EP1250379A1

EP1250379A1 - Method for preparing polyorganosiloxanes by polymerisation catalysed by a catalytic system based of triflic acid or triflic acid derivatives

Info

Publication number: EP1250379A1
Application number: EP00985435A
Authority: EP
Inventors: Christian Bordone; Jean-Roger Desmurs; Léon GHOSEZ; José MARTINS; Gérard Mignani
Original assignee: Rhodia Chimie SAS
Current assignee: Rhodia Chimie SAS
Priority date: 1999-12-17
Filing date: 2000-12-14
Publication date: 2002-10-23
Also published as: IL150211A0; BR0016767A; CN1414991A; WO2001044349A1; JP2003517072A; PL355873A1; RU2002119012A; US20030109659A1; FR2802540B1; AU2185601A; MXPA02005915A; KR20020063235A; US6737495B2; FR2802540A1; CA2394266A1

Abstract

The invention concerns a method for preparing polyorganosiloxanes (POS) by (a) condensation polymerisation of monosilanes and/or acyclic siloxanes bearing reactive Si-OR units with R = H, or alkyl, or by (b) redistribution/ condensation polymerisation of siloxane compounds based on cyclosiloxanes and/or acyclic siloxanes capable of bearing reactive Si-OR units such as defined above, Si-H or Si-alkenyl units, in the presence of an acid catalyst. Said method is characterised in that it consists in using at least a catalyst of the following formula (I) (CmF2m+1SO2)nA wherein: m is an integer not less than 1; n is an integer equal to 1 or 2 and A represents OH, NH2 or NH with: (i) n = 1 and A = OH or (ii) n = 1 and A = NH2 or (iii) n = 2 and A = NH; provided that, when said catalyst corresponds to formula (I) (i), it is brought in the presence of an inert support in mass amount QM, expressed in weight % relative to the total mass (a) of monosilanes and/or acyclic siloxanes or (b) of the initial siloxane compounds, which is not more than 1.5. The invention also concerns a catalyst for use in the preparation of POS by said process (a) or (b) consisting of at least a compound selected among the compound of formula I(ii), the compound of formula I(iii) and mixtures thereof.

Description

PROCESS FOR THE PREPARATION OF POLYORGANOSILOXANES BY

CATALYZED POLYMERIZATION BY A CATALYTIC SYSTEM BASED

TRIFLIC ACID OR TRIFLIC ACID DERIVATIVES

The field of the invention is that of the preparation of silicones or polyorganosiloxanes. hereafter designated by POS. The development of silicones can be done in particular via polymerization by opening cyclic oligosiloxane rings (polymerization by redistribution) or else by polycondensation of SiOH silanol units carried by silanes, oligoorganosiloxanes or polyorganosiloxanes. The SiOH units involved in the polycondensation can result from the hydrolysis of alkoxy SiOR units with R = alkyl.

The polycondensation polymerization reactions which are of interest in the context of the invention are more particularly those whose catalysis is ensured by acid catalytic systems. Thus, according to another of its aspects, the invention also relates to acid catalytic systems comprising derivatives of triflic acid.

Numerous processes have already been known for a long time for manufacturing polydiorganosiloxane oils or gums, by acid or basic catalysis, heterogeneous or homogeneous, from cyclic or acyclic oligomers called oligoorganosiloxanes (OOS). (see the work of WALTER NOLL, Chemistry and Technology of silicons; Editions 1968 in English language ACADEMIC PRESS, pages 209 to 218).

These processes lead to oils or gums which are, in particular, the basic constituents of mono-or bicomponent polydiorganosiloxane compositions. hardening in elastomers in the presence of too large a catalyst, hot or at room temperature. The starting materials for these polymerizations can comprise: silanols

R2Si (OH) 2 or OOSs with silanol ends resulting from the hydrolysis of chlorosilanes (R2SiCb); hydroxylated silanes or hydroxylated OOS resulting from the hydrolysis of alkoxylated silanes or alkoxylated OOS; polyorganosiloxanes with silanol ends; or alternatively cyclosiloxanes which undergo cycle opening, then redistribution and polymerization.

