GB2465409A

GB2465409A - Sealant

Info

Publication number: GB2465409A
Application number: GB0818926A
Authority: GB
Inventors: Peter David Young
Original assignee: SEAL Ltd X
Current assignee: SEAL Ltd X
Priority date: 2008-10-16
Filing date: 2008-10-16
Publication date: 2010-05-26
Also published as: GB0818926D0

Abstract

A hydrophilic cold cure sealant product that comprises: (a) hydrophilic monofunctional monomer, which is acrylate or methacrylate monomer, in an amount of from 60 to 95wt% by total weight of monomer; (b) cross-linking agent, which is polyfunctional monomer suitable for cross-linking the monomer (a), in an amount of from 1 to 35wt% by total weight of monomer; (c) a polymerisation catalyst, which is a C2-C20 organic peroxide, in an amount of from 0.1 to 5wt% by total weight of monomer; (d) a polymerisation accelerant, which is an aromatic amine, in an amount of from 0.1 to 5wt% by total weight of monomer, wherein the hydrophilic monofunctional monomer (a) and the cross-linking agent (b) make up 80wt% or more of the total monomer content. For preference the monofunctional monomer (a) is (i) hydroxypropyl methacrylate or (ii) hydroxypropyl methacrylate and isotridecylmethacrylate, for preference, cross-linker (b) is triethylene glycol dimethacrylate, whilst (c) is preferably benzoyl peroxide, and preferably (d) is N,N-dimethyl-p-toluidine.

Description

SEALANT

The present invention relates to a sealant, and to methods of sealing voids using said sealant.

Fillers for filling gaps or cracks in a substrate have been used for many years. For example, epoxy based or polyester based putty fillers, plaster of Paris fillers, and proprietary plaster based fillers such as Polyfilla, are well known.

Sealants are also known for use in relation to voids/porosity in a porous substrate, including concrete, wood, metal, stone, clay, fabric, or leather substrates. However, such sealants will commonly coat the surface of the substrate, forming a hydrophobic film over the voids, rather than filling the voids.

Some sealants, such as epoxy type sealants, which contain extenders and solvents to reduce their viscosity, are injected under pressure and subsequently cure over a period of time.

The present invention provides, in a first aspect, a hydrophilic cold cure sealant product that comprises: (a) hydrophilic monofunctional monomer, which is acrylate or methacrylate monomer, in an amount of from 60 to 95wt% by total weight of monomer; (b) cross-linking agent which is polyfunctional monomer suitable for cross-linking the monomer (a), in an amount of from 1 to 35wt% by total weight of monomer; (c) a polymerisation catalyst, which is a C2-C20 organic peroxide, in an amount of from 0.1 to 5wt% by total weight of monomer; (d) a polymerisation accelerant, which is an aromatic amine, in an amount of from 0.1 to 5wt% by total weight of monomer, wherein the hydrophilic monofunctional monomer (a) and the cross-linking agent (b) make up 8Owt% or more of the total monomer content.

The sealant product is suitable for use in filling the voids/porosity in porous substrates, including porous concrete, wood, metal, stone, clay, fabric, or leather substrates. Generally, any absorbent substrate can be treated provided that it is not prone to be incompatible with the sealant.

The sealant product can also be used to fully encapsulate products, e.g. to seal products from exposure to moisture.

When a sealant product cures, it will normally shrink (e.g. by 10 to 15% by volume). However, as the present sealant product is hydrophilic, once it has cured and shrunk within the void it can subsequently absorb atmospheric moisture and thus expand to fill the void. Advantageously, therefore, under damp conditions, the sealant product of the present invention will ensure that the void is properly filled with sealant and thus the substrate is sealed. This is especially an advantage when using the sealant of the present invention to seal a substrate from moisture ingress; in such a use the sealant is applied in dry conditions, shrinks on curing and then when the substrate is next exposed to moisture the sealant will expand to fill the void and provide a complete barrier to the moisture.

Further, the sealant product of the present invention is more able to adapt to its environment than known sealant products. The cured product becomes ductile on absorption of moisture and therefore is able to move with the substrate rather than being too strong and unyielding.

