Silicone rubber composition

Abstract

The present disclosure relates to a silicone-based composition comprising one or more non-fluorinated polydiorganosiloxane polymers and silica filler, the silica filler being at least partially treated with a fluorinated hydrophobic treatment agent; a method for preparing the composition and its use in manufacturing insulators for high voltage applications, especially high voltage direct current (HVDC) applications, and in manufacturing accessories such as cable joints, cable terminal applications, and connectors. These treatment agents are selected from: one or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or one or more fluorinated silanediols, and / or one or more fluorinated trialkoxysilanes, and / or one or more fluorinated silazanes, or mixtures thereof.

Description

[0001] The present disclosure relates to a silicone-based composition comprising one or more non-fluorinated polydiorganosiloxane polymers and a silica filler at least partially treated with a fluorinated hydrophobic treatment agent, a method of preparing the composition and its use in the manufacture of insulators for high voltage applications, especially high voltage direct current (HVDC) applications, and in the manufacture of accessories such as cable joints, cable terminal applications and connectors.

[0002] While in most cases alternating current (AC) is preferred for supplying power to end users, long distance power transmission for distances such as >1000km can be carried out using high voltage direct current (HVDC) systems as it involves lower electrical losses and is therefore potentially cheaper. Long distance HVDC transmission is typically carried out in three ways: overhead, for example via iron towers; through underground systems; and, where necessary, under the sea via "submersible" systems, etc. It is perhaps fair to say that underground systems may be more aesthetically pleasing to the public than iron towers, which, while practical, may be considered unsightly. However, underground HVDC transmission is the most challenging for suppliers because, compared to overhead and submersible systems, it typically involves the use of multiple sections of cable connected together by cable joints every 1km to 2km. Therefore, while any kind of HVDC transmission requires cable joints, this requirement is particularly prominent in the case of underground systems.

[0003] However, in the case of AC current transmission systems, the insulation materials used are not always transferable to DC transmission systems, since the electrical stresses are significantly different for AC and DC conditions, not least because the insulation materials are exposed to higher continuous electrical stresses under DC conditions, which can lead to dielectric breakdown of the material. Dealing with such issues has become particularly important today, considering that HVDC voltage requirements for new cables and cable accessories are constantly increasing and may now be >500kV or even >800kV.

[0004] In the transmission of direct current, power cable systems have a resistive electric field distribution characteristic, where the electric field distribution depends on the volume resistivity. In contrast, for joints to be used in high voltage alternating current applications, it is important to minimize any difference in dielectric constant between the cable insulation and the joint insulation to achieve the desired performance.

[0005] Thus, for an HVDC system, for example in a junction box of an HVDC power cable, the cable is surrounded by an inner layer of "cable insulation material", which may be made of a suitable material such as cross-linked polyethylene (XLPE), and said cable insulation material is surrounded by a layer of another insulating material, which is usually referred to as "joint insulation material" and is usually provided in the form of ethylene propylene diene monomer rubber (EPDM) or silicone rubber elastomeric material. Therefore, in high voltage direct current applications, it is important to minimize any difference in volume resistivity between the cable insulation material and the joint insulation material in order to ensure that the electric field is evenly distributed at the contact surface between them in order to avoid, for example, dielectric breakdown. Therefore, it is desirable that the joint insulation material and the cable insulation material are designed to have volume resistivity values ​​that are as close to each other as possible.

[0006] The current approach of using a combination of cross-linked polyethylene (XLPE) as cable insulation and silicone rubber-based elastomeric materials as joint insulation has stability issues due to differences in their electrical properties. Typically, unmodified silicone rubber elastomeric materials are too insulating compared to XLPE at the same electric field strength. Silicone rubber-based materials are excellent electrical insulators after curing into the final product, typically with a volume resistivity less than or equal to (≥) 10 15 ohm-cm, but this is much larger than the typical volume resistivity of XLPE.

[0007] Historically, the industry solution has been to introduce conductive fillers (e.g., metal powders, metal flakes, carbon black, or carbon nanotubes) or semiconductive fillers into silicone rubber compositions to make silicone rubber elastomeric materials made therefrom sufficiently conductive to distribute local DC loads through slightly conductive silicone elastomeric products made from conductive LSR compositions, thereby providing 10 10 ohm-cm to 10 15 ohm-cm or alternatively 10 10 ohm-cm to 10 14 Bulk resistivity in the ohm-cm range.

[0008] However, while the use of these conductive fillers and / or semiconductive fillers can solve the problem of distributing local DC loads, the introduction of such fillers can create additional problems, particularly the inability to control and / or obtain uniform electrical properties within the silicone elastomer, thereby deteriorating physical properties and reducing dielectric strength.

[0009] It has recently been discovered that elastomeric materials made from compositions comprising a mixture of fluorinated polydiorganosiloxane polymers and non-fluorinated polydiorganosiloxane polymers prepared by mixing a fluorinated polydiorganosiloxane polymer matrix with a non-fluorinated polydiorganosiloxane polymer matrix, wherein the respective matrix comprises a polymer and a reinforcing filler, can provide insulating materials having a volume resistivity closer to that of cross-linked polyethylene without the need for conductive fillers or semi-conductive fillers. However, while a great improvement over the use of compositions solely of non-fluorinated polydiorganosiloxane polymers filled with conductive fillers, the use of such mixtures has potential disadvantages, namely that the fluorinated polydiorganosiloxane polymers are significantly more expensive to prepare, because the physical properties of the resulting elastomer may deteriorate with the proportion by weight % (wt%) of the fluorinated polydiorganosiloxane polymer in the polymer, and because mixtures of the fluorinated polydiorganosiloxane polymer and the non-fluorinated polydiorganosiloxane polymer may phase separate and thus may require a compatibilizer.

[0010] Therefore, there is still a need to develop silicone rubber insulation materials that can withstand the high electrical stresses imposed on cable insulation and cable joint insulation in high voltage direct current (HVDC) systems and high voltage alternating current (HVAC) systems. In the case of HVDC systems, it is desirable to provide silicone-based insulators whose electrical properties match the range of XLPE volume resistivity values, which may be advantageous for applications in high voltage direct current (HVDC) such as cables and cable joints.

[0011] It has now been determined that the need to utilize elastomers comprising a mixture of fluorinated polydiorganosiloxane polymers and non-fluorinated polydiorganosiloxane polymers, or silicone rubber compositions containing conductive fillers and / or semiconductive fillers, can be avoided by using one or more non-fluorinated polydiorganosiloxane polymers with a finely divided reinforcing silica filler that is at least partially treated with a fluorinated hydrophobic treating agent.

[0012] The present invention provides a curable silicone elastomer composition, which comprises:

[0013] (A) at least one non-fluorinated polydiorganosiloxane;

[0014] (B) at least one reinforcing silica filler at least partially hydrophobically treated with a fluorinated hydrophobic treating agent selected from:

[0015] One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or

[0016] One or more fluorinated silanediols, and / or

[0017] One or more fluorinated trialkoxysilanes, and / or

[0018] One or more fluorinated silazanes, or mixtures thereof;

[0019] and at least one of (C) or (D), wherein

[0020] (C) is at least one organohydrogenpolysiloxane (C)(i), at least one hydrosilylation catalyst (C)(ii), and optionally at least one cure inhibitor (C)(iii); and

[0021] (D) is at least one peroxide catalyst.

[0022] The present invention also provides a use of the curable silicone elastomer composition for or as a high voltage direct current insulator.

[0023] The curable silicone elastomer composition comprises:

[0024] (A) at least one non-fluorinated polydiorganosiloxane;

[0025] (B) at least one reinforcing silica filler at least partially hydrophobically treated with a fluorinated hydrophobic treating agent selected from:

[0026] One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or

[0027] One or more fluorinated silanediols, and / or

[0028] One or more fluorinated trialkoxysilanes, and / or

[0029] One or more fluorinated silazanes, or mixtures thereof;

[0030] and at least one of (C) or (D), wherein

[0031] (C) is at least one organohydrogenpolysiloxane (C)(i), at least one hydrosilylation catalyst (C)(ii), and optionally at least one cure inhibitor (C)(iii); and

[0032] (D) is at least one peroxide catalyst.

[0033] The present invention also provides a high voltage direct current insulator comprising an elastomeric product of a curable silicone elastomer composition, wherein the curable silicone elastomer composition comprises:

[0034] (A) at least one non-fluorinated polydiorganosiloxane;

[0035] (B) at least one reinforcing silica filler at least partially hydrophobically treated with a fluorinated hydrophobic treating agent selected from:

[0036] One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or

[0037] One or more fluorinated silanediols, and / or

[0038] One or more fluorinated trialkoxysilanes, and / or

[0039] One or more fluorinated silazanes, or mixtures thereof;

[0040] and at least one of (C) or (D), wherein

[0041] (C) is at least one organohydrogenpolysiloxane (C)(i), at least one hydrosilylation catalyst

[0042] (C)(ii) and optionally at least one cure inhibitor (C)(iii); and

[0043] (D) is at least one peroxide catalyst.

