MXPA01005754A - Method for preparing a silica suspension in a silicone matrix crosslinkable by polycondensation to form elastomers - Google Patents

Abstract

The invention concerns a method for preparing a silica suspension in a silicone matrix, said suspension capable of being used for producing organopolysiloxanes crosslinkable by polycondensation. The invention aims at seeking a technical compromise between the rheology of said compositions and the mechanical properties of the resulting crosslinked elastomers. As a solution, the invention discloses a method for preparing a silica suspension treated with organosilazane in a silicone material comprising a linear reactive polyorganosiloxane bearing for example at each chain end a hydroxy group. The invention is characterised in that it consists essentially in introducing the organosilozane in the preparation medium:before and/or substantially simultaneously before bringing together at least part of the silicone material and the particulate filler used, said organosilozane introduction being carried out with a fraction of organosilazane corresponding to a proportion ranging between 8%and 30%by dry weight relatively to the silica filler, and after bringing together the filler and all or part of the silicone material.

Description

PROCEDURE FOR PREPARING A SUSPENSION OF SILICA IN A RETICULABLE SILICONE MATRIX THROUGH POLYCONDENSATION TO FORM ELASTOMERS Description of the invention The domain of the invention is that of organopolysiloxane compositions crosslinkable or curable in silicone elastomers by polycondensation reactions where the main components are one or more reactive organopolysiloxanes and fillers. More precisely, the present invention is related to the preparation of an intermediate product useful for obtaining these silicone elastomers, and constituted by a suspension of reinforcing filler in at least one reactive polyorganosiloxane bearing condensable or hydrolysable functional groups, such as for example = Si-OH, capable of reacting between them and / or with a crosslinking agent chosen from organosilicon compounds that include more than two condensable or hydrolyzable functional groups. The present invention also relates to the preparation of crosslinkable or hardenable organopolysiloxane compositions in silicone elastomers by polycondensation reactions comprising, as a constituent, said reinforcing filler suspension. Reinforcing and non-reinforcing fillers are distinguished in silicone elastomers. The reinforcing fillers most commonly used with pyrogenic silicas and precipitated silicas having a BET surface > 40 m2 / g. These are the ultra-fine powders that owe their effect of reinforcement on the one hand to their morphology and on the other hand to the bonds or hydrogen bonds that are formed between the silanol groups on the surface of the silicas (3-6 SiOH / nm2 groups ) and the polyorganosiloxane chains (POS). These interactions between the filler and the polymer increase the viscosity and modify the behavior of the polymer in the vicinity of the solid surface of the charges. On the other hand, the bonds between the polymers and the fillers improve the mechanical properties but they can also cause a damaging premature hardening ("structuring") of the precursor compositions of the elastomers. The non-reinforcing fillers have an extremely weak interaction with the silicone polymer. It is for example chalk or gypsum, quartz powder, earth 3 diatoms, mica, kaolin, aluminas or oxides of iron. Its effect is often that of increase. the viscosity of non-crosslinked precursors of lo. elastomers, as well as the Shore hardness and the modulus of elasticity of the latter. The compositions can lead to silicone elastomers which also include catalysts, crosslinkers, and optionally pigments, adhesive agents, plasticizers and / or adhesion promoters. These polycondensation crosslinkable elastomers, also referred to as RTV polycondensation elastomers, are formed prior to crosslinking by casting, extrusion, calendering or compression molding, injection or transfer. The compositions of silicones crosslinkable or curable in elastomers by polycondensation at room temperature or at higher temperatures (< generally at 100 ° C), are conventionally packaged in the form of single component systems (ie comprising only one package) or two-component systems (that is, they comprise two parts packed separately, and that must be mixed at the time of use). In two-component systems, one of the components comprises the catalyst of the polycondensation reaction. This catalyst can be a metal compound, such as an organic tin compound. This component including the catalyst can also comprise the crosslinking agent. Such compositions may also be presented in the form of single component systems that crosslink from room temperature in the presence of water. The preparation of concentrated suspensions (pastes) of reinforcing silicas in reactive silicone oils, intended to produce the crosslinked elastomers by polycondensation, imposes problems of mixing the powder charge with the oil, and care must be taken particularly to obtain a uniform distribution of the charges in the suspension. Another difficulty to overcome is linked to the rheology of prepared suspensions. In fact, it is clear that the introduction into the silicone oil of a particular pulverulent filler with a very low granulometry necessarily induces a remarkable increase in viscosity. However, this characteristic, although it accompanies the obtaining of good mechanical properties for the crosslinked silicone elastomers comprising the suspension as a raw material, is prejudicial to the handling and to the shaping of the suspension and of the silicone compositions containing it. It is the most comfortable effect to manipulate for molding, extrusion or shaping, fluid compositions that lend themselves easily, to pumping, to runoff or to mixing with functional additives, among others. The problem considered here can therefore be summarized as the search for a technical compromise between the specifications, a priori antinomic, for the suspensions of particular fine loads in silicone oils, namely (i) the fineness of distribution of the particles in the matrix of sylicon; (2i) the adaptation of the rheology of the suspension handling constraints and (3i) the level of mechanical properties of the cross-linked silicone elastomers. The document FR-A-2,717,180 is inscribed in this problem and describes a process for preparing charged, two-component compositions crosslinkable in elastomers by means of polycondensation reactions, where the characteristic lies in the fact that the charge used, which is usually a silicon charge, which is mixed with the reactive POS carrying the condensable functional groups, is treated before its incorporation into the composition with a compatibilization agent, mainly of the silazane type, carrying out exclusively and exclusively this treatment at the dinner of a non-reactive POS, in particular a polydialkylsiloxane with trialkylsilyl endings. This mode of treatment can be carried out in two stages, first mixing the non-reactive POS and loading with a fraction of the treatment agent and, after homogenization of this first mixture, the remaining treatment agent is incorporated. This mode of treatment provides relatively fluid charge suspensions, but the Applicant is of the opinion that this is not without undesirable consequences at the level of the elastomers prepared from the compositions comprising this suspension. In fact, it is necessary to fear that the non-reactive POS, which is not bound to the surface of the silica and, for this reason, is badly anchored to the silicone network created in the course of cross-linking, and can exude from the pieces elastomeric made. In a technical context of this type, one of the essential objectives of the present invention is to provide a process for preparing a suspension of a particular charge treated with the aid of a compatibilizing agent, in a silicone oil, which may be useful this suspension as a raw material for the preparation of crosslinkable or hardenable compositions by polycondensation reactions in the polycondensation RTV elastomer, said process having to satisfy the following loading conditions: - uniformity and homogenization of the distribution of the charge in the oil of silicone, optimization of the dispersion, suspension that dries well (without runoff threshold) and viscosity adapted to handling and transformation of the suspension, good storage stability (drawability, viscosity, time of intake) of the hardenable compositions which comprise the suspension, properties Elastics (in particular, elongation at break, resistance to tearing) of elastomers of an acceptable level. Another essential objective of the invention is to provide a process for preparing a reinforcing filler / silicone oil suspension for 5 * RTV polycondensation elastomers, which is always put into operation, economical and applicable on an industrial scale. Another essential objective of the invention is to provide a process for obtaining a crosslinkable or hardenable silicone composition by polycondensation, which comprises as a constituent the suspension as obtained by the method considered above, which has good storage stability and which it leads to elastomers having mechanical properties of an acceptable level, that this composition is presented in the form of a single component composition or under that of a two component composition. These objectives, among others, are achieved by the present invention which relates to a process for preparing a suspension of a particular reinforcing filler, preferably of a siliceous nature, in a silicone material (MS): + the MS comprises: less a linear reactive POS that includes at each end of the chain at least two condensable groups (different from (OH) or hydrolysable), or a single hydroxyl group, - optionally at least one linear non-reactive POS which does not include the condensable, hydrolysable or hydroxyl group, optionally water, + said suspension is, mainly, usable to produce crosslinkable or hardenable silicone compositions by polycondensation, + said method is of the kind of those in which the particular reinforcing filler is treated with the aid of a compatibilizing agent (AC), and which is characterized in that it consists essentially of introducing the compatibilizing agent (AC) in the means for preparing the suspension: • on the one hand, before and / or substantially simultaneously with the incorporation, in at least a part of the silicone material MS put into operation, of the particular reinforcing load used, this introduction of AC is operated with a fraction of AC corresponding to a proportion that is in the range that goes from 8% to 30% in dry weight in relation to the particular reinforcing load, and on the other hand, after this incorporation of the load on at least a part of the MS. It is the merit of the inventors to have shown, after numerous investigations and experiments, that it would be quite surprising and unexpected to introduce the compatibilization agent (such as hexamethylene diisilazane known as HDMZ) before and after incorporation of the reinforcing filler in at least a part of the silicone material MS, with the condition according to which the fraction of the compatibilizing agent AC introduced before the incorporation of the charge, represents from 8% to 30% by weight of the reinforcing filler used. These original and advantageous embodiments make it possible to obtain suspensions with appropriate rheological qualities and viscoelastic behavior. In effect, these suspensions do not have a runoff threshold or a very weak threshold that is not detrimental to the applications. This considerably favors its start-up. In particular, they have a stable fluidity over time and adapted handling and transformation operations. Such as pumping, routing, mixing, shaping, molding, extruding, etc. One of the major interests of the invention is that that acquired on the plane of rheology does not exist to the detriment of the final mechanical properties of the crosslinked elastomer. The technical commitment is achieved. On the other hand, the methodology in question makes it possible to obtain homogeneous dispersions of the particular reinforcing load in the MS. In addition, this methodology does not significantly complicate the procedure. It is simple to put into operation and inexpensive. The particular reinforcing load usually used consists of a silicon charge. As a siliceous charge capable of being put into operation, all precipitated, or pyrogenic silicas (or combustion silicas) known to those skilin the art are suitable. Of course, cuts of different silicas can also be used. Preference is given to precipitated silicas and / or combustion silicas having a BET specific surface area greater than 40 m2 / g and, more precisely, between 50 and 300 m2 / g. More preferably, combustion silicas having the specific surface characteristics mentioned above are used. Even more preferably, the combustion silicas having a BET specific surface comprised between 170 and 230 m2 / g are used. In general, this reinforcing filler has an average particle dimension of less than 0.1 μm. The compatibilizing agent (AC) is chosen from organosilazanes and cycloorganosilazanes, which are liquid at a temperature of 23 ° C and under a pressure of 1010.8102 Pa, these compounds are used alone or as a mixture between them. It can be compounds such as hexamethyldisilazane, 1,3-divinyl-1,1,3, 3-tetramethyl-disilazane, hexamethylcyclotrisilazane, octamethylcyclotetrasilazane and mixtures of these compounds. Hexamethyldisilazane is preferred.

