U.S. patent application number 15/645421 was filed with the patent office on 2018-05-24 for preformed thermoplastic pavement marking and method utilizing large aggregate for improved skid resistance and reduced tire tracking.
This patent application is currently assigned to Flint Trading, Inc.. The applicant listed for this patent is Robert W Greer, Simon Yakopson. Invention is credited to Robert W Greer, Simon Yakopson.
Application Number | 20180142435 15/645421 |
Document ID | / |
Family ID | 44062292 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180142435 |
Kind Code |
A1 |
Greer; Robert W ; et
al. |
May 24, 2018 |
Preformed Thermoplastic Pavement Marking and Method Utilizing Large
Aggregate for Improved Skid Resistance and Reduced Tire
Tracking
Abstract
The present disclosure describes a preformed or in some cases a
hot applied thermoplastic marking composition comprising a planar
top surface portion and a planar bottom surface portion that are
coplanar to each other, wherein said bottom surface portion is
directly applied to a substrate via application of heat or pressure
or both heat and pressure and wherein said top surface portion
comprises an intermix that exits throughout said thermoplastic
composition and includes large grit size aggregate in the range of
about 8 to about 20 mesh or grit size, thereby reducing or
eliminating tire tracking while also improving long-term skid
resistance.
Inventors: |
Greer; Robert W; (Lexington,
NC) ; Yakopson; Simon; (Hickory, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Greer; Robert W
Yakopson; Simon |
Lexington
Hickory |
NC
NC |
US
US |
|
|
Assignee: |
Flint Trading, Inc.
Thomasville
NC
|
Family ID: |
44062292 |
Appl. No.: |
15/645421 |
Filed: |
July 10, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12592458 |
Nov 25, 2009 |
9732481 |
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15645421 |
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10816635 |
Apr 2, 2004 |
7645503 |
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12592458 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E01F 9/512 20160201;
Y10T 428/24372 20150115 |
International
Class: |
E01F 9/512 20160101
E01F009/512 |
Claims
1. A method of making a preformed or hot applied thermoplastic
marking composition comprising a planar top surface portion and a
planar bottom surface portion that are coplanar to each other,
wherein said bottom surface portion is directly applied to a
substrate via application of heat or pressure or both heat and
pressure and wherein said top surface portion comprises an intermix
that exits throughout said thermoplastic composition and includes
large grit size aggregate in the range of about 8 to about 20 mesh
or grit size, thereby reducing or eliminating tire tracking while
also improving long-term skid resistance.
2. The method of making the thermoplastic composition of claim 1,
wherein said aggregate comprises quartz, granite, corundum,
calcined clay, metal slag or any combination of said quartz,
granite, corundum, calcined clay, or metal slag.
3. The method of making the thermoplastic composition of claim 1,
wherein said thermoplastic marking composition is a sheathing, said
sheathing comprising anti-skid resistance materials including said
large grit size aggregate with and without retroreflective glass
beads, wherein said aggregate and glass beads are either in said
intermix or dropped onto said top surface portion before, during,
or after application to a substrate.
4. The method of making the thermoplastic composition of claim 1,
wherein said thermoplastic sheathing with said large grit size
aggregate and with and without retroreflective glass beads are
either in said intermix or dropped onto said top surface portion
before, during, or after application to a substrate and wherein
additional particles are dropped onto said top surface portion,
wherein said particles are aggregates, glass beads, including type
1 and type 3 glass beads, as well as large grit size aggregate in
the range of 8 to 20 mesh or grit size said aggregate comprising
corundum, crushed granite, crushed gravel, or quartz, or any
combination of said corundum, crushed granite, crushed gravel,
and/or quartz.
5. The method of making the thermoplastic composition of claim 1,
wherein said large grit size aggregate measures greater than 6 on
the Mohs Hardness Scale
6. The method of making the thermoplastic composition of claim 1,
wherein said aggregate provides a surface roughness measured using
a calibrated friction number F60, across a yielding values of about
0.17 to about 0.40
7. The method of making the thermoplastic composition of claim 1,
wherein said aggregate embedded within the surface of said top
surface portion provides a surface roughness which is measured as a
mean profile depth and wherein said mean profile depth is between
about 0.35 to about 0.75 millimeters.
8. The method of making the thermoplastic composition of claim 1,
wherein said bottom surface portion comprises an adhesive for
bonding said bottom surface portion to any paved surface.
9. The method of making the thermoplastic composition of claim 1,
wherein said top surface portion includes patterned markings,
wherein said patterned markings are lines, legends, arrows,
indicia, including colored surfaces and sections of said surfaces
other than or together with a white color.
10. The adhesive of claim 9, wherein said adhesive is sprayable
allowing for bridging said intersection on said planar bottom
surfaces of said grid section and said insert section forming said
unified pavement marking pattern and wherein said adhesive includes
ethylene vinyl acetate (EVA) based hot melt or other equivalent hot
melt polyamide resins.
11. The adhesive of claim 10, wherein said adhesive has a softening
point in a range of 90 degrees centigrade to about 210 degrees
centigrade and more preferably in a range of 90 degrees centigrade
to about 120 degrees centigrade
12. The adhesive of claim 9, wherein said adhesive comprises a
thermosetting adhesive.
13. The adhesive of claim 9, wherein said adhesive comprises a
thermoplastic adhesive.
