Soft loop laminate and method of making

There is provided a soft nonwoven fibrous loop material for use in hook and loop fastening systems. The nonwoven fibrous loop material of the invention contains an open fibrous loop layer comprised predominately of polypropylene polymer, copolymer or blend fibers. The nonwoven fibrous loop layer material is autogeneously bonded to a backing layer formed of polypropylene polymers or copolymers having a percent isotacticity of less than 70%, optionally with additional layers present provided so that the overall nonwoven fibrous loop material is a laminate having a circular bend stiffness of less than about 9 Newton and having tensile strength of at least 1500 g/2.54 cm-width.

BACKGROUND AND FIELD OF THE INVENTION 
The present invention relates to sheets of laminated loop material adapted 
to be cut into discrete loop patches for use in hook and loop fastening 
components for low cost applications, particularly disposable diapers and 
the like. 
Nonwoven loop materials intended for use in low cost applications, 
particularly in respect to disposable garments such as surgical gowns or 
disposable absorbent articles, such as diapers, have increased in 
popularity in recent years. This has resulted in intensive development 
efforts to provide a material that is both high performance for the 
intended user and low cost. The focus of these efforts has been on 
providing a low cost loop material which adequately functions to provide a 
resealable mechanical closure for a limited number of repeated 
applications. For these uses, it is not necessary that the loop material 
have sufficient integrity to enable long term repeat attachment and 
release cycles or resistance to washing. However, the loop material should 
provide a relatively high peel and secure closure for a limited number of 
use cycles. Knitted, woven or stitch-bonded and like traditional fabric 
materials have been proposed in these limited use garment loop 
applications. Generally, these traditional fabric materials provide more 
integrity than is needed for the limited use garment field, and are more 
expensive than required. Lower cost versions of these traditional loop 
fabric materials have lower fiber density per unit area and hence are 
lower performance. In response, it has been proposed in a number of patent 
applications to use nonwoven fabrics of a wide variety of types to form 
relatively low cost but high, short term performing loop materials. For 
example, U.S. Pat. No. 5,256,231 is an early patent that proposed the use 
of a nonwoven web, such as produced by a carding process, to form a loop 
material. In this patent, the nonwoven web is fed between two corrugating 
members which provide the nonwoven web material with loft or z-direction 
orientation. The corrugated web is given integrity in the x and y 
directions by extruding a thermoplastic backing layer onto tip portions of 
the corrugated nonwoven material, which is still maintained at this point 
in the corrugated state between at least one of the corrugating members 
and a nip backing member. Optional additional layers can be brought in, 
which additional layers can be printed to provide desired print patterns 
on the loop material. The process described in this patent provides highly 
advantageous low cost loop structures. However, particularly when bringing 
in an additional printed backing layer, the loop material tends to become 
excessively rigid, particularly when the loop materials are formed from 
the preferred polypropylene resins described. When a loop material is 
intended to be used in a disposable, absorbent garment, softness is an 
extremely important property in order to avoid discomfort for the wearer, 
as well as providing a conformable form-fitting garment. The use of 
polyethylene fibers and films or bi-component bonding fibers and the like 
can provide loop materials with increased softness, however, often at a 
significant cost increase, increased problems with manufacturability, 
and/or decreased loop performance. From the standpoint of cost and 
performance, it is preferable that the nonwoven web material be formed 
primarily from polypropylene fibers. However, polypropylene fibers present 
difficulties in providing a soft loop material in that a polypropylene 
backing or backing film layer is generally required in order to provide 
adequate fiber anchorage, and polypropylene backing films are relatively 
stiff. 
U.S. Pat. No. 5,614,281 describes a method for forming nonwoven loop 
materials by micrexing or creping a specific nonwoven material while 
simultaneously bonding it to a film or nonwoven backing material. The 
specific end product loop materials exemplified are described as being 
soft where the nonwoven web is formed from melt-spun fibers of a random 
copolymer of propylene and ethylene and the film backing layer is a blend 
of polypropylene with about 16% polyethylene. However, this process 
suffers from the disadvantage that the nonwoven loop material must be 
prebonded in order to survive the creping process which process results in 
significant shear forces on the web during creping. Prebonding decreases 
the penetrability of the web to hook materials, decreasing performance in 
the hook and loop laminate structure. The shear forces can also cause 
fibers to shed or become dislodged in the web. Creping also results in a 
web with uneven or irregular corrugations which results in uneven bonding 
to the backing layer. Further, the polypropylene film backing material 
specifically suggested is still relatively stiff. 
A number of other patents have proposed the use of nonwoven materials for 
use in forming loop structures including, for example, U.S. Pat. No. 
5,032,122, wherein a nonwoven web or series of filaments are bonded to a 
material in an oriented unstable state. The unstable oriented material is 
subsequently allowed to recover gathering the nonwoven web or fibers to 
form upstanding loop structures. WO 96/04812 describes a similar method 
for forming a loop material where the backing is an elastomeric material 
and the nonwoven web forming the loops is bonded to the backing with a 
specific bond pattern. This loop material would suffer from numerous 
disadvantages, such as being generally dimensionally unstable when elastic 
materials are provided as the backing; relatively low levels of bonding 
to, e.g., a nonwoven polypropylene loop material; require high cost 
backing materials; and are somewhat difficult to manufacture. A similar 
approach is described in WO 95/33390 where the backing is an elastomeric 
adhesive material. This elastomeric adhesive film described allegedly 
provides an unstable film material capable of retracting to form the 
attached nonwoven web into loops and also provide a certain level of 
bonding to the nonwoven material. This approach would generally suffer 
from the identical problems associated with the WO 96/4812 published 
application described above and also has generally poor adhesion 
properties. 
