is
moved in front of the output orifice of the nozzles so that its
back surface is contacted with the ejected hot gas then the base
softens. At the same time, the hot gas ejected from the nozzles
creates and maintains a gas flow along the back surface of the
base, typically parallel to the traveling direction of the base. If
the nozzles are fixed and the base is moving in a machine
direction, the hot gas flow will have a direction essentially both
parallel and opposite to the machine direction. The hot gas flow,
e.g. hot air flow, will exert a pulling force on the softened base,
dragging the back surface of the base. That will tend to stretch
the softened base. The faster the gas flows, the stronger this
stretching effect will be. With a low throughput arrangement, i.e.,
with low hot gas velocities, and especially with a thick base, a
base which is essentially free of molecular orientation can be
used. In case of higher throughputs and higher gas flow rates, and
especially with a thinner base this machine direction stretching of
the base can be very significant, which can be undesirable. For
example, stretching of the base in a lengthwise, machine direction
can make it difficult to control the thickness of the fastener or
can result in rolls of unspecified length. Stretching can also lead
to accidental breaking by thinning, tearing apart the base.
[0114] The effects of stretching can be counterbalanced by
providing a suitable molecular orientation in the base. The problem
of stretching can be solved if the base is provided with a
heat-shrink potential in the machine direction. The heat of the gas
will relax the orientation in the base, i.e., will tend to shrink
the base, which will counteract stretching by the heated gas flow.
Therefore, in a variation of the invention method, one or more gas
nozzles, adapted for ejecting heated gas, are provided. The back
surface of the base is contacted with the heated gas ejected by the
one or more gas nozzles while the base moves relative to the one or
more gas nozzles. The direction in which the base is moving is the
machine direction and is essentially within the plane of the base.
The base preferably has a heat-shrinkability in the machine
direction (the lengthwise heat shrinkability) of at least 1
percent. The fixing by heat includes heating the base above a heat
shrink temperature thereof.
[0115] As used herein, "heat-shrinkability" in a direction shall
mean, in the context of a material such as the base material, that
the material is capable of being decreased in its length in the
given direction, or dimension, in response to the transmission of
thermal energy into the material. The "heat shrinkability" of the
material is a percent value and equals 100 percent times the
difference between its pre-shrink length and post-shrink length,
divided by its preshrink length, in the given direction. The
post-shrink length, in a given direction, of the material means the
length of the material, in the given direction, after shrinking the
material, such as at a temperature of 170.degree. C. for 45
seconds. Shrinking can be determined, for example, by immersing the
material into hot silicon oil and letting it freely shrink. It was
found that using temperature of 140.degree. C. for 14 seconds
relaxes essentially all the shrink in usual polymer materials. As
used herein, the "shrinking temperature" of a material refers to
the temperature at which the material, exposed to an increasing
temperature, starts to heat-shrink.
[0116] The advantage of this variation of the methods of the
invention is that it helps counteract stretching effects exerted on
a softened base by ejected hot gas flow. With high production rates
lengthwise heat-shrinkability higher than 1 percent can provide
improved results. Therefore it is preferable if, in this variation
of the methods, a base having a lengthwise heat-shrinkability of at
least 10 percent, more preferably at least 20 percent, more
preferably at least 30 percent, even more preferably at least 40
percent, and even more preferably at least 50 percent is provided
for the contacting and the fixing depending on the forces created
by the hot gas flow and the production rate.
[0117] The stretching effect, exerted on the base by a lateral hot
gas flow is less significant, or even close to zero (depending on
the details of the nozzle arrangement) in the crosswise direction,
i.e., in the direction perpendicular to the direction of the
traveling path of the base (in a machine it is called the cross
machine direction). Therefore, if a base has a high heat-shrink
potential, or high heat-shrinkability in the crosswise direction,
the edges of the base can shrink or neck in, which results in
folding or wrinkling when contacted with the hot gas. This is
undesirable. Therefore it is preferable if the heat-shrinkability,
of the base in its in-plane direction perpendicular to the main or
machine direction is either zero, or lower than the lengthwise
heat-shrinkability. "Zero crosswise heat-shrinkability", as used
herein, includes the case in which the base exhibits an increase in
length, or stretch, rather than shrinking, in the crosswise
direction when exposed to heat. The advantage of this difference in
heat shrinkability is that it provides a differentiated
counteraction to the differentiated dragging effects of the hot gas
flow on the softened base in the two orthogonal dimensions.
Generally the heat-shrinkability, of the base in its in-plane
direction perpendicular to the main direction (the crosswise
direction) is lower than 50 percent. Preferably, the crosswise
heat-shrinkability is lower than 40 percent, more preferably lower
than 30 percent, even more preferably lower than 25 percent,
depending on the forces created by the hot gas flow and the
production rate. On the other hand, the base heated by the hot gas
will exhibit a crosswise thermal expansion which may cause wrinkles
in the product. That can be counterbalanced with a suitably low,
but positive level of heat-shrinkability provided in the base in
the crosswise direction. Therefore it is preferable, if, in the
aforementioned situation, the crosswise heat-shrinkability of the
base is at least 1 percent.
