Antistatic fabric and garment made therefrom

A garment for use in "clean rooms" is made from a tightly-woven, readily-cleanable, non-linting fabric with conductive filaments that provide anti-static properties. The conductive filaments are incorporated into the woven fabric of the garment so portions thereof constitute parts of the exterior of that garment to enable those conductive filaments to rapidly dissipate any charge of static electricity which may tend to develop on the surface of that garment. Those conductive filaments retain their ability to rapidly dissipate charges of static electricity despite repeated launderings of the garment in which they are incorporated.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
Charges of static electricity can develop on clothing as the wearers of the 
clothing move their arms and legs and also as they walk on non-conductive 
floor surfaces. When the relative humidity of the ambient atmosphere is 
very low, the charges of static electricity tend to develop readily; and 
those charges can become sizeable--in many instances reaching several 
thousands of volts. Static electricity charges are not only 
annoying--because they cause clothing to cling to the wearer's body, and 
also because they cause fine particles of lint and dust to collect on the 
clothing--but those charges can damage sensitive microcircuits, sensitive 
integrated circuits and other sensitive semi-conductors which are being 
handled by the wearer of the clothing. Specifically, charges of static 
electricity which are as small as six hundred volts can damage some 
sensitive microcircuits, sensitive integrated circuits and other sensitive 
semi-conductors. To minimize the development of charges of static 
electricity on clothing, and also to limit the sizes of any such charges 
which may develop on clothing, efforts have been made to incorporate 
electrically conductive elements into clothing or to apply antistatic 
chemicals to the clothing. 
2. Description of the Prior Art 
Antistatic chemicals are marketed in the form of additives to detergents, 
in the form of aerosol sprays to be sprayed onto clothing, and in the form 
of additives to "washes"; and those chemicals are helpful in reducing the 
tendency of clothing to cling to the wearer. However, those chemicals are 
not able to keep potentially-damaging charges of static electricity from 
developing on the surface of clothing. Also, those chemicals are not 
permanent in nature, and hence must be applied after each washing of the 
clothing. Further, some of those chemicals can form films on the surfaces 
of the clothing which can flake off and become contaminants, and hence 
make the treated clothing unusable in "clean rooms". In addition, those 
chemicals produce variable results where the persons who use those 
chemicals fail to use the specified amounts and proportions of those 
chemicals. 
Metallic laminate threads--each of which consisted of a bottom ply of thin 
narrow plastic, a middle ply of thin narrow metal and top ply of thin 
narrow plastic--have been used. However, the conductivity of the metal in 
the middle plies of those metallic laminate threads was so high that those 
middle plies were made with gaps therein to protect persons--who walked on 
rugs made with yarns in which those metallic laminate threads were 
incorporated--from the risk of electrocution. Those metallic laminate 
threads were rectangular in cross section and were relatively 
wide--frequently one hundredth of an inch wide; and hence were not usable 
in making thin, light clothing for "clean rooms". Also, because those 
middle plies of metal were extremely thin--frequently forty-five 
hundred-thousandths of an inch thick--and because only the thin edges 
thereof were exposed, those metallic laminate threads could not keep 
sizeable charges of static electricity from forming on the surfaces of any 
garment in which they might be incorporated. 
Large numbers of lengths of small diameter stainless steel threads or wire 
have been incorporated into yarns which have been used to weave fabrics; 
and those lengths of stainless steel threads or wire have enabled 
clothing, which was made from those fabrics, to discharge 
potentially-damaging charges of electricity and also to reduce the 
tendency of such clothing to cling to the wearer. However, those fabrics 
are not limited-linting fabrics, and hence they are not desirable for use 
in "clean rooms". 
Monofilaments of polymeric material have had conductive particles embedded 
in the surfaces thereof to make those monofilaments conductive; and those 
monofilaments have been incorporated into clothing. In some instances, 
those monofilaments have been incorporated into warp knit fabrics; and, 
when properly incorporated into such fabrics, those monofilaments have 
been able to keep potentially-damaging charges of static electricity from 
developing on the surface of clothing made from those fabrics. However, 
those warp knit fabrics could not substantially prevent the passage 
therethrough of hair and flaked-off particles of skin, and hence were not 
suitable for use in "clean rooms". Those monofilaments also have been 
incorporated into woven fabrics and, when so incorporated, those 
monofilaments have minimized the tendency of clothing, made from those 
fabrics, to cling to the wearer. However, those monofilaments were unable 
to keep potentially-damaging charges of static electricity from developing 
on the surface of clothing made from those fabrics. 