Other nonwoven loop fastening materials are described in U.S. Pat. Nos. 
5,470,417 and 5,326,612 which relate to non-corrugated, nonwoven materials 
having specific bonding patterns and layer structures used to form loop 
materials. 
Despite the extensive levels of activity and development efforts in using 
nonwoven fabrics for forming loop materials, there is still a need for 
providing a low cost, high performance nonwoven loop material which is 
also easy to manufacture, has good fiber to backing adhesion, and is soft 
and conformable with additionally having the ability to be bonded to a 
further layer having desirable properties such as a printing pattern while 
remaining relatively soft. 
SUMMARY OF THE INVENTION 
The present invention is related to a soft nonwoven fibrous loop material 
for use in hook and loop fastening systems. The nonwoven fibrous loop 
material of the invention contains an open fibrous loop layer comprised 
predominately of polypropylene polymer, copolymer or blend fibers. The 
preferred nonwoven fibrous loop layer has a sufficient degree of open 
areas between the fibers as to allow penetration and engagement by hook 
elements on complimentary hook materials and also a significant degree of 
z-direction loft such as to allow at least the fiber engaging portion of 
complimentary hook material elements to fully penetrate the nonwoven 
fibrous loop layer material and selectively engage fibrous loop structures 
present therein. The nonwoven fibrous loop layer material is autogeneously 
bonded to a backing layer formed of polypropylene polymers or copolymers 
having a percent isotacticity of less than 70%, optionally with additional 
layers present provided so that the overall nonwoven fibrous loop material 
is a laminate having a circular bend stiffness of less than about 9 Newton 
and having tensile strength at yield of at least 1500 g/2.54 cm-width.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 illustrates a first embodiment of a sheet of loop material according 
to the present invention, generally designated by the reference numeral 10 
which sheet of loop material 10 is adapted to be cut into pieces to form 
the loop portions for fasteners of the type intended for limited use 
garments and having releasably engagable hook and loop portions. Generally 
the sheet of loop material 10 has a backing 11 comprising a thermoplastic 
backing layer 12 formed from polypropylene polymer or copolymer, the 
polypropylene generally having an isotaticity of less than about 70 
percent. The backing layer 12 is preferably a film layer having a 
thickness in the range of about 0.00125 to 0.025 centimeters (0.0005 to 
0.010 inch) and also preferably having generally uniform morphology, and 
front and rear major surfaces 13 and 14. A multiplicity of fibers in a 
formed sheet of fibers 16 having generally non-deformed anchor portions 17 
is autogeneously bonded to the backing layer 12. The bonding locations 18 
in FIG. 1 are along the front surface 13 with arcuate portions 20 of the 
sheet of fibers 16 projecting from the front surface 13 of the backing 
layer 12 between the bonding locations 18. As shown in FIG. 1 the bonding 
locations can be continuous rows extending transversely across the sheet 
of loop material 10. However the bonding locations can be arranged in any 
pattern including, for example, intermittent lines, hexagonal cells, 
diamond cells, square cells, random point bonds, patterned point bonds, 
crosshatched lines, or any other regular or irregular geometric pattern. 
The arcuate portions 20 of the sheet of fibers 16 between adjacent bonding 
locations have a generally uniform maximum height from the backing layer 
12 of less than about 0.64 centimeters (0.250 inch) and preferably less 
than about 0.381 centimeters (0.150 inch). The height of the arcuate 
portions 20 of the formed sheet of fibers 16 is at least one third, and 
preferably one half to one and one half times the distance between 
adjacent bonding locations 18. The majority of the individual fibers in 
the sheet of fibers 16 are preferably less than 25 denier (preferably in 
the range of 1 to 20 denier) in size. The use of fibers in the sheet of 
fibers outside this range can be useful in certain circumstances in fiber 
blends or occasionally alone. However, the use of lower denier fibers, at 
least in part, are preferred in terms of providing soft loop materials 
with good engageability with the smaller hook elements generally used in 
low cost hook and loop fasteners. The loop material without the backing 
has a basis weight in the range of 5 to 300 grams per square meter (and 
preferably in the range of 15 to 100 grams per square meter) measured 
along the first surface 13. The fibers in the sheet of fibers should have 
sufficient space between them so that the open area between the fibers in 
the sheet of fibers 16 along the arcuate portions 20 (i.e., between about 
10 and 90 percent open area) afford ready penetration and engagement of 
the hook fiber engaging portion of a hook fastener element. Generally, 
this requires that the sheet of fibers is nonconsolidated or the fibers 
are not bonded at the points where the individual fibers cross. 
