Liquid silicone rubber composition

Abstract

The present disclosure relates to a hydrosilylation (addition) curable silicone rubber composition, a silicone elastomer material produced by curing the hydrosilylation (addition) curable silicone rubber composition and having improved high temperature (≧190°C) compression set according to ISO 815-1 Method A, and a method for preparing the silicone elastomer material.

Description

[Technical Field]

[0001] The present disclosure relates to hydrosilylation (addition) curable silicone rubber compositions, silicone elastomer materials produced by curing the hydrosilylation (addition) curable silicone rubber compositions and having improved high temperature (≧190°C) compression set according to ISO 815-1 Method A, and methods for preparing the silicone elastomer materials. The disclosure also extends to the use of such materials in or for the manufacture of silicone coatings for standard non-silicone insulation, the use of such materials as cable coatings, for example for safety cables, the use of such materials in cable accessories, such as electrical connectors, connector seals, terminals and wire seals and other electrical and electronic components, particularly for the automotive industry, and / or the use of such materials in hoses and gaskets, for example for vehicle engines.

[0002] 1. A hydrosilylation-curable silicone rubber composition comprising: (i) organopolysiloxane polymers having unsaturated (alkenyl and / or alkynyl) groups; (ii) compounds containing silicon-bonded hydrogen atoms, and (iii) a hydrosilylation catalyst; It is known in the art and is used to prepare silicone elastomer materials with 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 use in or for a wide range of electrical and / or insulating applications, such as electrical connectors commonly used to form closed electrical circuits in automotive, residential, and infrastructure environments.

[0003] For example, silicone elastomers (both liquid silicone rubber (LSR) and high consistency rubber (HCR)) are widely used as seals in and for electrical connectors due to their excellent balance of mechanical properties, chemical and thermal stability, and ease of processing. They can be used to mate rigid thermoplastic housing components, forming a tight connection that provides both electrical and environmental isolation to the connector interface. They can be used in automotive vehicles, which increasingly rely on electrical and electronic systems for their satisfactory operation, even more so since the introduction of electric and hybrid vehicles. Thus, electrical failures can lead to malfunctions or failures of devices such as radios, lights, and ventilation systems. Many of the electrical connectors used in such devices rely on the aforementioned silicone rubber materials to prevent electrical failures, which must be able to avoid, for example, vehicle failures during elevated engine temperatures.

[0004] Many of these applications require silicone elastomer materials to have low compression set, in addition to other uses such as electrical insulation and / or thermal stability. Compression set is an important 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 silicone elastomer material's ability to recover to its original thickness after being compressed for a specific period of time at a curing (elevated) temperature. Compression set values ​​can be measured, for example, according to industry standard ISO 815-1:2019 Methods A, B, or C and are specified as a percentage. For example, if there is complete recovery, i.e., the thickness of the test specimen is the same before and after the application of a load, the compression set is 0%. In contrast, if a 25% compression of the silicone elastomer material applied during testing remains unchanged when the load is removed, the compression set is 100% because it did not return to its original shape at all. Without being bound by any current theory, it is believed that the underlying cause of the inability of silicone-based elastomeric materials to recover to their original thickness after being compressed at cure (high) temperatures for a certain period of time is that hydrosilylation-curable silicone compositions often, if not always, do not undergo complete cure during standard curing processes. This is believed to be due, at least in part, to incomplete hydrosilylation due to steric hindrance during the interaction of the vinyl-containing silicone polymer, the Si-H crosslinker(s), and the hydrosilylation catalyst (most typically a platinum-based catalyst). Thus, when hydrosilylation-cured silicone elastomeric materials are compressed at elevated temperatures, further crosslinking can occur within the bulk of the silicone elastomeric material, specifically at previously unreacted Si-H sites. Furthermore, intermolecular bond formation can occur between polydimethylsiloxane (PDMS) chains, specifically at previously unreacted excess Si-H sites (via hydrolysis, oxidation, or thermally induced reaction pathways), 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 causes an increase in crosslink density within the silicone elastomer material, resulting in a more rigid structure that prevents the silicone elastomer material from returning to its original thickness after compression.

[0005] Many silicone elastomer materials have large compression sets, for example, greater than 50% or even greater than 60%, even after being compressed for short periods, such as 22 hours, at temperatures of 125°C and 150°C, and unless subjected to a post-cure heating process, may suffer problems caused by a consequent change in shape and / or a significant increase in hardness during long-term use in high-temperature applications. "Post-cure" is the simplest way to minimize compression set, in which case the hydrosilylation-cured silicone material is subjected to post-cure heating at 150°C or higher for a period of several hours, for example, 4 hours or more. However, post-cure is usually not commercially desirable or practically feasible in view of the increased energy consumption and delayed production time.

[0006] For many of the applications described above, it is typically desirable for silicone elastomeric materials to have compression set values ​​that are as low as possible, for example, 40% or less, over a wide range of temperatures.

[0007] 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 graded for their suitability for use over specific temperature ranges that meet the relevant automotive specification class for the given temperature range. Currently, there are five ranges, identified as T1 through T5: T1 is for the temperature class of -40℃ to +85℃, T2 is for the temperature range of -40°C to +100°C, T3 is for a temperature range of -40°C to +125°C, T4 is for a temperature range of -40°C to +150°C, and currently the highest grade is It is T5, which is for temperatures from -40℃ to 175℃.

[0008] Current sealed connector assemblies meet the T3 temperature class. However, vehicle manufacturers are developing vehicles that inevitably require them to withstand elevated temperatures in and around the vehicle engine due to, for example, better sealing, higher engine efficiency, and the use of turbochargers. Therefore, there is an increasing need for electrical connectors made from silicone rubber to function at even higher temperatures to meet T4 and T5 requirements.

[0009] Considering that it is undesirable to post-cure all elastomers after cure, various additives have been proposed to reduce compression set without the need for post-cure.

[0010] In U.S. Pat. No. 5,153,244, the compression set values ​​of hydrosilylation-cured silicones were substantially reduced by incorporating into the composition a phthalocyanine compound or a metal derivative of such a compound, where the metal was copper, nickel, cobalt, or iron.

[0011] In U.S. Patent No. 8,080,598 (B2), a diacylhydrazide compound such as dodecandioyl-di-(N'-salicyloyl)hydrazine (synonymous with 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide) and several other alternatives are used in combination with a cure inhibitor selected from acetylene-containing silanes, vinyl-containing low-molecular-weight organosiloxane compounds, or alcohol derivatives with a C-C triple bond to propose a hydrosilylation-cured silicone rubber with low compression set that does not require post-cure, thereby reducing compression set. The introduction to U.S. Patent No. 8,080,598 (B2) states, "Articles molded from organopolysiloxane rubber compositions curable by addition reaction and formulated with phthalocyanine compounds have limited practical use due to the coloration caused by the phthalocyanine." Despite the teachings of U.S. Pat. Nos. 8,080,598 (B2), 9,289,963 (B2), 9,598,575 (B2), and 10,000,680 (B2), there has been a return to using phthalocyanine compounds as compression set additives.

