Condensation curable silicone compositions

Abstract

This relates to a two-part condensation curable silicone composition, typically being room temperature vulcanisable (RTV), comprising a base Part and a catalyst Part in which the base Part comprises an -OH and / or a hydrolysable group containing diorganopolysiloxane polymer, filler(s) and at least one carbinol terminated polydimethylsiloxane rheology modifier which enhances the properties of said base Part prior to mixing with the catalyst Part and cure.

Description

[0001] CONDENSATION CURABLE SILICONE COMPOSITIONS This relates to a two-part condensation curable silicone composition, typically being room temperature vulcanisable (RTV), comprising a base Part and a catalyst Part in which the base Part comprises an -OH and / or a hydrolysable group containing diorganopolysiloxane polymer, filler(s) and at least one carbinol terminated polydimethylsiloxane rheology modifier which enhances the properties of said base Part prior to mixing with the catalyst Part and cure. Condensation curable silicone compositions especially those which are room temperature vulcanizable (RTV) are well known and are typically used as sealants and adhesives and the like. Generally, such compositions comprise: an -OH containing diorganopolysiloxane polymer and / or a hydrolysable group containing polydiorganosiloxane either of which may have one or more alkylene linkages between terminal silicon atoms; and one or more suitable cross-linking agents designed to react with the –OH and / or hydrolysable groups and thereby cross-link the composition; usually in the presence one or more fillers and one or more catalysts which upon cure form a cured silicone product such as a sealant. One or more additional ingredients such as diluents (e.g., plasticizers and / or extenders), chain extenders, flame retardants, solvent resistant additives, pigments / colorants, and biocides and the like are often also incorporated into these condensation curable silicone compositions as and when required. The condensation curable silicone compositions may be one-part compositions or multiple-part (usually two-part) compositions. One-part compositions are generally stored in a substantially anhydrous form to prevent premature cure. These tend to cure via a skin or diffusion cure process wherein an initial skin is obtained at the air / sealant interface once the sealant has been applied on to a target area and then the sealant cures from the air / sealant interface into the body of the sealant as moisture penetrates and diffuses through the uncured sealant from the air / sealant interface. Two-part compositions are usually divided into a base Part and a catalyst Part such that neither Part can cure until mixed with the other. Neither of the Parts in such compositions are substantially affected by atmospheric moisture, but once mixed together, the resulting mixture possesses excellent deep curability and enables substantially uniform curing throughout the entire body of the sealing material, which is often referred to as “bulk-curing” as opposed to skin or diffusion cure processes which occur with one- part compositions. Generally, conventional two-part organopolysiloxane compositions comprise: a first or base Part that contains one or more organopolysiloxane polymers having an average of at least two -OH groups or at least two hydrolysable groups per molecule or a mixture thereof and one or more fillers; and a second or catalyst Part (sometimes referred to as the catalyst or cure package) containing a carrier fluid such as an alkyl-terminated diorganopolysiloxane, one or more tin based catalysts and cross-linker. Either Part may additionally incorporate one or more optional additives, dependent on the end use. For example, the base Part may contain a rheology modifier, depending on the level and nature of the filler(s) present. In some instances, without any rheology modifier, a base Part of such a two-part condensation curable silicone composition may exhibit low extrusion rates and high slump. That is, higher viscosity at high shear rates (extrusion rate), but lower viscosity at low shear rates (slump). However, it has been found that the base Part of such compositions needs to have different viscosity profiles for different applications. For example, in the case of glazing and construction applications many users of two-part condensation curable silicone compositions need to pump base Part compositions long distances through lines and static mixers, for which higher extrusion rates are desirable to overcome pressure drops, but also need a non-slump characteristic to the base (non-slump being defined as a flow of less than 5 mm in a standard slump jig e.g., in accordance with ASTM D2202 – 00). Alternatively, two-part condensation curable silicone compositions used in e.g., automotive and the like gasketing applications require the use of a sealant that has a very high viscosity at high shear (i.e., a low extrusion rate to pass a “blow out” test – where a sealant has to perform before cure under high air pressure but also a high viscosity at low shear to prevent sealant from flowing out of the assembly, i.e., the non-slump characteristic of a flow of less than 5 mm in a standard slump jig e.g., in accordance with ASTM D2202 – 00). However, this has led to a long-term industrial issue as when present, the rheology modifier most often used historically, has been a short chain hydroxyl-terminated polydimethylsiloxane having a degree of polymerization of from about 10-15 and a viscosity of from 5- 50 mPa.s at 25oC which rheology modifiers are added to the base Part composition in an amount of from about 1 to 3 wt. % of the base Part composition and impart a non-slump characteristic to the base (non-slump being defined as a flow of less than 5 mm in a standard slump jig e.g., in accordance with ASTM D2202 – 00) but only imparts a modest reduction in high shear viscosity (i.e., extrusion rate). Addition of much more than 2% of such hydroxyl rheology modifiers in a base can interfere with a sealant’s ability to cure and / or cure speed once the two parts are mixed together, so significantly increasing the amount of short chain hydroxyl-terminated polydimethylsiloxane having a degree of polymerization of from about 10 to 15 and a viscosity of from 5 to 50 mPa.s at 25oC in a base Part composition to increase the extrusion rate is not a viable option. The present disclosure seeks to provide a high extrusion rate (greater than 200g / min in accordance with C603-14), non-slump (less than 5 mm in accordance with ASTM D2202) – 00 base Part composition of a two-part condensation curable silicone composition. There is provided herein a two-part condensation curable silicone composition having a base Part and a catalyst Part, wherein the base Part comprises the following components: (a) One or more siloxane polymers having at least two terminal hydroxyl or hydrolysable groups having a zero-shear viscosity of from 750 to 150,000 mPa.s at 25oC; (b) one or more optionally hydrophobically treated fillers in an amount of from 20 to 70 wt.% of the base Part composition; and (c) a rheology modifier having the structure: comprises a C2-C20 carbinol group that optionally contains ether, ester, or amine functionality or a mixture thereof; m is from 5 to 50; n is from 0 to 20; each x is independently 0 or 1, with the proviso that when each x is 0, n is from 2 to 20; in an amount of from 0.5 to 5 wt. % of the base Part composition. There is also provided a method of preparing a base Part of a two-part condensation curable silicone composition having a base Part and a catalyst Part as herein described, by introducing a rheology modifier (c) having the structure: R′′ comprises a C2-C20 carbinol group that optionally contains ether, ester, or amine functionality or a mixture thereof; m is from 5 to 50; n is from 0 to 20; each x is independently 0 or 1, with the proviso that when each x is 0, n is from 2 to 20; in an amount of from 0.5 to 5 wt. % of the base Part composition, which base Part composition otherwise comprises components (a) and (b) wherein (a) is one or more siloxane polymers having at least two terminal hydroxyl or hydrolysable groups having a zero-shear viscosity of from 750 to 150,000 mPa.s at 25oC; and (b) is one or more optionally hydrophobically treated fillers in an amount of from 20 to 70 wt.% of the base Part composition; and intermixing components (a), (b) and (c) together. There is also provided a use of a compound (c) having the structure: R′′ comprises a C2-C20 carbinol group that opt ona y conta ns et er, ester, or am ne unct ona ty or a mixture thereof; m is from 5 to 50; n is from 0 to 20; each x is independently 0 or 1, with the proviso that when each x is 0, n is from 2 to 20; in an amount of from 0.5 to 5 wt. % of the base Part composition; as a rheology modifier in a base Part of a two-part condensation curable silicone composition having a base Part and a catalyst Part, which base Part composition otherwise comprises components (a) and (b) wherein: (a) is one or more siloxane polymers having at least two terminal hydroxyl or hydrolysable groups having a zero-shear viscosity of from 750 to 150,000 mPa.s at 25oC; and (b) is one or more optionally hydrophobically treated fillers in an amount of from 20 to 70 wt.