Liquid silicone rubber composition

Abstract

The present disclosure relates to a hydrosilylated (addition) curable silicone rubber composition, to a silicone elastomeric material having improved high temperature (175 DEG C) compressive deformation according to ISO 815-1 process A, which silicone elastomeric material is produced by curing the hydrosilylated (addition) curable silicone rubber composition, the invention also relates to a method for preparing the silicone elastomer material. The disclosure also extends to uses of such materials.

Description

[0001] The present disclosure relates to a hydrosilylation (addition) curable silicone rubber composition, to a silicone elastomer material having improved high temperature (175° C.) compression set according to ISO 815-1 Method A, the silicone elastomer material being produced by curing the hydrosilylation (addition) curable silicone rubber composition, and to a method for preparing the silicone elastomer material. The present disclosure also extends to the use of such materials.

[0002] The hydrosilylation-curable silicone rubber composition contains

[0003] (i) an organopolysiloxane polymer having unsaturated (alkenyl and / or alkynyl) groups;

[0004] (ii) compounds containing silicon-bonded hydrogen atoms; and

[0005] (iii) a hydrosilylation catalyst,

[0006] These hydrosilylation-curable silicone rubber compositions are known in the art and are used to prepare silicone elastomer materials having a wide range of physical properties, including electrical insulation, heat resistance and thermal stability, frost resistance, abrasion resistance, flame retardancy, and long-term flexibility. This unique combination of properties makes elastomers made from liquid silicone rubber suitable for a wide range of electrical and / or insulating applications, such as for use in or for electrical connectors, which are typically used to create closed electrical circuits in automobiles, homes, and infrastructure.

[0007] For example, silicone elastomers, both liquid silicone rubber (LSR) and high consistency rubber (HCR), are widely used as seals in or for electrical connectors due to their excellent balance of mechanical properties, chemical stability, and thermal stability, as well as ease of processing. They can be used to mate with rigid thermoplastic housing components to form a tight connection, providing both electrical and environmental isolation to the connector joint. These materials can be used in motor vehicles, which increasingly rely on electrical and electronic systems for their entire operation, even more so since the introduction of electric and hybrid vehicles. As a result, electrical failures can cause devices such as radios, lights, ventilation devices, etc. to malfunction or be damaged. Many electrical connectors for such devices rely on the aforementioned silicone rubber materials to prevent electrical failures, and they need to be able to avoid failures of the vehicle, for example, at elevated engine temperatures.

[0008] In addition to their applications such as electrical insulation and / or thermal stability, many of these applications also require silicone elastomer materials to have low compression set. Compression set is a key property of silicone elastomer materials used in any of the above applications. Compression set is the thermally induced fatigue behavior of silicone elastomer materials, which can be defined as the loss of the ability of the silicone elastomer material to recover to its original thickness after being compressed for a specific period of time at a set (elevated) temperature. The compression set value can be measured, for example, according to industrial standard ISO 815-1:2019 method A, B or C, and determined as a percentage, so that if there is complete recovery, that is, if the thickness of the test sample is the same before and after the load is applied, the compression set value is 0%; on the contrary, if the 25% compression of the silicone elastomer material applied during the test remains unchanged when the load is removed, the compression set is 100% because it fails to fully recover to its initial shape. Without being bound by current theory, it is believed that the fundamental reason why silicone-based elastomeric materials cannot recover to their original thickness after being compressed at a set (elevated) temperature for a specified period of time is that hydrosilylation-curable silicone compositions generally (if not always) do not undergo complete curing during the standard curing process. This is believed to be (at least in part) due to incomplete hydrosilylation caused by steric hindrance during the interaction of the vinyl-containing silicone polymer, the Si-H crosslinker, and the hydrosilylation catalyst (most typically a platinum-based catalyst). Therefore, when the hydrosilylation-curable silicone elastomeric material is compressed at an elevated temperature, further crosslinking can occur within the silicone elastomeric material, particularly at previously unreacted Si-H positions. In addition, intermolecular bond formation can occur between polydimethylsiloxane (PDMS) chains, again particularly at previously unreacted Si-H excess positions (via hydrolysis, oxidation, or thermally induced reaction pathways), and thermal, oxidative, and thermo-oxidative rearrangements can occur within or between individual PDMS chains of the silicone elastomeric material. The occurrence of one or more of the above will result in an increase in the crosslink density within the silicone elastomeric material and therefore a more rigid structure, which prevents the silicone elastomeric material from returning to its original thickness after compression.

[0009] Many silicone elastomer materials have significant compression set, e.g., greater than 50% or even greater than 60% compression set even at temperatures of 125°C and 150°C after compression for short periods of time, e.g., 22 hours, and may suffer from problems caused by corresponding changes in shape and / or significant increases in hardness during extended use in high temperature applications unless they are subjected to a post-cure heating process. "Post-cure" is the most direct way to minimize compression set, wherein a hydrosilylation-cured silicone material is subjected to post-cure heating at a temperature of 150°C or higher for a period of several hours (e.g., four or more hours). However, post-cure is generally not commercially desirable or indeed feasible in view of the increased energy consumption and delays in manufacturing time.

[0010] Many of the above applications usually require that the compression set value of the silicone elastomer material within a wide temperature range be as low as possible, for example, not greater than 40%.

[0011] In the United States, electrical connector systems must meet the requirements of the SAE International USCAR-2 "Performance Specifications for Automotive Electrical Connector Systems" test regime. Sealed connector assemblies are graded so that their suitability for use over a specific temperature range meets a class of relevant automotive specifications for a given temperature range. There are currently five ranges identified as T1 to T5:

[0012] T1 is the temperature level from -40°C to +85°C;

[0013] T2 is the temperature range of -40°C to +100°C;

[0014] T3 is the temperature range of -40°C to +125°C;

[0015] T4 is the temperature range of -40℃ to +150℃; and the current highest grade is

[0016] T5 has a temperature range of -40°C to 175°C.

[0017] Current sealed connector assemblies meet the T3 temperature rating. However, as vehicle manufacturers develop vehicles, the vehicle engine and its surroundings need to withstand higher temperatures due to reasons such as better packaging, higher engine efficiency and the use of turbochargers. As a result, more and more electrical connectors made of silicone rubber need to operate at higher temperatures to meet T4 and T5 requirements.

[0018] Given that it is undesirable to compulsorily post-cure every elastomer after curing, various additives have been proposed for reducing compression set without the need for post-curing.

[0019] In US5153244, the compression set value of hydrosilylation-cured silicone is significantly reduced by introducing a phthalocyanine compound or a metal derivative of such a compound (wherein the metal is copper, nickel, cobalt or iron) into the composition.

[0020] US8080598B2 proposes a hydrosilylation-cured silicone rubber having low compression set without post-curing using a diacylhydrazide-based compound such as dodecanedioyl-di-(N'-salicyloyl)hydrazide, a synonym of which is 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide and several alternatives, in combination with a curing inhibitor selected from acetylene-containing silanes, vinyl-containing low molecular weight organosiloxane compounds or alcohol derivatives having carbon-carbon triple bonds to reduce compression set. The introduction of US8080598B2 states that "articles molded with an organopolysiloxane rubber composition curable by addition reaction and compounded with a phthalocyanine compound are limited in practical use due to coloration caused by phthalocyanine". Despite the teachings in US8080598B2, US9289963B2, US9598575B2 and US10000680B2, phthalocyanine compounds have been used as compression set additives.

[0021] However, most compression set additives used previously, such as the above-mentioned additives, are suitable for improving compression set after compression for at least 22 hours up to the upper limit of T5 (+175°C), and most silicone elastomers made of LSR currently can only mainly meet the requirements of T3 (up to 125°C) or T4 (up to 150°C) grades, with a compression set of less than or equal to (≤) 50% after compression for 1008 hours at the corresponding temperature. Therefore, they cannot effectively reduce the compression set to meet the newer target performance of the endurance test temperature of 175°C (T5), which is increasingly being considered / proposed due to the growing needs of the automotive industry and other industries.

[0022] The present invention provides a silicone rubber composition, which comprises the following components:

[0023] a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa.s to 100,000 mPa.s at 25°C;

[0024] b) organosilicon compounds having at least two, alternatively at least three Si—H groups per molecule;

[0025] c) optionally hydrophobically treated silica reinforcing fillers;

[0026] d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof;

[0027] e) a compression set additive selected from

[0028] (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally

[0029] (ii) one or more compounds selected from diacylhydrazide-based compounds;

[0030] The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (i.e., (i) + (ii));

[0031] f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount ranging from 0.25% to 5.0% by weight of the composition;

[0032] The total weight % of the composition is 100 weight %.

