Silicone-thermoplastic composite articles

Abstract

A method for maintaining the durability over time of a silicone-thermoplastic composite article comprising a flame retardant-free thermoplastic material and a silicone elastomer material by incorporating a stabilizing additive into the silicone elastomer material. The present disclosure also extends to improved silicone-thermoplastic composite articles and uses of such silicone-thermoplastic composite articles.

Description

[Technical Field]

[0001] The present disclosure relates to silicone-thermoplastic composite articles and methods for maintaining the durability over time of silicone-thermoplastic composite articles comprising flame retardant-free thermoplastic and silicone elastomeric materials by incorporating stabilizing additives into the silicone elastomeric materials, and the disclosure also extends to the use of such silicone-thermoplastic composite articles.

[0002] Curable silicone rubber compositions are known in the art and are 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 silicone elastomers suitable for use in a wide range of electrical and / or insulating applications. [Background technology]

[0003] For example, silicone elastomers made from either liquid silicone rubber (LSR) or high-consistency rubber (HCR) have been used in a wide variety of silicone-thermoplastic composite articles containing thermoplastic and silicone elastomer materials. The physical properties of the flame-retardant-free thermoplastic and silicone elastomer materials can provide composite articles with advantageous properties that would not be present if one or the other were used instead of the composite. However, depending on the application in which the composite is used, the physical properties and durability of the silicone elastomer in direct contact with the flame-retardant-free thermoplastic can be adversely affected, particularly when the composite article is subjected to heat and when the silicone elastomer is subjected to compressive forces during use. For example, at elevated temperatures (e.g., >85°C or >150°C), species from the flame-retardant-free thermoplastic can leach out of the plastic and diffuse into the silicone elastomer, potentially degrading the silicone elastomer and adversely affecting its physical properties, such as increased compression set.

[0004] For example, considering two thermoplastic materials commonly used in silicone-thermoplastic composite articles, it is believed that polyamide 66 (PA66) may release species such as adipic acid or carboxylic acid oligomers, and polybutylene terephthalate (PBT) may release esters of terephthalic acid, esters of benzoic acid, terephthalic acid, and benzoic acid, among others, as a result of thermal degradation when such composites are used at elevated temperatures.

[0005] PBT is also known to contain low molecular weight species that can be released even before a thermal decomposition event. Such species may contain acidic or -OH end groups inherent in the raw material, which can selectively migrate to the surface of the thermoplastic and diffuse into the silicone elastomer during compression heat aging.

[0006] One of the most common uses of silicone elastomer materials in silicone-thermoplastic composite articles is as a seal in or for electrical or electronic connectors, which 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, and ease of processing. Such electrical or electronic connectors can be used to mate with rigid thermoplastic housing components to form a tight connection that provides both electrical and environmental insulation for the connector joint to form a closed electrical circuit in, for example, automotive, residential, and infrastructure environments.

[0007] Such electrical or electronic connectors can be used, for example, in automobiles, which are becoming increasingly reliant on electrical and electronic systems, particularly with the development of electric and hybrid vehicles. In these applications, silicone rubber seals are subjected to mechanical compression and high temperatures, and may be exposed to the presence of moisture, oils and fuels, corrosive gases, and effluents from contacted materials (e.g., thermoplastic housings), yet must retain their mechanical integrity and dimensional stability to provide adequate sealing performance over their service life to prevent electrical failure.

[0008] Because devices such as radios, lighting, ventilation, etc. rely on the aforementioned silicone rubber materials as seals to prevent electrical failure, unwanted electrical failure can lead to malfunction or failure of such devices.

[0009] Silicone-thermoplastic composite articles are also useful in other applications where the cured silicone functions to seal, passivate, or protect components from environmental and mechanical attack, including heat, moisture, dust, and vibration, as exemplified by lid seals and adhesives for electronic module housings, gaskets or seals for radiator tanks or headlamp assemblies; and sealants or encapsulants for electrical or electronic components found in automotive, marine, aviation, aerospace, or other industrial applications.

[0010] Therefore, it is important that the silicone elastomer material maintain its physical properties to ensure the durability of both the silicone elastomer material itself and the silicone-thermoplastic composite article. One of the most important physical properties that a silicone rubber material must retain is a low compression set for applications requiring, for example, environmental and electrical insulation, and / or thermal stability.

[0011] 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 at a curing (elevated) temperature for a certain period of time. Compression set values ​​can be measured, for example, according to industry standard ASTM D395-18 Method A, B, or C, and are specified as a percentage. For example, if there is complete recovery, that is, if the thickness of the test specimen is the same before and after the application of load, the compression set is 0%; in contrast, if the 25% compression of the silicone elastomer material applied during the test remains unchanged when the load is removed, the compression set is 100% because it has not returned to its original shape at all.

[0012] 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 of time, such as 22 hours, at temperatures of 125°C and 150°C, and can suffer problems caused by the resulting change in shape and / or significant increase in hardness during long-term use in high temperature applications unless subjected to a post-cure heating process.

[0013] "Post-curing" is the simplest method to minimize compression set, in which the hydrosilylation or peroxide-cured silicone material is subjected to post-cure heating at 150°C or above for a period of several hours, e.g., 4 hours or more. However, post-curing is usually not commercially desirable or practical given the capital investment required, the increased energy consumption, and the need for delayed production times.

[0014] Many of the applications described above typically require silicone elastomer materials to have compression set values ​​that are as low as possible, for example, 40% or less, over a wide range of temperatures.

[0015] 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 suitability for use over specified temperature ranges that meet the class of the relevant automotive specification for that temperature range. There are currently five ranges, identified as T1 through T5. T1 is for the temperature range of -40°C to +85°C, 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 is currently the highest rating. It is T5 for temperatures between -40℃ and 175℃.

[0016] Given that it is undesirable to post-cure all silicone elastomers after curing, various additives have been proposed as alternative methods to reduce compression set.

[0017] However, industrial and vehicle components and modules are increasingly subjected to mechanical compression and are exposed to increasing operating temperatures above 125°C.

[0018] Thus, silicone elastomer materials used in combination with flame retardant-free thermoplastics in silicone-thermoplastic composite articles, for example in connector seal applications, can suffer premature seal failure after direct contact with the flame retardant-free thermoplastic.

[0019] It is an intent of the present disclosure to provide a means of maintaining the durability over time of a silicone-thermoplastic composite article comprising a flame retardant-free thermoplastic material and a silicone elastomeric material. Summary of the Invention

[0020] In this specification, (i) a flame retardant-free thermoplastic article having an accessible surface; (ii) a cured silicone elastomer portion in direct contact with the available surface of the flame retardant-free thermoplastic article (i), the cured silicone elastomer portion being the cured product of a silicone elastomer composition comprising 0.25% by weight to a maximum of 5% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; A silicone-thermoplastic composite article is provided, comprising:

[0021] Also provided is a method of making a silicone-thermoplastic composite article according to the above, comprising the steps of: (a) providing a curable silicone elastomer composition comprising 0.25 to up to 5 wt. % of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (b) curing the curable elastomer composition in a mold; (c) physically engaging the cured silicone elastomer with an available surface of the flame retardant-free thermoplastic article (i) to form a silicone-thermoplastic composite article; A method is provided that includes:

[0022] Also provided is a method for producing the aforementioned silicone-thermoplastic composite article, comprising the steps of: (a) providing a curable silicone elastomer composition comprising 0.25% by weight to a maximum of 5% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (b) contacting a curable silicone elastomer composition with an available surface of a flame retardant-free thermoplastic article (i); (c) curing the curable silicone elastomer composition in contact with the available surface of the flame retardant thermoplastic article to form a silicone-thermoplastic composite article; A method is provided which includes:

[0023] Also provided is a method for producing a silicone-thermoplastic composite article, the silicone-thermoplastic composite article comprising: (i) A thermoplastic article containing no flame retardant, a flame retardant-free thermoplastic article having an accessible surface; (ii) a silicone elastomer portion physically engaging an available surface of (i) the flame retardant-free thermoplastic; and The method comprises: (1) providing a curable silicone elastomer composition comprising a hydrosilylation-curable silicone elastomer composition or a free-radical-curable silicone elastomer composition, the curable silicone elastomer composition further comprises 0.25% by weight to a maximum of 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (2) introducing a desired amount of a curable silicone elastomer composition into the mold; (3) curing the curable silicone elastomer composition, thereby forming (ii) a silicone elastomer portion; and (4)(ii) physically engaging the silicone elastomer seal with an available surface of the (i) flame retardant-free thermoplastic article, thereby forming a silicone-thermoplastic composite.

[0024] In one latter embodiment, the silicone-thermoplastic composite article comprises: (ia) one or more electric wires; (ib) Electrical or electronic connector housings containing thermoplastic articles containing no flame retardant additives; 1. An electrical or electronic connector comprising: The electrical or electronic connector housing has a first (outer) available surface and a second (inner) surface opposite the outer surface; the second (inner) surface defines a cavity; The cavity accommodates one or more electrical wires (ia) therein; The silicone elastomer portion (ii) is a silicone elastomer seal, which is physically engaged with a first (outer) available surface of the electrical or electronic connector housing (ib).

[0025] Also disclosed is a method for maintaining the durability of a silicone elastomer part in physical contact with a flame retardant-free thermoplastic, the silicone elastomer part being subjected to mechanical compression and exposure to temperatures in excess of 85°C during use; (1') preparing a curable silicone elastomer composition, the curable silicone elastomer composition further comprising 0.25% by weight to a maximum of 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (2') introducing a desired amount of a curable silicone elastomer composition into a mold; (3') curing the curable silicone elastomer composition, thereby forming the silicone elastomer portion (ii); (4') physically engaging the silicone elastomer portion (ii) with an available surface of an electrical or electronic connector housing (ib) to form an electrical or electronic connector; A method is provided which includes:

[0026] The above method may include the step (5') of (i) connecting an electrical or electronic connector to a connector junction of an electrical circuit via one or more electrical wires, thereby providing environmental and electrical insulation for the one or more electrical wires (ia).