SUMMARY OF THE INVENTION 
The present invention provides a woven fabric that produces a charge decay 
of ninety percent from an applied voltage of five thousand volts within 
one-half of a second and that keeps charges of static electricity in 
excess of six hundred volts from developing on the surface thereof. That 
woven fabric has a plurality of non-conductive warp threads and a 
plurality of non-conductive fill threads; and each of those threads has a 
denier of about one hundred and fifty or greater. Where it has a plain 
weave and is in its finished state, that fabric has at least sixty-six 
warp threads per inch and at least fifty fill threads per inch. Where that 
woven fabric has a herringbone, twill or basket weave and is in its 
finished state, that fabric has at least seventy warp threads per inch and 
at least sixty fill threads per inch. A majority of the warp threads are 
non-textured threads made from a multiplicity of continuous filaments 
which are non-conductive, and hence the majority of the warp threads are 
non-textured, non-conductive, multi-filament threads. Similarly, a 
majority of the fill threads are non-textured threads made from a 
multiplicity of continuous filaments which are non-conductive, and hence 
the majority of the fill threads are non-textured, non-conductive, 
multi-filament threads. Each of a minority of the warp threads is 
conductive from end to end, because it includes a non-textured 
monofilament of plastic which has vast numbers of tiny conductive 
particles embedded in the surface thereof. That monofilament is ply 
twisted with at least one non-textured, non-conductive ply which is made 
from a multiplicity of continuous filaments that are non-conductive. 
Similarly, each of a minority of the fill threads is conductive from end 
to end, because it includes a non-textured monofilament of plastic which 
has vast numbers of tiny conductive particles embedded in the surface 
thereof. That monofilament is ply twisted with at least one non-textured, 
non-conductive ply which is made from a multiplicity of continuous 
filaments that are non-conductive. The diameter of each non-textured 
monofilament in the conductive warp threads, and the diameter of each 
non-textured monofilament in the conductive fill threads, is substantially 
smaller than the diameter of each non-textured, non-conductive ply in 
those threads; and hence the cross section of each of those non-textured 
monofilaments is very much smaller than the cross section of each of those 
non-textured, non-conductive plies. The resulting large disparity between 
the cross sections of the non-textured monofilament and of the 
non-textured, non-conductive ply or plies of each conductive warp or fill 
thread enables the non-textured, non-conductive ply or plies to provide 
the major portion of the strength of the conductive thread. Further, that 
large disparity enables that non-textured monofilament to be given, and to 
retain, the form of an open-type helix as it is ply-twisted with the 
non-textured, non-conductive ply or plies. Because each non-conductive ply 
of each conductive wrap or fill thread is made from non-textured 
continuous filaments, and hence is relatively thick and relatively strong, 
that non-conductive ply helps protect the non-textured monofilament from 
breaking as the conductive thread is incorporated into the woven fabric, 
and also as that woven fabric experiences local stresses during wear. 
Consequently, each of the conductive threads of the woven fabric provided 
by the present invention has a small diameter, non-textured continuous 
filament which is continuously and uninterruptedly conductive between the 
ends thereof, which is ply-twisted with one or more larger-diameter, 
stronger plies of non-textured, continuous, non-conductive filaments, and 
which has the major portion of the surface thereof exposed to constitute a 
portion of the surface of that conductive thread. 
It is, therefore, an object of the present invention to provide each 
conductive thread of a woven fabric with a small-diameter, non-textured, 
continuous filament which is continuously and uninterruptedly conductive 
between the ends thereof, which is ply-twisted with one or more 
larger-diameter, stronger plies of non-textured, continuous, 
non-conductive filaments, and which has the major portion of the surface 
thereof exposed to constitute a portion of the surface of that conductive 
thread. 
The woven fabric provided by the present invention produces a charge decay 
of ninety percent from an applied voltage of five thousand volts within 
one-half of a second; and hence rapidly dissipates any charges of static 
electricity which may develop on the surface of clothing made from that 
woven fabric. In addition, that woven fabric can limit the values of 
charges of static electricity, which a wearer's movements can cause to 
develop on clothing made from that woven fabric, to less than six hundred 
volts. As a result, the woven fabric provided by the present invention can 
be incorporated into clothing which will be worn by persons handling 
sensitive microelectric circuits, sensitive integrated circuits and other 
sensitive semi-conductive devices. It is, therefore, an object of the 
present invention to provide a woven fabric that produces a charge decay 
of ninety percent from an applied voltage of five thousand volts within 
one-half of a second and that can limit the values of charges of static 
electricity, which a wearer's movements can cause to develop on clothing 
made from that woven fabric, to less than six hundred volts. 
"Clean room" garments, which are made from the woven fabric of the present 
invention, have conductive threads in the warp, and also in the fill, 
thereof. As a result, each section of that garment can conduct static 
electric charges thereon to the peripheries of those sections. Where a 
section of that garment is connected to another section of that garment, a 
double needle, two-fold seam is used; and such a seam makes certain that 
several of the conductive threads of the one section engage one or more of 
the conductive threads of the other section. The engagements of those 
conductive threads enable any static electric charges on any one section 
of the garment to pass to any other section of that garment where those 
charges can be dissipated. It is, therefore, an object of the present 
invention to provide "clean room" garments which have conductive threads 
in the warp, and also in the fill, of the fabric of the sections thereof 
and which use double needle, two-fold seams to interconnect the sections 
thereof so several of the conductive threads of the one section engage one 
or more of the conductive threads of the other section. 
Other and further objects and advantages of the present invention should 
become apparent from an examination of the drawing and accompanying 
description. 
