Addition-cure silicone rubber

Abstract

This application presents and describes an addition-curable silicone rubber composition. In one embodiment, the addition-curable silicone rubber composition has minimal crystallization, as evidenced by a low softening point temperature, resulting in a cured silicone rubber that is substantially bubble-free. In one embodiment, an addition-curable silicone rubber composition is provided, comprising: (i) an alkenyl-functional siloxane containing aryl-functional siloxane units; (ii) a polyorganohydrogensiloxane; (iii) a hydrogensiloxane having six or fewer siloxane units; and (iv) a silylated silica filler. By controlling the amount of aryl-functional siloxane units, the amount of hydrogensiloxane with six or fewer siloxane units, and the degree of functionalization of the silica filler, it is possible to form a cured rubber material that exhibits excellent elastomeric properties at extremely low temperatures and is relatively bubble-free, ensuring good aesthetics and adequate mechanical properties of the cured article.

Description

[Technical Field]

[0001] Cross-reference to related technical fields This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 388,428, filed July 12, 2022, entitled Addition-Cure Silicone Rubber, the entire disclosure of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to addition-curable silicone rubber compositions, cured silicone rubbers formed from such compositions, and articles formed from such compositions. In particular, the present invention relates to addition-curable silicone rubber compositions that, when cured, form silicone rubbers that exhibit excellent physical properties, such as low-temperature flexibility, even at temperatures below -100°C, and a high degree of optical transparency. [Background technology]

[0003] Silicone rubber materials are used in a variety of applications. For example, they may be used to form conduits for holding or transporting fluids. In some industries, articles containing fluids may need to be kept at extremely low temperatures during transport and / or before use of the fluid. One example is the pharmaceutical industry, where pharmaceutical materials need to be stored at extremely low temperatures, ranging from below -30°C to below -100°C. Aircraft may contain, for example, O-rings, gaskets, hoses, tubing, and other rubber materials, which may be exposed to extreme temperature fluctuations and extremely low temperatures. However, conventional silicone rubbers typically lose flexibility when temperatures drop below -40°C. As a result, articles may become rigid or crack when exposed to extremely low temperatures.

[0004] The extrusion of silicone rubber tubing requires rapid cure and no outgassing. While some peroxide-curable silicone compositions can produce rubbers with good elastomeric properties even at low temperatures, peroxide-curable rubbers cure slower than addition-curable rubbers and are not suitable for many applications, such as tubing extrusion. In addition, peroxide curing typically requires an additional processing step to remove the peroxide from the system. Peroxide remaining in the system can produce toxic by-products, undesirable crosslinking, and outgassing.

[0005] On the other hand, addition-cured silicone rubbers may face the problem of outgassing during extrusion of tubing, which occurs due to the dehydrogenation condensation reaction between the low-volatility reactive silicone hydride and absorbed moisture. The outgassing that occurs during vulcanization may lead to the formation of bubbles, which not only affects the aesthetics of the tubing, but also the mechanical properties of the tubing.

[0006] Many industries use transparent articles to allow viewing of the contents of the article or the flow of liquids through the article. Conventional polydimethylsiloxane-based rubbers are generally translucent due to the slight difference in refractive index between the polydimethylsiloxane and the silica filler, and may not be suitable for applications requiring high transparency and low haze. Summary of the Invention

[0007] The following is a summary of the present disclosure to provide a basic understanding of some embodiments. This summary is not intended to identify key or critical elements or to define any limitations on the embodiments or claims. Furthermore, this summary may provide a simplified overview of some embodiments, which may also be described in more detail in other sections of the disclosure. Provided is an addition-curable silicone rubber. The silicone rubber composition provides a cured silicone rubber that exhibits low crystallization and low bubble content. In embodiments, the cured silicone rubber formed from the composition has a softening temperature as low as -110°C. In embodiments, the cured silicone rubber formed from the composition has a softening temperature as low as -115°C. In embodiments, the cured silicone rubber formed from the composition is substantially bubble-free. In embodiments, the cured silicone rubber formed from the composition is bubble-free.

[0008] In one embodiment, provided is an addition-curable silicone rubber composition comprising: (A) an alkenyl-functional siloxane containing aryl-functional siloxane units; and (B) a polyhydrogensiloxane; wherein the silicone rubber composition, in the cured state, has a softening temperature as low as -110°C using DSC; and / or the cured silicone rubber is substantially bubble-free.

[0009] In one embodiment, provided is an addition-curable silicone rubber composition comprising: (i) an alkenyl-functional organopolysiloxane containing aryl-functional siloxane units; (ii) a polyorganohydrogensiloxane; (iii) a hydrogensiloxane having 6 or fewer siloxane units; and (iv) a silylated silica filler.

[0010] In one embodiment, provided is an addition-curable silicone rubber composition comprising: (A) an alkenyl-functional siloxane containing aryl-functional siloxane units in an amount of about 4.8 mol % to about 13 mol %; (B) a polyhydrogensiloxane; (C) an organohydrogensiloxane (C) different from the polyhydrogensiloxane (B), the organohydrogensiloxane (C) having 6 or fewer siloxane units, wherein the organohydrogensiloxane (C) is present in an amount of 0.01 wt % to 0.8 wt % of the combined weight of (B) and (C); (D) a hydrosilylation catalyst; (E) a surface-modified silica; (F) optionally an inhibitor; and (G) optionally a co-additive.

[0011] In one embodiment, the surface-modified silica has at least three different types of silylating agents.

[0012] In one embodiment, the surface-modified silica is modified with both a silane and a siloxane.

[0013] In one embodiment, the surface-modified silica is modified with silanes, siloxanes, and silazanes.

[0014] In one embodiment according to any of the above embodiments, the surface-modified silica has at least 40 mole % of the surface silanols modified with functional groups.

[0015] In one embodiment according to any of the above embodiments, between 45 mol % and 85 mol % of the surface silanols of the surface-modified silica are modified with a functional group.

[0016] In one embodiment according to any of the above embodiments, the alkenyl-functional siloxane (A) has from about 5 mole % to about 10 mole % aryl-functional siloxane units.

[0017] In one embodiment according to any of the above embodiments, organohydrogensiloxane (C) is present in an amount of 0.05% to 0.6% by weight of the combined weight of (B) and (C).

[0018] In one embodiment according to any of the above embodiments, organohydrogensiloxane (C) is present in an amount of 0.1 wt % to 0.5 wt % of the combined weight of (B) and (C).

[0019] In one embodiment according to any of the above embodiments, the alkenyl-functional siloxane is of formula (I): M 1 a M 2Vi b D 1 c D 2Ar d D 3Vi e (I) where: M 1 (R 1 )3SiO 1 / 2 ; M 2Vi (R 2 )(R 3 )2SiO 1 / 2 ; D 1 (R 4 )2SiO 2 / 2 ; D 2Ar 2 is (R 5 )2SiO 2 / 2 ; D 3Vi (R 6 )(R 7 )SiO 2 / 2 ; c, d, and e are independently integers, where c+d+e is from about 10 to about 10,000; a is 0-2; b is 0-2; a+b=2; R 1 , R 3 , R 4 , and R 7is independently selected from C1-C10 alkyl; R 2 and R 6 are independently selected from C1-C10 alkyl and C2-C10 alkylene groups, with the proviso that R 2 and / or R 6 at least one of is C2-C10 alkylene; and R 5 is a C6-C30 aryl group, Here, D 2Ar The units are present in the vinyl functional siloxane (A) in an amount of from about 4.8 mole % to about 13 mole %.

