CA1246514A - Preformed polyurethane roadway-marking strip which is highly conformant to road surface roughness - Google Patents

Abstract

ABSTRACT

A preformed roadway-marking strip that is a poly-urethane resin film, which is wear resistant and has a roadway-marking function by the inclusion of anti-skid elements and light-retroreflecting elements, and a solid self-adhesive film which has the function to attach the marking strip to the roadway surface and, at the same time, to resist together with the polyurethane film to the traffic wear. The strip is preferrably a layer of aliphatic polyurethane resin, not exceeding one millimeter in thickness, which has exceptional conformability to the roadway surface and is characterized by high resistance to wear and tearing and a breaking elongation of not less than 50% and a permanent deformation of not less than 15%. The upper part of the layer of polyurethane film contains at least 10% pigments while the lower supporting part has a very low content of cadioptric elements, pigments and fillers.

Description

124~;i5 L4 This iFI~ention relates to. r~ad~ay ~arking st~ips and more particula~y to a pre~o~.~ed po~yuretha~e.roadway~
marking strip which is highly conformant to road surface rough-ness When referring herein to polyurethane resin? all iSocyana~e polymers:or copolymers ~ singly or in combination with other polymers - are meant to be includedO
The present Applicant has developed many inven-tions in the field of roadway marking tapes and has received many patents in several different countriesO These inventions all derive from the original preformed roadway-marking strip, which was basically a calendered elastomer and which was in-troduced on the world market right after the end of the second world warO In the above-mentioned inventions, the expanded or calendered supporting strip layer is typically ~ covered with a polymeric layer of material which, being very : resistant to wear and providing high anti-skid capability, provides long-lasting roadway-marking serviceO
Through these inventions made by the Applicant, the preformed road-marking strips became ~Icomposite~ struc- ;.
tures, with a supporting layer of rubber elastomer and a top anti-wear layer, the latter being the object of the patented technological developmentsO The support layer is generally modified as required by the new product, and is rarely mentioned in the Applicant's inventions (see the formulation of Example NoO 2, in Unlted States Patent 3?935~365O

,~

A special road-marking sector is the remnvahle type of prefor1ned road-m~rkincJ strip, the removal hein~ done either manually or by means of a mach.ine. This ty~e i~
especiall~,7 useful when roadwork .i~ being clone a.nd deviations or detours are necesssary. Applicant's U.S.A. Patent NQ.
31,~6~, the Reiss1le of Patent NQ. 4, 14~ 5, OVer.~ a removable pre~ormed roadway-marking strip whose supporting layer is an impregnated non-woven material havin~ hi.gh mechanical characteristics. This non-woven material cJuarantees removahility even after many months of use. It is completely impregnated by an impreynat,ing material but is also partially permeated by the 1na-terial which Gonstitutes the lower aclhes.ive layer and partial~y by the top layer which is the actual marking surface.

It was di~covered that, if appropriately formulated, the wear resistant polyurethane resin layer, together with the re~,ative adhesive layer, can supply the re~uired support without havi.ng to necessarily use'the layer of calendered e:Lastomer. In fact, such are the intrins:ic mechanica~
properties of suc:h a layer of polyurethane support material that its re~uired thickness can be considerably less than that of the layer of ca].endered elastomer. It never has to ; be more than one millimeter in thickness and -thu~ provides greater advantages as regards conformance to surface irregularities.

' ~L24~5~4 This polyuretha~ laye~ has to.be of the.ali:-phatic type9 at least at the top ma~king~layer surface, in order.to have the proper weather~resistant propertiesO It needs, therefore, to be produced in the factory at high temperatureso The polyurethane layer can be so effective as to permit the elimination of the non-woven fa~ric from the com-position, at least where removable roadway marking strips :~ designed for relatively short service life are concernedO
10 Constructed in this manner, the road-marking strip consists of just the polyurethane-resin layer - opportunely formulated - made adhesive on the-bottom side.. The::fundamental characteristics of this marking-strip composition (polyurethane -resin layer and special layer, or film, of adhesive material) 15 must be its ability to co~form to roadway-surface roughness without tearing occuring at any point. In order to have this capability, it was found that the polyurethane-resin support " layer has to be quite free, in the lower part of the layer, of catadioptric elements, pigments and fillersO The upper 20 roadway-marking surface does, of course, have to have pigments, : such as, for example, titanium oxide, to the extent of not less than 9%O
The polyurethane resin, to be conformable, must also have properties of high elongation, high permanent 25 deformation, high tearing resistance and low elastic returnO
The elongation to breakage should be at least 50%, and the permanent deformation should not be less than 15%o It was found that by choosing a structure that had a high molecular weight and hi~h ~;~e~a~ impediment, such as sterically-impeded 1~4~S~

