GB2554874A

GB2554874A - Spraying system for the restoration of resin-bound paved and block paved surfaces

Info

Publication number: GB2554874A
Application number: GB1617101.9A
Authority: GB
Inventors: Edward Penton Martin; Emma Dyas Katherine
Original assignee: Apollo Chemicals Ltd
Current assignee: Apollo Chemicals Ltd
Priority date: 2016-10-11
Filing date: 2016-10-11
Publication date: 2018-04-18
Also published as: GB201617101D0

Abstract

The spraying system comprises a pressurised container and a liquid formulation within the container. The formulation comprises 30-80 (40-70)% moisture cure, aliphatic, polyurethane pre-polymer, 1-15 (5-12)% crosslinking agent and polyurethane compatible liquid propellant. The crosslinking agent is preferably a bisoxazolidine. The preferred formulation also includes 10-50% polar solvent, an organotin catalyst, acidifying agent, fungicide, ultraviolet (UV) protector and antioxidant. Preferred propellants are dimethyl ether, propane butane mixture and liquid nitrogen. The system is used for the restoration of (preferably pressure washed) resin bound paved and block paved surfaces, preferably by spraying at 10-20 bar.

Description

(71) Applicant(s):

Apollo Chemicals Limited (Incorporated in the United Kingdom)

Sandy Way, Amington Industrial Estate, TAMWORTH, Staffordshire, B77 4DS, United Kingdom (72) Inventor(s):

Martin Edward Penton Katherine Emma Dyas (74) Agent and/or Address for Service:

Reddie & Grose LLP The White Chapel Building,

Whitechapel High Street, London, E1 8QS,

United Kingdom (51) INT CL:

B05D 1/02 (2006.01) B05D 3/10 (2006.01)

E01C 23/22 (2006.01) (56) Documents Cited:

EP 0140186 A2 CN 101994254 B

US 6610779 B1 JP H02027003 (58) Field of Search:

INT CL B05D, E01C Other: EPODOC; WPI (54) Title of the Invention: Spraying system for the restoration of resin-bound paved and block paved surfaces Abstract Title: Spraying system for applying polyurethane and crosslinking agent to paving (57) The spraying system comprises a pressurised container and a liquid formulation within the container. The formulation comprises 30-80 (40-70)% moisture cure, aliphatic, polyurethane pre-polymer, 1-15 (5-12)% crosslinking agent and polyurethane compatible liquid propellant. The crosslinking agent is preferably a bisoxazolidine. The preferred formulation also includes 10-50% polar solvent, an organotin catalyst, acidifying agent, fungicide, ultraviolet (UV) protector and antioxidant. Preferred propellants are dimethyl ether, propane butane mixture and liquid nitrogen. The system is used for the restoration of (preferably pressure washed) resin bound paved and block paved surfaces, preferably by spraying at 10-20 bar.

- 1 SPRAYING SYSTEM FOR THE RESTORATION OF RESIN-BOUND PAVED AND BLOCK PAVED SURFACES

The present invention relates to a spraying system for dispensing a coating composition to restore a permeable surface. The spraying system of the present invention finds particular application for the restoration of block paved or resin bound paved surfaces of driveways, pathways and the like.

Hard, substantially impermeable surfaces like concrete have traditionally been used for paving driveways, pathways, walkways, carparks and other light traffic areas. However, such surfaces have the drawback that they tend to accelerate rain going into the drains or the foul water sewer, and this may undesirably exacerbate flooding issues. In addition, because less water reaches the natural underground aquifers, even less water will be available to evaporate back into the air, and so the natural cooling effect associated with the water cycle may be at least partially lost. Therefore, permeable surfaces that allow water to soak through the surface into the ground below are generally preferable over hard, non-permeable surfaces for environmental reasons.