In one embodiment, the product comprises 3Owt% or less, by total weight of monomer, of components that are not components (a) to (d), such as 25wt% or less, preferably 2Owt% or less, such as lOwt% or less, 5wt% or less, 3wt% or less, or lwt% or less. The product may, for example, in one embodiment consist essentially of components (a) to (d).

Tn one embodiment, the sealant product has low water content, for example it may include 5wt% or less, by total weight of monomer, of water; such as lwt% or less, e.g. 0.5wt% or less of water.

In an alternative embodiment, the sealant may include water, for example in an amount of 3wt% or more, by weight of the monomer, preferably 5wt% or more, such as from 8 to l2wt%, e.g. from 8 to lOwt% or from to l2wt%, so that once the sealant has cured it is conditioned by the presence of the water to be more readily accessible to further absorption of water and thus further expansion, especially at lower concentrations.

In one embodiment an amount of water of up to l2wt%, by total weight of the sealant product, may be used, such as up to lOwt%. It has been found that the use of water amounts in the sealant product of up to about to 12 wt%, by weight of the total product, produces a tough hydrogel in the cured state, which may, for example, be beneficial for applications where ductile strength is key.

In the present application, a monomer having one radically polymerisable double bond in the molecule is referred to as a monofunctional monomer and a monomer having at two or more radically polymerisable double bonds in the molecule is referred to as a polyfunctional monomer.

The hydrophilic monofunctional monomer (a) may be a single hydrophilic monofunctional monomer or may be a mixture of two or more different hydrophilic monofunctional monomers.

The skilled man would understand that whilst all acrylates and methacrylates are somewhat polar, due to the ester group and the C=C double bond, this polarity can be offset to a great degree by the backbone structure of the monomer. Therefore acrylates and methacrylates with a long alkane/alkene backbone chain (e.g. those with 10 or more carbon atoms) would not overall be sufficiently polar to be considered as a hydrophilic monomer.

The hydrophilic monofunctional monomer (a) is preferably a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, or mixtures thereof.

Preferably in the hydroxyalkyl acrylate or hydroxyalkyl methacrylate the alkyl has 6 or fewer carbon atoms, in particular the alkyl may be C1-C6 straight or branched chain alkyl or C3-C6 cycloalkyl; more preferably the alkyl is a Cl-C4 straight or branched chain alkyl.

In particular, hydroxymethyl acrylate or methacrylate, hydroxyethyl acrylate or methacrylate, hydroxypropyl acrylate or methacrylate or hydroxybutyl acrylate or methacrylate may be used.

Preferably, the monomer (a) comprises hydroxypropyl methacrylate (HPMA).

It can be advantageous to use hydroxypropyl methacrylate (HPMA) or similar monomers as the monomer (a) because these are low viscosity monomers. This therefore permits the product to be easily applied in a relatively liquid form, e.g. using a pipette, spray or pump action container.

The hydrophilic monofunctional monomer (a) is present in an amount of from 60 to 95wt%, by total weight of monomer, for example from 70 to 95wt%, e.g. from 75 to 95wt%, such as from 80 to 95wt%.

The use of such monomer types means that the sealant will only cure in low oxygen, e.g. anaerobic, environments and therefore it is only once the sealant is within the voids that it will cure and harden; it will not cure in a normal atmospheric air environment. Low oxygen environments may in particular be those with 5vol% of oxygen or less, such as 3vol% or less, 2vol% or less or lvol% or less.

Small amounts of sealant product that are applied on the surface of the substrate will generally evaporate off. Generally, films having a thickness of 1mm or less will not cure, although they may remain tacky as the uncured monomer evaporates off.

This phenomenon of a thin layer of sealant at the substrate surface not curing, because of the richness of oxygen at the surface, may be used to good effect when it comes to sealing structures where there is a desire to maintain the original appearance, e.g. listed buildings and stately homes.

Films of greater depth may be applied where curing is desired on the surface, as this will allow curing to take place at the interface between the substrate surface and the layer of sealant as due to the thickness of film above the interface this region will be low in oxygen. The sealant will, however, not cure up to its outer surface unless sufficient heat is generated during the curing phase to drive off oxygen in this region.

The cross-linking agent (b) may be a single polyfunctional monomer or may be a mixture of two or more different polyfunctional monomers.

The cross-linking agent (b) is preferably a polyfunctional acrylate or methacrylate monomer, or a mixture thereof; in particular it may be an acrylate or methacrylate ester of a polyol, such as a diol or triol. The poiyoi may in particular be an alkylene poiyol or a polyalkylene polyol.

