Note: Descriptions are shown in the official language in which they were submitted.
t 31 1 351
HIGHI,y ~NONWOVE~7 FABRIC M~DE BY HYDROENTANGLEMENT
This invention relates to highly absorbent
hydroentangled nonwoven fabrics containing wood pulp
5 and textile length fibers, and to methods of their
preparation. In one of its more specific aspects, the
present invention relates to a uni~ue apertured or
nonapertured composite fabric consisting essentially of
a relatively high proportion of wood pulp intimately
10 entangled with synthetic staple fibers. In another of
its more specific aspects, a non-apertured, strong,
highly absorbent fabric suitable for use as disposable
surgical toweling is produced by blending wood pulp and
staple synthetic polymer fibers, dispersing the blend
15 of fibers in an aqueous carrier, forming a wet-laid web
of blended fibers, subjecting the wet-laid web to the
action of high pressure fluid jets, drying the web, and
subjecting the dried web to embossment with matched
dies.
23
Composite webs made up of various combinations of
fibers are known in the prior art. Nonwoven fabrics in
which staple length textile fibers are hydroentangled
with continuous f ilaments are disclosed in U.S.
25 3,494,821 and 4,144,370. In U.S. 3,917,785, staple
rayon fibers are blended with wood pulp, supported on
an impermeable patterned support, and subjected to the
force of water from jets to hydroentangle the fibers
and form an apertured fabric. In U.S. Patents Nos.
30 3,917,785 and 4,442,161, a layer of textile fibers,
which may be mixed with wood pulp, is supported on a
foraminous screen and hydroentangled by means of
. . .
- 2 ~ 3 5 t
hydraulic jets to form a non-woven fabric.
Nonwoven fibrous webs comprising mixtures of wood pulp
and synthetic fibers have high moisture absorption
capabilities and may be inexpensively produced by
conventional papermaking procedures. However, such
products also tend to have relatively low wet strength
properties and lack sufficient strength for many
applications, for example, for use as surgical towels,
household cloths, food service wipes and industrial
machinery wipes. The strength of such products may be
improved by including a bonding agent in the fiber
furnish or by application of an adhesive binder to the
formed web. While the strength characteristics of the
lS web are improved by use of an adhesive binder, such as
a synthetic resin latex, the liquid absorption
capability of the web is correspondingly decreased.
We have now discovered that a high strength, nonwoven
highly absorbent fabric having visual and clothlike
hand characteristics of a woven towel and superior
moisture absorption may be produced from a homogeneous
blend of 30 to 80 weight percent wood pulp and ~0 to 70
weight percent long synthetic fibers by forming first a
wet laid web or blanket of the fibers in the desired
relative proportions and subjecting the wet laid web to
hydroentanglement with sufficient energy to form a
relatively dense, cohesive, uniform fabric. In a
preferred embodiment, this fabric is then embossed at
room temperature between two matched, interpenetrating
dies. In one specific embodiment of this invention, a
wet laid web of wood pulp and staple synthetic staple
fibers is formed in known manner, dried, and, subjected
1 3 1 1 35 1
-- 3 --
to hydraulic entanglement. As a specific example, wet-
laid webs having a to~al basis weight of 3 to 5 ounces
per square yard made up of 50 to 75 weight percent wood
pulp and 25 to 50 weight percent polyester fibers
hydroentangled at an energy output of the order of
10,000 KPa produces a strong nonwoven fabric having
superior water absorption qualities as compared with
woven cotton huckaback towels and,when embossed as
disclosed herein, comparable hand characteristics with
clothlike softness and texture.
The nonwoven fabrics of this invention containing a
substantial proportion of wood pulp are strong when wet
and highly absorbent, and do not require stabilization
15 with a latex adhesive. The staple length fiber may be
produced by known methods from any of various synthetic
resins including polyolefins, nylons, polyesters, and
the like; polyester fibers are preferred.
