Silicone-thermoplastic composite article

Abstract

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

Description

[0001] The present disclosure relates to silicone - thermoplastic composite articles and methods for maintaining the durability over time of silicone - thermoplastic composite articles comprising a flame - retardant thermoplastic and the silicone elastomeric material by incorporating stabilizing additives into the silicone elastomeric material. The present 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 elastomeric materials having a wide range of physical properties, including electrical insulation, heat resistance and thermal stability, frost resistance, abrasion resistance, flame retardancy, and long - term flexibility. This unique combination of properties makes silicone elastomers suitable for a wide range of electrical and / or insulation applications.

[0003] For example, silicone elastomers made from liquid silicone rubber (LSR) or high - consistency rubber (HCR) have been used in a variety of silicone - thermoplastic composite articles, which increasingly include flame - retardant thermoplastics and silicone elastomeric materials. The physical properties of the thermoplastic material and the silicone elastomeric material can provide composite articles with advantageous properties that would not be present if one or the other were used instead of the composite. Recently, in view of the increasing safety requirements worldwide, there has been a tendency to incorporate flame - retardant additives into thermoplastic materials. This has proven highly beneficial for thermoplastics, but when used in combination in such composite articles, the durability of the silicone elastomeric material becomes a problem. Without being bound by current theory, it has been proposed that when in close contact, especially when compressed together, the flame - retardant additives migrate into the silicone elastomeric material over time, adversely affecting the physical properties and durability of the silicone elastomeric material. This is thought to cause a loss of durability of the silicone elastomeric material, leading to the failure of the composite article.

[0004] For example, one of the most common applications of silicone elastomeric materials in silicone - thermoplastic composite articles is as seals in electrical connectors or electronic connectors or for electrical connectors or electronic connectors that are commonly used to create a closed circuit in automotive, residential, and infrastructure environments. This is due to the excellent balance of its mechanical properties, chemical and thermal stability, and ease of processing. Such electrical connectors or electronic connectors can be used in conjunction with a rigid thermoplastic housing assembly to form a tight connection that provides both electrical isolation and environmental isolation of the connector joint to create a closed circuit in, for example, automotive, residential, and infrastructure environments.

[0005] Such electrical or electronic connectors can be used, for example, in motor vehicles that increasingly rely on electrical and electronic systems, especially 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 moisture, oil and fuel, corrosive gases, and the presence of effluents from contact materials (e.g., thermoplastic housings), but must maintain their mechanical integrity and dimensional stability to provide proper sealing performance during their service life and thus prevent electrical failures.

[0006] Silicone-thermoplastic composite articles can also be used in other applications where the cured silicone is used to seal, passivate, or protect component parts from environmental and mechanical challenges (including heat, moisture, dust, and vibration), as exemplified by cover seals and adhesives for electronic module housings; gaskets or seals for radiator tanks or headlamp assemblies; potting or encapsulating agents for electrical or electronic components found in automotive, marine, aviation, aerospace, or other industrial applications.

[0007] Therefore, for silicone elastomer materials, it is important to maintain their 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 silicone rubber materials need to maintain is low compression set for applications that require, for example, environmental and electrical insulation and / or thermal stability.

[0008] Compression set is the thermally induced fatigue behavior of a silicone elastomer material, which can be defined as the loss of the ability of the silicone elastomer material to return to its initial thickness after being compressed for a specific period of time at a set (elevated) temperature. The compression set value can be measured, for example, according to industrial standard ASTM D395-18 Method A, B, or C and is determined as a percentage such that if there is complete recovery, i.e., if the thickness of the test sample is the same before and after the application of the load, the compression set value is 0%; conversely, if 25% of the silicone elastomer material compressed during the test remains unchanged when the load is removed, the compression set is 100% because it fails to fully recover to its initial shape.

[0009] Many silicone elastomer materials have significant compression set, for example, even greater than 50% or even greater than 60% compression set after being compressed for a short period of, for example, 22 hours at temperatures of 125°C and 150°C, and may suffer problems caused by corresponding changes in shape and / or a significant increase in hardness during long-term use in high-temperature applications unless they are subjected to a post-cure heating process.

[0010] "Post-curing" is the most straightforward way to minimize compression set, where hydrosilylation or peroxide-cured silicone materials are subjected to post-curing heating for a period of several hours (e.g., four hours or more) at a temperature of 150 °C or higher. However, due to the increased energy consumption and the delay in manufacturing time, given the required capital investment, post-curing is generally not commercially desirable or indeed feasible.

[0011] Many of the above applications typically desire silicone elastomer materials with as low a compression set value as possible (e.g., not greater than 40%) over a wide temperature range.

[0012] In the United States, electrical connector systems must meet the requirements of the SAE International USCAR-2 "Performance Specification for Automotive Electrical Connector Systems" test regime. Sealed connector assemblies are classified so that the suitability of these sealed connector assemblies within a specific temperature range meets a class of relevant automotive specifications for a given temperature range. Currently, five ranges are identified as T1 - T5:

[0013] T1 is a temperature rating from -40 °C to +85 °C;

[0014] T2 is a temperature range from -40 °C to +100 °C;

[0015] T3 is a temperature range from -40 °C to +125 °C;

[0016] T4 is a temperature range from -40 °C to +150 °C; and the current highest rating is

[0017] T5 is for -40 °C to 175 °C.

[0018] Given the undesirability of post-curing each silicone elastomer after curing, various additives have been proposed as an alternative way to reduce compression set.

[0019] However, industrial and vehicle components and modules are increasingly subjected to mechanical compression and exposed to increased operating temperatures greater than 125 °C.

[0020] In addition, the increasing need for the manufacturing and automotive industries to meet more complex fire safety requirements and / or regulations has led to a greater demand for the use of flame retardant (FR) plastics, particularly flame retardant thermoplastics for, e.g., connector housings.

[0021] While the use of flame retardant thermoplastics has provided the ability to meet some fire safety requirements and / or regulations, it has been reported that many silicone elastomer materials used in combination with flame retardant thermoplastics in silicone-thermoplastic composite articles (e.g., in connector seal applications) suffer premature seal failure after having been in direct contact with plastics of a flame retardant grade. Despite their well-known advantages due to their physical properties, silicone elastomers are considered incompatible with flame retardant thermoplastics in some flame retardant grade systems due to premature failure.

[0022] The object of the present disclosure is to provide a means for maintaining the durability over time of a silicone-thermoplastic composite article comprising a flame retardant thermoplastic and a silicone elastomer material.

[0023] Provided herein is a silicone-thermoplastic composite article comprising:

[0024] (i) a thermoplastic article comprising one or more flame retardant additives, wherein the thermoplastic article has an available surface, and

[0025] (ii) a cured silicone elastomer portion in direct contact with the available surface of the thermoplastic article (i), wherein the silicone elastomer portion is a cured product of a silicone elastomer composition comprising from 0.25 wt% to at most 5 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof.

[0026] Also provided herein is a method of manufacturing a silicone-thermoplastic composite article, the method comprising:

[0027] (a) providing a curable silicone elastomer composition comprising from 0.25 wt% to at most 5 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, magnesium hydroxycarbonate, magnesium oxide, and mixtures thereof,

[0028] (b) curing the curable elastomer composition in a mold,

[0029] (c) physically joining the cured silicone elastomer to the available surface of a thermoplastic article (i) comprising one or more flame retardant additives to form a silicone-thermoplastic composite article.

[0030] Also provided herein is a method of manufacturing a silicone-thermoplastic composite article as described above, the method comprising:

[0031] (a) Provide a curable organosilicon elastomer composition comprising from 0.25 wt% to a maximum of 5 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof,

[0032] (b) Contact the available surface of a thermoplastic article (i) containing one or more flame retardant additives with the curable organosilicon elastomer composition

[0033] (c) Cure the curable organosilicon elastomer composition in contact with the available surface of the flame retardant thermoplastic article to form an organosilicon-thermoplastic composite article.

[0034] Also provided herein is a method for manufacturing an organosilicon-thermoplastic composite article, wherein the organosilicon-thermoplastic composite article comprises:

[0035] (i) A thermoplastic article containing one or more flame retardant additives,

[0036] wherein the thermoplastic article has an available surface; and

[0037] (ii) An organosilicon elastomer portion, wherein the organosilicon elastomer portion is physically joined to the available surface of (i) the thermoplastic article containing one or more flame retardant additives;

[0038] The method comprises:

[0039] (1) Provide a curable organosilicon elastomer composition comprising a hydrosilylation-curable organosilicon elastomer composition or a free-radical-curable organosilicon elastomer composition,

[0040] wherein the curable organosilicon elastomer composition further comprises from 0.25 wt% to a maximum of 5.0 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof;

[0041] (2) Introduce a desired amount of the curable organosilicon elastomer composition into a mold,

[0042] (3) Cure the curable organosilicon elastomer composition, thereby forming (ii) the organosilicon elastomer portion;

[0043] (4) Physically join (ii) the organosilicon elastomer seal to the available surface of (i) the thermoplastic article containing one or more flame retardant additives, thereby forming the organosilicon-thermoplastic composite article.

[0044] In one embodiment of the latter, the silicone - thermoplastic composite article is an electrical connector or an electronic connector, wherein the electrical connector or the electronic connector comprises:

[0045] (ia) one or more electrical wires;

[0046] (ib) an electrical connector housing or an electronic connector housing, which comprises a thermoplastic material and one or more flame - retardant additives,

[0047] wherein the electrical connector housing or the electronic connector housing (ib) has a first

[0048] (outer) usable surface and a second (inner) surface opposite to the outer surface,

[0049] wherein the second (inner) surface defines a cavity, and the cavity houses the one or more electrical wires (ia); and

[0050] the silicone elastomer part (ii) is a silicone elastomer seal, wherein the silicone elastomer seal is physically joined to the first (outer) usable surface of the electrical connector housing or the electronic connector housing (ib).

[0051] In the above - mentioned method, there may be a step (5), which comprises: connecting the electrical connector or the electronic connector to a connector joint of a circuit through (i) the one or more electrical wires, thereby providing environmental and electrical insulation for the one or more electrical wires (ia).

[0052] In addition, the electrical connector or the electronic connector can be heated at a temperature of ≥125 °C for 1008 hours, wherein the silicone elastomer seal is in a compressed state, for example, 25%.

[0053] There is also provided a method for maintaining the durability of a silicone elastomer part that physically contacts a flame - retardant thermoplastic with a usable surface, the silicone elastomer part being mechanically compressed and exposed to a temperature greater than 85 °C during use, the method comprising the following steps:

[0054] (1') Prepare a 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

[0055] (2') Introduce a desired amount of the curable silicone elastomer composition into a mold,

[0056] (3') Cure the curable silicone elastomer composition, thereby forming the silicone elastomer part (ii);

[0057] (4’) Physically bond the silicone elastomer portion (ii) to the available surface of the flame-retardant thermoplastic to form a silicone-thermoplastic composite article.

[0058] There is also provided a silicone elastomer seal that, in use, is subjected to mechanical compression and exposed to a temperature greater than 85 °C, and the silicone elastomer seal is obtained by a method comprising the steps of: (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, basic magnesium carbonate, magnesium oxide, and mixtures thereof

[0059] (2') Introduce a desired amount of the curable silicone elastomer composition into a mold,

[0060] (3') Cure the curable silicone elastomer composition, thereby forming the silicone elastomer seal (ii).

[0061] There is also provided the use of an additive in the amount of 0.25 wt% to a maximum of 5.0 wt% selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof as a stabilizing additive in a silicone elastomer portion in physical contact with a flame-retardant thermoplastic.

[0062] In one embodiment, in use, the silicone elastomer portion (e.g., a seal) is subjected to mechanical compression and exposed to a temperature greater than 85 °C, and / or the silicone elastomer portion (e.g., a seal) is additionally 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.

[0063] Surprisingly, it has been identified that the problems encountered when attempting to use a silicone elastomer material in combination with a flame-retardant thermoplastic / thermoplastic article containing one or more flame-retardant additives in a silicone-thermoplastic composite article (e.g., in a connector seal application), namely, the need to avoid premature failure of the silicone elastomer seal after direct contact with a flame-retardant grade thermoplastic, can be overcome by introducing a stabilizing additive in the form of an additive in the amount of 0.25 wt% to a maximum of 5.0 wt% into the silicone elastomer composition used to form, for example, the silicone elastomer seal in the silicone-thermoplastic composite article, the additive being selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof.

[0064] The addition of the stabilizing additive maintains the durability (e.g., mechanical integrity and dimensional stability) of the silicone elastomer portion in a silicone - thermoplastic composite article that includes a thermoplastic containing a flame - retardant additive, because although the flame - retardant additive migrates into the silicone elastomer, it appears to maintain the physical properties of the silicone elastomer, such as compression set. For example, it prevents any significant deterioration of the compression set of the silicone elastomer in a silicone elastomer seal that is subjected to mechanical compression during use and is exposed to temperatures greater than 85 °C, alternatively greater than 100 °C, alternatively greater than 125 °C. The silicone - thermoplastic composite articles as described herein are prepared using a combination of a silicone elastomer prepared from the compositions described herein and any suitable flame - retardant thermoplastic.

