EP2038354A1 - Siloxane-based lubricating composition releasing no hydrogen, its method of preparation and its use - Google Patents

Abstract

The present invention relates to a lubricating composition, in the form of an oil-in-water emulsion, based on a siloxane and not releasing hydrogen, particularly suitable for lubrication of: internal surfaces of uncured or unvulcanized envelopes intended for the manufacture of rubber pneumatic or semi-pneumatic tyres for vehicles; and of vulcanization bladders used for the shaping and vulcanizing of pneumatic or semi-pneumatic tyres.

Description

 Siloxane lubricating composition, not releasing hydrogen, process for its preparation and use

The invention relates to a lubricant composition particularly suitable for lubrication:

- internal surfaces of green or unvulcanized casings for the manufacture of pneumatic or semi-pneumatic tires for vehicles, and

vulcanizing bladders used in shaping and vulcanizing pneumatic or semi-pneumatic tires.

The invention also relates to vulcanization bladders coated with a lubricant composition according to the invention as well as pneumatic or semi-pneumatic tires coated with said lubricant composition.

According to two other aspects of its invention, the invention relates to the use of said lubricating compositions for the lubrication of vulcanization bladders and internal surfaces of raw or unvulcanized casings for the manufacture of pneumatic or semi-pneumatic tires for vehicles.

Rubber tires for vehicles are usually made by molding and vulcanizing a green or unvulcanized, uncured shell in a molding press in which the green shell is pressed out against the surface of a mold at means of an expandable bladder by an internal fluid. By this method, the green envelope is shaped against the outer surface of the mold which defines the pattern of the tread of the envelope and the configuration of the sidewalls. By heating, the casing is vulcanized. In general, the bladder is dilated by the internal pressure provided by a fluid such as hot gas, hot water and / or steam, which also participates in the heat transfer 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 envelope vulcanizing bladders is well known in the art.

It is recognized that there is substantial relative movement between the external contact surface of the bladder and the inner surface of the casing during the dilation phase of the bladder prior to complete vulcanization of the casing. Similarly, there is also considerable relative movement between the external contact surface of the bladder and the vulcanized inner surface of the casing, after the casing has been molded and vulcanized, during the deflation and removal of the bladder from the tire.

If proper lubrication is not provided between the bladder and the inner surface of the casing, the bladder generally tends to warp, resulting in deformation of the casing in the mold and also excessive wear and grinding. of the surface of the bladder itself. The surface of the bladder also tends to stick to the inner surface of the wrapper after the vulcanization of the wrapper and during the portion of the vulcanization cycle of the wrapper in which the bladder is deflated. In addition, air bubbles can be trapped between the surfaces of the bladder and the envelope, and promote the occurrence of vulcanization defects of the envelopes resulting from improper heat transfer.

For this reason, the outer surface of the bladder or the inner surface of the green or unvulcanized shell is coated with a suitable lubricant, sometimes referred to as "liner cement".

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

In particular, the lubricant compositions described in FR 2 494 294, 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 methylhydrogenosilane, dimethylhydrogenosilane, polymethylhydrogenosilane and polymethylhydrogensiloxane. The disadvantage of lubricating compositions of this type is their storage instability. In fact, the emulsion is creamed following the evolution of hydrogen during transport and the preservation of the lubricating 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 have excellent durability, lubricity and elasticity properties is therefore highly desirable. The compositions which are the subject of the patent application EP 635 559 are siloxane-based lubricant compositions which partially meet these requirements. These compositions are in particular more stable in that they do not emit hydrogen during storage. These compositions, which are in the form of emulsions, comprise, as essential constituents, a nonreactive polydimethylsiloxane, a reactive polydimethylsiloxane, preferably hydroxy-terminated or alkoxy-terminated, and a crosslinking agent. Their durability is however insufficient for practical use in the production of pneumatic or semi-pneumatic tires.

As another example of the prior art, mention may be made of the international application WO-A-03/087227 which describes a composition in the form of a silicone oil in water emulsion, based on siloxane which does not give off hydrogen, which is useful in molding-demolding tires comprising:

- (a) optionally at least one linear non-reactive polyorganosiloxane oil with lubricating properties, having a dynamic viscosity of the order of 5.10 ^-2 at 30.10 ² Pa.s at 25 ° C;

(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 200,000, especially from 5 × 10 ^-2 to 150,000, preferably from 5 × 10 ^-2 to 3,000. Pa.s at 25 ^° C .;

(b) at least one polyorganosiloxane resin bearing condensable hydroxyl substituents and having at least two siloxyl units; (c) at least one crosslinker soluble in the silicone phase comprising at least two functions capable of reacting with the polyorganosiloxane resin (b);

(d) at least one condensation catalyst capable of catalyzing the reaction of component (b) with component (c);

(e) at least one surfactant; and (f) water, the constituent (a) / constituent (a ') weight ratio being in the range of 0 to 10.

This composition when it is crosslinked on the bladder can play either the role of a lubricant composition, or the role of a primer with sufficient lubricating properties to thereby avoid the application of an additional lubricant composition.

A similar approach has been described in International Application WO-A-01/40417 also using a tin-based catalyst compound. However, although interesting for the lubrication aspect, this type of composition has the disadvantage of using metal-type condensation catalysts, for example based on tin, which are expensive and whose presence is not desirable. for reasons of toxicity. In addition, these emulsions have the disadvantage of a loss of activity after prolonged storage which contributes to a noticeable drop in the number of molding / demolding in mold pressing cycles / bladder release, implemented during the manufacture of bandages.

