U.S. patent number 3,753,826 [Application Number 05/125,239] was granted by the patent office on 1973-08-21 for methods of making nonwoven textile fabrics.
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Charles H. Plummer.
United States Patent |
3,753,826 |
Plummer |
August 21, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
METHODS OF MAKING NONWOVEN TEXTILE FABRICS
Abstract
A nonwoven textile fabric having excellent softness, drape, and
hand, good long and cross tensile strength, good wet abrasion
resistance and good washability, and good absorptive capacity and
opacity comprising: a relatively flat, sheet-like fibrous structure
of from about 30 percent by weight to about 90 percent by weight of
overlapping and intersecting structural fibers having an average
length of from about 1/4 inch to about 11/4 inches or more, and
from about 70 percent by weight to about 10 percent by weight of
relatively short fibers having an average length of from about 1/6
inch to about 1/25 inch or less; said structural fibers being
bonded together by a closely-spaced, non-migrating, intermittent
print pattern of discrete synthetic resin binder areas, and said
relatively short fibers being bonded together by a substantially
uniform, overall application of a relatively soft, synthetic resin
binder in an amount of from about 2 percent by weight to about 10
percent by weight, based on the total weight of the finished
nonwoven textile fabric. Methods of making such nonwoven textile
fabrics, and particularly methods involving the use of wet-forming
manufacturing techniques, are also included.
Inventors: |
Plummer; Charles H. (Princeton,
NJ) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
|
Family
ID: |
22418791 |
Appl.
No.: |
05/125,239 |
Filed: |
March 17, 1971 |
Current U.S.
Class: |
156/277; 156/291;
162/146; 162/185; 427/258; 428/206; 428/401; 442/146; 162/135;
162/149; 162/186; 428/198; 428/393; 442/147 |
Current CPC
Class: |
D21H
23/00 (20130101); D21H 25/06 (20130101); D21H
15/06 (20130101); Y10T 428/24826 (20150115); Y10T
442/2721 (20150401); Y10T 428/24893 (20150115); Y10T
428/2965 (20150115); Y10T 442/2713 (20150401); Y10T
428/298 (20150115) |
Current International
Class: |
D04H
1/64 (20060101); D21H 25/00 (20060101); D04H
1/66 (20060101); D21H 23/00 (20060101); D21H
25/06 (20060101); D21H 15/00 (20060101); D21H
15/06 (20060101); B32b 031/12 () |
Field of
Search: |
;161/146,148,156,170,59
;156/291 ;162/137,146 ;117/45,14A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Bell; James J.
Claims
What is claimed is:
1. A method of making a nonwoven textile fabric which
comprises:
1. forming a substantially uniform aqueous slurry of from about 30
percent by weight to about 90 percent by weight of structural
fibers having an average length of from about 1/4 inch to about
11/4 inches or more, and from about 70 percent by weight to about
10 percent by weight of relatively short fibers having an average
length of from about 1/6 inch to about 1/25 inch or less, and from
about 5 percent by weight to about 100 percent by weight of
discrete particles of heat activatable resin binder solids, based
on the total fiber weight in the aqueous slurry;
2. forming a relatively flat, sheet-like fibrous structure of such
structural fibers and relatively short fibers and discrete
particles of resin binder solids;
3. drying said fibrous structure at elevated temperatures whereby
said discrete particles of heat activatable resin binder solids
prebond said fibers in position;
4. applying a bonding agent to said dried, prebonded fibrous
structure and particularly the structural fibers therein in a
closely-spaced, intermittent print pattern of discrete synthetic
resin binder areas;
5. drying said fibrous structure at elevated temperatures whereby
said bonding agent bonds said fibrous structure in said
closely-spaced, intermittent print pattern;
6. applying a bonding agent to said dried, intermittently bonded
fibrous structure and particularly the relatively short fibers
therein in a substantially uniform overall application of a
relatively soft, synthetic resin binder in an amount equal to from
about 2 percent by weight to about 10 percent by weight, based on
the total weight of the finished nonwoven textile fabric; and
7. drying said fibrous structure at elevated temperatures whereby
said relatively soft resin binder bonds said fibrous structure in
overall fashion.