Because it provides a surface permeable to rainwater, resin bound paving is becoming a preferred alternative for forming and finishing the outer surfaces of driveways, pathways, and the like. The thickness of the resin bound layer can vary and will generally be adapted to the application and extent of traffic. Compared with asphalt, which is also porous, resin bound paving has the advantage that it allows for a more aesthetically pleasant finish and for a variety of patterns and colours. In addition, it is typically durable and low-maintenance, for example compared with loose gravel.

Block paving, like resin bound paving, may also help improve the visual impact of driveways and the like, and so it is another rather popular alternative to concrete. However, although gaps are present between adjacent blocks, block paving is not fully permeable, and so may not properly address the environmental issues referred to above.

Front garden driveway regulations in force in the UK require that householders apply for a planning permission if they wish to lay a traditional, impermeable driveway that does not control rainwater running off onto a road. By contrast, no planning permission is needed if a new or replacement driveway of any size uses permeable or porous surfacing, or if the rainwater is directed to a lawn or border to drain naturally. Thus, permeable surfaces like resin bound paving are becoming more popular because of this regulatory aspect, as well.

However, regular cleaning of such permeable paved surfaces will typically be needed, since leaves, oil, contaminants and debris may undesirably occlude the pores and gaps, which could progressively hinder rainwater permeation.

-2Further, it would generally be desirable to be able to restore the surface of resin bound paving to its original state, such as to re-establish its original appearance and take full advantage of their added aesthetic value. A similar need is also felt with block paved surfaces, the visual impact of which may also be partially impaired by the accumulation of dirt and debris.

Therefore, it would be desirable to provide a spraying system for dispensing a coating composition to restore a block paved or resin bound paved surface. In particular, it would be desirable to provide one such spraying system that renews the appearance of a resin bound paved surface while at the same time preserving the surface permeability.

In addition, it would be desirable to provide one such spraying system that allows a user to apply the coating composition easily and such that the treated surface can be used again within a reasonably short time. Further, it would be desirable to provide a method for restoring a block paved or resin bound paved surface.

According to an aspect of the present invention there is provided a spraying system for dispensing a coating composition to restore a block paved or resin bound paved surface, the spraying system comprising a pressurised container and a liquid formulation within the container. The formulation comprises from about 30 parts per hundred to about 80 parts per hundred of one or more moisture-cure aliphatic polyurethane pre-polymer. In addition, the formulation comprises from about 1 part per hundred to about 15 parts per hundred of a cross-linking agent, and a polyurethane-compatible liquid propellant.

According to a further aspect of the present invention there is provided a method for restoring a block paved or resin bound paved surface, the method comprising spraying over the permeable surface a coating composition comprising from about 30 parts per hundred to about 80 parts per hundred of one or more moisture-cure polyurethane pre-polymer, and from about 1 part per hundred to about 15 parts per hundred of a cross-linking agent.

It will be appreciated that any features described with reference to one aspect of the present invention are equally applicable to any other aspect of the invention.

As used herein, the term “pre-polymer” refers to a monomer or system of monomers that have been reacted to an intermediate molecular mass state. This material is capable of further polymerization by reactive groups to a fully cured high molecular weight state. As such, mixtures of reactive polymers with un-reacted monomers may also be referred to as pre-polymers. The term “pre-polymer” and “polymer precursor” may be interchanged. In more detail, the term “polyurethane pre-polymer” typically refers to monomeric di-isocyanates which serve as building blocks for polyurethane products. One such pre-polymer may be used in combination with a hardener comprising a poly-isocyanate.

As used herein, the term “aliphatic polyurethane pre-polymer” generally refers to molecules containing isocyanate and blocked isocyanate functionalities. The term “aliphatic” is used to

-3describe polyurethane pre-polymers in which carbon atoms form open chains, either straight or branched, rather than aromatic rings.

In the present specification, the term “deaerator” refers to a chemical additive capable of preventing or at least reducing the formation of foam and bubbles during the curing of the polyurethane system. One such additive may also be referred to as a “defoamer”.