In addition, the tire industry is always looking for lubricating compositions that make it possible to obtain both of the following properties:

good durability in direct bladder application (useful for the manufacture of heavy vehicle tires characterized by easy accessibility of the bladder bladder),

- Good durability in transfer of the envelope on the bladder (useful for the manufacture of light vehicle tire characterized by a difficult accessibility of the bladder bladder, hence the treatment of the raw tire and transfer on the bladder), and

good sliding properties (Kd less than 0.45).

The present invention provides an improved lubricating composition that does not release hydrogen, does not contain a metal condensation catalyst and further has excellent slip and durability characteristics, making them ideally suited for lubricating the bladders used in the process. vulcanization of pneumatic and semi-pneumatic tires of light and heavy vehicles.

The lubricant composition of the invention is a lubricant composition, in the form of an oil-in-water emulsion, based on siloxane and not releasing hydrogen, comprising:

(a) at least one non-reactive polydiorganosiloxane oil (A) with lubricating properties having a dynamic viscosity of the order of 20 to 100,000 mPa.s at 25 ^° C .; (b) at least one reactive linear polydiorganosiloxane oil (B) having per molecule at least two OH groups, said polydiorganosiloxane having a dynamic viscosity at 25 ^° C. of between 50 and 50 × 10 ⁶ mPa.s,

(c) optionally at least one polyorganosiloxane resin (C) carrying, before emulsification, condensable hydroxyl substituents and having before emulsification at least two different siloxyl units selected from those of formula ; (R 0) ₂ SiO ₂ z ₂ (D); R ⁰ SiO ₃ Z ₂ (T) and SiO _4/2 (Q), at least one of these units being a T or Q unit, in which R ⁰ represents a monovalent organic substituent, the average number per molecule of organic radicals R ⁰ for a silicon atom being included between 1 and 2; and said resin having a weight content of hydroxyl or alkoxy substituents of between 0.1 and 10% by weight, and preferably between 0.2 and 5% by weight,

(d) at least one crosslinking agent (D) soluble in the silicone phase,

(e) at least one water-soluble crosslinking agent (E) having the formula in its monomeric form:

(R ² ) (R ¹ ) NR ^a -Si (OH) ₃ in which R ^a represents a C 1 -C 20 alkylene group and R ¹ and R ² independently represent a hydrogen atom or a C ₁ -C ₆ alkyl group said crosslinking agent may be in oligomeric form by condensation of one or more silanol functions,

(f) at least one surfactant (F),

(g) water (K),

(h) at least one film-forming polymer (G), (i) optionally at least one thickener (H), Q), optionally at least one wetting agent (I), and

(k) optionally at least one additive (J), - with the additional conditions that:

(1) the amounts of surfactants and water being sufficient to obtain an oil-in-water emulsion, and (2) said lubricating composition does not contain a metal condensation catalyst.

The main advantage of the composition according to the invention is that it makes it possible to obtain a demolding and lubricating film, either by transfer or by direct application, which remains efficient for multiple demoldings, despite the absence of SiH functions.

The constituents (A), (B), (C), (D), (E), (F), (G), (H), (I), (J) and (K) of the emulsion are defined with reference to their initial chemical structure, that is to say the one that characterizes them before emulsification. Since they are in an aqueous medium, their structure is likely to be greatly modified following the hydrolysis and condensation reactions.

In the context of the invention, the term "non-reactive" is understood to mean 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.

As the preferred component (A), linear polydiorganosiloxanes with a repeating unit of formula V ¹ V ² SiO ₂ /, terminated at the chain ends by units V ³ V ⁴ V ⁵ SiO ₂ Z ₂ , V ¹ , may be mentioned. V ² , V ³ , V ⁴ and V ⁵ , identical or different, representing a group monovalent organic compound selected from alkyl, alkenyl, aryl, cycloalkyl, cycloalkenyl, aralkyl or alkaryl.

In these oils, alkyl denotes a saturated hydrocarbon group, linear or branched, preferably C ₁ -C ₁₈ (such as methyl, ethyl and propyl); alkenyl denotes a hydrocarbon group with ethylenic unsaturation (s), linear or branched, preferably C ₂ -C ₈ (such as vinyl, allyl and butadienyl); aryl denotes an aromatic group, mono- or polycyclic, hydrocarbon preferably C ₆ -C 10 _O (such as phenyl or naphthyl); cycloalkyl means a saturated carbocyclic group, mono- or polycyclic, preferably C ₃ -C ₈ (such as cyclohexyl); cycloalkenyl means a cycloalkyl group having one or more unsaturations, preferably C ₆ -C ₈ (such as cyclohexenyl); aralkyl means for example benzyl; alkaryl means, for example, tolyl or xylyl. More generally, alkaryl and aralkyl are groups in which the aryl and alkyl moieties are as defined above.

Advantageously, the substituents V ¹ , V ² , V ³ , V ⁴ and V ⁵ are identical to each other.

Preferably, the component (A) is a linear, non-functionalized polydimethylsiloxane, that is to say with recurring units of formula (CH 3) ₂ SiO 2/2 and having at its two ends (CHs) ₃ SiO _{2 2 units.} .

