U.S. patent number 3,694,867 [Application Number 05/061,352] was granted by the patent office on 1972-10-03 for separable clasp containing high-loft, non woven fabric.
This patent grant is currently assigned to Kimberly-Clark Corporation. Invention is credited to Robert J. Stumpf.
United States Patent |
3,694,867 |
Stumpf |
October 3, 1972 |
SEPARABLE CLASP CONTAINING HIGH-LOFT, NON WOVEN FABRIC
Abstract
A separable clasp comprising a male fastening member and a
female fastening member wherein the female member contains a
plurality of upstanding loops and the male member contains a
plurality of upstanding functional elements such as hooks or beaded
stems which can engage with the loops of the female member. The
female member is comprised of a high-loft, nonwoven fabric
comprising a substantially continuous backing layer of consolidated
flexible adhesive, and a multiplicity of staple length fibers
looped outwardly from said backing layer with the ends of such loop
imbedded in said backing layer, and said loops being twisted to be
in planes extending in the cross direction of the fabric.
Inventors: |
Stumpf; Robert J. (Appleton,
WI) |
Assignee: |
Kimberly-Clark Corporation
(Neenah, WI)
|
Family
ID: |
22035237 |
Appl.
No.: |
05/061,352 |
Filed: |
August 5, 1970 |
Current U.S.
Class: |
24/448 |
Current CPC
Class: |
A44B
18/0034 (20130101); Y10T 24/2758 (20150115) |
Current International
Class: |
A44B
18/00 (20060101); A44b 017/00 () |
Field of
Search: |
;24/204,21V |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gelak; Bernard A.
Claims
I claim as my invention:
1. In a separable clasp comprising a male fastening member and a
female fastening member, said female member containing a plurality
of loops and said male member containing a plurality of functional
elements which engage with the loops of the female member such that
it is difficult to separate the clasp by means of a shearing force
but that a peeling force can readily effect separation, the
improvement wherein the female member is comprised of a high-loft,
nonwoven fabric comprising a substantially continuous backing layer
of a consolidated open pattern of flexible adhesive, and a
multiplicity of staple length fibers, each of which are
individually looped outwardly from said backing layer with the ends
of each loop embedded in said backing layer, and said loops being
twisted to be in planes extending in the cross direction of the
fabric.
2. The separable clasp of claim 1 wherein the loops of the
high-loft, nonwoven fabric vary in height throughout the
fabric.
3. The separable clasp of claim 1 wherein the loops of the
high-loft, nonwoven fabric vary regularly in height throughout the
fabric.
4. In a separable clasp comprising a male fastening member and a
female fastening member, said female member containing a plurality
of loops and said male member containing a plurality of functional
elements adapted to engage the loops of the female member such that
it is difficult to separate the clasp by means of a shearing force
but that a peeling force can more easily effect separation, the
improvement wherein the female member is comprised of a high-loft,
nonwoven fabric comprising a substantially continuous backing layer
of consolidated flexible adhesive and a multiplicity of staple
length fibers each of which are individually looped outwardly from
said backing layer with the ends of each loop embedded in said
backing layer, each of said loops being twisted to lie in planes
extending in the cross direction of the fabric, said loops varying
in height regularly throughout the fabric and presenting a
plurality of loops extending above the average height of all of
said loops, said loops extending above said average height being
adapted to readily engage said functional elements of said male
member when said members were pressed into mutual engagement.
5. In a separable clasp comprising a male fastening member and a
female fastening member, said female member containing a plurality
of loops and said male member containing a plurality of functional
elements adapted to engage the loops of the female member such that
it is difficult to separate the clasp by means of a shearing force
but that a peeling force can more easily effect separation, the
improvement wherein the female member is comprised of a high-loft,
nonwoven fabric comprising a substantially continuous backing layer
of consolidated flexible adhesive and a multiplicity of staple
length fibers each of which are individually looped outwardly from
said backing layer with the ends of each loop embedded in said
backing layer, each of said loops being twisted to lie in planes
extending in the cross direction of the fabric, said loops varying
in height regularly throughout the fabric, the lower of said loops
tending to fill around and thereby support the higher loops so that
the top surface of the fabric is formed by the tops of the higher
loops, the higher loops being adapted to readily engage said
functional elements of said male member when said members are
pressed into mutual engagement.
