Primer for silicone rubber compositions and elastomeric materials

Abstract

A primer composition, including a silicone polyether, a reinforcing filler, one or more polydiorganosiloxane polymers, and a carrier, and its preparation and use are described. The primer composition is specifically designed for use with silicone elastomers, particularly addition (hydrosilylation) cured silicone elastomers, and its preparation and process for improving adhesion of the silicone elastomer composition to a pre-cured silicone elastomer material substrate.

Description

[Technical field]

[0001] This disclosure specifies a primer composition and its preparation and use. The primer composition is specifically designed for use with silicone elastomers (often referred to as "silicone rubbers"), particularly addition (hydrosilylation) cured silicone elastomers, and its preparation and process for improving adhesion of the silicone elastomer composition to a pre-cured silicone elastomer material substrate. Summary of the Invention [Problem to be solved by the invention]

[0002] Silicone elastomers have properties that make them preferable over other elastomers in many applications, such as thermal stability over a wide temperature range. Some applications where silicone elastomer / silicone elastomer overmolding is desired, such as subsea insulation, electrical insulation under high voltage, 3D printing, lenses, and consumer applications, require a strong bond to form between preformed silicone elastomer materials and uncured silicone elastomer compositions when they are cured. If adequate bonding to silicone elastomer substrates cannot be obtained directly, the bond strength can be improved by pretreating the substrate surface with a suitable primer.

[0003] For example, silicone elastomer insulation materials are used to insulate subsea oil and gas production facilities. In many subsea locations, for example where subsea oil and gas wells are located at depths of 1500m or more, the pipelines and wellheads are exposed to seawater that is only a few degrees above freezing (e.g., about 4-5°C). If not insulated, the hydrocarbon fluids produced at high temperatures in the production facilities would be cooled by the surrounding seawater, and as the temperature of the fluids approaches that of the seawater, they would form hydrates and paraffin wax in the pipelines, thereby restricting the flow of hydrocarbons and even causing blockages in the pipelines.

[0004] To perform well in this environment, the insulation must have low thermal conductivity, exhibit acceptable mechanical properties such as flexibility and impact resistance, be economical to install, and preferably be resistant to high temperature aqueous environments.

[0005] Liquid silicone rubber (LSR)-based materials made from organopolysiloxane polymers having viscosities up to about 500,000 mPa·s at 25°C have been used for undersea insulation and have the advantage over the above of being able to withstand wide temperature fluctuations without appreciable effect on their physical properties, and being virtually unaffected by UV radiation over long periods of time, as well as ozone, oil, salt, and water.

[0006] Furthermore, the relatively low viscosity of pre-cured LSR compositions makes it difficult to apply the compositions around subsea equipment such as pipes, wellheads and Christmas trees, and LSR insulation materials are applied to subsea equipment articles for insulation purposes using a continuous molding (cast-in-place) process. In such a process, a mold / form is placed in place around the article for a first section of insulation, liquid silicone rubber is then pumped in and cured to a predetermined hardness, and the mold / form is removed. The process is then repeated for a second section, and so on, for as many sections as are necessary to complete the insulation of all of the subsea equipment articles. However, such a continuous process results in many joints with adjacent LSR / LSR (silicone elastomer / silicone elastomer) interfaces.

[0007] Generally, the LSR used in such insulation applications will contain an excess of silicon-bonded hydrogen groups (Si-H groups) such that after curing, a sufficient proportion of unreacted Si-H groups will be available at the cured interface of the first section to interact with the unsaturated groups at the interface of the subsequently cured second section to fully cure the two sections to the desired crosslink density at the interface, such that such an interface will bond to one another in both subsea and all other applications mentioned above. The same is repeated between the cured interface of the second section and the uncured third section, with each subsequent section being cured in place in turn, until the subsea article is fully insulated and adjacent sections are bonded to one another sufficiently strongly against a cohesive failure event along the entire matrix.

[0008] However, it has been recognized that while silicone rubber insulation provides excellent insulating properties, the adhesion / bonding between adjacent interfaces of adjacent sections is often insufficient for the purposes, particularly when considered in terms of withstanding extreme temperature and environmental conditions.

[0009] A variety of primers have been proposed in the past to bond liquid silicone rubber to a substrate. The efficiency of the primer depends on both the chemical and surface properties of the substrate and the composition that bonds to the substrate, i.e., the nature of the adjacent interfaces of the adjacent insulation sections, the crosslinking system and the viscosity of the silicone rubber to be bonded. A variety of primers have been proposed, but most are combinations of two or more of organofunctional alkoxysilanes, such as tetraalkoxysilanes, epoxytrialkoxysilanes, vinyltrialkoxysilanes, and / or methacryloxypropyltrimethoxysilanes, or partial hydrolysis products of such organofunctional alkoxysilanes, SiH-functional intermediates, metal alkoxides, and / or metal chelates, such as titanates, often combined with a suitable solvent. They are provided as one-part or multi-part compositions that are mixed together immediately before use.

[0010] For example: (i) titanium alkoxide and alkyl polysilicate or a partial hydrolysis product thereof; (ii) a tetraalkyl titanate, at least one alkyl orthosilicate, and a hydrocarbon solvent; (iii) an organyloxysilane, such as a tetraalkyl titanate, for example tetraethyl orthosilicate, and an organic solvent; (iv) a silane not containing an amino or amide functionality, such as, for example, methacryloyloxypropyltrimethoxysilane, a metal ester, preferably an inorganic acid, and an organic solvent; (v) Tetraalkoxysilanes and / or their partial hydrolysis products, metal salts, alkoxides, or chelates and / or their partial hydrolysis products, silicone resins, and solvents.

[0011] In WO 2018 / 234783, which describes a subsea insulation system, two different primers were utilized. In this system, a double layer of silicone elastomer insulation was provided around a substrate, e.g., a metal pipe. A first primer was used to bond the silicone elastomer to the metal substrate, while a second primer was utilized to overmold and bond a second layer of silicone rubber onto the silicone rubber base layer. Although the description states that the primers may be the same, the examples state that they are different, and the primer at the silicone elastomer / silicone elastomer interface is: a) linear polydialkylsiloxanes having 3 to 15 silicon atoms, or alternatively 3 to 10 silicon atoms; b)R n Si-(OR 9 ) 4-n wherein n is 0, 1 or 2, preferably n is 0 or 1; R is a non-hydrolyzable silicon-bonded organic group such as a hydrocarbyl group; and each R 9 are the same or different alkoxy groups having 1 to 6 carbon atoms; c) General formula Ti[OR 2 ]4[In the formula, each R 2 represent a linear or branched monovalent primary, secondary or tertiary aliphatic hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different, d) R n Si-(OR 3 ) 4-n wherein n is 0, 1 or 2, preferably n is 0 or 1, R is as defined above, and each R 3 are the same or different and are alkoxy groups having 1 to 6 carbon atoms, or alkoxyalkylene groups in which the alkoxy group has 1 to 6 carbon atoms and the alkylene chain has 1 to 6 carbon atoms.

[0012] There remains a need in industry for a primer that is easy to apply in an industrial environment and provides strong adhesion between silicone elastomer and silicone elastomer layers.