As regards cyclic monomers, anionic polymerization (basic catalysis) has been widely used for the preparation of POS. Even if this anionic polymerization sometimes produces good yields, the cationic polymerization of cyclosiloxanes has proved more advantageous and has become necessary. Acid catalysis thus allows reactions to take place at room temperature. In addition, the cationic polymerization can be carried out on cyclosiloxane monomers carrying functional groups, for example SiH or SiCH2Cl, which are not compatible with the conditions of anionic processes. In any event, the opening polymerization of cyclosiloxane cycles using acid catalytic systems is very common in laboratories and in industry. The fact remains that the mechanisms governing this type of polymerization remain complex and are not always fully mastered. The literature includes numerous studies in which the starting materials or polymerization monomers are hexamethylcyclotrisiloxane (D3) or octamethylcyclotetrasiloxane (D4). These polymerizations are initiated by strong protonic acids such as H2SO4, HCIO4 or by LEWIS acids. Among these, trifluoromethane sulfonic acid (or triflic acid, represented by the abbreviation TFOH) has been widely studied.

Thus, American patent US-A-2 961 245 describes the mass polymerization by opening cycles of cyclotrisiloxane with fluorinated hydrocarbon radicals, in the presence of perfluoroalkanesulfonic acid (for example TFOH or its derivatives), and organosiloxanes linear with triorganosilyl ends (essentially hexamethyldisiloxane M2) used as chain blocking agent. There is thus obtained, after devolatilization, a fluorinated silicone oil whose viscosity is essentially regulated by the ratio of M2 / D3. The catalyst is optionally removed by distillation or washing.

In the process for the preparation of polydiorganosiloxanes with silanol ends according to patent EP-B1- 0 292 407, a polydimethylsiloxane oligomer with silanol ends, of viscosity 100 mPa · s at 25 ° C., under reduced pressure, at 110 °, is polycondensed. C and in the presence of TFOH. The water formed is removed and the polycondensation is stopped by adding a polysilazane such as hexamethylcyclotrisilazane. This product neutralizes the effect of the TFOH catalyst. British patent GB-A-1,325,654 teaches polymerization, in the presence of a perfluoroalkanesulfonic acid (for example TFOH) and of silica, of cyclic polysiloxanes D3 and D4. optionally in admixture with linear diorganopolysiloxanes type M2 blockers. At the end of the reaction, the catalyst can be neutralized with hexamethy Idisilazane. European patent EP-B1-0 133 975 describes the polycondensation in a solvent medium of linear and branched POSs with silanol functions, with a catalytic system comprising derivatives of triflic acid.

More recently, catalytic systems based on derivatives of triflic acid or of its counterparts have been used in the polymerization of cyclosiloxane monomers. The triflic acid derivatives considered are more especially those containing fluorine substituents. By way of example of perfluoroalkanesulfonic acid or known derivative, mention may be made of: C _n F2n + l SO3H, trimethylsilylester of triflic acid (CF3S03SiMe3: TMST), or benzyldimethylsilylester of triflic acid, associated with a selective proton trap (for example triethylamine, tri-N-butylamine, pyridine) or else a quaternary amo ium salt of triflic acid such as Bu4N ⁺ CF3Sθ3 ^" . Documents JP-A- 03 / 292,329, JP-A- 01/000 125, JP-A- 62/050 531 and US-A- 4,929,691 relate to catalysts of type C _n F2n + 1 SO3H. US-A-5,696,219 relates to a process for the preparation of polysiloxanes from cyclosiloxanes, functionalized with fluoroalkyl groups, according to a ring opening polymerization in the absence of an acidic catalytic system, in this case the catalytic system comprises silylesters of triflic acid and. in particular, the triflic acid trimethylsilylester CF3S03SiMe3 associated with a LEWIS base, acting as a proton trap, 2,6-ditertiobutylpyridine. Without this amino base, the polymerization does not take place. This amino base can be replaced with a salt of triflic acid such as tetrabutylammoni umtriflate.

European application EP-A-0 854 162 and Japanese application JP-A-04/268 333 also relate to the use of trimethylsilylester of triflic acid or TMST in the polymerization of cyclosiloxanes.

KAZMIERSKI et al. describe in Am. Chem. Soc. , Div. Poly. Chem., (1998) 439. the use of the silylester TMST associated with TFOH for the polymerization of 1,1-diphenyl 3,3,5,5-tetramethylcyclotrisiloxane.

In reality, as the article by G. TOSKAS et al. in Macromol. Chem. Phys. , 196 (1995) 2715, the role of TMST or triflic anhydride in the polymerization reactions of cyclosiloxanes is not that of a catalyst but rather that of an inhibitor of parasitic reaction of cyclization and linkage between chains polymers.