The constituent (A) is generally introduced into the composition in a proportion of 1 to 50 parts by weight per 100 parts by weight of the mixture of the constituents (A), (B), (C), (D), (E), ( F), (G), (H), (I) (J) and (K), preferably from 3 to 40, more preferably from 3 to 30 parts by weight.

Component (B) is a reactive linear polydiorganosiloxane oil having at least two OH groups per molecule having a dynamic viscosity at 25 ° C generally between 50 and 50 x 10 ⁶ mPa.s.

In the context of the invention, the term "reactive" refers to the reactivity of the component (B) with respect to the crosslinking agents (D) and / or (E) present in the composition.

Preferably, the component (B) reacts with the crosslinking agent under the conditions of preparation of the emulsion.

As a preferred component, the reactive polyorganosiloxane (B) comprises the following siloxyl units:

M = [(0H) (R ² ) ₂ SiOi _{/ 2} ] and D = [R ³ R ⁴ SiO ₂ Z ₂ ] formulas in which:

- R ² , R ³ and R ⁴ are radicals, which are identical or different, chosen from the group consisting of: linear or branched C ₁ -C ₆ alkyl radicals (such as, for example, methyl, ethyl, propyl, isopropyl or butyl, isobutyl, t-butyl, n-pentyl, n-hexyl), radicals cycloalkyl C ₃ C₆ alkyl (such as for example cyclopentyl, cyclohexyl), aryl radicals C ₆ -C _O (such as for example phenyl, naphthyl) and alkylarylene radicals C ₆ -C _S (such as for example tolyl , xylyl).

Among the preferred constituents for the reactive polyorganosiloxane (B), mention may be made of linear polyorganosiloxanes of formula:

in which n is an integer greater than or equal to 50, R ³ and R ⁴ , which may be identical or different, represent: a Ci-C ₆ alkyl; C ₃ -C ₅ cycloalkyl; C ₂ -C ₆ alkenyl; C ₅ -C ₈ cycloalkenyl, aryl, alkylarylene and arylalkylene; each of the aforementioned radicals being optionally substituted by a halogen atom (and preferably fluorine) or a cyano residue.

The most used oils, because of their availability in industrial products, are those for which R ³ and R ⁴ are independently selected from the group of radicals consisting of: a methyl, an ethyl, a propyl, an isopropyl, a cyclohexyl , vinyl, phenyl, and 3,3,3-trifluoropropyl. In a very preferred manner, at least about 80% by number of these radicals are methyl radicals.

According to the invention, it will be preferred, however, from polyorganosiloxane oils (B) already polymerized for the preparation of the emulsion, for example using the emulsification techniques of the silicone phase described in FR-A-2 697. 021.

According to a preferred embodiment of the invention, the reactive polyorganosiloxane (B) is an α, ω-dihydroxypolydimethylsiloxane.

In the context of the present invention, it is especially possible to use the α, ω-dihydroxypolydiorganosiloxanes prepared by the anionic polymerization process described in US Pat. Nos. 2,891,920 and especially US 3,294,725 (cited as reference). The constituent (B), when present, is used in a proportion of 1 to 50% by weight, and preferably 3 to 40% by weight and more preferably in a proportion of 5 to 30% by weight relative to the total weight. of the composition.

Component (C) is a polyorganosiloxane resin, carrier before emulsification of condensable hydroxyl groups.

In the constituent units of these resins, each substituent R ⁰ represents a monovalent organic group.

In general, R ⁰ is a C ₁ -C ₂₀ hydrocarbon radical optionally bearing one or more substituents.

Examples of hydrocarbon radicals are an aliphatic group, saturated or unsaturated, linear or branched, preferably having 1 to 10 carbon atoms; a saturated, unsaturated or aromatic carbocyclic, monocyclic or polycyclic group preferably having from 3 to 18 carbon atoms, more preferably from 5 to 10 carbon atoms; or a radical having an aliphatic portion as defined above and a carbocyclic portion as defined above.

The substituents of the hydrocarbon radical may be -OR 'or -O-CO-R' groups in which R 'is a hydrogen atom or hydrocarbon radical as defined above, unsubstituted. Silicone resins (C) are well-known branched organopolysiloxane polymers whose methods of preparation are described in numerous patents. As concrete examples of usable resins, mention may be made of hydroxylated or alkoxylated resins MQ, MDQ, DQ, DT and MDT and mixtures thereof. In these resins, each OH or alkoxyl group is carried by a silicon atom belonging to a M, D or T unit.

Preferably, examples of resins that may be used include hydroxylated organopolysiloxane resins not comprising, in their structure, a Q-unit. More preferentially, 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 or alkoxyl group ranging from 0.1 to 10% and more preferably from 0.2 to 5%. In this group of more preferable resins, those in which the average number of substituents R 0 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 substituents R 0 are methyl radicals.

The resin (C) is liquid at room temperature. In a preferred manner, the resin has a dynamic viscosity at 25 ° C. of between 0.2 and 200 Pa.s. The resin is incorporated in the lubricating composition in an amount of from 0 to 50 parts by weight per hundred parts by weight of the sum of the components (A), (B), (C), (D), (E), (F) , (G), (H), (I), (J) and (K) preferably from 0.1 to 30, more preferably from 0.2 to 10 parts by weight.