[0013] The present disclosure provides a primer composition, comprising: A) silicone polyether, B) reinforcing fillers, C) one or more polydiorganosiloxane polymers having a viscosity of 1000 to 500,000 mPa·s at 25°C and containing at least one alkenyl group or alkynyl group per molecule; D) a carrier.

[0014] It is understood that conventional primers generally contain chemically reactive components to enhance adhesion properties, such as alkoxysilanes, which are hydrolyzed with moisture after application in the primer and undergo a condensation reaction to improve adhesion with such primers, and thus primers also generally contain a condensation catalyst, usually a titanium and / or zirconium based condensation catalyst, to promote this hydrolysis / condensation reaction. It is therefore noted that the primers described herein are completely different formulations that do not substantially react when exposed to humidity.

[0015] Component A of the primers described herein is a silicone polyether, such as, for example, a copolymer that includes a combination of siloxane and polyether (ie, polyoxyalkylene) blocks.

[0016] Each silicone moiety of the silicone polyether has the formula (I): R a SiO (4-a) / 2 (I) where each R is independently selected from an aliphatic hydrocarbyl group, an aromatic hydrocarbyl group, or an organyl group (i.e., any organic substituent having one free valence at a carbon atom, regardless of the type of functional group). Examples of saturated aliphatic hydrocarbyls include, but are not limited to, alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl, and cycloalkyl groups such as cyclohexyl. Examples of unsaturated aliphatic hydrocarbyls include, but are not limited to, alkenyl groups such as vinyl, allyl, butenyl, pentenyl, cyclohexenyl, and hexenyl, and alkynyl groups. Examples of aromatic hydrocarbon groups include, but are not limited to, phenyl, tolyl, xylyl, benzyl, styryl, and 2-phenylethyl. Examples of organyl groups include, but are not limited to, halogenated alkyl groups such as chloromethyl and 3-chloropropyl, nitrogen-containing groups such as amino, amido, imino, and imido groups, and oxygen-containing groups such as polyoxyalkylene, carbonyl, alkoxy, and hydroxyl groups. Further organyl groups include sulfur-, phosphorus-, and / or boron-containing groups. In the polyethers, each R is generally independently selected from aliphatic hydrocarbyl and aromatic hydrocarbyl. The subscript "a" may be 0, 1, 2, or 3, but is generally predominantly 2 or 3.

[0017] The siloxy units in (I) above can be described by the contraction (abbreviation) notations "M", "D", "T", and "Q" when R is an organic group, typically a methyl group (for further teaching on silicone nomenclature, see Walter Noll, Chemistry and Technology of Silicones, dated 1962, Chapter I, pages 1-9). M units are siloxy units where a=3, i.e., RSiO 1 / 2 and D units are siloxy units where a=2, i.e., RSiO 2 / 2 where T units are siloxy units where a=1, i.e., RSiO 3 / 2 and Q units are siloxy units where a=0, i.e., SiO 4 / 2 Thus, when a in (I) above is 2, the siloxy units are D units, and when a is 3, the siloxy units are T units. Generally, in silicone polyethers, the silicone blocks comprise a chain of D units with branching via T units. Examples of typical R groups on the polydiorganosiloxane polymer (i) include primarily alkenyl, alkyl, and / or aryl groups, or alkyl groups having 1 to 6 carbons, or methyl groups. The groups may be pendant (on D or T siloxy units) or terminal (on M siloxy units).

[0018] The polyether portion of such copolymers has the integer average formula (-C n H 2n -O-) yThe polyoxyalkylene includes repeating units of oxyalkylene represented by the formula: [wherein n is an integer of 2 to 4, inclusive, and y is ≧4, i.e., at least 4]. Furthermore, the oxyalkylene units are not necessarily the same throughout the polyoxyalkylene, and may vary from unit to unit. The polyoxyalkylene may include, for example, oxyethylene units (-C2H4-O-), oxypropylene units (-C3H6-O-), or oxybutylene units (-C4H8-O-), or a combination thereof. Preferably, the polyoxyalkylene polymer backbone consists essentially of oxyethylene units or oxypropylene units. Other polyoxyalkylenes include, for example, those having the structure: -[-R e -O-(-R f -O-) h -Pn-CR g 2-Pn-O-(-R f -O-) q1 -R e ]- [In the formula, Pn represents a 1,4-phenylene group, each R e are the same or different, divalent hydrocarbon radicals having 2 to 8 carbon atoms, and each R f are the same or different and are an ethylene group or a propylene group, and each R g are the same or different and are a hydrogen atom or a methyl group, and each of the subscripts h and q1 is a positive integer in the range of 3 to 30.

[0019] One preferred type of polyether chain in the silicone polyether has the formula (-C n H 2n It is a polyoxyalkylene polymer containing a repeating unit of oxyalkylene of the formula: -O-), where n is an integer of 2 to 4, inclusive.

[0020] Generally, each polyoxyalkylene block Z 1 is attached to the siloxane block by a divalent organic group. This attachment is determined by the reaction used to prepare the block silicone polyether copolymer. 1The terminal divalent organic groups are independently selected from divalent hydrocarbons containing 2-30 carbons and divalent organofunctional hydrocarbons containing 2-30 carbons. Representative non-limiting examples of such divalent hydrocarbon groups include ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, and the like. Representative non-limiting examples of such divalent organofunctional hydrocarbon groups include acrylates and methacrylates. In one alternative, the divalent hydrocarbon groups include ethylene, propylene, butylene, pentylene, hexylene, heptylene, or octylene, or ethylene, propylene, butylene.

[0021] The silicone polyether may be of any type, for example, the silicone polyether may be an (AB)n type silicone polyether having repeating blocks of siloxane units and polyoxyalkylene organic units to form a copolymer, but in the present invention has an M end group, which is represented as follows: M(DZ 1 ) z M where M and D are defined above, and each Z 1 is a block of a polyoxyalkylene polymer chain, z is ≧2, and M is MeOHSiO 1 / 2 Alternatively, the silicone polyether may be MDZ 1 DM type [wherein M is MeOHSiO 1 / 2 or, for example, H-(O(CH2)2) d -O-(CH2)3-Si(CH3)2-O[Si(CH3)2-O] e -Si(CH3)2-(CH2)3-O-((CH2)2-O) d H wherein d and e are integers. 1 DZ 1 It may also be a silicone polyether.

[0022] Alternatively, the copolymer may take the form of a "rake" copolymer in which a predominantly linear polyorganosiloxane provides the backbone of the copolymer's structure with pendant organic blocks to form a rake shape, which is shown below: MD 1 x D 2 y M where M is defined above and D 1 is the formula (R 3 )2SiO 2 / 2 represents the unit of D 2 is the formula (R 3 )(Z 2 )SiO 2 / 2 In the formula, Z 2 represents a monovalent polyether block, R 3 is as stated above.

[0023] In one alternative, the copolymer is the ABA or (AB) copolymer described above. z For rake type copolymers, d is zero, 1, 2 or 3, or zero or 1, or zero.

[0024] The viscosity of the silicone polyether block copolymers of the ABA or (AB)n type is preferably between 1000 mPa·s and 200,000 mPa·s at 25° C. using a Brookfield® rotational viscometer with spindle (LV-4) and adjusting the speed depending on the viscosity of the polymer, where all viscosity measurements were taken at 25° C. unless otherwise specified.

