IE63399B1

IE63399B1 - Aqueous dispersion based on a silicone resin capable of crosslinking to an elastomer

Info

Publication number: IE63399B1
Application number: IE279389A
Authority: IE
Inventors: Michel Feder; Jean Ulrich
Original assignee: Rhone Poulenc Chimie
Priority date: 1988-08-31
Filing date: 1989-08-30
Publication date: 1995-04-19
Also published as: AU627217B2; PT91587A; KR900003306A; AU4086889A; JPH02105859A; JPH0645756B2; EP0359676A1; HUT53140A; IE892793L; DK175833B1; DE68910449T2; CN1030460C; EP0359676B1; CN1040997A; NO893437L; DK426689D0; FR2638166B1; ZA896630B; FI894073A; BR8904277A

Abstract

The present invention relates to an aqueous silicone dispersion which crosslinks to give an elastomer by elimination of water and which comprises: 100 parts of an emulsion (A) of the oil-in-water type, of an alpha , omega -(dihydroxy)polydiorganosiloxane stabilised with an anionic and/or nonionic surfactant, 1 to 100 parts of a hydroxylic silicone resin which, per molecule, exhibits at least 2 different units chosen from among those of the formulae R3SiO0.5, R2SiO, RSiO1.5 and SiO2 and having a content of hydroxyl groups of between 0.1 and 10% by weight, 0 to 250 parts of a non-siliceous inorganic filler and 0.01 to 3 parts of a metal compound which acts as a hardening catalyst, the said emulsion having a pH which is generally between 4 and 13 and a solids content of at least 40%. Use of the emulsions for the production of silicone elastomer joints, especially in the building industry.

Description

The present invention relates to aqueous dispersions based on a silicone resin capable of crosslinking to an elastomer.

US Patent US-A-2,891,920 describes a process for 5 emulsion polymerization of polydiorganosiloxane employing an acidic or basic catalyst in the presence of anionic, cationic or nonionic surface-active agents. This patent teaches that the emulsions obtained are stable in storage and, after addition of fillers, can be used to produce paints forming a continuous coating by elimination of water.

US Patent US-A-3,294,725 describes, in particular, the use of dodecylbenzenesulphonic acid in polymerizing polydiorganosiloxanes in emulsion. This patent teaches that, in order to obtain stable emulsions, it is desirable to control the pH of these emulsions at a value of approximately 7. This patent teaches that an elastomeric coating can be obtained from these neutralized emulsions, to which colloidal silica and a polyalkoxysilane have been added.

The teaching of US patent US-A-3,360,491 is similar to that of US-A-3,294,725, except that dodecylbenzenesulphonic acid is replaced by lauryl hydrogen sulphate.

US Patent US-A-3,355,406 describes, inter alia, a silicone latex comprising: r - a colloidal aqueous suspension of an α,w-(dihydroxy)polydiorganosiloxane, a filler essentially comprising a sesquisiloxane in the form of a colloidal suspension, - a catalyst which is an inorganic acid, a strong base, a dialkyltin diacylate or an organic or inorganic peroxide.

US Patent US-A-3,697,469 describes a particular process for emulsion polymerization of polydiorganosiloxanes and indicates the possibility of adding colloidal silica and a tin salt to this emulsion in order to obtain an elastomeric coating by evaporation of water.

French Patent FR-A-2,110,358 describes a silicone emulsion incorporating carbon black with a pH of between 6.5 and 9, which crosslinks to an electrically conductive elastomer after evaporation of water. The emulsion, additionally comprising a tin salt and a polyalkoxysilane, is not stable in storage and must be stored in two separate packages (two-component emulsion).

US Patents US-A-4,221,688 and US-A-4,244,849 and French Patent FR-A-2,463,163 describe silicone emulsions which are stable in storage and comprise: - an anionically stabilized emulsion of an a,w-(dihydroxy)polydiorganosiloxane polymer, a siliceous filler, - a tin salt, and if desired, a nonreinforcing filler.

The siliceous filler may be a colloidal silica (US-A-4,221,688), sodium silicate (US-A-4,244,849), or an amorphous silica in powder form (FR-A-2,463,163).

