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 (greater than or equal to (> = 175 DEG C) compressive deformation according to ISO 815-1 process A, 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 the use of such materials as silicone coatings in the manufacture of standard non-silicone insulators or for the manufacture of these coatings, as cable coatings, e.g. For safety cables, in cable accessories such as electrical connectors, connector seals, terminals, and wire seals, as well as in the manufacture of cable accessories such as electrical connectors, connector seals, terminals, and wire seals. The invention also relates to the use of the hose and washer for other electrical and electronic components, in particular for the automotive industry and / or for hoses and washers for, for example, vehicle engines or as these hoses and washers.

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, which silicone elastomer material is produced by curing the hydrosilylation (addition) curable silicone rubber composition, and to a method for preparing the silicone elastomer material. The invention also extends to the following uses of such materials: use in silicone coatings for manufacturing standard non-silicone insulators or for manufacturing these coatings, use as cable coatings, for example for safety cables, use in cable accessories such as electrical connectors, connector seals, terminals and wire seals, and use in other electrical and electronic components, in particular for the automotive industry and / or use as or in hoses and gaskets for vehicle engines, for example.

[0002] The hydrosilylation curable silicone rubber composition contains

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

[0004] (ii) a compound 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 insulation applications, such as use in or for electrical connectors, which are commonly used to create closed circuits in automotive, residential and infrastructure settings.

[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 isolation 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 full operation, even more so since the introduction of electric and hybrid vehicles. Thus, an electrical failure can cause malfunctions or damage to devices such as radios, lights, ventilation units, etc. 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 in vehicles, 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 a silicone elastomer material, which can be defined as the loss of the ability of the silicone elastomer material to return to its initial 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 is determined as a percentage such that if there is complete recovery, i.e., if the thickness of the test sample is the same before and after the application of the load, the compression set value is 0%; conversely, if 25% of the silicone elastomer material compressed during the test remains unchanged upon removal of the load, 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 elastomer materials cannot return to their original thickness after being compressed for a specified period of time at a set (elevated) temperature is that the hydrosilylation-cured silicone compositions generally (if not always) do not undergo complete curing during the standard curing process. This is thought to be (at least in part) due to incomplete hydrosilylation caused by steric hindrance during the interaction of vinyl-containing silicone polymers, Si-H crosslinkers, and hydrosilylation catalysts (most typically platinum-based catalysts). Thus, when a hydrosilylation-cured silicone elastomer material is compressed at an elevated temperature, further crosslinking can occur within the silicone elastomer material, particularly at previously unreacted Si-H sites. Additionally, intermolecular bond formation can occur between polydimethylsiloxane (PDMS) chains, again particularly at sites where there is an excess of previously unreacted Si-H (via hydrolysis, oxidation, or thermally induced reaction pathways), and thermal, oxidative, and thermo-oxidative rearrangements can occur within or between the individual PDMS chains of the silicone elastomer material. The occurrence of one or more of the above will result in an increase in the crosslink density within the silicone elastomer material and thus a more rigid structure, which prevents the silicone elastomer material from returning to its initial thickness after compression.

[0009] Many silicone elastomer materials have significant compression set, for example even greater than 50% or even greater than 60% compression set after a short period of compression, such as 22 hours, at temperatures of 125 °C and 150 °C, and may suffer problems caused by corresponding changes in shape and / or a significant increase in hardness during long-term use in high-temperature applications unless they undergo a post-cure heating process. "Post-curing" is the most straightforward way to minimize compression set, where 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 hours or more). However, given the increased energy consumption and delay in manufacturing time, post-curing is generally not commercially desirable or indeed feasible.

[0010] In many of the above applications, it is generally desired that the silicone elastomer material have as low a compression deformation value as possible over a wide temperature range, 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 Specification for Automotive Electrical Connector Systems" test regime. Sealed connector assemblies are classified so that their suitability over a specific temperature range meets a given class of automotive specifications for that temperature range. There are currently five ranges designated as T1 to T5:

[0012] T1 is a temperature class from -40°C to +85°C;

[0013] T2 is a temperature range from -40°C to +100°C;

[0014] T3 is a temperature range from -40°C to +125°C;

[0015] T4 is a temperature range from -40°C to +150°C; and the current highest class is

[0016] T5 with a temperature range from -40°C to 175°C.

[0017] Current sealed connector assemblies meet the T3 temperature class. However, when vehicle manufacturers develop vehicles, due to reasons such as the need for better encapsulation, higher engine efficiency, and the use of turbochargers, the vehicle engine and its surroundings need to withstand higher temperatures. Therefore, an increasing number of electrical connectors made of silicone rubber need to operate at higher temperatures to meet the requirements of T4 and T5.

[0018] Given that it is not desirable to force post-cure each elastomer after curing, a variety of additives have been proposed to reduce compression set without the need for post-cure.

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

[0020] US8080598B2 proposes a hydrosilylation-curable silicone rubber that has low compression set without post-curing with a diacylhydrazine-based compound such as dodecanedioyl-di-(N'-salicyl)hydrazine, its synonyms 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedioylhydrazine, and several alternatives, in combination with a cure inhibitor selected from an acetylene-containing silane, a vinyl-containing low molecular weight organosiloxane compound, or an alcohol derivative having a carbon-carbon triple bond, to reduce compression set. The introduction of US8080598B2 states that "articles molded from organopolysiloxane rubber compositions curable by addition reaction and compounded with phthalocyanine compounds are limited in their practical applications due to the coloring caused by phthalocyanine." Despite the teachings in US8080598B2, US9289963B2, US9598575B2, and US10000680B2, phthalocyanine compounds are still turned to as compression set additives.

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

[0022] The present disclosure provides a hydrosilylation-curable silicone rubber composition comprising the following components:

[0023] a) one or more polyorganosiloxanes having 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) an organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule;

[0025] c) an optionally hydrophobically treated silica reinforcing filler;

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

[0027] e) A phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium;

[0028] f) Urea present in an amount of 0.005% to 0.2% by weight of the composition; and

[0029] g) One or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate present in an amount of 0.25% to 5.0% by weight of the composition;

[0030] wherein the total weight percentage of the composition is 100% by weight.

[0031] There is also provided a silicone elastomer material which is a cured product of the above-described hydrosilylation-curable silicone rubber composition, and which has a compression set of not more than 20% after being compressed for 22 hours at a temperature of up to 190 °C, alternatively up to 200 °C, as measured by the method A of the industrial standard ISO 815-1:2019.

[0032] There is also provided a method for preparing a silicone elastomer material, the method comprising the steps of: mixing the following:

[0033] a) One or more polyorganosiloxanes each containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups and having a viscosity in the range of 1000 mPa·s to 100,000 mPa·s at 25 °C;

[0034] b) An organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule;

[0035] c) Optionally, a silica reinforcing filler which has been hydrophobically treated;

[0036] d) A hydrosilylation catalyst comprising a platinum group metal or a compound thereof or consisting of the same;

[0037] e) A phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium;

[0038] f) Urea present in an amount of 0.005% to 0.2% by weight of the composition; and

[0039] g) One or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate present in an amount of 0.25% to 5.0% by weight of the composition;

[0040] and curing the composition at a temperature of 80 °C to 200 °C.

