Coating Composition Field of the invention

The invention relates to a composition suitable for lining the inside of a pipe to extend its life. In particular the composition comprises an elastomer modified vinyl ester resin and reinforcing filler along with a reactive diluent such as vinyl toluene.

Background

Polyester composites are commonly used in fiber reinforced composites (FRC) to manufacture large structures such as yachts, small boats, swimming pools and so on. Polyester composites provide very good flexibility and mechanical strength at ambient temperature.

More recently, polyester composites have also been used to "build" new pipes inside old sewage pipes. This has the obvious advantage that the existing pipes can be left in situ even if they are no longer effective.

The testing regime for these new internal pipes has recently been strengthened. Current polyester composite materials often fail these new stricter requirements so improved performance, especially at high temperatures is needed.

One example of a polyester that has been used in the formation of these internal pipes is Isophthalic unsaturated polyester. Isophthalic unsaturated polyesters have low glass transition temperature and attractive mechanical properties. However, when an ester group based internal pipe is used, there is a possible vulnerability to hydrolysis in aqueous media especially in hotter conditions. Moisture or water absorption can affect the mechanical properties negatively over time .

Isophthalic unsaturated polyester resins have several “ester groups” in the backbone of the polymer, making it vulnerable to hydrolysis when immersed in hot water, leading to critical failure after aging in the pipes. Scheme 1: Isophthalic unsaturated polyester

Another type of binder which has also been used in this application area is vinyl esters such as bisphenol-A vinylester and Novolac Vinylester. These vinyl esters have fewer ester groups in the polymer backbone compared with the polyester polymers and are therefore more resistant to hydrolysis during water immersion. However, due to a higher glass transition temperature (Tg), they have limited flexibility, especially after aging. These resins can therefore be brittle which may lead to cracking risk of the coatings

Scheme 2 - Novolac vinyl ester

It would be beneficial to prepare resin compositions that combine the advantages of the Isophthalic unsaturated polyester and the novolac vinyl ester resin, in particular to achieve a combination of the flexibility of the Isophthalic unsaturated polyester and the water-resistance of the novolac vinyl ester resin. The inventors have now found that by using an elastomer modified vinyl ester, such as a bisphenol-A vinyl ester resin or elastomer modified Novolac vinyl ester, preferably diluted in vinyl toluene, the resulting composition can be used to provide a robust, flexible composite material for the pipe-renovation industry.

The coating compositions of the present invention comprising an elastomer modified vinyl ester resin provides a coating composition with a good balance between water immersion resistance (especially at higher temperatures) and mechanical properties. Reinforcing fillers are important to provide mechanical support to the coating films, prevent shrinkage of the coating film during curing and to provide a barrier effect. The coating compositions of the present invention also forms pipes with a very smooth surface and high resistance to grey and/or black water in sewage in an elongated service life time.

RU2365678 describes a method of obtaining a protective lining coating, including layer-by-layer coating of the surface of a product. The first layer is a highly elastic primer that has high adhesion to the material of the protected product.

US2015/0133597 describes elastomer modified vinyl resins in combination with nanoparticles for the production of composite materials, coatings, casting compositions, adhesives, and dental materials which have enhanced mechanical properties, particularly enhanced impact strength.

EP 0315086 D1 describes a low temperature curable composition containing a rubber modified mixture of vinyl ester resins. One vinyl ester resin is prepared from a polyglycidyl ether of an adduct of phenol and an ethylenically unsaturated hydrocarbon and the other vinyl ester resin is prepared from a diglycidyl ether of a bisphenol or a polyglycidyl ether of a phenol- or substituted phenol-aldehyde novolac resin. There is no mention of pipes.

No one before has suggested the use of the composition of the invention in relining pipes.

Summary of the invention

Viewed from one aspect the invention provides a composition comprising: i) an elastomer modified vinyl ester resin; ii) a flaky, fibrous or spherical microparticulate reinforcing filler, such as a glass particulate, e.g. glass flakes, ora mixture thereof; iii) a reactive diluent, for example vinyl toluene; and iv) a curing agent.

Viewed from another aspect the invention provides a composition comprising: i) 20 to 80 wt% of elastomer modified vinyl ester resin; ii) 10 to 30 wt% of a flaky, fibrous or spherical microparticulate reinforcing filler, such as a glass particulate, e.g. glass flakes, or a mixture thereof; iii) 10 to 50 wt% of reactive diluent such as vinyl toluene; iv) 1.0 to 5.0 wt% curing agent.

Viewed from another aspect the invention provides a composition comprising i) 20 to 80 wt% of elastomer modified vinyl ester resin; ii) 10 to 30 wt% a flaky, fibrous or spherical microparticulate reinforcing filler, such as a glass particulate, e.g. glass flakes, or a mixture thereof; iii) 10 to 50 wt% reactive diluent comprising a vinyl functionalised aromatic hydrocarbon; iv) 1.0 to 5.0 wt% curing agent.