According to one of these preferred methods of putting into operation, the method according to the invention comprises the following steps: - It is mixed in any order, possibly carrying out a premixing, of the (or of the) POS with the compatibilisation agent AC and optionally water: • (100-V-W) parts by weight of at least one reactive POS and optionally water minus a non-reactive POS. • 0 to 5 parts by weight of water, • 10 to 50 parts by weight of particular reinforcing filler, • and of a first fraction of AC representing 8% to 30% and, preferably, from 10% to 25% by weight dry reinforcing load; a second fraction of AC representing 2% to 25% and preferably 5% to 20% of the dry weight of the reinforcing filler is introduced into the mixture; it is allowed to react continuing the mixing; the mixture is heated by choosing a pressure / temperature pair in such a way that a devolatilization of the volatile elements and of at least a part of the water eventually present occurs; the devolatilized mixture is allowed to cool eventually; - and the suspension is eventually supplemented with the remainder of the reactive POS (s) (v parts by weight) and / or, optionally, the remainder of the unreactive POS (s) (parts in weigh); said method comprises the supplementary definition elements listed below: - the amount of the non-reactive POS (s), when used, (w parts by weight); - said procedure comprises the supplementary definition elements listed below. The amount of the non-reactive POS (s) when it is in the range of 1 to 100 parts by weight and, preferably, 30 to 80 parts by weight for 100 parts of the (or of) Reactive POS (s); The total amount of the compatibilizing agent AC is comprised between 10 and 45% of the weight of the reinforcing filler and, preferably between 15% and 40%; The symbol v goes from zero to 60 parts by weight and, preferably from zero to 50 parts by weight; The symbol w goes from zero to 50 parts by weight and, preferably from zero to 40 parts by weight; The sum v + w goes from zero to 60 parts by weight and, preferably from zero to 50 parts by weight. In other words, the method according to the invention allows access to a control of the viscosity of the suspension always maintaining at an acceptable (if not better) level the mechanical properties of the final elastomer obtained from the suspension. The mixing operations are carried out with the aid of known and appropriate devices. It can be for example: - arm mixers, - internal mixers, - planetary mixers, - paddle mixers in plowshare, - dual co-or counter-rotating mixers ios, - continuous extruder mixers, - or other continuous devices or discontinuous. The mixing operations are carried out at normal temperature and pressure and preferably under inert atmosphere (for example under N2). It is convenient that under these conditions, the POS used and also the compatibilization agent are in the liquid form to facilitate mixing. The particular reinforcing filler represents from 8% to 40% by weight of the suspension. In practice, this load is of the order of 28 to + 10%. To define more precisely, however this is not limiting, the preferred embodiment of the operation of the method according to the invention, it can be indicated that this comprises , in a first variant, the following steps: According to a first particular embodiment of the process of the invention, it comprises the following steps: -1- is proceeded to the homogenization of a mixture comprising all or part of the silicone oil, water and the first fraction of AC, -2- is added progressively the particular reinforcing load, to the mixture obtained in 1, -3- the mixture is continued without heating, -4- is gradually incorporated into the mixture obtained in 3, the second fraction of AC, -5- the unheated mixture is continued, -6- is devolatilized, preferably by heating to a temperature greater than or equal to 100 ° C under a pressure lower than the pressure at After evaporation of the microsphere or under the sweep of an inert gas, such as nitrogen, for example, the devolatilized mixture is left to cool, and the suspension is optionally supplemented with the remainder of the silicone oil. In stage 1 of the first variant as in stage 1 premium of the second variant described later, in the case of the expression "all or part of the silicone oil", it is intended to define the following three alternatives, among others: (i) it is in operation, either the whole of the reactive POS (s) and eventually all of the non-reactive POS (s) (ii) or a part of the (or of the) is put into operation POS reactive and possibly all of the non-reactive POS or, (iii) or a part of the reactive POS (or) and possibly a part of the non-reactive POS (s) is put into operation. According to the second variant of the preferred embodiment of the operation of the method according to the invention, the latter comprises the following steps: -1 '- A mixture comprising all or part of the silicone oil is homogenized. and the water, -2'- progressively incorporates the mixture obtained in 1 ', the particular reinforcing load and simultaneously the first fraction of AC, -3'- the mixture is continued without heating, -4'- the mixture is progressively incorporated obtained in 3 the second fraction of AC, -5 'the unheated mixture is continued, -6' is devolatilized, preferably by heating to a temperature > 100 ° C, under a pressure below atmospheric pressure or under the sweep of an inert gas, for example nitrogen, -1 '- the devolatilized mixture is allowed to cool down, -8'- and the suspension is eventually supplemented with the rest of the silicone oil. The characteristic of this second variant is linked to the fact that the particular reinforcing load and the first fraction of its compatibilizing agent are co-added. It is therefore possible to imagine carrying out a premixing of these two constituents or alternatively a concomitant introduction of these. According to a third variant of the preferred embodiment of the operation of the method according to the invention, which corresponds to the very preferential start-up mode, said procedure comprises the following steps: - - - homogenization is proceeded of a mixture comprising a portion of the reactive POS (s), all of the non-reactive (or) non-reactive, water and the first fraction of AC, -2- the particular reinforcing filler is progressively added to the the mixture obtained in 1", -3- the mixture is continued without heating, -4- is gradually incorporated into the mixture obtained in 3, the second fraction of AC, -5- the mixture is continued without heating, -6- devolatilizes, preferably by heating to a temperature >; 100 ° C under a pressure below atmospheric pressure or under a sweep of an inert gas such as nitrogen, -7- the devolatilized mixture is allowed to cool, -8- and the suspension is completed with the rest of the (or ) reactive POS (s) (in this variant: the symbol w defined above is equal to zero and the symbol v defined above is defined as zero and <60 parts by weight and, preferably <50 parts by weight ). To define otherwise the total amount of the AC used in the preferred embodiment where the reinforcing filler is of the silica and the AC agent is HMDZ, it can be indicated that this