Addition curing silicone rubber

Abstract

Addition cure silicone rubber compositions are shown and described herein. In one aspect, an addition cure silicone rubber composition provides a cured silicone rubber that has negligible crystallization (proved by low softening point temperatures) and is substantially free of bubbles. In one aspect, there is provided an addition cure silicone rubber composition comprising (i) an alkenyl functionalized siloxane comprising aryl functionalized siloxane units; (ii) a polyorganohydrosiloxane; (iii) a hydrosiloxane having six or less siloxane units; and (iii) a silylated silica filler. By controlling the amount of aryl-functionalized siloxane units, the amount of hydrogen siloxane having six or less siloxane units, and the degree of functionalization of the silica filler, a cured rubber material can be formed which exhibits excellent elastomeric properties at very low temperatures and can also be relatively bubble-free, and which can be used in the field of rubber materials. To ensure good aesthetics and sufficient mechanical properties of the cured article.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 388,428, filed on July 12, 2022, entitled “ADDITION-CURED SILICONE RUBBER,” the entire contents of which are incorporated by reference into the present disclosure. Technical Field

[0003] The present invention relates to addition-curing silicone rubber compositions, cured silicone rubbers formed from such compositions, and articles formed from such compositions. In particular, the present invention relates to addition-curing silicone rubber compositions which, when cured, form silicone rubbers that exhibit excellent physical properties such as flexibility and high light transmittance at low temperatures, even at temperatures below -100°C. Background Art

[0004] Silicone rubber materials are widely used in a variety of applications. For example, they can be used to form conduits that contain or transport fluids. In certain industries, products that store fluids need to be kept at extremely low temperatures during the transportation of the fluids and / or before use. An example is that in the pharmaceutical industry, pharmaceutical materials need to be stored in an extremely low temperature environment ranging from less than -30°C to less than -100°C. Aircraft may include rubber materials such as O-rings, gaskets, hoses, pipes, etc., which can withstand extreme temperature changes and extremely low temperatures. However, conventional silicone rubbers typically lose flexibility when the temperature drops below -40°C. This can cause the product to become brittle or crack when subjected to extremely low temperatures.

[0005] The extrusion of silicone rubber tubing requires rapid curing and no degassing. Although some peroxide-cured silicone rubber compositions can produce good elastomeric properties at low temperatures, the rubber curing of peroxide curing is slower than the rubber of addition curing, and is not suitable for many applications such as tubing extrusion. In addition, peroxide curing typically requires additional processing steps to remove peroxide from the system. The residual peroxide in the system can produce toxic by-products, unexpected crosslinking and degassing.

[0006] On the other hand, addition-cured rubber silicones can experience degassing issues during tubing extrusion due to dehydrogenative condensation reactions between low-volatility reactive silicone hydrides and adsorbed moisture. Degassing that occurs during vulcanization can lead to the formation of bubbles, which not only affects the appearance of the tubing, but can also impair its mechanical properties.

[0007] Many industries apply transparent articles so that the contents of the article can be seen or the flow of fluid through the article can be observed. Conventional polydimethylsiloxane-based rubbers are generally translucent due to the slight mismatch (difference) in the refractive index between polydimethylsiloxane and silica fillers, and thus cannot meet the applications requiring high clarity and low haze. Summary of the invention

[0008] An overview of the present disclosure is presented below to provide a basic understanding of some aspects. This overview is neither intended to identify key or important elements nor to define any limitations of the embodiments or claims. In addition, this overview may provide a simplified overview of some aspects that may be described in more detail in other parts of the present disclosure. An addition-cured silicone rubber composition is provided. The silicone rubber composition provides a cured silicone rubber exhibiting low crystallization and low bubble content. In an embodiment, the cured silicone rubber formed by the composition has a softening temperature as low as -110°C. In an embodiment, the cured silicone rubber formed by the composition has a softening temperature as low as -115°C. In an embodiment, the cured silicone rubber formed by the composition is substantially free of any bubbles. In an embodiment, the cured silicone rubber formed by the composition is free of bubbles.

[0009] In one aspect, an addition-cured silicone rubber composition is provided, comprising (A) an alkenyl-functionalized siloxane comprising aryl-functionalized 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 wherein the cured silicone rubber is substantially free of bubbles.

[0010] In one aspect, an addition-cured silicone rubber composition is provided, comprising (i) an alkenyl-functionalized organopolysiloxane comprising aryl-functionalized siloxane units, (ii) a polyorganohydrogensiloxane, (iii) a hydrogensiloxane having six or fewer siloxane units, and (iv) a silylated silica filler.

[0011] In one aspect, an addition-cured silicone rubber composition is provided, comprising (A) an alkenyl-functionalized siloxane containing aryl-functionalized siloxane units in an amount of about 4.8 mol % to about 13 mol %; (B) a polyhydrogensiloxane; (C) an organohydrogensiloxane different from the polyhydrogensiloxane (B), the organohydrogensiloxane (C) having six or fewer siloxane units, wherein the organohydrogensiloxane (C) is present in an amount of 0.01 wt % to 0.8 wt % based on the total weight of (B) and (C); (D) a hydrosilylation catalyst; (E) a surface-modified silica; (F) optionally an inhibitor; and (G) optionally an auxiliary additive.

[0012] In one embodiment, the surface modified silica has at least three different types of silylating agents.

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

[0014] In one embodiment, the surface modified silica is modified with silanes, siloxanes and silazanes.

[0015] In one embodiment according to any of the preceding embodiments, the surface modified silica has at least 40 mol % of surface silanols modified with functional groups.

[0016] In one embodiment according to any of the preceding embodiments, 45 mol % to 85 mol % of the surface silanols of the surface modified silica are modified with functional groups.

[0017] In one embodiment according to any of the preceding embodiments, the alkenyl functionalized siloxane (A) has from about 5 mol % to about 10 mol % of aryl functionalized siloxane units.

[0018] In one embodiment according to any of the preceding embodiments, the organohydrogensiloxane (C) is present in an amount of 0.05 wt % to 0.6 wt % based on the total weight of (B) and (C).

[0019] In one embodiment according to any of the preceding embodiments, the organohydrogensiloxane (C) is present in an amount of 1 wt % to 0.5 wt % of the total amount of (B) and (C).

[0020] In one embodiment according to any of the preceding embodiments, the alkenyl functionalized siloxane has formula (I):

[0021] M 1 a M 2Vi b D 1 c D 2Ar d D 3Vi e (I)

[0022] in:

[0023] M 1 Yes (R 1 )3SiO 1 / 2

[0024] M 2Vi Yes (R 2 )(R 3 )2SiO 1 / 2

[0025] D 1 Yes (R 4 )2SiO 2 / 2

[0026] D 2Ar 2 is (R 5 )2SiO 2 / 2

[0027] D 3Vi Yes (R 6 )(R 7 )SiO 2 / 2

[0028] c, d and e are independently integers, wherein c+d+e is from about 10 to about 10,000.

[0029] a is 0-2;

[0030] b is 0-2

[0031] a+b=2

[0032] R 1 , R 3 , R 4 and R 7 Independently selected from C1-C10 alkyl;

[0033] R 2 and R 6 are independently selected from C1-C10 alkyl and C2-C10 alkylene, provided that R 2 and / or R 6 At least one of them is C2-C10 alkylene; and

[0034] R 5 is a C6-C30 aromatic group,

[0035] Where D 2Ar The units are present in the vinyl functional siloxane (A) in an amount of about 4.8 mol % to about 13 mol %.