It is particularly preferred that the composition of the invention is sprayable, e.g. capable of being sprayed onto the inside surface of a pipe. It should not therefore be a laminate or contain fibrous sheets.

Viewed from another aspect the invention provides a composition as hereinbefore defined which has been cured.

Viewed from another aspect the invention provides a pipe comprising a cured composition as hereinbefore defined, especially wherein said pipe is located within another pipe.

Viewed from another aspect the invention provides a pipe comprising an internal coating comprising a cured composition as hereinbefore defined.

Viewed from another aspect the invention provides a process comprising applying a composition as hereinbefore defined to the inside walls of an existing pipe to form a coating thereon and allowing the composition to cure so as to form a coating or pipe within the existing pipe.

Viewed from another aspect the invention provides the use of a composition as hereinbefore defined to prepare a pipe within an existing pipe, such as a sewage pipe or to prepare a coating within a pipe, such as a sewage pipe.

Viewed from another aspect the invention provides the use of a composition as hereinbefore defined to coat the inside of a pipe, such as a sewage pipe so as to extend its serviceable life.

Definitions

As used herein the term “coating composition” refers to a composition that, when applied to a surface, forms a film or coating thereon.

As used herein the term “binder” refers to a polymer which forms a continuous film on a substrate surface when applied thereto. The other components of the composition are dispersed throughout the binder.

As used herein the term “epoxy” refers to a three-atom cyclic ether. As used herein the terms “curing accelerator” and “accelerator” are used synonymously and refer to compounds which increase the rate of the curing reaction to cure or harden the coating.

As used herein the term “curing agent” refers to a compound which, when mixed with a binder, e.g. elastomer modified vinyl ester resin, produces a cured or hardened coating by generating cross-links within the polymer. Sometimes curing agents are referred to as hardeners.

As used herein the term “filler” refers to a compound which increases the volume or bulk of a coating composition. They are substantially insoluble in the coating composition and are dispersed therein. When filler particle sizes are referred to herein, it is the particle size when they are added to the composition.

As used herein the term “weight % (wt%)”, when used in relation to individual constituents of the composition, e.g. reactive diluent, etc., refers to the actual weight of constituent, i.e. without volatile components present, unless otherwise specified.

As used herein the term “weight % (wt%)”, when used in relation to the coating compositions, refers to the weight relative to the total dry weight of the composition, i.e. excluding volatile components, unless otherwise specified.

The term (meth)acrylate covers both methacrylate and acrylate and (meth) indicates the optional presence of the methyl group.

The term microparticle is used herein to define a particle having a Z-average diameter of 1.0 to 1000 pm preferably as determined by ISO 22412:2017 using a Malvern Mastersizer 2000.

Detailed Description of Invention

This invention concerns a composition that can be applied to the inside surface of existing pipes which are reaching the end of their serviceable lives. Removing and replacing such pipes is often challenging as pipes are difficult to access. Such a process might require extensive and disruptive building works. Where the pipe is within a building such as an apartment, house, commercial building, office etc. such pipe replacement might involve digging up floors or removing walls.

Rather than remove and replace such pipes, the present invention seeks to coat the inside surface of the existing pipe with the composition of the invention and allow that composition to cure. The resulting coating effectively forms a new pipe within the existing pipe. The invention can therefore be seen as providing a new pipe within an existing pipe or simply re-lining an existing pipe with a coating that ensures that the pipe is serviceable once more.

The thickness of the coating (or new pipe) that forms within an existing pipe is ideally 1 to 20 mm, preferably 1 to 10 mm, further preferred 2 to 7 mm. In one particularly preferred option the thickness of the coating is 3 to 5 mm.

Importantly, the composition of the invention cures at ambient temperatures (15 - 40 °C) so there is no requirement to heat the system during a curing process. Also, the composition of the invention can be directly applied to the inside surface of an existing pipe without a primer layer.

The existing pipe might be made of plastic, steel, concrete, or any other typical pipe material. Conveniently, the invention is used to coat the inside of existing sewage pipes. Such pipes might be relatively old and may be made of steel or concrete. Such pipes are reaching the end of their lives and the present invention provides a solution to their replacement without the upheaval required to physically remove and replace such a pipe.

Pipes in which the composition of the invention can be applied are ones that carry water, often waste water, such as a sewage pipe.

The composition of the invention can be applied to the inside surface of an existing pipe using a remote coating apparatus placed within the pipe which can, for example, spray the composition on the walls of the pipe from within. All that is required therefore is a single access point to allow the coating apparatus, often a remote control robot, to be placed within the pipe. It may be that multiple coats are required to develop a layer of sufficient thickness inside the pipe. Where all the coats are of the same composition, we regard that as a single layer. It is however possible to apply the different compositions of the invention as multiple layers within a pipe. This is not however preferred.

Suitable pipe coating equipment is known and will not be further described herein. The present invention is directed to the nature of the composition used for coating the pipes not the mechanism of its application.