total amount of HMDZ is sufficient to operate at least one HMDZ mold. for a mold of the SiOH group located on the surface of the silica. In the case of the polyorganosiloxanes (POS) put into operation in the process of the invention, linear POSs will generally be chosen. As regards the reactive POS, it will be oils that respond to the following formula (1): YnR3n_SiO- -R2SiR02- -SiR3- nJ-n (1) In which: + R represents the identical or different monovalent hydrocarbon radicals, and Y represents the hydrolysable or condensable groups (different from OH) identical or different, or a hydroxyl group, + n is chosen between 1, 2 and 3 with n = 1, when Y is a hydroxyl, and x has a sufficient value to confer to the oils of the formula (1) a dynamic viscosity at 25 ° C comprised between 1,000 and 200,000 mPa. s and, preferably, between 5,000 and 80,000 mPa. s. As examples of radicals R, there may be mentioned alkyl radicals having from 1 to 8 carbon atoms such as methyl, ethyl, propyl, butyl, hexyl and octyl, the phenyl radicals. As examples of substituted R radicals, mention may be made of the 3, 3, 3-trifluoropropyl, chlorophenyl and betacyanoethyl radicals. Illustratively of the portions represented by the formula R2SiO can be cited those of the formulas: (CH3) 2SiO; CH3 (C6H5) YES; (C6H5) 2 Si0, CF3CH2CH2 (CH3) SiO; NC-CH2CH2 (CH3) SiO. In the products of the formula (1) generally used industrially, at least 80% by number of the radicals R are the methyl radicals, the other radicals can be in general the phenyl radicals. As examples of the hydrolysable groups Y, mention may be made of the amino, acylamino, aminoxy, ketiminoxy, iminoxy, enoxi, alkoxy, alkoxy-alken-oxy, acyloxy and phosphate groups and, for example, among these: - for the groups Y amino : the n-butylamino, sec-butylamino and cyclohexylamino groups, for the substituted acylamino N groups: the benzoylamino group, for the aminoxy groups: the dimethylaminoxy, diethylaminoxy, dioctylaminoxy and diphenylaminoxy groups, for the iminoxy and ketiminoxy groups: these acetophenone derivatives -oxime, acetone oxime, benzophenone oxime, methyl ethyl ketoxime, diisopropylketoxime and chlorocyclohexanone oxime, for Y groups alkoxy: groups having 1 to 8 carbon atoms such as methoxy, propoxy, isopropoxy, butoxy groups , hexyloxy and octyloxy, for the Y groups alkoxy-alkylene-oxy: the methoxy-ethylene-oxy group, for the Y-acyloxy groups: the groups having from 1 to 8 carbon atoms such as the formyloxy, acetoxy, propionyloxy and ethyl groups -2- hexanoyloxy, for the groups Y phosphate: those which are derived from the phosphate groups of dimethyl, diethyl phosphate and dibutyl phosphate: as condensable Y groups, there may be mentioned hydrogen atoms and halogen atoms, preferably chlorine. The reactive POSs used are preferably the α, β-dihydroxylated diorganopolysiloxanes of the formula (1) in which Y = OH, n = 1 and x have a sufficient value to give the polymers a dynamic viscosity at 25 ° C comprised between 1,000 and 200,000 mPa.s and, preferably, between 5,000 and 80,000 mPa. s. As regards the non-reactive POS, it will be oils that correspond to the following formula (2): R3-SiO- -R2SiR02- -SiR ^ (2) in which the R substituents, identical or different, have the same general or particular meanings as those given above for the reactive POS of the formula (1), and the symbol and it has a sufficient value to confer to the polymers a dynamic viscosity at 25 ° C between 10 and 10,000 mPa.s. and, preferably, between 30 and 2,000 mPa. s. It should be understood that, within the framework of the present invention, a mixture of several hydroxylated polymers differing from one another by the value of the viscosity and / or the nature of the substituents can be used as the hydroxylated POS of the formula (1). linked to the silicon atoms. It should further be noted that the hydroxylated polymers of the formula (1) may optionally comprise, on one side of the D portions of the formula R2SiO, the T portions of the formula RSi03 / 2 and / or the Si02 portions in the proportion of plus 1% (this percentage expresses the number of T and / or Q portions for 100 silicon atoms). The same notes apply to the non-reactive POS of formula (2). The vocation of the suspension of a reinforcing load in a MS silicone material prepared according to the invention, is to be used in obtaining silicone compositions, liquid or pasty, crosslinkable or hardenable by polycondensation in RTV silicone elastomer of polycondensation in the ambient atmosphere at normal temperature or at higher temperature. Thus, according to another of these aspects, the present invention relates to a process for obtaining an organopolysiloxane composition crosslinkable or curable by polycondensation, characterized in that it consists of mixing the following products: -A- the suspension as is prepared according to the procedure defined above: -B- optionally one or several semi-reinforcing, non-reinforcing or filler loads, -C- optionally water, -D- optionally one or more reactive, linear POS, including at each end of the chain at least two condensable or hydrolysable groups, or a single hydroxyl group, as the reactive POS of the formula (1) as defined above, -E- optionally one or several reactive POS of the formula (1) in the which x has a sufficient value to give the polymers a dynamic viscosity at 25 ° C comprised between 30 and 500 mPa.s and, preferably, between 35 and 100 mPa.s; -F- optionally one or several linear non-reactive POS not including the hydrolysable or hydroxyl condensable group, such as the non-reactive POS of the formula (2) as defined above; -G- one or more cross-linking agents chosen from: • a silane of the general formula: R4-aSYYa O) In which - the R substituents, identical or different, have the same general or particular meanings as those given above in formula (1) - the symbols Y ', identical or different, represent the same groups hydrolysable or condensable than those mentioned above with respect to the groups Y of the formula (1). • The partial hydrolysis products of a silane of the formula (3), The ingredient G is mandatory when the reagent (s) are POS a, β-dihydroxylated, and facultative (but desirable) when the reactive POS (s) include at each end of the chains the condensable (different from OH) or hydrolysable groups; -H- a crosslinking or hardening catalyst by polycondensation; -I- optionally one or more additives selected from pigments, plasticizers, other rheology modifiers, stabilizers and / or adhesion promoters; as far as B-loads are concerned, they generally have a particular diameter of more than 0.1 μm and are preferably chosen from crushed quartz, zirconates, calcined clays, diatomaceous earths, calcium carbonate, aluminas. They are used from 0 to 60 parts by weight and, preferably from to 50 parts by weight of the B-load (s) for 100 parts by weight of the total of reactive POS (POS of the suspension + ingredients D and E). As far as the water C is concerned, the amount used ranges from 0 to 2 parts by weight and, preferably, from 0 to 1 part by weight for 100 parts by weight of all the reactive POS. This water supply is not necessary if the reinforcing load suspension contains it sufficiently.

