EP1401992A1

EP1401992A1 - Method for preparing a lubricating composition based on polysiloxanes not releasing hydrogen

Info

Publication number: EP1401992A1
Application number: EP02745465A
Authority: EP
Inventors: Gérald GUICHARD; Ian Hawkins
Original assignee: Rhodia Chimie SAS
Current assignee: Rhodia Chimie SAS
Priority date: 2001-05-23
Filing date: 2002-05-22
Publication date: 2004-03-31
Also published as: FR2825099A1; CA2446627A1; WO2002094971A1; JP4313047B2; US20040209785A1; FR2825099B1; JP2004531413A; US7439211B2

Abstract

The invention concerns a method for preparing a lubricating composition, characterised in that it comprises mixing two previously prepared oil-in-water emulsions (A) and (B): the prior emulsion (A) comprises: (a) at least a non-reactive linear polyorganosiloxane oil comprising per molecule at least 2 % in number of organic substituents bound to the silicon atoms which are aryl, alkylarylene and/or arylenealkyl radicals; (b) at least a polyorganosiloxane resin bearing hydroxyl groups and comprising at least two different siloxyl units selected among those of formula (R1)3SiO1/2(M), (R1)2SiO2/2(D), R1SiO3/2(T) and SiO4/2(Q), one at least of said units being a unit T or Q, R1 representing an organic substituent; (c) at least a crosslinking agent soluble in the silicone phase comprising at least two functions capable of reacting with the polyorganosiloxane resin(s) (b); (d) a condensation catalyst capable of catalysing the reaction of the constituent (b) with the constituent (c); (e) a surfactant; and (f) water; the prior emulsion (B) comprises: (a') at least a reactive linear polyorganosiloxane oil comprising at least two OH groups per molecule, and the constituents (b), (c), (d), (e) and (f) mentioned above; each of the prior emulsions (A) and (B) comprises: 5 to 95 parts by weight of constituent (a) or (a'); 0.5 to 50 parts of constituent (b); 0.1 to 20 parts of constituent (c); 0.05 to 10 parts of constituent (d); for 100 parts of the sum (a) + (b) + (c) + (d) or (a') + (b) + (c) + (d); the amounts of surfactant and water being sufficient to obtain an oil-in-water emulsion; and the weight ratio emulsion (A)/emulsion (B) ranges between 1.5 and 4.

Description

PROCESS FOR THE PREPARATION OF A LUBRICANT COMPOSITION BASED ON POLYSILOXANES WHICH DOESN'T RELEASE HYDROGEN

the invention relates to an improved process for the preparation of a lubricating composition, suitable in particular for the lubrication of vulcanization bladders used during the shaping and vulcanization of pneumatic or semi-pneumatic tires. The invention also relates to the lubricant compositions thus obtained. It also relates to their use for the lubrication of various articles, in particular vulcanization bladders as well as pneumatic or semi-pneumatic tires. It also relates to various articles, in particular vulcanization bladders as well as pneumatic or semi-pneumatic tires, coated with said lubricating composition.

Rubber tires for vehicles are usually manufactured by molding and vulcanizing a raw (or unvulcanized) and unshaped casing, in a molding press in which the raw casing is pressed outward against the surface of a mold. by means of an internal fluid expandable bladder. By this method, the raw envelope is shaped against the external surface of the mold which defines the design of the tread of the envelope and the configuration of the sides. By heating, the envelope is vulcanized. In general, the bladder is expanded by the internal pressure supplied by a fluid such as hot gas, hot water and / or steam, which also participates in the transfer of heat for vulcanization. The envelope is then allowed to cool a little in the mold, this cooling being sometimes favored by the introduction of cold or cooler water into the bladder. Then the mold is opened, the bladder is deflated by releasing the pressure of the internal fluid and the envelope is removed from the envelope mold. This use of shell vulcanization bladders is well known in the art.

It is recognized that there is a significant relative movement between the external contact surface of the bladder and the internal surface of the envelope during the expansion phase of the bladder before the vulcanization of the envelope is complete. Likewise, there is also considerable relative movement between the external contact surface of the bladder and the vulcanized internal surface of the envelope, after the envelope has been molded and vulcanized, during deflation and extraction. of the bladder of the tire.

If adequate lubrication is not provided between the bladder and the inner surface of the envelope, the bladder generally tends to curl, which results in deformation of the envelope in the mold and also excessive wear and etching. from the surface of the bladder itself. The surface of the bladder also tends to stick on the inner surface of the envelope after the vulcanization of the envelope and during the part of the vulcanization cycle of the envelope during which the bladder is deflated. In addition, air bubbles can be trapped between the surfaces of the bladder and the envelope, and favor the appearance of vulcanization defects in the envelopes resulting from an inadequate heat transfer.

For this reason, the external surface of the bladder or the internal surface of the raw or unvulcanized casing is coated with an appropriate lubricant, sometimes referred to as "jacketing cement", so as to facilitate sliding, and thus minimizing the risks of sticking, between the external surface of the bladder and the internal surface of the raw envelope. In addition to excellent sliding properties, the various qualities which one should expect from a good lubricating composition are to have excellent durability properties (the durability of a lubricating composition corresponds to the number of tires produced without degradation of the external surface of the bladder) and excellent elasticity properties (marked by a tensile elongation at break of the film of crosslinked lubricating composition, at least equal to 200%, measured according to standard AFNOR-T 46002).

Numerous lubricant compositions have been proposed for this purpose in the art.

The lubricant compositions described in FR-A-2 494 294 are known in particular, which contain, as main constituents, a reactive polydimethylsiloxane preferably having hydroxyl end groups, a crosslinking agent preferably comprising Si-H functions and optionally a polycondensation catalyst.

Examples of crosslinking agent with Si-H function (s) are methyltrihydrogénosiiane and diméthyldihydrogénosilane. The disadvantage of lubricating compositions of this type is their instability on storage. There is indeed a creaming of the emulsion following the evolution of hydrogen during transport and storage of the lubricant composition. The evolution of hydrogen responsible for the instability of the compositions of the prior art results essentially from the decomposition of the constituents with Si-H function (s).

The preparation of lubricant compositions from constituents which do not include the Si-H function, and which moreover have excellent sliding properties, durability and elasticity is therefore highly desirable.

The compositions which are the subject of EP ^ A-0 635 559 are lubricating compositions based on polysiloxanes which partly meet these requirements. These compositions are in particular more stable in that they do not give off hydrogen during storage. These compositions, which are in the form of emulsions, comprise, as essential constituents, a non-reactive polydimethylsiloxane, a reactive polydimethylsiloxane, preferably with hydroxy or alkoxy termination and a crosslinking agent based on a hydrolysable organosilane. Their durability is however insufficient for practical use in the production of pneumatic or semi-pneumatic tires.

The present invention provides an improved process for the preparation of an improved lubricating composition which does not release hydrogen and which, moreover, has excellent sliding, durability and elasticity properties, which makes them perfectly suitable in particular for the lubrication of vulcanization bladders used during shaping and vulcanization of pneumatic and semi-pneumatic tires.