[0033] A silicone elastomer material is also provided, which is a cured product of the above-mentioned hydrosilylation-curable silicone rubber composition. When measured after compression at 175°C for 22 hours according to industrial standard specification ISO 815-1 Method A, the silicone elastomer material has a compression set of not more than 20%, preferably not more than 15%; alternatively, when measured after compression at 175°C for 168 hours (1 week) according to industrial standard specification ISO 815-1 Method A, the compression set is 30% or less, preferably 25% or less; alternatively, when measured after compression at 175°C for 504 hours according to industrial standard specification ISO 815-1 Method A, the compression set is 45% or less, preferably 35% or less; alternatively, when measured after compression at 175°C for 1008 hours according to industrial standard specification ISO 815-1 Method A, the compression set is 55% or less, preferably 50% or less.

[0034] Also provided is a method for preparing a silicone elastomer material, the method comprising the step of mixing a hydrosilylation-curable silicone rubber composition having the following components:

[0035] a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa.s to 100,000 mPa.s at 25°C;

[0036] b) organosilicon compounds having at least two, alternatively at least three Si—H groups per molecule;

[0037] c) optionally hydrophobically treated silica reinforcing fillers;

[0038] d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof;

[0039] e) a compression set additive selected from

[0040] (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally

[0041] (ii) one or more compounds selected from diacylhydrazide-based compounds;

[0042] The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (ie, (i) + (ii)); and

[0043] f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount ranging from 0.25% to 5.0% by weight of the composition;

[0044] wherein the total weight % of the composition is 100 weight %;

[0045] and curing the composition at a temperature of 80°C to 200°C.

[0046] Also provided is a silicone elastomer material, which is obtained or obtainable by a method comprising the steps of: mixing a hydrosilylation-curable silicone rubber composition having the following components:

[0047] a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa.s to 100,000 mPa.s at 25°C;

[0048] b) organosilicon compounds having at least two, alternatively at least three Si—H groups per molecule;

[0049] c) optionally hydrophobically treated silica reinforcing fillers;

[0050] d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof;

[0051] e) a compression set additive selected from

[0052] (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally

[0053] (ii) one or more compounds selected from diacylhydrazide-based compounds;

[0054] The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (ie, (i) + (ii)); and

[0055] f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount ranging from 0.25% to 5.0% by weight of the composition;

[0056] The total weight % of the composition is 100 weight %.

[0057] and curing the composition at a temperature of 80°C to 200°C;

[0058] When measured after compression at 175°C for 22 hours according to industrial standard specification ISO 815-1 Method A, the silicone elastomeric material has a compression set of no more than 20%, preferably no more than 15%; alternatively, when measured after compression at 175°C for 168 hours (1 week) according to industrial standard specification ISO 815-1 Method A, the compression set is 30% or less, preferably 25% or less; alternatively, when measured after compression at 175°C for 504 hours according to industrial standard specification ISO 815-1 Method A, the compression set is 45% or less, preferably 35% or less; alternatively, when measured after compression at 175°C for 1008 hours according to industrial standard specification ISO 815-1 Method A, the compression set is 55% or less, preferably 50% or less.

[0059] Also provided herein is the use of the following in a silicone rubber composition as a means of reducing the compression set of the silicone elastomeric material formed by curing the composition, when measured according to industry standard specification ISO 815-1 Method A:

[0060] e) a compression set additive selected from

[0061] (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally

[0062] (ii) one or more compounds selected from diacylhydrazide-based compounds;

[0063] The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (ie, (i) + (ii)); and

[0064] f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount ranging from 0.25% to 5.0% by weight of the composition;

[0065] The silicone rubber composition originally comprises the following components:

[0066] a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa.s to 100,000 mPa.s at 25°C;

[0067] b) organosilicon compounds having at least two, alternatively at least three Si—H groups per molecule;

[0068] c) optionally hydrophobically treated silica reinforcing fillers;

[0069] d) A hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof.

[0070] Component (a)

[0071] Component (a) of the composition is one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity ranging from 1000 mPa.s to 100,000 mPa.s at 25°C.

[0072] Component (a) is a polyorganosiloxane, such as a polydiorganosiloxane, having at least two unsaturated groups per molecule, the unsaturated groups being selected from alkenyl groups or alkynyl groups. Alternatively, component (a) has at least three unsaturated groups per molecule.

[0073] The unsaturated groups of component (a) may be at terminal positions, pendant positions, or both positions.

[0074] The alkenyl group may have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, alternatively 2 to 6 carbon atoms. Possible alkenyl groups are exemplified by, but not limited to, vinyl groups, allyl groups, methallyl groups, propenyl groups, and hexenyl groups and cyclohexenyl groups.

[0075] The alkynyl group may have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, alternatively 2 to 6 carbon atoms. The alkynyl group may be exemplified by, but not limited to, an ethynyl group, a propynyl group, and a butynyl group.

[0076] Component (a) has a plurality of units of formula (I): R' a SiO (4-a) / 2 (I)

[0077] Wherein each R' is independently selected from aliphatic hydrocarbon groups, aliphatic non-halogenated organic groups (i.e., any aliphatic organic substituent group 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. Examples of unsaturated aliphatic hydrocarbon groups include, but are not limited to, the alkenyl groups and alkynyl groups described above. Aliphatic non-halogenated organic groups are exemplified by, but not limited to, suitable nitrogen-containing groups such as acylamino, imino; oxygen-containing groups (such as polyoxyalkylene groups, carbonyl groups, alkoxy groups and hydroxyl groups). The subscript "a" is 0, 1, 2 or 3, typically in this case a is primarily 2, but may contain some units where a is 1 or 3.

[0078] When R' is an alkyl group as described above, alternatively, a methyl group, the siloxy units may be described by the shorthand nomenclature, i.e. - "M", "D", "T" and "Q". The M unit corresponds to a siloxy unit with a = 3, i.e. R 3 SiO 1 / 2 ; The D unit corresponds to a = 2 siloxy unit, that is, R 2 SiO 2 / 2 ; T unit corresponds to a = 1 siloxy unit, that is, R 1 SiO 3 / 2 ; Q unit corresponds to a = 0 silicon oxygen unit, that is, SiO 4 / 2 Polyorganosiloxanes such as the polydiorganosiloxane of component (a) are substantially linear but may contain a certain proportion of branches due to the presence of T units (as described previously) within the molecule, so that the average value of subscript a in structure (i) is about 2.

[0079] Examples of typical R' groups on the one or more polyorganosiloxanes of component (a) containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule mainly include alkyl groups, especially methyl and ethyl, alternatively methyl groups, but in addition to the required at least two unsaturated groups selected from alkenyl groups and / or alkynyl groups (usually alkenyl groups), aryl groups and / or fluoroalkyl groups, such as trifluoropropyl groups or perfluoroalkyl groups, may also be included. These groups may be in side chain positions (on D or T siloxy units) or may be in terminal positions (on M siloxy units).

[0080] Therefore, the polymer chain of component (a) can be selected from polydimethylsiloxane, alkylmethylpolysiloxane, alkylarylpolysiloxane or their copolymers (wherein mentioning alkyl means any suitable alkyl group, alternatively has an alkyl group of two or more carbons), provided that each component (a) polymer comprises at least two alkenyl groups and / or alkynyl groups, typically at least two alkenyl groups. Such polymer chains can have any suitable terminal groups, for example, they can be trialkyl end-capped, alkenyldialkyl end-capped, alkynyldialkyl end-capped, or can be end-capped with any other suitable terminal group combination, provided that each polymer contains at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule. In one embodiment, the terminal groups of such polymers do not include any silanol terminal groups.

[0081] Thus, for example, component (a) may be:

[0082] Dialkyl alkenyl terminated polydimethylsiloxanes, such as dimethylvinyl terminated polydimethylsiloxanes; dialkyl alkenyl terminated dimethylmethylphenylsiloxanes, such as dimethylvinyl terminated dimethylmethylphenylsiloxanes; trialkyl terminated dimethylmethylvinyl polysiloxanes; dialkyl vinyl terminated dimethylmethylvinyl polysiloxane copolymers; dialkyl vinyl terminated methylphenyl polysiloxanes, dialkyl alkenyl terminated methylvinylmethylphenylsiloxanes; dialkyl alkenyl terminated methylvinyldiphenylsiloxanes; dialkyl alkenyl terminated methylvinylmethylphenyldimethylsiloxanes; trimethyl terminated methylvinylmethylphenylsiloxanes; trimethyl terminated methylvinyldiphenylsiloxanes; or trimethyl terminated methylvinylmethylphenyldimethylsiloxanes.