[0065] Flame - retardant thermoplastics are commonly used in silicone - thermoplastic composite articles to form rigid components, where the silicone elastomer is molded or otherwise dispensed into a desired shape that is designed to form a tight connection over and / or around the thermoplastic article. Typically, the silicone elastomer is provided in a seal form designed to be combined with the rigid flame - retardant component to provide environmental and electrical insulation at the connector joint. The silicone - thermoplastic composite articles as described herein can contain any suitable flame - retardant thermoplastic that contains a thermoplastic with up to 10 wt% of one or more flame - retardant additives, or even more.

[0066] The thermoplastic can be, for example, a condensation polymer, which includes polyamides such as nylon, e.g., 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), etc., and polyoxymethylene, polyphenylene sulfide (PPS), polyacetal, polyamide-imide, polyphthalamide, polyetherimide, polyether ketone, polyether ether ketone, polyether ketone ether ketone, polyoxymethylene (acetal) homopolymer copolymer, syndiotactic polystyrene (sPS), and compatibilized blends of sPS and polyamide; condensation polymers such as polyesters, including polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyarylate (PAR), etc.; 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, etc.; 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 method is provided to be used in combination with PA6, PA6,6, PA6T / 6,6, PBT, PC, and PK, especially PA6, PA6,6, PA6T / PA6,6, and PBT. The thermoplastic can also contain about 25 wt% - 35 wt% of glass fiber (GF) as a reinforcing additive, e.g., PA6-GF25, PA6,6-GF25, PA6T / 6,6-GF33, PK-GF30, and PBT-GF30.

[0067] The flame retardant (FR) used in a flame-retardant thermoplastic / thermoplastic article containing one or more flame retardant additives can be any suitable flame retardant material, such as brominated flame retardants (e.g., hexabromocyclododecane, chlorinated paraffin), melamine-based flame retardants (e.g., melamine cyanurate and melamine polyphosphate), organophosphorus flame retardants (such as aromatic phosphorus flame retardants), polyphosphate flame retardants (such as ammonium polyphosphate, ammonium polyphosphate, triphenyl phosphate, dimethyl methylphosphonate, tris(2,3-dibromopropyl) phosphate (tribromone)), and metal hydroxide flame retardants (such as aluminum trihydrate), etc., and mixtures or derivatives thereof. Preferably, the flame retardant used is a non-halogenated flame retardant, alternatively a combination of an organophosphorus flame retardant and a melamine-based flame retardant with an inorganic phosphorus flame retardant, which is most commonly used in combination with a silicone elastomer in a silicone-thermoplastic composite article.

[0068] Flame retardants are classified according to their chemical structure in accordance with ISO 1043-4. The most relevant classes are:

[0069] FR(17): Combinations of aromatic brominated compounds (excluding brominated diphenyl ethers and biphenyls) with antimony compounds;

[0070] FR(30): Nitrogen compounds (limited to melamine, melamine cyanurate, urea);

[0071] FR(5X): Inorganic phosphorus compounds, where X = 0 and X = 1 correspond to ammonium orthophosphate and ammonium polyphosphate, respectively; and

[0072] FR(40): Halogen-free organophosphorus compounds such as triphenyl phosphate (TPP), resorcinol bis(diphenyl phosphate) (RDP), bisphenol A diphenyl phosphate (BADP), and tricresyl phosphate (TCP).

[0073] The silicone elastomer used in silicone - thermoplastic composite articles is typically molded or otherwise dispensed into a desired shape that is designed to form a tight bond over and / or around the thermoplastic article. It is hypothesized that when tightly secured over the thermoplastic material, species in the flame - retardant thermoplastic migrate into the silicone elastomer, and this adversely affects the chemical structure of the silicone elastomer and thus adversely affects the compression set loss in the silicone elastomer when in direct contact with the thermoplastic in the silicone - thermoplastic composite article.

[0074] As described herein, it has now been surprisingly identified that including 0.25 wt% to a maximum of 5.0 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof in a curable silicone elastomer composition for preparing a silicone elastomer significantly improves the physical properties (such as the retention of compression set properties) of the silicone elastomer when used, for example, in combination with a flame - retardant thermoplastic in the aforementioned silicone - thermoplastic composite article, maintaining its durability and avoiding 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), calcium carbonate (CaCO3) did not show an effect. Similarly, acid scavengers such as disodium phosphate (Na2HPO4) or conventional antioxidants and high - temperature compression set additives such as iron(III) oxide (Fe2O3), manganese carbonate (MnCO3), and copper phthalocyanine complexes do not provide any benefit.

[0075] Although not bound by this hypothesis, it is proposed that there are flame retardant species that migrate from the thermoplastic to the silicone elastomer by solid state diffusion, and that these species cause degradation of the silicone matrix, resulting in poor physical properties, including, for example, an increase in compression set.

[0076] It is also believed that the stabilizing additives herein interact with these diffusive species in a manner that prevents or slows down the degradation of the silicone elastomer. This appears to be 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), do not seem to have a similar effect.

[0077] Since the silicone elastomer used in silicone-thermoplastic composite articles is designed to form a tight bond over and / or around the thermoplastic article, when the silicone-thermoplastic composite article is an electrical or electronic connector, the silicone elastomer is designed / shaped to provide electrical isolation and environmental isolation to the connector joint. However, considering its positioning relative to other components, for example, within an engine, the silicone elastomer seal is under mechanical compression and exposed to high temperatures.

[0078] It can also be in the presence of moisture, oil, fuel, corrosive gases, and exposed to effluents from the materials it contacts (e.g., flame retardant plastics), and thus it is crucial that the silicone elastomer has a suitable compression set, which enables it to maintain its mechanical integrity and dimensional stability to provide proper sealing performance during its service life.

[0079] The silicone elastomer used in silicone-thermoplastic composite articles can be prepared by curing a suitable curable silicone elastomer composition selected from curable silicone elastomer compositions curable by hydrosilylation reaction or curable by free radical reaction. The curable silicone elastomer composition can be prepared from liquid silicone rubber (LSR) or high consistency rubber (HCR) because both produce silicone elastomers with an excellent balance of mechanical, chemical, and thermal stability upon curing.

[0080] Liquid silicone rubber is often a hydrosilylation curable silicone rubber composition, which comprises the following components:

[0081] 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;

[0082] b) an optionally hydrophobically treated silica reinforcing filler; and

[0083] c1) A hydrosilylation-curing package, which comprises

[0084] c1(i)) A silicone compound having at least two, alternatively at least three, Si-H groups per molecule; and

[0085] c1(ii)) A hydrosilylation catalyst comprising or consisting of a platinum group metal or its compound;

[0086] In the present disclosure, a liquid silicone rubber (LSR) composition must also incorporate an additional component (d), wherein:

[0087] (d) is a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof, in an amount of 0.25 wt% to at most 5.0 wt%.

[0088] Various optional additives suitable for applications of the elastomer produced by curing can also be incorporated into the composition.

[0089] High-consistency silicone rubbers generally contain much higher viscosity / chain length / molecular weight polymers, which are usually measured based on their Williams plasticity values rather than viscosity. The Williams plasticity is measured according to ASTM D-926-08. Due to its particularly high viscosity, it is commonly referred to as "polymer gum" in the industry.

[0090] Generally, high-consistency rubber compositions are different from the above-mentioned LSR compositions and comprise the following components:

[0091] a”) One or more polyorganosiloxanes having a Williams plasticity of at least 100 mm / 100 according to ASTM D-926-08, and

[0092] b”) Optionally, a silica reinforcing filler that has been hydrophobically treated.

[0093] High-consistency silicone rubber compositions can be hydrosilylation-curable. In this case, the polymer a' must also contain at least two unsaturated groups selected from alkenyl groups and alkynyl groups; and the composition comprises a hydrosilylation-curing package c1”) or a free-radical curing agent c2”), wherein

[0094] c1”) is a hydrosilylation-curing package, which comprises

[0095] c1(i)”) A silicone compound having at least two, alternatively at least three, Si-H groups per molecule; and

[0096] c1(ii)”) A hydrosilylation catalyst comprising or consisting of a platinum group metal or its compound;

[0097] Alternatively, the high-consistency silicone rubber composition can be free-radical cured, typically using organic peroxides. In the case where the composition used is a high-consistency silicone rubber composition, in this case, at least two unsaturated groups selected from alkenyl groups and alkynyl groups are optional in polymer a", and the composition additionally contains

[0098] c2") a free-radical curing agent.

[0099] In the present disclosure, the high-consistency silicone rubber composition must also incorporate an additional component (d"), wherein:

[0100] (d) is a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof in an amount of 0.25 wt% to a maximum of 5.0 wt%. Also, various optional additives suitable for the applications of the elastomers produced by curing can also be incorporated into the composition.

[0101] In the case of liquid silicone rubber:

[0102] Component (a)

[0103] Component (a) of the liquid silicone rubber composition is one or more polyorganosiloxanes having at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule and having a viscosity in the range of 1000 mPa·s to 100,000 mPa·s at 25°C.

[0104] Component (a) of the liquid silicone rubber composition is a polyorganosiloxane having at least two unsaturated groups per molecule, such as polydiorganosiloxane, and these unsaturated groups are selected from alkenyl groups or alkynyl groups. Alternatively, component (a) has at least three unsaturated groups per molecule.

[0105] The unsaturated groups of component (a) can be in terminal positions, side-chain positions, or both positions.

[0106] The alkenyl group can have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, alternatively 2 to 6 carbon atoms. Possible alkenyl groups are exemplified by but not limited to: vinyl group, allyl group, methallyl group, propenyl group, hexenyl group, and cyclohexenyl group.

[0107] The alkynyl group can have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, alternatively 2 to 6 carbon atoms. The alkynyl group can be exemplified by but not limited to: ethynyl group, propynyl group, and butynyl group.

[0108] Component (a) of the liquid organosilicon rubber composition has a plurality of units of formula (I): R’ a SiO (4-a) / 2 (I)

[0109] Wherein each R’ is independently selected from aliphatic hydrocarbon groups, aliphatic non-halogenated organic groups (i.e., any aliphatic organic substituent group having a free valence at a carbon atom, regardless of the type of functional group). Saturated aliphatic hydrocarbon groups are exemplified by, but not limited to, alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl, and octadecyl, and cycloalkyl groups such as cyclohexyl. Examples of unsaturated aliphatic hydrocarbon groups include, but are not limited to, the aforementioned alkenyl groups and alkynyl groups. Aliphatic non-halogenated organic groups are exemplified by, but not limited to, the following: suitable nitrogen-containing groups such as acylamino, imino; oxygen-containing groups (such as polyoxyalkylene groups, carbonyl groups, alkoxy groups, and hydroxyl groups). Additional organic groups may include phosphorus-containing groups, boron-containing groups. The subscript “a” is 0, 1, 2, or 3, and typically in this case a is mainly 2, but may contain some units where a is 1 or 3.

[0110] When R’ is an alkyl group as described above, typically a methyl group, the siloxy units can be described by a shorthand (abbreviated) nomenclature, namely - “M”, “D”, “T”, and “Q”. The M unit corresponds to the siloxy unit with a = 3, i.e., R’3SiO 1 / 2 ; the D unit corresponds to the siloxy unit with a = 2, i.e., R’2SiO 2 / 2 ; the T unit corresponds to the siloxy unit with a = 1, i.e., R’1SiO 3 / 2 ; the Q unit corresponds to the siloxy unit with a = 0, i.e., SiO 4 / 2 . The polyorganosiloxane of component (a) is substantially linear, but may contain a certain proportion of branches due to the presence of T units (as previously described) within the molecule, and thus the average value of the subscript a in structure (I) is about 2.

[0111] Typical examples of R’ groups on the polyorganosiloxane of component (a) that contain at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule mainly include alkyl groups, especially methyl and ethyl, alternatively methyl groups, but in addition to the required at least two unsaturated groups selected from alkenyl groups and / or alkynyl groups (usually alkenyl groups), may also include aryl groups and / or fluoroalkyl groups, such as trifluoropropyl groups or perfluoroalkyl groups. These groups can be in the side chain position (on the D or T silanyloxy units) or can be in the terminal position (on the M silanyloxy unit).

[0112] Accordingly, the polymer chains of component (a) of the liquid organosilicon rubber composition may be selected from polydimethylsiloxane, alkylmethylpolysiloxane, alkylarylpolysiloxane, or copolymers thereof (wherein alkyl means any suitable alkyl group, alternatively an alkyl group having two or more carbons), provided that each component (a) polymer contains at least two alkenyl groups and / or alkynyl groups, typically at least two alkenyl groups. Such polymer chains may have any suitable end groups, for example, they may be trialkyl-capped, alkenyldialkyl-capped, alkynyldialkyl-capped, or may be capped with any other suitable combination of end groups, provided that each polymer contains at least two unsaturated groups selected from alkenyl groups and alkynyl groups per molecule. In one embodiment, the end groups of such polymers do not include any silanol end groups.

[0113] Accordingly, for example, component (a) may be:

[0114] Dialkyl alkenyl-capped polydimethylsiloxane, such as dimethylvinyl-capped polydimethylsiloxane; dialkyl alkenyl-capped dimethylmethylphenylsiloxane, such as dimethylvinyl-capped dimethylmethylphenylsiloxane; trialkyl-capped dimethylmethylvinylpolysiloxane; dialkyl vinyl-capped dimethylmethylvinylpolysiloxane copolymer; dialkyl vinyl-capped methylphenylpolysiloxane, dialkyl alkenyl-capped methylvinylmethylphenylsiloxane; dialkyl alkenyl-capped methylvinyldiphenylsiloxane; dialkyl alkenyl-capped methylvinylmethylphenyldimethylsiloxane; trimethyl-capped methylvinylmethylphenylsiloxane; trimethyl-capped methylvinyldiphenylsiloxane; or trimethyl-capped methylvinylmethylphenyldimethylsiloxane. More preferably, it contains 0.5 wt% - 5 wt% of a phenyl organosilicon polymer.

