U.S. patent number 3,785,102 [Application Number 05/194,623] was granted by the patent office on 1974-01-15 for tacky floor pad.
This patent grant is currently assigned to Edward T. Strickland. Invention is credited to Homer C. Amos.
United States Patent |
3,785,102 |
Amos |
January 15, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
TACKY FLOOR PAD
Abstract
A throw-away pad, especially for use at the entrance to a clean
area but not exclusively for such use. Of multiple ply
construction, it comprises a plurality of very thin poly-ethylene
or polypropylene sheets, of suitable surface size and shape to
receive at least a pair of shod feet. Each sheet bears a very thin
coating of pressure-sensitive adhesive on its top surface. The
bottom surface of the pad, that is, the bottom of the lowermost
sheet thereof, also is coated with adhesive so that the pad, when
in use, is removably adhered to the floor. The pressure-sensitive
adhesive has a low modulus of elasticity, a high internal viscosity
and high surface free energy, so that it firmly and aggressively
grabs dirt from shoes of wheels passing over it, yet each sheet can
be readily peeled off after use to expose a fresh adhesive surface
to further traffic. The entire pad or stack is thin to present no
hazard or obstacle to foot or to wheeled vehicles, e.g., to a
gurney being wheeled into an operating room.
Inventors: |
Amos; Homer C. (Palm Springs,
CA) |
Assignee: |
Strickland; Edward T. (Palm
Springs, CA)
|
Family
ID: |
22718288 |
Appl.
No.: |
05/194,623 |
Filed: |
November 1, 1971 |
Current U.S.
Class: |
15/215; 428/40.1;
428/41.3; 52/309.3 |
Current CPC
Class: |
A47L
23/266 (20130101); Y10T 428/14 (20150115); Y10T
428/1452 (20150115) |
Current International
Class: |
A47L
23/00 (20060101); A47L 23/26 (20060101); A47l
023/22 () |
Field of
Search: |
;15/215,216 ;161/167
;52/173 ;117/93.1CD |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Perham; Alfred C.
Attorney, Agent or Firm: Wickersham; Robert E.
Claims
Having now described the invention, what is claimed is:
1. A thin, throw-away cleansing pad adhesively and removably
securable to a floor and adapted to form a substantially
unobstructing portion of a pathway for foot or wheeled-cart
traffic, comprising:
a. a plurality of sheets formed from a material selected from the
group consisting of polyethylene and polypropylene, in detachably
stacked arrangement,
b. each said sheet having an upper surface and a lower surface, the
upper surface only having been coronadischarge-treated to improve
adhesion thereto to an adhesive and rendering said upper surface
preferentially adherent to said adhesive relative to said untreated
lower surface, and
c. a thin pressure-sensitive adhesive coating substantially
covering and adhered to said upper surface of each said sheet and
constituting the only material in between successive said
sheets,
d. said adhesive coating on said sheet extending further outwardly
than such coating on the next higher sheet in said pad, to prevent
peel and unwanted delamination from normal use.
2. The pad of claim 1 wherein said adhesive is an acrylic latex
having a tack angle of from 20.degree. to 30.degree. and an
internal viscosity of several hours, as determined by the tests
described in this specification.
3. A pad as in claim 1 wherein each said sheet is from 0.002 to
0.004 inch in thickness and said adhesive coating is about 0.00003
to 0.0003 inch in thickness.
4. A pad as in claim 3 wherein said adhesive coating is about
0.0001 inch in thickness.
5. A pad as in claim 1 wherein said adhesive is an intimate
admixture of an acrylic resin and a surfactant in amount sufficient
to effect wetting when said admixture is coated onto a polyethylene
substrate, exhibits a Young's modulus of -45.degree. C. expressed
as glass temperature; and has a tack angle of about 20.degree. to
30.degree. and an internal viscosity of from 5 to 24 hours as
measured by the tests described herein by covering the steel
cylinder described in said tests with a clean polyethylene surface,
coating a polyethylene terephthalate strip with a layer of said
adhesive mixture 0.001 inch thick, applying said coated strip over
said polyethylene surface with 100 percent surface contact, hanging
a 100 gram weight on a trailing edge of said strip to peel said
strip from said surface to an equilibrium point, coming to a point
within 5.degree. of said equilibrium point within from 10 to 30
hours.