In the drawing and accompanying description, a preferred embodiment of the 
present invention is shown and described, but it is to be understood that 
the drawing and accompanying description are for the purpose of 
illustration only and do not limit the invention and that the invention 
will be defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawing in detail, the numeral 12 denotes a multiplicity 
of elongated filaments of very small diameter which are essentially 
parallel to each other and which coact to constitute one ply of a 
plural-ply conductive thread for woven fabrics that can be used in making 
garments which are usable in "clean rooms". Those elongated filaments are 
non-textured, continuous, non-conductive filaments. In the preferred 
embodiment of the present invention, the filaments 12 are standard and 
usual polyester filaments which are made by the Celanese Corporation or by 
the Eastman Chemical Company and which have such small diameters that 
thirty-six of them are needed to form a yarn of seventy denier. Two such 
yarns are then combined together to constitute, or to simulate, a single 
ply, as shown particularly by FIG. 2. Those yarns can be combined together 
in advance of, or during, the step wherein a non-textured, continuous, 
conductive monofilament 14 is combined with those yarns to form the 
conductive thread of the present invention. 
The monofilament 14 has conductive particles embedded in the surface 
thereof to render that non-textured, continuous monofilament capable of 
conducting static electricity. Although different non-textured, 
continuous, conductive monofilaments with embedded conductive particles 
could be used, it is preferred to use a 21-denier conductive nylon 6 
monofilament which is made by the Dow Badische Company. That monofilament 
has a denier of 21 plus or minus 2, a minimum tenacity of 3.5 grams per 
denier, a minimum extension of 20%, a shrinkage of 7.5% plus or minus 
21/2%, and a resistance of 5.times.10.sup.6 ohms per centimeter. The 
carbon particles in the surface of the monofilament 14 constitute, and 
provide, an essentially-continuous surface along the entire length of that 
monofilament. 
The diameter of the monofilament 14 is much smaller than the diameter of 
the conductive thread which includes that monofilament and the single, or 
simulated-single, ply constituted by the multiplicity of filaments 12. In 
the preferred embodiment of the present invention, the diameter of the 
monofilament 14 averages about fifty microns, the diameters of the 
conductive warp threads average about two hundred and ninety-six to three 
hundred and twelve microns, and the diameters of the conductive fill 
threads average about three hundred and twenty microns. As a result, the 
cross section of the monofilament 14 is smaller than three hundredths of 
one percent of the cross section of the conductive thread. 
The conductive thread of the present invention can be formed by initially 
combining a plurality of multi-filament yarns to make, or to simulate, a 
single, multi-filament ply and then ply-twisting that ply with the 
monofilament 14. Alternatively, that conductive thread can be made by 
initially keeping the plurality of multi-filament yarns separate from each 
other and then simultaneously ply-twisting them and the monofilament 
together. In addition, that conductive thread can be made by ply-twisting 
the monofilament with a single ply which has a large number of filaments 
and which has a cross section that is close to the sum of the cross 
sections of a plurality of multi-filament yarns. In each modification of 
the conductive thread of the present invention, the monofilament 14 will 
have the configuration of an open-type helix, and it will constitute an 
appreciable part of the outer surface of that conductive thread. FIGS. 1 
and 2 show the monofilament 14 as having mere line contact with a 
cylindrical "envelope" which is defined by the multitude of filaments 12; 
but that monofilament actually compresses longitudinally-spaced portions 
of that "envelope" so the conductive thread has a generally-variable 
diameter. That compressing will occur as that monofilament is ply-twisted 
with that "envelope"; and it will cause portions of that "envelope" to 
incline inwardly toward the monofilament 14 at shallow angles and then 
incline outwardly away from that monofilament at comparable shallow 
angles. However, the major portion of the monofilament 14 will be disposed 
outwardly of the axis of the conductive thread by a distance close to the 
radius of the "envelope". Also, the major portion of the surface of the 
monofilament 14 will constitute an appreciable part of the surface of the 
conductive thread. In the preferred embodiment of the present invention, 
the monofilament 14 and the multitude of filaments of the "envelope" are 
plytwisted so that monofilament makes about four to four and one-half 
turns per inch. That multitude of filaments makes about the same number of 
turns per inch. 
The carbon of the monofilament 14 and the nylon of that monofilament are 
desirable because they do not adversely affect human skin. Similarly, the 
polyester filaments 12 are desirable because they do not adversely affect 
human skin. The fact that the monofilament 14 has a cross section which is 
very substantially smaller than the overall cross section of the 
conductive thread and the fact that each of the filaments 12 has a cross 
section which is smaller than the cross section of that monofilament 
enable fabrics, which include that conductive thread, to be flexible and 
soft, to have a desirable "feel" and "hand", and to provide a desirable 
"cover" despite the hard and stiff nature of the nylon of that 
monofilament. 