Elastomer Modified Vinyl ester

The composition of the invention requires the use of an elastomer modified vinyl ester resin (VE resin). This acts as the binder in the composition. Vinyl ester resin, or often just vinyl ester, is a resin produced by the esterification of an epoxy resin with an acrylic or methacrylic acid. The "vinyl" group therefore refers to these acrylate ester substituents, which are prone to polymerize.

In one embodiment therefore the vinyl ester is the ester of an epoxy resin with an acrylic or methacrylic acid.

The epoxy resins used to synthesize the vinyl ester resins of the present invention may be an aliphatic and/oran aromatic epoxy resin. Preferably the epoxy resin is an aromatic epoxy resin.

Suitable aliphatic epoxy resins include epoxy and modified epoxy resins selected from cycloaliphatic epoxy such as hydrogenated bisphenol A, hydrogenated bisphenol A novolac and dicyclopentadiene based binders, glycidyl ethers such as polyglycidyl ethers of polyhydric alcohols, epoxy functional acrylic resins;or any combinations thereof.

Suitable aromatic epoxy resins includes epoxy and modified epoxy resins selected from bisphenol type epoxy resins such as bisphenol A, bisphenol F and bisphenol S, resorcinol diglycidyl ether (RDGE), novolac type epoxy resins such as phenolic novolac type binders (bisphenol A novolac, bisphenol S novolac, bisphenol F novolac) and cresol novolac type binder; or any combinations thereof.

In some preferred compositions the epoxy resin is an aromatic epoxy resin. Preferably, the aromatic epoxy resin is derived from a combination of a compound comprising at least one epoxide functionality with an aromatic co-reactant comprising at least two hydroxyl groups.

Preferred epoxy resins are bisphenol epoxy resins and novolac epoxy resins. Particularly preferred epoxy resins are bisphenol A and novolac epoxy resins.

In one preferred coating composition of the invention the epoxy resins include bisphenol A based resins, such as 4,4'-isopropylidenediphenol-epichlorohydrin resins. Bisphenol A epoxy resins will be known to those in the field and have the general structure below: Also of interest are Novolac epoxy resins which are derived from phenols and formaldehyde. Typically novolacs are prepared by the condensation of a mixture of p- and m-cresol with formaldehyde (as formalin).

The epoxy resins are esterified terminally with acrylic acid or methacrylic acid to form the vinyl ester resin.

The vinyl ester resin is functionalised with an elastomer component.

Elastomers (rubbers) are polymers that are very elastic. They are generally lightly cross-linked and amorphous with a glass transition temperature well below room temperature. They can be envisaged as one very large molecule of macroscopic size. The intermolecular forces between the polymer chains are rather weak. The crosslinks completely suppress irreversible flow but the chains are very flexible at temperatures above the glass transition, and a small force leads to a large deformation. Thus, elastomers have a low Young's modulus and very high elongation at break when compared with other polymers. The term elastomer is often used interchangeably with the term rubber, although the latter is preferred when referring to vulcanized rubbers.

The vinyl ester must contain or be provided with reactive groups which can react with groups on the elastomeric component and so bind the elastomeric component chemically into the resin.

This elastomeric component with reactive groups may structurally be a homopolymer or copolymer or homooligomer or cooligomer. The elastomeric component preferably has a glass transition temperature, Tg, of -20° C. or less.

When the elastomeric modified vinyl ester resin is cured, the resin forms “elastomeric domains”, which possess this stated glass transition temperature. The elastomeric domains are phases comprising essentially only the elastomeric component, which have been incorporated into the resin and which bring about modification of the mechanical properties, particularly the impact strength, flexibility and toughness. Within these elastomeric domains, between the elastomeric component molecules, for example, it may substantially be only van der Waals forces that act; in the border region with the resin matrix, the elastomeric component penetrates into the resin matrix, owing to the resin -reactive groups. After it is cured, the elastomeric modified vinyl ester is in a state which can be regarded as a borderline case between a true two-phase system (resin matrix with rubber domains) and an interpenetrating network. The groups in the elastomeric component that are reactive with the resin may, in particular, be reactive double bonds (vinyl groups or methacrylate groups, for example), epoxy groups or carboxy groups. The nature of the chemical link between the elastomeric component and the vinyl ester is not critical.

The glass transition temperature Tg of the elastomeric domains () is preferably not more than -30°C, more preferably not more than -40, -50 or -60°C. With preference it does not go below -100°C. The preferred glass transition temperature also depends on the intended application of the polymeric compositions of the invention.

The fraction of the elastomeric component in the elastomeric modified vinyl ester resin is preferably 2% to 30% by weight, preferably 4% to 18% by weight, more preferably 6% to 12% by weight.

The modification of the vinyl ester resin with the elastomeric component may take place before the epoxy resin reacts with the (meth)acrylic acid or after that reaction has taken place.

By way of example, a carboxy-fu notional liquid rubber such as the CTBN (carboxyl-terminated butadiene-acrylonitrile copolymers) can be reacted with an epoxy resin. The reaction product is subsequently reacted further with acrylic acid and/or methacrylic acid, so that the vinyl ester resin oligomers, which are to be cured in a subsequent step, are formed. A mixture of this kind is available commercially: for example, under the names Dion® 9500 from Reichhold/Polynt or Derakane® 8084 from Ashland.