6. The separable clasp of claim 5 wherein said fibers are heat set
in their looped condition such that said loops are less susceptible
to collapse or distortion due to repeated openings and closings of
said clasp.
7. The separable clasp of claim 6 wherein said heat set fibers are
polyester.
8. The separable clasp of claim 5 wherein said fibers have a denier
within the range of about 1.5 to about 15.
9. The separable clasp of claim 8 wherein said fibers have a denier
within the range of about 4 to about 8.
10. In a separable clasp comprising a male fastening member and a
female fastening member, said female member containing a plurality
of loops and said male member containing a plurality of functional
elements adapted to engage the loops of the female member such that
it is difficult to separate the clasp by means of a shearing force
but that a peeling force can more easily effect separation, the
improvement wherein the female member is comprised of a high-loft,
nonwoven fabric comprising a substantially continuous backing layer
of consolidated flexible adhesive and a multiplicity of staple
length fibers each of which are individually looped outwardly from
said backing layer with the ends of each loop embedded in said
backing layer, each of said loops being twisted to lie in planes
extending in the cross direction of the fabric, said loops varying
in height regularly throughout the fabric, and occurring in
sufficient density whereby the lower of said loops fill around and
maintain the upper loops in a generally perpendicular position
relative to the plane of said backing layer, said functional
elements of said male member being readily engaged with said higher
loops when said members are brought into mutual engagement subject
to a lower contact pressure and engaged with said lower loops when
said contact pressure is increased.
Description
DESCRIPTION OF THE INVENTION
During the past several years, the use of a new type of separable
clasp has steadily increased in applications where customary
buckles, zippers, buttons, or conventional sewing had previously
been employed. The clasp is perhaps best represented by those sold
under the trade name "Velcro." Such clasps consist of two parts
which when placed together resist separation when subjected to a
shearing force but which can be readily separated by peeling. One
of the parts is typically referred to as the male member and
consists of a fabric containing a plurality of upstanding hook
shaped elements. The other part of the clasp is the female member
and consists of a fabric containing on its surface a plurality of
upstanding loops. When the two members are pressed into
face-to-face contact the hooks engage the loops and it is very
difficult to separate the two parts by means of shearing forces.
However, since the hooks are generally prepared from a resilient
plastic material, when a peeling force is applied disengagement can
be easily effected since, under peeling, the hooks will readily
open.
It is an object of the present invention to provide a new separable
clasp having characteristics as above-described wherein the female
member is inexpensive to manufacture.
With respect to clasps as above-described it is desirable to
provide the purchases with a wide selection of clasps with varying
degrees of fastening tenacity. Such a selection is desirable since
for some applications such as a buckle replacement for trousers a
high degree of tenacity is required, whereas for other applications
such as a neck closing for gowns where a large amount of stress is
not present only a small amount of fastening tenacity is necessary.
One manner in which fastening tenacity can be modified is through a
modification of the loop structure of the female member. Clasps
containing a female member with a high loop density wherein the
loops are large generally have higher fastening tenacity than when
the female member contains sparsely spaced loops of low height.
Accordingly, it is a further object of the present invention to
provide a female clasp member which can be economically prepared by
a process which has a high degree of flexibility with respect to
changing loop density and loop height.
Other objects and advantages of the invention will become apparent
upon reading the following detailed description and upon reference
to the drawings, in which:
FIG. 1 is a schematic view, in side elevation, of one form of
apparatus which can be employed to prepare the high-loft, nonwoven
fabrics useful in the present invention;
FIG. 2 is a fragmentary plan view of an illustrative web of base
material while still supported on a conveyor belt somewhat
simplified and exaggerated for the sake of clarity of illustration,
with portions broken away to expose the various layers;
FIGS. 3a and 3b are greatly enlarged, simplified, and somewhat
exaggerated sectional views of commercially available male clasp
members.
FIGS. 4 and 5 are greatly enlarged, simplified, and somewhat
exaggerated sectional views taken in the directions indicated of
the fabric prepared with the apparatus illustrated in FIG. 1.
FIG. 6 is an enlarged schematic detail view, in side elevation, of
the forming drum and gathering blade of the apparatus shown in FIG.