The fact that the single, or simulated-single, ply of the conductive thread 
is made from a multitude of very small-diameter filaments enables the 
"envelope", which is defined by those filaments, to have sufficient 
yieldability and "give", in response to laterally-applied forces, to 
enable the conductive thread to coact with non-conductive threads in a 
woven fabric to provide the "cover" which is needed to resist the passage 
through that woven fabric of particles of skin and hair. That yieldability 
and "give" also enable such a woven fabric to be flexible enough and soft 
enough, to have a sufficiently desirable "feel" and "hand", and to permit 
the wearer of a garment, made from that woven fabric, to be comfortable. 
However, the single, or simulated-single, ply of the conductive thread 
must not have so much yieldability and "give", in response to 
laterally-directed forces, that the monofilament 14 could become "buried" 
within the "envelope"--defined by that single, or simulated-single, 
ply--during the ply-twisting of that monofilament with that single, or 
simulated-single, ply. Also, the single, or simulated-single, ply of the 
conductive thread must not have so much yieldability and "give", in 
response to laterally-directed forces, that the monofilament 14 could 
assume a random and irregular orientation or configuration during the 
ply-twisting of that monofilament with that single, or simulated-single, 
ply. The use of a non-textured, continuous, multi-filament single, or 
simulated-single, ply, which has a diameter that is several times larger 
than the diameter of the monofilament, provides the required yieldability 
and "give" in response to laterally-directed forces, and yet does not 
permit that monofilament to become "buried" in the "envelope", and does 
not permit that monofilament to assume a random and irregular orientation 
or configuration during the ply-twisting of that monofilament with that 
single, or simulated-single, ply. 
The open-type helical configuration of the monofilament 14 limits the 
tensile forces which can be applied to that monofilament during any 
stretching of the conductive thread as any woven fabric, in which that 
conductive thread is incorporated, flexes or stretches in use. Also, that 
open-type helical configuration keeps that monofilament from limiting the 
flexing or stretching of such a woven fabric. In addition, that open-type 
helical configuration coacts with the displacing of the major portion of 
that monofilament outwardly of the axis of the conductive thread, to 
expose the major portion of that monofilament. Such exposure is important 
because the 5.times.10.sup.6 ohms per centimeter resistance of that 
monofilament is far closer to the 2.times.7.sup.7 ohms per centimeter 
resistance of Bakelite 140, which is classified as a dielectric, than it 
is to the 3.5.times.10.sup.3 ohms per centimeter resistance of carbon, 
which is classified as a conductor. That exposure, plus the fact that the 
monofilament 14 is continuous and uninterrupted throughout the length of 
the conductive thread provided by the present invention--to provide a 
continuous and uninterrupted electrical path--enables that conductive 
thread to conduct charges of static electricity. All of this means that 
the present invention provides a conductive thread which enables fabrics 
that include that conductive thread to be flexible and soft, to have a 
desirable "feel" and "hand", to provide a desirable "cover", and to effect 
the discharging of charges of static electricity. 
The fact that the conductive thread of the present invention has a 
conductive monofilament which is plied, as an open-type helix, around an 
"envelope" that has a much larger cross section and that is defined by a 
multitude of non-textured, continuous filaments enables that conductive 
thread to be woven into a fabric. One preferred woven fabric that is made 
with that conductive thread has a 150 denier base yarn that is composed of 
thirty-two non-textured, continuous filaments of American Enka Semi-Dull 
Polyester; and that base yarn is used both in the warp and fill. When that 
woven fabric is in the greige state, it has seventy-two ends per inch and 
sixty-eight picks per inch, the conductive thread ends are spaced apart 
four hundred and six thousandths of an inch, and the conductive thread 
picks are spaced apart five hundred and fifteen thousandths of an inch. 
When a herringbone weave is used, the greige width is forty-nine inches, 
and the greige weight is four and five-hundredths of an ounce per lineal 
yard. After that woven fabric is finished, it has eighty-two ends per inch 
and sixty-eight picks per inch, the conductive thread ends are spaced 
apart about three-eights of an inch, and the conductive thread picks are 
spaced apart about one-half of an inch. 
A preferred woven fabric, that has a plain weave, has the same base yarn; 
but, in its finished state, that woven fabric has seventy-five ends and 
sixty picks. The conductive thread ends are spaced apart about 
three-eights of an inch and the conductive thread picks are spaced apart 
about one-half of an inch. 