[0036] In one embodiment according to any of the preceding embodiments, the polyhydrogensiloxane has formula (II):

[0037] M 3 f M 4H g D 4 h D 5H i D 6 j (II)

[0038] in

[0039] M 3 Yes (R 8 )3SiO 1 / 2

[0040] M 4H Yes (R 9 )(R 10 )2SiO 1 / 2

[0041] D 4 Yes (R 11 )2SiO 2 / 2

[0042] D 5H Yes (R 12 )(R 13 )SiO 2 / 2

[0043] D 6 Yes (R 14 )2SiO 2 / 2

[0044] f is 0-2;

[0045] g is 0-2;

[0046] f+g is 2;

[0047] h is 0-200;

[0048] i is 0-200;

[0049] j is 0-20;

[0050] h+i+j is 10-200;

[0051] g+i≥1;

[0052] R 8 , R 10 , R 11 and R 12 Independently selected from C1-C10 alkyl;

[0053] R 9 and R 13 are independently selected from H and C1-C10 alkyl, provided that R 10 or R 13 At least one of is H; and

[0054] R 14 It is a C6-C30 aryl group.

[0055] In one embodiment according to any of the preceding embodiments, the organohydrogensiloxane (C) is selected from compounds of formula (III), formula (IV), or mixtures thereof:

[0056] D 7 j D 8H k (III)

[0057] in

[0058] D 7 for (R 15 )2SiO 2 / 2 ;

[0059] D 8H for (R 17 )(R 16 )SiO 2 / 2 ;

[0060] j is 0-6;

[0061] k is 1-6;

[0062] j+k is 3-6;

[0063] R 15 are independently selected from C1-C10 alkyl; and

[0064] R 16 and R 17 are independently selected from H and C1-C10 alkyl, provided that R 16 and R 17 At least one of them is H;

[0065] M 5 l M 6H m D 9 n D 10H o (IV)

[0066] in

[0067] M 5 Yes (R 18 )3SiO 1 / 2

[0068] M 6H Yes (R 19 )(R 20 )2SiO 1 / 2

[0069] D 9 Yes (R 21 )2SiO 2 / 2

[0070] D 10H Yes (R 23)(R 22 )SiO 2 / 2

[0071] l is 0-2;

[0072] m is 0-2;

[0073] l+m is 2;

[0074] n is 0-4;

[0075] o is 0-4;

[0076] n+o≥1;

[0077] l+m+n+o is 3-6;

[0078] R 18 , R 20 and R 21 are independently selected from C1-C10 alkyl; and

[0079] R 19 , R 23 and R 22 are independently selected from H and C1-C10 alkyl, provided that R 19 , R 23 and / or R 22 At least one of them is H.

[0080] In another aspect, there is provided a silicone rubber formed from the addition-cured silicone rubber composition of any preceding aspect or embodiment.

[0081] In one embodiment, the silicone rubber is in the form of a tube, hose, gasket or O-ring.

[0082] In yet another aspect, there is provided a method of preparing a silicone rubber comprising curing the addition-cured silicone rubber composition of any preceding aspect or embodiment.

[0083] In yet another aspect, a silicone rubber composition is provided, comprising: (A) an alkenyl-functionalized siloxane comprising aryl-functionalized siloxane units; and (B) a polyhydrogensiloxane; wherein the silicone rubber composition in a cured state has a softening temperature as low as -110°C using differential scanning calorimetry (DSC); and / or wherein the cured silicone rubber is substantially free of bubbles.

[0084] In one embodiment, the amount of aryl functionalized siloxane units is from about 4.8 mol % to about 13 mol %.

[0085] In one embodiment, the silicone rubber includes an organohydrogensiloxane (C) having six or fewer siloxane units.

[0086] In one embodiment, the organohydrogensiloxane (C) is present in an amount of about 0.01 wt % to about 0.8 wt %, based on the total weight of (B) and (C).

[0087] In one embodiment according to any of the preceding embodiments, the silicone rubber comprises surface-modified silica.

[0088] In one embodiment, the surface modified silica includes silane functional groups.

[0089] In one embodiment according to any of the preceding embodiments, at least three different silylating agents are used.

[0090] In one embodiment according to any of the preceding embodiments, the surface modified silica is modified with silanes, siloxanes and silazanes.

[0091] In one embodiment according to any of the preceding embodiments, the surface modified silica has at least 40 mol % of surface silanols modified with functional groups.

[0092] In one embodiment according to any of the preceding embodiments, the silicone rubber composition in a cured state has a softening temperature as low as -115°C using DSC.

[0093] In another aspect, there is provided a use of the addition-cured silicone rubber composition according to any of the foregoing embodiments for preparing a catheter for medical applications. In one embodiment, the catheter is a tube (tubing). In one embodiment, the medical application is a pharmaceutical application. In one embodiment, the pharmaceutical application is for delivering drugs, vaccines, cell preparations or cell banks.

[0094] In yet another aspect, there is provided a use of an addition-cured silicone rubber composition according to any preceding embodiment for preparing an O-ring seal for a gasket. In one embodiment, the gasket is used in a component of an aircraft vehicle.

[0095] The compositions of the present invention, when cured, provide silicone rubbers having excellent physical properties even at extremely low temperatures, for example, at temperatures of about -100°C or less, and may also provide silicone rubbers having excellent clarity (transparency). Without being bound by any particular theory, applicants have discovered that controlling the aryl (e.g., phenyl) content of the alkenyl functionalized siloxane provides excellent elastomeric properties even at very low temperatures. It also produces silicone rubber compounds having high transparency. At the same time, controlling the amount of hydrogen siloxane having 6 or fewer siloxane units and employing surface modified silica fillers can reduce degassing in the system.

[0096] The following description discloses various illustrative aspects. Some improvements and novel aspects can be specifically identified, while other improvements and novel aspects can be apparent from the description and drawings. DETAILED DESCRIPTION

[0097] Reference will now be made to exemplary embodiments, examples of which are shown in the accompanying drawings. It should be understood that other embodiments may be utilized and that structural and functional changes may be made. In addition, the features of the various embodiments may be combined or changed. Therefore, the following description is presented only by way of illustration and should not limit in any way the various substitutions and modifications that may be made to the illustrated embodiments. In the present disclosure, many specific details provide a thorough understanding of the present disclosure. It should be understood that various aspects of the present disclosure may be practiced with other embodiments that do not necessarily include all aspects described herein, etc.

[0098] As used herein, the words "example" and "exemplary" mean an instance or illustration. The words "example" or "exemplary" do not indicate key or preferred aspects or implementations. Unless the context indicates otherwise, the word "or" is intended to be inclusive rather than exclusive. As an example, the phrase "A employs B or C" includes any inclusive arrangement (e.g., A employs B; A employs C; or A employs both B and C). On the other hand, unless the context indicates otherwise, the articles "a" and "an" are generally intended to mean "one or more".