[0115] Component (a) of the liquid organosilicon rubber composition has a viscosity of 1000 mPa·s to 100,000 mPa·s at 25°C, alternatively 5000 mPa·s to 75,000 mPa·s at 25°C, 10,000 mPa·s to 60,000 mPa·s at 25°C, and is preferably present in an amount of 25 wt% to 60 wt% of the composition, alternatively 30 wt% to 60 wt% of the composition, alternatively 35 wt% to 55 wt% of the composition. Unless otherwise specified, the viscosity may be measured at 25°C using a Brookfield with spindle LV-4 for viscosities exceeding 5,000 mPa·s TMA rotational viscometer (spindle LV-4 designed for viscosities in the range between 1,000 mPa·s and 2,000,000 mPa·s) is measured at the appropriate rpm, and for viscosities up to 15,000 mPa·s at 25 °C and the appropriate rpm a Brookfield with a cone-plate arrangement with cone CP-52 is used TM The rotational viscometer measures.

[0116] Component (b)

[0117] Component (b) of the liquid organosilicon rubber composition is an optionally hydrophobically treated silica reinforcing filler; the reinforcing filler of component (b) may be exemplified by fumed silica and / or precipitated silica and / or colloidal silica. In an alternative, the fumed silica, precipitated silica and / or colloidal silica are provided in a finely divided form.

[0118] Precipitated silica, fumed silica and / or colloidal silica are particularly preferred because of their relatively high surface area (especially when provided in a finely divided form, usually at least 50 m 2 / g (BET method according to ISO 9277:2010)). Fillers with a surface area of 50 to 450 m 2 / g (BET method according to ISO 9277:2010), alternatively 50 to 300 m 2 / g (BET method according to ISO 9277:2010) are typically used. All these types of silica are commercially available.

[0119] When the silica reinforcing filler (b) has natural hydrophilicity (e.g., untreated silica filler), it is usually treated with a treating agent to impart hydrophobicity to it. These surface-modified silica reinforcing fillers (b) do not agglomerate and can be uniformly incorporated into the polydiorganosiloxane polymer (a) described below because the surface treatment makes the filler easy to be wetted by component (a).

[0120] Typically, any low molecular weight silicone compound known in the art and suitable for preventing wrinkling of the liquid silicone rubber (LSR) composition during processing can be used to surface-treat the silica reinforcing filler (b) of the liquid silicone rubber composition. For example, silanes, polydiorganosiloxanes or silazanes, such as hexyl disilazane, short-chain siloxane diols, to impart hydrophobicity to the silica reinforcing filler (b) and thus make it easier to handle and obtain a homogeneous mixture with other components. Specific examples include, but are not limited to, silanol-terminated trifluoropropylmethylsiloxane, silanol-terminated vinylmethyl (ViMe) siloxane, silanol-terminated methylphenyl (MePh) siloxane, liquid hydroxy dimethyl-terminated polydiorganosiloxane having an average of 2 to 20 diorganosiloxane repeating units per molecule, hydroxy dimethyl-terminated phenylmethylsiloxane, hexaorganodisiloxanes such as hexamethyldisiloxane, divinyltetramethyldisiloxane; hexaorganodisilazanes, such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane and tetramethylbis(trifluoropropyl)disilazane; hydroxy dimethyl-terminated polydimethylmethylvinylsiloxane, octamethylcyclotetrasiloxane and silanes, including but not limited to methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, trichloromethylsilane.

[0121] In one embodiment, the treating agent can be selected from silanol-terminated vinylmethyl (ViMe) siloxane, liquid hydroxy dimethyl-terminated polydiorganosiloxane having an average of 2 to 20 diorganosiloxane repeating units per molecule, hexaorganodisiloxanes, such as hexamethyldisiloxane, divinyltetramethyldisiloxane; hexaorganodisilazanes, such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane; and hydroxy dimethyl-terminated polydimethylmethylvinylsiloxane, octamethylcyclotetrasiloxane and silanes, including but not limited to methyltriethoxysilane, dimethyldiethoxysilane and / or vinyltriethoxysilane. A small amount of water can be added together with the silica treating agent as a processing aid.

[0122] The surface treatment of the untreated silica reinforcing filler (b) of the liquid silicone rubber composition can be carried out before introducing the composition or in situ (i.e., in the presence of at least a portion of the other components of the composition herein, by blending these components together at room temperature or higher temperature until the filler is completely treated). Typically, the untreated silica reinforcing filler (c) is treated in situ with the treating agent in the presence of component (b), which results in the preparation of a silicone rubber matrix material that can subsequently be mixed with other components.

[0123] The silica reinforcing filler (b) of the liquid organosilicon rubber composition is optionally present in an amount of up to 40% by weight of the composition, alternatively 1.0% to 40% by weight of the composition, alternatively 5.0 wt.% to 35 wt.% of the composition, alternatively 10.0 wt.% to 35 wt.% of the composition.

[0124] Component (c1)

[0125] Component (c1) of the liquid organosilicon rubber composition is a hydrosilylation curing package, and the hydrosilylation curing package contains

[0126] (c1(i)) an organosilicon compound having at least two, alternatively at least three Si-H groups per molecule; and

[0127] (c1(ii)) a hydrosilylation catalyst containing or consisting of a platinum group metal or its compound;

[0128] Component (c1(i)) serves as a crosslinking agent and is provided in the form of an organosilicon compound having at least two, alternatively at least three Si-H groups per molecule. Component (c1(i)) of the liquid organosilicon rubber composition usually contains three or more silicon-bonded hydrogen atoms, so the hydrogen atoms can react with the unsaturated alkenyl groups and / or alkynyl groups of component (a) to form a network structure with them, and thereby cure the composition. When polymer (a) has more than two unsaturated groups per molecule, some or all of component (c1(i)) can alternatively have two silicon-bonded hydrogen atoms per molecule.

[0129] The molecular configuration of the organosilicon compound (c1(i)) having at least two, alternatively at least three Si-H groups per molecule is not particularly limited. It can be a linear, branched (linear with some branches due to the presence of T groups), cyclic or silicone resin-based polyorganosiloxane.

[0130] Although the molecular weight of component (c1(i)) is not particularly limited, using the test method described for component (a), the viscosity at 25 °C is usually 5 mPa·s to 50,000 mPa·s.

[0131] The silicon-bonded organic groups used in component (c1(i)) can be exemplified by: alkyl groups such as methyl, ethyl, propyl, n-butyl, tert-butyl, pentyl, hexyl; aryl groups such as phenyl, tolyl, xylyl or similar aryl groups; 3-chloropropyl, 3,3,3-trifluoropropyl or similar haloalkyl groups, preferably alkyl groups having 1 to 6 carbons, especially methyl, ethyl or propyl or phenyl. Preferably, the silicon-bonded organic groups used in component (c1(i)) are alkyl groups, alternatively methyl groups, ethyl groups or propyl groups.

[0132] Examples of the organosilicon compound (c1(i)) having at least two, alternatively at least three Si-H groups per molecule include, but are not limited to:

[0133] (a’) Trimethylsiloxy-terminated methylhydrogenpolysiloxane,

[0134] (b’) Trimethylsiloxy-terminated polydimethylsiloxane-methylhydrogensiloxane,

[0135] (c’) Dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymer,

[0136] (d’) Dimethylsiloxane-methylhydrogensiloxane cyclic copolymer,

[0137] (e’) Copolymer and / or organosilicon resin composed of (CH3)2HsiO 1 / 2 units, (CH3)3SiO 1 / 2 units and SiO 4 / 2 units,

[0138] (f’) Copolymer and / or organosilicon resin composed of (CH3)2HsiO 1 / 2 units and SiO 4 / 2 units,

[0139] (g’) Methylhydrogensiloxane cyclic homopolymer having 3 to 10 silicon atoms per molecule;

[0140] Alternatively, the component (c1(i)) crosslinking agent can be a filler, such as silica treated with one of the above substances, and mixtures thereof.

[0141] In one embodiment, the component (c1(i)) of the liquid organosilicon rubber composition is selected from methylhydrogenpolysiloxane terminated with trimethylsiloxy groups at both molecular ends; a copolymer of methylhydrogensiloxane and dimethylsiloxane terminated with trimethylsiloxy groups at both molecular ends; dimethylsiloxane terminated with dimethylhydrogensiloxy groups at both molecular ends; a copolymer of methylhydrogensiloxane and dimethylsiloxane terminated with dimethylhydrogensiloxy groups at both molecular ends.

[0142] The crosslinking agent (c1(i)) is 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 groups and / or alkynyl groups in component (a) is from 0.5:1 to 10:1. When the ratio is less than 0.5:1, a well-cured composition is not obtained. When the ratio exceeds 10:1, there is a tendency for the cured composition to increase in hardness when heated. Preferably, the amount of component (c1(i)) is such that the molar ratio of the silicon-bonded hydrogen atoms of component (b) to the alkenyl / alkynyl groups, alternatively alkenyl groups, of component (a) is in the range from 0.7:1.0 to at most 5.0:1.0, alternatively from 0.9:1.0 to 2.5:1.0, and further alternatively from 0.9:1.0 to 2.0:1.0.

[0143] The silicon-bonded hydrogen (Si-H) content of component (c1(i)) is determined by quantitative infrared analysis in accordance with ASTM E168. In this case, when relying on a hydrosilylation curing process, the ratio of silicon-bonded hydrogen to alkenyl (vinyl) and / or alkynyl is important. Generally speaking, this is determined by calculating the total weight % of alkenyl (e.g., vinyl) [V] in the composition and the total weight % of silicon-bonded hydrogen [H] in the composition, and assuming a molecular weight of 1 for hydrogen and a molecular weight of 27 for vinyl, the molar ratio of silicon-bonded hydrogen to vinyl is 27[H] / [V].

[0144] Generally, depending on the number of unsaturated groups in component (a) and the number of Si-H groups in component (c1(i)), component (c1(i)) will be present in the following amounts: 0.1% to 10% by weight of the rubber composition curable by hydrosilylation, alternatively 0.1% to 7.5% by weight of the organosilicon rubber composition curable by hydrosilylation, alternatively 0.5% to 7.5% by weight of this composition, and further alternatively 0.5% to 5% by weight of the silicone rubber composition curable by hydrosilylation.

[0145] Component (c1(ii))

[0146] Component (c1(ii)) of the liquid silicone rubber composition is a hydrosilylation catalyst comprising a platinum group metal or a compound thereof or consisting of a platinum group metal or a compound thereof. These catalysts are generally selected from catalysts of platinum group metals (platinum, ruthenium, osmium, rhodium, iridium, and palladium), or compounds of one or more of such metals. Alternatively, due to the high activity level of these catalysts in the hydrosilylation reaction, platinum and rhodium compounds are preferred, with platinum compounds being most preferred. In the hydrosilylation (or addition) reaction, a hydrosilylation catalyst such as component (c1(ii)) herein catalyzes the reaction between an unsaturated group (usually an alkenyl group, such as vinyl) and an Si-H group.

[0147] The catalyst (c1(ii)) of the liquid organosilicon rubber composition can be a platinum group metal, a platinum group metal deposited on a carrier (such as activated carbon, metal oxides such as alumina or silica, silica gel or charcoal powder), or a compound or complex of a platinum group metal. Preferably, the platinum group metal is platinum.

[0148] Examples of preferred hydrosilylation catalysts (c1(ii)) are platinum-based catalysts such as platinum black, platinum oxide (Adams catalyst), platinum on various solid carriers, chloroplatinic acid (e.g., hexachloroplatinic acid (Pt oxidation state IV) (Speier catalyst)), chloroplatinic acid in a solution of an alcohol (such as isooctanol or pentanol) (Lamoreaux catalyst), and complexes of chloroplatinic acid with ethylenically unsaturated compounds (such as olefins) and organosiloxanes containing ethylenically unsaturated silicon-bonded hydrocarbon groups, such as tetraethenyltetramethylcyclotetrasiloxane-platinum complex (Ashby catalyst). Soluble platinum compounds that can be used include, for example, platinum-olefin complexes of the formula (PtCl2. olefin)2 and H(PtCl3. olefin), and in this context, olefins having 2 to 8 carbon atoms, such as isomers of ethylene, propylene, butene, and isomers of octene, or cycloalkanes having 5 to 7 carbon atoms, such as cyclopentene, cyclohexene, and cycloheptene, are preferably used. Other soluble platinum catalysts are, for example, platinum-cyclopropane complexes of the formula (PtCl2C3H6)2, reaction products of hexachloroplatinic acid with alcohols, ethers, and aldehydes or mixtures thereof, or reaction products of hexachloroplatinic acid and / or its conversion products with vinyl-containing siloxanes (such as methylvinylcyclotetrasiloxane) in the presence of an ethanol solution containing sodium bicarbonate. Platinum catalysts having phosphorus and amine ligands, such as (Ph3P)2PtCl2, can also be used; and complexes of platinum with vinylsiloxanes, such as symmetric divinyltetramethyldisiloxane.