[0027] Additionally, the electrical connector may be heated to a temperature of 125° C. or greater for 1008 hours with the silicone elastomer seal in a compressed state, for example 25%.

[0028] Also provided is a silicone-thermoplastic composite article prepared by the above method, which may be an automotive part, a cable accessory such as an electrical or electronic connector having a silicone elastomer seal, an electrical component, an electronic component, a packaging component, a construction component, a household component, or a gasket.

[0029] Also, (i) A thermoplastic article containing no flame retardant, a flame retardant-free thermoplastic article having an accessible surface; (ii) a silicone elastomer seal that physically engages an available surface of the (i) thermoplastic article; and a silicone-thermoplastic composite article comprising: In use, the silicone elastomer seal: (1') preparing a curable silicone elastomer composition selected from a hydrosilylation reaction-curable silicone elastomer composition or a free radical reaction-curable silicone elastomer composition, wherein the curable silicone elastomer composition further comprises 0.25 wt % to a maximum of 5.0 wt % of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (2') introducing a desired amount of a curable silicone elastomer composition into a mold; (3') curing the curable silicone elastomer composition, thereby forming a silicone elastomer seal (ii), which is subjected to mechanical compression and exposure to temperatures in excess of 85°C.

[0030] Also disclosed is a method for preventing degradation of a silicone elastomer seal in physical contact with a flame retardant-free thermoplastic, the silicone elastomer seal being subjected to mechanical compression and exposure to temperatures in excess of 125°C during use; (1') preparing a curable silicone elastomer composition selected from a hydrosilylation reaction-curable silicone elastomer composition or a free radical reaction-curable silicone elastomer composition, wherein the curable silicone elastomer composition further comprises 0.25 wt % to a maximum of 5.0 wt % of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (2') introducing a desired amount of a curable silicone elastomer composition into a mold; (3') curing the curable silicone elastomer composition, thereby forming a silicone elastomer seal (ii); (4') physically engaging the silicone elastomer seal (ii) with an available surface of the electrical or electronic connector housing (ib), thereby forming the electrical or electronic connector.

[0031] (1') preparing a curable silicone elastomer composition selected from a hydrosilylation reaction-curable silicone elastomer composition or a free radical reaction-curable silicone elastomer composition, wherein the curable silicone elastomer composition further comprises 0.25 wt % to a maximum of 5.0 wt % of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (2') introducing a desired amount of a curable silicone elastomer composition into a mold; (3') curing the curable silicone elastomer composition, thereby forming the silicone elastomer part (ii), which is subjected to mechanical compression and exposed to temperatures exceeding 85°C during use.

[0032] 1. Use of 0.25 wt % to a maximum of 5.0 wt % of an additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof, as a stabilizing additive in a silicone elastomer seal in physical contact with a flame retardant-free thermoplastic that is subjected to mechanical compression and exposed to temperatures exceeding 85°C during use, wherein the silicone elastomer seal is otherwise formed from a curable silicone elastomer composition selected from a hydrosilylation reaction-curable silicone elastomer composition or a free radical reaction-curable silicone elastomer composition.

[0033] It has surprisingly been determined that the problem encountered when attempting to use silicone elastomer materials in combination with flame retardant-free thermoplastics in silicone-thermoplastic composite articles, such as connector seal applications, namely the need to avoid premature silicone elastomer seal failure after direct contact with the flame retardant-free thermoplastic, can be overcome by incorporating a stabilizing additive, for example in the form of 0.25 wt % to a maximum of 5.0 wt % of an additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof, into the silicone elastomer composition used to form the silicone elastomer seal in the silicone-thermoplastic composite article.

[0034] The addition of the stabilizing additive maintains the durability, such as mechanical integrity and dimensional stability, of the silicone elastomer portion in a silicone-thermoplastic composite article containing a flame-retardant-free thermoplastic, because it appears to maintain the physical properties of the silicone elastomer, such as compression set, despite the migration of the additive into the silicone elastomer. For example, it prevents any significant deterioration in silicone elastomer compression set in silicone elastomer seals that are subjected to mechanical compression during use and exposed to temperatures above 85°C, 100°C, or 125°C. The silicone-thermoplastic composite articles described herein are made using silicone elastomers made from the compositions described herein in combination with any suitable flame-retardant-free thermoplastic.

[0035] Flame retardant-free thermoplastics are typically used in silicone-thermoplastic composite articles to form a rigid component with a silicone elastomer molded or otherwise dispensed into a desired shape designed to form an intimate connection over and / or around the thermoplastic article. Usually, the silicone elastomer is provided in the form of a seal designed in conjunction with the rigid flame retardant-free component to provide both environmental and electrical insulation at the connector joint.

[0036] Thermoplastics that do not contain flame retardants include, for example, nylons, polyamides such as nylon 6 (PA6), nylon 6,6 (PA6,6), heat-resistant nylon 6T / 6,6 (PA6T / 6,6), nylon 6 / 10 (PA6 / 10), nylon 6 / 12 (PA6 / 12), nylon 11 (PA11), nylon 12 (PA12), and condensation polymers including polyoxymethylene, polyphenylene sulfide (PPS), polyacetal, polyamide-imide, polyphthalamide, polyetherimide, polyetherketone, polyetheretherketone, polyetherketoneetherketone, polyoxymethylene (acetal) homopolymer copolymer, syndiotactic polystyrene (sPS), and compatibilized blends of sPS with polyamide; polyethylene Condensation polymers such as polyesters including polypropylene terephthalate (PET), polybutylene terephthalate (PBT), polyarylate (PAR), and the like; polycarbonate (PC) (including impact-modified polycarbonate); polyethers such as polyphenylene oxide (PPO), maleic anhydride grafted polyphenylene oxide (PPO), maleic anhydride grafted olefin elastomers and plastomers, polysulfone, polyethersulfone, polyarylsulfone, polyphenylene ether, and the like; polypropylene, polyethylene, aliphatic polyketone (PK), thermoplastic styrene copolymers such as acrylonitrile styrene acrylate (ASA), acrylonitrile butadiene styrene (ABS), and styrene acrylonitrile (SAN); polymethyl methacrylate (PMMA), polyoxymethylene (POM). Preferably, this process is provided for use with PA6, PA6,6, PA6T / 6,6, PBT, PC, and PK, particularly PA6, PA6,6, PA6T / PA6,6, and PBT. The thermoplastic may also contain about 25-35 wt. % glass fiber (GF) as a toughening additive, such as PA6-GF25, PA6,6-GF25, PA6T / 6,6-GF33, PK-GF30, and PBT-GF30.

[0037] For the avoidance of doubt, the term flame retardant free is intended to mean, in relation to a flame retardant free thermoplastic, that no flame retardant additives have been intentionally added to the body of the thermoplastic.

[0038] The silicone elastomer used in the silicone-thermoplastic composite article is typically molded or otherwise dispensed into a desired shape designed to form an intimate connection on and / or around the flame-retardant-free thermoplastic article. It is speculated that species in the flame-retardant-free thermoplastic migrate into the silicone elastomer when firmly seated on the flame-retardant-free thermoplastic material, which adversely affects the chemical structure of the silicone elastomer and, consequently, the loss of compression set in the silicone elastomer when in direct contact with the flame-retardant-free thermoplastic in the silicone-thermoplastic composite article.

[0039] As described herein, it has now been surprisingly discovered that the inclusion of 0.25 wt. % to up to 5.0 wt. % of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof in a curable silicone elastomer composition used to make the silicone elastomer significantly improves the physical properties, such as retention of compression set properties, of silicone elastomers used in conjunction with flame-retardant-free thermoplastics in the aforementioned silicone-thermoplastic composite articles, thereby maintaining their durability and preventing premature failure of silicone elastomer parts, such as seals. This is particularly surprising because other materials, such as magnesium hydroxide (Mg(OH)2), zinc oxide (ZnO), and calcium carbonate (CaCO3), are ineffective. Similarly, acid scavengers, such as disodium phosphate (Na2HPO4), or conventional antioxidants and high-temperature compression set additives, such as iron(III) oxide (Fe2O3) and copper phthalocyanine complexes, do not offer any benefits.

[0040] Without being bound by this hypothesis, the inventors propose that there is migration of species from the flame retardant-free thermoplastic into the silicone elastomer by solid-state diffusion, and that these species cause degradation of the silicone matrix, resulting in poorer physical properties, including, by way of example, increased compression set.

[0041] It is also speculated that the stabilizing additives herein are believed to interact with these diffusible species in a manner that stops or slows down the degradation of the silicone elastomer. In the inventors' opinion, this is a surprising effect, especially since other materials that might be expected to have a similar effect, such as acid scavengers such as calcium carbonate, magnesium hydroxide, zinc oxide, etc., do not appear to have the same effect.

[0042] The silicone elastomers used in silicone-thermoplastic composite articles are designed to form tight connections on and / or around flame retardant-free thermoplastic articles, so if the silicone-thermoplastic composite article is an electrical or electronic connector, the silicone elastomer is designed / molded to provide both electrical and environmental insulation at the connector joint. However, given their location relative to other components, such as in an engine, the silicone elastomer seals are under mechanical compression and exposed to high temperatures.

[0043] They may also be in the presence of moisture, oil, fuel, corrosive gases, and may be exposed to effluents from materials with which they come into contact; therefore, it is important that the silicone elastomer have adequate compression set to allow it to retain its mechanical integrity and dimensional stability to provide adequate sealing performance over its service life.

[0044] The silicone elastomers used in the silicone-thermoplastic composite articles can be prepared by curing a suitable curable silicone elastomer composition selected from a hydrosilylation-curable silicone elastomer composition or a free-radical-curable silicone elastomer composition. The curable silicone elastomer composition can be made from either liquid silicone rubber (LSR) or high-consistency rubber (HCR), both of which, upon curing, yield silicone elastomers with an excellent balance of mechanical properties, chemical properties, and thermal stability.