1;
FIG. 7 is an enlarged schematic side elevational view illustrating,
in somewhat idealized fashion, successive stages in the sequence of
gathering and looping of individual fibers;
FIG. 8 is an enlarged schematic fragmentary view, taken
substantially along the line 8--8 of FIG. 7, here showing a
fragment of the fiber web and adhesive pattern with illustrative
fibers attached to the adhesive;
FIG. 9 is a simplified schematic view, taken substantially along
the line 9--9 of FIG. 7, here showing the fragment of the fiber web
and adhesive pattern depicted in FIG. 8 at a later stage in the
loop forming sequence;
FIG. 10 is a photographic reproduction of a sample of one form of
high-loft, nonwoven material made in accordance with the
description contained herein.
FIGS. 11 and 12, respectively, are enlarged photographic
reproductions of longitudinal and transverse sectional views of the
material shown in FIG. 10;
While the invention is susceptible of various modifications and
alternative forms, specific embodiments thereof have been shown by
way of example in the drawings and will herein be described in
detail. It should be understood, however, that it is not intended
to limit the invention to the particular forms disclosed, but, on
the contrary, the intention is to cover all modifications,
equivalents and alternatives falling within the spirit and scope of
the invention as expressed in the appended claims.
Briefly stated, the present invention centers on the discovery that
certain of the new high-loft, nonwoven fabrics described in my
co-pending application, Ser. No. 31,225, filed Apr. 23, 1970, which
is a continuation-in-part of U.S. application, Ser. No. 769,959,
filed Oct. 23, 1968, which is now abandoned, are particularly
suitable for use as the female member in a separable clasp such as
previously described. Particularly useful are those high-loft,
nonwoven fabrics described in Ser. No. 31,225 which are comprised
of a substantially continuous backing layer of consolidated
flexible adhesive and a multiplicity of staple length fibers looped
outwardly from said backing layer with the ends of each loop
imbedded in said backing layer, and said loops being twisted to lie
in a plane extending in the cross direction of the fabric. Female
clasp members of such fabrics can be inexpensively prepared.
Moreover, the height and density of the loops contained in the
fabric can be easily varied and, accordingly, a clasp with any
desired degree of fastening tenacity can be conveniently fashioned.
Those fabrics described in my aforementioned application wherein
the loops vary in height throughout the fabric are particularly
preferred here for use as a female member in a separable clasp.
As described in detail in my co-pending application, Ser. No.
31,225, high-loft, nonwoven fabrics can be prepared by taking a
base web of fibers, applying to one side of the web an open pattern
of adhesive, and then imbedding the fibers in the adhesive.
Different procedures can be used in preparing the base web. For
example, textile length fibers may be processed through
conventional cotton card machinery to produce a carded web for the
base web. In such a carded web 50 to 70 percent of the fibers may
be oriented substantially parallel with the machine direction. It
has been found, however, that the most uniform product has been
obtained by using base webs having a higher percentage of the
fibers alined with the machine direction such, merely by way of
example, as a highly drafted web in which, as a result of the
drafting process, 80 to 95 percent of the fibers may be alined with
the machine direction.
After obtaining the adhesive containing base material, the high
loft, nonwoven fabric is prepared by preforming the subsequent
steps of: 1) reactivating the open pattern of adhesive in which the
fibers are imbedded and, 2) consolidating the adhesive into a
substantially continuous backing layer, while 3) simultaneously
looping the portions of the fibers across the open spaces of the
adhesive outwardly from the backing layer formed by the
consolidated adhesive. The resulting product is characterized by
the high loft or deep pile of the loops of fibers which extend
outwardly from the adhesive backing. The particular depth of pile
or degree of loft of the loops, of course, depends upon a
combination of control parameters including, for example: the type
and denier of the base fibers; the amount and spacing of the
original adhesive pattern; the angle of the gathering balde; and
the relative speeds of fiber delivery to and fabric discharge from
the gathering blade; as will be discussed below.
Turning now to the drawings, FIG. 1 schematically illustrates an
exemplary apparatus for preparing the fabrics useful herein as
female clasp members. This apparatus includes a web forming section
10 and an adhesive compacting and fiber looping section 30. As
shown in FIG. 1, multiple silvers 11 of textile fibers are drawn
from their respective supply cans (not shown) into a draw frame 12
which comprises a series of pairs of grooved rolls 13; the rolls of
each pair being driven by appropriate gearing (not shown, but well
known in the art) at a peripheral rate of speed somewhat faster
than the rate of operation of the preceding pair. Merely by way of
example, the pairs of rolls 13 may be adjusted to provide an
over-all increase in speed and, therefore, an extent of fiber draw
on the order of 15:1 through the draw frame 12. As the juxtaposed
slivers pass through draw frame 12, the individual fibers are
drafted and spread out to form a flat, striated web of
substantially alined fibers as shown at 14. Web 14 is maintained
adjacent a supporting conveyor sheet 15 on the surface of which
adhesive has been previously applied in a preselected pattern.
