AU487397B2 - Improved road surface marking material - Google Patents

Description

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This invention relates to the art of marking road surfaces exposed to mark-obliterating traffic, and more particularly to the marking of traffic lines and other directional data upon the road surface of streets and highways, by applying and securing suitable road marking material on said road surface, whereby a marked road is provided. This art is well worked and widely known. According to prior art, traffic lines can be painted on the road surface, or formed thereon by applying molten material thereto, or also provided thereon by applying and adhesively securing a preliminarily manufactured tape material thereto. The thus formed or applied traffic line or other mark will therefore form of itself a part of the road surface and will be correspondingly subjected to the wear and progressively destructive action of traffic, particularly where such traffic includes the passage of fast and/or heavy vehicles. The problem involved in providing a road surface with traffic regulating marking having both the high visibility and non-skid properties has been extensively discussed and analyzed in applicant's prior British Patent Specification No. 1,032,813, Canadian Patent No. 754, 343 and in US Patent No. 3,399,607. There had been proposed to provide a compound marking material, the upper or exposed surface of which includes different parts arranged thereon, some of these parts being substantially smooth and suitably pigmented to provide high light reflectivity and, thus, high visibility, but having poor non-skid properties, while the remaining parts are formed of a compound having a high content of

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substantially hard and granulated components, such as sand

and quartz, to provide fairly good non-skid properties, such

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62. 67 0 n73 latter parts however providing poor visibility and being

undesirably receptive to dirt, rubber particles from vehicles'

tires and so on.

The Applicant has more recently proposed an improved

structure for forming signs on road surfaces. Such structure

has been described and claimed in co-pending Australian Patent

Specification No. 36,582/71.

According to this more advanced technology, there has

been provided a road marking material comprising an

elastomeric bese co.pcund having a smooth, substantially

planar and highly light-reflective surface adapted to face

away from the road surface, and a plurality of particles

having a hardness higher than 7 on the Mohs' hardness scale

and each including a lower portion embedded in and securely

bonded to said base compound and comprising an outer pointed

end portion, said pointed end portions being spaced from one

another by a substantial distance and imparting good anti-skid

properties to said surface. There has been described also

that such particles preferably consist of beryl or of

corundum crystals and have a particle size from one tenth to

one millimeter.

It is therefore an object.of this invention to provide

a further improved prefabricated road marking material, having

an upper surface and a plurality of upwardly turned pointed

hard particles partially extending outwardly from said

surface, the new material providing an unexpected sharp

improvement in anti-skid, wear resistance and/or high

visibility properties.

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62. 67 0 n"3 According to the present invention there is provided a

road marking material for use on a roadway surface so as

to provide a traffic regulating sign thereon, of the kind

comprising a layer including an elastomeric material, said

road marking material having a smooth upper surface with a

plurality of pointed hard particles upwardly extending above

said surface for imparting good anti-skid properties to said

surface, characterised in that a continuous upper layer

adjacent to said surface has at least part of said particles partially embedded therein, said upper layer consisting of

a polyamide resin or a polyurethane resin or a polyester

resin, compatible with said elastomeric material, said resin

being capable of wetting and having wetted said particles

when brought into contact therewith in its not set form,

said upper layer forming a bond with a base layer comprising

said elastomeric material, the bond extending through the

entire interfacial area between said upper layer and said

base layer, said particles consisting of a substance

having a hardness not less than 6 on the Mohs' Hardness

Scale, the thickness of the upper layer being such that the majority of said particles are embedded in said upper

layer for not less than half of their dimension perpendicular

to said surface.

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In other terms, the present improvement consists of

forming the upper layer of a road marking material with a

polymeric compound acting both as a binder on a substrate of

suitable known composition, which preferably includes a

rubbery copolymer (such as the composition described in

Example 2 of U.S. Patent No. 3,399,607) and as a part of the

roadable area, said layer having its thickness equal to or

greater than the average dimension of the hard particles, the

improvement comprising fitting such particles in such

polymeric -onpound before the setting thereof, so that the compound, which has wetted the particles and has ensured the

bond thereof to the marking material, forms also the upper

surface of said material.

