CN115989273A - Silicone foam elastomer and use thereof - Google Patents

Abstract

The present disclosure relates to curable and foamable silicone compositions, silicone foam elastomers prepared using the compositions, and methods for preparing the silicone foam elastomers in the form of silicone foam elastomer form-in-place foam gaskets (FIPFG). The present disclosure describes the use of a co-thixotropic agent (f) comprising one or more silyl-modified polyethers in an amount of from 0.5 to 3% by weight of the composition, and a standard thixotropic agent (e) such as silica, calcium carbonate, talc or mixtures thereof in an amount of from 2 to 5% by weight of the composition, the combination of which provides a significant increase in the thixotropy of the composition prior to curing.

Description

Silicone foam elastomer and use thereof

The present disclosure relates to curable and foamable silicone compositions, silicone foam elastomers prepared using the compositions, and methods for preparing the silicone foam elastomers in the form of silicone foam elastomer form-in-place foam gaskets (FIPFG).

Traditionally, gaskets are manufactured by punching the gasket out of an elastomeric sheet material, or by shaping the gasket by injection molding of an elastomeric compound or the like. Both of these methods require expensive tools such as punches and dies and result in a great deal of waste, all of which add to the cost of production of the final product. The introduction of foamed materials in liquid form directly into the housing components where they chemically react to form a suitable gasket is well known and is commonly referred to as "FIPFG" (form-in-place foam gasket). In the case of form-in-place foam gaskets, the foamed material is typically applied as a bead or strand of fluid elastomeric composition from a suitable applicator onto a target surface effective to create a mold for the desired gasket. The applicator used may be a pre-programmed robotic applicator such that the introduction of the fluid elastomeric strand may be controlled to provide a gasket having a desired shape and minimizing waste. Once the fluid elastomeric composition is fully introduced, it is cured in situ.

There are several chemical routes available to enable Room Temperature Vulcanizing (RTV) curable and foamable silicone compositions to be converted into FIPFG. Perhaps the most common foaming mechanism relies on the use of the hydrogen generated as a by-product during the curing process of such compositions to produce foam as a result of the reaction of the hydroxyl functional component with the silicon-bonded hydrogen atoms.

Curable and foamable silicone compositions of this type contain the following components

a) A polydiorganosiloxane having at least two unsaturated groups per molecule, the unsaturated groups being selected from alkenyl or alkynyl groups;

b) An organohydrogensiloxane having at least two, alternatively at least three, si-H groups per molecule;

c) One or more hydroxyl-containing blowing agents; and

d) A catalyst comprising or consisting of a platinum group metal or a compound of a platinum group metal.

When used to prepare a FIPFG, the properties of components a), b), and c) may be selected according to the desired physical properties and end use of the resulting silicone foamed elastomer, but such compositions may also require one or more additives for this purpose. For example, these additives may include one or more fillers and/or thixotropic agents, some of which may function as both fillers and thixotropic agents.

In the production of FIPFG, it is critical that the reactive mixture applied in liquid form remain in the liquid state long enough prior to foaming to prevent contamination and/or clogging of the applicator. Thus, prior to curing, the curable and foamable silicone composition should have a sufficiently low viscosity to be easily dispensed, but need to have sufficient thixotropy so that the dispensed fluid elastomeric composition does not slip once applied and prior to and/or during curing and foaming and has good dimensional stability so that there is substantially no change in the shape or position of the composition during and after curing. In many applications, the resulting silicone foam gaskets produced from the dispensed curable and foamable silicone compositions need to have good compressive force and compression set to ensure sealing performance and reliability.

Preferred thixotropic agents relied upon in curable and foamable silicone compositions are inorganic thixotropic agents such as silica and calcium carbonate. However, these thixotropic agents also act as reinforcing or semi-reinforcing fillers, thus limiting the content of such thixotropic agents in the composition to avoid a significant increase in viscosity and composition density, and thereby having a detrimental effect on the dispensability of the fluid elastomeric composition through an applicator, potentially causing blockages in the applicator and resulting in a high density and hardness of the resulting cured foam. Compression set can also be a problem for those products with too much filler.

In view of the foregoing, there remains an opportunity to provide curable and foamable silicone compositions that, upon curing and foaming, provide foamed gaskets having increased amounts of thixotropic agent present.

Provided herein is a curable and foamable silicone composition comprising the following components:

a) A polydiorganosiloxane having at least two unsaturated groups per molecule, the unsaturated groups being selected from alkenyl or alkynyl groups;

b) An organosilicon compound having at least two, alternatively at least three, si-H groups per molecule;

c) One or more hydroxyl-containing blowing agents; and

d) A hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound of a platinum group metal;

e) A thixotropic agent selected from the group consisting of silica, calcium carbonate, talc or mixtures thereof in an amount of from 2% to 5% by weight of the composition, and

f) A co-thixotropic agent comprising one or more silyl-modified polyethers in an amount of from 0.5% to 3% by weight of the composition.

It has been surprisingly found herein that the incorporation of a small amount (0.5 to 3% by weight of the composition) of a co-thixotropic agent comprising one or more silyl-modified polyethers (SMPs) (component f) in combination with component (e) improves the thixotropic properties of curable and foamable silicone compositions without the adverse effects caused by the incorporation of higher levels of thixotropic agents selected from silica and/or calcium carbonate.

Also provided is a silicone foamed elastomer obtained or obtainable by mixing and curing the above curable and foamable silicone composition, and/or a form-in-place foam gasket (FIPFG) obtained or obtainable by mixing and curing the above curable and foamable silicone composition. Also provided is a silicone foamed elastomer or foam-in-place gasket (FIPFG) comprising a cured product of the above curable and foamable silicone composition.

The present invention provides a process for preparing silicone foamed elastomers and/or foam-in-place gaskets (FIPFG) by mixing and curing a curable and foamable silicone composition comprising the following components:

a) A polydiorganosiloxane having at least two unsaturated groups per molecule, the unsaturated groups being selected from alkenyl or alkynyl groups;

b) An organohydrogensiloxane having at least two, alternatively at least three, si-H groups per molecule;

c) One or more hydroxyl-containing blowing agents; and

d) A hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound of a platinum group metal;

e) A thixotropic agent selected from the group consisting of silica, calcium carbonate or mixtures thereof in an amount of from 2% to 5% by weight of the composition, and

f) A co-thixotropic agent comprising one or more silyl-modified polyethers in an amount of from 0.5% to 3% by weight of the composition.

The present invention also provides for the use of the curable and foamable silicone composition for the preparation of silicone foamed elastomers and/or foam-in-place gaskets (FIPFG). In one embodiment, the silicone foam elastomer is provided as a form-in-place foam gasket (FIPFG).

The present disclosure also relates to a foamed silicone elastomer. In various embodiments, the foamed silicone elastomer is the reaction product of components (a) and (b) catalyzed by component (d), and the structure of the resulting foam is provided by hydrogen released as a result of the reaction of components (b) and (c) also catalyzed by component (d). The reaction product may also be formed in the presence of one or more additives. Such additives, if used, may be inert to, or reactive with, the other components of the composition.

All viscosity measurements referred to herein are measured at 25 ℃ unless otherwise indicated.

"hydrocarbyl" means a monovalent hydrocarbyl group that may be substituted or unsubstituted. Specific examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group, and the like.

"alkyl" means an acyclic, branched, or unbranched saturated monovalent hydrocarbon group. "aryl" means a cyclic, fully unsaturated hydrocarbon group. "aralkyl" means an alkyl group having a pendant aryl group and/or a terminal aryl group or an aryl group having a pendant alkyl group.

"alkenylene" means an acyclic, branched, or unbranched, divalent hydrocarbon group having one or more carbon-carbon double bonds. "alkylene" means an acyclic, branched, or unbranched saturated divalent hydrocarbon radical. "alkynylene" means an acyclic, branched, or unbranched divalent hydrocarbon radical having one or more carbon-carbon triple bonds. "arylene" means a cyclic, fully unsaturated divalent hydrocarbyl group.