2. A method of making a nonwoven textile fabric having excellent
softness, drape, and hand, good long and cross tensile strength,
good wet abrasion resistance and good washability, and good
absorptive capacity and opacity which comprises:
1. forming a relatively flat, sheet-like fibrous structure of from
about 30 percent by weight to about 90 percent by weight of
structural fibers having an average length of from about 1/4 inch
to about 11/4 inches or more and from about 70 percent by weight to
about 10 percent by weight of relatively short fibers having an
average length of from about 1/6 inch to about 1/25 inch or less
and from about 5 percent by weight to about 100 percent by weight
of discrete particles of resin binder solids, based on the total
fiber weight in the aqueous slurry;
2. drying said fibrous structure at elevated temperatures whereby
said discrete particles of resin binder solids prebond said fibers
in position;
3. applying a bonding agent to said dried, prebonded fibrous
structure and particularly the structural fibers therein in a
closely-spaced, non-migrating, intermittent print pattern of
discrete synthetic resin binder areas;
4. drying said fibrous structure at elevated temperatures whereby
said bonding agent bonds said fibrous structure in said
closely-spaced, intermittent print pattern;
5. applying a bonding agent to said dried, intermittently bonded
fibrous structure and particularly the relatively short fibers
therein in a substantially uniform overall application of a
relatively soft, synthetic resin binder in an amount equal to from
about 2 percent by weight to about 10 percent by weight, based on
the total weight of the finished nonwoven textile fabric; and
6. drying said fibrous structure at elevated temperatures whereby
said relatively soft resin binder bonds said fibrous structure in
overall fashion.
3. A method as defined in claim 1 wherein the concentration of the
fibers in the aqueous slurry ranges from about 1/20 percent by
weight to about 11/2 percent by weight, on a dry fiber weight
basis.
4. A method as defined in claim 1 wherein the concentration of the
fibers in the aqueous slurry ranges from about 1/10 percent by
weight to about 1 percent by weight.
5. A method as defined in claim 1 wherein the concentration of the
discrete particles of resin binder solids ranges from about 15
percent to about 40 percent by weight.
6. A method as defined in claim 1 wherein a resin deposition aid is
included in the aqueous slurry to promote the deposition and
adherence of the particulate resin solids to the individual
fibers.
7. A method as defined in claim 6 wherein the concentration of the
resin deposition aid in the aqueous slurry ranges from about 1/2
percent by weight to about 11/2 percent by weight, based on the
total dry resin solids in the aqueous slurry.
8. A method as defined in claim 2 wherein the structural fibers are
rayon fibers and the relatively short fibers are wood pulp
fibers.
9. A method as defined in claim 2 wherein the structural fibers
comprise a mixture of rayon fibers and polyamide nylon fibers and
the relatively short fibers are wood pulp fibers.
10. A method as defined in claim 2 wherein the relatively flat,
sheet-like fibrous structure is formed on a moving forming surface.
Description
BACKGROUND
Many people have been engaged for many years in the manufacture of
nonwoven textile fabrics which can be made without resorting to the
spinning, twisting, and twining of individual fibers into yarns and
strands, and the subsequent weaving, knitting, or other fabricating
of these yarns and strands into fabrics.
Such nonwoven textile fabrics have usually been manufactured by
laying down one or more fibrous layers or webs of textile length
fibers by dry textile carding techniques which normally align the
majority of the individual fibers more or less generally lengthwise
of the fibrous layer or web being prepared. The individual textile
length fibers of these carded fibrous webs are then bonded by
conventional bonding techniques, such as, for example, by
intermittent print pattern bonding, whereby a unitary,
self-sustaining nonwoven textile fabric having excellent softness,
drape, and hand is obtained. Such manufacturing techniques,
however, are relatively slow and it has always been desired that
manufacturing processes having greater production rates be devised.
Additionally, it is to be noted that such dry textile carding and
bonding techniques, unfortunately, are normally applicable only to
fibers having a textile cardable length of at least about 1/2 inch,
and preferably longer, and are not applicable to more economically
desirable short fibers, such as wood pulp fibers which have very
short lengths of from about 1/6 inch (0.167 inch) down to about
1/25 inch (0.040 inch), or even less. And, it is also to be noted
that the absorptive capacity and opacity of the resulting nonwoven
textile fabrics could stand improving in some uses and
applications.