The publication by A.TREHAN et al. in TETRAHEDRON LETTERS, Vol. 34. No 45, pages 7335-7338. 1993 describes a new catalyst for reactions between acetals and silylated nucleophiles. This new catalyst is trimethylsilylbis (fluorosulfonyl) imide.

In such a state of the art, one of the essential objectives of the present invention is to significantly improve the catalysis, homogeneous or heterogeneous, of industrial polymerization reactions by polycondensation of silanes or polysiloxanes with SiOH units, as well as by polymerization. by cyclosiloxane ring openings, for example of the D3 or D4 type.

The improvement targeted is an improvement in terms of control, reliability and productivity of industrial processes for the production of linear POS.

Another objective, aimed at improving the catalytic system, is to improve the quality of the POS products obtained, to optimize safety and to minimize the eco-toxic impacts of industrial processes.

Another essential objective of the invention is to provide the catalytic system making it possible to give the above-mentioned process the specifications set out above. Having set all these objectives among others, the Applicant has had the merit of isolating from the family of acid catalysts comprising triflic acid and its derivatives, a new, entirely innovative and efficient catalyst.

Hence it follows that the present invention relates first of all to a process for the preparation of polyorganosiloxanes (POS) by (a) polycondensation of monosilanes and / or acyclic siloxanes carrying reactive units Si-OR with R = H or alkyl, or by (b) redistribution / polycondensation of siloxane compounds based on cyclosiloxanes and / or acyclic siloxanes which can carry reactive Si-OR units as defined above, Si-H or Si-alkenyl, in the presence of a acid catalyst, said process being characterized in that at least one catalyst of the following formula (I) is used:

(I) (C _m F2m + l SO ₂ ) _n A in which:

Δ m is an integer greater than or equal to 1. preferably 1 <m <100, more preferably still 1 <m <10, and very especially m = 1; Δ n is an integer equal to 1 or 2 and A represents OH, NH2 or NH with: (i) n = 1 and A = OH or (ii) n = 1 and A = NH2 or (iii) n = 2 and A = NH;

Δ with the condition that, when this catalyst corresponds to formula I (i), it is supported on an inert material, preferably carbon black, in mass quantity QM expressed in% by weight relative to the total mass ( a) monosilanes and / or acyclic siloxanes or (b) starting siloxane compounds:

* QM <1.5,

* preferably QM <1,

* more preferably 0.01 <QM <1.

This particular group of catalysts of formula (I) makes it possible to obtain, with high kinetics, polydiorganosiloxanes and in particular polydimethylsiloxanes having desired degrees of polymerization.

The polymerizations carried out with the triflic acid derivatives of formula (I) are, at equal concentrations and under the same conditions as a conventional catalysis with triflic acid, clearly faster while leading to POSs of viscosity (molecular mass ) higher and having a residual volatile content at least equal.

In accordance with the invention, the starting materials ("monomers") are advantageously chosen from the group comprising:

/ the silanols of formula (II): R'R ² Si (OH) ₂ , • / linear hydroxylated oligo- or polyorganosiloxanes (OPOS-1) of formula (III): HO (R ³ R ⁴ SiO) _x H, cycloorganosiloxanes (COS) of formula (IV):

(R ⁵ R ⁶ SiO) _y , non-hydroxylated linear oligo- or polyorganosiloxanes (OPOS-2) of formula (V):

E 'E ² E ³ SiO- (R ⁷ R ⁸ SiO) z-SiE ⁴ E ⁵ E ⁶ , • / and their mixtures, with the following additional modalities: "the radicals R'to R ⁴ , R ⁷ and R ⁸ and E ¹ to E ° in the formulas (II), (III), (V) above are identical or different from each other and are chosen from the following radicals: hydrogen, C 1 -C ₃₀ alkyls ( preferably C, -C ₁₀ ), C -C ₃₀ alkenyls (preferably C -Cι ₀ ), and aryls optionally substituted - advantageously by halogens -; methyl, ethyl, propyl radicals. phenyl, vinyl. allyle and trifluoro-

3,3,3-propyl being particularly preferred,

• the radicals R and R in the formula (IV) above are identical or different between them and have the same meaning as that indicated in the context of the radicals R ¹ to R ⁴ , R ⁷ , R ⁸ and E ¹ to E ⁶ , or also represent an OR ⁹ group where R ⁹ is a hydrogen atom or a C ₁ -C ₅ alkyl