As used with respect to another group (e.g., a hydrocarbon group), the term "substituted" means that one or more hydrogen atoms in the hydrocarbon group have been replaced with another substituent, unless otherwise specified. Examples of such substituents include, for example, halogen atoms such as chlorine, fluorine, bromine, and iodine; halogen atom-containing groups such as chloromethyl group, perfluorobutyl group, trifluoroethyl group, and nonafluorohexyl group; an oxygen atom; oxygen atom-containing groups such as (meth) acrylic acid and carboxyl groups; a nitrogen atom; nitrogen atom-containing groups such as amines, amino functional groups, amido functional groups, and cyano functional groups; a sulfur atom; and groups containing a sulfur atom, such as mercapto groups.

M, D, T and Q units are generally denoted as R _u SiO( _4–u)/2 Wherein u is 3, 2, 1 and 0 for M, D, T and Q, respectively, and R is an independently selected hydrocarbyl group. M, D, T, Q represents one (Mono), two (Di), three (Tri) or four (Quad) oxygen atoms covalently bonded to a silicon atom that is attached to the rest of the molecular structure.

Component (a)

Component (a) is a polydiorganosiloxane having at least two unsaturated groups per molecule selected from alkenyl or alkynyl groups. Alternatively, component (a) has at least three unsaturated groups per molecule.

The unsaturated group of component (a) may be a terminal position, a side chain position, or both positions in component (a). For example, the unsaturated group can be an alkenyl group and/or an alkynyl group. Alkenyl groups are exemplified by, but not limited to: vinyl groups, allyl groups, methallyl groups, propenyl groups, and hexenyl groups. An alkenyl group may have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, alternatively 2 to 6 carbon atoms. Alkynyl groups may be exemplified by, but are not limited to: ethynyl, propynyl and butynyl groups. An alkynyl group can have 2 to 30, alternatively 2 to 24, alternatively 2 to 20, alternatively 2 to 12, alternatively 2 to 10, alternatively 2 to 6 carbon atoms.

Component (a) has a plurality of units of formula (I):

R _a SiO _(4-a)/2 (I)

wherein each R is independently selected from aliphatic hydrocarbon groups, aromatic hydrocarbon groups, or organo groups (i.e., any organic substituent having a free valence at a carbon atom, regardless of functional group type). The saturated aliphatic hydrocarbon group is exemplified by, but not limited to, the following groups: alkyl groups such as methyl, ethyl, propyl, pentyl, octyl, undecyl and octadecyl, and cycloalkyl groups such as cyclohexyl. Examples of unsaturated aliphatic hydrocarbon groups include, but are not limited to, the alkenyl and alkynyl groups described above. The aromatic hydrocarbon group is exemplified by, but not limited to, the following groups: phenyl, tolyl, xylyl, benzyl, styryl, and 2-phenylethyl. The organic group is exemplified by, but not limited to, the following groups: haloalkyl groups (excluding fluorine-containing groups), such as chloromethyl and 3-chloropropyl; nitrogen-containing groups (such as amino groups, amido groups, imino groups); oxygen-containing groups (such as polyoxyalkylene groups, carbonyl groups, alkoxy groups, and hydroxyl groups). Additional organic groups may include sulfur-containing groups, phosphorus-containing groups, boron-containing groups. Subscript "a" is 0, 1,2, or 3.

When R is a methyl group, the siloxy units can be described by the shorthand (abbreviated) nomenclature, "M", "D", "T", and "Q" (see Walter Noll, chemistry and Technology of Silicones,1962, chapter I, pages 1-9 for further teachings on the nomenclature of Silicones). M units correspond to siloxy units of a =3, i.e. R ₃ SiO _1/2 (ii) a The D unit corresponds to a siloxy unit of a =2I.e. R ₂ SiO _2/2 (ii) a The T units correspond to siloxy units of a =1, i.e. R ₁ SiO _3/2 (ii) a Q units correspond to siloxy units of a =0, i.e. SiO _4/2 . The polydiorganosiloxane of component (a) is substantially linear but may contain a proportion of polydiorganosiloxane, however due to the presence of T units (as previously described) within the molecule, there may be some branching and so the average value of a in structure (I) is about 2.

Examples of typical groups on component (a) mainly include alkenyl groups, alkynyl groups, alkyl groups and/or aryl groups, alternatively alkenyl groups, alkyl groups and/or aryl groups. These groups may be in pendant positions (on the D or T siloxy units) or may be terminal (on the M siloxy units).

The silicon-bonded organic groups other than alkenyl groups attached to component (a) are typically selected from: monovalent saturated hydrocarbon groups typically containing 1 to 10 carbon atoms, and monovalent aromatic hydrocarbon groups typically containing 6 to 12 carbon atoms, which are unsubstituted or substituted with groups that do not interfere with the cure of the compositions of the invention, such as halogen atoms. Preferred classes of silicon-bonded organic groups are, for example, alkyl groups such as methyl, ethyl and propyl; and aryl groups such as phenyl.

Component (a) may be selected from polydimethylsiloxanes containing, for example, alkenyl and/or alkynyl groups, alkylmethylpolysiloxanes, alkylarylpolysiloxanes or copolymers thereof (where alkyl is mentioned to mean an alkyl group having two or more carbons) and may have any suitable terminal group, for example they may be trialkyl-terminated, alkenyl dialkyl-terminated, alkynyl dialkyl-terminated or may be terminated with any other suitable combination of terminal groups, provided that each polymer contains at least two unsaturated groups per molecule selected from alkenyl and alkynyl groups. In one embodiment, the end groups of such polymers do not have silanol end groups.

Thus, for example, component (a) may be:

dialkylalkenyl-terminated polydimethylsiloxanes, such as dimethylvinyl-terminated polydimethylsiloxanes; dialkylalkenyl-terminated dimethyl methylphenylsiloxanes, such as dimethylvinyl-terminated dimethyl methylphenylsiloxane; trialkyl-terminated dimethyl methyl vinyl polysiloxane; a dialkyl vinyl terminated dimethyl methyl vinyl polysiloxane copolymer; a dialkylvinyl-terminated methylphenylpolysiloxane,

dialkylalkenyl-terminated methylvinylmethylphenylsiloxanes; dialkylalkenyl-terminated methylvinyldiphenylsiloxane; dialkylalkenyl-terminated methylvinylmethylphenyldimethylsiloxane; trimethyl end-capped methylvinylmethylphenylsiloxane; trimethyl end-capped methylvinyldiphenylsiloxane; or trimethyl end-capped methylvinylmethylphenyldimethylsiloxane.

In these embodiments, the generally substantially linear organopolysiloxane of component (a) is generally a flowable liquid at a temperature of 25 ℃. Generally, the substantially linear organopolysiloxane has a viscosity of from 100mpa.s to 1,000,000mpa.s, alternatively from 100mpa.s to 100,000mpa.s, at 25 ℃. The viscosity can be at 25 ℃ using a viscosity control system with a mandrel LV-4

Rotational viscometer (designed for viscosities in the range between 1,000mPa.s and 2,000,000mPa.s) or->

Rotational viscometer (designed for viscosities in the range between 15mpa.s to 20,000mpa.s) and measured according to the polymer viscosity adjustment speed.

Component (b)

Component (b) is an organosilicon compound having at least two, alternatively at least three, si-H groups per molecule. The organosilicon compound (b) functions as a crosslinking agent for the curing component (a) by an addition reaction of silicon-bonded hydrogen atoms with unsaturated groups in the component (a) catalyzed by the following component (d). Component (b) typically contains three or more silicon-bonded hydrogen atoms, such that the hydrogen atoms of this component can react sufficiently with the unsaturated groups of component (a) to form a network structure therewith, and thereby cure the composition. When component (a) has greater than (>) 2 unsaturated groups, alternatively alkenyl groups, per molecule, some or all of component (b) may alternatively have two silicon-bonded hydrogen atoms per molecule.

Component (b) may be a siloxane, for example an organohydrogensiloxane or a silane, for example a monosilane, disilane, trisilane or polysilane, provided that there are at least two, alternatively at least three, si-H groups per molecule. In acyclic polysilanes and polysiloxanes, the silicon-bonded hydrogen atoms can be located at terminal, pendant, or both terminal and pendant positions. Cyclosilanes and cyclosiloxanes typically have from 3 to 12 silicon atoms, alternatively from 3 to 10 silicon atoms, alternatively from 3 to 4 silicon atoms.

