Cardable hydrophobic polyolefin fiber, material and method for preparation thereof

An improved method for producing hydrophobic polyolefin-containing staple fiber for processing, with reduced waste and improved crimp by sequential treatment with two finish compositions comprising at least one neutralized phosphoric acid ester and at least one polysiloxane of defined classes and amounts.

The present invention relates to an improved process using topically 
applied fiber finishes to produce polyolefin-containing hydrophobic fiber 
or filament capable of accepting a high crimp without undue end waste from 
crimping, cutting and carding operations and without undue loss of desired 
hydrophobicity in the resulting fiber or nonwoven end product. 
BACKGROUND 
While the use of fiber finishes is well known in the textile art, attempts 
to broadly apply such knowledge to produce hydrophobic cardable staple 
fiber for fluid-absorbing products in the area of personal hygiene, such 
as catamenial devices, disposable diapers, incontinence pads and the like, 
have met with substantial technical problems. 
In general, such products require a fluid-absorbent core component, usually 
comprising one or more layers of absorbent material such as wood pulp, 
rayon, gauze, tissue and the like and, in some cases, synthetic 
hydrophilic material such as a hydrophilic polyurethane foam and paper 
absorbent powder. 
Such fluid-absorbing core is most frequently fabricated in the form of a 
bonded pad of wood pulp with or without super absorbent powder, and 
possesses a rectangular or somewhat oval shape. 
To protect a wearer's clothing, and surrounding areas from stain due to 
fluid leaks a fluid-impervious barrier sheet component is usually 
positioned external to the core component and the core is also separated 
from the body of the user by at least an internally-positioned 
water-permeable coversheet component. 
In general, the porosity and fluid-passing properties of the coversheet and 
the fluid repellant properties of the barrier layer plus lee cuffs and 
borders of the cover sheet are vital to the proper function of the 
finished product. 
A particularly troublesome technical problem arises when a high degree of 
hydrophobicity is desired on cuffs or borders in a diaper or similar 
product produced substantially from conventionally-bonded webs of 
hydrophobic fiber such as polyolefin-containing staple. This problem 
arises because untreated finish-free hydrophobic fiber quickly becomes 
unworkable due to friction and accumulated static charges generated during 
conventional processing such as spinning, crimping, cutting and carding. 
For this reason, the art recognizes and uses topically applied fiber 
finishes which can change fiber surface properties sufficiently to permit 
processing. Unfortunately, however, such treatment also produces fibers 
and webs which are substantially more hydrophilic than generally desired 
and difficult to control quality-wise. In particular, because of the 
nature of commercial high speed fiber-processing operations, and the 
unpredictable affinity of known finishing agents to individual batches or 
bales of hydrophobic fiber, it becomes very difficult to obtain a full 
crimp in the fiber component and to maintain a uniform hydrophobicity in 
the final non-woven product. 
It is an object of the present invention to prepare hydrophobic fiber or 
filament suitable for production of nonwoven material having a high 
hydrophobicity. 
It is a further object of the present invention to increase overall 
processing efficiency of polyolefin-containing fiber or filament as 
reflected in reduced waste and achievement of a higher crimp value. 
THE INVENTION 
The above objects are obtained in accordance with the present invention by 
processing polyolefin-containing spun fiber or filament in accordance with 
the steps of 
A. initially treating corresponding continuous spun fiber or filament with 
an effective amount, preferably varying from about 0.09%-0.5%, applied and 
based on fiber weight, of a first modifier composition comprising 
(a) up to about 40%, and preferably about 20 to 40%, by weight of modifier 
(spin finish) composition of at least one neutralized phosphoric acid 
ester represented by the formula 
##STR1## 
wherein Alk is individually defined as a lower alkyl group, such as a 1-8 
carbon alkyl and preferably a 1-4 carbon alkyl group; 
R is defined as an amino group or an alkali metal, 
n and m are individually defined as positive numbers of not less than about 
1, the sum of which is about 3; and 
(b) about 100%-60% by weight of first modifier composition of at least one 
polysiloxane represented by the formula 
##STR2## 
wherein X and Y are individually defined as a hydrophobic chemical end 
group such as a lower alkyl group, 
R' is individually-defined as a lower alkyl such as a methyl group, and 
o is defined as a positive number within the range of about 10-50 or 
higher; 
B. crimping the resulting continuous fiber or filament; 
C. applying to said continuous fiber or filament, preferably at a point 
proximate to said crimper, an effective amount, varying from about 
0.05%-0.80% by fiber weight, of a second modifier finish composition 
comprising 
(a) about 100%-50%, by weight of second modifier (over finish) composition, 
of at least one neutralized phosphoric acid ester represented by formula 
(1) supra; and 
(b) up to about 50%, by weight of second modifier composition, of at least 
one polysiloxane represented by formula (2) supra, in sufficient amount to 
obtain a final cumulative concentration within a range of about 0.01% to 
1.0% and preferably 0.03%-0.8%, based on fiber weight; 
D. processing the resulting modifier-treated fiber or filament, to obtain 
and compile one or more webs for bonding; and 
E. bonding the resulting web(s) in a conventional manner to obtain a 
desired hydrophobic nonwoven material. 
