Note: Descriptions are shown in the official language in which they were submitted.
P ~ 8 ~
SURFACE Y.AR~r'~ ST~IP A~D ~THODS
FOR PROVIDING IMPR~VED INTEGRITY A~D ADHESIO~
TO ROADWAYS A~D Tt~ LIK~.
The presene invent~on relaeas to surface marker
sCrips as for roadwavs, pavements and other surraces, be-
in~ more par-icuLar'v di~ec:ea to me~:~od, o- ?-~Vi~'?.g
better roaawa,v aahering and longer-life prope..ies to such
mar'.ter str~'?s, ana to marker strips or tapes with pre~o.m-
ed ridges aaherea to the roaawa,vs and the like or vas;lv
improved integrit,v and life chae, by reflection ana/or re-
troreflection from the ridges, enable enhanced visibilitv,
especiall,v upon illumination by the headlights of ap-
proaching vehicles.
A paramount problem with preformed plastic pavement
marker strips of the prior art is that of providing satis-
factor,v adherence to the road surface under the constant
heavy poundin~ of motor vehicle trafficO Unless the pave-
ment marker has a deformable layer of elastomeric material
which lacks memory positioned between the marker and the
road surface, good aahesion will not al~ays be achievea~
.
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This laver must aeform readilv and flow wichouc me~or-,
into the irre,~ular surface contours of the pave~ent. The
deformabilLtv ana ability to cold flow permits the
absorption of the energv of vehicle tire impacts which
would o~her~ise violentlv aislodae .he pavemenc ma.'~- as
the impact energ,v is aissipated. With an elastic materi-
al, adhesion to the road surface is weakened when the road
is wet because the stretch-return action of such a memory
material causes a pumping action to occur in which water-
bearin~ dirt i9 forced between the material ana the road
surface. Dirt then becomes deposited between the adhesive
material and the road surface and ultimately destro,vs the
adhesive properties holding the pavement marker to the
road.
While for some applLcations, techniques for aahesion
of the type employed with marker strips of my earlier
U.S. Letters Patent Nos. 3,920,346; 4,040,760; 4,069,787;
4,236,788 and 4,681,401 involving a thick mastic, providea
a measure of the deformabllity and cold flow characteris-
tic~ discussed above, for extenYive use and under severe
~2~
trafric ana temperature varying circ~mstances, however,
this technique proved at best to be onlv a co~promise.
Additionallv, the mastic aahesive proved difficult to
applv to the proauc~ in an economical manner. During e~-
tensive hea~ or su~mer, the adhesive had a tendenc~ to
flow reaailv as it became warm, with the result that the
pavement-~arker would cree? or move with very heavv
traffic. Sometimes the e~tremely low temperatures of win-
ter, moreover, would reauce the bonaing force between the
adhesive and the pavement marker with the disasterous re-
sult of removal bv snowplow action~
This problem of adequately securing a preformea plas~
tic pavemen~-marker tape to the road surface was also re-
cognized and partially solved in prior art U.S. Letters
Patent Nos. 3,399,607; 3,587,415 and 4,117,192 and
others. The techniques proposed in these patents involved
base materials which e~hibit desirable characteristics of
deformability and lack of memory or cold flow which will
provide conformability to the road surface and will absorb
the shock energy of vehicular traffic~ While useful for
2~
~,
preformea flat surface pave~ent-~arker tapes, however,
such techniques do not aaequately solve the problem for
strlps or tapes havin~ preformea ridges such as those dis-
closea in mv said earlie patents c~teà above. Because
such prior art material has no memory ana echibits cold
flow characteristics, any protruberance such as a ridge or
weage on the surface verv quickly disappears when impac~ed
by vehicular trafric so that the ridges flacten out and
lose shape under the pressure of the vehicle tires. This,
of course, aefeats the primary purpose of high visibility
of the protruberances or ridges at low veiwing angle~s. If
the ridges were comprisea of a harder or more rigid
materlal such as, for e~ample, polyvinyl choride or epoxy
or some other rigid or semi-rigid material, they would
soon be engulfed by the non-memory cola flo~
characteristic of the base mateslal undsr the pressure of
the traversing traffic. Once depressed into the base
material, the ridges would no longer protrude above a film
of rain water and would thus be useless as high visibility
ridges- for wet nigh~ visibilityO
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As disclosea in U.S. Letters Patent No. 4,4~,432
which incorporates the teachin~s of Patent No. 4,388,3S9,
an attempt was maae to solve this problem bv incluain~
reinforcin~ fi~ers with the mi~ of th2 non-~emor,~ cola-
flowing eLastomeric base material. It was hopea that the
fiber woula offer sufficient stiffness to overcome the
probl~m of losing the protruberances upon impact or high
volume vehicular traffic. This, however, has not proven
to be a completely successful solution; ana in a short
time, the protruberances become, in practice, flattened
into the base material where the,v lose their function and
utility.