[0025] When the copolymer is a rake copolymer, the organic component Z 2 is the formula (-C n H 2n It is preferable that the polyether-containing substituent is a polyether-containing substituent having a repeating oxyalkylene unit of the formula: Z -O- (wherein n is an integer of 2 to 4, inclusive). 1As previously described for , the polyether side chains may be linked to silicon atoms in the polymer backbone by divalent organic groups having terminal -OH or alkoxy groups, where the alkoxy groups have from 1 to 6 carbon atoms, or -OH or methoxy or ethoxy groups, or -OH groups. Typically, the polyether side chains in such rake copolymers contain from 2 to 150 alkylene oxide units per side chain.

[0026] The primer compositions herein are described as weight percent (wt%) of solids content, i.e., weight percent of the components of the primer excluding carrier (D), i.e., (A), (B), (C) and any additives, if present, and / or weight percent (wt%) of the total content of the composition including carrier (D), if present. In each example, when all components are added together, the composition equals 100 wt%. The silicone polyether (A) is present in an amount of 0.05wt% to 10wt% of the solid content of the composition, alternatively 0.05wt% to 7.5wt% of the solid content of the composition, alternatively 0.1wt% to 5.0%wt% of the solid content of the composition. Thus, for example, the silicone polyether is present in the total composition in an amount of 0.05wt% to 4wt% of the total composition, alternatively 0.05wt% to 2.5wt% of the total composition, alternatively 0.1wt% to 2.5wt% of the total composition.

[0027] Component (B) of the composition is a reinforcing filler such as finely divided fumed silica and / or finely divided precipitated silica and / or a suitable silicone resin.

[0028] Finely divided forms of silica are the preferred reinforcing fillers (B). Precipitated silica, fumed silica and / or colloidal silica are generally at least 50 ml. 2 They are particularly preferred due to their relatively high surface area of ​​50 to 450 m / g (BET method according to ISO 9277:2010). 2 / g (BET method according to ISO9277:2010), or 50-300m 2Use fillers with a surface area of ​​0.1 μm / g (BET method according to ISO 9277:2010). All these types of silica are commercially available.

[0029] If the reinforcing filler (B) is naturally hydrophilic (e.g., untreated silica filler), it is generally treated with a treating agent to render it hydrophobic. These surface-modified reinforcing fillers (B) do not aggregate and can be homogeneously incorporated into the polydiorganosiloxane polymer (C) described below, since the surface treatment allows the filler to be easily wetted by the polydiorganosiloxane polymer (C).

[0030] Generally, the reinforcing filler (B) is surface-treated with any low molecular weight organosilicon compound disclosed in the art that can be applied to prevent creping of the organosiloxane composition during processing.For example, organosilanes, polydiorganosiloxanes, or organosilazanes such as hexaalkyldisilazanes, short chain siloxane diols, fatty acids or fatty acid esters such as stearic acid esters, that can make the filler hydrophobic, making it easier to handle and obtain a homogeneous mixture with other components. Specific examples include, but are not limited to, silanol-terminated trifluoropropylmethylsiloxane, silanol-terminated vinylmethyl (ViMe)siloxane, tetramethyldi(trifluoropropyl)disilazane, tetramethyldivinyldisilazane, silanol-terminated MePhsiloxane, liquid hydroxyl-terminated polydiorganosiloxanes containing 2-20 repeating units of diorganosiloxane in each molecule, hexaorganodisiloxane, and hexaorganodisilazane. A small amount of water may be added as a processing aid together with the silica treating agent.

[0031] The surface treatment can be carried out prior to introduction into the composition or in situ (i.e., by mixing the other components together at room temperature in the presence of at least a portion of the compositions herein until the filler is completely treated). Typically, untreated reinforcing filler (B) is treated with a treating agent in situ in the presence of polydiorganosiloxane polymer (C), thereby preparing a silicone rubber base material which can then be mixed with the other components.

[0032] The reinforcing filler is 5.0wt%-40% of the solid content of the composition, alternatively 7.5-35wt% of the solid content of the composition, alternatively 10.0-35wt% based on the weight percent of the solid content of the composition. From this, the amount of reinforcing filler (B), e.g., micronized silica and / or silicone resin, in the primer composition herein is therefore, for example, 2.0-20wt% of the total composition, alternatively 2.5-15wt% of the total composition. In some cases, the amount of reinforcing filler may be 5.0-15wt% based on the weight of the total composition.

[0033] Component (C) is one or more polydiorganosiloxane polymers containing at least one alkenyl and / or at least one alkynyl group per molecule, or at least two alkenyl and / or alkynyl groups per molecule, or at least two alkenyl groups per molecule, and having a viscosity of 1000 to 500,000 mPa·s at 25° C. Similar to the siloxane chains in silicone polyether (A), polydiorganosiloxane polymer (C) has the formula (I): R a SiO (4-a) / 2 (I) wherein each R is independently selected from an aliphatic hydrocarbyl group, an aromatic hydrocarbyl group, or an organyl group (i.e., any organic substituent having one free valence at a carbon atom, regardless of the type of functional group). Examples of saturated aliphatic hydrocarbyl include, but are not limited to, alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl, and cycloalkyl groups such as cyclohexyl. Examples of unsaturated aliphatic hydrocarbyl include, but are not limited to, alkenyl groups such as vinyl, allyl, butenyl, pentenyl, cyclohexenyl, and hexenyl, and alkynyl groups. Examples of aromatic hydrocarbon groups include, but are not limited to, phenyl, tolyl, xylyl, benzyl, styryl, and 2-phenylethyl. Examples of organyl groups include, but are not limited to, halogenated alkyl groups such as chloromethyl and 3-chloropropyl, nitrogen-containing groups such as amino, amido, imino, and imido groups, and oxygen-containing groups such as polyoxyalkylene, carbonyl, alkoxy, and hydroxyl groups. Further organyl groups include sulfur-, phosphorus-, and / or boron-containing groups. The subscript "a" may be 0, 1, 2, or 3, but is generally predominantly 2 or 3.

[0034] Examples of typical groups on the polydiorganosiloxane polymer (C) include mainly alkenyl groups, alkyl groups, and / or aryl groups. The groups may be pendant (on D or T siloxy units) or terminal (on M siloxy units). Thus, suitable alkenyl groups in the polydiorganosiloxane polymer (C) generally contain 2 to 10 carbon atoms, such as vinyl, isopropenyl, allyl, and 5-hexenyl.

[0035] Generally, the silicon-bonded organic groups attached to the polydiorganosiloxane polymer (C), other than alkenyl groups, are selected from monovalent saturated hydrocarbon groups, typically containing from 1 to 10 carbon atoms, and monovalent aromatic hydrocarbon groups, typically containing from 6 to 12 carbon atoms, which are unsubstituted or substituted by groups, such as halogen atoms, that do not interfere with the curing of the compositions of the present invention. Preferred species of silicon-bonded organic groups are, for example, alkyl groups, such as methyl, ethyl, and propyl, and aryl groups, such as phenyl.