[0099] It should be understood that where ranges are provided in the specification and claims, numerical values ​​can be combined to form new and non-specified ranges. For example, the endpoints of component ranges can be used to form new and non-specified ranges.

[0100] Addition-cured rubber silicone compositions, cured rubber silicones from such compositions, and articles comprising such cured rubber silicones are provided. The addition-cured rubber silicone compositions provide cured rubber silicones that exhibit excellent elastomeric and other physical properties at low temperatures, even at temperatures of about -110°C or lower. In addition, the compositions of the present invention provide low bubble formation upon curing.

[0101] The addition-cured rubber silicone composition of the present invention includes a siloxane copolymer having aryl-functionalized siloxane units; a polyorganohydrogensiloxane; a hydrogensiloxane having a low content of an organohydrogensiloxane having six or fewer siloxane units; and a surface-modified silica filler in which a high percentage of the surface silanol groups are functionalized.

[0102] In one embodiment, the addition-cured rubber silicone composition includes (A) an alkenyl-functionalized siloxane copolymer of a dialkyl siloxane, an aryl-functionalized siloxane, and an alkyl-alkenyl-functionalized siloxane, wherein the aryl-functionalized siloxane units are in the range of 4.8-13 mol % and provide low temperature flexibility; (B) at least one polyhydrogensiloxane as a crosslinker; (C) a mixture of organohydrogensiloxanes having no more than six siloxane units in cyclic or linear form, and the total amount of component (C) is in the range of 0.01 wt % to 0.8 wt % of the amount of component (B); (D) at least one hydrosilylation catalyst comprising a transition metal to promote addition curing; (E) at least one surface-modified reinforcing silica filler, wherein at least 40 mol % of the surface silanol groups are functionalized (e.g., silylated); (F) optionally one or more inhibitors to component (D) to balance cure rate and pot life; and (G) optionally one or more auxiliary additives.

[0103] Component (A) is an organopolysiloxane having at least two alkenyl groups per molecule, and also contains aryl functionalized siloxane units. Alkenyl groups can be selected from any suitable alkenyl groups. In one embodiment, alkenyl groups are C2-C10 alkenyl groups, such as but not limited to vinyl, allyl, butenyl, pentenyl, hexenyl and heptenyl, wherein vinyl and hexenyl are particularly suitable. For the bonding position of alkenyl groups, in an embodiment, it is provided by the end of a molecular chain, a side chain of a molecular chain or an end of a molecular chain and a side chain of a molecular chain. In addition, in component (A), in addition to alkenyl groups, groups different from the silicon-bonded groups of alkenyl groups can be selected from substituted or unsubstituted monovalent hydrocarbon groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl and other alkyl groups. Component (A) also includes aryl functionalized siloxane units. Examples of suitable aryl groups include C6-C30 aryl groups, such as but not limited to phenyl, tolyl, xylyl and other aryl groups; benzyl, phenethyl and other aralkyl groups. The molecular structure of component (A) may be linear, partially branched linear, branched or network structure, and component (A) may be a mixture of two or more of the above-mentioned organopolysiloxanes of different molecular structures. In addition, the zero shear viscosity of component (A) at 37° C. as determined using a creep test on a controlled stress rheometer may be selected according to the needs of a specific purpose or intended application. In an embodiment, the zero shear viscosity of component (A) may be in the range of 100 Pascal seconds (Pa·s) to 1,000,000 Pa·s, and in particular in the range of 10,000 Pa·s to 100,000 Pa·s.

[0104] In one embodiment, examples of component (A) are dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers having both ends of the molecular chain capped with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers having both ends of the molecular chain capped with dimethylvinylsiloxane groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymers having both ends of the molecular chain capped with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymers having both ends of the molecular chain capped with dimethylvinylsiloxane groups, alkyl copolymers, dimethylsiloxane-methylphenylsiloxane copolymers having molecular chains terminated by dimethylvinylsiloxy groups at both ends, dimethylsiloxane-diphenylsiloxane copolymers having molecular chains terminated by dimethylvinylsiloxy groups at both ends, dimethylsiloxane-methylvinylsiloxane copolymers having molecular chains terminated by trimethylsiloxy groups at both ends, dimethylsiloxane-methylvinylsiloxane copolymers having molecular chains terminated by dimethylvinylsiloxy groups at both ends, polydimethylsiloxane having molecular chains terminated by dimethylvinylsiloxy groups at both ends, R3SiO 1 / 2 Unit and SiO 4 / 2 Unit-containing organopolysiloxane, RSiO 3 / 2 Unit organic polysiloxane, including R2SiO 2 / 2 Units and RSiO 3 / 2 Unit organic polysiloxane, including R2SiO 2 / 2 Unit, RSiO 3 / 2 and SiO 4 / 2 The organopolysiloxanes of the present invention are characterized in that the organopolysiloxanes are organic polysiloxanes of the present invention are organic polysiloxanes of the present invention and mixtures of two or more of the above organopolysiloxanes. The group R represents a substituted or unsubstituted monovalent hydrocarbon group, such as 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; benzyl, phenethyl and other aralkyl groups. In one embodiment, at least two R groups should be alkenyl groups.

[0105] In one embodiment, the alkenyl functionalized siloxane (A) is a copolymer of dialkyl siloxane, diaryl siloxane and alkyl-vinyl siloxane of formula (I):

[0106] M 1 a M 2Vi b D 1 c D 2Ar d D 3Vi e (I)

[0107] in:

[0108] M 1 Yes (R 1 )3SiO 1 / 2

[0109] M 2Vi Yes (R 2 )(R 3 )2SiO 1 / 2

[0110] D 1 Yes (R 4 )2SiO 2 / 2

[0111] D 2Ar Yes (R 5 )2SiO 2 / 2

[0112] D 3V Yes (R 6 )(R 7 )SiO 2 / 2

[0113] c, d, e are integers, wherein 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;

[0114] a is 0-2;

[0115] b is 0-2

[0116] a+b=2

[0117] R 1 , R 3 , R 4 and R 7 Independently selected from C1-C10 alkyl;

[0118] R 2 and R 6 are independently selected from C1-C10 alkyl and C2-C10 alkylene, provided that R 2 and / or R 6 At least one of them is C2-C10 alkylene; and

[0119] R 5 is a C6-C30 aromatic group,

[0120] Where D 2Ar The units are present in the vinyl functional siloxane (A) in an amount of from about 4.8 mol % to about 13 mol % of all siloxane units in component (A).

[0121] In one embodiment, D 2Ar The 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. 29 Si NMR spectroscopy (( 29 Si NMR) determination of D in component (A) 2Ar Without being bound by any particular theory, it has been found that providing a siloxane having a diphenylsiloxane content within this range provides a resultant silicone rubber having excellent elastomeric properties even at temperatures below -100°C.

[0122] In one embodiment, the alkyl group 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.

[0123] In one embodiment, the alkenyl group 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.

[0124] In one embodiment, aryl is independently selected from C6-C30 aryl, C7-C20 aryl or C8-C15 aryl. In one embodiment, aryl is phenyl.

[0125] In one embodiment, component (A) is present in the composition in an amount of about 40 wt % to about 90 wt %, about 50 wt % to about 80 wt %, or about 60 wt % to about 70 wt %, based on the weight of the composition.

[0126] 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.

