Note: Descriptions are shown in the official language in which they were submitted.
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1339327
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CHARGE DISSIPATIVE FLOOR TILES
Fleld of the Invention
The present invention relates to surface
covering products. In particular, the present invention
relates to surface covering products having static
dissipative electrical properties.
Backqround of the Invention
Static control problems have been recognized
and routinely addressed for years in the electronic
o manufacturing industries. As the miniaturization of
electrical equipment progresses and the growth of the
electronic industry continues, static control problems
have become more and more a sub~ect of serious concern
to the electronics industry. To put the problem into
perspective, it is known that someone walking across a
carpeted floor can accumulate more than 30,000 volts of
static charge, while published literature has referred
to 25 to 100 volts as critical static discharges which
could cause immediate and catastrophic damage to a sen-
sitive electronic chip. This demonstrates the need forprotecting the areas and enviro~ments where sophisti-
cated electronics equipment are manufactured and stored.
- 2 - 1339~27
It has been generally recognized that the pre-
vention of static discharge requires that the total
manufacturing and storage environment be constructed of
materials which are capable of dissipating static charges,
and that these materials be connected to a common ground.
In such an environment, it is critically important that
the flooring structure be protected against electro-
static discharge.
It has long been known that polymeric
materials, of the kinds typically employed in flooring
structures, such as polyvinyl chloride, are normally
insulative. They can be made conductive, however, by
incorporating either a conductive filler or an anti-
static agent in the polymer structure or by employing
both methods at the same time. When conductive fillers,
such as metallic materials or carbon blacks, are used,
the filler concentrations required to impart conductivity
to the polymer structure are usually relatively high,
typically thirty to fifty percent by volume. At such
concentrations, the appearance of the polymeric struc-
ture is usually black, gray, or brown, depending upon
the materials employed, and are not suitable for highly
decorative floor tile applications.
To protect a floor structure from accumulating
dirt and to improve the lustre or glossiness of a floor
structure, a floor polish is often used as a maintenance
aid. For most commercial conductive floor tiles or
sheet materials, especially those made with carbon and
other metallic materials, i.e., commercially available
carbon veined tiles and the like, such maintenance aids
are not recommended by the manufacturers. This is because
most commercially available floor polish materials are
insulative. They will interfere with the conducting
path formed by the carbon particles, or other metallic
materials therein, affecting the ab~lity of the conduc-
tive flooring structure to dissipate static charges.
For similar reasons, even a conductive floor
polish is often not recommended for use in the mainte-
- 3 - 133932~
nance of conductive floors, such as those employing
- carbon-veined tiles. This is typical because the con-
ductive floor polish is not usually as conductive as the
conductive floor itself. In addition, the residual
polish worn away by traffic also interferes with the
conducting path, further decreasing the charge dissipa-
tive efficiency of the conductive floor structure.
Antistatic agents, such as those containing
quaternary ammonium salt functionalities have been known
iO to impart charge dissipative properties to flooring
structures in the past. However, these antistatic
materials are sensitive to moisture and, in previous
uses, have affected the manufacturing processing charac-
teristics and performance characteristics of the floor-
ing structures in which they were employed. For example,
a floor structure containing moisture absorptive materials
might swell or grow in length where water is present. If
the moisture growth is high, the floor structure might
curl or buckle, causing what is commonly referred to as
a peak-seam in an installed floor structure. High mois-
ture growth is, therefore, generally considered to be a
high risk with respect to the performance of floor
coverings, particularly when installed on on-grade or
below-grade concrete sub-floors.
Objects of the Invention
It is an object of the present invention to
provide a surface covering product having static dissi-
pative electrical properties suitable for highly decora-
tive floor tile applications.
-It is a further object of the present inven-
tion to provide a surface covering product having static
dissipative electrical properties which can be main-
tained with commonly available commercial floor care
products.
It is a still further object of the present
invention to provide a surface covering product having
static dissipative electrical properties without the
moisture growth problems typical of antistatic agents.
- 1339327
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' According to the present invention, there is provided a
surface covering product having ~tatic dissipative electrical
properties comprising a consolidated agglomeration of first and
second portions of polymeric material, said first and
second portions being in the form of individual chips, the
first portion containing a substantial amount of an
antistatic agent whereby the material of the first portion
has a resistivity of less than 1011 ohms/square, and the
second portion containing only an insubstantial amount of
antistatic agent.
.0
Detailed Description of the Present Invention
By far, the predominant form of resilient
flooring used today is of the vinyl type, that is,
flooring which has a binder system based on polyvinyl
chloride, commonly referred to as PVC. This polymer by
itself i8 a very hard, tough, virtually intractable,
thermoplastic material that must be compounded with var-
ious additives to produce economically useful products.