[0083] Component a) has a viscosity of 1000 to 100,000 mPa.s at 25°C, alternatively 5000 to 75,000 mPa.s at 25°C, 10,000 to 60,000 mPa.s at 25°C, and is preferably present in an amount of 25 to 60 wt% of the composition, alternatively 30 to 60 wt% of the composition, alternatively 35 to 55 wt% of the composition. Viscosity may be increased at 25°C using a Brookfield with spindle LV-4 for viscosities exceeding 15,000 mPa.s. TM A rotational viscometer (spindle LV-4 designed for viscosities in the range of 1,000 mPa.s to 2,000,000 mPa.s) was measured at appropriate rpm, and for viscosities up to 15,000 mPa.s at 25°C and appropriate rpm a Brookfield with cone and plate arrangement with cone CP-52 was used. TM Rotational viscometer measurement.

[0084] Component (b)

[0085] Component (b) is used as a crosslinking agent and is provided in the form of an organosilicon compound having at least two, alternatively at least three Si-H groups per molecule. Component (b) typically contains three or more silicon-bonded hydrogen atoms, so that the hydrogen atoms can react with the unsaturated olefinic and / or alkynyl groups of component (a) to form a network structure therewith and thereby cure the composition. When polymer (a) has more than two unsaturated groups per molecule, some or all of component (b) may alternatively have two silicon-bonded hydrogen atoms per molecule.

[0086] The molecular configuration of the organosilicon compound (b) having at least two, alternatively at least three Si-H groups per molecule is not particularly limited. It may be a straight chain, a branched chain (a straight chain having some branches due to the presence of a T group), a cyclic chain, or a silicone resin-based polyorganosiloxane.

[0087] Although the molecular weight of component (b) is not particularly limited, the viscosity is generally from 5 mPa.s to 50,000 mPa.s at 25°C using the test method as described for component (a).

[0088] The silicon-bonded organic group used in component (b) can be exemplified by: alkyl groups such as methyl, ethyl, propyl, n-butyl, tert-butyl, pentyl, hexyl; aryl groups such as phenyl, tolyl, xylyl or similar aryl groups; 3-chloropropyl, 3,3,3-trifluoropropyl or similar halogenated alkyl groups, preferably alkyl groups having 1 to 6 carbons, in particular methyl, ethyl or propyl or phenyl. Preferably, the silicon-bonded organic group used in component (b) is an alkyl group, alternatively methyl, ethyl or propyl.

[0089] Examples of organosilicon compounds (b) having at least two, alternatively at least three Si-H groups per molecule include, but are not limited to:

[0090] (a') trimethylsiloxy-terminated methylhydrogenpolysiloxane,

[0091] (b') trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane,

[0092] (c') a dimethylsiloxane-methylhydrogensiloxane copolymer terminated with dimethylhydrogensiloxy groups,

[0093] (d') dimethylsiloxane-methylhydrogensiloxane cyclic copolymer,

[0094] (e') by (CH 3 ) 2 HkDJ 1 / 2Unit, (CH 3 ) 3 SiO 1 / 2 Unit and SiO 4 / 2 Unit composed of copolymers and / or silicone resins,

[0095] (f') by (CH 3 ) 2 HkDJ 1 / 2 Unit and SiO 4 / 2 Unit composed of copolymers and / or silicone resins,

[0096] (g') a methylhydrogensiloxane cyclic homopolymer having 3 to 10 silicon atoms per molecule;

[0097] Alternatively, component (b) the crosslinking agent may be a filler, such as silica treated with one of the above-mentioned substances, and mixtures thereof.

[0098] In one embodiment, component (b) is selected from methylhydrogenpolysiloxane terminated with trimethylsiloxy groups at both molecular ends; copolymers of methylhydrogensiloxane and dimethylsiloxane terminated with trimethylsiloxy groups at both molecular ends; dimethylsiloxane terminated with dimethylhydrogensiloxane at both molecular ends; copolymers of methylhydrogensiloxane and dimethylsiloxane terminated with dimethylhydrogensiloxy groups at both molecular ends.

[0099] The crosslinking agent (b) is generally present in the hydrosilylation-curable silicone rubber composition such that the molar ratio of the total number of silicon-bonded hydrogen atoms in component (b) to the total number of alkenyl groups and / or alkynyl groups in component (a) is from 0.5:1.0 to 10.0:1.0. When the ratio is less than 0.5:1, a well-cured composition is not obtained. When the ratio exceeds 10:1, there is a tendency for the cured composition to increase in hardness when heated. Preferably, the amount of component (b) is such that the molar ratio of silicon-bonded hydrogen atoms of component (ii) to alkenyl / alkynyl groups, alternatively alkenyl groups, of component (a) is in the range of 0.7:1.0 to 5.0:1.0, alternatively 0.9:1.0 to 2.5:1.0, and further alternatively 0.9:1.0 to 2.0:1.0.

[0100] The silicon-bonded hydrogen (Si-H) content of component (b) is determined using quantitative infrared analysis according to ASTM E168. In this case, when relying on a hydrosilylation cure process, the ratio of silicon-bonded hydrogen to alkenyl (vinyl) and / or alkynyl groups is important. Generally speaking, this is determined by calculating the total weight % of alkenyl (e.g., vinyl) [V] in the composition and the total weight % of silicon-bonded hydrogen [H] in the composition, and assuming that the molecular weight of hydrogen is 1 and the molecular weight of vinyl is 27, the molar ratio of silicon-bonded hydrogen to vinyl is 27 [H] / [V].

[0101] Typically, component (b) will be present in an amount ranging from 0.1% to 10% by weight of the hydrosilylation-curable silicone rubber composition, alternatively from 0.1% to 7.5% by weight of the hydrosilylation-curable silicone rubber composition, alternatively from 0.5% to 7.5% by weight of the composition, and further alternatively from 0.5% to 5% by weight of the hydrosilylation-curable silicone rubber composition, depending on the number of unsaturated groups in component (a) and the number of Si-H groups in component (b).

[0102] Component (c)

[0103] Component (c) is a silica reinforcing filler which is optionally hydrophobically treated; the reinforcing filler of component (c) can be exemplified by fumed silica and / or precipitated silica and / or colloidal silica. In an alternative, the fumed silica, precipitated silica and / or colloidal silica are provided in a finely divided form.

[0104] Precipitated silica, fumed silica and / or colloidal silica are preferred because of their relatively high surface areas (particularly when provided in finely divided form, typically at least 50 m 2 / g (BET method according to ISO 9277:2010)), so they are particularly preferred. Typically, materials with a surface area of ​​50 to 450 m 2 / g (according to BET method of ISO 9277:2010), alternatively 50 to 300 m 2 / g (BET method according to ISO 9277:2010) of filler. All these types of silica are commercially available.

[0105] When the silica reinforcing filler (c) has natural hydrophilicity (e.g., untreated silica filler), it is usually treated with a treating agent to impart hydrophobicity. These surface-modified silica reinforcing fillers (c) do not agglomerate and can be uniformly incorporated into the polydiorganosiloxane polymer (a) described below because the surface treatment makes the filler easily wetted by component (a).

[0106] In general, the silica reinforcing filler (c) may be surface treated with any low molecular weight silicone compound disclosed in the art to be suitable for preventing wrinkling of the liquid silicone rubber (LSR) composition during processing, for example, organosilanes, polydiorganosiloxanes or organosilazanes, such as hexaalkyldisilazane, short chain siloxane diols, to render the silica reinforcing filler (c) hydrophobic and thus easier to handle and obtain a homogeneous mixture with the other ingredients. Specific examples include, but are not limited to, silanol terminated trifluoropropylmethylsiloxane, silanol terminated vinylmethyl (ViMe) siloxane, silanol terminated methylphenyl (MePh) siloxane, liquid hydroxydimethyl terminated polydiorganosiloxanes containing an average of 2 to 20 repeating units of diorganosiloxane per molecule, hydroxydimethyl terminated phenylmethylsiloxane, hexaorganodisiloxanes such as hexamethyldisiloxane, divinyltetramethyldisiloxane; hexaorganodisilazanes such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane and tetramethylbis(trifluoropropyl)disilazane; hydroxydimethyl terminated polydimethylmethylvinylsiloxane, octamethylcyclotetrasiloxane and silanes including, but not limited to, methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, trichloromethylsilane. In one embodiment, the treating agent may be selected from silanol terminated vinylmethyl (ViMe) siloxanes, liquid hydroxydimethyl terminated polydiorganosiloxanes containing an average of 2 to 20 diorganosiloxane repeating units per molecule, hexaorganodisiloxanes such as hexamethyldisiloxane, divinyltetramethyldisiloxane; hexaorganodisilazanes such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane and hydroxydimethyl terminated polydimethylmethylvinylsiloxane, octamethylcyclotetrasiloxane and silanes including but not limited to methyltriethoxysilane, dimethyldiethoxysilane and / or vinyltriethoxysilane. A small amount of water may be added along with the silica treating agent as a processing aid.