[0045] Liquid silicone rubbers tend to be hydrosilylation-curable silicone rubber compositions that include the following components: a) one or more polyorganosiloxanes containing at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa·s to 100,000 mPa·s at 25°C; b) a silica reinforcing filler, which is optionally hydrophobized; and c1) c1(i)) organosilicon compounds having at least two or at least three Si—H groups per molecule, and c1(ii)) Hydrosilylation catalysts comprising or consisting of platinum group metals or compounds thereof. In the present disclosure, the liquid silicone rubber (LSR) composition must also incorporate an additional component (d), d) is 0.25% by weight to a maximum of 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof.

[0046] Various optional additives suitable for the application in which the elastomer resulting from the cure will be used may also be incorporated into the composition.

[0047] High-viscosity silicone rubbers usually contain much higher viscosity / chain length / molecular weight polymers, typically measured based on Williams plasticity values ​​rather than viscosity. Williams plasticity is measured according to ASTM D-926-08. Because of their exceptionally high viscosity, they are often referred to in the industry as "polymer gums."

[0048] Typically, the high consistency rubber composition differs from the LSR composition described above and includes the following components: a") one or more polyorganosiloxanes having a Williams plasticity number according to ASTM D-926-08 of at least 100 mm / 100, and b") Silica reinforcing filler, optionally hydrophobized.

[0049] The high consistency silicone rubber composition may be hydrosilylation cured, in which case polymer a' must also contain at least two unsaturated groups selected from alkenyl and alkynyl groups, and the composition comprises a hydrosilylation cure package c1") or a free radical curing agent c2"), c1”) is c1(i)") organosilicon compounds having at least two, or at least three Si-H groups per molecule, and c1(ii)") A hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof.

[0050] Alternatively, the highly viscous silicone rubber composition may be free-radical vulcanized, typically using an organic peroxide. When the composition used is a highly viscous silicone rubber composition, at least two unsaturated groups selected from alkenyl and alkynyl groups are optional in the polymer (a"); The composition further comprises c2") a free radical curing agent.

[0051] In the present disclosure, the high consistency silicone rubber composition must also incorporate an additional component (d"), (d") is 0.25% up to 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof. Again, various optional additives suitable for the application in which the elastomer resulting from the cure will be used may also be incorporated into the composition.

[0052] For liquid silicone rubber: Component (a) Component (a) of the liquid silicone rubber 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.

[0053] Component (a) of the liquid silicone rubber composition 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. Alternatively, component (a) has at least three unsaturated groups per molecule.

[0054] The unsaturated groups in component (a) may be at terminal, pendant, or both positions.

[0055] 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.

[0056] 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.

[0057] Component (a) of the liquid silicone rubber composition is a compound represented by 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 on 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 groups and imide groups, polyoxyalkylene groups, carbonyl groups, alkoxy groups, and oxygen-containing groups such as hydroxyl groups. Additional organyl groups may include phosphorus-containing groups and boron-containing groups. The subscript "a" is 0, 1, 2, or 3, typically where a is predominantly 2, but may contain some units where a is 1 or 3.

[0058] 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 / 2 The polydiorganosiloxanes of component (a) are substantially linear, but may contain a proportion 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.

[0059] 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).

[0060] Thus, the polymer chains of component (a) of the liquid silicone rubber composition may be selected from polydimethylsiloxane, alkylmethylpolysiloxane, alkylarylpolysiloxane, or copolymers thereof (reference to alkyl refers to any suitable alkyl group, or alternatively, an alkyl group having two or more carbon atoms), 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.

[0061] Thus, component (a) may be, for example, the following: The silicone 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, and more preferably contains 0.5 to 5% by weight of the phenyl silicone polymer.

[0062] Component a) of the liquid silicone rubber composition 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 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. Unless otherwise specified, viscosity can be measured using either a Brookfield™ rotational viscometer at 25°C at the appropriate rpm with spindle LV-4 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) at the appropriate rpm, or in cone-and-plate configuration with cone CP-52 for viscosities up to 15,000 mPa s, at the appropriate rpm and 25°C.

[0063] Ingredient (b) Component (b) of the liquid silicone rubber composition is a silica reinforcing filler that is optionally hydrophobized. The reinforcing filler of component (b) can 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.

[0064] 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.

[0065] If the silica reinforcing filler (b) 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 (b) 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.

[0066] Typically, the silica reinforcing filler (b) of the liquid silicone rubber composition may be surface treated with any low molecular weight organosilicon compound disclosed in the art that can be used to prevent creping of the liquid silicone rubber (LSR) composition during processing. For example, an organosilane, polydiorganosiloxane, or organosilazane, such as hexaalkyldisilazane or short-chain siloxanediol, may be used to render the silica reinforcing filler (b) hydrophobic, thereby making it 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.

[0067] 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.

[0068] The surface treatment of the untreated silica reinforcing filler (b) of the liquid silicone rubber composition 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 (b) is treated in situ with a treating agent in the presence of component (a), thereby preparing a silicone rubber base material that can later be mixed with the other ingredients.

[0069] The silica reinforcing filler (b) of the liquid silicone rubber composition is optionally present in an amount of 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, or alternatively from 10.0 to 35% by weight of the composition.

[0070] Component (c1) Component (c1) of the liquid silicone rubber composition is (c1(i)) an organosilicon compound having at least two or at least three Si—H groups per molecule, and (c1(ii)) A hydrosilylation cure package comprising a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof. Component (c1(i)) 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 (c1(i)) of the liquid silicone rubber composition 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 (c1(i)) can have two silicon-bonded hydrogen atoms per molecule.

[0071] The molecular structure of the organosilicon compound (c1(i)) having at least two, or alternatively 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.

[0072] The molecular weight of component (c1(i)) 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).

[0073] The silicon-bonded organic group used in component (c1(i)) 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 (c1(i)) is an alkyl group, or a methyl, ethyl, or propyl group.

[0074] Examples of organosilicon compounds (c1(i)) 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 cross-linking agent component (c1(i)) can be a filler, such as silica treated with one of the above, and mixtures thereof.

[0075] In one embodiment, component (c1(i)) of the liquid silicone rubber composition is selected from methylhydrogenpolysiloxanes terminated at both molecular ends with trimethylsiloxy groups; copolymers of methylhydrogensiloxanes terminated at both molecular ends with trimethylsiloxy groups and dimethylsiloxanes; dimethylsiloxanes terminated at both molecular ends with dimethylhydrogensiloxy groups; and copolymers of methylhydrogensiloxanes terminated at both molecular ends with dimethylhydrogensiloxy groups and dimethylsiloxanes.

[0076] The crosslinker (c1(i)) is generally present in the liquid silicone rubber composition in an amount 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 to 10:1. If this ratio is less than 0.5:1, a sufficiently cured composition will not be obtained. If this ratio is greater than 10:1, the hardness of the cured composition will tend to increase when heated.

[0077] Preferably, component (c1(i)) is present in an amount such that the molar ratio of silicon-bonded hydrogen atoms of component (b) to alkenyl / alkynyl or alkenyl groups of component (a) is in the range of from 0.7:1.0 to a maximum of 5.0:1.0, alternatively from 0.9:1.0 to 2.5:1.0, further alternatively from 0.9:1.0 to 2.0:1.0.

[0078] The silicon-bonded hydrogen (Si-H) content of component (c1(i)) 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].

[0079] Typically, depending on the number of unsaturated groups in component (a) and the number of Si—H groups in component (c1(i)), component (c1(i)) is present in an amount of 0.1 to 10 weight percent of the hydrosilylation-curable silicone rubber composition, alternatively 0.1 to 7.5 weight percent of the hydrosilylation-curable silicone rubber composition, alternatively 0.5 to 7.5 weight percent of the composition, or even 0.5 weight percent to 5 weight percent.

[0080] Component (c1(ii)) Component (c1(ii)) of the liquid silicone rubber 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 (c1(ii)) herein catalyze the reaction between unsaturated groups, usually alkenyl groups, such as vinyl, and Si-H groups.

[0081] The catalyst (c1(ii)) of the liquid silicone rubber composition can 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.

[0082] Examples of preferred hydrosilylation catalysts (c1(ii)) 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), and in this context, 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, hexachloroplatinic acid and alcohols, ethers, and aldehydes. and platinum-cyclopropane complexes of the formula (PtCl2C3H6)2, which are 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, e.g., (Ph3P)2PtCl2, and complexes of platinum with vinyl siloxanes such as sym-divinyltetramethyldisiloxane, can also be used.

[0083] 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 using the test method described for component (a).

[0084] While solvents such as organic solvents like toluene have historically been used as alternatives, the use of vinyl siloxane polymers is a much more preferred choice. These are described in U.S. Patent Nos. 3,715,334 and 3,814,730. In a preferred embodiment, component (c1(ii)) 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.

[0085] Component (c1(ii)) of the liquid silicone rubber composition 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 (c1(ii)). 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 (c1(ii)) 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.

[0086] (d) Stabilizing additives Component (d) of the liquid silicone rubber composition is from 0.25% up to 5.0% by weight of the composition, alternatively from 0.5% to 5% by weight of the composition, alternatively from 0.5% to 3% by weight of the composition, alternatively from 0.5% to 2% by weight of the composition, alternatively from 0.5% to 1.5% by weight of the composition, alternatively from 0.75% to 1.5% by weight of the composition, of a stabilizing additive for the composition selected from the group consisting of one or more magnesium carbonates, one or more magnesium hydroxycarbonates, magnesium oxide, and mixtures thereof. Alternatively, the stabilizing additive is one or more magnesium carbonates or one or more magnesium hydroxycarbonates selected from magnesite (MgCO3), barringtonite (MgCO3.2H2O), nesquehonite (MgCO3.3H2O), lansfordite (MgCO3.5H2O); and one or more magnesium hydroxycarbonates, such as pokrovskite (Mg2(CO3)(OH)2.0.5H2O), artenite, etc. (Mg2(CO3)(OH)2.3H2O), hydromagnesite (Mg5(CO3)4(OH)2.4H2O) (sometimes called light magnesium carbonate), dipingite (Mg5(CO3)4(OH)2.5H2O) (sometimes called heavy magnesium carbonate), georgiosite (Mg5(CO3)4(OH)2.5-6H2O) and sherkovite (Mg7(CO3)5(OH)4.24H2O).