[0041] There is also provided a silicone elastomer material, which is obtained or obtainable by a method comprising the following steps: mixing the following substances:

[0042] a) one or more polyorganosiloxanes having 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;

[0043] b) an organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule;

[0044] c) an optionally hydrophobic-treated silica reinforcing filler;

[0045] d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or its compound;

[0046] e) a phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium;

[0047] f) urea present in an amount of 0.005% to 0.2% by weight of the composition; and

[0048] g) one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate present in an amount of 0.25% to 5.0% by weight of the composition;

[0049] wherein the total weight percentage of the composition is 100% by weight;

[0050] and curing the composition at a temperature of 80 °C to 200 °C;

[0051] When measured according to the method A of the industrial standard specification ISO 815-1:2019, the silicone elastomer material has a compression set of not more than 20% after being compressed for 22 hours at a temperature of up to 190 °C, alternatively up to 200 °C.

[0052] There is also provided the use of the combination of components (e), (f), and (g), wherein

[0053] e) is a phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium;

[0054] f) is urea present in an amount of 0.005% to 0.2% by weight of the composition; and

[0055] g) one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate in an amount of 0.25 wt% to 5.0 wt% of the composition;

[0056] The use is as a means of reducing compression set in a silicone elastomer material, which is the cured product of a hydrosilylation-curable silicone rubber composition, the silicone rubber composition further comprising the following components:

[0057] a) one or more polyorganosiloxanes having 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;

[0058] b) an organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule;

[0059] c) an optionally hydrophobic treated silica reinforcing filler;

[0060] d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or its compound;

[0061] wherein the total weight % of the composition is 100 wt%.

[0062] It has been found that, compared with the two most preferred commercially available compression set additives, namely the aforementioned dodecanedioyl-di-(N'-salicyl)hydrazide (synonym: 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedioylhydrazide) and 3-(n-salicyl)amino-1,2,4-triazole (synonym: 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide), the composition containing components (e), (f), and (g) as described herein provides a silicone elastomer with consistently improved (lower) compression over a wide temperature range from 100 °C to about 200 °C or even 225 °C.

[0063] The components of the composition will be described in more detail below.

[0064] Component (a)

[0065] Component (a) of the composition is one or more polyorganosiloxanes having 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.

[0066] Component (a) is a polyorganosiloxane having at least two unsaturated groups per molecule, such as polydiorganosiloxane, and these unsaturated groups are selected from alkenyl groups or alkynyl groups. Alternatively, component (a) has at least three unsaturated groups per molecule.

[0067] The unsaturated group of component (a) can be at the terminal position, side chain position, or both positions.

[0068] The alkenyl group can 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 possible alkenyl groups are exemplified by but not limited to the following: vinyl group, allyl group, methallyl group, propenyl group, and hexenyl group, as well as cyclohexenyl group.

[0069] The alkynyl group can 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 can be exemplified by but not limited to the following: ethynyl group, propynyl group, and butynyl group.

[0070] Component (a) has multiple units of formula (I): R’ a SiO (4-a) / 2 (I)

[0071] where each R’ is independently selected from aliphatic hydrocarbon groups, aliphatic non-halogenated organic groups (i.e., any aliphatic organic substituent group having a 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 above-mentioned alkenyl groups and alkynyl groups. Aliphatic non-halogenated organic groups are exemplified by but not limited to the following: suitable nitrogen-containing groups such as amido, 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 mainly 2, but may contain some units where a is 1 or 3.

[0072] When R’ is an alkyl group as described above, typically a methyl group, the siloxy units can be described by a shorthand (abbreviated) nomenclature, namely - “M”, “D”, “T”, and “Q”. The M unit corresponds to the siloxy unit with a = 3, i.e., R 3 SiO 1 / 2 ; the D unit corresponds to the siloxy unit with a = 2, i.e., R 2 SiO 2 / 2 ; the T unit corresponds to the siloxy unit with a = 1, i.e., R 1 SiO 3 / 2 ; the Q unit corresponds to the siloxy unit with a = 0, i.e., SiO 4 / 2The polyorganosiloxanes such as the polydiorganosiloxanes of component (a) are substantially linear, but may contain a certain proportion of branches due to the presence of T units within the molecule (as previously described), and thus the average value of subscript a in structure (i) is about 2.

[0073] Examples of typical R' groups on the polyorganosiloxanes of component (a) which contain at least two one or more 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), may also include aryl groups and / or fluoroalkyl groups, such as trifluoropropyl groups or perfluoroalkyl groups. These groups can be in the side chain position (on D or T siloxy units) or can be in the terminal position (on M siloxy units).

[0074] Thus, the polymer chains of component (a) can be selected from polydimethylsiloxanes, alkylmethylpolysiloxanes, alkylarylpolysiloxanes or copolymers thereof (wherein alkyl means any suitable alkyl group, alternatively an alkyl group having two or more carbons), provided that each component (a) polymer contains at least two alkenyl groups and / or alkynyl groups, usually at least two alkenyl groups. Such polymer chains can have any suitable end groups, for example, they can be trialkyl-capped, alkenyldialkyl-capped, alkynyldialkyl-capped, or can be capped with any other suitable combination of end groups, provided that each polymer contains at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule. In one embodiment, the end groups of such polymers do not include any silanol end groups.

[0075] Thus, for example, component (a) can be:

[0076] Dialkyl alkenyl-capped polydimethylsiloxanes, such as dimethylvinyl-capped polydimethylsiloxanes; dialkyl alkenyl-capped dimethylmethylphenylsiloxanes, such as dimethylvinyl-capped dimethylmethylphenylsiloxanes; trialkyl-capped dimethylmethylvinylpolysiloxanes; dialkyl vinyl-capped dimethylmethylvinylpolysiloxane copolymers; dialkyl vinyl-capped methylphenylpolysiloxanes, dialkyl alkenyl-capped methylvinylmethylphenylsiloxanes; dialkyl alkenyl-capped methylvinyldiphenylsiloxanes; dialkyl alkenyl-capped methylvinylmethylphenyldimethylsiloxanes; trimethyl-capped methylvinylmethylphenylsiloxanes; trimethyl-capped methylvinyldiphenylsiloxanes; or trimethyl-capped methylvinylmethylphenyldimethylsiloxanes.

[0077] Component (a) has a viscosity of from 1000 mPa·s to 100,000 mPa·s at 25 °C, alternatively from 5000 mPa·s to 75,000 mPa·s at 25 °C, from 10,000 mPa·s to 60,000 mPa·s at 25 °C, and is preferably present in an amount of from 25% to 60% by weight, alternatively from 30% to 60% by weight, alternatively from 35% to 55% by weight of the composition. The viscosity can be measured at 25 °C using a Brookfield TM rotational viscometer with spindle LV-4 (spindle LV-4 designed for viscosities in the range of 1,000 mPa·s to 2,000,000 mPa·s) at an appropriate rpm, and for viscosities up to 15,000 mPa·s at 25 °C and appropriate rpm using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52.

[0078] Component (b)

[0079] Component (b) is used as a crosslinking agent and is provided in the form of a silicone compound having at least two, alternatively at least three Si-H groups per molecule. Component (b) usually contains three or more silicon-bonded hydrogen atoms, so that the hydrogen atoms can react with the unsaturated alkenyl and / or alkynyl groups of component (a) to form a network structure therewith, and thus cure the composition. When polymer (a) has more than two unsaturated groups per molecule, some or all of component (b) can alternatively have two silicon-bonded hydrogen atoms per molecule.