[0107] The surface treatment of the untreated silica reinforcing filler (c) can be performed prior to introduction into the composition or in situ (i.e., in the presence of at least a portion of the other ingredients of the composition herein, by blending the ingredients together at room temperature or above until the filler is completely treated). Typically, the untreated silica reinforcing filler (c) is treated in situ with a treating agent in the presence of component (a), which results in the preparation of a silicone rubber matrix material that can subsequently be mixed with the other ingredients.

[0108] Silica reinforcing filler (c) is optionally present in an amount up to 40 wt % of the composition, alternatively from 1.0 wt % to 40 wt % of the composition, alternatively from 5.0 wt % to 35 wt % of the composition, alternatively from 10.0 wt % to 35 wt % of the composition.

[0109] Component (d)

[0110] The component (d) of the composition is a hydrosilylation catalyst comprising or consisting of a platinum group metal or its compound. These catalysts are generally selected from catalysts of platinum group metals (platinum, ruthenium, osmium, rhodium, iridium and palladium), or compounds of one or more metals in such metals. Alternatively, due to the high activity level of these catalysts in the hydrosilylation reaction, platinum and rhodium compounds are preferred, with platinum compounds being the most preferred. In the hydrosilylation (or addition) reaction, a hydrosilylation catalyst such as component (d) herein catalyzes the reaction between an unsaturated group (generally an alkenyl group, for example, a vinyl group) and a Si-H group.

[0111] The catalyst (d) may be a platinum group metal, a platinum group metal deposited on a carrier such as activated carbon, a metal oxide such as alumina or silica, silica gel or charcoal powder, or a compound or complex of a platinum group metal. Preferably the platinum group metal is platinum.

[0112] Examples of preferred hydrosilylation catalysts (d) are platinum-based catalysts such as platinum black, platinum oxide (Adams catalyst), platinum on various solid supports, chloroplatinic acid such as hexachloroplatinic acid (Pt oxidation state IV) (Speier catalyst), chloroplatinic acid in solution in an alcohol such as isooctyl alcohol or amyl alcohol (Lamoreaux catalyst), and complexes of chloroplatinic acid with ethylenically unsaturated compounds such as olefins and organosiloxanes containing ethylenically unsaturated silicon-bonded hydrocarbon groups such as tetravinyltetramethylcyclotetrasiloxane-platinum complex (Ashby catalyst). Soluble platinum compounds that can be used include, for example, compounds of the formula (PtCl 2 .Olefins) 2 and H(PtCl 3 In the present context, preference is given to using platinum-olefin complexes of olefins having 2 to 8 carbon atoms, such as ethylene, propylene, isomers of butene and isomers of octene, or cycloalkanes having 5 to 7 carbon atoms, such as cyclopentene, cyclohexene and cycloheptene. Other soluble platinum catalysts are, for example, of the formula (PtCl 2 C 3 H 6 ) 2The platinum-cyclopropane complex of hexachloroplatinic acid, the reaction products of hexachloroplatinic acid with alcohols, ethers and aldehydes or mixtures thereof, or the reaction products of hexachloroplatinic acid and / or its conversion products with vinyl-containing siloxanes (such as methylvinylcyclotetrasiloxane) in the presence of an ethanolic solution containing sodium bicarbonate. Platinum catalysts with phosphorus and amine ligands, such as (Ph 3 P) 2 PtCl 2 ; and complexes of platinum with vinylsiloxanes, such as sym-divinyltetramethyldisiloxane.

[0113] Thus, specific examples of suitable platinum-based catalysts include:

[0114] (i) complexes of chloroplatinic acid and organosiloxanes containing ethylenically unsaturated hydrocarbon groups as described in US Pat. No. 3,419,593;

[0115] (ii) chloroplatinic acid in the form of hexahydrate or in anhydrous form;

[0116] (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;

[0117] (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

[0118] (v) Karstedt's catalyst, a platinum divinyltetramethyldisiloxane complex, typically containing about 1 wt% platinum in a vinylsiloxane polymer having a viscosity of about 200 to 750 mPa.s using the test method as described for component (a).

[0119] Solvents such as toluene and similar organic solvents have historically been used as alternatives, but the use of vinyl siloxane polymers is by far the preferred choice. These are described in US 3,715,334 and US 3,814,730. In a preferred embodiment, component (d) may be selected from coordination compounds of platinum. In one embodiment, hexachloroplatinic acid and its conversion products with vinyl-containing siloxanes, Karstedt catalysts and Speier catalysts are preferred.

[0120] Component (d) is typically present in an amount providing 0.1 ppm to 500 ppm (parts per million) of platinum atoms relative to the weight of the reactive ingredients, i.e., components (a) and (b). The catalyst may be added as a single substance or as a mixture of two or more different substances. Typically, depending on the form / concentration in which the catalyst is provided, the amount of the catalyst present will be in the range of 0.05 wt % to 1.5 wt %, alternatively 0.05 wt % to 1.0 wt %, alternatively 0.1 wt % to 1.0 wt %, alternatively 0.1 wt % to 0.5 wt % of the composition, wherein the platinum catalyst is provided in a masterbatch of a polymer (such as (a) described above).

[0121] Component (e)

[0122] Component e) is a compression set additive selected from

[0123] (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel,

[0124] cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally

[0125] (ii) one or more compounds selected from diacylhydrazide-based compounds;

[0126] The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (ie, (i) + (ii)).

[0127] Component (e)(i) is a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium or vanadium, for example, the phthalocyanine compound may have the following structure:

[0128]

[0129] Metal phthalocyanine such as copper phthalocyanine is shown below.

[0130]

[0131] In one embodiment, component (e)(i) comprises or consists of copper phthalocyanine. Any suitable form of copper phthalocyanine can be used, for example, β-type copper phthalocyanine of pigment 15:3 or 15:4, and α-type copper phthalocyanine of 15.2 can also be used. When sufficiently stable, α-type copper phthalocyanine of 15:1 is suitable, with β-type copper phthalocyanine of 15:3 or 15:4 being particularly preferred.

[0132] Component (e)(i) phthalocyanine compounds or metal derivatives of such compounds are present in an amount of 0.02 wt % to 2.5 wt % of the composition, or 0.02 wt % to 2.0 wt % of the composition.

[0133] However, it should be noted that it can be delivered alone or in the form of a masterbatch or mixture with, for example, a suitable polydimethylsiloxane, such as a dimethylvinyl terminated polydimethylsiloxane having a viscosity of 1000 mPa.s at 25°C to 25000 mPa.s at 25°C. For example, copper phthalocyanine in a dimethylvinyl terminated polydimethylsiloxane having a viscosity of 1,000 mPa.s at 25°C to 15,000 mPa.s at 25°C, or in a mixture comprising 10 wt% to 50 wt% of copper phthalocyanine and the remainder consisting of dimethylvinyl terminated polydimethylsiloxane having a viscosity of 1,000 mPa.s at 25°C to 15,000 mPa.s at 25°C. Specific examples include copper phthalocyanine having a viscosity of about 9000 mPa.s at 25°C (using a Brookfield 9000 rpm with a cone and plate arrangement with cone CP-52). TM 30 wt% copper phthalocyanine in vinyldimethylsiloxy-terminated polydimethylsiloxane with a viscosity of about 2000 mPa.s at 25° C. (rotational viscometer using a Brookfield viscometer with a cone and plate arrangement with cone CP-52 at 3 rpm) TM 15 wt % copper phthalocyanine in a vinyldimethylsiloxy terminated polydimethylsiloxane having a viscosity of 1.5 wt % (rotational viscometer). In this case, when provided as such a masterbatch or mixture, the masterbatch or mixture can be introduced into the composition in an amount of 0.2 wt % to 5 wt % of the composition, and such a masterbatch or mixture can contain about 10 wt % to 50 wt % of component (e)(i), with the remainder being a suitable polydimethylsiloxane.

[0134] When present, component (e)(ii) is one or more compounds selected from diacylhydrazide based compounds.

[0135] The diacylhydrazide-based compounds are represented by the following general formula:

[0136]

[0137] Where R 1 and R 2 may be the same or different and may be represented by a hydrogen atom, a hydroxyl group, an alkyl group, a substituted alkyl group, an aryl group, a phenolic group or a similar substituted aryl group, an aralkyl group or a substituted aralkyl group. 1 and R 2Includes monovalent hydrocarbon groups containing aromatic groups, phenols or similar substituted aromatic groups. Specific examples of the above-mentioned diacylhydrazide-based compounds are as follows: N,N'-diformylhydrazine, N,N'-diacetylhydrazine, N,N'-dipropionylhydrazine, N,N'-butylhydrazine, N-formyl-N'-acetylhydrazine, N,N'-dibenzoylhydrazine, N,N'-ditoluoylhydrazine, N,N'-disalicyloylhydrazine, N-formyl-N'-disalicyloylhydrazine, N-formyl-N'-butyl-substituted salicylhydrazine, N-acetyl-N'-salicyloylhydrazine, N-formyl-N'-butyl-substituted salicylhydrazine, N-acetyl-N'-salicyloylhydrazine, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, adipate di-(N'-salicyloyl)hydrazine or dodecanedioyl-di-(N'-salicyloyl)hydrazine.