[0087] High consistency silicone rubber composition For the high consistency rubber composition, components (b"), (c1") and (d") are the same as (b), (c1) and (d), respectively, of the liquid silicone rubber composition described above, except that component (a") is different, and component (c2"), a free radical curative, replaces component (c1"); (a") is chemically identical to component (a) of the LSR composition, but differs in that it has a much greater viscosity with a Williams plasticity of at least 100 mm / 100 as measured in accordance with ASTM D-926-08; At least two unsaturated groups per molecule (the unsaturated groups being selected from alkenyl or alkynyl groups) are required when component (c1") is used as a catalyst package, and are optional when component c is a free radical curing agent (c2"); and Component (c2"), the free radical curative of the high consistency rubber composition, is selected from suitable azo compounds or organic peroxides or a selection thereof. Any suitable peroxide catalyst may be utilized. Suitable organic peroxides include substituted or unsubstituted dialkyl-, alkylaroyl-, diaroyl-peroxides, such as benzoyl peroxide and 2,4-dichlorobenzoyl peroxide, ditertiarybutyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, bis(tert-butyldioxy)diisopropylbenzene bis(t-butylperoxy)-2,5-dimethylhexyne 2,4-dimethyl-2,5-di(t-butylperoxy)hexane, di-t-butyl peroxide, and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane. Mixtures of the above may also be used.

[0088] Typically, the amount of radical curing agent (c2") used in the high consistency rubber compositions described herein is from 0.2 to 3 wt. %, alternatively from 0.2 to 2 wt. %, in each case based on the weight of the composition.

[0089] Optional Additives In either case, whether the composition is a liquid silicone rubber composition or a high-consistency rubber composition, various optional additives may be incorporated into the composition to suit the application in which the elastomer resulting from the cure will be used. Examples include cure inhibitors, mold release agents, non-reinforcing fillers, adhesion catalysts, electrically conductive fillers, thermally conductive fillers, pot life extenders, lubricants, heat stabilizers, compression set additives, UV light stabilizers, fungicides, wetting agents, etc. When present, such optional additives may function as more than one type of additive.

[0090] Curing inhibitor Cure inhibitors are optionally used in hydrosilylation (addition) cure systems, for example, when the composition contains component C1, to prevent or delay the addition reaction cure 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, acetylenic alcohols, silylated acetylenic 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, with cyclic methylvinylsiloxanes being preferred.

[0091] 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.

[0092] Examples of acetylenic alcohols and their derivatives include 1-ethynyl-1-cyclohexanol (ETCH), 2-methyl-3-butyn-2-ol, 3-butyn-1-ol, 3-butyn-2-ol, propargyl alcohol, 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 acetylenic alcohols can include those compounds having at least one silicon atom.

[0093] 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.

[0094] 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.

[0095] 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 at 12 rpm using a cone-plate configuration with cone CP-52.

[0096] Non-reinforcing fillers Non-reinforcing fillers include ground quartz, diatomaceous earth, barium sulfate, iron oxide, titanium dioxide, and carbon black, talc, wollastonite, etc. Other fillers that can be used alone or in addition to the above include clays such as aluminite, calcium sulfate (anhydrite), gypsum, calcium sulfate, kaolin, aluminum trihydroxide, graphite, copper carbonates such as malachite, nickel carbonates such as zarachite, barium carbonates such as witherite, and / or strontium carbonates such as strontium stone.

[0097] Other fillers may include aluminum oxide, silicates from the group consisting of olivine, garnet, aluminosilicates; cyclic silicates, chain silicates, and layer silicates. The olivine family may include silicate minerals such as, but not limited to, forsterite and Mg2SiO4. The garnet family may include red garnet; Mg3Al2Si3O 12 ; green garnet; and Ca2Al2Si3O 12 Aluminosilicates include, but are not limited to, ground silicate minerals such as sillimanite; Al2SiO5; mullite; 3Al2O3.2SiO2; kyanite; and Al2SiO5. Cyclic silicates may also be utilized as non-reinforcing fillers, such as cordierite and Al3(Mg,Fe)2[Si4AlO 18 The chain silicate family includes, but is not limited to, ground silicate minerals such as wollastonite and Ca[SiO3]. Layered silicates may alternatively or additionally be used as non-reinforcing fillers; suitable groups include silicate minerals such as mica; K2AI; 14 [Si6Al2O 20 ](OH)4;phyllite;Al4[Si8O 20 ](OH)4; talc, Mg6[SiO 20 ](OH)4; serpentine, e.g. asbestos; kaolinite; Al4[Si4O 10 ](OH)8; and vermiculite. For the avoidance of doubt, component (d) is not considered a non-reinforcing filler.

[0098] Further additives include silicone fluids such as trimethylsilyl or OH-terminated siloxanes. Such trimethylsiloxy or OH-terminated polydimethylsiloxanes typically have viscosities of less than 150 mPa.s at 25°C, as measured using a Brookfield™ rotational viscometer at 12 rpm using a cone and plate configuration with a CP-52 cone. When present, such silicone fluids can be present in the liquid curable silicone rubber composition in an amount ranging from 0.1 to 5 weight percent (wt.%), based on the total weight of the composition, and can function as mold release agents.

[0099] Pigments and other colorants Examples of pigments include titanium dioxide, chromium oxide, bismuth vanadium oxide, iron oxide, and mixtures thereof.

[0100] Examples of colorants that can be used in the hydrosilylation-curable silicone coating composition include pigments, vat dyes, reactive dyes, acid dyes, chrome dyes, disperse dyes, cationic dyes, and mixtures thereof. The dual moisture-curable organopolysiloxane compositions described herein can further include one or more pigments and / or colorants, which can be added as needed. The pigments and / or colorants can be colored, white, black, metallic effect, and luminescent, such as fluorescent and phosphorescent. Pigments are used as needed to color the composition. Any suitable pigment may be used as long as it is compatible with the compositions herein. In dual moisture-curable organopolysiloxane compositions, pigments and / or colored (non-white) fillers, such as carbon black, may be used in the catalyst package to color the end sealant product.

[0101] Suitable white pigments and / or colorants include titanium dioxide, zinc oxide, lead oxide, zinc sulfide, lithopone, zirconium oxide, and antimony oxide.

[0102] Suitable non-white inorganic pigments and / or colorants include, but are not limited to, goethite, lepidocrocite, hematite, maghemite, and magnetite; iron oxide pigments such as black iron oxide, yellow iron oxide, brown iron oxide, and red iron oxide; blue iron pigments; chromium oxide pigments; cadmium pigments such as cadmium yellow, cadmium red, cadmium cinnabar; bismuth pigments such as bismuth vanadate and bismuth vanadate molybdate; mixed metal oxide pigments such as cobalt titanate green; chromate and molybdate pigments such as chrome yellow, molybdate red, and molybdate orange; ultramarine pigments; cobalt oxide pigments; nickel antimony titanate; lead chromium; carbon black, lamp black, and metallic effect pigments such as aluminum, copper, copper oxide, bronze, stainless steel, nickel, zinc, and brass.

[0103] Suitable organic non-white pigments and / or colorants include phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; monoarylide yellow, diarylide yellow, benzimidazolone yellow, heterocyclic yellow, DAN orange, quinacridone pigments such as quinacridone magenta and quinacridone violet, organic reds including metallized azo reds and non-metallized azo reds and other azo pigments, monoazo pigments, diazo pigments, azo pigment lakes, β-naphthol pigments, naphthol AS pigments, benzimidazolone pigments, diazo condensed pigments, isoindolinone and isoindoline pigments, polycyclic pigments, perylene and perinone pigments, thioindigo pigments, anthrapyrimidone pigments, flavanthrone pigments, anthanthrone pigments, dioxazine pigments, triarylcarbonium pigments, quinophthalone pigments, and diketopyrrolopyrrole pigments.

[0104] Typically, the pigment and / or colorant, when in the form of fine particles, has an average particle size in the range of 10 nm to 50 μm, preferably in the range of 40 nm to 2 μm.

[0105] lubricant As previously mentioned, compositions of the type described herein are often used as electrical or electronic connectors. Often, such electrical or electronic connectors are made from self-lubricating silicone elastomers designed to gradually leach out of the cured seal over time and lubricate the cable and connector assembly. Typically, polyphenylmethylsiloxanes and copolymers thereof, such as trimethylsilyl-terminated phenylmethylsiloxane dimethylsiloxane copolymers, and mixtures or derivatives thereof, having viscosities of 100 mPa.s to 200 mPa.s at 25°C using a Brookfield™ rotational viscometer at 12 rpm in a cone-plate configuration with a CP-52 cone, are In such situations, it is used as a lubricant. Examples of other lubricants that can be used alternatively or additionally include tetrafluoroethylene, resin powder, graphite, fluorinated graphite, talc, boron nitride, fluorinated oil, molybdenum disulfide, and mixtures or derivatives thereof. When present, such lubricants may be present in an amount of 1 to 7% by weight of the composition.

[0106] heat stabilizer The compositions herein may also include one or more inorganic heat stabilizers, used alone or in combination, such as hydrated cerium oxide, cerium hydroxide, cerium carboxylates and / or cerium esters such as cerium ethylhexanoate, hydrated aluminum oxide, red iron oxide, yellow iron oxide, carbon black, graphite, and zinc oxide.