When compared with the known aqueous emulsions of the prior art, these three patents teach that, in order to obtain a single-component emulsion which is stable in storage, the emulsion must be kept at an alkaline pH higher than 8.5 or 9, preferably higher than 10. In addition, a tin salt must be incorporated in the emulsion to shorten to a few days the emulsion maturing stage needed to obtain an emulsion which is capable of crosslinking.

Silicone emulsions containing fillers, which are stored at an acidic or neutral pH, usually have one or more of the following disadvantages: they are not stable in storage when packaged in a single package (single-component composition); they take an excessively long time to cure to an elastomer; - they are not thixotropic; and/or - they adhere only very weakly to the usual substrates.

Aqueous emulsions or dispersions based on a silicone resin and capable of crosslinking to an elastomer by eliminating water have already been described.

Thus, US Patent US-A-3,355,406, already referred to, describes a silicone latex consisting of an a,w(dihydroxy)polydiorganosiloxane, prepared preferably by emulsion polymerization and of a sesquisiloxane resin consisting of RSiO15 units (hydrocarbon R residue). The latex may additionally comprise a metal cure catalyst and an alkyltrialkoxysilane.

In US Patent US-A-4,554,187, the silicone resin associated with the a,w-(dihydroxy)polydiorganosiloxane is a reactive resin of low molecular weight, containing alkoxy or acyloxy groups.

In European Patent Application EP-A-266,729, the silicone resin associated with the a,w-(dihydroxy)polydiorganosiloxane and with the cure catalyst is a siliconate.

EP-A-304,719, published on first March 1989, teaches the use, instead of the siliconate, of a silicone resin of high molecular weight, insoluble in toluene and present in the form of an aqueous emulsion in which the particle (micelle) size is greater than 200 nanometres.

A silicone resin comprising up to 10% by weight of hydroxyl group may be associated with this siliconate.

In what follows, the percentages and parts are on a weight basis, unless stated otherwise.

The present invention provides an agueous silicone dispersion (emulsion), having an acidic or basic pH, capable of crosslinking to an elastomer by elimination of water under ambient temperature, and which avoids one or more of the disadvantages of the known emulsions.

The new aqueous silicone dispersions are stable in storage and crosslink correctly and sufficiently quickly to an elastomer by elimination of water at ambient temperature. The elastomer formed retains its mechanical properties as it ages. The maturing stage of the silicone dispersion can be carried out at a slightly raised temperature (20-60°C) and for a period of less than 48 hours.

The aqueous silicone disperson of the invention lead to an elastomer which exhibits an improved flame resistance, together with satisfactory adhesion to various substrates, particularly to glass, concrete and metals (steel, aluminium).

The compositions of the present invention comprise, by weight: (A) - 100 parts of an emulsion of the oil-in-water type of an a,w-(dihydroxy)polydiorganosiloxane containing at least one surface-active agent chosen from anionic and nonionic surface-active agents and mixtures thereof, (B) - 1 to 100 parts of a hydroxylated silicone resin containing, per molecule, at least two different units chosen from those of formulae: J^SiOg^M, R2Sio(D), RSiOle5(T) and SiO2((P, in which each of the radicals R, which are identical or different is vinyl, phenyl 3,3,3-trifluoropropyl, or linear or branched alkyl radicals containing from 1 to 6 carbon atoms, the said resin having a hydroxyl group weight content of between 0.1 and 10%, (C) - 0 to 250 parts of a nonsiliceous inorganic filler, and (D) - 0.01 to 3 parts of a metal cure catalyst compound, the said dispersion having a solids content of at least 40%, and excluding the presence of a siliconate corresponding to the formula R' -Si (OM+) m (OH) 3_m and/or its condensation products formed by removal of water, in which formula R' denotes identical or different hydrocarbon radicals containing 1 to 18 carbon atoms and capable of optionally being halogen atoms, amino radicals, ether radicals, ester radicals, epoxy radicals, mercapto radicals, cyano radicals or poly(glycol) radicals, the latter consisting of oxyethylene and/or oxypropylene units, m denotes a whole or fractional number between 0.1 and 3, and M denotes an alkali metal cation, an ammonium radical or a phosphonium radical. la The a,w-(dihydroxy)polydiorganosiloxanes should have © a viscosity of at least 100 mPa s at 25°C, preferably of at least 50,000 mPa s. At viscosities above 50,000 mPa s an elastomer is obtained exhibiting a combination of appropriate mechanical properties, particularly in respect of Shore A hardness and of elongation. Furthermore, an increase in viscosity results in improved retention of mechanical properties as the elastomer ages. The preferred viscosities in the case of the present invention are between 50,000 and 1,500,000 mPa s at 25°C.