[0118] The methods of the invention also include the step of
dispersing the polymer particles on the contact release surface so
as to form separate preform projections. Preferably it should be
avoided that many or most particles, which will form the preform
projections, touch adjacent particles, or preform projections,
before the preform projections are completed and solidified
(However, such an instance may be preferable if it is desired to
form "stacked" projections as described earlier). Premature
particle contact results in a unifying of the neighboring particles
or preform projections. However if in a fastener the engaging
projections are close to each other, the fixing strength of the
fastener is generally higher, i.e., the fastener performs better.
As in this method the dispersing, e.g., scattering, of the
particles is typically implemented as a stochastic process, the
closeness of the projections usually does not reach the
theoretically possible maximum value, i.e., the projections could
even be a bit closer to each other in the end product. After the
fastener is completed, a subsequent moderate heat shrinking of the
base can improve the relative closeness of the fastener engaging
projections if desired. However, in order to perform this step the
base of the formed fastener must have some heat-shrinkability.
Therefore it is advantageous if, in this variation of the methods
of the invention, the formed fastener base, has a residual
lengthwise heat-shrinkability of at least 1 percent. Preferably, a
formed fastener base, has a lengthwise heat-shrinkability of at
least 5 percent, more preferably at least 10 percent, more
preferably at least 15 percent, even more preferably at least 20
percent, even more preferably at least 25 percent in this
embodiment. In this method the formed fastener is subsequently
heat-shrunk at least in the main direction. This heat-shrinking can
be by any suitable way of transmission of thermal energy into the
formed fastener but preferably in a way such that the acute contact
angles, and the geometric features of the engaging projections in
general, are kept essentially intact or are at least suitably
protected. Preferably the heat energy is transmitted into the
formed fastener from the back surface of the base of the fastener.
For example this could be done by depositing hot material, e.g.,
hot melt adhesive, onto the back surface of the base as part of a
fixing of the fastener to a substrate. The heat-shrinking should be
kept at a low enough level so as to keep adjacent engaging
projections separate from each other sufficient for the engaging
fibers of a female fastener part to penetrate between adjacent
engaging projections. Preferably the fastener base is heat-shrunk
by about 0.1 to 25 percent or less.
[0119] Economical base materials, e.g., blown or cast thermoplastic
polymer films, may not be readily or economically available with
the appropriate heat shrink parameters, as these films often have
higher heat-shrinkability values than are required. A suitable base
can be produced from these economical base materials with a
pre-treating step. The pre-treating suitably decreases the
heat-shrinkability of the materially in a controlled, partial
relaxing of its molecular orientation without letting it shrink
entirely. Namely, if a high heat shrinkable film is mechanically
kept from freely shrinking and is simultaneously kept hot or
softened, its heat-shrinking potential or heat-shrinking capability
will gradually decrease with time without the material actually
decreasing in length or area to the corresponding extent. Therefore
it is preferable if these types of base materials are pre-treated
prior to contacting and fixing of the base material front surface
with preform projections. The pre-treating of the base comprises
providing a pre-treating release surface;
[0120] heating the pre-treating release surface to a suitable
temperature higher than the softening temperature of the front
surface of the base;
[0121] contacting and pressing the front surface of the base with
the pre-treating release surface thereby softening the front
surface;
[0122] keeping the softened front surface in contact with the
heated pre-treating release surface while preventing the base from
shrinking freely, for a suitable period of time thereby decreasing
at least its lengthwise heat-shrinkability;
[0123] providing, in the pre-treating release surface and in the
base, temperatures suitable for separating the base from the
pre-treating release surface; and
[0124] separating the base from the pre-treating release
surface.
[0125] The release surface used for the pre-treating, i.e., the
pre-treating release surface can be similar to or different from
the contact release surface discussed above. The pre-treating
release surface must be able to suitably release the base at the
right time. The base preferably is essentially prevented from any
shrinking, e.g. in order to maintain its regular dimensions, but
mainly its length. This could be done by keeping the base front
surface in full contact with the pre-treating release surface. For
that purpose, the tack between the softened front surface of the
base and the pre-treating release surface (e.g., a
polytetrafluoroethylene surface) can be exploited. In order to do
this residual air between the two surfaces should preferably be
removed while contacting and pressing the base to the pre-treating
release surface. The lengthwise heat-shrinkability of the base is
decreased to a suitable value while the crosswise
heat-shrinkability rate may (and preferably will) also be
decreased. The longer the contact time and higher the temperature,
the more the decrease in the heat-shrinkability will be, and
vice-versa.
[0126] It may be desirable if the length of the base at the start
of the process is not too much different from, or equivalent to,
the length of the fastener product made therefrom, at the end of
the process. As it was seen, this can be influenced by setting the
right lengthwise heat-shrinkability in the pre-treated base.