It has been found that the anti-skid properties provide. by the said hard and pointed particles ensure the most

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62 67 0 n3 desirable traffic safety and balance the skiddish nature

of the resinous surface. It has been further surprisingly

found that a greatly improved bond between the particles and

the material is ensured.

As a matter of fact, it has been found that when a

particle has been torn off from a prior art material, the

breaking of the bond occurs between the base compound and

the coated particle. By the improvement of the invention, the

hard particles are so firmly secured into and to the upper

polymeric layer, even if not more than half of the particle

is embedded thereinto, that the bond between the layer of the

polymeric material and the substrate occurs at the entire

interface between the said polymeric and substrate layer.

It has been still further found that the presence of said

hard particles at the upper face of the upper layer provides

an unexpectedly efficient protection of said layer against

wear even if the marked road is subject to the most severe traffic.

According to a not critical but advantageous feature

of the invention, the provision of a suitable amount of

pointed hard particles in the upper polymeric layer is

complemented by the provision of an additional amount of relatively small particles of substantially hard nature,

such as micronized quartz, said latter tiny particles

providing a great improvement to the wear resistance and to

the service life of the material.

These and other objects, feature and advantages of the

invention will be made apparent as this description proceeds,

reference now being made to the accompanying drawing, wherein: FIG. I is a diagrarmatic fragmentary sectional view of 7 487.397

62.67 0 n3 the upper layer of a material embodying the principle of

ensuring anti-skid properties by causing spaced hard particles

to upwardly extend above the upper otherwise smooth and

planar face of said material;

FIG. 2 is a greatly enlarged fragmentary sectional

view of the essential upper part of a material ac6ording to

the invention;

FIG. 3 similarly illustrates a modified embodiment of

the material;

FIG. 4 similarly illustrates a material including both

hard and anti-skid particles and optical components; and

FIG. 5 is a graph wherein the results of wear tests,

carried out on various compositions and materials, are

plotted.

FIG. 1 visualizes the essential concepts and the properties of a road marking material produced according

the most advanced technology referred to above. The greatly prevailing area (up to 70 percent and even more) of the

exposed surface of the marking, laid on and secured to a

road surface (not shown) consists of a smooth, planar and

near.ly tiform surface S of a layer of a material M, made

of a wear resisting polymeric composition and having high visibility properties. As well known to those skilled in the art, such high visability properties depend from a plurality

of factors, including a suitable pigmentation. More particularly ailefficient marking, such as a lane dividing

strip or similar traffic regulating sign, is required to

remain highly visible even after long use and to be not or

very scarcely receptive to dirt and to the dark rubber particles resulting from the wear and frictional stresses of o 487.397

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vehicle tyres. Therefore, such surface S and the material M

which forms said surface should not be porous and capable of

consistently forming a smooth, not porous and planar face

during its progressive wear at least for a part of its

thickness. A material having such desirable high visibility

properties has not, unavoidably, good non-skid properties. These latter properties, that is the ability of providing

an excellent frictional resistance to tangential stress T

applied by vehicle wheels, are provided by a plurality of

spaced pointed small juttings P, the height H of which might

be of very few tenths of millimeters, provided that such

points P are made of hard material and that they are firmly

secured to the material M to resist stress T. Such stress can

be exceedingly violent,for example when a vehicle is braked

to an emergency stop or subject to intense centrifugal forces.

Such points P are formed by the upwardly extended portion of

hard particles the remaining portion of which is embedded

into the material M, below the plane defined by the surface S.

The resistance to the shear force applied in direction

T (for example) is provided by the concurrence of three

factors: the deepness to which.the particles are embedded,

that is the ratio between their outwardly extended portion

and their embedded portion,; the strength and the coherence

of the material M, and the strength of the bond or

adhesion between the particles and the mass. It has been

found that the bond between any individual particle and a

resin which coats the particle and has wetted the particle

when contacted therewith, is very good, while the bond

between the coating resin and the binder or binders included

into a conventional road marking strip composition can be 9 487,397

62,67 0 n3 defective. It is to be noted that such composition normally

includes pigments, fillers and hardeners and therefore the

binder does not form a homogeneous and completely coherent

mass.

