Patent Description:
It is often necessary to provide thermal insulation for substrates useable subsea, such as may be used in hydrocarbon facilities. In such instances it is required to provide a bond between the substrate and the thermal insulation material which will be strong and long lasting in the harsh operating conditions experienced subsea.

There is a requirement therefore to provide tie coat structures which securely bond thermal insulation material to a substrate useable subsea, wherein the bond formed will be strong and long lasting in the harsh operating conditions experienced subsea.

All proportions referred to in this specification are indicated as weight % (wt/%).

<CIT> discloses a composition comprising (A) an alkenyl group-containing polydiorganosiloxane; (B) a condensation product of (a) a polydiorganosiloxane having hydroxyl group or an alkoxy group on opposite ends of the molecular chain and (b) a polyorganosiloxane containing R<NUM><NUM> SiO<NUM>/<NUM> unit and SiO<NUM> unit as critical components and also a HOSiO<NUM>/<NUM> unit in the molecule; (C1) a polyorganohydrosiloxane having at least three SiH groups per molecule; (C2) a polydiorganohydrosiloxane having SiH group on opposite ends; and (D) a platinum group metal catalyst.

<CIT> discloses a bioreactor for cultivating phototrophic organisms in an aqueous culture medium. The reactor parts and/or fittings that come into contact with the culture medium are entirely or partially coated with a silicone layer. The silicone layer can be an addition-crosslinking silicone rubber obtained by crosslinking multiply ethylenically unsaturated groups, preferably vinyl groups, of substituted organopolysiloxanes with organopolysiloxanes multiply substituted with Si-H groups in the presence of platinum catalysts.

<CIT> discloses a thermal insulation material for use subsea, the material comprising a platinum cured silicone resin matrix, and up to <NUM>% of a micronised polymer. The silicone resin may be a two-part system. The first part may include a crosslinker which may have a reactive Si-H group such as poly(hydromethylsiloxane-co-dimethylsiloxane). The second part may include a material with vinyl groups such as poly(vinylmethylsiloxane-co-dimethylsiloxane). The second part may also include a platinum catalyst and a silicone dye.

According to various, but not necessarily all, examples of the disclosure there is provided a method of bonding silicone thermal insulation material to a substrate useable subsea, the method comprising applying a silicone tie coat to the substrate to a thickness of at least <NUM>, the silicone tie coat being the reaction product of a mixture comprising polydiorganosiloxane polymer and an organohydrogensiloxane crosslinker, the reaction being catalyzed by a metallic catalyst, the method further comprising bonding silicone thermal insulation material to the silicone tie coat.

The silicone tie coat may have a thickness of about <NUM> to about <NUM>, and more particularly the silicone tie coat may have a thickness of about <NUM> to about <NUM>.

The polydiorganosiloxane polymer may comprise polymethylvinyl siloxane. The organohydrogensiloxane crosslinker may comprise polymethylhydro siloxane.

The metallic catalyst may be a platinum catalyst. The platinum catalyst may comprise an organoplatinum catalyst. The organoplatinum catalyst may comprise platinum divinyl tetramethyl disiloxane or cyclovinyl methyl siloxane complex.

The method may comprise adjusting the amount of metallic catalyst to control the reaction rate.

The reaction may require an organic solvent, wherein the method may comprise adjusting the amount of organic solvent to control the reaction rate.

According to various, but not necessarily all, examples of the disclosure there is provided a thermal insulation structure for a substrate useable subsea, the thermal insulation structure comprising a silicone tie coat bonded to silicone thermal insulation material, wherein the silicone tie coat is the reaction product of a mixture comprising polydiorganosiloxane polymer and an organohydrogensiloxane crosslinker, the reaction being catalyzed by a metallic catalyst, wherein the silicone tie coat has a thickness of at least <NUM>.

According to various, but not necessarily all, examples of the disclosure there is provided a thermally insulated substrate useable subsea, the thermally insulated substrate comprising a silicone tie coat bonded to the substrate and silicone thermal insulation material bonded to the silicone tie coat, the silicone tie coat providing a layer between the substrate and the silicone thermal insulation material, wherein the silicone tie coat is the reaction product of a mixture comprising polydiorganosiloxane polymer and an organohydrogensiloxane crosslinker, the reaction being catalyzed by a metallic catalyst, wherein the silicone tie coat has a thickness of at least <NUM>.

According to various, but not necessarily all, examples of the disclosure there may be provided examples as claimed in the appended claims.