[0138] Commercially produced compounds include, for example, N,N'-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, available as Irganox TM MD1024 was purchased from Ciba Specialty Chemicals Co., Ltd. and dodecanedioyl-bis-(N'-salicyloyl)hydrazine, a synonym of which is 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide, available as ADK STAB TM CDA-6 (hereinafter referred to as CDA-6) was commercially available from Adeka Corporation.

[0139] In one alternative, component (e)(ii) is dodecanediyl-bis-(N'-salicyloyl)hydrazine.

[0140] When present, component (e)(ii) is added in an amount from 0.001 wt % to 1.0 wt % of the composition, alternatively from 0.001 wt % to 0.5 wt % of the composition, alternatively from 0.01 wt % to 0.5 wt % of the composition, alternatively from 0.02 wt % to 0.5 wt % of the composition.

[0141] The compression set additive (e) is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition, alternatively 0.1 wt % to 3.5 wt % of the composition, alternatively 0.2 wt % to 3.0 wt % of the composition (ie, (i) + (ii)).

[0142] However, if calculated based on the presence of component (e)(i) in a masterbatch / blend with a suitable polysiloxane polymer, the compression set additive (e) (i.e., (e)(i) masterbatch / blend + (ii)) is from 0.2 wt % to 5.0 wt % of the composition, alternatively from 0.2 wt % to 5.0 wt % of the composition, alternatively from 0.25 wt % to 5.0 wt % of the composition, alternatively from 0.25 wt % to 4.0 wt % of the composition, alternatively from 0.25 wt % to 3.0 wt % of the composition, alternatively from 0.25 wt % to 2.0 wt % of the composition.

[0143] Component (f) Component (f) is one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate. Magnesium carbonate and basic magnesium carbonate are particularly preferred.

[0144] These may include magnesia (MgCO 3 ), dihydrate magnesite (MgCO 3 ·2H 2 O), nesquihonite (MgCO 3 ·3H 2 O), pentahydrate magnesite (MgCO 3 ·5H 2 O) in one or more magnesium carbonates; and one or more magnesium hydroxycarbonates, such as: magnesium white malachite (pokrovskite) (Mg 2 (CO 3 )(OH) 2 .0.5H 2 O), artinite (Mg 2 (CO 3 )(OH) 2 .3H 2 O), hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O) (sometimes called light magnesium carbonate), hydromagnesite (dypingite) (Mg 5 (CO 3 ) 4 (OH) 2 .5H 2 O) (sometimes called heavy magnesium carbonate), giorgiosite (Mg 5 (CO 3 ) 4 (OH) 2 .5-6H 2O) and shelkovite (Mg 7 (CO 3 ) 5 (OH) 4 .24H 2 O). Component (f) is present in the composition in an amount from 0.25 wt % to 5.0 wt % of the composition, alternatively from 0.25 wt % to 4.0 wt % of the composition, alternatively from 0.25 wt % to 3.0 wt % of the composition, alternatively from 0.25 wt % to 2.0 wt % of the composition.

[0145] Optional additives

[0146] Depending on the intended use, such hydrosilylation-curable silicone rubber compositions may also contain one or more optional additives. Examples include curing inhibitors, mold release agents, adhesion catalysts, peroxides, conductive fillers, thermally conductive fillers, pot life extenders, lubricants, mold release agents, UV light stabilizers, bactericides, wetting agents, and the like.

[0147] Curing inhibitor

[0148] When needed, use curing inhibitor to prevent or delay the addition reaction curing process, especially during storage.The optional addition reaction inhibitor based on the catalyst of platinum is well known in the art and includes hydrazine, triazole, phosphine, mercaptan, organic nitrogen compound, alkynol, methane silylation alkynol, maleate, fumarate, ethylenic or aromatic unsaturated amide, ethylenic unsaturated isocyanate, olefinic siloxane, unsaturated hydrocarbon monoester and diester, conjugated alkene-alkynes, hydroperoxide, nitrile and diaziridine.Can use the siloxane of alkenyl replacement as described in US3989667, wherein preferred cyclic methyl vinyl siloxane.

[0149] One class of known hydrosilylation reaction inhibitors are the acetylenic compounds disclosed in US 3445420. Alkynols such as 2-methyl-3-butyn-2-ol constitute a class of preferred inhibitors which will inhibit the activity of platinum-containing catalysts at 25° C. Compositions containing these inhibitors generally require heating at temperatures of 70° C. or above in order to cure at an achievable rate.

[0150] 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.

[0151] When present, inhibitor concentrations as low as 1 mole inhibitor per mole of catalyst metal will in some cases impart satisfactory storage stability and cure rates. In other cases, inhibitor concentrations of up to 500 moles inhibitor per mole of catalyst metal 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.

[0152] In one embodiment, when present, the inhibitor is selected from 1-ethynyl-1-cyclohexanol (ETCH) and / or 2-methyl-3-butyn-2-ol and is present in an amount from greater than zero to 0.1% by weight of the composition.

[0153] Lubricants

[0154] As previously noted, the compositions of the types described herein are generally used as electrical connectors. Typically such electrical connectors are made of self-lubricating silicone elastomers, which are designed to gradually ooze out and lubricate cables and connector components from a cured seal over time. Typically, polyphenylmethylsiloxane and copolymers thereof are used as lubricants in this case. Alternatively or in addition to this, the example of other lubricants that can be used includes tetrafluoroethylene, resin powder, graphite, graphite fluoride, talcum, boron nitride, fluorine oil, and mixtures or derivatives thereof. When present, such lubricants can be present in an amount of 1% by weight to 4% by weight of the composition.

[0155] In one embodiment, the compositions herein do not comprise urea in an amount of 0.005% to 0.2% by weight of the composition and / or do not comprise cyanuric acid, biuret, or mixtures thereof in an amount of 0.005% to 0.2% by weight of the composition.

[0156] Therefore, in one alternative, the present disclosure therefore provides a silicone rubber composition comprising any suitable combination of the following components:

[0157] a) one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from alkenyl groups and alkynyl groups and having a viscosity in the range of 1000 to 100,000 mPa.s at 25°C, alternatively 5000 to 75,000 mPa.s at 25°C, 10,000 to 60,000 mPa.s at 25°C, preferably present in an amount of 25 to 60% by weight of the composition, alternatively 30 to 60% by weight of the composition, alternatively 35 to 55% by weight of the composition. The viscosity can be in the range of 1,000 to 2,000,000 mPa.s at 25°C using a spindle LV-4 (designed for viscosities in the range of 1,000 to 2,000,000 mPa.s). The viscometer is rotated and the speed is adjusted according to the viscosity of the polymer.

[0158] b) an organosilicon compound having at least two, alternatively at least three Si-H groups per molecule, which may be present in an amount of 0.1% to 10% by weight of the silicone rubber composition, alternatively 0.1% to 7.5% by weight of the silicone rubber composition, alternatively 0.5% to 7.5% by weight, further alternatively 0.5% to 5% by weight of the composition;

[0159] c) silica reinforcing fillers, preferably in finely divided form and optionally hydrophobically treated; high surface area, generally at least 50 m 2 / g (according to BET method of ISO 9277:2010). The filler has 50m 2 / g to 450m 2 / g (according to BET method of ISO9277:2010), alternatively 50m 2 / g to 300m 2 The surface area of ​​the present invention is 200 wt % or more of the composition, preferably 1.0 wt % to 40 wt % of the composition, preferably 5.0 wt % of the composition, and preferably 20 wt % to 40 wt % of the composition.

[0160] to 35 wt %, alternatively 10.0 wt % to 35 wt % of the composition;

[0161] d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; in an amount, depending on the form / concentration in which the catalyst is provided, of 0.001 wt % to 3.0 wt % of the composition, alternatively 0.001 wt % to 1.5 wt % of the composition, alternatively 0.01 wt % to 1.5 wt % of the composition, alternatively 0.01 wt % to 0.01 wt % of the silicone rubber composition

[0162] to 0.1.0 wt %.