The term “organotin” is used herein to refer to a chemical compound based on tin with hydrocarbon substituents. One such additive is also at times referred to as a stannane. These compounds are useful as catalysis for the reaction of an isocyanate or blocked isocyanate functionality with a reactive hydrogen-containing compound in polyurethane coating formulations.

The term “polyurethane-compatible” is used herein to describe a propellant that has no tendency to react with the polyurethane pre-polymer before or during the curing process. In addition, a polyurethane-compatible propellant remains in solution without any undesirable phase separation during storage.

A spraying system in accordance with the present invention advantageously makes it possible for the user to apply in an easy and controlled manner a coating composition adapted to restore a block paved or resin bound paved surface, such as the surface of a driveway or pathway. This is made possible because a liquid formulation is provided within a pressurised container, the formulation containing polyurethane pre-polymer and a suitable cross-linking agent in relative amounts such as to lead to a fast curing. This is desirable in order to obtain a generally uniform coating and for the treated surface to be usable again as soon as possible.

In addition, the formulation comprises a propellant that is chemically compatible with polyurethane and is provided in the liquid/liquefied state. This is advantageous in that it is easier to maintain the necessary pressure within the container, such that the coating composition can be dispensed at a substantially constant flow rate during use and as the container is progressively emptied. In addition, the liquid propellant tends to vaporise as it leaves the pressurised container upon being dispensed, and so it is easier for the spraying system to from droplets of the coating composition having a desirable size.

Treatment by means of a spraying system in accordance with the invention forms a protective coating over a block paved or resin bound paved surface and restores it to its original look, such that its visual impact is significantly improved. At the same time, the permeability of the surface, in the case of a resin bound paved surface, is advantageously preserved.

In most general terms, a spraying system in accordance with the present invention comprises a pressurised container comprising a liquid formulation. The spraying system is adapted to dispense the liquid formulation onto a block paved or resin bound paved surface with a view to at least partly coating and restoring the surface. The pressurised container holds a liquid formulation comprising from about 30 parts per hundred to about 80 parts per hundred of at least one moisture-cure aliphatic polyurethane pre-polymer and from about 1 part per hundred

-4to about 15 parts per hundred of a cross-linking agent. In addition, the liquid formulation comprises a polyurethane-compatible liquid propellant.

An isocyanate group can react with any compound containing a reactive hydrogen. An isocyanate with an alcohol yields a urethane; reaction of an isocyanate with an amine yields urea, and reaction of an isocyanate with water results in intermediates which decompose to yield carbon dioxide and an amine, which can further react to again form urea. In order to prepare polymeric materials, in each pair of reacting molecules each compound must have at least two functional groups per molecule. Linear polymers are formed when both reaction partners are di-functional. The formation of three dimensional networks requires that at least one of the reaction partners have three or more reactive groups. Aliphatic di-isocyanate monomers are used in spraying systems in accordance with the present invention because they are much less reactive than their aromatic counterparts. In addition, urethane products made from aliphatic di-isocyanate monomers oxidize less easily than those prepared from aromatic di-isocyanates, especially when exposed to UV light. The higher resistance to UV light-induced degradation of products prepared from aliphatic di-isocyanates makes them preferable in for exterior coating applications where gloss and colour retention are of great relevance.

As a one-part product, the liquid formulation of a spraying system in accordance with the present invention relies on moisture or ambient water as the curing agent. This advantageously makes one such liquid formulation suitable for being conveniently dispensed from a pressurised container.

Preferably, the liquid formulation comprises at least about 40 parts per hundred of the at least one moisture-cure aliphatic polyurethane pre-polymer. In addition, or as an alternative, the liquid formulation preferably comprises less than about 70 parts per hundred of the at least one moisture-cure aliphatic polyurethane pre-polymer. In particularly preferred embodiments, the liquid formulation comprises from about 40 parts per hundred to about 70 parts per hundred of the at least one moisture-cure aliphatic polyurethane pre-polymer.