FIG. 2 illustrates a second embodiment of a sheet of loop material 
according to the present invention, generally designated by the reference 
numeral 10a, loop material 10a generally has the same structure as the 
sheet of loop material 10 (the same reference numerals being used with 
respect to the corresponding portion thereof) except that backing 11a of 
the sheet of loop material 10a includes a second sheet of backing 
material(s) 21. The second sheet of backing material 21 is adhered on the 
side 14 of the thermoplastic backing layer 12 opposite the sheet of fibers 
16. The second sheet of backing material 21 in the backing 11a of the 
sheet of loop material 10a preferably is a polymeric film or consolidated 
nonwoven web which can be printed on one of its surfaces to provide a 
sheet of loop material 10a on which the printing (which could be 
decorative, indicate a trade name, or provide instructions) can be clearly 
seen through the sheet of fibers 16. The second sheet of backing material 
21 is preferably a polyethylene film formed of a polyethylene polymer or 
copolymer, with blends also being possible. In this case the backing 
material 12 also preferably is a blend containing from 50 to 15 percent by 
weight polyethylene (preferably 30 to 15 percent) to allow autogeneous 
bonding between backing layers 12 and 21. The polyethylene polymer or 
copolymer content of backing layer 21 is preferably from 50 to 100, most 
preferably 80 to 100 percent by weight. The polyethylene polymer or 
copolymer can be low density, linear low density, ultra low density, high 
density, or elastomeric polyethylenes or copolymers, preferred are low 
density polyethylenes. 
FIG. 3 illustrates a third embodiment of a sheet of loop material according 
to the present invention, generally designated by the reference numeral 
10b, loop material 10b generally has the same structure as the sheet of 
loop material 10a (the same reference numerals being used with respect to 
the corresponding portion thereof). A multiplicity of fibers in a 
non-deformed sheet of fibers 16 having generally non-deformed anchor 
portions 37 is autogeneously bonded to the backing layer 12. The bonding 
locations 18 in FIG. 3 are along the front surface 13. As shown in FIG. 3 
the bonding locations can be a regular pattern of point bonds extending 
across the length and width of the sheet of loop material 10b. However the 
bonding locations can be arranged in any pattern including, for example, 
regular or intermittent lines, hexagonal cells, diamond square, square 
cells, random point bonds, crosshatched lines, or any other regular or 
irregular geometric pattern. 
FIG. 4 schematically illustrates a method and equipment for forming the 
sheet of loop material 10 shown in FIG. 1. The method illustrated in FIG. 
4 generally comprises forming a sheet of fibers using a nonwoven fiber web 
16 so that it has arcuate portions 20 projecting in the same direction 
from spaced generally parallel anchor portions 17 of nonwoven web 16, and 
bonding the spaced generally parallel anchor portions 17 of the nonwoven 
web 16 to the backing layer 12. This method is performed in the FIG. 4 
method by providing first and second corrugating members or rollers, 26 
and 27 each having an axis and including a plurality of circumferentially 
spaced generally axially extending ridges 28 around and defining its 
periphery, with spaces between the ridges 28 adapted to receive portions 
of the ridges 28 of the other corrugating member, 26 or 27, in meshing 
relationship with the nonwoven web or sheet of fiber 16 between the meshed 
ridges 28. The corrugating members 26 and 27 are mounted in axially 
parallel relationship with portions of the ridges 28 meshing generally in 
the manner of gear teeth; at least one of the corrugating members, 26 or 
27, is rotated; and the nonwoven web or other type of sheet of fibers 16 
is fed between the meshed portions of the ridges 28 of the corrugating 
members 26 and 27 to generally corrugate the sheet of fibers 16. The 
corrugated nonwoven web or other sheet of fibers 16 is retained along the 
periphery of the first corrugating member 26 after it has moved past the 
meshed portions of the ridges 28. In the FIG. 4 method a thermoplastic 
backing layer 12 is formed and bonded to the anchor portions 17 of the 
sheet of fibers 16 on the end surfaces of the ridges 28 on the first 
corrugating member 26 by extruding or coextruding the thermoplastic 
polypropylene backing layer 12 in a molten state from a die 24 into a nip 
between the anchor portions 17 of the sheet of fibers 16 on the periphery 
of the first corrugating member 26 and a cooling roll 25. This embeds the 
fibers of the nonwoven web or other sheet of fibers in the polypropylene 
backing layer. After cooling by the cooling roll 25 in the nip the sheet 
of loop material 10 is separated from the first corrugating member 26 and 
carried partially around the cooling roll 25 and through a nip between the 
cooling roller 25 and a pinch roller 29 to complete cooling and 
solidification of the polypropylene backing layer 12. 
An alternative to extruding a film 12 is supplying a preformed backing 
layer, for example, in the form of a backing film into the nip formed 
between the first corrugating member 26 and a roll 25. The ridges on the 
corrugating member 26 and/or the roll 25 are heated so as to thermally 
bond the film backing to the sheet of nonwoven fibers. This alternative 
applies to all the method embodiments shown in, for example, FIG. 4-8. 
