Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
  • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
  • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
  • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/28—Compounds of silicon
  • C09C1/30—Silicic acid
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/28—Compounds of silicon
  • C09C1/30—Silicic acid
  • C09C1/3009—Physical treatment, e.g. grinding; treatment with ultrasonic vibrations
  • C09C1/3018—Grinding
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/11—Powder tap density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/19—Oil-absorption capacity, e.g. DBP values
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]

Definitions

• the present invention relates to a process for the preparation of precipitated silica, in particular in the form of a powder.
• the invention also relates to the precipitation silicas thus obtained, as well as their use, in particular for the reinforcement of silicone elastomer matrices or based on silicone pastes.
• combustion silicas have been used, that is to say silicas obtained by a process consisting in reacting at high temperature tetrachlorosilane compounds with hydrogen and oxygen.
• the combustion silicas are generally expensive.
• these silicas are of lower cost and may have the required dispersibility characteristics within a silicone-based matrix.
• patent EP 1 860 066 describes a process for producing precipitated silica which is of particular interest for the reinforcement of silicone matrices, comprising a step of heat treatment at high temperature (300-800 ° C.) in a fluidized bed. Nevertheless, this step is expensive in energy and requires substantial industrial investments.
• an essential objective of the present invention is to provide a process for the preparation of precipitated silica which is simple to implement, does not require significant additional industrial investment or high energy expenditure compared to known methods and which allows the production of precipitated silica. obtaining dispersible precipitated silicas which can be used as fillers, in particular reinforcing fillers, in matrices containing silicones and to which they can confer good mechanical properties.
• the invention also aims to provide dispersible precipitation silicas that can be used as fillers, in particular reinforcing fillers, in matrices based on silicones and to which they can confer good mechanical properties.
• Another object of the invention is to provide a precursor organopolysiloxane composition of silicone elastomers comprising this dispersible precipitated silica.
• Another object of the present invention is to obtain a silicone elastomer comprising this dispersible precipitated silica.
• a final objective of the invention is the use of the precipitated silica thus obtained in tires, dentifrices, cosmetic compositions, compositions foodstuffs, pharmaceutical compositions, silicone compositions and elastomers.
• a process for preparing a precipitated silica X having improved dispersibility and reinforcing properties comprising the steps of: a) reacting at least one of a silicate with at least one acidifying agent, so as to obtain a suspension A of precipitated silica,
• mechanical mill an apparatus in which takes place the reduction of the particles by mechanical means (for example a jaw, hammer or knife mill).
• mechanical means for example a jaw, hammer or knife mill.
• fluid jet mills such as air jet mills where the particles are entrained by an air jet in an enclosure designed so that the particles undergo a large number of shocks.
• the inventors have had the merit of surprisingly and surprisingly revealing that a precipitation silica exhibiting dispersibility characteristics, a density and a moisture content particularly suitable for their use for the reinforcement of Silicone-based matrices can be obtained according to a silica precipitation process, provided that the grinding and drying step is simultaneously carried out in a mechanical grinder. Steps a), b) and c) of the process according to the invention are well described in the art.
• silica precipitated is carried out by precipitation reaction of a silicate, such as an alkali metal silicate (sodium silicate for example) with an acidifying agent (sulfuric acid for example).
• a silicate such as an alkali metal silicate (sodium silicate for example)
• an acidifying agent sulfuric acid for example.
• the mode of precipitation of the silica (step a)) can be arbitrary: in particular, by addition of acidifying agent to a silicate base stock or by simultaneous total or partial addition of acidifying agent and silicate on a stock of water or silicate.
• a silica slurry is obtained which is then separated (liquid-solid separation).
• This separation generally consists of a filtration which can be done according to any suitable method, for example press filter or belt filter or rotary vacuum filter, this filtration leading to the obtaining of a "filter cake"
• This cake of filtration obtained is subjected to one or more washing operation, generally with water, so as to reduce its salt content (step b)).
• it can also be subjected to a disintegration operation prior to the drying step.
• Drying of the filter cake (step c) is preferably by spray drying.
• any suitable type of atomizer in particular turbines, nozzles, liquid pressure or two-fluid atomizers.