When component (b) is a siloxane, it may comprise an organohydrogensiloxane, which may be a disiloxane, trisiloxane or polysiloxane. The organohydrogensiloxane can comprise any combination of M, D, T and/or Q siloxy units, so long as component (b) comprises at least two silicon-bonded hydrogen atoms. These siloxy units can be combined in a variety of ways to form cyclic, linear, branched, and/or resinous (three-dimensional network) structures. Component (b) can be monomeric, polymeric, oligomeric, linear, branched, cyclic, and/or resinous, depending on the selection of M, D, T and/or the Q unit.

Examples of component (b) include, but are not limited to:

(i) A trimethylsiloxy-terminated methylhydrogenpolysiloxane,

(ii) Trimethylsiloxy-terminated polydimethylsiloxane-methylhydrosiloxane,

(iii) A dimethylhydrogensiloxy terminated dimethylsiloxane-methylhydrogensiloxane copolymer,

(iv) A dimethylsiloxane-methylhydrogensiloxane cyclic copolymer,

(v) From (CH) ₃ ) ₂ HSiO _1/2 Unit and SiO _4/2 A copolymer of a combination of units of a copolymer,

(vi) From (CH) ₃ ) ₃ SiO _1/2 Unit, (CH) ₃ ) ₂ HSiO _1/2 Unit and SiO _4/2 A copolymer of units, and

(vii) As mentioned above, contain (CH) ₃ ) ₂ HSiO _1/2 Unit and (R) ² Z) _d (R ³ ) _e SiO _(4-d-e)/2 The copolymer of (1).

Although the viscosity of this component is not particularly limited, it may be usually 0.001Pa.s to 50Pa.s at 25 ℃ depending on the use of a composition having a spindle LV-4

Rotary viscometers (designed for viscosities in the range between 1,000-2,000,000mPa.s) or based on ^ based or based on LV-1 for viscosities less than 1000mPa.s>

Rotational viscometer (designed for viscosity in the range between 15mpa.s to 20,000mpa.s) and adjusts the speed according to the polymer viscosity.

Component (b) is typically such that the molar ratio of silicon-bonded hydrogen atoms in component (b) to the number of-OH groups in all unsaturated groups and component (c) in the composition is from 0.5 to 20; alternatively 0.5. When the ratio is less than 0.5. When the ratio exceeds 20. If desired, the amounts of the respective groups mentioned in the above ratios, for example, the silicon-bonded hydrogen (Si-H) content of organohydrogenpolysiloxane (b), can be determined using quantitative infrared analysis according to ASTM E168.

Typically component (b) is present in the composition in an amount of from 0.5 to 10% by weight of the total composition, as determined from the desired molar ratio of the total number of silicon-bonded hydrogen atoms in component (b) to the total number of all alkenyl and alkynyl groups in component (a) and the amount of hydroxyl groups in component (c).

Component (c)

Component (c) is one or more hydroxyl-containing blowing agents that will react with the crosslinking agent (b) in the presence of component (d) catalyst. Each component (c) has at least one OH group, alternatively at least two OH groups, and alternatively three or more OH groups. The OH groups can react with the Si-H groups of component (b) to generate hydrogen, upon which to generate foam. Each component (c) may be a suitable alcohol. These alcohols may be selected from aliphatic organic alcohols having 1 to 12 carbon atoms, such as low molecular weight alcohols including, but not limited to, methanol, ethanol, propanol, isopropanol, and the like, or alternatively benzyl alcohol.

In one embodiment, component (c) may be a diol. Examples of suitable diols include, but are not limited to, methylene glycol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, bisphenol A, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,7-heptanediol, 1,2-hexanediol, triethylene glycol, tripropylene glycol, neopentyl glycol, and combinations thereof. Alternatively, component (c) may be a triol.

In various embodiments, component (c) is selected from the group of low boiling alcohols. Such alcohols typically have a boiling point of less than about 120 ℃. The alcohol may or may not be anhydrous, but anhydrous (containing less than 1% by weight) water is generally preferred, based on the weight of the alcohol. Other suitable blowing agents are described in US4550125, US6476080 and US20140024731, which are incorporated herein by reference.

Component (c) is present in an amount to provide an OH content of about 10 parts per million (ppm) to 50,000ppm, alternatively about 100ppm to 20,000ppm, alternatively about 500ppm to 10,000ppm, alternatively about 500 to about 7500 ppm.

In other embodiments, component (c) is selected from the group of Si — OH polymers. In certain embodiments, the chemical blowing agent component (c) is selected from the group consisting of organosilanes and organosiloxanes having at least one silanol (Si-OH) group. Such compounds may have structures similar to those described above for components a) and B). Examples of suitable OH-functional compounds include dialkylsiloxanes, such as OH-terminated dimethylsiloxanes. Such silicones may have relatively low viscosities, such as from about 10mpa.s to about 5,000mpa.s, from about 10mpa.s to about 2,500mpa.s, from about 10mpa.s to about 1,000mpa.s, from about 10mpa.s to about 500mpa.s, or from about 10mpa.s to about 100mpa.s.

In various embodiments, the composition is substantially free of OH functional components other than component (c) that contribute to the release of hydrogen during the formation of the foamed silicone elastomer. Substantially free, generally means that the composition comprises <5, <4, <3, <2, <1, close to 0 or 0 wt% of such OH-functional components.

Component (d)

Component (d) is a catalyst comprising or consisting of a platinum group metal or a compound of a platinum group metal. By "platinum group" it is meant ruthenium, rhodium, palladium, osmium, iridium, and platinum, and complexes thereof. Platinum and platinum compounds are preferred because these catalysts have a high level of activity in hydrosilylation reactions.

Examples of preferred hydrosilylation catalysts (d) include, but are not limited to, platinum black, platinum on various solid supports, chloroplatinic acid, alcohol solutions of chloroplatinic acid, and complexes of chloroplatinic acid with ethylenically unsaturated compounds such as olefins and organosiloxanes containing silicon-bonded ethylenically unsaturated hydrocarbon groups. The catalyst (d) may be platinum metal, platinum metal deposited on a support such as silica gel or charcoal powder, or a compound or complex of a platinum group metal.

Examples of suitable platinum-based catalysts include

(i) Complexes of chloroplatinic acid with organosiloxanes containing ethylenically unsaturated hydrocarbon groups, as described in US3,419,593;

(ii) Chloroplatinic acid in the hexahydrate or anhydrous form;

(iii) A platinum-containing catalyst obtained by a process comprising the steps of: reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound (such as divinyltetramethyldisiloxane);

(iv) Olefin-platinum-silyl complexes, such as (COD) Pt (SiMeCl), as described in U.S. Pat. No. 6,605,734 ₂ ) ₂ Wherein "COD" is 1,5-cyclooctadiene; and/or

(v) Karstedt's catalyst, a platinum divinyl tetramethyl disiloxane complex typically containing about 1 weight percent platinum in a solvent such as toluene, may be used. These are described in US3,715,334 and US3,814,730.

When present, the hydrosilylation catalyst (d) is present in a catalytic amount, i.e., an amount or quantity sufficient to promote its reaction or cure under the desired conditions, in the total composition. Varying levels of hydrosilylation catalyst (d) can be used to tailor reaction rates and cure kinetics. The catalytic amount of hydrosilylation catalyst (d) is typically between 0.01ppm and 10,000 parts by weight per million (ppm) of a platinum group metal based on the combined weight of composition components (a) and (b); alternatively, between 0.01ppm and 5000 ppm; alternatively between 0.01ppm and 3,000ppm and alternatively between 0.01ppm and 1,000ppm. In particular embodiments, the catalytic amount of the catalyst can be in the range of from 0.01ppm to 1,000ppm, or from 0.01ppm to 750ppm, or from 0.01ppm to 500ppm, and alternatively from 0.01ppm to 100ppm of the metal, based on the weight of the composition. The ranges may relate only to the metal content in the catalyst or to the catalyst as detailed (including its ligands), but typically these ranges relate only to the metal content in the catalyst. The catalyst may be added as a single species or as a mixture of two or more different species. Typically, the amount of catalyst present will range from 0.001 wt% to 3.0 wt% of the composition, depending on the form/concentration of the catalyst package provided.