% of the base Part composition. In each of the above, the base Part composition containing component (c) has an extrusion rate of greater than 200g / min in accordance with ASTM C603-14, whilst having a slump of less than 5 mm in accordance with ASTM D2202 – 00. This disclosure is dealing with a problem found in the base Part of a two-part condensation curable silicone composition. Any suitable catalyst Part may be used in combination with the base Part composition described above comprising rheology modifier (c) described. For example, the catalyst Part may comprise a suitable carrier fluid, one or more tin based catalysts and cross-linker. The carrier fluid may be, for example, one of the following: (i) an alkyl-terminated diorganopolysiloxane, (ii) one or more silicon-free, branched polyethers comprising repeating units having the average formula (-CnH2n-O-)ywherein n is an integer from 3 to 6 inclusive and y is at least four, comprising one or more -OH terminal groups, -OR10terminal groups or -OH and -OR10terminal groups where R10is an optionally functionalised hydrocarbon group having from 1 to 12 carbons; as further described in WO2023055680A1 which is incorporated herein by reference; (iii) one or more polyarylorganosiloxane polymers which comprise a plurality of repeating -[Si(R4)(R5) – O]- units wherein each R4is a monovalent substituent comprising an aromatic group having from 6 to 18 carbons and each R5is a monovalent organic group having from 1 to 18 carbons as further described in WO2023055682A1 which is incorporated herein by reference; or one or more silicone copolymers comprising a plurality of repeating -[Si(R4)(R5) – O]- units wherein each R4is a monovalent substituent comprising an aromatic group having from 6 to 18 carbons and each R5is a monovalent organic group having from 1 to 18 carbons; or a mixture thereof as further described in WO2023055682A1 which is incorporated herein by reference; or (iv) one or more linear or branched polyethers comprising repeating units having the average formula (-CdH2d-O-)ewherein d is an integer from 3 to 6 inclusive and e is an integer of at least four, comprising either or both [(R4O)r(Y1)3-r– Si – W1v]– terminal groups or [(R4O)r(Y1)3-r – Si – W2– (Si(Y1)2-O)p – W3] - terminal groups, where each R4is a C1-10 alkyl group, each Y1may be the same or different and is an alkyl group containing from 1 to 8 carbons, r is 0, 1, 2 or 3; W1, W2and W3may be the same or are different and are divalent hydrocarbons having from 2 to 18 carbons, p is 1, 2, or 3. and v is 0 or 1 as further described in WO2023055681A1 which is incorporated herein by reference. In the present disclosure, the base Part comprises the following ingredients: Component (a): an organopolysiloxane polymer having an average of at least two -OH groups or hydrolysable groups per molecule; and a zero-shear viscosity of from 750 to 150,000mPa.s at 25oC. Component (a) may be any suitable an organopolysiloxane polymer having an average of at least two - OH groups or at least two hydrolysable groups per molecule or a mixture thereof; and a zero-shear viscosity of from 750 to 150,000mPa.s at 25oC; alternatively, any suitable organopolysiloxane polymer having at least two -OH groups or at least two hydrolysable groups per molecule or a mixture thereof; at least two -OH groups or hydrolysable groups per molecule; and a zero-shear viscosity of from 750 to 150,000mPa.s at 25oC. Component (a) may optionally one or more alkylene linkages between terminal silicon atoms. The at least two -OH groups or at least two hydrolysable groups per molecule or a mixture thereof are preferably silicon bonded groups and may be, but are not necessarily, terminal groups. In one embodiment, the hydrolysable groups are alkoxy groups having from one to 10 carbons. Illustrative alkoxy groups are methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, t-butoxy, isobutoxy, pentoxy, hexoxy and 2-ethylhexoxy; dialkoxy groups, such as methoxymethoxy or ethoxymethoxy an alkoxyaryloxy, such as ethoxyphenoxy groups. Alternatively, the alkoxy groups may contain from 1 to 6 carbons i.e., a methoxy, ethoxy, propoxy, isopropoxy, n-butoxy or t-butoxy group. For example, the organopolysiloxane polymer having an average of at least two -OH groups or at least two hydrolysable groups per molecule or a mixture thereof (a), of the base Part of the two-part condensation curable silicone composition described herein, may have the formula: X3-qRqSi-Z- (R1ySiO(4-y) / 2)z –SiR12 -Z-Si-RqX3-q (1) in which each X is independently an OH or an alkoxy group, each R is an alkyl, alkenyl or aryl group, each R1is an OH group an alkoxy group, an alkyl group, an alkenyl group or an aryl group and Z is oxygen or a divalent organic group, typically containing from 2 to 10 carbons; each q is independently 0, 1, 2 or 3, y is 0, 1 or 2, preferably 2 and z is an integer consistent with said organopolysiloxane polymer having a zero-shear viscosity of from 750 to 150,000mPa.s at 25oC. In the above formula each X is independently an OH or an alkoxy group, alternatively an alkoxy group having from 1 and 10 carbons. Illustrative alkoxy groups are methoxy, ethoxy, propoxy, isopropoxy, n- butoxy, t-butoxy, isobutoxy, pentoxy, hexoxy and 2-ethylhexoxy; dialkoxy groups, such as methoxymethoxy or ethoxymethoxy an alkoxyaryloxy, such as ethoxyphenoxy groups; alternatively, each X is an alkoxy group having from one and six carbons, alternatively having from one and four carbons i.e., methoxy, ethoxy, propoxy, isopropoxy, n-butoxy or t-butoxy group or alternatively is a methoxy or ethoxy group. Each R group is an alkyl, alkenyl or aryl group, alternatively each R is an alkyl group having from 1 to 6 carbons, an alkenyl group having from 2 to 6 carbons such as vinyl, allyl and hexenyl groups or an aryl group having from 6 to 12 carbons; alternatively, each R is an alkyl group having from 1 to 6 carbons, or an aryl group having from 6 to 12 carbons; alternatively each R is an alkyl group having from 1 to 6 carbons, alternatively each R is an ethyl group or a methyl group. In one embodiment R may include substituted aliphatic organic groups such as 3,3,3-trifluoropropyl groups aminoalkyl groups, polyaminoalkyl groups, and / or epoxyalkyl groups. Each R1is an OH group an alkoxy group, alkyl group, alkenyl group or aryl group. For the avoidance of doubt this means that cumulatively at least two X groups, at least two R1groups or at least one X group and one R1group per molecule are OH groups or alkoxy groups, preferably alkoxy groups. It is possible that some R1groups may be siloxane branches off the polymer backbone which branches may have terminal X groups as hereinbefore described. Each Z may be the same of different and is oxygen or a divalent organic group. When Z is a divalent organic group, it is typically an alkylene having from 2 to 10 carbons, such as for example, an ethylene, propylene, butylene, pentylene and / or hexylene group; alternatively, an alkylene group having 2 to 6 carbons, alternatively an alkylene group having from 2 to 5 carbons. The alkylene group may contain branching. Each subscript q is zero, 1, 2 or 3, alternatively each subscript q is 0, 1 or 2, alternatively each subscript q is 0 or 1. In one embodiment each q is zero and each Z is an alkylene having from 2 to 10 carbons. Each subscript y is 0, 1 or 2, and is preferably 2. Whilst y is 0, 1 or 2, substantially y= 2, e.g., at least 90%, alternatively 95% of R1ySiO(4-y) / 2groups are characterized with y = 2. Subscript z is an integer such that said organopolysiloxane polymer has a zero-shear viscosity of from 750 to 150,000mPa.s at 25oC, for example, z may be, but is not limited to, a suitable integer of from approximately 100 to 4000. The Degree of Polymerization (DP), (i.e., in the above formula z or substantially z), is usually defined as the number of monomeric units in a macromolecule or polymer or oligomer molecule of silicone. The term “substantially” is intended to mean almost all e.g., 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more of a value but not absolutely 100 %. Synthetic polymers invariably consist of a mixture of macromolecular species with different degrees of polymerization and therefore of different molecular weights. There are different types of average polymer molecular weight, which can be measured in different experiments. The two most important are the number average molecular weight (Mn) and the weight average molecular weight (Mw). The Mn and Mw of a siloxane polymer can be determined by gel permeation chromatography (GPC) with precision of about 10-15% using polystyrene standards. This technique is standard and yields Mw, Mn and polydispersity index (PI). The degree of polymerization (DP) =Mn / Mu where Mn is the number-average molecular weight coming from the GPC measurement and Mu is the molecular weight of a monomer unit. PI=Mw / Mn. The DP is linked to the viscosity of the polymer via Mw, the higher the DP, the higher the viscosity. In the present disclosure the number average molecular weight and weight average molecular weight values of component (a) herein may, for example, be determined using a Waters 2695 Separations Module equipped with a vacuum degasser, and a Waters 2414 refractive index detector (Waters Corporation of MA, USA). The analyses may then be performed using certified grade toluene flowing at 1.0 mL / min as the eluent. Data collection and analyses may be performed using Waters Empower GPC software. Unless otherwise indicated all viscosity measurement given are zero-shear viscosity (ηo) values, obtained by extrapolating to zero the value taken at low shear rates (or simply taking an average of values) in the limit where the viscosity-shear rate curve is rate-independent, which is a test-method independent value provided a suitable, properly operating rheometer is used. For example, the zero-shear viscosity of a substance at 25 °C may be obtained by using commercial rheometers such as an Anton-Parr MCR-301 rheometer