• the precipitated silica thus separated, filtered, optionally washed and dried can be subjected to a subsequent grinding so as to obtain the desired particle size.
• Different types of mill can be used such as air jet mills or mechanical grinders.
• silica manufacturing processes drying is preferably carried out prior to grinding. Indeed, during grinding the density of the precipitated silica will greatly decrease and consequently the powder volumes to be dried and transported increase considerably. In addition, the handling of small particle size powders imposes very important hygiene, safety and environmental constraints. It is therefore in the interest of any industrial to carry out the grinding step as late as possible in the process for producing a precipitated silica.
• a means for simultaneously grinding and drying is to regulate in step d) the temperature in the mechanical mill Z by means of an air supply heated to a temperature of between 50.degree. and 190 ° C, preferably between 60 and 150 ° C and even more preferably between 65 and 130 ° C.
• the temperature can be regulated also by means of a supply of a heated inert fluid (for example nitrogen or argon), but this variant leads to a higher operating cost.
• the grinding in step d) is carried out by means of a mechanical grinder Z by attrition and more particularly by means of a mechanical grinder Z by attrition in a grinding chamber provided with a rotor and a stator.
• the grinding of the particles takes place between the rotor and the stator.
• the fragmentation of the particles depends on the probability of impact between the grinding bodies and the particles.
• the product obtained therefore has a wide particle size distribution.
• the mechanical grinders can be equipped with particle classification systems by flight.
• step d) the mechanical mill Z is equipped with an integrated particle classification system for recovering precipitated silica particles X.
• step d) the mechanical mill Z is connected to an independent particle classification system for recovering precipitated silica particles X.
• step d) takes place at atmospheric pressure.
• CTAB The specific surface area which is measured according to the BRUNAUER-EMMET-TELLER method described in the Journal of the American Chemical Society, vol. 60, page 309 (February 1938).
• CTAB The specific surface area called CTAB, determined according to standard NFT 45007 (November 1987).
• the pH measured according to ISO 787/9 pH of a suspension at 5% in water.
• the moisture content (or residual water content) determined by the weight loss measured after heat treatment at 105 ° C for 2 hours (in% weight)
• the tap density or packed fill density (DRT) is determined according to standard NF T 30-042.
• the precipitation silicas generally contain, at least in trace amounts, a salt resulting from the action of the acidifying agents used on the silicates used.
• the precipitation silicas when the process of the invention specifically employs an alkali silicate as the precursor of silica and sulfuric acid as an acidifying agent, the precipitation silicas contain an alkali sulfate.
• the content of alkali sulphate in the silicas thus obtained is relatively low, most often such that the mass of sulphate ions present generally represents at most 1% by weight relative to the total mass of the dry material.
• the control of the sulfate content of the precipitated silica is important for some applications.
• sulfate levels in precipitated silica greater than 0.7% by weight lead to a coloration (yellowing) of the elastomers containing this silica. It is also known also that a high sulphate rate promotes a significant water recovery, hence the interest of keeping this sulphate rate as low as possible.
• the precipitated silica C has the following characteristics:
• CTAB surface area of between 50 and 300 m 2 / g
• the precipitated silica C has the following characteristics:
• the precipitated silica C has the following characteristics:
• the precipitated silica C is a water-dispersible silica on the type of silica Z160 ® marketed by Rhodia, silica Ultrasil ® marketed by Degussa or silica DRX190 ® marketed by PPG.
• step d) of the process where the grinding-drying is carried out simultaneously is important to note that some of the characteristics of the precipitated silica C are not modified during step d) of the process where the grinding-drying is carried out simultaneously. This is the case, for example, with CTAB, BET, pH and sulphate level.
• step d) of the process according to the invention enables us to improve the properties of the precipitated silica C by decreasing its moisture content, by decreasing its particle size and by decreasing its typed density.
• the size of the precipitated silica particles is measured with a laser granulometer (Malvern 2000 apparatus).
• the distribution values are expressed in cumulative volume. Thus 10% of the particles in volume have a size smaller than the value indicated by the Dv 10, 50% of the particles in volume have a size smaller than the value indicated by the Dv50 and 90% of the particles in volume have a smaller size than the value indicated by D v 90.