Therefore it is possible that in the pretreating process a
decreased value of lengthwise heat-shrinkability is achieved such
that the pre-treated base length is essentially the same as the
formed fastener length. Within this method step if the balance
decreased value can be continuously maintained by regulating,
during the pre-treating of the base, one or both of;
[0127] the temperature of the pre-treating release surface, and
[0128] the duration of the base contact with the pre-treating
release surface.
[0129] A practicable manufacturing arrangement using a pre-treating
step is using an endless release belt with a release outer belt
surface kept in a circulating motion along a belt path; and
[0130] for pre-treating the base a first portion of the outer belt
surface, being at a first location of the belt path, is used as the
pre-treating release surface; and
[0131] for forming the fastener from the pre-treated base a second
portion of the outer belt surface, being at a second location of
the belt path suitably displaced from the first location, is used
as the contact release surface; and
[0132] the base is provided in the form of a continuous base film
kept in a motion synchronous with the belt, and is contacted with
the outer belt surface at the first and second locations.
[0133] This solution is advantageous because a single release belt
is used for pre-treating the base and further producing the
fastener from the pre-treated base, which can provide for a zero
length-difference between the initial base and the final product.
This zero length-difference is desired to conveniently use the same
belt, running in all of its points with the same speed, for two
different purposes, i.e., for pre-treating the base on the one hand
and for depositing the particles to form preform projections and
contacting and fixing the pre-treated base therewith on the other
hand. The release surface speed at the first location is desirably
the same speed as the initial base speed and the release surface
speed at the second location is desirably the same speed of the
final formed fastener product. If the decreased value of lengthwise
heat-shrinkability of the base provided by the pre-treating
deviates from a balance value, this section of the base when in
free contact with the belt between the first and second belt
locations will tend to either get shorter or longer. That can be
detected by providing a base film buffer with dancing roller(s) and
detecting the trend of motion of the dancing roller(s). If the free
section of the base film between the two belt locations should
shorten then the lengthwise heat-shrinkability of the pre-treated
base could be decreased and vice versa. The lengthwise
heat-shrinkability of the pre-treated base can be decreased more by
elevating the temperature of the belt at the first location and/or
lengthening the first portion of the outer belt surface along which
the belt and the base are in contact thereby lengthening the
duration of the pre-treating of the base, and vice-versa. This
solution has an additional advantage that the outer release belt
surface is cleaned from any potential polymer particle
contamination by contacting the softened thermoplastic front
surface of the pre-treated base with the release belt with every
revolution of the belt.
[0134] It is further the object of the present invention to provide
a new fastener product, readily achievable through the methods
above, having corresponding advantages.
[0135] The product of the invention is a hook fastener for engaging
with a loop fabric, comprising a sheet-form base having a front
surface with a multiplicity of solid and preferably essentially
solid or rigid engaging projections. The engaging projections have
a top end and an attached end (which can also be termed throughout
as a foot). The attached end is joined to the base front surface at
a fixing portion. In that there is a fixing of the engaging
projections to the front surface of the base, the base and the
engaging projection can be formed of different materials or the
same materials. The engaging projections projecting from the base
front surface can be formed to have an essentially flat top by the
contact release surface. However, generally the top end has been
subject to a deformation treatment such that it has a different
form than the attached end of the engaging projection. If the
deformation surface and/or the contact release surface are flat
then the top end will be correspondingly flat as formed. The top
will also generally overhang the base at least partly, where the
overhanging portion is also referred to as a rim.
[0136] The top of the engaging projection as formed will also have
a definite edge bordering the top. The engaging projection will
also have a mantle surface, meeting the top along the edge,
extending from the edge of the top to the attached end of the
engaging projection at the front surface of the base. The mantle
surface and the top surface close to form acute edge angles
generally along the entire edge.
[0137] During use, the engaging projections should essentially
behave as solid bodies fixed to a base, which preferably is
flexible. As used herein, a strictly convex contour line of an
engaging projection, in a side view is convex when looking from the
outside and not straight. A strictly convex shape for the lower
surface of the overhanging rim or mantle surface has been found to
be beneficial because it gives a relatively large thickness to the
at least one engaging projection. In at least one side view of the
at least one engaging projection, the mantle surface is preferably
strictly convex at least at a part thereof adjacent to the edge.
This convex shape provides strength to the edge of the rim
overhanging the base. A convex shape also effectively leads
engaging fibers down towards the base, thereby reducing torque load
on the engaging projections and the base where they are attached,
as was discussed above. In a different preferred embodiment the
engaging projection is strictly tapered from the top to the front
surface of the base in at least one side view of the at least one
engaging projection.
[0138] The invention fastener has desired advantages. It can
provide good shear strength engagement with low loft loop fabrics,
including ultra thin nonwoven fabrics. It can also provide shear
strength in all directions and is therefore essentially isotropic.
The invention fastener can also be manufactured with dense and
small projections with generally flat tops and a flexible base
making it skin-friendly. There is great flexibility in selecting
the base relative to the particles forming the engaging
projections. The invention fastener can also be low cost.