Underlying the present invention, on the other hand,
is the discovery that a combined-layerea non-vulcanizea
and vulcanizable rubber sheeting can admirably provide a
superior solution to the above-mentioned problems. The
conformability and shock energy absorbing features of a
non~vulcanized elastomeric rubber sheetlng when combined
with a vulcanizable elastomeric rubber serving as the top
portion oE the tsoe or strip nd in which the protruber-
-6~ 2~
ances or riages are for~ea enables ~.he attainment ot the
noveL results herein. After vulcanizing the top laver
containing the riages, the ria~es can be stretc~ea or
flat~enei or otherwise ae? essea or ae-ormed bv vehicular
trafr'c, ~u:, because or their me~ory cha.ac:e- s;~cs,
will be restorea to their original sha?e a-ter cessation
of saia tra fic. While the elastic proper.y of the vul-
canized top portion comprising the riage structure con-
tains sufficient memory to permit such restoration or
shape, such is not enou~h to inhibit aeformabilitv of the
soft elastomeric bottom portion which conforms to the roaa
surface and which, with its non-memory property, reaaily
absorbs the shock energy of the wheel impacts of the
vehicular traffic.
An object of the invention, accordingly, is to pro-
vide a new ana improvea marker strip or tape for roadways
and the llke that is not subject to the previously descri-
bed short-comings of prior devices but that, through a
layered co~binaeion of a non-vulcani~ed lower rubber-like
surface that conformably adheres to the roadway and an
~2~8~
upper vulcanized rubber-like surface containing the marke-
ridges provldes long-lasting adhesion and integrity. of the
rid~es during use.
Othe- ana furthe- obiec.s will be e~olained he~ein-
a^;ar and are mo.e pa-~'cularly delinea e3 in ~he a??e~ded
claims.
In summarv, however, from one of its im30rtant
aspects, the invention embodies a roadwav mar'~er strip for
adhesivelv attaching along its bottom sur-ace to the road-
way, comprising a rubber-like sheet the bottom laver a~d
surface of which is of cold-flow characteristics and the
upper layer and surface o which is deformed into success-
ive protruberances such as ridges and wedges from which
incident light from a vehicle traveling along the roadwav
may be reflected or retro reflected to'indicate the road-
way direction, ~ith the upper layer being cross-link-
vulcanized to enable res~oration of depression of the pro-
~ruberances caused by vehicle wheels traveling thereover
while the strip conformably adheres to the roaaway. Pre-
ferred and best ~ode embodiment details are hereinafter
presented.
7a
Ik has also been ascertained that the invention
concept applies to marker strips without embossed
protuberances. In this aspect, the invention relates to a
roadway marker strip for adhesive attachment along a bottom
surface of the strip to a roadway, comprising a rubber-like
sheet having a bottom layer and flat surface which possess
cold-flow substantially memory-free characteristics and an
upper layer and surface from which incident light from a
vehicle traveling along the roadway may be reflected to
ln indicate a roadway direction, the upper layer and surface of
the sheet only being cross-link-vulcanized so as to possess
substantial memory enabling restoration of depression of the
upper surface caused by a vehicle, while the sheet bottom
layer remains unvulcanized and conformably adheres to the
roadway.