[0127] The bonding position of the silicon-bonded hydrogen atom can be anywhere as required, and can be set at the end of the molecular chain, the side chain of the molecular chain, or the end of the molecular chain and the side chain of the molecular chain. In addition, in component (B), the silicon-bonded group may be a substituted or unsubstituted monovalent hydrocarbon group, except for alkenyl, such as methyl, ethyl, propyl, butyl, pentyl, hexyl. The molecular structure of component (B) may be a straight chain, a partially branched straight chain, a branched chain or a network structure, and component (B) may be a mixture of two or more of the above-mentioned organopolysiloxanes with different molecular structures. In addition, the component (B) according to DIN53019 at 20°C and 10s -1The viscosity at a shear rate of 1.34° is preferably in the range of 1 mPa·s to 50,000 mPa·s, particularly preferably in the range of 5 mPa·s to 1,000 mPa·s.

[0128] Non-limiting examples of the siloxane according to component (B) include, but are not limited to: methylhydrogenpolysiloxane having both ends of the molecular chain terminated by trimethylsiloxy groups; dimethylsiloxane-methylhydrogensiloxane copolymer having both ends of the molecular chain terminated by trimethylsiloxy groups; polydimethylsiloxane having both ends of the molecular chain terminated by dimethylhydrogensiloxy groups, methylhydrogenpolysiloxane having both ends of the molecular chain terminated by dimethylhydrogensiloxy groups; dimethylsiloxane-methylhydrogensiloxane copolymer having both ends of the molecular chain terminated by dimethylhydrogensiloxy groups; dimethylsiloxane-diphenylsiloxane copolymer having both ends of the molecular chain terminated by dimethylhydrogensiloxy groups ; a dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymer having both ends of the molecular chain terminated by dimethylhydrogensiloxaneoxy groups, a dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymer having both ends of the molecular chain terminated by trimethylsiloxy groups; a dimethylsiloxane-methylphenylsiloxane copolymer having both ends of the molecular chain terminated by dimethylhydrogensiloxaneoxy groups; a dimethylmethylhydrogensiloxane-methylphenylsiloxane copolymer having both ends of the molecular chain terminated by dimethylhydrogensiloxaneoxy groups, a dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymer having both ends of the molecular chain terminated by trimethylsiloxy groups; containing R′3SiO 1 / 2 Unit and SiO 4 / 2 The organopolysiloxane of R′SiO 3 / 2 Unit organopolysiloxane, comprising R′2Si O 2 / 2 Unit and R′SiO 3 / 2 Unit organopolysiloxane, comprising R′2Si O 2 / 2 Unit, R′SiO 3 / 2 andSiO 4 / 2 The organopolysiloxanes of organopolysiloxanes containing 1,2-dimethyl-1-nitropropene units, and mixtures of two or more of the above organopolysiloxanes. The group R' represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, such as methyl, ethyl, propyl, butyl, pentyl, hexyl and other alkyl groups; phenyl, tolyl, xylyl and other aryl groups; benzyl, phenyl and other aralkyl groups; 3-chloropropyl, 3,3,3-trifluoropropyl and other halogenated alkyl groups. However, it is preferred that at least two R' groups should be hydrogen atoms.

[0129] In one embodiment, component (B) has formula (II):

[0130] M 3 f M 4Hg D 4 h D 5H i D 6 j (II)

[0131] in

[0132] M 3 Yes (R 8 )3SiO 1 / 2

[0133] M 4H Yes (R 9 )(R 10 )2SiO 1 / 2

[0134] D 4 Yes (R 11 )2SiO 2 / 2

[0135] D 5H Yes (R 12 )(R 13 )SiO 2 / 2

[0136] D 6 Yes (R 14 )2SiO 2 / 2

[0137] f is 0-2;

[0138] g is 0-2;

[0139] f+g is 2;

[0140] h is 0-200;

[0141] i is 0-200;

[0142] j is 0-20;

[0143] h+i+j is 10-200;

[0144] g+i≥1;

[0145] R 8 , R 10 , R 11 and R 12 Independently selected from C1-C10 alkyl;

[0146] R 9 and R 13 are independently selected from H and C1-C10 alkyl, provided that R 10 or R 13At least one of them is H.

[0147] R 14 is a C6-C30 aromatic group,

[0148] In one embodiment, the alkyl group 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.

[0149] In one embodiment, aryl is independently selected from C6-C30 aryl, C7-C20 aryl or C8-C15 aryl. In one embodiment, aryl is phenyl.

[0150] Component (C) is a hydrogen siloxane having six or fewer siloxane units. Component (C) may be a linear or cyclic siloxane. In one embodiment, component (C) is selected from a compound of formula (III), formula (IV) or a mixture of two or more thereof:

[0151] D 7 j D 8H k (III)

[0152] in

[0153] D 7 for (R 15 )2SiO 2 / 2 ;

[0154] D 8H for (R 16 )(R 17 )SiO 2 / 2 ;

[0155] j is 0-6;

[0156] k is 1-6;

[0157] j+k is 3-6;

[0158] R 15 are independently selected from C1-C10 alkyl; and

[0159] R 16 and R 17 are independently selected from H and C1-C10 alkyl, provided that R 16 and R 17 At least one of them is H;

[0160] M 5 l M 6H m D 9 nD 10H o (IV)

[0161] in

[0162] M 5 Yes (R 18 )3SiO 1 / 2

[0163] M 6H Yes (R 19 )(R 20 )2SiO 1 / 2

[0164] D 9 Yes (R 21 )2SiO 2 / 2

[0165] D 10H Yes (R 23 )(R 22 )SiO 2 / 2

[0166] l is 0-2;

[0167] m is 0-2;

[0168] l+m is 2;

[0169] n is 0-4;

[0170] o is 0-4;

[0171] n+o≥1;

[0172] m+o≥1;

[0173] l+m+n+o is 3-6;

[0174] R 18 , R 20 and R 21 are independently selected from C1-C10 alkyl; and

[0175] R 19 , R 23 and R 22 are independently selected from H and C1-C10 alkyl, provided that R 19 , R 23 and / or R 22 At least one of them is H.

[0176] In one embodiment, component (C) comprises a cyclic hydrogen siloxane of formula (III). In one embodiment, j is 0 and k is 3-6. In one embodiment, j is 0 and k is 3.

[0177] In one embodiment, the alkyl group in formula (III) or (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 (IV) is methyl.

[0178] Where components (B) and (C) are provided, it is to be understood that they may be provided individually or as a mixture.

[0179] In one embodiment, components (B) and (C) are present in the composition in an amount from about 0.3 wt % to about 1.2 wt %, from about 0.5 wt % to about 1 wt %, or from about 0.6 wt % to about 0.9 wt %, wherein component (C) is present in an amount from about 0.01 wt % to about 0.8 wt %, from about 0.02 wt % to about 0.7 wt %, from about 0.05 wt % to about 0.6 wt %, from about 0.1 wt % to about 0.5 wt %, or from about 0.1 wt % to about 0.4 wt %, based on the total weight of components (B) and (C).

[0180] The percentage of component (C) in the mixture of components (B) and (C) was determined using gas chromatography (GC) performed directly on the mixture. D4 (octamethylcyclotetrasiloxane) was used as an internal standard for quantification.