[0036] The molecular structure of the polydiorganosiloxane polymer (C) is generally linear, although some branching may be present due to the presence of T units within the molecule (as discussed above).

[0037] The viscosity of the polydiorganosiloxane polymer (C) must be at least 1000 mPa·s at 25° C. The upper viscosity limit of the polydiorganosiloxane polymer (C) is limited to a maximum viscosity of 500,000 mPa·s at 25° C.

[0038] Typically, the or each polydiorganosiloxane containing at least two silicon-bonded alkenyl groups per molecule of component (C) has a viscosity of from 1000 mPa·s to 150,000 mPa·s at 25° C., alternatively from 1000 mPa·s to 125,000 mPa·s at 25° C., alternatively from 1000 mPa·s to 50,000 mPa·s at 25° C. In each of the above cases, the viscosity is measured according to the cup / spindle method of ASTM D1084 Method B, using the most appropriate spindle from the Brookfield® RV or LV range of viscosity ranges.

[0039] The polydiorganosiloxane polymer (C) is selected from, for example, polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes, or copolymers thereof, containing alkenyl and / or alkynyl groups, and has any suitable end group, for example, they may be trialkyl-terminated, alkenyldialkyl-terminated, or terminated with any other suitable combination of end groups, provided that each polymer contains at least two alkenyl groups in the molecule. Alternatively, the polydiorganosiloxane may be partially fluorinated, for example, containing trifluoroalkyl, such as trifluoropropyl, and / or perfluoroalkyl groups. Thus, the polydiorganosiloxane polymer (C) may be, for example, dimethylvinyl-terminated polydimethylsiloxane, dimethylvinylsiloxy-terminated dimethylmethylphenylsiloxane, trialkyl-terminated dimethylmethylvinylpolysiloxane, or dialkylvinyl-terminated dimethylmethylvinylpolysiloxane copolymer.

[0040] For example, a polydiorganosiloxane polymer (C) containing two terminal alkenyl groups is represented by the general formula (II): R'R''R'''SiO-(R''R''SiO) m -SiR'''R''R'(II)

[0041] In formula (II), each R' is an alkenyl or alkynyl group generally containing 2 to 10 carbon atoms. Alkenyl groups include, but are not limited to, vinyl, propenyl, butenyl, pentenyl, hexenyl, alkenylated cyclohexyl groups, heptenyl, octenyl, nonenyl, decenyl, or similar linear and branched alkenyl groups, and alkenylated aromatic ring structures. Alkynyl groups are selected from, but are not limited to, ethynyl, propynyl, butynyl, pentynyl, hexynyl, alkenylated cyclohexyl groups, heptenyl, octenyl, nonenyl, decynyl, or similar linear and branched alkenyl groups, and alkenylated aromatic ring structures.

[0042] R″ does not contain ethylenic unsaturation, and each R″ may be the same or different and is independently selected from monovalent saturated hydrocarbon groups, typically containing 1 to 10 carbon atoms, and monovalent aromatic hydrocarbon groups, typically containing 6 to 12 carbon atoms. R″ may be unsubstituted or substituted with one or more groups (such as halogen atoms) that do not interfere with curing of the compositions of the invention. R′″ is R′ or R″.

[0043] One or more polydiorganosiloxane polymers (C) having a viscosity of 1000-500,000 mPa·s at 25° C. and containing at least one alkenyl or alkynyl group per molecule are present in an amount of 40-90 wt % of the solids content of the composition, alternatively 45-85 wt % of the solids content of the composition, alternatively 50-85 wt % of the solids content of the composition. Thus, organopolysiloxane polymer (C) is typically a dimethylvinyl-terminated polydimethylsiloxane present in an amount of 15-45 wt % of the total composition, alternatively 15-40 wt % of the total composition, alternatively 15-35 wt % of the total composition.

[0044] Component D of the composition is a suitable carrier, i.e., a suitable diluent that reduces the viscosity of the composition containing components A, B, and C to allow application to the substrate in the form of a low-viscosity liquid by a suitable method, such as application with a spray, roller, brush, knife coater, or in certain circumstances may be coated by immersing the substrate in a bath of primer. Any suitable carrier can be used for this purpose. The carrier may optionally be volatile, so that component D can at least partially evaporate after application. Carriers include short-chain siloxanes containing 3 to 20 silicon atoms in the siloxane backbone, or 3 to 10 silicon atoms in the siloxane backbone, or 3 to 6 silicon atoms in the siloxane backbone, which may be linear, branched, or cyclic, although linear short-chain siloxanes are preferred. It is preferred that none of such siloxanes are VOC compounds that evaporate at or near room temperature. The carrier may also be a suitable organic carrier, which is volatile to allow partial evaporation after application, if deemed appropriate. Examples include toluene, xylene, and similar aromatic hydrocarbon solvents, n-hexane, ligroin, kerosene, mineral spirits, and similar aliphatic hydrocarbon solvents, cyclohexane, decahydronaphthalene, and similar cycloaliphatic hydrocarbon solvents, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, amyl alcohol, hexyl alcohol, and similar alcohol solvents, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and similar ketone solvents, diethyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane, and similar ether solvents, diethyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, and other carbonate solvents, ethyl acetate, n-propyl acetate, isobutyl acetate, and other acetates, malonates, succinates, glutarates, adipates, phthalates, and other ester solvents.

[0045] The solids content of the primer can be diluted with the carrier in any amount suitable for the application in which it is to be used. For example, per 100 parts by weight of the solids of the composition (i.e., (A)+(B)+(C)+additives), the carrier (D) is present in an amount of 20 to 150 parts by weight, alternatively 70 to 150 parts by weight. Thus, for example, the carrier is present in the primer in an amount of 50 wt% to 80 wt% of the total composition, alternatively 55 wt% to 75 wt% of the total composition.

[0046] As mentioned above, optionally, the primer may include one or more additional components, such as one or more organohydrogenpolysiloxanes or hydrosilylation catalysts (but not both together, as this may accelerate the cure from occurring). Examples of organohydrogenpolysiloxanes that can be included in the primer, if desired, include, for example: (a) trimethylsiloxy-terminated methylhydrogenpolysiloxane, (b) trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane; (c) dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymer; (d) dimethylsiloxane-methylhydrogensiloxane cyclic copolymers; (e)(CH3)2HSiO 1 / 2 Unit: (CH3)3SiO 1 / 2 Units, and SiO 4 / 2 copolymers and / or silicone resins consisting of units; (f)(CH3)2HSiO 1 / 2 Units and SiO 4 / 2 copolymers and / or silicone resins consisting of units; (g)(CH3)2HSiO 1 / 2 Units, SiO 4 / 2 Units, and (C6H5)3SiO 1 / 2 Included are copolymers and / or silicone resins consisting of units, as well as alternatives in which methyl is replaced with phenyl or other alkyl groups.

[0047] Alternatively, the organohydrogenpolysiloxane may be a filler, such as silica, that has been treated with one of the above. The SiH compounds are described in more detail below.