A second synthesis route, involves the separate synthesis of the elastomeric component and the base vinyl ester resin. In this case, as the elastomeric component, for example, a carboxy-terminated liquid rubber (CTBN, for example) can either be epoxy-functionalized, e.g. with a diepoxide or vinyl-functionalized e.g. with a glycidyl methacrylate; the liquid rubber functionalized with reactive groups in this way are then mixed with the vinyl ester resin.

In the course of the curing reaction, phase separation then occurs, and in the resin matrix there is formation of the rubber domains, already described, which are incorporated chemically in the matrix.

The rubber domains in the cured composition preferably possess an average size, as determined by SEM orTEM, of 0.05 to 20 pm, more preferably 0.1 to 10 pm, more preferably 0.2 to 4 pm. The elastomer modified vinyl ester resin may preferably be a rubber modified vinyl ester resin.

Examples of the elastomeric component are diene polymers such as copolymers of dienes such as 1,3-diene monomers and polar, ethylenically unsaturated comonomers. The diene used can be butadiene, isoprene or chloroprene, preferably butadiene. Examples of polar, ethylenically unsaturated comonomers are acrylic acid, methacrylic acid, C1-4 alkyl esters of acrylic or methacrylic acid, such as their methyl or ethyl esters, amides of acrylic or methacrylic acid, fumaric acid, itaconic acid, maleic acid or their C1 -4-alkyl esters or monoesters, or maleic or itaconic anhydride, vinyl esters such as vinyl acetate, for example, or, in particular, acrylonitrile or methacrylonitrile.

Especially preferred copolymers are carboxyl-terminated butadiene- acrylonitrile copolymers (CTBN), which are offered in liquid form under the trade name Hycar by the company Lubrizol. These copolymers have molecular weights of between 2000 and 5000 and acrylonitrile contents of between 10% and 30%. Specific examples are Hycar CTBN 1300 X 8, or 1300 X 13. CTBN derivatives may likewise be used. Mention may be made, byway of example, of the CTBN derivatives termed CTBNX, in which there are additional acid functions in the chain.

Other suitable CTBN derivatives are functionalized with epoxy groups or vinyl groups at the end of the linear oligomer. Epoxy functionalization can be achieved by reactions of the terminal carboxyl groups of CTBN with polyfunctional epoxides. Vinyl functionalization is achieved by reaction of these groups with a glycidyl acrylate or glycidyl methacrylate. From the company Lubrizol, these copolymers are available under the name VTBNX (vinyl-functionalized) or ETBN (epoxy-functionalized). Particular suitability is possessed by VTBNX 1300 X 33, VTBNX 1300 X 43, ETBN 1300 X 40, and ETBN 1300 X 44.

The elastomeric component may also be based upon, for example, polysiloxane or polyurethane polymers.

The composition of the invention comprises 20 to 80 wt% by dry weight of the coating composition of the elastomer modified vinyl ester, such as 30 to 80 wt%, such as 30 to 60 wt.%. The elastomer modified vinyl ester is often supplied in a reactive diluent so this should betaken into account when determining the amounts of reactive diluent and elastomer modified vinyl ester in the composition.

The elastomer modified vinyl ester resin product produced is then typically dissolved in a reactive diluent. Reactive Diluent

The composition of the invention also contains a reactive diluent. The reactive diluent acts simultaneously as a solvent and as a reactive component of the composition. The reactive diluent is therefore involved in the curing reaction of the composition.

Suitable reactive diluents include vinyl and/or (meth)acrylate functional reactive diluents.

Examples of suitable reactive diluents are styrene, a-, o-, m-, p-alkyl, nitro, cyano, amide, or ester derivatives of styrene, chlorostyrene, vinyl toluene, divinylbenzene, di(meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, (meth)acrylic acid, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, tetra hydrofury I (meth)acrylate, acetoacetoxyethyl (meth)acrylate, (meth)acrylic esters such as dicyclopentenyloxyethyl (meth)acrylate and phenoxyethyl (meth)acrylate, (meth)acrylic acid amide, N, N-(meth)acrylic acid amide, (meth)acrylic acid aniline; unsaturated dicarboxylic acid diesters such as diethyl citraconate, monomaleimide compounds such as N-phenyl maleimide, N- (meth) acryloyl phthalimide and the like. In addition, compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di (meth)acrylate and 1,6-hexanediol di(meth)(meth) acrylic acid ester compound having two or more (meth)acryloyl groups can also be used. These radical polymerizable unsaturated monomers can be used alone or in combination. In one preferred option vinyl functional reactive diluents are used, preferably vinyl functional aromatic compounds such as styrene and vinyl toluene are used. Preferably vinyl toluene is used as the reactive diluent. Vinyl toluene is a particularly preferred reactive diluent because it has a high flash point, low odour and a good HSE profile. The amount of reactive diluent in the composition of the invention is preferably

2.0 to 50 wt%, such as 10 to 50 wt%, such as 15 to 40 wt%, such as 20 to 35 wt.% based on dry weight of the coating composition.