[0044] In another embodiment, the present invention also provides a high voltage direct current insulator comprising an elastomeric product obtained by curing or capable of being obtained by curing an organosilicon elastomer composition, the organosilicon elastomer composition comprising:

[0045] (A) at least one non-fluorinated polydiorganosiloxane;

[0046] (B) at least one reinforcing silica filler at least partially hydrophobically treated with a fluorinated hydrophobic treating agent selected from:

[0047] One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or

[0048] One or more fluorinated silanediols, and / or

[0049] One or more fluorinated trialkoxysilanes, and / or

[0050] One or more fluorinated silazanes, or mixtures thereof;

[0051] and at least one of (C) or (D), wherein

[0052] (C) is at least one organohydrogenpolysiloxane (C)(i), at least one hydrosilylation catalyst (C)(ii), and optionally at least one cure inhibitor (C)(iii); and

[0053] (D) is at least one peroxide catalyst.

[0054] The present invention also provides a method for preparing a curable silicone elastomer composition, the curable silicone elastomer composition comprising:

[0055] (A) at least one non-fluorinated polydiorganosiloxane;

[0056] (B) at least one reinforcing silica filler, the at least one reinforcing silica filler being at least partially hydrophobically treated with a fluorinated hydrophobic treating agent selected from:

[0057] One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or

[0058] One or more fluorinated silanediols, and / or

[0059] One or more fluorinated trialkoxysilanes, and / or

[0060] One or more fluorinated silazanes, or mixtures thereof;

[0061] and at least one of (C) and optionally (D), wherein

[0062] (C) is a hydrosilylation cure package comprising at least one organohydrogenpolysiloxane (C)(i), at least one hydrosilylation catalyst (C)(ii), and optionally at least one cure inhibitor (C)(iii); and

[0063] (D) is at least one peroxide catalyst; wherein:

[0064] (i) preparing a silicone matrix composition by mixing a non-fluorinated polydiorganosiloxane (A) with at least one reinforcing silica filler; and

[0065] (ii) introducing component (C), or a mixture of component (C) and component (D) and storing the resulting composition; wherein when the composition contains a hydrosilylation cure package (C), the composition is stored in two or more portions, wherein components (C)(i) and (C)(ii) are maintained in separate portions;

[0066] Characterized in that the at least one reinforcing silica filler is at least partially treated with a fluorinated treatment agent before or during step (i).

[0067] The composition as described above does not contain a fluorinated polydiorganosiloxane polymer containing silanol groups and having greater than (>) 20 repeating siloxane units.

[0068] For purposes of this application, the term "free of" is understood to mean free of fluorinated polydiorganosiloxane other than trace impurities and residual unreacted filler treating agent.

[0069] Preferably, the composition contains less than or equal to (≤) 0.1 wt. % of conductive filler or semiconductive filler or mixture thereof, based on the composition, and in one embodiment, the composition described above contains 0 (zero) wt. % of conductive filler or semiconductive filler.

[0070] When (C) the hydrosilylation curing package is present in the composition, the non-fluorinated polydiorganosiloxane (A) must contain at least one, alternatively at least two unsaturated groups such as alkenyl groups or alkynyl groups per molecule. However, when component (D) is the sole catalytic means of the curing process, it is preferred, but not required, that at least one alkenyl group or alkynyl group per molecule, alternatively at least two alkenyl groups or alkynyl groups per molecule are present in component (A).

[0071] For the purposes of this application, "substituted" means that one or more hydrogen atoms in a hydrocarbon group are replaced by another substituent. Examples of such substituents include, but are not limited to, halogen atoms such as chlorine, bromine, and iodine; groups containing halogen atoms (except fluorine), such as chloromethyl; oxygen atoms; groups containing oxygen atoms, such as (meth)acrylic acid and carboxyl; nitrogen atoms; groups containing nitrogen atoms, such as amino functional groups, amido functional groups, and cyano functional groups; sulfur atoms; and groups containing sulfur atoms, such as mercapto groups.

[0072] It has been discovered herein that silicone rubber compositions containing a non-fluorinated silicone polymer and a reinforcing silica filler, wherein at least a portion of the silica is treated with a fluorinated hydrophobic treatment selected from the group consisting of:

[0073] One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or

[0074] One or more fluorinated silanediols, and / or

[0075] One or more fluorinated trialkoxysilanes, and / or

[0076] one or more fluorinated silazanes,

[0077] or mixtures thereof. The modified silica treatment using the fluorinated treatment agent is used to reduce the volume resistivity of the silicone rubber to at most 60% of the volume resistivity of a comparable silicone rubber prepared without the modified silica treatment, which is a desired target range for typical volume resistivities of XLPE materials used as cable insulation materials. It has been surprisingly found that the use of silica at least partially treated with the fluorinated treatment agent can potentially be used in combination with different silicone rubbers such as liquid silicone rubber (LSR) and high consistency rubber (HCR) to target the electrical properties of these materials to a desired range by varying the content of silica treated with the fluorinated treatment agent within the range of treated silica required in the composition.

[0078] Surprisingly, it has been found that if the amount of silica treated with the fluorinated treatment agent is varied within the amount of silica treated in the current composition, then no fluorinated polydiorganosiloxane polymer conductive filler or semiconductive filler is required in the silicone rubber composition herein to obtain a silicone elastomer having a desired volume resistivity. It will also be demonstrated that the silicone rubber formulations that can be utilized may include liquid silicone rubber compositions or high consistency silicone rubber based materials utilizing polydiorganosiloxane polymer gums. By using silica treated with the fluorinated treatment agent as the only fluorinated portion of the composition, it has been found that we are able to effectively obtain a wide range of volume resistivities while only varying the loading of silica treated with the fluorinated treatment agent as shown in the examples, which is more economical than previous solutions and has the advantage of avoiding compatibility and other type of problems previously encountered with previous solutions to this problem.

[0079] The polydiorganosiloxane polymer (A) has a plurality of units of formula (I):

[0080] R a SiO (4-a) / 2 (I)

[0081] Wherein each R is independently selected from aliphatic hydrocarbon groups, aromatic hydrocarbon groups or organic groups (i.e., any organic substituent having one free valence at a carbon atom, regardless of the type of functional group). Saturated aliphatic hydrocarbon groups 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 hydrocarbon groups are exemplified by, but not limited to, alkenyl groups (such as vinyl, allyl, butenyl, pentenyl, cyclohexenyl and hexenyl); and alkynyl groups. Aromatic hydrocarbon groups are exemplified by, but not limited to, phenyl, tolyl, xylyl, benzyl, styryl and 2-phenylethyl. The organic group is exemplified by, but not limited to, a halogenated alkyl group (excluding fluorine-containing groups), such as chloromethyl and 3-chloropropyl; a nitrogen-containing group (such as an amino group, an acylamino group, an imino group, an imino group); an oxygen-containing group (such as a polyoxyalkylene group, a carbonyl group, an alkoxy group, and a hydroxyl group). Additional organic groups may include sulfur-containing groups, phosphorus-containing groups, and boron-containing groups. The subscript "a" is 0, 1, 2, or 3.

[0082] When R is a methyl group, the siloxy units can be described by the shorthand (abbreviated) nomenclature, i.e., "M," "D," "T," and "Q" (see Walter Noll, Chemistry and Technology of Silicones, 1962, Chapter I, pp. 1-9 for further teaching on silicone nomenclature). The M unit corresponds to a siloxy unit in which a=3, i.e., R 3 SiO 1 / 2 ; The D unit corresponds to a siloxy unit in which a=2, i.e. R 2 SiO 2 / 2 ; T unit corresponds to a siloxy unit in which a=1, i.e. R 1 SiO 3 / 2 ; Q unit corresponds to a siloxy unit where a=0, i.e. SiO 4 / 2 .

[0083] Examples of typical groups on the non-fluorinated polydiorganosiloxane polymer (A) include primarily alkenyl groups, alkyl groups and / or aryl groups. These groups may be in side chain positions (on D or T siloxy units) or may be at the end (on M siloxy units). As previously mentioned, when component (C) participates in the curing process, alkenyl groups and / or alkynyl groups are essential, but if the only catalyst used in the curing process is component (D), alkenyl groups and / or alkynyl groups are optional. Therefore, when present, suitable alkenyl groups in component (A) typically contain 2 to 10 carbon atoms, with preferred examples being vinyl, isopropenyl, allyl and 5-hexenyl.

[0084] The silicon-bonded organic groups other than alkenyl groups attached to component (A) are generally selected from: monovalent saturated hydrocarbon groups generally containing 1 to 10 carbon atoms, and monovalent aromatic hydrocarbon groups generally containing 6 to 12 carbon atoms, which are unsubstituted or substituted with groups that do not interfere with the curing of the composition of the present invention (such as halogen atoms). Preferred species of silicon-bonded organic groups are, for example, alkyl groups such as methyl, ethyl and propyl; and aromatic groups such as phenyl.