In accordance with the present invention, the synthetic
textile fibers are blended with wood pulp and formed
into a web by a wet-laying process technique as
utilized in the paper and nonwovens industries. One or
more such composite wet-laid webs are then subjected to
25 hydraulic entanglement producing a uniform spunlaced
composite fabric with superior water absorption
properties. A preferred method and apparatus for
hydraulically entangling the fibers is disclosed in
U.S. Patent No. 3,494,821.
Preferably, the composite we~-laid web is produced by a
conventional wet-laid papermaking method by dispersing
' . '~
4 1 31 1 351
a uniform furnish of wood pulp fibers and staple
synthetic fibers onto a foraminous screen of a
conventional papermaking machine. V.S. Patent No.
4,081,319 to Conway and U.S. Patent No. 4,200,48~ to
Brandon et âl. disclose wet-laying methods which may be
used to produce a uniform web of wood pulp and staple
fibers. A preferred method of dispersing a mixture of
staple fibers and wood pulp is disclosed in u.S.
Patent No. 4,925,528 filed April 6, 1987.
10 While various wood pulps may be incorporated into the
finished fabric by the method disclosed herein, those
pulps which are characterized by long, flexible fibers
of a low coarseness index are preferred. Wood fibers
with an average fiber length of three to five
15 millimeters are especially suited for use in the
spunlaced fabrics. Western red cedar, redwood and
northern softwood kraft pulps, for example, are among
the more desirable wood pulps useful in the nonwoven
spunlaced fabrics of my invention.
20 Staple fiber length is an important factor affecting
the strength and abrasion resistance of the resulting
fabric. Staple fibers which are either too short or
too long do not entangle as well as those in the range
of from about one-quarter inch to about one inch with a
25 diameter range of 0.5 to 3 denier. Staple fibers in
the range of one-half inch to seven-eighths inch in
length and a diameter in the range of 0.5 to 2.9 denier
are preferred for use in the process of this invention.
Shorter staple fiber lengths in the range of from about
30 one-quarter to one-half inch result in lowered tear
'A~,
~ 5 ~ 1311351
strength of the finished product. Tbe staple fiber~
may be round, elliptical, or scalloped oval in cross
section.
The wood pulp content of the improved nonwoven web
produced in accordance with the present invention may
be in the range of from about 30 weight percent to
about 80 weight percent. For most applications, a wood
pulp content in the range from about 55 weight percent
to 65 weight percent is preferred. The higher levels
of wood pulp impart increase absorbency of the product,
but usually result in some loss of abrasion resistance,
and tensile strength.
In carrying out the process of the present invention,
the entangling treatment described in the prior art,
for example, by the hydroentanglement process disclosed
in U.S. Patent No. 3,485,706 to F. J. Evans, or
3,560,326 to Bunting, Jr., et al., may be employed. As
known in the art, the product fabric may be patterned by
carrying out the hydroentanglement operation on a
patterned screen or foraminous support. Nonpatterned
products also may be produced by supporting the layer or
layers of fibrous material on a smooth supporting surface
during the hydroentanglement treatment as disclosed in
U.S. Patent No. 3,493,462 to Bunting, Jr., et al.
The basis weight of the finished fabric may range from
about 1 ounce per square yard to about 10 ounces per
square yard. The lower limit generally defines the
minimum weight at which acceptable water absorption and
web strength can be attained. The upper limit
1 31 1 351
-- 6 --
generally defines the weight above which the water jets
are not effective to produce a uniformly entangled web.
The wet-laid web may be -produced on-site and fed
5 directly from the web-forming apparatus to the
hydroentanqling apparatus without the need for drying
or bondin~ of the web prior to hydroentanglement.
Alternatively, the wet-laid composite web may be
produced at a separate site, dried and supplied in
10 rolls to the site of the hydroentanglement device.
The separately formed wet-laid web containing the
staple length textile fibers and wood pulp fibers is
hydroentangled by water jets while supported on a
15 foraminous screen or belt, preferably one made up of
synthetic continuous filaments woven into a screen.