In this embodiment, the conveyor sheet 15 comprises an endless
conveyor belt treated on at least its upper surface with a release
agent. One example of such a belt comprises woven glass fiber with
a surface coating of tetrafluoroethylene resin. Other examples of
release coatings are well known, and comprise such materials as
silicone, fatty acid metal complexes, certain acrylic polymers, and
the like. Heat resistant films or thin metal sheets treated with
release agents may also be used as the carrier sheet.
Prior to the time the web 14 is picked up by the belt 15, the
latter has imprinted on its release-treated surface a pattern of
flexible, thermoplastic adhesive such as is shown at 16 in FIG. 2.
It will be understood that, as shown in FIG. 1, the adhesive is
actually on the underside of belt 15 which becomes the upper
surface after passing around roll 17, at which time the adhesive
pattern 16 directly contacts the fiber web 14. The pattern is shown
as being visible in FIG. 2 only for illustrative purposes.
The belt 15 is fed around roll 17 at a speed slightly in excess of
the delivery speed of the final pair of rolls 13 of draw frame 12
in order to maintain web 14 under slight tension, whereby the
individual highly drafted fibers are retained in their alined and
tensioned condition. Drive rolls 18, 19 are rotated (by suitable
drive means, not shown) to drive belt 15 at a speed sufficient to
maintain the proper tension on the web 14.
In the method shown for applying adhesive, the belt 15 is fed
through a nip formed between a printing roll 20 and a back-up roll
21 maintained in very light pressure engagement therewith. The
surface of printing roll 20 is provided with an intaglio pattern to
which adhesive may be supplied in various ways well known to those
skilled in the art. For example, in patent application, Ser. No.
769,959, a system is schematically disclosed wherein the lower
portion of the printing roll 20 picks up adhesive directly from a
dip pan, with excess adhesive being removed by a doctor blade, thus
leaving only the intaglio patterned surface filled. However, in the
practice of the present invention, it has been found that more
satisfactory results are obtained by pumping or otherwise
transferring adhesive 22 from a supply pan 23 to a reservoir
located immediately above an inclined doctor blade 24--the
reservoir being defined in part by the upper surface of the
inclined doctor blade and the adjacent portion of the rotating
peripheral surface of the printing roll 20. Thus, as the printing
roll 20 rotates (in a counterclockwise direction as viewed in FIG.
1), the intaglio patterned surface thereof is filled with adhesive
22, excess adhesive is removed by the doctor blade 24, and a
metered amount of adhesive is then transferred to the underside of
release coated belt 15 in a preselected pattern. The pattern shown
in FIG. 2 is in the form of an open diamond pattern of
adhesive.
The particular dimensions of the intaglio pattern employed and,
indeed, the actual pattern itself, are not critical in the
preparation of fabrics useful as female clasp members. Thus,
patterns other than the illustrative diamond pattern hereinabove
referred to can be utilized as will hereinafter be discussed. For
illustrative purposes, however, it is noted that excellent results
have been achieved where a diamond pattern was employed in which
adjacent lines of adhesive were spaced apart in both directions by
one-half inch, and wherein the intaglio printing roll 20 had
adhesive cells or lines 0.010 inch deep and 0.050 inch wide.
Since the surface of belt 15 is treated with a release coating, the
adhesive remains substantially on the surface with no penetration
therein and is preferably in a somewhat tacky condition. The
printed belt is drawn from the printing nip around roll 17
positioned closely adjacent the output end of draw frame 12 and, as
stated above, at a speed slightly in excess of the delivery speed
of the last two rolls in the draw frame. The web 14 emerging from
the draw frame 12 is deposited on the tacky adhesive 16 on belt 15
and held in tensioned engagement therewith by the adhesive and the
above-mentioned speed differential. This continuous tension
prevents the fibers in the web from losing their highly-drafted and
alined condition.