[0085] The non-fluorinated polydiorganosiloxane polymers may be selected from polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes or copolymers thereof containing, for example, alkenyl and / or alkynyl groups (wherein the reference to alkyl means an alkyl group having two or more carbons), and may have any suitable end groups, for example, they may be trialkyl terminated, alkenyldialkyl terminated, alkynyldialkyl terminated, or may be terminated with any other suitable combination of end groups, provided that each polymer contains at least two unsaturated groups selected from alkenyl and alkynyl groups per molecule. Preferably, the end groups of such polymers have less than (<) 10% by weight of silanol end groups, alternatively no silanol end groups. Thus, for example, the non-fluorinated polydiorganosiloxane polymer may be a dimethylvinyl terminated polydimethylsiloxane, a dimethylvinylsiloxy terminated dimethylmethylphenylsiloxane, a trialkyl terminated dimethylmethylvinylpolysiloxane or a dialkylvinyl terminated dimethylmethylvinylpolysiloxane copolymer.

[0086] The molecular structure of component (A) is generally linear, however, some branching may be present due to the presence of T units within the molecule (as described above). In order to achieve useful levels of physical properties in the elastomer prepared by curing the composition as described above, the molecular weight of component (A) should be sufficient to achieve a viscosity of at least 1000 mPa.s at 25°C, using the cup / spindle method of ASTM D 1084 Method B for the viscosity range obtained from The most suitable mandrel is in the RV or LV range. The upper limit of the molecular weight of component (A) is not particularly limited and is generally limited only by the processability of the LSR composition of the present invention.

[0087] However, (A) may be a gum. The polydiorganosiloxane gum has a viscosity of at least 1,000,000 mPa.s at 25°C. However, due to the difficulty in measuring viscosities above these values, gums are often described by means of their Williams plasticity values ​​according to ASTM D-926-08 rather than by viscosity. Thus, the polydiorganosiloxane gum (A) has a viscosity that results in a Williams plasticity of at least 30 mm / 100 measured according to ASTM D-926-08, alternatively at least 50 mm / 100 measured according to ASTM D-926-08, alternatively at least 100 mm / 100 measured according to ASTM D-926-08, alternatively from 100 mm / 100 to 300 mm / 100 measured according to ASTM D-926-08.

[0088] An example of component (A) is a polydiorganosiloxane containing alkenyl groups at both terminals, and which is represented by the general formula (II):

[0089] R'R"R"'SiO-(R"R"'SiO) m -SiOR”'R”R'(II)

[0090] In formula (II), each R' is an alkenyl group, which typically contains 2 to 10 carbon atoms, such as vinyl, allyl and 5-hexenyl.

[0091] R" contains no ethylenic unsaturation, each R" may be the same or different and is independently selected from a monovalent saturated hydrocarbon group (which typically contains 1 to 10 carbon atoms) and a monovalent aromatic hydrocarbon group (which typically contains 6 to 12 carbon atoms). R" may be unsubstituted or substituted with one or more groups that do not interfere with the curing of the composition of the present invention, such as halogen (excluding fluorine) atoms. R"' is R' or R". For the avoidance of doubt, no R"', R' or R" groups in the polymer of component (A) may contain a fluorine group or any fluorine-containing group. As described above, when the polymer is designed to be used as part of an LSR composition, the letter m represents a degree of polymerization suitable for component (A) to have a viscosity of 1,000 mPa.s to 100,000 mPa.s at 25°C, according to the cup / spindle method of ASTM D 1084 method B, using the viscosity range obtained from The most suitable mandrel is in the RV or LV range. However, if (A) is in the form of a gum, the value of m will be significantly greater since its viscosity is > 1,000,000 mPa.s at 25°C, typically significantly > 1,000,000 mPa.s at 25°C, and the Williams plasticity measurement is determined rather than viscosity.

[0092] The alkenyl groups and / or alkynyl groups of component (A) are determined according to ASTM E168 using quantitative infrared analysis.

[0093] (B) Reinforced silica filler

[0094] Component B is a reinforcing silica filler that is at least partially hydrophobically treated with the fluorinated treating agent to achieve high levels of physical properties that characterize certain types of cured silicone elastomers that can be prepared using the compositions herein, providing a reinforcing silica filler (B) such as a finely divided silica filler that is at least partially hydrophobically treated with the fluorinated treating agent.

[0095] Finely divided forms of silica can be selected, for example, from fumed silica, precipitated silica and / or colloidal silica. They are particularly preferred because they have a particle size of generally at least 50 m 2 / g relatively high surface area. Usually, a surface area of ​​100 m 2 / g to 600m 2 / g, or 100m 2 / g to 500m 2 / g (according to ISO 9277:2010 using BET method), or 200m 2 / g to 400m 2 / g (using the BET method according to ISO 9277:2010) of filler surface area.

[0096] When the Part B reinforcing silica fillers are naturally hydrophilic (e.g., untreated silica fillers), they are typically surface treated with one or more known filler treatment agents to prevent a phenomenon known as "wrinkling" or "wrinkle hardening" during processing of the curable composition.

[0097] The reinforcing silica filler may be treated prior to introduction into the composition or in situ (i.e., by blending these components together in the presence of at least a portion of the other components of the composition as described above until the surface treatment of the filler is complete and evenly dispersed to form a homogenous material). In one embodiment, the untreated filler (B) is treated in situ with the treating agent in the presence of component (A).

[0098] In the composition of the present invention, the reinforcing silica filler (B) is at least partially used

[0099] Surface treatment with a fluorinated hydrophobic treatment agent selected from the following:

[0100] One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or

[0101] One or more fluorinated silanediols, and / or

[0102] One or more fluorinated trialkoxysilanes, and / or

[0103] One or more fluorinated silazanes, or mixtures thereof.

[0104] The fluorinated treating agent may include a silanol terminated fluorinated siloxane oligomer,

[0105] The silanol terminated fluorinated siloxane oligomer comprises 2 to 20 siloxane units having the formula:

[0106] (R 2 Z) d (R 3 ) e SiO (4-d-e) / 2

[0107] in

[0108] Each R 2 can be the same or different and represent a branched or straight-chain fluoroalkyl group having 1 to 8 carbon atoms;

[0109] Each Z can be the same or different and represents a divalent alkylene group, a hydrocarbon ether or a hydrocarbon thioether containing at least two carbon atoms; wherein each R 2 The group is connected to the silicon atom via the Z group,

[0110] Each R 3 are the same or different and represent an alkyl group having 1 to 10 carbon atoms, d may be 1 to 3, and e may be 0 to 3, wherein (d+e) is 1 to 3.

[0111] Suitable saturation R 3 Examples of groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, hexyl, 2-ethylhexyl, octyl, isooctyl and decyl, alternatively having 1 to 6 carbons, alternatively methyl, ethyl, propyl, isopropyl, n-butyl or tert-butyl, alternatively methyl or ethyl, alternatively methyl;

[0112] Preferably, R 2 represents a fluoroalkyl group having at least one carbon atom, alternatively 1 to 8 carbon atoms, in the total range of 5 mol % to 100 mol % of the fluorinated siloxane units. Each fluoroalkyl group present has at least one -CF bond. R 2 The groups may be the same or different and may have a normal structure or a branched structure. Preferably at least some, most preferably greater than 50 mol % of the fluoroalkyl groups are perfluoroalkyl groups. Examples include: CF 3 -、C 2 F 5 -、C 3 F7 -, such as CF 3 CF 2 CF 2 -or (CF 3 ) 2 CF-、C 4 F 9 -, such as CF 3 CF 2 CF 2 CF 2 -、(CF 3 ) 2 CFCF 2 -、(CF 3 ) 3 C- and CF 3 CF 2 (CF 3 )CF-;C 5 F 11 Such as CF 3 CF 2 CF 2 CF 2 CF 2 -、C 6 F 13 -, such as CF 3 (CF 2 ) 4 CF 2 -;C 7 F 14 -, such as CF 3 (CF 2 CF 2 ) 3 -; and C 8 F 17 .

[0113] Each perfluoroalkyl group is bonded to the silicon atom through Z, which is a divalent spacer group containing carbon atoms, hydrogen atoms and optionally oxygen atoms and / or sulfur atoms, which are present as ether bonds and thioether bonds, respectively. Sulfur atoms and oxygen atoms (if present) must be bonded only to carbon atoms.

[0114] Each Z group can have any structure containing the listed elements, but is preferably an alkylene group (ie, an acyclic, branched or unbranched saturated divalent hydrocarbon group). Examples of suitable alkylene groups include -CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH(CH 3 )CH 2 -、-(CH 2 CH2 ) 2 - and -CH(CH 3 )CH 2 CH 2 -. In one embodiment, each fluorinated group R 2 Z preferably has the formula R 2 CH 2 CH 2 –, that is, Z is a vinyl group.

[0115] As described above, d may be 1 to 3, and e may be 0 to 3, wherein (d+e) is 1 to 3, alternatively (d+e) is 2 or 3, alternatively (d+e) is 2, wherein d=1 and e=1. Preferably, when e>0, R 3 At least 90% of the groups are methyl groups, and more preferably all are methyl groups.

[0116] The fluorinated siloxane oligomer may additionally comprise non-fluorinated siloxane units having the formula in a proportion of up to about 90%, alternatively up to about 80%, of the total number of units per molecule:

[0117] (R 4 ) c SiO (4-c) / 2

[0118] Where R 4 represents an optionally substituted saturated or unsaturated silicon-bonded monovalent hydrocarbon group, wherein c=0 to 3, but preferably the average value of c is about 2. Each R 4 No fluorine (so R 4 cannot contain any previously identified fluorinated substituents).