More recently, people have been engaged in the manufacture of
nonwoven textile fabrics by wet-forming techniques on conventional
or modified papermaking machines or similar apparatus. Such
manufacturing techniques have much higher production rates and are
applicable to very short fibers such as wood pulp fibers.
Unfortunately, however, difficulties are often encountered in the
use of the longer textile length fibers in such wet-forming
manufacturing techniques.
Additionally, it has been found that such conventional or modified
wet-forming manufacturing techniques, when subsequently combined
with conventional saturation or over-all bonding techniques, are
normally incapable of producing nonwoven textile fabrics which have
the necessary softness, drape, and hand, and esthetic qualities of
nonwoven textile fabrics, along with the other qualities,
properties, and characteristics required for nonwoven textile
fabrics. This is particularly true when the nonwoven textile
fabrics are to be used in the single-use or limited re-use
disposable field, such as for disposable apparel, linens, cleaning
and wiping cloths, bandages, dressings, pads, surgical drapes and
gowns, diaper linings and facings, etc.
THE INVENTIVE CONCEPT
It has been found that nonwoven textile fabrics having excellent
softness, drape, and hand, as well as good long and cross tensile
strength, good wet abrasion resistance and good washability, and
good absorptive capacity and opacity can be made by:
1. forming a substantially uniform aqueous slurry of from about 30
percent by weight to about 90 percent by weight of structural
fibers having an average length of from about 1/4 inch to about
11/4 inches or more, and from about 70 percent by weight to about
10 percent by weight of relatively short fibers having an average
length of from about 1/6 inch to about 1/25 inch or less;
2. forming a relatively flat, sheet-like fibrous structure of such
structural fibers and relatively short fibers;
3. bonding said fibrous structure and particularly the structural
fibers therein with a closely-spaced, non-migrating, intermittent
print pattern of discrete synthetic resin binder areas; and
4. bonding said fibrous structure and particularly the relatively
short fibers therein with a substantially uniform over-all
application of a relatively soft, synthetic resin binder in an
amount equal to from about 2 percent by weight to about 10 percent
by weight, based on the total weight of the finished nonwoven
textile fabric.
In the following specification and accompanying drawings, there is
described and illustrated a preferred embodiment of the invention
but it is to be understood that the inventive concept is not to be
considered as limited to the particular embodiment disclosed except
as determined by the scope of the appended claims. More
specifically, the illustrative embodiment relates to wet-forming
methods but it is to be appreciated that other equivalent
manufacturing processes can be used in the application of the
principles of the present inventive concept. Referring to the
accompanying drawings:
FIG. 1 is a schematic drawing showing a typical flow chart of a
wet-forming manufacturing process, representing a preferred
embodiment of the present inventive concept; and
FIG. 2 is a schematic drawing showing in cross-section the
idealized internal construction of the finished nonwoven textile
fabric of the present invention.
In the drawings and with particular reference to FIG. 1, there is
schematically shown the discharge portion 10 of a papermaking
machine headbox associated with a conventional stock chest (not
shown) wherein the fibers are formed into a substantially uniform
aqueous slurry, preferably in the presence of discrete resin binder
particles or like materials and a deposition aid, if required or
desired.
STOCK CHEST PREPARATION
The concentration of the fibers in the stock chest aqueous slurry
is on the order of from about 1/20 percent by weight to about 11/2
percent by weight, on a dry fiber weight basis. Preferably, such
range of fiber concentration in the aqueous slurry is from about
1/10 percent by weight to about 1 percent by weight.
The concentration of the resin binder particles or like materials
in the stock chest aqueous slurry depends on the amount of resin
binder particles which are intended to be deposited on the
individual fibers. The range extends from about 5 percent by weight
to about 100 percent by weight of dry resin solids, based on the
total dry fiber weight in the stock chest, and preferably extends
from about 15 percent by weight to about 40 percent by weight.
The concentration of the deposition aid in the stock chest slurry
should be enough to bring about satisfactory deposition of the
resin particles on the fibers in the aqueous slurry. Normally, such
concentration is in the range of from about 1/2 percent by weight
to about 11/2 percent by weight, based on the total dry resin
solids in the stock chest. Less than about 1/2 percent by weight of
a deposition aid may be used, particularly in the case of nonionic
or cationic resin emulsions. More than 11/2 percent by weight may
be used, particularly when the cationic charge on the particular
deposition aid is low. This is basically not desirable inasmuch as
a deposition aid having a low cationic charge will necessitate
greater concentrations in its use which is commercially
undesirable.