The crosslinker (D) soluble in the silicone phase comprises at least two functions capable of reacting with the resin (C) so as to cause a crosslinking of said resin. Advantageously, said reactive functions of the crosslinking agent (D) react with the resin (C) under the conditions for preparing the emulsion.

The crosslinking agent (D) preferably has the formula:

Y _is Si (Zi) _{4 - a} wherein: a is 0, 1 or 2; Y is a monovalent organic group; and the groups Zi, which are identical or different, are selected from -OX _a; and -O-N = CX ¹ X ² wherein X _a , X _b , X ¹ and X ² are independently linear or branched, saturated or unsaturated aliphatic hydrocarbons, preferably C ₁ -

C20 (for example C ₁ -C ₁ O); it being understood that X ¹ and X ² may further represent a hydrogen atom and that X _a is a radical optionally substituted with (C 1 -C 10) alkoxy.

According to a preferred embodiment of the invention, a represents 1, so that the crosslinking agent (D) has the formula: YSi (Zi) ₃ .

More preferably, the Zi groups are identical to each other.

A preferred group of crosslinker (D) is formed by all organotrialkoxysilanes, organotriacyloxysilanes, organotrioximosilanes and tetraalkylsilicates.

More generally, with respect to the symbol Y, the expression "organic monovalent group" especially includes aliphatic radicals, saturated or unsaturated, linear or branched C ₁ -C ₃₀ ; carbocyclic radicals, mono- or polycyclic, saturated, unsaturated or aromatic C ₆ -C ₃₀ ; as well as the radicals having both an aliphatic portion as defined above and a carbocyclic portion as defined above; each of these radicals being optionally substituted with an amino, epoxy, thiol or ester function. Examples of groups Y are more particularly the (C 1 -C 10) alkyl, (C ₁ -C ₁₀ ) alkoxy or (C ₂ -C 10) alkenyl radicals, optionally substituted by a group:

Epoxy; • thiol;

• (C ₃ -C ₈ ) cycloalkyl optionally substituted by epoxy;

(C 1 -C 10) alkylcarbonyloxy optionally substituted with epoxy;

(C ₂ -C 10) alkenylcarbonyloxy optionally substituted with epoxy;

• (C ₃ -C ₈ ) cycloalkylcarbonyloxy optionally substituted by epoxy; (C ₆ -C 10) arylcarbonyloxy;

R ¹ N (R ¹ ) (R ² ) are as defined above;

• -R ^ NH-R'-NR ² wherein R ^ ^a, R ^b, R ¹ and R ² are as defined above;

or R ^a , R ^b , R ¹ and R ² , R ³ and R ⁴ represent alkyl groups, linear or branched, or aryl and preferably C ₁ -C ₃ O.

Preferably, R ³ represents a methyl, phenyl or benzyl group and R ⁴ represents a hydrogen atom or a methyl group.

Even more preferably, Y is unsubstituted C ₂ -C ₁₀ alkenyl; or a C ₁ -C ₁₀ alkyl optionally substituted with a group chosen from:

• thiol; (C 1 -C 10) alkylcarbonyloxy optionally substituted with epoxy;

• (C ₃ -C ₈ ) cycloalkyl optionally substituted by epoxy;

• (C ₂ -C 10) alkenylcarbonyloxy; and

-R ^a -N (R ¹ ) (R ² ) wherein R ^a represents a C ₁ -C ₆ alkylene and R ¹ , R ² independently represent a hydrogen atom, a C ₃ -C ₈ cycloalkyl or an aryl in C ₆ -C 10 and in particular a phenyl.

By way of example, Y represents an aminopropyl, ethylaminopropyl, n-butylaminoethyl, cyclohexylaminopropyl or phenylaminoethyl group. aminoethylaminopropyl, dimethylaminopropyl, glycidyloxypropyl, 3,4-epoxycyclohexylethyl, mercaptopropyl, methacryloxypropyl, methyl, ethyl or vinyl.

The Z groups are preferably selected from alkoxy groups, C ₁ -C ₁ O, alkylcarbonyloxy C ₁ -C ₁ O; or an oxime group

-O-N = CX ³ X ⁴ wherein X ³ and X ⁴ are independently a hydrogen atom or a C ₁ -C ₁₀ alkyl.

Preferably, Z 1 is methoxy, ethoxy, propoxy, methoxyethoxy, acetoxy or an oxime group.

A particularly preferred group of constituents (D) is formed by alkyltrialkoxysilanes of formula YSi (Zi) ₃ in which Y is an alkyl group, especially a C ₁ -C 30 alkyl group, preferably a C ₁ -C ₁ O group and Zi is an alkoxy group. , in particular C ₁ -C ₂ 0, preferably C ₁ -C ₁ O.

Among these, mention may be made of methyltrimethoxysilane and methyltriethoxysilane.

