WO2020132013A1

WO2020132013A1 - Silicone rubber compositions and elastomeric materials

Info

Publication number: WO2020132013A1
Application number: PCT/US2019/067085
Authority: WO
Inventors: Lauren Tonge
Original assignee: Dow Silicones Corp
Current assignee: Dow Silicones Corp
Priority date: 2018-12-19
Filing date: 2019-12-18
Publication date: 2020-06-25
Anticipated expiration: 2021-06-19

Abstract

A subsea insulation silicone rubber composition includes (a) a polydiorganosiloxane gum, having a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, from 0.15 to 0.3 weight % of alkenyl groups and/or alkynyl groups per molecule; and which is present in the composition in an amount of from 15 to 70% wt. of the composition; (b) a treated reinforcing filler in an amount of 5 to 40% wt. of the composition; and (c) a curing agent selected from either (i) a peroxide curing agent in an amount of from 0.3 to 3% wt. or (ii) a hydro silylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst, or (iii) a mixture of (i) and (ii).

Description

SILICONE RUBBER COMPOSITIONS AND ELASTOMERIC MATERIALS

[0001] The present invention relates to an elastomeric high consistency rubber insulation material for use on subsea oil and gas production equipment, a composition used in the making of the elastomeric material and articles made from the elastomeric material and a means of protecting a subsea oil and gas production equipment.

[0002] Subsea wells and pipelines are used globally in connection with the production of hydrocarbons, in the form of oil and/or gas. A well extends from the seabed to the required depth at which the hydrocarbon reservoir is located and recovery of the hydrocarbons from the well to the surface is typically carried out using pipes, often referred to as“subsea risers”. Subsea risers extend from a well head or manifold on the seabed to a platform or vessel tethered on the surface above the well. It is not unusual for the risers to extend over hundreds or indeed thousands of meters between the wellhead and the surface.

[0003] In order for extraction to be viable a number of issues need to be dealt with not least insulation of the subsea risers, because of the temperature of the surrounding seawater to prevent restricted flow or even blockages of the hydrocarbons within the subsea risers between the well head and the platform/vessel and also the corrosive environment, i.e. the sea water itself.

[0004] In many subsea locations e.g. where subsea oil and gas wells are located at depths of 1500m or greater, the pipelines and wellhead equipment are exposed to seawater which is just a few degrees above freezing (e.g. about 4 to 5°C). In the absence of insulation hot produced hydrocarbon fluids within the production equipment are cooled by the surrounding seawater which, if the temperature of the fluids approach the seawater temperature, can result in hydrates and paraffin waxes being formed within the pipe line consequentially causing a restriction of hydrocarbon flow or even blockages within the pipelines. Hence, the application of thermal insulation to subsea oil and gas equipment to minimise the reduction in temperature of the hydrocarbons whilst being transported through the pipeline is essential both for the technical feasibility and practical viability of deep sea extraction with the benefits including, for example

(i) a higher production rate by maintaining high oil temperature and increasing flow rates;

(ii) lower processing costs by elimination of the requirement to reheat crude oil for water separation upon its arrival at the platform; prevention of hydrate and wax formation by maintaining the oil temperature above that at which hydrates form, in turn eliminating pipe blockages which would increase production costs;

(iii) elimination of the need for methanol injection to overcome the problems described above; and

(iv) reduction in the requirement for internal cleaning of pipes.

[0005] Suitable insulation materials also need to be unaffected by the extreme temperatures of the hydrocarbon fluids exiting the well. In some cases the temperature of the exiting fluids may reach 150°C or higher, and the fluids will consequently heat both the surrounding equipment and the insulation. Therefore, any insulation material which is used on such wells must be able to withstand these extreme temperatures without detriment to its thermal or mechanical properties.

[0006] To perform successfully in this environment, a thermal insulation material must have a low thermal conductivity, exhibit acceptable mechanical properties such as flexibility and impact resistance, and be economical to install and preferably should be resistant to high temperature aqueous environments.

[0007] A variety of insulation materials for this application are known, for example syntactic phenolic foams and high temperature epoxy resins have been used because they can withstand these relatively high temperatures but unfortunately they are inherently brittle and as such are unable to meet the flexibility and impact resistance requirements. Furthermore, because of their brittle nature and exothermic curing properties, these materials are difficult and expensive to install and repair.

[0008] Other prior art insulating materials used include amine cured epoxy materials, urethanes and polypropylenes, however whilst these exhibit acceptable flexibility and impact resistance characteristics they are unable to withstand the relatively high flow temperatures of the

hydrocarbons being extracted.

[0009] Liquid silicone rubber based materials made using organopolysiloxane polymers having viscosities of up to about 500,000 mPa.s at 25°C have been utilised for subsea insulation but whilst having advantages over the above because of the ability to withstand wide temperature variations without an appreciable effect on their physical properties and being virtually unaffected by ultraviolet radiation, even over long periods of time, ozone, oil, salt, water and the like, they have had adhesion problems after exposure to the high temperatures of the hydrocarbons transported through the riser pipes.

[0010] Furthermore, because of the relatively low viscosity of the pre-cured LSR compositions, it is difficult to apply the compositions around subsea equipment, such as the pipes, wellheads and Christmas trees. Generally currently molds or forms have to be utilised, where possible, to define the desired shape of the insulation around the pipe or the like being insulated. The molds/forms are placed in position and liquid silicone mbber is subsequently pumped in, cured, and the forms removed.

[0011] Deep sea oil extraction equipment requires insulation to maintain the oil at high temperature, often about 130 °C with identified projects as high as 200 °C, through seawater, typically at 4 °C, to provide flow assurance. Liquid silicone rubbers (LSRs) are beneficial to complex structures due to their flowable nature and good ambient cure profile, but the current samples are unstable on exposure to water at these high temperatures, with plaques losing tensile strength and elongation at break on hot wet aging.