[0080] The molecular configuration of the silicone compound (b) having at least two, alternatively at least three Si-H groups per molecule is not particularly limited. It can be a linear, branched (linear with some branches due to the presence of T groups), cyclic or silicone resin-based polyorganosiloxane.

[0081] Although the molecular weight of component (b) is not particularly limited, using the test method as described for component (a), the viscosity is usually from 5 mPa·s to 50,000 mPa·s at 25 °C.

[0082] The silicon-bonded organic groups used in component (b) may 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 haloalkyl groups, preferably alkyl groups having 1 to 6 carbons, especially methyl, ethyl or propyl or phenyl. Preferably, the silicon-bonded organic groups used in component (b) are alkyl groups, alternatively methyl, ethyl or propyl.

[0083] Examples of the organosilicon compound (b) having at least two, alternatively at least three Si-H groups per molecule include, but are not limited to:

[0084] (a’) Methylhydrogenpolysiloxane endblocked with trimethylsilyloxy,

[0085] (b’) Polydimethylsiloxane-methylhydrogensiloxane endblocked with trimethylsilyloxy,

[0086] (c’) Dimethylhydrogensiloxane endblocked with dimethylhydrogensiloxy-dimethylsiloxane-methylhydrogensiloxane copolymer,

[0087] (d’) Dimethylsiloxane-methylhydrogensiloxane cyclic copolymer,

[0088] (e’) Copolymer and / or organosilicon resin composed of (CH 3 ) 2 HSiO 1 / 2 units, (CH 3 ) 3 SiO 1 / 2 units and SiO 4 / 2 units,

[0089] (f’) Copolymer and / or silicone resin composed of (CH 3 ) 2 HSiO 1 / 2 units and SiO 4 / 2 units,

[0090] (g’) Methylhydrogensiloxane cyclic homopolymer having 3 to 10 silicon atoms per molecule;

[0091] Alternatively, the component (b) crosslinking agent may be a filler, such as silica treated with one of the above substances, and mixtures thereof.

[0092] In one embodiment, component (b) is selected from methylhydrogenpolysiloxanes endblocked with trimethylsilyloxy groups at both molecular ends; copolymers of methylhydrogensiloxane and dimethylsiloxane endblocked with trimethylsilyloxy groups at both molecular ends; dimethylsiloxanes endblocked with dimethylhydrogensiloxy groups at both molecular ends; copolymers of methylhydrogensiloxane and dimethylsiloxane endblocked with dimethylhydrogensiloxy groups at both molecular ends.

[0093] 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 this ratio is less than 0.5:1, a well-cured composition is not obtained. When this 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 the silicon-bonded hydrogen atoms of component (ii) to the 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.

[0094] The silicon-bonded hydrogen (Si-H) content of component (b) is determined by quantitative infrared analysis in accordance with ASTM E168. In this case, when relying on the hydrosilylation curing process, the ratio of silicon-bonded hydrogen to alkenyl (vinyl) and / or alkynyl 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 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].

[0095] Generally, depending on the number of unsaturated groups in component (a) and the number of Si-H groups in component (b), component (b) will be present in the following amounts: 0.1 wt% to 10 wt% of the hydrosilylation-curable silicone rubber composition, alternatively 0.1 wt% to 7.5 wt% of the hydrosilylation-curable silicone rubber composition, alternatively 0.5 wt% to 7.5 wt% of the composition, and further alternatively 0.5 wt% to 5 wt% of the hydrosilylation-curable silicone rubber composition.

[0096] Component (c)

[0097] Component (c) is an optionally hydrophobically treated silica reinforcing filler; the reinforcing filler of component (c) may 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.

[0098] Precipitated silica, fumed silica and / or colloidal silica are particularly preferred because of their relatively high surface area (especially when provided in a finely divided form, usually at least 50 m2 / g (BET method according to ISO 9277:2010)). Fillers with a surface area of 50 to 450 m2 / g (BET method according to ISO 9277:2010), alternatively 50 to 300 m2 / g (BET method according to ISO 9277:2010) are typically used. All these types of silica are commercially available.

[0099] When the silica reinforcing filler (c) is naturally hydrophilic (e.g., untreated silica filler), it is usually treated with a treating agent to impart hydrophobicity thereto. 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 easy to be wetted by component (a).

[0100] Generally, the silica reinforcing filler (c) can be surface-treated with any low molecular weight silicone compound disclosed in the art that is suitable for preventing wrinkling of liquid silicone rubber (LSR) compositions during processing. For example, organosilanes, polydiorganosiloxanes or organosilazanes, such as hexadecyl disilazane, short-chain siloxane diols, to impart hydrophobicity to the silica reinforcing filler (c), and thus it is easier to handle and obtain a homogeneous mixture with other components. Specific examples include, but are not limited to, silanol-terminated trifluoropropylmethylsiloxane, silanol-terminated vinylmethyl (ViMe) siloxane, silanol-terminated methylphenyl (MePh) siloxane, liquid hydroxy dimethyl-terminated polydiorganosiloxane having an average of 2 to 20 repeating units of diorganosiloxane per molecule, hydroxy dimethyl-terminated phenylmethylsiloxane, hexaorganodisiloxanes such as hexamethyldisiloxane, divinyltetramethyldisiloxane; hexaorganodisilazanes, such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane and tetramethylbis(trifluoropropyl)disilazane; hydroxy dimethyl-terminated polydimethylmethylvinylsiloxane, octamethylcyclotetrasiloxane and silanes, including but not limited to methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, trichloromethylsilane.

[0101] In one embodiment, the treating agent may be selected from silanol-terminated vinylmethyl (ViMe) siloxanes, liquid hydroxy-dimethyl-terminated polydiorganosiloxanes having an average of 2 to 20 diorganosiloxane repeating units per molecule, hexaorganodisiloxanes such as hexamethyldisiloxane, divinyltetramethyldisiloxane; hexaorganodisilazanes such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane; and hydroxy-dimethyl-terminated polydimethylmethylvinylsiloxane, octamethylcyclotetrasiloxane and silanes, including but not limited to methyltriethoxysilane, dimethyldiethoxysilane and / or vinyltriethoxysilane. A small amount of water may be added together with the silica treating agent as a processing aid.

[0102] The surface treatment of the untreated silica reinforcing filler (c) can be carried out before introducing the composition or in situ (i.e., in the presence of at least a portion of the other components of the present composition, by blending these components together at room temperature or higher temperature until the filler is completely treated). Generally, the untreated silica reinforcing filler (c) is treated in situ with the 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 other components.

[0103] The silica reinforcing filler (c) is optionally present in the composition in an amount of up to 40 wt%, alternatively 1.0 wt% to 40 wt% of the composition, alternatively 5.0 wt% to 35 wt% of the composition, alternatively 10.0 wt% to 35 wt% of the composition.

[0104] Component (d)

[0105] Component (d) of the composition is a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof. These catalysts are generally selected from catalysts of platinum group metals (platinum, ruthenium, osmium, rhodium, iridium and palladium), or compounds of one or more of 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 most preferred. In the hydrosilylation (or addition) reaction, a hydrosilylation catalyst such as component (d) herein catalyzes the reaction between an unsaturated group (usually an alkenyl group, e.g., vinyl) and a Si-H group.