For present purposes the term "polyolefin-containing spun fiber or 
filament" includes continuous as well as staple melt spun fibers which are 
obtainable from conventionally blended isotactic polypropylene as well as 
art-recognized hydrophobic copolymers thereof with ethylene, 1-butene, 
4-methylpentene-1 and the like. The resulting blended and extruded spun 
melt conveniently has a weight average varying from about 3.times.10.sup.5 
to about 5.times.10.sup.5, a molecular weight distribution of about 
2.0-12.0, a melt flow rate of about 5-70 g/10 minutes, and a spin 
temperature conveniently within a range of about 220.degree. 
C.-325.degree. C. 
Also includible within the spun melt are various art-recognized fiber 
additives, including pH stabilizers such as calcium stearate, 
antioxidants, pigments, including whiteners and colorants such as 
TiO.sub.2 and the like. Generally such additives vary, in total amount, 
from about 0.05%-3% by weight of spun melt. 
The present invention is found particularly applicable to high speed 
production of a variety of nonwoven materials utilizing webs obtained, for 
instance, from carded staple and may also comprise additional web 
components such as fibrillated film and the like. In each case, the 
fiber-handling difficulties generated by friction and accumulated static 
charge can be minimized or avoided without unacceptable sacrifice in 
bonding characteristics (i.e. strength), loss in fluid permeability or 
desired hydrophobic properties of the final product. 
In this regard the term "processing", as above-applied in process step "D", 
is inclusive of art-recognized web formation techniques applicable to 
continuous as well as crimped, cut and carded staple fiber, the crimping 
step, in the former case, being optional with respect to webs formed 
solely of fiber or filament. 
Continuous spun fiber or filaments used to form webs within the scope of 
the present invention preferably comprise topically treated spun melt 
staple fiber, filament, or fibrillated film of bicomponent or monofilament 
types, the above-defined modifier compositions or finishes being 
conventionally applied by drawing over a feed wheel partially immersed in 
a bath of an above-defined modifier composition, dipped therein, or 
sprayed in effective amount for fiber processing, and dried. 
For present purposes, webs used to form nonwovens within the scope of the 
present invention can be formed by spun bonded, melt blown or conventional 
"Dry" carded Process using staple fiber and bonded together using 
techniques employing adhesive binders (U.S. Pat. No. 4,535,013), calender 
rolls, hot air, sonic, laser, pressure bonding, needle punching and the 
like, known to the art. 
Webs used to fabricate nonwoven material can also usefully comprise 
conventional sheath/core (concentric or otherwise) or side-by-side 
bicomponent fiber or filament, alone or combined with treated or untreated 
homogenous-type fiber or filament and/or fibrillated film. 
Also within the scope of the present invention is the use of nonwovens 
comprised of one or more bonded webs of modifier-treated polyolefin fiber- 
and/or fiber-like (fibrillated film) components having a mixed fiber 
denier of homogeneous and/or bicomponent types not exceeding about 40 dpf. 
Such webs preferably utilize fiber or filaments within a range of about 
0.1-40 dpf. 
In addition, the resulting nonwoven material can be embossed and/or 
calender printed conventionally with various designs and colors, as 
desired, to increase loft, augment wet strength, and provide easy market 
identification. 
In further addition, webs used in forming nonwovens within the scope of the 
present invention are produced from one or more types of conventionally 
spun fibers or filaments having, for instance, round, delta, trilobal, or 
diamond cross sectional configurations, or mixtures thereof. 
Nonwoven cover stock of the above-defined types can usefully vary in weight 
from about 10-45 gm yd.sup.2 or higher. 
The invention is further illustrated but not limited by the following 
Example and Tables:

EXAMPLE 1 
A. Polypropylene fiber samples S-1 and S-2 are separately spun from 
separate resin batches in flake form generally characterized as follows: 
crystallinity 60%, 
molecular weight distribution 6.4 
melt flow 3.2 g/10 minutes 
which are individually processed in an impact blender. After 30 minutes the 
spun mixes having MFR values within a range of 24-27, are spun through a 
210 circular hole spinnerette at 280.degree. C. The resulting spun 
filament, is air quenched at room temperature, and stretched at 
115.degree. C. (4.times.) to obtain 2.0-2.54 dpf circular filaments, to 
which spin and over finishes are applied upstream and downstream of 
conventional crimping steps by passing the test filaments over a feed or 
kiss wheel partly immersed in a first modifier finish composition 
consisting of Lurol.RTM. AS-Y.sup.(*1) /LE458HS polysiloxane 
emulsion.sup.(*2) (5%/95% by weight), contact being of sufficient duration 
to topically apply about 0.40% and 0.59% based on dried spin composition 
(based on tow weight). The coated continuous filaments are then 
conventionally batch crimped at 100.degree. C. and thereafter passed over 
a second kiss roll at sufficient speed and concentration to coat the spun 
finished fiber with an over finish consisting of 100% Lurol AS-Y to impart 
0.1% overfinish to the fiber. 