More specifically, the present invention relates to a process for the preparation of a lubricating composition in the form of an oil-in-water emulsion, characterized in that it comprises the direct mixing of two oil-in-water emulsions (A) and (B) made beforehand, said prior emulsions (A) and (B) meeting the following characteristics of constitution (i) to (4i): (i) the prior emulsion (A) comprises:

(a) at least one non-reactive linear polyorganosiloxane oil with lubricating properties, having a dynamic viscosity of the order of 5.10 ^"2 to 30.10 ²

Pa.s at 25 ° C and consisting of a linear homopoiymer or copolymer:

- of which, per molecule, the monovalent organic substituents, identical or different from one another, bonded to silicon atoms are chosen from alkyl, cycoalkyl, alkenyl, aryl, alkylarylene and arylalkylene radicals,

- And, preferably, of which, per molecule, at least 2% by number of said monovalent organic substituents linked to silicon atoms are aryl, alkylarylene and / or arylalkylene radicals;

(b) at least one polyorganosiloxane resin carrying, before emulsification, of condensable hydroxyl substituents and comprising before emulsification at least two different siloxy units chosen from those of formula (R ¹ ) ₃ SiOι / ₂ (M); (R ¹ ) ₂ Siθ _2/2 (D); R Si0 ₃₂ (T) and Si0 _4/2 (Q), at least one of these units being a T or Q unit, formulas in which R ¹ represents a monovalent organic substituent, the average number per molecule of organic radicals R ¹ for a silicon atom being between 1 and 2; and said resin having a content by weight of hydroxyl substituents ranging from 0.1 to 10% by weight, and preferably from 0.2 to 5% by weight; (c) at least one crosslinker soluble in the silicone phase comprising at least two functions capable of reacting with the (or) resin (s) polyorganosiloxane (s) (b);

(d) a condensation catalyst capable of catalyzing the reaction of component (b) with component (c);

(e) a surfactant; and

(f) water,

(2i) the prior emulsion (B) comprises:

(a ') at least one reactive linear polyorganosiloxane oil comprising at least two OH groups per molecule and having a dynamic viscosity ranging from 5.10 ^{' 2} to 30.10 ² Pa.s at 25 ° C; and the constituents (b), (c), (d), (e) and (f) mentioned above with regard to the constitution of the prior emulsion (A); (3i) each of the previous emulsions (A) and (B) has the following composition by weight, the composition by weight of (A) possibly being identical or different from that of (B):

- from 5 to 95 parts by weight of the constituent (a) for the emulsion (A) or of the constituent (a ¹ ) for the emulsion (B);

- from 0.5 to 50 parts by weight of component (b); - from 0.1 to 20 parts by weight of the constituent (c);

- from 0.05 to 10 parts by weight of the constituent (d); per 100 parts by weight of the sum of the constituents (a) + (b) + (c) + (d) or (a ¹ ) + (b) + (c) + (d); the quantities of surfactants and of water being sufficient for obtaining an oil-in-water emulsion; and

(4i) the emulsion (A) / emulsion (B) weight ratio, at the time of mixing the pre-emulsions, is in the range from 1.5 to 4, preferably from 1.8 to 3, and so more preferred from 2.1 to 2.6.

The constituents (a), (a ¹ ), (b), (c), (d) and (e) of the emulsions are defined with reference to their initial chemical structure, that is to say that which characterizes them before emulsification.

As soon as they are in an aqueous medium, the structure of the constituents is liable to be greatly modified following the hydrolysis and condensation reactions.

By dynamic viscosity is meant in the context of the invention the Newtonian type viscosity, that is to say the dynamic viscosity, measured in a manner known per se at a given temperature, at a sufficiently low shear rate gradient so that the viscosity measured is independent of the speed gradient. Each of the non-reactive polydiorganosiloxane oils of component (a) has a dynamic viscosity generally between 5.10 ^"2 and 30.10 ² Pa.s at 25 ° C. Preferably, the dynamic viscosity varies between 5.10 ^{" 2} and 30 Pa.s, better still between 0.1 and 5 Pa.s. In the context of the invention, the term "non-reactive" means an oil which, under the conditions of emulsification, preparation of the lubricating composition and use, does not react chemically with any of the constituents of the composition.

By way of preferred constituent (a), mention may be made of linear polyorganosiloxanes:

- formed along each chain: • units of formula R ² R ³ Si0 ₂₂ , possibly associated with units of formula (R ² ) ₂ Si0 _2/2 ,

• of the units of formula (R ^ SiO ^, optionally combined with units of formula (R ²⁾ ₂ SiO _{_2/2,} and

• of the units of formula R ² R ³ and Si0 ₂₂ units of formula (R ³⁾ ₂ Si0 _2/2, optionally combined with units of formula (R ²⁾ ₂ SiO _{_2/2,}

- And blocked at each end of the chain by a motif of formula (R) ₃ SiOι _{/ 2 in} which the radicals R ⁴ , which are identical or different, are radicals R ² and R ³ ;

- where the radicals R ² and R ³ , monovalent organic substituents of the various siloxyl units mentioned above, have the following definitions: • the radicals R ² , identical or different from each other, are chosen from: linear or branched alkyl radicals in CτC ₆ (such as for example methyl, ethyl, propyl, isopropyl, butyie, isobutyl, t-butyl, n-pentyl, n-hexyl), C ₃ -C ₈ cycloalkyl radicals (such as for example cyclopentyl, cyclohexyl), and linear or branched C ₂ -C ₈ alkenyl radicals (such as for example vinyl, allyl),

• the radicals R ³ , identical or different from each other, are chosen from: aryl radicals C ₆ -C ₁₀ (such as for example phenyl, naphthyl), alkylarylene radicals C ₆ -Cι ₅ (such as for example tolyls , xylyl), C ₆ -C ₅ arylalkylene radicals (such as for example benzyl); and - where 5 to 50%, and better still 8 to 35%, in number of the substituents R ² , R ³ and R ⁴ are aromatic radicals R ³ .

The presence in the polyorganosiloxane (s) forming the constituent (a), in admixture with the siloxylated conforming units mentioned above, of units of different structure, for example of formula R Si0 _{3 2} and / or Si0 ₂ n ' is not excluded in the proportion of at most 2% (this% expressing the number of units R ⁴ Si0 _3/2 and / or Si0 _4/2 for

100 silicon atoms). More preferably, component (a) consists of at least one linear polyorganosiloxane:

- formed along each chain:

• units of formula R ² R ³ Siθ ₂₂ associated with units of formula (R ^ SiO ^, • units of formula (R ^ SiO ^ associated with units of formula (R ² ) ₂ Si0 ₂₂ ;

- And blocked at each chain end with a motif of formula (R ² ) ₃ Si0 _{1 2} ;

- where the radicals R ² and R ³ have the following definitions:

• the radicals R ² , identical or different between them, are chosen from the methyl, ethyl, propyl and isopropyl radicals, “the radicals R ³ , identical or different from each other, are chosen from the phenyl, tolyl and benzyl radicals; and

- where 5 to 50%, and better still 8 to 35%, in number of the substituents R ² and R ³ are phenyl, tolyl and / or benzyl radicals.

Advantageously, at least one linear polyorganosiloxane is used as constituent (a) having, per molecule, a ratio (in number) of aromatic substituents R ³ / Si at least equal to 0.04, preferably ranging from 0.09 to 1 and better going from 0.16 to 0.7.

Component (a) is generally introduced into the prior emulsion (A) at a rate of 5 to 95 parts by weight per 100 parts by weight of the mixture of constituents (a) + (b) + (c) + (d), preferably 50 to 95, more preferably 75 to 95.

Each of the reactive linear polydiorganosiloxane oils of component (a ¹ ) having at least two OH groups per molecule, has a dynamic viscosity at 25 ° C generally between 5.10 ^"2 and 30.10 ² Pa.s. Preferably, the viscosity varies between 5.10 ² and 30 Pa.s, better still between 0.1 and 5 Pa.s. In the context of the invention, the term "reactive" designates the reactivity of the constituent

(a ¹ ) with regard to the crosslinking agents (c) and / or (g) present in the prior emulsions (A) and (B); the optional component (g) will be defined later in this specification.

Preferably, the constituent (a ¹ ) reacts with the crosslinking agent under the conditions for preparing the emulsion. The monovalent organic substituents of the oil (a ') are: linear or branched alkyl radicals; linear or branched alkenyl radicals; cycloalkyl or cycloalkenyl radicals; cycloalkylalkylene or cycloalkenylalkylene radicals; these radicals are optionally substituted by -OH and / or amino (optionally substituted) and / or halogen and / or cyano groups. The substituent of the amino group can be an alkyl radical, a cycloaikyl radical or a cycloalkyialkylene radical. Mention may be made, as halogen, of chlorine, fluorine, bromine or iodine, fluorine being more specifically suitable.

Advantageously, the organic substituents of (or) oil (s) (a ′) are: CC ₆ alkyl radicals; C ₃ -C ₈ cycloalkyls; C ₂ -C ₈ alkenyls; or C ₅ -C ₈ cycloalkenyl; said radicals optionally substituted with hydroxyl and / or amino (optionally substituted), and / or halo, and / or cyano.

The substituents of the amino group are for example: (d-CeJalkyle; (C ₂ -C ₈ ) alkenyl; (C ₃ -C ₈ ) cycloalkyle.