The sheet of fibers is preferably in the form of a nonwoven web product 
such as can be formed from loose discrete fibers using a carding machine 
30, which nonwoven web of randomly oriented fibers 16 has enough integrity 
to be fed from the, e.g., carding machine 30 into the nip between the 
corrugating members 26 and 27 (if needed, a conveyer (not shown) could be 
provided to help support and guide the nonwoven web 16 between the carding 
machine 30 and the corrugating members 26 and 27). When such a nonwoven 
web 16 is used, preferably the first corrugating member 26 has a rough 
finish (e.g., formed by sand blasting), the second corrugating member 27 
has a smooth polished finish, and the first corrugating member 26 is 
heated to a temperature slightly above the temperature of the second 
corrugating member 26 so that the nonwoven web 16 will preferentially stay 
along the surface of the first corrugating member 26 and be carried to the 
nip between the first corrugating member and the roller 25 after passing 
through the nip between the corrugating members 26 and 27. 
Optionally, the backing 11 of the sheet of loop material 10 can be printed 
on its surface opposite the sheet of fibers 16 through the use of a 
printer 31, either in the production line as illustrated, or as a separate 
operation. Alternatively, a printer 31 could be used to print on and 
thereby color or print a pattern on the sheet of fibers 16 either in the 
production line as illustrated or as a separate operation. 
Corrugating members 26 and 27, as shown in FIG. 4, adapted to have a sheet 
of fibers 16 fed into them can have ridges 28 oriented generally in the 
range of 0 to 45 degrees with respect to its axes, but preferably have its 
ridges 28 oriented at 0 degrees with respect to (or parallel to) its axes 
which simplifies making of the corrugating members 26 and 27. 
FIG. 5 schematically illustrates a second embodiment for forming sheets of 
loop materials 10a, as shown in FIG. 2, which method is generally the same 
and uses much of the same equipment as is illustrated in FIG. 4 (with 
similar portions of that equipment having the same reference numerals), 
except for the addition of means including a pinch roller 34 for feeding 
the sheet of backing material 21 or 22 into the nip between the first 
corrugating roller 26 and the roller 25 along the surface of the roller 25 
which results in the extruded molten thermoplastic backing layer 12 from 
the die 24 being deposited between the formed sheet of fibers 16 and the 
sheet of backing material 21. The sheet of loop material 10a is then 
separated from the first corrugating member 26 and carried partially 
around the cooling roll 25 with its backing 11a against the cooling roll 
25 to complete cooling and solidification of its thermoplastic backing 
layer 12. 
The cooling roll 25 in the embodiment shown in FIGS. 4-6, using an extruded 
film backing, can be water cooled and have a chrome plated periphery. 
Alternatively, the cooling roll 25 may have an outer rubber layer defining 
its surface which may be preferred for forming the sheet of loop material 
10a if the sheet of backing material 22 is of a material (e.g., paper) 
that tends to restrict heat transfer into the cooling roll 25. If roll 25 
is a heated roll this could be by means of an oil or water heated roll or 
an induction roll. 
The sheet of backing material 21 incorporated in the backing 11a could be a 
woven, knitted, needle punched, nonwoven or other solid or porous layer of 
intertwined fibers, or could be a continuous polymeric film which allows 
the backing to be printed by conventional methods along one of its 
surfaces with graphics (such as advertising, instructions or locating 
marks) which will be visible through the loop portions 20 of the sheet of 
fibers 16 due to its large percentage of open area. Such film used for the 
sheet of backing material 21 may be single or multiple layer(s) of a 
polymeric material, however, is preferably a soft film material such as 
ethylene vinyl acetate or polyethylene, as described above. The sheet of 
backing material 21 could also be a layer of pressure sensitive adhesive 
on a release liner. The release liner would contact the cooling roller 25, 
resulting in the layer of pressure sensitive adhesive being disposed along 
the rear surface of the layer of thermoplastic material 12 with the 
release liner over the layer of pressure sensitive adhesive and removable 
so that the pressure sensitive adhesive could be used to adhere the sheet 
of loop material 10a to a substrate. 
Preferably for an extrusion bonded or thermally bonded method using 
corrugating rolls 26 and 27 and a nip roll 25, the drives for the 
corrugating members 26 and 27 and for the roller 25 can be rotated at a 
surface speed that is the same as or different than, the surface speed of 
the first corrugating member 26. When the roller 25 and the first 
corrugating member 26 are rotated so that they have the same surface 
speed, the sheet of fibers 16 will have about the same shape along the 
backing 11 or 11a as it had along the periphery of the first corrugating 
member 26 as is illustrated in FIGS. 1 and 2. When the roller 25 and the 
first corrugating member 26 are rotated so that the roller 25 has a 
surface speed that is slower than the surface speed of the first 
corrugating member 26, (e.g., one quarter or one half) the anchor portions 
17 of the sheet of fibers 16 will be moved closer together in the backing 
layer 12 at the nip between the roller 25 and the first corrugating member 
26, resulting in greater density of the loop portions 20 along the backing 
11 or 11a than when the cooling roller 25 and the first corrugating member 
26 are rotated so that they have the same surface speed. 
FIG. 6 schematically illustrates a third embodiment for forming the sheet 
of loop material 10b of FIG. 3, which method is generally the same and 
uses much of the same equipment as is illustrated in FIG. 6 (with similar 
portions of that equipment having the same reference numerals), except 
that the first and second corrugating member 26 and 27 are replaced by 
first and second cylindrical rollers 44 and 45. The sheet of fibers 16 is 
fed between the rollers 44 and 45 in a substantially non-deformed state. 