Each of those preferred forms of woven fabric can meet the requirements of 
the NFPA 56A test, of the AATCC Test Method 76-1978, and of the Federal 
Test Method 101B. Specifically, when each of those fabrics is tested in 
accordance with Sections 4663 and 4664 of NFPA Code 56A, it exhibits a 
charge decay of ninety percent from an applied voltage of five thousand 
volts within one-half of a second, and it also displays a surface 
resistivity which does not exceed 1.times.10.sup.11 ohms. Actually, each 
of those woven fabrics has a higher capability for discharging charges of 
static electricity than is required by any of those tests. Specifically, 
each of those fabrics can limit the maximum charge which can develop on 
the surface of any new garment, into which it is incorporated, to less 
than six hundred volts, as shown by the following chart of the results of 
tests made, in a thirty percent relative-humidity atmosphere, on a 
coverall (garment A) which was made from a woven fabric having no 
conductive threads, on a coverall (garment B) which was made from the 
hereinbefore-described herringbone fabric, on a laboratory coat (garment 
C) which was made from a fabric having no conductive threads, and on a 
laboratory coat (garment D) which was made from the hereinbefore-described 
herringbone fabric: 
______________________________________ 
State of 
Maximum Measured Charges 
Garment 
Garment A Garment B Garment C 
Garment D 
______________________________________ 
As 50-100 less than 50 volts (a 
50 volts (a 300 
removed 
volts 50 volts 2500 volt 
volt "hot spot" 
from "hot spot" 
due to the re- 
package due to the 
moval of the 
removal garment from 
of the its plastic pack- 
garment 
from its 
age was noted) 
plastic 
package 
was noted) 
As worn 
less than less than less than 
less than 
50 volts 50 volts 50 volts 
50 volts 
______________________________________ 
Garments A and B, and an identical set of garments A and B, were delivered 
to a commercial dry-cleaning establishment and were subjected to fifty dry 
cleanings. Thereafter, they provided the following results in a thirty 
percent relative-humidity atmosphere: 
______________________________________ 
Maximum Measured Charges 
State of Garment 
Garment A Garment B 
______________________________________ 
Back of garment as 
Greater than 0 
received from dry 
5000 volts 
cleaner 
Front of garment 
Greater than 0 
as received from 
5000 volts 
dry cleaner 
As worn 3000-5000 volts 
0 
______________________________________ 
A further set of garments A and B was delivered to that dry-cleaning 
establishment and subjected to fifty commercial dry cleanings; but, during 
the last two dry-cleanings, those garments received a clear solvent rinse 
with no detergent or softener. Thereafter, they provided the following 
results in a thirty percent relative-humidity atmosphere: 
______________________________________ 
Maximum Measured Charges 
State of Garment 
Garment A Garment B 
______________________________________ 
Back of garment 
4400-5000 volts 
0 
as received from 
dry cleaner 
Front of garment 
5000-5500 volts 
50 volts 
as received from 
dry cleaner 
As worn 2000 volts 0 
______________________________________ 
A still further set of garments A and B was delivered to a commercial 
laundry and was subjected to fifty commercial launderings. Thereafter, 
that set was tested in a thirty percent relative-humidity atmosphere with 
the following results: 
______________________________________ 
Maximum Measured Charges 
State of Garment Garment A Garment B 
______________________________________ 
As removed from 50-100 volts 
50 volts 
dryer used by laundry 
Back of garment 200 volts 0 
before it was worn 
Front of garment 2000 volts 50 volts 
before it was worn 
As worn 50-100 volts 
0 
______________________________________ 
Yet another set of garments A and B was subjected to fifty launderings; but 
a softener-antistatic chemical was used during each of those launderings. 
The use of that chemical seemed to have little effect, other to tend to 
reduce the wrinkling in the garments. 
Garments C and D were worn for five days, and then were subjected to a test 
in a thirty percent relative-humidity atmosphere with the following 
results: 
______________________________________ 
Maximum Measured Charges 
State of Garment 
Garment C Garment D 
______________________________________ 
As worn 1000-3000 volts 
0-150 volts 
Seat area 3000 volts 1500 volts 
After wearing 2500-5000 volts 
50-150 volts 
Seat area greater than 5000 volts 
after wearing 5000 volts 
______________________________________ 
A microscopic examination of conductive threads in the seat area of garment 
D showed that the weight of the wearer had forced the monofilaments 14 to 
displace enough of the small filaments 12 of the conductive threads to 
cause appreciable portions of those monofilaments to penetrate the 
"envelopes" defined by those small filaments. The resulting reductions in 
the exposed areas of those monofilaments reduced the ability of the seat 
area of garment D to collect and dissipate charges of static electricity. 
The charges on the portions of garment D which were close to, but which 
were not parts of, the seat area of that garment did not exceed 150 volts, 
because the monofilaments of the conductive threads in those portions did 
not appreciably penetrate the "envelopes" of those conductive threads. As 
a result, except where heavy forces were applied to the fabric of garment 
D, that fabric was able to limit charges thereon to considerably less than 
six hundred volts. 
The dry cleanings were carried out as follows: 
______________________________________ 
Machine: Permac 
Load: 200 lbs, dry, synthetic 
Solvent: Perchloroethylene, stabilized 
Basic cycle: 
a. Degrease, 150.degree. F. and water injection 
b. Rinse, 150.degree. F. and detergent injection 
c. Flush, cool down 
d. Finish 
______________________________________ 
The discharge from the degreasing cycle was filtered, distilled and 
re-used, the discharge from the rinse cycle was filtered and then directed 
to a holding tank, and the solvent in the holding tank was used for the 
degreasing cycle. The detergent included a fabric softener/anti stat made 
by Fabritec International of Cincinnati, Ohio and marketed as Emerbrite 
No. 7525 of Emery Industries. 