(methyl, ethyl and propyl radicals being preferred),

• the different symbols x. y and z which appear in formulas (III), (IV) and (V) are whole or fractional numbers which vary in the following intervals: • OPOS-1 (III): x = from 2 to 1000, preferably from 2 to 500. and better from 2 to 100, ¹ COS (IV): y = from 3 to 12. preferably from 3 to 8 and better from 3 to 5, • OPOS-2 (V): z = from 2 to 1000, preferably from 2 to 500 and better still from 2 to 100. The silanols of formula (II) are, for example, hydrolysis products of chlorosilanes resulting from direct synthesis. These silanols of formula (II) just like the OPOS-1 of formula (III) can also come from the hydrolysis of alkoxylated precursors carrying SiOR units with R = alkyl.

The COS cycloorganosiloxanes of formula (IV) are, for example, products of the D3 or D4 type which react according to a cycle opening (redistribution) and polycondensation mechanism. According to a preferred characteristic of the invention, a mixture is selected as starting materials:

• several COS (IV) between them, or

- / at least one COS (IV) with at least one OPOS-1 (III) and / or with at least one OPOS-2 (V), mixture in which the siloxane compounds used have formulas where the symbols R ³ to R ⁸ and E ¹ to E ⁶ are chosen from the group formed by a hydrogen atom, a methyl radical or a vinyl radical.

According to a more preferred characteristic, the following mixtures: "of octamethyltetracyclosiloxane (D4) and of hexamethyldisiloxane (M2),

• hydrogenethyltetracyclosiloxane (D'4) and dihydrogenotetra-methyldisiloxane (M2 ')

. of D4 and D'4 ^a of vinylmethvltetracyclosiloxane (D4 ^l ) and of divinyltetramethyl-disiloxane (M2 Vi)

"of α, ω-dihydroxylated polydimethylsiloxane and of D4. such a mixture being contained in chlorosilane hydrolysates (Silox).

• Silox and M2

• D4 and M'2 "from D4, M2 and polymethylhydrogenosiloxane with trimethylsilyl ends are very specially selected.

Silox are mixtures of α, ω-dihydroxylated oligo- or polyorganosiloxane and cyclosiloxanes. These mixtures come from the direct synthesis of organochlorosilanes (ROCHOW synthesis) and from the hydrolysis of the chlorosilanes obtained.

Taking an interest in triflic acid derivatives in order to use them as an industrial catalyst for polymerizing silicones can be compared to an inventive step against an unfavorable prejudice weighing on triflic acid, in particular because of the known difficulty in neutralizing this acid (very unstable TFOH salt) and in its corrosive nature.

According to a first embodiment corresponding to a heterogeneous catalysis with a catalyst (I) corresponding to formula I (i): CmF2m + lS l3H, a catalyst (I) is used which is supported on an inert material, of preferably carbon black. The polymerization is then optionally stopped by adding an acid neutralizer I (i) and the support comprising the catalyst I (i) is then removed from the reaction medium. The preparation of the catalyst supported on an inert material is generally carried out by simple addition of the catalyst (I) to the chosen support, this operation can be conducted beforehand or at the time of the preparation of the polymerization reaction medium.

The polymerizations carried out with this supported triflic acid I (i), preferably on carbon black are advantageous in that they lead to a medium which is easier to neutralize at the end of the polymerization. Indeed, compared to a catalysis in homogeneous phase, the residual acidity is much lower and one can thus obtain silicone oils having a better temperature and storage stability.

Furthermore, this system allows, all conditions equal, moreover, significantly faster polymerization kinetics than those observed for heterogeneous catalysts on acid soil, while leading to products with similar characteristics in terms of viscosity and rate volatile.

In addition, the polymerization according to this first embodiment is possible at temperatures ranging from room temperature (23 ° C) to 150 ° C or even more.

According to a second embodiment corresponding to a heterogeneous catalysis, a catalyst (I) or a mixture of catalysts (I) corresponding to the formula (s) I (ii) (C _m F2 _{m) is used.} + lS02) NH2 and / or I (iii): (C _m F2m + l S02) 2NH and supported on an inert material, preferably carbon black. The polymerization is then optionally stopped by adding a neutralizer to the supported catalyst (s) I (ii) and or I (iii), and finally the support comprising the catalyst (s) is removed from the reaction medium. (s) I (ii) and or I (iii).