Component (e)

Component (e) is a thixotropic agent that can hold the composition by surface tension when added to the composition, but can separate or slip when sufficient force is applied, resulting in thixotropy or shear thinning, wherein the viscosity is non-newtonian and becomes lower as shear force or time increases. The thixotropic agent may comprise a suitable silica, such as precipitated silica, fumed silica, and the like, calcium carbonate, and/or talc. In the case of silica and calcium carbonate, which may be used as reinforcing filler or semi-reinforcing filler, respectively, the reinforcing effect is similar to the thixotropic effect and the reinforcing effect, and without being bound to the current theory, is believed to be caused by the interaction between the silicone polymer and the filler surface. Increasing the silica and/or calcium carbonate content will result in greater thixotropic effects and increase the elastomeric properties, such as tensile strength, of the subsequently cured composition.

For example, the thixotropic agent (e) may contain one or more of precipitated calcium carbonate, ground calcium carbonate, fumed silica, colloidal silica, and/or precipitated silica. Typically, the surface area of the thixotropic agent (e) measured according to the BET method is at least 15m2/g for precipitated calcium carbonate, alternatively from 15m2/g to 50m2/g for precipitated calcium carbonate, alternatively from 15m2/g to 25m2/g, according to ISO 9277. The silica thixotropic agent (e) typically has a surface area of at least 50m2/g. In the case of high surface area fumed silica and/or high surface area precipitated silica, these may have a surface area of from 75m2/g to 450m2/g measured using the BET method according to ISO 9277, 2010, alternatively from 100m2/g to 300m2/g measured using the BET method according to ISO 9277. Thixotropic agents are typically present in an amount of 2% to 5% by weight of the composition. It was found that if a larger amount of silica is added, a reduction in compression set can result.

Component (f)

Component (f) curable and foamable silicone composition herein is one or more silyl modified polyethers in an amount of 0.5 to 3% by weight of the composition. Silyl-modified polyethers are defined as having a polyether backbone and at least two (R) per molecule ¹⁰ ) _m (Y ¹ ) _3-m Polymers of-Si groups, in which each R is ¹⁰ Is a hydroxyl or hydrolyzable group, each Y ¹ Is an alkyl group containing 1 to 8 carbons and m is 1,2 or 3.

(R) of silyl-modified polyether (f) ¹⁰ ) _m (Y ¹ ) _3-m The — Si groups may be linked to the polyether backbone by any suitable linkage, or may be bonded directly to the polyether where appropriate. For example, (R) ¹⁰ ) _m (Y ¹ ) _3-m the-Si group may be a terminal group connected to the polyether polymer backbone via:

(R ¹⁰ ) _m (Y ¹ ) _3-m –Si-D–[NH-C(＝O)] _k -

wherein R is ¹⁰ 、Y ¹ And m is as described above, D is divalent C _2-6 Alkylene, alternatively C _2-4 Alkylene, alternatively ethylene or propylene, and k is 1 or 0. Silyl-modified polyethers can thus be described as

(R ¹⁰ ) _m (Y ¹ ) _3-m –Si-D-[NH-C(＝O)] _k -O[CH(CH ₃ )–CH ₂ -O] _u –[C(＝O)–NH] _k –D–Si(Y ¹ ) _3-m (R ¹⁰ ) _m

Wherein in the above examples, for illustrative purposes, the polyether repeating groups are oxypropylene groups

[CH(CH ₃ )–CH ₂ -O]Wherein u is the number of repeating units.

(R ¹⁰ ) _m (Y ¹ ) _3-m Each substituent R in the-Si group ¹⁰ May independently be a hydroxyl group or a hydrolyzable group. The hydrolyzable groups may be selected from acyloxy groups (e.g., acetoxy, octanoyloxy, and benzoyloxy groups); ketoximino groups (e.g., dimethylketoximino and isobutylketoximino); alkoxy groups (e.g., methoxy, ethoxy, and propoxy) and alkenyloxy groups (e.g., isopropenyloxy and 1-ethyl-2-methylvinyloxy). However, it is preferred that each R is an OH group or an alkoxy group having from 1 to 10 carbons, or an OH group or an alkoxy group having from 1 to 6 carbons, or an OH group, a methoxy group or an ethoxy group, or a methoxy group or an ethoxy group. Substituent Y ¹ Is an alkyl group containing 1 to 8 carbons, alternatively 1 to 6 carbons, alternatively 1 to 4 carbons. Therefore, when R is ¹⁰ When it is OH or a hydrolyzable group and the hydrolyzable group is an alkoxy group, (R) ¹⁰ ) _m (Y ¹ ) _3-m the-Si group may be selected from- (Y) ¹ )SiOH ₂ 、-(Y ¹ ) ₂ SiOH、-Y ¹ Si(OR ^b ) ₂ 、-Si(OR ^b ) ₃ 、-(Y ¹ ) ₂ SiOR ^b Wherein R is ^b Is an alkyl group having 1 to 8 carbons.

When the silyl-modified organic polymer (a) is an alkoxysilyl-terminated polyether as previously described, the polymer backbone is exemplified in the above structure as

(-C _p H _2p -O-) _y

Wherein p is an integer from 2 to 4 inclusive, and y is ≧ 4, i.e., an integer of at least four.

Examples may be polyethers having repeating groups, e.g.

[CH(CH ₃ )–CH ₂ -O] _y

The number average molecular weight (Mn) of each polyether can range from about 300 to about 10,000, which can be determined by ASTM D5296-05 and calculated as polystyrene molecular weight equivalents. Furthermore, the oxyalkylene units need not be the same throughout the polyoxyalkylene, but may differ from unit to unit. The polyalkylene oxides may comprise, for example, oxyethylene units (-C) ₂ H ₄ -O-), an oxypropylene unit (-C) ₃ H ₆ -O-) or oxybutylene unit (-C) ₄ H ₈ -O-) or mixtures thereof. Preferably, the polyoxyalkylene polymer backbone consists essentially of oxyethylene units or oxypropylene units. The polyoxyalkylenes typically have terminal hydroxyl groups and can be readily modified with moisture-curable silyl groups, for example by reaction with an excess of an alkyltrialkoxysilane to introduce terminal alkyldialkoxysilyl groups, as previously discussed. Alternatively, the polymerization may occur via a hydrosilylation type process. Polyoxyalkylenes composed entirely or predominantly of oxypropylene units have properties suitable for many sealant and/or adhesive applications.

Other polyoxyalkylenes may comprise units such as the following structures:

-[-R ^e -O-(-R ^f -O-) _h -Pn-CR ^g ₂ -Pn-O-(-R ^f -O-) _q1 -R ^e ]-

wherein Pn is 14-phenylene radical, each R ^e Identical or different and are divalent hydrocarbon radicals having from 2 to 8 carbon atoms, each R ^f Identical or different and is an ethylene radical or a propylene radical, each R ^g Identical or different and are a hydrogen atom or a methyl group, and each subscript h and q1 is a positive integer in the range of from 3 to 30.

Component (f) is added to the composition in an amount of 0.5 to 3% by weight of the composition.

It has been found that where a high level of thixotropy is required for the end application, the combination of component (e) with a co-thixotropic agent in the form of component (f) enhances the thixotropic properties of the curable and foamable silicone composition without significantly increasing the viscosity and composition density due to, for example, the high aspect ratio values required to cure the gasket rather than increasing the level of component (e) content, and thus has an adverse effect on the dispensability of the curable and foamable silicone composition through an applicator, potentially causing blockages in the applicator and resulting in a cured foam of high density and hardness and reduced compression set due to the presence of too much component (e). As an example, a known solution to improve the aspect ratio of a form-in-place foam gasket (FIPFG) is to increase the amount of a thixotropic agent (component (e) herein), such as silica or calcium carbonate, in the composition from which it is made, but at the same time increase the aspect ratio of the form-in-place foam gasket, increasing the content of silica and calcium carbonate in the composition has the negative effects described above. Surprisingly, however, it is possible to reduce the amount of thixotropic agent (component (e)) by maintaining a relatively low level of thixotropic agent, e.g. 5% by weight or less of the composition, but an amount of component (f) is introduced into the composition to increase the aspect ratio of the foam-in-place gasket (FIPFG). It can be seen that the thixotropy of the curable and foamable silicone composition is significantly improved with a small amount of component (f) in combination with component (e).