[0012] However, most of the previously available compression set additives, such as those mentioned above, are suitable for improving compression set after at least 22 hours of compression at the upper limit of T5 (+175°C), and most current silicone elastomers made from LSR mainly only meet the requirements of class T3 (up to 125°C) or T4 (up to 150°C), with a compression set of 50% or less after 1008 hours of compression at the respective temperatures. Therefore, they cannot work well enough to reduce compression set for the newer target performance at the permanent test temperature of 175°C (T5), which is being increasingly considered / proposed due to the ever-increasing demands of the automotive industry, etc.

[0013] Provided herein is a hydrosilylation-curable silicone rubber composition comprising the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl 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, or alternatively at least three, Si-H groups per molecule; c) silica reinforcing fillers, which are optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) phthalocyanine compounds or metal derivatives of such compounds, wherein the metals are copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium, and are present in an amount of 0.02% to 2.5% by weight of the composition; f) cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; and g) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25 to 2.0% by weight of the composition; A hydrosilylation-curable silicone rubber composition is provided, wherein the total weight percent of the composition is 100 weight percent.

[0014] Also provided is a silicone elastomer material that is the cured product of the hydrosilylation-curable silicone rubber composition, which has a compression set of 15% or less, preferably 10% or less, when measured according to industry standard ISO 815-1, Method A, after compression for 22 hours at 175°C, and a compression set of 20% or less, preferably 15% or less, when measured according to industry standard ISO 815-1, Method A, after compression for 22 hours at 200°C; or a compression set of 30% or less, preferably 25% or less, when measured according to industry standard ISO 815-1, Method A, after compression for 168 hours at 175°C, and a compression set of 40% or less, preferably 35% or less, when measured according to industry standard ISO 815-1, Method A, after compression for 168 hours (one week) at 200°C.

[0015] Also disclosed is a process for making a silicone elastomer material, comprising: a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl 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, or alternatively at least three, Si-H groups per molecule; c) silica reinforcing fillers, which are optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) phthalocyanine compounds or metal derivatives of such compounds, wherein the metals are copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium, and are present in an amount of 0.02% to 2.5% by weight of the composition; f) cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; and g) mixing one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25 to 2.0% by weight of the composition; and curing the composition at a temperature of from 80°C to 200°C.

[0016] Also, a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl 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, or alternatively at least three, Si-H groups per molecule; c) silica reinforcing fillers, which are optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) phthalocyanine compounds or metal derivatives of such compounds, wherein the metals are copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium, and are present in an amount of 0.02% to 2.5% by weight of the composition; f) cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; and g) mixing one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25-2.0% by weight of the composition, wherein the total weight percent of the composition is 100% by weight; and curing the composition at a temperature of from 80°C to 200°C; The silicone elastomer material has a compression set of 20% or less after being compressed for 22 hours at temperatures up to 190°C, or up to 200°C, when measured according to industry standard ISO 815-1:2019 Method A.

[0017] Also, the use of a combination of components (e), (f), and (g), e) is a phthalocyanine compound or a metal derivative of such a compound, the metals being copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium; f) is cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; g) is one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25 to 2.0% by weight of the composition; The use is as a means of reducing compression set in a silicone elastomeric material that is the cured product of a hydrosilylation-curable silicone rubber composition, the hydrosilylation-curable silicone rubber composition otherwise comprising the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl 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, or alternatively at least three, Si-H groups per molecule; c) silica reinforcing fillers, which are optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; There is also provided a use wherein the total weight percent of the composition is 100 weight percent.

[0018] It has been found that the compositions described herein containing components (e), (f), and (g) result in silicone elastomers with consistently improved (lower) compression over a wide temperature range of 100°C to about 190°C, or even 200°C or even 225°C, compared to two of the most preferred commercially available compression set additives, namely, the aforementioned dodecandioyl-di-(N'-salicyloyl)hydrazine, which is synonymous with 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide, and 3-(n-salicyloyl)amino-1,2,4-triazole, which is synonymous with 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide.

[0019] The components of the composition are described in greater detail below.

[0020] Component (a) Component (a) of the composition is one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups and having a viscosity in the range of 1000 mPa·s to 100,000 mPa·s at 25°C.

[0021] Component (a) is a polydiorganosiloxane, such as a polydiorganosiloxane having at least two unsaturated groups per molecule, the unsaturated groups being selected from alkenyl or alkynyl groups, or alternatively, component (a) has at least three unsaturated groups per molecule.

[0022] The unsaturated groups in component (a) may be at terminal, pendant, or both positions.

[0023] 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, allyl, methallyl, propenyl, and hexenyl groups, and cyclohexenyl groups.

[0024] Alkynyl groups may have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, or alternatively 2 to 6 carbon atoms. Alkynyl groups may be exemplified by, but not limited to, ethynyl, propynyl, and butynyl groups.

[0025] Component (a) is a compound having a plurality of units of formula (I): R' a SiO (4-a) / 2 (I), where each R' is independently selected from an aliphatic hydrocarbyl group or an aliphatic non-halogenated organyl group (an organyl group is any aliphatic organic substituent having one free valence at a carbon atom, regardless of the type of functional group). Saturated aliphatic hydrocarbyls are exemplified by, but not limited to, alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl, and cycloalkyl groups such as cyclohexyl. Unsaturated aliphatic hydrocarbyls are exemplified by, but not limited to, the alkenyl and alkynyl groups listed above. Aliphatic non-halogenated organyl groups are exemplified by, but not limited to, suitable nitrogen-containing groups such as amide and imide groups, polyoxyalkylene groups, carbonyl groups, alkoxy groups, and oxygen-containing groups such as hydroxyl groups. The subscript "a" is 0, 1, 2, or 3; typically, in this case, a is predominantly 2, but some units where a is 1 or 3 may be included.

[0026] Siloxy units can be described by an abbreviated nomenclature, i.e., "M," "D," "T," and "Q," where R' is as above or an alkyl group, typically a methyl group, and M units are siloxy units where a=3, i.e., R'SiO 1 / 2 and the D units are siloxy units where a=2, i.e., R'2SiO 2 / 2 and the T unit is a siloxy unit where a=1, i.e., R'1SiO 3 / 2 and the Q units are siloxy units where a=0, i.e., SiO 4 / 2The polydiorganosiloxanes, such as the polyorganosiloxanes of component (a), are substantially linear but may contain a percentage of branching due to the presence of T units (as described above) within the molecule, such that the average value of the subscript a in structure (I) is about 2.

[0027] Typical examples of R' groups on the one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from component (a) alkenyl and alkynyl groups include primarily alkyl groups, particularly methyl and ethyl, or methyl groups, but may also include aryl groups and / or fluoroalkyl groups, such as trifluoropropyl or perfluoroalkyl groups, in addition to the required at least two unsaturated groups selected from alkenyl and / or alkynyl groups, typically alkenyl groups. These groups may be in pendant positions (on D or T siloxy units) or terminal (on M siloxy units).