6. A pad as in claim 5 wherein said adhesive contains about 0.4
percent of said surfactant and about 99.60 percent of said acrylic
resin.
7. A pad as in claim 1 wherein each said sheet has a corner area
free of adhesive to enable grasping and removal of said sheet.
8. A pad as in claim 1 having beveled edges tapered inwardly by
virture of each sheet being larger in both lengthwise and widthwise
dimensions than the sheet above it, the area of a lower sheet which
projects beyond the sheet above being non-adhesive.
9. A pad as in claim 1 wherein each said adhesive coating extends
outwardly at least one-sixteenth inch farther than the next higher
coating.
10. A pad as in claim 1 wherein the lowermost sheet is coated with
the same adhesive on its bottom surface in a thicker coating.
11. A clean room entryway including in combination:
a. an entrance doorway leading into said clean room,
b. a corridor leading to said doorway and having a floor, and
c. an unframed pad assembly having beveled edges, for cleaning
shoes and wheels disposed adhesively directly to said floor just
outside said doorway and large enough to receive the full perimeter
of such wheel, and longer than a large step taken by a person
walking, whereby to remove dust and dirt from wheels and shoes
coming into contact therewith,
d. said pad assembly comprising at least one stack of a plurality
of sheets formed from a material selected from the group consisting
of polyethylene and polypropylene, in detachably stacked
arrangement, the upper surface only of each said sheet being
corona-discharge treated to greatly improve adhesion, each said
sheet having a thin layer of pressure-sensitive adhesive,
substantially covering and adhered to said upper surface thereof
and constituting the only material in between sheets, each
downwardly succeeding layer of said adhesive extending outwardly
farther than the next adjacent upper layer thereof to prevent peel
and unwanted lamination being brought about by normal use.
12. A clean room entryway as in claim 11 wherein each said sheet is
from 0.0002 to 0.004 inch in thickness and each said adhesive layer
is about 0.0001 inch in thickness.
13. A clean room entryway as in claim 11 wherein said adhesive is
an acrylic latex adhesive, has a Young's modulus of from about
-30.degree. C. to about -50.degree. C. expressed as glass
temperature, a tack angle of from 20.degree. to 30.degree. and an
internal viscosity of from 10 to 30 hours when measured by tests
described in this specification.
14. A clean room entryway as in claim 11 wherein said pad is
adhered to said floor by the same adhesive material in a thicker
layer.
15. A clean room entryway as in claim 11 wherein each said sheet
has a corner portion freed of adhesive to enable grasping and
lifting.
16. A clean room entryway as in claim 15 wherein each said
succeeding layer of said adhesive extends at least 1/16 inch
outwardly from said adjacent upper layer. 17A clean room comprising
walls, floor and ceiling defining a room, a doorway in one said
wall, a hallway floor outside said doorway, and an unframed
cleaning pad having beveled edges and adhesively and removably
secured directly to said floor outside of said doorway and adapted
to receive on its upper surface foot traffic and wheeled traffic,
said pad being larger than a long step taken by a walking person
and adapted to receive the full perimeter of the wheel of a wheeled
cart, whereby to remove dust and dirt from wheels and shoes coming
into contact therewith, said pad comprising a plurality of thin
sheets formed from a material selected from the group consisting of
polyethylene and polypropylene, in detachably stacked arrangement,
each said sheet having a layer of pressure-sensitive adhesive
substantially covering the upper face thereof, said upper face only
having been corona-discharge pretreated to improve adhesion to an
adhesive, each said sheet except the bottom being from 0.002 to
0.003 inch in thickness and said adhesive layer being from 0.00003
to 0.0003 inch in thickness, said pad having a thicker bottom sheet
with a bottom surface and a thicker layer of adhesive disposed
thereover to adhere said pad to said floor, each downwardly
succeeding layer of said adhesive extending outwardly farther than
the next adjacent upper layer of said adhesive in order to prevent
undesired peeling upon
normal use. 18. A clean room as in claim 17 wherein said
first-mentioned
adhesive layer is 0.001 inch in thickness. 19. A clean room as in
claim 17 wherein said first mentioned adhesive has a Young's
modulus of from -30.degree.C. to -55.degree.C. expressed as glass
temperature, a tack angle of from 20.degree. to 30.degree. and an
internal viscosity of from 10 to 30 hours when measured by tests
described in this specification.