Curing Agent/Initiator The elastomer modified vinyl ester resin of the present invention may be cured by using heat, a radical initiator and/or by using a photo radical initiator.

Preferably a radical initiator is used.

Preferably the radical initiator is used together with an accelerator, i.e. a compound that accelerates the curing reaction.

Preferred radical initiators are organic peroxides. Examples of preferred organic peroxides are diacyl peroxide such as benzoyl peroxide, peroxyester such as t-butyl peroxy benzoate, hydroperoxide such as cumene hydroperoxide, dialkyl peroxide such as dicumyl peroxide, ketone peroxide such as methyl ethyl ketone peroxide and acetylacetone peroxide, peroxy ketals, alkyl ester peroxide and percarbonate peroxide.

In one preferred embodiment the radical initiator is a ketone peroxide such as methyl ethyl ketone peroxide.

A photo radical initiator may also be used as a curing agent in the present invention. Examples of suitable photo radical initiators are benzoin ethers such as benzoin alkyl ether, benzophenones such as benzophenone, benzyl, methyl orthobenzoyl benzoate, benzyl dimethyl ketal, 2,2-diethoxy Acetophenones such as acetophenone, 2-hydroxy-2-methylpropiophenone, 4-isopropyl-2-hydroxy-2- methylpropiophenone, 1,1-dichloroacetophenone, 2-chlorothioxanthone, 2- methylthioxanthone, 2-thioxanthones such as isopropyl thioxanthone and the like.

The curing agent/initiator is preferably added in an amount of 0.1 to 15 wt.%, more preferably 0.5 to 10 wt.%, further preferred 1 to 5 wt. % of the dry weight of the coating composition.

Accelerator

An accelerator is often used in combination with the curing agent. If curing takes place at elevated temperatures (about 80° C., for example), it is possible for the curing reaction to take place without the addition of an accelerator. Preferably an accelerator is used in combination with the curing agent.

The accelerator may therefore be a curing catalyst. One example of suitable accelerators are cobalt compounds (i.e. cobalt catalysts) such as cobalt naphthenate, cobalt octoate, neodecanoic cobalt and cobalt hydroxide. In one preferred embodiment, cobalt octoate is used as a curing accelerator. Amine functional compounds may also be used as curing accelerator. In one preferred embodiment a mixture of an amine functional compound and a cobalt compound is used.

Examples of suitable amine functional compounds are aromatic amines such as N, N-dimethylaniline, N, N-diethylaniline, N, N-dimethyl- p-toluidine, N-methyl-N- b-hydroxyethylaniline, N-butyl-N-beta-hydroxyethylaniline, N-methyl-N-beta- hydroxyethyl-p-toluidine, N- butyl-N-beta- hydroxyethyl-p-toluidine, N-methyl- N, N, N-di (b-hydroxyethyl) aniline, N, N-di (b-hydroxypropyl) aniline, N, N-di (b-hydroxy Ethyl) -p-toluidine, N, N-di (b-hydroxypropyl) -p-toluidine and N, N- diisopropylol-p- toluidine.

Aliphatic amide may also be used such a N, N-dimethylacetoacetamide, N,N- diethylacetoacetamide,

In one preferred embodiment N, N-dimethylacetoacetamide is used as a curing accelerator. In another preferred embodiment N, N-dimethylacetoacetamide is used together with cobalt octoate as accelerators.

The accelerator is preferably added in an amount of 0.005 to 5 wt.%, more preferably 0.01 to 2 wt%, further preferred 0.02 to 1 wt.% based on the dry weight of the coating composition.

Flaky, fibrous or spherical microparticulate reinforcing filler

The coating composition of the present invention comprises a reinforcing filler. The reinforcing filler is important to improve the mechanical properties of the coating film, prevent shrinkage of the coating film during curing and to improve water resistance and barrier properties.

The reinforcing filler suitable in the present invention is selected from flaky fillers, fibres and spherical filler microparticles. Mixtures of these reinforcing fillers can also be used. Nanoparticulate silica, for example, offers no reinforcing effect and is not suitable as a reinforcing filler. In particular, nanoparticles of diameter 5 to 150 nm are too small to offer a reinforcing effect.

Preferably the reinforcing filler is a flaky filler, preferably glass flakes.

The flaky filler is typically an inorganic pigment which is lamellar or plate-like in structure. Preferably, the aspect ratio of the flaky filler is more than 3, such as more than 6, preferably more than 10. The aspect ratio can be measured by for example using scanning electron microscopy (SEM). The aspect ratio can also be calculated by using the following formula: average particle size D50/average thickness.

The thickness of the flaky filler is preferably 0.1 to 15 pm, more preferably 0.5 to 10 pm and still more preferably 1 .0 to 8.0 pm. The thickness of the flaky filler can be measured by, for example, scanning electron microscopy (SEM).