FIBERS USED
The substantially uniformly dispersed fibers in the stock chest
leading to the discharge portion 10 comprise from about 30 percent
by weight to about 90 percent by weight of structural textile
length fibers ST having an average length of from about 1/4 inch to
about 11/4 inches or more and from about 70 percent by weight to
about 10 percent by weight of relatively short fibers W having an
average length of from about 1/6 inch (0.167 inch) to about 1/25
inch (0.040 inch) or less.
STRUCTURAL FIBERS
The structural textile length fibers ST may be selected from a
large group of natural, synthetic or man-made fibers such as: the
cellulosic fibers, notably cotton, regenerated cellulose (both
viscose and cuprammonium processes), cellulose acetate, and
cellulose triacetate; the non-cellulosic fibers such as: the
polyamide fibers, notably nylon 6,6 and 6; the polyesters, notably
"Dacron", "Fortrel " and "Kodel"; the acrylics, notably "Creslan",
"Acrilan" and "Orlon"; the modacrylics, notably "Dynel" and
"Verel"; the polyolefins, especially polypropylene and
polyethylene, notably "Vectra" and "Herculon"; the spandexes,
notably "Lycra" and "Unel"; the fluorocarbons, notably "Teflon" TFE
and FEP; etc. These fibers may be used by themselves, or in various
combinations and blends of two or more species in varying
percentages, as desired or required.
The denier of the synthetic or man-made structural fibers ST may be
varied relatively widely, depending on the circumstances, and vary
from about 11/2 denier to about 6 denier, with lower deniers to
about 3/4 or less, and higher deniers to about 9, 15, or more,
being of use in special circumstances.
SHORT FIBERS
The remaining fibers in the stock chest slurry are wood pulp
fibers, or other short fibers W.
Unbeaten or unrefined wood pulp fibers, or at least relatively
unbeaten or unrefined wood pulp fibers are preferably used inasmuch
as beating and refining are rather severe mechanical treatments,
and beat and macerate the fibers whereby enhanced hydration bonding
is obtained which is not desired in the present inventive concept
and which leads to a product which undesirably has increased
stiffness, harshness, and a papery hand.
Although unbeaten hardwood sulfite pulp will be disclosed as the
preferred type of wood pulp fiber used in the application of the
present invention, substantially any type of wood pulp, either
hardwood or softwood, is of use. Examples of other types of wood
pulp are: sulfite pulps in which the cooking liquor, calcium or
magnesium bisulfite, is acid, or sodium sulfite which is neutral or
slightly alkaline; soda pulps in which the cooking liquor, caustic
soda, is alkaline; kraft or sulfate pulps in which the cooking
liquor, sodium hydroxide and sodium sulfide, is alkaline, etc.
Although wood pulp fibers are preferred in the application of the
present inventive concept, other short fibers or fibrous materials
are of use. Examples of such short fibers or fibrous materials
having lengths of from about 1/6 inch to about 1/25 inch or less
are: cotton linters, bagasse, flax, flax straw, jute, straw,
bamboo, esparto grass, rayon, rags, and the like, as well as
industrial waste products such as macerated or particulate
materials from rag, cotton seed hulls, corn stalks, bamboo stalks,
etc.
Viscose rayon fibers are the preferred structural textile length
fiber. Othr structural textile length fibers, as listed herein, may
be included in amounts up to about 30 percent by weight of the
total structural fiber weight. The relatively short fibers which
are usually wood pulp fibers may be included in amounts from about
10 percent by weight up to as high as about 70 percent by weight of
the total fiber weight and preferably from about 20 percent by
weight to about 50 percent by weight.
It is essential that all these fibers be dispersible, or at least
be capable of being dispersed, substantially uniformly in the
aqueous slurry. Dispersion aids may be used to assist or promote
such uniformity of dispersion.
RESIN BINDER PARTICLES
During the dispersion of the fibers in the stock chest, they may
have incorporated thereon from about 5 percent by weight to about
100 percent by weight, and preferably from about 15 percent by
weight to about 40 percent by weight, based on the weight of the
dry fibers, of discrete particles of a synthetic resin binder
B.