[0048] The hydrosilylation catalyst that can be used as an additive in the primer is any suitable hydrosilylation catalyst that can be used to cure the hydrosilylation curable silicone composition described below.In particular, it is one of platinum metals (platinum, ruthenium, osmium, rhodium, iridium, and palladium) or one or more compounds of such metals.Platinum and platinum compounds are preferred due to the high activity level of these catalysts in hydrosilylation reaction.If necessary, any of the hydrosilylation catalysts shown below can be introduced into the primer.

[0049] Thus, the primers are A) a silicone polyether in an amount of 0.05 wt% to 10 wt% of the solids content of the composition, alternatively 0.05 wt% to 7.5 wt% of the solids content of the composition, alternatively 0.1% to 5.0 wt% of the solids content of the composition; B) a reinforcing filler in an amount of 5.0 to 40 wt%, alternatively 7.5 to 35 wt%, alternatively 10.0 to 35 wt%, based on the weight percent solids content of the composition; C) one or more polydiorganosiloxane polymers having a viscosity of 1000 to 500,000 mPa·s at 25°C and containing at least one alkenyl or alkynyl group per molecule in an amount of 40 to 90 wt% of the solids content of the composition, alternatively 45 to 85 wt% of the solids content of the composition, alternatively 50 to 85 wt% of the solids content of the composition, where the solids content of the composition does not include the carrier (D), i.e., the composition content of (A), (B), (C) and all additives, if present; The carrier (D) is present in an amount of 20 to 150 parts by weight, alternatively 70 to 150 parts by weight, per 100 parts by weight of the solids of the composition. The solids content of the composition is the total combination of the components of the composition excluding the carrier (D), i.e., (A), (B), (C) and any additives, if present, such that the solids content of the composition in wt % totals 100 wt %.

[0050] Thus, by way of example, if the carrier is included in the overall composition, the total composition is as follows;- A) a silicone polyether in an amount of 0.05 wt% to 4 wt% of the composition, alternatively 0.05 wt% to 2.5 wt% of the composition, alternatively 0.1 wt% to 2.5 wt% of the composition; B) a reinforcing filler in an amount of 2.0 to 20 wt.%, alternatively 2.5 to 15 wt.%, alternatively 5.0 to 15 wt.%, based on the weight of the composition; C) one or more polydiorganosiloxane polymers having a viscosity of 1000 to 500,000 mPa·s at 25°C and containing at least one alkenyl or alkynyl group per molecule, in an amount of 15 to 45 wt% of the composition, or 15 to 40 wt% of the total composition, or 15 to 35 wt% of the composition; D) A carrier in the range of 50 wt% to 80 wt%, or 55 wt% to 75 wt% of the composition. The total composition is any combination of the above alone or with additional additives, and the total composition, including the content of component (D), totals 100%.

[0051] As mentioned above, for many years, primers used to improve the adhesion of silicone elastomers to substrates generally rely on "reactive chemical processes", such as alkoxysilanes, which must be hydrolyzed with moisture and then undergo condensation reactions, a process that is optionally accelerated by the use of condensation catalysts such as titanium or zirconium-based compounds. The composition of our primer is considered to be non-reactive, since there is no catalyst or curing agent present to induce crosslinking, and no reaction occurs by itself before the application of the curable silicone elastomer composition.

[0052] Most prior art primers for silicone materials require a period of time, e.g., at least 20 or 30 minutes, to air dry and evaporate the volatile carrier and / or vulcanize / condense, but given that the components of the primers described herein generally do not react with each other, a curable silicone rubber composition can be applied over the primer of the present invention immediately after application of the primer, although some shorter drying time may be required if the carrier is volatile.

[0053] The preparation of the above-mentioned primer composition is carried out in any suitable manner, for example by homogeneously mixing components (A), (B), (C) and any other components present in the composition in the carrier (D) in a suitable mixing unit. The initial mixture can be either the complete composition or in the form of a concentrate or masterbatch that is diluted by the addition of further carrier (D).

[0054] From this, there is also provided a method for improving the adhesion of silicone rubber to a substrate by applying the primer composition of the present invention to the substrate. Advantageously, no pretreatment or cleaning step is required on the substrate cured, for example by corona treatment, plasma treatment, flame treatment, UV irradiation, or the like, before applying the primer. The primer composition can be applied using any suitable known method, for example, depending on the viscosity of the primer composition, the primer may be applied by spray, roll, brush, knife coater, or the like, or the substrate may be coated by immersion in a bath of primer, in certain circumstances. Generally, immediately after application, a uniform primer film is obtained covering the substrate. However, if necessary, the primer may be air-dried at room temperature on the substrate surface for a period of time, for example, 2 to 10 minutes, before applying the silicone elastomer composition. Alternatively, the substrate coated with the primer may be heated to accelerate the drying process, if deemed necessary. The primer coating on the substrate generally ranges from 0.01 to 3 mm in thickness, alternatively from 0.01 to 2 mm in thickness. After a uniform primer film is formed covering the substrate, a curable silicone elastomer composition is applied in the required form and then cured to obtain an overmolded composite having an adhesive bond between the original silicone rubber substrate and the curable composition applied thereto. A hydrosilylation-curable elastomer composition can be overmolded onto a hydrosilylation-cured substrate to which the primer has been previously applied, and the subsequently cured overmolded layer appears to remain reliably adhered to the previously cured substrate.

[0055] The silicone elastomer substrate is prepared by curing a peroxide crosslinking or hydrosilylation (addition) crosslinking silicone elastomer composition, or similarly by curing a fluorosilicone elastomer composition. Typically, such compositions also contain fillers and / or suitable curing packages as described herein. The substrate is cured from a composition comprising any suitable organosiloxane homopolymer, copolymer, or mixture of these polymers, where the repeating unit is, for example, one or more of dimethylsiloxane, methylvinylsiloxane, methylphenylsiloxane, phenylvinylsiloxane, 3,3,3-trifluoropropylmethylsiloxane, 3,3,3-trifluoropropylvinylsiloxane, and / or 3,3,3-trifluoropropylphenylsiloxane.

[0056] The substrate compositions described herein can be cured with a hydrosilylation cure package, as described below, or with a peroxide catalyst or a mixture of different types of peroxide catalysts.

[0057] The peroxide catalyst may be any commercially available peroxide known for use in curing silicone and / or fluorosilicone 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. In general, the amount of peroxide catalyst used in the compositions described herein is 0.2 to 3 wt%, alternatively 0.2 to 2 wt%, in each case based on the weight of the composition.

[0058] Suitable organic peroxides include, for example, substituted or unsubstituted dialkyl-, alkylaroyl-, diaroyl-peroxides such as benzoyl peroxide and 2,4-dichlorobenzoyl peroxide, ditertiary butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, bis(t-butylperoxyisopropyl)benzene, bis(t-butylperoxy)-2,5-dimethylhexyne, 2,4-dimethyl-2,5-di(t-butylperoxy)hexane, di-t-butyl peroxide, and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane. When the substrate composition is cured with a peroxide, the composition further comprises an organohydrogenpolysiloxane having at least two, alternatively at least three, Si-H groups per molecule, as described below.

[0059] The hydrosilylation-curable silicone elastomer composition for use in application to the primed silicone elastomer substrate comprises (i) one or more polydiorganosiloxane polymers, such as component C in the primer composition described above; and (ii) A hydrosilylation cure package along with a reinforcing filler, typically a silica reinforcing filler such as component B in the primer composition. The hydrosilylation cure package contains an organohydrogenpolysiloxane having at least two, or alternatively at least three, Si-H groups per molecule (iii), a hydrosilylation catalyst (iv), and, optionally, a cure inhibitor (v).