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The invention will now be described wich re~erence to the
acco~panving drawings,
Figure 1 o which i9 a cross-section through a single
pl,V rub~e- s'hee~ing prior to e~bossino the protrube-ances
or r-'dg2c;
Figur2 2 is a cross-section through a single plv rub-
ber she-~ing ar~er embossing the protruberances or riages;
Figure 3 is a cross-section through a double ply rub-
be sheeting prior to embossing the protruberances or
riages;
Figure 4 is a cross-section through a double ply rub-
ber sheetin~ afcer embossing the protruberances or riages;
and
Flgures 5 and 6 are cross-sections similar to Figures
2 and 4 after the protruberances ha~e been formea and
showing retro-reflection glass microsphere distribueion on
the surfaces.
Referring to the drawings~ the base material 1 of the
marker strip or tape is shown as comprised of a non-
vulcanized rubber mixture in sheet form which lacks memory
_9_
and is easily deformea beca~lse it is sofc and e~hibitscold flow charac~eristics. It is comprised of a rubber
polymer sllch as acrvLonitrile-butaaiene in a non- vulcan-
ized s:a~e. In adaitlon re rforcing fibe-s, a pig~en~,
and othe processing ai~s are also incl-ded. An eca~ple
of a typical formulation is listed in Table I in which the
reinrorc-ng fiber is given as wood pulp-like cellulose
fibers. Other tvpes or fibers including thermoplastic re-
lnforcing fibers may be used without seriously degrading
the defor~ability characteris~ic of the sheeting. In
accordance with the invention, the bottom portion or laver
of this material is left in this un-vulcanized cold-flow
non-memory condition, ana is attached by adhesive 6
(Figures 5 and 6) along the bottom surface to the roaaway
R. The top portion of the rubber sheeting material com-
prising the marker strip, however, i5 to be vulcanized to
provide it with memory characteristics. Toward this end,
the top la~er may be treated as~by a shallow laver of per-
oxide material 1' which pene~rates the rubber sheeting to
a limited dep.h depicted by the speckled area of Flgures 1
.
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ana 2. Because or the presenca of pe~o~ide or equivale~
treatmene, chis re~yion of the rubber sheeting can be reaa-
ilv cross-linked or vulcanizea bv the addicion of heat.
P ior to the heat, lt has the same character s~-cs as ~he
re~.ai~da o~ the shea~; i.e. is is sort, easilv ae ~-mei
ana lacks memorv. As illustrared in Figure 2, the sheet
of Figure 1 has been e~bossea ln the top sur~ace ~i.h pro-
truaing wedges or ridges 3 ana then heat is appliea imme-
diately therear~er in order to cross-link or vulcanize ana
harden this riagea top layer that haa been permeated with
peroxiae, imparting to the riages a permanent memory such
that they can maintain shape with cola flow after vehicu-
lar depression, while the bottom of the sheeting 1 remains
unvulcanized (not cross-linkea) and thus aeformable and
memory-free to provide ~he necessary shock energy absorp-
tion of vehicular traffic and with conformability, to
assist the adhesion in securing the marker to ~he road
surface R. The protruding ridges or weages 3 may be in
the form of transversely extending parallel rows, succes-
sively longitudinally spaced along thr stript and may be
2 ~ ~ 3 ~
segmentea inCo ria~e or weage blocks, if desirea, prefer-
ably with a trapezoidal crosssection proviaing inclinea or
near-vercLcal front and rear surfaces 1 for reflecting
incident low-angle heaalieht illuminaeion as desc lbe~ in
said pa~ea~s.