As preferred constituent (a ¹ ), mention may be made of linear polyorganosiloxanes of formula:

in which n is an integer greater than or equal to 10, R ⁵ and R ⁶ , identical or different, represent: (CC ₆ ) alkyl; (C ₃ -C ₈ ) cycloalkyl; (C ₂ -C ₈ ) alkenyl; (C ₅ -C ₈ ) cycloalkenyl; each of the aforementioned radicals being optionally substituted with a halogen atom (and preferably fluorine) or a cyano residue.

The oils of component (a ¹ ) most used, because of their availability in industrial products, are those for which R ⁵ and R ⁶ are independently chosen from methyl, ethyl, propyl, isopropyl, cyclohexyl, vinyl and 3.3 3-trifluoropropyie. Very preferably, 80% by number of these radicals are methyl radicals.

In practice, preference will be given, as oil (s) (a '), to α, ω-dihydroxypolydimethylsiloxanes, and in particular oils of this type prepared by the anionic polymerization process described in the aforementioned American patents: US 2 891,920 and especially US 3,294,725 (cited as reference). The constituent (a ') is introduced into the prior emulsion (B) at a rate of 5 to

95 parts by weight per 100 parts by weight of the mixture of the constituents

(a ¹ ) + (b) + (c) + (d), preferably at a rate of 50 to 95, better still at a rate of 75 to 95.

Component (b) is formed of at least one polyorganosiloxane resin, carrier before emulsification of condensed hydroxyl groups. In the constituent units of these resins, each substituent R ¹ represents a monovalent organic group. In general, R ¹ is a Cι-C ₂₀ hydrocarbon radical optionally carrying one or more substituents.

Examples of hydrocarbon radicals are: an alkyl radical, linear or branched, having from 1 to 6 carbon atoms; an alkenyl radical, linear or branched, having from 2 to 8 carbon atoms; a cycloaikyl radical having from 3 to 8 carbon atoms; or a cycloalkenyl radical having 5 to 8 carbon atoms.

The substituents of the hydrocarbon radical may be groups -OR 'or -O-CO-R' in which R 'is a hydrocarbon radical as defined above for R ¹ , unsubstituted. Other substituents of the hydrocarbon radical can be amino, amidated, epoxidized or ureido functions.

By way of example of substituents of the hydrocarbon radical, there are the amino functions of formula:

• -R _a -NR ⁷ R ⁸ in which: R _a represents a valential bond or represents a divalent alkylene radical, linear or branched, in C C-io; and R ⁷ and R ⁸ independently represent: H; a (C -, - C ₆ ) alkyl radical; a (C ₃ -C ₈ ) cycloalkyl radical; or an (C ₆ -Cι ₀ ) aryl radical;

• -R _b -NH-R _c -NR ⁷ R ⁸ in which R _b and R _c , identical or different, are as defined for R _a above; and R ⁷ and R ⁸ are as defined above;

• the formula function:

in which R ⁹ and R ¹¹ , identical or different, represent:

(CC ₃ ) aikyle and for example methyl; or (C ₆ -C ₁₀ ) aryl and for example phenyl;

R ¹⁰ represents: a hydrogen atom; (Cι-C ₆ ) alkyl, for example methyl; (C ₂ -C ₇ ) alkylcarbonyl; (C ₆ -Cι ₀ ) aryl and for example phenyl; (C ₆ -C ₁₀ ) aryl- (C CeJalkylène and for example benzyl; or alternatively R ¹⁰ represents O; and • the function of formula:

in which R ⁹ and R ¹⁰ are as defined above. It is however preferable that the concentration of -OR ′, -O-CO-R ′, amino, amidated, epoxidized or ureido functions, when they are present in the resin, is limited, so as not to exceed the tolerance threshold beyond which the stability of the emulsion would be compromised.

The silicone resins (b) are well-known branched organopolysiloxane polymers whose methods of preparation are described in numerous patents. As concrete examples of resins which can be used, mention may be made of MQ, MDQ,

DQ, DT and hydroxylated MDT and mixtures thereof. In these resins, each OH group is carried by a silicon atom belonging to an M, D or T motif.

Preferably, as examples of resins which can be used, mention may be made of hydroxylated organopolysiloxane resins not comprising, in their structure, a Q motif. More preferably, mention may be made of hydroxylated DT and MDT resins comprising - at least 20% by weight of T units and having a weight content of hydroxyl group ranging from 0.1 to 10% and better still from 0.2 to 5%. In this group of more preferred resins, those where the average number of substituents R ¹ for a silicon atom is comprised, per molecule, between 1.2 and 1.8, are more particularly suitable. Even more advantageously, resins of this type are used, in the structure of which at least 80% by number of the substituents R ¹ are methyl radicals.

The resin (b) is liquid at room temperature. Preferably, the resin has a dynamic viscosity at 25 ° C of between 0.2 and 200 Pa.s.

The resin is incorporated in the preliminary emulsions (A) and (B) in an amount of 0.5 to 50 parts by weight per hundred parts by weight of the sum of the constituents (a), (b), (c) and (d ) or (a ¹ ), (b), (c) and (d), preferably at a rate of 3 to 30, better still from 5 to 15 parts by weight.

Component (c) consisting of at least one crosslinker soluble in the silicone phase comprises at least two functions capable of reacting with the resin (s) (b) so as to cause crosslinking of the resin (s) (s). Advantageously, said reactive functions of the crosslinker react with the resin under the conditions for preparing the emulsion. By way of preferred constituent (c), mention may be made of the crosslinking agents of formula:

Y _a Si (Zi) _4-a in which: a is 0, 1 or 2; - Y is a monovalent organic group; and the groups Zi, identical or different, are chosen from: -OX _a , - o— ç— Xb o and -0-N = CX ₁ X ₂ , in which X _a , X _b , Xi and X ₂ are independently of linear or branched C ₁ -C ₁₀ alkyl radicals; it being understood that X ^ and X ₂ may also represent hydrogen and that X _a is a radical optionally substituted by (CC ₃ ) aicoxy.

According to a more preferred embodiment of the invention, a represents 0 or 1, so that the crosslinker has the formula: Si (Zi) ₄ or YSi (Zi) ₃ .

More preferably, the groups Zi are identical to each other. A more preferred group of crosslinkers is formed in particular by all of the organotrialcoxysilanes, organotriacyloxysilanes, organotrioximosilanes and tetraaikylsilicates.

As regards the Y groups, the radicals are chosen more particularly: (C CeJalkyle; (C ₂ -C ₈ ) alkenyl; (C ₃ -C ₈ ) cycloalkyle; (C ₆ -Cι ₀ ) aryl; (C ₆ -C ₁₅ ) alkylarylene; or (C ₆ -C ₁₅ ) arylalkylene.

By way of example of groups Y, mention may be made of methyl, ethyl, vinyl or phenyl radicals.

The Zi groups are advantageously chosen from (CτC ₁₀ ) alkoxy; ; (C-ι-C ₁₀ ) alkylcarbonyloxy; or an oxime group -0-N = CX ₁ X ₂ in which X ₁ and X ₂ are independently H or (CrC- ^ alkyl.

Preferably, Zi represents methoxy, ethoxy, propoxy, methoxyethoxy, acetoxy or an oxime group.

As especially preferred constituent (c), mention may be made of the alkyltrialkoxysilane (s) of formula YSi (Zi) ₃ in which Y is (C ^ CeJalkyle ou (C ₂ -C ₈ ) alkenyl and Zi is ( CiC-io) alkoxy.

Among these, mention may be made of methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane and / or vinyltrimethoxysilane.

Each prior emulsion (A) and (B) comprises from 0.1 to 20 parts by weight, per hundred parts by weight of the sum of the constituents (a) + (b) + (c) + (d) or (a ¹ ) + (b) + (c) + (d), of the constituent (c), preferably from 0.2 to 10 parts by weight, better still from 0.5 to 5. The condensation catalyst (d) is chosen from those conventionally used in the art for catalyzing the crosslinking of resins of type (b) using crosslinking agents of type (c) defined above.

Examples of catalysts which can be used in the context of the invention are organometail salts, and titanates such as tetrabutyl orthotitanate. As the organometallic salt, there may be mentioned zirconium naphthenate and zirconium octylate.