[0139] Preferred forms of the product, some of them corresponding
to the preferable embodiments of the methods described above, can
offer various advantages.
[0140] First it is advantageous if the fastener engaging
projections, in at least one side view of the mantle surface are
strictly convex at least in all portions adjacent to the side edge.
Further, it is advantageous, if the fastener engaging projections
in each side view of the mantle surface are is strictly convex at
least in all portions adjacent to the side edge. It is also
advantageous if the fastener engaging projections, in each side
view strictly tapers from the top to the front surface of the base.
The mantle surface 17 and the top surface 14 of the engaging
projections define edge angles 18. These edge angles 18 are
advantageously along the entirety of the edge and have an angle of
between 15.degree. to 85.degree. or between 30.degree. and
80.degree.. It is further advantageous if the fastener engaging
projections 13, are strictly convex in at least one side view of
the entire mantle surface 17. This effectively leads the engaging
fibers down to the front surface 20 of the base 4, to reduce torque
load. It is further advantageous if the fastener comprises engaging
projections 13, which are strictly convex in each side view of the
entire mantle surface 17.
[0141] It is also advantageous if, the material of the front
surface of the base differs from the material of at least one
engaging projections mantle surface where they are attached. Such
an arrangement can be achieved by the use of base film and preform
projections comprised of different materials, with the use of
compatibilizing layers if necessary, as discussed previously. It is
even more advantageous if the material of the front surface of the
base is softer than the material of the mantle surface of the at
least one engaging projection as determined, for example, by
differing Shore hardness values.
[0142] It is also advantageous for some uses if the fastener base
is elastically extensible within a plane of the base, and the
material of the mantle surface of the at least one engaging
projection is non elastomeric. The base can comprise elastomer
materials including elastic laminates or the like. This can make an
elastic fastener product, which can be especially beneficial, for
example, with diapers and wrapping tapes.
[0143] In addition, the invention fastener can also be used in
other fields, such as in self adhesive fastener tapes for fixing
carpets or polymer sheets to floors or tiles and fabrics to walls
of a room.
[0144] The invention fastener can also be formed on the surface of
a variety of base materials. This could be a film as described
above but could be any suitable surface such as a fabric, nonwoven,
metal sheet or foil, molded plastic, paper, breathable film,
laminate etc, as described above for the first method. For example,
engaging projections could be formed on a water insulating membrane
used for insulating flat roofs of buildings against rain. This
membrane could then be fixed on top of a nonwoven felt on the roof.
This system would provide water insulation in combination with a
beneficial, lateral vapour migration in the felt, under the
insulating membrane.
[0145] As it has been said, it is a further object of the present
invention to provide improved disposable diapers using the
invention fastener.
[0146] In this aspect, a disposable diaper comprises:
[0147] a bodyside surface;
[0148] an opposite, outer surface, comprising a nonwoven
fabric;
[0149] at least one male fastening component of the present
invention for fixing the diaper about a wearer;
[0150] at least one female fastening component, comprising fabric,
for separably engaging with the at least one male fastening
component during the fixing. The female fastening component may be
formed by the nonwoven fabric on the outer surface of the diaper.
The separable engagement between the at least a portion of the
nonwoven fabric of the outer surface of the diaper and the at least
one male fastening component of the invention preferably has a
shear strength of at least 4.9N.
[0151] The term "diaper", as used herein, also includes infant
training pants, incontinence garments and the like. The said
portion of the nonwoven fabric of the outer surface can be a
strengthened portion where, the fibers of the nonwoven of the outer
surface take part in engaging with the male fastening component.
The said portion can be strengthened, for example, by providing a
sufficiently stiff film layer under the nonwoven or by impregnating
the nonwoven of the outer surface etc. The term "shear strength"
refers to a peak shear strength or force achieved during a shear
separation of the male fastener from the female fastener component.
An appropriate selection of the nonwoven on the outer surface of
the diaper and the male fastener component of the present invention
will result in the fastener being capable of engaging with the
nonwoven outer shell of the diaper strongly enough to securely keep
the soiled diaper in a folded state without a separately provided
loop. With a suitable selection of a nonwoven on the outer surface
of the diaper, the fastener can be attachable to any suitable point
of the diaper outer shell and the attachment of fixing is
comfortable and secure. Preferably, the whole of the nonwoven of
the outer surface is such a suitable nonwoven.
[0152] To make it even more secure, it is preferable if, in the
diaper, the separable engagement, between the engagable portion of
the nonwoven fabric of the outer surface and the at least one male
fastening component of the invention, has a shear strength of at
least 9.8 N.
[0153] In an even more preferable diaper, the at least one female
fastening component is constituted by at least a portion of the
nonwoven fabric of the outer surface.
