GB2113234A

GB2113234A - Method of marking a trafficway surface

Info

Publication number: GB2113234A
Application number: GB08301040A
Authority: GB
Inventors: Norman Smith
Original assignee: SOMERFORD PLASTICS Ltd
Current assignee: SOMERFORD PLASTICS Ltd
Priority date: 1982-01-14
Filing date: 1983-01-14
Publication date: 1983-08-03
Also published as: GB8301040D0

Abstract

A trafficway surface (e.g. road, taxiway) is marked by applying a polyurethane thereto. The polyurethane may be produced by impingement mixing of two or more polyurethane forming components. One component may be MDI or MDI modified with a glycol or amine and the other component may be a polyol or an alkoxylated polyol. A hydroxy or amine cross-linking agent may be incorporated in one of the components as may a catalyst.

Description

SPECIFICATION Method of marking a trafficway surface This invention relates to a method of marking a trafficway surface.

The term trafficway surface as used herein covers any area on which traffic may move as well as regions adjacent such areas. The term trafficway surface thus covers areas such as car parks, pavements etc. It should also be understood that the term 'traffic' covers, in addition to cars, lorries and buses, other types of vehicle which move along the ground. Thus the term 'trafficway surface' covers, in addition to roads, areas such as aircraft taxiways, runways etc.

The application of markings to a trafficway surface is of course well known. Such markings take the form of, for example, la-ne markings, hazard warning lines, "no parking" restrictions, parking bays for vehicles etc.

Hitherto, the compositions used for marking trafficway surfaces by spray application have required two vehicles for providing the marking on the traffic-way. This obviously represents a considerable expense both in capital outlay and the labour involved in applying the marking.

It is an object of this invention to obviate or mitigate the abovementioned disadvantages.

According to the present invention there is provided a method of marking a trafficway surface wherein the marking comprises a polyurethane.

Preferably the polyurethane is sprayed onto the highway surface, e.g. from a spray unit provided on a vehicle which travels along the trafficway applying the marking as required.

Preferably the polyurehane is produced by mixing together immediately prior to spraying two or more components which react together preferably practically instantaneously, to give the desired polyurethane. The polyurethane may be produced by impingement mixing of the polyurethane forming components in a suitable mixing chamber from which mixing chamber the product is immediately sprayed. In this case, the reactants are oniy mixed together during the time that a marking is being laid down.

The reactants to be mixed together to produce the polyurethane may comprises a di- or higher functionality isocyanate and a polyol.

The isocyanate may be any isocyanate normally used for polyurethane production but it is preferred to use diphenyl methane diisocyanate (MDI) or an isocyanate based thereon. Thus MDI may be used in any one of its various forms, e.g.

pure, polymeric or a variant formed by reaction of MDI with a polylol or amine.

The preferred isocyanate is a glycol modified MDI such as available from Imperical Chemical Industries plc. under the Registered Trade Mark Suprasec VM30.

Solid isocyanates should be dissolved in a suitable solvent to permit the mixing stage to be effected.

The polyol may be, for example, a diol or triol and may be alkoxylated to form, for example, ethylene oxide or propylene oxide based polyether derivatives. Most preferably the polyol is, or is based on, high molecular weight triols with a hydroxyl value of 25 to 60.

The preferred polyol is an ethylene oxide tipped triol.

Preferably also a cross-linking agent is used in addition to the polyol and the isocyanate. For preference the cross-linking agent, when used, is a hydroxy or amino compound. The cross-linking compound preferably has a functionality of 2 to 4 and a hydroxyi value of 300 to 2,000. Examples of suitable cross-linking agents include triethanolamine, ethylene glycol, glycerol, butane diol, alkoxylated ethylene diamine, and diethylene toluene diamine.

Normally a catalyst is added to one component of the polyurethane forming system (i.e. polyol or isocyanate). These may be conventional organometallic or amine catalysts, for example stannous octanoate, dibutyl tin dilaurate, dimethyl cyclohexylamine or DABCO. The catalyst may be used in conventional amounts.

Other conventional polyurethane additives, e.g.

silicone surfactants, fire retardants etc., may be incorporated in one or other of the components to be reacted together.

Additionally, a blowing agent (e.g. fluorocarbon (11) or water) may be included to produce a low degree of foaming to give the final polyurethane composition a degree of resilience.

Pigments as required may be dispersed in one of the reactants, preferably the polyol, before mixing is effected.

When a pigment is used, it is preferably incorporated in an amount of 2 to 10% by weight of the polyurehane. Exampies of pigments are titanium dioxide (white) and lead chromate (yeilow).

Conventional components such as reflective materials (e.g. glass beads) and anti-skid materials e.g. calcined flint) may be applied to the polyurethane marking as soon as it has been applied to the trafficway.