14. The method of making thermoplastic composition wherein said
thermoplastic comprises an independent thermoplastic grid section,
and an independent thermoplastic insert section, and wherein said
insert section resides within said grid section and each said
insert section is coplanar, and wherein said grid section and said
insert section both comprise a planar top surface portion and a
planar bottom surface portion that are coplanar to each other, such
that said grid section is in direct contact with and adjacent to
said insert section thereby forming an intersection between said
grid section and said insert section, and further comprising an
adhesive backing layer on said planar bottom surface, said adhesive
backing layer bridging and bonding said planar bottom surface to
form a unified pavement marking pattern thereby preventing
dislodging or separation of said pavement marking pattern during
handling, movement, transportation before application of said
pre-bonded pavement marking to the top of a pavement surface by
application of heat or pressure or both heat and pressure, and
further comprising large grit size aggregate in the range of about
8 to about 20 mesh or grit size that reduces tire tracking and
improves long-term skid resistance.
15. The method of making the thermoplastic composition of claim 14,
comprising said grid and a plurality of inserts, each of said
inserts separated by said grid.
Description
PRIORITY
[0001] The present application is a divisional of and claims
priority under 35 U.S.C. .sctn. 120 from U.S. patent application
Ser. No. 12/592,458 entitled, "Preformed Thermoplastic Pavement
Marking and Method Utilizing Large Aggregate for Improved Long Term
Skid Resistance and Reduced Tire Tracking", filed 25 Nov. 2009,
which is a Continuation-in-Part of and claims priority under 35
U.S.C. .sctn. 120 from U.S. patent application Ser. No. 10/816,635
filed Apr. 2, 2004 and entitled, "Pavement Marking Pattern and
Method", granted on Jan. 12, 2010 as U.S. Pat. No. 7,645,503.
FIELD OF THE INVENTION
[0002] The invention herein pertains to thermoplastic pavement
marking materials comprising large grit size aggregate to improve
long-term skid resistance and reduce tire tracking, and
particularly pertains to such markers as lines, legends, arrows,
indicia, and decorative marking including pavement marking patterns
utilizing thermoplastic sheeting which utilize an adhesive
(sprayable or otherwise) to maintain the integrity of the pattern
prior to its application to a substrate.
BACKGROUND OF THE INVENTION
[0003] Traffic markings convey information to drivers and
pedestrians by providing exposed visible, reflective, colored
and/or tactile surfaces that serve as indicia. In the past, such a
function was typically accomplished by painting a traffic surface.
Modern marking materials offer significant advantages over paint
such as dramatically increased visibility and/or reflectance,
improved durability, and temporary removable marking options.
Examples of modern pavement marking materials are thermoplastic,
pavement marking sheet materials, tapes and raised pavement
markers.
[0004] Preformed and hot applied thermoplastic materials used as
pavement markings or for other indicia possess many advantages
compared to paints and other less durable markings. These materials
can be used for years. Known materials using high friction
aggregates on the surface to improve friction has been known. The
surface applied aggregates provide good initial values, however as
the surface is worn due to traffic, the skid resistance decreases.
After surface layers containing anti-skid materials become worn out
these aggregate materials loose their effectiveness and become
slippery because they do not contain high friction particles (of
sufficient size to provide good skid properties).
[0005] Current thermoplastics include small particulate aggregate
to improve the skid-resistant properties of the markers. However,
over time, it has been shown that when such particulates are too
small, they become worn too quickly and thus do not provide
sufficient skid-resistance for high traffic areas. Today's
thermoplastic materials do not include properties of long-term skid
resistance and reduced tire tracking. In addition today's preformed
thermoplastic decorative patterned materials do not include both
the properties of facilitated assembly via an adhesive spray and
long-term skid resistance and reduced tire tracking.
[0006] A review of these issues demonstrates the need for
thermoplastic products that both reduces tire tracking and improves
long term skid resistance once the marking product has been
installed on the road surface and also ensures that the integrity
of the product (and pattern if so desired) is maintained during
handling and installation.
DESCRIPTION OF RELEVANT ART
[0007] U.S. Pat. No. 3,958,891 to Eigenmann, Ludwig, and not
assigned, describes an aggregate for securing in a layer of
material which is used to form a traffic-regulating indicium, so as
to improve the nighttime visibility characteristics and anti-skid
characteristics of the traffic-regulating indicium. The aggregate
comprises a core body surrounded at least partially by a mass of
shock-absorbent binder substance and a plurality of elements that
improve either nighttime visibility or anti-skid properties, or
both. The elements are arranged in and bound by the binder
substance such that the latter substantially fills the interspaces
between at least the majority of adjacent pairs of the
aforementioned elements, some of which being arranged adjacent to
an external surface of the mass so as to impart a roughened texture
to the external surface, thereby permitting the aggregate to be
firmly secured in the traffic-regulating indicium. The remainder of
the elements are distributed among different levels interiorly of
the mass so that progressive wear of the aggregate and concomitant
detachment of elements from the aggregate causes exposure of others
of the elements, thereby conveying long-term durability to the
traffic-regulating indicium.
[0008] U.S. Pat. No. 4,020,211 to Eigermann, Luwig and not assigned
describes a new material adapted to be laid down and adhesively
secured on a road surface to provide a traffic regulating sign with
the material which has an upper surface exposed to traffic and
provided with a plurality of sharp tips projecting above the
surface for imparting good non-skid properties thereto, the new
material comprising an upper layer adjacent to the upper surface,
at least partially embedding hard particles to form sharp tips and
consists of a polymeric resin having a high molecular cohesion such
as a polyamide resin, a polyurethane resin or a polyterephthalic
resin, thereby adding improved wear resistance properties to
non-skid and high visibility properties.
[0009] U.S. Pat. No. 4,937,124 to Pafilis, Michail and not
assigned, describes a nonskid element as an antislipping means on a
carpet-like floor covering. The nonskid element is a web that
includes a plain bottom wall, and the bottom wall includes a
covering with band-like holding pins.