[0106] The catalyst (d) can be a platinum group metal, a platinum group metal deposited on a support (such as activated carbon, metal oxides 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.

[0107] 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 (e.g., hexachloroplatinic acid (Pt in the IV oxidation state) (Speier catalyst)), chloroplatinic acid in a solution of an alcohol (e.g., isooctanol or pentanol) (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 tetraethenyltetramethylcyclotetrasiloxane-platinum complex (Ashby catalyst). Soluble platinum compounds that can be used include, for example, platinum-olefin complexes of the formula (PtCl 2 . olefin) 2 and H(PtCl 3 . olefin). In this context, olefins having 2 to 8 carbon atoms, such as isomers of ethylene, propylene, butene, and isomers of octene, or cycloalkanes having 5 to 7 carbon atoms, such as cyclopentene, cyclohexene, and cycloheptene, are preferably used. Other soluble platinum catalysts are, for example, platinum-cyclopropane complexes of the formula (PtCl 2 C 3 H 6 ), 2 reaction products of hexachloroplatinic acid with alcohols, ethers, and aldehydes or mixtures thereof, or reaction products of hexachloroplatinic acid and / or its transformation products with vinyl-containing siloxanes such as methylvinylcyclotetrasiloxane in the presence of an ethanol solution containing sodium bicarbonate. Platinum catalysts having phosphorus and amine ligands can also be used, such as (Ph 3 P) 2 PtCl 2 ; and complexes of platinum with vinyl-containing siloxanes such as symmetric divinyltetramethyldisiloxane.

[0108] Thus, specific examples of suitable platinum-based catalysts include

[0109] (i) complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups, as described in US 3,419,593;

[0110] (ii) chloroplatinic acid in the hexahydrate form or the anhydrous form;

[0111] (iii) platinum-containing catalysts obtained by a method comprising the step of reacting chloroplatinic acid with an aliphatic unsaturated organosilicon compound such as divinyltetramethyldisiloxane;

[0112] (iv) olefin-platinum-silyl complexes as described in US Patent 6,605,734, such as (COD)Pt(SiMeCl 2 ) 2, where "COD" is 1,5 - cyclooctadiene; and / or

[0113] (v) A Karstedt catalyst, a platinum divinyltetramethyldisiloxane complex, typically containing about 1 wt% platinum in a vinylsiloxane polymer having a viscosity of about 200 mPa·s to 750 mPa·s, typically using the test method as described for component (a).

[0114] Solvents such as toluene and similar organic solvents have historically been used as alternatives, but the use of vinylsiloxane polymers has so far been the preferred choice. These are described in US 3,715,334 and US 3,814,730. In a preferred embodiment, component (d) can 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.

[0115] 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 components, i.e., components (a) and (b). The catalyst can be added as a single substance or as a mixture of two or more different substances. Generally, depending on the form / concentration of the catalyst provided, the amount of the catalyst present will be in the range of 0.05 wt% - 1.5 wt%, alternatively 0.05 wt% - 1.0 wt%, alternatively 0.1 wt% - 1.0 wt%, alternatively 0.1 wt% to 0.5 wt% of the composition, where the platinum catalyst is provided in the masterbatch of the polymer (such as (a) as described above).

[0116] Component (e)

[0117] Component (e) of the hydrosilylation - curable silicone rubber composition is a phthalocyanine compound or a metal derivative of such a compound, where the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, or vanadium. For example, the phthalocyanine compound can have the following structure:

[0118]

[0119] Metal phthalocyanines such as copper phthalocyanine are as follows:

[0120]

[0121] In one embodiment, component (e) comprises or consists of copper phthalocyanine. Any suitable form of copper phthalocyanine can be used, such as the beta form of copper phthalocyanine of Pigment 15:3 or 15:4, and the alpha form of copper phthalocyanine of 15.2 can also be used. When sufficiently stable, the alpha form of copper phthalocyanine of 15:1 is suitable, and among them, the beta form of copper phthalocyanine of 15:3 or 15:4 is particularly preferred. The phthalocyanine compound of component (e) or a metal derivative of such a compound is present in the composition in an amount of 0.02% to 2.5% by weight of the composition, alternatively 0.1% to 2.5% by weight of the composition, alternatively 0.2% to 2.0% by weight of the composition.

[0122] It should be noted, however, 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 is 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% to 50% by weight of copper phthalocyanine and the balance consisting of a 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 30% by weight of copper phthalocyanine in a vinyldimethylsilyloxy-terminated polydimethylsiloxane having a viscosity of about 9000 mPa·s at 25°C (using a Brookfield TM rotational viscometer with a cone and plate arrangement with cone CP-52), and 15% by weight of copper phthalocyanine in a vinyldimethylsilyloxy-terminated polydimethylsiloxane having a viscosity of about 2000 mPa·s at 25°C (using a Brookfield TM rotational viscometer with a cone and plate arrangement with cone CP-52). In this case, when provided in such a masterbatch or mixture, the masterbatch or mixture is introduced into the composition in an amount of 0.2% to 5% by weight of the composition, and such a masterbatch or mixture can contain about 10% to 50% by weight of component (e), with the balance being a suitable polydimethylsiloxane.

[0123] Component (f)

[0124] Component f) is urea, an organic compound having the following chemical formula

[0125]

[0126] Urea is present in the compositions herein in an amount of from 0.005% to 0.2% by weight of the composition, alternatively from 0.01% to 0.2% by weight of the composition, alternatively from 0.05% to 0.2% by weight of the composition and is widely commercially available.

[0127] Component (g)

[0128] Component (g) is one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate or manganese carbonate. Magnesium carbonate and basic magnesium carbonate are particularly preferred.

[0129] These may include one or more magnesium carbonates selected from magnesite (MgCO 3 ), nesquehonite (MgCO 3 ·2H 2 O), lansfordite (MgCO 3 ·3H 2 O), pentahydromagnesite (MgCO 3 ·5H 2 O); and one or more basic magnesium carbonates such as 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 referred to as light magnesium carbonate), dypingite (Mg 5 (CO 3 ) 4 (OH) 2 .5H 2 O) (sometimes referred to as heavy magnesium carbonate), giorgiosite (Mg 5 (CO 3 ) 4 (OH) 2 .5-6H 2 O) and shelkovite (Mg 7 (CO 3 ) 5 (OH) 4 .24H 2(O). The component (g) is present in the composition in an amount of 0.25% to 5.0% by weight of the composition, alternatively 0.25% to 4.0% by weight of the composition, alternatively 0.25% to 3.0% by weight of the composition, alternatively 0.25% to 2.0% by weight of the composition.

[0130] Optional additive

[0131] Depending on the intended use, such a hydrosilylation-curable silicone rubber composition may also contain one or more optional additives. Examples include cure inhibitors, mold release agents, adhesion catalysts, peroxides, conductive fillers, heat conductive fillers, storage life extenders, lubricants, heat stabilizers, metal deactivators, UV light stabilizers, bactericides, wetting agents, etc.