[0028] Thus, the polymer chains of component (a) may be selected from polydimethylsiloxane, alkylmethylpolysiloxane, alkylarylpolysiloxane, or copolymers thereof (reference to alkyl refers to any suitable alkyl group, or alternatively, alkyl groups having two or more carbons), provided that each component (a) polymer contains at least two alkenyl and / or alkynyl groups, typically at least two alkenyl groups. Such polymer chains may have any suitable end groups, such as trialkyl-terminated, alkenyl-dialkyl-terminated, alkynyl-dialkyl-terminated, or any other suitable combination of end groups, provided that each polymer contains at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups. In one embodiment, the end groups of such polymers are completely free of silanol end groups.

[0029] Thus, component (a) may be, for example, the following: The alkyl group may be a dialkylalkenyl-terminated polydimethylsiloxane such as a dimethylvinyl-terminated polydimethylsiloxane, a dialkylalkenyl-terminated dimethylmethylphenylsiloxane such as a dimethylvinyl-terminated dimethylmethylphenylsiloxane, a trialkyl-terminated dimethylmethylvinylpolysiloxane, a dialkylvinyl-terminated dimethylmethylvinylpolysiloxane copolymer, a dialkylvinyl-terminated methylphenylpolysiloxane, a dialkylalkenyl-terminated methylvinylmethylphenylsiloxane, a dialkylalkenyl-terminated methylvinyldiphenylsiloxane, a dialkylalkenyl-terminated methylvinylmethylphenyldimethylsiloxane, a trimethyl-terminated methylvinylmethylphenylsiloxane, a trimethyl-terminated methylvinyldiphenylsiloxane, or a trimethyl-terminated methylvinylmethylphenyldimethylsiloxane.

[0030] 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, or 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 of the composition, alternatively from 30 to 60% by weight of the composition, alternatively from 35 to 55% by weight of the composition. Viscosity can be measured using either a Brookfield™ rotational viscometer at 25°C and appropriate rpm with spindle LV-4 (spindle LV-4 designed for viscosities in the range of 1,000 to 2,000,000 mPa s) for viscosities above 15,000 mPa s, or a Brookfield™ rotational viscometer in cone-plate configuration with cone CP-52 at appropriate rpm and 25°C for viscosities up to 15,000 mPa s.

[0031] Ingredient (b) Component (b) functions as a crosslinker and is provided in the form of an organosilicon compound having at least two, or 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 alkenyl and / or alkynyl groups of component (a) to form a network therewith, thereby curing the composition. Alternatively, if polymer (a) has more than two unsaturated groups per molecule, some or all of component (b) can have two silicon-bonded hydrogen atoms per molecule.

[0032] The molecular structure of the organosilicon compound (b) having at least two or at least three Si-H groups per molecule is not particularly limited. It may be a polyorganosiloxane, which may be linear, branched (linear with some branches through the presence of T groups), cyclic, or silicone resin-based.

[0033] The molecular weight of component (b) is not particularly limited, but the viscosity is typically 5 to 50,000 mPa.s at 25° C. using the test method described for component (a).

[0034] The silicon-bonded organic group used in component (b) can be exemplified by alkyl groups such as methyl, ethyl, propyl, n-butyl, t-butyl, pentyl, hexyl, etc.; aryl groups such as phenyl, tolyl, xylyl, or similar aryl groups; 3-chloropropyl, 3,3,3-trifluoropropyl, or similar halogenated alkyl groups, and is preferably an alkyl group having 1 to 6 carbon atoms, particularly a methyl, ethyl, or propyl group, or a phenyl group. Preferably, the silicon-bonded organic group used in component (b) is an alkyl group, or a methyl, ethyl, or propyl group.

[0035] Examples of organosilicon compounds (b) having at least two, or alternatively at least three, Si—H groups per molecule include, but are not limited to: (a') trimethylsiloxy-terminated methylhydrogenpolysiloxane, (b') trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane; (c') dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymer; (d') dimethylsiloxane-methylhydrogensiloxane cyclic copolymer; (e')(CH3)2HSiO 1 / 2 Units: (CH3)3SiO 1 / 2 units, and SiO 4 / 2 copolymers and / or silicone resins consisting of units, (f')(CH3)2HSiO 1 / 2 units, and SiO 4 / 2 copolymers and / or silicone resins consisting of units, (g') Methylhydrogensiloxane cyclic homopolymer having 3 to 10 silicon atoms per molecule. Alternatively, the crosslinker, component (b), can be a filler, such as silica treated with one of the above, and mixtures thereof.

[0036] In one embodiment, component (b) is selected from methylhydrogenpolysiloxanes terminally terminated with trimethylsiloxy groups; copolymers of methylhydrogensiloxanes terminally terminated with trimethylsiloxy groups and dimethylsiloxanes; dimethylsiloxanes terminally terminated with dimethylhydrogensiloxy groups; and copolymers of methylhydrogensiloxanes terminally terminated with dimethylhydrogensiloxy groups and dimethylsiloxanes.

[0037] Crosslinker (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 and / or alkynyl groups in component (a) is 0.5:1.0 to 10.0:1.0. If this ratio is less than 0.5:1, a sufficiently cured composition will not be obtained. If this ratio exceeds 10:1, the hardness of the cured composition tends to increase when heated. Preferably, component (b) is present in an amount such that the molar ratio of silicon-bonded hydrogen atoms in component (b) to alkenyl / alkynyl or alkenyl groups in 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, or even alternatively 0.9:1.0 to 2.0:1.0.

[0038] The silicon-bonded hydrogen (Si-H) content of component (b) is determined using quantitative infrared analysis according to ASTM E168. For the present invention, the ratio of silicon-bonded hydrogen to alkenyl (vinyl) and / or alkynyl is important when relying on a hydrosilylation cure process. Generally, this is determined by calculating the total weight percent of alkenyl groups, e.g., vinyl [V], in the composition and the total weight percent of silicon-bonded hydrogen [H] in the composition; if the molecular weight of hydrogen is 1 and the molecular weight of vinyl is 27, then the molar ratio of silicon-bonded hydrogen to vinyl is 27 [H] / [V].

[0039] Typically, component (b) is present in an amount of 0.1 to 10% by weight of the hydrosilylation-curable silicone rubber composition, alternatively 0.1 to 7.5% by weight of the hydrosilylation-curable silicone rubber composition, alternatively 0.5 to 7.5% by weight of the hydrosilylation-curable silicone rubber composition, and further alternatively 0.5% to 5% by weight, depending on the number of unsaturated groups in component (a) and the number of Si—H groups in component (b).

[0040] Ingredient (c) Component (c) is a silica reinforcing filler that has been optionally hydrophobized. The reinforcing filler of component (c) may be exemplified by fumed silica and / or precipitated silica and / or colloidal silica. In one alternative, the fumed silica, precipitated silica and / or colloidal silica are provided in micronized form.