[0119] As mentioned above, R 4 represents an optionally substituted saturated or unsaturated silicon-bonded monovalent hydrocarbon group. Preferably, each R 4 The alkyl radicals may be the same or different and may be selected from: C1 to C10 alkyl groups; alkenyl groups such as vinyl groups and allyl groups; and / or aryl groups such as phenyl, tolyl, benzyl, β-phenylethyl and styryl. When alkenyl groups are present, each alkenyl group may have 2 to 8 carbon atoms, or each alkenyl group may be a vinyl group.

[0120] Fluorinated siloxane oligomers having 2 to 20 siloxane units can be exemplified by the following formula:

[0121] HO-[(R 2 Z) d (R 3 ) e Si-O] f -H

[0122] Where R 2 , Z, d, R 3 and e are as defined above, and f is 2 to 20.

[0123] Fluorinated silanediols can be exemplified by the following formula:

[0124] (HO) 2 Si(R 2 Z)(R 3 )

[0125] Where R 2 , Z and R 3 Each is as defined above.

[0126] Fluorinated trialkoxysilanes can be exemplified by the following formula:

[0127] R 2 Z-Si(R g ) 3

[0128] Where R 2 As defined above, and each R g May be the same or different and are alkoxy groups having 1 to 6 carbons, alternatively alkoxy groups having 1 to 4 carbons, alternatively tert-butoxy, ethoxy or methoxy groups.

[0129] Fluorinated silazanes can be exemplified by the following formula:

[0130] ((R 2 Z)(R 3 ) 2 -Si) 2 -NH

[0131] Where R 2 , Z and R 3 Each is as defined above. In an alternative embodiment, each R 3 Having 1 to 6 carbons, alternatively 1 to 3 carbons, alternatively ethyl or methyl.

[0132] The fluorinated treatment agent can be, for example, selected from the group of trifluoropropyltrialkoxysilanes, such as trifluoropropyltrimethoxysilane and trifluoropropyltriethoxysilane; silanol-terminated trifluoropropylalkylsiloxanes having 2 to 20 siloxane repeating units and in which the alkyl group has 1 to 6 carbons, such as silanol-terminated trifluoropropylmethylsiloxane having 2 to 20 siloxane repeating units and silanol-terminated trifluoropropylethylsiloxane having 2 to 20 siloxane repeating units; and bis(trifluoropropyldialkyl)silazanes, wherein each alkyl group has 1 to 6 carbons, alternatively 1 to 3 carbons, alternatively a methyl or ethyl group.

[0133] The treating agents are primarily used to render the filler hydrophobic and thereby easier to handle and obtain a homogeneous mixture with the other components, although, as previously mentioned, it has been determined herein that by varying the amount of reinforcing filler treated with one or more of the above-mentioned fluorinated treating agents, the volume resistivity of the resulting elastomeric material can be varied.

[0134] The remainder of the reinforcing silica (B), if any, is treated with a non-fluorinated hydrophobic treatment agent such as, for example, an organosilane, a polydiorganosiloxane or an organosilazane, a hexaalkyldisilazane, a short-chain siloxane diol, a fatty acid or a fatty acid ester such as a stearate; all of which are non-fluorinated. Again, this is to render the remaining reinforcing silica (B) filler hydrophobic and thus easier to handle and obtain a homogeneous mixture with the other ingredients.

[0135] Specific examples include, but are not limited to, hexaorganodisiloxane, hexaorganodisilazane, non-fluorinated liquid hydroxyl-terminated polydiorganosiloxane containing an average of 2 to 20 diorganosiloxane repeating units, and the like.

[0136] In either treatment case described above, a small amount of water or ammonium hydroxide may be added along with the silica treatment agent as a processing aid. The surface treatment of the fillers makes them easily wetted by the polymer of component (A). These surface modified fillers do not agglomerate and can be incorporated uniformly into component (A), resulting in improved room temperature mechanical properties of the uncured composition.

[0137] The amount of silica reinforcing filler used in the compositions described herein is typically about 1% to 40% by weight (weight percent) of the composition, alternatively 5% to 35% by weight of the composition, alternatively 10% to 35% by weight of the composition, alternatively 15% to 35% by weight of the composition. The treating agent used is typically added in an amount of 1% to 10% by weight of the total composition, alternatively 1% to 10% by weight of the total composition (i.e., after mixing Part A and Part B when stored as a multi-part composition).

[0138] In one embodiment, at least 20% by weight of the total silica surface is treated with a fluorinated hydrophobic treatment agent. The fluorinated hydrophobic treatment agent may be uniformly distributed over the entire silica surface when the mixture of the fluorinated treatment agent and the non-fluorinated treatment agent is applied to the silica simultaneously, or may be concentrated on certain portions of the silica surface when the silica is treated individually or sequentially or in situ using a suitable treatment process as desired; alternatively, at least 30% by weight of the total weight of the reinforced silica (B); alternatively, at least 40% by weight of the total weight of the reinforced silica (B); alternatively, at least 50% by weight of the total weight of the reinforced silica (B); alternatively, at least 60% by weight of the total weight of the reinforced silica (B); alternatively, at least 80% by weight of the total weight of the reinforced silica (B); or alternatively, 100% by weight of the total weight of the reinforced silica (B). In the above, the maximum value in each case is the % by weight of the total weight of the reinforcing silica (B).

[0139] The composition is cured using a curing package of at least one of component (C), component (D), or a mixture of components (C) and (D), wherein

[0140] (C) is at least one organohydrogenpolysiloxane (C)(i), at least one hydrosilylation catalyst (C)(ii), and optionally at least one cure inhibitor (C)(iii); and

[0141] (D) is at least one peroxide catalyst.

[0142] (C) (i) Organohydrogenpolysiloxane

[0143] When present, component (C)(i) is an organohydrogenpolysiloxane that acts as a crosslinking agent for curing component (A) by causing silicon-bonded hydrogen atoms in component (C)(i) to undergo addition reaction with alkenyl groups in component (A) under the catalytic activity of component (C)(ii). Component (C)(i) typically contains 3 or more silicon-bonded hydrogen atoms so that the hydrogen atoms of this component can react sufficiently with the alkenyl groups of component (A) to form a network structure therewith and thereby cure the composition. When component (A) has >2 alkenyl or alkynyl groups, alternatively alkenyl groups, per molecule, some or all of component (C)(i) may alternatively have 2 silicon-bonded hydrogen atoms per molecule.

[0144] The molecular configuration of component (C) (i) is not particularly limited, and it may be linear, branched linear or cyclic. Although the viscosity of the component is not particularly limited, the viscosity may generally be 0.001 Pa.s to 50 Pa.s at 25° C., using the cup / spindle method of ASTM D 1084 Method B for the viscosity range obtained from The most suitable mandrel is in the RV or LV range to obtain good miscibility with component (A).

[0145] Component (C)(i) is typically added in an amount such that the molar ratio of the total number of silicon-bonded hydrogen atoms in component (C)(i) to the total number of all alkenyl groups and alkynyl groups, alternatively alkenyl groups, in component (A) is from 0.5:1 to 20:1. When the ratio is less than 0.5:1, a well-cured composition is not obtained. When the ratio exceeds 20:1, there is a tendency for the cured composition to increase in hardness when heated. The silicon-bonded hydrogen (Si-H) content of the organohydrogenpolysiloxane (C)(i) is determined using quantitative infrared analysis according to ASTM E168.

[0146] Examples of component (C)(i) include, but are not limited to:

[0147] (i) trimethylsiloxy-terminated methylhydrogenpolysiloxane,

[0148] (ii) trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane,

[0149] (iii) a dimethylsiloxane-methylhydrogensiloxane copolymer terminated with dimethylhydrogensiloxy groups,

[0150] (iv) a dimethylsiloxane-methylhydrogensiloxane cyclic copolymer,

[0151] (v) By (CH 3 ) 2 HSiO 1 / 2 Unit and SiO 4 / 2 The copolymers consist of units,

[0152] (vi) By (CH 3 ) 3 SiO 1 / 2 Unit, (CH 3 ) 2 HSiO 1 / 2 Unit and SiO 4 / 2 A copolymer composed of units, and

[0153] (vii) as described above containing (CH 3 ) 2 HSiO 1 / 2 Unit and (R 2 Z) d (R 3 ) e SiO (4-d-e) / 2 of copolymers.

[0154] Typically component (C)(i) is present in the composition in an amount of from 0.5% to 10% by weight of the total composition, the amount being determined depending on the desired molar ratio of the total number of silicon-bonded hydrogen atoms in component (C)(i) to the total number of all alkenyl groups and alkynyl groups as previously described.

[0155] (C) (ii) Hydrosilylation Catalyst

[0156] When a hydrosilylation catalyst (C)(ii) is present, it is one of the platinum group metals (platinum, ruthenium, osmium, rhodium, iridium and palladium), or a compound of one or more of such metals. Platinum and platinum compounds are preferred because these catalysts have a high level of activity in the hydrosilylation reaction.