[0107] metal deactivator The composition may incorporate one or more metal deactivators selected from diacylhydrazide compounds, aminotriazole compounds, and amino-containing triazine compounds. Alternatively, the metal deactivator may be an amino-containing triazine compound or a compound having a molecular weight of 120 to 700 and a phenolic group and an amide bond in its skeleton. Typically, the metal deactivator has a melting point of 80°C or higher and 300°C or lower, and the melting point is measured using differential scanning calorimetry (DSC). The melting point can be measured by DSC in accordance with JIS K 7121-1978 "Testing Methods for Transition Temperatures of Plastics." A DSC measurement pan containing a polyester resin (A) sample was placed in the DSC measurement apparatus, heated to 320°C at a heating rate of 10°C / min under a nitrogen atmosphere, and held at that temperature for 5 minutes. The temperature was then lowered to 30°C by measuring the temperature drop at 10°C / min. The temperature at the apex of the endothermic peak during heating is defined as the "melting point."

[0108] Diacylhydrazide compounds are represented by the following general formula:

[0109] [ka] In the formula, R 1 and R 2 R may be the same or different and may be represented by a hydrogen atom, a hydroxyl group, an alkyl group, a substituted alkyl group, an aryl group, a phenolic group or similar substituted aryl group, an aralkyl group, or a substituted aralkyl group. 1 and R 2Preferably, comprises a monovalent hydrocarbon group, including an aryl group, a phenol, or a similar substituted aryl group. Specific examples of the diacylhydrazide compound include N,N'-diformylhydrazine, N,N'-diacetylhydrazine, N,N'-dipropionylhydrazine, N,N'-butylhydrazine, N-formyl-N'-acetylhydrazine, N,N'-dibenzoylhydrazine, N,N'-ditritoylhydrazine, N,N'-disalicyloylhydrazine, N-formyl-N'-disalicyloylhydrazine, N-formyl-N'-butyl-substituted salicyloylhydrazine, N-acetyl-N'-salicyloylhydrazine, N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, di-(N'-salicyloyl)hydrazine adipate, and dodecandioyl-di-(N'-salicyloyl)hydrazine.

[0110] Illustrative examples of such commercially produced compounds are N,N'-bis-[3-(3,5-di-t-butyl-4-hydroxy-phenyl)propionyl]hydrazine, sold by BASF as Irganox™ MD1024, and dodecandioyl-di-(N'-salicyloyl)hydrazine, a synonym for 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide, sold commercially by Adeka Corporation as ADK STAB™ CDA-6 (hereinafter referred to as CDA-6). N'1,N'12-bis(2-hydroxybenzoyl)dodecane dihydrazide is commercially available from ADEKA Corporation as ADK STAB™ CDA-6S, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine is commercially available from ADEKA Corporation as ADK STAB™ CDA-10, and N,N'-bis-3-(3,5-di-tert-butyl-4 hydroxyphenyl)propionylhexamethylenediamine is commercially available from Kawaguchi Chemical Industry Co., Ltd. as ANTAGE HP-300.

[0111] The aminotriazole compound is represented by the following general formula (2):

[0112] [ka] In the formula, R 4 and R 5 are the same or different and are each a hydrogen atom, an alkyl group, a substituted alkyl group, a substituted aryl group, a carboxyl group, an acyl group, an alkyl ester group, an aryl ester group, a halogen atom, or an alkali metal; R 3 may represent a hydrogen atom or an acyl group; R 5 may be an acyl group, preferably a salicyloyl group, a benzoyl group, or a similar acyl group having an aromatic ring. Examples of such compounds include 3-amino-1,2,4-triazole, 3-amino-1,2,4-triazole-carboxylic acid, 3-amino-5-methyl-1,2,4-triazole, 3-amino-5-heptyl-1,2,4-triazole, etc.; or an acid amide derivative of an amino-triazole compound in which the hydrogen atom of the triazole-bonded amino group is replaced with an acyl group, such as 3-(N-salicyloyl)amino-1,2,4-triazole or 3-(N-acetyl)amino-1,2,4-triazole-5-carboxylic acid. Among these, the acid amide derivative of an aminotriazole compound is most preferred because it does not retard the curing rate of the addition reaction-curable silicone rubber composition.

[0113] An example of a commercially produced compound of this type is 3-(n-salicyloyl)amino-1,2,4-triazole (synonym for 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide), which is commercially available from Adeka Corporation as ADK STAB™ CDA-1 and in blends as ADK STAB CDA-1M. A further commercially available example is Aadestab™ ZS-27 from Adeka Corporation, the major component of which is understood to be 2,4,6-triamino-1,3,5-triazine. In one embodiment, the composition contains a metal deactivator as described above.

[0114] In one alternative, component (e)(ii) is dodecadioyl-di-(N'-salicyloyl)hydrazine or 3-(N-salicyloyl)amino-1,2,4-triazole.

[0115] When present, component (e)(ii) is added in an amount of 0.001 to 1.0% by weight of the composition, alternatively in an amount of 0.001 to 0.5% by weight of the composition, alternatively in an amount of 0.01 to 0.5% by weight of the composition, alternatively in an amount of 0.05 to 0.5% by weight of the composition.

[0116] Thus, the liquid silicone rubber compositions used to produce the silicone elastomers herein may include 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., and 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. as described above. b) silica reinforcing fillers, preferably in finely divided form and optionally hydrophobized, having a high surface area, typically at least 50 m / g (BET method according to ISO 9277:2010), or 50 to 450 m / g (BET method according to ISO 9277:2010), or 50 to 300 m / g (BET method according to ISO 9277:2010), typically representing 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, or alternatively 10.0 to 35% by weight of the composition; Component (c1) of the liquid silicone rubber composition is (c1(i)) an organosilicon compound having at least two or at least three Si—H groups per molecule, and (c1(ii)) A hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof. and a hydrosilylation cure package comprising:

[0117] The organosilicon compound having at least two, alternatively at least three, Si—H groups per molecule (c1(i)), as described above, may be present in an amount of 0.1 to 10% by weight of the liquid 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 composition, or even 0.5% to 5% by weight of the composition.

[0118] Component (c1(ii)) of the liquid silicone rubber composition is a hydrosilylation catalyst comprising or consisting of a platinum group metal or compound thereof, as described above, 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 0.01 to 1.5% by weight, 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. Component (d") is 0.25% up to 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof, provided that the total weight percent of the composition is 100% by weight.

[0119] 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.

[0120] Thus, high consistency rubber compositions that can be used to produce the silicone elastomers herein can include any suitable combination of the following ingredients: a″: one or more polyorganosiloxanes having a Williams plasticity of at least 100 mm / 100 according to ASTM D-926-08, where the hydrosilylation-curable polymer a″ must also contain at least two unsaturated groups selected from alkenyl and alkynyl groups, although the at least two unsaturated groups selected from alkenyl and alkynyl groups are optional in polymer a″ if the high consistency rubber composition is to be free-radical cured. This component a″ is 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. b") a silica reinforcing filler, which is the same as component (b) above for the liquid silicone rubber composition; Component (c1") of the high consistency rubber is a hydrosilylation cure package, which is used when the high consistency rubber is a hydrosilylation (addition) curable composition, and has the same composition and amount as component (c1) of the liquid silicone rubber composition. The component c2″ free radical curative of the high consistency rubber composition is selected from suitable azo compounds or organic peroxides or a selection thereof. The amount of radical curative (c2″) utilized in the high consistency rubber compositions described herein is 0.2 to 3 wt %, alternatively 0.2 to 2 wt %, in each case based on the weight of the composition. Again, component (d) is from 0.25% up to 5.0% by weight of the composition, alternatively from 0.5% to 5%, alternatively from 0.5% to 3%, alternatively from 0.5% to 2%, alternatively from 0.5% to 1.5%, alternatively from 0.75% to 1.5% by weight of the composition of a stabilizing additive selected from the group consisting of one or more magnesium carbonates, one or more magnesium hydroxycarbonates, magnesium oxide, and mixtures thereof; However, the total weight percent of the composition is 100 weight percent.

[0121] 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.

[0122] When the silicone elastomers used herein are prepared from liquid silicone rubber compositions as described above, such compositions are hydrosilylation curable and are typically stored in two or more parts prior to use. 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, if present, silica reinforcing filler (b), a catalyst (c1(ii)), Part (B) typically comprises the crosslinker component (c1(ii)), and, if present, the optional inhibitor, as well as the remaining polyorganosiloxane (a) and / or silica reinforcing filler (b).

[0123] It is important that the catalyst (c1(ii)) is stored separately from the crosslinker (c1(ii)) to prevent premature curing during storage.

[0124] Component (d), 0.25% to a maximum of 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof, may be stored in either Part (A) or Part (B), or both, so long as it does not adversely affect the storage of any of the essential ingredients present in each part. Alternatively, if desired, component (d) may be added to the remaining composition, i.e., the combination of the Part (A) and Part (B) compositions, either at the time or after the Part (A) and Part (B) compositions are mixed together prior to use.

[0125] 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.

[0126] The composition can be designed to be mixed in any suitable weight ratio, for example, part (A):part (B) can be mixed in a ratio of 10:1 to 1:10, alternatively 5:1 to 1:5, alternatively 2:1 to 1:2, with a weight ratio of 1:1 being most preferred.

[0127] 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 (b) 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.

[0128] 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).

[0129] 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.

[0130] The compositions of parts (A) and (B) can be designed to be mixed in any suitable ratio, for example, part (A):(B) can be mixed together in a weight ratio of 10:1 to 1:10, alternatively 5:1 to 1:5, alternatively 2:1 to 1:2, but most preferably in a 1:1 weight ratio.

[0131] Prior to use, the respective Part (A) and Part (B) compositions are mixed together in the desired ratio.

[0132] Curing of the hydrosilylation-curable silicone rubber composition on a substrate can be carried out, for example, in a mold and injection molded to form a molded part using, for example, a Liquid Injection Molding System (LIMS), press molding, extrusion, transfer molding, press vulcanization, or calendering.