Organic polyethylene glycols were tried as an alternative to SMP, but these did not respond as well synergistically in terms of thixotropy, and it was crucial that no but phase separation problems were found which would have a poor shelf life impact effect. The use of silicone polyether copolymers as an alternative to SMP was also analyzed, but the thixotropic improvement using them as a co-thixotropic agent for component (e) was also not as good as for component (f) above.

One or more optional additives

The composition may optionally further comprise additional ingredients or components (or "additives"), particularly where the ingredients or components do not interfere with the curing and/or foaming of the composition. Examples of additional ingredients include, but are not limited to, resins, surfactants; a stabilizer; a tackifier; colorants, including dyes and pigments; an antioxidant; a carrier vehicle; a heat stabilizer; a flame retardant; a flow control additive; an inhibitor; non-reinforcing (sometimes referred to as extending) fillers.

One or more of the additives can be present in any suitable weight percentage (wt%) of the composition, such as about 0.1 wt% to about 15 wt%, about 0.5 wt% to about 5 wt%, or about 0.1 wt% or less, about 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or about 15 wt% or more of the composition. Suitable amounts of additives can be readily determined by those skilled in the art based on, for example, the type of additive and the desired result. Certain optional additives are described in more detail below.

The composition may also contain an organopolysiloxane resin ("resin") as a resin foam stabilizer. The resin has a branched or three-dimensional network molecular structure. The resinous organopolysiloxane may be in liquid or solid form at 25 ℃, optionally dispersed in a carrier that can dissolve and/or disperse the resin therein.

In particular embodiments, the resinous organopolysiloxane may be exemplified by: organopolysiloxanes containing only T units, organopolysiloxanes containing T units in combination with other siloxy units (e.g., M, D and/or Q siloxy units), or organopolysiloxanes containing Q units in combination with other siloxy units (i.e., M, D and/or T siloxy units). Typically, the resin comprises T units and/or Q units. Specific examples are vinyl terminated silsesquioxanes or MQ resins.

For example, the resin may be formed from a plurality of groups of the formula:

R ⁵ _f″ SiO _(4-f″)/2

wherein each R ⁵ Is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 20 carbon atoms, for example an alkyl group such as methyl, ethyl, propyl, hexyl, octyl, dodecyl, tetradecyl, hexadecyl and octadecyl, or an aromatic group having 6 to 20 carbons such as benzyl and phenethyl groups, and wherein each f "is 0 to 4. If the resin is a T resin, the majority of the groups have f "of 1, and if the resin is an MQ resin, the majority of the groups contain groups in which f" is 0 (Q group) or 4 (M group), as previously discussed.

Suitable pigments may include carbon black such as acetylene black, titanium dioxide, chromium oxide, zinc oxide, bismuth vanadium oxide, iron oxide, and mixtures thereof.

The composition may additionally comprise one or more non-reinforcing fillers. Examples of finely divided non-reinforcing fillers include crushed quartz, diatomaceous earth, barium sulfate, iron oxide, titanium dioxide and carbon black, talc, and wollastonite. Other fillers that may be used alone or in addition to those described above include carbon nanotubes, such as multi-walled carbon nanotubes aluminite, hollow glass spheres, calcium sulfate (anhydrite), gypsum, calcium sulfate, magnesium carbonate (e.g. hydromagnesite, with the formula Mg ₅ (CO ₃ ) ₄ (OH) ₂ ·4H ₂ Hydrated magnesium carbonate mineral of O); clays (such as kaolin), aluminium hydroxide, magnesium hydroxide (brucite), graphite, copper carbonates (such as malachite), nickel carbonates (such as nernstone), barium carbonates (such as witherite) and/or strontium carbonates (such as strontianite). Further alternative fillers include alumina, silicates selected from the group consisting of: olivine and garnet; an aluminosilicate; a cyclosilicate; a chain silicate; and sheet silicates. In certain embodiments, the composition comprises at least one filler comprising hollow particles, such as hollow spheres. Such fillers may be used to facilitateThe porosity and/or total void fraction of the foam, and may provide other advantages, such as flame retardancy. Thus, for FIPFG, if a large amount of filler is required in the composition, non-reinforcing fillers are preferred over, for example, silica reinforcing fillers because reinforcing fillers create the problems described above.

The non-reinforcing filler (when present) and/or component (e) may optionally be surface treated with a treating agent. The treating agent used may be selected from, for example, one or more of an organosilane, a polydiorganosiloxane or organosilazane, a hexaalkyldisilazane, a short chain siloxane diol, a fatty acid or a fatty acid ester such as a stearate to render one or more of the fillers hydrophobic and thus easier to handle and obtain a homogeneous mixture with the other components. Specific examples include, but are not limited to, liquid hydroxyl-terminated polydiorganosiloxanes containing an average of 2 to 20 diorganosiloxane repeating units per molecule (which may optionally contain fluorine groups and/or fluorine-containing groups if desired), hexaorganodisiloxanes, hexaorganodisilazanes, and the like. A small amount of water may be added along with the silica treatment as a processing aid. The surface treatment of the fumed silica makes it readily wettable by the polymer (a).

The compositions as described herein may also contain an inhibitor of hydrosilylation reaction to inhibit curing of the composition. Hydrosilylation reaction inhibitors are used to prevent or delay the hydrosilylation reaction curing process, especially during storage, when desired. Optional hydrosilylation reaction inhibitors for platinum-based catalysts are well known in the art and include hydrazines, triazoles, phosphines, thiols, organic nitrogen compounds, acetylenic alcohols, silylized acetylenic alcohols, maleates, fumarates, ethylenically or aromatic unsaturated amides, ethylenically unsaturated isocyanates, olefinic siloxanes, unsaturated hydrocarbon mono-and diesters, conjugated ene-alkynes (such as 3-methyl-3-penten-1-yne, 3,5-dimethyl-3-hexen-1-yne), hydroperoxides, nitriles, and diazepanes. Alkenyl substituted siloxanes such as those described in US3989667 may be used, with cyclic methylvinylsiloxanes such as 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane being preferred.

One known class of hydrosilylation inhibitors includes the acetylenic compounds disclosed in US 3445420. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors that will inhibit the activity of platinum-containing catalysts at 25 ℃. Compositions containing these inhibitors typically require heating at temperatures of 70 ℃ or above in order to cure at a practical rate.

Examples of alkynols and derivatives thereof include 3-methyl-1-butin-3-ol, 1-ethynyl-1-cyclohexanol (ETCH), 2-methyl-3-butin-2-ol, 3-butin-1-ol, 3-butin-2-ol, propargyl alcohol, 1-phenyl-2-propyn-1-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-phenyl-1-butin-3-ol, 1-ethynyl cyclopentanol, 3-methyl-1-penten-4-yn-3-ol, and mixtures thereof. Alkynol derivatives may include those compounds having at least one silicon atom.

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

In various embodiments, the composition further comprises an adhesion promoter. The adhesion promoter may improve the adhesion of the foam to the substrate contacted during curing. In certain embodiments, the adhesion promoter is selected from organosilicon compounds having at least one alkoxy group bonded to a silicon atom in the molecule. Examples of such alkoxy groups are methoxy groups, ethoxy groups, propoxy groups, butoxy groups and methoxyethoxy groups. Further, examples of the non-alkoxy group bonded to the silicon atom of the organosilicon compound are: substituted or unsubstituted monovalent hydrocarbon groups such as alkyl groups, alkenyl groups, aryl groups, aralkyl groups, haloalkyl groups, and the like; epoxy-containing monovalent organic groups such as 3-glycidoxypropyl groups, 4-glycidoxybutyl groups, or similar glycidoxyalkyl groups; 2- (3,4-epoxycyclohexyl) ethyl group, 3- (3,4-epoxycyclohexyl) propyl group, or similar epoxycyclohexylalkyl group; and a 4-oxetanyl group, an 8-oxetanyl group or a similar oxetanyl group; monovalent organic groups having an acrylic group such as 3-methacryloxypropyl group and the like; and a hydrogen atom.