The launderings were carried out as follows: 
______________________________________ 
Machine: 
Landau, 1200 lbs capacity with 4 split pockets 
Load: 900 lbs dry, synthetic 
Basic cycle: 
a. Flush: 3 minutes at 135.degree. F., 2 minutes 
at 160.degree. F. 
b. Break: add 20 lbs orthosilicate, agitate 
for 12 minutes at 160.degree. F. (McKesson-Robbins, 
Triton 48 oz) 
c. Flush: 2 minutes at 160.degree. F. 
d. Suds: add 4 lbs orthosilicate, agitate 
for 7 minutes at 160.degree. F. 
e. Flush: 2 minutes at 160.degree. F.; 2 minutes at 150.degree. 
F. 
f. Bleach: add 6 gal, 1% Na hypochlorite, 
agitate for 7 minutes at 145.degree. F. 
g. Flush and cool down: 2 minutes at 150.degree. F., 
2 minutes at 140.degree. F., add antichlor and 
thiosulfite and agitate at 120.degree. F. for 
5 minutes 
h. Finishing: tumble dry for 10 minutes at 
160.degree. F., cool down for 5 minutes 
______________________________________ 
Where a set of garments A and B was treated with a softener-antistatic 
chemical, Wallerstein AS-20 was added to flush and cool down cycle at 1/2 
oz/100 lbs. 
An additional set of garments A and B was given a fifty-first laundering so 
the tests could be made as those garments were removed from the dryer. The 
relative humidity in the laundry was fifty percent; and, as garment A was 
removed from the dryer, charges from 400-800 were measured. Also, 1100 
volts were measured at one spot on that garment. One minute thereafter, 
the range of charges had dropped to 100-200 volts and the spot voltage had 
dropped to 400 volts. Immediately after garment B was removed from the 
dryer, the charges thereon ranged from 0-150 volts. One minute thereafter, 
the range of charges had dropped to 0-50 volts. 
Other garments A and B were tested to determine the static decay times in 
seconds after fifty dry cleanings: 
______________________________________ 
Static Decay Time 
Nature and State of Garment 
in Seconds 
______________________________________ 
Garment A removed from package 
3.9 seconds 
Garment B removed from package 
less than one-tenth of 
a second 
Garment A washed fifty-one times 
7.3 seconds 
Garment B washed fifty-one times 
0.22 seconds 
Garment A dry-cleaned fifty times 
acted as insulator 
Garment B dry-cleaned fifty times 
2.8 seconds 
______________________________________ 
The 2.8 seconds reading, which was obtained on the garment B that had been 
dry cleaned fifty times, is due to a degradation of the monofilment 14 by 
the solvents which were used in the dry cleaning operations. Specifically, 
microscopic examinations of the monofilaments of various conductive 
threads in the woven fabric in garment B, after that garment had been 
given fifty dry cleanings, showed discontinuities in the conductive 
surfaces which are constituted by the carbon particles of those 
monofilaments. No such degradation was noted even after the fifty-first 
laundering; and hence the fabrics which are made from the conductive 
thread of the present invention are effective for longer periods of time 
when they are laundered rather than dry cleaned. 
The ability of garments, which are made from fabrics that utilize the 
conductive thread of the present invention, to pass the NFPA 56A test 
enables those garments to be used in places where static electric charges 
can damage sensitive microcircuits, sensitive integrated circuits and 
other sensitive semi-conductors. Further, because the conductive thread of 
the present invention can be incorporated into woven fabrics which provide 
"cover" that resists the passage of hair and flaked-off particles of skin, 
that conductive thread can be used in woven fabrics which are made into 
garments for "clean room". Where the conductive thread of the present 
invention is incorporated into herringbone twill or basket woven fabrics 
for "clean room" garments, each of those fabrics should have a total 
combined surface area (TCSA) in excess of forty thousand microns per 
square inch. 
The TCSA, in microns per square inch, of a woven fabric is determined by 
the formula Dw+Df=TCSA; where Dw is the number of ends per inch multiplied 
by the average diameter of those ends in microns, and where Df is the 
number of picks per inch multiplied by the average diameter of those picks 
in microns. Where a woven fabric for a "clean room" garment has a 
herringbone, a twill or a basket weave, Dw should be at least 21,980 
microns and Df should be at least 18,840 microns so the TCSA would be at 
least 40,820 microns per square inch. The maximum TCSA, which could be 
provided for a fabric that used a herringbone, twill or basket weave and 
that was used in making garments for "clean rooms", is limited only by the 
maximum number of ends and picks that can be woven commercially. 
Where a woven fabric for a "clean room" garment has a plain weave, Dw 
should be at least 20,724 microns and Df should be at least 15,700 microns 
so the TCSA would be at least 36,424 microns per square inch. The maximum 
TCSA, which could be provided for a fabric that used a plain weave and 
that was used in making garments for "clean rooms", is limited only by the 
maximum number of ends and picks that can be woven commercially. 