[0012] Manufacturers therefore are continually seeking alternative improved solutions in improving the thermal stability of said hydro silylation cured compositions so as to provide improved subsea insulation. [0013] There is provided a subsea insulation silicone rubber composition comprising

polydiorganosiloxane gum (a), having a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, from 0.15 to 0.3 weight % of alkenyl groups and/or alkynyl groups per molecule; and which is present in the composition in an amount of from 15 to 70% wt. of the composition;

(b) a treated reinforcing filler in an amount of 5 to 40% wt. of the composition;

(c) a curing agent selected from either (i) a peroxide curing agent in an amount of from 0.3 to

3% wt. or (ii) a hydrosilylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst or a mixture thereof.

[0014] There is also provided an elastomeric subsea insulation silicone rubber material which material is the cured product of a composition comprising

polydiorganosiloxane gum (a),

having a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D- 926-08, from 0.15 to 0.3 weight % of alkenyl groups and/or alkynyl groups per molecule; and which is present in the composition in an amount of from 15 to 70% wt. of the composition;

[0015] There is provided an elastomeric subsea insulation silicone rubber material obtainable or obtained by curing a composition comprising

a composition comprising

polydiorganosiloxane gum (a),

(c) a curing agent selected from either (i) a peroxide curing agent in an amount of from 0.3 to 3% wt. or (ii) a hydrosilylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst or a mixture thereof .

[0016] The total weight % of the composition is always 100% wt Values of vinyl content are the cumulative totals of the weight % of vinyl groups in the composition, i.e. typically in gums/polymers, determined using quantitative infra-red spectroscopy in accordance with ASTM E168.

[0017] There is provided a use of a subsea insulation silicone rubber composition comprising polydiorganosiloxane gum (a),

(c) a curing agent selected from either (i) a peroxide curing agent in an amount of from 0.3 to 3% wt. or (ii) a hydrosilylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst or a mixture thereof.

[0018] There is provided a method of making an elastomeric subsea insulation silicone rubber material by mixing and curing a composition comprising

[0019] There is also provided a subsea article at least partially insulated by an elastomeric subsea insulation silicone rubber material as hereinbefore described.

[0020] The composition may include one or more optional additives but the total weight % of the composition is 100 wt. % and the content of unsaturated groups in polydiorganosiloxane gum (a) is determined using quantitative infra-red analysis in accordance with ASTM E168. ASTM is ASTM International, West Conshohocken, PA, USA.

[0021] There is also provided a hydrolytically stable silicone rubber composition comprising polydiorganosiloxane gum (a), having a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, from 0.15 to 0.3 weight % of alkenyl groups and/or alkynyl groups per molecule; and which is present in the composition in an amount of from 15 to 70% wt. of the composition;

(c) a curing agent selected from either (i) a peroxide curing agent in an amount of from 0.3 to 3% wt. or (ii) a hydrosilylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon-bonded hydrogen atoms per molecule and a hydro silylation catalyst or a mixture thereof , which upon cure is hydrolytically stable at temperatures > 150°C. The composition is suitable for use as insulation for subsea applications and any other applications requiring thermal stability.

[0022] A hydrolytically stable silicone rubber material comprising the cured product of the following composition

(c) a curing agent selected from either (i) a peroxide curing agent in an amount of from 0.3 to 3% wt. or (ii) a hydro silylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon-bonded hydrogen atoms per molecule and a hydro silylation catalyst or a mixture thereof, which is hydrolytically stable at temperatures > 150°C.

Polydiorganosiloxane gum (a)

[0023] Polydiorganosiloxane gum (a) has

a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D-926-08, and from 0.15 to 0.3 weight % of alkenyl groups and/or alkynyl groups per molecule; and said Polydiorganosiloxane gum (a) is present in the composition in an amount of from 15 to 70% wt. of the composition.

[0024] Polydiorganosiloxane gum (a) has multiple units of the formula (I):

RaSiO_{(4 a)/2} (I)

in which each R is independently selected from aliphatic hydrocarbyl, aromatic hydrocarbyl, or organyl group (that is any organic substituent group, regardless of functional type, having one free valence at a carbon atom). Saturated aliphatic hydrocarbyls are exemplified by, but not limited to alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl and cycloalkyl groups such as cyclohexyl. Unsaturated aliphatic hydrocarbyls are exemplified by, but not limited to, alkenyl groups such as vinyl, allyl, butenyl, pentenyl, cyclohexenyl and hexenyl; and by alkynyl groups. Aromatic hydrocarbon groups are exemplified by, but not limited to, phenyl, tolyl, xylyl, benzyl, styryl, and 2-phenylethyl. Organyl groups are exemplified by, but not limited to, halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl; nitrogen containing groups such as amino groups, amido groups, imino groups, imido groups; oxygen containing groups such as polyoxyalkylene groups, and carbonyl groups. Further organyl groups may include sulfur containing groups, fluoro containing groups, phosphorus containing groups, boron containing groups. The subscript“a” is 0, 1, 2 or 3 but is for most units 2. Gum (a) contains at least two vinyl groups molecule.

[0025] Siloxy units may be described by a shorthand (abbreviated) nomenclature, namely - "M," "D," "T," and "Q", when R is a methyl group (further teaching on silicone nomenclature may be found in Walter Noll, Chemistry and Technology of Silicones, dated 1962, Chapter I, pages 1-9).

The M unit corresponds to a siloxy unit where a = 3, that is R3S1O1_/2; the D unit corresponds to a siloxy unit where a = 2, namely R2S1O2_/2; the T unit corresponds to a siloxy unit where a = 1, namely

R1S1O3_/2; the Q unit corresponds to a siloxy unit where a = 0, namely SiCEa-

[0026] Examples of typical functional groups on polydiorganosiloxane gum (a)

include alkenyl, such as vinyl; alkyl such as methyl, or alkyl chains up to 8 carbon atoms; aryl, such as phenyl. The functional group may be in a pendent position (on a D or T siloxy unit), or may be terminal (on an M siloxy unit).

