Note: Descriptions are shown in the official language in which they were submitted.
3~97
1.
- The present invention re ~tes to novel nonwoven
~ materials and, in particular, materials which are suitable
; as all purpose wipes which possess the attributes of woven
cloth. The invention is especially concerned with providing
a disposable wipe material for use in industrial applications.
The launderable cloth industrial towel and rags
salvaged from discarded clothing and the like constitute the
principal wipe market as such exists today. The launderable
towel has generally good wiping properties and high fluid
retention capacity. However, it lacks uniformity, usually
contains residual oils, and, perhaps most importantly, may
contain metal chips or the like abrasive materials which
can adversely affect persons using the wipe or sensitive
wipe surfaces such as printing plates or rolls. As to rags,
these are generally non-uniform in size, composition and
wiping properties. Moreover, with the increasing use of
hydrophobic synthetic fibers in fabric manufacture~ the use
of rags as fluid wipes is generally decreasing.
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A disuosa~le wi~e material which could be
inexpensively manufacture would be highly desirable.
Heretof~re, the problem has been in providing such a disposable
material which simulates launderable cloth with respect to
softness and wiping characteristics and which also posseses
adequate strength for all wipe applications. ~hile disposable
fabrics have been suggested as wipes for certain applications r
problems have generally been encountered when the objective
is to provide an "all purpose" wipe which is useful for
(1) wiping oils, (2) solvent cleaning and (3) wet wiping.
The difficulty arises since each of these types of wipe
applications requiresgenerally different product characteristics.
- Use of oil wipes is most frequently encountered
in general machine shop applications for cleaning machinery,
parts and operator's hands. The wipe must have a small pore
structure to permit the capillaries to exert a high force to
remove oil or otller liquids. It must also have a high fluid
capacity. Moreover, since the wipe is ordinarily dry when
~ use is initiated, it should be soft and conformable, presenting
` a cotton-like feel in order to subjectively indicate absorbency.
.
Iheselatter features are customarily lacking in many disposable
wipes which possess a plastic-like surface feel due to the
presence of binders.
Solvent wipes are frequently used in the printing
industry and in cleaning metal surfaces prior to painting.
The wipes are generally presaturated with a solvent, the
saturated wipe then being rubbed over the surface to be
cleaned with the solvent being squeezed out by the rubbing
action. The wipe then must re-absorb the squeezed out solvent
and dissolved material. A dry wipe is then commonly used to
dry the clean surface. As is apparent, the solvent wipe must
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hold a large voiullle o~ solvent, relea.e the solvent undcr
pressure and then re-absorb most of it while a-t the same time
being resistant to solvent attack.
Wet wipes are used in basically three applications.
The first is similar to the above described solvent wiping
except that the wipe is presaturated with a soapy water solu-
tion rather than a solvent and is used to remove dirt and
water soluble stains. Wipes used to absorb large volume
spills, e.g. drinks, are also generally t~rmed wet wipes
although initially used in the dry state. These wipes need
a high fluid retention capacity and also must permit the
squeezing out of a major portion of absorbed liquid in order
to permit reuse. Reuse, of course, avoids the necessity of
- using a second dry wipe to effectively clean up the spill.
A final "wet" wipe application is that termea "wet dusting".
Such.a wipe must simply hold a small amount of fluid which
then acts as a glue for dust particles and the like which
are to be removed from a surface.
U. S. Patents Nos. 3,317,367 (Koller) and 3,366,532
(Maskey and Cox) and Swedish patent specification No. 327,821
(Lindquist) illustrate various wipe materials including
~ - structures bonded with regenerated cellulose. U.S. Patent
- No. 3,657,035, reissued as Re. 27,8~0 (Politzer, Alibeckoff
and Wang) illustrates the preparation of laminates of a
reticulated regnerated cellulose layer and layers of
cellulose fibers which are stated to be improved cleaning
- and wiping articles.
Among some of the major problems which have been
encountered in providing a suitable all purpose wipe are the
3~ inability to provide a sot, dry cloth-like material which
is resistant to solvents, has very little tendency to lint,
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h~s adequa~e sur~ace abrasion resistance to last through
its intended use, and has adequate wet body. As to this
latter characteristic t the wipe must be capable of retaining
its sheet-li]ie characteristics when wet and not wad or
otherwise become an unusable mass of mat~rial requirin~
unfolding and the like.
The principal object of the present invention
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resides in providing an improved disposable all purpose wipe
material which closely simulates launderable cloth in its
softness and wiping characteristics.
In connection with the principal object, an
important object of the present invention is to provide a
soft, dry, nonwoven, solvent resistant material which can
absorb and hold large volumes of water, oil or solvent, and
which is sufriciently compressible so that liquids absorbed
therein can be efficiently squeezed out.