The web is transported on the scree~n under several
water jet manifolds of the type described in U.S.
Patent No. 3,485,706. ~he water jets entangle the
~0 discrete staple fibers and wood fibers present in the
wet-laid web producing an intimately blended strong
absorbent composite fabric. After drying and
embossing with matched dies at room temperature, the
- resulting fabric is soft and is a suitable material for
25 conversion to surgeon's hand towel~ and other products
useful in disposable personal care or health care
applications, or as durable, multiple use products.
Food service wipes, domestic hand towels or dish
towels, and other utility wipes made up of spunlaced
30 synthetic staple fibers and wood pulp are stronger,
more absorbent and generally superior in service to
cloth toweling and similar products made up of
hydroentangled rayon bonded with latex or those made ~f
7 t31 135~
scrim reinforced cellulose tissue.
Colored fabrics may be made up from dyed wood pulp, or
dyed or pigmented textile staple fibers or both.
The fabric may be sterilized by currently known and
commercially available sterilization processes, e.g.,
gamma irradiation, ethylene oxide gas, steam, and
electron beam methods of sterilization.
By proper selection of the entangling screen, the
fabric may be given a fine linen like pattern and
texture. This fabric also may be post embossed with a
matched die pattern at room temperature; the
15 combination of embossing and fine linen like screen
pattern imparts a unique appearance, clothlike feel,
bulk, softness and texture to the fabric.
Optionally, a small amount of binder may be
20 incorporated in or applied to the surface of the
hydroentangled web to improve its abrasion resistance
and reduce linting. A low lint count is an important
quality of wipes for use in clean rooms. A wide
` variety of latex binders, thermoplastic binder fibers
25 and thermoplastic powders are available as binders or
wet strength binders.
Fig. l is a simplified, diagrammatic perspective view
o hydroentanglement apparatus illustrating one
30 specific embodiment of a suitable method for making the
nonwoven fabric of this invention from one or more wet-
laid webs.
.
.
t3~ ~5t
-- 8 --
Fig. 2 is a bar graph illustratinq the absorption rate
of samples, the test results of which are reported in
Table I.
. . .
Fig. 3 illustrates graphically the absorbency under
load of the samples reported in Table I.
Fig. 4 is a vertical cross-sectional view along the
plane 4-4 of Fig. 5 illustrating on an enlarged scale a
dry hydroentangled web pressed bPtween the surfaces of
matched die embossing rolls.
Fig. 5 is a plan view of an enlarged section of a web
embossed in a preferred embossment pattern.
Fig. 6 is a developed cross-sectional view on an
enlarged scale illustrating the surfaces of matched
dies and their relationship to the web during the
embossing process.
Preformed wet-laid webs 11, 12, 13 and 14 made up of an
intimate blend of staple fibers and wood pulp are drawn
from supply rolls 15, 16, 17 and 18 over guide rolls
21, 22, 23 and 24 by feed rolls 26 and 27 onto a
foraminous carrier belt 28. A woven polyester screen
formed of a flexible material is suitable as a carrier
belt for transporting the wet-laid webs through the
hydroentanglement apparatus to form a uniform fabric
web 40. The carrier belt 28 is supported on rolls 31,
32, 33 and 34, one or more of which may be driven by
suitable means, not illustrated. A pair of rolls 36
and 37 remove the hydroentan~led web fabric 40 from the
belt 28 for drying and subsequent embossing treatment.