• the precipitated silica X obtainable by the process of the invention has the following characteristics:
• the precipitated silica X that can be obtained by the process of the invention has the following characteristics:
• the precipitated silica X according to the invention has a D v 10 ⁇ 12 ⁇ and even more preferentially D v 10 ⁇ 8 ⁇ .
• the precipitated silica X according to the invention has a D v 90 ⁇ 25 ⁇ and even more preferentially D v 90 ⁇ 22 ⁇ .
• the present invention also relates to a precursor organopolysiloxane composition of silicone elastomers comprising precipitated silica X according to the invention or as obtained by the process according to the invention.
• organopolysiloxane compositions comprising precipitated silica X
• the organopolysiloxane compositions for obtaining the EVCs according to the invention comprise (in parts by weight):
• 25 ° C may for example be a chain of siloxyl units of formula R 2 SiO 2/2 , blocked at each end of its chain by a siloxyl unit of formula R 3 SiOi / 2 and / or a radical of formula OR '; in these formulas the R symbols, which are identical or different, represent methyl, ethyl, n-propyl, phenyl, vinyl or 3,3,3-trifluoropropyl radicals, at least 60% of these radicals being methyl and at most 3% being vinyl, the symbol R 'represents a hydrogen atom, an alkyl radical having 1 to 4 carbon atoms, a betamethoxy-ethyl radical.
• the diorganopolysiloxane oil (4) having a viscosity of at most 5,000 mPa.s at 25 ° C. can be formed of a chain of siloxyl units of formula R " 2 SiO 2/2 blocked at each end of its chain by a radical of formula OR 'in these formulas the symbols R ", identical or different, represent methyl, phenyl or vinyl radicals, at least 40% of these radicals being methyl and the symbol R' has the meaning given above.
• the diorganopolysiloxane oil (4) may be present in an amount of from 0 to 15 parts, preferably from 0.3 to 12 parts per 100 parts of gum (1).
• This oil or these oils are linear polymers of relatively low viscosity, at most 5,000 mPa.s at 25 ° C, preferably at most 4,000 mPa.s at 25 ° C, of which the diorganopolysiloxane chain is formed essentially of the units of the aforementioned formula R " 2 Si0 2/2 , this chain is blocked at each end by a radical of the aforementioned formula OR '.
• the meaning of the symbols R" and R ' has been explained previously. Preferably, are used:
• dimethylpolysiloxane oils blocked at each end of their chain by hydroxyl, methoxyl or betamethoxyethoxyl radicals and whose viscosity is between 10 and 200 mPa.s at 25 ° C .;
• methylphenylpolysiloxane oils consisting of CH 3 (C 6 H 5 ) SiO 2/2 units , blocked at each end of their chain by hydroxyl and / or methoxyl radicals, and whose viscosity is between 40 and 2000 mPa. s at 25 ° C.
• the organic peroxides (2) are used in a proportion of 0.1 to 7 parts, preferably 0.2 to 5 parts, per 100 parts of the gums (1). They are well known to those skilled in the art and more particularly include benzoyl peroxide, 2,4-dichloro-benzoyl peroxide, dicumyl peroxide, 2,5-dimethyl (tert-butylperoxy) -2,5-hexane, sodium perbenzoate and the like. t-butyl, peroxy t-butyl and isopropyl carbonate, di-t-butyl peroxide, bis (t-butylperoxy) -1,1 trimethyl-3,3,5 cyclohexane. These various peroxides decompose at sometimes different temperatures and speeds. They are chosen and their quantity is adapted according to the desired conditions.
• Another subject of the present invention is a silicone elastomer comprising precipitated silica X according to the invention or as obtained by the process according to the invention.
• a final subject of the invention relates to the use of precipitated silica X according to the invention or as obtained by the process according to the invention in tires, dentifrices, cosmetic compositions, food compositions, pharmaceutical compositions silicone compositions and elastomers.
• the precipitated silicas of the present invention can also be advantageously used as reinforcing filler in matrices based on organic polymers, and in particular in matrices based on one or more elastomers, natural or synthetic, and in particular in matrices based on rubber, and more particularly based on natural or synthetic rubbers, SBR type or butyl rubber in particular.