According to a third embodiment corresponding to a homogeneous phase catalysis, a catalyst (I) or a mixture of catalysts (I) corresponding to the formula (s) I (ii) and / or is used. I (iii) in liquid form which is mixed with the reaction medium comprising the starting materials and the polymerization is stopped by adding a neutralizer to the catalyst (s) (I) and optionally the medium is filtered reaction to remove solid residues.

This homogeneous catalysis with trifluoromethanesulfonimide (TFSI) allows rapid polymerization, in particular with regard to a heterogeneous catalysis on acid earth, all conditions being equal elsewhere and for end products with similar characteristics.

In addition, this TFSI catalyzed polymerization is possible at temperatures ranging from room temperature (23 ° C) to 150 ° C or even higher.

It thus appears that the catalyst according to the invention is of the type is heterogeneous when it is TFOH. either heterogeneous or homogeneous when it comes to TFSI. According to a preferred embodiment of the invention, the catalyst concentration is adjusted

(CC) to the following values (molar concentration in% o relative to all of the starting silicon products):

- wide interval of variation of CC: 0.1 <CC <10,

- preferably: 1 <CC <8,

- and more preferably still: 3 <CC <5. It is highly preferable, for the polymerization to proceed correctly, that the reaction atmosphere be free of moisture. Thus, it is advantageous to work under an atmosphere of neutral gas, for example argon or nitrogen.

The reaction pressure is advantageously normal and the temperature can range from room temperature (23 ° C) to a temperature of 150 ° C or more. The polymerization is stopped by deactivating the catalyst. As soon as it is an acid catalyst, deactivation can take place using a basic neutralizer. As a compound of this type, there may be mentioned for example: sodium carbonate (Na ₂ CO ₃ ) and sodium bicarbonate (NaHCO ₃ ).

Neutralization is all the more necessary when it is a homogeneous catalysis since in such a case, unlike heterogeneous catalysis, the catalyst is not removed at the end of the reaction.

Advantageously, the fluorinated chain C _m F2m + 1 can be lengthened so as to increase the acidity of the catalyst and subsequently its efficiency.

In the foregoing, it has been explained that the catalyst according to the invention, when it is a heterogeneous catalysis, is supported on an inert material, preferably carbon black. It would not go beyond the scope of the present invention, by carrying out, in order to obtain this supported catalyst, a grafting of the catalytic functions of the compounds (I) of type

TFOH or TFSI on supports, for example of the polymer resins, clay, silica or any other solid support stable and inert under the conditions of the present invention. According to another of these aspects, the present invention relates to a catalyst useful for the preparation of polyorganosiloxanes (POS) by (a) polycondensation of

(mono) silanes and / or acyclic siloxanes carrying reactive Si-OR units with R = H or alkyl, or by (b) redistribution / polycondensation of siloxane compounds based on cyclosiloxanes and / or acyclic siloxanes which may carry units Si-OR reagents as defined above, Si-H or Si-alkenyl, in the presence of an acid catalyst, said catalyst being characterized in that it comprises at least one compound chosen from the compounds of the following formulas:

I (ii) → (C _m F ₂ m + l S02) NH ₂ I (iii) → (C _m F ₂ m + l S02) 2NH and their mixtures.

The catalyst TFSI according to the invention I (ii) and I (iii) is clearly more efficient than a conventional catalyst of the H2SO4 or TFOH type in terms of reaction kinetics. In addition, compared to TFOH, it makes it possible to obtain POSs of viscosity (molecular mass) higher with a lower residual volatility rate, under the same qualitative and quantitative conditions. In addition, the TFSI is stable and easy to handle.

The examples which follow will make it possible to better understand the process and the catalyst according to the invention by highlighting all their advantages and the possible variants of implementation.

The starting materials chosen without limitation in these examples are octamethylcyclosiloxane (D4) and a chain blocker consisting of rhexamethyldisiloxane (M2).

EXAMPLES

Examples 1 to 4: polymerization of D4 and M2 to synthesize an α.ω- bis (trimethylsilyl) polydimethylsiloxane (PDMS) oil in the presence of a control catalytic system consisting of TFOH or of a catalytic system according to the invention based on from TFSI I (iii)

A - procedure: D4 and M2 (molar purity> 99.9% by gas chromatography) are dried beforehand for 24 hours over magnesium sulfate. They are then enclosed in an argon vacuum, degassed several times, then dried over a 4 Å molecular sieve. The catalysts TFOH (RHODIA product with molar purity> 99%) and TFSI (CF ₃ SO ₂ ) ₂ NH (SIGMA product with 97% molar purity) are stored under argon in airtight containers and in the refrigerator. They are then introduced under an argon atmosphere into a glove box and used directly. A 250 ml three-necked flask. previously placed under vacuum, then placed under argon, equipped with magnetic stirring, a heating system and a septum for sampling the reaction mass and injecting the catalyst and a system allowing the circulation of Argon is introduced into a glove box and under an argon atmosphere.