[0163] e) a compression set additive selected from

[0164] (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally

[0165] (ii) one or more compounds selected from diacylhydrazide-based compounds;

[0166] The compression set additive is cumulatively present in an amount from 0.02 wt % to 3.5 wt % of the composition, alternatively from 0.1 wt % to 3.5 wt % of the composition, alternatively from 0.2 wt % to 3.0 wt % of the composition (i.e., (i) + (ii)); and

[0167] f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount of 0.25% to 5.0% by weight of the composition, alternatively 0.25% by weight of the composition

[0168] to 4.0 wt %, alternatively 0.25 wt % to 3.0 wt %, alternatively 0.25 wt % to 2.0 wt % of the composition;

[0169] Provided that the total weight % of the composition is 100 weight %. The composition may also contain one or more of the above-mentioned optional additives in the amounts again indicated, provided that the total weight % of the composition is 100 weight %.

[0170] The above hydrosilylation-curable silicone rubber composition is usually stored in two or more parts before use. In the case of a two-part composition, the two parts are usually referred to as part (A) and part (B):

[0171] In addition to the polyorganosiloxane (a) and the filler (c) (when present), part (A) generally contains a catalyst (d), and

[0172] Part (B) generally comprises the crosslinker component (b), and, when present, optionally an inhibitor and the remainder of the polyorganosiloxane (a) and / or silica reinforcing filler (c).

[0173] It is important to store the catalyst (d) separately from the crosslinking agent (b) to prevent premature curing during storage.

[0174] Each of components (e)(i) and / or (e)(ii) and / or (f) may be stored separately or together in part (A) or part (B) or in both parts, provided that they do not negatively affect each other or the storage of any necessary ingredients present in the respective parts. Alternatively, if desired, components (e)(i) and / or (e)(ii) may be added to the remaining composition, i.e., to the combination of the part (A) and part (B) compositions, during or after mixing the part (A) composition and the part (B) composition together prior to use.

[0175] Any optional additives other than the inhibitors described above may be incorporated in either part (A) or part (B) or in both parts, provided that they do not adversely affect the storage of any essential ingredients present in the respective parts.

[0176] The composition may be designed to be mixed in any suitable ratio, for example Part A:Part B may be mixed together in a weight ratio of 10:1 to 1:10, alternatively 5:1 to 1:5, alternatively 2:1 to 1:2, but most preferably a 1:1 weight ratio.

[0177] The ingredients / components in each of part (A) and / or part (B) may be mixed together individually in the corresponding parts, or may be introduced into the composition in a pre-made combined form, for example to facilitate mixing of the final composition. For example, components (a) and (c) are typically mixed together to form an LSR polymer base or masterbatch before the other ingredients are introduced. These may then be mixed with the other ingredients of the directly prepared part, or may be used to prepare a pre-made concentrate commonly referred to in the industry as a masterbatch.

[0178] In this case, one or more masterbatches may be used to successfully mix the ingredients to form the part (A) and / or part (B) compositions in order to facilitate mixing of the ingredients. For example, a "fumed silica" masterbatch may be prepared. This is essentially an LSR silicone rubber base with an in-situ treated silica reinforcing filler (c).

[0179] Parts A and B of the composition can be prepared by combining all of their respective components at ambient temperature. Any mixing technique and apparatus described in the prior art can be used for this purpose. The specific apparatus to be used will depend on the components and the viscosity of the final composition. Suitable mixers may include, but are not limited to, kneading mixers, static mixers in liquid injection molding machines, Z-blade mixers, two-roll mills (open mills), three-roll mills, Rheomix OS Lab mixer, screw extruder or twin screw extruder etc. High speed mixers such as those sold by, for example, Hauschild and as DC 150.1FV, DAC 400FVZ or DAC 600FVZ may alternatively be used. It may be desirable to cool the components during mixing to avoid premature solidification of the composition.

[0180] Prior to use, the respective Part (A) and Part (B) compositions are mixed together in the desired ratio.

[0181] The curing of the hydrosilylation-curable silicone rubber composition on the substrate can be carried out, for example, in a mold to form a molded part by injection molding using, for example, a liquid injection molding system (LIMS) compression molding, extrusion molding, transfer molding, pressurized vulcanization, or calendaring. Compression set test pieces can be molded into suitable shapes, such as cylindrical disks with a diameter of 29.0 mm ± 0.5 mm and a thickness of 12.5 mm ± 0.5 mm, and they are compressed 25% to a thickness of about 9.38 mm. These test pieces can be prepared in a mold, or alternatively can be cut out from a pressed sheet of silicone elastomer material.

[0182] The LSR buttons (previously cured at 175°C for 10 minutes) are held between two metal plates in a convection oven under compression for a suitable period of time, typically 22 hours at elevated temperature, after which the compression is released and the test piece is allowed to recover to a thickness close to the starting thickness, thereby allowing the compression set to be determined.

[0183] The hydrosilylation-curable silicone rubber composition is cured at any suitable temperature, for example, at a temperature of 80°C to 200°C, alternatively about 100°C to 180°C, alternatively about 120°C to 180°C. As indicated above, one of the standard methods for reducing compression set has historically been post-curing, with the goal of reducing the number of curable groups that may cure under compression. It has been surprisingly found that the composition as defined herein does not appear to particularly benefit from a post-curing process, as will be further explained below.

[0184] As for the method of manufacturing the two-part silicone rubber composition as described above, the method may include the following steps:

[0185] (i) preparing a silicone base composition comprising components (a) a polymer and (c) a silica reinforcing filler;

[0186] (ii) dividing the obtained base material into two parts, part (A) and part (B), and introducing the catalyst (d) into part (A) and part (B)

[0187] In part (A), the crosslinking agent (b) and the inhibitor (if any) are introduced into part (B)

[0188] in the compound;

[0189] (iii) introducing other components and any other optional additives into either part (A) or part (B)

[0190] or both; and

[0191] (iv) storing the Part (A) and Part (B) compositions separately.

[0192] In an alternative process, component (e) or component (e)(i) is not introduced separately into component (A) or component (B), but is introduced as part of the mixing process when the part (A) and part (B) compositions are mixed together before use, such as in a mixing process before injection molding.

[0193] Typically, the compositions of Part (A) and Part (B) are thoroughly mixed in the appropriate weight ratio as described above, and are thoroughly mixed immediately before use to avoid premature curing. Curing is then carried out in a curing stage.

[0194] If / when component (e) or component (e)(i) is introduced together with part (A) and part (B) during the mixing process, typically the weight ratio of part (A) and part (B) will remain the same, for example, if part (A) and part (B) are mixed in a 1:1 weight ratio, then before, for example, molding, there may be, for example, 49.5 weight percent of each of part (A) and part (B) and 1 weight percent of component (e) or component (e)(i) mixed together.

[0195] Thus, it has been found that when used in combination with component (e), the introduction of component (f) (one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate) into the silicone rubber composition herein in an amount of 0.25% to 5.0% by weight of the composition results in surprisingly improved compression set. It has also been determined that component (f) can be introduced into component (A), component (B), component (A) and component (B), and / or can be mixed with component (e) or component (e)(i) and introduced with it when introduced separately from part (A) and part (B) as described above.

[0196] The low compression set silicone elastomer compositions and methods herein can be used in applications such as acting as a barrier to prevent absorption or penetration of air, dust, noise, liquids, gaseous materials, or dirt.The silicone elastomer materials having low compression set as described herein can be used in gaskets.

[0197] They are also used in a wide range of electrical and / or insulating applications. In the case of electrical applications, they can be used for wiring / cables / power supplies, etc. For example, the silicone elastomer materials produced by the compositions described herein can be used in a variety of applications, such as silicone coatings as standard non-silicone insulators, as cable coatings such as safety cables, for cable accessories such as electrical connectors, terminals and wire seals. Electrical connectors are generally used to produce closed circuits in automobiles, residences and infrastructure due to the excellent balance of their mechanical properties, chemical stability and thermal stability, ease of processing and the availability of self-lubricating formulations. They can be used to match rigid thermoplastic housing components to provide electrical isolation and environmental isolation to the connector joint, preventing moisture, oil and fuel and corrosive gases that may exist, for example. The silicone elastomer prepared using the compositions herein has a suitable low compression set at high temperatures, to provide mechanical integrity and dimensional stability electrical connectors, etc. as described above, thereby providing excellent sealing performance during the service life.

[0198] Such electrical connectors, terminals and wire seals can be used in automotive applications for electric vehicle (EV) battery packs, EV batteries, control units in EVs (e.g., motor control unit (MCU) devices), lamp housings, fuse boxes, air filters, waterproof connectors, air conditioners, lighting devices, electronic components. They can also be used in or for spark plugs, such as spark plug boots for internal combustion engines.