[0020] In one embodiment according to any of the above embodiments, the polyhydrogensiloxane is of formula (II): M 3 f M 4H g D 4 h D 5H i D 6 j (II) where M 3 (R 8 )3SiO 1 / 2 ; M 4H (R 9 )(R 10 )2SiO 1 / 2 ; D 4 (R 11 )2SiO 2 / 2 ; D 5H (R 12 )(R 13 )SiO 2 / 2 ; D 6 (R 14 )2SiO 2 / 2 ; f is 0-2; g is 0-2; f+g is 2; h is 0-200; i is 0-200; j is 0-20; h+i+j is 10-200; g+i ≥ 1; R 8 , R 10 , R 11 , and R 12 is independently selected from C1-C10 alkyl; R 9 and R 13 are independently selected from H and C1-C10 alkyl, with the proviso that R 10 or R 13 at least one of is H; and R 14 is a C6-C30 aryl group.

[0021] In one embodiment according to any of the above embodiments, the organohydrogensiloxane (C) is selected from a compound of formula (III), a compound of formula (IV), or a mixture thereof: D 7 j D 8H k (III) where D 7 (R 15 )2SiO 2 / 2 ; D 8H (R 17 )(R 16 )SiO 2 / 2 ; j is 0-6; k is 1-6; j+k is 3-6; R 15 is independently selected from C1-C10 alkyl; and R 16 and R 17 are independently selected from H and C1-C10 alkyl, with the proviso that R 16 and R 17 At least one of is H; M 5 l M 6H m D 9 n D 10H o (IV) where M 5 (R 18 )3SiO 1 / 2 ; M 6H (R 19 )(R 20 )2SiO 1 / 2 ; D 9 (R 21 )2SiO 2 / 2 ; D 10H (R 23 )(R 22 )SiO 2 / 2 ; l is 0-2; m is 0-2; l+m is 2; n is 0-4; o is 0-4; n+o ≥ 1; l+m+n+o is 3-6; R 18 , R 20 , and R 21 is independently selected from C1-C10 alkyl; and R 19 , R 23 , and R 22 are independently selected from H and C1-C10 alkyl, with the proviso that R 19 , R 23 , and / or R 22 At least one of is H.

[0022] In another embodiment, there is provided a silicone rubber formed from the addition-curable silicone rubber composition of any of the above aspects or embodiments.

[0023] In one embodiment, the silicone rubber is in the form of a tube, a hose, a gasket, or an O-ring.

[0024] In yet another embodiment, a method for making a silicone rubber is provided, comprising curing the addition-cure silicone rubber composition of any of the above aspects or embodiments.

[0025] In yet another embodiment, there is provided a silicone rubber composition comprising: (A) an alkenyl-functional siloxane comprising aryl-functional siloxane units; and (B) a polyhydrogensiloxane; wherein the silicone rubber composition in the cured state has a softening temperature as low as -110°C using differential scanning calorimetry (DSC); and / or the cured silicone rubber is substantially bubble-free.

[0026] In one embodiment, the aryl-functional siloxane units are present in an amount of from about 4.8 mole % to about 13 mole %.

[0027] In one embodiment, the silicone gum comprises an organohydrogensiloxane (C) having 6 or fewer siloxane units.

[0028] In one embodiment, organohydrogensiloxane (C) is present in an amount of about 0.01% to about 0.8% by weight, based on the combined weight of (B) and (C).

[0029] In one embodiment according to any of the above embodiments, the silicone rubber comprises surface-modified silica.

[0030] In one embodiment, the surface-modified silica comprises silane functional groups.

[0031] In one embodiment according to any of the above embodiments, at least three different silylating agents are used.

[0032] In one embodiment according to any of the above embodiments, the surface-modified silica is modified with silanes, siloxanes, and silazanes.

[0033] In one embodiment according to any of the above embodiments, the surface-modified silica has at least 40 mole % of the surface silanols modified with a functional group.

[0034] In one embodiment according to any of the above embodiments, the silicone rubber composition has a softening temperature in the cured state as low as -115°C using DSC.

[0035] In a further embodiment, provided is the use of an addition-curable silicone rubber composition according to any of the above embodiments for the manufacture of a conduit for a medical application. In one embodiment, the conduit is a tube. In one embodiment, the medical application is a pharmaceutical application. In one embodiment, the pharmaceutical application is for the delivery of drugs, vaccines, cell formulations, or cellular materials.

[0036] In yet another embodiment, provided is the use of an addition-curable silicone rubber composition according to any of the above embodiments for the manufacture of an O-ring seal for a gasket. In one embodiment, the gasket is used in an aircraft component.

[0037] When cured, the composition provides a silicone rubber with excellent physical properties even at extremely low temperatures, for example, near or below -100°C, and can also provide a silicone rubber with excellent transparency (transparency). Without being bound by any particular theory, the applicant has discovered that controlling the aryl (e.g., phenyl) content of the alkenyl-functional siloxane provides excellent elastomeric properties even at extremely low temperatures. This also results in a silicone rubber compound with high transparency. On the other hand, controlling the amount of hydrogen siloxanes with 6 or fewer siloxane units and using surface-modified silica fillers can reduce outgassing in the system.

[0038] The following description discloses various exemplary embodiments. Some improvements and novel aspects may be explicitly identified, while others may be apparent from the description and illustrations. DETAILED DESCRIPTION OF THE INVENTION

[0039] Reference will now be made to exemplary embodiments, examples of which are illustrated in the accompanying drawings. As will be understood, other embodiments may be utilized, and structural and functional changes may be made. Furthermore, features of various embodiments may be combined or varied. Thus, the following description is provided by way of example only, and is not intended to limit in any way the various alternatives and modifications that may be made to the illustrated embodiments. In this disclosure, numerous specific details are set forth to provide a thorough understanding of the disclosed subject matter. It should be understood that embodiments of the present disclosure may be embodied in other embodiments, including but not limited to, all embodiments set forth herein or elsewhere.

[0040] As used herein, the terms "example" and "exemplary" mean illustrative or illustrative. The terms "example" and "exemplary" do not indicate required or preferred implementations or embodiments. The term "or" is intended to be inclusive rather than exclusive, unless the context indicates otherwise. For example, the phrase "A uses B or C" includes any inclusive permutation (e.g., A uses B; A uses C; or A uses both B and C). As a separate matter, the articles "a" and "an" are generally intended to mean "one or more," unless the context indicates otherwise.

[0041] Where ranges are presented in the specification and claims, it is understood that numerical values may be combined to form new, open-ended ranges, for example, the endpoints of ranges for components may be used to form new, open-ended ranges.

[0042] Provided are addition-curable silicone rubber compositions, cured silicone rubbers formed from such compositions, and articles containing the cured silicone rubbers. The addition-curable silicone rubber compositions produce cured silicone rubbers that exhibit excellent elastomeric and other physical properties at low temperatures, even at or below about -110°C. Additionally, the compositions produce low bubble formation upon curing.

[0043] The addition-curable silicone rubber composition of the present invention comprises a siloxane copolymer having aryl-functional siloxane units; a polyorganohydrogensiloxane; a hydrogensiloxane having a low organohydrogensiloxane content and 6 or fewer siloxane units; and a surface-modified silica filler having a high proportion of surface silanol groups functionalized thereon.

[0044] In one embodiment, the addition-curable silicone rubber composition comprises: (A) an alkenyl-functional siloxane copolymer of a dialkylsiloxane, an aryl-functional siloxane, and an alkyl-alkenyl-functional siloxane, wherein the aryl-functional siloxane units are from about 4.8 mol % to about 13 mol % and provides low temperature flexibility; (B) at least one polyhydrogensiloxane as a crosslinker; and (C) a mixture of organohydrogensiloxanes with not more than 6 siloxane units in either cyclic or linear configuration. (D) at least one hydrosilylation catalyst comprising a transition metal that promotes addition cure; (E) at least one surface-modified reinforcing silica filler, wherein at least 40 mole percent of the surface silanol groups are functionalized (e.g., silylated); (F) optionally, one or more inhibitors for component (D) to balance cure rate and pot life; and (G) optionally, one or more auxiliary additives.