Where a garment is made from woven fabric in which the conductive thread of 
the present invention is incorporated, the various sections of that 
garment must be able to interchange any charges of static electricity 
thereon. The present invention makes certain that such charges can be 
interchanged by providing double needle, two fold seams between contiguous 
sections of the garment; and one such seam is shown in FIG. 3. One section 
of the garment is denoted by the numeral 20, it has a J-shaped fold 22 
adjacent one edge thereof, and it has an electrically-conductive grid whic 
is constituted by conductive warp threads 24 and conductive fill threads 
26. Another section of the garment is denoted by the numeral 28, it has a 
J-shaped fold 30 adjacent one edge thereof, and it has an 
electrically-conductive grid which is constituted by conductive warp 
threads 32 and conductive fill threads 34. The free edge of the section 20 
is disposed within, and is concealed by, the J-shaped fold 30 of the 
section 28, and the free edge of the section 28 is disposed within, and is 
concealed by, the J-shaped fold 22 of the section 20. As a result, the 
resulting two fold seam totally encloses the free edges of the sections 20 
and 28. Two rows of stitching 36 and 38 are indicated by dashed lines; and 
the row of stitching 36 will pass through the un-bent portion of the 
section 28, through the reversely-folded portion of the section 28, and 
through the un-bent portion of the section 20. The row of stitching 38 
will pass through the un-bent portion of the section 28, through the 
reversely-folded portion of the section 20, and through the un-bent 
portion of the section 20. As a result, both of the needles, and the 
thread therein, will pass through only three, rather than four, layers of 
woven fabric in the seam. 
It will be noted that the conductive warp threads 24 in the section 20 will 
engage at least one conductive fill thread 34 in the reversely-folded 
portion of the section 28, and also will engage at least two conductive 
fill threads 34 in the un-bent portion of that section. Similarly, it will 
be noted that the conductive warp threads 32 of the section 28 will engage 
at least one conductive fill thread 26 in the reversely-folded portion of 
the section 20, and also will engage at least two of the conductive fill 
threads 26 in the un-bent portion of the section 20. The resulting 
engagements between those conductive warp and conductive fill threads will 
make certain that any charges of static electricity which are collected by 
the conductive warp threads 24 of section 20 will be transferred to the 
conductive warp threads 32 of section 28 and vice versa. In this way, 
garments that are made from woven fabrics which incorporate the conductive 
threads of the present invention can provide full assurance that--except 
in the seat and in other areas of heavy use--the average values of charges 
of static electricity will be less than six hundred volts. 
The non-textured, continuous filaments 12, which are used in making the 
conductive threads of the present invention, are important in limiting the 
stretching of those conductive threads, in providing strength for those 
conductive threads, in resisting the penetration of the inner surfaces of 
the monofilaments 14 into the "envelopes" defined by the filaments 12 of 
those conductive threads, and in limiting the porosity and linting of 
woven fabrics in which the conductive threads are incorporated. Where the 
filaments 12 are made from polyester, they make the resulting woven 
fabrics wear-resistant, soil-resistant, strong, and resistant to 
shrinkage. However, if desired, the filaments 12 could be made from 
polypropylene, nylon, or equivalent polymers. 
The monofilament 14 preferably is made from nylon, and carbon particles are 
the preferred conductive particles that are embedded in the surface of 
that monofilament. However, if desired, metallic particles, rather than 
carbon particles, could be embedded in the surface of the nylon 
monofilament 14. If it ever became commercially practical to form 
polyester monofilaments with conductive particles embedded in the surfaces 
thereof, those monofilaments could be used in place of the impregnated 
nylon monofilaments 14. Similarly, if it ever became commercially 
practical to form polypropylene monofilaments with conductive particles 
embedded in the surfaces thereof, those monofilaments could be substituted 
for the impregnated nylon monofilaments. 