Other suitable crosslinking agents (D) are described in US 4,889,770, such as: beta-aminoethyltrimethoxysilane,

beta-aminoethyltriethoxysilane,

beta-aminoethyltriisopropoxysilane,

gamma-aminopropyltrimethoxysilane,

gamma-aminopropyltriethoxysilane, gamma-aminopropyltri (n-propoxy) silane,

gamma-aminopropyl (n-butoxy) silane,

delta-aminobutyltrimethoxy silane,

epsilon-aminohexyltriethoxysilane,

4-aminocyclohexyltriethoxysilane, 4-aminophenyltrimethoxy silane,

N-aminoethyl-gamma-aminopropyltrimethoxy silane,

N-aminoethyl-gamma-aminopropyltriethoxy silane,

beta-glycidoxyethyltrimethoxysilane,

N-aminoethyl-N-aminoethyl-gamma-aminopropyltrimethoxysilane (or DYNASILANE TRIAMO)

beta-glycidoxyethyltriethoxysilane,

gamma-glycidoxypropyltriethoxysilane,

beta- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, beta- (3,3-epoxycyclohexyl) ethyltriethoxysilane,

gamma- (3,4-epoxycyclohexyl) propyltriethoxysilane,

gamma-mercaptopropyltrimethoxysilane,

gamma-mercaptopropyltriethoxysilane, gamma-methacryloxypropyltrimethoxysilane,

gamma-methacryloxypropyltriethoxysilane,

methyltrimethoxysilane,

ethyltriethoxysilane,

vinyltrimethoxysilane, allyltrimethoxysilane, and

the corresponding compounds in which the alkoxy groups have been replaced by alkylcarbonyloxy or oximes groups.

The crosslinking agent (D) is incorporated in the lubricating composition in a proportion of 0.01 to 30 parts by weight per hundred parts by weight of the sum of the constituents (A), (B), (C), (D), (E ), (F), (G), (H), (I), (J) and (K) and preferably in an amount of from 0.01 to 20, more preferably from 0.01 to 10 parts by weight.

Examples of crosslinking agent (E) water-soluble include 3- aminopropyltrihydroxysilane or compound Silquest VS ^® 142 marketed by Witco-OSI, in aqueous solution, which consists of a silane oligomer described below, partially condensed via its SiOH functions:

For the purposes of the present invention, the term "water-solubility" means the ability of a product to dissolve in water at a temperature of 25 ° C., at least 5% by weight.

This component (E) is used in a proportion of 0.01 to 50 parts by weight per hundred parts by weight of the sum of the constituents (A), (B), (C), (D), (E), (F) ), (G), (H), (I), (J) and (K) preferably from 0.1 to 20 parts by weight, and more preferably from 0.1 to 10 parts by weight.

The nature of the surfactant (F) will be easily determined by those 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 the anionic surfactant, there may be mentioned alkali metal salts of aromatic hydrocarbon sulfonic acids or alkali metal salts of alkylsulphuric acids.

Nonionic surfactants are more particularly preferred in the context of the invention. Among these, there may be mentioned alkyl or aryl ethers of polyalkylene oxide, polyoxyethylenated sorbitan stearate, polyoxyethylenated sorbitan oleate having a saponification number of 102 to 108 and a hydroxyl number of 25 to 35 and cetylstearyl ethers and poly (ethylene oxide) ethers.

As the polyalkylene ether aryl ether, mention may be made of polyoxyethylenated alkylphenols. As alkyl ether of polyalkylene oxide, mention may be made of polyethylene glycol isodecyl ether and polyethylene glycol trimethylnonyl ether containing from 3 to 15 ethylene oxide units per molecule.

The amount of surfactant (F) is a function of the type of each constituent present and the nature of the surfactant used. As a general rule, the composition comprises from 0.1 to 10% by weight of surfactant per 100 parts by weight of the sum of the constituents (A), (B), (C), (D), (E), (F) ), (G), (H), (I), (J) and (K) more preferably from 0.1 to 5% by weight.

Examples of film-forming polymers (G) are organic polymer latices, for example styrene-acrylic copolymers or commercially available latices such as, for example, styrene / alkyl acrylate or styrene / alkyl acrylate / acrylic acid copolymers RHODOPAS ^® range (eg RHODOPAS ^® DS910, RHODOPAS ^® DS2800, RHODOPAS ^® DS 1003, RHODOPAS ^® DS2818, RHODOPAS ^® DS2810 sold by RHODIA), styrene / alkyl acrylate latex LIPATON ^® sold by POLYMER LATEX society and styrene / acrylate or styrene / acrylate / acrylic acid UC range AR ^® latex sold by the company Dow Chemical, Acronal ^® S400ap sold by BASF and sold Primal ^® 325GB by Rohm & Haas.

Advantageously, the film-forming polymer (G) is selected from styrene / alkyl acrylate or styrene / acrylate / acrylic acid in the range RHODOPAS ^®. According to a first preferred embodiment, the film-forming polymer (G) comes from the polymerization:

at least one alkyl (meth) acrylate monomer chosen from the group consisting of: methyl (meth) acrylate, ethyl (meth) acrylate or hydroxyethyl (meth) acrylate, propyl or hydroxypropyl, butyl or hydroxybutyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate,

a styrene monomer, and

- optionally at least one monomer selected from the group consisting of: acrylic acid and methacrylic acid.

According to a second embodiment, the film-forming polymer (G) comes from the polymerization:

at least one alkyl (meth) acrylate monomer chosen from the group consisting of: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate and (meth) butyl acrylate,

a styrene monomer, and

- optionally at least one monomer selected from the group consisting of: acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid.

According to a third embodiment, the film-forming polymer (G) is chosen from: styrene / butyl acrylate / acrylic acid copolymers with the following weight ratios relative to the total weight of the copolymer:

styrene monomer: between 25 and 55% by weight, butyl acrylate monomer: between 74.5 and 40% by weight, and

acrylic acid monomer: between 0.5 and 5% by weight.