The alkylene group may suitably be a C1-C6 alkylene.

The cross-linking agent may by symmetric or asymmetric. For example, the cross linking agent may be a symmetrical monomer with two methacryloyl groups or two acryloyl groups, or may be an asymmetric monomer with one acryloyl group, or one methacryloyl group, or one methacryloyl group and one acryloyl group.

Examples of cross-linking agents include difunctional monomers such as ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethyl ene glycol diacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, tripropylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,4-butanediol dimethyacrylate, hexane diol diacrylate, 1,3-butylene glycol diacrylate, triisopropylene glycol diacrylate; and trifunctional monomers such as trimethyloipropane triacrylate, trimethylolpropane trimethacrylate, glyceryl triacrylate, trimethylolpropane triethoxy triacrylate, and pentaerythritol triacryl ate.

Propoxylated and ethoxylated versions of these monomers may also be considered.

In one embodiment, the polyfunctional monomer is a difunctional monomer. In another embodiment, the polyfunctional monomer is a trifunctional monomer.

The cross-linking agent may preferably be a difunctional or trifunctional monomer which is an acrylate or methacrylate ester of ethylene glycol or polyethylene glycol.

Preferably, the cross-linking agent comprises triethylene glycol dimethacrylate (TEDMA).

The cross-linking agent (b) is present in an amount of from 1 to 35wt%, by total weight of monomer, e.g. from 3 to 25wt%, such as from 4 to 2Owt%, for example from 5 to l5wt%.

In one embodiment, the monomer (a) and the cross-linking agent (b) make up 85wt% or more of the monomer content, preferably 9Owt% or more, for example 95wt% or more, such as 98wt% or more, e.g. 99wt% or more; in one embodiment the monomer (a) and the cross-linking agent (b) make up 100% of the monomer content.

The polymerisation catalyst (c) may be a single organic peroxide catalyst or a mixture of two or more organic peroxide catalysts.

The polymerisation catalyst (c) may be any organic peroxide of formula ROOR' where R and R' may be the same or different and are selected from hydrogen and hydrocarbons, and where there are a total of from 2 to carbon atoms present.

The groups R and R' may in particular be selected from hydrogen, alkyl, aryl and alkanoyl groups. The alkyl and alkanoyl groups may suitably be C2-C14 groups, and the aryl C6-C14 groups. For example, the alkyl and alkanoyl groups may suitably be C3-C12 groups, and the aryl C6-C12 groups. The hydrocarbon groups may be substituted, for example with halo groups, hydroxy groups, amino groups, or alkoxy groups, or may be In one embodiment, there are from 3 to 18 carbon atoms present in the organic peroxide, for example from 4 to 17 carbon atoms, such as from 5 to 15 carbon atoms.

In one embodiment, one of R and R' is hydrogen and the other is a hydrocarbon, i.e. the peroxide is a hydroperoxide. Suitable hydroperoxides for use in this embodiment include methyl ethyl ketone hydroperoxide, di-isopropyl benzene hydroperoxide, t-butyl hydroperoxide, and cumene hydroperoxide.

In another embodiment, both R and R' are hydrocarbons. Suitable peroxides for use in this embodiment include dibenzoyl peroxide (commonly known as benzoyl peroxide), diacetyl peroxide, dodecanoyl peroxide, t-butyl peroxy isopropyl carbonate, t-butyl perbenzoate, 2,2- bis(t-butyl peroxy) butane, bis(1-hydroxy-cyclohexyl) butane and bis(1 -hydroxy-cyclohexyl) peroxide.

Preferably the catalyst comprises benzoyl peroxide (BP).

The polymerisation catalyst (c) is present in an amount of from 0.1 to 5wt%, by total weight of monomer, such as from 0.5 to 4wt%, e.g. from ito 3wt%.

The polymerisation accelerant (d) may be a single aromatic amine, or a mixture of two or more aromatic amines.

The polymerisation accelerant (d) may be any aromatic amine, including aniline, toluidine, xylidine, aminopyridine, aminoglutethimide, aminobenzoic acid and aminobenzaldehyde, and substituted derivatives thereof, and mixtures thereof.