A clean room as in claim 19 wherein the second-mentioned adhesive
is
the same as the first-mentioned adhesive. 21. A clean room as in
claim 17 wherein each sheet has a corner portion freed of adhesive
to enable
grasping and lifting. 22. A clean room as in claim 17 wherein each
said succeeding layer of said adhesive extends at least
one-sixteenth inch
outwardly from said adjacent upper layer. 23. A thin, throw-away
cleansing pad adhesively and removably securable to a floor and
adapted to form a substantially unobstructing portion of a pathway
for foot or wheeled-cart traffic, comprising:
a. a plurality of sheets formed from a material selected from the
group consisting of polyethylene and polypropylene in detachably
stacked arrangement, each said sheet having an upper surface and a
lower surface, and
b. a thin pressure-sensitive adhesive coating substantially
covering and adhered to said upper surface of each said sheet and
constituting the only material in between successive said
sheets,
c. said adhesive coating on each sheet extending further outwardly
than such coating on the next higher sheet in said pad, to prevent
peel and unwanted delamination from normal use.
Description
BACKGROUND OF THE INVENTION
This invention relates to a throw-away pad of tacky- or
sticky-surfaced sheets for removing dust and dirt from shoe soles,
wheels and the like passing thereover, to assist in maintaining a
clean area such as a hospital room or surgery in the desired clean
condition. The pad or stack of sheets is adhered removably to a
floor in suitable relationship to the room to be protected, and
each sheet can be separately removed as used to present a fresh
tacky surface for use.
With the rise of modern technology, "clean rooms" have become
increasingly important. In the surgery, scrupulous cleanliness is
vitally important to prevent infection. The indiscriminate use of
antibiotics has caused the emergence of strains of resistant
bacteria, and the unpleasant result has been that hospitals,
instead of being sanctuaries of sterility, have become a source of
new infections that are extremely difficult to combat. More
scrupulous cleanliness is a better answer to the problem than is
the continual indiscriminate use of antibiotics.
Similarly, in areas where microcircuitry and delicate space-age
instruments are manufactured, one speck of dust can cause failure.
Hence, techniques insuring the highest possible degree of
cleanliness have received intensive study.
Two fruitful sources of dirt are shoe soles and cart wheels. Many
efforts have been made to find an easy and convenient but yet
effective method for removing dust and dirt from shoes, and in the
case of surgeries, from the wheels of the cart on which the patient
is moved about. Heretofore, such removal has been of varying
degrees of efficacy -- or lack of it -- and of inconvenience. For
example, air blast systems have not been very effective, and
disinfectant wash troughs have been messy and have been impractical
for cart wheels.
Various types of sticky pads have been tried heretofore, but have
exhibited certain disadvantages. In our co-pending patent
application, Ser. No. 47,453 filed June 18, 1970 now U.S. Pat. No.