[0132] Curing inhibitor

[0133] When needed, a cure inhibitor is used to prevent or delay the addition reaction curing process, especially during storage. Optional addition reaction inhibitors for platinum-based catalysts are well known in the art and include hydrazine, triazole, phosphine, thiol, organic nitrogen compounds, alkynols, methanesilylated alkynols, maleate esters, fumarate esters, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, vinyl siloxanes, unsaturated hydrocarbon monoesters and diesters, conjugated ene-ynes, hydroperoxides, nitriles, and diaziridines. Vinyl-substituted siloxanes as described in US3989667 can be used, where cyclic methyl vinyl siloxanes are preferred.

[0134] A class of known hydrosilylation reaction inhibitors are the acetylenic compounds disclosed in US3445420. Alkynols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors, which will inhibit the activity of platinum-containing catalysts at 25 °C. Compositions containing these inhibitors generally need to be heated at a temperature of 70 °C or above in order to cure at an achievable rate.

[0135] 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.

[0136] When present, an inhibitor concentration of metal as low as 1 mole inhibitor / mole catalyst will, in some cases, confer satisfactory storage stability and cure rate. In other cases, an inhibitor concentration of up to 500 moles inhibitor / mole catalyst of metal is required. The optimum concentration of a given inhibitor in a given composition is readily determined by routine experimentation. Depending on the concentration and form in which the selected inhibitor is provided / commercially available, when present in the composition, the inhibitor is generally present in an amount of 0.0125% to 10% by weight of the composition.

[0137] 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 greater than zero to 0.1% by weight of the composition.

[0138] Release agent

[0139] Any suitable release agent can be utilized. For example, it can be a hydroxyl dimethyl terminated polydimethylsiloxane having a viscosity of about 21 mPa·s at 25 °C, which viscosity is measured at 12 rpm using a Brookfield TM rotational viscometer with spindle LV-2.

[0140] Lubricant

[0141] Any suitable lubricant can be used. Examples of suitable lubricants include silicone oils such as trimethylsilyl terminated phenylmethylsiloxane dimethylsiloxane copolymer having a viscosity of 100 mPa·s to 200 mPa·s at 25 °C using the viscosity test method as described for component (a), and mixtures or derivatives thereof.

[0142] In an alternative embodiment herein, the composition does not contain a diacylhydrazine-based compound.

[0143] Thus, in an alternative, the present disclosure thus provides a silicone rubber composition comprising any suitable combination of the following components:

[0144] a) One or more polyorganosiloxanes having 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; alternatively, one or more polyorganosiloxanes having a viscosity of 5000 mPa·s to 75,000 mPa·s at 25 °C, or 10,000 mPa·s to 60,000 mPa·s at 25 °C, preferably present in an amount of 25% to 60% by weight of the composition, alternatively in an amount of 30% to 60% by weight of the composition, alternatively in an amount of 35% to 55% by weight of the composition. The viscosity can be measured at 25 °C using a rotational viscometer with spindle LV-4 (designed for viscosities in the range of 1,000 mPa·s to 2,000,000 mPa·s) and adjusting the speed according to the polymer viscosity.

[0145] 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, and further alternatively 0.5% to 5% by weight of the composition;

[0146] c) A silica reinforcing filler, preferably in a finely divided form and optionally hydrophobically treated; having a high surface area, typically at least 50 m2 / g (by the BET method according to ISO 9277:2010). The filler has a surface area of 50 m2 / g to 450 m2 / g (by the BET method according to ISO 9277:2010), alternatively 50 m2 / g to 300 m2 / g (by the BET method according to ISO 9277:2010) and is typically present in the following amounts: up to 40% by weight of the composition, alternatively 1.0% to 40% by weight of the composition, alternatively 5.0% to 35% by weight of the composition, alternatively 10.0% to 35% by weight of the composition;

[0147] d) A hydrosilylation catalyst comprising or consisting of a platinum group metal or its compound; the amount depends on the form / concentration of the catalyst provided and is in the range of 0.001% to 3.0% by weight of the composition, alternatively 0.001% to 1.5% by weight of the composition, alternatively 0.01% to 1.5% by weight of the composition, alternatively 0.01% to 0.10% by weight of the silicone rubber composition.

[0148] e) A phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium;

[0149] f) urea in an amount of 0.005% to 0.2% by weight of the composition; and

[0150] g) one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate or manganese carbonate, in an amount of 0.25% to 5.0% by weight of the composition, alternatively 0.25% to 4.0% by weight of the composition, alternatively 0.25% to 3.0% by weight of the composition, alternatively 0.25% to 2.0% by weight of the composition;

[0151] Provided that the total weight % of the composition is 100% by weight.

[0152] The composition may also contain one or more of the above-mentioned optional additives in the amounts indicated again, provided that the total weight % of the composition is 100% by weight.

[0153] The above-mentioned hydrosilylation-curable silicone rubber composition is usually stored in two or more parts before use. In the case of a two-part composition, these two parts are usually referred to as part (A) and part (B):

[0154] In addition to the polyorganosiloxane (a) and the silica reinforcing filler (c), part (A) usually contains a catalyst (d), and

[0155] Part (B) usually includes a crosslinking agent component (b), and optionally an inhibitor when present, and the remaining polyorganosiloxane (a) and / or silica reinforcing filler (c).

[0156] It is important to store the catalyst (d) separately from the crosslinking agent (b) to prevent premature curing during storage.

[0157] Components (e), (f) and (g) can be stored in part (A) or part (B) or in both parts, provided that they do not negatively affect the storage of any essential components present in the corresponding part (including that components (e), (f) and (g) do not negatively affect each other). Alternatively, if desired, components (e), (f) and (g) can be added to the remaining composition during or after mixing the part (A) composition and the part (B) composition before use, i.e., added to the combination of the part (A) and part (B) compositions.

[0158] Any optional additives other than the inhibitors described above can be incorporated in part (A) or part (B) or in both parts, provided that they do not negatively affect the storage of any essential components present in the corresponding part.

[0159] The composition can be designed to be mixed in any suitable ratio, for example, part (A): part (B) can be mixed together in a ratio of 10:1 to 1:10, alternatively 5:1 to 1:5, alternatively 2:1 to 1:2, but most preferably in a ratio of 1:1.

[0160] The ingredients / components in each of part (A) and / or part (B) can be individually mixed together in the corresponding part, or can be introduced into the composition in the form of a prefabricated combination, for example, to facilitate mixing of the final composition. For example, components (a) and (c) are usually mixed together before introducing other ingredients to form an LSR polymer base or masterbatch. These can then be mixed with other ingredients of the directly prepared part, or can be used to prepare prefabricated concentrates commonly referred to as masterbatches in the industry.

[0161] In this case, in order to facilitate mixing of the ingredients, one or more masterbatches can be used to successfully mix the ingredients to form part (A) and / or part (B) compositions. For example, a "fumed silica" masterbatch can be prepared. This is actually an LSR silicone rubber base with in-situ treated silica reinforcing filler (c).

[0162] Parts A and B of the composition can be prepared by combining all of their respective components at ambient temperature. Any mixing techniques and devices described in the prior art can be used for this purpose. The specific device to be used will depend on the components and the viscosity of the final composition. Suitable mixers can 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, Haake TM Rheomix OS Lab mixers, single-screw extruders or twin-screw extruders, etc. Alternatively, high-speed mixers such as those sold by, for example, Hauschild and designated as DC 150.1FV, DAC 400FVZ or DAC600FVZ can be used. It may be desirable to cool the components during mixing to avoid premature curing of the composition.