[0041] Precipitated, fumed and / or colloidal silicas have a relatively high surface area, especially when provided in micronized form, typically at least 50 m 2 / g (BET method according to ISO9277:2010), it is particularly preferred. Typically, it is 50 to 450 m 2 / g (BET method according to ISO9277:2010), or 50 to 300 m 2 Fillers with a surface area of ​​0.15 mJ / g (BET method according to ISO 9277:2010) are used. All of these types of silica are commercially available.

[0042] If the silica reinforcing filler (c) is naturally hydrophilic (e.g., untreated silica filler), it is typically treated with a treating agent to render it hydrophobic. These surface-modified silica reinforcing fillers (c) do not agglomerate, and the surface treatment allows the filler to be readily wetted by component (a), allowing them to be homogeneously incorporated into the polydiorganosiloxane polymer (a) described below.

[0043] Typically, the silica reinforcing filler (c) may be surface treated with any low molecular weight organosilicon compound disclosed in the art that can be applied to prevent creping of liquid silicone rubber (LSR) compositions during processing. For example, an organosilane, polydiorganosiloxane, or organosilazane, such as hexaalkyldisilazane or short-chain siloxanediol, can be used to render the silica reinforcing filler (c)(s) hydrophobic, thereby making them easier to handle and to obtain a homogeneous mixture with other ingredients. Specific examples include silanol-terminated trifluoropropylmethylsiloxane, silanol-terminated vinylmethyl (ViMe) siloxane, and silanol-terminated methylphenyl (methyl siloxane). hydroxyldimethyl-terminated polydiorganosiloxanes containing an average of 2 to 20 diorganosiloxane repeating units in each molecule, hydroxyldimethyl-terminated phenylmethylsiloxanes, hexaorganodisiloxanes such as hexamethyldisiloxane, divinyltetramethyldisiloxanes; hexaorganodisilazanes such as hexamethyldisilazane (hexamethyldisilazane, HMDZ), divinyltetramethyldisilazane, and tetramethyldi(trifluoropropyl)disilazane; hydroxyldimethyl-terminated polydimethylmethylvinylsiloxanes, octamethylcyclotetrasiloxanes, and silanes including, but not limited to, methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, chlorotrimethylsilane, dichlorodimethylsilane, and trichloromethylsilane.

[0044] In one embodiment, the treating agent may be selected from silanol-terminated vinylmethyl (ViMe) siloxanes, liquid hydroxyldimethyl-terminated polydiorganosiloxanes containing an average of 2 to 20 diorganosiloxane repeating units in each molecule, hexaorganodisiloxanes such as hexamethyldisiloxane, divinyltetramethyldisiloxane, hexaorganodisilazanes such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane, and hydroxyldimethyl-terminated polydimethylmethylvinylsiloxanes, octamethylcyclotetrasiloxane, and methyltriethoxysilane, dimethyldiethoxysilane, and / or vinyltriethoxysilane. A small amount of water may be added with the silica treating agent as a processing aid.

[0045] The surface treatment of the untreated silica reinforcing filler (c) may be carried out either prior to its introduction into the composition, or in situ (i.e., by blending the other ingredients of the compositions herein together at room temperature or above, in the presence of at least a portion of these ingredients, until the filler is fully treated. Typically, the untreated silica reinforcing filler (c) is treated in situ with a treating agent in the presence of component (a), thereby preparing a silicone rubber base material that can then be mixed with the other ingredients.

[0046] The silica reinforcing filler (c) is optionally present in an amount up to 40% by weight of the composition, alternatively from 1.0 to 40% by weight of the composition, alternatively from 5.0 to 35% by weight of the composition, alternatively from 10.0 to 35% by weight of the composition.

[0047] Ingredient (d) Component (d) of the composition is a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof. They are typically selected from catalysts of platinum group metals (platinum, ruthenium, osmium, rhodium, iridium, and palladium) or compounds of one or more of such metals. Alternatively, platinum and rhodium compounds are preferred due to the high activity levels of these catalysts in hydrosilylation reactions, with platinum compounds being most preferred. In the hydrosilylation (or addition) reaction, hydrosilylation catalysts such as component (d) herein catalyze the reaction between an unsaturated group, typically an alkenyl group, such as vinyl, and an Si-H group.

[0048] Catalyst (d) may be a platinum group metal, a platinum group metal deposited on a support such as activated carbon, a metal oxide such as aluminum oxide or silicon dioxide, silica gel or powdered charcoal, or a compound or complex of a platinum group metal. Preferably, the platinum group metal is platinum.

[0049] 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's catalyst), chloroplatinic acid in solution in an alcohol such as isooctanol or amyl alcohol (Lamoreaux's catalyst), and complexes of chloroplatinic acid with ethylenically unsaturated compounds such as olefins and organosiloxanes containing ethylenically unsaturated silicon-bonded hydrocarbon groups, such as tetra-vinyl-tetramethylcyclotetrasiloxane-platinum complex (Ashby's catalyst). Usable soluble platinum compounds include, for example, platinum-olefin complexes of the formula (PtCl2.(olefin)2 and H(PtCl3.olefin), in which the use of alkenes 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, is preferred. Other soluble platinum catalysts are, for example, platinum-cyclopropane complexes of the formula (PtCl2C3H6)2. Examples include 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 sodium bicarbonate in an ethanolic solution. Platinum catalysts with phosphorus and amine ligands, such as (Ph3P)2PtCl2, and complexes of platinum with vinyl siloxanes, such as sym-divinyltetramethyldisiloxane, can also be used.

[0050] Therefore, specific examples of suitable platinum-based catalysts include: (i) complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups, as described in U.S. Pat. No. 3,419,593; (ii) chloroplatinic acid in either the hexahydrate or anhydrous form; (iii) platinum-containing catalysts obtained by a process comprising reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane; (iv) alkene-platinum-silyl complexes described in U.S. Pat. No. 6,605,734, such as (COD)Pt(SiMeCl) (where “COD” is 1,5-cyclooctadiene), and / or (v) Karstedt catalysts, platinum divinyltetramethyldisiloxane complexes typically containing about 1% by weight of platinum in a vinylsiloxane polymer having a viscosity of about 200-750 mPa.s using the test method described for component (a).

[0051] While solvents such as organic solvents like toluene have historically been used as alternatives, the use of vinyl siloxane polymers is by far the preferred choice. These are described in U.S. Patent Nos. 3,715,334 and 3,814,730. In a preferred embodiment, component (d) can be selected from platinum coordination compounds. In one embodiment, hexachloroplatinic acid and its conversion products with vinyl-containing siloxanes, Karstedt's catalyst, and Speier's catalyst are preferred.