[0027] The polydiorganosiloxane gum (a) may be selected from polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes, and mixtures thereof but in each instance contains at least two alkenyl groups per molecule, alternatively at least two vinyl groups per molecule. They may be linear or branched or cyclic but typically will be linear or branched. The polysiloxanes may have any suitable terminal groups, for example, they may be trialkyl terminated, alkenyldialkyl terminated, hydroxydialkyl terminated, alkoxydialkyl terminated or may be terminated with any other suitable terminal group combination.

[0028] Polydiorganosiloxane gum (a) may further be selected from polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes, hydroxyl functional siloxanes, and mixtures thereof.

[0029] Examples of polydiorganosiloxane gum (a) include polydiorganosiloxanes containing alkenyl groups at the two terminals and may be represented by the general formula (I):

R^,R"R"^,SiO-(R"R"^,SiO)m-SiOR^,"R"R' (I)

[0030] In formula (I), each R' is an alkenyl group, which typically contains from 2 to 10 carbon atoms, such as vinyl, allyl, and 5-hexenyl.

[0031] R" does not contain ethylenic unsaturation, Each R" may be the same or different and is individually selected from monovalent saturated hydrocarbon group, which typically contain from 1 to 10 carbon atoms, and monovalent aromatic hydrocarbon group, which typically contain from 6 to 12 carbon atoms. R" may be unsubstituted or substituted with one or more groups that do not interfere with curing of this inventive composition, such as halogen atoms. R'" is R' or R". The letter m represents a degree of polymerization suitable for polydiorganosiloxane gum (a) to have a viscosity of at least l,000,000mPa.s at 25°C.

[0032] The polydiorganosiloxane gum (a) typically has a viscosity of at least 1,000,000 mPa.s at 25°C. However, because of the difficulty in measuring viscosity above these values, gums tend to be described by way of their Williams plasticity values in accordance with ASTM D-926-08 as opposed to by viscosity. As hereinbefore stated the polydiorganosiloxane gum (a) has a viscosity resulting in a Williams’s plasticity of at least 30mm/100 measured in accordance with ASTM D- 926-08, alternatively at least 50mm/100 measured in accordance with ASTM D-926-08, alternatively at least lOOmm/100 measured in accordance with ASTM D-926-08, alternatively alternatively at least 125mm/100, alternatively 125mm/100 to 300mm/100 measured in accordance with ASTM D-926-08. Polydiorganosiloxane gum (a) is present in the composition in an amount of from 15 to 70% wt. of the composition; alternatively 15 to 60% by weight.

[0033] The composition enclosed herein may comprise a plurality of organopolysiloxane gums including organopolysiloxane gum (a) wherein other gums are not required to have from 0.15 to 0.3 weight % of unsaturated groups, typically alkenyl and/or alkynyl groups determined using quantitative infra-red spectroscopy in accordance with ASTM E168.

(b) Reinforcing filler

[0034] Component (b) of the composition is a reinforcing filler such as finely divided silica. Silica and other reinforcing fillers (b) are often treated with one or more known filler treating agents to prevent a phenomenon referred to as "creping" or "crepe hardening" during processing of the curable composition.

[0035] Finely divided forms of silica are preferred reinforcing fillers (b). Colloidal silicas are particularly preferred because of their relatively high surface area, which is typically at least 50 m²/g (BET method in accordance with ISO 9277: 2010). Fillers having surface areas of from 50 to 450 m²/g (BET method in accordance with ISO 9277: 2010), alternatively of from 50 to 300 m²/g (BET method in accordance with ISO 9277: 2010), are typically used. For the avoidance of doubt colloidal silicas as described herein may be can be provided in the form of precipitated silica and/or fumed silica. Both types of silica are commercially available.

[0036] The amount of reinforcing filler (b) e.g. finely divided silica in the composition herein is from 5 to 40%wt, alternatively of from 5 to 30%wt. In some instances, the amount of reinforcing filler may be of from 7.5 to 30%wt alternatively from 10 to 30% wt. based on the weight of the composition.

[0037] When reinforcing filler (b) is naturally hydrophilic (e.g. untreated silica fillers), it is treated with a treating agent to render it hydrophobic. These surface modified reinforcing fillers (b) do not clump, and can be homogeneously incorporated into polydiorganosiloxane gum (a) as the surface treatment makes the fillers easily wetted by polydiorganosiloxane gum (a). This results in improved room temperature mechanical properties of the compositions and resulting cured materials cured therefrom.

[0038] The surface treatment may be undertaken prior to introduction in the composition or in situ (i.e. in the presence of at least a portion of the other ingredients of the composition herein by blending these ingredients together at room temperature or above until the filler is completely treated. Typically, untreated reinforcing filler (b) is treated in situ with a treating agent in the presence of polydiorganosiloxane gum (a), whereafter mixing a silicone rubber base composition is obtained, to which other ingredients may be added e.g. catalyst/curing agent to render the composition curable.

[0039] It has been identified that by ensuring the filler is treated with treating agents which provide the subsequently treated filler with < 3% by weight of the unsaturated groups in the total composition. Generally said unsaturated group is an alkenyl group having from 2 to 10 carbons, alternatively alkenyl groups having between 1 and 6 carbons, alternatively vinyl , propenyl and/or hexenyl groups. Typically reinforcing filler (b) may be surface treated with any low molecular weight organosilicon compounds disclosed in the art with the proviso that subsequently treated filler (b) must have with < 3% by weight of the unsaturated groups in the total composition. Hence, preferably the treating agent utilised is preferably substantially free of unsaturated groups and /or subsequent to hydrophobic treating the reinforcing filler has substantially no unsaturated groups, not least alkenyl groups such as vinyl groups.

[0040] For the avoidance of doubt substantially free of unsaturated groups applicable to prevent creping of organosiloxane compositions during processing. For example organosilanes, polydiorganosiloxanes, or organosilazanes e.g. hexaalkyl disilazane, short chain siloxane diols or fatty acids or fatty acid esters such as stearates to render the filler(s) hydrophobic and therefore easier to handle and obtain a homogeneous mixture with the other ingredients. Specific examples include but are not restricted to silanol terminated trifluoropropylmethyl siloxane,

tetramethyldi(trifluoropropyl)disilazane, silanol terminated MePh siloxane, liquid hydroxyl- terminated polydiorganosiloxane containing an average from 2 to 20 repeating units of

diorganosiloxane in each molecule, hexaorganodisiloxane, hexaorganodisilazane. A small amount of water can be added together with the silica treating agent(s) as processing aid.