The particular resin binder which is incorporated on the fibers is
selected from a relatively large class of synthetic resins well
known in the art for bonding or adhering fibers of fibrous
materials together. Such resins may be of the internal or self
cross-linking type, the cross-linkable type which are cross-linked
by added cross-linking agents, or the non-cross-linked or
non-cross-linkable type. Examples of such synthetic resins include:
polymers and copolymers of vinyl ethers; vinyl halides such as
plasticized and unplasticized polyvinyl chloride, polyvinyl
chloride-polyvinyl acetate, ethylene-vinyl chloride, etc.; polymers
and copolymers of vinyl esters such as plasticized and
unplasticized polyvinyl acetate, ethylene-vinyl acetate,
acrylic-vinyl acetate, etc.; polymers and copolymers of the
polyacrylic resins such as ethyl acrylate, methyl acrylate, butyl
acrylate, ethylbutyl acrylate, ethyl hexyl acrylate, hydroxyethyl
acrylate, dimethyl amino ethyl acrylate, etc.; polymers and
copolymers of the polymethacrylic resins such as methyl
methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl
methacrylate, etc.; polymers and copolymers of acrylonitrile,
methacrylonitrile, acrylamide, N-isopropyl acrylamide, N-methylol
acrylamide, methacrylamide, etc.; vinylidene polymers and
copolymers, such as polyvinylidene chloride, polyvinylidene
chloride-vinyl chloride, polyvinylidene chloride-ethyl acrylate,
polyvinylidene chloride-vinyl chloride-acrylonitrile, etc.;
polymers and copolymers of polyolefinic resins including
polyethylene, polypropylene, ethylene-vinyl chloride and
ethylene-vinyl acetate which have been listed previously; the
synthetic rubbers such as 1,2-butadiene, 1,3-butadiene,
2-ethyl-1,3-butadiene, high, medium and carboxylated
butadiene-acrylonitrile, butadiene-styrene, chlorinated rubber,
etc., natural latex; the polyurethanes, the polyamides; the
polyesters; the polymers and copolymers of the styrenes including
styrene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene,
4-ethyl styrene, 4-butyl styrene, natural latex; phenolic
emulsions; etc.
These resins may be used either as homopolymers comprising a single
repeating monomer unit, or they may be used as copolymers
comprising two, three, or more different monomer units which are
arranged in random fashion, or in a definite ordered alternating
fashion, within the polymer chain. Also included within the
inventive concept are the block polymers comprising relatively long
blocks of different monomer units in a polymer chain and graft
polymers comprising chains of one monomer attached to the backbone
of another polymer chain.
RESIN DEPOSITION AIDS
The deposition of the synthetic resin binder particles on the
individual fibers may be accomplished in many ways at various
points in the manufacturing process but, preferably, is
accomplished by stock chest deposition techniques. Such techniques
generally include (1) the formation of a substantially uniform,
aqueous slurry of the fibers which will make up the fibrous
structure or web and (2) the inclusion in the aqueous slurry of the
synthetic resin binder particles which are to be deposited on and
adhered to the individual fibers. Deposition aids may be used, if
necessary, to promote the deposition and adherence of the synthetic
resin particles on the individual fibers. Examples of such
deposition aids are Rohm & Haas Deposition Aid S-243,
polyethylene imine, alum, polymeric amines, polymeric amides,
cationic starch, etc.
FORMATION OF THE FIBROUS STRUCTURE
Returning to the drawings and particularly FIG. 1 therein, the
aqueous slurry containing the structural fibers ST and the short
fibers W which have incorporated therewith the discrete particles
of resin binder B is discharged through discharge portion 10 onto
the open screen-like surface of a moving forming surface 20 which
is provided with underlying conventional suction boxes (not shown)
whereby a considerable part of the water is drained rapidly from
the aqueous slurry to form a relatively flat, sheet-like fibrous
structure S in the area 12 of the forming surface 20.
A rectilinearly moving forming surface 20 is disclosed herein but
it is to be appreciated that this is merely illustrative of the
present inventive concept, and that other forming surfaces such as
Fourdrinier wires, inclined wires, screens, belts, rotating
cylinders, etc., are of use.
The fibrous structure S is then forwarded to drying means 30 which
preferably take the form of a series of heated rotatable drying
cylinders. Other drying means such as a single large drying drum,
or a heated oven, or the like, are of use, if they are capable of
providing an elevated drying, bonding and curing temperature in the
range of from about 200.degree. F. to about 350.degree. F. or
higher, if desired or required.