[0052] Component (d) is typically present in an amount of platinum atoms providing 0.1 to 500 ppm (parts per million) based on the weight of the reactive raw materials, components (a) and (b). The catalyst may be added as a single species or as a mixture of two or more different species. Typically, depending on the form / concentration in which the catalyst is provided, the amount of catalyst present ranges from 0.05 to 1.5 wt. % of the composition, alternatively from 0.05 to 1.0 wt. % of the composition, alternatively from 0.1 to 1.0 wt. %, alternatively from 0.1 to 0.5 wt. %, and the platinum catalyst is provided in a masterbatch of a polymer such as (a) above.

[0053] Ingredient (e) 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:

[0054] [ka]

[0055] A metal phthalocyanine, for example, copper phthalocyanine, is shown below.

[0056] [ka]

[0057] In one embodiment, component (e) comprises or consists of copper phthalocyanine. Any suitable form of copper phthalocyanine can be utilized, such as the pigmentary 15:3 beta or 15:4 beta forms of copper phthalocyanine, or the 15:2 alpha form of copper phthalocyanine. The 15:1 alpha form of copper phthalocyanine is suitable if it is sufficiently stable. The 15:3 beta or 15:4 beta forms of copper phthalocyanine are particularly preferred. The component (e) phthalocyanine compound or metal derivative of such a compound is present 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.

[0058] However, it should be noted that it can be delivered alone or in a masterbatch or mixture with, for example, a suitable polydimethylsiloxane, such as a dimethylvinyl-terminated polydimethylsiloxane having a viscosity of from 1000 mPa.s at 25° C. to 25,000 mPa.s at 25° C. For example, copper phthalocyanine in a dimethylvinyl-terminated polydimethylsiloxane having a viscosity of from 1000 mPa.s at 25° C. to 15,000 mPa.s at 25° C. in a mixture containing 10 to 50% by weight copper phthalocyanine, the balance consisting of a dimethylvinyl-terminated polydimethylsiloxane having a viscosity of from 1000 mPa.s at 25° C. to 15,000 mPa.s at 25° C. Specific examples include 30% by weight copper phthalocyanine in a vinyldimethylsiloxy end-blocked polydimethylsiloxane having a viscosity of about 9000 mPa·s at 25° C. (using a Brookfield™ rotational viscometer in cone-plate configuration with a CP-52 cone at 3 rpm) and 15% by weight copper phthalocyanine in a vinyldimethylsiloxy end-blocked polydimethylsiloxane having a viscosity of about 2000 mPa·s at 25° C. (using a Brookfield™ rotational viscometer in cone-plate configuration with a CP-52 cone at 3 rpm). In such cases, when provided as such a masterbatch or mixture, the masterbatch or mixture may be incorporated into the composition in an amount of 0.2 to 5% by weight of the composition, and such masterbatch or mixture may comprise about 10 to 50% by weight of component (e), the remainder being the suitable polydimethylsiloxane.

[0059] Component (f) Component f) is cyanuric acid, biuret, or a mixture thereof.

[0060] For the avoidance of doubt, please note: Cyanuric acid exists in tautomeric equilibrium of 1,3,5-triazine-2,4,6-triol (structure 1 below) and its tri-keto tautomer 1,3,5-triazinane-2,4,6-trione (structure 2 below). It should be understood that references herein to cyanuric acid are intended to encompass both tautomers.

[0061] [ka]

[0062] Biuret is a compound with the following structure:

[0063] [ka]

[0064] It has several other names, including 2-imidodicarboxylic acid diamide and carbamyl urea, but is referred to herein as biuret.

[0065] Cyanuric acid, biuret, or mixtures thereof are present in the compositions herein in an amount of 0.005 to 0.2% by weight of the composition and are widely available commercially.

[0066] Ingredients (g) Component (g) is one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate, with magnesium carbonate and magnesium hydroxycarbonate being particularly preferred.

[0067] These may include one or more magnesium carbonates selected from magnesite (MgCO), barlintonite (MgCO.2H0), nesquihonite (MgCO.3H0), lansfordite (MgCO.5H0), and one or more magnesium hydroxycarbonates such as pokrovskite (Mg(CO)(OH)0.5H0), artinite (Mg(CO)(OH)3H0), hydromagnesite (Mg(CO)(OH)4H0), sometimes referred to as light magnesium carbonate, diepingite (Mg(CO)(OH)5H0), sometimes referred to as heavy magnesium carbonate, georgiosite (Mg(CO)(OH)6H0), and sherkovite (Mg(CO)(OH)4.2H0). Component (f) is present in the composition in an amount from 0.25 to 5.0% by weight of the composition, alternatively from 0.25 to 4.0% by weight of the composition, alternatively from 0.25 to 3.0% by weight of the composition, alternatively from 0.25 to 2.0% by weight of the composition.

[0068] Optional Additives Such hydrosilylation-curable silicone rubber compositions may also contain one or more optional additives depending on the intended use, such as cure inhibitors, mold release agents, adhesion catalysts, peroxides, electrically conductive fillers, thermally conductive fillers, pot life extenders, lubricants, heat stabilizers, metal deactivators, UV light stabilizers, fungicides, wetting agents, and the like.

[0069] Curing inhibitor Cure inhibitors are optionally 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 hydrazines, triazoles, phosphines, mercaptans, organic nitrogen compounds, acetylene alcohols, silylated acetylene alcohols, maleates, fumarates, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, olefinic siloxanes, unsaturated hydrocarbon monoesters and diesters, conjugated ene-ynes, hydroperoxides, nitriles, and diaziridines.Alkenyl-substituted siloxanes such as those described in U.S. Pat. No. 3,989,667 may also be used, of which cyclic methylvinylsiloxanes are preferred.

[0070] One class of known hydrosilylation reaction inhibitors is the acetylenic compounds disclosed in U.S. Patent No. 3,445,420. Acetylenic alcohols, such as 2-methyl-3-butyn-2-ol, constitute a preferred class of inhibitors, which suppress the activity of platinum-containing catalysts at 25° C. Typically, compositions containing these inhibitors must be heated to temperatures above 70° C. in order to cure at a practical rate.

[0071] Examples of acetylene alcohols and their derivatives include 1-ethynyl-1-cyclohexanol (ETCH), 2-methyl-3-butyn-2-ol, 3-butyn-1-ol, 3-butyn-2-ol, propargyl alcohol, 1-phenyl-2-propyn-1-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclopentanol, 3-methyl-1-penten-4-yn-3-ol, and mixtures thereof. Derivatives of acetylene alcohols can include those compounds having at least one silicon atom.

[0072] When present, inhibitor concentrations as low as 1 mole of inhibitor per mole of catalyst metal provide satisfactory storage stability and cure rates. In other cases, inhibitor concentrations of up to 500 moles of inhibitor per mole of catalyst metal are required. The optimum concentration for 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 commercially provided / available, inhibitors, if present in the composition, are typically present in amounts of 0.0125 to 10 weight percent of the composition.