The organic radicals of the a,w-(dihydroxy)polydiorganosiloxanes are monovalent hydrocarbon radicals containing up to 6 carbon atoms each, optionally substituted by cyano or fluoro groups, the radicals which are generally employed because of their availability in industrial products are methyl, ethyl, propyl, phenyl, vinyl, and 3,3,3trifluoropropyl radicals. At least 80% of the number of these radicals are generally methyl radicals.

In the present invention it is more especially preferable to employ the a,w-(dihydroxy)polydiorganosiloxanes prepared by the anionic polymerization process described in the abovementioned US Patents: US-A-2,891,920 and, particularly, US-A-3,294,725 (which are mentioned as a reference). The polymer obtained is stabilized anionically with a surface-active agent which, in accordance with the teaching of US-A-3,294,725, is preferably an alkali metal salt of an aromatic hydrocarbon sulphonic acid, the free acid also acting as a polymerization catalyst.

The preferred catalyst and surface-active agent are dodecylbenzenesulphonic acid and its alkali metal salts, especially its sodium salt. If desired, other anionic or nonionic surface-active agents may be added. However, such additives are not essential because, in accordance with the teaching of US-A-3,294,725, the quantity of anionic surfaceactive agent resulting from the neutralization of the sulphonic acid is sufficient to stabilize the polymer emulsion. This quantity is generally less than 3%, preferably 1.5%, of the weight of the emulsion.

This emulsion polymerization process is particularly advantageous because it makes it possible to obtain the emulsion (A) directly. Furthermore, this process enables a,w-(dihydroxy)polydiorganosiloxane emulsions (A) of very high viscosity to be potentially obtained without difficulty.

To prepare the emulsion (A) it is also possible to start with an already polymerized a,w-(dihydroxy)polydiorganosiloxane, and then to convert it into an aqueous emulsion by stabilizing the emulsions with an anionic and/or nonionic surface-active agent according to a process which is well known to the specialist and described in detail in the literature (see, for example, French Patents FR-A-2,064,563, FR-A-2,094,322, FR-A-2,114,230 and European Patent Application EP-A-169,098).

According to this process, the a,w-(dihydroxy)polydiorganosiloxane polymers are mixed simply by stirring with the anionic or nonionic surface-active agent with the latter optionally in aqueous solution. Water is then added if necessary and the whole is converted into a fine and homogeneous emulsion by passing through a conventional colloid mill.

The millbase obtained is subsequently diluted with a suitable quantity of water and an emulsion (A) stabilized with an anionic or nonionic surface-active agent and stable in storage is thus obtained.

The quantity of anionic and nonionic surface-active agent which can be employed is that commonly employed for making use of the emulsification process, particularly those described in the abovementioned patents and in US-A2,891,920.

In the present invention, the preferred anionic surface-active agents are the alkali metal salts of aromatic hydrocarbon sulphonic acids. The preferred nonionic surfaceactive agents are polyoxyethylenated alkylphenols. These nonionic surface-active agents are obviously the same as those which may be added, if desired, to the emulsions (A) obtained by emulsion polymerization as indicated above.

The emulsion (A) prepared by emulsion polymerization or by emulsifying the silicone polymer is in the form of an oil-in-water emulsion and preferably has a solids content of more than 45% by weight.

From 1 to 100, preferably from 2 to 20 parts, calculated on a solids content basis, of a hydroxylated silicone resin (B) are incorporated per 100 parts of emulsion (A) .

The hydroxylated silicone resin (B) has a hydroxyl group weight content of between 0.1 and 10%, preferably between 1 and 6%.

This resin (B) contains, per molecule, at least two different units chosen from those of formulae: R3SiO0<5 (M unit), R2S1O (D unit), RSiO^.s (T unit) and S1O2 (Q unit). Methyl, ethyl, isopropyl, tert-butyl and n-hexyl radicals may be mentioned as examples of alkyl radicals R.