The drying at such an elevated temperature serves to activate the
bonding characteristics of the resin binder particles, whereby the
individual fibers become bonded to each other. This is particularly
important in the case of the short fibers, such as wood pulp
fibers, which are effectively bonded and locked in position.
The resin binder particles thus act as a prebonding agent and
stabilize the fibrous structure so that it is self-sustaining and
can be readily handled and easily manipulated during subsequent
processing. Other pre-bonding means may be employed, provided they
are capable of supplying the necessary strength and coherency
properties and characteristics required during subsequent
processing.
The dried, pre-bonded fibrous structure is then passed through
additional bonding apparatus 40 wherein there is applied an
additional bonding agent 42 in the form of an intermittent print
pattern of closely-spaced discrete binder areas 76. The particular
print pattern is selected from a large group of commercially known
intermittent print patterns such as, for example, illustrated in U.
S. Pat. Nos. 2,705,498, 2,705,687, 2,705,688, 2,880,111 and
3,009,822.
These intermittent, print patterns are closely spaced and are
intended to bond even the shortest of the structural fibers in more
than one place to develop the required long and cross tensile
strength and other qualities, properties, and characteristics
required in the finished nonwoven textile fabric.
The synthetic resins which are used to additionally bond the
individual structural fibers are selected from the group of
synthetic resins listed hereinbefore. The amount of synthetic resin
binder applied is in the range of from about 1 percent by weight to
about 30 percent by weight, based on the weight of the nonwoven
textile fabric being bonded.
Within the more commercial aspects of the present invention,
however, the amount of the applied synthetic resin binder is in the
range of from about 10 percent by weight to about 20 percent by
weight, based on the weight of the nonwoven textile fabric being
bonded.
The surface coverage of the binder areas varies widely, depending
upon the requirements and needs of the particular circumstances.
Normally, a surface coverage of from about 10 percent to about 35
percent of the nonwoven textile fabric is found satisfactory.
It is to be noted that the closely-spaced intermittent print
pattern bonding takes place on a dry fibrous substrate in order to
limit or restrict the binder migration which would take place if
the bonding were to take place on a wet fibrous substrate.
Limitation or restriction of binder migration maintains the
softness, drape and hand of the resulting nonwoven textile fabric
which otherwise could be lost if the binder migration was
uncontrolled.
In the event that the application of binder takes place on a wet
fibrous substrate, then resort is had to non-migrating binders,
such as viscose (see U. S. Pat. 3,009,822), or to various binder
migration control systems such as described in copending,
commonly-assigned patent application entitled "Improved Resin
Binder Compositions, Methods of Utilizing the Same and Resulting
Products", Ser. No. 109,026, filed on or about Jan. 22, 1971, now
U.S. Pat. No. 3,706,595.
A second dryer 46 is used to dry the fibrous structure subsequent
to the intermittent print pattern bonding. This dryer 46 may
comprise a series of heated drying cylinders, or a single large
heated drying drum, or a heated oven, or the like, as described
previously.
The dried, intermittently print pattern bonded fibrous structure is
then forwarded to an overall or saturation bonding device or padder
50 whereat an additional binder 52 is applied in overall fashion.
Such overall bonding securely ties together the fibrous structure
and particularly the relatively short fibers therein. The amount of
binder 52 applied in such treatment is in the range of from about 2
percent by weight to about 10 percent by weight, based on the total
weight of the finished non-woven textile fabric.
Within the more commercial aspects of the present invention,
however, the range of the weight of the applied overall binder is
from about 2 percent by weight to about 5 percent by weight, based
on the total weight of the finished nonwoven textile fabric.
The particular resin which is applied in overall fashion may be
selected from the resins mentioned previously herein, with the
condition, however, that the resin, when dried and cured, be
relatively soft so as to provide the desired softness, drape and
hand. Notable examples of resins suitable for such purpose include
acrylic means such as polyethylacrylate; methacrylic resins such as
copolymers of methyl methacrylate and ethyl hexyl acrylate;
polyolefin and vinyl resins such as copolymers of ethylene and
vinyl acetate; carboxylated butadiene-styrene copolymers; etc. The
degree of softness is, of course, determined by the requirements
and needs of the particular situation and the particular
product.