[0154] Such a selection of the nonwoven of the outer surface of the
diaper, and the suitable kind of fastener makes using of a separate
frontal tape comprising a special loop fabric in the landing zone
unnecessary. This provides considerable cost saving. It just needs
a suitable surface area selected for the fastener to achieve a
desired fixing strength for securing the diaper around a wearer
during use.
[0155] It is even more preferable, if in the latter diaper, the
separable engagement between at least a portion of the nonwoven
fabric of the outer surface of the diaper and the at least one
invention male fastening component has a shear strength of at least
2.5 N/cm.sup.2. Here the necessary shear strength is specified as a
shear strength specific of 1 cm.sup.2 unit area of contact surface
between the nonwoven and the fastener.
[0156] To make it even more secure, it is further preferable if, in
the diaper, the separable engagement, between at least a portion of
the nonwoven fabric of the outer surface and the at least one male
fastening component, has a shear strength of at least 3.5
N/cm.sup.2.
[0157] It is a further object of the present invention to provide
an improved wrapping tape. Such wrapping tape has a first side with
an exposed textile or nonwoven material, and an opposite second
side, comprising a male fastening component of the present
invention suitable for engaging with the textile or nonwoven
material for fixing the wrapping tape around an object. The textile
or nonwoven material also includes low loft fabrics with some free
fibers capable of mechanically engaging with the male fastener
materials of the present invention. The advantages of this wrapping
tape are that it has fine touch, is easy to write upon with ink,
can be flexible, extensible or stretchable, is inexpensive, and is
novel in its appearance. With a porous, e.g., micro-perforated or
nonwoven, base and a suitable nonwoven loop textile, this wrapping
tape even be used as house wrap.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0158] Reference is made to the method depicted in FIG. 1a. Using a
subset method of the invention, polymer powder granules are
provided, as polymer particles 36. A base 4 sheet is fed into the
system from a suitable source. A contact release surface 40 is
provided on a release conveyor 39 that is driven around two drive
rollers 11. The contact release surface 40 is kept horizontal.
[0159] At the beginning of the operation cycle, the horizontal
contact release surface 40 is kept at an elevated temperature by a
hot plate 24. This could be done under the release conveyor 39,
though further hot chambers, on the top side of a release conveyor,
could also be utilized. A scatter unit 42 is used to evenly
disperse the polymer particles 36 onto a stationary mask 31, (a
perspective view of a possible stationary mask 31 is shown in FIG.
1b), with solid regions 33 intersecting falling particles and open
areas 32 allowing particles to fall onto the moving release surface
40 in a predetermined pattern. The mask could also in this version
be apertures built into the scatter unit 42. With a stationary mask
the particles will be deposited in continuous rows in the
continuous method shown in FIG. 1a. The rows can be made
discontinuous by interrupting the flow of particles for a period of
time. The rows can be made to oscillate if the stationary mask is
moved in the crossweb direction in a oscillatory fashion. The
particles are distributed on the contact release surface 40 to form
preform projections 37. The release surface 40 can be cooled prior
to the heating element 24. Cooling is also important for later
preserving the contact angle of the preform projections 37, and can
be provided by a steel cooling plate 45 at a controlled temperature
under the contact release surface 40. The cooled preform
projections 44 are made solid and suitable for contacting with the
front surface 20 of the base 4. The base 4 is laid over the preform
projections 44 on the contact release surface 40. The front surface
20 of the base 4 contacts the terminal ends of the preform
projections 44. A hot air blowing unit 23 can be fixed above the
back surface 3 of the base 4. Hot gas 21 is blown on the back
surface 3 of the base 4, which could be done while the release
conveyor 39 and the base 4 are together kept in motion in a lateral
direction 25. Each point of the base 4 is exposed to the hot air
for a time sufficient to soften and fix the terminal ends of the
preform projections 44 to the front surface 20 of the base 4. Then
the base 4 is cooled, which could be done by air blower 12. The
base 4, with the engaging projections 13 fixed thereto, is
separated and removed from the contact release surface 40, and is
then wound up on a reel (not shown).
[0160] Using this method the engaging projections 13 formed will
have flattened tops 14, with a rim overhanging the base 4 typically
in all directions, and bordered, typically all around, by an edge
15 whose angle 18 essentially corresponds to the contact angle 38.
The vast majority of the engaging projections 13 will strictly
taper (strictly convex), in each side view thereof, from the
flattened top 14 to the attached end 16 at the front surface 20 of
the base 4 (This also applies to the engaging projections discussed
hereafter).
[0161] Reference is made to the method depicted in FIG. 2a. Using a
subset method of the invention polymer powder granules are
provided, as polymer particles 36. A base 4 sheet is fed into the
system from a suitable source. A contact release surface 40 is
provided on a release conveyor 39 that is driven around two drive
rollers 11. The contact release surface 40 is kept horizontal. A
moving mask 41 is provided in the form of an endless belt.