Following deposit of web component 14 on the adhesive printed belt
15, the belt is drawn around a heated curing drum 29 where fusing
and curing of the adhesive is substantially completed while the web
14 is maintained in firm contact therewith to bond the individual
fibers. To insure effective heating and fusing of the adhesive, it
is desirable that travel of the combined belt and web be around a
substantial portion of the drum 29. In the illustrated embodiment,
a fly roll 29a is positioned to apply tension on the combined belt
and web as they travel around the drum 29 to insure complete
imbedment of the fibers in the adhesive. The fibers of the web 14
are thus bonded together while retaining their highly drafted and
substantially alined condition in the particular pattern in which
they were deposited on the open pattern of adhesive 16 printed on
the belt 15.
After leaving the fly roll 29a, the combined web 14 and belt 15 are
preferably passed over the drive roll 19, which also serves as a
cooling drum to set the adhesive. The bonded web 14 is stripped
from the release-coated surface of the belt 15 by the guide roll 31
as the web leaves the cooling drum 19.
While various well-known adhesives may be employed in the foregoing
process, advantages reside in the use of plastisols, which are
colloidal dispersions of synthetic resins in a suitable organic
ester plasticizer, and which, under the influence of heat, provide
good binding power while remaining soft and flexible. While many
adhesives of this type are known, those found particularly useful
for incorporation in the product of this invention include vinyl
chloride polymers, and copolymers of vinyl chloride with other
vinyl resins, plasticized by organic phthalates, sebacates, or
adipates. These provide a fast curing plastisol adhesive
characterized by relatively low viscosity, low migration
tendencies, and minimum volatility. Such adhesives remain soft and
flexible after curing, and can be reactivated by subsequent
heating.
It has been found that other adhesives may be employed in the
process--for example, organisols utilizing resins such as the vinyl
chloride polymers and copolymers. Furthermore, still other
adhesives may be employed provided that they satisfy specified
characteristics in the base web produced in the web forming section
10, and in the finished fabric produced in the adhesive compacting
and fiber looping section 30 (FIG. 1). In general, such adhesives
should be applied to the base web by procedures which will not
disarrange the fibrous structure of the web; such adhesives should
heat-set at temperatures below the degradation temperature of the
fibers in the base web 14 to secure bonding of the fibers to the
adhesive; such adhesives should be reactivatable in the subsequent
adhesive gathering and consolidation stage of the process; and such
adhesives should form a flexible backing layer for the finished
fabric and should strongly bond the fiber loops in place. For
example, emulsions of thermoplastic resins such as acrylics and
rubber-like compounds, illustratively ABS, have the requisite
properties to serve as the bonding adhesive for the web 14.
In carrying out the illustrated process, the base material, made as
heretofore described and comprising a web 14 of highly drafted
fibers imbedded in an open adhesive pattern, is fed into the
adhesive consolidating and fiber looping section 30 of the
apparatus shown in FIG. 1. As shown here, the web 14 continues
directly from the web forming section 10 to the consolidating and
looping section 30. It should be appreciated, however, that the web
14 discharged from section 10 could be rolled up for storage or
transport and then subsequently unrolled and fed into section
30.
As illustrated in FIG. 1, the web 14, while still under tension, is
fed around an idler roll 32 and on to the surface of a heated
forming drum 37. In its preferred embodiment, the drum 37 is made
of metal with a highly polished, chromium plated surface which is
heated and maintained at a temperature of approximately 250.degree.
F. Also, the web 14 is arranged to travel a substantial distance
around the drum 37 with the open pattern of adhesive 16 in contact
with the heated rum surface. As the web 14 is fed onto the drum 37,
the heat from the drum surface reactivates and softens the adhesive
printed on the underside of the web, causing it to be tacky and to
adhere slightly to the drum surface, thereby maintaining the web
under constant tension. The drum temperature, which is maintained
at about 250.degree. F., is, however, maintained below the melting
point of the adhesive to prevent dispersion of the adhesive into
the fibers of the web.
Further with respect to the illustrated process, the web 14 of
fibers and softened adhesive is reformed by the cooperative action
of the drum 37 and a gathering blade 38 having a flat edge 39. The
blade edge 39 operates to consolidate the open adhesive pattern 16
into a substantially continuous backing layer of adhesive, while
simultaneously looping the fibers of the web outwardly from between
the open spaces in the original adhesive pattern. The reformed and
consolidated material 40 then leaves the blade edge 39 and moves
onto a flat take-off surface 41 and a discharge conveyor 52.