t 3t t 35t
g
Several orifice manifolds 41, 42 and 43 are positioned
above the belt 28 to discharge small diameter, high
velocity jet streams of water onto the wet-laid webs
and resulting composite web 40 as it moves from rolls
5 26 and 27 to rolls 36 and 37. Each of the manifolds
41, 42 and 43 is connected with a source of water under
pressure through conduits 46, 47 and 48, and each is
provided with one row of 0.005 inch diameter orifices
spaced on 0.025 inch centers (to provide 40 orifices
iO per linear inch) along the lowermost surface of each of
the manifolds. The spacing between the orifice outlets
of the manifolds and the web directly beneath each
manifold is preferably in the range of from about one-
quarter inch to abut one-half inch. Water from jets
- 15 discharged from the orifices which passes through the
web 40 and the screen 28 is removed by vacuum boxes 51~
52 and 53. Although only three manifolds are
illustrated, representing three separate pressure
stages, as many as fourteen manifolds are preferred,
~0 the first two operating at a manifold pressure of about
200 psig and the remainder at pressures in the range of
400 to 800 psig as described in the specific examples
herein.
25 In accordance with this invention, after the
hydroentangled web 40 is dried by conventional drying
apparatus, not illustrated, the dried web is embossed
with matched embossing dies as illustrated in Figs. 4
to 6. An enlarged section of embossed web 40 is
30 illustrated in Fig. 5 in a plan view with an arrow
indicating the machine direction of the web. The rows
of embossments 4~' are depressed into the upper surface
. . .
1 31 1 351
-- 10 --
of the hydroentangled web 40 while alternate rows of
embossments 44' are impressed into the web from its
opposite side. This type of embossing is known in the
art as "perfembossing".
Fig. 4 is a cross-sectional view, greatly enlarged in
scale, of the embossed web of Fig. 5 taken along the
plane 4-4 of Fig. 5. As illustrated, the impressions
from the bosses or "knuckles" of the embossing tool are
10 spaced apart by a distance greater than the width of
the boss. This produces a uniform pattern on both
sides of the web.
Fig. 6 is a developed cross-sectional view taken along
15 the plane 6-6 of Fig. 5 illustrating the relationships
of ~he web and the embossing dies during the process of
embossment. For the purpose of simplification and
clarity of illustration, the surfaces of the
cylindrical embossing rolls 43 and 45 are shown as flat
20 plates 43 and 45. Fig. 6 is in three sections A-A,
B-B, and C-C, corresponding to planes A-A, B-B, and C-C
of Fig. 4. The bosses 42 extending downward from the
surface 43 of the upper embossing roll form depressions
42' of Figs. 4 and 5 in the upper surface of web 40
25 while the bosses 44 extending upward from the surface
45 of the lower embossing roll form impressions 44' of
Figs. 4 and 5 on the lower surface of web 40.
Steel-to-steel matched embossing rolls marketed by
30 Industrial Engraving Company under the trade
designation I-8306 are capable of operation to produce
the patterns illustrated in Fig. 5. The embossing roll
43 may be provided with continuous raised lands 46
- 11 - 1 3~ 1 351
interconnecting bosses 42, and embossing roll 45 may be
provided with continuous raised lands 4B
interconnecting bosses 44.
..
5 Embossment of the hydroentangled web 40 in this manner
improves absorbency and appearance of the finished
product and greatly improves the hand of the fabric as
demonstrated in Examples 7 and 8, herein below.
EXAMPLE 1
In this example, a 2/1 twill, 31 x 25 mesh,
polyethylene terephthalate (PET) screen from National
15 Wire Fabric Corporation having a warp diameter of
0.0199 inch and a shute diameter o~ 0.0197 inch with an
open area of 22.9 percent and an air permeability of
590 cubic eet per minute is used as the carrier belt
for the hyaroentanglement operation.
A wet laid 3.8 oz./s~. yd. (79 lb./ream) web is
prepared from a mixture of 60 weight percent long fiber
northern softwood kraft pulp and 40 weight percent of
1.5 denier by three-quarter inch polyethylene
25 terephthalate (PET) staple fibers. The web is passed
at a speed of 240 ft./min. under water jets from a
manifold provided with a row of 0.005 inch diameter
orifices spaced 0.025 inch apart extending across the
full width of the web. The fibers in the web are
30 hydroentangled by subjecting them to two passes under
the rows of water jets operating at a manifold pressure
of 200 psig (1380 KPa), four passes at a manifold
pressure of 400 psig (2760 KPa), and eiqht passes at a
131 1351
- 12 -
mani~old pressure of 800 psig (5520 KPa).