Said catalyst is preferably a tin catalytic compound, generally an organotin salt. The organotin salts which can be used are described in particular in the work by

NOLL, Chemistry and Technology of Silicones Académie Press (1968), page 337. One can also define as catalytic compound with tin, either distannoxanes, or polyorganostannoxanes, or the reaction product of a tin salt, in particular of a tin dicarboxylate on ethyl polysilicate, as described in US-A-3,862,919.

The reaction product of an alkyl silicate or an alkyltrialkoxysilane on (dibutyltin diacetate as described in Belgian patent BE-A-842,305 may also be suitable.

Alternatively, a tin II salt, such as SnCI ₂ or stannous octoate, is used.

Advantageously, the catalyst is the tin salt of an organic acid, such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctate, zinc naphthenate, cobalt naphthenate, zinc octylate, cobalt octylate and dioctyltin di (isomercaptoacetate). The preferred tin salts are the tin bischelates (EP-A-147 323 and

EP-A-235 049), diorgano-tin dicarboxylates and, in particular, dibutyl- or dioctyltin diversatates (British patent GB-A-1 289 900, dibutyl- or dioctyltin diacetate, dibutyl dilaurate) or dioctyltin or the hydrolysis products of the precipitated species (for example diorgano and polystannoxanes). The catalyst (d) is generally introduced into each of the prior emulsions (A) and (B) in an amount of 0.05 to 10 parts by weight, per hundred parts by weight of the sum of the constituents (a) + (b) + (c) + (d) or (a ') + (b) + (c) + (d), preferably correctly from 0.08 to 5 parts by weight, and better still from 0.1 to 2 parts by weight.

Dioctyltin dilaurate is most particularly preferred. The nature of the surfactant (e) will be easily determined by a person skilled in the art, the objective being to prepare a stable emulsion. The anionic, cationic, nonionic and zwitterionic surfactants can be used alone or as a mixture.

As anionic surfactant, there may be mentioned the alkali metal salts of aromatic sulfonic hydrocarbon acids or the alkali metal salts of alkylsulfuric acids.

Non-ionic surfactants are more particularly preferred in the context of the invention. Among these, mention may be made of alkyl or aryl ethers of poly (alkylene oxide), polyoxyethylenated sorbitan hexastearate, polyoxyethylenated sorbitan oleate having a saponification number from 102 to 108 and a hydroxyl number from 25 to 35 and the ethers of cetylstearyl and poly (ethylene oxide).

As poly (alkylene oxide) aryl ether, polyoxyethylenated alkylphenols may be mentioned. As alkyl ether of poly (alkylene oxide), there may be mentioned isodecyl ether of polyethylene glycol and trimethylnonyl ether of polyethylene glycol containing 3 to 15 units of ethylene oxide per molecule. The amount of surfactant (e) depends on the type of each of the constituents present as well as on the very nature of the surfactant used. As a general rule, each prior emulsion comprises from 0.5 to 10% by weight of surfactant (better still from 0.5 to 5% by weight) and from 40 to 95% by weight of water (better still from 45 to 90 % in weight).

Advantageously, each prior emulsion (A) and (B) or only one of the two prior emulsions (A) or (B) may further comprise a constituent (g) consisting of at least one water-soluble crosslinking agent chosen from silanes and / or hydroxylated polydiorganosiloxanes, said crosslinking agent carrying, per molecule, in addition to at least one OH group, at least one organic group with function Fr, Fr representing a. optionally substituted amino function, epoxy, acryloyl (-CH ₂ = CH- CO-) optionally substituted, methacryloyl (-CH ₂ = C (CH ₃ ) -CO-) optionally substituted, ureido (NH ₂ -CO-NH-) optionally substituted, optionally substituted thiol or halogen.

Within the meaning of the present invention, water-solubility should be understood to mean the ability of a product to dissolve in water at a temperature of 25 ° C, at least 5% by weight.

The optional organic substituents of the crosslinking agent other than the OH group (s) and the Fr function organic group (s) are: alkyl radicals, linear or branched, having from 1 to 6 carbon atoms; cycloalkyl radicals having from 3 to 8 carbon atoms; alkenyl radicals, linear or branched, having from 2 to 8 carbon atoms; aryl radicals having 6 to 10 carbon atoms; alkylarylene radicals having 6 to 15 carbon atoms; or arylalkylene radicals having 6 to 15 carbon atoms. According to a preferred embodiment of the invention, Fr is an optionally substituted amino function.

Thus, an organic group with a preferred Fr function is a group of formula: -R _a -NR ⁷ R ⁸

-R _b -NH-R ₀ -NR ⁷ R ⁸

where R _a , R _b , R _G , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are as defined above with regard to the definition of constituent (b).

According to a more preferred embodiment of the invention, the water-soluble crosslinking agent has the formula:

R ⁸ R ⁷ NR _a -Si (OH) ₃ in which R _a , R ⁷ and R ⁸ are as defined above. Even more preferably, R _a represents (CrC ₁₀ ) alkylene, and R ⁷ and R ⁸ independently represent a hydrogen atom or a (CC ₆ ) alkyl group.

By way of example, mention may be made of 3-aminopropyltrihydroxysilane.

The water-soluble crosslinking agent can also be a linear and / or cyclic hydroxylated polydiorganosiloxane, with MD (if linear) and / or D (if cyclic) siloxy units, and / or a hydroxylated polydiorganosiloxane resin having, in its structure, units siloxyls T optionally associated with units M and or D and / or T, or alternatively siloxyl units Q associated with units M and / or D.

This linear, cyclic or network polydiorganosiloxane is not substituted by organic hydrolyzable functions such as alkoxy functions.

In these polydiorganosiloxanes, the siloxyl units M, D, T and Q are defined as follows: unit M = G ₃ SiOι, ₂ unit D = G ₂ SiO _2/2 T unit = GSi0 _{_3/2} Q unit = Si0 _2,

G being an organic substituent which meets the definition given above for the “optional organic substituents” either represents a hydroxyl group or else is a function Fr, it being understood that in each molecular structure, at least one of the symbols G represents a group hydroxyl and at least one other of the symbols G represents a function Fr.

Preferably, G is: (Ci-CeJalkyle (for example methyl, ethyl, isopropyl, tert-butyl and n-hexyl); hydroxyl; (C ₂ -C ₈ ) alkenyl (for example vinyl or allyl); or even a function Fr, the preferred functions Fr being as defined above.

As linear hydroxyl polydiorganosiloxanes which can be used as crosslinking agent (g), mention may be made of polymethylsiloxane, the two ends of which contain a hydroxyl and therefore each silicon atom in the chain carries a function Fr.

This constituent (g), when it is present in the prior emulsion (A) or (B) or in the two emulsions, is used in an amount of 0.5 to 15 parts by weight per hundred parts by weight of the sum of constituents (a) + (b) + (c) + (d) + (g) or (a ') + (b) + (c)

⁺ (d) + (g), preferably in an amount of 0.6 to 5 parts by weight, and better in an amount of 0.8 to 3 parts by weight.

The presence of component (g) notably improves the durability of the lubricating composition.

Each prior emulsion (A) and (B) or only one of the two prior emulsions (A) or (B) may also contain one or more additional ingredients such as, for example, film-forming polymers, complementary lubricants, anti-friction agents, coalescing agents, wetting or dispersing agents, mineral fillers, air release agents, anti-foaming agents, thickeners, stabilizers, preservatives such as biocides and antifungals, in amounts which can vary considerably, for example, between 0.2 and 50% by weight of the prior emulsion.

Mention may be made, as film-forming polymer, of styrene-acrylic copolymers.

Examples of thickeners are cellulosic (carboxymethylcellulose), acrylic, polyurethane thickeners, hydrocolloid gums (xanthan gum) and mixtures thereof.

As a coalescing agent, glycols and / or aliphatic petroleum fractions (petroleum distillation fractions) may be used. Wetting or dispersible agents which can be used in the context of the invention are, for example, phosphates and / or polyacrylics, such as for example sodium hexametaphosphate and sodium polyacrylates.

The prior emulsions (A) and (B) can be prepared in a conventional manner by using conventional methods of the prior art.