The fabric can be taken from the discharge conveyor and then cut
into appropriate sizes for use in a clasp as the female member in
combination with a suitable male member. FIGS. 3a and 3b
illustrate, in cross-section, two commercially available types of
male members, though it is to be understood that the high-loft,
nonwoven female members described herein can be used in combination
with any male member which contains functional elements which will
engage with the loops of the high-loft, nonwoven fabric to form a
clasp having the separation characteristics previously described.
The male member shown in FIG. 3a is illustrative of the "Velcro"
type of fastener and contains a base sheet of material containing,
as the functional elements, a plurality of upstanding hooks of a
flexible resilient material extending generally vertically from the
base sheet. The male member shown in FIG. 3b illustrates a further
type of commercially available male member. As can be seen the
functional elements of this member are beads contained on the ends
of resilient stems which vertically extend from a base sheet of
material.
Turning now to FIGS. 7-9, the method of making the high-loft,
nonwoven fabric 40 useful as the female member will be explained in
greater detail in connection with an illustrative sequence of the
gathering and looping of a single fiber of the web 14 and the
consolidation of its two original points of adhesive attachment in
the pattern 16. As seen in FIG. 8, the fiber has a portion P which
extends across the open space of the diamond pattern of adhesive 16
from point A to point B where it is imbedded in the adhesive.
Referring to FIG. 7, the series of views in this Figure illustrates
how the portion P of the fiber is formed into a loop; viz., when
point A being carried around the heated drum 37 impinges against
the gathering blade edge 39, its forward motion is halted and it is
scraped along the surface of the drum, while point B continues to
advance with the drum surface since, due to its softened and tacky
condition, it adheres to the smooth drum surface. As point B
advances relative to point A, the portion P of the fiber between
points A and B is caused to bow outwardly from the drum surface.
Finally, point B overtakes point A and these points of adhesive are
substantially consolidated as seen in FIG. 9. In the meantime,
fiber portion P has been looped outwardly from the drum
surface.
It will, of course, be understood that while looping of fiber
portion P is occurring, additional adhesive points C-D, etc.,
travelling around the drum 37 impinge against the gathering blade
edge 39 causing a consolidation of these adhesive points and
looping of their intermediate fiber portions P.sub.1 as is also
indicated in FIG. 9. This occurs simultaneously at all points
across the web at the blade edge, producing a substantially
continuous backing layer of adhesive from which extends the
multiplicity of loops formed by the fibers of the base web. The
thus formed substantially consolidated layer of adhesive is carried
away from the blade edge 39 along the take-off surface 41 and
provides a substantially continuous backing layer for the outwardly
looped fibers, thus producing the fabric 40.
While in the process for forming the high loft, nonwoven fabric
illustrated herein, it is desired to achieve substantially complete
consolidation of the adhesive into a continuous backing layer, in
practice it has been found that the degree of consolidation varies
randomly throughout the substantially continuous backing and,
therefore, it is possible to draw the fabric slightly, thus
producing a substantially continuous adhesive backing layer with
random openings therethrough. Since complete consolidation, while
desirable, is not necessarily always attained, the degree of
consolidation is defined herein, and in the appended claims, in
terms such as "to consolidate" the "open adhesive pattern into a
substantially continuous adhesive layer." Thus, those skilled in
the art will appreciate that terms such as "consolidate" as used
herein and in the appended claims are intended to connote an
arrangement for consolidating or compacting the open adhesive
pattern into a substantially continuous adhesive backing
layer--albeit that such "substantially continuous backing" may
have, and often will have, small random fissures and gaps
therein.
Another important characteristic of the illustrated fabric is that
not only does each fiber portion P loop outwardly from the drum
surface but, also, as the loop is formed it turns, reaching a
position in the fabric 40 generally perpendicular to the direction
of the original alinement of fiber portion P. Thus, the fiber loops
arrange themselves so that the plane of each loop is substantially
normal to the original fiber alinement shown in FIG. 8. The reason
for the loop twisting as it is formed may be explained by this
observation. If two spaced points of a single fiber not in a web
are brought together, it has been observed that the fiber will form
a loop and, as the loop is formed, it twists towards a position of
minimum internal stress, turning through an angle which tends to
approach 180.degree. F. In carrying out the method of the
invention, because of the great number of fibers in the web and
their proximity one to another, each fiber loop engages the
neighboring fiber loops with the result that all the loops are
blocked from turning beyond the plane substantially normal to the
machine direction, and are constrained in that position by the
interference between the loops.