or a TA Instruments AR-2000 rheometer equipped with cone-and-plate fixtures of suitable diameter to generate adequate torque signal at a series of low shear rates, such as 0.01 s-1, 0.1 s-1and 1.0 s-1while not exceeding the torque limits of the transducer. Alternatively, the viscosity of component (a) may be measured at 25oC in accordance with the ASTM D4287 Cone and Plate Method using a Brookfield DV-III Ultra Rheometer. In a still further the viscosity measurements may be obtained using an ARES parallel plate rheometer. (TA Instruments) with a dynamic frequency sweep was performed from 0.1 to 100 rad / s using 0.1% strain, 25 mm plates, and a 2 mm gap. The latter was preferred herein. The viscosity of component (a) is from 750 to 150,000mPa.s at 25oC, alternatively from 1000 to 125,000mPa.s at 25oC, alternatively from 1000 to 100,000mPa.s at 25oC, alternatively 10,000 to 100,000mPa.s at 25oC, alternatively 20,000 to 80,000mPa.s at 25oC. The organopolysiloxane polymer (a) described above is present in the base Part of the two-part condensation curable silicone composition in an amount of from 30 to 90 weight % (wt. %) of the composition; alternatively, 30 to 80 wt. % of the composition; alternatively, 35 to 80 wt. % of the composition. Organopolysiloxane polymer (a) can be a single siloxane represented by Formula (1) or it can be mixtures of organopolysiloxane polymers represented by the aforesaid formula. Hence, it may be a "siloxane polymer mixture" so organopolysiloxane polymer (a) is meant to include any individual organopolysiloxane polymer (a) or mixtures of organopolysiloxane polymer (a). Component (b) one or more fillers in an amount of from 20 to 70 wt.% of the base Part composition Component (b) may include one or more reinforcing fillers, one or more non-reinforcing fillers or a mixture thereof. The one or more reinforcing fillers which may be present in the composition as component (b) herein may for example be selected from precipitated silica, fumed silica, precipitated calcium carbonate, or a mixture comprising two or more thereof. Preferably they are provided in a finely divided form. Typically, the surface area of the reinforcing filler (b) is at least 15 m² / g in the case of precipitated calcium carbonate measured in accordance with the BET method (ISO 9277: 2010), alternatively 15 to 50 m² / g, alternatively 15 to 25 m² / g. Silica reinforcing fillers have a typical surface area of at least 50 m² / g in accordance with the BET method (ISO 9277: 2010). In the case of high surface area fumed silica and / or high surface area precipitated silica, these may have surface areas of from 75 to 400 m² / g measured in accordance with the BET method (ISO 9277: 2010), alternatively of from 100 to 300 m² / g in accordance with the BET method (ISO 9277: 2010). The reinforcing fillers (b) which may be present in the base Part of the two-part condensation curable silicone composition may be hydrophobically treated for example with one or more aliphatic acids, e.g., a fatty acid such as stearic acid or a fatty acid ester such as a stearate, or with organosilanes, organosiloxanes, or organosilazanes hexaalkyl disilazane or short chain siloxane diols to render the filler(s) hydrophobic and therefore easier to handle and obtain a homogeneous mixture with the other adhesive components. Specific examples organosilanes, organosiloxanes, or organosilazanes may include, but are not restricted to, silanol terminated trifluoropropylmethylsiloxane, silanol terminated vinyl methyl (ViMe) siloxane, silanol terminated methyl phenyl (MePh) siloxane, liquid hydroxyldimethyl-terminated polydiorganosiloxane containing an average from 2 to 20 repeating units of diorganosiloxane in each molecule, hydroxyldimethyl terminated phenylmethyl Siloxane, hexaorganodisiloxanes, such as hexamethyldisiloxane, divinyltetramethyldisiloxane; hexaorganodisilazanes, such as hexamethyldisilazane (HMDZ), divinyltetramethyldisilazane and tetramethyldi(trifluoropropyl)disilazane; hydroxyldimethyl terminated polydimethylmethylvinyl siloxane, octamethyl cyclotetrasiloxane, and silanes including but not limited to methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, chlorotrimethyl silane, dichlorodimethyl silane, trichloromethyl silane. The surface treatment of the fillers makes them easily wetted by component (a). These surface modified fillers are preferably in a finely divided form and do not clump and can be homogeneously incorporated into the siloxane polymer (a). This results in improved room temperature mechanical properties of the uncured compositions. The fillers may be pre-treated or may be treated in situ when being mixed with component (a). A small amount of water can be added together with the silica treating agent(s) as processing aid. Depending on the filler(s) chosen (when present) the reinforcing fillers of component (b) may be present in an amount of from 2.5 to 60 wt. % of the composition. In the case when the selected fillers are precipitated silica and / or fumed silica or a combination thereof the inorganic fillers (b) are present in a range of from about 5.0 to 35 wt. % of the composition, alternatively of from 5 to 30 wt. % of the composition, alternatively of from 5 to 25 wt. % of the composition. However, when reinforcing filler of component (b) is precipitated calcium carbonate, the composition will tend to include a larger wt. % of the composition, e.g., from 10 to 60 wt. % of the composition, alternatively of from 30 to 60 wt. % of the composition, alternatively of from 35 to 55 wt. % of the composition. When component (b) is a mixture of silica and precipitated calcium carbonate the wt. % will typically somewhere therebetween. Non-reinforcing fillers The base Part of the two-part condensation curable silicone composition herein may additionally comprise one or more non-reinforcing fillers as component (b) herein. These are also preferably provided in a finely divided form. They may be selected from one or more of the following aluminite, calcium sulphate (anhydrite), gypsum, nepheline, syenite, ground calcium carbonate, quartz, calcium sulphate, magnesium carbonate, clays such as kaolin, aluminium trihydroxide, magnesium hydroxide (brucite), graphite, copper carbonate, e.g., malachite, nickel carbonate, e.g., zarachite, barium carbonate, e.g., witherite and / or strontium carbonate e.g., strontianite. Silicates from the group consisting of olivine group; garnet group; aluminosilicates; ring silicates; chain silicates; and sheet silicates. The olivine group comprises silicate minerals, such as but not limited to, forsterite and Mg2SiO4. The garnet group comprises ground silicate minerals, such as but not limited to, pyrope; Mg3Al2Si3O12; grossular; and Ca2Al2Si3O12. Aluminosilicates comprise ground silicate minerals, such as but not limited to, sillimanite; Al2SiO5; mullite; 3Al2O3.2SiO2; kyanite; and Al2SiO5. The ring silicates group comprises silicate minerals, such as but not limited to, cordierite and Al3(Mg,Fe)2[Si4AlO18]. The chain silicates group comprises ground silicate minerals, such as but not limited to, wollastonite and Ca[SiO3]. The sheet silicates group comprises silicate minerals, such as but not limited to, mica; K2AI14[Si6Al2O20](OH)4; pyrophyllite; Al4[Si8O20](OH)4; talc; Mg6[Si8O20](OH)4; serpentine for example, asbestos; Kaolinite; Al4[Si4O10](OH)8; and vermiculite. The non-reinforcing fillers of component (b), when present, may also be hydrophobically treated as described above. And when present may be present in amounts up to about 60 wt. % of the composition but typically are found in lower amounts in combination with some reinforcing filler. In a preferred embodiment the base Part of the two-part condensation curable silicone composition as described herein contains one or more fillers as described in component (b). Component (c) Rheology Modifier The base Part of the two-part condensation curable silicone composition as hereinbefore described also comprises a rheology modifier of the structure: comprises a C2-C20 carbinol group that optionally contains ether, ester, or amine functionality or a mixture thereof; m is from 5 to 50; alternatively from 5 to 40, alternatively from 5 to 30, n is from 0 to 20, alternatively from 0 to 10, alternatively from 0 to 5, alternatively 0; each x is independently 0 or 1, with the proviso that when each x is 0, n is from 2 to 20. In one embodiment when one x is 1 and the other x is 0 then n is from 1 to 20. In one embodiment the base Part has an extrusion rate of greater than 200g / min in accordance with ASTM C603-14, whilst also having a slump of less than 5 mm in accordance with ASTM D2202 – 00. It will be appreciated that for this case the degree of polymerization of component (c) herein is m + n in the above. Preferably, in the case of rheology modifier (c) based on the above structure m + n = degree of polymerization = from 5 to 50, alternatively, when n is zero m = degree of polymerization = from 5 to 50, alternatively in rheology modifier (c) of the base Part, m + n = degree of polymerization = from 5 to 30, alternatively m = degree of polymerization = from 5 to 30, and n is 0. Furthermore, where n is > 0, R′′ may further comprise from 1 or from 2, to 20 or to 10 or to 7 structural units of a C2-C20 hydrocarbyl group that optionally contains ether, ester, or amine groups, but no carbinol groups. As used herein, the term “carbinol group” refers to a branched or linear alkyl group that contains one or more hydroxyl groups. For example, these may include any one of the following end groups which may be linked directly to a terminal silicon in the above formula via an ethylene bridge.