A first method consists in emulsifying, in an aqueous phase comprising all of the water-soluble constituents, a mixture of the lipophilic constituents (a) or (a '), (b), (c), (d), in the presence of the surfactant (e).

Modifications to this process are naturally conceivable. An oil-in-water preemulsion can first be prepared from only a few of the constituents forming the final emulsion. Then the missing constituents can be added, either directly to the emulsion (case of water-soluble constituents), or subsequently in the form of emulsion (case of constituents soluble in the silicone phase). Thus, the catalyst (d) and the film-forming polymer can be added, either directly to the silicone phase before emulsification, or after formation of the emulsion, in the form of an additional emulsion.

The emulsification can be direct or proceed by inversion. In the case where one proceeds by inversion, it may be advantageous to prepare a preemulsion containing only a small proportion of water, to carry out its inversion (for example by grinding), then dilute the resulting emulsion with water remaining, optionally added with one or more water-soluble constituents.

A preferred variant consists in particular in preparing an oil-in-water preemulsion comprising all of the constituents (a) or (a '), (b) and (c) and optionally (g), in the presence of the surfactant (e) before add the missing constituents to this preemulsion in the form of additional emulsion (s).

Thus, according to another of its aspects, the invention relates to a process for the preparation of a lubricating composition in the form of an oil-in-water emulsion, characterized in that it comprises the steps (1) and ( 2) following: - step (1) where the prior emulsions (A) and (B) are prepared, at room temperature (23 ° C) using the same operating mode comprising the sequences α, β and γ consisting:

• sequence α: emulsify in water (f), a mixture of non-reactive polydiorganosiloxane oil (s) (a) (case of emulsion (A)) or reactive (s) (a ′) (case of the emulsion (B)), of polyorganosiloxane resin (s) (b), and of crosslinker (s) solubied (s) in the silicone phase (c), in the presence of surfactant (e), so as to prepare an oil-in-water type emulsion, optionally by first preparing a thick oil-in-water phase, then by secondly diluting with water the thick phase obtained, • β sequence: add to the previous emulsion, containing all of the constituents (a) or (a '), (b), (c) and (e), an emulsion of the catalyst (d) in water, • γ sequence: then optionally dilute the medium with water according to the desired dry extract rate; - step (2) where, at room temperature (23 ° C), the prior emulsion (A) and the previous emulsion (B) are mixed, operating with moderate stirring, according to the proportions which have been defined above in paragraph (4i) of the characteristics of constitution of the prior emulsions (A) and (B). The emulsification, at the α sequence, can be direct or proceed by inversion. It is preferable to operate by inversion.

When a water-soluble crosslinking agent (g) is incorporated into the prior emulsion (s), it is preferably incorporated, in the form of an aqueous solution, at the same time as the catalyst ( d), to an oil-in-water emulsion containing all of the constituents (a) or (a), (b), (c) and (e). The additional catalyst emulsion (d) as well as any emulsion added to the emulsion resulting from the sequence α is preferably prepared in the presence of the same surfactant as with the sequence α. However, one can consider the use of any other type of surfactant, such as for example a poly (vinyl alcohol). The latter surfactant is particularly useful in the case where it is desired to prepare an additional emulsion of a tin catalyst.

The additional ingredient (s) mentioned above, when one or more is used, can advantageously be incorporated, in whole or in part, in the prior emulsion (s) ( s) at the level of the sequence α and / or at the level of the sequence β and / or at the level of the possible sequence γ. The method of the invention may further comprise an additional step of heating the resulting lubricating composition, for example at a temperature ranging from 30 to 40 ° C. This step accelerates the crosslinking processes. It can be replaced by a step of storing the lubricating composition at room temperature (23 ° C.) until complete crosslinking. The oils and resins (a), (a ¹ ) and (b) as well as the crosslinkers (c) and (g) are commercially available or easily accessible to those skilled in the art by implementing the conventional methods described in the prior art.

When the resin (b) or the crosslinker (c) are functionalized, the functionalization is easily carried out by substitution or appropriate addition reaction.

When the optional constituent (g) represents a hydroxylated water-soluble silicone resin, this can be obtained: → by cohydrolysis:

- At least one silane (S ^ substituted by Fr functions and by Hydrolysable Functional Organic Substitutes (Sofh) identical or different from each other, preferably -OR _d with R _d = alkyl radical;

- With at least one silane (S ₂ ) substituted by Sofh which are identical or different from each other and relative to those of (S-,), with the exclusion of substituents Fr;

- »by heterocondensation of hydroiysates derived from silanes Si and S ₂ ; → then by "stripping" or steam entrainment of hydroiysates derived from Sofh. Within the meaning of the invention, the hydrolysable organofunctional substituents (Sofh) capable of generating volatile organic compounds (VOCs) in situ during crosslinking by condensation are, for example, alkoxy, acetoxy, ketiminoxy, enoxy. Insofar as the most common sofh are alkoxyls -OR _d , the heterocondensation mechanisms involved are of the OH / OH and OH / OR _{d type} , these OH or OR _d being carried by the hydroiysates derived from silanes Si and S ₂ . Hydroiysates derived from Sofh are alcohols, in this case.

Thus in practice, the silane Si is advantageously a trialcoxysilane, preferably a trimethoxysilane, a triethoxysilane, a methyldimethoxysilane or a methyidiethoxysilane, carrying an amino function Fr of the type:

• 3-aminopropyl;

• N-methyl-3-aminopropyl:

• N-aminoethyl-3-aminopropyl; • C ₆ H ₅ CH ₂ NH (CH ₂ ) ₂ NH- (CH ₂ ) ₃ -;

• 3-ureidopropyl;

• 3-methacryloxypropyl: CH ₂ = C (CH ₃ ) -COO- (CH ₂ ) ₃ -;

• 3-glycidyioxypropyl: H2C— CH— CHzOfCH B- (the ^other substituents of Si in the crosslinking agent (g) being in this case free of

Sofh) • 3-mercaptopropyl;

• 3-chloropropyl.

As regards S ₂ , the Sofhs which it comprises are preferably C 1 -C ₆ alkoxy radicals, for example: methoxy, ethoxy or propoxy. This silane S ₂ , preferably an alkoxysilane, can also contain at least one CC ₆ alkyl substituent, for example: methyl, ethyl, propyl.

These resins produced by heterocondensation of Si and S ₂ are described, in particular, in European patent application EP-A-0 675 128, the content of which is incorporated by reference in the present description. According to a second embodiment, the optional crosslinker (g) is a resin obtained:

→ by hydrolysis of a S ₃ silane substituted with Fr and Sofh, → by homocondensation of the S ₃ hydrolyzed silanes,

- "and by" stripping "steam entrainment of hydroiysates derived from Sofh. The silane S ₃ is preferably a substituted alkoxysilane Fr. It may be, for example, a trialcoxysilane making it possible to obtain a hydroxylated resin with T units, also called T (OH) resin.

This silane S ₃ can be of the same type as the silane S _T as defined above. The functions Fr substituting S ₃ correspond to the same definition as that given above.

As an illustration of this second embodiment of a crosslinking agent (g) of the polydiorganosiloxane resin type, mention may be made of that obtained from γ-aminopropyltriethoxysilane hydrolyzed and subjected to a "stripping" of the ethanol formed by the hydrolysis. . The polyhomocondensed resin obtained is a mixture of oligomers containing from 4 to 10 silicon and comprising units: T (OH) = R "Si (OH) θ _2/2 T = R" Si0 _3/2

T (OH) ₂ = R "Si (OH) ₂ O _{ι 2} T (OH) ₃ = R" Si (OH) ₃ , these units being respectively present in decreasing quantity, with R "= NH ₂ - (CH ₂ ) - _3. They 'act for example of an amino resin T (OH).

Also within the scope of the present invention are the lubricant compositions which can be obtained by implementing the process which has just been described, comprising the direct mixing of the two emulsions (A) and (B) made beforehand. Another subject of the invention is the use of the lubricant composition thus obtained for the lubrication of various articles. More particularly, the invention relates to the use of the lubricating composition for the lubrication of the vulcanization bladder, made of rubber and expandable, during the shaping and vulcanization of pneumatic or semi-pneumatic tires.

