Meltblown wiper incorporating a silicone surfactant

A wiper comprising a meltblown polypropylene substrate containing a wetting agent. The preferred wetting agent is a functional organosilicone surfactant and the most preferred are DOW CORNING X2-8239 and UCARSIL.RTM. EPS. The wiper can be manufactured at low cost, wipes well for both oil and water and has improved hydrophilicity and durability over prior art wipers.

BACKGROUND OF THE INVENTION 
The present invention relates to wipers for industrial and other 
applications involving the absorption of water, oil and other liquid 
materials. Such wipers can take the form of a fabric which can be used, 
for example, in maintenance shop, auto repair, and industrial facility 
cleanup, in hand wiping, and in any application in which it is desirable 
to have a single material that wipes well for both oil and water. Since 
wiping is, in most cases, performed by hand, it is desired to obtain a 
wiper that wipes clean with a minimum effort, preferably on the first 
application. Most paper wipers, while inexpensive, are only effective for 
a single use and then must be disposed. Cloth wipers, which are most often 
used in industrial applications, are expensive and therefore must be 
reused for economy, and also must be laundered. It is therefore desirable 
to obtain a low-cost wiper with high absorbability that is durable and 
thus can be used more than once and then disposed. 
As disclosed in U.S. Pat. No. 4,307,143, many forms of wipers are available 
for various applications. In general, however, prior wipers can be 
classified as either paper or cloth. Paper wipers are inexpensive; 
however, they are suited primarily for use in wiping aqueous materials and 
are not entirely satisfactory for use with oil. Paper wipers also are 
primarily suitable for only a single use and then must be disposed. Cloth 
wipers, on the other hand, while suitable for wiping both oils and water, 
are expensive and must be laundered. In addition, unless care is taken in 
laundering, water absorption rates for cloth wipers can be adversely 
affected. Non-woven wipers made from rayon, which may also include other 
ingredients such as pulp, for example, and other synthetic materials, have 
been available, but in general fail to provide good wiping properties with 
both oil and water and may entail a cost that prevents disposability 
except in special applications. Finally, both natural and synthetic 
sponges are in widespread use for wiping, but are even more expensive. 
Examples of prior wipers within these broad classifications are contained 
in the following U.S. patents which are intended to be representative and 
not exhaustive: U.S. Pat. No. 3,477,084 to Thomas; U.S. Pat. No. 3,520,016 
to Meitner; U.S. Pat. No. 3,546,056 to Thomas; U.S. Pat. No. 3,650,882 to 
Thomas; and U.S. Pat. No. Re. 27,820 to Politzer et al. 
The preparation of polyolefin microfiber webs is also known and described 
in Wente, Industrial and Engineering Chemistry, Volume 48, No. 8 (1965), 
pp. 1342-1346, as well as U.S. Pat. No. 3,978,185 to Buntin et al., U.S. 
Pat. No. 3,795,571 to Prentice, U.S. Pat. No. 3,811,957 to Buntin, and 
U.S. Pat. No. 4,307,143 to Meitner. The Buntin et al. patent and the U.S. 
Pat. No. 4,307,143 to Meitner both disclose that meltblown polyolefins are 
useful as wiping cloths and hydrocarbon absorption material. However, the 
wipers as described in these publications each are deficient to a 
significant degree in one or more of the following properties: cost, 
combined oil and water wiping, clean wiping, physical properties, or 
durability. 
It is an object of the present invention to provide a wiper that is 
inexpensive to produce. 
It is another object of the present invention to provide a wiper that wipes 
well for both oil and water residues. 
It is a further object of the present invention to provide a wiper that 
enables clean wiping by fully absorbing a liquid material on the first 
application. 
It is a further object of the present invention to provide a wiper that has 
improved durability over paper wipers and thus can be reused. 
It is a further object of the invention to provide a wiper that exhibits 
durable hydrophilicity, i.e., the wiper retains its absorbency after 
multiple uses. 
Additional objects and advantages of the invention will be set forth in 
part in the description which follows, and in part will be obvious from 
the description, or may be learned by practice of the invention. The 
objects and advantages of the invention may be realized and obtained by 
means of the instrumentalities and combinations particularly pointed out 
in the appended claims. 
SUMMARY OF THE INVENTION 
To achieve the foregoing objects, and in accordance with the purposes of 
the invention as embodied and broadly described herein, the present 
invention provides a wiper comprising a meltblown polypropylene substrate 
which incorporates a wetting agent capable of imparting durable 
hydrophilicity to the wiper. 