[0181] The composition includes a hydrosilylation catalyst (D) to promote the addition reaction of the alkenyl functional groups of component (A) with 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 alkenyl functional groups with hydride groups. Suitable hydrosilylation catalysts include, but are not limited to, metals or metal compounds, wherein the metal is selected from nickel, palladium, platinum, rhodium, iridium, ruthenium and osmium, or as taught in US3,159,601; US3,159,662 (Ashby); US3,419,593; US3,715,334; US3,775,452: US3,220,970 (Lamoreaux) and US3,814,730 (Karstedt).

[0182] These catalysts are added to the composition in an amount of 0.5 to 500 ppm, preferably 1 to 100 ppm, most preferably 1.5 to 10 ppm, based on the total weight of the composition.

[0183] In one embodiment, the catalyst is selected from a platinum-containing catalyst. 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.

[0184] The typical platinum-containing catalyst component in the organopolysiloxane composition of the present invention is chloroplatinic acid in any form, such as the readily available hexahydrate form or anhydrous form, because it is easily dispersed in the organosiloxane system. A particularly useful form of chloroplatinic acid is the composition obtained when it reacts with an aliphatic unsaturated organosilicon compound such as divinyltetramethyl-disiloxane or tetravinyltetramethyl-tetracyclosiloxane disclosed in US 3,419,593, which are incorporated herein by reference. Ashby catalysts, Karstedt catalysts, and Lamoreaux catalysts are conventional catalysts that can be used to cure silicone rubber compositions. It should be understood herein that any known or commercially used photoactivated catalyst, most specifically a photoactivated platinum catalyst, can be used herein. In one embodiment, the photoactivated platinum catalyst is selected from n-1,2-dihydro-1,4 ... 5 -cyclopentadienyl platinum(IV) complexes, bis(β-diketonate)platinum(II) complexes, bis(phosphine)platinum(II) complexes, cyclooctadieneplatinum(II) complexes and mixtures thereof, more specifically trimethyl(methylcyclopentadienyl)platinum(IV) or platinum(II) acetylacetonate.

[0185] The composition also comprises a surface modified silica filler (E). The silica particles contain residual silanol groups (-Si-OH) on their surface. The modified silica particles are provided by reacting the silanol groups with desired functional groups. In one embodiment, the silica particles are modified with silane to provide silylated silica.

[0186] The silica particles are not particularly limited and can be selected as needed. 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 are those that can be obtained in aqueous media. Colloidal silica in aqueous media is generally obtained in a stable form, such as those stabilized with sodium ions, ammonia or aluminum ions. Colloidal silica can have a particle size of 5 to 250 nanometers, more specifically 6 to 150 nanometers, or even 8 to 85 nanometers. The Brunauer-Emmett-T eller (BET) specific surface area of ​​the silica filler can be 50 to 400 m 2 / g, preferably 150 to 350m 2 / g.

[0187] In one embodiment, the particle size of the colloidal silica is measured according to ASTM E2490-09 (2015), Standard Guide for Measurement of Particle Size Distribution of Nanomaterials in Suspension by Dynamic Light Scattering (DLS).

[0188] Colloidal silica particles (also referred to herein as silica sol) can be derived, for example, from precipitated silica, microsilica (silica fume), pyrogenic silica (fumed silica) or silica gel of sufficient purity and mixtures thereof; they can be silanized by the method described in WO2004 / 035474. Silica sol can also be typically obtained from water glass, as disclosed in US5,368,833.

[0189] The silica particles may be modified with any suitable silylating agent. In one embodiment, the silica may 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, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxypropyltriethoxysilane, octyltrimethoxysilane, ethyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, dimethyldimethylethoxysilane, 3-chloropropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, isobutyltriethoxysilane, trimethylethoxysilane, silanes containing epoxy groups (epoxysilanes), glycidyloxy and / or glycidyloxypropyl groups, such as γ-glycidyloxypropyltrimethoxysilane, γ-glycidyloxypropylmethyldiethoxysilane, (3-glycidyloxypropyl)triethoxysilane, (3-glycidyloxypropyl)hexyltrimethoxysilane, β-(3,4-epoxycyclohexyl)-ethyltriethoxysilane; silanes containing vinyl groups, such as vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri-(2-methoxyethoxy)silane, vinylmethyldimethoxysilane, vinyltriisopropoxysilane; hexamethyldisiloxane, trimethylsilyl chloride, vinyltriethoxysilane, hexamethyldisilazane, octamethylcyclotetrasiloxane, polydimethylsiloxane, and mixtures thereof. According to one embodiment, a silane compound having a mercapto functional group can be used, such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, HS(CH2)3, Si(OCH3)3, a mercaptosilane having at least one hydroxyalkoxysilyl group and / or a cyclic dialkoxysilyl group, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane. In addition, a silicon dioxide powder surface-treated with an organic silicon compound such as polydimethylsiloxane, octamethylcyclotetrasiloxane or hexamethyldisilazane can be used.

[0190] Silazanes such as disilazane may also be used to provide modified silica. Disilazanes that may be used include, for example, but are not limited to, hexamethyldisilazane, divinyltetramethyldisilazane, and bis(3,3-trifluoropropyl)tetramethyldisilazane. Cyclosilazanes are also suitable and include, for example, octamethylcyclotetrasilazane.

[0191] In one embodiment, the surface modified silica filler is modified with multiple silylating agents. In an embodiment, the surface modified silica filler is modified with three or more types of silylating agents. In an 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.

[0192] The silica particles used in the present composition have at least 40 mol% of functionalized (e.g., silylated) surface silanol groups. In one embodiment, 40 mol% to about 100 mol% of the silanol groups are silylated, and about 45 mol% to about 85 mol%, about 50 mol% to about 70 mol% of the silanol groups are silylated. The percentage of silylated surface silanols in the fumed silica can be calculated using 29 Si cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (CP / MAS NMR) was measured at a contact time of 10 ms. For example, the BET surface area is 200 m 2 / g of fumed silica can have about 30 mol% functionalized surface silanol groups when treated with octamethylcyclotetrasiloxane. The same fumed silica can have about 40 mol% functionalized surface silanol groups when treated with both octamethylcyclotetrasiloxane and hexamethyldisilazane.

[0193] The surface modified silica particles can be present in the composition in an amount from about 1 wt % to about 50 wt %, from about 15 wt % to about 40 wt %, or from about 25 wt % to about 35 wt %, based on the weight of the composition.

[0194] The composition may further contain additives typical for silicone rubber compositions, including fillers, rheology control agents, reactive and non-reactive plasticizers, adhesion promoters, various reinforcing agents, pigments, dyes, flame retardants, heat stabilizers, UV stabilizers, and the like.

[0195] Inhibitors may also be used. Inhibitors are controlled regulated additives for the processing time and crosslinking rate of curable silicone rubber compositions. These inhibitors and stabilizers may be, for example, acetylenic alcohols such as ethynyl cyclohexanol and 2-methyl-3-butyn-2-ol, polymethylvinylcyclosiloxanes such as methylvinylcyclotetrasiloxane, low molecular weight silicone oils with vinyldimethylsiloxy end groups, trialkylcyanurates, maleic acid alkyl esters such as diallyl maleate and dimethyl maleate, fumaric acid alkyl esters such as diethyl fumarate and diallyl fumarate, organic hydroperoxides such as cumene hydroperoxide, tert-butyl hydroperoxide and pinane hydroperoxide (pinane), organic peroxides, benzotriazoles, organic sulfoxides, organic amines and amides, phosphites, phosphites, nitrile, diaziridine and oxime.