[0010] U.S. Pat. No. 5,077,117 to Harper, et. al., describes a
pavement marking material comprising a flexible base sheet that is
conformable to an irregular pavement surface. A durable,
wear-resistant, polymeric top layer is adhered to one surface of
the base sheet. The top layer is capable of undergoing brittle
fracture at a temperature from 0 degrees Centigrade to 45 degrees
Centigrade such that when the base sheet conforms to an irregular
surface the top layer readily forms ruptures to relieve stress
build-up in the top layer as the regions of the top layer defined
by the ruptures remain adhered to and follow the conformance of the
base sheet. A plurality of particles are embedded in and protrude
from the top layer. The particles comprise retroreflective beads
and skid-resistant granules. In a preferred embodiment, the top
layer is characterized by a Young's modulus of from about 50,000
psi to about 300,000 psi, and a percent elongation at break of from
about 4% to about 35%.
[0011] U.S. Pat. No. 6,217,252 to Tolliver, Howard R, et. al., and
assigned to 3M, describes a method for marking a transportation
surface in which the surface is heated to a temperature above the
ambient temperature and a finely-divided, free flowing,
flame-sprayable, powder binder material selected from the group
consisting of acrylic polymers and copolymers, olefin polymers and
copolymers having a number average molecular weight greater than
10,000, urethane polymers and copolymers, curable epoxy resins,
ester polymers and copolymers, and blends thereof is melted or
substantially softened. The molten or softened binder is then
applied to the surface with a particulate topcoat or particulate
filler selected from the group consisting of reflective elements;
skid-resistant particles, magnetizable particles and mixtures
thereof, and finally the applied materials are allowed to cool to
form a marker in which the binder adheres directly to the
surface.
[0012] U.S. Pat. No. 3,935,365 to Eigenmann, Ludwig, and not
assigned, describes a tape material for securement to primer layers
provided on roadway pavements so as to form traffic-regulating
indicia on the latter. The tape material comprises a first layer
that contains a polymeric binder having high molecular cohesion and
one surface adapted to face towards a roadway pavement and another
surface adapted to be exposed to traffic, a plurality of hard
particles having a minimum of about 6 on the Mohs' Hardness Scale,
some of which should have a sharp tip, distributed among various
levels of the aforementioned first layer, and a second layer
adapted to be secured to a primer layer on the roadway pavement
bonded to one surface of the first layer. The second layer is
compatible with the first layer so that a firm bond is formed
between them. It is also compatible with the primer layer so that a
bond forms between them when the tape material is placed on the
primer layer. This tape material imparts good anti-ski properties
to a traffic-regulating indicium formed therewith due to the
presence of the tips of the hard particles, which provide gripping
areas when exposed. It is also an effective skid-resister during
wear of the traffic-regulating indicium due to the distribution of
the hard particles among various levels of the first layer, which
enables fresh hard particles to become exposed as hard particles
next to the latter are removed by wear.
[0013] U.S. Pat. No. 5,053,253 to Haenggi, Robert, et. al., and
assigned to Minnesota Mining and Manufacturing Company, describes a
method of producing skid-resistant substrate marking sheet in which
a base sheet is provided and an upward face of the base sheet is
coated with a liquid bonding material. A plurality of ceramic
skid-resistant spheroids is embedded in the liquid bonding
material, wherein the ceramic spheroids are characterized by having
rounded surfaces and no substantial points and characterized by
Krumbein roundness of at least 0.8. The liquid bonding material is
then cured to a solid adherent polymeric matrix coating with the
ceramic skid-resistant spheroids partially embedded, wherein the
spheroids comprise a fired ceramic made from various raw
materials.
[0014] U.S. Pat. No. 5,094,902 to Haenggi, Robert, et. al., and
assigned to Minnesota Mining and Manufacturing Company, describes a
skid-resistant, surface marking material, comprising a polymer
matrix phase having a top surface and a plurality of opaque,
skid-resistant ceramic spheroids partially embedded in and
protruding from the top surface of the polymer matrix phase,
wherein said ceramic spheroids have rounded surfaces and no
substantial points, and wherein said ceramic spheroids have a
Krumbein roundness of at least 0.8.
[0015] U.S. Pat. No. 6,679,650 to Britt, Jerry, et. al., and
assigned to Ennis Paint Incorporated, describes a marked pavement
system comprising a pavement surface, a first marking stripe
adhered to the top of the pavement surface with a thickness of at
least about 40 mils to about 110 mils and comprised of a solidified
thermoplastic resin composition with a black pigment, and a second
marking stripe adhered to the surface of the first marking stripe
with a thickness of at least 40 mils to 750 mils. The second
marking stripe should be narrower than the first marking stripe and
comprised of a solidified thermoplastic resin composition with a
pigment that visibly contrasts with the first marking stripe,
wherein the marked pavement system is highly visible during the
daylight hours and during periods of rain.
[0016] U.S. Pat. No. 5,536,569 to Lasch, James E., et. al., and
assigned to Minnesota Mining and Manufacturing Company, describes a
conformable pavement marking with a top surface useful as a marking
indicium and a bottom surface, the marking sheet comprising a
conformance layer with a thickness of 75 to 1250 micrometers of a
composite material. The composite material should include 50 to 85
volume percent of a ductile thermoplastic polymer selected from the
group consisting of polyethylene, polypropylene, polybutylene,
ethylene copolymers, polyvinylidene fluoride,
polytetrafluoroethylene, polyvinyl polymers, polyamides, and
polyurethanes, and 15 to 50 volume percent mineral particulate with
a mean particle size of at least 1 micrometer. The conformance
layer requires, when tested at 25 degrees Celsius using a standard
tensile strength apparatus, not more than 35 Newtons force per
centimeter of width to deform a sample to 115% of the original
sample length when tested at a strain rate of 0.05 sec-1. The top
layer is distinct from the conformance layer, 80-250 micrometers
thick, and is made of a thermoplastic polyolefin.