Related to this object is the further objective
of providing a disposable wipe material which, after squeezing
when wet~ substantially reassumes its original form so as to
be capable of again absorbing and holding large volumes of
liquid. -
An additional important ob]ect lies in providing
a nonwoven disposable wipe material which is highly conformable
both to the hand of the user and to the wipe surface.
Yet a further object resides in providing a strong
nonwoven wipe material which is substantially lint free,
abrasion resistant and which possesses a functionally useful
wet body.
Still another objective of the present invention
3~ is to provide an inexpensive and commercially feasible process
for preparing disposable wipe materials having the above-
identified sought after attributes.
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Other objects and advantages of the present
; invention will be apparent as the following description
proceeds, taken in conjunction with the accompanying
drawings, in which:
Figure 1 is a schematic, highly idealized,
fragmentary perspective view of a material constructed in
accordance with the invention.
Fig. 2 is a schematic illustration of one manner
in which materials embodying the features of the present
invention can be prepared.
Fig. 3 is a photomicrograph taken at 80X magnifi-
cation of a portion of the surface of material prepared in
accordance with the present invention; and
Figs. 4 and 5 are photomicrographs taken at 300X
magnification of a cross section of a central portion of
material prepared in accordance with the present invention.
While the present invention is susceptible of
various modifications and alternative constructions, there
is shown in the drawings and will herein be described in
detail the preferred embodiments. It is to be understood,
however, that it is not intended to limit the invention to
the specific forms disclosed. On the contrary, the invention
is to cover all modifications and alternative constructions
falling within the spirit and scope of the invention as
expressed in the appended claims.
Turning now to the drawings, a soft, absorbent
nonwoven material 10 constructed in accordance with the
invention is illustrated in a highly idealized fashion in
Fig. 1. The wiping surfaces of the material 10 are defined
by the two outermost X-Y planes of the illustrated structure
with the material thickness lying in the Z-direction. The
ma~rial l~ consis~ 4s~qentlally o~ a ~hree dimensional web
of an open array of long fib~rs 12 adhere~1 together by
regeneratecl cellulose ~ragments l4 to form a coheren~ structure.
I~he fibers 12 of the web are randomly arranged in
an open array with a predominant number thereof lying sub-
stantially in the X-Y ~lanes of the material in order to
pxovide good strength characteristics in the baSic sheet
directions. However, it is an important aspect of the
present invention that a minor fraction, e.g , about 5-25%,
of the fibers 12 have substantial Z-direction orientation
intersecting the X-Y planes of the material. In addition
to integrating the material so as to provide delamination
resistance and abrasion resistance, the presence of such
Z-direction oriented fibers is also believed to contribute
to several other desirable features of the material. Being
oriented out of the basic sheet direct on, tha fibers provide
-desirable material resiliency contributing to softness and
also aid ln preventing collapse of the open array when the
material is wetted. -
~ Turning specifically to the regenerated aellulose
fragments 14, the nature of the frayments as well as their
distribution in the material are important features of the
illustrated material. As is evident from the photographs,
~the regenerated cellulose is, indeed, present as fragments
as distinguished from a continuous network throughout the
material. On the other hand, as illustrated in Fig. 3, the
individual fragments are larger and are highly reticulated and
porous in structure on and adjacent to the surfaces of the
material as contrasted with the center region where less
reticulated and smaller fragments are present (Figs. 4 and 5~.
~1hile the bonding which is achieved by adherence of the
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fragments to the fibers is adequate to provide a useful
wipe, the fact that the cellulose is present as fragments,
having a fine reticulated structure contributes to softness
and conformability of the mater:ial.
Referring to Figs. 1 and 3-5, it will be noted
that the regenerated cellulose fragments are dispersed in
a random fashion throughout the open array of fibers.
However, as illustrated schematically in Fig. 1, the
fragment size and concentration of regenerated cellulose
is greatest in those regions at and adjacent to the wiping
surfaces and progressively diminishes toward the midsection
of the material. Due to the greater concentration of
regenerated cellulose at the surface and associated
increased fiber bonding, the material has good surface
abrasion resistance. The diminished degree of bonding in
the central region, due to the lower concentration of
regenerated cellulose, enhances conformability and drap~
ability of the material.
While there is a diminished intensity of bonding
-20 toward the midsection of the material, it should be appre-
ciated that, due to the presence of Z-direction oriented
fibers extending across the midsection, the material of
the present invention is in fact an integrated, coherent
single web.