100 g of D4 and 1.35 g of M2 are introduced into the flask at 25 ° C. The polymerization is started (t = 0 h) by adding the catalyst to the monomer and to the blocker using a syringe at 25 ° C. in a concentration of 4% o relative to D4 + M2 (molar). The reaction mixture is stirred continuously. The polymerization is then either carried out at 25 ° C or the temperature is gradually raised to 100 ° C (rise in 10 min) for a period of 5 h. The polymerization is followed over time by measuring the viscosity of the corresponding non-devolatilized oil on successive samples of samples (10 ml) (at 0.5, 3 and 5 h of reaction). The polymerization reaction is stopped by adding an excess of sodium bicarbonate (0.126 g - 1.5 mmol). The mixture is then directly filtered on neutral earth (clarcel) or, for samples for analysis, also after neutralization (neutralizing: 0.0126 g - 0.15 mmol), on a 0.45 μm Millipore filter to remove residues solid. A transparent and limpid oil is obtained, the viscosity and the rate of volatiles being immediately measured in a Chopin oven (1 g of oil at 150 ° C. / 2 h). An acidity level is also measured and it is less than 2 mg / kg HC1 equivalent.

B - experimental conditions and results: The type and mass of the catalyst, the polymerization temperature (25 or 100 ° C) and the results obtained in terms of viscosity of the oils synthesized before devolatilization and in terms of mass percentage of volatiles are given in the Table 1 below.

Table 1: polymerization of the mixture of D4 and M2 and synthesis of the oil, ω- bis (trimethylsilyl) polydimethylsiloxane catalyzed by TFOH (controls) and TFSI = I (iii).

1) 0.0013 moles (4% o molar relative to D4 + M2) 2) Viscosity (in mPa.s) at 25 ° C after x hours (xh) of reaction time for the PDMS obtained before devolatilization 3) analysis of PDMS by steric exclusion chromatography or GPC ("Gel Permeation Chromatography") before devolatilization (without elimination of low molecular weight compounds) 4) analysis of PDMS after devolatilization (that is to say after elimination of low weight compounds molecular) 5) degree of theoretical DPn polymerization = 4 [D4] / [M2] = 162 6) M (actual mass of the structure PDMS:

Me ₃ SiO- (Me ₂ SiO) _DPn -SiMe ₃ and calculated from DPn after ethoxylation. Mw and Mn are given in standard polystyrene equivalents.

Examples 5 to 8: polymerization of D4 and M2 to synthesize α, ω- bis (trimethylsilyl) polydimethylsiloxane oil using a homogeneous catalytic system based on triflic acid alone (control) or with using a heterogeneous catalytic system constituted by triflic acid TFOH supported on carbon black (NC)

A - operating mode:

D4 and M2 (molar purity> 99.9% by gas chromatography) are dried beforehand for 24 hours over magnesium sulfate. They are then enclosed in an argon vacuum, degassed several times, then dried over a 4 A molecular sieve. The TFOH catalyst (RHODIA product with molar purity> 99%) is stored under argon in airtight containers and in the refrigerator. Carbon black is a product of CECA (Type 4S). They are then introduced under an argon atmosphere into a glove box and used directly.

A 250 ml three-necked flask, previously placed under vacuum, then placed under argon, equipped with magnetic stirring, a heating system and an inlet for the reaction mass samples and the introduction of the catalyst and d 'a system allowing the circulation of argon is introduced into a glove box and under an argon atmosphere.

100 g of D4 and 1.35 g of M2 are introduced into the flask at 25 ° C. In the case of the TFOH / NC catalytic system, carbon black (0.26 g) is also introduced. The polymerization is started (t = 0 h) by adding the catalyst to the monomer and to the blocker using a syringe at 25 ° C. in a concentration of 4% o relative to D4 + M2 (molar). The reaction mixture is stirred continuously. The polymerization is then either carried out at 25 ° C or the temperature is gradually raised to 100 ° C (rise in 10 min) for a period of 5 h. The polymerization is followed over time by measuring the viscosity of the corresponding non-devolatilized oil on successive samples of samples (10 ml) (at 0.5.3 and 5 h of reaction).