These silicone resins are known branched organopolysiloxane polymers and their methods of preparation are described in the patent literature. MQ resins, MDQ resins, TD resins and MDT resins may be mentioned as examples of suitable resins. Resins which are solid or liquid at ambient temperature may be employed. These resins may be incorporated in aqueous emulsions, in solution in an organic solvent or a silicone oil, or else in the form of aqueous emulsions.

It is recommended to employ liquid or solid silicone resins which have a relatively low average molecular mass for example, generally below 25,000 and which are soluble in toluene. Such resins may be of the MQ, MDQ, TD and MDT type.

Contrary to the teaching of EP 304,719, the silicone resins can be employed as such without being emulsified beforehand or without being necessarily prepared beforehand by emulsion polymerization. In addition, the aqueous emulsions of these resins do not necessarily need to have a particle size of at least 200 nanometres as taught by EP 304,719.

Aqueous emulsions of silicone resins which can be employed are described, for example, in Patents US-A4,028,339, US-A-4,052,331, US-A-4,056,492, US-A-4,525,502 and US-A 4,717,599, which are mentioned as a reference.

Another constituent of the dispersion according to the invention is the addition of 0 to 250, preferably of 5 to 200, parts of a semireinforcing or packing nonsiliceous inorganic filler (C). The fillers (C) have a particle size which is generally between 1 and 300 μτη and a BET surface area of less than 50 m2/g.

Examples of the fillers (C) which may be used individually or in a mixture are carbon black, titanium dioxide, aluminium oxide, hydrated alumina, expanded vermiculite, unexpanded vermiculite, calcium carbonate, zinc oxide, mica, talc, iron oxide, barium sulphate and slaked lime. These fillers (C) are introduced into the emulsion (A) in the form of dry powder, which may be for example, simply mixed in.

According to an alternative form of the invention, it has been found that if the filler (C) consists substantially only of hydrated alumina, expanded vermiculite and/or unexpanded vermiculite in a proportion of 5 to 250, preferably of 50 to 200, parts per 100 parts of emulsion (A), an elastomer is obtained which has a particularly high flame resistance which is not obtained with the other categories of filler (C) which are mentioned above, particularly with aluminium oxide or unhydrated alumina. Ceramic or aramide fibres may also be incorporated according to the teaching of EP-A-212,827.

The metal cure catalyst compounds (D) are essentially carboxylic acid salts and halides of metals chosen from lead, zinc, zirconium, titanium, iron, tin, barium, calcium and manganese. The constituent (D) is preferably a catalytic tin compound and generally an organotin salt. It is preferably introduced in the form of an aqueous emulsion. The organotin salts which can be used are described particularly in the work by Noll, Chemistry and Technology of Silicones, Academic Press (1968), page 337.

The reaction product of a tin salt, particularly of a tin dicarboxylate with ethyl polysilicate, as described in patent US-A-3,862,919, may also be employed as a catalytic tin compound. It is also possible to employ the reaction product of an alkyl silicate or of an alkyltrialkoxysilane with dibutyltin diacetate, as described in Belgian Patent BE-A-842,305.

The preferred tin salts are tin bischelates (EP-A147,323 and EP-A-235,049), diorganotin dicarboxylates and, in particular, dibutyl- or dioctyltin diversatates (British Patent GB-A-1,289,900), dibutyl- or dioctyltin diacetate, and dibutyl- or dioctyltin dilaurate. From 0.01 to 3, preferably from 0.05 to 2, parts of organotin salt are employed per 100 parts of (A).

As an alternative, a siliceous additive (E) chosen form sodium silicate (0.3 to 30 parts) and a reinforcing or semireinforcing siliceous filler (1 to 150 parts) may also be incorporated, per 100 parts of emulsion (A).

These siliceous fillers are chosen from colloidal silica or pyrogenic and precipitated silica powders or a mixture thereof. Pyrogenic silica is preferred. However, semireinforcing siliceous fillers such as diatomaceous earths and ground quartz may also be employed.

The sum of the parts of (C) + (E) should be less than 300 parts per 100 parts of emulsion (A).

Pyrogenic and precipitated silica powders are well known; they are employed particularly as fillers in silicone elastomer compositions which can be vulcanized to a silicone rubber by heating. These powders have a mean particle size which is generally below 0.1 gm and a BET specific surface are higher than 50 m2/g, preferably between 150 and 350 m2/g.