[0162] At the beginning of the operation cycle, the horizontal
contact release surface 40 is kept at an elevated temperature by a
hot plate 29. This could be done under the release conveyor 39,
though further hot chambers, on the top side of a release conveyor,
could also be utilized. A scatter unit 42 is used to evenly
disperse the polymer particles 36 onto the moving mask 41 (A
perspective view of a possible moving mask 41 is shown in FIG. 2b.
This mask would serve to deposit particles in a pattern of squares
and circles). Solid regions 33 of the mask 31 intersect falling
particles and open areas 46 of the mask 31 allow particles to fall
onto the release surface 40 in a predetermined pattern determined
by the mask when the moving mask 41 and the contact release surface
40 are moving at the same relative speeds. With a moving mask the
particles can be deposited in discrete shapes in the continuous
method shown in FIG. 2a. In this case the mask should be rotating
at approximately the same speed as the release surface 40, at least
such that the particles from one mask open area 46 do not end up
getting randomly scattered on the release surface 40 or merged with
particles from an adjacent open area 46. If it is desired to
provide the shaped regions (e.g. squares, circles, etc.) with
minimum distortion, the mask should move in tandem with the contact
release surface; that is, at very close to the same speed. The
regions with particles could be distributed in other patterns if
the moving mask rows are made to oscillate or move in the in the
cross direction. As in the method of FIG. 1, the particles are that
are distributed on the contact release surface 40 form preform
projections 37, then form cooled preform projections 44, then are
contacted with and attached to the front surface 20 of base 4, as
described for the embodiment of FIG. 1. Particles that intersect
the solid areas 43 of mask 41 may be removed, for example by
contacting the moving mask with a sticky roll, vacuum agitation or
the like. Ideally the particles are removed for recycling to the
scatter unit 42, for example by use of vacuum scavenging system
45.
[0163] A further subset method is depicted in FIG. 3a. A first type
of polymer powder granules are provided, as polymer particles 36. A
base 4 sheet is fed into the system from a suitable source. The
contact release surface 40 is provided on a release conveyor 39
which is driven around two drive rollers 11. The contact release
surface 40 is kept horizontal. A first moving mask 41 and a second
moving mask 41' are provided in the form of endless belts.
[0164] At the beginning of the operation cycle, the horizontal
contact release surface 40 is kept at an elevated temperature by a
hot plate 24. This could be done under the release conveyor 39,
though further hot chambers, on the top side of a release conveyor,
could also be utilized. In a first deposition station 88, a first
scatter unit 42 is used to disperse the polymer particles 36 onto
the first moving mask 41 (A perspective view of a first moving mask
41 is shown in FIG. 3b.). Solid regions 33 of the mask intersect
falling particles and open areas 46 allow particles to fall onto
the contact release surface 40 in a predetermined pattern. Movement
of the mask 41 with the contact release surface can be synchronized
as described in the method of FIG. 2a. The particles so deposited
form the first type of preform projections 37 in discrete areas on
the contact release surface. Optionally, the deposited preform
projections 37 can be cooled as previously described. The contact
release surface 40 is then passed through a second deposition
station comprising a second moving mask 41' and a second scatter
unit 42' which is used to disperse a second type of polymer powder
granules 36' (A perspective view of a possible second moving mask
41' is shown in FIG. 3c). Solid regions 33 of the mask intersect
falling particles and open areas 46 allow particles to fall onto
the release surface 40 in second areas of the contact release
surface in a predetermined pattern. Movement of the second mask is
synchronized with the contact release surface as done with the
first mask. The contact release surface may be heated (or reheated,
if a cooling step was used subsequent to the first deposition) via
second heating element 24 as done for the first deposition. The
particles so deposited form the second type of preform projections
37'. The contact release surface bearing the preform projections is
then passed by cooling element 45 so as to form cooled preform
projections 44 and 44', after which base 4 is contacted with the
terminal ends of the cooled preform projections attaching them to
the base and forming engaging elements 13 and 13', in the manner
described for the embodiment of FIG. 1a. Vacuum scavenging systems
(not shown) as described in FIG. 2a may be used to retrieve the
polymer particles that intersected the solid areas 33 of mask 41.
This embodiment would serve to provide a base film bearing rows of
discrete circles of engaging projections of one type, and discrete
squares of engaging projections of another type.
[0165] The method depicted in FIG. 4a is a further first subset
method of the invention. Using this method of the invention polymer
powder granules are provided, as polymer particles 36'. A base 4
sheet is fed into the system from a suitable source. The contact
release surface 40 is provided on a release conveyor 39 that is
driven around two drive rollers 11. The contact release surface 40
is kept horizontal. An electrostatic deposition unit 52 is
provided, comprising two electrodes. Electrode 54 is held at low
voltage (typically, zero or ground voltage) while electrode 53 is
held at a higher voltage. Electrode 53 is positioned underneath a
moving mask 41 while electrode 54 is positioned above a contact
release surface 40. Moving mask 41 is provided with solid regions
43 and with open areas 46, and can be synchronized with the speed
of contact release surface 40 as described above.