The lubricant composition of the invention can be applied in any way, and for example by spraying, brushing or even using a sponge or a brush. I! it is preferable to operate so as to cover the article to be coated with an even layer of coating.

The lubrication of the vulcanization bladder used during the shaping and vulcanization of pneumatic or semi-pneumatic tires can be carried out in two different ways.

When manufacturing pneumatic or semi-pneumatic tires, a raw tire is placed in a tire mold, an expandable bladder is placed in the mold, the mold is closed and the bladder is expanded by applying internal fluid pressure. hot, so that the bandage is pressed against the mold, shaped and vulcanized. The mold is then opened, the bladder is deflated and the bandage is recovered, shaped and vulcanized. The same bladder is used for the manufacture of approximately a few hundred bandages.

The expandable rubber bladder used during the manufacture of the tires is initially coated with a lubricating composition according to the invention. Initially, the lubrication of the bladder is direct. Then there is a phenomenon of exhaustion of the lubricating effect of this bladder.

In this subsequent phase, it is the internal surface of the bandage (that which comes into contact with the bladder) which is coated with the lubricating composition. There is regeneration of the lubrication of the rubber bladder by transfer from the tire. In general, the mold pressing / bladder release cycles implemented during the manufacture of the tires follow one another as follows:

the bladder initially coated with the lubricating composition (direct lubrication) and heated to 80-180 ° C, and preferably to 130-170 ° C, is used (without subsequent coating of the bladder, but by coating the first bandage or the first two bandages) for 5 to 10 cycles (each cycle leading to the production of a different bandage), then

the following cycles are carried out by using this same bladder (for which the lubrication coating is exhausted) from pneumatic or semi-pneumatic tires which are then each time coated with the lubricant composition of the invention: bladder lubrication takes place in this case by transfer.

The present invention therefore also relates to the use of the lubricating composition for the lubrication of raw pneumatic or semi-pneumatic tires, comprising or not comprising on their external surface elements which will constitute the external tread intended to come into contact with the ground.

The lubricant composition of the invention does not comprise any Si-H bonding component so that the risk of evolution of hydrogen during storage or transport is zero.

The lubricant composition of the invention also exhibits excellent sliding properties, durability and elasticity.

Advantageously, the expandable rubber bladder, before being coated on its external surface (that which comes into contact with the tire) with a lubricating composition prepared according to the process of the present invention, can undergo a pretreatment consisting in applying in any way (for example by spraying, brushing, or using a sponge or a brush) a regular layer of a primary composition in the form of an oil-in-water emulsion, said emulsion being obtained by the process comprising the direct mixing of the two oil-in-water emulsions (A) and (B) made in the prelims, which are defined above, but this time using proportions of the two previous emulsions (A) and ( B) which are such that the weight ratio emulsion (A) / emulsion (B), at the time of direct mixing, is now in the range from 0.1 to 0.7, preferably from 0.3 to 0 , 5, and more preferably from 0.35 to 0.45. The present invention also relates to articles lubricated using the lubricant composition capable of being obtained by implementing the process which has just been described, comprising the direct mixing of the two emulsions (A) and (B) made prior.

More particularly, the invention relates to: - an expandable rubber bladder coated on its external surface with a composition according to the invention, for the shaping and vulcanization of pneumatic or semi-pneumatic tires;

- an expandable rubber bladder obtainable by heating the expandable bladder defined above, in particular at 80-180 ° C (preferably 130-170 ° C), so as to ensure total crosslinking of the crosslinkable constituents of the emulsion;

- A pneumatic or semi-pneumatic raw tire with or without elements which will constitute its external tread intended to come into contact with the ground, coated on its internal surface with a lubricating composition according to the invention.

The following examples which illustrate the invention demonstrate the excellent lubricating properties of the compositions of the invention. EXAMPLE 1

This example illustrates a lubricating composition (lubricating composition 1) prepared according to the process of the present invention comprising a water-soluble crosslinking agent (component (g)

Step 1) :

The previous emulsions (A) and (B) are prepared, the nature and proportions of their constituents being given in Tables 1 and 2 respectively.

TABLE 1: emulsion (A)

⁽¹⁾ siloxane oil phenylated: M = (CH ₃₎ ₃ Si0 _{1 2} D = (CH ₃₎ ₂ SiO _{_2/2} _D ^{P / M} e _{= motjf} (c ₆ H ₅₎ (CH ₃₎ SiO _{2 / 2}

Ph = C ₆ H ₅ ⁽²⁾ MDT resin having a hydroxylation rate of 0.5% by weight, an average number per molecule of organic radicals for a silicon atom of 1.5, a dynamic viscosity at 25 ° C of 0.1 Pa. s and the following proportions of siloxy units:

M: 17% by mole

D: 26%> in mole

T: 57% o by mole.

^(3, 37.5% by weight dioctyltin dilaurate emulsion in water prepared using polyvinyl alcohol as a surfactant.

⁽⁾ Mixture of 15% water and 85% isotridecyl alcohol ethoxylated with 8 to 9 moles of ethylene oxide per mole of isotridecyl alcohol.

⁽⁵⁾ Aqueous solution containing 23%) by weight of silane.

⁽¹⁾ MDT resin having a hydroxylation rate of 0.5% by weight, an average number per molecule of organic radicals for a silicon atom of 1.5, a dynamic viscosity at 25 ° C of 0.1 Pa. s and the following proportions of siloxy units: M: 17% by mole

D: 26% by mole

T: 57% by mole.

⁽²⁾ 37.5% dioctyltin dilaurate emulsion by weight in water prepared using polyvinyl alcohol as a surfactant. ^(3> Mixture of 15% water and 85% isotridecyl alcohol ethoxylated by 8 to

9 moles of ethylene oxide per mole of isotridecyl alcohol.

⁽⁴⁾ Aqueous solution containing 23% by weight of silane.

The preliminary emulsons (A) and (B) are prepared using the same procedure, comprising the following sequences α and β:

Sequence:

A mixture of non-reactive phenylated siloxane oil (case of emulsion (A)) or reactive hydroxylated polydimethylsiloxane oil (case of emulsion (B)), MDT-OH resin, methyltriethoxysilane, surfactant and a part of distilled water (according to a water / surfactant ratio of 1, 2, or 2.35% by weight of water) is homogenized beforehand with moderate stirring (50 revolutions / minute) for 15 minutes at temperature ambient (23 ° C).

The mixture thus obtained is treated by grinding until phase inversion using a Moritz ^® mill, to pass a fluid phase water / oil to a thick oil phase / water.

The dilution of the thick phase obtained is carried out with average stirring in 40 minutes, using a quantity of distilled water determined to obtain an emulsion whose dry matter is 50% (i.e. 45.59% by weight d 'water). The bactericidal agent and the antioxidant agent are added during dilution.

Sequence B:

The silane (g) and the catalyst (d) are added to the previously produced emulsion, then homogenization with moderate stirring is carried out for 10 minutes, followed by filtration. The biocide and the antifoam are then added to the emulsion, and the mixture is stirred for another 10 minutes. The emulsion thus obtained is characterized by an average particle size of 0.4 μm.

The xanthan gum and the wetting agent are loaded into another container, mixed for 10 minutes with vigorous stirring, then added to the emulsion previously produced. Stirred further, at moderate speed, for 30 minutes.

The final emulsion is characterized by a proportion of dry matter (60 min, 120 ° C) of 48.8% by weight.

2nd step) :

The prior emulsions (A) and (B), prepared as indicated above, are mixed at ambient temperature (23 ° C.), operating with moderate stirring (50 revolutions / minute) for 15 minutes, the prior emulsions (A ) and (B) being entered in the following respective proportions:

TABLE 3: lubricating composition 1

The lubricating composition 1 obtained is characterized by an average particle size (measured before the addition of xanthan gum and the wetting agent) of 0.4 μm and a proportion of dry matter (60 min, 120 ° C.) of 48, 8% by weight.

EXAMPLES 2 AND 3

Example 2: this is a comparative example which illustrates a lubricating composition (lubricating composition 2) prepared, not by direct mixing of two prior emulsions (A) and (B), but by directly producing a single emulsion from of the mixture of constituents (a) and (a ') with the other constituents and additional ingredients. A single emulsion is therefore prepared, the nature and proportions of the constituents of which are given in Table 4 below:

TABLE 4: lubricating composition 2

Legends ⁽¹⁾ to ⁽⁵⁾ : cf. at the bottom of table 1.