[0045] Component (A) is an organopolysiloxane having at least two alkenyl groups per molecule and containing aryl-functional siloxane units. The alkenyl groups can be selected from any suitable alkenyl group. In one embodiment, the alkenyl groups are C2-C10 alkenyl groups, such as, but not limited to, vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl, with vinyl and hexenyl being particularly suitable. The attachment positions of the alkenyl groups, in embodiments, can be at the end(s) of the molecular chain, at a side chain, or at the end(s) of the molecular chain and a side chain. Additionally, in component (A), silicon-bonded groups other than alkenyl groups can be selected from substituted or unsubstituted monovalent hydrocarbon groups, excluding alkenyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and other alkyl groups. Component (A) also contains aryl-functional siloxane units. Examples of suitable aryl groups include C6-C30 aryl groups, including, but not limited to, phenyl, tolyl, xylyl, and other aryl groups; benzyl, phenethyl, and other aralkyl groups. The molecular structure of component (A) can be linear, partially branched linear, branched, or network, and component (A) can be a mixture of two or more of the above-described organopolysiloxanes with different molecular structures. Additionally, the zero-shear viscosity of component (A) at 37°C, determined using a creep test on a stress-controlled rheometer, can be selected as desired for a particular purpose or intended application. In embodiments, the zero-shear viscosity of component (A) can range from 100 Pascal seconds (Pa·s) to 1,000,000 Pa·s, particularly from 10,000 Pa·s to 100,000 Pa·s.

[0046] In one embodiment, component (A) is a dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer terminated at both molecular chain ends with trimethylsiloxy groups, a dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer terminated at both molecular chain ends with dimethylvinylsiloxy groups, a dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer terminated at both molecular chain ends with trimethylsiloxy groups, or a dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer terminated at both molecular chain ends with dimethylvinylsiloxy groups. dimethylsiloxane-methylphenylsiloxane copolymers terminated at both molecular chain ends with dimethylvinylsiloxy groups; dimethylsiloxane-diphenylsiloxane copolymers terminated at both molecular chain ends with dimethylvinylsiloxy groups; dimethylsiloxane-methylvinylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups; dimethylsiloxane-methylvinylsiloxane copolymers terminated at both molecular chain ends with dimethylvinylsiloxy groups; polydimethylsiloxanes terminated at both molecular chain ends with dimethylvinylsiloxy groups; R3SiO 1 / 2 Units and SiO 4 / 2 Organopolysiloxanes containing RSiO units 3 / 2 Organopolysiloxanes containing the unit R2SiO 2 / 2 Units and RSiO 3 / 2 Organopolysiloxanes containing the unit R2SiO 2 / 2 Units, RSiO 3 / 2 units, and SiO 4 / 2Examples include organopolysiloxanes containing units, and mixtures of two or more of the above organopolysiloxanes. The radical R represents a substituted or unsubstituted monovalent hydrocarbon group, exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, and other alkyl groups; vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, and other alkenyl groups; phenyl, tolyl, xylyl, and other aryl groups; and benzyl, phenethyl, and other aralkyl groups. In one embodiment, at least two R radicals are alkenyl groups.

[0047] In one embodiment, the alkenyl-functional siloxane (A) is a copolymer of a dialkylsiloxane, a diarylsiloxane, and an alkyl-vinylsiloxane of formula (I): M 1 a M 2Vi b D 1 c D 2Ar d D 3Vi e (I) where: M 1 (R 1 )3SiO 1 / 2 ; M 2Vi (R 2 )(R 3 )2SiO 1 / 2 ; D 1 (R 4 )2SiO 2 / 2 ; D 2Ar (R 5 )2SiO 2 / 2 ; D 3V (R 6 )(R 7 )SiO 2 / 2 ; c, d, e are integers and c+d+e is from about 10 to 10,000, preferably from 100 to 10,000, more preferably from 400 to 10,000, even more preferably from 1,000 to about 10,000; a is 0-2; b is 0-2; a+b=2; R 1 , R 3 , R 4 , and R 7 is independently selected from C1-C10 alkyl; R 2 and R 6 are independently selected from C1-C10 alkyl and C2-C10 alkylene groups, with the proviso that R 2 and / or R 6 at least one of is C2-C10 alkylene; and R 5 is a C6-C30 aryl group, Here, D 2Ar The units are present in the vinyl-functional siloxane (A) in an amount of from about 4.8 mole percent to about 13 mole percent of all siloxane units in component (A).

[0048] In one embodiment, D 2Ar The D units are present in an amount of about 4.8 mol % to about 13 mol %, about 5 mol % to about 10 mol %, or about 5.2 mol % to about 8 mol % of all siloxane units in component (A). 2Ar The unit of mole % is 29 Si magnetic resonance spectroscopy ( 29 The diphenylsiloxane content is determined by quantification using Si NMR. Without being bound by any particular theory, it has been found that using siloxanes with a diphenylsiloxane content within this range provides excellent elastomeric properties to the resulting silicone rubber, even at temperatures below -100°C.

[0049] In one embodiment, the alkyl groups in Formula (I) can be independently selected from C1-C10 alkyl, C2-C8 alkyl, or C4-C6 alkyl. In one embodiment, the alkyl group in Formula (I) is methyl.

[0050] In one embodiment, the alkenyl groups in Formula (I) can be independently selected from C2-C10 alkenyl functional groups, C3-C9 alkenyl functional groups, or C4-C8 alkenyl functional groups. In one embodiment, the alkenyl functional groups in Formula (I) are independently selected from C2-C3 alkenyl functional groups. In one embodiment, the alkenyl functional group is vinyl.

[0051] In one embodiment, the aryl groups are independently selected from C6-C30 aryl groups, C7-C20 aryl groups, or C8-C15 aryl groups. In one embodiment, the aryl group is phenyl.

[0052] In one embodiment, component (A) is present in the composition in an amount of from about 40% to about 90% by weight, from about 50% to about 80% by weight, or from about 60% to about 70% by weight, based on the weight of the composition.

[0053] Components (B) and (C) act as crosslinkers for the alkenyl-functional siloxane component (A). Component (B) is an organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule. Component (C) is an organohydrogensiloxane having six or fewer siloxane units.

[0054] The bonding positions of the silicon-bonded hydrogen atoms can be any desired location, and can be provided at the molecular chain end(s), at the molecular chain side chain, or at the molecular chain end(s) and at the molecular chain side chain. Additionally, the silicon-bonded groups in component (B) can be substituted or unsubstituted monovalent hydrocarbon groups, excluding alkenyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and the like. The molecular structure of component (B) can be linear, partially branched linear, branched, or network structure, and component (B) can be a mixture of two or more of the above-mentioned organopolysiloxanes with different molecular structures. Additionally, the thermal stability of component (B) at 20°C and 10s according to DIN 53019 is -1The viscosity at a shear rate of 1000 to 50,000 mPa·s is preferably in the range of 1 mPa·s to 50,000 mPa·s, and particularly preferably in the range of 5 mPa·s to 1,000 mPa·s.