As shown in FIG. 2, the particles C, such as hard

crystals, are embedded into a layer of material 1.1formed by

polymerized and cross-linked resin which has wetted such

particles when contacted therewith before being cross-linked

and which has a high internal molecular cohesion. The thick-

ness of said layer is at least preferably more than the

dimension D of the embedded portion of same particles, such

dimension being at least equal to the extension or height H

of same particles above the surface S, which is formed by

said polymeric material which can bind itself to a deformable

substrate (not shown) of suitable composition (such as that

described in Example 2 of U.S. Patent No. 3,399,607) at the

entire interfacial area between the upper layer and the

substrate. Said substrate may consist of a resin or binder

impregnated fabric.

As shown in FIG. 3, above the upper surface S' of the

material there are upwardly extended'exposed portions of hard

particles, to form anti-skid points P, and extremely small

points P' formed by tiny particles C' applied over or dispersed

within the upper layer. Such tiny particles provide an

unexpected resistance for the surface S, the wear of which is

drastically reduced, even if such tiny particles C' consist

of material of hardness less than 7 but preferably not less

than 6 on the MohS' Hardness Scale, such as micromized

quartz, for example.

As shown in FIG. 4, the layer of material M embeds, 48 7,3 97

62 67 0 n3 additionally to hard particles C providing the anti-skid

points P (and possibly tiny surface protective particles),

optical elements adapted to improve nighttime visibility,

such as reflex-reflective glass beads 0' and/or compound

directionally reflective transparent spheres O" having a

monolayer of reflective beads thereabout. Such optical

elements are known in the art and form no part of this

invention, except as to the fact of being partially embedded

into and firmly secured to a layer M of a polymeric material

which has wetted such elements when contacted therewith and

which is adapted for interfacial adhesion and bond with a

substrate of at least partial elastomeric or deformable

nature, for its adaptation to the road surface uneveness.

Several tests have been carried on to ascertain the

unexpected results of the invention. Such tests have been

carried out by actually simulating the behaviour of the

marked road under heavy traffic by rolling loaded conventional

vehicles' wheels, at different speeds and at various braked

and steered conditions, along a circular path covered with a

highway pavement on which samples of the road marking

material have been adhesively secured. The tests have been

performed also in various ambient conditions to simulate hot

and cold climates, rain and severe weather in general.

Steady good results have been obtained by a material

the upper layer of which consists of polyurethane resin

(specifically, use has been made of the commercial resin

"Desmodur cross-linked with "Desmophen 800", manufactured

and sold by Fardenfabriken Bayer containing 12 percent

by weight titanium dioxide. Comparable results have, however,

been obtained by making use of other di- and tri-isocyanates,

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62 67 0 n3 cross-linked with hydroxy group including polyesters and

polymers, as well as of polyterephthalic resins. In the graph of FIG. 5 the progressive wear is plotted as a function of time in months of simulated severe actual service on a highway. Curves A/5 and B/5 refer to materials including an upper layer consisting of the above

polyurethane resin incorporating 10 percent by weight corundem

and quartz crystals of average size of 0.5 mm. Curve illustrates the resistance to wear of a similar compound,

which includes 35 percent by weight quartz crystals (hardness about) of nearly microscopical granulation (the commercial "micronized quartz") only. The curves D/5, E/5 and F/5 indicate the wear resistance,

under similar conditions, of the best available prior art.

composition and including a binder of elastomeric nature (the elastoplastic compound described in the French Patent No.

2,097,941 and of Canadian Patent No. 929,696) to which there have been added 10 percent by weight of the corundum particles

of sample of curve A/5 and respectively 10 percent by weight

of the quartz particles of the material of curve B/5, and percent by weight of the micronized quartz of the material

of curve

From a comparison of the curves of the graph the

importance of embedding into and securing the hard particles

to a continuous layer of a polymeric resin having both the

properties of wetting the particles when contacted therewith

and of having a very high internal molecular cohesion, are evident. The resistance to wear of the material of the

invention, even if provided with anti-skid particles of quartz (curve the hardness of which is comparable with that of 12 48 7.3 97