[0002] . Hence, the rheology modifiers (c) may be selected from hydroxyalkoxypropyl-terminated polydimethylsiloxanes, [3-(2,3-dihydroxyalkoxy)propyl]-terminated polydimethylsiloxanes, [3-[3-[bis(2- hydroxypropyl)amino]-2-hydroxyalkoxy]propyl]-terminated polydimethylsiloxanes or a mixture thereof. In the above preferably the alkoxy groups have from 1 to 6 carbons, alternatively are selected from methoxy, ethoxy and propoxy groups. Specific examples include hydroxyethoxypropyl-terminated polydimethylsiloxanes, [3-(2,3-dihydroxypropoxy)propyl]-terminated polydimethylsiloxanes, [3-[3- [bis(2-hydroxypropyl)amino]-2-hydroxypropoxy]propyl]-terminated polydimethylsiloxanes or mixtures thereof with the proviso that they all fall within the requirements of the structure of component (c). Specific examples of rheology modifier (c) include for the sake of example, (where m + n = the degree of polymerisation), one or more of a Hydroxyethoxypropyl-terminated polydimethylsiloxane where m = 7 and n = 0, a Hydroxyethoxypropyl-terminated polydimethylsiloxane where m = 20 and n = 0, a [3-(2,3-dihydroxypropoxy)propyl]-terminated polydimethylsiloxane where m = 7 and n = 0, a [3-(2,3-dihydroxypropoxy)propyl]-terminated polydimethylsiloxane where m = 20 and n = 0, a [3-[3-[bis(2-hydroxypropyl)amino]-2-hydroxypropoxy]propyl]- polydimethylsiloxane where m = 7 and n = 0, or a [3-[3-[bis(2-hydroxypropyl)amino]-2-hydroxypropoxy]propyl]-terminated polydimethylsiloxane where m = 20 and n = 0, and a hydroxypropyl-terminated polydimethylsiloxane where m = 7 and n = 0, Rheology modifier (c) is present in the composition in an amount of from 0.1 to 5 wt. % of the base Part composition, alternatively 0.1 to 4 wt. % of the base Part composition, alternatively 0.1 to 3 wt. % of the base Part composition, alternatively 0.1 to 2.5 wt. % of the base Part composition, 0.2.5 to 2.5 wt. % of the base Part composition, alternatively 0.5 to 2.5 wt. % of the base Part composition. The base Part of the two-part condensation curable silicone composition may also comprise one or more optional additives. Optional additives Optional additives may be added to the base Part of the two-part condensation curable silicone composition as described herein if deemed necessary. These may include, but are not limited, to one or more of the following: plasticizers and / or extenders, pigments & colorants, antioxidants, UV and / or light stabilizers and fungicides and / or biocides. One or more plasticizer(s), one or more extender(s) or a mixture thereof The base Part of the two-part condensation curable silicone composition as described above may also include one or more plasticizer(s), one or more extender(s) or a mixture thereof. These may be in the form of silicone or organic fluids which are unreactive with organopolysiloxane polymer(s) (a) of the base Part. If present the plasticizer or extender content will be present in an amount of from 5 to 30 wt. % of the base Part of the two-part condensation curable silicone composition, alternatively from 5 to 20 wt. % of the composition. Examples of non-reactive silicone fluids useful as plasticizers include polydiorganosiloxanes such as polydimethylsiloxane having terminal triorganosiloxy groups wherein the organic substituents are, for example, methyl, vinyl or phenyl or combinations of these groups. Such polydimethylsiloxanes can for example have a zero-shear viscosity of from about 5 to about 100,000 mPa.s at 25oC (measured as described above). Alternatively compatible organic plasticisers may be utilised additionally to or instead of the silicone fluid plasticiser. These may include dialkyl phthalates wherein the alkyl group may be linear and / or branched and contain from six to 20 carbon atoms such as dioctyl, dihexyl, dinonyl, didecyl, diallanyl and other phthalates, and analogous adipate, azelate, oleate and sebacate esters; polyols such as ethylene glycol and its derivatives; and organic phosphates such as tricresyl phosphate and / or triphenyl phosphates. Examples of extenders for use in compositions herein include mineral oil based (typically petroleum based) paraffinic hydrocarbons, mixtures of paraffinic and naphthenic hydrocarbons, paraffin oils comprising cyclic paraffins and non-cyclic paraffins and hydrocarbon fluids containing naphthenics, polycyclic naphthenics and paraffins, or polyalkylbenzenes such as heavy alkylates (alkylated aromatic materials remaining after distillation of oil in a refinery). Examples of such extenders are discussed in GB2424898 the content of which is hereby enclosed by reference. Pigments and / or colorants The base Part of two-part condensation curable silicone composition as described above may further comprise one or more pigments and / or colorants. The pigments and / or colorants may be coloured, white, black, metal effect, and luminescent e.g., fluorescent or phosphorescent. Pigments are utilized to colour the two-part condensation curable silicone composition as required. Any suitable pigment may be utilized providing it is compatible with the composition herein. In compositions as described above pigments and / or coloured (non-white) fillers e.g., carbon black may be utilized to colour the end sealant product. Suitable white pigments and / or colorants include titanium dioxide, zinc oxide, lead oxide, zinc sulfide, lithophone, zirconium oxide, and antimony oxide. Suitable non-white inorganic pigments and / or colorants include, but are not limited to, iron oxide pigments such as goethite, lepidocrocite, hematite, maghemite, and magnetite black iron oxide, yellow iron oxide, brown iron oxide, and red iron oxide; blue iron pigments; chromium oxide pigments; cadmium pigments such as cadmium yellow, cadmium red, and cadmium cinnabar; bismuth pigments such as bismuth vanadate and bismuth vanadate molybdate; mixed metal oxide pigments such as cobalt titanate green; chromate and molybdate pigments such as chromium yellow, molybdate red, and molybdate orange; ultramarine pigments; cobalt oxide pigments; nickel antimony titanates; lead chrome; carbon black (when present, carbon black will function as both a non-reinforcing filler and colorant); lampblack, and metal effect pigments such as aluminium, copper, copper oxide, bronze, stainless steel, nickel, zinc, and brass. Suitable organic non-white pigments and / or colorants include phthalocyanine pigments, e.g., phthalocyanine blue and phthalocyanine green; monoarylide yellow, diarylide yellow, benzimidazolone yellow, heterocyclic yellow, DAN orange, quinacridone pigments, e.g., quinacridone magenta and quinacridone violet; organic reds, including metallized azo reds and nonmetallized azo reds and other azo pigments, monoazo pigments, diazo pigments, azo pigment lakes, β-naphthol pigments, naphthol AS pigments, benzimidazolone pigments, diazo condensation pigment, isoindolinone, and isoindoline pigments, polycyclic pigments, perylene and perinone pigments, thioindigo pigments, anthrapyrimidone pigments, flavanthrone pigments, anthanthrone pigments, dioxazine pigments, triarylcarbonium pigments, quinophthalone pigments, and diketopyrrolo pyrrole pigments. Typically, the pigments and / or colorants, when particulates, have average particle diameters in the range of from 10 nm to 50 µm, preferably in the range of from 40 nm to 2 µm. The pigments and / or colorants when present are present in the range of from 2, alternatively from 3, alternatively from 5 to 20 wt. % of the composition. Antioxidant Any suitable antioxidant(s) may be utilised, if deemed required. Examples may include: ethylene bis (oxyethylene) bis(3-tert-butyl-4-hydroxy-5(methylhydrocinnamate) 36443-68-2; tetrakis[methylene(3,5- di-tert-butyl-4-hydroxy hydrocinnamate)]methane 6683-19-8; octadecyl 3,5-di-tert-butyl-4- hydroxyhyrocinnamate 2082-79-3; N,N’-hexamethylene-bis (3,5-di-tert-butyl-4- hydroxyhyrocinnamamide) 23128-74-7; 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid,C7-9 branched alkyl esters 125643-61-0; N-phenylbenzene amine, reaction products with 2,4,4-trimethylpentene 68411- 46-1; e.g., anti-oxidants sold under the IrganoxTMname from BASF. UV and / or light stabilizers UV and / or light stabilizers may include, for the sake of example include benzotriazole, ultraviolet light absorbers and / or hindered amine light stabilizers (HALS) such as the TINUVINTMproduct line from Ciba Specialty Chemicals Inc. Biocides Biocides may additionally be utilized in the base Part of two-part condensation curable silicone composition as hereinbefore described if required. It is intended that the term “biocides” includes bactericides, fungicides and algicides, and the like. Suitable examples of useful biocides, which may be utilized in compositions as described herein, include, for the sake of example: Carbamates such as methyl-N-benzimidazol-2-ylcarbamate (carbendazim) and other suitable carbamates, 10,10’-oxybisphenoxarsine, 2-(4-thiazolyl)-benzimidazole, N-(fluorodichloromethylthio)phthalimide, diiodo methyl p-tolyl sulfone, if appropriate in combination with a UV stabilizer, such as 2,6-di(tert-butyl)-p-cresol, 3-iodo-2-propinyl butylcarbamate (IPBC), zinc 2-pyridinethiol 1-oxide, triazolyl compounds and isothiazolinones, such as 4,5-dichloro-2-(n-octyl)-4- isothiazolin-3-one (DCOIT), 2-(n-octyl)-4-isothiazolin-3-one (OIT) and n-butyl-1,2-benzisothiazolin-3- one (BBIT). Other biocides might include for example Zinc Pyridinethione, 1-(4-Chlorophenyl)-4,4- dimethyl-3-(1,2,4-triazol-1-ylmethyl)pentan-3-ol and / or 1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3- dioxolan-2-yl] methyl]-1H-1,2,4-triazole. The fungicide and / or biocide may suitably be present in an amount of from greater than 0 to 0.3wt. % of the two-part condensation curable silicone composition and may be present in an encapsulated form where required such as described in EP2106418. As described above there is provided a method of making a base comprising components (a), (b) and (c) herein together with additives present. Any suitable mixing means may be used to make the base, for example a speedmixer such as a DAC 600.2 VAC-P Speedmixer, a Turello mixer or twin-screw extruder. As previously indicated the two-part composition may comprise any suitable catalyst Part. Typically, the catalyst Part comprises the following components: (d) a suitable carrier fluid, (e) one or more tin based catalysts; and (f) cross-linker. The catalyst Part of the composition may also comprise one or more of the optional additives described above for example one or more adhesion promoters as described above and may also comprise an amount of component (b) filler. Component (d) a suitable carrier fluid The carrier fluid may be, for example, one or more of the following: (i) an alkyl-terminated diorganopolysiloxane, (ii) one or more silicon-free, branched polyethers comprising repeating units having the average formula (-CnH2n-O-)ywherein n is an integer from 3 to 6 inclusive and y is at least four, comprising one or more -OH terminal groups, -OR10terminal groups or -OH and -OR10terminal groups where R10is an optionally functionalised hydrocarbon group having from 1 to 12 carbons; as further described in WO2023055680A1 which is incorporated herein by reference; (iii) one or more polyarylorganosiloxane polymers which comprise a plurality of repeating -[Si(R4)(R5) – O]- units wherein each R4is a monovalent substituent comprising an aromatic group having from 6 to 18 carbons and each R5is a monovalent organic group having from 1 to 18 carbons as further described in WO2023055681A1 which is incorporated herein by reference; or one or more silicone copolymers comprising a plurality of repeating -[Si(R4)(R5) – O]- units wherein each R4is a monovalent substituent comprising an aromatic group having from 6 to 18 carbons and each R5is a monovalent organic group having from 1 to 18 carbons; or a mixture thereof as further described in WO2023055682A1 which is incorporated herein by reference; or (iv) one or more linear or branched polyethers comprising repeating units having the average formula (-CdH2d-O-)ewherein d is an integer from 3 to 6 inclusive and e is an integer of at least four, comprising either or both [(R4O)r(Y1)3-r – Si – W1v ]– terminal groups or [(R4O)r(Y1)3-r – Si – W2– (Si(Y1)2-O)p – W3] - terminal groups, where each R4is a C1-10alkyl group, each Y1may be the same or different and is an alkyl group containing from 1 to 8 carbons, r is 0, 1, 2 or 3; W1, W2and W3may be the same or are different and are divalent hydrocarbons having from 2 to 18 carbons, p is 1, 2, or 3; and v is 0 or 1 as further described in WO2023055681A1 which is incorporated herein by reference. Typically, the carrier fluid, is present in the catalyst package in an amount of from 30 to 80 weight % (wt. %), alternatively 40 to 65 wt. % of the total weight of the catalyst package. Component (e) one or more tin based catalysts Component (e), the organotin condensation catalyst may be any suitable organotin condensation catalyst. Examples of suitable organotin condensation catalysts include tin triflates, dialkyltin compounds, selected from dimethyltin di-2-ethylhexanoate, dimethyltin dilaurate, di-n-butyltin diacetate (DBTDA), di-n-butyltin di-2-ethylhexanoate, dimethyltin dineodecanoate (DMTDN), dioctyltin dineodecanoate (DOTDN), di-n-butyltin dicaprylate, di-n-butyltin di-2,2-dimethyl octanoate, di-n-butyltin octanoate, di- n- butyltin dilaurate (DBTDL), di-n-butyltin distearate, di-n-butyltin dimaleate, di-n-butyltin dioleate, di- n-octyltin di-2-ethylhexanoate, di-n-octyltin di-2,2-dimethyl octanoate, di-n-octyltin dimaleate, dipropyl tin bis(acetylacetonate), dibutyl tin bis(acetylacetonate), dipentyl tin bis(acetylacetonate), dihexyl tin bis(acetylacetonate), dioctyl tin bis(acetylacetonate), didecyl tin bis(acetylacetonate), didodecyl tin bis(acetylacetonate), di-n-octyl tin dilaurate (DOTDL), di-n-butyl tin oxide, carbomethoxyphenyl tin trisuberate, tin butyrate, butyltintri-2-ethylhexoate, tin naphthenate, isobutyltintriceroate, tin octoate, triethyltin tartrate and di-n-octyl tin oxide. Said organotin condensation catalyst of component (e) herein is present in an amount of from 0.001 to 1.0 wt. % of the catalyst Part composition, alternatively from 0.01 to 0.75 wt.