Reactive type resins, and particularly those of the thermosetting
variety, which actually react with and heavily cross-link a
cellulosic fibrous structure, to yield hard, crease resistant
finishes of a permanent press type are to be avoided. Examples of
such reactive type resins are ethylene urea formaldehyde, melamine
formaldehyde, etc., which not only cross-link with themselves but
additionally and undesirably cross-link with the cellulosic fibrous
structure itself.
Another dryer 56, similar to any of the drying devices described
previously, may be employed to dry the nonwoven textile fabric.
Subsequent to drying, the non-woven textile fabric is forwarded to
and wound on a batcher 60 or other re-wind device.
If desired, additional treatments may be applied to the nonwoven
textile fabric subsequent to the drying operation in dryer 56 in
order to achieve specific purposes and particular properties. An
additional over-saturation in a second conventional padder or the
like (not shown) with an additional binder or other additives or
other treating agents may be resorted to, for example, in order to
attain special properties. Such other additives and treating agents
include water-proofing agents, water-repellent agents,
flame-proofing agents, insect or vermin-proofing materials, dyes
and pigments, and the like. Such additional treatment may be used
to apply the additional specialty treatment agent or other additive
to the extent of from about 2 percent by weight to about 50 percent
by weight, based on the weight of the nonwoven textile fabric being
treated. Another dryer (not shown), similar to any of the drying
devices described previously, may be employed to dry the nonwoven
textile fabric, prior to forwarding to the batcher or re-wind
device.
In FIG. 2, there is schematically shown in cross-section the
idealized internal construction of a typical nonwoven textile
fabric 70 of the present invention.
The structural textile length fibers ST and the relatively short
fibers W are shown, bonded into a unitary structure by the binder B
in the areas 76 and by the overall saturation bonding which
substantially uniformly impregnates the entire nonwoven textile
fabric.
Nonwoven textile fabrics made by the techniques described herein
are found to have excellent softness, drape, and hand, good long
and cross tensile strength, good wet abrasion resistance and good
washability, and good absorptive capacity and opacity. They are of
excellent use as diaper and other facings, towels and wipes,
operating room products such as drapes and gowns, and other uses
mentioned herein.
The weights of such finished nonwoven textile fabrics vary widely
depending upon the particular uses and intended applications.
Within the more commercial aspects of the present invention,
finished fabric weights of from about 200 grains per square yard to
about 1,200 grains per square yard are contemplated. Within the
broader aspects of the present invention, however, heavier or
lighter fabrics may be made for special uses and applications.
The invention will be further described by reference to the
following Examples wherein there are disclosed preferred
embodiments of the present invention. However, it is to be
appreciated that such Examples are illustrative and not limitative
of the broader aspects of the inventive concept.
EXAMPLE I
A wet-formed, nonwoven textile fabric is prepared as follows:
The fibrous structure comprises: 75 percent by weight of rayon
fibers having a denier of 1.5 and a length of 3/8 inch; and 25
percent by weight of unbeaten and unrefined hardwood sulfite wood
pulp fibers. These fibers are slurried to a consistency of about 1
percent by weight in a stock chest containing about 50 percent by
weight, based on the total dry fiber weight, of Rohm & Haas
Resin Emulsion E-631, a self cross-linking (methylol functionality)
anionic ethyl acrylate acrylic binder, and about 1 percent by
weight, based on the total dry resin solids, of Rohm & Haas
Deposition Aid S-243, a moderate molecular weight cationic
polyelectrolyte (hydroxy group functionality) deposition aid. When
formed on a moving forming surface as shown in FIG. 1, the total
weight of the fibrous structure is 230 grains per square yard, of
which 184 grains is the fiber weight and 46 is the resin particle
weight. This is equivalent to a 20% add-on of resin binder
particles.
This fibrous structure is then dried by being passed over heated
drying cylinders at a temperature of about 250.degree. F. The
individual overlapping and intersecting fibers are bonded to each
other.
The dried nonwoven textile fabric is then passed through an
intermittent print pattern bonding apparatus of a conventional
design. The print pattern comprises a double-diagonal diamond
pattern (see FIG. 3, U. S. Pat. No. 2,705,498) wherein there are
five lines per inch, with each line 0.020 inch wide, as measured on
the binder applying roll. The binder is Rohm & Haas HA-8,
primarily a polyethyl acrylate. Lateral migration is minimal. The
total finished weight of the nonwoven textile fabric is 291 grains.