The fact that the fiber loops are constrained from achieving a
condition of minimum internal stress is felt to be a contributing
factor which renders the illustrated fabrics particularly useful as
female members. In such an unrelaxed condition, the loops tend to
be very resilient and readily engageable with the functional
element of the male fastening member. In this respect, it should be
noted that in actual use the female member should be positioned
such that the plane of the loops is at substantially a right angle
with respect to the direction in which shear forces are
anticipated. For example, when the clasp is used as a belt buckle
replacement, the female member should be secured to the belt, e.g.,
by adhesive attachment, such that the plane of the loops, i.e., the
cross machine direction of the fabric as made, is substantially
perpendicular to the length of the belt.
The above-discussed arrangement of the loops normal to the machine
direction is clearly evidenced by reference to FIG. 11, which is a
reproduction of an enlarged photograph of a transverse sectional
view of fabric made in accordance with the method discussed above.
The fiber loops and their attachment to the adhesive layer appear
in FIG. 11, while in FIG. 12, which is a sectional view taken
parallel to the machine direction and, thus, at right angles to
FIG. 11, the fiber loops are viewed from their edge and for the
main part are not discernible in this view as loops.
It is important to note, however, that throughout the fabric the
heights of the fiber loops vary according to the spacing between
the points of attachment of each fiber to the open adhesive pattern
in the base web. Referring to FIGS. 4, 8 and 9, it will be seen,
for example, that the loop formed by the fiber portion P.sub.1
between the points of adhesive attachment C, D will have a lower
height than the loop formed by the longer fiber portion P between
the points A, B. On the other hand, however, successive loops in
adjacent diamonds, when viewed in a vertical section taken along
the machine direction (FIG. 5), will have the same height since the
fiber length P will remain the same between successive sets of
points A, B. This results in a dense fabric with the lower loops
supporting and filling around the higher loops and the top surface
of the fabric being formed by the tops of the higher loops.
While a fabric such as above-discussed wherein the loops vary in
height regularly throughout the fabric is preferred for use as a
female clasp member since the lower loops tend to maintain the
higher loops in an upright position where they can be most readily
engaged by the functional element of the male member, fabrics with
a uniform loop height can be employed. Similarly, fabrics with
varying loop heights prepared by using adhesive patterns other than
the above-illustrated diamond patterned are useful as female clasp
members. The previously referred to co-pending application, Ser.
No. 31,225, contains numerous illustrations of adhesive patterns
which can be used in order to prepare fabrics with various surface
textures and reference is directed thereto.
The loop height of the high-loft, nonwoven fabrics useful as female
clasp members is important in achieving a desired degree of
fastening tenacity. As explained in detail in Ser. No. 31,225, a
major factor affecting the loop height is the spacing between
points of fiber adhesive attachment A-B, C-D, etc (FIG. 8). Greater
spacing will result in higher loop heights. Moreover, to obtain
maximum thickness (loop height) of a fabric with a given adhesive
pattern, the blade edge angle .alpha. (FIG. 6) should be such as to
produce not only sufficient consolidation of the adhesive layer to
provide good fiber attachment throughout the fabric but, also,
sufficient consolidation to insure the production of a maximum
number of full height fiber loops. Thus, the blade angle should not
be so great as to skive the web off the roll nor so low as to
prevent the fabric from flowing evenly and smoothly off the drum
surface.
The combination of a diamond adhesive pattern such as illustrated
in FIG. 2 wherein adjacent line of adhesive are spaced about 0.75
inch--0.5 inch apart and a blade edge angle .alpha. of about
45.degree.-53.degree. has been found to provide a fabric which is
useful as a female clasp member where high fastening tenacity is
required. Where a fabric with a somewhat lesser degree of fastening
tenacity is wanted, such can be easily obtained by progressively
increasing the blade angle, e.g., up to about 60.degree.. Less
tenacity can also be achieved by decreasing the adhesive line
spacing e.g., down to about 0.25 inch, in which case blade angles
of about 17.degree.-34.degree. inch are particularly useful. Thus,
by appropriately varying either or both the blade angle or adhesive
pattern, a clasp can be fashioned with a desired degree of
tenacity.
As again fully explained in co-pending application, Ser. No.