In accordance with the invention, the preferred wetting agent applied to 
the meltblown polypropylene substrate is a functional organosilicone 
surfactant and most preferred is an aqueous solution of an 
organomethoxysiloxane, specifically Dow Corning X2-8239, or an aqueous 
solution of an epoxypolyoxyalkylene modified organosilicone, specifically 
UCARSIL.RTM. EPS. 
The accompanying drawing, which is incorporated in and constitutes a part 
of this specification, together with the description, serves to explain 
the principles of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference will now be made in detail to the presently preferred embodiments 
of the invention. 
In accordance with the present invention, the meltblown polypropylene 
substrate produced for the wipers of the present invention are 
manufactured in accordance with the process described in U.S. Pat. No. 
3,978,185 to Buntin et al. which is incorporated herein by reference in 
its entirety. Briefly, the process involves extruding a fiber-forming 
thermoplastic polymer resin, polypropylene, in molten form through 
orifices of a heated nozzle into a stream of hot gas, such as water vapor, 
to attenuate the molten resin as fibers which form a fiber stream, the 
fibers being collected on a receiver in the path of the fiber stream to 
form a non-woven mat. 
In accordance with the invention, the meltblown polypropylene substrate 
preferably has a basis weight ranging from 1.0 to 4.0 oz. per square yard, 
preferably incorporates the wetting agent in an amount ranging from 0.1% 
to 2.0% by weight, preferably is formed from fibers having an average 
diameter less than 10 microns, e.g., ranging from 1 to 10 microns, and is 
preferably pattern bonded with a bond area coverage sufficient to provide 
adequate strength to maintain the utility of the wiper. 
The meltblown polypropylene substrate of the wiper of the present invention 
preferably contains from 0.1% to 2.0% by weight of the wetting agent. The 
substrate should take up a sufficient amount of the surfactant wetting 
agent to provide the desired absorbency and durability. The solution of 
wetting agent applied to the substrate in the present invention is 
preferably an aqueous solution of a functional organosilicone present in 
an amount ranging from 0.75% to 3.0% by weight. Employing such 
concentrations will result in a satisfactory amount of the organosilicone 
wetting agent being taken up by the polypropylene substrate. 
As utilized herein, the term functional organosilicone refers to an 
organosilicone containing a functional group. 
The exact mechanism which enables retention of the wetting agent on the 
fiber surface is not critical to the invention. The mechanism is believed 
to consist of chemical bonding through active sites synthesized into the 
compounds as disclosed by U.S. Pat. No. 4,579,964 to Totten et al. and 
U.S. Pat. No. 4,184,004 to Pines et al. However, exemplary durability is 
obtained regardless of whether or not the polypropylene is capable of 
reacting with the organosilicone, perhaps through adsorption onto the 
fiber surface rendering the wetting agent resistant to leaching in aqueous 
solutions, or coating of the fibers with a network of self reacted or 
crosslinked surfactant which resists solubilization in aqueous solutions. 
In accordance with the invention, the wetting agent applied to the 
meltblown polypropylene substrate is preferably a functional 
organosilicone surfactant, and most preferably is an 
organomethoxysiloxane, i.e., Dow Corning X2-8239, or an 
epoxypolyoxyalkylene modified organosilicone, i.e., UCARSIL.RTM. EPS. 
UCARSIL.RTM. EPS is believed to be disclosed by U.S. Pat. No. 4,184,004 to 
Pines et al. which is incorporated herein by reference in its entirety. 
The formula for UCARSIL.RTM. EPS is believed to be: 
EQU MD.sub.x D'.sub.y D".sub.z M I 
wherein M, in each occurrence, is an end-capping unit of the formula 
A.sub.3 SiO.sub.1/2 in which each A, individually, is a monovalent 
organic radical free of olefinic unsaturation, such as a monovalent 
hydrocarbon radical, preferably alkyl having from 1 to 13 carbon atoms, or 
a hydrocarbyloxy in which the hydrocarbyl moiety is free of olefinic 
unsaturation and is preferably alkoxy containing from 1 to 13 carbon 
atoms, or a hydroxyl-terminated radical which is bonded to the silicon 
through a 1 to 13 carbon chain; or A is hydroxyl bonded directly to the 
silicon atom; or the M groups can be--in one or both occurrences--alkoxy 
of 1 to about 13 carbon atoms. 