With respect to the reactive POS D, when used, the amount used represents % to 70% and, preferably, from 30% to 60% of the weight of all the reactive POS. As regards the reactive POS E of low viscosity, the amount used represents from 0% to 10% and, preferably, from 0.5% to 5% of the weight of the whole or of the reactive POS. As regards the non-reactive POS F of low viscosity, the amount used represents from 0 to 40 parts by weight and, preferably from 0 to 30 parts by weight for 100 parts by weight of all the POS reactive As examples of monomeric silanes G, polyacyloxysilanes, polyalkoxysilanes, polyketiminoxysilanes and polyiminoxysilanes, and in particular the following silanes: CH 3 SI (OCOCH 3) 3, C 2 H 5 Si (OCOCH 3) 3; (CH2 = CH) Si (OCOCH3) 3; C 6 H 5 Si (OCOCH 3) 3; CF3CH2CH2Si (OCOCH3) 3; NC-CH2CH2Si (0C0CH3) 3; CH2ClSi (OCOCH2CH3) 3; CH3Si [ON = C (CH3) C2H5] 2 (OCH2CH2OCH3); CH3Si [ON = CH- (CH3) 2] 2 (OCH2CH2OCH3); Yes (OC2H5) 4; Yes (0-n-C3H7) 4; Si (0-isoC3H7) 4; Si (OC2H4OCH3) 4; CH3Si (OCH3) 3; CH2 = CHSi (OCH3) 3; CH3Si (OC2H4OCH3) 3; ClCH2Si (OC2H5) 3; CH2 = CHSi (OC2H4OCH3) 3. Partial hydrolysis products, for example, polyacoxysilanes, commonly referred to as alkyl polysilicates, are well known products. The most commonly used product is ethyl polysilicate 40® from the partial hydrolysis of Si (OC2H5) 4. The crosslinking agents G used preferably in the case of the preferred use of the α, β-dihydroxylates of the formula (1), are the alkyltrialkoxysilanes and the tetraalkoxysilanes of the formula (3) where R represents an alkyl radical having 1 to 4 carbon atoms, and the partial hydrolysis products of these preferred silanes. When at least one crosslinking agent is used G, the amount is generally between 0.5 and 20 parts by weight and, preferably, between 1 and 10 parts by weight for 100 parts by weight of all the reactive POS. Compositions of crosslinkable silicones by polycondensation in elastomer generally comprise from 0.01 to 10 parts by weight of the catalyst H and preferably from 0.001 to 5 parts by weight of the H catalyst for 100 parts by weight of all the reactive POS.

