CA1322486C - Surface marker strip and method of providing improved integrity and adhesion to roadways and the like - Google Patents

Abstract

ABSTRACT

An improved roadway marker rubber-like strip in which the upper layer is deformed into protruberances such as wedges or ridges, preferably provided with a coating of exposed retro-reflective beads, that have been cross-link-vulcanized to provide the same with memory that permits shape restoration following depression by vehicle traffic, and a cold-flow un-vulcanized bottom layer adhered to the roadway and conforming without memory to the same under vehicle traffic.

Description

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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

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~, 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

, 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-~2~8~

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 ~2~8~

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 ~2~

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
-~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) 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 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 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.

Claims (14)

What is claimed is:

1. A roadway marker strip for adhesively attaching along its bottom surface to the roadway, compris-ing a rubber-like sheet the bottom layer and sur-face or which is of cold-flow characteristics and the upper layer and surface of which is deformed into successive protruberances such as ridges and wedges from which incident light from a vehicle traveling along the roadway may be reflected or retro-reflected to indicate the roadway direc-tion, with the upper layer being cross-link-vulcanized to enable restoration of depression of the protruberances caused by vehicle wheels traveling thereover while the strip conformably adheres to the roadway.

2. A roadway marker strip as claimed in claim 1 and in which at least the forward and rearward edges of the protruberances are coated with retrore-flective beads partially embedded in the vulcan-ized ridges or wedges and partially exposed therefrom.

3. A roadway marker strip as claimed in claim 1 and in which the upper and bottom layers are part of an integral rubber sheet the upper ridged portion of which only has been vulcanized.

4. A roadway marker strip as claimed in claim 1 and in which the upper and bottom layers are a pair of laminated rubber sheets with only the upper ridged layer vulcanized.

5. A roadway marker strip as claimed in claim 1 and in which the bottom layer has been provided with adhesive along its exposed surface for contacting the roadway.

6. A roadway marker strip as claimed in claim 1 and in which the strip comprises the materials of Table I and Table II.

7. A method of preparing a roadway marker and the like, that comprises, treating the upper layer and surface of a rubber-like sheet to condition the same for heat treatment that will cross-link-vulcanize such layer and surface; deforming the upper layer and surface as by embossing into successive protruberances from which incident light from a vehicle traveling along the roadway may be reflected; cross-link-vulcanizing the de-formed upper layer and surface under heat while maintaining cold-flow characteristics in the bot-tom layer and surface of the sheet; and adhering the said bottom surface to a roadway to enable conformance to the same under vehicle traffic while enabling restoration of depression of the upper surface protruberances under such traffic.

8. A method as claimed in claim 7 and in which retro-reflective beads are coated on at least the for-ward and rearward edges of said protruberances before such vulcanizing, with the beads partially exposed therefrom.

9. A method as claimed in claim 7 and in which said beads are applied in a binder that cures with the said upper layer and surface.

10. A method as claimed in claim 7 and in which the strip is compounded of the materials of Table I.

11. A method as claimed in claim 7 and in which said treating is with sulfur, with said upper layer being a separate sheet that is vulcanized and laminated to a separate cold-flow rubber bottom sheet.

12. A roadway marker strip for adhesive attach-ment along a bottom surface of the strip to a roadway, comprising a rubber-like sheet having a bottom layer and flat surface which posses 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 indi-cate a roadway direction, said 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.

13. A roadway marker strip as claimed in Claim 12, and in which the said upper layer and surface is modified by successively positioned partially embedded retroreflective bead protuberances therein.

14. A roadway marker strip as claimed in Claim 12, and in which the said upper layer and surface con-tains successively positioned retroreflective beads therein.