The film-forming polymer (G) is incorporated in the lubricating composition in a proportion of 0.1 to 50 parts by weight (dry) per hundred parts by weight of the sum of the constituents (A), (B), (C), (D) ), (E), (F), (G), (H), (I), (J) and (K) and preferably from 1 to 45, more preferably from 5 to 40 parts by weight. The lubricating composition according to the present invention may optionally contain one or more additional ingredients such as thickeners (H), wetting agents (I) and additives (J) well known to those skilled in the art.

As an example of thickeners (H), mention may be made of: cellulosic thickeners

(carboxymethylcellulose), acrylics, polyurethane, hydrocolloid gums (xanthan gum) and mixtures thereof.

As an example of a wetting agent (I), mention may be made of: phosphates and / or polyacrylates, such as, for example, sodium hexametaphosphate and sodium polyacrylates.

Examples of additives (J) include: complementary lubricants and anti-friction agents, coalescing agents, dispersants, air-release agents, anti-foam agents, stabilizers, preservatives such as biocides, antifungals in amounts that can vary considerably, for example between 0.2 and 50% by weight relative to the total weight of the composition.

As a coalescing agent, it will be possible to use glycols and / or aliphatic petroleum fractions (petroleum distillation fractions).

The compositions of the invention may be prepared conventionally using standard methods of the state of the art.

Emulsification can be direct or by inversion.

For direct emulsification, the process consists in emulsifying in an aqueous phase containing the surfactant a mixture of constituents (a), (b), (c), (d) and (f). An oil-in-water emulsion is obtained directly. Then the missing constituents can be added, either directly to the emulsion (case of the water-soluble constituents), or later in the form of emulsion (case of the constituents soluble in the silicone phase).

The particle size of the emulsion obtained above can be adjusted by conventional methods known to those skilled in the art, in particular by continuing the stirring in the reactor for a suitable period. Usually, the processes of the invention are carried out at room temperature. Preferably, the temperature rise that can result from the grinding or stirring steps is limited. In particular, we choose to stay below 60 or 65 ° C.

Constituents (A) to (K) are commercially available or readily available to those skilled in the art by use of conventional methods described in the prior art.

The present invention also relates to the articles lubricated with the lubricating composition of the invention as well as the use of the lubricating composition of the invention for the lubrication of various articles.

More particularly, the invention relates to:

an expandable rubber bladder coated on its external surface with a composition according to the invention, for shaping and vulcanizing pneumatic or semi-pneumatic tires;

an expandable rubber bladder coated with a lubricating agent that can be obtained after drying at room temperature or by heating the expandable bladder defined above, in particular at 80-150 ° C. (preferably 100-150 ° C.) , so as to ensure the total crosslinking of the crosslinkable constituents of the emulsion. The crosslinking of the lubricating film by heating can be carried out in an oven or directly in the tire manufacturing press during the preheating of the bladder;

a raw tire or semi-pneumatic tire comprising elements which will constitute its outer tread intended to come into contact with the ground, coated on its inner surface with a composition according to the invention; and

the use of a lubricant composition according to the invention during the shaping and vulcanization of pneumatic or semi-pneumatic tires, for the lubrication of the expandable vulcanizing bladder made of rubber or the pneumatic or semi-pneumatic tire raw before its vulcanization.

The lubricating composition of the invention can be applied in any way, for example by spraying, brushing or using a sponge, a piece of tissue or a brush. It is preferable to operate so as to cover the article to be coated with a regular layer of coating.

The lubricant composition is either applied to the bladder, the inner surface of the uncured tire ("the inner liner") or both. This combination allows the tire uncooked to slide on the bladder (bladder) when the press closes while ensuring a good progress of the step of release of the baked tire (vulcanized). This prevents the adhesion of the vulcanized tire on the bladder. Thus, the number of demoulding possible by application of release agent, but also the number of possible moldings by bladder is increased without loss of quality in the vulcanized tire, particularly in terms of the symmetry of the tires thus obtained.

The lubricant composition of the invention further has excellent slip and durability properties.

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

EXAMPLE 1

An emulsion A (invention) is prepared whose nature and the proportions of these constituents are respectively given in Table 1 below:

TABLE 1 Emulsion A (Invention)

⁽¹⁾ MDT resin having a hydroxylation level 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 siloxyl units:

M: 17 mol%

D: 26 mol%

T: 57 mol%. The% indicated below are by weight relative to the total weight of the composition.

Preparation of a composition A according to the invention

The lubricating composition of Table 1 was prepared as indicated below. In an IKA ^® reactor equipped with a scraper, a mixture consisting of non-reactive polydimethylsiloxane (A), reactive oil (B), resin (C), methyltriethoxysilane (D), surfactant (F) and one part of distilled water (in a water / surfactant ratio of 0.9) is homogenized.

A phase inversion is observed. Indeed, the system evolves from a water / oil phase to a thick oil / water phase.

The dilution of the thick phase obtained is carried out with medium agitation, using the amount of distilled water remaining. The other constituents are added at the end of the dilution, a homogenization with moderate stirring is carried out.

The emulsion obtained is characterized by an average particle size of 0.500 μm, a Brookfield viscosity of 180cps (A3V100) and a proportion of dry matter (60 min, 120 ° C.) of 34.0% by weight.

