US3782843A

US3782843A - Road surface marking material and marked road

Info

Publication number: US3782843A
Application number: US00153218A
Authority: US
Inventors: L Eigenmann
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1970-06-16
Filing date: 1971-06-15
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01
Also published as: FR2097941A5; SE361694B; CA929696A; DE2130529A1; JPS5420778B1; BE768577A; GB1359036A; NL7108294A

Abstract

The disclosure describes the provision on the pavement of streets and highways, of traffic regulating lines and signs having an upper surface exposed to traffic and consisting of the upper face of a layer secured on and to said pavement, said surface being essentially planar, smooth, neither receptive nor retentive of dirt and having high light reflectivity. A plurality of protuberances jointly covering not more than 10, and preferably not more than 5, percent of the area of said surface are spacedly arranged thereon, each protuberance having a sharp tip formed by the upwardly projecting portion of crystal particles, such as corundum of hardness greater than value 7 of the Mohs'' Scale and firmly secured to said layer, thereby providing non-skid properties to said upper surface.

Description

United States Patent 1 Eigenmann Jan. 1,1974

1 1 ROAD SURFACE MARKING MATERIAL AND MARKED ROAD [21] Appl. No.: 153,218

[30] Foreign Application Priority Data June 16, 1970 Italy 26063 A/7O [52] US. Cl. 404/9 [51] Int. Cl E0lf 9/00 [58] Field of Search 94/5, 1.5, 22; 404/9 [56] References Cited UNITED STATES PATENTS 2,948,201 8/1960 Nagin 94/5 1,986,591 1/1935 Meyer 94/l.5

2,706,936 4/1955 Willson 94/5 2,330,365 9/1943 Jackson 117/26 2,216,250 10/1940 Nelson 94/5 2,246,898 6/1941 Sayre 94/5 2,294,491 9/1942 Walker 94/5 X 3,334,555 8/1967 Nagin.... 94/5 X 3,396,641 8/1968 Welty 94/22 3,565,661 2/1971 Harrison 117/9 3,459,106 8/1969 Johnson 94/22 X Primary Examiner-Nile C. Byers, Jr. Attorney-Michael S. Striker [5 7] ABSTRACT The disclosure describes the provision on the pavement of streets and highways, of traffic regulating lines and signs having an upper surface exposed to traffic and consisting of the upper face of a layer secured on and to said pavement, said surface being essentially planar, smooth, neither receptive nor retentive of dirt and having high light reflectivity. A plurality of protuberances jointly covering not more than 10, and preferably not more than 5, percent of the area of said surface are spacedly arranged thereon, each protuberance having a sharp tip formed by the upwardly projecting portion of crystal particles, such as corundum of hardness greater than value 7 of the Mohs Scale and firmly secured to said layer, thereby providing non-skid properties to said upper surface.

16 Claims, 9 Drawing Figures PATENTEBJM 1 m4 3.782.843

sum

2 or 2 INVENTOR. w 016 Ell't'U/MA ROAD SURFACE MARKING MATERIAL AND MARKED ROAD BACKGROUND OF THE INVENTION This invention relates to the art of marking surfaces which are exposed to mark-obliterating traffic, and more particularly to the marking of traffic lines and other directional data upon the pavement of streets and highways, by applying and securing road marking material on said pavement, whereby a marked road is provided.

This art is a well worked one and widely known. The marks, most commonly traffic lines, can be painted on the road surface or pavement, formed thereon by applying molten material thereto, or provided thereon by applying and adhesively securing 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 fast and/or heavy vehicles. This action is most severe when the vehicles are accelerating, braking and steering on the part of said roadway surface formed by the traffic line which, therefore, most also possess fairly good non-skid properties for safety of traffic. On the other hand, the very purpose of such markings is to provide directional data to motorists. Consequently, such pavement and traffic data signs must be easily visible to motorists and be capable of maintaining such visibility for a long service period even if substantially worn.