The average particle size D ₅ o of the flaky filler is preferably 5 to 500 pm, more preferably 10 to 400 pm, further preferred 20 to 300 pm as measured by laser diffraction. Preferred flaky fillers are talc, mica and glass flakes. In one particularly preferred embodiment the flaky filler is glass flakes.

Glass flakes are different from other forms of glass, including glass spheres, in their aspect ratio, size distribution and density.

Glass flakes are much thinner than they are wide. Preferably the glass flakes are substantially planar.

Preferred glass flakes have a thickness of 0.1 to 15 pm, more preferably 0.5 to 10 pm and still more preferably 1 to 8 pm. Particularly preferred glass flakes have a thickness of 2 to 7 pm. The thickness of the glass flakes can be measured by, for example, scanning electron microscopy (SEM). Preferred glass flakes have a particle size D ₉₈ , of 200 to 1000 microns, more preferably 300 to 700 microns as measured by laser diffraction. Preferred glass flakes have an average particle size D ₅ o of 50 to 400 pm, and preferably 100 to 300 pm as measured by laser diffraction. The particle sizes of glass flakes referred to herein are the size of the flakes when they are added to the composition and prior to any extrusion or milling process.

Preferred glass flakes, have a bulk density of 1 to 5 g/cm ³ and more preferably 2 to 3 g/cm ³ .

Glass flakes that are suitable for use in the compositions of the present invention are commercially available from Nippon Sheet Glass and Glassflake Ltd. Optionally the glass flakes used in the compositions of the present invention are coated. The glass flakes may be coated with silanes such as vinyl functional silane, (meth) acrylic functional silane, amine functional silane and epoxy functional silane. In one preferred option the glass flakes are uncoated glass flakes. The amount of glass flakes present in the coating composition of the invention is preferably 5 to 45 wt%, more preferably 10 to 30 wt% and still more preferably 15 to 25 wt%, based on the dry weight of the coating composition.

The fibers suitable as a reinforcing filler in the coating composition of the present invention include inorganic fibers and organic fibers. Preferably the fibre is an inorganic fibre. Typical inorganic fibers include: carbide fibers, such as boron carbide fibers, silicon carbide fibers, niobium carbide fibers, etc.; nitride fibers, such as silicon nitride fibers; boron containing fibers, such as boron fibers, boride fibers; silicon containing fibers, such as silicon fibers, alumina-boron silica fibers, E-glass (non-base aluminum borates) fibers, C-glass (non-base or low base sodalime- aluminumborosilicate) fibers, A-glass (base -sodalime-silicate) fibers, S-glass fibers, inorganic glass fibers, quartz fibers, etc. The glass fibers may include E-glass fibers, C-glass fibers, A-glass fibers, S-glass fibers, etc. Useful inorganic fibers also include ceramic fibers and basalt fibers. In one preferred option the fibre is a glass fibre.

Preferred organic fibres are carbon fibres and Kevlar (para-aramid) fibres.

The spherical filler microparticles suitable as a reinforcing filler in the present invention may be organic or inorganic spherical filler microparticles. Preferably the spherical filler microparticles are inorganic spherical filler microparticles.

The spherical filler microparticles may be hollow or non-hollow. In one preferred embodiment the spherical filler microparticles are hollow. This means the microparticles have a void or cavity in their centres. This void or empty space is filled with gas, preferably air.

Suitable hollow, inorganic, spherical, filler microparticles are commercially available. Examples of commercially available hollow, inorganic, spherical filler microparticles include FilliteCenosphere, Poraver (expanded glass), Thermospheres, Omega spheres (available from e.g. 3M, Trelleborg, Potters, SMC minerals) and Hollolite.

Preferably the hollow, inorganic, spherical, filler microparticles have a low density, e.g. the density of the hollow, inorganic, spherical, filler microparticles might be 0.1 to 1 gem ^-3 , more preferably 0.2 to 0.8 gem ^-3 , and still more preferably 0.25 to 0.5 gem ^-3 , e.g. as specified on the technical specification provided by suppliers.

The inorganic spherical filler microparticles may also be non-hollow.

Preferably the inorganic, spherical, filler microparticles present in the coating compositions of the present invention have a crush strength of at least 3000 psi, e.g. as determined by the Nitrogen Isostatic Crush Strength test. The inorganic, spherical, filler microparticles present in the coating compositions of the present invention comprise, and more preferably consist, of glass, ceramic, calcium aluminium cement or metal oxide. More preferably the inorganic, spherical, filler microparticles present in the coating compositions of the present invention comprise, and still more preferably consist, of glass. This is because glass particles provide a good balance of crush strength, hardness and conductivity.

Optionally the inorganic, spherical, filler microparticles present in the coating compositions of the present invention may be surface treated. Some examples of surface treatment include treatment to alter the hydrophobicity of the surface, to improve compatibility with the binder and/or to facilitate chemical incorporation into the binder. In one preferred option the inorganic, spherical, filler microparticles are not surface treated.