The organosilicon compounds typically have silicon-bonded alkenyl groups or silicon-bonded hydrogen atoms. Further, the organosilicon compound generally has at least one monovalent organic group containing an epoxy group in the molecule, because of the ability to impart good adhesion to various types of substrates. Examples of this type of organosilicon compound are organosilane compounds, organosiloxane oligomers and alkyl silicates. Examples of the molecular structure of the organosiloxane oligomer or the alkyl silicate are a linear structure, a partially branched linear structure, a branched structure, a cyclic structure, and a network structure. Linear structures, branched structures and network structures are typical. Examples of organosilicon compounds of this type are: silane compounds such as 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and the like; a siloxane compound having at least one silicon-bonded alkenyl group or silicon-bonded hydrogen atom and at least one silicon-bonded alkoxy group in a molecule; a mixture of a silane compound or a siloxane compound having at least one silicon-bonded alkoxy group and a siloxane compound having at least one silicon-bonded hydroxyl group and at least one silicon-bonded alkenyl group in a molecule; and methyl polysilicate, ethyl polysilicate and ethyl polysilicate containing epoxy groups.

The content of the adhesion promoter in the composition is not particularly limited. In certain embodiments, the adhesion-imparting agent is present in an amount of about 0.01 to about 10 parts by mass per 100 total parts by mass of components (a) and (b).

Foam

The curable and foamable silicone composition as described herein produces an open-cell foam and/or a closed-cell foam. When the foam is a closed cell foam, the density may be measured by any suitable method, for example by archimedes' principle, using the scale and density kit, and following the standard instructions associated therewith. A suitable balance is a Mettler-Tollido XS205DU balance with density kit (Mettler-Toledo XS205DU balance). When the closed cell foam may have a density of 0.01 g/cc g/cm ³ To 5g/cm ³ Alternatively 0.05g/cm ³ To 2.5g/cm ³ Alternatively 0.1g/cm ³ To 2.0g/cm ³ Alternatively 0.1g/cm ³ To 1.5g/cm ³ 。

If the density is too high, the foam may be too heavy or too stiff for some applications. If the density is too low, the foam may lack the structural integrity required for certain applications.

The average pore diameter may be determined by any suitable method, for example according to ATSM method D3576-15, optionally with the following modifications:

(1) Imaging the froth using an optical or electron microscope, rather than projecting the image on a screen; and

(2) A line of known length spanning more than 15 cells is drawn instead of a 30mm line.

The curable and foamable silicone compositions as described herein typically have pores that are uniform in size and/or shape. Typically, the foam has an average pore size of from 0.001mm to 5mm, alternatively from 0.001mm to 2.5mm, alternatively from 0.001mm to 1mm, alternatively from 0.001mm to 0.5mm, alternatively from 0.001mm to 0.25mm, alternatively from 0.001mm to 0.1mm, alternatively from 0.001mm to 0.05mm.

Typically, the FIPFG prepared using the curable and foamable silicone composition as described herein has an aspect ratio of at least 0.625. This can be measured using any suitable method, for example, a sample of the cured foam strip can be cut into two portions and then the cross-sectional height and width can be measured using a suitable digital caliper, for example, mitutoyo America Corporation of Aurora, illinois, usa, with a 0.01mm accuracy absolute caliper.

The curable and foamable silicone compositions as described herein are typically stored in two parts to avoid premature curing. These two parts are commonly referred to as part a and part B. A two-part composition is used such that the components (a) polymer, (b) crosslinker, (c) blowing agent, and (d) catalyst are not all stored together. For example, part a may comprise components (a), (c) and (d), and part B comprises at least components (a) and (B), wherein part a is free of component (B) crosslinker, and part B is free of component (d) catalyst. Preferably, when present, the reaction inhibitor is present in part a with component (d), but additionally each of the other optional components of the composition may be present in either or both of part a and part B, or may be introduced into one or more further parts separate from the two parts if desired (so that the system may be a three-part system or a more part system). In one embodiment, the thixotropic agent (e) and the co-thixotropic agent (f) are stored in the part B composition along with the component (B) crosslinker. The two part composition can be designed to be mixed together in any suitable ratio, depending on the content and concentration of the ingredients present in each part, for example the two part composition can be mixed together in a part a: part B weight ratio of from 15 to 1:1.

In one embodiment, for compositions in which the part a composition and the part B composition are mixed together in a 1:1 weight ratio, the part a composition may comprise the ingredients in table 1a and the part B composition may comprise the ingredients in table 1B. It is to be understood that for any composition, the total composition in weight% (wt.%) is 100 wt.%.

Table 1 a-examples of part a compositions

Table 1B-examples of part B compositions

	By weight%
		Component (a)	80 to 87
Component (b) a crosslinking agent	10 to 15
		Silicon dioxide (thixotropic agent)	2.0 to 5.0
Silyl-modified polyethers (co-thixotropic agents)	0.5 to 5

The curable and foamable silicone composition can be prepared and supplied by any suitable method to form a silicone foam elastomer form-in-place foam gasket (FIPFG).

The method may for example comprise the steps of:

(i) Mixing the part a composition and the part B composition to form a foam from the curable and foamable silicone composition described above;

(ii) (ii) delivering the foam prepared in step (i) to a suitable applicator;

(iii) Dispensing the resulting foam from the applicator onto a substrate surface; and

(iv) Enabling the foam to cure and provide the silicone foam elastomer FIPFG.

Prior to step (i) of the above process, the ingredients of the part a composition are blended together and separately the ingredients of the part B composition are also blended together to form the respective part a and part B compositions.

For example, part a composition may comprise one or more polymers according to component (a) as described above, components (c) and (d) and optionally a part of thixotropic agent (e). Part a compositions may also include one or more of the optional components described above, for example inhibitors, non-reinforcing fillers, pigments or colorants and/or MQ resin foam stabilizers.

For example, part B blend compositions may comprise one or more of the above optional components according to the polymer of component (a), components (B), (f) and the remaining component (e) as described above, such as pigments or colorants and/or MQ resin foam stabilizers.

Typically, the part a and part B compositions are stored for a period of time prior to use. In step (i), the part a and part B compositions are mixed to form a foam of the curable and foamable silicone composition described above. Any suitable mixer may be used, for example the mixer may be a static mixer or a stirred tank or the like suitable for effecting thorough mixing of the respective blend compositions. Optionally, the mixing vessel is temperature controlled so that the mixed part a and part B compositions can be maintained within a desired temperature range.

In step (ii), the foam produced in step (i) is delivered to a suitable applicator. This can be controlled by a pump to control the cell size of the silicone elastomer foam produced herein. In view of the fact that the foam produced is used to make silicone foam elastomer form-in-place foam gaskets (FIPFG), preferably the applicator is a pre-programmed or programmable robotic applicator that can be used to apply the composition onto a target substrate surface, which may be planar, or more likely provided with grooves into which the foam is introduced. The composition should be used in an amount to provide a gasket with satisfactory performance while minimizing waste. Typically, the applicator will be programmed to apply an optimised quantity of foam at a predetermined dispensing flow rate, such that the gasket is applied as and when required, and then allowed to cure in place. If desired, the gasket may be heated to aid in its curing.

For optimum performance, FIPFG preferably requires a balance of characteristics. The uncured gasket formulation needs to be a liquid with a sufficiently low viscosity to be easily dispensed through the applicator (and avoid clogging in the applicator) while not slumping after dispensing to maintain the shape and size of the selected gasket. Thus, each blend/composition of part a, part B, and resulting combination thereof, when formed first, can have a wide range of viscosities, depending on the ingredients used. In various embodiments, the composition has a viscosity of about 1,000mpa.s to 100,000mpa.s, alternatively 1,000mpa.s to 50,000mpa.s, alternatively 1,000mpa.s to 25,000mpa.s, alternatively 1,000mpa.s to 10,000mpa.s, alternatively 1,000mpa.s to about 7,500mpa.s, and alternatively 2,500mpa.s to 5,000mpa.s. Viscosity can be determined using any suitable method understood in the art, for example, using a probe having a mandrel LV-4

Rotational viscometer (designed for viscosities in the range between 1,000mPa.s and 2,000,000mPa.s) or->

Rotational viscometer (designed for viscosities in the range between 15mpa.s-20,000mpa.s) and speed was adjusted according to polymer viscosity.