[0199] Other applications include exterior waterproofing applications and equipment designed for drip / trick irrigation applications (e.g., micro-irrigation systems that slowly drip water and nutrients from above the soil surface or buried below the ground surface to plant roots). As such, they are used to make automotive parts, such as cable accessories; electrical and electronic parts; packaging parts; structural parts, such as sealants; and home furnishing parts. Example

[0200] Unless otherwise specified, all viscosities are measured at 25° C. Unless otherwise specified, the viscosities of the various components in the following examples were measured using a Brookfield 1000 with spindle LV-4 for viscosities exceeding 15,000 mPa.s. TM A rotational viscometer (spindle LV-4 designed for viscosities in the range of 1,000 mPa.s to 2,000,000 mPa.s) was measured at appropriate rpm, and for viscosities up to 15,000 mPa.s a Brookfield with cone and plate arrangement with cone CP-52 was used at appropriate rpm. TM Rotational viscometer measurement.

[0201] All compression set results were performed according to industry standard specification ISO 815-1:2019 Method A, where a cylindrical disk with a diameter of 29.0 mm ± 0.5 mm and a thickness of 12.5 mm ± 0.5 mm was compressed 25% to approximately 9.38 mm thickness. Under compression, LSR buttons (previously cured at 175°C for 10 minutes) were placed in a convection oven between two metal plates and held at elevated temperatures for a specified period of time (see table below), after which the compression was released and the test piece was allowed to recover to a thickness close to the starting thickness, allowing the compression set to be determined.

[0202] Three Part A and Part B compositions were prepared based on the 2-part liquid silicone rubber elastomer compositions (Elas. 1, 2 and 3) shown in Table 1 as standard starting compositions.

[0203] Table 1: 2-part liquid silicone rubber elastomer compositions (Elas. 1, 2 and 3)

[0204]

[0205] In Table 1:

[0206] Masterbatch 1: Masterbatch 1 contains:

[0207] 70.8 parts by weight of dimethylvinylsiloxy terminated polydimethylsiloxane having a viscosity of about 53,000 mPa.s at 25° C., the viscosity being measured using a Brookfield with spindle LV-4 TM The rotational viscometer was measured at 6 rpm, and

[0208] The surface area of ​​22.4 parts by weight is about 300m 2 / g of fumed silica filler. The silica is hydrophobized and does not contain vinyl functional groups;

[0209] Masterbatch 2: Masterbatch 2 contains:

[0210] 66.6 parts by weight of dimethylvinylsiloxy terminated polydimethylsiloxane having a viscosity of about 55 Pa.s at 25° C., the viscosity being measured using a Brookfield with spindle LV-4. TM The rotational viscometer was measured at 6 rpm, and

[0211] The surface area of ​​25.8 parts by weight is about 300m 2 / g of fumed silica filler. The silica is hydrophobized and has about 0.178 mmol / g of vinyl functional groups.

[0212] The values ​​given as parts by weight are not percentage values ​​and therefore do not necessarily add to 100.

[0213] Polymer 1: Polymer 1 is a vinyl dimethyl terminated polydimethylsiloxane having a viscosity of 53,000 mPa.s at 25°C as measured using a Brookfield TM The rotational viscometer was measured at 6 rpm.

[0214] Polymer 2: Polymer 2 is a vinyl terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a viscosity of 370 mPa.s at 25°C measured at 12 rpm using a Brookfield 1000 with a cone and plate arrangement with cone CP-52. TM Rotational viscometer measurement,

[0215] Crosslinker 1: Crosslinker 1 is trimethyl terminated polymethylhydrogendimethylsiloxane having a viscosity of 30 mPa.s at 25°C as measured using a Brookfield 1000 with cone and plate arrangement with cone CP-52. TM The rotational viscometer was measured at 12 rpm.

[0216] Release agent: The release agent is a hydroxydimethyl terminated polydimethylsiloxane having a viscosity of about 21 mPa.s at 25°C, which is measured using a Brookfield TM The rotational viscometer was measured at 12 rpm.

[0217] Cyclotetrasiloxane: Cyclotetrasiloxane is tetravinyl-tetramethyl-cyclotetrasiloxane

[0218] Phenyl Methyl Siloxane Copolymer: Phenyl Methyl Siloxane Copolymer is a trimethylsilyl terminated phenyl methyl siloxane dimethyl siloxane copolymer having a viscosity of 125 mPa.s at 25°C as measured using a Brookfield 1000 with cone and plate arrangement with cone CP-52. TM The rotational viscometer was measured at 12 rpm.

[0219] CDA 6: CDA 6 is dodecanedioyl-bis-(N'-salicyloyl)hydrazine, a synonym of which is 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide, which is used as ADK STAB TM CDA-6 is commercially available from Adeka Corporation.

[0220] In the corresponding use. The part (A) and part (B) compositions are mixed together in a 1:1 weight ratio. Except for the examples and comparative examples prepared using Elas.3, which contains a small amount of CDA-6 in the part B composition, in the examples herein, the composition is prepared with compression set additives (e)(i), (e)(ii) and / or (e)(iii), which are added during or after the relevant part (A) composition and part (B) composition are mixed together. Therefore, in Ex.2, which introduces a combined amount of 4.6 weight percent, the cured final mixture is a combination of 47.7% part (A) as defined in Table 1 above, 47.7% part (B) as defined in Table 1 above, together with different amounts of compression set additives.

[0221] The Part A and Part B compositions of Elas. 1 described above were used to prepare the test samples shown in Table 2 below.

[0222] Table 2a: Composition using Elas.1 as LSR

[0223]

[0224] wherein Cupc Add.1 is a mixture of 30 wt% copper phthalocyanine in vinyldimethylsiloxy terminated polydimethylsiloxane having a viscosity of about 9000 mPa.s at 25°C;

[0225] MgCO 3 (1) Light magnesium carbonate (Mg) sold as Sigma-Aldrich product number 13118 5 (CO 3 ) 4 (OH) 2 .4H 2 O)(Basic magnesium carbonate (purum, light, > / =40% Mg (as MgO), powder (light)))

[0226] Unless otherwise stated, the resulting silicone rubbers were not post-cured. Post-cured samples were post-cured at 200°C for 4 hours. Unless otherwise stated, all subsequent compression set results were determined according to International Organization for Standardization (ISO) Test 815-1:2019 Method A as described above. After curing, the elastomers prepared using the compositions described in Table 2a were subjected to compression at 175°C for 22 hours.

[0227] Table 2b: Compression set results after compression at 175°C for 22 hours using the compositions from Table 2a, giving the maximum Close integer.

[0228] Compressed at 175℃ for 22 hours Ref.1 58 C.1 18 Example 1 15 Example 2 11

[0229] While C.1, Ex.1, and Ex.2 all show compression set better than the reference sample, it can be seen that the combination of CDA-6, copper phthalocyanine, and magnesium carbonate in Ex.2 provides the best compression set results after 22 hours.

[0230] In another series of Examples and Comparative Examples, samples were prepared according to the compositions shown in Table 3a, using Part A and Part B of Elas.3 to prepare the alkaline composition.

[0231] Table 3a: Compression set additives at different concentrations added to Elas.3 (part B contains 0.05 wt. % CDA-6, so when Part A and Part B are mixed together, the content of CDA-6 is 0.025 wt %).

[0232]

[0233] Cupc Add.2 is a Brookfield with a cone and plate arrangement with cone CP-52 at 25°C of about 2000 mPa.s (at 3 rpm using a cone and plate arrangement with cone CP-52). TM The viscosity of the mixture was measured by rotational viscometer (15 wt% copper phthalocyanine in vinyldimethylsiloxy terminated polydimethylsiloxane). The presence of 3 wt% Cupc Add.2 equals 0.45 wt% copper phthalocyanine present in the composition.

[0234] Table 3b: Compression set results after compression at 175°C for 22 hours and 168 hours (give the nearest integer) number).

[0235] Compressed at 175℃ for 22 hours Compression at 175°C for 168 hours Comparison 2 23 44 Comparison 3 17 30 Example 3 8 16 Example 4 6 13 Compare 5 (PC) 8 Example 5 6 Example 6 (PC) 4

[0236] Increasing the amount of CDA-6 did not result in any improvement in compression set. In fact, increasing the presence of CDA-6 appeared to worsen the results presented herein.

[0237] It should be noted that in Table 2b, Comparative Examples 2 and 3 give worse results than Comparative Example 1, which is considered to confirm the significant negative impact of the presence of CDA-6. Examples 3 to 6 show the positive effect of CuPc. The presence of both magnesium carbonate and magnesium hydroxide improves the results, but the composition containing magnesium carbonate gives better overall results.

[0238] Comparative Example 5 shows the post-curing effect of magnesium carbonate, so it can be seen that there is a synergistic effect when CuPc is combined with magnesium carbonate and magnesium hydroxide, but the combination of CuPc and magnesium carbonate appears to be superior.