[0133] In the case of a process for producing a two-part silicone rubber composition as described above, the process comprises: (i) preparing a silicone-based composition comprising components (a) a polymer and (c) a silica reinforcing filler; (ii) dividing the resulting base into two parts, i.e., part (A) and part (B), and introducing the catalyst (d) into part (A) and the 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); and (iv) storing the part (A) and part (B) compositions separately.

[0134] Typically, when used, the (A) and (B) part compositions are thoroughly mixed in the appropriate weight ratios as described above immediately prior to use to avoid premature curing. The curing step is then carried out. The hydrosilylation-curable silicone rubber composition is cured at any suitable temperature, 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.

[0135] The hydrosilylation-curable high-consistency rubber options may be prepared in a similar manner as described above, if desired. However, provided that component (a") is a silicone rubber having a Williams plasticity of at least 100 mm / 100 according to ASTM D-926-08, if the composition is to be used immediately, the composition may generally be prepared by combining all of the components together at ambient temperature to form a one-part composition. Typically, the base, if additionally present, is prepared first, and then the remaining components can be introduced into the mixture in any suitable order, to allow the reinforcing silica filler (b") to be treated in situ with the hydrophobizing treatment agent simultaneously with mixing of the polymer with the filler and any other additional treatment agents.

[0136] 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 ingredients and the final curable coating composition. Suitable mixers include, but are not limited to, paddle-type mixers, such as planetary mixers, and kneader-type mixers. However, when component (a") is a rubber, mixing is preferably carried out using a kneading mixer, as previously specified. It may be desirable to cool the ingredients during mixing to avoid premature curing of the composition.

[0137] Also described herein is a process for preparing a high consistency silicone rubber elastomer, which comprises: (i) preparing a silicone rubber-based composition comprising components (a), (b), and (c) described above; (ii) mixing components (d), (e) and simultaneously or subsequently (f) into the silicone rubber base of step (i); and (iii) curing the composition.

[0138] Step (i) can be accomplished by mixing component polymer (a") and filler (b") together with the treating agent at a temperature ranging from 80°C to 250°C, alternatively from 100°C to 220°C, alternatively from 120°C to 200°C, for a time period of 30 minutes to 2 hours, alternatively from 40 minutes to 2 hours, alternatively from 45 minutes to 90 minutes, ensuring that the reinforcing silica filler is treated in situ with the hydrophobic treating agent, all of which is thoroughly mixed into component (a"). The resulting base can then be cooled to about room temperature (23°C to 25°C).

[0139] Then, simultaneously or subsequently, the remaining ingredients, as well as optional inhibitors (e.g., ethynylcyclohexanol (ETCH)) and any other optional additives, can be added in any suitable order or simultaneously and mixed until homogeneous.

[0140] Once prepared, the composition cures due to the reactivity of the polymer, hydrosilylation crosslinker, and hydrosilylation catalyst. Typically, curing occurs at temperatures between 80°C and 180°C, alternatively between 100°C and 170°C, alternatively between 120°C and 170°C. This can be accomplished in any suitable manner, such as by introducing the composition into a mold and then press-curing for a suitable period of time, e.g., 2 to 10 minutes, or as otherwise desired or necessary. Alternatively, the hydrosilylation-curable, heat-stabilized silicone rubber composition of the present invention may be further processed by injection molding, encapsulation molding, press molding, dispenser molding, extrusion molding, transfer molding, press vulcanization, centrifugal casting, calendar molding, bead application, or blow molding. If desired, and if necessary, samples may be further post-cured by heating to temperatures between 130°C and 200°C for up to 4 hours.

[0141] Once prepared, the silicone elastomer article can be placed in its functional location on and / or around the flame retardant-free thermoplastic article to provide the final silicone-thermoplastic composite article, which is then placed / adapted into position for use as needed as part of a manufacturing process, etc.

[0142] Silicone-thermoplastic composite articles can be used in a wide range of applications in industrial settings, homes, and increasingly in automobiles. In automotive applications, they are particularly well known as rigid housing parts for electrical or electronic connector housings used to form closed electrical circuits in automotive, residential, and infrastructure environments, although they may be used as battery components, in charging and powertrain components for electric vehicles, and in noise and vibration applications.

[0143] They are also utilized in a wide range of electrical and / or insulating applications, for example, in cable accessories such as electrical or electronic connectors, terminations, and wire seals. Electrical or electronic connectors are commonly used to form 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 flame-retardant-free thermoplastic housing components to provide both electrical and environmental isolation to connector junctions from, for example, the potential presence of moisture, oil and fuel, and corrosive gases. Silicone elastomers made using the compositions herein have suitably low compression set at high temperatures, providing mechanical integrity and dimensional stability to electrical or electronic connectors such as those described above, and providing excellent sealing performance over their lifetime. Thus, they are used in or for the manufacture of automotive parts, cable accessories; electrical and electronic components; packaging components; building components such as sealants; and household components. In one embodiment, the cable accessory is an electrical or electronic connector with a silicone elastomer seal.

[0144] The following examples are intended to illustrate, but not limit, the disclosure herein. [Example]

[0145] 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 at the 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, 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.

[0146] The stability of physical properties provided by the introduction of the stabilizing additive herein is illustrated in the following examples by evaluating changes in compression set, which is believed to be caused by the stabilizing additive counteracting the weakening effect on the silicone elastomer caused by species migrating into it from the flame-retardant-free thermoplastic. The compression set results provided were certified according to industry standard ASTM D395-18, Method B, in which a cylindrical disk measuring 29.0 mm ± 0.5 mm in diameter and 12.5 mm ± 0.5 mm in thickness was compressed 25% to a thickness of approximately 9.38 mm. Under compression, an LSR button (cured by direct compression molding into a button mold at 171°C for 20 minutes) was sandwiched on both the top and bottom with a substrate (metal or flame-retardant-free thermoplastic) and placed in a conventional compression fixture. Thin metal shim plates were used, as necessary, to adjust for variability in substrate thickness. Unless otherwise noted, samples were placed in a convection oven at a specific oven temperature set for 25% compression and a specified time period (hours (h)). Subsequently, the compression was released and the test specimen was allowed to recover for 30 minutes before compression set measurement.

[0147] A series of two-part liquid silicone rubber elastomer compositions were prepared as shown in Tables 1a, 2a and 6a below.

[0148] The flame retardant-free thermoplastics utilized in the examples were: Unfilled PA66: Tecamid manufactured by Ensinger, available from McMaster Carr (Elmhurst, Illinois, USA) as part number 8539K311.

[0149] PA66 GF25: Thermoplastic PA66-GF25 is a commercially available 25% glass fiber reinforced (GF25) PA6,6 known as DURETHAN™ AKV25 from Lanxess.

[0150] PA6-GF25: Thermoplastic PA6-GF25 is a commercially available 25% glass fiber reinforced (GF25) PA6 known as DURETHAN™ BKV25 from Lanxess.

[0151] PBT GF30: Thermoplastic PBT GF30, a 30% glass fiber reinforced (GF30) PBT commercially available from Dupont known as ULTRADUR™ B 4300 G6 NAT.

[0152] For the avoidance of doubt, in the above, PA = polyamide and PBT = polybutylene terephthalate.

[0153] The following ingredients are mentioned where relevant in the compositions used: Fumed silica 1: approx. 250 m 2 Treated fumed silica (untreated) in the form of dimethylvinylated and trimethylated treated fumed silica having a BET surface area of ​​1.0 g / g.

[0154] Fumed silica 2: approx. 400 m 2 Treated fumed silica (untreated) in the form of dimethylvinylated and trimethylated treated fumed silica having a BET surface area of ​​1.0 g / g.

[0155] Polymer 1: A vinyldimethyl-terminated polydimethylsiloxane having a viscosity of 53,000 mPa.s at 25° C. as measured using a Brookfield™ rotational viscometer at 6 rpm with spindle LV-4.

[0156] Polymer 2: 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.

[0157] Silica Masterbatch 1: 66.6 wt. % dimethylvinylsiloxy terminated polydimethylsiloxane having a viscosity of about 53,000 mPa.s at 25°C and a total vinyl content of 0.17 wt. %, and about 250 m 2 A dispersion of 33.4 wt % dimethylvinylated and trimethylated treated fumed silica (untreated) with a BET surface area of ​​1.0 g / g.

[0158] Silica Masterbatch 2: 70.8 wt. % dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 53,000 mPa.s at 25°C and a total vinyl content of 0.062 wt. %, and about 250 m 2 A dispersion of 29.2 wt. % trimethylated fumed silica (untreated) with a BET surface area of ​​1.0 g / g.

[0159] Crosslinker 1: 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.

[0160] Crosslinker 2: A dimethyl, methylhydrogen siloxane with methyl silsesquioxane having a viscosity of 15 mPa.s at 25° C. using a Brookfield™ rotational viscometer in cone-plate configuration with cone CP-52 at 12 rpm.

[0161] Inhibitor: 1-ethynyl-cyclohexanol (ETCH).

[0162] Additive 1: Tetravinyl-tetramethyl-cyclotetrasiloxane.

[0163] Additive 2: 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.

[0164] Additive 3: Trimethylsilyl-terminated phenylmethylsiloxane dimethylsiloxane copolymer having a viscosity of 125 mPa.s at 25° C. using a Brookfield™ rotational viscometer in cone-plate configuration with cone CP-52 at 12 rpm.

[0165] Additive 4: Dodecandioyl-di-(N'-salicyloyl)hydrazine, which is synonymous with 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedihydrazide, commercially available from Adeka Corporation as ADK STAB™ CDA-6.

[0166] Additive 5: A hydroxydimethyl-terminated polydimethylsiloxane having a viscosity of about 42 mPa.s at 25° C. using a Brookfield™ rotational viscometer at 12 rpm using a cone-and-plate configuration with cone CP-52.

[0167] Stabilizing Additive 1: A dispersion of 85 wt. % dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 2000 mPa.s at 25°C, and 15 wt. % copper phthalocyanine commercially available from Toyocolor as LIONOL BLUE FG-7330, using a Brookfield™ rotational viscometer at 3 rpm using a cone-plate configuration with cone CP-52.