This represents a print binder add-on of 60 grains per square yard,
or about 26 percent by weight, based on the weight of the fabric
being bonded.
The dried intermittently print pattern bonded nonwoven textile
fabric is then passed through a saturation bonding device or padder
and approximately 3 percent by weight on a dry solids basis of a
soft acrylic resin Rohm & Haas HA-8 (primarily a polyethyl
acrylate) is substantially uniformly applied thereto.
Drying then takes place in a conventional dryer and the finished
nonwoven fabric is wound on a take-up roll or batcher.
The nonwoven textile fabric has excellent softness, drape and hand,
as well as good long and cross tensile stength, good wet abrasion
resistance and good washability, and good absorptive capacity and
opacity. It is suitable for use as a diaper facing.
EXAMPLE II
The procedures of Example I are followed substantially as set forth
therein with the exception that the fiber blend is 40 percent rayon
fibers and 60 percent wood pulp fibers.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE III
The procedures of Example I are followed substantially as set forth
therein with the exception that the fiber mixture comprises 65
percent by weight of the rayon fibers, 25 percent by weight of the
wood pulp fibers, and 10 percent by weight of polyamide nylon 6,6
having a denier of 6 and a length of 3/4 inch.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE IV
The procedures of Example I are followed substantially as set forth
therein with the exception that the rayon fibers have an average
length of 1/2 inch, instead of 3/8 inch.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE V
The procedures of Example I are followed substantially as set forth
therein with the exception that the rayon fibers have an average
length of 1/4 inch, instead of 3/8 inch.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE VI
The procedures of Example I are followed substantially as set forth
therein with the exception that the resin formulation used for the
overall bonding is a soft, carboxylated butadiene (54%)-styrene
(43%) resin.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE VII
The procedures of Example I are followed substantially as set forth
therein with the exception that the resin used for the overall
bonding is a soft copolymer of ethylene (30%) and vinyl acetate
(70%).
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE VIII
The procedures of Example I are followed substantially as set forth
therein with the exception that the resin used for the overall
bonding is a soft copolymer of methyl methacrylate (40%) and ethyl
hexyl acrylate (60%).
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE IX
The procedures of Example I are followed substantially as set forth
therein with the exception that the print binder resin comprises
National Starch 25-4260, primarily a soft self-reactive acrylic
copolymer resin. The saturation bath comprises the same resin
formulation.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE X
The procedures of Example I are followed substantially as set forth
therein with the exception that the intermittent print pattern
binder is viscose instead of polyethyl acrylate. The fiber weight
is increased to 220 grains per square yard, the stock chest resin
add-on is 56 grains per square yard, and the binder add-on is
reduced to 4 percent by weight, based on the weight of the nonwoven
textile fabric being bonded, which reduces the finished product
weight accordingly to about 295 grains per square yard.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE XI
The procedures of Example I are followed substantially as set forth
therein with the exception that the closely-spaced intermittent
print pattern comprises 12 lines per inch with each line 0.015 inch
wide having an angle of 45.degree. to the long axis.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE XII
The procedures of Example I are followed substantially as set forth
therein with the exception that the closely-spaced intermittent
print pattern comprises 10 lines per inch with each line 0.020 inch
wide.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE XIII
The procedures of Example I are followed substantially as set forth
therein with the exception that the closely-spaced intermittent
print pattern comprises miniature circular areas 0.015 inch in
diameter spaced 0.015 inch from adjacent binder areas in a square
pattern as described in Example III of U. S. Pat. 2,880,111.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
EXAMPLE XIV
The procedures of Example I are followed substantially as set forth
therein with the exception that the nonwoven textile fabric is
given an additional special treatment in another padder containing
a conventional flame-proofing agent. The amount of add-on of the
flame-proofing agent is 10 percent by weight.
The results are good and are generally comparable to those set
forth in Example I. The resulting product is commercially
acceptable.
Although several specific examples of the inventive concept have
been described, the same should not be construed as limited thereby
nor to the specific features mentioned therein but to include
various other equivalent features as set forth in the claims
appended hereto. It is understood that any suitable changes,
modifications and variations may be made without departing from the
spirit and scope of the invention.
* * * * *