[0055] Non-limiting examples of siloxanes according to component (B) include, but are not limited to, methylhydrogenpolysiloxanes terminated at both molecular chain ends with trimethylsiloxy groups; dimethylsiloxane-methylhydrogensiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups; polydimethylsiloxanes terminated at both molecular chain ends with dimethylhydrogensiloxy groups, methylhydrogenpolysiloxanes terminated at both molecular chain ends with dimethylhydrogensiloxy groups; dimethylsiloxane-methylhydrogensiloxane copolymers terminated at both molecular chain ends with dimethylhydrogensiloxy groups; dimethylsiloxane-diphenylsiloxane copolymers terminated at both molecular chain ends with dimethylhydrogensiloxy groups; Dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymers terminated at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups; dimethylsiloxane-methylphenylsiloxane copolymers terminated at both molecular chain ends with dimethylhydrogensiloxy groups; dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymers terminated at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups; R'3SiO 1 / 2 Units and SiO 4 / 2 Organopolysiloxanes containing units, R'SiO 3 / 2 Organopolysiloxanes containing units, R'2SiO 2 / 2 Units and R'SiO 3 / 2 Organopolysiloxanes containing units, R'2SiO 2 / 2Units, R'SiO 3 / 2 Units and SiO 4 / 2 The radical R' is a hydrogen atom or represents a substituted or unsubstituted monovalent hydrocarbon group, exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, and other alkyl groups; phenyl, tolyl, xylyl, and other aryl groups; benzyl, phenethyl, and other aralkyl groups; 3-chloropropyl, 3,3,3-trifluoropropyl, and other halogenated alkyl groups. Preferably, however, at least two R' radicals are hydrogen atoms.

[0056] In one embodiment, component (B) has formula (II): M 3 f M 4H g D 4 h D 5H i D 6 j (II) where M 3 (R 8 )3SiO 1 / 2 ; M 4H (R 9 )(R 10 )2SiO 1 / 2 ; D 4 (R 11 )2SiO 2 / 2 ; D 5H (R 12 )(R 13 )SiO 2 / 2 ; D 6 (R 14 )2SiO 2 / 2 ; f is 0-2; g is 0-2; f+g is 2; h is 0-200; i is 0-200; j is 0-20; h+i+j is 10-200; g+i ≥ 1; R 8 , R 10 , R 11 , and R 12 is independently selected from C1-C10 alkyl; R 9 and R 13 are independently selected from H and C1-C10 alkyl, with the proviso that R 10 or R 13 at least one of is H, R 14 is a C6-C30 aryl group.

[0057] In one embodiment, the alkyl groups in Formula (II) can be independently selected from C1-C10 alkyl, C2-C8 alkyl, or C4-C6 alkyl. In one embodiment, the alkyl group in Formula (II) is methyl.

[0058] In one embodiment, the aryl groups are independently selected from C6-C30 aryl groups, C7-C20 aryl groups, or C8-C15 aryl groups. In one embodiment, the aryl group is phenyl.

[0059] Component (C) is a hydrogen siloxane having 6 or fewer siloxane units. This component (C) can be a linear or cyclic siloxane. In one embodiment, component (C) is selected from a compound of formula (III), a compound of formula (IV), or a mixture of two or more thereof: D 7 j D 8H k (III) where D 7 (R 15 )2SiO 2 / 2 ; D 8H (R 16 )(R 17 )SiO 2 / 2 ; j is 0-6; k is 1-6; j+k is 3-6; R 15 is independently selected from C1-C10 alkyl; and R 16 and R 17 are independently selected from H and C1-C10 alkyl, with the proviso that R 16 and R 17 at least one of is H; M 5 l M 6H m D 9 n D 10H o (IV) where M 5 (R 18 )3SiO 1 / 2 ; M 6H (R 19 )(R 20 )2SiO 1 / 2 ; D 9 (R 21 )2SiO 2 / 2 ; D 10H (R 23 )(R 22 )SiO 2 / 2 ; l is 0-2; m is 0-2; l+m is 2; n is 0-4; o is 0-4; n+o ≥ 1; m+o ≥ 1; l+m+n+o is 3-6; R 18 , R 20 , and R 21 is independently selected from C1-C10 alkyl; and R 19 , R 23 , and R 22 are independently selected from H and C1-C10 alkyl, with the proviso that R 19 , R 23, and / or R 22 At least one of is H.

[0060] In one embodiment, component (C) comprises a cyclic hydrogensiloxane of formula (III): In one embodiment, j is 0 and k is 3-6. In one embodiment, j is 0 and k is 3.

[0061] In one embodiment, the alkyl groups in Formula (III) or Formula (IV) can be independently selected from C1-C10 alkyl, C2-C8 alkyl, or C4-C6 alkyl. In one embodiment, the alkyl group in Formula (III) or Formula (IV) is methyl.

[0062] In providing components (B) and (C), it will be understood that they can be provided separately or as a mixture.

[0063] In one embodiment, component (B) and component (C) are present in the composition in an amount of about 0.3 wt % to about 1.2 wt %, about 0.5 wt % to about 1 wt %, or about 0.6 wt % to about 0.9 wt %, and wherein component (C) is present in an amount of about 0.01 wt % to about 0.8 wt %, about 0.02 wt % to about 0.7 wt %, about 0.05 wt % to about 0.6 wt %, about 0.1 wt % to about 0.5 wt %, or about 0.1 wt % to about 0.4 wt %, based on the combined amount of component (B) and component (C).

[0064] The proportion of component (C) in a mixture of components (B) and (C) is determined using gas chromatography (GC) performed directly on the mixture. D4 (octamethylcyclotetrasiloxane) is used as an internal standard for quantification.

[0065] The composition includes a hydrosilylation catalyst (D) for promoting the addition reaction between the alkenyl functional group of component (A) and the Si-H functional groups of components (B) and (C). The hydrosilylation catalyst is not particularly limited and can be selected from any catalyst suitable for promoting the hydrosilylation of an alkenyl functional group with a hydride group. Suitable hydrosilylation catalysts include, but are not limited to, metals or metal compounds, where the metal is selected from the group consisting of nickel, palladium, platinum, rhodium, iridium, ruthenium, and osmium, or are taught in U.S. Pat. No. 3,159,601; U.S. Pat. No. 3,159,662 (Ashby); U.S. Pat. No. 3,419,593; U.S. Pat. No. 3,715,334; U.S. Pat. No. 3,775,452; U.S. Pat. No. 3,220,970 (Lamoreaux); and U.S. Pat. No. 3,814,730 (Karstedt).

[0066] The amount of these catalysts added to the composition is from 0.5 to 500 ppm based on the total weight of the composition, preferably between 1 and 100 ppm based on the total weight of the composition, and most preferably between 1.5 and 10 ppm.

[0067] In one embodiment, the catalyst is selected from platinum-containing catalysts. Examples of suitable platinum-containing catalyst components include, but are not limited to, platinum metal; platinum metal on a support such as silica gel or powdered charcoal; or a compound or complex of platinum metal.

[0068] A typical platinum-containing catalyst component in the organopolysiloxane composition of the present invention is chloroplatinic acid in any form, such as the hexahydrate, which is readily available, or the anhydrous form, which is preferred for its ease of dispersion in organosiloxane systems. A particularly useful form of chloroplatinic acid is the composition obtained when it reacts with an aliphatically unsaturated organosilicon compound, such as divinyltetramethyldisiloxane, or tetravinyltetramethyltetracyclosiloxane, as disclosed in U.S. Pat. No. 3,419,593, which is incorporated herein by reference. Ashby's catalyst, Karstedt's catalyst, and Lamoreaux's catalyst are conventional catalysts that may be used to cure silicone rubber compositions. As understood herein, any known or commercially available photoactivated catalyst, most specifically a photoactivated platinum catalyst, may be used herein. In one embodiment, the photoactivated platinum catalyst is 5 -cyclopentadienyl platinum(IV) complexes, bis(b-diketonate) platinum(II) complexes, bis(phosphine) platinum(II) complexes, cyclooctadiene platinum(II) complexes, and mixtures thereof, more particularly trimethyl(methylcyclopentadienyl)platinum(IV) or platinum(II) acetylacetonate.