The polymerization reaction is stopped by adding an excess of sodium bicarbonate (0.126 g - 1.5 mmol). The mixture is then directly filtered on neutral earth (clarcel) or, for samples for analysis, also after neutralization (neutralizing: 0.0126 g - 0.15 mmol), on a 0.45 μm Millipore filter to remove residues solid. A transparent and limpid oil is obtained, the viscosity and the rate of volatiles being immediately measured in a Chopin oven (1 g of oil at 150 ° C. / 2 hrs). B - experimental conditions and results:

Table 2 below gives the type and mass of the catalyst, the polymerization temperature 25 or 100 ° C., as well as the results in terms of viscosity of the oils obtained before devolatilization and in terms of mass percentage of volatiles.

Table 2: Polymerization of D4 and M2 and synthesis of the α, ω-bis (trimethylsilyl) polydimethylsiloxane oil catalyzed by TFOH alone (control) or supported on carbon black (NC)

* Viscosity measured at 25 ° C after x hours (xh) of polymerization on a non-devolatilized oil. ** Acidity expressed in mg / kg of HCl equivalents. It is measured after addition of the neutralizer.

Comparative examples 9 to 12: polymerization of D4 and M2 to synthesize α, ω-bis (trimethylsilyl) polydimethylsiloxane oil using a heterogeneous catalytic system consisting of an acidic earth (tonsil)

A - operating mode:

® The procedure used for a Tonsil catalysis (TONSIL product

OPTIMUM 210 FF from Sûd-Chemie) is broadly identical to that of the previous examples (Apparatus, charges, temperature, polymerization, sampling, filtration, analyzes). The only differences concern:

- the introduction of the catalyst without the use of a syringe. - neutralization which is useless: the final filtration is sufficient to remove the catalyst without residual traces of acidity in the medium (acidity rate <3 mg / kg of HCl equivalent).

B - experimental conditions and results: Table 3 below gives the type and mass of the catalyst, the polymerization temperature (25 ° or 100 ° C), and the results in terms of viscosity of the oils obtained before devolatilization and in terms mass percentage of volatiles.

Table 3 Polymerization of D4 and M2 and synthesis of α, ω-bis (trimethylsilyl) polydimethylsiloxane oil catalyzed by Tonsil

* Viscosity measured at 25 ° C after x hours (x h) of polymerization on a non-devolatilized oil. ** Acidity expressed in mg / kg of HCl equivalents. It is measured after addition of the neutralizer.

Similar polymerizations at 25 ° C to 100 ° C, carried out with 0.5 g of Tonsil, confirm these results.

Claims

1 - Process for the preparation of polyorganosiloxanes (POS) by (a) polycondensation of monosilanes and / or acyclic siloxanes carrying reactive Si-OR units with R = H or alkyl, or by (b) redistribution / polycondensation of siloxane-based compounds cyclosiloxanes and optionally acyclic siloxanes which can carry reactive Si-OR units as defined above, Si-H or Si-alkenyl, in the presence of an acid catalyst, said process being characterized in that one implements at least one catalyst of the following formula (I): (I) (C _m F ₂ m + l S02) n A in which:

Δ m is an integer greater than or equal to 1;

Δ n is an integer equal to 1 or 2 and A represents OH, NH2 or NH with: (i) n = 1 and A = OH or (ii) n = 1 and A = NH2 θu

(iii) n = 2 and A = NH;

Δ with the conditions according to which: • when this catalyst corresponds to formula I (i), it is placed in the presence of an inert support in mass quantity

QM, expressed in% by weight relative to the total mass (a) of the monosilanes and / or acyclic siloxanes or (b) of the starting siloxane compounds, which is equal to or less than 1.5; and • when this catalyst corresponds to formula I

(iii): either it is supported on an inert material in the case of the preparation of polyorganosiloxanes (POS) by (a) polycondensation of monosilanes and / or acyclic siloxanes or by (b) redistribution / polycondensation of siloxane compounds based on cyclosiloxanes and optionally acyclic siloxanes. or it is used in liquid form in the case of the preparation of polyorganosiloxanes (POS) by (b) polycondensation redistribution of siloxane compounds based on cyclosiloxanes and optionally acyclic siloxanes.