EXAMPLE 2 - Invention

An emulsion B (Invention) is prepared according to the same procedure as that of Example 1. The nature and the proportions of these constituents are respectively given in Table 2 below:

TABLE 2 Emulsion B (Invention)

⁽¹⁾ MDT resin having a hydroxylation level 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 siloxyl units:

M: 17 mol%

D: 26 mol%

T: 57 mol%. The emulsion obtained is characterized by an average particle size of 0.510 μm, a Brookfield viscosity of 271cps (A3V100) and a proportion of dry matter (60 min, 120 ° C.) of 31.0% by weight.

EXAMPLE 3 - Comparative

A C (Comparative) emulsion is prepared according to the same procedure as that of Example 1. The nature and proportions of these constituents are respectively given in Table 3 below:

TABLE 3 Emulsion C (Comparative)

⁽¹⁾ MDT resin having a hydroxylation level 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 siloxyl units:

M: 17 mol% D: 26 mol%

T: 57 mol%.

The emulsion obtained is characterized by an average particle size of 0.300 μm, a Brookfield viscosity of 342cps (A3V100) and a proportion of dry matter (60 min, 120 ° C.) of 29.1% by weight.

EXAMPLE 4 - Comparative

A D (Comparative) emulsion is prepared according to the same procedure as that of Example 1. The nature and proportions of these constituents are respectively given in Table 4 below:

TABLE 4 Emulsion D (Comparative)

⁽¹⁾ MDT resin having a hydroxylation level 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 siloxyl units:

M: 17 mol%

D: 26 mol%

T: 57 mol%.

The emulsion obtained is characterized by an average particle size of 0.550 μm, a Brookfield viscosity of 358cps (A3V100) and a proportion of dry matter (60 min, 120 ° C.) of 32.0% by weight. EXAMPLE 5 - Comparative

An emulsion E (Comparative) is prepared according to the same procedure as that of Example 1. The nature and the proportions of these constituents are respectively given in Table 5 below:

TABLE 5 Emulsion E (Comparative)

⁽¹⁾ MDT resin having a hydroxylation level 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 siloxyl units:

M: 17 mol%

D: 26 mol%

T: 57 mol%. The emulsion obtained is characterized by an average particle size of 0.500 μm, a Brookfield viscosity of 175cps (A3V100) and a proportion of dry matter (60 min, 120 ° C.) of 24.3% by weight.

Application Properties

The properties of the compositions are measured by evaluating coefficients of friction and durability.

A low coefficient of friction reflects good sliding properties.

The tests for measuring friction coefficients and durability were adapted to the application of the lubricating composition on an expandable rubber bladder.

Slip test

The purpose of this test is to appreciate the sliding power of a lubricant composition placed at the interface between the inflatable bladder and the inner surface of the tire casing.

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 fixed weight, under which is fixed a tire casing film (50 x 75 mm).

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

The coefficient of friction is measured using a tensiometer (at a speed of 50 mm / min.). Five successive passages are made on the same inflatable bladder sample by changing each time the tire casing sample.

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

The five passages give information on the depletion of the lubricant composition during successive feeds.

This sliding test is perfectly representative of the performances to be achieved on the industrial tool, it is a first criterion of selection.

Durability test The durability of a lubricating composition corresponds to the number of tires made without degradation of the surface of the inflatable bladder. An inflatable bladder film, previously treated with the lubricating composition to be evaluated, is pressed in contact with a film tire casing, uncured, according to a series of pressure and temperature cycles simulating the manufacturing steps of a tire on the industrial tool.

The tire casing film is replaced at each feed. The test is finished when the two surfaces in contact remain stuck. The lubricating composition on the surface of the film of the inflatable bladder is exhausted and no longer acts as a lubricating interface.

Sustainability test by transfer

The durability of a lubricating composition corresponds to the number of tires produced without degradation of the surface of the inflatable bladder. An inflatable bladder film is pressed into contact with an unvulcanized tire casing film, according to a series of pressure and temperature cycles simulating the manufacturing steps of a tire on the industrial tool.

The first molded tire casing film is pretreated with the lubricating composition to be evaluated to simulate the transfer of the lubricating agent from the tire casing to the bladder. The tire casing film is subsequently replaced at each molding by an untreated film. The test is finished when the two surfaces in contact remain stuck. The lubricating composition on the surface of the film of the inflatable bladder is exhausted and no longer acts as a lubricating interface.

The test results are shown in Table 5.

TABLE 5

Note that it is very difficult to obtain a composition that makes it possible to obtain both of the following properties:

good durability in direct bladder application (useful for the manufacture of heavy vehicle tires characterized by easy accessibility of the bladder bladder),

- Good durability in transfer of the envelope on the bladder (useful for the manufacture of light vehicle tire characterized by a difficult accessibility of the bladder bladder, hence the treatment of the raw tire and transfer on the bladder), and

good sliding properties (Kd less than 0.45).

The compositions according to the invention make it possible to obtain the three properties which makes it possible to use them in the manufacture of heavy or light tires.