Properties of the resulting hard finished nonwoven
fabric produced in this example are shown in the
5 accornpanying Table I (Specimen A) in comparison with
the properties of several commercially available
products including the conventional "huck" (huckaback)
cotton towels.
1311351
-- 13 --
TABLE I
SPECIMEN A B ~l) C (2) D (3)
B~sis Weight
(oz/sq yd) 3.8 3.1 2.25 7.8
Thickness (mils) 35 25 18 57
Grab Tensile (lb)
MD Wet 19 6 5 97
CD Wet 19 5 5 82
Grab Elongation (~)
MD Wet 90 25 34 34
CD Wet 100 50 26 26
Elmendor~ Tear (g)
MD Wet 1600 200 80 4000
CD Wet 1900 220 50 4000
Absorption Capacity
(g/g) 6.2 4.2 3.6 3.2
Area C~pacity
(g/m ) 850 450 280 936
Wicking Rate
(g/g/sec)X 1000 38.7 29.9 26.8 16.8
Bulk Density
~cc/g) 8.2 6.1 5.8 4.8
Flammability (sec)
NFPA-702 - MD - 6.5 5.5 4.3 16.8
- CD 7.4 6.5 4.4 25.6
J ~ 25
(1) Sample B is a hydroentangled 100% rayon fiber
towel containing a latex binder sold under the trade
name J&J Surgisorb, by Johnson & Johnson, New
Brunswick, New Jersey.
(2) S~mple C is a scrim reinforced tissue product
having two to four plies of wood cellulose tissue
rein~orced by an internal web of synthetic fiber sold
under the trade name Kaycel by Kimberly Clark
Corporation of Neenah, Wisconsin.
(3) Sample D is a generic huckaback woven cotton
towel.
. ~ 35
- 14 - 1 31 1 351
It will be evident from the foregoing example that the
nonwoven fabric of this invention (Sample A) provides
superior absorption capacity as compared with
conventional huckaback woven cotton towels (Sample D)
and currently available non-woven fabrics represented
by Samples B and C. The absorption capacity of Sample
A of our nonwoven fabric is twice that of the huck
towel, on a weight basis while the nonwoven fabric is
approximately 50~ lighter in basis weight. Even at the
lower basis weight, the fluid area capacity of the
nonwoven fabric (Sample A) compares favorably with that
of the huck towel (Sample D).
EXAMPLES 2 TO 5
In these examples, fabrics are produced by forming wet-
laid webs of varying fiber compositions and subjecting
the ~e~laid webs to the conditions described in
Example 1. The forming screen in Examples 2 and 3 is
the same as that of Example 1. In Example 4, the
forming screen is made up of PET fibers with a warp
diameter of 0.024 inch and a shute diameter of 0.028
inch and an air permeability of 555 cfm. The forming
screen of Example 5 is made up of PET fibers with a
warp diameter of 0.042 inch, and shute diameter of
0.049 inch.
In Examples 2 and 3, the fabric is made up from four
layers of preformed and dried wet-laid substrate webs
as illustrated in Fig. 1 of the dra~7ings. The PET
component of Examples 2 and 3 is three-quarters inch,
1.5 denier staple fibers; in Examples 4 and 5, the PET
fibers are three-quarters inch by 1.2 denier. In
l~t 135t
- 15 -
Examples 4 and 5, the fabric is made ~p from two layers
of preformed and dried wet-laid substrate webs.
Physical properties of the finished fabrics are shown
5 in Table II. The data from Specimen A of Example 1 are
repeated for comparison purposes.