The problems involved in providing a roadway surface marking material having both high visibility and good non-skid properties have been discussed and analysed in my prior British Pat. specification No. 1,032,813, Canadian Pat. No. 754,343 and, more extensively, in U.S. Pat. No. 3,399,607. Reference is herein made to my said prior patent specifications for more complete knowledge of the prior art which is most pertinent to this invention. Further, in these prior patent specifications I have proposed a solution for such problems by providing 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 pretty hard and granulated components, such as sand and quartz, to provide fairly good non-skid properties, such latter parts, however, providing poor visibility.

Extensive experimentation with prior art materials has however, led to the finding that the problem of preventing the skidding of vehicles upon a fairly visible road pavement marking has not been satisfactorily solved. The conventionally used granulated materials and some of the fillers in the rubber compositions of the vehicle tire-shoes or treads can include components having a hardness of up to value 7 of the Mohs scale and, therefore, such components can abrade the marking material components at the surface of the traffic regulating sign. Further, the closely spaced and small cavities existing between the granules at the surface of the sign readily accept and retain dirt, particularly the small rubber particles detached from the vehicle tire treads, and such a surface will rapidly darken and, in addition, is very difficult to clean.

It is, therefore, an object of this invention to provide a new and surprisingly advantageous road pavement marking material which provides, in service, a road surface having both good non-skid properties and high visibility. Further, the new material of the invention is distinguished in that it has an essentially uniform surface possessing, both good non-skid and light reflective properties, is substantially non-receptive to dirt and dirt particles, and is more wear resistant than conventional road pavement marking materials when in' service, even when subjected to the most severe traffic abuse, abrasive and shearing forces.

A further object of this invention is to provide a new and advantageous marked road having a road surface, part of which is formed by the upper or exposed surface of a layer of predetermined configuration for providing a traffic regulating line or other sign, the said upper surface being essentially planar, smooth and so colored to provide high light reflectivity, that is to be properly visible to motorists, and being also non-skid, that is, having a suitably high adherence coefficient.

BRIEF SUMMARY OF THE INVENTION According to the invention, in its broadest aspect, the new material comprises a base compound adapted to provide, when applied, secured and set on a road pavement so as to form a traffic regulating line or sign, an essentially compact, smooth and suitably pigmented surface having high light reflective properties (that is a highly visible surface). The new material also comprises a minor amount of hard particles, each of which projects, in part, above said surface so as to form spaced biting points thereon. The particles are advantageously formed from crystals having a hardness substantially higher than the value 7 of the Mohs Scale, and preferably not less than the value 8 of this scale. The protuberances formed by said points, taken jointly, should cover no more than 10 percent and, preferably, no more than 5 percent of said surface. Each one of the particles is intimately contacted by a binder which wets the particle when contacted therewith and which forms part of or is compatible with, the binder component or components of the said base compound.

Preferably, the said particles consist of corundum (Al O hardness 9). Other minerals can, however, be used, such as beryl (Be Al (SiO hardness 8) and other crystals or crystallizable compounds which can be found in nature or man-made, provided that they have a hardness substantially above the value 7 of the Mohs Scale and have very sharp edges and pointed ends.

Further, the average dimension of each particle should preferably be not less than 0.1 millimeter and not substantially greater than 1 millimeter. Taking into account the cost of large crystals and unexpected findings of the invention, as explained below, dimensions from 0.5 to 0.8 millimeter and averaging about 0.7 millimeter have been found preferable. In view of the same consideration and findings, the content of the particles in the base compound forming at least the upper layer of the material in service on the road pavement comprises between 5 percent and 20 percent by weight, preferably about 10 percent by weight, of said base compound.

As stated above, the particles must be contacted by and maintained in intimate contact with a binder which, when contact is made, can wet the surfaces of the crystals. A number of compounds are suitable for use as binders. Preferably, the binder is selected from the group consisting of polyester resins, acrylic and metacrylic resins, polyvinyl butyrals, and, most advantageously epoxy resins. Inorganic binders can also be used, such as, for example, silicate binders added to chlorinated rubber latex.