In formula I above, D represents a unit of the formula R.sub.2 SiO wherein 
R, in each occurrence, is a monovalent hydrocarbon radical free of 
acetylenic unsaturation. Illustrative of the monovalent radicals 
represented by R one can mention alkyl groups containing from 1 to 10 
carbon atoms such as methyl, ethyl, propyl, butyl, isobutyl, amyl, hexyl, 
octyl, and decyl; alkenyl groups such as vinyl, allyl, butadienyl, 
1-pentenyl and the like; aryl radicals, including fused ring structures, 
such as phenyl, p-phenyl-phenyl, naphthyl, anthryl, and the like; aralkyl 
radicals such as phenylmethyl and phenylcyclohexyl; alkaryl radicals such 
as tolyl, xylyl, ethylphenyl, alpha or beta-methylnaphthyl, and the like; 
and cycloalkyl radicals such as cyclopentyl, cyclohexyl, and cyclobutyl. 
Preferred R radicals are alkyl, with methyl being particularly preferred. 
In formula I above, D' represents a unit of the formula RR'SiO wherein R 
has the same meaning as stated in the definition of D above, and R' is a 
polyoxyalkylene unit of the formula 
EQU --C.sub.n H.sub.2n (OC.sub.2 H.sub.4).sub.a (OC.sub.3 H.sub.6).sub.b OR"II 
wherein n is an integer having an average value of from 1 to 8; R" is 
hydrogen, acyl of 1 to 8 carbon atoms, or a monovalent hydrocarbon radical 
from 1 to 13 carbon atoms which is free from olefinic unsaturation; and a 
and b are integers such that the sum of a+b is at least 5 and can be up to 
about 200, and the quantity a/(a+b) has a value of from 1.0 to 0; 
preferably, a and b are integers such that the sum a+b has a value of at 
least 20 and the quantity a/(a+b) has a value from 0.25 to 1.0. In formula 
II above, the oxyethylene and oxypropylene moieties can be linked in a 
random chain or in a block chain such as a block chain structure of the AB 
or ABA type, or a chain having both blocked and random sections. 
In formula I above, D" is a unit of the formula RR"'SiO, wherein R has the 
same meaning as stated in the definition of D above, and R"' is a 
monovalent organic radical containing at least one vicinal epoxy group of 
the structure 
##STR1## 
The monovalent organic radicals represented by R"' which contain epoxy 
groups are, exclusive of the oxirane oxygen necessarily present, 
preferably hydrocarbon radicals free of acetylenic unsaturation or 
containing in addition to carbon and hydrogen only ether or carbonyl 
oxygen. Such R"' radicals include 
3,4-epoxycyclohexyl-6-methyl-3,4-epoxycyclohexyl; 
3-4-epoxycyclohexyl-1-ethyl; 9,10-epoxyoctadecyl; gamma-glycidoxypropyl; 
p-(2,3-epoxybutyl)phenyl; and 3-(2,3-epoxybutyl)cyclohexyl. The vicinal 
epoxy group can be, but need not be, a terminal group of the R"' radical. 
Because of the ready availability of precursors and the excellent results 
obtained using the final product, the preferred M and D units of formula I 
are, respectively, (CH.sub.3).sub.3 SiO.sub.1/2 and (CH.sub.3).sub.2 SIO 
and the preferred D' units are 
##STR2## 
In formula I above x, y, and z are each integers and have the following 
average values: 
x=10 to 5,000 
y=1 to x; 
z=1 to 0.5x, provided that 
Y+z.ltoreq.0.75x 
preferably 
x=25 to 1,000, 
y=1 to 0.5x provided that 
z=1 to 0.25x 
y+z.ltoreq.0.5x 
most preferably 
x=50 to 300, 
y=1 to 0.25x, 
z=1 to 0.15x, provided that 
y+z.ltoreq.0.25x 
The surfactant in an aqueous solution may be applied to the substrate in 
any manner but is preferably applied to the polypropylene as it exits the 
orifice of the extruder. 
The following examples further illustrate a preferred embodiment of the 
present invention. The examples should in no way be considered limiting, 
but are merely illustrative of the various features of the present 
invention. 
EXAMPLE 1 
A meltblown polypropylene wiper was produced by extruding Himont PF-011 
98.5% polypropylene resin through a commercial melt blowing line. A 1% 
solution of wetting agent (i.e. 495 g H.sub.2 O/5 g wetting agent) was 
applied to the molten resin exiting the extruder at a rate of one pound of 
solution per pound of substrate produced. The fibers were then collected 
to form a non-woven mat. The resulting fabric wiper had a basis weight of 
2.5 oz./sq. yard and a per cent bond area ranging between 10 and 15%. 
In order to compare the hydrophilic dissipation between the meltblown wiper 
of the present invention containing an organosilicone surfactant, and 
meltblown wipers containing other surfactants, a test procedure was 
conducted as follows: 
1. An 8".times.8" sample of the meltblown polypropylene fabric was cut out. 
2. The sample was submerged in 600 ml. of tap water. 
3. The sample was stirred in the water with a glass rod at 20 rotations. 
4. The sample was run through an Atlas Wringer with 40 total pounds of 
weight on the rolls. 