[0168] Stabilizing Additive 2: A dispersion of 50 wt. % dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of about 2000 mPa.s at 25°C, and 50 wt. % iron (III) oxide, commercially available as BAYFERROX™ 110 M from Lanxess, using a Brookfield™ rotational viscometer at 3 rpm using a cone-plate configuration with cone CP-52.

[0169] Stabilizing Additive 3: Magnesium hydroxide commercially available as Versamag™ from Akrochem.

[0170] Stabilizing Additive 4: Ground calcium carbonate having an average particle size of 3 μm, commercially available as Atomite™ from Imerys.

[0171] Stabilizing Additive 5: Ammonium stearate surface treated ground calcium carbonate having an average particle size of 3 μm, commercially available from Imerys as Gama-Sperse™ CS-11.

[0172] Stabilizing Additive 6: Zinc oxide from Sigma Aldrich, catalog number 96479.

[0173] Stabilizing Additive 7: Dibasic sodium phosphate from Sigma Aldrich, catalog number S9763.

[0174] Stabilizing Additive 8: Magnesium carbonate hydrate, commercially available from Akrochem as Akrochem™ Light Magnesium Carbonate.

[0175] Stabilizing Additive 9: Magnesium oxide commercially available as MAGOX™ 98 HR from Premier Magnesia, LLC.

[0176] In the following examples, utilizing the above, the compositions shown in Tables 1a, 2a and 6a were all prepared as follows. For the compositions of Tables 1a and 2a, two-part compositions were prepared: blending treated fumed silica 1, polymers 1 and 2, catalyst, additives 1, 2 and 3, and stabilizing additives into a first part, part A; Treated fumed silica 1, polymers 1 and 2, crosslinker 1, inhibitor, additives 2, 3, and 4, and stabilizing additive were blended together to form the second part, Part B.

[0177] A two-part LSR composition with the composition in Table 6a was prepared as follows: blending the treated fumed silica 2, polymers 1 and 2, catalyst, additives 1 and 5, and stabilizing additive into a first part, part A; The treated fumed silica 2, polymers 1 and 2, crosslinker 2, inhibitor, additive 5, and stabilizing additive were blended together to form the second part, Part B.

[0178] For each composition, the respective Parts A and B were mixed in a 1:1 weight ratio until homogeneous to yield a liquid curable silicone elastomer composition, which was then cured as described above by direct compression molding into a button mold at 171°C for 20 minutes.

[0179] The compositions of Reference Example 1 and Comparative Examples 1 to 7 (Comp. 1 to 7) are shown in Table 1a. Comparative Examples 1-7 were tested to evaluate the suitability of "Stabilizing Additives" 1-7 in stabilizing silicone rubber when in direct contact with flame-retardant-free thermoplastic materials. In most cases, it was expected that the selected "Stabilizing Additives" would help stabilize the silicone elastomer. Reference Example 1 did not contain the proposed stabilizer.

[0180] [Table 1]

[0181] To evaluate the capacity of each "stabilizer" utilized in the compositions used, the samples of Reference Example 1 (Ref. 1) and Comparative Examples 1 to 7 were in each case (a) In the first test, the sample was sandwiched between aluminum substrates (Al) on both the top and bottom. (b) In a second test, an identical sample was sandwiched at both the top and bottom with one of the flame retardant-free thermoplastics mentioned above, as indicated.

[0182] The samples were compressed at 25% at 175°C for 168 hours according to ASTM D395-18 Method B.

[0183] Each of C.1-C.7 was evaluated to determine how many "stabilizers" functioned to stabilize the silicone elastomer samples tested. The results are shown in Table 1b below.

[0184] The percentage change in compression set of unfilled PA66 relative to Al was calculated by calculating the difference in compression set between the aluminum substrate and the unfilled PA66 substrate (this is the case in Reference Example 1). (44.1-34.7=9.4) This value was then determined by determining it as a percentage of the aluminum value (e.g., (9.4 / 34.7)×100=27.1%).

[0185] [Table 2]

[0186] The comparative examples of compositions containing heat stabilizers reported in the prior art to improve the compression set of silicone elastomers, such as copper phthalocyanine (C.1) and iron oxide (C.2), show a higher percent change in compression set than Reference Example 1.

[0187] Similar findings were observed for compositions containing acid scavengers reported in the prior art, such as magnesium hydroxide (C.3), which exhibited a percent change of 39.7%.

[0188] Comparative Examples (C.4 to C.7) correspond to liquid curable silicone elastomer compositions containing a stabilizing additive that acts as an acid scavenger.

[0189] The percent change in compression set for these comparative examples was higher when in contact with an unfilled PA66 substrate than Reference Example 1. For example, the percent change for the C.4 composition containing calcium carbonate was 34% when in contact with unfilled PA66.

[0190] This was considered surprising as it would have been expected that some of the above would be determined to be suitable stabilizing additives that would stabilize the compression set results and thus help maintain the durability over time of silicone elastomers in direct contact with flame retardant-free thermoplastics, for example in silicone-thermoplastic composites.

[0191] The above was considered surprisingly insufficient, because one or two of the stabilizing additives proposed above were expected to successfully help maintain the durability of silicone elastomers, but in most cases, significantly poor compression set results were achieved.In fact, what is even more surprising is that despite the introduction of the additives, the results were only slightly improved at best compared to Reference Example 1, but generally significantly worse.In the end, none of the above was considered to be a suitable stabilizing additive that would help maintain the durability of silicone elastomers that are in direct contact with thermoplastics over time, for example in silicone-thermoplastic composites.

[0192] A further series of samples were prepared and similarly tested for compression set. The compositions used to make the elastomer samples are detailed in Table 2a below for Reference Example 1 and Examples 1-3.

[0193] Inventive Examples 1-3 disclosed in Table 2a correspond to liquid curable silicone elastomer compositions containing a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, and magnesium oxide, such as light magnesium carbonate (hydromagnesite) (Akrochem) and Magox™ 98HR magnesium oxide (Premier Magnesia, LCC).

[0194] [Table 3]

[0195] The samples were cured and tested as before, and the compression set results at 175°C for 168 hours are provided in Table 2b below.

[0196] [Table 4]

[0197] Examples 1 and 2 contain 1.0 and 1.5 wt. % of stabilizing additive 8 (light magnesium carbonate, also known as hydromagnesite), respectively. When contacted with an unfilled PA66 substrate, they exhibited a percent change in compression set of 6.2 and -20.1, respectively, which is significantly lower than Reference Example 1 (27.1%). The negative percent change in Example 2 means that the compression set of Example 2, which contains 1.5 wt. % light magnesium carbonate in unfilled PA66, was lower (40.5%) than that of Reference Example 1 (45.3%).

[0198] Similarly, a lower percent change in compression set (-6.2%) was obtained for Example 3, which contained Stabilizing Additive 9 (Magox™ 98 HR magnesium oxide).

[0199] The LSR compositions identified as Examples 1 and 3 in Table 2a above were also used as the LSR compositions in Examples 4 and 5, respectively, in contact with PA66-GF25, a glass fiber reinforced thermoplastic containing no flame retardant. The results of Reference Example 1 and Examples 4 and 5 when contacted with PA66-GF25 at 175°C for 168 hours are provided in Table 3 below.

[0200] [Table 5]

[0201] Examples 4 and 5 have the same compositions as Examples 1 and 3, each containing 1 wt. % of Stabilizing Additives 8 and 9. The percent change in compression set for Examples 4 and 5 in PA66-GF25 was -8.2 and -9.2, respectively, which is lower than Reference Example 1 (12.7%), thus confirming the benefit of Stabilizing Additives 8 and 9 in another type of flame retardant-free thermoplastic.

[0202] The LSR compositions identified as Examples 1 and 3 in Table 2a above were also used as the LSR compositions in Examples 6 and 7, respectively, in contact with a glass fiber reinforced thermoplastic, PA6-GF25, which did not contain any flame retardant additives.

[0203] The results of Reference Example 1 and Examples 6 and 7 when contacted with PA6-GF25 at 125° C. for 1008 hours are provided in Table 4 below.

[0204] [Table 6]

[0205] The compression set changes of Examples 6 (46.4%) and 7 (47.9%) when in contact with PA6-GF25 are significantly improved compared to the results seen using Reference Example 1 (74.4%), thus demonstrating the benefit of stabilizing additives 8 and 9 in another type of flame retardant-free thermoplastic under different test conditions.

[0206] The LSR compositions identified as Examples 1 and 3 in Table 2a above were also used as the LSR compositions in Examples 8 and 9, respectively, in contact with a glass fiber reinforced thermoplastic, PBT GF30, which does not contain a flame retardant. The results of Reference Example 1 and Examples 8 and 9 when contacted with PBT GF30 at 125°C for 1008 hours are provided in Table 5 below.

[0207] [Table 7]

[0208] The compression set change of Examples 8 and 9 in contact with PBT GF30 for 1008 hours at 125°C was lower than the material of Comparative Example 1, again demonstrating the benefit of stabilizing additives 8 and 9 in a thermoplastic that does not contain another type of flame retardant.

[0209] Further comparisons were made using the compositions of Table 6a. In Reference Example 2 and Example 10, Additives 3 (trimethylsilyl-terminated phenylmethylsiloxane dimethylsiloxane copolymer) or 4 (ADK STAB™ CDA-6) are absent. Thus, Example 10 does not contain Additives 3 or 4, but does contain Stabilizing Additive 8 (light magnesium carbonate).

[0210] [Table 8]

[0211] Reference Example 2 and Example 10 were tested for compression set after contact with PA66-GF25 at 175°C for 168 hours, and the results are shown in Table 6b below.

[0212] [Table 9]

[0213] It can be seen that the percent change in compression set for Example 10 in PA66-GF25 is -13.8%, which is lower than that of Reference Example 2 (7.9%).