[0069] The composition further comprises a surface-modified silica filler (E). The silica particles contain residual silanol groups (-Si-OH) on the surface. The modified silica particles are produced by reacting the silanol groups with a desired functional group. In one embodiment, the silica particles are modified with a silane to produce silylated silica.

[0070] The silica particles are not particularly limited and can be selected as desired. In one embodiment, the silica particles are colloidal silica. Generally, any colloidal silica can be used. Examples of suitable colloidal silica include, but are not limited to, fumed colloidal silica and precipitated colloidal silica. Particularly suitable colloidal silica is obtained in an aqueous medium. Colloidal silica in an aqueous medium is usually available in a stabilized form, such as that stabilized with sodium ions, ammonia, or aluminum ions. The colloidal silica may have a particle size of 5 to 250 nanometers, more specifically 6 to 150 nanometers, or even 8 to 85 nanometers. The silica filler may have a particle size of 50 to 400 nm. 2 / g, preferably 150 to 350 m 2 / g Brunauer-Emmett-Teller (BET) specific surface area.

[0071] In one embodiment, the particle size of the colloidal silica is determined in accordance with ASTM E2490-09(2015), Standard Guide for Measuring Particle Size Distribution of Nanomaterials in Suspension by Dynamic Light Scattering (DLS).

[0072] Colloidal silica particles, which may be referred to herein as silica sol, may be derived from, for example, precipitated silica, microsilica (silica fume), pyrogenic silica (fumed silica), or silica gel of sufficient purity, and mixtures thereof; and may be silanized by the methods described in WO 2004 / 035474. Silica sols may also typically be obtained from water glass, as disclosed, for example, in US 5,368,833.

[0073] The silica particles can be modified with any suitable silylating agent. In one embodiment, the silica can be functionalized with an organosilane, an alkylsilane, and / or a silazane. Examples of suitable silylating agents for modifying silica particles include, but are not limited to, tris-(trimethoxy)silane, octyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane; bis-(3-[triethoxysilyl]propyl)polysulfide, beta-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltriisopropoxysilane, gamma-methacryloxypropyltriethoxysilane, octyltrimethyloxysilane, ethyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, dimethyldimethoxysilane, 3-chloropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, i-butyltriethoxysilane, trimethylethoxysilane, silane, phenyldimethylethoxysilane; epoxy group (epoxy silane), glycidoxy and / or glycidoxypropyl group-containing silanes such as gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, (3-glycidoxypropyl)triethoxysilane, (3-glycidoxypropyl)hexyltrimethoxysilane, beta-(3,4-epoxycyclohexyl)-ethyltriethoxysilane; vinyl group-containing silanes such as vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris-(2-methoxyethoxy)silane, vinylmethyldimethoxysilane, vinyltriisopropoxysilane; hexamethyldisiloxane, trimethylsilyl chloride, vinyltriethoxysilane, hexamethyldisilazane, tetramethyldivinyldisilazane, octamethylcyclotetrasiloxane, polydimethylsiloxane, and mixtures thereof.According to one embodiment, silane compounds with mercapto functional groups may be used, such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, HS(CH2)3, Si(OCH3)3, mercaptosilanes having at least one hydroxyalkoxysilyl group and / or cyclic dialkoxysilyl group, gamma-mercaptopropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, and gamma-mercaptopropyltrimethoxysilane. Furthermore, silica powders surface-treated with organosilicon compounds such as polydimethylsiloxane, octamethylcyclotetrasiloxane, or hexamethyldisilazane may be used.

[0074] Silazanes, such as disilazanes, can also be used to provide modified silica. Examples of disilazanes that can be used include, but are not limited to, hexamethyldisilazane, divinyltetramethyldisilazane, and bis(3,3-trifluoropropyl)tetramethyldisilazane. Cyclosilazanes are also suitable, and include, for example, octamethylcyclotetrasilazane.

[0075] In one embodiment, the surface-modified silica filler is modified with multiple silylating agents. In one embodiment, the surface-modified silica filler is modified with three or more types of silylating agents. In one embodiment, the surface-modified silica filler is modified with a silylating agent selected from silanes and siloxanes. In one embodiment, the surface-modified silica filler is modified with a silylating agent selected from silanes, siloxanes, and silazanes.

[0076] The silica particles for use in the compositions of the present invention have at least 40 mol% of the surface silanol groups functionalized (e.g., silylated). In one embodiment, 40 mol% to about 100 mol% of the silanol groups are silylated, about 45 mol% to about 85 mol%, or about 50 mol% to about 70 mol% of the silanol groups are silylated. The percentage of silylated surface silanols in fumed silica is: 29 The specific surface area can be determined using Si cross-polarization and magic angle spinning magnetic resonance spectroscopy (CP / MAS NMR) with a contact time of 10 ms. 2 / g of fumed silica can be functionalized to approximately 30 mole percent of the surface silanol groups when treated with octamethylcyclotetrasiloxane. The same fumed silica can be functionalized to approximately 40 mole percent of the surface silanol groups when treated with both octamethylcyclotetrasiloxane and hexamethyldisilazane.

[0077] The surface-modified silica particles can be present in the composition in an amount of about 1 wt % to about 50 wt %, about 15 wt % to about 40 wt %, or about 25 wt % to about 35 wt %, based on the weight of the composition.

[0078] The composition may further contain additives typical of silicone rubber compositions, including fillers, rheology control agents, reactive and non-reactive plasticizers, adhesion promoters, various reinforcing agents, pigments, dyes, flame retardants, heat stabilizers, and UV stabilizers, among others.

[0079] Inhibitors may also be used. Inhibitors are additives used to controllably adjust the processing time and crosslinking rate of the curable silicone rubber composition. Such inhibitors and stabilizers may be, for example, acetylene alcohols such as ethynylcyclohexanol and 2-methyl-3-butyn-2-ol, polymethylvinylcyclosiloxanes such as methylvinylcyclotetrasiloxane, low molecular weight siloxane oils with vinyldimethylsiloxy end groups, trialkyl cyanurates, alkyl maleates such as diallyl maleate and dimethyl maleate, alkyl fumarates such as diethyl fumarate and diallyl fumarate, organic hydroperoxides such as cumene hydroperoxide, tert-butyl hydroperoxide and pinane hydroperoxide, organic peroxides, benzotriazoles, organic sulfoxides, organic amines and amides, phosphines, phosphites, nitriles, diallysines and oximes.

[0080] The silicone rubber composition can be compression cured for 10 minutes at 175° C. In one embodiment, the silicone rubber composition is cured through a vertical tubing extrusion line at a linear speed of 20 feet per minute, where a 2-foot long lower oven chamber is set at 480° C. and a 2-foot long upper oven chamber is set at 420° C.

[0081] Silicone rubber substrates can be prepared by converting a curable silicone composition into a desired shape by conventional methods, such as compression molding, injection molding, extrusion, and calendering; and then curing the composition.As used herein, the term "curing" refers to converting a liquid or semi-solid composition into a crosslinked product.Examples of curable silicone compositions include, but are not limited to, hydrosilylation curable silicone compositions, ultraviolet radiation curable silicone compositions, and high-energy radiation curable silicone compositions.