[0149] Thus, specific examples of suitable platinum-based catalysts include

[0150] (i) Complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups described in US 3,419,593;

[0151] (ii) Chloroplatinic acid in the form of hexahydrate or anhydrous form;

[0152] (iii) Platinum-containing catalysts obtained by a method including the step of reacting chloroplatinic acid with an aliphatic unsaturated organosilicon compound (such as divinyltetramethyldisiloxane); (iv) Olefin-platinum-silyl complexes as described in US Patent 6,605,734, such as (COD)Pt(SiMeCl2)2, where "COD" is 1,5-cyclooctadiene; and / or

[0153] (v) Karstedt catalyst, platinum divinyltetramethyldisiloxane complex, typically contains about 1 wt% of platinum in a vinylsiloxane polymer having a viscosity of about 200 to 750, typically using the test method as described for component (a).

[0154] Solvents such as toluene and similar organic solvents have historically been used as alternatives, but the use of vinylsiloxane polymers has so far been the preferred choice. These are described in US 3,715,334 and US 3,814,730. In a preferred embodiment, component (c1(ii)) can be selected from coordination compounds of platinum. In one embodiment, hexachloroplatinic acid and its conversion products with vinyl-containing siloxanes, Karstedt catalyst, and Speier catalyst are preferred.

[0155] Component (c1(ii)) of the liquid organosilicon rubber composition is typically present in an amount providing 0.1 ppm to 500 ppm (parts per million) of platinum atoms relative to the weight of the reactive components, i.e., components (a) and (c1(ii)). The catalyst can be added as a single substance or as a mixture of two or more different substances. Generally, depending on the form / concentration of the catalyst (c1(ii)) provided, the amount of catalyst present will be in the range of 0.05 wt% - 1.5 wt%, alternatively 0.05 wt% - 1.0 wt%, alternatively 0.1 wt% - 1.0 wt%, alternatively 0.1 wt% to 0.5 wt% of the composition, where the platinum catalyst is provided in the masterbatch of the polymer (such as (a) as described above).

[0156] (d) Stabilizing additive

[0157] Component (d) of the liquid organosiloxane rubber composition is from 0.25% to at most 5.0% by weight of the composition, alternatively from 0.5% to 5% by weight of the composition, 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 selected from the group consisting of: one or more magnesium carbonates, one or more hydroxy magnesium carbonates, magnesium oxide and mixtures thereof. Alternatively, the stabilizing additive comprises one or more magnesium carbonates or hydroxy magnesium carbonates selected from magnesite (MgCO3), barringtonite (MgCO3.2H2O), nesquehonite (MgCO3.3H2O), lansfordite (MgCO3.5H2O); and one or more hydroxy magnesium carbonates such as pokrovskite (Mg2(CO3)(OH)2.0.5H2O), fiber magnesite (Mg2(CO3)(OH)2.3H2O), hydromagnesite (Mg5(CO3)4(OH)2.4H2O) (sometimes referred to as light magnesium carbonate), artinite (Mg5(CO3)4(OH)2.5H2O) (sometimes referred to as heavy magnesium carbonate), giorgiosite (Mg5(CO3)4(OH)2.5 - 6H2O) and shelkovite (Mg7(CO3)5(OH)4.24H2O).

[0158] High-consistency silicone rubber composition

[0159] In the case of a high-consistency rubber composition, components (b”), (c1”) and (d”) are the same as (b), (c1) and (d) of the above liquid organosiloxane rubber composition, respectively. However, component (a”) is different and component (c2”) is a free-radical curing agent instead of component (c1”), where:

[0160] (a”) is chemically consistent with component (a) of the LSR composition, but has the following differences in that it has a much higher viscosity, which has a Williams plasticity of at least 100 mm / 100 measured according to ASTM D-926-08; and

[0161] When component (c1”) is used as a catalyst package, at least two unsaturated groups selected from alkenyl groups or alkynyl groups are required per molecule, and when component c is a free-radical curing agent (c2”), the unsaturated groups are optional; and

[0162] Component (c2 ” )

[0163] The component (c2”), i.e., the free radical curing agent of the high-consistency rubber composition, is selected from suitable azo compounds or organic peroxides or a selection thereof. Any suitable peroxide catalyst can be utilized. Suitable organic peroxides include substituted or unsubstituted dialkyl peroxides, alkyl aryl acyl peroxides, and diacyl peroxides, such as benzoyl peroxide and 2,4-dichlorobenzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, bis(tert-butylperoxy)diisopropylbenzene, bis(tert-butylperoxy)-2,5-dimethylhexine, 2,4-dimethyl-2,5-bis(tert-butylperoxy)hexane, di-tert-butyl peroxide, and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane. Mixtures of the above can also be used.

[0164] Generally, the amount of the free radical curing agent (c2”) used in the high-consistency rubber composition as described herein is, in each case, from 0.2% by weight to 3% by weight, alternatively 0.2% by weight to 2% by weight, based on the weight of the composition.

[0165] Optional additive

[0166] In each case, i.e., regardless of whether the composition is a liquid silicone rubber composition or a high-consistency rubber composition, various optional additives suitable for the applications for which the elastomer to be produced by curing will be used can also be incorporated into the composition. Examples include curing inhibitors, release agents, non-reinforcing fillers, adhesion catalysts, conductive fillers, heat-conductive fillers, shelf-life extenders, flame retardants, lubricants, heat stabilizers, compression set additives, UV light stabilizers, bactericides, wetting agents, etc. When present, the optional additives can serve as more than one type of additive.

[0167] Curing inhibitor

[0168] When needed, a curing inhibitor is used in a hydrosilylation (addition) curing system, for example, when the composition contains component C1, to prevent or delay the addition reaction curing process, especially during storage. Optional addition reaction inhibitors for platinum-based catalysts are well known in the art and include hydrazine, triazole, phosphine, thiol, organic nitrogen compounds, alkynols, methanesilylated alkynols, maleates, fumarates, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, ethylenic siloxanes, mono- and diesters of unsaturated hydrocarbons, conjugated enyne, hydroperoxides, nitriles, and diaziridines. Vinyl-substituted siloxanes as described in US3989667 can be used, and cyclic methyl vinyl siloxanes are preferred therein.

[0169] A known class of hydrosilylation reaction inhibitors are the acetylenic compounds disclosed in US3445420. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors, which will inhibit the activity of platinum-containing catalysts at 25 °C. Compositions containing these inhibitors typically need to be heated at a temperature of 70 °C or above in order to cure at an achievable rate.

[0170] 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. Acetylenic alcohol derivatives can include those compounds having at least one silicon atom.

[0171] When present, an inhibitor concentration as low as 1 mole inhibitor / mole of metal catalyst will, in some cases, impart satisfactory storage stability and cure rate. In other cases, an inhibitor concentration of up to 500 moles inhibitor / mole of metal catalyst is required. The optimal concentration of a given inhibitor in a given composition can be readily determined by routine experimentation. Depending on the concentration and form in which the selected inhibitor is provided / commercially available, when present in the composition, the inhibitor is typically present in an amount of 0.0125% to 10% by weight of the composition.

[0172] In one embodiment, when present, the inhibitor is selected from 1-ethynyl-1-cyclohexanol (ETCH) and / or 2-methyl-3-butyn-2-ol, and is present in an amount greater than zero to 0.1% by weight of the composition.

[0173] Release agent

[0174] Any suitable release agent can be utilized. For example, it can be a hydroxyl-terminated dimethylpolysiloxane having a viscosity of about 21 mPa·s at 25 °C, which viscosity is measured using a Brookfield TM rotational viscometer with a cone-plate arrangement having a cone CP-52 at 12 rpm.

[0175] Non-reinforcing filler

[0176] Non-reinforcing fillers can include, such as, ground quartz, diatomaceous earth, barium sulfate, iron oxide, titanium dioxide, and carbon black, talc, wollastonite. Fillers that can be used alone or in addition to the above include bauxite, calcium sulfate (anhydrite), gypsum, calcium sulfate, clays such as kaolin, aluminum trihydrate, graphite, copper carbonate such as malachite, nickel carbonate such as violarite, barium carbonate such as witherite, and / or strontium carbonate such as strontianite.

[0177] Other fillers can include aluminum oxide, silicates selected from the group consisting of: olivines; garnets; aluminosilicates; ring silicates; chain silicates; and sheet silicates. Olivines include silicate minerals such as, but not limited to, forsterite and Mg2SiO4. Garnets include ground silicate minerals such as, but not limited to, pyrope; Mg3Al2Si3O 12 ; grossular; and Ca2Al2Si3O 12 . Aluminosilicates include ground silicate minerals such as, but not limited to, sillimanite; Al2SiO5; mullite; 3Al2O3.2SiO2; kyanite; and Al2SiO5. Ring silicates can be used as non-reinforcing fillers, and these include silicate minerals such as, but not limited to, cordierite and Al3(Mg,Fe)2[Si4AlO 18 . Chain silicates include ground silicate minerals such as, but not limited to, wollastonite and Ca[SiO3]. Sheet silicates can alternatively or in addition be used as non-reinforcing fillers, and suitable classes include silicate minerals such as, but not limited to, mica; K2AI 14 [Si6Al2O 20 (OH)4; pyrophyllite; Al4[Si8O 20 (OH)4; talc; Mg6[Si8O 20 (OH)4; serpentine, such as asbestos; kaolinite; Al4[Si4O 10 (OH)8; and vermiculite. For the avoidance of doubt, component (d) is not considered a non-reinforcing filler.

[0178] TM Other additives include silicone fluids such as trimethylsilyl or OH-terminated siloxanes. Such trimethylsilyloxy or OH-terminated polydimethylsiloxanes generally have a viscosity of <150 mPa.s at 25 °C, which is measured using a Brookfield

[0179] Pigments and other colorants rotational viscometer with a cone-plate arrangement with a cone CP-52 at 12 rpm. When present, such silicone fluids can be present in the liquid curable silicone rubber composition in an amount in the range of 0.1 wt% to 5 wt% (wt%) based on the total weight of the composition, and can be used as a release agent.

[0180] Examples of pigments include titanium dioxide, chromium(III) oxide, bismuth vanadium oxide, iron oxide, and mixtures thereof.

[0181] Examples of colorants that can be used in the organosilicon coating compositions curable by hydrosilylation include pigments, vat dyes, reactive dyes, acid dyes, chrome dyes, disperse dyes, cationic dyes, and mixtures thereof. The two-part moisture-curable organopolysiloxane compositions as described herein can also contain one or more pigments and / or colorants, which can be added if desired. 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 pigments that provide compatibility with the compositions herein can be utilized. In the two-part moisture-curable organopolysiloxane compositions, pigments and / or colored (non-white) fillers such as carbon black can be used in the catalyst package to color the final sealant product.

[0182] Suitable white pigments and / or colorants include titanium dioxide, zinc oxide, lead oxide, zinc sulfide, lithopone, zirconium oxide, and antimony oxide.

[0183] Suitable non-white inorganic pigments and / or colorants include, but are not limited to, iron oxide pigments such as goethite, lepidocrocite, hematite, maghemite, and magnetite black iron oxides, yellow iron oxides, brown iron oxides, and red iron oxides; blue iron pigments; chromium oxide pigments; cadmium pigments such as cadmium yellow, cadmium red, and cadmium vermilion; bismuth pigments such as bismuth vanadate and bismuth molybdate vanadate; 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 chromate; carbon black; lamp black; and metallic effect pigments such as aluminum, copper, copper oxide, bronze, stainless steel, nickel, zinc, and brass.

[0184] 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 condensation pigments, isoindolinone and isoindoline pigments, polycyclic pigments, perylene and violanthrone pigments, thioindigo pigments, anthrapyrimidine pigments, flavanthrone pigments, anthraquinone pigments, dioxazine pigments, triarylmethonium pigments, quinophthalone pigments, and diketopyrrolopyrrole pigments.

[0185] Typically, pigments and / or colorants, when in particulate form, have an average particle size in the range of 10 nm to 50 μm, preferably in the range of 40 nm to 2 μm.

[0186] Lubricant

[0187] As previously indicated, compositions of the type described herein are typically used as electrical or electronic connectors. Typically, such electrical or electronic connectors are made of self-lubricating silicone elastomers that are designed to gradually exude over time from the cured seal and lubricate the cable and connector assembly. Typically, polyphenylmethylsiloxanes and their copolymers, such as trimethylsilyl-terminated phenylmethylsiloxane dimethylsiloxane copolymers, have a viscosity of 100 mPa·s to 200 mPa·s at 25 °C, which is measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with a cone CP-52 at 12 rpm, and mixtures or derivatives thereof. These are used as lubricants in such cases. 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 can be present in an amount of 1 wt% to 7 wt% of the composition.

[0188] Heat stabilizer

[0189] The compositions of the present invention may also contain one or more inorganic heat stabilizers used alone or in combination, such as hydrated cerium oxide, cerium hydroxide, cerium carboxylate, and / or cerium esters, such as cerium ethylhexanoate, hydrated aluminum oxide, red iron oxide, yellow iron oxide, carbon black, graphite, and zinc oxide.