The sheet of fibers 16 is retained along the periphery of the first roller 
44 the extruded molten thermoplastic backing layer 12 from the die 24 is 
deposited between the sheet of fibers 16 along the periphery of the first 
corrugating member 44 and the sheet of backing material 25. The molten 
polypropylene backing layer 12 envelopes and adheres to fibers on one face 
of the sheet of fibers 16 and to the sheet of backing material 21. The 
sheet of loop material 10b is then separated from the first roller 44 and 
carried partially around the cooling roll 25 to complete cooling and 
solidification of the thermoplastic backing 12. The roll 45 is preferably 
smooth and roll 44 is provided with ridges or peaks and valleys. The roll 
44 is preferably heated to consolidate a nonwoven web of polypropylene 
fibers at the ridges or peaks first in the nip formed by 45 and 44 and 
then in the nip formed by roll 44 and roll 25. The polypropylene backing 
layer 12 envelop the fibers preferentially at these consolidated portions 
forming a loop material without arcuate portions. 
The equipment illustrated in FIG. 6 could also be used to form the sheet of 
loop material 10b by not feeding the sheet of backing material 21 or 22 
around the roller 25. 
FIGS. 7 and 8 illustrate two different corrugating members. One or a pair 
of cylindrical heated corrugating members 65 could be substituted for the 
corrugating member 26 and 27 or 44 to form a sheet of loop material using 
generally the methods described above with reference to FIGS. 4-6. The 
corrugating member 65 and its mating corrugating member, if provided, each 
have an axis and includes a plurality of ridges 56 or 66. The ridges 66 or 
56 on each corrugating member defining spaces between the ridges 56 or 66, 
which spaces can be adapted to receive a portion of the ridges of another 
corrugating member in meshing relationship in the manner of a pair of 
gears. If desired, the ridges on a first corrugating member could be 
arranged in any suitable pattern including forming words, numbers or 
symbols to, for example, to form a trademark on the sheet of loop material 
60. 
The backing layer 12 preferably is a polypropylene homopolymer or copolymer 
film containing 30 to 100 weight percent of the low isotacticity 
polypropylene, preferably 50 to 85 weight percent, blended with 0 to 70 
percent of a polyethylene polymer or copolymer, preferably 15 to 50 
percent of the polyethylene polymer or copolymer. The backing layer 12 can 
contain other components such as higher isotacticity polypropylene (which 
can, in part, replace the low isotacticity polypropylene), other 
thermoplastic polymers, dyes, pigments, or melt additives provided that 
these additional components do not adversely affect the bonding of the 
backing layer 12 to the fibrous loop layer and/or the additionally 
supplied backing layer 21 or the like. The backing layer 12 can also be a 
coextruded film where at least the layer in contact with the sheet of 
fibers has the above percentages of polypropylene polymer and the backing 
as a whole has the above percentage of low isotacticity polypropylene. For 
example, a coextruded film layer 12 could comprise one or more 
polyethylene layers with intervening layers of polyethylene/polypropylene 
blends. Other tie layers and layer combinations are possible with use of 
the at least one polypropylene layer as described above. 
The sheet of fibers 16 preferably is a nonwoven fibrous web material 
provided by carding as described above; however, other suitable methods 
for forming a fibrous nonwoven web can be used to form a nonwoven fibrous 
web loop layer such as Rando webs, airlaid webs, spun-lace webs, spun-bond 
webs, or the like. Generally, a nonwoven fibrous loop material using the 
above described webs is preferably not prebonded or consolidated to 
maximum the open area between the fibers. However, in order to allow 
preformed webs to be handled, it is necessary on occasion to provide 
suitable point bonding and the like which should be at a level only 
sufficient to provide integrity to unwind the preformed web from a roll 
and into the forming process for creating the invention nonwoven fibrous 
loop material. 
Generally, the nonbonded portions of the sheet of fibers is from 65 to 95 
percent providing bonding areas over from 5 to 35 percent of the cross 
sectional area the sheet of fibers, preferably the overall bonded area of 
the sheet of fibers is from 15 to 25 percent. The bonded areas include 
those areas of the sheet of fibers bonded to the backing layer as well as 
any prebonded or consolidated areas provided to improve web integrity. The 
specific bonding portions or areas bonded to the backing layer generally 
can be any width; however, preferably are from 0.01 to 0.2 centimeters in 
its narrowest width dimension. Adjacent bonding portions are generally on 
average spaced from 0.1 to 2.0 cm, and preferably 0.2 to 1.0 cm, apart. 
When the bonded portions are in the form of point bonds, the points are 
generally of substantially circular shape providing circular bonds 
preferably formed either by extrusion bonding or thermal bonding. Other 
shapes in the bonded and unbonded portions are possible, providing 
unbonded mounds or arcuate portions which are circular, triangular, 
hexagonal, or irregular in shape. 
The basis weight of a sheet of fibers such as a nonwoven fibrous loop layer 
is substantially increased in the case of a corrugated loop layer which 
can increase the basis weight of the sheet of fibers 50 percent or more. 
If the loop layer is not corrugated, this increase in basis weight is not 
present in which case substantially higher basis weight webs and like 
sheets of fibers can be used as described above. 
The fibers forming the sheet of fibers are generally polypropylene polymer 
or copolymer fibers within the above described denier range on average. 