[0082] Cured rubber articles produced from compositions according to the present technology exhibit excellent elastomeric properties even at low temperatures, including temperatures below -100°C, below -110°C, and even below -115°C. In one embodiment, silicone rubbers produced from compositions according to the present technology are substantially bubble-free. In one embodiment, silicone rubbers produced from compositions according to the present technology have a transmittance of 85% or higher, 90% or higher, or 95% or higher.

[0083] The compositions of the present invention can be used to form articles of desired shapes for various purposes or end uses. Examples of suitable articles include, but are not limited to, conduits, gaskets, seals, O-rings, and the like. Conduits can include, but are not limited to, tubes, pipes, channels, and the like. Articles formed from the compositions of the present invention can be used in a variety of end uses and applications. In one embodiment, the articles can be used in aeronautical engineering applications. For example, articles formed from the compositions of the present invention can be used as or in connection with aircraft components. Aircraft include both airplanes and aerospace vehicles, i.e., the components can be used in aircraft operating inside or outside the Earth's atmosphere.

[0084] In one embodiment, an article formed from the composition can be used as a conduit for transporting substances or fluids therein. Conduits can include tubes, pipes, channels, and the like. Conduits formed from the composition can be used in a wide variety of applications, including, but not limited to, medical applications. The conduits can be used to transport fluids in various medical applications, such as for pharmaceutical applications, such as the transport of drugs, medications, vaccines, cell formulations, plasma and other fluids, and the like.

[0085] Implementations and embodiments of the present technology may be further understood with reference to the following examples, which are for the purpose of illustrating implementations and embodiments of the present technology and are not intended to limit the technology to those specific embodiments.

[0086] [Example]

[0087] As shown in Table 1, the softening point of a dimethylsiloxane copolymer can be lowered from -40°C to -115°C by introducing only 5 mol% of diphenylsiloxane units into the polydimethylsiloxane chain. Without being bound by any particular theory, randomly dispersed bulky diphenylsiloxane units can effectively suppress the crystallization of polydimethylsiloxane. When more diphenylsiloxane units were introduced up to 14 mol%, the softening point increased to -98°C due to the increase in the glass transition temperature.

[0088] [Table 1]

[0089] The thermal properties of the samples (e.g., softening point) are determined using a differential scanning calorimeter (DSC). In the temperature range of -180°C to +100°C, the heating rate was 10°C / min with a 5-minute wait time between steps using a TA Instruments Discovery 2500 DSC. For crystalline polymers, the softening point is their melting point, and for amorphous polymers, the softening point is their glass transition temperature.

[0090] Example 1

[0091] In a double sigma blade dough mixer, 64.5 parts of a copolymer 1 of dimethylsiloxane, diphenylsiloxane, and dimethylvinylsiloxane (Component A), having a viscosity of 63,000 Pa·s and containing 5.3 mole % diphenylsiloxane units and 0.012 mole / kg vinyl groups (Si-vinyl), were mixed with the following silylating agents: 1.9 parts silanol-terminated polydimethylsiloxane of 30 cSt viscosity, 0.85 parts hexamethyldisilazane, and 0.15 parts tetramethyldivinyldisilazane. 2 30.8 parts of a pretreated fumed silica filler having a Brunauer-Emmett-Teller (BET) specific surface area of 1 / g and subsequently treated with octamethylcyclotetrasiloxane (D4) at 265°C for 2 hours was charged into a kneader. The mixture was heated to 160°C and then held at 160°C for at least 2 hours under a nitrogen inerting blanket to allow for proper reaction between any remaining surface silanols on the pretreated filler surface and the three silylating agents. The filler obtained after this additional in-situ treatment was considered Component E. At least three different types of silylating agents were used to produce Component E, which contains D4, a silanol-terminated silicone, and two disilazanes, making the component sufficiently hydrophobic to minimize water absorption, thereby reducing the water content in the silicone compound. After the silicone compound had cooled to below 70°C, 0.8 parts of a blend of dimethylhydrogensiloxy-terminated poly(dimethylsiloxane-co-methylhydrosiloxane) (Component B) and a methylhydrosiloxane compound (Component C) was added. The blend contained 8.1 moles / kg of silicon hydride groups (SiH) as determined by Fourier transform infrared spectroscopy. Component B has the formula M H 2D 50 D H 50 Component C had D H 3. D x D H y (where x and y = 0-6, x + y = 4-6), and M m M H n Dx D H y (where m and n = 0-2, x and y = 0-4, m + n = 2, and m + n + x + y = 3-6). As determined by GC, 0.13 wt. % of Component C was present in this blend of B and Component C. Finally, 0.009 parts of 1-ethynyl-1-cyclohexanol (Component F) was added to the mixture as a platinum inhibitor to complete the silicone rubber base compound. Separately, a platinum catalyst masterbatch (Component D) was prepared by mixing 1 part of the above-described Component A with 0.017 parts of Ashby's platinum catalyst solution in tetramethyltetravinylcyclotetrasiloxane containing 1.75 wt. % platinum.

[0092] The silicone rubber base compound and platinum masterbatch were mixed in a 99:1 ratio and compression cured at 175°C for 10 minutes. The molar ratio of SiH to Si-vinyl in this catalyzed blend was 2.9. The cured article exhibited high transparency, with a 90% transmission at 2 mm and a 12% haze according to ASTM D1003. The cured article also exhibited good mechanical properties, including a high tear resistance of 49 N / mm according to ASTM D-624. The cured article had a softening point of -114°C according to DSC measurements.

[0093] The catalyzed blend was also extruded into tubing with a 9 / 16 inch outer diameter, a 5 / 16 inch inner diameter, and a 1 / 8 inch wall thickness. The tubing was extruded vertically with a 2-foot-long lower oven chamber set at 480°C and a 2-foot-long upper oven chamber set at 425°C. The line speed was set at 20 feet per minute. The extrusion process was smooth and produced clear, bubble-free tubing. The tubing was wound hot at the end of the extrusion line. The wound tubing did not stick together even after overnight storage, indicating complete vulcanization during extrusion; otherwise, the tubing would have fused together during storage.

[0094] Example 2

[0095] Example 2 used the same composition as Example 1, except that the amounts of both the platinum catalyst (ingredient D) and inhibitor (ingredient F) were reduced by half. As shown in Table 2, Example 2 exhibited the same optical, mechanical, and thermal properties as Example 1. When extruding the tube at the same line speed as Example 1, it was necessary to increase the temperature of the lower chamber to 535°C and the temperature of the upper chamber to 480°C to maintain an adequate cure rate and prevent the wound tube from sticking together during storage. The extruded tube was clear and bubble-free, just like Example 1.

[0096] Example 3

[0097] Example 3 used a different copolymer 2 of dimethylsiloxane, diphenylsiloxane, and dimethylvinylsiloxane as component A. Copolymer 2 contained 6 mol% diphenylsiloxane units and had a viscosity of 70,000 Pa·s. Its Si-vinyl content remained the same as that of Copolymer 1. The resulting silicone rubber exhibited good tear resistance of 33 N / mm according to ASTM D-624, which was lower than that of Example 1. The silicone rubber maintained high transparency, with a transmittance of 90% and a haze of 12% according to ASTM D1003. The silicone rubber had a low softening point of −115°C according to DSC. Tube extrusion was performed smoothly under the same extrusion conditions as Example 1. The tube was bubble-free, and the wound tubes did not stick together even after storage.