Curing Agent

[0041] The composition as described herein is cured using a curing agent (c) selected from either (i) a peroxide curing agent in an amount of from 0.3 to 3% wt. of the composition and or (ii) a hydrosilylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon- bonded hydrogen atoms per molecule and a hydrosilylation catalyst.

[0042] Any suitable organic peroxide curing agent (c)(i) may be utilized. The peroxide catalyst may be any of the well-known commercial peroxides used to cure silicone elastomer compositions. The amount of organic peroxide used is determined by the nature of the curing process, the organic peroxide used, and the composition used. A part of the selection of suitable organic peroxide is to consider the ability to heat the equipment being insulated either in the open or under pressure. Typically the amount of peroxide catalyst utilised in a composition as described herein is from 0.2 to 3% wt., alternatively 0.2 to 2% wt. in each case based on the weight of the composition.

Some commonly used organic peroxides include benzoyl peroxide, 1 ,4- dichlorobenzyl peroxide, 2,4-dichlorobenzyl peroxide, 2,4-dichlorobenzoyl peroxide, 1 ,4-dimethylbenzyl peroxide, 2,4- dimethylbenzyl peroxide, di-i-butyl peroxide, dicumyl peroxide, tertiary butyl-perbenzoate, monochlorobenzoyl peroxide, ditertiary-butyl peroxide, 2,5-bis-(tertiarybutyl-peroxy)-2,5- dimethylhexane, 1 ,l-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, tertiary-butyl-trimethyl peroxide, n-butyl-4,4-bis(t-butylperoxy) valerate, 1 , l-bis(t-butylperoxy)-3,3,5- trimetylcyclohexane, t-butylperoxyisopropylcarbonate, and t-butyl perbenzoate. Mixtures of the above may also be used.

[0043] The composition herein may alternatively cured by hydrosilylation using a hydrosilylation cure package (c)(ii).

Organohvdrogenpolvsiloxane Cross-linkers

[0044] When cured via hydrosilylation the hydrosilylation cure package (c)(ii)must comprise one or more organohydrogenpolysiloxane(s), which operate(s) as cross-linker(s) for polydiorganosiloxane gum (a). They will undergo a hydrosilylation (addition) reaction by way of its silicon-bonded hydrogen atoms with the unsaturated (alkenyl) groups in polydiorganosiloxane gum (a) catalysed by one or more hydrosilylation catalysts discussed below. The organohydrogenpolysiloxane normally contains 3 or more silicon-bonded hydrogen atoms per molecule so that the hydrogen atoms of this ingredient can sufficiently react with the alkenyl groups of polydiorganosiloxane gum (a) to form a network structure therewith and thereby cure the composition.

[0045] The molecular configuration of the organohydrogenpolysiloxane is not specifically restricted, and it can be straight chain, branch-containing straight chain, or cyclic. While the molecular weight of this ingredient is not specifically restricted, the viscosity is typically from 0.001 to 50 Pa.s at 25 °C relying on the cup/spindle method of ASTM D 1084-16, Method B, with the most appropriate spindle from the Brookfield® RV or LV range for the viscosity range, unless otherwise indicated.

[0046] The organohydrogenpolysiloxane is typically added in an amount such that the molar ratio of silicon bonded hydrogen atoms to unsaturated (e.g. vinyl (Vi)) groups in the composition is from 0.75 : 1 to 2 : 1.

[0047] Examples of the organohydrogenpolysiloxane in the hydrosilylation cure package (c)(ii) include, but are not limited to, the following:

(i) trimethylsiloxy-terminated methylhydrogenpolysiloxane,

(ii) trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane,

(iii) dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymers,

(iv) dimethylsiloxane-methylhydrogensiloxane cyclic copolymers,

(v) copolymers composed of (CH₃)₂HSiOi_/2 units and S1O4/2 units, and (vi) copolymers composed of (CHsbSiOia units, (CHskHSiOia units, and S1O4/2 units.

[0048] When present such cross-linkers are present the amount used is within the range described above, i.e. dependent on the molar ratio of silicon bonded hydrogen atoms to Vi groups discussed above but in terms of weight % they will typically be present in the composition in an amount somewhere within the approximate range of 2 to 10% by weight of the composition but this may vary depending on the cross-linker chosen.

Hydrosilylation catalyst

[0049] As hereinbefore described when the composition is cured via a hydrosilylation reaction it must comprise a hydrosilylation cure package (c)(ii) comprising a hydrosilylation (addition cure) catalyst. Hydrosilylation (addition cure) catalysts are generally metals or metal based compounds selected from the platinum metals, i.e. platinum, ruthenium, osmium, rhodium, iridium and palladium, or a compound of such metals. The metals include platinum, palladium, and rhodium but platinum and rhodium compounds are preferred due to the high activity level of these catalysts for hydrosilylation reactions.

[0050] Example of preferred hydrosilylation catalysts include but are not limited to platinum black, platinum on various solid supports, chloroplatinic acids, alcohol solutions of chloroplatinic acid, and complexes of chloroplatinic acid with ethylenically unsaturated compounds such as olefins and organosiloxanes containing ethylenically unsaturated silicon-bonded hydrocarbon groups. The hydrosilylation catalyst can be platinum metal, platinum metal deposited on a carrier, such as silica gel or powdered charcoal, or a compound or complex of a platinum group metal.