31,225, a further method by which the structure of the fabric
prepared by the process illustrated herein can be varied is by
controlling the take away speed ratio of the fabric from the blade
edge (i.e., the ratio of the surface speed of the drum 37 to the
actual take away speed). Thus, increasing the take away speed ratio
serves to increase the density of the fabric produced. In
combination with the above-discussed adhesive patterns and blade
angles, a take away speed ratio of about 10:1 - 20:1 is generally
useful while most fabrics will be prepared with a ratio of about
13:1 - 17:1. The higher ratios are associated with the preparation
of female members for use in clasps having greater fastening
tenacity.
The amount of adhesive used in forming the fabric, the type and
amount of fiber employed, and the length and denier of the fiber
can also be important in obtaining an appropriate female clasp
member. In general the amount of adhesive used is based on the
amount of fiber present and should be sufficient to effect
completely secure attachment of the fiber ends. On a weight basis,
the adhesive should be present in an amount at least equal to the
fiber weight and, preferably, at least equal to about twice fiber
weight. The amount of fiber used directly influences the bulk of
the fabric. For use as a female member in a clasp, fabrics with a
basis weight of about 200-500, and preferably 300-400,
grms./yd..sup.2 are useful, and an amount of fiber should be
employed to achieve this weight, keeping in mind that certain
process conditions such as take away speed can also influence
fabric weight.
Concerning fiber type, fibers prepared from a thermoplastic polymer
such as a polyester are preferred, but other fibers such as those
of regenerated cellulose, acrylics, and polypropylene can also be
used. Polyesters, however, are preferred since they are readily
available at high tenacity and the loops of such fibers can be heat
set in their looped shape on the forming drum 37 and are thus less
susceptible to collapse or distortion on repeated openings and
closings of the clasp. While, at a minimum, fiber length should be
such that individual fibers span over adjacent lines of adhesive,
it is preferred that individual fibers span over three or more
adhesive lines in order to enhance fiber securement in the fabric.
To this end, fibers with a length of about 2-4 inches are
preferably employed. The denier of useful fibers is also important
since fiber loops of very thin fibers, e.g., less that about 1.5
denier, tend to break as the clasp is repeatedly opened and closed.
Fibers having deniers in the range of about 4-8 are preferred.
While fibers with higher deniers, e.g., up to about 15, can be
used, it should be noted that, for a given fabric weight, the use
of high denier fibers reduces the number of fibers and,
accordingly, the number of loops which are present.
The following example illustrates the preparation of a high-loft,
nonwoven fabric which can be used as a female member in a separable
clasp containing a male and female member.
EXAMPLE
The apparatus illustrated in FIG. 1 was used. The base web was made
from 3 inch staple, 6 denier polyester fiber and had a weight as it
came off the curing drum 29 of 27 grams./sq.yd. This weight was
made up of 8 grams of fiber and 19 grams of adhesive in the base
web material. The adhesive was a plastisol containing 100 parts
Geon 135 polyvinyl chloride resin, 60 parts dioctyl phthalate
plasticizer, and 2 parts Cab-O-Sil pyrogenic silica. The adhesive
was applied in diagonal lines one-half inch apart in both
directions forming a diamond pattern in which the lines of adhesive
were approximately 0.010 inch deep and 0.050 inch wide. In the
first stage of forming the base web 14, the curing drum 29 was
operated at 350.degree. F. and at a surface speed of 50 ft./minute.
The base web 14 was then carried at 50 ft./minute lineal speed to
the heating drum 37 which was operated at 320.degree. F., and
around the drum to the gathering blade 38. The lip of the take away
surface 41 was positioned tight against the blade edge and less
than one thirty-second inch below the corner of the blade edge. The
blade angle .alpha. was 53.degree. and the take away speed was
15:1.
The fabric so prepared is suitable for use as the female member in
a separable clasp, and clasps containing this fabric can be used in
the many applications where clasps of this type are finding
increasing use. Due to the fact that the female member described
herein is inexpensive to prepare, clasps containing such are
particularly suitable for use in applications where adjustability
such as that provided by a belt is desired. Being comparatively
inexpensive, adjustability can be achieved by using a long strip of
this female member in combination with only a short strip of the
normally more expensive male member without an appreciable increase
in clasp cost compared with an unadjustable clasp wherein both male
and female members are short strips. Thus, clasps containing the
present high-loft, nonwoven fabric are expected to find
considerable use in applications such as gown closing means where
adjustability of the gown to fit various sizes of people is a
necessary requirement.
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