The fibers can be continuous or discontinuous. Discontinuous fibers are 
used for example, for air laid or carded webs. The fiber length is not 
critical except in that the fibers length should be at least twice the 
average distance between adjacent bonding portion locations, preferably at 
least five times the average adjacent bonding distance. The sheet of 
fibers can contain other fibers blended with the polypropylene fibers such 
as polyethylene fibers, bonding fibers, coextruded fibers or the like. 
However, these fibers should generally be less than 50 percent of the 
total fibers by weight, preferably less than 30 percent by weight. 
Generally, these added fibers are not preferred in that they add cost or 
decrease performance. It is also possible to add further fibrous layers 
such as by needlepunching to the side of the polypropylene fibrous layer 
opposite that bonded to the backing layer. 
In order to maintain the desirable softness of the sheet of fibrous loop 
material, the backing layer or layers generally has a thickness from 30 to 
300 microns, preferably from 50 to 200 microns providing a soft nonwoven 
fibrous loop material laminate having an overall circular bend stiffness 
of less than 9N, preferably less than 7N, and most preferably from 6N to 
2N, while also providing a sheet of loop material having sufficient 
tensile strength in order to be reliably used in continuous manufacturing 
techniques requiring a dimensionally stable material. The tensile strength 
of the sheet of loop material in at least one direction is at least about 
1200 g/2.54 cm, preferably at least 1600 g/2.54 cm. If a secondary backing 
layer(s) is employed, the combined backing thickness is sufficient to 
provide a laminate having the above circular bend stiffness and tensile 
properties which generally is provided by having the combined backing 
layers having the above described overall thickness dimensions. However, 
the overall thickness dimensions can vary significantly depending on the 
selection of the materials used to form the backing layers (e.g., 12 and 
21). Particularly, if additional nonfilm type material are used, such as 
thicker nonwovens or foam material, which could permit a significantly 
thicker overall backing. 
Test Methods 
135 Degree Peel Test 
The 135 degree peel test was used to measure the amount of force that was 
required to peel a strip of a hook fastener material from a sample of the 
loop fastener material. The test was carried out at constant temperature 
and humidity in a room set at 23.degree. C. and 50% relative humidity. 
A 2 inch.times.5 inch (5.08 cm.times.12.7 cm) piece of the loop material to 
be tested was securely placed on a 2 inch.times.5 inch (5.08.times.12.7 
cm) steel panel by using a double-coated adhesive tape. The loop material 
was placed onto the panel with the cross direction of the loop material 
parallel to the long dimension of the panel. A 0.75 inch.times.1 inch 
(1.90 cm.times.2.54 cm) strip of the hook fastener test material 
(XMH-5145, available from 3M Company) with a paper leader attached was 
then centrally placed on the loop panel so that the leading edge of the 
hook strip was along the length of the panel. The sample was rolled by 
hand, once in each direction, using a 4.5 pound (1000 gram) roller. The 
sample panel was then placed in a 135 degree peel jig and the jig was 
placed into the bottom jaw of an Instron.TM. constant rate of extension 
tensile tester. Without pre-peeling the sample, the end of the paper 
leader was placed in the upper jaw of the tensile tester so that there was 
no slack in the leader. A crosshead speed of 12 inch (30.5 cm) per minute, 
was used to record the peel which was maintained at 135 degrees. The load 
required to remove the hook fastener strip from the loop material was 
reported in grams/2.54 cm-width. Reported values in the table are an 
average of from 8-10 tests. Fiber pull out was also noted if it was 
observed during the peel testing. 
Machine Direction (MD) Tensile Strength (Load at Yield) 
This test method was a modified version of ASTM D 882 and was used to 
determine the tensile and elongation properties of the loop material. The 
test was carried out at constant temperature and humidity in a room set at 
23.degree. C. and 50% relative humidity. A 1 inch.times.3 inch (2.54 
cm.times.7.62 cm) strip of loop material was cut in the machine direction. 
The strip was mounted in the jaws of an Instron.TM. constant rate of 
extension tensile tester, with the upper and lower jaws of the tester 
spaced 1 inch (2.54 cm) apart. The jaws were then separated at a rate of 
10 inch (25.4 cm) per minute until the yield point was reached. The load 
at yield was recorded in pounds/inch-width and was converted to grams/2.54 
cm width. The data (in grams/2.54 cm width) is given in Table II. Each 
data point represents an average of at least two tests. 
Circular Bend Stiffness Test 
The stiffness of the loop materials was tested using the Circular Bend 
Stiffness Test according to ASTM D 4302. The fabric stiffness tester used 
for testing was Model No. DFG10A available from J. A. King and Co., 
Greensboro, N.C. Per ASTM D 4302, a plunger was used to force a flat 
folded swatch of a 4 inch.times.8 inch (10.2 cm.times.20.3 cm) sample of 
the loop material through an orifice in a platform (loop side out). The 
maximum force required to push the sample through the orifice was an 
indication of the loop material's stiffness or resistance to bending. The 
more conformable the loop material, the lower was the resistance, thus 
requiring less force to push it through the orifice. The results were 
recorded in pounds-force and were converted to newtons. The data is given 
in Table II (in newtons). Each data point represents an average of ten 
tests. 