For a better understanding of various examples that are useful for understanding the detailed description, reference will now be made by way of example only.

Examples of the disclosure provide a silicone tie coat for bonding thermal insulation material to a substrate useable subsea, and in particular for bonding silicone thermal insulation material to a substrate useable subsea.

The term 'substrate' covers subsea equipment useable subsea, and also thermal insulation material. Substrates useable subsea comprise, for example, subsea equipment as may be used in hydrocarbon facilities. Items of subsea equipment which benefit from thermal insulation include: wellheads and Xmas trees, spool pieces, manifolds, risers, pipelines and pipeline field joints. In such applications, the thermal insulation maintains the temperature of the extracted fluids as they pass through portions of the equipment exposed to the cooling effects of sea water.

When the substrate is subsea equipment, the subsea equipment may comprise any suitable material. For instance, the subsea equipment may be an epoxy phenolic coated metallic substrate, an epoxy substrate, a metallic substrate, such as steel, or a polypropylene, polyurethane or dicyclopentadiene substrate, or polymer based fibre reinforced composite.

When the substrate is thermal insulation material, the thermal insulation material may comprise, for example, polyolefin based thermal insulation material, phenolic based thermal insulation material, epoxy modified olefin based thermal insulation material, or other silicone based thermal insulation material.

Accordingly, in some examples the silicone tie coat may be bonded directly to subsea equipment. Subsequently, a thermal insulation layer, for example a silicone thermal insulation material, would then be bonded to the silicone tie coat layer. The surface of the subsea equipment may have been modified prior to application of the silicone tie coat, for instance, by plasma treatment, flame ionisation, chemical etching or shot blasting, or by an anticorrosive coating, for example, being applied.

In other examples, the silicone tie coat may be bonded to a thermal insulation layer on subsea equipment. In such examples, the thermal insulation layer would therefore be the 'substrate'. Subsequently, a further thermal insulation material, for example a silicone thermal insulation material, would then be bonded to the silicone tie coat layer. The resultant structure would therefore comprise two thermal insulation layers bonded together by the silicone tie coat. The two thermal insulation layers may comprise the same or different materials. In such structures, a further tie coat may bond a one of the thermal insulation layers to the subsea equipment. The further tie coat may be a silicone tie coat according to examples of the disclosure. A structure comprising more than two layers of thermal insulation may be provided, for example, a structure may comprise a first layer of thermal insulation bonded to a second layer of thermal insulation by a silicone tie coat, and a third layer of thermal insulation bonded to the second layer of thermal insulation by a further silicone tie coat. The silicone tie coat may be according to examples of the disclosure.

The silicone tie coat is the reaction product of a mixture comprising a polydiorganosiloxane polymer and an organohydrogensiloxane crosslinker. The reaction is catalyzed by a metallic catalyst.

The silicone tie coat has a thickness of at least about <NUM> (micrometer). Accordingly, the silicone tie coat is not a crystalline brittle molecular film.

The silicone tie coat forms a layer on the substrate. The layer formed has a thickness of at least about <NUM>.

Examples of the disclosure also provide a method of bonding thermal insulation material to a substrate useable subsea. The method comprises applying a silicone tie coat to the substrate to a thickness of at least <NUM>, and subsequently applying a thermal insulation material to the silicone tie coat.

Examples of the disclosure also provide a thermal insulation structure for a substrate useable subsea. The thermal insulation structure comprises a silicone tie coat bonded to a thermal insulation material. The silicone tie coat has a thickness of at least about <NUM>.

Examples of the disclosure also provide a thermally insulated substrate useable subsea. The thermally insulated substrate comprises a silicone tie coat bonded to the substrate and to thermal insulation material. The silicone tie coat provides a layer between the substrate and the thermal insulation material. The silicone tie coat has a thickness of at least about <NUM>.

In some examples, the silicone tie coat has a thickness of about <NUM> to about <NUM>, and more particularly has a thickness of about <NUM> to about <NUM>.

The relative thickness of the silicone tie coat provides flexibility since the coating is more elastomeric. Accordingly, the silicone tie coat is more resistant to in use fracturing or cracking. Further, the relative thickness of the silicone tie coat provides an in use damping effect in terms of any structural movement between the thermal insulation and substrate, for example, due to the differential between thermal expansion coefficients such as may be experienced where there is rapid cooling of equipment (blowdown) or physically applied stress. The risk of disbondment is therefore reduced.