[0017] U.S. Pat. No. 6,790,880 to Purgett, Mark, et. al., and
assigned to 3M, describes a pavement marking comprising a binder
having polyurea groups, wherein the binder is prepared from a
coating composition comprising one or more aliphatic secondary
amines, one or more polylsocynanates, and at least about 15 weight
percent non-soluble material based on the weight of the final dried
coating, and reflective elements. The patent also discloses the
pavement marking wherein the binder is a sprayable, two-part
coating composition.
[0018] U.S. Pat. No. 6,116,814 to Dietrichson, Stein, and assigned
to Rieber & Son, Division Nor-Skilt, describes a method for
applying markings or signs on a surface in which a primer layer
comprising an uncured plastic material with two or more components
is applied to the surface, a heated mass comprised of a
thermoplastic material is laid down on the primer layer, and the
curing of the primer layer is initiated by the heat of the
aforementioned heated mass.
[0019] U.S. Pat. No. 3,664,242 to Harrington, Thomas, et. al., and
assigned to Minnesota Mining and Manufacturing Company, describes a
method for forming a marking on a roadway that is ready to bear
wheeled road traffic within seconds after application. First, the
surface of the roadway is momentarily heated to a temperature
between 150 and 500 degrees Fahrenheit. Next, the thus-heated
roadway is projected toward a marking material that comprises a
continuous stream of solid particles that are capable of passing a
screen of about 20 mesh with at least about 80 weight percent being
retained on a screen of about 200 mesh, are non-tacky,
non-blocking, free-flowing, and solid at temperatures up to about
120 degrees Fahrenheit, and include a coloring agent in an amount
sufficient to color a marking formed from the marking material and
an organic thermoplastic phase that accounts on the average for at
least about 25 volume percent of the marking material and
principally comprises a polyamide condensation product of
polycarboxylic acid and polyamine. Finally, the individual
particles are heated as the proceed toward the roadway to a
temperature above 150 degrees Fahrenheit sufficient to at least
soften a major portion of the organic thermoplastic phase of the
particles before they reach the pavement, the heated condition of
the roadway and the particles being such that the particles wet and
bond rapidly to the surface of the pavement and coalesce into a
film, which subsequently becomes solid, non-tacky, and capable of
bearing wheeled road traffic without tracking.
[0020] Great Britain Patent Application No. GB 2429978A to Aubree,
Barry Mark, and assigned to Barry Mark Aubree, describes a method
of producing a thermoplastic road-marking composition that
comprises mixing an opaque pigment, a translucent particulate
thermoplastic material and reflective glass beads such that when
the thermoplastic material is subsequently melted to bind the
composition and the composition is laid as a marking, the glass
beads on the visible surface of the markings are not substantially
obscured by the opaque pigment. The application also presents a
thermoplastic road-marking composition comprising a mixture of a
particulate filler material, a pigment, a translucent thermoplastic
material and reflective glass beads wherein the pigment clings to
the filler material and the reflective glass beads are generally
clear of the pigment. Accordingly, the thermoplastic road-marking
immediately has retroreflectivity without the requirement for an
additional operation of adding glass beads to the surface of the
marking and without the need to let the road-marking wear before it
becomes retroreflective.
[0021] WIPO Patent Application No. WO03064771A1 to Hong, Le Hoa,
et. al., and assigned to Avery Dennison Corporation, describes a
method for securing a preformed pavement marking construction with
a top surface and at least one perimeter edge to pavement with a
relatively flat roadway surface. The method includes adhering the
preformed pavement marking construction the roadway surface,
providing a curable structural adhesive, and applying the curable
structural adhesive to the at least one perimeter edge such that
the curable structural adhesive overlaps a portion of the top
surface of the preformed pavement marking construction at its at
least one perimeter edge and a portion of the roadway surface.
Finally, the curable structural adhesive is cured to form a
traffic-bearing top surface extending between the roadway surface
and the preformed pavement marking construction.
[0022] The disclosed review of the relevant art shows the need for
a thermoplastic pavement marking method using an adhesive
(sprayable or otherwise) that maintains the integrity of the
pattern and a thermoplastic pavement marking composition that
includes large grit size aggregate to improve long term skid
resistance and reduce tire-tracking.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a diagram of a type of preformed thermoplastic
pavement marker, which is more fully described below.
DETAILED DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 illustrates a typical partial decorative pavement
marking pattern (10) for application to concrete, asphalt or other
suitable substrates. Marking pattern (10) is a brick and mortar
pattern used herein for illustration purposes but as would be
understood various other thermosetting and thermoplastic patterns
are commercially available such as (90) herringbone, cobblestone,
pavement slabs, horizontal signage, logos and other designs. Also,
while many colors are available for the pavement marking patterns,
typically different sections of each pattern are of different
colors, such as a "light" grid or mortar color and a "darker" brick
or insert color. The marking patterns typically consist of two or
more sections.
[0025] Preferred marking pattern (10) shown for demonstration
purposes consists of two separate thermoplastic sections, first
section (11) represents a grid or mortar joint and second section
(12) represents a brick or insert (14) with borders (18) as
represented. Sections (11) and (12) are generally formed
independent of each other due to the differences in color. Pavement
marking pattern (10) is planar and is conventionally formed from a
standard thermoplastic. The top portion (11) of the marking pattern
is bordered. Large aggregates (20) are shown throughout the marker
patterns.