[0060] The hydrosilylation-curable silicone elastomer composition used for application to the primed silicone elastomer substrate is cured using a hydrosilylation catalyst package in the form of: (iii) an organohydrogenpolysiloxane having at least two or at least three Si-H groups per molecule; (iv) a hydrosilylation catalyst, and optionally (v) Curing inhibitor.

[0061] (iii) Organohydrogenpolysiloxane The organohydrogenpolysiloxane (iii) of the hydrosilylation-curable silicone elastomer composition used in application to the primed silicone elastomer substrate functions as a crosslinker that cures polymer (i) by an addition / hydrosilylation reaction of alkenyl groups in polymer (i) with silicon-bonded hydrogen atoms in component (iii), catalyzed by component (iv) described below.

[0062] Typically, organohydrogenpolysiloxane (iii) contains three or more silicon-bonded hydrogen atoms that can react with unsaturated alkenyl or alkynyl groups in polymer (i) to form a network therewith and cure the composition. Alternatively, when polymer (i) has more than two alkenyl or alkynyl groups per molecule, some or all of organohydrogenpolysiloxane (iii) may have two silicon-bonded hydrogen atoms per molecule.

[0063] The molecular structure of organohydrogenpolysiloxane (iii) is not specifically limited, and may be linear, partially branched linear, cyclic, or silicone resin-based. The molecular weight of this component is not particularly limited, but the viscosity is generally 0.001 to 50 Pa.s at 25°C using the Brookfield® RV or LV range spindle most appropriate for the viscosity range in the cup / spindle method of ASTM D1084 Method B in order to obtain good miscibility with polymer (i).

[0064] The organohydrogenpolysiloxane (iii) of the hydrosilylation-curable silicone elastomer composition used for application to a primed silicone elastomer substrate is generally added in an amount such that the molar ratio of the total number of silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (iii) to the total number of alkenyl / alkynyl groups in the polymer (i) is 0.5:1 to 20:1. When this ratio is less than 0.5:1, a sufficiently cured composition is not obtained. When this ratio is greater than 20:1, the hardness of the cured composition tends to increase when heated.

[0065] Examples of organohydrogenpolysiloxanes (iii) include, but are not limited to, the following: (a) trimethylsiloxy-terminated methylhydrogenpolysiloxane, (b) trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane; (c) dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymer; (d) dimethylsiloxane-methylhydrogensiloxane cyclic copolymers; (e)(CH3)2HSiO 1 / 2 Unit: (CH3)3SiO 1 / 2 Units, and SiO 4 / 2 copolymers and / or silicone resins consisting of units; (f)(CH3)2HSiO 1 / 2 Units and SiO 4 / 2 copolymers and / or silicone resins consisting of units; (g)(CH3)2HSiO 1 / 2 Units, SiO 4 / 2 Units and (C6H5)3SiO 1 / 2 Copolymers of units and / or silicone resins, and alternatives thereof where the methyl is replaced by a phenyl group or other alkyl group. Alternatively, component (iii) may be a filler, such as a silica that has been treated with one of the above.

[0066] The silicon-bonded hydrogen (Si-H) content of the organohydrogenpolysiloxane (iii) of the hydrosilylation-curable silicone elastomer composition used for application to the primed silicone elastomer substrate is determined using quantitative infrared analysis according to ASTM E168. In the present invention, the ratio of silicon-bonded hydrogen to alkenyl (vinyl) and / or alkynyl is important when relying on the hydrosilylation curing process. Generally, this is determined by calculating the total wt% of alkenyl groups in the composition, e.g., vinyl [V], and the total wt% of silicon-bonded hydrogen [H] in the composition, where the molar ratio of silicon-bonded hydrogen to vinyl is 27 [H] / [V], where the molecular weight of hydrogen is 1 and the molecular weight of vinyl is 27.

[0067] (iv) Hydrosilylation catalyst When present, the hydrosilylation catalyst (iv) of the hydrosilylation-curable silicone elastomer composition used in application to the primed silicone elastomer substrate is preferably one of the platinum metals (platinum, ruthenium, osmium, rhodium, iridium, and palladium) or one or more compounds of such metals. Platinum and platinum compounds are preferred due to the high activity levels of these catalysts in hydrosilylation reactions.

[0068] Examples of suitable hydrosilylation catalysts (iv) include, but are not limited to, platinum black, platinum on various solid supports, chloroplatinic acid, alcoholic 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. Catalyst (iv) is platinum metal, a platinum group metal deposited on a support such as silica gel or powdered charcoal, or a compound or complex of platinum metal.

[0069] Examples of suitable platinum-based catalysts include: (i) complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups, as described in U.S. Pat. No. 3,419,593; (ii) Chloroplatinic acid in either the hexahydrate or anhydrous form; (iii) platinum-containing catalysts obtained by a process comprising reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound, such as divinyltetramethyldisiloxane; (iv) alkene-platinum-silyl complexes as described in U.S. Pat. No. 6,605,734, such as (COD)Pt(SiMeCl2)2, where "COD" is 1,5-cyclooctadiene; and / or (v) Karstedt's catalysts, which are complexes of platinum and divinyltetramethyldisiloxane, typically containing about 1 wt. % platinum in a solvent such as toluene, as described in U.S. Patents 3,715,334 and 3,814,730.

[0070] The hydrosilylation catalyst (iv) of the hydrosilylation-curable silicone elastomer composition used for application to the primed silicone elastomer substrate is present in the overall composition in a catalytic amount, i.e., an amount or quantity sufficient to catalyze the addition / hydrosilylation reaction and cure the composition into an elastomeric material under desired conditions. Various concentrations of the hydrosilylation catalyst (iv) can be used to adjust the reaction rate and cure rate. The catalytic amount of the hydrosilylation catalyst (iv) is generally from 0.01 ppm to 10,000 ppm, alternatively from 0.01 to 5000 ppm, alternatively from 0.01 to 3,000 ppm, alternatively from 0.01 to 1,000 ppm, by weight of platinum metal per million parts (ppm) based on the weight of the polymer (i) and filler (ii) of the composition. In certain embodiments, the catalytic amount of catalyst ranges from 0.01 to 1,000 ppm, alternatively 0.01 to 750 ppm, alternatively 0.01 to 500 ppm, alternatively 0.01 to 100 ppm metal based on the weight of the composition. The ranges may relate to only the metal content in the catalyst, or to the entire catalyst (including its ligands), as specified, but typically these ranges relate to only the metal content in the catalyst. The catalyst may be added as a single species or as a mixture of two or more different species. Generally, depending on the form / concentration in which the catalyst package is provided, the amount of catalyst present ranges from 0.001 to 3.0 wt% of the composition.