[0190] Metal deactivator

[0191] The composition may incorporate one or more metal deactivators selected from diacylhydrazine-based compounds, aminotriazole-based compounds, and aminotriazine-containing compounds. Alternatively, the metal deactivator has a molecular weight of 120 to 700 and is a triazine compound containing an amino group or a compound having a phenolic group and an amide bond in the main chain. Generally, the metal deactivator has a melting point of 80 °C or higher and 300 °C or lower, where the melting point is measured by differential scanning calorimetry (DSC). The melting point can be determined by differential scanning calorimetry (DSC) according to JIS K 7121-1978 "Testing Methods for Transition Temperatures of Plastics". In this apparatus, a DSC measurement pan sealed with a polyester resin (A) sample is set, heated to 320 °C at a heating rate of 10 °C / min in a nitrogen atmosphere, and held at this temperature for 5 minutes. By measuring the temperature decrease at 10 °C / min, the temperature is decreased to 30 °C. The temperature at the apex of the endothermic peak during heating is defined as the "melting point".

[0192] The diacylhydrazine-based compound is represented by the following general formula:

[0193]

[0194] where R 1 and R 2 may be the same or different and may be represented by: a hydrogen atom, a hydroxyl group, an alkyl group, a substituted alkyl group, an aryl group, a phenolic group or a similar substituted aryl group, an aralkyl group or a substituted aralkyl group. Preferably, R 1 and R 2 contain a monovalent hydrocarbon group containing an aryl group, a phenolic group or a similar substituted aryl group. Specific examples of the above diacylhydrazine-based compounds are as follows: N,N'-dimethylhydrazine, N,N'-diacetylhydrazine, N,N'-dipropionylhydrazine, N,N'-butylhydrazine, N-formyl-N'-acetylhydrazine, N,N'-dibenzoylhydrazine, N,N'-dimethylbenzoylhydrazine, N,N'-disalicylhydrazine, N-formyl-N'-disalicylhydrazine, N-formyl-N'-butyl-substituted salicylhydrazine, N-acetyl-N'-salicylhydrazine, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propargyl]hydrazine, di-(N'-salicyl) adipate or dodecanedioyl-di-(N'-salicyl)hydrazine.

[0195] Commercially produced above compounds include, for example, N,N'-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine), which is produced by BASF under the name Irganox TMMD1024 is for sale, dodecanedioyl-bis-(N'-salicyl)hydrazine, the synonyms of which are 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedioylhydrazine, which is used as ADK STAB TM CDA-6 is commercially available and obtained from Adeka Corporation (hereinafter referred to as CDA-6); N'1,N'12-bis(2-hydroxybenzoyl)dodecanedioylhydrazine, which is used as ADK STAB TM CDA-6S is obtained from Adeka Corporation, and N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, which is used as ADK STAB TM CDA-10 is obtained from Adeka Corporation, and N,N'-bis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionylhexamethylenediamine, which is obtained from Kawaguchi Chemical Industry as ANTAGE HP-300.

[0196] The amino-triazole-based compound is represented by the following general formula (2):

[0197]

[0198] R 4 and R 5 are the same or different and are represented by: 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 or an alkali metal; R 3 can represent a hydrogen atom or an acyl group. R 5 can be an acyl group, preferably a salicyl group, a benzoyl group or a similar acyl group having an aromatic ring. Examples of the above compounds can 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 amide derivatives of amino-triazole-based compounds, in which the hydrogen atom of the triazole-bonded amino group is replaced by an acyl group, for example, 3-(N-salicyl)amino-1,2,4-triazole or 3-(N-acetyl)amino-1,2,4-triazole-5-carboxylic acid. Among the above compounds, the most preferred are the amide derivatives of amino-triazole-based compounds because these compounds do not delay the curing rate of the addition-reaction-curable silicone rubber composition.

[0199] Examples of commercially produced compounds of this type are 3-(salicyl)amino-1,2,4-triazole (synonym 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide), which is available commercially from Adeka Corporation as ADK STAB TM CDA-1 and as a blend with ADK STABCDA-1M. Another commercial example is Adekastab from Adeka Corporation TM ZS-27, the main component of which is understood to be 2,4,6-triamino-1,3,5-triazine.

[0200] In an alternative, component (e)(ii) is dodecanedioyl-di-(N”-salicyl)hydrazide or 3-(N-salicyl)amino-1,2,4-triazole.

[0201] When present, component (e)(ii) is usually added in an amount of 0.001 wt% to 1.0 wt% of the composition, alternatively 0.001 wt% to 0.5 wt% of the composition, alternatively 0.01 wt% to 0.5 wt% of the composition, alternatively 0.05 wt% to 0.5 wt% of the composition.

[0202] In one embodiment, the composition contains a metal deactivator as described above.

[0203] Thus, the liquid silicone rubber composition for producing the silicone elastomer herein may comprise any suitable combination of the following components:

[0204] 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; alternatively 5000 mPa·s to 75,000 mPa·s at 25 °C, 10,000 mPa·s to 60,000 mPa·s at 25 °C, preferably present in an amount of 25 wt% to 60 wt% of the composition, alternatively in an amount of 30 wt% to 60 wt% of the composition, alternatively in an amount of 35 wt% to 55 wt% of the composition. The viscosity can be measured at 25 °C as described above;

[0205] b) a silica reinforcing filler, which is preferably in a finely divided form and optionally hydrophobized; having a high surface area, which is usually at least 50 m 2 / g (BET method according to ISO 9277:2010). The silica reinforcing filler (c) has 50 m 2 / g to 450 m 2 / g (BET method according to ISO 9277:2010), alternatively 50 m 2 / g to

[0206] 300 m 2 / g (BET method according to ISO 9277:2010) and is typically present in an amount of: up to 40 wt% of the composition, alternatively 1.0 wt% of the composition

[0207] to 40 wt%, alternatively 5.0 wt.% to 35 wt.% of the composition, alternatively 10.0 wt.% to 35 wt.% of the composition;

[0208] Component (c1) of the liquid organosilicon rubber composition is a hydrosilylation curing package, and the hydrosilylation curing package comprises

[0209] (c1(i)) an organosilicon compound having at least two, alternatively at least three Si-H groups per molecule; and

[0210] (c1(ii)) a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof;

[0211] The organosilicon compound (c1(i)) having at least two, alternatively at least three Si-H groups per molecule as described above may be present in an amount of 0.1 wt% to 10 wt% of the liquid organosilicon rubber composition, alternatively 0.1 wt% to 7.5 wt% of the organosilicon rubber composition that can be hydrosilylation cured, alternatively 0.5 wt% to 7.5 wt% of the composition, and further alternatively 0.5 wt% to 5 wt%.

[0212] Component (c1(ii)) of the liquid organosilicon rubber composition is a hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound thereof as described above; its amount depends on the form / concentration of the catalyst provided and is in the range of 0.001 wt% to 3.0 wt% of the composition, alternatively 0.001 wt% to 1.5 wt% of the composition, alternatively 0.01 wt% to 1.5 wt% of the composition, and alternatively 0.01 wt% to 0.1 wt% of the silicone rubber composition.

[0213] Component (d) is a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof in an amount of 0.25 wt% to a maximum of 5.0 wt%;

[0214] Provided that the total wt% of the composition is 100 wt%.

[0215] The composition may also contain one or more of the above-mentioned optional additives in the amounts indicated again, provided that the total weight % of the composition is 100% by weight.

[0216] Thus, the high-consistency rubber composition useful for producing the silicone elastomers herein may comprise any suitable combination of the following components:

[0217] a”) one or more polyorganosiloxanes having a Williams plasticity of at least 100 mm / 100 according to ASTM D-926-08, wherein when the polymer a” is curable by hydrosilylation

[0218] must also contain at least two unsaturated groups selected from alkenyl groups and alkynyl groups, while when the high-consistency rubber composition is cured by free radicals, at least two unsaturated groups selected from alkenyl groups and alkynyl groups are optional in the polymer a”; this component a” is preferably present in the composition in an amount of 25% to 60% by weight, alternatively in an amount of 30% to 60% by weight, alternatively in an amount of 35% to 55% by weight.

[0219] b”) a silica reinforcing filler, which is the same as component (b) of the liquid silicone rubber composition above;

[0220] The component (c1”) of the high-consistency rubber is a hydrosilylation curing package and is used when the high-consistency rubber is a composition curable by hydrosilylation (addition) and has the same composition and amount as component (c1) of the above liquid silicone rubber composition; location,

[0221] Component c2”, i.e., the free radical curing agent of the high-consistency rubber composition, is selected from suitable azo compounds or organic peroxides or a selection thereof; the amount of the free radical curing agent (c2”) used in the high-consistency rubber composition as described herein is in each case 0.2% to 3% by weight, alternatively 0.2% to 2% by weight, based on the weight of the composition;

[0222] In addition, component (d) is 0.25% to a maximum of 5.0% by weight, alternatively 0.5% to 5% by weight, alternatively 0.5% to 3% by weight, alternatively 0.5% to 2% by weight, alternatively 0.5% to 1.5% by weight, alternatively 0.75% to 1.5% by weight of a stabilizing additive selected from the group consisting of: one or more magnesium carbonates, one or more hydroxy magnesium carbonates, magnesium oxide, and mixtures thereof;

[0223] provided that the total weight % of the composition is 100% by weight.

[0224] The composition may also contain one or more of the above-mentioned optional additives in the amounts indicated again, provided that the total weight % of the composition is 100% by weight.

[0225] When the silicone elastomer used herein is prepared from a liquid silicone rubber composition as described above, such compositions are hydrosilylation curable and are generally stored in two or more parts prior to use. In the case of a two-part composition, the two parts are generally referred to as part (A) and part (B):

[0226] In addition to the polyorganosiloxane (a) and the silica reinforcing filler (b) (when present), part (A) generally contains a catalyst (c1(ii)), and

[0227] Part (B) generally contains a crosslinking agent component (c1(ii)), and optionally an inhibitor when present, as well as the remaining polyorganosiloxane (a) and / or silica reinforcing filler (b).

[0228] It is important to store the catalyst (c1(ii)) separately from the crosslinking agent (c1(ii)) to prevent premature curing during storage.

[0229] Component (d), namely 0.25% to a maximum of 5.0% by weight of a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof. It can be stored in part (A) or part (B) or in both parts, provided that these parts do not negatively affect the storage of any essential components present in the respective parts. Alternatively, if desired, component (d) can be added to the remaining composition, i.e., to the combination of part (A) and part (B) compositions, during or after mixing part (A) composition and part (B) composition together prior to use.

[0230] Any optional additives other than the inhibitors described above can be incorporated in part (A) or part (B) or in both parts, provided that they do not negatively affect the storage of any essential components present in the respective parts.

[0231] The composition can be designed to be mixed in any suitable ratio, for example, part (A): part (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 a weight ratio of 1:1.

[0232] The ingredients / components in each of part (A) and / or part (B) can be individually mixed together in the corresponding part, or can be introduced into the composition in a prefabricated combination form, for example, to facilitate the mixing of the final composition. For example, components (a) and (b) are usually mixed together before introducing other ingredients to form an LSR polymer base or masterbatch. These can then be mixed with other ingredients of the directly prepared part, or can be used to prepare prefabricated concentrates commonly referred to as masterbatches in the industry.

[0233] In this case, in order to facilitate the mixing of the ingredients, one or more masterbatches can be used to successfully mix the ingredients to form part (A) and / or part (B) compositions. For example, a "pyrogenic silica" masterbatch can be prepared. This is actually an LSR silicone rubber base with in-situ treated silica reinforcing filler (c).

[0234] Parts A and B of the composition can be prepared by combining all their respective components at ambient temperature. Any mixing techniques and devices described in the prior art can be used for this purpose. The specific device to be used will depend on the components and the viscosity of the final composition. Suitable mixers can include, but are not limited to, kneading mixers, static mixers in liquid injection molding machines, Z-blade mixers, two-roll mills (open mills), three-roll mills, Haake TM Rheomix OS Lab mixers, single-screw extruders or twin-screw extruders, etc. Optionally, high-speed mixers such as those sold by, for example, Hauschild and as DC 150.1FV, DAC 400FVZ or DAC600FVZ can be used. It may be desirable to cool the components during mixing to avoid premature curing of the composition.

[0235] Parts (A) and (B) compositions can be designed to be mixed in any suitable weight ratio, for example, part (A): part B can be mixed together in a weight ratio of 10:1 to 1:10, or 5:1 to 1:5, or 2:1 to 1:2, but most preferably in a weight ratio of 1:1.

[0236] Before use, the corresponding parts (A) and (B) compositions are mixed together in the desired ratio.

[0237] The hydrosilylation-curable silicone rubber composition can be cured on a substrate, for example, in a mold, to form a molded part by injection molding such as compression molding, extrusion molding, transfer molding, pressure vulcanization or calendering using, for example, a liquid injection molding system (LIMS).

[0238] Regarding the method of manufacturing a two-part silicone rubber composition as described above, the method can include the following steps:

[0239] (i) Prepare a silicone base composition comprising component (a) a polymer and (c) a silica reinforcing filler,

[0240] (ii) Divide the resulting base into two parts, part (A) and part (B), introduce catalyst (d) into part (A), and introduce crosslinker (b) and inhibitor (if present) into part (B) composition.

[0241] (iii) Introduce any other optional additives of other components into either or both of part (A) and part (B); and

[0242] (iv) Store part (A) and part (B) compositions separately.