[0051] For example suitable platinum based catalysts include

(i) complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups are described in US 3,419,593;

(ii) chloroplatinic acid, either in hexahydrate form or anhydrous form;

(iii) a platinum-containing catalyst which is obtained by a method comprising reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound, such as di vinyl tetramethyldisiloxane ;

(iv) alkene-platinum-silyl complexes as described in US Pat. No. 6,605,734 such as (COD)Pt(SiMeCl2)2 where“COD” is 1,5-cyclooctadiene; and/or

(v) Karstedt's catalyst, a platinum divinyl tetramethyl disiloxane complex typically containing about 1 wt.% of platinum in a solvent, such as toluene may be used. These are described in US3,715,334 and US3,814,730. [0052] When present, the hydrosilylation catalyst is present in the total composition in a catalytic amount, i.e., an amount or quantity sufficient to promote a reaction or curing thereof at desired conditions. Varying levels of the hydrosilylation catalyst can be used to tailor reaction rate and cure kinetics. The catalytic amount of the hydrosilylation catalyst is generally between 0.01 ppm, and 10,000 parts by weight of platinum-group metal, per million parts (ppm), based on the combined weight of the components (a) and (b); alternatively between 0.01 and 5000ppm; alternatively between 0.01 and 3,000 ppm, and alternatively between 0.01 and 1,000 ppm. In specific embodiments, the catalytic amount of the catalyst may range from 0.01 to 1,000 ppm, alternatively 0.01 to 750 ppm, alternatively 0.01 to 500 ppm and alternatively 0.01 to 100 ppm of metal based on the weight of the composition. The ranges may relate solely to the metal content within the catalyst or to the catalyst altogether (including its ligands) as specified, but typically these ranges relate solely to the metal content within the catalyst. The catalyst may be added as a single species or as a mixture of two or more different species. Typically, dependent on the form/concentration in which the catalyst package is provided the amount of catalyst present will be within the range of from 0.001 to 3.0% by weight of the composition.

Additives

[0053] Additives may be present in the composition depending on the intended use of the curable silicone elastomer composition. For example, when the composition is cured via hydrosilylation, inhibitors designed to inhibit the reactivity of the hydrosilylation catalysts may be utilised.

inhibitor

[0054] To obtain a longer working time or pot life of the silicone rubber composition when a hydrosilylation (addition cure) package (c) (ii) is being utilised, a suitable inhibitor may be incorporated into the composition in order to retard or suppress the activity of the catalyst.

[0055] Inhibitors of platinum metal based catalysts, generally a platinum metal based catalyst are well known in the art. Hydrosilylation or addition-reaction inhibitors include hydrazines, triazoles, phosphines, mercaptans, organic nitrogen compounds, acetylenic alcohols, silylated acetylenic alcohols, maleates, fumarates, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, olefinic siloxanes, unsaturated hydrocarbon monoesters and diesters, conjugated ene-ynes, hydroperoxides, nitriles, and diaziridines. Alkenyl- substituted siloxanes as described in US 3,989,667 may be used, of which cyclic methylvinylsiloxanes are preferred.

[0056] Another class of known inhibitors of platinum catalysts includes the acetylenic compounds disclosed in US 3,445,420. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors that will suppress the activity of a platinum- containing catalyst at 25 °C. Compositions containing these inhibitors typically require heating at temperature of 70 °C or above to cure at a practical rate.

[0057] Examples of acetylenic alcohols and their derivatives include 1-ethynyl-l- cyclohexanol (ETCH), 2-methyl-3-butyn-2-ol, 3-butyn-l-ol, 3-butyn-2-ol,

propargylalcohol, 2-phenyl-2-propyn-l-ol, 3,5-dimethyl- l-hexyn-3-ol, 1- ethynylcyclopentanol, l-phenyl-2-propynol, 3 -methyl- l-penten-4-yn-3-ol, and mixtures thereof.

[0058] When present, inhibitor concentrations as low as 1 mole of inhibitor per mole of the metal of catalyst in hydrosilylation (addition cure) package (c) (ii)will in some instances impart satisfactory storage stability and cure rate. In other instances inhibitor

concentrations of up to 500 moles of inhibitor per mole of the metal of catalyst in hydrosilylation (addition cure) package (c) (ii) are required. The optimum concentration for a given inhibitor in a given composition is readily determined by routine experimentation. Dependent on the concentration and form in which the inhibitor selected is

provided/available commercially, when present in the composition, the inhibitor is typically present in an amount of from 0.0125 to 10% by weight of the composition. Mixtures of the above may also be used.

Other Additives

[0059] Other commonly used additives may be present in the composition as and when required depending on the intended use of the curable silicone elastomer composition. These may include non-reinforcing fillers, non-conductive fillers (including non-metallic beads), pot life extenders, flame retardants, pigments, colouring agents, adhesion promoters, chain extenders heat stabilizers, compression set improvement additives and mixtures thereof.

Non-reinforcing filler

[0060] When present, non-reinforcing fillers may comprise crushed quartz, diatomaceous earths, barium sulphate, iron oxide, titanium dioxide and carbon black, wollastonite and platelet type fillers such as, graphite, graphene, talc, mica, clay, sheet silicates, kaolin, montmorillonite and mixtures thereof. Other non-reinforcing fillers which might be used alone or in addition to the above include aluminite, calcium sulphate (anhydrite), gypsum, calcium sulphate, magnesium carbonate, aluminium trihydroxide, magnesium hydroxide (brucite), graphite, copper carbonate, e.g. malachite, nickel carbonate, e.g. zarachite, barium carbonate, e.g. witherite and/or strontium carbonate e.g. strontianite.

[0061] Non-reinforcing fillers may alternatively or additionally be selected from aluminium oxide, silicates from the group consisting of olivine group; garnet group;

aluminosilicates; ring silicates; chain silicates; and sheet silicates. The olivine group comprises silicate minerals, such as but not limited to, forsterite and Mg₂Si0₄. The garnet group comprises ground silicate minerals, such as but not limited to, pyrope; Mg AhShOir; grossular; and Ca₂Al₂Si₃0i₂. Aluninosilicates comprise ground silicate minerals, such as but not limited to, sillimanite; AI₂S1O₅ ; mullite; 3AI₂O₃.2S1O₂; kyanite; and AhSiCT The ring silicates group comprises silicate minerals, such as but not limited to, cordierite and Al₃(Mg,Fe)₂[Si₄A10i₈]. The chain silicates group comprises ground silicate minerals, such as but not limited to, wollastonite and CafSiCh].