high volume aromatic rings, :the..tendency to c~ystal~iz.e was reduced and a product ha~ing the desired properties was ~ore easily obtainedO Along this line, t~e following aromatic ethoxyla.ted products gave interesting results:
bisphenol and ethylene oxide bisphenol and propylene oxide : resorcinol and ethylene oxide :; resorclnol and propylene oxide ~; n,n bis (hydroxyethyl) aniline The obtained results can be further improved and made much more conformant to the desired end product by using tri- or tetrafunctional ramifications which are made bifunctional by stopping one or two of these chains, possibly the long ones, in order to prevent the association of the polymer main moleculesu Tri- or tetra-dimensional polyalcohol molecules, bloc~ed into just:two reactive groups by means of monoisocyanates or fatty acids can be usedO Triols, having a molecular weight of from 900 to 6000, are especially effective.
:: The following are specific examples:
20 blocked with monoisocyanates:
castor oil polyester triols (mOw. up to 4000) polyether triols (m.wO up to 6000) polybutadiene triol 25 blocked with oleate:
. pentaerythrol dioleate trimethyl-propane mono-oleate .

_ 5 _ The following is an example of~ carXyi~g out the invention:
Preparation of the prepolymer:
; polyester : i000 p~
hydroxyalkylbisphenol : 800 po castor oil, partially esterified: 80Q po IPDI : 2000 pO
; TiO2 : amt~ req'd xylene : 190 p.
When producing the strip,~the prepolymer is polymerized in the ratio of 100 to 64 with the following mixture:
polyester diol : 100 p0 hydroxyalkylbisphenol : 50 p.
tinoctoate : amtO req'd Alkylbisphenol has an inelastic structure, high molecular :
volume, high steric impediment, increases breaking modulus and reduces return speed. Treated castor oil increases tear resistance, permanent deformation and reduces return speedO
Another example of the invention is as follows:
IPDI : 127 gr polypropylene glycol (m.w~ 1000): 68 gr bis-hydroxypropylbisphenol : 9 gr pentaerythritol dioIea~e : 113 gr To 100 gr of this prepolymer, the following is added:
polyethilene adipic glycol (m.w. 2000): 63 gr n,n bis-hydroxyethylaniline : 12 gr tinoctoate catalyst : amtO
req'd ~4f~5:~