Preferably the inorganic, spherical, filler microparticles have a Z-average diameter of 1.0 to 100 pm, more preferably 1.0 to 80 pm and still more preferably 10- 50 pm, as determined by ISO 22412:2017 using a Malvern Mastersizer2000.

It is of course possible to use a mixture of flaky, fibrous and/or spherical microparticulate fillers.

The amount of reinforcing filler present in the coating composition of the invention is preferably 5 to 45 wt%, more preferably 10 to 30 wt% and still more preferably 15 to 25 wt%, based on the dry weight of the coating composition. If a mixture of fillers is used then these percentages refer to the total filler content.

It will be appreciated that the microparticles present in the coating compositions of the present invention must be suitable for the intended use, such as lining the inside of a pipe. A fiber glass sheet is not particulate and could not be used for inner lining of pipes by spraying.

Other Additives

The composition of the invention may comprise a variety of other standard additives. Ideally the total of these other additives contributes to 15 wt% or less of the composition, such as 10 wt% or less.

A polymerization inhibitor may be added to the coating composition of the present invention. Examples of suitable polymerization inhibitors are hydroquinone, trihydrobenzene, benzoquinone, P-benzoquinone, methylhydroquinone, trimethylhydroquinone, hydroquinone monomethyl ether, t-butylhydroquinone, catechol, t-butylcatechol, 2,6-di-t-butyl-4-methylphenol, and the like. One preferred inhibitor is t-butylcatechol.

The inhibitor is preferably added in an amount of 0.01 to 5 wt.%, more preferably 0.02 to 2 wt%, further preferred 0.05 to 1 wt.% based on the dry weight of the coating composition.

The composition of the invention may comprise conventional additives such as thixotropic agents, waxes, plasticisers, defoamer, fillers and colouring agents.

Waxes may be added to the coating composition of the present invention. The waxes aid the curing process by acting as an oxygen blocking agent on the surface of the coating. Oxygen from the air may interfere with the curing process giving insufficient curing on the surface of the coating film.

Examples of suitable waxes are petroleum waxes, olefin waxes and polar waxes. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and the like. Examples of olefin waxes include polyethylene, polypropylene and the like. Examples of the polar wax include waxes having a polar group (such as a hydroxyl group and an ester group) introduced into these petroleum waxes, olefin waxes, unsaturated fatty acid esters such as oleic acid, linoleic acid, linolenic acid, and the like.

The amount of wax in the composition of the invention is preferably 0.05 to 5 wt.%, more preferably 0.01 to 2 wt.%, further preferred 0.05 to 0.5 wt.% based on the dry weight of the coating composition.

Thixotropic additives may be added to the coating composition to ensure for example good application properties and storage stability. Examples of suitable thixotropic agents are clay, organic bentonite, organic amide wax, polyethylene glycol, glycerin, polyhydroxycarboxylic acid amide, organic quaternary ammonium salt, polycarboxylic acid and fumed silica. Particularly preferred thixotropic additives are fumed silica and polycarboxylic acid based additives.

In one preferred option the thixotropic additive is a polyhydroxy carboxylic acid amine solution such as RHEOBYK R 605 from BYK.

In another preferred option the thixotropic additive is based on fumed silica. The fumed silica may be unmodified, hydrophilic fumed silica or the surface of the fumed silica may have been hydrophobically modified with for example silanes and siloxanes. Examples of suitable commercially available hydrophilic fumed silicas mayinclude AEROSIL 50, AEROSIL 90 G, AEROSIL 130, AEROSIL 200, AEROSIL 300 from Evonik.

One or more thixotropic additives may be used in the coating composition of the present invention. Preferably a combination of two different thixotropic additives are used. One particularly preferred combination is the combination of a polycarboxylic acid amine thixotropic additive and fumed silica.

The amount of thixotropic agent added to the coating composition of the invention is preferably 0.1 to 10 wt.%, more preferably 0.2 to 7 wt.%, further preferred 0.5 to 5 wt.% based on the dry weight of the coating composition.

Plasticizers such as fatty acid esters, chlorinated paraffin, phosphoric acid esters and phthalic acid esters may be added to the coating composition of the present invention. Preferably the plasticizer is a fatty acid ester such as linseed oil.

The amount of plasticizer added to the coating composition of the invention is preferably 0.1 to 10 wt.%, more preferably 0.2 to 7 wt.%, further preferred 0.5 to 5 wt.% based on the dry weight of the coating composition.

Examples of fillers suitable in the present invention are titanium dioxide, kaolin, calcium carbonate, aluminium hydroxide, fly ash, barium sulphate, clay and glass powder.

Examples of suitable colouring agents are organic pigments, inorganic pigments, dyes and the like.

Defoamers may also be added to the coating compositions of the invention. Examples of suitable defoamers are silicone, acrylic and/or vinyl based defoamers. Preferably the defoamers are acrylic and or vinyl based. In one preferred option the defoamers are free of silicone. Other defoamers such as benzotriazole and 2,4- benzophenone based defoamers may also be used.

Further, a hindered amine type ultraviolet absorber may also be added to the coating composition of the present invention.