[0157] Examples of preferred hydrosilylation catalysts (C)(ii) include, but are not limited to, platinum black, platinum on various solid supports, chloroplatinic acid, alcohol solutions of chloroplatinic acid, and complexes of chloroplatinic acid with ethylenically unsaturated compounds (such as olefins) and organosiloxanes containing silicon-bonded ethylenically unsaturated hydrocarbon groups. Catalyst (C)(ii) may be platinum metal, platinum metal deposited on a support (such as silica gel or charcoal powder), or a compound or complex of a platinum group metal.

[0158] Examples of suitable platinum-based catalysts include

[0159] (i) complexes of chloroplatinic acid and organosiloxanes containing ethylenically unsaturated hydrocarbon groups as described in US Pat. No. 3,419,593;

[0160] (ii) chloroplatinic acid in the form of hexahydrate or in anhydrous form;

[0161] (iii) a platinum-containing catalyst obtained by a process comprising the steps of: reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane;

[0162] (iv) Olefin-platinum-silyl complexes such as (COD)Pt(SiMeCl) as described in U.S. Pat. No. 6,605,734 2 ) 2 , wherein "COD" is 1,5-cyclooctadiene; and / or

[0163] (v) Karstedt's catalysts, platinum divinyltetramethyldisiloxane complexes typically containing about 1 wt% platinum in a solvent such as toluene can be used. These are described in US Pat. Nos. 3,715,334 and 3,814,730.

[0164] When the hydrosilylation catalyst (C) (ii) is present, it is present in the total composition in a catalytic amount, i.e., an amount or quantity sufficient to promote its reaction or curing under the desired conditions. Different levels of hydrosilylation catalyst (C) (ii) can be used to tailor the reaction rate and curing kinetics. Based on the combined weight of composition components (a) and (b), the catalytic amount of the hydrosilylation catalyst (C) (ii) is typically between 0.01 ppm and 10,000 parts by weight of the platinum group metal per million parts (ppm); alternatively between 0.01 ppm and 5000 ppm; alternatively between 0.01 ppm and 3,000 ppm and alternatively between 0.01 ppm and 1,000 ppm. In specific embodiments, the catalytic amount of the catalyst may be in the range of 0.01 ppm to 1,000 ppm, or 0.01 ppm to 750 ppm, or 0.01 ppm to 500 ppm, and or 0.01 ppm to 100 ppm of the metal, based on the weight of the composition. The ranges may relate to the metal content in the catalyst alone or to the catalyst as a whole (including its ligands) as detailed, but typically these ranges relate to the metal content in the catalyst alone. The catalyst may be added as a single substance or as a mixture of two or more different substances. Typically, the amount of catalyst present will be in the range of 0.001 wt % to 3.0 wt % of the composition, depending on the form / concentration in which the catalyst package is provided.

[0165] Inhibitor (C)(iii)

[0166] The composition of components (A), (C)(i) and (C)(ii) described above may begin to cure at ambient temperature. When (C)(i) and (C)(ii) are present, a suitable hydrosilylation reaction inhibitor (C)(iii) may also be used to delay or inhibit the activity of the catalyst in order to obtain a longer working time or pot life of the hydrosilylation curing composition. Hydrosilylation reaction inhibitors are well known in the art and include hydrazines, triazoles, phosphines, thiols, organic nitrogen compounds, alkynols, methyl silylated alkynols, maleates, fumarates, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, olefinic siloxanes, unsaturated hydrocarbon monoesters and diesters, conjugated ene-ynes, hydroperoxides, nitriles and diaziridines.

[0167] One class of known hydrosilylation reaction inhibitors includes the acetylenic compounds disclosed in US 3,445,420. Alkynols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors that will inhibit the activity of platinum-containing catalysts at 25° C. Compositions containing these inhibitors typically require heating at temperatures of 70° C. or above in order to cure at an achievable rate.

[0168] Examples of alkynols 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, 1-phenyl-2-propyn-1-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclopentanol, 3-methyl-1-pentene-4-yn-3-ol, and mixtures thereof. Alkynol derivatives may include those compounds having at least one silicon atom.

[0169] When present, inhibitor concentrations as low as 1 mole inhibitor per mole metal of catalyst (C)(ii) will in some cases impart satisfactory storage stability and cure rates. In other cases, inhibitor concentrations of up to 500 moles inhibitor per mole metal of catalyst (C)(ii) are required. The optimum concentration of a given inhibitor in a given composition is readily determined by routine experimentation. When present in the composition, the inhibitor is typically present in an amount of 0.0125% to 10% by weight of the composition, depending on the concentration and form in which the selected inhibitor is provided / commercially available.

[0170] When component C is relied upon to cure the composition, typically the composition will be stored in two parts (commonly referred to as part A and part B) with the intention of separating components (C)(i) and (C)(ii) prior to curing. Typically, when component (C)(iii) is present, it is present in the same part as the crosslinker (C)(i). Such 2-part compositions are designed to be easily mixed immediately prior to use and typically the weight ratio of part A:part B is from 15:1 to 1:1.

[0171] (D) Peroxide Catalyst

[0172] Alternatively or additionally, the compositions as described herein may be cured with a peroxide catalyst (D) or a mixture of different types of peroxide catalysts.

[0173] The peroxide catalyst may be any of the well-known commercial peroxides used for curing 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. Typically, the amount of peroxide catalyst used in the composition as described herein is 0.2% to 3% by weight, alternatively 0.2% to 2% by weight, based in each case on the weight of the composition.

[0174] Suitable organic peroxides are substituted or unsubstituted dialkyl peroxides, alkylaroyl peroxides, diaroyl peroxides, for example benzoyl peroxide and 2,4-dichlorobenzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, bis(tert-butylperoxyisopropyl)benzene, bis(tert-butylperoxy)-2,5-dimethylhexyne, 2,4-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane. Mixtures of the above may also be used.

[0175] Optional additional ingredients

[0176] Additional optional ingredients may be present in the silicone rubber composition depending on its intended use. Examples of such optional ingredients include thermally conductive fillers, non-thermally conductive fillers, pot life extenders, flame retardants, lubricants, non-reinforcing fillers, compression set additives, pigments, colorants, tackifiers, chain extenders, silicone polyethers, mold release agents, diluents, solvents, UV light stabilizers, fungicides, wetting agents, heat stabilizers, compression set additives, plasticizers, and mixtures thereof.

[0177] Pot life extending agents, such as triazoles, may be used, but are not considered necessary within the scope of the present invention.The liquid curable silicone rubber composition may therefore be free of pot life extending agents.

[0178] Examples of flame retardants include aluminum trihydrate, magnesium hydroxide, chlorinated paraffin, hexabromocyclododecane, triphenyl phosphate, dimethyl methylphosphonate, tris(2,3-dibromopropyl)phosphate (tribromide), and mixtures or derivatives thereof.

[0179] Examples of lubricants include graphite, talc, boron nitride, molybdenum disulfide, and mixtures or derivatives thereof.

[0180] Additional additives include silicone fluids such as trimethyl terminated or dimethylhydroxy terminated siloxanes, typically having a viscosity of <150 mPa.s at 25°C, using the cup / spindle method of ASTM D 1084 Method B for the viscosity range obtained from The most suitable mandrel is in the RV or LV range. When such silicone fluid is present, it may be present in the liquid curable silicone rubber composition in an amount ranging from 0.1 to 5 weight percent (% wt.), based on the total weight of the composition.

[0181] Examples of pigments include titanium dioxide, chromium oxide, bismuth vanadium oxide, iron oxide, and mixtures thereof.

[0182] Examples of adhesion promoters include alkoxysilanes containing methacrylic acid groups or acrylic acid groups, such as methacryloxymethyl-trimethoxysilane, 3-methacryloxypropyl-trimethoxysilane, 3-methacryloxypropyl-methyldimethoxysilane, 3-methacryloxypropyl-dimethylmethoxysilane, 3-methacryloxypropyl-triethoxysilane, 3-methacryloxypropyl-methyldiethoxysilane, 3-methacryloxyisobutyl-trimethoxysilane, or similar methacryloxy-substituted alkoxysilanes; 3-acryloxypropyl-trimethoxysilane, 3-acryloxypropyl-methyldimethoxysilane, 3-acryloxypropyl-dimethyl-methoxysilane, 3-acryloxypropyl-triethoxysilane, or similar acryloxy-substituted alkyl-containing alkoxysilanes; zirconium chelate compounds such as Zirconium (IV) tetraacetylacetonate, zirconium (IV) hexafluoroacetylacetonate, zirconium (IV) trifluoroacetylacetonate, zirconium (IV) tetrakis (ethyl trifluoroacetylacetonate), zirconium tetrakis (2,2,6,6-tetramethyl-heptanethiosulfate), dibutoxybis (ethylacetone) zirconium (IV), diisopropoxybis (2,2,6,6-tetramethyl-heptanethiosulfate) zirconium or similar zirconium complexes with β-diketone (including alkyl-substituted and fluorine-substituted forms thereof); and epoxy-containing alkoxysilanes such as 3-glycidyloxypropyl trimethoxysilane, 3-glycidyloxypropyl triethoxysilane, 3-glycidyloxypropyl methyl dimethoxysilane, 4-glycidyloxybutyl trimethoxysilane, 5,6-epoxyhexyl triethoxysilane, 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane or 2-(3,4-epoxycyclohexyl) ethyl triethoxysilane.