The incorporation of this siliceous additive (E) in the emulsion (A) by any suitable means, particularly by stirring, greatly increases the viscosity of the emulsion (A) which, as a result, has a paste-like consistency.

It has been found, in accordance with the present invention, that the addition of this siliceous additive (E) is sufficient to impart a more or less marked ’’thixotropic character to the dispersion. The emulsion, for example when extracted from a storage cartridge, adheres even to a vertical substrate without running and cures to an elastomer by evaporation of water at ambient temperature. An emulsion which does not flow can also be obtained by using calcium carbonate whose mean particle diameter is less than 0.1 gm as filler (C). Obviously, slight heating (to approximately 4080°C) of the composition to accelerate the evaporation of water is not excluded from the scope of the invention.

Various additives enabling the properties of emulsions and of the elastomers formed from the emulsions by elimination of water to be modified may be added to the dispersions of the present invention. It is possible to incorporate adhesion promoters (F), preferably organotrialkoxysilanes such as, for example, /-aminopropyltriethoxysilane, N-(aminoethyl)-y-aminopropyltrimethoxysilane, vinyltrimethoxysilane, alkyl silicates such as methyl silicate or ethyl silicate or a product of their partial hydrolysis, ie. alkyl polysilicates such as methyl polysilicate and ethyl polysilicate, in a proportion of 0.1 to 20 parts of adhesion promoter per 100 parts of emulsions (A) .

The organotrialkoxysilanes and the alkyl silicates preferably correspond to the general formula: R'aSi(OR2)4_a in which R2 is an alkyl radical containing from 1 to 4 atoms, R' may be identical to R2 or is a vinyl, ^-aminopropyl, or N(aminoethyl)-tf-aminopropyl radical and a is 1 or 0.

The dispersions according to the invention have a pH value which is generally between 4 and 13. This value depends on the nature of the ingredients constituting the dispersion, in particular on the level of the surfactant and of the catalyst in the emulsion (A) and on the level of the filler (C).

Depending on the applications which are envisaged, dispersions which have a pH of between 4 and 7 may be prepared by adding an inorganic or organic acid, preferably an oxygenated boron derivative. Dispersions which have a pH of between 7 and 13 may be prepared by adding an inorganic or organic base, as described in greater detail below.

Other examples of additives which may be mentioned are fungicides and foam suppressors, as well as thixotroping agents such as carboxymethyl cellulose, xanthan gum and polyvinyl alcohol.

The dispersions according to the invention may be employed, more particularly in the building industry, for producing caulking and seals.

The dispersions according to the invention may be prepared in the following manner: The starting point is an emulsion (A) prepared either by an emulsion polymerization process which gives an emulsion stabilized by an anionic and, if desired, nonionic surfaceactive agent, or by emulsifying an a,w(dihydroxy)polydiorganosiloxane to give an emulsion stabilized with an anionic and/or nonionic surface-active agent.

To prepare the dispersions it is recommended to add the metal cure catalyst compound (D), preferably in the form of an agueous emulsion, to the emulsion (A) at ambient temperature. The pH of the mixture may be adjusted to a value above 7, and generally below 13, by means of an inorganic or organic base, preferably by means of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide. Alternatively the pH may be adjusted to a value below 7 and above 4, by adding an appropriate quantity of an oxygenated boron derivative chosen from boric oxide, boric acids and borates.

Primary amines such as diethylamine may be employed as an organic base. However, preferably, the pH is adjusted with an appropriate quantity of an inorganic base introduced in the form of an aqueous solution preferably chosen from solutions of alkali metal and alkaline-earth metal hydroxides such as sodium hydroxide, potassium hydroxide, and solutions of calcium hydroxide, barium hydroxide and magnesium hydroxide. However, alkaline earth metal hydroxides may be introduced directly in a solid form.

Boric oxide is also called boric anhydride.

Orthoboric acid, metaboric acid and tetraboric acid may be mentioned as boric acids. Triorganoborates and inorganic borates can be employed as borates. Triethyl borate, triphenyl borate, tribenzyl borate, tricyclohexyl borate, trisroethylsilyl borate, tri(t-butyl) borate, diammonium tetraborate, ammonium pentaborate, sodium tetraborate decahydrate (borax), potassium pentaborate, magnesium diborate, calcium monoborate, barium triborate and zinc metaborate can be employed in the present invention. The products of partial hydrolysis of these borates may also be employed.