Film Bond Failure Test 
The Film Bond Failure Test was used to obtain an indication of the bond 
strength between the polypropylene backing layer and a printed film 
backing layer. A piece of the loop material was placed loop side down on a 
cutting surface. Without damaging the thermoplastic backing layer, a razor 
blade was then used to score lines on the printed film backing layer. The 
lines were placed approximately 1 cm apart in a cross-hatched pattern. An 
approximately 1 inch.times.5 inch (2.5 cm.times.12.7 cm) piece of filament 
tape (Scotch brand available from 3M Company) was rolled down two times 
onto the printed film backing using a using a 4.5 pound (1000 gram) 
roller. The tape was peeled by hand as fast as possible at an approximate 
180.degree. angle. If the printed film delaminated from the thermoplastic 
backing layer it was noted as a bond failure. 
Materials 
7C50 is an ethylene-propylene impact copolymer resin available from Union 
Carbide Corp., having an isotacticity of 89.6% as determined by .sup.13 
Carbon Nuclear Magnetic Resonance (.sup.13 C NMR).sup.1. 
"SRD" 7560 is an ethylene-propylene impact copolymer resin available from 
Union Carbide Corp. 
"REXFLEX" W101 is a polypropylene homopolymer having a melt flow rate (MFR) 
of 14, and an isotacticity of 48.5% (as determined by .sup.13 C 
NMR.sup.1), available from Rexene Corp. 
"REXFLEX" W112 is a polypropylene homopolymer having a MFR of 20, and an 
isotacticity of 50.8% (as determined by .sup.13 C NMR.sup.1), available 
from Rexene Corp. 
"REXFLEX" W108 is a polypropylene homopolymer having a MFR of 20, and an 
isotacticity of 67.3% (as determined by .sup.13 C NMR.sup.1), available 
from Rexene Corp. 
"REXFLEX" W104 is a polypropylene homopolymer having a MFR of 30, and an 
isotacticity that is the same as "REXFLEX" W112, available from Rexene 
Corp. 
1020 is a low density polyethylene resin having a melt index (MI) of 2.0 
and a density of 0.923 grams/cm.sup.2. available from Rexene Corp. 
1058 is a low density polyethylene resin having a MI of 5.5 and a density 
of 0.922 grams/cm.sup.2, available from Rexene Corp. 
"PETROTHENE" 951 is a low density polyethylene resin having a MI of 2.2 and 
a density of 0.92 grams/cm.sup.2, available from Quantum Chemical Corp. 
"PLEXAR" 5298 is a modified ethylene-vinyl acetate copolymer tie-layer 
resin available from Quantum Chemical Corp. 
.sup.1 ".sup.13 C NMR" spectra were obtained in a solution of 
dichlorobenzene at 110.degree. C. on a Unity 500 MHz NMR Spectrometer 
according to known standard methods. 
EXAMPLES 
All of the loop materials in the Examples were prepared in accordance with 
the method described in Example 3 and illustrated in FIG. 6 of U.S. Pat. 
No. 5,256,231. The fibers that were used to prepare the carded sheet of 
fibers for the loop materials were 9 denier polypropylene fibers obtained 
under the commercial designation T-196 from Hercules, Inc. The basis 
weight of the sheet of fibers (after corrugation) was 45 
grams/meter.sup.2. The sheet of backing material that was adhered on the 
side of the thermoplastic backing layer opposite the sheet of fibers was a 
1 mil (25.4 microns) thick blown polyethylene printed film (#CP4-4 
available from Crystal Print, Little Chute, Wis.) except for Comparative 
Examples C1, C23, C24 and Examples 20-22 which utilized a 1.2 mil (30.5 
microns) cast polypropylene film. The polypropylene (PP) and polyethylene 
(PE) resin types and ratios (by weight) that were used to extrude the 
thermoplastic backing layer for the Examples are given in Table I. For the 
examples the basis weight of the thermoplastic backing layer was 45 
grams/meter.sup.2 except for Examples 7 and 8 which had basis weights of 
40 grams/meter.sup.2, and Examples 20-22 and Comparative Examples C23 and 
C24 which had basis weights of 35 grams/meter.sup.2. 
TABLE I 
______________________________________ 
Example PP Resin Type 
PE Resin Type 
PP:PE 
______________________________________ 
C1 7C50 -- 100:0 
C2 7C50 -- 100:0 
C3 SRD 7560 -- 100:0 
C4 SRD 7560 1058 75:25 
C5 SRD 7560 1058 50:50 
C6 SRD 7560 1058 25:75 
C7 -- 1058 0:100 
8 "REXFLEX" "PETROTHENE" 
50:50 
W104 NA951 
9 "REXFLEX" "PLEXAR" 5298 
50:50 
W101 
10 "REXFLEX" 1058 75:25 
W112 
11 "REXFLEX" 1058 25:75 
W112 
12 "REXFLEX" 1020 75:25 
W112 
13 "REXFLEX" 1020 50:50 
W112 
14 "REXFLEX" 1020 25:75 
W112 
15 "REXFLEX" 1058 75:25 
W101 
16 "REXFLEX" 1058 25:75 
W101 
17 "REXFLEX" 1020 75:25 
W101 
18 "REXFLEX" 1020 50:50 
W101 
19 "REXFLEX" 1020 25:75 
W101 
20 "REXFLEX" -- 100:0 
W101 
21 "REXFLEX" -- 100:0 
W104 
22 "REXFLEX" -- 100:0 
W108 
C23 7C50 -- 100:0 
C24 SRD 7560 -- 100:0 
______________________________________ 
The loop materials were tested for 135 Degree Peel, MD Tensile at Yield, 
Circular Bend Stiffness and Film Bond Failure as described above. Results 
are given in Table II. 