[0163] Before use, the corresponding part (A) and part (B) compositions are mixed together in the desired ratio.

[0164] The hydrosilylation-curable silicone rubber composition can be cured on a substrate, for example, in a mold, to form a molded part by injection molding such as compression molding, extrusion molding, transfer molding, pressure vulcanization or calendering using, for example, a liquid injection molding system (LIMS). Compression set test specimens can be molded into a suitable shape, such as a cylindrical disk with a diameter of 29.0 mm ± 0.5 mm and a thickness of 12.5 mm ± 0.5 mm, and they are compressed by 25% to a thickness of about 9.38 mm. These test specimens can be prepared in a mold, or alternatively can be cut from a pressed sheet of silicone elastomer material.

[0165] Under compression, an LSR button (previously cured at 175 °C for 10 minutes) is held between two metal plates in a convection oven for a suitable period of time, typically 22 hours at an 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 determination of the compression deformation.

[0166] The hydrosilylation-curable silicone rubber composition cures 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 of reducing compression deformation has historically been post-curing, with the aim of reducing the number of curable groups that may cure under compression during use as a gasket. It has surprisingly been found that the compositions as defined herein do not appear to benefit from the post-curing process, which will be further explained below.

[0167] In terms of the method of manufacturing the two-part silicone rubber composition as described above, the method may comprise the following steps:

[0168] (i) preparing a silicone base composition comprising component (a) a polymer and (c) a silica reinforcing filler;

[0169] (ii) dividing the resulting base into two parts, part (A) and part (B), introducing catalyst (d) into part (A), and introducing crosslinker (b) and inhibitor (if present) into part (B) composition;

[0170] (iii) introducing any other optional additives of other components into either or both of part (A) and part (B); and

[0171] (iv) storing part (A) and part (B) compositions separately.

[0172] In an alternative method, component (e) is not introduced separately into component (A) or component (B), but is introduced as part of the mixing process, for example during the mixing process before injection molding, when part (A) and part (B) compositions are mixed together.

[0173] Typically, part (A) and part (B) compositions are thoroughly mixed in a suitable weight ratio as described above, thoroughly mixed immediately before use to avoid premature curing. Then the curing stage is carried out for curing.

[0174] If / when component (e) is introduced together with parts (A) and (B) during mixing, typically, the weight ratio of parts (A) and (B) will remain the same. For example, if parts (A) and (B) are mixed in a 1:1 weight ratio, then prior to, for example, molding, there may be, for example, 49.5 wt% of each of parts (A) and (B) and 1 wt% of component (e) mixed together.

[0175] The low compression set silicone elastomer compositions and methods herein can be used in applications such as acting as a barrier against the absorption or penetration of air, dust, noise, liquids, gaseous substances, or dirt. The silicone elastomer materials having low compression set as described herein can be used for gaskets.

[0176] They are also used in a wide range of electrical and / or insulation applications. In the case of electrical applications, they can be used for wiring / cables / power supplies, etc. For example, the silicone elastomer materials produced from the compositions herein can be used in a variety of applications, such as a silicone coating for standard non-silicone insulators, a cable coating for, for example, safety cables, for cable accessories such as electrical connectors, terminals, and wire seals. Electrical connectors, due to their excellent balance of mechanical properties, chemical stability, and thermal stability, ease of processing, and availability of self-lubricating formulations, are commonly used to create closed circuits in automotive, residential, and infrastructure settings. They can be used in mating with rigid thermoplastic housing components to provide both electrical isolation and environmental isolation to the connector joint, preventing, for example, moisture, oil, and fuel that may be present, as well as corrosive gases. The silicone elastomers prepared using the compositions herein have a suitable low compression set at elevated temperatures to provide the mechanical integrity and dimensional stability as described above for electrical connectors, etc., thus providing excellent sealing performance during the service life.

[0177] 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 intercoolers and / or spark plugs, such as a spark plug shield for an internal combustion engine.

[0178] Other applications include external waterproofing applications. Thus, they are used in the manufacture of automotive components such as cable accessories; electrical and electronic components; packaging components; structural components such as sealants; home components. Examples

[0179] Unless otherwise specified, all viscosities are measured at 25 °C. Unless otherwise stated, the viscosities of the individual components in the following examples are measured using a Brookfield TM rotary viscometer with spindle LV-4 (designed for viscosities in the range of 1,000 mPa·s to 2,000,000 mPa·s) at the appropriate rpm, and for viscosities up to 15,000 mPa·s using a Brookfield TM rotary viscometer with a cone-plate arrangement with cone CP-52 at the appropriate rpm.

[0180] All compression set results are carried out according to industrial standard specification ISO 815-1:2019 Method A, where a cylindrical disc with a diameter of 29.0 mm ± 0.5 mm and a thickness of 12.5 mm ± 0.5 mm is compressed by 25% to a thickness of approximately 9.38 mm. Under compression, an LSR button (previously cured at 175 °C for 10 minutes) is held between two metal plates in a convection oven for a suitable period of time, typically for 22 hours at an elevated temperature, after which the compression is released and the test piece is allowed to recover to a thickness close to the starting thickness, thus allowing determination of the compression set.

[0181] A series of compositions are prepared using the two-part liquid silicone rubber elastomer compositions (Elas.1 and Elas.2) shown in Table 1 as standard starting compositions:

[0182] Table 1: 2 - part liquid silicone rubber (LSR) elastomer compositions (Elas.1–2)

[0183]

[0184] For the avoidance of doubt, in the examples herein, components (e), (f), and (g) (if present in each case) are added during or after mixing the relevant part (A) composition and part (B) composition to prepare the composition. Thus, in the case of introducing 0.1 wt% of a compression set additive, the final cured mixture is a combination of 49.95% of part (A) as defined in Table 1 above, 49.95% of part (B) as defined in Table 1 above together with 0.1 wt% of the compression set additive.

[0185] In the above compositions:

[0186] Masterbatch 1 : Masterbatch 1 contains:

[0187] 70.8 parts by weight of dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 53,000 mPa·s at 25°C, which viscosity is measured at 6 rpm using a Brookfield TM rotational viscometer with spindle LV-4, and

[0188] 22.4 parts by weight of fumed silica filler having a surface area of about 300 m 2 / g. The silica is hydrophobized and free of vinyl functional groups;

[0189] Masterbatch 2 : Masterbatch 2 contains:

[0190] 66.6 parts by weight of dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 55 Pa·s at 25°C, which viscosity is measured at 6 rpm using a Brookfield TM rotational viscometer with spindle LV-4, and

[0191] 25.8 parts by weight of fumed silica filler having a surface area of about 300 m 2 / g. The silica is hydrophobized and has about 0.178 mmol / g of vinyl functional groups.

[0192] The parts by weight values given are not percentage values and thus do not need to add up to 100.