[0243] Generally, when in use, part (A) and part (B) compositions are thoroughly mixed at a suitable weight ratio as described above, and thoroughly mixed immediately before use to avoid premature curing. Then a curing stage is carried out for curing. The hydrosilylation-curable silicone rubber composition cures at any suitable temperature, for example, cures at a temperature of 80 °C to 200 °C, alternatively about 100 °C to 180 °C, alternatively about 120 °C to 180 °C. As indicated above, one of the standard methods for reducing compression set has historically been post-curing, aiming to reduce the number of curable groups that may cure under compression during use as a gasket.

[0244] If desired, a high-consistency rubber option of hydrosilylation-curable can be prepared in a manner similar to that described above. However, since component (a”) is a silicone gum having a Williams plasticity of at least 100 mm / 100 according to ASTM D-926-08, in the case of using the composition immediately, the composition can generally be prepared by combining all components at ambient temperature to form a one-part composition. Generally, the base is first prepared so that the reinforcing silica filler (b”) can be treated in situ with a hydrophobic treatment agent while mixing the polymer and the filler and any other treatment agents (when present additionally), and then the remaining ingredients can be introduced into the mixture in any suitable order.

[0245] Any mixing techniques and devices described in the prior art can be used for this purpose. The specific device to be used will be determined by the components and the viscosity of the final curable coating composition. Suitable mixers include but are not limited to paddle mixers, such as planetary mixers and kneader-type mixers. However, when component (a”) is a gum, it is preferred to carry out mixing, as described above, using a kneader mixer. It may be desirable to cool the components during mixing to avoid premature curing of the composition.

[0246] A method for preparing a high-consistency silicone rubber elastomer is also described herein, the method comprising the following steps:

[0247] (i) Prepare a silicone rubber base composition comprising components (a), (b) and (c) as described above,

[0248] (ii) Mix components (d), (e) and, simultaneously or subsequently, component (f) into the silicone rubber base from step (i); and

[0249] (iii) Cure the composition.

[0250] Step (i) can be achieved by mixing the component polymer (a”) and the filler (b) with the treating agent (c) together for a period of 30 minutes to 2 hours, alternatively 40 minutes to 2 hours, alternatively 45 minutes to 90 minutes at a temperature in the range of 80 °C to 250 °C, alternatively 100 °C to 220 °C, alternatively 120 °C to 200 °C, to ensure that the reinforcing silica filler is treated in-situ with the hydrophobic treating agent and is thoroughly mixed into component (a”). The resulting base can then be cooled to approximately room temperature (23 °C to 25 °C).

[0251] The remaining components and, optionally, an inhibitor (e.g., ethynylcyclohexanol (ETCH)) and any other optional additives can then be added simultaneously or subsequently, in any suitable order, or simultaneously and mixed to homogeneity.

[0252] Once prepared, the composition will cure due to the reactivity of the polymer, the hydrosilylation crosslinker and the hydrosilylation catalyst. Generally, curing will occur at a temperature between 80 °C and 180 °C, alternatively between 100 °C and 170 °C, alternatively between 120 °C and 170 °C. This can be carried out in any suitable manner, for example, the composition can be introduced into a mold and then pressure-cured for a suitable time, such as 2 to 10 minutes, or as otherwise desired or required. The hydrosilylation-curable thermally stable silicone rubber composition of the present invention can alternatively be further processed by injection molding, encapsulation molding, compression molding, dispenser molding, extrusion molding, transfer molding, compression vulcanization, centrifugal compression vulcanization, calendering, bead application or blow molding. When needed, the sample can be additionally post-cured by heating to a temperature of 130 °C to 200 °C for up to 4 hours.

[0253] Once prepared, the silicone elastomeric article can be placed in its functional position on and / or around the thermoplastic article to provide the final silicone-thermoplastic composite article. Subsequently, the silicone-thermoplastic composite article is placed / assembled in position to be used as part of a manufacturing process, etc. and when needed as part of a manufacturing process, etc.

[0254] Silicone - thermoplastic composite products can be used in a wide range of applications in industrial scenarios, households, and increasingly in automobiles. In automotive applications, they can be used as battery components, charging components, and powertrain components for electric vehicles, as well as for noise and vibration applications. However, it is particularly well - known that they are rigid housing components for electrical connector housings or electronic connector housings used to create closed circuits in automotive, residential, and infrastructure environments.

[0255] They are also used in a wide range of electrical applications and / or insulation applications, such as for cable accessories like electrical connectors or electronic connectors, terminals, and wire seals. Electrical connectors or electronic connectors are commonly used to create closed circuits in automotive, residential, and infrastructure environments due to the excellent balance of their mechanical properties, chemical and thermal stability, ease of processing, and availability of self - lubricating formulations. They can be used in conjunction with rigid thermoplastic housing components to provide electrical isolation and environmental isolation to connector joints, preventing the potential presence of, for example, moisture, oil, fuel, and corrosive gases. The silicone elastomers prepared using the compositions herein have suitable low compression set at high temperatures, thus providing mechanical integrity and dimensional stability for electrical connectors or electronic connectors, etc., as described above, and thus providing excellent sealing performance during the service life. Therefore, they are used in or for manufacturing automotive parts, cable accessories; electrical and electronic components; packaging components; building components such as sealants; household components. In one embodiment, the cable accessory is an electrical connector or electronic connector with a silicone elastomer seal.

[0256] The following examples are intended to illustrate and not limit the present disclosure herein. Examples

[0257] Unless otherwise specified, all viscosities are measured at 25 °C. Unless otherwise stated, the viscosities of the individual components in the following examples are measured using a Brookfield rotational viscometer with spindle LV - 4 for viscosities exceeding 15,000 mPa·s (spindle LV - 4 designed for viscosities in the range of 1,000 mPa·s - 2,000,000 mPa·s) at the appropriate rpm, and for viscosities up to 15,000 mPa·s using a Brookfield rotational viscometer with a cone - plate arrangement with cone CP - 52 at the appropriate rpm. TM rotational viscometer (spindle LV - 4 designed for viscosities in the range of 1,000 mPa·s - 2,000,000 mPa·s) at the appropriate rpm, and for viscosities up to 15,000 mPa·s using a Brookfield rotational viscometer with a cone - plate arrangement with cone CP - 52 at the appropriate rpm. TM rotational viscometer measurement.

[0258] The stability of the physical properties caused by the stabilizing additives introduced herein is illustrated by evaluating the change in compression deformation in the following examples, which is believed to be caused by the stabilizing additives counteracting the weakening effect of the flame retardants migrated from the thermoplastics into the silicone elastomers being tested. The compression results provided are according to the industrial standard specification ASTM D395 - 18 Method B, where a cylindrical disk with a diameter of 29.0 mm ± 0.5 mm and a thickness of 12.5 mm ± 0.5 mm is compressed by 25% to a thickness of approximately 9.38 mm. Under compression, the silicone elastomer button is clamped between the top and bottom with a substrate (metal or plastic) and placed in a normal compression fixture. When needed, thin metal shims are used to adjust the variability of the substrate thickness. Unless otherwise stated, the samples are placed in a convection oven and compressed by 25% at an oven temperature set to specific conditions. Subsequently, the compression is released, and the test pieces are allowed to recover for 30 minutes before the compression deformation measurement is made. A series of 2 - part liquid silicone rubber elastomers and peroxide - cured silicone rubber compositions are prepared as indicated in Tables 1a, 2a, 4, and 5 below.

[0259] In the compositions used, the following components are mentioned where appropriate:

[0260] Fumed silica 1: Treated fumed silica (untreated) in the form of fumed silica treated with dimethylethylenation and trimethylation having a BET surface area of approximately 250 m 2 / g.

[0261] Fumed silica 2: Treated fumed silica (untreated) in the form of fumed silica treated with dimethylethylenation and trimethylation having a BET surface area of approximately 400 m 2 / g.

[0262] Fumed silica 3: Hydrophilic fumed silica having a specific surface area of 200 m2 / g.

[0263] Precipitated silica: Precipitated silica from Tosoh Silica Corporation.

[0264] Polymer 1: Vinyl - dimethyl - terminated polydimethylsiloxane having a viscosity of 53,000 mPa.s at 25°C, which viscosity is measured at 6 rpm using a Brookfield TM rotational viscometer with spindle LV - 4

[0265] Polymer 2: Vinyl-terminated poly(dimethylsiloxane-co-methylvinylsiloxane) having a viscosity of 370 mPa·s at 25 °C, which viscosity is measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm.

[0266] Silica masterbatch 1: A dispersion of 66.6 wt% dimethylethenylsilanyloxy-terminated polydimethylsiloxane having a viscosity of about 53,000 mPa·s at 25 °C and a total vinyl content of 0.17 wt%, and 33.4 wt% of pyrogenic silica that has been dimethylethenylated and trimethylated and has a BET surface area (untreated) of about 250 m 2 / g.

[0267] Silica masterbatch 2: A dispersion of 70.8 wt% dimethylethenylsilanyloxy-terminated polydimethylsiloxane having a viscosity of about 53,000 mPa·s at 25 °C and a total vinyl content of 0.062 wt%, and 29.2 wt% of pyrogenic silica that has been trimethylated and has a BET surface area (untreated) of about 250 m 2 / g.

[0268] Silicone rubber 1: A dimethyl, methylvinyl, hydroxy-terminated silicone rubber having a Williams plasticity of 160 mm / 100 and a vinyl content of 1.37 wt%.

[0269] Silicone rubber 2: A dimethylethenyl-terminated, dimethyl, methylvinylsiloxane rubber having a Williams plasticity of 155 mm / 100 and a vinyl content of 0.06 wt%.

[0270] Silicone rubber 3: A dimethylethenyl-terminated dimethylsiloxane rubber having a Williams plasticity of 154 mm / 100 and a vinyl content of 0.01 wt%.

[0271] Crosslinker 1: Trimethyl-terminated polymethylhydrodimethysiloxane having a viscosity of 30 mPa·s at 25 °C, which viscosity is measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm.

[0272] Crosslinker 2: A dimethyl, methylhydrogensiloxane and methyl sesquisiloxane having a viscosity of 15 mPa·s at 25 °C, which viscosity is measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm.

[0273] Inhibitor: 1-ethynyl-cyclohexanol (ETCH).

[0274] Peroxide catalyst: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0275] Additive 1: Tetravinyl-tetramethyl-cyclotetrasiloxane.

[0276] Additive 2: Hydroxydimethyl-terminated polydimethylsiloxane having a viscosity of approximately 21 mPa·s at 25 °C, this viscosity being measured using a Brookfield TM rotational viscometer with spindle LV-2 at 12 rpm.

[0277] Additive 3: Trimethylsilyl-terminated phenylmethylsiloxane dimethylsiloxane copolymer having a viscosity of 125 mPa·s at 25 °C, this viscosity being measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm.

[0278] Additive 4: Dodecanedioyl-di-(N'-salicyl)hydrazine, the synonym of which is 1-N',12-N'-bis(2-hydroxybenzoyl)dodecanedioylhydrazine, commercially available as ADK STAB TM CDA-6 and commercially obtained from Adeka Corporation.

[0279] Additive 5: Hydroxydimethyl-terminated polydimethylsiloxane having a viscosity of approximately 42 mPa·s at 25 °C, this viscosity being measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm.

[0280] Additive 6: Dimethylmethylvinylhydroxy-terminated siloxane having a viscosity of approximately 23 mPa·s at 25 °C, this viscosity being measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm.

[0281] Additive 7: Methylphenyl, hydroxy-terminated siloxane having a viscosity of approximately 500 mPa·s at 25 °C, this viscosity being measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 12 rpm.

[0282] Additive 8: A dispersion of 60% by weight of a dimethylvinyl-terminated, dimethyl, methylvinylsiloxane gum having a Williams plasticity of 155 mm / 100 and a vinyl content of 0.06% by weight and 40% by weight of calcium stearate.

[0283] Additive 9: Quartz commercially available as Silverbond 915 from Inabata & Co., Ltd.

[0284] Additive 10: A dispersion of 57% by weight of a dimethylvinyl-terminated dimethylsiloxane gum having a Williams plasticity of 154 mm / 100 and a vinyl content of 0.01% by weight and 43% by weight of cerium oxide.

[0285] Additive 11: 1,4-Butanediol.

[0286] Stabilizing Additive 1: Manganese(II) carbonate with catalog number 377449 from Sigma Aldrich

[0287] Stabilizing Additive 2: A dispersion of 85% by weight of a dimethylvinylsilyloxy-terminated polydimethylsiloxane having a viscosity of about 2000 mPa·s at 25°C, the viscosity being measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 3 rpm, and 15% by weight of copper phthalocyanine commercially available as LIONOL BLUE FG-7330 from Toyocolor.

[0288] Stabilizing Additive 3: A dispersion of 50% by weight of a dimethylvinylsilyloxy-terminated polydimethylsiloxane having a viscosity of about 2000 mPa·s at 25°C, the viscosity being measured using a Brookfield TM rotational viscometer with a cone-plate arrangement with cone CP-52 at 3 rpm.

[0289] As BAYFERROX TM 50% by weight of iron(III) oxide commercially available as 110M from anxess.