[0073] In one embodiment, the inhibitor, if present, is selected from 1-ethynyl-1-cyclohexanol (ETCH) and / or 2-methyl-3-butyn-2-ol and is present in an amount greater than 0 to 0.1% by weight of the composition.

[0074] release agent Any suitable release agent may be utilized, such as a hydroxydimethyl-terminated polydimethylsiloxane having a viscosity of about 21 mPa.s at 25° C. as measured using a Brookfield™ rotational viscometer with spindle LV-2 at 12 rpm.

[0075] lubricant Any suitable lubricant may be used. An example of a suitable lubricant is a silicone-containing oil such as a trimethylsilyl-terminated phenylmethylsiloxane dimethylsiloxane copolymer having a viscosity of 100 mPa.s to 200 mPa.s at 25°C using the viscosity test method described for component (a) and mixtures or derivatives thereof.

[0076] In one alternative embodiment herein, the composition does not include a diacylhydrazide compound.

[0077] Thus, in one alternative, the present disclosure provides a silicone rubber composition comprising any suitable combination of the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups, and having a viscosity in the range of 1000 mPa·s to 100,000 mPa·s at 25° C., alternatively 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 30 to 60% by weight of the composition, alternatively 35 to 55% by weight of the composition. Viscosity can be measured at 25° C. using a Brookfield® rotational viscometer with spindle LV-4 (designed for viscosities in the range of 1,000 to 2,000,000 mPa·s), with the speed adapted depending on the polymer viscosity. b) organosilicon compounds 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 of the composition, and further alternatively 0.5% to 5% by weight; c) preferably in finely divided form, optionally hydrophobized, typically at least 50 m 2 / g (BET method according to ISO9277:2010), a high surface area silica reinforcing filler. 50-450m 2 / g (BET method according to ISO9277:2010), or 50 to 300 m 2 a filler having a surface area of ​​0.05 wt.% / g (BET method according to ISO 9277:2010), typically present in an amount of up to 40 wt.% of the composition, alternatively from 1.0 to 40 wt.% of the composition, alternatively from 5.0 to 35 wt.% of the composition, alternatively from 10.0 to 35 wt.% of the composition; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof, in an amount ranging from 0.001 to 3.0% by weight of the composition, alternatively from 0.001 to 1.5% by weight of the composition, alternatively from 0.001 to 1.5% by weight, or alternatively from 0.01 to 0.1.0% by weight of the silicone rubber composition, depending on the form / concentration in which the catalyst is provided; e) phthalocyanine compounds or metal derivatives of such compounds, wherein the metals are copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium, and are present in an amount of 0.02% to 2.5% by weight of the composition; f) cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; and g) 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 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; However, the total weight percent of the composition is 100 weight percent.

[0078] The composition may also contain one or more of the above optional additives in the amounts specified, where again, the total weight percent of the composition is 100 weight percent.

[0079] The hydrosilylation-curable silicone rubber compositions described above are typically stored prior to use in two or more parts. In the case of two-part compositions, the two parts are typically referred to as part (A) and part (B). Part (A) typically contains, in addition to polyorganosiloxane (a) and silica reinforcing filler (c), a catalyst (d); Part (B) typically includes the crosslinker component (b), and, if present, the optional inhibitor, as well as the remaining polyorganosiloxane (a) and / or silica reinforcing filler (c).

[0080] It is important that the catalyst (d) be stored separately from the crosslinker (b) to prevent premature curing during storage.

[0081] Components (e), (f), and (g) can be stored in either Part (A) or Part (B), or in both parts, so long as they do not adversely affect the storage of any of the essential ingredients present in each part, including components (e), (f), and (g) with each other. Alternatively, if desired, components (e), (f), and (g) can be added to the remaining composition, i.e., to the combined Part (A) and Part (B) compositions, either when or after mixing the Part (A) and Part (B) compositions together prior to use.

[0082] Any optional additives other than the inhibitors mentioned above may be present in either part (A) or part (B), or both parts, as long as they do not adversely affect the storage of any of the essential ingredients present in each part.

[0083] 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, with a 1:1 ratio being most preferred.

[0084] The ingredients / components of Part (A) and / or Part (B) may be mixed together individually in their respective parts, or may be introduced into the composition in a pre-prepared combination, e.g., to facilitate mixing of the final composition. For example, components (a) and (c) are often mixed together to form an LSR polymer base or masterbatch before the other ingredients are introduced. These may then be mixed directly with the other ingredients of the part being manufactured, or may be used to make pre-prepared concentrates, commonly referred to in the industry as masterbatches.

[0085] In this case, to facilitate the mixing of the ingredients, one or more masterbatches can be utilized to successfully mix the ingredients to form the (A) and / or (B) part compositions. For example, a "fumed silica" masterbatch can be prepared, which is effectively an LSR silicone rubber base containing an in-situ treated silica reinforcing filler (c).

[0086] Parts A and B of the composition can be prepared by combining all of the respective components at ambient temperature. Any mixing technique and equipment described in the prior art can be used for this purpose. The specific equipment used will depend on the viscosity of the components and the final composition. Suitable mixers include, but are not limited to, kneader mixers, static mixers in liquid injection molding machines, Z-blade mixers, two-roll mills (open mills), three-roll mills, Haake™ Rheomix OS Lab mixers, single-screw extruders, or twin-screw extruders. Alternatively, speed mixers such as the DC150.1FV, DAC400FVZ, or DAC600FVZ models available from Hauschild can be used. It may be desirable to cool the components during mixing to prevent premature hardening of the composition.

[0087] Prior to use, the respective Part (A) and Part (B) compositions are mixed together in the desired ratio.

[0088] Curing of the hydrosilylation-curable silicone rubber composition on the substrate can be carried out, for example, in a mold, and a molded part can be formed by injection molding, for example, using a liquid injection molding system (LIMS), press molding, extrusion molding, transfer molding, press vulcanization, or calendaring. Compression set specimens can be molded into suitable shapes, for example, cylindrical disks 29.0 mm ± 0.5 mm in diameter and 12.5 mm ± 0.5 mm thick, which are compressed 25% to a thickness of approximately 9.38 mm. They can be prepared in a mold or cut from a pressed sheet of silicone elastomer material.

[0089] Under compression, the LSR button (previously cured at 175°C for 10 minutes) was held between two metal plates in a convection oven at elevated temperature for a suitable time, typically 22 hours, after which the compression was released and the specimen was allowed to recover to a thickness close to the starting thickness to determine the compression set.

[0090] The hydrosilylation-curable silicone rubber composition is cured at any suitable temperature, such as, for example, from 80° C. to 200° C., alternatively from about 100° C. to 180° C., alternatively from about 120° C. to 180° C. As noted above, one standard method for reducing compression set has historically been post-curing, aimed at reducing the number of curable groups that can cure under compression during use as a gasket.