The compositions described herein foam and cure when mixed at room temperature and humidity, but heat can be used to accelerate curing if desired. After curing, the gasket may undergo post-curing if desired. Post-curing can be used to stabilize the properties of the cured gasket over a short period of time (e.g., 30 minutes to 3 hours, e.g., 1 hour).

After curing and optional post-curing, appropriate softness characteristics, compression set, and in some cases high gasket aspect ratios are required. The adjustment of the properties in the uncured and cured states is a function of the reactants, the relative stoichiometry of the reactants. As previously discussed, it was found that combining components (e) and (f) herein provides good thixotropic pre-cure without the negative effects caused by using high levels of silica and calcium carbonate. This results in a low reinforcing filler content, which helps to avoid the composition having a high viscosity level. Low filler concentrations favor lower viscosity formulations for improved dispensability. Softer materials may also be obtained by making the elastomeric product softer. However, softening the elastomeric product material often results in some sacrifice in compression set. Each characteristic may vary depending on material selection and stoichiometry, filler type and concentration, and conditions used to crosslink the formulation to produce a cured gasket. The balance of properties will vary in response to the specific requirements of a given application of the form-in-place gasket. Custom formulated to meet the basic task of many applications of the gasket formulation according to the invention.

An additional advantage that has been identified in the disclosure herein is the ability to use the curable and foamable silicone composition as a means to repair preformed gaskets in the event of damage or failure. Gaskets of the type described herein were previously considered irreparable, but this assumption has been shown to be incorrect when using the compositions herein as foam gaskets, where the composition is dispensed onto a lower substrate, cured, and then a lid or upper substrate is placed on top and locked in place if necessary.

Gaskets made from the curable and foamable silicone compositions as described herein were found to adhere well to a variety of substrates, and it is believed that the use of co-thixotropic agent (f) enhances this feature when present in combination with component (e). Suitable substrates include aluminum, stainless steel, concrete and Sheet Molding Composites (SMC), glass fiber reinforced polyester materials.

The FIPFGs, compositions, foams, and methods of the present disclosure may be used to form applications, for example, to act as a barrier against absorption or permeation of air, dust, noise, liquid, gaseous substances, or dirt. Gaskets are ideal for sound attenuation, vibration attenuation, dampening elements, moisture protection, chemical protection, and air sealing. Examples of suitable applications include automotive gasket applications, such as gaskets for Electric Vehicle (EV) battery packs, EV batteries, control units in EVs, lamp housings, fuse boxes, air filters, oil pan gaskets, oil enclosure gaskets, oil screen gaskets, timing belt cover upper gaskets, timing rocker cover lower gaskets; gaskets for consumer appliances, such as waterproof connectors, air conditioners, lighting devices, electronic components, housings, preferably control cabinets, lights, drums (packaging) or filter housings, are attached in situ to a substrate by foaming as described herein. Other applications include exterior waterproofing applications.

The following examples, which illustrate the compositions, foams and methods, are intended to illustrate, but not to limit the invention.

Examples

The compositions are produced using different types and amounts of components. These are described in detail below. All amounts are in weight percent unless otherwise indicated. All viscosities were measured at 25 ℃ as discussed above. The viscosity of the individual components can be determined by any suitable method, for example using a viscosity measuring device with a mandrel LV-4

Rotational viscometer (designed for viscosities in the range between 1,000mPa.s and 2,000,000mPa.s) or ^ based on viscosity less than 1000mPa.s with spindle LV-1>

Rotational viscometer (designed for viscosities in the range between 15mpa.s to 20,000mpa.s) and measured according to the polymer viscosity adjustment speed. The alkenyl and/or alkynyl content of the polymer and the silicon-bonded hydrogen (Si-H) content and/or silanol content of the composition are determined according to ASTM E168 using quantitative infrared analysis.

In the following examples, the same standard part a composition was used throughout, and the compositions used are described in table 2 below:

table 2: part A compositions for all examples

BET values are supplier data or measured according to ISO 9277. The hydromagnesite non-reinforcing filler used is UltraCarb ^TM C5-25 was purchased from LKAB Minerals AB from Lu Le (Lulea Sweden) Sweden, sweden.

The mixtures of examples and comparative examples were tested by varying the content of the part B composition. The compositions of examples 1 to 5 are provided in table 3a, and the compositions of comparative examples 1-5 (C1-C5) are provided in table 3 b.

Table 3a: part B compositions of examples 1 to 5

Silica 2 has a mean specific surface area (BET) of 150m ² G and 190m ² Between/g of fumed silica treated with dimethyldichlorosilane;

x-linker was used in all examples and comparative examples and was a trimethyl endcapped methylhydrogenpolysiloxane having a viscosity of about 30mpa.s at 25 ℃;

Co-T A1 is the name KANEKA by the Kaneka chemical (Kaneka)

SAX520 commercially sold trimethoxysilyl terminated polyether with a viscosity of 46Pa.s (supplier data);

Co-T A is the name KANEKA by Brillouin chemistry

SAX510 commercially sold trimethoxysilyl terminated polyether having a viscosity of 46Pa.s (supplier data)

Co-T A is manufactured by Risun Polymer Co., ltd. By RISUN

30000T Trimethoxysilyl terminated polyether having a viscosity of 30,000mPa.s.

Table 3b: part B composition of C.1 to 5

Polymer 1, silica 2 and the x-linker are as described above.

Co-T A is trimethoxy dimethyl disiloxane ethylene having a viscosity of 400mPa.s at 25 ℃

A blocked polydimethylsiloxane;

Co-T A is a dimethyl (polyether) -terminated polydimethylsiloxane having a viscosity of 305mPa.s;

and

Co-T A is trimethylsiloxy terminated having a viscosity of 10,000mPa.s at 25 deg.C

Dimethyl methyl (polyether) siloxane copolymers.

The viscosities of the part B compositions described in tables 3a and 3B were measured at 25 ℃ using a shear rate scanning method using a Discovery Hybrid Rheometer (HR-10) from TA Instruments using 20mm plate pans (TA Instruments). The results are depicted in tables 4a and 4b below:

table 4a: viscosity (Pa.s) shear rate 0.1/s for part B compositions of the examples

Table 4b: viscosity (Pa.s) shear rate of comparative example part B composition 0.1/s

The viscosities of examples 2, c.2, c.4 and c.5 were compared in the shear rate range between 0.1/s and 10/s using the above described equipment and the results are shown in table 4c below.

TABLE 4c viscosity (Pa.s) as a function of shear rate

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It can be seen that example 2 exhibits excellent thixotropic properties when compared to c.2 and the viscosity of the part B composition of example 2, with a high viscosity at low shear rates compared to c.2. Furthermore, comparative examples c.4 and c.5 used silicone polyethers as a co-thixotropic agent as opposed to silyl modified polyethers, and it can be seen that example 2 currently exhibits the best performance.

The composition is then prepared. In each of the examples and comparative examples, the part A composition and the part B composition were mixed in a weight ratio of 1: 1. After mixing, a foam is generated and delivered to an applicator for application to the surface of a substrate to produce a FIPFG "(form-in-place foam gasket) if desired.

For the physical property tests being performed, samples were prepared as follows:

15g of part A and 15g of part B were mixed in a high-speed mixer (Speedmixer) at 2000rpm for 10s. Thereafter, the resulting mixture was foamed at room temperature for 5 minutes. The resulting foamed samples were then post-cured in an oven at 100 ℃ for 1 hour. The thickness of the test specimen was found to be controlled at about 6.5mm. The following test methods were relied upon:

density (kg/m) was measured by cutting the cured foam into regular cube shapes ³ ) And density is determined by measuring weight and volume.

Hardness (Shore 00) was measured according to ASTM D2240-15e 1.