To adjust the final pH of the dispersion to a value of between 4 and 7 it is generally sufficient to add to the dispersion from 0.1 to 5 parts of an oxygenated boron derivative per 100 parts of emulsion (A).

The fillers (C) and, if desired (E), are added, followed by the resin (B), which may optionally be in organic solution or in a silicone oil, or otherwise in the form of an agueous emulsion.

A trimethylsilyl-blocked polydimethylsiloxane with a viscosity of between 100 and 5,000 mPa s at 25’C may be employed as a silicone oil.

The final emulsion obtained is homogenized and then degassed and is subseguently packaged in a package which is impervious to atmospheric oxygen and to water vapour.

The constituents (A), (B), (C), (D) and, if desired, (E) and (F) are mixed in such guantities that the final emulsion has a solids content of more than 40%, preferably more than 60%, but generally below 90%.

The dispersions according to the invention may be employed as a paint capable of crosslinking as a thin layer. They then preferably have a solids content of between 40 and %.

To determine the solids content, 2 g of dispersion are placed in an aluminium weighing dish and this is heated for one hour to 150’C in an oven with air circulation.

After cooling, the dish is reweighed and the residual material is determined as a percentage of the initial 2 g, representing the solids content.

According to a preferred alternative form of the invention, following the preparation process, the dispersion undergoes a maturing stage at ambient temperature or at a temperature between 20 and 90°C for a few hours to a few days. This maturing stage consists simply in heating, if desired, and allowing the dispersion to stand in the absence of atmospheric oxygen before use.

In what follows or what precedes, the percentages and parts are on a weight basis, unless stated otherwise.

The following Examples illustrate the invention.

- EXAMPLE 1: Preparation of the emulsion (A): this is obtained by emulsion polymerization of a,w(dihydroxy)polydimethylsiloxane oil having a viscosity of 100 mPa s at 25°C in the presence of dodecylbenzenesulphonic acid.

When the viscosity of the oil reaches 106 mPa s at 25°C the polymerization is stopped by neutralizing the catalyst.

The emulsion (A) obtained has a solids content of 59%. 1.5 parts of agueous emulsion (D) containing 37% by weight of dioctyltin dilaurate are added to 100 parts of emulsion (A) with stirring. 1.2 parts of diethylamine and 60 parts of filler (C), which is precipitated CaCO3 with a mean particle size of 0.07 Mm are then added. 8.3 parts of a toluene-soluble hydroxylated silicone resin (B) containing 1% by weight of hydroxyl groups and consisting of 2% by weight of CH3SiOle5 unit, 61.5% by weight of (CH3)2SiO unit and 36.5% by weight of (CH3)3SiO0>5 unit with a molecular mass of 4000 with an R/Si = 1.77 are added, as such, to the emulsion obtained.

The final dispersion obtained has a pH of 9.5. It is homogenized for 30 minutes and is then packaged in a package which is impervious to atmospheric oxygen and to water vapour.

After 4 days' storage, samples of the dispersion are spread out with a doctor blade to form a film 2 mm thick, which is left to dry for 7 days at ambient temperature.

The following mechanical properties of the dried film are measured: - the Shore A hardness (SAH) according to ASTM standard D 2240, - the tensile strength (TS) according to AFNOR standard T 46 002 corresponding to ASTM standard D 412, in MPa, - the elongation at break (EB) in % according to AFNOR standard T 46 002, - the elasticity modulus (EM) at 100% elongation according to AFNOR standard T 46 002, in MPa.

The mechanical properties of the product obtained are collated in Table 1 below.

- EXAMPLES 2 TO 3 The operating procedure of Example 1 is repeated except that the 8.3 parts of resin (B) are replaced by: u - in Example 2: 8.8 parts of a toluene- and xylenefr soluble resin containing 2.2% by weight of hydroxyl group, consisting of 70% by weight of CH3SiOle5 unit and 30% by weight of (CH3)2SiO unit with a molecular mass of 1300 and having an R/Si - 1.3. The final emulsion obtained has a pH of 8.5; " in Example 3: 4:1 parts of a solution, containing 70% by weight in toluene, of a resin containing 2.2% by weight of hydroxyl group, consisting of 73% by weight of c6H5siol.5 unit and 27% by weight of (CH3)2SiO unit and having an R/Si of 1.4. The final emulsion obtained has a pH of 8.5.