[0214] In summary, all ten examples performed dramatically better than their respective Reference Examples 1 and 2 and indeed all comparative examples. Given the results for the compositions in Table 1, and given that failure was expected before the examples were run, this improvement was dramatic and truly surprising.

[0215] It appears that there is a form of synergy caused by using magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide or mixtures, where such materials successfully interact with species migrating within the silicone elastomer in the composite, preventing deterioration of compression set and thus maintaining the durability of the silicone in the composite article despite their physical interaction with the thermoplastic.

[0216] In a further set of examples, Examples 11, 12, and 13 correspond to liquid curable silicone elastomer compositions made with silica masterbatches 1 and 2, and containing stabilizing additives 8 (light magnesium carbonate (hydromagnesite, Akrochem), 9 (Magox™ 98 HR magnesium oxide, Premier Magnesia, LCC), and 10 (basic magnesium carbonate, light, catalog number AC211070010, Thermo Scientific™). The compositions are shown in Table 7a below. For Examples 11-13 in Table 7a, the liquid curable silicone elastomer compositions were prepared using the masterbatches to prepare two-part compositions. blending MB1 and MB2, polymer 2, catalyst, additives 1, 2, and 3, and stabilizing additives into a first part (part A); Masterbatches MB1 and MB2, Polymer 2, Crosslinker 1, Inhibitor, Additives 2, 3, and 4, and Stabilizing Additives were blended into the second part, Part B. Once prepared, the two parts were mixed together in a 1:1 weight ratio until homogeneous to yield a liquid curable silicone elastomer composition, which was then cured as described above by direct compression molding into a button mold at 171°C for 20 minutes.

[0217] [Table 10]

[0218] These samples were cured and tested in the usual manner as described above, and the compression set results are shown in Table 7b below.

[0219] [Table 11]

[0220] The compression set changes of Examples 11, 12 and 13 when in contact with PA66-GF25 were -24.1%, -15.7% and -26.4%, which were lower than the defined criteria.

Claims

1. (i) a flame retardant-free thermoplastic article, the flame retardant-free thermoplastic article having an available surface; (ii) a cured silicone elastomer portion in direct contact with the available surface of the flame retardant-free thermoplastic article (i), the cured silicone elastomer portion being the cured product of a silicone elastomer composition comprising 0.25% by weight to a maximum of 5% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof.

2. 2. The silicone-thermoplastic composite article of claim 1, wherein the flame retardant-free thermoplastic article (i) is selected from polyamide, polyoxymethylene, polyphenylene sulfide (PPS), polyacetal, polyamide-imide, polyphthalamide, polyetherimide, polyetherketone, polyetheretherketone, polyetherketoneetherketone, polyoxymethylene (acetal) homopolymer copolymer, syndiotactic polystyrene (sPS), compatibilized blends of sPS with polyamide; polyester, polycarbonate (PC), polyether, maleic anhydride grafted polyphenylene oxide (PPO), maleic anhydride grafted olefin elastomers and plastomers, polysulfone, polyethersulfone, polyarylsulfone, polyphenylene ether, polypropylene, polyethylene, aliphatic polyketone (PK) thermoplastic styrene copolymer, polymethyl methacrylate (PMMA), polyoxymethylene (POM).

3. 3. The silicone-thermoplastic composite article of claim 2, wherein the flame retardant-free thermoplastic article (i) comprises PA6, PA6,6, PA6T / 6,6, PBT, PC and PK, in particular PA6, PA6,6, PA6T / PA6,6, and PBT, and may optionally contain up to about 25-35 wt. % glass fiber (GF) as a toughening additive.

4. The stabilizing additive is magnesite (MgCO ３ ), Burlingtonite (MgCO ３ . 2H ２ O), nesquehonite (MgCO ３ .3H ２ O), Lansfordite (MgCO ３ . 5H ２ O); and one or more magnesium hydroxycarbonates, such as pokrovskite (Mg ２ (CO ３ ) (OH) ２ . 0.5H ２ O), artenite (Mg ２ (CO ３ ) (OH) ２ .3H ２ O), hydromagnesite (Mg ５ (CO ３ ) ４ (OH) ２ .4H ２ O), dipingite (Mg ５ (CO ３ ) ４ (OH) ２ . 5H ２ O), giorgiosite (Mg ５ (CO ３ ) ４ (OH) ２ . 5-6H ２ O) and sherkovite (Mg ７ (CO ３ ) ５ (OH) ４ . 24 hours ２ 4. The silicone-thermoplastic composite article of any one of claims 1 to 3, wherein the silicone-thermoplastic composite article is selected from the group consisting of hydroxybenzoates, ...

5. 5. The silicone-thermoplastic composite article of claim 4, wherein the metal deactivator(s) are selected from diacylhydrazide-based compounds, aminotriazole-based compounds, amino-containing triazine-based compounds, or mixtures thereof.

6. 6. The silicone-thermoplastic composite article of any one of claims 1 to 5, wherein in use, the silicone elastomer portion is sandwiched between two articles, at least one of which is a flame retardant-free thermoplastic article.

7. The silicone-thermoplastic composite article of any one of claims 1 to 6, wherein, in use, the silicone elastomer portion is subjected to mechanical compression and exposure to temperatures above 85°C.

8. 8. The silicone-thermoplastic composite article according to any one of claims 1 to 7, wherein the silicone elastomer portion is the cured product of a hydrosilylation-curable silicone elastomer composition or a free-radical-curable silicone elastomer composition.

9. The silicone-thermoplastic composite article of any one of claims 1 to 8, which is an automotive part, a cable accessory, an electrical part, an electronic part, a packaging part, a building part, a household part, or a gasket.

10. 10. The silicone-thermoplastic composite article of claim 9, which is an electrical or electronic connector with a silicone elastomer seal, or an electrical or electronic module housing with an optionally sealed lid, a radiator tank, a valve cover assembly, a sealed headlamp assembly, an embedded or encapsulated electronic component.

11. A method for producing the silicone-thermoplastic composite article of any one of claims 1 to 10, comprising: (a) providing a curable silicone elastomer composition comprising 0.25 to up to 5 wt. % of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (b) curing the curable elastomer composition in a mold; (c) physically engaging the cured silicone elastomer with an available surface of a flame retardant-free thermoplastic article (i) to form a silicone-thermoplastic composite article.

12. A method for producing the silicone-thermoplastic composite article of any one of claims 1 to 8, comprising: (a) providing a curable silicone elastomer composition comprising 0.25% by weight to a maximum of 5% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (b) contacting the curable silicone elastomer composition with an available surface of a flame retardant-free thermoplastic article (i); (c) curing the curable silicone elastomer composition in contact with the available surface of the flame retardant thermoplastic article to form a silicone-thermoplastic composite article.

13. 1. A method for producing a silicone-thermoplastic composite article, the silicone-thermoplastic composite article comprising: (i) A flame retardant-free thermoplastic article, a flame retardant-free thermoplastic article having an accessible surface; (ii) a silicone elastomer portion (i) physically engaging the available surface of the flame retardant-free thermoplastic; The method comprises: (1) providing a curable silicone elastomer composition comprising a hydrosilylation reaction-curable silicone elastomer composition or a free radical reaction-curable silicone elastomer composition, the curable silicone elastomer composition further comprises 0.25% to a maximum of 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (2) introducing a desired amount of the curable silicone elastomer composition into a mold; (3) curing the curable silicone elastomer composition, thereby forming (ii) the silicone elastomer portion; and (4)(ii) physically engaging the silicone elastomer seal with (i) the available surface of the flame retardant-free thermoplastic article, thereby forming the silicone-thermoplastic composite article.

14. 14. A method for producing a silicone-thermoplastic composite article according to claim 13, wherein the silicone-thermoplastic composite article comprises: (ia) one or more electrical wires; (ib) an electrical or electronic connector housing comprising a flame retardant-free thermoplastic article; 1. An electrical or electronic connector comprising: the electrical or electronic connector housing having a first available surface and a second surface opposite the outer surface; the second surface defines a cavity; the cavity accommodates therein the one or more electrical wires (ia); The method of claim 1, wherein said silicone elastomer portion (ii) is a silicone elastomer seal, said silicone elastomer seal being physically engaged with said first available surface of said electrical or electronic connector housing (ib).

15. 1. A method for maintaining the durability of a silicone elastomer part in physical contact with a flame retardant-free thermoplastic, the silicone elastomer part being subjected to mechanical compression and exposure to temperatures above 85°C during use; (1') preparing a curable silicone elastomer composition, said curable silicone elastomer composition further comprising 0.25% by weight to a maximum of 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof; (2') introducing a desired amount of the curable silicone elastomer composition into a mold; (3') curing the curable silicone elastomer composition, thereby forming the silicone elastomer portion (ii); (4') physically engaging said silicone elastomer portion (ii) with said available surface of said electrical or electronic connector housing (ib) to form said electrical or electronic connector.

16. 1. Use of 0.25 wt % to a maximum of 5.0 wt % of an additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof as a stabilizing additive in a silicone elastomer portion that is in physical contact with a flame retardant-free thermoplastic in a silicone-thermoplastic composite article.

17. The magnesium carbonate and magnesium hydroxycarbonate are 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 17. The use according to claim 16, wherein the antibacterial agent is selected from the group consisting of:

18. 18. Use according to claim 16 or 17, wherein the silicone elastomer part in use is subjected to mechanical compression and exposed to temperatures of 85°C or higher.

19. The use according to claim 16, 17 or 18, wherein the silicone-thermoplastic composite article is an automotive part, a cable accessory, an electrical part, an electronic part, a packaging part, a building part, a household part or a gasket.

20. 20. The use of claim 16, 17, 18 or 19, wherein the silicone-thermoplastic composite article is an electrical or electronic connector with a silicone elastomer seal, or an electrical or electronic module housing with an optionally sealed lid, a radiator tank, a valve cover assembly, a sealed headlamp assembly, an embedded or encapsulated electronic component.

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