It is one of the most adaptable polymeric materials and
is used for applications as widely divergent as rigid
pipe to almost jelly-like fishing lures. Because of
this adaptability it is well suited to the manufacture
of both flexible and ~emi-rigid flooring materials.
Polyvinyl chloride's high molecular weight and
chemical and physical nature allow it to accommodate
relatively large amounts of inert filler and it can be
plasticized effectively and permanently to create
materials with a wide range of flexibilities. Polyvinyl
chloride is inherently resistant to acids, alkali and
many organic solvents. ~t does not hydrolyse even when
in continuous contact with molsture. Because of its
chlorine content, the polymer is also inherently fire
resistant and as a plastic material is generally classi-
fied as self-extinguishing. Plasticized material is
less fire resistant than rigid PVC, but can usually be
formulated for use as a floor covering to pass the flame
spread and smoke generation limitations of most building
codes.
.~,
1339327
When properly compounded and processed, PVC
can be a clear, colorless material or pigmented to pro-
duce the full range of colors in transparent or opaque
forms.
Polymeric material, as used throughout this
specification, is intended to include polyvinyl chloride
in its various forms. The vinyl resins used in flooring
may be homopolymers, i.e., polymers consisting of only
vinyl chloride units, or copolymers, consisting of vinyl
chloride and other structural units, such as vinyl ace-
tate. The molecular weights of these resins typically
range from about 40,000 to about 200,000 atomic mass
units. The higher molecular weight polymers have greater
ultimate tensile strength and abrasion resistance and
are generally used in flooring wear layers, while the
lower molecular weight polymers are most useful in pro-
ducing foams for cushioned flooring. As a general rule,
vinyl homopolymers are typically used in vinyl sheet
goods and Type III solid vinyl tile, while Type IV vinyl
composition tiles typically contain copolymers of vinyl
chloride and vinyl acetate.
To protect the polymeric material from degra-
dation during processing and during its use as flooring
material, vinyl co~pounds must be stabilized against the
effects of heat and ultraviolet radiation. The most
common stabilizers used in flooring are soaps of barium,
calcium and zinc; organo-tin compounds; epoxidized soy
bean oils and tallate esters; and organic phosphites.
Polymeric materials for flooring uses, even
for use in relat~ely r~gid Type IV viny~ composition
tiles, contain plasticizers to provide flexibility and
to facilitate processing. The most frequently used
plasticizer ~s dioctyl phthalate (DOP). Others that
may be found in flooring use include butylbenzyl phtha-
late (BBP), al~ylaryl phosphates, other phthalate esters
of both aliphatic and aromatic alcohols, chlorinated
hydrocarbons, and various other high boiling esters.
~he selection of the proper type and amount of plasti-
A~'
- 6 _ 1339327
cizer is often cr1tical in the formulation of flooring
compounds because of the interaction of flexibility
requirements, resistance to staining, reaction with
maintenance finishes, and processing requirements.
In most tile and sheet flooring, the stabi-
lized and plasticized vinyl formulation is mixed with
varying amounts of inorganic filler to provide mass and
thickness at a reasonable cost. The most common filler
typically found in flooring is crushed limestone (cal-
cium carbonate). Others that may be employed include
talcs, clays and feldspars. In addition to providing
bulk at reasonable cost, the use of inorganic f illers in
flooring structures provides increased dimensional sta-
bility, resistance to cigarette burns, improved flame
spread ratings and reduced smoke generation.
Pigments are used in f looring products to pro-
vide both opacity and color to the f inished products.
The typically preferred white pigment is titanium dio-
xide and colored pigments are preferably inorganic.
Certain colors only available as lakes, such as the
phthalocyanine blues and greens, must be resistant to
the effects of alkali and light fading.
Finally, in order to pass certain code
requirements with regard to fire and~smoke properties
various additives may be employed to reduce f lame spread
and smoke generation ratings. These compounds include
alumina trihydrate, antimony trioxide, phosphate or
chlorinated hydrocarbon plasticizers, zinc oxide, and
boron compounds. Cushioned flooring containing chemi-
cally expanded foam is usually compounded with azobis~
formamide blowing agents. Various other processing aids
and lubricants may also be employed.
Probably the most widely used resilient floor-
ing product is vinyl composition tile, as described by
Federal Specification SS-T-312b, Type IV, Composition I.