• the silicas obtained according to the process of the invention have good quality of dispersibility and reinforcement within polymer and elastomer matrices, where they make it possible in particular to increase the resistance to abrasion, which can prove to be interesting in the context of the constitution of tires.
• the precipitated silicas of the present invention may also be advantageously used as thickening agents in organic or aqueous media, preferably in aqueous media, and especially in toothpastes.
• the silicas obtained according to the invention may be useful in many other fields of customary use of precipitated silicas, for example for the manufacture of paints or papers. They are particularly useful as a carrier in food or cosmetic compositions.
• the silicas obtained according to the process of the present invention are, moreover, silicas which are particularly well suited in the field of galenics.
• the silicas of the present invention are particularly suitable as fillers, carriers and / or excipients within pharmaceutical compositions.
• Table 1 below describes the commercial silicas used to obtain the silicas according to the invention.
• the average particle size D v 50 is between 9 and 12.5 microns and the moisture content is less than 5% by weight.
• silicas S1 to S3 milled and simultaneously dried silicas, obtained by the process according to the invention (silicas S1 to S3), as well as those milled conventionally, that is to say without simultaneous drying (comparative silicas C1 to C3), were used as reinforcing fillers in two heat-vulcanizable silicone compositions.
• Silicone composition A (all parts are by weight)
• Vi corresponds to vinyl for all of the examples
• the composition thus obtained is introduced into a two-roll mill and 1.25 parts of 2,4-dichloro-benzoyl peroxide diluted to 50% by weight in a silicone oil. added as a catalyst.
• a fraction of the homogeneous mass obtained on the kneader is used to measure the mechanical properties of the silicone elastomer resulting from the hot vulcanization of the polyorganosiloxane composition.
• the homogeneous mass fraction taken is then vulcanized in press for 8 minutes at 1 ⁇ 5 ° C operating in a suitable mold to obtain plates 2 mm thick.
• plates are obtained in the non-annealed state (NR). These plates are then annealed or aged for 4 hours at 200 ° C. Standardized samples are then taken from all these plates and the following properties are measured:
• Table 4 shows the mechanical properties of the silicone elastomers obtained by using the milled silicas and simultaneously dried by the process according to the invention (Examples A1 to A3 with the silicas S1 to S3) and the conventionally milled silicas, that is to say ie without simultaneous drying (Comparative Examples AC1 to AC3 with C1 to C3 silicas).
• Table 4 Mechanical properties of elastomers derived from silicone compositions A
• Silicone composition B (all parts are by weight)
• the composition thus obtained is introduced into a two-roll kneader and 0.6 parts of 2,5-dimethyl-2,5bis (tert-butylperoxy) -2,5-hexane diluted to 75% by weight in a silicone oil is added as a catalyst.
• a fraction of the homogeneous mass obtained on the kneader is used to measure the mechanical properties of the silicone elastomer resulting from the hot vulcanization of the polyorganosiloxane composition.
• the homogeneous mass fraction taken is then vulcanized in press for 10 minutes at 170 ° by operating in a suitable mold to obtain plates of 2 mm thick.
• plates are obtained in the non-annealed state (NR). These plates are then annealed or aged for 4 hours at 200 ° C. Standardized samples are then taken from all these plates and the same properties are measured as for the silicone composition A.
• Table 6 shows the mechanical properties of the silicone elastomers obtained by using the milled silicas and dried simultaneously by the process according to the invention (Examples B1 to B3 with the silicas S1 to S3) and those milled conventionally, that is to say say without simultaneous drying (Comparative Examples BC1 to BC3 with C1 to C3 silicas). TABLE 6 Elastomeric Mechanical Properties Resulting from the Silicone B Compositions

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• 2010
  • 2010-12-20 JP JP2012545265A patent/JP2013515661A/ja active Pending
  • 2010-12-20 US US13/518,856 patent/US20120329937A1/en not_active Abandoned
  • 2010-12-20 EP EP10800734A patent/EP2523905A1/fr not_active Withdrawn
  • 2010-12-20 WO PCT/EP2010/070204 patent/WO2011076716A1/fr active Application Filing
  • 2010-12-20 CN CN2010800635029A patent/CN102753479A/zh active Pending
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