It has been observed that when the liquid formulation comprises one such amount of the at least one moisture-cure aliphatic polyurethane pre-polymer, certain properties of the paved surface, particularly in the case of a resin bound aggregate, are greatly improved following treatment with a spraying system in accordance with the invention. This relates, in particular, to weatherability and gloss retention.

Preferably, the liquid formulation comprises at least about 5 parts per hundred of the crosslinking agent. In addition, or as an alternative, the liquid formulation preferably comprises less than about 12 parts per hundred of the cross-linking agent. In particularly preferred embodiments, the liquid formulation comprises from about 5 parts per hundred to about 12 parts per hundred of the cross-linking agent.

-5Preferably, the one or more aliphatic polyurethane pre-polymer are selected from the group consisting of aliphatic di-isocyanates, aliphatic polyisocyanates, isocyanate-terminated prepolymers and mixtures thereof. Examples of suitable compounds include Trixene SC 7931 (by Baxenden). By selecting specific pre-polymers, properties of the coating may be adjusted and optimised, such as hardness, toughness, gloss retention and weatherability.

In some embodiments, the liquid formulation may also contain a hardener. One suitable hardener is Desmodur ® Z 4470 MPA/XY (by Covestro). Preferably, the liquid formulation comprises at least about 15 parts per hundred of the hardener. Even more preferably, the liquid formulation comprises at least about 20 parts per hundred of the hardener. In addition, or as an alternative, the liquid formulation preferably comprises less than about 35 parts per hundred of the hardener. More preferably, the liquid formulation comprises less than about 30 parts per hundred of the hardener. In some particularly preferred embodiments, the liquid formulation comprises from about 20 parts per hundred to about 30 parts per hundred of the hardener.

In a preferred embodiment, the cross-linking agent comprises a bisoxazolidine. Bisoxazolidines are chemical compounds that contain two oxazolidine rings - each ring comprising three carbons, a nitrogen and an oxygen. The rings hydrolyse in the presence of moisture to give amine and hydroxyl groups, which can then react with di-isocyanates to form a coating. The use of a bisoxazolidine in a polyurethane system can advantageously prevent the unwanted reaction between isocyanate functionalities and moisture which may result in coating defects, due to carbon dioxide release. The nature of the linker connecting the two oxazolidine rings may impact the flexibility and elongation properties of the cured polyurethane system, and so the use of one such cross-linking agent advantageously enables a finer control of the properties of the coating. An example of one such urethane bisoxazolidine is Trixene SC 7906 (by Baxenden).

Preferably, the liquid formulation comprises from about 7 parts per hundred to about 15 parts per hundred of cross-linking agent. More preferably, the liquid formulation comprises at least about 9 parts per hundred of cross-linking agent. In addition, or as an alternative, the liquid formulation preferably comprises less than about 13 parts per hundred of cross-linking agent. In some particularly preferred embodiments, the liquid formulation comprises from about 9 parts per hundred to about 13 parts per hundred of cross-linking agent.

Preferably, the liquid formulation further comprises a deaerator. This is advantageous in that, by limiting the formation of bubbles and foam, it is possible to prevent the formation of superficial defects of the polyurethane coating, so that the visual impact of the coating is enhanced. In addition, in the case of a resin bound paved surface, it is easy to preserve the permeability of the treated surface, such that rainwater permeation is not prevented at any time. A suitable example of one such deaerator is BYK-A 535 (by Altana).

-6Preferably, the liquid formulation further comprises from about 10 parts per hundred to about 50 parts per hundred of a solvent, preferably a polar solvent. This advantageously makes it possible for the density and viscosity of the formulation to be finely tuned. In particular, where the formulation comprises a significant amount of a substantially solid pre-polymer or hardener or both, it is desirable to combine one such compound with a solvent so that the formulation is easy to atomise and dispense in the form of a spray. Suitable solvents will be known to the skilled person. A preferred example of a suitable solvent is ethyl acetate.