In particular, substituted derivatives may be used whereby one or both hydrogen groups on the nitrogen of the amine group are substituted with hydrocarbons, such as alkyl or alkoxy groups. The hydrocarbon substituents may, for example, be C1-C6 hydrocarbons, e.g. Cl, C2, C3 or C4 hydrocarbons, such as methyl, ethyl, propyl, hydroxymethyl, hydroxyethyl and hydroxypropyl.

The polymerisation accelerant may be an aromatic amine with any suitable number of carbon atoms. Preferably, the aromatic amine has from 6 to 20 carbon atoms, such as from 6 to 18 carbon atoms, preferably from 8 to 16 carbon atoms.

In one embodiment, the aromatic amine is a tertiary amine. In particular, the aromatic amine may be a tertiary amine where the nitrogen of the amine group is substituted with hydrocarbon substituent groups, for example C1-C6 hydrocarbons, e.g. Cl, C2, C3 or C4 hydrocarbons. The hydrocarbons may in particular be alkyl or alkoxy groups.

Examples of polymerisation accelerants that can be used include aniline, N,N-dimethylaniline, N, N-diethylaniline, toluidine, N, N-dimethyl p- toluidine, N,N-dimethyl aminoglutethimide, N,N-di(hydroxyethyl) p-toluidine, N,N-di(hydroxypropyl) p-toluidine, 4-N,N-dimethyl aminopyridine, 3-N, N-dimethyl aminobenzoic acid, 4-N,N-dimethyl aminobenzoic acid and 4-N,N-dimethyl aminobenzaldehyde.

Preferably, the accelerant comprises N, N-dimethyl p-toluidine (DMPT).

The polymerisation accelerant is present in an amount of from 0.1 to 5wt%, by total weight of monomer, such as from 0.5 to 4wt%, e.g. from ito 3wt%.

In one embodiment the product may further comprise an inhibitor, for example in amounts of 3wt% or less, by total weight of monomer, such as from 0.01 to 2wt%. Any known inhibitors, such as hydroquinone and substituted hydroquinones, e.g. methyihydroxyquinone, or butylated hydroxytoluene, may be used.

In one embodiment the product may further comprise a thinner or diluent.

Suitably this may be a cross-linker product. The product may, for example, further comprise a thinner or diluent which is a low molecular weight monomer (e.g. with a molecular weight of 150 or less) such as methyl methacrylate monomer. This may be included in an amount of lOwt% or less, by total weight of monomer, such as from 1 to 5wt% or from 5 to lOwt%.

It can be advantageous to add methyl methacrylate monomer to the formulation to reduce viscosity and/or enhance penetration of the substrate.

In one embodiment the product may further comprise a flexibilising agent. Flexibilising agents are known in the art for producing a flexible cured monomer. This agent may be included in an amount of lOwt% or less, by total weight of monomer, such as from 1 to 5wt% or from 5 to lOwt%.

In one embodiment, the product contains no solvents. In another embodiment, the product contains solvent, e.g. in an amount of l2wt% or less, by total weight of monomer, such as lOwt% or less or 5wt% or less; for example there may be 3wt% or less, 2wt% or less, lwt% or less or 0.5wt% or less of solvent.

In one embodiment, the product contains no hydrophobic monomers.

In another embodiment, the product contains hydrophobic monomers in an amount of 2Owt% or less, by total weight of monomer, such as l5wt% or less or lOwt% or less. For example, the product may contain hydrophobic monomers in an amount of 5wt% or less, by total weight of monomer, such as 2wt% or less, e.g. lwt% or less, such as 0.5wt% or less.

It may be beneficial in some embodiments to include some hydrophobic monomer, e.g. in an amount of from 1 to 2Owt%, by total weight of monomer, such as from 5 to l5wt%. Hydrophobic monomers that may be mentioned are acrylates and methacrylates with a long alkane/alkene backbone chain (e.g. those with 10 or more carbon atoms, such as 11 or more or 12 or more carbon atoms), such as isotridecyl methacrylate or isotridecyl acrylate.

Specifically, for sealants to be used in applications where high levels of moisture absorption are not required some hydrophobic monomer may suitably be incorporated. For instance, the hydrophilic monomer HPMA which can be used as monomer (a) can absorb up to l2wt% water in the liquid state; such high levels of water absorption will not always be required or desired. Therefore by including an amount of hydrophobic monomer this water absorption ability of the sealant product can be reduced to suit particular needs.