While the present invention is intended for use in such
tile, as the specification and Examples describe, it
will be-obvious to one skilled in the art that the prin-
- 1339327
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ciples will also be applicable to various other types of
flooring, particularly sheet flooring formed from sten-
cil lay-ups or fused particles.
A typical formulation for vinyl composition
tile is:
Percent by Wei~ht
Vinyl Resin 12.5
~ydrocarbon Resin 2.5
Plasticizer 4.0
Stabilizer 1.0
Fillers and Pigments 80.0
Vinyl composition tile is highly filled and
the primary filler is calcium carbonate, or crushed
limestone. The ingredients are typically mixed in a
high power, high shear, heated mixer, such as a "Banbury
Mixer"to combine and fuse them together into a heavy
dough-like mass. This mass is then banded on a two roll
mill and in the manufacture of grained or ~aspe'd tile,
accent colors, of the same or a similar composltion
material, may be added to t~e mill nip.
For the purposes of the present invention,
however, the material can be sheeted and cooled, then cut
into individual chips of regular or irregular dimension,
the term "chips", as used herein, including structures of
any shape, including those in which all three dimensions
are substantially equal (cubes) as well as those in which
one dimension is substantially less than the other two.
An assortment of such chips prepared in suitable colors
are then arranged in a metal frame and consolidated with
heat and pressure into an aggomeration.
Alternatively, non-conductive chips and con-
ductive chips, separately prepared, may be mechanically
mixed, such as in a"Baker Perkin" mixer,and subsequently
sheeted out as a mixed-chlp condùctive structure using a
two-roll mill.
* Trademark
1339327
-7a-
-
A factory finish may be applled to the hot con-
solidated agglomerationto enhance colors, provlde uni-
form gloss, prevent blocking in storage and protect the
product during installation. Such finishes, as weli as
wax finishes applled to conductive flooring in use have
in the past acted to insulate flooring material unless
such finishes and waxes were formulated to be conductive.
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- 8 - 1339327
For reasons which are as yet unexplained, such conductive
finishes and waxes do not appear to be necessary with
the products of the present invention as the products of
the present invention appear to maintain their conduc-
tive properties even with the application of a limitedamount of conventional finishes and waxes.
Vinyl composition tile is typically offered in
several gauges and sizes depending on intended end use.
For residential applications, vinyl composition tile is
offered in so-called service gauge which is 1/16 inch
(1.6 mm) thick.
For commercial markets, vinyl composition tile
is typically offered in 3/32 inch (2.4 mm) and 1/8 inch
(3.2 mm) gauges, the latter being most frequently specified
for heavy traffic. The standard size of vinyl composition
tile is 12 inches by 12 inches, (about 0.3 m square)
although other sizes may be commercially available.
The performance re~uirements, outlined in
Federal Specification SS-T-312b, include size, thickness,
squareness, and dimensional stability tolerances. These
factors are critically important in the finished appear-
ance of the installed tile floor. Other characteristics
contained in the specification are solvent resistance,
indentation requirements, deflection, volatility, and
impact resistance.
Vinyl composition tile is a fairly rigid
material, and at room temperature will not bend acutely
without breaking. However, if deflected very slowly, it
will bend. This attribute is necessary to successfully
install the material over normal subfloors that are not
perfectly flat allowing it to conform to subfloor irre-
gularities. Commercial installation of vinyl composi-
tion tile is usual~y done with a full spread of asphalt
adhesive and the tile is set into the adhesive after the
solvent has evaporated. Solventless adhesives are also
available containing emulsified asphalt and resins for
areas where solvent vapors are undesirable. Rubber
latex adhesives also are used where black asphalt adhe-
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1339327
g
sives would be undesirable and for use over preexisting
tile floors. Such adhesives are often available in con-
ductive forms for use with the tile of the present
invent ion.
Vinyl composition tile is generally considered
the standard or base grade commercial finish flooring.
It has the lowest relative installed cost and has per-
formed satisfactorily in commercial environments for
many years. The major market segment for such tile use
today is the mercantile market, where vinyl composition
tile has been used almost exclusively for the general
floor area of grocery stores, supermarkets, and discount
department stores. It is also used extensively in
schools, health care facilities and to a lesser extent
in offices, banks, and light industries.
There is no minimum binder level requirement
for Type IV (vinyl composition) tile, and this is the
primary difference between vinyl composition tile and
Type III vinyl tile or "solid" vinyl tile. The Federal
Specification SS-T-312b requires that the minimum binder
level of Type III tile shall not be less than 34%, and
defines binder to include vinyl resin(s), plasticizers
and stabilizers. Vinyl tile is considerably more flexi-
ble than vinyl composition tile, but it is also signifi-
cantly more expensive, because of its higher binder
level.