More preferably, the liquid formulation comprises at least about 15 parts per hundred of a polar solvent. In addition, or as an alternative, the liquid formulation preferably comprises less than about 30 parts per hundred of a polar solvent. In particularly preferred embodiments, the liquid formulation comprises from about 15 parts per hundred to about 30 parts per hundred of a polar solvent.

Preferably, the formulation further comprising an organotin catalyst. As was mentioned above, the use of polyurethanes based on aliphatic isocyanates is highly desirable in the context of the present application because these polyurethanes have particularly good UV-stability. However, aliphatic isocyanates (in particular, cycloaliphatic isocyanates) may have an undesirably low reactivity, and the use of an organotin catalyst is advantageous in that it promotes the curing reaction and thus increases the reaction rate. Suitable organotin catalysts include compounds based on dibutyltin dilaurate, dibutyltin diacetate and mixtures thereof. An example of one such catalyst is METATIN™ (by Dow). Preferably, the formulation comprises less than 1 part per hundred of the organotin catalyst.

In preferred embodiments, the formulation further comprises an UV-protector or an antioxidant or both. Further additives may be included in the formulation to improve the properties of the coating. In particular, by including an UV-protector or an antioxidant it is advantageously possible to preserve the aesthetic features of the coating for a longer time, such that subsequent restoring treatments of the surface are not required too frequently. Preferably, the liquid formulation comprises less than 1 part per hundred of the UV-protector or antioxidant.

In preferred embodiments, the liquid formulation further comprises an acidifying agent. A slightly acidic environment is advantageous in that limits possible increases in viscosity within the pressurised container, which may undesirably impair the sprayability of the formulation. Suitable acidifying agents include hydrochloric acid, aromatic acyl halides, aliphatic acyl halides, etc. A preferred example of an acyl halide suitable for use as an acidifying agent in a spraying system in accordance with the invention is benzoyl chloride.

Preferably, the formulation comprises less than 0.05 parts per hundred of the acidifying agent. The liquid formulation may further comprise a fungicide.

-Ί Preferably, the propellant is selected from the group consisting of dimethyl ether (DME), propane/butane mixes, liquefied nitrogen, 134a propellant and mixtures thereof. In preferred embodiments, the propellant is a dimethyl ether propellant.

More preferably, the propellant-to-liquid-formulation ratio in a spraying system according to 5 the present invention is from about 1:4 to about 2:3. It has been found that propellant-to-liquidformulation ratios in the pressurised container falling within such range are associated with good sprayability and make it possible for the liquid formulation contained in the pressurised container to be dispensed substantially in its entirety. This is clearly advantageous in that wastes are greatly limited and a more efficient use of materials is made.

Preferably, a pressure within the pressurised container is from about 10 bar to about 20 bar.

In general, the pressure within the canister may vary depending on the headspace in the canister - the smaller the headspace, the higher the pressure.

Spraying systems as described above find application in methods for restoring a block paved or resin bound paved surface. One such method comprises spraying over the surface a coating composition comprising: from about 40 parts per hundred to about 80 parts per hundred of one or more moisture-cure polyurethane pre-polymer and from about 1 part per hundred to about 15 parts per hundred of a cross-linking agent. For example, the formulation may conveniently be sprayed from a portable pressurised canister provided with a nozzle adapted to atomise the coating composition into droplets of a suitable size.

Preferably, once such method further comprises pressure washing the block paved or resin bound paved surface prior to the step of spraying the coating composition over the surface.

The invention will now be further described by means of the following:

EXAMPLE 1

A liquid formulation was prepared containing:

Compound	Amount [pph]
Desmodur Z4470 (aliphatic poly-isocyanate - hardener)	20
Trixene SC7931 (isocyanate terminated pre-polymer)	40
Trixene SC7906 (urethane bisoxazolidine)	10
Ethyl Acetate (solvent)	28.18
BYK A535 (deaerator)	1
Metatin 712 ES (organotin catalyst)	0.4
Tinuvin B75 (antioxidant, light stabiliser, UV absorber)	0.4
Benzoyl chloride (acidifying agent)	0.02

-8The liquid formulation was loaded into a canister along with a DME propellant to provide a spraying system. The propellant-to-liquid-formulation ratio in the canister was about 2:5. The pressure within the canister was about 15 Bar.