3,717,897, there is described the construction of an inexpensive
washable pad which can be made by anyone skilled in the art of
coating adhesives. The cost of the pad originally is quite low, and
it can be washed with water, or soapy water, to remove adhering
dirt, so that its use is inexpensive. Furthermore, it can be washed
repeatedly without substantially losing its effectiveness, so that
the cost per fresh sticky surface is extremely low. However, as
hourly wages climb ever higher and higher much effort is being
expended to cut man-hours to an absolute minimum, resulting in a
marked trend to one-use throw-aways, even in such items as
hypodermic syringes. The pad of the present invention avoids the
labor attendant upon renewing the fresh sticky surface by washing
and provides such surface merely by peeling off the used sheet to
expose such desired surface for contained use of the overall pad,
and makes such a method economically feasibly by reason of its
extremely low-cost construction.
SUMMARY OF THE INVENTION
The pad of this invention employs a polyethylene or polypropylene
sheet which can be walked on and wheeled over without tearing or
destruction. A pressure-sensitive adhesive advantageously has been
found to remove dirt from shoes and wheels while at the same time
it readily releases the polyethylene or polypropylene sheet which
covers it to enable presentation of a fresh adhesive surface for
use. The polyethylene or polypropylene is of such strength that
very thin sheets can be used, and a very thin coating of the
adhesive described can be employed, thus providing an overall pad
which is sufficiently thin, even with a relatively large number of
sheets, that there is substantially no obstruction to walking or to
wheeling a cart over the surface of the starting pad, and, of
cours, even less as use and removal of sheets proceeds. The
adhesive is not unpleasant to walk upon, and, on the other hand,
the last sheet can be stripped from the floor without delamination
or tearing when it is completely used or when the pad is to be
removed for any reason.
The sheets are assembled with the intervening and exterior coatings
of adhesive in a manner to provide a pad having the above
advantages and other advantages that will become apparent from the
description herein. When a dust-trap floor pad is designed to have
a highly aggressive tack to catch and hold dirt well, and is also
designed to have sufficiently low adhesion to the surface beneath
in order to make it easy to remove when it has completed its
service life, then a new problem arises. If a clean wheel or shoe
is pressed upon it, then the possibility appears of pulling the
whole sheet loose, the sheet possibly ending up wrapped around the
shoe or wheel.
We have found that in the middle of the sheet the vacuum under the
sheet prevents this catastrophic failure, and that such failures
are initiated by a peel at the edges. Protection of the edge,
therefore, prevents such failure, and we have found that if the
adhesive on the under side of a sheet extends outwardly slightly
further than the adhesive on the top side thereof, a peel will not
be initiated. This differential can be as small as one-sixteenth
inch and still be remarkably effective, and it can be as large as
about one-fourth inch. One method of achieving this differential is
the beveling of the completed pad, which serves to compress the pad
to the floor, thereby preventing up-pull. A 5/8 to 7/8 inch bevel
on a 10-level pad has been found to be an inexpensive but effective
method of preventing lift-up or undesired removal of a sheet. The
beveled edge may be dusted with a non-adhesive powder to prevent
adhesion in this area. In a beveled stack-pad some provision is
made to facilitate the removal of a layer when it has completed its
useful life, for example, providing predetermined adhesive-free
areas at an edge or corner portion of each sheet to enable grasping
and pulling off of the sheet from the pad.
While any very aggressive pressure-sensitive adhesive mass based on
natural or synthetic rubber may be used herein, the
pressure-sensitive adhesive preferred for use herein is an acrylic
latex, acrylic because of the very stable properties and long shelf
life of acrylics, and latex because of the economy, safety, and
convenience of latices as compared with solutions. Such latex of
the proper physical properties has been found to adhere
sufficiently firmly to the untreated surface of the polyethylene or
polypropylene substrate so that the pad produced is stable in form
for handling or shipping, but the latex releases the polyethylene
or polypropylene readily when it is desired to tear away a used
sheet. Acrylics, in sharp contrast to most adhesive masses, provide
an almost indefinitely long shelf life to the product with no
deterioration or shift in properties, and the product exhibits
relative insensitivity to heat and cold. No solvent is required to
apply the latex, thus lowering the costs in manufacturing the pad,
and the latex exhibits no flammability, while air pollution is
avoided by its use without added solvent. Furthermore, this
adhesive is effective in an extremely thin coating layer. The
acrylic adhesive used herein is substantially non-reactive, i.e.,
of negligible further polymerization, and is of comparatively low
molecular weight, for a latex, to obtain a very high surface free
energy, i.e., soluble or nearly so in organic solvents such as
tetrahydrofuran. A suitable acrylic latex, for example, is an
emulsion polymer prepared from lower alkyl acrylates as the main
monomers, having a pH of 6 to 6.5, viscosity of between 100 and 300
at a spindle/speed of 2/60, of 57 percent solids, and having a
calculated glass transition temperature of -46.degree. C.