% of the catalyst Part composition, alternatively 0.05 to 0.5 wt.% of the catalyst Part composition, alternatively 0.05 to 0.25 wt.% of the catalyst Part composition. Cross-Linker (f) Cross-linker (f) utilized herein has the structure R5c -Si-R64-c wherein each R5is an alkoxy group having from 1 to 10 carbons, each R6is selected from is a non-hydrolysable silicon-bonded organic group, and c is 2, 3 or 4. Each R5may be a ketoximino group (for example dimethyl ketoximo, and isobutylketoximino); an alkoxy group (for example methoxy, ethoxy, iso-butoxy and propoxy) or an alkenyloxy group (for example isopropenyloxy and 1-ethyl-2-methylvinyloxy). For example, R5may be the sake of example methoxy, ethoxy, propoxy iso-propoxy, butoxy, t-butoxy, pentoxy (amyloxy), isopentoxy (isoamyloxy), hexoxy and isohexoxy. In one embodiment all R5groups present are the same. Each R6group may be any suitable non- hydrolysable silicon-bonded organic group, such as an alkyl group having from 1 to 6 carbons (for example methyl, ethyl, propyl, and butyl); an alkenyl group having from 2 to 6 carbons, (for example vinyl and allyl) cycloalkyl groups (for example cyclopentyl and cyclohexyl); aryl groups (for example phenyl, and tolyl); aralkyl groups (for example 2-phenylethyl). It will be seen that subscript c maybe 2, 3 or 4. Typically, crosslinker (f) may only function as a cross-linker when subscript c is 2 if, the polymer present in the base part composition comprises more than two -OH or hydrolysable groups per molecule otherwise it will solely cause chain-extension and not functioning as a cross-linker. Preferably subscript c is either 3 or 4 for cross-linking purposes but it is to be understood that in some cases, it is desirable to include a fraction of di(alkoxy)functional silanes (c=2) in a mixture with tri or tetrafunctional alkoxysilanes (c=3 or 4) to impart chain-extension and flexibility. Silanes which can be used as cross-linkers (f) include bis (trimethoxysilyl)hexane, 1,2-bis (triethoxysilyl)ethane, alkyltrialkoxysilanes such as methyltrimethoxysilane (MTM) and methyltriethoxysilane, alkenyltrialkoxy silanes such as vinyltrimethoxysilane and vinyltriethoxysilane, isobutyltrimethoxysilane (iBTM). Other suitable silanes include ethyltrimethoxysilane, phenyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, cyanoethyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane (tetraethyl orthosilicate), tetrapropoxysilane (tetrapropyl orthosilicate) and tetrapentoxysilane (tetraamyl orthosilicate); or alternatively alkoxytrioximosilane, alkenyltrioximosilane, methyltris(methylethylketoximo)silane, vinyl-tris-methylethylketoximo)silane, methyltris(methylethylketoximino)silane, alkenyl alkyl dialkoxysilanes such as vinyl methyl dimethoxysilane, vinyl ethyldimethoxysilane, vinyl methyldiethoxysilane, vinylethyldiethoxysilane, alkenylalkyldioximosilanes such as vinyl methyl dioximosilane, vinyl ethyldioximosilane, vinyl methyldioximosilane, vinylethyldioximosilane and / or methylphenyl-dimethoxysilane. The cross-linker (f) used may also comprise any combination of two or more of the above. The catalyst package may comprise from 1 to 30 wt. % of cross-linker (f), alternatively 5 to 25 wt. % of cross-linker (f). The catalyst Part may alternatively or additionally incorporate one or more optional additives such as those previously mentioned. Likewise, the catalyst Part contains only appropriate optional additives which will not negatively affect the catalyst Part during storage. Hence, when present the catalyst Part tends to contain adhesion promoter additives. The base Part of the two-part condensation curable silicone compositions, will comprise organopolysiloxane polymer (a) in an amount of from about 30 to 90 weight % (wt. %) of the base part of the composition; one or more fillers in an amount of from 20 to 70 wt.% of the base Part composition ; and and the rheology modified as described herein in an amount of from 0.5 to 5 wt. % of the base Part composition; with the total wt. % of the base part being 100 wt. % Any suitable catalyst Part may be utilised in combination with the above base Part composition. These will typically contain carrier fluid (d), tin-based catalyst (e), cross-linkers (f) and optionally some filler (b) and one or more of the optional additives mentioned above such as one or adhesion promoters., with the total wt. % of the catalyst Part being 100 wt. %. The catalyst Part may also include suitable optional additives including those not suitable for incorporation in the base Part such as one or more adhesion promoters. Adhesion Promoter Any suitable adhesion promoter may be utilised in the catalyst Part of the two-part condensation curable silicone composition as hereinbefore described. These may include alkoxysilanes of the formula R14hSi(OR15)(4-h)where subscript h is 1, 2, or 3, alternatively h is 3. Each R14is independently a monovalent organofunctional group selected from an epoxy functional group such as glycidoxypropyl or (epoxycyclohexyl)ethyl, an amino functional group such as aminoethylaminopropyl or aminopropyl, a methacryloxypropyl, a mercapto functional group such as mercaptopropyl or an unsaturated organic group. Each R15is independently an unsubstituted, saturated hydrocarbon group of at least 1 carbon atom. R15may have 1 to 4 carbon atoms, alternatively 1 to 2 carbon atoms. R15is exemplified by methyl, ethyl, n-propyl, and iso- propyl. Alternatively, the optional adhesion promoter may be selected from one or more mercaptopropyltrialkoxysilanes, an aminopropyltriethoxysilane, an aminopropyltrimethoxysilane or an amine of the structure: R20k (R21O)3-kSi-Z5-N(H)- (CH2)m‘ - NH2 in which R20is an alkyl group containing from 1 to 10 carbon atoms; each R21may be the same or different and is H or R20, Z5is a linear or branched alkylene group having from 2 to 10 carbon atoms, m’ is from 2 to 10 and k is zero or 1. R20is an alkyl group containing from 1 to 10 carbon atoms, alternatively R20is an alkyl group containing from 1 to 6 carbon atoms, alternatively, R20is a methyl or ethyl group. Each R21may be the same or different and is H or R20, alternatively each R21is R20. In one alternative all R21groups are the same. When the R21groups are the same, it is preferred that they are methyl or ethyl groups. Z5is a linear or branched alkylene group having from 2 to 10 carbons, alternatively from 2 to 6 carbons, for example Z5may be a propylene group, a butylene group or an isobutylene group. There may be from 2 to 10 m groups, in one alterative m may be from 2 to 6, in another alternative m may be from 2 to 5, in a still further alternative m may be 2 or 3, alternatively m is 2. In the two-part condensation curable silicone composition, the components of each part are mixed together in amounts within the ranges given above and then the base part composition and the catalyst package composition are inter-mixed in a predetermined ratio e.g., from 15:1 to 1:1, alternatively from 14:1 to 5:1 alternatively from 14:1 to 7:1. If the intended mixing ratio of the base part: catalyst package is 15:1 or greater, no filler will be generally utilized in the catalyst package. However, if the intended mixing ratio of the base part : catalyst package is less than 15:1 an increasing amount filler may be utilized in the catalyst Part up to the maximum of 50wt. % of the catalyst Part, if the intended ratio is 1:1. The two parts of the two-part condensation curable silicone composition can be prepared by mixing the ingredients employing any suitable mixing equipment. In use the base part and the catalyst part are mixed together in the predefined ratios in a suitable mixer and then the resulting mixture is applied onto a target substrate surface. A two-part condensation curable silicone composition when utilized as a sealant composition as described above may be a gunnable sealant composition, i.e., it can be extruded into or onto a target by extrusion through a sealant gun nozzle. Such gunnable sealants may be used for (i) space / gap filling applications; (ii) seal applications, such as sealing the edge of a lap joint in a construction membrane; or (iii) seal penetration applications, e.g., sealing a vent in a construction membrane; (iv) adhering at least two substrates together. (v) a laminating layer between two substrates to produce a laminate of the first substrate, the sealant product and the second substrate. In the case of two-part condensation curable silicone compositions e.g., silicone sealant compositions as hereinbefore described, there is also provided a method for filling a space between two substrates so as to create a seal therebetween, comprising: a’) providing a two-part condensation curable silicone composition comprising a base part and a catalyst part composition as hereinbefore described, mixing together and either: b’) applying the two-part moisture cure organopolysiloxane composition of step (a’) to a first substrate, and bringing a second substrate in contact therewith, or c’) filling a space formed by the arrangement of a first substrate and a second substrate with the two- part moisture cure organopolysiloxane composition of step (a’); and curing. The composition provided herein can be used for a wide range of applications for example in silicone structural glazing, Do-it-yourself (DIY) applications, industrial assembly and maintenance, fenestration applications (windows and door manufacture) and weather proofing applications. Examples In the present examples all viscosity measurement were taken at 25oC. Unless otherwise indicated all viscosity measurement given are zero-shear viscosity values as defined previously, obtained using an ARES parallel plate rheometer. (TA Instruments) with a dynamic frequency sweep was performed from 0.1 to 100 rad / s using 0.1% strain, 25 mm plates, and a 2 mm gap. Five points per decade were collected and the zero-shear viscosity value obtained. The reported zero-shear viscosity (ηo) values are an average, and the polymers all displayed non-Newtonian behavior in that the viscosity was consistent across the shear rate range. Furthermore, the number average molecular weight (Mn) values provided below were determined using a Waters 2695 Separations Module equipped with a vacuum degasser, and a Waters 2414 refractive index detector (Waters Corporation of MA, USA). The analyses were performed using certified grade toluene flowing at 1.0 mL / min as the eluent, using polystyrene calibration standards. Data collection and analyses were performed using Waters EmpowerTMGPC software (Waters Corporation of MA, USA). A series of base compositions were prepared. Excepting Ref.1 which contained no rheology modifier, each base composition comprised polymers, a hydrophobically treated precipitated calcium carbonate filler and a rheology modifier as described herein (Table 1c) or a comparative rheology modifier (Table 1b).