[0196] The silicone rubber composition may be press cured at 175°C for 10 minutes. In one embodiment, the silicone rubber composition is cured via a vertical tubing extrusion line at a line speed of 20 ft / min with a two foot long lower oven chamber set at 480°C and a two foot long upper oven chamber set at 420°C.

[0197] The silicone rubber substrate can be prepared by converting the curable silicone composition into a desired shape by conventional methods such as compression molding, injection molding, extrusion and calendaring; and then curing the composition. As used herein, the term "curing" refers to the conversion of a liquid or semi-solid composition into a cross-linked 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.

[0198] 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, the silicone rubber prepared from the composition according to the present technology is substantially free of bubbles. In one embodiment, the silicone rubber produced from the composition according to the present technology has a transmittance of 85% or more, 90% or more, 95% or more.

[0199] 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, etc. Conduits may include, but are not limited to, tubing, pipelines, channels, etc. The articles formed by the present composition can be used for a variety of end uses and applications. In one embodiment, the articles can be used for aviation applications. For example, the articles formed by the present composition can be used as components on aircraft vehicles or in combination with components on aircraft vehicles. Aircraft vehicles include both aviation and aerospace vehicles, that is, components can be used on aircraft operating within or outside the Earth's atmosphere.

[0200] In one embodiment, the article formed from the composition can be used as a conduit for transporting materials or fluids therein. The conduit can include tubing, pipes, channels, etc. The conduit formed from the composition can be used for a variety of applications, including but not limited to medical applications. The conduit can be used to transport fluids in various medical applications. This can be used for medical applications, such as the delivery of drugs, medicines, vaccines, cell preparations, plasma, other such fluids, etc.

[0201] Aspects and embodiments of the present technology may be further understood through the following examples. The examples are for the purpose of illustrating aspects and embodiments of the present technology and are not intended to limit the present technology to those specific examples.

[0202] Example

[0203] As shown in Table 1, when only about 5 mol% of diphenylsiloxane units are introduced into the polydimethylsiloxane chain, the softening point of the dimethylsiloxane copolymer can be reduced from -40°C to -115°C. Without being bound by any particular theory, the randomly distributed bulky diphenylsiloxane units can effectively inhibit the crystallization of polydimethylsiloxane. When more diphenylsiloxane units are introduced at 14 mol%, the softening point is subsequently increased to -98°C due to the increase in its glass transition temperature.

[0204] Table 1. Softening points of dimethylsiloxane copolymers end-capped with vinyldimethylsiloxy groups at both ends and containing different amounts of diphenylsiloxane units.

[0205]

[0206]

[0207] The thermal properties (e.g., softening point) of the samples were determined using differential scanning calorimetry (DSC). A TA Instruments Discovery 2500 DSC was used over a temperature range of -180°C and +100°C, with a heating rate of 10°C / min, and a 5 minute wait between steps. For crystalline polymers, the softening point is its melting point, and for amorphous polymers, the softening temperature is its glass transition temperature.

[0208] Example 1

[0209] In a double sigma blade mass 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 mol% of diphenylsiloxane units and 0.012 mol / kg of vinyl (Si-vinyl) were mixed with the following silylating agents: 1.9 parts of a silanol-stopped polydimethylsiloxane having a viscosity of 30 cSt, 0.85 parts of hexamethyldisilazane and 0.15 parts of tetramethyldivinyldisilazane. Then 30.8 parts of a pretreated fumed silica filler, which initially had a mass of 320 m 2 / g of Brunauer-Emmett-Teller (BET) specific surface area, and then treated with octamethylcyclotetrasiloxane (D4) at 265°C for 2 hours. The mixture was heated to 160°C and then kept at 160°C for at least 2 hours under a nitrogen inertization blanket to allow sufficient reaction between the residual surface silanols on the pretreated filler surface and the above three silylating agents. After this additional in-situ treatment, the resulting filler was considered as component E. At least three different types of silylating agents were used in the formation of component E, which included D4, a silanol-terminated silicone and two disilazanes, making it sufficiently hydrophobic to minimize its moisture adsorption and thereby reduce the moisture content in the silicone compound. After the silicone compound was cooled to below 70°C, 0.8 parts of a blend of dimethylhydrogensiloxy-terminated poly(dimethylsiloxane-co-methylhydrogensiloxane) (component B) and a methylhydrogensiloxane compound (component C) were added. The blend contained 8.1 mol / kg of silicon hydride groups (SiH) as determined by Fourier transform infrared measurement. Component B has the formula M H 2D 50 D H 50 Component C is D H 3. D x D H y (where x and y = 0-6, and x+y = 4-6) and M m M H n D x D H y(where m and n = 0-2, x and y = 0-4, m+n = 2, and m+n+x+y = 3-6). 0.13 wt% of component C was present in this blend of components B and C as determined by GC. Finally, 0.009 parts of 1-ethynyl-1-cyclohexanol (component F) as a Pt inhibitor was added to the mixture to complete the silicone rubber base compound. Separately, a Pt catalyst masterbatch (component D) was prepared by mixing 1 part of the above component A and 0.017 parts of a solution of Ashby Pt catalyst in tetramethyltetravinylcyclotetrasiloxane containing 1.75 wt% Pt.

[0210] The silicone rubber base compound and the Pt masterbatch were mixed in a ratio of 99:1 and press cured at 175°C for 10 minutes. The molar ratio of SiH to Si-vinyl in the catalytic blend was 2.9. The cured article exhibited high transparency with 12% haze and 90% transmittance at 2 mm according to ASTM D1003. It also exhibited good mechanical properties with a high tear resistance of 49 N / mm according to ASTM D-624. The cured article had a softening point of -114°C as measured by DSC.

[0211] The catalyzed blend was also subjected to extrusion into 9 / 16" OD and 5 / 16" ID tubing with a 1 / 8" wall thickness. The tubing extrusion was run 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 ran smoothly and produced a clear, bubble-free tubing. While the tubing was still hot, the tubing was coiled together at the end of the extrusion line. The coiled tubing did not stick together after overnight storage, indicating that vulcanization was complete during extrusion; otherwise, the tubing would have fused together during storage.

[0212] Example 2

[0213] Example 2 uses the same composition as Example 1, except that the amount of both the Pt catalyst (component D) and the inhibitor (component F) is halved. It exhibits the same optical, mechanical and thermal properties as Example 1, as shown in Table 2. During the extrusion of the tube at the same line speed as Example 1, the temperature of the lower chamber must be increased to 535°C and the temperature of the upper chamber to 480°C to maintain a sufficient curing rate so that the coiled tube does not stick together when stored. The extruded tube is also transparent and bubble-free, as in Example 1.