[0062] Suitable sheet silicates e.g. silicate minerals which may be utilised include but are not limited to mica; K₂AIi₄[Si₆Al₂0₂o](OH)₄; pyrophyllite; AUISisChoKOH h; talc;

Mg₆[Si₈0₂o](OH)₄; serpentine for example, asbestos; Kaolinite; AI₄I S1₄O _{] 0} KOH Js; and vermiculite.

[0063] In one embodiment the non-reinforcing filler may include glass or the like micro beads or microspheres to enhance the thermal insulation of the material. The micro beads or microspheres may be glass e.g. for example borosilicate glass micro-beads and/or microspheres. When present, the non-reinforcing filler(s) is/are present up to a cumulative total of from 1 to 50% wt. of the composition.

[0064] Whenever deemed necessary the non-reinforcing filler may also be treated as described above with respect to the reinforcing fillers (b) to render them hydrophobic and thereby easier to handle and obtain a homogeneous mixture with the other components. As in the case of the reinforcing fillers (b) surface treatment of the non-reinforcing fillers makes them easily wetted by polydiorganosiloxane gum (a) which may result in improved properties of the compositions, such as better processability (e.g. lower viscosity, better mold releasing ability and/or less adhesive to processing equipment, such as two roll mill), heat resistance, and mechanical properties. [0065] Examples of non-conductive fillers include quartz powder, diatomaceous earth, talc, clay, mica, calcium carbonate, magnesium carbonate, non-metallic beads, hollow glass, glass fibre, hollow resin and plated powder, and mixtures or derivatives thereof.

[0066] Pot life extenders, such as triazole, may be used, but are not considered necessary in the scope of the present invention. The liquid curable silicone elastomer composition may thus be free of pot life extender.

[0067] Examples of flame retardants include aluminium trihydrate, magnesium hydroxide, calcium carbonate, zinc borate, wollastonite, mica and chlorinated paraffins,

hexabromocyclododecane, triphenyl phosphate, dimethyl methylphosphonate, tris(2,3- dibromopropyl) phosphate (brominated tris), and mixtures or derivatives thereof.

[0068] Examples of lubricants include tetrafluoroethylene, resin powder, graphite, fluorinated graphite, talc, boron nitride, fluorine oil, silicone oil, phenyl functional silicone oil, molybdenum disulfide, and mixtures or derivatives thereof.

[0069] Further additives include silicone fluids, such as trimethyl terminated siloxanes. Such trimethylterminated polydimethylsiloxanes typically have a viscosity < 150 mPa.s at 25°C. When present such silicone fluid may be present in the liquid curable silicone elastomer composition in an amount ranging of from 0.1 to 5% weight, based on the total weight of the composition. Other additives include silicone resin materials, which may or may not contain alkenyl groups.

[0070] Examples of pigments include carbon black, iron oxides, titanium dioxide, chromium oxide, bismuth vanadium oxide and mixtures or derivatives thereof.

[0071] Examples of colouring agents include vat dyes, reactive dyes, acid dyes, chrome dyes, disperse dyes, cationic dyes and mixtures thereof.

[0072] Examples of adhesion promoters include silane coupling agents, alkoxysilane containing methacrylic groups or acrylic groups such as methacryloxymethyl- trimethoxysilane, 3-methacryloxypropyl-tirmethoxysilane, 3-methacryloxypropyl- methyldimethoxysilane, 3-methacryloxypropyl-dimethylmethoxysilane, 3- methacryloxypropyl-triethoxysilane, 3-methacryloxypropyl-methyldiethoxysilane, 3- methacryloxyisobutyl-trimethoxysilane, or a similar methacryloxy-substituted alkoxysilane; 3-acryloxypropyl-trimethoxysilane, 3-acryloxypropyl-methyldimethoxysilane, 3- acryloxypropyl-dimethyl-methoxysilane, 3-acryloxypropyl-triethoxysilane, or a similar acryloxy-substituted alkyl-containing alkoxysilane; zirconium chelate compound such as zirconium (IV) tetraacetyl acetonate, zirconium (IV) hexafluoracetyl acetonate, zirconium (IV) trifluoroacetyl acetonate, tetrakis (ethyltrifluoroacetyl acetonate) zirconium, tetrakis (2,2,6,6-tetramethyl-heptanethionate) zirconium, zirconium (IV) dibutoxy

bis(ethylacetonate ), diisopropoxy bis (2,2,6,6-tetramethyl-heptanethionate) zirconium, or similar zirconium complexes having b-diketones (including alkyl-substituted and fluoro- substituted forms thereof); epoxy-containing alkoxysilanes such as 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl

methyldimethoxysilane, 4-glycidoxybutyl trimethoxysilane, 5,6-epoxyhexyl triethoxysilane, 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, or 2-(3,4-epoxycyclohexyl)

ethyltriethoxysilane.

[0073] Examples of chain extenders include disiloxane or a low molecular weight polyorganosiloxane containing two silicon-bonded hydrogen atoms at the terminal positions. The chain extender typically reacts with the alkenyl groups of polydiorganosiloxane gum (a), thereby linking two or more molecules of polydiorganosiloxane gum (a) together and increasing its effective molecular weight and the distance between potential cross-linking sites.

[0074] A disiloxane is typically represented by the general formula (HR¾Si)₂0. When the chain extender is a polyorganosiloxane, it has terminal units of the general formula

HR¾SiOi/2 and non-terminal units of the formula R^b2SiO. In these formulae, R^a and R^b individually represent unsubstituted or substituted monovalent hydrocarbon groups that are free of ethylenic unsaturation, which include, but are not limited to alkyl groups containing from 1 to 10 carbon atoms, substituted alkyl groups containing from 1 to 10 carbon atoms such as chloromethyl and 3,3,3-trifluoropropyl, cycloalkyl groups containing from 3 to 10 carbon atoms, aryl containing 6 to 10 carbon atoms, alkaryl groups containing 7 to 10 carbon atoms, such as tolyl and xylyl, and aralkyl groups containing 7 to 10 carbon atoms, such as benzyl.