Production of such a polymer is described in Belgian Pat. No.
749,689.
In acrylics, the modulus of elasticity can be quite accurately
defined in a roundabout way in terms of the "glass temperature,"
i.e., the temperature at which the torsional modulus is 300
kg/cm.sup.2. The acrylic latex used herein should have a glass
temperature of about -45.degree. C., or in the range of from about
-30.degree. C. to about -55.degree. C., so that it is very soft to
enhance adhesion but is not too soft for durability. It has a high
internal viscosity which is suitably measured by a method
hereinafter described, to give for the present adhesive a tack
angle of from 20.degree. to 30.degree. against a clean polyethylene
surface, and an internal viscosity of several hours, advantageously
from 5 to 24 hours.
Internal viscosity in a solid may be a new concept to some people,
and an example may help: a vinyl garden hose has a high internal
viscosity, while gum rubber has a low internal viscosity. Even
though it may be "harder," a gum rubber tube suffers no harm from
being run over by a car, while a vinyl garden hose (especially if
old and cold) can be cracked to pieces by the same treatment,
because it cannot deform quickly enough, due to its higher internal
viscosity. If the rubber tube be heavy and firm, it may require
more weight to flatten it than to flatten the vinyl hose; moreover,
the rubber flattens partway immediately and stays there, while the
vinyl slowly flattens out completely. Hence, the vinyl is
considered "softer" because it flattens out further, but it is slow
to do so, because it has a higher internal viscosity.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention and some modes of carrying it out will be illustrated
by the following more specific description and by the annexed
drawings, wherein:
FIG. 1 is a schematic view of the placement of a pad according to
this invention in a corridor of a building and just outside the
door or entrance to a clean room;
FIG. 2 is an enlarged view in side elevation of a pad according to
this invention, showing beveled edges and adhesive-free corner
surfaces at one end of the sheets to facilitate removal of a single
sheet for renewal of surface; the view is broken in the middle in
order to conserve space;
FIG. 3 is a partial top enlarged view of the stack or pad of FIG.
2, illustrating one means of forming the adhesive-free corner
surfaces;
FIG. 4 is a partial side view of the article of FIG. 3 after corner
treatment and showing a few sheets of the pad or stack, placement
of the adhesive thereon, and the freed corner edges; and
FIG. 5 is a view in perspective of a test-apparatus comprising a
polished steel cylinder with scribed lines, with adhesive-coated
strip on test and shown in alternative positions.
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIGS. 2, 3 and 4, the pad 15 comprises a plurality of
sheets 16, suitably five to fifty, of such sheets 16, each being
coated with a layer 17 of acrylic latex adhesive as described
herein. Each sheet 16 is very thin, being from 0.002 to 0.003 inch
in thickness, and is of standard grade polyethylene or
polypropylene, in either case with heavy corona discharge adhesion
treatment on one surface which is readily available in commerce at
no additional cost. When the treated surface is coated with the
adhesive, good adhesion is obtained between the polyethylene or
polypropylene and the coating. Further, by this means the required
differential in adhesion between upper and lower surface is
achieved, so that as a used sheet is stripped off, the adhesive
mass always comes away clean from the lower surface of the used
sheet, and never delaminates away from the upper surface of the new
sheet beneath. The layer 17 of the pressure-sensitive adhesive is
extremely thin, being from 0.00003 to 0.0003 inch, advantageously
0.0001 inch in thickness. Thus, the pad 15 containing ten such
coated sheets is less than one thirty-second inch in thickness and
does not present an obstacle to foot traffic or cause jarring or
shock to a patient on a gurney when wheeled over such pad 15.