The marked road obtained by forming or applying thereon a layer of a marking material as above comprises, therefore, a traffic regulating line or sign having an essentially planar, smooth, substantially compact surface which is highly visible and neither receptive to nor retentive of dirt, said surface being, however, interrupted by spaced protuberances having sharp and pointed tips, the said protuberances not covering more than 10 percent and, preferably, not more than 5 percent, of the entire surface of the line or sign, the said tips being formed by upwardly projecting portions of crystal particles which are partly embedded and firmly secured within the layer and which have a hardness greater than 7 and, preferably, greater than 8 on the Mohs Scale.

These and other important aspects, features and advantages of the invention will now be made fully apparent by reference to the accompanying drawings.

THE VIEWS OF THE DRAWINGS FIGS. 1 to 4 inclusive are fragmentary and purely diagrammatical vertical sectional views of surface portions of roadway pavement marking materials having different surface characteristics;

FIG. 5 is a fragmentary sectional view of a material according to the invention and produced in the form of a substantially plastic tape; and

FIGS. 6 to 9 are graphs wherein certain findings, effects and features of the invention are visualized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 through 4 inclusive, FIG. 1 illustrates a purely theoretical surface S, which is supposed to be perfectly planar, smooth and compact, and comprises the upper face of a suitable pigmented and compounded layer made by painting, or forming or laying a tape material on a roadway pavement, said material comprising binder, filler and pigment components for providing a clear coloured (such as white) traffic regulating sign capable of reasonably resisting traffic. A surface such as S above is neither receptive to nor retentive of dirt, rubber particles and so on, which are readily removed by wind, rain and traffic. It ensures good daytime and nighttime visibility until the marking material is noticeably destroyed.

On the other hand, such a surface S cannot provide a suitable adherence for the vehicles tire treads. It is slippery, and particularly so when wet. That is, it does not possess that non-skid property which is essential for ensuring safe movement and control of vehicles which travel rapidly thereon.

FIG. 2 illustrates a surface S, which is supposed to be the best, according to current art, for providing good adherence, that is, which is supposed to possess the best non-skid properties available from the current art. Such a surface S, is rough, that is, it can be assumed to comprise a plurality of closely spaced points P which are supposed to provide a grip for the vehicles wheels. A surface such as S, can be provided, according to the art, by a material including a large amount of a granulated filler, such as sand. Even if a suitably colored, pig mented and compounded material is used for producing a white or clear traffic regulating line or sign provided with such a rough surface, said surface will become dark and very poorly visible in a few days or weeks under heavy traffic, because the cavities between the points P and receptive to and retentive of dirt and rubber particles which fill such cavities such as indicated at A in FIG. 2.

Additionally, the points P will be more or less quickly erased and rounded off by the traffic, whereby a surface such as S, will become progressively less nonskid without appreciable improvement of its poor visibility.

FIG. 3 diagrammatically illustrates a more realistic surface S which is generally planar and smooth as the surface S of FIG. 1, but not completely compacted. It has minor cavities positioned here and there, in which dirt is collected and retained. If the sum of the surface areas of such cavities does not amount to more than 10 percent or, preferably, 5 percent of the entire surface S its visibility will not be substantially impaired. To provide a roadway pavement marking material adapted to form a surface such as at S and providing very good visibility as well as fair resistance to traffic and to weathering and, generally, possessing any desirable property except for a good adherence coefficient, is well within the knowledge of those skilled in the art.

FIG. 4 broadly illustrates the concept of the invention. There is provided a non-skid, high visibility surface Sp having percent, at least, of its area formed by a planar, smooth and satisfyingly compact pigmented surface S, with less than 10 percent of its area consisting of spaced protuberances, each comprising a sharp point P of a substance harder than 7 on the Mohs Scale and firmly secured to the body of the material. The prevailing planar surface S is pigmented and formed from a compound adapted to provide the desired high visibility and, since the surface S is neither receptive to nor retentive of dirt, it maintains these desirable properties so long as the sign remains substantially sound. Well sharpened points P, covering about 2 percent of the entire surface Sp, have been proved to ensure a quite satisfying adherence, such as an adherence coefficient of over 40 when defined in terms of angle to the horizontal at which a force, corresponding to the weight applied to a loaded tire wheel, causing skidding (such as in direction T) of said wheel along the surface under test is directed.