[0214] Example 3

[0215] Example 3 uses different copolymers 2 of dimethylsiloxane, diphenylsiloxane and dimethylvinylsiloxane as component A. Copolymer 2 contains 6 mol% of diphenylsiloxane units and has a viscosity of 70,000 Pa.s. Its Si-vinyl content remains the same as copolymer 1. The resulting silicone rubber shows good tear resistance at 33 N / mm according to ASTM D-624, but it is lower than the tear resistance of Example 1. It maintains high transparency, with a transmittance of 90% and a haze of 12% according to ASTM D1003. It has a low softening point of -115°C according to DSC. Pipe extrusion runs smoothly under the same extrusion conditions as in Example 1. The pipe is bubble-free and the wound pipe does not stick together during storage.

[0216] Example 4

[0217] Example 4 used 62.5 parts of copolymer 1, 2 parts of dimethylsiloxane and dimethylvinylsiloxane copolymer 0, which does not contain any diphenylsiloxane units, and has a viscosity of 25,000 Pa.s and a vinyl content of 0.028 mol / kg (Si-vinyl). The other inputs are the same as those used in Example 1. Due to the inclusion of copolymer 0 without phenyl, the mole % of diphenylsiloxane units in component A is reduced from 5.3 mol % (as in Example 1) to 5.1 mol %. As a result, the subsequent vulcanized silicone rubber has a slightly higher softening point at -112°C. Its transparency is also slightly reduced, with a transmittance of 87% and a haze of 15%, which may be due to the slight immiscibility between copolymer 1 containing diphenyl and copolymer 0 without diphenyl. The material still exhibits good mechanical properties, with a high tear resistance of 49 N / mm according to ASTM D-624. Pipe extrusion is also run as in Example 1. The pipe is bubble-free, and the wound pipe does not stick together when stored.

[0218] Comparative Example 1

[0219] When more component C was incorporated into Example 1, its concentration in the blend of components B and C increased from 0.13 wt% to 2.4 wt%, the resulting material developed bubbles during tubing extrusion, and the bubbles could not be eliminated by adjusting the extrusion conditions. Without being bound by any particular theory, the bubbles may be caused by higher levels of volatile SiH compounds that react with moisture and release hydrogen. The softening point of the tubing remained the same as Example 1 because the diphenyl content remained the same as Example 1, as shown in Table 2.

[0220] Mechanical and optical properties were measured for press-cured sheets (rather than extruded pipes) according to ASTM D-624 and D-1003, respectively. Unlike extruded pipes, press-cured sheets rarely contain bubbles because they typically use high pressure (e.g., 200 psi) during vulcanization. Such high pressure can squeeze bubbles (if any) out of the sheet during vulcanization. Unfortunately, pipe extrusion is generally carried out at ambient pressure (i.e., about 0 psi), making it easy to retain bubbles that may be generated by side reactions such as dehydrogenation condensation. Pipe extrusion also uses much higher temperatures (400°C, compared to 175°C for press-curing) to ensure rapid and sufficient curing during the process. High temperatures are also conducive to side reactions, such as degassing condensation reactions, making pipe extrusion more prone to bubbles.

[0221] Comparative Example 1 exhibits similar mechanical and optical properties compared to Example 1, as shown in Table 2. For example, the press-cured sheet still exhibits high transparency with a haze of 12% at 2 mm and a transmittance of 90% according to ASTM D1003, and it still has a high tear resistance of 44 N / mm according to ASTM D-624. However, when extruding the composition containing a much higher volatile SiH content than Example 1, outgassing and bubble formation are inevitable.

[0222] Comparative Example 2

[0223] When less silylating agent is used during the cooking step, wherein the silanol-terminated silicone is omitted compared to Example 2, the component (E) generated in situ will tend to have more unreacted silanols on the filler surface. The resulting material produces bubbles during pipe extrusion, which cannot be eliminated by adjusting the extrusion conditions. The amount of component (B) and (C) blend is adjusted accordingly to maintain the same SiH to Si-vinyl ratio as in Example 2, and the weight % of component (C) in the mixture remains the same, which is 0.13%. Similar to Comparative Example 1, the press-cured sheet has no bubbles, thereby showing a high tear strength of 55N / mm according to ASTM D-624, a high transmittance of 91% according to ASTM D1003, and a low haze of 12%. However, compared to Example 2, this composition with less filler treatment inevitably forms bubbles.

[0224] Comparative Examples 3 and 4

[0225] The component (E) used in Comparative Examples 3 and 4 was different from that in Example 1. During the preparation step, a BET specific surface area of ​​320 m 2 / g of untreated fumed silica filler was used instead of the pretreated silica filler. As a result, only two types of silylating agents (silanol-terminated silicone and disilazane) were used in Comparative Examples 3 and 4, compared with three different types of silylating agents (D4, silanol-terminated silicone and disilazane) used in Example 1. The former would tend to produce a component (E) with more unreacted silanol.

[0226] In Comparative Example 3, the same large amount of component (C) as in Comparative Example 1 (2.40 wt%) was used. Many bubbles were observed during tube extrusion. When the level of component (C) was reduced to 0.89 wt% in Comparative Example 4, bubble generation was reduced, although not completely eliminated. Reducing the amount of low volatility SiH compound appears to help improve the bubble problem during tube extrusion.

[0227] The press cured sheets were free of bubbles. Thus, both compositions produced high tear strength (39 N / mm), high transmittance (90%) and low haze (12%), as shown in Table 2. Due to the appropriate amount of their diphenylsiloxane content, both compositions also produced a softening point of -114°C in the cured article, also shown in Table 2. However, their lower level of silylation on the silica filler and their higher content of component (C) compared to Examples 1-4 (see Table 2) made them all unsuitable for producing useful pipes due to bubble formation during extrusion.

[0228] Comparative Example 5

[0229] Compared to Example 4, significantly more Copolymer 0 was added while replacing an equal amount of Copolymer 1. As shown in Table 2, the mole % of diphenylsiloxane units in all siloxane units in Component A was reduced to 4.6%. Although the resulting material produced bubble-free tubing upon extrusion, probably due to its thorough silylation on the silica surface using three different types of silylating agents and an appropriate amount of Component C (same as Example 4, see Table 2), it lost its low temperature flexibility. The softening point increased significantly to -56°C, probably due to the incorporation of too much dimethylsiloxane polymer and the dilution of the total diphenylsiloxane content. Due to a certain immiscibility between the diphenyl-containing Copolymer 1 and the diphenyl-free Copolymer 0, the transparency was also greatly affected, with a much lower transmittance of 76% and a higher haze of 35%.

[0230] Table 2 Composition (in parts by weight) and corresponding properties of each embodiment

[0231]

[0232]

[0233]

[0234] From Table 2 above, it is very clear that the examples of the present invention (Examples 1 to 4 of the above table) result in compositions that are substantially free of bubbles, but have a softening point of less than -110 degrees Celsius (particularly -114, -112 or -115 degrees Celsius). It is noteworthy that this desirable combination of properties is achieved without compromising high (33 or 49 N / mm) tear strength and high (87-91%) percent transmittance to visible light. However, in contrast, all compositions of the comparative examples having a desired softening point of -114 degrees Celsius have significant bubble formation, which is very undesirable commercially.