[0239] Examples 4 and 5 effectively give the same expected results since they are different samples of the same composition. Example 6 is the same composition but the material is post cured and, perhaps surprisingly, the post cured material has only a slight further improvement. Thus, even without post curing, Examples 4 and 5 show very good initial compression set.

[0240] A further series of experiments were carried out using the compositions described in Table 4a to prepare test samples. In these examples, the effect of post-curing was considered to be the effect of magnesium carbonate alone in combination with CDA-6 present in the initial composition.

[0241] Table 4a: Compression set additives at different concentrations added to Elas.3 (part B

[0242]

[0243] The compression set results for the elastomers prepared from the above compositions at 175°C for different time periods are provided in Table 4b.

[0244] Table 4b: Compression set after heating / compression at 175°C using Elas.3 and classified compositions (give the closest integer).

[0245]

[0246] Contains 0.05 wt% CDA-6, so when Part A and Part B are mixed together, the CDA-6 content is 0.025 wt%).

[0247]

[0248] It is found in Table 4b that the post-curing shown in Comparative Examples 7 and 8 does not significantly improve the compression set after compression at 175°C compared to Comparative Examples 6 and 7, respectively, regardless of the duration between 22 hours and 1008 hours. Comparative Example 8, which only adds magnesium carbonate to Elas.3, gives the worst results in compression set, even with post-curing. The compositions of Comparative Examples 6 and 7 do not contain magnesium carbonate and give better results than Comparative Example 8, but the best results (especially after 1008 hours of compression) are obtained from Examples 7 and 8, which contain CDA-6 in elas.3 together with a combination of copper phthalocyanine and magnesium carbonate.

[0249] Another series of experiments was carried out after preparing and curing another series of compositions as shown in Table 5a. In this case, Elas.2 was used as defined in Table 1. Therefore, the basic elas.2 composition used did not contain a compression set additive.

[0250] Table 5a: A series of compositions tested using Elas.2 as the alkaline composition

[0251]

[0252] The above MgCO 3 (2) Dypingite (Mg 5 (CO 3 ) 4 (OH) 2 .5H2 O), sometimes referred to as heavy magnesium carbonate.

[0253] Table 5b: Compression set after compression at 175°C for different time periods as indicated using Elas.2 and classified additives (Give the nearest integer).

[0254] 22h 168h 504h 1008h Ref.2 57 68 75 82 Ref.3 9 28 42 57 C.9 15 37 51 70 C.10 57 65 66 74 C.11 53 63 65 76 C.12 6 18 29 43 C.13 12 27 41 56 C.14 12 32 47 60 Example 9 7 19 34 42 Example 10 7 17 31 40 Embodiment 11 6 21 36 47 Example 12 6 24 39 51

[0255] It should be understood that the use of copper phthalocyanine is necessary to achieve excellent long-term compression set performance. The use of magnesium carbonate shows marginal improvement over pure CuPc. Although the presence of CDA-6 appears to benefit initial compression set, in the CuPc / MgCO 3 It seems that once the optimum is reached, the positive effect of CDA-6 over longer periods of time appears to be much smaller, which may ultimately be detrimental to compression set.

Claims

1. A silicone rubber composition, comprising the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa.s to 100,000 mPa.s at 25°C; b) organosilicon compounds having at least two, alternatively at least three Si—H groups per molecule; c) optionally hydrophobically treated silica reinforcing fillers; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) a compression set additive selected from (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally (ii) one or more compounds selected from diacylhydrazide-based compounds; The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (ie, (i) + (ii)); and f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount ranging from 0.25% to 5.0% by weight of the composition; The total weight % of the composition is 100 weight %.

2. The silicone rubber composition according to claim 1, wherein the component (e)(i) is copper phthalocyanine present in the composition in an amount of 0.02% to 2.5% by weight of the composition.

3. A silicone rubber composition according to any preceding claim, wherein component (e)(i) is delivered alone or in the form of a masterbatch or mixture with a dimethylvinyl terminated polydimethylsiloxane having a viscosity of from 1000 mPa.s at 25°C to 25000 mPa.s at 25°C.

4. A silicone rubber composition according to any preceding claim, wherein component (f) is magnesium carbonate, magnesium hydroxycarbonate or mixtures thereof in an amount of 0.25 to 5.0 wt% of the composition.

5. The silicone rubber composition according to claim 4, wherein the magnesium carbonate, magnesium hydroxycarbonate or mixture is selected from MgCO3, MgCO3.2H2O, MgCO3.3H2O, MgCO3.5H2O, Mg2(CO3)(OH)2.0.5H2O, Mg2(CO3)(OH)2.3H2O, Mg5(CO3)4(OH)2.4H2O, Mg5(CO3)4(OH)2.5H2O, Mg5(CO3)4(OH)2.5-6H2O and Mg7(CO3)5(OH)4.24H2O.

6. A silicone rubber composition according to any preceding claim wherein component (e)(ii) is present in an amount of from 0.001% to 1.0% by weight of the composition.

7. A silicone elastomeric material which is a cured product of the hydrosilylation-curable silicone rubber composition, and which has a compression set of not more than 20% when measured after compression at 175°C for 22 hours according to industrial standard specification ISO 815-1 Method A.

8. A method for preparing a silicone elastomer material, the method comprising the steps of mixing a hydrosilylation-curable silicone rubber composition having the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa.s to 100,000 mPa.s at 25°C; b) organosilicon compounds having at least two, alternatively at least three Si—H groups per molecule; c) optionally hydrophobically treated silica reinforcing fillers; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) a compression set additive selected from (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally (ii) one or more compounds selected from diacylhydrazide-based compounds; The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (ie, (i) + (ii)); and f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount ranging from 0.25% to 5.0% by weight of the composition; wherein the total weight % of the composition is 100 weight %; and curing the composition at a temperature of 80°C to 200°C.

9. A method for preparing a silicone elastomer material according to claim 8, wherein the magnesium carbonate, magnesium hydroxycarbonate or mixture of component (f) is selected from MgCO3, MgCO3.2H2O, MgCO3.3H2O, MgCO3.5H2O, Mg2(CO3)(OH)2.0.5H2O, Mg2(CO3)(OH)2.3H2O, Mg5(CO3)4(OH)2.4H2O, Mg5(CO3)4(OH)2.5H2O, Mg5(CO3)4(OH)2.5-6H2O and Mg7(CO3)5(OH)4.24H2O.

10. A silicone elastomer material obtained or obtainable by a method comprising the steps of: mixing the hydrosilylation-curable silicone rubber composition according to any one of claims 1 to 6, and curing the composition at a temperature of 80°C to 200°C; The silicone elastomeric material has a compression set of no greater than 20% when measured according to industry standard specification ISO 815-1 Method A after compression at 175°C for 22 hours.

11. Use of the following in a silicone rubber composition as a means of reducing the compression set of the silicone elastomeric material formed by curing of the composition, when measured according to industry standard specification ISO 815-1 Method A: e) a compression set additive selected from (i) a phthalocyanine compound or a metal derivative of such a compound, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium and vanadium; and optionally (ii) one or more compounds selected from diacylhydrazide-based compounds; The compression set additive is cumulatively present in an amount of 0.02 wt % to 3.5 wt % of the composition (ie, (i) + (ii)); and f) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate or manganese carbonate in an amount ranging from 0.25% to 5.0% by weight of the composition; The silicone rubber composition originally comprises the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa.s to 100,000 mPa.s at 25°C; b) organosilicon compounds having at least two, alternatively at least three Si—H groups per molecule; c) optionally hydrophobically treated silica reinforcing fillers; d) A hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof.

12. The use according to claim 11, wherein the magnesium carbonate, magnesium hydroxycarbonate or mixture is selected from MgCO3, MgCO3.2H2O, MgCO3.3H2O, MgCO3.5H2O, Mg2(CO3)(OH)2.0.5H2O, Mg2(CO3)(OH)2.3H2O, Mg5(CO3)4(OH)2.4H2O, Mg5(CO3)4(OH)2.5H2O, Mg5(CO3)4(OH)2.5-6H2O and Mg7(CO3)5(OH)4.24H2O.

13. Use of the silicone elastomeric material according to claim 7 or claim 10 in the manufacture of automotive parts, such as cable accessories; electrical and electronic parts; packaging parts; structural parts, such as sealants; household parts; and gasket sealants.

14. Use of a silicone elastomer material according to claim 12, wherein the cable accessories are electrical connectors, electrical terminals and wire seals.

15. Use of the curable silicone rubber composition according to any one of claims 1 to 6 in or for the manufacture of automotive parts, cable accessories; electrical and electronic parts; packaging parts; structural parts such as sealants; household parts; and gasket sealants.

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