Aspect ratio

In the case of the aspect ratio, the mixture of part a and part B is in the form of a string and waits for it to fully foam. The height and width of the foam were measured using a Sanfeng absolute caliper from Osa, illinois, with a 0.01mm accuracy, and the aspect ratio of the cured sample was calculated.

Adhesion testing：

The part a and part B compositions were mixed in a 1:1 weight ratio as previously described and a sufficient amount of each mixture was dispensed

(i) An aluminum substrate and

(ii) An SMC substrate;

the foamed silicone strips are then cured on the substrate surface. The dispensed strips were left to foam for 5 minutes at room temperature on the respective substrates and then post-cured for 1h in an oven at 100 ℃.

The silicone foam was peeled from the substrate and visually evaluated for the level of cohesive failure of adhesion. For the avoidance of doubt, adhesion Failure (AF) refers to the condition (poor adhesion) when the coating separates cleanly (peels) from the substrate. Cohesive Failure (CF) was observed when the coating itself broke without separating from the substrate. In some cases, a hybrid failure mode may be observed; i.e. some areas are stripped off (i.e. AF) and some areas remain covered by a coating (i.e. CF). In such cases, the portions of the surface that exhibit CF (% CF) behavior have been determined. The sum of% CF +% AF =100%.

Compression set：

Compression set testing was performed according to ASTM D395 test method B. Three tests were performed:

(i) In a first step, the sample is compressed to 50% of its original thickness and placed in an oven at 85 ℃ for 1 week;

(ii) In a second step, the sample is compressed to 50% of its original thickness and placed in an oven at 85 ℃ and 85% Relative Humidity (RH) for 1000 hours;

(iii) In a third step, a thermal shock test was performed in which (a) each test specimen was placed in a test mold and compressed to 50% of its original thickness. The resulting mold containing the sample was placed in an oven at 125 ℃ for a period of 30 minutes. After a period of 30 minutes, the temperature of the oven was automatically changed from 125 ℃ to-40 ℃ and the sample was held at-40 ℃ for a period of 30 minutes. After a period of 30 minutes, the sample was transferred back to a temperature of 125 ℃ for another 30 minutes. The thermal shock treatment was repeated for 1000 hours, and then the test specimens were removed from the oven and the thickness of each test specimen was measured and compared to its original thickness.

The cured samples of each example were analyzed and the results are shown in table 5a below. The cured samples of each comparative example were analyzed and the results are shown in table 5b below.

Table 5a: physical characteristics of the examples

Table 5b: physical characteristics of comparative examples

From the results, it can be seen that the aspect ratio of the embodiments herein is significantly better. The use of silicone polyether copolymers resulted in a ratio of c.4 and c.5 of 0.6, but the examples herein gave results with an h/w ratio of at least 0.625, which would require much greater viscosity or additional thixotropic properties than the comparative examples, e.g., from 1200pa.s to 1600pa.s.

It can be seen that for a foam line with a height of 5mm and a width of 11.9mm, the H/W ratio =5/11.9=0.42; whereas for a foam cord with a height of 5mm but a width of 6.7mm, the H/W ratio =5/6.7=0.75. It will be appreciated that if the user wishes to dispense foam having a height of 5cm, the higher the H/W ratio, the smaller the width will be, which can save much space and cost to the user (6.7 cm width compared to 12 cm).

Claims (16)

1. A curable and foamable silicone composition comprising the following components:

a) A polydiorganosiloxane having at least two unsaturated groups per molecule, the unsaturated groups being selected from alkenyl groups or alkynyl groups;

b) An organosilicon compound having at least two, alternatively at least three, si-H groups per molecule;

c) One or more hydroxyl-containing blowing agents; and

d) A hydrosilylation catalyst comprising or consisting of a platinum group metal or a compound of a platinum group metal;

e) A thixotropic agent selected from the group consisting of silica, calcium carbonate, talc or mixtures thereof in an amount of from 2 to 5% by weight of the composition, and

f) A co-thixotropic agent comprising one or more silyl-modified polyethers in an amount of from 0.5% to 3% by weight of the composition.

2. The curable and foamable silicone composition of claim 1 wherein component c) one or more hydroxyl-containing blowing agents are selected from aliphatic organic alcohols having from 1 to 12 carbon atoms; aliphatic organic diols having 1 to 12 carbon atoms, benzyl alcohols and/or organosilanes and organosiloxanes having at least one silanol (Si-OH) group.

3. The curable and foamable silicone composition of any preceding claim wherein the or each silyl-modified polyether of co-thixotropic agent (f) is a polyether having a polyether backbone and at least two (R) per molecule ¹⁰ ) _m (Y ¹ ) _3-m Polymers of-Si groups, in which each R is ¹⁰ Being a hydroxyl group or a hydrolyzable group, each Y ¹ Is an alkyl group containing 1 to 8 carbons and m is 1,2 or 3.

4. The curable and foamable silicone composition of claim 3 wherein the co-thixotropic agent (f) isOr each of the one or more silyl-modified polyethers comprises a group selected from oxyethylene groups (-C) ₂ H ₄ -O-), an oxypropylene group (-C) ₃ H ₆ -O-), oxybutylene unit (-C) ₄ H ₈ -O-) or a mixture of any two or more thereof.

5. The curable and foamable silicone composition according to any preceding claim, wherein the composition may further comprise one or more additives selected from resin foam stabilizers, non-reinforcing fillers, reaction inhibitors, pigments or colorants, and mixtures thereof.

6. The curable and foamable silicone composition according to any preceding claim, wherein the composition is stored prior to use as a two-part a composition and a part B composition, the part a composition comprising components (a), (c) and (d) and optionally a part of thixotropic agent (e) and optionally one or more additives selected from: inhibitors, non-reinforcing fillers, pigments or colorants and/or MQ resin foam stabilizers; the part B composition comprises components (a), (B), part or all of component (e), and component (f).

7. A silicone foamed elastomer obtained or obtainable by mixing and curing the curable and foamable silicone composition according to any preceding claim.

8. A form-in-place foam gasket (FIPFG) comprising a cured product of the curable and foamable silicone composition of any one of claims 1 to 6.

9. The form-in-place foam gasket (FIPFG) of claim 8, having an aspect ratio of at least 0.625.

10. The Form In Place Foam Gasket (FIPFG) of claim 8 or 9, which is adhesively adhered to aluminum, stainless steel, concrete and Sheet Molding Composite (SMC) substrates.

11. A process for preparing a shaped-in-place foam gasket (FIPFG) by mixing and curing the curable and foamable silicone composition according to any one of claims 1 to 6.

12. The method for preparing a form-in-place foam gasket (FIPFG) according to claim 11, comprising the steps of:

(i) Mixing a part a composition comprising components (a), (c) and (d) and optionally a portion of thixotropic agent (e) and optionally one or more additives selected from the group consisting of: inhibitors, non-reinforcing fillers, pigments or colorants and/or MQ resin foam stabilizers; the part B composition comprises components (a), (B), part or all of component (e) and component (f);

(ii) (ii) conveying the foam prepared in step (i) to a suitable applicator;

(iii) Dispensing the resulting foam from the applicator onto a substrate surface; and

(iv) The foam was allowed to cure and provided a silicone foam elastomer FIPFG.

13. The process for making a shaped in place foam gasket (FIPFG) of claim 12, wherein said applicator is a pre-programmed or programmable robotic applicator.

14. Use of a curable and foamable silicone composition for the preparation of a foam-in-place gasket (FIPFG).

15. Use of a shaped in place foam gasket (FIPFG) according to claim 8, 9 or 10 as 14, comprising acting as a barrier against absorption or penetration of air, dust, noise, liquid, gaseous substances or dirt; sound damping, vibration damping, shock absorbing elements, moisture barriers, chemical protection, and/or external water barriers.

16. Use of a shaped in place foam gasket (FIPFG) according to claim 15 for automotive gasket applications selected from the group consisting of: a gasket for an electric vehicle battery pack, a gasket for a control unit in an electric vehicle, a light cover, a fuse box, an air filter, an oil pan gasket, an oil enclosure gasket, an oil screen gasket, a timing belt cover upper gasket, and/or a timing rocker cover lower gasket.