" - 16 - 131 1351 ``
. . .
mAB L E I I
SPECIMEN A E F G H
EXAklPL~ 1 2 3 4 5_
Fiber Composition
5~wt. %) Pulp 60 50 75 60 60
,' PET 40 50 25 40 40
Forming Screen
Mesh (per in) 31x2431x25 31x25 22x23 20~16
Twill 2/1 2/1 2/1 2/1 2/1
Basis Weight
10toz/sq yd) 3.8 3.8 3.8 3.8 3.8
Thickness (mils) 35 27 38 44 48
Peak Grab Tensile
Dry(lbs) MD 42.3 25.0 32.0 40.5 41.7
CD 39.6 16.0 22.0 40.7 35.3
15Wet(lbs) MD 19 12.0 14.0 26.5 22.6
CD 19 6.0 10.0 26.4 22.9
Peak Grab Elongation
Dry(~) MD 39.3 53.1 47.8 57.3 53.3
CD 48.2 94.5 66.3 62.4 71.7
Dry(%) MD 90 81.9 54.5 79.8 86.7
20CD 100102.6 107.4 85.4 98.9
Slemndor Tear
Dry(g) MD 1470 1100 950 1650 1633
CD 1065 850 1083 1483 1833
Wet(g) MD 1600 1100 950 2733 3800
CD 1900 580 583 3133 2475
25 Mullen Burst (p5i) 122 63 68 87 93
Air Permeability
(cfm) - 230 98 223 248
Absorptive Capacity
(g/g) 6.2 7.2 5.97 7.55 7.57
~P Y
(g/m ) 850 802 802 866 833
Wicking Rate
(g/g/sec)X 1000 38.7 46.6 32.9 20.78 34.45
Flammability (sec)
MD 6.5 4.2 5.2 7.6 9.4
NFPA-702 CD 7.4 5.3 5.7 7.4 11.0
- 17 - 13~13~1
EXAMPLE 6
A fabric is made up from a wet-laid web composed of 60
weight percent cotton linters and 40 weight percent
5 three-quarter inch by 1.2 denier polyethylene
terephthalate (PET)..staple fibers on the forming screen
and under the conditions described in Example 1.
Physical properties of the product are listed in Table
10 III.
131 1351
- 18 -
TABL~ III
Example 6
Basis Weight (oz/yd2) 4.9
5 Thickness (mils) 43.6
Peak Grab Tensile
Wet(lb) MD 21.3
CD 2~.0
Peak Grab Elongation
Wet(%) MD 84.5
10CD 83.1
Elmendorf Tear
Wet(g) MD 3100
CD 3800
~bsorption Capacity (g/g) -- 5.59
Wicking Rate (g/g/sec)X 1000 7.34
~rea Capacity (g/m2) 85
Flammability (sec)
NFP~-702 MD 10.9
20CD 9.2
In the following examples, nonwoven hydroentangled
fabrics were produced from wet laid webs,dried and
embossed between steel-to-steel matched embossing
25 rolls. The matched steel rolls supplied by Industrial
Engraving Co. were-provided with an elongate hexagonal
protuberances or knuckles as illustrated in Fig. 4. In
these examples, the embossing rolls were adjusted to
produce a center float half step perforation pattern as
30illustrated in Fig. 5. The knuckles on each of the
embossing rolls have an overall lonyitudinal base
dimension in the machine direction of 0.114 inch, a
base width in the cross machine direction of 0.030
131 t351
- 19 -
inch, a height of 0.046 inch, a machine direction
spacing of 0.029 inch, and a spacing of 0.148 inch in
the cross machine direction. The sides of the knuckles
have a slope of 3 from the vertical plane or radius of
5 the roll; the slope of the end of a knuckle is 25
relative to the vertical or radius of the roll.