The modulus of the silicone tie coat may be less than the modulus of the thermal insulation to further improve the damping effect.

Further, the relative thickness of the silicone tie coat reduces its susceptibility to particulate contamination which is problematic with thinner tie coat layers. Sensitivity to substrate surface preparation is therefore reduced.

The bonds formed between the substrate and silicone tie coat, and the silicone tie coat and the thermal insulation are therefore more robust, for example, in peel and pull off tests. Such bonds will therefore be stronger and longer lasting in the harsh operating conditions experienced subsea. Accordingly, the adhesion provided is robust and is not affected by the environmental conditions of the cure.

The silicone tie coat acts as an adhesive between the thermal insulation and the substrate.

Table <NUM> provides examples of reaction mixtures used to form a silicone tie coat according to examples of the disclosure. Table <NUM> indicates the specific component used, and in brackets the general term being used for that specific component.

Table <NUM> above provides details of five different reaction mixtures (reaction mixtures <NUM> to <NUM>). The amounts of components indicated are weight %.

In the above specific examples, the reaction to form a silicone tie coat according to examples of the disclosure is initiated when polymethylvinyl siloxane, polymethylhydro siloxane and platinum catalyst are combined. In practice, the components of the reaction mixtures detailed in Table <NUM> above may be split across multiple parts prior to being mixed together. For example, polymethylvinyl siloxane and platinum catalyst may be provided in a first part and polymethylhydro siloxane, along with the remainder of the components, may be provided in a second part. The only limitation is that all of polymethylvinyl siloxane, polymethylhydro siloxane and platinum catalyst are not provided in a one of the parts. Accordingly, polymethylvinyl siloxane and polymethylhydro siloxane may be provided in the same part, provided the platinum catalyst is not provided in that part. The two parts can then be mixed together immediately prior to use.

In some examples a three-part system may be provided in which a one of the parts comprises catalysts.

The components and relative amounts thereof may be adjusted according to each specific application, for instance, to bond to different substrates.

The solvent acts as a carrier and/or diluent. The solvent is volatile and is not therefore present in the silicone tie coat which is formed as the reaction product.

In some examples, the reaction mixture may also comprise dimethoxyethane (DME). In such examples the reaction mixture may comprise up to about <NUM> wt/% DME.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% solvent, and more particularly between <NUM> wt/% and <NUM> wt/% solvent.

The metallic catalyst facilitates an addition reaction between polydiorganosiloxane polymer and organohydrogensiloxane crosslinker. In the described examples the addition reaction is between polymethylvinyl siloxane and polymethylhydro siloxane. This process cures the reaction mixture to provide the silicone tie coat.

In some examples the metallic catalyst is a platinum group hydrosilylation catalyst present. The platinum catalyst may be, for example, platinum divinyl tetramethyl disiloxane or cyclovinyl methyl siloxane complex.

The metallic catalyst is present in an amount sufficient to effect curing of the reaction mixture. The amount of metallic catalyst provided in the reaction mixture may be adjusted to control the rate of curing.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% metallic catalyst, and more particularly between <NUM> wt/% and <NUM> wt/% metallic catalyst.

The inhibitor acts to slow, and/or stabilise and/or regulate the reaction between polydiorganosiloxane polymer and organohydrogensiloxane crosslinker. The inhibitor may comprise tetramethyl tetravinyl cyclotetrasiloxane, or trimethyl trivinyl cyclotrisiloxane, or pentamethyl pentavinyl cyclopentasiloxane.

In some examples, the reaction mixture comprises a combination of the above inhibitors.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% inhibitor, and more particularly between <NUM> wt/% and <NUM> wt/% inhibitor.

In the described examples the organohydrogensiloxane crosslinker is polymethylhydrosiloxane. The organohydrogensiloxane crosslinker has a molecular weight of between about <NUM> to about <NUM>,<NUM>, and more particularly between about <NUM> to about <NUM>,<NUM>, and a viscosity between about <NUM> to about <NUM> cP, and more particularly between about <NUM> to about <NUM> cP.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% organohydrogensiloxane crosslinker, and more particularly between <NUM> wt/% and <NUM> wt/% organohydrogensiloxane crosslinker.