The product is suitably provided as a two container product, wherein the cross-linking agent (b) is provided in the first container and the polymerisation catalyst (c) is provided in the second container.

Accordingly, in a second aspect the invention provides a two container cold cure sealant product, comprising a first container and a second container, and the components of a sealant product according to any one of the preceding claims, wherein the cross-linking agent (b) is provided in the first container and the polymerisation catalyst (c) is provided in the second container.

In one embodiment, the accelerant (d) is provided in the first container with the cross-linking agent (b).

The monofunctional monomer (a) may be provided in the first container, in the second container, or in both the first container and the second container.

When the monofunctional monomer (a) is provided in both the first container and the second container, it may suitably be split between the two containers in a weight ratio of from 40:60 to 60:40, preferably from 45:55 to 55:45, more preferably approximately 50:50 between the two containers.

The second container may optionally include inhibitor. In particular, when the second container includes some or all of the monomer (a) together with the catalyst (c) the second container may suitably include inhibitor. Suitable inhibitors and amounts are mentioned above. This provides an improved shelf life.

The contents of the two containers may be combined when the end user is ready to use the sealant on a substrate, e.g. to fill voids/porosity in such substrates. The substrates may, for example, be porous concrete, wood, metal, stone, clay, fabric, or leather substrates. Aluminium fabrications, that need sealing, such as aircraft fuselages, can, for example, be considered.

The contents of the two containers may preferably be mixed and then applied to the substrate. They may be mixed in the first container, or in the second container, or in a separate container.

Alternatively the contents of the two containers may be separately applied to the substrate and mixed in situ.

The provision of the product in a two container form in accordance with the invention gives a product that has excellent shelf life and stability.

In one embodiment, the contents of the first container are a different colour to the contents of the second container. In particular, colorant, such as a pigment or dye, may be added to the contents of one or both of the containers.

In one embodiment, the colours of the contents of the first container and second container are independently selected from white, pink, red, orange, yellow, green, blue, purple, grey, brown and black.

The colours of the contents of the first and second containers may be chosen such that when the contents of the first and second containers are mixed together the mixture is a third colour. For example, the colours yellow and blue may be chosen for the contents of the first and second container, so that when mixed the resultant product is green, or the colours yellow and red may be chosen for the contents of the first and second container, so that when mixed the resultant product is orange.

The invention provides, in a third aspect, a method of filling one or more voids in a substrate, which method comprises: (i) providing a sealant product in accordance with the first aspect; (ii) applying the sealant product to the voids; and (iii) allowing the sealant product to cure in the voids.

In one embodiment, the sealant product is provided in a two container form and the contents of the two containers are mixed prior to applying the product in step (ii). In particular, the sealant product may be provided as a two container cold cure sealant product in accordance with the second aspect.

In step (iii) the curing is suitably effected as a cold cure, i.e. there is no requirement to heat the product above ambient temperature for the curing to occur. The skilled man will, of course, appreciate that some heat is liberated during curing and can be as much as 110°C if the sealant has no heat sink. The curing occurs in a low oxygen environment, e.g. an anaerobic environment.

The gel time for the product may be from about 2 to 5 minutes or more.

The void may be a void/porosity in a porous substrate. The void may also be any crack, hole or gap in a substrate which is any material, for example a crack, hole or gap in a wall, roof, window frame or door frame.

In one embodiment, the substrate is a porous substrate such as a porous concrete, wood, metal, stone, clay, fabric, or leather substrate.

Aluminium fabrications that need sealing, such as aircraft fuselages, can, for example, be considered.

The sealant product may be applied into the voids/porosity by any suitable means, for example it may be applied using a pipette, a syringe, a pump action container, or a spray.

It is also possible to spread the product over the surface of the substrate, for example using a trowel or brush or roller. In such an embodiment the product may be applied to cover the surface in a thin layer (e.g. 1mm or less) and enter the voids; any product or dampness remaining on the surface will evaporate whilst the product in the voids will cure.