FIG. 5 illustrates an example of the manner in which such an improved surface Sp of the invention can be provided. In the body M of a suitably compounded and pigmented road marking tape material providing the desired high visibility prevailing surface portion S, there is embedded and uniformly dispersed nearly 10 percent by weight of corundum particles or crystals C. The greatest dimension of said particles C averages 0.7 millimeter (compare the scale accompanying FIG. 5). Each particle C is enclosed within a thin but adherent coating L of a binder which wets the particle when applied thereto, and which is compatible with the components of the base body M. Where the particles C project above the planar surface S, their coatings L will life of the traffic regulating sign. As the thickness of the sign-forming material decreases, the underlying particles C will appear on the surface, thus maintaining the non-skid properties. Additionally, it has been found that, upon wearing of base body M, only some of the particles C are torn off and lost whereas the remainder are pressed and fitted into the base body thereby increasing the number of the points. As a matter of fact, it has been surprisingly found that the non-skid properties of a material according to the invention can improve upon actual use and service on the road.

Certain further aspects and features of the invention will now be briefly discussed with reference to the graphs of FIGS. 6 to 9 inclusive.

' FIG. 6 illustrates how the use of very hard particles has improved the life of the material. Curve I/6 indicates the percent decrease of the thickness (percent Ts), which was originally 1.8 mm., of one of the best available tape materials, which has been improved by the addition of 10 percent by weight of corundum particles (10 percent C), upon extended service under heavy traffic, the length of service being indicated in terms of months (ms) on the abscissa. Curve II/6 refers to a similar material wherein the particles, in the same amount and of the same dimensions (averaging 0.7 millimeters), were of quartz (I percent Q). The durability of the material is more than doubled when corundum particles are used instead of quartz particles.

FIG. 7 illustrates the importance of an intimate and effective binding of the particles to the base compound. Curve I/7 indicates the proportional decrease in roughness (R), in terms of adherence coefficient, of the material of curve [/6 above during months (ms) of use in comparison with curve II/7 which refers to the same material, but wherein the particles had not been properly wetted by the binder when first brought into contact therewith.

FIG. 8 illustrates the effect of the dimensions of the crystals, in millimeters (mm.C), upon the roughness (R) or adherence coefficient; the curves [/8 and 11/8 relate to material including 10 percent by weight of corundum particles refer to freshly applied material and to material which had been in service for 12 months, respectively. It is seen that while smaller crystals provide for a very good adherence in a new material, bigger crystals averaging 0.7 millimeters allow a good adherence to be maintained over an extended service period whereas the use of still bigger but costly crystals can be considered as superfluous.

The graph of FIG. 9 has a particular interest because it illustrates that it is advantageous not to have the points P too closely spaced. It relates the decrease in the grade of whiteness (W, measured according to the Grey Scale British Standard, BS 2662/61) of the surface Sp (FIG. of a material to the percentage by weight (percent C) of corundum particles contained in the mterial, the particles having an average dimension of 0.7 millimeter. Curve I/9 refers to freshly laid materials and curve II/9 refers to the same materials after one year of service under severe traffic. It is seen that by limiting the corundum content to less than about 15 percent and, preferably, to less than about percent (which is quite a bit in excess of the amount required for ensuring very good adherence) a material capable of maintaining a very good visibility upon extended use can be provided. This is evidently a result of the fact that proportionately large spaces are formed between points P which are not too closely spaced and the fact that the planar surface S is neither receptive to nor retentive of dirt.