SUMMARY OF THE INVENTION
[0026] The present disclosure describes a preformed thermoplastic
pavement marking or hot melt applied material with improved long
term skid resistance and reduced tire tracking once the pavement
marking has been adhered to road surfaces or other solid
substrates. The need exists to produce preformed thermoplastic
pavement marking materials with improved skid resistance,
especially for use in wet conditions and over long term use to
reduced tire tracking--a real detriment to the usefulness of
thermoplastic pavement markings in locations where they are
desirable. The preformed thermoplastic material of the present
invention is comprised of about 20% binder and 80% "intermix",
where the intermix includes non-organics such as silica, calcium,
and other inorganic pigments as well as large high friction
aggregate capable of passing through sieves sizes of about 4 to
about 12 together with somewhat smaller aggregate that is applied
to the surface either prior to, or during installation. The surface
applied anti-skid materials provide high initial friction
properties, while large size aggregate in the intermix provides
long term skid resistance and improves initial friction properties
by creating an appropriately textured surface.
[0027] To achieve the desired traction and friction properties it
should be recognized that there is a difference between slip
resistance, which relates to traffic traveling over the pavement
markers at a slow speed and to pedestrian traffic traveling over
the same pavement marker surfaces and related to the static COF
(coefficient of friction). Skid resistance relates, however to
traffic traveling over the pavement markers at high speed, and
depends on surface texture. Skid resistance is more applicable to
the type of vehicular traffic.
[0028] Common test methods for measuring the effectiveness of these
pavement markers for slip and skid resistance include BPN (ASTM
E303), which is the most commonly used test methodology but does
not reflect performance at high speeds and does not provide for
measuring static COF values.
[0029] Instead, the "Locked Wheel Test" which produces "FN" or
Friction number and described by ASTM E274 is used by many states
within the United States and provides a methodology for measuring
friction values at high speeds, simulates real traffic conditions,
and requires actual road installation. There are also other test
methods for measuring friction at high speeds. Results from
different test methods can be normalized or combined using the IFI
(International Friction Index, ASTM E1960) which provides for
combining friction and texture indices (F60 and S.sub.p).
[0030] The required materials for the present invention to achieve
both the necessary slip and skid resistance are those that contain
high friction large aggregates in the intermix with a weight
percent content of from 5 percent to 65 percent. The optimal size
of the large aggregates is from about 4 to about 16 grit depending
on the specific thickness of the thermoplastic sheets that contain
the marker patterns--confirm sizes The present invention also
includes cases where the thermoplastic road marker patterns contain
surface applied large aggregate in a range from about 14 to about
20 grit Product using small particle aggregate sizes (approximately
24 grit or mesh) covered the surface area of the thermoplastic
marking sheets more effectively, however, these aggregates did not
provide the required skid or tire track resistance.
[0031] It has been shown that it is possible to use single grit
size aggregate in the intermix. The use of an intermix of different
grit sized aggregates in different proportions based on the need
for the future use of different materials (larger sizes for thicker
and larger thermoplastic sheets and smaller aggregates for narrow
strips) is also part of the present disclosure.
[0032] The aggregates used primarily exhibit a Mohs hardness of
greater than 6, including corundum, quartz, granite, calcined clay,
nickel slag, silicon dioxide and others (trade names of such
materials include Mulcoa grades 47, 60 and 70, AlphaStar.RTM.,
Ultrablast.RTM., and Alodur.RTM. which provide hardness ratings in
the range of 6.5 to 9). A portion of the intermix used with the
thermoplastic road marking includes 16 grit size aggregate also
with a hardness in the Mohs scale reading of greater than 6, which
has never been tried before in preformed or hot melt applied
thermoplastic surface applications, and has resulted in improved
friction.
[0033] An additional desired result is improved overall skid
resistance of the preformed thermoplastic markers without any
associated discoloration. The aforestated special aggregates also
improve the coefficient of sliding friction (COF) as determined per
the ASTM E274 test. As the COF decreases below a certain level on
the surrounding asphalt, a small wheel grabs onto the asphalt and
if the COF is reduced on the pavement marking too much, undesirable
skidding will occur. It is desirable that the COF of the preformed
or hot melt thermoplastic match or be greater than the road
pavement surface. The COF, in this case, as measured per ASTM E274
requires using a small cart pulled behind a car with a wheel
attached to the bottom of the cart that rides at the speed of the
car, thus touching the pavement surface, which eventually results
in locking the wheel, thereby allowing for measurement of the force
of the cart on the surface.
[0034] In this case, the result of using large particle aggregates
is anti-intuitive, in that as there is more "gripping" to the
thermoplastic marker surface adhered to the underneath pavement
surface, the traffic that travels over this maker pavement surface
with the special aggregate results in providing less tire tracking
and skid marks. Tire tracking is measured by the size and number of
undesirable resultant markings caused by traffic as well as
discoloration of the thermoplastic marking surface. The reduction
in COF does, however, correlate with increasing skid and when the
COF increases, this will correlate with decreasing skid.
[0035] Therefore, a surprising result found during the course of
experimentation and resulting in an important embodiment of the
present application is that these thermoplastic marking surfaces
stay cleaner and possess less tire tracking than marking surfaces
without the special large aggregate particles described above.
[0036] There is a strong need in the industry to provide a layer of
preformed thermoplastic so that these marking surfaces are skid
resistant and are used for any crosswalk material. There is also a
requirement that the skid resistance (which is quantified by
friction number) also provides tire tracking reduction.