In one embodiment, prior to step (ii) dry filler is introduced into the voids. For example, the dry filler may be granular or fabric filler, such as sand, slate powder, sawdust, wood chips, mineral fillers, or cotton wool. Any dry filler product that will absorb but not react with the sealant product may be considered. Preferably any granular material used is coarse free flowing grain rather than powder.

Preferably the average diameter of the particles in the filler is 2mm or greater, such as 3mm or greater. In one embodiment, 5Owt% or more of the particles in the filler have a particle diameter of 2mm or greater, such as 3mm or greater; for example 9Owt% or more of the particles in the filler may have a particle diameter of 2mm or greater, such as 3mm or greater; it may be that lOOwt% of the particles in the filler have a particle diameter of 2mm or greater, such as 3mm or greater.

When the sealant product is applied to a void that contains such dry filler, the sealant product is absorbed around the dry filler by capillary attraction and the combined filler plus sealant then cures to give a solid mass within the void. As the void is saturated with the sealant a strong interface with the interior surfaces of the void is achieved.

This option is particularly useful when dealing with voids that would normally not hold the non cured sealant product well, due to its low viscosity. The use of dry filler ensures that sufficient sealant product is drawn into and held within the void before curing.

The invention provides, in a fourth aspect, a method of encapsulating a substrate, which method comprises: (i) providing a sealant product in accordance with the first aspect; (ii) applying the sealant product to encapsulate the substrate; and (iii) allowing the sealant product to cure.

The gel time for the product may be from about 2 to 5 minutes or more.

The sealant product may be applied to encapsulate the substrate by any suitable means, for example it may be injected to the relevant area to encapsulate the substrate, e.g. using a pipette or syringe.

The substrate may alternatively be dipped into the sealant product.

Alternatively, the sealant product may be applied to the substrate using a pump action container or a spray. It is also possible to spread the product over the surface of the substrate, for example using a trowel or brush or roller. The product may be applied to cover the surface in a sufficiently thick layer (e.g. 2mm or more) to ensure that the interface between the substrate and the sealant product is sufficiently anaerobic that the sealant product will cure.

The substrate may be any product that requires encapsulation, e.g. to protect the product from moisture.

In one such embodiment the substrate may be an electrical component, such as windings. In order to encapsulate the electrical component the sealant may be applied over the entire electrical component or the electrical component may be dipped in the sealant product.

In another such embodiment the substrate may be a reinforcing metal product, such as the steel reinforcements in concrete structures, e.g. bridges. The sealant product of the invention may be injected to the relevant area to encapsulate the rusted metal, to control/prevent further deterioration.

The invention also provides, in a fifth aspect, the use of a product in accordance with the first aspect or second aspect to fill a void in a substrate.

The substrate may be a porous substrate, such as a porous concrete, wood, metal, stone, clay, fabric, or leather substrate.

The void may also be any crack, hole or gap in a substrate which is any material, for example a crack, hole or gap in a wall, roof, window frame or door frame.

The sealant product may also be used as an adhesive, as when it cures it will form a bond between any two surfaces it contacts. As mentioned above, curing will occur in any low oxygen environment; this may be achieved by pushing the two substrate surfaces together. Also, if a layer of sealant that is sufficiently thick, e.g. 1mm or more, is applied then the part of this layer at the interface between the sealant and the substrate surface will cure even before the substrate surfaces are pressed together.

Accordingly, the invention also provides, in a sixth aspect, the use of a product in accordance with the first aspect or second aspect to adhere two surfaces together.

The low viscosity of the sealant product permits improved wetting of the surfaces, thus causing better adhesion of the surfaces. It also allows the two surfaces to nest closer together than would be possible with high viscosity adhesive.

The sealant products may generally have low viscosities, such as a viscosity of 85 Zahn seconds or less when measured in a Zahn No: 1 cup at 18°C, preferably 70 Zahn seconds or less, such as 60 Zahn seconds or less; more preferably 50 Zahn seconds or less, e.g. 40 Zahn seconds or less, or 30 Zahn seconds or less.

I may be that the sealant products have viscosities, when considered in centipoise, of 85 centipoises or less.

The invention also provides, in a seventh aspect, the use of a product in accordance with the first aspect or second aspect to seal a substrate, such as a porous substrate, e.g. a porous concrete, wood, metal, stone, clay, fabric, or leather substrate.

In one embodiment, the product is used to seal riveted fabrications; this may be used to improve structural strength and/or to reduce vibration.