Until the present invention, static dissipa-
tive flooring of the vinyl composition tile type has
not been commercially successful, chiefly because of
moisture growth problems. Type III vinyl tile alterna-
tives containing conductive material, however, have
remained expensive alternatives.
There are two general classes of materials
available which will dissipate static charges. The
first class of these i5 referred to as "conductive"
materials, and typically have resistivities in the range
of 103 to 106 ohms/square. Charge dissipative materials,
or static dissipative materials, the second class, typi-
-
- 10 - 1 33 9 3 27
cally have resistivities in the range of 106 to 10
ohms/square.
Static dissipative electrical properties as
referred to herein, means that the resistivity of a
material should be less than 1011 ohms/square. In addi-
tion, a material should have a charge decay rate, for
SOOo volts to 0 volts, of no more than 2.0 seconds.
Type III vinyl flooring tiles are commercially
available which incorporate carbon black or metallic
materials. These tiles, because of the coloration of
the high filler content, are not believed to be suitable
for highly decorative floor tile applications. In addi-
tion, because of the cost of the conductive filler
material, and the high binder level, such tiles tend to
i5 be expensive.
Vinyl composition flooring tiles have previ-
ously been known which have employed antistatic agents
containing quaternary ammonium salt functionalities.
However, these were flooring tiles of the kind known as
"straight grain", in which the antistatic agent was sub-
stantially uniformly distributed. Such products, while
they met the static dissipative electrical property
requirements, defined above, demonstrated serious mois-
ture growth problems which may have limited their use-
fulness in certain applications.
It has now been determined that a slightlymodified construction of flooring tile, employing a com-
pressed agglomerationof individual chips, can achieve
the same or similar electrical properties without the
moisture growth problems known to the prior art.
This has been accomplished, quite surprisingly,
by limiting the presence of the antistatic agent to only
a portion of the individual chips or minimizing the
amount of the antistatic agent in a portion of the indi-
vidual chips. As the examples which follow will demon-
strate, static dissipative electrical properties are
affected only slightly, while moisture growth properties
fall dramatically as the proportion of individual chips
A~i
..
1339327
containing a charge dissipating amount of antistat is
reduced. While even a small reduction in the proportion
of chips containing the typical level of antistat will
serve the purposes of the present invention, it has been
demonstrated that better results are obtained lf the
proportion of chips containing a charge dissipating
amount of antistat represent between from about twenty-
five (25X) to about eighty-five (85X) by weight of the
overall composition. Still better results are obtained
if the proportion of chips containing the charge dissi-
pating amount of antistat represent between from about
thirty-five percent (35%) and about seventy percent
(70%) by weight of the overall composition.
Although it is assumed that other antistatic
agents may be operable in the practice of the present
invention, such agents containing quaternary ammonium
saltfunctionalities have demonstrated static dissipative
electrical properties in flooring tiles which meet other
physical requirements. Such antistatic agents include
"Larostat 264A",commercially available from the Jordan
Chemical company; "Cyastat LS" , commercially available
from American Cyanamid; and "Hexcel 106G, commercially
available from the Hexcel Corporation. "Larostat 264A" is
soya dimethyl ethyl ammonium ethyl sulphate.
As detailed in the Examples which follow, it
has been found, surprisingly, that the charge dissipa-
tive tiles of the present invention may be maintained
with minimal applications of commonly available commer-
cial floor care products without significant loss of
their charge dissipative characteristics. In fact, some
data generated seems to indicate that an increase in
such characteristics may be measured. Applicants do not
propose any explanation for the increased conductivity
of the normally insulative floor finishing material.
Example 1
Vinyl composition tiles were prepared by mix-
ing and consolidating vinyl composition material in chip
form. Specifically, the vinyl composition material had
the following formulation in parts by weight:
* Trademark
** Trademark
B * * * Trademark
1339327
- 12 -
Polyvinyl chloride resin 121.00
Hydrocarbon resin 10.00
Phthalic ester plastlclzer40.50
Stabilizer 6.00
Titanium dioxide (opacifier) ~.80
Crushed Limestone (40 mesh)815.00
To a portion of this material was added 1.5%
of an antistatic agent, "Larostat 264A", commercially
available from the Jordan Chemical Company. After dicing
lo both vinyl structures into chips with a dimension of about
1/4 inches, (about 6.25 mm) floor tiles were prepared by
mixing the chips in the proportions shown in Table l and
filling a metal frame. The chips were subsequently hot-
pressed for ten (10) minutes at 310~F (about 154~C), at a
pressure of lO00 pounds per square inch (7MPa). Electrical
properties and moisture growth characteristics for the
resulting tiles are also given in Table 1.