In a preferred embodiment, the composition comprising: i) 25 to 60 wt% of elastomer modified vinyl ester; ii) 10 to 30 wt% of a reinforcing filler, such as a glass particulate e.g. glass flakes; iii) 20 to 45 wt% of reactive diluent such as vinyl toluene; iv) 1.0 to 5.0 wt% curing agent.

In a preferred embodiment, the composition comprising: i) 30 to 45 wt% of elastomer modified vinyl ester; ii) 15 to 25 wt% of a reinforcing filler, such as a glass particulate e.g. glass flakes; iii) 20 to 40 wt% of reactive diluent such as vinyl toluene; iv) 1.0 to 5.0 wt% curing agent.

Preparation

The coating composition of the invention can readily be prepared by mixing the components in appropriate weight percentages. It will be appreciated that the curing agent must be separated from the elastomer modified vinyl ester binder in storage. The composition of the invention is therefore ideally supplied in a kit of parts in which a first part A) comprises the elastomer modified vinyl ester binder and a part B) comprises the curing agent. Other components of the composition can be supplied in either part A) or B) but it is preferred if other components are supplied in part A). In particular the reactive diluent should be included in part A).

When the coating composition is ready for use, the component B) containing the curing agent can be combined with component A) in an appropriate ratio. The composition should ideally be used rapidly thereafter. The invention will now be described with reference to the following non limiting examples and figures.

Brief Description of the Figures:

Figure 1A-F shows the graphs from mechanical testing using a Universal testing machine (UTM). The graphs on the left side (1 A-C) shows the mechanical properties of the coatings after curing at room temperature. The graphs on the right side (1 D-F) shows the mechanical properties after the coatings has been heated at 80 °C for 72 hours. The 3 different curves in one graph represents 3 parallels of the same sample. Examples - Determination Methods

Mechanical test

The mechanical testing was performed according to IS0178: 2010. The samples had a 3 mm thickness, 50 mm length and 10 mm with. Preparation of coating compositions

Component A as described in table 2 was prepared using high speed dispersion to mix all components homogenously. The resin was added first and stirred at low speed, then fumed silica, other additives and fillers were added. The reactive diluent was then added. The temperature was kept below 45 °C during the mixing to avoid initiating a curing reaction for the resin.

Component A and B were mixed shortly before preparation of the samples for testing.

Preparation of samples for mechanical testing

Component A was mixed thoroughly with Component B, using a high speed mixer at up to 1600 rpm for 1 min. The mixture was then poured into a rectangular silicone mould. The silicone mould was then placed inside a vacuum oven for at least 24 hours to remove trapped air bubbles. After the curing was complete, the coating films were cut into (d ^* b ^* l) rectangular structure samples (3 mm thickness, 50 mm length and 10 mm with) suitable for Universal Testing Machine (UTM).

Table 1 List of components

The following compositions are prepared:

Table 2 (wt%)

In the figures, the results from the mechanical testing of the cured coating compositions in Example 1 and comparative examples 2 and 3 are shown. The mechanical properties of the coatings were tested both after curing at room temperature and after the coatings had been heated at 80°C for 72 hours. The reason the cured coating compositions were heated is that the mechanical properties of the coating compositions may change after heating and in order to be suitable coatings for internal pipes the mechanical properties of the coatings must be sufficient also after heating.

In order to pass the test, it must be possible to subject the sample to a 1.5% 3-point bending strain without the sample breaking. The bending strain is shown on the x-axis and the 1.5% limit is illustrated by the vertical line in the graphs. The 1.5% bending strain is chosen as the test criteria because this reflects the expected thermo-expansion of the coatings when used within a pipe. If the coating cannot withstand this thermo-expansion it will crack in the pipes.

In order to withstand the thermo-expansion and the 1.5% bending strain used in the tests the coatings must have a high toughness and flexibility.

Graph 1A and 1D shows the results for the coating composition of the invention in example 1. Graph 1A shows the mechanical properties of the cured coating composition after curing at ambient temperature and Graph 1 D shows the mechanical properties of the coating after heating at 80 °C. It can be seen that both samples are able to withstand the 1.5% bending strain without breaking. When the curves stop, that indicates that the coating sample broke. The three different curves in the same graph represents three parallels of the same sample.

Graph 1B and 1E shows the results for the coating composition of Comparative example 2. It can be seen that for the coating cured at ambienttemperature (Graph 1 B) one of the parallels did not break before the 1.5% bending strain but the two other parallels did. Graph 1 E shows that after heating at 80 °C the coating composition loses some of the toughness and flexibility and then breaks before 1.5% bending strain is applied. Graph 1C and 1F shows the results for the coating composition in Comparative example 3. It can be seen that both after curing at ambient temperature and after heating at 80°C the samples break before 1.5% bending strain is applied.

These test result clearly show that the coating composition comprising the elastomer modified vinyl ester resin (example 1) has significantly improved mechanical properties compared to the coating compositions comprising a polyester resin (Comparative example 2) and a novolac vinyl ester resin (Comparative example 3).