[0235] What has been described above includes embodiments of the present specification. Of course, for the purpose of describing the present specification, it is not possible to describe every conceivable combination of components or methods, but it will be appreciated by those of ordinary skill in the art that many further combinations and arrangements of the present specification are possible. Therefore, the present specification is intended to cover all such changes, modifications and variations that fall within the spirit and scope of the appended claims. In addition, with respect to the use of the term "include" in the detailed description or in the claims, such term is intended to be inclusive in a manner similar to the term "comprise" because "comprise" is interpreted when used as a transitional word in the claims.

[0236] The foregoing description identifies various non-limiting embodiments of addition-cured silicone rubber compositions, silicone rubbers formed from such compositions, and articles containing such silicone rubbers. Modifications may occur to those skilled in the art and those who can make and use the present 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 claims.

Claims

1. An addition-cured silicone rubber composition comprising: (A) an alkenyl-functionalized siloxane comprising aryl-functionalized siloxane units in an amount of about 4.8 mol % to about 13 mol %,; (B) polyhydrogensiloxane; (C) an organohydrogensiloxane different from the polyhydrogensiloxane (B), the organohydrogensiloxane (C) having six or fewer siloxane units, wherein the organohydrogensiloxane (C) is present in an amount of 0.01 wt % to 0.8 wt % based on the total weight of (B) and (C); (D) a hydrosilylation catalyst; (E) surface-modified silica; (F) optionally an inhibitor; and (G) Optionally, auxiliary additives.

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

3. The addition-cured silicone rubber composition of claim 2, wherein the surface-modified silica is modified with both silane and siloxane.

4. The addition-cured silicone rubber composition of claim 2, wherein the surface-modified silica is modified with silane, siloxane and silazane.

5. The addition-curing silicone rubber composition of any one of claims 2 to 4, 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 any one of claims 2 to 4, wherein 45 mol% to 85 mol% of the surface silanols of the surface-modified silica are modified with a functional group.

7. The addition-cured silicone rubber composition according to any one of claims 1 to 6, wherein the alkenyl-functionalized siloxane (A) has from about 5 mol% to about 10 mol% of aryl-functionalized siloxane units.

8. The addition-cured silicone rubber composition of any one of claims 1 to 7, wherein the organohydrogensiloxane (C) is present in an amount of 0.05 wt% to 0.6 wt% based on the total weight of (B) and (C).

9. The addition-cured silicone rubber composition of any one of claims 1 to 8, wherein the organohydrogensiloxane (C) is present in an amount of 0.1 wt% to 0.5 wt% based on the total amount of (B) and (C).

10. The addition-cured silicone rubber composition of any one of claims 1 to 9, wherein the alkenyl-functionalized siloxane has formula (I): M 1 a M 2Vi b D 1 c D 2Ar d D 3Vi e (I) in: M 1 for (R 1 )3SiO 1 / 2 M 2Vi for (R 2 )(R 3 )2SiO 1 / 2 D 1 for (R 4 )2SiO 2 / 2 D 2Ar 2 is (R 5 )2SiO 2 / 2 D 3Vi for (R 6 )(R 7 )SiO 2 / 2 c, d and e are independently integers, wherein 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 7 Independently selected from C1-C10 alkyl; R 2 and R 6 are independently selected from C1-C10 alkyl and C2-C10 alkylene, provided that R 2 and / or R 6 At least one of them is C2-C10 alkylene; and R 5 is a C6-C30 aromatic group, Where D 2Ar The units are present in the vinyl functional siloxane (A) in an amount of about 4.8 mol % to about 13 mol %.

11. The addition-cured rubber silicone composition of any one of claims 1 to 10, wherein the polyhydrogensiloxane has formula (II): M 3 f M 4H g D 4 h D 5H i D 6 j (II) in M 3 for (R 8 )3SiO 1 / 2 M 4H for (R 9 )(R 10 )2SiO 1 / 2 D 4 for (R 11 )2SiO 2 / 2 D 5H for (R 12 )(R 13 )SiO 2 / 2 D 6 for (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 Independently selected from C1-C10 alkyl; R 9 and R 13 are independently selected from H and C1-C10 alkyl, provided that R 10 or R 13 At least one of is H; and R 14 It is a C6-C30 aromatic group.

12. The addition-cured silicone rubber composition according to any one of claims 1 to 11, wherein the organohydrogensiloxane (C) is selected from compounds of formula (III), formula (IV) or mixtures thereof: D 7 j D 8H k (III) in D 7 for (R 15 )2SiO 2 / 2 ; D 8H for (R 17 )(R 16 )SiO 2 / 2 ; j is 0-6; k is 1-6; j+k is 3-6; R 15 are independently selected from C1-C10 alkyl; and R 16 and R 17 are independently selected from H and C1-C10 alkyl, provided that R 16 and R 17 At least one of them is H; M 5 l M 6H m D 9 n D 10H o (IV) in M 5 for (R 18 )3SiO 1 / 2 M 6H for (R 19 )(R 20 )2SiO 1 / 2 D 9 for (R 21 )2SiO 2 / 2 D 10H for (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 are independently selected from C1-C10 alkyl; and R 19 , R 23 and R 22 are independently selected from H and C1-C10 alkyl, provided that R 19 , R 23 and / or R 22 At least one of them is H.

13. A silicone rubber formed from the addition-cured silicone rubber composition of any one of claims 1 to 12.

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

15. A method for preparing a silicone rubber, comprising curing the addition-curing silicone rubber composition of any one of claims 1 to 12.

16. A silicone rubber composition comprising: (A) an alkenyl-functionalized siloxane comprising aryl-functionalized siloxane units; and (B) polyhydrogensiloxane; wherein the silicone rubber composition in a cured state has a softening temperature as low as -110°C using differential scanning calorimetry (DSC); and / or wherein the cured silicone rubber is substantially free of bubbles.

17. The silicone rubber composition of claim 16, wherein the amount of the aryl functionalized siloxane units is from about 4.8 mol% to about 13 mol%.

18. The silicone rubber composition according to claim 16 or 17, further comprising an organohydrogensiloxane (C) having six or less siloxane units.

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

20. The silicone rubber composition of any one of claims 16 to 19, further comprising surface-modified silica.

21. The silicone rubber composition of claim 20, wherein the surface modified silica comprises silane functional groups.

22. The silicone rubber composition according to claim 20 or 21, wherein at least three different silylating agents are used.

23. The addition-cured silicone rubber composition of claim 22, wherein the surface-modified silica is modified with silanes, siloxanes and silazanes.

24. The addition-cured silicone rubber composition of any one of claims 20 to 22, wherein the surface-modified silica has at least 40 mole % of surface silanols modified with functional groups.

25. The silicone rubber composition of any one of claims 16 to 24, wherein the silicone rubber composition in a cured state has a softening temperature as low as -115°C using DSC.

26. Use of the addition-cured silicone rubber composition of any one of claims 1 to 12 or 16 to 24 for the preparation of catheters for medical applications.

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

28. The use according to claim 26 or 27, wherein the medical application is a pharmaceutical application.

29. The use of claim 28, wherein the medical application is for the delivery of drugs, vaccines, cell preparations or cell banks.

30. Use of the addition-cured silicone rubber composition of any one of claims 1 to 12 or 16 to 24 for the preparation of an O-ring seal for a gasket.

31. The use according to claim 30, wherein the gasket is used in a component of an aircraft vehicle.

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