FNT *1 A neutralized phosphoric acid/alcohol ester product of George A. 
Goulston Company of Monroe, N.C. 
FNT 2 LE-458HS, a product of Union Carbide Corporation. 
After air drying, the coated and processed test fiber is chopped to 1.5" 
length staple and set aside for conventional tests. Test results are 
summarized and reported in Table I below, in which the relative retained 
hydrophobicity as determined by fiber contact angle.sup.(*3) of the 
processed fiber is indicated in column 3 and the relative amounts of 
spinned finish (first modifier) an over finish (second modifier) are set 
out in columns 5 and 6 and by footnote. 
FNT (*3) % of fiber having a contact angle greater than 90 
B. Polypropylene samples S-3 through S-6 obtained from a resin batch 
essentially as described in Example 1-A are spun, air quenched and crimped 
as described therein, using different spin finish (first modifier) and 
over finish (second modifier) compositions identically applied by using a 
Kiss roll to impart from 0.1%-0.5% (dry fiber weight) of spin finish and 
0%-0.10% (dry fiber weight) over finish to obtain a total residual finish 
(after crimp) of about 0.2%-0.3% by weight. The crimping conditions are 
kept constant as an example in A. The observed waste (i.e. residue left on 
spool) and imparted crimp is also recorded in Table II below. 
TABLE I 
__________________________________________________________________________ 
STAPLE PROPERTIES 
Percent by 
Weight 
Finish *5 *6 
Color 
Degree of *4 
Tow Staple 
Fiber 
Tenacity 
Elongation 
Spin Fin. 
Over Fin. 
Sample # 
Type 
Hydrophobicity 
MFR 
(*5) 
(*6) 
Dpf 
gms % Cpi 
Type/AMT 
Type/AMT 
__________________________________________________________________________ 
S-1 195 
5 26.8 
0.4 0.3 2.0 
2.10 236.6 
34.1 
262/0.6 
263/0.1 
S-2 195 
5 24.4 
0.59 
0.25 
2.07 
2.72 226.1 
25.2 
262/0.6 
263/0.1 
__________________________________________________________________________ 
*4 Relative hydrophobicity of the finished and processed fiber; 
1 = substantially hydrophilic, 
5 = substantially hydrophobic. 
*5 Finish #262: 
95% Polydimethylsiloxane Emulsion (LE45BHS) 
5% Lurol ASY 
*6 Finish #263 
100% Lurol ASY 
TABLE II 
__________________________________________________________________________ 
Spin Over Total 
Crimps 
Waste 
Sample 
Spin Finish Type 
Finish Level 
Over Finish Finish Level 
Finish 
per Inch 
(%) 
__________________________________________________________________________ 
S-3 (*7) 
66% LE458HS, 33% Lurol ASY 
0.45% None 0.0% 0.25% 
30.1 
2.1% 
S-4 50% LE458HS, 50% Lurol ASY 
0.36% 50% LE458HS/50% Lurol ASY 
0.09% 0.29% 
29.5 
2.3% 
S-5 50% LE458HS, 50% Lurol ASY 
0.25% 50% LE458HS/50% Lurol ASY 
0.08% 0.22% 
27.0 
3.7% 
S-6 100% Lurol ASY 
0.16% 95% LE458HS/5% Lurol ASY 
0.10% 0.20% 
24.0 
4.45% 
__________________________________________________________________________ 
*7 Sample Did Not Card Due to Jamming. 
C. Polypropylene resin samples corresponding to those identified as samples 
S-3 and S-6 in Example 1B and Table II are routinely tested to determine 
differences in percent hydrophobicity*7 obtained in the processed and 
finished fiber utilizing different spin finish (step one) and over finish 
(step two) based on fiber contact angle determinations. Test results are 
reported in Table III below. 
FNT 7 Wilhelmy; The Physical Chemistry of Surfaces; 3rd Ed. Wiley & Sons, 1976; 
page 344. 
TABLE III 
______________________________________ 
FIBER AVG..sup..theta. a 
RANGE OF.sup..theta. a 
% HYDROPHOBICITY 
______________________________________ 
S-6 97 80-110 95 
S-3 102 95-110 100 
______________________________________