The invention also provides, in an eighth aspect, the use of a product in accordance with the first aspect or second aspect to encapsulate a substrate; for example to encapsulate an electrical component, such as windings, or to encapsulate a reinforcing metal product, such as the steel reinforcements in concrete structures, e.g. bridges.

The present invention will now be further illustrated by means of the following non-limiting example.

Example

Formulation A (all amounts are given as weight % by total weight of monomer) 96% hydroxypropyl methacrylate (HPMA) 4% triethylene glycol dimethacrylate (TEDMA) 4% benzoyl peroxide (BP) 3% N,N-dimethyl p-toluidine (DMPT) Formulation B (all amounts are given as weight % by total weight of monomer) 60% hydroxypropyl methacrylate (HPMA) 40% triethylene glycol dimethacrylate (TEDMA) 3% benzoyl peroxide (BP) 2% N,N-dimethyl p-toluidine (DMPT) Formulation C (all amounts are given as weight % by total weight of monomer) 70% hydroxypropyl methacrylate (HPMA) 20% isotridecyl methacrylate (ITDM) 10% triethylene glycol dimethacrylate (TEDMA) 4% benzoyl peroxide (BP) 3% N,N-dimethyl p-toluidine (DMPT) The formulation A had a viscosity of 29 Zahn seconds when measured in a No: 1 Zahn Cup at 18°C.

The formulations A, B and C were each provided as a two container product.

For the formulations A and B, the first container contained HPMA, TEDMA and DMPT and the second container contained HPMA and BP.

For the formulation C, the first container contained HPMA, ITDM, TEDMA and DMPT and the second container contained HPMA, ITDM and BP.

In order to improve the shelf life of the contents of the second container, a small amount (e.g. 0.2%) of inhibitor, such as butylated hyclroxytoluene inhibitor, may be added.

The total amount of HPMA was split approximately 50:50 between the two containers but with a � 5% degree of accuracy.

For formulation C, the total amount of ITDM was also split approximately 50:50 between the two containers but with a � 5% degree of accuracy.

The contents of the containers may have colorant added. For example, the content of the first container may be coloured blue and the contents of the second container may be coloured yellow.

The contents of the first container are mixed with the contents of the second container prior to use.

Once the mixed sealant product is introduced into a low oxygen environment, such as an anaerobic environment, e.g. once it is inserted into a void, it will cure. Although the product shrinks on curing, due to its hydrophilic nature it subsequently absorbs moisture and thus can expand. Provided the atmosphere is sufficiently damp it can expand to fully fill the void.

The sealant product is a cold cure product, not needing external heat.

The sealant product may be used to fill voids/porosity in a porous substrate, such as a porous concrete, wood, metal, stone, clay, fabric, or leather substrate.

The sealant product may suitably be applied into the void using a pipette, a pump action container, or a spray.

The sealant formulations A, B and C were tested as follows: Test procedure Take a normal house brick and break it into smaller portions and then fit the parts back together. Take and secure two mating parts of the brick, having mating faces of at least 40 to 50mm long and similar in depth.

Stand the face upper most and apply the mixed sealant by pipette at the rate of absorption of the crack. Continue the application until saturation of the crack is observed.

Leave the test piece to cure and stand for 24 hrs. Then cement an open ended clear glass tube over the centre of the crack, using silicone cement, and leave to cure for lhr. Fill the tube with water and mark the initial water level. Leave for 24 hrs and note any loss.

For each of the formulations tested no significant loss was noted, other than what might be expected from evaporation. This indicates that the sealant had successfully formed a water tight seal between the parts of the brick.