ExamPle 7
In this example, a nonwoven fabric is produced by
10 forming a wet-laid substrate (95 lb./ream) of 60%
Northern softwood kraft and 40% of three-quarter inch
by 1.5 denier PET staple fiber. The forming screen in
this example is the same as that of Example 1. The web
was subjected to two passes under the rows of water
15 jets operating at a manifold pressure of 200 psig
(1380) KPa), ~our passes at a manifold pressure of 800
psig (5520 KPa) and 4 passes at 1600 psig (11040 KPa)
affecting intimate entanglement of the wood fibers and
staple fibers.
The web was then dried and embossed with matched
(Industrial Engraving I-8306) steel-to-steel embossing
rolls. We used two levels of penetration of either 25
of 50 mils and the rolls were set either at a side
25 contact or center float for both full or half step
perforating condition. Absorbent properties of the
resulting finished nonwoven fabric produced in this
example are shown in Table IV.
-
~31 1351
- 20 -
TABLE IV
SPECIMEN J (unembossed) K (embossed)
EX~MPLE 6 7
Fiber Composition
Pulp (w~ %) 60 60
PET (wt %) 40 40
Basis Weight
(oz/sq yd) 4.68 4.75
(g/sq m) 158.9 161.3
Bulk*
(cc/g) 5.0 6.9
Absorptive capacity
(g/g~ 4.29 4.69
(g/m ) 682 75
Initial Wicking Rate
(g/g/sec)X 1000 5.1 9.8
Absorption Time (sec)
89 83
*Measured under 7 g/cm2 con~ining pressure.
ExamPle 8
A wet laid web having a basis weight of 3.8 ounces per
square yar~, as in Example 1, was prepared and dried
and then hydroentangled at a speed of 40 feet per
25 minute under two rows of wAter jet operating at a
manifold pressure of ~00 psig, two rows at 900 psig,
and one row at 1200 psig followed by two rows at 400
psig on the reverse side of t-he fabric. After drying,
the hydroentangled fabric was embossed at 40 feet per
30 minute with the pattern illustrated in Fig. 5 at 50
mils penetration. Properties of the embossed and
unembossed webs are set forth in Table V.
1 3 1 1 35 1
- 21 -
TABLE V
SPECIMEN L (unembossed) M (embossed)
EXAMPLE 6 7
Basis ~eight
(g/~l ) 127 127
(oz/yd2) 3.74 3-74
Dry Bulk (Load = 7 g/cm2)
(cc/g) 6.1 10.5
Wet Bulk (Load = 7 g/cm2)
(cc/g) 5.8 9.5
Wet Bulk Under Load
(cc/g) 4.6 6.4
(Load = 100 g/cm2)
Wet Bulk After Load
Removal ~cc/g) 5.4 7.8
Wet Bulk Recovery After
~emoval of Load (%) 17 22
Absorption capacity
(g/9) 5 6.7
20 Area capacity (g/m2) 635 850
Softness (Loop Test)*
MD 57 23
CD ............ 25 5
; Softness (Sensory)** 65 82
25 Hand Crush (Sensory)** 55 87
*Lower number = softer end product.
**~igher number = softer end product.
30 With reference to Table 5, it will be observed that
embossment improved the dry bulk (measured under 7
g/cm2 confining pressure) of the product was improved
by 70 percent. The first value is the bulk of the
13~ 1351
- 2~ -
specimen after absorption of water under a load of 7
g/cm2. The second value is determined after placing a
load of lO0 g/cm2 on the wet specimen and the final
value is determined after removal of the load. The wet
3 5 bulk recovery, reported in percent, is calculated from
the wet bulk under load and the wet bulk after removal
of the load. The wet bulk recovery of the specimens
shows that the embossed specimen has the greater
resilience. It can be observed that the absorbency per
10 square meter of the product, related to its resilience,
increased by more than 33 percent.