As stated above, nearly any good compound adapted for providing a high visibility traffic regulating sign on a roadway pavement can be improved according to the invention by adding and binding thereto from 5 percent to 15 percent and, preferably, about 10 percent of very hard particles, as above. For example, such improved materials could be provided as follows: Example I A road marking tape material to be adhesively secured on a suitably prepared roadway pavement can be produced from the following composition, by weight:

Butadiene-acrylonitrile copolymer, having The above composition is actually a modification of Example 2 described in my prior U.S. Pat. No. 3,399,607, where the composition of the High reflectivity base strip component has been indicated. The modification resides in the fact that, while in the prior art the filler materials comprised 28 parts by weight of micromized calcium carbonate, 14 parts of such carbonate has been substituted for by a corresponding amount, by weight, of resin coated corundum crystals. This modification confirms that a good prior art material, suitably compounded for providing the most desirable visibility but having an undesirably low adherence coefficient, can be surprisingly improved, as far as this latter feature and property is concerned, by the addition of very hard crystals which are capable of forming sharp points.

EXAMPLE II Traffic regulating lines and signs can be made by painting the roadway pavement with a paint of the following composition:

Epoxy resin (such as ARALDITE LY 556, by

To such a base paint can be added about 10 percent by weight of corundum as above, the corundum not requiring a coating because the resin of the paint wets the crystals. Similarly, polyester resin based, metacrylic resin based, polyester polyamide based and also chlorinated rubber based paints can be improved by the addition of crystals having a hardness well above the value 7 of the Mohs Scale.

While the invention has been described and shown with reference to a few forms and embodiments thereof, it is obvious that the invention itself is not limited to the very details shown, and that further modifications and variations thereof will be,obvious to those skilled in the art.

I claim:

1. A marker, particularly for use on a roadway pavement so as to provide a traffic regulating indicium, comprising a base compound including a first binder and having a smooth, substantially planar and highly light-reflective surface adapted to face away from said pavement; a plurality of particles securely bonded to said base compound and each having a largest dimension between substantially 0.1 and 1 millimeters and a hardness substantially higher than 7 on the Mohs" Hardness Scale, at least some of said particles including an upper portion extending outwardly from said surface and comprising a pointed end portion, said end portions being spaced from one another by a substantial distance and imparting good anti-skid properties to said surface, and said upper portions together constituting at most 10% of the total area of sai d sur face, whereby the light-reflectivity of sai d marker is high due to the small fraction of the total area of said highly light-reflective surface constituted by said upper portions, and the dirt-retentivity of said marker is low due to the substantial spacing between said end portions which makes it difficult for dirt to be retained in the fiat-bottomed recesses between said end portions; and

,a second binder intimately contacting said particles,

said second binder wetting said particles when contacted therewith and being compatible with said first binder.

2. A marker as defined in claim 1, wherein at least some of said particles comprise a-crystalline substance having a hardness of at least 8 on the Mohs Hardness Scale.

3. A marker as defined in claim 1, wherein at least some of said particles comprise a crystalline substance having a hardness of at least 9 on the Mohs Hardness Scale.

4. A marker as defined in claim 1, wherein at least some of said particles are selected from the group consisting of berylium and corundum.

5. A marker as defined in claim 1, wherein said largest dimension is substantially 0.50.8 millimeters, and the average being substantially 0.7 millimeters.

6. A marker as defined in claim 1, wherein said particles comprise substantially -20 percent by weight of said marker.

7. A marker as defined in claim 6, wherein said particles comprise substantially 10 percent by weightof said marker.

8. A marker as defined in claim 1, wherein said second binder is selected from the group consisting of epoxy, resins, polyester resins, acrylic resins, metacrylic resins, polyvinyl butyral and inorganic binders added to chlorinated rubber.

9. A marker as defined in claim 1, said base compound being in the form of a tape; and wherein said second binder entirely coats said particles, the thus coated particles being dispersed within said base tape.

10. A marker as defined in claim 1, said base compound being a paint; and wherein said paint comprises said second binder as a binder component thereof.