2 - Method according to claim 1 characterized in that the starting materials are chosen from the group comprising:

/ the silanols of formula (II): R ¹ R ² Si (OH) ₂ ,

- linear hydroxylated oligo- or polyorganosiloxanes (OPOS-1) of formula (III): HO (R ³ R ⁴ SiO) _x H, cycloorganosiloxanes (COS) of formula (IV): / (R ⁵ R ⁶ SiO) _y , non-hydroxylated linear oligo- or polyorganosiloxanes (OPOS-2) of formula (V):

E'E ² E SiO- (R ⁷ R ⁸ SiO) _z -SiE ⁴ E ⁵ E ⁶ , and their mixtures, with the following additional methods:

The radicals R ′ to R ⁴ , R ⁷ and R ⁸ and E ¹ to E ⁶ in the formulas (II), (III), (V) above are identical or different between them and are chosen from the following radicals : hydrogen, C 1 -C ₃₀ alkyls, C ₂ -C ₃₀ alkenyls and optionally substituted aryls, »the radicals R ⁵ and R ⁶ in formula (IV) above are identical or different between them and have the same meaning as that indicated in the context of the radicals R ¹ to R ⁴ , R ⁷ , R ⁸ and E ¹ to E ⁶ , or also represent a group OR ⁹ where R ⁹ is a hydrogen atom or a C ₁ -C ₅ alkyl,

• the different symbols x, y and z which appear in formulas (III), (IV) and (V) are whole or fractional numbers which vary in the following intervals:

• OPOS-1 (III): x = from 2 to 1000,

• COS (IV): y = from 3 to 12,

• OPOS-2 (V): z = from 2 to 1000.

3 - Method according to claim 2. characterized in that a mixture of:

/ of several COS (IV) together, or of at least one COS (IV) with at least one OPOS-1 (III) and / or with at least one OPOS-2 (V), mixture in which the siloxane compounds used have formulas where the symbols R ³ to R ⁸ and E ¹ to E ⁶ are chosen from the group formed by a hydrogen atom, a methyl radical or a vinyl radical.

4 - Method according to any one of claims 1 to 3, characterized by the following points:

• the catalyst (I), which corresponds to formula I (i): C _m F2m + lS03H is supported on an inert material,

The polymerization is optionally stopped by adding a neutralizer of the supported acid I (i),

• then the support comprising the catalyst I (i) is removed from the reaction medium. 5 - Method according to any one of claims 1 to 3, characterized by the following points:

• the catalyst (I) or the mixture of catalyst (I) corresponding to the formula (s) (I) (ii) (C _m F _{2m +} ιSO) NH and / or I (iii) C _m F _2m + ι SO ₂ ) ₂ NH is supported on an inert material, • the polymerization is optionally stopped by adding a neutralizing agent (s) of catalyst (s) I (ii) and / or I (iii) supported (s),

• the support comprising the catalyst (s) I (ii) and / or I (iii) is removed from the reaction medium.

6 - Method according to any one of claims 1 to 3 characterized by the following points:

• using a catalyst or mixture of catalysts (I) corresponding to formula (s) I (ii) and / or I (iii) in liquid form which is mixed with the reaction medium comprising the products at the start, “the polymerization is stopped by adding a neutralizing agent (s) of catalyst (s) (I) and optionally the reaction medium is filtered to remove the solid residues.

7 - Method according to one of claims 1 to 6, characterized in that the catalyst concentration (CC) is adjusted to the following values (molar concentration in% o relative to all of the starting silicon products): 0 , 1 <CC <10.

8 - Process according to any one of claims 4 to 7 characterized in that the polymerization is carried out at a temperature ranging from room temperature (23 ° C) to a temperature of 150 ° C.

9 - Method according to any one of claims 4 to 6, characterized in that one selects as neutralizing at least one compound based on sodium carbonate and / or sodium bicarbonate.

10 - Catalyst useful for the preparation of polyorganosiloxanes (POS) by (a) polycondensation of (mono) silanes and / or acyclic siloxanes carrying reactive units Si-OR with R = H or alkyl, or by (b) redistribution / polycondensation of siloxane compounds based on cyclosiloxanes and optionally on acyclic siloxanes which can carry reactive Si-OR units as defined above, Si-H or Si-alkenyl, in the presence of an acid catalyst, said catalyst being characterized in that it comprises at least one compound chosen from the following compounds:

• the compounds of formula I (ii) → (C _m F2m + l Sθ2) NH ₂ ,

• and their mixtures with the compounds of formula I (iii) → - (C _m F2m + l Sθ2) 2NH.