Figures 3 ana 4 illustrate another methoa or accom-
plishin~ ehe same effectO In this case, the rubber sheet-
ing base material consists o~ a two-ply laminate compris-
ing a vulcanizable upper layer 2 laminated on top of a
non-vulcanizable rubber sheeting layer 1. Layer 2 may
contain the same ingredients as layer 1 ln addi~ion to
vulcanizing agents, such as sulfur (Table II) or other
compounds which react with the rubber to cross-link or
vulcanize it to completion after the protruberances 3,
Figure 4, have been formed. Once vulcani~ed, the protru-
berances or ridges will maintain their shapes because the
vulcanization process proviaes the material with a memory
ana a degree of surface hardness.
In Figure 5, the top-embossed surface of Figure 4 has
a retro-reflecting bead-bonding layer 4 covering the en~
' ' ' ' ' ' ',, '' ' '
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tire sur~ace. This laver mav be anv suitable beaa bonaing
layer such as a vinvl acetate copolvmer, a polvurethane,
an epoxv or any maeerial which will satisfactorilv bona
the ~lass ree-oreflective mic~os?he-es 5 to the st~ucture,
curing aur--~ the cur n~ OL- ~he u~er laver or the s~.-p.
The be~d bonain~ lzver ~ can be a?pliea to the surface
ei~her Drlor to or after the riages are embossea or othe--
wise for~ea. The coating or glass microspheres or beaas 5
is appliea to this laver 4 prior to solidification of the
layer. After vulcanization of the top riagea layer, the
beads become secured in a partially embedaed manner there-
in with the beaas partially exposed including especially
on the inclinea or near-vertical front and rear surfaces
1" of the riages or protruberances facing traffic.
As shown in the cross seceion of Figure 6, the glass
microspheres 7 are embeddea in the cross-linkea top por-
tion of the rubber sheeting of~Figure 2. This can be
accomplished prior to embossing or during the embossing
process itself. The glass microspheFes 7 are only par-
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tLally e~beddea on the near-ver~ical or inclinea faces of
the ridges 3, whereas those shown tvp~cally at 8 are fullv
embedded durin~ the embossment. In order to promote adhe-
sion of these ~icsospheres to the produc~ has been
found thar s'lane is helprul eithe- incor?ora;ec wi:h che
base material or as a coating on the microspheres or
both. The aahesive laver 6, shown in Fi~ures 5 and 6,
bonds the marker to the roaa surface R ana should e~ert as
little influenc~ as possible on the conformabilitv char-
acteristics of the product to insure good adhesion to the
road surface.
The marker strips or tapes of the invention may be
formed by the following illustrative methoas of construc~
tion which provide the ability to maintain the ridgea
shape and still permit road surface conformability to
assist in good adhesion thereto.
EXA~PLE 1
The ingredients listed in Table 1 below, were com-
pounded using a lab roll mill and calender to form a sheet
approximately 0.050 inch thick by 4 inches ~ide by several
feet long. A squeegee was then used to apply a liquid
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layer of methanol ana t-bucyl perbenzoate onto the sur~ace
Oe the sheetin~ where a limited penetration of the surface
with resulting peroxiae occurea. After drving wi~h warm
a'r for 30 seconcs, the sheetine was then passea between a
n'? rolle ana a pat;erne~ embossing dLum ro im~-ess a
riagea pattern 3 into the top surface of the sheering.
The embossed material was then heatea a~ 350F for 3
minutes auring which time the upper layer 1' (Figure 2) of
the rubber sheeting i~pregnated with the peroxiae became
cross-linked. The surface aurometer was measured at
65-70, whereas before treatment with the peroxiae it was
only 40.
The embossed strip containing the ridged pattern was
then positioned beneath a flat sheet of metal and the
wheel of a 1 1/2 ton pick-up truck which was allowed to
stand over this strip for 10 minutes, depressing the
ridges. Inspec~iGn of the sample showed that the riages
had flattened ~o approximately 10% of their normal
heiRht. After a 10-minute waiting period, it was observed
that the strip showed full recovery of thé ridges and
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restoration to original shape. A similar test but without
application of the peroxide faile~ to recover at aLl when
subjected to the wheel loading for as short a eime as 15
seconds.