[0098] Example 4

[0099] Example 4 used 62.5 parts of Copolymer 1 and 2 parts of Copolymer 0, a dimethylsiloxane and dimethylvinylsiloxane copolymer containing no diphenylsiloxane units, a viscosity of 25,000 Pa·s, and a vinyl content of 0.028 mol / kg (Si-vinyl). The other ingredients were the same as those used in Example 1. By including Copolymer 0, which does not contain phenyl groups, the mole percent of diphenylsiloxane units in Component A was reduced from 5.3 mole percent (in Example 1) to 5.1 mole percent. As a result, the subsequently vulcanized silicone rubber had a slightly higher softening point at −112°C. Its transparency also decreased slightly to 87% clarity and 15% haze, likely due to some incompatibility between the diphenyl-containing Copolymer 1 and the diphenyl-free Copolymer 0. The material still exhibited good mechanical properties and a high tear resistance of 49 N / mm according to ASTM D-624. The extrusion of the tube also went well, similar to Example 1. The tube was bubble-free and the wound tubes did not stick together even after storage.

[0100] Comparative Example 1

[0101] When more Component C was incorporated relative to Example 1, increasing the concentration of Components B and C in the blend from 0.13 wt.% to 2.4 wt.%, the resulting material produced bubbles upon extrusion into a tube, which could not be eliminated by adjusting the extrusion conditions. Without being bound by any particular theory, these bubbles may be caused by high levels of volatile SiH components reacting with moisture to release hydrogen gas. The softening point of the tube remained the same as in Example 1, as shown in Table 2.

[0102] Mechanical and optical properties were measured on the compression-cured sheet (rather than the extruded tube) according to ASTM D-624 and D-1003, respectively. Unlike the extruded tube, the compression-cured sheet typically contains few bubbles due to the high pressure (e.g., 200 psi) used during vulcanization. This high pressure allows any bubbles present to be forced out of the sheet during vulcanization. Unfortunately, tube extrusion is generally carried out at atmospheric pressure (i.e., approximately 0 psi), which makes it more likely to retain bubbles that can form from side reactions such as dehydrogenation condensation. Tube extrusion also uses higher temperatures (400°C compared to 175°C for compression curing) to ensure rapid and adequate cure during the process. Higher temperatures are also more likely to cause side reactions such as condensation reactions that release gases, making tube extrusion more susceptible to bubble formation.

[0103] As shown in Table 2, Comparative Example 1 exhibits similar mechanical and optical properties compared to Example 1. For example, the compression-cured sheet still exhibits high transparency of 90% transmission and 12% haze at 2 mm according to ASTM D1003, and also has high tear resistance of 44 N / mm according to ASTM D-624. However, when this composition, which has a much higher volatile SiH content than Example 1, is extruded, outgassing and bubble formation cannot be avoided.

[0104] Comparative Example 2

[0105] When less silylating agent is used during the preparation process—here, silanol-terminated silicone is omitted compared to Example 2—the in-situ generated component (E) tends to have more unreacted silanols on the filler surface. The resulting material generates bubbles during tube extrusion, which cannot be removed by adjusting the extrusion conditions. The blend amounts of components (B) and (C) were adjusted accordingly to maintain the same SiH to Si-vinyl ratio as in Example 2, and the weight percent of component (C) in the mixture remained the same at 0.13%. Similar to Comparative Example 1, the compression-cured sheet was bubble-free, thereby exhibiting a high tear resistance of 55 N / mm according to ASTM D-624, as well as a high transmittance of 91% and a low haze of 12% according to ASTM D1003. However, with this composition, which uses less filler treatment compared to Example 2, bubble formation is inevitable.

[0106] Comparative Examples 3 and 4

[0107] The component (E) used in Comparative Examples 3 and 4 is different from that in Example 1. During the preparation process, instead of pretreated silica filler, a silica filler with a BET specific surface area of 320 m 2 / g of untreated fumed silica filler was used. As a result, only two types of silylating agents (silanol-terminated silicone and disilazane) were used in Comparative Examples 3 and 4, compared to three different types of silylating agents (D4, silanol-terminated silicone, and disilazane) used in Example 1. The latter tend to produce component (E) with more unreacted silanols.

[0108] Comparative Example 3, like Comparative Example 1, uses a higher amount of component (C) (2.40 wt%). Many bubbles were observed during extrusion of the tube. When the level of component (C) was reduced to 0.89 wt% in Comparative Example 4, bubble formation was reduced but not completely eliminated. Reducing the amount of low-volatility SiH compound appears to improve the bubble problem during extrusion of the tube.

[0109] The compression-cured sheets are bubble-free. As a result, as shown in Table 2, both the compositions of Comparative Examples 3 and 4 have high tear strength (39 N / mm), high transmittance (90%), and low haze (12%). Both of these compositions also have a softening point of −114° C. in the cured articles, based on the appropriate amount of diphenylsiloxane content, as also shown in Table 2. However, due to the lower silylation level on the silica filler and the higher content of component (C) compared to Examples 1-4 (see Table 2), neither of these compositions are suitable for the manufacture of tubing due to bubble formation during extrusion.

[0110] Comparative Example 5

[0111] Compared with Example 4, significantly more Copolymer 0 was charged, while simultaneously replacing the same amount of Copolymer 1. The mole percent of diphenylsiloxane units among all siloxane units in Component A was reduced to 4.6%, as shown in Table 2. Perhaps due to adequate silylation on the silica surface by using three different types of silylating agents and an appropriate amount of Component C (same as in Example 4, see Table 2), the resulting material produced bubble-free tubes upon extrusion, but flexibility at low temperatures was lost. The softening point dramatically increased to -56°C, likely due to the incorporation of excess dimethylsiloxane-based polymer and dilution of the overall diphenylsiloxane content. Clarity was also significantly impaired, with transmittance much lower at 76% and haze much higher at 35%, likely due to some immiscibility between the diphenyl-containing Copolymer 1 and the diphenyl-free Copolymer 0.

[0112] [Table 2] JPEG2025526283000003.jpg173169

[0113] From Table 2 above, it is abundantly clear that the examples of the present invention (Examples 1 through 4 in the table above) result in compositions that are substantially free of bubbles and have softening points below -110°C (specifically -114°C, -112°C, or -115°C). It is noteworthy that this desirable combination of attributes is achieved without sacrificing high tear strength (33 or 49 N / mm) and high transmittance to visible light (87-91%). In contrast, however, all of the comparative compositions having the desired softening point of -114°C exhibit significant bubble formation, which is commercially highly undesirable.

[0114] The foregoing description includes examples of the present specification. Of course, for purposes of describing the present specification, it is not possible to describe every conceivable combination of components or methodologies, but one of ordinary skill in the art may recognize that many additional combinations and permutations of the present specification are possible. Accordingly, the present specification is intended to embrace all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent the term "comprising" is used in the detailed description or the claims, it is intended to be inclusive in the same manner as "including," but in the same manner as "comprising" is interpreted when used as a transitional term in the claims.

[0115] The foregoing description identifies various, non-limiting embodiments of addition-curable silicone rubber compositions, silicone rubbers formed from such compositions, and articles including such silicone rubbers. Modifications may occur to those skilled in the art and those who may make and use the invention. The disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of the invention or the subject matter set forth in the following claims.

Claims

1. Addition-curing type silicone rubber composition: (A) Alkenyl-functional siloxanes containing approximately 4.8 mol% to approximately 13 mol% of aryl-functional siloxane units; (B) Polyhydrogen siloxane; (C) an organohydrogensiloxane different from polyhydrogensiloxane (B), where organohydrogensiloxane (C) has 6 or fewer siloxane units, and where organohydrogensiloxane (C) is present in an amount of 0.01% to 0.8% by weight of the total weight of (B) and (C); (D) Hydrosilylation catalyst; (E) Surface-modified silica; (F) an optional inhibitor; and (G) Optional auxiliary additives An addition-curing silicone rubber composition containing the above.