[0037] An additional embodiment and surprising result is that in
the past, without the use of these large aggregate materials, the
wheel path or track is almost always darker in the section of the
surface where the vehicle travels over the marking, so that normal
free rolling traffic which passes over the thermoplastic pavement
markers will cause darkening. In the case of the present invention,
this is not true and this undesirable result has been eliminated.
The turning traffic, which causes more tire shear, also does not
cause darker tire tracking.
[0038] In the present invention, the use of uniform particulate
material or blends of particulate materials for the aggregate with
differing hardness values, providing more economical solutions, can
be introduced into the intermix during formulation. The
introduction of these blends usually occurs prior to extrusion and
completion of the thermoplastic pavement marking. The aggregates
and other particles such as glass beads, including type 1 and type
3 glass beads, and the inorganic choices stated above can also,
however, be dropped on the hot material during installation and
completely embedded into body of the thermoplastic marking material
in that fashion. The preformed thermoplastic surface marking
product can be applied using pressure sensitive adhesives as well
as by flame torching.
[0039] The resultant properties of the (once applied) thermoplastic
marking surfaces were measured using International Friction Index
(IFI) consisting of two parameters: [0040] F60--calibrated friction
at 60 km/h calculated from DFT20--friction measured at 20 km/h
[0041] S.sub.p--speed constant that depends on surface texture
presented as MPD (mean profile depth, mm).
[0042] Materials without large high friction aggregate have an F60
of about 0.07 to about 0.10 and an MPD of 0.15 mm to about 0.3 mm.
Depending on the aggregate size used in the present invention, when
the intermix becomes exposed, the F60 increases to between about
0.17 to about 0.4 and the MPD to between about 0.50 mm to about
0.75 mm. For comparison hot mix asphalt has an F60 value of about
0.25 after being exposed to traffic extended lengths of time.
[0043] In addition, in recent years increasing numbers of
municipalities, office complexes, shopping centers and other
commercial developments have utilized thermoplastic pavement
markings with various patterns and designs to guide, decorate, and
protect high traffic areas such as highways, pedestrian crosswalks,
parking lots and business entrances. Such patterns may include a
first section or grid, for example to represent the mortar joints
in a "brick" design and a plurality of second sections or "bricks"
which are coplanar therewith, usually in a color different from the
mortar color. The second section or bricks which are separately
manufactured are inserted into the first section or grid before
application of the pattern to the pavement. Various two section
marking patterns are commonly available such as: herringbone,
standard brick, cobblestone, paving slabs and many other designs.
Marking patterns with more than two sections are also commonly
available such as horizontal highway and street signage, logos and
many others.
[0044] As hereinbefore mentioned, these marking patterns consist of
two or more independent sections which must be carefully assembled
and handled before applying to pavements such as asphalt, concrete
or other suitable substrates. These marking patterns are placed at
desired locations such as road crosswalks, intersections, parking
lots or other sites. In some cases heat is then applied to soften
the pavement marking pattern causing it to firmly adhere to the
substrate. Various adhesives can also be used to adhere the marking
pattern to the substrate.
[0045] While the purchase of such pavement marking patterns is
relatively inexpensive, much time and labor is devoted to the
assembly and application of the pattern to the substrate. Most
patterns consist of two or more sections which are independently
formed for manual assembly at the job site and time and effort is
needed to assemble and maintain the integrity of a pattern before
the heat treatment. Usually the pattern placed on the substrate
must be moved manually for adjustment purposes. During such
movement, the independent sections in the pattern inadvertently
become unaligned, requiring reinsertion or realignment. If the
realignment is not precisely accomplished, the marking pattern will
have lost its integrity and the entire pattern must be removed
manually from the substrate, the substrate cleaned and a second
attempt at the application made with the reinserted or new marking
pattern. This re-application results in extra time, labor, and
materials. In the past, to maintain the integrity of the marking
pattern before the heat treatment and during the handling and
placement, "spot adhesives" have been used which remain somewhat
"tacky" after being applied to the bottom of the patterns at the
grid intersections to maintain pattern integrity. However, these
small adhesive circles or "spots" are generally a different type of
polymer than the marking pattern and can prevent proper attachment
and easy movement of the marking pattern on the substrate at the
spot adhesive locations before and during the heat application of
the marking. Also, certain spot adhesives are not compatible with
the plastic materials from which the patterns are formed and can
cause the pavement marking sections to separate from the substrate
after the heat application, as only a weak bond is formed with the
substrate.
[0046] The major object of the present invention is to provide for
long term skid resistance and reduced tire tracking through the
addition of large grit size aggregate. The above stated objectives
are realized by providing a conventional pavement marking pattern
formed of a thermosetting or thermoplastic which may have two or
more sections, manually joined by bridging the bottom surface
thereof with an adhesive having substantially the same temperature
softening point as the sections of the marking pattern. The
adhesive can be sprayed primarily along the intersections of the
pattern to cover a percentage (approximately from 5% to 90%) of the
patterned bottom surface area while bridging the intersections. The
more intricate the pattern (with more joints or intersections) the
greater the percentage of adhesive coverage required. The spray
adhesive can be a typical polyamide, EVA based hot melt adhesive or
other, such as styrene-isoprene-styrene copolymers,
styrene-butadiene-styrene copolymers, ethylene ethyl acrylate
copolymers, and polyurethane reactive, and preferably consists of a
hot melt polyamide resin based adhesive which is sprayed in a
circular or spiral string like configuration at a temperature at or
above its softening point. The sprayed hot adhesive strikes the
marking pattern and adheres, bridging and bonding the pattern
sections to maintain pattern integrity during subsequent handling.
Uni-Rez 2633 as sold by Arizona Chemical Company of P.O. Box
550850, Jacksonville, Fla. 32225 is the main ingredient in the
preferred hot melt adhesive. The preferred hot melt adhesive is
formulated with Uni-Rez 2633, ester modified rosins, fillers,
extenders, levelers and other conventional components.