[0290] Stabilizing Additive 4: Magnesium hydroxide commercially available as Versamag TM from Akrochem

[0291] Stabilizing Additive 5: Ground calcium carbonate with an average particle size of 3 μm commercially available as Atomite TM from Imerys.

[0292] Stabilizing Additive 6: As Gama-Sperse TMCS-11 is a ground calcium carbonate surface-treated with ammonium stearate and having an average particle size of 3 μm, commercially obtained from Imerys.

[0293] Stabilizing additive 7: Zinc oxide with catalog number 96479 from Sigma Aldrich.

[0294] Stabilizing additive 8: Disodium hydrogen phosphate with catalog number S9763 from Sigma Aldrich.

[0295] Stabilizing additive 9: As Akrochem TM Magnesium carbonate hydrate, commercially obtained as light magnesium carbonate from Akrochem.

[0296] Stabilizing additive 10: As MAGOX TM Magnesium oxide, commercially obtained as 98HR from Premier Magnesia, LLC.

[0297] Stabilizing additive 11: Basic light magnesium carbonate with catalog number AC211070010 from Thermo Scientific TM

[0298] In the following examples, Tables 1a, 2a, and 4a describe two-part LSR compositions. The compositions depicted in Tables 1a and 2a are prepared as follows:

[0299] In the case of the compositions in Tables 1a and 2a, a two-part LSR composition is prepared:

[0300] The treated pyrogenic silica 1, polymers 1 and 2, catalyst, additives 1, 2, and 3, and stabilizing additives are blended into the first part, Part A, and

[0301] The treated pyrogenic silica 1, polymers 1 and 2, crosslinking agent 1, inhibitor, additives 2, 3, and 4, and stabilizing additives are blended together into the second part, Part B.

[0302] In the case of the compositions in Table 4, a two-part LSR composition is prepared as follows:

[0303] The treated pyrogenic silica 2, polymers 1 and 2, catalyst, additives 1 and 5, and stabilizing additives are blended into the first part, Part A, and

[0304] The treated pyrogenic silica 2, polymers 1 and 2, crosslinking agent 2, inhibitor, additives 5, and stabilizing additives are blended together into the second part, Part B.

[0305] In each composition, the corresponding parts A and B were mixed together in a 1:1 weight ratio until homogeneous to obtain a liquid-curable silicone elastomer composition, which was then cured by direct compression molding into a button mold at 171 °C for 20 minutes.

[0306] The compositions of Reference 1 and Comparative Examples 1 to 8 (Comparative Examples 1 to 8) are depicted in Table 1a.

[0307] Table 1a: Composition (wt%) of Reference 1 and Comparative Compositions C.1 to C.8

[0308]

[0309]

[0310] To evaluate the ability of each "stabilizer" used in the compositions of Table 1a, the samples of Reference 1 and Comparative Examples 1 to 8 were, in each case,

[0311] (a) sandwiched between a top and bottom aluminum substrate (Al) in a first test, and (b) sandwiched between a top and bottom 25% glass fiber-reinforced (GF25), flame retardant PA6,6 / 6T-GF25 FR(40) (a halogen-free flame retardant PA6,6 / 6T containing an organophosphate flame retardant, commercially available as Zytel TM FR95G25V0NH NC010 obtained commercially from Dupont) in a second test.

[0312] The samples were compressed at 25% at 175 °C for 168 hours according to ASTM D395-18 Method B.

[0313] Each of C.1 to C.8 was evaluated to determine how much "stabilizer" served to stabilize the silicone elastomer samples tested and was not negatively affected by the presence of the flame retardant. The results are depicted in Table 1b below.

[0314] The percentage change in compression set of PA6,6 / 6T-GF25 FR(40) relative to Al was determined by calculating the difference between the compression set value when aluminum was the substrate and the compression set value when PA6,6 / 6T-GF25 FR(40) was the substrate. For Reference 1, this percentage change was

[0315] 54.8 – 34.7 = 20.1

[0316] And then this value was determined as a percentage of the aluminum value. For example,

[0317] (20.1 / 34.7) × 100 = 57.9%

[0318] Table 1b: Compression set (%) results of the cured samples of Reference 1 and C.1 - C8 after compression at 175 °C for 168 hours according to ASTM D395-18 Method BResults of compression set (%) of the samples

[0319]

[0320]

[0321] Comparative examples of compositions containing heat stabilizers reported in the prior art are used to improve the compression set of silicone elastomers, and these silicone elastomers such as manganese carbonate (C.1), copper phthalocyanine (C.2), and iron oxide (C.3) show a higher percentage change in compression set than the reference 1 material. For example, when in contact with PA6,6 / 6T-GF25 FR(40), C.1 containing manganese carbonate shows a percentage change of 64.8%.

[0322] Similar findings were observed for compositions containing acid scavengers such as magnesium hydroxide (C.4) reported in the prior art, which shows a percentage change of 81.2%.

[0323] Comparative examples (C.5 to C.8) correspond to liquid-curable silicone elastomer compositions containing stabilizing additives used as acid scavengers.

[0324] When in contact with the PA6,6 / 6T-GF25 FR(40) substrate, the percentage change in compression set of these comparative examples is similar to or higher than that of the reference 1 material. For example, when in contact with PA6,6 / 6T-GF25 FR(40), the percentage change of the C.5 composition containing calcium carbonate is 58.8%.

[0325] The above is considered surprisingly poor because it has been expected that one or two of the stabilizing additives proposed above would successfully help maintain the durability of the silicone elastomer, but significantly worse compression set results were achieved in each case. In fact, even more surprisingly, although the additives were introduced, the results were at best similar to reference 1, but mainly significantly worse. Finally, none of the above is considered a suitable stabilizing additive to help maintain the durability of the direct contact between the silicone elastomer and the thermoplastic, such as the durability over time in a silicone-thermoplastic composite.

[0326] Another series of samples were prepared and the compression set was tested in the same manner. The compositions used to produce the elastomer samples are detailed in Table 2a below, relative to reference 1 and Examples 1 to 5. Although Examples 44 and 5 were compressed between substrates of thermoplastic PA66-GF25FR(40), the samples were prepared, cured, and the compression set was tested in the same manner as described above.

[0327] Examples 1 to 3 of the present invention disclosed in Table 2a correspond to a liquid-curable silicone elastomer composition in contact with PA6,6 / 6T-GF25 FR(40), the liquid-curable silicone elastomer composition containing a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, and magnesium oxide, such as light magnesium carbonate (hydromagnesite) (Akrochem) and Magox TM 98HR magnesium oxide (Premier Magnesia, LCC).

[0328] Examples 4 and 5 correspond to a liquid-curable silicone elastomer composition containing stabilizing additive 9 (Example 4) and stabilizing additive 10 (Example 5) in contact with an alternative thermoplastic PA66-GF25 FR(40), which is a commercially available 25% glass fiber-reinforced (GF25), halogen-free flame retardant PA6,6 containing an organophosphate flame retardant, called DURETHAN TM AKV25FN04, from Lanxess.

[0329] Table 2a: Composition (wt%) of Examples 1 to 5

[0330] Ingredient Example 1 Example 2 Example 3 Example 4 Example 5 Fumed silica 1 30.10 29.95 30.10 30.10 30.10 Polymer 1 59.40 59.10 59.40 59.40 59.40 Polymer 2 4.95 4.92 4.95 4.95 4.95 Karstedt catalyst 0.18 0.18 0.18 0.18 0.18 Crosslinking agent 1 1.60 1.59 1.60 1.60 1.60 Inhibitor 0.03 0.03 0.03 0.03 0.03 Additive 1 0.09 0.09 0.09 0.09 0.09 Additive 2 0.78 0.78 0.78 0.78 0.78 Additive 3 1.85 1.84 1.85 1.85 1.85 Additive 4 0.02 0.02 0.02 0.02 0.02 Stabilizing additive 9 1.00 1.50 0.00 1.00 0.00 Stabilizing additive 10 0.00 0.00 1.00 0.00 1.00

[0331] These samples were cured and tested in the same manner as described above, and the results are provided in Table 2b below.

[0332] Table 2b: Compression set (%) results of the cured samples of Reference 1 and Examples 1 to 5 of A6T / 66-GF25 FR (40) and PA66-GF25 FR(40) after compression at 175 °C for 168 hours according to ASTM D395-18 Method B

[0333] Reference 1 Reference 1 Example 1 Example 2 Example 3 Example 4 Example 5 Aluminum 34.7 34.7 35.2 45.3 40.3 35.2 40.3 PA6T / 66-GF25FR(40) 54.8 39.6 40.5 43.8 PA66-GF25FR(40) 62.7 42.7 47.4 % Change 57.9 80.7 12.5 -10.6 8.7 21.3 17.6

[0334] When in contact with a PA6T / 66-GF25 FR(40) substrate, Examples 1 and 2 containing 1.0 wt% and 1.5 wt% of stabilizing additive 9 (light magnesium carbonate, also called hydromagnesite), respectively, showed percentage changes in compression set of 12.5% and -10.6%, respectively, which were significantly lower than that of Reference 1. The negative percentage change in Example 2 means that the compression set (40.5%) of Example 2 containing 1.5 wt% of light magnesium carbonate in PA6T / 66-GF25 FR(40) was lower than that in Al (45.3%).

[0335] Similarly, Example 3 containing stabilizing additive 10 (Magox TM 98 HR magnesium oxide) obtained a lower percentage change in compression set (8.7%), which was also lower than that of the reference material 1.

[0336] The percentage changes in compression set for Examples 4 and 5 in PA66-GF25 FR(40) were 21.3 and 17.6, respectively, which were lower than the percentage change for Reference 1 in this plastic (80.7%), thus confirming the benefits of stabilizing additives 9 and 10 in another type of flame retardant grade thermoplastic.

[0337] When contacted with PBT GF25 FR(30 + 5x) (designated ULTRADUR TM B4450 G5, from DuPont) at 125 °C for 1008 hours, they were again evaluated using the LSR compositions identified in Table 2a above. The results are provided in Table 3 below.

[0338] Examples 6 and 7 had the same composition as Example 4 containing stabilizing additive 9. Examples 8 and 9 had the same composition as Example 5 containing stabilizing additive 10.

[0339] Examples 6 and 8 were contacted with PBT GF25 FR(30 + 5x) (designated ULTRADUR B4450 G5, from DuPont), and Examples 7 and 9 were contacted with PBT GF25 FR(40) (designated POCAN BFN4231, from Lanxess).

[0340] The compression set of Examples 6 and 8 changed when contacted with PBT GF25 FR(30 + 5x), and Examples 7 and 9 showed a significant improvement compared to the results observed using the Reference 1 composition when contacted with PBT GF25 FR(40), thus demonstrating the benefits of stabilizing additives 9 and 10 in another type of flame retardant grade thermoplastic and under different test conditions.

[0341] Table 3: Compression set (%) results of the cured samples of Reference 1 and Examples 6 to 9 after compression at 125 °C for 1008 hours according to ASTM D395-18 Method B Results of compression set (%) of the samples

[0342] Reference 1 Reference 1 Example 6 Example 7 Example 8 Example 9 Aluminum 22.7 22.7 16.8 16.8 16.3 16.3 PBT GF25FR(30 + 5x) 34.1 22.8 21.3 PBT GF25FR(40) 35.6 20.8 19.9 % Change 50.2 56.8 35.7 23.8 30.7 22.1

[0343] Further comparisons were made using the compositions in Table 4a, where there were no additives 3 and 4 in Reference 2 or Example 10. Example 10 shown in Table 4a corresponds to a liquid curable silicone elastomer composition without additive 3 (trimethylsilyl terminated phenylmethylsiloxane dimethylsiloxane copolymer) or additive 4 (ADK STAB TM CDA-6).

[0344] They did contain stabilizing additive 9 (light magnesium carbonate).

[0345] Table 4a: Composition (wt%) of Reference 2 and Example 10

[0346] Reference 2 Example 10 Fumed silica 2 32.91 32.58 Polymer 1 59.34 58.75 Polymer 2 5.03 4.98 Karstedt catalyst 0.17 0.17 Inhibitor 0.04 0.04 Crosslinking agent 2 1.19 1.18 Additive 1 0.07 0.07 Additive 5 1.25 1.24 Stabilizing additive 9 0.00 1.00 Total 100.00 100.00

[0347] Reference 2 and Example 10 were tested after contact with PA66-GF25 FR(40), and the results are depicted in Table 4b below.

[0348] Table 4b. Compression set of the cured samples after compression at 175 °C for 168 hours according to ASTM D395-18 Method B (%) results 。

[0349] Reference 2 Example 10 Aluminum 51.7 47.1 PA66-GF25FR(40) 64.4 50.3 % Change 24.6 6.8

[0350] It should be understood that the percentage change in compression set for Example 10 in PA66-GF25 FR(40) is 6.8, which is significantly lower than that of Reference 2.

[0351] In another series of examples (Examples 11, 12, and 13) disclosed in Table 5a, the compositions used corresponded to liquid curable silicone elastomer compositions made from silica masterbatches 1 and 2 and containing stabilizing additives 9 (light magnesium carbonate (hydromagnesite, Akrochem), 10 (Magox TM 98HR magnesium oxide, Premier Magnesia, LCC) and 11 (basic light magnesium carbonate, catalog number AC211070010, Thermo Scientific TM ). In the case of Examples 11 to 13 in Table 5a, masterbatches were used to prepare liquid curable silicone elastomer compositions to prepare two-part compositions:

[0352] MB1 and MB2, Polymer 2, catalyst, Additives 1, 2, and 3, and stabilizing additives were blended into the first part (Part A), and

[0353] 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 produce a liquid curable silicone elastomer composition, which was then cured as indicated above by direct compression molding into a button mold at 171 °C for 20 minutes.