[0166] At the beginning of the operation, particles 36 are
dispensed into a vertically configured electrostatic deposition
unit 52 (not shown) such as by being injected laterally into the
gap between lower plate 53 and moving mask 41. This may be done by
means of e.g. spraying the particles or bringing them into the gap
via a belt conveyor from which the particles are dislodged by the
electric field. Or, the electrode 53 could be a rotating drum
electrode, a belt electrode or the like for both conveying and
charging the particles. Under the influence of the electric field
established by electrodes 53 and 54, particles 36 develop a charge
to comprise charged particles 36', and are then driven vertically
upwards. The charged particles 36' that penetrate through the open
areas of moving mask 41 continue to move upwards until they impinge
on contact release surface 40. The charged particles may be held on
the contact release surface 40 against the force of gravity by the
residual electrostatic force between the particles and the contact
release surface until the contact release surface moves such that
the particles are atop the release conveyor and no such assistance
is necessary. The release conveyor then continues such that the
particles are carried into proximity with heating element 24 (as in
the configuration illustrated in FIG. 4a). Alternatively, heating
element 24 can be placed such that the particles 36' are heated
immediately upon deposition (as in the embodiment described with
reference to FIG. 1), so that wetting forces may assist in holding
the particles on the release surface, until the release conveyor 39
moves sufficiently such that the particles 36' are on the upward
facing surface of the release conveyor 39. Subsequent processing to
contact and attach the preform projections 36' to the base film are
as described previously. Particles that intersect solid areas 43 of
mask 41 may fall off on their own due to gravity (once the moving
mask carries them out of the electric field), or can be removed
such as with a vacuum scavenging system as described for FIG.
2a.
[0167] The method depicted in FIG. 5a is a further subset method of
the invention This method is similar to that of FIG. 4a except that
no mask is used; rather, electrode 54 is provided as a rotating
patterned belt electrode, e.g. a metal belt electrically connected
to counterpart electrode 53. Moving belt electrode 54 is positioned
behind (above) the moving contact release surface 40 and is
typically synchronized to move at the a matching speed as discussed
above. In one embodiment, electrode 54 comprises a metal belt that
has regions 46 cut out, as shown in the perspective view of FIG.
5b. Using a method of the invention, polymer powder granules are
injected into the gap between lower electrode 54 and contact
release surface 40 and develop a charge. The charged polymer
particles 36' will then be driven upwards, concentrating
preferentially along lines that are aligned with solid sections 33
of belt electrode 54 (i.e. being less concentrated along lines that
align with the cutout holes in electrode 54). The particles thus
impinge on release surface 40 in a pattern corresponding to that
established by the patterned belt electrode 54. In an alternative
embodiment, electrode 53 can also be a patterned moving belt
electrode, and can move in tandem with electrode 54, so as to
achieve further concentration of the particles in the desired areas
of the contact release surface. Further processing of the particles
on base sheet 4 is as described with regard to FIG. 4a (In this
instance there is no mask from which particles need be
removed.)
[0168] The method depicted in FIG. 6a is a subset method of the
invention. Using this method of the invention, polymer powder
granules are provided, as polymer particles 36. A base 4 sheet is
fed into the system from a suitable source. The base 4 sheet in
this embodiment is provided with regions 5 (FIG. 6b) that will
preferably bond to the preform projections and areas 6 that will
preferably not bond to the preform projections (as shown in FIG.
6b). The contact release surface 40 is provided on a release
conveyor 39 that is driven around two drive rollers 11. The contact
release surface 40 is kept horizontal. No mask is used.
[0169] At the beginning of the operation cycle, the horizontal
contact release surface 40 is kept at an elevated temperature by a
hot plate 24. This could be done under the release conveyor 39,
though further hot chambers, on the top side of a release conveyor,
could also be utilized. A scatter unit 42 is used to evenly
disperse the polymer particles 36 onto the release surface 40. The
particles are distributed on the contact release surface 40 to form
preform projections 37. Cooling is provided by a cooling plate 45
at a controlled temperature under the contact release surface 40
forming cooled preform projections 44. The cooled preform
projections 44 are made solid at least in part. The base 4 is laid
over the preform projections 44 on the contact release surface 40.
The front surface 20 of the base 4 contacts the terminal ends of
the preform projections 44. A hot air blowing unit 23 can be fixed
above the back surface 3 of the base 4. Hot gas 21 is blown on the
back surface 3 of the base 4, which could be done while the release
conveyor 39 and the base 4 are together kept in motion in a lateral
direction 25. Each point of the base 4 is exposed to the hot air
for a time sufficient to soften and fix the terminal ends of the
preform projections 44 to the front surface 20 of the base 4. The
base is then cooled which could be done by air blower 12. The base
4, together with the engaging projections 13 fixed thereto, in the
regions 5 that will preferably bond to the preform projections 44,
is separated and removed from the contact release surface 40.
Unbonded preform projections 44 on nonbonding areas 6 of the base
film 4, or on the contact release surface 40, may be removed such
as by vacuum removal device 49 or by sticky rolls.