[0047] In a typical manufacturing process, various sections of a
pavement marking pattern (e.g. a brick and mortar pattern or any
other desired pattern) are factory assembled and while in assembled
form, the bottom of the pattern is sprayed with the hot melt
adhesive described above using preferably spray gun model:
Hysol-175-spray as manufactured by Loctite Corporation of 1001 Tout
Brook Crossing, Rocky hill, Connecticut 06067, having various
pressures and nozzle settings to select from, depending on the
viscosity of the particular adhesive employed. A circular or spiral
string-like adhesive configuration is preferred for the spray.
[0048] Once the sprayed hot melt adhesive has cooled, the grid and
inserts are suitably bridged and joined and the pavement marking
pattern is packaged for shipment. Upon receipt at the job site, the
packages are opened and after the intended substrate, usually
asphalt or concrete is properly cleaned and swept, the marking
pattern is then placed on the substrate without concern of
disassembly during handling, movement and adjustment. Once suitably
placed, a heat application is delivered from a conventional source
which softens the marking pattern and the underlying sprayed
adhesive, both of which have the approximate same temperature
softening point to thereby affix the pavement marking pattern to
the substrate. Time and labor are thereby saved as the marking
pattern sections have been adhered to form a unified pattern by the
hot melt adhesive.
[0049] As stated above, the present invention includes larger grit
size aggregate than is normally used in similar preformed
thermoplastic pavement marking products. Specifically, the
aggregate should be between 8 and 12 mesh (grit) in size and may be
comprised of quartz, corundum, crushed gravel, crushed granite, or
any combination thereof. The aggregate used may also measure 6 or
greater on the Mohs Hardness Scale. This larger grit size improves
the skid resistance properties of the pavement marker and also
significantly reduces tire tracking in comparison to other similar
products, because it ensures that the product wears down more
slowly, conveying greater durability and also longer term skid
resistance--often through the end-of-life of the applied preformed
thermoplastic.
[0050] Other advantages achieved using these working examples
include the fact that when the surface applied aggregate provides
high initial skid resistance using aggregate in the intermix, the
surface maintains high skid properties during the entire period of
use of the pavement markings and al so provides increasing skid
resistance.
[0051] Another unexpected effect of the use of large aggregate
intermix within the preformed thermoplastic or hot melt applied
markers, is the decrease or essentially complete elimination of
tire skid marks on the thermoplastic marking surfaces. Bigger
aggregates leading to reduction or elimination of tire tracking was
also an unexpected result.
[0052] Among additional objectives of the invention include
providing a relatively inexpensive pavement marking pattern having
two or more sections in which the sections are joined by use of an
applied adhesive and to provide a method for forming a pavement
marking pattern which allows cost efficient factory assembly of the
pattern and which prevents dislodging and separation of the pattern
sections during handling, transportation and application.
[0053] Other objects of the invention are to provide an adhesive
which can be conveniently sprayed onto the back of pavement marking
patterns which will sufficiently adhere thereto and prevent
separation of the sections during handling, and not deteriorate the
bond between the pavement marking pattern and the substrate and to
provide a method for easy application of the adhesively sprayed
marking pattern to the substrate.
[0054] It should be understood that although examples are given it
should not be construed that these are examples provide the only
examples of the invention and that variations of the present
invention are possible, while adhering to the inventive concept
herein disclosed.
[0055] Incorporation of large grit aggregate into the pavement
marking pattern allows for manufacturing with decorative markings
on the surface of the preformed thermoplastic sheets that provides
excellent anti-skid properties.
WORKING AND COMPARATIVE EXAMPLES
Test Methodology
[0056] The surface texture of the preformed thermoplastic is
measured using a laser-based Circular Track Meter (CTM) with a
vertical resolution of 3 microns (.mu.m). The texture is reported
in terms of the Mean Profile Depth (MPD) in millimeters. Then the
friction of the surface is measured using a Dynamic Friction Tester
(DFT). In the DFT, a disk with three rubber sliders attached to the
disk rotates at tangential velocities up to 90 km/h then drops onto
the surface. The torque generated, as the disk slows once it
engages the surface, provides an indication of the friction at
various speeds. The output from the DFT is reported as unitless DFT
numbers at various speeds (typically 20, 40, 60 and 80 km/h). The
DFT and CTM instruments are manufactured by NIPPO Sangyo Co.
(Japan). Together, the results from the CTM and DFT are used to
calculate a value known as the International Friction Index (IFI,
F60). The IFI can also be estimated by other types of equipment
including the widely used ASTM E274 towed friction trailer test
method as well as the British pendulum test method and results of
different test methods have been found to correlate.
Working Example 1
[0057] An example of the hydrocarbon resin composition for the
preformed thermoplastic of the present invention is provided as
follows:
TABLE-US-00001 Material composition Escorez 1315- 10% C5
hydrocarbon resin- 5% Refined mineral oil- 2% Escorene EVA MV 02514
3% Fumed silica- 0.5% Titanium dioxide (Rutile)- 10% Glass beads
Type 1- 30% Corundum Grit 12 20% CaCO3- 19.5%
[0058] The material composition has a softening temperature (Ring
and Ball) of 118.degree. C. measured according to ASTM D36-06
entitled "Standard Test Method for Softening Point of Bitumen
(Ring-and-Ball Apparatus)".
[0059] The thermoplastic material composition was extruded using a
casting die to create 125 mil thick preformed thermoplastic sheets.