[0193] Polymer 1 : Polymer 1 is a dimethylvinyl-terminated polydimethylsiloxane having a viscosity of 53,000 mPa·s at 25°C, which viscosity is measured at 6 rpm using a Brookfield TM rotational viscometer with spindle LV-4,

[0194] Polymer 2 : Polymer 2 is a vinyl-terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a viscosity of 370 mPa·s at 25°C, which viscosity is measured at 12 rpm using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52,

[0195] Crosslinker 1 : Crosslinker 1 is a trimethyl-terminated polymethylhydrodimethysiloxane having a viscosity of 30 mPa·s at 25°C, which viscosity is measured at 12 rpm using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52,

[0196] Release agent: The release agent is a hydroxyl-terminated dimethylpolysiloxane with a viscosity of approximately 21 mPa·s at 25 °C, which viscosity is measured using a Brookfield TM rotational viscometer with spindle LV-2 at 12 rpm,

[0197] Cyclotetrasiloxane : The cyclotetrasiloxane is tetravinyl-tetramethyl-cyclotetrasiloxane

[0198] Lubricant : The lubricant is a phenylmethylsiloxane copolymer, a trimethylsilyl-terminated phenylmethylsiloxane dimethylsiloxane copolymer, which has a viscosity of 125 mPa·s at 25 °C, which viscosity is measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm,

[0199] CDA6 : CDA 6 is dodecanedioyl-di-(N'-salicyl)hydrazide, the synonyms of which are 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedioylhydrazide, which is commercially available as ADK STAB TM CDA-6 is commercially obtained from Adeka Corporation.

[0200] In use, part (A) and part (B) compositions are mixed together in a 1:1 weight ratio. The resulting composition is inserted into a suitable mold and cured at 175 °C for a period of 10 minutes to form a button-shaped object with a thickness of 12.5 mm and a diameter of 29 mm. Unless otherwise stated, the resulting silicone rubber is not post-cured. The post-cured samples are post-cured at 200 °C for 4 hours. Unless otherwise stated, all subsequent compression set results are determined according to the International Organization for Standardization (ISO) test 815-1:2019 method A.

[0201] In the examples

[0202] Component (e) is exemplified as copper phthalocyanine and introduced into the composition in the form of a copper phthalocyanine additive, which copper phthalocyanine additive comprises 15% copper phthalocyanine in a vinyldimethylsiloxy polydimethylsiloxane having a viscosity of about 2000 mPa·s at 25 °C (using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 3 rpm) and is hereinafter referred to as "Cupc add";

[0203] Component (f) urea (if present) is from Sigma-Aldrich product number U0631 (BioXtra, pH 7.5 - 9.5 (20 °C, 5 M in H2 introduced in the form of an O solution;

[0204] The component (g) in the examples is hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O), which is sometimes referred to as light magnesium carbonate and is sold under the Sigma - Aldrich product number 13118 (basic magnesium carbonate (purum, light, ≥ 40% Mg (calculated as MgO), powder (light))).

[0205] Table 2a: Comparative compositions prepared using elas.2, containing 0.025 wt% of CDA - 6 but no urea

[0206]

[0207] The value of the Cupc additive for component e) in parentheses refers to the actual weight % amount of Cupc in the composition. For example, the difference between 3 and 0.45 (wt%) is the amount of silicone present.

[0208] The compression set of the cured products of Comparative Examples 1 to 5 compositions shown in Table 2a was tested for different periods of up to 1008 hours at 175 °C, and the results are shown in Table 2b.

[0209] Table 2b: Compression set results (given to the nearest integer) after testing elastomer samples prepared from Comparative Examples 1 to 5 at 175 °C for up to 1008 hours of the compression set test

[0210]

[0211]

[0212] The results show that in the absence of urea, the combination of CDA - 6, copper phthalocyanine, and magnesium carbonate provides the best compression set results. It should also be noted that the presence of the CDA - 6 / CuPc combination enables the 1008 - h test of hard and soft LSRs at 175 °C to produce a compression set (CS) value of less than 50%. It should be understood that the compositions of Comparative Example 1 and Comparative Example 2 are the same, but there is a slight improvement in the compression set result after the elastomer sample of Comparative Example 2 has been post - cured. Similarly, Comparative Example 3 and Comparative Example 4 have the same composition, but Comparative Example 4 is post - cured, which results in slightly better compression set results.

[0213] The same test was repeated using the same compositions as in Table 2b, but with compression carried out at 200 °C instead of 175 °C, and the results are listed in Table 2c.

[0214] Table 2c: Compression set results (given to the nearest integer) after testing Comparative Examples 1 to 5 at 200 °C for up to 1008 hours

[0215] 22h 168h 504h 1008h Comparative Example 1 11 43 60 83 Comparative Example 2 (PC) 9. 40 57 83 Comparative Example 3 11 33 50 83 Comparative Example 4 (PC) 9 32 49 83 Comparative Example 5 17 57 75 93

[0216] As can be seen from Table 2b and Table 2c, although the combination of CDA-6, CuPc, and magnesite provided an excellent starting point for the 1008 h test at 175 °C, they gave poorer results when the compression test was carried out after compression at 200 °C for some time. In fact, in most cases, the compression deformation was about 50% or more after only 504 h, and was very high after 1008 h. It was confirmed that after compression for up to 504 h, the compression deformation results of the post-cured samples did improve, but after long-term testing (1008 h), the post-cured samples were as poor as the non-post-cured samples.

[0217] A further series of examples were carried out in which urea was incorporated either alone or in combination with other ingredients / components. The compositions used are shown in Table 3a. In these examples, elas.1 was used, so the compositions did not contain CDA-6 as CDA-6 was absent from the composition.

[0218] Table 3a: Comparative compositions 6 to 9 and Example 1 using Elas.1 which does not contain any CDA - 6

[0219]

[0220] Table 3b: Compression set results (given to the nearest integer) of the elastomers prepared from Comparative Examples 6 to 9 and Example 1 after compression at 175 °C for the specified period 。

[0221] 22 hrs 168 hrs 504 hrs Comparative Example 6 16 39 59 Comparative Example 7 15 59 62 Comparative Example 8 12 21 29 Comparative Example 9 7 18 27 Example 1 13 21 26

[0222] Table 3c: Compression set results (given to the nearest integer) of the elastomers prepared from Comparative Examples 6 to 9 and Example 1 after compression at 200 °C for the specified period 。

[0223] 22 hrs 168 hrs 504 hrs 1008 hrs Comparative Example 6 25 75 104 107 Comparative Example 7 35 73 98 106 Comparative Example 8 16 31 61 78 Comparative Example 9 11 30 62 82 Example 1 16 30 58 74

[0224] Example 1 in which Cupc, urea, and hydromagnesite were all present showed the best compression deformation performance at two temperature ranges for a longer test period (at least after 504 h). This indicates that the introduction of urea led to an improvement in stability compared to when CDA-6 was used.

[0225] Table 4a: Compositions of Comparative Example 12 and Examples 7 to 9 prepared using Elas 3

[0226]

[0227] The compression deformation of the compositions shown in Table 4a was then tested at high temperature, and the results are provided in Table 4b below.

[0228] Table 4b: Compression set results (given to the nearest integer) of the first series of test pieces after compression at 200 °C for 168 hours and a basic study of the compression set of the second series of test pieces after compression at 225 °C for 72 hours. In each case, the samples had been post - cured at 200 °C for 4 hours before the compression set test

[0229] At 200 °C for 168 hours At 225 °C for 72 hours Comparative Example 10 36 58 Example 2 35 48 Example 83 35 49 Example 4 37 54

[0230] It can be seen that when measuring the compression deformation after compression at 200 °C for 168 hours, the performance of all samples is similar. However, after compression at a higher temperature of 225 °C for only 72 hours, Comparative Example 10 containing CDA-6 gives worse compression deformation results. The samples using the combination of Cupc, hydromagnesite and urea provide lower compression deformation. Although the composition containing CDA-6 seems to give good initial results, as time and temperature increase, the results of the composition containing CDA-6 become worse compared to the results of the examples according to the present disclosure.