62, 67 0 n3 some fillers of the rubbery compounds of tires and that of

sand and powdery materials which can be found on highways,

is sharply greater than that of a conventional material

including particles of the hardest material, that is corundum

crystals (curve

The non-skid properties of the materials of curves

and B/5 were comparable with that of the materials of curves

and respectively E/5 and F/5, as measured on new and

freshly laid-down material. As soon as the materials were

subject to a wear over 150 to 200 microns (the scale of

FIG. 5) a substantial drop has been experienced in the

comparison samples of curves D/5 and E/5. It has been found

that such drop has been promoted by the fact that as soon as

the wear of surface S led to the uncovering of about one

third of the height of the particles, most of such particles

were torn off from the material including an elastomeric

binder and were no longer effective as anti-skid elements,

while in the material consisting of the above described

polymeric resin, most of the particles which, during the

progressive wear of the material had been more than half

exposed over the surface S, were still firmly bound to the

material and efficiently acting as anti-skid elements.

Therefore, in the material of the invention, the density or

population of the spaced anti-skid elements does not

substantially decrease during wear, until actual destruction

of the material upper layer.

It is evident that the proper combination of anti-skid

prcperty and of high visibility property, this latter property

including scarce dirt retentiveness, depends on the density

or population of the hard points P on the surface S. The

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62. 67 0 n3 above indicated percentages indicate a desirable provision

of at least 30 points per square centimeter, a higher number

up to 50 and more points being generally preferred.

Further, a sharp improvement has been experienced when

tests have been performed by simulating the dynamic action of

vehicles travelling at high but currently attainable speed.

The results of said tests, confirmed by actual experimentation

on a highway, have shown that the vehicle speed has a marked

influence in tearing off particles from the material. This

aspect of the behaviour of road surface marking materials

has not apparently been thoroughly taken into account by the' prior art.

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Claims (1)

1. 62 67 0 n3 The claims defining the invention are as follows:-

   i. A road marking material for use on a roadway surface so as

   to provide a traffic regulating sign thereon, of the kind

   comprising a layer including an elastomeric material, said

   road marking material having a smooth upper surface with a

   plurality of pointed hard particles upwardly extending above

   said surface for imparting good anti-skid properties to said

   surface, characterised in that a continuous upper layer adjacent to said surface has at least part of said particles

   partially embedded therein, said upper layer consisting of

   a polyamide resin or a polyurethane resin or a polyester

   resin, compatible with said elastomeric material, said resin

   being capable of wetting and having wetted said particles

   when brought into contact therewith in its not set form,

   said upper layer forming a bond with a base layer comprising

   said elastomeric material, the bond extending through the

   entire interfacial area between said upper layer and said

   base layer, said particles consisting of a substance

   having a hardness not less than 6 on the Mohs' Hardness

   Scale, the thickness of the upper layer being such that

   the majority of said particles are embedded in said upper

   layer for not less than half of their dimension perpendicular to said surface.

   2. A material as defined in claim i, wherein said particles

   are present in an amount of at least 30 per square centimeter

   of surface.

   3. A material as defined in claim 1 wherein the said polymeric

   resin consists of a polyisocyanate cross-linked with hydroxy

   groups.

   4. A material as defined in any preceding claim, wherein

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   62,67 0n3 said hard particles comprise crystals of average dimensions

   of about 0.5 millimeter.

   A material as defined in claim 4, wherein said crystals

   consist of quartz.

   6. A material as defined in claim 4, wherein said crystals

   consist of beryl or corundum.

   7. A material as defined in claim 1 or claim 2, wherein

   said particles comprise tiny crystals of micronized granulation.

   8. A material as defined in claim 7, wherein said

   particles comprise commercial micronized quartz.

   9. A material as defined in any preceding claim, wherein

   said layer comprises at least 10 percent by weight of said

   hard particles.

   A material as defined in claim 7, wherein said layer

   comprises at least 35 percent of said tiny crystals.

   11. An improved road marking material substantially as

   hereinbefore described with reference to any one of Figures

   1 to 4 of the accompanying drawings.

   .Dated this 23rd day of September 1977

   LUDWIG EIGENMANN By his Patent Attorneys DAVIES COLLISON

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