[0071] When the hydrosilylation-curable silicone elastomer composition used for application to the silicone elastomer substrate primed as described above is cured by addition / hydrosilylation reaction component (v), an inhibitor may be used to inhibit the cure of the composition. These inhibitors (v) are used to retard or inhibit the activity of the catalyst, thereby preventing premature curing during storage and / or to increase the working time or pot life of the hydrosilylation-curable composition. Inhibitors (v) for hydrosilylation catalysts (iv), such as platinum metal-based catalysts, are known in the art and 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, mono- and diesters of unsaturated hydrocarbons, conjugated eneines, hydroperoxides, nitriles, and diaziridines.

[0072] One class of known inhibitors (v) of hydrosilylation catalysts such as platinum catalysts (iv) includes the acetylenic compounds disclosed in U.S. Pat. No. 3,445,420. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors that suppress the activity of platinum-containing catalysts at 25° C. Generally, compositions containing these inhibitors must be heated to temperatures of 70° C. or higher in order to cure at a practical rate.

[0073] Examples of acetylenic alcohols and their derivatives include 1-ethynyl-1-cyclohexanol (ETCH), 2-methyl-3-butyn-2-ol, 3-butyn-1-ol, 3-butyn-2-ol, propargyl alcohol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclopentanol, 1-phenyl-2-propynol, 3-methyl-1-penten-4-yn-3-ol, and mixtures thereof.

[0074] When present, in some instances, sufficient storage stability and cure speed can be obtained with inhibitor concentrations as low as 1 mole of inhibitor per mole of catalyst (iv) metal. In other instances, inhibitor concentrations of up to 500 moles of inhibitor per mole of catalyst (iv) metal are required. The optimum concentration of a given inhibitor (v) in a given hydrosilylation-curable silicone elastomer composition used for application to a primed silicone elastomer substrate is readily determined by routine experimentation. Depending on the concentration and form in which the selected inhibitor is commercially provided / available, when present in the composition, the inhibitor is generally present in an amount of 0.0125-10 wt% of the composition. Mixtures of the above may also be used.

[0075] Typically, hydrosilylation-curable silicone elastomer compositions used for application to primed silicone elastomer substrates, as discussed further below, are stored in two parts, often referred to as Part A and Part B, to separate the organohydrogenpolysiloxane (iii) and catalyst (iv) prior to curing. Such two-part compositions are configured for easy mixing immediately prior to use, and typically have a weight ratio of Part A:Part B of 15:1 to 1:1.

[0076] Further optional ingredients Depending on its intended use, additional optional ingredients may be present in the silicone elastomer composition. Examples of such optional ingredients include electrically and thermally conductive fillers, non-conductive fillers, pot life extenders, flame retardants, lubricants, non-reinforcing fillers, pigment colorants, chain extenders, mold release agents, UV light stabilizers, germicides, wetting agents, heat stabilizers, compression set improving additives, and mixtures thereof.

[0077] The silicone rubber composition is applied onto a primer-treated substrate by injection molding, encapsulation molding, press molding, dispenser molding, extrusion molding, transfer molding, press vulcanization, centrifugal casting, calendaring, bead coating, 3D printing, or blow molding, depending on the viscosity, application, etc.

[0078] The silicone rubber composition is cured as required depending on the type of cure package used. Typically, it is preferred to use high temperatures, for example, about 80°C to 150°C, for the cure of hydrosilylation cure systems, but in some applications where the primers herein are suitable, such as silicone rubber compositions for subsea use, temperatures from room temperature to 80°C, or even lower, such as room temperature, i.e., about 23-25°C to about 50°C, are used for the cure process.

[0079] The primer is suitable for applications where silicone elastomer / silicone elastomer overmolding is desired, such as subsea insulation, electrical insulation under high voltage, 3D printing, lenses, automotive applications and consumer applications, i.e., where a strong bond needs to be formed between preformed silicone elastomer materials and uncured hydrosilylation curable silicone elastomer compositions when they are cured. Although overmolding includes similar silicone elastomers, i.e., those having the same or very similar uncured composition, one particularly important application of the primer herein is to aid in the adhesion of silicone elastomer materials having different properties, such as different Shore A hardness, different colors, different optical transparency, or other differences in physical properties that are beneficial to combine. Thus, the primer as described above is suitable for bonding composite parts of articles such as housings, plugs and connectors for automotive applications with silicone seals or gaskets, parts of various sensors, membranes, diaphragms, climate control ventilation parts, etc. Composite parts also include devices such as masks, goggles, tubing and valve catheters, ostomy appliances, respiratory appliances, feeding appliances, contact lenses, hearing aids, orthotics, prostheses, etc. Other composite parts requiring two silicone layers with different physical properties (when cured) include seals and surfaces in shower heads, bakeryware, spatulas, home appliances, shoes, footwear, sports and leisure articles, diving masks, face masks, pacifiers and other baby articles, feeding aids, white goods and other kitchen articles, etc. Electronic applications include silicone elastomer composites such as cell phone cover seals, cell phone accessories, precision electronics, electrical switches and switch covers, watches and wristbands, wearable electronic devices, etc.

[0080] For subsea insulation, silicone elastomer materials are particularly suitable since any insulation used must be able to withstand the extreme temperatures of the hydrocarbon fluids coming out of the well, which can sometimes reach 150°C or more, without their thermal or mechanical properties being adversely affected. The insulation must be resistant to the corrosive nature of seawater from just below the surface to a depth of about 50m, as it may be subject to underwater turbulence due to weather and weather conditions prevailing in the sea. Thus, in some instances, the silicone elastomer composition used may contain syntactic media such as microspheres or glass microspheres, especially borosilicate glass microspheres.

[0081] Typically, in subsea applications, the silicone elastomer composition used for the continuous casting (cast-in-place) of the insulation material has the same or very similar composition as the substrate before curing. Due to the relatively low viscosity of the hydrosilylation curable silicone elastomer composition used for the subsea insulation material, it is applied to the subsea equipment article for insulation purposes using a continuous casting (cast-in-place) process. In such a process, a mold / form is placed in the location of the first section of insulation material around the article, then liquid silicone rubber is pumped in and cured to a predetermined hardness, and the mold / form is removed. The process is then repeated for the second section, and thus for as many sections as are necessary to complete the insulation of all of the subsea equipment article. However, such a continuous process results in multiple joints with adjacent silicone elastomer / silicone elastomer interfaces, and it has been recognized that while the silicone elastomer insulation material provides excellent insulation, the adhesion / bonding between adjacent interfaces of adjacent sections is often insufficient for the purpose, especially considering the extreme temperature and environmental conditions it must withstand. It has been found that use of the above-described primer improves adhesion at the interface between a pre-cured silicone elastomer material and an adjacent cast-in-place cured silicone elastomer material.

[0082] The primers described above can be used, for example, on piping including riser pipes, wellheads, Christmas trees, spool pieces, manifolds, risers, such as pipelines, jumpers, pipeline end terminations (PLETs), pipeline end manifolds (PLEMs), coupling covers, dog houses (i.e., rooms generally close to the floor of an oil rig with steel sides and an access door usually close to the drill control section), etc. They are generally flush with the rig floor, but can be cantilevered out from the main substructure supporting the rig and / or pipe field joints using a cast in place process by applying the primers to the surface of the pre-cured silicone elastomer material before introducing and curing further sections of silicone elastomer material (LSR) to ensure adhesion between multiple joints of the subsea insulation.