[0075] Further examples of chain extenders include tetramethyldihydrogendisiloxane or dimethylhydrogen-terminated polydimethylsiloxane.

[0076] Where the optional additives may be used for more than one reason e.g. as a non reinforcing filler and flame retardant, when present they may function in both roles. When or if present, the aforementioned additional ingredients are cumulatively present in an amount of from 0.1 to 30% wt, alternatively of from 0.1 to 20%wt based on the weight of the composition.

[0077] The composition of the present invention may be prepared by combining all of ingredients at ambient or elevated temperature as desired. Any mixing techniques and devices described in the prior art can be used for this purpose, e.g. suitable mixers and mills for high consistency rubber compositions. The particular device to be used will be determined dependent on the viscosities of ingredients and the final curable coating composition. Suitable mixers include but are not limited to paddle type mixers and kneader type mixers capable of mixing high consistency materials. Cooling of ingredients during mixing may be desirable to avoid premature curing of the composition.

[0078] When the composition is cured using a peroxide curing agent, typically gum (a) and reinforcing filler (b) are initially mixed together to form a base. The reinforcing filler may be hydrophobically treated before mixing or alternatively may be treated in situ by introducing a hydrophobic treating agent as hereinbefore described into the mixture when preparing the base. Once the base has been prepared the peroxide curing agent is added and mixed into the base composition to form a curable compound.

[0079] When the composition is cured via a hydrosilylation process the composition is comprising polymer (a), filler (b), cross-linker and hydrosilylation catalyst as the basic ingredients. In order to avoid premature cure they are stored in two parts prior to use.

Typically the hydrosilylation catalyst is placed in one part, often referred to as Part A and the cross-linker and if present the inhibitor, is/are placed in the second part, often referred to as Part B. The other ingredients may typically be present in either or both compositions. The part A and Part B compositions are then mixed immediately prior to use. The mixing ratios by weight will depend on the level of ingredients in each part and can vary for part A to part B from about 15 : 1 to 1 to 1, typically dependent on whether components (a) and/or (b) are in both components and indeed the amounts in each. Typically in the present invention it is anticipated that more often than not components (a) and (b) will be in both parts in relatively equal amounts and therefore part A : Part B will be in a ratio of from 5 : 1 to 1 : 1, alternatively from 3 : 1 to 1 : 1.

[0080] The silicone rubber composition may dependent on viscosity and application etc., be further processed by injection moulding, encapsulation moulding, press moulding, dispenser moulding, extrusion moulding, transfer moulding, press vulcanization, centrifugal casting, calendering, bead application or blow moulding.

[0081] The silicone rubber composition may be cured at room temperature, by way of a hot air oven, by autoclave, inductive heating or even by way of a salt bath. The

composition may be cured at any suitable temperature e.g. from room temperature to 250°C, typically dependent on the curing agent(s) being used. In the case of a peroxide curing agent cure will take place at a temperature between about 70°C to 250°C alternatively 80°C to 225°C, alternatively from 90°C to 200°C. The temperature for curing via hydrosilylation however is typically from 25°C to 150°C, alternatively between 40°C to 150°C, alternatively between 50°C to 130°C.

[0082] Where the optional additives may be used for more than one reason e.g. as a non reinforcing filler and flame retardant, when present they may function in both roles. When or if present, the aforementioned additional ingredients are cumulatively present in an amount of from 0.1 to 30% wt., alternatively of from 0.1 to 20%wt. based on the weight of the composition.

[0083] Elastomeric subsea insulation silicone rubber material as hereinbefore described may be utilised in the thermal insulation of, for example, piping including riser pipes, wellheads, Xmas trees, spool pieces, manifolds, risers and pipe field joints.

[0084] Clearly any insulation material or system must be capable of being easily formed into complex shapes to accommodate the components of a pipe line assembly. The utilisation of suitable high consistency silicone rubber compositions as described above, given their much higher viscosity enable alternative and potentially easier processes for insulating the pipes to be utilised, e.g. they may be applied by hand, wrapping, extrusion, and/or calendaring, prior to cure or indeed any other suitable means of application utilising the highly viscous nature of the composition as described herein can be used and as such can avoid the need for molds or forms and the related processing relied upon for applying prior used liquid silicone rubber compositions.

[0085] The following examples, illustrating the compositions and components of the compositions, elastomers, and methods, are intended to illustrate and not to limit the invention.

EXAMPLES

[0086] Uncured high Consistency silicone rubber compositions containing silicone gums and treated fillers are generally referred to as bases. Bases plus curatives in the uncured state are generally referred to as compounds. Unless otherwise indicated Williams plasticity for each gum was determined in accordance with ASTM D-926-08. All viscosities measured were done so at 25 °C relying on the cup/spindle method of ASTM D 1084 Method B, with the most appropriate spindle from the Brookfield® RV or LV range for the viscosity range, unless otherwise indicated. The alkenyl and/or alkynyl and/or Si-H content of polymers was determined using quantitative infra-red analysis in accordance with ASTM E168.

[0087] The following ingredients were used in the examples

Silicone Gums:

• Silicone Gum Gl: Dimethylvinyl-terminated dimethyl Siloxane gum having a having a Williams plasticity of 154mm/100 and a vinyl content of 0.01 % wt.

• Silicone Gum G2: Dimethylvinyl-terminated Dimethyl, Methylvinyl Siloxane gum having a Williams plasticity of 155mm/100 and a vinyl content of 0.06 wt %.

• Silicone Gum G3 : Dimethylvinyl-terminated Dimethyl, Methylvinyl Siloxane gum having a Williams plasticity of 154mm/100 and a vinyl content of 0.22 wt. %.