According to the first variant of the process for obtaining a silicone composition crosslinkable or hardenable by polycondensation in elastomer, a composition of a single component (ie of a single packaging) intended to crosslink in the presence of moisture, in particular of the humidity provided by the ambient air or by the water present and / or added within the composition, at room temperature and / or under the effect of the temperature that can go, for example from 25 ° C to a lower value at 100 ° C. In this case, the crosslinking catalyst H used is a metal catalyst which is preferably chosen from tinmonocarboxylates, diorganotin dicarboxylates, a valence tin chelate IV, a hexacoordinated valence tin chelate IV, an organic derivative of titanium, an organic derivative of zirconium. The proportion of the catalyst of the single-component compositions is generally between 0.001 and 0.1 part by weight for 100 parts by weight of the whole or the reactive POS. According to a second variant of the process for preparing the crosslinkable compositions in elastomers: each composition is produced in the form of a system of two components (or two packagings) Cl and C2, intended to be brought into contact with one another to conduct a RTV polycondensation elastomer, and it is done in such a way that only one of the Cl or C2 parts contains the catalyst H and optionally the crosslinking agent (s) G. In the case of the two-component compositions, the The catalyst H used is preferably an organic tin derivative such as that defined above, an amine or a mixture of these species. The catalyst ratio of the two component compositions is generally between 0.1 and 5 parts by weight for 100 parts by weight of all the reactive POS. The following examples illustrate: the preparation of the reinforcing filler suspensions in a silicone material, according to the invention, the application of these suspensions as a raw material for the preparation of two-component compositions crosslinkable in polycondensation RTV silicone elastomers, as well as the evaluation of the viscoelastic properties of the suspensions and the mechanical properties of the crosslinked elastomers obtained from said suspensions.