The bottom sheet, or all of them, may be of colored polyethylene or
polypropylene, or the whole set may be transparent, or they or some
of them may be imprinted with a decorative design, as desired.
Since the bottom sheet must be of sufficient strength to withstand
removal without tearing from a floor whose adhesion may be greater
than untreated polyethylene or polypropylene, a heavier film such
as 0.004 inch is preferred.
Each sheet 16 is of polyethylene or polypropylene of the thickness
described, and it is coated with a layer 17 of the acrylic adhesive
over the entire upper surface of each sheet 16, except that a
corner area or portion 18 is free of adhesive so that the sheet 16
can be easily grasped and stripped off after use. This is shown in
exaggerated form in FIG. 4, and will be further described below.
The lowermost sheet 16 has on its undersurface 22 a layer 23 of
adhesive to removably affix the pad 15 to floor 14. The adhesive 23
may cover all of the underside of the lowest layer or a portion
only, such as the edge portions. As shown in FIG. 1, the pad 15 or
several such pads are arranged to be large enough to cover the
floor area just outside of the entryway 11 so that all persons or
the full perimeter of the wheels of vehicles entering the clean
room 14 must pass thereover, and the adhesive layer 17 removes dust
and dirt from wheels and shoes as they come into contact with such
layer 17. After use, and as determined by the appearance of the top
sheet, it is stripped off and a fresh surface exposed, down to the
last sheet 16 of the stack 15.
We have found that the same coating may be used as the adhesive 23
which holds the pad 15 to the floor. However, since there is little
control over the type of surface to which the pad 15 may be called
upon to adhere, it has been found preferable to have this
particular adhesive coating 23 thicker, such as a thickness of
0.0015 inch.
Internal viscosity is inconvenient to measure in terms of poises,
and surface free energy is so difficult to measure in terms of ergs
per square centimeter as to be impractical. Therefore, we have
devised a simple empirical test to evaluate adhesives for possible
use in the present invention.
FIG. 5 shows a polished steel cylinder 25, two inches in diameter,
scribed with fine lines 26 parallel to the axis 27 and 5.degree.
apart over 90.degree. of its surface 28. The cylinder 25 is mounted
firmly in cantilever with the axis horizontal, in the position
shown in FIG. 5. The cylinder 25 is covered with a cemented-on film
of clear untreated polyethylene or polypropylene. A one mil film of
the adhesive 29 under test is cast on a polyethylene terephthalte
(Mylar) strip 30 of one mil thickness, which is then trimmed to a
width of one inch. The polyethylene or polypropylene surface of the
cylinder 25 is washed carefully with methyl ethyl ketone, and the
strip 30 is placed over the scribed lines 26 and one end 31 draped
over the top. The strip 30 is pressed firmly against the cylinder
25 to attain as near as possible 100 percent contact area. A
100-gram weight 32 is hung gently on the trailing end 33 and the
time noted at the 90.degree. position. The progress of the peel
line is noted from time to time and it should come to a point
within 5.degree. of its final position in the times noted below.
The total time allowed must be ample to ascertain that the peel
line has in fact stopped moving, to insure that internal viscosity
is not affecting the result. If the line is still moving after 30
hours, the formulation may be discarded as having too high an
internal viscosity for a shoe-cleaning pad.
From this test, two things can be learned:
1. The stopping position of the peel line is a measure of the
permanent tack of the adhesive in question against clean untreated
polyethylene or polypropylene. Much experience has shown that the
optimum for best all-around performance of the coatings 17 and 22
is given by an adhesive that stops at approximately 35.degree..