The mechanical properties of the products are collated in Table 1 below.

TABLE 1 EXAMPLES 1 2 3 SAH 13 16 10 TS (MPa) 1.27 1.36 1.38 EB (X) 1 021 1 020 1 306 EM (MPa) 0.17 0.20 0.12 - EXAMPLES 4 TO 6 The operating procedure of Example 1 is followed precisely, except that the 1.2 parts of diethylamine are replaced by: - in Example 4: 4 parts of an agueous solution containing 20% of potassium hydroxide. The final emulsion has a pH of 11; - in Example 5: 4 parts of a solution containing 20% of potassium hydroxide and 0.5 part of ethyl polysilicate (ethyl silicate 4 0®) . The pH is 11; - in Example 6: 4 parts of a solution containing 20% of potassium hydroxide and 1 part of ethyl polysilicate. The pH is 11. strand 4 mm in thickness is deposited onto a glass or concrete substrate. After 10 days, the adhesion of the elastomer found is assessed by pulling the strand manually.

The adhesion strength of the films has been classified in 3 categories: - good adhesion, ie. the strand cannot be parted from its substrate (marked ++), - average adhesion, ie. the strand peels off with difficulty and in small areas (marked +), - absence of adhesion, ie. the strand peels off easily (marked 0).

The mechanical properties of the products and the results of the adhesion tests are collated in Table 2 below.

TABLE 2 EXAMPLES 4 5 6 SAH 15 23 27 TS (MPa) 1.76 1.2 1.67 EB (%) 986 730 704 EM (MPa) 0.19 0.29 0.45 Glass adhes ion + + + + + Concrete adhesion + + + - EXAMPLE 7 The operating procedure of Example 1 is repeated, except that: - the 8.3 parts of MDT resin are replaced by 7 parts of an MQ resin in solution in toluene, which has 2% by weight of hydroxyl group and consists of 50% by weight of M unit and 50% by weight of Q unit having a molecular mass of 10,000 and an R/Si of 1.3, and - the 1.2 parts of diethylamine are replaced by 4 parts of a solution containing 20% by weight of potassium hydroxide.

The mechanical properties of the product obtained and the assessment of adhesion are collated in Table 3 below.

- EXAMPLE 8: The operating procedure of Example 7 is repeated and, in addition, 1 part of ethyl polysilicate (ethyl silicate 4C@) is added.

- EXAMPLE 9: The operating procedure of Example 2 is repeated except that: a) - the 1.2 parts of diethylamine are replaced by 0.59 part of boric acid, (b) - the 1.5 parts of catalysing emulsion (D) are replaced by 1.5 parts of catalysing emulsion containing 37% by weight of a tin compound which is the reaction product of one mole of dioctyltin oxide with one mole of versatic acidR with elimination of the water formed, c) - a maturing stage of 2 hours 30 minutes at 80°C is carried out on the dispersion obtained before the dispersion is packaged in a sealed package.

The mechanical properties of the products obtained are collated in Table 3 below; TABLE 3 EXAMPLES 7 8 9 SAH 7 13 16 IS 0.9 0.36 1.0A EB 1 377 680 1 010 EM 0.15 0.2 0. 19 Glass adhesion + + + + Cone rete adhes ion ♦ + + -