EXAMPLES Example 1 (1) Preparation of a suspension according to the invention, with introductions of the compatibilizing agent before and after the incorporation of the reinforcing filler. In a 1.5-liter arm mixer, enter at room temperature (23 ° C) and in order: 351 g of non-reactive POS in the form of a blocked polydimethylsiloxane oil at each end of the chains for a portion (CH3) 3SiO? / Having a viscosity of 50 mPa.s at 25 ° C, - 143 g of reactive POS in the form of a hydroxylated polydimethylsiloxane oil, blocked at each end of the chains with a proportion (CH3) ) 2 (OH) SiO? / 2 having a viscosity of 20,000 mPa. s at 25 ° C and having 0.0527% by weight of hydroxyl radicals, 22 g of water, and 55 g of hexamethyldisilazane. After the homogenization, carried out after 30 minutes, 338 g of a combustion silica characterized by its BET specific surface and 200 m2 / g are added in portions in 180 minutes. The mixture is continued by stirring, without heating, for 60 minutes and, after this time, 33 g are added. additional hexamethyldisilazane. The mixing is continued by stirring without heating for 30 minutes and, after this time, a heating step is started in the course of which the reaction mass is placed under a pressure below atmospheric pressure, of the order of 13 at 4 40.102Pa, when the temperature reaches approximately 80 ° C; the heating is continued for 150 minutes until reaching 120 ° C, temperature that is maintained immediately for 120 minutes. At the end of this time, the heating is stopped and the atmospheric pressure is restored and, when the temperature drops again to approximately 65 ° C, 377 g of reactive POS defined above are added in three portions, and mixing is continued until the homogenization of this suspension. The viscosity of the obtained suspension is measured by means of a standard vicosimeter of the BROOKFIELD type according to the indications of the standard AFNOR-NFT-76106, and by means of a CARRIMED dynamic rheometer, type CSL, equipped in a flat cone geometry, operating under the following conditions: • measurement mode: imposed oscillation and constraint, • imposed constraint: 3 Pa. • Frequencies: 1 Hz, • Plane cone geometry of the measurement: diameter = 4 cm, angle = 2 °. As a result, the relationship of the values of the elastic moduli G 'and viscous moduli G "that are representative of the viscoelastic behavior of the suspension will be presented 2) The preparation of a crosslinkable organopolysiloxane composition by polycondensation, according to the invention, which it is presented in the form of a two component system (parts Cl and C2) intended to be brought into contact with one another to lead to a polycondensation RTV elastomer.

Part Cl (base mixture): In a laboratory mixer comprising a 0.5 liter container and a paddle-type central stirrer, it is charged at room temperature (23 ° C) and the following ingredients are carefully mixed: 235 g of the suspension obtained at the exit of phase 1) described above, 70 g of crushed quartz having a particle size of 2.5 μm corresponding to its average diameter called x, d 50", - 90 g of reactive POS in the form of a polydimethylsiloxane oil hydroxylated blocked at each end of the chains by a portion (CH3) 2 (OH) SiO? / 2 having a viscosity of 14,000 mPa.s at 25 ° C and having 0.0646% by weight of hydroxyl radicals, - 1.6 g of reactive POS in the form of a hydroxylated polydimethylsiloxane oil blocked at each end of the chain by a portion (CH3) 2 (OH) SiO? / 2 having a viscosity of 40 mPa.s at 25 ° C and which has 4.93% by weight of hydroxyl radicals, and OR 4. g of water, Part C2 (catalyzed mixture) This part is obtained by carefully mixing the following ingredients: Ethyl polysilicate 40® from the partial hydrolysis of Si (OC2H5) 4 (87.5% by weight) and di-n-butyltin dilaurate (12.5% by weight). The RTV composition is obtained by mixing 100 parts by weight of the Cl part to 2 parts by weight of the C2 part. The RTV composition is transformed by crosslinking after several hours at room temperature (23 ° C) in a silicone elastomer; the following mechanical properties are measured after 4 days of crosslinking in an atmosphere regulated at 23 ° C and at 50% relative humidity: Shore A hardness, annotated DSA (measurements made according to the indications of DIN-53505); resistance to rupture, in Mpa, annotated R / R, and elongations at rupture, in%, annotated A / R, (measurements made in accordance with the instructions in the AFNOR-NFT-46002 standard), resistance to tearing in N / mm, RD annotation (measurements made in accordance with the instructions in ASTM-D-6224 A).