[0183] Examples of chain extenders include disiloxanes or low molecular weight polyorganosiloxanes containing two silicon-bonded hydrogen atoms at the terminal positions. Chain extenders typically react with the alkenyl groups of component (A) to link two or more molecules of component (A) together and increase their effective molecular weight and the distance between potential crosslinking sites.

[0184] Disiloxane is generally represented by the general formula (HR a 2 Si) 2 When the chain extender is a polyorganosiloxane, it has the general formula HR a 2 SiO 1 / 2 The terminal unit and formula R b 2 Non-terminal unit of SiO. In these formulas, R a and R bEach represents an unsubstituted or substituted monovalent hydrocarbon group free of ethylenic unsaturation and fluorine content, including but not limited to alkyl groups containing 1 to 10 carbon atoms, substituted alkyl groups containing 1 to 10 carbon atoms (such as chloromethyl), cycloalkyl groups containing 3 to 10 carbon atoms, aryl groups 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).

[0185] Other examples of chain extenders include tetramethyldihydrogendisiloxane or dimethyl hydrogen terminated polydimethylsiloxane.

[0186] The chain extender may be added in an amount of 1 to 10 parts by weight, typically 1 to 10 parts per 100 parts of component (A), based on the weight of component (A).

[0187] Examples of heat stabilizers include metal compounds such as red iron oxide, yellow iron oxide, iron hydroxide, cerium oxide, cerium hydroxide, lanthanum oxide, copper phthalocyanine, aluminum hydroxide, fumed titanium dioxide, iron naphthenate, cerium naphthenate, cerium dimethylpolysiliconate, and acetylacetonate of a metal selected from copper, zinc, aluminum, iron, cerium, zirconium, titanium, etc. The amount of the heat stabilizer present in the composition may range from 0.01 wt % to 1.0 wt % of the total composition.

[0188] Therefore, the present invention provides a silicone rubber composition comprising:

[0189] Component (A) in an amount of 40 to 95 wt % of the composition.

[0190] Component (B) in an amount of 5 to 60 wt% of the composition. For any composition, the total wt% of the composition is 100 wt%.

[0191] When the composition is cured by hydrosilylation, the composition may include 0.5 wt % to 10 wt % of component (C) (i), 0.01 wt % to 1 wt % of component (C) (ii) and 0 wt % to 1 wt % of component (C) (iii). For any composition, the total weight % of the composition is 100 wt %. In such cases, the composition will be stored in two parts, part A and part B, before use. Typically, part A will contain a portion of component (A), a portion of component (B) and component (C) (ii), and part B will contain the remainder of components (A) and (B) and component (C) (i). When there is an optional inhibitor (C) (iii), it may be present in either or both of part (A) or part (B) of the composition. The optional ingredients present in the composition may be introduced into either or both of part A or part B of the composition as needed, provided that they do not cause any negative effects on the respective parts. The two-part composition may be designed to be mixed together in any suitable ratio, such as 15:1 to 1:1. In case the ratio is 15:1 or greater, part B may comprise only the cross-linker (C) (i) and the optional inhibitor (C) (iii).

[0192] The curable silicone elastomer composition can be prepared by the following method:

[0193] (i) preparing a silicone matrix composition by mixing a non-fluorinated polydiorganosiloxane (A) with at least one reinforcing silica filler; and

[0194] (ii) introducing component (C), component (D), or a mixture of component (C) and component (D) and storing the resulting composition; wherein when the composition contains a hydrosilylation cure package (C), the composition is stored in two or more parts, wherein components (C)(i) and (C)(ii) are maintained in separate parts;

[0195] Characterized in that, as described above, the at least one reinforcing silica filler is at least partially treated with a fluorinated treatment agent before or during step (i).

[0196] In one embodiment, the reinforcing silica filler is treated with a treating agent prior to step (i) of the method. In this embodiment, all of the reinforcing silica filler is treated with a fluorinated treating agent prior to step (i), or alternatively, a portion of the reinforcing silica filler is treated with a fluorinated treating agent prior to step (i), and the remainder is treated with a non-fluorinated treating agent prior to step (i). In this embodiment, once the reinforcing silica filler has been treated prior to step (i), the treated reinforcing silica filler is mixed with a non-fluorinated polydiorganosiloxane (A) to form the matrix resulting from step (i) of the method. In another alternative, the silica may be treated simultaneously or sequentially by a mixture of a fluorinated treating agent and a non-fluorinated treating agent.

[0197] In an alternative embodiment, the non-fluorinated polydiorganosiloxane (A) may be divided into a plurality of predetermined aliquots, wherein each aliquot is mixed in situ with a predetermined amount of reinforcing silica filler and a fluorinated treatment agent or a non-fluorinated treatment agent, such that a plurality of partial matrices are prepared using the reinforcing silica filler treated in situ, and then the plurality of partial matrices are subsequently mixed together to obtain the final product of step (i). In this embodiment, at least one aliquot of the non-fluorinated polydiorganosiloxane (A) is mixed with a fluorinated treatment agent.

[0198] In an alternative embodiment, the non-fluorinated polydiorganosiloxane (A) is mixed in situ with one or more aliquots of the reinforcing silica filler and one or more aliquots of the fluorinated treating agent, so that the reinforcing silica filler is treated in situ to obtain the final product of step (i).

[0199] In an alternative embodiment, the non-fluorinated polydiorganosiloxane (A) is mixed in situ with one or more aliquots of the reinforcing silica filler and one or more aliquots of a mixture of 0 wt % to 100 wt % fluorinated treating agent and 0 wt % to 100 wt % non-fluorinated treating agent, so that the reinforcing silica filler is treated in situ to obtain the final product of step (i), provided that on average at least 20 wt % of the silica is treated with the fluorinated treating agent.

[0200] The resulting product of step (i) can be divided into a matrix used as part A and a matrix used as part B. Alternatively, when the composition is cured by hydrosilylation, two separate matrixes can be prepared at the end of step (i). These matrixes can have the same or different compositions. For example, the matrix of composition part A can utilize a fluorinated treatment agent, a non-fluorinated treatment agent, or a mixture of the fluorinated treatment agent and a non-fluorinated treatment agent. Similarly, the matrix of composition part B can utilize a fluorinated treatment agent, a non-fluorinated treatment agent, or a mixture of a fluorinated treatment agent and a non-fluorinated treatment agent. In each case, at least the matrix of the part A composition or the matrix of the part B composition must contain a reinforcing silica filler that is at least partially treated with a fluorinated treatment agent.

[0201] Regardless of the method used to achieve the above objectives, the amount of reinforcing silica filler treated with the fluorinated treating agent present in the composition is designed to provide an elastomeric product having a volume resistivity within a predetermined range when cured so as to be compatible with the volume resistivity of adjacent cable insulation materials, such as cross-linked polyethylene.

[0202] Any mixing technique and apparatus described in the prior art may be used for this purpose. The particular apparatus to be used will be determined by the individual components and the viscosity of the final curable coating composition. Suitable mixers include, but are not limited to, paddle mixers and kneader type mixers. It may be desirable to cool the components during mixing to avoid premature solidification of the composition.

[0203] When the composition herein is designed as an LSR composition, the viscosity of the composition is in the range of 10 Pa.s to 1,000 Pa.s, alternatively 10 Pa.s to 500 Pa.s, alternatively 100 Pa.s to 500 Pa.s, in each case measured at 25°C using a cone-plate rheometer at 10 -1 s rate measurement or according to the Williams plasticity measurement for most viscous materials where (A) comprises at least one gum.

[0204] The silicone rubber composition of the present invention may alternatively be further processed by injection molding, encapsulation molding, compression molding, dispenser molding, extrusion molding, transfer molding, press vulcanization, centrifugal casting, calendaring, bead application or blow molding.

[0205] The curing of the curable silicone rubber composition can be carried out as required by the type of silicone rubber used. Typical curing temperatures can be in the range of 80°C to 200°C, alternatively 100°C to 170°C. The time of curing will depend on the selected curing temperature and method, but will generally be about 5 minutes to 1 hour. In addition, if desired, the resulting cured elastomer can be post-cured. If desired, any suitable post-curing can be performed. For example, the cured elastomer can be post-cured in an oven at a temperature of 150°C to 250°C, alternatively 170°C to 230°C, for a predetermined period of time, such as 2 hours to 10 hours, as required.

[0206] Curing may occur, for example, in a mold to form a molded silicone article.For example, the composition may be injection molded to form an article, or the composition may be overmolded by injection molding around an article or on a substrate.

[0207] Also provided herein is a high voltage insulator, alternatively a high voltage direct current insulator, comprising an elastomeric product of the curable silicone elastomer composition described herein and / or a high voltage insulator, alternatively a high voltage direct current insulator, comprising an elastomeric product obtained by curing the silicone elastomer composition as described herein. Typically, the composition contains less than or equal to (≤) 0.1% by weight of a conductive filler or a semiconductive filler or a mixture thereof, and in one embodiment, the composition contains 0 (zero)% by weight of a conductive filler.