Softness of the specimens was measured by the so-called
Loop Method and by a sensory softness test panel. The
15 Loop Test Method is designed for determining the
softness of flexible sheet materials by measuring the
force required to cause a specimen, which was
previously formed into a loop and held in a specimen
holder, to buckle. In this test, if the treated
20 specimen re~uires a lower force to bend than untreated
specimen, then that specimen is softer. At least five
specimens 88.9 mm X 25.4 mm (3.5 in. by 1 in.), in both
machine and cross direction are selected ~or testing
and the results averaged. These samples (conditioned
25 at 23 degree F and 50~ RH) were tested by the Loop
Softness Tester and the result recorded in table V.
The force required to buckle the embossed specimens,
for both machine and cross machine directions, is
considerably lower than for the unembossed specimens.
30 The softness of this product was also measured by a
group of twenty in-house softness panelists. This test
result (Table V) also conirmed the results obtained by
the Loop Test Method.
131 1351
As indicated in Table III, embossment of the
hydroentangled dry nonwoven web by this method of
embossment enhanced the absorption rate and increased
the absorption capacity of the web. In addition, the
5 apparent bulk, softness and hand of the product was
comparable to that of the huck towel of Example l.
From the foregoing examples, it will be seen that the
nonwoven fabric of Example l, Specimen A of Table I,
` 10 compares favorably with that produced in Example 5,
particularly with respect to wicking rate, area
capacity and absorption capacity.
In the foregoing examples, the Elmendorf tear strength,
15 reported in grams is determined by repeated tests on an
Elmendorf tear tester using single ply test strips.
Thickness, reported in mils, is determined with an
Aime~ 212.5 lot tester on a single ply of the
specimen.
The absorption capacity in Examples 1 to 3 and 6 to 8
is determined by a fluid absorption test method which
measures tne ability of a material to absorb as much
fluid as it will hold without being flooded. A
25 material sample is placed over a sintered glass porous
plate and liquid from a reservoir is allowed to flow
through the plate as it is absorbed by the material
undergoing test. The weight of the reservoir is
recorded before the test and again after the sample no
30longer absorbs additional fluid and has reached its
maximum fluid saturation without flooding. The liquid
absorption ratio is calculated and reported as the
- 24 - 131 13~t
amount of ~luid in grams absorbed per gram of the
material sample. Liquid absorption ratio is
independent of the sample's actual weight.
5 The wicking rate is a method used to determine the time
elapsed in seconds for a liquid to travel 6 centimeters
along a vertically suspended 2.5 x 10 cm ~est specimen
with the lower end in contact with the liquid. The
sample weight is recorded before and after the liquid
10 has reached the six centimeter mark. The vertical
wicking rate is reported as the ratio of the liquid
weight to sample dry weight divided by the time elapsed
in seconds (g of liquid/g dry weight of sample/sec).
This ratio is then multiplied by 526. The test is
15 repeated on specimens cut from the material in both the
machine direction and the cross direction and the
average is reported.
The method for determining absorbency under load or wet
20 resiliency properties of nonwoven fabrics measures the
absorbency of the material under load; specifically, it
measures the absorbency capacity of the test specimen
after successively increasing the load over the sample
in 500 gram weight increments. The test is conducted
25 as described above, and absorption capacity is
determined in 500 gram increments from 50 grams to 2500
grams load weight.
Area Capacity is a~aerived number indicating the liquid
30 holding capacity of a sample and is expressed in grams
per square meter. Area capacity is calculated by
multiplying the absorptive capacity of the test
material expressed in grams of liquid per gram of
material by the basis weight in grams per square meter.
The Mullen Burst test (ASTM-D3786-802) is used to
determine the bursting strength of fabrics and films in
5 a hydraulic diaphragm type bursting tester. The
bursting strength i5 .eported in pounds per square inch
hydraulic pressure required to rupture a 1.2 inch
diameter test specimen by distending it with force
applied from one side by a flexible diaphragm of the
10 same ~iameter as that of the specimen.
Grab Tensile and Grab Elongation are measured by ASTM
D1682-64 test method, to determine the load in pounds
and elongation in percent at the break point in a
15 constant rate of extension tester.
Flammability is determined by using NFPA Test Method
Number 702.
.