[0231] Table 5a: Compositions of Comparative Example 12 and Examples 7 to 9 prepared using Elas 3

[0232]

[0233] Table 5b below summarizes the compression deformation results of Comparative Example 10, Comparative Example 11 and Example 6.

[0234] Table 5b: Comparison of the compression set (given to the nearest integer) of Comparative Example 11, Comparative Example 12 and Example 5 after aging at 225 °C for 72 hours

[0235] At 225 °C for 72 hours Comparative Example 11 53 Comparative 12 50 Example 5 47

[0236] It can be seen that compared with the composition containing only the CuPc additive, the composition containing urea, hydromagnesite and phthalocyanone ketone shows better results even without post-curing (Example 6). However, as expected, the post-cured sample (Comparative Example 11) is slightly better than the non-post-cured sample (Comparative Example 10).

Claims

1. A hydrosilylation-curable silicone rubber composition, said composition comprising the following components: a) one or more polyorganosiloxanes having 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) an organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule; c) an optionally hydrophobic-treated silica reinforcing filler; d) a hydrosilylation catalyst comprising a platinum group metal or a compound thereof or consisting of the same; e) a phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium; f) urea present in an amount of 0.005% to 0.2% by weight of the composition; and g) one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate present in an amount of 0.25% to 5.0% by weight of the composition; wherein the total weight percentage of the composition is 100% by weight.

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

3. The hydrosilylation-curable silicone rubber composition according to any one of the preceding claims, wherein component (e) is delivered alone or in the form of a masterbatch or mixture with dimethylvinyl-terminated polydimethylsiloxane having a viscosity of 1000 mPa·s at 25 °C to 25,000 mPa·s at 25 °C.

4. The hydrosilylation-curable silicone rubber composition according to any one of the preceding claims, wherein component (g) is magnesium carbonate, basic magnesium carbonate, or a mixture thereof present in an amount of 0.25% to 5.0% by weight of the composition.

5. The hydrosilylation-curable silicone rubber composition according to claim 4, wherein the magnesium carbonate, basic magnesium carbonate or mixture is selected from MgCO 3 , MgCO 3 .2H 2 O, MgCO 3 .3H 2 O, MgCO 3 .5H 2 O, Mg 2 (CO 3 )(OH) 2 .0.5H 2 O, Mg 2 (CO 3 )(OH) 2 .3H 2 O, Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O, Mg 5 (CO 3 ) 4 (OH) 2 .5H 2 O, Mg 5 (CO 3 ) 4 (OH) 2 .5-6H 2 O and Mg 7 (CO 3 ) 5 (OH) 4 .24H 2 O.

6. A silicone elastomer material, said silicone elastomer material being a cured product of the hydrosilylation-curable silicone rubber composition according to any one of the preceding claims.

7. A silicone elastomer material, said silicone elastomer material being obtained or obtainable by a method comprising the following steps: mixing the following: a) one or more polyorganosiloxanes having 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) an organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule; c) an optionally hydrophobic-treated silica reinforcing filler; d) a hydrosilylation catalyst comprising a platinum group metal or a compound thereof or consisting of the same; e) a phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium; f) urea in an amount of 0.005% to 0.2% by weight of the composition; and g) one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate in an amount of 0.25% to 5.0% by weight of the composition; wherein the total weight % of the composition is 100% by weight; and curing the composition at a temperature of 80°C to 200°C.

8. The silicone elastomer material according to claim 6 or 7, which has a compression set of no more than 20% after being compressed for 22 hours at a temperature of up to 190°C, alternatively up to 200°C, when measured according to Method A of Industrial Standard Specification ISO 815-1:2019.

9. A method for preparing the silicone elastomer material according to claim 6, the method comprising the steps of: mixing the following: a) one or more polyorganosiloxanes having 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) an organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule; c) an optionally hydrophobic treated silica reinforcing filler; d) a hydrosilylation catalyst comprising a platinum group metal or its compound or consisting thereof; e) a phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium; f) urea in an amount of 0.005% to 0.2% by weight of the composition; and g) one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate in an amount of 0.25% to 5.0% by weight of the composition; and curing the composition at a temperature of 80°C to 200°C.

10. A method for preparing the silicone elastomer material according to claim 9, wherein component (g) is magnesium carbonate, basic magnesium carbonate, or a mixture thereof in an amount of 0.25% to 5.0% by weight of the composition.

11. A method for preparing the silicone elastomer material according to claim 10, wherein the magnesium carbonate, basic magnesium carbonate or mixture is selected from MgCO 3 、MgCO 3 .2H 2 O、MgCO 3 .3H 2 O、MgCO 3 .5H 2 O、Mg 2 (CO 3 )(OH) 2 .0.5H 2 O、Mg 2 (CO 3 )(OH) 2 .3H 2 O、Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O、Mg 5 (CO 3 ) 4 (OH) 2 .5H 2 O、Mg 5 (CO 3 ) 4 (OH) 2 .5-6H 2 O and Mg 7 (CO 3 ) 5 (OH) 4 .24H 2 O。 12. Use of a combination of components (e), (f), and (g), wherein: e) is a phthalocyanine compound or a metal derivative of such a compound present in an amount of 0.02% to 2.5% by weight of the composition, wherein the metal is copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium; f) is urea in an amount of 0.005% to 0.2% by weight of the composition; and g) is one or more of magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, or manganese carbonate in an amount of 0.25% to 5.0% by weight of the composition; the use being as a means for reducing the compression set in a silicone elastomer material, which is a cured product of a hydrosilylation-curable silicone rubber composition that originally comprises the following components: a) One or more polyorganosiloxanes each containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups and having a viscosity in the range of 1000 mPa·s to 100,000 mPa·s at 25 °C; b) An organosilicon compound having at least two, alternatively at least three, Si-H groups per molecule; c) Optionally, a silica reinforcing filler treated with a hydrophobic treatment; d) A hydrosilylation catalyst comprising or consisting of a platinum group metal or its compound; wherein the total weight % of the composition is 100% by weight.

13. Use according to claim 12, wherein the component (g) is magnesium carbonate, basic magnesium carbonate or a mixture thereof, and the magnesium carbonate, basic magnesium carbonate or a mixture thereof is selected from MgCO 3 、MgCO 3 .2H 2 O、MgCO 3 .3H 2 O、MgCO 3 .5H 2 O、Mg 2 (CO 3 )(OH) 2 .0.5H 2 O、Mg 2 (CO 3 )(OH) 2 .3H 2 O、Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O、Mg 5 (CO 3 ) 4 (OH) 2 .5H 2 O、Mg 5 (CO 3 ) 4 (OH) 2 .5-6H 2 O and Mg 7 (CO 3 ) 5 (OH) 4 .24H 2 O。 14. Use of the silicone elastomer material according to claim 6, 7 or 8 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.

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

16. Use of the hydrosilylation-curable silicone rubber composition according to any one of claims 1 to 5 in the manufacture of automotive parts, cable accessories; electrical and electronic parts; packaging parts; structural parts such as sealants; household parts; and gasket sealants or for the manufacture thereof.

Images