As is evident from the above description, the soft,
absorbent product of this invention consists of two essential
constituents, i.e., a three dimensional web of an open array
of long fibers, a fraction of which have Z-direction orienta-
tion, and regenerated cellulose fragments. It should be noted
that, as opposed to many regenerated cellulose containing
materials, the present product is soft when dry -- there being
no necessity for including customary liquid softenlng agents
or humectants. The product is also distinguishable from
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many conventional nonwoven materials which include wet
laid ~issue and the like highly compacted, i.e., non-open,
fibrous webs as necessary components. It is similarly to
be distinguished from those nonwoven products which neces-
sarily include one or more plies of fibrous webs integrated
together by means of a laminating adhesive material or the
like. In contrast to the above t~pes of structures, the
present materials have the desirable combination of softness,
conformability, strength, and absorbency characteristics
which permit them to function very advantageously as all-
purpose wipe materials.
However, it should be understood that products of
the present invention can contain ingredients or constituents
other than the fibers and fragments so long as the presence
of such added elements does not substantially detract from
the desirable product attributes described herein. For
example, for ease in processing, the open array of fibers
can be lightly prebonded after formation with a suitable
adhesive in amounts up to' for example, about 25%; based on
the long fiber weight. The use of webs which contain, in
addition to the fibers, such adhesives also results in a
desirable increase in abrasion resistance, particularly when
the regenerated cellulose is present in a low concentration.
A general manner of preparing the products of the
present invention involves initially forming a fibrous web
having the characteristics above described, impregnating the
formed web with a viscose solution and thereafter regenerating
the viscose in a manner which results in the above described
fragment formation.
Concerning initial web formation, it is important
tha~ the web be mostly fashioned from long, textile-length
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~i~ers rath~r than the short fib~rs c~stomarily uscd
in paper makin~ appl ication~. In thj s respect, webs prepared
from fibers prcdominantly having a length of about 1/~-2 inches,
preferably, 1/2-1 inch, are most useful. Inclusion of sub-
stantial quantities, e.g., more than 50% and generally more
than 25~, of shorter fibers leads to undesirable linting of
the resultant product and requires excessive quantities of
regenerated cellulose in order to effectively bond the
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structure. This, in turn, adversely affects product soft-
ness and conformabilityO In this respect, products having
the desirable attributes identified herein have a re~enerated
cellulose content of about 10-50%, preferably, 25-40%, based
on the web weight. Also the use of long fibers enhances
the integrity of the web particularly in the Z-direction.
~hile fibers longer than about 2 inches can be
used, it is economically unattractive to prepare webs con-
taining such fibers in substantial quantities. Webs prepared
from normally hydrophilic fibers such as wool, cotton, rayon,
- etc., are preferred though the web can also contain hydrophobic
synthetic fibers such as acrylics, polyesters, polyolefins,
- etc. The fibers have a denier of less than about 15 and,
preferably, less than about 6. Conventional waste fiber stock
is generally preferred for use herein due to its inexpensiveness.
-Airlaying techniques such as random web forming are
generally suitable for preparing the initial open array of
fibers. When webs are formed in such a manner at basis
weights in excess of about 30 grams/yd.2, the requisite fiber
-- distribution and orientation discussed previously is achieved,
though for wipe applications a basis weight of at least about
~d 60 grams/yd.2 is preferred. From an economic viewpoint, there
is little incentive for preparing wipes with webs having a
- basis weight in excess of about 150 grams/yd.2 and generally
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in exc~ss ~ lOOy/yd.. It is also within the scope of
the present invention to utilize a web t~hich, after forma-
tion, ls further integrated such as by needling or the
like. Such webs can be easily handled without supplemental
adhesives and the finished material exhibits particularly
outstanding surface abrasion resistance.
After formation of the base fiber web, impregnation
of the web with a viscose solution can be effected. As
illustrated in Fig. 2, a preferred method for accomplishing
this involves sandwiching the web 16 between two driven screens
18, 20 and then vertically passin~ the sand~riched structure
between two squeeze rolls 22, 24~ As the sandwiched structure
passes between the squeeze rolls, viscose contained in the
pools 26, 28 located above each squeeze roll is farced into
- the web-with the viscose concentration gradually diminlshing
toward the -~eb mid section. The screens support the web as
it is impregnated and, once impregnation has been effected,
~he screens are removed from the impregnated web. If, as
indicated previously, the web l~ is lightly prebonded or
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further integrated, use of the screens may not be needed.
- In order to conveniently effect impregnation and
to achieve fragment formation in the manner hereinafter
described, the viscose used in connection with thè process
illustrated in Fig. 2 should be in a highly foamed state.
As described in U.S. Patent No. 3,657,035 (Re. 27,820) viscose
solutions having a high alkalinity (a weight ratio of sodium
hydroxide to viscose cellulose exceeding 0.9:1.0 and,
preferably at least 1:1) and containing a surfactant can be
readily foamed even at high viscose cellulose concentration,
e.g. 7~ by weight and above. Furthermore, it has been found
that exceptionally soft materials embodying the attrihutes
of the present invention can be provided by utilizing a viscose
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foam ~hereirl, at xanthation, a hi~h C~2 concentration~ e.y.,
yreater than ~0% based on ~ -c~llulose, is present.