The apparatus for producing and applying the polyurethane may comprise a spray gun in which the reactants for producing the desired polyurethane are mixed and then immediately sprayed onto the surface to be marked. The reactants are supplied separately to the gun by means of, for example, respective double-acting proportioning pumps each of which deliver one of the ingredients to the gun in the correct ratio relative to the or each other ingredient.

The apparatus is preferably such that, when the gun is closed (i.e. the reactants are not being mixed and no product is being ejected) the pumps 'stall' so that they no longer pump the respective reactants to the gun. However, as soon as the gun is opened, mixing immediately recommences.

Heaters may be installed between each proportioning pump and the gun to ensure that each reactant is at the correct viscosity for supply to, and mixing in, the gun.

The gun may be of the type having a mixing chamber with ports for the supply to the chamber of each reactant such that the reactants impinge upon each other when admitted to the chamber.

Such a gun may include a cylindrical mixing chamber (into which the ports open) and a valving rod slidable to open and close the ports when the gun is in an operating or shut-down condition respectively. The chamber may also have an outlet adapted to produce a sprayed pattern of desired configuration, e.g. a line of a particular width. The valving rod should make positive contact with the inside surface of the chamber and of the outlet such that, when the gun is shutoff by moving the rod to close the ports, residual mixed material is purged from the chamber and the outlet since such residual material may inpair a subsequent mixing operation or cause deformation of the pattern of the polyurethane being sprayed.

Suitable apparatus for effecting the mixing and spraying is the H-ll Proportioner and gun available from Gusmer Corporation of New Jersey, U.S.A.

In one specific example of the invention the above-described apparatus may be used to produce a road marking from Suprasec VM20 (isocyanate) and pigment containing polyol composition comprising an ethylene oxide tipped triol containing diethylene toluene diamine.

Dibutyl tin dilaurate is used as catalyst.

The polyol composition and isocyanate are supplied to the mixing chamber by their respective proportioning pumps in a volume ratio of polyol composition:isocyanate of 4:1.

The advantages of the present invention are that only one vehicle is required to apply the marking, as compared to two vehicles for conventional spray applied thermoplastic road - marking compositions, and also that the polyurethane retains its flexibility and cohesive strength under a wide range of temperature conditions which allows the composition to be used in widely differing climates.

Claims

1. A method of marking a trafficway surface wherein the marking comprises a polyurethane.

2. A method as claimed in claim 1 wherein the polyurethane is applied by spraying.

3. A method as claimed in claim 2 wherein the polyurethane is produced by mixing immediately prior to spraying at least two components which react together to produce a polyurethane.

4. A method as claimed in claim 3 wherein said mixing is effected by impingement of said components.

5. A method as claimed in any one of claims 1 to 4 wherein the polyurethane is produced from a polyfunctional isocyanate and a polyol.

6. A method as claimed in claim 5 wherein the isocyanate is, or is based on, diphenyl methane diisocyanate (MDI).

7. A method as claimed in claim 6 wherein the isocyanate is MDI modified by reaction with a polyol or amine.

8. A method as claimed in claim 7 wherein the isocyanate is a glycol modified MDI.

9. A method as claimed in any one of claims 5 to 8 wherein the polyol is a diol or triol.

10. A method as claimed in claim 9 wherein the polyol is a triol with a hydroxyl number of 25 to 60.

11. A method as claimed in any one of claims 5 to 10 wherein the polyol is alkoxylated.

12. A method as claimed in claim 11 wherein the polyol is an ethylene oxide or propylene oxide based polyether derivative.

13. A method as claimed in claim 12 wherein the polyol is an ethylene oxide tipped triol.

14. A method as claimed in any one of claims 5 to 13 wherein a cross-linking agent is used in addition to the polyol and isocyanate.

1 5. A method as claimed in claim 14 wherein the cross-linking agent is a hydroxy or amino compound.

16. A method as claimed in claim 14 wherein the cross-linking agent has a hydroxyl number of 300 to 2,000.

17. A method as claimed in any one of claims 14 to 1 6 wherein the cross-linking agent has a functionality of 2 to 4.

18. A method as claimed in claim 14 wherein the cross-linking agent is selected from triethanolamine, ethylene glycol, glycerol, butane diol, alkoxylated ethylene diamine and diethylene toluene diamine.

19. A method as claimed in any one of claims 5 to 1 8 wherein a catalyst is included in one component of the poiyurethane forming system.

20. A method as claimed in claim 19 wherein the catalyst is an organometallic or amine catalyst.

21. A method as claimed in claim 20 wherein the catalyst is selected from stannous octanoate, dibutyl tin dilaurate and dimethyl cyclohexylamine.

22. A method as claimed in any one of claims 5 to 21 wherein a pigment is included in one component of the polyurethane forming system.

23. A method of marking a trafficway surface substantially as hereinbefore described.