Claims

1. An aqueous silicone dispersion capable of crosslinking to an elastomer by elimination of water under ambient conditions, which comprises, by weight: (A) - 100 parts of an emulsion of the ,oil-in water type of an a,w-(dihydroxy)polydiorganosiloxane containing at least one surface-active agent chosen from anionic and nonionic surface-active agents and mixtures thereof, (B) - 1 to 100 parts of a hydroxylated silicone resin containing, per molecule, at least two different units chosen from those of formulae: R3SiO 0> 5( M ), R 2 SiO( D ), RSiO 1>5 ( T ) and SiO 2 ( Q ), in which each of the radicals R, which are identical or different is vinyl, phenyl, 3,3,3-trifluoropropyl, or linear or branched alkyl radicals containing from 1 to 6 carbon atoms, the said resin having a hydroxyl group weight content of between 0.1 and 10%, (C) - 0 to 250 parts of a nonsiliceous inorganic filler, and (D) - 0.01 to 3 parts of a metal cure catalyst compound, I* 26a the said dispersion having a solids content of at least 40%, and excluding the presence of a siliconate corresponding to the formula R'-Si (O'M + ) m (OH) 3 _ m and/or its condensation products formed by removal of water, in which formula R' denotes identical or different hydrocarbon radicals containing 1 to 18 carbon atoms and capable of optionally being halogen atoms, amino radicals, ether radicals, ester radicals, epoxy radicals, mercapto radicals, cyano radicals or poly(glycol) radicals, the latter consisting of oxyethylene and/or oxypropylene units, m denotes a whole or fractional number between 0.1 and 3, and M denotes an alkali metal cation, an ammonium radical or a phosphonium radical.

2. An aqueous silicone dispersion according to claim 1 wherein the emulsion (A) has a solids content of at least 45% by weight.

3. An aqueous silicone dispersion according to claim f· ‘•f :v * V · >5 - 27 1 or 2 wherein the emulsion (A) has a viscosity at 25°C of between 50,000 and 1,500,000 mPas.

4. An aqueous silicone dispersion according to any one of claims 1 to 3 wherein the surface-active agent is an alkali metal salt of an aromatic hydrocarbon sulphonic acid or a polyoxyethylenated alkylphenol.

5. An aqueous silicone dispersion according to any one of claims 1 to 4 wherein the emulsion (A) comprises a,w - (dihydroxy)polydimethylsiloxane oil and a surface active agent.

6. An aqueous silicone dispersion according to any one of claims 1 to 5 wherein the resin (B) is a MQ, MDQ, TD or MDT resin or a mixture thereof.

7. An agueous silicone dispersion according to any one of claims 1 to 6 wherein the resin (B) is a toluenesoluble liquid or solid resin with an average molecular mass below 25,000.

8. An aqueous silicone dispersion according to any one of claims 1 to 7 which comprises from 2 to 20 parts of hydroxylated silicone resin (B).

9. An agueous silicone dispersion according to any one of claims 1 to 8, which comprises from 5 to 200 parts by weight of filler (C).

10. An agueous silicone dispersion according to any one of claims 1 to 9 which comprises from 50 to 200 parts of an inorganic filler (C).

11. An aqueous silicone dispersion according to any one of claims 1 to 10 wherein the filler (C) comprises hydrated alumina, alumina, calcium carbonate, expanded vermiculite, unexpanded vermiculite, carbon black, zinc 5 oxide, titanium dioxide, mica, talc, iron oxide, barium sulphate, slaked lime or mixtures thereof.

12. An aqueous silicone dispersion according to Claim 11, wherein the calcium carbonate has a mean particle diameter of less than O.lgm. 10

13. An aqueous silicone dispersion according to any one of claims 1 to 12, wherein the metal cure catalyst (D) is an aqueous emulsion of an organotin salt.

14. An aqueous silicone dispersion according to any one of claims 1 to 13 which comprises from 0.05 to 2 parts of 15. A diorganotin dicarboxylate (D).

15. An aqueous silicone dispersion according to any one of claims 1 to 14 wherein the said dispersion has a solids content of at least 60%.

16. An aqueous silicone dispersion according to any 20 one of claims 1 to 15 which comprises, per 100 parts of an emulsion (A), a siliceous additive (E) of sodium silicate (0.3 to 30 parts) and/or a reinforcing or semireinforcing siliceous filler, (1 to 150 parts), wherein the ratio of the parts of [(C) + (E)) to (A) is less than 3:1.

17. An aqueous silicone dispersion according to any one of claims Ito 16, which additionally comprises from 0.01 to 20 parts by weight of an adhesion promoter (F) which is an organotrialkoxysilane, an alkyl silicate or an alkyl 5 polysilicate.

18. An aqueous silicone dispersion according to any one of claims 1 to 17 which comprises from 0.1 to 5 parts of an oxygenated boron derivative per 100 parts of emulsion (A).

19. An agueous silicone dispersion substantially as 10 described in any one of Examples 1 to 9.

20. An elastomer seal which comprises an aqueous silicone dispersion according to any one of claims 1 to 19 which has been cured.