5. The sample was dried in a lab oven at 150.degree. F. for 15 minutes. 
6. The water absorbency rate (WAR) was measured in seconds per 0.1 ml. The 
entire procedure was then repeated with the same sample at reference step 
2 for five additional cycles with the WAR measured for each cycle. 
7. Steps 1-6 were then repeated a total of five times using different 
samples and the results were averaged. 
The purpose of this rewetting durability procedure is to simulate repeated 
uses of the disposable wiper and to determine the number of cycles it 
takes for the surfactant to become completely dispersed from the 
substrate. 
The results of these tests utilizing various surfactants on a meltblown 
polypropylene substrate are shown in Table I. These results present the 
water absorption rates (WAR) in sec/0.1 ml and are an average of the five 
test readings. 
TABLE I 
__________________________________________________________________________ 
NUMBER OF CYCLES 
0 1 2 3 4 5 
WAR (Sec./0.1 ml.) 
__________________________________________________________________________ 
AEROSOL .RTM. OT-75 
.79 
95.6 
&gt;180 
&gt;180 
&gt;180 
&gt;180 
UCARSIL .RTM. EPS 
.28 
.55 
7.12 
12.5 
25.2 
57.8 
DOW CORNING .27 
20.2 
&gt;180 
&gt;180 
&gt;180 
&gt;180 
X2-5176 
SURFYNOL .RTM. 440 
.32 
&gt;180 
&gt;180 
&gt;180 
&gt;180 
&gt;180 
SURFYNOL .RTM. 465 
2.3 
&gt;180 
&gt;180 
&gt;180 
&gt;180 
&gt;180 
DOW CORNING .27 
.37 
.66 
6.5 
6.4 
135.4 
X2-8239 
__________________________________________________________________________ 
AEROSOL is a registered trademark of American Cyanamid Company 
UCARSIL is a registered trademark of Union Carbide Corporation 
SURFYNOL is a registered trademark of Air Products and Chemicals, Inc. 
UCARSIL.RTM. EPS is the epoxcypolyoxyalkylene modified organosilicone 
utilized in a preferred embodiment of the present invention and is 
disclosed in U.S. Pat. No. 4,184,004 to Pines et al. AEROSOL.RTM. OT is a 
dioctyl sodium sulfosuccinate in a mixture of solvents and is one of the 
wetting agents disclosed in U.S. Pat. No. 4,307,143 to Meitner for 
treating a meltblown synthetic substrate to produce a wiper. DOW CORNING 
X2-5176 is a silicone glycol copolymer surfactant. Surfynol.RTM. 440 and 
465 are both ethoxylated 2,4,7,9-tetra-methyl-5-decyne-4,7,-diol. DOW 
CORNING X2-8239 is an organomethoxysiloxane. 
The test results presented in Table I are graphically illustrated by the 
attached figure. The results of the tests indicate that the UCARSIL.RTM. 
EPS and DOW CORNING X2-8239 surfactants incorporated into a meltblown 
polypropylene substrate provide in most cases improved and at least 
comparable initial absorption rates for water (0 cycle result) and provide 
greatly improved water absorption rates when the wiper is reused (cycles 
1-5). Therefore, the wiper of the present invention achieves improved or 
at least comparable water absorption rates and greatly improved durable 
hydrophilicity compared to prior art wipers utilizing different wetting 
agents. 
EXAMPLE 2 
To determine the amount of UCARSIL EPS wetting agent applied to the 
polypropylene substrate (% by weight), the following test was conducted. 
A 1% aqueous solution of UCARSIL EPS was applied to the melt blown 
polypropylene substrate as in Example 1. Three samples of the wiper 
material (each weighing approximately 10 grams) were soxhlet-extracted 
with 250 ml of distilled water. A control sample containing no wetting 
agent was also soxhlet-extracted with 250 ml of distilled water. The 
average amount of wetting agent extracted from the three samples was 
calculated to be 0.00517 grams per gram of fabric by utilizing an analysis 
of surface tension of the extracted liquid. The surface tension of the 
control sample was the same as distilled water. The results of this test 
indicate that the % by weight of the UCARSIL EPS wetting agent on the 
polypropylene substrate as produced in Example 1 was 0.517%. 
Although the present invention has been described in connection with 
preferred embodiments, it is understood that modifications and variations 
may be resorted to without departing from the spirit and scope of the 
invention. Such modifications are considered to be within the purview and 
scope of the invention and the appended claims.