As the sheets were extruded glass beads were dropped onto the
melted thermoplastic material. Subsequently at a location further
from the die exit on the manufacturing line, corundum grit 16 was
added to the thermoplastic and indented visual heating indicators
were applied to the surface.
[0060] Using a Flint-2000 propane torch, the material composition
was applied on two square cement boards (20 inches by 20 inches).
One of the panels was tested after application, another was abraded
(sand blasted) to expose the intermix aggregate.
[0061] The properties of material tested with DFT and CTM as
described above are provided in Table 1 below;
TABLE-US-00002 TABLE 1 DFT, F60, and MPD Values for Working Example
1 Example 1 DFT20 F60 MPD, mm As Applied 0.733 0.425 0.61 After
Abrasion 0.853 0.455 0.71
Working Example 2
[0062] An example of preformed thermoplastic material based on an
alkyd resin composition is provided as:
TABLE-US-00003 Material Composition for Working Example 2 Polyamide
resin Uni-Rez 2633 7.2% Modified rosin resin Sylvacote 4981- 6.8%
Phthalate plasticizer- 2.8% PE based wax- 2.0% Fumed silica- 0.5%
Corundum grit 16 30% TiO2- 10% CaCO3- 40.7%
[0063] The material composition softening temperature (R&B) is
124.degree. C.
[0064] The material composition was extruded, applied on cement
boards, and tested similarly to the Example 1 except that corundum
grit 24 was dropped on the surface during extrusion. The results
are provided in Table 2 below:
TABLE-US-00004 TABLE 2 DFT, F60, and MPD Values for Working Example
2 Example 2 DFT20 F60 MPD, mm As Applied 0.517 0.266 0.463 After
Abrasion 0.794 0.379 0.51
Working Example 3
TABLE-US-00005 [0065] Alkyd type base layer for hot applied
formulation Modified rosin resin Sylvacote 4981- 8% Modified rosin
resin Sylvacote 7021- 9% Castor oil based plasticizer- 3% PE based
wax- 2.0% Quartz mix with grit 12 to 20 gradation 30% TiO2- 10%
CaCO3- 38%
[0066] The material composition softening temperature (R&B) is
121.degree. C.
[0067] The formulation, after mixing, provided 4-inch wide
draw-down plaques. No anti-skid aggregate was applied to the
surface of the plaques. While still warm and sufficiently flexible
the draw-down plaques were applied to the cement boards covering
the entire 20.times.20 inch area and creating sufficient space for
testing, using CMT and DFT testers. One of the boards was tested
after application and another after abrasion by sand blasting to
expose intermix aggregate.
TABLE-US-00006 TABLE 3 DFT, F60, and MPD Values for Working Example
3 Example 3 DFT20 F60 MPD, mm As Applied 0.15 0.13 0.34 After
Abrasion 0.70 0.33 0.46
Working Example 4
[0068] An application of preformed thermoplastic insignia using
adhesive backed preformed thermoplastic sheeting was also tested.
Pressure sensitive adhesive (PSA) was applied to the sheets of
material made according to the Example 2 and pre-cut in the shape
of AASHTO approved letters. The letters were applied at the
intersection to create a warning "STOP" sign using a READYMARK.RTM.
tamper. The friction properties of these preformed thermoplastic
sheets yielded results similar to the "as applied" properties
presented in Example 2.
Working Example 5
[0069] A decorative brick pattern was made using colored and
patterned thermoplastic sheeting manufactured according to the
Example 1 including a dark red color for bricks and a white color
for the grout. The sections of the patterned thermoplastic sheeting
were joined together using EVA based hot melt adhesive. Sheeting
was applied to the crosswalk and exhibited properties similar to
the "as applied" properties presented in Example 1.
Working Example 6
[0070] Alkyd based material with blended large aggregate
intermix
TABLE-US-00007 Material Composition for Working Example 6 Polyamide
resin Uni-Rez 2633- 7.5% Modified rosin resin Sylvacote 4981- 6.5%
Phthalate plasticizer- 3.2% PE based wax- 1.6% Fumed silica- 0.5%
Corundum grit 12 5% Mulcoa 47, gradation 8-20 grit 25% TiO2- 10%
CaCO3- 40.7%
[0071] Material was processed according to Example 1, with a 90 mil
thickness and corundum grit (or mesh size) 24 was applied during
extrusion.
TABLE-US-00008 TABLE 4 DFT, F60, and MPD Values for Working Example
4 Example 6 DFT20 F60 MPD, mm As Applied 0.47 0.248 0.46 After
Abrasion 0.754 0.392 0.51
Comparative Example 1
[0072] As an illustration, Comparative Example 1 uses smaller
aggregate in the intermix. The preformed thermoplastic was
identical to that of Working Example 2, except that the Corundum
grit 30 was used in the intermix and as a drop on instead of
corundum grit 16.
TABLE-US-00009 Material Composition for Comparative Example 1
Polyamide resin Uni-Rez 2633- 7.2% Modified rosin resin Sylvacote
4981- 6.8% Phthalate plasticizer- 2.8% PE based wax- 2.0% Fumed
silica- 0.5% Corundum grit 30 30% TiO2- 10% CaCO3- 40.7%
TABLE-US-00010 TABLE 5 DFT, F60, and MPD Values for Comparative
Example 1 Comp. Example 1 DFT20 F60 MPD, mm As Applied 0.42 0.192
0.28 After Abrasion 0.36 0.172 0.26
[0073] The data shown above, in Table 5 when compared with the
previous Tables (1-4) clearly indicates the (heretofore unexpected)
improvement over the small size corundum after abrasion (wear) for
DFT20 (0.70 vs. 0.36) and calibration friction number F60
(0.35-0.45 vs. 0.17).
* * * * *