[0354] Table 5a. Composition (wt%) of Examples 11 to 13

[0355] Ingredient Example 11 Example 12 Example 13 Silica masterbatch 1 84.12 85.12 83.13 Silica masterbatch 2 5.00 4.00 6.00 Polymer 2 5.00 5.00 5.00 Karstedt catalyst 0.19 0.19 0.19 Crosslinking agent 1 1.87 1.87 1.86 Inhibitor 0.03 0.03 0.03 Additive 1 0.10 0.10 0.10 Additive 2 0.79 0.79 0.79 Additive 3 1.87 1.87 1.87 Additive 4 0.03 0.03 0.03 Stabilizing additive 9 1.00 0.00 0.00 Stabilizing additive 10 0.00 1.00 0.00 Stabilizing additive 11 0.00 0.00 1.00

[0356] These samples were cured and tested in the conventional manner as discussed above, and the compression set results are provided in Table 5b below.

[0357] Table 5b: Compression set (%) results of the cured samples of Examples 11 to 13 after compression at 175 °C for 168 hours according to ASTM D395-18 Method B Results of compression set (%) of the samples

[0358]

[0359]

[0360] When in contact with PA66-GF25 FR(40), the compression set changes of Examples 11, 12, and 13 are -5.9%, -7.1%, and 5.1%, respectively, showing a great improvement compared with the reference results.

[0361] In another set of results, a peroxide-cured composition was prepared and cured. The compositions used described in Table 6a were prepared by mixing silicone rubbers 1, 2, and 3, pyrogenic silica 3, precipitated silica, and additives 3, 5, 6, 7, 8, 9, 10, and 11.

[0362] Then the silicone base was ground together with a peroxide catalyst.

[0363] Once the peroxide was completely mixed in the product, a stabilizing additive was added and the mixture was ground an additional 7 - 10 times to ensure good mixing. Then the silicone rubber was cured by direct compression molding into buttons at 171°C for 15 minutes, followed by post-curing at 200°C for 4 hours.

[0364] Table 6a. Composition (wt%) of Reference 3 and Example 14

[0365] Reference 3 Example 14 Silicone 1 1.45 1.45 Silicone 2 41.32 41.32 Silicone 3 13.77 13.77 Fumed silica 3 19.79 19.79 Precipitated silica 2.83 2.83 Additive 3 4.53 4.53 Additive 5 3.68 3.68 Additive 6 0.17 0.17 Additive 7 0.68 0.68 Additive 8 0.28 0.28 Additive 9 10.15 10.15 Additive 10 1.01 1.01 Additive 11 0.34 0.34 Base 100.00 100.00 Peroxide catalyst 0.8 0.8 Stabilizing additive 9 1

[0366] Thus, Example 14 disclosed in Table 6a corresponds to a peroxide-cured silicone rubber containing stabilizing additive 9. According to ASTM D395-18 Method B, after compression at 175°C for 168 hours, the compression set (%) results of the cured samples of Reference 3 and Example 11 were determined, and the results are depicted in Table 65b below.

[0367] Table 6b. Compression deformation of the cured sample after 168 hours of compression at 175 °C according to ASTM D395-18 Method B (%) Results 。

[0368]

[0369] It can be seen that after testing at 175°C for 168 hours, the percentage change in compression set of Example 14 in PA6T / 66-GF33 FR(40) plastic is 38.1%, which is less than that of Reference 3, which shows the benefit of providing compression set stability when in contact with FR-grade thermoplastics in a peroxide-cured system using this magnesium additive.

[0370] In summary, all eleven examples gave significantly better results than the corresponding reference examples 1, 2, and 3 and virtually all comparative examples. Considering the results of the compositions in Table 1, failure had been anticipated before conducting the examples, so the improvement was significant and surprising.

[0371] There appears to be some form of synergistic effect caused by the use of magnesium carbonate, basic magnesium carbonate, magnesium oxide, or mixtures, and such materials successfully interact with species in the silicone elastomer migrating into the composite, thereby preventing deterioration of compression set and thus maintaining the durability of the silicone in the composite article, despite their physical interaction with the thermoplastic.

Claims

1. An organosilicon - thermoplastic composite article, the organosilicon - thermoplastic composite article comprising (i) a thermoplastic article, the thermoplastic article comprising one or more flame - retardant additives, wherein the thermoplastic article has an available surface, and (ii) a cured organosilicon elastomer portion, the cured organosilicon elastomer portion being in direct contact with the available surface of the thermoplastic article (i), wherein the organosilicon elastomer portion is a cured product of an organosilicon elastomer composition comprising 0.25 wt% to up to 5 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof.

2. The organosilicon - thermoplastic composite article according to claim 1, wherein the thermoplastic article (i) is selected from polyamide, polyoxymethylene, polyphenylene sulfide (PPS), polyacetal, polyamide - imide, polyphthalamide, polyetherimide, polyether ketone, polyether ether ketone, polyether ketone ether ketone, polyoxymethylene (acetal) homopolymers and copolymers, syndiotactic polystyrene (sPS), compatibilized blends of sPS and polyamide, polyester, polycarbonate (PC), polyether, maleic anhydride - grafted polyphenylene ether (PPO), maleic anhydride - grafted olefinic elastomers and plastomers, polysulfone, polyethersulfone, polyarylsulfone, polyphenylene ether, polypropylene, polyethylene, aliphatic polyketone (PK), thermoplastic styrene copolymers, polymethyl methacrylate (PMMA), polyoxymethylene (POM).

3. The organosilicon - thermoplastic composite article according to claim 2, wherein the thermoplastic article (i) comprises PA6, PA6,6, PA6T / 6,6, PBT, PC, and PK, especially PA6, PA6,6, PA6T / PA6,6, and PBT, and optionally can comprise up to about 25 wt% - 35 wt% of glass fiber (GF) as a reinforcing additive.

4. The organosilicon - thermoplastic composite article according to any one of the preceding claims, wherein the thermoplastic article comprises at least one flame - retardant additive selected from the group consisting of brominated flame retardants, chlorinated paraffins, melamine - based flame retardants, organophosphorus flame retardants, polyphosphate flame retardants, and metal hydroxide flame retardants such as aluminum trihydrate, etc., and mixtures or derivatives thereof.

5. The organosilicon - thermoplastic composite article according to any one of the preceding claims, wherein the stabilizing additive is selected from magnesite (MgCO3), hydromagnesite (MgCO3·2H2O), nesquehonite (MgCO3·3H2O), lansfordite (MgCO3·5H2O); and One or more hydroxy carbonates such as artinite (Mg2(CO3)(OH)2.0.5H2O), hydromagnesite (Mg2(CO3)(OH)2.3H2O), nesquehonite (Mg5(CO3)4(OH)2.4H2O), lansfordite (Mg5(CO3)4(OH)2.5H2O), barringtonite (Mg5(CO3)4(OH)2.5-6H2O) and shelkovite (Mg7(CO3)5(OH)4.24H2O) and optionally capable of containing one or more metal deactivators.

6. The organosilicon - thermoplastic composite article according to claim 5, wherein the metal deactivator is selected from diacyl hydrazide - based compounds, aminotriazole - based compounds, aminotriazine - containing compounds or mixtures thereof.

7. The organosilicon - thermoplastic composite article according to any one of the preceding claims, wherein in use, the organosilicon elastomeric portion is sandwiched between two articles, at least one of the two articles being a thermoplastic article containing one or more flame - retardant additives.

8. The organosilicon - thermoplastic composite article according to any one of the preceding claims, wherein in use, the organosilicon elastomeric portion is subjected to mechanical compression and exposed to a temperature greater than 85 °C.

9. The organosilicon - thermoplastic composite article according to any one of the preceding claims, wherein the organosilicon elastomeric portion is a cured product of a hydrosilylation - curable organosilicon elastomer composition or a free - radical - curable organosilicon elastomer composition.

10. The organosilicon - thermoplastic composite article according to any one of the preceding claims, wherein the organosilicon - 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.

11. The organosilicon - thermoplastic composite article according to claim 10, wherein the organosilicon - thermoplastic composite article is an electrical connector or an electronic connector having: an organosilicon elastomeric seal or an electrical module housing optionally having a sealing cover or an electronic module housing optionally having a sealing cover, a radiator water tank, a valve cover assembly, a sealed headlight assembly, a potted electronic component or an encapsulated electronic component.

12. A method of manufacturing an organosilicon - thermoplastic composite article according to any one of the preceding claims, the method comprising: (a) providing a curable organosilicon elastomer composition comprising 0.25 wt% to a maximum of 5 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, hydroxy carbonate, magnesium oxide and mixtures thereof, (b) curing the curable elastomer composition in a mold, (c) physically joining the cured organosilicon elastomer to an available surface of a thermoplastic article (i) containing one or more flame - retardant additives to form an organosilicon - thermoplastic composite article.

13. A method of manufacturing an organosilicon - thermoplastic composite article according to any one of claims 1 to 11, the method comprising (a) Provide a curable silicone elastomer composition comprising from 0.25 wt% to up to 5 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof, (b) Bring the curable silicone elastomer composition into contact with an available surface of a thermoplastic article (i) comprising one or more flame retardant additives (c) Cure the curable silicone elastomer composition in contact with the available surface of the flame retardant thermoplastic article to form a silicone-thermoplastic composite article.

14. A method for manufacturing a silicone-thermoplastic composite article, wherein the silicone-thermoplastic composite article comprises (i) a thermoplastic article comprising one or more flame retardant additives, wherein the thermoplastic article has an available surface; and (ii) a silicone elastomer portion, wherein the silicone elastomer portion is physically bonded to the available surface of (i) the thermoplastic article; The method comprises: (1) Provide a curable silicone elastomer composition comprising a silicone elastomer composition curable by hydrosilylation reaction or a silicone elastomer composition curable by free radical reaction, wherein the curable silicone elastomer composition further comprises from 0.25 wt% to up to 5.0 wt% of a stabilizing additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof; (2) Introduce a desired amount of the curable silicone elastomer composition into a mold, (3) Cure the curable silicone elastomer composition, thereby forming (ii) the silicone elastomer portion; (4) Physically bond (ii) the silicone elastomer seal to the available surface of (i) the thermoplastic article, thereby forming the silicone-thermoplastic composite article.

15. A method for manufacturing a silicone-thermoplastic composite article according to claim 14, wherein the silicone-thermoplastic composite article is an electrical connector or an electronic connector, and wherein the electrical connector or electronic connector comprises: (ia) one or more electrical wires; (ib) an electrical connector housing or an electronic connector housing comprising a thermoplastic material and one or more flame retardant additives, wherein the electrical connector housing or electronic connector housing (ib) has a first available surface and a second surface opposite the outer surface wherein the second surface defines a cavity, and the cavity houses therein the one or more electrical wires (ia); and the silicone elastomer portion (ii) is a silicone elastomer seal, wherein the silicone elastomer seal is physically bonded to the first available surface of the electrical connector housing or electronic connector housing (ib).

16. A method for maintaining the durability of a silicone elastomer portion in physical contact with a flame retardant thermoplastic having an available surface, the silicone elastomer portion being subjected to mechanical compression and exposed to a temperature greater than 85 °C in use, the method comprising the steps of: (1') Prepare a 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, basic magnesium carbonate, magnesium oxide, and mixtures thereof. (2') Introduce a desired amount of the curable silicone elastomer composition into a mold. (3') Cure the curable silicone elastomer composition, thereby forming the silicone elastomer part (ii). (4) Physically bond the silicone elastomer part (ii) to the available surface of the flame-retardant thermoplastic to form a silicone-thermoplastic composite article.

17. Use of 0.25 wt% to a maximum of 5.0 wt% of an additive selected from the group consisting of magnesium carbonate, basic magnesium carbonate, magnesium oxide, and mixtures thereof as a stabilizing additive in a silicone elastomer part in physical contact with a flame-retardant thermoplastic in a silicone-thermoplastic composite article.

18. The use according to claim 17, wherein the magnesium carbonate and the basic magnesium carbonate are selected from MgCO3, MgCO3·2H2O, MgCO3·3H2O, MgCO3·5H2O, Mg2(CO3)(OH)2·0.5H2O, Mg2(CO3)(OH)2·3H2O, Mg5(CO3)4(OH)2·4H2O, Mg5(CO3)4(OH)2·5H2O, Mg5(CO3)4(OH)2·5 - 6H2O, and Mg7(CO3)5(OH)4·24H2O.

19. The use according to claim 17 or 18, wherein the silicone elastomer part is subjected to mechanical compression and exposed to a temperature of 85 °C or higher during use.

20. The use according to claim 17, 18, or 19, 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.

21. The use according to claim 17, 18, 19, or 20, wherein the silicone-thermoplastic composite article is an electrical connector or an electronic connector having: a silicone elastomer seal or an electrical module housing optionally having a sealing cover or an electronic module housing optionally having a sealing cover, a radiator water tank, a valve cover assembly, a sealed headlight assembly, a potted electronic component, or an encapsulated electronic component.

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