[0003] Table 1a: Components of base composition Ref.1 All Examples and comparatives Polymer 1 was a dimethylhydroxyl terminated polydimethylsiloxane having a zero-shear viscosity of about 13,000 mPa.s at 25 ºC and a degree of polymerization of 612; Polymer 2 was a dimethylhydroxyl terminated polydimethylsiloxane having a zero-shear viscosity of about 2000 mPa.s at 25 ºC and a degree of polymerization of 354;The fatty acid-treated calcium carbonate was UltraPflexTMcommercially available from Specialty Minerals Inc. Table 1b: Rheology modifiers used in Ref.1, and C.1 to 4 Rheology modifier R f 1 N n S W ere PDMS stands or poydmet ys oxane Hydroxyl-terminated PDMS (DP 12) has the structure: HO -Si(CH3)2 – O –[ Si(CH3)2 -O]12 - (CH3)2Si – OH Hydroxyethoxypropyl-terminated PDMS (DP 118) has the structure: [3-(2,3-dihydroxypropoxy)propyl]-terminated PDMS (DP 118) has the structure: - - s - y o ypopy a o- -y roxypropoxy]propyl]-terminated PDMS (DP 118) has the structure: Rheology modifier h l i S S Wherein Hydroxyethoxypropyl-terminated PDMS (DP =m = 7) has the structure: Hydroxyethoxypropyl-terminated PDMS (DP = m = 20) has the structure: PDMS (DP = m =7) has the structure: HO OH O - PDMS (DP = m =20) has the structure: [3-[3-[bis(2-hydroxypropyl)amino]-2-hydroxypropoxy]propyl]-terminated PDMS (DP = m = 7) has the structure: [3-[3-[bis(2-hydroxypropyl)amino]-2-hydroxypropoxy]propyl]-terminated PDMS (DP = m = 20) has the structure: y roxypropy - erm na e S ( = m = ) was a 600.2 VAC-P Speedmixer from Hauschild GmbH & Co KG, using 300 Max Tall cups. The polymer and rheology modifier (when present) were added into the mixing cup and initially mixed for 45 seconds at 1500 rpm. The calcium carbonate filler was then added and mixing continued for 45 seconds at 1500 rpm after which the cup was scraped down and the mixing regime repeated again. Mixing continued for a further minute under vacuum after which the vacuum was released for a final mixing step of 30seconds at 800 rpm. The base compositions depicted in Table 1a, 1b and 1c were then assessed for slump and extrusion rate. Slump was tested according to ASTM D2202. A slump jig was filled with base and leveled with a spatula. The jig was placed upright and the base was pushed out onto the jig surface. The slump was measured after ten minutes. Target values were less than 5mm. Extrusion rate was tested in accordance with ASTM C603-14 using a Nordson EFD Ultra® 2400 Series Dispensing Workstation at 90 psi (621 kPa) for three seconds using a PPG 440 tapered nozzle with a 1 / 8” (3.175mm) orifice. Values reported are an average of three and the target was to have an extrusion rate of greater than 200g / min.