)EW-no67
TAB~E 1
Surface Resistivity Surface Resistivity
at 50~ Relative Humidity at 15% Relative Humidity
Xatio of Chips Sile Mounted 011 Tile Mounted On Charge Decay
Containing Anti- a Plywood Board a Plywo~d ~oard Rate at 13X
Stat to Chips Not With a Conductive With a Conductive Relative Moisture
Containing Antistat Tile Alone Adhesive Tile Alone Adhesive Humidity Growth
100/0 1.8xlO8ohm~sq 8.7xlO70hm/sq 8.7xlO9ohm/sq 3.7xlO8ohm/sq0.01 sec. 5.61%
60/40 2.0xlO8ohm/sq 8.5xlO70hm/sq 1.9xlO9ohm/sq 4.5xlO8ohm/sq0.02 sec. 1.25%
50/50 4.0xlO8ohm/sq l.OxlO8ohm/sq 8.9xlO30hm~sq 6.5xlO8ohm/sq0.02 sec. 0.84% .;~
45/55 5.3xlO8ohm/sq 4.2xlO8ohm/sq 3.4xlO9ohm/sq 1.7xlO9ohm/sq0.04 sec. 0.66%
40/60 5.7xlO8ohm/sq 3.2xlO8ohm/sq 3.OxlO9ohm/sq 6.5xlO8ohm~sq0.03 sec. 0.32%
35/65 1.6xlO9ohm/sq 5.4xlO8ohm/sq 1.5xlOlOohm/sq 2.4xlO9ohm/sq0.48 sec. 0.16%
0/100 5.0xlOl30hm/sq 1.5xlOl30hm/sq 6.0xlOl30hm/sq 3.0xlOl30hm/sq> 6 sec. 0.14%
C~
C~
.
-
14
Example 2 1339327
Vinyl composition tiles were prepared from theconductive and non-conductive chips prepared in Example
1. Such chips were combined in the proportions set out
in Table II, mechanically mixed in a "Baker Perkin" mixer,
and subsequently sheeted out using a two-roll mill and
cut into tiles. As shown in Table II, the vinyl compo-
sition tiles prepared in this manner possessed electri-
cal dissipative properties and mechanical properties
similar to the tiles of Example 1.
* Trademark
33932r7
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- 16 -
ExamPle 3 ~ 7
A volume of vinyl composition tilesl~e3re9 pre-
pared by separately mixing batches of materials having
the compositions listed by welghts in Table 3A in a
"Baker-Perkin" mixer. Each batch had a temperature of
between 280~F (138~C) to 285~~ (140~C) at the end of about fifteen
~15) minutes of mixing. Mottle chips or accent colors
prepared of the same compositions beforehand were added
and mixing continued for approximately one minute at the
same temperature.
Each mixed vinyl composition was then sheeted
off in a mill to make a jaspe blanket. The front mill
roll was ad~usted to approximately 210~F. (99~C) wh~e the back
roll was m~int~ined between 250~F. and 270~F (121~C and 132~C). The blaIl-
ket was then die-cut into cubes or furnish.
After batches A through F were converted into
cubes in this manner, they were blended and mixed in an
equal ratio and transferred to a metal screen carrier.
The mixed vinyl cubes were then carried through a cham-
ber heated to between 330~F. and 350~F (166~C and 177~C), to partially
soften the vinyl cubes. The mixed and temperature con-
ditioned cubes were then fed through a set of calender
rolls equipped with an oscillating blade to consolidate
the structure. The temperature of the top roll was
2s m~int~ined behveen 220~F. and 225~~ (104~C and 107~C), while the bottom
roll was m~int~ined at between 330~F. and 350~F (166~C aIld 177~C).
After this consolidation step, the blanket was
reheated and fed into a consolidator to effect the final
gauge reduction and facing operation before being
punched into twelve inch by twelve inch (12" x 12") (about 0.3 m square) one-
- eighth inch (1/8") (about 3.2 mm) thick tiles.
The tile produced in this manner met the
indentation, impact resistance, deflection and volatil-
ity requirements of Federal Specification SS-T-312B for
Type IV vinyl composition tile. Dimensional properties
did not meet specification requirements, but it was
believed that processing ad~ustments would overcome this
problem. The tiles also demonstrated excellent electri-
cal charge dissipating characteristics, as shown in
Table 3B.