[0208] The cured product of the above composition can be used as a high voltage insulator suitable for reducing electrical stress in high voltage direct current (HVDC) applications (i.e., power cable systems, etc.). As previously mentioned, a high voltage insulator, alternatively a high voltage direct current insulator, is provided comprising an elastomeric product of the silicone elastomer composition described herein. The high voltage insulator, alternatively a high voltage direct current insulator can be used alone, or can form a part of an article or component, such as a composite part of a component, such as in cable accessories as a cable joint or cable terminal material, a sheath, a sleeve and / or other accessories in high voltage direct current applications, in field grading components as a suitable insulating layer, and in other suitable cable accessories and connectors.

[0209] In another embodiment, a method for manufacturing an insulator or a field grading component including the insulator for high voltage insulator applications, alternatively high voltage direct current (HVDC) applications, is provided, the method comprising the following steps: i) shaping an appropriate amount of the silicone composition as described above by appropriate means (such as, for example, by extrusion or using a mold), and ii) curing the shaped composition to form a shaped insulator or a field grading component including the insulator.

[0210] The above-mentioned high voltage insulator, alternatively high voltage DC insulator, may be part of a cable accessory for high voltage DC applications, such as a cable joint, cable terminal or cable connector which may for example seal the end of a cable having thermoplastic or rubber cable insulation.

[0211] The present invention also provides a method for sealing and / or insulating connected cables or closing cable ends by using a cable joint as described above, the method comprising the following steps: (i) providing an insulated wire having a thermoplastic or elastomeric multilayer sheath suitable for DC insulation and a bare wire or connector, and (ii) encapsulating the bare wire or connector, in the manner of: placing the hole of the tubular previously molded and cured cable joint as described above on the surface of the insulating sheath of (i) while mechanically extending the joint, so that an overlap of approximately greater than 0.5 cm is achieved between the formed silicone cable joint and the sheath on the wire insulation, whereby the silicone cable joint seals the insulation of the insulated wire protected by the sheath through the mechanical pressure of the relaxed joint, thereby forming an encapsulated insulation also for the bare wire and the connector.

[0212] The composition as described herein can be used to make a cable joint intended to seal the cable end of one or more cables having a thermoplastic polyolefin or rubber cable insulation, wherein the cable joint seals the cable end of one or more cables having a thermoplastic polyolefin or rubber cable insulation.

[0213] The composition as described herein can be used as a cable joint or cable termination material in high voltage DC applications (such as high voltage DC power cable applications) in the manufacture of cable accessories. The cured silicone composition according to the present invention can be used to construct all kinds of field grading components, such as geometric field grading components, capacitive field grading components, refractive field grading components, resistive field grading components or non-linear field grading components for high voltage DC (HVDC) applications. The cured silicone composition can also be used in field grading components for high voltage DC (HVDC) applications, wherein the cured silicone composition is essentially or exclusively used as an insulator in the insulating layer, which further contributes to electrical stress reduction in addition to the field grading material. In some cases, it can also be used as a field grading material, in particular, as a field grading material in resistive field grading components, cable joints, cable termination applications, cable accessories and connectors.

[0214] For example, in the case of a high voltage DC cable joint, a cable joint for connecting a pair of high voltage DC power cables may be provided, the cable joint comprising means for receiving and connecting a pair of high voltage DC cables, a cable insulation layer adapted to surround the high voltage DC cables when in the cable joint, and a layer of silicone rubber joint insulation material surrounding the cable insulation material in the cable joint, the silicone rubber joint insulation material being as described above and adapted to have a volume resistivity within a predetermined range of the volume resistivity of the cable insulation material. Preferably, the cable insulation material is made of cross-linked polyethylene. During assembly of the cable joint, the volume resistivity of the cable insulation material is determined, for example, according to standard test method ASTM D257-14 for DC resistance or conductivity of insulating materials, and then a suitable silicone rubber joint insulation material designed to have an approximate volume resistivity according to ASTM D257-14 is prepared as described herein. Example

[0215] In the following examples and compositions, unless otherwise indicated, all viscosities are given at 25°C and are measured according to the cup / spindle method of ASTM D 1084, Method B, using the viscosity ranges obtained from Most suitable mandrels are in the RV or LV range. Williams plasticity values ​​are available according to ASTM D-926-08. Vinyl content and Si-H content of the polymer are determined by quantitative IR according to ASTM E168.

[0216] Example 1

[0217] Liquid silicone rubber compositions using non-fluorinated polydiorganosiloxane polymers were prepared as LSR Matrix 1 and LSR Matrix 2 as shown in Table 1a below. Fumed silica was treated in situ during the preparation of the corresponding LSR matrices.

[0218] Table 1a: Composition of LSR matrix 1 and LSR matrix 2 (wt%)

[0219]

[0220] LSR Matrix 1 and LSR Matrix 2 were mixed together in the ratios shown in Table 1.b, Examples 1.1 to 1.8.

[0221] Table 1b: Amounts of LSR Matrix 2 and LSR Matrix 1 in the composition

[0222]

[0223] This mixture of the two matrices depicted in Table 1b was then mixed with other ingredients to obtain a series of curable compositions containing different amounts of silica treated with fluorinated filler as shown in Table 1c.

[0224] Table 1c: Curable formulations

[0225]

[0226]

[0227] Given that the samples were immediately tested, a two-part composition was not required and the ingredients in Composition Part B of the two-part composition as described above were generally mixed directly into each of the alternative mixtures of LSR Base 1 and LSR Base 2 according to Table 1c above.

[0228] The resulting different samples were prepared as curable sheets, which were press-cured at 120° C. for 10 minutes to form 0.5 mm thick cured sheets. The volume resistivity was measured at room temperature with a polarization voltage of 1000 V and a polarization time of 60 s. It should be noted that 1.1 is considered a comparative example because it is the only example in Table 1b that does not contain silica treated with a fluorinated treatment agent.

[0229] After curing, test the cured sheets in the range of 0.5 mm to 2 mm in thickness using ASTM D257-14 "Standard Test Methods for DC Resistance or Conductance of Insulating Materials". 8009 test cell to measure volume resistivity. 51 / 2-position Model 6517B Electrometer / High Resistance Meter coupling, controlled by Model 6524 High Resistance Measurement Software: D257.

[0230] Within the Model 6524 High Resistance Measurement Software, the alternating polarity test is implemented as a "Hi-R" test to minimize the effects of background current. This is described in detail in the Keithley white paper "Improving the Repeatability of Ultra-High Resistance and Resistivity Measurements" by Adam Daire.

[0231] Hi-R alternating polarity testing is used to minimize the effects of background current. This method is designed to improve high resistance / resistivity measurements that are prone to large errors due to background current.

[0232] To isolate the excitation current from the background current, an alternating polarity excitation voltage is used. When the alternating polarity method is used, the electrometer's voltage source output alternates between the following two voltages at timed intervals (measurement time): offset voltage + AC voltage and offset voltage - AC voltage.

[0233] A current measurement (Imeas) is performed at the end of each alternation. After collecting four Imeas values, the current reading is calculated (Icalc). Icalc is the binomial weighted average of the last four current measurements (Imeas1 to Imeas4):

[0234] Icalc=(1*Imeas1-3*Imeas2+3*Imeas3-1*Imeas4) / 8

[0235] The signs used for the four terms are the polarity of the alternating portion of the voltage that produces the corresponding current. This calculation of the excitation current is not affected by the background current level, slope, or curvature, thereby effectively isolating the excitation current from the background current. The result is that the excitation current and the resistance or resistivity calculated therefrom have repeatable values. The time dependence of the excitation current is a material property. That is, different results will be obtained when different measurement times are used due to material characteristics.

[0236] A measurement time of 60 seconds was used with 3 voltage cycles of typically +1000 V then -1000 V. From the 6 resulting measured currents, the software obtained 3 Icalc values, discarded the first of these values, and then used the next 2 values ​​to calculate the volume resistivity (VR) from the following formula:

[0237] Volume resistivity = (V 最大值 –V 最小值 )×area / (2×Icalc×sample thickness)

[0238] The two resulting volume resistivity values ​​were averaged to give the final value.The results for each combination are depicted in Table 1d below.

[0239] Table 1d: Volume resistivity results

[0240]

[0241] Here, Examples 1.2 to 1.8 having different levels of silica fillers treated with a fluorination treatment agent showed lower volume resistivity than Comparative Example 1.1 not containing a silica filler treated with a fluorination treatment agent.

[0242] Additional samples 1.2, 1.3, 1.4, 1.6 and 1.8 were prepared, in which case they were post-cured at 200°C for 4 hours (4h) and further volume resistivity tested at higher polarization voltages, longer polarization times and higher temperatures, the results of which are provided in Table 1e below.

[0243] Table 1e: Volume resistivity results at higher electric fields and longer poling times.

[0244]

[0245] Here, Examples 1.4, 1.6 and 1.8 continue to show lower volume resistivity than the 1.1 comparative example over a range of polarization voltages, polarization times and temperatures.

[0246] Example 2 High-viscosity rubber example

[0247] Preparation of high consistency rubber substrates. Blends of HCR 1 and HCR 2 having the compositions shown in Table 2a were prepared in various ratios as shown in Table 2b to provide Examples 2.1 to 2.8. The substrate compositions used are described in Table 2a below.