[0004] Table 2a: Slump and extrusion rate results for Ref.1 and C.1 to C.4 Ref.1 C.1 C.2 C.3 C.4 Slump (mm) 22.6 2.5 3.8 1.3 1.3 Table 2b: Slump and extrusion rate results for Ex.1 to 7 Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Ex.7 Slump (mm) 2.5 2.5 2.5 2.5 2.5 1.25 1.25 p characteristics of the Ex.1 to 7 were all well inside the target values. In order to assess the ability of these improved base compositions to cure and the physical properties of the resulting cured sealants, each base composition depicted in Table 1a, 1b and 1c was mixed with and cured using a laboratory catalyst Part based on the disclosure of WO2023055680A1 in a base Part : catalyst Part weight ratio of 10 : 1. The composition of the catalyst Part used for these examples is depicted in Table 3 below. Table 3: Composition of catalyst Part used to assess cure properties and physical properties Component wt.% The carbon black used in the following examples was SR511 commercially available from Tokai Carbon CB Ltd. The Fumed silica used in the examples was AerosilTMR974 commercially available from Evonik treated with dimethyldichlorosilane. The composition once mixed was allowed to cure for 7 days at room temperature (approximately 23 to 25oC) unless otherwise indicated. Tack free time (TFT) was assessed to indicate properties of cure. TFT was measured following a draw down was made using a 100-mil (0.254cm) drawdown bar on standard polyethylene film. Care was taken to ensure a smooth surface, free of imperfections such as air bubbles or drag marks. Time was noted once a slab of the sealant had been prepared. The samples were cured at 70Fahrenheit (about 21oC) and 40% relative humidity. The surface of the sealant was touched with a 0.25 inch (0.625cm) wide strip of polyethylene film and the TFT was reached when the strip of polyethylene film no longer adhered to the sample. After cure, the physical properties of test pieces of each cured sealant made using the respective base composition depicted in Table 1a, 1b and 1c were undertaken. Durometer was measured in accordance with ASTM D2240 on a ShoreTMConveloader CV-71200 type A. Samples were stacked ½” (1.27cm) thick. Tensile and elongation were tested in according to ASTM D412. Dogbone shaped samples were cut using die DIN S2 and pulled on an RT / 5 Testing machine commercially available from MTS Systems Corporation. Data was collected and analyzed using Test Works Elite v.2.3.6. The results for Ref.1 and Comparatives 1 to 4 are depicted in Table 4a and those for Ex.1 to 7 are depicted in Table 4b. Table 4a: Cure properties and physical property results for Ref.1 and C.1 to 4 Target Ref.1 C.1 C.2 C.3 C.4 i 8