The process used to prepare the lubricating composition 2 is identical to the process, comprising the sequences α and β, described in step (1) of Example 1. The emulsion obtained is characterized by an average particle size (measured before the addition of xanthan gum and the wetting agent) of 0.402 μm and a proportion of dry matter (60 min, 120 ° C.) of 48.5% in weight.

Example 3: this is another comparative example which illustrates a lubricating composition (lubricating composition 3) prepared by directly producing, there too, a single emulsion from the constituents and additional ingredients, the nature and proportions of which are given in the following table 5:

TABLE 5: lubricating composition 3

Legends ⁽¹⁾ to ⁽⁾ : cf. at the bottom of table 2.

The process used to prepare the lubricating composition 3 is identical to the process, comprising the sequences α and β, described in step (1) of Example 1. The emulsion obtained is characterized by an average particle size (measured before the addition of xanthan gum and the wetting agent) of 0.402 μm and a proportion of dry matter (60 min, 120 ° C.) of 48.5% in weight.

The properties of the lubricating compositions 1, 2 and 3 of Examples 1 (Table 3), 2

(Table 4) and 3 (Table 5) were measured by evaluating the coefficients of friction and durability.

A low coefficient of friction reflects good sliding properties. The tests for measuring the coefficients of friction and of the durability were adapted to the application of the lubricating composition on an expandable rubber bladder.

Slip test

The objective of this test is to assess the sliding power of a lubricating composition placed at the interface between the inflatable bladder and the internal surface of the tire envelope.

This test is carried out by sliding on a rubber surface, the composition of which is that of the inflatable bladder, a metal pad of determined weight, under which is fixed a tire casing film (50 × 70 mm).

The surface of the inflatable bladder is previously treated with the lubricating composition according to a procedure close to that used in production.

The coefficient of friction is measured using a dynamometer (at the speed of 100 mm / min). Five successive passages are carried out on the same inflatable bladder sample, each time changing the tire envelope sample.

The lower the values of the coefficient of friction, the better the sliding properties of the lubricant composition will be.

The five passages give information on the exhaustion of the lubricating composition during successive moldings.

This slip test is representative of the performance to be achieved on the industrial tool, it is a first selection criterion.

Durability test

The durability of a lubricating composition corresponds to the number of tires produced without degrading the surface of the inflatable bladder. An inflatable bladder film, previously treated with the lubricating composition to be evaluated, is pressed in contact with an unvulcanized tire casing film, according to a series of pressure and temperature cycles simulating the stages of manufacturing a pneumatic on the industrial tool. The tire cover film is replaced with each mold. The test is finished when the two surfaces in contact remain bonded. The lubricating composition on the surface of the inflatable bladder film is exhausted and no longer plays the role of lubricating interface.

Table 6 below reports the coefficients of friction obtained on each pass for each of the lubricant compositions 1, 2 and 3 of Examples 1, 2 and 3. The results were obtained after one week of storage of the lubricant compositions 1, 2 and 3.

TABLE 6

It is clear from Table 6, that the coefficients of friction measured in the case of compositions 2 and 3 of Comparative Examples 2 and 3 are greater than those measured in the case of composition 1 according to the invention. Table 7, given below, reports the durability of composition 1 according to the invention, and of compositions 2 and 3 of comparative examples 2 and 3.

TABLE 7

Claims

CLAIMS 1. Process for the preparation of a lubricating composition in the form of an oil-in-water emulsion, characterized in that it comprises the direct mixing of two oil-in-water emulsions (A) and (B) made beforehand, said preliminary emulsions (A) and (B) meeting the following characteristics of constitution (i) to (4i): (i) the prior emulsion (A) comprises:

(a) at least one non-reactive linear polyorganosiloxane oil with lubricating properties, having a dynamic viscosity of the order of 5.10 ² to 30.10 ² Pa.s at 25 ° C and consisting of a linear homopolymer or copolymer including, per molecule, the monovalent organic substituents, identical or different from one another, bonded to the silicon atoms are chosen from alkyl, cycoalkyl, alkenyl, aryl, alkylarylene and arylalkylene radicals;

(b) at least one polyorganosiloxane resin carrying, before emulsification, condensable hydroxyl substituents and comprising before emulsification at least two different siloxy units chosen from those of formula

(R ¹ ) ₃ Si0 _1/2 (M); (R ¹ ) ₂ Siθ ₂ β (D); R ¹ Si0 ₃₂ (T) and Si0 _4/2 (Q), at least one of these units being a T or Q unit, formulas in which R ¹ represents a monovalent organic substituent, the average number per molecule of organic radicals R ¹ for a silicon atom being between 1 and 2; and said resin having a content by weight of hydroxyl substituents ranging from 0.1 to 10% by weight;

(c) at least one crosslinker soluble in the silicone phase comprising at least two functions capable of reacting with the (or) resin (s) polyorganosiloxane (s) (b); (d) a condensation catalyst capable of catalyzing the reaction of the constituent

(b) with the constituent (c);

(e) a surfactant; and

(f) water,

(2i) the prior emulsion (B) comprises: (a ¹ ) at least one reactive linear polyorganosiloxane oil comprising at least two OH groups per molecule and having a dynamic viscosity ranging from 5.10 ^"2 to 30.10 ² Pa.s at 25 ° C; and the constituents (b), (c), (d), (e) and (f) mentioned above with regard to the constitution of the prior emulsion (A); (3i) each of the prior emulsions (A) and (B) has the following composition by weight, the composition by weight of (A) possibly being identical or different from that of (B): - from 5 to 95 parts by weight of the constituent (a) for the emulsion (A) or of the constituent (a ¹ ) for the emulsion (B);

- from 0.5 to 50 parts by weight of component (b);

- from 0.1 to 20 parts by weight of the constituent (c); - from 0.05 to 10 parts by weight of the constituent (d); per 100 parts by weight of the sum of the constituents (a) + (b) + (c) + (d) or (a ') + (b) + (c) + (d); the quantities of surfactants and of water being sufficient for obtaining an oil-in-water emulsion; and (4i) the emulsion (A) / emulsion (B) weight ratio, at the time of mixing the preliable emulsions, is in the range from 1.5 to 4.

2. Method according to claim 1, characterized in that the catalyst (d) is a tin catalyst, for example the tin salt of an organic acid.

3. Method according to claim 2, characterized in that the catalyst (d) is a dialkyltin dicarboxylate.

4. Method according to any one of the preceding claims, characterized in that the constituent (c) is chosen from organotrialcoxysilanes, organotriacyloxysilanes, organotrioximosiians and tetraalkylsilicates.

5. Method according to claim 4, characterized in that the constituent (c) consists in at least one alkyltriaicoxysilane of formula YSiZ ₃ in which Y is (CC ₆ ) alkyl or (C ₂ -C ₈ ) alkenyl, and Z is ( CC ₁₀ ) alkoxy.

6. Method according to any one of the preceding claims, characterized in that the constituent (a) consists in at least one non-reactive linear polyorganosiloxane oil which is a linear homopolymer or copolymer of which, per molecule, at least 2% by number of monovalent organic substituents linked to silicon atoms are aryl, alkylarylene and / or arylalkylene radicals.