• Silicone Gum G4: Dimethylvinyl-terminated dimethyl Siloxane gum having a Williams plasticity of 135mm/100 and a vinyl content of 0.72% wt.

Silicone Fluids:

· Silicone Fluid FI: Dimethylvinyl-terminated Dimethyl, Methylvinyl Siloxane having a viscosity of 150,000 mPa.s at 25 °C and a vinyl content of 7.5 % wt.

• Silicone Fluid F2: trimethyl terminated dimethyl, Methylvinyl, Siloxane with

Methylphenyl silsesquioxane having a viscosity of 1500 mPa.s at 25 °C and a vinyl content of 5 % wt.

· Silicone Fluid F3 : Tetramethyltetravinylcyclotetrasiloxane

Catalysts

• Peroxide PI: Bis-(2,4-dichlorobenzoyl) peroxide, 50% concentration in silicone oil Additives

• Additive Al: 60% Manganese 2-Ethylhexanoate in naphtha

• Additive A2: 50% ceric hydroxide in a silicone carrier

• Additive A3: 3% masterbatch of magnesium oxide in a silicone rubber carrier

[0088] The approximate compositions of the different bases used in the examples and comparative examples are provided in Table 1. Table 1: Composition of Bases Tested

0089] The source of unsaturation (vinyl) content was determined using quantitative infra-red analysis in accordance with ASTM E168 for all the bases and is depicted below in Table 2 Table 2 Sources of unsaturation and amounts present

[0090] The following catalyst and additives were introduced into the Bases described in Tables 1 and 2 to form their respective compounds by mixing 100 part by weight of base with

1.0 part of Additive A2 per hundred parts of base (phr)

1.0 part of Additive A3 per hundred parts of base (phr); and

1.2 parts of Peroxide PI per hundred parts of base (phr).

[0091] The resulting compounds were cured in 1.91mm (0.075 inch thick) slabs; for 5 minutes at 120°C.

[0092] The physical properties of the above were determined after cure and also after periods of heat aging for 1, 2 and 3 weeks to assess fluid resistance. Shore A Durometer was measured using ASTM D2240. Tensile Strength (MPa), and Elongation (%), were measured using ASTM D412 Die C. Heat aging was undertaken by placing sample slabs in a Parr vessel in distilled water and heated to 170°C and maintained at that temperature for the desired period of time. Prior to testing aged samples were cooled to room temperature and tested without dryout.

[0093] The physical property results measured in accordance with the above and the results are tabulated in Tables were prepared Tables 3a and 3b below.

Table 3a Physical Properties of samples tested

Table 3b Physical Properties of samples tested

[0094] It will be seen that whilst both the examples and the comparatives both have good physical properties prior to aging but it will be seen that upon aging the physical properties of the comparatives, especially tensile strength and elongation become significantly worse whilst those of the Examples maintain their physical properties results for the initial measurements.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A subsea insulation silicone rubber composition comprising

3% wt. or (ii) a hydrosilylation cure package comprising an organohydrogenpolysiloxane having

3 or more silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst or a mixture thereof.

2. A subsea insulation silicone rubber composition in accordance with claim 1 wherein < 3% by weight of the alkenyl or alkynyl groups per molecule are provided by treated reinforcing filler (b).

3. A subsea insulation silicone rubber composition in accordance with claim 1 or 2 wherein the composition is applied to an article prior to cure by hand, wrapping, extrusion, and/or calendaring and then is cured in place.

4. A subsea insulation silicone rubber composition in accordance with any preceding claim wherein polydiorganosiloxane gum (a), has a Williams plasticity of at least 125mm/100 in accordance with ASTM D-926-08.

5. A subsea insulation silicone rubber composition in accordance with any preceding claim wherein the composition includes one or more additives selected from cure inhibitors, non reinforcing fillers, non-conductive fillers, pot life extenders, flame retardants, pigments, colouring agents, adhesion promoters, chain extenders heat stabilizers and/or compression set improvement additives.

6. An elastomeric subsea insulation silicone rubber material which material is the cured

product of a composition in accordance with any one of claims 1 to 5.

7. An elastomeric subsea insulation silicone rubber material obtainable or obtained by curing a composition comprising

polydiorganosiloxane gum (a),

having a Williams plasticity of at least 30mm/100 measured in accordance with ASTM D- 926-08, from 0.15 to 0.3 weight % of alkenyl groups and/or alkynyl groups per molecule; and which is present in the composition in an amount of from 15 to 70% wt. of the composition; (b) a treated reinforcing filler in an amount of 5 to 40% wt. of the composition;

8. An elastomeric subsea insulation silicone rubber material in accordance with claim 6 or 7 wherein the material has an initial elongation of at least 150%.

9. A use of a subsea insulation silicone rubber composition comprising

polydiorganosiloxane gum (a),

(c) a curing agent selected from either (i) a peroxide curing agent in an amount of from 0.3 to 3% wt. or (ii) a hydrosilylation cure package comprising an organohydrogenpolysiloxane having 3 or more silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst or a mixture thereof in the manufacture of piping wellheads, Xmas trees, spool pieces, manifolds, risers and pipe field joints.

10. A method of making an elastomeric subsea insulation silicone rubber material by mixing and curing a composition in accordance with any one of claims 1 to 5.

11. A method of making an elastomeric subsea insulation silicone rubber material in accordance with claim 10 wherein a composition in accordance with any one of claims 1 to 5 is applied to an article, prior to cure, by hand, wrapping, extrusion, and/or calendaring and then curing in place.

12. A subsea article insulated at least partially by an elastomeric subsea insulation silicone rubber material in accordance with claim 6 or 7.

13. A subsea article in accordance with claim 12 wherein the subsea article is selected from piping wellheads, Xmas trees, spool pieces, manifolds, risers and pipe field joints.

14. A subsea insulation silicone rubber composition in accordance with any one of claims 1 to 5 which, upon cure, is hydrolytically stable at temperatures > 150°C.

15. An elastomeric subsea insulation silicone rubber material in accordance with claim 6 or 7 which is hydrolytically stable at temperatures > 150°C.