[0091] In the case of the process for producing the two-part silicone rubber composition described above, the process comprises: (i) preparing a silicone-based composition comprising component (a) a polymer and component (c) a silica reinforcing filler; (ii) dividing the resulting base into two parts, i.e., part (A) and part (B), introducing catalyst (d) into the part (A) composition and crosslinker (b) and inhibitor (if present) into the part (B) composition; (iii) introducing any other optional additives into either or both of part (A) and part (B); (iv) storing the part (A) composition and the part (B) composition separately; may include:

[0092] In an alternative process, component (e) is not introduced into either component (A) or component (B) when they are separate, but is introduced as part of the mixing process when the part (A) composition and the part (B) composition are mixed together prior to use, for example, during mixing prior to injection molding.

[0093] Typically, the Part A and Part B compositions are thoroughly mixed in the preferred weight ratios described above immediately prior to use to avoid premature curing, followed by the cure stage.

[0094] If / when component (e) is introduced together with parts (A) and (B) during the mixing process, typically the weight ratio of parts (A) and (B) remains the same, for example, if parts (A) and (B) are mixed in a 1:1 weight ratio, there may be, for example, 49.5 wt. % each of parts (A) and (B), and 1 wt. % of component (e) mixed together prior to molding.

[0095] The low compression set silicone elastomer compositions and methods herein are useful in applications such as acting as a barrier to prevent absorption or penetration of air, dust, noise, liquids, gaseous substances, or dirt. Silicone elastomer materials with low compression set as described herein may be used in gaskets.

[0096] They are also utilized in a wide range of electrical and / or insulating applications. In electrical applications, they can be useful in wiring, cabling, power supplies, and the like. For example, silicone elastomer materials obtained from the compositions described herein can be utilized in a variety of applications, such as silicone coatings for standard non-silicone insulation, cable coatings for safety cables, and cable accessories such as electrical connectors, terminals, and wire seals. Electrical connectors are commonly used to create closed electrical circuits in automotive, residential, and infrastructure environments due to their excellent balance of mechanical properties, chemical and thermal stability, ease of processing, and the availability of self-lubricating formulations. They can be used to mate rigid thermoplastic housing components to electrically and environmentally isolate connector joints from, for example, moisture, oils and fuels, and corrosive gases that may be present. Silicone elastomers made using the compositions herein have suitably low compression set at high temperatures, providing electrical connectors and the like with the mechanical integrity and dimensional stability described above, and exhibiting excellent sealing performance over their service life.

[0097] Such electrical connectors, terminals, and wire seals may be used in automotive applications for electric vehicle (EV) battery packs, EV batteries, control units within EVs, such as motor control unit (MCU) devices, lamp housings, fuse boxes, air filters, waterproof connectors, air conditioners, lighting systems, intercoolers, and / or electronic components. They may also be used in or for spark plugs, such as spark plug boots for combustion engines.

[0098] Other applications include external waterproofing applications, and therefore they are used in the manufacture of automotive parts, structural parts such as cable accessories, electrical and electronic parts, packaging parts, sealants, household appliance parts, etc. [Example]

[0099] All viscosities were measured at 25° C. unless otherwise indicated. Viscosities of individual components in the following examples were measured using a Brookfield™ rotational viscometer with spindle LV-4 at the appropriate rpm for viscosities above 15,000 mPa s (spindle LV-4 designed for viscosities in the range of 1,000 to 2,000,000 mPa s), and in cone-and-plate configuration with cone CP-52 at the appropriate rpm for viscosities up to 15,000 mPa s, unless otherwise noted.

[0100] All compression set results are certified according to industry standard ISO 815-1:2019 Method A, where a cylindrical disk 29.0 ± 0.5 mm in diameter and 12.5 ± 0.5 mm thick is compressed 25% to a thickness of approximately 9.38 mm. Under compression, the LSR button (previously cured at 175°C for 10 minutes) is held between two metal plates in a convection oven at elevated temperature for a suitable time, typically 22 hours, after which the compression is released and the specimen allowed to recover to a thickness close to the starting thickness to determine the compression set.

[0101] A series of compositions were prepared using the two-part liquid silicone rubber elastomer composition (Elas.) shown in Table 1 as the standard starting composition.

[0102] [Table 1]

[0103] For the avoidance of doubt, in the examples herein, compositions were prepared in which components (e), (f), and (g), in each instance present, were added at the time or after the associated Part (A) and Part (B) compositions were mixed together. Thus, when 0.1 wt. % compression set additive was introduced, the final cured mixture was a combination of 49.95% Part (A) as defined in Table 1 above, 49.95% Part (B) as defined in Table 1 above, and 0.1 wt. % compression set additive.

[0104] In the above composition, Masterbatch 1: Masterbatch 1 is 70.8 parts by weight of a dimethylvinyl-terminated polydimethylsiloxane having a viscosity of about 53,000 mPa.s at 25°C as measured using a Brookfield™ rotational viscometer at 6 rpm with spindle LV-4; 22.4 parts by weight, 300m 2 and a hydrophobic fumed silica having a surface area of ​​1 / g, wherein the silica is hydrophobized and does not contain vinyl functional groups.

[0105] Masterbatch 2: Masterbatch 2 is 66.6 parts by weight of a dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 55 Pa.s at 25°C as measured using a Brookfield™ rotational viscometer at 6 rpm with spindle LV-4; 25.8 parts by weight, 300m 2and a hydrophobic fumed silica having a surface area of ​​about 0.178 mmol / g, the silica being hydrophobized and having a vinyl functionality of about 0.178 mmol / g.

[0106] The parts by weight values ​​given are not percentage values ​​and therefore do not necessarily add up to 100.

[0107] Polymer 2: Polymer 2 is a vinyl-terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a viscosity of 370 mPa.s at 25°C using a Brookfield™ rotational viscometer in cone-plate configuration with cone CP-52 at 12 rpm.

[0108] Crosslinker 1: Crosslinker 1 was a trimethyl-terminated polymethylhydrogendimethylsiloxane having a viscosity of 30 mPa.s at 25°C using a Brookfield™ rotational viscometer in cone-plate configuration with cone CP-52 at 12 rpm.

[0109] Mold Release Agent: The mold release agent was a hydroxydimethyl-terminated polydimethylsiloxane having a viscosity of about 21 mPa.s at 25° C. as measured using a Brookfield™ rotational viscometer at 12 rpm with spindle LV-2.

[0110] Cyclotetrasiloxane: The cyclotetrasiloxane was tetravinyl-tetramethyl-cyclotetrasiloxane.

[0111] CDA6: CDA6 is dodecandioyl-di-(N'-salicyloyl)hydrazine, a synonym of which is 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide, and is commercially available from Adeka as ADK STAB™ CDA-6.

[0112] During use, the Part (A) composition and the Part (B) composition were mixed together in a 1:1 weight ratio. The resulting composition was inserted into a suitable mold and cured at 175°C for 10 minutes as a 12.5 mm thick, 29 mm diameter button. Unless otherwise noted, the resulting silicone rubber was not post-cured. Post-cured samples were post-cured at 200°C for 4 hours. Unless otherwise noted, all compression set results below were determined according to International Organization for Standardization (ISO) Test 815-1:2019, Method A.