~B
:
- 17 -
Table 3A 1339327
Product Formulations (%)
A B C D E F
Limestone 80.3581.05 80.75 ~8.60 79.25 78.93
Pigments 2.00 1.30 1.60 1.95 1.30 1.62
Antistat 0.00 0.00 0.00 1.60 1.60 1.60
(Larostat 264-A)
Vinyl Resin11.4511.4511.45 12.65 12.65 12.65
Hydrocarbon
iO Resin 1.15 1.15 1.15 1.15 1.15 1.15
Plasticizer4.40 4.40 4.40 3.40 3.40 3.40
Stabilizer 0.65 0.65 0.65 0.65 0.65 0.65
1339327
- 18 -
Table 3B
Surface Resistivity
Relative Humidity Tile Alone Tile with Conductive
(%) (ohms/sq.) Adhesive (ohms/sq.)
6 to 9 x 108 2 to 4 x 108
4 to 7 x 109 5 to 8 x 108
NFPA 99 Resistance
2 to 10 x 1o6 ohms
(measured with Meggameter)
Static Decay Rate (5000 Volts to 0 Volts at 15%
Relative Humidity)
Tile Alone 0.06 to 0.08 seconds
Tile with Condutive
Adhesive 0.01 to 0.02 seconds
Triboelectric Char~in~ Measured at 50% Relative
Humidity with a NASA Rubbing Wheel Tribocharge Test
Apparatus)
2000 to 4000 Volts
19- 1339327
Example 4
This example compares the use of commercial
conductive floor polish in maintaining commercially
available carbon-veined conductive floor tile and the
charge dissipative tile of this invention as prepared in
Example 3. In this example, nine (9) 12" x 12" (about 0.3 m square) tiles
selected from each of commercial carbon-veined tiles,
charge dissipative tiles of Example 3 and commercially-
available vinyl composition tiles were installed in a
iO contiguous side by side array in a hallway over a cement
substrate floor base. A commercially-available carbon
filled latex-base conductive adhesive, measured to have
a surface resistivity of 4 x 105 ohms/square, was used for
the installation. After cleaning the tiles with deter-
gent and clean water to clear dirt from the tile sur-
face, four coats of a commercially-available conductive
floor polish were applied to the tiles following ordi-
nary and typical floor polish application procedures.
The surface resistivities of the coated floor tiles were
monitored periodically after the conductive floor wax
was applied and the results of these measurements are
reported in Table 4. The resistivity measurements were
done in accordance with the ASTM D-257 method using a
concentric ring electrode, the Ike Probe from the
Electro-tech System Inc., and a Dr. Thiedig Milli-T0
multi range resistivity meter for registering the read
out. As shown in the table, the initial conductivity,
which is the inverse of the resistivity, of the coated
carbon-veined conductive tile is about the same in mag-
nitude as the non-conductive vinyl composition tile.
For the charge dissipative tiles, however, the conduc-
tive floor polish shows a synergistic effect in conduc-
tivity yielding a conductivity higher than that of the
untreated charge dissipative tiles or the vinyl tile
with conductive floor wax. It should be noted further
that the conductivity of the treated charge dissipative
tiles was measured to be higher than the conductivity
measured for either treated or non-treated carbon-veined
tiles. -
B
- 20 - 1 339327 L
After one week with traffic, the conductive
floor wax appeared to partially wear off, as indicated
by the loss in conductivity of the treated vinyl tiles,
but the treated charge dissipative tiles still showed
higher conductivity then the non-treated charge dissi-
pative tile samples. The treated carbon-veined tiles,
on the other hand, shows a much greater loss in conduc-
tivity. In this case, the conductivity of the conduc-
tive polish treated carbon-veined tiles was measured to
be about one order of magnitude lower than the conduc-
tivity of non-treated carbon-veined tiles.
After two weeks of traffic and wear, the con-
ductive polish appeared to wear off further, and the
conductivity of the treated vinyl tile was further
reduced. While the conductivity of the treated carbon-
veined tiles were still lower than the conductivity of
the untreated carbon-veined tiles, no loss in conductiv-
ities were measured in the non-treated and treated
charge dissipative tiles of the present invention.
Example 5
- This example demonstrates the effects of using
a non-conductive floor polish in the maintenance of
charge dissipative floor tiles. The charge dissipative
tile samples installed on a cement base substrate
described in Example 4 were stripped and cleaned follow-
ing ordinary floor maintenance procedures. One coat of
a floor finish coating (a commercial acrylic base floor
polish material) was applied to a portion of the charge
dissipative tile samples. The surface resistivities of
treated and non-treated charge dissipative tiles were
monitored in a similar fashion as described in Example 4.