The low elastic ~e.tur~.~f~e~ deformation o-this product results in improved marking-st~ip~e~icien'cy because the catadioptric glass elements in ,the strip are not easily released by t~e strip under the mechanical action produced by the tra~ficO The best way to produce the marking strip is to lay.the,liquid polyurethane ilm onto a solid self-adhesive film, whic'h is applied to release paper, and then proceed with the reticulation to harden the film~ This polyurethane film plus the self-adhesive film form a single structure 10 which has the mechanical purpose of resisting.to the action of the traffic wearO
The following is an example of a solid sel-adhesive formulation which applies to this present invention:
CARIFLEX 1107 : 100 pO
POLYSAR BUTYL : 30 p.
VISTANEX LMMH : 50 pO
PENTALIN H : 135 pO
HERCOLIN D : 30 p.
IRGA~OX 1010 : 1 p.
20~ CKR 1634 RESIN: 5 PD
The components are all melted together~
The support film can be made cheaper by applying a TDI-based film to the solid adhesive. An example of this film is:
~ 25 polyester : lono pO
hydroxyalkylbisphenol : 800 pO
castor oil, partially esterified: 800 pO
TDI : 1570 pO
TiO2 : amtO r~q'd ~'~4~51 xylene : 190 pO
This support film, as described, wi~h a thick~ess ~f, say7 2 tenths of a milimeter, is covered ~ith a film of polyuret~ane resin of the IPDI type, as descri~ed above9 which is weather resistantO Anti-skîd material is introduced into this resin film, such as car~orundum particles, for example, and catadiop-tric elements, such as, for example, glass ~eads.
The marking strips on the market today, which incorporate catadioptric elements, have the big drawback of having a short optical service life, not long enough for the specific application~ Glass catadioptric elements have a tendency to be expulsed from the strip, after a more-or-less short time, as a result of the mechanical action of the traffic wearO In this regard, we cite the final report, lS "Performance of Pre~ormed Plastic Tapes", dated October, 1982, by the Virginia Highway and Transportation Research Depart-ment.
Better results are obtained with preformed road-way-marking strips using polyurethane resin, but the results are still not satisfactoryO Of course, the expulsion of the glass catadioptric elements from the strip is not only a function of the retention capability of the film but, also, a function of the mechanical expulsion action on the element from the polyurethane resin subjected to mechanical stress.
It is evident that the sIower the elastic return and the l~ss said elastic return, the less chance there is of ex-pulsionO The most important factor, however, is the attach-ment of the catadioptric glass elements to the polyurethane resin. It has been found that organic silanes or ~2~5~gL
, orthotitanates containing a~ ~east t~o active hydrogens ~
that is, hydrogens that can react ~ith t~e iso`cyanics groups of the prepolymer ~ produce ~ilms that form a considerable bond between the film and the catadioptric elements, because silanes or orthotitanates act as chain extenders and the chains chemically bond themselves to both the glass and the urethane polymerO
The chain extenders must be at least bifuntlonalO
This is important because a monof~mctional extender will produce a product having very low mechanical characteristicsO
The active hydrogens can be of the hydroxyl type, such as in butandiol, or the amine type, such as in ethylendiamine~
Treatment of the glass catadioptric elements with either o~
the chain extenders, silane or orthotitanate, is best done in a rotary mixer at low or medium temperatureO Best results are obtained with Union Carbide Silane A 1120 or Dow Corning Silane 6020 and, for the titanate, with isopropyltriricinoil-titanateO About 0O5% Silane 1120 at 90C is applied to the beads O The beads thus coated are then immersed in the ure-thane prepolymer, which constitutes the upper layer of theroad-marking strip The silane amine groups thus bond them-selves to the isocyanics groups of the reactive mixture and form a very tenaceous silane-urethane layerO This urethane prepolymer, which has to react with the chain extender, must therefore have a slight stechiometric excessO
If the catadioptric elements are to be properly stored, they must be covered with the chain extender~ firsti:
of all, and then treated with the urethane prepolymer at 70-80Cj w~en the reaction is terminated the catadioptric ~L24~5:~

~ g elements can be storedQ
The film formed by~first covering the catadiop~
tric elements with t~e chain ext~nder:and then with the uret~ane resin has very high mechanical strength character-istics, as regards the bond created between the catadioptricelements and the urethane resin, thus malcing it more difficult for the catadioptric elements to be ejected from the uret~ane resin by the traffic wear~
It has been found that ~he polyurethane resin, as described above, works very well also for impregnating the non-woven fabric used in the production of removable roadway-marking strip and maintains its removability efficiency even after a considerable length of service (see Reissue Noc 31,669 mentioned earlier)c Since the non-woven fabric extends the service life of the roadway-marking strip, strips manufactured in this manner are characterized by having a long ser-~ice lifeO The preformed roadway~
marking strip consists, actually, of two layers of polyure-thane resin, the upper layer - which provides long marking-strip service life characteristics - being further reinforced by the protective action of the impregnated layerO
- The marking strip not only has an exceptionally long service life but also has high conformability properties as regards roadway surface roughnessO The presence of the non-woven fabric in the strip, furthermore, provides the guarantee of being able to remove the marking strip at any particular moment in its long service lifeO

s:~

When the marki~g strip ,is.~pplied using,t~e self-adhesi~e, which is do~e at ~oom temperatu-,res, remo~a~ is do~e manual~yO When the strip is:applied using a mo~ten adhesi.~e, removal is done by a machine, using,heat~ ' :5 Insertion of the non-woven fabric is best done : after ha~ing first,laid the support layer~ according to the two-layer:technique, and ~efore,laying~the markîng film layer : onto this support layerO

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A preformed roadway marking strip comprising:
(a) a polyurethane resin support film having a thickness no more than one millimeter produced under high temperature and further including:
i. an adhesive supported on the bottom side;
ii. a lower layer free of catadioptric material, pigments and fillers;
iii. an upper aliphatic layer including at least 9% titanium oxide said polyurethane having a high molecular weight and volume and having a sterical impediment providing a reduced tendency to crystalize, and said polyurethane resin film further having characteristics, as follows:
(a) high elongation to breakage, at least 50%;
(b) high permanent deformation, not less than 15%;
(c) high tearing resistance;
(d) low elastic return.

2. A preformed roadway marking strip as in Claim 1, wherein said sterical impediment is in the form of high volume aromatic rings within the molecular chain.

3. A preformed roadway marking strip as in Claim 2, wherein said high volume aromatic rings are in the form of partially blocked hydroxyl groups.