Example 2 (comparative example) 1) Preparation of a suspension with introduction of the entire compatibilizing agent after incorporation of the reinforcing filler. Example 1, phase 1), is reproduced approximately when one starts by loading 422 g of non-reactive POS in the mixer in the form of a blocked polydimethylsiloxane oil at each end of the chains for a portion (CH3) 3SiO ? / 2 which has a viscosity of 500 mPa. s at 25 ° C and 42 g of water. After homogenization, 287 g of the combustion silica are added in portions in 180 minutes. After 60 minutes of mixing, 58 g of hexamethyldisilazane are added in 50 minutes. The mixture is continued for 60 minutes before starting the stage where a heating is operated, then heating under reduced pressure and cooling, stage which is the same as described above When the temperature is again lowered to approximately 65 ° C 279 g of reactive POS are added in three portions in the form of a hydroxylated polydimethylsiloxane oil blocked at each end of the chains by a portion (CH3) 2 (OH) SiO? / 2 having a viscosity of 14,000. mPa. s and having 0.0646% by weight of hydroxyl radicals, and mixing is continued until homogenization of this suspension. 2) Preparation of the two-component organopolysiloxane composition, crosslinkable by polycondensation. It is operated exactly as indicated above in example 1 phase 2).

Example 3 (comparative example) 1) Preparation of a suspension with introduction of the entire compatibilizing agent with the incorporation of the reinforcing filler. Example 1 phase 1), is reproduced except that here begins by loading into the mixer: 351 g of non-reactive POS (viscosity of 50 mPa.s), 143 g of reactive POS (viscosity of 20,000 mPa.s), 22 g of water and 87 g of hexamethyldisilazane After 30 minutes of stirring, 338 g of the combustion silica are added in portions in 180 minutes. Mixing is continued by stirring for 60 minutes before starting the stage where a heating is operated, then heating under reduced pressure and cooling, a step which is the same as described above. When the temperature is again lowered to approximately 65 ° C they are added in three portions 377 g of reactive POSS (viscosity 200,000 mPa.s), and mixing is continued until homogenization of this suspension. 2) Preparation of a two-component organopolysiloxane composition, crosslinkable by polycondensation. It is operated exactly as indicated above in example 1, phase 2) The values found, concerning the rheology of the suspensions and the mechanical properties of the elastomers, are reported in the following table: The two-stage treatment (before and after the incorporation of the reinforcing filler) of the reinforcing filler by the compatibilizing agent (example 1) leads to a suspension where the rheological behavior is not affected and is typical of a product that drips well, and that allows the realization of an elastomer having good mechanical properties and, in particular, a resistance to tearing which is improved.

Claims (11)

1. Process for preparing a suspension of a particular reinforcing filler in a silicone material (MS): + the MS comprises: at least one linear reactive POS including at each end of the chain at least two condensable or hydrolysable groups, or one single hydroxyl group, optionally at least one linear non-reactive POS which does not include the condensable, hydrolysable or hydroxyl group, optionally water, + said suspension is, mainly, usable to produce crosslinkable or hardenable silicone compositions by polycondensation, + said process is of the genus of those in which the particular reinforcing filler is treated with the aid of a compatibilization agent (AC), and which is characterized in that it consists essentially of introducing the compatibilizing agent (AC) into the suspension preparation means: part, before and / or substantially simultaneously with the incorporation, in at least a part of the material of silicone MS put into operation, of the particular reinforcing load used, this introduction of AC is operated with a fraction of AC corresponding to a proportion that ranges from 8% to 30% dry weight in relation to the particular reinforcing load, and on the other hand, after this incorporation of the load in at least a part of the MS.

2. Method according to claim 1, characterized in that it comprises the following steps: - It is mixed in any order, possibly carrying out a premixing, of the (or) POS with the compatibilisation agent AC and optionally water: (100-VW) parts by weight of at least one reactive POS and optionally water minus a non-reactive POS. 0 to 5 parts by weight of water, 10 to 50 parts by weight of particular reinforcing filler, and of a first fraction of AC representing 8% to 30 of the dry weight of the reinforcing filler; 10 a second fraction of AC is introduced into the mixture which represents 2% to 25% of the dry weight of the reinforcing filler; it is allowed to react continuing the mixing; the mixture is heated by choosing a pair of 15 pressure / temperature in such a way that a devolatilization of the volatile elements and of at least a part of the water eventually present occurs; the mixture is allowed to cool 20 devolatilized; and the suspension is eventually supplemented with the remainder of the reactive POS (s) (v parts by weight) and / or with, optionally, the remainder of the non-reactive POS (s) (s) ( 25 parts by weight); said method comprises the supplementary definition elements listed below: - the amount of the non-reactive POS (s), when used, (w parts by weight); when it is in the range from 1 to 100 parts in for 100 parts of the reactive POS (s); the total amount of the compatibilizing agent AC is comprised between 10 and 45% of the weight of the reinforcing filler; - the symbol v goes from zero to 60 parts by weight; the symbol goes from zero to 50 parts by weight; • the sum v + w goes from zero to 60 parts by weight.