Claims

1 - Lubricant composition, in the form of an oil-in-water emulsion, based on siloxane and not releasing hydrogen, comprising: (a) at least one non-reactive polydiorganosiloxane oil (A) with lubricating properties having a dynamic viscosity of order of 20 to 100,000 mPa.s at 25 ° C;

(b) at least one reactive linear polydiorganosiloxane oil (B) having at least two OH groups per molecule, said polydiorganosiloxane having a dynamic viscosity at 25 ° C of between 50 and 50 x 10 ⁶ mPa.s, (c) optionally at least a polyorganosiloxane resin (C) carrying, before emulsification, condensable hydroxyl substituents and having before emulsification at least two different siloxyl units selected from those of formula (R °) ₃ SiOi _{/ 2} (M); (R ⁰ ) 2SiO 2/2 (D); R ° SiO 3/2 (T) and SiO 4/2 (Q), at least one of these units being a T or Q unit, in which R ⁰ represents a monovalent organic substituent, the average number per molecule of organic radicals. R ⁰ for a silicon atom being between 1 and 2; and said resin having a weight content of hydroxyl or alkoxy substituents of between 0.1 and 10% by weight, and preferably between 0.2 and 5% by weight,

(d) at least one crosslinking agent (D) soluble in the silicone phase,

(e) at least one water-soluble crosslinking agent (E) having the formula in its monomeric form:

(R ² ) (R ¹ ) NR ^a -Si (OH) ₃ wherein R ^a is a C 1 -C 20 alkylene group with R ¹ and R ² independently represent a hydrogen atom or a C ₁ -C ₆ alkyl group said crosslinking agent may be in oligomeric form by condensation of one or more silanol functions,

(f) at least one surfactant (F),

(g) water (K),

(h) at least one film-forming polymer (G), (i) optionally at least one thickener (H), (J) optionally at least one wetting agent (I), and

(k) optionally at least one additive (J), with the additional conditions that:

(1) the amounts of surfactants and water being sufficient to obtain an oil-in-water emulsion, and (2) said lubricating composition does not contain a metal condensation catalyst.

2 - Composition according to claim 1 wherein the film-forming polymer (G) is an organic polymer latex, preferably a styrene-acrylic copolymer. 3 - Composition according to claim 1 wherein the film-forming polymer (G) comes from the polymerization:

at least one alkyl (meth) acrylate monomer chosen from the group consisting of: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate and (meth) butyl acrylate,

a styrene monomer, and

- optionally at least one monomer selected from the group consisting of: acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid.

4 - Composition according to claim 1 wherein the crosslinker (D) soluble in the silicone phase is selected from organotrialcoxysilanes, organotriacyloxysilanes, organotrioximosilanes and tetraalkylsilicates.

5 - Composition according to claim 4, characterized in that the crosslinker (D) soluble in the silicone phase is an alkyltrialkoxysilane of formula YSiZ ₃ in which Y is an alkyl group and Z is an alkoxy group.

6 - Composition according to any one of the preceding claims, characterized in that the non-reactive polydiorganosiloxane oil (A) is a linear polydiorganosiloxane with repeating units of formula (R) ₂ SiO _2/2 , terminated at its chain ends by (R) ₃ SiOi _{Z2 units} , wherein R is a monovalent organic group selected from the group consisting of alkyls, alkenyls, aryls, cycloalkyls, cycloalkenyls, aralkyls and alkaryls.

7 - Composition according to claim 4, characterized in that the non-reactive polydiorganosiloxane oil (A) is a polydimethylsiloxane.

8 - Composition according to any one of the preceding claims, characterized in that the polyorganosiloxane resin (C) is a hydroxylated DT or MDT resin comprising at least 20% by weight of T units and having a weight content of hydroxyl groups ranging from , 1 to 10%, preferably 0.2 to 5%. 9 - Composition according to claim 6, characterized in that the polyorganosiloxane resin (C) has a dynamic viscosity at 25 ° C of between 0.2 and 200 000 mPa.s.

10 - Composition according to claim 1, characterized in that the reactive linear polydiorganosiloxane oil (B) has the formula:

in which n is an integer greater than or equal to 50, R ³ and R ⁴ , which may be identical or different, represent: a Ci-C ₆ alkyl; C ₃ -C ₅ cycloalkyl; C ₂ -C ₆ alkenyl; Cs-Cs cycloalkenyl, aryl, alkylarylene and arylalkylene; each of the aforementioned radicals being optionally substituted by a halogen atom (and preferably fluorine) or a cyano residue.

11 - Composition according to any one of the preceding claims, characterized in that it comprises from 0.5 to 10% by weight of surfactant relative to the total weight of the composition.

12 - Raw pneumatic or semi-pneumatic tire comprising elements which will constitute its external tread intended to come into contact with the ground, coated on its inner surface with a composition according to any one of claims 1 to 11.

13 - Expandable bladder rubber coated on its outer surface with a composition according to any one of claims 1 to 11 for the shaping and vulcanization of pneumatic or semi-pneumatic tires. 14 - Expandable rubber bladder obtainable by drying at room temperature or by heating at a temperature of 80 to 150 ° C of a bladder according to claim 13.

15 - article coated with a composition according to any one of claims 1 to 11.

16 - Article obtainable by heating an article according to claim 15.

17 - Use of a lubricant composition according to any one of claims 1 to 11 for lubricating an article.

18 - Use of a lubricating composition according to any one of claims 1 to 11 during the shaping and vulcanization of pneumatic or semi-pneumatic tires, for lubricating an expandable rubber vulcanizing bladder.