11. A marked road, comprising a roadway pavement; and at least one traffic regulating indicium provided on said pavement and including a layer of a base compound having a smooth, substantially planar and highly light-reflective upper surface, said indicium further including a plurality of particles each having a largest dimension between substantially 0.1 and 1 millimeters and a hardness substantially higher than 7 on the Mohs Hardness Scale securely bonded to said layer, at least some of said particles having an upper portion projecting above said upper surface and comprising a pointed end portion, said end portions being spaced from one another by a substantial distance and imparting good anti-skid properties to said upper surface, and said upper portions together constituting at most 10 percent of the total area of said upper surface, whereby the light-reflectivity of said indicium is high due to the small fraction of the total area of said highly lightreflective upper surface constituted by said upper portions, and the dirt-retentivity of said indicium is low due to the substantial spacing between said end portions which makes it difficult for dirt to be retained in the flat-bottomed recesses between said end portions.

12. A marked road as defined in claim 11, said layer being in the form of a tape; and further comprising adhesive means for adhesively securing said layer to said pavement.

13. A marked road as defined in claim 12; further comprising a binder material; and wherein said binder material entirely coats said particles, the thus coated particles being dispersed within said tape, and said binder material being adapted to be removed from said end portions by the wearing actionyof trafiic.

14. A marked road as defined in claim 11, said layer being a painted layer; and further comprising a binder component in said painted layer, said particles being dispersed within said painted layer and bonded thereto by said binder component.

15. A marked road as defined in claim 11, wherein said upper portions together constitute at most 5 percent of the total area of said upper surface.

16. A marked road as defined in claim 11, wherein said particles comprise corundum particles.

Claims

1. A marker, particularly for use on a roadway pavement so as to provide a traffic regulating indicium, comprising a base compound including a first binder and having a smooth, substantially planar and highly light-reflective surface adapted to face away from said pavement; a plurality of particles securely bonded to said base compound and each having a largest dimension between substantially 0.1 and 1 millimeters and a hardness substantially higher than 7 on the Mohs'' Hardness Scale, at least some of said particles including an upper portion extending outwardly from said surface and comprising a pointed end portion, said end portions being spaced from one another by a substantial distance and imparting good anti-skid properties to said surface, and said upper portions together constituting at most 10% of the total area of said surface, whereby the light-reflectivity of said marker is high due to the small fraction of the total area of said highly light-reflective surface constituted by said upper portions, and the dirt-retentivity of said marker is low due to the substantial spacing between said end portions which makes it difficult for dirt to be retained in the flat-bottomed recesses between said end portions; and a second binder intimately contacting said particles, said second binder wetting said particles when contacted therewith and being compatible with said first binder.

2. A marker as defined in claim 1, whErein at least some of said particles comprise a crystalline substance having a hardness of at least 8 on the Mohs'' Hardness Scale.

3. A marker as defined in claim 1, wherein at least some of said particles comprise a crystalline substance having a hardness of at least 9 on the Mohs'' Hardness Scale.

5. A marker as defined in claim 1, wherein said largest dimension is substantially 0.5-0.8 millimeters, the average being substantially 0.7 millimeters.

6. A marker as defined in claim 1, wherein said particles comprise substantially 5-20 percent by weight of said marker.

7. A marker as defined in claim 6, wherein said particles comprise substantially 10 percent by weight of said marker.

11. A marked road, comprising a roadway pavement; and at least one traffic regulating indicium provided on said pavement and including a layer of a base compound having a smooth, substantially planar and highly light-reflective upper surface, said indicium further including a plurality of particles each having a largest dimension between substantially 0.1 and 1 millimeters and a hardness substantially higher than 7 on the Mohs'' Hardness Scale securely bonded to said layer, at least some of said particles having an upper portion projecting above said upper surface and comprising a pointed end portion, said end portions being spaced from one another by a substantial distance and imparting good anti-skid properties to said upper surface, and said upper portions together constituting at most 10 percent of the total area of said upper surface, whereby the light-reflectivity of said indicium is high due to the small fraction of the total area of said highly light-reflective upper surface constituted by said upper portions, and the dirt-retentivity of said indicium is low due to the substantial spacing between said end portions which makes it difficult for dirt to be retained in the flat-bottomed recesses between said end portions.

13. A marked road as defined in claim 12; further comprising a binder material; and wherein said binder material entirely coats said particles, the thus coated particles being dispersed within said tape, and said binder material being adapted to be removed from said end portions by the wearing action of traffic.