3. Process according to claim 1 or 2, characterized in that it comprises the following steps: 1) proceeds to the homogenization of a mixture comprising all or part of the silicone oil, water and the first fraction of AC, 2) is progressively adds the particular reinforcing filler, to the mixture obtained in 1, 3) the mixture is continued without heating, 4) the mixture obtained in 3 is progressively incorporated, the second fraction of AC, 5) the mixture is continued without heating, 6) is devolatilized 7) the devolatilized mixture is allowed to cool, 8) and the suspension is eventually supplemented with the rest of the silicone oil.

4. The process according to claim 1 or 2, characterized in that it comprises the following steps: -1'- proceed to the homogenization of a mixture comprising all or part of the silicone oil and water, -2 '- the mixture obtained in 1' is progressively incorporated, the particular reinforcing load and simultaneously the first fraction of AC, -3'- the mixture is continued without heating, -4 '- is progressively incorporated to the mixture obtained in 3, the second fraction of AC, -5'- the unheated mixture is continued, -6'- is devolatilized, -1 '- the devolatilized mixture is allowed to cool, -8'- and the suspension is eventually supplemented with the rest of the silicone oil.

5. Process according to claim 1 or 2, characterized in that it comprises the following steps: -1"- proceeds to the homogenization of a mixture comprising a part of reactive (or) POS, all of the (or ) POS not reactive, the water and the first fraction of AC, -2- is added progressively the particular reinforcing load to the mixture obtained in 1", -3- continues the mixture without heating, -4- is gradually incorporated into the mixture obtained in 3, the second fraction of AC, -5- the mixture is continued unheated, -6- is devolatilized, -7- the devolatilized mixture is allowed to cool, -8- and the suspension is completed with the remainder of the mixture. (or of the) reactive POS.

6. Method according to any of claims 1 or 5, characterized in that the particular reinforcing filler consists of a siliceous filler selected from the group consisting of the precipitation silicas, the combustion silicas and their mixtures, these silicas having a BET specific surface area greater than 40 m2 / g.

7. Process according to any of claims 1 to 6, characterized in that the compatibilizing agent AC is chosen from the organosilazanes and the cycloorganosilazanes, which are liquid at a temperature of 23 ° C and under a pressure of 10-10.8x102 Pa, these compounds they are used alone or as a mixture between them.

8. Method according to any of claims 1 to 7, characterized in that the reactive POS respond to the following formula 1: YnR3n_SiO- -R2SiR02- -SÍR3_nYn (1) In which: + R represents the identical or different monovalent hydrocarbon radicals, and Y represents the hydrolysable or condensable groups (different from OH) identical or different, or a hydroxyl group, + n is chosen between 1, 2 and 3 with n = 1, when Y is a hydroxyl, and x has a sufficient value to confer to the oils of the formula (1) a dynamic viscosity at 25 ° C comprised between 1,000 and 200,000 mPa.s.

9. The method according to any of claims 1 to 8, characterized in that the non-reactive POS respond to the following formula (2): R3_SiO- -R2SiR02- -SÍR, (2) and In which: + the R substituents, identical or different, represent the monovalent hydrocarbon radicals, + the symbol y has a sufficient value to confer to the polymers a dynamic viscosity at 25 ° C comprised between 10 and 10,000 mPa. s.

10. Process for obtaining a crosslinkable or hardened organopolysiloxane composition by polycondensation, characterized in that it consists in mixing the following products: -A- the suspension as prepared according to the process defined according to any of claims 1 to 9, -B- . Optionally one or more semi-reinforcing, non-reinforcing or filler loads, C- optionally water, -D- optionally one or several reactive POS as defined in claim 1 or 8, -E- optionally one or several reactive POS as defined in claim 8 wherein the symbol x of formula (1) has a sufficient value to give the polymers a dynamic viscosity at 25 ° C comprised between 30 and 500 mPa.s; -F- optionally one or more non-reactive POS as defined in claim 1 or 9, -G- one or more cross-linking agents chosen from: • a silane of the general formula R4-aSiY '(3; In which the substituents R, identical or different, have the same general or particular meanings as those given above in formula (1) of claim 8, - the symbols Y ', identical or different, represent the same hydrolyzable or condensable groups than those mentioned above with respect to the groups Y of the formula (1) of claim 8, "The partial hydrolysis products of a silane of the formula (3), The ingredient G is mandatory when the reagent (s) are POS. ,? -dihydroxylated, and optional (but desirable) when the reactive POS (s) include at each end of the chains the condensable (different from OH) or hydrolysable groups; -H- a crosslinking or hardening catalyst by polycondensation; -I- optionally one or more additives selected from pigments, plasticizers, other rheology modifiers, stabilizers and / or adhesion promoters;

11. The method according to claim 10, characterized in that: each composition is produced in the form of a two-component system Cl or C2, intended to be brought into contact with one another to conduct a polycondensation RTV elastomer, and in such a way that only one of the Cl or C2 parts contains the catalyst H and possibly the cross-linking agents G.