[0248] Table 2a: Composition of HCR 1, HCR 2 and HCR 3

[0249]

[0250] In HCR 1 and HCR 2, a commercially available hydrosilylation cure catalyst package (XIAMETER 5000 from Dow Silicones Corporation, Midland Michigan USA) comprising a platinum catalyst, a Si-H containing crosslinker, and a cure inhibitor was used. TM These ingredients may be added in any suitable order, for example, XIAMETER TM RBM-9200 inhibitor, followed by XIAMETER TM RBM-9202 catalyst, finally add XIAMETER TM RBM-9201 Crosslinker. Add these ingredients in order, adding the inhibitor first (when present). The inhibitor should be well dispersed before adding the catalyst. Add the crosslinker last.

[0251] In the case of using a peroxide catalyst to cure HCR 3, 100 parts by weight of the composition shown in Table 2a above were mixed with 1 part by weight of a 45% paste of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in silicone. This is commercially available under a number of trade names such as DHBP-45-PSI (United Initiators). The volume resistivity results for HCR 3 were measured in the same manner as above and were found to be 8.12×10 13 ohm-cm.

[0252] Cured Sheet

[0253] Cured sheets of 0.5 mm thickness were prepared using a compression mold at a hydraulic press setting of 300 psi (2.17 MPa) and a temperature of 120° C. for 10 minutes, hung in a ventilated oven, and post-cured at 200° C. for up to 4 hours. The volume resistivity results of the HCR 1 and HCR 2 sheets were determined as previously described and are listed in Table 2b below.

[0254] Table 2b: Volume resistivity results

[0255] Example % of HCR 1 % of HCR 2 Average volume resistivity (ohm-cm) 2.1 Comparative Example 100.00 0.00 <![CDATA[1.03×10 15 ]]> 2.2 Comparative Example 100.00 0.00 <![CDATA[1.06×10 15 ]]> 2.3 75.00 25.00 <![CDATA[5.09×10 14 ]]> 2.4 50.01 49.99 <![CDATA[2.36×10 14 ]]> 2.5 50.00 50.00 <![CDATA[2.18×x10 14 ]]> 2.6 24.98 75.02 <![CDATA[4.71×10 13 ]]> 2.7 0.00 100.00 <![CDATA[2.26×10 12 ]]> 2.8 0.00 100.00 <![CDATA[1.90×10 12 ]]>

[0256] Here, Examples 2.3 to 2.8 having different levels of silica filler treated with a fluorinated treating agent exhibit lower volume resistivity than Comparative Examples 2.1 or 2.2 having no fluorinated silicone treated silica.

[0257] Additional samples 2.1, 2.6 and 2.7 were prepared, in which case they were post-cured at 200°C for up to 4h and further volume resistivity tested at higher polarization voltage, longer polarization time and higher temperature, the results of which are provided in Table 2c below.

[0258] Table 2c: Volume resistivity results at higher electric fields and longer poling times .

[0259]

[0260] Examples 2.6 and 2.7 continue to show lower volume resistivity than Comparative Example 2.1 over a range of polarization voltages and polarization times.

[0261] Example 3

[0262] Liquid silicone rubber compositions using non-fluorinated polydiorganosiloxane polymers were prepared as LSR Matrix 3 and LSR Matrix 4 as shown in Table 3a below. Fumed silica was treated in situ during the preparation of the LSR matrix or HCR.

[0263] Table 3a: Composition of LSR Matrix 3 and LSR Matrix 4

[0264]

[0265] The material was cured using the same formulation as shown in Table 1b, except that the mixture of LSR Matrix 1 and LSR Matrix 2 was replaced with LSR Matrix 3 or LSR Matrix 4. Sheets of 0.5 mm thickness were cured at 120°C for 10 minutes and then the volume resistivity was measured in the manner described above, and the results are depicted in Table 3c below.

[0266] Table 3c: Volume resistivity results

[0267] Example LSR matrix Average volume resistivity (ohm-cm) 1.1 Comparative Example 100% LSR matrix 1 <![CDATA[7.57×10 14 ]]> 1.4 50% LSR matrix 1, 50% LSR matrix 2 <![CDATA[1.89×10 14 ]]> 2.3 LSR matrix 3 <![CDATA[9.24×10 13 ]]> 2.4 LSR matrix 4 <![CDATA[1.87×10 12 ]]>

[0268] Thus, these examples where the fumed silica was treated with a mixture of fluorinated and non-fluorinated treatment agents exhibited lower volume resistivities than the volume resistivity obtained in Example 1.4 where LSR matrices 1 and 2 were blended after silica treatment. All examples exhibited lower volume resistivities than the 1.1 comparative example, regardless of the method used to prepare the mixture of fluorinated and non-fluorinated treatment agents.

Claims

1. A curable silicone elastomer composition comprising (A) at least one non-fluorinated polydiorganosiloxane; (B) at least one reinforcing silica filler, the at least one reinforcing silica filler being at least partially hydrophobically treated with a fluorinated hydrophobic treating agent selected from: One or more silanol-terminated fluorinated siloxane oligomers having 2 to 20 siloxane units, and / or One or more fluorinated silanediols, and / or One or more fluorinated trialkoxysilanes, and / or One or more fluorinated silazanes, or mixtures thereof; and at least one of (C) or (D), wherein (C) is at least one organohydrogenpolysiloxane (C)(i), at least one hydrosilylation catalyst (C)(ii) and optionally at least one cure inhibitor (C)(iii); and (D) is at least one peroxide catalyst; in, The reinforcing silica filler is the only fluorinated portion of the composition.

2. The curable silicone elastomer composition according to claim 1, It is characterized in that The composition contains ≤0.1 wt. % of a conductive filler or a semiconductive filler or a mixture thereof, based on the composition, and / or is characterized in that, when (C) a hydrosilylation curing package is present in the composition, (A) must contain at least two alkenyl groups or alkynyl groups per molecule; and / or The invention is characterized in that the filler (B) is at least partially treated with one or more fluorinated treatment agents selected from the group consisting of trifluoropropyltrimethoxysilane and trifluoropropyltriethoxysilane; silanol-terminated trifluoropropylalkylsiloxane having 2 to 20 siloxane repeating units and wherein the alkyl group has 1 to 6 carbons; and bis(trifluoropropyldialkyl)silazane wherein each alkyl group has 1 to 6 carbons to render the filler hydrophobic. 3 . A high voltage insulator comprising an elastomer product of the curable silicone elastomer composition according to claim 1 .

4. The high voltage insulator according to claim 3, used as an insulator suitable for reducing electrical stress in high voltage direct current applications.

5. The high voltage insulator according to claim 3, which is used alone or as a part of a product or a component.

6. The high voltage insulator according to claim 5, wherein the article or component is a cable accessory.

7. The high voltage insulator according to claim 3, wherein the high voltage insulator is a high voltage direct current insulator.

8. A method for preparing the curable silicone elastomer composition according to claim 1, comprising: (i) preparing a silicone matrix composition by mixing a non-fluorinated polydiorganosiloxane (A) with at least one reinforcing silica filler; and (ii) introducing component (C), component (D), or a mixture of component (C) and component (D) and storing the resulting composition; wherein when the composition contains a hydrosilylation cure package (C), the composition is stored in two or more portions, wherein components (C)(i) and (C)(ii) are maintained in separate portions; It is characterized in that The at least one reinforcing silica filler is at least partially treated with a fluorinated treating agent prior to or during step (i).

9. The method according to claim 8, It is characterized in that treating part of the reinforcing silica filler with a fluorinated treating agent prior to step (i) and treating the remainder with a non-fluorinated treating agent prior to step (i), or Characterized in that the non-fluorinated polydiorganosiloxane (A) is divided into a plurality of predetermined aliquots, wherein each aliquot is mixed in situ with a predetermined amount of reinforcing silica filler and a fluorination treatment agent, so that a plurality of partial matrices are prepared using the reinforcing silica filler treated in situ, and then the plurality of partial matrices are mixed together to obtain the final product of step (i), or Characterized in that the non-fluorinated polydiorganosiloxane (A) is mixed in situ with the reinforcing silica filler and the fluorination treating agent so that the reinforcing silica filler is treated in situ to obtain the final product of step (i), or Characterized in that the non-fluorinated polydiorganosiloxane (A) is mixed in situ with the reinforcing silica filler and a mixture of a fluorinated treatment agent and a non-fluorinated treatment agent, so that the reinforcing silica filler is treated in situ to obtain the final product of step (i).

10. A method for manufacturing a high voltage direct current insulator, wherein the curable silicone elastomer composition of claim 1 is introduced into a mold to form a molded silicone article prior to curing.

11. The method for manufacturing a high voltage direct current insulator according to claim 10, in, The curable silicone elastomer composition is injection molded to form an article or overmolded by injection molding around an article.

12. Use of the curable silicone elastomer composition according to claim 1 for or as a high voltage direct current insulator.

13. Use of the curable silicone elastomer composition according to claim 1 for reducing electrical stress in high voltage direct current applications.

14. Use of the curable silicone elastomer composition according to claim 1 as an insulator for high voltage direct current applications.

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