TABLE II 
______________________________________ 
Circular 
Bend MD Tensile 135 Degree 
Example Stiffness at Yield Peel Film Bond 
______________________________________ 
C1 16.4 3995 621 no 
delamination 
C2 13.7 3541 554 delaminated 
C3 13.3 3437 605 delaminated 
C4 9.43 2828 495 deiaminated 
C5 7.30 2483 509* no 
delamination 
C6 7.16 2329 343* no 
delamination 
C7 7.43 2088 --** no 
delamination 
8 4.76 1952 616 no 
delamination 
9 5.21 1861 525 no 
delamination 
10 5.74 2329 782 no 
delamination 
11 6.01 2193 698* no 
delamination 
12 5.56 2056 1056 no 
delamination 
13 5.78 2374 652 no 
delamination 
14 6.41 2769 768* no 
delamination 
15 4.58 2088 479 no 
delamination 
16 6.67 2438 531* no 
delamination 
17 4.54 2134 614 no 
delamination 
18 4.76 2347 585 no 
delamination 
19 4.85 2270 689* no 
delamination 
20 6.76 -- -- -- 
21 7.48 -- -- -- 
22 8.99 -- -- -- 
C23 11.9 -- -- -- 
C24 11.3 -- -- -- 
______________________________________ 
*Fiber pull out observed 
**Complete fiber pull out observed 
The examples show that softer, more conformable loop materials can be 
obtained by using lower crystallinity polypropylene and blends with 
polyethylene as the extrudate for the thermoplastic backing layer of the 
loop material. This can be achieved while maintaining good bond strength 
between the polypropylene fibers and the backing layer of the loop 
material. Good bond strength was also maintained between an additional 
printed polyethylene film backing layer and the backing layer comprising 
the lower crystalline polypropylene polymer and blends. 
Comparative Example C1, prepared by extrusion bonding a higher 
crystallinity polypropylene thermoplastic backing layer in combination 
with a printed cast polypropylene film backing layer, was very stiff and 
non-conformable. The stiffness of the loop material was reduced somewhat 
by extrusion bonding this polypropylene thermoplastic backing layer to a 
printed polyethylene film backing layer (Comparative Examples C2 and C3); 
however, delamination between the two backing layers readily occurred. A 
softer loop material which had good bond strength between the backing 
layer and the printed polyethylene film backing layer was obtained when a 
100% polyethylene extrudate was used for the backing layer (Comparative 
Example C7); however, fiber pull out was observed during peel testing 
indicating poor bond strength between the polypropylene fibers and the 
polyethylene backing layer of the loop material. Stiffness was also 
reduced somewhat, and the bond strength between the backing layer and the 
printed polyethylene film backing layer improved, by using blends of 
conventional higher crystallinity polypropylenes and polyethylene for the 
thermoplastic backing layer (Comparative Examples C4, C5, and C6); 
however, this resulted in either poor bonding between the polypropylene 
fibers and the thermoplastic backing layer (C5 and C6) or in poor bonding 
strength between the blended thermoplastic backing layer and the printed 
film layer (C4). 
The Examples also show that as the amount of the lower crystallinity 
polypropylene in the extrudate blend was increased, the softness of the 
loop material also increased. However, fiber pullout was observed when the 
extrudate blends contained lower levels of the lower crystallinity 
polypropylene (25%), suggesting that a decrease in the bond strength 
between the polypropylene fibers and the blended backing layer was 
beginning to occur. 
Examples 25 and 26 and Comparative Example 27 
Examples 25 and 26 and Comparative Example 27 were prepared in a manner 
similar to that described for the Examples above except that a preformed 
backing was thermally bonded to the corrugated fiber sheet instead of 
extruding a thermoplastic backing layer to the fiber sheet. This type of 
thermal bonded loop material and the method for making it is generally 
described in European Patent No. 341 993 B1. The carded web was prepared 
from 15 denier polypropylene fibers (Type EC-486 available from Synthetic 
Industries) and was point bonded (bond area 15%). The basis weight of the 
fiber sheet (before corrugation) was 45 grams/meter.sup.2. For these 
examples the basis weight of the film backing was 80 grams/meter.sup.2. 
The film backing compositions are given in Table III along with 135 Degree 
Peel and Circular Bend Stiffness data. 
TABLE III 
______________________________________ 
PE 135 Circular 
PP Resin Resin Degree Bend 
Example Type Type PP:PE Peel Stiffness 
______________________________________ 
25 "REXFLEX 1020 75:25 
1304 12.0 
"W112 
26 "REXFLEX -- 100:0 1296 10.7 
"W112 
C27 SRD 7560 -- 100:0 1100 25.8 
______________________________________ 
These examples demonstrate that soft loop materials can be made by thermal 
bonding a film backing to a fibrous sheet when the film backings comprise 
lower crystallinity polypropylene.