[0170] The method depicted in FIG. 7a is a further subset method of
the invention. Using this method of the invention, polymer powder
granules are provided, as polymer particles 36. A base 4 sheet is
fed into the system from a suitable source. The base 4 sheet in
this embodiment is masked using a transfer masking belt 71 provided
with open areas 75 that will allow the preform projections to
contact the base sheet 4 and solid areas 76 that will not allow
preform projections to contact base sheet 4 (In this configuration
the masking belt 71 should be sufficiently thin that the preform
projections are able to protrude or pushed through the open areas
so as to contact the base sheet.). One such belt is shown n FIG.
7b. The contact release surface 40 is provided on a release
conveyor 39 that is driven around two drive rollers 11. The contact
release surface 40 is kept horizontal.
[0171] At the beginning of the operation cycle, the horizontal
contact release surface 40 is kept at an elevated temperature by a
hot plate 24. This could be done under the release conveyor 39,
though further hot chambers, on the top side of a release conveyor,
could also be utilized. A scatter unit 42 is used to evenly
disperse the polymer particles 36 onto the release surface 40. The
particles are distributed on the contact release surface 40 to form
preform projections 37. Cooling is provided by a cooling plate 45
at a controlled temperature under the contact release surface 40 so
as to form cooled preform projections 44. The cooled preform
projections 44 are made solid and suitable for contacting with the
front surface 20 of the base 4. The base 4 is laid over the preform
projections 44 on the contact release surface 40. The front surface
20 of the base 4 contacts the terminal ends of the preform
projections 44 through the open areas 75 provided in the transfer
masking belt 71. A hot air blowing unit 23 can be fixed above the
back surface 3 of the base 4. Hot gas 21 is blown on the back
surface 3 of the base 4, which could be done while the release
conveyor 39 and the base 4 are together kept in motion in a lateral
direction 25. Each point of the base 4 is exposed to the hot air
for a time sufficient to soften and fix the terminal ends of the
preform projections 44 to the front surface 20 of the base 4. Then
the base is cooled which could be done by air blower 12. The base
4, together with the engaging projections 13 fixed thereto in the
areas open, through the open areas 75 is separated and removed from
the contact release surface 40, which could then wound up in a
reel. Any remaining preform projections 44 on the contact release
surface or on the transfer masking belt 71 may be removed by a
removal device such as described for FIG. 6a.
Example
Method for Discrete Deposition of Particles on a Base Film
[0172] A process was set up similar to that depicted in FIG. 2a. A
contact release surface was provided comprising a
polytetrafluoroethylene-coated glass fiber web, with a slightly
textured surface, available from Lorincz kft, Hungary, under the
designation Chemglas 100-6. The surface energy of the contact
release surface 40 was about 18.5 mJ/m.sup.2. The contact release
surface was present as a horizontal sheet on the top surface of a
shuttle that could be moved laterally, in order to simulate the
continuous belt conveyor system of FIG. 2a.
[0173] Polypropylene particles of size range of about 200-500
microns diameter were placed into a gravity-operated scatter unit
(a hopper with a feeding wheel and an underlying screen).
[0174] At the beginning of the operation cycle, the horizontal
contact release surface was brought to a temperature of about
170.degree. C. by a heating element located underneath the conveyor
shuttle. A masking template with discrete shape patterns similar to
that shown in FIG. 2b was placed on the top of the contact release
surface 40. The shuttle was moved laterally at approximately 0.17
meters per second underneath the scatter unit, which was used to
disperse the polymer particles on the heated contact release
surface at an average density of about 16 g/m.sup.2 in the particle
deposited regions. The particles were heated by the heat of the
contact release surface and thereby softened or melted into a
semiliquid state. Several seconds after the particles were
distributed on the release surface, they formed preform
projections. Then the release surface was moved over a cooling
plate and halted in position so as to cool the contact release
surface to a temperature of about 70.degree. C. The preform
projections were thus made solid and suitable for contacting with
the front surface of a base film.
[0175] A base film was provided comprising a polypropylene film
with a basis weight of 74 g/m.sup.2 (available under product
designation FL-3054 from 3M Company, St Paul, Minn.). The base film
was laid over the preform projections on the contact release
surface such that the front surface of the base contacted the
terminal ends of the preform projections. A hot air blowing unit
which was fixed about 15 mm above the back surface of the base
film, was used to blow air at a measured temperature of about
600.degree. C. against the back surface of the base. The shuttle,
which carried the release contact surface with the preform
projections and base film, was moved laterally at approximately
0.17 meters per second underneath the hot air blowing unit. Each
point of the base was thus exposed to the hot air, for a short
period (typically one second or less), such that the base was
softened enough to be fixed with the terminal ends of the preform
projections. The terminal ends also melted from the heat to a
suitable extent to fuse the preform projections to the base. The
base film with attached projections was then cooled. The base,
together with the engaging projections fixed thereto, was then
removed from the contact release surface.
* * * * *