Preformed Polyurethane Roadway-Marking Strip Which Is Highly Conformant to Road Surface Roughness

The following are specific examples:

blocked with monoisocyanates:

castor oil

polyester triols (m.w. up to 4000)

polyether triols (m.w. up to 6000)

polybutadiene triol

blocked with oleate:

pentaerythrol dioleate

trimethyl-propane mono-oleate

The following is an example of carrying out the invention:

Preparation of the prepolymer:

polyester: 1000 p.

hydroxyalkylbisphenol: 800 p.

castor oil, partially esterified: 800 p.

IPDI : 2000 p.

TiO.sub.2 : 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 p.

hydroxyalkylbisphenol: 50 p.

tinoctoate: amt. 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 speed.

Another example of the invention is as follows:

IPDI: 127 gr

pblypropylene glycol (m.w. 1000): 68 gr

bis-hydroxypropylbisphenol: 9 gr

pentaerythritol dioleate: 113 gr

To 100 gr of this prepolymer, the following is added:

polyethylene adipic glycol (m.w. 2000) : 63 gr

n,n bis-hydroxyethylaniline: 12 gr

tinoctoate catalyst : amt req'd

The low elastic return after deformation of this product results in improved marking-strip efficiency because the catadioptric glass elements in the strip are not easily released by the strip under the mechanical action produced by the traffic. The best way to produce the marking strip is to lay the liquid polyurethane film onto a solid self-adhesive film, which 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 which has the mechanical purpose of resisting to the action of the traffic wear. The following is an example of a solid self-adhesive formulation which applies to this present invention:

CARIFLEX: 1107 100 p.

POLYSAR BUTYL: 30 p.

VISTANEX LMMH: 50 p.

PENTALIN H: 135 p.

HERCOLIN D: 30 p.

IRGANOX 1010: 1 p.

CKR 1634 RESIN: 5 p.

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:

polyester: 1000 p.

hydroxyalkylbisphenol: 800 p.

castor oil, partially esterified: 800 p.

TDI: 1570 p

TiO.sub.2 : amt. req'd

xylene: 190 p.

This support film, as described, with a thickness of, say, 2 tenths of a millimeter, is covered with a film of polyurethane resin of the IPDI type, as described above, which is weather resistant. Anti-skid material is introduced into this resin film, such as carborundum particles, for example, and catadioptric elements, such as, for example, glass beads.

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 wear. In this regard, we cite the final report, "Performance of Preformed Plastic Tapes", dated Oct., 1982, by the Virginia Highway and Transportation Research Department.

Better results are obtained with preformed roadway-marking strips using polyurethane resin, but the results are still not satisfactory. 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 slower the elastic return and the less said elastic return, the less chance there is of expulsion. The most important factor, however, is the attachment of the catadioptric glass elements to the polyurethane resin. It has been found that organic silanes or orthotitanates containing at least two active hydrogens--that is, hydrogens that can react with the isocyanics groups of the prepolymer--produce films 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 polymer.

The chains extenders must be at least bifunctional. This is important because a monofunctional extender will produce a product having very low mechanical characteristics. 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 of the chain extenders, silane or orthotitanate, is best done in a rotary mixer at low or medium temperature. Best results are obtained with Union Carbide Silane A 1120 or Dow Corning Silane 6020 and, for the titanate, with isopropyltriricinoiltitanate. About 0,5% Silane 1120 at 90.degree. C. is applied to the beads. The beads thus coated are then immersed in the urethane prepolymer, which constitutes the upper layer of the road-marking strip. The silane amine groups thus bond themselves to the isocyanics groups of the reactive mixture and form a very tenaceous silane-urethane layer. This urethane prepolymer, which has,; to react with the chain extender, must therefore have a slight stoichiome excess.

If the catadioptric elements are to be properly stored, they must be covered with the chain extender, first of all, and then treated with the urethane prepolymer at 70-80.degree. C.; when the reaction is terminated the catadioptric elements can be stored.

The film formed by first covering the catadioptric elements with the chain extender and then with the urethane resin has very high mechanical strength characteristics, as regards the bond created between the catadioptric elements and the urethane resin, thus making it more difficult for the catadioptric elements to be ejected from the urethane resin by the traffic wear.

It has been found that the 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 No. 31,669 mentioned earlier). Since the nonwoven fabric extends the service life of the roadway-marking strip, strips manufactured in this manner are characterized by having a long service life. The preformed roadway-marking strip consists, actually, of two layers of polyurethane resin, the upper layer--which provides long marking-strip service life characteristics-- being further reinforced by the protective action of the impregnated layer.

The marking strip not only has an exceptionally long service life but also has high conformability properties as regards roadway surface roughness. 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 life.

When the marking strip is applied using the self-adhesive, which is done at room temperatures, removal is done manually When the strip is applied using a molten adhesive, removal is done by a machine, using heat.

Insertion of the non-woven fabric is best done after having first laid the support layer, according to the two-layer technique, and before laying the marking film layer onto this support layer.