7. Method according to claim 6, characterized in that the constituent (a) is chosen from linear polyorganosiloxanes: - formed along each chain:

• units of formula R ² R ³ Si0 ₂₂ , optionally associated with units of formula (R ^ iO ^, • units of formula (R ^ SiO ^, optionally associated with units of formula (R ^ SiO ^, and

• units of formula R ² R ³ Si0 ₂₂ and units of formula (R ³ ) ₂ Si0 ₂₂ , possibly associated with units of formula (R ² ) ₂ Si0 ₂₂ , - and blocked at each chain end by a unit of formula (R ⁴ ) ₃ Si0-ι _{/ 2 in} which the radicals R ⁴ , which are identical or different, are radicals R ² and R ³ ; where the radicals R ² and R ³ , monovalent organic substituents of the various siloxyl units mentioned above, have the following definitions:

• the radicals R ² , identical or different from each other, are chosen from: linear or branched Cι-C ₆ alkyl radicals (such as for example methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, n- pentyl, n-hexyl), C ₃ -C ₈ cycloalkyl radicals (such as for example cyclopentyl, cyclohexyl), and linear or branched C ₂ -C ₈ alkenyl radicals (such as for example vinyl, allyl), the radicals R ³ , identical or different from each other, are chosen from: aryl radicals C ₆ -C ₁₀ (such as for example phenyl, naphthyl), alkylarylene radicals C ₆ -C ₁₅ (such as for example tolyls, xylyl), C ₆ -C ₁₅ arylalkylene radicals (such as, for example, benzyl); and

- where 5 to 50% by number of the substituents R ² , R ³ and R ⁴ are aromatic radicals R ³ .

8. Method according to claim 7, characterized in that the constituent (a) consists in at least one linear polyorganosiloxane:

- formed along each chain:

• units of formula R ² R ³ Siθ _2/2 associated with units of formula (R ² ) ₂ SiO;> _{/ 2} , • units of formula (R ³ ) ₂ SiO;> _{/ 2} associated with units of formula (R ^ SiO ^;

- and blocked at each chain end by a motif of formula (R ² ) ₃ SiO- | _{/ 2} ;

- where the radicals R ² and R ³ have the following definitions:

• the radicals R ² , identical or different between them, are chosen from the methyl, ethyl, propyl and isopropyl radicals, • the radicals R ³ , identical or different from each other, are chosen from the phenyl, tolyl and benzyl radicals; and where 5 to 50% by number of the substituents R ² and R ³ are phenyl, tolyl and / or benzyl radicals

9. Method according to any one of the preceding claims, characterized in that the constituent (a ') consists in at least one polyorganosiloxane of formula:

in which n is an integer greater than or equal to 10, R ⁵ and R ⁶ , identical or different, represent (d-CeJalkyle; (C ₃ -C ₈ ) cycloalkyle; (C ₂ -C ₈ ) alkenyl;

(C ₅ -C ₈ ) cycloalkenyl; each of the aforementioned radicals being optionally substituted by a halogen atom or a cyano residue.

10. Process according to any one of the preceding claims, characterized in that each resin of component (b) is a hydroxylated DT or MDT resin comprising at least 20% by weight of T units and having a content by weight of hydroxyl groups ranging from 0.1 to 10%.

11. Method according to any one of the preceding claims, characterized in that each resin of the constituent (b) has a dynamic viscosity at 25 ° C of between 0.2 and 200 Pa.s.

12. Method according to any one of the preceding claims, characterized in that each prior emulsion (A) and (B) or only one of the two prior emulsions (A) or (B) further comprises from 0.5 to 15 parts by weight, per hundred parts by weight of the sum of the constituents (a) + (b) + (c) + (d) + (g) or (a ') + (b) + (c) + (d) + (g), of a constituent (g) consisting of at least one water-soluble crosslinking agent chosen from silanes and or hydroxylated polydiorganosiloxanes (POS), said crosslinking agent being, per molecule, in addition to at least one OH group, at least one organic group with function F _r , F _r being chosen from optionally substituted amino, epoxy, acryloyl (CH ₂ = CH-CO) optionally substituted, methacryloyl (CH ₂ = C (CH ₃ ) -CO-) functions ) optionally substituted, ureido (NH ₂ -CO-NH-) optionally substituted, thiol optionally substituted and halogen.

13. Method according to claim 12, characterized in that the crosslinking agent has the formula R ⁸ R ⁷ NR _a -Si (OH) ₃ in which R _a represents (dC ^ alkylene and R ⁷ and R ⁸ represent a atom d hydrogen or an aikyle group (CrC ₆ ).

14. Method according to any one of the preceding claims, characterized in that each prior emulsion (A) and (B) or only one of the two prior emulsions (A) or (B) further comprises one or more additional ingredients chosen from film-forming polymers, complementary lubricants, anti-friction agents, coalescing agents, wetting or dispersing agents, mineral fillers, air release agents, anti-foaming agents, thickeners, stabilizers, and preservatives such as biocides and antifungals.

15. Method according to any one of the preceding claims, characterized in that each prior emulsion (A) and (B) comprises, in identical or different amount, from 0.5 to 10% by weight of surfactant and from 40 to 95% by weight of water.

16. Method according to any one of the preceding claims, characterized in that it comprises the following steps (1) and (2):

- step (1) where the prior emulsions (A) and (B) are prepared, at room temperature (23 ° C), using the same procedure comprising the sequences α, β and γ consisting of:

• sequence α: emulsify in water (f), a mixture of non-reactive polydiorganosiloxane oil (s) (a) (case of emulsion (A)) or reactive (s) (a ') (case of the emulsion (B)), of polyorganosiloxane resin (s) (b), and of crosslinker (s) soluble (s) in the silicone phase (c), in the presence of the surfactant (e), so as to prepare an emulsion of the oil-in-water type, optionally by firstly preparing a thick oil-in-water phase, then by secondly diluting with water of the thick phase obtained,

Β sequence: add to the previous emulsion, containing all of the constituents (a) or (a '), (b), (c) and (e), an emulsion of the catalyst (d) in water, • γ sequence: then optionally dilute the medium with water depending on the desired dry extract rate; step (2) where, at room temperature (23 ° C), the prior emulsion (A) and the previous emulsion (B) are mixed, operating under moderate stirring, according to the proportions which have been defined above paragraph (4i) of the characteristics of constitution of the previous emulsions (A) and (B).

17. The method of claim 16, characterized in that, when a water-soluble crosslinking agent (g) is incorporated in the (or the) emulsion (s) prior (s), it is incorporated in the form of a aqueous solution, at the same time as the catalyst (d), in an oil-in-water emulsion containing all of the constituents (a) or (a ¹ ), (b), (c) and (e).

18. Lubricating compositions capable of being obtained by implementing the method according to any one of claims 1 to 17, comprising the direct mixing of the two emulsions (A) and (B) made beforehand.

19. Use of a lubricant composition according to claim 18 for the lubrication of an article.

20. Use according to claim 19, characterized in that: - lubrication of the expandable vulcanization rubber bladder is carried out, during the shaping and vulcanization of pneumatic or semi-pneumatic tires, and / or

- lubrication of raw pneumatic or semi-pneumatic tires, with or without elements on their external surface which will constitute the external tread intended to come into contact with the ground.

21. Use according to any one of claims 19 and 20, characterized in that the expandable rubber bladder, before being coated on its external surface (that which comes into contact with the tire) with a lubricating composition prepared according to the method according to any one of claims 1 to 17, undergoes a pretreatment consisting in applying in any way a regular layer of a primary composition in the form of an oil-in-water emulsion, said emulsion being obtained by the process comprising the direct mixing of the two oil-in-water emulsions (A) and (B) made in the prelims, which are defined above, but this time using proportions of the two previous emulsions (A) and (B) which are such that the weight ratio emulsion (A) / emulsion (B), at the time of direct mixing, is now in the range from 0.1 to 0.7.

22. Article coated with a composition according to claim 18.

23. An article obtainable by heating an article according to claim 22.

24. Article according to claim 22, characterized in that it consists of an expandable rubber bladder coated on its external surface with a composition according to claim 18, for the shaping and vulcanization of pneumatic or semi-pneumatic tires.

25. Article according to claims 23 and 24, characterized in that the expandable rubber bladder is obtained by heating a coated bladder at a temperature of 80 to 180 ° C.

26. Article according to claim 22, characterized in that it consists of a pneumatic or semi-pneumatic raw tire comprising or not elements which will constitute its external tread intended to come into contact with the ground, coated on its internal surface d 'A composition according to claims 18.

27. Primary compositions in the form of an oil-in-water emulsion, said emulsion being capable of being obtained by the process according to any one of claims 1 to 17, comprising the direct mixing of the two oil-in emulsions -water (A) and (B) made at the prerequisites, which are defined above, but this time using proportions of the two prior emulsions (A) and (B) which are such that the weight ratio emulsion (A) / emulsion ( B), at the time of direct mixing, is now in the range of 0.1 to 0.7.