As compared with ordinary viscose solutions
which have a specific ~ravity of about 1.12, viscose foam
used in the present process desirably has a specific gravity
between about O.lS and 0.6 and contains a high concentration
of very fine air bubbles. While the most useful and preferred
- foams contain about 6-8% dissolved viscose cellulose, foams
with lower concentrations formed at lower alkalinity can also
be used, particularly when the long fiber web has a high basis
weight.
Referring still to Fig. 2, after viscose foam
impregnation, the viscose in the web is then coagulated and
regenerated in a manner such that the product having the
- desirable characteristics with respect to regenerated cellu-
losa fragment formation and distrihution is obtained. Accordingly,
in keeping with the present invention, coagulation and regenera-
tion are accomplished by passing the web through a hot, e.g.
75 C. - 100C., preferably 95C.-100C. 7 aqueous solution con-
taining about 10 to 30% sodium sulphate and about 0.~ to 15
sulphuric acid.
,
- While the precise mechanism of fragment formation
which occurs on regeneration is not fully understood, it is
believed that regenerated cellulose fragment formation is
attributable to the fact that the viscose is present as a foam
and that regeneration is effected at a high temperature. Being
foamed with the accompanyiny inclusion of substantial quantities
of fine air bubbles permits rapid penetration of hot acid into
the web interior. Furthermore, the hot acid also expands the
air inside the bubbles which accellerates the rate of penetration
of acid and c~ntribut:es to fine reticulated fragment formation.
In turn, this effects rapid release of gas accompanying regenera~
tion which effectively "explodes" the viscose into fine fragments
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o~regenerated cellulose. In addition to fragment formation,
the described process of regeneration is also believed to
open up the material, thus enhancing its softness and its
capacity for absorbing and holding fluids.
Subsequent to regeneration, the material containing
the cellulose fragments can be subjected to conventional
washing, bleaching and drying techniques. In addition, the
softness and absorbency characteristics of the material can
be further enhanced by suitable embossing or other like
techniques. Additional softening is particularly desirable ;~
when the product is dried by passage over hot cans or the
like which tend to consolidate the web. For wipe applica-
tions, materials having a z-direction thickness of about
.035 inch - .065 inch are preferred. ~;
EXAMPLE
A web having a basis weight of about 65 grams/yd.2
and 42" wide was prepared using a Rando* Webber (Curalator
Corp.) from conventional waste fiber stock (50% cotton, 10%
rayon, 40% polyester - average fiber length about 0.75 inch
spread, about 1/3 inch - 1 inch). The web so formed was
lightly prebonded by spraying with "Geon"~ 576 adhesive with
an adhesive add-on of about 14 grams/yd.2 and heated to
effect drying. ; -
Using a process such as schematically illustrated
in Fig. 2, the web was then impregnated with viscose foam
having a specific gravity of about .34. Prior to foaming,
0.5%, based on viscose weight, of "Triton"* BG 10 surfactant
was added to the viscose. Foaming was accomplished by air
injection using a "VOTATOR"* line mixer. The unfoamed viscose
had a specific gravity of about 1.1 and contained water,
about 7% dissolved cellulose, 10.5% NaOH, and 1.8% xanthate
B
*Trademark - 12 -
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sulfur (2.6~ tot~l sulfur) .
Viscose impregnation was effected at a speed of
about 15 feet/min. using 12 inch diameter, 46 inch long
neoprene rubber covered rolls (about 60 durometers) in
pressure contact provided by 60 psig compressed air using
a 3 inch diameter piston. Fourty-four inch wide stainless
steel screens were used having a wire diameter of 0.065
inch and 32 x 32 mesh.
~ fter impregnation, the material was passed at
15 feet/minute for about 30 feet through an aqueous coagula-
tion regeneration bath maintained at about 96 C. which
contained 22~ sodium sulfate, 60 grams/liter H2SO4 and had
a specific gravity of about 1.25 at 35 C. Thereafter and
in conventional fashion, the web can be passed through a
dilute acid post regeneration and acid recovery bath,
deacidified with water, desulfurized with a Na2S, NaOH
solution, washed, bleached, washed again and finally can
be dried by passage through a hot air impingement oven.
The product so prepared containing 28% regenerated
cellulose fragments based on prebonded web is illustrative
of a material which fully satisfies the aims and objectives
of the present invention. The material is soft, conformable
and possesses those desirable attributes heretofore identified
which render it very suitable as an all-purpose wipe. The
principal fiber bonding agent is the porous regenerated
cellulose which is absorbent itself and consequently the
material has highly advantageous~fluld wiping characteristics.
And, by being distributed therein in the described fragmentary
manner, the material is soft and conformable Where additional
softness is especially desirable, the material can be lightly
pin embossed, dry creped, etc. to accentuate this feature.
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