No loss in conductivity was found between the treated
and non-treated charge dissipative tile samples as shown
in Table~5. The treated charge dissipative tiles,
however, demonstrated superior resistance to dirt pick-
up when compared to the non-treated charge dissipative
tiles.
1339327
Example 6
When a floor polish i5 used in maintaining
conductive floor tiles in an ESD protected area, it
requires that the polish should not ~nterfere with the
charge dissipating efficiency of the tile and that the
triboelectric charge generation should be no greater
than the generation of the tile alone. In this example,
the triboelectric charging of untreated charge dissipa-
tive tile and charge dissipative tile coated with a com-
iO mercial acrylic floor polish were compared. The measure-
ment of triboelectric charging was done in accordance
with the AATCC Test Method 134-1979 (Electrostatic
Propensity of Carpets, AATCC Test Method 134-19~9,
American Association of Textile Chemist and Colorists,
Research Triangle Park, NC, revised 19~9), commonly
known as the "step test". Four different types of shoe
sole materials were used in this test, they include neo-
prene A, neoprene 8, leather and~Neolite" -Table 6 sum-
marizes the charge generation measured at different
humidities. As shown, the triboelectric charges generated
from the untreated charge dissipative tile and the
charge dissipative tile treated with one coat of a com-
merc~al acrylic floor polish are about the same.
* Trademark
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Table 6
- Triboelectric Charge (Volts at 33% Relative Humidity)
Neoprene A Neoprene B Leather Neolite
Commercial PVC Tile 2010 870 3100 5050
Commercial PVC Tile
with Commercial Non-
Conductive Polish . 600 340 980 2030
Charge Dissipative Tile30 141 64 298
Charge Dissipative Tile
with Commercial Non-
Conductive Polish 32 -100 50 -194
Triboelectric Char~e tVolts at 50% Relative Humidity)
Neoprene A Neoprene B Leather Neolite
Commercial PVC Tile 460 - 949 2060
Charge Dissipative Tile 3 -24 6 -7
Charge Dissipative Tile C~
with Commercial Non-
Conductive Polish -10 -36 -15 -72
- 25 - 1339327
Example 7
To avoid waste, improve consolidation and
improve processing in the manufacture of floor tiles, it
is standard practice to recycle the punch frame scrap
into the vinyl composition tile batch in the form of a
remix. Of course, since the punch frame scrap includes
some antistatic agent, this recycling of the remix
introduces a low level of antistatic agent throughout
any composition in which the remix is added.
In this example, the remix was added to both
of the fresh or virgin compositions, the first including
antistatic agent and the second including no antistatic
agent. Note that since the mottle which contains no
antistatic agent is added at the end of the mixing step
to break up the base batch of mixed virgin and remix
compositions to improve feeding of the tile composition
through the mill chute, the mottle composition is not
intimately mixed and the tile compositions includes
mottle areas which do not contain an antistatic agent.
The tile sample was made by preparing chips
50% of which contained antistatic agent and 50% of which
did not contain antistatic agent. The formulations are
set forth below in parts by weight.
With Without
Antistat Antistat
Base Material
Virgin Formulation
Polyvinyl chloride resin336.0 303.0
Alpha methyl styrene tackifier 24.0 24.0
Phthalic ester plasticizer 49.4 99.0
Stabilizer 14.4 14.4
Titanium dioxide opacifier 130.7 98.8
Crushed limestone 1~90.2 1860.8
Antistat-Larostat 264A 55.3 ----
2400.0 2400.0
Remix 600.0 600.0
Mottle 780.0 780.0
3780.0 3780.0
- 26 - 1339327 .
Two mottles were prepared at a thickness of
100 mils with two different pigmentations. The formula-
tion in parts by weight for the mottles were:
Polyvinyl chloride resin 83.6
S Alpha methyl styrene tackifier 14.2
Phthalic ester plasticizer 30.2
Stabilizer 6.6
Titanium dioxide opacifier 22.4
Crushed limestone 623.0
:o 780.0
Each mottle was premixed in an "Eirich" mixer
for about three minutes, brought to a.temperature of
about 340~F to about 370~F (about 171~C to about 188~C) in a "FalTel" mixer
in about 30 seconds, and sheeted off a two roll mill to a thickness of about 100mils (25.4 ,um). The sheet was ground into chips having a minimllm dimension
of about 1/4 inch to about 3/4 inch (about 6.4 mm to about 19.1 mm).