[0113] In the examples, component (e) is exemplified as copper phthalocyanine and is introduced into the composition in the form of a copper phthalocyanine additive comprising 15% copper phthalocyanine in a vinyldimethylsiloxypolydimethylsiloxane having a viscosity of about 2000 mPa.s at 25°C (using a Brookfield™ rotational viscometer in cone-plate configuration with cone CP-52 at 3 rpm), hereinafter referred to as "Cupc"; Component (f), cyanuric acid, biuret, or a mixture thereof, when present, is introduced in the form of a 5 molar aqueous solution (BioXtra, pH 7.5-9.5 (20°C, 5M in HO), commercially available from Sigma-Aldrich under product number U0631); Component (g) in the examples was hydromagnesite (Mg5(CO3)4(OH)2.4H2O), sometimes called light magnesium carbonate, sold by Sigma-Aldrich under product number 13118 (basic magnesium carbonate (pure, light, >40% Mg (as MgO) base, light, powder (light))). A series of samples were prepared based on Elas.1, the composition of which is given in Table 2a.

[0114] [Table 2]

[0115] Melamine, also known as 1,3,5-triazine-2,4,6-triamine, has the following structure:

[0116] [ka]

[0117] It was introduced into the composition in the form of a microcrystalline material sold by Sigma-Aldrich under the number M2659.

[0118] In Table 2b, Example 1 and Comparative 1 and Comparative 2 were tested for compression set (to the nearest whole number) after 22 hours at 175°C and 22, 168, 504 and 1008 hours at 200°C.

[0119] [Table 3]

[0120] A further series of results was undertaken. In the following cases, the samples were post-cured before analysis. The results are provided in Table 2c below.

[0121] [Table 4]

[0122] The two combinations containing cyanuric acid and CDA-6, respectively, performed nearly equally well at temperatures of 175°C and 200°C, but the cyanuric acid / hydromagnesite / copper phthalocyanine combination clearly performed best at 72 hours / 225°C. The sample set using melamine instead of cyanuric acid exhibited poorer compression set results across the entire temperature range.

Claims

1. 1. A hydrosilylation-curable silicone rubber composition comprising the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups and having a viscosity in the range of 1,000 mPa s to 100,000 mPa s at 25°C; b) organosilicon compounds having at least two, or alternatively at least three, Si—H groups per molecule; c) a silica reinforcing filler, optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) phthalocyanine compounds or metal derivatives of such compounds, wherein the metals are copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium, and are present in an amount of 0.02% to 2.5% by weight of the composition; f) cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; and g) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25 to 2.0% by weight of the composition; A hydrosilylation-curable silicone rubber composition, wherein the total weight percent of said composition is 100 weight percent.

2. 10. The hydrosilylation-curable silicone rubber composition of 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. 3. The hydrosilylation-curable silicone rubber composition of claim 1, wherein component (e) is delivered alone or in a masterbatch or mixture with a dimethylvinyl-terminated polydimethylsiloxane having a viscosity of from 1000 mPa s at 25°C to 25,000 mPa s at 25°C.

4. 4. The hydrosilylation-curable silicone rubber composition according to claim 1, wherein component (g) is magnesium carbonate, magnesium hydroxycarbonate, or a mixture thereof in an amount of 0.25 to 5.0 weight percent of the composition.

5. The magnesium carbonate, magnesium hydroxycarbonate, or mixture is 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 . 24 hours ２ 5. The hydrosilylation-curable silicone rubber composition of claim 4, wherein the hydroxyl group is selected from the group consisting of hydroxyl groups, ...

6. A silicone elastomer material which is the cured product of the hydrosilylation-curable silicone rubber composition of any one of claims 1 to 5.

7. A silicone elastomer material, comprising: a) one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups and having a viscosity in the range of 1,000 mPa s to 100,000 mPa s at 25°C; b) organosilicon compounds having at least two, or alternatively at least three, Si—H groups per molecule; c) a silica reinforcing filler, optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) phthalocyanine compounds or metal derivatives of such compounds, wherein the metals are copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium, and are present in an amount of 0.02% to 2.5% by weight of the composition; f) cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; and g) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25 to 2.0% by weight of the composition; mixing the the total weight percent of the composition is 100 weight percent; and curing said composition at a temperature of from 80°C to 200°C.

8. 8. The silicone elastomer material of claim 6 or 7, having a compression set of 20% or less after compression for 22 hours at temperatures up to 190°C, alternatively up to 200°C, measured according to industry standard ISO 815-1:2019 Method A.

9. 7. A method for preparing the silicone elastomer material of claim 6, comprising: a) one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups and having a viscosity in the range of 1,000 mPa s to 100,000 mPa s at 25°C; b) organosilicon compounds having at least two, or alternatively at least three, Si—H groups per molecule; c) a silica reinforcing filler, optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; e) phthalocyanine compounds or metal derivatives of such compounds, wherein the metals are copper, nickel, cobalt, iron, manganese, chromium, zinc, platinum, palladium, and vanadium, and are present in an amount of 0.02% to 2.5% by weight of the composition; f) cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; and g) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25 to 2.0% by weight of the composition; and mixing the and curing the composition at a temperature of from 80°C to 200°C.

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

11. The magnesium carbonate, magnesium hydroxycarbonate, or mixture is 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 . 24 hours ２ 11. The method for preparing a silicone elastomer material according to claim 10, wherein the silicone elastomer is selected from the group consisting of methyl, methyl, methylpropyl ...

12. Use of a combination of components (e), (f), and (g), e) 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, and vanadium, and is present in an amount of 0.02% to 2.5% by weight of the composition; f) is cyanuric acid, biuret, or a mixture thereof in an amount of 0.005 to 0.2% by weight of the composition; g) one or more of magnesium hydroxide, magnesium carbonate, magnesium hydroxycarbonate, or manganese carbonate in an amount of 0.25 to 2.0% by weight of said composition; The use is as a means of reducing compression set in a silicone elastomer material that is the cured product of a hydrosilylation-curable silicone rubber composition, the hydrosilylation-curable silicone rubber composition otherwise comprising the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups and having a viscosity in the range of 1,000 mPa s to 100,000 mPa s at 25°C; b) organosilicon compounds having at least two, or alternatively at least three, Si—H groups per molecule; c) a silica reinforcing filler, optionally hydrophobized; d) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof; The total weight percent of the composition is 100 weight percent.

13. Component (g) is 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 . 24 hours ２ 13. The use according to claim 12, wherein the magnesium carbonate, magnesium hydroxycarbonate, or mixture thereof is selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium carbonate, magnesium carbonate-hydroxycarbonate ...

14. 9. 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. 15. The 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 or for the manufacture of automotive parts, cable accessories, electrical and electronic parts, packaging parts, structural parts such as sealants, household parts, gasket sealants, and the like.

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