Claims

CLAIMS1. A hydrophilic cold cure sealant product that comprises: (a) hydrophilic monofunctional monomer, which is acrylate or methacrylate monomer, in an amount of from 60 to 95wt% by total weight of monomer; (b) cross-linking agent, which is polyfunctional monomer suitable for cross-linking the monomer (a), in an amount of from 1 to 35wt% by total weight of monomer; (c) a polymerisation catalyst, which is a C2-C20 organic peroxide, in an amount of from 0.1 to 5wt% by total weight of monomer; (d) a polymerisation accelerant, which is an aromatic amine, in an amount of from 0.1 to 5wt% by total weight of monomer, wherein the hydrophilic monofunctional monomer (a) and the cross-linking agent (b) make up 8Owt% or more of the total monomer content.
2. The product of claim 1, wherein the product comprises from 75 to 95wt% or less, by total weight of monomer, of hydrophilic monofunctional monomer (a).
3. The product of claim 1 or claim 2, wherein the hydrophilic monofunctional monomer (a) is a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, or mixtures thereof.
4. The product of claim 3, wherein the hydrophilic monofunctional monomer (a) is selected from hydroxymethyl acrylate, hydroxymethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate and hydroxybutyl methacrylate.
5. The product of any one of the preceding claims, wherein the cross-linking agent (b) is a polyfunctional acrylate or methacrylate monomer, or a mixture thereof.
6. The product of claim 5, wherein the cross-linking agent is a difunctional or trifunctional monomer which is an acrylate or methacrylate ester of ethylene glycol or polyethylene glycol.
7. The product of any one of the preceding claims, wherein the polymerisation catalyst (c) is an organic peroxide of formula: ROOR' wherein R and R' may be the same or different and are selected from hydrogen, C2-C14 alkyl, C6-C14 aryl and C2-C14 alkanoyl groups.
8. The product of any one of the preceding claims wherein the polymerisation catalyst (c) is an organic peroxide having from 5 to 15 carbon atoms.
9. The product of any one of the preceding claims wherein the polyrnerisation accelerant (d) is a tertiary aromatic amine where the substituent groups on the nitrogen of the amine group are C1-C6 hydrocarbons.
10. The product of any one of the preceding claims wherein the polymerisation accelerant (d) is selected from aniline, toluidine, xylidine, aminopyridine, aminoglutethimide, aminobenzoic acid and aminobenzaldehyde, substituted derivatives thereof, and mixtures thereof.
11. The product of claim 10 wherein the polymerisation accelerant (d) is a substituted derivative of aniline, toluidine, xylidine, aminopyridine, aminoglutethimide, aminobenzoic acid or aminobenzaldehyde, whereby one or both hydrogen groups on the nitrogen of the amine group are substituted with C1-C6 alkyl or alkoxy groups.
12. The product of any one of the preceding claims wherein the product further comprises one or more of: (a) an inhibitor, in an amount of 3wt% or less by total weight of monomer; (b) a thinner or diluent, in an amount of lOwt% or less, by total weight of monomer; (c) a flexibilising agent, in an amount of lOwt% or less, by total weight of monomer.
13. A two container cold cure sealant product, comprising a first container and a second container, and the components of a sealant product according to any one of the preceding claims, wherein the cross-linking agent (b) is provided in the first container and the polymerisation catalyst (c) is provided in the second container.
14. The product of claim 13 wherein the accelerant (d) is provided in the first container.
15. The product of claim 13 or claim 14, wherein some or all of monomer (a) is provided in the second container, together with an inhibitor.
16. A method of filling voids in a substrate, which method comprises: (i) providing a sealant product in accordance with any one of claims ito 12; (ii) applying the sealant product to the voids; and (iii) allowing the sealant product to cure in the voids.
17. The method of claim 16 wherein the substrate is a porous concrete, wood, metal, stone, clay, fabric, or leather substrate.
18. The method of claim 16 or claim 17 wherein prior to step (ii) dry filler is introduced into the voids.
19. A method of encapsulating a substrate, which method comprises: (i) providing a sealant product in accordance with any one of claims ito 12; (ii) applying the sealant product to encapsulate the substrate; and (iii) allowing the sealant product to cure.
20. The method of claim 19, wherein the substrate is an electrical component or a reinforcing metal product.
21. The method of any one of claims 16 to 20 wherein the sealant product is provided in the form of a two container product according to any one of claims 13 to 15 and the contents of the two containers are mixed prior to applying the product in step (ii).
22. The use of a product in accordance with any one of claims 1 to 15 to fill a void in a substrate.
23. The use of claim 21, wherein the void is pores in a porous substrate, or any crack, hole or gap in any substrate.
24. The use of a product in accordance with any one of claims 1 to 15 to adhere two surfaces together.
25. The use of a product in accordance with any one of claims 1 to 15 to seal a substrate.
26. The use of a product in accordance with any one of claims 1 to 15 to encapsulate a substrate.