The virgin formulation was charged into a Type
F mixer with remix. The remix was formed by grinding
punch frame scrap and reject tiles into about 1/4 inch (about 6.4 mm)
chips. The virgin formulation and remix were ~ixed in
the presence of heat in a Type F mixer for about 17
minutes. The mottle was then added and the mixing con-
tinued for about two minutes. The antistatic and non-
2s antistatic vinyl composition of mottle and base material
were sheeted off a mill and diced into chips. The chips
were then blended in a 50/50 ratio and reconsolidated
under heat and pressure in a tile line calendar to make
the finished static dissipative tile.
The moisture growth of the finished tile was
0.6X with acceptable electrical properties. See Table 7
following Example 8. At equilibrium the percent
antistatic agent is as follows:
With Without
AntistatAntistat
Virgin 2.3% 0%
Remix 0.87% 0.8~%
Base 2.02% 0.17%
Mottle 0% 0%
B
* Trademark
** Trademark
- 27 ~ 1339~7
Since the mottle is not homogeneously distrib-
uted within the tile chips, there are regions (approx-
imately 20%) of the tile chips without any a~lisla~ic agent.
About 40% of the tile chips has 2.0% antistatic agent and
5 about 40% of the tile chips has 0.17% antistatic agent.
Example 8
To simplify the manufacturing process and
reduce the chance of errors, the above described process
was modified to introduce the antistatic agent only in
the mottle. Since the base material of intimately mixed
virgin and remix formulations include antistatic agent
from the remix, some antistatic agent is distributed
throughout the t$1e composition. However, the concen-
tration of antistatic agent in the base material is not
high enough to contrlbute substantially to the moisture
growth problem or have the desired static dissipative
properties. Such a level of antistatic agent is deemed
to be an insubstantial amount. Preferably the amount of
antistatic agent in the base material is less than 0.25%
and less than one tenth of the antistatic composition in
the mottle.
The antistatic mottle composition was prepared
by premixing the following formulation (ln parts by
weight) in an "Eirich" rnixer for about six minutes,
Antistatic Mottle
Polyvinyl chloride resin 242.0
Alpha methyl styrene tackifier 20.0
Phthalic ester plasticizer 48.0
Stabilizer 17.2
Titanium dioxide opacifier 21.4
Crushed limestone 1612.4
Larostat 264A antistatic agent 39.0
2000.0
~ ~ .
- -
- 2B - 1339327
The mottle composit~on was then brought up to
about 340~F to 370~F (about 171~C to about 188~C) in a Farrel mixer in about
30 seconds. The mixed composition was then sheeted o~ a ~vo roll mill to a
thickness of about 100 mils (25.4 ,um) and ground into chips.
It is surprising and unexpected that the
antistatic agent cont~inin~ mottle composition can be fused in a
Farrel mixer. One would expect the antistatic agent to
be destroyed at the temperatures reached in the high
.0 intensity Farrel mixer. However, the antistatic agent
is subjected to the high intensity mixing for only a
brief time.
! The fresh or virgin composition had the fol-
lowing formulation in parts by weight:
Virqin Composition
Polyvinyl chloride resin 70.0
Alpha methyl styrene tackifier 5.6
Phthalic ester plasticizer 23.5
Stabilizer 3.4
Titanium dioxide opacifier 6.0
Crushed limestone 451.5
560.0
The virgin composition and remix were processed
in a manner similar to Example ~. Two tests were run,
the first with 40X mottle and the second with 33.3%
mottle. The following pounds of the components were
charged into Type F mixers. The percent of the tile
composition is indicated in the parenthesis.
Test 1 ~ Test 2
Remix 160 (11.9%) 240 (20%~
Virgin 640 (4~.4%) 560 (46.7%)
After mixing for about 17 minutes 550 lbs. (about 250 kg)
(40.7%) mottle was added in Test 1 and 400 lb. (about 182 kg) (33.3~o) mot-
tle was added in Test 2. After addition of the mottle,
mixing was continued for about two minutes. The tile
composition was then sheeted, diced into about 1/4 inch (about 6.4 mm)
cubes, and reconsolidated under heat and pressure using
an oscillating blade in a calendar nip.
1339327
- 29 -
If the mottle and base material are different
colors or shades, a straight grain or, mottled or jaspe
sheet is produced. By blending cubes of different col-
ors before the reconsolidation, a wide variety of pat--
tern coloration and design can be achieved.
The surface resistivity of tiles made by the
processes of Examples 7 and 8 were as follows:
Table 7
Surface Resistivity
iORelative Example 8 Example 8
Humidity Example 7(40% mottle) (33.3% mottle)
(%) (ohms/sq)(ohms/sq) (ohms/sq)
1.6 x 1091.6 x 109 1.3 x 109
8.5 x 101~ 4.9 x 101~ 5.6 x 101~