In the described examples the polydiorganosiloxane polymer is polymethylvinyl siloxane. The polydiorganosiloxane polymer has a molecular weight between about <NUM> to about <NUM>,<NUM>, and more particularly between about <NUM> to about <NUM>, and a viscosity between about <NUM> to about <NUM>,<NUM> cP, and more particularly about <NUM> to about <NUM>,<NUM> cP.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% polydiorganosiloxane polymer, and more particularly between <NUM> wt/% and <NUM> wt/% polydiorganosiloxane polymer.

In the described examples polydimethylsiloxane (PDMS) is provided as a carrier for the platinum catalyst. PDMS has a viscosity of about <NUM> cP.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% carrier, and more particularly between <NUM> wt/% and <NUM> wt/% carrier.

In the described examples, a blue dye is provided as a visual aid to mixing and application of the silicone tie coat to a substrate.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% dye, and more particularly between <NUM> wt/% and <NUM> wt/% dye.

The additives may comprise, for example, adhesion promoters, wetting agents, dispersing agents, rheology modifiers, viscosity modifiers, and surfactants.

The reaction mixture to form the silicone tie coat may comprise between <NUM> wt/% and <NUM> wt/% additives, and more particularly between <NUM> wt/% and <NUM> wt/% additives.

Examples of the disclosure also provide a method of bonding a thermal insulation material to a substrate useable subsea. The method comprising applying a silicone tie coat to the substrate to a thickness of at least <NUM>, and subsequently applying a thermal insulation material to the silicone tie coat.

In examples where the components of the reaction mixture to form the silicone tie coat are provided in two parts, the two parts are mixed together immediately before application to a substrate. The subsequent reaction mixture is then applied to a surface of a substrate, for example, by spraying, brushing, or rolling the reaction mixture onto the surface to provide a layer of silicone tie coat on the surface of the substrate. This may be a manual or automated process. The silicone tie coat is therefore a wet applied coating.

Thermal insulation, for example silicone thermal insulation, is subsequently applied to the silicone tie coat layer, for instance, by spraying, brushing or rolling a wet mixture which subsequently cures to provide a layer of thermal insulation. The thermal insulation may be syntactic. The resultant product is a thermally insulated substrate useable subsea.

In one example, the substrate is a pipeline useable subsea. The silicone tie coat is therefore applied directly to the surface of the pipeline. In another example, the substrate is a thermal insulation material, for instance a phenolic based thermal insulation material, which covers a pipeline useable subsea. The silicone tie coat is therefore applied directly to the surface of the thermal insulation.

The reaction mixture may cure at ambient temperature (<NUM> to <NUM>). A relatively high level of metallic catalyst negates the need to heat cure the reaction mixture. The reaction mixture may be tailored to cure at different rates, for example, by varying the amount of catalyst and/or solvent present in the reaction mixture. Accordingly, the cure rate is adjustable and can be tailored to suit different applications. For example, a relative long cure rate may be appropriate for subsequent over moulding with silicone thermal insulation material.

If required, the rate of curing may be accelerated by heating the reaction mixture. The reaction mixture may be heated up to <NUM>, for instance, by use of a heat gun. A relatively short cure rate may be appropriate for applications such as pipeline field joint coating.

The thickness of the silicone tie coat may be measured by a wet film comb immediately after application whilst the silicone tie coat is still wet, or a dry film gauge after the silicone tie coat has cured.

In some examples, the surface of the substrate may be modified prior to application of the silicone tie coat, for instance, by plasma treatment, flame ionisation, shot blasting or chemical etching.

There is thus described a silicone tie coat, a method of bonding thermal insulation material to a substrate useable subsea, a thermal insulation structure for a substrate useable subsea, and a thermally insulated substrate useable subsea, with a number of advantages as detailed above and as follows. Furthermore, the reaction mixture does not require a certain level of atmospheric moisture (humidity) to cure since a metallic catalyst is used to cure the reaction mixture to provide a silicone tie coat according to examples of the disclosure. The silicone tie coat according to examples of the disclosure can therefore be applied irrespective of the environmental conditions.

The term "comprise" is used in this document with an inclusive not an exclusive meaning. If it is intended to use "comprise" with an exclusive meaning then it will be made clear in the context by referring to "comprising only one.

Claim 1:
A method of bonding silicone thermal insulation material to a substrate useable subsea, the method comprising:
applying a silicone tie coat to the substrate to a thickness of at least <NUM>, the silicone tie coat being the reaction product of a mixture comprising polydiorganosiloxane polymer and an organohydrogensiloxane crosslinker, the reaction being catalyzed by a metallic catalyst,
the method further comprising bonding silicone thermal insulation material to the silicone tie coat.