[0005] Table 4b: Cure properties and physical property results for Ex.1 to 7 Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Ex.7 TFT (min) 37 48 40 40 34 38 55 9 It will be appreciated that both the Examples 1 to 7 and the comparatives and Ref.1 cure and physical properties met the targets set (shown in Table 4a. Hence, the pre-cure properties can be seen to be significantly improved in accordance with the disclosure herein and most importantly the cure properties and physical properties are not negatively affected when using the base Part compositions in accordance with this disclosure to form sealants in combination with a suitable catalyst Part as depicted herein.

Claims

CLAIMS 1. A two-part condensation curable silicone composition having a base Part and a catalyst Part, wherein the base Part comprises the following components: (a) One or more siloxane polymers having at least two terminal hydroxyl or hydrolysable groups having a zero-shear viscosity of from 750 to 150,000 mPa.s at 25oC; (b) one or more optionally hydrophobically treated fillers in an amount of from 20 to 70 wt.% of the base Part composition; and (c) a rheology modifier having the structure: whereor a C2-C20 carbinol group that optionally contains ether, ester, or amine functionality or a mixture thereof; m is from 5 to 50; n is from 0 to 20; each x is independently 0 or 1, with the proviso that when each x is 0, n is from 2 to 20; in an amount of from 0.5 to 5 wt. % of the base Part composition.

2. A two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 1, wherein the base Part has an extrusion rate of greater than 200g / min in accordance with ASTM C603-14, whilst also having a slump of less than 5 mm in accordance with ASTM D2202 – 00.

3. A two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 1 or 2 wherein in rheology modifier (c) of the base part, m + n = from 5 to 50.

4. A two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 1, 2 or 3 wherein in rheology modifier (c) of the base Part, m + n = = from 5 to 30.

5. A two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 1, 2, 3 or 4 wherein the carbinol group of component (c) is one of the following end groups linked directly to a terminal silicon an ethylene bridge.. wo-par con ensa on cura e s cone compos on av ng a ase ar an a caa yst Part in accordance with claim 1, 2, 3, 4 or 5 wherein rheology modifier (c) is selected from one or more of a Hydroxyethoxypropyl-terminated polydimethylsiloxane where m = 7 and n = 0, Hydroxyethoxypropyl-terminated polydimethylsiloxane where m = 20 and n = 0, [3-(2,3-dihydroxypropoxy)propyl]-terminated polydimethylsiloxane where m = 7 and n = 0, [3-(2,3-dihydroxypropoxy)propyl]-terminated polydimethylsiloxane where m = 20 and n = 0, [3-[3-[bis(2-hydroxypropyl)amino]-2-hydroxypropoxy]propyl]- polydimethylsiloxane where m = 7 and n = 0, or [3-[3-[bis(2-hydroxypropyl)amino]-2-hydroxypropoxy]propyl]-terminated polydimethylsiloxane where m = 20 and n = 0, and Hydroxypropyl-terminated polydimethylsiloxane where m = 7 and n = 0,7. A two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 1, 2, 3, 4, 5 or 6 wherein the catalyst part comprises a carrier fluid, one or more tin based catalysts and cross-linker.

8. A two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 7 wherein the carrier fluid of the catalyst Part comprises one of the following: (i) an alkyl-terminated diorganopolysiloxane, (ii) one or more silicon-free, branched polyethers comprising repeating units having the average formula (-CnH2n-O-)ywherein n is an integer from 3 to 6 inclusive and y is at least four, comprising one or more -OH terminal groups, -OR10terminal groups or -OH and -OR10terminal groups where R10is an optionally functionalised hydrocarbon group having from 1 to 12 carbons; (iii) one or more polyarylorganosiloxane polymers which comprise a plurality of repeating - [Si(R4)(R5) – O]- units wherein each R4is a monovalent substituent comprising an aromatic group having from 6 to 18 carbons and each R5is a monovalent organic group having from 1 to 18 carbons; or one or more silicone copolymers comprising a plurality of repeating -[Si(R4)(R5) – O]- units wherein each R4is a monovalent substituent comprising an aromatic group having from 6 to 18 carbons and each R5is a monovalent organic group having from 1 to 18 carbons; or a mixture thereof; or (iv) one or more linear or branched polyethers comprising repeating units having the average formula (-CdH2d-O-)ewherein d is an integer from 3 to 6 inclusive and e is an integer of at least four, comprising either or both [(R4O)r(Y1)3-r – Si – W1v ]– terminal groups or [(R4O)r(Y1)3-r – Si – W2– (Si(Y1)2-O)p – W3] - terminal groups, where each R4is a C1-10 alkyl group, each Y1may be the same or different and is an alkyl group containing from 1 to 8 carbons, r is 0, 1, 2 or 3; W1, W2and W3may be the same or are different and are divalent hydrocarbons having from 2 to 18 carbons, p is 1, 2, or 3; and v is 0 or 1.

9. A method of preparing a base Part of a two-part condensation curable silicone composition having a base Part and a catalyst Part, in accordance with any one of claims 1 to 8 by introducing rheology modifier (c) having the structure:w ere eac R s ndependent y C1-C10 a y or p eny; each R′′ comprises a C2-C20 carbinol group that optionally contains ether, ester, or amine functionality or a mixture thereof; m is from 5 to 50; n is from 0 to 20; each x is independently 0 or 1, with the proviso that when each x is 0, n is from 2 to 20; in an amount of from 0.5 to 5 wt. % of the base Part composition, which base Part composition otherwise comprises components (a) and (b) wherein (a) is one or more siloxane polymers having at least two terminal hydroxyl or hydrolysable groups having a zero-shear viscosity of from 750 to 150,000 mPa.s at 25oC; and (b) is one or more optionally hydrophobically treated fillers in an amount of from 20 to 70 wt.% of the base Part composition; and intermixing components (a), (b) and (c) together.

10. A method of preparing a base Part composition of a two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 9 wherein after mixing the base Part has an extrusion rate of greater than 200g / min in accordance with ASTM C603-14, whilst also having a slump of less than 5 mm in accordance with ASTM D2202 – 00.

11. A method of preparing a base Part composition of a two-part condensation curable silicone composition having a base Part and a catalyst Part in accordance with claim 9 or 10, which base part is then mixed with the catalyst part to form a condensation curable silicone composition.

12. A method for filling a space between two substrates so as to create a seal therebetween, comprising: a’) providing a two-part condensation curable silicone composition comprising a base part and a catalyst part composition in accordance with any one of claims 1 to 8, mixing together and either: b’) applying the two-part moisture cure organopolysiloxane composition of step (a’) to a first substrate, and bringing a second substrate in contact therewith, or c’) filling a space formed by the arrangement of a first substrate and a second substrate with the two-part moisture cure organopolysiloxane composition of step (a’); and curing.

13. A use of a compound (c) having the structure:R′′ comprises a C2-C20 carbinol group that optionally contains ether, ester, or amine functionality or a mixture thereof; m is from 5 to 50; n is from 0 to 20; each x is independently 0 or 1, with the proviso that when each x is 0, n is from 2 to 20; in an amount of from 0.5 to 5 wt. % of the base Part composition; as a rheology modifier in a base Part of a two-part condensation curable silicone composition having a base Part and a catalyst Part, which base Part composition otherwise comprises components (a) and (b) wherein: (a) is one or more siloxane polymers having at least two terminal hydroxyl or hydrolysable groups having a zero-shear viscosity of from 750 to 150,000 mPa.s at 25oC; and (b) is one or more optionally hydrophobically treated fillers in an amount of from 20 to 70 wt.% of the base Part composition.

14. Use in accordance with claim 13, wherein the base Part has an extrusion rate of greater than 200g / min in accordance with ASTM C603-14, whilst also having a slump of less than 5 mm in accordance with ASTM D2202 – 00.

15. Use of a two-part condensation curable silicone composition having a base Part and a catalyst Part, in accordance with any one of claims 1 to 8 as a sealant in silicone structural glazing, Do-it-yourself (DIY) applications, industrial assembly and maintenance, fenestration applications and weather proofing applications.

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