Values in the range of about 15.degree. to about 50.degree. will
give reasonable success, and very good results are obtained in a
range of about 25.degree. to about 40.degree..
2. The length of time from start to within 5.degree. of finish (the
finish is surprisingly definite though the high "cold flow"
contributes a very slow movement of about 3.degree. or 4.degree.
per day after the true peel motion has ceased) is a measure of the
internal viscosity. The time should be in the range of 600 to 1,800
minutes, preferably from 900 to 1,500 minutes, and optimum results
are generally obtained at about 1,200 minutes.
In a typical example according to this invention, a series of
sheets of standard grade polyethylene having heavy corona discharge
treatment on the upper surface thereon are cut to the desired size
to make a pad suitable for placement before an entryway to a
surgical operating room in a hospital. The polyethylene sheet
material is from 0.002 to 0.003 inch in thickness. If thinner than
0.002 inch, the sheet may tear easily, and if it is thicker than
0.003 inch it is unnecessarily thick and expensive. The sheets 16
are of such size to be wide enough to span the entryway for which
the pad 15 is intended and longer than a large step taken by a
walking person, and will also receive the full perimeter of the
wheel of such wheeled cart as may be encountered, for example, a
hospital gurney. The size of the sheets may be such that they may
be used in modular fashion, and two or three or more may be placed
side by side to cover wide areas. A mixture is prepared of an
acrylic latex, or of latices, to arrive at the properties described
above, and of a surfactant such as sodium salt of a sulfonated
alkyl ester, available in commerce under the trademark Triton Gr -
5, sufficient, suitably about 0.22 percent by weight of the total
mixture, to effect good wetting when the mixture is coated onto the
polyethylene. If desired, bacteriostats or anti-static components
or both may be added. After these components are thoroughly admixed
to form the desired adhesive, it is coated onto each sheet to cover
the treated surface. The surface of each sheet as described is
completely covered, and the sheets are stacked upon each other in
the order of sheet of polyethylene - adhesive layer - sheet of
polyethylene, etc. until from five to 50 of such sheets have been
assembled into a stack. The bottom sheet is covered with the
adhesive on its underside to cause it to adhere in place to the
floor, and the assembled stack is beveled on all four sides,
suitably about 5/8 to 7/8 inch for a 10-sheet stack. The procedure
with polypropylene sheets is the same.
A pad of thick felt or polyurethane foam, or like absorbent
material 35 is placed diagonally across a corner of pad 15. By any
desired method, such as spraying, for example, the pad is wetted
with a small amount of a suitable solvent for the adhesive, such as
toluene, and the whole allowed to stand for several minutes, after
which the pad is removed. It is then found that each sheet 16 up
the stepped bevel has lifted along the corner portion 18 to a width
of about one-fourth inch. Excess solvent is then blown off and talc
or other suitable dry powdered, preferably mineral, solid is
brushed under the lifted edges, the powder destroying the
effectiveness of any adhesive which it covers.
When the pad is in place on a floor etc., as each sheet is
exhausted of its dirt-grabbing property, it can be grasped by the
hand or otherwise at the lifted corner to be pulled off to expose a
fresh, clean adhesive surface.
The stack or pad is now ready for use and is placed before an
entryway to a surgical operating room or industrial clean-room on
the floor of the corridor leading thereto. After foot traffic and
normal wheeled traffic have passed over the top sheet for from
several hours to several days, depending on the traffic, and the
adhesive has grabbed the pulled dirt and lint therefrom, the sheet
is grasped by its adhesive-free edge and stripped from the stack,
exposing the next adhesive surface for use.
The pad is also useful at the doors of clean rooms in hospitals or
in homes or wherever dust control and cleanliness are desired.
It will be understood that the above specific description and the
drawings have been given for purposes of illustration only and that
variations and moficiations can be made therein without departing
from the spirit and scope of the appended claims.
* * * * *