The spraying system was successfully used to apply a coating over the resin bound paved 5 surface of a driveway which had been previously pressure-washed. This restored the resin bound paved surface whilst preserving its porosity.

Accelerated aging tests have been carried out on a cured film formed by dispensing the liquid formulation from a spraying system in accordance with the present invention over a substrate and a cured film formed from a resin used in the manufacturing of conventional, io commercially available, resin bound paved surfaces and applied on the same substrate. These tests were devised, in particular, to assess the resistance of the treated surface to UV radiation. The results have shown that while the resin conventionally used for binding together aggregates tends to lose essentially all of its gloss over a period of 6 months, the cured film of the present invention displays a significantly increased resistance to UV radiation and the gloss of the surface is advantageously preserved for as long as a year and a half.

Claims

1. A spraying system for dispensing a coating composition to restore a block paved or resin bound paved surface, the spraying system comprising a pressurised container and a liquid formulation within the container, the formulation comprising:

from about 30 parts per hundred to about 80 parts per hundred of one or more moisturecure aliphatic polyurethane pre-polymer;

from about 1 part per hundred to about 15 parts per hundred of a cross-linking agent; and a polyurethane-compatible liquid propellant.

2. A spraying system according to claim 1, wherein the liquid formulation comprises from about 40 parts per hundred to about 70 parts per hundred of the one or more moisture-cure aliphatic polyurethane pre-polymer.

3. A spraying system according to claim 1 or 2, wherein the liquid formulation comprises from about 5 parts per hundred to about 12 parts per hundred of the cross-linking agent.

4. A spraying system according to any one of the preceding claims, wherein the one or more aliphatic polyurethane pre-polymer are selected from the group consisting of aliphatic diisocyanates, aliphatic polyisocyanates, isocyanate-terminated prepolymers and mixtures thereof.

5. A spraying system according to any one of the preceding claims, wherein the cross-linking agent comprises a bisoxazolidine.

6. A spraying system according to any one of the preceding claims, wherein the formulation further comprises a deaerator.

7. A spraying system according to any one of the preceding claims, wherein the formulation further comprises from about 10 parts per hundred to about 50 parts per hundred of a polar solvent.

8. A spraying system according to any one of the preceding claims, wherein the formulation further comprising an organotin catalyst.

9. A spraying system according to any one of the preceding claims, wherein the formulation further comprising an UV- protector or an antioxidant or both.

10. A spraying system according to any one of the preceding claims further comprising an acidifying agent.

11. A spraying system according to any one of the preceding claims, wherein the formulation 5 comprises a fungicide.

12. A spraying system according to any one of the preceding claims, wherein the propellant is selected from the group consisting of dimethyl ether, propane/butane mixes, liquefied nitrogen, 134a propellants and mixtures thereof.

io

13. A spraying system according to any one of the preceding claims, wherein the propellantto-liquid-formulation ratio is from about 1:4 to about 2:3.

14. A spraying system according to any one of the preceding claims, wherein a pressure within 15 the pressurised container is from about 10 bar to about 20 bar.

15. A method for restoring a block paved or resin bound paved surface, the method comprising spraying over the surface a coating composition comprising:

from about 30 parts per hundred to about 80 parts per hundred of one or more moisture-cure 20 polyurethane pre-polymer;

from about 1 part per hundred to about 15 parts per hundred of a cross-linking agent.

16. A method according to claim 15 further comprising pressure washing the block paved or resin bound paved surface prior to the step of spraying the coating composition over the surface.

Intellectual

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Office

Application No: GB 1617101.9 Examiner: Mr Robert Black