2. The addition-curing silicone rubber composition according to claim 1, wherein the surface-modified silica has at least three different types of silylation agents.

3. The addition-curing silicone rubber composition according to claim 1, wherein the surface-modified silica is modified with both silane and silazane.

4. The addition-curing silicone rubber composition according to claim 1, wherein the surface-modified silica is modified with silane, siloxane, and silazane.

5. The addition-curing silicone rubber composition according to claim 1, wherein the surface-modified silica has at least 40 mol% of surface silanols modified with functional groups.

6. The addition-curing silicone rubber composition according to claim 1, wherein 45 mol% to 85 mol% of the surface silanol of the surface-modified silica is modified with functional groups.

7. The addition-curing silicone rubber composition according to claim 1, wherein the alkenyl-functionalized siloxane (A) has about 5 mol% to about 10 mol% aryl-functionalized siloxane units.

8. Organohydrogensiloxane (C) is present in an amount of 0.05% to 0.6% by weight of the total weight of (B) and (C). The addition-curing type silicone rubber composition according to claim 1.

9. The addition-curing silicone rubber composition according to claim 1, wherein organohydrogensiloxane (C) is present in an amount of 0.1% to 0.5% by weight of the total weight of (B) and (C).

10. Alkenyl-functionalized siloxanes are given by formula (I): M １ ａ M ２Ｖｉ ｂ D １ ｃ D ２Ａｒ ｄ D ３Ｖｉ ｅ (I) It is, and here: M １ is (R １ ) ３ SiO １／２ ; M ２Ｖｉ is (R ２ ) (Caution ３ ) ２ SiO １／２ ; D １ is (R ４ ) ２ SiO ２／２ ; D ２Ａｒ ２ is (R ５ ) ２ SiO ２／２ ; D ３Ｖｉ is (R ６ ) (Caution ７ ) SiO ２／２ ; c, d, and e are independent integers, and c + d + e is approximately 10 to approximately 10,000. a is 0-2; b is 0-2; a + b = 2; R １ , R ３ , R ４ , and R ７ These are independently selected from C1-C10 alkyl groups; R ２ and R ６ R is independently selected from C1-C10 alkyl and C2-C10 alkylene groups, however R ２ and / or R ６ At least one of them is a C2-C10 alkylene; and R ５ is a C6-C30 aryl group, Here D ２Ａｒ The unit is present in vinyl-functionalized siloxane (A) in an amount of approximately 4.8 mol% to approximately 13 mol%. The addition-curing type silicone rubber composition according to claim 1.

11. Polyhydrogensiloxane is given by formula (II): - ３ ｆ - ４Ｈ ｇ 0 ４ ｈ 0 ５Ｈ ｉ 0 ６ ｊ (A) It is, and here M ３ is (R ８ ) ３ SiO １／２ ; M ４Ｈ is (R ９ ) (Caution １０ ) ２ SiO １／２ ; D ４ is (R １１ ) ２ SiO ２／２ ; D ５Ｈ is (R １２ ) (Caution １３ ) SiO ２／２ ; D ６ is (R １４ ) ２ SiO ２／２ ; f is 0-2; g is 0-2; f + g is 2; h is 0-200; i is 0-200; j is 0-20; h + i + j is 10 - 200; g+i is ?1; R ８ , R １０ , R １１ , and R １２ These are independently selected from C1-C10 alkyl groups; R ９ and R １３ R is independently selected from H and C1-C10 alkyl groups, however R １０ or R １３ At least one of them is H; and R １４ It is a C6-C30 aryl group. The addition-curing type silicone rubber composition according to claim 1.

12. The organohydrogensiloxane (C) is selected from the compound of formula (III), the compound of formula (IV), or a mixture thereof: D ７ ｊ D ８Ｈ ｋ (III) Here D ７ is (R １５ ) ２ SiO ２／２ ; D ８Ｈ is (R １７ ) (Caution １６ ) SiO ２／２ ; j is 0-6; k is 1-6; j + k is 3 - 6; R １５ These are independently selected from C1-C10 alkyl groups; and R １６ and R １７ are independently selected from H and C1-C10 alkyl, provided that at least one of R １６ and R １７ is H; M ５ ｌ M ６Ｈ ｍ D ９ ｎ D １０Ｈ ｏ (IV) Here M ５ is (R １８ ) ３ SiO １／２ ; M ６Ｈ is (R １９ ) (Caution ２０ ) ２ SiO １／２ ; D ９ is (R ２１ ) ２ SiO ２／２ ; D １０Ｈ is (R ２３ ) (Caution ２２ ) SiO ２／２ ; l is 0-2; m is 0-2; l + m is 2; n is 0-4; o is 0-4; n + o is ? 1; l + m + n + o is 3 - 6; R １８ , R ２０ , and R ２１ These are independently selected from C1-C10 alkyl groups; and R １９ , R ２３ , and R ２２ R is independently selected from H and C1-C10 alkyl groups, however R １９ , R ２３ , and / or R ２２ At least one of them is H. The addition-curing type silicone rubber composition according to claim 1.

13. A silicone rubber formed from an addition-curing silicone rubber composition according to any one of claims 1 to 12.

14. The silicone rubber according to claim 13, in the form of a tube, hose, gasket, or O-ring.

15. A method for producing silicone rubber, comprising curing an addition-curing type silicone rubber composition according to any one of claims 1 to 12.

16. An addition-curing silicone rubber composition, comprising: (A) Alkenyl-functionalized siloxanes containing aryl-functionalized siloxane units; and (B) Contains polyhydrogensiloxane; Here, the silicone rubber composition has a low softening temperature of -110°C in the cured state, as measured by differential scanning calorimeter (DSC); and / or the cured silicone rubber is substantially bubble-free.

17. The addition-curing silicone rubber composition according to claim 16, wherein the amount of aryl-functionalized siloxane units is approximately 4.8 mol% to approximately 13 mol%.

18. The addition-curing silicone rubber composition of claim 16, further comprising an organohydrogensiloxane (C) having 6 or fewer siloxane units.

19. The addition-curing silicone rubber composition of claim 18, wherein organohydrogensiloxane (C) is present in an amount of about 0.01% to about 0.8% by weight based on the total weight of (B) and (C).

20. The addition-curing silicone rubber composition according to claim 16, further comprising surface-modified silica.

21. The addition-curing silicone rubber composition of claim 20, wherein the surface-modified silica contains a silane functional group.

22. The addition-curing silicone rubber composition of claim 20, wherein at least three different silylation agents are used.

23. The addition-curing silicone rubber composition according to claim 22, wherein the surface-modified silica is modified with silane, siloxane, and silazane.

24. The addition-curing silicone rubber composition of claim 20, wherein the surface-modified silica has at least 40 mol% of surface silanols modified with functional groups.

25. The addition-curing type silicone rubber composition according to claim 16, wherein the silicone rubber composition has a low softening temperature of -115°C in the cured state using DSC.

26. Use of any addition-curing silicone rubber composition according to claims 1 to 12 or claims 16 to 24 for the manufacture of conduits for medical applications.

27. The use of claim 26, wherein the conduit is a tube.

28. The use described in claim 26 is for medical purposes, specifically for pharmaceutical purposes.

29. The use of claim 28 is for the pharmaceutical application of transporting drugs, vaccines, cell formulations, or cell materials.

30. Use of any addition-curing silicone rubber composition according to claims 1 to 12 or claims 16 to 24 for the manufacture of O-ring seals for gaskets.

31. The use of the gasket in claim 30, which is used in aircraft components.