S-mi'ar shape recove-J or res.oration fro~ de?ression
has been observed with actual vehicular travel as well.
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TABLE I
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~aterialParts bv Weight
Acrvlonitrile butadiene 100
non-crosslinkea elaseomer
~ Vcar 102~" suDDliea bv
B~. Gooaric~)
Chlorinaeea paraffin 70
('-Chlorowax 10-S" suppliea bv
Diamond Shamrock)
Chlorinaeea paraffin 5
("Chlorowa~ 40")
Reinforcing wood-pulp-like 120
cellulose fibersl
Plgment2 l30
Glass microspheres 200
(0.003 inch average diameter ~ith
a refractive index of l.5)
Silica filler ("~ysil 233" supplied by 20
PPG Industries)
______ ________ ___________ ___ _________________________
l ('Interfi~" supplied by Sulllvan Ch~mical)
2 Tltanium dloxide ("Tronox CR800" supplied by Kerr-
McGee Chemical)
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TABLE II
Material Parts bv ~eight
Precipit~ted sulfur 3
-18- ~2
EXAI~PL 2
The ingrediencs in TABLE 1 were compounded inco sheet
form as in E~A~PLE 1 to form two separate sheecs I and 2
(Figure 3). The sheet 1 was calenderea to a thickness of
0.0~0 inch. The laver Z, ar~er the ad^it,o~ or prec'?ita-
ted sul-ur in the amoun~ of 3" total weight of rubber, was
calenaered to produce a 0.020 inch thick sheet. The
sheets 1 and 2 were then lam~natea together and impressed
with a ridgea pattern 3 and heated at 350F for 9 minu~es
durin~ which time the sulfur reacted with the rubber co
effect vulcanization of the upper embossed layer 2
~Figure 4). As in EXAMPLE 1, the strip was subjected to
the truck tire ~eight for 10 minutes and reacted in a sim-
ilar manner to the previous test, recovering fully after a
10 minute waiting period.
EXA~PLE 3
The procedure of EXAMPLE 2 was repeated except that a
layer of isocyanate polyol liquia polyurethane such as
sold under the trademark "Amershield" of Ameron Company,
was applied on top of the sulfur-containing layer ana a
- 1 9 -
laver o~ glass ~icrospheres 5 (Figure 5) ~as appliea to
the liquia polyurethane laver 4 prior to e~bossing the
ridgea pattern. AEter the polyurethane was drv ~o the
touch, the maeerial ~as embossea ana then sub ~c e~ to
350~F hea; L^Or 9 minu;es. The t.uc~ ti.e tes. resul-s
were similar to those of E~A~L~ 1 and the glass micro-
spheres were noted to be unchangea ana firmly anchorea.
E~ PL~ 4
The proceaure of EXA~PLE 2 was repeated excep~ that,
prior to embossing, the sulfur-containlng top surface 2
was given an overcoat of a 20~ solution of Dow Corning
Z6040 "Silane" in methanol, followed by application of
glass microspheres. The treated sheet was then subjected
to 350F for 30 seconds and then embossed with a ridgea
pattern. The embossing procedure caused the bPaas 7 to be
partially embedded on the near vertical faces ana almost
entirely embeaded on ehe horizontal surfaces (Figure 6).
After embossing, the sheet was heated at 350F for 9
minutes to complete the vulcanization of the sulfur con-
taiaing layer~ The truck tire test results were similar
-20
to those o~ E~A~PLE 1 and ehe glass microspheres were
observed to be unchanged and securelv anchored to the
vulcanized rubber.
Further modifications will also occur to thos~
s'~illed in this ar~ and such a~e considerea to ~ail wirhin
the spirit and scope of the invention as defined in the
appenaed claims.