Although the preferred embodiment of conductive thread provided by the 
present invention utilizes a non-textured, continuous 21 denier nylon 6 
monofilament which has fine carbon particles embedded in the surface 
thereof, and also utilizes two non-textured, continuous, 70 denier 
polyester yarns--each of which has thirty-six filaments, other conductive 
threads could be used. The following list of usable conductive threads is 
representative and is not exhaustive; but it should be noted that in each 
of those conductive threads the percent of weight of the monofilament to 
the total weight is at least nine and one-half percent: 
______________________________________ 
Percent of weight 
of monofilament 
Denier of Denier of yarn or 
to weight of 
Monofilament 14 
yarns used in "envelope" 
conductive thread 
______________________________________ 
15 2 40 yarns 15.7 
15 2 50 yarns 13.0 
15 2 70 yarns 9.6 
15 1 80 yarn 15.7 
15 1 135 yarn 10.0 
15 1 140 yarn 9.6 
21 2 40 yarns 21.0 
21 2 90 yarns 10.4 
21 2 95 yarns 9.9 
21 1 80 yarn 21.0 
21 1 170 yarn 10.9 
21 1 190 yarn 9.9 
20 2 40 yarns 20.0 
20 2 90 yarns 10.0 
20 2 95 yarns 9.5 
20 1 80 yarn 20.0 
20 1 180 yarn 10.0 
20 1 190 yarn 9.5 
30 2 40 yarns 27.2 
30 2 100 yarns 13.0 
30 1 80 yarn 27.2 
30 1 200 yarn 13.0 
40 2 40 yarns 33.3 
40 2 100 yarns 16.6 
40 1 80 yarn 33.3 
40 1 200 yarn 16.6 
______________________________________ 
Where a woven fabric has a herringbone weave with eighty-two ends and 
sixty-eight picks in the finished state, where that fabric has a 
non-textured, continuous 21 denier nylon 6 carbon-impregnated monofilament 
14 in each conductive thread thereof, where that fabric has two 
non-textured, continuous 70 denier polyester yarns--each of which has 
thirty-six filaments therein--in each conductive thread thereof, and where 
each monofilament is formed as an open-type helix with from four to four 
and one-half turns per inch, each of those monofilaments is successively 
(a) visible in its full width, (b) visible in less than its full width as 
it passes around one side of the "envelope" of its conductive thread, (c) 
is not visible because it is rearward of that "envelope", and (d) is not 
visible because it is overlain by a transversely-directed thread of the 
woven fabric. However, in each lineal inch of each monofilament 14 of a 
conductive warp thread, from four tenths to fifty-two hundredths of an 
inch will be visible. In each lineal inch of each monofilament 14 of a 
conductive fill thread, from thirty-three hundredths to forty-two 
hundredths of an inch will be visible. The average percent of the visible 
length of the monofilament 14 of a conductive warp thread is about 
forty-three percent; and the average percent of the visible length of the 
monofilament 14 of a conductive fill thread is about thirty-six hundredths 
of an inch. 
The relatively-high resistance and the relatively-small diameter of each 
monofilament 14 amply protects the wearer of any garment, which is made 
from a woven fabric incorporating the conductive thread of the present 
invention, from any electrocution hazard. Yet, by causing that 
monofilament to have the configuration of an open-type helix that has the 
major portion of the surface thereof exposed, by spacing the conductive 
threads of a woven fabric apart a distance no greater than one-half of an 
inch, by providing sufficient monofilaments 14 to make the percent of 
weight of those monofilaments to the total weights of the conductive 
threads at least nine and one-half percent, and by causing an average of 
at least thirty-six percent of the lengths of those monofilaments to be 
visible at one surface of that woven fabric, the present invention enables 
all areas of a garment--which are made from such a woven fabric and which 
are not subject to heavy wear--to provide a charge decay of ninety percent 
from an applied voltage of five thousand volts within one-half of a second 
and also to limit the charges of static electricity thereon to less than 
six hundred volts. Further, by using a multitude of fine, non-textured, 
continuous polyester filaments in the "envelopes" of the conductive 
threads of such a woven fabric, the present invention enables that fabric 
to be flexible and soft, to have a desirable "feel" and "hand", and to 
provide a "cover" which will resist the passage of hair and particles of 
skin through that fabric. 
The grid-like arrangement of the conductive threads 24 and 26 in the 
section 20 of FIG. 3, and the grid-like arrangement of the conductive 
threads 32 and 34 of the section 28 in that view are very desirable, 
because they facilitate the discharging of static electric charges--even 
if portions of the carbon-impregnated surfaces of the monofilaments 14 of 
the conductive threads become degraded by repeated dry cleanings. Also, 
those grid-like arrangements are very desirable in making certain that a 
number of electrical contacts will automatically be established between 
the conductive threads of contiguous sections of a garment when those 
sections are sewn together by a double J-shaped seam. However, if a 
garment were to be laundered and not dry cleaned, and if the seams between 
adjacent sections of that garment were to be made with sufficient lapping 
and with sufficient angular displacement between the conductive threads of 
those sections to make certain that a number of electrical contacts were 
established between the conductive warp threads of those sections, that 
garment could be made from a fabric wherein no conductive fill threads 
were used. 
As shown by FIG. 3, each conductive warp thread will usually be spaced from 
each other conductive warp thread. Also, each conductive fill thread can 
be spaced from each other conductive fill thread. However, where a fabric 
is woven in a box loom, the conductive fill threads of that fabric can be 
formed as spaced pairs of side-by-side conductive threads. 
In the drawing and accompanying description, the conductive thread includes 
only one conductive monofilament 14. However, if desired, the conductive 
thread of the present invention could be made to include two or more 
conductive monofilaments. One such conductive thread could include two 
fifteen denier non-textured, continuous, conductive monofilaments and two 
fifty denier non-textured, continuous, multi-filament yarns. Other such 
conductive threads could be used with different combinations of 
non-textured, continuous, conductive monofilaments and non-textured, 
continuous non-conductive multi-filament plies. The use of a single, 
relatively-large, conductive monofilament 14 in each conductive thread is 
preferred, because such a monofilament is stronger than two conductive 
monofilaments of half the diameter. Also, it is easier to make a single, 
relatively-large, conductive monofilament than it would be to make two 
conductive monofilaments of half the diameter. 
Whereas the drawing and accompanying description have shown and described a 
preferred embodiment of the present invention, it should be apparent to 
those skilled in the art that various changes may be made in the form of 
the invention without affecting the scope thereof.