[0083] The following examples illustrating compositions and composition components, elastomers, and methods are intended to illustrate but not limit the invention. EXAMPLES

[0084] In the following examples, the ingredients used in the following examples and tables are listed below. DOWSIL™ 3-6060 Prime Coat Primer - a commercial primer for silicones manufactured by Dow Silicones, Michigan, USA; Silicone polyethers - are dimethyl(propyl(poly(EO))hydroxy)siloxy terminated dimethylsiloxane polymers, the structure of which is H-(O(CH2)2) d -O-(CH2)3-Si(CH3)2-O[Si(CH3)2-O] e -Si(CH3)2-(CH2)3-O-((CH2)2-O) d H, Its viscosity is 320 mPa·s at 25°C; Treated fumed silica is fumed silica that has been treated with hexamethyldisilazane (HMDZ); The vinyl polymer is a dimethylvinyl-terminated polydimethylsiloxane having a viscosity of 2000 mPa·s at 25°C; The Si-H polymer is a trimethyl-terminated dimethylmethylhydrogensiloxane with a viscosity of 5 mPa·s at 25°C and 0.76 wt% Si-H.

[0085] The compositions shown in Table 1 are not in accordance with the disclosure herein and are all comparative primer compositions, except for Comparative Example 1, which is a comparative reference example that does not use any type of primer. [Table 1]

[0086] The compositions of three examples of the present disclosure are shown in Table 2 below. [Table 2]

[0087] To test the comparative primers, they were used in combination with a commercially available subsea insulation material, DOWSil™ XTI-1003 RTV silicone rubber insulation, which is a room temperature vulcanizing, two-part, hydrosilylation curing composition designed specifically, but not exclusively, for subsea insulation applications.

[0088] 100 parts of DOWSiL™ XTI-1003 base were mixed homogeneously with 10 parts of DOWSiL™ XTI-1003 hardener and degassed in a vacuum desiccator. The resulting mixture was then poured into an open-top mold (300 x 300 mm) using a cast-in-place process in a layer of 5 mm thickness. The material was left to cure for 24 h at room temperature in the laboratory. After 24 h, an experimental primer was applied by brush onto the cured surface. Visual control was performed to ensure good surface coverage with primer. After drying the used experimental primer for 10 minutes, the first molded part coated with primer was overmolded with the same 5 mm thickness of freshly mixed DOWSiL™ XTI-1003 RTV silicone rubber insulation. The overmolded combination was then allowed to rest for an additional 24 h to allow a second molded portion of DOWSil™ XTI-1003 RTV silicone rubber insulation to cure at room temperature under the same laboratory conditions.

[0089] The 180° peel test method was used to determine the peel force between two layers of overmolded samples that were bonded together with the aid of the primer used in each example. After the second molding material was fully cured, 30 mm wide strips were cut for testing. Testing was performed on a Hegewald&Peschke Universalprufmachine H10TMC 900 Watt machine using the following parameters; Test speed: 100mm / min. Load cell 100kN, Test length: minimum 50mm.

[0090] The test results for the comparative primers tested are shown in Table 3 below, and the test results for the examples of the present disclosure are shown in Table 4 below. [Table 3] [Table 4]

[0091] From the comparison of the Comparative Examples and Examples above, several conclusions can be drawn. It can be seen that the peel force results of the Examples are significantly better than when used in combination with any of the Comparative Primers in Table 1. More specifically, a comparison of Comparative Example 3 with Example 1 shows that polyether is required in the adhesive composition reinforced by the primer, and without the polyether, the adhesion results were poor (Comparative Example 3). Similarly, a comparison of Comparative Example 5 with Example 1 also shows that silica is required for the primer to produce good adhesion. Furthermore, Comparative Example 4 shows from the peel test that adhesion is poor in the absence of both polyether and silica. Although the introduction of the Si-H polymer improves adhesion, it was surprisingly found from a comparison of Examples 1 and 2 that better peel test performance results were obtained when the Si-H polymer was not present in the primer composition (although the results when it was present were still much better than all the Comparative Examples in Table 1). Example 3 shows that increasing the amount of silicone polyether and silica did not improve the results of the Examples. Finally, Comparative Examples 7 and 8 show that the combination of carrier and polyether did not function as a primer as evidenced by poor peel test results, and the use of silicone polyether alone in Comparative Example 8 did not function at all.

Claims

1. 1. A primer composition comprising: A) a silicone polyether in an amount of 0.05 wt % to 4 wt % of the total composition; B) a reinforcing filler in an amount of 2.0 to 20 wt % of the total composition; C) one or more polydiorganosiloxane polymers having a viscosity of 1000 to 500,000 mPa·s at 25° C. and containing at least one alkenyl or alkynyl group per molecule, in an amount of 15 to 45 wt % of the total composition; and D) a carrier in the range of 50 wt % to 80 wt % of the total composition; Including, Component (A) is a compound represented by the formula H-(O(CH ２ ) ２ ) ｄ -O-(CH ２ ) ３ -Si(CH ３ ) ２ -O[Si(CH ３ ) ２ -O] ｅ -Si(CH ３ ) ２ - (CH ２ ) ３ -O-((CH ２ ) ２ -O) ｄ -H, where d and e are integers. is an ABA type silicone polyether of the formula: Component (B) is fumed silica and / or precipitated silica, Component (C) is a dimethylvinyl-terminated polydimethylsiloxane; A primer composition in which component (D) is a short chain siloxane containing 3 to 20 silicon atoms.

2. 10. A method for preparing the primer composition of claim 1, comprising homogeneously dissolving or mixing components (A), (B), and (C) in carrier (D).

3. 3. The method of claim 2, wherein the primer compositions are mixed together and then diluted with additional carrier (D).

4. 11. A method for improving adhesion of a silicone elastomer to a pre-cured silicone elastomer substrate comprising applying a primer composition according to claim 1 to a silicone elastomer substrate, optionally air drying or baking said primer composition to form a uniform primer film covering said substrate, applying a hydrosilylation-curable silicone rubber composition to said primer-coated substrate to obtain a composite, and curing said composite to obtain a silicone elastomer adhesively bonded to the silicone elastomer substrate.

5. 5. The method of improving adhesion of a silicone elastomer to a pre-cured silicone elastomer substrate according to claim 4, wherein the substrate is prepared from a peroxide cured silicone elastomer composition and / or a hydrosilylation curable cured silicone elastomer composition.

6. 6. The method of claim 4 or 5, wherein the hydrosilylation-curable silicone rubber composition is applied onto the primed substrate by injection molding, cast-in-place process, encapsulation molding, press molding, dispenser molding, extrusion molding, transfer molding, press vulcanization, centrifugal casting, calendaring, bead coating, 3D printing, or blow molding.

7. 7. The method of claim 4, 5, or 6, wherein the hydrosilylation-curable silicone rubber composition is applied onto the primed substrate using a continuous molding process for applying subsea insulation.

8. 13. A silicone elastomer composite which is a plurality of silicone elastomer articles bonded together or overmolded with the primer of claim 1.

9. 10. The silicone elastomer composite of claim 8, wherein the composite is used in subsea insulation, electrical insulation under high voltage, lenses, and / or automotive applications.

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